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Sample records for metal mixture responses

  1. Toxic responses of bivalves to metal mixtures

    SciTech Connect

    Mathew, P.; Menon, N.R. )

    1992-02-01

    Although there is a growing body of information on the toxicity of individual heavy metals to economically important on the toxicity of individual heavy metals to economically important species of bivalves, literature on the lethal toxicity of metal mixtures to bivalves under controlled conditions is rather limited. In the present investigation the toxic effects of combinations of copper - mercury and copper - mercury and copper - cadmium at lethal levels of two marine bivalve species, Perna indica and Donax incarnatus, have been delineated.

  2. Toxicological responses of environmental mixtures: Environmental metal mixtures display synergistic induction of metal-responsive and oxidative stress genes in placental cells.

    PubMed

    Adebambo, Oluwadamilare A; Ray, Paul D; Shea, Damian; Fry, Rebecca C

    2015-12-15

    Exposure to elevated levels of the toxic metals inorganic arsenic (iAs) and cadmium (Cd) represents a major global health problem. These metals often occur as mixtures in the environment, creating the potential for interactive or synergistic biological effects different from those observed in single exposure conditions. In the present study, environmental mixtures collected from two waste sites in China and comparable mixtures prepared in the laboratory were tested for toxicogenomic response in placental JEG-3 cells. These cells serve as a model for evaluating cellular responses to exposures during pregnancy. One of the mixtures was predominated by iAs and one by Cd. Six gene biomarkers were measured in order to evaluate the effects from the metal mixtures using dose and time-course experiments including: heme oxygenase 1 (HO-1) and metallothionein isoforms (MT1A, MT1F and MT1G) previously shown to be preferentially induced by exposure to either iAs or Cd, and metal transporter genes aquaporin-9 (AQP9) and ATPase, Cu(2+) transporting, beta polypeptide (ATP7B). There was a significant increase in the mRNA expression levels of ATP7B, HO-1, MT1A, MT1F, and MT1G in mixture-treated cells compared to the iAs or Cd only-treated cells. Notably, the genomic responses were observed at concentrations significantly lower than levels found at the environmental collection sites. These data demonstrate that metal mixtures increase the expression of gene biomarkers in placental JEG-3 cells in a synergistic manner. Taken together, the data suggest that toxic metals that co-occur may induce detrimental health effects that are currently underestimated when analyzed as single metals.

  3. Children Exposed to Metals Mixtures Demonstrate Dysregulation of Infectious Disease Response

    EPA Science Inventory

    Exposure to toxic metals can have harmful health effects, particularly in children. Although studies have investigated the individual effects toxic metals have on gene expression and health outcomes, there are no studies assessing the effect of metal mixtures on gene expression p...

  4. Metal-Polycyclic Aromatic Hydrocarbon Mixture Toxicity in Hyalella azteca. 1. Response Surfaces and Isoboles To Measure Non-additive Mixture Toxicity and Ecological Risk.

    PubMed

    Gauthier, Patrick T; Norwood, Warren P; Prepas, Ellie E; Pyle, Greg G

    2015-10-06

    Mixtures of metals and polycyclic aromatic hydrocarbons (PAHs) occur ubiquitously in aquatic environments, yet relatively little is known regarding their potential to produce non-additive toxicity (i.e., antagonism or potentiation). A review of the lethality of metal-PAH mixtures in aquatic biota revealed that more-than-additive lethality is as common as strictly additive effects. Approaches to ecological risk assessment do not consider non-additive toxicity of metal-PAH mixtures. Forty-eight-hour water-only binary mixture toxicity experiments were conducted to determine the additive toxic nature of mixtures of Cu, Cd, V, or Ni with phenanthrene (PHE) or phenanthrenequinone (PHQ) using the aquatic amphipod Hyalella azteca. In cases where more-than-additive toxicity was observed, we calculated the possible mortality rates at Canada's environmental water quality guideline concentrations. We used a three-dimensional response surface isobole model-based approach to compare the observed co-toxicity in juvenile amphipods to predicted outcomes based on concentration addition or effects addition mixtures models. More-than-additive lethality was observed for all Cu-PHE, Cu-PHQ, and several Cd-PHE, Cd-PHQ, and Ni-PHE mixtures. Our analysis predicts Cu-PHE, Cu-PHQ, Cd-PHE, and Cd-PHQ mixtures at the Canadian Water Quality Guideline concentrations would produce 7.5%, 3.7%, 4.4% and 1.4% mortality, respectively.

  5. Exposure to metals mixtures: Genomic alterations of infectious disease response pathways in children exposed to environmedntal metals

    EPA Science Inventory

    Exposure to toxic metals can have harmful health effects, particularly in children. Although studies have investigated the individual effects toxic metals have on gene expression and health outcomes, there are no studies assessing the effect of metal mixtures on gene expression p...

  6. A multimodal imaging workflow to visualize metal mixtures in the human placenta and explore colocalization with biological response markers.

    PubMed

    Niedzwiecki, Megan M; Austin, Christine; Remark, Romain; Merad, Miriam; Gnjatic, Sacha; Estrada-Gutierrez, Guadalupe; Espejel-Nuñez, Aurora; Borboa-Olivares, Hector; Guzman-Huerta, Mario; Wright, Rosalind J; Wright, Robert O; Arora, Manish

    2016-04-01

    Fetal exposure to essential and toxic metals can influence life-long health trajectories. The placenta regulates chemical transmission from maternal circulation to the fetus and itself exhibits a complex response to environmental stressors. The placenta can thus be a useful matrix to monitor metal exposures and stress responses in utero, but strategies to explore the biologic effects of metal mixtures in this organ are not well-developed. In this proof-of-concept study, we used laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to measure the distributions of multiple metals in placental tissue from a low-birth-weight pregnancy, and we developed an approach to identify the components of metal mixtures that colocalized with biological response markers. Our novel workflow, which includes custom-developed software tools and algorithms for spatial outlier identification and background subtraction in multidimensional elemental image stacks, enables rapid image processing and seamless integration of data from elemental imaging and immunohistochemistry. Using quantitative spatial statistics, we identified distinct patterns of metal accumulation at sites of inflammation. Broadly, our multiplexed approach can be used to explore the mechanisms mediating complex metal exposures and biologic responses within placentae and other tissue types. Our LA-ICP-MS image processing workflow can be accessed through our interactive R Shiny application 'shinyImaging', which is available at or through our laboratory's website, .

  7. Systematic Proteomic Approach to Characterize the Impacts of Chemical Interactions on Protein and Cytotoxicity Responses to Metal Mixture Exposures

    EPA Science Inventory

    Chemical interactions have posed a big challenge in toxicity characterization and human health risk assessment of environmental mixtures. To characterize the impacts of chemical interactions on protein and cytotoxicity responses to environmental mixtures, we established a systems...

  8. Predicting the toxicity of metal mixtures

    USGS Publications Warehouse

    Balistrieri, Laurie S.; Mebane, Christopher A.

    2013-01-01

    The toxicity of single and multiple metal (Cd, Cu, Pb, and Zn) solutions to trout is predicted using an approach that combines calculations of: (1) solution speciation; (2) competition and accumulation of cations (H, Ca, Mg, Na, Cd, Cu, Pb, and Zn) on low abundance, high affinity and high abundance, low affinity biotic ligand sites; (3) a toxicity function that accounts for accumulation and potency of individual toxicants; and (4) biological response. The approach is evaluated by examining water composition from single metal toxicity tests of trout at 50% mortality, results of theoretical calculations of metal accumulation on fish gills and associated mortality for single, binary, ternary, and quaternary metal solutions, and predictions for a field site impacted by acid rock drainage. These evaluations indicate that toxicity of metal mixtures depends on the relative affinity and potency of toxicants for a given aquatic organism, suites of metals in the mixture, dissolved metal concentrations and ratios, and background solution composition (temperature, pH, and concentrations of major ions and dissolved organic carbon). A composite function that incorporates solution composition, affinity and competition of cations for two types of biotic ligand sites, and potencies of hydrogen and individual metals is proposed as a tool to evaluate potential toxicity of environmental solutions to trout.

  9. Study of the factors influencing the metals solubilisation from a mixture of waste batteries by response surface methodology.

    PubMed

    Tanong, Kulchaya; Coudert, Lucie; Chartier, Myriam; Mercier, Guy; Blais, Jean-François

    2017-02-22

    This paper presents an innovative process for the recovery of valuable metals from a mixture of spent batteries. Different types of batteries, including alkaline, zinc-carbon (Zn-C), nickel cadmium (Ni-Cd), nickel metal hydride (Ni-MH), lithium ion (Li-ion) and lithium metallic (Li-M) batteries, were mixed according to the proportion of the Canadian sales of batteries. A Box-Behnken design was applied to find the optimum leaching conditions allowing a maximum of valuable metal removals from a mixture of spent batteries in the presence of an inorganic acid and a reducing agent. The results highlighted the positive effect of sodium metabisulfite on the performance of metals removal, especially for Mn. The solid/liquid ratio and the concentration of H2SO4 were the main factors affecting the leaching behavior of valuable metals (Zn, Mn, Cd, Ni) present in spent batteries. Finally, the optimum leaching conditions were found as follows: one leaching step, solid/liquid ratio = 10.9%, [H2SO4] = 1.34 M, sodium metabisulfite (Na2S2O5) = 0.45 g/g of battery powder and retention time = 45 min. Under such conditions, the removal yields achieved were 94% for Mn, 81% for Cd, 99% for Zn, 96% for Co and 68% for Ni.

  10. Role of oxidative stress in transformation induced by metal mixture.

    PubMed

    Martín, Silva-Aguilar; Emilio, Rojas; Mahara, Valverde

    2011-01-01

    Metals are ubiquitous pollutants present as mixtures. In particular, mixture of arsenic-cadmium-lead is among the leading toxic agents detected in the environment. These metals have carcinogenic and cell-transforming potential. In this study, we used a two step cell transformation model, to determine the role of oxidative stress in transformation induced by a mixture of arsenic-cadmium-lead. Oxidative damage and antioxidant response were determined. Metal mixture treatment induces the increase of damage markers and the antioxidant response. Loss of cell viability and increased transforming potential were observed during the promotion phase. This finding correlated significantly with generation of reactive oxygen species. Cotreatment with N-acetyl-cysteine induces effect on the transforming capacity; while a diminution was found in initiation, in promotion phase a total block of the transforming capacity was observed. Our results suggest that oxidative stress generated by metal mixture plays an important role only in promotion phase promoting transforming capacity.

  11. The life-table demographic response of freshwater rotifer Brachionus calyciflorus to multi-metal (Cu, Zn, Cd, Cr, and Mn) mixture interaction.

    PubMed

    Xu, Xiao-Ping; Xi, Yi-Long; Huang, Lin; Xiang, Xian-Ling

    2014-08-01

    The effects of multi-metal mixtures on the life-table demography of rotifers are not well known. In this study, the freshwater rotifer Brachionus calyciflorus was exposed to mixture of Cu, Zn, Cd, Cr, and Mn, and the life-table demographic parameters including net reproductive rate, generation time, life expectancy at hatching, and intrinsic rate of population increase were calculated. The results showed that interactions between a given element concentration, except Mn, and the other four elements mixture concentration affected the intrinsic rate of population increase (p < 0.01). Interactions between Zn concentration, as well as Mn, and the other four elements mixture concentration affected the net reproductive rate and the life expectancy at hatching, respectively (p < 0.05). The variation of parameters with the rise of the other four elements mixture concentrations from 0 to high was mainly attributed to the difference of interaction among the five metals mixture with different ratio of concentrations.

  12. Method of producing homogeneous mixed metal oxides and metal-metal oxide mixtures

    DOEpatents

    Quinby, Thomas C.

    1978-01-01

    Metal powders, metal oxide powders, and mixtures thereof of controlled particle size are provided by reacting an aqueous solution containing dissolved metal values with excess urea. Upon heating, urea reacts with water from the solution leaving a molten urea solution containing the metal values. The molten urea solution is heated to above about 180.degree. C. whereupon metal values precipitate homogeneously as a powder. The powder is reduced to metal or calcined to form oxide particles. One or more metal oxides in a mixture can be selectively reduced to produce metal particles or a mixture of metal and metal oxide particles.

  13. Development and application of a multimetal multibiotic ligand model for assessing aquatic toxicity of metal mixtures.

    PubMed

    Santore, Robert C; Ryan, Adam C

    2015-04-01

    A multimetal, multiple binding site version of the biotic ligand model (mBLM) has been developed for predicting and explaining the bioavailability and toxicity of mixtures of metals to aquatic organisms. The mBLM was constructed by combining information from single-metal BLMs to preserve compatibility between the single-metal and multiple-metal approaches. The toxicities from individual metals were predicted by assuming additivity of the individual responses. Mixture toxicity was predicted based on both dissolved metal and mBLM-normalized bioavailable metal. Comparison of the 2 prediction methods indicates that metal mixtures frequently appear to have greater toxicity than an additive estimation of individual effects on a dissolved metal basis. However, on an mBLM-normalized basis, mixtures of metals appear to be additive or less than additive. This difference results from interactions between metals and ligands in solutions including natural organic matter, processes that are accounted for in the mBLM. As part of the mBLM approach, a technique for considering variability was developed to calculate confidence bounds (called response envelopes) around the central concentration-response relationship. Predictions using the mBLM and response envelope were compared with observed toxicity for a number of invertebrate and fish species. The results show that the mBLM is a useful tool for considering bioavailability when assessing the toxicity of metal mixtures.

  14. Combined toxicity of heavy metal mixtures in liver cells.

    PubMed

    Lin, Xialu; Gu, Yuanliang; Zhou, Qi; Mao, Guochuan; Zou, Baobo; Zhao, Jinshun

    2016-09-01

    With rapid industrialization, China is now facing great challenges in heavy metal contamination in the environment. Human exposure to heavy metals through air, water and food commonly involves a mixture consisting of multiple heavy metals. In this study, eight common heavy metals (Pb, Cd, Hg, Cu, Zn, Mn, Cr, Ni) that cause environmental contamination were selected to investigate the combined toxicity of different heavy metal mixtures in HL7702 cells. Toxicity (24 h LC50 ) of each individual metal on the cells ranked Hg > Cr = Cd > Cu > Zn > Ni > Mn > Pb; toxicity of the different mixtures ranked: M5 > M3PbHgCd > M5+Mn > M5+Cu > M2CdNi > M4A > M8-Mn > M8 > M5+Zn > M4B > M8-Cr > M8-Zn > M8-Cu > M8-Pb > M8-Cd > M8-Hg > M8-Ni > M3PbHgNi > M3CuZnMn. The cytotoxicity data of individual metals were successfully used to build the additive models of two- to eight-component metal mixtures. The comparison between additive model and combination model or partly additive model was useful to evaluate the combined effects in mixture. Synergistic, antagonistic or additive effects of the toxicity were observed in different mixtures. These results suggest that the combined effects should be considered in the risk assessment of heavy metal co-exposure, and more comprehensive investigations on the combined effects of different heavy metal mixtures are needed in the future. Copyright © 2016 John Wiley & Sons, Ltd.

  15. Accumulation and effects of metal mixtures in two seaweed species.

    PubMed

    Jarvis, Tayler A; Bielmyer-Fraser, Gretchen K

    2015-05-01

    Metal pollution, due to various anthropogenic sources, may pose a threat to marine ecosystems. Metals can be introduced into food chains via bioaccumulation in primary producers, and may potentially lead to toxic effects. Macroalgae are used as food by a wide variety of organisms, and are therefore extremely important in aquatic systems. This study investigated the accumulation and effects of metals in two macroalgae species. The green seaweed, Ulva lactuca and the red seaweed, Agardhiella subulata were each concurrently exposed to five metals (Cu, Ni, Pb, Cd, and Zn) and U. lactuca was also exposed to each metal individually for 48 h. Metal accumulation in the seaweed was measured, and various photosynthetic parameters were assessed, using imaging pulse amplitude modulated (PAM) fluorometry. Increased metal accumulation occurred in both seaweed species after 48 h exposure to metal mixtures and each metal individually. The distribution of metals in both seaweed species changed with increasing metal exposure concentrations, resulting in higher proportions of Cu and Zn in the metal-exposed groups, as compared to respective controls. Further, U. lactuca accumulated higher concentrations of metals when exposed to each metal individually rather than in metal mixtures, suggesting interactions among metals for uptake and/or bioaccumulation. Significant impairment of photosynthetic parameters in U. lactuca was observed after exposure to 100 and 1000 μg/L metal mixtures, as well as 100 μg/L of either Cd or Cu. These results demonstrate metal bioaccumulation and toxic effects in important primary producers, and may have implications for higher trophic levels.

  16. Effects of metal salt mixtures on Daphnia magna reproduction

    SciTech Connect

    Biesinger, K.E.; Christensen, G.M.; Fiandt, J.T.

    1986-02-01

    Three binary metal experiments were conducted using a complete block design; testing the chlorides of Cd, Hg, and Zn individually and in combinations of Cd-Hg, Cd-Zn, and Zn-Hg on Daphnia magna reproduction. These mixtures were tested at one-half, once, and twice the 16% reproductive impairment concentration previously determined for individual metals. The Cd-Hg, Cd-Zn, and Zn-Hg mixtures all showed significant reductions in reproduction at concentrations where the metal salts alone caused no significant effect.

  17. Thermally responsive aqueous silicate mixtures and use thereof

    SciTech Connect

    Smith, W.H.; Vinson, E.F.

    1987-02-03

    A method is described of plugging or sealing a zone in a subterranean formation comprising: (a) contacting the zone with an aqueous silicate composition consisting essentially of (i) an aqueous solution containing an alkali metal silicate; and, (ii) a thermally responsive gelation activator selected from the group consisting of lactose, dextrose, fructose, galactose, mannose, mantose, xylose and mixtures thereof; and (b) activating the gelation activator in response to a thermal change in the composition within the formation whereby the silicate composition is caused to form a gel in the zone.

  18. Enhanced selective metal adsorption on optimised agroforestry waste mixtures.

    PubMed

    Rosales, Emilio; Ferreira, Laura; Sanromán, M Ángeles; Tavares, Teresa; Pazos, Marta

    2015-04-01

    The aim of this work is to ascertain the potentials of different agroforestry wastes to be used as biosorbents in the removal of a mixture of heavy metals. Fern (FE), rice husk (RI) and oak leaves (OA) presented the best removal percentages for Cu(II) and Ni(II), Mn(II) and Zn(II) and Cr(VI), respectively. The performance of a mixture of these three biosorbents was evaluated, and an improvement of 10% in the overall removal was obtained (19.25mg/g). The optimum mixture proportions were determined using simplex-centroid mixture design method (FE:OA:RI=50:13.7:36.3). The adsorption kinetics and isotherms of the optimised mixture were fit by the pseudo-first order kinetic model and Langmuir isotherm. The adsorption mechanism was studied, and the effects of the carboxylic, hydroxyl and phenolic groups on metal-biomass binding were demonstrated. Finally, the recoveries of the metals using biomass were investigated, and cationic metal recoveries of 100% were achieved when acidic solutions were used.

  19. Metal-halide mixtures for latent heat energy storage

    NASA Technical Reports Server (NTRS)

    Chen, K.; Manvi, R.

    1981-01-01

    Some candidates for alkali metal and alkali halide mixtures suitable for thermal energy storage at temperatures 600 C are identified. A solar thermal system application which offer advantages such as precipitation of salt crystals away from heat transfer surfaces, increased thermal conductivity of phase change materials, corrosion inhibition, and a constant monotectic temperature, independent of mixture concentrations. By using the lighters, metal rich phase as a heat transfer medium and the denser, salt rich phase as a phase change material for latent heat storage, undesirable solidification on the heat transfer surface may be prevented, is presented.

  20. Effects of metal and organophosphate mixtures on Ceriodaphnia dubia survival and reproduction.

    PubMed

    Mahar, Amy M; Watzin, Mary C

    2005-07-01

    The toxicity of mixtures of copper, zinc, and diazinon were determined for Ceriodaphnia dubia using 7-d survival and reproduction tests. Fifteen treatments, including combinations of the chemicals at 0, 25, 50, 75, and 100% of their individual median lethal concentrations, adding up to one toxic unit (TU) were tested. The TU was then used to classify each mixture response as additive, greater than additive, or less than additive. For survival, additive responses occurred in the 75% zinc plus 25% diazinon and the 50% copper plus 25% zinc plus 25% diazinon treatments. For reproduction, additive responses occurred in the 75% copper plus 25% zinc, 75% copper plus 25% diazinon, and 75% zinc plus 25% diazinon treatments. Copper and zinc played a greater role in toxicity than diazinon did. Less-than-additive interactions were found in all remaining mixtures, perhaps because of differences in mode of action between diazinon and metals. Consideration of dose-response curves can help to explain inconsistencies regarding toxic response in treatments with different ratios of the same chemicals. As TU percentages changed, mixture components were taken from different locations on differently shaped dose-response curves. Because most responses were less than additive, however, water-quality criteria based on individual concentrations probably are protective for most metal-organophosphate mixtures.

  1. Metal-halide mixtures for latent heat energy storage

    NASA Technical Reports Server (NTRS)

    Chen, K.; Manvi, R.

    1981-01-01

    Alkali metal and alkali halide mixtures are identified which may be suitable for thermal energy storage at temperatures above 600 C. The use of metal-halides is appropriate because of their tendency to form two immiscible melts with a density difference, which reduces scale formation and solidification on heat transfer surfaces. Also, the accumulation of phase change material along the melt interface is avoided by the self-dispersing characteristic of some metal-halides, in particular Sr-SrCl2, Ba-BaCl2, and Ba-BaBr2 mixtures. Further advantages lie in their high thermal conductivities, ability to cope with thermal shock, corrosion inhibition, and possibly higher energy densities.

  2. MRNA and miRNA expression patterns associated to pathways linked to metal mixture health effects.

    PubMed

    Martínez-Pacheco, M; Hidalgo-Miranda, A; Romero-Córdoba, S; Valverde, M; Rojas, E

    2014-01-10

    Metals are a threat to human health by increasing disease risk. Experimental data have linked altered miRNA expression with exposure to some metals. MiRNAs comprise a large family of non-coding single-stranded molecules that primarily function to negatively regulate gene expression post-transcriptionally. Although several human populations are exposed to low concentrations of As, Cd and Pb as a mixture, most toxicology research focuses on the individual effects that these metals exert. Thus, this study aims to evaluate global miRNA and mRNA expression changes induced by a metal mixture containing NaAsO2, CdCl2, Pb(C2H3O2)2·3H2O and to predict possible metal-associated disease development under these conditions. Our results show that this metal mixture results in a miRNA expression profile that may be responsible for the mRNA expression changes observed under experimental conditions in which coding proteins are involved in cellular processes, including cell death, growth and proliferation related to the metal-associated inflammatory response and cancer.

  3. Modeling and interpreting biological effects of mixtures in the environment: introduction to the metal mixture modeling evaluation project.

    PubMed

    Van Genderen, Eric; Adams, William; Dwyer, Robert; Garman, Emily; Gorsuch, Joseph

    2015-04-01

    The fate and biological effects of chemical mixtures in the environment are receiving increased attention from the scientific and regulatory communities. Understanding the behavior and toxicity of metal mixtures poses unique challenges for incorporating metal-specific concepts and approaches, such as bioavailability and metal speciation, in multiple-metal exposures. To avoid the use of oversimplified approaches to assess the toxicity of metal mixtures, a collaborative 2-yr research project and multistakeholder group workshop were conducted to examine and evaluate available higher-tiered chemical speciation-based metal mixtures modeling approaches. The Metal Mixture Modeling Evaluation project and workshop achieved 3 important objectives related to modeling and interpretation of biological effects of metal mixtures: 1) bioavailability models calibrated for single-metal exposures can be integrated to assess mixture scenarios; 2) the available modeling approaches perform consistently well for various metal combinations, organisms, and endpoints; and 3) several technical advancements have been identified that should be incorporated into speciation models and environmental risk assessments for metals.

  4. Electrochemical response of carbon paste electrode modified with mixture of titanium dioxide/zirconium dioxide in the detection of heavy metals: lead and cadmium.

    PubMed

    Nguyen, Phuong Khanh Quoc; Lunsford, Suzanne K

    2012-11-15

    A novel carbon modified electrode was developed by incorporating titanium dioxide/zirconium dioxide into the graphite carbon paste electrode to detect heavy metals-cadmium and lead. In this work, the development of the novel titanium dioxide/zirconium dioxide modified carbon paste electrode was studied to determine the optimum synthesis conditions related to the temperature, heating duration, amount and ratio of titanium dioxide/zirconium dioxide, and amount of surfactant, to create the most reproducible results. Using cyclic voltammetric (CV) analysis, this study has proven that the novel titanium dioxide/zirconium dioxide can be utilized to detect heavy metals-lead and cadmium, at relatively low concentrations (7.6×10(-6) M and 1.1×10(-5) M for Pb and Cd, respectively) at optimum pH value (pH=3). From analyzing CV data the optimal electrodes surface area was estimated to be 0.028 (±0.003) cm(2). Also, under the specific experimental conditions, electron transfer coefficients were estimated to be 0.44 and 0.33 along with the heterogeneous electron transfer rate constants of 5.64×10(-3) and 2.42×10(-3) (cm/s) for Pb and Cd, respectively.

  5. Comparative Analysis of Stress Induced Gene Expression in Caenorhabditis elegans following Exposure to Environmental and Lab Reconstituted Complex Metal Mixture

    PubMed Central

    Kumar, Ranjeet; Pradhan, Ajay; Khan, Faisal Ahmad; Lindström, Pia; Ragnvaldsson, Daniel; Ivarsson, Per; Olsson, Per-Erik; Jass, Jana

    2015-01-01

    Metals are essential for many physiological processes and are ubiquitously present in the environment. However, high metal concentrations can be harmful to organisms and lead to physiological stress and diseases. The accumulation of transition metals in the environment due to either natural processes or anthropogenic activities such as mining results in the contamination of water and soil environments. The present study used Caenorhabditis elegans to evaluate gene expression as an indicator of physiological response, following exposure to water collected from three different locations downstream of a Swedish mining site and a lab reconstituted metal mixture. Our results indicated that the reconstituted metal mixture exerted a direct stress response in C. elegans whereas the environmental waters elicited either a diminished or abrogated response. This suggests that it is not sufficient to use the biological effects observed from laboratory mixtures to extrapolate the effects observed in complex aquatic environments and apply this to risk assessment and intervention. PMID:26168046

  6. Method of treating alkali metal sulfide and carbonate mixtures

    DOEpatents

    Kohl, Arthur L.; Rennick, Robert D.; Savinsky, Martin W.

    1978-01-01

    A method of removing and preferably recovering sulfur values from an alkali metal sulfide and carbonate mixture comprising the steps of (1) introducing the mixture in an aqueous medium into a first carbonation zone and reacting the mixture with a gas containing a major amount of CO.sub.2 and a minor amount of H.sub.2 S; (2) introducing the resultant product from step 1 into a stripping zone maintained at subatmospheric pressure, and contacting this product with steam to produce a gaseous mixture, comprising H.sub.2 S and water vapor, and a liquor of reduced sulfide content; (3) introducing the liquor of reduced sulfide content into a second carbonation zone, and reacting the liquor with substantially pure gaseous CO.sub.2 in an amount sufficient to precipitate bicarbonate crystals and produce an offgas containing CO.sub.2 and H.sub.2 S for use in step 1; (4) recovering the bicarbonate crystals from step 3, and thermally decomposing the crystals to produce an alkaline metal carbonate product and a substantially pure CO.sub.2 offgas for use in step 3.

  7. A mixture hierarchical model for response times and response accuracy.

    PubMed

    Wang, Chun; Xu, Gongjun

    2015-11-01

    In real testing, examinees may manifest different types of test-taking behaviours. In this paper we focus on two types that appear to be among the more frequently occurring behaviours – solution behaviour and rapid guessing behaviour. Rapid guessing usually happens in high-stakes tests when there is insufficient time, and in low-stakes tests when there is lack of effort. These two qualitatively different test-taking behaviours, if ignored, will lead to violation of the local independence assumption and, as a result, yield biased item/person parameter estimation. We propose a mixture hierarchical model to account for differences among item responses and response time patterns arising from these two behaviours. The model is also able to identify the specific behaviour an examinee engages in when answering an item. A Monte Carlo expectation maximization algorithm is proposed for model calibration. A simulation study shows that the new model yields more accurate item and person parameter estimates than a non-mixture model when the data indeed come from two types of behaviour. The model also fits real, high-stakes test data better than a non-mixture model, and therefore the new model can better identify the underlying test-taking behaviour an examinee engages in on a certain item.

  8. Transcriptional responses to complex mixtures - A review

    EPA Science Inventory

    Exposure of people to hazardous compounds is primarily through complex environmental mixtures, those that occur through media such as air, soil, water, food, cigarette smoke, and combustion emissions. Microarray technology offers the ability to query the entire genome after expos...

  9. Metal mixture modeling evaluation project: 2. Comparison of four modeling approaches.

    PubMed

    Farley, Kevin J; Meyer, Joseph S; Balistrieri, Laurie S; De Schamphelaere, Karel A C; Iwasaki, Yuichi; Janssen, Colin R; Kamo, Masashi; Lofts, Stephen; Mebane, Christopher A; Naito, Wataru; Ryan, Adam C; Santore, Robert C; Tipping, Edward

    2015-04-01

    As part of the Metal Mixture Modeling Evaluation (MMME) project, models were developed by the National Institute of Advanced Industrial Science and Technology (Japan), the US Geological Survey (USA), HDR|HydroQual (USA), and the Centre for Ecology and Hydrology (United Kingdom) to address the effects of metal mixtures on biological responses of aquatic organisms. A comparison of the 4 models, as they were presented at the MMME workshop in Brussels, Belgium (May 2012), is provided in the present study. Overall, the models were found to be similar in structure (free ion activities computed by the Windermere humic aqueous model [WHAM]; specific or nonspecific binding of metals/cations in or on the organism; specification of metal potency factors or toxicity response functions to relate metal accumulation to biological response). Major differences in modeling approaches are attributed to various modeling assumptions (e.g., single vs multiple types of binding sites on the organism) and specific calibration strategies that affected the selection of model parameters. The models provided a reasonable description of additive (or nearly additive) toxicity for a number of individual toxicity test results. Less-than-additive toxicity was more difficult to describe with the available models. Because of limitations in the available datasets and the strong interrelationships among the model parameters (binding constants, potency factors, toxicity response parameters), further evaluation of specific model assumptions and calibration strategies is needed.

  10. Metal Mixture Modeling Evaluation project: 2. Comparison of four modeling approaches

    USGS Publications Warehouse

    Farley, Kevin J.; Meyer, Joe; Balistrieri, Laurie S.; DeSchamphelaere, Karl; Iwasaki, Yuichi; Janssen, Colin; Kamo, Masashi; Lofts, Steve; Mebane, Christopher A.; Naito, Wataru; Ryan, Adam C.; Santore, Robert C.; Tipping, Edward

    2015-01-01

    As part of the Metal Mixture Modeling Evaluation (MMME) project, models were developed by the National Institute of Advanced Industrial Science and Technology (Japan), the U.S. Geological Survey (USA), HDR⎪HydroQual, Inc. (USA), and the Centre for Ecology and Hydrology (UK) to address the effects of metal mixtures on biological responses of aquatic organisms. A comparison of the 4 models, as they were presented at the MMME Workshop in Brussels, Belgium (May 2012), is provided herein. Overall, the models were found to be similar in structure (free ion activities computed by WHAM; specific or non-specific binding of metals/cations in or on the organism; specification of metal potency factors and/or toxicity response functions to relate metal accumulation to biological response). Major differences in modeling approaches are attributed to various modeling assumptions (e.g., single versus multiple types of binding site on the organism) and specific calibration strategies that affected the selection of model parameters. The models provided a reasonable description of additive (or nearly additive) toxicity for a number of individual toxicity test results. Less-than-additive toxicity was more difficult to describe with the available models. Because of limitations in the available datasets and the strong inter-relationships among the model parameters (log KM values, potency factors, toxicity response parameters), further evaluation of specific model assumptions and calibration strategies is needed.

  11. Effects of binary mixtures of inducers (toluene analogs) and of metals on bioluminescence induction of a recombinant bioreporter strain.

    PubMed

    Kong, In Chul

    2014-10-13

    This paper investigated the effects of binary mixtures of bioluminescence inducers (toluene, xylene isomers, m-toluate) and of metals (Cu, Cd, As(III), As(V), and Cr) on bioluminescence activity of recombinant (Pm-lux) strain KG1206. Different responses and sensitivities were observed depending on the types and concentrations of mixtures of inducers or metals. In the case of inducer mixtures, antagonistic and synergistic modes of action were observed, whereas metal mixtures showed all three modes of action. Antagonistic mode of action was most common for mixtures of indirect inducers, which showed bioluminescence ranging from 29% to 62% of theoretically expected effects (P(E)). On the other hand, synergistic mode of action was observed for mixtures of direct and indirect inducers, which showed bioluminescence between 141% and 243% of P(E). In the case of binary metal mixtures, bioluminescence activities were ranged from 62% to 75% and 113% to 164% of P(E) for antagonistic and synergistic modes of action, respectively (p-values 0.0001-0.038). Therefore, mixture effects could not be generalized since they were dependent on both the types and concentrations of chemicals, suggesting that biomonitoring may constitute a better strategy by investigating types and concentrations of mixture pollutants at contaminated sites.

  12. Testing an application of a biotic ligand model to predict acute toxicity of metal mixtures to rainbow trout.

    PubMed

    Iwasaki, Yuichi; Kamo, Masashi; Naito, Wataru

    2015-04-01

    The authors tested the applicability of a previously developed biotic ligand model (BLM) to predict acute toxicity of single metals and metal mixtures (cadmium, lead, and zinc) to rainbow trout fry (Oncorhynchus mykiss) from a single available dataset. The BLM used in the present study hypothesizes that metals inhibit an essential cation (calcium) and organisms die as a result of its deficiency, leading to an assumption that the proportion of metal-binding ligand (f) is responsible for the toxic effects of metals on the survival of rainbow trout. The f value is a function of free-ion concentrations of metals computed by a chemical speciation model, and the function has affinity constants as model parameters. First, the survival effects of single metals were statistically modeled separately (i.e., f-survival relationship) by using the generalized linear mixed model with binomial distribution. The modeled responses of survival rates to f overlapped reasonably irrespective of metals tested, supporting the theoretical prediction from the BLM that f-survival relationships are comparable regardless of metal species. The authors thus developed the generalized linear mixed model based on all data pooled across the single-metal tests. The best-fitted model well predicted the survival responses observed in mixture tests (r = 0.97), providing support for the applicability of the BLM to predict effects of metal mixtures.

  13. Speciation studies and toxicity assessment of complex heavy metal mixtures

    SciTech Connect

    Bundy, K.J.; Mowat, F.

    1996-12-31

    The Microtox{trademark} bioassay and polarographic techniques were used together to identify specific oxidation states and toxicity of metals. The bioassay is based on light reduction by bioluminescent bacteria upon exposure to toxicants. In polarography, a mercury drop substrate`s potential is changed, and the substance of interest is electrochemically reduced. Reduction current is proportional to its concentration. The toxicity of solutions containing heavy metal pollutants was measured. Mercury was found to be most toxic with an acute one minute EC{sub 50} of 0.0162 mg/l. Cu(I) was least toxic. Speciation effects were observed; e.g., Cr(III) was less toxic than Cr(VI); Cu(II) was more toxic than Cu(I). Polarography (which is usually not used for multielement analysis) has been extended to Pb(II) and Cd(II) solution mixtures. Various mixtures were tested to determine if toxicity was predictable from that of individual components, or whether synergistic/antagonistic reactions occur. The resultant EC{sub 50} for a 50-50 As(V)/Cd(II) mixture was consistent with additive behavior; Pb(II)/Cd(II) and Pb(II)/Cu(I) mixtures exhibited antagonistic and synergistic interactions, respectively. Sediments soaked with Pb(II) and Cr(III) have been studied to determine the toxicity. For competitive sorption, the EC{sub 50} value is twice that for Cr(III) alone, presumably because preferential Cr(III) adsorption occurs, blocking Pb(II) adsorption to kaolin.

  14. Acute phytotoxicity of seven metals alone and in mixture: Are Italian soil threshold concentrations suitable for plant protection?

    SciTech Connect

    Baderna, Diego Lomazzi, Eleonora; Pogliaghi, Alberto; Ciaccia, Gianluca; Lodi, Marco; Benfenati, Emilio

    2015-07-15

    Metals can pollute soils in both urban and rural areas with severe impacts on the health of humans, plants and animals living there. Information on metal toxicity is therefore important for ecotoxicology. This study investigated the phytotoxicity of different metals frequently found as pollutants in soils: arsenic, cadmium, chromium, lead, mercury, nickel and zinc. Cucumber (Cucumis sativus), sorghum (Sorghum saccharatum) and cress (Lepidium sativum) seeds were used as models for other plants used in human nutrition such as cereals, rice, fruits and vegetables. The 72-h germination rate and root elongations were selected as short-term ecotoxicological endpoints in seeds exposed to single metals and mixtures. Metals were spiked onto OECD standard soils in concentrations comparable to current Italian contamination threshold concentrations for residential and commercial soils. Arsenic, chromium, mercury and nickel were the most toxic metals in our experimental conditions, particularly to cress seeds (5.172, 152 and 255.4 mg/kg as 72 h IC50 for arsenic, mercury and nickel respectively). Italian limits were acceptable for plant protection only for exposure to each metal alone but not for the mixtures containing all the metals concentrations expected by their respective legislative threshold. The effects of the mixture were class-specific: trends were comparable in dicots but different in monocots. The response induced by the mixture at high concentrations differed from that theoretically obtainable by summing the effects of the individual metals. This might be due to partial antagonism of the metals in soil or to the formation of complexes between the metals, which reduce the bioavailability of the pollutants for plants. - Graphical abstract: Metals investigated: Arsenic, Cadmium, Chromium, Lead, Mercury, Nickel and Zinc. - Highlights: • The short-term phytotoxicity of seven metals was investigated with 3 higher plants. • Italian limits for arsenic and nickel in

  15. Toxicity Assessment of Binary Metal Mixtures (Copper-Zinc) to Nitrification in Soilless Culture with the Extended Biotic Ligand Model.

    PubMed

    Liu, Aiju; Li, JinXin; Li, Menghong; Niu, Xiao Yin; Wang, Jun

    2017-02-01

    Metals are always found in the environment as mixtures rather than as solitary elements. Only a limited number of studies have developed appropriate models that incorporate bioavailability to estimate the toxicity of heavy-metal mixtures. In the present study, we explored the applicability of two extended biotic ligand model (BLM) approaches-BLM-f mix and BLM-toxicity unit (TU)-to predict and interpret mixture toxicity with the assumption that interactions between metal ions obey the BLM theory. Exposure assays of single and mixed metals were performed with inoculums of an ammonia-oxidizing bacterium SD5 isolated from soil. Nitrification of the cultures was the end point used to quantify the toxic response. The results indicated that the developed BLM-f mix approach could well estimate the single toxicity of Cu(2+) and Zn(2+) as well as their binary mixture toxicity to nitrification with >90% of toxicity variation explained. Assuming that metal ions compete with each other for binding at a single biotic ligand, the BLM-f mix approach (root-mean-square error [RMSE] = 19.66, R (2) = 0.8879) showed better predictive power than the BLM-TU approach (RMSE = 31.12, R (2) = 0.6892). The present study supports the use of the accumulation of metal ions at the biotic ligands as predictor of toxicity of single metals and metal mixtures.

  16. Exposure to Mixtures of Metals and Neurodevelopmental Outcomes: A Review

    PubMed Central

    von Stackelberg, Katherine; Guzy, Elizabeth; Chu, Tian; Henn, Birgit Claus

    2016-01-01

    Current risk assessment guidance calls for an individual chemical-by-chemical approach that fails to capture potential interactive effects of exposure to environmental mixtures in the context of genomic influences. As an exploratory analysis, we develop a systematic review of prenatal and perinatal exposure to mixtures of lead (Pb), arsenic (As), cadmium (Cd), and manganese (Mn) and nonspecific developmental outcomes in children, including reduced IQ and decreased performance on developmental tests, using an adverse outcome pathway (AOP) framework to integrate lines of evidence based on evolving guidance developed by the Organization for Economic Cooperation and Development (OECD). Toxicological evidence suggests a greater than additive effect of combined exposures to As-Pb-Cd and Mn in the presence of one or more metals. Several epidemiologic studies also suggest synergistic effects from binary combinations of Pb-As and Pb-Cd. However, monitoring data from the National Health and Nutrition Examination Survey (NHANES) reveals the majority of the U.S. population has biomarker levels below those corresponding to exposure concentrations from the epidemiologic studies. This systematic review integrates relevant and diverse data sources using an AOP framework and provides an initial application of the OECD guidance in the context of potential neurodevelopmental toxicity of several metals, recognizing the evolving nature of regulatory interpretation and acceptance. PMID:26096925

  17. Toxicity of binary mixtures of metals and pyrethroid insecticides to Daphnia magna Straus. Implications for multi-substance risks assessment.

    PubMed

    Barata, Carlos; Baird, D J; Nogueira, A J A; Soares, A M V M; Riva, M C

    2006-06-10

    Two different concepts, termed concentration addition (CA) and independent action (IA), describe general relationships between the effects of single substances and their corresponding mixtures allowing calculation of an expected mixture toxicity on the basis of known toxicities of the mixture components. Both concepts are limited to cases in which all substances in a mixture influence the same experimental endpoint, and are usually tested against a "fixed ratio design" where the mixture ratio is kept constant throughout the studies and the overall concentration of the mixture is systematically varied. With this design, interaction among toxic components across different mixture ratios and endpoints (i.e. lethal versus sublethal) is not assessed. In this study lethal and sublethal (feeding) responses of Daphnia magna individuals to single and binary combinations of similarly and dissimilarly acting chemicals including the metals (cadmium, copper) and the pyrethroid insecticides (lambda-cyhalothrin and deltamethrin) were assayed using a composite experimental design to test for interactions among toxic components across mixture effect levels, mixture ratios, lethal and sublethal toxic effects. To account for inter-experiment response variability, in each binary mixture toxicity assay the toxicity of the individual mixture constituents was also assessed. Model adequacy was then evaluated comparing the slopes and elevations of predicted versus observed mixture toxicity curves with those estimated for the individual components. Model predictive abilities changed across endpoints. The IA concept was able to predict accurately mixture toxicities of dissimilarly acting chemicals for lethal responses, whereas the CA concept did so in three out of four pairings for feeding response, irrespective of the chemical mode of action. Interaction effects across mixture effect levels, evidenced by crossing slopes, were only observed for the binary mixture Cd and Cu for lethal effects

  18. A Mixture Rasch Model with Item Response Time Components

    ERIC Educational Resources Information Center

    Meyer, J. Patrick

    2010-01-01

    An examinee faced with a test item will engage in solution behavior or rapid-guessing behavior. These qualitatively different test-taking behaviors bias parameter estimates for item response models that do not control for such behavior. A mixture Rasch model with item response time components was proposed and evaluated through application to real…

  19. Layer modeling of zinc removal from metallic mixture of waste printed circuit boards by vacuum distillation.

    PubMed

    Gao, Yujie; Li, Xingang; Ding, Hui

    2015-08-01

    A layer model was established to elucidate the mechanism of zinc removal from the metallic mixture of waste printed circuit boards by vacuum distillation. The removal process was optimized by response surface methodology, and the optimum operating conditions were the chamber pressure of 0.1Pa, heating temperature of 923K, heating time of 60.0min, particle size of 70 mesh (0.212mm) and initial mass of 5.25g. Evaporation efficiency of zinc, the response variable, was 99.79%, which indicates that the zinc can be efficiently removed. Based on the experimental results, a mathematical model, which bears on layer structure, evaporation, mass transfer and condensation, interprets the mechanism of the variable effects. Especially, in order to reveal blocking effect on the zinc removal, the Blake-Kozeny-Burke-Plummer equation was introduced into the mass transfer process. The layer model can be applied to a wider range of metal removal by vacuum distillation.

  20. Metal mixture modeling evaluation project: 3. Lessons learned and steps forward.

    PubMed

    Farley, Kevin J; Meyer, Joseph S

    2015-04-01

    A comparison of 4 metal mixture toxicity models (that were based on the biotic ligand model [BLM] and the Windermere humic aqueous model using the toxicity function [WHAM-FTOX ]) was presented in a previous paper. In the present study, a streamlined version of the 4 models was developed and applied to multiple data sets and test conditions to examine key assumptions and calibration strategies that are crucial in modeling metal mixture toxicity. Results show that 1) a single binding site on or in the organism was a useful and oftentimes sufficient framework for predicting metal toxicity; 2) a linear free energy relationship (LFER) for bidentate binding of metals and cations to the biotic ligand provided a good first estimate of binding coefficients; 3) although adjustments in metal binding coefficients or adjustments in chemical potency factors can both be used in model calibration for single-metal exposures, changing metal binding coefficients or chemical potency factors had different effects on model predictions for metal mixtures; and 4) selection of a mixture toxicity model (based on concentration addition or independent action) was important in predicting metal mixture toxicity. Moving forward, efforts should focus on reducing uncertainties in model calibration, including development of better methods to characterize metal binding to toxicologically active binding sites, conducting targeted exposure studies to advance the understanding of metal mixture toxicity, and further developing LFERs and other tools to help constrain the model calibration.

  1. Complex mixtures, complex responses: Assessing pharmaceutical mixtures using field and laboratory approaches

    USGS Publications Warehouse

    Schoenfuss, Heiko L.; Furlong, Edward T.; Phillips, Patrick J.; Scott, Tia-Marie; Kolpin, Dana W.; Cetkovic-Cvrlje, Marina; Lesteberg, Kelsey E.; Rearick, Daniel C.

    2016-01-01

    Pharmaceuticals are present in low concentrations (<100 ng/L) in most municipal wastewater effluents but may be elevated locally because of factors such as input from pharmaceutical formulation facilities. Using existing concentration data, the authors assessed pharmaceuticals in laboratory exposures of fathead minnows (Pimephales promelas) and added environmental complexity through effluent exposures. In the laboratory, larval and mature minnows were exposed to a simple opioid mixture (hydrocodone, methadone, and oxycodone), an opioid agonist (tramadol), a muscle relaxant (methocarbamol), a simple antidepressant mixture (fluoxetine, paroxetine, venlafaxine), a sleep aid (temazepam), or a complex mixture of all compounds. Larval minnow response to effluent exposure was not consistent. The 2010 exposures resulted in shorter exposed minnow larvae, whereas the larvae exposed in 2012 exhibited altered escape behavior. Mature minnows exhibited altered hepatosomatic indices, with the strongest effects in females and in mixture exposures. In addition, laboratory-exposed, mature male minnows exposed to all pharmaceuticals (except the selective serotonin reuptake inhibitor mixture) defended nest sites less rigorously than fish in the control group. Tramadol or antidepressant mixture exposure resulted in increased splenic T lymphocytes. Only male minnows exposed to whole effluent responded with increased plasma vitellogenin concentrations. Female minnows exposed to pharmaceuticals (except the opioid mixture) had larger livers, likely as a compensatory result of greater prominence of vacuoles in liver hepatocytes. The observed alteration of apical endpoints central to sustaining fish populations confirms that effluents containing waste streams from pharmaceutical formulation facilities can adversely impact fish populations but that the effects may not be temporally consistent. The present study highlights the importance of including diverse biological endpoints spanning

  2. Complex mixtures, complex responses: Assessing pharmaceutical mixtures using field and laboratory approaches.

    PubMed

    Schoenfuss, Heiko L; Furlong, Edward T; Phillips, Pat J; Scott, Tia-Marie; Kolpin, Dana W; Cetkovic-Cvrlje, Marina; Lesteberg, Kelsey E; Rearick, Daniel C

    2016-04-01

    Pharmaceuticals are present in low concentrations (<100 ng/L) in most municipal wastewater effluents but may be elevated locally because of factors such as input from pharmaceutical formulation facilities. Using existing concentration data, the authors assessed pharmaceuticals in laboratory exposures of fathead minnows (Pimephales promelas) and added environmental complexity through effluent exposures. In the laboratory, larval and mature minnows were exposed to a simple opioid mixture (hydrocodone, methadone, and oxycodone), an opioid agonist (tramadol), a muscle relaxant (methocarbamol), a simple antidepressant mixture (fluoxetine, paroxetine, venlafaxine), a sleep aid (temazepam), or a complex mixture of all compounds. Larval minnow response to effluent exposure was not consistent. The 2010 exposures resulted in shorter exposed minnow larvae, whereas the larvae exposed in 2012 exhibited altered escape behavior. Mature minnows exhibited altered hepatosomatic indices, with the strongest effects in females and in mixture exposures. In addition, laboratory-exposed, mature male minnows exposed to all pharmaceuticals (except the selective serotonin reuptake inhibitor mixture) defended nest sites less rigorously than fish in the control group. Tramadol or antidepressant mixture exposure resulted in increased splenic T lymphocytes. Only male minnows exposed to whole effluent responded with increased plasma vitellogenin concentrations. Female minnows exposed to pharmaceuticals (except the opioid mixture) had larger livers, likely as a compensatory result of greater prominence of vacuoles in liver hepatocytes. The observed alteration of apical endpoints central to sustaining fish populations confirms that effluents containing waste streams from pharmaceutical formulation facilities can adversely impact fish populations but that the effects may not be temporally consistent. The present study highlights the importance of including diverse biological endpoints spanning

  3. Acute phytotoxicity of seven metals alone and in mixture: Are Italian soil threshold concentrations suitable for plant protection?

    PubMed

    Baderna, Diego; Lomazzi, Eleonora; Pogliaghi, Alberto; Ciaccia, Gianluca; Lodi, Marco; Benfenati, Emilio

    2015-07-01

    Metals can pollute soils in both urban and rural areas with severe impacts on the health of humans, plants and animals living there. Information on metal toxicity is therefore important for ecotoxicology. This study investigated the phytotoxicity of different metals frequently found as pollutants in soils: arsenic, cadmium, chromium, lead, mercury, nickel and zinc. Cucumber (Cucumis sativus), sorghum (Sorghum saccharatum) and cress (Lepidium sativum) seeds were used as models for other plants used in human nutrition such as cereals, rice, fruits and vegetables. The 72-h germination rate and root elongations were selected as short-term ecotoxicological endpoints in seeds exposed to single metals and mixtures. Metals were spiked onto OECD standard soils in concentrations comparable to current Italian contamination threshold concentrations for residential and commercial soils. Arsenic, chromium, mercury and nickel were the most toxic metals in our experimental conditions, particularly to cress seeds (5.172, 152 and 255.4 mg/kg as 72 h IC50 for arsenic, mercury and nickel respectively). Italian limits were acceptable for plant protection only for exposure to each metal alone but not for the mixtures containing all the metals concentrations expected by their respective legislative threshold. The effects of the mixture were class-specific: trends were comparable in dicots but different in monocots. The response induced by the mixture at high concentrations differed from that theoretically obtainable by summing the effects of the individual metals. This might be due to partial antagonism of the metals in soil or to the formation of complexes between the metals, which reduce the bioavailability of the pollutants for plants.

  4. Joint toxic action of binary metal mixtures of copper, manganese and nickel to Paronychiurus kimi (Collembola).

    PubMed

    Son, Jino; Lee, Yun-Sik; Kim, Yongeun; Shin, Key-Il; Hyun, Seunghun; Cho, Kijong

    2016-10-01

    The joint toxic effects of binary metal mixtures of copper (Cu), manganese (Mn) and nickel (Ni) on reproduction of Paronhchiurus kimi (Lee) was evaluated using a toxic unit (TU) approach by judging additivity across a range of effect levels (10-90%). For all metal mixtures, the joint toxic effects of metal mixtures on reproduction of P. kimi decreased in a TU-dependent manner. The joint toxic effects of metal mixtures also changed from less than additive to more than additive at an effect level lower than or equal to 50%, while a more than additive toxic effects were apparent at higher effect levels. These results indicate that the joint toxicity of metal mixtures is substantially different from that of individual metals based on additivity. Moreover, the close relationship of toxicity to effect level suggests that it is necessary to encompass a whole range of effect levels rather than a specific effect level when judging mixture toxicity. In conclusion, the less than additive toxicity at low effect levels suggests that the additivity assumption is sufficiently conservative to warrant predicting joint toxicity of metal mixtures, which may give an additional margin of safety when setting soil quality standards for ecological risk assessment.

  5. pH-Dependent Metal Ion Toxicity Influences the Antibacterial Activity of Two Natural Mineral Mixtures

    PubMed Central

    Cunningham, Tanya M.; Koehl, Jennifer L.; Summers, Jack S.; Haydel, Shelley E.

    2010-01-01

    Background Recent studies have demonstrated that several mineral products sold for medicinal purposes demonstrate antimicrobial activity, but little is known about the physicochemical properties involved in antibacterial activity. Methodology/Principal Findings Using in vitro mineral suspension testing, we have identified two natural mineral mixtures, arbitrarily designated BY07 and CB07, with antibacterial activity against a broad-spectrum of bacterial pathogens. Mineral-derived aqueous leachates also exhibited antibacterial activity, revealing that chemical, not physical, mineral characteristics were responsible for the observed activity. The chemical properties essential for bactericidal activity against Escherichia coli were probed by testing antibacterial activity in the presence of metal chelators, the hydroxyl radical scavenger, thiourea, and varying pH levels. Chelation of the BY07 minerals with EDTA or desferrioxamine eliminated or reduced BY07 toxicity, respectively, suggesting a role of an acid-soluble metal species, particularly Fe3+ or other sequestered metal cations, in mineral toxicity. This conclusion was supported by NMR relaxation data, which indicated that BY07 and CB07 leachates contained higher concentrations of chemically accessible metal ions than leachates from non-bactericidal mineral samples. Conclusions/Significance We conclude that the acidic environment of the hydrated minerals significantly contributes to antibacterial activity by increasing the availability and toxicity of metal ions. These findings provide impetus for further investigation of the physiological effects of mineral products and their applications in complementary antibacterial therapies. PMID:20209160

  6. Evaluating the suitability of Hydrobia ulvae as a test species for sediment metal toxicity testing applying a tissue residue approach to metal mixtures in laboratory and field exposures.

    PubMed

    Campana, Olivia; Rodríguez, Antonio; Blasco, Julián

    2013-05-01

    A major weakness in evaluating the suitability of a biomonitor organism is the poor ability to predict the variability of the bioavailability of metals from measured environmental concentrations. In this study, the intertidal gastropod Hydrobia ulvae was used to evaluate its suitability as a test organism for assessing sediment metal toxicity. Toxicity tests were run with sediments spiked with copper, cadmium and zinc applied both as single metal and as a mixture to investigate toxicological interactions evaluating different lethal and sublethal effects. Dose-response relationships were constructed based both on tissue residue approach and particulate metal concentrations. Because metal-spiked sediments used in routine toxicity tests often do not exhibit the same adsorption/desorption kinetics as the natural sediments, the laboratory results were compared to 10-d bioassays conducted with natural field sediments collected from the Guadalete estuary (SW Spain). Highly significant correlations between tissue residue concentrations and particulate metal concentrations were found for all metal-spiked or field-collected and demonstrated that: (i) H. ulvae readily accumulated copper and cadmium in response to contamination and (ii) dietary uptake was determined to be the most significant route of metal exposure. The comparison of the modeled tissue residue-response curve developed from the mixture tests was in good agreement with the results from the bioassay conducted with field sediments and strongly demonstrated that H. ulvae is also a suitable test organism for assessing copper sediment toxicity. In contrast, the dose-response curve expressed as a function of total particulate metal concentrations would fail in predicting effect, erroneously assessing higher metal toxicity.

  7. Mixtures of Estrogenic Chemicals Enhance Vitellogenic Response in Sea Bass

    PubMed Central

    Correia, Ana D.; Freitas, Sandro; Scholze, Martin; Goncalves, José F.; Booij, Petra; Lamoree, Marja H.; Mañanós, Evaristo; Reis-Henriques, Maria A.

    2007-01-01

    Background The potential impact of natural and synthetic estrogens on aquatic ecosystems has attracted considerable attention because it is currently accepted that their joint effects are more severe when they are present in mixtures. Although it is well-known that they occur as mixtures in the marine environment, there is little information about the combined effects of estrogenic chemicals on marine biota. Objective In 14-day tests with juvenile sea bass, we analyzed singly and in combination the estrogenic activity of estradiol (E2), ethynylestradiol (EE2), and bisphenol A (BPA) using vitellogenin induction as an end point. Methods Fish were exposed to each compound, and on the basis of these concentration–response data, we predicted mixture effects by applying the model of concentration addition. The mixtures were tested using a fixed-ratio design, and the resulting mixture effects were compared to the predictions. Results EE2 was the most potent steroid, with an EC50 (median effective concentration) of 0.029 μg/L, 3.6 times more potent than E2 (EC50 = 0.104 μg/L); BPA was the least potent chemical, with an EC50 of 77.94 μg/L. The comparative assessment yielded a good agreement between observed and predicted mixture effects. Conclusions This study demonstrates the potential hazard of these compounds to seawater life by their ability to act together in an additive manner. It provides evidence that concentration addition can be used as a predictive tool for assessing the combined effects of estrogenic chemicals in marine ecosystems. PMID:18174959

  8. Low concentrations of metal mixture exposures have adverse effects on selected biomarkers of Xenopus laevis tadpoles.

    PubMed

    Yologlu, Ertan; Ozmen, Murat

    2015-11-01

    Polluted ecosystems may contain mixtures of metals, such that the combinations of metals, even in low concentrations, may cause adverse effects. In the present study, we focused on toxic effects of mixtures of selected metals, the LC50 values, and also their safety limit in aquatic systems imposed by the European legislation using a model organism. Xenopus laevis tadpoles were used as test organisms. They were exposed to metals or their combinations due to 96-h LC50 values. Glutathione S-transferase (GST), glutathione reductase (GR), acetylcholinesterase (AChE), carboxylesterase (CaE), glutathione peroxidase (GPx), and catalase (CAT) levels were evaluated. Metallothionein concentrations were also determined. The LC50s for Cd, Pb, and Cu were calculated as 5.81mg AI/L, 123.05mg AI/L, and 0.85mg AI/L, respectively. Low lethality ratios were observed with unary exposure of each metal in lower concentrations. Double or triple combinations of LC50 and LC50/2 concentrations caused 100% lethality with Cd+Cu and Pb+Cd+Cu mixtures, while the Pb+Cu mixture also caused high lethal ratios. The selected enzyme activities were significantly affected by metals or mixtures, and dose-related effects were determined. The metallothionein levels generally increased as related to concentration in unary metals and mixtures. Acceptable limit values of unary metals and mixtures did not significantly change metallothionein levels. The results suggest that oxidative stress-related mechanisms are involved in the toxicity induced by selected metals with combinations of very low concentrations.

  9. Cyclic electrowinning/precipitation (CEP) system for the removal of heavy metal mixtures from aqueous solutions

    PubMed Central

    Grimshaw, Pengpeng; Calo, Joseph M.; Hradil, George

    2011-01-01

    The description and operation of a novel cyclic electrowinning/precipitation (CEP) system for the simultaneous removal of mixtures of heavy metals from aqueous solutions are presented. CEP combines the advantages of electrowinning in a spouted particulate electrode (SPE) with that of chemical precipitation and redissolution, to remove heavy metals at low concentrations as solid metal deposits on particulate cathode particles without exporting toxic metal precipitate sludges from the process. The overall result is very large volume reduction of the heavy metal contaminants as a solid metal deposit on particles that can either be safely discarded as such, or further processed to recover particular metals. The performance of this system is demonstrated with data on the removal of mixtures of copper, nickel, and cadmium from aqueous solutions. PMID:22102792

  10. Shock compression response of Ti+B reactive powder mixtures

    NASA Astrophysics Data System (ADS)

    Gonzales, M.; Gurumurthy, A.; Kennedy, G. B.; Gokhale, A. M.; Thadhani, N. N.

    2014-05-01

    The shock compression response of Ti+2B (1:2 Ti:B stoichiometric ratio) reactive powder mixtures at ~50% theoretical material density (TMD) is investigated for shock pressures up to 5 GPa to investigate the possible shock-induced chemical reactivity of this highly exothermic mixture. The shock adiabat is produced from instrumented parallel-plate gas-gun impact experiments on encapsulated powders using poly-vinylidene fluoride (PVDF) stress gauges to measure the input and propagated stresses and wave speed in the powder. The shock compression regime is probed from crush-up to full density and onward to assess the potential onset of a shock-induced chemical reaction event in the powder mixture. A series of two-dimensional continuum meso-scale simulations on validated simulated microstructures are performed to predict the shock compression response and identify the meso-scale mechanics that are essential for reaction. The suitability of the synthetic microstructural representations is evaluated by comparing the experimental and predicted pressure traces.

  11. Shock compression response of Ti+B reactive powder mixtures

    NASA Astrophysics Data System (ADS)

    Gonzales, Manny; Gurumurthy, Ashok; Kennedy, Gregory; Gokhale, Arun; Thadhani, Naresh

    2013-06-01

    The shock compression response of Ti+2B (1:2 Ti:B stoichiometric ratio) reactive powder mixtures at ~50% theoretical material density (TMD) is investigated for shock pressures up to 5 GPa to investigate the possible shock-induced chemical reactivity of this highly exothermic mixture. The shock adiabat is produced from instrumented parallel-plate gas-gun impact experiments on encapsulated powders using poly-vinylidene fluoride (PVDF) stress gauges to measure the input and propagated stress and wave speed in the powder. The shock compression regime is probed from crush-up to full density and onward to assess the potential onset of a shock-induced chemical reaction event in the powder mixture. A series of two-dimensional continuum meso-scale simulations on real and simulated microstructures are performed to predict the shock compression response and identify the meso-scale mechanics that is essential for the so-called ``ballotechnic'' reaction. These meso-scale mechanics are investigated through stereological evolution metrics that track particle interface evolution and their respective field variables. The suitability of the synthetic microstructural representations is evaluated by comparing the experimental and predicted pressure traces. We gratefully acknowledge support and funding from DTRA through Grant No. HDTRA1-10-1-0038 and the National Defense Science and Engineering Graduate (NDSEG) Fellowship through the High Performance Computing and Modernization Office (HPCMO).

  12. Metal silicate mixtures - Spectral properties and applications to asteroid taxonomy

    NASA Technical Reports Server (NTRS)

    Cloutis, Edward A.; Smith, Dorian G. W.; Lambert, Richard St. J.; Gaffey, Michael J.

    1990-01-01

    The reflectance spectra of combinations of olivine, orthopyroxene, and iron meteorite metal are experimentally studied, and the obtained variations in spectral properties are used to constrain the physical and chemical properties of the assemblages. The presence of metal most noticeably affects band area ratios, peak-to-peak and peak-to-minimum reflectance ratios, and band widths. Band width and band areas are useful for determining metal abundance in olivine and metal and orthopyroxene and metal assemblages, respectively. Mafic silicate grain size variations are best determined using band depth criteria. Band centers are most useful for determining mafic silicate composition. An application of these parameters to the S-class asteroid Flora is presented.

  13. Effect of a metal mixture on cadmium accumulation in transplanted macrophytes

    SciTech Connect

    Stewart, A.R.

    1995-12-31

    The effect of a metal mixture (Cu, Zn, Pb and Ni) on Cd accumulation in the freshwater macrophyte Eriocaulon septangulare, was examined in a mesocosm experiment at the Experimental Lakes Area, northwestern, Ontario. Cd was added alone to treatment 1 and together with the metal mixture (at three increasing levels) to treatments 2, 3, and 4. Each treatment was represented by two mesocosms. Macrophytes were collected from the littoral region of lake 104, transported to nearby Roddy lake, and planted in plastic gardening trays containing exposed limnocorral sediments. The trays were lowered to the bottom of the limnocorrals and after 40 and 80 days the macrophytes were analyzed for metal content. The transplanted macrophytes accumulated Cd in both their shoots and roots. On day 40, Cd levels in the shoots of macrophytes exposed to the highest level of metal mixture were lower than in shoots from macrophytes exposed to cadmium alone, Between day 40 to day 80 Cd was lost from the shoots of macrophytes in all treatments. Cd levels in roots were higher in macrophytes exposed to the metal mixture on day 40 and significantly higher on day 80 compared to exposure to Cd alone. Elevated Cd levels in the roots of macrophytes exposed to the metal mixture reflected higher Cd levels in the water. The macrophyte Eriocaulon shows promise in environmental monitoring where test species are transplanted.

  14. A review of toxicity and mechanisms of individual and mixtures of heavy metals in the environment.

    PubMed

    Wu, Xiangyang; Cobbina, Samuel J; Mao, Guanghua; Xu, Hai; Zhang, Zhen; Yang, Liuqing

    2016-05-01

    The rational for the study was to review the literature on the toxicity and corresponding mechanisms associated with lead (Pb), mercury (Hg), cadmium (Cd), and arsenic (As), individually and as mixtures, in the environment. Heavy metals are ubiquitous and generally persist in the environment, enabling them to biomagnify in the food chain. Living systems most often interact with a cocktail of heavy metals in the environment. Heavy metal exposure to biological systems may lead to oxidation stress which may induce DNA damage, protein modification, lipid peroxidation, and others. In this review, the major mechanism associated with toxicities of individual metals was the generation of reactive oxygen species (ROS). Additionally, toxicities were expressed through depletion of glutathione and bonding to sulfhydryl groups of proteins. Interestingly, a metal like Pb becomes toxic to organisms through the depletion of antioxidants while Cd indirectly generates ROS by its ability to replace iron and copper. ROS generated through exposure to arsenic were associated with many modes of action, and heavy metal mixtures were found to have varied effects on organisms. Many models based on concentration addition (CA) and independent action (IA) have been introduced to help predict toxicities and mechanisms associated with metal mixtures. An integrated model which combines CA and IA was further proposed for evaluating toxicities of non-interactive mixtures. In cases where there are molecular interactions, the toxicogenomic approach was used to predict toxicities. The high-throughput toxicogenomics combines studies in genetics, genome-scale expression, cell and tissue expression, metabolite profiling, and bioinformatics.

  15. Lead, Arsenic, and Manganese Metal Mixture Exposures: Focus on Biomarkers of Effect.

    PubMed

    Andrade, V M; Mateus, M L; Batoréu, M C; Aschner, M; Marreilha dos Santos, A P

    2015-07-01

    The increasing exposure of human populations to excessive levels of metals continues to represent a matter of public health concern. Several biomarkers have been studied and proposed for the detection of adverse health effects induced by lead (Pb), arsenic (As), and manganese (Mn); however, these studies have relied on exposures to each single metal, which fails to replicate real-life exposure scenarios. These three metals are commonly detected in different environmental, occupational, and food contexts and they share common neurotoxic effects, which are progressive and once clinically apparent may be irreversible. Thus, chronic exposure to low levels of a mixture of these metals may represent an additive risk of toxicity. Building upon their shared mechanisms of toxicity, such as oxidative stress, interference with neurotransmitters, and effects on the hematopoietic system, we address putative biomarkers, which may assist in assessing the onset of neurological diseases associated with exposure to this metal mixture.

  16. Lead, arsenic and manganese metal mixture exposures: focus on biomarkers of effect

    PubMed Central

    Andrade, VL; Mateus, ML; Batoréu, MC; Aschner, M; Marreilha dos Santos, AP

    2015-01-01

    Summary The increasing exposure of human populations to excessive levels of metals continues to represent a matter of public health concern. Several biomarkers have been studied and proposed for the detection of adverse health effects induced by lead (Pb), arsenic (As) and manganese (Mn); however, these studies have relied on exposures to each single metal, which fails to replicate real-life exposure scenarios. These 3 metals are commonly detected in different environmental, occupational and food contexts and they share common neurotoxic effects, which are progressive and once clinically apparent may be irreversible. Thus, chronic exposure to low levels of a mixture of these metals represents an additive risk of toxicity. Building upon their shared mechanisms of toxicity, such as oxidative stress, interference with neurotransmitters and effects on hematopoietic system, we address putative biomarkers, which may be assist in assessing onset of neurological diseases associated with exposure to this metal mixture. PMID:25693681

  17. Ecotoxicity of mixtures of metals to the zebra mussel Dreissena polymorpha

    SciTech Connect

    Kraak, M.H.S.; Lavy, D.; Schoon, H.; Toussaint, M.; Peeters, W.H.M.; Straalen, N.M. . Dept. of Aquatic Ecotoxicology)

    1994-01-01

    The effects of equitoxic mixtures of CuCl[sub 2], ZnCl[sub 2], and CdCl[sub 2] on the filtration rate of the freshwater mussel Dreissena polymorpha were determined. The amounts of added metals were expressed in toxic units, and a range of toxic units was tested. Cu + Zn was less than concentration additive, Zn + Cd was concentration additive, and Cu + Cd was more than concentration additive in their effects on the filtration rate of Dreissena polymorpha. An equitoxic mixture of all three metals was concentration additive. The effects of a mixture could not be predicted from the effects of the single metals. The concentrations at which Cu and Cd contributed to the toxicity of a mixture of Cu + Zn + Cd were at or below the NOECs for these metals, determined in single-metal toxicity tests. At low but elevated Cu and Zn concentrations in water, no accumulation of these metals in the mussels took place; Cd, on the contrary, was accumulated at all Cd concentrations in the water.

  18. Toxic effect of metal cation binary mixtures to the seaweed Gracilaria domingensis (Gracilariales, Rhodophyta).

    PubMed

    Mendes, Luiz Fernando; Stevani, Cassius Vinicius; Zambotti-Villela, Leonardo; Yokoya, Nair Sumie; Colepicolo, Pio

    2014-01-01

    The macroalga Gracilaria domingensis is an important resource for the food, pharmaceutical, cosmetic, and biotechnology industries. G. domingensis is at a part of the food web foundation, providing nutrients and microelements to upper levels. As seaweed storage metals in the vacuoles, they are considered the main vectors to magnify these toxic elements. This work describes the evaluation of the toxicity of binary mixtures of available metal cations based on the growth rates of G. domingensis over a 48-h exposure. The interactive effects of each binary mixture were determined using a toxic unit (TU) concept that was the sum of the relative contribution of each toxicant and calculated using the ratio between the toxicant concentration and its endpoint. Mixtures of Cd(II)/Cu(II) and Zn(II)/Ca(II) demonstrated to be additive; Cu(II)/Zn(II), Cu(II)/Mg(II), Cu(II)/Ca(II), Zn(II)/Mg(II), and Ca(II)/Mg(II) mixtures were synergistic, and all interactions studied with Cd(II) were antagonistic. Hypotheses that explain the toxicity of binary mixtures at the molecular level are also suggested. These results represent the first effort to characterize the combined effect of available metal cations, based on the TU concept on seaweed in a total controlled medium. The results presented here are invaluable to the understanding of seaweed metal cation toxicity in the marine environment, the mechanism of toxicity action and how the tolerance of the organism.

  19. Dose-response curve estimation: a semiparametric mixture approach.

    PubMed

    Yuan, Ying; Yin, Guosheng

    2011-12-01

    In the estimation of a dose-response curve, parametric models are straightforward and efficient but subject to model misspecifications; nonparametric methods are robust but less efficient. As a compromise, we propose a semiparametric approach that combines the advantages of parametric and nonparametric curve estimates. In a mixture form, our estimator takes a weighted average of the parametric and nonparametric curve estimates, in which a higher weight is assigned to the estimate with a better model fit. When the parametric model assumption holds, the semiparametric curve estimate converges to the parametric estimate and thus achieves high efficiency; when the parametric model is misspecified, the semiparametric estimate converges to the nonparametric estimate and remains consistent. We also consider an adaptive weighting scheme to allow the weight to vary according to the local fit of the models. We conduct extensive simulation studies to investigate the performance of the proposed methods and illustrate them with two real examples.

  20. Predicting the response of olfactory sensory neurons to odor mixtures from single odor response

    PubMed Central

    Marasco, Addolorata; De Paris, Alessandro; Migliore, Michele

    2016-01-01

    The response of olfactory receptor neurons to odor mixtures is not well understood. Here, using experimental constraints, we investigate the mathematical structure of the odor response space and its consequences. The analysis suggests that the odor response space is 3-dimensional, and predicts that the dose-response curve of an odor receptor can be obtained, in most cases, from three primary components with specific properties. This opens the way to an objective procedure to obtain specific olfactory receptor responses by manipulating mixtures in a mathematically predictable manner. This result is general and applies, independently of the number of odor components, to any olfactory sensory neuron type with a response curve that can be represented as a sigmoidal function of the odor concentration. PMID:27053070

  1. Predicting the response of olfactory sensory neurons to odor mixtures from single odor response

    NASA Astrophysics Data System (ADS)

    Marasco, Addolorata; de Paris, Alessandro; Migliore, Michele

    2016-04-01

    The response of olfactory receptor neurons to odor mixtures is not well understood. Here, using experimental constraints, we investigate the mathematical structure of the odor response space and its consequences. The analysis suggests that the odor response space is 3-dimensional, and predicts that the dose-response curve of an odor receptor can be obtained, in most cases, from three primary components with specific properties. This opens the way to an objective procedure to obtain specific olfactory receptor responses by manipulating mixtures in a mathematically predictable manner. This result is general and applies, independently of the number of odor components, to any olfactory sensory neuron type with a response curve that can be represented as a sigmoidal function of the odor concentration.

  2. Mixtures of herbicides and metals affect the redox system of honey bees.

    PubMed

    Jumarie, Catherine; Aras, Philippe; Boily, Monique

    2017-02-01

    The increasing loss of bee colonies in many countries has prompted a surge of studies on the factors affecting bee health. In North America, main crops such as maize and soybean are cultivated with extensive use of pesticides that may affect non-target organisms such as bees. Also, biosolids, used as a soil amendment, represent additional sources of metals in agroecosystems; however, there is no information about how these metals could affect the bees. In previous studies we investigated the effects of environmentally relevant doses of herbicides and metals, each individually, on caged honey bees. The present study aimed at investigating the effects of mixtures of herbicides (glyphosate and atrazine) and metals (cadmium and iron), as these mixtures represent more realistic exposure conditions. Levels of metal, vitamin E, carotenoids, retinaldehyde, at-retinol, retinoic acid isomers (9-cis RA, 13-cis RA, at-RA) and the metabolites 13-cis-4-oxo-RA and at-4-oxo-RA were measured in bees fed for 10 days with contaminated syrup. Mixtures of herbicides and cadmium that did not affect bee viability, lowered bee α- and β-carotenoid contents and increased 9-cis-RA as well as 13-cis-4-oxo-RA without modifying the levels of at-retinol. Bee treatment with either glyphosate, a combination of atrazine and cadmium, or mixtures of herbicides promoted lipid peroxidation. Iron was bioconcentrated in bees and led to high levels of lipid peroxidation. Metals also decreased zeaxanthin bee contents. These results show that mixtures of atrazine, glyphosate, cadmium and iron may affect different reactions occurring in the metabolic pathway of vitamin A in the honey bee.

  3. Mechanical effects during pulsed laser and metals interaction in glycerol-water mixtures

    NASA Astrophysics Data System (ADS)

    Liu, Xiu Mei; He, Jie; Lu, Jian; Ni, Xiao Wu

    2008-03-01

    In order to study the effect of viscosity on the mechanical effects during laser-metal interaction, the transient forces loading on a metal plate in various glycerol-water mixtures are investigated by a fiber-optic diagnostic technique based on optical beam deflection (OBD). The experimental results show that a target in glycerol mixtures is impacted in turn by laser-plasma ablation force and high-speed liquid-jet impulse induced by bubbles collapse in the vicinity of a solid boundary. The amplitudes of the two forces decrease monotonously with less laser energy. Furthermore, strong differences of mechanical effects are observed in the glycerol mixtures and water. Viscosity has the effect of dampening mechanical energy. And increased viscosity is seen to decrease the amplitudes of the two forces but increase bubble life-time.

  4. Differences in the accumulation and tissue distribution of Pb, Cd, and Cu in Mediterranean mussels (Mytilus galloprovincialis) exposed to single, binary, and ternary metal mixtures.

    PubMed

    García-Navarro, José A; Franco, Lorena; Romero, Diego

    2017-01-12

    Heavy metals often accumulate in complex mixtures in the environment and are currently a source of concern in many marine ecosystems. Pb, Cd, and Cu are regarded as priority hazardous metals due to their great persistence, bioaccumulation, and toxicity. The aim of the present study was to investigate the tissue accumulation and distribution of these heavy metals in Mediterranean mussels (Mytilus galloprovincialis) exposed to binary and ternary mixtures of metals as opposed to only single exposures. Heavy metal concentrations in the digestive gland, gills, and the other soft tissues were determined by inductively coupled plasma optical emission spectrometry (ICP-OES), and the distribution of each metal was analyzed according to compartments. The concentrations of Pb, Cd, and Cu increased significantly in the group exposed to the ternary mixture; however, there was no common response pattern to exposure in single and binary mixtures. Above all, the metals concentrated in the digestive gland, although the percentages of each element varied between compartments and varied between tissues according to the treatment.

  5. Development and validation of a metal mixture bioavailability model (MMBM) to predict chronic toxicity of Ni-Zn-Pb mixtures to Ceriodaphnia dubia.

    PubMed

    Nys, Charlotte; Janssen, Colin R; De Schamphelaere, Karel A C

    2017-01-01

    Recently, several bioavailability-based models have been shown to predict acute metal mixture toxicity with reasonable accuracy. However, the application of such models to chronic mixture toxicity is less well established. Therefore, we developed in the present study a chronic metal mixture bioavailability model (MMBM) by combining the existing chronic daphnid bioavailability models for Ni, Zn, and Pb with the independent action (IA) model, assuming strict non-interaction between the metals for binding at the metal-specific biotic ligand sites. To evaluate the predictive capacity of the MMBM, chronic (7d) reproductive toxicity of Ni-Zn-Pb mixtures to Ceriodaphnia dubia was investigated in four different natural waters (pH range: 7-8; Ca range: 1-2 mM; Dissolved Organic Carbon range: 5-12 mg/L). In each water, mixture toxicity was investigated at equitoxic metal concentration ratios as well as at environmental (i.e. realistic) metal concentration ratios. Statistical analysis of mixture effects revealed that observed interactive effects depended on the metal concentration ratio investigated when evaluated relative to the concentration addition (CA) model, but not when evaluated relative to the IA model. This indicates that interactive effects observed in an equitoxic experimental design cannot always be simply extrapolated to environmentally realistic exposure situations. Generally, the IA model predicted Ni-Zn-Pb mixture toxicity more accurately than the CA model. Overall, the MMBM predicted Ni-Zn-Pb mixture toxicity (expressed as % reproductive inhibition relative to a control) in 85% of the treatments with less than 20% error. Moreover, the MMBM predicted chronic toxicity of the ternary Ni-Zn-Pb mixture at least equally accurately as the toxicity of the individual metal treatments (RMSEMix = 16; RMSEZn only = 18; RMSENi only = 17; RMSEPb only = 23). Based on the present study, we believe MMBMs can be a promising tool to account for the effects of water

  6. Toxicity of binary mixtures of metal oxide nanoparticles to Nitrosomonas europaea.

    PubMed

    Yu, Ran; Wu, Junkang; Liu, Meiting; Zhu, Guangcan; Chen, Lianghui; Chang, Yan; Lu, Huijie

    2016-06-01

    Although the widely used metal oxide nanoparticles (NPs) titanium dioxide NPs (n-TiO2), cerium dioxide NPs (n-CeO2), and zinc oxide NPs (n-ZnO) have been well known for their potential cytotoxicities to environmental organisms, their combined effects have seldom been investigated. In this study, the short-term binary effect of n-CeO2 and n-TiO2 or n-ZnO on a model ammonia oxidizing bacterium, Nitrosomonas europaea were evaluated based on the examinations of cells' physiological, metabolic, and transcriptional responses. The addition of n-TiO2 mitigated the negative effect of more toxic n-CeO2 and the binary toxicity (antagonistic toxicity) of n-TiO2 and n-CeO2 was generally lower than the single NPs induced one. While the n-CeO2/n-ZnO mixture exerted higher cytotoxicity (synergistic cytotoxicity) than that from single NPs. The increased addition of the less toxic n-CeO2 exaggerated the binary toxicity of n-CeO2/n-ZnO mixture although the solubility of n-ZnO was not significantly affected, which excluded the contribution of the dissolved Zn ions to the enhancement of the combined cytotoxicity. The cell membrane disturbances and NP internalizations were detected for all the NP impacted cultures and the electrostatic interactions among the two distinct NPs and the cells were expected to play a key role in mediating their direct contacts and the eventual binary nanotoxicity to the cells.

  7. NOx, FINE PARTICLE AND TOXIC METAL EMISSIONS FROM THE COMBUSTION OF SEWAGE SLUDGE/COAL MIXTURES: A SYSTEMATIC ASSESSMENT

    SciTech Connect

    Jost O.L. Wendt

    2001-01-31

    This research project focuses on pollutants from the combustion of mixtures of dried municipal sewage sludge (MSS) and coal. The objective is to determine the relationship between (1) fraction sludge in the sludge/coal mixture, and (2) combustion conditions on (a) NOx concentrations in the exhaust, (b) the size segregated fine and ultra-fine particle composition in the exhaust, and (c) the partitioning of toxic metals between vapor and condenses phases, within the process. To this end we shall use an existing 17kW downflow laboratory combustor, available with coal and sludge feed capabilities. The proposed study will be conducted in concert with an existing ongoing research on toxic metal partitioning mechanisms for very well characterized pulverized coals alone. Both high NOx and low NOx combustion conditions will be investigated (unstaged and staged combustion). The proposed work uses existing analytical and experimental facilities and draws on 20 years of research on NO{sub x} and fine particles that has been funded by DOE in this laboratory. Four barrels of dried sewage sludge are currently in the laboratory. Insofar as possible pertinent mechanisms will be elucidated. Tradeoffs between CO{sub 2} control, NO{sub x} control, and inorganic fine particle and toxic metal emissions will be determined. For the First Quarter of this three year project work has centered around recruiting a graduate student to take responsibility for execution of portions of the research, and modifying the furnace and supporting equipment to allow the combustion of coal/MMS mixtures. We have readied the analytical panel for measuring NO{sub x} and other gaseous pollutants. We expect initial experiments for data gathering for coal/MSS mixtures to commence in the next Quarter.

  8. Optimization of composite flour biscuits by mixture response surface methodology.

    PubMed

    Okpala, Laura C; Okoli, Eric C

    2013-08-01

    Biscuits were produced from blends of pigeon pea, sorghum and cocoyam flours. The study was carried out using mixture response surface methodology as the optimization technique. Using the simplex centroid design, 10 formulations were obtained. Protein and sensory quality of the biscuits were analyzed. The sensory attributes studied were appearance, taste, texture, crispness and general acceptability, while the protein quality indices were biological value and net protein utilization. The results showed that while the addition of pigeon pea improved the protein quality, its addition resulted in reduced sensory ratings for all the sensory attributes with the exception of appearance. Some of the biscuits had sensory ratings, which were not significantly different (p > 0.05) from biscuits made with wheat. Rat feeding experiments indicated that the biological value and net protein utilization values obtained for most of the biscuits were above minimum recommended values. Optimization suggested biscuits containing 75.30% sorghum, 0% pigeon pea and 24.70% cocoyam flours as the best proportion of these components. This sample received good scores for the sensory attributes.

  9. Decomposition of polychlorinated biphenyls in soil with a dispersion mixture of metallic calcium and calcium oxide.

    PubMed

    Mitoma, Yoshiharu; Mallampati, Srinivasa Reddy; Miyata, Hideaki; Kakeda, Mitsunori

    2013-02-01

    This study describes the decomposition of polychlorinated biphenyls (PCBs) in soil with dispersion mixtures of metallic calcium (Ca) and calcium oxide (CaO) at different temperatures. In these experiments, naturally moisturized and contaminated soil (1.0 g [31 ppm PCBs]), CaO (dried 2.0 wt%), and metallic Ca (0.01 g [0.25 mmol]) were introduced into a stainless steel pressure reactor under 0.1 MPa N(2) gas. The mixtures were stirred magnetically and heated at 260, 280, and 300 °C, respectively. Soil treatment with metallic Ca and CaO under various temperature conditions is extremely effective for degrading existing PCBs. Decomposition resulted from dechlorination (DC). Initial moisture in soil acted as a hydrogen source during stirring. Soil moisture can be beneficial for hydrodechlorination in the presence of metallic Ca and CaO. Furthermore, metallic Ca and CaO can greatly increase the number of collisions and mutual refinement. Treatment at 260, 280, and 300 °C combined with metallic Ca and CaO is effective for the decomposition (approximately 95 % DC) of PCBs in soil under natural moisture conditions.

  10. Nonlocal optical response in metallic nanostructures.

    PubMed

    Raza, Søren; Bozhevolnyi, Sergey I; Wubs, Martijn; Asger Mortensen, N

    2015-05-13

    This review provides a broad overview of the studies and effects of nonlocal response in metallic nanostructures. In particular, we thoroughly present the nonlocal hydrodynamic model and the recently introduced generalized nonlocal optical response (GNOR) model. The influence of nonlocal response on plasmonic excitations is studied in key metallic geometries, such as spheres and dimers, and we derive new consequences due to the GNOR model. Finally, we propose several trajectories for future work on nonlocal response, including experimental setups that may unveil further effects of nonlocal response.

  11. Mechanical mixtures of metal oxides and phosphorus pentoxide as novel precursors for the synthesis of transition-metal phosphides.

    PubMed

    Guo, Lijuan; Zhao, Yu; Yao, Zhiwei

    2016-01-21

    This study presents a new type of precursor, mechanical mixtures of metal oxides (MOs) and phosphorus pentoxide (P2O5) are used to synthesize Ni2P, Co2P and MoP phosphides by the H2 reduction method. In addition, this is first report of common solid-state P2O5 being used as a P source for the synthesis of metal phosphides. The traditional precursors are usually prepared via a complicated preparation procedure involving dissolution, drying and calcination steps. However, these novel MOs/P2O5 precursors can be obtained only by simple mechanical mixing of the starting materials. Furthermore, unlike the direct transformation from amorphous phases to phosphides, various specific intermediates were involved in the transformation from MOs/P2O5 to phosphides. It is worthy to note that the dispersions of Ni2P, Co2P and MoP obtained from MOs/P2O5 precursors were superior to those of the corresponding phosphides prepared from the abovementioned traditional precursors. It is suggested that the morphology of the as-prepared metal phosphides might be inherited from the corresponding MOs. Based on the results of XRD, XPS, SEM and TEM, the formation pathway of phosphides can be defined as MOs/P2O5 precursors → complex intermediates (metals, metal phosphates and metal oxide-phosphates) → metal phosphides.

  12. Beat Cepheids as Probes of Stellar and Galactic Metallicity. II. Opacities with the AGS Mixture

    NASA Astrophysics Data System (ADS)

    Buchler, J. Robert

    2008-06-01

    It is well known that the mere location of a beat Cepheid model in a period ratio versus period diagram (Petersen diagram) puts constraints on its metallicity Z. But these bounds are sensitive to the mixture of elements that are lumped into the parameter Z. In this short paper we update the previous results that were based on the Grevesse-Noels solar mixture to the recent, revised Asplund, Grevesse, & Sauval (AGS) solar mixture. We also examine the effect of the envelope depth on the accuracy of the computed pulsation periods. We find that for low-period Cepheids with high Z the customary approximation of envelope pulsation breaks down. It is necessary to compute stellar models that extend to the center and to include burning and composition inhomogeneities in the modeling. Fortunately, however, most beat Cepheids that have been observed so far seem to avoid that regime.

  13. Heavy metal balances of an Italian soil as affected by sewage sludge and Bordeaux mixture applications

    SciTech Connect

    Moolenaar, S.W.; Beltrami, P.

    1998-07-01

    Applications of sewage sludge and Bordeaux mixture (Bm) (a mixture of copper sulfate and lime) add heavy metals to the soil. At an experimental farm in the Cremona district (Italy), the authors measured current heavy metal contents in soil and their removal via harvested products. They also measured heavy metal adsorption by soil from this farm. With these data, projections were made of the long-term development of heavy metal (Cd, Cu, and Zn) contents in soil, crop removal, and leaching at different application rates of sewage sludge and Bm. These projections were compared with existing quality standards of the European Union (EU) and Italy with regard to soil and groundwater. The calculations reveal that the permitted annual application rates of sewage sludge and Bm are likely to result in exceedance of groundwater and soil standards. Sewage sludge applications, complying with the Italian legal limits, may pose problems for Cd, Cu, and Zn within 30, 70, and 100 yr, respectively. Furthermore, severe Cu pollution of integrated and especially organic (Bm only) vineyards is unavoidable with the currently allowed application rates of Bm. The results suggest that the current Italian soil protection policy as well as the EU policy are not conducive of a sustainable heavy metal management in agroecosystems.

  14. Electrostatic separator for micronized mixtures of metals and plastics originating from waste electric and electronic equipment

    NASA Astrophysics Data System (ADS)

    Messal, Sara; Corondan, Razvan; Chetan, Ionut; Ouiddir, Rabah; Medles, Karim; Dascalescu, Lucian

    2015-10-01

    In spite of their extensive use for processing mixtures of granules exceeding 1 mm in size, very few industrial electrostatic separators are capable of handling micronized metals and plastics originating from waste electric and electronic equipment. The aim of the present work is to validate the possibility of using a novel belt-type electrostatic separator for the selective sorting of such particulate mixtures, the dimensions of which are in the order of 0.1 mm. In this type of separator, the metal particles get charged by electrostatic induction in contact with the grounded metal belt electrode, while the plastics remain uncharged in the electric field and are collected separately. The experiments are performed with 2-g samples of a mixture composed in equal proportions (50% - 50%) of Aluminium and Acrylonitrile Butadiene Styrene (ABS) particles of average diameter ranging between 125 μm and 250 μm. They enabled the evaluation of the effects and the interaction of two control variables of the process: the angle of inclination of the roll-type electrode and the high voltage applied to it.

  15. A NONADDITITIVE TUMOR RESPONSE TO A MIXTURE OF DISINFECTION BY-PRODUCTS

    EPA Science Inventory

    Current default risk assessments for chemical mixtures assume additivity of carcinogenic effects, but this may not be consistent with the actual biological response. We used a rodent model of hereditary renal cancer to investigate the carcinogenic response of a mixture of drinkin...

  16. EVALUATING QUANTITATIVE FORMULAS FOR DOSE-RESPONSE ASSESSMENT OF CHEMICAL MIXTURES

    EPA Science Inventory

    Risk assessment formulas are often distinguished from dose-response models by being rough but necessary. The evaluation of these rough formulas is described here, using the example of mixture risk assessment. Two conditions make the dose-response part of mixture risk assessment d...

  17. An NCME Instructional Module on Latent DIF Analysis Using Mixture Item Response Models

    ERIC Educational Resources Information Center

    Cho, Sun-Joo; Suh, Youngsuk; Lee, Woo-yeol

    2016-01-01

    The purpose of this ITEMS module is to provide an introduction to differential item functioning (DIF) analysis using mixture item response models. The mixture item response models for DIF analysis involve comparing item profiles across latent groups, instead of manifest groups. First, an overview of DIF analysis based on latent groups, called…

  18. Olivine-metal mixtures: Spectral reflectance properties and application to asteroid reflectance spectra

    NASA Astrophysics Data System (ADS)

    Cloutis, Edward A.; Sanchez, Juan A.; Reddy, Vishnu; Gaffey, Michael J.; Binzel, Richard P.; Burbine, Thomas H.; Hardersen, Paul S.; Hiroi, Takahiro; Lucey, Paul G.; Sunshine, Jessica M.; Tait, Kimberly T.

    2015-05-01

    Olivine-rich asteroids appear to be common in the main asteroid belt as well as present in the near-Earth asteroid population. There are a number of meteorite classes that are dominated by olivine ± metal. To determine whether relationships exist between these asteroids and meteorites, we spectrally characterized a number of olivine + meteoritic metal powder intimate and areal mixtures, pallasite slabs, and olivine powders on a metal slab. Our goal is to understand the spectral characteristics of olivine + metal assemblages and develop spectral metrics that can be used to analyze reflectance spectra of olivine-dominated asteroids. We found that the major olivine absorption band in the 1 μm region is resolvable in intimate mixtures for metal abundances as high as ∼90 wt.%. The wavelength position of the 1 μm region olivine absorption band center is sensitive to Fa content but insensitive to other variables. However, the band minimum position moves to shorter wavelengths with increasing metal abundance due to changes in spectral slope. The full width at half maximum (FWHM) of this band and reflectance at 1.8 μm are both most sensitive to olivine Fa content, metal abundance, and grain size, and much less to the presence of nanophase iron that reddens spectra. Reflectance at 0.56 μm and the 1.8/0.56 μm reflectance ratio are sensitive to these same parameters as well as to nanophase iron-associated spectral reddening. The wavelength position of the local reflectance maximum in the 0.7 μm region moves to longer wavelengths with increasing metal abundance and is most useful for constraining metal abundance in high metal-content mixtures. Pallasite slab spectra differ in a number of respects from powdered assemblages and multiple spectral parameters can be used to discriminate them. The spectra of increasingly fine-grained olivine + metal assemblages and those involving low-Fa olivine show increasing spectral dominance by metal. Systematic application of multiple

  19. Low concentration toxic metal mixture interactions: Effects on essential and non-essential metals in brain, liver, and kidneys of mice on sub-chronic exposure.

    PubMed

    Cobbina, Samuel J; Chen, Yao; Zhou, Zhaoxiang; Wu, Xueshan; Feng, Weiwei; Wang, Wei; Mao, Guanghua; Xu, Hai; Zhang, Zhen; Wu, Xiangyang; Yang, Liuqing

    2015-08-01

    The deleterious effects of long term exposure to individual toxic metals in low doses are well documented. There is however, a paucity of information on interaction of low dose toxic metal mixtures with toxic and essential metals. This study reports on interactions between low dose mixtures of lead (Pb), mercury (Hg), arsenic (As) and cadmium (Cd) and toxic and essential metals. For 120d, six groups of forty mice each were exposed to metal mixtures, however, the control group was given distilled water. Exposure to Pb+Cd increased brain Pb by 479% in 30d, whiles Pb+Hg+As+Cd reduced liver Hg by 46.5%, but increased kidney As by 130% in 30d. Brain Cu, increased by 221% on Pb+Hg+As+Cd exposure, however, liver Ca reduced by 36.1% on Pb+Hg exposure in 60-d. Interactions within metal mixtures were largely synergistic. Principal component analysis (PCA) showed that low dose metal exposures influenced greatly levels of Hg (in brain and liver) and As (brain). The influence exerted on essential metals was highest in liver (PC1) followed by kidney (PC2) and brain (PC3). Exposure to low dose metal mixtures affected homeostasis of toxic and essential metals in tissues of mice.

  20. Nonequilibrium multiphase mixture modeling of energetic material response

    SciTech Connect

    Baer, M.R.; Hertel, E.; Bell, R.

    1995-12-31

    To model the shock-induced behavior of porous or damaged energetic materials, a nonequilibrium mixture theory has been developed and incorporated into the shock physics code, CTH. Foundation for this multiphase model is based on a continuum mixture formulation given by Baer and Nunziato. In this nonequilibrium approach, multiple thermodynamic and mechanics fields are resolved including the effects of material relative motion, rate-dependent compaction, drag and heat transfer interphase effects and multiple-step combustion. Benchmark calculations are presented which simulate low-velocity piston impact on a propellant porous bed and experimentally-measured wave features are well replicated with this model. This mixture model introduces micromechanical models for the initiation and growth of reactive multicomponent flow which are key features to describe shock initiation and self-accelerated deflagration-to-detonation combustion behavior. To complement one-dimensional simulation, two dimensional numerical simulations are presented which indicate wave curvature effects due to the loss of wall confinement.

  1. Toxicity to Eisenia andrei and Folsomia candida of a metal mixture applied to soil directly or via an organic matrix.

    PubMed

    Natal-da-Luz, T; Ojeda, G; Pratas, J; Van Gestel, C A M; Sousa, J P

    2011-09-01

    Regulatory limits for chemicals and ecological risk assessment are usually based on the effects of single compounds, not taking into account mixture effects. The ecotoxicity of metal-contaminated sludge may, however, not only be due to its metal content. Both the sludge matrix and the presence of other toxicants may mitigate or promote metal toxicity. To test this assumption, the toxicity of soils recently amended with an industrial sludge predominantly contaminated with chromium, copper, nickel, and zinc and soils freshly spiked with the same mixture of metals was evaluated through earthworm (Eisenia andrei) and collembolan (Folsomia candida) reproduction tests. The sludge was less toxic than the spiked metal mixture for E. andrei but more toxic for F. candida. Results obtained for the earthworms suggest a decrease in metal bioavailability promoted by the high organic matter content of the sludge. The higher toxicity of the sludge for F. candida was probably due to the additive toxic effect of other pollutants.

  2. Interactive effects of waterborne metals in binary mixtures on short-term gill-metal binding and ion uptake in rainbow trout (Oncorhynchus mykiss).

    PubMed

    Niyogi, Som; Nadella, Sunita R; Wood, Chris M

    2015-08-01

    Metal binding to fish gills forms the basis of the biotic ligand model (BLM) approach, which has emerged as a useful tool for conducting site-specific water quality assessments for metals. The current BLMs are designed to assess the toxicity of individual metals, and cannot account for the interactive effects of metal mixtures to aquatic organisms including fish. The present study was designed mainly to examine the interactive effects of waterborne metals (Cd, Zn, Cu, Ag, and Ni) in specific binary combinations on short-term (3h) gill-metal binding and essential ion (Ca(2+) and Na(+)) uptake (a physiological index of toxicity) in fish, using juvenile freshwater rainbow trout (Oncorhynchus mykiss) as the model species. We hypothesized that binary mixtures of metals that share a common mode of uptake and toxicity (e.g., Cd and Zn - Ca(2+) antagonists, Cu and Ag - Na(+) antagonists) would reduce the gill binding of each other via competitive interactions and induce less than additive effects on ion transport. In addition, the mixture of metals that have different modes of uptake and toxicity (e.g., Cd and Cu, or Cd and Ni) would not exhibit any interactive effects either on gill-metal binding or ion transport. We found that both Zn and Cu reduced gill-Cd binding and vice versa, however, Ni did not influence gill-Cd binding in fish. Surprisingly, Ag was found to stimulate gill-Cu binding especially at high exposure concentrations, whereas, Cu had no effect on gill-Ag binding. The inhibitory effect of Cd and Zn in mixture on branchial Ca(2+) uptake was significantly greater than that of Cd or Zn alone. Similarly, the inhibitory effect of Cu and Ag in mixture on branchial Na(+) uptake was significantly greater than that of Cu or Ag alone. The inhibitory effects of Cd and Zn mixture on Ca(2+) uptake as well as Cu and Ag mixture on Na(+) uptake were found to follow the principles of simple additivity. In contrast, no significant additive effect on either Ca(2+) or Na

  3. Preliminary investigation of a technique to separate fission noble metals from fission product mixtures

    SciTech Connect

    Mellinger, G.B.; Jensen, G.A.

    1982-08-01

    A variation of the gold-ore fire assay technique was examined as a method for recovering Pd, Rh and Ru from fission products. The mixture of fission product oxides is combined with glass-forming chemicals, a metal oxide such as PbO (scavenging agent), and a reducing agent such as charcoal. When this mixture is melted, a metal button is formed which extracts the noble metals. The remainder cools to form a glass for nuclear waste storage. Recovery depended only on reduction of the scavenger oxide to metal. When such reduction was achieved, no difference in noble metal recovery efficiency was found among the scavengers studied (PbO, SnO, CuO, Bi/sub 2/O/sub 3/, Sb/sub 2/O/sub 3/). Not all reducing agents studied, however, were able to reduce all scavenger oxides to metal. Only graphite would reduce SnO and CuO and allow noble metal recovery. The scavenger oxides Sb/sub 2/O/sub 3/, Bi/sub 2/O/sub 3/, and PbO, however, were reduced by all of the reducing agents tested. Similar noble metal recovery was found with each. Lead oxide was found to be the most promising of the potential scavengers. It was reduced by all of the reducing agents tested, and its higher density may facilitate the separation. Use of lead oxide also appeared to have no deterimental effect on the glass quality. Charcoal was identified as the preferred reducing agent. As long as a separable metal phase was formed in the melt, noble metal recovery was not dependent on the amount of reducing agent and scavenger oxide. High glass viscosities inhibited separation of the molten scavenger, while low viscosities allowed volatile loss of RuO/sub 4/. A viscosity of approx. 20 poise at the processing temperature offered a good compromise between scavenger separation and Ru recovery. Glasses in which PbO was used as the scavenging agent were homogeneous in appearance. Resistance to leaching was close to that of certain waste glasses reported in the literature. 12 figures. 7 tables.

  4. Metal-Polycyclic Aromatic Hydrocarbon Mixture Toxicity in Hyalella azteca. 2. Metal Accumulation and Oxidative Stress as Interactive Co-toxic Mechanisms.

    PubMed

    Gauthier, Patrick T; Norwood, Warren P; Prepas, Ellie E; Pyle, Greg G

    2015-10-06

    Mixtures of metals and polycyclic aromatic hydrocarbons (PAHs) are commonly found in aquatic environments. Emerging reports have identified that more-than-additive mortality is common in metal-PAH mixtures. Individual aspects of PAH toxicity suggest they may alter the accumulation of metals and enhance metal-derived reactive oxygen species (ROS). Redox-active metals (e.g., Cu and Ni) are also capable of enhancing the redox cycling of PAHs. Accordingly, we explored the mutual effects redox-active metals and PAHs have on oxidative stress, and the potential for PAHs to alter the accumulation and/or homeostasis of metals in juvenile Hyalella azteca. Amphipods were exposed to binary mixtures of Cu, Cd, Ni, or V, with either phenanthrene (PHE) or phenanthrenequinone (PHQ). Mixture of Cu with either PAH produced striking more-than-additive mortality, whereas all other mixtures amounted to strictly additive mortality following 18-h exposures. We found no evidence to suggest that interactive effects on ROS production were involved in the more-than-additive mortality of Cu-PHE and Cu-PHQ mixtures. However, PHQ increased the tissue concentration of Cu in juvenile H. azteca, providing a potential mechanism for the observed more-than-additive mortality.

  5. Optical properties of silicon titanium oxide mixtures prepared by metallic mode reactive sputtering.

    PubMed

    Rademacher, Daniel; Bräuer, Günter; Fritz, Benjamin; Vergöhl, Michael

    2012-11-20

    In this paper different SiO(2)-TiO(2) mixtures are prepared by metallic mode reactive sputtering. The samples were sputtered from cylindrical targets in a sputter-up configuration using an additional plasma source for oxidization. The different ratios of SiO(2) and TiO(2) in the mixtures are prepared by a target sputtering power variation. Optical film properties of the mixtures such as refractive index, which is determined by ellipsometric measurements, and optical bandgap, which is measured by photometric (transmission) measurements, are investigated. The thin-film structure is investigated by x-ray diffraction analysis and the stress of the films is presented. It is shown that the metallic mode reactive sputtering in the present configuration is applicable to continuously tune optical and mechanical properties. Finally the sputtered mixed materials are compared with other optical standard materials such as Nb(2)O(5), Ta(2)O(5), HfO(2), and Al(2)O(3).

  6. Investigation of antioxidant properties of metal ascorbates and their mixtures by voltammetry

    NASA Astrophysics Data System (ADS)

    Vtorushina, A. N.; Nikonova, E. D.

    2015-04-01

    The paper describes modern ways for selection of anti-radical substances. Molding of such components with a carbon-based material decreases the rate of its oxidative destruction. Addition of such a component to a carbon-based material decreases the rate of its oxidative destruction. The purpose of this study is to determine the antioxidant activity of ascorbates metals (Ca, Mg, Li, Co, Fe), used in the practice of medicine, as well as mixtures based on them together with well-known antioxidants. In this article we examine the effect of metals on the process of ascorbate oxygen electroreduction. From these ascorbates lithium and magnesium ascorbate showed the greatest activity toward cathode oxygen reduction process. Also mixtures with well-known examined antioxidants ascorbate (glucose, dihydroquercetin) were investigated at different concentrations of components. It is shown that the multicomponent mixtures exhibit lower activity than the individual drugs. Recommended the creation of drugs on the basis of ascorbate Mg and Li with not more than 3 number of components.

  7. Contributions of a compost-biochar mixture to the metal sorption capacity of a mine tailing.

    PubMed

    Forján, R; Asensio, V; Rodríguez-Vila, A; Covelo, E F

    2016-02-01

    One technique applied to restore degraded or contaminated soils is to use amendments made of different types of waste materials, which in turn may contain metals such as Cu, Pb and Zn. For this reason, it is important to determine the capacity of the soil to retain these materials, and to compare the sorption capacity between an amended soil and another unamended soil. The aim of this study was to determine the mobility and availability of these metals in the soil after applying the amendment, and how it affected the soil's sorption capacity. Sorption isotherms were compared with the empirical models of Langmuir and Freundlich to estimate the sorption capacity. The overall capacity of the soils to sorb Cu, Pb or Zn was evaluated as the slope Kr. The amendments used in this study were a mixture made of compost and biochar in different proportions (20, 40, 60, 100 %), which were applied to the mine tailing from a settling pond from a copper mine. The mine tailing that were amended with the mixture of compost and biochar had a higher sorption capacity than the mine tailing from the unamended pond, and their sorption isotherms had a greater affinity towards Cu, Pb and Zn than the mine tailing that was studied. Therefore, the results obtained show that adding a mixture of compost and biochar favours the retention of Cu, Pb and Zn in mine tailing.

  8. Reductive dechlorination of chlorinated alkanes and alkenes by iron metal and metal mixtures

    SciTech Connect

    Orth, R.G.; McKenzie, D.E.

    1995-12-31

    Reductive dechlorination using zero valent metals such as iron has seen an increase in interest over the past few years with the extension of iron dechlorination to in-situ treatment of ground water using a process developed by Gillham and O`Hannes in 1994. Earlier applications included the use of metals for water treatment for the degradation of halogenated pesticides. This increased interest is demonstrated by the recent ACS symposium on zero valent metal dechlorination. The work that will be presented involves the reduction of selected chlorinated alkanes and alkenes beginning with chlorobutanes. The position of the chlorines on the carbon chain relative to each other was studied by determining the rates of the dechlorination processes. These studies were carried out in seated batch reactors so that loss of the chlorinated hydrocarbons was minimized and total carbon and chloride mass balances could be obtained. The goal of the studies was to understand the mechanism of the reaction that is believed to follow metal corrosion processes involving two electron transfer reactions.

  9. The effects of high metal concentrations in soil-compost mixtures on soil enzymes.

    PubMed

    Warman, P R; Munroe, M D

    2010-10-01

    The study was undertaken to determine the impact of high-metal composts on the activities of four soil enzymes. High concentrations of metal salts (Cr, Cu, Ni or a Co-Mo-Pb combination) were added to feedstocks during the thermophilic stage of composting. These four metal-enriched composts and an unamended control compost were then mixed with soil collected from long-term agriculture plots under organic management or conventional management. The compost-soil mixtures were prepared at two rates (1:1 or 1:3 compost:soil, v/v) and incubated at 20 degrees C for three weeks. These 20 combinations plus the five composts and the two soils were added to pots and incubated for three weeks. Following incubation, soil enzyme activities (acid phosphatase, arysulfatase, dehydrogenase, phosphodiesterase) were measured using traditional assay procedures. Compared to the control, none of the high-metal composts inhibited soil enzyme activity. Notably, the Cu compost treatment produced significantly higher activity of all four enzymes in the soil compared to the control. Previous soil management influenced the activity of three enzymes, arysulfatase and dehydrogenase had greater activity in the organic soil while phosphatase activity was greater in the conventional soil. Increasing the proportion of compost in the pot had a positive effect on phosphodiesterase activity only. In conclusion, the high-metal compost treatments either enhanced or caused no adverse effects on soil enzyme activity.

  10. Bioavailability of cyanide and metal-cyanide mixtures to aquatic life.

    PubMed

    Redman, Aaron; Santore, Robert

    2012-08-01

    Cyanide can be toxic to aquatic organisms, and the U.S. Environmental Protection Agency has developed ambient water-quality criteria to protect aquatic life. Recent work suggests that considering free, rather than total, cyanide provides a more accurate measure of the biological effects of cyanides and provides a basis for water-quality criteria. Aquatic organisms are sensitive to free cyanide, although certain metals can form stable complexes and reduce the amount of free cyanide. As a result, total cyanide is less toxic when complexing metals are present. Cyanide is often present in complex effluents, which requires understanding how other components within these complex effluents can affect cyanide speciation and bioavailability. The authors have developed a model to predict the aqueous speciation of cyanide and have shown that this model can predict the toxicity of metal-cyanide complexes in terms of free cyanide in solutions with varying water chemistry. Toxicity endpoints based on total cyanide ranged over several orders of magnitude for various metal-cyanide mixtures. However, predicted free cyanide concentrations among these same tests described the observed toxicity data to within a factor of 2. Aquatic toxicity can be well-described using free cyanide, and under certain conditions the toxicity was jointly described by free cyanide and elevated levels of bioavailable metals.

  11. Microgravity effects on electrodeposition of metals and metal-cermet mixtures

    NASA Technical Reports Server (NTRS)

    Maybee, George W.; Riley, Clyde; Coble, H. Dwain

    1987-01-01

    An experimental system, designed to investigate the potential advantages of electrodeposition in microgravity, is being developed by the McDonnell Douglas Astronautics Company-Huntsville Division and the University of Alabama in Huntsville. It is intended to fly as an Orbiter payload when NASA resumes STS operations. The system will provide power, thermal conditioning, command and control for the production of electrodeposits; system performance data will be recorded for post-flight analysis. Plated metal surfaces will be created using simple electrolytic cells with pure metal electrodes immersed in aqueous electrolytic solutions. Crystalline structure and other properties will be analyzed to identify differences between samples produced in flight and those obtained from ground-based operations.

  12. An effects addition model based on bioaccumulation of metals from exposure to mixtures of metals can predict chronic mortality in the aquatic invertebrate Hyalella azteca.

    PubMed

    Norwood, Warren P; Borgmann, Uwe; Dixon, D George

    2013-07-01

    Chronic toxicity tests of mixtures of 9 metals and 1 metalloid (As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Tl, and Zn) at equitoxic concentrations over an increasing concentration range were conducted with the epibenthic, freshwater amphipod Hyalella azteca. The authors conducted 28-d, water-only tests. The bioaccumulation trends changed for 8 of the elements in exposures to mixtures of the metals compared with individual metal exposures. The bioaccumulation of Co and Tl were affected the most. These changes may be due to interactions between all the metals as well as interactions with waterborne ligands. A metal effects addition model (MEAM) is proposed as a more accurate method to assess the impact of mixtures of metals and to predict chronic mortality. The MEAM uses background-corrected body concentration to predict toxicity. This is important because the chemical characteristics of different waters can greatly alter the bioavailability and bioaccumulation of metals, and interactions among metals for binding at the site of action within the organism can affect body concentration. The MEAM accurately predicted toxicity in exposures to mixtures of metals, and predicted results were within a factor of 1.1 of the observed data, using 24-h depurated body concentrations. The traditional concentration addition model overestimated toxicity by a factor of 2.7.

  13. Bundles of aligned carbon nanotubes obtained by the pyrolysis of ferrocene hydrocarbon mixtures: role of the metal nanoparticles produced in situ

    NASA Astrophysics Data System (ADS)

    Satishkumar, B. C.; Govindaraj, A.; Rao, C. N. R.

    1999-07-01

    Aligned nanotube bundles have been produced by the pyrolysis of ferrocene along with methane, acetylene or butane. Ferrocene-acetylene mixtures are found to be ideal for the production of compact aligned nanotube bundles. The nanotube bundles are associated with iron nanoparticles of diameters in the range 2-13 nm. These nanoparticles are ferromagnetic, showing low saturation magnetization compared to bulk iron. The ferromagnetism of the transition metal nanoparticles is likely to be responsible for the alignment of the nanotubes.

  14. Cancer Dose-Response Assessment for Polychlorinated Biphenyls (PCBs) and Application to Environmental Mixtures

    EPA Pesticide Factsheets

    This report updates the cancer dose-response assessment for PCBs and shows how information on toxicity, disposition, and environmental processes can be considered together to evaluate health risks from PCB mixtures in the environment.

  15. Assessment of toxic interactions of heavy metals in multi-component mixtures using sea urchin embryo-larval bioassay.

    PubMed

    Xu, Xue; Li, Yan; Wang, Yuan; Wang, Yonghua

    2011-02-01

    The toxicities of copper, lead, zinc and cadmium ions and various concentrations of mixtures of them were studied using sea urchin (Strongylocentyotus intermedius) embryo-larval bioassay. Toxic unit analysis was used to determine type of joint action for each mixture combination (binary, ternary and quaternary). For the majority of the binary combinations, the interactions were of synergistic nature, but in ternary or quaternary mixtures, the joint action was mainly concentration additive, while antagonism was only observed for two mixtures (Cu+Pb and Zn+Cd) among all the 11 combinations. Two prevailing theoretical models: the concentration addition (CA) model and the independent action (IA) model were used to predict the mixture toxicities. The weak correlation obtained (R≃0.55) indicated that the hypotheses of mode of action involved in the two models to some extent failed to describe the behavior of the mixture system. Then a novel bio-concentration factor-based model was developed and was successful to predict the toxicities of mixtures, with an obtained R of 0.92. This model indicated that in a mixture system of heavy metals, the joint toxicity was mainly determined by the combined action of bio-concentrations of metals other than the simply similar (CA) or dissimilar (IA) modes of action of the mixture components.

  16. Toxicity assessment due to sub-chronic exposure to individual and mixtures of four toxic heavy metals.

    PubMed

    Cobbina, Samuel J; Chen, Yao; Zhou, Zhaoxiang; Wu, Xueshan; Zhao, Ting; Zhang, Zhen; Feng, Weiwei; Wang, Wei; Li, Qian; Wu, Xiangyang; Yang, Liuqing

    2015-08-30

    Humans are exposed to a cocktail of heavy metal toxicants in the environment. Though heavy metals are deleterious, there is a paucity of information on toxicity of low dose mixtures. In this study, lead (Pb) (0.01mg/L), mercury (Hg) (0.001mg/L), cadmium (Cd) (0.005mg/L) and arsenic (As) (0.01mg/L) were administered individually and as mixtures to 10 groups of 40 three-week old mice (20 males and 20 females), for 120 days. The study established that low dose exposures induced toxicity to the brain, liver, and kidney of mice. Metal mixtures showed higher toxicities compared to individual metals, as exposure to low dose Pb+Hg+Cd reduced brain weight and induced structural lesions, such as neuronal degeneration in 30-days. Pb+Hg+Cd and Pb+Hg+As+Cd exposure induced hepatocellular injury to mice evidenced by decreased antioxidant activities with marginal increases in MDA. These were accentuated by increases in ALT, AST and ALP. Interactions in metal mixtures were basically synergistic in nature and exposure to Pb+Hg+As+Cd induced renal tubular necrosis in kidneys of mice. This study underlines the importance of elucidating the toxicity of low dose metal mixtures so as to protect public health.

  17. Uptake of iodide by a mixture of metallic copper and cupric compounds

    SciTech Connect

    Lefevre, G.; Alnot, M.; Ehrhardt, J.J.; Bessiere, J.

    1999-05-15

    Environmental contaminants harmful to the health of present and future generations involve nuclear fission products as iodine radioisotopes. {sup 129}I is potentially one of the more mobile products because of its long half-life and its tendency to go into solution as an anion that is not retarded with silicate minerals. Ability of copper/cupric compound mixtures to remove iodide from solution was investigated to predict sorption of radioactive iodine in the environment and to assess their use in a nuclear reprocessing method. Thermodynamic calculations were performed to study the stability of such mixtures in solution and to obtain equilibrium constants of Cu(0)/Cu(II)/I{sup {minus}} and Cu(0)/Cu(II)/Cl{sup {minus}} systems. Both calculations and experimental results showed that a Cu(0)/Cu{sub 3}(OH){sub 2}(CO{sub 3}){sub 2} (azurite) mixture selectively uptakes iodide ions (initial concentrations: 10{sup {minus}2} and 10{sup {minus}1} M) in the presence of 10{sup {minus}1} M chloride ions. Reaction of iodide with copper powder and azurite crystal or copper plate and azurite powder have also been investigated, leading to precipitation of CuI onto massive copper phase. The different solids were separately analyzed by XPS and MEB-EDX, giving some insight in the uptake mechanism. It is proposed that soluble copper released by the cupric compound is reduced at the surface of metallic copper, leading to a preferential precipitation of CuI on copper surface.

  18. Accurate prediction of the response of freshwater fish to a mixture of estrogenic chemicals.

    PubMed

    Brian, Jayne V; Harris, Catherine A; Scholze, Martin; Backhaus, Thomas; Booy, Petra; Lamoree, Marja; Pojana, Giulio; Jonkers, Niels; Runnalls, Tamsin; Bonfà, Angela; Marcomini, Antonio; Sumpter, John P

    2005-06-01

    Existing environmental risk assessment procedures are limited in their ability to evaluate the combined effects of chemical mixtures. We investigated the implications of this by analyzing the combined effects of a multicomponent mixture of five estrogenic chemicals using vitellogenin induction in male fathead minnows as an end point. The mixture consisted of estradiol, ethynylestradiol, nonylphenol, octylphenol, and bisphenol A. We determined concentration-response curves for each of the chemicals individually. The chemicals were then combined at equipotent concentrations and the mixture tested using fixed-ratio design. The effects of the mixture were compared with those predicted by the model of concentration addition using biomathematical methods, which revealed that there was no deviation between the observed and predicted effects of the mixture. These findings demonstrate that estrogenic chemicals have the capacity to act together in an additive manner and that their combined effects can be accurately predicted by concentration addition. We also explored the potential for mixture effects at low concentrations by exposing the fish to each chemical at one-fifth of its median effective concentration (EC50). Individually, the chemicals did not induce a significant response, although their combined effects were consistent with the predictions of concentration addition. This demonstrates the potential for estrogenic chemicals to act additively at environmentally relevant concentrations. These findings highlight the potential for existing environmental risk assessment procedures to underestimate the hazard posed by mixtures of chemicals that act via a similar mode of action, thereby leading to erroneous conclusions of absence of risk.

  19. Accurate Prediction of the Response of Freshwater Fish to a Mixture of Estrogenic Chemicals

    PubMed Central

    Brian, Jayne V.; Harris, Catherine A.; Scholze, Martin; Backhaus, Thomas; Booy, Petra; Lamoree, Marja; Pojana, Giulio; Jonkers, Niels; Runnalls, Tamsin; Bonfà, Angela; Marcomini, Antonio; Sumpter, John P.

    2005-01-01

    Existing environmental risk assessment procedures are limited in their ability to evaluate the combined effects of chemical mixtures. We investigated the implications of this by analyzing the combined effects of a multicomponent mixture of five estrogenic chemicals using vitellogenin induction in male fathead minnows as an end point. The mixture consisted of estradiol, ethynylestradiol, nonylphenol, octylphenol, and bisphenol A. We determined concentration–response curves for each of the chemicals individually. The chemicals were then combined at equipotent concentrations and the mixture tested using fixed-ratio design. The effects of the mixture were compared with those predicted by the model of concentration addition using biomathematical methods, which revealed that there was no deviation between the observed and predicted effects of the mixture. These findings demonstrate that estrogenic chemicals have the capacity to act together in an additive manner and that their combined effects can be accurately predicted by concentration addition. We also explored the potential for mixture effects at low concentrations by exposing the fish to each chemical at one-fifth of its median effective concentration (EC50). Individually, the chemicals did not induce a significant response, although their combined effects were consistent with the predictions of concentration addition. This demonstrates the potential for estrogenic chemicals to act additively at environmentally relevant concentrations. These findings highlight the potential for existing environmental risk assessment procedures to underestimate the hazard posed by mixtures of chemicals that act via a similar mode of action, thereby leading to erroneous conclusions of absence of risk. PMID:15929895

  20. Decomposition mechanism of methylene blue caused by metallic iron-maghemite mixture

    NASA Astrophysics Data System (ADS)

    Kubuki, Shiro; Shibano, Koya; Akiyama, Kazuhiko; Homonnay, Zoltán; Kuzmann, Ernő; Ristić, Mira; Nishida, Tetsuaki

    2013-04-01

    Decomposition mechanism of methylene blue (MB) caused by a mixture of metallic iron-maghemite (Fe0- γFe2O3) was investigated by means of 57Fe-Mössbauer spectroscopy, X-ray diffractometry (XRD), Ultraviolet-Visible Absorption Spectroscopy (UV-vis) and electrospray-ionization mass spectroscopy (ESI-MS). Ten day-leaching test of 10 μmol L - 1 MB aqueous solution and Fe0- γFe2O3 mixture (mass ratio 3:7) showed a decrease in the concentration from 10.5 to 4.45 μmol L - 1 with first-order rate constant ( k) of 1.57 × 10^{-1} day - 1. An ESI-MS study of Fe0- γFe2O3 mixture (3:7) after the leaching test revealed new peaks at m/ z of 100, 110 and 137 due to fragmentation of MB, in addition to those observed at m/ z of 284, 270 and 256 which were ascribed to MB, Azure B and Azure A, respectively. 57Fe-Mössbauer spectra of Fe0- γFe2O3 mixture (3:7) resulted in a decrease in absorption area ( A) for Fe0 ( δ = 0.00±0.01 mm s - 1, H int = 33.0±0.1 T) from 37.5 to 21.3, 9.7, 7.9, 7.0 and 4.5±0.5 %, together with an increase in A from 0.0 to 5.0, 13.8, 17.2, 21.0 and 22.4±0.5 % for octahedral ( O h) iron (FeII + FeIII) of Fe3O4. XRD study of these samples indicated that the peak intensity at 2 Θ of 44.7° being ascribed to Fe0 was decreased, while that of 35.6° due to Fe3O4 was almost constant; relative peak ratio of Fe0/Fe3O4 was decreased from 26.3 to 2.76 after the leaching, indicating that Fe0 in the Fe0- γFe2O3 mixture was oxidized to Fe3O4. These experimental results suggest that Fe0- γFe2O3 mixture could be utilized for the cleaning or decomposition of toxic organic compounds like trichloroethylene.

  1. Theoretic model and computer simulation of separating mixture metal particles from waste printed circuit board by electrostatic separator.

    PubMed

    Li, Jia; Xu, Zhenming; Zhou, Yaohe

    2008-05-30

    Traditionally, the mixture metals from waste printed circuit board (PCB) were sent to the smelt factory to refine pure copper. Some valuable metals (aluminum, zinc and tin) with low content in PCB were lost during smelt. A new method which used roll-type electrostatic separator (RES) to recovery low content metals in waste PCB was presented in this study. The theoretic model which was established from computing electric field and the analysis of forces on the particles was used to write a program by MATLAB language. The program was design to simulate the process of separating mixture metal particles. Electrical, material and mechanical factors were analyzed to optimize the operating parameters of separator. The experiment results of separating copper and aluminum particles by RES had a good agreement with computer simulation results. The model could be used to simulate separating other metal (tin, zinc, etc.) particles during the process of recycling waste PCBs by RES.

  2. Evaluating quantitative formulas for dose-response assessment of chemical mixtures.

    PubMed

    Hertzberg, Richard C; Teuschler, Linda K

    2002-12-01

    Risk assessment formulas are often distinguished from dose-response models by being rough but necessary. The evaluation of these rough formulas is described here, using the example of mixture risk assessment. Two conditions make the dose-response part of mixture risk assessment difficult, lack of data on mixture dose-response relationships, and the need to address risk from combinations of chemicals because of public demands and statutory requirements. Consequently, the U.S. Environmental Protection Agency has developed methods for carrying out quantitative dose-response assessment for chemical mixtures that require information only on the toxicity of single chemicals and of chemical pair interactions. These formulas are based on plausible ideas and default parameters but minimal supporting data on whole mixtures. Because of this lack of mixture data, the usual evaluation of accuracy (predicted vs. observed) cannot be performed. Two approaches to the evaluation of such formulas are to consider fundamental biological concepts that support the quantitative formulas (e.g., toxicologic similarity) and to determine how well the proposed method performs under simplifying constraints (e.g., as the toxicologic interactions disappear). These ideas are illustrated using dose addition and two weight-of-evidence formulas for incorporating toxicologic interactions.

  3. Component information is preserved in glomerular responses to binary odor mixtures in the moth Spodoptera littoralis.

    PubMed

    Carlsson, Mikael A; Chong, Kwok Ying; Daniels, Wiltrud; Hansson, Bill S; Pearce, Tim C

    2007-06-01

    Natural odors are often complex mixtures of different compounds. These mixtures can be perceived to have qualities that are different from their components. Moreover, components can be difficult to distinguish within a blend, even if those components are identifiable when presented individually. Thus, odor components can interact along the olfactory pathway in a nonlinear fashion such that the mixture is not perceived simply as the sum of its components. Here we investigated odor-evoked changes in Ca2+ concentration to binary blends of plant-related substances in individually identified glomeruli in the moth Spodoptera littoralis. We used a wide range of blend ratios and a range of concentrations below the level at which glomerular responses become saturated. We found no statistically significant cases where the mixture response was greater than both component responses at the same total concentration (synergistic interactions) and no statistically significant cases where the mixture response was less than either component presented individually (suppressive interactions). Therefore, we conclude that, for the plant mixtures studied, information of their components is preserved in the neural representations encoded at the first stage of olfactory processing in this moth species.

  4. Headgroup interactions and ion flotation efficiency in mixtures of a chelating surfactant, different foaming agents, and divalent metal ions.

    PubMed

    Svanedal, Ida; Boija, Susanne; Norgren, Magnus; Edlund, Håkan

    2014-06-10

    The correlation between interaction parameters and ion flotation efficiency in mixtures of chelating surfactant metal complexes and different foaming agents was investigated. We have recently shown that chelating surfactant 2-dodecyldiethylenetriaminepentaacetic acid (4-C12-DTPA) forms strong coordination complexes with divalent metal ions, and this can be utilized in ion flotation. Interaction parameters for mixed micelles and mixed monolayer formation for Mg(2+) and Ni(2+) complexes with the chelating surfactant 4-C12-DTPA and different foaming agents were calculated by Rubingh's regular solution theory. Parameters for the calculations were extracted from surface tension measurements and NMR diffusometry. The effects of metal ion coordination on the interactions between 4-C12-DTPA and the foaming agents could be linked to a previously established difference in coordination chemistry between the examined metal ions. As can be expected from mixtures of amphoteric surfactants, the interactions were strongly pH-dependent. Strong correlation was found between interaction parameter β(σ) for mixed monolayer formation and the phase-transfer efficiency of Ni(2+) complexes with 4-C12-DTPA during flotation in a customized flotation cell. In a mixture of Cu(2+) and Zn(2+), the significant difference in conditional stability constants (log K) between the metal complexes was utilized to selectively recover the metal complex with the highest log K (Cu(2+)) by ion flotation. Flotation experiments in an excess concentration of metal ions confirmed the coordination of more than one metal ion to the headgroup of 4-C12-DTPA.

  5. Mixture Experiments

    SciTech Connect

    Piepel, Gregory F.

    2007-12-01

    A mixture experiment involves combining two or more components in various proportions or amounts and then measuring one or more responses for the resulting end products. Other factors that affect the response(s), such as process variables and/or the total amount of the mixture, may also be studied in the experiment. A mixture experiment design specifies the combinations of mixture components and other experimental factors (if any) to be studied and the response variable(s) to be measured. Mixture experiment data analyses are then used to achieve the desired goals, which may include (i) understanding the effects of components and other factors on the response(s), (ii) identifying components and other factors with significant and nonsignificant effects on the response(s), (iii) developing models for predicting the response(s) as functions of the mixture components and any other factors, and (iv) developing end-products with desired values and uncertainties of the response(s). Given a mixture experiment problem, a practitioner must consider the possible approaches for designing the experiment and analyzing the data, and then select the approach best suited to the problem. Eight possible approaches include 1) component proportions, 2) mathematically independent variables, 3) slack variable, 4) mixture amount, 5) component amounts, 6) mixture process variable, 7) mixture of mixtures, and 8) multi-factor mixture. The article provides an overview of the mixture experiment designs, models, and data analyses for these approaches.

  6. NOx, FINE PARTICLE AND TOXIC METAL EMISSIONS FROM THE COMBUSTION OF SEWAGE SLUDGE/COAL MIXTURES: A SYSTEMATIC ASSESSMENT

    SciTech Connect

    Jost O.L. Wendt

    2003-06-02

    This research project focuses on pollutants from the combustion of mixtures of dried municipal sewage sludge (MSS) and coal. The objective is to determine the relationship between (1) fraction sludge in the sludge/coal mixture, and (2) combustion conditions on (a) NOx concentrations in the exhaust, (b) the size segregated fine and ultra-fine particle composition in the exhaust, and (c) the partitioning of toxic metals between vapor and condenses phases, within the process.

  7. A Mixture Proportional Hazards Model with Random Effects for Response Times in Tests

    ERIC Educational Resources Information Center

    Ranger, Jochen; Kuhn, Jörg-Tobias

    2016-01-01

    In this article, a new model for test response times is proposed that combines latent class analysis and the proportional hazards model with random effects in a similar vein as the mixture factor model. The model assumes the existence of different latent classes. In each latent class, the response times are distributed according to a…

  8. The mechanisms associated with the development of hypertension after exposure to lead, mercury species or their mixtures differs with the metal and the mixture ratio.

    PubMed

    Wildemann, Tanja M; Siciliano, Steven D; Weber, Lynn P

    2016-01-02

    Hypertension is considered to be the most important risk factor for the development of cardiovascular diseases. Beside life-style risk factors, exposure to lead and mercury species are increasingly discussed as potential risk factors. Although there are a few previous studies, the underlying mechanism by which exposure to lead and mercury disturb blood pressure regulation is not currently understood. Potential mechanisms are oxidative stress production, kidney damage and activation of the renin-angiotensin system (RAS), all of which can interact to cause dysregulation of blood pressure. Male rats (Wistar) were exposed to lead, inorganic mercury, methylmercury or two mixtures of all three metals for four weeks through the drinking water. The two mixture ratios were based on ratios of known reference values or environmental exposure from the literature. To investigate the potential mechanism of actions, blood pressure was measured after four weeks and compared to plasma nitrotyrosine or reduced/oxidized glutathione levels in liver as markers for oxidative stress. Plasma renin and angiotensin II levels were used as markers for RAS activation. Finally, kidney function and injury were assessed via urinary and plasma creatinine levels, creatinine clearance and urinary kidney-injury molecule (KIM-1). While exposure to lead by itself increased oxidative stress and kidney damage along with blood pressure, inorganic mercury did not affect blood pressure or any end-point examined. Conversely, methylmercury instead increased RAS activation along with blood pressure. Surprisingly, when administered as mixtures, lead no longer increased oxidative stress or altered kidney function. Moreover, the mixture based on an environmental ratio no longer had an effect on blood pressure, while the reference value ratio still retained an increase in blood pressure. Based on our results, the prominent mechanism of action associated with the development of hypertension seems to be oxidative

  9. Tolerance and hyperaccumulation of a mixture of heavy metals (Cu, Pb, Hg, and Zn) by four aquatic macrophytes.

    PubMed

    Romero-Hernández, Jorge Alberto; Amaya-Chávez, Araceli; Balderas-Hernández, Patricia; Roa-Morales, Gabriela; González-Rivas, Nelly; Balderas-Plata, Miguel Ángel

    2017-03-04

    In the present investigation, four macrophytes, namely Typha latifolia (L.), Lemna minor (L.), Eichhornia crassipes (Mart.) Solms-Laubach, and Myriophyllum aquaticum (Vell.) Verdc, were evaluated for their heavy metal (Cu, Pb, Hg, and Zn) hyperaccumulation potential under laboratory conditions. Tolerance analyses were performed for 7 days of exposure at five different treatments of the metals mixture (Cu(+2), Hg(+2), Pb(+2), and Zn(+2)). The production of chlorophyll and carotenoids was determined at the end of each treatment. L. minor revealed to be sensitive, because it did not survive in all the tested concentrations after 72 hours of exposure. E. crassipes and M. aquaticum displayed the highest tolerance to the metals mixture. For the most tolerant species of aquatic macrophytes, The removal kinetics of E. crassipes and M. aquaticum was carried out, using the following mixture of metals: Cu (0.5 mg/L) and Hg, Pb, and Zn 0.25 mg/L. The obtained results revealed that E. crassipes can remove 99.80% of Cu, 97.88% of Pb, 99.53% of Hg, and 94.37% of Zn. M. aquaticum withdraws 95.2% of Cu, 94.28% of Pb, 99.19% of Hg, and 91.91% of Zn. The obtained results suggest that these two species of macrophytes could be used for the phytoremediation of this mixture of heavy metals from the polluted water bodies.

  10. Evaluating Complex Mixtures in the Zebrafish Embryo by Reconstituting Field Water Samples: A Metal Pollution Case Study.

    PubMed

    Michiels, Ellen D G; Vergauwen, Lucia; Hagenaars, An; Fransen, Erik; Dongen, Stefan Van; Van Cruchten, Steven J; Bervoets, Lieven; Knapen, Dries

    2017-03-02

    Accurately assessing the toxicity of complex, environmentally relevant mixtures remains an important challenge in ecotoxicology. The goal was to identify biological effects after exposure to environmental water samples and to determine whether the observed effects could be explained by the waterborne metal mixture found in the samples. Zebrafish embryos were exposed to water samples of five different sites originating from two Flemish (Mol and Olen, Belgium) metal contaminated streams: "Scheppelijke Nete" (SN) and "Kneutersloop" (K), and a ditch (D), which is the contamination source of SN. Trace metal concentrations, and Na, K, Mg and Ca concentrations were measured using ICP-MS and were used to reconstitute site-specific water samples. We assessed whether the effects that were observed after exposure to environmental samples could be explained by metal mixture toxicity under standardized laboratory conditions. Exposure to "D" or "reconstituted D" water caused 100% mortality. SN and reconstituted SN water caused similar effects on hatching, swim bladder inflation, growth and swimming activity. A canonical discriminant analysis confirmed a high similarity between both exposure scenarios, indicating that the observed toxicity was indeed primarily caused by metals. The applied workflow could be a valuable approach to evaluate mixture toxicity that limits time and costs while maintaining biological relevance.

  11. Evaluating Complex Mixtures in the Zebrafish Embryo by Reconstituting Field Water Samples: A Metal Pollution Case Study

    PubMed Central

    Michiels, Ellen D. G.; Vergauwen, Lucia; Hagenaars, An; Fransen, Erik; Dongen, Stefan Van; Van Cruchten, Steven J.; Bervoets, Lieven; Knapen, Dries

    2017-01-01

    Accurately assessing the toxicity of complex, environmentally relevant mixtures remains an important challenge in ecotoxicology. The goal was to identify biological effects after exposure to environmental water samples and to determine whether the observed effects could be explained by the waterborne metal mixture found in the samples. Zebrafish embryos were exposed to water samples of five different sites originating from two Flemish (Mol and Olen, Belgium) metal contaminated streams: “Scheppelijke Nete” (SN) and “Kneutersloop” (K), and a ditch (D), which is the contamination source of SN. Trace metal concentrations, and Na, K, Mg and Ca concentrations were measured using ICP-MS and were used to reconstitute site-specific water samples. We assessed whether the effects that were observed after exposure to environmental samples could be explained by metal mixture toxicity under standardized laboratory conditions. Exposure to “D” or “reconstituted D” water caused 100% mortality. SN and reconstituted SN water caused similar effects on hatching, swim bladder inflation, growth and swimming activity. A canonical discriminant analysis confirmed a high similarity between both exposure scenarios, indicating that the observed toxicity was indeed primarily caused by metals. The applied workflow could be a valuable approach to evaluate mixture toxicity that limits time and costs while maintaining biological relevance. PMID:28257097

  12. Stimulus-responsive metal-organic frameworks.

    PubMed

    Nagarkar, Sanjog S; Desai, Aamod V; Ghosh, Sujit K

    2014-09-01

    Materials that can recognize the changes in their local environment and respond by altering their inherent physical and/or chemical properties are strong candidates for future "smart" technology materials. Metal-organic frameworks (MOFs) have attracted a great deal of attention in recent years owing to their designable architecture, host-guest chemistry, and softness as porous materials. Despite this fact, studies on the tuning of the properties of MOFs by external stimuli are still rare. This review highlights the recent developments in the field of stimulus-responsive MOFs or so-called smart MOFs. In particular, the various stimuli used and the utility of stimulus-responsive smart MOFs for various applications such as gas storage and separation, sensing, clean energy, catalysis, molecular motors, and biomedical applications are highlighted by using representative examples. Future directions in the developments of stimulus-responsive smart MOFs and their applications are proposed from a personal perspective.

  13. Investigating the Impact of Item Parameter Drift for Item Response Theory Models with Mixture Distributions

    PubMed Central

    Park, Yoon Soo; Lee, Young-Sun; Xing, Kuan

    2016-01-01

    This study investigates the impact of item parameter drift (IPD) on parameter and ability estimation when the underlying measurement model fits a mixture distribution, thereby violating the item invariance property of unidimensional item response theory (IRT) models. An empirical study was conducted to demonstrate the occurrence of both IPD and an underlying mixture distribution using real-world data. Twenty-one trended anchor items from the 1999, 2003, and 2007 administrations of Trends in International Mathematics and Science Study (TIMSS) were analyzed using unidimensional and mixture IRT models. TIMSS treats trended anchor items as invariant over testing administrations and uses pre-calibrated item parameters based on unidimensional IRT. However, empirical results showed evidence of two latent subgroups with IPD. Results also showed changes in the distribution of examinee ability between latent classes over the three administrations. A simulation study was conducted to examine the impact of IPD on the estimation of ability and item parameters, when data have underlying mixture distributions. Simulations used data generated from a mixture IRT model and estimated using unidimensional IRT. Results showed that data reflecting IPD using mixture IRT model led to IPD in the unidimensional IRT model. Changes in the distribution of examinee ability also affected item parameters. Moreover, drift with respect to item discrimination and distribution of examinee ability affected estimates of examinee ability. These findings demonstrate the need to caution and evaluate IPD using a mixture IRT framework to understand its effects on item parameters and examinee ability. PMID:26941699

  14. Response Times to Gustatory–Olfactory Flavor Mixtures: Role of Congruence

    PubMed Central

    Shepard, Timothy G.; Veldhuizen, Maria G.

    2015-01-01

    A mixture of perceptually congruent gustatory and olfactory flavorants (sucrose and citral) was previously shown to be detected faster than predicted by a model of probability summation that assumes stochastically independent processing of the individual gustatory and olfactory signals. This outcome suggests substantial integration of the signals. Does substantial integration also characterize responses to mixtures of incongruent flavorants? Here, we report simple response times (RTs) to detect brief pulses of 3 possible flavorants: monosodium glutamate, MSG (gustatory: “umami” quality), citral (olfactory: citrus quality), and a mixture of MSG and citral (gustatory–olfactory). Each stimulus (and, on a fraction of trials, water) was presented orally through a computer-operated, automated flow system, and subjects were instructed to press a button as soon as they detected any of the 3 non-water stimuli. Unlike responses previously found to the congruent mixture of sucrose and citral, responses here to the incongruent mixture of MSG and citral took significantly longer (RTs were greater) and showed lower detection rates than the values predicted by probability summation. This outcome suggests that the integration of gustatory and olfactory flavor signals is less extensive when the component flavors are perceptually incongruent rather than congruent, perhaps because incongruent flavors are less familiar. PMID:26304508

  15. Heavy metals (Pb, Cd, As and MeHg) as risk factors for cognitive dysfunction: A general review of metal mixture mechanism in brain.

    PubMed

    Karri, Venkatanaidu; Schuhmacher, Marta; Kumar, Vikas

    2016-12-01

    Human exposure to toxic heavy metals is a global challenge. Concurrent exposure of heavy metals, such as lead (Pb), cadmium (Cd), arsenic (As) and methylmercury (MeHg) are particularly important due to their long lasting effects on the brain. The exact toxicological mechanisms invoked by exposure to mixtures of the metals Pb, Cd, As and MeHg are still unclear, however they share many common pathways for causing cognitive dysfunction. The combination of metals may produce additive/synergetic effects due to their common binding affinity with NMDA receptor (Pb, As, MeHg), Na(+) - K(+) ATP-ase pump (Cd, MeHg), biological Ca(+2) (Pb, Cd, MeHg), Glu neurotransmitter (Pb, MeHg), which can lead to imbalance between the pro-oxidant elements (ROS) and the antioxidants (reducing elements). In this process, ROS dominates the antioxidants factors such as GPx, GS, GSH, MT-III, Catalase, SOD, BDNF, and CERB, and finally leads to cognitive dysfunction. The present review illustrates an account of the current knowledge about the individual metal induced cognitive dysfunction mechanisms and analyse common Mode of Actions (MOAs) of quaternary metal mixture (Pb, Cd, As, MeHg). This review aims to help advancement in mixture toxicology and development of next generation predictive model (such as PBPK/PD) combining both kinetic and dynamic interactions of metals.

  16. Impairment of humoral immune responses in mice exposed to nitrogen dioxide and ozone mixtures

    SciTech Connect

    Fujimaki, H.

    1989-04-01

    The relationship between immune defense mechanisms and environmental pollutants remains unknown because of uncertainty about the effects of combined or mixed pollutants. To investigate whether exposure to toxic gas mixtures change the effect of a single gas exposure on immune function, BALB/c mice were continuously exposed to 4.0 ppm nitrogen dioxide (NO/sub 2/), 0.8 ppm ozone (O/sub 3/), or the mixture of NO/sub 2/ plus O/sub 3/ for 3, 7, 14, and 56 days. Organ weights (lung, thymus, and spleen) and antibody responses to sheep red blood cells (SRBC), and to DNP-Ficoll were measured immediately after the exposure. Lung weights in mice exposed to O/sub 3/ or the mixture were increased significantly in all exposure periods. The weights of thymus and spleen in mice exposed for 3, 7, and 14 days to the mixture were decreased. O/sub 3/ exposure for 56 days showed significant decreases of the weights of both organs. Antibody response to SRBC in mice exposed for 3, 7, and 14 days to O/sub 3/ or the mixture was markedly suppressed, but exposure to the mixture for 56 days did not show the suppression of anti-SRBC antibody response. No differences in anti-DNP antibody response between exposed and control mice were observed, except those exposed to O/sub 3/ or the mixture for 14 days. These results suggest that mixed gas exposures variously modify the effects of a single gas exposure on antibody production in mice.

  17. Hydrogen generation using silicon nanoparticles and their mixtures with alkali metal hydrides

    NASA Astrophysics Data System (ADS)

    Patki, Gauri Dilip

    mole of Si. We compare our silicon nanoparticles (˜10nm diameter) with commercial silicon nanopowder (<100nm diameter) and ball-milled silicon powder (325 mesh). The increase in rate upon decreasing the particle size to 10 nm was even greater than would be expected based upon the increase in surface area. While specific surface area increased by a factor of 6 in going from <100 nm to ˜10 nm particles, the hydrogen production rate increased by a factor of 150. However, in all cases, silicon requires a base (e.g. NaOH, KOH, hydrazine) to catalyze its reaction with water. Metal hydrides are also promising hydrogen storage materials. The optimum metal hydride would possess high hydrogen storage density at moderate temperature and pressure, release hydrogen safely and controllably, and be stable in air. Alkali metal hydrides have high hydrogen storage density, but exhibit high uncontrollable reactivity with water. In an attempt to control this explosive nature while maintaining high storage capacity, we mixed our silicon nanoparticles with the hydrides. This has dual benefits: (1) the hydride- water reaction produces the alkali hydroxide needed for base-catalyzed silicon oxidation, and (2) dilution with 10nm coating by, the silicon may temper the reactivity of the hydride, making the process more controllable. Initially, we analyzed hydrolysis of pure alkali metal hydrides and alkaline earth metal hydrides. Lithium hydride has particularly high hydrogen gravimetric density, along with faster reaction kinetics than sodium hydride or magnesium hydride. On analysis of hydrogen production we found higher hydrogen yield from the silicon nanoparticle—metal hydride mixture than from pure hydride hydrolysis. The silicon-hydride mixtures using our 10nm silicon nanoparticles produced high hydrogen yield, exceeding the theoretical yield. Some evidence of slowing of the hydride reaction rate upon addition of silicon nanoparticles was observed.

  18. Mixture Random-Effect IRT Models for Controlling Extreme Response Style on Rating Scales

    PubMed Central

    Huang, Hung-Yu

    2016-01-01

    Respondents are often requested to provide a response to Likert-type or rating-scale items during the assessment of attitude, interest, and personality to measure a variety of latent traits. Extreme response style (ERS), which is defined as a consistent and systematic tendency of a person to locate on a limited number of available rating-scale options, may distort the test validity. Several latent trait models have been proposed to address ERS, but all these models have limitations. Mixture random-effect item response theory (IRT) models for ERS are developed in this study to simultaneously identify the mixtures of latent classes from different ERS levels and detect the possible differential functioning items that result from different latent mixtures. The model parameters can be recovered fairly well in a series of simulations that use Bayesian estimation with the WinBUGS program. In addition, the model parameters in the developed models can be used to identify items that are likely to elicit ERS. The results show that a long test and large sample can improve the parameter estimation process; the precision of the parameter estimates increases with the number of response options, and the model parameter estimation outperforms the person parameter estimation. Ignoring the mixtures and ERS results in substantial rank-order changes in the target latent trait and a reduced classification accuracy of the response styles. An empirical survey of emotional intelligence in college students is presented to demonstrate the applications and implications of the new models. PMID:27853444

  19. Pheromones as mixtures: geometric designs and response surface modeling for optimization of mating disruption of the citrus leafminer Phyllocnistis citrella

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Pheromone blends composed of one or more components are mixtures. Mixtures present a unique problem for experiment design when response (e.g., insect attraction to a blend) is a function of proportionality of the blend's components. In mixtures, the ingredients must total to a constant value. Prop...

  20. Marsh plant response to metals: Exudation of aliphatic low molecular weight organic acids (ALMWOAs)

    NASA Astrophysics Data System (ADS)

    Rocha, A. Cristina S.; Almeida, C. Marisa R.; Basto, M. Clara P.; Vasconcelos, M. Teresa S. D.

    2016-03-01

    Metal exposure is known to induce the production and secretion of substances, such as aliphatic low molecular weight organic acids (ALMWOAs), into the rhizosphere by plant roots. Knowledge on this matter is extensive for soil plants but still considerably scarce regarding marsh plants roots adapted to high salinity media. Phragmites australis and Halimione portulacoides, two marsh plants commonly distributed in European estuarine salt marshes, were used to assess the response of roots of both species, in terms of ALMWOAs exudation, to Cu, Ni and Cd exposure (isolated and in mixture since in natural environment, they are exposed to mixture of metals). As previous studies were carried out in unrealistic and synthetic media, here a more natural medium was selected. Therefore, in vitro experiments were carried out, with specimens of both marsh plants, and in freshwater contaminated with two different Cu, Ni and Cd concentrations (individual metal and in mixture). Both marsh plants were capable of liberating ALMWOAs into the surrounding medium. Oxalic, citric and maleic acids were found in P. australis root exudate solutions and oxalic and maleic acids in H. portulacoides root exudate solutions. ALMWOA liberation by both plants was plant species and metal-dependent. For instance, Cu affected the exudation of oxalic acid by H. portulacoides and of oxalic and citric acids by P. australis roots. In contrast, Ni and Cd did not stimulate any specific response. Regarding the combination of all metals, H. portulacoides showed a similar response to that observed for Cu individually. However, in the P. australis case, at high metal concentration mixture, a synergetic effect led to the increase of oxalic acid levels in root exudate solution and to a decrease of citric acid liberation. A correlation between ALMWOAs exudation and metal accumulation could not be established. P. australis and H. portulacoides are considered suitable metal phytoremediators of estuarine impacted areas

  1. ACUTE TOXICITY OF FIVE SEDIMENT-ASSOCIATED METALS, INDIVIDUALLY AND IN A MIXTURE, TO THE ESTUARINE MEIOBENTHIC HARPACTICOID COPEPOD AMPHIASCUS TENUIREMIS. (R825279)

    EPA Science Inventory

    Abstract

    The acute effects of many individual, seawater-solubilized metals on meiobenthic copepods and nematodes are well known. In sediments, however, metals most often occur as mixtures, and it is not known whether such mixtures exhibit simple additive toxicity to me...

  2. Partial characterization of different mixtures of solids by measuring the optical nonlinear response.

    PubMed

    Strachan, Clare J; Lee, Chris J; Rades, Thomas

    2004-03-01

    We report on the theoretical basis and first experimental results of a new method based on optical nonlinearity, for characterising crystallinity and polymorphism of pharmaceuticals in the solid state. Once the theoretical basis of optical nonlinearity of crystalline structures is established, a new and rapid method based on this physical theory can be developed to quantitatively determine polymorphism or crystallinity. An apparatus was set up to measure the second harmonic response of powdered samples when irradiated with a pulsed laser source. The response of quartz-glass, enalapril maleate forms I-II and enalapril maleate form II-PVP mixtures were measured and modeled. It was found that the quartz-glass system showed high sensitivity to the presence of quartz and was well predicted by our theoretical model. The response of enalapril maleate polymorph mixtures was also sensitive to changes in the polymorph ratio. The theoretical predictions of the polymorph mixtures agreed quantitatively with the experimental results. The response of enalapril maleate form II-PVP mixtures agreed quantitatively with the physical model and showed extremely low noise and high sensitivity, giving very promising limits of detection (LOD) and quantification (LOQ) of 0.12 and 0.41%, respectively. This rapid, novel technique has potential for industrial monitoring of pharmaceutical manufacturing processes.

  3. Adaptive stress response pathways induced by environmental mixtures of bioaccumulative chemicals in dugongs.

    PubMed

    Jin, Ling; Gaus, Caroline; Escher, Beate I

    2015-06-02

    To address the poorly understood mixture effects of chemicals in the marine mammal dugong, we coupled equilibrium-based passive sampling in blubber to a range of in vitro bioassays for screening mixtures of bioaccumulative chemicals. The modes of action included early effect indicators along important toxicity pathways, such as induction of xenobiotic metabolism, and some integrative indicators downstream of the molecular initiating event, such as adaptive stress responses. Activation of aryl hydrocarbon receptor (AhR) and Nrf2-mediated oxidative stress response were found to be the most prominent effects, while the p53-mediated DNA damage response and NF-κB-mediated response to inflammation were not significantly affected. Although polychlorinated dibenzo-p-dioxins (PCDDs) quantified in the samples accounted for the majority of AhR-mediated activity, PCDDs explained less than 5% of the total oxidative stress response, despite their known ability to activate this pathway. Altered oxidative stress response was observed with both individual chemicals and blubber extracts subject to metabolic activation by rat liver S9 fraction. Metabolic activation resulted in both enhanced and reduced toxicity, suggesting the relevance and utility of incorporating metabolic enzymes into in vitro bioassays. Our approach provides a first insight into the burden of toxicologically relevant bioaccumulative chemical mixtures in dugongs and can be applied to lipid tissue of other wildlife species.

  4. Subchronic exposure to a mixture of groundwater-contaminating metals through drinking water induces oxidative stress in male rats.

    PubMed

    Jadhav, Sachin Hanmantrao; Sarkar, Souvendra Nath; Kataria, Meena; Tripathi, Harish Chandra

    2007-03-01

    The current study examines the oxidative stress-inducing potential of a mixture of metals, representative of groundwater contamination in different areas of India. Male albino rats were exposed to the mixture through drinking water for 90 days at 0, 1, 10 and 100 times the mode concentrations of the metals in contaminated waters and at concentrations equal to their WHO maximum permissible limit (MPL) in drinking water. The endpoints evaluated were lipid peroxidation (LPO), GSH content and activities of superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase in heart, liver, kidney and brain. MPL and 1× levels did not induce any alterations. The mixture at 10× and 100× doses increased LPO and decreased GSH level and activities of the antioxidases in kidney, liver and brain, but no alterations were observed in heart. An inverse correlation between LPO and GSH or antioxidaes and a positive correlation between GSH and glutathione peroxidase or glutathione reductase were found in the affected organs. The findings suggest that the mixture induces oxidative stress and decreases antioxidant status in 10× and 100× the mode concentrations of the metals in drinking water.

  5. Expanding metal mixture toxicity models to natural stream and lake invertebrate communities.

    PubMed

    Balistrieri, Laurie S; Mebane, Christopher A; Schmidt, Travis S; Keller, Wendel Bill

    2015-04-01

    A modeling approach that was used to predict the toxicity of dissolved single and multiple metals to trout is extended to stream benthic macroinvertebrates, freshwater zooplankton, and Daphnia magna. The approach predicts the accumulation of toxicants (H, Al, Cd, Cu, Ni, Pb, and Zn) in organisms using 3 equilibrium accumulation models that define interactions between dissolved cations and biological receptors (biotic ligands). These models differ in the structure of the receptors and include a 2-site biotic ligand model, a bidentate biotic ligand or 2-pKa model, and a humic acid model. The predicted accumulation of toxicants is weighted using toxicant-specific coefficients and incorporated into a toxicity function called Tox, which is then related to observed mortality or invertebrate community richness using a logistic equation. All accumulation models provide reasonable fits to metal concentrations in tissue samples of stream invertebrates. Despite the good fits, distinct differences in the magnitude of toxicant accumulation and biotic ligand speciation exist among the models for a given solution composition. However, predicted biological responses are similar among the models because there are interdependencies among model parameters in the accumulation-Tox models. To illustrate potential applications of the approaches, the 3 accumulation-Tox models for natural stream invertebrates are used in Monte Carlo simulations to predict the probability of adverse impacts in catchments of differing geology in central Colorado (USA); to link geology, water chemistry, and biological response; and to demonstrate how this approach can be used to screen for potential risks associated with resource development.

  6. Expanding metal mixture toxicity models to natural stream and lake invertebrate communities

    USGS Publications Warehouse

    Balistrieri, Laurie S.; Mebane, Christopher A.; Schmidt, Travis S.; Keller, William (Bill)

    2015-01-01

    A modeling approach that was used to predict the toxicity of dissolved single and multiple metals to trout is extended to stream benthic macroinvertebrates, freshwater zooplankton, and Daphnia magna. The approach predicts the accumulation of toxicants (H, Al, Cd, Cu, Ni, Pb, and Zn) in organisms using 3 equilibrium accumulation models that define interactions between dissolved cations and biological receptors (biotic ligands). These models differ in the structure of the receptors and include a 2-site biotic ligand model, a bidentate biotic ligand or 2-pKa model, and a humic acid model. The predicted accumulation of toxicants is weighted using toxicant-specific coefficients and incorporated into a toxicity function called Tox, which is then related to observed mortality or invertebrate community richness using a logistic equation. All accumulation models provide reasonable fits to metal concentrations in tissue samples of stream invertebrates. Despite the good fits, distinct differences in the magnitude of toxicant accumulation and biotic ligand speciation exist among the models for a given solution composition. However, predicted biological responses are similar among the models because there are interdependencies among model parameters in the accumulation–Tox models. To illustrate potential applications of the approaches, the 3 accumulation–Tox models for natural stream invertebrates are used in Monte Carlo simulations to predict the probability of adverse impacts in catchments of differing geology in central Colorado (USA); to link geology, water chemistry, and biological response; and to demonstrate how this approach can be used to screen for potential risks associated with resource development.

  7. Tissue Response to Base-Metal Dental Alloys.

    DTIC Science & Technology

    RESPONSE(BIOLOGY), *CASTING ALLOYS, *BASE METAL, * DENTAL PROSTHESES, TISSUES(BIOLOGY), COMPATIBILITY, NICKEL ALLOYS, BERYLLIUM, DENTISTRY, CANCER, HISTOLOGY, DENTAL IMPLANTOLOGY , COBALT ALLOYS, CHROMIUM ALLOYS.

  8. Fitting a Mixture Item Response Theory Model to Personality Questionnaire Data: Characterizing Latent Classes and Investigating Possibilities for Improving Prediction

    ERIC Educational Resources Information Center

    Maij-de Meij, Annette M.; Kelderman, Henk; van der Flier, Henk

    2008-01-01

    Mixture item response theory (IRT) models aid the interpretation of response behavior on personality tests and may provide possibilities for improving prediction. Heterogeneity in the population is modeled by identifying homogeneous subgroups that conform to different measurement models. In this study, mixture IRT models were applied to the…

  9. Faster Response for Memory-Metal Actuators

    NASA Technical Reports Server (NTRS)

    Ruoff, C. F.

    1985-01-01

    Cooling accelerated by attaching Peltier junction. Electric current carries heat to or from junction between two dissimilar metals, direction of heat flow depending on direction of current and particular metals used. Direction of current is opposite to that of same two metals operating as thermocouple.

  10. Microporous metal-organic framework with dual functionalities for highly efficient removal of acetylene from ethylene/acetylene mixtures

    NASA Astrophysics Data System (ADS)

    Hu, Tong-Liang; Wang, Hailong; Li, Bin; Krishna, Rajamani; Wu, Hui; Zhou, Wei; Zhao, Yunfeng; Han, Yu; Wang, Xue; Zhu, Weidong; Yao, Zizhu; Xiang, Shengchang; Chen, Banglin

    2015-06-01

    The removal of acetylene from ethylene/acetylene mixtures containing 1% acetylene is a technologically very important, but highly challenging task. Current removal approaches include the partial hydrogenation over a noble metal catalyst and the solvent extraction of cracked olefins, both of which are cost and energy consumptive. Here we report a microporous metal-organic framework in which the suitable pore/cage spaces preferentially take up much more acetylene than ethylene while the functional amine groups on the pore/cage surfaces further enforce their interactions with acetylene molecules, leading to its superior performance for this separation. The single X-ray diffraction studies, temperature dependent gas sorption isotherms, simulated and experimental column breakthrough curves and molecular simulation studies collaboratively support the claim, underlying the potential of this material for the industrial usage of the removal of acetylene from ethylene/acetylene mixtures containing 1% acetylene at room temperature through the cost- and energy-efficient adsorption separation process.

  11. Heavy metals retention capacity of a non-conventional sorbent developed from a mixture of industrial and agricultural wastes.

    PubMed

    Agouborde, Lina; Navia, Rodrigo

    2009-08-15

    Zinc and copper removal from aqueous solutions using brine sediments (industrial residue), sawdust (agricultural residue) and the mixture of both materials has been researched through batch and column tests. Brine sediments were found to be mainly constituted by halite and calcite, while its main cations exchangeable were sodium, calcium, magnesium and potassium. In sawdust the main exchangeable cations detected were calcium, magnesium, sodium and potassium. FT-IR spectra of sawdust and brine sediment-sawdust mixture showed that brine sediments produced important changes in carboxylic, alcoholic and phenolic groups present in the sawdust. The maximum zinc adsorption capacity was found to be 4.85, 2.58 and 5.59 mg/g using an adsorbent/solution ratio of 1/40, for brine sediments, sawdust and the mixture, respectively. For copper, the maximum adsorption capacity was found to be 4.69, 2.31 and 4.33 mg/g, using adsorbent/solution ratios of 1/40, for brine sediments, sawdust and the mixture, respectively. Maximum copper adsorption capacity of the mixture, on the contrary to zinc adsorption, was lightly inferior to maximum adsorption capacity obtained in brine sediments. Adsorption isotherms data adjusted better to the Langmuir model. Additionally, columns reached the saturation point at 690 min for zinc and 360 min for copper. The main mechanism involved in the removal of both metals may be the ionic exchange between sodium and calcium ions present in brine sediments and H(+) present in functional groups of sawdust. The use of brine sediments, sawdust and their mixture, presents an interesting option both, for wastewater decontamination (as a possible non-conventional sorbent for the removal of heavy metals) and as a waste recycling option.

  12. Ab initio interaction potentials and scattering lengths for ultracold mixtures of metastable helium and alkali-metal atoms

    NASA Astrophysics Data System (ADS)

    Kedziera, Dariusz; Mentel, Łukasz; Żuchowski, Piotr S.; Knoop, Steven

    2015-06-01

    We have obtained accurate ab initio +4Σ quartet potentials for the diatomic metastable triplet helium+alkali-metal (Li, Na, K, Rb) systems, using all-electron restricted open-shell coupled cluster singles and doubles with noniterative triples corrections CCSD(T) calculations and accurate calculations of the long-range C6 coefficients. These potentials provide accurate ab initio quartet scattering lengths, which for these many-electron systems is possible, because of the small reduced masses and shallow potentials that result in a small amount of bound states. Our results are relevant for ultracold metastable triplet helium+alkali-metal mixture experiments.

  13. Toxicity and bioaccumulation of a mixture of heavy metals in Chironomus tentans (Diptera: Chironomidae) in synthetic sediment

    SciTech Connect

    Harrahy, E.A.; Clements, W.H.

    1997-02-01

    This research investigated toxicity and bioaccumulation of a mixture of Cd, Cu, Pb, and Zn in Chironomus tentans in synthetic sediment, and compared predicted to measured steady-state bioaccumulation factors (BAFs). In a toxicity test, C. tentans were exposed to various dilutions of a base concentration (1.0 X) of a mixture of the four metals (5 {micro}g/g Cd. 10 {micro}g/g Cu. 70 {micro}g/g Pb, and 300 {micro}g/g Zn) in synthetic sediment. Mortality ranged from 17 to 100%. To measure bioaccumulation of the metals, C. tentans were exposed to 0.35 X the base concentration for a period of up to 14 d in two uptake tests. Bioaccumulation of all four metals increased over the 14-d uptake phases. Concentrations of metals in chironomids were significantly correlated with exposure time in the uptake phases. Only concentrations of copper approached background levels after 7 d depuration. Uptake rate coefficients and elimination rate constants were determined for each metal. Bioaccumulation factors were highest for Cd and lowest for Pb. With the exception of Pb, steady-state BAFs were within a factor of about two of those calculated using the first-order kinetic model. The high BAFs calculated may indicate greater bioavailability in synthetic sediment. Studies comparing toxicity and bioaccumulation of natural and synthetic sediments are necessary before the use of synthetic sediments is widely adopted.

  14. Exchangeable Ions Are Responsible for the In Vitro Antibacterial Properties of Natural Clay Mixtures

    PubMed Central

    Otto, Caitlin C.; Haydel, Shelley E.

    2013-01-01

    We have identified a natural clay mixture that exhibits in vitro antibacterial activity against a broad spectrum of bacterial pathogens. We collected four samples from the same source and demonstrated through antibacterial susceptibility testing that these clay mixtures have markedly different antibacterial activity against Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA). Here, we used X-ray diffraction (XRD) and inductively coupled plasma – optical emission spectroscopy (ICP-OES) and – mass spectrometry (ICP-MS) to characterize the mineralogical and chemical features of the four clay mixture samples. XRD analyses of the clay mixtures revealed minor mineralogical differences between the four samples. However, ICP analyses demonstrated that the concentrations of many elements, Fe, Co, Cu, Ni, and Zn, in particular, vary greatly across the four clay mixture leachates. Supplementation of a non-antibacterial leachate containing lower concentrations of Fe, Co, Ni, Cu, and Zn to final ion concentrations and a pH equivalent to that of the antibacterial leachate generated antibacterial activity against E. coli and MRSA, confirming the role of these ions in the antibacterial clay mixture leachates. Speciation modeling revealed increased concentrations of soluble Cu2+ and Fe2+ in the antibacterial leachates, compared to the non-antibacterial leachates, suggesting these ionic species specifically are modulating the antibacterial activity of the leachates. Finally, linear regression analyses comparing the log10 reduction in bacterial viability to the concentration of individual ion species revealed positive correlations with Zn2+ and Cu2+ and antibacterial activity, a negative correlation with Fe3+, and no correlation with pH. Together, these analyses further indicate that the ion concentration of specific species (Fe2+, Cu2+, and Zn2+) are responsible for antibacterial activity and that killing activity is not solely attributed to pH. PMID:23691149

  15. Estimating the pi* goodness of fit index for finite mixtures of item response models.

    PubMed

    Revuelta, Javier

    2008-05-01

    Testing the fit of finite mixture models is a difficult task, since asymptotic results on the distribution of likelihood ratio statistics do not hold; for this reason, alternative statistics are needed. This paper applies the pi* goodness of fit statistic to finite mixture item response models. The pi* statistic assumes that the population is composed of two subpopulations - those that follow a parametric model and a residual group outside the model; pi* is defined as the proportion of population in the residual group. The population was divided into two or more groups, or classes. Several groups followed an item response model and there was also a residual group. The paper presents maximum likelihood algorithms for estimating item parameters, the probabilities of the groups and pi*. The paper also includes a simulation study on goodness of recovery for the two- and three-parameter logistic models and an example with real data from a multiple choice test.

  16. Immunosuppressive effect of subchronic exposure to a mixture of eight heavy metals, found as groundwater contaminants in different areas of India, through drinking water in male rats.

    PubMed

    Jadhav, S H; Sarkar, S N; Ram, G C; Tripathi, H C

    2007-10-01

    Immunotoxicity is an important health hazard of heavy metal exposure. Because the risk of combined exposure in the population cannot be neglected, we examined whether subchronic exposure to a mixture of metals (arsenic, cadmium, lead, mercury, chromium, nickel, manganese, and iron) via drinking water at contemporary Indian groundwater contamination levels and at concentrations equivalent to the WHO maximum permissible limit (MPL) in drinking water can induce immunotoxicity in male rats. Data on groundwater contamination with metals in India were collected from literature and metals were selected on the basis of their frequency of occurrence and contamination level above the MPL. Male albino Wistar rats were exposed to the mixture at 0, 1, 10, and 100 times the mode concentrations (the most frequently occurring concentration) of the individual metals in drinking water for 90 days. In addition, one group was exposed to the mixture at a concentration equal to the MPL of the individual metal and another group was used as positive control for immune response studies. The end points assessed were weights of organs, hematological indices, humoral and cell-mediated immune responses, and histopathology of skin and spleen. The MPL and 1x doses did not significantly affect any of the parameters and none of the doses induced any significant changes after 30 days of exposure. The mixture at 10x and 100x doses increased the relative weight of the spleen, but that of thymus, adrenals, and popliteal lymphnodes were increased with the 100x dose. After 90 days, 10x and 100x doses decreased serum protein and globulin contents and increased the albumin:globulin ratio; the albumin level was decreased only with the 100x dose. After 60 days, the total erythrocyte count (TEC), hemoglobin (Hb) level, and packed cell volume (PCV) were decreased with the 100x dose, whereas after 90 days, 10x and 100x doses reduced the TEC, total leukocyte count, Hb level, PCV, mean corpuscular volume, and

  17. Proteomic analysis in Daphnia magna exposed to As(III), As(V) and Cd heavy metals and their binary mixtures for screening potential biomarkers.

    PubMed

    Le, Thai-Hoang; Lim, Eun-Suk; Hong, Nam-Hui; Lee, Sung-Kyu; Shim, Yon Sik; Hwang, Jin Rae; Kim, Yang-Hoon; Min, Jiho

    2013-11-01

    In this study, the effects of three widespread heavy metals, As(III), As(V) and Cd, and their binary mixtures on the proteomic profile in D. magna were examined to screen novel protein biomarkers using the two-dimensional gel electrophoresis method (2DE). Ten 20d daphnia were exposed to the LC20 concentrations for each of a total of 8 treatments, including the control, As(III), As(V), Cd, [As(III)+As(V)], [As(III)+Cd], [As(V)+Cd], and [As(III), As(V), Cd], for 24h before protein isolation. Three replicates were performed for each treatment. These protein samples were employed for 2DE experiments with a pH gradient gel strip from pH 3 to pH 10. The protein spots were detected by a silver staining process and their intensities were analyzed by Progenesis software to discover the differentially expressed proteins (DEPs) in response to each heavy metal. A total of 117 differentially expressed proteins (DEPs) were found in daphnia responding to the 8 treatments and mapped onto a 2D proteome map, which provides some information of the molecular weight (MW) and pI value for each protein. All of these DEPs are considered as potential candidates for protein biomarkers in D. magna for detecting heavy metals in the aquatic ecosystem. Comparing the proteomic results among these treatments suggested that exposing D. magna to binary mixtures of heavy metals may result in some complex interactive molecular responses within them, rather than just the simple sum of the proteomic profiles of the individual chemicals, (As(III), As(V), and Cd).

  18. Removing lead from metallic mixture of waste printed circuit boards by vacuum distillation: factorial design and removal mechanism.

    PubMed

    Li, Xingang; Gao, Yujie; Ding, Hui

    2013-10-01

    The lead removal from the metallic mixture of waste printed circuit boards by vacuum distillation was optimized using experimental design, and a mathematical model was established to elucidate the removal mechanism. The variables studied in lead evaporation consisted of the chamber pressure, heating temperature, heating time, particle size and initial mass. The low-level chamber pressure was fixed at 0.1 Pa as the operation pressure. The application of two-level factorial design generated a first-order polynomial that agreed well with the data for evaporation efficiency of lead. The heating temperature and heating time exhibited significant effects on the efficiency, which was validated by means of the copper-lead mixture experiments. The optimized operating conditions within the region studied were the chamber pressure of 0.1 Pa, heating temperature of 1023 K and heating time of 120 min. After the conditions were employed to remove lead from the metallic mixture of waste printed circuit boards, the efficiency was 99.97%. The mechanism of the effects was elucidated by mathematical modeling that deals with evaporation, mass transfer and condensation, and can be applied to a wider range of metal removal by vacuum distillation.

  19. Impacts of mixtures of herbicides on molecular and physiological responses of the European flounder Platichthys flesus.

    PubMed

    Evrard, Estérine; Marchand, Justine; Theron, Michaël; Pichavant-Rafini, Karine; Durand, Gaël; Quiniou, Louis; Laroche, Jean

    2010-09-01

    The widespread use of pesticides results in a growing contamination of the aquatic environment. The effects of (1) a simple mixture of a glyphosate-based formulation and AMPA (Aminomethylphosphonic acid--a primary metabolite of glyphosate) and of (2) a more complex mixture of herbicides (glyphosate/AMPA/mecoprop/acetochlor/2,4D) were explored on the molecular and physiological responses of the European flounder Platichthys flesus, considering a long-term and environmentally realistic contamination. Molecular responses were identified using suppression subtractive hybridization on liver samples: the level of gene transcription was significantly different between contaminated fishes vs control ones for 532 sequences, after a 62-day contamination. Among them, 222 sequences were identified by homology with data-based sequences; they encoded several metabolic pathways including: methionine and lipid metabolism, immunity, protein regulation, coagulation and energetic metabolism. Expression pattern of nine transcripts in the liver was confirmed by real-time PCR. The molecular study underlined that potential markers of liver injury were expressed for both mixtures, in particular betaine homocysteine methyl transferase and chemotaxin. Physiological responses were analysed considering blood parameters and condition factor; after the two months contamination period; no significant physiological difference was detected between contaminated and control fish.

  20. Unprecedentedly high selective adsorption of gas mixtures in rho zeolite-like metal-organic framework: a molecular simulation study.

    PubMed

    Babarao, Ravichandar; Jiang, Jianwen

    2009-08-19

    We report a molecular simulation study for the separation of industrially important gas mixtures (CO(2)/H(2), CO(2)/CH(4), and CO(2)/N(2)) in rho zeolite-like metal-organic framework (rho-ZMOF). Rho-ZMOF contains a wide-open anionic framework and charge-balancing extraframework Na(+) ions. Two types of binding sites for Na(+) ions are identified in the framework. Site I is in the single eight-membered ring, whereas site II is in the alpha-cage. Na(+) ions at site I have a stronger affinity for the framework and thus a smaller mobility. The binding sites in rho-ZMOF resemble those in its inorganic counterpart rho-zeolite. CO(2) is adsorbed predominantly over other gases because of its strong electrostatic interactions with the charged framework and the presence of Na(+) ions acting as additional adsorption sites. At ambient temperature and pressure, the CO(2) selectivities are 1800 for the CO(2)/H(2) mixture, 80 for the CO(2)/CH(4) mixture, and 500 for the CO(2)/N(2) mixture. Compared with other MOFs and nanoporous materials reported to date, rho-ZMOF exhibits unprecedentedly high selective adsorption for these gas mixtures. This work represents the first simulation study to characterize extraframework ions and examine gas separation in a charged ZMOF. The simulation results reveal that rho-ZMOF is a promising candidate for the separation of syngas, natural gas, and flue gas.

  1. Effect of hardness on acute toxicity of metal mixtures using Daphnia magna: prediction of acid mine drainage toxicity.

    PubMed

    Yim, Jin Hee; Kim, Kyoung W; Kim, Sang D

    2006-11-02

    In this study, the effect of hardness on the combined outcome of metal mixtures was investigated using Daphnia magna. The toxic unit (TU) was calculated using modified LC(50) values based on the hardness (i.e., LC(50-soft) and LC(50-hard)). From a bioassay test, the degree of sensitivity to hardness on the toxicity changes was in the order: Cdmixture toxicity tests, the difference in the test solution hardness was found to clearly cause different toxicities, as determined by the TU calculated by the LC(50-hard), using the toxicity of a standard culture medium as the reference. That is, approximately four to five times higher toxicity was observed in soft (i.e., 44+/-4 mg/L as CaCO(3)) rather than hard water (i.e., 150+/-10mg/L as CaCO(3)) test solutions. In the tests where the modified reference toxicity values (i.e., LC(50-soft) and LC(50-hard) for soft and hard test solution, respectively) obtained from the individual metal toxicity tests with different hardness were used to calculate the TU, the results showed very similar D. magna toxicities to those of the TU from the mixture of soft and hard test solutions, regardless of the hardness. According to the toxicity results of the mixture, the aquatic toxic effects of the acid mine drainage (AMD) collected from mine areas that contained metal mixtures were investigated using Daphnia magna and the modified LC(50) value of the TU hardness function calculated for varying solution hardness. The results of the biological WET test closely matched our overall prediction, with significant correlation, having a p-value of 0.513 in one way ANOVA test (n=19). Therefore, this study revealed that the predicted toxicity of the metal mixture agreed well with the biological toxicity test when the modified LC(50) value was employed as the basis of hardness in the TU calculation.

  2. Thermal Hazard Evaluation of Cumene Hydroperoxide-Metal Ion Mixture Using DSC, TAM III, and GC/MS.

    PubMed

    You, Mei-Li

    2016-04-28

    Cumene hydroperoxide (CHP) is widely used in chemical processes, mainly as an initiator for the polymerization of acrylonitrile-butadiene-styrene. It is a typical organic peroxide and an explosive substance. It is susceptible to thermal decomposition and is readily affected by contamination; moreover, it has high thermal sensitivity. The reactor tank, transit storage vessel, and pipeline used for manufacturing and transporting this substance are made of metal. Metal containers used in chemical processes can be damaged through aging, wear, erosion, and corrosion; furthermore, the containers might release metal ions. In a metal pipeline, CHP may cause incompatibility reactions because of catalyzed exothermic reactions. This paper discusses and elucidates the potential thermal hazard of a mixture of CHP and an incompatible material's metal ions. Differential scanning calorimetry (DSC) and thermal activity monitor III (TAM III) were employed to preliminarily explore and narrate the thermal hazard at the constant temperature environment. The substance was diluted and analyzed by using a gas chromatography spectrometer (GC) and gas chromatography/mass spectrometer (GC/MS) to determine the effect of thermal cracking and metal ions of CHP. The thermokinetic parameter values obtained from the experiments are discussed; the results can be used for designing an inherently safer process. As a result, the paper finds that the most hazards are in the reaction of CHP with Fe(2+). When the metal release is exothermic in advance, the system temperature increases, even leading to uncontrollable levels, and the process may slip out of control.

  3. Characterization of the effects of binary metal mixtures on short-term uptake of Ag, Cu, and Ni by rainbow trout (Oncorhynchus mykiss).

    PubMed

    Brix, Kevin V; Tellis, Margaret S; Crémazy, Anne; Wood, Chris M

    2016-11-01

    Single metal Biotic Ligand Models (BLMs) have been developed for a number of metals and model organisms. While these BLMs improve our ability to regulate metals in the aquatic environment, in reality, organisms are often simultaneously exposed to metal mixtures. Recently, several attempts have been made to develop mixture BLMs (mBLMs). Some of these models assume competitive interactions between all metals, while others assume only metals with a similar mode of action (e.g., Na(+) or Ca(2+) antagonists) will competitively interact. To begin testing these assumptions in the mBLM framework, standard 3-h gill metal binding assays with Ag, Cu, and Ni (primary metals), were performed in vivo on freshwater rainbow trout. Fish were exposed across a range of concentrations encompassing the 96-h LC50 for that metal to characterize uptake kinetics for each of these three primary metals (radiolabelled) in the presence and absence of a secondary metal (Ag, Cd, Cu, Ni, Pb, or Zn; not radiolabelled). We observed a complex series of interactions in binary mixtures that frequently contradicted theoretical expectations. Metals with similar modes of action did competitively interact in some instances, but not others, and when they did compete the competition was not necessarily reciprocal (e.g., Cu inhibited Ag uptake but Ag did not inhibit Cu uptake). We also observed examples of interactions between metals with dissimilar modes of action and several examples of metals stimulating the uptake of other metals. The underlying mechanisms for these unexpected interactions are unclear, but suggest that many of the current assumptions in mBLMs regarding the number and types of metal uptake sites and corresponding metal interactions are not correct. Careful characterization of metal mixture interactions is clearly needed before a reliable mBLM can be developed.

  4. Transcriptional responses in male Japanese medaka exposed to antiandrogens and antiandrogen/androgen mixtures.

    PubMed

    Sun, Liwei; Peng, Tao; Liu, Fang; Ren, Lin; Peng, Zuhua; Ji, Guorong; Zhou, Yinfang; Fu, Zhengwei

    2016-11-01

    The occurrence of androgenic endocrine disrupting chemicals (EDCs) in water is thought to be linked to deviation from normal male developmental and reproductive functions in exposed aquatic organisms. Because aquatic environments represent a chemically complex medium, the combined effects of androgenic EDCs require urgent attention. In the present study, the effects of two model androgen receptor (AR) antagonists, flutamide (FLU), and vinclozolin (VIN), were first determined individually in male Japanese medaka using the transcriptional response for genes associated with the hypothalamic-pituitary-gonadal axis. The fish were further exposed to binary mixtures of VIN and 17β-trenbolone (TRE, AR agonist) to confirm the theoretical opposing effects of the AR antagonist and agonist. The results showed that exposure to FLU or VIN alone induced very similar transcriptional responses, demonstrating that gene transcription analysis could be successfully employed in identifying the action of single chemicals. For example, both exposures increased the transcription of cyp17b but decreased that of cyp19b in the gonad, demonstrating the compensatory response for AR blockage. However, in the case of exposure to mixtures, although the joint antagonistic action of TRE and VIN affected the most genes, the transcription profiles after exposure to mixtures were not consistent with expectations based on the results for individual chemicals, such as hepatic vtg, and star or cyp19a in gonads. Therefore, the limitation of gene transcription analyses in exposures to mixtures, as well as the potential for the extrapolation of single chemicals, should be considered in future studies. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1591-1599, 2016.

  5. Toxicogenomic responses in rainbow trout (Oncorhynchus mykiss) hepatocytes exposed to model chemicals and a synthetic mixture.

    PubMed

    Finne, E F; Cooper, G A; Koop, B F; Hylland, K; Tollefsen, K E

    2007-03-10

    As more salmon gene expression data has become available, the cDNA microarray platform has emerged as an appealing alternative in ecotoxicological screening of single chemicals and environmental samples relevant to the aquatic environment. This study was performed to validate biomarker gene responses of in vitro cultured rainbow trout (Oncorhynchus mykiss) hepatocytes exposed to model chemicals, and to investigate effects of mixture toxicity in a synthetic mixture. Chemicals used for 24h single chemical- and mixture exposures were 10 nM 17alpha-ethinylestradiol (EE2), 0.75 nM 2,3,7,8-tetrachloro-di-benzodioxin (TCDD), 100 microM paraquat (PQ) and 0.75 microM 4-nitroquinoline-1-oxide (NQO). RNA was isolated from exposed cells, DNAse treated and quality controlled before cDNA synthesis, fluorescent labelling and hybridisation to a 16k salmonid microarray. The salmonid 16k cDNA array identified differential gene expression predictive of exposure, which could be verified by quantitative real time PCR. More precisely, the responses of biomarker genes such as cytochrome p4501A and UDP-glucuronosyl transferase to TCDD exposure, glutathione reductase and gammaglutamyl cysteine synthetase to paraquat exposure, as well as vitellogenin and vitelline envelope protein to EE2 exposure validated the use of microarray applied to RNA extracted from in vitro exposed hepatocytes. The mutagenic compound NQO did not result in any change in gene expression. Results from exposure to a synthetic mixture of the same four chemicals, using identical concentrations as for single chemical exposures, revealed combined effects that were not predicted by results for individual chemicals alone. In general, the response of exposure to this mixture led to an average loss of approximately 60% of the transcriptomic signature found for single chemical exposure. The present findings show that microarray analyses may contribute to our mechanistic understanding of single contaminant mode of action as well

  6. Transcriptional responses indicate attenuated oxidative stress in the springtail Folsomia candida exposed to mixtures of cadmium and phenanthrene.

    PubMed

    de Boer, Muriel E; Ellers, Jacintha; van Gestel, Cornelis A M; den Dunnen, Johan T; van Straalen, Nico M; Roelofs, Dick

    2013-05-01

    Since the 'omics revolution', the assessment of toxic chemical mixtures has incorporated approaches where phenotypic endpoints are connected to a mechanistic understanding of toxicity. In this study we determined the effect of binary mixtures of cadmium and phenanthrene on the reproduction of Folsomia candida and investigated the cellular mechanisms underlying this response. Mixture toxicity modeling showed an antagonistic deviation from concentration addition for reproduction effects of the mixtures. Subsequent transcriptional response analysis was done using five mixtures at the modeled 50 % effect level for reproduction. The transcription profiles of 86 high throughput RT-qPCR assays were studied by means of partial least squares regression analysis. The first and second principal components (PCs) were correlated with global responses to cadmium and phenanthrene, while correlations with the mixture treatments were found in the higher PCs. Specifically associated with the mixture treatments were a biotransformation phase II gene, four mitochondrial related genes and a gene involved in the biosynthesis of antioxidant selenoproteins. Membrane integrity related gene inductions were correlated with the single phenanthrene treatment but not with the mixtures. Immune and inflammatory response assays did not correlate with any of the mixtures. These results suggest moderated oxidative stress, a higher mitochondrial maintenance and less compromised membrane function in the mixture exposed samples compared to the separate cadmium or phenanthrene exposures. The antagonism found for inhibition of reproduction may partially originate from these differences. Mechanistic studies on mixture toxicity can ultimately aid risk assessment by defining relevant toxicity pathways in organisms exposed to real-world mixture exposures present in the field.

  7. Perturbation theory of structure in classical liquid mixtures: Application to metallic systems near phase separation. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Henderson, R. L.

    1974-01-01

    The partial structure factors of classical simple liquid mixtures near phase separation are dicussed. The theory is developed for particles interacting through pair potentials, and is thus appropriate both to insulating fluids, and also to metallic systems if these may be described by an effective ion-ion pair interaction. The motivation arose from consideration of metallic liquid mixtures, in which resistive anomalies have been observed near phase separation. A mean field theory correction appropriate to 3 pair potential for the effects of correlated motions in the reference fluid is studied. The work is cast in terms of functions which are closely related to the direct correlation functions of Ornstein and Zernike. The results are qualitatively in accord with physical expectations. Quantitative agreement with experiment seems to turn on the selection of the hard core reference potential in terms of the metallic effective pair potential. It is suggested that the present effective pair potentials are perhaps not properly used to calculate the metallic structure factors at long wavelength.

  8. NOx, FINE PARTICLE AND TOXIC METAL EMISSIONS FROM THE COMBUSTION OF SEWAGE SLUDGE/COAL MIXTURES: A SYSTEMATIC ASSESSMENT

    SciTech Connect

    Jost O.L. Wendt

    2001-08-01

    This research project focuses on pollutants from the combustion of mixtures of dried municipal sewage sludge (MSS) and coal. The objective is to determine the relationship between (1) fraction sludge in the sludge/coal mixture, and (2) combustion conditions on (a) NOx concentrations in the exhaust, (b) the size segregated fine and ultra-fine particle composition in the exhaust, and (c) the partitioning of toxic metals between vapor and condenses phases, within the process. To this end work is progress using an existing 17kW downflow laboratory combustor, available with coal and sludge feed capabilities. The proposed study will be conducted in concert with an existing ongoing research on toxic metal partitioning mechanisms for very well characterized pulverized coals alone. Both high NOx and low NOx combustion conditions will be investigated (unstaged and staged combustion). The proposed work uses existing analytical and experimental facilities and draws on 20 years of research on NO{sub x} and fine particles that has been funded by DOE in this laboratory. Four barrels of dried sewage sludge are currently in the laboratory. Insofar as possible pertinent mechanisms will be elucidated. Tradeoffs between CO{sub 2} control, NO{sub x} control, and inorganic fine particle and toxic metal emissions will be determined. For the Third Quarter of this project we present our data on trace metal partitioning obtained from combustion of MSS and Gas, MSS and Coal and Coal and Gas alone.

  9. The Kinetic Signature of Toxicity of Four Heavy Metals and Their Mixtures on MCF7 Breast Cancer Cell Line †

    PubMed Central

    Egiebor, Egbe; Tulu, Adam; Abou-Zeid, Nadia; Aighewi, Isoken Tito; Ishaque, Ali

    2013-01-01

    This study evaluated the kinetic signature of toxicity of four heavy metals known to cause severe health and environmental issues—cadmium (Cd), mercury (Hg) lead (Pb) arsenic (As)—and the mixture of all four metals (Mix) on MCF7 cancer cells, in the presence and absence of the antioxidant glutathione (GSH). The study was carried out using real time cell electronic sensing (RT-CES). RT-CES monitors in real time the electrical impedance changes at the electrode/culture medium interface due to the number of adhered cells, which is used as an index of cell viability. Cells were seeded for 24 h before exposure to the metals and their mixtures. The results showed that in the presence and absence of cellular glutathione, arsenic was the most cytotoxic of all five treatments, inducing cell death after 5 h of exposure. Lead was the least cytotoxic in both scenarios. In the presence of cellular GSH, the cytotoxic trend was As > Cd > MIX > Hg > Pb, while in the absence of GSH, the cytotoxic trend was As > Hg > MIX > Cd > Pb. The findings from this study indicate the significance of glutathione-mediated toxicity of the metals examined—particularly for mercury—and may be clinically relevant for disorders such as autism spectrum disorder where decreased glutathione-based detoxification capacity is associated with increased mercury intoxication. PMID:24157516

  10. Physiological and transcriptional responses of Nitrosomonas europaea to TiO2 and ZnO nanoparticles and their mixtures.

    PubMed

    Yu, Ran; Wu, Junkang; Liu, Meiting; Chen, Lianghui; Zhu, Guangcan; Lu, Huijie

    2016-07-01

    The short-term combined effects of two most extensively used nanoparticles (NPs) TiO2 NPs (n-TiO2) and ZnO NPs (n-ZnO) versus their individual cytotoxicities on a model ammonia-oxidizing bacterium, Nitrosomonas europaea, were investigated at both physiological and transcriptional levels. n-ZnO exerted more serious impairment effects on cell morphology, cell density, membrane integrity, and ammonia monooxygenase activity than n-TiO2. However, the co-existing n-TiO2 displayed a dose-dependent mitigation effect on n-ZnO cytotoxicity. Consistently, the n-TiO2 and n-ZnO mixture-impacted global transcriptional expression profile, obtained with the whole-genome microarray technique, was more comparable to the n-TiO2-impacted one than that impacted by n-ZnO. The expressions of numerous genes associated with heavy metal scavenging, DNA repair, and oxidative stress response were less up-regulated under the binary impacts of NP mixture than n-ZnO. Moreover, only n-ZnO alone stimulated the up-regulations of heavy metal resistance genes, which further implied the capacity of co-existing n-TiO2 to alleviate n-ZnO cytotoxicity. In addition, the damage of cell membrane structures and the suppression of cell membrane biogenesis-related gene expressions under the influence of either individual NPs or their combinations strongly suggested that the interruption of cell membranes and the associated metabolic activities would probably be one of NPs' critical cytotoxicity mechanisms.

  11. Response dynamics of bluff-body stabilized conical premixed turbulent flames with spatial mixture gradients

    SciTech Connect

    Chaudhuri, Swetaprovo; Cetegen, Baki M.

    2009-03-15

    Response of bluff-body stabilized conical turbulent premixed flames was experimentally studied for a range of excitation frequencies (10-400 Hz), mean flow velocities (5, 10 and 15 m/s) and three different spatial mixture distributions (uniform, inner and outer enrichment). Upstream excitation was provided by a loudspeaker producing velocity oscillation amplitudes of about 8% of the mean flow velocity. Flame response was detected by a photomultiplier observing the CH{sup *} emission from the flame. The studied turbulent flames exhibited transfer function characteristics of a low-pass filter with a cutoff Strouhal number between 0.08 and 0.12. The amplification factors at low frequencies ranged from 2 to 20 and generally increased for mean flow velocities from 5 to 15 m/s. The highest levels of amplification were found for the outer mixture enrichment followed in decreasing order by uniform and inner mixture gradient cases. The high levels of flame response for the outer enrichment case were attributed to the enhanced flame-vortex interaction in outer jet shear layer. At high excitation levels (u{sup '}/U{sub m}{approx}0.3) for U{sub m}=5 m/ s where non-linear flame response is expected, the flame exhibited a reduced amplitude response in the frequency range between 40 and 100 Hz for the uniform and outer equivalence ratio gradient cases and no discernible effect for the inner equivalence ratio gradient. In all cases, transfer function phase was found to vary linearly with excitation frequency. Finally, a relationship between the amplitude characteristics of the bluff-body wake transfer function and flame blowoff equivalence ratio was presented. (author)

  12. Accumulation and regulation effects from the metal mixture of Zn, Pb, and Cd in the tropical shrimp Penaeus vannamei.

    PubMed

    Núñez-Nogueira, Gabriel; Fernández-Bringas, Laura; Ordiano-Flores, Alfredo; Gómez-Ponce, Alejandro; de León-Hill, Claudia Ponce; González-Farías, Fernando

    2012-12-01

    Environmental metal pollution is one of the major problems faced by humankind. This type of pollution affects aquatic systems (estuaries, coastal lagoons, etc.), which are very dynamic systems, therefore making the study of the effects on the organisms that inhabit them an essential issue. In this study, the capacity of metal regulation by decapod crustacean Penaeus vannamei juveniles was determined. The effects of zinc, lead, and cadmium were tested individually and as a metal mixture exposure to determine possible synergism. The results showed that juvenile shrimps were capable of regulating zinc and lead, whereas cadmium was accumulated without any excretion, at least within the concentrations studied. It was also proved that under the estuarine conditions tested here, P. vannamei juveniles showed capacity to act as a bioindicator for cadmium.

  13. Study of metal transfer in CO2 laser+GMAW-P hybrid welding using argon-helium mixtures

    NASA Astrophysics Data System (ADS)

    Zhang, Wang; Hua, Xueming; Liao, Wei; Li, Fang; Wang, Min

    2014-03-01

    The metal transfer in CO2 Laser+GMAW-P hybrid welding by using argon-helium mixtures was investigated and the effect of the laser on the mental transfer is discussed. A 650 nm laser, in conjunction with the shadow graph technique, is used to observe the metal transfer process. In order to analyze the heat input to the droplet and the droplet internal current line distribution. An optical emission spectroscopy system was employed to estimate default parameter and optimized plasma temperature, electron number densities distribution. The results indicate that the CO2 plasma plume have a significant impact to the electrode melting, droplet formation, detachment, impingement onto the workpiece and weld morphology. Since the current distribution direction flow changes to the keyhole, to obtain a metal transfer mode of one droplet per pulse, the welding parameters should be adjusted to a higher pulse time (TP) and a lower voltage.

  14. PROCEDURES FOR DERIVING EQUILIBRIUM PARTITIONING SEDIMENT BENCHMARKS (ESBS) FOR THE PROTECTION OF BENTHIC ORGANISMS: METALS MIXTURES (CADMIUM, COPPER, LEAD, NICKEL, SILVER, AND ZINC)

    EPA Science Inventory

    This equilibrium partitioning sediment benchmark (ESB) document describes procedures to derive concentrations of metal mixtures in sediment which are protective of the presence of benthic organisms. The equilibrium partitioning (EqP) approach was chosen because it accounts for t...

  15. THE CARCINOGENIC RESPONSE TO A MIXTURE OF DRINKING WATER DISINFECTION BY-PRODUCTS (DBP) WAS LESS THAN ADDITIVE

    EPA Science Inventory

    THE CARCINOGENIC RESPONSE TO A MIXTURE OF DRINKING WATER DISINFECTION BY -PRODUCTS (DBP) W AS LESS THAN ADDITIVE.

    Current default risk assessments for chemical mixtures assume additivity of carcinogenic effects but this may under or over represent the actual biological res...

  16. Empirical evaluation of sufficient similarity in dose-response for environmental risk assessment of a mixture of 11 pyrethroids.

    EPA Science Inventory

    Chemical mixtures in the environment are often the result of a dynamic process. When dose-response data are available on random samples throughout the process, equivalence testing can be used to determine whether the mixtures are sufficiently similar based on a pre-specified biol...

  17. Enhanced Mixture Separations of Metal Adducted Tetrasaccharides Using Frequency Encoded Ion Mobility Separations and Tandem Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Morrison, Kelsey A.; Bendiak, Brad K.; Clowers, Brian H.

    2016-10-01

    Using five isomeric tetrasaccharides in combination with seven multivalent metals, the impact on mobility separations and resulting CID spectra were examined using a hybrid ion mobility atmospheric pressure drift tube system coupled with a linear ion trap. By enhancing the duty cycle of the drift tube system using a linearly chirped frequency, the collision-induced dissociation spectra were encoded in the mobility domain according to the drift times of each glycan isomer precursor. Differential fragmentation patterns correlated with precursor drift times ensured direct assignment of fragments with precursor structure whether as individual standards or in a mixture of isomers. In addition to certain metal ions providing higher degrees of separation than others, in select cases more than one arrival time distribution was observed for a single pure carbohydrate isomer. These observations suggest the existence of alternative coordination sites within a single monomeric species, but more interesting was the observation of different fragmentation ion yields for carbohydrate dimers formed through metal adduction. Positive-ion data were also compared with negative-ion species, where dimer formation did not occur and single peaks were observed for each isomeric tetrasaccharide-alditol. This enhanced analytical power has implications not only for carbohydrate molecules but also for a wide variety of complex mixtures of molecules where dissociation spectra may potentially be derived from combinations of monomeric, homodimeric, and heterodimeric species having identical nominal m/z values.

  18. NOx, FINE PARTICLE AND TOXIC METAL EMISSIONS FROM THE COMBUSTION OF SEWAGE SLUDGE/COAL MIXTURES: A SYSTEMATIC ASSESSMENT

    SciTech Connect

    Jost O.L. Wendt

    2003-01-31

    This research project focuses on pollutants from the combustion of mixtures of dried municipal sewage sludge (MSS) and coal. The objective is to determine the relationship between (1) fraction sludge in the sludge/coal mixture, and (2) combustion conditions on (a) NOx concentrations in the exhaust, (b) the size segregated fine and ultra-fine particle composition in the exhaust, and (c) the partitioning of toxic metals between vapor and condenses phases, within the process. The proposed study will be conducted in concert with an existing ongoing research on toxic metal partitioning mechanisms for very well characterized pulverized coals alone. Both high NOx and low NOx combustion conditions will be investigated (unstaged and staged combustion). Tradeoffs between CO{sub 2} control, NO{sub x} control, and inorganic fine particle and toxic metal emissions will be determined. Previous research results have demonstrated that the inhalation of coal/MSS ash particles cause an increase in lung permeability than coal ash particles alone. Elemental analysis of the coal/MSS ash particles showed that Zn was more abundant in these ash particles than the ash particles of coal ash alone.

  19. NOx, FINE PARTICLE AND TOXIC METAL EMISSIONS FROM THE COMBUSTION OF SEWAGE SLUDGE/COAL MIXTURES: A SYSTEMATIC ASSESSMENT

    SciTech Connect

    Jost O.L. Wendt

    2001-05-04

    This research project focuses on pollutants from the combustion of mixtures of dried municipal sewage sludge (MSS) and coal. The objective is to determine the relationship between (1) fraction sludge in the sludge/coal mixture, and (2) combustion conditions on (a) NO{sub x} concentrations in the exhaust, (b) the size segregated fine and ultra-fine particle composition in the exhaust, and (c) the partitioning of toxic metals between vapor and condenses phases, within the process. To this end we shall use an existing 17kW downflow laboratory combustor, available with coal and sludge feed capabilities. The proposed study will be conducted in concert with an existing ongoing research on toxic metal partitioning mechanisms for very well characterized pulverized coals alone. Both high NO{sub x} and low NO{sub x} combustion conditions will be investigated (unstaged and staged combustion). The proposed work uses existing analytical and experimental facilities and draws on 20 years of research on NO{sub x} and fine particles that has been funded by DOE in this laboratory. Four barrels of dried sewage sludge are currently in the laboratory. Insofar as possible pertinent mechanisms will be elucidated. Tradeoffs between CO{sub 2} control, NO{sub x} control, and inorganic fine particle and toxic metal emissions will be determined.

  20. NOx, FINE PARTICLE AND TOXIC METAL EMISSIONS FROM THE COMBUSTION OF SEWAGE SLUDGE/COAL MIXTURES: A SYSTEMATIC ASSESSMENT

    SciTech Connect

    Jost O.L. Wendt

    2002-02-05

    This research project focuses on pollutants from the combustion of mixtures of dried municipal sewage sludge (MSS) and coal. The objective is to determine the relationship between (1) fraction sludge in the sludge/coal mixture, and (2) combustion conditions on (a) NO{sub x} concentrations in the exhaust, (b) the size segregated fine and ultra-fine particle composition in the exhaust, and (c) the partitioning of toxic metals between vapor and condenses phases, within the process. To this end work is progress using an existing 17kW downflow laboratory combustor, available with coal and sludge feed capabilities. The proposed study will be conducted in concert with an existing ongoing research on toxic metal partitioning mechanisms for very well characterized pulverized coals alone. Both high NO{sub x} and low NO{sub x} combustion conditions will be investigated (unstaged and staged combustion). The proposed work uses existing analytical and experimental facilities and draws on 20 years of research on NO{sub x} and fine particles that has been funded by DOE in this laboratory. Four barrels of dried sewage sludge are currently in the laboratory. Insofar as possible pertinent mechanisms will be elucidated. Tradeoffs between CO{sub 2} control, NO{sub x} control, and inorganic fine particle and toxic metal emissions will be determined. For the Fifth Quarter of this project we focus on determining whether certain trace metals are associated with certain major species, such as calcium and iron. To this end we present data showing correlations between As, Se,and Sb and major species, such as Ca and Fe. Conversely, lack of correlation between trace metals and elements, such as aluminum can also be used to infer lack of chemical association.

  1. EXPRESSION OF RAINBOW TROUT P450 MRNA IN RESPONSE TO MIXTURES OF B[A]P, CADMIUM, AND ESTRADIOL

    EPA Science Inventory

    A great deal of uncertainty exists regarding the response of biological indicators of exposure to mixtures of chemical stressors. Enzymatic transformation systems that are exposed to xenobiotic insult may interact unpredictably when more than one stressor is present. In particu...

  2. Calcium fluxes in juvenile tilapia, Oreochromis mossambicus, exposed to sublethal waterborne Cd, Cu or mixtures of these metals

    SciTech Connect

    Pelgrom, S.M.G.J.; Lock, R.A.C.; Balm, P.H.M.; Bonga, S.E.W.

    1997-04-01

    In juvenile tilapia the effects of waterborne Cu, Cd, and combinations of these metals on whole-body Ca fluxes were studied, using {sup 45}Ca as tracer. The maintenance of Ca homeostasis in fish is crucial throughout life but is especially important in young fish; Ca is also critical for growth. Single metal exposure had no effect on Ca fluxes after 6 d of exposure. In fish coexposed to 200 {micro}g Cu L{sup {minus}1} + 70 {micro}g Cd L{sup {minus}1} however, Ca influx was significantly decreased, whereas Ca efflux was not affected. As a result, the net flux was decreased. Because the effect on Ca fluxes observed in Cu/Cd-coexposed fish could not have been predicted from the effects of single metal exposures, this study underscores the impact of interactions between toxicants. Because natural freshwaters are commonly polluted by mixtures of metals, interactions between toxicants are important in risk assessment of heavy metals.

  3. Classification of herbal mixtures on the basis of some metals content using pattern recognition techniques.

    PubMed

    Suchacz, Bogdan; Wesolowski, Marek

    2013-04-01

    The purpose of this study was to investigate the content of trace elements in relation to the composition of domestic herbal mixtures. Cluster analysis, principal components analysis, and self-organizing maps were applied to identify existing relationships. The concentrations of Ni, Pb, Cd, Cr, Cu, Fe, Mn, Zn in 81 samples of herbal mixtures were determined with application of FAAS. The study showed that the levels of trace elements in some herbal mixtures of the same composition were comparable. The projection of herbal samples onto topological maps of adjustable sizes allowed recognition of the identical herbal preparations characterized by dissimilar levels of trace elements. The elements which played the most important role in recognition of the herbal samples were Mn, Ni, Zn and partly Cu, Fe and Cd.

  4. Molecular dynamics investigation of separation of hydrogen sulfide from acidic gas mixtures inside metal-doped graphite micropores.

    PubMed

    Huang, Pei-Hsing

    2015-09-21

    The separation of poisonous compounds from various process fluids has long been highly intractable, motivating the present study on the dynamic separation of H2S in acidic-gas-mixture-filled micropores. The molecular dynamics approach, coupled with the isothermal-isochoric ensemble, was used to model the molecular interactions and adsorption of H2S/CO2/CO/H2O mixtures inside metal-doped graphite slits. Due to the difference in the adsorption characteristics between the two distinct adsorbent materials, the metal dopant in the graphitic micropores leads to competitive adsorption, i.e. the Au and graphite walls compete to capture free adsorbates. The effects of competitive adsorption, coupled with changes in the gas temperature, concentration, constituent ratio and slit width on the constituent separation of mixtures were systematically studied. The molecule-wall binding energies calculated in this work (those of H2S, H2O and CO on Au walls and those of H2O, CO and CO2 on graphite walls) show good agreement with those obtained using density functional theory (DFT) and experimental results. The z-directional self-diffusivities (Dz) for adsorbates inside the slit ranged from 10(-9) to 10(-7) m(2) s(-1) as the temperature was increased from 10 to 500 K. The values are comparable with those for a typical microporous fluid (10(-8)-10(-9) m(2) s(-1) in a condensed phase and 10(-6)-10(-7) m(2) s(-1) in the gaseous state). The formation of H-bonding networks and hydrates of H2S is disadvantageous for the separation of mixtures. The results indicate that H2S can be efficiently separated from acidic gas mixtures onto the Au(111) surface by (i) reducing the mole fraction of H2S and H2O in the mixtures, (ii) raising the gas temperature to the high temperature limit (≥400 K), and (iii) lowering the slit width to below the threshold dimension (≤23.26 Å).

  5. Modeling of Copper(II), Cadmium(II), and Lead(II) Adsorption on Red Mud from Metal-EDTA Mixture Solutions.

    PubMed

    Güçlü; Apak

    2000-08-15

    The adsorption of toxic heavy metal cations, i.e., Cu(II), Cd(II), and Pb(II), from metal-EDTA mixture solutions on a composite adsorbent having a heterogeneous surface, i.e., bauxite waste red mud, has been investigated and modeled with the aid of a modified surface complexation approach in respect to pH and complexant dependency of heavy metal adsorption. EDTA was selected as the modeling ligand in view of its wide usage as an anthropogenic chelating agent and abundance in natural waters. The adsorption experiments were conducted for metal salts (nitrates), metal-EDTA complexes alone, or in mixtures containing (metal+metal-EDTA). The adsorption equilibrium constants for the metal ions and metal-EDTA complexes were calculated. For all studied cases, the solid adsorbent phase concentrations of the adsorbed metal and metal-EDTA complexes were found by using the derived model equations with excellent compatibility of experimental and theoretically generated adsorption isotherms. The model was useful for metal and metal-EDTA mixture solutions either at their natural pH of equilibration with the sorbent, or after pH elevation with NaOH titration up to a certain pH. Thus adsorption of every single species (M(2+) or MY(2-)) or of possible mixtures (M(2+)+MY(2-)) at natural pH or after NaOH titration could be calculated by the use of simple quadratic model equations, once the initial concentrations of the corresponding species, i.e., [M(2+)](0) or [MY(2-)](0), were known. The compatibility of theoretical and experimental data pairs of adsorbed species concentrations was verified by means of nonlinear regression analysis. The findings of this study can be further developed so as to serve environmental risk assessment concerning the expansion of a heavy metal contaminant plume with groundwater move ment in soil consisting of hydrated-oxide type minerals. Copyright 2000 Academic Press.

  6. Integrated photo-responsive metal oxide semiconductor circuit

    NASA Technical Reports Server (NTRS)

    Jhabvala, Murzban D. (Inventor); Dargo, David R. (Inventor); Lyons, John C. (Inventor)

    1987-01-01

    An infrared photoresponsive element (RD) is monolithically integrated into a source follower circuit of a metal oxide semiconductor device by depositing a layer of a lead chalcogenide as a photoresistive element forming an ohmic bridge between two metallization strips serving as electrodes of the circuit. Voltage from the circuit varies in response to illumination of the layer by infrared radiation.

  7. Development of Metal/Polymer Mixtures for Micro Powder Injection Moulding

    NASA Astrophysics Data System (ADS)

    Quinard, C.; Barriere, T.; Gelin, J. C.

    2007-04-01

    Important research tasks at ENSMM/LMA are concerned for the development of mixtures of Fine powders associated to polymer binders dedicated to the powder injection moulding (PIM) and to the powder injection micro-moulding (μPIM) in accordance with many works already carried out with different feedstock suppliers dedicated to the macro-components.

  8. Efficient destruction of CF4 through in situ generation of alkali metals from heated alkali halide reducing mixtures.

    PubMed

    Lee, Myung Churl; Choi, Wonyong

    2002-03-15

    Perfluorocarbons (PFCs) are the most potent green house gases that are very recalcitrant at destruction. An effective way of converting PFCs using hot solid reagents into safe products has been recently introduced. By investigating the thermal reductive destruction of tetrafluoromethane (CF4) we provided new insight and more physicochemical consideration on this novel process. The complete destruction of CF4was successfully achieved by flowing the gas through a heated reagent bed (400-950 degrees C) that contained powder mixtures of alkali halides, CaO, and Si. The silicon acted as a reducing agent of alkali halides for the in-situ production of alkali metals, and the calcium oxide played the role of a halide ion acceptor. The absence of any single component in this ternary mixture drastically reduced the destruction efficiency of CF4. The CF4 destruction efficiencies with the solid reagent containing the alkali halide, MX, increased in the order of Li approximately Na < K < Cs for alkali cations and I < Br < Cl < F for halide anions. This trend agreed with the endothermicity of the alkali metal generation reaction: the higher the endothermicity, the lower the destruction efficiency. Alkali metal generation was indirectly detected by monitoring H2 production from its reaction with water. The production of alkali metals increased with NaF, KF, and CsF in this order. The CsF/CaO/Si system exhibited the complete destruction of CF4 at as low as 600 degrees C. The solid product analysis by X-ray diffraction (XRD) showed the formation of CaF2 and the depletion of Si with black carbon particles formed in the solid reagent residue. No CO/CO2 and toxic HF and SiF4 formation were detected in the exhaust gas.

  9. NOx, FINE PARTICLE AND TOXIC METAL EMISSIONS FROM THE COMBUSTION OF SEWAGE SLUDGE/COAL MIXTURES: A SYSTEMATIC ASSESSMENT

    SciTech Connect

    Jost O.L. Wendt

    2002-08-15

    This research project focuses on pollutants from the combustion of mixtures of dried municipal sewage sludge (MSS) and coal. The objective is to determine the relationship between (1) fraction sludge in the sludge/coal mixture, and (2) combustion conditions on (a) NOx concentrations in the exhaust, (b) the size segregated fine and ultra-fine particle composition in the exhaust, and (c) the partitioning of toxic metals between vapor and condenses phases, within the process. The proposed study will be conducted in concert with an existing ongoing research on toxic metal partitioning mechanisms for very well characterized pulverized coals alone. Both high NOx and low NOx combustion conditions will be investigated (unstaged and staged combustion). Tradeoffs between CO2 control, NOx control, and inorganic fine particle and toxic metal emissions will be determined. Previous research has yielded data on trace metal partitioning for MSS by itself, with natural gas assist, for coal plus MSS combustion together, and for coal alone. We have re-evaluated the inhalation health effects of ash aerosol from combustion of MSS both by itself and also together with coal. We have concluded that ash from the co-combustion of MSS and coal is very much worse from an inhalation health point of view, than ash from either MSS by itself or coal by itself. The reason is that ZnO is not the ''bad actor'' as had been suspected before, but the culprit is, rather, sulfated Zn. The MSS supplies the Zn and the coal supplies the sulfur, and so it is the combination of coal and MSS that makes that process environmentally bad. If MSS is to be burned, it should be burned without coal, in the absence of sulfur.

  10. Stimuli responsive release of metalic nanoparticles on semiconductor substrates.

    PubMed

    Santiago-Cordoba, Miguel; Topal, Özge; Allara, David L; Kalkan, A Kaan; Demirel, Melik C

    2012-04-10

    Optically active metal nanoparticles have been of recent and broad interest for applications to biomarker detection because of their ability to enable high sensitivity enhancements in various optical detection techniques. Here, we report stimuli responsive release of metallic nanoparticles on a semiconductor thin film array structure based on pH change. The metallic nanoparticles are obtained by a simple redox procedure on the semiconductor surface. This approach allows controlling nanoparticle surface coatings in situ for biomolecule conjugation, such as DNA probes on nanoparticles, and rapid stimuli responsive release of these nanoparticles upon pH change.

  11. Chemical induction of tumors in oysters by a mixture of aromatic and chlorinated hydrocarbons, amines and metals

    SciTech Connect

    Gardner, G.R.; Pruell, R.J.; Malcolm, A.R.

    1992-01-01

    Tumors were induced in eastern oysters (Crassostrea virginica) by a mixture of aromatic hydrocarbons, an aromatic amine, polychlorinated biphenyls, chlorinated hydrocarbons, a nitrosoamine and heavy metals. Kidney and enteric tumors developed in oysters following exposure to a mixture containing 3,4-benzopyrene, 1,2-benzanthracene, 2-aminofluorene, N-nitrosodiethylamine, technical chlordane, Aroclors 1242 and 1254, p,p'-DDE, cadmium (CdCl2), chromium (K2CrO4) and lead (Pb(NO3)2). 2-Aminofluorene and N-nitrosodiethylamine, not measured in Black Rock Harbor sediment, were both added at 0.6 and 6.0 micrograms/g dry sediment. A 3% prevalence of low-grade renal and gastrointestinal tumors developed after 30 days in oysters fed water-column suspended sediment particulate spiked with the mixture of chemicals. Disease progression was most advanced in enteric adenomas. Both types are comparable to those produced after 30 days in the same organs by chemically contaminated Black Rock Harbor sediment.

  12. Combining a finite mixture distribution model with indicator kriging to delineate and map the spatial patterns of soil heavy metal pollution in Chunghua County, central Taiwan.

    PubMed

    Lin, Yu-Pin; Cheng, Bai-You; Shyu, Guey-Shin; Chang, Tsun-Kuo

    2010-01-01

    This study identifies the natural background, anthropogenic background and distribution of contamination caused by heavy metal pollutants in soil in Chunghua County of central Taiwan by using a finite mixture distribution model (FMDM). The probabilities of contaminated area distribution are mapped using single-variable indicator kriging and multiple-variable indicator kriging (MVIK) with the FMDM cut-off values and regulation thresholds for heavy metals. FMDM results indicate that Cr, Cu, Ni and Zn can be individually fitted by a mixture model representing the background and contamination distributions of the four metals in soil. The FMDM cut-off values for contamination caused by the metals are close to the regulation thresholds, except for the cut-off value of Zn. The receiver operating characteristic (ROC) curve validates that indicator kriging and MVIK with FMDM cut-off values can reliably delineate heavy metals contamination, particularly for areas lacking background information and high heavy metal concentrations in soil.

  13. Screening Metal-Organic Frameworks by Analysis of Transient Breakthrough of Gas Mixtures in a Fixed Bed Adsorber

    SciTech Connect

    Krishna, Rajamani; Long, Jeffrey R.

    2011-07-07

    Metal–organic frameworks (MOFs) offer considerable potential for separating a variety of mixtures that are important in applications such as CO₂ capture and H₂ purification. In view of the vast number of MOFs that have been synthesized, there is a need for a reliable procedure for comparing screening and ranking MOFs with regard to their anticipated performance in pressure swing adsorption (PSA) units. For this purpose, the most commonly used metrics are the adsorption selectivity and the working capacity. Here, we suggest an additional metric for comparing MOFs that is based on the analysis of the transient response of an adsorber to a step input of a gaseous mixture. For a chosen purity of the gaseous mixture exiting from the adsorber, a dimensionless breakthrough time τ{sub break} can be defined and determined; this metric determines the frequency of required regeneration and influences the productivity of a PSA unit. The values of τ{sub break} are dictated both by selectivity and by capacity metrics .By performing transient adsorber calculations for separation of CO₂/H₂, CO₂/CH₄, CH₄/H₂, and CO₂/CH₄/H₂ mixtures, we compare the values of τbreak to highlight some important advantages of MOFs over conventionally used adsorbents such as zeolite NaX. For a given separation duty, such comparisons provide a more realistic ranking of MOFs than afforded by either selectivity or capacity metrics alone. We conclude that breakthrough calculations can provide an essential tool for screening MOFs.

  14. Heterogeneous mixtures of elliptical particles: Directly resolving local and global properties and responses

    NASA Astrophysics Data System (ADS)

    Liu, Qianlong; Reifsnider, Kenneth L.

    2013-02-01

    In our earlier papers, Prosperetti’s seminal Physalis method for fluid flows was extended to directly resolve electric fields in finite-sized particles and to investigate accurately the mutual fluid-particle, particle-particle, and particle-boundary interactions for circular/spherical particles. For the first time, the method makes the accurate prediction of the local charge distribution, force and torque on finite-sized particles possible. In the present work, the method is extended to heterogeneous mixtures of elliptical particles to further investigate the effects of the orientation and anisotropy. The direct resolution of the effect of fields in heterogeneous mixtures of elliptical particles to determine local and global properties and responses has many applications in engineering, mechanics, physics, chemistry, and biology. The method can be applied to heterogeneous materials, heterogeneous functional materials, microfluidics, and devices such as electric double layer capacitors. In the present paper, the accuracy of the method is extensively investigated even for very challenging problems, for example, for elongated rod-like particles with very high aspect ratios. The accuracy and efficiency of the method suggests that it can be used for many important applications of broad interest.

  15. NOx, FINE PARTICLE AND TOXIC METAL EMISSIONS FROM THE COMBUSTION OF SEWAGE SLUDGE/COAL MIXTURES: A SYSTEMATIC ASSESSMENT

    SciTech Connect

    Jost O.L. Wendt

    2002-02-05

    This research project focuses on pollutants from the combustion of mixtures of dried municipal sewage sludge (MSS) and coal. The objective is to determine the relationship between (1) fraction sludge in the sludge/coal mixture, and (2) combustion conditions on (a) NO{sub x} concentrations in the exhaust, (b) the size segregated fine and ultra-fine particle composition in the exhaust, and (c) the partitioning of toxic metals between vapor and condenses phases, within the process. To this end work is progress using an existing 17kW downflow laboratory combustor, available with coal and sludge feed capabilities. The proposed study will be conducted in concert with an existing ongoing research on toxic metal partitioning mechanisms for very well characterized pulverized coals alone. Both high NO{sub x} and low NO{sub x} combustion conditions will be investigated (unstaged and staged combustion). The proposed work uses existing analytical and experimental facilities and draws on 20 years of research on NO{sub x} and fine particles that has been funded by DOE in this laboratory. Four barrels of dried sewage sludge are currently in the laboratory. Insofar as possible pertinent mechanisms will be elucidated. Tradeoffs between CO{sub 2} control, NO{sub x} control, and inorganic fine particle and toxic metal emissions will be determined. Progress in the Sixth Quarter (January 1, 2002 through March 31, 2002) was slow because of slagging problems in the combustor. These required the combustor to be rebuilt, a job that is not yet complete. A paper describing our results heretofore has been accepted by the Journal Environmental Science and Technology.

  16. Auditory steady state responses and cochlear implants: Modeling the artifact-response mixture in the perspective of denoising

    PubMed Central

    Mina, Faten; Attina, Virginie; Duroc, Yvan; Veuillet, Evelyne; Truy, Eric; Thai-Van, Hung

    2017-01-01

    Auditory steady state responses (ASSRs) in cochlear implant (CI) patients are contaminated by the spread of a continuous CI electrical stimulation artifact. The aim of this work was to model the electrophysiological mixture of the CI artifact and the corresponding evoked potentials on scalp electrodes in order to evaluate the performance of denoising algorithms in eliminating the CI artifact in a controlled environment. The basis of the proposed computational framework is a neural mass model representing the nodes of the auditory pathways. Six main contributors to auditory evoked potentials from the cochlear level and up to the auditory cortex were taken into consideration. The simulated dynamics were then projected into a 3-layer realistic head model. 32-channel scalp recordings of the CI artifact-response were then generated by solving the electromagnetic forward problem. As an application, the framework’s simulated 32-channel datasets were used to compare the performance of 4 commonly used Independent Component Analysis (ICA) algorithms: infomax, extended infomax, jade and fastICA in eliminating the CI artifact. As expected, two major components were detectable in the simulated datasets, a low frequency component at the modulation frequency and a pulsatile high frequency component related to the stimulation frequency. The first can be attributed to the phase-locked ASSR and the second to the stimulation artifact. Among the ICA algorithms tested, simulations showed that infomax was the most efficient and reliable in denoising the CI artifact-response mixture. Denoising algorithms can induce undesirable deformation of the signal of interest in real CI patient recordings. The proposed framework is a valuable tool for evaluating these algorithms in a controllable environment ahead of experimental or clinical applications. PMID:28350887

  17. THE CARCINOGENIC RESPONSE OF TSC2 MUTANT LONG EVANS (EKER) RATS TO A MIXTURE OF DRINKING WATER DISINFECTION BY-PRODUCTS WAS LESS THAN ADDITIVE

    EPA Science Inventory

    Cancer risk assessment methods for chemical mixtures in drinking water are not well defined. Current default risk assessments for chemical mixtures assume additivity of carcinogenic effects but this may not represent the actual biological response. A rodent model of hereditary ...

  18. Differential metal response and regulation of human heavy metal-inducible genes.

    PubMed

    Murata, M; Gong, P; Suzuki, K; Koizumi, S

    1999-07-01

    A number of heavy metal-inducible genes have been reported, but their ranges of response to various metal species are not well known. It is also unclear if these genes are regulated through common mechanisms. To answer these questions, we compared induction kinetics of human metal-inducible genes including the MT-IIA (coding for a metallothionein isoform), hsp70 (coding for the 70-kDa heat-shock protein), and c-fos genes in HeLa cells exposed to Zn, Cd, Ag, Hg, Cu(II), Co, or Ni ions. Transcripts from these three genes were increased after exposure to wide ranges of metals, but each gene was unique in its induction kinetics. Generally, induction was observed at lower metal concentrations in the order of MT-IIA, hsp70, and c-fos. These genes also showed differential responses in time course: more rapid induction was observed in the order of c-fos, hsp70, and MT-IIA after exposure to Zn or Cd. Since the metal-responsive element (MRE) and heat shock element (HSE) of the MT-IIA and hsp70 genes, respectively, are thought to be the cis-acting DNA elements that mediate metal response, we compared the properties of proteins that specifically bind to these elements. MRE-binding activity was detected only in the extract from cells exposed to Zn. By contrast, HSE-binding activity was detected in extracts from cells treated with Zn, Cd, Ag, and Cu. The former was also activated by Zn in vitro, while the latter was not. Each of these DNA-binding activities showed no affinity to the recognition sequence of the other. These results demonstrate that the human metal-inducible genes have broad ranges of response to a variety of heavy metals, but suggest that they are probably regulated through independent mechanisms.

  19. Determination of metallic iron in a mixture of lime, calcium sulphide and pyrrhotite.

    PubMed

    Sastri, V S

    A method is described for the determination of metallic iron in a complex matrix consisting of calcium oxide, calcium sulphide, carbon and pyrrhotite. The procedure consists of leaching the sample with 5% ammonium chloride solution (10% sucrose solution in some cases) followed by treatment with mercury(II) chloride solution and titration with dichromate solution.

  20. Persistent activation of DNA damage signaling in response to complex mixtures of PAHs in air particulate matter

    SciTech Connect

    Jarvis, Ian W.H.; Bergvall, Christoffer; Bottai, Matteo; Westerholm, Roger; Stenius, Ulla; Dreij, Kristian

    2013-02-01

    Complex mixtures of polycyclic aromatic hydrocarbons (PAHs) are present in air particulate matter (PM) and have been associated with many adverse human health effects including cancer and respiratory disease. However, due to their complexity, the risk of exposure to mixtures is difficult to estimate. In the present study the effects of binary mixtures of benzo[a]pyrene (BP) and dibenzo[a,l]pyrene (DBP) and complex mixtures of PAHs in urban air PM extracts on DNA damage signaling was investigated. Applying a statistical model to the data we observed a more than additive response for binary mixtures of BP and DBP on activation of DNA damage signaling. Persistent activation of checkpoint kinase 1 (Chk1) was observed at significantly lower BP equivalent concentrations in air PM extracts than BP alone. Activation of DNA damage signaling was also more persistent in air PM fractions containing PAHs with more than four aromatic rings suggesting larger PAHs contribute a greater risk to human health. Altogether our data suggests that human health risk assessment based on additivity such as toxicity equivalency factor scales may significantly underestimate the risk of exposure to complex mixtures of PAHs. The data confirms our previous findings with PAH-contaminated soil (Niziolek-Kierecka et al., 2012) and suggests a possible role for Chk1 Ser317 phosphorylation as a biological marker for future analyses of complex mixtures of PAHs. -- Highlights: ► Benzo[a]pyrene (BP), dibenzo[a,l]pyrene (DBP) and air PM PAH extracts were compared. ► Binary mixture of BP and DBP induced a more than additive DNA damage response. ► Air PM PAH extracts were more potent than toxicity equivalency factor estimates. ► Larger PAHs (> 4 rings) contribute more to the genotoxicity of PAHs in air PM. ► Chk1 is a sensitive marker for persistent activation of DNA damage signaling from PAH mixtures.

  1. A differential array of metalated synthetic receptors for the analysis of tripeptide mixtures.

    PubMed

    Wright, Aaron T; Anslyn, Eric V; McDevitt, John T

    2005-12-14

    A novel library of resin-bound receptors within a cross-reactive differential array for the identification and discrimination of tripeptides and tripeptide mixtures is reported. Pattern recognition using principal component analysis showed complete discrimination of four similar tripeptides and three tripeptide mixtures. The library is comprised of a Cu(II)-centered core with two proximally appended tripeptide arms emanating outward. One tripeptide arm was prepared using combinatorial chemistry to generate the differential nature of the library. Thirty resin-bound receptors were randomly selected from the library and placed within a silicon microchip array that included integrated microfluidics elements, and an indicator-uptake assay was used for colorimetric signaling. The indicator Orange G yielded an accurate measure of the degree of association between receptors and analytes as determined by kinetic analysis of the indicator-uptake assays. Within this paper we detail the method used for differential sensing using a novel receptor library. This work further demonstrates the power and utility of a differential array of synthetic receptors for identification and discrimination of complex bioanalytes.

  2. A homogeneous transition metal complex for clean hydrogen production from methanol-water mixtures

    NASA Astrophysics Data System (ADS)

    Rodríguez-Lugo, Rafael E.; Trincado, Mónica; Vogt, Matthias; Tewes, Friederike; Santiso-Quinones, Gustavo; Grützmacher, Hansjörg

    2013-04-01

    The development of an efficient catalytic process that mimics the enzymatic function of alcohol dehydrogenase is critical for using biomass alcohols for both the production of H2 as a chemical energy carrier and fine chemicals under waste-free conditions. Dehydrogenation of alcohol-water mixtures into their corresponding acids with molecular hydrogen as the sole by-product from the reaction can be catalysed by a ruthenium complex with a chelating bis(olefin) diazadiene ligand. This complex, [K(dme)2][Ru(H)(trop2dad)], stores up to two equivalents of hydrogen intramolecularly, and catalyses the production of H2 from alcohols in the presence of water and a base under homogeneous conditions. The conversion of a MeOH-H2O mixture proceeds selectively to CO2/H2 gas formation under neutral conditions, thereby allowing the use of the entire hydrogen content (12% by weight). Isolation and characterization of the ruthenium complexes from these reactions suggested a mechanistic scenario in which the trop2dad ligand behaves as a chemically ‘non-innocent’ co-operative ligand.

  3. A homogeneous transition metal complex for clean hydrogen production from methanol-water mixtures.

    PubMed

    Rodríguez-Lugo, Rafael E; Trincado, Mónica; Vogt, Matthias; Tewes, Friederike; Santiso-Quinones, Gustavo; Grützmacher, Hansjörg

    2013-04-01

    The development of an efficient catalytic process that mimics the enzymatic function of alcohol dehydrogenase is critical for using biomass alcohols for both the production of H2 as a chemical energy carrier and fine chemicals under waste-free conditions. Dehydrogenation of alcohol-water mixtures into their corresponding acids with molecular hydrogen as the sole by-product from the reaction can be catalysed by a ruthenium complex with a chelating bis(olefin) diazadiene ligand. This complex, [K(dme)2][Ru(H)(trop2dad)], stores up to two equivalents of hydrogen intramolecularly, and catalyses the production of H2 from alcohols in the presence of water and a base under homogeneous conditions. The conversion of a MeOH-H2O mixture proceeds selectively to CO2/H2 gas formation under neutral conditions, thereby allowing the use of the entire hydrogen content (12% by weight). Isolation and characterization of the ruthenium complexes from these reactions suggested a mechanistic scenario in which the trop2dad ligand behaves as a chemically 'non-innocent' co-operative ligand.

  4. Recovery of metals from a mixture of various spent batteries by a hydrometallurgical process.

    PubMed

    Tanong, Kulchaya; Coudert, Lucie; Mercier, Guy; Blais, Jean-Francois

    2016-10-01

    Spent batteries contain hazardous materials, including numerous metals (cadmium, lead, nickel, zinc, etc.) that are present at high concentrations. Therefore, proper treatment of these wastes is necessary to prevent their harmful effects on human health and the environment. Current recycling processes are mainly applied to treat each type of spent battery separately. In this laboratory study, a hydrometallurgical process has been developed to simultaneously and efficiently solubilize metals from spent batteries. Among the various chemical leaching agents tested, sulfuric acid was found to be the most efficient and cheapest reagent. A Box-Behnken design was used to identify the influence of several parameters (acid concentration, solid/liquid ratio, retention time and number of leaching steps) on the removal of metals from spent batteries. According to the results, the solid/liquid ratio and acid concentration seemed to be the main parameters influencing the solubilization of zinc, manganese, nickel, cadmium and cobalt from spent batteries. According to the results, the highest metal leaching removals were obtained under the optimal leaching conditions (pulp density = 180 g/L (w/v), [H2SO4] = 1 M, number of leaching step = 3 and leaching time = 30 min). Under such optimum conditions, the removal yields obtained were estimated to be 65% for Mn, 99.9% for Cd, 100% for Zn, 74% for Co and 68% for Ni. Further studies will be performed to improve the solubilization of Mn and to selectively recover the metals.

  5. Assessing the impact of As-Cd-Pb metal mixture on cell transformation by two-stage Balb/c 3T3 cell assay.

    PubMed

    Rodríguez-Sastre, M A; Rojas, E; Valverde, M

    2014-07-01

    Human beings are exposed to metals as a consequence of various industrial activities, including glass production, agrochemical production, metallurgy and battery manufacture. New data about the possible mechanisms involved in the carcinogenic activity of these metals are constantly being reported. Exposure to complex mixtures of metals is more likely to occur than exposure to a single metal alone. Among these elements, arsenic, cadmium and lead are ubiquitous air and water pollutants that continue to threaten the quality of public health around the world. The aim of the present study was to evaluate the capability of a mixture of 2 µM NaAsO2, 2 µM CdCl2 and 5 µM Pb(C2H3O2)2·3H2O at relevant epidemiological concentrations to induce cell transformation processes. Transforming potential was determined by a murine two-stage Balb/c 3T3 cell assay. Cell viability, reactive oxygen species (ROS), DNA damage, cell cycle analysis, senescence, generation time and metallothionein expression were also evaluated. The results showed that the metal mixture induced morphological cell transformation only when acting as initiator stimuli of the process. A decrease in cell viability was observed at the promotion stage, a time during which ROS increase, especially when a metal mixture was applied as a promoter stimulant. Changes in DNA damage were not observed throughout the assay; however, we observed G1 cell cycle arrest. The metal mixture, acting as a promoter, is capable of inducing senescence, but metals employed as initiators with 12-O-tetradecanoylphorbol-13-acetate as a promoter are capable of causing avoidance of senescence and triggering the transformation potential of the cells.

  6. Thermoelastic response of thin metal films and their adjacent materials

    SciTech Connect

    Kang, S.; Yoon, Y.; Kim, J.; Kim, W.

    2013-01-14

    A pulsed laser beam applied to a thin metal film is capable of launching an acoustic wave due to thermal expansion. Heat transfer from the thin metal film to adjacent materials can also induce thermal expansion; thus, the properties of these adjacent materials (as well as the thin metal film) should be considered for a complete description of the thermoelastic response. Here, we show that adjacent materials with a small specific heat and large thermal expansion coefficient can generate an enhanced acoustic wave and we demonstrate a three-fold increase in the peak pressure of the generated acoustic wave on substitution of parylene for polydimethylsiloxane.

  7. Response of bacterial isolates from Antarctic shallow sediments towards heavy metals, antibiotics and polychlorinated biphenyls.

    PubMed

    Lo Giudice, Angelina; Casella, Patrizia; Bruni, Vivia; Michaud, Luigi

    2013-03-01

    The response of bacterial isolates from Antarctic sediments to polychlorinated biphenyls (Aroclor 1242 mixture), heavy metal salts (cadmium, copper, mercury and zinc) and antibiotics (ampicillin, chloramphenicol, kanamycin and streptomycin) was investigated. Overall, the ability to growth in the presence of Aroclor 1242 as a sole carbon source was observed for 22 isolates that mainly belonged to Psychrobacter spp. Tolerance to the heavy metals assayed in this study was in the order of Cd > Cu > Zn > Hg and appeared to be strictly related to the metal concentrations, as determined during previous chemical surveys in the same area. With regards to antibiotic assays, the response of the isolates to the tested antibiotics ranged from complete resistance to total susceptibility. In particular, resistances to ampicillin and chloramphenicol were very pronounced in the majority of isolates. Our isolates differently responded to the presence of toxic compounds primarily based on their phylogenetic affiliation and secondarily at strain level. Moreover, the high incidence of resistance either to metal or antibiotics, in addition to the capability to grow on PCBs, confirm that bacteria are able to cope and/or adapt to the occurrence pollutants even in low human-impacted environments.

  8. Endothelial Cellular Responses to Biodegradable Metal Zinc.

    PubMed

    Ma, Jun; Zhao, Nan; Zhu, Donghui

    Biodegradable zinc (Zn) metals, a new generation of biomaterials, have attracted much attention due to their excellent biodegradability, bioabsorbability, and adaptability to tissue regeneration. Compared with magnesium (Mg) and iron (Fe), Zn exhibits better corrosion and mechanical behaviors in orthopedic and stent applications. After implantation, Zn containing material will slowly degrade, and Zn ions (Zn(2+)) will be released to the surrounding tissue. For stent applications, the local Zn(2+)concentration near endothelial tissue/cells could be high. However, it is unclear how endothelia will respond to such high concentrations of Zn(2+), which is pivotal to vascular remodeling and regeneration. Here, we evaluated the short-term cellular behaviors of primary human coronary artery endothelial cells (HCECs) exposed to a concentration gradient (0-140 μM) of extracellular Zn(2+). Zn(2+) had an interesting biphasic effect on cell viability, proliferation, spreading, and migration. Generally, low concentrations of Zn(2+) promoted viability, proliferation, adhesion, and migration, while high concentrations of Zn(2+) had opposite effects. For gene expression profiles, the most affected functional genes were related to cell adhesion, cell injury, cell growth, angiogenesis, inflammation, vessel tone, and coagulation. These results provide helpful information and guidance for Zn-based alloy design as well as the controlled release of Zn(2+)in stent and other related medical applications.

  9. Metal hydride differential scanning calorimetry as an approach to compositional determination of mixtures of hydrogen isotopologues and helium

    SciTech Connect

    Robinson, David B.; Luo, Weifang; Cai, Trevor Y.; Stewart, Kenneth D.

    2015-09-26

    Gaseous mixtures of diatomic hydrogen isotopologues and helium are often encountered in the nuclear energy industry and in analytical chemistry. Compositions of stored mixtures can vary due to interactions with storage and handling materials. When tritium is present, it decays to form ions and helium-3, both of which can lead to further compositional variation. Monitoring of composition is typically achieved by mass spectrometry, a method that is bulky and energy-intensive. Mass spectrometers disperse sample material through vacuum pumps, which is especially troublesome if tritium is present. Moreover, our ultimate goal is to create a compact, fast, low-power sensor that can determine composition with minimal gas consumption and waste generation, as a complement to mass spectrometry that can be instantiated more widely. We propose calorimetry of metal hydrides as an approach to this, due to the strong isotope effect on gas absorption, and demonstrate the sensitivity of measured heat flow to atomic composition of the gas. Peak shifts are discernible when mole fractions change by at least 1%. A mass flow restriction results in a unique dependence of the measurement on helium concentration. We present a mathematical model as a first step toward prediction of the peak shapes and positions. The model includes a useful method to compute estimates of phase diagrams for palladium in the presence of arbitrary mixtures of hydrogen isotopologues. As a result, we expect that this approach can be used to deduce unknown atomic compositions from measured calorimetric data over a useful range of partial pressures of each component.

  10. Metal hydride differential scanning calorimetry as an approach to compositional determination of mixtures of hydrogen isotopologues and helium

    DOE PAGES

    Robinson, David B.; Luo, Weifang; Cai, Trevor Y.; ...

    2015-09-26

    Gaseous mixtures of diatomic hydrogen isotopologues and helium are often encountered in the nuclear energy industry and in analytical chemistry. Compositions of stored mixtures can vary due to interactions with storage and handling materials. When tritium is present, it decays to form ions and helium-3, both of which can lead to further compositional variation. Monitoring of composition is typically achieved by mass spectrometry, a method that is bulky and energy-intensive. Mass spectrometers disperse sample material through vacuum pumps, which is especially troublesome if tritium is present. Moreover, our ultimate goal is to create a compact, fast, low-power sensor that canmore » determine composition with minimal gas consumption and waste generation, as a complement to mass spectrometry that can be instantiated more widely. We propose calorimetry of metal hydrides as an approach to this, due to the strong isotope effect on gas absorption, and demonstrate the sensitivity of measured heat flow to atomic composition of the gas. Peak shifts are discernible when mole fractions change by at least 1%. A mass flow restriction results in a unique dependence of the measurement on helium concentration. We present a mathematical model as a first step toward prediction of the peak shapes and positions. The model includes a useful method to compute estimates of phase diagrams for palladium in the presence of arbitrary mixtures of hydrogen isotopologues. As a result, we expect that this approach can be used to deduce unknown atomic compositions from measured calorimetric data over a useful range of partial pressures of each component.« less

  11. Raman analysis of complex pigment mixtures in 20th century metal knight shields of the Order of the Elephant.

    PubMed

    Lauridsen, Clara Bratt; Sanyova, Jana; Simonsen, Kim Pilkjær

    2015-11-05

    The pigment composition of six painted metal knight shields of the Order of the Elephant dating from the second half of the 20th century belonging to the Danish royal collection were studied using Raman microscopy. By focusing a 785 nm laser with a 50× objective on particles in paint cross sections, it was possible to identify the following 20 compounds: hematite, goethite, chrome red/orange, chrome yellow, zinc chrome yellow, carbon black, toluidine red PR3, chlorinated para red PR4, dinitroaniline orange PO5, phthalocyanine blue PB15, indanthrone blue PB60, ultramarine, Prussian blue, lead white, anatase, rutile, calcium carbonate, barium sulphate, gypsum and dolomite. The components were frequently present in complex pigment mixtures. Additional information was obtained by elemental analysis with scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) to identify cobalt blue, zinc white and cadmium red, as well as to indicate the presence of zinc white in some pigment mixtures. The study allowed a comparison between the industrially applied preparation layers and the artistic paint layers applied by the heraldic painter. Differences in the choice of paint and pigment types were observed on the earliest knight shields, demonstrating a general delay of industrial materials into artist paints.

  12. FINE PARTICAL AND TOXIC METAL EMISSIONS FROM THE COMBUSTION OF SEWAGE SLUDGE/COAL MIXTURES: A SYSTEMATIC ASSESSMENT

    SciTech Connect

    Jost O.L. Wendt; Wayne S. Seames; Art Fernandez

    2003-09-21

    This research project focuses on pollutants from the combustion of mixtures of dried municipal sewage sludge (MSS) and pulverized coal. The objective was to determine potential tradeoffs between CO{sub 2} mitigation through using a CO{sub 2} neutral fuel, such as municipal sewage sludge, and the emergence of other potential problems such as the emission of toxic fly ash particles. The work led to new insight into mechanisms governing the partitioning of major and trace metals from the combustion of sewage sludge, and mixtures of coal and sewage sludge. The research also showed that the co-combustion of coal and sewage sludge emitted fine particulate matter that might potentially cause greater lung injury than that from the combustion of either coal alone or municipal sewage sludge alone. The reason appeared to be that the toxicity measured required the presence of large amounts of both zinc and sulfur in particles that were inhaled. MSS provided the zinc while coal provided the sulfur. Additional research showed that the toxic effects could most likely be engineered out of the process, through the introduction of kaolinite sorbent downstream of the combustion zone, or removing the sulfur from the fuel. These results are consequences of applying ''Health Effects Engineering'' to this issue. Health Effects Engineering is a new discipline arising out of this work, and is derived from using a collaboration of combustion engineers and toxicologists to mitigate the potentially bad health effects from combustion of this biomass fuel.

  13. Calculation of K{sub {infinity}} for homogeneous {sup 235}U metal mixtures: Will the real K{sub {infinity}} please stand up?

    SciTech Connect

    Jordan, W.C.; Petrie, L.M.; Wright, R.Q.; Parks, C.V.

    1997-06-01

    This paper very briefly analyzes a journal article about calculating k{sub {infinity}} for metals mixed with uranium 235, and compares the article results with other calculation methods. The article suggested that continuous energy cross sections gave more accurate results than groupwise cross sections. The mixtures described in the article were dry, fast systems with several unusual characteristics; however, the majority of multigroup libraries used for analysis were developed for well moderated thermal systems. The results of calculations performed using several different codes and cross sections for three uranium/metal mixtures are presented in this paper. 1 tab.

  14. Perinatal and Childhood Exposure to Cadmium, Manganese, and Metal Mixtures and Effects on Cognition and Behavior: A Review of Recent Literature

    PubMed Central

    Sanders, Alison P.; Henn, Birgit Claus; Wright, Robert O.

    2015-01-01

    Lead (Pb) and mercury (Hg) neurotoxicity is well established. In recent years, a growing body of evidence suggests that environmental exposure to other metals including arsenic (As), cadmium (Cd), manganese (Mn), and their mixtures also pose public health threats. In this paper we summarize the recent literature examining the relationship of prenatal and childhood environmental metal exposures with cognitive and behavioral outcomes in children. We conducted a literature search to identify epidemiologic studies that examined the relationship of Cd, Mn, and metal mixtures with children’s neurodevelopmental/cognitive and behavioral outcomes. We restricted the search to peer-reviewed studies published in English between January 2009 and March 2015. We identified a total of 31 articles of which 16, 17, and 16 studies examined the effects of Cd, Mn, or metal mixtures, respectively. Based on our review, there is suggestive evidence that prenatal/childhood Cd exposure may be associated with poorer cognition, but additional research is clearly needed. We found little evidence of behavioral effects of early life Cd exposure, and no studies found a significant relationship with attention deficit hyperactivity disorder. Studies of early life Mn exposure consistently reported negative impacts on both cognition and behavior. There is also growing evidence that co-exposure to multiple metals can result in increased neurotoxicity compared to single metal exposures, in particular during early life. Few studies have evaluated behavioral effects related to metal co-exposures. PMID:26231505

  15. Histogram-based classification with Gaussian mixture modeling for GBM tumor treatment response using ADC map

    NASA Astrophysics Data System (ADS)

    Huo, Jing; Kim, Hyun J.; Pope, Whitney B.; Okada, Kazunori; Alger, Jeffery R.; Wang, Yang; Goldin, Jonathan G.; Brown, Matthew S.

    2009-02-01

    This study applied a Gaussian Mixture Model (GMM) to apparent diffusion coefficient (ADC) histograms to evaluate glioblastoma multiforme (GBM) tumor treatment response using diffusion weighted (DW) MR images. ADC mapping, calculated from DW images, has been shown to reveal changes in the tumor's microenvironment preceding morphologic tumor changes. In this study, we investigated the effectiveness of features that represent changes from pre- and post-treatment tumor ADC histograms to detect treatment response. The main contribution of this work is to model the ADC histogram as the composition of two components, fitted by GMM with expectation maximization (EM) algorithm. For both pre- and post-treatment scans taken 5-7 weeks apart, we obtained the tumor ADC histogram, calculated the two-component features, as well as the other standard histogram-based features, and applied supervised learning for classification. We evaluated our approach with data from 85 patients with GBM under chemotherapy, in which 33 responded and 52 did not respond based on tumor size reduction. We compared AdaBoost and random forests classification algorithms, using ten-fold cross validation, resulting in a best accuracy of 69.41%.

  16. Selective Single-Step Separation of a Mixture of Three Metal Ions by a Triphasic Ionic-Liquid-Water-Ionic-Liquid Solvent Extraction System.

    PubMed

    Vander Hoogerstraete, Tom; Blockx, Jonas; De Coster, Hendrik; Binnemans, Koen

    2015-08-10

    In a conventional solvent extraction system, metal ions are distributed between two immiscible phases, typically an aqueous and an organic phase. In this paper, the proof-of-principle is given for the distribution of metal ions between three immiscible phases, two ionic liquid phases with an aqueous phase in between them. Three-liquid-phase solvent extraction allows separation of a mixture of three metal ions in a single step, whereas at least two steps are required to separate three metals in the case of two-liquid-phase solvent extraction. In the triphasic system, the lower organic phase is comprised of the ionic liquid betainium- or choline bis(trifluoromethylsulfonyl)imide, whereas the upper organic phase is comprised of the ionic liquid trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)imide. The triphasic system was used for the separation of a mixture of tin(II), yttrium(III), and scandium(III) ions.

  17. Heavy Metal Stress and Some Mechanisms of Plant Defense Response

    PubMed Central

    Emamverdian, Abolghassem; Ding, Yulong; Mokhberdoran, Farzad; Xie, Yinfeng

    2015-01-01

    Unprecedented bioaccumulation and biomagnification of heavy metals (HMs) in the environment have become a dilemma for all living organisms including plants. HMs at toxic levels have the capability to interact with several vital cellular biomolecules such as nuclear proteins and DNA, leading to excessive augmentation of reactive oxygen species (ROS). This would inflict serious morphological, metabolic, and physiological anomalies in plants ranging from chlorosis of shoot to lipid peroxidation and protein degradation. In response, plants are equipped with a repertoire of mechanisms to counteract heavy metal (HM) toxicity. The key elements of these are chelating metals by forming phytochelatins (PCs) or metallothioneins (MTs) metal complex at the intra- and intercellular level, which is followed by the removal of HM ions from sensitive sites or vacuolar sequestration of ligand-metal complex. Nonenzymatically synthesized compounds such as proline (Pro) are able to strengthen metal-detoxification capacity of intracellular antioxidant enzymes. Another important additive component of plant defense system is symbiotic association with arbuscular mycorrhizal (AM) fungi. AM can effectively immobilize HMs and reduce their uptake by host plants via binding metal ions to hyphal cell wall and excreting several extracellular biomolecules. Additionally, AM fungi can enhance activities of antioxidant defense machinery of plants. PMID:25688377

  18. Heavy metal stress and some mechanisms of plant defense response.

    PubMed

    Emamverdian, Abolghassem; Ding, Yulong; Mokhberdoran, Farzad; Xie, Yinfeng

    2015-01-01

    Unprecedented bioaccumulation and biomagnification of heavy metals (HMs) in the environment have become a dilemma for all living organisms including plants. HMs at toxic levels have the capability to interact with several vital cellular biomolecules such as nuclear proteins and DNA, leading to excessive augmentation of reactive oxygen species (ROS). This would inflict serious morphological, metabolic, and physiological anomalies in plants ranging from chlorosis of shoot to lipid peroxidation and protein degradation. In response, plants are equipped with a repertoire of mechanisms to counteract heavy metal (HM) toxicity. The key elements of these are chelating metals by forming phytochelatins (PCs) or metallothioneins (MTs) metal complex at the intra- and intercellular level, which is followed by the removal of HM ions from sensitive sites or vacuolar sequestration of ligand-metal complex. Nonenzymatically synthesized compounds such as proline (Pro) are able to strengthen metal-detoxification capacity of intracellular antioxidant enzymes. Another important additive component of plant defense system is symbiotic association with arbuscular mycorrhizal (AM) fungi. AM can effectively immobilize HMs and reduce their uptake by host plants via binding metal ions to hyphal cell wall and excreting several extracellular biomolecules. Additionally, AM fungi can enhance activities of antioxidant defense machinery of plants.

  19. Meso-Scale Heterogeneity Effects on the Bulk Shock Response of Ti+Al+B Reactive Powder Mixtures

    NASA Astrophysics Data System (ADS)

    Gonzales, Manny; Gurumurthy, Ashok; Kennedy, Gregory; Gokhale, Arun; Thadhani, Naresh

    2015-06-01

    Highly heterogeneous reactive powder mixtures including Ti+2B (Stoichiometric 1:2) and an Al-containing mixture (Ti+2B+50%Al by vol.) are studied to ascertain the shock compression response and potential reaction behavior. The transit time through the pressed powder mixture compacts is monitored using poly-vinylidene fluoride (PVDF) stress gauges and used to compute a wave speed through the compact. The stress states at the back of the powder (measuring the state of the compacted and potentially transformed powder) are compared with thermodynamic mixture theories as well as meso scale microstructure-based simulations to identify the onset of anomalous behavior which can be traced to highly exothermic reaction in this system. Shock compression experiments show highly dispersive wave fronts when measured from the back surface of the powder compact, which are compared with meso scale simulations considering varying starting mixture states. These simulations also provide microstructure evolution parameters during shock compression which are stereologically evaluated to establish the state of the material present under the experimental conditions. An analysis of the effects of starting mixture conditions on the stress at the back surface is also presented. We gratefully acknowledge support and funding from DTRA through Grant No. HDTRA1-10-1-0038.

  20. Mixture Item Response Theory-MIMIC Model: Simultaneous Estimation of Differential Item Functioning for Manifest Groups and Latent Classes

    ERIC Educational Resources Information Center

    Bilir, Mustafa Kuzey

    2009-01-01

    This study uses a new psychometric model (mixture item response theory-MIMIC model) that simultaneously estimates differential item functioning (DIF) across manifest groups and latent classes. Current DIF detection methods investigate DIF from only one side, either across manifest groups (e.g., gender, ethnicity, etc.), or across latent classes…

  1. Effects of subchronic exposure via drinking water to a mixture of eight water-contaminating metals: a biochemical and histopathological study in male rats.

    PubMed

    Jadhav, S H; Sarkar, S N; Patil, R D; Tripathi, H C

    2007-11-01

    In the current study, we examined whether subchronic exposure via drinking water to low doses of a mixture of metals (arsenic, cadmium, lead, mercury, chromium, manganese, iron, and nickel), found as contaminants in various water sources of India, and to concentrations equivalent to WHO maximum permissible limits (MPL) in drinking water for individual metals, can alter systemic physiology of male rats. Data on water contamination with metals in India were collected from the literature and metals were selected on the basis of their frequency of occurrence and contamination level above MPL. Male Wistar rats were exposed to the mixture at 0, 1, 10, and 100 times the mode concentrations (the most frequently occurring concentration) of the individual metals via drinking water for 90 days. One more group of rats was exposed to the mixture at a concentration equivalent to the MPL (WHO) in drinking water for individual metals. Toxic potential of the mixture was evaluated by assessing general toxicological end points, serum chemistry and histopathology of vital organs. The mixture decreased body weight and water consumption and increased weights of brain, liver, and kidneys with 10x and 100x doses. After 30 days of exposure, no appreciable changes were found in any blood clinical markers. After 60 days, only the 100x dose, while after 90 days both 10x and 100x doses increased activities of aspartate aminotransferase and alkaline phosphatase and levels of urea nitrogen and creatinine and decreased total protein and albumin levels, but alanine aminotransferase activity and glucose level were not affected. At 10x and 100x exposure levels, qualitatively similar, but dose-dependent vascular, degenerative, and necrotic changes were observed in brain, liver, and kidney. The results indicate that subchronic exposure to the metal mixture affected general health of male rats by altering the functional and structural integrity of kidney, liver, and brain at 10 and 100 times the mode

  2. Finite Mixture Dynamic Regression Modeling of Panel Data with Implications for Dynamic Response Analysis

    ERIC Educational Resources Information Center

    Kaplan, David

    2005-01-01

    This article considers the problem of estimating dynamic linear regression models when the data are generated from finite mixture probability density function where the mixture components are characterized by different dynamic regression model parameters. Specifically, conventional linear models assume that the data are generated by a single…

  3. Do varying aquatic plant species affect phytoplankton and crustacean responses to a nitrogen-permethrin mixture?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Hydraulically connected wetland microcosms vegetated with either Typha latifolia or Myriophyllum aquaticum were amended with an NH4NO3 and permethrin mixture to assess the effectiveness of both plant species in mitigating ecological effects of the pollutant mixture on phytoplankton (as chlorophyll a...

  4. Transcriptomic responses of European flounder (Platichthys flesus) liver to a brominated flame retardant mixture.

    PubMed

    Williams, Tim D; Diab, Amer M; Gubbins, Matt; Collins, Catherine; Matejusova, Iveta; Kerr, Rose; Chipman, James K; Kuiper, Raoul; Vethaak, A Dick; George, Stephen G

    2013-10-15

    Male European flounder (Platichthys flesus) were exposed to a technical mixture of brominated diphenyl ethers (PDBEs, DE-71, Pentamix) that had been purified to remove contaminating dioxins. Controls were exposed to carrier solvent alone. Fish were exposed to decadally increasing concentrations of Pentamix via both sediment and spiked food. The GENIPOL P. flesus cDNA microarray, differentially expressed gene profiling (DEG) and quantitative PCR were employed to detect hepatic transcriptional differences between exposed fish and controls. Gene transcriptional changes were more sensitive to Pentamix exposure than biomarkers measured previously. Pentamix exposure induced transcripts coding for enzymes of xenobiotic metabolism (CYP1A, aldo-keto reductases) and elicited endocrine disruption (vitellogenin and thyroid hormone receptor alpha), with effects on CYP1A and VTG occurring at the highest exposure. Ontology analysis clearly showed dose-responsive changes indicative of oxidative stress, induction of mitochondrial dysfunction, and apoptosis. We conclude that exposure to PBDEs in both sediment and food has a significant adverse effect on a broad range of crucial biochemical processes in the livers of this widely distributed estuarine fish species, the flounder.

  5. Responses of a free-living benthic marine nematode community to bioremediation of a PAH mixture.

    PubMed

    Louati, Hela; Said, Olfa Ben; Soltani, Amel; Cravo-Laureau, Cristiana; Duran, Robert; Aissa, Patricia; Mahmoudi, Ezzeddine; Pringault, Olivier

    2015-10-01

    The objectives of this study were (1) to assess the responses of benthic nematodes to a polycyclic aromatic hydrocarbon (PAH) contamination and (2) to test bioremediation techniques for their efficiency in PAH degradation and their effects on nematodes. Sediments with their natural nematofauna communities from Bizerte lagoon (Tunisia) were subjected to a PAH mixture (100 ppm) of phenanthrene, fluoranthene, and pyrene during 30 days. Nematode abundance and diversity significantly decreased, and the taxonomic structure was altered. Results from multivariate analyses of the species abundance data revealed that PAH treatments were significantly different from the control. Spirinia parasitifera became the dominant species (70 % relative abundance) and appeared to be an "opportunistic" species to PAH contamination while Oncholaimus campylocercoides and Neochromadora peocilosoma were strongly inhibited. Biostimulation (addition of mineral salt medium) and bioaugmentation (inoculation of a hydrocarbonoclastic bacterium) were used as bioremediation techniques. Bioremediation treatments enhanced degradation of all three PAHs, with up to 96 % degradation for phenanthrene resulting in a significant stimulation of nematode abundance relative to control microcosms. Nevertheless, these treatments, especially the biostimulation provoked a weak impact on the community structure and diversity index relative to the control microcosms suggesting their feasibility in biorestoration of contaminated sediments.

  6. Responses of phytoplankton and Hyalella azteca to agrichemical mixtures in a constructed wetland mesocosm.

    PubMed

    Lizotte, Richard E; Testa, Sam; Locke, Martin A; Steinriede, R Wade

    2013-10-01

    We assessed the capability of a constructed wetland to mitigate toxicity of a variety of possible mixtures, such as nutrients only (NO) (nitrogen [N], phosphorus [P]), pesticides only (PO) (atrazine, S-metolachlor, permethrin), and nutrients + pesticides on phytoplankton chlorophyll-a, on 48-h aqueous Hyalella azteca survival and 10-day sediment H. azteca survival and growth. Water and sediment were collected at 10-, 20-, and 40-m distances from inflow and analyzed for nutrients, pesticides, chlorophyll-a, and H. azteca laboratory bioassays. Phytoplankton chlorophyll-a increased 4- to 10 -fold at 7 days after NO treatment. However, responses of chlorophyll-a to PO and nutrients + pesticides were more complex with associated decreases at only 20 m for pesticides only and 10 and 40 m for nutrients + pesticides treatments. H. azteca aqueous survival decreased within the first 48 h of dosing at 10- and 20-m distances during PO and nutrients + pesticides treatments in association with permethrin concentrations. H. azteca sediment survival was unaffected, whereas 10-day growth decreased within 1 day of dosing at all sites during nutrients + pesticides treatment. Constructed wetlands were shown to be an effective agricultural best-management tool for trapping pollutants and mitigating ecological impacts of run-off in agricultural watersheds.

  7. Vapors and Droplets Mixture Deposition of Metallic Coatings by Very Low Pressure Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Vautherin, B.; Planche, M.-P.; Bolot, R.; Quet, A.; Bianchi, L.; Montavon, G.

    2014-04-01

    In recent years, the very low pressure plasma-spraying (VLPPS) process has been intensely developed and implemented to manufacture thin, dense and finely structured ceramic coatings for various applications, such as Y2O3 for diffusion barriers, among other examples. This paper aims at presenting developments carried out on metallic coatings. Aluminum was chosen as a demonstrative material due to its "moderate" vaporization enthalpy (i.e., 38.23 KJ cm-3) compared to the one of copper (i.e., 55.33 KJ cm-3), cobalt (i.e., 75.03 KJ cm-3), or even tantalum (i.e., 87.18 KJ cm-3). The objective of this work is primarily to better understand the behavior of a solid precursor injected into the plasma jet leading to the formation of vapors and to better control the factors affecting the coating structure. Nearly dense aluminum coatings were successfully deposited by VLPPS at 100 Pa with an intermediate power plasma torch (i.e., Sulzer Metco F4 type gun with maximum power of 45 kW). Optical emission spectroscopy (OES) was implemented to study and analyze the vapor behavior into the plasma jet. Simplified CFD modeling allowed better understanding of some of the thermo-physical mechanisms. The effect of powder-size distribution, substrate temperature and spray distance were studied. The phase composition and microstructural features of the coatings were characterized by XRD and SEM. Moreover, Vickers microhardness measurements were implemented.

  8. Impact of benzo(a)pyrene, Cu and their mixture on the proteomic response of Mytilus galloprovincialis.

    PubMed

    Maria, V L; Gomes, T; Barreira, L; Bebianno, M J

    2013-11-15

    In natural waters, chemical interactions between mixtures of contaminants can result in potential synergistic and/or antagonic effects in aquatic animals. Benzo(a)pyrene (BaP) and copper (Cu) are two widespread environmental contaminants with known toxicity towards mussels Mytilus spp. The effects of the individual and the interaction of BaP and Cu exposures were assessed in mussels Mytilus galloprovincialis using proteomic analysis. Mussels were exposed to BaP [10 μg L(-1) (0.396 μM)], and Cu [10 μg L(-1) (0.16 μM)], as well as to their binary mixture (mixture) for a period of 7 days. Proteomic analysis showed different protein expression profiles associated to each selected contaminant condition. A non-additive combined effect was observed in mixture in terms of new and suppressed proteins. Proteins more drastically altered (new, suppressed and 2-fold differentially expressed) were excised and analyzed by mass spectrometry, and eighteen putatively identified. Protein identification demonstrated the different accumulation, metabolism and chemical interactions of BaP, Cu and their mixture, resulting in different modes of action. Proteins associated with adhesion and motility (catchin, twitchin and twitchin-like protein), cytoskeleton and cell structure (α-tubulin and actin), stress response (heat shock cognate 71, heat shock protein 70, putative C1q domain containing protein), transcription regulation (zinc-finger BED domain-containing and nuclear receptor subfamily 1G) and energy metabolism (ATP synthase F0 subunit 6 protein and mannose-6-phosphate isomerase) were assigned to all three conditions. Cu exposure alone altered proteins associated with oxidative stress (glutathione-S-transferase) and digestion, growth and remodelling processes (chitin synthase), while the mixture affected only one protein (major vault protein) possibly related to multi drug resistance. Overall, new candidate biomarkers, namely zinc-finger BED domain-containing protein, chitin

  9. Gene Expression Responses in Male Fathead Minnows Exposed to Binary Mixtures of an Estrogen and Antiestrogen

    EPA Science Inventory

    Aquatic organisms are continuously exposed to complex mixtures of chemicals, many of which can interfere with their endocrine system, resulting in impaired reproduction, development or survival, among others. In order to analyze the effects and mechanisms of action of estrogen...

  10. Population growth rate responses of Ceriodaphnia dubia to ternary mixtures of specific acting chemicals: pharmacological versus ecotoxicological modes of action.

    PubMed

    Barata, Carlos; Fernández-San Juan, María; Feo, Maria Luisa; Eljarrrat, Ethel; Soares, Amadeu M V M; Barceló, Damià; Baird, Donald J

    2012-09-04

    When considering joint toxic apical effects at higher levels of biological organization, such as the growth of populations, the so-called pharmacological mode of action that relies on toxicological mechanistic effects on molecular target sites may not be relevant. Such effects on population growth rate will depend on the extent to which juvenile and adult survival rates and production rates (juvenile developmental rates and reproduction) are affected by toxic exposure and also by the sensitivity of population growth rates to life-history changes. In such cases, the ecotoxicological mode of action, defined as the crucial life-history trait processes and/or xenobiotic-life-history trait interactions underlying a toxicological effect on population growth rate, should be considered. Life-table response experiments with the crustacean Ceriodaphnia dubia exposed to single and ternary mixtures of nine compounds were conducted to test the hypothesis that joint effects on population growth rates could be predicted from the mixture constituent ecotoxicological mode of action. Joint effects of mixtures containing pharmacologically dissimilar compounds (cadmium, λ-cyhalothrin, and chlorpyrifos) that differentially affected life-history traits contributing to population growth rates were accurately predicted by the independent-action concept. Conversely, the concentration-addition concept accurately predicted joint effects of two different mixtures: one containing pharmacologically similar acting pyrethroids that also affected similarly life-history traits, the other one that included pharmacologically dissimilar compounds (3,4-dichloroaniline, sodium bromide, and fenoxycarb) acting mainly on reproduction rates. These results indicate that when assessing combined effects on population growth rate responses, selection of mixture toxicity conceptual models based on the ecotoxicological mode of action of mixture constituents provided more accurate predictions than those based on

  11. Meso-scale heterogeneity effects on the bulk shock response of Ti+2B reactive powder mixtures

    NASA Astrophysics Data System (ADS)

    Gonzales, Manny; Gurumurthy, Ashok; Kennedy, Gregory B.; Gokhale, Arun M.; Thadhani, Naresh N.

    2017-01-01

    Highly heterogeneous reactive powder mixtures containing Ti+2B (Stoichiometric 1:2) are studied to ascertain the shock compression response and potential reaction behavior. The transit time through the pressed powder mixture compacts is monitored using poly-vinylidene fluoride (PVDF) stress gauges and used to compute a wave speed through the compact. The stress states at the back of the powder (measuring the state of the compacted and potentially transformed powder) are compared with thermodynamic mixture theories as well as meso-scale microstructure-based simulations to identify the onset of anomalous behavior which can be traced to highly exothermic reaction in this system. Shock compression experiments show highly dispersive wave fronts when measured from the back surface of the powder compact, which are compared with meso-scale simulations considering varying starting mixture states. These simulations also provide microstructure evolution parameters during shock compression which are stereologically evaluated to establish the state of the material present under the experimental conditions. An analysis of the effects of starting mixture conditions on the stress at the back surface is also presented.

  12. Understanding the biological responses of nanostructured metals and surfaces

    NASA Astrophysics Data System (ADS)

    Lowe, Terry C.; Reiss, Rebecca A.

    2014-08-01

    Metals produced by Severe Plastic Deformation (SPD) offer distinct advantages for medical applications such as orthopedic devices, in part because of their nanostructured surfaces. We examine the current theoretical foundations and state of knowledge for nanostructured biomaterials surface optimization within the contexts that apply to bulk nanostructured metals, differentiating how their microstructures impact osteogenesis, in particular, for Ultrafine Grained (UFG) titanium. Then we identify key gaps in the research to date, pointing out areas which merit additional focus within the scientific community. For example, we highlight the potential of next-generation DNA sequencing techniques (NGS) to reveal gene and non-coding RNA (ncRNA) expression changes induced by nanostructured metals. While our understanding of bio-nano interactions is in its infancy, nanostructured metals are already being marketed or developed for medical devices such as dental implants, spinal devices, and coronary stents. Our ability to characterize and optimize the biological response of cells to SPD metals will have synergistic effects on advances in materials, biological, and medical science.

  13. Colonisation of a Zn, Cd and Pb hyperaccumulator Thlaspi praecox Wulfen with indigenous arbuscular mycorrhizal fungal mixture induces changes in heavy metal and nutrient uptake.

    PubMed

    Vogel-Mikus, Katarina; Pongrac, Paula; Kump, Peter; Necemer, Marijan; Regvar, Marjana

    2006-01-01

    Plants of the Zn, Cd and Pb hyperaccumulator Thlaspi praecox Wulfen (Brassicaceae) inoculated or not with indigenous arbuscular mycorrhizal (AM) fungal mixture were grown in a highly Cd, Zn and Pb contaminated substrate in order to evaluate the functionality of symbiosis and assess the possible impact of AM colonisation on heavy metal uptake and tolerance. The results suggest AM development in the metal hyperaccumulating T. praecox is favoured at elevated nutrient demands, e.g. during the reproductive period. AM colonisation parameters positively correlated with total soil Cd and Pb. Colonised plants showed significantly improved nutrient and a decreased Cd and Zn uptake as revealed by TRXRF, thus confirming the functionality of the symbiosis. Reduced heavy metal uptake, especially at higher soil metal contents, indicates a changed metal tolerance strategy in colonised T. praecox plants. This is to our knowledge the first report on AM colonisation of the Zn, Cd and Pb hyperaccumulator T. praecox in a greenhouse experiment.

  14. CADDIS Volume 2. Sources, Stressors and Responses: Metals

    EPA Pesticide Factsheets

    Introduction to the metals module, when to list metals as a candidate cause, ways to measure metals, simple and detailed conceptual diagrams for metals, metals module references and literature reviews.

  15. The influence of SWCNT-metallic nanoparticle mixtures on the desorption properties of milled MgH2 powders.

    PubMed

    Amirkhiz, Babak Shalchi; Danaie, Mohsen; Mitlin, David

    2009-05-20

    We have examined the effect of single-walled carbon nanotube (SWCNT)-metallic nanoparticle additions on the hydrogen desorption behavior of MgH(2) after high-energy co-milling. The metallic nanoparticles were the catalysts used for the SWCNT growth. The co-milling consisted of high-energy planetary milling in an inert argon environment of the hydride powder mixed with the SWCNTs. Identically milled pure MgH(2) powders were used as a baseline. The composites were tested using a combined differential scanning calorimeter and thermogravimetric analyzer, while the microstructures were examined using a variety of techniques including x-ray diffraction and transmission electron microscopy (TEM). We found that the SWCNT-nanoparticle additions do have an influence on the desorption kinetics. However, the degree to which they are effective depends on the composite's final state. The optimum microstructure for sorption, obtained after 1 h of co-milling, consists of highly defective SWCNTs in intimate contact with metallic nanoparticles and with the hydride. This microstructure is optimum, presumably because of the dense and uniform coverage of the defective SWCNTs on the MgH(2) surface. Prolonged co-milling of 7 h destroys the SWCNT structure and reduces the enhancement. Even after 72 h of co-milling, when the SWCNTs are completely destroyed, the metallic nanoparticles remain dispersed on the hydride surfaces. This indicates that the metallic nanoparticles alone are not responsible for the enhanced sorption and that there is indeed something catalytically unique about a defective SWCNT-metal combination. Cryo-stage TEM analysis of the hydride powders revealed that they are nanocrystalline and in some cases multiply twinned. To our knowledge this is the first study where the structure of milled alpha- MgH(2) has been directly imaged. Since defects are an integral component of hydride-to-metal phase transformations, such analysis sheds new insight regarding the fundamental

  16. Biochemical responses and metals levels in Ruditapes decussatus after exposure to treated municipal effluents.

    PubMed

    Kamel, Naouel; Jebali, Jamel; Banni, Mohamed; Ben Khedher, Sana; Chouba, Lassaad; Boussetta, Hamadi

    2012-08-01

    This study assessed the responses of biochemical biomarkers and metals levels in Ruditapes decussatus exposed to the increasing concentrations of treated municipal effluents (TME) discharged into the Tunisian coastal area. Clams were exposed to 0%, 1%, 3% and 10% for 7 and 14 day and the following biochemical responses were measured: (1) catalase activity and lipid peroxidation levels (TBARS) as oxidative stress biomarkers, (2) gluthathione S-transferase (GST) activity as a phase II conjugation enzyme; (3) cholinesterase activity (ChE) as biomarker of neurotoxicity, and (4) metallothioneins as a proteins highly induced by heavy metals. A significant uptake of Cu, Cd and Zn in digestive gland and serious biochemical alterations were observed. Thus, exposure of clams to croissant concentration of TME have the potential to increase the oxidative stress biomarkers (TBARS, CAT activity) and MT levels; and decrease ChE activity in both gills and digestive gland. Current experimental results suggest that CAT, GST, ChE activities and MT and TBARs levels in gills and digestive gland of clam R. decussatus are sensitive and suitable responses for assessing the effects of anthropogenic contaminants on the aquatic ecosystems, particularly effluent complex mixtures.

  17. Immunomodulation by heavy metals tested individually or in mixtures in rainbow trout (Oncorhynchus mykiss) exposed in vivo

    SciTech Connect

    Sanchez-Dardon, J.; Voccia, I.; Hontela, A.; Chilmonczyk, S.; Dunier, M.; Boermans, H.; Blakley, B.; Fournier, M.

    1999-07-01

    The objective of this study was to evaluate the effect of heavy metals, at environmentally relevant concentrations, on the immune response of rainbow trout. Trout were exposed for 30 d to cadmium chloride (CdCl{sub 2}), mercuric chloride (HgCl{sub 2}), or zinc chloride (ZnCl{sub 2}) either individually or in combinations: CdCl{sub 2}/HgCl{sub 2}, CdCl{sub 2}/ZnCl{sub 2}, HgCl{sub 2}/ZnCl{sub 2}, or CdCl{sub 2}/HgCl{sub 2}/ZnCl{sub 2}. Following the 30-d exposure, parameters of the nonspecific cellular immune response (phagocytosis, respiratory burst, and lymphoblastic proliferation) and of the nonspecific humoral immune response (lysozyme activity and the level of immunoglobulin) were measured. The results obtained indicate that individually, all three metals induce significant immunomodulations. However, the toxicity of mercury or cadmium is significantly reduced in fish simultaneously exposed to zinc, indicating that a protection is afforded by zinc against cadmium- and mercury-induced immunotoxicity.

  18. Evaluation of the joint-action toxicity of binary mixtures of heavy metals against the mangrove periwinkle Tympanotonus fuscatus var radula (L.).

    PubMed

    Otitoloju, Adebayo Akeem

    2002-11-01

    The joint-action toxicity of binary mixtures of heavy metal compounds prepared in predefined ratios of 4:1, 3:2, 1:1, 2:3, and 1:4 (wt/wt) of Zn:Cu, Zn:Cd, and Cd:Cu, respectively, and tested against the mangrove periwinkle Tympanotonus fuscatus were carried out in laboratory bioassays. The interactions between binary mixtures showed significant departures from the action of the individual constituent metals when acting singly. On the basis of the models such as isobole representations, synergistic ratios (SRs), and concentration-addition models used for the joint-action evaluations, the interactions between the constituent metals in the various test proportions of the mixtures were largely in conformity with the models of antagonism. Furthermore, in most of the test combinations of the binary mixtures, the Zn compound was found to consistently reduce the toxic effect of Cu and Cd compounds when tested jointly against T. fuscatus. The possibility of utilizing the observed antagonistic interactions between Zn(2+) and Cd(2+) in the management of Cd-contaminated waterbodies was discussed and the synergistic ratio model was singled out as a better candidate model for joint-action toxicity evaluations, which are aimed at establishing environmental safe limits of pollutants.

  19. Deterioration of yttria-stabilized zirconia by boron carbide alone or mixed with metallic or oxidized Fe, Cr, Zr mixtures

    NASA Astrophysics Data System (ADS)

    De Bremaecker, A.; Ayrault, L.; Clément, B.

    2014-08-01

    In the frame of severe accident conditions (PHEBUS FPT3 test), different experiments were carried out on the interactions of 20% yttria-stabilized zirconia (YSZ) and 20% ceria-stab zirconia with boron carbide or its oxidation products (B2O3): either tests under steam between 1230° and 1700 °C with B4C alone or B4C mixed with metals, either tests under Ar with boron oxide present in a mixture of iron and chromium oxides. In all cases an interaction was observed with formation of intergranular yttrium borate. At 1700 °C boron oxide is able to “pump out” the Y stabiliser from the YSZ grains but also some trace elements (Ca and Al) and to form a eutectic containing YBO3 and yttrium calcium oxy-borate (YCOB). At the same time a substantial swelling (“bloating”) of the zirconia happens, qualitatively similar to the foaming of irradiated fuel in contact with a Zr-melt. In all samples the lowering of the Y (or Ce)-content in the YSZ grains is so sharp that in the interaction layers zirconia is no longer stabilized. This is important when YSZ is envisaged as simulant of UO2 or as inert matrix for Am-transmutation.

  20. Some enzymatic/nonenzymatic antioxidants as potential stress biomarkers of trichloroethylene, heavy metal mixture, and ethyl alcohol in rat tissues.

    PubMed

    Tabrez, Shams; Ahmad, Masood

    2011-04-01

    Enzymatic and nonenzymatic antioxidants serve as an important biological defense against environmental pollutants. Various enzymatic and nonenzymatic antioxidants as a stress biomarker in liver and kidney of rat were investigated. The antioxidant enzymes that were analyzed included superoxide dismutase (SOD), catalase, glutathione reductase (GR), glutathione-S-transferase (GST), and glutathione peroxidase. Levels of lipid peroxidation (LPO), reduced glutathione (GSH), as well as hydrogen peroxide (H(2)O(2)) were also measured in homogenates of the liver and kidney of the treated animals to determine oxidative stress induced by trichloroethylene (TCE), ethyl alcohol, and heavy metal mixture (H.M.M) individually and in different combinations. An increase up to the extent of 382% in malonaldehyde, a marker of LPO, was recorded in almost all the treatment groups in both the tissues. Similarly, a rise of 218% in GST activity was also recorded in kidney of TCE-treated animals. Although H.M.M ingestion resulted in significant change of 125% in SOD activity of hepatic tissue, the level of GR was increased by 93% in the renal tissue of the exposed rats. Solitary dose of alcohol in general did not show a significant change. Moreover, the changes in the levels of antioxidants were much more prominent when these toxicants were given in combination rather than alone. Overall, these results demonstrate the changes in the levels of antioxidant enzymes and GSH system, as well as alterations in the LPO and H(2)O(2) levels as a result of test toxicants.

  1. Nonlinear plasmon response in highly excited metallic clusters

    SciTech Connect

    Calvayrac, F.; Reinhard, P.G.; Suraud, E.

    1995-12-15

    We present a dynamical study of the electron response of metallic clusters in the nonlinear regime, as excited, e.g., in ion-cluster interactions or with intense laser beams. We use a quantal time-dependent local-density approximation in axial symmetry to describe the electron dynamics. Ions are either treated in a jellium approximation or explicitly. We find different dynamical regimes depending on the symmetries of the ionic background.

  2. A multistimuli-responsive photochromic metal-organic gel.

    PubMed

    Wei, Shi-Chao; Pan, Mei; Li, Kang; Wang, Sujuan; Zhang, Jianyong; Su, Cheng-Yong

    2014-04-02

    A photochromic metal-organic gel with thermo-, photo-, and anion-responsive behavior is obtained. Unusually, heating of the Al-ligand solution leads to gel formation and cooling to room temperature reverses the process to reform the solution. The gel is sensitive to weakly coordinating anions. Additionally, reversible photochromic transformations take place both in the solution and gel states, accompanied by reversibly switched luminescence.

  3. Treatment of electronic waste to recover metal values using thermal plasma coupled with acid leaching--a response surface modeling approach.

    PubMed

    Rath, Swagat S; Nayak, Pradeep; Mukherjee, P S; Roy Chaudhury, G; Mishra, B K

    2012-03-01

    The global crisis of the hazardous electronic waste (E-waste) is on the rise due to increasing usage and disposal of electronic devices. A process was developed to treat E-waste in an environmentally benign process. The process consisted of thermal plasma treatment followed by recovery of metal values through mineral acid leaching. In the thermal process, the E-waste was melted to recover the metal values as a metallic mixture. The metallic mixture was subjected to acid leaching in presence of depolarizer. The leached liquor mainly contained copper as the other elements like Al and Fe were mostly in alloy form as per the XRD and phase diagram studies. Response surface model was used to optimize the conditions for leaching. More than 90% leaching efficiency at room temperature was observed for Cu, Ni and Co with HCl as the solvent, whereas Fe and Al showed less than 40% efficiency.

  4. Nonlinear THz response of metallic armchair graphene nanoribbon superlattices

    NASA Astrophysics Data System (ADS)

    Wang, Yichao; Andersen, David R.

    2016-11-01

    We study the third order THz nonlinear response of metallic armchair graphene nanoribbon superlattices in the presence of an elliptically-polarized excitation field using the time dependent perturbation theory. For a one-dimensional Kronig-Penney potential of infinite length, the nonlinear response can be described perturbatively by a low energy \\mathbf{k}\\centerdot \\mathbf{p} N-photon coupling model. Remarkably, as shown by Burset et al the energy dispersion of the metallic band in the direction parallel to the superlattice wavevector is independent of the applied superlattice potential while the energy dispersion in the direction perpendicular to the superlattice wavevector depends strongly on the superlattice parameters. As a result, we predict novel behavior for the nonlinear response of single layer metallic acGNR superlattices to an applied elliptically-polarized electric field. Our work shows that the superlattice potential, periodicity, Fermi level, excitation field polarization state, and temperature all play a significant role in the resulting THz nonlinear conductances.

  5. Response of a salt marsh microbial community to metal contamination

    NASA Astrophysics Data System (ADS)

    Mucha, Ana P.; Teixeira, Catarina; Reis, Izabela; Magalhães, Catarina; Bordalo, Adriano A.; Almeida, C. Marisa R.

    2013-09-01

    Salt marshes are important sinks for contaminants, namely metals that tend to accumulate around plant roots and could eventually be taken up in a process known as phytoremediation. On the other hand, microbial communities display important roles in the salt marsh ecosystems, such as recycling of nutrients and/or degradation of organic contaminants. Thus, plants can benefit from the microbial activity in the phytoremediation process. Nevertheless, above certain levels, metals are known to be toxic to microorganisms, fact that can eventually compromise their ecological functions. In this vein, the aim of present study was to investigate, in the laboratory, the effect of selected metals (Cd, Cu and Pb) on the microbial communities associated to the roots of two salt marsh plants. Sediments colonized by Juncus maritimus and Phragmites australis were collected in the River Lima estuary (NW Portugal), and spiked with each of the metals at three different Effects Range-Median (ERM) concentrations (1, 10×, 50×), being ERM the sediment quality guideline that indicates the concentration above which adverse biological effects may frequently occur. Spiked sediments were incubated with a nutritive saline solution, being left in the dark under constant agitation for 7 days. The results showed that, despite the initial sediments colonized by J. maritimus and P. australis displayed significant (p < 0.05) differences in terms of microbial community structure (evaluated by ARISA), they presented similar microbial abundances (estimated by DAPI). Also, in terms of microbial abundance, both sediments showed a similar response to metal addition, with a decrease in number of cells only observed for the higher addition of Cu. Nevertheless, both Cu and Pb, at intermediate metals levels promote a shift in the microbial community structure, with possibly effect on the ecological function of these microbial communities in salt marshes. These changes may affect plants phytoremediation

  6. Stratification effects on laminar premixed-flame response to mixture perturbations

    NASA Astrophysics Data System (ADS)

    Casey, Tiernan; Chen, Jyh-Yuan

    2015-11-01

    While complete mixing on the molecular level is desirable for ensuring that combustion processes are limited by chemical kinetics rather than mass transport, it is often the case that practical devices operate with some degree of unmixedness. As such, phenomena such as ignition or flame propagation will inevitably occur in regions that exhibit mixture or thermal non-uniformity. Here we present unsteady simulations of laminar premixed flames in the low-Mach limit subject to mixture perturbations of varying wavelength and amplitude, and qualify their effect on the flame behavior. When flames experience variations in mixture the transport processes in the flame zone vary with time and the flame behavior can depend on the burned gas history. Also, the possibility of extending flames beyond their flammability limits so as to maximize the overall mass of fuel burned is explored by exploiting these unsteady effects.

  7. Delineating ion-ion interactions by electrostatic modeling for predicting rhizotoxicity of metal mixtures to lettuce Lactuca sativa.

    PubMed

    Le, T T Yen; Wang, Peng; Vijver, Martina G; Kinraide, Thomas B; Hendriks, A Jan; Peijnenburg, Willie J G M

    2014-09-01

    Effects of ion-ion interactions on metal toxicity to lettuce Lactuca sativa were studied based on the electrical potential at the plasma membrane surface (ψ0 ). Surface interactions at the proximate outside of the membrane influenced ion activities at the plasma membrane surface ({M(n+)}0). At a given free Cu(2+) activity in the bulk medium ({Cu(2+)}b), additions of Na(+), K(+), Ca(2+), and Mg(2+) resulted in substantial decreases in {Cu(2+)}0. Additions of Zn(2+) led to declines in {Cu(2+)}0, but Cu(2+) and Ag(+) at the exposure levels tested had negligible effects on the plasma membrane surface activity of each other. Metal toxicity was expressed by the {M(n+)}0 -based strength coefficient, indicating a decrease of toxicity in the order: Ag(+)  > Cu(2+)  > Zn(2+). Adsorbed Na(+), K(+), Ca(2+), and Mg(2+) had significant and dose-dependent effects on Cu(2+) toxicity in terms of osmolarity. Internal interactions between Cu(2+) and Zn(2+) and between Cu(2+) and Ag(+) were modeled by expanding the strength coefficients in concentration addition and response multiplication models. These extended models consistently indicated that Zn(2+) significantly alleviated Cu(2+) toxicity. According to the extended concentration addition model, Ag(+) significantly enhanced Cu(2+) toxicity whereas Cu(2+) reduced Ag(+) toxicity. By contrast, the response multiplication model predicted insignificant effects of adsorbed Cu(2+) and Ag(+) on the toxicity of each other. These interactions were interpreted using ψ0, demonstrating its influence on metal toxicity.

  8. Dose-response relationship of an environmental mixture of pyrethroids following an acute oral administration in the rat

    EPA Science Inventory

    Dose-response relationship of an environmental mixture of pyrethroids following an acute oral administration in the rat M.F. Hughes1, D.G. Ross1, J.M. Starr1, E.J. Scollon1,2, M.J. Wolansky1,3, K.M. Crofton1, M.J. DeVito1,4 1U.S. EPA, ORD, Research Triangle Park, NC, 2U.S. EPA,...

  9. Antioxidant and lipid peroxidation responses in Mytilus galloprovincialis exposed to mixtures of benzo(a)pyrene and copper.

    PubMed

    Maria, V L; Bebianno, M J

    2011-06-01

    This study aimed to assess the antioxidant system potential and lipid peroxidative effects, in the gill and digestive gland of Mytilus galloprovincialis exposed to individual and binary mixtures of benzo(a)pyrene (BaP) and Cu for 7 days. Data demonstrated that in mussels exposed to BaP antioxidant enzymes (catalase--CAT, total glutathione peroxidase--tGPx, glutathione S-transferase--GST and glutathione reductase--GR) and lipid peroxidation (LPO) increased in the gill. On the contrary, in the digestive gland inhibitory antioxidant effects (superoxide dismutase-SOD, GR, metallothioneins-MT) and no changes in LPO levels were detected. Cu was also a potent oxidant agent since MT and LPO levels increased in mussel gill, despite no LPO effect in the digestive gland. For both single contaminants the organ specificity and distinct physiologic/metabolism roles were evident in terms of antioxidant capacity. Gill SOD inhibition, MT and GST unchanged was a result of "simple independent action" of exposure to BaP and Cu. "Interactions" in the binary mixtures, led to absence of changes in LPO effects. In the digestive gland, BaP and Cu interactions were also responsible for the GST and LPO enhancement (antagonistic effects). The current findings demonstrate the differences in antioxidant responses where the organ dependency highlights each contaminant particular mode of action. Generally, in the gill "non-interactive" effects occurred with the lowest Cu concentration while "interactions" exist for the mixture with the highest Cu concentrations. In the digestive gland, "interactions" and "no interaction" effects occurred in all the binary mixtures. Complex contaminant mixtures interact differently based on target tissue which may lead to an imbalance in the mussels health status.

  10. Response of electrochemical oxygen sensors to inert gas-air and carbon dioxide-air mixtures: measurements and mathematical modelling.

    PubMed

    Walsh, P T; Gant, S E; Dowker, K P; Batt, R

    2011-02-15

    Electrochemical oxygen gas sensors are widely used for monitoring the state of inertisation of flammable atmospheres and to warn of asphyxiation risks. It is well established but not widely known by users of such oxygen sensors that the response of the sensor is affected by the nature of the diluent gas responsible for the decrease in ambient oxygen concentration. The present work investigates the response of electrochemical sensors, with either acid or alkaline electrolytes, to gas mixtures comprising air with enhanced levels of nitrogen, carbon dioxide, argon or helium. The measurements indicate that both types of sensors over-read the oxygen concentrations when atmospheres contain high levels of helium. Sensors with alkaline electrolytes are also shown to underestimate the severity of the hazard in atmospheres containing high levels of carbon dioxide. This deviation is greater for alkaline electrolyte sensors compared to acid electrolyte sensors. A Computational Fluid Dynamics (CFD) model is developed to predict the response of an alkaline electrolyte, electrochemical gas sensor. Differences between predicted and measured sensor responses are less than 10% in relative terms for nearly all of the gas mixtures tested, and in many cases less than 5%. Extending the model to simulate responses of sensors with acid electrolytes would be straightforward.

  11. Multiple Responses of Gram-Positive and Gram-Negative Bacteria to Mixture of Hydrocarbons

    PubMed Central

    Marilena Lăzăroaie, Mihaela

    2010-01-01

    Most of our knowledge about pollutants and the way they are biodegraded in the environment has previously been shaped by laboratory studies using hydrocarbon-degrading bacterial strains isolated from polluted sites. In present study Gram-positive (Mycobacterium sp. IBBPo1, Oerskovia sp. IBBPo2, Corynebacterium sp. IBBPo3) and Gram-negative (Chryseomonas sp. IBBPo7, Pseudomonas sp. IBBPo10, Burkholderia sp. IBBPo12) bacteria, isolated from oily sludge, were found to be able to tolerate pure and mixture of saturated hydrocarbons, as well as pure and mixture of monoaromatic and polyaromatic hydrocarbons. Isolated Gram-negative bacteria were more tolerant to mixture of saturated (n-hexane, n-hexadecane, cyclohexane), monoaromatic (benzene, toluene, ethylbenzene) and polyaromatic (naphthalene, 2-methylnaphthalene, fluorene) hydrocarbons than Gram-positive bacteria. There were observed cellular and molecular modifications induced by mixture of saturated, monoaromatic and polyaromatic hydrocarbons to Gram-positive and Gram-negative bacteria. These modifications differ from one strain to another and even for the same bacterial strain, according to the nature of hydrophobic substrate. PMID:24031541

  12. PHOTOCHEMICAL PRODUCTS IN URBAN MIXTURES ENHANCE INFLAMMATORY RESPONSES IN LUNG CELLS

    EPA Science Inventory

    Complex urban air mixtures that realistically mimic urban smog can be generated for investigating adverse health effects. "Smog chambers" have been used for over 30 yr to conduct experiments for developing and testing photochemical models that predict ambient ozone (O(3)) concent...

  13. Responses of phytoplankton and Hyalella azteca to agrichemical mixtures in a constructed wetland mesocosms

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We assessed the capability of a constructed wetland to mitigate toxicity of a variety of possible mixtures such as nutrients only (N, P), pesticides only (atrazine, S-metolachlor, permethrin), and nutrients+pesticides on phytoplankton chlorophyll a, 48 h aqueous Hyalella azteca survival, and 10 d se...

  14. Modelling interactions of acid–base balance and respiratory status in the toxicity of metal mixtures in the American oyster Crassostrea virginica

    PubMed Central

    Macey, Brett M.; Jenny, Matthew J.; Williams, Heidi R.; Thibodeaux, Lindy K.; Beal, Marion; Almeida, Jonas S.; Cunningham, Charles; Mancia, Annalaura; Warr, Gregory W.; Burge, Erin J.; Holland, A. Fred; Gross, Paul S.; Hikima, Sonomi; Burnett, Karen G.; Burnett, Louis; Chapman, Robert W.

    2010-01-01

    Heavy metals, such as copper, zinc and cadmium, represent some of the most common and serious pollutants in coastal estuaries. In the present study, we used a combination of linear and artificial neural network (ANN) modelling to detect and explore interactions among low-dose mixtures of these heavy metals and their impacts on fundamental physiological processes in tissues of the Eastern oyster, Crassostrea virginica. Animals were exposed to Cd (0.001–0.400 µM), Zn (0.001–3.059 µM) or Cu (0.002–0.787 µM), either alone or in combination for 1 to 27 days. We measured indicators of acid–base balance (hemolymph pH and total CO2), gas exchange (Po2), immunocompetence (total hemocyte counts, numbers of invasive bacteria), antioxidant status (glutathione, GSH), oxidative damage (lipid peroxidation; LPx), and metal accumulation in the gill and the hepatopancreas. Linear analysis showed that oxidative membrane damage from tissue accumulation of environmental metals was correlated with impaired acid–base balance in oysters. ANN analysis revealed interactions of metals with hemolymph acid–base chemistry in predicting oxidative damage that were not evident from linear analyses. These results highlight the usefulness of machine learning approaches, such as ANNs, for improving our ability to recognize and understand the effects of subacute exposure to contaminant mixtures. PMID:19958840

  15. Modelling interactions of acid-base balance and respiratory status in the toxicity of metal mixtures in the American oyster Crassostrea virginica.

    PubMed

    Macey, Brett M; Jenny, Matthew J; Williams, Heidi R; Thibodeaux, Lindy K; Beal, Marion; Almeida, Jonas S; Cunningham, Charles; Mancia, Annalaura; Warr, Gregory W; Burge, Erin J; Holland, A Fred; Gross, Paul S; Hikima, Sonomi; Burnett, Karen G; Burnett, Louis; Chapman, Robert W

    2010-03-01

    Heavy metals, such as copper, zinc and cadmium, represent some of the most common and serious pollutants in coastal estuaries. In the present study, we used a combination of linear and artificial neural network (ANN) modelling to detect and explore interactions among low-dose mixtures of these heavy metals and their impacts on fundamental physiological processes in tissues of the Eastern oyster, Crassostrea virginica. Animals were exposed to Cd (0.001-0.400 microM), Zn (0.001-3.059 microM) or Cu (0.002-0.787 microM), either alone or in combination for 1 to 27 days. We measured indicators of acid-base balance (hemolymph pH and total CO(2)), gas exchange (Po(2)), immunocompetence (total hemocyte counts, numbers of invasive bacteria), antioxidant status (glutathione, GSH), oxidative damage (lipid peroxidation; LPx), and metal accumulation in the gill and the hepatopancreas. Linear analysis showed that oxidative membrane damage from tissue accumulation of environmental metals was correlated with impaired acid-base balance in oysters. ANN analysis revealed interactions of metals with hemolymph acid-base chemistry in predicting oxidative damage that were not evident from linear analyses. These results highlight the usefulness of machine learning approaches, such as ANNs, for improving our ability to recognize and understand the effects of sub-acute exposure to contaminant mixtures.

  16. The effect of low-temperature transformation of mixtures of sewage sludge and plant materials on content, leachability and toxicity of heavy metals.

    PubMed

    Gondek, Krzysztof; Baran, Agnieszka; Kopeć, Michał

    2014-12-01

    The aim of the study was to determine the influence of the process of low-temperature transformation and the addition of plant material to sewage sludge diversifying the content of mobile forms of heavy metals and their ecotoxicity. The experimental design included: sewage sludge+rape straw, sewage sludge+wheat straw, sewage sludge+sawdust, sewage sludge+bark and sewage sludge with no addition. The mixtures were subjected to thermal transformation in a chamber furnace, under conditions without air. The procedure consisted of two stages: the first stage (130°C for 40 min) focused on drying the material, whereas in the second stage (200°C for 30 min) proper thermal transformation of materials took place. Thermal transformation of the materials, caused an increase in total contents of heavy metals in comparison to the material before transformation. From among elements, the cadmium content changed the most in materials after thermal transformation. As a result of thermal transformation, the content of water soluble form of the heavy metals decreased significantly in all the prepared mixtures. Low toxicity of the extracts from materials for Vibrio fischeri and Lepidium sativum was found in the research, regardless of transformation process. L. sativum showed higher sensitivity to heavy metals occurring in the studied extracts from materials than V. fischeri, evidence of which are the positive significant correlations between the content of metals and the inhibition of root growth of L. sativum.

  17. Plant response to FBC waste-coal slurry solid mixtures. Technical report, 1 March--31 May 1994

    SciTech Connect

    Darmody, R.G.; Dunker, R.E.; Dreher, G.B.; Roy, W.R.; Steel, J.D.

    1994-09-01

    The goal of this project is to test the feasibility of stabilizing coal slurry solids (CSS) wastes by directly seeding plants into the waste. This is not done conventionally because the waste can generate toxic amounts of sulfuric acid. The approach is to neutralize the potential acidity by mixing fluidized bed combustion (FBC) waste into the slurry. If successful, this approach would both help dispose of FBC wastes while providing a more economical slurry stabilization technique. The project involves growing forage plants in CSS-FBC mixtures in the greenhouse. In the first two quarters the authors designed the experiment, secured greenhouse space, purchased the seeds, collected, dried, analyzed the FBC and CSS samples. The samples represent a typical range of properties. They retrieved two FBC and two CSS samples. One CSS sample had a relatively high CaCO{sub 3} content relative to the pyrite content and required no FBC to neutralize the potential acidity. The other CSS sample required from 4.2 to 2.7% FBC material to neutralize its potential acidity. This report covers the third quarter of the project. The authors produced the CSS-FBC mixtures, analyzed the soil fertility parameters of the mixtures,, planted the crops, and monitored their growth. All mixtures support at least some plant growth, although some plants did better than others. It is too early to analyze the results statistically. Next quarter the plants will be harvested, yields calculated, mineral uptake evaluated, and a final report will be written on plant response to CSS-FBC mixtures.

  18. Response of brown hisex chicks to low levels of Jatropha curcas, Ricinus communis or their mixture.

    PubMed

    el Badwi, S M; Mousa, H M; Adam, S E; Hapke, H J

    1992-08-01

    Feeding Jatropha curcas seed at 0.5% of the basic diet for 2 w was not lethal to chicks. In chicks fed 0.5% Ricinus communis seed or a mixture of 0.5% J curcas + 0.5% R communis for 2 w, there was dullness, poor growth, locomotor disturbance and death. Pathological changes were correlated with alterations in clinical chemistry and hematology.

  19. Investigation of simultaneous biosorption of copper(II) and chromium(VI) on dried Chlorella vulgaris from binary metal mixtures: Application of multicomponent adsorption isotherms

    SciTech Connect

    Aksu, Z.; Acikel, U.; Kutsal, T.

    1999-02-01

    Although the biosorption of single metal ions to various kinds of microorganisms has been extensively studied and the adsorption isotherms have been developed for only the single metal ion situation, very little attention has been given to the bioremoval and expression of adsorption isotherms of multimetal ions systems. In this study the simultaneous biosorption of copper(II) and chromium(VI) to Chlorella vulgaris from a binary metal mixture was studied and compared with the single metal ion situation in a batch stirred system. The effects of pH and single- and dual-metal ion concentrations on the equilibrium uptakes were investigated. In previous studies the optimum biosorption pH had been determined as 4.0 for copper(II) and as 2.0 for chromium(VI). Multimetal ion biosorption studies were performed at these two pH values. It was observed that the equilibrium uptakes of copper(II) or chromium(VI) ions were changed due to the biosorption pH and the presence of other metal ions. Adsorption isotherms were developed for both single- and dual-metal ions systems at these two pH values, and expressed by the mono- and multicomponent Langmuir and Freundlich adsorption models. Model parameters were estimated by nonlinear regression. It was seen that the adsorption equilibrium data fitted very well to the competitive Freundlich model in the concentration ranges studied.

  20. Smart responsive microcapsules capable of recognizing heavy metal ions.

    PubMed

    Pi, Shuo-Wei; Ju, Xiao-Jie; Wu, Han-Guang; Xie, Rui; Chu, Liang-Yin

    2010-09-15

    Smart responsive microcapsules capable of recognizing heavy metal ions are successfully prepared with oil-in-water-in-oil double emulsions as templates for polymerization in this study. The microcapsules are featured with thin poly(N-isopropylacrylamide-co-benzo-18-crown-6-acrylamide) (P(NIPAM-co-BCAm)) membranes, and they can selectively recognize special heavy metal ions such as barium(II) or lead(II) ions very well due to the "host-guest" complexation between the BCAm receptors and barium(II) or lead(II) ions. The stable BCAm/Ba(2+) or BCAm/Pb(2+) complexes in the P(NIPAM-co-BCAm) membrane cause a positive shift of the volume phase transition temperature of the crosslinked P(NIPAM-co-BCAm) hydrogel to a higher temperature, and the repulsion among the charged BCAm/Ba(2+) or BCAm/Pb(2+) complexes and the osmotic pressure within the P(NIPAM-co-BCAm) membranes result in the swelling of microcapsules. Induced by recognizing barium(II) or lead(II) ions, the prepared microcapsules with P(NIPAM-co-BCAm) membranes exhibit isothermal and significant swelling not only in outer and inner diameters but also in the membrane thickness. The proposed microcapsules in this study are highly attractive for developing smart sensors and/or carriers for detection and/or elimination of heavy metal ions.

  1. Mixture-amount design and response surface modeling to assess the effects of flavonoids and phenolic acids on developmental performance of Anastrepha ludens

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A mixture-amount experimental design and response surface modeling were used to study the effects of three flavonoids and two phenolic acids, alone or in mixtures, in an artificial larval diet on the development and survival of Mexican fruit fly (Anastrepha ludens [Loew]). Pupal weight, percentage o...

  2. Ultrafast response sensor to formaldehyde gas based on metal oxide.

    PubMed

    Choi, N-J; Lee, H-K; Moon, S E; Kim, J; Yang, W S

    2014-08-01

    Thick film semiconductor gas sensors based on indium oxide were fabricated on Si substrate. The sensing materials on Si substrate were characterized using optical microscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM), and so on. They were very fine and uniform and we found out that particle sizes were about 20~30 nm through XRD analysis. Gas responses of fabricated sensors were measured in a chamber where gas flow was controlled by mass flow controller (MFC). Their resistance changes were monitored in real time by using data acquisition board and personal computer. Gas response characteristics were examined for formaldehyde (HCHO) gas which was known as the cause of sick building syndrome. Particularly, the sensors showed responses to formaldehyde gas at sub ppm (cf, standard of natural environment in building is about 80 ppb by ministry of environment in Korea), as a function of operating temperatures and gas concentrations. Also, we investigated sensitivity, repetition, selectivity, response speed and reproducibility of the sensors. The lowest detection limit is HCHO 25 ppb and sensitivity at 800 ppb is over 25% at 350 °C operating temperature. The response time (8 s) and recovery time (15 s) to HCHO gas at 200 ppb were very fast compared to other commercial products in flow type measurement condition. Repetition measurement was very good with ±3% in full measurement range. The fabricated metal oxide gas sensor showed good performance to HCHO gas and proved that it could be adaptable to indoor environment in building.

  3. Transcriptional response of lysozyme, metallothionein, and superoxide dismutase to combined exposure to heavy metals and bacteria in Mactra veneriformis.

    PubMed

    Fang, Yan; Yang, Hongsheng; Liu, Baozhong; Zhang, Libing

    2013-01-01

    The response of the defense components lysozyme (LYZ), metallothionein (MT), and superoxide dismutase (SOD) to combined exposure to heavy metals and bacteria was assessed at transcriptional level in the surf clam Mactra veneriformis. First, the full-length LYZ cDNA containing 808 nucleotides and encoding 194 deduced amino acids was identified from the clam. Multiple alignments revealed that MvLYZ had a high identity with invertebrate-type LYZs from other mollusks. Next, clams were exposed to Vibrio parahaemolyticus and a mixture of cadmium and mercury, alone or in combination, for 7 days. Cumulative mortality of clams and mRNA expressions of the three defense components were analyzed. The highest cumulative mortality took place in the combined treatment on day 7. The expression of the three genes was up-regulated in response to treatments compared to the control with different response times and transcriptional levels; the response to combined exposure occurred earlier than to single exposure. Among the experimental groups, MvLYZ expression and MvSOD expression peaked in the combined treatment on day 3, whereas MvMT expression peaked in heavy metals treatment on day 5. Furthermore, interactive effects of heavy metals and Vibrio on transcriptional response changed over the exposure time. Therefore, transcriptional regulation of the three genes under combined exposure was more complex than under single exposure.

  4. Transcriptomes of the Extremely Thermoacidophilic Archaeon Metallosphaera sedula Exposed to Metal “Shock” Reveal Generic and Specific Metal Responses

    PubMed Central

    Wheaton, Garrett H.; Mukherjee, Arpan

    2016-01-01

    ABSTRACT The extremely thermoacidophilic archaeon Metallosphaera sedula mobilizes metals by novel membrane-associated oxidase clusters and, consequently, requires metal resistance strategies. This issue was examined by “shocking” M. sedula with representative metals (Co2+, Cu2+, Ni2+, UO22+, Zn2+) at inhibitory and subinhibitory levels. Collectively, one-quarter of the genome (554 open reading frames [ORFs]) responded to inhibitory levels, and two-thirds (354) of the ORFs were responsive to a single metal. Cu2+ (259 ORFs, 106 Cu2+-specific ORFs) and Zn2+ (262 ORFs, 131 Zn2+-specific ORFs) triggered the largest responses, followed by UO22+ (187 ORFs, 91 UO22+-specific ORFs), Ni2+ (93 ORFs, 25 Ni2+-specific ORFs), and Co2+ (61 ORFs, 1 Co2+-specific ORF). While one-third of the metal-responsive ORFs are annotated as encoding hypothetical proteins, metal challenge also impacted ORFs responsible for identifiable processes related to the cell cycle, DNA repair, and oxidative stress. Surprisingly, there were only 30 ORFs that responded to at least four metals, and 10 of these responded to all five metals. This core transcriptome indicated induction of Fe-S cluster assembly (Msed_1656-Msed_1657), tungsten/molybdenum transport (Msed_1780-Msed_1781), and decreased central metabolism. Not surprisingly, a metal-translocating P-type ATPase (Msed_0490) associated with a copper resistance system (Cop) was upregulated in response to Cu2+ (6-fold) but also in response to UO22+ (4-fold) and Zn2+ (9-fold). Cu2+ challenge uniquely induced assimilatory sulfur metabolism for cysteine biosynthesis, suggesting a role for this amino acid in Cu2+ resistance or issues in sulfur metabolism. The results indicate that M. sedula employs a range of physiological and biochemical responses to metal challenge, many of which are specific to a single metal and involve proteins with yet unassigned or definitive functions. IMPORTANCE The mechanisms by which extremely thermoacidophilic archaea resist

  5. Cerebrolysin, a mixture of neurotrophic factors induces marked neuroprotection in spinal cord injury following intoxication of engineered nanoparticles from metals.

    PubMed

    Menon, Preeti Kumaran; Muresanu, Dafin Fior; Sharma, Aruna; Mössler, Herbert; Sharma, Hari Shanker

    2012-02-01

    Spinal cord injury (SCI) is the world's most disastrous disease for which there is no effective treatment till today. Several studies suggest that nanoparticles could adversely influence the pathology of SCI and thereby alter the efficacy of many neuroprotective agents. Thus, there is an urgent need to find suitable therapeutic agents that could minimize cord pathology following trauma upon nanoparticle intoxication. Our laboratory has been engaged for the last 7 years in finding suitable therapeutic strategies that could equally reduce cord pathology in normal and in nanoparticle-treated animal models of SCI. We observed that engineered nanoparticles from metals e.g., aluminum (Al), silver (Ag) and copper (Cu) (50-60 nm) when administered in rats daily for 7 days (50 mg/kg, i.p.) resulted in exacerbation of cord pathology after trauma that correlated well with breakdown of the blood-spinal cord barrier (BSCB) to serum proteins. The entry of plasma proteins into the cord leads to edema formation and neuronal damage. Thus, future drugs should be designed in such a way to be effective even when the SCI is influenced by nanoparticles. Previous research suggests that a suitable combination of neurotrophic factors could induce marked neuroprotection in SCI in normal animals. Thus, we examined the effects of a new drug; cerebrolysin that is a mixture of different neurotrophic factors e.g., brain-derived neurotrophic factor (BDNF), glial cell line derived neurotrophic factor (GDNF), nerve growth factor (NGF), ciliary neurotrophic factor (CNTF) and other peptide fragments to treat normal or nanoparticle-treated rats after SCI. Our observations showed that cerebrolysin (2.5 ml/kg, i.v.) before SCI resulted in good neuroprotection in normal animals, whereas nanoparticle-treated rats required a higher dose of the drug (5.0 ml/kg, i.v.) to induce comparable neuroprotection in the cord after SCI. Cerebrolysin also reduced spinal cord water content, leakage of plasma proteins

  6. The Challenge of Peat Substitution in Organic Seedling Production: Optimization of Growing Media Formulation through Mixture Design and Response Surface Analysis.

    PubMed

    Ceglie, Francesco Giovanni; Bustamante, Maria Angeles; Ben Amara, Mouna; Tittarelli, Fabio

    2015-01-01

    Peat replacement is an increasing demand in containerized and transplant production, due to the environmental constraints associated to peat use. However, despite the wide information concerning the use of alternative materials as substrates, it is very complex to establish the best materials and mixtures. This work evaluates the use of mixture design and surface response methodology in a peat substitution experiment using two alternative materials (green compost and palm fibre trunk waste) for transplant production of tomato (Lycopersicon esculentum Mill.); melon, (Cucumis melo L.); and lettuce (Lactuca sativa L.) in organic farming conditions. In general, the substrates showed suitable properties for their use in seedling production, showing the best plant response the mixture of 20% green compost, 39% palm fibre and 31% peat. The mixture design and applied response surface methodology has shown to be an useful approach to optimize substrate formulations in peat substitution experiments to standardize plant responses.

  7. The Challenge of Peat Substitution in Organic Seedling Production: Optimization of Growing Media Formulation through Mixture Design and Response Surface Analysis

    PubMed Central

    Ceglie, Francesco Giovanni; Bustamante, Maria Angeles; Ben Amara, Mouna; Tittarelli, Fabio

    2015-01-01

    Peat replacement is an increasing demand in containerized and transplant production, due to the environmental constraints associated to peat use. However, despite the wide information concerning the use of alternative materials as substrates, it is very complex to establish the best materials and mixtures. This work evaluates the use of mixture design and surface response methodology in a peat substitution experiment using two alternative materials (green compost and palm fibre trunk waste) for transplant production of tomato (Lycopersicon esculentum Mill.); melon, (Cucumis melo L.); and lettuce (Lactuca sativa L.) in organic farming conditions. In general, the substrates showed suitable properties for their use in seedling production, showing the best plant response the mixture of 20% green compost, 39% palm fibre and 31% peat. The mixture design and applied response surface methodology has shown to be an useful approach to optimize substrate formulations in peat substitution experiments to standardize plant responses. PMID:26070163

  8. [Colorimetric study of color reproduction in porcelain-fused-to-metal restoration. The application of Kubelka-Munk theory in porcelain mixtures].

    PubMed

    Ishikawa, S; Miyoshi, F; Ishibashi, K

    1990-06-01

    To get a more natural and harmonious color of porcelain-fused-to-metal restorations, an objective and precise systematic method from shade selection to color evaluation is needed. Thus, the absorption and scattering coefficients were determined to develop a CCM system for porcelain-fused-to-metal restorations. The Kubelka-Munk Theory was applied on the dental porcelain, opaque, dentin, and enamel. From these data, we predicted the color of the porcelain mixtures from the both coefficients. From the results of comparing the spectral curves and analyzing the color differences between measured values and predicted values of porcelain mixtures, the following was analysed; 1. In opaque, spectral curves of the predicted and measured values were exactly alike and the mean dE between two values was 0.39. 2. In dentin, the spectral curved of the predicted and measured values were exactly alike, and the mean dE was 1.13. The measured values indicated a slight increase in the level of chroma and lightness. 3. In enamel, the spectral curves were exactly alike and the mean dE was 1.16. The measured values indicated a slight decrease in the level of lightness. Therefore, it was possible to predict the color of opaque, dentin and enamel porcelain mixtures, by applying the Kubelka-Munk Theory.

  9. Mixture toxicity and interactions of copper, nickel, cadmium, and zinc to barley at low effect levels: Something from nothing?

    PubMed

    Versieren, Liske; Evers, Steffie; De Schamphelaere, Karel; Blust, Ronny; Smolders, Erik

    2016-10-01

    Metal contamination is mostly a mixture of different metals, and these multicomponent mixtures can produce significant mixture effects. The present study was set up to investigate the toxicity of multiple metal mixtures of Cu, Ni, Cd, and Zn to plants at metal doses individually causing low-level phytotoxic effects. Barley (Hordeum vulgare L.) root elongation toxicity tests were performed in resin-buffered nutrient solutions to control metal speciation. Treatments included single-metal concentrations and binary, ternary, and quaternary mixtures. Mixtures of different metals at free ion concentrations, each causing <10% inhibition of root elongation, yielded significant mixture effects, with inhibition reaching up to 50%. The independent action (IA) model predicted mixture toxicity statistically better than the concentration addition (CA) model, but some synergisms relative to the IA model were observed. These synergisms relative to IA were most pronounced in quaternary mixtures and when the dose-response curves had steep slopes. Generally, antagonistic interactions relative to the CA model were observed. Increasing solution Zn concentrations shifted metal interactions (CA based) from additive or slightly synergistic at background Zn concentrations to antagonistic at higher Zn concentrations, suggesting a protective effect of Zn. Overall, the present study shows that the CA model can be used as a conservative model to predict metal mixture toxicity to barley. Environ Toxicol Chem 2016;35:2483-2492. © 2016 SETAC.

  10. In vitro expression of hard metal dust (WC-Co) - responsive genes in human peripheral blood mononucleated cells

    SciTech Connect

    Lombaert, Nooemi Lison, Dominique; Van Hummelen, Paul; Kirsch-Volders, Micheline

    2008-03-01

    Hard metals consist of tungsten carbide (WC) and metallic cobalt (Co) particles and are important industrial materials produced for their extreme hardness and high wear resistance properties. While occupational exposure to metallic Co alone is apparently not associated with an increased risk of cancer, the WC-Co particle mixture was shown to be carcinogenic in exposed workers. The in vitro mutagenic/apoptogenic potential of WC-Co in human peripheral blood mononucleated cells was previously demonstrated by us. This study aimed at obtaining a broader view of the pathways responsible for WC-Co induced carcinogenicity, and in particular genotoxicity and apoptosis. We analyzed the profile of gene expression induced in vitro by WC-Co versus control (24 h treatment) in human PBMC and monocytes using microarrays. The most significantly up-regulated pathways for WC-Co treated PBMC were apoptosis and stress/defense response; the most down-regulated was immune response. For WC-Co treated monocytes the most significantly up- and down-regulated pathways were nucleosome/chromatin assembly and immune response respectively. Quantitative RT-PCR data for a selection of the most strongly modulated genes (HMOX1, HSPA1A, HSPA1L, BNIP3, BNIP3L, ADORA2B, MT3, PLA2G7, TNFAIP6), and some additionally chosen apoptosis related genes (BCL2, BAX, FAS, FASL, TNF{alpha}), confirmed the microarray data after WC-Co exposure and demonstrated limited differences between the Co-containing compounds. Overall, this study provides the first analysis of gene expression induced by the WC-Co mixture showing a large profile of gene modulation and giving a preliminary indication for a hypoxia mimicking environment induced by WC-Co exposure.

  11. Material response from Mach 0.3 burner rig combustion of a coal-oil mixture

    NASA Technical Reports Server (NTRS)

    Santoro, G. J.; Calfo, F. D.; Kohl, F. J.

    1981-01-01

    Wedge shaped specimens were exposed to the combustion gases of a Mach 0.3 burner rig fueled with a mixture of 40 weight percent micron size coal particles dispersed in No. 2 fuel oil. Exposure temperature was about 900 C and the test duration was about 44 one hour cycles. The alloys tested were the nickel base superalloys, IN-100, U-700 and IN-792, and the cobalt base superalloy, Mar-M509. The deposits on the specimens were analyzed and the extent of corrosion/erosion was measured. The chemical compositions of the deposits were compared with the predictions from an equilibrium thermodynamic analysis. The experimental results were in very good agreement with the predictions.

  12. Tube radial distribution phenomenon with a two-phase separation solution of a fluorocarbon and hydrocarbon organic solvent mixture in a capillary tube and metal compounds separation.

    PubMed

    Kitaguchi, Koichi; Hanamura, Naoya; Murata, Masaharu; Hashimoto, Masahiko; Tsukagoshi, Kazuhiko

    2014-01-01

    A fluorocarbon and hydrocarbon organic solvent mixture is known as a temperature-induced phase-separation solution. When a mixed solution of tetradecafluorohexane as a fluorocarbon organic solvent and hexane as a hydrocarbon organic solvent (e.g., 71:29 volume ratio) was delivered in a capillary tube that was controlled at 10°C, the tube radial distribution phenomenon (TRDP) of the solvents was clearly observed through fluorescence images of the dye, perylene, dissolved in the mixed solution. The homogeneous mixed solution (single phase) changed to a heterogeneous solution (two phases) with inner tetradecafluorohexane and outer hexane phases in the tube under laminar flow conditions, generating the dynamic liquid-liquid interface. We also tried to apply TRDP to a separation technique for metal compounds. A model analyte mixture, copper(II) and hematin, was separated through the capillary tube, and detected with a chemiluminescence detector in this order within 4 min.

  13. Understanding the sensor response of metal-decorated carbon nanotubes.

    PubMed

    Kauffman, Douglas R; Sorescu, Dan C; Schofield, Daniel P; Allen, Brett L; Jordan, Kenneth D; Star, Alexander

    2010-03-10

    We have explored the room temperature response of metal nanoparticle decorated single-walled carbon nanotubes (NP-SWNTs) using a combination of electrical transport, optical spectroscopy, and electronic structure calculations. We have found that upon the electrochemical growth of Au NPs on SWNTs, there is a transfer of electron density from the SWNT to the NP species, and that adsorption of CO molecules on the NP surface is accompanied by transfer of electronic density back into the SWNT. Moreover, the electronic structure calculations indicate dramatic variations in the charge density at the NP-SWNT interface, which supports our previous observation that interfacial potential barriers dominate the electrical behavior of NP-SWNT systems.

  14. Synergistic effects of perfluoroalkyl acids mixtures with J-shaped concentration-responses on viability of a human liver cell line.

    PubMed

    Hu, Jiayue; Li, Juan; Wang, Jianshe; Zhang, Aiqian; Dai, Jiayin

    2014-02-01

    Some perfluoroalkyl acids (PFAAs) are highly persistent and bioaccumulative, resulting in their broad coexisting distribution in humans and the environment. Our aim was to investigate the individual and joint effects of PFAAs on cellular viability of a human liver cell line (HL-7702) using the MTT assay. Equipartition ray design and equivalent-effect concentration ratio (EECR) mixtures were used to investigate the binary and multiple effects of PFAAs, respectively. All tested PFAAs mixtures and the individuals (except perfluorododecanoic acid (PFDoDA) and perfluorotetradecanoic acid (PFTeDA)) showed obvious non-monotonic J-shaped concentration-response curves (CRC) on HL-7702. The inhibitory effect of individual PFAAs increased with the elongation of the carbon chain and was dominated by their molecular volume. The three binary mixtures (PFOA/S, PFHxA/S and PFBA/S) showed that synergistic effects occurred under effective inhibitory concentrations (IC) of IC0, IC10, and IC50 in mixtures, while for IC-20 the synergistic effect only occurred under higher PFSA proportion in mixtures. Furthermore, EECR mixtures of the nine individual PFAAs with J-shaped CRC also showed synergistic effects. However, mixtures of the eleven individual PFAAs including those with S-shaped CRC resulted in partial addition effects on HL-7702. Our results indicated that the individual stimulatory responses of HL-7702 to PFAA may produce adverse effects in mixtures at relevant dose levels.

  15. Induction of several acute-phase protein genes by heavy metals: A new class of metal-responsive genes

    SciTech Connect

    Yiangou, Minas; Ge, Xin; Carter, K.C.; Papaconstantinou, J. Shriners Burns Institute, Galveston, TX )

    1991-04-16

    Acute-phase reactants, metallothioneins, and heat-shock proteins are the products of three families of genes that respond to glucocorticoids and cytokines. Metallothioneins and heat-shock proteins, however, are also stimulated by heavy metals whereas very little is known about the effect of heavy metals on acute-phase-reactant genes. The authors have studied the effect of heavy metals (Hg, Cd, Pb, Cu, Ni, and Zn) and Mg on the acute-phase reactants {alpha}{sub 1}-acid glycoprotein, C-reactive protein, {alpha}{sub 1}-antitrypsin and {alpha}{sub 1}-antichymotrypsin. {alpha}{sub 1}-Acid glycoprotein and C-reactive protein mRNA levels were increased severalfold in livers of heavy-metal-treated Balb/c mice. The strongest induction was mediated by Hg, followed in order of response by Cd > Pb > Cu > Ni > Zn > Mg. None of the metals affected the mRNA levels of albumin, {alpha}{sub 1}-antitrypsin, and {alpha}{sub 1}-antichymotrypsin. Furthermore, failure to repress albumin, a negative acute-phase reactant, indicated that the induction of these genes was not due to a metal-mediated inflammatory response. The metals also induced {alpha}{sub 1}-acid glycoprotein and C-reactive protein in adrenalectomized animals, indicating that induction by the heavy metals is not mediated by the glucocorticoid induction pathway. Sequence analysis has revealed a region of homology to metal-responsive elements in the {alpha}{sub 1}-acid glycoprotein and C-reactive protein promoters. The studies indicate that the induction of {alpha}{sub 1}-acid glycoprotein and C-reactive protein by heavy metals may be regulated by these metal-responsive elements at the level of transcription.

  16. Macromolecular Response of Individual Algal Cells to Nutrient and Atrazine Mixtures within Biofilms

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Pollutant effects on biofilm physiology are difficult to assess due to differential susceptibility of species and difficulty separating individual species for analysis. Also,measuring whole assemblage responses such as metabolism can mask species-specific responses, as some species may decrease and ...

  17. Stress responses and metal tolerance of Chlamydomonas acidophila in metal-enriched lake water and artificial medium.

    PubMed

    Spijkerman, Elly; Barua, Deepak; Gerloff-Elias, Antje; Kern, Jürgen; Gaedke, Ursula; Heckathorn, Scott A

    2007-07-01

    Chlamydomonas acidophila faces high heavy-metal concentrations in acidic mining lakes, where it is a dominant phytoplankton species. To investigate the importance of metals to C. acidophila in these lakes, we examined the response of growth, photosynthesis, cell structure, heat-shock protein (Hsp) accumulation, and metal adsorption after incubation in metal-rich lake water and artificial growth medium enriched with metals (Fe, Zn). Incubation in both metal-rich lake water and medium caused large decreases in photosystem II function (though no differences among lakes), but no decrease in growth rate (except for medium + Fe). Concentrations of small Hsps were higher in algae incubated in metal-rich lake-water than in metal-enriched medium, whereas Hsp60 and Hsp70A were either less or equally expressed. Cellular Zn and Fe contents were lower, and metals adsorbed to the cell surface were higher, in lake-water-incubated algae than in medium-grown cells. The results indicate that high Zn or Fe levels are likely not the main or only contributor to the low primary production in mining lakes, and multiple adaptations of C. acidophila (e.g., high Hsp levels, decreased metal accumulation) increase its tolerance to metals and permit survival under such adverse environmental conditions. Supposedly, the main stress factor present in the lake water is an interaction between low P and high Fe concentrations.

  18. A Cleaner Process for Selective Recovery of Valuable Metals from Electronic Waste of Complex Mixtures of End-of-Life Electronic Products.

    PubMed

    Sun, Zhi; Xiao, Y; Sietsma, J; Agterhuis, H; Yang, Y

    2015-07-07

    In recent years, recovery of metals from electronic waste within the European Union has become increasingly important due to potential supply risk of strategic raw material and environmental concerns. Electronic waste, especially a mixture of end-of-life electronic products from a variety of sources, is of inherently high complexity in composition, phase, and physiochemical properties. In this research, a closed-loop hydrometallurgical process was developed to recover valuable metals, i.e., copper and precious metals, from an industrially processed information and communication technology waste. A two-stage leaching design of this process was adopted in order to selectively extract copper and enrich precious metals. It was found that the recovery efficiency and extraction selectivity of copper both reached more than 95% by using ammonia-based leaching solutions. A new electrodeposition process has been proven feasible with 90% current efficiency during copper recovery, and the copper purity can reach 99.8 wt %. The residue from the first-stage leaching was screened into coarse and fine fractions. The coarse fraction was returned to be releached for further copper recovery. The fine fraction was treated in the second-stage leaching using sulfuric acid to further concentrate precious metals, which could achieve a 100% increase in their concentrations in the residue with negligible loss into the leaching solution. By a combination of different leaching steps and proper physical separation of light materials, this process can achieve closed-loop recycling of the waste with significant efficiency.

  19. Responsive metal/polymer nanocomposites via photothermal effect

    NASA Astrophysics Data System (ADS)

    Seyhan, Merve; Rende, Deniz; Huang, Liping; Malta, Seyda; Ozisik, Rahmi; Baysal, Nihat

    2013-03-01

    Metal nanoparticles can efficiently generate heat when exposed to electromagnetic radiation. The amount of heat generated and the temperature increase depends on the number of nanoparticles and their shape. In the current work, gold nanoparticles (AuNPs) were used as heat sources within polyethylene oxide (600,000 g/mol) via the photothermal effect. AuNPs were synthesized through Frens method, and were characterized using TEM. A laser source with a wavelength of 532 nm was used to heat AuNPs. Raman spectroscopy data showed that irradiation of AuNPs led to increasing temperature profiles in the vicinity of AuNPs, which is a result of the surface plasmon resonance. This property of AuNPs would enable the control of viscoelastic response of the polymer by altering crystallinity and temperature of the polymer matrix, thereby, providing responsive materials. This work is partially supported by NSF CMMI-1200270 and DUE-1003574. MS was supported by TUBITAK 2214 grant. NB was supported by TUBITAK 2219 grant.

  20. Engineering Cellular Response Using Nanopatterned Bulk Metallic Glass

    PubMed Central

    2015-01-01

    Nanopatterning of biomaterials is rapidly emerging as a tool to engineer cell function. Bulk metallic glasses (BMGs), a class of biocompatible materials, are uniquely suited to study nanopattern–cell interactions as they allow for versatile fabrication of nanopatterns through thermoplastic forming. Work presented here employs nanopatterned BMG substrates to explore detection of nanopattern feature sizes by various cell types, including cells that are associated with foreign body response, pathology, and tissue repair. Fibroblasts decreased in cell area as the nanopattern feature size increased, and fibroblasts could detect nanopatterns as small as 55 nm in size. Macrophages failed to detect nanopatterns of 150 nm or smaller in size, but responded to a feature size of 200 nm, resulting in larger and more elongated cell morphology. Endothelial cells responded to nanopatterns of 100 nm or larger in size by a significant decrease in cell size and elongation. On the basis of these observations, nondimensional analysis was employed to correlate cellular morphology and substrate nanotopography. Analysis of the molecular pathways that induce cytoskeletal remodeling, in conjunction with quantifying cell traction forces with nanoscale precision using a unique FIB-SEM technique, enabled the characterization of underlying biomechanical cues. Nanopatterns altered serum protein adsorption and effective substrate stiffness, leading to changes in focal adhesion density and compromised activation of Rho-A GTPase in fibroblasts. As a consequence, cells displayed restricted cell spreading and decreased collagen production. These observations suggest that topography on the nanoscale can be designed to engineer cellular responses to biomaterials. PMID:24724817

  1. Optimized pH-responsive film based on a eutectic mixture-plasticized chitosan.

    PubMed

    Pereira, Pamela F; Andrade, Cristina T

    2017-06-01

    Chitosan (CS, 2g/100mL)/curcumin 1g/100mL in acetic acid aqueous solution were used to prepare films to be used as food indicator. Microcrystalline cellulose (MCC) and a eutectic mixture (DES) were incorporated as reinforcing and plasticizing agents, respectively. The MCC content (133 mas%) and DES composition (7.93 mass%), based on CS dry mass, were optimized. The properties of the DES-plasticized film were compared to those for the unplasticized and glycerol (G)-plasticized CS films. The DES-plasticized film presented initial temperature of thermal decomposition at 267.7°C, dynamic glass transition at 149.3°C, water vapor permeability of 7.21×10(-10)gs(-1)m(-1)Pa(-1), water solubility of 3.07% and stress at break of 20.1MPa. The incorporation of MCC contributed to increase the crystallinity of the composite films. Colorimetric tests, carried out in aqueous environments for the DES-plasticized film, revealed accentuated color changes, mainly at pHs higher than pH 8.

  2. The Accuracy of Computerized Adaptive Testing in Heterogeneous Populations: A Mixture Item-Response Theory Analysis

    PubMed Central

    Kopec, Jacek A.; Wu, Amery D.; Zumbo, Bruno D.

    2016-01-01

    Background Computerized adaptive testing (CAT) utilizes latent variable measurement model parameters that are typically assumed to be equivalently applicable to all people. Biased latent variable scores may be obtained in samples that are heterogeneous with respect to a specified measurement model. We examined the implications of sample heterogeneity with respect to CAT-predicted patient-reported outcomes (PRO) scores for the measurement of pain. Methods A latent variable mixture modeling (LVMM) analysis was conducted using data collected from a heterogeneous sample of people in British Columbia, Canada, who were administered the 36 pain domain items of the CAT-5D-QOL. The fitted LVMM was then used to produce data for a simulation analysis. We evaluated bias by comparing the referent PRO scores of the LVMM with PRO scores predicted by a “conventional” CAT (ignoring heterogeneity) and a LVMM-based “mixture” CAT (accommodating heterogeneity). Results The LVMM analysis indicated support for three latent classes with class proportions of 0.25, 0.30 and 0.45, which suggests that the sample was heterogeneous. The simulation analyses revealed differences between the referent PRO scores and the PRO scores produced by the “conventional” CAT. The “mixture” CAT produced PRO scores that were nearly equivalent to the referent scores. Conclusion Bias in PRO scores based on latent variable models may result when population heterogeneity is ignored. Improved accuracy could be obtained by using CATs that are parameterized using LVMM. PMID:26930348

  3. The Quantitative Resolution of a Mixture of Group II Metal Ions by Thermometric Titration with EDTA. An Analytical Chemistry Experiment.

    ERIC Educational Resources Information Center

    Smith, Robert L.; Popham, Ronald E.

    1983-01-01

    Presents an experiment in thermometric titration used in an analytic chemistry-chemical instrumentation course, consisting of two titrations, one a mixture of calcium and magnesium, the other of calcium, magnesium, and barium ions. Provides equipment and solutions list/specifications, graphs, and discussion of results. (JM)

  4. A pH-responsive cleavage route based on a metal-organic coordination bond.

    PubMed

    Xing, Lei; Zheng, Haoquan; Che, Shunai

    2011-06-20

    The physical or chemical event that generally causes stimuli responses is limited to the formation or destruction of secondary forces, such as hydrogen bonding, hydrophobic effects, electrostatic interactions, and simple reactions. Here, pH-responsive behavior of metal-organic coordination bonding, which is intrinsic to natural systems (e.g., transferrin recycling in cells), is becoming a strong candidate for a new stimulus-responsive route. We have designed a simple pH-responsive release system by integrating a metal ion and ligand or self-assembling these species with biodegradable host molecules to form nanoparticles with "metal-ligand" or "host-metal-ligand" architectures. The cleavage of either or both the "metal-ligand" or the "host-metal" coordination bond in response to pH variations causes significant damage to the nanoparticles and the subsequent release of ligand molecules under designated pH conditions.

  5. Metal mixtures in urban and rural populations in the US: The Multi-Ethnic Study of Atherosclerosis and the Strong Heart Study☆

    PubMed Central

    Pang, Yuanjie; Peng, Roger D.; Jones, Miranda R.; Francesconi, Kevin A.; Goessler, Walter; Howard, Barbara V.; Umans, Jason G.; Best, Lyle G.; Guallar, Eliseo; Post, Wendy S.; Kaufman, Joel D.; Vaidya, Dhananjay; Navas-Acien, Ana

    2016-01-01

    Background Natural and anthropogenic sources of metal exposure differ for urban and rural residents. We searched to identify patterns of metal mixtures which could suggest common environmental sources and/or metabolic pathways of different urinary metals, and compared metal-mixtures in two population-based studies from urban/sub-urban and rural/town areas in the US: the Multi-Ethnic Study of Atherosclerosis (MESA) and the Strong Heart Study (SHS). Methods We studied a random sample of 308 White, Black, Chinese-American, and Hispanic participants in MESA (2000–2002) and 277 American Indian participants in SHS (1998–2003). We used principal component analysis (PCA), cluster analysis (CA), and linear discriminant analysis (LDA) to evaluate nine urinary metals (antimony [Sb], arsenic [As], cadmium [Cd], lead [Pb], molybdenum [Mo], selenium [Se], tungsten [W], uranium [U] and zinc [Zn]). For arsenic, we used the sum of inorganic and methylated species (∑As). Results All nine urinary metals were higher in SHS compared to MESA participants. PCA and CA revealed the same patterns in SHS, suggesting 4 distinct principal components (PC) or clusters (∑As-U-W, Pb-Sb, Cd-Zn, Mo-Se). In MESA, CA showed 2 large clusters (∑As-Mo-Sb-U-W, Cd-Pb-Se-Zn), while PCA showed 4 PCs (Sb-U-W, Pb-Se-Zn, Cd-Mo, ∑As). LDA indicated that ∑As, U, W, and Zn were the most discriminant variables distinguishing MESA and SHS participants. Conclusions In SHS, the ∑As-U-W cluster and PC might reflect groundwater contamination in rural areas, and the Cd-Zn cluster and PC could reflect common sources from meat products or metabolic interactions. Among the metals assayed, ∑As, U, W and Zn differed the most between MESA and SHS, possibly reflecting disproportionate exposure from drinking water and perhaps food in rural Native communities compared to urban communities around the US. PMID:26945432

  6. cDNA microarray assessment of early gene expression profiles in Escherichia coli cells exposed to a mixture of heavy metals.

    PubMed

    Gómez-Sagasti, María T; Becerril, José M; Martín, Iker; Epelde, Lur; Garbisu, Carlos

    2014-08-01

    Many contaminated sites are characterized by the presence of different metals, thus increasing the complexity of toxic responses in exposed organisms. Within toxicogenomics, transcriptomics can be approached through the use of microarrays aimed at producing a genetic fingerprint for the response of model organisms to the presence of chemicals. We studied temporal changes in the early gene expression profiles of Escherichia coli cells exposed to three metal doses of a polymetallic solution over three exposure times, through the application of cDNA microarray technology. In the absence of metals, many genes belonging to a variety of cellular functions were up- and down-regulated over time. At the lowest metal dose, an activation of metal-specific transporters (Cus and ZraP proteins) and a mobilization of glutathione transporters involved in metal sequestration and trafficking was observed over time; this metal dose resulted in the generation of ROS capable of stimulating the transcription of Mn-superoxide dismutase, the assembly of Fe-S clusters and the synthesis of cysteine. At the intermediate dose, an overexpression of ROS scavengers (AhpF, KatG, and YaaA) and heat shock proteins (ClpP, HslV, DnaK, and IbpAB) was observed. Finally, at the highest dose, E. coli cells showed a repression of genes related with DNA mutation correctors (MutY glycopeptidases).

  7. Demographic and growth responses of a guerrilla and a phalanx perennial grass in competitive mixtures

    USGS Publications Warehouse

    Humphrey, David L.; Pyke, David A.

    1998-01-01

    The advantages of guerrilla and phalanx growth for the guerrilla Elymus lanceolatus ssp. lanceolatus and phalanx E. l. ssp. wawawaiensis were evaluated over 2 years in two taxon mixtures with a range of densities of each subspecies and under two levels of watering. Ramet numbers and biomass of the guerrilla subspecies were higher than those of the phalanx grass in the first year but in the second year declined greatly, while the phalanx grass showed no change in biomass and an increase in ramet numbers. High neighbour densities affected the phalanx subspecies more strongly than the guerrilla subspecies in the first year, but in the second year there were few differences between subspecies. Biomass of the guerrilla grass remained greater than that of the phalanx grass but ramet numbers were similar in the second year. For both subspecies in both years, probability of flowering decreased at higher neighbour densities, indicating adaptation for competitive ability. In the first year, biomass was more strongly reduced by densities than flowering was, but in the second year, when crowding was apparently greater, flowering was more severely affected. Genet survival was high and similar for both subspecies. The presumed advantage of guerrilla subspecies in exploiting open space was supported. The guerrilla grass exploited resources more quickly in the first year by faster growth and greater ramet production, but its biomass, ramet numbers and rhizome growth, and thus its advantage, were reduced in the second year. The phalanx subspecies had slower growth, produced more ramets in later years, and delayed flowering until later years. Although less able to exploit open resources, it appeared adapted to more stressful conditions, and may be able to exploit temporal resource pulses more effectively.

  8. Acute toxicity of binary and ternary mixtures of Cd, Cu, and Zn to Daphnia magna.

    PubMed

    Meyer, Joseph S; Ranville, James F; Pontasch, Mandee; Gorsuch, Joseph W; Adams, William J

    2015-04-01

    Standard static-exposure acute lethality tests were conducted with Daphnia magna neonates exposed to binary or ternary mixtures of Cd, Cu, and Zn in moderately hard reconstituted water that contained 3 mg dissolved organic carbon/L added as Suwannee River fulvic acid. These experiments were conducted to test for additive toxicity (i.e., the response to the mixture can be predicted by combining the responses obtained in single-metal toxicity tests) or nonadditive toxicity (i.e., the response is less than or greater than additive). Based on total metal concentrations (>90% dissolved) the toxicity of the tested metal mixtures could be categorized into all 3 possible additivity categories: less-than-additive toxicity (e.g., Cd-Zn and Cd-Cu-Zn mixtures and Cd-Cu mixtures when Cu was titrated into Cd-containing waters), additive toxicity (e.g., some Cu-Zn mixtures), or more-than-additive toxicity (some Cu-Zn mixtures and Cd-Cu mixtures when Cd was titrated into Cu-containing waters). Exposing the organisms to a range of sublethal to supralethal concentrations of the titrated metal was especially helpful in identifying nonadditive interactions. Geochemical processes (e.g., metal-metal competition for binding to dissolved organic matter and/or the biotic ligand, and possibly supersaturation of exposure waters with the metals in some high-concentration exposures) can explain much of the observed metal-metal interactions. Therefore, bioavailability models that incorporate those geochemical (and possibly some physiological) processes might be able to predict metal mixture toxicity accurately.

  9. Responses of the European flounder (Platichthys flesus) to a mixture of PAHs and PCBs in experimental conditions.

    PubMed

    Dupuy, Célie; Galland, Claire; Devaux, Alain; Bony, Sylvie; Loizeau, Véronique; Danion, Morgane; Pichereau, Vianney; Fournier, Michel; Laroche, Jean

    2014-12-01

    A multibiomarker approach was developed to evaluate the juvenile European flounder responses to a complex mixture of 9 polycyclic aromatic hydrocarbons (PAHs) and 12 polychlorinated biphenyls (PCBs). Exposure was performed through contaminated food pellets displaying: (1) PAH and PCB levels similar to those detected in the heavily polluted Seine estuary, respectively in sediments and in flatfish and (2) ten times these concentrations. Several biomarkers of the immune system (e.g., lysozyme concentration and gene expression of complement component C3 and TNF-receptor), DNA damage (e.g., Comet assay), energetic metabolism (e.g., activity of cytochrome C oxidase), detoxification process (e.g., cytochrome P450 1A1 expression level: CYP1A1; betaine homocysteine methyl transferase expression level: BHMT) were investigated after 14 and 29 days of contamination, followed by a 14-days recovery period. After 29 days of contamination, the detoxification activity (CYP1A1 expression level) was positively correlated with DNA damages; the increase of the BHMT expression level could also be related to the detoxification process. Furthermore, after the recovery period, some biomarkers were still upregulated (i.e., CYP1A1 and BHMT expression levels). The immune system was significantly modulated by the chemical stress at the two concentration levels, and the lysozyme appeared to be the most sensitive marker of the mixture impact.

  10. Effect of microemulsions on transdermal delivery of citalopram: optimization studies using mixture design and response surface methodology.

    PubMed

    Huang, Chi-Te; Tsai, Ming-Jun; Lin, Yu-Hsuan; Fu, Yaw-Sya; Huang, Yaw-Bin; Tsai, Yi-Hung; Wu, Pao-Chu

    2013-01-01

    The aim of this study was to evaluate the potential of microemulsions as a drug vehicle for transdermal delivery of citalopram. A computerized statistical technique of response surface methodology with mixture design was used to investigate and optimize the influence of the formulation compositions including a mixture of Brij 30/Brij 35 surfactants (at a ratio of 4:1, 20%-30%), isopropyl alcohol (20%-30%), and distilled water (40%-50%) on the properties of the drug-loaded microemulsions, including permeation rate (flux) and lag time. When microemulsions were used as a vehicle, the drug permeation rate increased significantly and the lag time shortened significantly when compared with the aqueous control of 40% isopropyl alcohol solution containing 3% citalopram, demonstrating that microemulsions are a promising vehicle for transdermal application. With regard to the pharmacokinetic parameters of citalopram, the flux required for the transdermal delivery system was about 1280 μg per hour. The microemulsions loaded with citalopram 3% and 10% showed respective flux rates of 179.6 μg/cm(2) and 513.8 μg/cm(2) per hour, indicating that the study formulation could provide effective therapeutic concentrations over a practical application area. The animal study showed that the optimized formulation (F15) containing 3% citalopram with an application area of 3.46 cm(2) is able to reach a minimum effective therapeutic concentration with no erythematous reaction.

  11. Effect of microemulsions on transdermal delivery of citalopram: optimization studies using mixture design and response surface methodology

    PubMed Central

    Huang, Chi-Te; Tsai, Ming-Jun; Lin, Yu-Hsuan; Fu, Yaw-Sya; Huang, Yaw-Bin; Tsai, Yi-Hung; Wu, Pao-Chu

    2013-01-01

    The aim of this study was to evaluate the potential of microemulsions as a drug vehicle for transdermal delivery of citalopram. A computerized statistical technique of response surface methodology with mixture design was used to investigate and optimize the influence of the formulation compositions including a mixture of Brij 30/Brij 35 surfactants (at a ratio of 4:1, 20%–30%), isopropyl alcohol (20%–30%), and distilled water (40%–50%) on the properties of the drug-loaded microemulsions, including permeation rate (flux) and lag time. When microemulsions were used as a vehicle, the drug permeation rate increased significantly and the lag time shortened significantly when compared with the aqueous control of 40% isopropyl alcohol solution containing 3% citalopram, demonstrating that microemulsions are a promising vehicle for transdermal application. With regard to the pharmacokinetic parameters of citalopram, the flux required for the transdermal delivery system was about 1280 μg per hour. The microemulsions loaded with citalopram 3% and 10% showed respective flux rates of 179.6 μg/cm2 and 513.8 μg/cm2 per hour, indicating that the study formulation could provide effective therapeutic concentrations over a practical application area. The animal study showed that the optimized formulation (F15) containing 3% citalopram with an application area of 3.46 cm2 is able to reach a minimum effective therapeutic concentration with no erythematous reaction. PMID:23919086

  12. Role of nitroreduction in the synergistic mutational response induced by mixtures of 1- and 3-nitrobenzo(a)pyrene in Salmonella typhimurium

    SciTech Connect

    Thornton-Manning, J.R.; Campbell, W.L.; Hass, B.S.; Chen, J.J.; Fu, P.P.; Cerniglia, C.E.; Heflich, R.H. )

    1989-01-01

    Previous studies showed that binary mixtures of the environmental pollutants 1- and 3-nitrobenzo(a)pyrene produced a synergistic mutational response in the Salmonella reversion assay. Since nitroreduction is believed to mediate the direct-acting mutagenicity of the individual compounds, the authors have examined the role of nitroreduction in the mutagenicity of mixtures of 1- and 3-nitrobenzo(a)pyrene in the Salmonella plate incorporation assay. While mixtures of 1- and 3-nitrobenzo(a)pyrene induced up to 183% more revertants in strain TA98 than produced by equivalent amounts of the individual compounds, in the nitroreductase-deficient strain TA98NR the same mixtures only induced up to 57% more revertants than the individual compounds. Analysis of mixtures of 1- and 3-nitrosobenzo(a)pyrene for mutation induction in TA98 yielded no evidence of a synergistic effect between the compounds. Salmonella cultures were also incubated with mixtures of 1- and 3-nitrobenzo(a)pyrene, as well as with equivalent amounts of the individual compounds. In two experiments, nitroreductive ability, as measured by the amount of 1-nitropyrene metabolized to 1-aminopyrene in 1 hr, was increased 9 to 105% in cultures pretreated with the mixtures as compared with cultures pretreated with the individual compounds. The results of this study support the hypothesis that nitroreduction is a major factor in the synergistic mutatonal response induced by 1- and 3-nitrobenzo(a)pyrene in Salmonella typhimurium.

  13. Vermicomposting of Tea Factory Coal Ash: metal accumulation and metallothionein response in Eisenia fetida (Savigny) and Lampito mauritii (Kinberg).

    PubMed

    Goswami, L; Sarkar, S; Mukherjee, S; Das, S; Barman, S; Raul, P; Bhattacharyya, P; Mandal, N C; Bhattacharya, S; Bhattacharya, S S

    2014-08-01

    Earthworms can accumulate heavy metals in their intestines to a great extent. Impact of feed materials and duration of metal exposure on natural activity of earthworms are rather unclear; this investigation therefore addresses the impact of metal rich Tea Factory Coal Ash (TFCA) on reproduction, composting and metal accumulation ability of Eisenia fetida and Lampito mauritii. Earthworm count and cocoon production increased significantly during vermicomposting. pH of the vermicomposted mixtures shifted toward neutrality, total organic C decreased substantially and total N enhanced significantly compared to composting. High heavy metal (Mn, Zn, Cu, As) accumulation was recorded in the intestine of both the earthworm species. Moreover, gradual increase in the metal-inducible metallothionein concentration indicated the causal mechanism of metal accumulation in these species. TFCA+cow dung (CD) (1:1) were most favorable feed mixture for E. fetida and TFCA+CD (1:2) were good for L. mauritii in regard to metal accumulation and compost quality.

  14. Characterisation of metals in the electronic waste of complex mixtures of end-of-life ICT products for development of cleaner recovery technology

    SciTech Connect

    Sun, Z.H.I.; Xiao, Y.; Sietsma, J.; Agterhuis, H.; Visser, G.; Yang, Y.

    2015-01-15

    Highlights: • New characterisation methodology has been established to understand an industrially processed ICT waste. • Particle size distribution, composition, thermal–chemical behaviour and occurrence of metals were considered. • The characterisation provides direct guidelines for values recovery from the waste. - Abstract: Recycling of valuable metals from electronic waste, especially complex mixtures of end-of-life information and communication technology (ICT) products, is of great difficulty due to their complexity and heterogeneity. One of the important reasons is the lack of comprehensive characterisation on such materials, i.e. accurate compositions, physical/chemical properties. In the present research, we focus on developing methodologies for the characterisation of metals in an industrially processed ICT waste. The morphology, particle size distribution, compositional distribution, occurrence, liberation as well as the thermo-chemical properties of the ICT waste were investigated with various characterisation techniques, including X-ray Fluorescence Spectrometry (XRF), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) with energy dispersed spectroscopy (EDS). Due to the high heterogeneity of the material, special sample preparation procedures were introduced to minimise the discrepancies during compositional analyses. As a result, a clearer overview of the ICT waste has been reached. This research provides better understanding of the extractability of each metal and improves the awareness of potential obstacles for extraction. It will lead to smarter decisions during further development of a clean and effective recovery process.

  15. A preliminary study for removal of heavy metals from acidic synthetic wastewater by using pressmud-rice husk mixtures

    NASA Astrophysics Data System (ADS)

    Ahmad, H.; Ee, C. J.; Baharudin, N. S.

    2016-06-01

    The study was carried out to evaluate the effect of combining pressmud and rice husk in the removal efficiencies of heavy metals in acidic synthetic wastewater. The ratios of pressmud to rice husk were varied at different percentages of weight ratio (0%, 20%, 40%, 60% 80% and 100%) and removal of heavy metals concentrations was observed. The result showed that the removal efficiency was increased with the addition of pressmud by up to almost 100%. Pressmud alone was able to remove 95% to 100% of heavy metals while rice husk alone managed to remove only 10% to 20% of heavy metals. The study also demonstrated that pressmud behaved as a natural acid neutralizer. Hence, the initial pH of the synthetically prepared acidic wastewater which was below 2 also was increased to pH ranging from 6 to 8.

  16. Subtleties of human exposure and response to chemical mixtures from spills.

    PubMed

    Phetxumphou, Katherine; Dietrich, Andrea M; Shanaiah, Narasimhamurthy; Smiley, Elizabeth; Gallagher, Daniel L

    2016-07-01

    Worldwide, chemical spills degrade drinking water quality and threaten human health through ingestion and inhalation. Spills are often mixtures of chemicals; thus, understanding the interaction of chemical and biological properties of the major and minor components is critical to assessing human exposure. The crude (4-methylcyclohexyl)methanol (MCHM) spill provides an opportunity to assess such subtleties. This research determined the relative amounts, volatilization, and biological odor properties of minor components cis- and trans-methyl-4-methylcyclohexanecarboxylate (MMCHC) isomers and major components cis- and trans-4-MCHM, then compared properties and human exposure differences among them. (1)H nuclear magnetic resonance and chromatography revealed that the minor MMCHC isomers were about 1% of the major MCHM isomers. At typical showering temperature of 40 °C, Henry's law constants were 1.50 × 10(-2) and 2.23 × 10(-2) for cis- and trans-MMCHC, respectively, which is 20-50 fold higher than for 4-MCHM isomers. The odor thresholds were 1.83 and 0.02 ppb-v air for cis- and trans-MMCHC, which were both described as predominantly sweet. These data are compared to the higher 120 ppb-v air and 0.06 ppb-v odor thresholds for cis- and trans-4-MCHM, for which the trans-isomer had a dominant licorice descriptor. Application of a shower model demonstrated that while MMCHC isomers are only about 1% of the MCHM isomers, during showering, the MMCHC isomers are 13.8% by volume (16.3% by mass) because of their higher volatility. Trans-4-MCHM contributed about 82% of the odor because of higher volatility and lower odor threshold, trans-MMCHC, which represents 0.3% of the mass, contributed 18% of the odor. This study, with its unique human sensory component to assess exposure, reaffirmed that hazard assessment must not be based solely on relative concentration, but also consider the chemical fate, transport, and biological properties to determine the actual levels of

  17. Response of selected plant and insect species to simulated SRM exhaust mixtures and to exhaust components from SRM fuels

    NASA Technical Reports Server (NTRS)

    Heck, W. W.

    1980-01-01

    The possible biologic effects of exhaust products from solid rocket motor (SRM) burns associated with the space shuttle are examined. The major components of the exhaust that might have an adverse effect on vegetation, HCl and Al2O3 are studied. Dose response curves for native and cultivated plants and selected insects exposed to simulated exhaust and component chemicals from SRM exhaust are presented. A system for dispensing and monitoring component chemicals of SRM exhaust (HCl and Al2O3) and a system for exposing test plants to simulated SRM exhaust (controlled fuel burns) are described. The effects of HCl, Al2O3, and mixtures of the two on the honeybee, the corn earworm, and the common lacewing and the effects of simulated exhaust on the honeybee are discussed.

  18. Magnetic response measurements of mesoscopic superconducting and normal metal rings

    NASA Astrophysics Data System (ADS)

    Bluhm, Hendrik

    The main part of this thesis reports three experiments on the magnetic response of mesoscopic superconducting and normal metal rings using a scanning SQUID microscope. The first experiment explores the magnetic response and fluxoid transitions of superconducting, mesoscopic bilayer aluminum rings in the presence of two coupled order parameters arising from the layered structure. For intermediate couplings, metastable states that have different phase winding numbers around the ring in each of the two order parameters were observed. Larger coupling locks the relative phase, so that the two order parameters are only manifest in the temperature dependence of the response. With increasing proximitization, this signature gradually disappears. The data can be described with a two-order-parameter Ginzburg-Landau theory. The second experiment concentrates on fluxoid transitions in similar, but single-layer rings. Near the critical temperature, the transitions, which are induced by applying a flux to the ring, only admit a single fluxoid at a time. At lower temperatures, several fluxoids enter or leave at once, and the final state approaches the ground state. Currently available theoretical frameworks cannot quantitatively explain the data. Heating and quasiparticle diffusion are likely important for a quantitative understanding of this experiment, which could provide a model system for studying the nonlinear dynamics of superconductors far from equilibrium. The third and most important scanning SQUID study concerns 33 individual mesoscopic gold rings. All measured rings show a paramagnetic linear susceptibility and a poorly understood anomaly around zero field, both of which are likely due to unpaired defect spins. The response of sufficiently small rings also has a component that is periodic in the flux through the ring, with a period close to h/e. Its amplitude varies in sign and magnitude from ring to ring, and its typical value and temperature dependence agree with

  19. A multivariate assessment of innate immune-related gene expressions due to exposure to low concentration individual and mixtures of four kinds of heavy metals on zebrafish (Danio rerio) embryos.

    PubMed

    Cobbina, Samuel Jerry; Xu, Hai; Zhao, Ting; Mao, Guanghua; Zhou, Zhaoxiang; Wu, Xueshan; Liu, Hongyang; Zou, Yanmin; Wu, Xiangyang; Yang, Liuqing

    2015-12-01

    Concerns over the potential health effects of mixtures of low concentration heavy metals on living organisms keep growing by the day. However, the toxicity of low concentration metal mixtures on the immune system of fish species has rarely been investigated. In this study, the zebrafish model was employed to investigate the effect on innate immune and antioxidant-related gene expressions, on exposure to environmentally relevant concentrations of individual and mixtures of Pb (0.01 mg/L), Hg (0.001 mg/L), As (0.01 mg/L) and Cd (0.005 mg/L). Messenger-RNA (mRNA) levels of IL1β, TNF-α, IFNγ, Mx, Lyz, C3B and CXCL-Clc which are closely associated with the innate immune system were affected after exposing zebrafish embryos to metals for 120 h post fertilization (hpf). Individual and mixtures of metals exhibited different potentials to modulate innate-immune gene transcription. IL1β genes were significantly up regulated on exposure to Pb + As (2.01-fold) and inhibited on exposure to Pb + Hg + Cd (0.13-fold). TNF-α was significantly inhibited on exposure to As (0.40-fold) and Pb + As (0.32-fold) compared to control. Metal mixtures generally up regulated IFNγ compared to individual metals. Additionally, antioxidant genes were affected, as CAT and GPx gene expressions generally increased, whiles Mn-SOD and Zn/Cu-SOD reduced. Multivariate analysis showed that exposure to individual metals greatly influenced modulation of innate immune genes; whiles metal mixtures influenced antioxidant gene expressions. This suggests that beside oxidative stress, there may be other pathways influencing gene expressions of innate immune and antioxidant-related genes. Low concentration heavy metals also affect expression of development-related (wnt8a and vegf) genes. Altogether, the results of this study clearly demonstrate that low concentration individual and mixtures of metals in aquatic systems will greatly influence the immune system. It is indicative that mechanisms associated with

  20. Incorporation of in situ exposure and biomarkers response in clams Ruditapes philippinarum for assessment of metal pollution in coastal areas from the Maluan Bay of China.

    PubMed

    Wang, Zaosheng; Yan, Changzhou; Vulpe, Chris D; Yan, Yijun; Chi, Qiaoqiao

    2012-01-01

    The clams Ruditapes philippinarum were used to assess the impact of metal contaminants when transplanted to seven study sites along the Maluan Bay (China). Metal concentrations in digestive gland tissues of clams after 7-day in situ cage exposure were determined in conjunction with antioxidant enzyme activities. The results showed the importance of specific antioxidant biomarkers to assess complex pollutant mixtures and their good correlations to the pollutant compositions of deployment sites. Multivariate analysis indicated causal relationship between the chemicals at each study site and the biochemical "response" of the caged clams at these sites and demonstrated the potential presence of two different contaminant sources. This study suggested that the incorporation of tissue residue analysis with biomarkers response in caged clams together with factor analysis can be a useful biomonitoring tool for the identification of causal toxic pollutants and the assessment of complex metal pollutions in marine coastal environment.

  1. Characterization of gene expression changes associated with MNNG, arsenic, or metal mixture treatment in human keratinocytes: application of cDNA microarray technology.

    PubMed Central

    Bae, Dong-Soon; Hanneman, William H; Yang, Raymond S H; Campain, Julie A

    2002-01-01

    The identification of molecular markers related to critical biological processes during carcinogenesis may aid in the evaluation of carcinogenic potentials of chemicals and chemical mixtures. Work from our laboratory demonstrated that a single treatment with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) enhanced spontaneous malignant transformation of the human keratinocyte cell line RHEK-1. In contrast, chronic low-level exposure of cells to arsenic alone or in a mixture containing arsenic, cadmium, chromium, and lead inhibited malignant conversion. To identify changes in gene expression that influence these different outcomes, cDNA microarray technology was used. Analysis of multiple human arrays in MNNG-transformed RHEK-1 cells, designated OM3, and those treated with arsenic or the arsenic-containing metal mixture showed unique patterns of gene expression. Genes that were overexpressed in OM3 included oncogenes, cell cycle regulators, and those involved in signal transduction, whereas genes for DNA repair enzymes and inhibitors of transformation and metastasis were suppressed. In arsenic-treated cells, multiple DNA repair proteins were overexpressed. Mixture-treated cells showed increased expression of a variety of genes including metallothioneins and integrin 4. These cells showed decreased expression of oncogenes, DNA repair proteins, and genes involved in the mitogen-activated protein kinase pathway. For comparison we are currently analyzing gene expression changes in RHEK-1 cells transformed by other means. The goal of these studies is to identify common batteries of genes affected by chemical modulators of the carcinogenic process. Mechanistic studies may allow us to correlate alterations in their expression with sequential stages in the carcinogenic process and may aid in the risk assessment of other xenobiotics. PMID:12634122

  2. Responses of buried corrugated metal pipes to earthquakes

    SciTech Connect

    Davis, C.A.; Bardet, J.P.

    2000-01-01

    This study describes the results of field investigations and analyses carried out on 61 corrugated metal pipes (CMP) that were shaken by the 1994 Northridge earthquake. These CMPs, which include 29 small-diameter (below 107 cm) CMPs and 32 large-diameter (above 107 cm) CMPs, are located within a 10 km{sup 2} area encompassing the Van Normal Complex in the Northern San Fernando Valley, in Los Angeles, California. During the Northridge earthquake, ground movements were extensively recorded within the study area. Twenty-eight of the small-diameter CMPs performed well while the 32 large-diameter CMPs underwent performances ranging from no damage to complete collapse. The main cause of damage to the large-diameter CMPs was found to be the large ground strains. Based on this unprecedented data set, the factors controlling the seismic performance of the 32 large-diameter CMPs were identified and framed into a pseudostatic analysis method for evaluating the response of large diameter flexible underground pipes subjected to ground strain. The proposed analysis, which is applicable to transient and permanent strains, is capable of describing the observed performance of large-diameter CMPs during the 1994 Northridge earthquake. It indicates that peak ground velocity is a more reliable parameter for analyzing pipe damage than is peak ground acceleration. Results of this field investigation and analysis are useful for the seismic design and strengthening of flexible buried conduits.

  3. Plasmon Response and Electron Dynamics in Charged Metallic Nanoparticles.

    PubMed

    Zapata Herrera, Mario; Aizpurua, Javier; Kazansky, Andrey K; Borisov, Andrei G

    2016-03-22

    Using the time-dependent density functional theory, we perform quantum calculations of the electron dynamics in small charged metallic nanoparticles (clusters) of spherical geometry. We show that the excess charge is accumulated at the surface of the nanoparticle within a narrow layer given by the typical screening distance of the electronic system. As a consequence, for nanoparticles in vacuum, the dipolar plasmon mode displays only a small frequency shift upon charging. We obtain a blue shift for positively charged clusters and a red shift for negatively charged clusters, consistent with the change of the electron spill-out from the nanoparticle boundaries. For negatively charged clusters, the Fermi level is eventually promoted above the vacuum level leading to the decay of the excess charge via resonant electron transfer into the continuum. We show that, depending on the charge, the process of electron loss can be very fast, on the femtosecond time scale. Our results are of great relevance to correctly interpret the optical response of the nanoparticles obtained in electrochemistry, and demonstrate that the measured shift of the plasmon resonances upon charging of nanoparticles cannot be explained without account for the surface chemistry and the dielectric environment.

  4. The response of the polarized Fermi mixture to an artificial vector potential: The interaction strength and imbalance chemical potential effects

    NASA Astrophysics Data System (ADS)

    Ebrahimian, N.; Safiee, Z.

    2017-03-01

    We consider a polarized Fermi mixture (with normal-superfluid phase separation), subjected to artificial vector potential. We concentrate on the BCS regime with various interaction strengths and numerically obtain the polarisability of the system. We obtain the functional dependence of the polarisability of the system on frequency and the relevant physical parameters, namely the interaction strength, the mass ratio, the average and imbalance chemical potentials. Also, we find the special frequency (ωs), for which the rate of the response of system to the potential is changed and the cut-off frequency (ωcutoff), for which the response starts to become infinity. We investigate the behavior of the curves of polarisability versus proper physical parameters for ω <ωs and ωs < ω <ωcutoff at a nonzero temperature and interpret the existence of special and cut-off frequencies via the propagator concept (of particles or holes). Also, we offer the explanation of the minimum energy required for the occurrence of the pair-breaking process and the existence of the cut-off frequency, which is different with respect to the conventional superfluid Fermi gas, and is related to the relevant physical parameters. Finally, the system's response can be controlled by relevant physical parameters, such as interaction strength.

  5. Assessment of a mussel as a metal bioindicator of coastal contamination: relationships between metal bioaccumulation and multiple biomarker responses.

    PubMed

    Chandurvelan, Rathishri; Marsden, Islay D; Glover, Chris N; Gaw, Sally

    2015-04-01

    This is the first study to use a multiple biomarker approach on the green-lipped mussel, Perna canaliculus to test its feasibility as a bioindicator of coastal metal contamination in New Zealand (NZ). Mussels were collected from six low intertidal sites varying in terms of anthropogenic impacts, within two regions (West Coast and Nelson) of the South Island of NZ. Trace elements, including arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), nickel (Ni), and zinc (Zn), were measured in the gills, digestive gland, foot and mantle, and in the surface sediments from where mussels were collected. Metal levels in the sediment were relatively low and there was only one site (Mapua, Nelson) where a metal (Ni) exceeded the Australian and New Zealand Interim Sediment Quality Guideline values. Metal levels in the digestive gland were generally higher than those from the other tissues. A variety of biomarkers were assessed to ascertain mussel health. Clearance rate, a physiological endpoint, correlated with metal level in the tissues, and along with scope for growth, was reduced in the most contaminated site. Metallothionein-like protein content and catalase activity in the digestive gland, and catalase activity and lipid peroxidation in the gill, were also correlated to metal accumulation. Although there were few regional differences, the sampling sites were clearly distinguishable based on the metal contamination profiles and biomarker responses. P. canaliculus appears to be a useful bioindicator species for coastal habitats subject to metal contamination. In this study tissue and whole organism responses provided insight into the biological stress responses of mussels to metal contaminants, indicating that such measurements could be a useful addition to biomonitoring programmes in NZ.

  6. Biomonitoring of humans exposed to arsenic, chromium, nickel, vanadium, and complex mixtures of metals by using the micronucleus test in lymphocytes.

    PubMed

    Annangi, Balasubramanyam; Bonassi, Stefano; Marcos, Ricard; Hernández, Alba

    Various metals have demonstrated genotoxic and carcinogenic potential via different mechanisms. Until now, biomonitoring and epidemiological studies have been carried out to assess the genotoxic risk to exposed human populations. In this sense, the use of the micronucleus assay in peripheral blood lymphocytes has proven to be a useful tool to determine increased levels of DNA damage, as a surrogate biomarker of cancer risk. Here we review those biomonitoring studies focused on people exposed to arsenic, chromium, nickel, vanadium and complex mixtures of metals. Only those studies that used the frequency of micronuclei in binucleated (BNMN) cells have been taken into consideration, although the inclusion of other biomarkers of exposure and genotoxicity are also reflected and discussed. Regarding arsenic, most of the occupational and environmental biomonitoring studies find an increase in BNMN among the exposed individuals. Thus, it seems conclusive that arsenic exposure increases the risk of exposed human populations. However, a lack of correlation between the level of exposure and the increase in BNMN is also common, and a limited number of studies evaluated the genotype as a risk modulator. As for chromium, a BNMN increase in occupationally exposed subjects and a correlation between level of exposure and effect is found consistently in the available literature. However, the quality score of the studies is only medium-low. On the other hand, the studies evaluating nickel and vanadium are scarce and lacks a correct characterization of the individual exposure, which difficult the building of clear conclusions. Finally, several studies with medium-high quality scores evaluated a more realistic scenario of exposure which takes into account a mixture of metals. Among them, those which correctly characterized and measured the exposure were able to find association with the level of BNMN. Also, several genes associated with DNA damage repair such as OGG1 and XRCC1 were

  7. The influence of a surfactant, linear alkylbenzene sulfonate, on the estrogenic response to a mixture of (xeno)estrogens in vitro and in vivo.

    PubMed

    Harris, Catherine A; Brian, Jayne V; Pojana, Giulio; Lamoree, Marja; Booy, Petra; Marcomini, Antonio; Sumpter, John P

    2009-01-18

    The effect of the presence of a surfactant on the activity of a mixture of environmental estrogens was assessed. In their natural habitat, fish are subject not only to exposure to mixtures of estrogenic compounds, as has been addressed in previous publications, but also to other confounding factors (chemical, physical and biological), which may, in theory, affect their responses to such compounds. To assess the potential for such interference, the commonly occurring surfactant, linear alkylbenzene sulfonate (LAS), was applied to the yeast estrogen screen at various concentrations, independently and together with a mixture of estrogens at constant concentrations. LAS enhanced the estrogenic activity of the mixture, an effect which became less pronounced over the course of time. This information was used to design an in vivo study to assess induction of vitellogenin in fathead minnows exposed to the same mixture of estrogens plus LAS. A similar trend was observed, that is, the response was enhanced, but the effect became less pronounced as the study progressed. However, the enhanced response in vivo occurred only at the highest concentration of LAS tested (362microg/L), and was transient because it was no longer apparent by the end of the study. Although LAS is a significant contaminant in terms of both concentration and frequency of detection in the aquatic environment, these data do not suggest that it will have a significant impact on the response of fish to environmental estrogens.

  8. Toxic metal accumulation, responses to exposure and mechanisms of tolerance in plants.

    PubMed

    Clemens, S

    2006-11-01

    Over the past 200 years emissions of toxic heavy metals have risen tremendously and significantly exceed those from natural sources for practically all metals. Uptake and accumulation by crop plants represents the main entry pathway for potentially health-threatening toxic metals into human and animal food. Of major concern are the metalloids arsenic (As) and selenium (Se), and the metals cadmium (Cd), mercury (Hg), and lead (Pb). This review discusses the molecular mechanisms of toxic metal accumulation in plants and algae, the responses to metal exposure, as well as our understanding of metal tolerance and its evolution. The main emphasis will be on cadmium, which is by far the most widely studied of the non-essential toxic metals/metalloids. Entry via Zn2+, Fe2+, and Ca2+ transporters is the molecular basis of Cd2+ uptake into plant cells. Much less is known about the partitioning of non-essential metals and about the genes underlying the enormous diversity among plants with respect to Cd accumulation in different tissues. Numerous studies have described symptoms and responses of plants upon toxic metal exposure. Mysterious are primary targets of toxicity, the degree of specificity of responses, the sensing and the signaling events that lead to transcriptional activation. All plants apparently possess a basal tolerance of toxic non-essential metals. For Cd and As, this is largely dependent on the phytochelatin pathway. Not understood is the molecular biology of Cd hypertolerance in certain plant species such as the metallophytes Arabidopsis halleri or Thlaspi caerulescens.

  9. Characterisation of metals in the electronic waste of complex mixtures of end-of-life ICT products for development of cleaner recovery technology.

    PubMed

    Sun, Z H I; Xiao, Y; Sietsma, J; Agterhuis, H; Visser, G; Yang, Y

    2015-01-01

    Recycling of valuable metals from electronic waste, especially complex mixtures of end-of-life information and communication technology (ICT) products, is of great difficulty due to their complexity and heterogeneity. One of the important reasons is the lack of comprehensive characterisation on such materials, i.e. accurate compositions, physical/chemical properties. In the present research, we focus on developing methodologies for the characterisation of metals in an industrially processed ICT waste. The morphology, particle size distribution, compositional distribution, occurrence, liberation as well as the thermo-chemical properties of the ICT waste were investigated with various characterisation techniques, including X-ray Fluorescence Spectrometry (XRF), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) with energy dispersed spectroscopy (EDS). Due to the high heterogeneity of the material, special sample preparation procedures were introduced to minimise the discrepancies during compositional analyses. As a result, a clearer overview of the ICT waste has been reached. This research provides better understanding of the extractability of each metal and improves the awareness of potential obstacles for extraction. It will lead to smarter decisions during further development of a clean and effective recovery process.

  10. Accumulation of metals in selected macrophytes grown in mixture of drain water and tannery effluent and their phytoremediation potential.

    PubMed

    Kumar, Narendra; Bauddh, Kuldeep; Dwivedi, Neetu; Barman, S C; Singh, D P

    2012-09-01

    Phytoremediation is an emerging, ecofriendly and economically feasible technique for the restoration of heavy metals contaminated environment. In the present investigation, five native macrophytes growing naturally in a drain receiving tannery effluent viz Bacopa monnieri, Eichhornia crassipes, Hydrilla verticillata, Ipomoea aquatica and Marsilea minuta were evaluated for their heavy metal (Cr, Cu, Ni and Pb) accumulation potential in field conditions at Unnao, U.P., India. The results showed that metal accumulation by these macrophytes differed among species and tissue parts. The concentration of Cr, Cu, Ni and Pb in the root tissues were estimated in the range 3.38-45.59,1.01-16.85,1.81-4.43 and 1.02-4.24 microg g(-1) d.wt., whereas the corresponding shoot values were 8.79-48.81, 1.01-8.67, 0.84-2.89 and 1.02-2.84 for Cr, Cu, Ni and Pb respectively. Among the studied plants the translocation factor (TF) ranged between 1.07-2.60, 0.75-3.83, 1.44-2.57 and 0.49-3.76 for Cr, Cu, Ni and Pb, respectively. The highest metal TF was found in M. minuta (2.60, 3.83 and 2.57) for Cr, Cu and Ni respectively, whereas Pb was best translocated (3.76) by B. monnieri. Roots and shoots of the studied macrophytes showed a value of greater than 1 for metal enrichment coefficient. Findings suggest that E. crassipes can be used for phytoremediation of Cu and Ni whereas M. minuta and H. verticillata can be applied for the removal of Cr and Pb respectively from the contaminated water bodies.

  11. Metal-insulator transition characteristics of vanadium dioxide thin films synthesized by ultrasonic nebulized spray pyrolysis of an aqueous combustion mixture

    NASA Astrophysics Data System (ADS)

    Bharathi, R.; Naorem, Rameshwari; Umarji, A. M.

    2015-08-01

    We report the synthesis of high quality vanadium dioxide (VO2) thin films by a novel spray pyrolysis technique, namely ultrasonic nebulized spray pyrolysis of aqueous combustion mixture (UNSPACM). This simple and cost effective two step process involves synthesis of a V2O5 film on an LaAlO3 substrate followed by a controlled reduction to form single phase VO2. The formation of M1 phase (P21/c) is confirmed by Raman spectroscopic studies. A thermally activated metal-insulator transition (MIT) was observed at 61 ^\\circ C, where the resistivity changes by four orders of magnitude. Activation energies for the low conduction phase and the high conduction phase were obtained from temperature variable resistance measurements. The infrared spectra also show a dramatic change in reflectance from 13% to over 90% in the wavelength range of 7-15 μ m. This indicates the suitability of the films for optical switching applications at infrared frequencies.

  12. Effects of Monotypic and Binary Mixtures of Metal Oxide Nanoparticles on Microbial Growth in Sandy Soil Collected from Artificial Recharge Sites

    PubMed Central

    Ko, Kyung-Seok; Ha, Kyoochul; Kong, In Chul

    2015-01-01

    The potential effects of monotypic and binary metal oxide nanoparticles (NPs, ZnO, NiO, Co3O4 and TiO2) on microbial growth were evaluated in sandy soil collected from artificial recharge sites. Microbial growth was assessed based on adenosine triphosphate (ATP) content, dehydrogenase activity (DHA), and viable cell counts (VCC). Microbial growth based on ATP content and VCC showed considerable differences depending on NP type and concentration, whereas DHA did not significantly change. In general, ZnO NPs showed the strongest effect on microbial growth in all measurements, showing an EC50 value of 10.9 mg/L for ATP content. The ranking (EC50) of NPs based on their effect on microbial growth assessed by ATP content and VCC was ZnO > Co3O4 > NiO > TiO2. Upon exposure to binary NP mixtures, synergistic and additive modes of action were observed for ATP content and VCC, respectively. The ranges of observed (P(O)) and expected (P(E)) activity were 83%–92% and 78%–82% of the control (p-value 0.0010) based on ATP content and 78%–95% and 72%–94% of the control (p-value 0.8813) based on VCC under the tested conditions, respectively. The results indicate that the effects of NP mixtures on microbial growth in the sandy soil matrix were as great, or greater, than those of single NPs. Therefore, understanding the effects of single NPs and NP mixtures is essential for proper ecological risk assessment. Additionally, these findings demonstrate that the evaluation of NP effects may be profoundly influenced by the method of microbial growth measurement. PMID:26610489

  13. Effect of Cd(2+) and Cd(2+)/auxin mixtures on lipid monolayers - Model membrane studies on the role of auxins in phytoremediation of metal ions from contaminated environment.

    PubMed

    Hąc-Wydro, Katarzyna; Mach, Marzena; Węder, Karolina; Pająk, Katarzyna; Wydro, Paweł

    2017-03-23

    In this work Langmuir monolayer experiments were performed to analyze the effect of Cd(2+) ions and their mixtures with synthetic auxin (1-naphthaleneacetic acid - NAA) on lipid films. These investigations were motivated by the fact that auxins act effectively as the agents improving the removal of metal ions from contaminated water and soil by plants (phytoextraction), and although their mechanism of action in this area is still unclear, it was suggested that it can be membrane-related. The experiments were done for one component (1,2-dipalmitoyl-sn-glycero-3-phosphocholine - DPPC; 1,2-dioleoyl-sn-glycero-3-phosphocholine - DOPC; 1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (sodium salt) - DPPG) monolayers and mixed (DPPG/DOPC and DPPG/DPPC) films treated as model of plant leaves membranes. The monolayer properties were analyzed based on the surface pressure-area isotherms obtained during film compression, stability measurements and Brewster angle microcopy studies. The collected results together with the data presented in literature evidenced that both metal ions and auxins modify lipid system properties and by using them in a combination it is possible to weaken the influence of sole metal ions on membrane organization. This seems to be in agreement with the hypothesis that the role of plant growth regulators in increasing phytoextraction effectiveness may be membrane-related. However, further experiments are required to find possible correlations between the type and concentration of metal ion, composition of membrane or structural elements in auxin molecule and observed alterations in membrane properties.

  14. New studies of optical pumping, spin resonances, and spin exchange in mixtures of inert gases and alkali-metal vapors

    NASA Astrophysics Data System (ADS)

    Jau, Yuan-Yu

    In this thesis, we present new studies of alkali-hyperfine resonances, new optical pumping of alkali-metal atoms, and the new measurements of binary spin-exchange cross-section between alkali-metal atoms and xenon atoms. We report a large light narrowing effect of the hyperfine end-resonance signals, which was predicted from our theory and observed in our experiments. By increasing the intensity of the circularly polarized pumping beam, alkali-metal atoms are optically pumped into a state of static polarization, and trapped into the hyperfine end-state. Spin exchange between alkali-metal atoms has minimal effect on the end-resonance of the highly spin-polarized atoms. This new result will possibly benefit the design of atomic clocks and magnetometer. We also studied the pressure dependence of the atomic-clock resonance linewidth and pointed out that the linewidth was overestimated by people in the community of atomic clock. Next, we present a series study of coherent population trapping (CPT), which is a promising technique with the same or better performance compared to the traditional microwave spectroscopy. For miniature atomic clocks, CPT method is thought to be particularly advantages. From our studies, we invented a new optical-pumping method, push-pull optical pumping, which can pump atoms into nearly pure 0-0 superposition state, the superposition state of the two ground-state hyperfine sublevels with azimuthal quantum number m = 0. We believe this new invention will bring a big advantage to CPT frequency standards, the quantum state preparation for cold atoms or hot vapor, etc. We also investigated the pressure dependence of CPT excitation and the line shape of the CPT resonance theoretically and experimentally. These two properties are important for CPT applications. A theoretical study of "photon cost" of optical pumping is also presented. Finally, we switch our attention to the problem of spin exchange between alkali-metal atoms and xenon gas. This

  15. Effects of interdigitated platinum finger geometry on spectral response characteristics of germanium metal-semiconductor-metal photodetectors.

    PubMed

    Yang, Hyun-Duk; Janardhanam, V; Shim, Kyu-Hwan; Choi, Chel-Jong

    2014-10-01

    We fabricated interdigitated germanium (Ge) metal-semiconductor-metal photodetectors (MSM PDs) with interdigitated platinum (Pt) finger electrodes and investigated the effects of Pt finger width and spacing on their spectral response. An increase in the incident optical power enhances the creation of electron-hole pairs, resulting in a significant increase in photo current. Lowering of the Schottky barrier could be a main cause of the increase in both photo and dark current with increasing applied bias. The manufactured Ge MSM PDs exhibited a considerable spectral response for wavelengths in the range of 1.53-1.56 μm, corresponding to the entire C-band spectrum range. A reduction in the area fraction of the Pt finger electrode in the active region by decreasing and increasing finger width and spacing, respectively, led to an increase in illuminated active area and suppression of dark current, which was responsible for the improvement in responsivity and quantum efficiency of Ge MSM PDs.

  16. Biosynthesis of metal-binding polypeptides and their precursors in response to cadmium in Datura innoxia

    SciTech Connect

    Jackson, P.J.; Delhaize, E.; Kuske, C.R.

    1991-01-01

    Metal-tolerant Datura innoxia cells synthesize large amounts of a class of metal-binding polypeptides, poly({gamma}-glutamylcysteinyl) glycines (({gamma}-EC){sub n}G, n=2-5), when exposed to Cd. These polypeptides have a high affinity for Cd (2) and certain other metal ions and are thought to play a role in metal tolerance in higher plants. ({gamma}-EC){sub n}G is biosynthetically derived from glutathione. Therefore, the response of Datura cells to Cd must include an increase in production of glutathione and its precursors, since cells rapidly accumulate very high concentrations of these metal-binding polypeptides. The biosynthesis of ({gamma}-EC){sub n}Gs, glutathione, and cysteine in response to Cd exposure is described. The physiological significance of the synthesis of these polypeptides and their precursors and its relevance to Cd tolerance and metal homeostasis are discussed. 34 refs., 6 figs., 1 tab.

  17. Effects of dietary mixture of garlic (Allium sativum), coriander (Coriandrum sativum) and probiotics on immune responses and caecal counts in young laying hens.

    PubMed

    Lee, J S; Kim, M J; Park, S H; Lee, S B; Wang, T; Jung, U S; Im, J; Kim, E J; Lee, K W; Lee, H G

    2016-09-28

    This study was conducted to evaluate the effects of a combined mixture of phytogenic extracts (garlic and coriander) and probiotics on growth performance and immune responses in laying hens based on the results of in vitro studies to screen for immunomodulatory potency of each ingredient. Several parameters of immunomodulatory potency were estimated using lamina propria leucocytes (LPLs) isolated from rat intestinal mucosa tissue. Results show that the combined mixture enhanced LPLs proliferation, increased LPL-mediated cytotoxicity against YAC-1 tumour cells, and decreased lipopolysaccharide (LPS)-induced cytokine production including tumour necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) in LPLs. For in vivo study, laying hens (n = 50/each diet group) were fed with control diet, a diet containing antibiotics (0.01% per kg feed) or the combined mixture (0.02% per kg feed) for 21 days. The dietary combined mixture improved egg production (p < 0.05) but not growth performance and carcass traits. Interestingly, the patterns of suppressing plasma IFN-γ productions during inflammation by LPS injection and decreasing caecal E. coli counts in the combined mixture group were comparable to those in the antibiotics group. Taken together, our results suggested that the 0.02% of combined mixture of phytogenic extracts and probiotics as ingredients has potential immunomodulatory effects in laying hens.

  18. A Mixture of Persistent Organic Pollutants and Perfluorooctanesulfonic Acid Induces Similar Behavioural Responses, but Different Gene Expression Profiles in Zebrafish Larvae

    PubMed Central

    Khezri, Abdolrahman; Fraser, Thomas W. K.; Nourizadeh-Lillabadi, Rasoul; Kamstra, Jorke H.; Berg, Vidar; Zimmer, Karin E.; Ropstad, Erik

    2017-01-01

    Persistent organic pollutants (POPs) are widespread in the environment and some may be neurotoxic. As we are exposed to complex mixtures of POPs, we aimed to investigate how a POP mixture based on Scandinavian human blood data affects behaviour and neurodevelopment during early life in zebrafish. Embryos/larvae were exposed to a series of sub-lethal doses and behaviour was examined at 96 h post fertilization (hpf). In order to determine the sensitivity window to the POP mixture, exposure models of 6 to 48 and 48 to 96 hpf were used. The expression of genes related to neurological development was also assessed. Results indicate that the POP mixture increases the swimming speed of larval zebrafish following exposure between 48 to 96 hpf. This behavioural effect was associated with the perfluorinated compounds, and more specifically with perfluorooctanesulfonic acid (PFOS). The expression of genes related to the stress response, GABAergic, dopaminergic, histaminergic, serotoninergic, cholinergic systems and neuronal maintenance, were altered. However, there was little overlap in those genes that were significantly altered by the POP mixture and PFOS. Our findings show that the POP mixture and PFOS can have a similar effect on behaviour, yet alter the expression of genes relevant to neurological development differently. PMID:28146072

  19. Mixture-amount design and response surface modeling to assess the effects of flavonoids and phenolic acids on developmental performance of Anastrepha ludens.

    PubMed

    Pascacio-Villafán, Carlos; Lapointe, Stephen; Williams, Trevor; Sivinski, John; Niedz, Randall; Aluja, Martín

    2014-03-01

    Host plant resistance to insect attack and expansion of insect pests to novel hosts may to be modulated by phenolic compounds in host plants. Many studies have evaluated the role of phenolics in host plant resistance and the effect of phenolics on herbivore performance, but few studies have tested the joint effect of several compounds. Here, we used mixture-amount experimental design and response surface modeling to study the effects of a variety of phenolic compounds on the development and survival of Mexican fruit fly (Anastrepha ludens [Loew]), a notorious polyphagous pest of fruit crops that is likely to expand its distribution range under climate change scenarios. (+)- Catechin, phloridzin, rutin, chlorogenic acid, and p-coumaric acid were added individually or in mixtures at different concentrations to a laboratory diet used to rear individuals of A. ludens. No effect was observed with any mixture or concentration on percent pupation, pupal weight, adult emergence, or survival from neonate larvae to adults. Larval weight, larval and pupal developmental time, and the prevalence of adult deformities were affected by particular mixtures and concentrations of the compounds tested. We suggest that some combinations/concentrations of phenolic compounds could contribute to the management of A. ludens. We also highlight the importance of testing mixtures of plant secondary compounds when exploring their effects upon insect herbivore performance, and we show that mixture-amount design is a useful tool for this type of experiments.

  20. Modes of metal toxicity and impaired branchial ionoregulation in rainbow trout exposed to mixtures of Pb and Cd in soft water.

    PubMed

    Birceanu, Oana; Chowdhury, M Jasim; Gillis, Patricia L; McGeer, James C; Wood, Chris M; Wilkie, Michael P

    2008-09-29

    Models such as the Biotic Ligand Model (BLM) predict how natural organic matter (NOM) and competing ions (e.g., Ca(2+), H(+) and Na(+)) affect metal bioavailability and toxicity in aquatic organisms. However, such models focus upon individual metals, not metal mixtures. This study determined whether Pb and Cd interact at the gill of rainbow trout (Oncorhynchus mykiss) when trout were exposed to environmentally relevant concentrations of these metals (Cd<100 nmol L(-1); Pb<500 nmol L(-1)) in soft (<100 micromol Ca(2+)L(-1)), moderately acidic (pH 6.0) water. The 96-h LC50 for Pb was 482 nmol L(-1), indicating that Pb was one-order of magnitude more toxic in soft, acidic water than in harder, circumneutral pH waters. The LC50 for Cd alone was also low, 6.7 nmol L(-1). Surprisingly, fish acclimated to soft water had multiple populations of Pb-gill and Cd-gill binding sites. A low capacity, high affinity population of Pb-gill binding sites had a B(max) of 18.2 nmol g(-1) wet weight (ww) and apparent K(Pb-gill)=7.05, but a second low affinity population could not be saturated up to free Pb concentrations approaching 4000 nmol L(-1). Two populations of Cd-gill binding sites were characterized: a high affinity, low capacity population with an apparent K(Cd-gill)=7.33 and B(max)=1.73 nmol g(-1) ww, and a low affinity, high capacity population with an apparent K(Cd-gill)=5.86, and B(max)=13.7 nmol g(-1) ww. At low concentrations, Cd plus Pb accumulation was less than additive because Cd out-competed Pb for gill binding sites, which were likely apical Ca(2+)-channels. While disturbances to Ca(2+) influx were caused by Cd alone, Pb alone had no effect. However, Pb exacerbated Cd-induced disturbances to Ca(2+) influx demonstrating that, although Pb- plus Cd-gill binding was less than additive due to competition, the effects (ionic disturbances) were more than additive (synergistic). Pb was also likely binding to intracellular targets, such as branchial carbonic anhydrase

  1. Brassinosteroids and Response of Plants to Heavy Metals Action

    PubMed Central

    Rajewska, Iwona; Talarek, Marta; Bajguz, Andrzej

    2016-01-01

    Brassinosteroids (BRs) are a widespread group of plant hormones. These phytohormones play a crucial role in the regulation of growth and development of various plant species, and they demonstrate high biological activity. BRs are considered to demonstrate protective activity in the plants exposed to various stresses. Due to rapid industrialization and urbanization, heavy metals have become one of the most important plant stressors. In plants, accumulation of heavy metals beyond the critical levels leads to oxidative stress. However, BRs may inhibit the degradation of lipids, resulted from the overproduction of reactive oxygen species under stress conditions, and increase the activity of antioxidants. They also have the ability to promote phytochelatins synthesis. PMID:27242833

  2. Toxicological responses in SW mice exposed to inhaled pyrolysates of polymer/tobacco mixtures and blended tobacco.

    PubMed

    Werley, Michael S; Lee, K Monika; Lemus-Olalde, Ranulfo

    2009-12-01

    Modern cigarette manufacturing is highly automated and produces millions of cigarettes per day. The potential for small inclusions of non-cigarette materials such as wood, cardboard packaging, plastic, and other materials exists as a result of bulk handling and high-speed processing of tobacco. Many non-tobacco inclusions such as wood, paper, and cardboard would be expected to yield similar pyrolysis products as a burning cigarette. The aircraft industry has developed an extensive literature on the pyrolysis products of plastics, however, that have been reported to yield toxic by-products upon burning, by-products that have been lethal in animals and humans upon acute exposure under some exposure conditions. Some of these smoke constituents have also been reported in cigarette smoke. Five synthetic polymers, nylon 6, acrylonitrile-butadiene-styrene (ABS), nylon 12, nylon 6,6, and acrylonitrile-butadiene (AB), and the natural polymer wool were evaluated by adding them to tobacco at a 3, 10, and 30% inclusion level and then pyrolyzing the mixture. The validated smoke generation and exposure system have been described previously. We used the DIN 53-436 tube furnace and nose-only exposure chamber in combination to conduct exposures in Swiss-Webster mice. Potentially useful biological endpoints for predicting hazards in humans included sensory irritation and pulmonary irritation, respiratory function, clinical signs, body weights, bronchoalveolar lavage (BAL) fluid analysis, carboxyhemoglogin, blood cyanide concentrations, and histopathology of the respiratory tract. Chemical analysis of selected smoke constituents in the test atmosphere was also performed in order to compare the toxicological responses with exposure to the test atmospheres. Under the conditions of these studies, biological responses considered relevant and useful for prediction of effects in humans were found for sensory irritation, body weights, BAL fluid analysis, and histopathology of the nose

  3. Naloxone/alum mixture a potent adjuvant for HIV-1 vaccine: induction of cellular and poly-isotypic humoral immune responses.

    PubMed

    Velashjerdi Farahani, Sima; Reza Aghasadeghi, Mohammad; Memarnejadian, Arash; Faezi, Sobhan; Shahosseini, Zahra; Mahdavi, Mehdi

    2016-03-01

    In the present study we used a fusion peptide from HIV-1 p24 and Nef as vaccine model and adjuvant activity of Naloxone/alum mixture was evaluated in a peptide vaccine model. HIV-1 p24-Nef fusion peptide was synthesized. Female BALB/c mice were divided into five groups. The first group immunized subcutaneously with the p24-Nef fusion peptide adjuvanted with Naloxone/alum mixture and boosted with same protocol. The second was immunized with fusion peptide adjuvanted in alum. The control groups were injected with NLX (Group 3), Alum (Group 4), or PBS (Groups 5) under the same conditions. To determine the type of induced immune response, sera and splenocytes were analyzed by commercial ELISA method for total IgG and isotypes and cytokine secretion (IL-4 & IFN-γ), respectively. We have also used the ELISPOT assay to monitor changes in the frequency of IFN-γ-producing T cells. The proliferation of T cells was assessed using Brdu method and T-cell cytotoxicity was assessed with CFSE method. Immunization of mice with HIV-1 p24-Nef fusion peptide formulated in Naloxone/alum mixture significantly increased lymphocyte proliferation and shifted cytokine responses toward Th1 profile compared to all other groups. Analysis of humoral immune responses revealed that administration of HIV-1 p24-Nef fusion peptide with Naloxone/alum mixture significantly increased specific IgG responses and also increased IgG1,IgG2a, IgG2b, IgG3, and IgM vs. alum-adjuvanted vaccine groups. Naloxone/alum mixture as an adjuvant could improve cellular and humoral immune response for HIV vaccine model and this adjuvant maybe useful for HIV vaccine model in human clinical trial.

  4. Fano response induced by the interference between localized plasmons and interface reflections in metal-insulator-metal waveguide structure

    NASA Astrophysics Data System (ADS)

    Li, Hong-Ju; Wang, Ling-Ling; Zhai, Xiang

    2016-06-01

    The original Fano response induced by the interference between the localized plasmons and interface-reflected surface plasmon polaritons in a single metal-insulator-metal waveguide with two parallel separated metal strips is predicted theoretically through the coupled mode theory combined with the Fano function. The prominent asymmetric line shape resulting from the coupling between the discrete dipole resonance formed between metal strips and an interface-reflected-induced continuum is confirmed by the performed numerical simulations. The novel Fano spectrum is tuned easily by varying the length and coupling distance of metal strips. By introducing another separated metal strip, the outstanding double Fano behavior is obtained, and the corresponding underlying physics is illustrated. In particular, based on the performed refractive index sensing spectra, the high sensitivity of 855 nm/RIU and figure of merit up to 30 are achieved via the double Fano resonance. Undoubtedly, such ingenious structure may benefit the fabrications of nano-integrated plasmonic devices for optical switching and sensing.

  5. Detection of Fe2+ in acetonitrile/water mixture by new 8-hydroxyquinolin based sensor through metal displacement mechanism

    NASA Astrophysics Data System (ADS)

    Karaoglu, Kaan; Turker Akcay, H.; Yilmaz, Ismail

    2017-04-01

    A 8-hydroxyquinoline-based (8-HQ) fluorescent ligand (2) was designed and synthesized by condensation of pyridine-2-carboxaldehide with 2-(quinolin-8-yloxy)acetohydrazide (1). Fluorometric titrations with various metal ions in 1:1 M ratio showed that Cu2+ and Ni2+ ions were fully quenched the fluorescence intensity of 2. But, a significant enhancement in the fluorescent intensity was observed when the bound Ni2+ and Cu2+ ions in the 2–Ni and 2–Cu complexes were displaced by Cr3+ and Fe+2 ions, respectively. While 2–Ni exhibited low sensitivity toward Cr3+ ion, the fluorescent titration measurements showed that 2–Cu could be a good ''on-off-on'' selective and sensitive sensor (S) candidate for determination of Fe2+ in aqueous medium.

  6. Metal transcription factor-1 regulation via MREs in the transcribed regions of selenoprotein H and other metal- responsive genes

    PubMed Central

    Stoytcheva, Zoia R.; Vladimirov, Vladimir; Douet, Vanessa; Stoychev, Ilko; Berry, Marla J.

    2009-01-01

    Selenoprotein H is a redox-sensing DNA binding protein that upregulates genes involved in antioxidant responses. Given the known links between oxidative stress and heavy metals, we investigated the potential for regulation of selenoprotein H by metals. In silico analysis of the selenoprotein H genes from nine species reveals multiple predicted metal response elements (MREs). To validate MRE function, we investigated the effects of zinc or cadmium addition and metal-responsive transcription factor 1 (MTF-1) knockout on selenoprotein H mRNA levels. Chromatin immunoprecipitation was used to directly assess physical binding of the transcription factor to MREs in the human and mouse selenoprotein H genes. The results reported herein show that selenoprotein H is a newly identified target for MTF-1. Further, whereas nearly all prior studies of MREs focused on those located in promoters, we demonstrate binding of MTF-1 to MREs located downstream of the transcription start sites in the human and murine selenoprotein H genes. Finally, we identified MREs in downstream sequences in 15 additional MTF-1 regulated genes lacking promoter MREs, and demonstrated MTF-1 binding in three of these genes. This regulation via sequences downstream of promoters highlights a new direction for identifying previously unrecognized target genes for MTF-1. PMID:19913599

  7. The diversity of nitric oxide function in plant responses to metal stress.

    PubMed

    He, Huyi; He, Longfei; Gu, Minghua

    2014-04-01

    Nitric oxide (NO) emerges as signalling molecule, which is involved in diverse physiological processes in plants. High mobility metal interferes with NO signaling. The exogenous NO alleviates metal stress, whereas endogenous NO contributes to metal toxicity in plants. Owing to different cellular localization and concentration, NO may act as multifunctional regulator in plant responses to metal stress. It not only plays a crucial role in the regulation of gene expression, but serves as a long-distance signal. Through tight modulation of redox signaling, the integration among NO, reactive oxygen species and stress-related hormones in plants determines whether plants stimulate death pathway or activate survival signaling.

  8. A mixture of peptides and sugars derived from plant cell walls increases plant defense responses to stress and attenuates ageing-associated molecular changes in cultured skin cells.

    PubMed

    Apone, Fabio; Tito, Annalisa; Carola, Antonietta; Arciello, Stefania; Tortora, Assunta; Filippini, Lucio; Monoli, Irene; Cucchiara, Mirna; Gibertoni, Simone; Chrispeels, Maarten J; Colucci, Gabriella

    2010-02-15

    Small peptides and aminoacid derivatives have been extensively studied for their effect of inducing plant defense responses, and thus increasing plant tolerance to a wide range of abiotic stresses. Similarly to plants, these compounds can activate different signaling pathways in mammalian skin cells as well, leading to the up-regulation of anti-aging specific genes. This suggests the existence of analogous defense response mechanisms, well conserved both in plants and animal cells. In this article, we describe the preparation of a new mixture of peptides and sugars derived from the chemical and enzymatic digestion of plant cell wall glycoproteins. We investigate the multiple roles of this product as potential "biostimulator" to protect plants from abiotic stresses, and also as potential cosmeceutical. In particular, the molecular effects of the peptide/sugar mixture of inducing plant defense responsive genes and protecting cultured skin cells from oxidative burst damages were deeply evaluated.

  9. Removal of copper, nickel and chromium mixtures from metal plating wastewater by adsorption with modified carbon foam.

    PubMed

    Lee, Chang-Gu; Lee, Soonjae; Park, Jeong-Ann; Park, Chanhyuk; Lee, Sang Jeong; Kim, Song-Bae; An, Byungryul; Yun, Seong-Taek; Lee, Sang-Hyup; Choi, Jae-Woo

    2017-01-01

    In this study, the characterizations and adsorption efficiencies for chromium, copper and nickel were evaluated using manufacture-grade Fe2O3-carbon foam. SEM, XRD, XRF and BET analyses were performed to determine the characteristics of the material. Various pore sizes (12-420 μm) and iron contents (3.62%) were found on the surface of the Fe2O3-carbon foam. Fe2O3-carbon foam was found to have excellent adsorption efficiency compared to carbon foam for mixed solutions of cationic and anionic heavy metals. The adsorption capacities for chromium, copper and nickel were 6.7, 3.8 and 6.4 mg/g, respectively, which were obtained using a dual exponential adsorption model. In experiments with varying dosages of the Fe2O3 powder, no notable differences were observed in the removal efficiency. In a fixed-bed column test, Fe2O3-carbon foam achieved adsorption capacities for chromium, copper and nickel of 33.0, 12.0 and 9.5 mg/g, respectively, after 104 h. Based on these results, Fe2O3-carbon foam was observed to be a promising material for treatment of plating wastewater.

  10. Cellular responses of osteoblast-like cells to 17 elemental metals.

    PubMed

    Zhang, Dongmei; Wong, Cynthia S; Wen, Cuie; Li, Yuncang

    2017-01-01

    Elemental metals have been widely used to alloy metallic orthopedic implants. However, there is still insufficient research data elucidating the cell responses of osteoblastic cells to alloying elemental metals, which impedes the development of new metallic implant materials. In this study, the cellular responses of osteoblast-like cells (SaOS2) to 17 pure alloying elemental metals, that is, titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), manganese (Mn), iron (Fe), ruthenium (Ru), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), silicon (Si), and tin (Sn) were comparatively investigated in vitro. Cellular responses including intracellular total protein synthesis and collagen content, cell adhesion, cell proliferation, and alkaline phosphatase (ALP) activity on these elemental metals were systematically assessed and compared. It was found that these elemental metals could be categorized into three groups based on the cellular functions on them. Group 1, including Ti, Zr, Hf, Nb, Ta, Cr, Ru, and Si, showed excellent cell proliferation and varied ALP activity for SaOS2 cells. Cells exposed to Group 2, including Mo and Sn, although initially attached and grew, did not proliferate over time. In contrast, Group 3, including V, Mn, Fe, Co, Ni, Cu, and Zn, showed severe cytotoxicity toward SaOS2 cells. It is vital to consider the cell responses to the elemental metals when designing a new metallic implant material and the findings of this study provide insights into the biological performance of the elemental metals. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 148-158, 2017.

  11. Air pollution-related metals induce differential cytokine responses in bronchial epithelial cells.

    PubMed

    Låg, M; Øvrevik, J; Totlandsdal, A I; Lilleaas, E M; Thormodsæter, A; Holme, J A; Schwarze, P E; Refsnes, M

    2016-10-01

    Different transition metals have been shown to induce inflammatory responses in lung. We have compared eight different metal ions with regard to cytokine responses, cytotoxicity and signalling mechanisms in a human lung epithelial cell model (BEAS-2B). Among the metal ions tested, there were large differences with respect to pro-inflammatory potential. Exposure to Cd(2+), Zn(2+) and As(3+) induced CXCL8 and IL-6 release at concentrations below 100μM, and Mn(2+) and Ni(2+) at concentrations above 200μM. In contrast, VO4(3-), Cu(2+) and Fe(2+) did not induce any significant increase of these cytokines. An expression array of 20 inflammatory relevant genes also showed a marked up-regulation of CXCL10, IL-10, IL-13 and CSF2 by one or more of the metal ions. The most potent metals, Cd(2+), Zn(2+) and As(3+) induced highest levels of oxidative activity, and ROS appeared to be central in their CXCL8 and IL-6 responses. Activation of the MAPK p38 seemed to be a critical mediator. However, the NF-κB pathway appeared predominately to be involved only in Zn(2+)- and As(3+)-induced CXCL8 and IL-6 responses. Thus, the most potent metals Cd(2+), Zn(2+) and As(3+) seemed to induce a similar pattern for the cytokine responses, and with some exceptions, via similar signalling mechanisms.

  12. Catalytic hydrothermal treatment of pulping effluent using a mixture of Cu and Mn metals supported on activated carbon as catalyst.

    PubMed

    Yadav, Bholu Ram; Garg, Anurag

    2016-10-01

    The present study was performed to investigate the performance of activated carbon-supported copper and manganese base catalyst for catalytic wet oxidation (CWO) of pulping effluent. CWO reaction was performed in a high pressure reactor (capacity = 0.7 l) at temperatures ranging from 120 to 190 °C and oxygen partial pressures of 0.5 to 0.9 MPa with the catalyst concentration of 3 g/l for 3 h duration. With Cu/Mn/AC catalyst at 190 °C temperature and 0.9 MPa oxygen partial pressures, the maximum chemical oxygen demand (COD), total organic carbon (TOC), lignin, and color removals of 73, 71, 86, and 85 %, respectively, were achieved compared to only 52, 51, 53, and 54 % removals during the non-catalytic process. Biodegradability (in terms of 5-day biochemical oxygen demand (BOD5) to COD ratio) of the pulping effluent was improved to 0.38 from an initial value of 0.16 after the catalytic reaction. The adsorbed carbonaceous fraction on the used catalyst was also determined which contributed meager TOC reduction of 3-4 %. The leaching test showed dissolution of the metals (i.e., Cu and Mn) from the catalysts in the wastewater during CWO reaction at 190 °C temperature and 0.9 MPa oxygen partial pressures. In the future, the investigations should focus on the catalyst reusability.

  13. Biomarker responses and disease susceptibility in juvenile rainbow trout Oncorhynchus mykiss fed a high molecular weight PAH mixture.

    PubMed

    Bravo, C F; Curtis, L R; Myers, M S; Meador, J P; Johnson, L L; Buzitis, J; Collier, T K; Morrow, J D; Laetz, C A; Loge, F J; Arkoosh, M R

    2011-03-01

    Juvenile rainbow trout were fed a diet containing an environmentally relevant mixture of 10 high molecular weight polycyclic aromatic hydrocarbons (PAHs) at a dose of 0.66 or 7.82 µg PAH · g fish(-1) · d(-1). At 3, 7, 14, and 28 d, biomarkers of aryl hydrocarbon receptor activation (AHR), hepatic microsomal ethoxyresorufin-O-deethylase (EROD) activity, and cytochrome P4501A (CYP1A)-associated staining increased 14- to 26-fold and 6- to 14-fold, respectively, in fish fed 7.82 µg PAH · g fish (-1) · d(-1). Cytochrome P4501A-associated staining increased 2- to 9-fold on days 3, 7, and 28 in fish fed 0.66 µg PAH · g fish(-1) · d(-1). Bile fluorescent aromatic compounds served as a biomarker of exposure and confirmed that PAH exposure was consistent over 50 d. DNA damage in blood cells, protein oxidation, and lipid peroxidation in the kidney were biomarkers of oxidative stress and all increased in fish fed 7.82 µg PAH · g fish(-1) · d(-1). Fish fed 0.66 µg PAH · g fish(-1) · d(-1) had elevated DNA damage in blood cells but increased protein oxidation or lipid peroxidation in the kidney were not observed. Challenge with Aeromonas salmonicida, at lethal concentration (LC) 20, decreased survival in fish previously fed either 0.66 µg PAH · g fish(-1) · d(-1) or 7.82 µg PAH · g fish(-1) · d(-1) relative to fish fed the control diet. In general, biomarkers of both AHR activation and oxidative stress peaked at 3 to 14 d then declined at 28 to 50 d of PAH exposure and an increase in susceptibility to disease was observed at 50 d. These results link PAH exposure to biomarker responses that may be useful as early indicators of population level responses, such as mortality resulting from an increase in disease susceptibility.

  14. Mixture of polysaccharide and nucleic acid extracted from Bacillus Calmette-Guerin (BCG) enhances immune response of infectious bursal disease virus vaccine in chickens.

    PubMed

    Wang, X B; Liu, Z J; Lv, Y J; Long, Y; Bao, E D

    2016-05-12

    In this study, the immune response induced by a mixture of polysaccharide and nucleic acid extracted from Bacillus Calmette-Guerin (BCG) was evaluated in chickens inoculated with infectious bursal disease virus (IBDV) vaccine. After the mixture was injected intramuscularly at a dose of 0.075, 0.15 or 0.3 mg·kg(-1)·day(-1) for 3 days, the 14-day-old chickens were inoculated with the attenuated IBDV vaccine via intranasal and ocular routes. The relative weight of bursa of Fabricius (BF) and thymus, the serum IBD antibody titer, the CD4+/CD8+ ratio, and the concentrations of IFN-γ, IL-2 and IL-6 in peripheral blood were investigated on days 5, 15 and 25. The IBD antibody titer in BCG-treated groups was higher than in the negative control and only IBD-vaccinated chickens, indicating that the mixture of BCG can significantly enhance chicken humoral response. CD4+/CD8+ and the secretions of IFN-γ, IL-2 and IL-6 were also clearly increased compared with that in the negative control and IBD-vaccinated chickens, indicating that the mixture can also enhance the cell-mediated immune response. The results also showed that the relative weights of BF and thymus increased after chickens were inoculated with BCG, indicating that the BCG mixture can clearly enhance the immunity of IBD-vaccine and can be expected to be viewed as a candidate for a new type of immune adjuvant.

  15. Attenuated total reflection response to wavelength tuning of plasmon-induced transparency in a metal-insulator-metal structure.

    PubMed

    Matsunaga, Kouki; Watanabe, Takeshi; Neo, Yoichiro; Matsumoto, Takahiro; Tomita, Makoto

    2016-11-15

    We experimentally demonstrated a plasmon-induced transparency in a metal-insulator-metal (MIM) structure based on the attenuated total reflection (ATR) response. Here, the MIM waveguide (MIMWG) mode and the surface plasmon polariton (SPP) resonance mode acted as low- and high-Q resonance modes, respectively. The dependence of the resonance angles of SPP and MIMWG mode resonances on the incident wavelength differed, which allowed the coupling condition between the two modes to be tuned via the wavelength. When the resonance angles of the two modes coincided, the ATR response showed a symmetric plasmon-induced transparency spectrum; in contrast, when the resonance angles were detuned, the ATR exhibited a sharp asymmetric spectrum characteristic to off-resonance Fano interference.

  16. Optical response of alkali metal atoms confined in nanoporous glass

    SciTech Connect

    Burchianti, A; Marinelli, C; Mariotti, E; Bogi, A; Marmugi, L; Giomi, S; Maccari, M; Veronesi, S; Moi, L

    2014-03-28

    We study the influence of optical radiation on adsorption and desorption processes of alkali metal atoms confined in nanoporous glass matrices. Exposure of the sample to near-IR or visible light changes the atomic distribution inside the glass nanopores, forcing the entire system to evolve towards a different state. This effect, due to both atomic photodesorption and confinement, causes the growth and evaporation of metastable nanoparticles. It is shown that, by a proper choice of light characteristics and pore size, these processes can be controlled and tailored, thus opening new perspectives for fabrication of nanostructured surfaces. (nanoobjects)

  17. Genome-Wide Analyses of Metal Responsive Genes in Caenorhabditis elegans

    PubMed Central

    Caito, Samuel; Fretham, Stephanie; Martinez-Finley, Ebany; Chakraborty, Sudipta; Avila, Daiana; Chen, Pan; Aschner, Michael

    2012-01-01

    Metals are major contaminants that influence human health. Many metals have physiologic roles, but excessive levels can be harmful. Advances in technology have made toxicogenomic analyses possible to characterize the effects of metal exposure on the entire genome. Much of what is known about cellular responses to metals has come from mammalian systems; however the use of non-mammalian species is gaining wider attention. Caenorhabditis elegans is a small round worm whose genome has been fully sequenced and its development from egg to adult is well characterized. It is an attractive model for high throughput screens due to its short lifespan, ease of genetic mutability, low cost, and high homology with humans. Research performed in C. elegans has led to insights in apoptosis, gene expression, and neurodegeneration, all of which can be altered by metal exposure. Additionally, by using worms one can potentially study mechanisms that underline differential responses to metals in nematodes and humans, allowing for identification of novel pathways and therapeutic targets. In this review, toxicogenomic studies performed in C. elegans exposed to various metals will be discussed, highlighting how this non-mammalian system can be utilized to study cellular processes and pathways induced by metals. Recent work focusing on neurodegeneration in Parkinson’s disease will be discussed as an example of the usefulness of genetic screens in C. elegans and the novel findings that can be produced. PMID:22514555

  18. METALert - an emergency response system for China for heavy metals in the environment

    NASA Astrophysics Data System (ADS)

    Joris, Ingeborg; Seuntjens, Piet; Dams, Jef; Desmet, Nele; Van Looy, Stijn; Raymaekers, Jens; Decorte, Lieve; Raben, Ingrid; Thijssen, Chris; Zhang, Hongzhen; Dong, Jingqi; Zhang, Qianwen

    2016-04-01

    The rapid industrialisation and economic growth of China has resulted in a mirrored increase of environmental issues and threats, which make the updating of the current environmental emergency response protocols very important. Heavy metal pollution accidents with high environmental risks are happening more frequently than ever in recent years. Despite efforts made by the authorites in respect to the formulation of sound policy, efficient technical methods and regulations for dealing with appropriate responses to emergency environmental incidents related to heavy metal pollution are still lacking. METALert is a generic Emergency Response System (ERS) for accidental pollution incidents caused by key heavy metal related industries in China and developed to support China in achieving its environmental targets. The METALert tool is based on environmental models for forecasting, simulation and visualisation of dispersion of heavy metal pollution in water, air and soil. The tool contains a generic database with scenarios for accidental release of metals in typical accidents related to the five key heavy metal industries in China. The tool can calculate the impact of an accident in water, air and soil and is evaluated and demonstrated for a river basin in the Chenzhou area, an important heavy metal mining area in China. The setup of the tool, the background models and the application in Chenzhou will be presented.

  19. Metal Dealing at the Origin of the Chordata Phylum: The Metallothionein System and Metal Overload Response in Amphioxus

    PubMed Central

    Capdevila, Mercè; Palacios, Òscar; Atrian, Sílvia

    2012-01-01

    Non-vertebrate chordates, specifically amphioxus, are considered of the utmost interest for gaining insight into the evolutionary trends, i.e. differentiation and specialization, of gene/protein systems. In this work, MTs (metallothioneins), the most important metal binding proteins, are characterized for the first time in the cephalochordate subphylum at both gene and protein level, together with the main features defining the amphioxus response to cadmium and copper overload. Two MT genes (BfMT1 and BfMT2) have been identified in a contiguous region of the genome, as well as several ARE (antioxidant response element) and MRE (metal response element) located upstream the transcribed region. Their corresponding cDNAs exhibit identical sequence in the two lancelet species (B. floridae and B. lanceolatum), BfMT2 cDNA resulting from an alternative splicing event. BfMT1 is a polyvalent metal binding peptide that coordinates any of the studied metal ions (Zn, Cd or Cu) rendering complexes stable enough to last in physiological environments, which is fully concordant with the constitutive expression of its gene, and therefore, with a metal homeostasis housekeeping role. On the contrary, BfMT2 exhibits a clear ability to coordinate Cd(II) ions, while it is absolutely unable to fold into stable Cu (I) complexes, even as mixed species. This identifies it as an essential detoxification agent, which is consequently only induced in emergency situations. The cephalochordate MTs are not directly related to vertebrate MTs, neither by gene structure, protein similarity nor metal-binding behavior of the encoded peptides. The closest relative is the echinoderm MT, which confirm proposed phylogenetic relationships between these two groups. The current findings support the existence in most organisms of two types of MTs as for their metal binding preferences, devoted to different biological functions: multivalent MTs for housekeeping roles, and specialized MTs that evolve either as Cd

  20. Metal dealing at the origin of the Chordata phylum: the metallothionein system and metal overload response in amphioxus.

    PubMed

    Guirola, Maria; Pérez-Rafael, Sílvia; Capdevila, Mercè; Palacios, Oscar; Atrian, Sílvia

    2012-01-01

    Non-vertebrate chordates, specifically amphioxus, are considered of the utmost interest for gaining insight into the evolutionary trends, i.e. differentiation and specialization, of gene/protein systems. In this work, MTs (metallothioneins), the most important metal binding proteins, are characterized for the first time in the cephalochordate subphylum at both gene and protein level, together with the main features defining the amphioxus response to cadmium and copper overload. Two MT genes (BfMT1 and BfMT2) have been identified in a contiguous region of the genome, as well as several ARE (antioxidant response element) and MRE (metal response element) located upstream the transcribed region. Their corresponding cDNAs exhibit identical sequence in the two lancelet species (B. floridae and B. lanceolatum), BfMT2 cDNA resulting from an alternative splicing event. BfMT1 is a polyvalent metal binding peptide that coordinates any of the studied metal ions (Zn, Cd or Cu) rendering complexes stable enough to last in physiological environments, which is fully concordant with the constitutive expression of its gene, and therefore, with a metal homeostasis housekeeping role. On the contrary, BfMT2 exhibits a clear ability to coordinate Cd(II) ions, while it is absolutely unable to fold into stable Cu (I) complexes, even as mixed species. This identifies it as an essential detoxification agent, which is consequently only induced in emergency situations. The cephalochordate MTs are not directly related to vertebrate MTs, neither by gene structure, protein similarity nor metal-binding behavior of the encoded peptides. The closest relative is the echinoderm MT, which confirm proposed phylogenetic relationships between these two groups. The current findings support the existence in most organisms of two types of MTs as for their metal binding preferences, devoted to different biological functions: multivalent MTs for housekeeping roles, and specialized MTs that evolve either as Cd

  1. Oxidative stress and reduced responsiveness of challenged circulating leukocytes following pulmonary instillation of metal-rich particulate matter in rats

    PubMed Central

    2014-01-01

    Welding fume is an exposure that consists of a mixture of metal-rich particulate matter with gases (ozone, carbon monoxide) and/or vapors (VOCs). Data suggests that welders are immune compromised. Given the inability of pulmonary leukocytes to properly respond to a secondary infection in animal models, the question arose whether the dysfunction persisted systemically. Our aim was to evaluate the circulating leukocyte population in terms of cellular activation, presence of oxidative stress, and functionality after a secondary challenge, following welding fume exposure. Rats were intratracheally instilled (ITI) with PBS or 2 mg of welding fume collected from a stainless steel weld. Rats were sacrificed 4 and 24 h post-exposure and whole blood was collected. Whole blood was used for cellular differential counts, RNA isolation with subsequent microarray and Ingenuity Pathway Analysis, and secondary stimulation with LPS utilizing TruCulture technology. In addition, mononuclear cells were isolated 24 h post-exposure to measure oxidative stress by flow cytometry and confocal microscopy. Welding fume exposure had rapid effects on the circulating leukocyte population as identified by relative mRNA expression changes. Instillation of welding fume reduced inflammatory protein production of circulating leukocytes when challenged with the secondary stimulus LPS. The effects were not related to transcription, but were observed in conjunction with oxidative stress. These findings support previous studies of an inadequate pulmonary immune response following a metal-rich exposure and extend those findings showing leukocyte dysfunction occurs systemically. PMID:25123171

  2. Metallothionein induction as a measure of response to metal exposure in aquatic animals.

    PubMed Central

    Roesijadi, G

    1994-01-01

    Metallothioneins (MTs) are considered central in the intracellular regulation of metals such as copper, zinc, and cadmium. Increased MT synthesis is associated with increased capacity for binding these metals and protection against metal toxicity. Recent advances in the biochemistry and molecular biology of MTs have facilitated research on MTs in aquatic species. For the bivalve mollusc Crassostrea virginica, a species frequently used in studies on the toxicology and environmental monitoring of metals, the primary structure for MT has been deduced from analysis of the proteins and cDNA. Procedures for analysis of MT synthesis and MT gene expression have been applied in studies of response to metal exposure. Induction of specific MT forms by Cd is concentration- and time-dependent. The levels of MT-bound metals exhibit a strong relationship with the cytosolic metal concentrations in a metal-exposed natural population of oysters. Ribonuclease protection assays using sequence-specific antisense RNA probes have shown that the MT mRNA structure in this natural population exhibits considerable individual variability in the 3'-untranslated region. Although yet to be substantiated, the possibility exists that the distribution of this variability may be related to the level of environmental metal contamination. One probe derived from the coding region is suitable for use in quantitative RPAs for oyster MT mRNAs. PMID:7713043

  3. Community response patterns: evaluating benthic invertebrate composition in metal-polluted streams.

    PubMed

    Pollard, A I; Yuan, L

    2006-04-01

    Human activities are modifying the condition and character of ecosystems at a rapid rate. Because of these rapid changes, questions concerning how ecosystems and their assemblages respond to anthropogenic stressors have been of general interest. Accurate prediction of assemblage composition in ecosystems with anthropogenic degradation requires that we assess both how assemblages respond to stressors and the generality of the responses. We ask whether assemblage composition among stream sites becomes more similar after exposure to a common stressor. Using data from biological monitoring programs in the southern Rocky Mountain ecoregion of Colorado and in West Virginia, we compare benthic invertebrate similarity and assemblage composition among sites having different levels (background, low, medium, and high) of heavy-metal pollution. Invertebrate assemblages were most similar within the background metal category, and similarity was progressively lower in low, medium, and high metal categories. An analysis of the frequency of occurrence of genera within metal categories reveals taxonomic shifts that conform to expectations based on metal tolerance of benthic invertebrates. However, different metal-tolerant genera were found at different metal-impacted sites, suggesting that local abiotic and biotic processes may influence the identity of the metal-tolerant genera that become established in polluted sites. Low community similarity in the medium and high-metal categories suggests that accurate prediction of assemblage composition at impacted sites may be challenging.

  4. Synthesis and characterization of a new inorganic cation-exchanger-Zr(IV) tungstomolybdate: analytical applications for metal content determination in real sample and synthetic mixture.

    PubMed

    Nabi, Syed Ashfaq; Naushad, Mu; Inamuddin

    2007-04-02

    An amorphous sample of inorganic cation-exchanger Zr(IV) tungstomolybdate was prepared by mixing varying ratios of 0.1M aqueous solution of sodium tungstate and 0.1M aqueous solution of sodium molybdate into 0.1M aqueous solution of zirconium oxychloride at pH 1. This cation-exchanger was found to have a good ion-exchange capacity (2.40 mequiv.g(-1) for Na(+)), high thermal and chemical stability. A tentative structural formula was proposed on the basis of chemical composition, FTIR and thermogravimetric analysis. Distribution coefficients (K(d)) values of metal ions in various solvent systems were determined. Some important and analytically difficult quantitative binary separations viz. Ni(II)-Pb(II), Ni(II)-Zn(II), Ni(II)-Cd(II), Mg(II)-Al(III), etc. were achieved. The practical applicability of the cation-exchanger was demonstrated in the separation of Cu(II)-Zn(II) from a synthetic mixture as well as from real samples of pharmaceutical formulation and brass alloy.

  5. Effects of low-dose exposure to pesticide mixture on physiological responses of the Pacific oyster, Crassostrea gigas.

    PubMed

    Geret, F; Burgeot, T; Haure, J; Gagnaire, B; Renault, T; Communal, P Y; Samain, J F

    2013-12-01

    This study investigated the effects on the physiology of Pacific oyster, Crassostrea gigas, of a mixture of pesticides containing 0.8 μg L(-1) alachlor, 0.6 μg L(-1) metolachlor, 0.7 μg L(-1) atrazine, 0.6 μg L(-1) terbuthylazine, 0.5 μg L(-1) diuron, 0.6 μg L(-1) fosetyl aluminum, 0.05 μg L(-1) carbaryl, and 0.7 μg L(-1) glyphosate for a total concentration of 4.55 μg L(-1) . The total nominal concentration of pesticides mixture corresponds to the pesticide concentrations in the shellfish culture area of the Marennes-Oleron basin. Two varieties of C. gigas were selected on the foreshore, based on their characteristics in terms of resistance to summer mortality, to assess the effects of the pesticide mixture after 7 days of exposure under controlled conditions. The early effects of the mixture were assessed using enzyme biomarkers of nitrogen metabolism (GS, glutamine synthetase), detoxification metabolism (GST, glutathione S-transferase), and oxidative stress (CAT, catalase). Sublethal effects on hemocyte parameters (phagocytosis and esterase activity) and DNA damages (DNA adducts) were also measured. Changes in metabolic activities were characterized by increases in GS, GST, and CAT levels on the first day of exposure for the "resistant" oysters and after 3-7 days of exposure for the "susceptible" oysters. The formation of DNA adducts was detected after 7 days of exposure. The percentage of hemocyte esterase-positive cells was reduced in the resistant oysters, as was the hemocyte phagocytic capacity in both oyster varieties after 7 days of exposure to the pesticide mixture. This study highlights the need to consider the low doses and the mixture of pesticides to evaluate the effects of these molecules on organisms.

  6. Evaluation of cotton burdock (Arctium tomentosum Mill.) responses to multi-metal exposure.

    PubMed

    Al Harbawee, Waad E Q; Kluchagina, Alina N; Anjum, Naser A; Bashmakov, Dmitry I; Lukatkin, Alexander S; Pereira, Eduarda

    2017-02-01

    Plants have immense potential for their use in the minimization of emerging environmental pollution issues. Under simulated laboratory conditions, this work investigated the growth and biochemical responses of 14-day-old cotton burdock (Arctium tomentosum Mill.) seedlings to the body burdens of multi-metals including Pb, Cu, Ni, and Zn (1.0 μM-10 mM). Biochemical traits (superoxide generation, lipid peroxidation, content of total peroxides), growth traits (axial organs growth, dry weight accumulation, leaf area), and also metal body burdens varied with types and concentrations of metals. Results indicated a significant tolerance of A. tomentosum to multi-metals that can be implicated for its potential role in the metal phytoremediation programs.

  7. Protein-responsive assemblies from catechol-metal ion supramolecular coordination.

    PubMed

    Yuan, C; Chen, J; Yu, S; Chang, Y; Mao, J; Xu, Y; Luo, W; Zeng, B; Dai, L

    2015-03-21

    Supramolecular self-assembly driven by catechol-metal ion coordination has gained great success in the fabrication of functional materials including adhesives, capsules, coatings and hydrogels. However, this route has encountered a great challenge in the construction of nanoarchitectures in the absence of removable templates, because of the uncontrollable crosslinking of catechol-metal ion coordination. Herein, we show that a supramolecular approach, combining both catechol-metal ion coordination and polymer self-assembly together, can organize polymers into hybrid nanoassemblies ranging from solid particles, homogeneous vesicles to Janus vesicles. Without the introduction of a specific binding ligand or complicated molecular design, these assemblies can totally disassemble in response to proteins. UV/vis absorption, fluorescence quenching and recovery investigations have confirmed that proteins can seize metal ions from the hybrid nanoassemblies, thus causing the degradation of catechol-metal ion coordination networks.

  8. Generalized Redox-Responsive Assembly of Carbon-Sheathed Metallic and Semiconducting Nanowire Heterostructures.

    PubMed

    Choi, Sinho; Kim, Jieun; Hwang, Dae Yeon; Park, Hyungmin; Ryu, Jaegeon; Kwak, Sang Kyu; Park, Soojin

    2016-02-10

    One-dimensional metallic/semiconducting materials have demonstrated as building blocks for various potential applications. Here, we report on a unique synthesis technique for redox-responsive assembled carbon-sheathed metal/semiconducting nanowire heterostructures that does not require a metal catalyst. In our approach, germanium nanowires are grown by the reduction of germanium oxide particles and subsequent self-catalytic growth during the thermal decomposition of natural gas, and simultaneously, carbon sheath layers are uniformly coated on the nanowire surface. This process is a simple, reproducible, size-controllable, and cost-effective process whereby most metal oxides can be transformed into metallic/semiconducting nanowires. Furthermore, the germanium nanowires exhibit stable chemical/thermal stability and outstanding electrochemical performance including a capacity retention of ∼96% after 1200 cycles at the 0.5-1C rate as lithium-ion battery anode.

  9. Planarians in toxicology. Responses of asexual Dugesia dorotocephala to selected metals

    SciTech Connect

    Kapu, M.M.; Schaeffer, D.J. )

    1991-08-01

    The planarian Dugesia dorotocephala is a freshwater invertebrate found in unpolluted flowing surface waters. Planarians have a sensitive nervous system with synapses and true brain and evidence these in a variety of social and response behaviors. The inclusion of planarians in a screening battery would provide improved sensitivity in detecting toxicity because planarians commonly respond to lower levels of contamination than do other species. Numerous toxicity test have been conducted to determine the acute and chronic effects of toxicants to provide data necessary for the development of water quality criteria. The appropriateness of Illinois water quality standards for metals was investigated using a 1-hr behavioral test based on the responses of the planarian D. dorotocephala. One possible difficulty with water quality standards for metals is that the standard for each metal is usually established without regard to the effects of other metals present in the receiving water.

  10. The elastic-plastic response of metal films subjected to ultrafast laser-generated shocks

    NASA Astrophysics Data System (ADS)

    Whitley, Von; McGrane, Shawn; Bolme, Cynthia; Moore, David

    2011-06-01

    We have measured the free-surface response of metal films with nominal thicknesses ranging from 500 nm to 8 μm to shocks generated from chirped ultrafast lasers. We launch a single laser generated stress wave into the metal film, but measure two stress waves on the free surface separated in time. The two waves correspond to the elastic and plastic response of the thin metal films. Using ultrafast dynamic ellipsometry, we have measured the separation of the elastic and plastic waves to times as short as 20 picoseconds and measured peak elastic free surface velocities as high as 1.4 km/s in aluminum. We will discuss the experimental results we have measured for aluminum, copper and other metals.

  11. Nonlocal optical response of metal nanostructures with arbitrary shape.

    SciTech Connect

    McMahon, J. M.; Gray, S. K.; Schatz, G. C.; Northwestern Univ.

    2009-08-28

    We present an implementation of Maxwell's equations that incorporates the spatially nonlocal response of materials, an effect necessary to describe the optical properties of structures with features less than 10 nm. For the first time it is possible to investigate the nonlocal optical response of structures without spherical or planar shape, and outside of the electrostatic limit. As an illustration, we calculate the optical properties of Au nanowires and show that nonlocal effects are particularly important in structures with apex features, even for arbitrarily large sizes.

  12. pH-Responsive Capsules Engineered from Metal-Phenolic Networks for Anticancer Drug Delivery.

    PubMed

    Ping, Yuan; Guo, Junling; Ejima, Hirotaka; Chen, Xi; Richardson, Joseph J; Sun, Huanli; Caruso, Frank

    2015-05-06

    A new class of pH-responsive capsules based on metal-phenolic networks (MPNs) for anticancer drug loading, delivery and release is reported. The fabrication of drug-loaded MPN capsules, which is based on the formation of coordination complexes between natural polyphenols and metal ions over a drug-coated template, represents a rapid strategy to engineer robust and versatile drug delivery carriers.

  13. Dynamic response time of a metal foam magneto-rheological damper

    NASA Astrophysics Data System (ADS)

    Yan, Yao X.; Hui, Liu X.; M, Yu; J, Fu; Dong, Liao H.

    2013-02-01

    Magneto-rheological (MR) dampers are a promising type of semi-active control device for various dynamic systems. Recently, low-cost MR dampers without any sealing structure have been required. Motivated by the desire to overcome the need for the costly dynamic seals of conventional MR dampers, a new type of metal foam MR damper is proposed in this study and the dynamic response performance is also investigated. The metal foam is firmly adhered to a working cylinder to store the unexcited MR fluids. In the action of a magnetic field, MR fluids will be extracted from the metal foam and fill up the shear gap to produce the MR effect. Three time parameters related to response time are introduced to further describe the dynamic response process. The results show that, due to the period required for extracting the MR fluids out from the metal foam, the time to produce the damper force of the metal foam MR damper is longer than for conventional fluid-filled MR dampers. The response time of the metal foam MR damper will change with different currents and shear rates. Given a constant shear rate, in a small range of currents (0-1.5 A), the response time decreases rapidly as the operating current increases; however, there is a slower change rate in larger ranges. To evaluate the effect of shear rate on response time, shear rates ranging from 2 to 10 s-1 are tested, and the results demonstrate that with increasing shear rates the response time decreases.

  14. Accumulation of heavy metals and antioxidant responses in Vicia faba plants grown on monometallic contaminated soil.

    PubMed

    Nadgórska-Socha, Aleksandra; Kafel, Alina; Kandziora-Ciupa, Marta; Gospodarek, Janina; Zawisza-Raszka, Agnieszka

    2013-02-01

    The purpose of this study was to explore the effects of soil contamination by selected metals (cadmium, copper, nickel, lead or zinc) on the antioxidant response of Vicia faba plants. The levels of the antioxidants: glutathione, proline, non-protein thiols, as well as guaiacol peroxidase and catalase activities were measured in the upper parts of plants. Additionally, the potential bioavailability of metals in the soil and their concentrations in V. faba plants were compared. Treatment with metal caused the problem of an elevation in its bioavailability in soil and its concentration in leaves and stems. The most serious problems seemed to be metal elevations in soil, especially Zn and Ni as well as in the aerial parts of V. faba plants. The antioxidant responses appeared to be metal specific. The elevation of guaiacol peroxidase activity in leaves and stems as well as the proline in leaves was the only more general reaction to metal exposure. Upon analysis of the effects of soil metal contamination on V. faba plants, we recommend the use of some measurements such as guaiacol peroxidase activity and proline level as useful tools in biological monitoring.

  15. Oxidative stress responses in the animal model, Daphnia pulex exposed to a natural bloom extract versus artificial cyanotoxin mixtures.

    PubMed

    Esterhuizen-Londt, Maranda; von Schnehen, Marie; Kühn, Sandra; Pflugmacher, Stephan

    2016-10-01

    In the natural environment, Daphnia spp. are constantly exposed to a complex matrix of biomolecules, especially during cyanobacterial bloom events. When cyanobacterial cells decay, not only are toxic secondary metabolites known as cyanotoxins released, but also multiple other secondary metabolites, some of which act as enzyme inhibitors. The present study examined the effects of such a natural toxin matrix (crude extract from a bloom) versus artificial toxin mixtures in terms of oxidative stress in Daphnia pulex. The results indicate that there is no significant effect on the survival of D. pulex. However, exposure to the bloom extract resulted in increased lipid peroxidation over a shorter exposure period and reduced antioxidative enzyme activities when compared to the artificial mixtures. The daphnids also needed a longer recovery time to reduce the increased cellular hydrogen peroxide concentration associated with the exposure to the crude extract than with the artificial mixtures. The results indicate a significant difference between the bloom crude extract and the two synthetic mixtures for all stress markers tested, indicating enhanced toxicity of the bloom extract.

  16. Response of pinto bean plants exposed to O/sub 3/, SO/sub 2/, or mixtures at varying temperatures

    SciTech Connect

    Miller, C.A.; Davis, D.D.

    1981-08-01

    Pinto bean plants (Phaseolus vulgaris L. ev. Pinto 111) in the uniforliolate leaf stage were exposed for 3 hours to 0.8 ppm SO/sub 2/, 0.25 ppm O/sub 3/ or a mixture of the 2 pollutants at these concentrations at 15, 24, or 32/sup 0/C. Foliage exposed to O/sub 3/ alone developed adaxial stipple and leaves exposed to SO/sub 2/ alone developed interveinal necrosis. The mixture of O/sub 3/ and SO/sub 2/ induce O/sub 3/-type symptoms at 32/sup 0/ and SO/sub 2/-type symptoms at 15/sup 0/. Both symptom types were present at 24/sup 0/. Some abaxial glazing or silvering was also induced by the mixture, and was most common at 15/sup 0/ and 24/sup 0/. Ozone and SO/sub 2/ each induced greater foliar injury at 15/sup 0/ or 32/sup 0/, as compared to 24/sup 0/. The mixture of O/sub 3/ and SO/sub 2/ induced greatest macroscopic foliar injury at 15/sup 0/. The degree of adaxial vs abaxial leaf surface injury varied with temperature.

  17. Responses of Hyalella azteca to a Pesticide-Nutrient Mixture in Vegetated and Non-vegetated Wetland Mesocosms

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Aquatic vegetation has been shown to improve water quality by trapping and processing contaminants such as pesticides, nutrients and sediments. Currently there is little information regarding effects of pesticide and nutrient mixtures on aquatic biota in these systems and the influence aquatic vege...

  18. Bioaccumulation and metabolomics responses in oysters Crassostrea hongkongensis impacted by different levels of metal pollution.

    PubMed

    Cao, Chen; Wang, Wen-Xiong

    2016-09-01

    Jiulong River Estuary, located in southern China, was heavily contaminated by metal pollution. In this study, the estuarine oysters Crassostrea hongkongensis were transplanted to two sites with similar hydrological conditions but different levels of metal pollution in Jiulong River Estuary over a six-month period. We characterized the time-series change of metal bioaccumulation and final metabolomics responses of oysters. Following transplantation, all metals (Cd, Cu, Cr, Ni, Pb, and Zn) in the oyster digestive glands had elevated concentrations over time. By the end of six-month exposure, Cu, Zn and Cd were the main metals significantly differentiating the two sites. Using (1)H NMR metabolite approach, we further demonstrated the disturbance in osmotic regulation, energy metabolism, and glycerophospholipid metabolism induced by metal contaminations. Six months later, the oysters transplanted in the two sites showed a similar metabolite variation pattern when compared with the initial oysters regardless of different metal levels in the tissues. Interestingly, by comparing the oysters from two sites, the more severely polluted oysters accumulated significantly higher amounts of osmolytes (betaine and homarine) and lower energy storage compounds (glycogen) than the less polluted oysters; these changes could be the potential biomarkers for different levels of metal pollution. Our study demonstrated the complexity of biological effects under field conditions, and NMR metabolomics provides an important approach to detect sensitive variation of oyster inner status.

  19. High responsivity A-plane GaN-based metal-semiconductor-metal photodetectors for polarization-sensitive applications

    SciTech Connect

    Navarro, A.; Rivera, C.; Pereiro, J.; Munoz, E.; Imer, B.; DenBaars, S. P.; Speck, J. S.

    2009-05-25

    The fabrication and characterization of metal-semiconductor-metal polarization-sensitive photodetectors based on A-plane GaN grown on R-plane sapphire substrates is reported. These photodetectors take advantage of the in-plane crystal anisotropy, which results in linear dichroism near the band gap energy. The high resistivity of the A-plane GaN material leads to extremely low dark currents. For an optimized finger spacing of 1 {mu}m, dark current density and responsivity at 30 V are 0.3 nA/mm{sup 2} and 2 A/W, respectively. A maximum polarization sensitivity ratio of 1.8 was determined. In a differential configuration, the full width at half maximum of the polarization-sensitive region is 8.5 nm.

  20. Metal-responsive promoter DNA compaction by the ferric uptake regulator

    PubMed Central

    Roncarati, Davide; Pelliciari, Simone; Doniselli, Nicola; Maggi, Stefano; Vannini, Andrea; Valzania, Luca; Mazzei, Luca; Zambelli, Barbara; Rivetti, Claudio; Danielli, Alberto

    2016-01-01

    Short-range DNA looping has been proposed to affect promoter activity in many bacterial species and operator configurations, but only few examples have been experimentally investigated in molecular detail. Here we present evidence for a metal-responsive DNA condensation mechanism controlled by the Helicobacter pylori ferric uptake regulator (Fur), an orthologue of the widespread Fur family of prokaryotic metal-dependent regulators. H. pylori Fur represses the transcription of the essential arsRS acid acclimation operon through iron-responsive oligomerization and DNA compaction, encasing the arsR transcriptional start site in a repressive macromolecular complex. A second metal-dependent regulator NikR functions as nickel-dependent anti-repressor at this promoter, antagonizing the binding of Fur to the operator elements responsible for the DNA condensation. The results allow unifying H. pylori metal ion homeostasis and acid acclimation in a mechanistically coherent model, and demonstrate, for the first time, the existence of a selective metal-responsive DNA compaction mechanism controlling bacterial transcriptional regulation. PMID:27558202

  1. Fibroblast Response to Lanthanoid Metal Ion Stimulation: Potential Contribution to Fibrotic Tissue Injury

    PubMed Central

    Jenkins, William; Perone, Patricia; Walker, Kyle; Bhagavathula, Narasimharao; Aslam, Muhammad Nadeem; DaSilva, Marissa; Dame, Michael K.; Varani, James

    2011-01-01

    The purpose of this study was to compare each of the 14 naturally occurring lanthanoid metal ions for ability to stimulate pro-fibrotic responses in human dermal fibroblasts. When fibroblasts were exposed to individual lanthanoids over the concentration range of 1–100 μM, increased proliferation was observed with each of the agents as compared with control cells that were already proliferating rapidly in a growth factor-enriched culture medium. Dose-response differences were observed among the individual metal ions. Matrix metalloproteinase-1 (MMP-1) and tissue inhibitor of metalloproteinase-1 levels were also increased in response to lanthanoid exposure but type I procollagen production was not. A dose–response relationship between induction of proliferation and increased MMP-1 was observed. Non-lanthanoid transition metal ions (aluminum, copper, cobalt, iron, magnesium, manganese, nickel, and zinc) were examined in the same assays; there was little stimulation with any of these metals. When epidermal keratinocytes were examined in place of dermal fibroblasts, there was no growth stimulation with any of the lanthanoids. Several of the lanthanoid metals inhibited keratinocyte proliferation at higher concentrations (50–100 μM). PMID:21484406

  2. Effect of metal coordination on photocurrent response properties of a tetrathiafulvalene organogel film.

    PubMed

    Ji, Shu-Fang; Sun, Yong-Gang; Huo, Peng; Shen, Wei-Chun; Huang, Yu-De; Zhu, Qin-Yu; Dai, Jie

    2014-04-07

    Organic low molecular weight gelators with a tetrathiafulvalene (TTF) unit have received considerable attention because the formed gels usually exhibit redox active response and conducting or semiconducting properties. However, to our knowledge, metal coordination systems have not been reported for TTF-derived gels up to date. We have designed and synthesized a series of TTF derivatives with a diamide-diamino moiety that can coordinate to specific metal ions with square coordination geometry. Gelation properties and morphologies of the films prepared by the gelators in different hydrophobic solvents are characterized. The TTF derivative with a dodecyl group shows effective gelation properties, and electrodes with the organogel films are prepared. The effect of the Ni(II) and Cu(II) coordination on the photocurrent response property of the electrodes is examined. The metal square coordination significantly increases the photocurrent response. This gel system is the first metal coordination related TTF-gel-based photoelectric material. The mechanism of the metal coordination-improved photocurrent response property is discussed based on the crystal structural analysis and theoretical calculations.

  3. Ultrafast nonlinear plasmonic response of a single metal nano-object (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Vallee, Fabrice; Del Fatti, Natalia; Crut, Aurélien; Maioli, Paolo

    2016-09-01

    The surface plasmon resonances (SPR) of metallic layers and localized SPR of metallic nano-objects have been extensively investigated during the last decade, opening the way to development of optical plasmon-based devices. As SPRs are associated to electromagnetic local field enhancement, they also lead to enhancement of the system optical nonlinearity, which can be exploited to investigate fundamental processes at nanoscale (e.g., electron and lattice kinetics), and for designing active plasmonic devices. Understanding and modelling the optical nonlinearities of plasmonic systems are thus of both fundamental and technological interests. With the advance of single nanoparticle spectroscopy methods, the nonlinear optical response of a single nano-object can now be addressed, which, associated to determination of its morphology by electron microscopy, opens the way to detailed modeling of the optical nonlinearity of metallic confined system. In this context we discuss experimental and theoretical investigations of the ultrafast response of individual model metallic nano-objects, either formed by a single particle or by two interacting particles at a nanometric distance (Fano resonance regime). The results show that their specific third-order nonlinear response can be fully associated to enhancement of the bulk metal nonlinear response by plasmonic effects. This paves the way toward quantitative modelling of ultrafast active plasmonic, and investigation of energy and charge exchanges in multi-material nano-objects by ultrafast nonlinear spectroscopy.

  4. Stimuli-Responsive Metal Organic Frameworks: Stimuli-Responsive Metal Organic Frameworks for Energy-Efficient Post Combustion Capture

    SciTech Connect

    2010-07-01

    IMPACCT Project: A team led by three professors at Texas A&M is developing a subset of metal organic frameworks that respond to stimuli such as small changes in temperature to trap CO2 and then release it for storage. These frameworks are a promising class of materials for carbon capture applications because their structure and chemistry can be controlled with great precision. Because the changes in temperature required to trap and release CO2 in Texas A&M’s frameworks are much smaller than in other carbon capture approaches, the amount of energy or stimulus that has to be diverted from coal-fired power plants to accomplish this is greatly reduced. The team is working to alter the materials so they bind only with CO2, and are stable enough to withstand the high temperatures found in the chimneys of coal-fired power plants.

  5. Phytoplankton responses to atmospheric metal deposition in the coastal and open-ocean Sargasso Sea.

    PubMed

    Mackey, Katherine R M; Buck, Kristen N; Casey, John R; Cid, Abigail; Lomas, Michael W; Sohrin, Yoshiki; Paytan, Adina

    2012-01-01

    This study investigated the impact of atmospheric metal deposition on natural phytoplankton communities at open-ocean and coastal sites in the Sargasso Sea during the spring bloom. Locally collected aerosols with different metal contents were added to natural phytoplankton assemblages from each site, and changes in nitrate, dissolved metal concentration, and phytoplankton abundance and carbon content were monitored. Addition of aerosol doubled the concentrations of cadmium (Cd), cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), and nickel (Ni) in the incubation water. Over the 3-day experiments, greater drawdown of dissolved metals occurred in the open ocean water, whereas little metal drawdown occurred in the coastal water. Two populations of picoeukaryotic algae and Synechococcus grew in response to aerosol additions in both experiments. Particulate organic carbon increased and was most sensitive to changes in picoeukaryote abundance. Phytoplankton community composition differed depending on the chemistry of the aerosol added. Enrichment with aerosol that had higher metal content led to a 10-fold increase in Synechococcus abundance in the oceanic experiment but not in the coastal experiment. Enrichment of aerosol-derived Co, Mn, and Ni were particularly enhanced in the oceanic experiment, suggesting the Synechococcus population may have been fertilized by these aerosol metals. Cu-binding ligand concentrations were in excess of dissolved Cu in both experiments, and increased with aerosol additions. Bioavailable free hydrated Cu(2+) concentrations were below toxicity thresholds throughout both experiments. These experiments show (1) atmospheric deposition contributes biologically important metals to seawater, (2) these metals are consumed over time scales commensurate with cell growth, and (3) growth responses can differ between distinct Synechococcus or eukaryotic algal populations despite their relatively close geographic proximity and taxonomic similarity.

  6. Phytoplankton responses to atmospheric metal deposition in the coastal and open-ocean Sargasso Sea

    PubMed Central

    Mackey, Katherine R. M.; Buck, Kristen N.; Casey, John R.; Cid, Abigail; Lomas, Michael W.; Sohrin, Yoshiki; Paytan, Adina

    2012-01-01

    This study investigated the impact of atmospheric metal deposition on natural phytoplankton communities at open-ocean and coastal sites in the Sargasso Sea during the spring bloom. Locally collected aerosols with different metal contents were added to natural phytoplankton assemblages from each site, and changes in nitrate, dissolved metal concentration, and phytoplankton abundance and carbon content were monitored. Addition of aerosol doubled the concentrations of cadmium (Cd), cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), and nickel (Ni) in the incubation water. Over the 3-day experiments, greater drawdown of dissolved metals occurred in the open ocean water, whereas little metal drawdown occurred in the coastal water. Two populations of picoeukaryotic algae and Synechococcus grew in response to aerosol additions in both experiments. Particulate organic carbon increased and was most sensitive to changes in picoeukaryote abundance. Phytoplankton community composition differed depending on the chemistry of the aerosol added. Enrichment with aerosol that had higher metal content led to a 10-fold increase in Synechococcus abundance in the oceanic experiment but not in the coastal experiment. Enrichment of aerosol-derived Co, Mn, and Ni were particularly enhanced in the oceanic experiment, suggesting the Synechococcus population may have been fertilized by these aerosol metals. Cu-binding ligand concentrations were in excess of dissolved Cu in both experiments, and increased with aerosol additions. Bioavailable free hydrated Cu2+ concentrations were below toxicity thresholds throughout both experiments. These experiments show (1) atmospheric deposition contributes biologically important metals to seawater, (2) these metals are consumed over time scales commensurate with cell growth, and (3) growth responses can differ between distinct Synechococcus or eukaryotic algal populations despite their relatively close geographic proximity and taxonomic similarity. PMID

  7. Response of macroinvertebrate communities to temporal dynamics of pesticide mixtures: A case study from the Sacramento River watershed, California.

    PubMed

    Chiu, Ming-Chih; Hunt, Lisa; Resh, Vincent H

    2016-12-01

    Pesticide pollution from agricultural field run-off or spray drift has been documented to impact river ecosystems worldwide. However, there is limited data on short- and long-term effects of repeated pulses of pesticide mixtures on biotic assemblages in natural systems. We used reported pesticide application data as input to a hydrological fate and transport model (Soil and Water Assessment Tool) to simulate spatiotemporal dynamics of pesticides mixtures in streams on a daily time-step. We then applied regression models to explore the relationship between macroinvertebrate communities and pesticide dynamics in the Sacramento River watershed of California during 2002-2013. We found that both maximum and average pesticide toxic units were important in determining impacts on macroinvertebrates, and that the compositions of macroinvertebrates trended toward taxa having higher resilience and resistance to pesticide exposure, based on the Species at Risk pesticide (SPEARpesticides) index. Results indicate that risk-assessment efforts can be improved by considering both short- and long-term effects of pesticide mixtures on macroinvertebrate community composition.

  8. Behavioral responses of the invasive Halyomorpha halys (Stål) to traps baited with stereoisomeric mixtures of 10,11-epoxy-1-bisabolen-3-OL.

    PubMed

    Leskey, Tracy C; Khrimian, Ashot; Weber, Donald C; Aldrich, Jeffrey C; Short, Brent D; Lee, Doo-Hyung; Morrison, William R

    2015-04-01

    The brown marmorated stink bug, Halyomorpha halys, is an invasive insect in the United States that is capable of inflicting significant yield losses for fruit, vegetable, and soybean growers. Recently, a male-produced aggregation pheromone of H. halys was identified as a 3.5:1 mixture of (3S,6S,7R,10S)-10,11-epoxy-1-bisabolen-3-ol and (3R,6S,7R,10S)-10,11-epoxy-1-bisabolen-3-ol, two stereoisomers of a natural sesquiterpene with a bisabolane skeleton, potentially existing in 16 stereoisomeric forms. In this study, we assessed attraction to pheromonal and non-pheromonal stereoisomeric mixtures of 10,11-epoxy-1-bisabolen-3-ol, which are easier to synthesize than single isomers, and evaluated dose-dependent responses to attractive mixtures in field trials. Some treatments not containing the natural pheromone components were moderately active in field-trapping studies, signifying that some stereoisomers of 10,11-epoxy-1-bisabolen-3-ol are sufficiently similar to the true pheromone in structure to trigger behavioral responses. Importantly, we found that mixtures of stereoisomers containing pheromone components were also highly attractive to H. halys, even in the presence of multiple "unnatural" stereoisomers. Further, adult and nymphal captures were dose-dependent, regardless of whether the lure contained pheromonal or non-pheromonal components. Our findings of attraction to pheromonal and non-pheromonal stereoisomers and lack of inhibition from non-pheromonal stereoisomers of 10,11-epoxy-1-bisabolen-3-ol increase the flexibility of developing pheromone-based products for H. halys.

  9. Phytoremediation of heavy metals by Alternanthera bettzickiana: Growth and physiological response.

    PubMed

    Tauqeer, Hafiz Muhammad; Ali, Shafaqat; Rizwan, Muhammad; Ali, Qasim; Saeed, Rashid; Iftikhar, Usman; Ahmad, Rehan; Farid, Mujahid; Abbasi, Ghulam Hassan

    2016-04-01

    The present study was aimed to evaluate the morphological, physiological and biochemical responses of Alternanthera Bettzickiana (Regel) G. Nicholson plant subjected to different levels of cadmium (Cd) and lead (Pb) (0, 0.5, 1.0 and 2.0 mM) stress. A. bettzickiana was able to accumulate Cd and Pb in different plant parts and total uptake of both metals was higher in shoots than roots. Plant growth, biomass and photosynthetic pigments increased with increasing metal concentrations, up to 1.0 mM, in soil and then decreased with higher metal levels. The activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) increased under lower metal levels (0.5 and 1.0 mM) while decreased at higher metal levels (2.0 mM). Leaf and root electrolyte leakage (EL), malondialdehyde (MDA) and hydrogen peroxide (H2O2) contents decreased at lower metal levels (≤1.0 mM) while increased at higher levels. The present study clearly signifies the potential of A. bettzickiana plant towards Cd and Pb tolerance and accumulation especially at lower metal levels.

  10. Aeroelastic response of metallic and composite propfan models in yawed flow

    NASA Technical Reports Server (NTRS)

    Kaza, Krishna Rao V.; Williams, Marc H.; Mehmed, Oral; Nerayanan, G. V.

    1988-01-01

    An analytical investigation of aeroelastic response of metallic and composite propfan models in yawed flow was performed. The analytical model is based on the normal modes of a rotating blade and the three dimensional unsteady lifting surface aerodynamic theory including blade mistuning. The calculated blade stresses or strains are compared with published wind tunnel data on two metallic and three composite propfan wind tunnel models. The comparison shows a good agreement between theory and experiment. Additional parametric results indicate that blade response is very sensitive to the blade stiffness and also to blade frequency and mode shape mistuning. From these findings, it is concluded that both frequency and mode shape mistuning should be included in aeroelastic response analysis. Furthermore, both calculated and measured strains show that combined blade frequency and mode shape mistuning has beneficial effects on response due to yawed flow.

  11. Long-term environmental exposure to metals (Cu, Cd, Pb, Zn) activates the immune cell stress response in the common European sea star (Asterias rubens).

    PubMed

    Matranga, V; Pinsino, A; Randazzo, D; Giallongo, A; Dubois, P

    2012-05-01

    The common sea star Asterias rubens represents a key-species of the North-Eastern Atlantic macro benthic community. The cells of their immune system, known as coelomocytes, are the first line of defence against environmental hazards. Here, we report the results of investigations on the immune cells response of sea stars exposed to marine environmental pollution for long periods. We show that levels of the heat shock cognate protein 70 (HSC70) in coelomocytes from A. rubens, which were collected during a field study in the Sǿrfjord (North Sea, SW coast of Norway) along a contamination gradient, are directly associated with the long-term accumulation of Cd, Cu heavy metals exclusively in the tegument. Conversely, Pb and Zn accumulation in the tegument did not relate to HSC70 levels and none of the metals were found accumulated in the pyloric coeca. In addition the coelomocytes from A. rubens, collected in high and low metal impacted stations were examined by a proteomic approach using two-dimensional electrophoresis (2DE). By comparison of the proteomic maps, we observed that 31 protein spots differed in their relative abundance, indicating a gene expression response to the metal mixture exposure. All together, our results confirm that the echinoderm immune cells are a suitable model for the assessment of long-term exposure to environmental pollution, moreover that the increased level of HSC70 can be considered a signal of an acquired tolerance within a large spectrum of protein profile changes occurring in response to metal contamination.

  12. Transcriptional response of yellow perch to changes in ambient metal concentrations-A reciprocal field transplantation experiment.

    PubMed

    Bougas, Bérénice; Normandeau, Eric; Grasset, Julie; Defo, Michel A; Campbell, Peter G C; Couture, Patrice; Bernatchez, Louis

    2016-04-01

    Recent local adaptation to pollution has been evidenced in several organisms inhabiting environments heavily contaminated by metals. Nevertheless, the molecular mechanisms underlying adaptation to high metal concentrations are poorly understood, especially in fishes. Yellow perch (Perca flavescens) populations from lakes in the mining area of Rouyn-Noranda (QC, Canada) have been faced with metal contamination for about 90 years. Here, we examine gene transcription patterns of fish reciprocally transplanted between a reference and a metal-contaminated lake and also fish caged in their native lake. After four weeks, 111 genes were differentially transcribed in metal-naïve fish transferred to the metal-contaminated lake, revealing a plastic response to metal exposure. Genes involved in the citric cycle and beta-oxidation pathways were under-transcribed, suggesting a potential strategy to mitigate the effects of metal stress by reducing energy turnover. However, metal-contaminated fish transplanted to the reference lake did not show any transcriptomic response, indicating a reduced plastic response capability to sudden reduction in metal concentrations. Moreover, the transcription of other genes, especially ones involved in energy metabolism, was affected by caging. Overall, our results highlight environmental stress response mechanisms in yellow perch at the transcriptomic level and support a rapid adaptive response to metal exposure through genetic assimilation.

  13. Luminescent metal-organic framework films as highly sensitive and fast-response oxygen sensors.

    PubMed

    Dou, Zhongshang; Yu, Jiancan; Cui, Yuanjing; Yang, Yu; Wang, Zhiyu; Yang, Deren; Qian, Guodong

    2014-04-16

    Luminescent metal-organic framework films, CPM-5⊃Tb(3+) and MIL-100(In)⊃Tb(3+), have been constructed by postfunctionalization of two porous indium-organic frameworks with different structures, respectively. The MIL-100(In)⊃Tb(3+) film shows high oxygen sensitivity (KSV = 7.59) and short response/recovery time (6 s/53 s).

  14. Differences in metabolism between the biofilm and planktonic response to metal stress.

    PubMed

    Booth, Sean C; Workentine, Matthew L; Wen, Jing; Shaykhutdinov, Rustem; Vogel, Hans J; Ceri, Howard; Turner, Raymond J; Weljie, Aalim M

    2011-07-01

    Bacterial biofilms are known to withstand the effects of toxic metals better than planktonic cultures of the same species. This phenomenon has been attributed to many features of the sessile lifestyle not present in free-swimming populations, but the contribution of intracellular metabolism has not been previously examined. Here, we use a combined GC-MS and (1)H NMR metabolomic approach to quantify whole-cell metabolism in biofilm and planktonic cultures of the multimetal resistant bacterium Pseudomonas fluorescens exposed to copper ions. Metabolic changes in response to metal exposure were found to be significantly different in biofilms compared to planktonic cultures. Planktonic metabolism indicated an oxidative stress response that was characterized by changes to the TCA cycle, glycolysis, pyruvate and nicotinate and niacotinamide metabolism. Similar metabolic changes were not observed in biofilms, which were instead dominated by shifts in exopolysaccharide related metabolism suggesting that metal stress in biofilms induces a protective response rather than the reactive changes observed for the planktonic cells. From these results, we conclude that differential metabolic shifts play a role in biofilm-specific multimetal resistance and tolerance. An altered metabolic response to metal toxicity represents a novel addition to a growing list of biofilm-specific mechanisms to resist environmental stress.

  15. Thermomechanical response of metal foam sandwich panels for structural thermal protection systems in hypersonic vehicles

    NASA Astrophysics Data System (ADS)

    Rakow, Joseph F.

    Sandwich panels with metal foam cores are proposed for load-bearing structural components in actively cooled thermal protection systems for aerospace vehicles. Prototype acreage metal foam sandwich panels (MFSP's) are constructed and analyzed with the central goal of characterizing the thermomechanical response of the system. MFSP's are subjected to uniform temperature fields and equibiaxial loading in a novel experimental load frame. The load frame exploits the mismatch of coefficients of thermal expansion and allows for thermostructural experimentation without the endemic conflict of thermal and mechanical boundary conditions. Back-to-back strain gages and distributed thermocouples capture the in-plane response of the panels, including buckling and elastic-plastic post-buckling. The out-of-plane response is captured via moire interferometry, which provides a visualization of evolving mode shapes throughout the post-buckling regime. The experimental results agree with an analytical prediction for critical temperatures in sandwich panels based on a Rayleigh-Ritz minimization of the energy functional for a Reissner-Mindlin plate. In addition, a three-dimensional finite element model of the non-linear thermomechanical response of the panel-frame experimental system is developed and the results are shown to agree well with the experimentally identified response of MFSP's. Central to analytical and numerical characterization of MFSP's is an understanding of the response of metal foam under shear loading. The shear response of metal foam is captured experimentally, providing density-dependent relationships for material stiffness, strength, and energy absorption. Speckle photography is employed to identify microstructural size effects in the distribution of strain throughout metal foam under shear loading. In addition, a micromechanical model is established for the density-dependent shear modulus of metal foam, which allows for the coupling of cell-level imperfections

  16. A DOSE-RESPONSE STUDY OF THE TOXICITY OF A MIXTURE OF 7N-METHYL CARBAMATE PESTICIDES IN ADULT, MALE RATS.

    EPA Science Inventory

    There is scarce knowledge regarding the toxicity of pesticide mixtures, especially mixtures of the anticholinesterase N-methyl carbamates. A mixture study was conducted using 7 N-methyl carbamates (carbaryl, carbofuran, formetanate HCl, methiocarb, methomyl, oxamyl, and propoxur...

  17. Use of pruned computational neural networks for processing the response of oscillating chemical reactions with a view to analyzing nonlinear multicomponent mixtures.

    PubMed

    Hervás, C; Toledo, R; Silva, M

    2001-01-01

    The suitability of pruned computational neural networks (CNNs) for resolving nonlinear multicomponent systems involving synergistic effects by use of oscillating chemical reaction-based methods implemented using the analyte pulse perturbation technique is demonstrated. The CNN input data used for this purpose are estimates provided by the Levenberg-Marquardt method in the form of a three-parameter Gaussian curve associated with the singular profile obtained when the oscillating system is perturbed by an analyte mixture. The performance of the proposed method was assessed by applying it to the resolution of mixtures of pyrogallol and gallic acid based on their perturbating effect on a classical oscillating chemical system, viz. the Belousov-Zhabotinskyi reaction. A straightforward network topology (3:3:2, with 18 connections after pruning) allowed the resolution of mixtures of the two analytes in concentration ratios from 1:7 to 6:2 with a standard error of prediction for the testing set of 4.01 and 8.98% for pyrogallol and gallic acid, respectively. The reduced dimensions of the selected CNN architecture allowed a mathematical transformation of the input vector into the output one that can be easily implemented via software. Finally, the suitability of response surface analysis as an alternative to CNNs was also tested. The results were poor (relative errors were high), which confirms that properly selected pruned CNNs are effective tools for solving the analytical problem addressed in this work.

  18. Composite metal membrane

    DOEpatents

    Peachey, N.M.; Dye, R.C.; Snow, R.C.; Birdsell, S.A.

    1998-04-14

    A composite metal membrane including a first metal layer of Group IVB met or Group VB metals, the first metal layer sandwiched between two layers of an oriented metal of palladium, platinum or alloys thereof is provided together with a process for the recovery of hydrogen from a gaseous mixture including contacting a hydrogen-containing gaseous mixture with a first side of a nonporous composite metal membrane including a first metal of Group IVB metals or Group VB metals, the first metal layer sandwiched between two layers of an oriented metal of palladium, platinum or alloys thereof, and, separating hydrogen from a second side of the nonporous composite metal membrane.

  19. Composite metal membrane

    DOEpatents

    Peachey, Nathaniel M.; Dye, Robert C.; Snow, Ronny C.; Birdsell, Stephan A.

    1998-01-01

    A composite metal membrane including a first metal layer of Group IVB met or Group VB metals, the first metal layer sandwiched between two layers of an oriented metal of palladium, platinum or alloys thereof is provided together with a process for the recovery of hydrogen from a gaseous mixture including contacting a hydrogen-containing gaseous mixture with a first side of a nonporous composite metal membrane including a first metal of Group IVB metals or Group VB metals, the first metal layer sandwiched between two layers of an oriented metal of palladium, platinum or alloys thereof, and, separating hydrogen from a second side of the nonporous composite metal membrane.

  20. Quantitative proteomics of heavy metal stress responses in Sydney rock oysters.

    PubMed

    Muralidharan, Sridevi; Thompson, Emma; Raftos, David; Birch, Gavin; Haynes, Paul A

    2012-03-01

    Currently, there are few predictive biomarkers in key biomonitoring species, such as oysters, that can detect heavy metal pollution in coastal waterways. Several attributes make oysters superior to other organisms for positive biomonitoring of heavy metal pollution. In particular, they are filter feeders with a high capacity for bioaccumulation. In this study, we used two proteomics approaches, namely label-free shotgun proteomics based on SDS-PAGE gel separation and gas phase fractionation, to investigate the heavy metal stress responses of Sydney rock oysters. Protein samples were prepared from haemolymph of oysters exposed to 100 μg/L of PbCl(2), CuCl(2), or ZnCl(2) for 4 days in closed aquaria. Peptides were identified using a Bivalvia protein sequence database, due to the unavailability of a complete oyster genome sequence. Statistical analysis revealed 56 potential biomarker proteins, as well as several protein biosynthetic pathways to be greatly impacted by metal stress. These have the potential to be incorporated into bioassays for prevention and monitoring of heavy metal pollution in Australian oyster beds. The study confirms that proteomic analysis of biomonitoring species is a promising approach for assessing the effects of environmental pollution, and our experiments have provided insights into the molecular mechanisms underlying oyster stress responses.

  1. Contribution of proteomic studies towards understanding plant heavy metal stress response

    PubMed Central

    Hossain, Zahed; Komatsu, Setsuko

    2013-01-01

    Modulation of plant proteome composition is an inevitable process to cope with the environmental challenges including heavy metal (HM) stress. Soil and water contaminated with hazardous metals not only cause permanent and irreversible health problems, but also result substantial reduction in crop yields. In course of time, plants have evolved complex mechanisms to regulate the uptake, mobilization, and intracellular concentration of metal ions to alleviate the stress damages. Since, the functional translated portion of the genome plays an essential role in plant stress response, proteomic studies provide us a finer picture of protein networks and metabolic pathways primarily involved in cellular detoxification and tolerance mechanism. In the present review, an attempt is made to present the state of the art of recent development in proteomic techniques and significant contributions made so far for better understanding the complex mechanism of plant metal stress acclimation. Role of metal stress-related proteins involved in antioxidant defense system and primary metabolism is critically reviewed to get a bird’s-eye view on the different strategies of plants to detoxify HMs. In addition to the advantages and disadvantages of different proteomic methodologies, future applications of proteome study of subcellular organelles are also discussed to get the new insights into the plant cell response to HMs. PMID:23355841

  2. Genetic responses to metal contamination in two clams: Ruditapes decussatus and Ruditapes philippinarum.

    PubMed

    Moraga, D; Mdelgi-Lasram, E; Romdhane, M S; El Abed, A; Boutet, I; Tanguy, A; Auffret, M

    2002-01-01

    Coastal ecosystems are subjected to a wide variety of disturbances, including those due to xenobiotics of agricultural and industrial origin. These pollutants as heavy metals can modify the genetic diversity of populations by favouring or counter-selecting certain alleles or genotypes by differential mortality. In the present study, two genetic markers (phosphoglucomutase and glucosephosphate isomerase) and a protein marker (metallothionein) were monitored in order to determine the impact of heavy metals in different clam populations. Analysis of the genetic structure of the clam populations examined reveals that those inhabiting environments contaminated by heavy metals exhibit a higher allelic diversity and possess alleles at PGM loci that could be selected by the presence of heavy metals. The evaluation of metallothionein levels using a specific polyclonal antibody developed in the Pacific oyster (Crassostrea gigas) demonstrated the existence of a relationship between metallothionein concentrations and the level of metal pollution for clam populations sampled from different sites. An inter-specific difference was also detected between Ruditapes decussatus and Ruditapes philippinarum living in sympatry at the same site, suggesting a differential response of these two species upon exposure to an identical heavy metal concentration.

  3. Thickness dependence of surface plasmon resonance sensor response for metal ion detection

    NASA Astrophysics Data System (ADS)

    Jung, Seung-A.; Lee, Taek-Sung; Kim, Won Mok; Lee, Kyeong-Seok; Jeong, Doo Seok; Lee, Wook Seong; Kim, Inho

    2013-08-01

    Surface plasmon resonance (SPR) sensor is one of the most viable technologies for portable and highly sensitive sensing in clinical and environmental applications. A lot of research on SPR sensors based on plasticized polyvinyl chloride (PVC) sensing layers for detection of various metal ions has been well reported, but a study on their correlation between sensing layer thickness and sensor response has been rarely done. The purpose of this study is to investigate thickness dependence of sensing layers on the response time and the sensitivity of SPR sensors based on plasticized PVC. Calcium ionophore was incorporated in the sensing layers for calcium ion detection. Our experimental results showed that thicker sensing layers exhibited higher sensitivity and wider detection range but longer response time. We discussed metal ion diffusion in plasticized sensing layers by correlating numerical calculations with experimental ones in order to understand temporal response of our SPR sensor. The response time also relied on the flow rate of calcium ion solutions, indicating that metal ion diffusion in bulk media is one of the limiting factors.

  4. Physiological responses of switchgrass (Panicum virgatum L.) to organic and inorganic amended heavy-metal contaminated chat tailings

    SciTech Connect

    Youngman, A.L.

    1997-12-31

    Study plots established at the Galena subsite of the Cherokee County Superfund Site in Southeastern Kansas by the US Bureau of Mines in 1990 were examined during the summer of 1996 to determine whether physiological criteria could be used to determine suitability of switchgrass for remediation of heavy-metal contaminated substrates. Switchgrass was chosen because it was the most frequently encountered species on these plots. Treatment plots included a treatment control, an organic residue treatment of 89.6 Mg Ha{sup {minus}1} composted cattle manure, and two inorganic fertilizer treatments recommended for either native grass or grass/legume mixtures. Plant response variables were photosynthetic rate, leaf conductance to water vapor, internal concentration of carbon dioxide in leaves, foliar transpiration rate, leaf water-use-efficiency, predawn leaf xylem water potential, and midday leaf xylem water potential. Predawn and midday xylem water potentials were higher for grass/legume inorganic treatment than for the other inorganic treatments. Leaf conductances were lower for organically treated plots than those plots not organically amended and both photosynthesis and transpiration were lower for organically treated plots. Leaf conductances and transpiration were higher for grass/legume treated plots than for plots lacking inorganic treatment. Water-use-efficiency was higher for native grass inorganically treated plots than for other inorganic treatments.

  5. Photocurrent response of carbon nanotube-metal heterojunctions in the terahertz range.

    PubMed

    Wang, Yingxin; Zhang, Guowei; Qiao, Lingbo; Wei, Jinquan; Zhu, Jia-Lin; Chen, Zhiqiang; Zhao, Ziran; Sun, Jia-Lin

    2014-03-10

    We investigate the optoelectronic properties of a carbon nanotube (CNT)-metal heterostructure in the terahertz range. On the basis of terahertz time-domain spectroscopy characterization of a double-walled CNT (DWNT) film, we present and analyze the photocurrent measurement for a DWNT-nickel heterojunction illuminated by continuous-wave terahertz radiation. A significant current across the junction directly induced by terahertz excitation is observed and a negative photoconductivity behavior is found to occur in the device. The photocurrent shows a linear response to the bias voltage and the illumination power within the examined range. These phenomena support the feasibility of using CNT-metal heterojunctions as novel terahertz detectors.

  6. Chelating fibers prepared with a wet spinning technique using a mixture of a viscose solution and a polymer ligand for the separation of metal ions in an aqueous solution.

    PubMed

    Kagaya, Shigehiro; Miyazaki, Hiroyuki; Inoue, Yoshinori; Kato, Toshifumi; Yanai, Hideyuki; Kamichatani, Waka; Kajiwara, Takehiro; Saito, Mitsuru; Tohda, Koji

    2012-02-15

    Chelating fibers containing polymer ligands such as carboxymethylated polyallylamine, carboxymethylated polyethyleneimine, and a copolymer of diallylamine hydrochloride/maleic acid were prepared with a wet spinning technique using mixtures of a viscose solution and the polymer ligands. The chelating fibers obtained effectively adsorbed various metal ions, including Cd(II), Co(II), Cr(III), Cu(II), Fe(III), Mn(II), Ni(II), Pb(II), Ti(IV), and Zn(II). The metal ions adsorbed could be readily desorbed using 0.1 or 0.5 mol L(-1) HNO(3). The chelating fiber containing carboxymethylated polyallylamine was available for the separation of some metal ions in synthetic wastewater containing a large amount of Na(2)SO(4). The wet spinning technique using a solution containing a base polymer and a polymer ligand was quite simple and effective and would be applicable for preparing various chelating fibers.

  7. Comparative study of hematological responses to platinum group metals, antimony and silver nanoparticles in animal models.

    PubMed

    Newkirk, Catherine E; Gagnon, Zofia E; Pavel Sizemore, Ioana E

    2014-01-01

    Research was conducted to examine the hematological effects of heavy metals (platinum (Pt ((IV))), palladium (Pd ((II))), rhodium (Rh ((III))), antimony (Sb ((III)) and Sb ((V))), and silver nanoparticles (AgNPs)) on white blood cells in mammalian (rat) and avian (chick embryo) models. These metals are used in many everyday products and are accumulating in our environment. Six-week old Sprague-Dawley female rats were treated daily by gavage and six-day old, fertile, specific pathogen-free white leghorn strain chick embryos' eggs were injected on days 7 and 14 of incubation with 0.0, 1.0, 5.0 or 10.0 ppm concentrations of Pt ((IV)) and a platinum group metal (PGM) mix of Pt ((IV)), Pd ((II)) and Rh ((III)). Chick embryos were also tested with 1.0 or 5.0 ppm of antimony compounds (Sb ((III)) and Sb ((V))) and 0.0, 15.0, 30.0, 60.0, or 100.0 ppm of silver nanoparticles (AgNPs). After 8 weeks of treatment, blood was obtained from the rats by jugular cut down and from chick embryos on day 20 of incubation by heart puncture. Blood smears were made and stained and a differential white cell count was performed on each. Examination of the smears revealed unconventional dose responses, stimulation of the immune response, and decreases in leukocyte production with various metals and concentrations. Chick embryos responded differently than rats to Pt and the PGM mix; suggesting that species differences and/or stage of development are important components of response to heavy metals. Route of administration of the metals might also influence the response. All of the heavy metals tested affected the immune responses of the tested animals as demonstrated by changes in the types and numbers of leukocytes. Our findings warrant further research to determine the mechanism of these effects and to understand and prevent toxicological effects in humans and other living organisms.

  8. Trace metal pyritization variability in response to mangrove soil aerobic and anaerobic oxidation processes.

    PubMed

    Machado, W; Borrelli, N L; Ferreira, T O; Marques, A G B; Osterrieth, M; Guizan, C

    2014-02-15

    The degree of iron pyritization (DOP) and degree of trace metal pyritization (DTMP) were evaluated in mangrove soil profiles from an estuarine area located in Rio de Janeiro (SE Brazil). The soil pH was negatively correlated with redox potential (Eh) and positively correlated with DOP and DTMP of some elements (Mn, Cu and Pb), suggesting that pyrite oxidation generated acidity and can affect the importance of pyrite as a trace metal-binding phase, mainly in response to spatial variability in tidal flooding. Besides these aerobic oxidation effects, results from a sequential extraction analyses of reactive phases evidenced that Mn oxidized phase consumption in reaction with pyrite can be also important to determine the pyritization of trace elements. Cumulative effects of these aerobic and anaerobic oxidation processes were evidenced as factors affecting the capacity of mangrove soils to act as a sink for trace metals through pyritization processes.

  9. A fast response hydrogen sensor with Pd metallic grating onto a fiber's end-face

    NASA Astrophysics Data System (ADS)

    Yan, Haitao; Zhao, Xiaoyan; Zhang, Chao; Li, Qiu-Ze; Cao, Jingxiao; Han, Dao-Fu; Hao, Hui; Wang, Ming

    2016-01-01

    We demonstrated an integrated hydrogen sensor with Pd metallic grating fabricated on a fiber end-face. The grating consists of three thin metal layers in stacks, Au, WO3 and Pd. The WO3 is used as a waveguide layer between the Pd and Au layer. The Pd layer is etched by using a focused ion beam (FIB) method, forming a Pd metallic grating with period of 450 nm. The sensor is experimentally exposed to hydrogen gas environment. Changing the concentration from 0% to 4% which is the low explosive limit (LEL), the resonant wavelength measured from the reflection experienced 28.10 nm spectral changes in the visible range. The results demonstrated that the sensor is sensitive for hydrogen detection and it has fast response and low temperature effect.

  10. Enhanced immune responses of foot-and-mouth disease vaccine using new oil/gel adjuvant mixtures in pigs and goats.

    PubMed

    Park, Min-Eun; Lee, Seo-Yong; Kim, Rae-Hyung; Ko, Mi-Kyeong; Lee, Kwang-Nyeong; Kim, Su-Mi; Kim, Byoung-Kwan; Lee, Jong-Soo; Kim, Byounghan; Park, Jong-Hyeon

    2014-09-08

    The immunity and protective capability produced by vaccines can vary remarkably according to the kinds of adjuvants being used. In the case of foot-and-mouth disease (FMD) vaccines in pigs, only oil-adjuvant vaccines have been used, and these tend to show lower immunity in pigs than in cattle. New adjuvants for these vaccines are therefore needed. We made different experimental FMD vaccines using new adjuvants (ISA 201, Carbigen, Emulsigen-D) and well-known adjuvants (ISA 206, aluminum hydroxide gel) and then conducted tests to compare the enhancement in pig immunity. More effective immune responses and protection against challenge were observed with the new adjuvants Emulsigen-D and ISA 201 compared to existing adjuvants. In the case of dairy goats, a mixture of Emulsigen-D and aluminum hydroxide gel produced rapid neutralizing antibody responses that were similar to results from tests conducted with pigs.

  11. Surface anchored metal-organic frameworks as stimulus responsive antifouling coatings.

    PubMed

    Sancet, Maria Pilar Arpa; Hanke, Maximilian; Wang, Zhengbang; Bauer, Stella; Azucena, Carlos; Arslan, Hasan K; Heinle, Marita; Gliemann, Hartmut; Wöll, Christof; Rosenhahn, Axel

    2013-12-01

    Surface-anchored, crystalline and oriented metal organic frameworks (SURMOFs) have huge potential for biological applications due to their well-defined and highly-porous structure. In this work we describe a MOF-based, fully autonomous system, which combines sensing, a specific response, and the release of an antimicrobial agent. The Cu-containing SURMOF, Cu-SURMOF 2, is stable in artificial seawater and shows stimulus-responsive anti-fouling properties against marine bacteria. When Cobetia marina adheres on the SURMOF, the framework's response is lethal to the adhering microorganism. A thorough analysis reveals that this response is induced by agents secreted from the microbes after adhesion to the substrate, and includes a release of Cu ions resulting from a degradation of the SURMOF. The stimulus-responsive antifouling effect of Cu-SURMOF 2 demonstrates the first application of Cu-SURMOF 2 as autonomous system with great potential for further microbiological and cell culture applications.

  12. Response of FCC and BCC Metals to High-Amplitude Dynamic Compression

    NASA Astrophysics Data System (ADS)

    Meyers, Marc; Remington, Bruce; Maddox, Brian; Bringa, Eduardo; Park, Hye-Sook; Lu, Chia-Hui

    2013-06-01

    The experimentally observed response of FCC and BCC metals to high-amplitude compressive waves is compared with analytical predictions using constitutive models based on dislocations and twinning and with molecular dynamics simulations. In FCC metals (Cu and Ni), the predictions of dislocation densities from a homogeneous nucleation model are close to those of molecular dynamics simulations. Both are orders of magnitude higher than experimentally observed residual dislocation densities. MD calculations predict a drastic decrease in dislocation densities upon unloading, bringing the values in agreement with measurements. For BCC metals (Ta), on the residual densities are close to predictions of Orowan dislocation multiplication. Due to the much higher Peierls-Nabarro stress, the MD simulations predict much lower dislocation densities than in FCC metals subjected to similar pressures. At higher amplitudes, both FCC and BCC metals experience extensive twinning. The threshold pressure for twinning is successfully modeled by constitutive model based on a critical shear stress for twinning, at the imposed strain rate and temperature. Research funded by UCOP/UC Labs Program.

  13. [Magnetic Response of Dust-loaded Leaves in Parks of Shanghai to Atmospheric Heavy Metal Pollution].

    PubMed

    Liu, Fei; Chu, Hui-min; Zheng, Xiang-min

    2015-12-01

    To reveal the magnetic response to the atmospheric heavy metal pollution in leaves along urban parks, Camphor leaf samples, widely distributed at urban parks, were collected along the year leading wind direction of Shanghai, by setting two vertical and horizontal sections, using rock magnetic properties and heavy metal contents analysis. The results showed that the magnetic minerals of samples were predominated by ferromagnetic minerals, and both the concentration and grain size of magnetite particles gradually decreased with the winter monsoon direction from the main industrial district. A rigorous cleaning of leaves using ultrasonic agitator washer could remove about 63%-90% of low-field susceptibility values of the leaves, and this strongly indicated that the intensity of magnetic signal was mainly controlled by the PMs accumulated on the leaves surfaces. Moreover, there was a significant linear relationship between heavy metals contents (Fe, Mn, Zn, Cu, Cr, V and Pb) and magnetic parameters (0.442 ≤ R ≤ 0.799, P < 0.05), which suggested that magnetic parameters of urban park leaves could be used as a proxy for atmospheric heavy metal pollution. The results of multivariate statistical analysis showed that the content of magnetic minerals and heavy metal indust-loaded tree leaves was affected by associated pollution of industry and traffic.

  14. Leaf biochemical responses and fruit oil quality parameters in olive plants subjected to airborne metal pollution.

    PubMed

    Fourati, Radhia; Scopa, Antonio; Ben Ahmed, Chedlia; Ben Abdallah, Ferjani; Terzano, Roberto; Gattullo, Concetta Eliana; Allegretta, Ignazio; Galgano, Fernanda; Caruso, Marisa Carmela; Sofo, Adriano

    2017-02-01

    This study was carried out in two olive orchards (Olea europaea L., cv. Chemlali) located in a polluted area near a fertilizers factory and in a control unpolluted site, managed with similar cultivation techniques. The aim was to investigate the physiological and biochemical responses of polluted plants (PP), exposed to atmospheric metal contamination (Cd, Cu, Fe, Mn, Ni and Pb) as compared to control plants (CP). Leaves, roots and fruits of PP showed a depression of their non-enzymatic and enzymatic antioxidant defences and a disruption of their hormonal homeostasis. The anomalous physiological status of PP was also demonstrated by the lower values of pigments in leaves and fruits, as compared to CP. Atmospheric metals negatively affected olive oil chemical and sensory quality. However, despite metal deposition on fruit surfaces, the accumulation of potentially toxic metals in olive oil was negligible. Considering that olive oil is an important food product worldwide and that many productive olive orchards are exposed to several sources of pollution, this work could contribute to clarify the effects of atmospheric metal pollution on olive oil quality and its potential toxicity for humans.

  15. Effects of sewage sludge fertilizer on heavy metal accumulation and consequent responses of sunflower (Helianthus annuus).

    PubMed

    Belhaj, Dalel; Elloumi, Nada; Jerbi, Bouthaina; Zouari, Mohamed; Abdallah, Ferjani Ben; Ayadi, Habib; Kallel, Monem

    2016-10-01

    Use of sewage sludge, a biological residue produced from sewage treatment processes in agriculture, is an alternative disposal technique of waste. To study the usefulness of sewage sludge amendment for Helianthus annuus, a pot experiment was conducted by mixing sewage sludge at 2.5, 5, and 7.5 % (w/w) amendment ratios to the agricultural soil. Soil pH decreased whereas electrical conductivity, organic matter, total N, available P, and exchangeable Na, K, and Ca increased in soil amended with sewage sludge in comparison to unamended soil. Sewage sludge amendment led to significant increase in Pb, Ni, Cu, Cr, and Zn concentrations of soil. The increased concentration of heavy metals in soil due to sewage sludge amendment led to increases in shoot and root concentrations of Cr, Cu, Ni, and Zn in plant as compared to those grown on unamended soil. Accumulation was more in roots than shoots for most of the heavy metals. Moreover, high metal removal for the harvestable parts of the crops was recorded. Sewage sludge amendment increased root and shoot length, leaves number, biomass, and antioxidant activities of sunflower. Significant increases in the activities of antioxidant enzymes and in the glutathione, proline, and soluble sugar content in response to amendment with sewage sludge may be defense mechanisms induced in response to heavy metal stress. Graphical abstract Origin, fate and behavior of sewage sludge fertilizer.

  16. An integrated insight into the response of sedimentary microbial communities to heavy metal contamination

    PubMed Central

    Yin, Huaqun; Niu, Jiaojiao; Ren, Youhua; Cong, Jing; Zhang, Xiaoxia; Fan, Fenliang; Xiao, Yunhua; Zhang, Xian; Deng, Jie; Xie, Ming; He, Zhili; Zhou, Jizhong; Liang, Yili; Liu, Xueduan

    2015-01-01

    Response of biological communities to environmental stresses is a critical issue in ecology, but how microbial communities shift across heavy metal gradients remain unclear. To explore the microbial response to heavy metal contamination (e.g., Cr, Mn, Zn), the composition, structure and functional potential of sedimentary microbial community were investigated by sequencing of 16S rRNA gene amplicons and a functional gene microarray. Analysis of 16S rRNA sequences revealed that the composition and structure of sedimentary microbial communities changed significantly across a gradient of heavy metal contamination, and the relative abundances were higher for Firmicutes, Chloroflexi and Crenarchaeota, but lower for Proteobacteria and Actinobacteria in highly contaminated samples. Also, molecular ecological network analysis of sequencing data indicated that their possible interactions might be enhanced in highly contaminated communities. Correspondently, key functional genes involved in metal homeostasis (e.g., chrR, metC, merB), carbon metabolism, and organic remediation showed a higher abundance in highly contaminated samples, indicating that bacterial communities in contaminated areas may modulate their energy consumption and organic remediation ability. This study indicated that the sedimentary indigenous microbial community may shift the composition and structure as well as function priority and interaction network to increase their adaptability and/or resistance to environmental contamination. PMID:26391875

  17. CADDIS Volume 2. Sources, Stressors and Responses: Metals - Detailed Conceptual Model Diagram

    EPA Pesticide Factsheets

    Introduction to the metals module, when to list metals as a candidate cause, ways to measure metals, simple and detailed conceptual diagrams for metals, metals module references and literature reviews.

  18. CADDIS Volume 2. Sources, Stressors and Responses: Metals - Point Sources from Industry

    EPA Pesticide Factsheets

    Introduction to the metals module, when to list metals as a candidate cause, ways to measure metals, simple and detailed conceptual diagrams for metals, metals module references and literature reviews.

  19. CADDIS Volume 2. Sources, Stressors and Responses: Metals - Simple Conceptual Model Diagram

    EPA Pesticide Factsheets

    Introduction to the metals module, when to list metals as a candidate cause, ways to measure metals, simple and detailed conceptual diagrams for metals, metals module references and literature reviews.

  20. The response of dark septate endophytes (DSE) to heavy metals in pure culture.

    PubMed

    Ban, Yihui; Tang, Ming; Chen, Hui; Xu, Zhouying; Zhang, Haihan; Yang, Yurong

    2012-01-01

    Dark septate endophytes (DSE) occur widely in association with plants exposed to heavy metal stress. However, little is known about the response of DSE exposed to heavy metals. In this study, five DSE were isolated from the roots of Astragalus adsurgens Pall. seedlings growing on lead-zinc mine tailings in China. Based on morphological characteristics and DNA sequence analyses, the isolates were identified as Gaeumannomyces cylindrosporus, Paraphoma chrysanthemicola, Phialophora mustea, Exophiala salmonis, and Cladosporium cladosporioides. G. cylindrosporus was selected to explore responses to Pb stress. Scanning electron microscopic observations of G. cylindrosporus grown on solid medium revealed curling of hyphae and formation of hyphal coils in response to Pb. In contrast, in liquid medium, hyphae became thick and swollen with an increase in Pb (II) concentration. We interpret that these changes are related to the variation in cell wall components. We also demonstrated that fungal melanin content increased with the addition of Pb(II). Melanin, as an important component in the cell wall, is known to be an essential antioxidant responsible for decreasing heavy metal toxicity. We also measured the total soluble protein content and glutathione (GSH) concentrations in G. cylindrosporus and found that they initially increased and then decreased with the increase of Pb(II) concentrations. The antioxidant enzyme activities were also examined, and the results showed that superoxide dismutase (SOD) activity was significantly positively correlated with Pb(II) concentrations (r = 0.957, P<0.001). Collectively, our observations indicate that the intracellular antioxidant systems, especially fungal melanin, play an important role in abating the hazards of heavy metals.

  1. Amelioration of experimental autoimmune encephalomyelitis by probiotic mixture is mediated by a shift in T helper cell immune response.

    PubMed

    Kwon, Ho-Keun; Kim, Gi-Cheon; Kim, Young; Hwang, Won; Jash, Arijita; Sahoo, Anupama; Kim, Jung-Eun; Nam, Jong Hee; Im, Sin-Hyeog

    2013-03-01

    The immunomodulatory effect of probiotics has been shown mainly in gastro-intestinal immune disorders and little information is available on the inflammation of central nervous system. Recently we reported that IRT5 probiotics, a mixture of 5 probiotics, could suppress diverse experimental inflammatory disorders. In this study, we evaluated the prophylactic and therapeutic effects of IRT5 probiotics in experimental autoimmune encephalomyelitis (EAE), a T cell mediated inflammatory autoimmune disease of the central nervous system. Pretreatment of IRT5 probiotics before disease induction significantly suppressed EAE development. In addition, treatment with IRT5 probiotics to the ongoing EAE delayed the disease onset. Administration of IRT5 probiotics inhibited the pro-inflammatory Th1/Th17 polarization, while inducing IL10(+) producing or/and Foxp3(+) regulatory T cells, both in the peripheral immune system and at the site of inflammation. Collectively, our data suggest that IRT5 probiotics could be applicable to modulate T cell mediated neuronal autoimmune diseases, including multiple sclerosis.

  2. Nonlocal response of metallic nanospheres probed by light, electrons, and atoms.

    PubMed

    Christensen, Thomas; Yan, Wei; Raza, Søren; Jauho, Antti-Pekka; Mortensen, N Asger; Wubs, Martijn

    2014-02-25

    Inspired by recent measurements on individual metallic nanospheres that cannot be explained with traditional classical electrodynamics, we theoretically investigate the effects of nonlocal response by metallic nanospheres in three distinct settings: atomic spontaneous emission, electron energy loss spectroscopy, and light scattering. These constitute two near-field and one far-field measurements, with zero-, one-, and two-dimensional excitation sources, respectively. We search for the clearest signatures of hydrodynamic pressure waves in nanospheres. We employ a linearized hydrodynamic model, and Mie-Lorenz theory is applied for each case. Nonlocal response shows its mark in all three configurations, but for the two near-field measurements, we predict especially pronounced nonlocal effects that are not exhibited in far-field measurements. Associated with every multipole order is not only a single blueshifted surface plasmon but also an infinite series of bulk plasmons that have no counterpart in a local-response approximation. We show that these increasingly blueshifted multipole plasmons become spectrally more prominent at shorter probe-to-surface separations and for decreasing nanosphere radii. For selected metals, we predict hydrodynamic multipolar plasmons to be measurable on single nanospheres.

  3. Quantification of size effects in the magnetoelectric response of metallic glass/PVDF laminates

    NASA Astrophysics Data System (ADS)

    Lasheras, A.; Gutiérrez, J.; Barandiarán, J. M.

    2016-05-01

    Metallic glass/polyvinylidene fluoride three-layered magnetoelectric laminated composites have been studied. Size effects in the magnetoelectric response arisen both from the reduction of the length of the laminate and from the increase of the operating frequency have been quantified for the lengths ranging from 3 cm down to 0.5 cm. It has been concluded that the decrease in this magnetoelectric response arises mainly from the demagnetizing effects, with reductions of 86% for the longest laminate that increase up to 99% for the shortest one. From these values, an intrinsic magnetoelectric coefficient of 325 V/cm Oe has been obtained.

  4. Influence of fiber architecture on the elastic an d inelastic response of metal matrix composites

    NASA Technical Reports Server (NTRS)

    Arnold, Steven M.; Pindera, Marek-Jerzy; Wilt, Thomas E.

    1995-01-01

    This three part paper focuses on the effect of fiber architecture (i.e., shape and distribution) on the elastic and inelastic response of metal matrix composites. The first part provides an annotative survey of the literature, presented as a historical perspective, dealing with the effects of fiber shape and distribution on the response of advanced polymeric matrix and metal matrix composites. Previous investigations dealing with both continuously and discontinuously reinforced composites are included. A summary of the state-of-the-art will assist in defining new directions in this quickly reviving area of research. The second part outlines a recently developed analytical micromechanics model that is particularly well suited for studying the influence of these effects on the response of metal matrix composites. This micromechanics model, referred to as the generalized method of cells (GMC), is capable of predicting the overall, inelastic behavior of unidirectional, multi-phased composites given the properties of the constituents. In particular, the model is sufficiently general to predict the response of unidirectional composites reinforced by either continuous or discontinuous fibers with different inclusion shapes and spatial arrangements in the presence of either perfect or imperfect interfaces and/or interfacial layers. Recent developments regarding this promising model, as well as directions for future enhancements of the model's predictive capability, are included. Finally, the third pan provides qualitative results generated using GMC for a representative titanium matix composite system, SCS-6/TlMETAL 21S. Results are presented that correctly demonstrate the relative effects of fiber arrangement and shape on the longitudinal and transverse stress-strain and creep response, with both strong and weak fiber/matrix interfacial bonds. The fiber arrangements include square, square diagonal, hexagonal and rectangular periodic arrays, as well as a random array. The

  5. The detoxification responses, damage effects and bioaccumulation in the scallop Chlamys farreri exposed to single and mixtures of benzo[a]pyrene and chrysene.

    PubMed

    Guo, Ruiming; Pan, Luqing; Lin, Pengfei; Zheng, Lei

    2017-01-01

    This study aimed to investigate the detoxification responses, damage effects and biotransformation in scallop Chlamys farreri exposed to benzo[a]pyrene (BaP) (0.1, 1μg/L), chrysene (CHR) (0.1, 1μg/L) and BaP+CHR (0.1+0.1, 1+1μg/L) for 15days. Results demonstrated that BaP and CHR concentration (BaPmixtures of BaP and CHR. Heat shock protein 90 (HSP90) and aryl hydrocarbon receptor nuclear translocator (ARNT) mRNA expression was significantly elevated at days 1, 10 and 15. Detoxification enzymes of 7-ethoxyresorufin O-deethylase (EROD), uridine-diphosphate-glucuronyl-transferase (UGT) and sulfotransferase (SULT) were significantly induced and then became stable gradually while glutathione-S-transferase (GST) was inhibited in the mixtures of BaP and CHR at days 10 and 15. Superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT) and glutathione (GSH) were all stimulated especially in the mixtures of BaP and CHR. The levels of DNA strand breaks, lipid peroxidation (LPO) and protein carbonyl (PC) contents showed damage effects exposed BaP and CHR. All the results indicated that BaP and CHR have similar induced effect and a majority of the biomarkers pointed to a more toxic effect when BaP and CHR were mixed. These will provide a solid foundation for the study of PAHs detoxification mechanism in bivalves and valuable information for marine pollution monitoring.

  6. A gradient Markov chain Monte Carlo algorithm for computing multivariate maximum likelihood estimates and posterior distributions: mixture dose-response assessment.

    PubMed

    Li, Ruochen; Englehardt, James D; Li, Xiaoguang

    2012-02-01

    Multivariate probability distributions, such as may be used for mixture dose-response assessment, are typically highly parameterized and difficult to fit to available data. However, such distributions may be useful in analyzing the large electronic data sets becoming available, such as dose-response biomarker and genetic information. In this article, a new two-stage computational approach is introduced for estimating multivariate distributions and addressing parameter uncertainty. The proposed first stage comprises a gradient Markov chain Monte Carlo (GMCMC) technique to find Bayesian posterior mode estimates (PMEs) of parameters, equivalent to maximum likelihood estimates (MLEs) in the absence of subjective information. In the second stage, these estimates are used to initialize a Markov chain Monte Carlo (MCMC) simulation, replacing the conventional burn-in period to allow convergent simulation of the full joint Bayesian posterior distribution and the corresponding unconditional multivariate distribution (not conditional on uncertain parameter values). When the distribution of parameter uncertainty is such a Bayesian posterior, the unconditional distribution is termed predictive. The method is demonstrated by finding conditional and unconditional versions of the recently proposed emergent dose-response function (DRF). Results are shown for the five-parameter common-mode and seven-parameter dissimilar-mode models, based on published data for eight benzene-toluene dose pairs. The common mode conditional DRF is obtained with a 21-fold reduction in data requirement versus MCMC. Example common-mode unconditional DRFs are then found using synthetic data, showing a 71% reduction in required data. The approach is further demonstrated for a PCB 126-PCB 153 mixture. Applicability is analyzed and discussed. Matlab(®) computer programs are provided.

  7. Lettuce (Lactuca sativa L.) leaf-proteome profiles after exposure to cylindrospermopsin and a microcystin-LR/cylindrospermopsin mixture: a concentration-dependent response.

    PubMed

    Freitas, Marisa; Campos, Alexandre; Azevedo, Joana; Barreiro, Aldo; Planchon, Sébastien; Renaut, Jenny; Vasconcelos, Vitor

    2015-02-01

    The intensification of agricultural productivity is an important challenge worldwide. However, environmental stressors can provide challenges to this intensification. The progressive occurrence of the cyanotoxins cylindrospermopsin (CYN) and microcystin-LR (MC-LR) as a potential consequence of eutrophication and climate change is of increasing concern in the agricultural sector because it has been reported that these cyanotoxins exert harmful effects in crop plants. A proteomic-based approach has been shown to be a suitable tool for the detection and identification of the primary responses of organisms exposed to cyanotoxins. The aim of this study was to compare the leaf-proteome profiles of lettuce plants exposed to environmentally relevant concentrations of CYN and a MC-LR/CYN mixture. Lettuce plants were exposed to 1, 10, and 100 μg/l CYN and a MC-LR/CYN mixture for five days. The proteins of lettuce leaves were separated by two-dimensional electrophoresis (2-DE), and those that were differentially abundant were then identified by matrix-assisted laser desorption/ionization time of flight-mass spectrometry (MALDI-TOF/TOF MS). The biological functions of the proteins that were most represented in both experiments were photosynthesis and carbon metabolism and stress/defense response. Proteins involved in protein synthesis and signal transduction were also highly observed in the MC-LR/CYN experiment. Although distinct protein abundance patterns were observed in both experiments, the effects appear to be concentration-dependent, and the effects of the mixture were clearly stronger than those of CYN alone. The obtained results highlight the putative tolerance of lettuce to CYN at concentrations up to 100 μg/l. Furthermore, the combination of CYN with MC-LR at low concentrations (1 μg/l) stimulated a significant increase in the fresh weight (fr. wt) of lettuce leaves and at the proteomic level resulted in the increase in abundance of a high number of proteins. In

  8. Innate immune responses and efficacy of using mushroom beta-glucan mixture (MBG) on orange-spotted grouper, Epinephelus coioides, aquaculture.

    PubMed

    Chang, Ching-Sheng; Huang, Shih-Ling; Chen, Sherwin; Chen, Shiu-Nan

    2013-07-01

    This study attempts to describe the effects of innate immunity responses and field application of mushroom beta-glucan mixture (MBG) in cultured orange-sported grouper, Epinephelus coioides. Chemical analysis for MBG showed that the mixture contains 34.06% of macro-molecular polymers with bio-active linkage such as 3-; 3,4- and 4,6-glucopyranosyl and 6-linked galactopyranosyl residues. Study performed on the innate immunity showed that oral ingestion of MBG at 1.0 g and 2.0 g per kilogram of feed levels may significantly enhance the lysozyme activity, alternative complement activity, phagocytic activity and respiration burst of the experimental groupers. Observation on the experimental challenge of pathogen showed that uses of MBG at 0.1% and 0.2% levels in feed might significantly enhance the protection of grouper against Vibrio alginolyticus. Field trials performed on short and long-term culture showed that feeding of diet containing 0.1% or 0.2% of MBG may significantly enhance the survival of cultured groupers up to 16% when compared with those obtained from controls.

  9. High resolution coral records of reactive and micronutrient trace metals: Monitoring biological responses to flood plumes.

    NASA Astrophysics Data System (ADS)

    Wyndham, T. D.; McCulloch, M. T.; Decarlo, E. H.

    2004-12-01

    The influences of flood plumes on the coastal ocean are difficult to investigate because they are intermittent, transient and highly variable in nature. The application of trace metals in coral carbonates as proxy recorders of marine environmental conditions has been demonstrated as an excellent method for overcoming these difficulties. Coral records of trace metals have been widely used to provide historical records of physical impacts of flood plumes such changing salinity (δ O18), sediment load (Ba) and anthropogenic inputs such as heavy metal pollution (eg. Pb, Cd). Despite successful applications to physical properties, the use of coral records to monitoring the biologic responses to these changing environmental conditions has proved more difficult. With improvements in analytical techniques however, it is now possible to investigate coral records of reactive (rare earth elements) and micronutrient (eg Mn, Zn and Cu) trace metals, which can be used to more widely explore the biogeochemical implications of flood plumes to the coastal ocean. We have obtained high resolution temporal records of rare earth elements, Cu, Zn, Mn and Sn, from corals from two locations, (1) near Townsville on the Great Barrier Reef (GBR) and (2) Kaneohe Bay on Oahu, Hawaii. Both of these locations often display large phytoplankton blooms following flood events, providing a good opportunity to test the idea that coral records can be used to monitor the biological response to flood plumes. These coral records show significant responses to flood plumes that can only be attributed to biogeochemical cycling that occurs as a result of the flood plume influence, rather than the flood plume itself. Thus a mechanism for exploring the biological response to flood plumes is provided. It has generally proven difficult however, to interpret these coral records without a good understanding of the coastal processes. Therefore we also include evidence from direct trace metal measurements of a

  10. Immune responses to vaccines involving a combined antigen-nanoparticle mixture and nanoparticle-encapsulated antigen formulation.

    PubMed

    Zhang, Weifeng; Wang, Lianyan; Liu, Yuan; Chen, Xiaoming; Liu, Qi; Jia, Jilei; Yang, Tingyuan; Qiu, Shaohui; Ma, Guanghui

    2014-07-01

    Many physicochemical characteristics significantly influence the adjuvant effect of micro/nanoparticles; one critical factor is the kinetics of antigen exposure to the immune system by particle-adjuvanted vaccines. Here, we investigated how various antigen-nanoparticle formulations impacted antigen exposure to the immune system and the resultant antigen-specific immune responses. We formulated antigen with poly(lactic-co-glycolic acid) (PLGA) nanoparticles by encapsulating antigen within nanoparticles or by simply mixing soluble antigen with the nanoparticles. Our results indicated that the combined formulation (composed of antigen encapsulated in nanoparticles and antigen mixed with nanoparticles) induced more powerful antigen-specific immune responses than each single-component formulation. Mice immunized with the combined vaccine formulation displayed enhanced induction of antigen-specific IgG antibodies with high avidity, increased cytokine secretion by splenocytes, and improved generation of memory T cell. Enhanced immune responses elicited by the combined vaccine formulation might be attributed to the antigen-depot effect at the injection site, effective provision of both adequate initial antigen exposure and long-term antigen persistence, and efficient induction of dendritic cell (DC) activation and follicular helper T cell differentiation in draining lymph nodes. Understanding the effect of antigen-nanoparticle formulations on the resultant immune responses might have significant implications for rational vaccine design.

  11. Behavioral avoidance: Possible mechanism for explaining abundanc and distribution of trout species in a metal-impacted river

    USGS Publications Warehouse

    Hansen, James A.; Woodward, Daniel F.; Little, Edward E.; DeLonay, Aaron J.; Bergman, Harold L.

    1999-01-01

    Behavioral avoidance of metal mixtures by rainbow trout (Oncorhynchus mykiss) was determined in the laboratory under water quality conditions that simulated the upper Clark Fork River, Montana, USA. A metal mixture with a fixed ratio of observed ambient metal concentrations (12 μg/L Cu:1.1 μg/L Cd:3.2 μg/L Pb:50 μg/L Zn) was used to determine avoidance in a countercurrent avoidance chamber. Rainbow trout avoided all metal concentrations tested from 10 to 1,000% of the simulated ambient metal mixture. The behavioral response of rainbow trout to the metal mixture was more sensitive than the response of brown trout (Salmo trutta) previously reported from the same laboratory under the same experimental conditions. Additionally, rainbow trout that were acclimated to the simulated ambient metal mixture for 45 d preferred clean water and avoided higher metal concentrations. Therefore, our laboratory experiments on the behavioral avoidance responses of rainbow trout, as well as previously reported experiments on brown trout, show that both species will avoid typical metal concentrations observed on the Clark Fork River. And the greater sensitivity of rainbow trout to the metal mixture may explain, in part, why rainbow trout populations appear to be more severely affected, compared to brown trout populations, in the upper Clark Fork River.

  12. Behavioral avoidance: Possible mechanism for explaining abundance and distribution of trout species in a metal-impacted river

    SciTech Connect

    Hansen, J.A.; Bergman, H.L.; Woodward, D.F.; Little, E.E.; DeLonay, A.J.

    1999-02-01

    Behavioral avoidance of metal mixtures by rainbow trout (Oncorhynchus mykiss) was determined in the laboratory under water quality conditions that simulated the upper Clark Fork River, Montana, USA. A metal mixture with a fixed ratio of observed ambient metal concentrations (12 {micro}g/L Cu:1.1 {micro}g/L Cd:3.2 {micro}g/L Pb:50 {micro}g/L Zn) was used to determine avoidance in a countercurrent avoidance chamber. Rainbow trout avoided all metal concentrations tested from 10 to 1,000% of the simulated ambient metal mixture. The behavioral response of rainbow trout to the metal mixture was more sensitive than the response of brown trout (Salmo trutta) previously reported from the same laboratory under the same experimental conditions. Additionally, rainbow trout that were acclimated to the simulated ambient metal mixture for 45 d preferred clean water and avoided higher metal concentrations. Therefore, laboratory experiments on the behavioral avoidance responses of rainbow trout, as well as previously reported experiments on brown trout, show that both species will avoid typical metal concentrations observed on the Clark Fork River. And the greater sensitivity of rainbow trout to the metal mixture may explain, in part, why rainbow trout populations appear to be more severely affected, compared to brown trout populations, in the upper Clark Fork River.

  13. Metabolic responses to metal pollution in shrimp Crangon affinis from the sites along the Laizhou Bay in the Bohai Sea.

    PubMed

    Xu, Lanlan; Ji, Chenglong; Zhao, Jianmin; Wu, Huifeng

    2016-12-15

    Marine environment in the Laizhou Bay is potentially contaminated by metals from industrial discharges. In this study, metal concentrations in shrimps Crangon affinis indicated that two typical sites (S6283 and S5283) close to Longkou and Zhaoyuan cities along the Laizhou Bay have been contaminated by metals, including Cd, As, Cu, Ni, Co, and Mn. In particular, Cd and As were the main metal contaminants in S6283. In S5283, however, Cu was the most important metal contaminant. The metabolic responses in the shrimps indicated that the metal pollution in S6283 and S5283 induced disturbances in osmotic regulation and energy metabolism and reduced anaerobiosis, lipid metabolism, and muscle movement. However, alteration in the levels of dimethylglycine, dimethylamine, arginine, betaine, and glutamine indicated that the metal pollution in S5283 induced osmotic stress through different pathways compared to that in S6283. In addition, dimethylamine might be the biomarker of Cu in shrimp C. affinis.

  14. Optical response and gas sequestration properties of metal cluster supported graphene nanoflakes.

    PubMed

    Chakraborty, Debdutta; Chattaraj, Pratim Kumar

    2016-07-28

    The possibility of obtaining metal cluster (M3O(+), M = Li, Na, K) supported pristine, B-doped and BN-doped graphene nanoflakes (GR, BGR and BNGR, respectively) has been investigated by carrying out density functional theory (DFT) based calculations. Thermochemical analysis reveals the good stability of M3O(+)@GR/BGR/BNGR moieties. The dynamic stability of M3O(+)@GR/BGR/BNGR moieties is confirmed through an atom-centered density matrix propagation simulation at 298 K up to 500 fs. Orbital and electrostatic interactions play pivotal roles in stabilizing the metal-cluster supported graphene nanoflakes. The metal clusters lower the Fermi levels of the host nanoflakes and enable them to exhibit reasonably good optical response properties such as polarizability and static first hyperpolarizability. In particular, Na3O(+)/K3O(+)@BGR complexes exhibit very large first hyperpolarizability values at the static field limit. All the M3O(+)@BGR/BNGR moieties demonstrate broadband optical absorption encompassing the ultraviolet, visible as well as infrared domains. The metal-cluster supported graphene nanoflakes, in general, can sequestrate polar molecules, viz. CO, NO and CH3OH, in a thermodynamically more favorable way than GR, BGR and BNGR. In the adsorbed state, the CO, NO and CH3OH molecules, in general, attain an 'active' state as compared to their free counterparts.

  15. Structure and magnetic response of a residual metal catalyst in highly purified single walled carbon nanotubes.

    PubMed

    Bittova, Barbara Pacakova; Kalbac, Martin; Kubickova, Simona; Mantlikova, Alice; Mangold, Stephen; Vejpravova, Jana

    2013-04-28

    This article presents methods for detailed physical analysis of partial steps leading to the removal of residual metal catalyst nanoparticles (NPs) from single walled carbon nanotubes (SWCNTs) and options for detecting negligible amounts of metal in samples possessing diamagnetic response. Based on the previous knowledge of the composition, structure and magnetic properties of NPs included in the commercial HiPco_raw and HiPco_SP SWCNTs, the properties of remaining NPs after the multi-step purification (oxidation followed by mild acid treatment) and annealing both under static and dynamic vacuum have been investigated. Thermogravimetry, X-ray diffraction, static and dynamic magnetic property measurements and the Extended X-ray Absorption Fine Structure (EXAFS) experiments have been performed. The data provide information about the nature of the residual NPs in purified SWCNTs, which is crucial for further understanding of the purification processes and their improvement. It has been demonstrated that even if all macroscopic methods indicate a high purity of the treated sample, a non-negligible amount of the metal may still be present and the metal content has to be examined using local and element sensitive probes such as EXAFS.

  16. Response of selected plant and insect species to simulated solid rocket exhaust mixtures and to exhaust components from solid rocket fuels

    NASA Technical Reports Server (NTRS)

    Heck, W. W.; Knott, W. M.; Stahel, E. P.; Ambrose, J. T.; Mccrimmon, J. N.; Engle, M.; Romanow, L. A.; Sawyer, A. G.; Tyson, J. D.

    1980-01-01

    The effects of solid rocket fuel (SRF) exhaust on selected plant and and insect species in the Merritt Island, Florida area was investigated in order to determine if the exhaust clouds generated by shuttle launches would adversely affect the native, plants of the Merritt Island Wildlife Refuge, the citrus production, or the beekeeping industry of the island. Conditions were simulated in greenhouse exposure chambers and field chambers constructed to model the ideal continuous stirred tank reactor. A plant exposure system was developed for dispensing and monitoring the two major chemicals in SRF exhaust, HCl and Al203, and for dispensing and monitoring SRF exhaust (controlled fuel burns). Plants native to Merritt Island, Florida were grown and used as test species. Dose-response relationships were determined for short term exposure of selected plant species to HCl, Al203, and mixtures of the two to SRF exhaust.

  17. Adsorptive separation of xenon/krypton mixtures using a zirconium-based metal-organic framework with high hydrothermal and radioactive stabilities.

    PubMed

    Lee, Seung-Joon; Yoon, Tae-Ung; Kim, Ah-Reum; Kim, Seo-Yul; Cho, Kyung-Ho; Hwang, Young Kyu; Yeon, Jei-Won; Bae, Youn-Sang

    2016-12-15

    The separation of xenon/krypton mixtures is important for both environmental and industrial purposes. The potential of three hydrothermally stable MOFs (MIL-100(Fe), MIL-101(Cr), and UiO-66(Zr)) for use in Xe/Kr separation has been experimentally investigated. From the observed single-component Xe and Kr isotherms, isosteric heat of adsorption (Qst(o)), and IAST-predicted Xe/Kr selectivities, we observed that UiO-66(Zr) has the most potential as an adsorbent among the three candidate MOFs. We performed dynamic breakthrough experiments with an adsorption bed filled with UiO-66(Zr) to evaluate further the potential of UiO-66(Zr) for Xe/Kr separation under mixture flow conditions. Remarkably, the experimental breakthrough curves show that UiO-66(Zr) can efficiently separate the Xe/Kr mixture. Furthermore, UiO-66(Zr) maintains most of its Xe and Kr uptake capacity, as well as its crystallinity and internal surface area, even after exposure to gamma radiation (2kGy) for 7h and aging for 16 months under ambient conditions. This result indicates that UiO-66(Zr) can be considered to be a potential adsorbent for Xe/Kr mixtures under both ambient and radioactive conditions.

  18. Effect of heavy metals on growth response and antioxidant defense protection in Bacillus cereus.

    PubMed

    Behera, Madhumita; Dandapat, Jagneshwar; Rath, Chandi Charan

    2014-11-01

    Bacterial cells in aerobic environment generate reactive oxygen species which may lead to oxidative stress, induced by a wide range of environmental factors including heavy metals. In the present context an attempt has been made to determine the toxic impact of cadmium and copper on growth performance, oxidative stress, and relative level of antioxidant protection in Bacillus cereus. Outcome of this study suggests that both the metal ions depleted the growth rate in this organism with respect to time and concentration of the metal ions. CdCl2 exposure induced extracellular glutathione (GSH) production, whereas, its level was declined in response to CuSO4. Superoxide dismutase (SOD) activity and hydrogen peroxide (H2 O2 ) content was elevated under CdCl2 stress but the activity of catalase (CAT) was inhibited. In contrast, incubation of bacteria with CuSO4 exhibited decreased SOD activity with concomitant rise in CAT activity and H2 O2 content. We also observed elevation of intracellular GSH level in this bacteria following supplementation of N-acetyl cysteine (NAC) in the medium. Overall findings of this study indicated differential toxicity of CdCl2 and CuSO4 in inducing oxidative stress, depleting growth rate and the possible involvement of GSH and CAT in adaptive antioxidant response.

  19. Third-order terahertz response of gapped, nearly-metallic armchair graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Wang, Yichao; Andersen, David R.

    2016-11-01

    We use time dependent perturbation theory to study the terahertz nonlinear response of gapped intrinsic and extrinsic nearly-metallic armchair graphene nanoribbons of finite length under an applied electric field. Generally, the nonlinear conductances exhibit contributions due to single-photon, two-photon, and three-photon processes. The interference between each of these processes results in remarkably complex behavior for the third-order conductances, including quantum dot signatures that should be measurable with a relatively simple experimental configuration. Notably, we observe sharp resonances in the isotropic third-order response due to the Van Hove singularities in the density of states at one-, two-, and three-photon resonances. However, these resonances are absent in the anisotropic third-order response; a result of the overall symmetry of the system.

  20. Third-order nonlinear optical response in quantum dot-metal nanoparticle hybrid structures

    NASA Astrophysics Data System (ADS)

    Liu, X. N.; Yao, D. Z.; Zhou, H. M.; Chen, F.; Xiong, G. G.

    2013-12-01

    Third-order nonlinear optical response of a semiconductor quantum dot, modulated by the metal nanoparticle (MNP), has been studied by using the effective mass and the rotating wave approximation. Considering multiple effects in the local and nonlocal optical response of the MNP, the dependence of the dispersion and the absorption on the size of the hybrid system are investigated in detail. By controlling the geometrical parameters of the hybrid structure and the direction of the electric field polarization, a significant enhancement of the nonlinear response is shown. The enhancement factor is nearly two orders of the magnitude, which is consistent with the experiment. Compared to the results obtained with the local effect, the center frequency shows blueshift obviously in the case of the nonlocal effect. In particular, the presence of the MNP leads to a strong absorption band appearance, which promises applications in the field of light transmission and the optical switching.

  1. Polarization field gradient effects in inhomogeneous metal-ferroelectric bilayers: Optical response and band gap tunability

    NASA Astrophysics Data System (ADS)

    Vivas C., H.; Vargas-Hernández, C.

    2012-06-01

    Optical constants, reflectivity response and direct band gap energy (Egd) were calculated and simulated by developing an electrodynamic-based model for a three medium system, namely vacuum/ferroelectric film/metallic substrate. Depolarization effects due to the contact between the metallic substrate and the FE film, as well as the spatially dependent profile of the dielectric susceptibility ε(z) enter into the formalism by adapting the phenomenological Landau-Ginzburg-Devonshire theory (LGD). Absorption coefficient is obtained from the Lambert-Beer-Bouguer (LBB) approximation and the direct band gap energy as a function of the characteristic length is calculated by using the general Tauc power law. Numerical simulations lead to range of values for tunable Egd from 2.6 to 2.8 eV for characteristic lengths up to 30% the thickness of the film, in concordance with recent reports.

  2. Spirulina-Templated Metal Microcoils with Controlled Helical Structures for THz Electromagnetic Responses

    PubMed Central

    Kamata, Kaori; Piao, Zhenzi; Suzuki, Soichiro; Fujimori, Takahiro; Tajiri, Wataru; Nagai, Keiji; Iyoda, Tomokazu; Yamada, Atsushi; Hayakawa, Toshiaki; Ishiwara, Mitsuteru; Horaguchi, Satoshi; Belay, Amha; Tanaka, Takuo; Takano, Keisuke; Hangyo, Masanori

    2014-01-01

    Microstructures in nature are ultrafine and ordered in biological roles, which have attracted material scientists. Spirulina forms three-dimensional helical microstructure, one of remarkable features in nature beyond our current processing technology such as lithography in terms of mass-productivity and structural multiplicity. Spirulina varies its diameter, helical pitch, and/or length against growing environment. This unique helix is suggestive of a tiny electromagnetic coil, if composed of electro-conductive metal, which brought us main concept of this work. Here, we describe the biotemplating process onto Spirulina surface to fabricate metal microcoils. Structural parameters of the microcoil can be controlled by the cultivation conditions of Spirulina template and also purely one-handed microcoil can be fabricated. A microcoil dispersion sheet exhibited optically active response attributed to structural resonance in terahertz-wave region. PMID:24815190

  3. Spirulina-templated metal microcoils with controlled helical structures for THz electromagnetic responses.

    PubMed

    Kamata, Kaori; Piao, Zhenzi; Suzuki, Soichiro; Fujimori, Takahiro; Tajiri, Wataru; Nagai, Keiji; Iyoda, Tomokazu; Yamada, Atsushi; Hayakawa, Toshiaki; Ishiwara, Mitsuteru; Horaguchi, Satoshi; Belay, Amha; Tanaka, Takuo; Takano, Keisuke; Hangyo, Masanori

    2014-05-12

    Microstructures in nature are ultrafine and ordered in biological roles, which have attracted material scientists. Spirulina forms three-dimensional helical microstructure, one of remarkable features in nature beyond our current processing technology such as lithography in terms of mass-productivity and structural multiplicity. Spirulina varies its diameter, helical pitch, and/or length against growing environment. This unique helix is suggestive of a tiny electromagnetic coil, if composed of electro-conductive metal, which brought us main concept of this work. Here, we describe the biotemplating process onto Spirulina surface to fabricate metal microcoils. Structural parameters of the microcoil can be controlled by the cultivation conditions of Spirulina template and also purely one-handed microcoil can be fabricated. A microcoil dispersion sheet exhibited optically active response attributed to structural resonance in terahertz-wave region.

  4. Spirulina-Templated Metal Microcoils with Controlled Helical Structures for THz Electromagnetic Responses

    NASA Astrophysics Data System (ADS)

    Kamata, Kaori; Piao, Zhenzi; Suzuki, Soichiro; Fujimori, Takahiro; Tajiri, Wataru; Nagai, Keiji; Iyoda, Tomokazu; Yamada, Atsushi; Hayakawa, Toshiaki; Ishiwara, Mitsuteru; Horaguchi, Satoshi; Belay, Amha; Tanaka, Takuo; Takano, Keisuke; Hangyo, Masanori

    2014-05-01

    Microstructures in nature are ultrafine and ordered in biological roles, which have attracted material scientists. Spirulina forms three-dimensional helical microstructure, one of remarkable features in nature beyond our current processing technology such as lithography in terms of mass-productivity and structural multiplicity. Spirulina varies its diameter, helical pitch, and/or length against growing environment. This unique helix is suggestive of a tiny electromagnetic coil, if composed of electro-conductive metal, which brought us main concept of this work. Here, we describe the biotemplating process onto Spirulina surface to fabricate metal microcoils. Structural parameters of the microcoil can be controlled by the cultivation conditions of Spirulina template and also purely one-handed microcoil can be fabricated. A microcoil dispersion sheet exhibited optically active response attributed to structural resonance in terahertz-wave region.

  5. Propensity to metal accumulation and oxidative stress responses of two benthic species (Cerastoderma edule and Nephtys hombergii): are tolerance processes limiting their responsiveness?

    PubMed

    Marques, Ana; Piló, David; Araújo, Olinda; Pereira, Fábio; Guilherme, Sofia; Carvalho, Susana; Santos, Maria Ana; Pacheco, Mário; Pereira, Patrícia

    2016-05-01

    The chronic exposure of benthic organisms to metals in sediments can lead to the development of tolerance mechanisms, thus diminishing their responsiveness. This study aims to evaluate the accumulation profiles of V, Cr, Co, Ni, As, Cd, Pb and Hg and antioxidant system responses of two benthic organisms (Cerastoderma edule, Bivalvia; Nephtys hombergii, Polychaeta). This approach will provide clarifications about the ability of each species to signalise metal contamination. Organisms of both species were collected at the Tagus estuary, in two sites with distinct contamination degrees (ALC, slightly contaminated; BAR, highly contaminated). Accordingly, C. edule accumulated higher concentrations of As, Pb and Hg at BAR compared to ALC. However, antioxidant responses of C. edule were almost unaltered at BAR and no peroxidative damage occurred, suggesting adjustment mechanisms to the presence of metals. In contrast, N. hombergii showed a minor propensity to metal accumulation, only signalising spatial differences for As and Pb and accumulating lower concentrations of metals than C. edule. The differences in metal accumulation observed between species might be due to their distinctive foraging behaviour and/or the ability of N. hombergii to minimise the metal uptake. Despite that, the accumulation of As and Pb was on the basis of the polychaete antioxidant defences inhibition at BAR, including CAT, SOD, GR and GPx. The integrated biomarker response index (IBRv2) confirmed that N. hombergii was more affected by metal exposure than C. edule. In the light of current findings, in field-based studies, the information of C. edule as a bioindicator should be complemented by that provided by another benthic species, since tolerance mechanisms to metals can hinder a correct diagnosis of sediment contamination and of the system's health. Overall, the present study contributed to improve the lack of fundamental knowledge of two widespread and common estuarine species, providing

  6. Plant responses to abiotic stresses: heavy metal-induced oxidative stress and protection by mycorrhization.

    PubMed

    Schützendübel, Andres; Polle, Andrea

    2002-05-01

    cadmium results in unspecific necrosis. Plants in certain mycorrhizal associations are less sensitive to cadmium stress than non-mycorrhizal plants. Data about antioxidative systems in mycorrhizal fungi in pure culture and in symbiosis are scarce. The present results indicate that mycorrhization stimulated the phenolic defence system in the Paxillus-Pinus mycorrhizal symbiosis. Cadmium-induced changes in mycorrhizal roots were absent or smaller than those in non-mycorrhizal roots. These observations suggest that although changes in rhizospheric conditions were perceived by the root part of the symbiosis, the typical Cd-induced stress responses of phenolics were buffered. It is not known whether mycorrhization protected roots from Cd-induced injury by preventing access of cadmium to sensitive extra- or intracellular sites, or by excreted or intrinsic metal-chelators, or by other defence systems. It is possible that mycorrhizal fungi provide protection via GSH since higher concentrations of this thiol were found in pure cultures of the fungi than in bare roots. The development of stress-tolerant plant-mycorrhizal associations may be a promising new strategy for phytoremediation and soil amelioration measures.

  7. Detection and aggregation of the antitumoral drug parietin in ethanol/water mixture and on plasmonic metal nanoparticles studied by surface-enhanced optical spectroscopy: Effect of pH and ethanol concentration.

    PubMed

    Lopez-Tobar, Eduardo; Verebova, Valeria; Blascakova, Ludmila; Jancura, Daniel; Fabriciova, Gabriela; Sanchez-Cortes, Santiago

    2016-04-15

    In the present paper, we have investigated the effect of ethanol in aqueous media, the pH and the presence of Ag nanoparticles (NPs) on the aggregation processes of the antitumoral anthraquinone parietin in aqueous media and on the metal surface. UV-visible absorption, fluorescence and Raman spectra of parietin were used for such purpose. The present study provides information about the deprotonation and molecular aggregation processes occurring in parietin under different environments: ethanol/water mixture and when adsorbed onto Ag nanoparticles. The effect of ethanol on the optical properties of parietin in alcohol-water mixtures was also investigated at different ethanol concentrations with the time. For the case of the adsorption and organization of parietin molecules on the surface of Ag NPs, special attention was paid to the use of surface-enhanced optical techniques, SEF (surface-enhanced fluorescence) and SERS (surface-enhanced Raman scattering), for the characterization of the parietin aggregates and the ionization of the molecule on the surface. In particular, we have studied the variation of the SEF signal with the pH, which depends on the molecular organization of the molecule on the surface. Furthermore, a detailed analysis of the SERS spectra at different pH was accomplished and the main Raman bands of the protonated, mono-deprotonated and di-deprotonated parietin were identified. Finally, the second ionization pK of parietin on metal NPs was deduced from the SERS spectra.

  8. Detection and aggregation of the antitumoral drug parietin in ethanol/water mixture and on plasmonic metal nanoparticles studied by surface-enhanced optical spectroscopy: Effect of pH and ethanol concentration

    NASA Astrophysics Data System (ADS)

    Lopez-Tobar, Eduardo; Verebova, Valeria; Blascakova, Ludmila; Jancura, Daniel; Fabriciova, Gabriela; Sanchez-Cortes, Santiago

    2016-04-01

    In the present paper, we have investigated the effect of ethanol in aqueous media, the pH and the presence of Ag nanoparticles (NPs) on the aggregation processes of the antitumoral anthraquinone parietin in aqueous media and on the metal surface. UV-visible absorption, fluorescence and Raman spectra of parietin were used for such purpose. The present study provides information about the deprotonation and molecular aggregation processes occurring in parietin under different environments: ethanol/water mixture and when adsorbed onto Ag nanoparticles. The effect of ethanol on the optical properties of parietin in alcohol-water mixtures was also investigated at different ethanol concentrations with the time. For the case of the adsorption and organization of parietin molecules on the surface of Ag NPs, special attention was paid to the use of surface-enhanced optical techniques, SEF (surface-enhanced fluorescence) and SERS (surface-enhanced Raman scattering), for the characterization of the parietin aggregates and the ionization of the molecule on the surface. In particular, we have studied the variation of the SEF signal with the pH, which depends on the molecular organization of the molecule on the surface. Furthermore, a detailed analysis of the SERS spectra at different pH was accomplished and the main Raman bands of the protonated, mono-deprotonated and di-deprotonated parietin were identified. Finally, the second ionization pK of parietin on metal NPs was deduced from the SERS spectra.

  9. Constitutional self-selection of [2 x 2] homonuclear grids from a dynamic mixture of copper(I) and silver(I) metal complexes.

    PubMed

    Barboiu, Mihail; Petit, Eddy; van der Lee, Arie; Vaughan, Gavin

    2006-01-23

    This paper describes the controlled self-selection and quantitative parallel amplification of the homonuclear grid architectures derived from the same ligand 1 of different conformational geometries and Cu+ and Ag+ metal ions of different coordination behavior and ionic size.

  10. Optimization of polyphenol extraction from red grape pomace using aqueous glycerol/tartaric acid mixtures and response surface methodology.

    PubMed

    Makris, Dimitris P; Passalidi, Vassiliki; Kallithraka, Stamatina; Mourtzinos, Ioannis

    2016-01-01

    Grape pomace is a food industry waste containing a high burden of antioxidant polyphenols and several methodologies have been developed for their efficient extraction. However, a sustainable and environmentally friendly process should involve recovery means composed of benign, non-toxic solvents, such as tartaric acid and glycerol, which are natural food constituents. In this line, this study examined the extraction of polyphenols using aqueous tartaric acid/glycerol solutions. The aim was to assess the role of acid and glycerol concentration in the extraction yield, employing a Box-Behnken experimental design and response surface methodology. The results showed that solutions containing only glycerol (20%, w/v) are more suitable for retrieving polyphenols, flavonoids, and pigments from grape pomace, while tartaric acid exerted a negative effect in this regard, when tested at concentrations up to 2% (w/v).

  11. Effects of defined mixtures of persistent organic pollutants (POPs) on multiple cellular responses in the human hepatocarcinoma cell line, HepG2, using high content analysis screening.

    PubMed

    Wilson, Jodie; Berntsen, Hanne Friis; Zimmer, Karin Elisabeth; Frizzell, Caroline; Verhaegen, Steven; Ropstad, Erik; Connolly, Lisa

    2016-03-01

    Persistent organic pollutants (POPs) are toxic substances, highly resistant to environmental degradation, which can bio-accumulate and have long-range atmospheric transport potential. Most studies focus on single compound effects, however as humans are exposed to several POPs simultaneously, investigating exposure effects of real life POP mixtures on human health is necessary. A defined mixture of POPs was used, where the compound concentration reflected its contribution to the levels seen in Scandinavian human serum (total mix). Several sub mixtures representing different classes of POPs were also constructed. The perfluorinated (PFC) mixture contained six perfluorinated compounds, brominated (Br) mixture contained seven brominated compounds, chlorinated (Cl) mixture contained polychlorinated biphenyls and also p,p'-dichlorodiphenyldichloroethylene, hexachlorobenzene, three chlordanes, three hexachlorocyclohexanes and dieldrin. Human hepatocarcinoma (HepG2) cells were used for 2h and 48h exposures to the seven mixtures and analysis on a CellInsight™ NXT High Content Screening platform. Multiple cytotoxic endpoints were investigated: cell number, nuclear intensity and area, mitochondrial mass and membrane potential (MMP) and reactive oxygen species (ROS). Both the Br and Cl mixtures induced ROS production but did not lead to apoptosis. The PFC mixture induced ROS production and likely induced cell apoptosis accompanied by the dissipation of MMP. Synergistic effects were evident for ROS induction when cells were exposed to the PFC+Br mixture in comparison to the effects of the individual mixtures. No significant effects were detected in the Br+Cl, PFC+Cl or total mixtures, which contain the same concentrations of chlorinated compounds as the Cl mixture plus additional compounds; highlighting the need for further exploration of POP mixtures in risk assessment.

  12. Bulk and surface electromagnetic response of metallic metamaterials to convection electrons

    NASA Astrophysics Data System (ADS)

    So, Jin-Kyu; Jang, Kyu-Ha; Park, Gun-Sik; Garcia-Vidal, F. J.

    2011-08-01

    The electromagnetic response of three-dimensional metallic metamaterials with isotropic effective index of refraction to fast-moving electrons is studied by numerical simulations. The considered metamaterials can support Cerenkov radiation [P. A. Cherenkov, Dokl. Akad. Nauk SSSR 2, 451 (1934)], and their effective dielectric behavior is confirmed by the detailed angular dependence of the generated radiation cone on the kinetic energy of electrons. Moreover, in addition to the predicted bulk modes, surface electromagnetic excitation is observed in a specific type of metamaterials and its dispersion is sensitive to the thickness of the subwavelength rods.

  13. A porphyrin-based metal-organic framework as a pH-responsive drug carrier

    NASA Astrophysics Data System (ADS)

    Lin, Wenxin; Hu, Quan; Jiang, Ke; Yang, Yanyu; Yang, Yu; Cui, Yuanjing; Qian, Guodong

    2016-05-01

    A low cytotoxic porphyrin-based metal-organic framework (MOF) PCN-221, which exhibited high PC12 cell viability via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium (MTT) assay, was selected as an oral drug carrier. Methotrexate (MTX) was chosen as the model drug molecule which was absorbed into inner pores and channels of MOFs by diffusion. PCN-221 showed high drug loading and sustained release behavior under physiological environment without "burst effect". The controlled pH-responsive release of drugs by PCN-221 revealed its promising application in oral drug delivery.

  14. Trajectories of Microbial Community Function in Response to Accelerated Remediation of Subsurface Metal Contaminants

    SciTech Connect

    Firestone, Mary

    2015-01-14

    Objectives of proposed research were to; Determine if the trajectories of microbial community composition and function following organic carbon amendment can be related to, and predicted by, key environmental determinants; Assess the relative importance of the characteristics of the indigenous microbial community, sediment, groundwater, and concentration of organic carbon amendment as the major determinants of microbial community functional response and bioremediation capacity; and Provide a fundamental understanding of the microbial community ecology underlying subsurface metal remediation requisite to successful application of accelerated remediation and long-term stewardship of DOE-IFC sites.

  15. Toxic responses of medaka, d-rR strain, to polychlorinated naphthalene mixtures after embryonic exposure by in ovo nanoinjection: A partial life-cycle assessment

    SciTech Connect

    Villalobos, S.A.; Papoulias, D.M.; Meadows, J.; Blankenship, A.L.; Pastva, S.D.; Kannan, K.; Hinton, D.E.; Tillitt, D.E.; Giesy, J.P.

    2000-02-01

    Polychlorinated naphthalenes (PCNs) are organic compounds with some chemical properties and uses similar to polychlorinated biphenyls. Polychlorinated naphthalenes have been detected in biota from certain aquatic environments. The toxicities of several PCN technical mixtures (Halowax) to medaka (Oryzias latipes) were determined by use of an embryo nanoinjection method. Medaka eggs (early gastrula) were injected with 0.5 nl of triolein (vehicle control) or 0.5 nl of four to five graded doses (0.3--30 ng/egg) of Halowax 1014, Halowax 1013, or Halowax 1051 in triolein. Following exposure, embryos developed, and fry were reared to sexual maturity (4 months), at which time they were euthanized. Responses were evaluated as early life stage (ELS) and early adult life stage (EALS) assessments. For ELS, lethality and sublethal alterations in embryos and larvae (<16 d old), such as craniofacial, cardiovascular, and myoskeletal deformities and abnormal or delayed hatch, were monitored for the first 9 d, and a dose severity index was computed. The EALS assessment examined the survival of 16-d-old larvae until early adulthood (123 {+-} 3 d old), including gonadosomatic index (GSI) and morphometry. Halowax 1014 was found to be the most toxic mixture (LD50 4.2 ng/egg), whereas Halowax 1013 and 1051 were significantly less toxic (LD50s could not be determined). The gonadosomatic index of females was significantly less in fish dosed with Halowax 1014 or 1051. The LD50 for medaka embryos nanoinjected with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is about 0.75 pg/egg. Thus, Halowax 1014 was 5,585-fold less potent than TCDD. For Halowax 1014, ELS assessments accurately predicted the results of EALS assessments.

  16. Toxic responses of medaka, D-rR strain, to polychlorinatednaphthalene mixtures after embryonic exposure by in ovo nanoinjection: A partial life-cycle assessment

    USGS Publications Warehouse

    Villalobos, Sergio A.; Papoulias, Diana M.; Meadows, John C.; Blankenship, Alan L.; Pastva, Stephanie D.; Kannan, Kurunthachalam; Hinton, D.E.; Tillitt, Donald E.; Giesy, John P.

    2000-01-01

    Polychlorinated naphthalenes (PCNs) are organic compounds with some chemical properties and uses similar to polychlorinated biphenyls. Polychlorinated naphthalenes have been detected in biota from certain aquatic environments. The toxicities of several PCN technical mixtures (Halowax) to medaka (Oryzias latipes) were determined by use of an embryo nanoinjection method. Medaka eggs (early gastrula) were injected with 0.5 nl of triolein (vehicle control) or 0.5 nl of four to five graded doses (0.3-30 ng/egg) of Halowax 1014, Halowax 1013, or Halowax 1051 in triolein. Following exposure, embryos developed, and fry were reared to sexual maturity (4 months), at which time they were euthanized. Responses were evaluated as early life stage (ELS) and early adult life stage (EALS) assessments. For ELS, lethality and sublethal alterations in embryos and larvae ( < 16 d old), such as craniofacial, cardiovascular, and myoskeletal deformities and abnormal or delayed hatch, were monitored for the first 9 d, and a dose severity index was computed. The EALS assessment examined the survival of 16-d-old larvae until early adulthood (123 ?? 3 d old), including gonadosomatic index (GSI) and morphometry. Halowax 1014 was found to be the most toxic mixture (LD50 4.2 ng/egg), whereas Halowax 1013 and 1051 were significantly less toxic (LD50s could not be determined). The gonadosomatic index of females was significantly less in fish dosed with Halowax 1014 or 1051. The LD50 for medaka embryos nanoinjected with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is about 0.75 pg/egg. Thus, Halowax 1014 was 5,585-fold less potent than TCDD. For Halowax 1014, ELS assessments accurately predicted the results of EALS assessments.

  17. Thermophilic bioleaching of heavy metals from waste sludge using response surface methodology.

    PubMed

    Chen, Shen-Yi; Chen, Wen-Hsing

    2013-01-01

    The bioleaching process is considered to be more efficient and environmentally friendly than conventional technologies for removal of heavy metals from waste sludge. The objective of this study was to develop an optimal thermophilic bioleaching process for the treatment of waste sludge containing high concentrations of heavy metals. In this study, two operating parameters, sludge solid content and sulfur (substrate) concentration, were studied based on a central composite design (CCD) for their metal solubilization and solid degradation performances. The optimal bioleaching operation conditions were then determined using the response surface methodology (RSM). The results indicated that an increase in sludge solid content range from 0.5% to 5.0% resulted in a decrease in the pH reduction rate due to the increase in buffering capacity. The rate of acidification corresponded to sulfur concentration until sulfur itself became inhibitory. At sulfur concentration beyond approximately 2.75%, the lower acidification rate was caused by a lower bacteria growth rate. Similar trends were also observed in the variations of ORP and sulfate concentrations during this thermophilic bioleaching process. At the optimum conditions of a sludge solid content of 0.5% and sulfur concentration of 2.5%, the thermophilic bioleaching process achieved the maximum solubilization of 97%, 99%, 99% and 78% for Cu, Zn, Ni and Pb, respectively. At the same time, the maximum SS and VSS destruction efficiency were 69% and 63%, respectively.

  18. Physiological responses of Tillandsia albida (Bromeliaceae) to long-term foliar metal application.

    PubMed

    Kováčik, Jozef; Klejdus, Bořivoj; Stork, František; Hedbavny, Josef

    2012-11-15

    The impact of 2-month foliar application of cadmium, nickel and their combination (10 μM) on Tillandsia albida was studied. Cadmium caused damage of tissue but assimilation pigments were depressed in Cd+Ni variant only. Stress-related parameters (ROS and peroxidase activities) were elevated by Cd and Cd+Ni while MDA content remained unaffected. Free amino acids accumulated the most in Ni alone but soluble proteins were not influenced. Among phenolic acids, mainly vanillin contributed to increase of their sum in all variants while soluble phenols even decreased in Cd+Ni and flavonols slightly increased in Cd variants. Phenolic enzymes showed negligible responses to almost all treatments. Mineral nutrients (K, Ca, Na, Mg, Fe, and Zn) were not affected by metal application but N content increased. Total Cd or Ni amounts reached over 400 μg g(-1) DW and were not affected if metal alone and combined treatment is compared while absorbed content differed (ca. 50% of total Cd was absorbed while almost all Ni was absorbed). These data indicate tolerance of T. albida to foliar metal application and together with strong xerophytic morphology, use for environmental studies is recommended.

  19. Anion exchange of organic carboxylate by soils responsible for positive Km-fc relationship from methanol mixture.

    PubMed

    Kim, Minhee; Han, Junho; Hyun, Seunghun

    2013-09-01

    The cosolvency model was not applicable for predicting the sorption of organic carboxylic acids. The reason of inapplicability was investigated by analyzing the solubility (Sm) and sorption (Km) of benzoic acid, 2,4-dichlorophenoxyacetic acid (2,4-D), and 2,4,6-trichlorophenol (2,4,6-TCP). The Sm and Km by two iron-rich soils was measured as a function of methanol volume fraction (fc), electrolyte compositions, and pH(app). For 2,4,6-TCP, the Km of both neutral and anion species was well-explainable by the cosolvency model, exemplifying the knowledge of cosolvency power (σ) being sufficient to describe its sorption. However, for benzoic acid and 2,4-D, the Km of organic anions increased with fc, illustrating the organic carboxylate to be responsible for the deviation. The Sm of organic anions was not affected by the ionic valence (Ca(2+) vs. K(+)) of liquid phase. Among hydrophilic quantities of the 2,4-D sorption, the fraction of anion exchange increased with fc while the fraction of Ca-bridge decreased in the same range. Adding solvent in soil-water system is likely to render soil surface charge more positive, fortifying the anion exchange, but opposing the formation of Ca-bridging. Therefore, it can be concluded that the positive Km-fc relationship is due to the anion exchange of organic carboxylate with positively charged soil surface, whose contribution is >50% of overall sorption at solvent-free system and becomes greater with fc up to 82%.

  20. Investigation by response surface methodology of the combined effect of pH and composition of water-methanol mixtures on the stability of curcuminoids.

    PubMed

    D'Archivio, Angelo Antonio; Maggi, Maria Anna

    2017-03-15

    Response surface methodology, coupled to a full factorial three-level experimental design, was applied to investigate the combined influence of pH (between 7.0 and 8.6) and composition of methanol-water mixtures (between 30 and 70% v/v of methanol content) on the stability of curcumin and its analogues demethoxycurcumin and bisdemethoxycurcumin. The response plots revealed that addition of methanol noticeably improved the stability of curcuminoids, this effect being both pH- and structure-dependent. In the central point of the experimental domain, half-life times of curcumin, demethoxycurcumin and bisdemethoxycurcumin were 3.8±0.2, 27±2 and 251±17h, respectively. Stability of curcuminoids increased at lower pH and higher methanol content and decreased in the opposite vertex of the experimental domain. These results can be interpreted by assuming that addition of methanol to water produces a different variation of pH of the medium and apparent pKa values of the ionisable groups of curcuminoids.

  1. Three novel superoxide dismutase genes identified in the marine polychaete Perinereis nuntia and their differential responses to single and combined metal exposures.

    PubMed

    Won, Eun-Ji; Ra, Kongtae; Kim, Kyung-Tae; Lee, Jae-Seong; Lee, Young-Mi

    2014-09-01

    To identify superoxide dismutase (SOD) genes and evaluate their usefulness as potential markers for monitoring metal toxicity in aquatic environment, we cloned, sequenced, and characterized 3 SOD genes (Cu/Zn-SOD1, Cu/Zn-SOD2, and Mn-SOD) from the marine polychaete Perinereis nuntia. The accumulated metal contents and expressions of 3 SOD genes were compared after exposure to single and combinations of heavy metals, As, Ni, and Pb. The deduced amino acid sequences of the 3 SODs had evolutionary conserved domains, such as metal binding sites, and signature sequences. The phylogenetic analysis revealed that Cu/Zn-SOD1, Cu/Zn-SOD2, and Mn-SOD were clustered with extracellular Cu/Zn-SOD, intracellular Cu/Zn-SOD and mitochondrial Mn-SOD, respectively, of other species. The accumulated contents of Ni and Pb increased significantly in a time - dependent manner after exposure to both single and combination of the metals. However, the concentration of As did not change significantly in the exposure test. The quantitative real-time polymerase chain reaction (PCR) array showed that the 3 SOD genes had differential expression patterns depending on the exposure condition. The expression of all SODs mRNAs was significantly elevated in response to Pb alone and in combination with As. The mRNA level of Cu/Zn-SOD1 was the highest after exposure to Pb alone, while that of Mn-SOD was remarkably enhanced after exposure to a combination of As and Pb. Exposure to Ni alone rapidly elevated the expression of Cu/Zn-SOD1 and Mn-SOD mRNA, which then gradually decreased. Exposure to As had no significant effect on the modulation of any of the SOD genes of P. nuntia. These results suggest that all SOD genes might play important roles in cellular protection as antioxidant enzymes against heavy metal toxicity via different modes of action in P. nuntia and might have the potential to act as indicators in an environment containing a mixture of metals.

  2. Metal dusting of nickel-containing alloys

    SciTech Connect

    Baker, B.A.; Smith, G.D.

    1998-12-31

    Metal dusting is a catastrophic form of carburization which leads to pitting and grooves as the affected metal disintegrates into a mixture of powdery carbon, metallic particles, and possibly oxides and carbides. This high temperature carburization mode is not yet well understood and while relatively infrequent, can be economically disastrous when it does occur in large and complex chemical and petrochemical process streams. References in the literature show that all classes of heat resistant alloys are prone to metal dusting, given the necessary and specific environmental conditions. These same references describe the environments that plague nickel-containing alloys and are used as the basis for postulation on the probable corrosion mechanisms responsible for metal dusting. Using alloy 800 and other nickel-containing alloys and metal dusting atmospheres, an effort is made to examine the steps in the metal dusting process and the temperature ranges over which metal dusting occurs.

  3. Bioleaching mechanism of heavy metals in the mixture of contaminated soil and slag by using indigenous Penicillium chrysogenum strain F1.

    PubMed

    Deng, Xinhui; Chai, Liyuan; Yang, Zhihui; Tang, Chongjian; Wang, Yangyang; Shi, Yan

    2013-03-15

    The ability and bioleaching mechanism of heavy metals by Penicillium chrysogenum in soils contaminated with smelting slag were examined in this study. Batch experiments were performed to investigate the growth kinetics of P. chrysogenum, organic acids production and to compare the removal efficiencies of heavy metals between bioleaching with P. chrysogenum and chemical organic acids. The results showed that the bioleaching had higher removals than chemical leaching, and the removal percentages of Cd, Cu, Pb, Zn, Mn and Cr reached up to 74%, 59%, 24%, 55%, 57% and 25%, respectively. Removal efficiencies of heavy metals (15.41 mg/50 mL) by bioleaching were higher than chemical leaching with 0.5% of citric acid (15.15 mg/50 mL), oxalic acid (8.46 mg/50 mL), malic acid (11.35 mg/50 mL) and succinic acid (10.85 mg/50 mL). The results of transmission electron microscope (TEM) showed that no damage was obviously observed on the surface of the living cell except for thinner cell wall, discontinuous plasma membrane, compartmentalized lumen and concentrated cytoplasm during bioleaching process. The activity of extracellular glucose oxidase (GOD) produced by P. chrysogenum is influenced severely by the multi-heavy metal ions. The result implied that P. chrysogenum can be used to remove heavy metals from polluted soil and smeltery slag.

  4. Chromatic Mechanical Response in 2-D Layered Transition Metal Dichalcogenide (TMDs) based Nanocomposites

    NASA Astrophysics Data System (ADS)

    Rahneshin, Vahid; Khosravi, Farhad; Ziolkowska, Dominika A.; Jasinski, Jacek B.; Panchapakesan, Balaji

    2016-10-01

    The ability to convert photons of different wavelengths directly into mechanical motion is of significant interest in many energy conversion and reconfigurable technologies. Here, using few layer 2H-MoS2 nanosheets, layer by layer process of nanocomposite fabrication, and strain engineering, we demonstrate a reversible and chromatic mechanical response in MoS2-nanocomposites between 405 nm to 808 nm with large stress release. The chromatic mechanical response originates from the d orbitals and is related to the strength of the direct exciton resonance A and B of the few layer 2H-MoS2 affecting optical absorption and subsequent mechanical response of the nanocomposite. Applying uniaxial tensile strains to the semiconducting few-layer 2H-MoS2 crystals in the nanocomposite resulted in spatially varying energy levels inside the nanocomposite that enhanced the broadband optical absorption up to 2.3 eV and subsequent mechanical response. The unique photomechanical response in 2H-MoS2 based nanocomposites is a result of the rich d electron physics not available to nanocomposites based on sp bonded graphene and carbon nanotubes, as well as nanocomposite based on metallic nanoparticles. The reversible strain dependent optical absorption suggest applications in broad range of energy conversion technologies that is not achievable using conventional thin film semiconductors.

  5. Chromatic Mechanical Response in 2-D Layered Transition Metal Dichalcogenide (TMDs) based Nanocomposites

    PubMed Central

    Rahneshin, Vahid; Khosravi, Farhad; Ziolkowska, Dominika A.; Jasinski, Jacek B.; Panchapakesan, Balaji

    2016-01-01

    The ability to convert photons of different wavelengths directly into mechanical motion is of significant interest in many energy conversion and reconfigurable technologies. Here, using few layer 2H-MoS2 nanosheets, layer by layer process of nanocomposite fabrication, and strain engineering, we demonstrate a reversible and chromatic mechanical response in MoS2-nanocomposites between 405 nm to 808 nm with large stress release. The chromatic mechanical response originates from the d orbitals and is related to the strength of the direct exciton resonance A and B of the few layer 2H-MoS2 affecting optical absorption and subsequent mechanical response of the nanocomposite. Applying uniaxial tensile strains to the semiconducting few-layer 2H-MoS2 crystals in the nanocomposite resulted in spatially varying energy levels inside the nanocomposite that enhanced the broadband optical absorption up to 2.3 eV and subsequent mechanical response. The unique photomechanical response in 2H-MoS2 based nanocomposites is a result of the rich d electron physics not available to nanocomposites based on sp bonded graphene and carbon nanotubes, as well as nanocomposite based on metallic nanoparticles. The reversible strain dependent optical absorption suggest applications in broad range of energy conversion technologies that is not achievable using conventional thin film semiconductors. PMID:27713550

  6. Chromatic Mechanical Response in 2-D Layered Transition Metal Dichalcogenide (TMDs) based Nanocomposites.

    PubMed

    Rahneshin, Vahid; Khosravi, Farhad; Ziolkowska, Dominika A; Jasinski, Jacek B; Panchapakesan, Balaji

    2016-10-07

    The ability to convert photons of different wavelengths directly into mechanical motion is of significant interest in many energy conversion and reconfigurable technologies. Here, using few layer 2H-MoS2 nanosheets, layer by layer process of nanocomposite fabrication, and strain engineering, we demonstrate a reversible and chromatic mechanical response in MoS2-nanocomposites between 405 nm to 808 nm with large stress release. The chromatic mechanical response originates from the d orbitals and is related to the strength of the direct exciton resonance A and B of the few layer 2H-MoS2 affecting optical absorption and subsequent mechanical response of the nanocomposite. Applying uniaxial tensile strains to the semiconducting few-layer 2H-MoS2 crystals in the nanocomposite resulted in spatially varying energy levels inside the nanocomposite that enhanced the broadband optical absorption up to 2.3 eV and subsequent mechanical response. The unique photomechanical response in 2H-MoS2 based nanocomposites is a result of the rich d electron physics not available to nanocomposites based on sp bonded graphene and carbon nanotubes, as well as nanocomposite based on metallic nanoparticles. The reversible strain dependent optical absorption suggest applications in broad range of energy conversion technologies that is not achievable using conventional thin film semiconductors.

  7. Pulmonary function responses of young and older adults to mixtures of O sub 3 , NO sub 2 and PAN

    SciTech Connect

    Drechsler-Parks, D.M.; Bedi, J.F.; Horvath, S.M. )

    1989-05-01

    The pulmonary function of 32 nonsmokers (eight men and eight women, 18-26 years of age; eight men and eight women, 51-76 years of age) was measured before and after two-hour exposures to (1) filtered air (FA), (2) 0.45 ppm ozone (O3), (3) 0.13 ppm peroxyacetyl nitrate + 0.45 ppm O3 (PAN/O3), (4) 0.60 ppm nitrogen dioxide + 0.45 ppm O3 (NO2/O3), and (5) 0.13 ppm PAN + 0.60 ppm NO2 + 0.45 ppm O3 (PAN/NO2/O3). Subjects alternated 20-minute periods of rest and exercise (ventilation = 25 L/min). Forced vital capacity (FVC) was measured pre-exposure and five-minutes after each exercise period. Forced expiratory volume in one sec (FEV1.0) and forced expiratory flow between 25 and 75 percent of FVC (FEF25-75%) were calculated from the FVC tests. Data were analyzed by 4-factor analysis of variance (sex, age, time period, exposure). The responses of men and women were similar. FA exposure induced no effects. The young subjects' decrements in FVC, FEV1.0 and FEF25-75% became significant (P less than 0.01) after the second exercise period of the O3, NO2/O3 and PAN/NO2/O3 exposures, while the PAN/O3 decrements were significant (P less than 0.01) after the first exercise period. Although PAN/O3 induced significant decrements earlier than the other conditions including O3, the mean pre- to post-exposure decrements for the four conditions including O3 were similar. In contrast, the older subjects had smaller and fewer significant decrements in pulmonary functions. They had significant mean decrements in FVC following the third exercise period of the NO2/O3 and PAN/NO2/O3 exposures, in FEV1.0 after the third exercise period of the PAN/O3 and NO2/O3 exposures, and in FEF 25-75% beginning after the second exercise period of the NO2/O3 exposure.

  8. A universal approach to predicting temperature response of metallic parts to spray quenching

    NASA Astrophysics Data System (ADS)

    Mudawar, Issam; Deiters, Thomas A.

    1995-02-01

    A new method was developed to predict the temperature response of metallic parts to spray quenching below the film boiling regime. Local heat flux measurements in surfaces subjected to full cone and hollow cone sprays revealed existing correlations based on local values of volumetric spray flux, Sauter mean diameter, and mean drop velocity are both accurate and spatially independent in the transition boiling and nucleate boiling regimes, but less accurate in the single-phase regime due to liquid run-off effects. It is shown how the instantaneous spatial distribution of the heat transfer coefficient can be predicted from a mapping of the spatial distribution of the spray hydrodynamic parameters. The validity of this approach is demonstrated by comparing numerical predictions to the temperature response of a large rectangular aluminum block subjected on one surface to a nonuniform water spray. It is shown that the new method is universally applicable to sprays having drastically different patterns.

  9. Enhanced electromechanical response of Ionic Polymer-Metal Composite (IPMC) actuators by various Nafion roughening levels

    NASA Astrophysics Data System (ADS)

    Wang, Yanjie; Liu, Jiayu; Chen, Hualing

    2016-04-01

    Recently, Ionic polymer metal composites (IPMCs), becoming an increasingly popular material, are used as soft actuators for its inherent properties of light weight, flexibility, softness, especial efficient transformation from electrical energy to mechanical energy with large bending strain response to low activation voltage. This paper mainly focuses on the suitable conditions for surface-roughening of Nafion 117 membrane. The surfaces of Nafion membrane were pretreated and optimized by sandblasting, mainly considering the change of sandblasting time and powder size. The modified surfaces are characterized in terms of their topography from the confocal laser scanning microscope (CLSM) and SEM. Then, the detailed change in surface and interfacial electrodes and performances for IPMC actuators prepared by the roughened membranes, were measured and discussed. The results show that an optimized roughening condition with large interface area (capacitance) can effectively increases the electromechanical responses of IPMC.

  10. The Professional Context as a Predictor for Response Distortion in the Adaption-Innovation Inventory--An Investigation Using Mixture Distribution Item Response Theory Models

    ERIC Educational Resources Information Center

    Fischer, Sebastian; Freund, Philipp Alexander

    2014-01-01

    The Adaption-Innovation Inventory (AII), originally developed by Kirton (1976), is a widely used self-report instrument for measuring problem-solving styles at work. The present study investigates how scores on the AII are affected by different response styles. Data are collected from a combined sample (N = 738) of students, employees, and…

  11. Ph responsive capsules containing composite coatings for corrosion inhibition in metal alloys

    NASA Astrophysics Data System (ADS)

    Kashi, Kiran Bhat

    Hexavalent chromes have been used as effective corrosion inhibitors due to their high inhibitor efficiency and low cost for the protection of several metal alloys. However, owing to their toxicity federal legislations restrict the use and distribution of these highly toxic materials. The need for an environmentally friendly yet effective alternative to the chrome based corrosion inhibitors has led to the investigation of rare earth metals as potential candidates. Cerium is one such rare earth metal that has received considerable attention as an alternative to hexavalent chromes. However, the high water solubility of some of the cerium salts makes it difficult for the incorporation of such salts in coatings. In this work, pH responsive microcapsules containing cerium salts were synthesized using an internally phase separated emulsion polymerization technique. Core shell microcapsule consisting of a water core containing dissolved cerium salts were synthesized. The synthesized capsules were characterized using characterization techniques such as Fourier Transform Infrared (FTIR) spectroscopy, UV-vis spectroscopy, Dynamic Mechanical Analysis (DMA), Thermo-Gravimetric Analysis (TGA), and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The structure and morphology of the capsules were studied using electron microscopy techniques. The synthesized capsules were dispersed in 2K epoxy coatings and applied on aluminum alloy 2024 T-3 and cold rolled steel substrates. These coatings were exposed to salt spray (ASTM B117) and electrochemically evaluated using electrochemical impedance spectroscopy (EIS), potentio-dynamic(PD) polarization, cyclic voltammetry(CV), open circuit potential(OCP) measurements. Localized corrosion assessment was also performed on the coated metal alloys using Scanning electrochemical microscopy (SECM) to understand the mechanism of corrosion inhibition using cerium encapsulated microcapsules.

  12. The development dynamics of the maize root transcriptome responsive to heavy metal Pb pollution.

    PubMed

    Gao, Jian; Zhang, Yongzhong; Lu, Chaolong; Peng, Hua; Luo, Mao; Li, Gaoke; Shen, Yaou; Ding, Haiping; Zhang, Zhiming; Pan, Guangtang; Lin, Haijian

    2015-03-06

    Lead (Pb), as a heavy metal element, has become the most important metal pollutant of the environment. With allocating a relatively higher proportion of its biomass in roots, maize could be a potential important model to study the phytoremediation of Pb-contaminated soil. Here we analyzed the maize root transcriptome of inbred lines 9782 under heavy metal lead (Pb) pollution, which was identified as a non-hyperaccumulator for Pb in roots. In the present study, more than 98 millions reads were mapped to define gene structure and detect polymorphism, thereby to qualify transcript abundance along roots development under Pb treatment. A total of 17,707, 17,440, 16,998 and 16,586 genes were identified in maize roots at four developmental stages (0, 12 h, 24 h and 48 h) respectively and 2,825, 2,626, 2161 and 2260 stage-specifically expressed genes were also identified respectively. In addition, based on our RNA-Seq data, transcriptomic changes during maize root development responsive to Pb were investigated. A total of 384 differentially expressed genes (DEGs) (log2Ratio ≥ 1, FDR ≤ 0.001) were identified, of which, 36 genes with significant alteration in expression were detected in four developmental stages; 12 DEGs were randomly selected and successful validated by qRT-PCR. Additionally, many transcription factor families might act as the important regulators at different developmental stages, such as bZIP, ERF and GARP et al. These results will expand our understanding of the complex molecular and cellular events in maize root development and provide a foundation for future study on root development in maize under heavy metal pollution and other cereal crops.

  13. The Optical Response of Strongly Coupled Quantum Dot- Metal Nanoparticle Hybrid Systems

    NASA Astrophysics Data System (ADS)

    Artuso, Ryan Domenick

    In this thesis, we study, theoretically, hybrid systems composed of semiconducting quantum dots (SQDs) and metallic nanoparticles (MNPs) which are coupled by means of an applied optical field. Systems composed of SQDs and MNPs have recently been a very active area of research. Such structures are considered to be viable candidates for use in nanodevices in quantum information and nanoscale excitation transfer. The goal of this thesis is to investigate the interactions of the constituent particles and predict the hybrid response of SQD/MNP systems. We first study a single SQD coupled to a spherical MNP, and explore the relationship between the size of the constituents and the response of the system. We identify four distinct regimes of behavior in the strong field limit that each exhibit novel properties, namely, the Fano regime, exciton induced transparency, suppression and bistability. In chapter 3, we will explore these four regimes in detail and set bounds on each. In chapter 4, we then show that the response of the system can be tailored by engineering metal nanoparticle shape and the exciton resonance of SQDs to control the local-fields that couple the MNPs and SQDs. We identify regimes where dark modes and higher order multipolar modes can influence hybrid response. External fields do not directly drive MNP dark modes, so SQD/MNP coupling is dominated by the local induced coupling, providing a situation in which the induced self-interaction could be probed using near field techniques. Finally, we consider a system of two SQDs coupled to a MNP. In particular, we identify and address issues in modeling the system using a semiclassical approach, which can lead to unstable and chaotic behavior in a strong SQD-SQD coupling regime. When we model the system using a more quantum mechanical approach, this chaotic regime is absent. Finally, we compare the two models on a system with a strong plasmon-mediated interaction between the SQDs and a weak direct interaction

  14. Examining the effects of metal mining mixtures on fathead minnow (Pimephales promelas) using field-based multi-trophic artificial streams.

    PubMed

    Rozon-Ramilo, Lisa D; Dubé, Monique G; Rickwood, Carrie J; Niyogi, Som

    2011-09-01

    This study illustrates the use of a mesocosm approach for assessing the independent effects of three treated metal mine effluents (MME) discharging into a common receiving environment and regulated under the same regulation. A field-based, multi-trophic artificial stream study was conducted in August 2008 to assess the effects of three metal mining effluents on fathead minnow (Pimephales promelas) in a 21-day reproduction bioassay. The nature of the approach allowed for assessment of both dietary and waterborne exposure pathways. Elements (e.g. Se, Co, Cl, Cu, Fe) were analyzed in several media (water, sediments) and tissues (biofilm, Chironomus dilutus, female fathead minnow (FHM) body, ovary, liver, gills). Significant increases in metal and micronutrient concentrations were observed in the water and biofilm tissues in all MME treatments [20% surface water effluent (SWE), 30% mine water effluent (MWE), and 45% process water effluent (PWE)], compared to reference. However, copper was the only element to significantly increase in the sediments when exposed to PWE. Co and Ni increased significantly in C. dilutus tissues in SWE (1.4- and 1.5-fold, respectively), Cu and Se also increased in chironomid tissues in PWE (5.2- and 3.3-fold, respectively); however, no significant increases in metals or micronutrients occurred in chironomid tissues when exposed to MWE compared to reference. There were no significant increases in metal concentrations in female FHM tissues (body, liver, gonads, gills) in any of the treatments suggesting that metals were either not bioavailable, lost from the females via the eggs, or naturally regulated through homeostatic mechanisms. Cumulative number of eggs per female per day increased significantly (∼127%) after exposure to SWE and decreased significantly (∼33%) after exposure to PWE when compared to reference. Mean total number of days to hatch was reduced in PWE compared to reference. This study shows the importance of isolating

  15. Characterization of a novel rice metallothionein gene promoter: its tissue specificity and heavy metal responsiveness.

    PubMed

    Dong, Chun-Juan; Wang, Yun; Yu, Shi-Shi; Liu, Jin-Yuan

    2010-10-01

    The rice (Oryza sativa L.) metallothionein gene OsMT-I-4b has previously been identified as a type I MT gene. To elucidate the regulatory mechanism involved in its tissue specificity and abiotic induction, we isolated a 1 730 bp fragment of the OsMT-I-4b promoter region. Histochemical β-glucuronidase (GUS) staining indicated a precise spacial and temporal expression pattern in transgenic Arabidopsis. Higher GUS activity was detected in the roots and the buds of flower stigmas, and relatively lower GUS staining in the shoots was restricted to the trichomes and hydathodes of leaves. No activity was observed in the stems and seeds. Additionally, in the root of transgenic plants, the promoter activity was highly upregulated by various environmental signals, such as abscisic acid, drought, dark, and heavy metals including Cu²(+) , Zn²(+) , Pb²(+) and Al³(+) . Slight induction was observed in transgenic seedlings under salinity stress, or when treated with Co²(+) and Cd²(+) . Promoter analysis of 5'-deletions revealed that the region -583/-1 was sufficient to drive strong GUS expression in the roots but not in the shoots. Furthermore, deletion analysis indicated important promoter regions containing different metal-responsive cis-elements that were responsible for responding to different heavy metals. Collectively, these findings provided important insight into the transcriptional regulation mechanisms of the OsMT-I-4b promoter, and the results also gave us some implications for the potential application of this promoter in plant genetic engineering.

  16. Responsive nanoporous metals: recoverable modulations on strength and shape by watering

    NASA Astrophysics Data System (ADS)

    Ye, Xing-Long; Liu, Ling-Zhi; Jin, Hai-Jun

    2016-08-01

    Many biological materials can readily modulate their mechanical properties and shape by interacting with water in the surrounding environment, which is essential to their high performance in application. In contrast, typical inorganic materials (such as the metals) cannot change their strength and shape without involving thermal/mechanical treatments. By introducing nano-scale porous structure and exploiting a simple physical concept—the water-capillarity in nanopores, here we report that a ‘dead’ metal can be transformed into a ‘smart’ material with water-responsive properties. We demonstrate that the apparent strength, volume and shape of nanoporous Au and Au(Pt) can be modulated in situ, dramatically and recoverably, in response to water-dipping and partial-drying. The amplitude of strength-modulation reaches 20 MPa, which is nearly 50% of the yield strength at initial state. This approach also leads to reversible length change up to 1.3% in nanoporous Au and a large reversible bending motion of a bi-layer strip with tip displacement of ∼20 mm, which may be used for actuation. This method is simple and effective, occurring in situ under ambient conditions and requiring no external power, analogous to biological materials. The findings may open up novel applications in many areas such as micro-robotics and bio-medical devices.

  17. Responsive nanoporous metals: recoverable modulations on strength and shape by watering.

    PubMed

    Ye, Xing-Long; Liu, Ling-Zhi; Jin, Hai-Jun

    2016-08-12

    Many biological materials can readily modulate their mechanical properties and shape by interacting with water in the surrounding environment, which is essential to their high performance in application. In contrast, typical inorganic materials (such as the metals) cannot change their strength and shape without involving thermal/mechanical treatments. By introducing nano-scale porous structure and exploiting a simple physical concept-the water-capillarity in nanopores, here we report that a 'dead' metal can be transformed into a 'smart' material with water-responsive properties. We demonstrate that the apparent strength, volume and shape of nanoporous Au and Au(Pt) can be modulated in situ, dramatically and recoverably, in response to water-dipping and partial-drying. The amplitude of strength-modulation reaches 20 MPa, which is nearly 50% of the yield strength at initial state. This approach also leads to reversible length change up to 1.3% in nanoporous Au and a large reversible bending motion of a bi-layer strip with tip displacement of ∼20 mm, which may be used for actuation. This method is simple and effective, occurring in situ under ambient conditions and requiring no external power, analogous to biological materials. The findings may open up novel applications in many areas such as micro-robotics and bio-medical devices.

  18. Transcriptomic Analysis of Cadmium Stress Response in the Heavy Metal Hyperaccumulator Sedum alfredii Hance

    PubMed Central

    Yang, Xiaoe; Liu, Jian-Xiang

    2013-01-01

    The Sedum alfredii Hance hyperaccumulating ecotype (HE) has the ability to hyperaccumulate cadmium (Cd), as well as zinc (Zn) and lead (Pb) in above-ground tissues. Although many physiological studies have been conducted with these plants, the molecular mechanisms underlying their hyper-tolerance to heavy metals are largely unknown. Here we report on the generation of 9.4 gigabases of adaptor-trimmed raw sequences and the assembly of 57,162 transcript contigs in S. alfredii Hance (HE) shoots by the combination of Roche 454 and Illumina/Solexa deep sequencing technologies. We also have functionally annotated the transcriptome and analyzed the transcriptome changes upon Cd hyperaccumulation in S. alfredii Hance (HE) shoots. There are 110 contigs and 123 contigs that were up-regulated (Fold Change ≧2.0) and down-regulated (Fold Change ≦0.5) by chronic Cd treatment in S. alfredii Hance (HE) at q-value cutoff of 0.005, respectively. Quantitative RT-PCR was employed to compare gene expression patterns between S. alfredii Hance (HE) and non-hyperaccumulating ecotype (NHE). Our results demonstrated that several genes involved in cell wall modification, metal translocation and remobilization were more induced or constitutively expressed at higher levels in HE shoots than that in NHE shoots in response to Cd exposure. Together, our study provides large-scale expressed sequence information and genome-wide transcriptome profiling of Cd responses in S. alfredii Hance (HE) shoots. PMID:23755133

  19. Thermoelastic response of metal matrix composites with large-diameter fibers subjected to thermal gradients

    NASA Technical Reports Server (NTRS)

    Aboudi, Jacob; Pindera, Marek-Jerzy; Arnold, Steven M.

    1993-01-01

    A new micromechanical theory is presented for the response of heterogeneous metal matrix composites subjected to thermal gradients. In contrast to existing micromechanical theories that utilize classical homogenization schemes in the course of calculating microscopic and macroscopic field quantities, in the present approach the actual microstructural details are explicitly coupled with the macrostructure of the composite. Examples are offered that illustrate limitations of the classical homogenization approach in predicting the response of thin-walled metal matrix composites with large-diameter fibers when subjected to thermal gradients. These examples include composites with a finite number of fibers in the thickness direction that may be uniformly or nonuniformly spaced, thus admitting so-called functionally gradient composites. The results illustrate that the classical approach of decoupling micromechanical and macromechanical analyses in the presence of a finite number of large-diameter fibers, finite dimensions of the composite, and temperature gradient may produce excessively conservative estimates for macroscopic field quantities, while both underestimating and overestimating the local fluctuations of the microscopic quantities in different regions of the composite. Also demonstrated is the usefulness of the present approach in generating favorable stress distributions in the presence of thermal gradients by appropriately tailoring the internal microstructure details of the composite.

  20. High-frequency response of subwavelength-structured metals in the petahertz domain.

    PubMed

    Weiner, J; Nunes, Frederico D

    2008-12-22

    Electromagnetic plane waves, incident on and reflecting from a dielectric-conductor interface, set up a standing wave in the dielectric with the B-field adjacent to the conductor. It is shown here how the harmonic time variation of this B-field induces an E-field and a conduction current J (c) within the skin depth of a real metal; and that at frequencies in the visible and near-infrared range, the imaginary term sigmai of the complex conductivity sigma = sigma(r) + isigma(i) dominates the optical response. Continuity conditions of the E-field through the surface together with the in-quadrature response of the conductivity determine the phase relation between the incident E-M field and J(c). If slits or grooves are milled into the metal surface, a displacement current in the dielectric gap and oscillating charge dipoles at the structure edges are established in quadrature phase with incident field. These dipoles radiate into the aperture and launch surface waves from the edges. They are the principle source of light transmission through the apertures.

  1. Nicotianamine synthase gene family as central components in heavy metal and phytohormone response in maize.

    PubMed

    Zhou, Mei-Liang; Qi, Lei-Peng; Pang, Jun-Feng; Zhang, Qian; Lei, Zhi; Tang, Yi-Xiong; Zhu, Xue-Mei; Shao, Ji-Rong; Wu, Yan-Min

    2013-06-01

    Nicotianamine (NA) is an important divalent metal chelator and the main precursor of phytosiderophores. NA is synthesized from S-adenosylmethionine in a process catalyzed by nicotianamine synthase (NAS). In this study, a set of structural and phylogenetic analyses have been applied to identify the maize NAS genes based on the maize genome sequence release. Ten maize NAS genes have been mapped; seven of them have not been reported to date. Phylogenetic analysis and expression pattern from microarray data led to their classification into two different orthologous groups. C-terminal fusion of ZmNAS3 with GFP was found in the cytoplasm of Arabidopsis leaf protoplast. Expression analysis by reverse transcription polymerase chain reaction revealed ZmNAS genes are responsive to heavy metal ions (Ni, Fe, Cu, Mn, Zn, and Cd), and all 10 ZmNAS genes were only observed in the root tissue except of ZmNAS6. The promoter of ZmNAS genes was analyzed for the presence of different cis-element response to all kinds of phytohormones and environment stresses. We found that the ZmNAS gene expression of maize seedlings was regulated by jasmonic acid, abscisic acid, and salicylic acid. Microarray data demonstrated that the ZmNAS genes show differential, organ-specific expression patterns in the maize developmental steps. The integrated comparative analysis can improve our current view of ZmNAS genes and facilitate the functional characterization of individual members.

  2. Synthesis of air stable FeCo/C alloy nanoparticles by decomposing a mixture of the corresponding metal-acetyl acetonates under their autogenic pressure.

    PubMed

    Holodelshikov, Elena; Perelshtein, Ilana; Gedanken, Aharon

    2011-02-21

    A mixture of Fe(AcAc)(2) and Co(AcAC)(2) was thermolyzed in a closed cell under the autogenic pressure of the reactants. The nature of the products was temperature dependent. The reaction is a one-stage, simple, efficient, and solvent-free method to prepare FeCo alloy nanoparticles protected by a carbon shell. Particle sizes of 60-150 were obtained covered by a carbon layer of 3-4 nm. The air stability of these particles is also demonstrated.

  3. Toxicity of a hazardous chemical mixture in the planarian, Dugesia dorotocephala

    SciTech Connect

    Ramsdell, H.S.; Matthews, C.M.

    1995-12-31

    The responses of the planarian, Dugesia dorotocephala to toxic chemical mixtures representative of water contaminants associated with hazardous waste sites have been studied in laboratory experiments. These free-living flatworms are readily maintained under laboratory conditions and are a useful invertebrate model for toxicology studies. Their widespread occurrence also makes them potentially useful for environmental studies. Mature asexual Dugesia dorotocephala were exposed for 14 days to mixtures of seven contaminants frequently detected in water at hazardous waste sites. The complete 1X mixture contained both metals (As, 3.1 ppm; Cr, 0.7 ppm; Pb, 3.7 ppm) and organics (chloroform, 1.5 ppm; benzene, 5.0 ppm; phenol, 3.4 ppm; trichloroethylene, 3.8 ppm). Groups of planaria were treated with the complete mixture at 0.1X, 1X and 10X concentrations. Additional groups were exposed to the metals-only or organics-only submixtures, also at 0.1X, 1X and 10X concentrations. Treatment solutions were renewed daily. Suppression of fissioning was observed in all of the 1X and 10X treatment groups. Significant mortality occurred only in the 10X complete and 1 0X metals-only treatments. It appears that the toxic effects of the complete mixture are primarily associated with the metal components.

  4. Separation and Identification of a Mixture of Group 6 Transition-Metal Carbonyl Compounds Using GC-MS in the General Chemistry Curriculum

    ERIC Educational Resources Information Center

    Fong, Lawrence K.

    2004-01-01

    Students in the general chemistry course are advised to scrutinize data obtained by gas chromatograph (GC) for segregation, and mass spectroscopy (MS) for recognizing combination of group 6 transition-metal carbonyl compounds. The GC-MS method arouses students' interest, as it can be applied to real-world situations, such as the routine…

  5. Differential expression of metallothioneins in response to heavy metals and their involvement in metal tolerance in the symbiotic basidiomycete Laccaria bicolor.

    PubMed

    Reddy, M Sudhakara; Prasanna, Lakshmi; Marmeisse, R; Fraissinet-Tachet, L

    2014-10-01

    Cysteine-rich peptides such as metallothioneins (MTs) are involved in metal homeostasis and detoxification in many eukaryotes. We report the characterization and expression of two MT genes, LbMT1 and LbMT2 from the ectomycorrhizal fungus Laccaria bicolor under metal stress conditions. LbMT1 and LbMT2 differ with respect to the length of the encoded peptides (58 versus 37 aa, respectively) and also by their expression patterns in response to metals. The expression levels of both LbMT1 and LbMT2 increased as a function of increased external Cu concentration, the expression levels for LbMT2 were always significantly higher compared with those of LbMT1. Only LbMT1, but not LbMT2, responded to Cd supply in the range of 25-100 µM while Zn did not affect the transcription of either LbMT1 or LbMT2. Both genes also responded to oxidative stress, but to a lesser extent compared to their responses to either Cu or Cd stress. Heterologous complementation assays in metal-sensitive yeast mutants indicated that both LbMT1 and LbMT2 encode peptides capable of conferring higher tolerance to both Cu and Cd. The present study identified LbMTs as potential determinants of the response of this mycorrhizal fungus to Cu and Cd stress.

  6. Shock Wave Response of Iron-based In Situ Metallic Glass Matrix Composites

    PubMed Central

    Khanolkar, Gauri R.; Rauls, Michael B.; Kelly, James P.; Graeve, Olivia A.; Hodge, Andrea M.; Eliasson, Veronica

    2016-01-01

    The response of amorphous steels to shock wave compression has been explored for the first time. Further, the effect of partial devitrification on the shock response of bulk metallic glasses is examined by conducting experiments on two iron-based in situ metallic glass matrix composites, containing varying amounts of crystalline precipitates, both with initial composition Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4. The samples, designated SAM2X5-600 and SAM2X5-630, are X-ray amorphous and partially crystalline, respectively, due to differences in sintering parameters during sample preparation. Shock response is determined by making velocity measurements using interferometry techniques at the rear free surface of the samples, which have been subjected to impact from a high-velocity projectile launched from a powder gun. Experiments have yielded results indicating a Hugoniot Elastic Limit (HEL) to be 8.58 ± 0.53 GPa for SAM2X5-600 and 11.76 ± 1.26 GPa for SAM2X5-630. The latter HEL result is higher than elastic limits for any BMG reported in the literature thus far. SAM2X5-600 catastrophically loses post-yield strength whereas SAM2X5-630, while showing some strain-softening, retains strength beyond the HEL. The presence of crystallinity within the amorphous matrix is thus seen to significantly aid in strengthening the material as well as preserving material strength beyond yielding. PMID:26932846

  7. Bioaccumulation of heavy metals by shrimp (Litopenaeus schmitti): A dose-response approach for coastal resources management.

    PubMed

    Nascimento, Juliana Ribeiro; Sabadini-Santos, Elisamara; Carvalho, Cassia; Keunecke, Karina Annes; César, Ricardo; Bidone, Edison D

    2017-01-30

    We reveal a dose-response relationship for bioaccumulation of Zn, Cu and Cr in shrimp Litopenaeus schmitti from Sepetiba Bay, Rio de Janeiro, Brazil. Our model estimates the current risk (AD50 was 70% of the legal limit) and the daily metal uptake rate for each metal. It can also evaluate the relative reliability of predictions for tissue concentrations reaching the legal limits for human consumption (approximately 1year) and predictions related to asymptotic length, arising from (i) direct regression of the metal concentration (MeC) versus total length (TL) and age (duration of exposure), and (ii) correlation of the incorporation rate (IR=MeC/TL) with age. Metal incorporation rates (IR), i.e. a kinetic proxy for absorption during growth up to attainment of asymptotic length, decrease with age, reflecting a slow-down in metal absorption. This pattern mitigates the high initial concentrations observed for juveniles.

  8. Mechanism Underlying Time-dependent Cross-phenomenon between Concentration-response Curves and Concentration Addition Curves: A Case Study of Sulfonamides-Erythromycin mixtures on Escherichia coli

    NASA Astrophysics Data System (ADS)

    Sun, Haoyu; Ge, Hongming; Zheng, Min; Lin, Zhifen; Liu, Ying

    2016-09-01

    Previous studies have identified a phenomenon in which the concentration-response curves (CRCs) for mixtures cross the curves for concentration addition model when predicting or judging joint toxic actions. However, mechanistic investigations of this phenomenon are extremely limited. In this study, a similar phenomenon was observed when we determined the joint toxic actions of sulfonamides (SAs) and erythromycin (ERY) on Escherichia coli (E. coli), which we named the “cross-phenomenon”, and it was characterized by antagonism in the low-concentration range, addition in the medium-concentration range, and synergism in the high-concentration range. The mechanistic investigation of the cross-phenomenon was as follows: SAs and ERY could form a double block to inhibit the bacterial growth by exhibiting a synergistic effect; however, the hormetic effect of SAs on E. coli led to antagonism in the low-concentration range, resulting from the stimulation of sdiA mRNA expression by SAs, which increased the expression of the efflux pump (AcrAB-TolC) to discharge ERY. Furthermore, this cross-phenomenon was observed to be a time-dependent process induced by the increase of both the concentration and extent of stimulation of sdiA mRNA with exposure time. This work explains the dose-dependent and time-dependent cross-phenomenon and provides evidence regarding the interaction between hormesis and cross-phenomenon.

  9. Relative Spectral Mixture Analysis for monitoring natural hazards that impact vegetation cover: the importance of the nonphotosynthetic fraction in understanding landscape response to drought, fire, and hurricane damage

    NASA Astrophysics Data System (ADS)

    Okin, G. S.

    2007-12-01

    Remote sensing provides a unique ability to monitor natural hazards that impact vegetation hydrologically. Here, the use of a new multitemporal remote sensing technique that employs free, coarse multispectral remote sensing data is demonstrated in monitoring short- and long-term drought, fire occurrence and recovery, and damage to hurricane-related mangrove ecosystems and subsequent recovery of these systems. The new technique, relative spectral mixture analysis (RSMA), provides information about the nonphotosynthetic fraction (nonphotosynthetic vegetation plus litter) of ground cover in addition to the green vegetation fraction. In some cases, RSMA even provides an improved ability to monitor changes in the green fraction compared to traditional vegetation indices or standard remote sensing products. In arid and semiarid regions, the nonphotosynthetic fraction can vary on an annual basis significantly more than the green fraction and is thus perfectly suited for monitoring drought in these regions. Mortality of evergreen trees due to long-term drought also shows up strongly in the nonphotosynthetic fraction as green vegetation is replaced by dry needles and bare trunks. The response of the nonphotosynthetic fraction to fire is significantly different from that of drought because of the combustion of nonphotosynthetic material. Finally, damage to mangrove ecosystems from hurricane damage, and their subsequent recovery, is readily observable in both the green and nonphotosynthetic fractions as estimated by RSMA.

  10. Mechanism Underlying Time-dependent Cross-phenomenon between Concentration-response Curves and Concentration Addition Curves: A Case Study of Sulfonamides-Erythromycin mixtures on Escherichia coli

    PubMed Central

    Sun, Haoyu; Ge, Hongming; Zheng, Min; Lin, Zhifen; Liu, Ying

    2016-01-01

    Previous studies have identified a phenomenon in which the concentration-response curves (CRCs) for mixtures cross the curves for concentration addition model when predicting or judging joint toxic actions. However, mechanistic investigations of this phenomenon are extremely limited. In this study, a similar phenomenon was observed when we determined the joint toxic actions of sulfonamides (SAs) and erythromycin (ERY) on Escherichia coli (E. coli), which we named the “cross-phenomenon”, and it was characterized by antagonism in the low-concentration range, addition in the medium-concentration range, and synergism in the high-concentration range. The mechanistic investigation of the cross-phenomenon was as follows: SAs and ERY could form a double block to inhibit the bacterial growth by exhibiting a synergistic effect; however, the hormetic effect of SAs on E. coli led to antagonism in the low-concentration range, resulting from the stimulation of sdiA mRNA expression by SAs, which increased the expression of the efflux pump (AcrAB-TolC) to discharge ERY. Furthermore, this cross-phenomenon was observed to be a time-dependent process induced by the increase of both the concentration and extent of stimulation of sdiA mRNA with exposure time. This work explains the dose-dependent and time-dependent cross-phenomenon and provides evidence regarding the interaction between hormesis and cross-phenomenon. PMID:27644411

  11. Comparative sodium transport patterns provide clues for understanding salinity and metal responses in aquatic insects.

    PubMed

    Scheibener, S A; Richardi, V S; Buchwalter, D B

    2016-02-01

    The importance of insects in freshwater ecosystems has led to their extensive use in ecological monitoring programs. As freshwater systems are increasingly challenged by salinization and metal contamination, it is important to understand fundamental aspects of aquatic insect physiology (e.g., osmoregulatory processes) that contribute to insect responses to these stressors. Here we compared the uptake dynamics of Na as NaCl, NaHCO3 and Na2SO4 in the caddisfly Hydropsyche betteni across a range of Na concentrations (0.06-15.22 mM) encompassing the vast majority of North American freshwater ecosystems. Sulfate as the major anion resulted in decreased Na uptake rates relative to the chloride and bicarbonate salts. A comparison of Na (as NaHCO3) turnover rates in the caddisfly Hydropsyche sparna and the mayfly Maccaffertium sp. revealed different patterns in the 2 species. Both species appeared to tightly regulate their whole body sodium concentrations (at ∼47±1.8 μmol/g wet wt) across a range of Na concentrations (0.06-15.22 mM) over 7 days. However, at the highest Na concentration (15.22 mM), Na uptake rates in H. sparna (419.1 μM Na g(-1) hr(-1) wet wt) appeared close to saturation while Na uptake rates in Maccaffertium sp. were considerably faster (715 g μM Na g(-1) hr(-1) wet wt) and appeared to not be close to saturation. Na efflux studies in H. sparna revealed that loss rates are commensurate with uptake rates and are responsive to changes in water Na concentrations. A comparison of Na uptake rates (at 0.57 mM Na) across 9 species representing 4 major orders (Ephemeroptera, Plecoptera, Trichoptera and Diptera) demonstrated profound physiological differences across species after accounting for the influence of body weight. Faster Na uptake rates were associated with species described as being sensitive to salinization in field studies. The metals silver (Ag) and copper (Cu), known to be antagonistic to Na uptake in other aquatic taxa did not generally

  12. The involvement of HSP22 from bay scallop Argopecten irradians in response to heavy metal stress.

    PubMed

    Zhang, Lei; Wang, Lingling; Song, Linsheng; Zhao, Jianmin; Qiu, Limei; Dong, Chaohua; Li, Fengmei; Zhang, Huan; Yang, Guanpin

    2010-04-01

    Heat shock protein 22 (HSP22) is an important member of small heat shock protein (sHSP) subfamily which plays a key role in the process of protecting cells, facilitating the folding of nascent peptides, and responding to stress. In the present study, the cDNA of HSP22 was cloned from Argopecten irradians (designated as AiHSP22) by rapid amplification cDNA end (RACE) based on the expressed sequence tags (ESTs). The full-length cDNA of AiHSP22 was of 1,112 bp, with an open reading frame of 588 bp encoding a polypeptide of 195 amino acids. The deduced amino acid sequence of AiHSP22 showed high similarity to previously identified HSP22s. The expression patterns of AiHSP22 mRNA in different tissues and in haemocytes of scallops exposed to Cd(2+), Pb(2+) or Cu(2+) were investigated by real-time quantitative RT-PCR. The mRNA of AiHSP22 was constitutively expressed in all examined tissues, including haemocyte, muscle, kidney, gonad, gill and heart. The expression level in heart and muscle was higher than that in other tissues. The mRNA level of AiHSP22 in haemocytes was up-regulated after a 10 days exposure of scallops to Cu(2+), Pb(2+) and Cd(2+). However, the expression of AiHSP22 did not increase linearly along with the rise of heavy metal concentration. Different concentrations of the same metal resulted in different effects on AiHSP22 expression. The sensitive response of AiHSP22 to Cu(2+), Pb(2+) and Cd(2+) stress indicated that it could be developed as an indicator of exposure to heavy metals for the pollution monitoring programs in aquatic environment.

  13. Evaluation of a novel inhalation exposure system to determine acute respiratory responses to tobacco and polymer pyrolysate mixtures in Swiss-Webster mice.

    PubMed

    Werley, Michael S; Lee, K Monica; Lemus, Ranulfo

    2009-07-01

    Modern cigarette production processes are highly automated and yield millions of cigarettes per day. The forming cigarette and its components contact many different materials in the production process, some of which may leave minute residues. The potential for small inclusions of non-cigarette materials such as wood, plastic, cardboard and other materials exists from the bulk handling and processing of tobacco, in spite of vigilant workers and numerous online systems designed to keep the tobacco stream clean. Currently, there are no published methods that describe an approach to evaluate the potential toxicological impact of these non-tobacco residues and inclusions on the biological activity from exposure to the complex mixture of tobacco smoke. There are, however, many methods which describe toxicological evaluation approaches for pure materials, particularly synthetic polymers. We used the Deutsche Institute fur Normung (DIN) 53-436 tube furnace and nose-only exposure chamber in combination to conduct pilot studies in Swiss-Webster mice in order to develop a standardized methodology for the evaluation of sensory irritation and other potentially useful biological endpoints for predicting any potential hazards. Sensory and/or pulmonary irritation was assessed based on respiratory function parameters using the ASTM E981-84 method described by Alarie (1966) in mice, exposed to test atmospheres of 100% tobacco pyrolysate or tobacco/polymer pyrolysate mixtures. Other biological evaluations included respiratory function parameters, clinical signs, body weights, bronchoalveolar lavage fluid analysis, carboxyhemoglobin, blood cyanide concentrations and histopathology of the respiratory tract. These pilot studies have demonstrated that such an approach can detect biological changes resulting from exposure to unique tobacco/polymer pyrolysates. Small differences were detected in the sensory irritation responses (respiratory function), activation state of pulmonary

  14. Use of Doehlert and constrained mixture designs in the development of a photo-oxidation procedure using UV radiation/H₂O₂ for decomposition of landfill leachate samples and determination of metals by flame atomic absorption spectrometry.

    PubMed

    Bezerra, Marcos A; Souza, Antônio D S; Oliveira, Rafael V; Oliveira, Djalma M; Cardoso, Luiz A M; Sousa Filho, Hélio R

    2015-03-01

    This work proposes the use of photo-oxidation degradation with UV radiation/H2O2 as sample treatment for the determination of Fe, Zn, Mn, Ni and Co in municipal solid waste landfill leachate by flame atomic absorption spectrometry (FAAS). Three variables (pH, irradiation time and buffer concentration) were optimized using Doehlert design and the proportions of mixture components submitted to UV radiation (leachate sample, buffer solution and H2O2 30%, v/v) were optimized using a constrained mixture design. Using the experimental conditions established, this procedure allows limits of detection of 0.075, 0.025, 0.010, 0.075 and 0.041 µg mL-1, and the precision levels expressed as relative standard (%RSD, 0.5 µg mL-1) were 3.6, 1.8, 1.3, 3.3 and 1.7%, for Fe, Mn, Zn, Ni and Co respectively. Recovery tests were carried out for evaluation of the procedure accuracy and recoveries were between 92 and 106% for the studied metals. This procedure has been applied for the analysis of the landfill leachate collected in Jequié, a city of the southwestern region of the State of Bahia, Brazil. The results were compared with those obtained by acid digestion. There was no significant difference between the results obtained by the two methods based on paired t-test at 95% confidence level.

  15. Dermatotoxicity of cutting fluid mixtures:in vitro and in vivo studies.

    PubMed

    Monteiro-Riviere, Nancy A; Inman, Alfred O; Barlow, Beth M; Baynes, Ronald E

    2006-01-01

    Cutting fluids are widely used in the metal-machining industry to lubricate and reduce heat generation when metals are cut by a metal-cutting tool. These cutting fluids have caused occupational irritant contact dermatitis (OICD), and many of the additives used in these cutting fluid mixtures are thought to be responsible for OICD in workers. The purpose of this study was to assess single or various combinations of these additives in initiating the OICD response following an acute 8-hour exposure in porcine skin in vivo and in vitro using the isolated perfused porcine skin flap (IPPSF) and human epidermal keratinocytes (HEK). Pigs (n = 4) were exposed to 5% mineral oil (MO) or 5% polyethylene glycol (PEG) aqueous mixtures containing various combinations of 2% triazine (TRI), 5% triethanolamine (TEA), 5% linear alkylbenzene sulfonate (LAS), or 5% sulfurized ricinoleic acid (SRA). Erythema and edema were evaluated and skin biopsies for histopathology were obtained at 4 and 8 hours. IPPSFs (n = 4) were exposed to control MO or PEG mixtures and complete MO or PEG mixtures, and perfusate samples were collected hourly to determine interleukin- (IL-) 8 release. The only significant (p < 0.05) mixture effects observed in IPPSFs were with SRA + MO that caused an increase in IL-8 release after 1 or 2 hours' exposure. In vivo exposure to TRI alone appeared to increase erythema, edema, and dermal inflammation compared to the other additives, while SRA alone was least likely to initiate a dermal inflammatory response. In 2-component mixture exposures, the presence of TRI appeared to increase the dermal inflammatory response at 4 and 8 hours especially with the PEG mixtures. In the 3- and 4-component mixtures, MO mixtures are more likely to incite an inflammatory response than PEG mixtures. TRI exhibited the highest toxicity toward HEK, which correlates well to the in vivo irritation and morphology results. In summary, these preliminary studies suggest that the biocide, TRI, is

  16. Single Exposure to near Roadway Particulate Matter Leads to Confined Inflammatory and Defense Responses: Possible Role of Metals.

    PubMed

    Pardo, Michal; Shafer, Martin M; Rudich, Assaf; Schauer, James J; Rudich, Yinon

    2015-07-21

    Inhalation of traffic-associated atmospheric particulate matter (PM2.5) is recognized as a significant health risk. In this study, we focused on a single ("subclinical response") exposure to water-soluble extracts from PM collected at a roadside site in a major European city to elucidate potential components that drive pulmonary inflammatory, oxidative, and defense mechanisms and their systemic impacts. Intratracheal instillation (IT) of the aqueous extracts induced a 24 h inflammatory response characterized by increased broncho-alveolar lavage fluid (BALF) cells and cytokines (IL-6 and TNF-α), increased reactive oxygen species production, but insignificant lipids and proteins oxidation adducts in mouse lungs. This local response was largely self-resolved by 48 h, suggesting that it could represent a subclinical response to everyday-level exposure. Removal of soluble metals by chelation markedly diminished the pulmonary PM-mediated response. An artificial metal solution (MS) recapitulated the PM extract response. The self-resolving nature of the response is associated with activating defense mechanisms (increased levels of catalase and glutathione peroxidase expression), observed with both PM extract and MS. In conclusion, metals present in PM collected near roadways are largely responsible for the observed transient local pulmonary inflammation and oxidative stress. Simultaneous activation of the antioxidant defense response may protect against oxidative damage.

  17. An Investigation of High-Cycle Fatigue Models for Metallic Structures Exhibiting Snap-Through Response

    NASA Technical Reports Server (NTRS)

    Przekop, Adam; Rizzi, Stephen A.; Sweitzer, Karl A.

    2007-01-01

    A study is undertaken to develop a methodology for determining the suitability of various high-cycle fatigue models for metallic structures subjected to combined thermal-acoustic loadings. Two features of this problem differentiate it from the fatigue of structures subject to acoustic loading alone. Potentially large mean stresses associated with the thermally pre- and post-buckled states require models capable of handling those conditions. Snap-through motion between multiple post-buckled equilibrium positions introduces very high alternating stress. The thermal-acoustic time history response of a clamped aluminum beam structure with geometric and material nonlinearities is determined via numerical simulation. A cumulative damage model is employed using a rainflow cycle counting scheme and fatigue estimates are made for 2024-T3 aluminum using various non-zero mean fatigue models, including Walker, Morrow, Morrow with true fracture strength, and MMPDS. A baseline zero-mean model is additionally considered. It is shown that for this material, the Walker model produces the most conservative fatigue estimates when the stress response has a tensile mean introduced by geometric nonlinearity, but remains in the linear elastic range. However, when the loading level is sufficiently high to produce plasticity, the response becomes more fully reversed and the baseline, Morrow, and Morrow with true fracture strength models produce the most conservative fatigue estimates.

  18. Steps toward thin film metal thermistors with microsecond time response for shock temperature measurements of polymers

    NASA Astrophysics Data System (ADS)

    Taylor, N. E.; Williamson, D. M.; Jardine, A. P.

    2014-05-01

    Equations of state can be used to predict the relationship between pressure, volume and temperature. However, in shock physics, they are usually only constrained by experimental observations of pressure and volume. Direct observation of temperature in a shock is therefore valuable in constraining equations of state. Bloomquist and Sheffield (1980, 1981) and Rosenberg and Partom (1984) have attempted such observations in poly(methyl methacrylate) (PMMA). However, their results disagree strongly above 2GPa shock pressure. Here we present an improved fabrication technique, to examine this outstanding issue. We make use of the fact that the electrical resistivity of most metals is a known function of both pressure and temperature. If the change in resistance of a thin metal thermistor gauge is measured during a shock experiment of known pressure, the temperature can be calculated directly. The time response is limited by the time taken for the gauge to reach thermal equilibrium with the medium in which it is embedded. Gold gauges of thickness up to 200 nm have been produced by thermal evaporation, and fully embedded in PMMA. These reach thermal equilibrium with the host material in under 1 us, allowing temperature measurement within the duration of a plate impact experiment.

  19. Thin film metal thermistors with microsecond time response for shock temperature measurements of polymers

    NASA Astrophysics Data System (ADS)

    Taylor, Nicholas; Williamson, David; Jardine, Andrew

    2013-06-01

    Equations of state can be used to predict the relationship between pressure, volume and temperature. However, in shock physics, they are usually only constrained by experimental observations of pressure and volume. Direct observation of temperature in a shock is therefore valuable in constraining equations of state. Bloomquist and Sheffield (1980, 1981) and Rosenberg and Partom (1984) have attempted such observations in PMMA. However, their results disagree strongly above 2 GPa shock pressure. Here we present an improved fabrication technique, to examine this outstanding issue. We make use of the fact that the electrical resistivity of most metals is a known function of both pressure and temperature. If the change in resistance of a thin metal thermistor gauge is measured during a shock experiment of known pressure, the temperature can be calculated directly. The time response is limited by the time taken for the gauge to reach thermal equilibrium with the medium in which it is embedded. Gold gauges of thickness up to 200 nm have been produced by evaporation, and fully embedded in PMMA. These reach thermal equilibrium with the host material in under 1 μs, allowing temperature measurement within the duration of a plate impact experiment.

  20. Co-sputtered metal and polymer nanocomposite films and their electrical responses for gas sensing application

    NASA Astrophysics Data System (ADS)

    Rujisamphan, Nopporn; Murray, Roy E.; Deng, Fei; Supasai, Thidarat

    2016-04-01

    Titanium and polytetrafluoroethylene (Ti-PTFE) nanocomposite thin films were successfully fabricated on glass substrates using a combination of dc and rf magnetron sputtering. When the Ti-PTFE composites were prepared at below the percolation threshold i.e. 27% metal volume filling (F), Ti clusters with the average sizes of 7 ± 2 nm were found. As the Ti content was increased above the percolation threshold (F = 62%), the connecting regions of Ti were formed within the polymer matrix and the electrical property changed rapidly from insulator-like to metal-like properties. The Ti-PTFE composites prepared near the percolation threshold showed the electrical response to different volatile organic compounds (VOCs). The sensitivity significantly depended upon the VOCs concentrations. These composites devices showed the presence of distinct chemical bonds of Csbnd C, Csbnd CF, Csbnd F and CF2 and TiF in TiO2 on the surface as investigated by X-ray photoelectron spectroscopy (XPS) while the surface morphology, characterized by atomic force microscopy (AFM) presented the root mean square (RMS) surface roughness of 13.3 nm. Cross-section transmission electron microscopy (TEM) images of the device revealed Ti clusters dispersed in PTFE matrix with particle sizes varied between 10 nm and 30 nm.