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Sample records for composition risks degradation

  1. Degraded water quality influences microbial community composition and perception of health risks in the Chattooga River.

    PubMed

    Kent, Angela D; Bayne, Zachary L

    2010-09-01

    Bacterial skin infections are a chronic problem among whitewater rafters on the Chattooga River in the southeastern United States; however, little is known about the source of such infections. The Chattooga River is a federally designated "Wild and Scenic" river, with a forested riparian buffer zone designed to protect water quality in the river. Riverine water quality can be negatively impacted by tributaries that are not protected by federal guidelines. Water quality in Stekoa Creek, a major tributary of the Chattooga River, is degraded by sediment that runs off from construction sites near the creek, as well as fecal coliform contamination from wastewater treatment facilities. Degraded water quality may impact the health of visitors recreating on the river, as well as recreation industry workers. We demonstrate that inputs from the impaired creek influence microbial community composition in Chattooga River waters. A survey of whitewater raft guides was conducted to collect data on incidence of skin infection, and to assess perceived health risk from recreation activities. Whitewater rafting guides working on the Chattooga River reported concerns about their personal health related to degraded water quality and microbial contamination from Stekoa Creek. Incidence of bacterial skin infection and perceived health risk was strongly correlated among the whitewater rafting guides (r = 0.67). Concerns about environmental quality appear to be shaped by the incidence of skin infection. Such concerns are also correlated with changes in recreation practices among whitewater rafting guides (r = 0.67).

  2. Composite of PAH-degrading endophytic bacteria reduces contamination and health risks caused by PAHs in vegetables.

    PubMed

    Wang, Jian; Liu, Juan; Ling, Wanting; Huang, Qingguo; Gao, Yanzheng

    2017-11-15

    Vegetables accumulate polycyclic aromatic hydrocarbons (PAHs) at high concentrations when grown in contaminated sites. Inoculation with PAH-degrading endophytic bacteria (EBPAH) has been recognized as one of the most promising ways to remove PAHs from plant bodies; however, the performance of single endophytic bacteria is generally limited. This investigation used a composite of eight EBPAH to reduce the contamination and health risk posed by 16 EPA priority PAHs in vegetables including Chinese cabbage (Brassica chinensis L.) and pakchoi (Brassica campestris L.). Composite EBPAH have strong PAH degradation abilities, and more than 65% of ∑PAH were degraded after 10-day insuspension with composite EBPAH. Vegetable were contacted with composite EBPAH by seed soaking (SS) and leaf painting (LP) with an EBPAH cell incubation at OD600nm=0.2-1.5. Compared with those in non-inoculated controls, the ∑PAH concentrations in edible parts of Chinese cabbage and pakchoi colonized by composite EBPAH via SS and LP with bacterial suspension at OD600nm=0.2-1.5 were 42.07-70.77% and 15.79-53.20% lower, and the incremental lifetime cancer risk (ILCR) values for males and females were 31.78-84.08% and 26.60-83.40% smaller, respectively. SS was the optimal inoculation method for reducing PAH concentrations and ILCR values. Our results indicate that inoculating plants with composite EBPAH can lower the health risk posed by vegetables contaminated with PAHs, and may be used to mitigate plant PAH contamination. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Photovoltaic Degradation Risk: Preprint

    SciTech Connect

    Jordan, D. C.; Kurtz, S. R.

    2012-04-01

    The ability to accurately predict power delivery over the course of time is of vital importance to the growth of the photovoltaic (PV) industry. Important cost drivers include the efficiency with which sunlight is converted into power, how this relationship changes over time, and the uncertainty in this prediction. An accurate quantification of power decline over time, also known as degradation rate, is essential to all stakeholders - utility companies, integrators, investors, and researchers alike. In this paper we use a statistical approach based on historical data to quantify degradation rates, discern trends and quantify risks related to measurement uncertainties, number of measurements and methodologies.

  4. Hydrolytic degradation of dental composites.

    PubMed

    Söderholm, K J; Zigan, M; Ragan, M; Fischlschweiger, W; Bergman, M

    1984-10-01

    The leakage of filler elements from four composites after storage in water was investigated by use of atomic absorption spectrophotometry. The results confirmed previous findings that leaching of silicon from different composites is strongly dependent on filler composition. Consideration of the total filler surface of each composite material indicated that quartz as well as pyrolytic silica-containing composites leached less silicon than did composites containing fillers of strontium and/or barium glasses. A correlation between leakage and crack formation in the matrix appeared to exist for all composites except for the microfilled resin. These cracks were explained as a result of osmotic pressure built up at the matrix-filler interface due to hydrolytic degradation of the filler. Of the investigated materials, the microfilled resin was found to be the most stable material in a wet environment with respect to crack formation. This finding was explained by filler composition, filler form, and the specific structure of the microfilled resin.

  5. Environmental Degradation of High Temperature Composites

    DTIC Science & Technology

    1992-04-01

    A study was performed to assess the effect of galvanic corrosion phenomena on the strength of graphite/bismaleimide( BMI ) composites . The results...indicate that degradation occurred in BMI composites galvanically coupled to aluminum alloys. The mechanism responsible for the degradation involves

  6. Polymer Composites Corrosive Degradation: A Computational Simulation

    NASA Technical Reports Server (NTRS)

    Chamis, Christos C.; Minnetyan, Levon

    2007-01-01

    A computational simulation of polymer composites corrosive durability is presented. The corrosive environment is assumed to manage the polymer composite degradation on a ply-by-ply basis. The degradation is correlated with a measured pH factor and is represented by voids, temperature and moisture which vary parabolically for voids and linearly for temperature and moisture through the laminate thickness. The simulation is performed by a computational composite mechanics computer code which includes micro, macro, combined stress failure and laminate theories. This accounts for starting the simulation from constitutive material properties and up to the laminate scale which exposes the laminate to the corrosive environment. Results obtained for one laminate indicate that the ply-by-ply degradation degrades the laminate to the last one or the last several plies. Results also demonstrate that the simulation is applicable to other polymer composite systems as well.

  7. 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.

  8. 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 VScomposites ranked as follows: Durafill VS>Z-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

  9. Pre-heating mitigates composite degradation.

    PubMed

    Silva, Jessika Calixto da; Rogério Vieira, Reges; Rege, Inara Carneiro Costa; Cruz, Carlos Alberto dos Santos; Vaz, Luís Geraldo; Estrela, Carlos; Castro, Fabrício Luscino Alves de

    2015-01-01

    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 VScomposites ranked as follows: Durafill VS>Z-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.

  10. Degraded environments alter prey risk assessment.

    PubMed

    Lönnstedt, Oona M; McCormick, Mark I; Chivers, Douglas P

    2012-01-01

    Elevated water temperatures, a decrease in ocean pH, and an increasing prevalence of severe storms have lead to bleaching and death of the hard corals that underpin coral reef ecosystems. As coral cover declines, fish diversity and abundance declines. How degradation of coral reefs affects behavior of reef inhabitants is unknown. Here, we demonstrate that risk assessment behaviors of prey are severely affected by coral degradation. Juvenile damselfish were exposed to visual and olfactory indicators of predation risk in healthy live, thermally bleached, and dead coral in a series of laboratory and field experiments. While fish still responded to visual cues in all habitats, they did not respond to olfactory indicators of risk in dead coral habitats, likely as a result of alteration or degradation of chemical cues. These cues are critical for learning and avoiding predators, and a failure to respond can have dramatic repercussions for survival and recruitment.

  11. Thermal Degradation of Lead Monoxide Filled Polymer Composite Radiation Shields

    SciTech Connect

    Harish, V.; Nagaiah, N.

    2011-07-15

    Lead monoxide filled Isophthalate resin particulate polymer composites were prepared with different filler concentrations and investigated for physical, thermal, mechanical and gamma radiation shielding characteristics. This paper discusses about the thermo gravimetric analysis of the composites done to understand their thermal properties especially the effect of filler concentration on the thermal stability and degradation rate of composites. Pristine polymer exhibits single stage degradation whereas filled composites exhibit two stage degradation processes. Further, the IDT values as well as degradation rates decrease with the increased filler content in the composite.

  12. Thermal Degradation of Lead Monoxide Filled Polymer Composite Radiation Shields

    NASA Astrophysics Data System (ADS)

    Harish, V.; Nagaiah, N.

    2011-07-01

    Lead monoxide filled Isophthalate resin particulate polymer composites were prepared with different filler concentrations and investigated for physical, thermal, mechanical and gamma radiation shielding characteristics. This paper discusses about the thermo gravimetric analysis of the composites done to understand their thermal properties especially the effect of filler concentration on the thermal stability & degradation rate of composites. Pristine polymer exhibits single stage degradation whereas filled composites exhibit two stage degradation processes. Further, the IDT values as well as degradation rates decrease with the increased filler content in the composite.

  13. Analysis of the Degradation of a Model Dental Composite

    PubMed Central

    Koin, P.J.; Kilislioglu, A.; Zhou, M.; Drummond, J.L.; Hanley, L.

    2008-01-01

    Dental composites undergo material property changes during exposure to the oral environment and may release compounds of potential toxicity, such as bisphenol A. Degradation of dental composites was studied in a simplified overlayer model in which bisphenol A diglycidyl methacrylate (BisGMA) was covalently bound to a porous silicon oxide surface. It was hypothesized that the chemical structure of this overlayer would allow release of bisphenol A, BisGMA, and the decomposition products thereof, upon exposure to water for an extended period. Liquid chromatography mass spectrometry found leaching of intact BisGMA and several degradation products that contained the bisphenol A moiety from the overlayer into distilled water after 2 wks of aging. The absence of bisphenol A release from the overlayer reduces concerns regarding its potential health risk in dental composites. Nevertheless, health concerns might arise with respect to BisGMA and the leached degradation products, since they all contain the bisphenol A moiety. Abbreviations: BisGMA, bisphenol A diglycidyl methacrylate; HPLC, high-performance liquid chromatography; LCMS, liquid chromatography mass spectrometry; MA, methacrylic acid; MPS, 3-(trimethoxysilyl) propyl methacrylate; m/z, mass-to-charge ratio; and TIC, total ion chromatogram. PMID:18573987

  14. Polymer composites including natural additives degradation rate indication

    NASA Astrophysics Data System (ADS)

    Ananyev, V. V.; Nagornova, I. V.; Bablyuk, E. B.; Vasilyev, I. Yu.; Varepo, L. G.

    2017-08-01

    The low density polyethylene and starches (native and thermoplastic) polymer compounds degradation rate diagnostic and prediction method based on the vapor permeability and degradation index determination was considered. Both the degradation index defined by the modified Sturm test, and permeability were compared to the actual and varying depending on the composition rheological, mechanical and morphological features of the composite films structure produced by the laboratory extruder. Films permeability measuring by means of the gas chromatography made possible to increase the evaluation accuracy by two orders. The symbate correlation dependence between the indexes characterizing water ingress into the composite (vapor permeability) and the degradation evaluating characteristic (degradation index) was defined to exist.

  15. Biocarrier composition for and method of degrading pollutants

    DOEpatents

    Fliermans, C.B.

    1994-01-01

    The present invention relates to biocarrier compositions that attract and bond pollutant-degrading antigens that will degrade the pollutants. Biocarriers are known generally as a variety of inert or semi-inert compounds or structures having the ability to sequester (attract), hold and biomagnify (enhance) specific microorganisms within their structure. Glass or polystyrene beads are the most well known biocarriers. The biocarrier, which is preferably in the form of glass microspheres, is coated with an antibody or group of antibodies that attract and react specifically with certain pollutant-degrading antigens. The antibody, once bonded to the biocarrier, is used by the composition to attract and bond those pollutant-degrading antigens. Each antibody is specific for an antigen that is specific for a given pollutant. The resulting composition is subsequently exposed to an environment contaminated with pollutants for degradation. In the preferred use, the degrading composition is formed and then injected directly into or near a plume or source of contamination.

  16. Soil-ecological risks for soil degradation estimation

    NASA Astrophysics Data System (ADS)

    Trifonova, Tatiana; Shirkin, Leonid; Kust, German; Andreeva, Olga

    2016-04-01

    Soil degradation includes the processes of soil properties and quality worsening, primarily from the point of view of their productivity and decrease of ecosystem services quality. Complete soil cover destruction and/or functioning termination of soil forms of organic life are considered as extreme stages of soil degradation, and for the fragile ecosystems they are normally considered in the network of their desertification, land degradation and droughts /DLDD/ concept. Block-model of ecotoxic effects, generating soil and ecosystem degradation, has been developed as a result of the long-term field and laboratory research of sod-podzol soils, contaminated with waste, containing heavy metals. The model highlights soil degradation mechanisms, caused by direct and indirect impact of ecotoxicants on "phytocenosis- soil" system and their combination, frequently causing synergistic effect. The sequence of occurring changes here can be formalized as a theory of change (succession of interrelated events). Several stages are distinguished here - from heavy metals leaching (releasing) in waste and their migration downward the soil profile to phytoproductivity decrease and certain phytocenosis composition changes. Phytoproductivity decrease leads to the reduction of cellulose content introduced into the soil. The described feedback mechanism acts as a factor of sod-podzolic soil self-purification and stability. It has been shown, that using phytomass productivity index, integrally reflecting the worsening of soil properties complex, it is possible to solve the problems dealing with the dose-reflecting reactions creation and determination of critical levels of load for phytocenosis and corresponding soil-ecological risks. Soil-ecological risk in "phytocenosis- soil" system means probable negative changes and the loss of some ecosystem functions during the transformation process of dead organic substance energy for the new biomass composition. Soil-ecological risks estimation is

  17. Controlled degradation pattern of hydroxyapatite/calcium carbonate composite microspheres.

    PubMed

    Yang, Ning; Zhong, Qiwei; Zhou, Ying; Kundu, Subhas C; Yao, Juming; Cai, Yurong

    2016-06-01

    Hydroxyapatite (HAP) is widely used in clinic due to its good biocompatibility and osteoconductivity except for its slow degradation speed. In the present study, spherical calcium carbonate (CaCO3 ) is fabricated in the presence of silk protein sericin, which is transmuted into HAP microsphere in phosphate solution with the assistance of microwave irradiation. The effect of reaction conditions on the conversion of CaCO3 is investigated including reaction time, chemical composition of phosphate solution, and microwave power to get a series of HAP/CaCO3 composites. The degradation property of the composites is evaluated in vitro. Results show the degradation speed of the composite with higher HAP content is slower. The degradation rate of the composite could be changed effectively by modulating the proportion of HAP and CaCO3 . This work provides a feasible method for the preparation of spherical HAP/CaCO3 composite with controllable degradability. The composite thus obtained may be an ideal material for bone tissue engineering application. Microsc. Res. Tech. 79:518-524, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  18. Radiation Degradation of Polytetrafluoroethylene-Lead Composites

    NASA Astrophysics Data System (ADS)

    Karmakar, Sanat; Lawrence, Falix; Mallika, C.; Mudali, U. Kamachi

    2015-11-01

    Composites of polytetrafluoroethylene (PTFE) with Pb (0-15 wt.%) were fabricated and irradiated up to 50 kGy in a 60Co-gamma chamber to evaluate the effect of Pb in improving the radiation tolerance of PTFE. Thermal and mechanical properties were measured for the irradiated and un-irradiated PTFE samples and its composites. The number average molecular weight of PTFE was estimated at different doses from the enthalpy of crystallization values obtained by Differential Scanning Calorimetry. Reduction in the percentage increase in the enthalpy of crystallization and melting of PTFE-15% Pb composite, during irradiation indicated the stabilizing effect of lead on PTFE. Surface morphology of PTFE and its composites revealed that the formation of micro-cracks and blisters in PTFE, owing to radiation damage was controlled by lead. Elongation at break values and SEM images of the irradiated composites indicated that 15% Pb offered better stability to PTFE than 10% Pb.

  19. Compositional Effects on Electromechanical Degradation of RAINBOW Actuators

    NASA Technical Reports Server (NTRS)

    Dausch, David E.; Wise, Stephanie A.

    1998-01-01

    The effect of ceramic composition on the electromechanical displacement degradation of RAINBOW (Reduced and Internally Biased Oxide Wafer) actuators was investigated. RAINBOWs were fabricated from commercially available PZT-5H and PZT-5A piezoelectric disks as well as from tape cast PLZT piezoelectric 7/65/35 and electrostrictive 9/65/35 compositions. Displacement properties were measured at low electric fields (10 to 13 kV/cm) under loads of 0 to 500 g, and displacement degradation as a function of time was observed over 107 cycles. The PZT-5A and PLZT 9/65/35 compositions exhibited minimal decrease in displacement when load was applied. Furthermore, these compositions retained approximately 65 percent of their initial displacement after 10(exp 7) cycles under a load of 300 g. PZT-5H and PLZT 7/65/35 degraded completely under these conditions.

  20. Interply layer degradation effects on composite structural response

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Williams, G. C.

    1983-01-01

    Recent research activities at NASA Lewis Research Center to computationally evaluate the effects of interply layer progressive weakening (degradation) on the structural response of a composite beam are summarized. The structural responses of interest include: (1) bending, (2) buckling, (3) free vibrations, (4) periodic excitation, and (5) impact. Finite element analysis was used for the computational evaluations. The interply layer degradation effects on the various structural responses were determined and assessed as a function of the interply layer modulus varying from 1 million psi down to 1000 psi and even lower for some limiting cases. The results obtained show that the interply layer degradation has generally negligible effects on composite structural response and, therefore, structural integrity, unless the interply layer modulus degrades to about 10,000 psi or less.

  1. Degradable Biopolymer Composites Made from Seed Proteins

    USDA-ARS?s Scientific Manuscript database

    Zein is a prolamine of maize. Conventionally, 70-90% aqueous ethanol has been used to dissolve zein. Monitoring the variation of hydrodynamic radii of zein molecules in aqueous ethanol revealed that zein aggregates in the solvent and that the degree of aggregation depends on the composition of the...

  2. Degradation of graphite/polymer composites in seawater

    SciTech Connect

    Tucker, W.C. )

    1991-12-01

    Glass-reinforced plastics have a substantial history of use in sea water. With the advent of high-performance graphite fibers offering greater stiffness than glass, some marine engineering applications may be implemented where glass was unsuitable. However, the nobility of graphite in the galvanic series makes it an extremely efficient cathode when coupled with metals in seawater. Degradation of the cathodic composite material is an unexpected result of the corrosion chemistry in natural seawater. Deep submergence of composite materials introduces another potential degradative mechanism in seawater due to an increase moisture uptake by damage-dependent mechanisms. In this paper other environmental exposure to sunlight, deep submergence and cyclic thermal changes which show potential for degradation of composites are discussed.

  3. Thermal Degradation of Filler/PP Composite and Its Depression

    NASA Astrophysics Data System (ADS)

    Hosoi, Hiroshi; Funami, Fumiyasu; Yasuda, Naoki; Nomura, Manabu; Yui, Hiroshi; Ikuta, Nobuo

    To examine thermal degradation accelerated by filling inorganic particles in polypropylene (PP), the composites were made with three types of inorganic powders : talc, magnesium hydroxide, and mica. They were easily degraded with the fillers in this order in the thermal aging test. A commercial heat resistance agent, ‘Plenlizer MK-400’, was added while making the composites. The degradation resistance of the agent remarkably appeared in the reverse order. That is, thermal degradation was most depressed in talc-filled composite with the agent. In another experience, soxhlet extraction was carried out to the filler with an organic solvent, o-xylene, that was able to dissolve PP. A lot of inorganic ions were detected in the extractant. In particular, the detected amount of aluminum ion increased in the order of talc, magnesium hydroxide, and mica. This order was the same as the fillers indicated by the degree of degradation. Infrared analysis of the agent with inorganic ions in chloroform showed that the peaks due to the agent were much stronger with aluminum ion than those with iron ion. These results suggested that a cause of degradation was aluminum ion dispersed from particles to PP matrix during the molding.

  4. Cariogenic bacteria degrade dental resin composites and adhesives.

    PubMed

    Bourbia, M; Ma, D; Cvitkovitch, D G; Santerre, J P; Finer, Y

    2013-11-01

    A major reason for dental resin composite restoration replacement is related to secondary caries promoted by acid production from bacteria including Streptococcus mutans (S. mutans). We hypothesized that S. mutans has esterase activities that degrade dental resin composites and adhesives. Standardized specimens of resin composite (Z250), total-etch (Scotchbond Multipurpose, SB), and self-etch (Easybond, EB) adhesives were incubated with S. mutans UA159 or uninoculated culture medium (control) for up to 30 days. Quantification of the BisGMA-derived biodegradation by-product, bishydroxy-propoxy-phenyl-propane (BisHPPP), was performed by high-performance liquid chromatography. Surface analysis of the specimens was performed by scanning electron microscopy (SEM). S. mutans was shown to have esterase activities in levels comparable with those found in human saliva. A trend of increasing BisHPPP release throughout the incubation period was observed for all materials and was more elevated in the presence of bacteria vs. control medium for EB and Z250, but not for SB (p < .05). SEM confirmed the increased degradation of all materials with S. mutans UA159 vs. control. S. mutans has esterase activities at levels that degrade resin composites and adhesives; degree of degradation was dependent on the material's chemical formulation. This finding suggests that the resin-dentin interface could be compromised by oral bacteria that contribute to the progression of secondary caries.

  5. Degradable Polymer Composites Fabricated from Starch and Alkyl Cyanoacrylate Monomer

    USDA-ARS?s Scientific Manuscript database

    Degradable polymer composites are fabricated from alkyl cyanoacrylate monomer and starch without special equipment. Alkyl cyanoacrylate, which is a major component of “super glue”, is a monomer that polymerizes at room temperature in the presence of initiators. During the fabrication of polymer com...

  6. Cariogenic Bacteria Degrade Dental Resin Composites and Adhesives

    PubMed Central

    Bourbia, M.; Ma, D.; Cvitkovitch, D.G.; Santerre, J.P.; Finer, Y.

    2013-01-01

    A major reason for dental resin composite restoration replacement is related to secondary caries promoted by acid production from bacteria including Streptococcus mutans (S. mutans). We hypothesized that S. mutans has esterase activities that degrade dental resin composites and adhesives. Standardized specimens of resin composite (Z250), total-etch (Scotchbond Multipurpose, SB), and self-etch (Easybond, EB) adhesives were incubated with S. mutans UA159 or uninoculated culture medium (control) for up to 30 days. Quantification of the BisGMA-derived biodegradation by-product, bishydroxy-propoxy-phenyl-propane (BisHPPP), was performed by high-performance liquid chromatography. Surface analysis of the specimens was performed by scanning electron microscopy (SEM). S. mutans was shown to have esterase activities in levels comparable with those found in human saliva. A trend of increasing BisHPPP release throughout the incubation period was observed for all materials and was more elevated in the presence of bacteria vs. control medium for EB and Z250, but not for SB (p < .05). SEM confirmed the increased degradation of all materials with S. mutans UA159 vs. control. S. mutans has esterase activities at levels that degrade resin composites and adhesives; degree of degradation was dependent on the material’s chemical formulation. This finding suggests that the resin-dentin interface could be compromised by oral bacteria that contribute to the progression of secondary caries. PMID:24026951

  7. 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.

  8. 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.

  9. Glass fibres reinforced polyester composites degradation monitoring by surface analysis

    NASA Astrophysics Data System (ADS)

    Croitoru, Catalin; Patachia, Silvia; Papancea, Adina; Baltes, Liana; Tierean, Mircea

    2015-12-01

    The paper presents a novel method for quantification of the modifications that occur on the surface of different types of gel-coated glass fibre-reinforced polyester composites under artificial UV-ageing at 254 nm. The method implies the adsorption of an ionic dye, namely methylene blue, on the UV-aged composite, and computing the CIELab colour space parameters from the photographic image of the coloured composite's surface. The method significantly enhances the colour differences between the irradiated composites and the reference, in contrast with the non-coloured ones. The colour modifications that occur represent a good indicative of the surface degradation, alteration of surface hydrophily and roughness of the composite and are in good correlation with the ATR-FTIR spectroscopy and optical microscopy results. The proposed method is easier, faster and cheaper than the traditional ones.

  10. Defining land degradation and desertification risk using simple indicators

    NASA Astrophysics Data System (ADS)

    Kairis, Or.

    2012-04-01

    A methodology has been developed for defining land degradation and desertification risk by using simple indicators related to soil, climate, vegetation, social economic, and land management characteristics. A number of 72 candidate indicators have been identified and analyzed for assessing land desertification risk under various processes and causes of degradation. Data were collected from 1672 field sites located in 17 study sites located in various environmental, social and economical conditions. The main processes or causes of land degradation and desertification identified in the study field sites were soil erosion, soil salinization, water stress, overgrazing, and forest fires. The number of candidate indicators defined for each process or cause of land degradation was ranged from 16 to 50. Classes have been defined for each indicator and numbers have been assigned for each class according to its importance on desertification. After creating the appropriate data basis, a forward stepwise statistical analysis was conducted for all indicators corresponding to each process or cause of land degradation and the sensitivity of each indicator to desertification risk was identified. Algorithms were derived for each process or cause that can be easily used for identifying land degradation and desertification risk at farm level. The performance of the derived methodology was assessed using the independent indicators soil erosion, soil organic matter content, and soil aggregate stability. The analysis of the data have shown that the used candidate indicators were significantly reduced to a number of effective indicators ranging from 8 to 17 in the various processes or causes of land degradation and desertification. Among the most important indicators identified as affecting land degradation and desertification risk were rain seasonality, soil depth, slope gradient, plant cover, rate of burned area, grazing control, rate of land abandonment, land use intensity, population

  11. Long Term Degradation of Resin for High Temperature Composites

    NASA Technical Reports Server (NTRS)

    Patekar, Kaustubh A.

    2000-01-01

    The durability of polymer matrix composites exposed to harsh environments is a major concern. Surface degradation and damage are observed in polyimide composites used in air at 125 to 300 C. It is believed that diffusion of oxygen into the material and oxidative chemical reactions in the matrix are responsible. Previous work has characterized and modeled diffusion behavior, and thermogravimetric analyses (TGAs) have been carried out in nitrogen, air, and oxygen to provide quantitative information on thermal and oxidative reactions. However, the model developed using these data was not able to capture behavior seen in isothermal tests, especially those of long duration. A test program that focuses on lower temperatures and makes use of isothermal tests was undertaken to achieve a better understanding of the degradation reactions under use conditions. A new low-cost technique was developed to collect chemical degradation data for isothermal tests lasting over 200 hr in the temperature range 125 to 300 C. Results indicate complex behavior not captured by the previous TGA tests, including the presence of weight-adding reactions. Weight gain reactions dominated in the 125 to 225 C temperature range, while weight loss reactions dominated beyond 225 C. The data obtained from isothermal tests was used to develop a new model of the material behavior. This model was able to fully capture the behavior seen in the tests up to 275 C. Correlation of the current model with both isothermal data at 300 C and high rate TGA test data is mediocre. At 300 C and above, the reaction mechanisms appear to change. Attempts (which failed) to measure non-oxidative degradation indicate that oxidative reactions dominate the degradation at low temperatures. Based on this work, long term isothermal testing in an oxidative atmosphere is recommended for studying the degradation behavior of this class of materials.

  12. Cavity degradation risk insurance assessment. Final report

    SciTech Connect

    Hampson, C.; Neill, P.; de Bivort, L.

    1980-01-01

    This study examined the risks and risk management issues involved with the implementation by electric power utilities of compressed air energy storage and underground pumped hydro storage systems. The results are listed in terms of relative risks for the construction and operation of these systems in different geologic deposits, with varying amounts of pressurization, with natural or man-made disasters in the vicinity of the storage equipment, and with different modes of operating the facilities. (LCL)

  13. Factors Controlling Elevated Temperature Strength Degradation of Silicon Carbide Composites

    NASA Technical Reports Server (NTRS)

    2005-01-01

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

  14. Environmental aging degradation in continuous fiber ceramic composites

    SciTech Connect

    Plucknett, K.P.; Lin, H.T.; Braski, D.N.; Becher, P.F.

    1995-12-31

    The thermal stability of two-continuous fiber ceramic composites (CFCC`s) has been assessed. A Nicalon/CaO-Al{sub 2}O{sub 3}-SiO{sub 2} (CAS) glass-ceramic composite has been subjected to unstressed, oxidation heat treatments between 375 and 1200{degrees}C, after which the material was tested in flexure at room temperature. The static fatigue behavior of a chemical vapor infiltrated (CVI) Nicalon/SiC ceramic matrix composite has been assessed in air, between 425 and 1150{degrees}C, both with and without protective seal coating. Severe property degradation was observed due to oxidation of the graphite fiber/matrix interlayer in both CFCC`s.

  15. Environmentally degradable bio-based polymeric blends and composites.

    PubMed

    Chiellini, Emo; Cinelli, Patrizia; Chiellini, Federica; Imam, Syed H

    2004-03-15

    Blends and composites based on environmentally degradable-ecocompatible synthetic and natural polymeric materials and fillers of natural origin have been prepared and processed under different conditions. Poly(vinyl alcohol) (PVA) was used as the synthetic polymer of choice by virtue of its capability to be processed from water solution or suspension as well as from the melt by blow extrusion and injection molding. Starch and gelatin were taken as the polymeric materials from renewable resources. The fillers were all of natural origin, as waste from food and agro-industry consisted of sugar cane bagasse (SCB), wheat flour (WF), orange peels (OR), apple peels (AP), corn fibres (CF), saw dust (SD) and wheat straw (WS). All the natural or hybrid formulations were intended to be utilized for the production of: a) Environmentally degradable mulching films (hydro-biomulching) displaying, in some cases, self-fertilizing characteristics by in situ spraying of water solutions or suspensions; b) Laminates and containers to be used in agriculture and food packaging by compression and injection molding followed by baking. Some typical prototype items have been prepared and characterized in relation to their morphological and mechanical properties and tested with different methodology for their propensity to environmental degradation and biodegradation as ultimate stage of their service life. A relationship between chemical composition and mechanical properties and propensity to biodegradation has been discussed in a few representative cases.

  16. 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

  17. Biological degradation and composition of inedible sweetpotato biomass

    NASA Technical Reports Server (NTRS)

    Trotman, A. A.; Almazan, A. M.; Alexander, A. D.; Loretan, P. A.; Zhou, X.; Lu, J. Y.

    1996-01-01

    Many challenges are presented by biological degradation in a bioregenerative Controlled Ecological Life Support System (CELSS) as envisioned by the U.S. National Aeronautics and Space Administration (NASA). In the studies conducted with biodegradative microorganism indigenous to sweetpotato fields, it was determined that a particle size of 75 microns and incubation temperature of 30 degrees C were optimal for degradation. The composition of the inedible biomass and characterization of plant nutrient solution indicated the presence of potential energy sources to drive microbial transformations of plant waste. Selected indigenous soil isolates with ligno-cellulolytic or sulfate-reducing ability were utilized in biological studies and demonstrated diversity in ability to reduce sulfate in solution and to utilize alternative carbon sources: a lignin analog--4-hydroxy, 3-methoxy cinnamic acid, cellulose, arabinose, glucose, sucrose, mannitol, galactose, ascorbic acid.

  18. Biological degradation and composition of inedible sweetpotato biomass

    NASA Astrophysics Data System (ADS)

    Trotman, A. A.; Almazan, A. M.; Alexander, A. D.; Loretan, P. A.; Zhou, X.; Lu, J. Y.

    1996-01-01

    Many challenges are presented by biological degradation in a bioregenerative Controlled Ecological Life Support System (CELSS) as envisioned by the U.S. National Aeronautics and Space Administration (NASA). In the studies conducted with biodegradative microorganism indigenous to sweetpotato fields, it was determined that a particle size of 75 microns and incubation temperature of 30 degC were optimal for degradation. The composition of the inedible biomass and characterization of plant nutrient solution indicated the presence of potential energy sources to drive microbial transformations of plant waste. Selected indigenous soil isolates with ligno-cellulolytic or sufate-reducing ability were utilized in biological studies and demonstrated diversity in ability to reduce sulfate in solution and to utilize alternative carbon sources: a lignin analog-4-hydroxy, 3-methoxy cinnamic acid, cellulose, arabinose, glucose, sucrose, mannitol, galactose, ascorbic acid.

  19. Biological degradation and composition of sweet potato biomass - errata

    NASA Astrophysics Data System (ADS)

    Trotman, A. A.; Almazan, A. M.; Alexander, A. D.; Loretan, P. A.; Zhou, X.; Lu, J. Y.

    1996-01-01

    Many challenges are presented by biological degradation in a bioregenerative Controlled Ecological Life Support System as envisioned by the U.S. National Aeronautics and Space Administration. In studies conducted with biodegradative microorganisms indigenous to sweetpotato fields, it was determined that a particle size of 75 microns and incubation temperature of 30 degC were optimal for degradation. The composition of the biomass and characterization of plant nutrient solution indicated the presence of potential energy sources to drive microbial transformations of plant waste. Selected indigenous soil isolates with ligno-cellulolytic or sulfate-reducing ability were utilized in biological studies and demonstrated diversity in their ability to reduce sulfate in solution and to utilize alternative carbon sources: a lignin analog 4-hydroxy, 3-methoxy cinnamic acid, cellulose, arabinose, glucose, sucrose, mannitol, galactose, ascorbic acid.

  20. Thermal Degradation and Combustion Behavior of Polypropylene/MWCNT Composites

    NASA Astrophysics Data System (ADS)

    Zaikov, G. E.; Rakhimkulov, A. D.; Lomakin, S. M.; Dubnikova, I. L.; Shchegolikhin, A. N.; Davidov, E. Ya.

    2010-06-01

    Studies of thermal and fire-resistant properties of the polypropylene/multi-walled carbon nanotube composites (PP/MWCNT) prepared by means of melt intercalation are discussed. The sets of the data acquired with the aid of non-isothermal TG experiments have been treated by the model kinetic analysis. The thermal-oxidative degradation behavior of PP/MWCNT and stabilizing effect caused by addition of MWCNT has been investigated by means of TGA and EPR spectroscopy. The results of cone calorimetric tests lead to the conclusion that char formation plays a key role in the mechanism of flame retardation for nanocomposites. This could be explained by the specific antioxidant properties and high thermal conductivity of MWCNT which determine high-performance carbonization during thermal degradation process. Comparative analysis of the flammability characteristics for PP-clay/MWCNT nanocomposites was provided in order to emphasize the specific behavior of the nanocomposites under high-temperature tests.

  1. Biological degradation and composition of inedible sweetpotato biomass.

    PubMed

    Trotman, A A; Almazan, A M; Alexander, A D; Loretan, P A; Zhou, X; Lu, J Y

    1996-01-01

    Many challenges are presented by biological degradation in a bioregenerative Controlled Ecological Life Support System (CELSS) as envisioned by the U.S. National Aeronautics and Space Administration (NASA). In the studies conducted with biodegradative microorganism indigenous to sweetpotato fields, it was determined that a particle size of 75 microns and incubation temperature of 30 degrees C were optimal for degradation. The composition of the inedible biomass and characterization of plant nutrient solution indicated the presence of potential energy sources to drive microbial transformations of plant waste. Selected indigenous soil isolates with ligno-cellulolytic or sulfate-reducing ability were utilized in biological studies and demonstrated diversity in ability to reduce sulfate in solution and to utilize alternative carbon sources: a lignin analog--4-hydroxy, 3-methoxy cinnamic acid, cellulose, arabinose, glucose, sucrose, mannitol, galactose, ascorbic acid.

  2. 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

  3. High Temperature Degradation Mechanisms in Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Cunningham, Ronan A.; McManus, Hugh L.

    1997-01-01

    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 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

  4. The composition and degradability of upland dissolved organic matter

    NASA Astrophysics Data System (ADS)

    Moody, Catherine; Worrall, Fred; Clay, Gareth

    2016-04-01

    In order to assess controls on the degradability of DOM in stream water, samples of dissolved organic matter (DOM) and particulate organic matter (POM) were collected every month for a period of 24 months from an upland, peat-covered catchment in northern England. Each month the degradability of the DOM was assessed by exposing river water to light for up to 24 hours, and the change in the dissolved organic carbon (DOC) concentration in the water was measured. To provide context for the analysis of DOM and its degradability, samples of peat, vegetation, and litter were also taken from the same catchment and analysed. The organic matter samples were analysed by several methods including: elemental analysis (CHN and O), bomb calorimetry, thermogravimetric analysis, pyrolysis GC/MS, ICP-OES, stable isotope analysis (13C and 15N) and 13C solid state nuclear magnetic resonance (NMR). The water samples were analysed for pH, conductivity, absorbance at 400nm, anions, cations, particulate organic carbon (POC) and DOC concentrations. River flow conditions and meteorology were also recorded at the site and included in the analysis of the composition and degradability of DOM. The results of multiple regression models showed that the rates of DOC degradation were affected by the N-alkyl, O-alkyl, aldehyde and aromatic relative intensities, gross heat, OR and C:N. Of these, the N-alkyl relative intensity had the greatest influence, and this in turn was found to be dependent on the rainfall and soil temperature in the week before sampling.

  5. Molecular profiling of permafrost soil organic carbon composition and degradation

    NASA Astrophysics Data System (ADS)

    Gu, B.; Mann, B.

    2014-12-01

    Microbial degradation of soil organic matter (SOM) is a key process for terrestrial carbon (C) cycling, though the dynamics of these transformations remain unclear at the molecular level. This study reports the application of ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) to profile molecular components of Arctic SOM collected from the surface water and the mineral horizon of a low-centered polygon soil at Barrow Environmental Observatory (BEO), Barrow, Alaska. Soil samples were subjected to anaerobic warming experiments for a period of 40 days, and the SOM was extracted before and after the incubation to determine the components of organic C that were degraded over the course of the study. A CHO index based on molecular composition data was utilized to codify SOM components according to their observed degradation potential. Carbohydrate- and lignin-like compounds in the water-soluble fraction (WSF) demonstrated a high degradation potential, while structures with similar stoichiometries in the base-soluble fraction (BSF) were not readily degraded. The WSF of SOM also shifted to a wider range of measured molecular masses including an increased prevalence of larger compounds, while the size distribution of compounds in the BSF changed little over the same period. Additionally, the molecular profiling data indicated an apparently ordered incorporation of organic nitrogen in the BSF immobilized as primary and secondary amines, possibly as components of N-heterocycles, which may provide insight into nitrogen immobilization or mobilization processes in SOM. Our study represents an important step forward for studying Arctic SOM with improved understanding of the molecular properties of soil organic C and the ability to represent SOM in climate models that will predict the impact of climate change on soil C and nutrient cycling.

  6. Degradation, fatigue and failure of resin dental composite materials

    PubMed Central

    Drummond, James L.

    2008-01-01

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

  7. Degradation, Fatigue, and Failure of Resin Dental Composite Materials

    SciTech Connect

    Drummond, J.L.

    2008-11-03

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

  8. [Degradation of cassava residue by the cellulose degradation composite microbial system MC1].

    PubMed

    Guo, Peng; Wang, Xiao-Fen; Zhu, Wan-Bin; Cheng, Xu; Cui, Zong-Jun

    2008-03-01

    The lignocelluloses of cassava residue are good biomass resources. They are mainly used to produce feeds and alcohol. It is a promising approach to utilize them to produce methane. But it is difficult to use cassava residue for producing methane because of its dispersive solid matter and much water. A cellulose degradation composite microbial system MC1 was applied to degrade cassava residue discarded from cassava starch manufactory, and the composition of the lignocelluloses and the soluble ingredients of cassava residue were analyzed. After 18 days' cultivation, the total weight of the cassava residue was reduced by 47.3%, the cellulose, hemi-cellulose and lignin of the cassava residue were reduced by 22.7%, 90.4% and 11.3%, respectively, and 85% of the whole weight relief was made by MC1 within 6 days. The soluble ingredients of the cassava residue were increased from the incipient 18% to 33% in the third day which was the peak value in the process. The total amount of the volatile products, analyzed by GC-MS, came to a maximum in the sixth day. Twelve kinds of volatile products in the fermentation broth were determined, in which ethanol, acetic acid, 1, 2-ethanediol, butanoic acid and glycerine were the major compounds, and they can be utilized by methanogenic organism directly or be changed into compounds that can be utilized by methanogens organism directly. Accordingly, it is very hopeful to use MC1 to degrade cassava residue as a method of prefermentation in methane fermentation.

  9. Production of Insecticide Degradates in Juices: Implications for Risk Assessment.

    PubMed

    Radford, Samantha A; Panuwet, Parinya; Hunter, Ronald E; Barr, Dana Boyd; Ryan, P Barry

    2016-06-08

    This study was designed to observe the production of degradates of two organophosphorus insecticides and one pyrethroid insecticide in beverages. Purified water, white grape juice, apple juice, and red grape juice were fortified with 500 ng/g malathion, chlorpyrifos, and permethrin, and aliquots were extracted for malathion dicarboxylic acid (MDA), 3,5,6-trichloro-2-pyridinol (TCPy), and 3-phenoxybenzoic acid (3-PBA) several times over a 15 day period of being stored in the dark at 2.5 °C. Overall, first-order kinetics were observed for production of MDA, and statistically significant production of TCPy was also observed. Statistically significant production of 3-phenoxybenzoic acid was not observed. Results indicate that insecticides degrade in food and beverages, and this degradation may lead to preexisting insecticide metabolites in the beverages. Therefore, it is suggested that caution should be exercised when using urinary insecticide metabolites to assess exposure and risk.

  10. Resorbable composites with bioresorbable glass fibers for load-bearing applications. In vitro degradation and degradation mechanism.

    PubMed

    Lehtonen, Timo J; Tuominen, Jukka U; Hiekkanen, Elina

    2013-01-01

    An in vitro degradation study of three bioresorbable glass fiber-reinforced poly(l-lactide-co-dl-lactide) (PLDLA) composites was carried out in simulated body fluid (SBF), to simulate body conditions, and deionized water, to evaluate the nature of the degradation products. The changes in mechanical and chemical properties were systematically characterized over 52 weeks dissolution time to determine the degradation mechanism and investigate strength retention by the bioresorbable glass fiber-reinforced PLDLA composite. The degradation mechanism was found to be a combination of surface and bulk erosion and does not follow the typical core-accelerated degradation mechanism of poly(α-hydroxyacids). Strength retention by bioresorbable glass fiber-reinforced PLDLA composites can be tailored by changing the oxide composition of the glass fibers, but the structure-property relationship of the glass fibers has to be understood and controlled so that the phenomenon of ion leaching can be utilized to control the degradation rate. Therefore, these high performance composites are likely to open up several new possibilities for utilizing resorbable materials in clinical applications which could not be realized in the past.

  11. [Biological degradation of sticky-gene compositions in different type soils].

    PubMed

    Votselko, S K; Iamborko, N A; Litvinchuk, O A; Dankevitch, L A; Shkatula, Iu N

    2012-01-01

    The ability of native microbial associations from different types of soils to degrade sticky-gene composition which were created on the EPAA basis have been determined. The ecological safety and harmlessness of sticky-gene composition, its slow degradation by soils microorganisms and providing long-term influence (impact) of preparations introduced on plants protection have been shown. The conditions of gray forest and sod podzol soil are the most favorable for the sticky-gene composition degradation. Sticky-gene composition degradation goes slower in sandy soil conditions.

  12. Cleanup of contaminated soil -- Unreal risk assumptions: Contaminant degradation

    SciTech Connect

    Schiffman, A.

    1995-12-31

    Exposure assessments for development of risk-based soil cleanup standards or criteria assume that contaminant mass in soil is infinite and conservative (constant concentration). This assumption is not real for most organic chemicals. Contaminant mass is lost from soil and ground water when organic chemicals degrade. Factors to correct for chemical mass lost by degradation are derived from first-order kinetics for 85 organic chemicals commonly listed by USEPA and state agencies. Soil cleanup criteria, based on constant concentration, are then corrected for contaminant mass lost. For many chemicals, accounting for mass lost yields large correction factors to risk-based soil concentrations. For degradation in ground water and soil, correction factors range from greater than one to several orders of magnitude. The long exposure durations normally used in exposure assessments (25 to 70 years) result in large correction factors to standards even for carcinogenic chemicals with long half-lives. For the ground water pathway, a typical soil criterion for TCE of 1 mg/kg would be corrected to 11 mg/kg. For noncarcinogens, correcting for mass lost means that risk algorithms used to set soil cleanup requirements are inapplicable for many chemicals, especially for long periods of exposure.

  13. Thermo-Oxidative Degradation Of SiC/Si3N4 Composites

    NASA Technical Reports Server (NTRS)

    Baaklini, George Y.; Batt, Ramakrishna T.; Rokhlin, Stanislav I.

    1995-01-01

    Experimental study conducted on thermo-oxidative degradation of composite-material specimens made of silicon carbide fibers in matrices of reaction-bonded silicon nitride. In SiC/Si3N4 composites of study, interphase is 3-micrometers-thick carbon-rich coat on surface of each SiC fiber. Thermo-oxidative degradation of these composites involves diffusion of oxygen through pores of composites to interphases damaged by oxidation. Nondestructive tests reveal critical exposure times.

  14. 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.

  15. Relationship between chemical composition and in situ rumen degradation characteristics of maize silages in dairy cows.

    PubMed

    Ali, M; van Duinkerken, G; Cone, J W; Klop, A; Blok, M C; Spek, J W; Bruinenberg, M H; Hendriks, W H

    2014-11-01

    Several in situ studies have been conducted on maize silages to determine the effect of individual factors such as maturity stage, chop length and ensiling of maize crop on the rumen degradation but the information on the relationship between chemical composition and in situ rumen degradation characteristics remains scarce. The objectives of this study were to determine and describe relationships between the chemical composition and the rumen degradation characteristics of dry matter (DM), organic matter (OM), CP, starch and aNDFom (NDF assayed with a heat stable amylase and expressed exclusive of residual ash) of maize silages. In all, 75 maize silage samples were selected, with a broad range in chemical composition and quality parameters. The samples were incubated in the rumen for 2, 4, 8, 16, 32, 72 and 336 h, using the nylon bag technique. Large range was found in the rumen degradable fractions of DM, OM, CP, starch and aNDFom because of the broad range in chemical composition and quality parameters. The new database with in situ rumen degradation characteristics of DM, OM, CP, starch and aNDFom of the maize silages was obtained under uniform experimental conditions; same cows, same incubation protocol and same chemical analysis procedures. Regression equations were developed with significant predictors (P<0.05) describing moderate and weak relationships between the chemical composition and the washout fraction, rumen undegradable fraction, potentially rumen degradable fraction, fractional degradation rate and effective rumen degradable fraction of DM, OM, CP, starch and aNDFom.

  16. Relative humidity and temperature dependence of mechanical degradation of natural fiber composites

    NASA Astrophysics Data System (ADS)

    Pan, YiHui; Zhong, Zheng

    2016-06-01

    In this paper, the mechanical degradation of natural fiber composites is studied with the consideration of the relative humidity and the temperature. A nonlinear constitutive model is established, which employs an internal variable to describe the mechanical degradation related to the energy dissipation during moisture absorption. The existing experimental researches demonstrated that the mechanical degradation is an irreversible thermodynamic process induced by the degradation of fibers and the damages of interfaces between fiber and matrix, both of which depend on the variation of the relative humidity or the temperature. The evolution of the mechanical degradation is obtained through the determination of dissipation rates as a function of the relative humidity and the temperature. The theoretically predicted mechanical degradations are compared with experimental results of sisal fiber reinforced composites subject to different relative humidity and temperatures, and a good agreement is found.

  17. Predictable bacterial composition and hydrocarbon degradation in Arctic soils following diesel and nutrient disturbance

    PubMed Central

    Bell, Terrence H; Yergeau, Etienne; Maynard, Christine; Juck, David; Whyte, Lyle G; Greer, Charles W

    2013-01-01

    Increased exploration and exploitation of resources in the Arctic is leading to a higher risk of petroleum contamination. A number of Arctic microorganisms can use petroleum for growth-supporting carbon and energy, but traditional approaches for stimulating these microorganisms (for example, nutrient addition) have varied in effectiveness between sites. Consistent environmental controls on microbial community response to disturbance from petroleum contaminants and nutrient amendments across Arctic soils have not been identified, nor is it known whether specific taxa are universally associated with efficient bioremediation. In this study, we contaminated 18 Arctic soils with diesel and treated subsamples of each with monoammonium phosphate (MAP), which has successfully stimulated degradation in some contaminated Arctic soils. Bacterial community composition of uncontaminated, diesel-contaminated and diesel+MAP soils was assessed through multiplexed 16S (ribosomal RNA) rRNA gene sequencing on an Ion Torrent Personal Genome Machine, while hydrocarbon degradation was measured by gas chromatography analysis. Diversity of 16S rRNA gene sequences was reduced by diesel, and more so by the combination of diesel and MAP. Actinobacteria dominated uncontaminated soils with <10% organic matter, while Proteobacteria dominated higher-organic matter soils, and this pattern was exaggerated following disturbance. Degradation with and without MAP was predictable by initial bacterial diversity and the abundance of specific assemblages of Betaproteobacteria, respectively. High Betaproteobacteria abundance was positively correlated with high diesel degradation in MAP-treated soils, suggesting this may be an important group to stimulate. The predictability with which bacterial communities respond to these disturbances suggests that costly and time-consuming contaminated site assessments may not be necessary in the future. PMID:23389106

  18. Predictable bacterial composition and hydrocarbon degradation in Arctic soils following diesel and nutrient disturbance.

    PubMed

    Bell, Terrence H; Yergeau, Etienne; Maynard, Christine; Juck, David; Whyte, Lyle G; Greer, Charles W

    2013-06-01

    Increased exploration and exploitation of resources in the Arctic is leading to a higher risk of petroleum contamination. A number of Arctic microorganisms can use petroleum for growth-supporting carbon and energy, but traditional approaches for stimulating these microorganisms (for example, nutrient addition) have varied in effectiveness between sites. Consistent environmental controls on microbial community response to disturbance from petroleum contaminants and nutrient amendments across Arctic soils have not been identified, nor is it known whether specific taxa are universally associated with efficient bioremediation. In this study, we contaminated 18 Arctic soils with diesel and treated subsamples of each with monoammonium phosphate (MAP), which has successfully stimulated degradation in some contaminated Arctic soils. Bacterial community composition of uncontaminated, diesel-contaminated and diesel+MAP soils was assessed through multiplexed 16S (ribosomal RNA) rRNA gene sequencing on an Ion Torrent Personal Genome Machine, while hydrocarbon degradation was measured by gas chromatography analysis. Diversity of 16S rRNA gene sequences was reduced by diesel, and more so by the combination of diesel and MAP. Actinobacteria dominated uncontaminated soils with <10% organic matter, while Proteobacteria dominated higher-organic matter soils, and this pattern was exaggerated following disturbance. Degradation with and without MAP was predictable by initial bacterial diversity and the abundance of specific assemblages of Betaproteobacteria, respectively. High Betaproteobacteria abundance was positively correlated with high diesel degradation in MAP-treated soils, suggesting this may be an important group to stimulate. The predictability with which bacterial communities respond to these disturbances suggests that costly and time-consuming contaminated site assessments may not be necessary in the future.

  19. Environmental degradation and health risks in Beijing, China.

    PubMed

    Qi, Jun; Yang, Linsheng; Wang, Wuyi

    2007-01-01

    As China's capital city, Beijing is experiencing unprecedented environmental degradation accompanied by complex interactions between urbanization and global environmental change, which places human health at risk on a large spatial and temporal scale. For sustainable development that supports environmental and human health in Beijing and during the upcoming "green" Olympic games in 2008, experts and political leaders must acknowledge the urgent health risks from environmental changes related to urbanization. A range of urban health hazards and associated health risks in Beijing result from a variety of factors including heat islands, air pollution, water crisis, soil pollution, infectious diseases, and urban consumerism; in addition, some hazardous health conditions are associated with inequality in living and working conditions. The authors suggest 2 main areas for policy action and research direction: (1) the need to get full-scale information related to environmental monitoring data and health data (and then to provide new methodological approaches and techniques to implement interventions) and (2) the need for effective cooperation among different sectors.

  20. Microbial Degradation of Polyhydroxyalkanoates with Different Chemical Compositions and Their Biodegradability.

    PubMed

    Volova, Tatiana G; Prudnikova, Svetlana V; Vinogradova, Olga N; Syrvacheva, Darya A; Shishatskaya, Ekaterina I

    2017-02-01

    The study addresses degradation of polyhydroxyalkanoates (PHA) with different chemical compositions-the polymer of 3-hydroxybutyric acid [P(3HB)] and copolymers of P(3HB) with 3-hydroxyvalerate [P(3HB/3HV)], 4-hydroxybutyrate [P(3HB/4HB)], and 3-hydroxyhexanoate [P(3HB/3HHx)] (10-12 mol%)-in the agro-transformed field soil of the temperate zone. Based on their degradation rates at 21 and 28 °C, polymers can be ranked as follows: P(3HB/4HB) > P(3HB/3HHx) > P(3HB/3HV) > P(3HB). The microbial community on the surface of the polymers differs from the microbial community of the soil with PHA specimens in the composition and percentages of species. Thirty-five isolates of bacteria of 16 genera were identified as PHA degraders by the clear zone technique, and each of the PHA had both specific and common degraders. P(3HB) was degraded by bacteria of the genera Mitsuaria, Chitinophaga, and Acidovorax, which were not among the degraders of the three other PHA types. Roseateles depolymerans, Streptomyces gardneri, and Cupriavidus sp. were specific degraders of P(3HB/4HB). Roseomonas massiliae and Delftia acidovorans degraded P(3HB/3HV), and Pseudoxanthomonas sp., Pseudomonas fluorescens, Ensifer adhaerens, and Bacillus pumilus were specific P(3HB/3HHx) degraders. All four PHA types were degraded by Streptomyces.

  1. Photocatalytic activity of titania nanotube (tint)-carbon nanotube (CNT) composite for degradation of phenol

    NASA Astrophysics Data System (ADS)

    Heltina, Desi; Wulan, Praswasti P. D. K.; Slamet

    2017-05-01

    In this study, a composite of titania nanotube (TiNT)-carbon nanotube (CNT) was synthesized using a method of mixing. The titania nanotube -carbon nanotube composite is applied to increase the photocatalytic activity for phenol degradation. The titania nanotube-carbon nanotube composites were characterized by x-ray diffraction (XRD), scanning electron microscope (SEM), UV-vis diffuse reflectance spectroscopy and spectrophotometer. The presence of carbon nanotube on composite have a beneficial effect on photocatalytic performance titania nanotube (TiNT) a marked increase in the photocatalytic degradation of phenol. The results show that the highest activity nanocomposite sample is observed for CNT load 2 wt.%. For this purpose, a morphology of the nanocomposites and crystalline phases investigated. The photocatalytic activity composite of TiNT - CNT for phenol degradation was afterward evaluated and discussed.

  2. Dietary fat composition and dementia risk.

    PubMed

    Morris, Martha Clare; Tangney, Christine C

    2014-09-01

    This is a qualitative review of the evidence linking dietary fat composition to the risk of developing dementia. The review considers laboratory and animal studies that identify underlying mechanisms as well as prospective epidemiologic studies linking biochemical or dietary fatty acids to cognitive decline or incident dementia. Several lines of evidence provide support for the hypothesis that high saturated or trans fatty acids increase the risk of dementia and high polyunsaturated or monounsaturated fatty acids decrease risk. Dietary fat composition is an important factor in blood-brain barrier function and the blood cholesterol profile. Cholesterol and blood-brain barrier function are involved in the neuropathology of Alzheimer's disease, and the primary genetic risk factor for Alzheimer's disease, apolipoprotein E-ε4, is involved in cholesterol transport. The epidemiologic literature is seemingly inconsistent on this topic, but many studies are difficult to interpret because of analytical techniques that ignored negative confounding by other fatty acids, which likely resulted in null findings. The studies that appropriately adjust for confounding by other fats support the dietary fat composition hypothesis.

  3. Degradable/non-degradable polymer composites for in-situ tissue engineering small diameter vascular prosthesis application.

    PubMed

    Wang, Fujun; Mohammed, Abedalwafa; Li, Chaojing; Ge, Peng; Wang, Lu; King, Martin W

    2014-01-01

    Various tissue-engineered vascular grafts have been studied in order to overcome the clinical disadvantages associated with conventional prostheses. However, previous tissue-engineered vascular grafts have possessed insufficient mechanical properties and thus have generally required either preoperative cellular manipulation or the use of bioreactors to improve their performance. In this study, we focused on the concept of in situ cellularization and developed a tissue-engineered vascular graft with degradable/non-degradable polymer composites for arterial reconstruction that would facilitate the renewal of autologous tissue without any pretreatment. Additionally, these composites are designed to improve the mechanical performance of a small-diameter vascular prosthesis scaffold that is made from a flexible membrane of poly(e-caprolactone) (PCL). The PCL scaffold was reinforced by embedding a tubular fabric that was knitted from polyethylene terephthalate (PET) yarns within the freeze-dried composite structure. Adding this knitted fabric component significantly improved the mechanical properties of the composite scaffold, such as its tensile strength and initial modulus, radial compliance, compression recovery, and suture retention force. Finally, this reinforced composite structure is a promising candidate for use as a tissue-engineered scaffold for a future small diameter vascular prosthesis.

  4. Preparation of bismuth titanate/calcium alginate composite bead and its photocatalytic degradation of dye pollutants

    NASA Astrophysics Data System (ADS)

    Gan, Huihui; Dong, Nanyang; Lu, Linxiao; Fu, Yan; Zhang, Huining; Qian, Yongxin; Zhang, Kefeng; Jin, Huixia

    2017-08-01

    In this study, the bismuth titanate/calcium alginate composite bead was synthesized by immobilizing bismuth titanate Bi4Ti3O12 particles into 1.5% sodium alginate (SA) matrix. The Bi4Ti3O12 particles were characterized by X-ray diffraction (XRD). The photocatalytic activity for the degradation of dye Rhodamine B in solution by as-prepared bismuth titanate/calcium alginate composite bead was investigated. The as-prepared composite beads CA/BTO-700 exhibited best photocatalytic efficiency for the degradation of RhB compared with CA/BTO-800 and CA/BTO-900 under simulated solar light. After 4 cycles in photocatalytic degradation of RhB, the degradation rate of the CA/BTO-700 nearly remained unchanged.

  5. Gamma irradiation assisted fungal degradation of the polypropylene/biomass composites

    NASA Astrophysics Data System (ADS)

    Butnaru, Elena; Darie-Niţă, Raluca Nicoleta; Zaharescu, Traian; Balaeş, Tiberius; Tănase, Cătălin; Hitruc, Gabriela; Doroftei, Florica; Vasile, Cornelia

    2016-08-01

    White-rot fungus Bjerkandera adusta has been tested for its ability to degrade some biocomposites materials based on polypropylene and biomass (Eucalyptus globulus, pine cones, and Brassica rapa). γ-irradiation was applied to initiate the degradation of relatively inert polypropylene matrix. The degradation process has been studied by scanning electron microscopy, atomic force microscopy, infrared spectroscopy, contact angle measurements, rheological and chemiluminescence tests. These analyses showed that the polypropylene/biomass composites properties are worsen under the action of the selected microorganism. The formation of cracks and scrap particles over the entire matrix surface and the decrease of the complex viscosity values, as well as the dynamic moduli of gamma irradiated PP/biomass composite and exposed to Bjerkandera adusta fungus, indicate fungal efficiency in composite degradation.

  6. Development of Degradable Polymer Composites from Starch and Poly(alkyl cyanoacrylate)

    USDA-ARS?s Scientific Manuscript database

    This report describes the development of degradable polymer composites that can be made at room temperature without special equipment. The developed composites are made from poly(alkyl cyanoacrylate) and starch. Alkyl cyanoacrylate monomers are mixed with starch and the polymerization reaction of ...

  7. Development of degradable polymer composites from starch and poly(alkyl cyanoacrylate)

    USDA-ARS?s Scientific Manuscript database

    This report describes the development of degradable polymer composites that can be made at room temperature without special equipments. The developed composites were made from poly(alkyl cyanoacrylate) and starch. Alkyl cyanoacrylate monomers were mixed with starch and the polymerization reaction ...

  8. Application of nano-TiO2/LDPE composite film on photocatalytic oxidation degradation of dichloromethane.

    PubMed

    Suwannahong, Kowit; Liengcharernsit, Winai; Sanongraj, Wipada; Kruenate, Jittiporn

    2012-09-01

    This study focused on the photocatalytic destruction of dichloromethane (DCM) in indoor air using the nano-TiO2/LDPE composite film as an economical photocatalyst. The nano-TiO2 was dispersed in a polyethylene matrix to form composite film. The photocatalytic activity of the nano-TiO2/LDPE composite films was evaluated through the degradation of dichloromethane(DCM) under UV-C irradiance at specific wavelength of 254 nm. The percentage of nano-TiO2 contents varied from 0, 5, and 10% (wt cat./wt LDPE composite film). The results derived from the kinetic model revealed that the photocatalytic rates of 5 and 10 wt.% nano-TiO2/ LDPE composite films follow the first order reaction while the rate of the film without TiO2 followed the zero order reaction. At low concentration of DCM, the rate of photocatalytic degradation of the DCM was slower than that at high DCM concentration. The 10 wt.% of TiO2 content of the nano-TiO2/LDPE composite film yielded the highest degradation efficiency of 78%, followed by the removal efficiency of 55% for the 5 wt.% of TiO2 content of the nano-TiO2/LDPE composite film. In contrast with the composite film containing nano-TiO2, the LDPE film without adding nano-TiO2 expressed the degradation efficiency of 28%.

  9. Degradation and drug release of phosphate glass/polycaprolactone biological composites for hard-tissue regeneration.

    PubMed

    Kim, Hae-Won; Lee, Eun-Jung; Jun, In-Kook; Kim, Hyoun-Ee; Knowles, Jonathan C

    2005-10-01

    Phosphate-based glass (P-glass) and poly(epsilon-caprolactone) (PCL) composites were fabricated in a sheet form by solvent extraction and thermal pressing methods, and the antibiotic drug Vancomycin was loaded within the composites for use as a hard-tissue regenerative. The degradation and drug-release rate of the composites in vitro were tailored by modifying the glass composition: 0.45 P(2)O(5)-x CaO-(0.55-x)Na(2)O, where x=0.2, 0.3, 0.4, and 0.5. Compared to pure PCL, all the P-glass/PCL composites degraded to a higher degree, and the composite with lower-CaO glass showed a higher material loss. This was attributed mainly to the dissolution of the glass component. The glass dissolution also increased the degradation of PCL component in the composites. The Vancomycin release from the composites was strongly dependent on the glass composition. Drug release in pure PCL was initially abrupt and flattened out over a prolonged period. However, glass/PCL composites (particularly in the glass containing higher-CaO) exhibited a reduced initial burst and a higher release rate later. Preliminary cell tests on the extracts from the glass/PCL composites showed favorable cell proliferation, but the level was dependent on the ionic concentration of the extracts. The cell proliferation on the diluted extracts from the composite with higher-CaO glass was significantly higher than that on the blank culture dish. These observations confirmed that the P-glass/PCL composites are potentially applicable for use as hard-tissue regeneration and wound-healing materials because of their controlled degradation and drug-release profile as well as enhanced cell viability.

  10. Composite Flood Risk for New Jersery

    EPA Pesticide Factsheets

    The Composite Flood Risk layer combines flood hazard datasets from Federal Emergency Management Agency (FEMA) flood zones, NOAA's Shallow Coastal Flooding, and the National Hurricane Center SLOSH model for Storm Surge inundation for category 1, 2, and 3 hurricanes. Geographic areas are represented by a grid of 10 by 10 meter cells and each cell has a ranking based on variation in exposure to flooding hazards: Moderate, High and Extreme exposure. Geographic areas in each input layers are ranked based on their probability of flood risk exposure. The logic was such that areas exposed to flooding on a more frequent basis were given a higher ranking. Thus the ranking incorporates the probability of the area being flooded. For example, even though a Category 3 storm surge has higher flooding elevations, the likelihood of the occurrence is lower than a Category 1 storm surge and therefore the Category 3 flood area is given a lower exposure ranking. Extreme exposure areas are those areas that are exposed to relatively frequent flooding. The ranked input layers are then converted to a raster for the creation of the composite risk layer by using cell statistics in spatial analysis. The highest exposure ranking for a given cell in any of the three input layers is assigned to the corresponding cell in the composite layer. For example, if an area (a cell) is rank as medium in the FEMA layer, moderate in the SLOSH layer, but extreme in the SCF layer, the cell will be consider

  11. Composite Flood Risk for Pueto Rico

    EPA Pesticide Factsheets

    The Composite Flood Risk layer combines flood hazard datasets from Federal Emergency Management Agency (FEMA) flood zones, NOAA's Shallow Coastal Flooding, and the National Hurricane Center SLOSH model for Storm Surge inundation for category 1, 2, and 3 hurricanes.Geographic areas are represented by a grid of 10 by 10 meter cells and each cell has a ranking based on variation in exposure to flooding hazards: Moderate, High and Extreme exposure. Geographic areas in each input layers are ranked based on their probability of flood risk exposure. The logic was such that areas exposed to flooding on a more frequent basis were given a higher ranking. Thus the ranking incorporates the probability of the area being flooded. For example, even though a Category 3 storm surge has higher flooding elevations, the likelihood of the occurrence is lower than a Category 1 storm surge and therefore the Category 3 flood area is given a lower exposure ranking. Extreme exposure areas are those areas that are exposed to relatively frequent flooding.The ranked input layers are then converted to a raster for the creation of the composite risk layer by using cell statistics in spatial analysis. The highest exposure ranking for a given cell in any of the three input layers is assigned to the corresponding cell in the composite layer.For example, if an area (a cell) is rank as medium in the FEMA layer, moderate in the SLOSH layer, but extreme in the SCF layer, the cell will be considere

  12. Composite Flood Risk for New York

    EPA Pesticide Factsheets

    The Composite Flood Risk layer combines flood hazard datasets from Federal Emergency Management Agency (FEMA) flood zones, NOAA's Shallow Coastal Flooding, and the National Hurricane Center SLOSH model for Storm Surge inundation for category 1, 2, and 3 hurricanes.Geographic areas are represented by a grid of 10 by 10 meter cells and each cell has a ranking based on variation in exposure to flooding hazards: Moderate, High and Extreme exposure. Geographic areas in each input layers are ranked based on their probability of flood risk exposure. The logic was such that areas exposed to flooding on a more frequent basis were given a higher ranking. Thus the ranking incorporates the probability of the area being flooded. For example, even though a Category 3 storm surge has higher flooding elevations, the likelihood of the occurrence is lower than a Category 1 storm surge and therefore the Category 3 flood area is given a lower exposure ranking. Extreme exposure areas are those areas that are exposed to relatively frequent flooding.The ranked input layers are then converted to a raster for the creation of the composite risk layer by using cell statistics in spatial analysis. The highest exposure ranking for a given cell in any of the three input layers is assigned to the corresponding cell in the composite layer.For example, if an area (a cell) is rank as medium in the FEMA layer, moderate in the SLOSH layer, but extreme in the SCF layer, the cell will be considere

  13. Composite Flood Risk for Virgin Island

    EPA Pesticide Factsheets

    The Composite Flood Risk layer combines flood hazard datasets from Federal Emergency Management Agency (FEMA) flood zones, NOAA's Shallow Coastal Flooding, and the National Hurricane Center SLOSH model for Storm Surge inundation for category 1, 2, and 3 hurricanes.Geographic areas are represented by a grid of 10 by 10 meter cells and each cell has a ranking based on variation in exposure to flooding hazards: Moderate, High and Extreme exposure. Geographic areas in each input layers are ranked based on their probability of flood risk exposure. The logic was such that areas exposed to flooding on a more frequent basis were given a higher ranking. Thus the ranking incorporates the probability of the area being flooded. For example, even though a Category 3 storm surge has higher flooding elevations, the likelihood of the occurrence is lower than a Category 1 storm surge and therefore the Category 3 flood area is given a lower exposure ranking. Extreme exposure areas are those areas that are exposed to relatively frequent flooding.The ranked input layers are then converted to a raster for the creation of the composite risk layer by using cell statistics in spatial analysis. The highest exposure ranking for a given cell in any of the three input layers is assigned to the corresponding cell in the composite layer.For example, if an area (a cell) is rank as medium in the FEMA layer, moderate in the SLOSH layer, but extreme in the SCF layer, the cell will be considere

  14. Photoelectrocatalytic degradation of Rhodamine B using graphene and titanium dioxide composite catalyst

    NASA Astrophysics Data System (ADS)

    Zhao, Yu; Du, Wen-Han; Chen, Lei; Xiao, Jin; Xiong, Chao; Yuan, Hong-Chun

    2017-07-01

    Graphene and titanium dioxide (TiO2) composite catalyst has been synthesized by hydrothermal synthesis method, and used for the degradation of Rhodamine B (Rh.B) in water. The photoelectrocatalytic activity of this composite was evaluated by decomposing of Rh.B in water under visible or UV light irradiation. The degradation results indicated that the photoelectrocatalytic performance of this composite catalyst was greatly enhanced due to the improved adsorption performance and separation efficiency of photo-generated carriers possibly. The composite with graphene content of 10 wt.% exhibited superior activity under UV light irradiation. After 30 min of reaction, the photoelectrocatalytic degradation ratio of Rh.B was about 96% when pH = 6-7. The results of this work provide a good method for the treatment of organic wastewater with high performance.

  15. Cytocompatibility, degradation, mechanical property retention and ion release profiles for phosphate glass fibre reinforced composite rods.

    PubMed

    Felfel, R M; Ahmed, I; Parsons, A J; Palmer, G; Sottile, V; Rudd, C D

    2013-05-01

    Fibre reinforced composites have recently received much attention as potential bone fracture fixation applications. Bioresorbable composites based on poly lactic acid (PLA) and phosphate based glass fibre were investigated according to ion release, degradation, biocompatibility and mechanical retention profiles. The phosphate based glass fibres used in this study had the composition of 40P2O5-24MgO-16CaO-16Na2O-4Fe2O3 in mol% (P40). The degradation and ion release profiles for the composites showed similar trends with the amount of sodium and orthophosphate ions released being greater than the other cations and anions investigated. This was attributed to low Dietzal's field strength for the Na(+) in comparison with Mg(2+) and Ca(2+) and breakdown of longer chain polyphosphates into orthophosphate ions. P40 composites exhibited good biocompatibility to human mesenchymal stem cells (MSCs), which was suggested to be due to the low degradation rate of P40 fibres. After 63 days immersion in PBS at 37 °C, the P40 composite rods lost ~1.1% of mass. The wet flexural, shear and compressive strengths for P40 UD rods were ~70%, ~80% and ~50% of their initial dry values after 3 days of degradation, whereas the flexural modulus, shear and compressive strengths were ~70%, ~80%, and ~65% respectively. Subsequently, the mechanical properties remained stable for the duration of the study at 63 days. The initial decrease in mechanical properties was attributed to a combination of the plasticisation effect of water and degradation of the fibre-matrix interface, with the subsequent linear behaviour being attributed to the chemical durability of P40 fibres. P40 composite rods showed low degradation and ion release rates, good biocompatibility and maintained mechanical properties similar to cortical bone for the duration of the study. Therefore, P40 composite rods have huge potential as resorbable intramedullary nails or rods. Copyright © 2013 Elsevier B.V. All rights reserved.

  16. Long-term thermal degradation and alloying constituent effects on five boron/aluminum composites

    NASA Technical Reports Server (NTRS)

    Olsen, G. C.

    1982-01-01

    Thermal exposure effects on the properties of five boron/aluminum composite systems were experimentally investigated. The composite systems were 49 volume percent boron fibers (203 micron diameter) in aluminum-alloy matrices 1100 Al, 2024 Al, 3003 Al, 5052 Al, and 6061 Al. Specimens were thermally exposed up to 10,000 hours at 500 K and 590 K, up to 500 hours at 730 K, and up to 10,000 hours at 500 K and 590 K, up to 500 hours at 730 K, and up to 2000 thermal cycles between 200 K and 590 K. Composite longitudinal and transverse tensile strengths, longitudinal compression strength, and in-plane shear strength were determined. None of the systems was severely degraded by exposure at 590 K. The best performing system was B-2024 Al. Effects of matrix alloys on degradation mechanisms were experimentally investigated. Composite specimens and individual fibers were metallurgically analyzed with a scanning electron microscope and an electron microprobe to determine failure characteristics, chemical element distribution, and reaction layer morphology. Alloying constituents were found to be affect the composite degradation mechanisms as follows: alloys containing iron, but without manganese as a stabilizer, caused increased low-temperature degradation; alloys containing magnesium, iron, or manganese caused increased degradation; and alloys containing copper caused increased fiber strength.

  17. Spectroscopic study on the in vitro degradation of a biodegradable composite periodontal membrane

    NASA Astrophysics Data System (ADS)

    Taddei, P.; Simoni, R.; Fini, G.

    2001-05-01

    The hydrolithic in vitro degradation of a commercial biodegradable hydroxyapatite (HA)-polymer (poly(ɛ-caprolactone)-poly(oxyethylene)-poly(ɛ-caprolactone) block copolymer, PCL-POE-PCL) composite membrane was investigated by Raman and IR spectroscopies in three aqueous media at 37°C; 0.01 M NaOH solution, saline phosphate buffer (SPB) at pH 7.4 and simulated body fluid (SBF) buffered at pH 7.5. The vibrational results showed that the polymeric component undergoes preferential degradation of POE blocks while HA is removed by the degradation media faster than the polymer. Vibrational spectroscopy appeared to be a valid non-destructive method for investigating the degradation mechanism of the composite membrane.

  18. 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

  19. Production of Degradable Biopolymer Composites by Particle-bonding

    USDA-ARS?s Scientific Manuscript database

    Conventionally, polymer composites had been manufactured by mixing the component materials in the extruder at high temperature. Agricultural biopolymers are usually mixtures of many types of compounds; when used as raw materials, however, high-temperature process causes unwanted consequences such a...

  20. Effect of glass composition on the degradation properties and ion release characteristics of phosphate glass--polycaprolactone composites.

    PubMed

    Prabhakar, Roopa L; Brocchini, Steve; Knowles, Jonathan C

    2005-05-01

    A series of polycaprolactone and ternary-based (Na(2)O)(0.55-x)(CaO)(x)(P(2)O(5))(0.45) glass composites were created, each containing 20% volume percentage of glass with various calcium compositions. A short-term degradation study was carried out to investigate the physical and ion release behaviour of these composites, utilising analytical techniques such as dynamical mechanical analysis, and ion chromatography. All the composites experienced significant loss of weight and stiffness throughout the study, with the 24 mol% calcium composites losing the greatest amount of weight and stiffness. The pH profile of the aqueous solutions in which the composites were placed were initially acidic, but began to neutralise mid-way through the study, with the 36 mol% solution achieving the most acidic conditions. The ion release behaviour mirrored the mass loss behaviour of the glass component of the composites. The cations (sodium and calcium ions) release was comparable with the initial stages of composite mass degradation, both of which exhibited almost immediate release when placed into solution. The 24 mol% composites underwent rapid rates of cation release, while the 36 mol% experienced the slowest rates of release. By contrast, anion (phosphates and polyphosphates) release showed a dissimilar trend, with rapid release of the P(2)O(7) and P(3)O(10) occurring during the first few hours in solution, whilst the P(3)O(9) structure released steadily during the first 48 h in solution. Finally, PO(4) release was at a constant rate over the duration of the study, releasing up to 300 ppm from the 32 and 36 mol% samples by the end of 200 h. To summarise, these results show that by combining phosphate glasses with biodegradable polymer, it is possible to create composites whose rate of degradation can be controlled to meet the needs of their end application.

  1. An Insidious Mode of Oxidative Degradation in a SiC-SiC Composite

    NASA Technical Reports Server (NTRS)

    Ogbuji, Linus U. J. T.

    1997-01-01

    The oxidative durability of a SiC-SiC composite with Hi-Nicalon fiber and BN interphase was investigated at 800 C (where pesting is known to occur in SiC-SiC composites) for exposure durations of up to 500 hours and in a variety of oxidant mixes and flow rates, ranging from quasi-stagnant room air, through slow flowing O2 containing 30-90% H2O, to the high-velocity flame of a burner rig. Degradation of the composite was determined from residual strength and fracture strain in post-exposure mechanical tests and correlated with microstructural evidence of damage to fiber and interphase. The severest degradation of composite behavior was found to occur in the bumer rig, and is shown to be connected with the high oxidant velocity and substantial moisture content, as well as a thin sublayer of carbon indicated to form between fiber and interphase during composite processing.

  2. 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 is studied systematically in an attempt to determine the mechanism of the resulting strength degradation. The results indicate that thermally cycling of B-Al represents a more severe condition than equivalent time at temperature. Degradation of composite tensile strength from about 1.3 GN/sq m to as low as 0.34 GN/sq m was observed after 3000 cycles to 420 C for 203-micron 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. On the basis of various thermal-cycling studies and electron diffraction analysis, a mechanism is favored in which B reacts with Al, freshly exposed by cold working during cycling, to form AlB2. The nonuniform interface reaction leads to a highly flawed and weakened B fiber.

  3. Degradation of corn stalk by the composite microbial system of MC1.

    PubMed

    Guo, Peng; Wang, Xiaofen; Zhu, Wanbin; Yang, Hongyan; Cheng, Xu; Cui, Zongjun

    2008-01-01

    The composite microbial system of MC1 was used to degrade corn stalk in order to determine properties of the degraded products as well as bacterial composition of MC1. Results indicated that the pH of the fermentation broth was typical of lignocellulose degradation by MC1, decreasing in the early phase and increasing in later stages of the degradation. The microbial biomass peaked on the day 3 after degradation. The MC1 efficiently degraded the corn stalk by nearly 70% during which its cellulose content decreased by 71.2%, hemicellulose by 76.5% and lignin by 24.6%. The content of water-soluble carbohydrates (WSC) in the fermentation broth increased progressively during the first three days, and decreased thereafter, suggesting an accumulation of WSC in the early phase of the degradation process. Total levels of various volatile products peaked in the third day after degradation, and 7 types of volatile products were detected in the fermentation broth. These were ethanol, acetic acid, 1,2-ethanediol, propanoic acid, butanoic acid, 3-methyl-butanoic acid and glycerine. Six major compounds were quantitatively analysed and the contents of each compound were ethanol (0.584 g/L), acetic acid (0.735 g/L), 1,2-ethanediol (0.772 g/L), propanoic acid (0.026 g/L), butanoic acid (0.018 g/L) and glycerine (4.203 g/L). Characterization of bacterial cells collected from the culture solution, based on 16S rDNA PCR-DGGE analysis of DNAs, showed that the composition of bacterial community in MC1 coincided basically with observations from previous studies. This indicated that the structure of MC1 is very stable during degradation of different lignocellulose materials.

  4. Characterization of Degradation Progressive in Composite Laminates Subjected to Thermal Fatigue and Moisture Diffusion by Lamb Waves

    PubMed Central

    Li, Weibin; Xu, Chunguang; Cho, Younho

    2016-01-01

    Laminate composites which are widely used in the aeronautical industry, are usually subjected to frequency variation of environmental temperature and excessive humidity in the in-service environment. The thermal fatigue and moisture absorption in composites may induce material degradation. There is a demand to investigate the coupling damages mechanism and characterize the degradation evolution of composite laminates for the particular application. In this paper, the degradation evolution in unidirectional carbon/epoxy composite laminates subjected to thermal fatigue and moisture absorption is characterized by Lamb waves. The decrease rate of Lamb wave velocity is used to track the degradation evolution in the specimens. The results show that there are two stages for the progressive degradation of composites under the coupling effect of thermal cyclic loading and moisture diffusion. The present work provides an alternative to monitoring the degradation evolution of in-service aircraft composite Laminates. PMID:26907283

  5. Characterization of Degradation Progressive in Composite Laminates Subjected to Thermal Fatigue and Moisture Diffusion by Lamb Waves.

    PubMed

    Li, Weibin; Xu, Chunguang; Cho, Younho

    2016-02-19

    Laminate composites which are widely used in the aeronautical industry, are usually subjected to frequency variation of environmental temperature and excessive humidity in the in-service environment. The thermal fatigue and moisture absorption in composites may induce material degradation. There is a demand to investigate the coupling damages mechanism and characterize the degradation evolution of composite laminates for the particular application. In this paper, the degradation evolution in unidirectional carbon/epoxy composite laminates subjected to thermal fatigue and moisture absorption is characterized by Lamb waves. The decrease rate of Lamb wave velocity is used to track the degradation evolution in the specimens. The results show that there are two stages for the progressive degradation of composites under the coupling effect of thermal cyclic loading and moisture diffusion. The present work provides an alternative to monitoring the degradation evolution of in-service aircraft composite Laminates.

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

    NASA Technical Reports Server (NTRS)

    McManus, Hugh L.; Chamis, Christos C.

    1996-01-01

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

  7. In vitro degradation of porous PLLA/pearl powder composite scaffolds.

    PubMed

    Liu, Y S; Huang, Q L; Kienzle, A; Müller, W E G; Feng, Q L

    2014-05-01

    The in vitro degradation behavior of poly-L-lactide (PLLA), PLLA/aragonite pearl powder and PLLA/vaterite pearl powder scaffolds was investigated. The scaffolds were soaked in phosphate buffer solution (PBS) up to 200 days. Scanning electron microscopy (SEM), gel permeation chromatography (GPC), and differential scanning calorimetry (DSC) were used to observe any degradation of the scaffolds. Degradation behaviors such as changes in pH, porosity, bulk density, water absorption, weight loss and mechanical properties were discussed. The results show that a gradual increase of the pH in composite scaffolds can decrease the rate of hydrolysis of PLLA. PLLA/vaterite and PLLA/aragonite scaffolds have a similar degradation behavior but a slower rate of degradation than PLLA.

  8. Potential risks of pesticide degradates to aquatic life

    USGS Publications Warehouse

    Boxall, Alistair; Sinclair, C.; Koplin, Dana W.

    2006-01-01

    Recent advances in analytical methodology and greater access to analytical standards have led to the detection of degradates from a wide variety of pesticides and other compounds in surface water, ground water, precipitation, air, and sediment (Boxall and others, 2004). Many of these degradates are more persistent in the environment than their parent compounds, and many are more mobile, as well.

  9. Environmental degradation of microbial polyhydroxyalkanoates and oil palm-based composites.

    PubMed

    Salim, Y S; Sharon, A; Vigneswari, S; Mohamad Ibrahim, M N; Amirul, A A

    2012-05-01

    This paper investigates the degradation of polyhydroxyalkanoates and its biofiber composites in both soil and lake environment. Time-dependent changes in the weight loss of films were monitored. The rate of degradation of poly(3-hydroxybutyrate) [P(3HB)], poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-23 mol% 4HB)] and poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-4-hydroxybutyrate) [P(3HB-co-9 mol% 3HV-co-19 mol% 4HB)] were investigated. The rate of degradation in the lake is higher compared to that in the soil. The highest rate of degradation in lake environment (15.6% w/w week(-1)) was observed with P(3HB-co-3HV-co-4HB) terpolymer. Additionally, the rate of degradation of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-38 mol% 3HV)] was compared to PHBV biofiber composites containing compatibilizers and empty fruit bunch (EFB). Here, composites with 30% EFB displayed the highest rate of degradation both in the lake (25.6% w/w week(-1)) and soil (15.6% w/w week(-1)) environment.

  10. Degradation in the Dentin-Composite Interface Subjected to Multi-Species Biofilm Challenges

    PubMed Central

    Li, Yuping; Carrera, Carola; Chen, Ruoqiong; Li, Jianying; Patricia, Lenton; Rudney, Joel. D.; Jones, Robert S.; Aparicio, Conrado; Fok, Alex

    2013-01-01

    Oral biofilms can degrade the components in dental resin-based composite restorations, thus compromising marginal integrity and leading to secondary caries. In this study, we investigated the mechanical integrity of the dentin-composite interface challenged with multi-species oral biofilms. While most studies used single-species biofilms, we used a more realistic, diverse biofilm model produced directly from plaques collected from donors with a history of early childhood caries. Dentin–composite disks were made using bovine incisor roots filled with Z100™ or Filtek™ LS (3M ESPE). The disks were incubated for 72hr in paired CDC biofilm reactors, using a previously published protocol. One reactor was pulsed with sucrose, and the other was not. A sterile saliva-only control group was run with sucrose pulsing. The disks were fractured under diametral compression to evaluate their interfacial bond strength. Surface deformation of the disks was mapped using digital image correlation (DIC) to ascertain fracture origin. Fracture surfaces were examined using SEM/EDS to assess demineralization and interfacial degradation. Dentin demineralization was greater under sucrose-pulsed biofilms, as the pH dropped below 5.5 during pulsing, with LS and Z100 specimens suffering similar degrees of surface mineral loss. Biofilm growth with sucrose pulsing also caused preferential degradation of the composite-dentin interface, depending on the composite/adhesive system used. Specifically, Z100 specimens showed greater bond strength reduction and more frequent cohesive failure in the adhesive layer. This was attributed to the inferior dentin coverage by Z100 adhesive which possibly led to a higher level of chemical and enzymatic degradation. The results suggested that factors other than dentin demineralization were also responsible for interfacial degradation. We have thus developed a clinically relevant in vitro biofilm model which would allow us to effectively assess the

  11. Degradation in the dentin-composite interface subjected to multi-species biofilm challenges.

    PubMed

    Li, Y; Carrera, C; Chen, R; Li, J; Lenton, P; Rudney, J D; Jones, R S; Aparicio, C; Fok, A

    2014-01-01

    Oral biofilms can degrade the components in dental resin-based composite restorations, thus compromising marginal integrity and leading to secondary caries. This study investigates the mechanical integrity of the dentin-composite interface challenged with multi-species oral biofilms. While most studies used single-species biofilms, the present study used a more realistic, diverse biofilm model produced directly from plaques collected from donors with a history of early childhood caries. Dentin-composite disks were made using bovine incisor roots filled with Z100(TM) or Filtek(TM) LS (3M ESPE). The disks were incubated for 72 h in paired CDC biofilm reactors, using a previously published protocol. One reactor was pulsed with sucrose, and the other was not. A sterile saliva-only control group was run with sucrose pulsing. The disks were fractured under diametral compression to evaluate their interfacial bond strength. The surface deformation of the disks was mapped using digital image correlation to ascertain the fracture origin. Fracture surfaces were examined using scanning electron microscopy/energy-dispersive X-ray spectroscopy to assess demineralization and interfacial degradation. Dentin demineralization was greater under sucrose-pulsed biofilms, as the pH dropped <5.5 during pulsing, with LS and Z100 specimens suffering similar degrees of surface mineral loss. Biofilm growth with sucrose pulsing also caused preferential degradation of the composite-dentin interface, depending on the composite/adhesive system used. Specifically, Z100 specimens showed greater bond strength reduction and more frequent cohesive failure in the adhesive layer. This was attributed to the inferior dentin coverage by Z100 adhesive, which possibly led to a higher level of chemical and enzymatic degradation. The results suggested that factors other than dentin demineralization were also responsible for interfacial degradation. A clinically relevant in vitro biofilm model was therefore

  12. Modeling rates of DOC degradation using DOM composition and hydroclimatic variables

    NASA Astrophysics Data System (ADS)

    Moody, C. S.; Worrall, F.

    2017-05-01

    The fluvial fluxes of dissolved organic carbon (DOC) from peatlands form an important part of that ecosystem's carbon cycle, contributing approximately 35% of the overall peatland carbon budget. The in-stream processes acting on the DOC, such as photodegradation and biodegradation, can lead to DOC loss and thus contribute CO2 to the atmosphere. The aim of this study was to understand what controls the rates of DOC degradation. Water samples from a headwater, peat-covered catchment, were collected over a 23 month period and analyzed for the DOC degradation rate and dissolved organic matter (DOM) composition in the context of hydroclimatic monitoring. Measures of DOM composition included 13C solid-state nuclear magnetic resonance spectroscopy, bomb calorimetry, and elemental analysis. Regression analysis showed that there was a significant role for the composition of the DOM in controlling degradation with degradation rates significantly increasing with the proportion of aldehyde and carboxylic acid functional groups but decreasing with the proportion of N-alkyl functional groups. The highest rates of DOC degradation occurred when aldehyde functionality was at its greatest and this occurred on the recession limb of storm hydrographs. Including this knowledge into models of fluvial carbon fate for an 818 km2 catchment gave an annual average DOC removal rate of 67% and 50% for total organic carbon, slightly lower than previously predicted. The compositional controls suggest that DOM is primarily being used as a ready energy source to the aquatic ecosystem rather than as a nutrient source.

  13. Scanning electron microscopy and roughness study of dental composite degradation.

    PubMed

    Soares, Luís Eduardo Silva; Cortez, Louise Ribeiro; Zarur, Raquel de Oliveira; Martin, Airton Abrahão

    2012-04-01

    Our aim was to test the hypothesis that the use of mouthwashes, consumption of soft drinks, as well as the type of light curing unit (LCU), would change the surface roughness (Ra) and morphology of a nanofilled composite resin (Z350® 3M ESPE). Samples (80) were divided into eight groups: Halogen LCU, group 1, saliva (control); group 2, Pepsi Twist®; group 3, Listerine®; group 4, Colgate Plax®; LED LCU, group 5, saliva; group 6, Pepsi Twist®; group 7, Listerine®; group 8, Colgate Plax®. Ra values were measured at baseline, and after 7 and 14 days. One specimen of each group was prepared for scanning electron microscopy analysis after 14 days. The data were subjected to multifactor analysis of variance at a 95% confidence followed by Tukey's honestly significant difference post-hoc test. All the treatments resulted in morphological changes in composite resin surface, and the most significant change was in Pepsi Twist® groups. The samples of G6 had the greatest increase in Ra. The immersion of nanofilled resin in mouthwashes with alcohol and soft drink increases the surface roughness. Polymerization by halogen LCU (reduced light intensity) associated with alcohol contained mouthwash resulted in significant roughness on the composite.

  14. Water absorption and tensile strength degradation of Petung bamboo (Dendrocalamus asper) fiber—reinforced polymeric composites

    NASA Astrophysics Data System (ADS)

    Judawisastra, H.; Sitohang, R. D. R.; Rosadi, M. S.

    2017-09-01

    Bamboo fibers have attracted great interest and are believed to have the potential as natural fiber for reinforcing polymer composites. This research aims to study water absorption behavior and its effect to tensile strength of the composites made from petung bamboo fiber, which is one of the most grown bamboo species in Indonesia. Unidirectional (UD) and random composites were manufactured using wet hand lay-up method. Examinations were carried out by means of boiling water immersion test, tensile test, scanning electron microscopy and Fourier transform infrared spectroscopy. Water absorption of UD petung bamboo fiber/polyester composites is higher than that of random composites, i.e. 3.6% compared to 2.2%. This was due to higher fiber volume fraction of the UD composites. Water absorption caused irreversible tensile strength degradation on the composites. The initial properties of the composites were not recovered even after drying. The absorbed water decreased the tensile strength by 6% in UD composites and 38% in random composites. This was most likely to occur due to the permanent interfacial degradation.

  15. Resistance of radiation-induced tropical wood-polymer composites to fungal degradation

    NASA Astrophysics Data System (ADS)

    Chia, L. H. L.; Lim, V. S. L.; Yap, M. G. S.

    The resistance of six tropical hardwoods to fungal degradation by two wild-type strains of Phanerochaete chrysosporium Burdsall was investigated using vermiculite burial and wood-block weight loss techniques. Radiation-induced wood-polymer composites (WPC), based on two hardwoods Ramin and Rubber-wood with methyl methacrylate, were prepared, and samples were also exposed to the wood-rotting fungus. A significant improvement in resistance to fungal decay was observed in the WPC. Scanning-electron micrographs of the two woods and their composites after fungal degradation are presented and discussed.

  16. Efficient photocatalytic degradation of gaseous formaldehyde by the TiO{sub 2}/tourmaline composites

    SciTech Connect

    Zhang, Gaoke Qin, Xi

    2013-10-15

    Graphical abstract: - Highlights: • The TiO{sub 2}/tourmaline composites were prepared by a sol–gel method. • The composites exhibited excellent photocatalytic activity and good stability. • The physicochemical property of tourmaline may be favor for the degradation of HCHO. • The mixed-phase of anatase and rutile TiO{sub 2} may be favor for the degradation of HCHO. - Abstract: The TiO{sub 2} supported tourmaline composites were prepared by a sol–gel method and used as a photocatalyst for the degradation of formaldehyde (HCHO). The composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), N{sub 2} adsorption–desorption, Fourier transform infrared (FT-IR) spectroscopy and UV–vis diffuse reflectance spectroscopy (UV–vis DRS). The results indicate that the mixed-phase of anatase and rutile exists in the TiO{sub 2}/tourmaline composites. The specific surface area of the TiO{sub 2}/tourmaline composites is much higher than that of the pure TiO{sub 2}. The TiO{sub 2}/tourmaline composites exhibited excellent photocatalytic activity for the degradation of HCHO, which was 6 times higher than that of the pure TiO{sub 2}. Moreover, the excellent photocatalytic activity of the composites was fully maintained after five photocatalytic cycles, which may be attributed to the physicochemical property of tourmaline and the mixed-phase of anatase and rutile in the TiO{sub 2}/tourmaline composites.

  17. Mechanical, degradation and cytocompatibility properties of magnesium coated phosphate glass fibre reinforced polycaprolactone composites.

    PubMed

    Liu, Xiaoling; Hasan, Muhammad S; Grant, David M; Harper, Lee T; Parsons, Andrew J; Palmer, Graham; Rudd, Chris D; Ahmed, Ifty

    2014-11-01

    Retention of mechanical properties of phosphate glass fibre reinforced degradable polyesters such as polycaprolactone and polylactic acid in aqueous media has been shown to be strongly influenced by the integrity of the fibre/polymer interface. A previous study utilising 'single fibre' fragmentation tests found that coating with magnesium improved the fibre and matrix interfacial shear strength. Therefore, the aim of this study was to investigate the effects of a magnesium coating on the manufacture and characterisation of a random chopped fibre reinforced polycaprolactone composite. Short chopped strand non-woven phosphate glass fibre mats were sputter coated with degradable magnesium to manufacture phosphate glass fibre/polycaprolactone composites. The degradation behaviour (water uptake, mass loss and pH change of the media) of these polycaprolactone composites as well as of pure polycaprolactone was investigated in phosphate buffered saline. The Mg coated fibre reinforced composites revealed less water uptake and mass loss during degradation compared to the non-coated composites. The cations released were also explored and a lower ion release profile for all three cations investigated (namely Na(+), Mg(2+) and Ca(2+)) was seen for the Mg coated composite samples. An increase of 17% in tensile strength and 47% in tensile modulus was obtained for the Mg coated composite samples. Both flexural and tensile properties were investigated and a higher retention of mechanical properties was obtained for the Mg coated fibre reinforced composite samples up to 10 days immersion in PBS. Cytocompatibility study showed both composite samples (coated and non-coated) had good cytocompatibility with human osteosarcoma cell line.

  18. Strength Degradation of Aramid-Fiber/Epoxy Composites

    DTIC Science & Technology

    1980-04-01

    detailed dimensions of the samples are specified by ASTM Standard D 3039 . Longitudinal compression (test ’b’) was performed . in a "Celanese" fixture. The...58.1%, Density of fiber-1.45 gm/cc, Density of matrix- 1.189 gin/cc; void volume fraction is 2.5% ( ASTM D2734). We note from Figures 1 and 2 that...Testing and Design, ASTM , STP 617, 1976. 2. G. S. Springer and C. H. Shen, "Effect of Moisture and Temperature on Tensile Strength of Composite Materials

  19. In vitro degradation of biodegradable polylactic acid/magnesium composites: Relevance of Mg particle shape.

    PubMed

    Cifuentes, S C; Gavilán, R; Lieblich, M; Benavente, R; González-Carrasco, J L

    2016-03-01

    Absorbable medical devices must be developed in order to have an appropriate degradation rate in agreement with the healing rate of bone in the implantation site. In this work, biodegradable composites formed by a polylactic acid matrix reinforced with 10%wt. magnesium microparticles were processed and their in vitro degradation investigated during 28 days. A joint analysis of the amount of H2 released, the changes in pH in buffered (PBS) and non-buffered media (distilled water), the variations in mass, microstructure and the mechanical performance of the specimens was developed. The main aim was to elucidate the relevance of Mg particles shape on tailoring the degradation kinetics of these novel composites. The results show that the shape of the Mg reinforcing particles plays a crucial role in the degradation rate of PLA/Mg composites, with spherical particles promoting a lower degradation rate than irregular particles. This fact is only partially due to the smaller surface area to volume ratio of the spherical particles. Irregular particles promote a faster formation of cracks and, therefore, an increasingly faster degradation of the polymeric matrix. In every case, the amount of H2 released by the composites was well below that released by monolithic Mg. The pH of PBS during degradation remained always within 7.2 and 7.4. PLA/Mg reinforced with spherical particles retains more than 90% of its mechanical properties after 7 days of immersion and more than 60% after 28 days. The increasing demand for temporary orthopaedic implants is the driving force to seek new strategies to decrease costs and simultaneously improve patients comfort as well as simplify surgical procedures. Resorbable medical devices must be developed in order to have an appropriate degradation rate in agreement with the healing rate of bone. We are presenting for the first time results of the degradation kinetics of a new material based on polylactic acid reinforced with 10%wt. Mg microparticles

  20. Fabrication, characterization, and in vitro degradation of composite scaffolds based on PHBV and bioactive glass.

    PubMed

    Li, Haiyan; Du, Ruilin; Chang, Jiang

    2005-10-01

    Composite scaffolds of polyhydroxybutyrate-polyhydroxyvalerate (PHBV) with sol-gel-derived bioactive glass (BG, 58S) are fabricated by compression molding, thermal processing, and salt particulate leaching method. Structure and mechanical properties of the scaffolds are determined. The bioactivity of the composites is evaluated by soaking the scaffolds in a simulated body fluid (SBF), and the formation of the apatite layer on the scaffolds is determined by scanning electron microscopy (SEM) and energy-dispersive spectrometry (EDS). The results show that the PHBV/BG composites are bioactive as they induce the formation of apatite on the composite scaffolds after soaking in SBF for 3 days. In addition, the measurements of the water contact angles suggest that incorporation of BG into PHBV can improve the hydrophilicity of the composites and the enhancement is dependent on the BG content. Furthermore, the degradation assessment of the scaffolds is performed in phosphate-buffered saline (PBS) solution at 37 C. Weight loss and water absorption of the scaffolds, pH of the incubation media, and molecular weight measurements of the PHBV in the scaffolds are used to monitor the degradation of the scaffolds during a nine-week incubation in PBS. It has been found that the incorporation of bioactive glass into the PHBV delayed the degradation of PHBV in the composite scaffolds for the period investigated. The present results show not only a useful method to prepare composite scaffolds with improved properties but also a way of adjusting the in vitro degradation behavior of composite scaffolds by tailoring the content of bioactive glass.

  1. 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.

  2. Composite nanofibers for highly efficient photocatalytic degradation of organic dyes from contaminated water.

    PubMed

    Mohamed, Alaa; El-Sayed, Ramy; Osman, T A; Toprak, M S; Muhammed, M; Uheida, A

    2016-02-01

    In this study highly efficient photocatalyst based on composite nanofibers containing polyacrylonitrile (PAN), carbon nanotubes (CNT), and surface functionalized TiO2 nanoparticles was developed. The composite nanofibers were fabricated using electrospinning technique followed by chemical crosslinking. The surface modification and morphology changes of the fabricated composite nanofibers were examined through SEM, TEM, and FTIR analysis. The photocatalytic performance of the composite nanofibers for the degradation of model molecules, methylene blue and indigo carmine, under UV irradiation in aqueous solutions was investigated. The results demonstrated that high photodegradation efficiency was obtained in a short time and at low power intensity compared to other reported studies. The effective factors on the degradation of the dyes, such as the amount of catalyst, solution pH and irradiation time were investigated. The experimental kinetic data were fitted using pseudo-first order model. The effect of the composite nanofibers as individual components on the degradation efficiency of MB and IC was evaluated in order to understand the overall photodegradation mechanism. The results obtained showed that all the components possess significant effect on the photodegradation activity of the composite nanofibers. The stability studies demonstrated that the photodegradation efficiency can remain constant at the level of 99% after five consecutive cycles. Copyright © 2015 Elsevier Inc. All rights reserved.

  3. Changes in composition, cellulose degradability and biochemical methane potential of Miscanthus species during the growing season.

    PubMed

    Peng, Xiaowei; Li, Chao; Liu, Jing; Yi, Zili; Han, Yejun

    2017-03-24

    The composition, cellulose degradability and biochemical methane potential (BMP) of M. sinensis, M. floridulus, Miscanthus×giganteus and M. lutarioriparius were investigated concomitantly at different growth/harvest times during their growing season. For all the four species, there was only a slight change in the compositional content. Meanwhile there was a huge change in the BMP values. At the growth time of 60days the BMPs ranged from 247.1 to 266.5mlg(-1)VS. As growth time was prolonged, the BMPs decreased by 11-35%. For each species, the BMP was positively correlated to the cellulose degradability with the correlation coefficients (R(2)) ranging from 0.8055 to 0.9925. This suggests that besides the biomass yield, it is justifiable to consider cellulose degradability when selecting the suitable harvest time for biofuels production from Miscanthus, especially in tropical and subtropical regions where Miscanthus can be harvested twice or more within a year.

  4. FT-Raman spectroscopy study of organic matrix degradation in nanofilled resin composite.

    PubMed

    Soares, Luís Eduardo Silva; Nahórny, Sídnei; Martin, Airton Abrahão

    2013-04-01

    This in vitro study evaluated the effect of light curing unit (LCU) type, mouthwashes, and soft drink on chemical degradation of a nanofilled resin composite. Samples (80) were divided into eight groups: halogen LCU, HS--saliva (control); HPT--Pepsi Twist®; HLC--Listerine®; HCP--Colgate Plax®; LED LCU, LS--saliva (control); LPT--Pepsi Twist®; LLC--Listerine®; LCP--Colgate Plax®. The degree of conversion analysis and the measure of the peak area at 2,930 cm-1 (organic matrix) of resin composite were done by Fourier-transform Raman spectroscopy (baseline, after 7 and 14 days). The data were subjected to multifactor analysis of variance (ANOVA) at a 95% confidence followed by Tukey's HSD post-hoc test. The DC ranged from 58.0% (Halogen) to 59.3% (LED) without significance. Differences in the peak area between LCUs were found after 7 days of storage in S and PT. A marked increase in the peak intensity of HLC and LLC groups was found. The soft-start light-activation may influence the chemical degradation of organic matrix in resin composite. Ethanol contained in Listerine® Cool Mint mouthwash had the most significant degradation effect. Raman spectroscopy is shown to be a useful tool to investigate resin composite degradation.

  5. Chemical composition and cell wall polysaccharide degradability of pith and rind tissues from mature maize internodes

    USDA-ARS?s Scientific Manuscript database

    This study was undertaken to identify tissue-specific biochemical traits that may be targeted in breeding programs for improving forage digestibility. We compared cell wall chemical composition and 24- and 96-h in vitro degradabilities in separated pith and rind tissues of the fourth above-ground in...

  6. Chemical composition and cell wall polysaccharide degradability of pith and rind tissues from mature maize internodes

    USDA-ARS?s Scientific Manuscript database

    Our study was undertaken to identify tissue-specific biochemical traits that may be targeted in breeding programs for improving forage digestibility. We compared cell wall chemical composition and 24- and 96-h in vitro degradabilities in separated pith and rind tissues from six maize inbred lines. A...

  7. Development of a degradable cement of calcium phosphate and calcium sulfate composite for bone reconstruction.

    PubMed

    Guo, H; Wei, J; Liu, C S

    2006-12-01

    A new type of composite bone cement was prepared and investigated by adding calcium sulfate (CS) to calcium phosphate cement (CPC). This composite cement can be handled as a paste and easily shaped into any contour, which can set within 5-20 min, the setting time largely depending on the liquid-solid (L/S) ratio; adding CS to CPC had little effect on the setting time of the composite cements. No obvious temperature increase and pH change were observed during setting and immersion in simulated body fluid (SBF). The compressive strength of the cement decreased with an increase in the content of CS. The degradation rate of the composite cements increased with time when the CS content was more than 20 wt%. Calcium deficient apatite could form on the surface of the composite cement because the release of calcium into SBF from the dissolution of CS and the apatite of the cement induced the new apatite formation; increasing the content of CS in the composite could improve the bioactivity of the composite cements. The results suggested that composite cement has a reasonable setting time, excellent degradability and suitable mechanical strength and bioactivity, which shows promising prospects for development as a clinical cement.

  8. [Investigation on degradation of polypropylene/stabilizers composites irradiated by gamma rays].

    PubMed

    Zhou, Li-juan; Zhang, Xiu-qin; Zhao, Ying; Yang, Ming-shu; Wang, Du-jin; Xu, Duan-fu

    2010-10-01

    The degradation behavior of polypropylene and polypropylene/stabilizer composites, caused by gamma radiation, was studied in the present work The stabilizers used were hindered phenol antioxidant and hindered amine light stabilizer. FTIR spectroscopy and DSC analysis were used to determine the structural variation induced by gamma radiation. It can be seen that the evolution of PP and composites PP/stabilizers on gamma irradiation is an increase in absorbance in the hydroxyl and carbonyl absorption regions. Carbonyl index calculated from FTIR spectra was used to characterize the rate of degradation. When the irradiation dose was small (<50 kGy), the degradation of pure polypropylene and polypropylene/stabilizers composites was not obvious; while the irradiation dose increased (> or =50 kGy), the carbonyl indexes of all the samples increased obviously, and the degradation degree of polypropylene/stabilizer composites was bigger than pure polypropylene. This result might be partially attributed to the molecular chain scission of hindered phenol and hindered amine under larger irradiation dose. The chain scission of stabilizers forms hydroperoxides and peroxide radicals, catalyzing the degradation of polypropylene. As the irradiation dose was small (<50 kGy), the crystallization temperatures of pure polypropylene and polypropylene/stabilizer composites all showed no remarkable changes; as the irradiation dose exceeded 50 kGy, the crystallization temperatures of pure polypropylene and polypropylene/stabilizer composites all decreased obviously. Correspondingly, the melting peaks of both pure polypropylene and polypropylene/stabilizer composites moved to lower temperature and split into two peaks with increasing the irradiation dose. The decrease of crystallization and melting temperatures might be attributed to the destruction of chemical structure and stereo-regularity of the molecular chain, due to the increasing of carbonyl and hydroxyl groups brought by the

  9. Silicon-Based Ceramic-Matrix Composites for Advanced Turbine Engines: Some Degradation Issues

    NASA Technical Reports Server (NTRS)

    Thomas-Ogbuji, Linus U. J.

    2000-01-01

    SiC/BN/SiC composites are designed to take advantage of the high specific strengths and moduli of non-oxide ceramics, and their excellent resistance to creep, chemical attack, and oxidation, while circumventing the brittleness inherent in ceramics. Hence, these composites have the potential to take turbine engines of the future to higher operating temperatures than is achievable with metal alloys. However, these composites remain developmental and more work needs to be done to optimize processing techniques. This paper highlights the lingering issue of pest degradation in these materials and shows that it results from vestiges of processing steps and can thus be minimized or eliminated.

  10. Intermediate Temperature Strength Degradation in SiC/SiC Composites

    NASA Technical Reports Server (NTRS)

    Morscher, Gregory N.; Cawley, James D.; Levine, Stanley (Technical Monitor)

    2001-01-01

    Woven silicon carbide fiber-reinforced, silicon carbide matrix composites are leading candidate materials for an advanced jet engine combustor liner application. Although the use temperature in the hot region for this application is expected to exceed 1200 C, a potential life-limiting concern for this composite system exists at intermediate temperatures (800 +/- 200 C), where significant time-dependent strength degradation has been observed under stress-rupture loading. A number of factors control the degree of stress-rupture strength degradation, the major factor being the nature of the interphase separating the fiber and the matrix. BN interphases are superior to carbon interphases due to the slower oxidation kinetics of BN. A model for the intermediate temperature stress-rupture of SiC/BN/SiC composites is presented based on the observed mechanistic process that leads to strength degradation for the simple case of through-thickness matrix cracks. The approach taken has much in common with that used by Curtin and coworkers, for two different composite systems. The predictions of the model are in good agreement with the rupture data for stress-rupture of both precracked and as-produced composites. Also, three approaches that dramatically improve the intermediate temperature stress-rupture properties are described: Si-doped BN, fiber spreading, and 'outside debonding'.

  11. Preparation of PVA/TiO2 Composites Nanofibers by using Electrospinning Method for Photocatalytic Degradation

    NASA Astrophysics Data System (ADS)

    Nasikhudin; Ismaya, E. P.; Diantoro, M.; Kusumaatmaja, A.; Triyana, K.

    2017-05-01

    PVA/TiO2 composites nanofibers have been prepared by using electrospinning method. Electrospinning was performed at a voltage of 15 kV, with a tip-collector distance of 14 cm. The PVA/TiO2 composites nanofibers were characterized by FTIR, SEM, and EDAX. The results showed that PVA/TiO2 composites nanofibers were successfully formed. SEM observation showed that the nanofibers has several hundred nanometers with a smooth surface and have TiO2 nanoparticle distributed in the nanofibers. FTIR result shows a functional group of PVA and EDAX result demonstrates the presence of TiO2 in the nanofibers. The photocatalytic activity of PVA/TiO2 composites nanofibers were investigated for the degradation of methylene blue under UV light. The PVA/TiO2 composite nanofibers suspending in the dye solution have dye removal of 70% dye was degraded in 5 h. As a comparison, the TiO2 powder that has dye removal of 95% dye was degraded in 5 h. Photocatalytic activity of PVA/TiO2 nanofiber was lower than TiO2 powder, but PVA/TiO2 nanofiber was more efficient than TiO2 powder regarding process treatments photocatalytic.

  12. Evaluating Anthropogenic Risk of Grassland and Forest Habitat Degradation Using Land-Cover Data

    EPA Science Inventory

    The effects of landscape context on habitat quality are receiving increased attention in conservation biology. The objective of this research is to demonstrate an approach to mapping and evaluating the anthropogenic risks of grassland and forest habitat degradation by examining ...

  13. Evaluating Anthropogenic Risk of Grassland and Forest Habitat Degradation Using Land-Cover Data

    EPA Science Inventory

    The effects of landscape context on habitat quality are receiving increased attention in conservation biology. The objective of this research is to demonstrate an approach to mapping and evaluating the anthropogenic risks of grassland and forest habitat degradation by examining ...

  14. The effect of sand composition on the degradation of buried oil.

    PubMed

    Fernández-Fernández, Sandra; Bernabeu, Ana M; Rey, Daniel; Mucha, Ana P; Almeida, C Marisa R; Bouchette, Frédéric

    2014-09-15

    The potential effects of the mineralogical composition of sediment on the degradation of oil buried on sandy beaches were investigated. Toward that purpose, a laboratory experiment was carried out with sandy sediment collected along NW Iberian Peninsula beaches, tar-balls from the Prestige oil spill (NW Spain) and seawater. The results indicate that the mineralogical composition is important for the physical appearance of the oil (tar-balls or oil coatings). This finding prompted a reassessment of the current sequence of degradation for buried oil based on compositional factors. Moreover, the halo development of the oil coatings might be enhanced by the carbonate concentration of the sand. These findings open new prospects for future monitoring and management programs for oiled sandy beaches.

  15. The Influence of Copolymer Composition on PLGA/nHA Scaffolds' Cytotoxicity and In Vitro Degradation.

    PubMed

    Díaz, Esperanza; Puerto, Igor; Ribeiro, Silvie; Lanceros-Mendez, Senentxu; Barandiarán, José Manuel

    2017-07-06

    The influence of copolymer composition on Poly(Lactide-co-Glycolide)/nanohydroxyapatite (PLGA/nHA) composite scaffolds is studied in the context of bone tissue engineering and regenerative medicine. The composite scaffolds are fabricated by thermally-induced phase separation and the effect of bioactive nanoparticles on their in vitro degradation in phosphate-buffered solution at 37 °C is analyzed over eight weeks. The indirect cytotoxicity evaluation of the samples followed an adaptation of the ISO 10993-5 standard test method. Based on the measurement of their molecular weight, molar mass, pH, water absorption and dimensions, the porous scaffolds of PLGA with a lower lactide/glycolide (LA/GA) molar ratio degraded faster due to their higher hydrophilicity. All of the samples without and with HA are not cytotoxic, demonstrating their potential for tissue engineering applications.

  16. The Influence of Copolymer Composition on PLGA/nHA Scaffolds’ Cytotoxicity and In Vitro Degradation

    PubMed Central

    Díaz, Esperanza; Puerto, Igor; Ribeiro, Silvie; Lanceros-Mendez, Senentxu; Barandiarán, José Manuel

    2017-01-01

    The influence of copolymer composition on Poly(Lactide-co-Glycolide)/nanohydroxyapatite (PLGA/nHA) composite scaffolds is studied in the context of bone tissue engineering and regenerative medicine. The composite scaffolds are fabricated by thermally-induced phase separation and the effect of bioactive nanoparticles on their in vitro degradation in phosphate-buffered solution at 37 °C is analyzed over eight weeks. The indirect cytotoxicity evaluation of the samples followed an adaptation of the ISO 10993-5 standard test method. Based on the measurement of their molecular weight, molar mass, pH, water absorption and dimensions, the porous scaffolds of PLGA with a lower lactide/glycolide (LA/GA) molar ratio degraded faster due to their higher hydrophilicity. All of the samples without and with HA are not cytotoxic, demonstrating their potential for tissue engineering applications. PMID:28684725

  17. LEO degradation of graphite and carbon-based composites aboard Space Shuttle Flight STS-46

    NASA Technical Reports Server (NTRS)

    Spady, Blaine R.; Synowicki, R. A.; Hale, Jeffrey S.; Devries, M. J.; Woollam, John A.; Moore, Arthur W.; Lake, Max

    1995-01-01

    Six different types of carbon and carbon-boron nitride composites were exposed to low Earth orbit aboard Space Shuttle flight STS-46. The samples received a nominal atomic oxygen fluence of 2.2 x 10(exp 20) atoms/sq cm in 42 hours of exposure. Pyrolytic graphite and highly oriented pyrolytic graphite showed significant degradation, and the measured erosion yield was within a factor of two of published values. The erosion yield of pyrolytic boron nitride was found to be 2.6 x 10(exp 26) cu cm/atom in plasma asher exposure, over 42 times lower than that of pyrolytic graphite. This low erosion yield makes graphite plus boron nitride mixtures quite resistant to low Earth orbit exposure. Evidence suggests that the graphitic component was preferentially etched, leaving the surface boron nitride rich. Degradation resistance increases with boron nitride composition. Carbon fiber/carbon composites degraded in low Earth orbit, and the carbon pitch binder was found to etch more easily than the graphite fibers which have much higher degradation resistance.

  18. Synthesis of TiO2 /CNT Composites and its Photocatalytic Activity Toward Sudan (I) Degradation.

    PubMed

    Miribangul, Amat; Ma, Xiaoli; Zeng, Chen; Zou, Huan; Wu, Yahui; Fan, Tengpeng; Su, Zhi

    2016-07-01

    Semiconductor photocatalysis has the potential for achieving sustainable energy generation and degrading organic contaminants. In TiO2 , the addition of carbonaceous nanomaterials has attracted extensive attention as a means to increase its photocatalytic activity. In this study, composites of TiO2 and carbon nanotubes (CNT) in various proportions were synthesized by the hydrothermal method. The crystalline structures, morphologies, and light absorption properties of the TiO2 /CNT photocatalysts were characterized by PXRD, TEM and UV-Vis absorption spectra. The photocatalytic efficiency of the composites was evaluated by the degradation of Sudan (I) in UV-Vis light. Introducing 0.1-0.5 wt% CNT was shown to substantially improve the photoactivity of TiO2 . The composite with 0.3 wt% CNT showed the best catalytic activity, and its reaction activation energy was calculated as 39.57 kJ mol(-1) from experimental rates. The degradation products of Sudan (I) with different irradiation durations were characterized by Fourier transform infrared spectroscopy, and a degradation reaction process was proposed. © 2016 The American Society of Photobiology.

  19. Staining of in vivo subsurface degradation in dental composites with silver nitrate

    SciTech Connect

    Mair, L.H. )

    1991-03-01

    A previously reported technique for staining areas of degradation in dental composite restorations was evaluated in 51 removed restorations. The staining reagent was silver nitrate, which penetrated the degraded subsurface as ionic silver and was subsequently developed into colored deposits of metallic silver. Several artefacts were recognized that resulted in an apparent image of subsurface stain. Most importantly, the presence of a layer of adsorbed silver on the edge of the specimen exaggerated the extent of staining. In order for the true depth of stain to be determined, thin sections of the materials should first be examined with a stereomicroscope to distinguish any contribution from adsorbed silver on the specimen edge. With this regimen, no stain was present in 41% of the restorations, and in a further 30%, the depth of stain was less than 50 microns. In two composites, the depth of stain was greater than 900 microns, and in a number of specimens, localized stain was found in association with attrition scars. Energy-dispersive x-ray analysis indicated that the amount of silver present in the degraded layers was very small. Overall, the results indicated that the staining technique is useful in the study of composite degradation.

  20. Influence of engine coolant composition on the electrochemical degradation behavior of EPDM radiator hoses

    SciTech Connect

    Vroomen, G.L.M.; Lievens, S.S.; Maes, J.P.

    1999-08-01

    EPDM (ethylene-propylene rubber) has been used for more than 25 years as the main elastomer in radiator hoses because it offers a well-balanced price/performance ratio in this field of application. Some years ago the automotive and rubber industry became aware of a problem called electrochemical degradation and cracking. Cooling systems broke down due to a typical cracking failure of some radiator hoses. Different test methods were developed to simulate and solve the problem on laboratory scale. The influence of different variables with respect to the electrochemical degradation and cracking. Cooling systems broke down due to a typical cracking failure of some radiator hoses. Different test methods were developed to simulate and solve the problem on laboratory scale. The influence of different variables with respect to the electrochemical degradation process has been investigated, but until recently the influence of the engine coolant was ignored. Using a test method developed by DSM elastomers, the influence of the composition of the engine coolant as well as of the EPDM composition has now been evaluated. This paper gives an overview of test results with different coolant technologies and offers a plausible explanation of the degradation mechanisms as a function of the elastomer composition.

  1. [Optimizing management on degraded grassland in Xilin River Basin based on ecological risk assessment].

    PubMed

    Gu, Xiao-he; He, Chun-yang; Pan, Yao-zhong; Li, Xiao-bing; Zhu, Wen-quan; Zhu, Xiu-fang

    2007-05-01

    By the methods of remote sensing (RS) and geographic information system (GIS), and based on the estimations of degradation degree, risk degree and easy-restoration degree of degraded grasslands, an ecological management index (EMI) model of grassland was established to approach the practical ways of optimizing management of degraded grassland. A case study in the Xilin River Basin of Inner Mongolia showed that this model could quantitatively analyze the degradation degree, risk degree and easy-restoration degree of the grasslands under different optimizing management levels, which was of significance for applying rational measures with pertinence, and beneficial to the optimal allocation of resources during the management of degraded grassland. The EMI model could integrate most concerned information, which made it applicable widely.

  2. Kinetic viscoelasticity modeling applied to degradation during carbon-carbon composite processing

    NASA Astrophysics Data System (ADS)

    Drakonakis, Vassilis M.; Seferis, James C.; Wardle, Brian L.; Nam, Jae-Do; Papanicolaou, George C.; Doumanidis, Charalambos C.

    2010-04-01

    Kinetic viscoelasticity modeling has been successfully utilized to describe phenomena during cure of thermoset based carbon fiber reinforced matrices. The basic difference from classic viscoelasticity is that the fundamental material descriptors change as a result of reaction kinetics. Accordingly, we can apply the same concept for different kinetic phenomena with simultaneous curing and degradation. The application of this concept can easily be utilized in processing and manufacturing of carbon-carbon composites, where phenolic resin matrices are cured degraded and reinfused in a carbon fiber bed. This work provides a major step towards understanding complex viscoelastic phenomena that go beyond simple thermomechanical descriptors.

  3. [Degradation of polyhydroxyalkanoates and the composition of microbial destructors under natural conditions].

    PubMed

    Volova, T G; Gladyshev, M I; Trusova, M Iu; Zhila, N O

    2006-01-01

    The degradation dynamics of polyhydroxyalkanoates of different composition has been studied in an eutrophic storage reservoir for two seasons. It has been shown that the biodegradation of polymers under natural conditions depends not only on their structure and physicochemical properties but also, to a great extent, on a complex of weather-climatic conditions affecting the state of the reservoir ecosystem. The molecular genetic analysis of 16S rRNA has revealed bacterial species (clones) probably involved in the degradation of polyhydroxyalkanoates in a model storage reservoir.

  4. Photocatalytic degradation of methyl orange over ITO/Cds/ZnO interface composite films.

    PubMed

    Wei, Shouqiang; Shao, Zhongcai; Lu, Xudong; Liu, Ying; Cao, Linlin; He, Yan

    2009-01-01

    ITO/CdS/ZnO interface composite films were successfully prepared by subsequent electrodeposition of CdS and ZnO onto indium tin oxide (ITO) glass substrates. The obtained ITO/CdS/ZnO composite films were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-Vis spectroscopy. The photocatalytic activity of ITO/CdS/ZnO composite films were investigated using methyl orange (MO) as a model organic compound under UV light irradiation. The influence of operating parameters on MO degradation including initial concentration of MO, pH value of solution, and inorganic anion species over the composite films were examined. A blue shift of absorption threshold was observed for the ITO/CdS/ZnO film in comparison with ITO/ZnO film. ITO/CdS/ZnO composite films prepared under specific conditions showed a higher photocatalytic activity than that of ITO/ZnO films. It was also found that the photocatalytic degradation of MO on the composite films followed pseudo-first order kinetics.

  5. Synthesis of nano-TiO2/diatomite composite and its photocatalytic degradation of gaseous formaldehyde

    NASA Astrophysics Data System (ADS)

    Zhang, Guangxin; Sun, Zhiming; Duan, Yongwei; Ma, Ruixin; Zheng, Shuilin

    2017-08-01

    The TiO2/diatomite composite was synthesized through a mild hydrolysis of titanyl sulfate. The prepared composite was characterized by X-ray diffraction, N2 adsorption-desorption, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and UV-vis diffused reflectance spectroscopy. The results demonstrate that the anatase TiO2 nanopartilces anchored on the surface of diatomite with Ti-O-Si bonds between diatomite and TiO2. The photodegradation of gaseous formaldehyde under UV irradiation by the TiO2/diatomite composite was studied under various operating conditions, including relative humidity, illumination intensity and catalyst amount, which have significant influence on the degradation process. The TiO2/diatomite composite exhibited better photocatalytic activity than pure TiO2, which could be attributed to the favorable nanoparticles dispersibility and strong formaldehyde adsorption capacity. In addition, the composite exhibited outstanding reusability over five cycles. The TiO2/diatomite composite shows great promising application foreground in formaldehyde degradation.

  6. Composite tin and zinc oxide nanocrystalline particles for enhanced charge separation in sensitized degradation of dyes.

    PubMed

    Bandara, J; Tennakone, K; Jayatilaka, P P B

    2002-10-01

    Composite ZnO/SnO2 catalyst has been studied for the sensitized degradation of dyes e.g. Eosin Y (2', 4', 5', 7'-tetrabromofluorescein disodium salt) in relation to efficient charge separation properties of the catalyst. Improved photocatalytic activity was observed in the case of ZnO/SnO2 composite catalyst compared to the catalytic activity of ZnO, SnO2 or TiO2 powder. The suppression of charge recombination in the composite ZnO/SnO2 catalyst led to higher catalytic activity for the degradation of Eosin Y. Degradation of Eosin follows concomitant formation of CO2 and formation of CO2 followed a pseudo-first-order rate. Photoelectrochemical cells constructed using SnO2, ZnO, ZnO/SnO2 sensitized with Eosin Y showed V(oc) of 175, 306, 512 mV/cm2 and I(sc) of 50, 70, 200 microA/cm2 respectively. A higher irreversible degradation of Eosin Y and higher V(oc) observed on composite ZnO/SnO2 than ZnO and SnO2 separately can be considered as a proof of enhanced charge separation of ZnO/SnO2 catalyst. Eosin Y showed a higher emission decreases on ZnO/SnO2 composite than on individual ZnO, SnO2 or TiO2 indicating dominance of the charge injection process. Photoinjected electrons are tunneled from ZnO to SnO2 particles accumulating injected electrons in the conduction bands allowing wider separation of excited carriers.

  7. 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.

  8. Development of a composite soil degradation assessment index for cocoa agroecosystems in southwestern Nigeria

    NASA Astrophysics Data System (ADS)

    Adenrele Adeniyi, Sunday; de Clercq, Willem Petrus; van Niekerk, Adriaan

    2017-08-01

    Cocoa agroecosystems are a major land-use type in the tropical rainforest belt of West Africa, reportedly associated with several ecological changes, including soil degradation. This study aims to develop a composite soil degradation assessment index (CSDI) for determining the degradation level of cocoa soils under smallholder agroecosystems of southwestern Nigeria. Plots where natural forests have been converted to cocoa agroecosystems of ages 1-10, 11-40, and 41-80 years, respectively representing young cocoa plantations (YCPs), mature cocoa plantations (MCPs), and senescent cocoa plantations (SCPs), were identified to represent the biological cycle of the cocoa tree. Soil samples were collected at a depth of 0 to 20 cm in each plot and analysed in terms of their physical, chemical, and biological properties. Factor analysis of soil data revealed four major interacting soil degradation processes: decline in soil nutrients, loss of soil organic matter, increase in soil acidity, and the breakdown of soil textural characteristics over time. These processes were represented by eight soil properties (extractable zinc, silt, soil organic matter (SOM), cation exchange capacity (CEC), available phosphorus, total porosity, pH, and clay content). These soil properties were subjected to forward stepwise discriminant analysis (STEPDA), and the result showed that four soil properties (extractable zinc, cation exchange capacity, SOM, and clay content) are the most useful in separating the studied soils into YCP, MCP, and SCP. In this way, we have sufficiently eliminated redundancy in the final selection of soil degradation indicators. Based on these four soil parameters, a CSDI was developed and used to classify selected cocoa soils into three different classes of degradation. The results revealed that 65 % of the selected cocoa farms are moderately degraded, while 18 % have a high degradation status. The numerical value of the CSDI as an objective index of soil degradation

  9. Photocatalytic degradation of commercially sourced naphthenic acids by TiO2-graphene composite nanomaterial.

    PubMed

    Liu, Juncheng; Wang, Lin; Tang, Jingchun; Ma, Jianli

    2016-04-01

    Naphthenic acids (NAs) are a major contributor to the toxicity in oil sands process-affected water (OSPW), which is produced by hot water extraction of bitumen. NAs are extremely difficult to be degraded due to its complex ring and side chain structure. Photocatalysis is recognized as a promising technology in the removal of refractory organic pollutants. In this work, TiO2-graphene (P25-GR) composites were synthesized by means of solvothermal method. The results showed that P25-GR composite exhibited better photocatalytic activity than pure P25. The removal efficiency of naphthenic acids in acid solution was higher than that in neutral and alkaline solutions. It was the first report ever known on the photodegradation of NAs based on graphene, and this process achieved a higher removal rate than other photocatalysis degradation of NAs in a shorter reaction time. LC/MS analysis showed that macromolecular NAs (carbon number 17-22, z value -2) were easy to be degraded than the micromolecular ones (carbon number 11-16, z value -2). Furthermore, the reactive oxygen species that play the main role in the photocatalysis system were studied. It was found that holes and ·OH were the main reactive species in the UV/P25-GR photocatalysis system. Given the high removal efficiency of refractory organic pollutants and the short degradation time, photodegradation based on composite catalysts has a broad and practical prospect. The study on the photodegradation of commercially sourced NAs may provide a guidance for the degradation of OSPW NAs by this method.

  10. Fabrication, gastromucoadhesivity, swelling, and degradation of zein-chitosan composite ultrafine fibers.

    PubMed

    Wongsasulak, Saowakon; Puttipaiboon, Natthon; Yoovidhya, Tipaporn

    2013-06-01

    Fabrication, via electrospinning, and characterization of an ultrafine structure architected from a blend of hydrophobic zein and hydrophilic chitosan (CS) were conducted. Poly(ethylene oxide) (PEO) and nonionic surfactant, namely, Tween 40, were employed to improve the electrospinnability of the blend, while ethanol was used as a solvent for zein. The effects of ethanol (EtOH) concentration (85% and 90%) and ratio of zein/PEO/CS (95/2.5/2.5 and 87.5/10/2.5) on the fiber morphology as well as gastromucoadhesivity against porcine stomach mucosa were then investigated; polymer-mucosa adhesion was also investigated via Fourier-transform infrared spectroscopy. Swelling and degradation of the composite ultrafine fibers were investigated under 2 simulated gastric conditions, namely, at pH 2 without pepsin and at pH 1.2 with pepsin. Using 85% EtOH as a solvent for zein resulted in a spider-web-like morphology; the maximum detachment force (MDF), which is an indirect indicator of the gastromucoadhesivity was nevertheless higher. Zein-based ultrafine fibers exhibited higher MDF than the zein-PEO-CS composite; however, the cohesiveness of the composite fibers was higher. FTIR spectroscopic results indicated molecular interactions between the composite fibers and mucin functional groups. Swelling of the composite ultrafine fibers in simulated gastric fluid (SGF) at pH 2 without pepsin was not different from that in SGF at pH 1.2 with pepsin. Nevertheless, degradation of the composite fibers in SGF at pH 2 without pepsin was much less than that in SGF at pH 1.2 with pepsin; only 20% degradation was noted in the former case. © 2013 Institute of Food Technologists®

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

    PubMed

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

    2013-04-01

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

  12. Effect of presilanization filler decontamination on aesthetics and degradation resistance of resin composites.

    PubMed

    Yoshida, Yasuhiro; Shirai, Kenichi; Shintani, Hideaki; Okazaki, Masayuki; Suzuki, Kazuomi; Van Meerbeek, Bart

    2002-12-01

    Filler-matrix coupling determines, to a large extent, the mechanical strength and clinical longevity of dental composites. The aim of this study was to examine how far a methodology to decontaminate filler prior to silanization may improve aesthetic performance in addition to physico-mechanical properties such as degradation resistance. It was reported that filler particles are surrounded and wrapped by a film that consists of multiple layers of silane molecules. X-ray photoelectron spectroscopy, however, revealed that silanization of filler particles largely depended upon siloxane bridge (Si-O-Si) formation between the silica surface and the silane molecule rather than on intermolecular bonding between adjacent silane molecules. In this study, we showed that filler decontamination resulted in a higher translucency, thereby providing a better aesthetic potential. In addition, experimental composites produced following presilanization decontamination of filler revealed a higher Vickers hardness value and a diametral tensile strength that was resistant to degradation by thermo-cycling.

  13. 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.

  14. Effect of Adventitious Carbon on the Environmental Degradation of SiC/BN/SiC Composites

    NASA Technical Reports Server (NTRS)

    Ogbuji, L. U. J. T.; Yun, H. M.; DiCarlo, J.

    2002-01-01

    Pesting remains a major obstacle to the application of SiC/SiC composites in engine service and selective degradation of the boron nitride interphase at intermediate temperatures is of primary concern. However, significant progress has been made on interphase improvement recently and we now know more about the phenomenon and ways to suppress it. By screening SiC/BN/SiC materials through characterization of strength and microstructures after exposure in a burner rig, some factors that control pesting in these composites have been determined. A key precaution is careful control of elemental carbon presence in the interphase region.

  15. Compositional changes adjacent to grain boundaries during electrical degradation of a ZnO varistor

    SciTech Connect

    Chiang, Y.; Kingery, W.D.; Levinson, L.M.

    1982-03-01

    Compositional changes adjacent to grain boundaries in heavily degraded samples of a ZnO varistor containing the additives Bi and Co have been observed with the scanning transmission electron microscope. A marked asymmetry in the distribution of Bi and Co with respect to the physical location of the boundary is found, consistent with the accumulation of mobile cations on one side of the boundary under the influence of a dc electric field.

  16. Activity, biomass and composition of microbial communities and their degradation pathways in exposed propazine soil.

    PubMed

    Jiang, Chen; Lu, Yi Chen; Xu, Jiang Yan; Song, Yang; Song, Yue; Zhang, Shu Hao; Ma, Li Ya; Lu, Feng Fan; Wang, Ya Kun; Yang, Hong

    2017-11-01

    Propazine is a s-triazine herbicide widely used for controlling weeds for crop production. Its persistence and contamination in environment nagatively affect crop growth and food safety. Elimination of propazine residues in the environment is critical for safe crop production. This study identified a microbial community able to degrade propazine in a farmland soil. About 94% of the applied propazine was degraded within 11 days of incubation when soil was treated with 10mgkg(-1) propazine as the initial concentration. The process was accompanied by increased microbial biomass and activities of soil enzymes. Denaturing gradient gel electrophoresis (DGGE) revealed multiple bacterial strains in the community as well as dynamic change of the composition of microbial community with a reduced microbial diversity (H' from 3.325 to 2.78). Tracking the transcript level of degradative genes AtzB, AtzC and TrzN showed that these genes were induced by propazine and played important roles in the degradation process. The activities of catalase, dehydrogenase and phenol oxidase were stimulated by propazine exposure. Five degradation products (hydroxyl-, methylated-, dimeric-propazine, ammeline and ammelide) were characterized by UPLC-MS(2), revealing a biodegradation of propazine in soil. Several novel methylated and dimeric products of propazine were characterized in thepropazine-exposed soil. These data help understand the pathway, detailed mechanism and efficiency of propazine biodegradation in soil under realistic field condition. Copyright © 2017 Elsevier Inc. All rights reserved.

  17. Degradation of chloroacetanilide herbicides and bacterial community composition in lab-scale wetlands.

    PubMed

    Elsayed, Omniea Fawzy; Maillard, Elodie; Vuilleumier, Stéphane; Millet, Maurice; Imfeld, Gwenaël

    2015-07-01

    Degradation of chloroacetanilide herbicides rac-metolachlor, acetochlor, and alachlor, as well as associated bacterial populations, were evaluated in vertical upflow wetland columns using a combination of hydrochemical and herbicide analyses, and DNA-based approaches. Mass dissipation of chloroacetanilides, continuously supplied at 1.8-1.9 μM for 112 days, mainly occurred in the rhizosphere zone under nitrate and sulphate-reducing conditions, and averaged 61±14%, 52±12% and 29±19% for acetochlor, alachlor and rac-metolachlor, respectively. Metolachlor enantiomer fractions of 0.494±0.009 in the oxic zone and 0.480±0.005 in the rhizosphere zone indicated preferential biodegradation of the S-enantiomer. Chloroacetanilide ethane sulfonic acid and oxanilic acid degradates were detected at low concentrations only (0.5 nM), suggesting extensive degradation and the operation of yet unknown pathways for chloroacetanilide degradation. Hydrochemical parameters and oxygen concentration were major drivers of bacterial composition, whereas exposure to chloroacetanilides had no detectable impact. Taken together, the results underline the importance of anaerobic degradation of chloroacetanilides in wetlands, and highlight the potential of complementary chemical and biological approaches to characterise processes involved in the environmental dissipation of chloroacetanilides.

  18. Photocatalytic degradation of trichloroethylene in aqueous phase using nano-ZNO/Laponite composites.

    PubMed

    Joo, Jin Chul; Ahn, Chang Hyuk; Jang, Dae Gyu; Yoon, Young Han; Kim, Jong Kyu; Campos, Luiza; Ahn, Hosang

    2013-12-15

    The feasibility of nano-ZnO/Laponite composites (NZLc) as a valid alternative to TiO2 to mineralize trichloroethylene (TCE) without difficulties for recovery of photocatalysts was evaluated. Based on the experimental observations, the removal of TCE using NZLc under UV irradiation was multiple reaction processes (i.e., sorption, photolysis, and photocatalysis). Sorption of TCE was thermodynamically favorable due to the hydrophobic partitioning into crosslinked poly vinyl alcohol, and the adsorption onto high-surface-area mineral surfaces of both ZnO and Laponite. The degradation efficiency of TCE can be significantly improved using NZLc under UV irradiation, indicating that ZnO-mediated heterogeneous photocatalytic degradation occurred. However, the degradation efficiency was found to vary with experimental conditions (e.g., initial concentration of TCE, loading amount of NZLc, the intensity of light and initial solution pH). Although the removal of TCE by NZLc was found to be a complex function of sorption, photolysis, and photocatalysis, the photocatalytic degradation of TCE on the surface of ZnO was critical. Consequently, developed NZLc can be applied as a valid alternative to suspended TiO2 powder, and overcome drawbacks (e.g., filtration and recovery of photocatalysts) in degradation of TCE for various water resources.

  19. Degradation in Thermal Properties and Morphology of Polyetheretherketone-Alumina Composites Exposed to Gamma Radiation

    NASA Astrophysics Data System (ADS)

    Lawrence, Falix; Mishra, Satyabrata; Mallika, C.; Kamachi Mudali, U.; Natarajan, R.; Ponraju, D.; Seshadri, S. K.; Sampath Kumar, T. S.

    2012-07-01

    Sheets of polyetheretherketone (PEEK) and PEEK-alumina composites with micron-sized alumina powder with 5, 10, 15, 20, and 25% by weight were fabricated, irradiated with gamma rays up to 10 MGy and the degradation in their thermal properties and morphology were evaluated. The radicals generated during irradiation get stabilized by chain scission and crosslinking. Chain scission is predominant on the surface and crosslinking is predominant in the bulk of the samples. Owing to radiation damage, the glass transition temperature, T g increased for pure PEEK from 136 to 140.5 °C, whereas the shift in T g for the composites decreased with increase in alumina content and for PEEK-25% alumina, the change in T g was insignificant, as alumina acts as an excitation energy sink and reduces the crosslinking density, which in turn decreased the shift in T g towards higher temperature. Similarly, the melting temperature, T m and enthalpy of melting, Δ H m of PEEK and PEEK-alumina composites decreased on account of radiation owing to the restriction of chain mobility and disordering of structures caused by crosslinks. The decrease in T m and Δ H m was more pronounced in pure PEEK and the extent of decrease in T m and Δ H m was less for composites. SEM images revealed the formation of micro-cracks and micro-pores in PEEK due to radiation. The SEM image of irradiated PEEK-alumina (25%) composite showed negligible micro-cracks and micro-pores, because of the reinforcing effect of high alumina content in the PEEK matrix which helps in reducing the degradation in the properties of the polymer. Though alumina reduces the degradation of the polymer matrix during irradiation, an optimum level of ceramic fillers only have to be loaded to the polymer to avoid the reduction in toughness.

  20. Effect of in vitro degradation of poly(D,L-lactide)/beta-tricalcium composite on its shape-memory properties.

    PubMed

    Zheng, Xiaotong; Zhou, Shaobing; Yu, Xiongjun; Li, Xiaohong; Feng, Bo; Qu, Shuxin; Weng, Jie

    2008-07-01

    The in vitro degradation characteristic and shape-memory properties of poly(D,L-lactide) (PDLLA)/beta-tricalcium phosphate (beta-TCP) composites were investigated because of their wide application in biomedical fields. In this article, PDLLA and crystalline beta-TCP were compounded and interesting shape-memory behaviors of the composite were first investigated. Then, in vitro degradation of the PDLLA/beta-TCP composites with weight ratios of 1:1, 2:1, and 3:1 was performed in phosphate buffer saline solution (PBS) (154 mM, pH 7.4) at 37 degrees C. The effect of in vitro degradation time for PDLLA/beta-TCP composites on shape-memory properties was studied by scanning electron microscopy, differential scanning calorimetry, gel permeation chromatography, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The changes of structural morphology, glass transition temperature (T(g)), molecular weight, and weight loss of composites matrix and pH change of degradation medium indicated that shape-memory effects at different degradation time were nonlinearly influenced because of the breaking down of polymer chain and the formation of degradation products. Furthermore, the results from XRD and FTIR implied that the degradation products, for example, hydroxyapatite (HA), calcium hydrogen phosphate (CaHPO(4)), and calcium pyrophosphate (Ca(2)P(2)O(7)) phases also had some effects on shape-memory properties during the degradation.

  1. Thermal Degradation, Mechanical Properties and Morphology of Wheat Straw Flour Filled Recycled Thermoplastic Composites

    PubMed Central

    Mengeloglu, Fatih; Karakus, Kadir

    2008-01-01

    Thermal behaviors of wheat straw flour (WF) filled thermoplastic composites were measured applying the thermogravimetric analysis and differential scanning calorimetry. Morphology and mechanical properties were also studied using scanning electron microscope and universal testing machine, respectively. Presence of WF in thermoplastic matrix reduced the degradation temperature of the composites. One for WF and one for thermoplastics, two main decomposition peaks were observed. Morphological study showed that addition of coupling agent improved the compatibility between WFs and thermoplastic. WFs were embedded into the thermoplastic matrix indicating improved adhesion. However, the bonding was not perfect because some debonding can also be seen on the interface of WFs and thermoplastic matrix. In the case of mechanical properties of WF filled recycled thermoplastic, HDPE and PP based composites provided similar tensile and flexural properties. The addition of coupling agents improved the properties of thermoplastic composites. MAPE coupling agents performed better in HDPE while MAPP coupling agents were superior in PP based composites. The composites produced with the combination of 50-percent mixture of recycled HDPE and PP performed similar with the use of both coupling agents. All produced composites provided flexural properties required by the ASTM standard for polyolefin-based plastic lumber decking boards. PMID:27879719

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

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

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

  3. Effect of enzymatic degradation of chitosan in polyhydroxybutyrate/chitosan/calcium phosphate composites on in vitro osteoblast response.

    PubMed

    Giretova, Maria; Medvecky, Lubomir; Stulajterova, Radoslava; Sopcak, Tibor; Briancin, Jaroslav; Tatarkova, Monika

    2016-12-01

    Polyhydroxybutyrate/chitosan/calcium phosphate composites are interesting biomaterials for utilization in regenerative medicine and they may by applied in reconstruction of deeper subchondral defects. Insufficient informations were found in recent papers about the influence of lysozyme degradation of chitosan in calcium phosphate/chitosan based composites on in vitro cytotoxicity and proliferation activity of osteoblasts. The effect of enzymatic chitosan degradation on osteoblasts proliferation was studied on composite films in which the porosity of origin 3D scaffolds was eliminated and the surface texture was modified. The significantly enhanced proliferation activity with faster population growth of osteoblasts were found on enzymatically degraded biopolymer composite films with α-tricalcium phosphate and nanohydroxyapatite. No cytotoxicity of composite films prepared from lysozyme degraded scaffolds containing a large fraction of low molecular weight chitosans (LMWC), was revealed after 10 days of cultivation. Contrary to above in the higher cytotoxicity origin untreated nanohydroxyapatite films and porous composite scaffolds. The results showed that the synergistic effect of surface distribution, morphology of nanohydroxyapatite particles, microtopography and the presence of LMWC due to chitosan degradation in composite films were responsible for compensation of the cytotoxicity of nanohydroxyapatite composite films or porous composite scaffolds.

  4. 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

  5. Degradation of Al/SiCp composites produced with rice-hull ash and aluminum cans.

    PubMed

    Escalera-Lozano, R; Gutiérrez, C A; Pech-Canul, M A; Pech-Canul, M I

    2008-01-01

    The use of recycling aluminum from beverage containers and rice-hull ash (RHA) offers to be an attractive alternative for the economic production of Al/SiCp composites. However, corrosion phenomena in the composites represent technological barriers yet to be resolved before they can be exploited to their full potential. A simple methodology involving characterization by XRD, SEM, EDX, FTIR and ICP was designed in order to investigate the causes of the rapid degradation in a humid environment of Al/SiCp composites produced with RHA and aluminum cans. Results reveal that the use of RHA was beneficial to avoid degradation through the formation and subsequent hydration of the Al4C3 phase. However with condensed moisture acting as an electrolyte, localized corrosion took place with aggressive damage manifested by the disintegration of the composite into a powdery mixture. The relevant corrosion mechanism was mainly attributed to microgalvanic coupling between the Mg2Si intermetallic compound and the matrix (although other phases such as SiC, Si, MgAl2O4 could also work as microcathodes).

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

    PubMed

    Davies, Peter

    2016-07-13

    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'.

  7. Fabrication of novel magnesium-matrix composites and their mechanical properties prior to and during in vitro degradation.

    PubMed

    Dezfuli, Sina Naddaf; Leeflang, Sander; Huan, Zhiguang; Chang, Jiang; Zhou, Jie

    2017-03-01

    In our previous study, we developed Mg-matrix composites with bredigite as the reinforcing phase and achieved improved degradation resistance in comparison with Mg. However, the effects of materials processing method and process parameters on the mechanical behavior of the composites before and during degradation were still unknown. This research was aimed at determining the mechanical properties of Mg-bredigite composites prior to and during degradation. It was found that by optimizing the process parameters of Pressure Assisted Sintering (PAS), low-porosity Mg-bredigite composites with strong interfaces between homogeneously distributed bredigite particles and the Mg matrix could be fabricated. By reinforcing Mg with 20vol% bredigite particles, the ultimate compressive strength and ductility of Mg increased by 67% and 111%, respectively. The in vitro degradation rate of the Mg-20% bredigite composite in a cell culture medium was 24 times lower than that of monolithic Mg. As a result of retarded degradation, the mechanical properties of the composite after 12 days of immersion in the cell culture medium were comparable to those of cortical bone. The encouraging results of this research warrant further investigations on the in vivo degradation behavior and mechanical properties of the composites. Copyright © 2016 Elsevier Ltd. All rights reserved.

  8. In vitro studies of degradation and bioactivity of aliphatic polyester composites

    NASA Astrophysics Data System (ADS)

    Chouzouri, Georgia

    In spite of numerous publications on the potential use of combinations of aliphatic polyester composites containing bioactive fillers for bone regeneration, little information exists on the combined in vitro mechanisms involving simultaneously diffusion for polymer degradation and bioactivity through nucleation and growth of apatite in simulated body fluid (SBF) solution. The objective of this study is to contribute to the understanding of the fundamentals in designing non-porous, solid materials for bone regeneration, from experimental data along with their engineering interpretation. Bioactivity, in terms of apatite growth, was assessed through several experimental methods such as scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray-diffraction (XRD) and changes in ion concentration. In the case of the six neat fillers evaluated, the filler shape, form and chemical structure showed significant differences in bioactivity response. Bioglass and calcium silicate fillers showed faster nucleation and growth rates in the screening experiments. Composites at 30% by weight filler were prepared by solution and/or melt mixing. Polycaprolactone (PCL) composites containing five different fillers were evaluated. Solution processed PCL/calcium silicate (CS) samples showed faster bioactivity, as determined by apatite growth, compared to melt mixed samples. The onset time for bioactivity was different for all PCL composites. The limited bioactivity in the PCL composites over longer periods of time could be attributed to the PCL hydrophobicity leading to a slow polymer degradation rate, and also to the lack of SBF replenishment. For both polylactic acid (PLA) composites containing CS and bioglass, significant growth was observed after one week and in the case of CS was still evident after four weeks immersion. However, at prolonged time periods no further bioactivity was observed, although ion release results indicated a faster release rate that would

  9. Preparation and photocatalytic properties of TiO2/mica composite for acetaldehyde degradation

    NASA Astrophysics Data System (ADS)

    Ozawa, Masakuni; Matui, Hidetomo; Suzuki, Suguru

    2016-01-01

    TiO2/mica composite was prepared by mixing mica and acidic solution of hydrolyzed titanium tetraisopropoxide, and characterized by X-ray diffraction (XRD), thermogravimetry and differential thermal analysis (TG-DTA), and N2 adsorption measurement. The results of experiments showed that the material had a catalytic composite powder structure containing pillared fragments with TiO2 after calcination at 300-800 °C. The resulting TiO2/mica exhibited good thermal stability, as indicated by its porosity and surface area, and interlayer stability of powders after calcination at 800 °C. The photocatalytic performances of these porous mica/TiO2 composites were evaluated by gaseous acetaldehyde degradation. The superior photocatalyic property was demonstrated and the maximum removal efficiency was up to 99% within 90 min, and the reaction kinetics was discussed.

  10. Factors influencing the thermally-induced strength degradation of B/Al composites

    NASA Technical Reports Server (NTRS)

    Dicarlo, J. A.

    1982-01-01

    Literature data related to the thermally-induced strength degradation of B/Al composites were examined in the light of fracture theories based on reaction-controlled fiber weakening. Under the assumption of a parabolic time-dependent growth for the interfacial reaction product, a Griffith-type fracture model was found to yield simple equations whose predictions were in good agreement with data for boron fiber average strength and for B/Al axial fracture strain. The only variables in these equations were the time and temperature of the thermal exposure and an empirical factor related to fiber surface smoothness prior to composite consolidation. Such variables as fiber diameter and aluminum alloy composition were found to have little influence. The basic and practical implications of the fracture model equations are discussed.

  11. Thermal Degradation, Mechanical Properties and Morphology of Wheat Straw Flour Filled Recycled Thermoplastic Composites.

    PubMed

    Mengeloglu, Fatih; Karakus, Kadir

    2008-01-24

    Thermal behaviors of wheat straw flour (WF) filled thermoplastic compositeswere measured applying the thermogravimetric analysis and differential scanningcalorimetry. Morphology and mechanical properties were also studied using scanningelectron microscope and universal testing machine, respectively. Presence of WF inthermoplastic matrix reduced the degradation temperature of the composites. One for WFand one for thermoplastics, two main decomposition peaks were observed. Morphologicalstudy showed that addition of coupling agent improved the compatibility between WFs andthermoplastic. WFs were embedded into the thermoplastic matrix indicating improvedadhesion. However, the bonding was not perfect because some debonding can also be seenon the interface of WFs and thermoplastic matrix. In the case of mechanical properties ofWF filled recycled thermoplastic, HDPE and PP based composites provided similar tensileand flexural properties. The addition of coupling agents improved the properties ofthermoplastic composites. MAPE coupling agents performed better in HDPE while MAPPcoupling agents were superior in PP based composites. The composites produced with thecombination of 50-percent mixture of recycled HDPE and PP performed similar with theuse of both coupling agents. All produced composites provided flexural properties requiredby the ASTM standard for polyolefin-based plastic lumber decking boards.

  12. Continuous and cyclic thermal exposure induced degradation in boron reinforced 6061 aluminum composites

    NASA Technical Reports Server (NTRS)

    Olsen, G. C.; Tompkins, S. S.

    1977-01-01

    Boron reinforced 6061 aluminum (B/Al) composite was continuously exposed at 728 K for up to 240 hours and cyclically exposed between 293 K and 728 K for up to 6000 three-minute cycles. Room temperature tensile strengths were measured and the specimens were metallographically examined. The data suggest that, in addition to AlB2 formation, magnesium in the matrix diffused to the reaction layer and formed (Al,Mg)B2. This formation could weaken the matrix and embrittle the reaction layer. Continuous exposure degraded the strength of the B/Al specimens about 28% in 240 hours. However, the fracture mode, one indicative of high strength interfaces, did not change. The strength degradation was attributed to crack initiation in the brittle reaction layer causing stress concentrations in the fibers. Cyclic exposure degraded the strength of the B/Al about 34% in 6000 cycles. The fracture mode of the cyclic exposure specimens showed transition toward a mode characteristic of low interfacial strength. The lower interfacial strengths were attributed to stress fields induced by differential thermal expansion. Cyclic exposure degraded the strength of the B/Al specimens more than continuous exposure for similar cumulative exposure times.

  13. Photocatalytic performance of TiO2-zeolite templated carbon composites in organic contaminant degradation.

    PubMed

    Donphai, Waleeporn; Kamegawa, Takashi; Chareonpanich, Metta; Nueangnoraj, Khanin; Nishihara, Hirotomo; Kyotani, Takashi; Yamashita, Hiromi

    2014-12-07

    TiO2 composites with zeolite templated carbon (TiO2-ZTC) and activated carbon (TiO2-AC) were prepared and used as the photocatalysts for comparative studies with pure TiO2. TiO2-ZTC exhibited the highest rate of methylene blue degradation with a rate approximately 4 and 400 times higher than those of TiO2-AC and pure TiO2, respectively. Moreover, the highest catalytic performance of TiO2-ZTC in gas-phase degradation of acetone was approximately 1.1 and 12.9 times higher than TiO2-AC and pure TiO2, respectively. These outstanding performances could be attributed to high surface area, pore volume, and hydrophobic surface properties, leading to improvement in the adsorption properties of organic molecules.

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

    NASA Astrophysics Data System (ADS)

    Modi, K. B.; Natarajan, Kalithasan; Kathad, C. R.; Shah, S. J.; Raval, P. Y.; Pathak, T. K.; Meshiya, U. M.; Vyas, K. G.; Bajaj, H. C.; Tayade, R. J.

    2016-05-01

    Nanoparticles of semiconductor TiO2, zinc ferrite (ZnFe2O4) and ZnFe2O4-TiO2 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 N2 adsorption analysis while the presence of TiO2 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 irradiation of ultraviolet light. The result revealed that 77, 73 and 70% of NB was degraded using TiO2, ZnFe2O4 and ZnFe2O4-TiO2 photocatalysts after 4h in the presence of UV irradiation. The composite photocatalyst was found easy to separate from the treated solution.

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

    SciTech Connect

    Modi, K. B.; Kathad, C. R.; Raval, P. Y.; Meshiya, U. M.; Vyas, K. G.; Natarajan, Kalithasan; Bajaj, H. C.; Tayade, R. J.; Shah, S. J.; Pathak, T. K.

    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 irradiation 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.

  16. Influence of the polymerization process on composite resistance to chemical degradation by food-simulating liquids.

    PubMed

    Yap, Adrian U J; Wattanapayungkul, P; Chung, S M

    2003-01-01

    This study determined the influence of curing lights and modes on composite resistance to chemical degradation by various food-simulating liquids. Two different types of curing light (Halogen [H]-Elipar Trilight, 3M-ESPE; LED [L]-Freelight, 3M-ESPE) and two curing modes (standard [S]; exponential [E) were evaluated in the study. Forty-five composite (Z100 [3M-ESPE]) specimens were made for each light-curing mode combination (HS, HE, LS and LE). The specimens were randomly divided into five groups of nine and exposed to the following food-simulating liquids (FSL) for one week at 37 degrees C: distilled water, 50% aqueous ethanol solution, heptane and citric acid. Specimens stored in air were used as control. After the one week conditioning period, hardness testing was conducted with a digital microhardness tester (load = 500 gf; dwell time = 15 seconds). Mean hardness (HK)/hardness deterioration (deltaHK) were subsequently computed and data was subjected to analysis using ANOVA/Scheffe's test (p < 0.05). The resistance of composite to chemical degradation by FSL was light/curing mode dependent. Significant differences in HK and deltaHK were observed among the four curing techniques after conditioning in some FSL and air. After conditioning in water and citric acid, specimens polymerized with HE underwent significantly more softening compared to specimens polymerized with HS, LS and LE.

  17. Effects of cultivars on ensiling characteristics, chemical composition, and ruminal degradability of pea silage.

    PubMed

    Mustafa, A F; Seguin, P; Ouellet, D R; Adelye, I

    2002-12-01

    A study was conducted to determine the effects of cultivar on ensiling characteristics, chemical composition and ruminal nutrient degradability of pea (Pisum sativum L.) silage. The cultivars evaluated were Lenca (L), Carneval (C), and Delta (D). Peas were field-grown and forage was harvested and ensiled in mini-silos for 0, 2, 4, 8, 16, and 70 d. The ensiled forage of all cultivars went through a rapid fermentation with a sharp reduction in pH during the first 2 days of ensiling. Extensive proteolysis took place between 0 and 2 d as indicated by a reduction in true protein and neutral detergent insoluble protein (NDICP) and an increase in nonprotein nitrogen. Chemical analysis of the 70 d silage showed that cultivar L contained higher neutral detergent fiber (NDF) and acid detergent fiber and lower starch levels than C and D. Crude protein was highest for C (20.5% DM), intermediate for D (19.0% DM) and lowest for L (17.9% DM). Distribution of protein fractions showed that L contains lower soluble protein and higher NDICP levels than the other two pea cultivars. However, no difference in acid detergent insoluble protein levels was observed between the three cultivars. Results of the in situ incubation experiment indicated that L had lower ruminal DM (69.2 vs 74.0%) and CP (84.1 vs 90.6%) degradabilities than C or D. However, ruminal degradability of NDF was similar among the three cultivars (average of 32.9%). It was concluded that chemical composition and ruminal nutrient degradability of pea silage are significantly influenced by cultivars.

  18. Influence of dynamic compressive loading on the in vitro degradation behavior of pure PLA and Mg/PLA composite.

    PubMed

    Li, Xuan; Qi, Chenxi; Han, Linyuan; Chu, Chenglin; Bai, Jing; Guo, Chao; Xue, Feng; Shen, Baolong; Chu, Paul K

    2017-08-04

    The effects of dynamic compressive loading on the in vitro degradation behavior of pure poly-lactic acid (PLA) and PLA-based composite unidirectionally reinforced with micro-arc oxidized magnesium alloy wires (Mg/PLA) are investigated. Dynamic compressive loading is shown to accelerate degradation of pure PLA and Mg/PLA. As the applied stress is increased from 0.1 MPa to 0.9 MPa or frequency from 0.5 Hz to 2.5 Hz, the overall degradation rate goes up. After immersion for 21 days at 0.9 MPa and 2.5 Hz, the bending strength retention of the composite and pure PLA is 60.1% and 50%, respectively. Dynamic loading enhances diffusion of small acidic molecules resulting in significant pH decrease in the immersion solution. The synergistic reaction between magnesium alloy wires and PLA in the composite is further clarified by electrochemical tests. The degradation behavior of the pure PLA and PLA matrix in the composite under dynamic conditions obey the first order degradation kinetics and a numerical model is postulated to elucidate the relationship of the bending strength, stress, frequency, and immersion time under dynamic conditions. We systematically study the influence of dynamic loading on the degradation behavior of pure PLA and Mg/PLA. Dynamic compressive loading is shown to accelerate degradation of pure PLA and Mg/PLA. The synergistic reaction between magnesium alloy wires and PLA in the composite is firstly clarified by electrochemical tests. The degradation behavior of the pure PLA and PLA matrix in the composite under dynamic conditions obey the first order degradation kinetics. Then, a numerical model is postulated to elucidate the relationship of the bending strength, stress, frequency, and immersion time under dynamic conditions. Copyright © 2017. Published by Elsevier Ltd.

  19. Degradation Potential of Bulk Versus Incrementally Applied and Indirect Composites: Color, Microhardness, and Surface Deterioration.

    PubMed

    El Gezawi, M; Kaisarly, D; Al-Saleh, H; ArRejaie, A; Al-Harbi, F; Kunzelmann, K H

    This study investigated the color stability and microhardness of five composites exposed to four beverages with different pH values. Composite discs were produced (n=10); Filtek Z250 (3M ESPE) and Filtek P90 (3M ESPE) were applied in two layers (2 mm, 20 seconds), and Tetric N-Ceram Bulk Fill (TetricBF, Ivoclar Vivadent) and SonicFill (Kerr) were applied in bulk (4 mm) and then light cured (40 seconds, Ortholux-LED, 1600 mW/cm(2)). Indirect composite Sinfony (3M ESPE) was applied in two layers (2 mm) and cured (Visio system, 3M ESPE). The specimens were polished and tested for color stability; ΔE was calculated using spectrophotometer readings. Vickers microhardness (50 g, dwell time=45 seconds) was assessed on the top and bottom surfaces at baseline, 40 days of storage, subsequent repolishing, and 60 days of immersion in distilled water (pH=7.0), Coca-Cola (pH=2.3), orange juice (pH=3.75), or anise (pH=8.5) using scanning electron microscopy (SEM). The materials had similar ΔE values (40 days, p>0.05), but TetricBF had a significantly greater ΔE than P90 or SF (40 days). The ΔE was less for P90 and TetricBF than for Z250, SonicFill, and Sinfony (60 days). Repolishing and further immersion significantly affected the ΔE (p<0.05) except for P90. All composites had significantly different top vs bottom baseline microhardnesses. This was insignificant for the Z250/water, P90/orange juice (40 days), and Sinfony groups (40 and 60 days). Immersion produced variable time-dependent deterioration of microhardness in all groups. Multivariate repeated measures analysis of variance with post hoc Bonferroni tests were used to compare the results. ΔE and microhardness changes were significantly inversely correlated at 40 days, but this relationship was insignificant at 60 days (Pearson test). SEM showed degradation (40 days) that worsened (60 days). Bulk-fill composites differ regarding color-stability and top-to-bottom microhardness changes compared with those of other

  20. Characterization of lignocellulosic compositions' degradation during chicken manure composting with added biochar by phospholipid fatty acid (PLFA) and correlation analysis.

    PubMed

    Liu, Ning; Zhou, Jialiang; Han, Lujia; Huang, Guangqun

    2017-05-15

    Biorefractory high polymer lignocellulosic compositions may limit rapid composting and stable decomposition. Because their degradation during composting is not well understood, the correlation with microbial community profiles was assessed to reveal degradation mechanism of lignocellulosic compositions. Testing of chicken manure aerobic composting with added biochar was performed using phospholipid fatty acid (PLFA) and correlation analysis. Results demonstrated a good composting effect with good dynamic correlation between microbial characteristic (PLFA) and lignocellulosic compositions' degradation ratio. The prediction model for hemicellulose degradation ratio (R(2)=0.97, SEP=3.24) and the prediction model for cellulose degradation ratio (R(3)=0.94, SEP=3.09), built using PLFA 16:0-18:2ω6c and PLFA 18:2ω6c-18:3ω3 as the arguments had good predictive ability. Based on microbial analysis and quantitative characterization of the degradation ratio, the prediction models provided methodological support for delineating the mechanism of lignocellulosic compositions' degradation during chicken manure aerobic composting with added biochar.

  1. Evaluating anthropogenic risk of grassland and forest habitat degradation using land-cover data

    Treesearch

    Kurt Riitters; James Wickham; Timothy Wade

    2009-01-01

    The effects of landscape context on habitat quality are receiving increased attention in conservation biology. The objective of this research is to demonstrate a landscape-level approach to mapping and evaluating the anthropogenic risks of grassland and forest habitat degradation by examining habitat context as defined by intensive anthropogenic land uses at multiple...

  2. Hydrolytic degradation of composites of poly(L-lactide-co-epsilon-caprolactone) 70/30 and β-tricalcium phosphate.

    PubMed

    Ahola, Niina; Veiranto, Minna; Rich, Jaana; Efimov, Alexander; Hannula, Markus; Seppälä, Jukka; Kellomäki, Minna

    2013-11-01

    There is an increasing need for synthetic bone substitute materials that decrease the need for allografts and autografts. In this study, composites of β-tricalcium phosphate and a biodegradable poly(L-lactide-co-ε-caprolactone) were manufactured using extrusion to form biodegradable composites with high β-tricalcium phosphate contents for osteoconductivity. The hydrolytic degradation of the composites containing 0, 10, 20, 35 and 50% of β-tricalcium phosphate was studied in vitro for 52 weeks. During the study, it was observed that β-tricalcium phosphate did not have an effect on the degradation rate of the polymer matrix. However, the crystallinity of the materials increased throughout the test series and changes in glass transition temperatures were also observed as the comonomer ratio of the polymer matrix changed as the degradation proceeded. The results show that the materials have desirable degradation properties and, thus, possess great potential as bioabsorbable and osteoconductive bone filling materials.

  3. One-step solvothermal synthesis of magnetic Fe3O4-graphite composite for Fenton-like degradation of levofloxacin.

    PubMed

    Wang, Long; Zhao, Qi; Hou, Juan; Yan, Jin; Zhang, Fengshuang; Zhao, Jiahui; Ding, Hong; Li, Yi; Ding, Lan

    2016-01-01

    A novel Fe3O4-graphite composite was prepared, characterized, and investigated as a heterogeneous Fenton-like catalyst for the degradation of levofloxacin (LEV) in an aqueous solution. The results revealed that the Fe3O4-graphite composite exhibited excellent properties for the degradation and mineralization of LEV, achieving a nearly complete degradation of 50 mg L(-1) LEV in 15 min and 48% of total organic carbon removal in 60 min under optimal conditions. A large electronic conjugation structure exists in graphite, which may lead to the fast production of •OH radical species because of the easy reduction of Fe(III) to Fe(II). In addition, we observed that the graphite can degrade LEV in the presence of H2O2. Therefore, the synergistic results of the graphite structure and Fe3O4 magnetic nanoparticles (MNPs) may contribute to the high catalytic activity of the Fe3O4-graphite composite. Compared with pure Fe3O4 MNPs, lesser iron leaching of the Fe3O4-graphite composite was observed during the degradation of LEV. The degradation efficiency of LEV remained approximately 80% at the fifth recycling run, which indicates that the Fe3O4-graphite composite has potential applications in water treatment for removing organic pollutants.

  4. High-Risk Human Papillomavirus E7 Proteins Target PTPN14 for Degradation

    PubMed Central

    Münger, Karl; Howley, Peter M.

    2016-01-01

    ABSTRACT The major transformation activity of the high-risk human papillomaviruses (HPV) is associated with the E7 oncoprotein. The interaction of HPV E7 with retinoblastoma family proteins is important for several E7 activities; however, this interaction does not fully account for the high-risk E7-specific cellular immortalization and transformation activities. We have determined that the cellular non-receptor protein tyrosine phosphatase PTPN14 interacts with HPV E7 from many genus alpha and beta HPV types. We find that high-risk genus alpha HPV E7, but not low-risk genus alpha or beta HPV E7, is necessary and sufficient to reduce the steady-state level of PTPN14 in cells. High-risk E7 proteins target PTPN14 for proteasome-mediated degradation, which requires the ubiquitin ligase UBR4, and PTPN14 is degraded by the proteasome in HPV-positive cervical cancer cell lines. Residues in the C terminus of E7 interact with the C-terminal phosphatase domain of PTPN14, and interference with the E7-PTPN14 interaction restores PTPN14 levels in cells. Finally, PTPN14 degradation correlates with the retinoblastoma-independent transforming activity of high-risk HPV E7. PMID:27651363

  5. Degradable Chitosan-Collagen Composites Seeded with Cells as Tissue Engineered Heart Valves.

    PubMed

    Fu, Jian-Hua; Zhao, Man; Lin, Yan-Rong; Tian, Xu-Dong; Wang, Ya-Dong; Wang, Zhen-Xing; Wang, Le-Xin

    2017-01-01

    Degradable collagen-chitosan composite materials have been used to fabricate tissue engineered heart valves. The aims of this study were to demonstrate that the collagen-chitosan composite scaffolds are cytocompatible, and endothelial cells can be differentiated from bone marrow mesenchymal stem cells (BMSCs) when seeded onto the scaffolds. The adhesion and biological activities of the seeded cells were also investigated. Collagen-chitosan composite material was used as the cell matrix, and smooth muscle cells, fibroblasts and BMSCs were used as seed cells. After four weeks of in vitro culture, the smooth muscle cells, fibroblasts, and BMSCs were sequentially seeded into the collagen-chitosan composite material. After four weeks in culture, the cellular density and activity were assessed on segments of the tissue engineered heart valve scaffolds to determine the cell viability and proliferation in the collagen-chitosan composite material. The tissue engineered heart valves stained positively for both smooth muscle actin and endothelial cell factor VIII, suggesting that the seeded cells were in fact smooth muscle cells, fibroblasts, and endothelial cells. The 6-ketone prostaglandin content, as measured by radioimmunoassay, of the collagen-chitosan cell culture fluid was higher than that of the serum-free medium (P <0.01). Light and electron microscopy showed that the seeded cells had shapes similar to the morphology of smooth muscle cells, fibroblasts, and endothelial cells. Endothelial cells can be differentiated from BMSCs when seeded onto the collagen-chitosan composite scaffolds. The seeded cells retained their biological activity after being cultured in vitro and seeded into the collagen-chitosan composite material. Copyright © 2016 Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) and the Cardiac Society of Australia and New Zealand (CSANZ). Published by Elsevier B.V. All rights reserved.

  6. Graphene-SnO2 composites for highly efficient photocatalytic degradation of methylene blue under sunlight.

    PubMed

    Seema, Humaira; Christian Kemp, K; Chandra, Vimlesh; Kim, Kwang S

    2012-09-07

    Graphene sheets decorated with SnO(2) nanoparticles (RGO-SnO(2)) were prepared via a redox reaction between graphene oxide (GO) and SnCl(2). Graphene oxide (GO) was reduced to graphene (RGO) and Sn(2+) was oxidized to SnO(2) during the redox reaction, leading to a homogeneous distribution of SnO(2) nanoparticles on RGO sheets. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images show uniform distribution of the nanoparticles on the RGO surface and high-resolution transmission electron microscopy (HRTEM) shows an average particle size of 3-5 nm. The RGO-SnO(2) composite showed an enhanced photocatalytic degradation activity for the organic dye methylene blue under sunlight compared to bare SnO(2) nanoparticles. This result leads us to believe that the RGO-SnO(2) composite could be used in catalytic photodegradation of other organic dyes.

  7. Partially degradable film/fabric composites: textile scaffolds for liver cell culture.

    PubMed

    Karamuk, E; Mayer, J; Wintermantel, E; Akaike, T

    1999-09-01

    In this study, a composite scaffold combining textile superstructures and biomimetic glycopolymers is introduced, which may allow engineering of organotypic liver tissue in vitro. Woven poly(ethylene therephtalat) (PET) fabrics were coated on one side with a thin biodegradable polymer film (poly[D-L-lactic-co-glycolic acid] PLGA), in order to obtain a polar structure. The composite structure ensured the stability of the membrane during in vitro degradation, independently of mesh size. Matrix porosity increased when a polymer blend matrix was used. For hepatocyte culturing studies, the scaffolds were additionally coated with an artificial glycopolymer (poly[N-p-vinylbenzyl-D-lactoamide], PVLA) in order to improve cell attachment. It was observed that formation of aggregates depends on the scaffold geometry as well as on the pretreatment and medium conditions. After 4 days in culture, the pores of the fabric were filled with aggregates illustrating the possibility of immobilizing hepatocyte aggregates in well-defined spatial configurations on textile structures.

  8. Photocatalytic degradation of dye using CeO2/SCB composite catalysts

    NASA Astrophysics Data System (ADS)

    Channei, Duangdao; Nakaruk, Auppatham; Phanichphant, Sukon

    2017-08-01

    The main task of the present work is to enhance the photocatalytic degradation efficiency of methylene blue (MB) by using CeO2/sugarcane bagasse (SCB) composite catalysts. Homogeneous precipitation method was used to synthesis CeO2-SCB composite catalysts by adding SCB powder to precursor solution of Ce base-metal. The structural analytical data indicated the pure cubic fluorite structure of CeO2. Morphological images revealed the coating of CeO2 layer on high surface area of SCB core-shell. The chemical analysis presented spectrum of the Ce 3d in CeO2/SCB sample existed in the form of the Ce3 + and Ce4 + mixed- valence states. Optical spectra showed the shift of absorption edge towards longer visible region upon supporting CeO2 with SCB. The main chemical composition of the SCB was K, Ca, and Si. Furthermore, recombination of the photogenerated electrons and holes was identified by photoluminescence techniques (PL), the data suggested inhibition of electron-hole pairs recombination by the cations from SCB loaded in CeO2/SCB composite. Photocatalytic activity of CeO2/SCB catalyst was investigated via the degradation of MB under UV-A irradiation. Experimental kinetic data followed the pseudo-first order model. CeO2 supported with SCB adsorbent had higher photocatalytic activity in dye wastewater treatment compared to the pure CeO2. The proposed mechanism explaining the high photocatalytic efficiency of CeO2/SCB was associated with high surface properties and the suppression of recombination of the photogenerated electron-hole pairs by the SCB adsorbent.

  9. Gene expression patterns of wood decay fungi Postia placenta and Phanerochaete chrysosporium are influenced by wood substrate composition during degradation

    Treesearch

    Oleksandr Skyba; Daniel Cullen; Carl J. Douglas; Shawn D. Mansfield

    2016-01-01

    Identification of the specific genes and enzymes involved in the fungal degradation of lignocellulosic biomass derived from feedstocks with various compositions is essential to the development of improved bioenergy processes. In order to elucidate the effect of substrate composition on gene expression in wood-rotting fungi, we employed microarrays based on the...

  10. Thermal properties of extruded injection-molded poly (lactic acid) and milkweed composites: degradation kinetics and enthalpic relaxation

    USDA-ARS?s Scientific Manuscript database

    Currently, most polymer composites utilize petroleum-based materials that are non-degradable and difficult to recycle or incur substantial cost for disposal. Green composites can be used in nondurable limited applications. In order to determine the degree of compatibility between Poly (lactic Acid...

  11. Study of the thermal degradation mechanism of a composite propellant. [using electron microscopes

    NASA Technical Reports Server (NTRS)

    Schmidt, W. G.

    1975-01-01

    The current experimental program was designed to systematically investigate the role of the oxidizer in the thermal degradation process of composite propellants. The scanning electron microscope (SEM) was used to examine the failure sites in thermally degraded propellant samples. The formulation variables tested were oxidizer purity, oxidizer particle size, and oxidizer to binder bonding agent. The binder, a saturated hydrocarbon, was kept constant throughout the experiments. The oxidizers were: AP, chlorate-doped AP, arsenate-doped AP, and phosphate-doped AP. The oxidizer particle size distribution was 60% of the large fraction and 40% of the small fraction. The bonding agent, when present, was used at the 0.15% level. The data showed that both the oxidizer purity and particle size had an important affect on the thermal degradation process. The affect of the oxidizer particle size was more noticeable at the higher temperature and stress levels. An examination of the failure site, by SEM, of propellants subject to these latter conditions indicated that the fracturing of the large oxidizer particles led to the propellant cracking.

  12. Effect of dietary starch level and its rumen degradability on lamb meat fatty acid composition.

    PubMed

    Oliveira, Maria A; Alves, Susana P; Santos-Silva, José; Bessa, Rui J B

    2017-01-01

    Forty lambs were fed one of four diets supplemented with a linseed and sunflower oil blend but differing in starch level (mid, ≈35 vs. high, ≈50%) and starch rumen degradability (mid, ≈70 vs. high, ≈80%). The effects of diet on growth, carcass traits and meat fatty acid (FA) composition, with emphasis on biohydrogenation intermediates were evaluated. Lambs stayed on trial for 5weeks until slaughter. Treatment had no effect on animal performance and carcass traits. High-degradability diets decreased (P=0.04) meat shear force compared with mid-degradability diets. Lipid content of meat was unaffected by the diet. Mid-starch diets increased (P<0.05) the saturated FA and cis-MUFA but decreased (P<0.05) the trans-MUFA, particularly the t10-18:1, when compared with high-starch diets. The t11-18:1 (0.7% of total FA) and c9,t11-18:2 (<0.3%) remained low and the 18:3n-3 remained high (1.74%) and unaffected by diet. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. Effects of resource addition on recovery of production and plant functional composition in degraded semiarid grasslands.

    PubMed

    Chen, Qing; Hooper, David U; Li, Hui; Gong, Xiao Ying; Peng, Fei; Wang, Hong; Dittert, Klaus; Lin, Shan

    2017-02-28

    Degradation of semiarid ecosystems from overgrazing threatens a variety of ecosystem services. Rainfall and nitrogen commonly co-limit production in semiarid grassland ecosystems; however, few studies have reported how interactive effects of precipitation and nitrogen addition influence the recovery of grasslands degraded by overgrazing. We conducted a 6-year experiment manipulating precipitation (natural precipitation and simulated wet year precipitation) and nitrogen (0, 25 and 50 kg N ha(-1)) addition at two sites with different histories of livestock grazing (moderately and heavily grazed) in Inner Mongolian steppe. Our results suggest that recovery of plant community composition and recovery of production can be decoupled. Perennial grasses provide long-term stability of high-quality forage production in this system. Supplemental water combined with exclosures led, in the heavily grazed site, to the strongest recovery of perennial grasses, although widespread irrigation of rangeland is not a feasible management strategy in many semiarid and arid regions. N fertilization combined with exclosures, but without water addition, increased dominance of unpalatable annual species, which in turn retarded growth of perennial species and increased inter-annual variation in primary production at both sites. Alleviation of grazing pressure alone allowed recovery of desired perennial species via successional processes in the heavily grazed site. Our experiments suggest that recovery of primary production and desirable community composition are not necessarily correlated. The use of N fertilization for the management of overgrazed grassland needs careful and systematic evaluation, as it has potential to impede, rather than aid, recovery.

  14. Risk assessment and predator learning in a changing world: understanding the impacts of coral reef degradation

    NASA Astrophysics Data System (ADS)

    Chivers, Douglas P.; McCormick, Mark I.; Allan, Bridie J. M.; Ferrari, Maud C. O.

    2016-09-01

    Habitat degradation is among the top drivers of the loss of global biodiversity. This problem is particularly acute in coral reef system. Here we investigated whether coral degradation influences predator risk assessment and learning for damselfish. When in a live coral environment, Ambon damselfish were able to learn the identity of an unknown predator upon exposure to damselfish alarm cues combined with predator odour and were able to socially transmit this learned recognition to naïve conspecifics. However, in the presence of dead coral water, damselfish failed to learn to recognize the predator through alarm cue conditioning and hence could not transmit the information socially. Unlike alarm cues of Ambon damselfish that appear to be rendered unusable in degraded coral habitats, alarm cues of Nagasaki damselfish remain viable in this same environment. Nagasaki damselfish were able to learn predators through conditioning with alarm cues in degraded habitats and subsequently transmit the information socially to Ambon damselfish. Predator-prey dynamics may be profoundly affected as habitat degradation proceeds; the success of one species that appears to have compromised predation assessment and learning, may find itself reliant on other species that are seemingly unaffected by the same degree of habitat degradation.

  15. Risk assessment and predator learning in a changing world: understanding the impacts of coral reef degradation

    PubMed Central

    Chivers, Douglas P.; McCormick, Mark I.; Allan, Bridie J. M.; Ferrari, Maud C. O.

    2016-01-01

    Habitat degradation is among the top drivers of the loss of global biodiversity. This problem is particularly acute in coral reef system. Here we investigated whether coral degradation influences predator risk assessment and learning for damselfish. When in a live coral environment, Ambon damselfish were able to learn the identity of an unknown predator upon exposure to damselfish alarm cues combined with predator odour and were able to socially transmit this learned recognition to naïve conspecifics. However, in the presence of dead coral water, damselfish failed to learn to recognize the predator through alarm cue conditioning and hence could not transmit the information socially. Unlike alarm cues of Ambon damselfish that appear to be rendered unusable in degraded coral habitats, alarm cues of Nagasaki damselfish remain viable in this same environment. Nagasaki damselfish were able to learn predators through conditioning with alarm cues in degraded habitats and subsequently transmit the information socially to Ambon damselfish. Predator-prey dynamics may be profoundly affected as habitat degradation proceeds; the success of one species that appears to have compromised predation assessment and learning, may find itself reliant on other species that are seemingly unaffected by the same degree of habitat degradation. PMID:27611870

  16. Preparation, Characterization and Thermal Degradation of Polyimide (4-APS/BTDA)/SiO2 Composite Films

    PubMed Central

    Ahmad, Mansor Bin; Gharayebi, Yadollah; Salit, Mohd. Sapuan; Hussein, Mohd. Zobir; Ebrahimiasl, Saeideh; Dehzangi, Arash

    2012-01-01

    Polyimide/SiO2 composite films were prepared from tetraethoxysilane (TEOS) and poly(amic acid) (PAA) based on aromatic diamine (4-aminophenyl sulfone) (4-APS) and aromatic dianhydride (3,3,4,4-benzophenonetetracarboxylic dianhydride) (BTDA) via a sol-gel process in N-methyl-2-pyrrolidinone (NMP). The prepared polyimide/SiO2 composite films were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and thermogravimetric analysis (TGA). The FTIR results confirmed the synthesis of polyimide (4-APS/BTDA) and the formation of SiO2 particles in the polyimide matrix. Meanwhile, the SEM images showed that the SiO2 particles were well dispersed in the polyimide matrix. Thermal stability and kinetic parameters of the degradation processes for the prepared polyimide/SiO2 composite films were investigated using TGA in N2 atmosphere. The activation energy of the solid-state process was calculated using Flynn–Wall–Ozawa’s method without the knowledge of the reaction mechanism. The results indicated that thermal stability and the values of the calculated activation energies increased with the increase of the TEOS loading and the activation energy also varied with the percentage of weight loss for all compositions. PMID:22606014

  17. Preparation, characterization and thermal degradation of polyimide (4-APS/BTDA)/SiO(2) composite films.

    PubMed

    Ahmad, Mansor Bin; Gharayebi, Yadollah; Salit, Mohd Sapuan; Hussein, Mohd Zobir; Ebrahimiasl, Saeideh; Dehzangi, Arash

    2012-01-01

    Polyimide/SiO(2) composite films were prepared from tetraethoxysilane (TEOS) and poly(amic acid) (PAA) based on aromatic diamine (4-aminophenyl sulfone) (4-APS) and aromatic dianhydride (3,3,4,4-benzophenonetetracarboxylic dianhydride) (BTDA) via a sol-gel process in N-methyl-2-pyrrolidinone (NMP). The prepared polyimide/SiO(2) composite films were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and thermogravimetric analysis (TGA). The FTIR results confirmed the synthesis of polyimide (4-APS/BTDA) and the formation of SiO(2) particles in the polyimide matrix. Meanwhile, the SEM images showed that the SiO(2) particles were well dispersed in the polyimide matrix. Thermal stability and kinetic parameters of the degradation processes for the prepared polyimide/SiO(2) composite films were investigated using TGA in N(2) atmosphere. The activation energy of the solid-state process was calculated using Flynn-Wall-Ozawa's method without the knowledge of the reaction mechanism. The results indicated that thermal stability and the values of the calculated activation energies increased with the increase of the TEOS loading and the activation energy also varied with the percentage of weight loss for all compositions.

  18. Enhanced photoelectrocatalytic activity for dye degradation by graphene-titania composite film electrodes.

    PubMed

    Wang, Peifang; Ao, Yanhui; Wang, Chao; Hou, Jun; Qian, Jin

    2012-07-15

    Graphene-titania composite film electrodes have been fabricated by a dip-coating method. Transmission electron microscopy (TEM) images show that the titania nanoparticles were dispersed uniformly, with only a little aggregation on the surface and edges of the graphene sheets. XRD analysis showed that the composite electrodes comprised the anatase phase of titania with just a little rutile phase. The photoelectrocatalytic activities of the as-prepared samples were investigated by studies of the degradation of Reactive Brilliant Red dye X-3B (C.I. reactive red 2). An enhancement of the photocurrents was observed using the graphene-titania composite electrodes, compared with pure titania film electrodes, under UV light irradiation. This improvement is attributed to the following two reasons: enhanced migration efficiency of the photo-induced electrons and enhanced adsorption activity of the dye molecules. In addition, we investigated the effects of graphene content and pH values on the photoelectrocatalytic activity of the as-prepared composite film electrodes. Results showed that there was an optimal amount of 5% (initial graphite oxide content).

  19. Composite risk scores for predicting dementia.

    PubMed

    Stephan, Blossom C M; Tang, Eugene; Muniz-Terrera, Graciela

    2016-03-01

    A key priority in dementia research is the development of tools to identify individuals at high risk of dementia. This is important to prevent or delay dementia onset and as we move towards personalized medicine. Numerous models (n > 50) for predicting dementia have been developed. These vary in the number (0 to 20+) and type (e.g. demographics, health, neuropsychological, and genetic) of predictor variables used for risk calculation, follow-up length (1-20 years) and age at screening (mid vs laterlife). Evaluation of the models shows that most have moderate-to-poor predictive accuracy. Few have been externally validated, raising questions about their generalizability outside the cohorts from which they were developed. The results highlight that if additional models are proposed the field will be overwhelmed with many competing risk models, making it difficult to reach consensus on which is best. Numerous models for predicting dementia have been proposed but are limited by a lack of external validation and evaluation of economic impact. Innovative methods and data designs may be needed to improve derivation of dementia risk scores. Having a method for predicting dementia risk could transform medical research and allow for earlier testing of intervention strategies.

  20. Oxidatively Degradable Poly(thioketal urethane)/Ceramic Composite Bone Cements with Bone-Like Strength.

    PubMed

    McEnery, Madison A P; Lu, Sichang; Gupta, Mukesh K; Zienkiewicz, Katarzyna J; Wenke, Joseph C; Kalpakci, Kerem N; Shimko, Daniel; Duvall, Craig L; Guelcher, Scott A

    2016-01-01

    Synthetic bone cements are commonly used in orthopaedic procedures to aid in bone regeneration following trauma or disease. Polymeric cements like PMMA provide the mechanical strength necessary for orthopaedic applications, but they are not resorbable and do not integrate with host bone. Ceramic cements have a chemical composition similar to that of bone, but their brittle mechanical properties limit their use in weight-bearing applications. In this study, we designed oxidatively degradable, polymeric bone cements with mechanical properties suitable for bone tissue engineering applications. We synthesized a novel thioketal (TK) diol, which was crosslinked with a lysine triisocyanate (LTI) prepolymer to create hydrolytically stable poly(thioketal urethane)s (PTKUR) that degrade in the oxidative environment associated with bone defects. PTKUR films were hydrolytically stable for up to 6 months, but degraded rapidly (<1 week) under simulated oxidative conditions in vitro. When combined with ceramic micro- or nanoparticles, PTKUR cements exhibited working times comparable to calcium phosphate cements and strengths exceeding those of trabecular bone. PTKUR/ceramic composite cements supported appositional bone growth and integrated with host bone near the bone-cement interface at 6 and 12 weeks post-implantation in rabbit femoral condyle plug defects. Histological evidence of osteoclast-mediated resorption of the cements was observed at 6 and 12 weeks. These findings demonstrate that a PTKUR bone cement with bone-like strength can be selectively resorbed by cells involved in bone remodeling, and thus represent an important initial step toward the development of resorbable bone cements for weight-bearing applications.

  1. Influence of Mechanical and Chemical Degradation in the Surface Roughness, Gloss, and Color of Microhybrid Composites.

    PubMed

    Lemos, Cleidiel Aa; Mauro, Silvio J; Dos Santos, Paulo H; Briso, Andre Lf; Fagundes, Ticiane C

    2017-04-01

    The aim of this study was to investigate the association of different degradations on the roughness, gloss, and color changes of microhybrid composites. Ten specimens were prepared for Charisma, Amelogen Plus, Point 4, and Opallis resins. Surfaces were polished and baseline measurements of roughness, gloss, and color were recorded. Specimens were then submitted to chemical and mechanical challenges, and the specimens were reevaluated. Roughness and gloss were analyzed by Kruskal -Wallis and Dunn's test (p < 0.05). Color change (ΔE) was analyzed by one-way analysis of variance and Tukey's tests (p < 0.05). The initial and final data were compared using the Wilcoxon test (p < 0.05). Spearman test checked the correlation between the roughness and gloss (p < 0.05). Regarding surface roughness and gloss, there was no difference between composites before challenges. However, all composites showed a significant increase of roughness after challenges, with highest values for Charisma. The gloss was influenced by challenges, evidencing the best gloss for Point 4. Charisma showed the highest value of color change. There was no correlation between surface roughness and gloss for the initial analysis, and after the challenges. Composites were influenced by association of challenges, and Charisma showed the highest changes for roughness, gloss, and color. The type of composite resin influenced the properties of materials, which are surface roughness, gloss, and color change. The dentist should be aware of the performance of different brands, to choose the correct required composite resin for each type of patient or region to be restored.

  2. Effects of dry method esterification of starch on the degradation characteristics of starch/polylactic acid composites.

    PubMed

    Zuo, Ying Feng; Gu, Jiyou; Qiao, Zhibang; Tan, Haiyan; Cao, Jun; Zhang, Yanhua

    2015-01-01

    Maleic anhydride esterified corn starch was prepared by dry method. Esterified starch/polylactic acid (PLA) biodegradable composite was produced via melt extrusion method with blending maleic anhydride esterified corn starch and PLA. The influence of the dry method esterification of starch on the degradation characteristics of starch/PLA composites was investigated by the natural aging degradation which was soil burial method. Test results of mass loss rate showed that the first 30 days of degradation was mainly starch degradation, and the degradation rate of esterified starch/PLA (ES/PLA) was slower than that of native starch/PLA (NS/PLA). Therefore, the damage degree of ES/PLA on the surface and inside was smaller than that of NS/PLA, and the infrared absorption peak intensities of C-O, C=O and C-H were stronger than that of NS/PLA. With the increasing time of soil burial degradation, the damage degree of NS/PLA and ES/PLA on the exterior and interior were gradually increased, whereas the infrared absorption peak intensities of C-O, C=O and C-H were gradually decreased. The XRD diffraction peak intensity of PLA in composites showed an increased trend at first which was then followed by a decreased one along with the increasing time of soil burial degradation, indicating that the degradation of amorphous regions of PLA was earlier than its crystalline regions. When the soil burial time was the same, the diffraction peak intensity of PLA in ES/PLA was stronger than that of NS/PLA. If the degradation time was the same, T0, Ti and residual rate of thermal decomposition of NS/PLA were larger than those of ES/PLA. The tensile strength and bending strength of composites were decreased gradually with soil burial time increasing. Both the tensile strength and bending strength of ES/PLA were stronger than those of NS/PLA.

  3. Relating the Chemical Composition of Dissolved Organic Matter Draining Permafrost Soils to its Photochemical Degradation in Arctic Surface Waters.

    NASA Astrophysics Data System (ADS)

    Ward, C.; Cory, R. M.

    2015-12-01

    Thawing permafrost soils are expected to shift the chemical composition of DOM exported to and degraded in arctic surface waters. While DOM photo-degradation is an important component of the freshwater C cycle in the Arctic, the molecular controls on DOM photo-degradation remain poorly understood, making it difficult to predict how shifting chemical composition may alter DOM photo-degradation in arctic surface waters. To address this knowledge gap, we quantified the susceptibility of DOM draining the shallow organic mat and the deeper permafrost layer to complete photo-oxidation to CO₂ and partial photo-oxidation to compounds that remain in the DOM pool, and investigated changes in DOM chemical composition following sunlight exposure. DOM leached from the organic mat contained higher molecular weight, more oxidized and unsaturated aromatic species compared to permafrost DOM. Despite significant differences in initial chemical composition, permafrost and organic mat DOM had similar susceptibilities to complete photo-oxidation to CO₂. Concurrent losses of carboxyl moieties and shifts in chemical composition during photo-degradation indicated that carboxyl-rich tannin-like compounds in both DOM sources were likely photo-decarboxylated to CO₂. Permafrost DOM had a higher susceptibility to partial photo-oxidation compared to organic mat DOM, potentially due to a lower abundance of phenolic compounds that act as "antioxidants" and slow the oxidation of DOM. These results demonstrated how chemical composition controls the photo-degradation of DOM in arctic surface waters, and that DOM photo-degradation will likely remain an important component of the freshwater C budget in the Arctic with increased export of permafrost DOM to surface waters.

  4. Culture & differentiation of mesenchymal stem cell into osteoblast on degradable biomedical composite scaffold: In vitro study

    PubMed Central

    Jain, Krishan G.; Mohanty, Sujata; Ray, Alok R.; Malhotra, Rajesh; Airan, Balram

    2015-01-01

    degradable 3D composite may have great potential to be used as scaffold in bone tissue engineering. PMID:26831424

  5. Sustainable Energy Solutions Task 4.2: UV Degradation Prevention on Fiber-Reinforced Composite Blades

    SciTech Connect

    Janet M. Twomey, PhD

    2010-04-30

    EXECUTIVE SUMARRY Use of wind energy has expanded very quickly because of the energy prices, environmental concerns and improved efficiency of wind generators. Rather than using metal and alloy based wind turbine blades, larger size fiber (glass and carbon) reinforced composite blades have been recently utilized to increase the efficiency of the wind energy in both high and low wind potential areas. In the current composite manufacturing, pre-preg and vacuum-assisted/heat sensitive resin transfer molding and resin infusion methods are employed. However, these lighter, stiffer and stronger composite blades experience ultraviolet (UV) light degradation where polymers (epoxies and hardeners) used for the blades manufacturing absorb solar UV lights, and cause photolytic, thermo-oxidative and photo-oxidative reactions resulting in breaking of carbon-hydrogen bonds, polymer degradation and internal and external stresses. One of the main reasons is the weak protective coatings/paints on the composite blades. This process accelerates the aging and fatigue cracks, and reduces the overall mechanical properties of the blades. Thus, the lack of technology on coatings for blade manufacturing is forcing many government agencies and private companies (local and national windmill companies) to find a better solution for the composite wind blades. Kansas has a great wind potential for the future energy demand, so efficient wind generators can be an option for continuous energy production. The research goal of the present project was to develop nanocomposite coatings using various inclusions against UV degradation and corrosion, and advance the fundamental understanding of degradation (i.e., physical, chemical and physiochemical property changes) on those coatings. In pursuit of the research goal, the research objective of the present program was to investigate the effects of UV light and duration on various nanocomposites made mainly of carbon nanotubes and graphene nanoflakes

  6. Al2O3 fiber strength degradation in metal and intermetallic matrix composites

    NASA Technical Reports Server (NTRS)

    Draper, S. L.; Locci, I. E.

    1994-01-01

    The mechanisms for fiber damage in single crystal Al2O3 fiber-reinforced composites were investigated. Both fiber fragmentation and fiber strength degradation were observed in composites with a variety of matrix compositions. Four mechanisms that may be contributing to the fiber strength loss have been proposed and include matrix reaction, reaction with binders, residual stress-induced damage, and pressure from hot pressing. The effect of matrix reaction was separated from the other three effects by sputter-coating the matrices on cleaned fibers and annealing with a temperature profile that simulates processing conditions. These experiments revealed that Y and Cr in FeCrAlY base alloys and Zr in NiAl alloys reacted with the fiber, and grooves and adherent particles were formed on the fiber surface which were responsible for the strength loss. The effects of the matrix reaction appeared to dominate over the other possible mechanisms, although evidence for reaction with binders was also found. Ridges on the fiber surface, which reflected the grain boundaries of the matrix, were also observed. In order for single-crystal Al2O3 to be used as a fiber in MMC's and IMC's, a matrix or protective coating which minimizes matrix reaction during processing will be necessary. Of the matrices investigated, the Thermo-span(sup TM) alloy was the least damaging to fiber properties.

  7. Constitutive Modeling for Particle-Dispersed Composites with Degradation Due to Interfacial Damage

    SciTech Connect

    Chang, Huajian

    2002-07-01

    The composite materials are susceptible to interfacial delamination. The overall properties of composites will degrade dramatically if the interface between the particles and the matrix material undertakes interfacial damage. In present paper, the effects of interfacial delamination on the macro properties of composites are evaluated by the Equivalent Inclusion Method (EIM) with some modifications and supplementation on the conventional one, which was originally proposed by Eshelby. The meso-local behaviors of particle, matrix, as well as their interface are theoretically modeled, and the relationships between these behaviors and the macro stress/stress field are established. Upon modeling the damaged interface with spring layers and making equivalent of stress and strain inside a real particle to those inside the corresponding virtual inclusion, a modified Eshelby tensor and the damage-relevant tensor of the inclusions are derived explicitly. These tensors can be conveniently incorporated into the constitutive model, and make it available to assess the effects of delamination. Some numerical calculations are carried out to verify the performance of the present model. (author)

  8. The effect of mouthrinses on salivary sorption, solubility and surface degradation of a nanofilled and a hybrid resin composite.

    PubMed

    Almeida, Giselle Soares; Poskus, Laiza Tatiana; Guimarães, José Guilherme Antunes; da Silva, Eduardo Moreira

    2010-01-01

    This in vitro study evaluated the effect of mouth rinses on salivary sorption (Sp), solubility (Sl) and surface degradation of a nanofilled (Z350) and hybrid (P60) resin composite. Specimens (6 mm in diameter and 1 mm thick) of a nanofilled and hybrid resin composite were immersed in artificial saliva at 37 degrees C for seven days. Twice a day, the samples (n = 5) were immersed in 20 ml of three mouth rinses: Listerine, Plax Mint and Plax. A control group was maintained in artificial saliva. Sp and Sl were evaluated based on ISO 4049:2000(E) and surface degradation by scanning electron microscopy-SEM. The degree of conversion (DC%) of resin composites was obtained by using an FT-IR spectrometer equipped with an attenuated total reflectance crystal (ATR). The data were analyzed using the Student's t-test, ANOVA and Tukey test for multiple comparisons. No significant difference in DC% was found between the two resin composites (p < 0.05). The highest sorption rate was presented by the nanofilled composite exposed to Listerine (p < 0.05). The hybrid composite in the control group (artificial saliva) and Plax presented the lowest sorption (p < 0.05). The highest solubility was presented by the two resin composites exposed to Listerine (p < 0.05). SEM analysis showed that mouth rinses produced more severe surface degradation in the nanofilled composite.

  9. 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 (Ea) and pre-exponential factor (k0) consequently increasing the degradation rate of PLA. Under a compression stress of 1MPa, Ea and k0 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.

  10. Mechanical property degradation and chemical interactions in Borsic/titanium composite

    NASA Technical Reports Server (NTRS)

    Brewer, W. D.; Unnam, J.; Tenney, D. R.

    1979-01-01

    A study was undertaken to identify the mechanisms of mechanical property degradation in a Borsic (silicon-carbide coated boron) fiber reinforced Ti-3Al-2.5V composite exposed to elevated temperature. Samples containing 0.45 volume fraction of fibers were exposed, in vacuum, to temperatures from 700 K to 1255 K for times up to 240 hours. Room temperature tensile properties of unidirectional material were determined in both the longitudinal and transverse directions, before and after high-temperature exposure. Electron micro-probe analysis, scanning electron microscopy, and X-ray diffraction were used to determine the compounds formed and the extent of interaction between the boron, SiC coating, and matrix materials.

  11. Edible fungus degrade bisphenol A with no harmful effect on its fatty acid composition.

    PubMed

    Zhang, Chengdong; Li, Mingzhu; Chen, Xiaoyan; Li, Mingchun

    2015-08-01

    Bisphenol A (BPA) is an endocrine-disrupting chemical that is ubiquitous in the environment because of its broad industrial use. The authors report that the most widely cultivated mushroom in the world (i.e., white-rot fungus, Pleurotus ostreatus) efficiently degraded 10mg/L of BPA in 7 days. Extracellular laccase was identified as the enzyme responsible for this activity. LC-MS analysis of the metabolites revealed the presence of both low- and high-molecular-weight products obtained via oxidative cleavage and coupling reactions, respectively. In particular, an analysis of the fatty acid composition and chemical structure of the fungal mycelium demonstrated that exposure to BPA resulted in no harmful effects on this edible fungus. The results provide a better understanding of the environmental fate of BPA and its potential impact on food crops.

  12. Thermo-oxidative degradation assessment in quasi-isotropic carbon fiber/epoxy composites

    NASA Astrophysics Data System (ADS)

    Daily, Connor; Barnard, Dan J.; Jones, Roger W.; McClelland, John F.; Bowler, Nicola

    2015-03-01

    Components made from polymer matrix composites (PMCs) are finding increasing use in armored vehicles for the purpose of weight savings and fuel efficiency. Often times, these PMC components are installed next to engines, or in other high-temperature environments within the vehicle. The present work investigates the change in surface chemistry and its correlation with changes in the interlaminar shear strength (ILSS) due to accelerated thermo-oxidative aging of a quasi-isotropic carbon fiber reinforced epoxy laminate. Samples are aged isothermally at various temperatures whose selection is guided by degradation steps revealed by thermo-gravimetric analysis. Fourier transform infrared (FTIR) photoacoustic spectroscopy is utilized to identify the chemical changes due to aging, and compression-test results reveal a non-linear decrease in ILSS with increasing aging temperature. A correlation between the FTIR and ILSS data sets suggests that nondestructive FTIR techniques may be used for assessing ILSS of PMCs.

  13. Experimental insights into the importance of aquatic bacterial community composition to the degradation of dissolved organic matter

    PubMed Central

    Logue, Jürg B; Stedmon, Colin A; Kellerman, Anne M; Nielsen, Nikoline J; Andersson, Anders F; Laudon, Hjalmar; Lindström, Eva S; Kritzberg, Emma S

    2016-01-01

    Bacteria play a central role in the cycling of carbon, yet our understanding of the relationship between the taxonomic composition and the degradation of dissolved organic matter (DOM) is still poor. In this experimental study, we were able to demonstrate a direct link between community composition and ecosystem functioning in that differently structured aquatic bacterial communities differed in their degradation of terrestrially derived DOM. Although the same amount of carbon was processed, both the temporal pattern of degradation and the compounds degraded differed among communities. We, moreover, uncovered that low-molecular-weight carbon was available to all communities for utilisation, whereas the ability to degrade carbon of greater molecular weight was a trait less widely distributed. Finally, whereas the degradation of either low- or high-molecular-weight carbon was not restricted to a single phylogenetic clade, our results illustrate that bacterial taxa of similar phylogenetic classification differed substantially in their association with the degradation of DOM compounds. Applying techniques that capture the diversity and complexity of both bacterial communities and DOM, our study provides new insight into how the structure of bacterial communities may affect processes of biogeochemical significance. PMID:26296065

  14. The Sustainable Release of Vancomycin and Its Degradation Products From Nanostructured Collagen/Hydroxyapatite Composite Layers.

    PubMed

    Suchý, Tomáš; Šupová, Monika; Klapková, Eva; Horný, Lukáš; Rýglová, Šárka; Žaloudková, Margit; Braun, Martin; Sucharda, Zbyněk; Ballay, Rastislav; Veselý, Jan; Chlup, Hynek; Denk, František

    2016-03-01

    Infections of the musculoskeletal system present a serious problem with regard to the field of orthopedic and trauma medicine. The aim of the experiment described in this study was to develop a resorbable nanostructured composite layer with the controlled elution of antibiotics. The layer is composed of collagen, hydroxyapatite nanoparticles, and vancomycin hydrochloride (10 wt%). The stability of the collagen was enhanced by means of cross-linking. Four cross-linking agents were studied, namely an ethanol solution, a phosphate buffer solution of N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride/N-hydroxysuccinimide, genipin, and nordihydroguaiaretic acid. High performance liquid chromatography was used so as to characterize the in vitro release rates of the vancomycin and its crystalline degradation antibiotically inactive products over a 21-day period. The maximum concentration of the released active form of vancomycin (approximately 265 mg/L) exceeded the minimum inhibitory concentration up to an order of 17 times without triggering the burst releasing effect. At the end of the experiment, the minimum inhibitory concentration was exceeded by up to 6 times (approximately 100 mg/L). It was determined that the modification of collagen with hydroxyapatite nanoparticles does not negatively influence the sustainable release of vancomycin. The balance of vancomycin and its degradation products was observed after 14 days of incubation.

  15. Some effects of metallic substrate composition on degradation of thermal barrier coatings

    SciTech Connect

    Wright, I.G.; Pint, B.A.; Lee, W.Y.; Alexander, K.B.; Pruessner, K.

    1997-12-31

    Comparisons have been made in laboratory isothermal and cyclic oxidation tests of the degradation of oxide scales grown on single crystal superalloy substrates and bond coating alloys intended for use in thermal barrier coatings systems. The influence of desulfurization of the superalloy and bond coating, of reactive element addition to the bond coating alloy, and of oxidation temperature on the spallation behavior of the alumina scales formed was assessed from oxidation kinetics and from SEM observations of the microstructure and composition of the oxide scales. Desulfurization of nickel-base superalloy (in the absence of a Y addition) resulted in an increase in the lifetime of a state-of-the-art thermal barrier coating applied to it compared to a Y-free, non-desulfurized version of the alloy. The lifetime of the same ceramic coating applied without a bond coating to a non-desulfurized model alloy that formed an ideal alumina scale was also found to be at least four times longer than on the Y-doped superalloy plus state-of-the-art bond coating combination. Some explanations are offered of the factors controlling the degradation of such coatings.

  16. In-situ polymerisation of fully bioresorbable polycaprolactone/phosphate glass fibre composites: In vitro degradation and mechanical properties.

    PubMed

    Chen, Menghao; Parsons, Andrew J; Felfel, Reda M; Rudd, Christopher D; Irvine, Derek J; Ahmed, Ifty

    2016-06-01

    Fully bioresorbable composites have been investigated in order to replace metal implant plates used for hard tissue repair. Retention of the composite mechanical properties within a physiological environment has been shown to be significantly affected due to loss of the integrity of the fibre/matrix interface. This study investigated phosphate based glass fibre (PGF) reinforced polycaprolactone (PCL) composites with 20%, 35% and 50% fibre volume fractions (Vf) manufactured via an in-situ polymerisation (ISP) process and a conventional laminate stacking (LS) followed by compression moulding. Reinforcing efficiency between the LS and ISP manufacturing process was compared, and the ISP composites revealed significant improvements in mechanical properties when compared to LS composites. The degradation profiles and mechanical properties were monitored in phosphate buffered saline (PBS) at 37°C for 28 days. ISP composites revealed significantly less media uptake and mass loss (p<0.001) throughout the degradation period. The initial flexural properties of ISP composites were substantially higher (p<0.0001) than those of the LS composites, which showed that the ISP manufacturing process provided a significantly enhanced reinforcement effect than the LS process. During the degradation study, statistically higher flexural property retention profiles were also seen for the ISP composites compared to LS composites. SEM micrographs of fracture surfaces for the LS composites revealed dry fibre bundles and poor fibre dispersion with polymer rich zones, which indicated poor interfacial bonding, distribution and adhesion. In contrast, evenly distributed fibres without dry fibre bundles or polymer rich zones, were clearly observed for the ISP composite samples, which showed that a superior fibre/matrix interface was achieved with highly improved adhesion.

  17. Photocatalytic, sonocatalytic and sonophotocatalytic degradation of Rhodamine B using ZnO/CNTs composites photocatalysts.

    PubMed

    Ahmad, M; Ahmed, E; Hong, Z L; Ahmed, W; Elhissi, A; Khalid, N R

    2014-03-01

    A series of ZnO nanoparticles decorated on multi-walled carbon nanotubes (ZnO/CNTs composites) was synthesized using a facile sol method. The intrinsic characteristics of as-prepared nanocomposites were studied using a variety of techniques including powder X-ray diffraction (XRD), high resolution transmission electron microscope (HR-TEM), transmission electron microscope (TEM), scanning electron microscope (SEM) with energy dispersive X-ray analysis (EDX), Brunauer Emmett Teller (BET) surface area analyzer and X-ray photoelectron spectroscopy (XPS). Optical properties studied using UV-Vis diffuse reflectance spectroscopy confirmed that the absorbance of ZnO increased in the visible-light region with the incorporation of CNTs. In this study, degradation of Rhodamine B (RhB) as a dye pollutant was investigated in the presence of pristine ZnO nanoparticles and ZnO/CNTs composites using photocatalysis and sonocatalysis systems separately and simultaneously. The adsorption was found to be an essential factor in the degradation of the dye. The linear transform of the Langmuir isotherm curve was further used to determine the characteristic parameters for ZnO and ZCC-5 samples which were: maximum absorbable dye quantity and adsorption equilibrium constant. The natural sunlight and low power ultrasound were used as an irradiation source. The experimental kinetic data followed the pseudo-first order model in photocatalytic, sonocatalytic and sonophotocatalytic processes but the rate constant of sonophotocatalysis is higher than the sum of it at photocatalysis and sonocatalysis process. The sonophotocatalysis was always faster than the respective individual processes due to the more formation of reactive radicals as well as the increase of the active surface area of ZnO/CNTs photocatalyst. Chemical oxygen demand (COD) of textile wastewater was measured at regular intervals to evaluate the mineralization of wastewater.

  18. Degradation and environmental risk of surfactants after the application of compost sludge to the soil

    SciTech Connect

    Gonzalez, M.M.; Martin, J.; Camacho-Munoz, D.; Santos, J.L.; Aparicio, I.

    2012-07-15

    Highlights: Black-Right-Pointing-Pointer Degradation of surfactants in soil amended with sewage sludge during 100 days. Black-Right-Pointing-Pointer Temperature influences on the degradation of the studied compounds. Black-Right-Pointing-Pointer Overall, the LAS degradation is faster than the NP compounds degradation. Black-Right-Pointing-Pointer Therefore, the LAS presented lower environmental risk than the NP compounds. - Abstract: In this work, the degradation of anionic and non-ionic surfactants in agricultural soil amended with sewage sludge is reported. The compounds analysed were: linear alkylbenzene sulphonates (LAS) with a 10-13 carbon alkylic chain, and nonylphenolic compounds (NPE), including nonylphenol (NP) and nonylphenol ethoxylates with one and two ethoxy groups (NP1EO and NP2EO). The degradation studies were carried out under winter (12.7 Degree-Sign C) and summer (22.4 Degree-Sign C) conditions in Andalusia region. The concentration of LAS was reduced to 2% of the initial concentration 100 day after sludge-application to the soil. The half-life time measured for LAS homologues were ranged between 4 and 14 days at 12.7 Degree-Sign C and between 4 and 7 days at 22.4 Degree-Sign C. With regard to NPE compounds, after 8 and 4 days from the beginning of the experiment at 12.7 and 22.4 Degree-Sign C, respectively, their concentration levels were increased to 6.5 and 13.5 mg/kg dm (dry matter) as consequence of the degradation of nonylphenol polyethoxylates. These concentration levels were reduced to 5% after 63 and 70 days for 12.7 Degree-Sign C and 22.4 Degree-Sign C, respectively. The half-life times measured for NPEs were from 8 to 16 days at 12.7 Degree-Sign C and from 8 to 18 days at 22.4 Degree-Sign C. Environmental risk assessment revealed that for LAS homologues no environment risk could be expected after 7 and 8 days of sludge application to the soil for 22.4 and 12.7 Degree-Sign C, respectively; however, potential toxic effects could be

  19. Electrochemical detection and degradation of ibuprofen from water on multi-walled carbon nanotubes-epoxy composite electrode.

    PubMed

    Motoc, Sorina; Remes, Adriana; Pop, Aniela; Manea, Florica; Schoonman, Joop

    2013-04-01

    This work describes the electrochemical behaviour of ibuprofen on two types of multi-walled carbon nanotubes based composite electrodes, i.e., multi-walled carbon nanotubes-epoxy (MWCNT) and silver-modified zeolite-multi-walled carbon nanotubes-epoxy (AgZMWCNT) composites electrodes. The composite electrodes were obtained using two-roll mill procedure. SEM images of surfaces of the composites revealed a homogeneous distribution of the composite components within the epoxy matrix. AgZMWCNT composite electrode exhibited the better electrical conductivity and larger electroactive surface area. The electrochemical determination of ibuprofen (IBP) was achieved using AgZMWCNT by cyclic voltammetry, differential-pulsed voltammetry, square-wave voltammetry and chronoamperometry. The IBP degradation occurred on both composite electrodes under controlled electrolysis at 1.2 and 1.75 V vs. Ag/AgCl, and IBP concentration was determined comparatively by differential-pulsed voltammetry, under optimized conditions using AgZMWCNT electrode and UV-Vis spectrophotometry methods to determine the IBP degradation performance for each electrode. AgZMWCNT electrode exhibited a dual character allowing a double application in IBP degradation process and its control.

  20. Mechanical properties and in vitro evaluation of bioactivity and degradation of dexamethasone-releasing poly-D-L-lactide/nano-hydroxyapatite composite scaffolds.

    PubMed

    Chen, Ling; Tang, Chak Yin; Tsui, Chi Pong; Chen, Da Zhu

    2013-06-01

    The purpose of this study was to fabricate drug-release nano-composite scaffolds and perform in vitro evaluation of their mechanical properties, bioactivity, biodegradability and drug release behaviors. Porous drug-release poly-d-l-lactide (PDLLA) composite scaffolds filled with different amounts of nano-hydroxyapatite (nano-HAp) were prepared by a technique combining polymer coagulation, cold compression moulding, salt leaching and drug coating. Apatite detected on the scaffolds after exposure to a simulated body fluid showed improvement in bioactivity and the apatite formation ability through the addition of the nano-HAp content in the composites. Nano-HAp incorporation and apatite formation made a positive impact on the mechanical properties of the scaffolds; however, plasticization and degradation of PDLLA had a negative impact. The pH-compensation effect of the composite scaffolds can reduce the risk of chronic inflammation complications. The fabrication method in this study can produce scaffolds with controllable structure, appropriate mechanical properties and degradation rates for cancellous bone repair applications.

  1. Degradation of Biofumigant Isothiocyanates and Allyl Glucosinolate in Soil and Their Effects on the Microbial Community Composition

    PubMed Central

    Hanschen, Franziska S.; Yim, Bunlong; Winkelmann, Traud; Smalla, Kornelia; Schreiner, Monika

    2015-01-01

    Brassicales species rich in glucosinolates are used for biofumigation, a process based on releasing enzymatically toxic isothiocyanates into the soil. These hydrolysis products are volatile and often reactive compounds. Moreover, glucosinolates can be degraded also without the presence of the hydrolytic enzyme myrosinase which might contribute to bioactive effects. Thus, in the present study the stability of Brassicaceae plant-derived and pure glucosinolates hydrolysis products was studied using three different soils (model biofumigation). In addition, the degradation of pure 2-propenyl glucosinolate was investigated with special regard to the formation of volatile breakdown products. Finally, the influence of pure glucosinolate degradation on the bacterial community composition was evaluated using denaturing gradient gel electrophoresis of 16S rRNA gene amplified from total community DNA. The model biofumigation study revealed that the structure of the hydrolysis products had a significant impact on their stability in the soil but not the soil type. Following the degradation of pure 2-propenyl glucosinolate in the soils, the nitrile as well as the isothiocyanate can be the main degradation products, depending on the soil type. Furthermore, the degradation was shown to be both chemically as well as biologically mediated as autoclaving reduced degradation. The nitrile was the major product of the chemical degradation and its formation increased with iron content of the soil. Additionally, the bacterial community composition was significantly affected by adding pure 2-propenyl glucosinolate, the effect being more pronounced than in treatments with myrosinase added to the glucosinolate. Therefore, glucosinolates can have a greater effect on soil bacterial community composition than their hydrolysis products. PMID:26186695

  2. Temperature sensitivity of organic matter degradation - effect of molecular composition and microbial metabolic status

    NASA Astrophysics Data System (ADS)

    Erhagen, B.; Sparrman, T.; Schleucher, J.; Ilstedt, U.; Nilsson, M.

    2009-12-01

    One of the awaited major climatic change feedbacks on the biosphere-atmosphere CO2 exchange is the change in degradation rate of organic material in response to increased temperature. Despite the recent intense research efforts on the temperature sensitivity of organic matter degradation, large uncertainties on the controlling factors still remain. Theoretical analysis reveals an increased temperature sensitivity with the degree of recalcitrance to decomposition of organic matter compounds. One crucial research issue is therefore to find suitable descriptors of the organic chemical composition that allow modeling of the temperature sensitivity in organic matter degradation. In addition we also hypothesize that the metabolic status of the microorganisms, i.e. the relative contribution of catabolic and anabolic activity to the CO2 production also importantly affects the temperature sensitivity of organic matter decomposition. In this study we show how the variation in temperature sensitivity of organic matter degradation can be ascribed both to the organic matter chemical composition as revealed by NMR spectroscopy and the variation in catabolic and anabolic activity respectively. To investigate the temperature response of degradation of soil organic material we conducted laboratorial incubations at four temperatures (4,9,14,19○C) of both soil organic matter (O horizon) and fresh litter from boreal forests. We used estimates on the different carbon forms, derived from CP-MAS NMR spectra to model the Q10 response as a function of the chemical constituents of the decomposing organic material. The litter and humus samples used in the study span a Q10 range from ~1.2- 3.7 with an average Q10-value of 1.8 for the litter samples and 3.2 for the humus samples. The result shows that the chemical fractions from the CP-MAS NMR spectra explain most of the variance in the Q10 response within litter and humus respectively. The best predictors of the temperature sensitivity of

  3. Mechanical fatigue degradation of ceramics versus resin composites for dental restorations.

    PubMed

    Belli, Renan; Geinzer, Eva; Muschweck, Anna; Petschelt, Anselm; Lohbauer, Ulrich

    2014-04-01

    . From all materials, e.max Press and Clearfil Majesty Posterior showed the lowest strength loss (29.6% and 32%, respectively), whereas the other materials lost between 41% and 62% of their flexural strength after cyclic loading. Dental ceramics and resin composite materials show equivalent fatigue strength degradation at loads around 0.5σin values. Apart from the zirconium oxide and the lithium disilicate ceramics, resin composites generally showed better σff after 10,000 cycles than the fluorapatite glass-ceramic and the feldspathic porcelain. Resin composite restorations may be used as an equivalent alternative to glass-rich-ceramic inlays regarding mechanical performance. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  4. Solution processable RGO-CdZnS composite for solar light responsive photocatalytic degradation of 4-Nitrophenol

    NASA Astrophysics Data System (ADS)

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

    2017-05-01

    We report the one pot single step synthesis and characterization of solution processable reduced graphene oxide (RGO) - cadmium zinc sulfide (CdZnS) nanocomposite materials. The composite was characterized structurally and morphologically by XRD and TEM studies. The reduction of GO in RGO-CdZnS composite, was confirmed by XPS and Raman spectroscopy. The photocatalytic activity of the RGO-CdZnS composite was investigated towards the degradation of 4-Nitrophenol. A notable increase of photocatalytic efficiency of RGO-CdZnS compare to controlled CdZnS was observed. Here RGO plays a crucial role to efficient photo induced charge separation from the CdZnS, and decreases the electron-hole recombination probability and subsequently enhanced the photocatalytic activity of the RGO-CdZnS composite material under simulated solar light irradiation. This work highlights the potential application of RGO-based materials in the field of photocatalytic degradation of organic water pollutant.

  5. Influence of chemical reactivities of lipids bound in different pools on their isotopic compositions during degradation in marine sediments

    NASA Astrophysics Data System (ADS)

    Sun, M.; Pan, H.; Culp, R.

    2013-05-01

    Lipid biomarkers and associated compound specific stable carbon isotope compositions have been widely applied to study biogeochemical cycling of organic matter in natural environments. This experimental study was specifically designed to examine the influence of chemical reactivities of lipid compounds bound in different pools on their isotopic composition during microbial degradation in marine sediments. 13C-labeled (labeling at different carbon positions of fatty acid chains) and unlabeled tripalmitins were spiked and incubated in natural oxic (top 1 cm) and anoxic (> 10 cm) marine sediments. In anoxic sediments, neither naturally-occurred fatty acids nor tripalmitin-derived 16:0 fatty acid were apparently degraded within two months and hence no significant variation in stable carbon isotopic composition of 16:0 fatty acid was observed. However, in oxic sediments, both naturally-occurred fatty acids and spiked tripalmitin-derived 16:0 fatty acid were degraded by 26% - 95% during incubation. For natural fatty acids such as 14:0, 16:1, 18:1, 20:5/20:4, and >C20:0, degradation rates varied according to the following order: polyunsaturated > monounsaturated > short chain saturated > long chain saturated fatty acids, which reflects variable reactivities of natural lipid compounds from different sources. Tripalmitin-derived 16:0 fatty acid degraded at an at least 2-3× faster rate compared to naturally-occurred 16:0 in sediments. Meanwhile, isotopic compositions of 16:0 fatty acid in the oxic sediments shifted negatively during incubation. It appears that the isotopic shifts are dependent on the amount of 13C-labeled compound spiked into the sediments but not related to the labeling position of 13C in the molecular structure. The results from this study provide direct evidence that the relative reactivities of lipid compounds from different sources (or different pools) can cause alterations in molecular isotopic composition during microbial degradation in natural

  6. Poly(vinylamine) microgel-dextran composite hydrogels: characterisation; properties and pH-triggered degradation.

    PubMed

    McCann, Judith; Behrendt, Jonathan M; Yan, Junfeng; Halacheva, Silvia; Saunders, Brian R

    2015-07-01

    The present study involves an investigation of the formation, characterisation and triggered-degradation of mixed dispersions involving cationic poly(vinylamine-co-bis(ethyl vinylamine) ether) (PVAM-BEVAME) microgel (MG) particles and partially oxidised dextran (Dexox). In this approach to colloidal hydrogel composite formation, imine bonds were formed by reaction between aldehyde groups of Dexox and the primary amine groups on the MG particles. The composite hydrogels contained MG particles that were externally cross-linked by Dexox to form an elastically effective network with high storage modulus (G') values and low tanδ (=G″/G', where G″ is the loss modulus) values. The G' values for the MG-Dexox gels increased exponentially with increasing mass ratio (MR) of Dexox to MG. Interestingly, the yield strains determined from rheology also increased with MR and yield strains of up to 130% were measured. Au nanoparticles of comparable size to the Dexox chains adsorbed to the surface of the MG particles, which suggests that the pore size of the MG particles may have been smaller than that of the Dexox coils. The MG-Dexox gels were also subjected to acidic conditions to demonstrate pH-triggered gel network breakdown via imine bond cleavage. We show that new PVAM MG/aldehyde mixtures studied here for the first time form ductile and versatile colloidal gels and our new method provides a route to increasing ductility of hydrogels containing MG particles.

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

    NASA Technical Reports Server (NTRS)

    Martin, Richard E.

    2010-01-01

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

  8. The contribution of fluvial fluxes to the greenhouse gas emissions from Peatlands - the composition and degradability of DOM

    NASA Astrophysics Data System (ADS)

    Worrall, Fred; Moody, Catharine

    2015-04-01

    The aim of these experiments was to better constrain the composition of dissolved organic matter (DOM), and what affect the hydrological conditions of the river have on the composition and degradability. The composition of the DOM was compared to other organic matter from an upland peat dominated catchment, to add information to the carbon budget of the ecosystem. Various analytical techniques, including thermal, calorific and elemental, were applied to solid DOM collected monthly from an upland headwater stream, along with samples of peat, vegetation, litter and particulate organic matter (POM) from the same catchment. A sub-set of the samples were also analysed with solid-state 13C NMR, which was used to look at the carbon functional groups in the compounds. The results showed that the DOM was compositionally distinct from the other samples, even the POM, especially in regard to the oxidation state of the matter. A principal component analysis showed a three end-member mixing system, with the end members differing significantly in their degree of unsaturation, aromaticity and oxidative ratio. The composition of the solid DOM was also compared with the initial rates of DOC degradation in water samples taken at the same time as the DOM, and compared to the hydrological and metereological conditions on the sampling day and during the previous week. It was found that there was a link between the degradability in the light (total degradation), in the dark (biodegradation) and the difference between the two (photodegradation), and that the flow conditions of the river influence the composition and therefore the degradability of the DOM.

  9. Effect of acidic solutions on the surface degradation of a micro-hybrid composite resin.

    PubMed

    Münchow, Eliseu A; Ferreira, Ana Cláudia A; Machado, Raissa M M; Ramos, Tatiana S; Rodrigues-Junior, Sinval A; Zanchi, Cesar H

    2014-01-01

    Composite resins may undergo wear by the action of chemical substances (e.g., saliva, alcohol, bacterial acids) of the oral environment, which may affect the material's structure and surface properties. This study evaluated the effect of acidic substances on the surface properties of a micro-hybrid composite resin (Filtek Z-250). Eighty specimens were prepared, and baseline hardness and surface roughness (KMN0 and Ra0, respectively) were measured. The specimens were subjected to sorption (SO) and solubility (SL) tests according to ISO 4049:2009, but using different storage solutions: deionized water; 75/25 vol% ethanol/water solution; lactic acid; propionic acid; and acetic acid. The acids were used in two concentrations: PA and 0.02 N. pH was measured for all solutions and final hardness (KMN1) and surface roughness (Ra1) were measured. Data were analyzed with paired t-tests and one-way ANOVA and Tukey's test (a=5%). All solutions decreased hardness and increased the Ra values, except for the specimens stored in water and 0.02 N lactic acid, which maintained the hardness. All solutions produced similar SO and SL phenomena, except for the 0.02 N lactic acid, which caused lower solubility than the other solutions. Ethanol showed the highest pH (6.6) and the 0.02 N lactic acid the lowest one (2.5). The solutions affected negatively the surface properties of the composite resin; in addition, an acidic pH did not seem to be a significant factor that intensifies the surface degradation phenomena.

  10. A comparative study on the in vivo degradation of poly(L-lactide) based composite implants for bone fracture fixation.

    PubMed

    Wang, Zongliang; Wang, Yu; Ito, Yoshihiro; Zhang, Peibiao; Chen, Xuesi

    2016-02-09

    Composite of nano-hydroxyapatite (n-HAP) surface grafted with poly(L-lactide) (PLLA) (g-HAP) showed improved interface compatibility and mechanical property for bone fracture fixation. In this paper, in vivo degradation of n-HAP/PLLA and g-HAP/PLLA composite implants was investigated. The mechanical properties, molecular weight, thermal properties as well as crystallinity of the implants were measured. The bending strength of the n- and g-HAP/PLLA composites showed a marked reduction from an initial value of 102 and 114 MPa to 33 and 24 MPa at 36 weeks, respectively. While the bending strength of PLLA was maintained at 80 MPa at 36 weeks compared with initial value of 107 MPa. The impact strength increased over time especially for the composites. Significant differences in the molecular weight were seen among all the materials and g-HAP/PLLA appeared the fastest rate of decrease than others. Environmental scanning electron microscope (ESEM) results demonstrated that an apparently porous morphology full of pores and hollows were formed in the composites. The results indicated that the in vivo degradation of PLLA could be accelerated by the g-HAP nanoparticles. It implied that g-HAP/PLLA composites might be a candidate for human non-load bearing bone fracture fixation which needs high initial strength and fast degradation rate.

  11. A comparative study on the in vivo degradation of poly(L-lactide) based composite implants for bone fracture fixation

    NASA Astrophysics Data System (ADS)

    Wang, Zongliang; Wang, Yu; Ito, Yoshihiro; Zhang, Peibiao; Chen, Xuesi

    2016-02-01

    Composite of nano-hydroxyapatite (n-HAP) surface grafted with poly(L-lactide) (PLLA) (g-HAP) showed improved interface compatibility and mechanical property for bone fracture fixation. In this paper, in vivo degradation of n-HAP/PLLA and g-HAP/PLLA composite implants was investigated. The mechanical properties, molecular weight, thermal properties as well as crystallinity of the implants were measured. The bending strength of the n- and g-HAP/PLLA composites showed a marked reduction from an initial value of 102 and 114 MPa to 33 and 24 MPa at 36 weeks, respectively. While the bending strength of PLLA was maintained at 80 MPa at 36 weeks compared with initial value of 107 MPa. The impact strength increased over time especially for the composites. Significant differences in the molecular weight were seen among all the materials and g-HAP/PLLA appeared the fastest rate of decrease than others. Environmental scanning electron microscope (ESEM) results demonstrated that an apparently porous morphology full of pores and hollows were formed in the composites. The results indicated that the in vivo degradation of PLLA could be accelerated by the g-HAP nanoparticles. It implied that g-HAP/PLLA composites might be a candidate for human non-load bearing bone fracture fixation which needs high initial strength and fast degradation rate.

  12. A comparative study on the in vivo degradation of poly(L-lactide) based composite implants for bone fracture fixation

    PubMed Central

    Wang, Zongliang; Wang, Yu; Ito, Yoshihiro; Zhang, Peibiao; Chen, Xuesi

    2016-01-01

    Composite of nano-hydroxyapatite (n-HAP) surface grafted with poly(L-lactide) (PLLA) (g-HAP) showed improved interface compatibility and mechanical property for bone fracture fixation. In this paper, in vivo degradation of n-HAP/PLLA and g-HAP/PLLA composite implants was investigated. The mechanical properties, molecular weight, thermal properties as well as crystallinity of the implants were measured. The bending strength of the n- and g-HAP/PLLA composites showed a marked reduction from an initial value of 102 and 114 MPa to 33 and 24 MPa at 36 weeks, respectively. While the bending strength of PLLA was maintained at 80 MPa at 36 weeks compared with initial value of 107 MPa. The impact strength increased over time especially for the composites. Significant differences in the molecular weight were seen among all the materials and g-HAP/PLLA appeared the fastest rate of decrease than others. Environmental scanning electron microscope (ESEM) results demonstrated that an apparently porous morphology full of pores and hollows were formed in the composites. The results indicated that the in vivo degradation of PLLA could be accelerated by the g-HAP nanoparticles. It implied that g-HAP/PLLA composites might be a candidate for human non-load bearing bone fracture fixation which needs high initial strength and fast degradation rate. PMID:26857951

  13. Fibro-porous poliglecaprone/polycaprolactone conduits: synergistic effect of composition and in vitro degradation on mechanical properties.

    PubMed

    Patel, Harsh N; Garcia, Roman; Schindler, Carrie; Dean, Derrick; Pogwizd, Steven M; Singh, Raj; Vohra, Yogesh K; Thomas, Vinoy

    2015-04-01

    Blends of poliglecaprone (PGC) and polycaprolactone (PCL) of varying compositions were electrospun into tubular conduits and their mechanical, morphological, thermal and in vitro degradation properties were evaluated under simulated physiological conditions. Generally, mechanical strength, modulus and hydrophilic nature were enhanced by the addition of PGC to PCL. An in vitro degradation study in phosphate-buffered saline (pH 7.3) was carried out for up to 1 month to understand the hydrolytic degradation effect on the mechanical properties in both the longitudinal and circumferential directions. Pure PCL and 4:1 PCL/PGC blend scaffolds exhibited considerable elastic stiffening after a 1 month in vitro degradation. Fourier transform infrared spectroscopic and DSC techniques were used to understand the degradation behavior and the changes in structure and crystallinity of the polymeric blends. A 3:1 PCL/PGC blend was concluded to be a judicious blend composition for tubular grafts based on overall results on the mechanical properties and performance after a 1 month in vitro degradation study.

  14. Photocatalytic degradation of methyl orange dye in water solutions in the presence of MWCNT/TiO{sub 2} composites

    SciTech Connect

    Da Dalt, S.; Alves, A.K.; Bergmann, C.P.

    2013-05-15

    Highlights: ► MWCNTs/TiO{sub 2} composites were obtained to degrade organic dyes in water. ► MWCNT/TiO{sub 2} composites were analyzed by photocatalysis and structural characterization. ► The photocatalytic shows efficient method for the degradation of dyes from aqueous effluents. - Abstract: The textile and dyestuff industries are the primary sources of the release of synthetic dyes into the environment and usually there are major pollutants in dye wastewaters. Because of their toxicity and slow degradation, these dyes are categorized as environmentally hazardous materials. In this context, carbon nanotubes/TiO{sub 2} (CNTs/TiO{sub 2}) composites were prepared using multi-walled CNTs (MWCNTs), titanium (IV) propoxide and commercial TiO{sub 2} (P25{sup ®}) as titanium oxide sources, to degrade the methyl orange dye in solution through photocatalyst activity using UV irradiation. The composites were prepared by solution processing followed by thermal treatment at 400, 500 and 600 °C. The heterojunction between nanotubes and TiO{sub 2} was confirmed by XRD, specific surface area. The coating morphology was observed with SEM and TEM.

  15. Biological degradation of wood-plastic composites (WPC) and strategies for improving the resistance of WPC against biological decay

    Treesearch

    Anke Schirp; Rebecca E. Ibach; David E. Pendleton; Michael P. Wolcott

    2008-01-01

    Much of the research on wood-plastic composites (WPC) has focused on formulation development and processing while high biological durability of the material was assumed. The gap between assumption and knowledge in biodeterioration of WPC needs to be reduced. Although some information on the short-term resistance of WPC against biological degradation is available, long-...

  16. Preparation of Ag2O/Ag2CO3/MWNTs composite photocatalysts for enhancement of ciprofloxacin degradation

    NASA Astrophysics Data System (ADS)

    Wang, Huiqin; Li, Jinze; Huo, Pengwei; Yan, Yongsheng; Guan, Qingfeng

    2016-03-01

    The Ag2O/Ag2CO3/multi-walled carbon nanotube (MWNTs) composite photocatalysts were prepared by calcination of the obtained precipitate. The structures and morphology of as-prepared composite photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, X-ray photoelectron spectroscopy (XPS). The Ag2O/Ag2CO3/MWNTs composite photocatalysts exhibit higher degradation rate of ciprofloxacin (CIP) than the pure Ag2CO3, Ag2O/Ag2CO3 and Ag2CO3/MWNTs under visible light irradiation. The amount of loaded Ag2CO3 onto MWNTs and calcined time for Ag2CO3/MWNTs were systematically investigated, and the optimal amount of loaded Ag2CO3 and calcined time of Ag2CO3/MWNTs are 150 wt% and 10 min, respectively. The highest photocatalytic degradation rate of CIP could reach 76% under optimal conditions. The active species trapping experiments were also analyzed, the results show that the holes are main contributor for the degradation processes of CIP, furthermore the electrons, rad O2- and rad OH are also crucially influenced the photocatalytic degradation processes of CIP. The possible photocatalytic processes of CIP with Ag2O/Ag2CO3/MWNTs composite photocatalyst are also proposed.

  17. In vitro and in vivo degradation evaluation of novel iron-bioceramic composites for bone implant applications.

    PubMed

    Ulum, M F; Arafat, A; Noviana, D; Yusop, A H; Nasution, A K; Abdul Kadir, M R; Hermawan, H

    2014-03-01

    Biodegradable metals such as magnesium, iron and their alloys have been known as potential materials for temporary medical implants. However, most of the studies on biodegradable metals have been focusing on optimizing their mechanical properties and degradation behavior with no emphasis on improving their bioactivity behavior. We therefore investigated the possibility of improving iron biodegradation rate and bioactivity by incorporating various bioactive bioceramics. The iron-based bioceramic (hydroxyapatite, tricalcium phosphate and biphasic calcium phosphate) composites were prepared by mechanical mixing and sintering process. Degradation studies indicated that the addition of bioceramics lowered the corrosion potential of the composites and slightly increased their corrosion rate compared to that of pure iron. In vitro cytotoxicity results showed an increase of cellular activity when rat smooth muscle cells interacted with the degrading composites compared to pure iron. X-ray radiogram analysis showed a consistent degradation progress with that found in vivo and positive tissue response up to 70 days implantation in sheep animal model. Therefore, the iron-based bioceramic composites have the potential to be used for biodegradable bone implant applications.

  18. Monitoring chemical degradation of thermally cycled glass-fibre composites using hyperspectral imaging

    NASA Astrophysics Data System (ADS)

    Papadakis, V. M.; Müller, B.; Hagenbeek, M.; Sinke, J.; Groves, R. M.

    2016-04-01

    Nowadays, the application of glass-fibre composites in light-weight structures is growing. Although mechanical characterizations of those structures are commonly performed in testing, chemical changes of materials under stresses have not yet been well documented. In the present work coupon tests and Hyperspectral Imaging (HSI) have been used to categorise possible chemical changes of glass-fibre reinforced polymers (GFRP) which are currently used in the aircraft industry. HSI is a hybrid technique that combines spectroscopy with imaging. It is able to detect chemical degradation of surfaces and has already been successfully applied in a wide range of fields including astronomy, remote sensing, cultural heritage and medical sciences. GFRP specimens were exposed to two different thermal loading conditions. One thermal loading condition was a continuous thermal exposure at 120°C for 24h, 48 h and 96h, i.e. ageing at a constant temperature. The other thermal loading condition was thermal cycling with three different numbers of cycles (4000, 8000, 12000) and two temperature ranges (0°C to 120°C and -25°C to 95°C). The effects of both conditions were measured using both HSI and interlaminar shear (ILSS) tests. No significant changes of the physical properties of the thermally cycled GFRP specimens were detected using interlaminar shear strength tests and optical microscopy. However, when using HIS, differences of the surface conditions were detected. The results showed that the different thermal loading conditions could be successfully clustered in different colours, using the HSI linear unmixing technique. Each different thermal loading condition showed a different chemical degradation level on its surface which was indicated using different colours.

  19. In vitro degradation, hemolysis, and cytocompatibility of PEO/PLLA composite coating on biodegradable AZ31 alloy.

    PubMed

    Wei, Zhongling; Tian, Peng; Liu, Xuanyong; Zhou, Bangxin

    2015-02-01

    Magnesium and its alloys have large potential as degradable and absorbable biomaterials because of their mechanical properties and biocompatibility. However, their corrosion resistance is usually inadequate especially in physiological environment, which limits their broad applications in biomedical areas. In this work, plasma electrolytic oxidized/poly(l-lactide) (PEO/PLLA) composite coating was successfully fabricated on biodegradable AZ31 alloy by combing PEO process and sealing with PLLA. The microstructure, elemental composition, and phase composition of the PEO/PLLA composite coating were investigated. The in vitro degradation of the PEO/PLLA composite coating in simulated body fluid (SBF) was also systematically evaluated. The results revealed that the PEO/PLLA composite coating improved the corrosion resistance of AZ31 alloy significantly. The corrosion potential shifted from -1.663V to more positive position -1.317 V and the corrosion current density was reduced with six-order of magnitude. The Mg(2+) ions, hydrogen release, and pH value change of solution caused by degradation were all decreased significantly. Moreover, the PEO process played a critical role in sustaining the integrity of the implant in long-term service. The result of hemolysis test showed that the PEO/PLLA composite coating vested AZ31 alloy a low hemolysis ratio (0.806 ± 0.771)%, which is much lower than the safe value of 5% according to ISO 10993-4. For the cytocompatibility test, compared with bare AZ31 alloy and PEO coating, MC3T3-E1 cells showed much better adhesion and proliferation on the PEO/PLLA composite coating with nearly 4-fold increase of cells after 7-day cultivation, indicating that the PEO/PLLA composite coating has good biocompatibility for biomedical applications.

  20. Preparation and characterization of bioactive and degradable composites containing ordered mesoporous calcium-magnesium silicate and poly(L-lactide)

    NASA Astrophysics Data System (ADS)

    Ji, Jiajin; Dong, Xieping; Ma, Xuhui; Tang, Songchao; Wu, Zhaoying; Xia, Ji; Wang, Quanxiang; Wang, Yutao; Wei, Jie

    2014-10-01

    Polylactide (PLA) and its copolymers have been widely used for bone tissue regeneration. In this study, a bioactive composite of ordered mesoporous calcium-magnesium silicate (m-CMS) and poly(L-lactide) (PLLA) was fabricated by melt blending method. The results indicated that the m-CMS particles were entrapped by polymer phase, and crystallinity of PLLA significantly decreased while the thermal stability of the m-CMS/PLLA composites was not obviously affected by addition of the m-CMS into PLLA. In addition, compared to PLLA, incorporation of the m-CMS into PLLA significantly improved the hydrophilicity, in vitro degradability and bioactivity (apatite-formation ability) of the m-CMS/PLLA composite, which were m-CMS content dependent. Moreover, it was found that incorporation of the m-CMS into PLLA could neutralize the acidic degradation by-products and thus compensated for the decrease of pH value. In cell culture experiments, the results showed that the composite enhanced attachment, proliferation and alkaline phosphatase activity (ALP) of MC3T3-E1 cells, which were m-CMS content dependent. The results indicated that the addition of bioactive materials to PLLA could result in a composite with improved properties of hydrophilicity, degradability, bioactivity and cytocompatibility.

  1. DEGRADATION SUSCEPTIBILITY METRICS AS THE BASES FOR BAYESIAN RELIABILITY MODELS OF AGING PASSIVE COMPONENTS AND LONG-TERM REACTOR RISK

    SciTech Connect

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

    2011-07-17

    Conventional probabilistic risk assessments (PRAs) are not well-suited to addressing long-term reactor operations. Since passive structures, systems and components are among those for which refurbishment or replacement can be least practical, they might be expected to contribute increasingly to risk in an aging plant. Yet, passives receive limited treatment in PRAs. Furthermore, PRAs produce only snapshots of risk based on the assumption of time-independent component failure rates. This assumption is unlikely to be valid in aging systems. The treatment of aging passive components in PRA does present challenges. First, service data required to quantify component reliability models are sparse, and this problem is exacerbated by the greater data demands of age-dependent reliability models. A compounding factor is that there can be numerous potential degradation mechanisms associated with the materials, design, and operating environment of a given component. This deepens the data problem since the risk-informed management of materials degradation and component aging will demand an understanding of the long-term risk significance of individual degradation mechanisms. In this paper we describe a Bayesian methodology that integrates the metrics of materials degradation susceptibility being developed under the Nuclear Regulatory Commission's Proactive Management of Materials of Degradation Program with available plant service data to estimate age-dependent passive component reliabilities. Integration of these models into conventional PRA will provide a basis for materials degradation management informed by the predicted long-term operational risk.

  2. COMPONENT DEGRADATION SUSCEPTIBILITIES AS THE BASES FOR MODELING REACTOR AGING RISK

    SciTech Connect

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

    2010-07-18

    The extension of nuclear power plant operating licenses beyond 60 years in the United States will be necessary if we are to meet national energy needs while addressing the issues of carbon and climate. Characterizing the operating risks associated with aging reactors is problematic because the principal tool for risk-informed decision-making, Probabilistic Risk Assessment (PRA), is not ideally-suited to addressing aging systems. The components most likely to drive risk in an aging reactor - the passives - receive limited treatment in PRA, and furthermore, standard PRA methods are based on the assumption of stationary failure rates: a condition unlikely to be met in an aging system. A critical barrier to modeling passives aging on the wide scale required for a PRA is that there is seldom sufficient field data to populate parametric failure models, and nor is there the availability of practical physics models to predict out-year component reliability. The methodology described here circumvents some of these data and modeling needs by using materials degradation metrics, integrated with conventional PRA models, to produce risk importance measures for specific aging mechanisms and component types. We suggest that these measures have multiple applications, from the risk-screening of components to the prioritization of materials research.

  3. Advanced oxidation kinetics and mechanism of preservative propylparaben degradation in aqueous suspension of TiO2 and risk assessment of its degradation products.

    PubMed

    Fang, Hansun; Gao, Yanpeng; Li, Guiying; An, Jibin; Wong, Po-Keung; Fu, Haiying; Yao, Side; Nie, Xiangping; An, Taicheng

    2013-03-19

    The absolute kinetic rate constants of propylparaben (PPB) in water with different free radicals were investigated, and it was found that both hydroxyl radicals (HO(•)) and hydrated electrons could rapidly react with PPB. The advanced oxidation kinetics and mechanisms of PPB were investigated using photocatalytic process as a model technology, and the degradation was found to be a pseudo-first-order model. Oxidative species, particularly HO(•), were the most important reactive oxygen species mediating photocatalytic degradation of PPB, and PPB degradation was found to be significantly affected by pH because it was controlled by the radical reaction mechanism and was postulated to occur primarily via HO(•)-addition or H-abstraction reactions on the basis of pulse radiolysis measurements and observed reaction products. To investigate potential risk of PPB to humans and aqueous organisms, the estrogenic assays and bioassays were performed using 100 μM PPB solution degraded by photocatalysis at specific intervals. The estrogenic activity decreased as PPB was degraded, while the acute toxicity at three trophic levels first increased slowly and then decreased rapidly as the total organic carbon decreased during photocatalytic degradation.

  4. Composition, assimilation and degradation of Phaeocystis globosa-derived fatty acids in the North Sea

    NASA Astrophysics Data System (ADS)

    Hamm, Christian E.; Rousseau, Veronique

    2003-12-01

    The fate of a Phaeocystis globosa bloom in the southern North Sea off Belgium, the Netherlands and Germany in May 1995 was investigated during a cruise with RV 'Belgica'. We used fatty acids as biomarkers to follow the fate of Phaeocystis-derived biomass of a Phaeocystis-dominated spring bloom. The bloom, in which up to >99% of the biomass was contributed by Phaeocystis, showed a fatty acid composition with a characteristically high abundance of polyunsaturated C 18-fatty acids, which increased in concentration with number of double bonds up to 18:5 (n-3), and high concentrations of 20:5 (n-3) and 22:6 (n-3). In contrast to most previous studies, fatty acid analysis of the mesozooplankton community (mainly calanoid copepods) and meroplankton ( Carcinus maenas megalope) indicated that P. globosa was a major component (ca. 70% and 50%, respectively) in the diet of these organisms. Massive accumulations of amorphous grey aggregates, in which Phaeocystis colonies were major components, were dominated by saturated fatty acids and contained only few of the polyunsaturated C 18-fatty acids. A hydrophobic surface slick that covered the water surface during the bloom showed very similar patterns. Foam patches contained few Phaeocystis-typical fatty acids, but increased amounts of diatom-typical compounds such as 16:1 (n-7) and 20:5 (n-3), and 38% fatty alcohols, indicating that wax esters dominated the lipid fraction in the foam with ca. 76% (w/w). The fatty acid compositions of surface sediment showed that no sedimentation of fresh Phaeocystis occurred during the study. The results indicate that Phaeocystis-derived organic matter degraded while floating or in suspension, and had not reached the sediment in substantial amounts.

  5. Changes in fatty acid composition of Stenotrophomonas maltophilia KB2 during co-metabolic degradation of monochlorophenols.

    PubMed

    Nowak, Agnieszka; Greń, Izabela; Mrozik, Agnieszka

    2016-12-01

    The changes in the cellular fatty acid composition of Stenotrophomonas maltophilia KB2 during co-metabolic degradation of monochlorophenols in the presence of phenol as well as its adaptive mechanisms to these compounds were studied. It was found that bacteria were capable of degrading 4-chlorophenol (4-CP) completely in the presence of phenol, while 2-chlorophenol (2-CP) and 3-chlorophenol (3-CP) they degraded partially. The analysis of the fatty acid profiles indicated that adaptive mechanisms of bacteria depended on earlier exposure to phenol, which isomer they degraded, and on incubation time. In bacteria unexposed to phenol the permeability and structure of their membranes could be modified through the increase of hydroxylated and cyclopropane fatty acids, and straight-chain and hydroxylated fatty acids under 2-CP, 3-CP and 4-CP exposure, respectively. In the exposed cells, regardless of the isomer they degraded, the most important changes were connected with the increase of the contribution of branched fatty acid on day 4 and the content of hydroxylated fatty acids on day 7. The changes, particularly in the proportion of branched fatty acids, could be a good indicator for assessing the progress of the degradation of monochlorophenols by S. maltophilia KB2. In comparison, in phenol-degrading cells the increase of cyclopropane and straight-chain fatty acid content was established. These findings indicated the degradative potential of the tested strain towards the co-metabolic degradation of persistent chlorophenols, and extended the current knowledge about the adaptive mechanisms of these bacteria to such chemicals.

  6. Retention and degradation of the cyanobacterial toxin cylindrospermopsin in sediments - the role of sediment preconditioning and DOM composition.

    PubMed

    Klitzke, Sondra; Apelt, Susann; Weiler, Christiane; Fastner, Jutta; Chorus, Ingrid

    2010-05-01

    Recent results show that cylindrospermopsin is more frequent and widespread in surface waters than previously assumed. Studies on the fate of CYN in sediments are lacking, but this is important if these resources are used for drinking-water production via sediment passage. Therefore, the aim of our study was to determine a) CYN retention in two sandy sediments as a function of flow rate, CYN concentration, the presence of DOM and the content of fines (1% and 4%, respectively) and b) the influence of sediment preconditioning and DOM composition of the water (aquatic DOM versus DOM released from lysed cells) on CYN degradation. Retention of CYN proved negligible under the investigated conditions. Degradation in virgin sediments showed the highest lag phases (20 days). Preconditioned sediments showed no lag phase. The presence of aquatic DOM yielded highest degradation rates (kappa(1)=0.46 and 0.49 day(-1)) without a lag phase. Readily available organic carbon sources were preferentially metabolized and hence induced a lag phase. Thus, the presence and composition of DOM in the water proved important for both CYN degradation rates in preconditioned sediments and for the lag phase. Cylindrospermopsin degradation took place solely in the sediment and not in the water body. Copyright 2009 Elsevier Ltd. All rights reserved.

  7. Degradation and biocompatibility of porous nano-hydroxyapatite/polyurethane composite scaffold for bone tissue engineering

    NASA Astrophysics Data System (ADS)

    Dong, Zhihong; Li, Yubao; Zou, Qin

    2009-04-01

    Porous scaffold containing 30 wt% nano-hydroxyapatite (n-HA) and 70 wt% polyurethane (PU) from castor oil was prepared by a foaming method and investigated by X-ray diffraction (XRD), Fourier transform infrared absorption (FTIR), scanning electron microscopy (SEM) techniques. The results show that n-HA particles disperse homogeneously in the PU matrix. The porous scaffold has not only macropores of 100-800 μm in size but also a lot of micropores on the walls of macropores. The porosity and compressive strength of scaffold are 80% and 271 kPa, respectively. After soaking in simulated body fluid (SBF), hydrolysis and deposition partly occur on the scaffold. The biological evaluation in vitro and in vivo shows that the n-HA/PU scaffold is non-cytotoxic and degradable. The porous structure provides a good microenvironment for cell adherence, growth and proliferation. The n-HA/PU composite scaffold can be satisfied with the basic requirement for tissue engineering, and has the potential to be applied in repair and substitute of human menisci of the knee-joint and articular cartilage.

  8. Rapid degradation of dyes in water by magnetic Fe(0)/Fe3O4/graphene composites.

    PubMed

    Chong, Shan; Zhang, Guangming; Tian, Huifang; Zhao, He

    2016-06-01

    Magnetic Fe(0)/Fe3O4/graphene has been successfully synthesized by a one-step reduction method and investigated in rapid degradation of dyes in this work. The material was characterized by N2 sorption-desorption, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), vibrating-sample magnetometer (VSM) measurements and X-ray photoelectron spectroscopy (XPS). The results indicated that Fe(0)/Fe3O4/graphene had a layered structure with Fe crystals highly dispersed in the interlayers of graphene, which could enhance the mass transfer process between Fe(0)/Fe3O4/graphene and pollutants. Fe(0)/Fe3O4/graphene exhibited ferromagnetism and could be easily separated and re-dispersed for reuse in water. Typical dyes, such as Methyl Orange, Methylene Blue and Crystal Violet, could be decolorized by Fe(0)/Fe3O4/graphene rapidly. After 20min, the decolorization efficiencies of methyl orange, methylene blue and crystal violet were 94.78%, 91.60% and 89.07%, respectively. The reaction mechanism of Fe(0)/Fe3O4/graphene with dyes mainly included adsorption and enhanced reduction by the composite. Thus, Fe(0)/Fe3O4/graphene prepared by the one-step reduction method has excellent performance in removal of dyes in water.

  9. Degradability, cytocompatibility, and osteogenesis of porous scaffolds of nanobredigite and PCL–PEG–PCL composite

    PubMed Central

    Hou, Jun; Fan, Donghui; Zhao, Lingming; Yu, Baoqin; Su, Jiacan; Wei, Jie; Shin, Jung-Woog

    2016-01-01

    Biocomposite scaffolds were fabricated by incorporation of nanobredigite (n-BD) into the polymer of poly(ε-caprolactone)–poly(ethyleneglycol)–poly(ε-caprolactone) (PCL–PEG–PCL). The results revealed that the addition of n-BD into PCL–PEG–PCL significantly improved water absorption, compressive strength, and degradability of the scaffolds of n-BD/PCL–PEG–PCL composite (n-BPC) compared with PCL–PEG–PCL scaffolds alone. In addition, the proliferation and alkaline phosphatase activity of MG63 cells cultured on n-BPC scaffolds were obviously higher than that cultured on PCL–PEG–PCL scaffolds. Moreover, the results of the histological evaluation from the animal model revealed that the n-BPC scaffolds significantly improved new bone formation compared with the PCL–PEG–PCL scaffolds, indicating good osteogenesis. The n-BPC scaffolds with good biocompatibility could stimulate cell proliferation, differentiation, and bone tissue regeneration and would be an excellent candidate for bone defect repair. PMID:27555774

  10. High-Capacity and Photoregenerable Composite Material for Efficient Adsorption and Degradation of Phenanthrene in Water.

    PubMed

    Liu, Wen; Cai, Zhengqing; Zhao, Xiao; Wang, Ting; Li, Fan; Zhao, Dongye

    2016-10-18

    We report a novel composite material, referred to as activated charcoal supported titanate nanotubes (TNTs@AC), for highly efficient adsorption and photodegradation of a representative polycyclic aromatic hydrocarbon (PAH), phenanthrene. TNTs@AC was prepared through a one-step hydrothermal method, and is composed of an activated charcoal core and a shell of carbon-coated titanate nanotubes. TNTs@AC offered a maximum Langmuir adsorption capacity of 12.1 mg/g for phenanthrene (a model PAH), which is ∼11 times higher than the parent activated charcoal. Phenanthrene was rapidly concentrated onto TNTs@AC, and subsequently completely photodegraded under UV light within 2 h. The photoregenerated TNTs@AC can then be reused for another adsorption-photodegradation cycle without significant capacity or activity loss. TNTs@AC performed well over a wide range of pH, ionic strength, and dissolved organic matter. Mechanistically, the enhanced adsorption capacity is attributed to the formation of carbon-coated ink-bottle pores of the titanate nanotubes, which are conducive to capillary condensation; in addition, the modified microcarbon facilitates transfer of excited electrons, thereby inhibiting recombination of the electron-hole pairs, resulting in high photocatalytic activity. The combined high adsorption capacity, photocatalytic activity, and regenerability/reusability merit TNTs@AC a very attractive material for concentrating and degrading a host of micropollutants in the environment.

  11. Sulfate radical-induced degradation of Acid Orange 7 by a new magnetic composite catalyzed peroxymonosulfate oxidation process.

    PubMed

    Chen, Dan; Ma, Xiaolong; Zhou, Jizhi; Chen, Xi; Qian, Guangren

    2014-08-30

    We synthesized a novel magnetic composite, Fe3O4/Cu(Ni)Cr-LDH, as a heterogeneous catalyst for the degradation of organic dyes in the solution using sulfate radical-based advanced oxidation processes. The physicochemical properties of the composite synthesized via two-step microwave hydrothermal method were characterized by several techniques, such as X-ray diffraction (XRD), inductively coupled plasma (ICP), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The degradation tests were performed at 25°C with Acid Orange 7 (AO7) initial concentration of 25mg/L and AO7/peroxymonosulfate (PMS) molar ratio of 1:10, which showed that the complete degradation by Fe3O4/Cu1.5Ni0.5Cr-LDH could be achieved and the mineralization rate could reach 46%. PMS was activated by Cu (II) and Fe (II/III) of Fe3O4/Cu(Ni)Cr-LDH to generate sulfate radicals (SO4(-)). Subsequently, the organic functional groups of AO7 molecules were destroyed by sulfate radicals (SO4(-)), inducing the degradation of AO7. Moreover, the catalytic behavior of the catalysts could be reused five times. Therefore, our work suggested that the Fe3O4/Cu(Ni)Cr-LDH composite could be applied widely for the treatment of organic dyes in wastewater. Copyright © 2014. Published by Elsevier B.V.

  12. Fracture Resistance of Hybrid Glass Matrix Composite and Its Degradation Due to Thermal Ageing and Thermal Shock

    NASA Astrophysics Data System (ADS)

    Dlouhý, Ivo; Chlup, Zdenêk; Atiq, Shabbar; Boccaccini, Aldo R.

    In brittle matrix composites reinforced by continuous ceramic fibres, the favourable fracture behaviour is provided by the presence of weak fibre/matrix interfaces, which lead to the fibre pullout effect [1]. The thermal stability and high temperature mechanical properties of silicate matrix composites reinforced by carbon and SiC based fibres in oxidising environments have been investigated quite extensively in the past by conducting thermal aging and thermal cycling experiments over a wide range of temperatures [2-5]. A common result of investigations conducted at temperatures in the range 500-700°C is that there is a decrease of tensile and flexural strength of the composites. It has been shown that this is the consequence of oxidation of the fibres, in case of carbon fibre reinforced composites, or of degradation of the fibre/matrix interphase, which is in fact a carbon-rich nanometric interfacial layer, in SiC fibre reinforced composites [2-5].

  13. Reduced graphene oxide-silver nanoparticle composite as visible light photocatalyst for degradation of colorless endocrine disruptors.

    PubMed

    Bhunia, Susanta Kumar; Jana, Nikhil R

    2014-11-26

    Sunlight-induced degradation of organic pollutants is an ideal approach for environmental pollution control and wastewater treatment. Although a variety of photocatalysts have been designed toward this goal, efficient degradation of colorless organic pollutants by visible light is a challenging issue. Here, we show that a reduced graphene oxide (rGO)-based composite with silver nanoparticle (rGO-Ag) can act as an efficient visible-light photocatalyst for the degradation of colorless organic pollutants. We have developed a simple, large-scale synthesis method for rGO-Ag and used it for the degradation of three well-known endocrine disruptors (phenol, bisphenol A, and atrazine) under UV and visible light. It is found that photocatalytic efficiency by rGO-Ag under visible light is significantly higher compared to that of rGO or silver nanoparticles. It is proposed that Ag nanoparticles offer visible-light-induced excitation of silver plasmons, and conductive rGO offers efficient charge separation and thus induces oxidative degradation of the organic pollutant. This approach can be extended for sunlight-induced degradation of different organic pollutants.

  14. Dynamic changes in the composite microbial system MC1 during and following its rapid degradation of lignocellulose.

    PubMed

    Hua, Binbin; Lü, Yucai; Wang, Jungang; Wen, Boting; Cao, Yanzhuan; Wang, Xiaofen; Cui, Zongjun

    2014-01-01

    To monitor the dynamics of the composite microbial system MC1 during its degradation of lignocellulose and to improve our understanding of the microbial communities involved in this biomass conversion, MC1 was characterized at eight time points over an 18-day, thermophilic, aerobic, static cultivation. We found the microbial communities to be dynamic, rhythmic consortia capable of changing in response to lignocellulose degradation. The growth curve over 18 days was M-shaped. Based on the quantitative changes in five major components of MC1 (Clostridium straminisolvens CSK-1, Clostridium sp. FG4, Pseudoxanthomonas sp. M1-3, Brevibacillus sp. M1-5, and Bordetella sp. M1-6), reduction in rice straw weight, cellulase (CMCase) activity, xylanase activity, and changes in medium pH, we found that the process comprised two identifiable phases. Rapid degradation occurred from day 0 to day 9, while the post-rapid degradation phase included days 10 to 18. Day 3 and day 12 were two key time points in the rapid degradation phase and post-rapid degradation phase, respectively. Two anaerobes, C. straminisolvens CSK-1 and Clostridium sp. FG4, dominated the MC1 system from day 0 to day 18.

  15. Potential role of gastrointestinal microbiota composition in prostate cancer risk

    PubMed Central

    2013-01-01

    Background Among men in the U.S., prostate cancer is the most common cancer and the second leading cause of cancer death. Despite its prevalence, there are few established risk factors for prostate cancer. Some studies have found that intake of certain foods/nutrients may be associated with prostate cancer risk, but few have accounted for how intake and metabolic factors may interact to influence bioavailable nutrient levels and subsequent disease risk. Presentation of the hypothesis The composition of the gastrointestinal (GI) microbiome may influence metabolism of dietary compounds and nutrients (e.g., plant phenols, calcium, choline) that may be relevant to prostate cancer risk. We, therefore, propose the hypothesis that GI microbiota may have a markedly different composition among individuals with higher prostate cancer risk. These individuals could have microbial profiles that are conducive to intestinal inflammation and/or are less favorable for the metabolism and uptake of chemopreventive agents. Testing the hypothesis Because very little preliminary data exist on this potential association, a case–control study may provide valuable information on this topic. Such a study could evaluate whether the GI microbial profile is markedly different between three groups of individuals: healthy men, those with latent prostate cancer, and those with invasive prostate cancer. Any findings could then be validated in a larger study, designed to collect a series of specimens over time. Implications of the hypothesis Given the plethora of information emerging from the Human Microbiome Project, this is an opportune time to explore associations between the microbiome and complex human diseases. Identification of profiles that alter the host’s risk for disease may clarify inconsistencies in the literature on dietary factors and cancer risk, and could provide valuable targets for novel cancer prevention strategies. PMID:24180596

  16. In vitro degradation behavior and cytocompatibility of biodegradable AZ31 alloy with PEO/HT composite coating.

    PubMed

    Tian, Peng; Liu, Xuanyong; Ding, Chuanxian

    2015-04-01

    Biodegradable magnesium-based implants have attracted much attention recently in orthopedic applications because of their good mechanical properties and biocompatibility. However, their rapid degradation in vivo will not only reduce their mechanical strength, but also induce some side effects, such as local alkalization and gas cavity, which may lead to a failure of the implant. In this work, a hydroxyapatite (HA) layer was prepared on plasma electrolytic oxidization (PEO) coating by hydrothermal treatment (HT) to fabricate a PEO/HT composite coating on biodegradable AZ31 alloy. The in vitro degradation behaviors of all samples were evaluated in simulated body fluid (SBF) and their surface cytocompatibility was also investigated by evaluating the adhesion and proliferation of osteoblast cells (MC3T3-E1). The results showed that the HA layer consisted of a dense inner layer and a needle-like outer layer, which successfully sealed the PEO coating. The in vitro degradation tests showed that the PEO/HT composite coating improved the corrosion resistance of AZ31 alloy in SBF, presenting nearly no severe local alkalization and hydrogen evolution. The lasting corrosion resistance of the PEO/HT composite coating may attribute to the new hydroxyapatite formation during the degradation process. Moreover, compared with AZ31 alloy and PEO coating, PEO/HT composite coating was more suitable for cells adhesion and proliferation, indicating improved surface cytocompatibility. The results show that the PEO/HT composite coating is promising as protective coating on biodegradable magnesium-based implants to enhance their corrosion resistance as well as improve their surface cytocompatibility for orthopedic applications.

  17. Degradation and environmental risk of surfactants after the application of compost sludge to the soil.

    PubMed

    González, M M; Martín, J; Camacho-Muñoz, D; Santos, J L; Aparicio, I; Alonso, E

    2012-07-01

    In this work, the degradation of anionic and non-ionic surfactants in agricultural soil amended with sewage sludge is reported. The compounds analysed were: linear alkylbenzene sulphonates (LAS) with a 10-13 carbon alkylic chain, and nonylphenolic compounds (NPE), including nonylphenol (NP) and nonylphenol ethoxylates with one and two ethoxy groups (NP1EO and NP2EO). The degradation studies were carried out under winter (12.7°C) and summer (22.4°C) conditions in Andalusia region. The concentration of LAS was reduced to 2% of the initial concentration 100 day after sludge-application to the soil. The half-life time measured for LAS homologues were ranged between 4 and 14days at 12.7°C and between 4 and 7 days at 22.4°C. With regard to NPE compounds, after 8 and 4days from the beginning of the experiment at 12.7 and 22.4°C, respectively, their concentration levels were increased to 6.5 and 13.5mg/kgdm (dry matter) as consequence of the degradation of nonylphenol polyethoxylates. These concentration levels were reduced to 5% after 63 and 70 days for 12.7°C and 22.4°C, respectively. The half-life times measured for NPEs were from 8 to 16 days at 12.7°C and from 8 to 18 days at 22.4°C. Environmental risk assessment revealed that for LAS homologues no environment risk could be expected after 7 and 8 days of sludge application to the soil for 22.4 and 12.7°C, respectively; however, potential toxic effects could be observed for the nonylphenolic compounds during the first 56 days after sludge application to the soil.

  18. Effects of Material Degradation on the Structural Integrity of Composite Materials: Experimental Investigation and Modeling of High Temperature Degradation Mechanisms

    NASA Technical Reports Server (NTRS)

    Cunningham, Ronan A.; McManus, Hugh L.

    1996-01-01

    It has previously been demonstrated that simple coupled reaction-diffusion models can approximate the aging behavior of PMR-15 resin subjected to different oxidative environments. Based on empirically observed phenomena, a model coupling chemical reactions, both thermal and oxidative, with diffusion of oxygen into the material bulk should allow simulation of the aging process. Through preliminary modeling techniques such as this it has become apparent that accurate analytical models cannot be created until the phenomena which cause the aging of these materials are quantified. An experimental program is currently underway to quantify all of the reaction/diffusion related mechanisms involved. The following contains a summary of the experimental data which has been collected through thermogravimetric analyses of neat PMR-15 resin, along with analytical predictions from models based on the empirical data. Thermogravimetric analyses were carried out in a number of different environments - nitrogen, air and oxygen. The nitrogen provides data for the purely thermal degradation mechanisms while those in air provide data for the coupled oxidative-thermal process. The intent here is to effectively subtract the nitrogen atmosphere data (assumed to represent only thermal reactions) from the air and oxygen atmosphere data to back-figure the purely oxidative reactions. Once purely oxidative (concentration dependent) reactions have been quantified it should then be possible to quantify the diffusion of oxygen into the material bulk.

  19. Changes in Carbon Isotope Composition of Methyl Halides Resulting from Biological and Chemical Degradation

    NASA Astrophysics Data System (ADS)

    Baesman, S. M.; Miller, L. G.; Oremland, R. S.

    2003-12-01

    Methyl bromide (MeBr), methyl chloride (MeCl) and methyl iodide (MeI) are reactive trace gases that are produced and released to the atmosphere at the Earths surface. These methyl halides have the potential to influence ozone levels in the stratosphere. Current estimates of the relative contributions of natural and anthropogenic sources of these methyl halides are the subject of considerable debate. In addition, there is uncertainty in the magnitude of some of the largest sinks for these compounds. Hence, the atmospheric budgets of MeBr, MeCl and MeI, while uncertain at present, may be better constrained using stable isotope ratio (13C/12C) mass balances of sources and sinks. Our work has focused on characterizing the effects upon δ 13C values of methyl halides released after reactions which discriminate in favor of 12C during removal processes. Previously, we determined very large fractionations of carbon isotopes by pure cultures of soil bacteria. Further, we have documented large fractionations (kinetic isotope effects or KIEs) of methyl halides in live soils. In the case of MeBr and MeI, substantial fractionation also occurred in heat-killed soil, suggesting that chemical degradation resulted in a shift in the stable isotopic composition. At elevated concentrations, for instance during agricultural soil fumigations, the δ 13C value of MeBr or MeI released from soil can be determined by flux measurements or soil profiles. However, more information is needed regarding the processes responsible for isotope fractionation to be able to extrapolate to areas where the concentration is low or direct measurement is not otherwise possible. We report here on measurements of the fractionation of carbon isotopes in methyl halides during degradation by chemical processes that are likely to occur in soil or seawater. These processes include aqueous hydrolysis and halide exchange and the methylation of organic matter using humic acid as the model methyl acceptor. Results are

  20. An investigation in the hygrothermal degradation of an E-glass/vinyl-ester composite in humid and immersion environments

    NASA Astrophysics Data System (ADS)

    Svetlik, Stephanie Laura

    The main goal of this research is to gain a fundamental understanding of the synergistic mechanisms of degradation for a model E-glass/vinyl-ester composite exposed to humid environments and to compare them to the mechanisms of degradation resulting from water immersion. Moisture sorption kinetics are assessed in terms of structural modification diffusion in order to understand how water sorption phenomena and leaching of low molecular weight species may be responsible for changes in material properties. Plasticization is identified using dynamic mechanical thermal analysis (DMTA) and is correlated to reversible degradation of the longitudinal tensile strength and short beam shear (SBS) strength. Tensile strength is also seen to decrease as a result of minimally reversible interfacial degradation, also identified through DMTA and SBS testing. Exposure to 18%RH and 50%RH results in material properties which remain within initial scatter except where increases in the glass transition temperature and SBS strength indicate matrix dominated strengthening also identified in material exposed to 99%RH and immersion at elevated temperatures. Tensile, SBS, and DMTA results all reveal degradation of the fiber resulting from exposure to high humidity and immersion environments at elevated temperatures. Scanning electron microscopy confirms the occurrence of interfacial debonding and fiber pitting. In material exposed to 80°C immersion, pitting of the fiber surface was identified at sites adjacent to kaolin clay, a hydrophilic particulate filler commonly used as a lubricant in pultrusion. Predictive degradation models are applied to tensile strength, SBS strength, and tensile failure strain results for 99%RH and immersion exposures, where irreversible degradation occurred at elevated temperatures. Degradation resulting from exposure to 99%RH and immersion is found to be equivalent. Predictive models show significant scatter based on the inability to isolate specific mechanisms

  1. Risk identification in haemodialysis patients by appropriate body composition assessment.

    PubMed

    Castellano, Sandra; Palomares, Inés; Moissl, Ulrich; Chamney, Paul; Carretero, Diana; Crespo, Antonio; Morente, Camilo; Ribera, Laura; Wabel, Peter; Ramos, Rosa; Merello, José Ignacio

    2016-01-01

    Circumstances such as gender, age, diabetes mellitus (DM) and renal failure impact on the body composition of patients. However, we use nutritional parameters such as lean and fat tissue with reference values from healthy subjects to assess the nutritional status of haemodialysis (HD) patients. To analyse body composition by bioimpedance spectroscopy (BIS) of 6395 HD patients in order to obtain reference values of lean tissue index (LTI) and fat tissue index (FTI) from HD patients; and to confirm its validity by showing that those patients with LTI below the 10th percentile calculated for their group have greatest risk of death. We used the BIS to determine the LTI and FTI in our cohort of HD patients in Spain. We calculated the 10th percentile and 90th percentile of LTI and FTI in each age decile for patients grouped by gender and presence of DM. We collected clinical, laboratory and demographic parameters. The LTI/FTI 10 and 90 percentile values varied by group (age, gender and presence of DM) and, after adjusting for other risk factors such as fluid overload, those patients with LTI lower than percentile 10 had a higher relative risk of death (OR 1.57) than those patients with higher values. Monitoring the LTI and FTI of patients on HD using suitable reference values may help to identify risk in this patient population. Copyright © 2016 Sociedad Española de Nefrología. Published by Elsevier España, S.L.U. All rights reserved.

  2. Continuous monitoring of the progressive degradation of a liquid composite by means of a noninvasive microwave resonator

    NASA Astrophysics Data System (ADS)

    Catala-Civera, Jose M.; Canos-Marin, Antoni J.; de los Reyes, E.

    2000-07-01

    Microwave control capabilities have been used to monitor the degradation of polyol, an alcohol composite material commonly used in the footwear industry for polymerization purposes. The liquid flows continuously inside a thin pipe and its desirable properties are altered with time associated to moisture absorption processes. Consequently, variations in the dielectric properties are involved, and they can be detected by permittivity measurements. In this paper, in order to obtain high sensitivity and resolution, a rectangular cavity resonator working at a fixed frequency was designed using as sample holder a rectangular pipe containing the liquid going through. Changes in the liquid modify the original response of the cavity with a non- degraded liquid and these differences have been used to determine the degree of degradation of the material. The final response of the microwave resonator was experimentally validated with measurements in a continuous line.

  3. Degradable Magnetic Composites for Minimally Invasive Interventions: Device Fabrication, Targeted Drug Delivery, and Cytotoxicity Tests.

    PubMed

    Peters, Christian; Hoop, Marcus; Pané, Salvador; Nelson, Bradley J; Hierold, Christofer

    2016-01-20

    Superparamagnetic nanoparticles and a functional, degradable polymer matrix based on poly(ethylene glycol) are combined to enable fully degradable magnetic microdevices for minimally invasive biomedical applications. A bioinspired helical microrobot platform mimicking Escherichia coli bacteria is fabricated and actuated using weak rotating magnetic fields. Locomotion based on corkscrew propulsion, targeted drug delivery, and low-degradation-product cytotoxicity are demonstrated. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Public Health Risk Conditioned by Chemical Composition of Ground Water

    NASA Astrophysics Data System (ADS)

    Yankovich, E.; Osipova, N.; Yankovich, K.; Matveenko, I.

    2016-03-01

    The article studies the public health potential risk originated from water consumption and estimated on the basis of the groundwater chemical composition. We have processed the results of chemical groundwater analysis in different aquifers of Tomsk district (Tomsk Oblast, Russia). More than 8400 samples of chemical groundwater analyses were taken during long-term observation period. Human health risk assessment of exposure to contaminants in drinking water was performed in accordance with the risk assessment guidance for public health concerning chemical pollution of the environment (Russian reference number: 2.1.10.1920-04-M, 2004). Identified potential risks were estimated for consuming water of each aquifer. The comparative analysis of water quality of different aquifers was performed on the basis of the risk coefficient of the total non-carcinogenic effects. The non-carcinogenic risk for the health of the Tomsk district population due to groundwater consumption without prior sanitary treatment was admitted acceptable. A rather similar picture is observed for all aquifers, although deeper aquifers show lower hazard coefficients.

  5. Assessing and monitoring the risk of land degradation in Baragan Plain, Romania, using spectral mixture analysis and Landsat imagery.

    PubMed

    Vorovencii, Iosif

    2016-07-01

    The fall of the communist regime in Romania at the end of 1989 and the ensuing transition to the market economy brought about many changes in the use of agricultural land. These changes combined with the action of climatic factors led, in most cases, to negative effects increasing the risk of degradation of agricultural land. This study aims to assess and monitor the risk of land degradation in Baragan Plain, Romania, for the period 1988-2011 using Landsat Thematic Mapper (TM) and Spectral Mixture Analysis (SMA). Each satellite image was classified through the Decision Tree Classifier (DTC) method; then, on the basis of certain threshold values, we obtained maps of land degradation and maps showing the passage from various classes of land use/land cover (LULC) to land degradation. The results indicate that during the intermediary periods there was an ascending and descending trend in the risk of land degradation determined by the interaction of climatic factors with the social-economic ones. For the entire period, the overall trend was ascending, the risk of land degradation increasing by around 4.60 % of the studied surface. Out of the climatic factors, high temperatures and, implicitly, drought were the most significant. The social-economic factors are the result of the changes which occurred after the fall of the communist regime, the most important being the fragmentation of agricultural land and the destruction of the irrigation system.

  6. EFFECTS OF ETHYLENE OXIDE RESTERILISATION AND IN-VITRO DEGRADATION ON MECHANICAL PROPERTIES OF PARTIALLY ABSORBABLE COMPOSITE HERNIA MESHES.

    PubMed

    Endogan, T; Ozyaylali, I; Kulacoglu, H; Serbetci, K; Kiyak, G; Hasirci, N

    2013-06-01

    Prosthetic mesh repair for abdominal wall hernias is widely used because of its technical simplicity and low hernia recurrence rates. The most commonly used material is pure polypropylene mesh, however newer composite materials are recommended by some centers because of their advantages. However, these meshes are more expensive than pure polypropylene meshes. Resterilisation of a pure polypropylene mesh has been shown to be quite safe, and many centers prefer slicing a large mesh into smaller pieces that suitable for hernia type or defect size. Nevertheless there is no data about the safety after resterilisation of the composite meshes. To search the effects of resterilisation and In vitro degradation in phosphate buffered saline solution on the physical structure and the mechanical properties of partially absorbable lightweigth meshes. Laboratory-based research. Two composite meshes were used in the study: One mesh is consisted of monofilament polypropylene and monofilament polyglecaprone--a copolymer of glycolide and epsilon (ε)-caprolactone--(Ultrapro®, 28 g/m2, Ethicon, Hamburg, Germany),andthe otherone consisted of multifilamentpolypropyleneandmultifilament polyglactine (Vypro II®, 30 g/m2,Ethicon, Hamburg, Germany). Two large meshes were cut into rectangular specimens sized 50x20 mm for mechanical testing and 20x20 mm for In vitro degradation experiments. Meshes were divided into control group with no resterilisation and gas resterilisation. Ethylene oxide gas sterilisation was performed at 55°C for 4.5 hours. In vitro degradation in 0.01 M phosphate buffered saline (PBS, pH 7.4) solution at 37 ± 1°C for 8 weeks was applied to one subgroup in each mesh group. Tensiometric measurements and scanning electron microscopyic evaluations were completed for control and resterilisation specimens. Regardless of resterilisation, when meshes were exposed to In vitro degradation, all mechanical parameters decreased significantly. Highest reduction in mechanical

  7. Effects of ethylene oxide resterilization and in-vitro degradation on mechanical properties of partially absorbable composite hernia meshes.

    PubMed

    Endogan, T; Ozyaylali, I; Kulacoglu, H; Serbetci, K; Kiyak, G; Hasirci, N

    2013-01-01

    Prosthetic mesh repair for abdominal wall hernias is widely used because of its technical simplicity and low hernia recurrence rates. The most commonly used material is pure polypropylene mesh, although newer composite materials are recommended by some centers due to their advantages.However, these meshes are more expensive than pure polypropylene meshes. Resterilization of a pure polypropylene mesh has been shown to be quite safe, and many centers prefer slicing a large mesh into smaller pieces, suitable for any hernia type or defect size. Nevertheless there is no data about the safety after resterilization of the composite meshes. The present study was carried out to investigate the effects of resterilization and in vitro degradation in phosphate buffered saline solution on the physical structure and the mechanical properties of partially absorbable lightweight meshes. Two composite meshes were used in the study: One mesh consists of monofilament polypropylene and monofilament polyglecaprone -a copolymer of glycolide and epsilon(ε)- caprolactone - (Ultrapro®, 28 g m2, Ethicon, Hamburg,Germany), and the other one consisted of multifilament polypropylene and multifilament polyglactine (Vypro II®, 30g m2, Ethicon, Hamburg, Germany). Two large meshes were cut into rectangular specimens sized 50 x 20 mm for mechanical testing and 20 x 20 mm for in vitro degradation experiments.Meshes were divided into control group with no resterilization and gas resterilization. Ethylene oxide gas sterilization was performed at 55°C for 4.5 hours. In vitro degradation in 0.01M phosphate buffered saline (PBS, pH 7.4) solution at 37 ± 1°C for 8 weeks was applied to one subgroup in each mesh group. Tensiometric measurements and scanning electronmicroscopic evaluations were completed for control and resterilization specimens. Regardless of resterilization, when the meshes were exposed to in vitro degradation, all mechanical parameters decreased significantly. Highest reduction in

  8. Environmental controls on fungal community composition and abundance over 3 years in native and degraded shrublands.

    PubMed

    Glinka, Clare; Hawkes, Christine V

    2014-11-01

    Soil fungal communities have high local diversity and turnover, but the relative contribution of environmental and regional drivers to those patterns remains poorly understood. Local factors that contribute to fungal diversity include soil properties and the plant community, but there is also evidence for regional dispersal limitation in some fungal communities. We used different plant communities with different soil conditions and experimental manipulations of both vegetation and dispersal to distinguish among these factors. Specifically, we compared native shrublands with former native shrublands that had been disturbed or converted to pasture, resulting in soils progressively more enriched in carbon and nutrients. We tested the role of vegetation via active removal, and we manipulated dispersal by adding living soil inoculum from undisturbed native sites. Soil fungi were tracked for 3 years, with samples taken at ten time points from June 2006 to June 2009. We found that soil fungal abundance, richness, and community composition responded primarily to soil properties, which in this case were a legacy of plant community degradation. In contrast, dispersal had no effect on soil fungi. Temporal variation in soil fungi was partly related to drought status, yet it was much broader in native sites compared to pastures, suggesting some buffering due to the increased soil resources in the pasture sites. The persistence of soil fungal communities over 3 years in this study suggests that soil properties can act as a strong local environmental filter. Largely persistent soil fungal communities also indicate the potential for strong biotic resistance and soil legacies, which presents a challenge for both the prediction of how fungi respond to environmental change and our ability to manipulate fungi in efforts such as ecosystem restoration.

  9. [Effect of the inoculant strain Sphingomonas paucimobilis 20006FA on the bacterial composition of a phenanthrene-degrading consortium].

    PubMed

    Madueño, L; Coppotelli, B M; Morelli, I S

    2009-01-01

    The effect of the inoculant strain Sphingomonas paucimobilis 20006FA on the bacterial composition of a phenanthrene-degrading consortium obtained from a pristine soil in sequencing batch cultures was studied. Inoculated (F200+1) and non-inoculated (F200) phenanthrene-degrading consortia, were obtained. Bacterial diversity of consortia was studied at cultivable (phenotype and genotype characterization) and non-cultivable (PCR-DGGE) levels. During the successive cultures, a loss in the phenanthrene-degrading capacity and a decrease in the bacterial diversity were observed in both consortia. Although inoculation did not produce any significant changes in the consortia phenanthrene-degrading capacity (29.9% F200 and 27.6% F200+1), it did produce changes in the bacterial composition, showing a differential structural dynamics in the DGGE profiles of the inoculated consortium. In both consortia, a dominant band placed at the same position as that of the DNA of the inoculant strain in the DGGE gel could be observed. However, isolated cultures from the consortia which had an identical band position to that of S. paucimobilis 20006FA in the PCR-DGGE profile showed low similarity with respect to the inoculant strain (RAPD).

  10. Fast-degrading PLA/ORMOGLASS fibrous composite scaffold leads to a calcium-rich angiogenic environment

    PubMed Central

    Sachot, Nadège; Roguska, Agata; Planell, Josep Anton; Lewandowska, Malgorzata; Engel, Elisabeth; Castaño, Oscar

    2017-01-01

    The success of scaffold implantation in acellular tissue engineering approaches relies on the ability of the material to interact properly with the biological environment. This behavior mainly depends on the design of the graft surface and, more precisely, on its capacity to biodegrade in a well-defined manner (nature of ions released, surface-to-volume ratio, dissolution profile of this release, rate of material resorption, and preservation of mechanical properties). The assessment of the biological behavior of temporary templates is therefore very important in tissue engineering, especially for composites, which usually exhibit complicated degradation behavior. Here, blended polylactic acid (PLA) calcium phosphate ORMOGLASS (organically modified glass) nanofibrous mats have been incubated up to 4 weeks in physiological simulated conditions, and their morphological, topographical, and chemical changes have been investigated. The results showed that a significant loss of inorganic phase occurred at the beginning of the immersion and the ORMOGLASS maintained a stable composition afterward throughout the degradation period. As a whole, the nanostructured scaffolds underwent fast and heterogeneous degradation. This study reveals that an angiogenic calcium-rich environment can be achieved through fast-degrading ORMOGLASS/PLA blended fibers, which seems to be an excellent alternative for guided bone regeneration. PMID:28744124

  11. Fast-degrading PLA/ORMOGLASS fibrous composite scaffold leads to a calcium-rich angiogenic environment.

    PubMed

    Sachot, Nadège; Roguska, Agata; Planell, Josep Anton; Lewandowska, Malgorzata; Engel, Elisabeth; Castaño, Oscar

    2017-01-01

    The success of scaffold implantation in acellular tissue engineering approaches relies on the ability of the material to interact properly with the biological environment. This behavior mainly depends on the design of the graft surface and, more precisely, on its capacity to biodegrade in a well-defined manner (nature of ions released, surface-to-volume ratio, dissolution profile of this release, rate of material resorption, and preservation of mechanical properties). The assessment of the biological behavior of temporary templates is therefore very important in tissue engineering, especially for composites, which usually exhibit complicated degradation behavior. Here, blended polylactic acid (PLA) calcium phosphate ORMOGLASS (organically modified glass) nanofibrous mats have been incubated up to 4 weeks in physiological simulated conditions, and their morphological, topographical, and chemical changes have been investigated. The results showed that a significant loss of inorganic phase occurred at the beginning of the immersion and the ORMOGLASS maintained a stable composition afterward throughout the degradation period. As a whole, the nanostructured scaffolds underwent fast and heterogeneous degradation. This study reveals that an angiogenic calcium-rich environment can be achieved through fast-degrading ORMOGLASS/PLA blended fibers, which seems to be an excellent alternative for guided bone regeneration.

  12. Resin Systems and Chemistry-Degradation Mechanisms and Durability in Long-Term Durability of Polymeric Matrix Composites. Chapter 1

    NASA Technical Reports Server (NTRS)

    Hinkley, Jeffrey A.; Connell, John W.

    2012-01-01

    In choosing a polymer-matrix composite material for a particular application, a number of factors need to be weighed. Among these are mechanical requirements, fabrication method (e.g. press-molding, resin infusion, filament winding, tape layup), and use conditions. Primary among the environmental exposures encountered in aerospace structures are moisture and elevated temperatures, but certain applications may require resistance to other fluids and solvents, alkaline agents, thermal cycling, radiation, or rapid, localized heating (for example, lightning strike). In this chapter, the main classes of polymer resin systems found in aerospace composites will be discussed. Within each class, their responses to environmental factors and the associated degradation mechanisms will be reviewed.

  13. Removal behaviors of sulfamonomethoxine and its degradation intermediates in fresh aquaculture wastewater using zeolite/TiO2 composites.

    PubMed

    Nomura, Youhei; Fukahori, Shuji; Fukada, Haruhisa; Fujiwara, Taku

    2017-10-15

    Removal efficiencies of sulfamonomethoxine (SMM) and its degradation intermediates formed by treatment with zeolite/TiO2 composites through adsorption and photocatalysis were investigated in fresh aquaculture wastewater (FAWW). Coexistent substances in the FAWW showed no inhibitory effects against SMM adsorption. Although coexistent substances in the FAWW inhibited the photocatalytic decomposition of SMM, the composites mitigated the inhibition, possibly because of concentration of SMM on their surface by adsorption. LC/MS/MS analyses revealed that hydroxylation of amino phenyl and pyrimidinyl portions, transformation of the amino group in the amino phenyl portion into a nitroso group, and substitution of the methoxy group with a hydroxyl group occurring in the initial reaction resulted in the formation of various intermediates during the photocatalysis of SMM. All detected intermediates had a ring structure, and almost all intermediates disappeared at the same time SMM was completely decomposed. Ph-OH formed by hydroxylation of the phenyl portion was detected upon decomposition of SMM during photocatalysis. The removal of Ph-OH by the composites proceeded more rapidly than that by TiO2 alone under ultraviolet irradiation. The SMM and Ph-OH were completely degraded by the composites within 30min, showing that the zeolite/TiO2 composites were effective in removing SMM and its intermediates from FAWW. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Degradation Factor Approach for Impacted Composite Structural Assessment: MSFC Center Director's Discretionary Fund Final Report, Project No. 96-17

    NASA Technical Reports Server (NTRS)

    Ortega, R.; Price, J. M.; Fox, D.

    2000-01-01

    This technical memorandum documents the results of the research to develop a concept for assessing the structural integrity of impacted composite structures using the strength degradation factor in conjunction with available finite element tools. For this purpose, a literature search was conducted, a plan for conducting impact testing on two laminates was developed, and a finite element model of the impact process was created. Specimens for the impact testing were fabricated to support the impact testing plan.

  15. Ternary composite scaffolds with tailorable degradation rate and highly improved colonization by human bone marrow stromal cells.

    PubMed

    Idaszek, J; Bruinink, A; Święszkowski, W

    2015-07-01

    Poly(ε-caprolactone), PCL, is of great interest for fabrication of biodegradable scaffolds due to its high compatibility with various manufacturing techniques, especially Fused Deposition Modeling (FDM). However, slow degradation and low strength make application of PCL limited only to longer-term bioresorbable and non-load bearing implants. To overcome latter drawbacks, ternary PCL-based composite fibrous scaffolds consisting of 70-95 wt % PCL, 5 wt % Tricalcium Phosphate (TCP) and 0-25 wt % poly(lactide-co-glycolide) (PLGA) were fabricated using FDM. In the present study, the effect of composition of the scaffolds on their mechanical properties, degradation kinetics, and surface properties (wettability, surface energy, and roughness) was investigated and correlated with response of human bone marrow mesenchymal stromal cells (HBMC). The presence of PLGA increased degradation kinetics, surface roughness and significantly improved scaffold colonization. Of the evaluated surface properties only the wettability was correlated with the surface area colonized by HBMC. This study demonstrates that introduction of PLGA into PCL-TCP binary composite could largely abolish the disadvantages of the PCL matrix and improve biocompatibility by increasing wettability and polar interactions rather than surface roughness. Additionally, we showed great potential of multicellular spheroids as a sensitive in vitro tool for detection of differences in chemistry of 3D scaffolds. © 2014 Wiley Periodicals, Inc.

  16. Composite scaffolds of dicalcium phosphate anhydrate /multi-(amino acid) copolymer: in vitro degradability and osteoblast biocompatibility.

    PubMed

    Yao, Qianqian; Ye, Jun; Xu, Qian; Mo, Anchun; Gong, Ping

    2015-01-01

    This study aims to evaluate in vitro degradability and osteoblast biocompatibility of dicalcium phosphate anhydrate/multi-(amino acid) (DCPA/MAA) composites prepared by in situ polymerization method. The results revealed that the composites could be slowly degraded in PBS solution, with weight loss of 9.5 ± 0.2 wt.% compared with 12.2 ± 0.2 wt.% of MAA copolymer after eight weeks, and the changes of pH value were in the range of 7.18-7.4 and stabilized at 7.24. In addition, the compressive strength of the composite decreased from 98 to 62 MPa while that of MAA copolymer from 117 to 86 MPa. Furthermore, with non-toxicity demonstrated by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide assay, the addition of DCPA to the MAA copolymer evidenced an enhancement of osteoblast differentiation and attachment compared with pure MAA materials regarding to alkaline phosphatase activity as well as initial cell adhesion. The results indicated that the DCPA/MAA scaffolds with good osteoblast biocompatibility, degradability, and sufficient strength had promising potential application in bone tissue engineering.

  17. [Selection of a composite microbial system MC1 with efficient and stability cellulose degradation bacteria and its function].

    PubMed

    Cui, Zongjun; Li, Meidan; Piao, Zhe; Huang, Zhiyong; Ishii, Masaharu; Igarashi, Yasuo

    2002-05-01

    Four groups of microbial mix culture with considerable capability of cellulose degradation were selected from four compost heaps, by combining the four groups, a composite microbial system MC1 with highly efficient cellulose degradation was obtained. It was found that 0.48 g of filter paper, 0.49 g of absorbent cotton, 0.19 g of wheat straw, or 0.08 g of wood residue can be degraded by 100 mL of MC1 at 50 degrees C with in 72 hours under static culture. The CM1 saccharification activity was much higher at 24th hours when degrading filter paper that was 122.3 U.mL-1. This capability of degradation maintained more than 20 days when the substrates were continually added. MC1 could be inoculated in a wide pH rang, from 4 to 10; however, the final pH would be changed to neutrality after incubation. The pH would be stability with filter paper between 6.0 and 6.5, and between 8.0 and 8.5 without the filter paper.

  18. Conductivity degradation of polyvinylidene fluoride composite binder during cycling: Measurements and simulations for lithium-ion batteries

    DOE PAGES

    Grillet, Anne M.; Humplik, Thomas; Stirrup, Emily K.; ...

    2016-07-02

    The polymer-composite binder used in lithium-ion battery electrodes must both hold the electrodes together and augment their electrical conductivity while subjected to mechanical stresses caused by active material volume changes due to lithiation and delithiation. We have discovered that cyclic mechanical stresses cause significant degradation in the binder electrical conductivity. After just 160 mechanical cycles, the conductivity of polyvinylidene fluoride (PVDF):carbon black binder dropped between 45–75%. This degradation in binder conductivity has been shown to be quite general, occurring over a range of carbon black concentrations, with and without absorbed electrolyte solvent and for different polymer manufacturers. Mechanical cycling ofmore » lithium cobalt oxide (LiCoO2) cathodes caused a similar degradation, reducing the effective electrical conductivity by 30–40%. Mesoscale simulations on a reconstructed experimental cathode geometry predicted the binder conductivity degradation will have a proportional impact on cathode electrical conductivity, in qualitative agreement with the experimental measurements. Lastly, ohmic resistance measurements were made on complete batteries. Direct comparisons between electrochemical cycling and mechanical cycling show consistent trends in the conductivity decline. This evidence supports a new mechanism for performance decline of rechargeable lithium-ion batteries during operation – electrochemically-induced mechanical stresses that degrade binder conductivity, increasing the internal resistance of the battery with cycling.« less

  19. Conductivity degradation of polyvinylidene fluoride composite binder during cycling: Measurements and simulations for lithium-ion batteries

    SciTech Connect

    Grillet, Anne M.; Humplik, Thomas; Stirrup, Emily K.; Roberts, Scott A.; Barringer, David A.; Snyder, Chelsea M.; Janvrin, Madison R.; Apblett, Christopher A.

    2016-07-02

    The polymer-composite binder used in lithium-ion battery electrodes must both hold the electrodes together and augment their electrical conductivity while subjected to mechanical stresses caused by active material volume changes due to lithiation and delithiation. We have discovered that cyclic mechanical stresses cause significant degradation in the binder electrical conductivity. After just 160 mechanical cycles, the conductivity of polyvinylidene fluoride (PVDF):carbon black binder dropped between 45–75%. This degradation in binder conductivity has been shown to be quite general, occurring over a range of carbon black concentrations, with and without absorbed electrolyte solvent and for different polymer manufacturers. Mechanical cycling of lithium cobalt oxide (LiCoO2) cathodes caused a similar degradation, reducing the effective electrical conductivity by 30–40%. Mesoscale simulations on a reconstructed experimental cathode geometry predicted the binder conductivity degradation will have a proportional impact on cathode electrical conductivity, in qualitative agreement with the experimental measurements. Lastly, ohmic resistance measurements were made on complete batteries. Direct comparisons between electrochemical cycling and mechanical cycling show consistent trends in the conductivity decline. This evidence supports a new mechanism for performance decline of rechargeable lithium-ion batteries during operation – electrochemically-induced mechanical stresses that degrade binder conductivity, increasing the internal resistance of the battery with cycling.

  20. Central composite design optimization of pilot plant fluidized-bed heterogeneous Fenton process for degradation of an azo dye.

    PubMed

    Aghdasinia, Hassan; Bagheri, Rasoul; Vahid, Behrouz; Khataee, Alireza

    2016-11-01

    Optimization of Acid Yellow 36 (AY36) degradation by heterogeneous Fenton process in a recirculated fluidized-bed reactor was studied using central composite design (CCD). Natural pyrite was applied as the catalyst characterized by X-ray diffraction and scanning electron microscopy. The CCD model was developed for the estimation of degradation efficiency as a function of independent operational parameters including hydrogen peroxide concentration (0.5-2.5 mmol/L), initial AY36 concentration (5-25 mg/L), pH (3-9) and catalyst dosage (0.4-1.2 mg/L). The obtained data from the model are in good agreement with the experimental data (R(2 )= 0.964). Moreover, this model is applicable not only to determine the optimized experimental conditions for maximum AY36 degradation, but also to find individual and interactive effects of the mentioned parameters. Finally, gas chromatography-mass spectroscopy (GC-MS) was utilized for the identification of some degradation intermediates and a plausible degradation pathway was proposed.

  1. Poly(propylene fumarate)/(calcium sulphate/beta-tricalcium phosphate) composites: preparation, characterization and in vitro degradation.

    PubMed

    Cai, Zhong-Yu; Yang, De-An; Zhang, Na; Ji, Cheng-Guang; Zhu, Lei; Zhang, Tao

    2009-02-01

    This study aimed to prepare a poly(propylene fumarate)/(calcium sulphate/beta-tricalcium phosphate) (PPF/(CaSO(4)/beta-TCP)) composite. We first examined the effects of varying the molecular weight of PPF and the N-vinyl pyrrolidinone (NVP) to PPF ratio on the maximum cross-linking temperature and the composite compressive strength and modulus. Then the in vitro biodegradation behaviour of PPF/(CaSO(4)/beta-TCP) composites was investigated. The effects of varying the molecular weight of PPF, the NVP/PPF ratio and the CaSO(4)/beta-TCP molar ratio on the weight loss and the composite compressive strength and modulus were examined. The cross-linking temperature, which increased with increasing molecular weight of PPF and NVP/PPF ratio, ranged from 41 to 43 degrees C for all formulations. The mechanical properties were increased by a decrease in the NVP/PPF ratio. For all formulations, the compressive strength values fell between 12 and 62 MPa, while the compressive modulus values fell between 290 and 1149 MPa. The weight loss decreased either with increasing molecular weight of PPF or with decreasing NVP/PPF ratio and CaSO(4)/beta-TCP molar ratio during degradation. The compressive strength and modulus increased with decreasing NVP/PPF ratio or decreasing CaSO(4)/beta-TCP ratio. The greatest weight loss over 6 weeks was 14.72%. For all formulations, the compressive modulus values fell between 57 and 712 MPa and the compressive strength fell between 0.5 and 21 MPa throughout 6 weeks degradation. Scanning electron microscopy and X-ray diffraction analysis of the PPF/(CaSO(4)/beta-TCP) composites demonstrated that hydroxyapatite was deposited on the surface of CaSO(4)/beta-TCP granules during degradation.

  2. Thermal degradation of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) over synthesized Fe-Al composite oxide.

    PubMed

    Yang, Fan; Li, Qianqian; Su, Guijin; Huang, Xinchen; Li, Binke; Zhao, Yanhui; Miao, Xue; Zheng, Minghui

    2016-05-01

    A series of Fe-Al composite oxides were synthesized by the hydrothermal method using different urea dosages and examined towards the degradation of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) at 300 °C. The as-prepared oxides were characterized by field-emission scanning electron microscopy, X-ray diffraction and energy-dispersive X-ray spectroscopy. The morphology and composition of the prepared materials could be regulated by controlling the urea concentration. Interestingly, these properties influenced the nature and amount of the hydrodebromination products generated during the degradation of BDE-47. The degradation of BDE-47 over the composite oxide prepared at a urea dosage of 3 mmol generated BDE-17 as the major isomer product, followed by BDE-28/33, -30, and -32, among the tribromodiphenyl ethers (tri-BDEs). Regarding the dibromodiphenyl ethers (di-BDEs) produced, the amount of the isomers decreased in the order of BDE-8/11 > BDE-7 > BDE-15 > BDE-10. And the BDE-1 among monobromodiphenyl was determined. In contrast, over the composite oxides prepared at urea dosages greater than 3 mmol, BDE-28/33 gradually become the major isomer product instead of BDE-17 among tri-BDEs. The amount of the other di-BDEs isomer such as BDE-15 and -10 approach to be comparable to that BDE-8/11. However, regardless of the urea dosage, BDE-47 converted into BDE-75 via an isomerization reaction. Based on these intermediate products identification, a possible hydrodebromination mechanism of BDE-47 over Fe-Al composite oxide was comprehensively traced. Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. Risk assessment of desert pollution on composite high voltage insulators.

    PubMed

    El-Shahat, Mohammed; Anis, Hussein

    2014-09-01

    Transmission lines located in the desert are subjected to desert climate, one of whose features is sandstorms. With long accumulation of sand and with the advent of moisture from rain, ambient humidity and dew, a conductive layer forms and the subsequent leakage current may lead to surface discharge, which may shorten the insulator life or lead to flashover thus interrupting the power supply. Strategically erected power lines in the Egyptian Sinai desert are typically subject to such a risk, where sandstorms are known to be common especially in the spring. In view of the very high cost of insulator cleaning operation, composite (silicon rubber) insulators are nominated to replace ceramic insulators on transmission lines in Sinai. This paper examines the flow of leakage current on sand-polluted composite insulators, which in turn enables a risk assessment of insulator failure. The study uses realistic data compiled and reported in an earlier research project about Sinai, which primarily included grain sizes of polluting sand as well as their salinity content. The paper also uses as a case study an ABB-designed composite insulator. A three-dimensional finite element technique is used to simulate the insulator and seek the potential and electric field distribution as well as the resulting leakage current flow on its polluted surface. A novel method is used to derive the probabilistic features of the insulator's leakage current, which in turn enables a risk assessment of insulator failure. This study is expected to help in critically assessing - and thus justifying - the use of this type of insulators in Sinai and similar critical areas.

  4. Risk assessment of desert pollution on composite high voltage insulators

    PubMed Central

    El-Shahat, Mohammed; Anis, Hussein

    2013-01-01

    Transmission lines located in the desert are subjected to desert climate, one of whose features is sandstorms. With long accumulation of sand and with the advent of moisture from rain, ambient humidity and dew, a conductive layer forms and the subsequent leakage current may lead to surface discharge, which may shorten the insulator life or lead to flashover thus interrupting the power supply. Strategically erected power lines in the Egyptian Sinai desert are typically subject to such a risk, where sandstorms are known to be common especially in the spring. In view of the very high cost of insulator cleaning operation, composite (silicon rubber) insulators are nominated to replace ceramic insulators on transmission lines in Sinai. This paper examines the flow of leakage current on sand-polluted composite insulators, which in turn enables a risk assessment of insulator failure. The study uses realistic data compiled and reported in an earlier research project about Sinai, which primarily included grain sizes of polluting sand as well as their salinity content. The paper also uses as a case study an ABB-designed composite insulator. A three-dimensional finite element technique is used to simulate the insulator and seek the potential and electric field distribution as well as the resulting leakage current flow on its polluted surface. A novel method is used to derive the probabilistic features of the insulator’s leakage current, which in turn enables a risk assessment of insulator failure. This study is expected to help in critically assessing – and thus justifying – the use of this type of insulators in Sinai and similar critical areas. PMID:25685525

  5. Effect of the preparation methods on architecture, crystallinity, hydrolytic degradation, bioactivity, and biocompatibility of PCL/bioglass composite scaffolds.

    PubMed

    Dziadek, Michal; Pawlik, Justyna; Menaszek, Elzbieta; Stodolak-Zych, Ewa; Cholewa-Kowalska, Katarzyna

    2015-11-01

    In this study, two different composition gel derived silica-rich (S2) or calcium-rich (A2) bioactive glasses (SBG) from a basic CaO-P2 O5 -SiO2 system were incorporated into poly(ε-caprolactone) (PCL) matrix to obtain novel bioactive composite scaffolds for bone tissue engineering applications. The composites were fabricated in the form of highly porous 3D scaffolds using following preparation methods: solvent casting particulate leaching (SCPL), solid-liquid phase separation, phase inversion (PI). Scaffolds containing 21% vol. of each bioactive glass were characterized for architecture, crystallinity, hydrolytic degradation, surface bioactivity, and cellular response. Results indicated that the use of different preparation methods leads to obtain highly porous (60-90%) materials with differentiated morphology: pore shape, size, and distributions. Thermal analysis (DSC) showed that the preparation method of materials and addition of bioactive glass particles into polymer matrix induced the changes of PCL crystallinity. Composites obtained by SCPL and PI method containing A2 SBG rapidly formed a hydroxyapatite calcium phosphate surface layer after incubation in SBF. Bioactive glasses used as filler in composite scaffolds could neutralize the released acidic by-products of the polymer degradation. Preliminary in vitro biological studies of the composites in contact with osteoblastic cells showed good biocompatibility of the obtained materials. Addition of bioactive glass into the PCL matrix promotes mineralization estimated on the basis of the ALP activity. These results suggest that through a process of selection appropriate methods of preparation and bioglass composition it is possible to design and obtain porous materials with suitable properties for regeneration of bone tissue.

  6. Electrochemical degradation of carbamazepine using modified electrode with graphene-AuAg composite

    NASA Astrophysics Data System (ADS)

    Pogacean, F.; Biris, A. R.; Socaci, C.; Floare-Avram, V.; Rosu, M. C.; Coros, M.; Pruneanu, S.

    2015-12-01

    Carbamazepine is a pharmaceutical drug which has been detected in surface and drinking water primarily due to human usage but also from the accidental disposal of pharmaceuticals into sewers. We have developed a graphene-modified electrode which was tested at the detection and degradation of carbamazepine. The oxidation process was studied by cyclic voltammetry in aqueous and organic solutions. The electrochemical degradation of carbamazepine was performed by polarizing the working electrode at a certain potential, for different times (from 5 to 60 minutes). The degradation efficiency was highly dependent on the type of solution and on the supporting electrolyte.

  7. Self-reinforced composites of bioabsorbable polymer and bioactive glass with different bioactive glass contents. Part II: In vitro degradation.

    PubMed

    Niemelä, Tiiu; Niiranen, Henna; Kellomäki, Minna

    2008-01-01

    The in vitro degradation behavior of self-reinforced bioactive glass-containing composites was investigated comparatively with plain self-reinforced matrix polymer. The materials used were spherical bioactive glass 13-93 particles, with a particle size distribution of 50-125 microm, as a filler material and bioabsorbable poly-L,DL-lactide 70/30 as a matrix material. The composites containing 0, 20, 30, 40 and 50 wt.% of bioactive glass were manufactured using twin-screw extruder followed by self-reinforcing. The samples studied were characterized determining the changes in mechanical properties, thermal properties, molecular weight, mass loss and water absorption in phosphate-buffered saline at 37 degrees C for up to 104 weeks. The results showed that the bioactive glass addition modified the degradation kinetics and material morphology of the matrix material. It was concluded that the optimal bioactive glass content depends on the applications of the composites. The results of this study could be used as a guideline when estimating the best filler content of other self-reinforced osteoconductive filler containing composites which are manufactured in a similar way.

  8. Mechanical and degradation properties of biodegradable Mg strengthened poly-lactic acid composite through plastic injection molding.

    PubMed

    Butt, Muhammad Shoaib; Bai, Jing; Wan, Xiaofeng; Chu, Chenglin; Xue, Feng; Ding, Hongyan; Zhou, Guanghong

    2017-01-01

    Full biodegradable magnesium alloy (AZ31) strengthened poly-lactic acid (PLA) composite rods for potential application for bone fracture fixation were prepared by plastic injection process in this work. Their surface/interfacial morphologies, mechanical properties and vitro degradation were studied. In comparison with untreated Mg rod, porous MgO ceramic coating on Mg surface formed by Anodizing (AO) and micro-arc-oxidation (MAO)treatment can significantly improve the interfacial binding between outer PLA cladding and inner Mg rod due to the micro-anchoring action, leading to better mechanical properties and degradation performance of the composite rods.With prolonging immersion time in simulated body fluid (SBF) solution until 8weeks, the MgO porous coating were corroded gradually, along with the disappearance of original pores and the formation of a relatively smooth surface. This resulted in a rapidly reduction in mechanical properties for corresponding composite rods owing to the weakening of interfacial binding capacity. The present results indicated that this new PLA-clad Mg composite rods show good potential biomedical applications for implants and instruments of orthopedic inner fixation. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. An amphiphilic degradable polymer/hydroxyapatite composite with enhanced handling characteristics promotes osteogenic gene expression in bone marrow stromal cells.

    PubMed

    Kutikov, Artem B; Song, Jie

    2013-09-01

    Electrospun polymer/hydroxyapatite (HA) composites combining biodegradability with osteoconductivity are attractive for skeletal tissue engineering applications. However, most biodegradable polymers such as poly(lactic acid) (PLA) are hydrophobic and do not blend with adequate interfacial adhesion with HA, compromising the structural homogeneity, mechanical integrity and biological performance of the composite. To overcome this challenge, we combined a hydrophilic polyethylene glycol (PEG) block with poly(d,l-lactic acid) to improve the adhesion of the degradable polymer with HA. The amphiphilic triblock copolymer PLA-PEG-PLA (PELA) improved the stability of HA-PELA suspension at 25wt.% HA content, which was readily electrospun into HA-PELA composite scaffolds with uniform fiber dimensions. HA-PELA was highly extensible (failure strain>200% vs. <40% for HA-PLA), superhydrophilic (∼0° water contact angle vs. >100° for HA-PLA), and exhibited an 8-fold storage modulus increase (unlike deterioration for HA-PLA) upon hydration, owing to the favorable interaction between HA and PEG. HA-PELA also better promoted osteochondral lineage commitment of bone marrow stromal cells in unstimulated culture and supported far more potent osteogenic gene expression upon induction than HA-PLA. We demonstrate that the chemical incorporation of PEG is an effective strategy to improve the performance of degradable polymer/HA composites for bone tissue engineering applications.

  10. Database for the degradation risk assessment of groundwater resources (Southern Italy)

    NASA Astrophysics Data System (ADS)

    Polemio, M.; Dragone, V.; Mitolo, D.

    2003-04-01

    The risk characterisation of quality degradation and availability lowering of groundwater resources has been pursued for a wide coastal plain (Basilicata region, Southern Italy), an area covering 40 km along the Ionian Sea and 10 km inland. The quality degradation is due two phenomena: pollution due to discharge of waste water (coming from urban areas) and due to salt pollution, related to seawater intrusion but not only. The availability lowering is due to overexploitation but also due to drought effects. To this purpose the historical data of 1,130 wells have been collected. Wells, homogenously distributed in the area, were the source of geological, stratigraphical, hydrogeological, geochemical data. In order to manage space-related information via a GIS, a database system has been devised to encompass all the surveyed wells and the body of information available per well. Geo-databases were designed to comprise the four types of data collected: a database including geometrical, geological and hydrogeological data on wells (WDB), a database devoted to chemical and physical data on groundwater (CDB), a database including the geotechnical parameters (GDB), a database concering piezometric and hydrological (rainfall, air temperature, river discharge) data (HDB). The record pertaining to each well is identified in these databases by the progressive number of the well itself. Every database is designed as follows: a) the HDB contains 1,158 records, 28 of and 31 fields, mainly describing the geometry of the well and of the stratigraphy; b) the CDB encompasses data about 157 wells, based on which the chemical and physical analyses of groundwater have been carried out. More than one record has been associated with these 157 wells, due to periodic monitoring and analysis; c) the GDB covers 61 wells to which the geotechnical parameters obtained by soil samples taken at various depths; the HDB is designed to permit the analysis of long time series (from 1918) of piezometric

  11. In vitro degradation and biocompatibility of Fe-Pd and Fe-Pt composites fabricated by spark plasma sintering.

    PubMed

    Huang, T; Cheng, J; Zheng, Y F

    2014-02-01

    In order to obtain biodegradable Fe-based materials with similar mechanical properties as 316L stainless steel and faster degradation rate than pure iron, Fe-5 wt.%Pd and Fe-5 wt.%Pt composites were prepared by spark plasma sintering with powders of pure Fe and Pd/Pt, respectively. The grain size of Fe-5 wt.%Pd and Fe-5 wt.%Pt composites was much smaller than that of as-cast pure iron. The metallic elements Pd and Pt were uniformly distributed in the matrix and the mechanical properties of these materials were improved. Uniform corrosion of Fe-Pd and Fe-Pt composites was observed in both electrochemical tests and immersion tests, and the degradation rates of Fe-Pd and Fe-Pt composites were much faster than that of pure iron. It was found that viabilities of mouse fibroblast L-929 cells and human umbilical vein endothelial cells (ECV304) cultured in extraction mediums of Fe-Pd and Fe-Pt composites were close to that of pure iron. After 4 days' culture, the viabilities of L-929 and ECV304 cells in extraction medium of experimental materials were about 80%. The result of direct contact cytotoxicity also indicated that experimental materials exhibited no inhibition on vascular endothelial process. Meanwhile, iron ions released from experimental materials could inhibit proliferation of vascular smooth muscle cells (VSMC), which may be beneficial for hindering vascular restenosis. Furthermore, compared with that of as-cast pure iron, the hemolysis rates of Fe-Pd and Fe-Pt composites were slightly higher, but still within the range of 5%, which is the criteria for good blood compatibility. The numbers of platelet adhered on the surface of Fe-Pd and Fe-Pt composites were lower than that of pure iron, and the morphology of platelets kept spherical. To sum up, the Fe-5 wt.%Pd and Fe-5 wt.%Pt composites exhibited good mechanical properties and degradation behavior, closely approaching the requirements for biodegradable metallic stents.

  12. Degradation of the current-carrying capacity of low-temperature superconducting composites under the action of thermal perturbations

    NASA Astrophysics Data System (ADS)

    Romanovskii, V. R.

    2016-10-01

    The stability of transport current introduced into a niobium titanium superconducting composite subjected to an external pulsed thermal perturbation has been studied. Stable states have been theoretically analyzed by solving Fourier and Maxwell equations that describe the thermoelectrodynamic states of lowtemperature superconductors with flux creep. It has been shown that, if the transport current is permanently introduced, subcritical thermal perturbations, i.e., perturbations that do not take the composite to a normal state provided that the current does not exceed the quench current, may result in the appearance of unstable current states. The higher the energy of the external thermal perturbation, the lower the instability onset current. It has been found that the degradation of the current-carrying capacity of the superconducting composite is due to intense heat release inside the superconductor, which is initiated by the thermal perturbations, and depends on the current input rate, the instant of time the current input is terminated, and cooling conditions.

  13. Electron donors and co-contaminants affect microbial community composition and activity in perchlorate degradation.

    PubMed

    Guan, Xiangyu; Xie, Yuxuan; Wang, Jinfeng; Wang, Jing; Liu, Fei

    2015-04-01

    Although microbial reduction of perchlorate (ClO4(-)) is a promising and effective method, our knowledge on the changes in microbial communities during ClO4(-) degradation is limited, especially when different electron donors are supplied and/or other contaminants are present. Here, we examined the effects of acetate and hydrogen as electron donors and nitrate and ammonium as co-contaminants on ClO4(-) degradation by anaerobic microcosms using six treatments. The process of degradation was divided into the lag stage (SI) and the accelerated stage (SII). Quantitative PCR was used to quantify four genes: pcrA (encoding perchlorate reductase), cld (encoding chlorite dismutase), nirS (encoding copper and cytochrome cd1 nitrite reductase), and 16S rRNA. While the degradation of ClO4(-) with acetate, nitrate, and ammonia system (PNA) was the fastest with the highest abundance of the four genes, it was the slowest in the autotrophic system (HYP). The pcrA gene accumulated in SI and played a key role in initiating the accelerated degradation of ClO4(-) when its abundance reached a peak. Degradation in SII was primarily maintained by the cld gene. Acetate inhibited the growth of perchlorate-reducing bacteria (PRB), but its effect was weakened by nitrate (NO3(-)), which promoted the growth of PRB in SI, and therefore, accelerated the ClO4(-) degradation rate. In addition, ammonia (NH4(+)), as nitrogen sources, accelerated the growth of PRB. The bacterial communities' structure and diversity were significantly affected by electron donors and co-contaminants. Under heterotrophic conditions, both ammonia and nitrate promoted Azospira as the most dominant genera, a fact that might significantly influence the rate of ClO4(-) natural attenuation by degradation.

  14. Study of photo catalytic degradation of an industrial dye Ujala Supreme and Methyl Orange using SnO2-rGO composites

    NASA Astrophysics Data System (ADS)

    Rambabu, P.; Srivastava, S. K.; Turpu, G. R.

    2016-05-01

    The photo degradation nature of Methyl Orange and Ujala Supreme dyes are studied using SnO2-rGO composites. Initially, the Graphene Oxide (GO) is prepared by modified Hummers method. Then SnO2-rGO composite is prepared solgel method by taking SnCl2 and GO as precursor materials. The obtained powders are annealed in N2 ambient for two hours in a quartz tube. The structure of the obtained powder composites shows high crystallinity from XRD measurements. The Raman studies also show the D and G bands for the GO. The degradation behaviour is studied for different times with the help of UV-Vis spectrometer. The absorbance graphs reveal that the Ujala Supreme dye is degraded much faster in presence of SnO2-rGO where as Methyl Orange has shown almost no effect on degradation in presence of SnO2-rGO composite.

  15. Body composition and risk for metabolic alterations in female adolescents

    PubMed Central

    de Faria, Eliane Rodrigues; Gontijo, Cristiana Araújo; Franceschini, Sylvia do Carmo C.; Peluzio, Maria do Carmo G.; Priore, Silvia Eloiza

    2014-01-01

    OBJECTIVE: To study anthropometrical and body composition variables as predictors of risk for metabolic alterations and metabolic syndrome in female adolescents. METHODS: Biochemical, clinical and corporal composition data of 100 adolescents from 14 to 17 years old, who attended public schools in Viçosa, Southeastern Brazil, were collected. RESULTS: Regarding nutritional status, 83, 11 and 6% showed eutrophia, overweight/obesity and low weight, respectively, and 61% presented high body fat percent. Total cholesterol presented the highest percentage of inadequacy (57%), followed by high-density lipoprotein (HDL - 50%), low-density lipoprotein (LDL - 47%) and triacylglycerol (22%). Inadequacy was observed in 11, 9, 3 and 4% in relation to insulin resistance, fasting insulin, blood pressure and glycemia, respectively. The highest values of the fasting insulin and the Homeostasis Model Assessment-Insulin Resistance (HOMA-IR) were verified at the highest quartiles of body mass index (BMI), waist perimeter, waist-to-height ratio and body fat percent. Body mass index, waist perimeter, and waist-to-height ratio were the better predictors for high levels of HOMA-IR, blood glucose and fasting insulin. Waist-to-hip ratio was associated to arterial hypertension diagnosis. All body composition variables were effective in metabolic syndrome diagnosis. CONCLUSIONS: Waist perimeter, BMI and waist-to-height ratio showed to be good predictors for metabolic alterations in female adolescents and then should be used together for the nutritional assessment in this age range. PMID:25119752

  16. Sonochemical Degradation of Reactive Black 5 with a Composite Catalyst of TiO2/Single-Walled Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Cho, Eunju; Choi, Jongbok; Lee, Yonghyeon; Park, Jeong Min; Khim, Jeehyeong

    2013-07-01

    In the sonocatalytic process, composites of TiO2-carbon were used because carbon provides more adsorption sites and acts like an electron sink to prevent the recombination of an electron/hole. Therefore, in the present study, the characteristics of a TiO2/single-walled carbon nanotubes catalyst (TiO2/SWCNTs) have been investigated, and the optimal weight ratio of SWCNTs and the dose for degradation of reactive black 5 (RB5) were also evaluated. TiO2/SWCNT composite was characterized using Brunauer-Emmett-Teller analysis, scanning electron microscopy, energy-dispersive X-ray diffraction microanalysis and spectra, and X-ray diffraction patterns. The degradation rate constants of RB5 with the ratio of SWCNTs were found to depend on the adsorption phenomenon of a surface catalyst, light absorbance, and the recombination of electrons and holes. As a result, the optimal ratio of carbon in the sono-TiO2/SWCNTs process for degradation of RB5 was TiO2:SWCNTs= 200:1. Additionally, the optimal dose of the catalyst was 0.5 g/L.

  17. Biocompatibility, degradability, bioactivity and osteogenesis of mesoporous/macroporous scaffolds of mesoporous diopside/poly(l-lactide) composite

    PubMed Central

    Liu, Zhulin; Ji, Jiajin; Tang, Songchao; Qian, Jun; Yan, Yonggang; Yu, Baoqing; Su, Jiacan; Wei, Jie

    2015-01-01

    Bioactive mesoporous diopside (m-DP) and poly(l-lactide) (PLLA) composite scaffolds with mesoporous/macroporous structure were prepared by the solution-casting and particulate-leaching method. The results demonstrated that the degradability and bioactivity of the mesoporous/macroporous scaffolds were significantly improved by incorporating m-DP into PLLA, and that the improvement was m-DP content-dependent. In addition, the scaffolds containing m-DP showed the ability to neutralize acidic degradation products and prevent the pH from dropping in the solution during the soaking period. Moreover, the scaffolds containing m-DP enhanced attachment, proliferation and alkaline phosphatase activity of MC3T3-E1 cells, which were also m-DP content-dependent. Furthermore, the histological and immunohistochemical analysis results showed that the scaffolds with m-DP significantly promoted new bone formation and improved the materials degraded in vivo, indicating good biocompatibility. The results suggested that the mesoporous/macroporous scaffolds of the m-DP/PLLA composite with osteogenesis had a potential for bone regeneration. PMID:26378120

  18. Enhanced photocatalytic degradation of phenol and photogenerated charges transfer property over BiOI-loaded ZnO composites.

    PubMed

    Jiang, Jingjing; Wang, Hongtao; Chen, Xiaodong; Li, Shuo; Xie, Tengfeng; Wang, Dejun; Lin, Yanhong

    2017-05-15

    In this paper, a series of BiOI/ZnO photocatalysts containing various BiOI contents were prepared by a facile two-step synthetic method. The structure and crystal phase, morphology, surface element analysis, optical property of as-prepared samples are measured by X-ray diffraction (XRD), Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and UV-Vis diffuse reflectance spectrometry (DRS). BiOI/ZnO photocatalytic activities of the prepared photocatalysts were evaluated by photocatalytic degradation of phenol under simulated light irradiation. The phenol degradation rate reached 99.9% within 2h under simulated solar light irradiation. The probable photocatalytic mechanism of composites photocatalysts is discussed by active species trapping experiments, the surface photovoltage (SPV), the transient photovoltage (TPV) and photoluminescence (PL) measurements. The results manifest that the superior photocatalytic activity of BiOI/ZnO composites is derived from the strong internal electric field between BiOI and ZnO, which is beneficial for the effective separation and transfer of photogenerated charges in ZnO. Moreover, the loading of BiOI on the surface of ZnO inhibited the recombination of photogenerated charge carriers in ZnO, resulting in excellent photocatalytic activity. On the contrary, the effect of an extension of the light absorption range induced by the introduction of BiOI on the phenol degradation activity is not significant.

  19. Photocatalytic activity of the binary composite CeO2/SiO2 for degradation of dye

    NASA Astrophysics Data System (ADS)

    Phanichphant, Sukon; Nakaruk, Auppatham; Channei, Duangdao

    2016-11-01

    In this study, CeO2 photocatalyst was modified by composite with SiO2 to increase efficiency and improve photocatalytic activity. The as-prepared SiO2 particles have been incorporated into the precursor mixture of CeO2 by homogeneous precipitation and subsequent calcination process. The phase compositions of CeO2 before and after compositing with SiO2 were identified by X-ray diffraction (XRD). The morphology and particle size of CeO2/SiO2 composite was analyzed by high resolution transmission electron microscopy (HRTEM) and field emission scanning electron microscopy (FESEM). The results showed SiO2 spheres with the particle size approximately 100-120 nm, and a uniform layer of CeO2 nanoparticles with a diameter of about 5-7 nm that were fully composite to the surfaces of SiO2. The X-ray photoelectron spectroscopy (XPS) technique was carried out in order to characterize the change in valence state and composite characteristic by shifted peaks of binding energies. The photocatalytic activity was studied through the degradation of Rhodamine B in aqueous solution under visible light exposure. The highest photocatalytic efficiency of CeO2/SiO2 composite was also obtained. To explain the high photocatalytic efficiency of CeO2/SiO2 composite, the proposed mechanism involves the high surface properties of the CeO2/SiO2 composite, as measured by Brunauer-Emmett-Teller (BET) method.

  20. Gene Expression Patterns of Wood Decay Fungi Postia placenta and Phanerochaete chrysosporium Are Influenced by Wood Substrate Composition during Degradation

    PubMed Central

    Skyba, Oleksandr; Cullen, Dan; Douglas, Carl J.

    2016-01-01

    ABSTRACT Identification of the specific genes and enzymes involved in the fungal degradation of lignocellulosic biomass derived from feedstocks with various compositions is essential to the development of improved bioenergy processes. In order to elucidate the effect of substrate composition on gene expression in wood-rotting fungi, we employed microarrays based on the annotated genomes of the brown- and white-rot fungi, Rhodonia placenta (formerly Postia placenta) and Phanerochaete chrysosporium, respectively. We monitored the expression of genes involved in the enzymatic deconstruction of the cell walls of three 4-year-old Populus trichocarpa (poplar) trees of genotypes with distinct cell wall chemistries, selected from a population of several hundred trees grown in a common garden. The woody substrates were incubated with wood decay fungi for 10, 20, and 30 days. An analysis of transcript abundance in all pairwise comparisons highlighted 64 and 84 differentially expressed genes (>2-fold, P < 0.05) in P. chrysosporium and P. placenta, respectively. Cross-fungal comparisons also revealed an array of highly differentially expressed genes (>4-fold, P < 0.01) across different substrates and time points. These results clearly demonstrate that gene expression profiles of P. chrysosporium and P. placenta are influenced by wood substrate composition and the duration of incubation. Many of the significantly expressed genes encode “proteins of unknown function,” and determining their role in lignocellulose degradation presents opportunities and challenges for future research. IMPORTANCE This study describes the variation in expression patterns of two wood-degrading fungi (brown- and white-rot fungi) during colonization and incubation on three different naturally occurring poplar substrates of differing chemical compositions, over time. The results clearly show that the two fungi respond differentially to their substrates and that several known and, more interestingly

  1. Substitution of common concentrates with by-products modulated ruminal fermentation, nutrient degradation, and microbial community composition in vitro.

    PubMed

    Ertl, P; Knaus, W; Metzler-Zebeli, B U; Klevenhusen, F; Khiaosa-Ard, R; Zebeli, Q

    2015-07-01

    A rumen simulation technique was used to evaluate the effects of the complete substitution of a common concentrate mixture (CON) with a mixture consisting solely of by-products from the food industry (BP) at 2 different forage-to-concentrate ratios on ruminal fermentation profile, nutrient degradation, and abundance of rumen microbiota. The experiment was a 2×2 factorial arrangement with 2 concentrate types (CON and BP) and 2 concentrate levels (25 and 50% of diet dry matter). The experiment consisted of 2 experimental runs with 12 fermentation vessels each (n=6 per treatment). Each run lasted for 10d, with data collection on the last 5d. The BP diets had lower starch, but higher neutral detergent fiber (NDF) and fat contents compared with CON. Degradation of crude protein was decreased, but NDF and nonfiber carbohydrate degradation were higher for the BP diets. At the 50% concentrate level, organic matter degradation tended to be lower for BP and CH4 formation per unit of NDF degraded was also lower for BP. The BP mixture led to a higher concentration of propionate and a lower acetate-to-propionate ratio, whereas concentrations of butyrate and caproate decreased. Concentrate type did not affect microbial community composition, except that the abundance of bacteria of the genus Prevotella was higher for BP. Increasing the concentrate level resulted in higher degradation of organic matter and crude protein. At the higher concentrate level, total short-chain fatty acid formation increased and concentrations of isobutyrate and valerate decreased. In addition, at the 50% concentrate level, numbers of protozoa increased, whereas numbers of methanogens, anaerobic fungi, and fibrolytic bacteria decreased. No interaction was noted between the 2 dietary factors on most variables, except that at the higher concentrate level the effects of BP on CH4 and CO2 formation per unit of NDF degraded, crude protein degradation, and the abundance of Prevotella were more prominent. In

  2. Composite hydrogel scaffolds with controlled pore opening via biodegradable hydrogel porogen degradation.

    PubMed

    Hawkins, Ashley M; Milbrandt, Todd A; Puleo, David A; Hilt, J Zach

    2014-02-01

    Poly(β-amino ester) (PBAE) biodegradable hydrogel systems have garnered much attention in recent years due to their appealing properties for biomedical applications. These hydrogel systems exhibit properties similar to natural soft tissue, degrade in aqueous environments, and have easily tunable properties that have been well studied and understood. In most cases, tissue engineering scaffolds must possess a three-dimensional interconnected porous network for tissue ingrowth and construct vascularization. Here, PBAE properties were explored and systems were selected to serve as both the pore-forming agent and the outer matrix of a scaffold that exhibits controlled pore opening upon degradation. To our knowledge, this is the first demonstration of a biodegradable hydrogel porogen system entrapped in a degradable hydrogel outer matrix. Scaffolds were prepared, and the degradation, compressive moduli, and porosity were analyzed. An added advantage of a degradable porogen is the potential for controlled drug release, and a model protein was released from the porogen particles to demonstrate this application. Finally, pluripotent cells seeded onto predegraded scaffolds were viable during the first 24 h of exposure, and furthermore, cell tracking confirmed the presence of cells within the pores of the scaffold. Overall, these present studies demonstrate the possibility of using these biodegradable hydrogel porogen-matrix systems as tissue engineering scaffolding materials.

  3. Nanostructured hydroxyapatite/poly(lactic-co-glycolic acid) composite coating for controlling magnesium degradation in simulated body fluid.

    PubMed

    Johnson, Ian; Akari, Khalid; Liu, Huinan

    2013-09-20

    Biodegradable magnesium (Mg) and its alloys have many attractive properties (e.g. comparable mechanical properties to cortical bone) for orthopedic implant applications, but they degrade too rapidly in the human body to meet clinical requirements. Nanostructured hydroxyapatite (nHA)/poly(lactic-co-glycolic acid) (PLGA) composite coatings provide synergistic properties for controlling degradation of Mg-based substrates and improving bone-implant integration. In this study, nHA/PLGA composites were spin coated onto Mg-based substrates and the results showed that the nHA/PLGA coatings retained nano-scale features with nHA dispersed in PLGA matrix. In comparison with non-coated Mg, the nHA/PLGA composite coated Mg increased the corrosion potential and decreased the corrosion current in revised simulated body fluid (rSBF). After 24 h of immersion in rSBF, increased calcium phosphate (CaP) deposition and formation of Mg-substituted CaP rosettes were observed on the surface of the nHA/PLGA coated Mg, indicating greater bioactivity. In contrast, no significant CaP was deposited on the PLGA coated Mg. Since both PLGA coating and nHA/PLGA coating showed some degree of delamination from Mg-based substrates during extended immersion in rSBF, the coating processing and properties should be further optimized in order to take full advantage of biodegradable Mg and nHA/PLGA nanocomposites for orthopedic applications.

  4. Visible light photocatalytic degradation of dyes by bismuth oxide-reduced graphene oxide composites prepared via microwave-assisted method.

    PubMed

    Liu, Xinjuan; Pan, Likun; Lv, Tian; Sun, Zhuo; Sun, Chang Q

    2013-10-15

    Bi2O3-reduced graphene oxide (RGO) composites were successfully synthesized via microwave-assisted reduction of graphite oxide in Bi2O3 precursor solution using a microwave system. Their morphologies, structures, and photocatalytic performance in the degradation of methylene blue (MB) and methyl orange (MO) were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectroscopy, UV-vis absorption spectroscopy, and electrochemical impedance spectroscopy, respectively. The results show that the RGO addition can enhance the photocatalytic performance of Bi2O3-RGO composites. Bi2O3-RGO composite with 2 wt.% RGO achieves maximum MO and MB degradation rates of 93% and 96% at 240min under visible light irradiation, respectively, much higher than those for the pure Bi2O3 (78% and 76%). The enhanced photocatalytic performance is ascribed to the increased light adsorption and the reduction in electron-hole pair recombination in Bi2O3 with the introduction of RGO.

  5. Nanostructured hydroxyapatite/poly(lactic-co-glycolic acid) composite coating for controlling magnesium degradation in simulated body fluid

    NASA Astrophysics Data System (ADS)

    Johnson, Ian; Akari, Khalid; Liu, Huinan

    2013-09-01

    Biodegradable magnesium (Mg) and its alloys have many attractive properties (e.g. comparable mechanical properties to cortical bone) for orthopedic implant applications, but they degrade too rapidly in the human body to meet clinical requirements. Nanostructured hydroxyapatite (nHA)/poly(lactic-co-glycolic acid) (PLGA) composite coatings provide synergistic properties for controlling degradation of Mg-based substrates and improving bone-implant integration. In this study, nHA/PLGA composites were spin coated onto Mg-based substrates and the results showed that the nHA/PLGA coatings retained nano-scale features with nHA dispersed in PLGA matrix. In comparison with non-coated Mg, the nHA/PLGA composite coated Mg increased the corrosion potential and decreased the corrosion current in revised simulated body fluid (rSBF). After 24 h of immersion in rSBF, increased calcium phosphate (CaP) deposition and formation of Mg-substituted CaP rosettes were observed on the surface of the nHA/PLGA coated Mg, indicating greater bioactivity. In contrast, no significant CaP was deposited on the PLGA coated Mg. Since both PLGA coating and nHA/PLGA coating showed some degree of delamination from Mg-based substrates during extended immersion in rSBF, the coating processing and properties should be further optimized in order to take full advantage of biodegradable Mg and nHA/PLGA nanocomposites for orthopedic applications.

  6. Association of extinction risk of saproxylic beetles with ecological degradation of forests in Europe.

    PubMed

    Seibold, Sebastian; Brandl, Roland; Buse, Jörn; Hothorn, Torsten; Schmidl, Jürgen; Thorn, Simon; Müller, Jörg

    2015-04-01

    To reduce future loss of biodiversity and to allocate conservation funds effectively, the major drivers behind large-scale extinction processes must be identified. A promising approach is to link the red-list status of species and specific traits that connect species of functionally important taxa or guilds to resources they rely on. Such traits can be used to detect the influence of anthropogenic ecosystem changes and conservation efforts on species, which allows for practical recommendations for conservation. We modeled the German Red List categories as an ordinal index of extinction risk of 1025 saproxylic beetles with a proportional-odds linear mixed-effects model for ordered categorical responses. In this model, we estimated fixed effects for intrinsic traits characterizing species biology, required resources, and distribution with phylogenetically correlated random intercepts. The model also allowed predictions of extinction risk for species with no red-list category. Our model revealed a higher extinction risk for lowland and large species as well as for species that rely on wood of large diameter, broad-leaved trees, or open canopy. These results mirror well the ecological degradation of European forests over the last centuries caused by modern forestry, that is the conversion of natural broad-leaved forests to dense conifer-dominated forests and the loss of old growth and dead wood. Therefore, conservation activities aimed at saproxylic beetles in all types of forests in Central and Western Europe should focus on lowlands, and habitat management of forest stands should aim at increasing the amount of dead wood of large diameter, dead wood of broad-leaved trees, and dead wood in sunny areas. © 2014 Society for Conservation Biology.

  7. Method and compositions for the degradation of tributyl phosphate in chemical waste mixtures

    DOEpatents

    Stoner, D.L.; Tien, A.J.

    1995-09-26

    A method and process are disclosed for the degradation of tributyl phosphate in an organic waste mixture and a biologically pure, novel bacteria culture for accomplishing the same. A newly-discovered bacteria (a strain of Acinetobacter sp. ATCC 55587) is provided which is combined in a reactor vessel with a liquid waste mixture containing tributyl phosphate and one or more organic waste compounds capable of functioning as growth substrates for the bacteria. The bacteria is thereafter allowed to incubate within the waste mixture. As a result, the tributyl phosphate and organic compounds within the waste mixture are metabolized (degraded) by the bacteria, thereby eliminating such materials which are environmentally hazardous. In addition, the bacteria is capable of degrading waste mixtures containing high quantities of tributyl phosphate (e.g. up to about 1.0% by weight tributyl phosphate). 6 figs.

  8. Method and compositions for the degradation of tributyl phosphate in chemical waste mixtures

    DOEpatents

    Stoner, Daphne L.; Tien, Albert J.

    1995-01-01

    A method and process for the degradation of tributyl phosphate in an organic waste mixture and a biologically pure, novel bacteria culture for accomplishing the same. A newly-discovered bacteria (a strain of Acinetobacter sp. ATCC 55587) is provided which is combined in a reactor vessel with a liquid waste mixture containing tributyl phosphate and one or more organic waste compounds capable of functioning as growth substrates for the bacteria. The bacteria is thereafter allowed to incubate within the waste mixture. As a result, the tributyl phosphate and organic compounds within the waste mixture are metabolized (degraded) by the bacteria, thereby eliminating such materials which are environmentally hazardous. In addition, the bacteria is capable of degrading waste mixtures containing high quantities of tributyl phosphate (e.g. up to about 1.0% by weight tributyl phosphate).

  9. Chitosan filled recycled low density polyethylene composite: Melt flow behaviour and thermal degradation properties

    NASA Astrophysics Data System (ADS)

    Lim, B. Y.; Voon, C. H.; Salmah, H.; Nordin, H.

    2016-07-01

    An environmentally friendly composite was fabricated from chitosan and recycled low density polyethylene (rLDPE) with the means of melt mixing at 180 °C. The composites were prepared in different loading (10, 20, 30 and 40 php) of chitosan. Due to the incompatibility between filler and matrix, a coupling agent, Ultraplus TP01, was added into the composites. The melt flow index (MFI) values of rLDPE/chitosan composites decreased with chitosan loading but increased with rise of temperature. With the presence of Ultraplus TP01, MFI values of composites were decreased. The thermal stability of rLDPE/chitosan was reduced with increase of chitosan loading but increased with addition of Ultraplus TP01. It was believed that Ultraplus TP01 had provided better interfacial bonding between chitosan and rLDPE, thus enhanced the thermal stability of rLDPE/chitosan composites.

  10. Effects of gamma irradiation on chemical composition and ruminal protein degradation of canola meal

    NASA Astrophysics Data System (ADS)

    Shawrang, P.; Nikkhah, A.; Zare-Shahneh, A.; Sadeghi, A. A.; Raisali, G.; Moradi-Shahrebabak, M.

    2008-07-01

    Gamma irradiation of canola meal (at doses of 25, 50 and 75 kGy) could alter its ruminal protein degradation characteristics by cross-linking of the polypeptide chains. This processing resulted in decrease (linear effect, P<0.001) of ruminal protein degradation and increase (linear effect, P<0.001) of intestinal protein digestibility. The results showed that gamma irradiation at doses higher than 25 kGy can be used as a cross-linking agent to improve protein properties of supplements in ruminant nutrition.

  11. Photocatalytic degradation of contaminants of concern with composite NF-TiO2 films under visible and solar light.

    PubMed

    Barndõk, H; Peláez, M; Han, C; Platten, W E; Campo, P; Hermosilla, D; Blanco, A; Dionysiou, D D

    2013-06-01

    This study reports the synthesis and characterization of composite nitrogen and fluorine co-doped titanium dioxide (NF-TiO(2)) for the removal of contaminants of concern in wastewater under visible and solar light. Monodisperse anatase TiO(2) nanoparticles of different sizes and Evonik P25 were assembled to immobilized NF-TiO(2) by direct incorporation into the sol-gel or by the layer-by-layer technique. The composite films were characterized with X-ray diffraction, high-resolution transmission electron microscopy, environmental scanning electron microscopy, and porosimetry analysis. The photocatalytic degradation of atrazine, carbamazepine, and caffeine was evaluated in a synthetic water solution and in an effluent from a hybrid biological concentrator reactor (BCR). Minor aggregation and improved distribution of monodisperse titania particles was obtained with NF-TiO(2)-monodisperse (10 and 50 nm) from the layer-by-layer technique than with NF-TiO(2) +monodisperse TiO(2) (300 nm) directly incorporated into the sol. The photocatalysts synthesized with the layer-by-layer method achieved significantly higher degradation rates in contrast with NF-TiO(2)-monodisperse titania (300 nm) and slightly faster values when compared with NF-TiO(2)-P25. Using NF-TiO(2) layer-by-layer with monodisperse TiO(2) (50 nm) under solar light irradiation, the respective degradation rates in synthetic water and BCR effluent were 14.6 and 9.5 × 10(-3) min(-1) for caffeine, 12.5 and 9.0 × 10(-3) min(-1) for carbamazepine, and 10.9 and 5.8 × 10(-3) min(-1) for atrazine. These results suggest that the layer-by-layer technique is a promising method for the synthesis of composite TiO(2)-based films compared to the direct addition of nanoparticles into the sol.

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

    PubMed

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

    2015-05-01

    The robust calcium carbonate composite ceramics (CC/PG) can be acquired by fast sintering calcium carbonate at a low temperature (650 °C) using a biocompatible, degradable phosphate-based glass (PG) as sintering agent. In the present study, the in vitro degradation and cell response of CC/PG were assessed and compared with 4 synthetic bone substitute materials, calcium carbonate ceramic (CC), PG, hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) ceramics. The degradation rates in decreasing order were as follows: PG, CC, CC/PG, β-TCP, and HA. The proliferation of rat bone mesenchymal stem cells (rMSCs) cultured on the CC/PG was comparable with that on CC and PG, but inferior to HA and β-TCP. The alkaline phosphatase (ALP) activity of rMSCs on CC/PG was lower than PG, comparable with β-TCP, but higher than HA. The rMSCs on CC/PG and PG had enhanced gene expression in specific osteogenic markers, respectively. Compared to HA and β-TCP, the rMSCs on the CC/PG expressed relatively lower level of collagen I and runt-related transcription factor 2, but showed more considerable expression of osteopontin. Although CC, PG, HA, and β-TCP possessed impressive performances in some specific aspects, they faced extant intrinsic drawbacks in either degradation rate or mechanical strength. Based on considerable compressive strength, moderate degradation rate, good cell response, and being free of obvious shortcoming, the CC/PG is promising as another choice for bone substitute materials. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. Adsorption and photocatalytic degradation of dyes on polyacrylamide/calcium alginate/TiO2 composite film

    NASA Astrophysics Data System (ADS)

    Wei, Shuxin; Zhao, Kongyin; Zhang, Xinxin; Fu, Yifan; Li, Zhihui; Xu, Sai; Wei, Junfu

    2015-03-01

    A casting solution was prepared by dispersing titanium dioxide (TiO2) nanoparticles in the sodium alginate and acrylamide aqueous solution. The casting solution was spread on a glass plate by a glass rod enlaced with brass wires to control the thickness of the sticky solution. Then polyacrylamide/calcium alginate/TiO2 (PAM/CA/T) composite film was obtained after UV irradiation and cross-linking by CaCl2. The PAM/CA/T film was characterized by scanning electron microscope and transmission electron microscope. The PAM/CA/T film had good strength and toughness. And they did not rupture after swelling in 5 wt.% NaCl solution and still had good mechanical properties. The adsorption properties of the PAM/CA/T film were investigated by using different dyes as the adsorbates. The photocatalytic degradation properties of these dyes on the PAM/CA/T films were also researched. The results indicated that there was no difference in the adsorption efficiency of PAM/CA film and PAM/CA/T-30 film. The adsorption rates of all the dyes were fast. The pre-adsorption of dyes had little effect on the catalytic degradation of dyes on PAM/CA/T film. The PAM/CA/T hydrogel film provided a suitable carrier for TiO2 in the photocatalytic degradation of dyes and the degradation efficiency of PAM/CA/T-30 film for methyl orange reached 80.76%. The PAM/CA/T film had good reusability and could degrade dyes in NaCl solution.

  14. A novel reducing graphene/polyaniline/cuprous oxide composite hydrogel with unexpected photocatalytic activity for the degradation of Congo red

    NASA Astrophysics Data System (ADS)

    Miao, Jie; Xie, Anjian; Li, Shikuo; Huang, Fangzhi; Cao, Juan; Shen, Yuhua

    2016-01-01

    In this work, a novel reducing graphene/polyaniline/cuprous oxide (RGO/PANI/Cu2O) composite hydrogel with a 3D porous network has been successfully prepared via a one-pot method in the presence of cubic Cu2O nanoparticles. The as-synthesized ternary composites hydrogel shows unexpected photocatalytic activity such that Congo red (CR) degradation efficiency can reaches 97.91% in 20 min under UV⿿vis light irradiation, which is much higher than that of either the single component (Cu2O nanoparticles), or two component systems (RGO/Cu2O composite hydrogel and PANI/Cu2O nanocomposites). Furthermore, the ternary composite hydrogel exhibits high stability and do not show any significant loss after five recycles. Such outstanding photocatalytic activity of the RGO/PANI/Cu2O composite hydrogel was ascribed to the high absorption ability of the product for CR and the synergic effect among RGO, PANI and Cu2O in photocatalytic process. The product of this work would provide a new sight for the construction of UV⿿vis light responsive photocatalyst with high performance.

  15. Characterizations of mortar-degraded spinney waste composite nominated as solidifying agent for radwastes due to immersion processes

    NASA Astrophysics Data System (ADS)

    Saleh, H. M.; Eskander, S. B.

    2012-11-01

    Immobilization process of radioactive wastes is a compromise between economic and reliability factors. It involves the use of inert and cheap matrices to fix the wastes in homogenous monolithic solid forms. The characteristics of the resulting waste form were studied in various disposal options before coming to the final conclusion concerning the solidification process. A proposed mortar composite is formed from a mixture of Portland cement and sand in the weight ratio of 0.33 which by slurry of degraded spinney waste fibers at the ratio of 0.7 relative to the Portland cement. The composite was prepared at the laboratory ambient conditions (25 ± 5 °C). The temperature changes accompanying the hydration process were followed up to 96 h. At the end of 28 days, curing period, the performance of the obtained composite was evaluated under immersion circumstances imitating a flooding scenario that could happen at a disposal site. Compressive strength, porosity and mass changes were investigated under complete static immersion conditions in three different leachants, namely acetic acid, groundwater and seawater for 48 weeks. X-ray and scanning electron microscopy were used to follow and evaluate the changes that may occur for the proposed composite under flooding conditions. Based on the experimental data reached, it could be concluded that the prepared mortar composite can be nominated as a matrix for solidification/stabilization of some radwaste categories, even under the aggressive attacks of various immersion media.

  16. Bifunctional AgCl/Ag composites for SERS monitoring and low temperature visible light photocatalysis degradation of pollutant

    NASA Astrophysics Data System (ADS)

    Dong, Lihong; Zhu, Junyi; Xia, Guangqing

    2014-12-01

    With the assistance of Polyvinylpyrrolidone (PVP), AgCl/Ag composites were fabricated in N, N-Dimethylformamide (DMF) solvent via a photoactivated route. The size of AgCl particles was in the range of 500 nm to 1 μm and the Ag particle's diameter was about 10-20 nm. Different from those core-shell structures reported before, the Ag nanoparticles were dispersed uniformly both on the surface and in the body of AgCl particles. The generation of such kind of composites was resulted from the reducing ability of DMF and light irradiation during the formation of AgCl particles. The as-obtained AgCl/Ag composites presented great activity for both surface-enhanced Raman scattering (SERS) detection and visible light photocatalytic degradation of organic dyes. Additionally, the AgCl/Ag composites could maintain high photocatalytic activity even though the ambient temperature was as low as 15 °C and recycle photocatalysis experiments indicated that the photocatalyst exhibited higher stability. Such kind of AgCl/Ag composites holds great potential for environmental monitoring devices and pollutant treatments.

  17. Influence of the composition of in-vitro azo-reducing systems on the degradation kinetics of the model compound amaranth.

    PubMed

    Maris, B; Verheyden, L; Samyn, C; Augustijns, P; Kinget, R; Van den Mooter, G

    2002-02-01

    The purpose of this study was to investigate the influence of the composition of in-vitro azo-reducing systems on the degradation kinetics of the model compound amaranth. The degradation kinetics of amaranth were determined under anaerobic conditions both in rat caecal content (ex-vivo) and in a variety of in-vitro degradation media derived from rat caecal content. It was observed that the reducing activity was highly dependent on the preparation method and composition of the degradation medium. In pure rat caecal content, the degradation of amaranth was apparent first order (k = 0.044 +/- 0.002 min(-1)), while dilution of the rat caecal content resulted in an apparent zero-order degradation. Both apparent zero- and first-order degradations were also observed in media made up of diluted rat caecal content to which cofactors such as NADP, D-glucose-6-phosphate, glucose-6-phosphate dehydrogenase and Bz were added. This study demonstrates that in-vitro azo-reducing kinetics are dependent on the composition and mode of preparation of the in-vitro media used. This has to be taken into account when evaluating the degradability of azo-aromatic drug delivery systems in-vitro.

  18. Degradation of lignocelluloses in rice straw by BMC-9, a composite microbial system.

    PubMed

    Zhao, Hongyan; Yu, Hairu; Yuan, Xufeng; Piao, Renzhe; Li, Hulin; Wang, Xiaofen; Cui, Zongjun

    2014-05-01

    To evaluate the potential utility of pretreatment of raw biomass with a complex microbial system, we investigated the degradation of rice straw by BMC-9, a lignocellulose decomposition strain obtained from a biogas slurry compost environment. The degradation characteristics and corresponding changes in the bacterial community were assessed. The results showed that rapid degradation occurred from day 0 to day 9, with a peak total biomass bacterium concentration of 3.3 × 10(8) copies/ml on day 1. The pH of the fermentation broth declined initially and then increased, and the mass of rice straw decreased steadily. The highest concentrations of volatile fatty acid contents (0.291 mg/l lactic acid, 0.31 mg/l formic acid, 1.93 mg/l acetic acid, and 0.73 mg/l propionic acid) as well as the highest xylanse activity (1.79 U/ml) and carboxymethyl cellulase activity (0.37 U/ml) occurred on day 9. The greatest diversity among the microbial community also occurred on day 9, with the presence of bacteria belonging to Clostridium sp., Bacillus sp., and Geobacillus sp. Together, our results indicate that BMC-9 has a strong ability to rapidly degrade the lignocelluloses of rice straw under relatively inexpensive conditions, and the optimum fermentation time is 9 days.

  19. Mechanical property degradation of graphite/polyimide composites after exposure to moisture or shuttle orbiter fluids

    NASA Technical Reports Server (NTRS)

    Lisagor, W. B.

    1979-01-01

    The effects of moisture exposure on the mechanical properties of graphite polyimide systems are presented. The mechanism of the degradation and the magnitude of the affect associated with specific mechanical properties is investigated. An experimental effort involving exposure to selected environmental variables and subsequent mechanical property testing and analysis is included.

  20. Impact of biofibers and coupling agents on the weathering characteristics of composites polymer degradation and stability

    USDA-ARS?s Scientific Manuscript database

    This paper explores the ultraviolet (UV) weathering performance of high density polyethylene (HDPE) composites with different biofiber fillers and coupling agent. Biofiber polymer composite (BFPC) material samples were prepared using oak, cotton burr and stem (CBS) or guayule bagasse as fiber source...

  1. Tensile properties of SiC/aluminum filamentary composites - Thermal degradation effects

    NASA Technical Reports Server (NTRS)

    Skinner, A.; Koczak, M. J.; Lawley, A.

    1982-01-01

    Aluminium metal matrix composites with a low cost fiber, e.g. SiC, provide for an attractive combination of high elastic modulus and longitudinal strengths coupled with a low density. SiC (volume fraction 0.55)-aluminum (6061) systems have been studied in order to optimize fiber composite strength and processing parameters. A comparison of two SiC/aluminum composites produced by AVCO and DWA is provided. Fiber properties are shown to alter composite tensile properties and fracture morphology. The room temperature tensile strengths appear to be insensitive to thermal exposures at 500 C up to 150 h. The elastic modulus of the composites also appears to be stable up to 400 C, however variations in the loss modulus are apparent. The fracture morphology reflects the quality of the interfacial bond, fiber strengths and fiber processing.

  2. Application of vibrational spectroscopy in the in vitro studies of carbon fiber-polylactic acid composite degradation.

    NASA Astrophysics Data System (ADS)

    Blazewicz, Marta; Gajewska, Maria Chomyszyn; Paluszkiewicz, Czeslawa

    1999-05-01

    Vibrational spectroscopy was used for assessment of new material for stomatology, for guided tissue regeneration (GTR) techniqe.Implants applied in the healing of periodontal defects using GTR technique have to meet stringent requirements concerning their chemical as well physical properties.At present the implants prepared from two layers membranes differing in porosity in their outer and inner layers are studied clinically. Composite plates prepared by us consist of three layers: polylactic acid film, carbon fibres coated with polylactic acid and carbon fabric.Vibrational spectroscopic studies of the material; polylactic acid- carbon fiber have made it possible to analyse chemical reactions occurring between the polymer and carbon surface. Analysis of the IR spectra of samples treated in Ringer solution allowed to describe the phenomena resulting from the composite degradation. It was shown that material biostability is related to the presence of carbon fibers.

  3. Visible light activated photocatalytic degradation of tetracycline by a magnetically separable composite photocatalyst: Graphene oxide/magnetite/cerium-doped titania.

    PubMed

    Cao, Muhan; Wang, Peifang; Ao, Yanhui; Wang, Chao; Hou, Jun; Qian, Jin

    2016-04-01

    In this study, magnetic graphene oxide-loaded Ce-doped titania (MGO-Ce-TiO2) hybridized composite was prepared by a facile method. The as-prepared samples exhibited good adsorption capacity, high visible-light photoactive and magnetic separability as a novel photocatalyst in the degradation of tetracyclines (TC). The intermediate products and photocatalytic route of TC were proposed based on the analysis results of LC-MS. Moreover, the repeatability of the photoactivity with the use of MGO-Ce-TiO2 was investigated in the multi-round experiments with the assistance of an applied magnetic field. Therefore, the prepared composite photocatalysts were considered as a kind of promising photocatalyst in a suspension reaction system, in which they can offer effectively recovery ability. The effect of MGO content on the photocatalytic performance was also studied, and an optimum content was obtained. Copyright © 2016 Elsevier Inc. All rights reserved.

  4. Preparation, characterization of C/Fe-Bi2WO6 nanosheet composite and degradation application of norfloxacin in water.

    PubMed

    Chen, Shijie; Li, Yingjie; Lü, Renjiang; Wang, Peng

    2013-08-01

    A novel C/Fe-Bi2WO6 nanosheet composite photocatalyst combining the properties of both semiconductor and Fenton like catalyst was prepared via a two-step method involving Resin carbonization and hydrothermal process. The samples were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectra (DRS), X-ray photoelectron spectroscopy (XPS), Fourier transformed infrared spectroscopy (FT-IR) and nitrogen adsorption-desorption measurements. Structure analyses indicated that C/Fe-Bi2WO6 presented a nanosheet and macro-meso dual porosity structure. The as-prepared composite exhibited high efficiency in the photocatalytic decomposition of norfloxacin (NOR) by the assistance of H2O2. This method is promising due to its inexpensive starting materials and good photocatalyst for degradation of emerging micropollutants.

  5. Adhesive strength of bone-implant interfaces and in-vivo degradation of PHB composites for load-bearing applications.

    PubMed

    Meischel, M; Eichler, J; Martinelli, E; Karr, U; Weigel, J; Schmöller, G; Tschegg, E K; Fischerauer, S; Weinberg, A M; Stanzl-Tschegg, S E

    2016-01-01

    Aim of this study was to evaluate the response of bone to novel biodegradable polymeric composite implants in the femora of growing rats. Longitudinal observation of bone reaction at the implant site (BV/TV) as well as resorption of the implanted pins were monitored using in vivo micro-focus computed tomography (µCT). After 12, 24 and 36 weeks femora containing the implants were explanted, scanned with high resolution ex vivo µCT, and the surface roughness of the implants was measured to conclude on the ingrowth capability for bone tissue. Scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to observe changes on the surface of Polyhydroxybutyrate (PHB) during degradation and cell ingrowth. Four different composites with zirconium dioxide (ZrO2) and Herafill(®) were compared. After 36 weeks in vivo, none of the implants did show significant degradation. The PHB composite with ZrO2 and a high percentage (30%) of Herafill® as well as the Mg-alloy WZ21 showed the highest values of bone accumulation (increased BV/TV) around the implant. The lowest value was measured in PHB with 3% ZrO2 containing no Herafill®. Roughness measurements as well as EDX and SEM imaging could not reveal any changes on the PHB composites׳ surfaces. Biomechanical parameters, such as the adhesion strength between bone and implant were determined by measuring the shear strength as well as push-out energy of the bone-implant interface. The results showed that improvement of these mechanical properties of the studied PHBs P3Z, P3Z10H and P3Z30H is necessary in order to obtain appropriate load-bearing material. The moduli of elasticity, tensile strength and strain properties of the PHB composites are close to that of bone and thus promising. Compared to clinically used PLGA, PGA and PLA materials, their additional benefit is an unchanged local pH value during degradation, which makes them well tolerated by cells and immune system. They might be used

  6. Solvothermal synthesis of graphene-Sb{sub 2}S{sub 3} composite and the degradation activity under visible light

    SciTech Connect

    Tao, Wenguang; Chang, Jiuli; Wu, Dapeng; Gao, Zhiyong; Duan, Xiaoli; Xu, Fang; Jiang, Kai

    2013-02-15

    Graphical abstract: Display Omitted Highlights: ► Graphene-Sb{sub 2}S{sub 3} composites were synthesized through a facile solvothermal method. ► Hydroxyl radicals are the main species responsible for the photodegradation activity. ► Graphene-Sb{sub 2}S{sub 3} demonstrated dramatically improved visible light degradation activity. -- Abstract: Novel graphene-Sb{sub 2}S{sub 3} (G-Sb{sub 2}S{sub 3}) composites were synthesized via a facile solvothermal method with graphene oxide (GO), SbCl{sub 3} and thiourea as the reactants. GO played an important role in controlling the size and the distribution of the formed Sb{sub 2}S{sub 3} nanoparticles on the graphene sheets with different density. Due to the negative surface charge, smaller Sb{sub 2}S{sub 3} particles size and efficient electrons transfer from Sb{sub 2}S{sub 3} to graphene, the composites demonstrated improved photodegradation activity on rhodamine B (RhB). Among these composites, the product G-Sb{sub 2}S{sub 3} 0.1, which was synthesized with the GO concentration of 0.1 mg/mL, exhibited the highest photodegradation activity owing to the considerable density of Sb{sub 2}S{sub 3} nanoparticles onto graphene sheet free of aggregation. Hydroxyl radicals (·OH) derived from conduction band (CB) electrons of Sb{sub 2}S{sub 3} is suggested to be responsible for the photodegradation of RhB. The high visible light degradation activity and the satisfactory cycling stability made the as-prepared G-Sb{sub 2}S{sub 3} 0.1 an applicable photocatalyst.

  7. Degradation pattern and risk assessment of carbendazim and mancozeb in mango fruits.

    PubMed

    Devi, P Ahila; Paramasivam, M; Prakasam, V

    2015-01-01

    A supervised field trial was conducted at four different agroclimatic locations in India to evaluate the dissipation pattern and risk assessment of carbendazim and mancozeb in mango fruits following foliar application of mixed formulation of carbendazim 12% and mancozeb 63% fungicide (SAAF-75WP) at recommended dose (90 + 472.5) and double the recommended dose (180 + 945 g a.i. ha(-1)). Average initial deposition of carbendazim was in the range of 1.12 to 2.7 and 1.95 to 4.09 mg kg(-1) and for mancozeb in the range of 2.25 to 2.71 and 4.17 to 5.96 mg kg(-1), given at respective doses. Residues of carbendazim and mancozeb were dissipated to the below detectable limit 7 days after spray at recommended dosage in all the locations. The fungicide degradation followed a first order kinetics with half-lives of 1-5 and 1-3 days, for carbendazim and mancozeb, respectively. The TMRC values, calculated from residue data generated from all four locations, were found to be below the MPI in mango fruit, and hence, the fungicide will not cause any adverse effect after consumption of mango fruits. This data could provide guidance for the proper and safe use of this fungicide mixture for managing disease incidence in mango in India.

  8. Effect of genotype on chemical composition, ruminal degradability and in vitro fermentation characteristics of maize residual plants.

    PubMed

    Zeller, F M E; Edmunds, B L; Schwarz, F J

    2014-10-01

    The objective of this study was to determine the changes to residual plant feeding value of early- and late-maturing maize varieties. The influence of the cell wall carbohydrate composition, in terms of neutral and acid detergent fibre (NDF and ADF) content, NDF and dry matter (DM) degradability, and in vitro organic matter digestibility and gas production on the feeding value of a range of maize genotypes, was measured. The different genotypes were allotted into two maturity groups (MG I--early to mid-early: S210-S240; MG II--mid-late to late: S 250-S280) and harvested at four different harvest dates (depending on the DM content of the kernels). The maize varieties of MG I had lower NDF and ADF contents and higher ruminal DM degradability, in vitro digestibility and gas production and thus a higher feeding value than MG II at the same stage of physiological maturity. A strong negative relationship between NDF content and the ruminal DM degradability (r = -0.81) was observed. The data indicate that the early-maturing varieties permit a larger flexibility in harvesting due to a longer period of starch inclusion into the kernel whilst simultaneously maintaining a good supply of rumen-available fibre. Conclusively, the higher feeding value of the early-maturing varieties, based on lower NDF and high DM digestibility, permits more flexibility in the harvesting period over the later-maturing varieties.

  9. Chemical composition and nutrient degradability in elephant grass silage inoculated with Streptococcus bovis isolated from the rumen.

    PubMed

    Ferreira, Daniele J; Zanine, Anderson M; Lana, Rogério P; Ribeiro, Marinaldo D; Alves, Guilherme R; Mantovani, Hilário C

    2014-03-01

    The objective of the present study was to assess the chemical and bromatological composition and in situ degradability of elephant grass silages inoculated with Streptococcus bovis isolated from cattle rumen. A complete randomized design was used with four treatments and six replications: elephant grass silage, elephant grass silage inoculated with 10(6) CFU/g Streptococcus bovis JB1 strains; elephant grass silage inoculated with 106 CFU/g Streptococcus bovis HC5 strains; elephant grass silage inoculated with 106 CFU/g Enterococcus faecium with six replications each. The pH and ammoniacal nitrogen values were lower (P<0.05) for the silages inoculated with Streptococcus bovis JB1 and HC5, respectively. The silage inoculated with Streptococcus bovis had a higher crude protein content (P<0.05) and there were no differences for the fiber contents in the silage. The (a)soluble fraction degradability, especially in the silages inoculated with Streptococcus bovis JB1 and HC5, had higher values, 30.77 and 29.97%, for dry matter and 31.01 and 36.66% for crude protein, respectively. Inoculation with Streptococcus bovis improved the fermentation profile, protein value and rumen degradability of the nutrients.

  10. p-Nitrophenol degradation by electro-Fenton process: Pathway, kinetic model and optimization using central composite design.

    PubMed

    Meijide, J; Rosales, E; Pazos, M; Sanromán, M A

    2017-10-01

    The chemical process scale-up, from lab studies to industrial production, is challenging and requires deep knowledge of the kinetic model and the reactions that take place in the system. This knowledge is also useful in order to be employed for the reactor design and the determination of the optimal operational conditions. In this study, a model substituted phenol such as p-nitrophenol was degraded by electro-Fenton process and the reaction products yielded along the treatment were recorded. The kinetic model was developed using Matlab software and was based on main reactions that occurred until total mineralization which allowed predicting the degradation pathway under this advanced oxidation process. The predicted concentration profiles of p-nitrophenol, their intermediates and by-products in electro-Fenton process were validated with experimental assays and the results were consistent. Finally, based on the developed kinetic model the degradation process was optimized using central composite design taking as key parameters the ferrous ion concentration and current density. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Composition and morphology characterization of exopolymeric substances produced by the PAH-degrading fungus of Mucor mucedo.

    PubMed

    Jia, Chunyun; Li, Xiaojun; Allinson, Graeme; Liu, Changfeng; Gong, Zongqiang

    2016-05-01

    To explore the role of exopolymeric substances (EPS) in the process of polycyclic aromatic hydrocarbons (PAH) biodegradation, the characteristics of EPS isolated from a PAH-degrading fungus were investigated firstly by spectrometric determination, microscopic observation, Fourier transform-infrared spectroscopy (FT-IR), and three-dimensional excitation-emission matrix fluorescence spectroscopy (3D-EEM), and then the PAH-degrading ability of isolated EPS was evaluated. The EPS compositions and morphology varied significantly with the extraction methods. EPS were mainly composed of proteins, carbohydrate, and humic-like substances, and the cation exchange resin (CER)-extracted EPS were granular while other EPS samples were all powders. Heating was the most effective treatment method, followed by the CER, centrifugation, and ultrasonication methods. However, 3D-EEM data demonstrated that heating treatment makes the mycelia lyse the most. Overall, therefore, the CER was the best EPS extraction method for Mucor mucedo (M. mucedo). The PAH degradation results indicated that 87 % of pyrene and 81 % of benzo[a]pyrene (B[a]P) were removed by M. mucedo over 12 days and 9 % more pyrene and 7 % more B[a]P were reduced after CER-extracted EPS addition of 465 mg l(-1). The investigation of EPS characterization and EPS enhancing PAH biodegradation is the premise for further in-depth exploration of the role of EPS contribution to PAH biodegradation.

  12. Fabrication of Sc2O3-magneli phase titanium composite electrode and its application in efficient electrocatalytic degradation of methyl orange

    NASA Astrophysics Data System (ADS)

    Bai, Hongmei; He, Ping; Chen, Jingchao; Liu, Kaili; Lei, Hong; Dong, Faqin; Zhang, Xingquan; Li, Hong

    2017-04-01

    Sc2O3-magneli phase titanium (Sc2O3-MPT) composite electrode was successfully fabricated via a simple pressing-sintering method and used for electrocatalytic degradation of methyl orange (MO). It was shown that Sc2O3 was successfully composited with MPT. Compared with MPT electrode, Sc2O3-MPT composite electrode had less spherical particles and more pores. Linear scanning voltammetry indicated that Sc2O3-MPT composite electrode presented higher oxygen evolution overpotential than MPT electrode, suggesting that Sc2O3-MPT electrode was much more suitable for the degradation of MO. The electrocatalytic degradation of MO was evaluated under different parameters including current density, temperature, initial pH and electrolysis time. Under the optimal parameters (current density 10 mA cm-2, temperature 25 °C, initial pH 3 and electrolysis time 120 min), the degradation efficiency of MO on Sc2O3-MPT composite electrode reached up to 90.16%. All these results demonstrated that Sc2O3-MPT composite electrode was effective for electrocatalytic degradation of MO and had a great potential application in the treatment of dyes wastewater.

  13. Use of different dietary protein sources for lactating goats: milk production and composition as functions of protein degradability and amino acid composition.

    PubMed

    Sanz Sampelayo, M R; Pérez, M L; Gil Extremera, F; Boza, J J; Boza, J

    1999-03-01

    To establish the effect of the nature of four different protein sources [fababeans, 27.8% crude protein (CP); sunflower meal, 41.7% CP; corn gluten feed, 18.8% CP; and cottonseed, 18.3% CP] on milk protein production by goats, the ruminal degradation of these feeds was studied as was the amino acid (AA) composition of the original material and that of the undegradable fractions of the protein sources. Four diets were designed; 20% of their protein was supplied by each of the different sources. Four groups of 5 Granadina goats were used to study the utilization of these diets for milk production. No significant differences were observed in dry matter intake or milk production. The milk produced by goats fed the diet containing sunflower meal had the lowest protein concentration; the highest milk protein concentration was observed for goats fed the diet containing corn gluten feed. From a multivariate analysis, it was deduced that the quickly degradable protein fraction in the rumen and the ruminally undegradable protein fraction were the components of the protein sources most directly related to the milk protein produced. Given the similar AA profiles of the undegradable fractions of the different protein sources, the possible supplementation achieved from these ruminally undegradable fractions must be established by the amount of protein supplied regardless of AA composition.

  14. Photocatalytic degradation and antimicrobial applications of F-doped MWCNTs/TiO2 composites

    NASA Astrophysics Data System (ADS)

    Sangari, M.; Umadevi, M.; Mayandi, J.; Pinheiro, Jean Patrick

    2015-03-01

    Multi-walled carbon nanotubes-fluorine-co-doped TiO2 composite was synthesized by the solid state method. The prepared photocatalysts were characterized by using XRD, FTIR and FE-SEM. In addition, the samples were evaluated for antimicrobial activity and photocatalytic activity. The composites exhibited enhanced absorption properties in the UV light range compared to pure TiO2. The MWCNTS-F-co-doped TiO2 composites showed significant photocatalytic activity in the generation of oxygen.

  15. Influence of Shear Stiffness Degradation on Crack Paths in Uni-Directional Composite Laminates

    NASA Technical Reports Server (NTRS)

    Satyanarayana, Arunkumar; Bogert, Phil B.

    2017-01-01

    Influence of shear stiffness degradation in an element, due to damage, on crack paths in uni-directional laminates has been demonstrated. A new shear stiffness degradation approach to improve crack path prediction has been developed and implemented in an ABAQUS/Explicit frame work using VUMAT. Three progressive failure analysis models, built-in ABAQUS (TradeMark), original COmplete STress Reduction (COSTR) and the modified COSTR damage models have been utilized in this study to simulate crack paths in five unidirectional notched laminates, 15deg, 30deg, 45deg, 60deg and 75deg under uniaxial tension load. Results such as crack paths and load vs. edge displacement curves are documented in this report. Modified COSTR damage model shows better accuracy in predicting crack paths in all the uni-directional laminates compared to the ABAQUS (TradeMark) and the original COSTR damage models.

  16. Controllable degradation of medical magnesium by electrodeposited composite films of mussel adhesive protein (Mefp-1) and chitosan.

    PubMed

    Jiang, Ping-Li; Hou, Rui-Qing; Chen, Cheng-Dong; Sun, Lan; Dong, Shi-Gang; Pan, Jin-Shan; Lin, Chang-Jian

    2016-09-15

    To control the degradation rate of medical magnesium in body fluid environment, biocompatible films composed of Mussel Adhesive Protein (Mefp-1) and chitosan were electrodeposited on magnesium surface in cathodic constant current mode. The compositions and structures of the films were characterized by atomic force microscope (AFM), scanning electron microscope (SEM) and infrared reflection absorption spectroscopy (IRAS). And the corrosion protection performance was investigated using electrochemical measurements and immersion tests in simulated body fluid (Hanks' solution). The results revealed that Mefp-1 and chitosan successfully adhered on the magnesium surface and formed a protective film. Compared with either single Mefp-1 or single chitosan film, the composite film of chitosan/Mefp-1/chitosan (CPC (chitosan/Mefp-1/chitosan)) exhibited lower corrosion current density, higher polarization resistance and more homogenous corrosion morphology and thus was able to effectively control the degradation rate of magnesium in simulated body environment. In addition, the active attachment and spreading of MC3T3-E1 cells on the CPC film coated magnesium indicated that the CPC film was significantly able to improve the biocompatibility of the medical magnesium. Copyright © 2016 Elsevier Inc. All rights reserved.

  17. Preventing collapsing of vascular scaffolds: The mechanical behavior of PLA/PCL composite structure prostheses during in vitro degradation.

    PubMed

    Li, Chaojing; Wang, Fujun; Chen, Peifeng; Zhang, Ze; Guidoin, Robert; Wang, Lu

    2017-11-01

    The success of blood conduit replacement with synthetic graft is highly dependent on the architecture, and mechanical properties of the graft, especially for biodegradable grafts serving as scaffolds for in-situ tissue engineering. Particularly, the property of the radial compression recovery represents a critical to keep the patency during biointegration. Bi-component composite vascular grafts (cVG) made of polylactic acid (PLA) fabric and polycaprolactone (PCL) were developed with superior mechanical properties. In this research, the compressive and tensile properties of the prototypes were characterized when they were subjected to accelerated degradation. In addition, the prepared cVG were analyzed by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and wide angle X-ray diffraction (WAXD) to illustrate the gradual loss of mechanical properties. The results demonstrated that the cVG retained the circular cross-section even through its tensile strength decreased during degradation. The cVG samples containing a high percentage of PLA fibers lost their tensile strength faster, while the samples with lower PLA percentage lost the compressive resistance strength more quickly. This unique fabric-based composite biodegradable vascular prosthesis with an outstanding radical compression recovery could be a good candidate for in-situ formation of tissue engineered vascular graft. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. Synergy between surface adsorption and photocatalysis during degradation of humic acid on TiO2/activated carbon composites.

    PubMed

    Xue, Gang; Liu, Huanhuan; Chen, Quanyuan; Hills, Colin; Tyrer, Mark; Innocent, Francis

    2011-02-15

    A photocatalyst comprising nano-sized TiO(2) particles on granular activated carbon (GAC) was prepared by a sol-dipping-gel process. The TiO(2)/GAC composite was characterized by scanning electron microscopy (SEM), X-ray diffractiometry (XRD) and nitrogen sorptometry, and its photocatalytic activity was studied through the degradation of humic acid (HA) in a quartz glass reactor. The factors influencing photocatalysis were investigated and the GAC was found to be an ideal substrate for nano-sized TiO(2) immobilization. A 99.5% removal efficiency for HA from solution was achieved at an initial concentration of 15 mg/L in a period of 3h. It was found that degradation of HA on the TiO(2)/GAC composite was facilitated by the synergistic relationship between surface adsorption characteristics and photocatalytic potential. The fitting of experimental results with the Langmuir-Hinshelwood (L-H) model showed that the reaction rate constant and the adsorption constant values were 0.1124 mg/(L min) and 0.3402 L/mg. The latter is 1.7 times of the calculated value by fitting the adsorption equilibrium data into the Langmuir equation.

  19. Degradation of methyl orange by composite photocatalysts nano-TiO2 immobilized on activated carbons of different porosities.

    PubMed

    Wang, Xiaojing; Liu, Yafei; Hu, Zhonghua; Chen, Yujuan; Liu, Wei; Zhao, Guohua

    2009-09-30

    Composite photocatalysts TiO(2) immobilized on granular activated carbons with different porosities (TiO(2)/AC) were prepared by a novel approach, dip-hydrothermal method using peroxotitanate as precursor. The TiO(2)/AC composites were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and the nitrogen absorption. Their photocatalytic activity was evaluated by degradation of methyl orange (MO). The results showed that nano-TiO(2) particles of anatase type were well deposited on the activated carbon surface. The porosity of activated carbon had significant influence on the adsorption, the amount of TiO(2) deposited on the external surface of AC and the activity of composite photocatalysts. The composite TiO(2)/AC made from proper mesoporosity AC exhibited higher catalytic activity than the mixture of powdered TiO(2) with AC. Furthermore, the mechanism of synergistic effect of AC adsorption and TiO(2) photocatalysis was discussed.

  20. Distortion of genetically modified organism quantification in processed foods: influence of particle size compositions and heat-induced DNA degradation.

    PubMed

    Moreano, Francisco; Busch, Ulrich; Engel, Karl-Heinz

    2005-12-28

    Milling fractions from conventional and transgenic corn were prepared at laboratory scale and used to study the influence of sample composition and heat-induced DNA degradation on the relative quantification of genetically modified organisms (GMO) in food products. Particle size distributions of the obtained fractions (coarse grits, regular grits, meal, and flour) were characterized using a laser diffraction system. The application of two DNA isolation protocols revealed a strong correlation between the degree of comminution of the milling fractions and the DNA yield in the extracts. Mixtures of milling fractions from conventional and transgenic material (1%) were prepared and analyzed via real-time polymerase chain reaction. Accurate quantification of the adjusted GMO content was only possible in mixtures containing conventional and transgenic material in the form of analogous milling fractions, whereas mixtures of fractions exhibiting different particle size distributions delivered significantly over- and underestimated GMO contents depending on their compositions. The process of heat-induced nucleic acid degradation was followed by applying two established quantitative assays showing differences between the lengths of the recombinant and reference target sequences (A, deltal(A) = -25 bp; B, deltal(B) = +16 bp; values related to the amplicon length of the reference gene). Data obtained by the application of method A resulted in underestimated recoveries of GMO contents in the samples of heat-treated products, reflecting the favored degradation of the longer target sequence used for the detection of the transgene. In contrast, data yielded by the application of method B resulted in increasingly overestimated recoveries of GMO contents. The results show how commonly used food technological processes may lead to distortions in the results of quantitative GMO analyses.

  1. Preparation and characterization of Nano-graphite/TiO2 composite photoelectrode for photoelectrocatalytic degradation of hazardous pollutant.

    PubMed

    Li, Dong; Jia, Jialin; Zhang, Yuhang; Wang, Na; Guo, Xiaolei; Yu, Xiujuan

    2016-09-05

    Nano-graphite(Nano-G)/TiO2 composite photoelectrode was fabricated via sol-gel reaction, followed by the hot-press approach. The morphology, structure and light absorption capability of composite was characterized by various characterizations. The photoelectrochemical property and photoelectrocatalytic(PEC) activity of photoelectrode were also investigated. Results revealed that anatase TiO2 nanoparticles with an average diameter of 10nm were dispersed uniformly on the thickness of 2-3nm Nano-G, and TiOC bond was formed. The absorption edge of Nano-G/TiO2 photoelectrode was red-shifted towards low energy region and the enhanced visible light absorption was obtained. The charge transfer resistance of Nano-G/TiO2 photoelectrode was significantly decreased after the addition of Nano-G. And its transient photoinduced current was 10.5 times the value achieved using TiO2 electrode. Nano-G/TiO2 photoelectrode displayed greatly enhanced PEC activity of 99.2% towards the degradation of phenol, which was much higher than the 29.1% and 58.3% degradation seen on TiO2 and Nano-G electrode, respectively. The highly efficient and stable PEC activity of Nano-G/TiO2 photoelectrode was attributed to the synergy effect between photocatalysis and electrocatalysis, as well as enhanced light absorption ability and higher separation efficiency of photogenerated charge carriers. Moreover, contribution of series of reactive species to the PEC degradation of Nano-G/TiO2 photoelectrode was determined.

  2. Hydrothermal and mechanical stresses degrade fiber-matrix interfacial bond strength in dental fiber-reinforced composites.

    PubMed

    Bouillaguet, Serge; Schütt, Andrea; Alander, Pasi; Schwaller, Patrick; Buerki, Gerhard; Michler, Johann; Cattani-Lorente, Maria; Vallittu, Pekka K; Krejci, Ivo

    2006-01-01

    Fiber-reinforced composites (FRCs) show great promise as long-term restorative materials in dentistry and medicine. Recent evidence indicates that these materials degrade in vivo, but the mechanisms are unclear. The objective of this study was to investigate mechanisms of deterioration of glass fiber-polymer matrix bond strengths in dental fiber-reinforced composites during hydrothermal and mechanical aging. Conventional three-point bending tests on dental FRCs were used to assess flexural strengths and moduli. Micro push-out tests were used to measure glass fiber-polymer matrix bond strengths, and nanoindentation tests were used to determine the modulus of elasticity of fiber and polymer matrix phases separately. Bar-shaped specimens of FRCs (EverStick, StickTech, and Vectris Pontic, Ivoclar-Vivadent) were either stored at room temperature, in water (37 and 100 degrees C) or subjected to ageing (10(6) cycles, load: 49 N), then tested by three-point bending. Thin slices were prepared for micro push-out and nanoindentation tests. The ultimate flexural strengths of both FRCs were significantly reduced after aging (p < 0.05). Both water storage and mechanical loading reduced the interfacial bond strengths of glass fibers to polymer matrices. Nanoindentation tests revealed a slight reduction in the elastic modulus of the EverStick and Vectris Pontic polymer matrix after water storage. Mechanical properties of FRC materials degrade primarily by a loss of interfacial bond strength between the glass and resin phases. This degradation is detectable by micro push-out and nanoindentation methods.

  3. In vitro degradation and cytotoxicity of Mg/Ca composites produced by powder metallurgy.

    PubMed

    Zheng, Y F; Gu, X N; Xi, Y L; Chai, D L

    2010-05-01

    Mg/Ca (1 wt.%, 5 wt.%, 10 wt.% Ca) composites were prepared from pure magnesium and calcium powders using the powder metallurgy method, aiming to enlarge the addition of Ca content without the formation of Mg(2)Ca. The microstructures, mechanical properties and cytotoxicities of Mg/Ca composite samples were investigated. The corrosion of Mg/Ca composites in Dulbecco's modified Eagle's medium (DMEM) for various immersion intervals was studied by electrochemical impedance spectroscopy measurements and environmental scanning electron microscope, with the concentrations of released Mg and Ca ions in DMEM for various immersion time intervals being measured. It was shown that the main constitutional phases were Mg and Ca, which were uniformly distributed in the Mg matrix. The ultimate tensile strength (UTS) and elongation of experimental composites decreased with increasing Ca content, and the UTS of Mg/1Ca composite was comparable with that of as-extruded Mg-1Ca alloy. The corrosion potential increased with increasing Ca content, whereas the current density and the impedance decreased. It was found that the protective surface film formed quickly at the initial immersion stage. With increasing immersion time, the surface film became compact, and the corrosion rate of Mg/Ca composites slowed down. The surface film consisted mainly of CaCO(3), MgCO(3)x3H(2)O, HA and Mg(OH)(2) after 72 h immersion in DMEM. Mg/1Ca and Mg/5Ca composite extracts had no significant toxicity (p>0.05) to L-929 cells, whereas Mg/10Ca composite extract induced approximately 40% reduced cell viability.

  4. Corrosion/Degradation Monitoring Technology for Composite Materials used to Extend Building Service Life

    DTIC Science & Technology

    2014-07-01

    Service Life Extension of Buildings” ERDC/CERL TR-14-9 ii Abstract Fiber -reinforced polymer (FRP) composites offer cost and performance advantages...for patching concrete structures that have corroded reinforcing steel, but the Army largely avoids structural composite repair applications because...calculated life- cycle return on investment for this application was 11.91. DISCLAIMER: The contents of this report are not to be used for advertising

  5. MITRA Virtual laboratory for operative application of satellite time series for land degradation risk estimation

    NASA Astrophysics Data System (ADS)

    Nole, Gabriele; Scorza, Francesco; Lanorte, Antonio; Manzi, Teresa; Lasaponara, Rosa

    2015-04-01

    This paper aims to present the development of a tool to integrate time series from active and passive satellite sensors (such as of MODIS, Vegetation, Landsat, ASTER, COSMO, Sentinel) into a virtual laboratory to support studies on landscape and archaeological landscape, investigation on environmental changes, estimation and monitoring of natural and anthropogenic risks. The virtual laboratory is composed by both data and open source tools specifically developed for the above mentioned applications. Results obtained for investigations carried out using the implemented tools for monitoring land degradation issues and subtle changes ongoing on forestry and natural areas are herein presented. In detail MODIS, SPOT Vegetation and Landsat time series were analyzed comparing results of different statistical analyses and the results integrated with ancillary data and evaluated with field survey. The comparison of the outputs we obtained for the Basilicata Region from satellite data analyses and independent data sets clearly pointed out the reliability for the diverse change analyses we performed, at the pixel level, using MODIS, SPOT Vegetation and Landsat TM data. Next steps are going to be implemented to further advance the current Virtual Laboratory tools, by extending current facilities adding new computational algorithms and applying to other geographic regions. Acknowledgement This research was performed within the framework of the project PO FESR Basilicata 2007/2013 - Progetto di cooperazione internazionale MITRA "Remote Sensing tecnologies for Natural and Cultural heritage Degradation Monitoring for Preservation and valorization" funded by Basilicata Region Reference 1. A. Lanorte, R Lasaponara, M Lovallo, L Telesca 2014 Fisher-Shannon information plane analysis of SPOT/VEGETATION Normalized Difference Vegetation Index (NDVI) time series to characterize vegetation recovery after fire disturbance International Journal of Applied Earth Observation and

  6. Changes in composition and porosity occurring during the thermal degradation of wood and wood components

    USGS Publications Warehouse

    Rutherford, David W.; Wershaw, Robert L.; Cox, Larry G.

    2005-01-01

    Samples of pine and poplar wood, pine bark, and purified cellulose and lignin were charred at temperatures ranging from 250?C to 500?C for times ranging from 1 hour to 168 hours. Changes in composition were examined by Fourier Transform Infrared (FTIR) and 13C Nuclear Magnetic Resonance (NMR) spectrometry, mass loss, and elemental composition (carbon, hydrogen, and oxygen) of the char. Structural changes were examined by changes in porosity as measured by nitrogen gas adsorption. 13C NMR spectrometry, mass loss, and elemental composition were combined to estimate the mass of aromatic and aliphatic carbon remaining in the char. Mass loss and elemental composition were combined to estimate the chemical composition of material lost for various time intervals of heating. These analyses showed that aliphatic components in the test materials were either lost or converted to aromatic carbon early in the charring process. Nitrogen adsorption showed that no porosity develops for any of the test materials with heating at 250?C, even though substantial loss of material and changes in composition occurred. Porosity development coincided with the loss of aromatic carbon, indicating that micropores were developing within a fused-ring matrix.

  7. Bovine meniscal tissue exhibits age- and interleukin-1 dose-dependent degradation patterns and composition-function relationships.

    PubMed

    Ling, Carrie H-Y; Lai, Janice H; Wong, Ivan J; Levenston, Marc E

    2016-05-01

    Despite increasing evidence that meniscal degeneration is an early event in the development of knee osteoarthritis, relatively little is known regarding the sequence or functional implications of cytokine-induced meniscal degradation or how degradation varies with age. This study examined dose-dependent patterns of interleukin-1 (IL-1)-induced matrix degradation in explants from the radially middle regions of juvenile and adult bovine menisci. Tissue explants were cultured for 10 days in the presence of 0, 1.25, 5, or 20 ng/ml recombinant human IL-1α. Juvenile explants exhibited immediate and extensive sulfated glycosaminoglycan (sGAG) loss and subsequent collagen release beginning after 4-6 days, with relatively little IL-1 dose-dependence. Adult explants exhibited a more graded response to IL-1, with dose-dependent sGAG release and a lower fraction of sGAG released (but greater absolute release) than juvenile explants. In contrast to juvenile explants, adult explants exhibited minimal collagen release over the 10-day culture. Compressive and shear moduli reflected the changes in explant composition, with substantial decreases for both ages but a greater relative decrease in juvenile tissue. Dynamic moduli exhibited stronger dependence on explant sGAG content for juvenile tissue, likely reflecting concomitant changes to both proteoglycan and collagen tissue components. The patterns of tissue degradation suggest that, like in articular cartilage, meniscal proteoglycans may partially protect collagen from cell-mediated degeneration. A more detailed view of functional changes in meniscal tissue mechanics with degeneration will help to establish the relevance of in vitro culture models and will advance understanding of how meniscal degeneration contributes to overall joint changes in early stage osteoarthritis. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:801-811, 2016. © 2015 Orthopaedic Research Society. Published by

  8. Polymorphisms within insulin-degrading enzyme (IDE) gene determine insulin metabolism and risk of type 2 diabetes.

    PubMed

    Rudovich, Natalia; Pivovarova, Olga; Fisher, Eva; Fischer-Rosinsky, Antje; Spranger, Joachim; Möhlig, Matthias; Schulze, Matthias B; Boeing, Heiner; Pfeiffer, Andreas F H

    2009-11-01

    Insulin-degrading enzyme (IDE) is the ubiquitously expressed major enzyme responsible for insulin degradation. Insulin-degrading enzyme gene is located on chromosome region 10q23-q25 and exhibits a well-replicated peak of linkage with type 2 diabetes (T2DM). Several genetic association studies examined IDE gene as a susceptibility gene for T2DM with controversial results. However, pathophysiological mechanisms involved have remained elusive. We verified associations of two IDE polymorphisms (rs1887922 and rs2149632) with T2DM risk in two independent German cohorts and evaluated in detail the association of common variants with insulin metabolism and glycemic traits. We confirmed previously published findings for diabetes-associated rs1887922 and rs2149632 in the European Prospective Investigation into Cancer and Nutrition-Potsdam cohort (n = 3049; RR 1.26, p = 0.003 and RR 1.33, p < 0.0001 for additive model). Haplotypes which carried one risk allele of rs2149632 or two risk alleles of both studied IDE SNPs also demonstrated a strong association with increased T2DM risk in this cohort (p = 0.001 and p < 0.0001, respectively). However, we found no significant T2DM association in the cross-sectional metabolic syndrome Berlin-Potsdam cohort (n = 1026). In nondiabetic subjects (NGT+IFG/IGT; n = 739), we found an association of rs2149632 with impaired glucose-derived insulin secretion and a trend to decreased insulin sensitivity for rs1887922. In the NGT subjects (n = 440), the association with decreased insulin secretion for rs2149632 remain significant, and the association with decreased hepatic insulin degradation for rs1887922 were observed additionally. This study validates and confirms the association of IDE polymorphisms with T2DM risk in the prospective German cohort and provides novel evidence of influences of IDE genetic variants on insulin metabolism.

  9. Towards Remotely Sensed Composite Global Drought Risk Modelling

    NASA Astrophysics Data System (ADS)

    Dercas, Nicholas; Dalezios, Nicolas

    2015-04-01

    , wildfire danger, range and pasture conditions and unregulated stream flows. Keywords Remote sensing; Composite Drought Indicators; Global Drought Risk Monitoring.

  10. Visible Light Assisted Heterogeneous Fenton-like Degradation of Organic Pollutant via α-FeOOH/Mesoporous Carbon Composites.

    PubMed

    Qian, Xufang; Ren, Meng; Zhu, Yao; Yue, Dongting; Han, Yu; Jia, Jinping; Zhao, Yixin

    2017-03-03

    A α-FeOOH/mesoporous carbon (α-FeOOH/MesoC) composite prepared by in situ crystallization of adsorbed ferric ions within carboxyl functionalized mesoporous carbon was developed as a novel visible light assisted heterogeneous Fenton-like catalyst. The visible light active α-FeOOH nanocrystals were encapsulated in the mesoporous frameworks accompanying with surface attached large α-FeOOH microcrystals via C-O-Fe bonding. Assisting with visible light irradiation on α-FeOOH/MesoC, the mineralization efficiency increased owing to the photocatalytic promoted catalyzing H2O2 beyond the photo-thermal effect. The synergistic effect between α-FeOOH and MesoC in α-FeOOH/MesoC composite improved the mineralization efficiency than the mixture catalyst of α-FeOOH and MesoC. The iron leaching is greatly suppressed on the α-FeOOH/MesoC composite. Interestingly, the reused α-FeOOH/MesoC composites showed much higher phenol oxidation and mineralization efficiencies than the fresh catalyst and homogeneous Fenton system (FeSO4/H2O2). The XPS, XRD, FTIR and textural property results reveal that the great enhancement comes from the interfacial emerged oxygen containing groups between α-FeOOH and MesoC after the first heterogeneous Fenton-like reaction. In summary, visible light induced photocatalysis assisted heterogeneous Fenton-like process in the α-FeOOH/MesoC composite system improved the HO• production efficiency and Fe(III)/Fe(II) cycle and further activated the interfacial catalytic sites, which finally realize an extraordinary higher degradation and mineralization efficiency.

  11. Changes in SOM composition and stability to microbial degradation over time in response to wood chip ash fertilisation

    NASA Astrophysics Data System (ADS)

    Hansen, Mette; Saarsalmi, Anna; Peltre, Clément

    2017-04-01

    Recirculation of nutrients from wood chip combustion by ash fertilisation of forest systems can be used to re-introduce nutrients that are otherwise lost, counteracting nutrient depletion due to whole tree harvesting. However, the effects of ash application on soil organic matter (SOM) composition, turnover and stability are unknown. The aim of the study was to investigate how ash fertilisation of forest soils affects SOM composition and stability to microbial degradation over time. O-horizon and 0-5 cm mineral soil samples were collected from two coniferous forest sites, one in Finland and one in Denmark, where ash had been spread at different times. Changes in SOM biodegradability were estimated based on an incubation experiment, expressed as percentage of initial carbon. Changes in SOM composition were characterised using thermal analysis and Fourier transform mid-infrared photoacoustic spectroscopy (FTIR-PAS) analysis of bulk soil samples. Ash fertilisation of forest soils affected SOM composition in the O-horizon, but not in the top 5 cm of the mineral soil. The pH and biodegradability of SOM were increased in the O-horizon. The changes in SOM composition consisted of enrichment of Fe- and Al-oxides/ hydroxides, depletion of carboxylic and aromatic groups and lower thermal stability in soils with older and greater ash application. Ash fertilisation increased soil pH, either right after ash application or through a buffering effect of the ash on acidification caused by decomposing needles over time. The increased pH due to ash fertilisation together with the nutrient inputs from the ash most likely stimulated SOM turnover. This in turn increased the labile fraction of SOM, whereby the thermal stability of SOM decreased as simpler compounds were formed.

  12. Energy-restricted diet benefits body composition but degrades bone integrity in middle-aged obese female rats.

    PubMed

    Shen, Chwan-Li; Zhu, Wenbin; Gao, Weimin; Wang, Shu; Chen, Lixia; Chyu, Ming-Chien

    2013-08-01

    This study investigates the effects of a restricted diet (RD) on body composition and musculoskeletal health along with endocrines and molecular mechanism in established mature obese rats. Twenty female rats were fed with a high-fat diet (HFD) ad libitum for 4 months and then assigned to either HFD or RD group for another 4 months. Another 10 rats were on a low-fat diet for 8 months. Outcome measures included body composition, bone mineral density, microarchitecrure, and strength; serum leptin, adiponectin, insulin-like growth factor I, and liver glutathione peroxidase activity; and protein expression and spleen tumor necrosis factor α messenger RNA expression. We hypothesized that mature obese rats on a 35% energy restriction diet for 4 months would improve body composition but degrade microstructural and mechanical properties of long bones, and such changes in musculoskeletal integrity are related to the modulation of obesity-related endocrines and proinflammation. Relative to HFD, RD benefited body composition (decreased body weight and %fat mass and increased %fat-free mass); decreased insulin-like growth factor I and leptin; elevated adiponectin, glutathione peroxidase activity and protein expression and tumor necrosis factor α messenger RNA expression; and suppressed bone formation and increased bone resorption, resulting in decreased trabecular and cortical bone volume, bone mineral density, and bone strength. Relative to low-fat diet, RD had a similar effect on body composition and serum markers but increased bone turnover rate and decreased bone mineral density and strength. Our data suggest that long-term RD has a negative impact on bone remodeling in obese female rats, probably through modification of endocrines and elevation of proinflammation. Copyright © 2013 Elsevier Inc. All rights reserved.

  13. Sustainable Energy Solutions Task 4.2: UV Degradation Prevention on Fiber-Reinforced Composite Blades. Final report

    SciTech Connect

    Twomey, Janet M.

    2010-03-01

    Use of wind energy has expanded very quickly because of the energy prices, environmental concerns and improved efficiency of wind generators. Rather than using metal and alloy based wind turbine blades, larger size fiber (glass and carbon) reinforced composite blades have been recently utilized to increase the efficiency of the wind energy in both high and low wind potential areas. In the current composite manufacturing, pre-preg and vacuum-assisted/heat sensitive resin transfer molding and resin infusion methods are employed. However, these lighter, stiffer and stronger composite blades experience ultraviolet (UV) light degradation where polymers (epoxies and hardeners) used for the blades manufacturing absorb solar UV lights, and cause photolytic, thermo-oxidative and photo-oxidative reactions resulting in breaking of carbon-hydrogen bonds, polymer degradation and internal and external stresses. One of the main reasons is the weak protective coatings/paints on the composite blades. This process accelerates the aging and fatigue cracks, and reduces the overall mechanical properties of the blades. Thus, the lack of technology on coatings for blade manufacturing is forcing many government agencies and private companies (local and national windmill companies) to find a better solution for the composite wind blades. Kansas has a great wind potential for the future energy demand, so efficient wind generators can be an option for continuous energy production. The research goal of the present project was to develop nanocomposite coatings using various inclusions against UV degradation and corrosion, and advance the fundamental understanding of degradation (i.e., physical, chemical and physiochemical property changes) on those coatings. In pursuit of the research goal, the research objective of the present program was to investigate the effects of UV light and duration on various nanocomposites made mainly of carbon nanotubes and graphene nanoflakes, contribute the

  14. Reliability, Risk and Cost Trade-Offs for Composite Designs

    NASA Technical Reports Server (NTRS)

    Shiao, Michael C.; Singhal, Surendra N.; Chamis, Christos C.

    1996-01-01

    Risk and cost trade-offs have been simulated using a probabilistic method. The probabilistic method accounts for all naturally-occurring uncertainties including those in constituent material properties, fabrication variables, structure geometry and loading conditions. The probability density function of first buckling load for a set of uncertain variables is computed. The probabilistic sensitivity factors of uncertain variables to the first buckling load is calculated. The reliability-based cost for a composite fuselage panel is defined and minimized with respect to requisite design parameters. The optimization is achieved by solving a system of nonlinear algebraic equations whose coefficients are functions of probabilistic sensitivity factors. With optimum design parameters such as the mean and coefficient of variation (representing range of scatter) of uncertain variables, the most efficient and economical manufacturing procedure can be selected. In this paper, optimum values of the requisite design parameters for a predetermined cost due to failure occurrence are computationally determined. The results for the fuselage panel analysis show that the higher the cost due to failure occurrence, the smaller the optimum coefficient of variation of fiber modulus (design parameter) in longitudinal direction.

  15. Neighbourhood social and socio-economic composition and injury risks.

    PubMed

    Reimers, Anne; Laflamme, Lucie

    2005-10-01

    To investigate whether social and socio-economic characteristics of the population within a parish influence childhood injury. The study encompasses all children aged 0-15 y living in Stockholm County over the 3-y period 1999-2001 (about 360,000 children per year), grouped into parish of residence (138 parishes). The effect of parish attributes on injury rate were analysed based on three indices (deprivation, socio-economic status and social integration) derived by a factor analysis of 11 characteristics of the parishes' population, each index being split into three levels. Childhood injury resulting in at least one night of hospitalization during the period 1999-2001 was considered (n = 5540) by index, and rate ratios were calculated for 12 injury causes using parishes forming the best level of the index as the reference group. Higher levels of deprivation negatively influenced pedestrian injury rates, had a protective effect on other traffic-related injuries, and negatively affected some other types of unintentional injuries. Higher concentrations of people with low socio-economic status did not impact on the risk of traffic and fall injuries, but increased that of burns/scalds and cases of poisoning. Parishes with lower levels of social integration had significantly higher rates of bicycle- and moped-related injuries, and also of self-inflicted ones. Compositional characteristics of the population in a residential area affect injury to varying degrees and direction according to type of injury. The underlying mechanisms are likely to be specific to injury type.

  16. The Degradation Behavior of SiCf/SiO2 Composites in High-Temperature Environment

    NASA Astrophysics Data System (ADS)

    Yang, Xiang; Cao, Feng; Qing, Wang; Peng, Zhi-hang; Wang, Yi

    2017-08-01

    SiCf/SiO2 composites had been fabricated efficiently by Sol-Gel method. The oxidation behavior, thermal shock property and ablation behavior of SiCf/SiO2 composites was investigated. SiCf/SiO2 composites showed higher oxidation resistance in oxidation atmosphere, the flexural strength retention ratio was larger than 90.00%. After 1300 °C thermal shock, the mass retention ratio was 97.00%, and the flexural strength retention ratio was 92.60%, while after 1500 °C thermal shock, the mass retention ratio was 95.37%, and the flexural strength retention ratio was 83.34%. After 15 s ablation, the mass loss rate was 0.049 g/s and recession loss rate was 0.067 mm/s. The SiO2 matrix was melted in priority and becomes loosen and porous. With the ablation going on, the oxides were washed away by the shearing action of the oxyacetylene flame. The evaporation of SiO2 took away large amount of heat, which is also beneficial to the protection for SiCf/SiO2 composites.

  17. Monitoring Poisson's Ratio Degradation of FRP Composites under Fatigue Loading Using Biaxially Embedded FBG Sensors.

    PubMed

    Akay, Erdem; Yilmaz, Cagatay; Kocaman, Esat S; Turkmen, Halit S; Yildiz, Mehmet

    2016-09-19

    The significance of strain measurement is obvious for the analysis of Fiber-Reinforced Polymer (FRP) composites. Conventional strain measurement methods are sufficient for static testing in general. Nevertheless, if the requirements exceed the capabilities of these conventional methods, more sophisticated techniques are necessary to obtain strain data. Fiber Bragg Grating (FBG) sensors have many advantages for strain measurement over conventional ones. Thus, the present paper suggests a novel method for biaxial strain measurement using embedded FBG sensors during the fatigue testing of FRP composites. Poisson's ratio and its reduction were monitored for each cyclic loading by using embedded FBG sensors for a given specimen and correlated with the fatigue stages determined based on the variations of the applied fatigue loading and temperature due to the autogenous heating to predict an oncoming failure of the continuous fiber-reinforced epoxy matrix composite specimens under fatigue loading. The results show that FBG sensor technology has a remarkable potential for monitoring the evolution of Poisson's ratio on a cycle-by-cycle basis, which can reliably be used towards tracking the fatigue stages of composite for structural health monitoring purposes.

  18. Modeling Strength Degradation of Fiber-Reinforced Ceramic-Matrix Composites Subjected to Cyclic Loading at Elevated Temperatures in Oxidative Environments

    NASA Astrophysics Data System (ADS)

    Longbiao, Li

    2017-04-01

    In this paper, the strength degradation of non-oxide and oxide/oxide fiber-reinforced ceramic-matrix composites (CMCs) subjected to cyclic loading at elevated temperatures in oxidative environments has been investigated. Considering damage mechanisms of matrix cracking, interface debonding, interface wear, interface oxidation and fibers fracture, the composite residual strength model has been established by combining the micro stress field of the damaged composites, the damage models, and the fracture criterion. The relationships between the composite residual strength, fatigue peak stress, interface debonding, fibers failure and cycle number have been established. The effects of peak stress level, initial and steady-state interface shear stress, fiber Weibull modulus and fiber strength, and testing temperature on the degradation of composite strength and fibers failure have been investigated. The evolution of residual strength versus cycle number curves of non-oxide and oxide/oxide CMCs under cyclic loading at elevated temperatures in oxidative environments have been predicted.

  19. [The surface degradation of various light-cured composite resins by thermal cycling].

    PubMed

    Hirabayashi, S; Nomoto, R; Harashima, I; Hirasawa, T

    1990-01-01

    The durability of four commercially available light-cured composite resins was investigated by thermal cycling, GR containing inorganic fillers treated with the graft polymerization of acryl ester, LF inorganic fillers treated with a silane coupling agent, PC silanized inorganic fillers and organic composite fillers, and the MFR-type SI containing the organic composite fillers. These materials were given 10,000, 30,000 and 50,000 thermal cycles (4 degrees C-60 degrees C) and the deterioration of materials by thermal cycling was evaluated by the measurement of the mechanical properties and the SEM observations of the surface of the thermocycled materials. Compressive strength and bending elastic moduli for all materials did not change greatly by thermal cycling. However, bending strength, toothbrush abrasion resistance and surface hardness decreased with increasing number of thermal cycles between 0 and 30,000, and changed little after 30,000 cycles. The percentage of bending strength after 50,000 thermal cycles to that of the non-thermocycled sample was 75% for GR, 60% for LF, 50% for PC and 65% for SI, respectively. Deterioration of materials was observed as cracks on the surface, which generated at the interface of the filler and matrix. The cracks generated relatively earlier during thermal cycling for SI and PC which contained the organic composite filler, later for LF which contained the silanized inorganic fillers, and the number of cracks on LF were fewer than SI and PC. On the other hand, for GR, no cracks were observed even after 50,000 thermal cycles. From these results, it can be presumed that the pre-treatment of filler by the graft polymerization is more effective to improve the durability of composite resin.

  20. ZnS/Ni{sub 2}P core/shell composites: Simple hydrothermal synthesis, characterization and its photocatalytic degradation of pyronine B

    SciTech Connect

    Liu, Shuling; Ma, Lanbing; Zhang, Hongzhe; Ma, Chenlu

    2016-05-15

    Highlights: • ZnS/Ni{sub 2}P composites have been firstly synthesized via a gentle hydrothermal route. • The composites have been characterized by XRD, SEM and TEM. • ZnS/Ni{sub 2}P showed enhanced photocatalytic degradation activity for pyronine B. • The reason for the enhanced photocatalytic activity has been discussed. - Abstract: ZnS/Ni{sub 2}P core/shell composites were successfully synthesized using a hydrothermal method. The composites have been characterized by XRD, SEM, TEM and the corresponding results showed that the composites were composed of the cubic ZnS microspheres, which were made up of ZnS nanoparticles, and Ni{sub 2}P nanoparticles coated on the surfaces of ZnS microspheres. Compared with ZnS microspheres, ZnS/Ni{sub 2}P core/shell composites showed enhanced photocatalytic degradation activity for pyronine B under UV irradiation. This may be related to the effective separation of photogenerated electron–hole pairs in ZnS/Ni{sub 2}P composites which can greatly reduce the chance of their recombination. Furthermore, superoxide ions and hydroxyl radical can be more easily produced through ZnS/Ni{sub 2}P composites, which is also beneficial for the degradation of pyronine B.

  1. Degradable Polymers and Block Copolymers from Electron-deficient Carbonyl Compounds (STIR) (7.3 Polymer Chemistry - Synthesis: Architecture and Composition)

    DTIC Science & Technology

    2015-04-23

    SECURITY CLASSIFICATION OF: Polyacetals are a readily degradable class of polymers with potential uses in the preparation of porous materials and...been reported in the literature to date, which has limited the investigation of these materials . Recently developed organocatalysis systems have been...Composition) Report Title Polyacetals are a readily degradable class of polymers with potential uses in the preparation of porous materials and patterned

  2. Mechanisms of degradation of graphite composites in a simulated space environment

    NASA Technical Reports Server (NTRS)

    Giori, C.; Yamauchi, T.; Rajan, K.; Mell, R.

    1983-01-01

    Attention is given to degradation mechanisms for graphite/polysulfone and graphite/epoxy laminates exposed to ultraviolet and high-energy electron radiation in vacuum up to 960 equivalent sun hours and to 10 to the 9th rads, respectively. The materials showed good electron radiation stability as indicated by the low G values for gas formation and no evidence of mechanical property changes. Quantum yields for gas formation indicate poor stability to ultraviolet radiation. Mechanical property measurements did not show significant changes up to 960 ESH, with the possible exception of P1700/C6000. The main products of irradiation were identified as hydrogen and methane, along with high levels of CO and CO2.

  3. Composition of Toluene-Degrading Microbial Communities from Soil at Different Concentrations of Toluene

    PubMed Central

    Hubert, Casey; Shen, Yin; Voordouw, Gerrit

    1999-01-01

    Toluene-degrading bacteria were isolated from hydrocarbon-contaminated soil by incubating liquid enrichment cultures and agar plate cultures in desiccators in which the vapor pressure of toluene was controlled by dilution with vacuum pump oil. Incubation in desiccators equilibrated with either 100, 10, or 1% (wt/wt) toluene in vacuum pump oil and testing for genomic cross-hybridization resulted in four genomically distinct strains (standards) capable of growth on toluene (strains Cstd1, Cstd2, Cstd5, and Cstd7). The optimal toluene concentrations for growth of these standards on plating media differed considerably. Cstd1 grew best in an atmosphere equilibrated with 0.1% (wt/wt) toluene, but Cstd5 failed to grow in this atmosphere. Conversely, Cstd5 grew well in the presence of 10% (wt/wt) toluene, which inhibited growth of Cstd1. 16S ribosomal DNA sequencing and cross-hybridization analysis indicated that both Cstd1 and Cstd5 are members of the genus Pseudomonas. An analysis of the microbial communities in soil samples that were incubated with 10% (wt/wt) toluene with reverse sample genome probing indicated that Pseudomonas strain Cstd5 was the dominant community member. However, incubation of soil samples with 0.1% (wt/wt) toluene resulted in a community that was dominated by Pseudomonas strain Q7, a toluene degrader that has been described previously (Y. Shen, L. G. Stehmeier, and G. Voordouw, Appl. Environ. Microbiol. 64:637–645, 1998). Q7 was not able to grow by itself in an atmosphere equilibrated with 0.1% (wt/wt) toluene but grew efficiently in coculture with Cstd1, suggesting that toluene or metabolic derivatives of toluene were transferred from Cstd1 to Q7. PMID:10388704

  4. Do new matrix formulations improve resin composite resistance to degradation processes?

    PubMed

    Fonseca, Andrea Soares Quirino da Silva; Gerhardt, Kátia Maria da Fonseca; Pereira, Gisele Damiana da Silveira; Sinhoreti, Mário Alexandre Coelho; Schneider, Luis Felipe Jochims

    2013-01-01

    The aim of this study was to determine the degradation resistance of three new formulations-silorane-, Ormocer- and dimer-acid-based materials-and compare them to the traditional dimethacrylate-based materials. One silorane- (Filtek P90, P90), one Ormocer- (Ceram-X, CX), one dimer-acid- (N'Durance, ND) and two dimethacrylate-based (Filtek P60, P60; Tetric Ceram, TC) materials were investigated. Water sorption (Wsp) and solubility (Wsl) were determined after the materials were immersed in water for 28 days. Knoop hardness (KH) was determined before and after 24 h immersion in pure ethanol. The flexural-strength (FS) was determined by the bending test after one-week storage in a dry environment or after one-week immersion in pure ethanol. Data were submitted to analysis of variance (ANOVA) and Tukey's test (95%). The three new formulations showed lower Wsp than the dimethacrylate-based formulation. CX (0.50 ± 0.17%) and ND (0.72 ± 0.19%) exhibited the lowest Wsp, whereas P90 (0.02 ± 0.03%) and P60 (0.04 ± 0.03%) showed the lowest Wsl. All resins showed reduced Knoop hardness number (KHN) after ethanol immersion. P60 presented the lowest decrease in KH value (19 ± 5%). TC (48 ± 3%) and P90 (39 ± 9%) showed the highest KHN decrease after ethanol storage. The FS of CX, ND and TC were affected by ethanol storage. The new formulations did not improve the degradation resistance, as compared with the traditional methacrylate-based materials.

  5. Composition of toluene-degrading microbial communities from soil at different concentrations of toluene

    SciTech Connect

    Hubert, C.; Shen, Y.; Voordouw, G. . Dept. of Biological Sciences)

    1999-07-01

    Toluene-degrading bacteria were isolated from hydrocarbon-contaminated soil by incubating liquid enrichment cultures and agar plate cultures in desiccators in which the vapor pressure of toluene was controlled by dilution with vacuum pump oil. Incubation in desiccators equilibrated with either 100, 10, or 1% (wt/wt) toluene in vacuum pump oil and testing for genomic cross-hybridization resulted in four genomically distinct strains (standards) capable of growth on toluene (strains Cstd1, Cstd2, and Cstd5, and Cstd7). The optimal toluene concentrations for growth of these standards on plating media differed considerably. Cstd1 grew best in an atmosphere equilibrated with 0.1% (wt/wt) toluene, but Cstd5 failed to grow in this atmosphere. Conversely, Cstd5 grew well in the presence of 10% (wt/wt) toluene, which inhibited growth of Cstd1. 16S ribosomal DNA sequencing and cross-hybridization analysis indicated that both Cstd1 and Cstd5 are members of the genus Pseudomonas. An analysis of the microbial communities in soil samples that were incubated with 10% (wt/wt) toluene with reverse sample genome probing indicated that Pseudomonas strain Cstd5 was the dominant community member. However, incubation of soil samples with 0.1% (wt/wt) toluene resulted in a community that was dominated by Pseudomonas strain Q7, a toluene degrader that has been described previously. Q7 was not able to grow by itself in an atmosphere equilibrated with 0.1% (wt/wt) toluene but grew efficiently in coculture with Cstd1, suggesting that toluene or metabolic derivatives of toluene were transferred from Cstd1 to Q7.

  6. Visible light photo-catalytic activity of C-PVA/TiO2 composites for degrading rhodamine B

    NASA Astrophysics Data System (ADS)

    Yang, Haigang; Zhang, Jianling; Song, Yuanqing; Xu, Shoubin; Jiang, Long; Dan, Yi

    2015-01-01

    In this article, a novel visible light (VL) active photo-catalyst, calcinated-poly (vinyl alcohol) (C-PVA)/TiO2 composites, was prepared by calcinating the films on glass substrates obtained from TiO2 sol and initially thermally treated PVA solution. The results showed that the C-PVA with conjugated C=C bonds was doped onto the surface of TiO2 and expanded the photo-response from ultraviolet spectrum of the TiO2 to VL spectrum of the composites; meanwhile, the photo-luminescence of C-PVA was quenched by TiO2, indicating charge transfer between C-PVA and TiO2. The C-PVA/TiO2 composites showed improved adsorption and photo-catalytic performances toward rhodamine B (RhB) compared to TiO2. When the mass feed ratio (P/T) of polymer (P) to TiO2 (T) increased from 1:10 to 1:2, the equilibrium adsorption ratio of C-PVA/TiO2 composites toward RhB continuously increased from 8.2 to 21.6%; while the VL photo-degradation ratio of RhB increased at first, achieving maximum value (92.2%) at P/T = 1:6, and then decreased consecutively. SEM images showed that there were lots of aggregates of TiO2 and C-PVA on the surface of the composites. Moreover, the morphologies of those aggregates were related to the value of P/T, and the dispersion of TiO2 in the C-PVA matrix was best while P/T = 1:6. The photo-catalytic activity of C-PVA/TiO2 composites was closely correlated to aggregate states of C-PVA and TiO2, while the adsorption performance was contributed to the exposed C-PVA on the surface of C-PVA/TiO2 composites.

  7. Mechanical Degradation of Graphite/PVDF Composite Electrodes: A Model-Experimental Study

    SciTech Connect

    Takahashi, Kenji; Higa, Kenneth; Mair, Sunil; Chintapalli, Mahati; Balsara, Nitash; Srinivasan, Venkat

    2015-12-11

    Mechanical failure modes of a graphite/polyvinylidene difluoride (PVDF) composite electrode for lithium-ion batteries were investigated by combining realistic stress-stain tests and mathematical model predictions. Samples of PVDF mixed with conductive additive were prepared in a similar way to graphite electrodes and tested while submerged in electrolyte solution. Young's modulus and tensile strength values of wet samples were found to be approximately one-fifth and one-half of those measured for dry samples. Simulations of graphite particles surrounded by binder layers given the measured material property values suggest that the particles are unlikely to experience mechanical damage during cycling, but that the fate of the surrounding composite of PVDF and conductive additive depends completely upon the conditions under which its mechanical properties were obtained. Simulations using realistic property values produced results that were consistent with earlier experimental observations.

  8. Mechanical Degradation of Graphite/PVDF Composite Electrodes: A Model-Experimental Study

    DOE PAGES

    Takahashi, Kenji; Higa, Kenneth; Mair, Sunil; ...

    2015-12-11

    Mechanical failure modes of a graphite/polyvinylidene difluoride (PVDF) composite electrode for lithium-ion batteries were investigated by combining realistic stress-stain tests and mathematical model predictions. Samples of PVDF mixed with conductive additive were prepared in a similar way to graphite electrodes and tested while submerged in electrolyte solution. Young's modulus and tensile strength values of wet samples were found to be approximately one-fifth and one-half of those measured for dry samples. Simulations of graphite particles surrounded by binder layers given the measured material property values suggest that the particles are unlikely to experience mechanical damage during cycling, but that the fatemore » of the surrounding composite of PVDF and conductive additive depends completely upon the conditions under which its mechanical properties were obtained. Simulations using realistic property values produced results that were consistent with earlier experimental observations.« less

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

    SciTech Connect

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

    2010-06-07

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

  10. Divergent selection for ester-linked diferulates in maize pith stalk tissues. Effects on cell wall composition and degradability.

    PubMed

    Barros-Rios, Jaime; Malvar, Rosa A; Jung, Hans-Joachim G; Bunzel, Mirko; Santiago, Rogelio

    2012-11-01

    Cross-linking of grass cell wall components through diferulates (DFAs) has a marked impact on cell wall properties. However, results of genetic selection for DFA concentration have not been reported for any grass species. We report here the results of direct selection for ester-linked DFA concentration in maize stalk pith tissues and the associated changes in cell wall composition and biodegradability. After two cycles of divergent selection, maize populations selected for higher total DFA (DFAT) content (CHs) had 16% higher DFAT concentrations than populations selected for lower DFAT content (CLs). These significant DFA concentration gains suggest that DFA deposition in maize pith parenchyma cell walls is a highly heritable trait that is genetically regulated and can be modified trough conventional breeding. Maize populations selected for higher DFAT had 13% less glucose and 10% lower total cell wall concentration than CLs, suggesting that increased cross-linking of feruloylated arabinoxylans results in repacking of the matrix and possibly in thinner and firmer cell walls. Divergent selection affected esterified DFAT and monomeric ferulate ether cross link concentrations differently, supporting the hypothesis that the biosynthesis of these cell wall components are separately regulated. As expected, a more higher DFA ester cross-coupled arabinoxylan network had an effect on rumen cell wall degradability (CLs showed 12% higher 24-h total polysaccharide degradability than CHs). Interestingly, 8-8-coupled DFAs, previously associated with cell wall strength, were the best predictors of pith cell wall degradability (negative impact). Thus, further research on the involvement of these specific DFA regioisomers in limiting cell wall biodegradability is encouraged.

  11. An analytical model for contaminant transport in landfill composite liners considering coupled effect of consolidation, diffusion, and degradation.

    PubMed

    Xie, Haijian; Yan, Huaxiang; Feng, Shijin; Wang, Qiao; Chen, Peixiong

    2016-10-01

    One-dimensional mathematical model is developed to investigate the behavior of contaminant transport in landfill composite liner system considering coupled effect of consolidation, diffusion, and degradation. The first- and second-type bottom boundary conditions are used to derive the steady-state and quasi-steady-state analytical solutions. The concentration profiles obtained by the proposed analytical solution are in good agreement with those obtained by the laboratory tests. The bottom concentration and flux of the soil liners can be greatly reduced when the degradation effect and porosity changing are considered. For the case under steady-state, the bottom flux and concentration for the case with t 1/2 =10 years can be 2.8 and 5.5 times lower than those of the case with t 1/2 =100 years, respectively. The bottom concentration and flux of the soil liners can be greatly reduced when the coefficient of volume compressibility decreases. For quasi-steady-state and with t 1/2 = 10 years, the bottom flux and concentration for the case with m v  = 0.02/MPa can be 17.4 and 21 times lower than the case with m v  = 0.5/MPa. This may be due to the fact that the true fluid velocity induced by consolidation is greater for the case with high coefficient of volume compressibility. The bottom flux for the case with single compacted clay liner (CCL) can be 1.5 times larger than that for the case with GMB/CCL considering diffusion and consolidation for DCM. The proposed analytical model can be used for verification of more complicated numerical models and assessment of the coupled effect of diffusion, consolidation, and degradation on contaminant transport in landfill liner systems.

  12. Salinity as a structuring factor for the composition and performance of bacterioplankton degrading riverine DOC.

    PubMed

    Langenheder, Silke; Kisand, Veljo; Wikner, Johan; Tranvik, Lars J

    2003-07-01

    Abstract The impact of salinity on the composition and functional performance (biomass production, growth efficiency and growth rates) of bacterial communities was investigated using batch cultures growing on dissolved organic carbon from a river draining into the Northern Baltic Sea. The cultures were adjusted to riverine or estuarine salinity levels and inoculated with bacteria from these two environments. Bacterial growth efficiencies differed in response to salinity and the origin of the inoculum. When salinity was adjusted to correspond to the salinity at the site where the inoculum was retrieved, growth efficiency was relatively high (11.5+/-2.6%). However, when bacteria were confronted with a shift in salinity, growth efficiency was lower (7.5+/-2.0%) and more of the utilized carbon was respired. In contrast, growth rates were higher when bacteria were exposed to a change in salinity. The composition of the bacterial communities developing in the batch cultures differed, as shown by 16S rDNA DGGE, depending on the origin of the inoculum and salinity. Reverse and direct DNA-DNA hybridization revealed salinity optima in the growth of specific bacterial strains as well as broader phylogenetic groups. Strains belonging to the alpha- and beta-Proteobacteria, Actinobacteria and gamma-Proteobacteria other than the genus Pseudomonas showed higher relative abundance under freshwater conditions, whereas strains of the genus Pseudomonas and the Cytophaga-Flavobacterium-Bacteroides group were favored by estuarine conditions. Generally, our results demonstrate functional changes associated with changes in community composition. We suggest that even moderate changes in salinity affect bacterial community composition, which subsequently leads to altered growth characteristics.

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  14. Efficient adsorption and photocatalytic degradation of Rhodamine B under visible light irradiation over BiOBr/montmorillonite composites.

    PubMed

    Xu, Chengqun; Wu, Honghai; Gu, Feng Long

    2014-06-30

    BiOBr/Na-montmorillonite composites (BiOBr-Mt) were prepared under laboratory ambient conditions by using the surfactant cetyltrimethylammonium bromide (CTAB) as the Br source and template, and the as-synthesized samples were characterized by XRD, FT-IR, FESEM, TEM equipped with EDS, BET and UV-vis DRS techniques. Interestingly, the particle size of BiOBr can be controlled by CTAB modified Na-montmorillonite. The photocatalytic activity of the as-prepared was further evaluated by decomposition of Rhodamine B (RhB) under visible light irradiation; the obtained results revealed that the BiOBr-Mt sample had strong photoabsorption in the visible light region. It has higher photocatalytic activity than pure BiOBr alone. There exists an efficient adsorption for RhB onto BiOBr-Mt contrast to that onto the pure BiOBr. The adsorption processes can be well described by pseudo-second-order kinetic model; meanwhile, the adsorption behaviors can be described by both Freundlich and Langmuir equations but the former was better. Additionally, the relevant adsorption and degradation mechanisms were explored and the possible mechanisms were presented. The photocatalytic activity has high effect both in acidic and basic conditions on the degradation reaction but in acidic condition is more favorable. After three recycles, BiOBr-Mt did not exhibit any significant loss of photocatalytic activity, confirming the photocatalyst was essentially stable.

  15. Concurrent photocatalytic hydrogen production and organic degradation by a composite catalyst film in a two-chamber photo-reactor.

    PubMed

    Wang, Xi; Li, Xiao-yan

    2013-01-01

    A novel visible light-driven photocatalyst film, MoS₂/Ag/TiO₂, was synthesized on a glass-fiber membrane. The composite catalyst film had a multi-layer structure with Ag as nanoconjunctions between the MoS₂ and TiO₂ layers. The catalyst film performed well for both photocatalytic hydrogen production and organic degradation in a two-chamber photo-reactor under either solar or visible light. Hydrogen was produced in the cathode side chamber while the model organic was decomposed in the anode side chamber. The specific hydrogen production rate went through a maximum of 85 mmol/m²-h with an energy conversion efficiency of 0.85%, while the maximum specific organic carbon removal for formic acid under solar light reached 1,520 mg/m²-h. It is apparent that Ag between the TiO₂ and MoS₂ layers allowed the transfer of photo-excited electrons via TiO₂ → Ag → MoS₂ for organic degradation and H⁺ reduction (e.g. hydrogen evolution) in two different chambers.

  16. Constitutive law describing the strength degradation kinetics of fibre-reinforced composites subjected to constant amplitude cyclic loading

    NASA Astrophysics Data System (ADS)

    D'Amore, Alberto; Grassia, Luigi

    2016-02-01

    A two-parameter model based on strength degradation was developed and its predictive reliability was checked on a series of fatigue life and residual strength data available in the literature. The modelling approach explicitly accounts for the maximum cyclic stress, σ_{max}, and the stress ratio, R= σ_{min} /σ_{max}, and requires a limited number of experimental fatigue life data to predict the cycle-by-cycle strength degradation kinetics until the "sudden drop" of strength before catastrophic failure. Different loading conditions were analysed for a large variety of composites, including short-glass-fibre-reinforced polycarbonate, [±45]S glass/epoxy laminates, [±35]_{2S} graphite/epoxy laminates, AS4 carbon/epoxy 3k/E7K8 plain weave fabric with [45/-45/90/45/-45/45/-45/0/45/-45]S layup, and [CSM/fabric/(CSM/UD)2]S glass/polyester laminate. The modelling approach indicates that the fatigue life and the residual strength are related to the statistical distribution of the static strength.

  17. Degradation and swelling issues of poly-(d,l-lactide)/β-tricalcium phosphate/calcium carbonate composites for bone replacement.

    PubMed

    Abert, Jessica; Amella, Alessandro; Weigelt, Simone; Fischer, Horst

    2016-02-01

    Recently a tri-phase material consisting of poly-(d,l-lactide) (PDLLA), β-tricalcium phosphate (β-TCP), and calcium carbonate (CC) was proposed as a novel bone substitute candidate. β-TCP is suitable because of its bone-like mineral phase, PDLLA is introduced as a biodegradable adhesive phase, and CC is essential for buffering the acidic degradation of the lactate component. We hypothesize that the amounts of the three different components in the composite material must be carefully balanced in order to avoid issues such as accelerated degradation or pronounced volumetric swelling. To prove this, granulates made of different mixing ratios of the tri-phase compound were prepared by grinding. Specimens of the different compounds were manufactured by a hot pressing process. The bending strength of the specimens was determined before and after storing in demineralized water and phosphate buffered saline (PBS). The particle size of the compound granulates was smaller than 100µm. A ratio of 60wt% of the PDLLA component indicated the best compromise between stability of test specimens based on a strong melting network and bone-like properties. The specimens exhibited a bending strength up to 90MPa. The strength increased with an increasing ratio of β-TCP to calcium carbonate (based on 60wt% PDLLA). A vast volumetric swelling up to 40%, and thus a huge reduction of the bending strength, was observed during the storage of specimens in PBS. A swelling and thus a volume increase could be critical, especially for using the tri-phase bone substitute compound as 3D scaffold with defined dimensions. This must be considered with regard to the composition of the compound and the scaffold design. Copyright © 2015 Elsevier Ltd. All rights reserved.

  18. Photocatalytic degradation of organic reactive dyes over MnTiO3/TiO2 heterojunction composites under UV-visible irradiation.

    PubMed

    Sivakumar, Santhanam; Selvaraj, Ayyasamy; Ramasamy, Anaipalayam Kandasamy

    2013-01-01

    In this study, the photocatalytic degradation of organic reactive dyes have been investigated using MnTiO3/TiO2 heterojunction composites in the presence of electron acceptors under UV-Visible light irradiation. This MnTiO3/TiO2 heterojunction composites were prepared by annealing different mass ratios of pyrophanite MnTiO3 (3-11 wt%) and TiO2 at 300°C. All the MnTiO3/TiO2 heterojunction composites were characterized by spectral techniques like X-ray diffraction (XRD), scanning electron microscope (SEM) and diffused reflectance UV-visible spectroscopic analysis (DRS). Among them, 9 wt% MnTiO3/TiO2 heterojunction composites exhibited higher photocatalytic activity for the degradation of Reactive Blue 4 (RB 4). The photocatalytic efficiency of 9 wt% MnTiO3/TiO2 heterojunction composites was further enhanced by the addition of substantial amount of electron acceptors like hydrogen peroxide (H2O2) and ammonium peroxydisulfate ([NH4]2S2O8). The presence of oxidants (electron acceptors) facilitates the fast degradation of dye solution even in higher concentration upto 200 mg/L. The photocatalytic activity of MnTiO3/TiO2 heterojunction composites was also studied for the degradation of other four different structured reactive dyes. The extent of mineralization of these organic reactive dyes during photocatalytic degradation was estimated from COD analysis. MnTiO3/TiO2 heterojunction composites was also found to have good photostability in the presence of oxidants.

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

    PubMed

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

    2014-01-01

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

  20. Effect of maturity at harvest on yield, chemical composition, and in situ degradability for annual cereals used for swath grazing.

    PubMed

    Rosser, C L; Górka, P; Beattie, A D; Block, H C; McKinnon, J J; Lardner, H A; Penner, G B

    2013-08-01

    The objective of this study was to determine how harvest maturity of whole-crop cereals commonly used in swath grazing systems in western Canada affects yield, chemical composition, and in situ digestibility. We hypothesized that the increase in yield with advancing maturity would not offset the decline in digestibility and, thus, the yield of effectively degradable DM (EDDM) would decline with advanced stages of maturity. Four replicate plots of barley (Hordeum vulgare L.; cv. CDC Cowboy), millet (Panicum milliaceum; cv. Red Proso), oat (Avena sativa L., spp.; CDC Weaver), and wheat (Triticum aestivum L.; cv. 07FOR21) were grown, with a subsection in each replicate harvested at 4 different maturities: head elongation, late milk, hard dough, and fully mature. At each stage of maturity, the wet and DM yields, and chemical composition (DM, OM, NDF, crude fat, and nonfiber carbohydrates; NFC) were determined. Whole-crop samples were ground (2-mm screen) and weighed into nylon bags (pore size of 53 ± 10 µm), and duplicate incubation runs were conducted by crop type. For each incubation run, nylon bags were randomly allocated (randomized by field replication, stage of maturity, and incubation time) to 1 of 7 heifers (32 bags/heifer during each run). Degradation rates were determined using a first-order kinetic model and data were analyzed with stage of maturity as a fixed effect and plot as a random effect. The DM, OM, and NFC yields increased linearly for barley and oat (P < 0.001), and increased quadratically for millet and wheat (P ≤ 0.025). Neutral detergent fiber yield increased linearly for barley (P = 0.005) and quadratically for millet, oat, and wheat (P = 0.044). There were no changes in CP yield observed for barley, millet, or oat with advancing maturity, but there was a linear increase observed for wheat (P = 0.002). The NFC concentration increased linearly for barley, millet, and oat (P < 0.001), and quadratically for wheat (P < 0.001), whereas the EDDM

  1. Fatigue degradation and life prediction of glass fabric polymer composites under tension/torsion biaxial loadings

    SciTech Connect

    Kawakami, H.; Fujii, T.J.; Morita, Y.

    1995-10-01

    Fatigue degradation and life prediction for a plain woven glass fabric reinforced polyester under tension/torsion biaxial loadings were investigated. Typical S-N diagrams were given at several biaxial ratios when the biaxial cyclic loads were proportionally applied to the specimens. A fatigue damage accumulation model based on the continuum damage mechanics theory was developed, where modulus decay ratios in tension and shear were used as indicators for damage variables (D). In the model, the damage variables are considered to be second-order tensors. Then, the maximum principal damage variable, D* is introduced. According to the similarity to the principal stress, D* is obtained as the maximum eigen value of damage tensor [D{prime}]. Under proportional tension/torsion loadings, fatigue lives were satisfactorily predicted at any biaxial stress ratios using the present model in which the fatigue characteristics only under uniaxial tension and pure torsion loadings were needed. For a certain biaxial stress ratio, the effect of loading path on the fatigue strength was examined. The experimental result does not show a strong effect of loading path on the fatigue life.

  2. Shifts in methanogenic community composition and methane fluxes along the degradation of discontinuous permafrost

    PubMed Central

    Liebner, Susanne; Ganzert, Lars; Kiss, Andrea; Yang, Sizhong; Wagner, Dirk; Svenning, Mette M.

    2015-01-01

    The response of methanogens to thawing permafrost is an important factor for the global greenhouse gas budget. We tracked methanogenic community structure, activity, and abundance along the degradation of sub-Arctic palsa peatland permafrost. We observed the development of pronounced methane production, release, and abundance of functional (mcrA) methanogenic gene numbers following the transitions from permafrost (palsa) to thaw pond structures. This was associated with the establishment of a methanogenic community consisting both of hydrogenotrophic (Methanobacterium, Methanocellales), and potential acetoclastic (Methanosarcina) members and their activity. While peat bog development was not reflected in significant changes of mcrA copy numbers, potential methane production, and rates of methane release decreased. This was primarily linked to a decline of potential acetoclastic in favor of hydrogenotrophic methanogens. Although palsa peatland succession offers similarities with typical transitions from fen to bog ecosystems, the observed dynamics in methane fluxes and methanogenic communities are primarily attributed to changes within the dominant Bryophyta and Cyperaceae taxa rather than to changes in peat moss and sedge coverage, pH and nutrient regime. Overall, the palsa peatland methanogenic community was characterized by a few dominant operational taxonomic units (OTUs). These OTUs seem to be indicative for methanogenic species that thrive in terrestrial organic rich environments. In summary, our study shows that after an initial stage of high methane emissions following permafrost thaw, methane fluxes, and methanogenic communities establish that are typical for northern peat bogs. PMID:26029170

  3. Effect of pyrolysis temperature on composition, surface properties and thermal degradation rates of Brazil Nut shells.

    PubMed

    Bonelli, P R; Della Rocca, P A; Cerrella, E G; Cukierman, A L

    2001-01-01

    Changes in chemical and surface characteristics of Brazil Nut shells (Bertholletia excelsa) due to pyrolysis at different temperatures (350 degrees C, 600 degrees C, 850 degrees C) were examined. For this purpose, proximate and ultimate analyses, physical adsorption measurements of N2 (-196 degrees C) and CO, (25 degrees C) as well as samples visualisation by scanning electronic microscopy (SEM) were performed. Appreciable differences in the residue characteristics, depending markedly on the pyrolysis temperature, were observed. Release of volatile matter led to the development of pores of different sizes. Progressive increases in micropore development with increasing pyrolysis temperature took place, whereas a maximum development of larger pores occurred at 600 degrees C. Furthermore, kinetics measurements of Brazil Nut shells pyrolysis from ambient temperature up to 900 degrees C were performed by non-isothermal thermogravimetric analysis. A model taking into account the significant changes in the residue during pyrolysis, through an increase in the activation energy with temperature and solid conversion, were found to properly fit the kinetics data over the wide range of degradation investigated.

  4. An experimental study of toughening and degradation due to microcracking in a ceramic composite

    SciTech Connect

    Han, L.X.; Suresh, S. . Div. of Engineering); Warren, R. )

    1992-02-01

    This paper reports on an experimental investigation that has been carried out to study the effects of controlled microcracking on the fracture resistance of brittle solids. The material chosen as a model system for the experimental study is an aluminum oxide reinforce with 33 vol.% SiC whiskers. The experimental program involves the determination of fracture toughness at room temperature on four-point flexure specimens continuing sharp, through-thickness precracks where different amounts of microcrack damage are introduced a priori at different elevated temperatures and tensile load levels. The room temperature fracture initiation toughness of the pre-damaged material with a controlled amount of small-scale microcracking ahead of the stationary macrocrack is compared and contrasted with that of the undamaged material and the enhancement or reduction in fracture initiation toughness is estimated. Detailed transmission election microscopy of the crack-tip damage zone has been conducted in an attempt to examine the mechanisms of permanent degradation and of microcrack formation.

  5. Shifts in methanogenic community composition and methane fluxes along the degradation of discontinuous permafrost.

    PubMed

    Liebner, Susanne; Ganzert, Lars; Kiss, Andrea; Yang, Sizhong; Wagner, Dirk; Svenning, Mette M

    2015-01-01

    The response of methanogens to thawing permafrost is an important factor for the global greenhouse gas budget. We tracked methanogenic community structure, activity, and abundance along the degradation of sub-Arctic palsa peatland permafrost. We observed the development of pronounced methane production, release, and abundance of functional (mcrA) methanogenic gene numbers following the transitions from permafrost (palsa) to thaw pond structures. This was associated with the establishment of a methanogenic community consisting both of hydrogenotrophic (Methanobacterium, Methanocellales), and potential acetoclastic (Methanosarcina) members and their activity. While peat bog development was not reflected in significant changes of mcrA copy numbers, potential methane production, and rates of methane release decreased. This was primarily linked to a decline of potential acetoclastic in favor of hydrogenotrophic methanogens. Although palsa peatland succession offers similarities with typical transitions from fen to bog ecosystems, the observed dynamics in methane fluxes and methanogenic communities are primarily attributed to changes within the dominant Bryophyta and Cyperaceae taxa rather than to changes in peat moss and sedge coverage, pH and nutrient regime. Overall, the palsa peatland methanogenic community was characterized by a few dominant operational taxonomic units (OTUs). These OTUs seem to be indicative for methanogenic species that thrive in terrestrial organic rich environments. In summary, our study shows that after an initial stage of high methane emissions following permafrost thaw, methane fluxes, and methanogenic communities establish that are typical for northern peat bogs.

  6. Enhanced Photocatalytic Degradation of Environmental Pollutants under Visible Irradiation by a Composite Coating.

    PubMed

    Liu, Shuqin; Hu, Qingkun; Qiu, Junlang; Wang, Fuxin; Lin, Wei; Zhu, Fang; Wei, Chaohai; Zhou, Ningbo; Ouyang, Gangfeng

    2017-05-02

    Although nanotechnology has offered effective and efficient solutions for environmental remediation, the full utilization of sustainable energy and the avoidance of secondary pollution are still challenges. Herein, we report a two-step modification strategy for TiO2 nanoparticles by first forming a thin, surface-adherent polydopamine (PDA) shell onto the nanoparticles and then assembling core-shell nanoparticles as a photodegradation coating. The composite coating modified from TiO2 could not only realize the highly efficient utilization of photons from the visible region but also avoid the secondary pollution of nanoparticles during application. Additionally, improvements in the adsorption ability after modification greatly facilitated the photocatalytic process of the modified materials. A preliminary in vivo study on Daphnia magna and a wastewater treatment experiment suggest that treatment with the composite coating can effectively eliminate fluorene and significantly reduce its lethality. We believe the two-step modification scheme can open new avenues for the facile modification of nanomaterials for designed purposes, especially in the field of environmental remediation.

  7. Studies of Local Degradation Phenomena in Composite Cathodes forLithium-Ion Batteries

    SciTech Connect

    Kerlau, M.; Marcinek, M.; Srinivasan, V.; Kostecki, R.M.

    2006-11-01

    {sup 13}C-carbon black substituted composite LiNi{sub 0.8}Co{sub 0.15}Al{sub 0.05}O{sub 2} cathodes were tested in model electrochemical cells to monitor qualitatively and quantitatively carbon additive(s) distribution changes within tested cells and establish possible links with other detrimental phenomena. Raman qualitative and semi-quantitative analysis of {sup 13}C in the cell components was carried out to trace the possible carbon rearrangement/movement in the cell. Small amounts of cathode carbon additives were found trapped in the separator, at the surface of Li-foil anode, in the electrolyte. The structure of the carried away carbon particles was highly amorphous unlike the original {sup 12}C graphite and {sup 13}C carbon black additives. The role of the carbon additive, the mechanism of carbon retreat in composite cathodes and its correlation with the increase of the cathode interfacial charge-transfer impedance, which accounts for the observed cell power and capacity loss is investigated and discussed.

  8. In vivo degradation of a poly(propylene fumarate)/beta-tricalcium phosphate injectable composite scaffold.

    PubMed

    Peter, S J; Miller, S T; Zhu, G; Yasko, A W; Mikos, A G

    1998-07-01

    This study was designed to investigate the in vivo biodegration and biocompatibility of a poly(propylene fumarate) (PPF)-based orthopedic biomaterial. The effects of varying the PPF to N-vinyl pyrrolidinone ratio and PPF to beta-tricalcium phosphate content were studied. The composite mechanical properties and local tissue interactions were analyzed over 12 weeks. An initial increase in both compressive modulus and strength was seen for composite formulations that incorporated beta-tricalcium phosphate. The samples incorporating a higher PPF to N-vinyl pyrrolidinone ratio reached a maximal compressive strength of 7.7 MPa and a maximal compressive modulus of 191.4 MPa at 3 weeks. The lower PPF to N-vinyl pyrrolidinone ratio samples gained a maximum compressive strength of 7.5 MPa initially and a compressive modulus of 134.0 MPa at 1 week. At 6 weeks, all samples for formulations incorporating beta-tricalcium phosphate crumbled upon removal and were not mechanically tested. Samples that did not incorporate beta-tricalcium phosphate were very weak and insufficient for bone replacement at the 4-day time point and beyond. Tissue interactions resulted in a mild inflammatory response at the initial time points and mature fibrous encapsulation by 12 weeks.

  9. Spatial evaluation of the risk of groundwater quality degradation. A comparison between disjunctive kriging and geostatistical simulation.

    PubMed

    Barca, E; Passarella, G

    2008-02-01

    In some previous papers a probabilistic methodology was introduced to estimate a spatial index of risk of groundwater quality degradation, defined as the conditional probability of exceeding assigned thresholds of concentration of a generic chemical sampled in the studied water system. A crucial stage of this methodology was the use of geostatistical techniques to provide an estimation of the above-mentioned probability in a number of selected points by crossing spatial and temporal information. In this work, spatial risk values were obtained using alternatively stochastic conditional simulation and disjunctive kriging. A comparison between the resulting two sets of spatial risks, based on global and local statistical tests, showed that they do not come from the same statistical population and, consequently, they cannot be viewed as equivalent in a statistical sense. At a first glance, geostatistical conditional simulation may appear to represent the spatial variability of the phenomenon more effectively, as the latter tends to be smoothed by DK. However, a close examination of real case study results suggests that disjunctive kriging is more effective than simulation in estimating the spatial risk of groundwater quality degradation. In the study case, the potentially 'harmful event' considered, threatening a natural 'vulnerable groundwater system,' is fertilizer and manure application.

  10. Preparation of graphene/TiO2 composites by nonionic surfactant strategy and their simulated sunlight and visible light photocatalytic activity towards representative aqueous POPs degradation.

    PubMed

    Li, Kexin; Xiong, Jingjing; Chen, Tong; Yan, Liushui; Dai, Yuhua; Song, Dongyang; Lv, Ying; Zeng, Zhenxing

    2013-04-15

    A series of graphene/TiO2 composites were fabricated using a single-step nonionic surfactant strategy combined with the solvothermal treatment technique. Their phase structure, morphology, porosity, optical absorption property, as well as composition and structure, were characterized. The as-prepared composites were successfully applied to degrade aqueous persistent organic pollutants (POPs) such as rhodamine B, aldicarb, and norfloxacin in simulated sunlight (λ>320 nm) and visible light (λ>400 nm) irradiation. The degradation mechanism and kinetics of aqueous POPs were studied in detail. The mineralization of aqueous POPs and the recyclability of the composites were also tested in the same condition. Copyright © 2013 Elsevier B.V. All rights reserved.

  11. Enhanced photocatalytic performance of BiOBr/NH2-MIL-125(Ti) composite for dye degradation under visible light.

    PubMed

    Zhu, Shuai-Ru; Liu, Peng-Fei; Wu, Meng-Ke; Zhao, Wen-Na; Li, Guo-Chang; Tao, Kai; Yi, Fei-Yan; Han, Lei

    2016-11-01

    Metal-organic frameworks (MOFs) are considered as suitable materials for various applications in the area of photocatalysis. On the other hand, 2D BiOBr materials are efficient for the photodegradation of organic dyes under visible light illumination. In this work, BiOBr/NH2-MIL-125(Ti) composite photocatalysts with different NH2-MIL-125(Ti) content were prepared by incorporating NH2-MIL-125(Ti) with BiOBr using a co-precipitation method. A series of characterizations confirmed the strong synergistic effect between BiOBr and NH2-MIL-125(Ti). In rhodamine B (RhB) degradation experiments, the composite photocatalyst with a mass percent of 7 wt% NH2-MIL-125(Ti) exhibited an improved photocatalytic activity compared to pristine BiOBr and NH2-MIL-125(Ti). Furthermore, the enhanced photocatalytic performance under visible light illumination could be attributed to the Ti(3+)-Ti(4+) intervalence electron transfer and synergistic effect between NH2-MIL-125(Ti) and BiOBr, and also resulted in a separation efficiency of photo-generated electron-hole pairs during the photocatalytic reaction. This study can open up numerous opportunities for the development of various MOF-based visible light photocatalysts when combined with 2D bismuth oxyhalide materials for applications in environmental cleaning.

  12. MO degradation by Ag-Ag2O/g-C3N4 composites under visible-light irradation.

    PubMed

    Wang, Xin; Yan, Jia; Ji, Haiyan; Chen, Zhigang; Xu, Yuanguo; Huang, Liying; Zhang, Qi; Song, Yanhua; Xu, Hui; Li, Huaming

    2016-01-01

    The paper demonstrated the synthesis of Ag-Ag2O/g-C3N4 nanoparticles via a simple liquid phase synthesis path and a facile calcination method. The synthesized Ag-Ag2O/g-C3N4 composites were well characterized by various analytical techniques, such as X-ray diffraction, Fourier transform infrared (FT-IR), X-ray photoemission spectroscopy, transmission electron microscopy, scanning electron microscopy, high resolution transmission electron microscopy, the UV-Vis diffuse-reflectance spectra and transient photocurrent. From the structure and surface characterization, it indicated that Ag-Ag2O/g-C3N4 composites were formed by an effective covering of g-C3N4 with Ag-Ag2O. The results revealed that the 50 wt% nanoparticle had a great effection on the degradation of the methyl orange (MO), which was almost 7.5 times as high as that of g-C3N4. Based on the experimental results, the possible photocatalytic mechanism with photogenerated holes as the main active species was presented.

  13. Thermal degradation of wood fibers during hot-pressing of MDF composites. Part I, Relative effects and benefits of thermal exposure

    Treesearch

    Jerrold E. Winandy; Andrzej M. Krzysik

    2007-01-01

    This research evaluated the potential of wood fiber to chemically decompose during hot-pressing. We evaluated changes in carbohydrate composition and structure as a function of multiple press temperatures (180°, 200°, and 220°C) and an array of hot-pressing durations from 180 to 2500 s. Results show how this thermal degradation in chemical composition directly results...

  14. Composition and pathogenic potential of a microbial bioremediation product used for crude oil degradation

    PubMed Central

    Tayabali, Azam F.; Coleman, Gordon; Crosthwait, Jennifer; Nguyen, Kathy C.; Zhang, Yan; Shwed, Philip

    2017-01-01

    A microbial bioremediation product (MBP) used for large-scale oil degradation was investigated for microbial constituents and possible pathogenicity. Aerobic growth on various media yielded >108 colonies mL-1. Full-length 16S rDNA sequencing and fatty acid profiling from morphologically distinct colonies revealed ≥13 distinct genera. Full-length 16S rDNA library sequencing, by either Sanger or long-read PacBio technology, suggested that up to 21% of the MBP was composed of Arcobacter. Other high abundance microbial constituents (>6%) included the genera Proteus, Enterococcus, Dysgonomonas and several genera in the order Bacteroidales. The MBP was most susceptible to ciprofloxacin, doxycycline, gentamicin, and meropenam. MBP exposure of human HT29 and A549 cells caused significant cytotoxicity, and bacterial growth and adherence. An acellular MBP filtrate was also cytotoxic to HT29, but not A549. Both MBP and filtrate exposures elevated the neutrophil chemoattractant IL-8. In endotracheal murine exposures, bacterial pulmonary clearance was complete after one-week. Elevation of pro-inflammatory cytokines IL-1β, IL-6, and TNF-α, and chemokines KC and MCP-1 occurred between 2h and 48h post-exposure, followed by restoration to baseline levels at 96h. Cytokine/chemokine signalling was accompanied by elevated blood neutrophils and monocytes at 4h and 48h, respectively. Peripheral acute phase response markers were maximal at 24h. All indicators examined returned to baseline values by 168h. In contrast to HT29, but similar to A549 observations, MBP filtrate did not induce significant murine effects with the indicators examined. The results demonstrated the potentially complex nature of MBPs and transient immunological effects during exposure. Products containing microbes should be scrutinized for pathogenic components and subjected to characterisation and quality validation prior to commercial release. PMID:28178315

  15. Composition and pathogenic potential of a microbial bioremediation product used for crude oil degradation.

    PubMed

    Tayabali, Azam F; Coleman, Gordon; Crosthwait, Jennifer; Nguyen, Kathy C; Zhang, Yan; Shwed, Philip

    2017-01-01

    A microbial bioremediation product (MBP) used for large-scale oil degradation was investigated for microbial constituents and possible pathogenicity. Aerobic growth on various media yielded >108 colonies mL-1. Full-length 16S rDNA sequencing and fatty acid profiling from morphologically distinct colonies revealed ≥13 distinct genera. Full-length 16S rDNA library sequencing, by either Sanger or long-read PacBio technology, suggested that up to 21% of the MBP was composed of Arcobacter. Other high abundance microbial constituents (>6%) included the genera Proteus, Enterococcus, Dysgonomonas and several genera in the order Bacteroidales. The MBP was most susceptible to ciprofloxacin, doxycycline, gentamicin, and meropenam. MBP exposure of human HT29 and A549 cells caused significant cytotoxicity, and bacterial growth and adherence. An acellular MBP filtrate was also cytotoxic to HT29, but not A549. Both MBP and filtrate exposures elevated the neutrophil chemoattractant IL-8. In endotracheal murine exposures, bacterial pulmonary clearance was complete after one-week. Elevation of pro-inflammatory cytokines IL-1β, IL-6, and TNF-α, and chemokines KC and MCP-1 occurred between 2h and 48h post-exposure, followed by restoration to baseline levels at 96h. Cytokine/chemokine signalling was accompanied by elevated blood neutrophils and monocytes at 4h and 48h, respectively. Peripheral acute phase response markers were maximal at 24h. All indicators examined returned to baseline values by 168h. In contrast to HT29, but similar to A549 observations, MBP filtrate did not induce significant murine effects with the indicators examined. The results demonstrated the potentially complex nature of MBPs and transient immunological effects during exposure. Products containing microbes should be scrutinized for pathogenic components and subjected to characterisation and quality validation prior to commercial release.

  16. Effects of species and season on chemical composition and ruminal crude protein and organic matter degradability of some multi-purpose tree species by West African dwarf rams.

    PubMed

    Arigbede, O M; Anele, U Y; Südekum, K-H; Hummel, J; Oni, A O; Olanite, J A; Isah, A O

    2012-04-01

    Seasonal chemical composition and ruminal organic matter (OM) and crude protein (CP) degradabilities were determined in four tropical multi-purpose tree species (MPTS) namely; Pterocarpus santalinoides, Grewia pubescens, Enterolobium cyclocarpum and Leucaena leucocephala. Three West African dwarf (WAD) rams fitted with permanent rumen cannula were used for the degradability trials. Foliage samples were collected four times to represent seasonal variations as follows: January--mid dry; April--late dry; July--mid rainy and October--late rainy seasons. Leaf samples were randomly collected from the trees for estimation of dry matter (DM) and chemical composition. Ruminal in sacco OM and CP degradabilities were estimated from residues in nylon bags. All samples had high CP (161-259 g/kg DM) and moderate fibre concentrations [neutral detergent fibre (without residual ash], 300-501 g/kg DM; acid detergent fibre (without residual ash), 225-409 g/kg DM and acid detergent lignin, 87-179 g/kg DM across seasons. Interaction effects of species and season on chemical composition were highly significant (p = 0.001) except for trypsin inhibitor (p = 0.614). The MPTS recorded more than 60% OM and CP degradability at 24 h, which implied that they were all highly degradable in the rumen. Their incorporation into ruminant feeding systems as dry season forage supplements is therefore recommended.

  17. Fabrication of efficient visible light activated Cu-P25-graphene ternary composite for photocatalytic degradation of methyl blue

    NASA Astrophysics Data System (ADS)

    Jin, Zheng; Duan, Wubiao; Liu, Bo; Chen, Xidong; Yang, Feihua; Guo, Jianping

    2015-11-01

    Cu-P25-graphene nanocomposite was fabricated through hydrothermal method at relatively low temperature. The technique used is P25-graphene (PG) binary composite was firstly prepared by P25 and graphite oxide (GO), and then Cu2+ ions were impregnated into PG composite. The prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectrum respectively. As the results showed, the Cu-P25-graphene (CPG) nanocomposites possessed the extended light absorption in visible light and better charge separation capability as compared to the pure P25 and PG system. Moreover, CPG-4 (4 mM Cu(NO3)2) showed the highest degradation rate of methyl blue (MB) under the visible light, which the removal efficiency can reach 98% after 100 min. The corresponding hydrogen evolution rate of CPG-4 was 7.9 times than pure P25. It was concluded that the synergistic effects of Cu2+ ions and graphene narrowed the band gap of TiO2 and promoted charge separation, which played significant roles for the enhancement of photoactivity of CPG composite catalysts. In addition, it was observed that the photodegradation of MB followed the first order reaction kinetics. The effects of pH values of MB solution for photocatalysts had also been investigated. The result confirmed that the optimum values of pH were found to be 7. Finally, the stability test of photocatalysts was carried out and the photocatalytic mechanism was explained concretely.

  18. How depositional conditions control input, composition, and degradation of organic matter in sediments from the Chilean coastal upwelling region

    NASA Astrophysics Data System (ADS)

    Niggemann, Jutta; Ferdelman, Timothy G.; Lomstein, Bente Aa.; Kallmeyer, Jens; Schubert, Carsten J.

    2007-03-01

    with a lower quality of the sedimentary OM at 23° S. Reaction rate constants for TOC degradation that were obtained from measured SRR ( kSRR; 0.0004-0.0022 yr -1) showed a good correspondence to kTOC that were derived from the depth profiles of TOC (0.0003-0.0014 yr -1). Both, kSRR and kTOC, reflect differences in OM composition. At 36° S they were related to the degradation state of bulk OM (represented by C/N-ratios), whereas near 23° S they were related to the freshness of a small fraction of labile OM (represented by CI). Our study shows that although rates of organic carbon accumulation were similar in both investigated sites, the extent and kinetics of organic carbon degradation were closely linked to differing depositional conditions.

  19. Optimisation of the operational conditions of trichloroethylene degradation using Trametes versicolor under quinone redox cycling conditions using central composite design methodology.

    PubMed

    Vilaplana, Marcel; García, Ana Belén; Caminal, Gloria; Guillén, Francisco; Sarrà, Montserrat

    2012-04-01

    Extracellular radicals produced by Trametes versicolor under quinone redox cycling conditions can degrade a large variety of pollutant compounds, including trichloroethylene (TCE). This study investigated the effect of the agitation speed and the gas-liquid phase volume ratio on TCE degradation using central composite design (CCD) methodology for a future scale-up to a reactor system. The agitation speed ranged from 90 to 200 rpm, and the volume ratio ranged from 0.5 to 4.4. The results demonstrated the important and positive effect of the agitation speed and an interaction between the two factors on TCE degradation. Although the volume ratio did not have a significant effect if the agitation speed value was between 160 and 200 rpm, at lower speed values, the specific pollutant degradation was clearly more extensive at low volume ratios than at high volume ratios. The fitted response surface was validated by performing an experiment using the parameter combination in the model that maximised TCE degradation. The results of the experiments carried out using different biomass concentrations demonstrated that the biomass concentration had a positive effect on pollutant degradation if the amount of biomass present was lower than 1.6 g dry weight l(-1). The results show that the maximum TCE degradation was obtained at the highest speed (200 rpm), gas-liquid phase volume ratio (4.4), and a biomass concentration of 1.6 g dry weight l(-1).

  20. Effect of denture-coating composite on Candida albicans biofilm and surface degradation after disinfection protocol.

    PubMed

    Silva, Matheus Jacobina; de Oliveira, Denise G; Marcillo, Oscar O; Neppelenbroek, Karin H; Lara, Vanessa S; Porto, Vinícius C

    2016-04-01

    Denture stomatitis is the most common pathology affecting denture wearers and its main cause is colonisation of dentures with Candida albicans. This study investigated the effectiveness of two commercial composite surface sealants (Biscover(®) LV and Surface Coat(®)) to reduce C. albicans biofilm colonisation on denture resin, as well as their surface integrity after disinfection cycles with 1% sodium hypochlorite solution. Heat-cured acrylic resin specimens were manufactured (10 mm × 10 mm × 1 mm). The specimen surfaces were mechanically polished to simulate rough or smooth denture surfaces. Four surface-treatment groups were tested: smooth surfaces [0.3 μm of mean roughness (Ra)]; rough surfaces (3 μm of Ra); rough surfaces treated with Biscover(®) LV; and rough surfaces treated with Surface Coat(®). Specimens of each group were randomly divided to undergo immersion in distilled water or 1% sodium hypochlorite for 30 or 90 cycles each. Specimens of all groups in each immersion solution were tested using a crystal violet (CV) staining assay for biofilm quantification and by scanning electron microscopy for visual analyses of surface integrity and biofilm structure. CV assay data were analysed using one-way analysis of variance (ANOVA) followed by Tukey's multiple comparison test (P < 0.05). The effectiveness and surface integrity of Biscover(®) LV-treated surfaces were similar to those of smooth surfaces, whereas Surface Coat(®) -treated surfaces presented a similar performance to rough surfaces in all solutions and cycles. These results suggest the possibility of clinical use of Biscover(®) LV for denture coating on surfaces in which mechanical polish is not indicated, such as the fitting surface. © 2016 FDI World Dental Federation.

  1. Solar photocatalytic degradation of 2,6-dinitro-p-cresol (DNPC) using multi-walled carbon nanotubes (MWCNTs)-TiO(2) composite photocatalysts.

    PubMed

    Wang, Hui; Wang, Hui-Long; Jiang, Wen-Feng

    2009-05-01

    Multi-walled carbon nanotubes (MWCNTs)-TiO(2) composite photocatalysts with excellent activity were prepared by sol-gel method in order to investigate its photocatalytic activity under solar irradiation for the degradation of 2,6-dinitro-p-cresol (DNPC) in aqueous solution. The prepared composite were analyzed by XRD, FTIR, SEM, TEM, TG-DTA and UV-vis absorption spectra techniques. The results showed that the composite can cause an obvious red shift of UV-vis spectra compared with pure TiO(2). The degradation of DNPC by MWCNTs-TiO(2) composite photocatalysts under solar irradiation was systematically studied by varying the experimental parameters such as pH value, irradiation time, the initial substrate concentration, reaction temperature, catalyst concentration, etc. The optimal conditions were a DNPC concentration of 33.4 mgL(-1) at pH 6.0 with MWCNTs-TiO(2) concentration of 6.0gL(-1) under solar irradiation for the illumination of 150 min. The presence of MWCNTs can enhance the photoefficiency of TiO(2). The highest efficiency on photodegradation of DNPC can be achieved with an optimal MWCNTs/TiO(2) mass ratio of 0.05%. The photocatalytic degradation of DNPC obeys a pseudo-first-order behavior according to the Langmuir-Hinshelwood model, and possible decomposing mechanisms are also discussed. The photocatalyst was used for five cycles with photocatalytic degradation efficiency still higher than 96%. The results of the study showed the feasible and potential use of MWCNTs-TiO(2) composite in degradation of toxic organic pollutants.

  2. Enhanced degradation of azo dye in wastewater by pulsed discharge plasma coupled with MWCNTs-TiO2/γ-Al2O3 composite photocatalyst.

    PubMed

    Li, Xin; Wang, Tiecheng; Qu, Guangzhou; Liang, Dongli; Hu, Shibin

    2016-05-01

    In order to improve the photocatalytic performance of TiO2 in pulsed discharge plasma systems, easily recycled multi-walled carbon nanotubes (MWCNTs)-TiO2 supported on γ-Al2O3 (MWCNTs-TiO2/γ-Al2O3) composite photocatalyst were prepared. The morphology and physicochemical properties of the prepared catalysts were investigated using XRD, SEM, FTIR and UV-vis spectroscopy. The photocatalytic activity was evaluated by degradation of azo dye acid orange II (AO7) in wastewater under pulsed discharge plasma. The results indicate that the MWCNTs-TiO2/γ-Al2O3 composite catalyst possesses enhanced photocatalytic activity facilitating the decomposition of AO7 compared with TiO2/γ-Al2O3 composite in pulsed discharge plasma systems. Under pulsed discharge plasma, almost 100% AO7 is degraded by the MWCNTs-TiO2/γ-Al2O3 composite after 60 min at optimal conditions. The degradation efficiency of AO7 is also affected by the dosage of the composite catalyst and pulsed discharge peak voltage. As the amount of MWCNTs-TiO2/γ-Al2O3 composite and pulsed discharge peak voltage increases, the degradation efficiency of AO7 increases. The photocatalyst was implemented for 6 cycles and the degradation efficiency of AO7 remains higher than 85% under pulsed discharge plasma. Results indicate that the catalyst displays easy separation and minimal deactivation after several uses. Possible decomposition mechanisms were also investigated. MWCNTs are capable of improving the photocatalytic activity of TiO2/γ-Al2O3 composite in pulsed discharge plasma systems primarily due to the photo-induced-electron absorption effect and the electron trap effect of MWCNTs. The results of this study establish the feasibility and potential implementation of MWCNTs-TiO2/γ-Al2O3 composites in pulsed discharge plasma systems for the degradation of dye wastewater.

  3. Preparation of Ag deposited TiO2 (Ag/TiO2) composites and investigation on visible-light photocatalytic degradation activity in magnetic field

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Ma, C. H.; Wang, J.; Li, S. G.; Li, Y.

    2014-12-01

    In this study, Ag deposited TiO2 (Ag/TiO2) composites were prepared by three different methods (Ultraviolet Irradiation Deposition (UID), Vitamin C Reduction (VCR) and Sodium Borohydride Reduction (SBR)) for the visible-light photocatalytic degradation of organic dyes in magnetic field. And then the prepared Ag deposited TiO2 (Ag/TiO2) composites were characterized physically by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The visible-light photocatalytic activities of these three kinds of Ag deposited TiO2 (Ag/TiO2) composites were examined and compared through the degradation of several organic dyes under visible-light irradiation in magnetic field. In addition, some influence factors such as visible-light irradiation time, organic dye concentration, revolution speed, magnetic field intensity and organic dye kind on the visible-light photocatalytic activity of Ag deposited TiO2 (Ag/TiO2) composite were reviewed. The research results showed that the presence of magnetic field significantly enhanced the visible-light photocatalytic activity of Ag deposited TiO2 (Ag/TiO2) composites and then contributed to the degradation of organic dyes.

  4. Degradation of TiB2/TiC Composites in Liquid Nd and Molten NdF3-LiF-Nd2O3 System

    NASA Astrophysics Data System (ADS)

    Wang, Huihua; Su, Lijuan; Wang, Deyong; Qu, Tianpeng; Tu, Ganfeng

    2016-11-01

    The degradation of titanium diboride (TiB2)/titanium carbide (TiC) composites in the liquid Nd and molten NdF3-Nd2O3-LiF salts is investigated at 1,060 °C, respectively. The penetration of TiB2/TiC composites by liquid Nd mainly depended on the grain boundaries and residual pores, even if the coherent interface is formed between TiB2 and TiC. The oxidation of TiB2 led to further interfacial chemistry reactions, which speeded up the degradation of TiB2/TiC composites at the initial stage in NdF3 -LiF-Nd2O3 system. After that, the degradation was slowed because of the formation of diffusion boundary layer, and then chemical penetration was replaced gradually by the physical penetration. The dissolved Ti in liquid Nd and NdF3-LiF-Nd2O3 melts are used to evaluate the corrosion rate of TiB2/TiC composites, and the calculated values were about 0.56 and 7.8 mm/year, respectively. After the penetration by liquid Nd and NdF3-LiF-Nd2O3 melts, the bending strengths of TiB2/TiC composites decreased and the fracture mode changed from transgranular to intergranular due to the decreased grain boundary force.

  5. Microwave-assisted in situ synthesis of reduced graphene oxide-BiVO4 composite photocatalysts and their enhanced photocatalytic performance for the degradation of ciprofloxacin.

    PubMed

    Yan, Yan; Sun, Shaofang; Song, Yang; Yan, Xu; Guan, Weisheng; Liu, Xinlin; Shi, Weidong

    2013-04-15

    To improve the photodegradation efficiency for ciprofloxacin (CIP), a new-type microwave-assisted in situ growth method is developed for the preparation of reduced graphene oxide (RGO) -BiVO4 composite photocatalysts. The as-produced RGO-BiVO4 composite photocatalysts show extremely high enhancement of CIP degradation ratio over the pure BiVO4 photocatalyst under visible light. Specially, the 2 wt% RGO-BiVO4 composite photocatalyst exhibits the highest CIP degradation ratio (68.2%) in 60 min, which is over 3 times than that (22.7%) of the pure BiVO4 particles. The enhancement of photocatalytic activities of RGO-BiVO4 photocatalysts can be attributed to the effective separation of electron-hole pairs rather than the improvement of light absorption. Copyright © 2013 Elsevier B.V. All rights reserved.

  6. Mechanics, degradability, bioactivity, in vitro, and in vivo biocompatibility evaluation of poly(amino acid)/hydroxyapatite/calcium sulfate composite for potential load-bearing bone repair.

    PubMed

    Fan, Xiaoxia; Ren, Haohao; Luo, Xiaoman; Wang, Peng; Lv, Guoyu; Yuan, Huipin; Li, Hong; Yan, Yonggang

    2016-03-01

    A ternary composite of poly(amino acid), hydroxyapatite, and calcium sulfate (PAA/HA/CS) was prepared using in situ melting polycondensation method and evaluated in terms of mechanical strengths, in vitro degradability, bioactivity, as well as in vitro and in vivo biocompatibility. The results showed that the ternary composite exhibited a compressive strength of 147 MPa, a bending strength of 121 MPa, a tensile strength of 122 MPa, and a tensile modulus of 4.6 GPa. After immersion in simulated body fluid, the compressive strength of the composite decreased from 147 to 98 MPa for six weeks and the bending strength decreased from 121 to 75 MPa for eight weeks, and both of them kept stable in the following soaking period. The composite could be slowly degraded with 7.27 wt% loss of initial weight after soaking in phosphate buffered solution for three weeks when started to keep stable weight in the following days. The composite was soaked in simulated body fluid solution and the hydroxyapatite layer, as flower-like granules, formed on the surface of the composite samples, showing good bioactivity. Moreover, it was found that the composite could promote proliferation of MG-63 cells, and the cells with normal phenotype extended and spread well on the composite surface. The implantation of the composite into the ulna of sheep confirmed that the composite was biocompatible and osteoconductive in vivo, and offered the PAA/HA/CS composite promising material for load-bearing bone substitutes for clinical application. © The Author(s) 2015.

  7. Persulfate activation by iron oxide-immobilized MnO2 composite: identification of iron oxide and the optimum pH for degradations.

    PubMed

    Jo, Young-Hoon; Do, Si-Hyun; Kong, Sung-Ho

    2014-01-01

    Iron oxide-immobilized manganese oxide (MnO2) composite was prepared and the reactivity of persulfate (PS) with the composite as activator was investigated for degradation of carbon tetrachloride and benzene at various pH levels. Brunauer-Emmett-Teller (BET) surface area of the composite was similar to that of pure MnO2 while the pore volume and diameter of composite was larger than those of MnO2. Scanning electron microscopy couples with energy dispersive spectroscopy (SEM-EDS) showed that Fe and Mn were detected on the surface of the composite, and X-ray diffraction (XRD) analysis indicated the possibilities of the existence of various iron oxides on the composite surface. Furthermore, the analyses of X-ray photoelectron (XPS) spectra revealed that the oxidation state of iron was identified as 1.74. In PS/composite system, the same pH for the highest degradation rates of both carbon tetrachloride and benzene were observed and the value of pH was 9. Scavenger test was suggested that both oxidants (i.e. hydroxyl radical, sulfate radical) and reductant (i.e. superoxide anion) were effectively produced when PS was activated with the iron-immobilized MnO2. Copyright © 2013 Elsevier Ltd. All rights reserved.

  8. Mishap risk control for advanced aerospace/composite materials

    NASA Technical Reports Server (NTRS)

    Olson, John M.

    1994-01-01

    Although advanced aerospace materials and advanced composites provide outstanding performance, they also present several unique post-mishap environmental, safety, and health concerns. The purpose of this paper is to provide information on some of the unique hazards and concerns associated with these materials when damaged by fire, explosion, or high-energy impact. Additionally, recommended procedures and precautions are addressed as they pertain to all phases of a composite aircraft mishap response, including fire-fighting, investigation, recovery, clean-up, and guidelines are general in nature and not application-specific. The goal of this project is to provide factual and realistic information which can be used to develop consistent and effective procedures and policies to minimize the potential environmental, safety, and health impacts of a composite aircraft mishap response effort.

  9. Cellulose-Enriched Microbial Communities from Leaf-Cutter Ant (Atta colombica) Refuse Dumps Vary in Taxonomic Composition and Degradation Ability.

    PubMed

    Lewin, Gina R; Johnson, Amanda L; Soto, Rolando D Moreira; Perry, Kailene; Book, Adam J; Horn, Heidi A; Pinto-Tomás, Adrián A; Currie, Cameron R

    2016-01-01

    Deconstruction of the cellulose in plant cell walls is critical for carbon flow through ecosystems and for the production of sustainable cellulosic biofuels. Our understanding of cellulose deconstruction is largely limited to the study of microbes in isolation, but in nature, this process is driven by microbes within complex communities. In Neotropical forests, microbes in leaf-cutter ant refuse dumps are important for carbon turnover. These dumps consist of decaying plant material and a diverse bacterial community, as shown here by electron microscopy. To study the portion of the community capable of cellulose degradation, we performed enrichments on cellulose using material from five Atta colombica refuse dumps. The ability of enriched communities to degrade cellulose varied significantly across refuse dumps. 16S rRNA gene amplicon sequencing of enriched samples identified that the community structure correlated with refuse dump and with degradation ability. Overall, samples were dominated by Bacteroidetes, Gammaproteobacteria, and Betaproteobacteria. Half of abundant operational taxonomic units (OTUs) across samples were classified within genera containing known cellulose degraders, including Acidovorax, the most abundant OTU detected across samples, which was positively correlated with cellulolytic ability. A representative Acidovorax strain was isolated, but did not grow on cellulose alone. Phenotypic and compositional analyses of enrichment cultures, such as those presented here, help link community composition with cellulolytic ability and provide insight into the complexity of community-based cellulose degradation.

  10. Cellulose-Enriched Microbial Communities from Leaf-Cutter Ant (Atta colombica) Refuse Dumps Vary in Taxonomic Composition and Degradation Ability

    PubMed Central

    Lewin, Gina R.; Johnson, Amanda L.; Soto, Rolando D. Moreira; Perry, Kailene; Book, Adam J.; Horn, Heidi A.; Pinto-Tomás, Adrián A.; Currie, Cameron R.

    2016-01-01

    Deconstruction of the cellulose in plant cell walls is critical for carbon flow through ecosystems and for the production of sustainable cellulosic biofuels. Our understanding of cellulose deconstruction is largely limited to the study of microbes in isolation, but in nature, this process is driven by microbes within complex communities. In Neotropical forests, microbes in leaf-cutter ant refuse dumps are important for carbon turnover. These dumps consist of decaying plant material and a diverse bacterial community, as shown here by electron microscopy. To study the portion of the community capable of cellulose degradation, we performed enrichments on cellulose using material from five Atta colombica refuse dumps. The ability of enriched communities to degrade cellulose varied significantly across refuse dumps. 16S rRNA gene amplicon sequencing of enriched samples identified that the community structure correlated with refuse dump and with degradation ability. Overall, samples were dominated by Bacteroidetes, Gammaproteobacteria, and Betaproteobacteria. Half of abundant operational taxonomic units (OTUs) across samples were classified within genera containing known cellulose degraders, including Acidovorax, the most abundant OTU detected across samples, which was positively correlated with cellulolytic ability. A representative Acidovorax strain was isolated, but did not grow on cellulose alone. Phenotypic and compositional analyses of enrichment cultures, such as those presented here, help link community composition with cellulolytic ability and provide insight into the complexity of community-based cellulose degradation. PMID:26999749

  11. Cellulose-Enriched Microbial Communities from Leaf-Cutter Ant (Atta colombica) Refuse Dumps Vary in Taxonomic Composition and Degradation Ability

    SciTech Connect

    Lewin, Gina R.; Johnson, Amanda L.; Soto, Rolando D. Moreira; Perry, Kailene; Book, Adam J.; Horn, Heidi A.; Pinto-Tomás, Adrián A.; Currie, Cameron R.

    2016-03-21

    Deconstruction of the cellulose in plant cell walls is critical for carbon flow through ecosystems and for the production of sustainable cellulosic biofuels. Our understanding of cellulose deconstruction is largely limited to the study of microbes in isolation, but in nature, this process is driven by microbes within complex communities. In Neotropical forests, microbes in leaf-cutter ant refuse dumps are important for carbon turnover. These dumps consist of decaying plant material and a diverse bacterial community, as shown here by electron microscopy. To study the portion of the community capable of cellulose degradation, we performed enrichments on cellulose using material from five Atta colombica refuse dumps. The ability of enriched communities to degrade cellulose varied significantly across refuse dumps. 16S rRNA gene amplicon sequencing of enriched samples identified that the community structure correlated with refuse dump and with degradation ability. Overall, samples were dominated by Bacteroidetes, Gammaproteobacteria, and Betaproteobacteria. Half of abundant operational taxonomic units (OTUs) across samples were classified within general containing known cellulose degraders, including Acidovorax, the most abundant OTU detected across samples, which was positively correlated with cellulolytic ability. Lastly, a representative Acidovorax strain was isolated, but did not grow on cellulose alone. Phenotypic and compositional analyses of enrichment cultures, such as those presented here, help link community composition with cellulolytic ability and provide insight into the complexity of community-based cellulose degradation.

  12. Cellulose-Enriched Microbial Communities from Leaf-Cutter Ant (Atta colombica) Refuse Dumps Vary in Taxonomic Composition and Degradation Ability

    DOE PAGES

    Lewin, Gina R.; Johnson, Amanda L.; Soto, Rolando D. Moreira; ...

    2016-03-21

    Deconstruction of the cellulose in plant cell walls is critical for carbon flow through ecosystems and for the production of sustainable cellulosic biofuels. Our understanding of cellulose deconstruction is largely limited to the study of microbes in isolation, but in nature, this process is driven by microbes within complex communities. In Neotropical forests, microbes in leaf-cutter ant refuse dumps are important for carbon turnover. These dumps consist of decaying plant material and a diverse bacterial community, as shown here by electron microscopy. To study the portion of the community capable of cellulose degradation, we performed enrichments on cellulose using materialmore » from five Atta colombica refuse dumps. The ability of enriched communities to degrade cellulose varied significantly across refuse dumps. 16S rRNA gene amplicon sequencing of enriched samples identified that the community structure correlated with refuse dump and with degradation ability. Overall, samples were dominated by Bacteroidetes, Gammaproteobacteria, and Betaproteobacteria. Half of abundant operational taxonomic units (OTUs) across samples were classified within general containing known cellulose degraders, including Acidovorax, the most abundant OTU detected across samples, which was positively correlated with cellulolytic ability. Lastly, a representative Acidovorax strain was isolated, but did not grow on cellulose alone. Phenotypic and compositional analyses of enrichment cultures, such as those presented here, help link community composition with cellulolytic ability and provide insight into the complexity of community-based cellulose degradation.« less

  13. Body composition assessment for the definition of cardiometabolic risk.

    PubMed

    Amato, M C; Guarnotta, V; Giordano, C

    2013-01-01

    Obesity is associated with a major prevalence of cardiovascular risk factors and high risk of cardiovascular events and contributes to the increase in cardiovascular morbidity and mortality worldwide. Beyond the fat mass per se, the pattern of fat distribution has a profound influence on cardiometabolic risk. The increase in abdominal adipose tissue confers an independent risk, while the amount of gluteofemoral body fat is thought to be protective. Changes in the capacity of different depots to store and release fatty acids and to produce adipocytokines are important determinants of fat distribution and its metabolic consequences. Because of the complexity of the assessment of body fat with imaging techniques, great attention has been paid to other measures of adiposity, such as waist circumference (WC), waist-to-hip ratio (WHR), and waist-to-height ratio (WHtR), which provide information on body fat distribution, although body mass index (BMI) is the established clinical measure to estimate the cardiovascular risk disease associated with excessive body weight. Abdominal obesity is a main predictive factor of the metabolic syndrome, so it is certain that it represents a better marker of cardiovascular risk than BMI. Visceral adiposity index (VAI) has recently proven to be a marker of visceral adipose distribution and function, associated with insulin sensitivity in patients at metabolic risk; however, the evidence needs to be further confirmed. In summary, BMI, WC, WHR, WHtR, and VAI are all useful tools for assessing adiposity/ obesity in clinical practice, and should be evaluated along with other cardiometabolic risk factors to define cardiovascular risk stratification.

  14. Fatigue damage evolution and property degradation of a SCS-6/Ti-22Al-23Nb orthorhombic titanium aluminide composite

    SciTech Connect

    Wang, P.C.; Jeng, S.M.; Yang, J.M.; Russ, S.M.

    1996-08-01

    The fatigue damage evolution and property degradation of a SCS-6/Ti-22Al-23Nb orthorhombic titanium aluminide composite under low cycle fatigue loading at room temperature was investigated. The fatigue test was conducted under a load-controlled mode with a load ratio (R) of 0.1, a frequency of 10 Hz, and a maximum applied stress ranging from 600 to 945 MPa. The stiffness reduction as well as the evolution of microstructural damage which includes matrix crack length, matrix crack density and interfacial debonding length as a function of fatigue cycles, and applied stresses were measured. An analytical model and a computer simulation were also developed to predict the residual stiffness and the post-fatigued tensile strength as a function of microstructural damage. Finally, a steady-state crack growth model proposed by Marshall et al. was used to predict the interfacial frictional stress and the critical crack length. Correlation between the theoretical predictions and experimental results were also discussed.

  15. DC Electrical Conductivity Retention, Optical Properties and Ammonia Sensing Analysis of Naturally Degraded CSA-Doped Graphene/polyaniline Composite Nanofibers Prepared with CTAB

    NASA Astrophysics Data System (ADS)

    Ghazali, Sayyed; Hossain, Muhammad M.; Khan, Abuzar; Khan, Mohd Y.; Hasan, Mudassir

    2017-01-01

    In this paper, we report surfactant-mediated synthesis of camphor sulfonic acid (CSA)-doped polyaniline/graphene (PANI/GN) composite nanofibers as an electrical conductor and excellent ammonia sensor. The synthesis was mediated by cetyltrimethylammonium bromide as surfactant. The as-synthesized composite nanofibers were characterized by Raman spectroscopy, scanning electron microscopy, tunneling electron microscopy, x-ray diffraction, diffused reflectance spectroscopy and differential scanning calorimetry. The electrical conductivity of the CSA-doped PANI/GN composite nanofibers was found to be remarkably enhanced as compared to the CSA-doped PANI. The boost in electronic conductivity could be attributed to an improved electronic interaction between CSA-doped PANI backbone and GN present in the composite system. The naturally degraded CSA-doped PANI/GN composite nanofibers showed a decrease in electrical conductivity but worked as a good ammonia sensor in open atmospheric conditions.

  16. Risk Assessment of Carbon Fiber Composite in Surface Transportation

    NASA Technical Reports Server (NTRS)

    Hathaway, W. T.; Hergenrother, K. M.

    1980-01-01

    The vulnerability of surface transportation to airborne carbon fibers and the national risk associated with the potential use of carbon fibers in the surface transportation system were evaluated. Results show airborne carbon fibers may cause failure rates in surface transportation of less than one per year by 1995. The national risk resulting from the use of carbon fibers in the surface transportation system is discussed.

  17. Composite Multilinearity, Epistemic Uncertainty and Risk Achievement Worth

    SciTech Connect

    E. Borgonovo; C. L. Smith

    2012-10-01

    Risk Achievement Worth is one of the most widely utilized importance measures. RAW is defined as the ratio of the risk metric value attained when a component has failed over the base case value of the risk metric. Traditionally, both the numerator and denominator are point estimates. Relevant literature has shown that inclusion of epistemic uncertainty i) induces notable variability in the point estimate ranking and ii) causes the expected value of the risk metric to differ from its nominal value. We obtain the conditions under which the equality holds between the nominal and expected values of a reliability risk metric. Among these conditions, separability and state-of-knowledge independence emerge. We then study how the presence of epistemic uncertainty aspects RAW and the associated ranking. We propose an extension of RAW (called ERAW) which allows one to obtain a ranking robust to epistemic uncertainty. We discuss the properties of ERAW and the conditions under which it coincides with RAW. We apply our findings to a probabilistic risk assessment model developed for the safety analysis of NASA lunar space missions.

  18. Probabilistic human health risk assessment of degradation-related chemical mixtures in heterogeneous aquifers: Risk statistics, hot spots, and preferential channels

    NASA Astrophysics Data System (ADS)

    Henri, Christopher V.; Fernández-Garcia, Daniel; Barros, Felipe P. J.

    2015-06-01

    The increasing presence of toxic chemicals released in the subsurface has led to a rapid growth of social concerns and the need to develop and employ models that can predict the impact of groundwater contamination on human health risk under uncertainty. Monitored natural attenuation is a common remediation action in many contamination cases. However, natural attenuation can lead to the production of daughter species of distinct toxicity that may pose challenges in pollution management strategies. The actual threat that these contaminants pose to human health depends on the interplay between the complex structure of the geological media and the toxicity of each pollutant byproduct. This work addresses human health risk for chemical mixtures resulting from the sequential degradation of a contaminant (such as a chlorinated solvent) under uncertainty through high-resolution three-dimensional numerical simulations. We systematically investigate the interaction between aquifer heterogeneity, flow connectivity, contaminant injection model, and chemical toxicity in the probabilistic characterization of health risk. We illustrate how chemical-specific travel times control the regime of the expected risk and its corresponding uncertainties. Results indicate conditions where preferential flow paths can favor the reduction of the overall risk of the chemical mixture. The overall human risk response to aquifer connectivity is shown to be nontrivial for multispecies transport. This nontriviality is a result of the interaction between aquifer heterogeneity and chemical toxicity. To quantify the joint effect of connectivity and toxicity in health risk, we propose a toxicity-based Damköhler number. Furthermore, we provide a statistical characterization in terms of low-order moments and the probability density function of the individual and total risks.

  19. Long-term composition dynamics of PAH-containing NAPLs and implications for risk assessment

    SciTech Connect

    Peters, C.A.; Knightes, C.D.; Brown, D.G.

    1999-12-15

    Subsurface contaminants such as coal tar, creosote, diesel fuel, and other petroleum-derived materials typically exist as very complex chemical mixtures. Risk assessment is useful for site management if a single metric can represent the composition-dependent risk profile of the mixture. This paper examines the factors governing human health risk assessment for multicomponent nonaqueous phase liquids (NAPLs) containing polycyclic aromatic hydrocarbons (PAHs). A model is presented describing the interdependence of the dissolution rates of individual compounds and the shifts in the NAPL composition that occur due to the large differences in aqueous solubilities. The model also accounts for solidification of the less soluble NAPL constituents. Thirty-year numerical simulations describe composition dynamics for natural environmental processes as well as three remediation processes: pump-and-treat, bioremediation, and solvent extraction. Carcinogenic risk due to ingestion of contaminated groundwater at the source is estimated, and its dependence on contaminant removal and NAPL composition shifts is described. When composition dynamics are slow, a compound like naphthalene has great potential to contribute to risk because it may persist in groundwater. When there is significant depletion of the lower molecular weight compounds, the risk is dominated by contributions from compounds such as benzo[a]pyrene. Remediation technologies have the greatest potential for risk reduction if they are effective in removing the more carcinogenic, high molecular weight compounds. Because PAHs can contribute to risk for different reasons and because of the interdependence of their behaviors, compositional approaches lead to better risk predictions for PAHs than simple lumped metrics such as total petroleum hydrocarbon (TPH).

  20. Ti/ZnO-MxOy composites (M = Al, Cr, Fe, Ce): synthesis, characterization and application as highly efficient photocatalysts for hexachlorobenzene degradation.

    PubMed

    Xia, Shengjie; Shao, Mengmeng; Zhou, Xiaobo; Pan, Guoxiang; Ni, Zheming

    2015-10-28

    A series of novel organic-inorganic nanoscale layered materials were synthesized by intercalating the Ti-containing Schiff base complex into the interlayer of the ZnM layered double hydroxides (LDHs, M = Al, Cr, Fe, Ce). The hybrid material was further calcined to make metal oxide composites with highly dispersed Ti elements (Ti/ZnO-MxOy). The structural characterization and photocatalytic results showed that, after intercalation and calcination, the metal oxide composites with a unique flower-like crystal morphology not only had high specific surface area, uniform pore size distribution and narrow band gap, but also showed extremely high photocatalytic performance for hexachlorobenzene (HCB) degradation. The Ti/ZnO-Cr2O3 composite with the narrowest band gap (2.40 eV) and the highest surface area (227 m(2)) showed the highest photocatalytic performance for HCB (95.5% within 240 min) among the four metal oxide composites. Particularly, it was found that composites derived from layered materials with different supramolecular structure of the host and guest showed different photocatalytic properties. In addition, based on the results from ESR, GC-MS and HPLC-MS, the type and amount of hydroxyl radicals, the decomposition intermediates and the pathway of HCB degradation photocatalyzed by Ti/ZnO-MxOy composites are also discussed in detail.

  1. Facile synthesis of zinc oxide nanoparticles decorated graphene oxide composite via simple solvothermal route and their photocatalytic activity on methylene blue degradation.

    PubMed

    Atchudan, Raji; Edison, Thomas Nesakumar Jebakumar Immanuel; Perumal, Suguna; Karthikeyan, Dhanapalan; Lee, Yong Rok

    2016-09-01

    Zinc oxide nanoparticles decorated graphene oxide (ZnO@GO) composite was synthesized by simple solvothermal method where zinc oxide (ZnO) nanoparticles and graphene oxide (GO) were synthesized via simple thermal oxidation and Hummers method, respectively. The obtained materials were thoroughly characterized by various physico-chemical techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Raman spectrum shows the intensity of D to G value was close to one which confirms the obtained GO and ZnO@GO composite possesses moderate graphitization. TEM images shows the ZnO nanoparticles mean size of 15±5nm were dispersed over the wrinkled graphene layers. The photocatalytic performance of ZnO@GO composite on degradation of methylene blue (MB) is investigated and the results show that the GO plays an important role in the enhancement of photocatalytic performance. The synthesized ZnO@GO composite achieves a maximum degradation efficiency of 98.5% in a neutral solution under UV-light irradiation for 15min as compared with pure ZnO (degradation efficiency is 49% after 60min of irradiation) due to the increased light absorption, the reduced charge recombination with the introduction of GO. Moreover, the resulting ZnO@GO composite possesses excellent degradation efficiency as compared to ZnO nanoparticles alone on MB. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. The investigation of sonocatalytic activity of Er3+:YAlO3/TiO2-ZnO composite in azo dyes degradation.

    PubMed

    Gao, Jingqun; Jiang, Renzheng; Wang, Jun; Kang, Pingli; Wang, Baoxin; Li, Ying; Li, Kai; Zhang, Xiangdong

    2011-03-01

    In this work, the emphasis was mainly placed on investigating the sonocatalytic activity of TiO(2)-ZnO mixed with Er(3+):YAlO(3), namely, Er(3+):YAlO(3)/TiO(2)-ZnO composite. It is able to utilize the sonoluminescence light to improve the sonocatalytic degradation of organic dyes. The Er(3+):YAlO(3) as up-conversion luminescence agent was synthesized by sol-gel and auto-combustion method, and then Er(3+):YAlO(3)/TiO(2)-ZnO composite as sonocatalyst were prepared by ultrasonic dispersion and liquids boil method. The prepared up-conversion luminescence agent and composites were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Acid Red B dye was selected to examine the sonocatalytic activity of Er(3+):YAlO(3)/TiO(2)-ZnO composite. The degradation reaction processes were monitored by UV-vis spectrophotometer and ion chromatogram. The influences on the activity of the Er(3+):YAlO(3)/TiO(2)-ZnO such as Ti/Zn molar ratio, heat-treated temperature and heat-treated time were studied. The results showed that the Er(3+):YAlO(3)/TiO(2)-ZnO composite exhibited a significantly high sonocatalytic activity compared with other catalysts in the degradation of Acid Red B. And the sonocatalyst with 1:1 Ti/Zn molar ratio heat-treated at 550°C for 60min showed the highest sonocatalytic activity. At last, the experiment also indicated that it has a good sonocatalytic activity to degrade other organic dyes.

  3. In vivo degradation and new bone formation of calcium phosphate cement-gelatin powder composite related to macroporosity after in situ gelatin degradation.

    PubMed

    Kasuya, Akihiro; Sobajima, Satoshi; Kinoshita, Mitsuo

    2012-07-01

    Calcium phosphate cement (CPC) is reported to have excellent biocompatibility and osteoconductivity. However, its biodegradability must be improved to promote bone regeneration. We have mixed gelatin powder with CPC to create a composite containing macropores with interconnectivity. Sixty rabbits were grouped as follows: 85 wt% CPC to 15 wt% gelatin powder (C15), 90 wt% CPC to 10 wt% gelatin powder (C10), 100 wt% CPC (C0) as control group and Sham group. Trabecular bone defects of distal femurs were made and implanted with the composites. The femurs were harvested for histomorphometry at 4, 12, 24 weeks after implantation, and mechanical testing at 3 days, 1, 4, 12, 24 weeks. Compared with C0, X-ray and micro-CT results of the composites revealed a progressive increase in the amount of CPC-gelatin powder composite which was replaced by trabeculae. New bone area increased from 3.8 to 18% in C10, and 4.2 to 22% in C15, residual composite area decreased from 65 to 31% in C10, and 70 to 20% in C15. The compressive strength of C15 was 9.2 MPa, which was inferior to 14.6 MPa (normal cancellous bone), but was 27.4 MPa in C10 at 1 week. Further improvement of this composite may make a suitable scaffold for bone regeneration.

  4. [Human health risk from the chemical composition of drinking water].

    PubMed

    Turbinskiĭ, V V; Masliuk, A I

    2011-01-01

    The maintenance and development of the centralized household underground water supply system in the closed administrative-territorial entity Seversk, Tomsk Region, when the aquifers are inadequately protected and there is a hydrological association of individual aquifers with polluted surface waters require a hygienic estimation based on the use of a risk methodology, including that considering the regional feature of sanitary situation establishment. No risk realization has been ascertained for damage to critical organs and systems in pediatric and adult populations under the population influence of the chemical substances available in drinking water.

  5. Diet composition and activity level of at risk and metabolically healthy obese American adults.

    PubMed

    Hankinson, Arlene L; Daviglus, Martha L; Van Horn, Linda; Chan, Queenie; Brown, Ian; Holmes, Elaine; Elliott, Paul; Stamler, Jeremiah

    2013-03-01

    Obesity often clusters with other major cardiovascular disease risk factors, yet a subset of the obese appears to be protected from these risks. Two obesity phenotypes are described, (i) "metabolically healthy" obese, broadly defined as body mass index (BMI) ≥ 30 kg/m(2) and favorable levels of blood pressure, lipids, and glucose; and (ii) "at risk" obese, BMI ≥ 30 with unfavorable levels of these risk factors. More than 30% of obese American adults are metabolically healthy. Diet and activity determinants of obesity phenotypes are unclear. We hypothesized that metabolically healthy obese have more favorable behavioral factors, including less adverse diet composition and higher activity levels than at risk obese in the multi-ethnic group of 775 obese American adults ages 40-59 years from the International Population Study on Macro/Micronutrients and Blood Pressure (INTERMAP) cohort. In gender-stratified analyses, mean values for diet composition and activity behavior variables, adjusted for age, race, and education, were compared between metabolically healthy and at risk obese. Nearly one in five (149/775 or 19%) of obese American INTERMAP participants were classified as metabolically healthy obese. Diet composition and most activity behaviors were similar between obesity phenotypes, although metabolically healthy obese women reported higher sleep duration than at risk obese women. These results do not support hypotheses that diet composition and/or physical activity account for the absence of cardiometabolic abnormalities in metabolically healthy obese. Copyright © 2012 The Obesity Society.

  6. Magnetic diatomite(Kieselguhr)/Fe2O3/TiO2 composite as an efficient photo-Fenton system for dye degradation

    NASA Astrophysics Data System (ADS)

    Barbosa, Isaltino A.; Zanatta, Lucas D.; Espimpolo, Daniela M.; da Silva, Douglas L.; Nascimento, Leandro F.; Zanardi, Fabrício B.; de Sousa Filho, Paulo C.; Serra, Osvaldo A.; Iamamoto, Yassuko

    2017-10-01

    We explored the potential use of diatomite/Fe2O3/TiO2 composites as catalysts for heterogeneous photo-Fenton degradation of methylene blue under neutral pH. Such system consists in magnetic solids synthesized by co-precipitation with Fe2+/Fe3+ in the presence of diatomite, followed by impregnation of TiO2. The results showed that the optimal amount of the catalyst was 2.0 g L-1, since aggregation phenomena become significant above this concentration, which decreases the photodegradation activity. The catalyst is highly efficient in the degradation of methylene blue and shows an easy recovery by an external magnetic field. This allows for an effective catalyst reuse without significant loss of activity in catalytic cycles, which is a highly interesting prospect for recyclable dye degradation systems.

  7. On the Composition of Risk Preference and Belief

    ERIC Educational Resources Information Center

    Wakkar, Peter P.

    2004-01-01

    Prospect theory assumes nonadditive decision weights for preferences over risky gambles. Such decision weights generalize additive probabilities. This article proposes a decomposition of decision weights into a component reflecting risk attitude and a new component depending on belief. The decomposition is based on an observable preference…

  8. On the Composition of Risk Preference and Belief

    ERIC Educational Resources Information Center

    Wakkar, Peter P.

    2004-01-01

    Prospect theory assumes nonadditive decision weights for preferences over risky gambles. Such decision weights generalize additive probabilities. This article proposes a decomposition of decision weights into a component reflecting risk attitude and a new component depending on belief. The decomposition is based on an observable preference…

  9. Synthesis of carbon nanotube-anatase TiO₂ sub-micrometer-sized sphere composite photocatalyst for synergistic degradation of gaseous styrene.

    PubMed

    An, Taicheng; Chen, Jiangyao; Nie, Xin; Li, Guiying; Zhang, Haimin; Liu, Xiaolu; Zhao, Huijun

    2012-11-01

    The carbon nanotube (CNT)-sub-micrometer-sized anatase TiO₂ sphere composite photocatalysts were synthesized by a facile one-step hydrothermal method using titanium tetrafluoride as titanium source and CNTs as structure regulator. Various technologies including X-ray diffraction, UV-visible absorption spectra, N₂ adsorption-desorption, scanning electron microscopy, and transmission electron microscopy were employed to characterize the structure properties of the prepared composite photocatalysts. The results indicated that the composite photocatalysts consisted of CNTs wrapping around the sub-micrometer-sized anatase TiO₂ spheres with controllable crystal facets and that the aggregated particles with average diameter ranged from 200 to 600 nm. The fabricated composite photocatalysts were used to degrade gaseous styrene in this work. As expected, a synergistic effect that remarkably enhancing the photocatalytic degradation efficiency of gaseous styrene by the prepared composite photocatalysts was observed in comparison with that the degradation efficiency using pure anatase TiO₂ and the adsorption of CNTs. Similar results were also confirmed in the decolorization of liquid methyl orange. Further investigation demonstrated that the synergistic effect in the photocatalytic activity was related to the structure of the sub-micrometer-sized anatase TiO₂ spheres and the significant roles of CNTs in the composite photocatalysts. By controlling the content of CNTs, the content of TiO₂ or the temperature during the hydrothermal synthesis process, anatase TiO₂ spheres with controllable crystallite size and dominant crystal facets such as {001}, {101}, or polycrystalline could be obtained, which was beneficial for the increase in the synergistic effect and further enhancement of the photocatalytic efficiencies.

  10. Preparation of reduced graphene oxide/meso-TiO2/AuNPs ternary composites and their visible-light-induced photocatalytic degradation n of methylene blue

    NASA Astrophysics Data System (ADS)

    Yang, Yongfang; Ma, Zheng; Xu, Lidong; Wang, Hefang; Fu, Nian

    2016-04-01

    Reduced graphene oxide/meso-TiO2/AuNPs (RGO/meso-TiO2/AuNPs) ternary composites were prepared via the addition of graphene oxide to the dispersion of meso-TiO2/AuNPs under hydrothermal conditions. The structure and the morphology of the RGO/meso-TiO2/AuNPs materials were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The photocatalytic activity of RGO/meso-TiO2/AuNPs was evaluated by degradation of methyl blue (MB) under visible-light illumination. The ternary composites present an extended light absorption range, efficient charge separation properties, high adsorption ability for MB and high photocatalytic degradation activity of MB compared to the meso-TiO2 and meso-TiO2/AuNPs.

  11. Sorption, degradation and leaching of the fungicide iprodione in a golf green under Scandinavian conditions: measurements, modelling and risk assessment.

    PubMed

    Strömqvist, Johan; Jarvis, Nicholas

    2005-12-01

    In cold climates, fungicides are used on golf greens to prevent snow mould causing serious damage to the turf. However, fungicide residues have been detected in runoff from golf courses, which may lead to restrictions on use. There is therefore an urgent need to improve understanding of the processes affecting leaching of fungicides from turfgrass systems to allow identification of green construction and management practices that minimize environmental impacts. In this study we monitored the leaching of the fungicide iprodione in a putting green. Sorption and degradation of iprodione was measured in batch and incubation experiments, and the simulation model MACRO was used as a risk assessment tool. Degradation of iprodione was bi-phasic, with a rapid initial phase (half-life 17 h) caused by enhanced biodegradation. Degradation rates slowed considerably after 5 days, with half-lives of up to 38 days. Sorption of iprodione was linear, with a K(oc) value of ca 400 cm(3) g(-1). MACRO reasonably accurately matched measured drainflows and concentrations of iprodione in soil and drainflow. However, peak concentrations in drainage were underestimated, which was attributed to preferential finger flow due to water repellency. The results also showed the importance of the organic matter content in the green root zone in reducing leaching. It was concluded that, with 'reasonable worst-case' use, losses of iprodione from greens can occur at concentrations exceeding water quality limits for aquatic ecosystems. Snow mould problems should be tackled by adopting green root zone mixes that minimize leaching and 'best management practices' that would avoid the need for intensive prophylactic use of fungicides.

  12. Fabrication and efficient photocatalytic degradation of methylene blue over CuO/BiVO{sub 4} composite under visible-light irradiation

    SciTech Connect

    Jiang Haiqing Endo, Hiromitsu; Natori, Hirotaka; Nagai, Masayuki; Kobayashi, Koichi

    2009-03-05

    CuO/BiVO{sub 4} composite photocatalysts were prepared by solution combustion synthesis method and impregnation technique. X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scan electron microscopy and UV-vis diffusion reflectance spectra were used to identify the physical properties and photophysical properties of CuO/BiVO{sub 4} composite photocatalysts. The photocatalysts exhibit the enhanced photocatalytic properties for degradation of methylene blue under visible-light ({lambda} > 420 nm). The mechanism of improved photocatalytic activity is also discussed.

  13. Investigation on solar photocatalytic degradation of various dyes in the presence of Er(3+):YAlO(3)/ZnO-TiO(2) composite.

    PubMed

    Wang, Jun; Li, Jia; Xie, Yingpeng; Li, Chengwu; Han, Guangxi; Zhang, Liquan; Xu, Rui; Zhang, Xiangdong

    2010-01-01

    In this work, Er(3+):YAlO(3)/ZnO-TiO(2) and ZnO-TiO(2) composites were prepared by the ultrasonic dispersion and liquid boiling method. In succession, they were then characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Acid red B as a model dye compound was degraded under solar light irradiation to evaluate the photocatalytic activities of the Er(3+):YAlO(3)/ZnO-TiO(2) and ZnO-TiO(2) composites. We found that the photocatalytic activity of ZnO-TiO(2) composite can be enhanced by adding an appropriate amount of Er(3+):YAlO(3). We reviewed influencing factors, such as Er(3+):YAlO(3) content, heat-treated temperature and heat-treated time on the photocatalytic activity of the Er(3+):YAlO(3)/ZnO-TiO(2) composites. In addition, the effects of solar light irradiation time, dye initial concentration, Er(3+):YAlO(3)/ZnO-TiO(2) amount and solution acidity on the photocatalytic degradation of acid red B dye in aqueous solution were investigated in detail. Simultaneously, the degradation and comparison of other dyes such as methyl orange (MO), rhodamine B (RM-B), azo fuchsine (AF), congo red (CG-R) and methyl blue (MB) were also reviewed. In addition, we attempted to explore both the principle of possible excitation of Er(3+):YAlO(3)/ZnO-TiO(2) under solar light irradiation and the mechanism of photocatalytic degradation. 2009. Published by Elsevier Ltd. All rights reserved.

  14. Development of a Composite Trauma Exposure Risk Index

    PubMed Central

    Liu, Honghu; Prause, Nicole; Wyatt, Gail E.; Williams, John K.; Chin, Dorothy; Davis, Teri; Loeb, Tamra; Marchand, Erica; Zhang, Muyu; Myers, Hector F.

    2015-01-01

    The high burden of exposure to chronic life adversities and trauma is quite prevalent, but assessment of this risk burden is uncommon in primary care settings. This calls for a brief, multiple dimensional mental health risk screening tool in primary care settings. We aimed to develop such a screening tool named the UCLA Life Adversities Screener (LADS). Using pooled data across four studies from the UCLA Center for Culture, Trauma and Mental Health Disparities, five domains of mental health risk including perceived discrimination, sexual abuse histories, family adversity, interpersonal violence, and trauma histories, were identified. Regression models for depression (Centers for Epidemiology Studies-Depression scale (CES-D)) and PTSD (Posttraumatic Diagnostic Scale (PDS)), controlling for demographic factors, were fitted to to develop a weighted continuous scale score for the UCLA LADS. Confirmatory factor analysis supported the five-domain structure, while Item Response Theory (IRT) endorsed the inclusion of each item. Receiver Operating Characteristic (ROC) analysis indicated that the score was predictive for classifying subjects as reaching clinical threshold criteria for either depression (Beck Depression Inventory-II (BDI-II) ≥14 or Patient Health Questionnaire-9 (PHQ-9) ≥ 10) or anxiety (Patient Health Questionnaire-13 (PHQ-13) ≥10). An optimal cut of 0.33 is suggested based on maximizing sensitivity and specificity of the LADS score, identifying patients at high risk for mental health problems. Given its predictive utility and ease of administration, the UCLA LADS could be useful as a screener to identify racial minority individuals in primary care settings who have a high trauma burden, needing more extensive evaluation. PMID:25984638

  15. Development of a composite trauma exposure risk index.

    PubMed

    Liu, Honghu; Prause, Nicole; Wyatt, Gail E; Williams, John K; Chin, Dorothy; Davis, Teri; Loeb, Tamra; Marchand, Erica; Zhang, Muyu; Myers, Hector F

    2015-09-01

    The high burden of exposure to chronic life adversities and trauma is quite prevalent, but assessment of this risk burden is uncommon in primary care settings. This calls for a brief, multiple dimensional mental health risk screening tool in primary care settings. We aimed to develop such a screening tool named the University of California, Los Angeles (UCLA) Life Adversities Screener (LADS). Using pooled data across 4 studies from the UCLA Center for Culture, Trauma, and Mental Health Disparities, 5 domains of mental health risk including perceived discrimination, sexual abuse histories, family adversity, intimate partner violence, and trauma histories, were identified. Regression models for depression (Centers for Epidemiology Studies Depression Scale) and posttraumatic stress disorder (Posttraumatic Diagnostic Scale), controlling for demographic factors, were fitted to develop a weighted continuous scale score for the UCLA LADS. Confirmatory factor analysis supported the 5-domain structure, while item response theory endorsed the inclusion of each item. Receiver operating characteristic analysis indicated that the score was predictive for classifying subjects as reaching clinical threshold criteria for either depression (Beck Depression Inventory-II ≥ 14 or Patient Health Questionnaire-9 ≥ 10) or anxiety (Patient Health Questionnaire-13 ≥10). An optimal cut of 0.33 is suggested based on maximizing sensitivity and specificity of the LADS score, identifying patients at high risk for mental health problems. Given its predictive utility and ease of administration, the UCLA LADS could be useful as a screener to identify racial minority individuals in primary care settings who have a high trauma burden, needing more extensive evaluation.

  16. Degrading habitats and the effect of topographic complexity on risk assessment

    PubMed Central

    McCormick, Mark I; Lönnstedt, Oona M

    2013-01-01

    Topographic complexity is a key component of habitats that influences communities by modulating the interactions among individuals that drive population processes such as recruitment, competition, and predation. A broad range of disturbance agents affect biological communities indirectly through their modifications to habitat complexity. Individuals that best judge the threat of predation within their environment and can trade-off vigilance against behaviors that promote growth will be rewarded with the highest fitness. This study experimentally examined whether topographic habitat complexity affected the way a damselfish assessed predation risk using olfactory, visual, or combined cues. Fish had higher feeding rates in the low complexity environment. In a low complexity environment, damage-released olfactory cues and visual cues of predators complemented each other in the prey's assessment of risk. However, where complexity was high and visual cues obscured, prey had lower feeding rates and relied more heavily on olfactory cues for risk assessment. Overall, fish appear to be more conservative in the high complexity treatment. Low complexity promoted extremes of behavior, with higher foraging activity but a greater response to predation threats compared with the high complexity treatment. The degree of flexibility that individuals and species have in their ability to adjust the balance of senses used in risk assessment will determine the extent to which organisms will tolerate modifications to their habitat through disturbance. PMID:24324872

  17. Degradation Dynamics and Dietary Risk Assessments of Two Neonicotinoid Insecticides during Lonicera japonica Planting, Drying, and Tea Brewing Processes.

    PubMed

    Fang, Qingkui; Shi, Yanhong; Cao, Haiqun; Tong, Zhou; Xiao, Jinjing; Liao, Min; Wu, Xiangwei; Hua, Rimao

    2017-03-01

    The degradation dynamics and dietary risk assessments of thiamethoxam and thiacloprid during Lonicera japonica planting, drying, and tea brewing processes were systematically investigated using high-performance liquid chromatography. The half-lives of thiamethoxam and thiacloprid were 1.0-4.1 d in the honeysuckle flowers and leaves, with degradation rate constants k ranging from -0.169 to -0.696. The safety interval time was 7 d. The sun- and oven-drying (70 °C) percent digestions were 59.4-81.0% for the residues, which were higher than the shade- and oven-drying percentages at lower temperatures (30, 40, 50, and 60 °C, which ranged from 37.7% to 57.0%). The percent transfers of thiamethoxam and thiacloprid were 0-48.4% and 0-25.2%, respectively, for the different tea brewing conditions. On the basis of the results of this study, abiding by the safety interval time is important, and using reasonable drying methods and tea brewing conditions can reduce the transfer of thiamethoxam and thiacloprid to humans.

  18. Photocatalytic degradation of imidacloprid by composite catalysts H3PW12O40/La-N-TiO2 under visible light.

    PubMed

    Liu, Xia; Xu, Gang; Feng, Chang-Gen

    2014-02-01

    Catalysts H3PW12O40/La-N-TiO2 were prepared and characterized by FT-IR, N2 adsorption-desorption analysis, SEM and UV-Vis diffuse reflection spectrum (DRS). It was demonstrated that Keggin structure of H3PW12O40 retained in composite materials by the FT-IR test; After doping La-N, the BET surface area of them is nearly 2 times as that of pure TiO2; the SEM images of the catalysts revealed that they were consist of relatively uniform spherical grains with good dispersion; UV-Vis DRS showed the photoresponse performance of the prepared composites for the visible light area were improved after doping La and N. The prepared composites were used as photocatalysts in degradation of pesticide imidacloprid. Results revealed that 30%H3 PW12O40/0.3%La-1.0%N-TiO2 possessed the best photocatalytic activity under visible light above 400 nm. Thus, imidacloprid were degraded 91.57% after 3 h irradiation. When 30% H3PW12O40/0.3%La-1.0%N-TiO2 was used as catalysts, degradation ration could even reach 98.89% after 6 h.

  19. 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.

  20. Degradation mechanism and kinetic model for photocatalytic oxidation of PVC-ZnO composite film in presence of a sensitizing dye and UV radiation.

    PubMed

    Chakrabarti, Sampa; Chaudhuri, Basab; Bhattacharjee, Sekhar; Das, Paramita; Dutta, Binay Kanti

    2008-06-15

    White or plastic pollution has become a serious concern to the environmentalists for the last few years. Degradation of waste plastics in conventional incinerators leads to emission of carcinogenic dioxins to the atmosphere. In this work, an attempt has been made for the photocatalytic degradation of polyvinyl chloride (PVC) using ZnO as semi-conductor catalyst in the form of PVC-ZnO composite film. The surface morphology as well as the FTIR spectroscopy of the irradiated film has been critically examined. The degradation was measured by weight loss data and was found to follow a pseudo-first order rate equation. The various parameters studied were loading of the semi-conductor, intensity of UV radiation and presence of Eosin Y as a sensitizing dye. It was observed that dye-sensitization enhanced degradation of PVC to a large extent. A possible mechanism has been suggested and the corresponding rate equation has been modeled for the dye-sensitized rate of degradation. The model has been validated by the experimental data.

  1. Photocatalytic decolorization and degradation of Congo Red on innovative crosslinked chitosan/nano-CdS composite catalyst under visible light irradiation.

    PubMed

    Zhu, Huayue; Jiang, Ru; Xiao, Ling; Chang, Yuhua; Guan, Yujiang; Li, Xiaodong; Zeng, Guangming

    2009-09-30

    The crosslinked chitosan/nano-CdS (CS/n-CdS) composite catalyst prepared by simulating bio-mineralization process was extensively characterized by FT-IR spectra, XRD, SEM, TEM and TGA. An azo dye, Congo Red (CR), was used as model pollutant to study its photocatalytic activity under visible light irradiation. The influences of catalyst amount, initial CR concentrations, pH of the reaction solution and different anions on CR decolorization and degradation reaction kinetics were investigated. Results of characterization indicated the successful formation of hexagonal phase of CdS on raw chitosan under mild conditions. The photocatalytic degradation was found to follow a pseudo-first-order kinetics according to Langmuir-Hinshelwood (L-H) model. The dye could be decolorized more efficiently in acidic media than alkaline media. The presence of NO(3)(-) accelerated evidently the degradation of CR, while the other chosen anions (Br(-), SO(4)(2-) and Cl(-)) had an inhibitory effect on the decolorization of CR, of which the inhibitory effect of Cl(-) was the most pronounced. UV-vis spectra were analyzed to indicate that degradation of CR in the solution was the break up of the NN bonds and degradation of aromatic fragment in this reaction system. The recycling experiments confirmed the relative stability of the catalyst.

  2. Chemical Composition, In vitro Gas Production, Ruminal Fermentation and Degradation Patterns of Diets by Grazing Steers in Native Range of North Mexico

    PubMed Central

    Murillo, M.; Herrera, E.; Carrete, F. O.; Ruiz, O.; Serrato, J. S.

    2012-01-01

    The objective of the study was to quantify annual and seasonal differences in the chemical composition, in vitro gas production, in situ degradability and ruminal fermentation of grazing steers’ diets. Diet samples were collected with four esophageal cannulated steers (350±3 kg BW); and four ruminally cannulated heifers (342±1.5 kg BW) were used to study the dry matter degradation and fermentation in rumen. Data were analyzed with repeated measurements split plot design. The crude protein, in vitro dry matter digestibility and metabolizable energy were higher during the first year of trial and in the summer (p<0.01). The values of calcium, phosphorus, magnesium, zinc and copper were higher in summer (p<0.05). The gas produced by the soluble and insoluble fractions, as well as the constant rate of gas production were greater in summer and fall (p<0.01). The ammonia nitrogen (NH3N) and total volatile fatty acids concentrations in rumen, the soluble and degradable fractions, the constant rate of degradation and the effective degradability of DM and NDF were affected by year (p<0.05) and season (p<0.01). Our study provides new and useful knowledge for the formulation of protein, energetic and mineral supplements that grazing cattle need to improve their productive and reproductive performance. PMID:25049495

  3. Putative Seedling Ferulate Ester (sfe) Maize Mutant: Morphology, Biomass Yield, and Stover Cell Wall Composition and Rumen Degradability

    USDA-ARS?s Scientific Manuscript database

    Ferulate cross linking of lignin to arabinoxylan contributes to poor cell wall degradability of grass forages. We hypothesized that reduced ferulate ester deposition will result in formation of fewer ferulate ether cross links and improved degradability. Objectives were to determine if the putative ...

  4. Targeted polypeptide degradation

    DOEpatents

    Church, George M [Brookline, MA; Janse, Daniel M [Brookline, MA

    2008-05-13

    This invention pertains to compositions, methods, cells and organisms useful for selectively localizing polypeptides to the proteasome for degradation. Therapeutic methods and pharmaceutical compositions for treating disorders associated with the expression and/or activity of a polypeptide by targeting these polypeptides for degradation, as well as methods for targeting therapeutic polypeptides for degradation and/or activating therapeutic polypeptides by degradation are provided. The invention provides methods for identifying compounds that mediate proteasome localization and/or polypeptide degradation. The invention also provides research tools for the study of protein function.

  5. Risk-based decision analysis of atmospheric emission alternatives to reduce ground water degradation on the European scale

    SciTech Connect

    Wladis, D.; Rosen, L.; Kros, H.

    1999-12-01

    Environmental degradation due to emissions of sulfur dioxide, nitrate oxides, and ammonia from diffuse sources amounts to substantial costs to society and so do the alternatives to protect and restore the environment. Damage to ground water includes acidification, aluminum leaching, elevated concentrations of nitrate, and eutrophication. Monetary risk-based decision analysis (on a national scale) is applied to compare alternative actions designed to protect ground water from further degradation. This decision analysis uses simulations of nitrate and aluminum concentrations over a 15 year period with two reduction scenarios for sulfur dioxide, nitrate oxides, and ammonia, and results in estimates of economic uncertainty. For each alternative, an objective function is estimated including the implementation costs, the economic risk associated with failure according to the selected decision criteria, and the economic benefits related to the implementation. The decision criteria are based on the European Community drinking water quality standards for nitrate and aluminum. The study aims at incorporating the hydrogeologic uncertainty resulting from the propagation of errors from data input to model out put. A range of economic values has been applied to the ground water resource to study the sensitivity of the decision analysis to valuing ground water. The results indicate that higher reduction rates of the studied pollutants reduce the economic uncertainty but also lead to larger total costs. The study also indicates that the economic uncertainty may be equal to the total cost provided by the objective function. The contamination level of nitrate is much more responsive to the reduction scenarios than the aluminum concentration. For high, but not unrealistic, ground water valuing, the economic uncertainty makes the decision between the studied alternatives unclear.

  6. Photocatalytic degradation of organic dyes by Er3+: YAlO3/Co- and Fe-doped ZnO coated composites under solar irradiation

    NASA Astrophysics Data System (ADS)

    Chen, Yang; Lu, Chunxiao; Tang, Liang; Song, Yahui; Wei, Shengnan; Rong, Yang; Zhang, Zhaohong; Wang, Jun

    2016-12-01

    In this work, the Er3+: YAlO3/Co- and Fe-doped ZnO coated composites were prepared by the sol-gel method. Then, they were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX). Photo-degradation of azo fuchsine (AF) as a model dye under solar light irradiation was studied to evaluate the photocatalytic activity of the Er3+: YAlO3/Co- and Fe-doped ZnO coated composites. It was found that the photocatalytic activity of Co- and Fe-doped ZnO composites can be obviously enhanced by upconversion luminescence agent (Er3+: YAlO3). Besides, the photocatalytic activity of Er3+: YAlO3/Fe-doped ZnO is better than that of Er3+: YAlO3/Co-doped ZnO. The influence of experiment conditions, such as the concentration of Er3+: YAlO3, heat-treatment temperature and time on the photocatalytic activity of the Er3+: YAlO3/Co- and Fe-doped ZnO coated composites was studied. In addition, the effects of solar light irradiation time, dye initial concentration, Er3+: YAlO3/Co- and Fe-doped ZnO amount on the photocatalytic degradation of azo fuchsine in aqueous solution were investigated in detail. Simultaneously, some other organic dyes, such as Methyl Orange (MO), Rhodamine B (RM-B), Acid Red B (AR-B), Congo Red (CR), and Methyl Blue (MB) were also studied. The possible excitation principle of Er3+: YAlO3/Co- and Fe-doped ZnO coated composites under solar light irradiation and the photocatalytic degradation mechanism of organic dyes were discussed.

  7. Sex composition of the workplace and mortality risk.

    PubMed

    Barclay, Kieron J

    2013-11-01

    This study uses Swedish occupational register data to examine whether the proportion of men in administrative workplaces in the Swedish public service affects all-cause mortality risks amongst both males and females of working age. Using piecewise constant survival models to analyse occupational data from the Swedish administrative registers from 1995 to 2007, it was found that for males, a 1% increase in the proportion of males was associated with a 1.3% increase in mortality risk (hazard ratio, HR 1.013, 95% CI 1.007-1.020, p<0.001), but no association was found for females (HR 1.004, 95% CI 0.996-1.012, p=0.297). Adjustments were made for age, family status, education, occupational status, occupational segregation by sex, the total number of individuals in the workplace, level of government, region, period and variables reflecting the workplace structure by age, age by sex, occupation and education. A higher proportion of males may be related to (i) an increased exposure to risky health behaviours such as alcohol consumption and unhealthy dietary patterns, (ii) a tendency towards sickness presenteeism, and (iii) an increase in the levels of several well-established emotional stressors in the workplace, leading to an increased level of psychosocial stress. The findings and potential extensions of this research are discussed.

  8. The National Carbon Filter Program. [to quantify the risk associated with use of graphite composites

    NASA Technical Reports Server (NTRS)

    Harris, L.

    1979-01-01

    An action plan formulated to address the rapid growth in the use of graphite reinforced composite materials and the potential for the release of free fibers is outlined. The role of various agencies with respect to the civil sector of the user community is discussed. Emphasis is placed on NASA responsibilities in the area of quantifying the risk associated with the use of graphite bearing composites in aircraft.

  9. Increasing risks related to landslides from degrading permafrost into new lakes in de-glaciating mountain ranges

    NASA Astrophysics Data System (ADS)

    Haeberli, Wilfried; Schaub, Yvonne; Huggel, Christian

    2017-09-01

    While glacier volumes in most cold mountain ranges rapidly decrease due to continued global warming, degradation of permafrost at altitudes above and below glaciers is much slower. As a consequence, many still existing glacier and permafrost landscapes probably transform within decades into new landscapes of bare bedrock, loose debris, sparse vegetation, numerous new lakes and steep slopes with slowly degrading permafrost. These new landscapes are likely to persist for centuries if not millennia to come. During variable but mostly extended future time periods, such new landscapes will be characterized by pronounced disequilibria within their geo- and ecosystems. This especially involves long-term stability reduction of steep/icy mountain slopes as a slow and delayed reaction to stress redistribution following de-buttressing by vanishing glaciers and to changes in mechanical strength and hydraulic permeability caused by permafrost degradation. Thereby, the probability of far-reaching flood waves from large mass movements into lakes systematically increases with the formation of many new lakes and systems of lakes in close neighborhood to, or even directly at the foot of, so-affected slopes. Results of recent studies in the Swiss Alps are reviewed and complemented with examples from the Cordillera Blanca in Peru and the Mount Everest region in Nepal. Hot spots of future hazards from potential flood waves caused by large rock falls into new lakes can already now be recognized. To this end, integrated spatial information on glacier/permafrost evolution and lake formation can be used together with scenario-based models for rapid mass movements, impact waves and flood propagation. The resulting information must then be combined with exposure and vulnerability considerations related to settlements and infrastructure. This enables timely planning of risk reduction options. Such risk reduction options consist of two components: Mitigation of hazards, which in the present

  10. Preparation of flower-like TiO{sub 2} sphere/reduced graphene oxide composites for photocatalytic degradation of organic pollutants

    SciTech Connect

    Kim, Tae-Woong; Park, Mira; Kim, Hak Yong; Park, Soo-Jin

    2016-07-15

    In this study, novel flower-like TiO{sub 2} sphere (FTS)/reduced graphene oxide (rGO) composites (FTS-G) were synthesized via a hydrothermal method. The photocatalytic performance of the FTS-G composites was evaluated through the photodegradation of rhodamine B (Rh B) and trichloroethylene (TCE) under simulated solar light irradiation. The rGO to FTS ratio in the composites significantly affected photocatalytic activity. The photocatalytic activities of FTS-Gs in the degradation of Rh B and TCE were superior to that of pure FTS. Of all the FTS-G composites tested, FTS-G with 1 wt% rGO (FTS-G-1) had the greatest photocatalytic activity, while FTS-G composites with rGO contents over 1 wt% had lower photocatalytic activities. Additionally, it is expected that the synthesis of FTS with a high specific surface area and well-developed pore structure and simultaneous conversion of GO to graphene-like rGO without the use of strong reducing agents could be a promising strategy to prepare other carbon-based flower-like TiO{sub 2} sphere composite photocatalysts. - Graphical abstract: Schematic illustration of high photocatalytic activity for FTS-G composites. Display Omitted.

  11. Preparation of MoO3/MoS2/TiO2 composites for catalytic degradation of methylene blue.

    PubMed

    Hwang, Moon-Jin; Han, Sang Wook; Nguyen, Thanh-Binh; Hong, Soon Cheol; Ryu, Kwang-Sun

    2012-07-01

    Metastable hexagonal MoO3 microrods were grown from bulk MoS2 and used as support materials for MoS2 and TiO2 nanoparticles. The hybrid composites that consisted of MoO3, MoS2, and TiO2 were prepared at a low temperature using the one-step synthesis method. The crystallinity and morphology of the MoO3/MoS2/TiO2 composites that were prepared using HNO3 and titanium tetraisopropoxide were compared with those of the MoO3/MoS2 composites that were prepared without titanium tetraisopropoxide. Titanium isopropoxide facilitated the formation of the MoO3 microrods from the oxidation of the bulk MoS2. The desired MoO3/MoS2/TiO2 composites were obtained using 0.5 g of bulk MoS2, 3-4 ml of HNO3, and 0.367 ml of titanium tetraisopropoxide. The MoO3/MoS2/TiO2 composites that were treated with ultrasonic waves showed rapid degradation of the methylene blue solution (2 x 10(-4) M) in the dark and good photocatalytic ability under ultraviolet light irradiation. The decomposition of methylene blue depended on the composition of the composite.

  12. Industrially synthesized single-walled carbon nanotubes: compositional data for users, environmental risk assessments, and source apportionment

    NASA Astrophysics Data System (ADS)

    Plata, D. L.; Gschwend, P. M.; Reddy, C. M.

    2008-05-01

    Commercially available single-walled carbon nanotubes (SWCNTs) contain large percentages of metal and carbonaceous impurities. These fractions influence the SWCNT physical properties and performance, yet their chemical compositions are not well defined. This lack of information also precludes accurate environmental risk assessments for specific SWCNT stocks, which emerging local legislation requires of nanomaterial manufacturers. To address these needs, we measured the elemental, molecular, and stable carbon isotope compositions of commercially available SWCNTs. As expected, catalytic metals occurred at per cent levels (1.3-29%), but purified materials also contained unexpected metals (e.g., Cu, Pb at 0.1-0.3 ppt). Nitrogen contents (up to 0.48%) were typically greater in arc-produced SWCNTs than in those derived from chemical vapor deposition. Toluene-extractable materials contributed less than 5% of the total mass of the SWCNTs. Internal standard losses during dichloromethane extractions suggested that metals are available for reductive dehalogenation reactions, ultimately resulting in the degradation of aromatic internal standards. The carbon isotope content of the extracted material suggested that SWCNTs acquired much of their carbonaceous contamination from their storage environment. Some of the SWCNTs, themselves, were highly depleted in 13C relative to petroleum-derived chemicals. The distinct carbon isotopic signatures and unique metal 'fingerprints' may be useful as environmental tracers allowing assessment of SWCNT sources to the environment.

  13. On the composition of risk preference and belief.

    PubMed

    Wakkar, Peter P

    2004-01-01

    Prospect theory assumes nonadditive decision weights for preferences over risky gambles. Such decision weights generalize additive probabilities. This article proposes a decomposition of decision weights into a component reflecting risk attitude and a new component depending on belief. The decomposition is based on an observable preference condition and does not use other empirical primitives such as statements of judged probabilities. The preference condition is confirmed by most of the experimental findings in the literature. The implied properties of the belief component suggest that, besides the often-studied ambiguity aversion (a motivational factor reflecting a general aversion to unknown probabilities), perceptual and cognitive limitations play a role: It is harder to distinguish among various levels of likelihood, and to process them differently, when probabilities are unknown than when they are known.

  14. Balancing the Rates of New Bone Formation and Polymer Degradation Enhances Healing of Weight-Bearing Allograft/Polyurethane Composites in Rabbit Femoral Defects

    PubMed Central

    Dumas, Jerald E.; Prieto, Edna M.; Zienkiewicz, Katarzyna J.; Guda, Teja; Wenke, Joseph C.; Bible, Jesse; Holt, Ginger E.

    2014-01-01

    There is a compelling clinical need for bone grafts with initial bone-like mechanical properties that actively remodel for repair of weight-bearing bone defects, such as fractures of the tibial plateau and vertebrae. However, there is a paucity of studies investigating remodeling of weight-bearing bone grafts in preclinical models, and consequently there is limited understanding of the mechanisms by which these grafts remodel in vivo. In this study, we investigated the effects of the rates of new bone formation, matrix resorption, and polymer degradation on healing of settable weight-bearing polyurethane/allograft composites in a rabbit femoral condyle defect model. The grafts induced progressive healing in vivo, as evidenced by an increase in new bone formation, as well as a decrease in residual allograft and polymer from 6 to 12 weeks. However, the mismatch between the rates of autocatalytic polymer degradation and zero-order (independent of time) new bone formation resulted in incomplete healing in the interior of the composite. Augmentation of the grafts with recombinant human bone morphogenetic protein-2 not only increased the rate of new bone formation, but also altered the degradation mechanism of the polymer to approximate a zero-order process. The consequent matching of the rates of new bone formation and polymer degradation resulted in more extensive healing at later time points in all regions of the graft. These observations underscore the importance of balancing the rates of new bone formation and degradation to promote healing of settable weight-bearing bone grafts that maintain bone-like strength, while actively remodeling. PMID:23941405

  15. Electrospun H4SiW12O40/cellulose acetate composite nanofibrous membrane for photocatalytic degradation of tetracycline and methyl orange with different mechanism.

    PubMed

    Li, Wei; Li, Tingting; Li, Guangtao; An, Libao; Li, Fan; Zhang, Zhiming

    2017-07-15

    H4SiW12O40 (SiW12)/cellulose acetate (CA) composite nanofibrous membrane was prepared by electrospinning in which CA was employed as the support of SiW12. Characterization with Fourier transformation infrared spectroscopy (FT-IR), Energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) indicated that SiW12 has been successfully loaded into the CA membrane and its Keggin structure remained intact. The as-prepared composite membrane exhibited enhanced photocatalytic activity in the decomposition of tetracycline (TC) and methyl orange (MO) compared with pure SiW12 under ultraviolet irradiation. The optimal mass ratio of SiW12 to CA was 1:4, and the corresponding degradation efficiency for TC and MO was 63.8% and 94.6%, respectively. It is noteworthy that the degradation rate of MO increased more evidently than that of TC under the same conditions, which may be attributed to the different role that CA nanofibrous membrane played in the TC and MO photodegradation process. Besides providing more contact area between SiW12 and the pollutant in TC photodegradation, CA membrane played an additional role that donated electron to SiW12 in the MO degradation process, leading to a different photocatalytic mechanism with greatly enhanced degradation rate. Moreover, the composite membrane presented an excellent reusability, which was mainly ascribed to the water-insolubility of CA and the hydrogen bonds between CA and SiW12. This work will be useful for the design of biopolymer-based membrane photocatalysts applied to antibiotics and dyes wastewater treatment. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Bi-functional Au/FeS (Au/Co3O4) composite for in situ SERS monitoring and degradation of organic pollutants

    NASA Astrophysics Data System (ADS)

    Ma, Shuzhen; Cai, Qian; Lu, Kailing; Liao, Fan; Shao, Mingwang

    2016-01-01

    The bi-functional Au/FeS (Au/Co3O4) composite was fabricated by in situ reducing Au nanoparticles onto the surface of FeS (Co3O4). The as-prepared FeS possessed a multi-structure composed of plenty of nanoplates, which were coated by Au nanoparticles with an average size of 47.5 nm. While the Co3O4 showed a thin hexagonal sheet containing Au nanoparticles on its surface with an average size of 79.0 nm. Both the as-prepared Au/FeS and Au/Co3O4 composites exhibited excellent SERS performance, capable of enhancing the Raman signals of R6G molecules with the enhancement factor up to 1.81 × 106 and 7.60 × 104, respectively. Moreover, Au/FeS (Au/Co3O4) composite also has been verified to have intrinsic peroxidase-like activity, which could decompose H2O2 into hydroxyl radicals and then degrade organic pollutants into small molecules. Therefore, SERS can be used to real-time and in situ monitoring the degradation process of R6G molecules, employing the Au/FeS (Au/Co3O4) composite both as SERS substrate and catalyst.

  17. Controlled structural and compositional characteristic of visible light active ZnO/CuO photocatalyst for the degradation of organic pollutant

    NASA Astrophysics Data System (ADS)

    Harish, S.; Archana, J.; Sabarinathan, M.; Navaneethan, M.; Nisha, K. D.; Ponnusamy, S.; Muthamizhchelvan, C.; Ikeda, H.; Aswal, D. K.; Hayakawa, Y.

    2017-10-01

    Degradation of organic pollutant using ZnO/CuO composites has become an attractive method for detoxification of water. The effect of copper acetate concentration and the functional properties of nanocomposites were investigated. The morphological analysis revealed that CuO nanoparticles dispersed uniformly on the surface of ZnO nanorods. X-ray photoelectron spectra analysis showed peak shift in the electronic states of Zn and Cu states. Elemental clearly confirms the presence of CuO were uniformly distributed on the surface of ZnO. The photocatalytic activity of ZnO/CuO composites was enhanced compared to pure ZnO under visible light irradiation. The optimal CuO content for the photocatalytic activity of the ZnO/CuO composites is 1%, which is almost ten times higher than that of pure ZnO. Owing to these synergic advantages, the degradation efficiency of ZnO/CuO composites reached 92.52% after 5 min of irradiation. The synergistic photocatalytic mechanism was proposed based on the photodegradation results.

  18. Fabrication of Z-scheme Ag3PO4/MoS2 composites with enhanced photocatalytic activity and stability for organic pollutant degradation

    NASA Astrophysics Data System (ADS)

    Zhu, Chaosheng; Zhang, Lu; Jiang, Bo; Zheng, Jingtang; Hu, Ping; Li, Sujuan; Wu, Mingbo; Wu, Wenting

    2016-07-01

    In this study, highly efficient visible-light-driven Ag3PO4/MoS2 composite photocatalysts with different weight ratios of MoS2 were prepared via the ethanol-water mixed solvents precipitation method and characterized by ICP, XRD, HRTEM, FE-SEM, BET, XPS, UV-vis DRS and PL analysis. Under visible-light irradiation, Ag3PO4/MoS2 composites exhibit excellent photocatalytic activity towards the degradation of organic pollutants in aqueous solution. The optimal composite with 0.648 wt% MoS2 content exhibits the highest photocatalytic activity, which can degrade almost all MB under visible-light irradiation within 60 min. Recycling experiments confirmed that the Ag3PO4/MoS2 catalysts had superior cycle performance and stability. The photocatalytic activity enhancement of Ag3PO4/MoS2 photocatalysts can be mainly ascribed to the efficient separation of photogenerated charge carriers and the stronger oxidation and reduction ability through a Z-scheme system composed of Ag3PO4, Ag and MoS2, in which Ag particles act as the charge separation center. The high photocatalytic stability is due to the successful inhibition of the photocorrosion of Ag3PO4 by transferring the photogenerated electrons of Ag3PO4 to MoS2. The evidence of the Z-scheme photocatalytic mechanism of the composite photocatalysts could be obtained from the active species trapping experiments and the photoluminescence technique.

  19. Degradation Mechanisms in Aluminum Matrix Composites: Alumina/Aluminum and Boron/Aluminum. Ph.D. Thesis - North Carolina State Univ. at Raleigh

    NASA Technical Reports Server (NTRS)

    Olsen, G. C.

    1981-01-01

    The effects of fabrication and long term thermal exposure (up to 10,000 hours at 590 K) on two types of aluminum matrix composites were examined. An alumina/aluminum composite, was made of continuous alpha Al2O3 fibers in a matrix of commercially pure aluminum alloyed with 2.8% lithium. The mechanical properties of the material, the effect of isothermal exposure, cyclic thermal exposure, and fatigue are presented. Two degradation mechanisms are identified. One was caused by formation of a nonstoichiometric alumina during fabrication, the other by a loss of lithium to a surface reaction during long term thermal exposure. The other composite, boron/aluminum, made of boron fibers in an aluminum matrix, was investigated using five different aluminum alloys for the matrices. The mechanical properties of each material and the effect of isothermal and cyclic thermal exposure are presented. The effects of each alloy constituent on the degradation mechanisms are discussed. The effects of several reactions between alloy constituents and boron fibers on the composite properties are discussed.

  20. Youth substance use and body composition: does risk in one area predict risk in the other?

    PubMed

    Pasch, Keryn E; Velazquez, Cayley E; Cance, Jessica Duncan; Moe, Stacey G; Lytle, Leslie A

    2012-01-01

    Both substance use and obesity are prevalent among youth. As youth age, substance use rates increase and over the past three decades, obesity rates among youth have tripled. While these two factors have both short- and long-term health impacts, little research has explored how substance use and obesity among youth may be related. This study explores the bi-directional longitudinal relationships between substance use and body composition. Participants (N = 704; 50.7% female) were mostly white (86.4%) with a baseline mean age of 14.7 years. Objectively measured body composition was used to calculate body mass index z-scores (BMI z-score) and percent body fat. Cross-lagged structural equation models, accounting for clustering at the school level, were run to determine the longitudinal association between body composition and self-reported substance use (alcohol, cigarette, and marijuana), adjusting for socio-demographic characteristics, pubertal status, and weight satisfaction. Baseline alcohol use predicted decreased BMI z-score at follow-up and a similar association with percent body fat approached significance. Baseline cigarette use predicted increased percent body fat. No longitudinal associations were seen between baseline body composition and future substance use. Our results suggest that substance use contributes to subsequent body composition; however, body composition does not contribute to subsequent substance use. Continued research that explores these relationships longitudinally is greatly needed.

  1. Tampon absorbency, composition and oxygen content and risk of toxic shock syndrome.

    PubMed

    Lanes, S F; Rothman, K J

    1990-01-01

    Tampon use has been identified as a major risk factor for toxic shock syndrome, although the etiologic role of tampons is not clearly understood. Two epidemiologic studies conducted to date have reported an association between tampon absorbency and risk of toxic shock syndrome. This finding is not corroborated by laboratory studies, however, which have suggested that absorbency may be a marker for other characteristics that create an environment conductive to the elaboration of toxic shock syndrome toxin 1. We used data from the previously reported Tri-state study to estimate simultaneously the effects of tampon oxygen content, absorbency and chemical composition. Although the data are sparse, oxygen content was more strongly associated with risk of toxic shock syndrome than either absorbency or chemical composition. The results suggest that it may be possible to develop a highly absorbent tampon that is not associated with a high risk of toxic shock syndrome.

  2. Nanostructured semiconductor films for photocatalysis. Photoelectrochemical behavior of SnO{sub 2}/TiO{sub 2} composite systems and its role in photocatalytic degradation of a textile azo dye

    SciTech Connect

    Vinodgopal, K.; Bedja, I.; Kamat, P.V.

    1996-08-01

    Nanostructured semiconductor films of SnO{sub 2}, TiO{sub 2}, and SnO{sub 2}/TiO{sub 2} have been employed for electrochemically assisted photocatalytic degradation of a textile azo dye naphthol blue black (NBB). The degradation rate is significantly higher for SnO{sub 2}/TiO{sub 2} composite films than SnO{sub 2} and TiO{sub 2} films alone. An effort has been made to correlate the photoelectrochemical behavior of these films to the rate of photocatalytic degradation of NBB. The enhanced degradation rate of NBB using composite semiconductor films is attributed to increased charge separation in these systems. Photoelectrochemical and photocatalytic degradation experiments carried out in both nitrogen- and oxygen-saturated solutions with an externally applied electrochemical bias provide useful information in optimizing semiconductor concentrations in a composite film. 83 refs., 9 figs., 1 tab.

  3. One-pot synthesis of ZnS/polymer composites in supercritical CO2-ethanol solution and their applications in degradation of dyes.

    PubMed

    Xie, Yun; Zhang, Chengliang; Miao, Shiding; Liu, Zhimin; Ding, Kunlun; Miao, Zhenjiang; An, Guimin; Yang, Zhenzhong

    2008-02-01

    A facile method to decorate the polymeric hollow spheres with ZnS nanoparticles has been presented. In this method, the precursors, Zn(Ac)(2)H(2)O and CH(3)CSNH(2), were first adsorbed by the polymer substrate in supercritical CO(2)-ethanol solution at 35 degrees C. Followed by heating the mixture at 100 degrees C for 2 h, ZnS/polymer composites were obtained. The as-produced ZnS/polymer composites were characterized by means of IR spectra, X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy. It was demonstrated that crystalline ZnS nanoparticles with size of 3-5 nm were uniformly decorated on the polymer spheres under suitable conditions. The resultant ZnS/polymer composites exhibited high efficiency for degrading eosin B, methyl orange and methylene blue under UV light irradiation.

  4. Fabrication and characterization of CdS doped TiO2 nanotube composite and its photocatalytic activity for the degradation of methyl orange.

    PubMed

    Chung, Jinwook; Kim, Seu-Run; Kim, Jong-Oh

    2015-01-01

    CdS doped TiO2 nanotube composite was fabricated by chemical bath deposition, and was characterized by the structural, spectral and photoelectrochemical properties. The results of the structural and spectral properties showed that CdS particles were successfully deposited onto the surface of TiO2 nanotube. It is demonstrated that CdS doped TiO2 nanotube composite improved the light harvesting ability. Power conversion efficiency of about 0.32% was observed. This value is about 2.9 times higher than that of pure TiO2 nanotube. The CdS doped TiO2 nanotube composite possesses relatively higher photocatalytic activity and photodegradation efficiency than that of pure TiO2 nanotube under UV light irradiation, and the degradation efficiency of methyl orange was about 42% at UV intensity of 32 W.

  5. Effects of mechanical loading on the degradability and mechanical properties of the nanocalcium-deficient hydroxyapatite–multi(amino acid) copolymer composite membrane tube for guided bone regeneration

    PubMed Central

    Duan, Hong; Yang, Hongsheng; Xiong, Yan; Zhang, Bin; Ren, Cheng; Min, Li; Zhang, Wenli; Yan, Yonggang; Li, Hong; Pei, Fuxing; Tu, Chongqi

    2013-01-01

    Background and methods Guided bone regeneration (GBR) is a new treatment for bone defects, and the property of membrane is critical to the success of GBR. This study focuses on a novel membrane tube for GBR, which was prepared by a nanocalcium-deficient hydroxyapatite–multi(amino acid) copolymer (n-CDHA-MAC) composite. The biomechanical strength and degradability of this membrane tube under mechanical loading after immersion in phosphate-buffered solution were investigated to evaluate the effects of mechanical loading on the membrane tube. The membrane-tube group with no mechanical loading and femora bone were used as controls. Results The compressive strength and bending strength of n-CDHA-MAC membrane tubes were 66.4 ± 10.2 MPa and 840.7 ± 12.1 MPa, which were lower than those of the goats’ femoral bones (69.0 ± 5.5 MPa and 900.2 ± 17.3 MPa), but there were no significant (P > 0.05) differences. In the in vitro degradability experiment, all membrane tubes were degradable and showed a surface-erosion degradation model. The PH of solution fluctuated from 7.2 to 7.5. The weight and mechanical strength of loaded tubes decreased more quickly than nonloaded ones, with significant differences (P < 0.05). However, the strength of the loaded group after degradation achieved 20.4 ± 1.2 MPa, which was greater than the maximum mechanical strength of 4.338 MPa based on goat femoral middle stationary state by three-dimensional finite-element analysis. Conclusions n-CDHA-MAC membrane tubes have good biomechanical strength during degradation under mechanical loading. Therefore, this membrane tube is an ideal GBR membrane for critical size defects of long bones in goats for animal experiments. PMID:23946651

  6. Effects of mechanical loading on the degradability and mechanical properties of the nanocalcium-deficient hydroxyapatite-multi(amino acid) copolymer composite membrane tube for guided bone regeneration.

    PubMed

    Duan, Hong; Yang, Hongsheng; Xiong, Yan; Zhang, Bin; Ren, Cheng; Min, Li; Zhang, Wenli; Yan, Yonggang; Li, Hong; Pei, Fuxing; Tu, Chongqi

    2013-01-01

    Guided bone regeneration (GBR) is a new treatment for bone defects, and the property of membrane is critical to the success of GBR. This study focuses on a novel membrane tube for GBR, which was prepared by a nanocalcium-deficient hydroxyapatite-multi(amino acid) copolymer (n-CDHA-MAC) composite. The biomechanical strength and degradability of this membrane tube under mechanical loading after immersion in phosphate-buffered solution were investigated to evaluate the effects of mechanical loading on the membrane tube. The membrane-tube group with no mechanical loading and femora bone were used as controls. The compressive strength and bending strength of n-CDHA-MAC membrane tubes were 66.4 ± 10.2 MPa and 840.7 ± 12.1 MPa, which were lower than those of the goats' femoral bones (69.0 ± 5.5 MPa and 900.2 ± 17.3 MPa), but there were no significant (P > 0.05) differences. In the in vitro degradability experiment, all membrane tubes were degradable and showed a surface-erosion degradation model. The PH of solution fluctuated from 7.2 to 7.5. The weight and mechanical strength of loaded tubes decreased more quickly than nonloaded ones, with significant differences (P < 0.05). However, the strength of the loaded group after degradation achieved 20.4 ± 1.2 MPa, which was greater than the maximum mechanical strength of 4.338 MPa based on goat femoral middle stationary state by three-dimensional finite-element analysis. n-CDHA-MAC membrane tubes have good biomechanical strength during degradation under mechanical loading. Therefore, this membrane tube is an ideal GBR membrane for critical size defects of long bones in goats for animal experiments.

  7. Body composition indices and predicted cardiovascular disease risk profile among urban dwellers in Malaysia.

    PubMed

    Su, Tin Tin; Amiri, Mohammadreza; Mohd Hairi, Farizah; Thangiah, Nithiah; Dahlui, Maznah; Majid, Hazreen Abdul

    2015-01-01

    This study aims to compare various body composition indices and their association with a predicted cardiovascular disease (CVD) risk profile in an urban population in Kuala Lumpur, Malaysia. A cross-sectional survey was conducted in metropolitan Kuala Lumpur, Malaysia, in 2012. Households were selected using a simple random-sampling method, and adult members were invited for medical screening. The Framingham Risk Scoring algorithm was used to predict CVD risk, which was then analyzed in association with body composition measurements, including waist circumference, waist-hip ratio, waist-height ratio, body fat percentage, and body mass index. Altogether, 882 individuals were included in our analyses. Indices that included waist-related measurements had the strongest association with CVD risk in both genders. After adjusting for demographic and socioeconomic variables, waist-related measurements retained the strongest correlations with predicted CVD risk in males. However, body mass index, waist-height ratio, and waist circumference had the strongest correlation with CVD risk in females. The waist-related indicators of abdominal obesity are important components of CVD risk profiles. As waist-related parameters can quickly and easily be measured, they should be routinely obtained in primary care settings and population health screens in order to assess future CVD risk profiles and design appropriate interventions.

  8. Degradation of chlorinated organic solvents in aqueous percarbonate system using zeolite supported nano zero valent iron (Z-nZVI) composite.

    PubMed

    Danish, Muhammad; Gu, Xiaogang; Lu, Shuguang; Naqvi, Muhammad

    2016-07-01

    Chlorinated organic solvents (COSs) are extensively detected in contaminated soil and groundwater that pose long-term threats to human life and environment. In order to degrade COSs effectively, a novel catalytic composite of natural zeolite-supported nano zero valent iron (Z-nZVI) was synthesized in this study. The performance of Z-nZVI-catalyzed sodium percarbonate (SPC) in a heterogeneous Fenton-like system was investigated for the degradation of COSs such as 1,1,1-trichloroethane (1,1,1-TCA) and trichloroethylene (TCE). The surface characteristics and morphology of the Z-nZVI composite were tested using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Total pore volume, specific surface area, and pore size of the natural zeolite and the Z-nZVI composite were measured using Brunauer-Emmett-Teller (BET) method. SEM and TEM analysis showed significant elimination of aggregation and well dispersion of iron nano particles on the framework of natural zeolite. The BET N2 measurement analysis indicated that the surface area of the Z-nZVI composite was 72.3 m(2)/g, much larger than that of the natural zeolite (0.61 m(2)/g). For the contaminant analysis, the samples were extracted with n-hexane and analyzed through gas chromatograph. The degradation of 1,1,1-TCA and TCE in the Z-nZVI-catalyzed percarbonate system were 48 and 39 % respectively, while strong augmentation was observed up to 83 and 99 %, respectively, by adding the reducing agent (RA), hydroxyl amine (NH2OH•HCl). Probe tests validated the presence of OH(●) and O2 (●-) which were responsible for 1,1,1-TCA and TCE degradation, whereas both free radicals were strengthened with the addition of RA. In conclusion, the Z-nZVI/SPC oxidation with reducing agent shows potential technique for degradation of groundwater contaminated by 1,1,1-TCA and TCE.

  9. Historical Perspective and Risk of Multiple Neglected Tropical Diseases in Coastal Tanzania: Compositional and Contextual Determinants of Disease Risk

    PubMed Central

    Armah, Frederick Ato; Quansah, Reginald; Luginaah, Isaac; Chuenpagdee, Ratana; Hambati, Herbert; Campbell, Gwyn

    2015-01-01

    Background In the past decade, research on neglected tropical diseases (NTDs) has intensified in response to the need to enhance community participation in health delivery, establish monitoring and surveillance systems, and integrate existing disease-specific treatment programs to control overlapping NTD burdens and detrimental effects. In this paper, we evaluated the geographical distribution of NTDs in coastal Tanzania. Methods and Findings We also assessed the collective (compositional and contextual) factors that currently determine risks to multiple NTDs using a cross sectional survey of 1253 individuals in coastal Tanzania. The results show that the effect size in decreasing order of magnitude for non-binary predictors of NTD risks is as follows: NTD comorbidities > poverty > educational attainment > self-reported household quality of life > ethnicity. The multivariate analysis explained 95% of the variance in the relationship between NTD risks and the theoretically-relevant covariates. Compositional (biosocial and sociocultural) factors explained more variance at the neighbourhood level than at the regional level, whereas contextual factors, such as access to health services and household quality, in districts explained a large proportion of variance at the regional level but individually had modest statistical significance, demonstrating the complex interactions between compositional and contextual factors in generating NTD risks. Conclusions NTD risks were inequitably distributed over geographic space, which has several important policy implications. First, it suggests that localities of high burden of NTDs are likely to diminish within statistical averages at higher (regional or national) levels. Second, it indicates that curative or preventive interventions will become more efficient provided they can be focused on the localities, particularly as populations in these localities are likely to be burdened by several NTDs simultaneously, further increasing

  10. High catalytic activity of magnetic CuFe2O4/graphene oxide composite for the degradation of organic dyes under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Chen, Peng; Xing, Xiang; Xie, Huifang; Sheng, Qi; Qu, Hongxia

    2016-09-01

    Magnetic CuFe2O4/graphene oxide composite (CuFe2O4/GO) has been synthesized by hydrothermal method and showed excellent visible-light-photocatalytic activity for the degradation of different dyes as Rhodamine B (RhB) and acid orange II (AO7) with no need of H2O2. The Structure and morphology were investigated by XRD, FTIR and TEM and the performance of the catalyst was systematically investigated under various experimental conditions as pH, the dosage of catalyst, dye initial concentration, etc. The dyes degradation on CuFe2O4/GO was also remained in a level in the presence of *OH2- radical scavenger (2-propanol), while it decreased in the presence of *O2- radical scavenger (benzoquinone) and h+ radical scavenger (ammonium oxalate), indicating that *O2- and h+ radicals were responsible for the dye degradation. The magnetic CuFe2O4/GO composite shows potential applications in organic dye water treatment due to its magnetically recyclability and powerful visible-light-photocatalytic activity.

  11. Hierarchical structured ZnFe2O4@RGO@TiO2 composite as powerful visible light catalyst for degradation of fulvic acid

    NASA Astrophysics Data System (ADS)

    Feng, Jiantao; Wang, Yechen; Hou, Yanhui; Li, Liangchao

    2017-05-01

    Hierarchical structured ZnFe2O4@reduced graphite oxide@TiO2 (ZnFe2O4@RGO@TiO2) nanocomposite was prepared by an electrostatic layer-by-layer route, which played a synthetic effect of Fenton oxidation of ZnFe2O4 and photocatalytic oxidation of TiO2 to degrade fulvic acid (FA) solution under visible-light irradiation. In this method, RGO, as the middle layer, can effectively promote the photo-induced electron flow between the ZnFe2O4 and TiO2 and further improve the efficiency of the photo-Fenton oxidation. The influencing factors on photo-Fenton oxidation, including solution pH, catalyst, and H2O2 dosage, have also been investigated. The results illustrated that the ternary composite presented the enhanced catalytic performance. Under visible light irradiation, the degradation efficiency of the sample on the FA solution can reach 95.4% within 3 h. In addition, the catalyst exhibited superior stability and reusability, and its degradation efficiency was still up to 90% after 5 cycles. Therefore, the composite will be a kind of efficient photocatalyst and had a promising application for visible-light driven destruction of organic pollutants.

  12. Preparation of flower-like TiO2 sphere/reduced graphene oxide composites for photocatalytic degradation of organic pollutants

    NASA Astrophysics Data System (ADS)

    Kim, Tae-Woong; Park, Mira; Kim, Hak Yong; Park, Soo-Jin

    2016-07-01

    In this study, novel flower-like TiO2 sphere (FTS)/reduced graphene oxide (rGO) composites (FTS-G) were synthesized via a hydrothermal method. The photocatalytic performance of the FTS-G composites was evaluated through the photodegradation of rhodamine B (Rh B) and trichloroethylene (TCE) under simulated solar light irradiation. The rGO to FTS ratio in the composites significantly affected photocatalytic activity. The photocatalytic activities of FTS-Gs in the degradation of Rh B and TCE were superior to that of pure FTS. Of all the FTS-G composites tested, FTS-G with 1 wt% rGO (FTS-G-1) had the greatest photocatalytic activity, while FTS-G composites with rGO contents over 1 wt% had lower photocatalytic activities. Additionally, it is expected that the synthesis of FTS with a high specific surface area and well-developed pore structure and simultaneous conversion of GO to graphene-like rGO without the use of strong reducing agents could be a promising strategy to prepare other carbon-based flower-like TiO2 sphere composite photocatalysts.

  13. Preparation and Characterization of Electro-Spun Fabricated Ag-TiO2 Composite Nanofibers and Its Enhanced Photo-Catalytic Activity for the Degradation of Congo Red.

    PubMed

    Jadhav, Arvind H; Zhang, Hongliang; Agyemang, Frank O; Hiremath, Vishwanath; Lee, Kyuyoung; Chandradass, Jeyaseelan; Seo, Jeong Gil; Kim, Hern

    2015-10-01

    Electro-spun fabricated TiO2 nanofibers were prepared by simple electro-spinning method, in subsequent step silver (Ag) was deposited using precipitation method and obtained Ag-TiO2 composite nanofibers. The properties and morphology of these prepared composite nanofibers were characterized by XRD, SEM, EDX, and TGA. The prepared electro-spun composite nanofibers were applied as catalyst for the photodegradation of Congo-red under immited solar light in aqueous solution. Result reveals that, Ag loaded TiO2 composite nanofibers were effectively increased photodegradation of Congo red compared with pure TiO2 nanofibers in analogous condition. As a result, 92.0% decomposition of Congo red was obtained by using 5 wt% of Ag loaded TiO2 composite nanofibers at room temperature in short reaction time using 300 W of solar light. In addition, photodegradation of Congo red was also studied under different experimental conditions such as amount of Ag loaded in TiO2 nanofibers and contact time. Moreover, we also studied sintering effect on TiO2 nanofibers and their consequent effect on photodegradation reaction. After completion of reaction, the nanofibers can be easily separated by filtration process and reused several times without significant loss of activity. Overall study reveals that, Ag-TiO2 composite nanofibers were strongly enhanced the surface activity for the photo catalytic degradation of Congo red under ambient condition.

  14. Projected Impact of Compositional Verification on Current and Future Aviation Safety Risk

    NASA Technical Reports Server (NTRS)

    Reveley, Mary S.; Withrow, Colleen A.; Leone, Karen M.; Jones, Sharon M.

    2014-01-01

    The projected impact of compositional verification research conducted by the National Aeronautic and Space Administration System-Wide Safety and Assurance Technologies on aviation safety risk was assessed. Software and compositional verification was described. Traditional verification techniques have two major problems: testing at the prototype stage where error discovery can be quite costly and the inability to test for all potential interactions leaving some errors undetected until used by the end user. Increasingly complex and nondeterministic aviation systems are becoming too large for these tools to check and verify. Compositional verification is a "divide and conquer" solution to addressing increasingly larger and more complex systems. A review of compositional verification research being conducted by academia, industry, and Government agencies is provided. Forty-four aviation safety risks in the Biennial NextGen Safety Issues Survey were identified that could be impacted by compositional verification and grouped into five categories: automation design; system complexity; software, flight control, or equipment failure or malfunction; new technology or operations; and verification and validation. One capability, 1 research action, 5 operational improvements, and 13 enablers within the Federal Aviation Administration Joint Planning and Development Office Integrated Work Plan that could be addressed by compositional verification were identified.

  15. Ag{sub 3}PO{sub 4}/ZnO: An efficient visible-light-sensitized composite with its application in photocatalytic degradation of Rhodamine B

    SciTech Connect

    Liu, Wei; Wang, Mingliang; Xu, Chunxiang; Chen, Shifu; Fu, Xianliang

    2013-01-15

    Graphical abstract: The free OH radicals generated in the VB of ZnO play the primary role in the visible-light photocatalytic degradation of RhB in Ag{sub 3}PO{sub 4}/ZnO system. The accumulated electrons in the CB of Ag{sub 3}PO{sub 4} can be transferred to O{sub 2} adsorbed on the surface of the composite semiconductors and H{sub 2}O{sub 2} yields. H{sub 2}O{sub 2} reacts with electrons in succession to produce active ·OH to some extent. Display Omitted Highlights: ► Efficient visible-light-sensitized Ag{sub 3}PO{sub 4}/ZnO composites were successfully prepared. ► Effect of Ag{sub 3}PO{sub 4} content on the catalytic activity of Ag{sub 3}PO{sub 4}/ZnO is studied in detail. ► Rate constant of RhB degradation over Ag{sub 3}PO{sub 4}(3.0 wt.%)/ZnO is 3 times that of Ag{sub 3}PO{sub 4}. ► The active species in RhB degradation are examined by adding a series of scavengers. ► Visible light degradation mechanism of RhB over Ag{sub 3}PO{sub 4}/ZnO is systematically studied. -- Abstract: The efficient visible-light-sensitized Ag{sub 3}PO{sub 4}/ZnO composites with various weight percents of Ag{sub 3}PO{sub 4} were prepared by a facile ball milling method. The photocatalysts were characterized by XRD, DRS, SEM, EDS, XPS, and BET specific area. The ·OH radicals produced during the photocatalytic reaction was detected by the TA–PL technique. The photocatalytic property of Ag{sub 3}PO{sub 4}/ZnO was evaluated by photocatalytic degradation of Rhodamine B under visible light irradiation. Significantly, the results revealed that the photocatalytic activity of the composites was much higher than that of pure Ag{sub 3}PO{sub 4} and ZnO. The rate constant of RhB degradation over Ag{sub 3}PO{sub 4}(3.0 wt.%)/ZnO is 3 times that of single-phase Ag{sub 3}PO{sub 4}. The optimal percentage of Ag{sub 3}PO{sub 4} in the composite is 3.0 wt.%. It is proposed that the ·OH radicals produced in the valence band of ZnO play the leading role in the photocatalytic degradation of

  16. Does household composition explain welfare regime poverty risks for older adults and other household members?

    PubMed

    Tai, Tsui-o; Treas, Judith

    2009-11-01

    This cross-national study examines the poverty of older adults and their household members and relates the risk of poverty to macrolevel state approaches to welfare as well as to microlevel composition of households. Data on individuals in households with older adults for 22 countries come from the Luxembourg Income Survey. Robust cluster analysis relates the risk of poverty to the type of state welfare regime; the characteristics of the household head (age, gender, marital status, and education); as well as the household's numbers of earners, older adults, and children. Persons in households with older adults are significantly less likely to be poor in countries with social democratic and conservative welfare regimes than in Taiwan, an exemplar of limited social welfare programs. Controlling for country differences in household composition increases the differences in poverty risks. Living with fewer children, more older adults, and more earners lowers the risk of poverty, as does having a married and better educated household head. Countries with more generous social welfare provisions have lower risks of poverty despite having household characteristics that are comparatively unfavorable. As Taiwan demonstrates, household composition, particularly a reliance on multigenerational households, compensates for limited state welfare programs.

  17. High photocatalytic degradation activity of the polyvinyl chloride (PVC)-vitamin C (VC)-TiO2 nano-composite film.

    PubMed

    Yang, Changjun; Gong, Chuqing; Peng, Tianyou; Deng, Kejian; Zan, Ling

    2010-06-15

    A novel photodegradable polyvinyl chloride (PVC)-vitamin C (VC)-TiO(2) nano-composite film was prepared by embedding VC modified nano-TiO(2) photocatalyst into the commercial PVC plastic. The solid-phase photocatalytic degradation behavior of PVC-VC-TiO(2) nano-composite film under UV light irradiation was investigated and compared with those of the PVC-TiO(2) film and the pure PVC film, with the aid of UV-Vis spectroscopy, scanning electron microscopy (SEM), weight loss monitoring, and X-ray diffraction spectra (XRD). The results show that PVC-VC-TiO(2) nano-composite film has a high photocatalytic activity; the photocatalytic degradation rate of it is two times higher than that of PVC-TiO(2) film and fifteen times higher than that of pure PVC film. The optimal mass ratio of VC to TiO(2) is found to be 0.5. The mechanism of enhancing photocatalytic activity is attributed to the formation of a Ti(IV)-VC charge-transfer complex with five-member chelate ring structure and a rapid photogenerated charge separation is thus achieved.

  18. Photocatalytic degradation of gaseous toluene over TiO{sub 2}-SiO{sub 2} composite nanotubes synthesized by sol-gel with template technique

    SciTech Connect

    Zou, Xuejun; Li, Xinyong; Qu, Zhenping; Zhao, Qidong; Shi, Yong; Chen, Yongying; Tade, Moses; Liu, Shaomin

    2012-02-15

    Graphical abstract: TiO{sub 2}-SiO{sub 2} nanotubes (b) were fabricated by sol-gel method using ZnO nanowires (a) as template. Highlights: Black-Right-Pointing-Pointer A simple method to prepare TiO{sub 2}-SiO{sub 2} nanotubes for photocatalytic toluene removal. Black-Right-Pointing-Pointer The TiO{sub 2}-SiO{sub 2} nanotubes have a small blue shift and higher absorption intensity. Black-Right-Pointing-Pointer The TiO{sub 2}-SiO{sub 2} nanotubes have an enhanced photoactivity in degrading gaseous toluene. -- Abstract: TiO{sub 2}-SiO{sub 2} composite nanotubes were successfully synthesized by a facile sol-gel technique utilizing ZnO nanowires as template. The nanotubes were well characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, N{sub 2} adsorption-desorption analysis and UV-vis diffuse reflectance spectroscopy. The nanotubular TiO{sub 2}-SiO{sub 2} composite photocatalysts showed diameter of 300-325 nm, fine mesoporous structure and high specific surface area. The results indicated that the degradation efficiency of gaseous toluene could get 65% after 4 h reaction using the TiO{sub 2}-SiO{sub 2} composite as the photocatalyst under UV light illumination, which was higher than that of P25.

  19. Role of polyaniline on the photocatalytic degradation and stability performance of the polyaniline/silver/silver phosphate composite under visible light.

    PubMed

    Bu, Yuyu; Chen, Zhuoyuan

    2014-10-22

    Polyaniline/silver/silver phosphate (PANI/Ag/Ag3PO4) composite was prepared by in situ depositing silver phosphate (Ag3PO4) nanoparticles on the surface of polyaniline (PANI). The best photocatalytic Rhodamine B degradation performance is obtained by the 20 wt % PANI/Ag/Ag3PO4 composite, which is approximately 4 times higher than that of pure Ag3PO4. Meanwhile, the photocatalytic stability of Ag3PO4 is significantly improved by introducing PANI into the PANI/Ag/Ag3PO4 composite. The dramatic promotion of the photocatalytic degradation performance and the photocatalytic stability can be attributed to the formation of a heterojunction electric field between PANI and Ag3PO4, which is approximately 90 mV and points from Ag3PO4 to PANI. The existence of this electric field can dramatically enhance the separation efficiency of the photogenerated electron-hole pairs, accelerate the transfer of photogenerated holes from Ag3PO4 to PANI and therefore inhibit the self-oxidation of Ag3PO4.

  20. Synthesized TiO2/ZSM-5 composites used for the photocatalytic degradation of azo dye: Intermediates, reaction pathway, mechanism and bio-toxicity

    NASA Astrophysics Data System (ADS)

    Zhou, Kefu; Hu, Xin-Yan; Chen, Bor-Yann; Hsueh, Chung-Chuan; Zhang, Qian; Wang, Jiajie; Lin, Yu-Jung; Chang, Chang-Tang

    2016-10-01

    In this study, a one-step solid dispersion method was used to synthesize titanium dioxide (TiO2)/Zeolite Socony Mobil-5 (ZSM-5) composites with substantially reduced time and energy consumption. A degradation efficiency of more than 95% was achieved within 10 min using 50% PTZ (synthesized TiO2/ZSM-5 composites with TiO2 contents of 50 wt% loaded on ZSM-5) at pH 7 and 25 °C. The possible degradation pathway of azo-dye Reactive Black 5 (RB5) was investigated using gas chromatography-mass spectrometry and ion chromatography (IC). The bonds between the N atoms and naphthalene groups are likely attacked first and cleaved by hydroxyl radicals, ultimately resulting in the decolorization and mineralization of the azo dye. A comparative assessment of the characteristics of abiotic and biotic dye decolorization was completed. In addition, the toxicity effects of the degradation intermediates of azo-dye RB5 on cellular respiratory activity were analyzed. The bio-toxicity results showed that the decay rate constants of CO2 production from the azo-dye RB5 samples at different degradation times increased initially and subsequently decreased, indicating that intermediates of higher toxicity could adhere to the catalyst surface and gradually destroyed by further photocatalytic oxidation. Additionally, 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 hydroxyl radicals are the main oxidation species in the photocatalytic process.

  1. Fabrication of novel visible-light-driven AgI/g-C3N4 composites with enhanced visible-light photocatalytic activity for diclofenac degradation.

    PubMed

    Zhang, Wei; Zhou, Li; Shi, Jun; Deng, Huiping

    2017-02-14

    A visible-light-driven heterostructured AgI/g-C3N4 was prepared by a deposition-precipitation method. The composition, structure, morphology, and optical properties of the photocatalyst were characterized by Brunauer-Emmett-Teller method (BET), X-ray powder diffraction (XRD), Fourier transform-infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), scanning electron microscope (SEM), UV-vis diffused reflectance spectroscopy (DRS), photoluminescence spectroscopy (PL), photocurrent, and electrochemical impedance spectroscopy (EIS), respectively. AgI/g-C3N4 composite photocatalysts exhibited higher photocatalytic activities than those of AgI nanoparticles and g-C3N4 in the degradation of diclofenac (a model anti-inflammatory medicine) under visible light irradiation (λ≥400nm). When the mass molar ratio of AgI was 45% in AgI/g-C3N4, the reaction rate constant of diclofenac degradation reached 0.561min(-1), which was almost 12.5 and 43.2 times higher than that achieved by AgI (0.045min(-1)) and g-C3N4 (0.013min(-1)). The h(+) and O2(-) were pinpointed as the main reactive species in the photocatalytic reaction using their obligate radical scavengers. Diclofenac was completely degraded and partly mineralized during the photodegradation. The main intermediates were determined by liquid chromatograph mass spectrometer (LC-MS), and toxicological assessments were carried out to evaluate the change of toxicity in the degradation process. In addition, the photocatalysts showed excellent stability over multiple reaction cycles. Finally, a possible photocatalytic and charge separation mechanism was proposed.

  2. Criteria for use of composite end points for competing risks-a systematic survey of the literature with recommendations.

    PubMed

    Manja, Veena; AlBashir, Siwar; Guyatt, Gordon

    2017-02-01

    Composite end points are frequently used in reports of clinical trials. One rationale for the use of composite end points is to account for competing risks. In the presence of competing risks, the event rate of a specific event depends on the rates of other competing events. One proposed solution is to include all important competing events in one composite end point. Clinical trialists require guidance regarding when this approach is appropriate. To identify publications describing criteria for use of composite end points for competing risk and to offer guidance regarding when a composite end point is appropriate on the basis of competing risks. We searched MEDLINE, CINAHL, EMBASE, The Cochrane's Central & Systematic Review databases including the Health Technology Assessment database, and the Cochrane's Methodology register from inception to April 2015, and candidate textbooks, to identify all articles providing guidance on this issue. Eligible publications explicitly addressed the issue of a composite outcome to address competing risks. Two reviewers independently screened the titles and abstracts for full-text review; independently reviewed full-text publications; and abstracted specific criteria authors offered for use of composite end points to address competing risks. Of 63,645 titles and abstracts, 166 proved potentially relevant of which 43 publications were included in the final review. Most publications note competing risks as a reason for using composite end points without further elaboration. None of the articles or textbook chapters provide specific criteria for use of composite end points for competing risk. Some advocate using composite end points to avoid bias due to competing risks and others suggest that composite end points seldom or never be used for this purpose. We recommend using composite end points for competing risks only if the competing risk is plausible and if it occurs with sufficiently high frequency to influence the interpretation

  3. A novel solid digestate-derived biochar-Cu NP composite activating H2O2 system for simultaneous adsorption and degradation of tetracycline.

    PubMed

    Fu, Dun; Chen, Zheng; Xia, Dong; Shen, Liang; Wang, Yuanpeng; Li, Qingbiao

    2017-02-01

    Solid digestate, a by-product of anaerobic digestion systems, has led to a range of environmental issues. In the present study, a novel composite based on a solid digestate-biochar-Cu NP composite was synthesized for tetracycline removal from an aqueous medium. The removal efficiency values for tetracycline (200 mg L(-1)) were 31.5% and 97.8%, respectively, by the biochar-Cu NP composite (0.5 g L(-1)) in the absence and presence of hydrogen peroxide (H2O2, 20 mM) within 6 h of reaction time. The possible degradation pathway of tetracycline was investigated using liquid chromatography-mass spectrometry. The desorption experiment results suggested that no significant concentration of tetracycline was detected on the composite after the reaction, but a small amount of intermediates in terms of total organic carbon (TOC) accounting for 3.1%, and 23.3% of the end-product NH4(+) was adsorbed onto the biochar sheets. The dispersive Cu NPs on the biochar resulted in an increase in the surface area and pore volume of the biochar-Cu NP composite, which enhanced tetracycline adsorption as well as the degradation efficiency. Relative tetracycline removal mechanisms were dominantly ascribed to ·OH generation from the Cu(II)/Cu(I) redox reaction with H2O2 and the electron-transfer process of free radicals (FRs) in biochar. The proposed approach serves dual purposes of waste digestate reuse and treatment of antibiotic pollutants. This study highlights the activation of H2O2 by the dispersive Cu NPs coupling with biochar derived from a waste solid digestate for tetracycline treatment. Copyright © 2016. Published by Elsevier Ltd.

  4. Hydrothermal-precipitation preparation of CdS@(Er(3+):Y3Al5O12/ZrO2) coated composite and sonocatalytic degradation of caffeine.

    PubMed

    Huang, Yingying; Wang, Guowei; Zhang, Hongbo; Li, Guanshu; Fang, Dawei; Wang, Jun; Song, Youtao

    2017-07-01

    Here, we reported a novel method to dispose caffeine by means of ultrasound irradiation combinated with CdS@(Er(3+):Y3Al5O12/ZrO2) coated composite as sonocatalyst. The CdS@(Er(3+):Y3Al5O12/ZrO2) was synthesized via hydrothermal-precipitation method and then characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX) and UV-vis diffuse reflectance spectra (DRS). After that, the sonocatalytic degradation of caffeine in aqueous solution was conducted adopting CdS@(Er(3+):Y3Al5O12/ZrO2) and CdS@ZrO2 coated composites as sonocatalysts. In addition, some influencing factors such as CdS and ZrO2 molar proportion, caffeine concentration, ultrasonic irradiation tim