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Sample records for understanding sorption mechanisms

  1. Understanding the sorption behavior of Pu{sup 4+} on poly(amidoamine) dendrimer functionalized carbon nanotube. Sorption equilibrium, mechanism, kinetics, radiolytic stability, and back-extraction studies

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Parveen [Indian Institute of Technology, Himachal Pradesh (India); Sengupta, Arijit [Bahbha Atomic Research Centre, Mumbai (India). Radiochemistry Div.; Deb, Ashish Kumar Singha; Ali, S. Musharaf [Bahbha Atomic Research Centre, Mumbai (India). Chemical Engineering Div.; Homi Bhabha National Institute, Mumbai (India); Dasgupta, Kinshuk [Bhabha National Institute, Mumbai (India). Mechanical Metallurgy Div.

    2017-07-01

    Poly(amidoamine) dendrimer functionalized carbon nanotube was demonstrated as highly efficient sorbent of the Pu{sup 4+} from radioactive waste solution. The second generation dendrimer was found to have more efficiency as compared to the 1{sup st} generation might be due to the availability of more functionality for coordinating to the Pu{sup 4+} ion. Analysis of different isotherm models revealed that, Langmuir isotherm was predominantly operating through chemi-sorption (with the sorption energy 10.07 and 16.95 kJ mol{sup -1} for 1{sup st} and 2{sup nd} generation dendrimer) with the sorption capacity 89.22 mg g{sup -1} and 92.48 mg g{sup -1} for 1{sup st} and 2{sup nd} generation dendrimer, respectively. Analysis of different sorption kinetics model revealed that the sorption proceeded via pseudo 2{sup nd} order reaction. The 2{sup nd} generation dendrimer was found to be radiolytically more stable while oxalic acid was found to be suitable for quantitative back extraction of Pu{sup 4+}.

  2. Sorption mechanisms of perfluorinated compounds on carbon nanotubes

    International Nuclear Information System (INIS)

    Deng Shubo; Zhang Qiaoying; Nie Yao; Wei Haoran; Wang Bin; Huang Jun; Yu Gang; Xing Baoshan

    2012-01-01

    Sorption of perfluorinated compounds (PFCs) on carbon nanotubes (CNTs) is critical for understanding their subsequent transport and fate in aqueous environments, but the sorption mechanisms remain largely unknown. In this study, the sorption of six PFCs on CNTs increased with increasing C-F chain length when they had a same functional group, and the CNTs with hydroxyl and carboxyl groups had much lower adsorbed amount than the pristine CNTs, indicating that hydrophobic interaction dominated the sorption of PFCs on the CNTs. Electrostatic repulsion suppressed the sorption of PFCs on the CNTs, resulting in the lower sorption with increasing pH. Hydrogen bonding interaction was negligible. The hydrophobic C-F chains can be closely adsorbed on the CNTs surface in parallel to the axis or along the curvature, making it impossible to form micelles on the CNT surface, leading to the lower sorption than other adsorbents. Highlights: ► Sorption capacities of PFOA on different CNTs are less than that on activated carbon and resins. ► Hydrophobic interaction is principally involved in the sorption of PFCs on CNTs. ► Electrostatic repulsion suppresses the sorption of PFCs on CNTs. - Hydrophobic interaction dominated the sorption of perfluorinated compounds on carbon nanotubes, while electrostatic repulsion suppressed their sorption.

  3. Understanding the sorption mechanisms of aflatoxin B1 to kaolinite, illite, and smectite clays via a comparative computational study.

    Science.gov (United States)

    Kang, Fuxing; Ge, Yangyang; Hu, Xiaojie; Goikavi, Caspar; Waigi, Michael Gatheru; Gao, Yanzheng; Ling, Wanting

    2016-12-15

    In current adsorption studies of biotoxins to phyllosilicate clays, multiply weak bonding types regarding these adsorptions are not well known; the major attractive forces, especially for kaolinite and illite, are difficult to be identified as compared to smectite with exchangeable cations. Here, we discriminated the bonding types of aflatoxin B1 (AFB1) contaminant to these clays by combined batch experiment with model computation, expounded their bonding mechanisms which have been not quantitatively described by researchers. The observed adsorbent-to-solution distribution coefficients (K d ) of AFB1 presented in increasing order of 18.5-37.1, 141.6-158.3, and 354.6-484.7L/kg for kaolinite, illite, and smectite, respectively. Normalization of adsorbent-specific surface areas showed that adsorption affinity of AFB1 is mainly dependent on the outside surfaces of clay aggregates. The model computation and test of ionic effect further suggested that weakly electrostatic attractions ((Si/Al-OH) 2 ⋯(OC) 2 ) are responsible for AFB1-kaolinite adsorption (K d , 18.5-37.1L/kg); a moderate electron-donor-acceptor attraction ((CO) 2 ⋯K + ⋯(O-Al) 3 ) is related to AFB1-illite adsorption (K d , 141.6-158.3L/kg); a strong calcium-bridging linkage ((CO) 2 ⋯Ca 2+ ⋯(O-Si) 4 ) is involved in AFB1-smectite adsorption (K d , 354.6-484.7L/kg). Changes in Gibbs free energy (ΔG°) suggested that the computed result is reliable, providing a good reproduction of AFB1-clay interaction. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Recent progress in sorption mechanisms and models

    International Nuclear Information System (INIS)

    Fedoroff, M.; Lefevre, G.

    2005-01-01

    reactivity of the different faces. Finally, we know more about the sorption processes and are able to model them with a better agreement with the real sorption mechanisms. However, this progress concerns a few simple systems and a further task will be the application of this knowledge to more complex systems. (authors)

  5. Water sorption in ionic liquids: kinetics, mechanisms and hydrophilicity.

    Science.gov (United States)

    Cao, Yuanyuan; Chen, Yu; Sun, Xiaofu; Zhang, Zhongmin; Mu, Tiancheng

    2012-09-21

    Most of the ionic liquids (ILs) are hygroscopic in air. The effects of structural factors of ILs (cation, anion, alkyl chain length at cation, and C2 methylation at cation) and external factors (temperature, relative humidity, and impurity) on the kinetics of water sorption by 18 ILs were investigated. A modified two-step sorption mechanism was proposed to correlate the water sorption data in the ILs. Three type of parameters (sorption capacity, sorption rate and degree of difficulty to reach sorption equilibrium) based on the modified two-step mechanism were derived to comprehensively characterize the water sorption processes. These parameters have similar tendencies, providing an efficient way to evaluate them by one parameter that can be easily obtained. The hydrophilicity of the ILs was classified to four levels (super-high, high, medium, low) according to the water sorption capacity. The results show that cation of the ILs also plays an important role in water sorption, and the impurities affect the water sorption enormously. Acetate and halogen-based ILs have the highest hydrophilicity when combined with the imidazolium or pyridinium cation.

  6. Arsenic Sorption on Mechanically Activated Magnetite and Olivine

    Directory of Open Access Journals (Sweden)

    Zdenka Bujňáková

    2012-12-01

    Full Text Available Arsenic sorption on mechanically activated minerals such as magnetite Fe3O4 (Kiruna, Sweden and olivine (Mg,Fe2SiO4 (Ǻheim,Norway has been studied and compared in this work. Experiments were carried out with non-activated and mechanically activatedsamples. The activation of both minerals was performed in a planetary mill at different milling conditions. The specific surface areaand consequent sorption activity were enhanced by mechanical activation. The using of olivine seems to be better than magnetite fromthe point of view of milling time, which is necessary for achievement of the same sorption effect.

  7. Mechanisms of metal sorption by biochars: Biochar characteristics and modifications.

    Science.gov (United States)

    Li, Hongbo; Dong, Xiaoling; da Silva, Evandro B; de Oliveira, Letuzia M; Chen, Yanshan; Ma, Lena Q

    2017-07-01

    Biochar produced by thermal decomposition of biomass under oxygen-limited conditions has received increasing attention as a cost-effective sorbent to treat metal-contaminated waters. However, there is a lack of information on the roles of different sorption mechanisms for different metals and recent development of biochar modification to enhance metal sorption capacity, which is critical for biochar field application. This review summarizes the characteristics of biochar (e.g., surface area, porosity, pH, surface charge, functional groups, and mineral components) and main mechanisms governing sorption of As, Cr, Cd, Pb, and Hg by biochar. Biochar properties vary considerably with feedstock material and pyrolysis temperature, with high temperature producing biochars with higher surface area, porosity, pH, and mineral contents, but less functional groups. Different mechanisms dominate sorption of As (complexation and electrostatic interactions), Cr (electrostatic interactions, reduction, and complexation), Cd and Pb (complexation, cation exchange, and precipitation), and Hg (complexation and reduction). Besides sorption mechanisms, recent advance in modifying biochar by loading with minerals, reductants, organic functional groups, and nanoparticles, and activation with alkali solution to enhance metal sorption capacity is discussed. Future research needs for field application of biochar include competitive sorption mechanisms of co-existing metals, biochar reuse, and cost reduction of biochar production. Published by Elsevier Ltd.

  8. Study of sorption mechanisms of europium(3) and uranium(6) ions on clays : impact of silicates

    International Nuclear Information System (INIS)

    Kowal-Fouchard, A.

    2002-11-01

    Bentonite clay has been selected as a potential buffer or backfill material in a number of disposal programmes for high level waste. In order to enhance the thermodynamic database of sorption phenomena at the solid-water interface, we have investigated sorption mechanisms of europium(III) and uranium(VI) ions onto montmorillonite and bentonite. Thermodynamic data were obtained for different ions concentrations, different background electrolytes and different ionic strengths. The structural identification of the surface complexes and sorption sites was carried out using two spectroscopies, XPS and TRLIFS, while sorption edges were performed using batch experiments. However, clays are complex minerals and in order to understand these sorption mechanisms we have studied europium(III) and uranium(VI) retention on a silica and an alumina because these solids are often considered as basic components of clays. The comparison of structural results shows that europium ions are significantly sorbed on permanently charged sites of clay until pH 7. But this ion is also sorbed on ≡SiOH and ≡AlOH sites of montmorillonite at pH higher than 6. Uranyl ions sorption on montmorillonite is mainly explained by retention of three complexes on ≡SiOH sites. Moreover, we have shown that nitrate ions and dissolved silicates affect on uranium(VI) sorption mechanisms onto alumina. Nevertheless, uranyl ions sorption on montmorillonite and bentonite only decreases with increasing carbonate concentration. Finally, all the sorption edges were then modeled using these results and a surface complexation model (2 pK and constant capacitance models). (author)

  9. Sorption mechanisms of chromate with coprecipitated ferrihydrite in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Mamun, Abdullah Al, E-mail: mamun@toki.waseda.jp [Graduate School of Creative Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555 (Japan); Morita, Masao, E-mail: masao.swimer@akane.waseda.jp [Graduate School of Creative Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555 (Japan); Matsuoka, Mitsuaki, E-mail: m-matsuoka@aoni.waseda.jp [Faculty of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555 (Japan); Tokoro, Chiharu, E-mail: tokoro@waseda.jp [Faculty of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555 (Japan)

    2017-07-15

    Highlights: • Coprecipitation showed twice the sorption density of simple adsorption at pH 5. • Mechanism shift from outer- to inner-sphere surface complexation at high Cr/Fe. • In coprecipitation the mechanism shift occurs at lower Cr/Fe ratios than adsorption. • Higher-molar-ratio bidentate binuclear Cr−Fe bonds; yielded ferrihydrite expansion. - Abstract: Hexavalent chromium (Cr(VI)) attracted researchers’ interest for its toxicity, natural availability and removal difficulty. Nevertheless, its sorption mechanism is not clearly understood yet. In this work, we elucidated the sorption mechanism of the co-precipitation of chromates with ferrihydrite through quantitative analysis. The influence of Cr/Fe molar ratio on sorption was investigated by zeta potential measurements, X-ray diffraction (XRD) and X-ray adsorption fine-structure analysis (XAFS). Coprecipitation at pH 5 showed almost twice the sorption density of adsorption at pH 5. In co-precipitation, a shift of the XRD peak due to inner-sphere sorption of chromate was observed at Cr/Fe molar ratio 0.5. For adsorption, the same peak shift was confirmed at Cr/Fe molar ratio of 1. Zeta potential at pH 5 suggested that the sorption mechanism changed at Cr/Fe molar ratio 0.25 for coprecipitation and at Cr/Fe molar ratio of 1 for adsorption. Fitting of Cr and Fe K-edge extended X-ray adsorption fine-structure suggested that ferrihydrite immobilized Cr(VI) via outer sphere surface complexation for lower Cr/Fe ratios and via inner-sphere surface complexation for higher molar ratios. At higher molar ratios, bidentate binuclear Cr−Fe bonds were well established, thus resulting in the expansion of the ferrihydrite structure.

  10. Sorption compressor/mechanical expander hybrid refrigeration

    Science.gov (United States)

    Jones, J. A.; Britcliffe, M.

    1987-01-01

    Experience with Deep Space Network (DSN) ground-based cryogenic refrigerators has proved the reliability of the basic two-stage Gifford-McMahon helium refrigerator. A very long life cryogenic refrigeration system appears possible by combining this expansion system or a turbo expansion system with a hydride sorption compressor in place of the usual motor driven piston compressor. To test the feasibility of this system, a commercial Gifford-McMahon refrigerator was tested using hydrogen gas as the working fluid. Although no attempt was made to optimize the system for hydrogen operation, the refrigerator developed 1.3 W at 30 K and 6.6 W at 60 K. The results of the test and of theoretical performances of the hybrid compressor coupled to these expansion systems are presented.

  11. PCB Congener Sorption To Carbonaceous Sediment Components: Macroscopic Comparison And Characterization Of Sorption Kinetics And Mechanism

    Science.gov (United States)

    Sorption of polychlorinated biphenyls (PCBs) to sediment is a key process in determining their mobility, bioavailability, and chemical decomposition in aquatic environments. In order to examine the validity of currently used interpretation approaches for PCBs sorption, comparati...

  12. Mechanisms of nickel sorption by a bacteriogenic birnessite

    Energy Technology Data Exchange (ETDEWEB)

    Pena, J.; Kwon, K.D.; Refson, K.; Bargar, J.R.; Sposito, G.

    2010-04-01

    A synergistic experimental-computational approach was used to study the molecular-scale mechanisms of Ni sorption at varying loadings and at pH 6-8 on the biogenic hexagonal birnessite produced by Pseudomonas putida GB-1. We found that Ni is scavenged effectively by bacterial biomass-birnessite assemblages. At surface excess values below 0.18 mol Ni kg{sup -1} sorbent (0.13 mol Ni mol{sup -1} Mn), the biomass component of the sorbent did not interfere with Ni sorption on mineral sites. Extended X-ray absorption fine structure (EXAFS) spectra showed two dominant coordination environments: Ni bound as a triple-corner-sharing (Ni-TCS) complex at vacancy sites and Ni incorporated (Ni-inc) into the MnO{sub 2} sheet, with the latter form of Ni favored at high sorptive concentrations and decreased proton activity. In parallel to our spectral analysis, first-principles geometry optimizations based on density functional theory (DFT) were performed to investigate the structure of Ni surface complexes at vacancy sites. Excellent agreement was achieved between EXAFS- and DFT-derived structural parameters for Ni-TCS and Ni-inc. Reaction-path calculations revealed a pH-dependent energy barrier associated with the transition from Ni-TCS to Ni-inc. Our results are consistent with the rate-limited incorporation of Ni at vacancy sites in our sorption samples, but near-equilibrium state of Ni in birnessite phases found in nodule samples. This study thus provides direct and quantitative evidence of the factors governing the occurrence of Ni adsorption versus Ni incorporation in biogenic hexagonal birnessite, a key mineral in the terrestrial manganese cycle.

  13. The sorption and mechanical properties of the modified cement matrix used for conditioning of radioactive waste

    International Nuclear Information System (INIS)

    Dogaru, Daniela; Nuculae, Ortenzia; Jinescu, Gheorghita; Duliu, Octavian; Dogaru, Gheorghe

    2008-01-01

    Full text: Radioactive contaminant sorption onto concrete represents one of the most important retardation mechanisms in engineered barriers such as the conditioning matrix itself, concrete walls and concrete floors. During the life of a disposal facility for radioactive waste, the sorption properties as well as the mechanical properties of the cement are affected by both external and internal processes. The most important sorbing material present in concrete is the hydrated cement. The sorption data obtained for specific cement or cement mixes in general may be used to characterize a given cement type. In order to improve the mechanical and sorption properties of the cement matrix, different additives were used in the laboratory tests. The used additives are known to have good sorption properties. The paper describes the influence of the concentration of additives on the mechanical and sorption properties of the cement matrix. As radioactive contaminants 134 Cs, 60 Co, 3 H, 241 Am were used. (authors)

  14. Sorption of chlorophenols on microporous minerals: mechanism and influence of metal cations, solution pH, and humic acid.

    Science.gov (United States)

    Yang, Hui; Hu, Yuanan; Cheng, Hefa

    2016-10-01

    Sorption of 2-chlorophenol (2-CP), 2,4-dichlorophenol (2,4-DCP), and 2,4,6-trichlorophenol (2,4,6-TCP) on a range of dealuminated zeolites were investigated to understand the mechanism of their sorption on microporous minerals, while the influence of common metal cations, solution pH, and humic acid was also studied. Sorption of chlorophenols was found to increase with the hydrophobicity of the sorbates and that of the microporous minerals, indicating the important role of hydrophobic interactions, while sorption was also stronger in the micropores of narrower sizes because of greater enhancement of the dispersion interactions. The presence of metal cations could enhance chlorophenol sorption due to the additional electrostatic attraction between metal cations exchanged into the mineral micropores and the chlorophenolates, and this effect was apparent on the mineral sorbent with a high density of surface cations (2.62 sites/nm(2)) in its micropores. Under circum-neutral or acidic conditions, neutral chlorophenol molecules adsorbed into the hydrophobic micropores through displacing the "loosely bound" water molecules, while their sorption was negligible under moderately alkaline conditions due to electrostatic repulsion between the negatively charged zeolite framework and anionic chlorophenolates. The influence of humic acid on sorption of chlorophenols on dealuminated Y zeolites suggests that its molecules did not block the micropores but created a secondary sorption sites by forming a "coating layer" on the external surface of the zeolites. These mechanistic insights could help better understand the interactions of ionizable chlorophenols and metal cations in mineral micropores and guide the selection and design of reusable microporous mineral sorbents for sorptive removal of chlorophenols from aqueous stream.

  15. Understanding Defense Mechanisms.

    Science.gov (United States)

    Cramer, Phebe

    2015-12-01

    Understanding defense mechanisms is an important part of psychotherapy. In this article, we trace the history of the concept of defense, from its origin with Freud to current views. The issue of defense as an unconscious mechanism is examined. The question of whether defenses are pathological, as well as their relation to pathology, is discussed. The effect of psychotherapy on the use of defenses, and their relation to a therapeutic alliance is explored. A series of empirical research studies that demonstrate the functioning of defense mechanisms and that support the theory is presented. Research also shows that as part of normal development, different defenses emerge at different developmental periods, and that gender differences in defense use occur.

  16. Capacity and mechanisms of ammonium and cadmium sorption on different wetland-plant derived biochars

    International Nuclear Information System (INIS)

    Cui, Xiaoqiang; Hao, Hulin; Zhang, Changkuan; He, Zhenli; Yang, Xiaoe

    2016-01-01

    The objective of this study was to investigate the relationship between Cd 2+ /NH 4 + sorption and physicochemical properties of biochars produced from different wetland plants. Biochars from six species of wetland plants (i.e., Canna indica, Pennisetum purpureum Schum, Thalia dealbata, Zizania caduciflora, Phragmites australis and Vetiveria zizanioides) were obtained at 500 °C and characterized, and their sorption for ammonium and cadmium was determined. There were significant differences in elemental composition, functional groups and specific surface area among the biochars derived from different wetland plant species. Sorption of ammonium and cadmium on the biochars could be described by a pseudo second order kinetic model, and the simple Langmuir model fits the isotherm data better than the Freundlich or Temkin model. The C. indica derived biochar had the largest sorption capacity for NH 4 + and Cd 2+ , with a maximum sorption of 13.35 and 125.8 mg g −1 , respectively. P. purpureum Schum derived biochar had a similar maximum sorption (119.3 mg g −1 ) for Cd 2+ . Ammonium sorption was mainly controlled by cation exchange, surface complexation with oxygen-containing functional groups and the formation of magnesium ammonium phosphate compounds, whereas for Cd 2+ sorption, the formation of cadmium phosphate precipitates, cation exchange and binding to oxygen-containing groups were the major possible mechanisms. In addition, the sorption of ammonium and cadmium was not affected by surface area and microporosity of the biochars. - Highlights: • Biochars varied in physicochemical properties and adsorption capacity. • Canna indica derived biochar has a high sorption capacity for Cd 2+ . • NH 4 + and Cd 2+ sorption on biochars fits a pseudo second order and Langmuir model. • Sorption mechanism is related to complexation, cation exchange and precipitation.

  17. Capacity and mechanisms of ammonium and cadmium sorption on different wetland-plant derived biochars

    Energy Technology Data Exchange (ETDEWEB)

    Cui, Xiaoqiang [Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058 (China); Hao, Hulin [Ningbo Raw Water Resource Research Academy, Ningbo (China); Zhang, Changkuan [Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058 (China); He, Zhenli [Indian River Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Fort Pierce, FL 34945 (United States); Yang, Xiaoe, E-mail: xyang571@yahoo.com [Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058 (China)

    2016-01-01

    The objective of this study was to investigate the relationship between Cd{sup 2+}/NH{sub 4}{sup +} sorption and physicochemical properties of biochars produced from different wetland plants. Biochars from six species of wetland plants (i.e., Canna indica, Pennisetum purpureum Schum, Thalia dealbata, Zizania caduciflora, Phragmites australis and Vetiveria zizanioides) were obtained at 500 °C and characterized, and their sorption for ammonium and cadmium was determined. There were significant differences in elemental composition, functional groups and specific surface area among the biochars derived from different wetland plant species. Sorption of ammonium and cadmium on the biochars could be described by a pseudo second order kinetic model, and the simple Langmuir model fits the isotherm data better than the Freundlich or Temkin model. The C. indica derived biochar had the largest sorption capacity for NH{sub 4}{sup +} and Cd{sup 2+}, with a maximum sorption of 13.35 and 125.8 mg g{sup −1}, respectively. P. purpureum Schum derived biochar had a similar maximum sorption (119.3 mg g{sup −1}) for Cd{sup 2+}. Ammonium sorption was mainly controlled by cation exchange, surface complexation with oxygen-containing functional groups and the formation of magnesium ammonium phosphate compounds, whereas for Cd{sup 2+} sorption, the formation of cadmium phosphate precipitates, cation exchange and binding to oxygen-containing groups were the major possible mechanisms. In addition, the sorption of ammonium and cadmium was not affected by surface area and microporosity of the biochars. - Highlights: • Biochars varied in physicochemical properties and adsorption capacity. • Canna indica derived biochar has a high sorption capacity for Cd{sup 2+}. • NH{sub 4}{sup +} and Cd{sup 2+} sorption on biochars fits a pseudo second order and Langmuir model. • Sorption mechanism is related to complexation, cation exchange and precipitation.

  18. Understanding the sorption and biotransformation of organic micropollutants in innovative biological wastewater treatment technologies.

    Science.gov (United States)

    Alvarino, T; Suarez, S; Lema, J; Omil, F

    2018-02-15

    New technologies for wastewater treatment have been developed in the last years based on the combination of biological reactors operating under different redox conditions. Their efficiency in the removal of organic micropollutants (OMPs) has not been clearly assessed yet. This review paper is focussed on understanding the sorption and biotransformation of a selected group of 17 OMPs, including pharmaceuticals, hormones and personal care products, during biological wastewater treatment processes. Apart from considering the role of "classical" operational parameters, new factors such as biomass conformation and particle size, upward velocity applied or the addition of adsorbents have been considered. It has been found that the OMP removal by sorption not only depends on their physico-chemical characteristics and other parameters, such as the biomass conformation and particle size, or some operational conditions also relevant. Membrane biological reactors (MBR), have shown to enhance sorption and biotransformation of some OMPs. The same applies to technologies bases on direct addition of activated carbon in bioreactors. The OMP biotransformation degree and pathway is mainly driven by the redox potential and the primary substrate activity. The combination of different redox potentials in hybrid reactor systems can significantly enhance the overall OMP removal efficiency. Sorption and biotransformation can be synergistically promoted in biological reactors by the addition of activated carbon. The deeper knowledge of the main parameters influencing OMP removal provided by this review will allow optimizing the biological processes in the future. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Advances in Understanding Sorption and Transport Processes Affecting the Fate of Environmental Pollutants in the Subsurface

    Science.gov (United States)

    Karapanagioti, H. K.; Werner, D.; Werth, C.

    2012-04-01

    The results of a call for a special issue that is now in press by the Journal of Contaminant Hydrology will be presented. This special issue is edited by the authors and is entitled "Sorption and Transport Processes Affecting the Fate of Environmental Pollutants in the Subsurface". A short abstract of each paper will be presented along with the most interesting results. Nine papers were accepted. Pollutants studied include: biocolloids, metals (arsenic, chromium, nickel), organic compounds such as hydrocarbons, chlorinated hydrocarbons, micropollutants (PAHs, PCBs), pesticides (glyphosate, 2,4-D). Findings presented in the papers include a modified batch reactor system to study equilibrium-reactive transport problems of metals. Column studies along with theoretical approximations evaluate the combined effects of grain size and pore water velocity on the transport in water saturated porous media of three biocolloids. A polluted sediment remediation method is evaluated considering site-specific conditions through monitoring results and modelling. A field study points to glogging and also sorption as mechanisms affecting the effectiveness of sub-surface flow constructed wetlands. A new isotherm model combining modified traditionally used isotherms is proposed that can be used to simulate pH-dependent metal adsorption. Linear free energy relationships (LFERs) demonstrate ability to predict slight isotope shifts into the groundwater due to sorption. Possible modifications that improve the reliability of kinetic models and parameter values during the evaluation of experiments that assess the sorption of pesticides on soils are tested. Challenges in selecting groundwater pollutant fate and transport models that account for the effect of grain-scale sorption rate limitations are evaluated based on experimental results and are discussed based on the Damköhler number. Finally, a thorough review paper presents the impact of mineral micropores on the transport and fate of

  20. A study of sorption mechanism onto cement hydrates by isotherm measurements

    International Nuclear Information System (INIS)

    Sugiyama, Daisuke; Fujita, Tomonari

    2003-01-01

    In the concept for TRU waste disposal in Japan, cement is a potential waste packaging and backfilling material and is expected to provide chemical containment. In particular, the sorption of radionuclides onto cement material, which controls the aqueous concentrations of elements in the porewater, is a very important parameter when considering the release of radionuclides from the near field of a repository. Many safety assessment calculations currently assume radionuclide retardation as linear sorption equilibrium and describe it with a distribution ratio (R d value). In this study, the sorption mechanism is discussed by measuring the sorption isotherm of caesium, strontium and thorium onto Ordinary Portland Cement (OPC) and Calcium Silicate Hydrate (C-S-H gel), to justify and support this assumption. In addition, the effect of competitive sorption between thorium and uranium and other groundwater ions is studied by examining sorption using a range of sodium chloride concentrations to simulate different groundwater ionic strengths. Based on the experimental results, we have showed that: Caesium and strontium sorb by substitution for Ca in C-S-H phases and the presence of some calcium sites with different ion-exchange log K values is suggested; Thorium would be fixed in a surface co-precipitation to form a solubility-limiting phase. The results of sorption experiments are reasonably well modelled by the ion-exchange model for caesium and strontium and the surface co-precipitation model for thorium, respectively. (author)

  1. Lead and cadmium sorption mechanisms on magnetically modified biochars

    Czech Academy of Sciences Publication Activity Database

    Trakal, L.; Veselská, V.; Šafařík, Ivo; Vítková, M.; Číhalová, S.; Komárek, M.

    2016-01-01

    Roč. 203, MAR (2016), s. 318-324 ISSN 0960-8524 R&D Projects: GA MŠk(CZ) LD14066 Institutional support: RVO:67179843 Keywords : pyrolysis bio-chars * aqueous-solutions * heavy-metals * removal * adsorption * water * contaminants * pb * temperatures * copper * Magnetic biochar * Fe oxide impregnation * Metal sorption * Cation release * Wastewater treatment Subject RIV: EI - Biotechnology ; Bionics Impact factor: 5.651, year: 2016

  2. Sorption mechanisms of sulfamethazine to soil humin and its subfractions after sequential treatments.

    Science.gov (United States)

    Guo, Xiaoying; Shen, Xiaofang; Zhang, Meng; Zhang, Haiyun; Chen, Weixiao; Wang, Hui; Koelmans, A A; Cornelissen, Gerard; Tao, Shu; Wang, Xilong

    2017-02-01

    Sorption mechanisms of an antibiotic sulfamethazine (SMT) to humin (HM) isolated from a peat soil and its subfractions after sequential treatments were examined. The treatments of HM included removal of ash, O-alkyl carbon, lipid, and lignin components. The HF/HCl de-ashing treatment removed a large amount of minerals (mainly silicates), releasing a fraction of hydrophobic carbon sorption domains that previously were blocked, increasing the sorption of SMT by 33.3%. The de-O-alkyl carbon treatment through acid hydrolysis greatly reduced polarity of HM samples, thus weakening the interaction between sorbents with water at the interfaces via H-bonding, leaving more effective sorption sites. Sorption of SMT via mechanisms such as van der Waals forces and π-π interactions was enhanced by factors of 2.04-2.50. After removing the lipid/lignin component with the improved Soxhlet extraction/acid hydrolysis, the organic carbon content-normalized sorption enhancement index E oc was calculated. The results demonstrated that the E oc-lipid for SMT (16.9%) was higher than E oc-lignin (10.1%), implying that removal of unit organic carbon mass of lipid led to a higher increase in sorption strength than that of lignin. As each component was progressively removed from HM, the sorption strength and isotherm nonlinearity of the residual HM samples for SMT were gradually enhanced. The K oc values of SMT by HM samples were positively correlated with their aromatic carbon contents, implying that π-π electron donor-acceptor interactions between the benzene ring of sorbate and the aromatic domains in HM played a significant role in their interactions. Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. Understanding mechanical ventilators.

    Science.gov (United States)

    Chatburn, Robert L

    2010-12-01

    The respiratory care academic community has not yet adopted a standardized system for classifying and describing modes of ventilation. As a result, there is enough confusion that patient care, clinician education and even ventilator sales are all put at risk. This article summarizes a ventilator mode taxonomy that has been extensively published over the last 15 years. Specifically, the classification system has three components: a description of the control variables within breath; a description of the sequence of mandatory and spontaneous breaths; and a specification for the targeting scheme. This three-level specification provides scalability of detail to make the mode description appropriate for the particular need. At the bedside, we need only refer to a mode briefly using the first or perhaps first and second components. To distinguish between similar modes and brand names, we would need to include all components. This taxonomy uses the equation of motion for the respiratory system as the underlying theoretical framework. All terms relevant to describing modes of mechanical ventilation are defined in an extensive appendix.

  4. SORPTION-DESORPTION MECHANISM OF Zn(II AND Cd(II ON CHITIN

    Directory of Open Access Journals (Sweden)

    Sri Juari Santosa

    2010-06-01

    Full Text Available This study reports the results of the elucidation of the sorption-desorption mechanism of Zn(II and Cd(II on chitin through the determination of capacity, energy, and rate constant of sorption as well as the investigation of their desorption properties in NaCl and Na2EDTA solutions. The chitin was isolated through deproteination followed by demineralization of crab (Portunus pelagicus Linn shell using NaOH solutions. The sorption of both metal ions followed the Langmuir isotherm model, resulting the sorption capacities of 3.2 x 10-4 and 2.8 x 10-4 mol g-1 for Zn(II and Cd(II, respectively, and sorption energies of 15.1 kJ mol-1 for Zn(II and 17.9 kJ mol-1 for Cd(II. It was also observed that Zn(II was sorbed slightly faster than Cd(II with first order sorption rate constants of 2.82 x 10-3 min-1 for Zn(II and 2.61 x 10-3 min-1 for Cd(II. The result of the desorption experiment showed that Cd(II and especially Zn(II could only be exchanged by Na(I after desorbing those metal ions by strong chelating agent of EDTA2-. The easier desorption of Zn(II than Cd(II by EDTA2- must be attributed by the smaller sorption energy of Zn(II and by harder acid property of Zn(II than Cd(II as EDTA2- contained hard electron donor elements.   Keywords: sorption, desorption, chitin, Zn(II, Cd(II

  5. Sorption mechanisms of phenanthrene, lindane, and atrazine with various humic acid fractions from a single soil sample.

    Science.gov (United States)

    Wang, Xilong; Guo, Xiaoying; Yang, Yu; Tao, Shu; Xing, Baoshan

    2011-03-15

    The sorption behavior of organic compounds (phenanthrene, lindane, and atrazine) to sequentially extracted humic acids and humin from a peat soil was examined. The elemental composition, XPS and (13)C NMR data of sorbents combined with sorption isotherm data of the tested compounds show that nonspecific interactions govern sorption of phenanthrene and lindane by humic substances. Their sorption is dependent on surface and bulk alkyl carbon contents of the sorbents, rather than aromatic carbon. Sorption of atrazine by these sorbents, however, is regulated by polar interactions (e.g., hydrogen bonding). Carboxylic and phenolic moieties are key components for H-bonding formation. Thermal analysis reveals that sorption of apolar (i.e., phenanthrene and lindane) and polar (i.e., atrazine) compounds by humic substances exhibit dissimilar relationships with condensation and thermal stability of sorption domains, emphasizing the major influence of domain spatial arrangement on sorption of organic compounds with distinct polarity. Results of pH-dependent sorption indicate that reduction in sorption of atrazine by the tested sorbents is more evident than phenanthrene with increasing pH, supporting the dependence of organic compound sorption on its polarity and structure. This study highlights the different interaction mechanisms of apolar and polar organic compounds with humic substances.

  6. Influence of water sorption on mechanical properties of injection-molded thermoplastic denture base resins.

    Science.gov (United States)

    Hamanaka, Ippei; Iwamoto, Misa; Lassila, Lippo; Vallittu, Pekka; Shimizu, Hiroshi; Takahashi, Yutaka

    2014-11-01

    This study investigated the influence of water sorption on certain mechanical properties of injection-molded thermoplastic denture base resins. Six thermoplastic resins (two polyamides, two polyesters, one polycarbonate, one polymethylmethacrylate) and a polymethylmethacrylate (PMMA) conventional heat-polymerized denture-based polymer, selected as a control, were tested. Specimens of each denture base material were fabricated according to ISO 1567 specifications and were either dry or water-immersed for 30 days (n = 10). The ultimate flexural strength, the flexural strength at the proportional limit and the elastic modulus of the denture base materials were calculated. Water sorption significantly decreased the ultimate flexural strength, the flexural strength at the proportional limit and the elastic modulus of one of the polyamides and the PMMAs. It also significantly increased the ultimate flexural strength of the polycarbonate. The mechanical properties of some injection-molded thermoplastic denture base resins changed after water sorption.

  7. Investigating the gas sorption mechanism in an rht -metal-organic framework through computational studies

    KAUST Repository

    Pham, Tony T.

    2014-01-09

    experimental results for the two groups are quantitatively different, the sorption mechanisms (for both crystal structures and sorbates) are broadly similar and not inconsistent with either set of experimental data; the theoretical sorption isotherms themselves resemble those by Eddaoudi et al. © 2013 American Chemical Society.

  8. Behaviors and mechanism of acid dyes sorption onto diethylenetriamine-modified native and enzymatic hydrolysis starch

    International Nuclear Information System (INIS)

    Wang Zuohua; Xiang Bo; Cheng Rumei; Li Yijiu

    2010-01-01

    In this paper, different starches were modified by diethylenetriamine. The native starch reacted with diethylenetriamine giving CAS, whereas the enzymatic hydrolysis starch was modified by diethylenetriamine producing CAES. Adsorption capacities of CAES for four acid dyes, namely, Acid orange 7 (AO7), Acid orange 10 (AO10), Acid green 25 (AG25) and Acid red 18 (AR18) have been determined to be 2.521, 1.242, 1.798 and 1.570 mmol g -1 , respectively. In all cases, CAES has exhibited higher sorption ability than CAS, and the increment for these dyes took the sequence of AO7 (0.944 mmol g -1 ) > AO10 (0.592 mmol g -1 ) > AR18 (0.411 mmol g -1 ) > AG25 (0.047 mmol g -1 ). Sorption kinetics and isotherms analysis showed that these sorption processes were better fitted to pseudo-second-order equation and Langmuir equation. Chemical sorption mechanisms were confirmed by studying the effects of pH, ionic strength and hydrogen bonding. Thermodynamic parameters of these dyes onto CAES and CAS were also observed and it indicated that these sorption processes were exothermic and spontaneous in nature.

  9. PAL application to the study of sorption mechanism in polymers - capillary effects

    International Nuclear Information System (INIS)

    Ito, Y.; Shimadzu, A.; Ikeda, K.

    1999-01-01

    The positron annihilation lifetime technique can be applied to the study of the sorption mechanism in polymers in a quite unique way. In our previous experiments it had been shown that τ 3 and I 3 of polymers show a V-shaped dependence as a function of the contact with vapours. The decreasing part of the V-shaped dependence had been attributed to the Langmuir-type sorption, and the increasing part of delayed occurrence of the Henry-type sorption. But since there was some doubt that the capillary effect, i.e. the vapour to be sorbed is deposited in between the polymer membranes, might be involved in the increasing part, we performed a careful experiment to avoid the capillary effect. We have performed further experiments in a careful conditions to avoid the capillary effect, and have observed the same V-shape as before. Thus our interpretation of the V-shaped dependence has been established. Furthermore, in another example it is shown a case where the capillary effect is observed. This latter case is an example how positron annihilation lifetime can distinguish the real sorption and false sorption (capillary effect). (author)

  10. New insights into the sorption mechanism of cadmium on red mud

    Energy Technology Data Exchange (ETDEWEB)

    Luo Lei [State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085 (China); Ministry of Agriculture Key Laboratory of Plant Nutrition and Nutrient Cycling, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081 (China); Ma Chenyan [State Key Laboratory of Synchrotron Radiation, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100039 (China); Ma Yibing, E-mail: ybma@caas.ac.cn [Ministry of Agriculture Key Laboratory of Plant Nutrition and Nutrient Cycling, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081 (China); Zhang Shuzhen; Lv Jitao [State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085 (China); Cui Mingqi [State Key Laboratory of Synchrotron Radiation, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100039 (China)

    2011-05-15

    Effectiveness and mechanism of cadmium (Cd) sorption on original, acidified and ball milling nano-particle red muds were investigated using batch sorption experiments, sequential extraction analysis and X-ray absorption near edge structure (XANES) spectroscopy. The maximum sorption capacity of Cd was 0.16, 0.19, and 0.21 mol/kg for the original, acidified, and nano-particle red muds at pH 6.5, respectively. Both acidification and ball-milling treatments significantly enhanced Cd sorption and facilitated transformation of Cd into less extractable fractions. The Cd L{sub III}-edge XANES analysis indicated the formation of inner-sphere complexes of Cd similar to XCdOH (X represents surface groups on red mud) on the red mud surfaces although outer-sphere complexes of Cd were the primary species. This work shed light on the potential application of red mud to remediate Cd-contaminated soils and illustrated the promising tool of XANES spectroscopy for speciation of multicomponent systems of environmental relevance. - Graphical abstract: Display Omitted Highlights: > Red mud has a strong affinity for Cd contaminants. > Ball-milling treatments significantly enhance Cd sorption on red mud. > Cadmium partially formed inner-sphere complexes on the red mud surfaces. > Red mud can be used to remediate Cd contaminated soils effectively. - Cadmium can be strongly sorbed and partially forms inner-sphere complexes on red mud.

  11. Effect of chromium speciation on its sorption mechanism onto grape stalks entrapped into alginate beads

    OpenAIRE

    Escudero, Carlos; Fiol, Núria; Villaescusa, Isabel; Bollinger, Jean-Claude

    2013-01-01

    Sorption of Cr(III) and Cr(VI) ions onto 2% grape stalk (GS) powder entrapped in a biopolymeric gel matrix of calcium alginate (CA) has been investigated and a mechanism for the retention of both, Cr(VI) and Cr(III) is proposed. Protons were found to be consumed in Cr(VI) sorption/reduction and to compete with Cr(III) for the sorbent active sites. Isotherm equilibrium was modelled according to Langmuir equation: maximum capacity was found to be 6.4 and 3.6 mg g−1 for Cr(III) and Cr(VI), respe...

  12. Sorption mechanisms of sulfamethazine to soil humin and its subfractions after sequential treatments

    NARCIS (Netherlands)

    Guo, X.; Shen, X.; Zhang, M.; Zhang, H.; Chen, W.; Wang, H.; Koelmans, A.A.; Cornelissen, G.; Tao, S.; Wang, X.

    2017-01-01

    Sorption mechanisms of an antibiotic sulfamethazine (SMT) to humin (HM) isolated from a peat soil and its subfractions after sequential treatments were examined. The treatments of HM included removal of ash, O-alkyl carbon, lipid, and lignin components. The HF/HCl de-ashing treatment removed a large

  13. Microbial Biofilms as a Mechanism for Metal Sorption on Plastic Debris

    Science.gov (United States)

    Richard, H.; Rochman, C. M.; Komada, T.; Carpenter, E. J.

    2016-02-01

    Heavy metals from the water column accumulate onto weathered plastic debris to a greater extent than onto virgin plastic. Hypothesized mechanisms that drive this process include oxidation by ultraviolet light, precipitation of metal ions onto the surface of the plastic, and biofilm growth. We provide the first example of research quantifying how biofilms influence metal sorption onto plastic debris. We conducted laboratory experiments to find out whether or not the presence of biofilms increases the sorption capacity of plastic debris, and also performed in situ experiments in the San Francisco Bay to compare low-density polyethylene, polylactic acid, and glass as substrates for fouling and metal sorption. This research reveals the potential for plastic debris to act as a vector bringing heavy metals into aquatic food webs relative to other debris materials.

  14. Sorption Mechanisms of Eu(3+) on CSH Phases of Hydrated Cements.

    Science.gov (United States)

    Pointeau, Ingmar; Piriou, Bernard; Fedoroff, Michel; Barthes, Marie-Genevieve; Marmier, Nicolas; Fromage, Francine

    2001-04-15

    The sorption mechanisms of Eu(3+) on calcium silicate hydrate (CSH) phases of hydrated cement were investigated as a tool for the prediction of the behavior of trivalent radionuclides with aged/degraded cements in radioactive waste repositories. Four techniques were used: site-selective and time-resolved luminescence spectroscopy, XPS, high-resolution SEM coupled with EDX, and XRD. Results showed that europium is not precipitated in the solution despite its low solubility limit. It is strongly retained on CSH, resulting in a more than 99.8% sorption rate. Two main sorption sites were characterized by luminescence spectroscopy. One site, with a long lifetime, can be interpreted as Eu included in the framework of CSH. Another one, with a shorter lifetime, can be interpreted as a site with a hydrated environment that is high but is less than that of europium hydroxide. It corresponds to superficial complexation or precipitation. Copyright 2001 Academic Press.

  15. Investigation of Sorption and Diffusion Mechanisms, and Preliminary Economic Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Bhave, Ramesh R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Jubin, Robert Thomas [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Spencer, Barry B. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Nair, Sankar [Georgia Inst. of Technology, Atlanta, GA (United States)

    2017-02-01

    This report describes the synthesis and evaluation of molecular sieve zeolite membranes to separate and concentrate tritiated water (HTO) from dilute HTO-bearing aqueous streams. Several monovalent and divalent cation exchanged silico alumino phosphate (SAPO-34) molecular sieve zeolite membranes were synthesized on disk supports and characterized with gas and vapor permeation measurements. The pervaporation process performance was evaluated for the separation and concentration of tritiated water. Experiments were performed using tritiated water feed solution containing tritium at the high end of the range (1 mCi/mL) anticipated in a nuclear fuel processing system that includes both acid and water streams recycling. The tritium concentration was about 0.1 ppm. The permeate was recovered under vacuum. The HTO/H2O selectivity and separation factor calculated from the measured tritium concentrations ranged from 0.99 to 1.23, and 0.83-0.98, respectively. Although the membrane performance for HTO separation was lower than expected, several encouraging observations including molecular sieving and high vapor permeance are reported. Additionally, several new approaches are proposed, such as tuning the sorption and diffusion properties offered by small pore LTA zeolite materials, and cation exchanged aluminosilicates with high metal loading. It is hypothesized that substantially improved preferential transport of tritium (HTO) resulting in a more concentrated permeate can be achieved. Preliminary economic analysis for the membrane-based process to concentrate tritiated water is also discussed.

  16. Mechanisms of trace metal sorption in Pseudomonas putida-birnessite assemblages

    Science.gov (United States)

    Peña, J.; Kwon, K. D.; Bargar, J. R.; Sposito, G.

    2012-04-01

    by solution pH, background electrolyte, surface loading, and time of Zn addition relative to MnO2 precipitation. Copper bonding at vacancy sites was found to be important as well, but the geometry of additional surface complexes, suggested by the EXAFS spectra, could not be identified. Based on the results from EXAFS spectroscopy, we concluded that the bacterial biomass does not limit Ni or Zn sorption at vacancy sites, contributing to metal sorption at very high surface loadings (> 0.1 mol Me mol-1 Mn). However, Cu, a transition metal with a high affinity for both organic and mineral functional groups and facile redox reactivity, was found to interact strongly with the biomass over all surface loadings investigated. This research advances our understanding of the surface reactivity of biogenic birnessite and sheds light on metal retention mechanisms in composite microbe-mineral assemblages, which regulate the concentrations and distribution of nutrient and toxicant metals in diverse ecosystems.

  17. An Impact of Mechanical Stress in Coal Briquettes on Sorption of Carbon Dioxide

    Science.gov (United States)

    Wierzbicki, Mirosław

    2017-09-01

    The presence of gases (methane or carbon dioxide) in hard coal is connected with numerous threats for miners employed in underground mining facilities. When analyzing the coal-methane system, it is necessary to determine the relationship between pressure and gas sorption. Such a relationship should be determined under conditions similar to the natural ones - when it comes to both temperature and pressure. The present paper discusses the results of research conducted with the use of coal briquettes under the state of mechanical stress. Carbon dioxide sorption isotherms were determined for different values of stress affecting the coal material. For five coal samples collected in different mines of the Upper Silesian Coal Basin, Langmuir's sorption isotherms were determined. The results point to significant impact that mechanical stress has upon the sorption process. It is about 1 percent of the value obtained for coal not subjected to stress per 1 MPa. The research results can also prove useful when analyzing hard coal seams from the perspective of their carbon dioxide sequestration abilities.

  18. Modeling the mechanism involved during the sorption of methylene blue onto fly ash.

    Science.gov (United States)

    Kumar, K Vasanth; Ramamurthi, V; Sivanesan, S

    2005-04-01

    Batch sorption experiments were carried out to remove methylene blue from its aqueous solutions using fly ash as an adsorbent. Operating variables studied were initial dye concentration, fly ash mass, pH, and contact time. Maximum color removal was observed at a basic pH of 8. Equilibrium data were represented well by a Langmuir isotherm equation with a monolayer sorption capacity of 5.718 mg/g. Sorption data were fitted to both Lagergren first-order and pseudo-second-order kinetic models and the data were found to follow pseudo-second-order kinetics. Rate constants at different initial concentrations were estimated. The process mechanism was found to be complex, consisting of both surface adsorption and pore diffusion. The effective diffusion parameter D(i) values were estimated at different initial concentrations and the average value was determined to be 2.063 x 10(-9)cm2/s. Analysis of sorption data using a Boyd plot confirms the particle diffusion as the rate-limiting step for the dye concentration ranges studied in the present investigation (20 to 60 mg/L).

  19. New insights into the sorption mechanism of cadmium on red mud.

    Science.gov (United States)

    Luo, Lei; Ma, Chenyan; Ma, Yibing; Zhang, Shuzhen; Lv, Jitao; Cui, Mingqi

    2011-05-01

    Effectiveness and mechanism of cadmium (Cd) sorption on original, acidified and ball milling nano-particle red muds were investigated using batch sorption experiments, sequential extraction analysis and X-ray absorption near edge structure (XANES) spectroscopy. The maximum sorption capacity of Cd was 0.16, 0.19, and 0.21 mol/kg for the original, acidified, and nano-particle red muds at pH 6.5, respectively. Both acidification and ball-milling treatments significantly enhanced Cd sorption and facilitated transformation of Cd into less extractable fractions. The Cd LIII-edge XANES analysis indicated the formation of inner-sphere complexes of Cd similar to XCdOH (X represents surface groups on red mud) on the red mud surfaces although outer-sphere complexes of Cd were the primary species. This work shed light on the potential application of red mud to remediate Cd-contaminated soils and illustrated the promising tool of XANES spectroscopy for speciation of multicomponent systems of environmental relevance. Copyright © 2011 Elsevier Ltd. All rights reserved.

  20. Effect of chromium speciation on its sorption mechanism onto grape stalks entrapped into alginate beads

    Directory of Open Access Journals (Sweden)

    Carlos Escudero

    2017-02-01

    Full Text Available Sorption of Cr(III and Cr(VI ions onto 2% grape stalk (GS powder entrapped in a biopolymeric gel matrix of calcium alginate (CA has been investigated and a mechanism for the retention of both, Cr(VI and Cr(III is proposed. Protons were found to be consumed in Cr(VI sorption/reduction and to compete with Cr(III for the sorbent active sites. Isotherm equilibrium was modelled according to Langmuir equation: maximum capacity was found to be 6.4 and 3.6 mg g−1 for Cr(III and Cr(VI, respectively. The important Ca2+ release observed when Cr(III is sorbed indicates that ion exchange is the main mechanism involved at concentrations lower than 200 mg L−1 while other mechanisms such as microprecipitation or coordination might take place for higher initial concentrations. In the case of Cr(VI, the sorption mechanism is based on the reduction to Cr(III promoted by both protons and the functional groups on the GS surface; this reduction-formed Cr(III is retained by the alginate gel matrix and by microprecipitation onto the surface of GS particles. ESR and SEM-EDX were used to identify chromium species sorbed on the solid phase. Results from this study suggest that GS entrapped in CA gel beads is an effective sorbent for both, Cr(III and Cr(VI removal from aqueous solutions.

  1. Geochemical and Spectroscopic Investigations of Cd and Pb Sorption Mechanisms on Contrasting Biochars: Engineering Implications

    Czech Academy of Sciences Publication Activity Database

    Trakal, L.; Bingöl, D.; Pohořelý, Michael; Hruška, M.; Komárek, M.

    2014-01-01

    Roč. 171, NOV 2014 (2014), s. 442-451 ISSN 0960-8524 R&D Projects: GA ČR(CZ) GA14-02219S Grant - others:GA MŠMT(CZ) LD13068 Institutional support: RVO:67985858 Keywords : biochar * metals * sorption mechanisms Subject RIV: DK - Soil Contamination ; De-contamination incl. Pesticides Impact factor: 4.494, year: 2014

  2. MOLECULAR DYNAMICS MODELING OF SORPTION OF PESTICIDES ONTO THE SURFACES OF KAOLINITE

    Science.gov (United States)

    To accurately predict the fate of contaminants in the environment and to make sound decisions about environmental remediation, we must accurately understand sorption mechanisms and surface reactivity of environmental particles. Sorption of selected pesticides on kaolinite surface...

  3. Understanding the mechanisms of lung mechanical stress

    Directory of Open Access Journals (Sweden)

    C.S.N.B. Garcia

    2006-06-01

    Full Text Available Physical forces affect both the function and phenotype of cells in the lung. Bronchial, alveolar, and other parenchymal cells, as well as fibroblasts and macrophages, are normally subjected to a variety of passive and active mechanical forces associated with lung inflation and vascular perfusion as a result of the dynamic nature of lung function. These forces include changes in stress (force per unit area or strain (any forced change in length in relation to the initial length and shear stress (the stress component parallel to a given surface. The responses of cells to mechanical forces are the result of the cell's ability to sense and transduce these stimuli into intracellular signaling pathways able to communicate the information to its interior. This review will focus on the modulation of intracellular pathways by lung mechanical forces and the intercellular signaling. A better understanding of the mechanisms by which lung cells transduce physical forces into biochemical and biological signals is of key importance for identifying targets for the treatment and prevention of physical force-related disorders.

  4. Study of sorption mechanisms of europium(3) and uranium(6) ions on clays : impact of silicates; Etude des mecanismes de retention des ions U(6) et Eu(3) sur les argiles: influence des silicates

    Energy Technology Data Exchange (ETDEWEB)

    Kowal-Fouchard, A

    2002-11-01

    Bentonite clay has been selected as a potential buffer or backfill material in a number of disposal programmes for high level waste. In order to enhance the thermodynamic database of sorption phenomena at the solid-water interface, we have investigated sorption mechanisms of europium(III) and uranium(VI) ions onto montmorillonite and bentonite. Thermodynamic data were obtained for different ions concentrations, different background electrolytes and different ionic strengths. The structural identification of the surface complexes and sorption sites was carried out using two spectroscopies, XPS and TRLIFS, while sorption edges were performed using batch experiments. However, clays are complex minerals and in order to understand these sorption mechanisms we have studied europium(III) and uranium(VI) retention on a silica and an alumina because these solids are often considered as basic components of clays. The comparison of structural results shows that europium ions are significantly sorbed on permanently charged sites of clay until pH 7. But this ion is also sorbed on {identical_to}SiOH and {identical_to}AlOH sites of montmorillonite at pH higher than 6. Uranyl ions sorption on montmorillonite is mainly explained by retention of three complexes on {identical_to}SiOH sites. Moreover, we have shown that nitrate ions and dissolved silicates affect on uranium(VI) sorption mechanisms onto alumina. Nevertheless, uranyl ions sorption on montmorillonite and bentonite only decreases with increasing carbonate concentration. Finally, all the sorption edges were then modeled using these results and a surface complexation model (2 pK and constant capacitance models). (author)

  5. Understanding hydrogen sorption in a metal-organic framework with open-metal sites and amide functional groups

    KAUST Repository

    Pham, Tony T.

    2013-05-09

    Grand canonical Monte Carlo (GCMC) studies of the mechanism of hydrogen sorption in an rht-MOF known as Cu-TPBTM are presented. The MOF is a decorated/substituted isostructural analogue to the unembellished rht-MOF, PCN-61, that was studied previously [ Forrest, K. A.J. Phys. Chem. C 2012, 116, 15538-15549. ]. The simulations were performed using three different hydrogen potentials of increasing complexity. Simulated hydrogen sorption isotherms and calculated isosteric heat of adsorption, Qst, values were in excellent agreement with the reported experimental data for only a polarizable model in one of four experimentally observed crystal structure configurations. The study demonstrates the ability of modeling to distinguish the differential sorption of distinct strucures; one configuration is found to be dominant due to favorable interactions with substrates. In addition, it was discovered that the presence of polar amide groups had a significant effect on the electrostatics of the Cu2+ ions and directs the low-pressure physisorption of hydrogen in the MOF. This is in contrast to what was observed in PCN-61, where an exterior copper ion had a higher relative charge and was the favored loading site. This tunability of the electrostatics of the copper ions via chemical substitution on the MOF framework can be explained by the presence of the negatively charged oxygen atom of the amide group that causes the interior Cu2+ ion to exhibit a higher positive charge through an inductive effect. Further, control simulations, taking advantage of the flexibility afforded by theoretical modeling, include artificially modified charges for both Cu2+ ions chosen equal to or with a higher charge on the exterior Cu2+ ion. This choice resulted in distinctly different hydrogen sorption characteristics in Cu-TPBTM with no direct sorption on the open-metal sites. Thus, this study demonstrates both the tunable nature of MOF platforms and the possibility for rational design of sorption

  6. Geochemical and spectroscopic investigations of Cd and Pb sorption mechanisms on contrasting biochars: engineering implications.

    Science.gov (United States)

    Trakal, Lukáš; Bingöl, Deniz; Pohořelý, Michael; Hruška, Miroslav; Komárek, Michael

    2014-11-01

    Biochars prepared from nut shells, plum stones, wheat straws, grape stalks and grape husks were tested as potential sorbents for Cd and Pb. Mechanisms responsible for metal retention were investigated and optimal sorption conditions were evaluated using the RSM approach. Results indicated that all tested biochars can effectively remove Cd and Pb from aqueous solution (efficiency varied between 43.8% and 100%). The removal rate of both metals is the least affected by the biochar morphology and specific surface but this removal efficiency is strongly pH-dependent. Results of variable metal removal combined with different optimized conditions explain the different metal sorption mechanisms, where the predominant mechanism is ion exchange. In addition, this mechanism showed very strong binding of sorbed metals as confirmed by the post-desorption of the fully metal-loaded biochars. Finally, these biochars could thus also be applicable for metal contaminated soils to reduce mobility and bioavailability of Cd and Pb. Copyright © 2014 Elsevier Ltd. All rights reserved.

  7. Uranyl ion sorption mechanisms on titanium oxide: a multi-scale approach

    International Nuclear Information System (INIS)

    Vandenborre, J.; Drot, R.; Simoni, E.; Dong, W.; Du, J.; Dossot, M.; Humbert, B.; Ehrhardt, J.J.

    2005-01-01

    Full text of publication follows: Radionuclides retention mechanisms onto mineral phases is of primary importance for nuclear waste management. The aim of the presented study is to demonstrate that it is possible to predict the retention properties of a methodological powdery substrate from the study of its natural crystallographic orientations. Among the radionuclides of interest, U(VI) can be seen as a model of the radionuclides oxo-cations. The substrate under study is the titanium oxide (TiO 2 ). In fact, rutile can be found as powder and also as manufactured single crystal which allows to study the retention processes on perfectly known crystallographic planes. Since the repartition of the different crystallographic orientations are known for the powder, the results obtained for the single crystals can directly be used to account for the powder retention properties. By using combined spectroscopic techniques such as TRLFS, XPS, DRIFT and SHG, it is possible to determine the nature of the reactive surface sites and also the surface species. XPS and TRLFS measurements allowed to determine that two same uranyl surface species were formed on titania (110) and (001). Only, the relative intensities of these species vary with the surface coverage. Atomic Force Microscopy was carried out to verify that no surface precipitation occurs for the higher surface coverages. Moreover, these analysis have also evidenced that the U(VI) sorption is homogeneous. These observations were corroborated by SHG experiments (mainly for (001)) which have also shown that the sorption occurs, in a first step, onto preferential surface symmetry axis. For rutile powder, the preferential crystallographic orientations are (110), (100) and (101) in the ratio 60/20/20. TRLFS and XPS experiments have shown that two uranyl surface species are formed whatever the pH value ranged from 1 to 5. The spectroscopic characteristics of these species are the same as the ones observed on (110) and (001

  8. Insights into the mechanisms of mercury sorption onto aluminum based drinking water treatment residuals

    International Nuclear Information System (INIS)

    Deliz Quiñones, Katherine; Hovsepyan, Anna; Oppong-Anane, Akua; Bonzongo, Jean-Claude J.

    2016-01-01

    Highlights: • Mercury sorption by Al-WTRs involves electrostatic forces and chemisorption. • Hg forms bonds with oxygen and sulfur atoms of Al-WTR’s organic ligands. • Mercury is incorporated into the residual fraction to form stable complexes. • Mercury binds mainly to SiO x species in the residual fraction. - Abstract: Several studies have demonstrated the ability of drinking water treatment residuals (WTRs) to efficiently sorb metal cations from aqueous solutions. Reported results have stimulated interest on the potential use of WTRs as sorbent for metal removal from contaminated aqueous effluents as well as in metal immobilization in contaminated soils. However, knowledge on mechanisms of metal sorption by WTRs remains very limited and data on the long-term stability of formed metal–WTR complexes as a function of changing key environmental parameters are lacking. In this study, chemical selective sequential extraction (SSE), scanning electron microscopy combined with X-ray energy dispersive spectrometer (SEM-EDS), and X-ray photoelectron spectroscopy (XPS) were used to gain insight into the different mechanisms of mercury (Hg) binding to aluminum based WTR (Al-WTRs). Results from sorption studies show that a significant portion of Hg becomes incorporated in the operationally defined residual fraction of Al-WTRs, and therefore, not prone to dissolution and mobility. The results of solid phase analyses suggested that Hg immobilization by Al-WTR occurs largely through its binding to oxygen donor atoms of mineral ligands driven by a combination of electrostatic forces and covalent bonding.

  9. Hydro-mechanical coupling and permeability of an unsaturated swelling clay under hydrous and thermal stress: sorption curve and water permeability

    International Nuclear Information System (INIS)

    Olchitzky, E.

    2002-02-01

    The use of swelling clay for engineered safety barriers of radioactive waste disposal require the understanding of its thermal-hydro-mechanical behaviour. This work concerns particularly the characterization and the modelling of the behaviour of one of these clays: the FoCa7 clay. The characteristics of the studied material are: the sorption (desorption) curve and the water permeability. For each of them, new experiments have allowed to acquire data in fields still few explored: in temperature (between 20 and 80 C) for the sorption curve and in the unsaturated field for the water permeability. The analysis of these results and of bibliographic data has allowed in one hand to estimate the importance of the hysteresis phenomenon and the temperature influence on the sorption curve and in another hand, to establish the requirement to introduce in the modelling of the sorption curve, a plastic parameter due to the irreversible deformations occurring during the compaction. Moreover, the tests carried out for data acquirement have been used too to give validation elements to the non linear behaviour laws proposed by O. Coussy and P. Dangla for the non saturated porous media. The particularity of these laws is to suppose the existence of an effective constraint in the non saturated field, this shows the importance of the validation elements presented here. (O.M.)

  10. Understanding Bohmian mechanics: A dialogue

    OpenAIRE

    Tumulka, Roderich

    2004-01-01

    This paper is an introduction to the ideas of Bohmian mechanics, an interpretation of quantum mechanics in which the observer plays no fundamental role. Bohmian mechanics describes, instead of probabilities of measurement results, objective microscopic events. In recent years, Bohmian mechanics has attracted increasing attention by researchers. The form of a dialogue allows me to address questions about the Bohmian view that often arise.

  11. Insights into the mechanisms of mercury sorption onto aluminum based drinking water treatment residuals.

    Science.gov (United States)

    Deliz Quiñones, Katherine; Hovsepyan, Anna; Oppong-Anane, Akua; Bonzongo, Jean-Claude J

    2016-04-15

    Several studies have demonstrated the ability of drinking water treatment residuals (WTRs) to efficiently sorb metal cations from aqueous solutions. Reported results have stimulated interest on the potential use of WTRs as sorbent for metal removal from contaminated aqueous effluents as well as in metal immobilization in contaminated soils. However, knowledge on mechanisms of metal sorption by WTRs remains very limited and data on the long-term stability of formed metal-WTR complexes as a function of changing key environmental parameters are lacking. In this study, chemical selective sequential extraction (SSE), scanning electron microscopy combined with X-ray energy dispersive spectrometer (SEM-EDS), and X-ray photoelectron spectroscopy (XPS) were used to gain insight into the different mechanisms of mercury (Hg) binding to aluminum based WTR (Al-WTRs). Results from sorption studies show that a significant portion of Hg becomes incorporated in the operationally defined residual fraction of Al-WTRs, and therefore, not prone to dissolution and mobility. The results of solid phase analyses suggested that Hg immobilization by Al-WTR occurs largely through its binding to oxygen donor atoms of mineral ligands driven by a combination of electrostatic forces and covalent bonding. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Kinetics and mechanism of the sorption of some aromatic amines onto amberlite IRA-904 anion-exchange resin

    Energy Technology Data Exchange (ETDEWEB)

    Zaki, A.B.; El-Sheikh, M.Y.; Evans, J.; El-Safty, S.A.

    2000-01-01

    The kinetics of the sorption of aromatic amines such as o-aminophenol (o-AP), o-phenylenediamine (o-PDA), and p-phenylenediamine (p-PDA) onto Amberlite anion-exchange resin in chloride form was investigated in batch experiments spectrophotometrically at different temperatures. The sorption rate is zero order in all amines sorbed, increasing directly in the order: p-PDA < o-PDA < o-AP, which corresponds to the sequence of the electrostatic contributions to the sorption interactions. The attainments of sorption equilibrium of aromatic amines is seen to be similar. The diffusion coefficients (D) have been calculated by using Fick's equation from the second portions of the sorption/desorption curves; D values ranged from 0.7 to 2.8 x 10{sup {minus}9} cm{sup 2}/s. These results, reflecting the diffusion mechanism, were ascribed to intraparticle diffusion. Arrhenius parameters for the diffusion process and the thermodynamic quantities for the process of equilibrium sorption have been estimated. The effect of a chemical oxidation reaction on intraparticle diffusion was investigated by measuring the intraparticle diffusion of amines during the redox reaction.

  13. Kinetics and Mechanism of the Sorption of Some Aromatic Amines onto Amberlite IRA-904 Anion-Exchange Resin.

    Science.gov (United States)

    Zaki; El-Sheikh; Evans; El-Safty

    2000-01-01

    The kinetics of the sorption of aromatic amines such as o-aminophenol (o-AP), o-phenylenediamine (o-PDA), and p-phenylenediamine (p-PDA) onto Amberlite anion-exchange resin in chloride form was investigated in batch experiments spectrophotometrically at different temperatures. The sorption rate is zero order in all amines sorbed, increasing directly in the order: p-PDAsorption interactions. The attainment of sorption equilibrium of aromatic amines is seen to be similar. The diffusion coefficients (D) have been calculated by using Fick's equation from the second portions of the sorption/desorption curves; D values ranged from 0.7 to 2.8x10(-9) cm(2)/s. These results, reflecting the diffusion mechanism, were ascribed to intraparticle diffusion. Arrhenius parameters for the diffusion process and the thermodynamic quantities for the process of equilibrium sorption have been estimated. The effect of a chemical oxidation reaction on intraparticle diffusion was investigated by measuring the intraparticle diffusion of amines during the redox reaction. Copyright 2000 Academic Press.

  14. Sorption mechanism of solvent vapors to coals; Sekitan eno yobai joki no shuchaku kiko no kaiseki

    Energy Technology Data Exchange (ETDEWEB)

    Shimizu, K.; Takanohashi, T.; Iino, M. [Tohoku University, Sendai (Japan). Institute for Chemical Reaction Science

    1996-10-28

    With an objective to clarify the interactions between micropore structure of coal and solvent reagents, a sorption experiment was carried out under solvent saturated vapor pressure. Low-volatile bituminous coal, Pocahontas No. 3 coal, has the aromatic ring structure developed, and makes solvent more difficult to diffuse into coal, hence sorption amount is small. Methanol has permeated since its polarity is high. High-volatile bituminous coal, Illinois No. 6 coal, makes solvent penetrate easily, and the sorption amount was large with both of aromatic and polar solvents. Since brown coal, Beulah Zap coal, contains a large amount of oxygen, and hydrogen bonding is predominant, sorption amount of cyclohexane and benzene having no polarity is small. Methanol diffuses while releasing hydrogen bond due to its polarity, and its sorption amount is large. A double sorption model is available, which expresses the whole sorption amount as a sum of physical sorption amount and amount of permeation into coal. This model was applied when it explained successfully the sorption behavior of the solvents relative to coals, excepting some of the systems. However, also observed were such abnormal behavior as sorption impediment due to interactions between coal surface and solvents, and permeation impediment due to hydroxyl groups inside the coals. 1 ref., 10 figs., 2 tabs.

  15. Understanding Mechanical Design with Respect to Manufacturability

    Science.gov (United States)

    Mondell, Skyler

    2010-01-01

    At the NASA Prototype Development Laboratory in Kennedy Space Center, Fl, several projects concerning different areas of mechanical design were undertaken in order to better understand the relationship between mechanical design and manufacturabiIity. The assigned projects pertained specifically to the NASA Space Shuttle, Constellation, and Expendable Launch Vehicle programs. During the work term, mechanical design practices relating to manufacturing processes were learned and utilized in order to obtain an understanding of mechanical design with respect to manufacturability.

  16. Understanding Mechanisms of Radiological Contamination

    Energy Technology Data Exchange (ETDEWEB)

    Rick Demmer; John Drake; Ryan James, PhD

    2014-03-01

    Over the last 50 years, the study of radiological contamination and decontamination has expanded significantly. This paper addresses the mechanisms of radiological contamination that have been reported and then discusses which methods have recently been used during performance testing of several different decontamination technologies. About twenty years ago the Idaho Nuclear Technology Engineering Center (INTEC) at the INL began a search for decontamination processes which could minimize secondary waste. In order to test the effectiveness of these decontamination technologies, a new simulated contamination, termed SIMCON, was developed. SIMCON was designed to replicate the types of contamination found on stainless steel, spent fuel processing equipment. Ten years later, the INL began research into methods for simulating urban contamination resulting from a radiological dispersal device (RDD). This work was sponsored by the Defense Advanced Research Projects Agency (DARPA) and included the initial development an aqueous application of contaminant to substrate. Since 2007, research sponsored by the US Environmental Protection Agency (EPA) has advanced that effort and led to the development of a contamination method that simulates particulate fallout from an Improvised Nuclear Device (IND). The IND method diverges from previous efforts to create tenacious contamination by simulating a reproducible “loose” contamination. Examining these different types of contamination (and subsequent decontamination processes), which have included several different radionuclides and substrates, sheds light on contamination processes that occur throughout the nuclear industry and in the urban environment.

  17. Using mechanisms of hydrolysis and sorption to reduce siloxanes occurrence in biogas of anaerobic sludge digesters

    DEFF Research Database (Denmark)

    Gatidou, Georgia; Arvaniti, Olga S.; Stasinakis, Athanasios S.

    2016-01-01

    Hydrolysis of hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), dodecamethylcyclohexasiloxane (D6) and dodecamethylcyclohexasilane (D6_silane) and their sorption to digested sludge was studied in batch experiments. Hydrolysis was affected...... of all siloxanes in biogas, enhancing their removal through hydrolysis and sorption to sludge....

  18. Equilibrium, kinetics, mechanism, and process design for the sorption of methylene blue onto rice husk.

    Science.gov (United States)

    Vadivelan, V; Kumar, K Vasanth

    2005-06-01

    Batch experiments were carried out for the sorption of methylene blue onto rice husk particles. The operating variables studied were initial solution pH, initial dye concentration, adsorbent concentration, and contact time. Equilibrium data were fitted to the Freundlich and Langmuir isotherm equations and the equilibrium data were found to be well represented by the Langmuir isotherm equation. The monolayer sorption capacity of rice husks for methylene blue sorption was found to be 40.5833 mg/g at room temperature (32 degrees C). The sorption was analyzed using pseudo-first-order and pseudo-second-order kinetic models and the sorption kinetics was found to follow a pseudo-second-order kinetic model. Also the applicability of pseudo second order in modeling the kinetic data was also discussed. The sorption process was found to be controlled by both surface and pore diffusion with surface diffusion at the earlier stages followed by pore diffusion at the later stages. The average external mass transfer coefficient and intraparticle diffusion coefficient was found to be 0.01133 min(-1) and 0.695358 mg/g min0.5. Analysis of sorption data using a Boyd plot confirms that external mass transfer is the rate limiting step in the sorption process. The effective diffusion coefficient, Di was calculated using the Boyd constant and was found to be 5.05 x 10(-04) cm2/s for an initial dye concentration of 50 mg/L. A single-stage batch-adsorber design of the adsorption of methylene blue onto rice husk has been studied based on the Langmuir isotherm equation.

  19. Equilibrium and kinetic mechanism for Reactive Black 5 sorption onto high lime Soma fly ash.

    Science.gov (United States)

    Eren, Zeynep; Acar, Filiz Nuran

    2007-05-08

    Batch adsorption studies were carried out for the sorption of C.I. Reactive Black 5, a reactive dye, onto high lime fly ash, obtained from Soma Thermal Power Plant (Turkey), to be low cost adsorbent. The effect of various experimental parameters such as contact time, adsorbent dose and initial dye concentration were investigated. Determination of the adsorption equilibrium concentrations was determined by UV-vis spectrophotometry analytical method. Equilibrium data were fitted to the Freundlich and Langmuir isotherm equations and the equilibrium data were found to be well represented by the Freundlich isotherm equation. The adsorption kinetics of C.I. Reactive Black 5 onto high lime fly ash were also studied to characterize of the surface complexation reaction. A pseudo-second-order mechanism has been developed to predict the rate constant of the adsorption, the equilibrium capacity and initial adsorption rate with the effect of initial concentration. A single-stage batch adsorber design of the adsorption of C.I. Reactive Black 5 onto high lime fly ash has been studied based on the Freundlich isotherm equation.

  20. Influence of organic fertilization on the sorption mechanisms of 241 Am in tropical soils

    International Nuclear Information System (INIS)

    Pereira, Tatiane Rocha

    2009-01-01

    In this work the mechanisms involved in the sorption of 241 Am were investigated depending on the physicochemical properties of some Brazilian soils and on alterations promoted by organic amendment. This experimental study was conducted in a controlled area, where pots containing different kinds of soils (histisol, ferralsol and nitisol), with different organic amendment doses (without amendment; 2 kg m -2 and 4 kg m -2 ) were artificially contaminated by radioactive solution water, which contained 241 Am. Migration studies, distribution (or partition) coefficient (KJ), bioavailability and organic matter were carried out in these soils, with ar without organic amendment. In order to evaluate the effective bioavailability of radionuclides, radish (Raphanus sativus L.) was cultivated in these pots, and later the concentration of 241 Am in radish's roots was measured. The main results show that 241 Am tends to be strongly attached to organic matter and that organic amendment in tropical soils minimizes the radionuclide studied desorption. Also, distribution (or partition) coefficient values for 241 Am were generated and these values are smaller than those ones determined for soils from temperate zones. Physical and chemical fractioning of organic matter were carried out. (author)

  1. Understanding biochar mechanisms for practical implementation

    Energy Technology Data Exchange (ETDEWEB)

    Glaser, Bruno [Halle-Wittenberg Univ. (Germany). Inst. fuer Agrar- und Ernaehrungeswissenschaften Bodenbiogeochemie; Kammann, Claudia [Arbeitskreis zur Nutzung von Sekundaerrohstoffen und fuer Klimaschutz (ANS) e.V., Braunschweig (Germany). Fachausschuss Biokohle; Hochschule Geisenheim Univ. (Germany). Klimafolgenforschung-Klimawandel in Spezialkulturen; Loewen, Achim (ed.) [Arbeitskreis zur Nutzung von Sekundaerrohstoffen und fuer Klimaschutz (ANS) e.V., Braunschweig (Germany); HAWK Hochschule fuer Angewandte Wissenschaft und Kunst Hildesheim, Holzminden, Goettingen (Germany). Fachgebiet Nachhaltige Energie- und Umwelttechnik NEUtec

    2015-07-01

    The conference on ''understanding biochar mechanisms for practical implementation'' 2015 at the Geisenheim University aims at understanding biochar mechanism, that are crucial for beneficial and safety biochar technology implementation. Further issues are ecotoxicology, biochar in agriculture, horticulture, and animal husbandry. Practical issues concern analysis and characterization of technological processes, sustainable uses and certification, regulation and marketing aspects. The Conference is structured in 10 sessions.

  2. Effect of Chemical Treatment on Mechanical and Water-Sorption Properties Coconut Fiber-Unsaturated Polyester from Recycled PET

    OpenAIRE

    Munirah Abdullah, Nurul; Ahmad, Ishak

    2012-01-01

    Coconut fibers were used as reinforcement for unsaturated polyester resin from recycled PET that has been prepared using glycolysis and polyesterification reaction. Various concentrations of alkali, silane, and silane on alkalized fiber were applied and the optimum concentration of treatments was determined. Morphological and mechanical properties of the composite have also been investigated to study the effect of fiber surface treatment. The influence of water uptake on the sorption characte...

  3. Sorption of ferrous iron by EPS from the acidophilic bacterium Acidiphilium Sp.: A mechanism proposal

    International Nuclear Information System (INIS)

    Tapia, J.M.; MuNoz, J.; Gonzlez, F.; Blazquez, M.L.; Ballester, A.

    2016-01-01

    The aim of this work was to assess the uptake of Fe(II) by extracellular polymeric substances (EPS) from the acidophilic bacterium Acidiphillium 3.2Sup(5). These EPS were extracted using EDTA. EPS of A. 3.2Sup(5) loaded in sorption tests with Fe(II), were characterized using the following experimental techniques: scanning electron microscopy (SEM) with energy dispersive X-ray microanalysis (EDX), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The experimental results indicate that EPS adsorb ferrous iron according to Freundlich model with a metal sorption uptake of K = 1.14 mg1−1/n L1/n g−1 and a sorption intensity of 1/n = 1.26. In addition, ferrous iron sorption by EPS took place by preferential interaction with the carboxyl group which promotes the formation of ferrous iron oxalates (FeC2O4). Since the interaction reaction was reversible (Log K = 0.77 ± 0.33), that means that the cation sorption can be reversed at convenience. (Author)

  4. Sorption of ferrous iron by EPS from the acidophilic bacterium Acidiphilium Sp.: A mechanism proposal

    Energy Technology Data Exchange (ETDEWEB)

    Tapia, J.M.; MuNoz, J.; Gonzlez, F.; Blazquez, M.L.; Ballester, A.

    2016-07-01

    The aim of this work was to assess the uptake of Fe(II) by extracellular polymeric substances (EPS) from the acidophilic bacterium Acidiphillium 3.2Sup(5). These EPS were extracted using EDTA. EPS of A. 3.2Sup(5) loaded in sorption tests with Fe(II), were characterized using the following experimental techniques: scanning electron microscopy (SEM) with energy dispersive X-ray microanalysis (EDX), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The experimental results indicate that EPS adsorb ferrous iron according to Freundlich model with a metal sorption uptake of K = 1.14 mg1−1/n L1/n g−1 and a sorption intensity of 1/n = 1.26. In addition, ferrous iron sorption by EPS took place by preferential interaction with the carboxyl group which promotes the formation of ferrous iron oxalates (FeC2O4). Since the interaction reaction was reversible (Log K = 0.77 ± 0.33), that means that the cation sorption can be reversed at convenience. (Author)

  5. Sorption by cation exchange

    International Nuclear Information System (INIS)

    Bradbury, M.H.; Baeyens, B.

    1994-04-01

    A procedure for introducing exchange into geochemical/surface complexation codes is described. Beginning with selectivity coefficients, K c , defined in terms of equivalent fractional ion occupancies, a general expression for the molar based exchange code input parameters, K ex , is derived. In natural systems the uptake of nuclides onto complex sorbents often occurs by more than one mechanism. The incorporation of cation exchange and surface complexation into a geochemical code therefore enables sorption by both mechanisms to be calculated simultaneously. The code and model concepts are tested against sets of experimental data from widely different sorption studies. A proposal is made to set up a data base of selectivity coefficients. Such a data base would form part of a more general one consisting of sorption mechanism specific parameters to be used in conjunction with geochemical/sorption codes to model and predict sorption. (author) 6 figs., 6 tabs., 26 refs

  6. Hydro-mechanical coupling and permeability of an unsaturated swelling clay under hydrous and thermal stress: sorption curve and water permeability; Couplage hydromecanique et permeabilite d'une argile gonflante non saturee sous sollicitations hydriques et thermiques: courbe de sorption et permeabilite a l'eau

    Energy Technology Data Exchange (ETDEWEB)

    Olchitzky, E

    2002-02-15

    The use of swelling clay for engineered safety barriers of radioactive waste disposal require the understanding of its thermal-hydro-mechanical behaviour. This work concerns particularly the characterization and the modelling of the behaviour of one of these clays: the FoCa7 clay. The characteristics of the studied material are: the sorption (desorption) curve and the water permeability. For each of them, new experiments have allowed to acquire data in fields still few explored: in temperature (between 20 and 80 C) for the sorption curve and in the unsaturated field for the water permeability. The analysis of these results and of bibliographic data has allowed in one hand to estimate the importance of the hysteresis phenomenon and the temperature influence on the sorption curve and in another hand, to establish the requirement to introduce in the modelling of the sorption curve, a plastic parameter due to the irreversible deformations occurring during the compaction. Moreover, the tests carried out for data acquirement have been used too to give validation elements to the non linear behaviour laws proposed by O. Coussy and P. Dangla for the non saturated porous media. The particularity of these laws is to suppose the existence of an effective constraint in the non saturated field, this shows the importance of the validation elements presented here. (O.M.)

  7. Sorption of organophosphate esters by carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Wei; Yan, Li [State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085 (China); Duan, Jinming [School of Environmental and Municipal Engineering, Xi’an University of Architecture and Technology, Xi’an 710055 (China); Jing, Chuanyong, E-mail: cyjing@rcees.ac.cn [State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085 (China)

    2014-05-01

    Graphical abstract: The interfacial interactions between the OPE molecules and CNTs. - Highlights: • Oxygen-containing groups on CNTs change the sorption property for OPEs. • Molecular configuration of OPEs has insignificant impact on their sorption. • Hydrophobic, π–π EDA and Brønsted acid–base interaction occurred between the CNTs and OPEs. - Abstract: Insights from the molecular-level mechanism of sorption of organophosphate esters (OPEs) on carbon nanotubes (CNTs) can further our understanding of the fate and transport of OPEs in the environment. The motivation for our study was to explore the sorption process of OPEs on multi-walled CNTs (MWCNTs), single-walled CNTs (SWCNTs) and their oxidized counterparts (O-MWCNTs and O-SWCNTs), and its molecular mechanism over a wide concentration range. The sorption isotherm results revealed that the hydrophobicity of OPEs dominated their affinities on a given CNT and the π–π electron donor–acceptor (EDA) interaction also played an important role in the sorption of aromatic OPEs. This π–π EDA interaction, verified with Raman and FT-IR spectroscopy, could restrict the radial vibration of SWCNTs and affect the deformation vibration γ(CH) bands of OPE molecules. The OPE surface coverage on CNTs, estimated using the nonlinear Dubinin–Ashtakhov model, indicated that the oxygen-containing functional groups on CNTs could interact with water molecules by H-bonding, resulting in a decrease in effective sorption sites. In addition, FTIR analysis also confirmed the occurrence of Brønsted acid–base interactions between OPEs and surface OH groups of SWCNTs. Our results should provide mechanistic insights into the sorption mechanism of OPE contaminants on CNTs.

  8. Effects and Mechanisms of Mechanical Activation on Hydrogen Sorption/ Desorption of Nanoscale Lithium Nitrides

    Energy Technology Data Exchange (ETDEWEB)

    Shaw, Leon, L.; Yang, Gary, Z.; Crosby, Kyle; Wwan, Xufei. Zhong, Yang; Markmaitree, Tippawan; Osborn, William; Hu, Jianzhi; Kwak, Ja Hun

    2012-04-26

    The objective of this project is to investigate and develop novel, mechanically activated, nanoscale Li3N-based and LiBH4-based materials that are able to store and release {approx}10 wt% hydrogen at temperatures near 100 C with a plateau hydrogen pressure of less than 10 bar. Four (4) material systems have been investigated in the course of this project in order to achieve the project objective. These 4 systems are (i) LiNH2+LiH, (ii) LiNH2+MgH2, (iii) LiBH4, and (iv) LiBH4+MgH2. The key findings we have obtained from these 4 systems are summarized below. *The thermodynamic driving forces for LiNH2+LiH and LiBH4 systems are not adequate to enable H2 release at temperatures < 100 C. *Hydrogen release in the solid state for all of the four systems is controlled by diffusion, and thus is a slow process. *LiNH2+MgH2 and LiBH4+MgH2 systems, although possessing proper thermodynamic driving forces to allow for H2 release at temperatures < 100 C, have sluggish reaction kinetics because of their diffusion-controlled rate-limiting steps. *Reducing particles to the nanometer length scale (< 50 nm) can improve the thermodynamic driving force to enable H2 release at near ambient temperature, while simultaneously enhancing the reaction kinetics as well as changing the diffusion-controlled rate-limiting step to gas desorption-controlled rate-limiting step. This phenomenon has been demonstrated with LiBH4 and offers the hope that further work along this direction will make one of the material systems, i.e., LiBH4, LiBH4+MgH2 and LiNH2+MgH2, possess the desired thermodynamic properties and rapid H2 uptake/release kinetics for on-board applications. Many of the findings and knowledge gained from this project have been published in archival refereed journal articles [1-15] and are accessible by general public. Thus, to avoid a bulky final report, the key findings and knowledge gained from this project will be succinctly summarized, particularly for those findings and knowledge

  9. Investigating the sorption behavior of cadmium from aqueous solution by potassium permanganate-modified biochar: quantify mechanism and evaluate the modification method.

    Science.gov (United States)

    Fan, Zixi; Zhang, Qian; Li, Meng; Niu, Dongyuan; Sang, Wenjiao; Verpoort, Francis

    2018-03-01

    In this work, a KMnO 4 -modified-biochar-based composite material with manganese oxide produced at 600 °C was fabricated to investigate the sorption mechanism of Cd(II) and to comprehensively evaluate the effect of the modification on biochar properties. Cd(II) adsorption mechanisms were mainly controlled by interaction with minerals, complexation with oxygen-containing functional groups, and cation-π interaction. The sorption capacity was significantly reduced after a deash treatment of biochar, almost shrunk by 3 and 3.5 times for pristine biochar (PBC) and modified biochar (MBC). For deashed PBC, oxygen-containing functional groups were the main contributor toward Cd(II) adsorption while interaction with minerals was significantly compromised and became negligible. The sorption capacity was also apparently decreased after the deash treatment of MBC; however, for deashed MBC, interaction with minerals still was the main contributor to the sorption ability, which could be attributed to the mechanism of interaction of Cd(II) with loaded MnO x on biochar. Cation-π interaction in MBC was notably enhanced compared to PBC due to the oxidation of KMnO 4 on biomass. Also, sorption performance by oxygen-containing functional groups was also enhanced. Hence, the modification by KMnO 4 has a significant effect on the Cd(II) sorption performance of biochar.

  10. Sorption of colloids, organics, and metals onto gas-water interfaces: Transport mechanisms and potential remediation technology. 1998 annual progress report

    International Nuclear Information System (INIS)

    Tokunaga, T.K.; Wan, J.

    1998-01-01

    'Although contaminant sorption at mineral surfaces has received much recognition as a major mechanism controlling contaminant behavior in subsurface environments, virtually no attention has been given to the possibility of contaminant sorption at gas-water interfaces. Moreover, no effort has yet been advanced to optimize such interactions for the purpose of facilitating in-situ remediation. Gas-water interfaces, unlike water-solid interfaces, are mobile. Therefore, associations of contaminants with gas-water interfaces can be very important not only in subsurface contaminant distributions, but also in contaminant transport, and potentially in remediation. The first objective of this research is to develop a quantitative understanding of interactions between contaminants and gas-water interfaces. The anticipated results will provide insights into the poorly understood phenomenon of contaminant interactions with the gas-water interface, and improve the current conceptual models of contaminant behavior in subsurface environments. The second purpose of this research is to explore the possibility of using surfactant stabilized microbubbles for in-situ remediation. Both pump-and-treat, and air sparging remediation methods are ineffective at displacing contaminants in zones which are advectively inaccessible. Stable microbubbles can migrate beyond preferential flow pathways and enter lower permeability zones by buoyant rise. The microbubbles can deliver oxygen and nutrients for promoting aerobic degradation of organic contaminants, and also deliver surfactants for emulsifying NAPLs.'

  11. U(VI) and Eu(III) ion sorption in the interface solution-phosphate solids: Structural study and mechanisms

    International Nuclear Information System (INIS)

    Drot, Romuald

    1998-01-01

    As part of the storage of nuclear wastes in a deep underground disposal, radionuclides sorption on geological or engineered barriers is one of the most important factor which could enhance retardation. Thus, the knowledge of such mechanisms is needed. For this purpose, we chose to experimentally define sorption equilibria before performing simulation of retention data. Several phosphate compounds are potential candidates as engineered barrier additives. We considered Th 4 (PO 4 ) 4 P 2 O 7 , Zr 2 O(PO 4 ) 2 which allow to study the effect of PO 4 and P 2 O 7 groups separately. Eu(III) and U(IV) ions were used as structural probes in order to simulate actinides (III) and (VI) behavior. X-ray powder diffraction, IR spectroscopy and electron probe microanalysis were used to characterized the synthesized solids. Electrophoretic measurements showed an amphoteric behavior of surface sites. Moreover, laser spectro-fluorimetry experiments indicated that no diffusion phenomena of the sorbed ion inside the solid occurs. Thus, we considered that a surface complexation model should be applied. Laser spectro-fluorimetry and XPS allowed to determine the nature of surface sites. ZrP 2 O 7 presents only one single site (P 2 O 7 groups) whereas Th 4 (PO 4 ) 4 P 2 O 7 and Zr 2 O(PO 4 ) 2 admit two types of sites (PO 4 /P 2 O 7 and PO 4 /oxo groups, respectively). Sorbed species were identified using laser spectro-fluorimetry which indicate that, in KNO 3 0.5 M medium and for a known surface site, there are two surface complexes for U(VI) (sorption of UO 2+ 2 et de UO 2 NO + 3 species) and only one for Eu(III) (sorption of EuNO 2+ 3 ). They are linked to the substrate as bidentate inner sphere complexes (EXAFS study). Surface acidity constants were determined by simulation of potentiometric titration curves obtained for each solid suspension using FITEQL code (CCM). As sorption equilibria were defined, experimental retention data simulation was performed with respect to structural

  12. Steady State Sorption Measurement and the Transport Mechanism in Polymeric Membrane during Vapor Permeation

    Czech Academy of Sciences Publication Activity Database

    Fialová, Kateřina; Petričkovič, Roman; Sharma, M.; Uchytil, Petr

    2006-01-01

    Roč. 275, 1-2 (2006), s. 166-174 ISSN 0376-7388 R&D Projects: GA ČR(CZ) GD203/03/H140; GA AV ČR(CZ) IAA4072402 Institutional research plan: CEZ:AV0Z40720504 Keywords : sorption * vapor permeation * diffusion coefficient Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 3.442, year: 2006

  13. Contribution to the study of sorption mechanisms at solid-liquid interfaces: application to the cases of apatites and oxy-hydroxides

    International Nuclear Information System (INIS)

    Duc, M.

    2002-11-01

    Sorption-desorption phenomena play an important role in the transport of toxic and radioactive elements in surface and underground water in contact with solid matter. Selenium, which is one of the long-lived radionuclides present in radioactive waste, is characterized by several oxidation states and by anionic species in aqueous solutions. In order to predict its transport, we need a good knowledge of its sorption processes. We have studied the sorption of Se(IV) and Se(VI) on two types of solids present in natural media or which have been proposed as additives to active barriers: hydroxy-apatites, fluoro-apatite and iron oxi-hydroxides (goethite and hematite). Sorption mechanisms have been studied through an approach including several different and complementary methods: titrimetry, zeta-metry, scanning and transmission electron microscopy, infrared spectroscopy, X-ray diffraction, X-ray photo electron spectroscopy, etc... Results showed that Se(VI) is much less sorbed than Se(VI) on both types of solids. For Se(IV) the sorption mechanisms are different for iron oxides and apatites. On oxides, sorption increases when pH decreases. It can be interpreted by a surface complexation model, essentially through an inner sphere complex (monodentate or bidentate). Modelling of Se sorption curves was performed after the determination of acido-basic properties of oxides. However, the determination of the intrinsic properties of oxides is disturbed by several parameters identified as impurities, evolution of the solid in solution, kinetic and solubility of the solid. For apatites, selenium sorption proceeds by exchange with superficial groups, with a maximum of fixation at approximately pH 8. Thanks to XPS measurements and the elaboration of a mathematical model, we could determine the depth of penetration of both selenium and cadmium on apatites. (author)

  14. Yucca Mountain Project far-field sorption studies and data needs

    International Nuclear Information System (INIS)

    Meijer, A.

    1990-09-01

    Batch sorption experiments in which radionuclides dissolved in groundwaters from Yucca Mountain were sorbed onto samples of crushed tuff have resulted in a substantial database of sorption coefficients for radionuclides of interest to the repository program. Although this database has been useful in preliminary evaluations of Yucca Mountain as a potential site for a nuclear waste repository, the database has limitations that must be addressed before it can be used for performance assessment calculations in support of a license application for a waste repository. The purpose of this paper is to: review the applicability of simple (constant) sorption coefficients in transport calculations; review and evaluate alternative methods for the derivation of sorption coefficients; summarize and evaluate the present YMP sorption database to identify areas of data sufficiency and significant data gaps; summarize our current understanding of pertinent sorption mechanisms and associated kinetic parameters; evaluate the significance to the YMP of potential problems in the experimental determination and field application of sorption coefficients as enumerated by the NRC (Nuclear Regulatory Commission, 1987) in its technical position paper on sorption; formulate and evaluate strategies for the resolution of NRC concerns regarding experimental problems; and formulate a position on the sorption coefficient database and the level of understanding of sorption mechanisms likely to be required in the licensing application. 75 refs., 1 fig., 2 tabs

  15. Improving students' understanding of quantum mechanics

    Science.gov (United States)

    Singh, Chandralekha

    2011-03-01

    Learning quantum mechanics is especially challenging, in part due to the abstract nature of the subject. We have been conducting investigations of the difficulties that students have in learning quantum mechanics. To help improve student understanding of quantum concepts, we are developing quantum interactive learning tutorials (QuILTs) as well as tools for peer-instruction. The goal of QuILTs and peer-instruction tools is to actively engage students in the learning process and to help them build links between the formalism and the conceptual aspects of quantum physics without compromising the technical content. They focus on helping students integrate qualitative and quantitative understanding, confront and resolve their misconceptions and difficulties, and discriminate between concepts that are often confused. In this talk, I will give examples from my research in physics education of how students' prior knowledge relevant for quantum mechanics can be assessed, and how learning tools can be designed to help students develop a robust knowledge structure and critical thinking skills. Supported by the National Science Foundation.

  16. Mechanism of Cu(II), Cd(II) and Pb(II) ions sorption from aqueous solutions by macroporous poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate)

    Energy Technology Data Exchange (ETDEWEB)

    Nastasović, Aleksandra B., E-mail: anastaso@chem.bg.ac.rs [University of Belgrade, Institute of Chemistry Technology and Metallurgy, Department of Chemistry, Department of Microelectronic Technologies, Njegoševa 12, Belgrade (Serbia); Ekmeščić, Bojana M. [University of Belgrade, Institute of Chemistry Technology and Metallurgy, Department of Chemistry, Department of Microelectronic Technologies, Njegoševa 12, Belgrade (Serbia); and others

    2016-11-01

    Highlights: • Macroporous PGME-deta sorption potential for Pb(II), Cd(II) and Cu(II) was studied. • Sorption kinetics obeyed pseudo-second order model. • Maximal Pb(II), Cd(II) and Cu(II) sorption capacities were 164, 152 and 120 mg g{sup −1}. • AFM indicates that metal sorption changes the size and morphology of PGME-deta. • XPS suggests complexation through the formation of Me−O and Me−N bonds in PGME-deta. - Abstract: The mechanism of Cu(II), Cd(II) and Pb(II) ions sorption from aqueous solutions by macroporous poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) (PGME) functionalized by reaction of the pendant epoxy groups with diethylene triamine (PGME-deta) was studied using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) analysis. Atomic force microscopy (AFM) and scanning energy-dispersive X-ray spectroscopy (SEM-EDX) were used for the determination of surface morphology of the copolymer particles. The sorption behavior of heavy metals Cu(II), Cd(II) and Pb(II) ions sorption was investigated in batch static experiments under non-competitive conditions at room temperature (298 K). The obtained results were fitted to pseudo-first order, pseudo-second order and intraparticle diffusion kinetic model. The kinetics studies showed that Cu(II), Cd(II) and Pb(II) sorption obeys the pseudo-second-order model under all investigated operating conditions with evident influence of pore diffusion.

  17. Sorption of Th(IV) onto ZnO nanoparticles and diatomite-supported ZnO nanocomposite. Kinetics, mechanism and activation parameters

    Energy Technology Data Exchange (ETDEWEB)

    Yusan, Sabriye; Aslani, Mahmut A.A.; Aytas, Sule [Ege Univ., Izmir (Turkey). Inst. of Nuclear Sciences; Bampaiti, Anastasia; Noli, Fotini [Aristotle University of Thessaloniki (Greece). Dept. of Chemistry; Erenturk, Sema [Istanbul Technical Univ., Ayazaga Campus, Maslak-Istanbul (Turkey). Energy Inst.

    2016-11-01

    In this study, for the first time ZnO nanoparticles and diatomite-supported ZnO nanocomposite have been utilized as adsorbent for the removal of Th(IV) ions from aqueous solutions under different experimental conditions. The Langmuir, Freundlich, Temkin and Dubinin- Radushkevich (D-R) isotherms were used to analyze the equilibrium data. The sorption equilibrium data were fitted well to the Langmuir isotherm with maximum sorption capacities values was found to be 1.105 mmol/g and 0.320 mmol/g for ZnO nanoparticles and diatomite supported ZnO nanocomposite, respectively. Pseudo-first and pseudo-second order equations, Intraparticle diffusion and Bangham's models were considered to evaluate the rate parameters and sorption mechanism. Sorption kinetics were better reproduced by the pseudo-second order model (R{sup 2} > 0.999), with an activation energy (E{sub a}) of +99.74 kJ/mol and +62.95 kJ/mol for ZnO nanoparticles and diatomite-supported ZnO nanocomposite, respectively. In order to specify the type of sorption reaction, thermodynamic parameters were also determined. The evaluated ΔG* and ΔH* indicate the non-spontaneous and endothermic nature of the reactions. The results of this work suggest that both of the used materials are fast and effective adsorbents for removing Th(IV) from aqueous solutions and chemical sorption plays a role in controlling the sorption rate.

  18. Polyethylenimine-modified fungal biomass as a high-capacity biosorbent for Cr(VI) anions: sorption capacity and uptake mechanisms.

    Science.gov (United States)

    Deng, Shubo; Ting, Yen Peng

    2005-11-01

    Heavy metal pollution in the aqueous environment is a problem of global concern. Biosorption has been considered as a promising technology for the removal of low levels of toxic metals from industrial effluents and natural waters. A modified fungal biomass of Penicillium chrysogenum with positive surface charges was prepared by grafting polyethylenimine (PEI) onto the biomass surface in a two-step reaction. The presence of PEI on the biomass surface was verified by FTIR and X-ray photoelectron spectroscopy (XPS) analyses. Due to the high density of amine groups in the long chains of PEI molecules on the surface, the modified biomass was found to possess positive zeta potential at pH below 10.4 as well as high sorption capacity for anionic Cr(VI). Using the Langmuir adsorption isotherm, the maximum sorption capacity for Cr(VI) at a pH range of 4.3-5.5 was 5.37 mmol/g of biomass dry weight, the highest sorption capacity for Cr(VI) compared to other sorbents reported in the literature. Scanning electronic microscopy (SEM) provided evidence of chromium aggregates formed on the biomass surface. XPS results verified the presence of Cr(III) on the biomass surface in the pH range 2.5-10.5, suggesting that some Cr(VI) anions were reduced to Cr(III) during the sorption. The sorption kinetics indicated that redox reaction occurred on the biomass surface, and whether the converted Cr(III) ions were released to solution or adsorbed on the biomass depended on the solution pH. Sorption mechanisms including electrostatic interaction, chelation, and precipitation were found to be involved in the complex sorption of chromium on the PEI-modified biomass.

  19. Understanding the molecular mechanisms of reprogramming

    Energy Technology Data Exchange (ETDEWEB)

    Krause, Marie N. [Gene Expression Laboratory, Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla 92037, CA (United States); University Hospital of Würzburg, Department of Pediatrics, 2 Josef-Schneiderstrasse, 97080 Würzburg (Germany); Sancho-Martinez, Ignacio [Gene Expression Laboratory, Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla 92037, CA (United States); Centre for Stem Cells and Regenerative Medicine, King' s College London, 28th Floor, Tower Wing, Guy' s Hospital, Great Maze Pond, London (United Kingdom); Izpisua Belmonte, Juan Carlos, E-mail: belmonte@salk.edu [Gene Expression Laboratory, Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla 92037, CA (United States)

    2016-05-06

    Despite the profound and rapid advancements in reprogramming technologies since the generation of the first induced pluripotent stem cells (iPSCs) in 2006[1], the molecular basics of the process and its implications are still not fully understood. Recent work has suggested that a subset of TFs, so called “Pioneer TFs”, play an important role during the stochastic phase of iPSC reprogramming [2–6]. Pioneer TFs activities differ from conventional transcription factors in their mechanism of action. They bind directly to condensed chromatin and elicit a series of chromatin remodeling events that lead to opening of the chromatin. Chromatin decondensation by pioneer factors progressively occurs during cell division and in turn exposes specific gene promoters in the DNA to which TFs can now directly bind to promoters that are readily accessible[2, 6]. Here, we will summarize recent advancements on our understanding of the molecular mechanisms underlying reprogramming to iPSC as well as the implications that pioneer Transcription Factor activities might play during different lineage conversion processes. - Highlights: • Pioneer transcription factor activity underlies the initial steps of iPSC generation. • Reprogramming can occur by cis- and/or trans- reprogramming events. • Cis-reprogramming implies remodeling of the chromatin for enabling TF accessibility. • Trans-reprogramming encompasses direct binding of Tfs to their target gene promoters.

  20. Understanding the H 2 Sorption Trends in the M-MOF-74 Series (M = Mg, Ni, Co, Zn)

    KAUST Repository

    Pham, Tony

    2015-01-15

    © 2014 American Chemical Society. Electronic structure calculations and simulations of H2 sorption were performed in four members of the M-MOF-74 series: Mg-MOF-74, Ni-MOF-74, Co-MOF-74, and Zn-MOF-74. Notable differences were observed in the partial charge and polarizability of the metal ions derived from the electronic structure calculations. The modeling parameters obtained from the electronic structure calculations were found to influence certain features in the experimentally observed H2 sorption trends in the M-MOF-74 series. The simulations were performed with the inclusion of explicit many-body polarization, which was required to reproduce the experimental H2 sorption observables (i.e., sorption isotherms and isosteric heats of adsorption (Qst)) and the H2-metal interaction in all four MOFs using classical molecular simulation. Consistent with experimental measurements, the simulations captured the following trend for the H2-metal interaction strength: Ni-MOF-74 > Co-MOF-74 > Mg-MOF-74 > Zn-MOF-74. The calculations revealed that stronger H2-metal interactions within the M-MOF-74 series corresponded to shorter H2-metal distances and higher induced dipoles on the metal-sorbed H2 molecules. In addition, it was observed that there was a strong correlation between the H2-metal interaction and the polarization contribution. Although Mg-MOF-74 has the highest calculated partial charge for the metal ion within the series, the Mg2+ ion has a very low polarizability compared to the other M2+ ions; this explains why the H2-metal interaction in this MOF is weaker compared to those for Ni-MOF-74 and Co-MOF-74. The sterics interactions, reflected in the crystal structure for all four MOFs, also played a role for the observed H2 sorption trends. Zn-MOF-74 has the lowest H2 uptakes and Qst within the series due to an unfavorable geometric environment for the Zn2+ ions within the ZnO5 clusters. Lastly, the two-dimensional quantum rotational levels were calculated for the H

  1. Modeling the sorption kinetic of metsulfuron-methyl on Andisols and Ultisols volcanic ash-derived soils: kinetics parameters and solute transport mechanisms.

    Science.gov (United States)

    Cáceres, Lizethly; Escudey, Mauricio; Fuentes, Edwar; Báez, María E

    2010-07-15

    Metsulfuron-methyl sorption kinetic was studied in Andisol and Ultisol soils in view of their distinctive physical and chemical properties: acidic pH and variable surface charge. Different kinetic models were applied to the experimental results. The pseudo-second-order model fitted sorption kinetics data better than the pseudo-first-order model. The rate constant and the initial rate constant values obtained through this model demonstrated the different behavior of metsulfuron-methyl in both kinds of soils, both parameters being the highest for Andisol. The application of Elovich equation, intraparticle diffusion model and a two-site nonequilibrium model (TSNE) allowed to conclude that: (i) the high organic matter content is the governing factor for Andisols where mass transfer across the boundary layer, and in a lesser degree, intraparticle diffusion were the two processes controlling sorption kinetic and (ii) the mineral composition was more relevant in Ultisols where rate was controlled almost exclusively by intraparticle diffusion into macropores and micropores. The slower sorption rate on Ultisols, the mechanism involved and the lower sorption capacity of this kind of soils must be taken into account to assess leaching behavior of this herbicide. 2010 Elsevier B.V. All rights reserved.

  2. Sorption Mechanisms for Mercury Capture in Warm Post-Gasification Gas Clean-Up Systems

    Energy Technology Data Exchange (ETDEWEB)

    Jost Wendt; Sung Jun Lee; Paul Blowers

    2008-09-30

    The research was directed towards a sorbent injection/particle removal process where a sorbent may be injected upstream of the warm gas cleanup system to scavenge Hg and other trace metals, and removed (with the metals) within the warm gas cleanup process. The specific objectives of this project were to understand and quantify, through fundamentally based models, mechanisms of interaction between mercury vapor compounds and novel paper waste derived (kaolinite + calcium based) sorbents (currently marketed under the trade name MinPlus). The portion of the research described first is the experimental portion, in which sorbent effectiveness to scavenge metallic mercury (Hg{sup 0}) at high temperatures (>600 C) is determined as a function of temperature, sorbent loading, gas composition, and other important parameters. Levels of Hg{sup 0} investigated were in an industrially relevant range ({approx} 25 {micro}g/m{sup 3}) although contaminants were contained in synthetic gases and not in actual flue gases. A later section of this report contains the results of the complementary computational results.

  3. A mechanistic approach to the generation of sorption databases

    International Nuclear Information System (INIS)

    Bradbury, M.H.; Baeyens, B.

    1992-01-01

    Sorption of radionuclides in the near and far fields of an underground nuclear waste repository is one of the most important processes retarding their release to the environment. In the vast majority of cases sorption data have been presented in terms of empirical parameters such as distribution coefficients and isotherm equations. A consequence of this empirical methodology is that the sorption data are only strictly valid under the experimental conditions at which they were measured. Implicit in this approach is the need to generate large amounts of data and fitting parameters necessary for an empirical description of sorption under all realistically conceivable conditions which may arise in space and time along the migration pathway to Man. An alternative approach to the problem is to try to understand, and develop model descriptions of, underlying retention mechanisms and to identify those systems parameters which essentially determine the extent of sorption. The aim of this work is to see to what extent currently existing mechanistic models, together with their associated data, can be applied to predict sorption data from laboratory experiments on natural systems. This paper describes the current status of this work which is very much in an early stage of development. An example is given whereby model predictions are compared with laboratory results for the sorption of Np at trace concentrations under oxidizing conditions on a series of minerals relevant to granite formations. 31 refs., 11 figs., 5 tabs

  4. Sorption of radionuclides on Yucca Mountain tuffs

    International Nuclear Information System (INIS)

    Meijaer, A.; Triay, I.; Knight, S.; Cisneros, M.

    1989-01-01

    A substantial database of sorption coefficients for important radionuclides on Yucca Mountain tuffs has been obtained by Los Alamos National Laboratory over the past ten years. Current sorption studies are focussed on validation questions and augmentation of the existing database. Validation questions concern the effects of the use of crushed instead of solid rock samples in the batch experiments, the use of oversaturated stock solutions, and variations in water/rock ratios. Sorption mechanisms are also being investigated. Database augmentation activities include determination of sorption coefficients for elements with low sorption potential, sorption on psuedocolloids, sorption on fracture lining minerals, and sorption kinetics. Sorption can provide an important barrier to the potential migration of radionuclides from the proposed repository within Yucca Mountain to the accessible environment. In order to quantify this barrier, sorption coefficients appropriate for the Yucca Mountain groundwater system must be obtained for each of the important radionuclides in nuclear waste. Los Alamos National Laboratories has conducted numerous batch (crushed-rock) sorption experiments over the past ten years to develop a sorption coefficient database for the Yucca Mountain site. In the present site characterization phase, the main goals of the sorption test program will be to validate critical sorption coefficients and to augment the existing database where important data are lacking. 11 refs., 1 fig., 3 tabs

  5. Mechanism of Cu(II), Cd(II) and Pb(II) ions sorption from aqueous solutions by macroporous poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate)

    Science.gov (United States)

    Nastasović, Aleksandra B.; Ekmeščić, Bojana M.; Sandić, Zvjezdana P.; Ranđelović, Danijela V.; Mozetič, Miran; Vesel, Alenka; Onjia, Antonije E.

    2016-11-01

    The mechanism of Cu(II), Cd(II) and Pb(II) ions sorption from aqueous solutions by macroporous poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) (PGME) functionalized by reaction of the pendant epoxy groups with diethylene triamine (PGME-deta) was studied using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) analysis. Atomic force microscopy (AFM) and scanning energy-dispersive X-ray spectroscopy (SEM-EDX) were used for the determination of surface morphology of the copolymer particles. The sorption behavior of heavy metals Cu(II), Cd(II) and Pb(II) ions sorption was investigated in batch static experiments under non-competitive conditions at room temperature (298 K). The obtained results were fitted to pseudo-first order, pseudo-second order and intraparticle diffusion kinetic model. The kinetics studies showed that Cu(II), Cd(II) and Pb(II) sorption obeys the pseudo-second-order model under all investigated operating conditions with evident influence of pore diffusion.

  6. Understanding molecular structure from molecular mechanics.

    Science.gov (United States)

    Allinger, Norman L

    2011-04-01

    Molecular mechanics gives us a well known model of molecular structure. It is less widely recognized that valence bond theory gives us structures which offer a direct interpretation of molecular mechanics formulations and parameters. The electronic effects well-known in physical organic chemistry can be directly interpreted in terms of valence bond structures, and hence quantitatively calculated and understood. The basic theory is outlined in this paper, and examples of the effects, and their interpretation in illustrative examples is presented.

  7. Thermodynamic analysis of water vapor sorption isotherms and mechanical properties of selected paper-based food packaging materials.

    Science.gov (United States)

    Rhim, Jong-Whan; Lee, Jun Ho

    2009-01-01

    Adsorption isotherms of 3 selected paper-based packaging materials, that is, vegetable parchment (VP) paper, Kraft paper, and solid-bleached-sulfate (SBS) paperboard, were determined at 3 different temperatures (25, 40, and 50 degrees C). The GAB isotherm model was found to fit adequately for describing experimental adsorption isotherm data for the paper samples. The monolayer moisture content of the paper samples decreased with increase in temperature, which is in the range of 0.0345 to 0.0246, 0.0301 to 0.0238, and 0.0318 to 0.0243 g water/g solid for the MG paper, the Kraft paper, and the SBS paperboard, respectively. The net isosteric heats of sorption (q(st)) for the paper samples decreased exponentially with increase in moisture content after reaching the maximum values of 18.51, 27.39, and 26.80 kJ/mol for the VP paper, the Kraft paper, and the SBS paperboard, respectively, at low-moisture content. The differential enthalpy and entropy of 3 paper samples showed compensation phenomenon with the isokinetic temperature of 399.7 K indicating that water vapor had been adsorbed onto the paper samples with the same mechanism. Depending on the paper material, tensile strength of paper samples was affected by moisture content.

  8. A new glance at ruthenium sorption mechanism on hydroxy, carbonate, and fluor apatites: Analytical and structural studies.

    Science.gov (United States)

    Tõnsuaadu, K; Gruselle, M; Villain, F; Thouvenot, R; Peld, M; Mikli, V; Traksmaa, R; Gredin, P; Carrier, X; Salles, L

    2006-12-15

    The sorption mechanism of Ru3+ ions on hydroxy (HAp), carbonate (CO3HAp), and fluor apatites (FAp) has been studied in detail. Ru apatites were obtained by reaction of the apatites with RuCl3 in aqueous solution. The structure and composition of the ruthenium-modified apatites were studied by several techniques: elemental analysis, XRD, EXAFS, IR, NMR, SEM-EDS, TEM, and thermal analysis. The amount of Ru in the modified apatite varies from 7.8 to 10.5 wt% and is not related to the initial composition or the specific surface area of the apatite. The different characterization techniques show that in the Ru-modified apatites Ru is surrounded by six oxygen atoms and do not contain any chlorine. For Ru-HAp and Ru-CO3HAp the new phase is amorphous whereas it is crystalline for FAp. The catalytic oxidation ability is higher for Ru-HAp and Ru-CO3HAp compared to Ru-FAp apatite in the oxidation of benzylic alcohol.

  9. Understanding Kinetic Energy paradox in Quantum Mechanics

    OpenAIRE

    Kornyushin, Yuri

    2008-01-01

    A concept of Kinetic Energy in Quantum Mechanics is analyzed. Kinetic Energy is not zero in many cases where there are no motion and flux. This paradox can be understood, using expansion of the wave function in Fourier integral, that is on the basis of virtual plane waves.

  10. The influence of water sorption-desorption cycles on the mechanical properties of composites based on recycled polyolefine and linen yarn production waste

    Science.gov (United States)

    Bakradze, G.; Kajaks, J.; Reihmane, S.; Krutohvostov, R.; Bulmanis, V.

    2007-11-01

    The effect of water on the mechanical properties (tensile modulus, ultimate tensile strength, tensile strain, and specific work at break) of both chemically treated and untreated composites based on a recycled low-density polyethylene and linen yarn production waste is analyzed. It is found that three water sorption-desorption cycles change the tensile properties of both the materials irreversibly. This effect is considered as the result of partial fracture of the fiber-matrix interface.

  11. Inhibitory effects of extracellular polymeric substances on ofloxacin sorption by natural biofilms.

    Science.gov (United States)

    Zhang, Liwen; Dong, Deming; Hua, Xiuyi; Guo, Zhiyong

    2018-06-01

    Natural biofilms have strong affinities for organic contaminants, and their extracellular polymeric substances (EPS) have been thought to control the sorption process. However, the role of EPS in the sorption of antibiotics, an emerging concern, is poorly understood. Here, soluble (SEPS) and bound EPS (BEPS) were extracted from intact biofilms incubated at different lengths of time to obtain SEPS- and BEPS-free biofilms. Batch sorption experiments and infrared spectroscopy were used to investigate the role of EPS in the sorption of ofloxacin (OFL) by natural biofilms. The sorption capacities of OFL onto intact biofilms were lower than that those onto SEPS-free and BEPS-free biofilms. Partition and Langmuir adsorption contributed to the sorption of OFL onto these biofilms. SEPS and BEPS suppressed partitioning of OFL into biofilm organic matter. Meanwhile, the formation of hydrogen bonds could affect the Langmuir adsorption of OFL onto BEPS-free biofilms. These sorption mechanisms occurred simultaneously and enhanced the sorption capacities of biofilms after EPS removal. The information obtained in this study is beneficial for understanding the interaction mechanisms between antibiotics and natural biofilms. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Highly Efficient Lead Distribution by Magnetic Sewage Sludge Biochar: Sorption Mechanisms and Bench Applications.

    Science.gov (United States)

    Ifthikar, Jerosha; Wang, Jia; Wang, Qiliang; Wang, Ting; Wang, Huabin; Khan, Aimal; Jawad, Ali; Sun, Tingting; Jiao, Xiang; Chen, Zhuqi

    2017-08-01

    Highly efficient magnetic sewage sludge biochar (MSSBC) discloses feasible fabrication process with lower production cost, superior adsorption capacity, usage of waste sewage sludge as resource, selected by external magnetic field and exceptional regeneration property. 2gL -1 MSSBC exhibited a high adsorption capacity of 249.00mgg -1 in 200ppmPb(II) and the lead-MSSBC equilibrium was achieved within one hour, owing to the existence of the copious active sites. The adsorption kinetics was well described by the pseudo-second-order model while the adsorption isotherm could be fitted by Langmuir model. Mechanism study demonstrated the adsorption involved electrostatic attraction, ion exchange, inner-sphere complexation and formation of co-precipitates at the surface of MSSBC. Additionally, adsorption performance maintained remarkable in a broad pH window. These outcomes demonstrated the promising waste resource utilization by a feasible approach that turns the solid waste of sewage sludge into biochar adsorbent with auspicious applications in elimination of Pb(II) from wastewater. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Sorption and mechanism of aqueous U(Ⅵ) onto red soil-colloid

    International Nuclear Information System (INIS)

    Xia Liangshu; Huang Xin; Cao Cuncun; Chen Wei; Lu Junwen

    2013-01-01

    By static adsorption experiments, the effects of pH, ionic strength, adsorption time, uranium initial concentration, adsorbent dosage, red soil-colloid size, and organic matters on the biosorption capacity of red soil-colloid extracted from the soil around uranium tailing for uranium were studied. The adsorption process was analyzed by thermodynamics and kinetics, and the adsorption mechanism was characterized by the element analysis, infrared spectroscopy and scanning electron microscopy. The results show that the adsorption capacity for U (Ⅵ) on red soil-colloid increases with the decrease of ionic strength or particle size, increases with the initial concentration of uranium, decreases with the increase of the amount of red soil-colloid; the saturated adsorption capacity q max can be up to 76.76 μg/mg by red soil-colloid which diameter is less than 1 μm at 25 ℃ and pH=3.5, when the ionic strength is 0.001 mol/L. FT-IR micrograph before and after red soil-colloid adsorbed uranyl ions indicates that the red soil-colloid are mainly composed of hydroxyl, carbonyl, Si-O, Si-O-Fe, etc. The adsorption of U (Ⅵ) on red soil-colloid follows Langmuir adsorption isotherm, and the pseudo-second-order equation provides the best correlation for the adsorption process. (authors)

  14. Sorption of beryllium from sulfuric acid solutions by aminocarboxylic polyampholites

    International Nuclear Information System (INIS)

    Pakholkov, V.S.; Tsevin, A.P.; Rychkov, V.N.

    1985-01-01

    Sorption of beryllium ions from BeSo 4 solutions by aminocarboxylic polyampholites at 18 deg C under steady-state conditions is studied. With the pH value growth the sorption of beryllium ions increases, that is characteristic for sorption according the cation exchange mechanism. Co- sorption of beryllium and uranium from BeSO 4 , UO 2 SO 4 , (NH 4 ) 2 SO 4 solution is considered, and possibility of sorption beryllium purification from uranium impurity is shown

  15. Contribution to the study of sorption mechanisms at solid-liquid interfaces: application to the cases of apatites and oxy-hydroxides; Contribution a l'etude des mecanismes de sorption aux interfaces solide-liquide: application aux cas des apatites et des oxy-hydroxydes

    Energy Technology Data Exchange (ETDEWEB)

    Duc, M

    2002-11-15

    Sorption-desorption phenomena play an important role in the transport of toxic and radioactive elements in surface and underground water in contact with solid matter. Selenium, which is one of the long-lived radionuclides present in radioactive waste, is characterized by several oxidation states and by anionic species in aqueous solutions. In order to predict its transport, we need a good knowledge of its sorption processes. We have studied the sorption of Se(IV) and Se(VI) on two types of solids present in natural media or which have been proposed as additives to active barriers: hydroxy-apatites, fluoro-apatite and iron oxi-hydroxides (goethite and hematite). Sorption mechanisms have been studied through an approach including several different and complementary methods: titrimetry, zeta-metry, scanning and transmission electron microscopy, infrared spectroscopy, X-ray diffraction, X-ray photo electron spectroscopy, etc... Results showed that Se(VI) is much less sorbed than Se(VI) on both types of solids. For Se(IV) the sorption mechanisms are different for iron oxides and apatites. On oxides, sorption increases when pH decreases. It can be interpreted by a surface complexation model, essentially through an inner sphere complex (monodentate or bidentate). Modelling of Se sorption curves was performed after the determination of acido-basic properties of oxides. However, the determination of the intrinsic properties of oxides is disturbed by several parameters identified as impurities, evolution of the solid in solution, kinetic and solubility of the solid. For apatites, selenium sorption proceeds by exchange with superficial groups, with a maximum of fixation at approximately pH 8. Thanks to XPS measurements and the elaboration of a mathematical model, we could determine the depth of penetration of both selenium and cadmium on apatites. (author)

  16. The influences of pH and ionic strength on the sorption of tylosin on goethite.

    Science.gov (United States)

    Guo, Xuetao; Yang, Chen; Wu, Yinai; Dang, Zhi

    2014-02-01

    As one of the widely used antibiotics in the world, the environmental risks of tylosin (TYL) received more and more attention. In order to assess its environmental fate and ecological effects accurately, it is necessary to understand the sorption properties of TYL on the soils/sediments. The sorption of TYL on goethite at different pH and ionic strength conditions were measured through a series of batch experiments and the sorption data of TYL were fitted by Freundlich and dual-mode sorption models. It was obvious that sorption was strongly dependent on pH and ionic strength. Sorption capacity of TYL increased as the pH increased and ionic strength decreased. The pH and ionic strength-dependent trends might be related with complexation between cationic/neutral TYL species and goethite. The sorption affinity of TYL on goethite decreased as ionic strength increased, which only occurred at higher TYL concentrations, suggested that inner complex might have dominated process at low concentrations and outer complex might occur at higher concentrations of TYL. Spectroscopic evidence indicated that tricarbonylamide and hydroxyl functional groups of TYL might be accounted for the sorption on mineral surfaces. The experimental data of TYL sorption could be fitted by surface complexation model (FITEQL), indicating that ≡FeOH with TYL interaction could be reasonably represented as a complex formation of a monoacid with discrete sites on goethite. The sorption mechanism of TYL might be related with surface complexation, electrostatic repulsion, and H-bounding on goethite. It should be noticed that the heterogeneous of sorption affinity of TYL on goethite at various environment to assess its environment risk.

  17. Impact of de-ashing humic Acid and humin on organic matter structural properties and sorption mechanisms of phenanthrene.

    Science.gov (United States)

    Yang, Yu; Shu, Liang; Wang, Xilong; Xing, Baoshan; Tao, Shu

    2011-05-01

    Organic matter-mineral interactions greatly affect the fate of hydrophobic organic compounds (HOCs) in the environment. In the present study, the impact of organic matter-mineral interaction on sorption of phenanthrene (PHE) by the original and de-ashed humic acids (HAs) and humin (HM) was examined. After de-ashing treatment, the overall polarity of organic matter in HAs and HM consistently decreased. Differently, the surface polarity of HAs increased but that of HM decreased. No correlation between K(oc) values of PHE by all tested sorbents and their bulk polarity was observed due to inaccessibility of a portion of interior sorption domains. The inaccessibility of interior sorption domains in HAs and HM was partly due to the crystalline structure in organic matter as indicated by differential scanning calorimetric (DSC) and ¹³C NMR data and the interference from minerals. A good correlation between surface polarity of the original and de-ashed HAs and HMs and their K(oc) values for PHE indicated its importance in HOC sorption. Dissimilar changes in surface polarity of HAs and HM after de-ashing treatment can be ascribed to the distinct interactions between organic matter and minerals. The solid-state ¹³C NMR, XPS, and elemental composition data of all tested sorbents revealed that a larger fraction of O atoms in HAs were involved in organic matter-mineral interaction as compared to HM. Results of this work highlight the importance of soil organic matter (SOM)-mineral interactions, surface polarity, and microscaled domain arrangement of SOM in HOC sorption.

  18. Sorption of benzothiazoles onto sandy aquifer material under equilibrium and nonequlibrium conditions

    Directory of Open Access Journals (Sweden)

    Kragulj Marijana M.

    2014-01-01

    Full Text Available In this study, the sorption behaviour of 1,3-benzothiazole (BT and 2-(methylthiobenzothiazole (MTBT was investigated on Danube geosorbent under equilibrium and nonequilibrium conditions. All sorption isotherms fitted well with the Freundlich model (R2=0.932-0.993. The results showed that organic matter of the Danube geosorbent has a higher sorption affinity for the more hydrophobic MTBT compared to BT. However, sorption-desorption experiments showed that MTBT was more easily desorbed than BT molecules, which indicates the importance of absorption relative to adsorption in the overall sorption mechanism of MTBT. In general, molecules of BT and MTBT were more easily desorbed in the lower concentration range, which resulted in an increase in the hysteresis indices with increasing concentrations. Column experiments revealed that retention of the investigated compounds on the aquifer material followed the compound’s hydrophobicity. BT showed a lower retention, in accordance with its lower sorption affinity obtained in the static experiments, while MTBT showed a greater sorption affinity, and thus had a longer retention time on the column. Thus during transport BT represent greater risk for groundwaters than MTBT. These results have increased our understanding of benzothiazoles sorption and desorption process which represent one of the most important factors which influence the behaviour of organic compounds in the environment.

  19. Sorption properties of carbon nanostructures

    International Nuclear Information System (INIS)

    Eletskii, Aleksandr V

    2004-01-01

    The current status of research in sorption properties of carbon nanotubes (CNTs) is reviewed. The structural peculiarities of CNTs, determining their sorption characteristics, are considered. The mechanisms of sorption of gaseous and condensed substances by such structures are analyzed. Special attention is paid to the problem of using CNTs for storing hydrogen and other gaseous substances. Methods for filling CNTs with liquid materials, based on capillary phenomena and wetting the graphite surface of the CNT with liquids of various nature, are considered. Properties of 'peapods' formed as a result of filling single-walled CNTs with fullerene molecules are reviewed. Also considered are perspectives on the applied usage of the sorption properties of CNTs in electrochemical and fuel cells, and material storage devices, as well as for producing superminiature metallic conductors. (reviews of topical problems)

  20. Sorption/desorption reversibility of polycyclic aromatic hydrocarbons (PAHs) in soils and carbonaceous materials

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Guohui

    2008-07-01

    Understanding sorption/desorption is an important prerequisite for the prediction of fate and transport of pollutants in the environment. During the last two decades, numerous studies have reported hysteresis phenomenon for the interaction of hydrophobic organic contaminants (HOCs) with natural organic matter (NOM). It manifests as nonsingular sorption/desorption isotherms or different rates for sorption and desorption, where during desorption a higher affinity of a compound on a given sorbent and a longer time scale for release than for sorption is observed. Other studies showed that some of the reported sorption/desorption hysteresis phenomena are due to experimental artifacts, mainly resulting from non-attainment of sorption equilibrium before desorption experiments, which result in 'pseudo-hysteresis'. Except for the hypothesis of sorbent reconfiguration, clear experimental evidence for the physical or chemical mechanisms proposed to lead to hysteresis is still lacking. In this study, sorption/desorption equilibrium and kinetics of phenanthrene sorption/desorption from two soils and three carbonaceous samples were investigated using both batch and column techniques. The main objective of this work was to monitor hysteresis phenomenon by carefully recovering the solute mass in the system and to compare sorption/desorption equilibria and kinetics thermodynamically. Nonsingular isotherms and higher desorption enthalpies as well as increased activation energies with proceeding desorption are expected if significant hysteresis exists. Sorption-desorption cycles were carried out to compare equilibrium isotherms and associated sorption/desorption enthalpies (AeH, isosteric heats). Instead of the traditional decant-and-refill batch method, the experiments were conducted using a newly designed batch protocol, which enables the determination of sorption/desorption isotherms at different temperatures using a closed batch system. This method additionally allows

  1. Uranium sorption from sulfate solutions by polyampholytes

    International Nuclear Information System (INIS)

    Rychkov, V.N.

    2003-01-01

    Uranium sorption from sulfate solutions by aminocarboxylic and aminophosphoric acid polyampholytes is studied. Effect of concentration of sulfuric acid, ammonium sulfate, ph value of solution and concentration of metal in solution on uranium absorptivity by ampholytes is studied. It is determined that sorption process is described satisfactorily by K d =KC p Z equation. Basing on calculated data on uranium ion state in sulfate solutions, analysis of results and data of IR spectroscopy conclusions about uranium sorption process mechanism are made [ru

  2. Transformation and Sorption of Illicit Drug Biomarkers in Sewer Systems: Understanding the Role of Suspended Solids in Raw Wastewater.

    Science.gov (United States)

    Ramin, Pedram; Libonati Brock, Andreas; Polesel, Fabio; Causanilles, Ana; Emke, Erik; de Voogt, Pim; Plósz, Benedek Gy

    2016-12-20

    Sewer pipelines, although primarily designed for sewage transport, can also be considered as bioreactors. In-sewer processes may lead to significant variations of chemical loadings from source release points to the treatment plant influent. In this study, we assessed in-sewer utilization of growth substrates (primary metabolic processes) and transformation of illicit drug biomarkers (secondary metabolic processes) by suspended biomass. Sixteen drug biomarkers were targeted, including mephedrone, methadone, cocaine, heroin, codeine, and tetrahydrocannabinol (THC) and their major human metabolites. Batch experiments were performed under aerobic and anaerobic conditions using raw wastewater. Abiotic biomarker transformation and partitioning to suspended solids and reactor wall were separately investigated under both redox conditions. A process model was identified by combining and extending the Wastewater Aerobic/anaerobic Transformations in Sewers (WATS) model and Activated Sludge Model for Xenobiotics (ASM-X). Kinetic and stoichiometric model parameters were estimated using experimental data via the Bayesian optimization method DREAM (ZS) . Results suggest that biomarker transformation significantly differs from aerobic to anaerobic conditions, and abiotic conversion is the dominant mechanism for many of the selected substances. Notably, an explicit description of biomass growth during batch experiments was crucial to avoid significant overestimation (up to 385%) of aerobic biotransformation rate constants. Predictions of in-sewer transformation provided here can reduce the uncertainty in the estimation of drug consumption as part of wastewater-based epidemiological studies.

  3. Sorption Energy Maps of Clay Mineral Surfaces

    International Nuclear Information System (INIS)

    Cygan, Randall T.; Kirkpatrick, R. James

    1999-01-01

    A molecular-level understanding of mineral-water interactions is critical for the evaluation and prediction of the sorption properties of clay minerals that may be used in various chemical and radioactive waste disposal methods. Molecular models of metal sorption incorporate empirical energy force fields, based on molecular orbital calculations and spectroscopic data, that account for Coulombic, van der Waals attractive, and short-range repulsive energies. The summation of the non-bonded energy terms at equally-spaced grid points surrounding a mineral substrate provides a three dimensional potential energy grid. The energy map can be used to determine the optimal sorption sites of metal ions on the exposed surfaces of the mineral. By using this approach, we have evaluated the crystallographic and compositional control of metal sorption on the surfaces of kaolinite and illite. Estimates of the relative sorption energy and most stable sorption sites are derived based on a rigid ion approximation

  4. Kinetics of volatile organic compound sorption/desorption on clay minerals

    Science.gov (United States)

    Morrissey, Fergus A.; Grismer, Mark E.

    1999-03-01

    Soils surrounding industrial sites or at locales where industrial chemicals are utilized, frequently become contaminated through unsuitable discharge of potentially hazardous organic compounds. The fate and transport of these chemicals must be sufficiently understood to predict detrimental environmental impacts and to develop technically and economically appropriate remedial action to minimize environmental degradation. Improving our understanding of the processes involved in organic pollutant vapor transport is important because the gas phase is often the most mobile, and therefore most potentially hazardous phase. In order to gain a better understanding of the basic kinetic processes affecting soil adsorption/desorption of volatile organic compounds (VOC's) in the vapor phase, we conducted VOC adsorption/desorption experiments using oven-dry clay minerals. Transient, isothermal, gravimetric sorption experiments using volatile organic compounds (VOC's) acetone, benzene and toluene onto pure clay minerals obtained from Ward's Scientific (kaolinite, illite, and Ca-montmorillonite) suggest a biphasic sorption mechanism on these minerals. Experimental results indicate that hydrophobic sorption onto oven-dry clay minerals with negligible soil organic matter is controlled by rates of inter-particle Fickian diffusion mechanisms, intra-particle Fickian diffusion mechanisms, and sorption kinetics. Using an analytical solution to Fick's Second Law where sorption is partitioned into macroscopic and microscopic domains, each with unique diffusion time constants, enables precise prediction of experimental sorption observations. Correlation coefficients of 0.999 were found between the parameter optimized analytical solution and very large sets of experimental data. Macroscopic diffusion coefficients ranged from 10 -2 to 10 -4 cm 2/min, while microscopic diffusion coefficients ranged from 10 -12 to 10 -17 cm 2/min. Sorption rates suggest that significant fractions of VOC

  5. Sorption mechanisms of selenium species (selenite and selenate) on copper-based minerals; Mecanismes de sorption des especes du selenium (selenite et seleniate) sur des mineraux a base de cuivre

    Energy Technology Data Exchange (ETDEWEB)

    Devoy, J

    2001-09-01

    The sorption of radionuclides on the surface of minerals represents a process capable to delay the migration of the elements from a spent fuel deep repository towards the biosphere. In the framework of a deep underground repository, an engineered clay barrier has a high trapping capacity for cationic radio-elements, in particular because of the negative charge of clay surfaces. However, anionic radioelements like selenium species, would be only weakly retained by chemical processes. In order to optimize the trapping capacity of a clay barrier with respect to anionic species, prospective studies are carried out in order to find and evaluate some minerals with specific chemical trapping functions. Among radionuclides, the case of selenium has to be considered because its isotope {sup 79}Se is present in radioactive wastes and has a half life time of 6.5 10{sup 4} years. It is also judicious to find a mineral capable of trapping simultaneously several anionic radio-elements. Copper oxides and sulfides (Cu{sub 2}O, CuO, Cu{sub 2}S, CuS, CuFeS{sub 2} and Cu{sub 5}FeS{sub 4}) are good adsorbents with respect to selenium species (selenite and selenate). These minerals, with their selenium retention properties, could be used also for the decontamination of soils and waters or to process industrial effluents. The sorption mechanisms have been studied in details for copper oxides (Cu{sub 2}O and CuO) with respect to selenite and selenate. Chalcomenite precipitates in acid pH conditions when selenite is added to a Cu{sub 2}O and CuO suspension. Selenate, in contact with cuprite (Cu{sub 2}O) leads also to a selenium-based precipitate in acid pH environment. For higher pH values, selenite and selenate are adsorbed on copper oxides (Cu{sub 2}O and CuO) and lead to internal and external sphere complexes, respectively. In the case of a selenite/cuprite mixture in basic pH environment and at the equilibrium, a chemical reaction occurs between the oxidation product of cuprite, Cu

  6. Sorption Characteristics of Mixed Molecules of Glutaraldehyde from Water on Mesoporous Acid-Amine Modified Low-Cost Activated Carbon: Mechanism, Isotherm, and Kinetics

    Directory of Open Access Journals (Sweden)

    Mukosha Lloyd

    2015-01-01

    Full Text Available The environmental discharge of inefficiently treated waste solutions of the strong biocide glutaraldehyde (GA from hospitals has potential toxic impact on aquatic organisms. The adsorption characteristics of mixed polarized monomeric and polymeric molecules of GA from water on mesoporous acid-amine modified low-cost activated carbon (AC were investigated. It was found that the adsorption strongly depended on pH and surface chemistry. In acidic pH, the adsorption mechanism was elaborated to involve chemical sorption of mainly hydroxyl GA monomeric molecules on acidic surface groups, while in alkaline pH, the adsorption was elaborated to involve both chemical and physical sorption of GA polymeric forms having mixed functional groups (aldehyde, carboxyl, and hydroxyl on acidic and amine surface groups. The optimum pH of adsorption was about 12 with significant contribution by cooperative adsorption, elucidated in terms of hydrogen bonding and aldol condensation. Freundlich and Dubinin-Radushkevich models were fitted to isotherm data. The adsorption kinetics was dependent on initial concentration and temperature and described by the Elovich model. The adsorption was endothermic, while the intraparticle diffusion model suggested significant contribution by film diffusion. The developed low-cost AC could be used to supplement the GA alkaline deactivation process for efficient removal of residual GA aquatic toxicity.

  7. Sorption and migration of neptunium in porous sedimentary materials

    International Nuclear Information System (INIS)

    Tanaka, Tadao; Mukai, Masayuki; Nakayama, Shinichi

    2005-01-01

    Column migration experiments of neptunium were conducted for porous sedimentary materials: coastal sand, tuffaceous sand, ando soil, reddish soil, yellowish soil and loess, and migration behavior, sorption mechanisms and chemical formation of Np were investigated. The migration behavior of Np in each material was much different each other, due to chemical formation in solution and/or sorption mechanism of Np. Mathematical models of different concepts were applied to the experimental results to interpret the sorption mechanism and the migration behavior. It can be concluded that both of instantaneous equilibrium sorption and sorption-desorption kinetics have to be considered to model the Np migration in sedimentary materials. (author)

  8. Understanding Mechanism of Photocatalytic Microbial Decontamination of Environmental Wastewater

    Directory of Open Access Journals (Sweden)

    Chhabilal Regmi

    2018-02-01

    Full Text Available Several photocatalytic nanoparticles are synthesized and studied for potential application for the degradation of organic and biological wastes. Although these materials degrade organic compounds by advance oxidation process, the exact mechanisms of microbial decontamination remains partially known. Understanding the real mechanisms of these materials for microbial cell death and growth inhibition helps to fabricate more efficient semiconductor photocatalyst for large-scale decontamination of environmental wastewater or industries and hospitals/biomedical labs generating highly pathogenic bacteria and toxic molecules containing liquid waste by designing a reactor. Recent studies on microbial decontamination by photocatalytic nanoparticles and their possible mechanisms of action is highlighted with examples in this mini review.

  9. AUTOMOTIVE DIESEL MAINTENANCE 2. UNIT I, UNDERSTANDING MECHANICAL CLUTCHES.

    Science.gov (United States)

    Minnesota State Dept. of Education, St. Paul. Div. of Vocational and Technical Education.

    ONE OF A 25-MODULE COURSE DESIGNED TO UPGRADE THE JOB SKILLS AND TECHNICAL KNOWLEDGE OF DIESEL MAINENANCE MECHANICS THIS MATERIAL WAS DEVELOPED BY INDUSTRIAL TRAINING AND SUBJECT-MATTER SPECIALISTS AND TESTED IN INDUSTRIAL TRAINING SITUATIONS. THE PURPOSE OF THIS FIRST UNIT IS TO DEVELOP AN UNDERSTANDING OF COMPONENTS, OPERATION, AND ADJUSTMENTS…

  10. Student Understanding of Time Dependence in Quantum Mechanics

    Science.gov (United States)

    Emigh, Paul J.; Passante, Gina; Shaffer, Peter S.

    2015-01-01

    The time evolution of quantum states is arguably one of the more difficult ideas in quantum mechanics. In this article, we report on results from an investigation of student understanding of this topic after lecture instruction. We demonstrate specific problems that students have in applying time dependence to quantum systems and in recognizing…

  11. Advanced waterflooding in chalk reservoirs: Understanding of underlying mechanisms

    DEFF Research Database (Denmark)

    Zahid, Adeel; Sandersen, Sara Bülow; Stenby, Erling Halfdan

    2011-01-01

    Over the last decade, a number of studies have shown SO42−, Ca2+ and Mg2+ to be potential determining ions, which may be added to the injected brine for improving oil recovery during waterflooding in chalk reservoirs. However the understanding of the mechanism leading to an increase in oil recove...... of a microemulsion phase could be the possible reasons for the observed increase in oil recovery with sulfate ions at high temperature in chalk reservoirs besides the mechanism of the rock wettability alteration, which has been reported in most previous studies.......Over the last decade, a number of studies have shown SO42−, Ca2+ and Mg2+ to be potential determining ions, which may be added to the injected brine for improving oil recovery during waterflooding in chalk reservoirs. However the understanding of the mechanism leading to an increase in oil recovery...

  12. Modeling PCN-61 and PCN-66: Isostructural rht -Metal–Organic Frameworks with Distinct CO 2 Sorption Mechanisms

    KAUST Repository

    Pham, Tony

    2014-11-05

    © 2014 American Chemical Society. Simulations of CO2 sorption were performed in two members of the highly tunable rht-metal-organic framework (MOF) platform: PCN-61 and PCN-66. These MOFs differ only in the triisophthalate ligand used to synthesize the respective MOFs. In PCN-61, the center of the ligand contains a benzene ring; this ring is substituted with a triphenylamine group in PCN-66. There are two chemically distinct Cu2+ ions that comprise the copper paddlewheels, [Cu2(O2CR)4], in all rht-MOFs. One type of Cu2+ ion, denoted Cu1, projects into the truncated tetrahedral (T-Td) and truncated octahedral (T-Oh) cages, while the other Cu2+ ion, denoted Cu2, projects into the cuboctahedral (cub-Oh) cages. Electronic structure calculations revealed that, in PCN-61, the Cu2 ions have a significantly higher partial positive charge than the Cu1 ions, whereas the opposite was observed in PCN-66. The simulations revealed that the CO2 molecules sorb initially onto the Cu2+ ions that have the higher partial positive charge, i.e., the Cu2 ions in PCN-61 and the Cu1 ions in PCN-66. This was demonstrated by examining the radial distribution function, g(r), about both Cu2+ ions and the modeled structure at low loading for both MOFs. This study provided insights into how differences in the charge distributions about the copper paddlewheels between two isostructural MOFs, arising from the choice of functionality on the ligand, can lead to different CO2 binding sites at low loading and suggests a more general conceptual framework for controlling sorption through the tuning of MOF electronics.

  13. Sorption of ionizable and ionic organic compounds to biochar, activated carbon and other carbonaceous materials.

    Science.gov (United States)

    Kah, Melanie; Sigmund, Gabriel; Xiao, Feng; Hofmann, Thilo

    2017-11-01

    The sorption of ionic and ionizable organic compounds (IOCs) (e.g., pharmaceuticals and pesticides) on carbonaceous materials plays an important role in governing the fate, transport and bioavailability of IOCs. The paradigms previously established for the sorption of neutral organic compounds do not always apply to IOCs and the importance of accounting for the particular sorption behavior of IOCs is being increasingly recognized. This review presents the current state of knowledge and summarizes the recent advances on the sorption of IOCs to carbonaceous sorbents. A broad range of sorbents were considered to evaluate the possibility to read across between fields of research that are often considered in isolation (e.g., carbon nanotubes, graphene, biochar, and activated carbon). Mechanisms relevant to IOCs sorption on carbonaceous sorbents are discussed and critically evaluated, with special attention being given to emerging sorption mechanisms including low-barrier, charge-assisted hydrogen bonds and cation-π assisted π-π interactions. The key role played by some environmental factors is also discussed, with a particular focus on pH and ionic strength. Overall the review reveals significant advances in our understanding of the interactions between IOCs and carbonaceous sorbents. In addition, knowledge gaps are identified and priorities for future research are suggested. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Advances in the understanding of crystal growth mechanisms

    CERN Document Server

    Nishinaga, T; Harada, J; Sasaki, A; Takei, H

    1997-01-01

    This book contains the results of a research project entitled Crystal Growth Mechanisms on an Atomic Scale, which was carried out for 3 years by some 72 reseachers. Until recently in Japan, only the technological aspects of crystal growth have been emphasized and attention was paid only to its importance in industry. However the scientific aspects also need to be considered so that the technology of crystal growth can be developed even further. This project therefore aimed at understanding crystal growth and the emphasis was on finding growth mechanisms on an atomic scale.

  15. Understanding Hydrogen Sorption in In- soc -MOF: A Charged Metal-Organic Framework with Open-Metal Sites, Narrow Channels, and Counterions

    KAUST Repository

    Pham, Tony

    2015-03-04

    © 2015 American Chemical Society. Grand canonical Monte Carlo (GCMC) simulations of hydrogen sorption were performed in In-soc-MOF, a charged metal-organic framework (MOF) that contains In3O trimers coordinated to 5,5′-azobis(1,3-benzenedicarboxylate) linkers. The MOF contains nitrate counterions that are located in carcerand-like capsules of the framework. This MOF was shown to have a high hydrogen uptake at 77 K and 1.0 atm. The simulations were performed with a potential that includes explicit many-body polarization interactions, which were important for modeling gas sorption in a charged/polar MOF such as In-soc-MOF. The simulated hydrogen sorption isotherms were in good agreement with experiment in this challenging platform for modeling. The simulations predict a high initial isosteric heat of adsorption, Qst, value of about 8.5 kJ mol-1, which is in contrast to the experimental value of 6.5 kJ mol-1 for all loadings. The difference in the Qst behavior between experiment and simulation is attributed to the fact that, in experimental measurements, the sorbate molecules cannot access the isolated cages containing the nitrate ions, the most energetically favorable site in the MOF, at low pressures due to an observed diffusion barrier. In contrast, the simulations were able to capture the sorption of hydrogen onto the nitrate ions at low loading due to the equilibrium nature of GCMC simulations. The experimental Qst values were reproduced in simulation by blocking access to all of the nitrate ions in the MOF. Furthermore, at 77 K, the sorbed hydrogen molecules were reminiscent of a dense fluid in In-soc-MOF starting at approximately 5.0 atm, and this was verified by monitoring the isothermal compressibility, βT, values. The favorable sites for hydrogen sorption were identified from the polarization distribution as the nitrate ions, the In3O trimers, and the azobenzene nitrogen atoms. Lastly, the two-dimensional quantum rotational levels

  16. Understanding and imitating unfamiliar actions: distinct underlying mechanisms.

    Directory of Open Access Journals (Sweden)

    Joana C Carmo

    Full Text Available The human "mirror neuron system" has been proposed to be the neural substrate that underlies understanding and, possibly, imitating actions. However, since the brain activity with mirror properties seems insufficient to provide a good description for imitation of actions outside one's own repertoire, the existence of supplementary processes has been proposed. Moreover, it is unclear whether action observation requires the same neural mechanisms as the explicit access to their meaning. The aim of this study was two-fold as we investigated whether action observation requires different processes depending on 1 whether the ultimate goal is to imitate or understand the presented actions and 2 whether the to-be-imitated actions are familiar or unfamiliar to the subject. Participants were presented with both meaningful familiar actions and meaningless unfamiliar actions that they had to either imitate or discriminate later. Event-related Potentials were used as differences in brain activity could have been masked by the use of other techniques with lower temporal resolution. In the imitation task, a sustained left frontal negativity was more pronounced for meaningless actions than for meaningful ones, starting from an early time-window. Conversely, observing unfamiliar versus familiar actions with the intention of discriminating them led to marked differences over right centro-posterior scalp regions, in both middle and latest time-windows. These findings suggest that action imitation and action understanding may be sustained by dissociable mechanisms: while imitation of unfamiliar actions activates left frontal processes, that are likely to be related to learning mechanisms, action understanding involves dedicated operations which probably require right posterior regions, consistent with their involvement in social interactions.

  17. Understanding mechanisms of toxicity: Insights from drug discovery research

    International Nuclear Information System (INIS)

    Houck, Keith A.; Kavlock, Robert J.

    2008-01-01

    Toxicology continues to rely heavily on use of animal testing for prediction of potential for toxicity in humans. Where mechanisms of toxicity have been elucidated, for example endocrine disruption by xenoestrogens binding to the estrogen receptor, in vitro assays have been developed as surrogate assays for toxicity prediction. This mechanistic information can be combined with other data such as exposure levels to inform a risk assessment for the chemical. However, there remains a paucity of such mechanistic assays due at least in part to lack of methods to determine specific mechanisms of toxicity for many toxicants. A means to address this deficiency lies in utilization of a vast repertoire of tools developed by the drug discovery industry for interrogating the bioactivity of chemicals. This review describes the application of high-throughput screening assays as experimental tools for profiling chemicals for potential for toxicity and understanding underlying mechanisms. The accessibility of broad panels of assays covering an array of protein families permits evaluation of chemicals for their ability to directly modulate many potential targets of toxicity. In addition, advances in cell-based screening have yielded tools capable of reporting the effects of chemicals on numerous critical cell signaling pathways and cell health parameters. Novel, more complex cellular systems are being used to model mammalian tissues and the consequences of compound treatment. Finally, high-throughput technology is being applied to model organism screens to understand mechanisms of toxicity. However, a number of formidable challenges to these methods remain to be overcome before they are widely applicable. Integration of successful approaches will contribute towards building a systems approach to toxicology that will provide mechanistic understanding of the effects of chemicals on biological systems and aid in rationale risk assessments

  18. Understanding the mechanism of nanoparticle formation in wire explosion process

    International Nuclear Information System (INIS)

    Bora, B.; Wong, C.S.; Bhuyan, H.; Lee, Y.S.; Yap, S.L.; Favre, M.

    2013-01-01

    The mechanism of nanoparticle formation by wire explosion process has been investigated by optical emission spectroscopy in Antony et al. 2010 [2] [J Quant Spectrosc Radiat Transfer 2010; 111:2509]. It was reported that the size of the nanoparticles formed in Ar ambience increases with increasing pressure, while an opposite trend was observed for the nanoparticles produced in N 2 and He ambiences. However, the physics behind this opposite trend seems unclear. In this work, we have investigated the probable mechanism behind the opposite trend in particle size with pressure of different gases and understand the mechanism of nanoparticle formation in wire explosion process. The experiment was carried out to investigate the effect of ambient gas species (Ar and N 2 ) and pressure on arc plasma formation and its corresponding effects on the characteristics of the produced nanoparticles in wire explosion process. Our results show that the arc plasma formation is probably the mechanism that may account for the opposite trend of particle size with pressure of different gases. -- Highlights: ► Cu nanoparticles have been synthesized by wire explosion technique. ► Investigate the effect of the ambient gas species and pressure. ► Arc plasma formation in wire explosion process is investigated. ► Arc plasma formation plays a crucial role in characteristic of the nanoparticles

  19. Understanding the thermal, mechanical and electrical properties of epoxy nanocomposites

    International Nuclear Information System (INIS)

    Sarathi, R.; Sahu, R.K.; Rajeshkumar, P.

    2007-01-01

    In the present work, the electrical, mechanical and thermal properties of epoxy nanocomposite materials were studied. The electrical insulation characteristics were analyzed through short time breakdown voltage test, accelerated electrical ageing test, and by tracking test. The breakdown voltage increases with increase in nano-clay content up to 5 wt%, under AC and DC voltages. The volume resistivity, permittivity and tan(δ) of the epoxy nanocomposites were measured. The Weibull studies indicate that addition of nanoclay upto 5 wt% enhances the characteristic life of epoxy nanocomposite insulation material. The tracking test results indicate that the tracking time is high with epoxy nanocomposites as compared to pure epoxy. Ageing studies were carried out to understand the surface characteristic variation through contact angle measurement. The hydrophobicity of the insulating material was analysed through contact angle measurement. The diffusion coefficients of the material with different percentage of clay in epoxy nanocomposites were calculated. The exfoliation characteristics in epoxy nanocomposites were analyzed through wide angle X-ray diffraction (WAXD) studies. The thermal behaviour of the epoxy nanocomposites was analyzed by carrying out thermo gravimetric-differential thermal analysis (TG-DTA) studies. Heat deflection temperature of the material was measured to understand the stability of the material for intermittent temperature variation. The dynamic mechanical analysis (DMA) results indicated that storage modulus of the material increases with small amount of clay in epoxy resin. The activation energy of the material was calculated from the DMA results

  20. Sorption of simazine to corn straw biochars prepared at different pyrolytic temperatures

    International Nuclear Information System (INIS)

    Zhang Guixiang; Zhang Qing; Sun Ke; Liu Xitao; Zheng Wenjuan; Zhao Ye

    2011-01-01

    Simazine sorption to corn straw biochars prepared at various temperatures (100-600 deg. C) was examined to understand its sorption behavior as influenced by characteristics of biochars. Biochars were characterized via elemental analysis, BET-N 2 surface area (SA), FTIR and 13 C NMR. Freundlich and dual-mode models described sorption isotherms well. Positive correlation between log K oc values and aromatic C contents and negative correlation between log K oc values and (O + N)/C ratios indicate aromatic-rich biochars have high binding affinity to simazine (charge transfer (π-π*) interactions) and hydrophobic binding may overwhelm H-bonding, respectively. Dual-mode model results suggest adsorption contribution to total sorption increases with carbonization degree. Positive correlation between amounts of adsorption (Q ad ) and SA indicates pore-filling mechanism. Comparison between our results and those obtained with other sorbents indicates corn straw biochars produced at higher temperature can effectively retain simazine. These observations will be helpful for designing biochars as engineered sorbents to remove triazine herbicides. - Highlights: → Biochars were characterized via elemental analysis, BET-N 2 , FTIR and 13 C NMR. → Freundlich and dual-mode models described sorption isotherms well. → Biochar produced at higher temperature had larger sorption capacity for simazine. → Aromatic-rich biochars have high binding affinity to simazine. → Dual-mode model results suggest adsorption contribution to total sorption. - The corn straw biochar prepared at higher temperature with stronger hydrophobicity, more aromatic C and larger surface area had higher sorption capacity for simazine.

  1. Sorption isolation of strontium from seawater

    International Nuclear Information System (INIS)

    Avramenko, V.A.; Zheleznov, V.V.; Kaplun, E.V.; Sokol'nitskaya, T.A.; Yukhkam, A.A.

    2001-01-01

    Sorption isolation of strontium from seawater is considered and prospects of use of selective adsorbents for purification of seawater or liquid radioactive wastes mixed with seawater from 90 Sr are discussed. Comparative analysis of sorptive properties of adsorbents of different nature is done. It is shown that sorption-reagent materials developed by authors can to afford effective separation of 90 Sr from seawater. Possible mechanism of strontium sorption by these adsorbents is considered. The prospect of their use for purification of liquid radioactive wastes from strontium is shown [ru

  2. Understanding Neurological Disease Mechanisms in the Era of Epigenetics

    Science.gov (United States)

    Qureshi, Irfan A.; Mehler, Mark F.

    2015-01-01

    The burgeoning field of epigenetics is making a significant impact on our understanding of brain evolution, development, and function. In fact, it is now clear that epigenetic mechanisms promote seminal neurobiological processes, ranging from neural stem cell maintenance and differentiation to learning and memory. At the molecular level, epigenetic mechanisms regulate the structure and activity of the genome in response to intracellular and environmental cues, including the deployment of cell type–specific gene networks and those underlying synaptic plasticity. Pharmacological and genetic manipulation of epigenetic factors can, in turn, induce remarkable changes in neural cell identity and cognitive and behavioral phenotypes. Not surprisingly, it is also becoming apparent that epigenetics is intimately involved in neurological disease pathogenesis. Herein, we highlight emerging paradigms for linking epigenetic machinery and processes with neurological disease states, including how (1) mutations in genes encoding epigenetic factors cause disease, (2) genetic variation in genes encoding epigenetic factors modify disease risk, (3) abnormalities in epigenetic factor expression, localization, or function are involved in disease pathophysiology, (4) epigenetic mechanisms regulate disease-associated genomic loci, gene products, and cellular pathways, and (5) differential epigenetic profiles are present in patient-derived central and peripheral tissues. PMID:23571666

  3. Sorption studies of uranium in sediment-groundwater systems from the natural analogue sites of Needle's Eye and Broubster

    International Nuclear Information System (INIS)

    Higgo, J.J.; Falck, W.E.; Hooker, P.J.

    1990-01-01

    This report describes the results of sorption experiments designed to provide essential data for migration modelling. Sorption of 233 U from natural ground-water onto peat from Broubster and silt from Needle's Eye was studied under atmospheric conditions and different pH regimes. The temperature was maintained at 10 0 C and, in the case of Needle's Eye silt, the kinetics of sorption were followed. The results were analyzed in conjunction with speciation modelling in an attempt to understand the sorption mechanisms and to extrapolate the findings to cover the range of conditions likely to be met in the field. This work is part of the CEC project Mirage - Second phase, research area 'Natural analogues'

  4. Sorption of radionuclides on mineral surfaces

    International Nuclear Information System (INIS)

    Berry, J.A.; Cowper, M.M.; Green, A.; Jefferies, N.L.; Linklater, C.M.

    1991-01-01

    The sorption of the radioelements uranium, caesium, radium and americium onto rocks and single mineral phases is being investigated in order to improve the understanding of sorption processes. The spatial distribution of uranium onto rock surfaces has been investigated by immersing thin sections of granite and sandstone into 0.8 ppm uranium solutions for periods of up to three months. The sections have been examined by a number of techniques such as RBS, PIXE and dynamic SIMS. In granite thin sections, uranium is preferentially sorbed onto phyllosilicate minerals (10 -8 g cm -2 ). In the sandstone, iron-rich phases dominate sorption. Enhanced levels of uranium sorption (10 -7 g cm -2 ) were observed on surfaces enriched with iron. Even within single mineral phases, inhomogeneities have been detected. Solution chemistry was also an important factor in uranium sorptive behaviour, with sorption from groundwater inhibited by comparison to that on mineralogically similar thin sections immersed in ultra-high purity water. The sorption of caesium from ultra-high purity water and a synthetic groundwater (0.065M NaCl brine) onto quartz, calcite and kaolinite has been studied by the batch sorption technique. Both calcite and quartz are nonsorbing whilst kaolinite is moderately sorbing. R D values from pure water experiments are a factor of 30 higher than those from groundwater, which reflects competition for cation exchange sites on the kaolinite surface between caesium and sodium and potassium in the groundwater. (author)

  5. Investigation of metal ions sorption of brown peat moss powder

    Science.gov (United States)

    Kelus, Nadezhda; Blokhina, Elena; Novikov, Dmitry; Novikova, Yaroslavna; Chuchalin, Vladimir

    2017-11-01

    For regularities research of sorptive extraction of heavy metal ions by cellulose and its derivates from aquatic solution of electrolytes it is necessary to find possible mechanism of sorption process and to choice a model describing this process. The present article investigates the regularities of aliovalent metals sorption on brown peat moss powder. The results show that sorption isotherm of Al3+ ions is described by Freundlich isotherm and sorption isotherms of Na+ i Ni2+ are described by Langmuir isotherm. To identify the mechanisms of brown peat moss powder sorption the IR-spectra of the initial brown peat moss powder samples and brown peat moss powder samples after Ni (II) sorption were studied. Metal ion binding mechanisms by brown peat moss powder points to ion exchange, physical adsorption, and complex formation with hydroxyl and carboxyl groups.

  6. The effect of organic amendment on mobility of cesium in tropical soils - The effect of organic amendment on sorption mechanisms for cesium and cobalt in tropical soils

    Energy Technology Data Exchange (ETDEWEB)

    Wasserman, M.A.V.; Santos-Oliveira, R. [Instituto de Engenharia nuclear/CNEN. Rua Helio de Almeida, 75. Cidade Universitaria - Ilha do Fundao, Rio de Janeiro, RJ. CEP 21941-906 (Brazil); Garcia, R.J.L.; Ferreira, A.C.M.; Rochedo, E.R.R.; Sobrinho, G.A.N. [Instituto de Radioprotecao e Dosimetria/CNEN. Av. Salvador Allende s /no. Rio de Janeiro, RJ. CEP: 22780-160 (Brazil); Perez, D.V. [Centro Nacional de Pesquisa de Solos/EMBRAPA. R. Jardim Botanico, 1024.Rio de Janeiro, RJ, CEP: 22460-000 (Brazil); Wasserman, J.C. [dUFF Network of Environment and Sustainable Development (REMADS-UFF), University Federal Fluminense, Niteroi, RJ (Brazil)

    2014-07-01

    This work aimed to investigate the mechanisms involved in the sorption of {sup 137}Cs and {sup 60}Co as a function of the physico-chemical properties of some types of Brazilian soils and the changes on the behavior of these radionuclides due to changes in soil properties promoted by organic amendment. The experimental study was conducted in a controlled area, where pots containing different types of soils (Ferralsol, Nitisol and Histosol) and different doses of organic amendment (no amendment; 2 kg.m{sup -2} and 4 kg.m{sup -2}) were spiked with {sup 137}Cs and {sup 60}Co. The organic amendment used in this experiment was obtained in the Unit of Compost of the Organic Material of Pinheiral (RJ, Brazil), where the compost is made up from the leaves swept from the streets of the Pinheiral city. The mobility of these radionuclides in the soil was assessed through sequential chemical extraction and desorption studies as a function of pH. The bioavailability was evaluated through the effective absorption of radionuclide by root crops (Raphanus sativus, L). This study evidenced that the organic amendment plays an important role in the desorption processes of cobalt and cesium, reducing desorption of both nuclides beneath higher organic amendment dose. This behavior was observed in acid conditions as well in alkaline. However extreme acid conditions may mobilize both radionuclides, although cobalt mobility was shown to be more sensitive to low pH than cesium. (authors)

  7. Understanding Liver Regeneration: From Mechanisms to Regenerative Medicine.

    Science.gov (United States)

    Gilgenkrantz, Hélène; Collin de l'Hortet, Alexandra

    2018-04-16

    Liver regeneration is a complex and unique process. When two-thirds of a mouse liver is removed, the remaining liver recovers its initial weight in approximately 10 days. The understanding of the mechanisms responsible for liver regeneration may help patients needing large liver resections or transplantation and may be applied to the field of regenerative medicine. All differentiated hepatocytes are capable of self-renewal, but different subpopulations of hepatocytes seem to have distinct proliferative abilities. In the setting of chronic liver diseases, a ductular reaction ensues in which liver progenitor cells (LPCs) proliferate in the periportal region. Although these LPCs have the capacity to differentiate into hepatocytes and biliary cells in vitro, their ability to participate in liver regeneration is far from clear. Their expansion has even been associated with increased fibrosis and poorer prognosis in chronic liver diseases. Controversies also remain on their origin: lineage studies in experimental mouse models of chronic injury have recently suggested that these LPCs originate from hepatocyte dedifferentiation, whereas in other situations, they seem to come from cholangiocytes. This review summarizes data published in the past 5 years in the liver regeneration field, discusses the mechanisms leading to regeneration disruption in chronic liver disorders, and addresses the potential use of novel approaches for regenerative medicine. Copyright © 2018 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.

  8. Bronchopulmonary dysplasia: understanding of the underlying pathological mechanisms

    Directory of Open Access Journals (Sweden)

    Daniela Fanni

    2014-06-01

    Full Text Available Bronchopulmonary dysplasia (BPD is a chronic lung disease occurring in preterm infants, typically before 28 weeks of gestational age, characterized by a prolonged need for supplemental oxygen or positive pressure ventilation. The normal stages of lung development and their relation to the timing of preterm birth is strategic in order to understand the pathogenesis of BPD. In embryonic and pseudoglandular stages the lungs arise from the anterior foregut as a bud where the branching morphogenesis generate a tree-like network of airways. The canalicular stage is characterized by increasing proliferation of distal lung epithelial cells and rapid expansion of the intra-acinar capillaries. The complexity of the airways increases, secondary crests begin to form and full maturation of the alveolus occurs during the saccular and the alveolar stages. Mesechyme components, expecially elastin and myofibroblast, display a major role in normal lung development. BPD is thought to result after an acute insult to the neonatal lung following therapy with oxygen supplementation and mechanical ventilation. Chorioamnionitis, infections and genetic susceptibly are hypothesized to contribute to the injury that affect the normal human lung development. Abnormalities in the mesenchyme were consistently seen in association with inhibition of alveolarization. The pathological features that characterize BPD are complex and differ according with the disease progression. Alveolar simplification, interstitial fibrosis, septal thickness, large airways, smooth muscle hypertrophy, fetal artery persistance and decrease in the arterial number can be histologically observed. In conclusion, in order to reach a complete clinical-pathological diagnosis, the correlation of the pathological features with the fundamental steps of lung morphogenesis and a strict dialogue between the neonatologist and the perinatal pathologist are required. Given these conditions, in our experience, a

  9. Understanding the mechanisms behind coking pressure: Relationship to pore structure

    Energy Technology Data Exchange (ETDEWEB)

    John J. Duffy; M. Castro Diaz; Colin E. Snape; Karen M. Steel; Merrick R. Mahoney [University of Nottingham, Nottingham (United Kingdom). Nottingham Fuel and Energy Centre, School of Chemical, Environmental and Mining Engineering

    2007-09-15

    Three low volatile coals A, B and C with oven wall pressures of 100 kPa, 60 kPa and 20 kPa respectively were investigated using high-temperature rheometry, {sup 1}H NMR, thermogravimetric analysis and SEM, with the primary aim to better understand the mechanisms behind the coking pressure phenomenon. Rheometer plate displacement measurements ({Delta}L) have shown differences in the expansion and contraction behaviour of the three coals, which seem to correlate with changes in rheological properties; while SEM images have shown that the expansion process coincides with development of pore structure. It is considered that the point of maximum plate height ({Delta}L{sub max}) prior to contraction may be indicative of a cell opening or pore network forming process, based on analogies with other foam systems. Such a process may be considered important for coking pressure since it provides a potential mechanism for volatile escape, relieving internal gas pressure and inducing charge contraction. For coal C, which has the highest fluidity {delta}L{sub max} occurs quite early in the softening process and consequently a large degree of contraction is observed; while for the lower fluidity coal B, the process is delayed since pore development and consequently wall thinning progress at a slower rate. When {Delta}L{sub max} is attained, a lower degree of contraction is observed because the event occurs closer to resolidification where the increasing viscosity/elasticity can stabilise the expanded pore structure. For coal A which is relatively high fluidity, but also high coking pressure, a greater degree of swelling is observed prior to cell rupture, which may be due to greater fluid elasticity during the expansion process. This excessive expansion is considered to be a potential reason for its high coking pressure. 58 refs., 15 figs., 1 tab.

  10. Plutonium sorption onto hematite colloids at femto- and nanomolar concentrations

    Energy Technology Data Exchange (ETDEWEB)

    Romanchuk, A.Yu.; Kalmykov, S.N.; Aliev, R.A. [Lomonosov Moscow State Univ., Moscow (Russian Federation). Radiochemistry Div.

    2011-07-01

    The surface-mediated reduction of Pu(VI) upon sorption onto hematite colloids is addressed in the paper that bring some new light on the mechanisms of interaction of Pu in high valence states with different Fe(III) oxides. We study the sorption of Pu taken at two different total concentrations around 10{sup -9} and 10{sup -14} M using {sup 239}Pu and short-lived {sup 237}Pu tracer. In order to conclude on the mechanisms of Pu sorption onto hematite, the kinetics of sorption of Pu(IV) and Pu(VI) at two concenrations is studied as well as its leaching behavior. The rate limiting step in Pu(VI) sorption is its surface-mediated reduction. The experimental evidence of the polymerization of Pu(IV) on the surface taken at Pu total concentration of {proportional_to} 10{sup -9} M is presented based on the kinetics of sorption and leaching behavior. (orig.)

  11. Understanding sleep-wake mechanisms and drug discovery.

    Science.gov (United States)

    Equihua-Benítez, Ana Clementina; Guzmán-Vásquez, Khalil; Drucker-Colín, René

    2017-07-01

    Although not discernible at first glance, sleep is a highly active and regulated brain state. Although we spend practically one third of our lifetimes in this stage, its importance is often taken for granted. Sleep loss can lead to disease, error and economic loss. Our understanding of how sleep is achieved has greatly advanced in recent years, and with that, the management of sleep disorders has improved. There is still room for improvement and recently many new compounds have reached clinical trials with a few being approved for commercial use. Areas covered: In this review, the authors make the case of sleep disorders as a matter of public health. The mechanisms of sleep transition are discussed emphasizing the wake and sleep promoting interaction of different brain regions. Finally, advances in pharmacotherapy are examined in the context of chronic insomnia and narcolepsy. Expert opinion: The orexinergic system is an example of a breakthrough in sleep medicine that has catalyzed drug development. Nevertheless, sleep is a topic still with many unanswered questions. That being said, the melanin-concentrating hormone system is becoming increasingly relevant and we speculate it will be the next target of sleep medication.

  12. AFFECTS OF MECHANICAL MILLING AND METAL OXIDE ADDITIVES ON SORPTION KINETICS OF 1:1 LiNH2/MgH2 MIXTURE

    Energy Technology Data Exchange (ETDEWEB)

    Erdy, C.; Anton, D.; Gray, J.

    2010-12-08

    The destabilized complex hydride system composed of LiNH{sub 2}:MgH{sub 2} (1:1 molar ratio) is one of the leading candidates of hydrogen storage with a reversible hydrogen storage capacity of 8.1 wt%. A low sorption enthalpy of {approx}32 kJ/mole H{sub 2} was first predicted by Alapati et al. utilizing first principle density function theory (DFT) calculations and has been subsequently confirmed empirically by Lu et al. through differential thermal analysis (DTA). This enthalpy suggests that favorable sorption kinetics should be obtainable at temperatures in the range of 160 C to 200 C. Preliminary experiments reported in the literature indicate that sorption kinetics are substantially lower than expected in this temperature range despite favorable thermodynamics. Systematic isothermal and isobaric sorption experiments were performed using a Sievert's apparatus to form a baseline data set by which to compare kinetic results over the pressure and temperature range anticipated for use of this material as a hydrogen storage media. Various material preparation methods and compositional modifications were performed in attempts to increase the kinetics while lowering the sorption temperatures. This paper outlines the results of these systematic tests and describes a number of beneficial additions which influence kinetics as well as NH{sub 3} formation.

  13. Iodine sorption by ion-exchange fiber on the basis of polyacrylonitrile and AV-17 anionite under static conditions

    International Nuclear Information System (INIS)

    Tarchigina, N.I.; Artemov, A.V.; Ksenzenko, V.I.

    1986-01-01

    Iodine sorption from natural waters by a qualitatively new sorbent - ion-exchange fiber on the basis of polyacrylonitrile and AV-17 anionite is investigated. Mechanism of iodine sorption by ion-exchange material is suggested. Iodine sorption kinetics by fibrous sorbent under static conditions is described. Iodine sorption efficient constants are determined by experimental data processing with the use of electronic computer

  14. Quantification of Cation Sorption to Engineered Barrier Materials Under Extreme Conditions

    International Nuclear Information System (INIS)

    Powell, Brian; Schlautman, Mark; Rao, Linfeng; Nitsche, Heino; Gregorich, Kenneth

    2016-01-01

    The objective of this research is to examine mechanisms and thermodynamics of actinide sorption to engineered barrier materials (iron (oxyhydr)oxides and bentonite clay) for nuclear waste repositories under high temperature and high ionic strength conditions using a suite of macroscopic and microscopic techniques which will be coupled with interfacial reaction models. Gaining a mechanistic understanding of interfacial processes governing the sorption/sequestration of actinides at mineral-water interfaces is fundamental for the accurate prediction of actinide behavior in waste repositories. Although macroscale sorption data and various spectroscopic techniques have provided valuable information regarding speciation of actinides at solid-water interfaces, significant knowledge gaps still exist with respect to sorption mechanisms and the ability to quantify sorption, particularly at high temperatures and ionic strengths. This objective is addressed through three major tasks: (1) influence of oxidation state on actinide sorption to iron oxides and clay minerals at elevated temperatures and ionic strengths; (2) calorimetric titrations of actinide-mineral suspensions; (3) evaluation of bentonite performance under repository conditions. The results of the work will include a qualitative conceptual model and a quantitative thermodynamic speciation model describing actinide partitioning to minerals and sediments, which is based upon a mechanistic understanding of specific sorption processes as determined from both micro-scale and macroscale experimental techniques. The speciation model will be a thermodynamic aqueous and surface complexation model of actinide interactions with mineral surfaces that is self-consistent with macroscopic batch sorption data, calorimetric and potentiometric titrations, X-ray absorption Spectroscopy (XAS, mainly Extended X-ray Absorption Fine Structure (EXAFS)), and electron microscopy analyses. The novelty of the proposed work lies largely in

  15. Quantification of Cation Sorption to Engineered Barrier Materials Under Extreme Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Powell, Brian [Clemson Univ., SC (United States); Schlautman, Mark [Clemson Univ., SC (United States); Rao, Linfeng [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Nitsche, Heino [Univ. of California, Berkeley, CA (United States); Gregorich, Kenneth [Univ. of California, Berkeley, CA (United States)

    2016-02-02

    The objective of this research is to examine mechanisms and thermodynamics of actinide sorption to engineered barrier materials (iron (oxyhydr)oxides and bentonite clay) for nuclear waste repositories under high temperature and high ionic strength conditions using a suite of macroscopic and microscopic techniques which will be coupled with interfacial reaction models. Gaining a mechanistic understanding of interfacial processes governing the sorption/sequestration of actinides at mineral-water interfaces is fundamental for the accurate prediction of actinide behavior in waste repositories. Although macroscale sorption data and various spectroscopic techniques have provided valuable information regarding speciation of actinides at solid-water interfaces, significant knowledge gaps still exist with respect to sorption mechanisms and the ability to quantify sorption, particularly at high temperatures and ionic strengths. This objective is addressed through three major tasks: (1) influence of oxidation state on actinide sorption to iron oxides and clay minerals at elevated temperatures and ionic strengths; (2) calorimetric titrations of actinide-mineral suspensions; (3) evaluation of bentonite performance under repository conditions. The results of the work will include a qualitative conceptual model and a quantitative thermodynamic speciation model describing actinide partitioning to minerals and sediments, which is based upon a mechanistic understanding of specific sorption processes as determined from both micro-scale and macroscale experimental techniques. The speciation model will be a thermodynamic aqueous and surface complexation model of actinide interactions with mineral surfaces that is self-consistent with macroscopic batch sorption data, calorimetric and potentiometric titrations, X-ray absorption Spectroscopy (XAS, mainly Extended X-ray Absorption Fine Structure (EXAFS)), and electron microscopy analyses. The novelty of the proposed work lies largely in

  16. Understanding the mechanism of base development of hydrogen silsesquioxane

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jihoon; Chao, Weilun; Liang, Xiaogan; Griedel, Brian D.; Olynick, Deirdre L

    2009-01-09

    There have been numerous studies of electron beam exposed hydrogen silsesquioxane (HSQ) development conditions in order to improve the developer contrast. For TMAH based development, improvements were made by going to higher TMAH normalities and heating the developer. Yang and Berggren showed development of electron beam exposed (HSQ) by NaOH with added Na salts (various anions) significantly improves the contrast. Here, we study the contrast and etching rates of 100 keV exposed HSQ in NaOH in the presence of LiCl, NaCl, and KCl salts and use this as a segway to understand the mechanisms governing contrast during development HSQ development. The basic mechanism of development of HSQ can be understood by comparing to etching of quartz in basic solutions. Hydroxide ions act as nucleophiles which attack silicon. When a silicon-oxygen bond of the Si-O-Si matrix is broken, Si-O{sup -} and Si-OH are formed which can reversibly react to form the original structure. When a Si-H bond is broken via reaction with hydroxide, Si-O{sup -} and H{sub 2} gas are formed. Salts can change the etching rates as a function of dose in a non-linear fashion to increase etch contrast. Figs. 1, 2, and 3 show contrast curves for HSQ developed in 0.25 N sodium hydroxide and with the addition of NaCl, LiCl and KCl salts at several concentrations. NaCl addition resulted in the highest contrast. Contrast improves with additional salt concentration while sensitivity decreases. Interestingly enough, addition of salt decreases the removal of material of NaOH alone at higher doses while increasing the rate at lower concentrations. Addition of LiCl salts improves contrast over NaOH alone. Furthermore, the sensitivity at all doses increases as the LiCl concentration increases, a salting out effect. Similar to NaCl salt behavior, the addition of KCl salts, improves contrast at the expense of sensitivity. However, unlike NaCl, even at very high doses, KCl addition increases removal rate of HSQ. We

  17. Characterization of U(VI) Sorption-Desorption Processes and Model Upscaling

    International Nuclear Information System (INIS)

    Bai, Jing; Dong, Wenming; Ball, William P.

    2006-01-01

    The objectives of the overall collaborative EMSP effort (with which this project is associated) were to characterize sorption and desorption processes of U(VI) on pristine and contaminated Hanford sediments over a range of sediment facies and materials properties and to relate such characterization both to fundamental molecular-scale understanding and field-scale models of geochemistry and mass transfer. The research was intended to provide new insights on the mechanisms of U(VI) retardation at Hanford, and to allow the development of approaches by which laboratory-developed geochemical models could be upscaled for defensible field-scale predictions of uranium transport in the environment. Within this broader context, objectives of the JHU-based project were to test hypotheses regarding the coupled roles of adsorption and impermeable-zone diffusion in controlling the fate and transport of U(VI) species under conditions of comparatively short-term exposure. In particular, this work tested the following hypotheses: (1) the primary adsorption processes in the Hanford sediment over the pH range of 7 to 10 are surface complexation reactions of aqueous U(VI) hydroxycarbonate and carbonate complexes with amphoteric edge sites on detrital phyllosilicates in the silt/clay size fraction; (2) macroscopic adsorption intensity (at given aqueous conditions) is a function of mineral composition and aquatic chemistry; and (3) equilibrium sorption and desorption to apply in short-term, laboratory-spiked pristine sediments; and (4) interparticle diffusion can be fully understood in terms of a model that couples molecular diffusion of uranium species in the porewater with equilibrium sorption under the relevant aqueous conditions. The primary focus of the work was on developing and applying both models and experiments to test the applicability of ''local equilibrium'' assumptions in the modeling interpretation of sorption retarded interparticle diffusion, as relevant to processes of

  18. Characterization of U(VI) Sorption-Desorption Processes and Model Upscaling

    Energy Technology Data Exchange (ETDEWEB)

    Bai, Jing; Dong, Wenming; Ball, William P.

    2006-10-12

    The objectives of the overall collaborative EMSP effort (with which this project is associated) were to characterize sorption and desorption processes of U(VI) on pristine and contaminated Hanford sediments over a range of sediment facies and materials properties and to relate such characterization both to fundamental molecular-scale understanding and field-scale models of geochemistry and mass transfer. The research was intended to provide new insights on the mechanisms of U(VI) retardation at Hanford, and to allow the development of approaches by which laboratory-developed geochemical models could be upscaled for defensible field-scale predictions of uranium transport in the environment. Within this broader context, objectives of the JHU-based project were to test hypotheses regarding the coupled roles of adsorption and impermeable-zone diffusion in controlling the fate and transport of U(VI) species under conditions of comparatively short-term exposure. In particular, this work tested the following hypotheses: (1) the primary adsorption processes in the Hanford sediment over the pH range of 7 to 10 are surface complexation reactions of aqueous U(VI) hydroxycarbonate and carbonate complexes with amphoteric edge sites on detrital phyllosilicates in the silt/clay size fraction; (2) macroscopic adsorption intensity (at given aqueous conditions) is a function of mineral composition and aquatic chemistry; and (3) equilibrium sorption and desorption to apply in short-term, laboratory-spiked pristine sediments; and (4) interparticle diffusion can be fully understood in terms of a model that couples molecular diffusion of uranium species in the porewater with equilibrium sorption under the relevant aqueous conditions. The primary focus of the work was on developing and applying both models and experiments to test the applicability of "local equilibrium" assumptions in the modeling interpretation of sorption retarded interparticle diffusion, as relevant to processes of U

  19. Mechanism on the sorption of heavy metals from binary-solution by a low cost montmorillonite and its desorption potential

    Directory of Open Access Journals (Sweden)

    Kovo G. Akpomie

    2015-09-01

    Full Text Available The potential of a low-cost Nigerian montmorillonite for the adsorption of Ni(II and Mn(II ions from aqueous solution was investigated by batch mode. XRD, SEM and BET analysis were used to characterize the adsorbent. The experiments were performed as a function of pH, particle size, adsorbent dose, initial metal ion concentration, contact time, ligands and temperature. The process was found to be dependent on all the parameters investigated, with a pH of 6.0 obtained for optimum removal of both metal ions. The Langmuir monolayer adsorption capacity of 166.67 and 142.86 mg/g was obtained for Ni(II and Mn(II ions respectively. The Freundlich isotherm gave the best fit to the experimental data than the Langmuir, Temkin and Dubinin–Radushkevich isotherms. The scatchard plot analysis indicated the existence of more than one type of active site on the montmorillonite which corroborates the good fit of the Freundlich model. The pseudo-first order, pseudo-second order and intraparticle diffusion models were applied to the kinetic data. The best fit was achieved with the pseudo-first order model and the existence of intraparticle diffusion mechanism was indicated. Thermodynamic studies showed an endothermic, dissociative, spontaneous and a physical adsorption process between the metal ions and the montmorillonite. Desorption studies revealed over 90% desorption of both metal ions from the metal loaded adsorbent.

  20. Impact of the simulated diagenesis on sorption of naphthalene and 1-naphthol by soil organic matter and its precursors.

    Science.gov (United States)

    Guo, Xiaoying; Wang, Xilong; Zhou, Xinzhe; Ding, Xing; Fu, Bin; Tao, Shu; Xing, Baoshan

    2013-01-01

    Soil organic matter (SOM) in a peat soil, humic acid, and humin and their precursors (i.e., cellulose and lignin) were treated at high temperature (250 and 400 °C) with high pressure in a sealed platinum reaction kittle to simulate the influence of diagenesis on their composition and structure, and impact of the simulated diagenesis on sorption behaviors of hydrophobic organic compounds (HOCs) (i.e., naphthalene and 1-naphthol) by these samples was investigated. High temperature and pressure treatment greatly influenced chemical composition and physical properties of the original samples and their sorption for both naphthalene and 1-naphthol. Sorption of naphthalene by all samples was jointly regulated by hydrophobic and π-π interactions with their alkyl and aromatic carbon moieties, which was derived from the positive correlation between total hydrophobic carbon content of all sorbents and their organic carbon content-normalized sorption coefficients (Koc) for this compound (p = 0.075). However, sorption of 1-naphthol by the tested sorbents was governed by hydrogen bonding with their O-containing polar functionalities, as derived from the positive correlation between Koc values of 1-Naph and their polarity index ((O+N)/C). Difference in sorption mechanisms of naphthalene and 1-naphthol by the original and treated samples noted the great influence of chemical composition of sorbates on their interaction and essential roles of specific interactions (e.g., hydrogen bonding) in sorption of polar compound (i.e., 1-naphthol) to these sorbents. Surface area (SA) and porosity data of sorbents obtained from N2 sorption-desorption isotherms at 77 K showed that new SA and pores were created during the diagenetic process of all original samples, which provided substantial sorption sites and thus enhanced sorption of naphthalene and 1-naphthol. Among all tested samples, physicochemical properties of cellulose were most strongly affected by the simulated diagenetic process

  1. Testosterone sorption and desorption: Effects of soil particle size

    Energy Technology Data Exchange (ETDEWEB)

    Qi, Yong, E-mail: yqi01@unomaha.edu [Civil Engineering Dept., University of Nebraska-Lincoln at Omaha Campus, Omaha, NE 68182 (United States); Zhang, Tian C. [Civil Engineering Dept., University of Nebraska-Lincoln at Omaha Campus, Omaha, NE 68182 (United States); Ren, Yongzheng [School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2014-08-30

    Graphical abstract: - Highlights: • Smaller soil particles have higher sorption and lower desorption rates. • The sorption capacity ranks as clay > silt > sand. • Small particles like clays have less potential for desorption. • Colloids (clays) have high potential to facilitate the transport of hormones in soil–water environments. - Abstract: Soils contain a wide range of particles of different diameters with different mobility during rainfall events. Effects of soil particles on sorption and desorption behaviors of steroid hormones have not been investigated. In this study, wet sieve washing and repeated sedimentation methods were used to fractionate the soils into five ranges. The sorption and desorption properties and related mechanisms of testosterone in batch reactors filled with fractionated soil particles were evaluated. Results of sorption and desorption kinetics indicate that small soil particles have higher sorption and lower desorption rates than that of big ones. Thermodynamic results show the sorption processes are spontaneous and exothermal. The sorption capacity ranks as clay > silt > sand, depending mainly on specific surface area and surface functional groups. The urea control test shows that hydrogen bonding contributes to testosterone sorption onto clay and silt but not on sand. Desorption tests indicate sorption is 36–65% irreversible from clay to sand. Clays have highest desorption hysteresis among these five soil fractions, indicating small particles like clays have less potential for desorption. The results provide indirect evidence on the colloid (clay)-facilitated transport of hormones (micro-pollutants) in soil environments.

  2. U(VI) and Eu(III) ion sorption in the interface solution-phosphate solids: Structural study and mechanisms; Sorption des ions U(VI) et Eu(III) a l`interface solution - solides phosphates: Etude structurale et mechanismes

    Energy Technology Data Exchange (ETDEWEB)

    Drot, Romuald [Inst. de Physique Nucleaire, Paris-11 Univ., 91 - Orsay (France)

    1998-09-18

    As part of the storage of nuclear wastes in a deep underground disposal, radionuclides sorption on geological or engineered barriers is one of the most important factor which could enhance retardation. Thus, the knowledge of such mechanisms is needed. For this purpose, we chose to experimentally define sorption equilibria before performing simulation of retention data. Several phosphate compounds are potential candidates as engineered barrier additives. We considered Th{sub 4}(PO{sub 4}){sub 4}P{sub 2}O{sub 7}, Zr{sub 2}O(PO{sub 4}){sub 2} which allow to study the effect of PO{sub 4} and P{sub 2}O{sub 7} groups separately. Eu(III) and U(IV) ions were used as structural probes in order to simulate actinides (III) and (VI) behavior. X-ray powder diffraction, IR spectroscopy and electron probe microanalysis were used to characterized the synthesized solids. Electrophoretic measurements showed an amphoteric behavior of surface sites. Moreover, laser spectro-fluorimetry experiments indicated that no diffusion phenomena of the sorbed ion inside the solid occurs. Thus, we considered that a surface complexation model should be applied. Laser spectro-fluorimetry and XPS allowed to determine the nature of surface sites. ZrP{sub 2}O{sub 7} presents only one single site (P{sub 2}O{sub 7} groups) whereas Th{sub 4}(PO{sub 4}){sub 4}P{sub 2}O{sub 7} and Zr{sub 2}O(PO{sub 4}){sub 2} admit two types of sites (PO{sub 4}/P{sub 2}O{sub 7} and PO{sub 4}/oxo groups, respectively). Sorbed species were identified using laser spectro-fluorimetry which indicate that, in KNO{sub 3} 0.5 M medium and for a known surface site, there are two surface complexes for U(VI) (sorption of UO{sup 2+}{sub 2} et de UO{sub 2}NO{sup +}{sub 3} species) and only one for Eu(III) (sorption of EuNO{sup 2+}{sub 3}). They are linked to the substrate as bidentate inner sphere complexes (EXAFS study). Surface acidity constants were determined by simulation of potentiometric titration curves obtained for each solid

  3. Enhanced PCBs sorption on biochars as affected by environmental factors: Humic acid and metal cations

    International Nuclear Information System (INIS)

    Wang Yu; Wang Lei; Fang Guodong; Herath, H.M.S.K.; Wang Yujun; Cang Long; Xie Zubin; Zhou Dongmei

    2013-01-01

    Biochar plays an important role in the behaviors of organic pollutants in the soil environment. The role of humic acid (HA) and metal cations on the adsorption affinity of polychlorinated biphenyls (PCBs) to the biochars in an aqueous medium and an extracted solution from a PCBs-contaminated soil was studied using batch experiments. Biochars were produced with pine needles and wheat straw at 350 °C and 550 °C under anaerobic condition. The results showed that the biochars had high adsorption affinity for PCBs. Pine needle chars adsorbed less nonplanar PCBs than planar ones due to dispersive interactions and separation. Coexistence of HA and metal cations increased PCBs sorption on the biochars accounted for HA adsorption and cation complexation. The results will aid in a better understanding of biochar sorption mechanism of contaminants in the environment. - Highlights: ► Application of the biochars for PCBs sorption was a new and effective way. ► The biochars had higher adsorption affinity for PCBs in the soil extracted solution. ► Pine needle chars adsorbed less nonplanar PCBs than planar ones. ► Coexisting humic acid or metal cations increased PCBs sorption on the biochars. - The biochars had higher adsorption affinity for PCBs in the extracted soil solution because coexisting humic acid and metal cations increased their sorption.

  4. Glyphosate sorption/desorption on biochars - interactions of physical and chemical processes.

    Science.gov (United States)

    Hall, Kathleen E; Spokas, Kurt A; Gamiz, Beatriz; Cox, Lucia; Papiernik, Sharon K; Koskinen, William C

    2018-05-01

    Biochar, a carbon-rich product of biomass pyrolysis, could limit glyphosate transport in soil and remediate contaminated water. The present study investigates the sorption/desorption behavior of glyphosate on biochars prepared from different hardwoods at temperatures ranging from 350 to 900 °C to elucidate fundamental mechanisms. Glyphosate (1 mg L -1 ) sorption on biochars increased with pyrolysis temperature and was highest on 900 °C biochars; however, total sorption was low on a mass basis (glyphosate in soils, did not alter biochar sorption capacities. Glyphosate did not desorb from biochar with CaCl 2 solution; however, up to 86% of the bound glyphosate was released with a K 2 HPO 4 solution. Results from this study suggest a combined impact of surface chemistry and physical constraints on glyphosate sorption/desorption on biochar. Based on the observed phosphate-induced desorption of glyphosate, the addition of P-fertilizer to biochar-amended soils can remobilize the herbicide and damage non-target plants; therefore, improved understanding of this risk is necessary. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

  5. Understanding human action: integrating meanings, mechanisms, causes, and contexts

    NARCIS (Netherlands)

    Keestra, M.; Repko, A.F.; Newell, W.H.; Szostak, R.

    2012-01-01

    Humans are capable of understanding an incredible variety of actions performed by other humans. Even though these range from primary biological actions like eating and fleeing, to acts in parliament or in poetry, humans generally can make sense of each other’s actions. Understanding other people’s

  6. Cadmium ion sorption onto lignocellulosic biosorbent modified by sulfonation: the origin of sorption capacity improvement.

    Science.gov (United States)

    Shin, Eun Woo; Rowell, Roger M

    2005-08-01

    Juniper (Juniperus monosperma), a small-diameter underutilized material, has been studied as a lignocellulosic biosorbent for removing heavy metals from water. In this study, juniper wood was modified by sulfonation to enhance sorption capacity for cadmium in water. The origin of the enhancement was investigated by observing the sorption behaviors and the change in surface functional group concentrations. Cadmium sorption by all juniper wood biosorbents studied was fast and the sorption capacity decreased with decreasing pH, similar to results found for other biosorbents. Sulfonated juniper was found to have at least twice the sorption capacity for cadmium removal from water compared to that of untreated juniper, though the sorption capacity increased with increasing pH. A slight increase in carboxylate content after sulfonation was likely responsible for a small portion of the enhancement. Elemental analysis showed an increase in sulfur content after sulfonation. Diffuse reflectance infrared Fourier transform (DRIFT) spectra showed a decrease in the band at 1660 cm(-1) in the range of carbonyl groups as a result of sulfonation. This indicates that coniferaldehyde groups in the lignin of juniper wood corresponding to this band were substituted into sulfonic acid groups after sulfonation. This interpretation was supported by both the color forming reaction with phloroglucinol-hydrochloric acid and the reaction mechanisms from the acid sulfite pulping process. Consequently, the enhancement of cadmium sorption capacity of juniper wood by sulfonation mainly originated from the production of sulfonic acid groups, which are binding sites for heavy metals.

  7. Insights into an intriguing gas sorption mechanism in a polar metal–organic framework with open-metal sites and narrow channels

    KAUST Repository

    Forrest, Katherine A.

    2014-01-01

    Simulations of H2 and CO2 sorption were performed in the metal-organic framework (MOF), [Cu(Me-4py-trz-ia)]. This MOF was recently shown experimentally to exhibit high uptake for H2 and CO2 sorption and this was reproduced and elucidated through the simulations performed herein. Consistent with experiment, the theoretical isosteric heat of adsorption, Qst, values were nearly constant across all loadings for both sorbates. The simulations revealed that sorption directly onto the open-metal sites was not observed in this MOF, ostensibly a consequence of the low partial positive charges of the Cu2+ ions as determined through electronic structure calculations. Sorption was primarily observed between adjacent carboxylate oxygen atoms (site 1) and between nearby methyl groups (site 2) of the organic linkers. In addition, saturation of the most energetically favorable sites (site 1) is possible only after filling a nearby site (site 2) first due to the MOF topology. This suggests that the lack of dependence on loading for the Qst is due to the concurrent filling of sites 1 and 2, leading to an observed average Qst value. © 2014 the Partner Organisations.

  8. Sorption properties of wool

    Directory of Open Access Journals (Sweden)

    Radetić Maja M.

    2004-01-01

    Full Text Available Strict ecological legislation, especially in highly developed countries, imposed requirements for the purification of industrial effluents and the need for efficient oil clean up after sea and inland water spills. Although numerous processes have been developed, the application of sorbents is still one of the most efficient methods to remove heavy metal ions, dyes and crude oil from water. Recently, special attention was paid to sorbents based on natural fibres. A review of studies concerning the sorption properties of wool is presented in this paper. The presence of various functional groups on the wool fibre surface contributes to the efficient sorption of heavy metal ions and dyes. A hydrophobic, scaly surface and fibre crimp strongly influence the high sorption capacity of wool for oil. Wool has great sorption potential even as a recycled material. Accordingly, it can be used as a viable substitute to commercially available synthetic sorbents that show poor biodegradab ility.

  9. Chemical alteration of calcium silicate hydrates in saline groundwater. Mechanism of sorption of Na on C-S-H and effect of NaCl on leaching of Ca from C-S-H

    International Nuclear Information System (INIS)

    Sugiyama, Daisuke; Fujita, Tomonari

    2004-01-01

    In the concept for TRU waste disposal in Japan, cement is a potential waste packaging and backfilling material and is expected to provide chemical containment. In the presence of some reactive ions in a saline groundwater, the chemical properties of cement materials should be affected. In this study, the mechanism of sorption of sodium (Na) on C-S-H and the effect of sodium chloride (NaCl) concentration on dissolution of Calcium Silicate Hydrate (C-S-H) are discussed by measuring the sorption isotherm of sodium onto C-S-H gel (Ca/Si = 0.65-1.2). Based on the experimental results, it is showed that sodium sorbs by substitution for Ca in C-S-H phases and leaching of Ca from C-S-H is enhanced in NaCl solution ( -1 mol dm -3 ). The results of sorption experiments are reasonably well modelled by the ion-exchange model assuming some calcium sites with different ion-exchange log K values. It is also suggested that the dissolution of C-S-H can be modelled reasonably well by considering the effect of ionic strength on activity coefficients of aqueous species for high Ca/Si ratio of C-S-H, and the effect of exchange of sodium with calcium of C-S-H on leaching of Ca becomes obvious for lower Ca/Si ratio of C-S-H. (author)

  10. Understanding the mechanism of base development of HSQ

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jihoon; Chao, Weilun; Griedel, Brian; Liang, Xiaogan; Lewis, Mark; Hilken, Dawn; Olynick, Deirdre

    2009-06-16

    We study the dissolution mechanism of HSQ (hydrogen silsesquioxane) in base solutions with the addition of chloride salts to elucidate the development mechanism. Reaction mechanisms are proposed based on the dissolution mechanism of quartz. Development kinetics points to two dose-dependent development mechanisms. Considering ion sizes, both hydrated and non-hydrated, and ion exchange, we propose that a combination of a surface dominated reaction at higher doses and a matrix dominated reaction at lower doses accounts for the high development contrast with a NaOH base/NaCl salt mixture. The interplay between the hydrated and non-hydrated ion size leads to higher contrast developers, such as tetramethyl ammonium hydroxide (TMAH) with NaCl.

  11. Status report on SIRS: sorption information retrieval system

    Energy Technology Data Exchange (ETDEWEB)

    Hostetler, D.D.; Serne, R.J.; Baldwin, A.J.; Petrie, G.M.

    1980-11-01

    Two major uses were identified for the Sorption Information Retrieval System: (1) to aid geochemists in the elucidation of sorption mechanisms; and (2) to aid safety assessment modelers in selection of Kds for any given scenerio. Other benefits such as providing an auditable vehicle for the Kd selection were also discussed.

  12. Synthesis of Nano-sized Boehmites for Optimum Phosphate Sorption

    DEFF Research Database (Denmark)

    Watanabe, Yujiro; Kasama, Takeshi; Fukushi, Keisuke

    2011-01-01

    the highest amount of phosphate sorption (1.73 mmol g-1 at pH 3.3) compared with Al-bearing materials. The reaction mechanism during phosphate sorption was described by the anion exchange reaction between phosphate ions in sodium phosphate solution and hydroxide ions on boehmite surfaces. Therefore...

  13. Status report on SIRS: sorption information retrieval system

    International Nuclear Information System (INIS)

    Hostetler, D.D.; Serne, R.J.; Baldwin, A.J.; Petrie, G.M.

    1980-11-01

    Two major uses were identified for the Sorption Information Retrieval System: (1) to aid geochemists in the elucidation of sorption mechanisms; and (2) to aid safety assessment modelers in selection of Kds for any given scenerio. Other benefits such as providing an auditable vehicle for the Kd selection were also discussed

  14. Long Term Sorption Diffusion Experiment (LTDE-SD). Performance of main in situ experiment and results from water phase measurements

    Energy Technology Data Exchange (ETDEWEB)

    Widestrand, Henrik; Byegaard, Johan; Nilsson, Kersti; Hoeglund, Susanne; Gustafsson, Erik (Geosigma AB, Uppsala (Sweden)); Kronberg, Magnus (Swedish Nuclear Fuel and Waste Management Co. (Sweden))

    2010-12-15

    The LTDE-SD experiment, (Long Term Sorption Diffusion Experiment) aimed at increasing the scientific knowledge of sorption and diffusion under in situ conditions and to provide data for performance and safety assessment calculations. Performance and results of the in situ experiment phase are presented in the report. In total, 21 radionuclide trace elements and one stable trace element were injected, circulated and sampled for approx6.5 months in a closed borehole section. The trace elements represented non-sorbing tracers and sorbing tracers for which the sorption was dominated by a cation exchange mechanism, a surface complexation mechanism, or dependent on an electrochemical reduction in order to reach the tetravalent state (oxidation state IV) considered very strongly sorbing. The borehole section in contact with the tracer labelled groundwater consisted in part of a natural fracture surface and a borehole section in the unaltered matrix rock, devoid of natural fractures. Water samples were regularly extracted and analysed for trace element concentration and a few ion exchange speciation and filtered samplings were also conducted. Independent colloid filtering and chemical speciation calculations were performed in support the evaluation. Sorption was demonstrated for a series of elements present in the experiment. The amounts lost of the different respective tracers from the aqueous phase follow very well the general understanding of the relative sorption strength of the tracers, as inferred from e.g. batch sorption experiments and dynamic in situ tracer experiments. The chemical speciation calculations of the different tracers were in line with the results of the ion exchange speciation performed during the experiment. With the exception of UO{sub 2} 2+ carbonate complexes formed, no strong indications were obtained that aqueous complexation prevents adsorption under the chemical conditions of the experiment. The 20 nm filtered sampling indicated that

  15. Sorption of 3,3',4,4'-tetrachlorobiphenyl by microplastics: A case study of polypropylene.

    Science.gov (United States)

    Zhan, Zhiwei; Wang, Jundong; Peng, Jinping; Xie, Qilai; Huang, Ying; Gao, Yifan

    2016-09-15

    Though plastics show good chemical inertness, they could sorb polychlorinated biphenyls (PCBs) and other toxic pollutants from the surrounding environment. Thus, ingestion of microplastics by marine organisms potentially enhances the transport and bioavailability of toxic chemicals. However, there is lack of studies on the sorption capacity, mechanism and factors affecting the sorption behavior. Here, sorption of PCBs by microplastics in the simulated seawater was studied using the batch oscillation equilibration technique, in which polypropylene (PP) and 3,3',4,4'-tetrachlorobiphenyl (PCB77) acted as model plastic and PCB, respectively. Factors including particle size, temperature and solution environment were investigated. Results showed that, equilibrium sorption time is about 8h and sorption capacity increase with decreasing particle size and temperature. Different sorption capacity in three solution environments was observed. Equilibrium data in three solution environments fitted very well to the Langmuir sorption model, indicating chemical sorption is the predominant mechanism. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. The Nobel Prize for understanding autophagy, a cellular mechanism ...

    Indian Academy of Sciences (India)

    The Nobel Prize in Physiology or Medicine, 2016, was awarded to Prof Yoshinori Ohsumi from TokyoInstitute of Technology, Yokohoma, Japan, for his work that helped in understanding the molecularmechanisms of autophagy, a process used by most eukaryotic cells to degrade a portion of cytoplasmincluding damaged ...

  17. Understanding "Understanding" Flow for Network-Centric Warfare: Military Knowledge-Flow Mechanics

    National Research Council Canada - National Science Library

    Nissen, Mark

    2002-01-01

    Network-centric warfare (NCW) emphasizes information superiority for battlespace efficacy, but it is clear that the mechanics of how knowledge flows are just as important as those pertaining to the networks and communication...

  18. Understanding the Role and Mechanism of Metformin in Obesity ...

    African Journals Online (AJOL)

    Metformin, a biguanide, is a widely used drug for the treatment of type 2 diabetes mellitus. The drug also found to be beneficial in other class of diseases like obesity but its role and mechanism of action in obesity is still not well established. A literature survey was done in order to evaluate the evidence supporting metformin ...

  19. Understanding the Mechanism behind Maternal Imprisonment and Adolescent School Dropout

    Science.gov (United States)

    Cho, Rosa M.

    2011-01-01

    This study empirically tested 3 mechanisms commonly suggested to disadvantage youths whose mothers are incarcerated in prison. An event history analysis of school dropout was conducted on a sample of 6,008 adolescents in a large city created by merging several Illinois state administrative data. Findings revealed that adolescents are indeed at…

  20. Understanding the biological mechanisms of Zika virus disease ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    This project will use advanced biomolecular, genomics and proteomics techniques to explain the molecular mechanisms by which the Zika virus infects and persists in the human body, how it affects the human reproductive and central nervous system, and how the risk of fetal abnormalities can be better predicted in infected ...

  1. Selective lanthanide sorption and mechanism using novel hybrid Lewis base (N-methyl-N-phenyl-1,10-phenanthroline-2-carboxamide) ligand modified adsorbent

    International Nuclear Information System (INIS)

    Awual, Md. Rabiul; Kobayashi, Tohru; Miyazaki, Yuji; Motokawa, Ryuhei; Shiwaku, Hideaki; Suzuki, Shinichi; Okamoto, Yoshihiro; Yaita, Tsuyoshi

    2013-01-01

    Highlights: •Hybrid Lewis base adsorbent was prepared for selective lanthanide (Eu, Sm) removal. •Common ions did not interfere due to strong interactions between Eu/Sm and adsorbent. •The adsorbent has good sorption and kinetic performances for potential applications. •The adsorption is reversible and adsorbent reusable in many cycles without any deterioration. -- Abstract: This study aims to develop a highly selective Lewis base adsorbent to investigate the selective sorption and recovery of Eu(III) and Sm(III) from wastewater. The oxygen and nitrogen donor atoms containing Lewis base N-methyl-N-phenyl-1,10-phenanthroline-2-carboxamide (MePhPTA) ligand was synthesized and subsequently an adsorbent was prepared by direct immobilization onto mesoporous silica. Determined maximum adsorption capacities were 125.63 and 124.38 mg/g for Eu(III) and Sm(III), respectively. Experiments with mixed-cations solutions showed that the sequence of preferential adsorption was Eu(III) > Sm(III). The lanthanide sorption by hybrid Lewis base adsorbent (HyLBA) was not adversely affected by the presence of sodium, potassium, calcium, magnesium, chloride, sulfate and nitrate ions due to strong affinity between hard Lewis acid lanthanide and hard Lewis base adsorbent. The crystallography for the Sm-MePhPTA complex suggested that MePhPTA was strongly coordinated to Sm(III) with oxygen and nitrogen by forming a stable complex with two 5-membered rings. The data clarified that bond lengths between Sm(III) and amide oxygen (2.475 Å) were shorter than Sm-N (2.662 Å) in phenanthroline moiety indicating strong oxygen driven HyLBA. The results suggested that HyLBA has a good prospect of promising applications for separation/sorption of lanthanide ions from effluents

  2. Sorption of methanol in alkali exchange zeolites

    NARCIS (Netherlands)

    Rep, M.; Rep, M.; Corma, Avelino; Palomares, A.E.; Palomares gimeno, A.E.; van Ommen, J.G.; Lefferts, Leonardus; Lercher, J.A.

    2000-01-01

    Metal cation methanol sorption complexes in MFI (ZSM5), MOR and X have been studied by in situ i.r. spectroscopy in order to understand the nature of interactions of methanol in the molecular sieve pores. The results show that (a) a freely vibrating hydroxy and methyl group of methanol exist on

  3. How Electroconvulsive Therapy Works?: Understanding the Neurobiological Mechanisms

    Science.gov (United States)

    Singh, Amit; Kar, Sujita Kumar

    2017-01-01

    Electroconvulsive therapy (ECT) is a time tested treatment modality for the management of various psychiatric disorders. There have been a lot of modifications in the techniques of delivering ECT over decades. Despite lots of criticisms encountered, ECT has still been used commonly in clinical practice due to its safety and efficacy. Research evidences found multiple neuro-biological mechanisms for the therapeutic effect of ECT. ECT brings about various neuro-physiological as well as neuro-chemical changes in the macro- and micro-environment of the brain. Diverse changes involving expression of genes, functional connectivity, neurochemicals, permeability of blood-brain-barrier, alteration in immune system has been suggested to be responsible for the therapeutic effects of ECT. This article reviews different neurobiological mechanisms responsible for the therapeutic efficacy of ECT. PMID:28783929

  4. Kinetic modeling of pH-dependent antimony (V) sorption and transport in iron oxide-coated sand.

    Science.gov (United States)

    Cai, Yongbing; Li, Lulu; Zhang, Hua

    2015-11-01

    Understanding the mechanisms and kinetics controlling the retention and transport of antimony (Sb) is prerequisite for evaluating the risk of groundwater contamination by the toxic element. In this study, kinetic batch and saturated miscible displacement experiments were performed to investigate effects of protonation-deprotonation reactions on sorption-desorption and transport of Sb(V) in iron oxide-coated sand (IOCS). Results clearly demonstrated that Sb(V) sorption was highly nonlinear and time dependent, where both sorption capacity and kinetic rates decreased with increasing solution pH. Breakthrough curves (BTCs) obtained at different solution pH exhibited that mobility of Sb(V) were higher under neutral to alkaline condition than under acidic condition. Because of the nonlinear and non-equilibrium nature of Sb(V) retention and transport, multi-reaction models (MRM) with equilibrium and kinetic sorption expressions were utilized successfully to simulate the experiment data. Equilibrium distribution coefficient (Ke) and reversible kinetic retention parameters (k1 and k2) of both kinetic sorption and transport experiment showed marked decrease as pH increased from 4.0 to 7.5. Surface complexation is suggested as the dominant mechanism for the observed pH-dependent phenomena, which need to be incorporated into the kinetic models to accurately simulate the reactive transport of Sb(V) in vadose zone and aquifers. Copyright © 2015. Published by Elsevier Ltd.

  5. Sorption of Europium in zirconium silicate

    International Nuclear Information System (INIS)

    Garcia R, G.

    2004-01-01

    Some minerals have the property of sipping radioactive metals in solution, that it takes advantage to manufacture contention barriers that are placed in the repositories of nuclear wastes. The more recent investigations are focused in the development of new technologies guided to the sorption of alpha emissors on minerals which avoid their dispersion in the environment. In an effort to contribute to the understanding of this type of properties, some studies of sorption of Europium III are presented like homologous of the americium, on the surface of zirconium silicate (ZrSiO 4 ). In this work the results of sorption experiences are presented as well as the interpretation of the phenomena of the formation of species in the surface of the zirconium silicate. (Author)

  6. Sorption of radionuclides by tertiary clays

    International Nuclear Information System (INIS)

    Wagner, J.F.; Czurda, K.A.

    1990-01-01

    The sorption capacity of different clay types for some metals (Co, Cs, Sr and Zn), occurring as common radionuclides in radioactive waste deposits, had been analysed by a static (batch technique) and a dynamic method (percolation tests, in which the driving force is a hydraulic gradient). Sorption capacity generally increased with an increasing pH of solution. A decrease of sorption capacity had been observed in the order Zn > Cs ≥ Co > Sr for the batch and Cs > Zn > Sr > Co for the percolation tests. Clay marls showed a distinctly higher sorption respectively retention capacity as pure clays. Sorption capacity depends on solution parameters like type and concentration of radionuclide, pH, salt concentration, etc., and on rock parameters like mineral content (e.g. swelling clay minerals and carbonates), organic material, rock pH, micro fabric, etc. A third parameter of great influence is the contact time between clay and solution. The adsorption isotherms reflect two different adsorption mechanisms: a very rapid adsorption (a few minutes) on the external surfaces of clay minerals and a slow adsorption process (weeks and longer), due to the diffusion of metal ions into the interlayer space of clay minerals. 12 refs., 9 figs., 1 tab

  7. Development of mechanistic sorption model and treatment of uncertainties for Ni sorption on montmorillonite/bentonite

    International Nuclear Information System (INIS)

    Ochs, Michael; Ganter, Charlotte; Tachi, Yukio; Suyama, Tadahiro; Yui, Mikazu

    2011-02-01

    Sorption and diffusion of radionuclides in buffer materials (bentonite) are the key processes in the safe geological disposal of radioactive waste, because migration of radionuclides in this barrier is expected to be diffusion-controlled and retarded by sorption processes. It is therefore necessary to understand the detailed/coupled processes of sorption and diffusion in compacted bentonite and develop mechanistic /predictive models, so that reliable parameters can be set under a variety of geochemical conditions relevant to performance assessment (PA). For this purpose, JAEA has developed the integrated sorption and diffusion (ISD) model/database in montmorillonite/bentonite systems. The main goal of the mechanistic model/database development is to provide a tool for a consistent explanation, prediction, and uncertainty assessment of K d as well as diffusion parameters needed for the quantification of radionuclide transport. The present report focuses on developing the thermodynamic sorption model (TSM) and on the quantification and handling of model uncertainties in applications, based on illustrating by example of Ni sorption on montmorillonite/bentonite. This includes 1) a summary of the present state of the art of thermodynamic sorption modeling, 2) a discussion of the selection of surface species and model design appropriate for the present purpose, 3) possible sources and representations of TSM uncertainties, and 4) details of modeling, testing and uncertainty evaluation for Ni sorption. Two fundamentally different approaches are presented and compared for representing TSM uncertainties: 1) TSM parameter uncertainties calculated by FITEQL optimization routines and some statistical procedure, 2) overall error estimated by direct comparison of modeled and experimental K d values. The overall error in K d is viewed as the best representation of model uncertainty in ISD model/database development. (author)

  8. Advances in understanding Giardia: determinants and mechanisms of chronic sequelae

    Science.gov (United States)

    Sartor, R. Balfour

    2015-01-01

    Giardia lamblia is a flagellated protozoan that is the most common cause of intestinal parasitic infection in children living in resource-limited settings. The pathogenicity of Giardia has been debated since the parasite was first identified, and clinical outcomes vary across studies. Among recent perplexing findings are diametrically opposed associations between Giardia and acute versus persistent diarrhea and a poorly understood potential for long-term sequelae, including impaired child growth and cognitive development. The mechanisms driving these protean clinical outcomes remain elusive, but recent advances suggest that variability in Giardia strains, host nutritional status, the composition of microbiota, co-infecting enteropathogens, host genetically determined mucosal immune responses, and immune modulation by Giardia are all relevant factors influencing disease manifestations after Giardia infection. PMID:26097735

  9. Sorption of nickel on chitosan

    International Nuclear Information System (INIS)

    Pivarciova, O.; Rosskopfova, O.; Galambos, M.

    2012-01-01

    This work was focused on the study of sorption properties of nickel on chitosan. Sorption of nickel on the selected sorbents was studied by batch method. Radionuclide 63 Ni was used as a tracer. Langmuir isotherm was used for interpretation of the sorption of nickel on chitosan by varying the concentration of Ni 2 + cations in aqueous phase.

  10. Understanding mechanisms of autoimmunity through translational research in vitiligo

    Science.gov (United States)

    Strassner, James P; Harris, John E

    2016-01-01

    Vitiligo is an autoimmune disease of the skin that leads to life-altering depigmentation and remains difficult to treat. However, clinical observations and translational studies over 30-40 years have led to the development of an insightful working model of disease pathogenesis: Genetic risk spanning both immune and melanocyte functions is pushed over a threshold by known and suspected environmental factors to initiate autoimmune T cell-mediated killing of melanocytes. While under cellular stress, melanocytes appear to signal innate immunity to activate T cells. Once the autoimmune T cell response is established, the IFN-γ-STAT1-CXCL10 signaling axis becomes the primary inflammatory pathway driving both progression and maintenance of vitiligo. This pathway is a tempting target for both existing and developing pharmaceuticals, but further detailing how melanocytes signal their own demise may also lead to new therapeutic targets. Research in vitiligo may be the future key to understand the pathogenesis of organ-specific autoimmunity, as vitiligo is common, reversible, progresses over the life of the individual, has been relatively well-defined, and is quite easy to study using translational and clinical approaches. What is revealed in these studies can lead to innovative treatments and also help elucidate the principles that underlie similar organ-specific autoimmune diseases, especially in cases where the target organ is less accessible. PMID:27764715

  11. Understanding the kinetic mechanism of RNA single base pair formation.

    Science.gov (United States)

    Xu, Xiaojun; Yu, Tao; Chen, Shi-Jie

    2016-01-05

    RNA functions are intrinsically tied to folding kinetics. The most elementary step in RNA folding is the closing and opening of a base pair. Understanding this elementary rate process is the basis for RNA folding kinetics studies. Previous studies mostly focused on the unfolding of base pairs. Here, based on a hybrid approach, we investigate the folding process at level of single base pairing/stacking. The study, which integrates molecular dynamics simulation, kinetic Monte Carlo simulation, and master equation methods, uncovers two alternative dominant pathways: Starting from the unfolded state, the nucleotide backbone first folds to the native conformation, followed by subsequent adjustment of the base conformation. During the base conformational rearrangement, the backbone either retains the native conformation or switches to nonnative conformations in order to lower the kinetic barrier for base rearrangement. The method enables quantification of kinetic partitioning among the different pathways. Moreover, the simulation reveals several intriguing ion binding/dissociation signatures for the conformational changes. Our approach may be useful for developing a base pair opening/closing rate model.

  12. Understanding the mechanisms of glutamine action in critically ill patients

    Directory of Open Access Journals (Sweden)

    Gisele P. Oliveira

    2010-06-01

    Full Text Available Glutamine (Gln is an important energy source and has been used as a supplementary energy substrate. Furthermore, Gln is an essential component for numerous metabolic functions, including acid-base homeostasis, gluconeogenesis, nitrogen transport and synthesis of proteins and nucleic acids. Therefore, glutamine plays a significant role in cell homeostasis and organ metabolism. This article aims to review the mechanisms of glutamine action during severe illnesses. In critically ill patients, the increase in mortality was associated with a decreased plasma Gln concentration. During catabolic stress, Gln consumption rate exceeds the supply, and both plasma and skeletal muscle pools of free Gln are severely reduced. The dose and route of Gln administration clearly influence its effectiveness: high-dose parenteral appears to be more beneficial than low-dose enteral administration. Experimental studies reported that Gln may protect cells, tissues, and whole organisms from stress and injury through the following mechanisms: attenuation of NF (nuclear factor-kB activation, a balance between pro- and anti-inflammatory cytokines, reduction in neutrophil accumulation, improvement in intestinal integrity and immune cell function, and enhanced of heat shock protein expression. In conclusion, high-doses of parenteral Gln (>0.50 g/kg/day demonstrate a greater potential to benefit in critically ill patients, although Gln pathophysiological mechanisms requires elucidation.A glutamina (Gln é uma importante fonte de energia e tem sido usada como substrato energético suplementar. Além disso, a Gln é um componente essencial para numerosas funções metabólicas tais como: homeostase ácido-base, gliconeogênese, transporte de nitrogênio e síntese de proteínas e ácidos nucléicos. Portanto, a glutamina desempenha um papel importante na homeostase celular e no metabolismo dos órgãos. Esse artigo objetiva rever os mecanismos de ação da glutamina na doen

  13. Understanding the removal mechanisms of PPCPs and the influence of main technological parameters in anaerobic UASB and aerobic CAS reactors.

    Science.gov (United States)

    Alvarino, T; Suarez, S; Lema, J M; Omil, F

    2014-08-15

    The removal of 16 Pharmaceutical and Personal Care Products (PPCPs) were studied in a conventional activated sludge (CAS) unit and an upflow anaerobic sludge blanket (UASB) reactor. Special attention was paid to each biomass conformation and activity as well as to operational conditions. Biodegradation was the main PPCP removal mechanism, being higher removals achieved under aerobic conditions, except in the case of sulfamethoxazole and trimetrophim. Under anaerobic conditions, PPCP biodegradation was correlated with the methanogenic rate, while in the aerobic reactor a relationship with nitrification was found. Sorption onto sludge was influenced by biomass conformation, being only significant for musk fragrances in the UASB reactor, in which an increase of the upward velocity and hydraulic retention time improved this removal. Additionally, PPCP sorption increased with time in the UASB reactor, due to the granular biomass structure which suggests the existence of intra-molecular diffusion. Copyright © 2014 Elsevier B.V. All rights reserved.

  14. Understanding cracking failures of coatings: A fracture mechanics approach

    Science.gov (United States)

    Kim, Sung-Ryong

    A fracture mechanics analysis of coating (paint) cracking was developed. A strain energy release rate (G(sub c)) expression due to the formation of a new crack in a coating was derived for bending and tension loadings in terms of the moduli, thicknesses, Poisson's ratios, load, residual strain, etc. Four-point bending and instrumented impact tests were used to determine the in-situ fracture toughness of coatings as functions of increasing baking (drying) time. The system used was a thin coating layer on a thick substrate layer. The substrates included steel, aluminum, polycarbonate, acrylonitrile-butadiene-styrene (ABS), and Noryl. The coatings included newly developed automotive paints. The four-point bending configuration promoted nice transversed multiple coating cracks on both steel and polymeric substrates. The crosslinked type automotive coatings on steel substrates showed big cracks without microcracks. When theoretical predictions for energy release rate were compared to experimental data for coating/steel substrate samples with multiple cracking, the agreement was good. Crosslinked type coatings on polymeric substrates showed more cracks than theory predicted and the G(sub c)'s were high. Solvent evaporation type coatings on polymeric substrates showed clean multiple cracking and the G(sub c)'s were higher than those obtained by tension analysis of tension experiments with the same substrates. All the polymeric samples showed surface embrittlement after long baking times using four-point bending tests. The most apparent surface embrittlement was observed in the acrylonitrile-butadiene-styrene (ABS) substrate system. The impact properties of coatings as a function of baking time were also investigated. These experiments were performed using an instrumented impact tester. There was a rapid decrease in G(sub c) at short baking times and convergence to a constant value at long baking times. The surface embrittlement conditions and an embrittlement toughness

  15. Understanding ozone mechanisms to alleviate ceramic membrane fouling

    Science.gov (United States)

    Chu, Irma Giovanna Llamosas

    Ceramic membranes are a strong prospect as an advanced treatment in the drinking water domain. But their high capital cost and the lack of specific research on their performance still discourage their application in this field. Thus, knowing that fouling is the main drawback experienced in filtration processes, this bench-scale study was aimed to assess the impact of an ozonation pre-treatment on the alleviation of the fouling of UF ceramic membranes. Preozonation and filtration steps were performed under two different pH and ozone doses. Chosen pH values were at the limits of natural surface waters range (6.5 and 8.5) to keep practicability. Raw water from the Thousand Isle's river at Quebec-Canada was used for the tests. The filtration setup involved an unstirred dead-end filtration cell operated at constant flux. Results showed that pre-oxidation by ozone indeed reduced the fouling degree of the membranes according to the dose applied (up to 60 and 85% for membranes 8 and 50 kDa, respectively). Direct NOM oxidation was found responsible for this effect as the presence of molecular ozone was not essential to achieve these results. In the context of this experiment, however, pH showed to be more effective than the ozonation pre-treatment to keep fouling at low levels: 70% lower at pH 6.5 than at pH 8.5 for un-ozonated waters, which was contrary to most of the literature found on the topic (Changwon, 2013; De Angelis & Fidalgo, 2013; Karnik et al., 2005; S. Lee & Kim, 2014). This behaviour results mainly from the operation mode used in the experiment, the electrical repulsions between MON molecules at basic pH that led to the accumulation of material on the feed side of the membranes (concentration polarisation) and ulterior cake formation. In addition, solution pH showed an influence in the definition of fouling mechanisms. At solution pH 6.5, which was precisely the isoelectric point of the membranes (+/-6.5), the blocking fouling mode was frequently detected

  16. Sixth-Grade Students' Progress in Understanding the Mechanisms of Global Climate Change

    Science.gov (United States)

    Visintainer, Tammie; Linn, Marcia

    2015-01-01

    Developing solutions for complex issues such as global climate change requires an understanding of the mechanisms involved. This study reports on the impact of a technology-enhanced unit designed to improve understanding of global climate change, its mechanisms, and their relationship to everyday energy use. Global Climate Change, implemented in…

  17. On the derivation of a sorption database

    International Nuclear Information System (INIS)

    Ewart, F.T.; Haworth, A.; Wisbey, S.J.

    1992-01-01

    The safety arguments in support of many radioactive waste repository concepts are heavily dependent on the existence of a sorption reaction. Such a reaction will, in the near field, reduce the magnitude of the release of a number of hazardous radionuclides so that their release to the geosphere is dispersed in time. In the geosphere, the sorption reactions provide a mechanism whereby the migration of the elements released from the repository is retarded and the radioisotopes then subsequently decay. The processes involved in sorption cannot in many cases be satisfactorily represented in thermodynamic terms such as are employed in the description of dissolution and precipitation. Experiments that investigate these reactions are not easy to perform. The sorption parameters that are obtained experimentally for the near field relate, in the UK case, to sorption on to a cementitious surface. These surfaces, since they consist substantially of calcium hydroxide or calcium silicate hydrates, control the aqueous chemistry, do not permit pH changes to be made and limit the range of concentrations of sorbate that may be used. In the far field, on the other hand, the surfaces are not in general so active with respect to the solution chemistry and data can be obtained across a wide spectrum of aqueous chemistries. These data, although they may be useful in testing and parameterizing models, may not have validity under field conditions since the minerals will, inevitably, react to the changes in water chemistry, over geological timescales. The uncertainties in the experimental data are, for many elements and solids, balanced by a reasonable agreement between workers in the values of the parameters used to describe sorption. 22 refs., 1 fig., 1 tab

  18. Understanding the removal mechanisms of PPCPs and the influence of main technological parameters in anaerobic UASB and aerobic CAS reactors

    International Nuclear Information System (INIS)

    Alvarino, T.; Suarez, S.; Lema, J.M.; Omil, F.

    2014-01-01

    Highlights: • Removals of 16 PPCPs under aerobic and anaerobic conditions were quantified. • Operation conditions (HRT, v up , biomass activity and conformation) influenced removal. • Highest removals associated to aerobic biodegradation. • Sorption was only relevant for lipophilic compounds in the UASB reactor. - Abstract: The removal of 16 Pharmaceutical and Personal Care Products (PPCPs) were studied in a conventional activated sludge (CAS) unit and an upflow anaerobic sludge blanket (UASB) reactor. Special attention was paid to each biomass conformation and activity as well as to operational conditions. Biodegradation was the main PPCP removal mechanism, being higher removals achieved under aerobic conditions, except in the case of sulfamethoxazole and trimetrophim. Under anaerobic conditions, PPCP biodegradation was correlated with the methanogenic rate, while in the aerobic reactor a relationship with nitrification was found. Sorption onto sludge was influenced by biomass conformation, being only significant for musk fragrances in the UASB reactor, in which an increase of the upward velocity and hydraulic retention time improved this removal. Additionally, PPCP sorption increased with time in the UASB reactor, due to the granular biomass structure which suggests the existence of intra-molecular diffusion

  19. Understanding the removal mechanisms of PPCPs and the influence of main technological parameters in anaerobic UASB and aerobic CAS reactors

    Energy Technology Data Exchange (ETDEWEB)

    Alvarino, T., E-mail: teresa.alvarino@usc.es; Suarez, S., E-mail: Sonia.suarez@usc.es; Lema, J.M., E-mail: juan.lema@usc.es; Omil, F., E-mail: francisco.omil@usc.es

    2014-08-15

    Highlights: • Removals of 16 PPCPs under aerobic and anaerobic conditions were quantified. • Operation conditions (HRT, v{sub up}, biomass activity and conformation) influenced removal. • Highest removals associated to aerobic biodegradation. • Sorption was only relevant for lipophilic compounds in the UASB reactor. - Abstract: The removal of 16 Pharmaceutical and Personal Care Products (PPCPs) were studied in a conventional activated sludge (CAS) unit and an upflow anaerobic sludge blanket (UASB) reactor. Special attention was paid to each biomass conformation and activity as well as to operational conditions. Biodegradation was the main PPCP removal mechanism, being higher removals achieved under aerobic conditions, except in the case of sulfamethoxazole and trimetrophim. Under anaerobic conditions, PPCP biodegradation was correlated with the methanogenic rate, while in the aerobic reactor a relationship with nitrification was found. Sorption onto sludge was influenced by biomass conformation, being only significant for musk fragrances in the UASB reactor, in which an increase of the upward velocity and hydraulic retention time improved this removal. Additionally, PPCP sorption increased with time in the UASB reactor, due to the granular biomass structure which suggests the existence of intra-molecular diffusion.

  20. Study of the enthalpy-entropy mechanism from water sorption of orange seeds (C. sinensis cv. Brazilian for the use of agro-industrial residues as a possible source of vegetable oil production

    Directory of Open Access Journals (Sweden)

    Daniele Penteado Rosa

    2013-02-01

    Full Text Available Orange seeds are a promising agroindustry-waste which can be implemented in the extraction and production of vegetable oil. The relationship between moisture content and water activity provides useful information for the processing and storage of this waste item. The aim of this study was to determine the mechanism of water sorption enthalpy-entropy of orange seeds (C. sinensis cv. Brazilians according to the moisture content. Therefore, desorption isotherms were determined at five different temperature (30, 40, 50, 60, and 70 ºC under a wide range of moisture content (0.005-0.057 kg kg-1 d.b. and water activity (0.02-0.756. Theoretical and empirical models were used for modeling the desorption isotherms. An analytical solution of the Clausius-Clapeyron equation was proposed to compute the isosteric heat of sorption, the differential entropy, and Gibbs free energy using the Oswin model when the effect of temperature on the hygroscopic equilibrium was considered.

  1. Technetium Sorption Media Review

    International Nuclear Information System (INIS)

    Duncan, J.B.; Kelly, S.E.; Robbins, R.A.; Adams, R.D.; Thorson, M.A.; Haass, C.C.

    2011-01-01

    This report presents information and references to aid in the selection of 99Tc sorption media for feasibility studies regarding the removal of 99Tc from Hanford's low activity waste. The report contains literature search material for sorption media (including ion exchange media) for the most tested media to date, including SuperLig 639, Reillex HPQ, TAM (Kruion), Purolite A520E and A530E, and Dowex 1X8. The U.S. Department of Energy (DOE), Office of River Protection (ORP) is responsible for management and completion of the River Protection Project (RPP) mission, which comprises both the Hanford Site tank farms and the Waste Treatment and Immobilization Plant (WTP). The RPP mission is to store, retrieve and treat Hanford's tank waste; store and dispose of treated wastes; and close the tank farm waste management areas and treatment facilities in a safe, environmentally compliant, cost-effective and energy-effective manner.

  2. TECHNETIUM SORPTION MEDIA REVIEW

    Energy Technology Data Exchange (ETDEWEB)

    DUNCAN JB; KELLY SE; ROBBINS RA; ADAMS RD; THORSON MA; HAASS CC

    2011-08-25

    This report presents information and references to aid in the selection of 99Tc sorption media for feasibility studies regarding the removal of 99Tc from Hanford's low activity waste. The report contains literature search material for sorption media (including ion exchange media) for the most tested media to date, including SuperLig 639, Reillex HPQ, TAM (Kruion), Purolite A520E and A530E, and Dowex 1X8. The U.S. Department of Energy (DOE), Office of River Protection (ORP) is responsible for management and completion of the River Protection Project (RPP) mission, which comprises both the Hanford Site tank farms and the Waste Treatment and Immobilization Plant (WTP). The RPP mission is to store, retrieve and treat Hanford's tank waste; store and dispose of treated wastes; and close the tank farm waste management areas and treatment facilities in a safe, environmentally compliant, cost-effective and energy-effective manner.

  3. Simulation of the Mechanism of Gas Sorption in a Metal–Organic Framework with Open Metal Sites: Molecular Hydrogen in PCN-61

    KAUST Repository

    Forrest, Katherine A.

    2012-07-26

    Grand canonical Monte Carlo (GCMC) simulations were performed to investigate hydrogen sorption in an rht-type metal-organic framework (MOF), PCN-61. The MOF was shown to have a large hydrogen uptake, and this was studied using three different hydrogen potentials, effective for bulk hydrogen, but of varying sophistication: a model that includes only repulsion/dispersion parameters, one augmented with charge-quadrupole interactions, and one supplemented with many-body polarization interactions. Calculated hydrogen uptake isotherms and isosteric heats of adsorption, Q st, were in quantitative agreement with experiment only for the model with explicit polarization. This success in reproducing empirical measurements suggests that modeling MOFs that have open metal sites is feasible, though it is often not considered to be well described via a classical potential function; here it is shown that such systems may be accurately described by explicitly including polarization effects in an otherwise traditional empirical potential. Decomposition of energy terms for the models revealed deviations between the electrostatic and polarizable results that are unexpected due to just the augmentation of the potential surface by the addition of induction. Charge-quadrupole and induction energetics were shown to have a synergistic interaction, with inclusion of the latter resulting in a significant increase in the former. Induction interactions strongly influence the structure of the sorbed hydrogen compared to the models lacking polarizability; sorbed hydrogen is a dipolar dense fluid in the MOF. This study demonstrates that many-body polarization makes a critical contribution to gas sorption structure and must be accounted for in modeling MOFs with polar interaction sites. © 2012 American Chemical Society.

  4. Cadmium sorption in solution by a chitin: effect of pH; Sorption du cadmium en solution par une chitine: effet du pH

    Energy Technology Data Exchange (ETDEWEB)

    Benguella, B.; Benaissa, H. [Universtie de Tlemcen, Lab. de Materiaux Sorbants et Traitement des Eaux, Dept. de Chimie, Faculte des Sciences, Tlemcen (Algeria)

    2001-07-01

    The pH is an essential factor to take into consideration in the sorption mechanisms of metals: it acts both on the metal speciation in solution and on the chemical behaviour of the surface of the sorbing material, and thus indirectly on the sorption mechanism. The effect of the initial pH of the solution on the cadmium sorption by raw state chitin has been studied in static conditions. The approach used is the determination of the sorption kinetics and equilibria for different values of initial pH (pH < 7-7.5). An increase of the initial pH value of the solution leads to an increase of the cadmium sorption capacity by chitin at the equilibrium. The Langmuir model has revealed to be convenient for a mathematical description of the sorption isotherms obtained. (J.S.)

  5. Radionuclide sorption-desorption pattern in soils from Spain

    Energy Technology Data Exchange (ETDEWEB)

    Gil-Garcia, C.J.; Rigol, A.; Rauret, G. [Departament de Quimica Analitica, Universitat de Barcelona, Marti i Franques 1-11, 3a Planta, 08028 Barcelona (Spain); Vidal, M. [Departament de Quimica Analitica, Universitat de Barcelona, Marti i Franques 1-11, 3a Planta, 08028 Barcelona (Spain)], E-mail: miquel.vidal@ub.edu

    2008-02-15

    The pattern of radiostrontium and radiocesium sorption-desorption was examined in 30 Spanish soils by the quantification of the distribution coefficients (K{sub d}) with batch tests, the evaluation of sorption reversibility with a single extraction, the estimation of sorption dynamics by the application of drying-wetting cycles, and the calculation of K{sub d}{sup adjusted} values as an input for risk assessment models. The data obtained overlapped with those found in soils from other climatic areas, suggesting identical interaction mechanisms and allowing the extrapolation of parameterisations and prediction models among different scenarios.

  6. Sorption of actinides onto nanodiamonds

    Energy Technology Data Exchange (ETDEWEB)

    Buchatskaya, Yulia; Romanchuk, Anna; Yakovlev, Ruslan; Kulakova, Inna [Lomonosov Moscow State Univ., Moscow (Russian Federation). Dept. of Chemistry; Shiryaev, Andrei [Russian Academy of Sciences, Moscow (Russian Federation). Frumkin Institute of Physical Chemistry and Electrochemistry; Russian Academy of Sciences, Moscow (Russian Federation). Inst. of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry; Kalmykov, Stepan [Lomonosov Moscow State Univ., Moscow (Russian Federation). Dept. of Chemistry; Russian Academy of Sciences, Moscow (Russian Federation). Frumkin Institute of Physical Chemistry and Electrochemistry; Russian Academy of Sciences, Moscow (Russian Federation). Vernadsky Institute of Geochemistry and Analytical Chemistry

    2015-06-01

    Detonation nanodiamonds (ND) present a significant part of nanocarbons group, which could be produced on commercial scale by detonation of explosives in a closed chamber. Their unique properties of high surface area, low weight and radiation resistance make ND a prospective candidate for applications in sorption processes in radiochemistry. To study the influence of surface chemistry on sorption properties, apristine sample of ND was treated with acids and hydrogen. The surface chemistry of the samples was characterised by infrared spectroscopy, X-ray photoelectron spectroscopy and Boehm titration. The sorption properties of ND were tested fordifferent radionuclides. The sorption capacity of ND was shown to be higher than those of commonly used radionuclide sorbents like activated carbon and compariable to other members of nanocarbon group like graphene oxide and carbon nanotubes. The sorption properties were shown to be influenced by the presence of oxygen-containing groups on the surface of ND. This represents an opportunity to increase the sorption capacity of ND.

  7. Lindane sorption and desorption behaviour on sediment organic matter

    Directory of Open Access Journals (Sweden)

    Tričković Jelena S.

    2013-01-01

    Full Text Available The work is concerned with the sorption and desorption behaviour of lindane on four humic acid fractions (HAs and two humin fractions, sequentially extracted from Ludas lake sediment. All sorption isotherms, fitted to a Freundlich model, were nonlinear. The isotherm linearity increased from 0.757 for the first extracted HA to 0.944 for the ninth HA showing a positive correlation with atomic H/C ratio, while a negative correlation between sorption coefficient and aliphaticity of the isolated HAs was observed. It has been shown that the sorption processes may be strongly influenced by the physical conformation of and accessibility to sediment organic matter (SOM, as demonstrated by high Koc and low n values of humin samples. Despite exhibiting the most nonlinear sorption isotherms, humin samples did not show a pronounced sorption-desorption hysteresis, while the most significant hysteresis was observed for three HA samples. These results support the hypothesis that the aromatic domains in SOM influence strongly the sorption and desorption behaviour of lindane. Our findings may be helpful in understanding the distribution, transport and fate of lindane in soils and sediments.

  8. Uranium sorption by tannin resins

    International Nuclear Information System (INIS)

    Olivares Rieumont, S.; Martinez Luzardo, J.; Torres Hernandez, J.; Lima Cazorla, D. de la Rosa.

    1998-01-01

    The sorption of uranium by immobilised Eucalyptus Saligna Sm. and Lysiloma latisiliqua L tannins was investigated. Immobilization condition were analyzed. These resins resulted suitable adsorbent for the concentration of uranium from aqueous systems. The sorption of uranium is pH dependent. At pH 5.5 maximum in sorption capacity is registered. The presence of appreciable amount of sodium chloride do not have any effect on uranium removal. Carbonate and calcium ions in concentrations similar to these that could be found in sea water and other natural water do not decrease the uranium uptake. Tannin resins can be used several times without an appreciable decay of their sorption capacity

  9. Understanding mechanisms of raveling to extend open graded friction course (OGFC) service life.

    Science.gov (United States)

    2016-03-01

    To understand the mechanisms of raveling in open graded friction course (OGFC) mixtures, this project was divided into experimental measurements and finite element (FE) modeling. For the experimental part, mixtures with good and poor field performanc...

  10. Variation in phenanthrene sorption coefficients with soil organic matter fractionation: the result of structure or conformation?

    Science.gov (United States)

    Bonin, Julia L; Simpson, Myrna J

    2007-01-01

    Sorption of phenanthrene to varying soil types was investigated to better understand sorption processes. Humic acid and humin fractions were isolated from each soil sample, and sorption coefficients were measured by batch equilibration. Samples were characterized by carbon analysis and 13C cross polarization magic angle spinning (CP/ MAS) nuclear magnetic resonance (NMR) spectroscopy. Measured organic carbon-normalized sorption coefficients (Koc) of the fractions were greater in all cases when compared to the soils. The humin fractions exhibited greater Koc values than did source samples, suggesting that fractionation may reorganize organic matter in humin resulting in an increased availability of and/or more favorable sorption domains. Mass balance calculations revealed that the sum of sorption to the fractions is greater than sorption to the whole sample. The greatest difference between sorption values was found to occur with the mineral soils, suggesting that clay minerals influence the physical conformation of soil organic matter (SOM) and availability of sorption domains. The mass balance, sorption data, and a lack of consistent trends between observed Kco values and solid-state 13C NMR data suggest that the physical conformation of SOM and chemical characteristics both play important roles in sorption processes.

  11. Sorption of Pseudomonas putida onto differently structured kaolinite minerals

    Science.gov (United States)

    Vasiliadou, I. A.; Papoulis, D.; Chrysikopoulos, C.; Panagiotaras, D.; Karakosta, E.; Fardis, M.; Papavassiliou, G.

    2010-12-01

    The presence of bio-colloids (e.g. bacteria and viruses) in the subsurface could be attributed to the release of particles from septic tanks, broken sewer lines or from artificial recharge with treated municipal wastewater. Bio-colloid transport in the subsurface is significantly affected by sorption onto the solid matrix. Bio-colloid attachment onto mobile or suspended in the aqueous phase soil particles (e.g. clay or other minerals) also may influence their fate and transport in the subsurface. The present study focuses on the investigation of Pseudomonas (Ps.) putida sorption onto well (KGa-1) and poorly (KGa-2) crystallized kaolinite minerals. Batch experiments were carried out to determine the sorption isotherms of Ps. putida onto both types of kaolinite particles. The sorption process of Ps. putida onto KGa-1 and KGa-2 is adequately described by a Langmuir isotherm. Attenuated Total Reflection Fourier Transform Infrared Spectroscopy as well as Nuclear Magnetic Resonance were employed to study the sorption mechanisms of Ps. putida. Experimental results indicated that KGa-2 presented higher affinity and sorption capacity than KGa-1. It was shown that electrostatic interactions and structural disorders can influence the sorption capacity of clay particles.

  12. Modeling Fission Product Sorption in Graphite Structures

    International Nuclear Information System (INIS)

    Szlufarska, Izabela; Morgan, Dane; Allen, Todd

    2013-01-01

    The goal of this project is to determine changes in adsorption and desorption of fission products to/from nuclear-grade graphite in response to a changing chemical environment. First, the project team will employ principle calculations and thermodynamic analysis to predict stability of fission products on graphite in the presence of structural defects commonly observed in very high-temperature reactor (VHTR) graphites. Desorption rates will be determined as a function of partial pressure of oxygen and iodine, relative humidity, and temperature. They will then carry out experimental characterization to determine the statistical distribution of structural features. This structural information will yield distributions of binding sites to be used as an input for a sorption model. Sorption isotherms calculated under this project will contribute to understanding of the physical bases of the source terms that are used in higher-level codes that model fission product transport and retention in graphite. The project will include the following tasks: Perform structural characterization of the VHTR graphite to determine crystallographic phases, defect structures and their distribution, volume fraction of coke, and amount of sp2 versus sp3 bonding. This information will be used as guidance for ab initio modeling and as input for sorptivity models; Perform ab initio calculations of binding energies to determine stability of fission products on the different sorption sites present in nuclear graphite microstructures. The project will use density functional theory (DFT) methods to calculate binding energies in vacuum and in oxidizing environments. The team will also calculate stability of iodine complexes with fission products on graphite sorption sites; Model graphite sorption isotherms to quantify concentration of fission products in graphite. The binding energies will be combined with a Langmuir isotherm statistical model to predict the sorbed concentration of fission products

  13. Modeling Fission Product Sorption in Graphite Structures

    Energy Technology Data Exchange (ETDEWEB)

    Szlufarska, Izabela [University of Wisconsin, Madison, WI (United States); Morgan, Dane [University of Wisconsin, Madison, WI (United States); Allen, Todd [University of Wisconsin, Madison, WI (United States)

    2013-04-08

    The goal of this project is to determine changes in adsorption and desorption of fission products to/from nuclear-grade graphite in response to a changing chemical environment. First, the project team will employ principle calculations and thermodynamic analysis to predict stability of fission products on graphite in the presence of structural defects commonly observed in very high- temperature reactor (VHTR) graphites. Desorption rates will be determined as a function of partial pressure of oxygen and iodine, relative humidity, and temperature. They will then carry out experimental characterization to determine the statistical distribution of structural features. This structural information will yield distributions of binding sites to be used as an input for a sorption model. Sorption isotherms calculated under this project will contribute to understanding of the physical bases of the source terms that are used in higher-level codes that model fission product transport and retention in graphite. The project will include the following tasks: Perform structural characterization of the VHTR graphite to determine crystallographic phases, defect structures and their distribution, volume fraction of coke, and amount of sp2 versus sp3 bonding. This information will be used as guidance for ab initio modeling and as input for sorptivity models; Perform ab initio calculations of binding energies to determine stability of fission products on the different sorption sites present in nuclear graphite microstructures. The project will use density functional theory (DFT) methods to calculate binding energies in vacuum and in oxidizing environments. The team will also calculate stability of iodine complexes with fission products on graphite sorption sites; Model graphite sorption isotherms to quantify concentration of fission products in graphite. The binding energies will be combined with a Langmuir isotherm statistical model to predict the sorbed concentration of fission

  14. Understanding the mechanism(s) of mosaic trisomy 21 by using DNA polymorphism analysis

    Energy Technology Data Exchange (ETDEWEB)

    Pangalos, C.; Abazis, D.; Avramopoulos, D.; Blouin, J.L.; Antonaraksi, S.E. (Univ. of Patras Medical School (Greece)); Raoul, O.; deBlois, M.C.; Prieur, M. (Cytogenetics Laboratory, Paris (France)); Schinzel, A.A.

    1994-03-01

    In order to investigate the mechanism(s) underlying mosaicism for trisomy 21, the authors genotyped 17 families with mosaic trisomy 21 probands, using 28 PCR-detectable DNA polymorphic markers that map in the pericentromeric region and long arm of chromosome 21. The percentage of cells with trisomy 21 in the probands' blood lymphocytes was 6%-94%. There were two classes of autoradiographic results: In class I, a third allele' of lower intensity was detected in the proband's DNA for at least two chromosome 21 markers. The interpretation of this result was that the proband had inherited three chromosomes 21 after meiotic nondisjunction (NDJ) (trisomy 21 zygote) and subsequently lost one because of mitotic (somatic) error, the lost chromosome 21 being that with the lowest-intensity polymorphic allele. The parental origin and the meiotic stage of NDJ could also be determined. In class II, a third allele' was never detected. In these cases, the mosaicism probably occurred either by a postzygotic, mitotic error in anormal zygote that followed a normal meiosis (class IIA mechanism); by premeiotic, mitotic NDJ yielding an aneusomic zygote after meiosis, and subsequent mitotic loss (class IIB mechanism); or by a meiosis II error with lack of crossover in the preceding meiosis I, followed by mitotic loss after fertilization (class IIC mechanism). Among class II mechanisms, the most likely is mechanism IIA, while IIC is the least likely. There were 10 cases of class I and 7 cases of class II results. Within class I, there were nine cases with maternal meitoic errors (six meiosis I and three meiosis II errors, on the basis of pericentromeric markers) and one with paternal meiosis I error. The postzygotic loss of chromosome 21 was determined in eight maternal class I cases, and it was maternally derived in five cases and paternally derived in three; this suggests that the postzygotic loss of chromosome 21 is probably random. 28 refs., 1 fig., 2 tabs.

  15. Development of a Self-Consistent Model of Plutonium Sorption: Quantification of Sorption Enthalpy and Ligand-Promoted Dissolution

    Energy Technology Data Exchange (ETDEWEB)

    Powell, Brian [Clemson Univ., SC (United States); Kaplan, Daniel I [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Arai, Yuji [Univ. of Illinois, Urbana-Champaign, IL (United States); Becker, Udo [Univ. of Michigan, Ann Arbor, MI (United States); Ewing, Rod [Stanford Univ., CA (United States)

    2016-12-29

    This university lead SBR project is a collaboration lead by Dr. Brian Powell (Clemson University) with co-principal investigators Dan Kaplan (Savannah River National Laboratory), Yuji Arai (presently at the University of Illinois), Udo Becker (U of Michigan) and Rod Ewing (presently at Stanford University). Hypothesis: The underlying hypothesis of this work is that strong interactions of plutonium with mineral surfaces are due to formation of inner sphere complexes with a limited number of high-energy surface sites, which results in sorption hysteresis where Pu(IV) is the predominant sorbed oxidation state. The energetic favorability of the Pu(IV) surface complex is strongly influenced by positive sorption entropies, which are mechanistically driven by displacement of solvating water molecules from the actinide and mineral surface during sorption. Objectives: The overarching objective of this work is to examine Pu(IV) and Pu(V) sorption to pure metal (oxyhydr)oxide minerals and sediments using variable temperature batch sorption, X-ray absorption spectroscopy, electron microscopy, and quantum-mechanical and empirical-potential calculations. The data will be compiled into a self-consistent surface complexation model. The novelty of this effort lies largely in the manner the information from these measurements and calculations will be combined into a model that will be used to evaluate the thermodynamics of plutonium sorption reactions as well as predict sorption of plutonium to sediments from DOE sites using a component additivity approach.

  16. Framework for Understanding the Patterns of Student Difficulties in Quantum Mechanics

    Science.gov (United States)

    Marshman, Emily; Singh, Chandralekha

    2015-01-01

    Compared with introductory physics, relatively little is known about the development of expertise in advanced physics courses, especially in the case of quantum mechanics. Here, we describe a framework for understanding the patterns of student reasoning difficulties and how students develop expertise in quantum mechanics. The framework posits that…

  17. Sorption of aromatic hydrocarbons onto montmorillonite as affected by norfloxacin

    Energy Technology Data Exchange (ETDEWEB)

    Pei, Zhiguo, E-mail: peizg@rcees.ac.cn [State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, PO Box 2871, Beijing 100085 (China); Kong, Jingjing [School of Chemistry and Materials, Fujian Normal University, Fuzhou 350007 (China); Shan, Xiao-quan; Wen, Bei [State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, PO Box 2871, Beijing 100085 (China)

    2012-02-15

    Graphical abstract: {sup 1}H NMR spectrum provided direct evidence for {pi}-{pi} and cation-{pi} complexation between PAHs and Nor{sup +} by ring-current-induced upfield chemical shifts of the amino group and methylene group of Nor{sup +}. Highlights: Black-Right-Pointing-Pointer Nor decreases 1,3-DNB sorption, and increases NAPH, PHEN and PYR sorption on montmorillonite. Black-Right-Pointing-Pointer Nor{sup {+-}} increased PHEN and PYR sorption more pronounced than Nor{sup +} and Nor{sup -}. Black-Right-Pointing-Pointer The corresponding mechanisms were described by FTIR and {sup 1}H NMR. - Abstract: Effect of norfloxacin (Nor) on the sorption of 1,3-dinitrobenzene (1,3-DNB), and PAHs (naphthalene (NAPH), phenanthrene (PHEN) and pyrene (PYR)) to K{sup +}-montmorillonite was studied. Nor suppressed 1,3-DNB sorption due to their competition for the same sorption sites. 1,3-DNB was sorbed on K{sup +}-montmorillonite surface via cation-polar interaction and n-{pi} electron donor-acceptor interaction. Nor also was sorbed on these sites through cation exchange, cation bridging and/or surface complexation. Nor increased three PAHs sorption on montmorillonite and the enhanced magnitude was positively correlated with the {pi}-donor strength of three PAHs. The enhanced sorption of PAHs by Nor was primarily attributed to {pi}-{pi} interaction between {pi}-electron-depleted quinoline ring of Nor and {pi}-electron-rich PAHs. Compared with cation (Nor{sup +}) and anion (Nor{sup -}), zwitterion (Nor{sup {+-}}) of Nor increased PHEN and PYR sorption more pronounced due to additional cation-{pi} interaction between the sorbed Nor{sup {+-}} and PAHs. {sup 1}H NMR spectrum provided direct evidence for {pi}-{pi} and cation-{pi} complexation between PAHs and Nor{sup +} in solution by ring-current-induced upfield chemical shifts of amino group and methylene group of Nor{sup +}.

  18. Sorption-cooled continuous miniature dilution refrigeration for astrophysical applications

    Science.gov (United States)

    May, Andrew J.; Calisse, Paolo G.; Coppi, Gabriele; Haynes, Vic; Martinis, Lorenzo; McCulloch, Mark A.; Melhuish, Simon J.; Piccirillo, Lucio

    2016-07-01

    A progress report is provided on the development of a tiltable continuous miniature dilution refrigerator and associated 3He/4He sorption coolers. These systems are currently being developed to provide sub-Kelvin cooling of the bolometer arrays for several ground- and balloon-based experiments which aim to measure the polarization of the Cosmic Microwave Background (QUBIC, LSPE and POLARBEAR-2). The novel tiltable miniaturised system benefits from a lack of external circulation pumps and a mechanically simple design. The condenser of the twin-pumped recirculating diluter is cooled continuously by two 3He/4He sorption coolers. The sorption pumps are operated by convective heat switches. The dilution unit features a thermally separated mixing chamber, still and step heat exchangers. The designs and analyses of both the sorption coolers and the diluter are reported; both systems have been manufactured and are presently under test.

  19. Sorption of a nonionic surfactant Tween 80 by minerals and soils

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Soyoung, E-mail: soyoung@pusan.ac.kr; Jeong, Hoon Young, E-mail: hjeong@pusan.ac.kr

    2015-03-02

    Highlights: • Tween 80 sorption varies significantly among soil minerals. • Sorption mechanisms and atomic compositions explain to mineral-specific sorption. • Clay minerals and SOM in soils are the key contributors to Tween 80 sorption. • Hysteresis suggests the potential difficulty in removing residual surfactants. - Abstract: Batch experiments were conducted to evaluate Tween 80 sorption by oxides, aluminosilicates, and soils. For oxides, the sorption by silica and alumina follow linear isotherms, and that by hematite follows a Langmuir isotherm. Considering isotherm type and surface coverage, Tween 80 may partition into the silica/alumina–water interface, whereas it may bind to hematite surface sites. Among aluminosilicates, montmorillonite shows the greatest sorption due to the absorption of Tween 80 into interlayers. For other aluminosilicates, it sorbs to surfaces, with the sorption increasing as plagioclase < vermiculite < kaolinite. This results from the relative reactivity among surface sites: ≡NaOH, ≡CaOH << ≡SiOH < ≡AlOH. Experiments using dry- and wet-sieved soils reveal that fine-grained clay minerals, difficult to separate by dry-sieving, contribute significantly to Tween 80 sorption. The greater sorption by untreated soils than H{sub 2}O{sub 2}-treated soils indicates that soil organic matter is a vital sorbent. The sorption hysteresis, contributed to by clay minerals and soil organic matter, is characterized by the greater sorption during the desorption than the sorption stages. This suggests the potential difficulty in removing surfactants from soils. Also, sorption of surfactants can adversely affect surfactant-enhanced remediation by decreasing the aquifer permeability and the availability of surfactants for micellar solubilization.

  20. New Drugs for Anemia Treatment Based on a New Understanding of the Mechanisms of Stress Erythropoiesis

    Science.gov (United States)

    2015-11-01

    Award Number: W81XWH-12-1-0449 TITLE: New Drugs for Anemia Treatment Based on a New Understanding of the Mechanisms of Stress Erythropoiesis...COVERED 1Sep2012 - 31Aug2015 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER New Drugs for Anemia Treatment Based on a New Understanding of the...cell formation in "Nan" (neonatal anemia ) mice, raising the level of red cells to almost normal. It also causes an increase in the numbers of splenic

  1. Sorption of Hydrophobic Organic Contaminants to Glacially Deposited Sediments of Central Illinois

    Science.gov (United States)

    Jeong, S.; Werth, C. J.; Wander, M. M.

    2003-04-01

    The nature and distribution of solid phase carbonaceous material strongly affect the sorption of hydrophobic organic contaminants (HOCs) to soils and sediments. High surface area carbonaceous materials (HSCM, e.g. charcoal, soot) and mature organic matter facies (e.g. humin, kerogen) exhibit high sorption capacities, nonlinear sorption isotherms, and sorption-desorption hysteresis. The accurate characterization of carbonaceous material type and distribution are crucial for prediction of the fate of HOCs in soils and sediments. The objectives of this work are to determine the type(s) of carbonaceous material that controls adsorption in central Illinois groundwater sediments, and to determine how oxidative weathering affects sorption capacity. Sediment samples were collected from oxidized and reduced zones of the Chanute Air Force Base in Rantoul (Illinois, USA) and treated to obtain fractions of the sediment samples enriched in different types of carbonaceous materials (e.g., humic acid, kerogen, black carbon). The different fractions were then evaluated for their sorption capacity and mechanism to sorb trichloroethylene (TCE), a common groundwater pollutant. Isotherm results indicate that kerogen primarily controls the sorption of TCE. Isotherm results also show that the Koc (sorption distribution coefficient normalized by the fraction of organic carbon) for the reduced sediment is larger than that for the oxidized sediment. Current experiments are focused on the question of whether kerogen oxidation or kerogen protection by mineral precipitates reduces the sorption capacity in the oxidized sediments, and on whether kerogen controls sorption in groundwater sediments not affected by glaciation.

  2. Sorption behavior of uranium(VI) on a biotite mineral

    International Nuclear Information System (INIS)

    Idemitsu, K.; Obata, K.; Furuya, H.; Inagaki, Y.

    1995-01-01

    Biotite has the most important role for the sorption of radionuclides in granitic rocks. Experiments on the sorption of uranium(VI) on biotite were conducted to understand the fundamental controls on uranium sorption on biotite mineral, including the effects of pH and uranium concentration in solution. Biotite powder (mesh 32--60) were washed with 1N HCl for a week and were rinsed twice with deionized water for a week. This HCl treatment was necessary to avoid the effects by other minerals. The agreement between surface adsorption coefficient, Ka, of both biotites with and without HCl treatment was within one order of magnitude. The peak Ka value was in the range of 0.1 to 0.01 cm 3 /cm 2 around pH 6. A comparison of aqueous uranium speciations and sorption results indicates that neutral uranyl hydroxide could be an important species sorbed on the biotite. Sequential desorption experiments with KCl and HCl solutions were also carried out after sorption experiments to investigate sorption forms of uranium. Approximately 20% of uranium in solution were sorbed on the biotite as an exchangeable ion. The fraction of exchangeable uranium had a little dependence on pH. The other uranium could not be extracted even by 6N HCl solution. It is possible that most of the uranium could be precipitated as U(IV) via Fe(II) reduction on the biotite surface

  3. Sorption of Groundwater Dissolved Organic Carbon onto Minerals

    Science.gov (United States)

    Rutlidge, H.; Oudone, P.; McDonough, L.; Meredith, K.; Andersen, M. S.; O'Carrol, D. M.; Baker, A.

    2017-12-01

    Our understanding of groundwater organic matter (OM) as a carbon source or sink in the environmental carbon cycle is limited. The dynamics of groundwater OM is mainly governed by biological processing and its sorption to minerals. In saturated groundwaters, dissolved OM (DOM) represents one part of the groundwater organic carbon pool. Without consideration of the DOM sorption, it is not possible to quantify governing groundwater OM processes. This research explores the rate and extent of DOM sorption on different minerals. Groundwater DOM samples, and International Humic Substances Society (IHSS) standard solutions, were analysed. Each was mixed with a range of masses of iron coated quartz, clean quartz, and calcium carbonate, and shaken for 2 hours to reach equilibrium before being filtered through 0.2 μm for total dissolved organic carbon (DOC) and composition analysis by size-exclusion chromatography-organic carbon detection (LC-OCD). Sorption isotherms were constructed and groundwater DOM sorption were compared to the sorption of IHSS standards. Initial results suggest that for the IHSS standards, the operationally-defined humic substances fraction had the strongest sorption compared to the other LC-OCD fractions and total DOC. Some samples exhibited a small increase in the low molecular weight neutral (LMW-N) aqueous concentration with increasing humic substances sorption. This gradual increase observed could be the result of humic substances desorbing or their breakdown during the experiment. Further results comparing these IHSS standards with groundwater samples will be presented. In conjunction with complementary studies, these results can help provide more accurate prediction of whether groundwater OM is a carbon source or sink, which will enable the management of the groundwater resources as part of the carbon economy.

  4. Understanding Creep Mechanisms in Graphite with Experiments, Multiscale Simulations, and Modeling

    Energy Technology Data Exchange (ETDEWEB)

    Eapen, Jacob [North Carolina State Univ., Raleigh, NC (United States); Murty, Korukonda [North Carolina State Univ., Raleigh, NC (United States); Burchell, Timothy [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2014-06-02

    Disordering mechanisms in graphite have a long history with conflicting viewpoints. Using Raman and x-ray photon spectroscopy, electron microscopy, x-ray diffraction experiments and atomistic modeling and simulations, the current project has developed a fundamental understanding of early-to-late state radiation damage mechanisms in nuclear reactor grade graphite (NBG-18 and PCEA). We show that the topological defects in graphite play an important role under neutron and ion irradiation.

  5. The implications of water extractable organic matter (WEOM) on the sorption of typical parent, alkyl and N/O/S-containing polycyclic aromatic hydrocarbons (PAHs) by microplastics.

    Science.gov (United States)

    Li, Ruilong; Tan, Huadong; Zhang, Linlin; Wang, Shaopeng; Wang, Yinghui; Yu, Kefu

    2018-03-15

    Microplastics sorption of persistent organic pollutants (POPs) was the core processes that cause negative effects to biota, and their influencing factors and related mechanisms are poorly understood. In this study, we explored the impacts of water extractable organic matter (WEOM), an important source of endogenous dissolved organic matter in mangrove sediment, on the sorption coefficients of typical parent, alkyl and N/O/S-containing polycyclic aromatic hydrocarbons (PAHs) by microplastics. The presence of L-WEOM (D) impeded the PAHs sorption as the coefficients (K f ) decreased to 10.17 (μg/kg)/(μg/L) n and to 8.39 (μg/kg)/(μg/L) n for fluorene (Flu) and 1-methyl-fluorene (1-M-Flu), respectively. The K f exhibited good linear relationships with the aliphaticity of L-WEOM (p  0.05). Under the presences of L-WEOM (D), (S) and (K), the lone pair electrons of N/O/S-containing PAHs was the dominant factor contributing to the obvious difference of the K f values from the other groups. Moreover, the largest impact of L-WEOM (D) on the Flu sorption was in the case of PVC microplastics, while almost no effect was in the case of PS microplastics. The findings of our work may be helpful in improving our understanding of the role of WEOM on the sorption of PAHs to microplastics in the field mangrove sediment. Copyright © 2018 Elsevier Inc. All rights reserved.

  6. Sorption of aromatic organic pollutants to grasses from water

    Science.gov (United States)

    Barbour, J.P.; Smith, J.A.; Chiou, C.T.

    2005-01-01

    The influence of plant lipids on the equilibrium sorption of three aromatic solutes from water was studied. The plant-water sorption isotherms of benzene, 1,2-dichlorobenzene, and phenanthrene were measured over a large range of solute concentrations using sealed vessels containing water, dried plant material, and solute. The plant materials studied include the shoots of annual rye, tall fescue, red fescue, and spinach as well as the roots of annual rye. Seven out of eight sorption isotherms were linear with no evidence of competitive effects between the solutes. For a given plant type, the sorption coefficient increased with decreasing solute water solubility. For a given solute, sorption increased with increasing plant lipid content. The estimated lipid-water partition coefficients of individual solutes were found to be significantly greater than the corresponding octanol-water partition coefficients. This indicates that plant lipids are a more effective partition solvent than octanol for the studied aromatic compounds. As expected, the solute lipid-water partition coefficients were log-linearly related to the respective water solubilities. For the compounds studied, partitioning into the lipids is believed to be the primary sorption mechanism. ?? 2005 American Chemical Society.

  7. Sixth-Grade Students' Progress in Understanding the Mechanisms of Global Climate Change

    Science.gov (United States)

    Visintainer, Tammie; Linn, Marcia

    2015-04-01

    Developing solutions for complex issues such as global climate change requires an understanding of the mechanisms involved. This study reports on the impact of a technology-enhanced unit designed to improve understanding of global climate change, its mechanisms, and their relationship to everyday energy use. Global Climate Change, implemented in the Web-based Inquiry Science Environment (WISE), engages sixth-grade students in conducting virtual investigations using NetLogo models to foster an understanding of core mechanisms including the greenhouse effect. Students then test how the greenhouse effect is enhanced by everyday energy use. This study draws on three data sources: (1) pre- and post-unit interviews, (2) analysis of embedded assessments following virtual investigations, and (3) contrasting cases of two students (normative vs. non-normative understanding of the greenhouse effect). Results show the value of using virtual investigations for teaching the mechanisms associated with global climate change. Interviews document that students hold a wide range of ideas about the mechanisms driving global climate change. Investigations with models help students use evidence-based reasoning to distinguish their ideas. Results show that understanding the greenhouse effect offers a foundation for building connections between everyday energy use and increases in global temperature. An impediment to establishing coherent understanding was the persistence of an alternative conception about ozone as an explanation for climate change. These findings illustrate the need for regular revision of curriculum based on classroom trials. We discuss key design features of models and instructional revisions that can transform the teaching and learning of global climate change.

  8. Sorption and Release of Organics by Primary, Anaerobic, and Aerobic Activated Sludge Mixed with Raw Municipal Wastewater

    Science.gov (United States)

    Modin, Oskar; Saheb Alam, Soroush; Persson, Frank; Wilén, Britt-Marie

    2015-01-01

    New activated sludge processes that utilize sorption as a major mechanism for organics removal are being developed to maximize energy recovery from wastewater organics, or as enhanced primary treatment technologies. To model and optimize sorption-based activated sludge processes, further knowledge about sorption of organics onto sludge is needed. This study compared primary-, anaerobic-, and aerobic activated sludge as sorbents, determined sorption capacity and kinetics, and investigated some characteristics of the organics being sorbed. Batch sorption assays were carried out without aeration at a mixing velocity of 200 rpm. Only aerobic activated sludge showed net sorption of organics. Sorption of dissolved organics occurred by a near-instantaneous sorption event followed by a slower process that obeyed 1st order kinetics. Sorption of particulates also followed 1st order kinetics but there was no instantaneous sorption event; instead there was a release of particles upon mixing. The 5-min sorption capacity of activated sludge was 6.5±10.8 mg total organic carbon (TOC) per g volatile suspend solids (VSS) for particulate organics and 5.0±4.7 mgTOC/gVSS for dissolved organics. The observed instantaneous sorption appeared to be mainly due to organics larger than 20 kDa in size being sorbed, although molecules with a size of about 200 Da with strong UV absorbance at 215–230 nm were also rapidly removed. PMID:25768429

  9. Sorption of chromium(VI) and chromium(III) on aluminium hydroxide

    International Nuclear Information System (INIS)

    Music, S.

    1986-01-01

    Factors that influence the sorption of Cr(VI) and Cr(III) on aluminium hydroxide were investigated. The sorption of chromates decreases as the pH of the suspension increases. The mechanism of CrOsub(4)sup(2-) sorption was interpreted in terms of reactions between chromates and -OH and/or Hsub(2)O groups at the hydroxide/liquid interface. It was shown that chromates are more tightly sorbed on aluminium hydroxide compared to other anions, e.g. chlorides. On the other hand, specifically absorbed anions, such as molybdates, compete strongly with chromates for the sorption sites. The sorption of chromium(III) increases with the pH of the suspension. Also, the sorption of chromium(III) is suppressed in the presence of citrate ions. The best conditions for the fixation of Cr(VI) and Cr(III) by aluminium hydroxide are presented. (author)

  10. Sorption of microamounts of Cesup(3+), Pmsup(3+), Gdsup(3+) and Ybsup(3+) on aluminium hydroxide

    International Nuclear Information System (INIS)

    Music, S.

    1986-01-01

    The sorption of microamounts of trivalent lanthanides (Lnsup(3+)) on freshly precipitated Al(OH)sub(3) was measured in dependence on pH and on the time of sorption. The influence of organic complexing ligands and inorganic electrolytes on the sorption process was also investigated. The mechanism of sorption is discussed. Freshly precipitated Al(OH)sub(3) could be used for the preconcentration of microamounts of trivalent lanthanides. However, the preconcentration was not quantitative in the presence of high concentrations of complexing ligands (citrate and similar) which formed strong complexes with Lnsup(3+) ions. (author)

  11. Sorption of chromium(III) and chromium(VI) on lead sulfide

    International Nuclear Information System (INIS)

    Music, S.

    1985-01-01

    The sorption of chromium(III) and chromium(VI) on lead sulfide was investigated in dependence on pH, time of sorption, and on the concnetrations of sorbate and sorbent. The mechanisms of the sorption of Crsup(3+) and CrOsub(4)sup(2-) traces on lead sulfide are discussed; a difference between CrOsub(4)sup(2-) sorption on PbS and α-Fesub(2)Osub(3) was found. Sulfates and molybdates affect the removal of chromates from aqueous solutions. Lead sulfide carrier prepared in this work was also used for the preconcentration of chromium(III) and chromium(VI) from tap water. (author)

  12. Effects of Representation Sequences and Spatial Ability on Students' Scientific Understandings about the Mechanism of Breathing

    Science.gov (United States)

    Wu, Hsin-Kai; Lin, Yu-Fen; Hsu, Ying-Shao

    2013-01-01

    The purpose of this study was to investigate the effects of representation sequences and spatial ability on students' scientific understandings about the mechanism of breathing in human beings. 130 seventh graders were assigned to two groups with different sequential combinations of static and dynamic representations: SD group (i.e., viewing…

  13. Enhanced understanding of the relationship between chemical modification and mechanical properties of wood

    Science.gov (United States)

    Charles R. Frihart; Daniel J. Yelle; John Ralph; Robert J. Moon; Donald S. Stone; Joseph E. Jakes

    2008-01-01

    Chemical additions to wood often change its bulk properties, which can be determined using conventional macroscopic mechanical tests. However, the controlling interactions between chemicals and wood take place at and below the scale of individual cells and cell walls. To better understand the effects of chemical additions to wood, we have adapted and extended two...

  14. Sorption of trivalent lanthanides and actinides onto montmorillonite: Macroscopic, thermodynamic and structural evidence for ternary hydroxo and carbonato surface complexes on multiple sorption sites.

    Science.gov (United States)

    Fernandes, M Marques; Scheinost, A C; Baeyens, B

    2016-08-01

    The credibility of long-term safety assessments of radioactive waste repositories may be greatly enhanced by a molecular level understanding of the sorption processes onto individual minerals present in the near- and far-fields. In this study we couple macroscopic sorption experiments to surface complexation modelling and spectroscopic investigations, including extended X-ray absorption fine structure (EXAFS) and time-resolved laser fluorescence spectroscopies (TRLFS), to elucidate the uptake mechanism of trivalent lanthanides and actinides (Ln/An(III)) by montmorillonite in the absence and presence of dissolved carbonate. Based on the experimental sorption isotherms for the carbonate-free system, the previously developed 2 site protolysis non electrostatic surface complexation and cation exchange (2SPNE SC/CE) model needed to be complemented with an additional surface complexation reaction onto weak sites. The fitting of sorption isotherms in the presence of carbonate required refinement of the previously published model by reducing the strong site capacity and by adding the formation of Ln/An(III)-carbonato complexes both on strong and weak sites. EXAFS spectra of selected Am samples and TRLFS spectra of selected Cm samples corroborate the model assumptions by showing the existence of different surface complexation sites and evidencing the formation of Ln/An(III) carbonate surface complexes. In the absence of carbonate and at low loadings, Ln/An(III) form strong inner-sphere complexes through binding to three Al(O,OH)6 octahedra, most likely by occupying vacant sites in the octahedral layers of montmorillonite, which are exposed on {010} and {110} edge faces. At higher loadings, Ln/An(III) binds to only one Al octahedron, forming a weaker, edge-sharing surface complex. In the presence of carbonate, we identified a ternary mono- or dicarbonato Ln/An(III) complex binding directly to one Al(O,OH)6 octahedron, revealing that type-A ternary complexes form with the one

  15. Sorption of polar and nonpolar aromatic compounds to four surface soils of eastern China

    International Nuclear Information System (INIS)

    Liu Ping; Zhu Dongqiang; Zhang Hua; Shi Xin; Sun Huiyu; Dang Fei

    2008-01-01

    Improved predictions on the fate of organic pollutants in surface environments require a better understanding of the underlying sorption mechanisms that control their uptake by soils. In this study, we monitored sorption of nine aromatic compounds with varying physicochemical properties (hydrophobicity, electron-donor/acceptor ability and polarity), including two polycyclic aromatic hydrocarbons, two chlorobenzenes, two nitroaromatic compounds, dichlobenil, carbaryl and 2,4-dichlorophenol in aqueous suspension of four surface soils of eastern China. The tested soils were characterized with respect to organic carbon (OC) content, black carbon content, mineralogy, morphology and size fraction to assess the role of the diverse soil characteristics in sorption. The results of this study show that not only the solute hydrophobicity and the OC content of soil are important to the retention of organic pollutants, but also the solute molecular structure and the soil nature. - In addition to the hydrophobicity of solute and the organic carbon content of soil, the solute molecular structure and the soil nature also determine the retention of organic pollutants by soils

  16. Sorption of tylosin and sulfamethazine on solid humic acid.

    Science.gov (United States)

    Guo, Xuetao; Tu, Bei; Ge, Jianhua; Yang, Chen; Song, Xiaomei; Dang, Zhi

    2016-05-01

    Tylosin (TYL) and sulfamethazine (SMT) are ionizable and polar antimicrobial compounds, which have seeped into the environment in substantial amounts via fertilizing land with manure or sewage. Sorption of TYL and SMT onto humic acid (HA) may affect their environmental fate. In this study, the sorption of TYL and SMT on HA at different conditions (pH, ionic strength) was investigated. All sorption isotherms fitted well to the Henry and Freundlich models and they were highly nonlinear with values of n between 0.5 and 0.8, which suggested that the HA had high heterogeneity. The sorption of TYL and SMT on HA decreased with increasing pH (2.0-7.5), implying that the primary sorption mechanism could be due to cation exchange interactions between TYL(+)/SMT(+) species and the functional groups of HA. Increasing ionic strength resulted in a considerable reduction in the Kd values of TYL and SMT, hinting that interactions between H bonds and π-π EDA might be an important factor in the sorption of TYL and SMT on HA. Results of Fourier transform infrared (FT-IR) and (13)C-nuclear magnetic resonance (NMR) analysis further demonstrated that carboxyl groups and O-alkyl structures in the HA could interact with TYL and SMT via ionic interactions and H bonds, respectively. Overall, this work gives new insights into the mechanisms of sorption of TYL and SMT on HA and hence aids us in assessing the environmental risk of TYL and SMT under diverse conditions. Copyright © 2015. Published by Elsevier B.V.

  17. Influence of organic fertilization on the sorption mechanisms of {sup 241} Am in tropical soils; A influencia da adubacao organica nos mecanismos de sorcao do {sup 241} Am em solos tropicais

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, Tatiane Rocha

    2009-07-01

    In this work the mechanisms involved in the sorption of {sup 241}Am were investigated depending on the physicochemical properties of some Brazilian soils and on alterations promoted by organic amendment. This experimental study was conducted in a controlled area, where pots containing different kinds of soils (histisol, ferralsol and nitisol), with different organic amendment doses (without amendment; 2 kg m{sup -2} and 4 kg m{sup -2}) were artificially contaminated by radioactive solution water, which contained {sup 241}Am. Migration studies, distribution (or partition) coefficient (KJ), bioavailability and organic matter were carried out in these soils, with ar without organic amendment. In order to evaluate the effective bioavailability of radionuclides, radish (Raphanus sativus L.) was cultivated in these pots, and later the concentration of {sup 241}Am in radish's roots was measured. The main results show that {sup 241}Am tends to be strongly attached to organic matter and that organic amendment in tropical soils minimizes the radionuclide studied desorption. Also, distribution (or partition) coefficient values for {sup 241}Am were generated and these values are smaller than those ones determined for soils from temperate zones. Physical and chemical fractioning of organic matter were carried out. (author)

  18. Unit Mechanisms of Fission Gas Release: Current Understanding and Future Needs

    Energy Technology Data Exchange (ETDEWEB)

    Tonks, Michael; Andersson , David; Devanathan, Ram; Dubourg, Roland; El-Azab, Anter A.; Freyss, Michel; Iglesias, Fernando; Kulacsy, Katalin; Pastore, Giovanni; Phillpot, Simon R.; Welland, Michael

    2018-03-16

    Gaseous fission product transport and release has a large impact on fuel performance, degrading fuel properties and, once the gas is released into the gap between the fuel and cladding, lowering gap thermal conductivity and increasing gap pressure. While gaseous fission product behavior has been investigated with bulk reactor experiments and simplified analytical models, recent improvements in experimental and modeling approaches at the atomistic and mesoscales are being applied to provide unprecedented understanding of the unit mechanisms that define the fission product behavior. In this article, existing research on the basic mechanisms behind the various stages of fission gas release during normal reactor operation are summarized and critical areas where experimental and simulation work is needed are identified. This basic understanding of the fission gas behavior mechanisms has the potential to revolutionize our ability to predict fission product behavior during reactor operation and to design fuels that have improved fission product retention. In addition, this work can serve as a model on how a coupled experimental and modeling approach can be applied to understand the unit mechanisms behind other critical behaviors in reactor materials.

  19. How LeuT shapes our understanding of the mechanisms of sodium-coupled neurotransmitter transporters.

    Science.gov (United States)

    Penmatsa, Aravind; Gouaux, Eric

    2014-03-01

    Neurotransmitter transporters are ion-coupled symporters that drive the uptake of neurotransmitters from neural synapses. In the past decade, the structure of a bacterial amino acid transporter, leucine transporter (LeuT), has given valuable insights into the understanding of architecture and mechanism of mammalian neurotransmitter transporters. Different conformations of LeuT, including a substrate-free state, inward-open state, and competitive and non-competitive inhibitor-bound states, have revealed a mechanistic framework for the transport and transport inhibition of neurotransmitters. The current review integrates our understanding of the mechanistic and pharmacological properties of eukaryotic neurotransmitter transporters obtained through structural snapshots of LeuT.

  20. Understanding the growth mechanism of carbon nanotubes via the ``cluster volume to surface area" model

    Science.gov (United States)

    Mandati, Sreekanth; Kunstmann, Jens; Boerrnert, Felix; Schoenfelder, Ronny; Ruemmeli, Mark; Kar, Kamal K.; Cuniberti, Gianaurelio

    2010-03-01

    The influence of mixed catalysts for the high yield production of carbon nanotubes (CNTs) has been studied systematically. Based on extensive experimental data a ``Catalyst Volume to Surface Area'' (CVSA) model was developed to understand the influence of the process parameters on the yield and CNT diameter distribution [1]. In our study, we present a refined version of the CVSA model developed by combining experiments and simulations. We discuss our current understanding of the growth mechanism and how the model might be used to increase CNT yields by using mixed catalysts.[4pt] [1] S. Tetali et al., ACS Nano (2009), DOI: 10.1021/nn9012548.

  1. Proteomic approaches to understanding the role of the cytoskeleton in host-defense mechanisms

    Science.gov (United States)

    Radulovic, Marko; Godovac-Zimmermann, Jasminka

    2014-01-01

    The cytoskeleton is a cellular scaffolding system whose functions include maintenance of cellular shape, enabling cellular migration, division, intracellular transport, signaling and membrane organization. In addition, in immune cells, the cytoskeleton is essential for phagocytosis. Following the advances in proteomics technology over the past two decades, cytoskeleton proteome analysis in resting and activated immune cells has emerged as a possible powerful approach to expand our understanding of cytoskeletal composition and function. However, so far there have only been a handful of studies of the cytoskeleton proteome in immune cells. This article considers promising proteomics strategies that could augment our understanding of the role of the cytoskeleton in host-defense mechanisms. PMID:21329431

  2. Understanding the Mechanisms of Radiation Belt Dropouts Observed by Van Allen Probes

    Science.gov (United States)

    Xiang, Zheng; Tu, Weichao; Li, Xinlin; Ni, Binbin; Morley, S. K.; Baker, D. N.

    2017-10-01

    To achieve a better understanding of the dominant loss mechanisms for the rapid dropouts of radiation belt electrons, three distinct radiation belt dropout events observed by Van Allen Probes are comprehensively investigated. For each event, observations of the pitch angle distribution of electron fluxes and electromagnetic ion cyclotron (EMIC) waves are analyzed to determine the effects of atmospheric precipitation loss due to pitch angle scattering induced by EMIC waves. Last closed drift shells (LCDS) and magnetopause standoff position are obtained to evaluate the effects of magnetopause shadowing loss. Evolution of electron phase space density (PSD) versus L* profiles and the μ and K (first and second adiabatic invariants) dependence of the electron PSD drops are calculated to further analyze the dominant loss mechanisms at different L*. Our findings suggest that these radiation belt dropouts can be classified into distinct classes in terms of dominant loss mechanisms: magnetopause shadowing dominant, EMIC wave scattering dominant, and combination of both mechanisms. Different from previous understanding, our results show that magnetopause shadowing can deplete electrons at L* 4. Compared to the magnetopause standoff position, it is more reliable to use LCDS to evaluate the impact of magnetopause shadowing. The evolution of electron PSD versus L* profile and the μ, K dependence of electron PSD drops can provide critical and credible clues regarding the mechanisms responsible for electron losses at different L* over the outer radiation belt.

  3. Comparative evaluation for the sorption capacity of four carbonaceous sorbents to phenol

    Directory of Open Access Journals (Sweden)

    Ding Feng Jin

    2016-10-01

    Full Text Available Sorption kinetics and isotherms of phenol by four carbonaceous sorbents (activated carbon (AC, mesoporous carbon (MPC, bamboo biochar (BBC and oak wood biochar (OBC were compared in this study. MPC has the fastest sorption rate and initial sorption potential, which were indicated by sorption rate constants and initial sorption rate “h” in a pseudo-second-order kinetic model. The ordered and straight pore structure of MPC facilitated the accessibility of phenol. The AC showed the greatest sorption capacity towards phenol with maximum sorption of 123 mg/g as calculated by the Langmuir model. High surface area, complexity of pore structure, and the strong binding force of the π–π electron-donor-acceptor interaction between phenol molecules and AC were the main mechanisms. The BBC and OBC had much slower sorption and lower sorption capacity (33.04 and 29.86 mg/g, respectively, compared to MPC (73.00 mg/g and AC, indicating an ineffective potential for phenol removal from water.

  4. Unified understanding of folding and binding mechanisms of globular and intrinsically disordered proteins.

    Science.gov (United States)

    Arai, Munehito

    2018-01-06

    Extensive experimental and theoretical studies have advanced our understanding of the mechanisms of folding and binding of globular proteins, and coupled folding and binding of intrinsically disordered proteins (IDPs). The forces responsible for conformational changes and binding are common in both proteins; however, these mechanisms have been separately discussed. Here, we attempt to integrate the mechanisms of coupled folding and binding of IDPs, folding of small and multi-subdomain proteins, folding of multimeric proteins, and ligand binding of globular proteins in terms of conformational selection and induced-fit mechanisms as well as the nucleation-condensation mechanism that is intermediate between them. Accumulating evidence has shown that both the rate of conformational change and apparent rate of binding between interacting elements can determine reaction mechanisms. Coupled folding and binding of IDPs occurs mainly by induced-fit because of the slow folding in the free form, while ligand binding of globular proteins occurs mainly by conformational selection because of rapid conformational change. Protein folding can be regarded as the binding of intramolecular segments accompanied by secondary structure formation. Multi-subdomain proteins fold mainly by the induced-fit (hydrophobic collapse) mechanism, as the connection of interacting segments enhances the binding (compaction) rate. Fewer hydrophobic residues in small proteins reduce the intramolecular binding rate, resulting in the nucleation-condensation mechanism. Thus, the folding and binding of globular proteins and IDPs obey the same general principle, suggesting that the coarse-grained, statistical mechanical model of protein folding is promising for a unified theoretical description of all mechanisms.

  5. Material properties of biofilms – key methods for understanding permeability and mechanics

    Science.gov (United States)

    Billings, Nicole; Birjiniuk, Alona; Samad, Tahoura S.; Doyle, Patrick S.; Ribbeck, Katharina

    2015-01-01

    Microorganisms can form biofilms, which are multicellular communities surrounded by a hydrated extracellular matrix of polymers. Central properties of the biofilm are governed by this extracellular matrix, which provides mechanical stability to the three-dimensional biofilm structure, regulates the ability of the biofilm to adhere to surfaces, and determines the ability of the biofilm to adsorb gasses, solutes, and foreign cells. Despite their critical relevance for understanding and eliminating of biofilms, the materials properties of the extracellular matrix are understudied. Here, we offer the reader a guide to current technologies that can be utilized to specifically assess the permeability and mechanical properties of the biofilm matrix and its interacting components. In particular, we highlight technological advances in instrumentation and interactions between multiple disciplines that have broadened the spectrum of methods available to conduct these studies. We review pioneering work that furthers our understanding of the material properties of biofilms. PMID:25719969

  6. Understanding the mechanism of catalytic fast pyrolysis by unveiling reactive intermediates in heterogeneous catalysis

    Science.gov (United States)

    Hemberger, Patrick; Custodis, Victoria B. F.; Bodi, Andras; Gerber, Thomas; van Bokhoven, Jeroen A.

    2017-06-01

    Catalytic fast pyrolysis is a promising way to convert lignin into fine chemicals and fuels, but current approaches lack selectivity and yield unsatisfactory conversion. Understanding the pyrolysis reaction mechanism at the molecular level may help to make this sustainable process more economic. Reactive intermediates are responsible for product branching and hold the key to unveiling these mechanisms, but are notoriously difficult to detect isomer-selectively. Here, we investigate the catalytic pyrolysis of guaiacol, a lignin model compound, using photoelectron photoion coincidence spectroscopy with synchrotron radiation, which allows for isomer-selective detection of reactive intermediates. In combination with ambient pressure pyrolysis, we identify fulvenone as the central reactive intermediate, generated by catalytic demethylation to catechol and subsequent dehydration. The fulvenone ketene is responsible for the phenol formation. This technique may open unique opportunities for isomer-resolved probing in catalysis, and holds the potential for achieving a mechanistic understanding of complex, real-life catalytic processes.

  7. Understanding the mechanism of catalytic fast pyrolysis by unveiling reactive intermediates in heterogeneous catalysis

    Science.gov (United States)

    Hemberger, Patrick; Custodis, Victoria B. F.; Bodi, Andras; Gerber, Thomas; van Bokhoven, Jeroen A.

    2017-01-01

    Catalytic fast pyrolysis is a promising way to convert lignin into fine chemicals and fuels, but current approaches lack selectivity and yield unsatisfactory conversion. Understanding the pyrolysis reaction mechanism at the molecular level may help to make this sustainable process more economic. Reactive intermediates are responsible for product branching and hold the key to unveiling these mechanisms, but are notoriously difficult to detect isomer-selectively. Here, we investigate the catalytic pyrolysis of guaiacol, a lignin model compound, using photoelectron photoion coincidence spectroscopy with synchrotron radiation, which allows for isomer-selective detection of reactive intermediates. In combination with ambient pressure pyrolysis, we identify fulvenone as the central reactive intermediate, generated by catalytic demethylation to catechol and subsequent dehydration. The fulvenone ketene is responsible for the phenol formation. This technique may open unique opportunities for isomer-resolved probing in catalysis, and holds the potential for achieving a mechanistic understanding of complex, real-life catalytic processes. PMID:28660882

  8. Improving student understanding of addition of angular momentum in quantum mechanics

    Directory of Open Access Journals (Sweden)

    Guangtian Zhu

    2013-01-01

    Full Text Available We describe the difficulties advanced undergraduate and graduate students have with concepts related to addition of angular momentum in quantum mechanics. We also describe the development and implementation of a research-based learning tool, Quantum Interactive Learning Tutorial (QuILT, to reduce these difficulties. The preliminary evaluation shows that the QuILT related to the basics of the addition of angular momentum is helpful in improving students’ understanding of these concepts.

  9. Understanding treatment effect mechanisms of the CAMBRA randomized trial in reducing caries increment

    OpenAIRE

    Cheng, J; Chaffee, BW; Cheng, NF; Gansky, SA; Featherstone, JDB

    2015-01-01

    © International & American Associations for Dental Research 2014. The Caries Management By Risk Assessment (CAMBRA) randomized controlled trial showed that an intervention featuring combined antibacterial and fluoride therapy significantly reduced bacterial load and suggested reduced caries increment in adults with 1 to 7 baseline cavitated teeth. While trial results speak to the overall effectiveness of an intervention, insight can be gained from understanding the mechanism by which an int...

  10. Comparing uranyl sorption complexes on soil and reference clays

    International Nuclear Information System (INIS)

    Chisholm-Brause, C.J.; Berg, J.M.; Conradson, S.D.; Morris, D.E.; McKinley, J.P.; Zachara, J.M.

    1993-01-01

    Clay minerals and other components in natural soils may play a key role in limiting the mobility of uranium in the environment through the formation of sorption complexes. Reference clays are frequently used as models to study sorption processes because they have well-known chemical and physical properties, but they may differ chemically and morphologically from clays derived from natural soils. Therefore, inferences based on reference clay data have been questioned. The authors have used luminescence and x-ray absorption spectroscopies to characterize the sorption complexes of aqueous uranyl (UO 2 2+ ) species on two soil smectites from the Kenoma and Ringold formations, and compared these results to those obtained on reference smectite clays. The pH dependence of uptake suggests that the ratio of sorption on amphoteric edge sites is greater for the soil smectites than for reference clays such as Wyoming montmorillonite (SWy-1). The luminescence spectra for uranyl sorbed to the soil clays are very similar to those for uranyl sorbed principally to the edge sites of SWy-1. This observation supports the solution data suggesting that adsorption to amphoteric sites is a more important mechanism for soil clays. However, the spectral data indicate that the sorption complexes on natural and reference clays are quite similar. Furthermore, as with the reference clays, the authors have found that the chemistry of the solution plays a greater role in defining the sorption complex than does the clay matrix. Thus, if differences in surface properties are adequately taken into account, the reference clays may serve as useful analogs for soil clays in investigations of metal-ion sorption

  11. Review of the sorption of actinides on natural minerals

    International Nuclear Information System (INIS)

    Beall, G.W.

    1981-01-01

    Over the past few years, a large body of data concerning sorption of actinides on geologic media has been built in connection with high-level-waste disposal. The primary aim of the work has been to allow predictions of the migration behavior of these radionuclides in the case of a breach of the repository that allowed groundwater flow through the repository. As a result of this work, some new backfill materials specifically tailored for the actinides have also been designed. Several major mechanisms of sorption that appear to dominate the sorption of actinides have emerged from these studies. These mechanisms can be divided into solution reactions dominated by hydrolysis, chemisorption reactions, and oxidation-reduction reactions. Each of these mechanisms will be discussed in detail, with experimental examples. Surprisingly, one mechanism, cation exchange, does not play an important role; why it fails to operate in any significant way in the environmental pH region will be discussed. The implications of the sorption mechanisms for waste forms and backfill materials will be discussed in detail. These discussions will center primarily around the valence state of the actinide in various waste forms and the effect of various anions on leachability from waste forms and backfill materials

  12. Sorption of Arsenite onto Mackinawite Coated Sand

    Science.gov (United States)

    Gallegos, T. J.; Hayes, K. F.; Abriola, L. M.

    2004-05-01

    Arsenic contamination of groundwater is a widespread problem affecting aquifers in the United States as well as abroad. Recent strengthening of the US EPA MCL for arsenic has prompted the need for technology capable of removing both arsenite and arsenate from solution. Arsenite, the more toxic form of arsenic, is more difficult to remove from anoxic zones in the subsurface. Studies by others have demonstrated the affinity of some types of iron sulfides for arsenite, such as troilite, pyrite, amorphous iron sulfide and mackinawite. However, these studies have not provided a comprehensive investigation of the macroscopic behavior of arsenite in the presence of crystalline mackinawite in a form that can be readily applied to real-world treatment technologies. This study examines the behavior of arsenite in the presence of mackinawite coated sand. PH edge results demonstrate that arsenite sorption onto mackinawite coated sand increases with increasing pH, reaching maximum removal at pH 10. Arsenite removal, albeit slight, occurring below pH 5 is independent of pH indicative of a different removal mechanism. Isotherm studies show that at low concentrations, removal is Langmuirian in nature. Arsenite sorption abruptly converts to linear behavior at high concentrations, possibly attributed to the saturation of the monolayer. Ionic strength effects were assessed by comparing pH edge data developed for three different concentrations of NaCl background electrolyte solution. Increases in ionic strength enhance the removal of arsenite from solution, suggesting possible inner-sphere surface complexation removal mechanisms. Information gathered in this study can be used to further develop surface complexation models to describe and predict reactivity of arsenite in the presence of mackinawite coated sands in anoxic regions. Mackinawite coated sands investigated here may provide a feasible reactive medium for implementation in above-ground sorption reactors or subsurface

  13. Using DVS-NIR to assess the water sorption behaviour and stability of a griseofulvin/PVP K30 solid dispersion.

    Science.gov (United States)

    Li, Wanjing; Buckton, Graham

    2015-11-30

    The purpose of this work was to investigate the distribution of water in a physically unstable amorphous solid dispersion (polyvinylpyrrolidone (PVP) and griseofulvin (as a model hydrophobic drug)), both as the sample absorbs water and during prolonged exposure to elevated humidity by use of dynamic vapour sorption combined with near infrared (DVS-NIR). The solid dispersion absorbed much less water than the sum of the water sorption of the individual components. This suggests that griseofulvin hindered PVP from absorbing water through the formation of the solid dispersion. Prolonged storage of the solid dispersion at 75% RH resulted in no significant mass change. Whilst this would usually be interpreted as the absence of crystallization, the NIR spectra demonstrated that crystallization occurred. The reason for the lack of a weight loss was that the expelled water from amorphous griseofulvin was sorbed by PVP, meaning that as the dispersion was broken by the crystallisation of griseofulvin, the PVP was once again free to sorb water (in line with the higher water sorption shown by PVP alone, and in contrast with the lower sorption of water by the solid dispersion). As water is a key factor in the physical stability of amorphous systems, understanding how and where water is absorbed and how this is liable to change is an important advance and offers promise in understanding the mechanism of stabilisation of solid dispersions, and therefore may be useful to predict the stability of new API dispersions. Copyright © 2015 Elsevier B.V. All rights reserved.

  14. Sorption data bases for generic Swiss argillaceous rock systems

    International Nuclear Information System (INIS)

    Bradbury, M. H.; Baeyens, B.; Thoenen, T.

    2010-09-01

    implies, these factors were used to convert the (predominantly) illite sorption values into sorption values valid for the defined generic conditions with regard to mineralogy and porewater composition. Conversion factors were used to adapt sorption values to mineralogy (CF min ), to pH value (CF pH ) and to radionuclide speciation (CF spec ). Finally, a Lab→Field conversion factor (CF Lab→Field ) was applied to adapt sorption data measured in dispersed systems (batch experiments) to intact rock under in-situ conditions. Calcareous rock is used in safety analyses as being representative of a clay rock which has lost most of its favorable sorption properties due to near-field effects such as alteration by an alkaline plume and subsequent processes. It is assumed that calcareous rocks do not contain any significant quantities of phyllosilicates and that only uptake data on calcite are relevant. Sorption data on calcite are extremely sparse and the uptake mechanisms are not fully understood. However, when the existing sorption data (log R d values) are plotted against the ionic radii of the respective metals, an acceptable linear correlation between these two quantities is found. This so-called linear free energy relationship is used to complement the sparse experimental data in the SDB for calcareous systems. (authors)

  15. Integrating Classical with Emerging Concepts for Better Understanding of Salinity Stress Tolerance Mechanisms in Rice

    Directory of Open Access Journals (Sweden)

    Navdeep Kaur

    2017-07-01

    Full Text Available Rice is an important cereal crop responsible for world's food security. The sensitivity of rice plants toward a range of abiotic stresses is a prime challenge for its overall growth and productivity. Among these, salinity is a major stress which results in a significant loss of global rice yield annually. For finding straightforward and strict future solutions in order to assure the food security to growing world population, understanding of the various mechanisms responsible for salt stress tolerance in rice is of paramount importance. In classical studies, identification of salt tolerant cultivars and the genetic markers linked to salt tolerance and breeding approaches have been given emphasis. It further affirmed on the identification of various pathways regulating the complex process of salt stress adaptation. However, only limited success has been achieved in these approaches as salt tolerance is a complex process and is governed by multiple factors. Hence, for better understanding of salt tolerance mechanisms, a comprehensive approach involving physiological, biochemical and molecular studies is much warranted. Modern experimental and genetic resources have provided a momentum in this direction and have provided molecular insights into different salt stress responsive pathways at the signaling and regulatory level. The integrative knowledge of classical and modern research of the understanding of salt stress adaptive pathways can help the researchers for designing effective strategies to fight against salt stress. Hence, the present review is focused on the understanding of the salt stress tolerance mechanisms in rice through the consolidative knowledge of classical and modern concepts. It further highlights the emerging new trends of salt stress adaptive pathways in rice.

  16. Sorption of Emerging Organic Wastewater Contaminants to Four Soils

    Directory of Open Access Journals (Sweden)

    Sarah Roberts

    2014-04-01

    Full Text Available Conventional onsite wastewater treatment system design relies on a septic tank and soil treatment unit (STU for treatment of wastewater and integration of the final effluent into the environment. Organic water contaminants (OWCs, chemicals found in pharmaceutical drugs, detergents, surfactants, and other personal care and cleaning products, have been observed in septic tank effluent and the environment. Sorption of OWC mass to soil is a key mechanism in the removal and retardation of many of these chemicals in effluent as it travels through an STU. The primary purpose of this study was to investigate the relationship between the fraction of organic carbon of soil and the equilibrium sorption partitioning coefficient of a selected group of relevant and diverse OWCs. A secondary goal is to evaluate current methods of modeling the sorption of selected OWCs in soil. Five point Freundlich isotherms were constructed from equilibrium sorption batch tests for target OWCs with four different soils. For soils with organic carbon fraction between 0.021 and 0.054, Kd values were calculated between 60 and 185 for 4-nonylphenol, 75 to 260 for triclosan, 115 to 270 for bisphenol-A, 3 to 255 for 17β-estradiol, 40 to 55 for 17α-ethynylestradiol, and 28 to 70 for estrone. An empirically derived, direct relationship between foc and Kd may be a useful approach to estimating sorption for a soil based on organic carbon content.

  17. Sorption and desorption of naphthalene by soil organic matter: importance of aromatic and aliphatic components.

    Science.gov (United States)

    Gunasekara, Amrith S; Xing, Baoshan

    2003-01-01

    Nonlinear isotherm behavior has been reported for the sorption of hydrophobic organic compounds (HOCs) in soil organic matter (SOM), but the exact mechanisms are unknown. Our objective was to provide insight into the sorption mechanism of HOCs in SOM by studying the sorption-desorption processes of naphthalene in a mineral soil, its humic fractions, and lignin. Additionally, humin and lignin were used for studying the effects of temperature and cosolvent on HOC sorption. All isotherms were nonlinear. The humin and lignin isotherms became more linear at elevated temperatures and with the addition of methanol indicating a condensed to expanded structural phase transition. Isotherm nonlinearity and hysteresis increased in the following order: soil humic acid (HA) soil soil humin. Of the samples, aliphatic-rich humin exhibited the largest degree of nonlinearity and had the highest sorption capacity for naphthalene. High nonlinearity and hysteresis in humin were most likely caused by its condensed structure. A novel aliphatic, amorphous condensed conformation is proposed. This conformation can account for both high sorption capacities and increased nonlinearity observed for aliphatic-rich samples and can explain many sorption disparities discussed in the literature. This study clearly illustrates the importance of both aliphatic and aromatic moieties for HOC sorption in SOM.

  18. An insight into the removal of fluoroquinolones in activated sludge process: Sorption and biodegradation characteristics.

    Science.gov (United States)

    Wang, Lu; Qiang, Zhimin; Li, Yangang; Ben, Weiwei

    2017-06-01

    The detailed sorption steps and biodegradation characteristics of fluoroquinolones (FQs) including ciprofloxacin, enrofloxacin, lomefloxacin, norfloxacin, and ofloxacin were investigated through batch experiments. The results indicate that FQs at a total concentration of 500μg/L caused little inhibition of sludge bioactivity. Sorption was the primary removal pathway of FQs in the activated sludge process, followed by biodegradation, while hydrolysis and volatilization were negligible. FQ sorption on activated sludge was a reversible process governed by surface reaction. Henry and Freundlich models could describe the FQ sorption isotherms well in the concentration range of 100-300μg/L. Thermodynamic parameters revealed that FQ sorption on activated sludge is spontaneous, exothermic, and enthalpy-driven. Hydrophobicity-independent mechanisms determined the FQ sorption affinity with activated sludge. The zwitterion of FQs had the strongest sorption affinity, followed by cation and anion, and aerobic condition facilitated FQ sorption. FQs were slowly biodegradable, with long half-lives (>100hr). FQ biodegradation was enhanced with increasing temperature and under aerobic condition, and thus was possibly achieved through co-metabolism during nitrification. This study provides an insight into the removal kinetics and mechanism of FQs in the activated sludge process, but also helps assess the environmental risks of FQs resulting from sludge disposal. Copyright © 2016. Published by Elsevier B.V.

  19. KINETIC STUDIES ON THE SORPTION OF LEAD AND CADMIUM ...

    African Journals Online (AJOL)

    Kinetic investigations are necessary for determining the rate of reaction and mechanism. The kinetics of the sorption of Pb2+ and Cd2+ from aqueous solution on to the biomass of C. bicolor was studied by batch equilibrium technique. The removal of the two metal ions was found to be > 60% depending on the initial metal ...

  20. Understanding cellular responses to toxic agents: a model for mechanism-choice in bacterial metal resistance.

    Science.gov (United States)

    Rouch, D A; Lee, B T; Morby, A P

    1995-02-01

    Bacterial resistances to metals are heterogeneous in both their genetic and biochemical bases. Metal resistance may be chromosomally-, plasmid- or transposon-encoded, and one or more genes may be involved: at the biochemical level at least six different mechanisms are responsible for resistance. Various types of resistance mechanisms can occur singly or in combination and for a particular metal different mechanisms of resistance can occur in the same species. To understand better the diverse responses of bacteria to metal ion challenge we have constructed a qualitative model for the selection of metal resistance in bacteria. How a bacterium becomes resistant to a particular metal depends on the number and location of cellular components sensitive to the specific metal ion. Other important selective factors include the nature of the uptake systems for the metal, the role and interactions of the metal in the normal metabolism of the cell and the availability of plasmid (or transposon) encoded resistance mechanisms. The selection model presented is based on the interaction of these factors and allows predictions to be made about the evolution of metal resistance in bacterial populations. It also allows prediction of the genetic basis and of mechanisms of resistance which are in substantial agreement with those in well-documented populations. The interaction of, and selection for resistance to, toxic substances in addition to metals, such as antibiotics and toxic analogues, involve similar principles to those concerning metals. Potentially, models for selection of resistance to any substance can be derived using this approach.

  1. Sorption of selenate on soils and pure phases: kinetic parameters and stabilisation

    Energy Technology Data Exchange (ETDEWEB)

    Loffredo, N. [Institut de Radioprotection et Surete Nucleaire (IRSN), DEI/SECRE/Laboratoire de Radioecologie et d' Ecotoxicologie, Cadarache, Bat 186, BP3, 13115 Saint-Paul-lez-Durance Cedex (France); Mounier, S. [Laboratoire PROTEE, Universite du Sud Toulon-Var, BP 20132, La Garde 83957 (France); Thiry, Y. [Agence Nationale pour la gestion des Dechets Radioactifs (Andra), Parc de la Croix Blanche, 1/7 rue Jean Monnet, 92298 Chatenay-Malabry Cedex (France); Coppin, F., E-mail: frederic.coppin@irsn.fr [Institut de Radioprotection et Surete Nucleaire (IRSN), DEI/SECRE/Laboratoire de Radioecologie et d' Ecotoxicologie, Cadarache, Bat 186, BP3, 13115 Saint-Paul-lez-Durance Cedex (France)

    2011-09-15

    due to outer sphere complexes, as for goethite, whereas for soil Bu the sorption was mainly attributed to inner sphere complexes followed by reduction mechanisms, probably initiated by microorganisms, in which no steady state was reached at the end of the 165 h experiments. The sorption of selenate decreased when concentrations reached 1 x 10{sup -3} mol L{sup -1}, due to solid saturation, except for aluminium hydroxide. Reduction of selenate seemed also to occur on goethite and soil Ro, for the same concentration, but without preventing a decrease in sorption. Thus, this work shows that the comparison of selenate behaviour between soil and pure phases helps to elucidate the main carrier phases and sorption mechanisms in soil. - Highlights: > We model selenate sorption on pure solid phases and on two soils. > No selenate sorption on calcite, humic acid and silica. > Selenate sorption as outer sphere complexes on goethite and one soil. > Selenate sorption as inner sphere complexes on aluminium hydroxide and other soil. > Data could be modelled with a two sites complexation model (equilibrium and kinetic).

  2. Kinetic and isotherm studies of bisphenol A adsorption onto orange albedo(Citrus sinensis): Sorption mechanisms based on the main albedo components vitamin C, flavones glycosides and carotenoids.

    Science.gov (United States)

    Kamgaing, Theophile; Doungmo, Giscard; Melataguia Tchieno, Francis Merlin; Gouoko Kouonang, Jimmy Julio; Mbadcam, Ketcha Joseph

    2017-07-03

    Orange albedo and its adsorption capacity towards bisphenol A (BPA) were studied. Adsorption experiments were conducted in batch mode at 25-55°C. Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and Fourier transform infrared (FTIR) spectroscopy were used to characterise the biosorbent. The effects of various parameters including adsorption time, equilibrium pH, adsorbent dosage and initial adsorbate concentration were investigated. The optimum contact time and pH for the removal of BPA were 60 min and 2, respectively. It was found that the adsorption isotherms best matched the Freundlich model, the adsorption of BPA being multilayer and that of the albedo surface heterogeneous. From the kinetic studies, it was found that the removal of BPA best matched the pseudo-second order kinetic model. An adsorption mechanism based on the albedo surface molecules is proposed and gives a good account of π-π interactions and hydrogen bonding. Orange albedo, with a maximum BPA loading capacity of 82.36 mg g -1 (significantly higher than that of most agricultural residues), is a good candidate for BPA adsorption in aqueous media.

  3. It's Rather like Learning a Language: Development of talk and conceptual understanding in mechanics lessons

    Science.gov (United States)

    Rincke, Karsten

    2011-01-01

    Although a broad literature exists concerning the development of conceptual understanding of force and other topics within mechanics, little is known about the role and development of students' talk about the subject. The paper presents an in-depth investigation of students' talk whilst being introduced to the concept of force. The main research goal was to investigate and understand how students develop an understanding of the concept of force and how they use and understand the term 'force'. Therefore, we make relation to the research field of students' preconceptions and the field of second language learning. Two classes of students (N = 47) were videotaped during a time period of nine lessons, each transcribed and analysed using a category system. Additional data were obtained via written tasks, logs kept by the students, and tests. The detailed analysis of the talk and the results of the tests indicate that students face difficulties in using the term 'force' scientifically similar to those in a foreign language instruction. Vygotsky already recognised a relationship between learning in science and learning a language. In this paper, important aspects of this relationship are discussed based upon empirical data. We conclude that in some respects it might be useful to make reference to the research related to language learning when thinking about improving science education. In particular, according to Selinker's concept of interlanguage describing language-learning processes within language instruction, the language used by the students during physics lessons can be viewed as a 'scientific interlanguage'.

  4. Understanding dental CAD/CAM for restorations--the digital workflow from a mechanical engineering viewpoint.

    Science.gov (United States)

    Tapie, L; Lebon, N; Mawussi, B; Fron Chabouis, H; Duret, F; Attal, J-P

    2015-01-01

    As digital technology infiltrates every area of daily life, including the field of medicine, so it is increasingly being introduced into dental practice. Apart from chairside practice, computer-aided design/computer-aided manufacturing (CAD/CAM) solutions are available for creating inlays, crowns, fixed partial dentures (FPDs), implant abutments, and other dental prostheses. CAD/CAM dental solutions can be considered a chain of digital devices and software for the almost automatic design and creation of dental restorations. However, dentists who want to use the technology often do not have the time or knowledge to understand it. A basic knowledge of the CAD/CAM digital workflow for dental restorations can help dentists to grasp the technology and purchase a CAM/CAM system that meets the needs of their office. This article provides a computer-science and mechanical-engineering approach to the CAD/CAM digital workflow to help dentists understand the technology.

  5. Sorption of antibiotic sulfamethoxazole varies with biochars produced at different temperatures

    International Nuclear Information System (INIS)

    Zheng, Hao; Wang, Zhenyu; Zhao, Jian; Herbert, Stephen; Xing, Baoshan

    2013-01-01

    Sorption of sulfonamides on biochars is poorly understood, thus sulfamethoxazole (SMX) sorption on biochars produced at 300–600 °C was determined as a function of pH and SMX concentration, as well as the inorganic fractions in the biochars. Neutral SMX molecules (SMX 0 ) were dominant for sorption at pH 1.0–6.0. Above pH 7.0, although biochars surfaces were negatively-charged, anionic SMX species sorption increased with pH and is regulated via charge-assisted H-bonds. SMX 0 sorption at pH 5.0 was nonlinear and adsorption-dominant for all the biochars via hydrophobic interaction, π–π electron donor–acceptor interaction and pore-filling. The removal of inorganic fraction reduced SMX sorption by low-temperature biochars (e.g., 300 °C), but enhanced the sorption by high-temperature biochars (e.g., 600 °C) due to the temperature-dependent inorganic fractions in the biochars. These observations are useful for producing designer biochars as engineered sorbents to reduce the bioavailability of antibiotics and/or predict the fate of sulfonamides in biochar-amended soils. -- Highlights: •Sulfamethoxazole (SMX) sorption on biochars at pH 5.0 was adsorption-dominant. •Removal of inorganic fractions in low-temperature biochars reduced SMX sorption. •Removal of inorganic fractions in high-temperature biochars enhanced SMX sorption. •Anionic SMX was adsorbed on negatively charged biochar via charge-assisted H-bond. -- Solution pH and biochar property control the sorption amount and mechanisms of antibiotic sulfamethoxazole

  6. Cognitive neuroepigenetics: the next evolution in our understanding of the molecular mechanisms underlying learning and memory?

    Science.gov (United States)

    Marshall, Paul; Bredy, Timothy W.

    2016-07-01

    A complete understanding of the fundamental mechanisms of learning and memory continues to elude neuroscientists. Although many important discoveries have been made, the question of how memories are encoded and maintained at the molecular level remains. So far, this issue has been framed within the context of one of the most dominant concepts in molecular biology, the central dogma, and the result has been a protein-centric view of memory. Here, we discuss the evidence supporting a role for neuroepigenetic mechanisms, which constitute dynamic and reversible, state-dependent modifications at all levels of control over cellular function, and their role in learning and memory. This neuroepigenetic view suggests that DNA, RNA and protein each influence one another to produce a holistic cellular state that contributes to the formation and maintenance of memory, and predicts a parallel and distributed system for the consolidation, storage and retrieval of the engram.

  7. Utilizing toxicogenomic data to understand chemical mechanism of action in risk assessment

    International Nuclear Information System (INIS)

    Wilson, Vickie S.; Keshava, Nagalakshmi; Hester, Susan; Segal, Deborah; Chiu, Weihsueh; Thompson, Chad M.; Euling, Susan Y.

    2013-01-01

    The predominant role of toxicogenomic data in risk assessment, thus far, has been one of augmentation of more traditional in vitro and in vivo toxicology data. This article focuses on the current available examples of instances where toxicogenomic data has been evaluated in human health risk assessment (e.g., acetochlor and arsenicals) which have been limited to the application of toxicogenomic data to inform mechanism of action. This article reviews the regulatory policy backdrop and highlights important efforts to ultimately achieve regulatory acceptance. A number of research efforts on specific chemicals that were designed for risk assessment purposes have employed mechanism or mode of action hypothesis testing and generating strategies. The strides made by large scale efforts to utilize toxicogenomic data in screening, testing, and risk assessment are also discussed. These efforts include both the refinement of methodologies for performing toxicogenomics studies and analysis of the resultant data sets. The current issues limiting the application of toxicogenomics to define mode or mechanism of action in risk assessment are discussed together with interrelated research needs. In summary, as chemical risk assessment moves away from a single mechanism of action approach toward a toxicity pathway-based paradigm, we envision that toxicogenomic data from multiple technologies (e.g., proteomics, metabolomics, transcriptomics, supportive RT-PCR studies) can be used in conjunction with one another to understand the complexities of multiple, and possibly interacting, pathways affected by chemicals which will impact human health risk assessment

  8. Oil sorbents with high sorption capacity, oil/water selectivity and reusability for oil spill cleanup.

    Science.gov (United States)

    Wu, Daxiong; Fang, Linlin; Qin, Yanmin; Wu, Wenjuan; Mao, Changming; Zhu, Haitao

    2014-07-15

    A sorbent for oil spill cleanup was prepared through a novel strategy by treating polyurethane sponges with silica sol and gasoline successively. The oil sorption capacity, oil/water selectivity, reusability and sorption mechanism of prepared sorbent were studied. The results showed that the prepared sorbent exhibited high sorption capacity and excellent oil/water selectivity. 1g of the prepared sorbent could adsorb more than 100 g of motor oil, while it only picks up less than 0.1 g of water from an oil-water interface under both static and dynamic conditions. More than 70% of the sorption capacity remained after 15 successive sorption-squeezing cycles, which suggests an extraordinary high reusability. The prepared sorbent is a better alternative of the commercial polypropylene sorbent which are being used nowadays. Copyright © 2014 Elsevier Ltd. All rights reserved.

  9. Sorption of uranium(VI) by La-Al-carboxymethyl konjac glucomannan microsphere sorbent

    International Nuclear Information System (INIS)

    Siyao Sun; Liping Wu; Xuegang Luo

    2017-01-01

    The microsphere of carboxymethyl konjac glucomannan immobilizing La 3+ and Al 3+ (CMKGM-La-Al) has been explored for sorption of U(VI). The maximum U(VI) sorption capacity of the microsphere is found to be 45.4 mg g -1 at pH 5. Experimental data are fitted well with the linear Langmuir and linear pseudo-first-order kinetic model. The sorption process is endothermic, spontaneous and favorable. The possible mechanism of CMKGM modification and sorption of U(VI) on CMKGM-La-Al involves ion exchange and coordination reaction. The comparison between CMKGM-La-Al and other sorbents suggests that CMKGM-La-Al can be considered as an effective sorbent for U(VI) sorption. (author)

  10. Sorption on inactive repository components

    International Nuclear Information System (INIS)

    Gardiner, M.P.; Smith, A.J.; Williams, S.J.

    1990-11-01

    The near-field of an intermediate level/low level radioactive waste repository will contain significant quantities of iron and steel, Magnox and Zircaloy. Their corrosion products may possess significant sorption capacity for radioelements. The sorption of americium and plutonium onto magnesium hydroxide, zirconium hydroxide, colloidal magnetite and colloidal haematite has been studied under conditions typical of the porewater of a cementitious near-field. R D values ≥ 10 5 m g -1 were measured for both actinides on the oxides and hydroxides. These values are at least as great as those measured on crushed 3:1 Blast Furnace Slag/Ordinary Portland cement. Competitive sorption experiments have shown that sorption onto the corrosion products does not take place in preference to that on the cement or the converse. Magnetite and haematite colloids are positively charged in cement-equilibrated water whilst zirconium hydroxide is negatively charged. Crushed cement was found to be positively charged. Simple experiments show that only a small proportion of haematite colloids is potentially mobile through a column of crushed cement. (author)

  11. Sorption on inactive repository components

    International Nuclear Information System (INIS)

    Gardiner, M.P.; Smith, A.J.; Williams, S.J.

    1990-07-01

    The near-field of an intermediate level/low level radioactive waste repository will contain significant quantities of iron and steel, Magnox and Zircaloy. Their corrosion products may possess significant sorption capacity for radioelements. The sorption of americium and plutonium onto magnesium hydroxide, zirconium hydroxide, colloidal magnetite and colloidal haematite has been studied under conditions typical of the porewater of a cementitious near-field. R D values ≥ 10 5 ml g -1 were measured for both actinides on the oxides and hydroxides. These values are at least as great at those measured on crushed 3:1 Blast Furnace Slag/Ordinary Portland Cement. Competitive sorption experiments have shown that sorption onto the corrosion products does not take place in preference to that on the cement or the converse. Magnetite and haematite colloids are positively charged in cement-equilibrated water whilst zirconium hydroxide is negatively charged. Crushed cement was found to be positively charged. Simple experiments show that only a small proportion of haematite colloids is potentially mobile through a column of crushed cement. (author)

  12. Equilibrium, kinetics and thermodynamic studies for sorption of chlorobenzenes on CTMAB modified bentonite and kaolinite.

    Science.gov (United States)

    Shu, Yuehong; Li, Laisheng; Zhang, Qiuyun; Wu, Honghai

    2010-01-15

    The sorption of chlorobenzenes (CBs) by cetyltrimethylammonium bromide (CTMAB) modified bentonite and kaolinite was investigated. The sorption isotherms for CBs were nearly linear, suggesting that sorption could be described by a distribution process. The distribution coefficient (K(d)) was primarily affected by the amount of sorbed surfactant. The organic carbon normalized sorption coefficient (K(oc)), however, was particularly dependent on arrangement of the surfactant cations. The K(d) of CBs was larger for CTMAB-bentonites than that for CTMAB-kaolinites, while the case for K(oc) was opposite. Thus, the clay mineral structure and morphology had a considerable influence on the surfactant arrangement, which was responsible for the partitioning of CBs. The sorption of CBs onto both CTMAB-bentonites and CTMAB-kaolinites followed pseudo-second-order kinetics. The intra-particle diffusion model for sorption was also investigated and compared to identify sorption mechanism. The sorption of CBs both on CTMAB-bentonites and CTMAB-kaolinites was exothermic in nature and accompanied by an increase in entropy and a decrease in Gibbs energy in the temperature range of 15-35 degrees C. The results indicated that CBs strongly interacted with CTMAB modified bentonite and kaolinite.

  13. Sorption of chlorimuron-ethyl on montmorillonite clays: effects of exchangeable cations, pH, and ionic strength.

    Science.gov (United States)

    Ren, Wenjie; Teng, Ying; Zhou, Qixing; Paschke, Albrecht; Schüürmann, Gerrit

    2014-10-01

    Sorption interaction of chlorimuron-ethyl with montmorillonite clays was investigated under varied types of exchangeable cation, pH, and ionic strength conditions. Chlorimuron-ethyl sorption on bentonites exhibited pronounced cation dependency, and the sorption ability increased as the sequence Ca(2+)- clay type and much weaker for montmorillonites. The decrease of pH at the range of 4.0-6.0 prominently increased sorption of chlorimuron-ethyl on all cation-exchanged montmorillonite clays, and nearly a neglected sorption (about 2 %) can be observed at pH over 7.0. In the presence of CaCl2, sorption of chlorimuron-ethyl on Fe(3+)-bentonite was promoted because of complexion of Ca(2+) and the surface of Fe(3+)-bentonite. However, as the concentration of CaCl2 increased, chlorimuron-ethyl sorption on Ca(2+)- and Fe(3+)-exchanged bentonite decreased, suggesting that Ca bridging was not the prevailing mechanism for sorption of chlorimuron-ethyl on these clays. Furthermore, chlorimuron-ethyl sorption was relatively sensitive to pH, and the change of pH may obscure effect of other factors on the sorption, so it was quite necessary to control pH at a constant value when the effect of other factor was being studied.

  14. Twenty-five years of progress in understanding pollination mechanisms in palms (Arecaceae)

    Science.gov (United States)

    Barfod, Anders S.; Hagen, Melanie; Borchsenius, Finn

    2011-01-01

    Background With more than 90 published studies of pollination mechanisms, the palm family is one of the better studied tropical families of angiosperms. Understanding palm–pollinator interactions has implications for tropical silviculture, agroforestry and horticulture, as well as for our understanding of palm evolution and diversification. We review the rich literature on pollination mechanisms in palms that has appeared since the last review of palm pollination studies was published 25 years ago. Scope and Conclusions Visitors to palm inflorescences are attracted by rewards such as food, shelter and oviposition sites. The interaction between the palm and its visiting fauna represents a trade-off between the services provided by the potential pollinators and the antagonistic activities of other insect visitors. Evidence suggests that beetles constitute the most important group of pollinators in palms, followed by bees and flies. Occasional pollinators include mammals (e.g. bats and marsupials) and even crabs. Comparative studies of palm–pollinator interactions in closely related palm species document transitions in floral morphology, phenology and anatomy correlated with shifts in pollination vectors. Synecological studies show that asynchronous flowering and partitioning of pollinator guilds may be important regulators of gene flow between closely related sympatric taxa and potential drivers of speciation processes. Studies of larger plant–pollinator networks point out the importance of competition for pollinators between palms and other flowering plants and document how the insect communities in tropical forest canopies probably influence the reproductive success of palms. However, published studies have a strong geographical bias towards the South American region and a taxonomic bias towards the tribe Cocoseae. Future studies should try to correct this imbalance to provide a more representative picture of pollination mechanisms and their evolutionary

  15. Sorption isotherms: A review on physical bases, modeling and measurement

    Energy Technology Data Exchange (ETDEWEB)

    Limousin, G. [Atomic Energy Commission, Tracers Technology Laboratory, 38054 Grenoble Cedex (France) and Laboratoire d' etude des Transferts en Hydrologie et Environnement (CNRS-INPG-IRD-UJF), BP 53, 38041 Grenoble Cedex (France)]. E-mail: guillaumelimousin@yahoo.fr; Gaudet, J.-P. [Laboratoire d' etude des Transferts en Hydrologie et Environnement (CNRS-INPG-IRD-UJF), BP 53, 38041 Grenoble Cedex (France); Charlet, L. [Laboratoire de Geophysique Interne et Techtonophysique - CNRS-IRD-LCPC-UJF-Universite de Savoie, BP 53, 38041 Grenoble Cedex (France); Szenknect, S. [Atomic Energy Commission, Tracers Technology Laboratory, 38054 Grenoble Cedex (France); Barthes, V. [Atomic Energy Commission, Tracers Technology Laboratory, 38054 Grenoble Cedex (France); Krimissa, M. [Electricite de France, Division Recherche et Developpement, Laboratoire National d' Hydraulique et d' Environnement - P78, 6 quai Watier, 78401 Chatou (France)

    2007-02-15

    The retention (or release) of a liquid compound on a solid controls the mobility of many substances in the environment and has been quantified in terms of the 'sorption isotherm'. This paper does not review the different sorption mechanisms. It presents the physical bases underlying the definition of a sorption isotherm, different empirical or mechanistic models, and details several experimental methods to acquire a sorption isotherm. For appropriate measurements and interpretations of isotherm data, this review emphasizes 4 main points: (i) the adsorption (or desorption) isotherm does not provide automatically any information about the reactions involved in the sorption phenomenon. So, mechanistic interpretations must be carefully verified. (ii) Among studies, the range of reaction times is extremely wide and this can lead to misinterpretations regarding the irreversibility of the reaction: a pseudo-hysteresis of the release compared with the retention is often observed. The comparison between the mean characteristic time of the reaction and the mean residence time of the mobile phase in the natural system allows knowing if the studied retention/release phenomenon should be considered as an instantaneous reversible, almost irreversible phenomenon, or if reaction kinetics must be taken into account. (iii) When the concentration of the retained substance is low enough, the composition of the bulk solution remains constant and a single-species isotherm is often sufficient, although it remains strongly dependent on the background medium. At higher concentrations, sorption may be driven by the competition between several species that affect the composition of the bulk solution. (iv) The measurement method has a great influence. Particularly, the background ionic medium, the solid/solution ratio and the use of flow-through or closed reactor are of major importance. The chosen method should balance easy-to-use features and representativity of the studied

  16. Sorption and desorption of carbamazepine from water by smectite clays.

    Science.gov (United States)

    Zhang, Weihao; Ding, Yunjie; Boyd, Stephen A; Teppen, Brian J; Li, Hui

    2010-11-01

    Carbamazepine is a prescription anticonvulsant and mood stabilizing pharmaceutical administered to humans. Carbamazepine is persistent in the environment and frequently detected in water systems. In this study, sorption and desorption of carbamazepine from water was measured for smectite clays with the surface negative charges compensated with K+, Ca2+, NH4+, tetramethylammonium (TMA), trimethylphenylammonium (TMPA) and hexadecyltrimethylammonium (HDTMA) cations. The magnitude of sorption followed the order: TMPA-smectite≥HDTMA-smectite>NH4-smectite>K-smectite>Ca-smectite⩾TMA-smectite. The greatest sorption of carbamazepine by TMPA-smectite is attributed to the interaction of conjugate aromatic moiety in carbamazepine with the phenyl ring in TMPA through π-π interaction. Partitioning process is the primary mechanism for carbamazepine uptake by HDTMA-smectite. For NH4-smectite the urea moiety in carbamazepine interacts with exchanged cation NH4+ by H-bonding hence demonstrating relatively higher adsorption. Sorption by K-, Ca- and TMA-smectites from water occurs on aluminosilicate mineral surfaces. These results implicate that carbamazepine sorption by soils occurs primarily in soil organic matter, and soil mineral fractions play a secondary role. Desorption of carbamazepine from the sorbents manifested an apparent hysteresis. Increasing irreversibility of desorption vs. sorption was observed for K-, Ca-, TMA-, TMPA- and HDTMA-clays as aqueous carbamazepine concentrations increased. Desorption hysteresis of carbamazepine from K-, Ca-, NH4-smectites was greater than that from TMPA- and HDTMA-clays, suggesting that the sequestrated carbamazepine molecules in smectite interlayers are more resistant to desorption compared to those sorbed by organic phases in smectite clays. Copyright © 2010 Elsevier Ltd. All rights reserved.

  17. Progress in Understanding Degradation Mechanisms and Improving Stability in Organic Photovoltaics

    KAUST Repository

    Mateker, William R.

    2016-12-23

    Understanding the degradation mechanisms of organic photovoltaics is particularly important, as they tend to degrade faster than their inorganic counterparts, such as silicon and cadmium telluride. An overview is provided here of the main degradation mechanisms that researchers have identified so far that cause extrinsic degradation from oxygen and water, intrinsic degradation in the dark, and photo-induced burn-in. In addition, it provides methods for researchers to identify these mechanisms in new materials and device structures to screen them more quickly for promising long-term performance. These general strategies will likely be helpful in other photovoltaic technologies that suffer from insufficient stability, such as perovskite solar cells. Finally, the most promising lifetime results are highlighted and recommendations to improve long-term performance are made. To prevent degradation from oxygen and water for sufficiently long time periods, OPVs will likely need to be encapsulated by barrier materials with lower permeation rates of oxygen and water than typical flexible substrate materials. To improve stability at operating temperatures, materials will likely require glass transition temperatures above 100 °C. Methods to prevent photo-induced burn-in are least understood, but recent research indicates that using pure materials with dense and ordered film morphologies can reduce the burn-in effect.

  18. Progress in Understanding Degradation Mechanisms and Improving Stability in Organic Photovoltaics.

    Science.gov (United States)

    Mateker, William R; McGehee, Michael D

    2017-03-01

    Understanding the degradation mechanisms of organic photovoltaics is particularly important, as they tend to degrade faster than their inorganic counterparts, such as silicon and cadmium telluride. An overview is provided here of the main degradation mechanisms that researchers have identified so far that cause extrinsic degradation from oxygen and water, intrinsic degradation in the dark, and photo-induced burn-in. In addition, it provides methods for researchers to identify these mechanisms in new materials and device structures to screen them more quickly for promising long-term performance. These general strategies will likely be helpful in other photovoltaic technologies that suffer from insufficient stability, such as perovskite solar cells. Finally, the most promising lifetime results are highlighted and recommendations to improve long-term performance are made. To prevent degradation from oxygen and water for sufficiently long time periods, OPVs will likely need to be encapsulated by barrier materials with lower permeation rates of oxygen and water than typical flexible substrate materials. To improve stability at operating temperatures, materials will likely require glass transition temperatures above 100 °C. Methods to prevent photo-induced burn-in are least understood, but recent research indicates that using pure materials with dense and ordered film morphologies can reduce the burn-in effect. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Understanding comorbidity among internalizing problems: Integrating latent structural models of psychopathology and risk mechanisms

    Science.gov (United States)

    Hankin, Benjamin L.; Snyder, Hannah R.; Gulley, Lauren D.; Schweizer, Tina H.; Bijttebier, Patricia; Nelis, Sabine; Toh, Gim; Vasey, Michael W.

    2016-01-01

    It is well known that comorbidity is the rule, not the exception, for categorically defined psychiatric disorders, and this is also the case for internalizing disorders of depression and anxiety. This theoretical review paper addresses the ubiquity of comorbidity among internalizing disorders. Our central thesis is that progress in understanding this co-occurrence can be made by employing latent dimensional structural models that organize both psychopathology as well as vulnerabilities and risk mechanisms and by connecting the multiple levels of risk and psychopathology outcomes together. Different vulnerabilities and risk mechanisms are hypothesized to predict different levels of the structural model of psychopathology. We review the present state of knowledge based on concurrent and developmental sequential comorbidity patterns among common discrete psychiatric disorders in youth, and then we advocate for the use of more recent bifactor dimensional models of psychopathology (e.g., p factor, Caspi et al., 2014) that can help to explain the co-occurrence among internalizing symptoms. In support of this relatively novel conceptual perspective, we review six exemplar vulnerabilities and risk mechanisms, including executive function, information processing biases, cognitive vulnerabilities, positive and negative affectivity aspects of temperament, and autonomic dysregulation, along with the developmental occurrence of stressors in different domains, to show how these vulnerabilities can predict the general latent psychopathology factor, a unique latent internalizing dimension, as well as specific symptom syndrome manifestations. PMID:27739389

  20. Features of Knowledge Building in Biology: Understanding Undergraduate Students’ Ideas about Molecular Mechanisms

    Science.gov (United States)

    Southard, Katelyn; Wince, Tyler; Meddleton, Shanice; Bolger, Molly S.

    2016-01-01

    Research has suggested that teaching and learning in molecular and cellular biology (MCB) is difficult. We used a new lens to understand undergraduate reasoning about molecular mechanisms: the knowledge-integration approach to conceptual change. Knowledge integration is the dynamic process by which learners acquire new ideas, develop connections between ideas, and reorganize and restructure prior knowledge. Semistructured, clinical think-aloud interviews were conducted with introductory and upper-division MCB students. Interviews included a written conceptual assessment, a concept-mapping activity, and an opportunity to explain the biomechanisms of DNA replication, transcription, and translation. Student reasoning patterns were explored through mixed-method analyses. Results suggested that students must sort mechanistic entities into appropriate mental categories that reflect the nature of MCB mechanisms and that conflation between these categories is common. We also showed how connections between molecular mechanisms and their biological roles are part of building an integrated knowledge network as students develop expertise. We observed differences in the nature of connections between ideas related to different forms of reasoning. Finally, we provide a tentative model for MCB knowledge integration and suggest its implications for undergraduate learning. PMID:26931398

  1. Sorption kinetics of diuron on volcanic ash derived soils.

    Science.gov (United States)

    Cáceres-Jensen, Lizethly; Rodríguez-Becerra, Jorge; Parra-Rivero, Joselyn; Escudey, Mauricio; Barrientos, Lorena; Castro-Castillo, Vicente

    2013-10-15

    Diuron sorption kinetic was studied in Andisols, Inceptisol and Ultisols soils in view of their distinctive physical and chemical properties: acidic pH and variable surface charge. Two types of kinetic models were used to fit the experimental dates: those that allow to establish principal kinetic parameters and modeling of sorption process (pseudo-first-order, pseudo-second-order), and some ones frequently used to describe solute transport mechanisms of organic compounds on different sorbents intended for remediation purposes (Elovich equation, intraparticle diffusion, Boyd, and two-site nonequilibrium models). The best fit was obtained with the pseudo-second-order model. The rate constant and the initial rate constant values obtained through this model demonstrated the behavior of Diuron in each soil, in Andisols were observed the highest values for both parameters. The application of the models to describe solute transport mechanisms allowed establishing that in all soils the mass transfer controls the sorption kinetic across the boundary layer and intraparticle diffusion into macropores and micropores. The slowest sorption rate was observed on Ultisols, behavior which must be taken into account when the leaching potential of Diuron is considered. Copyright © 2013 Elsevier B.V. All rights reserved.

  2. Understanding the Impact of Root Morphology on Overturning Mechanisms: A Modelling Approach

    Science.gov (United States)

    Fourcaud, Thierry; Ji, Jin-Nan; Zhang, Zhi-Qiang; Stokes, Alexia

    2008-01-01

    Background and Aims The Finite Element Method (FEM) has been used in recent years to simulate overturning processes in trees. This study aimed at using FEM to determine the role of individual roots in tree anchorage with regard to different rooting patterns, and to estimate stress distribution in the soil and roots during overturning. Methods The FEM was used to carry out 2-D simulations of tree uprooting in saturated soft clay and loamy sand-like soil. The anchorage model consisted of a root system embedded in a soil block. Two root patterns were used and individual roots removed to determine their contribution to anchorage. Key Results In clay-like soil the size of the root–soil plate formed during overturning was defined by the longest roots. Consequently, all other roots localized within this plate had no influence on anchorage strength. In sand-like soil, removing individual root elements altered anchorage resistance. This result was due to a modification of the shape and size of the root–soil plate, as well as the location of the rotation axis. The tap root and deeper roots had more influence on overturning resistance in sand-like soil compared with clay-like soil. Mechanical stresses were higher in the most superficial roots and also in leeward roots in sand-like soil. The relative difference in stresses between the upper and lower sides of lateral roots was sensitive to root insertion angle. Assuming that root eccentricity is a response to mechanical stresses, these results explain why eccentricity differs depending on root architecture. Conclusions A simple 2-D Finite Element model was developed to better understand the mechanisms involved during tree overturning. It has been shown how root system morphology and soil mechanical properties can modify the shape of the root plate slip surface as well as the position of the rotation axis, which are major components of tree anchorage. PMID:17942593

  3. Using the glacial geomorphology of palaeo-ice streams to understand mechanisms of ice sheet collapse

    Science.gov (United States)

    Stokes, Chris R.; Margold, Martin; Clark, Chris; Tarasov, Lev

    2017-04-01

    Processes which bring about ice sheet deglaciation are critical to our understanding of glacial-interglacial cycles and ice sheet sensitivity to climate change. The precise mechanisms of deglaciation are also relevant to our understanding of modern-day ice sheet stability and concerns over global sea level rise. Mass loss from ice sheets can be broadly partitioned between melting and a 'dynamic' component whereby rapidly-flowing ice streams/outlet glaciers transfer ice from the interior to the oceans. Surface and basal melting (e.g. of ice shelves) are closely linked to atmospheric and oceanic conditions, but the mechanisms that drive dynamic changes in ice stream discharge are more complex, which generates much larger uncertainties about their future contribution to ice sheet mass loss and sea level rise. A major problem is that observations of modern-day ice streams typically span just a few decades and, at the ice-sheet scale, it is unclear how the entire drainage network of ice streams evolves during deglaciation. A key question is whether ice streams might increase and sustain rates of mass loss over centuries or millennia, beyond those expected for a given ocean-climate forcing. To address this issue, numerous workers have sought to understand ice stream dynamics over longer time-scales using their glacial geomorphology in the palaeo-record. Indeed, our understanding of their geomorphology has grown rapidly in the last three decades, from almost complete ignorance to a detailed knowledge of their geomorphological products. Building on this body of work, this paper uses the glacial geomorphology of 117 ice streams in the North American Laurentide Ice Sheet to reconstruct their activity during its deglaciation ( 22,000 to 7,000 years ago). Ice stream activity was characterised by high variability in both time and space, with ice streams switching on and off in different locations. During deglaciation, we find that their overall number decreased, they occupied a

  4. Binary Component Sorption of Cadmium, and Copper Ions onto Yangtze River Sediments with Different Particle Sizes

    Directory of Open Access Journals (Sweden)

    Jianxin Fan

    2017-11-01

    Full Text Available Sorption is a crucial process that influences immobilization and migration of heavy metals in an aqueous environment. Sediments represent one of the ultimate sinks for heavy metals discharged into water body. Moreover, the particle size of sediments plays an extremely important role in the immobilization of heavy metals. In this study, the sorption and desorption of cadmium (Cd and copper (Cu onto sediments with different particle sizes were investigated to predict the rate and capacity of sorption, to understand their environmental behaviors in an aqueous environment. Batch sorption and kinetic experiments were conducted to obtain the retained amount and rate of Cd and Cu in a binary system. Experimental data were simulated using sorption models to ascertain the sorption capacity and the kinetic rate. Results of European Communities Bureau of Reference (BCR sequential extraction showed the highest concentration of Cd (0.344 mg kg−1, and its distribution varied with sediment particle size and site. Furthermore, most of Cu (approximately 57% to 84% existed as a residual fraction. The sorption of Cu onto six sediments followed a pseudo-first order reaction, whereas that of Cd followed a pseudo-second order reaction. Additionally, the competitive Langmuir model fitted the batch sorption experimental data extremely well. The highest sorption capacities of Cd and Cu reach 0.641 mmol kg−1 and 62.3 mmol kg−1, respectively, on the smallest submerged sediment particles. The amounts of Cu and Cd desorbed (mmol kg−1 increased linearly with the initial concentration increasing. Thus, sediment texture is an important factor that influences the sorption of heavy metal onto sediments.

  5. Gender differences in conceptual understanding of Newtonian mechanics: a UK cross-institution comparison

    International Nuclear Information System (INIS)

    Bates, Simon; Donnelly, Robyn; MacPhee, Cait; Sands, David; Birch, Marion; Walet, Niels R

    2013-01-01

    We present the results of a combined study from three UK universities where we investigate the existence and persistence of a performance gender gap in conceptual understanding of Newtonian mechanics. Using the Force Concept Inventory, we find that students at all three universities exhibit a statistically significant gender gap, with males outperforming females. This gap is narrowed but not eliminated after instruction, using a variety of instructional approaches. Furthermore, we find that before instruction the quartile with the lowest performance on the diagnostic instrument comprises a disproportionately high fraction (∼50%) of the total female cohort. The majority of these students remain in the lowest-performing quartile post-instruction. Analysis of responses to individual items shows that male students outperform female students on practically all items on the instrument. Comparing the performance of the same group of students on end-of-course examinations, we find no statistically significant gender gaps. (paper)

  6. Emerging understanding of the mechanism of action of Bronchial Thermoplasty in asthma.

    Science.gov (United States)

    d'Hooghe, J N S; Ten Hacken, N H T; Weersink, E J M; Sterk, P J; Annema, J T; Bonta, P I

    2018-01-01

    Bronchial Thermoplasty (BT) is an endoscopic treatment for moderate-to-severe asthma patients who are uncontrolled despite optimal medical therapy. Effectiveness of BT has been demonstrated in several randomized clinical trials. However, the asthma phenotype that benefits most of this treatment is unclear, partly because the mechanism of action is incompletely understood. BT was designed to reduce the amount of airway smooth muscle (ASM), but additional direct and indirect effects on airway pathophysiology are expected. This review will provide an overview of the different components of airway pathophysiology including remodeling, with the ASM as the key player. Current concepts in the understanding of BT clinical effectiveness with a focus on its impact on airway remodeling will be reviewed. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  7. The contributions of cognitive neuroscience and neuroimaging to understanding mechanisms of behavior change in addiction.

    Science.gov (United States)

    Morgenstern, Jon; Naqvi, Nasir H; Debellis, Robert; Breiter, Hans C

    2013-06-01

    In the last decade, there has been an upsurge of interest in understanding the mechanisms of behavior change (MOBC) and effective behavioral interventions as a strategy to improve addiction-treatment efficacy. However, there remains considerable uncertainty about how treatment research should proceed to address the MOBC issue. In this article, we argue that limitations in the underlying models of addiction that inform behavioral treatment pose an obstacle to elucidating MOBC. We consider how advances in the cognitive neuroscience of addiction offer an alternative conceptual and methodological approach to studying the psychological processes that characterize addiction, and how such advances could inform treatment process research. In addition, we review neuroimaging studies that have tested aspects of neurocognitive theories as a strategy to inform addiction therapies and discuss future directions for transdisciplinary collaborations across cognitive neuroscience and MOBC research. 2013 APA, all rights reserved

  8. FTIR spectrophotometry, kinetics and adsorption isotherms modeling, ion exchange, and EDX analysis for understanding the mechanism of Cd{sup 2+} and Pb{sup 2+} removal by mango peel waste

    Energy Technology Data Exchange (ETDEWEB)

    Iqbal, Muhammad [Biotechnology Group, Centre for Environment Protection Studies, PCSIR Laboratories Complex, Ferozepur Road, Lahore 54600 (Pakistan)], E-mail: iqbalm@fulbrightweb.org; Saeed, Asma [Biotechnology Group, Centre for Environment Protection Studies, PCSIR Laboratories Complex, Ferozepur Road, Lahore 54600 (Pakistan); Zafar, Saeed Iqbal [School of Biological Sciences, University of Punjab, Lahore 54590 (Pakistan)

    2009-05-15

    Mango peel waste (MPW) was evaluated as a new sorbent for the removal of Cd{sup 2+} and Pb{sup 2+} from aqueous solution. The maximum sorption capacity of Cd{sup 2+} and Pb{sup 2+} was found to be 68.92 and 99.05 mg g{sup -1}, respectively. The kinetics of sorption of both metals was fast, reaching at equilibrium in 60 min. Sorption kinetics and equilibria followed pseudo-second order and Langmuir adsorption isotherm models. FTIR analysis revealed that carboxyl and hydroxyl functional groups were mainly responsible for the sorption of Cd{sup 2+} and Pb{sup 2+}. Chemical modification of MPW for blocking of carboxyl and hydroxyl groups showed that 72.46% and 76.26% removal of Cd{sup 2+} and Pb{sup 2+}, respectively, was due to the involvement of carboxylic group, whereas 26.64% and 23.74% was due to the hydroxyl group. EDX analysis of MPW before and after metal sorption and release of cations (Ca{sup 2+}, Mg{sup 2+}, Na{sup +}, K{sup +}) and proton H{sup +} from MPW with the corresponding uptake of Cd{sup 2+} and Pb{sup 2+} revealed that the main mechanism of sorption was ion exchange. The regeneration experiments showed that the MPW could be reused for five cycles without significant loss in its initial sorption capacity. The study points to the potential of new use of MPW as an effective sorbent for the removal of Cd{sup 2+} and Pb{sup 2+} from aqueous solution.

  9. SORPTION AND SOLUBILITY OF LOW-SHRINKAGE RESIN-BASED DENTAL COMPOSITES

    Directory of Open Access Journals (Sweden)

    Sevda Yantcheva

    2016-04-01

    Full Text Available Background: Resin-based composites are well-established restorative materials. However, these materials may absorb significant amounts of water when exposed to aqueous environments. Sorption and solubility are affecting composite restorations by two different mechanisms; the first is the up taking of water producing an increased weight and the second is the dissolution of materials in water, leading to a weight reduction of the final conditioned samples. Objective: To measure the water sorption and solubility of different low-shrinkage resin-based composites. Six materials were selected: Filtek P60, Filtek Ultimate, SonicFill, Filtek Silorane, Kalore and Venus Diamond. Materials and methods: Five disc specimens were prepared of each material and polymerized with diode light-curing unit. Water sorption and solubility of the different materials were were calculated by means of weighting the samples before and after water immersion and desiccation. Data were statistically analyzed using Shapiro-Wilk One Way Analysis of Variance followed by the Holm-Sidak comparison test . Results: There were significant differences (p<=0.001 between materials regarding sorption and solubility. Regarding sorption F. Silorane showed lowest values, followed by SonicFill, without significant difference between them. Statistical significant differences exist between F. Silorane and F.P60, F. Ultimate, Kalore. Significant differences exist between SonicFill and F. Ultimate. F.Silorane (-0.018 and Kalore (-0.010 showed lowest values of solubility but there were marginal difference among all composites investigated. Conclusions: 1.The material with lowest values of sorption and solubility was F.Silorane. 2. The attained sorption and solubility values for composites are influenced by the differences in resin matrix composition and filler contend. 3. Modifications of dimethacrylate matrix did not minimize significantly sorption and solubility of composites. 4. Besides water

  10. New approach in modeling Cr(VI) sorption onto biomass from metal binary mixtures solutions

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Chang [College of Environmental Science and Engineering, Anhui Normal University, South Jiuhua Road, 189, 241002 Wuhu (China); Chemical Engineering Department, Escola Politècnica Superior, Universitat de Girona, Ma Aurèlia Capmany, 61, 17071 Girona (Spain); Fiol, Núria [Chemical Engineering Department, Escola Politècnica Superior, Universitat de Girona, Ma Aurèlia Capmany, 61, 17071 Girona (Spain); Villaescusa, Isabel, E-mail: Isabel.Villaescusa@udg.edu [Chemical Engineering Department, Escola Politècnica Superior, Universitat de Girona, Ma Aurèlia Capmany, 61, 17071 Girona (Spain); Poch, Jordi [Applied Mathematics Department, Escola Politècnica Superior, Universitat de Girona, Ma Aurèlia Capmany, 61, 17071 Girona (Spain)

    2016-01-15

    In the last decades Cr(VI) sorption equilibrium and kinetic studies have been carried out using several types of biomasses. However there are few researchers that consider all the simultaneous processes that take place during Cr(VI) sorption (i.e., sorption/reduction of Cr(VI) and simultaneous formation and binding of reduced Cr(III)) when formulating a model that describes the overall sorption process. On the other hand Cr(VI) scarcely exists alone in wastewaters, it is usually found in mixtures with divalent metals. Therefore, the simultaneous removal of Cr(VI) and divalent metals in binary mixtures and the interactive mechanism governing Cr(VI) elimination have gained more and more attention. In the present work, kinetics of Cr(VI) sorption onto exhausted coffee from Cr(VI)–Cu(II) binary mixtures has been studied in a stirred batch reactor. A model including Cr(VI) sorption and reduction, Cr(III) sorption and the effect of the presence of Cu(II) in these processes has been developed and validated. This study constitutes an important advance in modeling Cr(VI) sorption kinetics especially when chromium sorption is in part based on the sorbent capacity of reducing hexavalent chromium and a metal cation is present in the binary mixture. - Highlights: • A kinetic model including Cr(VI) reduction, Cr(VI) and Cr(III) sorption/desorption • Synergistic effect of Cu(II) on Cr(VI) elimination included in the model • Model validation by checking it against independent sets of data.

  11. Sorption of perfluoroalkyl substances in sewage sludge.

    Science.gov (United States)

    Milinovic, Jelena; Lacorte, Silvia; Rigol, Anna; Vidal, Miquel

    2016-05-01

    The sorption behaviour of three perfluoroalkyl substances (PFASs) (perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA) and perfluorobutanesulfonic acid (PFBS)) was studied in sewage sludge samples. Sorption isotherms were obtained by varying initial concentrations of PFOS, PFOA and PFBS. The maximum values of the sorption solid-liquid distribution coefficients (Kd,max) varied by almost two orders of magnitude among the target PFASs: 140-281 mL g(-1) for PFOS, 30-54 mL g(-1) for PFOA and 9-18 mL g(-1) for PFBS. Freundlich and linear fittings were appropriate for describing the sorption behaviour of PFASs in the sludge samples, and the derived KF and Kd,linear parameters correlated well. The hydrophobicity of the PFASs was the key parameter that influenced their sorption in sewage sludge. Sorption parameters and log(KOW) were correlated, and for PFOS (the most hydrophobic compound), pH and Ca + Mg status of the sludge controlled the variation in the sorption parameter values. Sorption reversibility was also tested from desorption isotherms, which were also linear. Desorption parameters were systematically higher than the corresponding sorption parameters (up to sixfold higher), thus indicating a significant degree of irreversible sorption, which decreased in the sequence PFOS > PFOA > PFBS.

  12. Stress Biology and Aging Mechanisms: Toward Understanding the Deep Connection Between Adaptation to Stress and Longevity

    Science.gov (United States)

    2014-01-01

    The rate of biological aging is modulated in part by genes interacting with stressor exposures. Basic research has shown that exposure to short-term stress can strengthen cellular responses to stress (“hormetic stress”). Hormetic stress promotes longevity in part through enhanced activity of molecular chaperones and other defense mechanisms. In contrast, prolonged exposure to stress can overwhelm compensatory responses (“toxic stress”) and shorten lifespan. One key question is whether the stressors that are well understood in basic models of aging can help us understand psychological stressors and human health. The psychological stress response promotes regulatory changes important in aging (e.g., increases in stress hormones, inflammation, oxidative stress, insulin). The negative effects of severe stress are well documented in humans. Potential positive effects of acute stress (stress resistance) are less studied, especially at the cellular level. Can stress resistance slow the rate of aging in humans, as it does in model organisms? If so, how can we promote stress resistance in humans? We urge a new research agenda embracing the continuum from cellular stress to psychological stress, using basic and human research in tandem. This will require interdisciplinary novel approaches that hold much promise for understanding and intervening in human chronic disease. PMID:24833580

  13. Stress biology and aging mechanisms: toward understanding the deep connection between adaptation to stress and longevity.

    Science.gov (United States)

    Epel, Elissa S; Lithgow, Gordon J

    2014-06-01

    The rate of biological aging is modulated in part by genes interacting with stressor exposures. Basic research has shown that exposure to short-term stress can strengthen cellular responses to stress ("hormetic stress"). Hormetic stress promotes longevity in part through enhanced activity of molecular chaperones and other defense mechanisms. In contrast, prolonged exposure to stress can overwhelm compensatory responses ("toxic stress") and shorten lifespan. One key question is whether the stressors that are well understood in basic models of aging can help us understand psychological stressors and human health. The psychological stress response promotes regulatory changes important in aging (e.g., increases in stress hormones, inflammation, oxidative stress, insulin). The negative effects of severe stress are well documented in humans. Potential positive effects of acute stress (stress resistance) are less studied, especially at the cellular level. Can stress resistance slow the rate of aging in humans, as it does in model organisms? If so, how can we promote stress resistance in humans? We urge a new research agenda embracing the continuum from cellular stress to psychological stress, using basic and human research in tandem. This will require interdisciplinary novel approaches that hold much promise for understanding and intervening in human chronic disease. © The Author 2014. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  14. Smartphone users: Understanding how security mechanisms are perceived and new persuasive methods

    Science.gov (United States)

    Alsaleh, Mansour; Alomar, Noura; Alarifi, Abdulrahman

    2017-01-01

    Protecting smartphones against security threats is a multidimensional problem involving human and technological factors. This study investigates how smartphone users’ security- and privacy-related decisions are influenced by their attitudes, perceptions, and understanding of various security threats. In this work, we seek to provide quantified insights into smartphone users’ behavior toward multiple key security features including locking mechanisms, application repositories, mobile instant messaging, and smartphone location services. To the best of our knowledge, this is the first study that reveals often unforeseen correlations and dependencies between various privacy- and security-related behaviors. Our work also provides evidence that making correct security decisions might not necessarily correlate with individuals’ awareness of the consequences of security threats. By comparing participants’ behavior and their motives for adopting or ignoring certain security practices, we suggest implementing additional persuasive approaches that focus on addressing social and technological aspects of the problem. On the basis of our findings and the results presented in the literature, we identify the factors that might influence smartphone users’ security behaviors. We then use our understanding of what might drive and influence significant behavioral changes to propose several platform design modifications that we believe could improve the security levels of smartphones. PMID:28297719

  15. Smartphone users: Understanding how security mechanisms are perceived and new persuasive methods.

    Science.gov (United States)

    Alsaleh, Mansour; Alomar, Noura; Alarifi, Abdulrahman

    2017-01-01

    Protecting smartphones against security threats is a multidimensional problem involving human and technological factors. This study investigates how smartphone users' security- and privacy-related decisions are influenced by their attitudes, perceptions, and understanding of various security threats. In this work, we seek to provide quantified insights into smartphone users' behavior toward multiple key security features including locking mechanisms, application repositories, mobile instant messaging, and smartphone location services. To the best of our knowledge, this is the first study that reveals often unforeseen correlations and dependencies between various privacy- and security-related behaviors. Our work also provides evidence that making correct security decisions might not necessarily correlate with individuals' awareness of the consequences of security threats. By comparing participants' behavior and their motives for adopting or ignoring certain security practices, we suggest implementing additional persuasive approaches that focus on addressing social and technological aspects of the problem. On the basis of our findings and the results presented in the literature, we identify the factors that might influence smartphone users' security behaviors. We then use our understanding of what might drive and influence significant behavioral changes to propose several platform design modifications that we believe could improve the security levels of smartphones.

  16. Understanding dental CAD/CAM for restorations--accuracy from a mechanical engineering viewpoint.

    Science.gov (United States)

    Tapie, Laurent; Lebon, Nicolas; Mawussi, Bernardin; Fron-Chabouis, Hélène; Duret, Francois; Attal, Jean-Pierre

    2015-01-01

    As is the case in the field of medicine, as well as in most areas of daily life, digital technology is increasingly being introduced into dental practice. Computer-aided design/ computer-aided manufacturing (CAD/CAM) solutions are available not only for chairside practice but also for creating inlays, crowns, fixed partial dentures (FPDs), implant abutments, and other dental prostheses. CAD/CAM dental practice can be considered as the handling of devices and software processing for the almost automatic design and creation of dental restorations. However, dentists who want to use dental CAD/CAM systems often do not have enough information to understand the variations offered by such technology practice. Knowledge of the random and systematic errors in accuracy with CAD/CAM systems can help to achieve successful restorations with this technology, and help with the purchasing of a CAD/CAM system that meets the clinical needs of restoration. This article provides a mechanical engineering viewpoint of the accuracy of CAD/ CAM systems, to help dentists understand the impact of this technology on restoration accuracy.

  17. Investigating and improving student understanding of the expectation values of observables in quantum mechanics

    Science.gov (United States)

    Marshman, Emily; Singh, Chandralekha

    2017-07-01

    The expectation value of an observable is an important concept in quantum mechanics since measurement outcomes are, in general, probabilistic and we only have information about the probability distribution of measurement outcomes in a given quantum state of a system. However, we find that upper-level undergraduate and PhD students in physics have both conceptual and procedural difficulties when determining the expectation value of a physical observable in a given quantum state in terms of the eigenstates and eigenvalues of the corresponding operator, especially when using Dirac notation. Here we first describe the difficulties that these students have with determining the expectation value of an observable in Dirac notation. We then discuss how the difficulties found via student responses to written surveys and individual interviews were used as a guide in the development of a quantum interactive learning tutorial (QuILT) to help students develop a good grasp of the expectation value. The QuILT strives to help students integrate conceptual understanding and procedural skills to develop a coherent understanding of the expectation value. We discuss the effectiveness of the QuILT in helping students learn this concept from in-class evaluations.

  18. Smartphone users: Understanding how security mechanisms are perceived and new persuasive methods.

    Directory of Open Access Journals (Sweden)

    Mansour Alsaleh

    Full Text Available Protecting smartphones against security threats is a multidimensional problem involving human and technological factors. This study investigates how smartphone users' security- and privacy-related decisions are influenced by their attitudes, perceptions, and understanding of various security threats. In this work, we seek to provide quantified insights into smartphone users' behavior toward multiple key security features including locking mechanisms, application repositories, mobile instant messaging, and smartphone location services. To the best of our knowledge, this is the first study that reveals often unforeseen correlations and dependencies between various privacy- and security-related behaviors. Our work also provides evidence that making correct security decisions might not necessarily correlate with individuals' awareness of the consequences of security threats. By comparing participants' behavior and their motives for adopting or ignoring certain security practices, we suggest implementing additional persuasive approaches that focus on addressing social and technological aspects of the problem. On the basis of our findings and the results presented in the literature, we identify the factors that might influence smartphone users' security behaviors. We then use our understanding of what might drive and influence significant behavioral changes to propose several platform design modifications that we believe could improve the security levels of smartphones.

  19. Towards understanding the mechanisms and the kinetics of nanoparticle penetration through protective gloves

    International Nuclear Information System (INIS)

    Vinches, L; Boutrigue, N; Zemzem, M; Hallé, S; Peyrot, C; Lemarchand, L; Wilkinson, K J; Tufenkji, N

    2015-01-01

    Parallel to the increased use of engineered nanoparticles (ENP) in the formulation of commercial products or in medicine, numerous health and safety agencies have recommended the application of the precautionary principle to handle ENP; namely, the recommendation to use protective gloves against chemicals. However, recent studies reveal the penetration of titanium dioxide nanoparticles through nitrile rubber protective gloves in conditions simulating occupational use. This project is designed to understand the links between the penetration of gold nanoparticles (nAu) through nitrile rubber protective gloves and the mechanical and physical behaviour of the elastomer material subjected to conditions simulating occupational use (i.e., mechanical deformations (MD) and sweat). Preliminary analyses show that nAu suspensions penetrate selected glove materials after exposure to prolonged (3 hours) dynamic deformations. Significant morphological changes are observed on the outer surface of the glove sample; namely, the number and the surface of the micropores on the surface increase. Moreover, nitrile rubber protective gloves are also shown to be sensitive to the action of nAu suspension and to the action of the saline solution used to simulate sweat (swelling). (paper)

  20. Understanding the mechanisms of familiar voice-identity recognition in the human brain.

    Science.gov (United States)

    Maguinness, Corrina; Roswandowitz, Claudia; Von Kriegstein, Katharina

    2018-03-31

    Humans have a remarkable skill for voice-identity recognition: most of us can remember many voices that surround us as 'unique'. In this review, we explore the computational and neural mechanisms which may support our ability to represent and recognise a unique voice-identity. We examine the functional architecture of voice-sensitive regions in the superior temporal gyrus/sulcus, and bring together findings on how these regions may interact with each other, and additional face-sensitive regions, to support voice-identity processing. We also contrast findings from studies on neurotypicals and clinical populations which have examined the processing of familiar and unfamiliar voices. Taken together, the findings suggest that representations of familiar and unfamiliar voices might dissociate in the human brain. Such an observation does not fit well with current models for voice-identity processing, which by-and-large assume a common sequential analysis of the incoming voice signal, regardless of voice familiarity. We provide a revised audio-visual integrative model of voice-identity processing which brings together traditional and prototype models of identity processing. This revised model includes a mechanism of how voice-identity representations are established and provides a novel framework for understanding and examining the potential differences in familiar and unfamiliar voice processing in the human brain. Copyright © 2018. Published by Elsevier Ltd.

  1. The use of micro-/milli-fluidics to better understand the mechanisms behind deep venous thrombosis

    Science.gov (United States)

    Schofield, Zoe; Alexiadis, Alessio; Brill, Alexander; Nash, Gerard; Vigolo, Daniele

    2016-11-01

    Deep venous thrombosis (DVT) is a dangerous and painful condition in which blood clots form in deep veins (e.g., femoral vein). If these clots become unstable and detach from the thrombus they can be delivered to the lungs resulting in a life threatening complication called pulmonary embolism (PE). Mechanisms of clot development in veins remain unclear but researchers suspect that the specific flow patterns in veins, especially around the valve flaps, play a fundamental role. Here we show how it is now possible to mimic the current murine model by developing micro-/milli-fluidic experiments. We exploited a novel detection technique, ghost particle velocimetry (GPV), to analyse the velocity profiles for various geometries. These vary from regular microfluidics with a rectangular cross section with a range of geometries (mimicking the presence of side and back branches in veins, closed side branch and flexible valves) to a more accurate venous representation with a 3D cylindrical geometry obtained by 3D printing. In addition to the GPV experiments, we analysed the flow field developing in these geometries by using computational fluid dynamic simulations to develop a better understanding of the mechanisms behind DVT. ZS gratefully acknowledges financial support from the EPSRC through a studentship from the Sci-Phy-4-Health Centre for Doctoral Training (EP/L016346/1).

  2. Understanding the molecular mechanisms of human microtia via a pig model of HOXA1 syndrome

    Directory of Open Access Journals (Sweden)

    Ruimin Qiao

    2015-06-01

    Full Text Available Microtia is a congenital malformation of the outer ears. Although both genetic and environmental components have been implicated in microtia, the genetic causes of this innate disorder are poorly understood. Pigs have naturally occurring diseases comparable to those in humans, providing exceptional opportunity to dissect the molecular mechanism of human inherited diseases. Here we first demonstrated that a truncating mutation in HOXA1 causes a monogenic disorder of microtia in pigs. We further performed RNA sequencing (RNA-Seq analysis on affected and healthy pig embryos (day 14.25. We identified a list of 337 differentially expressed genes (DEGs between the normal and mutant samples, shedding light on the transcriptional network involving HOXA1. The DEGs are enriched in biological processes related to cardiovascular system and embryonic development, and neurological, renal and urological diseases. Aberrant expressions of many DEGs have been implicated in human innate deformities corresponding to microtia-associated syndromes. After applying three prioritizing algorithms, we highlighted appealing candidate genes for human microtia from the 337 DEGs. We searched for coding variants of functional significance within six candidate genes in 147 microtia-affected individuals. Of note, we identified one EVC2 non-synonymous mutation (p.Asp1174Asn as a potential disease-implicating variant for a human microtia-associated syndrome. The findings advance our understanding of the molecular mechanisms underlying human microtia, and provide an interesting example of the characterization of human disease-predisposing variants using pig models.

  3. PHOSPHORUS SORPTION ISOTHERMS AND EXTERNAL ...

    African Journals Online (AJOL)

    ACSS

    both models fitted well with the P sorption data of the soils. The adsorption maxima (Xm) and bonding energy (b) values of the soils derived from Langmuir model were in the ranges of 560-833 mg P kg-1 and 0.16-20 L kg-1, respectively. The Freundlich capacity factor (Kf) ranged from 237 to 1200 mg kg-1.The EPRs of the ...

  4. Next Steps Toward Understanding Human Habitation of Space: Environmental Impacts and Mechanisms

    Science.gov (United States)

    Globus, Ruth

    2016-01-01

    factor alone implying at least some shared underlying mechanisms. Thus, both ground based and spaceflight research utilizing model organisms provide the opportunity to better understand environmental factors and biological mechanisms that contribute to human health and survival in space.

  5. Raman analysis of DLC coated engine components with complex shape: Understanding wear mechanisms

    International Nuclear Information System (INIS)

    Jaoul, C.; Jarry, O.; Tristant, P.; Merle-Mejean, T.; Colas, M.; Dublanche-Tixier, C.; Jacquet, J.-M.

    2009-01-01

    Hydrogenated amorphous carbon (a-C:H) films were deposited on flat samples and engine components using an industrial scale reactor. Characterization of the coating allowed validating its application on engine parts due to high hardness (32 GPa) and high level of adhesion achieved using sublayers. The original approach of this work concerned the use of Raman analysis not only on flat samples after tribometer tests but also directly on coated engine parts with complex shape (like cam/follower system), in order to understand wear mechanisms occurring in motorsport engines. As wear could lead to a coating thickness decrease, a particular attention was paid on the Raman signal of the sublayers. Among the different values extracted from Raman spectrum to characterize structural organization, the value of G peak intensity appeared as a criterion of validity of analyses because it is directly linked to the remaining thickness of the a-C:H layer. For flat samples tested on ball-on-disc tribometer, structure of a-C:H film observed by Raman spectroscopy in the wear track remained stable in depth. Then, a-C:H coated engine components were studied before and after working in real conditions. Two different wear mechanisms were identified. The first one did not show any structural modification of the bulk a-C:H layer. In the second one, the high initial roughness of samples (R t = 1.15 μm) lead to coating delaminations after sliding. Massive graphitization which decreases drastically mechanical properties of the coatings was observed by Raman analyses on the contact area. The increase of the temperature on rough edges of the scratches could explain this graphitization.

  6. Features of Knowledge Building in Biology: Understanding Undergraduate Students' Ideas about Molecular Mechanisms.

    Science.gov (United States)

    Southard, Katelyn; Wince, Tyler; Meddleton, Shanice; Bolger, Molly S

    2016-01-01

    Research has suggested that teaching and learning in molecular and cellular biology (MCB) is difficult. We used a new lens to understand undergraduate reasoning about molecular mechanisms: the knowledge-integration approach to conceptual change. Knowledge integration is the dynamic process by which learners acquire new ideas, develop connections between ideas, and reorganize and restructure prior knowledge. Semistructured, clinical think-aloud interviews were conducted with introductory and upper-division MCB students. Interviews included a written conceptual assessment, a concept-mapping activity, and an opportunity to explain the biomechanisms of DNA replication, transcription, and translation. Student reasoning patterns were explored through mixed-method analyses. Results suggested that students must sort mechanistic entities into appropriate mental categories that reflect the nature of MCB mechanisms and that conflation between these categories is common. We also showed how connections between molecular mechanisms and their biological roles are part of building an integrated knowledge network as students develop expertise. We observed differences in the nature of connections between ideas related to different forms of reasoning. Finally, we provide a tentative model for MCB knowledge integration and suggest its implications for undergraduate learning. © 2016 K. Southard et al. CBE—Life Sciences Education © 2016 The American Society for Cell Biology. This article is distributed by The American Society for Cell Biology under license from the author(s). It is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

  7. Sorption of small amounts of europium(III) on iron(III) hydroxide and oxide

    International Nuclear Information System (INIS)

    Music, S.; Gessner, M.; Wolf, R.H.H.

    1979-01-01

    The sorption of small amounts of europium(III) on iron(III) hydroxide and oxide has been studied as a function of pH. The mechanism of sorption is discussed. Optimum conditions have been found for the preconcentration of small or trace amounts of europium(III) by iron(III) hydroxide and oxide. The influence of complexing agents (EDTA, oxalate, tartrate and 5-sulfosalicylic acid) on the sorption of small amounts of europium(III) on iron(III) oxide has also been studied. (author)

  8. Nonlinear chemical sorption isotherms in the assessment of nuclear fuel waste disposal

    International Nuclear Information System (INIS)

    Walker, J.R.; LeNeveu, D.M.

    1987-01-01

    Radionuclides emplaced in an underground disposal vault can possibly migrate from the vault, and through the geosphere, to enter Man's environment. Chemical sorption is a primary mechanism for retarding this migration. The effects of nonlinear chemical sorption isotherms on radionuclide transport are discussed. A method is given by which nonlinear isotherms can be approximated by the linear sorption isotherm used in the vault submodel. The relevance of nonlinear isotherms to transport in the geosphere is discussed, and it is shown that the linear isotherm model is conservative for deep geologic disposal. 22 refs

  9. Understanding the hydrolysis mechanism of ethyl acetate catalyzed by an aqueous molybdocene: a computational chemistry investigation.

    Science.gov (United States)

    Tílvez, Elkin; Cárdenas-Jirón, Gloria I; Menéndez, María I; López, Ramón

    2015-02-16

    , in general, the information reported here could be of interest in designing new catalysts and understanding the reaction mechanism of these and other metal-catalyzed hydrolysis reactions.

  10. Effects of lead, cadmium, chromium, and arsenic on the sorption of lindane and norfloxacin by river biofilms, particles, and sediments.

    Science.gov (United States)

    Dong, Deming; Li, Lufeng; Zhang, Liwen; Hua, Xiuyi; Guo, Zhiyong

    2018-02-01

    The sorption of both classic and emerging organic contaminants onto aquatic solids is a critical process that controls their fate in natural waters. Sorption is affected by numerous factors, including coexisting heavy metals. The mechanisms of the influence of heavy metals, especially those occurring in acid radical anions, are still unclear. Here, the effects of Pb, Cd, Cr, and As on the sorption of lindane and norfloxacin (NOR) onto natural biofilms, suspended particles, and sediments from one river were investigated following batch equilibration methods. In addition, changes in representative components that have important roles in sorption from these solids in the presence and absence of metals were characterized by spectrum analyses. The results indicated that sorption of lindane and NOR on the three solids in the absence of heavy metals was highly linear and nonlinear, respectively. Pb and Cd promoted and Cr and As suppressed hydrophobic lindane sorption on the three solids. This was because Pb and Cd enhanced but Cr and As weakened the hydrophobicity of these solids. Pb, Cd, Cr, and As decreased NOR sorption on sediments and suspended particles at pH 5.7~6.3. This was due to electrostatic competition between cationic Pb/Cd and NORH 2 + , and the combination of Cr/As acid radicals with NORH 2 + , which suppressed its ion-exchange adsorption. Pb, Cd, Cr, and As generally increased the sorption of NOR onto the biofilms at pH 5.7~6.3. Pb and Cd strengthened the flocculation of dissolved organic matter combined with NORH 2 + onto the biofilms. Cr and As enhanced the hydrophilicity of biofilms, and then increased their sorption of NOR with active hydrophilic groups. The mechanisms of how different heavy metals affect NOR sorption by biofilms were more complicated than the mechanisms affecting lindane sorption, as well as by sediments and particles.

  11. Applicability of microautoradiography to sorption studies

    International Nuclear Information System (INIS)

    Thompson, J.L.; Wolfsberg, K.

    1979-01-01

    The technique of microautoradiography was applied to the study of the sorption of uranium and americium on five rock types which exist at the Nevada Test Site. It was found that autoradiograms could be prepared in a few days which would allow the specific minerals responsible for sorption to be identified. Furthermore, the state of aggregation of the sorbed species was clearly indicated. It was concluded that microautoradiography was a useful adjunct to currently used methods for studying sorption of certain radionuclides

  12. Effect of solution chemistry on arsenic sorption by Fe- and Al-based drinking-water treatment residuals.

    Science.gov (United States)

    Nagar, Rachana; Sarkar, Dibyendu; Makris, Konstantinos C; Datta, Rupali

    2010-02-01

    Drinking-water treatment residual (WTR) have been proposed as a low-cost alternative sorbent for arsenic (As) - contaminated aquatic and soil systems. However, limited information exists regarding the effect of solution chemistry on As sorption by WTR. A batch incubation study was carried out to investigate the effect of solution pH (3-9) on As(V) sorption by Al- and Fe-based WTR as a function of solid: solution ratio (SSR) and initial As concentration. The effect of competing ligands (phosphate-P(V) and sulfate), and complexing metal (calcium) on As(V) sorption envelopes at the optimum SSR (200gL(-1)) was also evaluated. At 200gL(-1) SSR, maximum As(V) sorption ( approximately 100%) exhibited by the Fe-WTR was limited at the pH range of 3-7, whereas, the Al-WTR demonstrated approximately 100% As(V) sorption in the entire pH range. The negative pH effect on As(V) sorption became more pronounced with increasing initial As concentrations and decreasing SSR. Sorption of As(V) by surfaces of both WTR decreased in the presence of P(V), exhibiting strong pH dependence. Only for the Fe-WTR, increased dissolved iron concentrations at pH>7 supported a Fe-hydroxide reductive dissolution mechanism to account for the enhanced As sorption at alkaline pH. Addition of sulfate did not influence As(V) sorption by both WTR. A cooperative effect of calcium on As(V) sorption was observed at alkaline pH due to the formation of a calcium-arsenate phase. The constant capacitance model provided reasonable fits to the sorption envelope data for both single ion and binary ion (As and P) systems, but it was unable to explain the enhanced As sorption by the Fe-WTR at pH>7.

  13. Sorption comparison between phenanthrene and its degradation intermediates, 9,10-phenanthrenequinone and 9-phenanthrol in soils/sediments.

    Science.gov (United States)

    Xiao, Di; Pan, Bo; Wu, Min; Liu, Ying; Zhang, Di; Peng, Hongbo

    2012-01-01

    The degradation intermediates of phenanthrene (PHE) may have increased health risks to organisms than PHE. Therefore, environmental fate and risk assessment studies should take into considerations of PHE degradation products. This study compared the sorption properties of PHE and its degradation intermediates, 9,10-phenanthrenequinone (PQN) and 9-phenanthrol (PTR) in soils, sediments and soil components. A relationship between organic carbon content (f(OC)) and single-point sorption coefficient (logK(d)) was observed for all three chemicals in 10 soils/sediments. The large intercept in the logf(OC)-logK(d) regression for PTR indicated that inorganic fractions control PTR sorption in soils/sediments. No relationship between specific surface area and K(d) was observed. This result indicated that determination of surface area based on gas sorption could not identify surface properties for PHE, PQN, and PTR sorption and thus provide limit information on sorption mechanisms. The high sorption and strong nonlinearity (low n values) of PTR in comparison to PHE suggested that the mobility of PTR could be lower than PHE. Increased mobility of PQN compared with PHE may be expected in soils/sediments because of PQN lower sorption. The varied sorption properties of the three chemicals suggested that their environmental risks should be assessed differently. Copyright © 2011 Elsevier Ltd. All rights reserved.

  14. The effect of salinity on the sorption of cadmium ions from aqueous medium on Fe(III-sepiolite

    Directory of Open Access Journals (Sweden)

    Habish Amal Juma

    2015-01-01

    Full Text Available In this study, the sorption of cadmium ions onto sepiolite modified with hydrated iron(III oxide, Fe(III-sepiolite, has been investigated in natural seawater, artificial seawater, aqueous solution of NaCl of the same ionic strength as the seawater and distilled water. The sorption experiments were performed as a function of the initial solution pH value, the initial metal concentration and the equilibration time, using the batch method. The equilibrium sorption data were analyzed by the Langmuir, Freundlich and Sips isotherm models and the kinetics of sorption was analyzed using the pseudo-first-order and the pseudo-second-order kinetic models. The maximum sorption capacity and the strength of the sorbate-sorbent bonds at initial pH = 7 were found to decrease in the following order: distilled water > NaCl solution > artificial seawater > natural seawater. The values of parameter nS in the Sips model, which fitted the equilibrium sorption results best, showed that heterogeneity of the sorbent surface was the highest in distilled water and the lowest in natural seawater. The sorption kinetic data fitted well with the pseudo-second-order kinetic model, which suggests that the rate-limiting step in Cd2+ sorption onto Fe(III-sepiolite could be chemisorption. The low desorption percentage in both distilled water and 0.001 M HNO3 indicated that sorption occurred mainly by chemisorption mechanisms. [Projekat Ministarstva nauke republike srbije, br. III 45019

  15. Optimization of Nano-Carbon Materials for Hydrogen Sorption

    Energy Technology Data Exchange (ETDEWEB)

    Yakobson, Boris I [Rice University

    2013-08-02

    Research undertaken has added to the understanding of several critical areas, by providing both negative answers (and therefore eliminating expensive further studies of unfeasible paths) and positive feasible options for storage. Theoretical evaluation of the early hypothesis of storage on pure carbon single wall nanotubes (SWNT) has been scrutinized with the use of comprehensive computational methods (and experimental tests by the Center partners), and demonstrated that the fundamentally weak binding energy of hydrogen is not sufficiently enhanced by the SWNT curvature or even defects, which renders carbon nanotubes not practical media. More promising direction taken was towards 3-dimensional architectures of high porosity where concurrent attraction of H2 molecule to surrounding walls of nano-scale cavities can double or even triple the binding energy and therefore make hydrogen storage feasible even at ambient or somewhat lower temperatures. An efficient computational tool has been developed for the rapid capacity assessment combining (i) carbon-foam structure generation, (ii) accurate empirical force fields, with quantum corrections for the lightweight H2, and (iii) grand canonical Monte Carlo simulation. This made it possible to suggest optimal designs for carbon nanofoams, obtainable via welding techniques from SWNT or by growth on template-zeolites. As a precursor for 3D-foams, we have investigated experimentally the synthesis of VANTA (Vertically Aligned NanoTube Arrays). This can be used for producing nano-foams. On the other hand, fluorination of VANTA did not show promising increase of hydrogen sorption in several tests and may require further investigation and improvements. Another significant result of this project was in developing a fundamental understanding of the elements of hydrogen spillover mechanisms. The benefit of developed models is the ability to foresee possible directions for further improvement of the spillover mechanism.

  16. Moisture sorption in naturally coloured cotton fibres

    Science.gov (United States)

    Ceylan, Ö.; De Clerck, K.

    2017-10-01

    Increasing environmental concerns have stimulated an interest in naturally coloured cottons. As many commercial and technical performance aspects of cotton fibres are influenced by their response towards atmospheric humidity, an in-depth research on moisture sorption behaviour of these fibres using dynamic vapour sorption is carried out. Significant differences were observed in sorption capacity and hysteresis behaviour of brown and green cotton fibres. These differences are mainly attributed to the variations in maturity and crystallinity index of the fibres. This study provides valuable insights into the moisture sorption behaviour of naturally coloured cotton fibres.

  17. Strontium sorption on Savannah River Plant soils

    International Nuclear Information System (INIS)

    Hoeffner, S.L.

    1984-12-01

    A laboratory study of strontium-85 sorption was conducted using Savannah River Plant soil and groundwater from the low-level waste burial ground. Systematic variation of soil and water composition indicates that strontium sorption is most strongly a function of pH. Changes in clay content and in K + , Ca 2+ , or Mg 2+ concentrations influence strontium sorption indirectly through the slight pH changes which result. The ions Na + , Cl - , and NO 3 - have no effect. Ferrous ion, added to groundwater to simulate the conditions of water at the bottom of waste trenches, did not account for low strontium sorption observed with some trench waters

  18. Understanding the molecular mechanism of pulse current charging for stable lithium-metal batteries.

    Science.gov (United States)

    Li, Qi; Tan, Shen; Li, Linlin; Lu, Yingying; He, Yi

    2017-07-01

    High energy and safe electrochemical storage are critical components in multiple emerging fields of technologies. Rechargeable lithium-metal batteries are considered to be promising alternatives for current lithium-ion batteries, leading to as much as a 10-fold improvement in anode storage capacity (from 372 to 3860 mAh g -1 ). One of the major challenges for commercializing lithium-metal batteries is the reliability and safety issue, which is often associated with uneven lithium electrodeposition (lithium dendrites) during the charging stage of the battery cycling process. We report that stable lithium-metal batteries can be achieved by simply charging cells with square-wave pulse current. We investigated the effects of charging period and frequency as well as the mechanisms that govern this process at the molecular level. Molecular simulations were performed to study the diffusion and the solvation structure of lithium cations (Li + ) in bulk electrolyte. The model predicts that loose association between cations and anions can enhance the transport of Li + and eventually stabilize the lithium electrodeposition. We also performed galvanostatic measurements to evaluate the cycling behavior and cell lifetime under pulsed electric field and found that the cell lifetime can be more than doubled using certain pulse current waveforms. Both experimental and simulation results demonstrate that the effectiveness of pulse current charging on dendrite suppression can be optimized by choosing proper time- and frequency-dependent pulses. This work provides a molecular basis for understanding the mechanisms of pulse current charging to mitigating lithium dendrites and designing pulse current waveforms for stable lithium-metal batteries.

  19. Uranyl sorption onto alumina

    International Nuclear Information System (INIS)

    Jacobsson, A.M.M.

    1997-01-01

    The mechanism for the adsorption of uranyl onto alumina from aqueous solution was studied experimentally and the data were modeled using a triple layer surface complexation model. The experiments were carried out at low uranium concentrations (9 x 10 -11 --5 x 10 -8 M) in a CO 2 free environment at varying electrolyte concentrations (0.01--1 M) and pH (4.5--12). The first and second acid dissociation constants, pK a1 and pK a2 , of the alumina surface were determined from potentiometric titrations to be 7.2 ± 0.6 and 11.2 ± 0.4, respectively. The adsorption of uranium was found to be independent of the electrolyte concentration. The authors therefore conclude that the uranium binds as an inner sphere complex. The results were modeled using the code FITEQL. Two reactions of uranium with the surface were needed to fit the data, one forming a uranyl complex with a single surface hydroxyl and the other forming a bridged or bidentate complex reacting with two surface hydroxyls of the alumina. There was no evidence from these experiments of site heterogeneity. The constants used for the reactions were based in part on predictions made utilizing the Hard Soft Acid Base, HSAB, theory, relating the surface complexation constants to the hydrolysis of the sorbing metal ion and the acid dissociation constants of the mineral oxide surface

  20. Nitrate sorption on activated carbon modified with CaCl2: Equilibrium, isotherms and kinetics

    Directory of Open Access Journals (Sweden)

    Zanella Odivan

    2015-01-01

    Full Text Available In this study, nitrate (NO3- removal from aqueous solutions was investigated using granular activated carbon (GAC modified with CaCl2. Batch sorption studies were performed as a function of sorbent dose, initial nitrate concentration and pH. Sorption was maximized between pH 3 and 9. Studies on the effect of pH showed that the ion exchange mechanism might be involved in the sorption process. The percentage of nitrate removed increased with increasing sorbent concentration, and the ideal sorbent dose was found to be 20 g•L-1. Four isotherm models-Langmuir, Freundlich, Redlich-Peterson and Sips-were used to fit the experimental data. The Redlich-Peterson isotherm model explained the sorption process well and showed the best coefficient of determination (0.9979 and Chi-square test statistic (0.0079. Using the Sips isotherm model, the sorption capacity (qe was found to be 1.93 mg nitrate per g of sorbent. Kinetic experiments indicated that sorption was a fast process, reaching equilibrium within 120 min. The nitrate sorption kinetic data were successfully fitted to a pseudo-second-order kinetic model. The overall results demonstrated potential applications of modified GAC for nitrate removal from aqueous solutions.

  1. [Surface Property and Sorption Characteristics of Phosphorus onto Surface Sediments in Sanggou Bay].

    Science.gov (United States)

    Zhu, Jia-mei; Cao, Xiao-yan; Liu, Su-mei; Wang, Li-sha; Yang, Gui-peng; Ge, Cheng-feng; Lu, Min

    2016-02-15

    Kinetic curves and isotherms were investigated to study the sorption mechanism of phosphorus onto the sediments of Sanggou Bay, together with the surface charge properties of sediments and the forms of phosphorus studied. The results showed that the sorption including a fast process and a slow one, and could be described by a two-compartment first order equation. The thermodynamic isotherms were well fitted with a modified Langmuir equation. The maximum adsorption capacity was larger in summer than in spring, and the smaller particle size was favorable to the sorption. The maximum adsorption capacities (Qm) were 0.0471-0.1230 mg x g(-1), and the zero equilibrium phosphorus concentration (EPC0) of the sediments ranged from 0.0596 mg x L(-1) to 0.1927 mg x L(-1), which indicated that the sediments from Sanggou Bay were sources of phosphorus. Inorganic phosphorus (IP) was the main form of total phosphorus (TP). The contents of exchangeable or loosely absorbed P and Fe-bound P increased significantly in the samples after sorption. The sorption process involved physical sorption and chemical sorption, with the former being the predominant.

  2. Phenanthrene sorption with heterogeneous organic matter in a landfill aquifer material

    Science.gov (United States)

    Karapanagioti, H.K.; Sabatini, D.A.; Kleineidam, S.; Grathwohl, P.; Ligouis, B.

    1999-01-01

    Phenanthrene was used as a model chemical to study the sorption properties of Canadian River Alluvium aquifer material. Both equilibrium and kinetic sorption processes were evaluated through batch studies. The bulk sample was divided into subsamples with varying properties such as particle size, organic content, equilibration time, etc. in order to determine the effect of these properties on resulting sorption parameters. The data have been interpreted and the effect of experimental variables was quantified using the Freundlich isotherm model and a numerical solution of Fick's 2nd law in porous media. Microscopic organic matter characterization proved to be a valuable tool for explaining the results. Different organic matter properties and sorption mechanisms were observed for each soil subsample. Samples containing coal particles presented high Koc values. Samples with organic matter dominated by organic coatings on quartz grains presented low Koc values and contained a high percentage of fast sorption sites. The numerical solution of Fick's 2ndlaw requires the addition of two terms (fast and slow) in order to fit the kinetics of these heterogeneous samples properly. These results thus demonstrate the need for soil organic matter characterization in order to predict and explain the sorption properties of a soil sample containing heterogeneous organic matter and also the difficulty and complexity of modeling sorption in such samples.

  3. Understanding creep in sandstone reservoirs - theoretical deformation mechanism maps for pressure solution in granular materials

    Science.gov (United States)

    Hangx, Suzanne; Spiers, Christopher

    2014-05-01

    Subsurface exploitation of the Earth's natural resources removes the natural system from its chemical and physical equilibrium. As such, groundwater extraction and hydrocarbon production from subsurface reservoirs frequently causes surface subsidence and induces (micro)seismicity. These effects are not only a problem in onshore (e.g. Groningen, the Netherlands) and offshore hydrocarbon fields (e.g. Ekofisk, Norway), but also in urban areas with extensive groundwater pumping (e.g. Venice, Italy). It is known that fluid extraction inevitably leads to (poro)elastic compaction of reservoirs, hence subsidence and occasional fault reactivation, and causes significant technical, economic and ecological impact. However, such effects often exceed what is expected from purely elastic reservoir behaviour and may continue long after exploitation has ceased. This is most likely due to time-dependent compaction, or 'creep deformation', of such reservoirs, driven by the reduction in pore fluid pressure compared with the rock overburden. Given the societal and ecological impact of surface subsidence, as well as the current interest in developing geothermal energy and unconventional gas resources in densely populated areas, there is much need for obtaining better quantitative understanding of creep in sediments to improve the predictability of the impact of geo-energy and groundwater production. The key problem in developing a reliable, quantitative description of the creep behaviour of sediments, such as sands and sandstones, is that the operative deformation mechanisms are poorly known and poorly quantified. While grain-scale brittle fracturing plus intergranular sliding play an important role in the early stages of compaction, these time-independent, brittle-frictional processes give way to compaction creep on longer time-scales. Thermally-activated mass transfer processes, like pressure solution, can cause creep via dissolution of material at stressed grain contacts, grain

  4. Towards Understanding the Catalytic Mechanism of Human Paraoxonase 1: Experimental and In Silico Mutagenesis Studies.

    Science.gov (United States)

    Tripathy, Rajan K; Aggarwal, Geetika; Bajaj, Priyanka; Kathuria, Deepika; Bharatam, Prasad V; Pande, Abhay H

    2017-08-01

    Human paraoxonase 1 (h-PON1) is a ~45-kDa serum enzyme that can hydrolyze a variety of substrates, including organophosphate (OP) compounds. It is a potential candidate for the development of antidote against OP poisoning in humans. However, insufficient OP-hydrolyzing activity of native enzyme affirms the urgent need to develop improved variant(s) having enhanced OP-hydrolyzing activity. The crystal structure of h-PON1 remains unsolved, and the molecular details of how the enzyme catalyses hydrolysis of different types of substrates are also not clear. Understanding the molecular details of the catalytic mechanism of h-PON1 is essential to engineer better variant(s) of enzyme. In this study, we have used a random mutagenesis approach to increase the OP-hydrolyzing activity of recombinant h-PON1. The mutants not only showed a 10-340-fold increased OP-hydrolyzing activity against different OP substrates but also exhibited differential lactonase and arylesterase activities. In order to investigate the mechanistic details of the effect of observed mutations on the hydrolytic activities of enzyme, molecular docking studies were performed with selected mutants. The results suggested that the observed mutations permit differential binding of substrate/inhibitor into the enzyme's active site. This may explain differential hydrolytic activities of the enzyme towards different substrates.

  5. Understanding the mechanisms of secondary nucleation for protein aggregation: an analytical approach

    Science.gov (United States)

    Michaels, Thomas; Knowles, Tuomas P. J.

    2013-03-01

    Filamentous protein self-assembly is a general type of behaviour accessible to a wide range of different polypeptide sequences. This phenomenon underlies key molecular events both in normal and aberrant biology, but a general theory of the crucial nucleation steps that govern this process has remained elusive. In this talk we discuss our attempts to provide a general description of secondary nucleation in filamentous protein assembly based on the Becker-Döring kinetic scheme to describe cluster-catalytic effects. This systematic procedure allows extracting low-dimensional systems of equations out of the full kinetic model, in a master equation formalism typically consisting of infinitely many coupled non-linear equations. Using this procedure, we propose and discuss various mechanisms that can underlie the secondary nucleation process. Using data curve-fitting and analysis we show that the addition of a monomer to heterogeneous nuclei is effectively irreversible and discuss the implications of our framework for the more general understanding of the physics of multi-step nucleation phenomena in nature.

  6. Understanding the mechanisms of sickle cell disease by simulations with a discrete particle model

    Science.gov (United States)

    Hui, Katrina; Lin, Guang; Pan, Wenxiao

    2013-01-01

    Sickle cell disease (SCD) is an inherited blood disorder characterized by rigid, sickle-shaped red blood cells (RBCs). Because of their rigidity and shape, sickle cells can get stuck in smaller blood vessels, causing blockages and depriving oxygen to tissues. This study develops and applies mathematical models to better understand the mechanism of SCD. Two-dimensional models of RBCs and blood vessels have been constructed by representing them as discrete particles interacting with different forces. The nonlinear, elastic property of healthy RBCs could be adequately reproduced using a cosine angle bending force and a worm-like chain spring force. With the ability to deform, RBCs can squeeze through narrow blood vessels. In modeling sickle cells as rigid bodies and applying repelling and friction forces from the blood vessel, this study shows that geometrical factors (dimensions of the sickle cell and blood vessels) as well as rigidity and adhesiveness of the sickle cell all play an important role in determining how, and if, sickle cells become trapped within narrow blood capillaries. With lack of data to validate the model, this study primarily provides a sensitivity analysis of factors influencing sickle cell occlusion and identified critical data to support future modeling.

  7. Sorption of Pesticides to Natural and Synthetic Nanoparticles

    Science.gov (United States)

    Guluzada, Leyla; Luo, Leilei; Pattky, Martin; Anwander, Reiner; Huhn, Carolin; Haderlein, Stefan

    2017-04-01

    Many organic pollutants tend to associate with particles in environment. Such interactions with solid surfaces may not only alter the reactivity and bioavailability of pesticides, but also their uptake. This alteration may occur both in the way and in the amount the compound enters the organisms. In its turn this may change the overall effects of these compounds on organisms and ecosystems. The main goal of the work presented here is to provide mechanistic information on the sorbate-sorbent interactions between nanoparticles and a set of pesticides under environmentally relevant and physiological conditions. As such, the work is part of the interdisciplinary graduate research program EXPAND at the University of Tübingen investigating molecular interactions between pesticides and particles to elucidate how such interactions impact the toxicological effects. To this end, natural and synthetic nanoparticles covering a wide range of physicochemical properties and pesticides for different target organisms were used. Sorption experiments were carried out with insecticides (imidacloprid; thiacloprid), fungicides (hexaconazole; propiconazole) and herbicides (glyphosate with its metabolite AMPA; glufosinate). The choice of the pesticides was based on their environmental significance and their mode of action. Both engineered nanoparticles with tailored surface properties and nanoparticles of natural origin were characterized and applied to cover various modes of sorptive interactions with the pesticides. The impact of various geochemical and physiological conditions including pH, temperature, ionic strength, background electrolytes and DOM (dissolved organic matter) on the sorption of the pesticides to nanoparticles was studied. Sorption kinetics and sorption isotherms were determined and the results are discussed in terms of predominant sorption mechanisms and the suitability of certain nanoparticles for toxicological studies in the framework of the EXPAND project.

  8. Sorption of polar and nonpolar organic contaminants by oil-contaminated soil.

    Science.gov (United States)

    Chen, Hong; Chen, Shuo; Quan, Xie; Zhao, Huimin; Zhang, Yaobin

    2008-12-01

    Sorption of nonpolar (phenanthrene and butylate) and polar (atrazine and diuron) organic chemicals to oil-contaminated soil was examined to investigate oil effects on sorption of organic chemicals and to derive oil-water distribution coefficients (K(oil)). The resulting oil-contaminated soil-water distribution coefficients (K(d)) for phenanthrene demonstrated sorption-enhancing effects at both lower and higher oil concentrations (C(oil)) but sorption-reducing (competitive) effects at intermediate C(oil) (approximately 1 g kg(-1)). Rationalization of the different dominant effects was attempted in terms of the relative aliphatic carbon content which determines the accessibility of the aromatic cores to phenanthrene. Little or no competitive effect occurred for butylate because its sorption was dominated by partitioning. For atrazine and diuron, the changes in K(d) at C(oil) above approximately 1 g kg(-1) were negligible, indicating that the presently investigated oil has little or no effect on the two tested compounds even though the polarity of the oil is much less than soil organic matter (SOM). Therefore, specific interactions with the active groups (aromatic and polar domains) are dominantly responsible for the sorption of polar sorbates, and thus their sorption is controlled by available sorption sites. This study showed that the oil has the potential to be a dominant sorptive phase for nonpolar pollutants when compared to SOM, but hardly so for polar compounds. The results may aid in a better understanding of the role of the aliphatic and aromatic domains in sorption of nonpolar and polar organic pollutants.

  9. Roles of functional groups of naproxen in its sorption to kaolinite.

    Science.gov (United States)

    Yu, Chenglong; Bi, Erping

    2015-11-01

    The sorption of acidic anti-inflammatory drugs to soils is important for evaluating their fate and transformations in the water-soil environment. However, roles of functional groups of ionisable drugs onto mineral surfaces have not been sufficiently studied. In this study, batch experiments of naproxen (NPX, anti-inflammatory drug) and two kinds of competitors to kaolinite were studied. The Kd of naproxen to kaolinite is 1.30-1.62 L kg(-1). The n-π electron donor-acceptor (n-π EDA) interaction between diaromatic ring of naproxen (π-electron acceptors) and the siloxane oxygens (n-donors) of kaolinite is the dominant sorption mechanism. The carboxyl group of naproxen can contribute to the overall sorption. A conception model was put forward to elucidate to sorption mechanisms, in which the contribution of n-π EDA and hydrogen bond to overall sorption was quantified. These sorption mechanisms can be helpful for estimating the fate and mobility of acid pharmaceuticals in soil-water environment. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. Examination of Pb2+ bio-sorption onto Rhodotorula mucilaginosa using response surface methodology.

    Science.gov (United States)

    Jiang, Bin-hui; Zhao, Yan; Zhao, Xin; Hu, Xiao-min; Li, Li

    2015-01-01

    With the rapid industrial development, wastewater has been a risk for environmental contamination. We aimed to explore the optimum condition and mechanism of Pb2+ bio-sorption onto Rhodotorula mucilaginosa WT6-5. Optimization of initial concentration of Pb2+, initial pH, and adsorption time for Pb2+ bio-sorption onto R. mucilaginosa WT6-5 was performed using response surface methodology. Field emission scanning electron microscopy, energy dispersive X-ray detection, X-ray fluorescence and Fourier transform infrared spectroscopy were used to analyze the mechanisms and characteristics of Pb2+ bio-sorption. A maximum Pb2+ bio-sorption capacity of 1.45 mg/g was obtained under the optimal conditions of initial concentration of Pb2+ (30 mg/L), initial pH (5.45) and adsorption time (25 minutes). Some Pb2+ remained after adsorption, and the -OH, -C=O and C-O functional groups were primarily involved in Pb2+ bio-sorption onto R. mucilaginosa WT6-5. The mechanism of Pb2+ bio-sorption involved chemical and biological actions, ion exchange and functional groups effects.

  11. Diffusion and sorption on hardened cement pastes - experiments and modelling results

    Energy Technology Data Exchange (ETDEWEB)

    Jakob, A.; Sarott, F.-A.; Spieler, P.

    1999-08-01

    Large parts of repositories for low and intermediate level radioactive waste consist of cementitious materials. Radionuclides are transported by diffusion in the cement matrix or, in case of fractured or highly permeable cement, by advection and dispersion. In this work we aim at a mechanistic understanding of diffusion processes of some reactive tracers. On the laboratory scale, ten through-diffusion experiments were performed to study these processes for Cl{sup -}, I{sup -}, Cs{sup +} and Ni{sup 2+} ions in a Sulphate Resisting Portland Cement (SRPC) equilibrated with an artificial pore water. Some of the experiments continued up to nearly three years with daily measurements. In all the experiments, a cement disk initially saturated with an artificial pore water was exposed on one side to a highly diluted solution containing the species of interest. On the second side, a near-zero concentration boundary was maintained to drive through-diffusion of the tracer. The changes of concentrations on both sides of the samples were monitored, allowing careful mass balances. From these data, values of the diffusive flux and the mass of tracer taken up by the cementitious material were determined as a function of time. In the subsequent modelling, the time histories of these tracer breakthroughs were fitted using five different models. The simplest model neglects all retarding mechanisms except pure diffusion. More complex models either account for instantaneous equilibrium sorption in form of linear or non-linear (Freundlich) sorption or for first-order sorption kinetics where the forward reaction may be linear or non-linear according to the Freundlich isotherm, while the back-reaction is linear. Hence, the analysis allows the extraction of the diffusion coefficient and parameter values for the sorption isotherm or rate-constants for sorption and desorption. The fits to the experimental data were carried out by an automated Marquardt-Levenberg procedure yielding error

  12. Current understanding of the driving mechanisms for spatiotemporal variations of atmospheric speciated mercury: a review

    Directory of Open Access Journals (Sweden)

    H. Mao

    2016-10-01

    Full Text Available Atmospheric mercury (Hg is a global pollutant and thought to be the main source of mercury in oceanic and remote terrestrial systems, where it becomes methylated and bioavailable; hence, atmospheric mercury pollution has global consequences for both human and ecosystem health. Understanding of spatial and temporal variations of atmospheric speciated mercury can advance our knowledge of mercury cycling in various environments. This review summarized spatiotemporal variations of total gaseous mercury or gaseous elemental mercury (TGM/GEM, gaseous oxidized mercury (GOM, and particulate-bound mercury (PBM in various environments including oceans, continents, high elevation, the free troposphere, and low to high latitudes. In the marine boundary layer (MBL, the oxidation of GEM was generally thought to drive the diurnal and seasonal variations of TGM/GEM and GOM in most oceanic regions, leading to lower GEM and higher GOM from noon to afternoon and higher GEM during winter and higher GOM during spring–summer. At continental sites, the driving mechanisms of TGM/GEM diurnal patterns included surface and local emissions, boundary layer dynamics, GEM oxidation, and for high-elevation sites mountain–valley winds, while oxidation of GEM and entrainment of free tropospheric air appeared to control the diurnal patterns of GOM. No pronounced diurnal variation was found for Tekran measured PBM at MBL and continental sites. Seasonal variations in TGM/GEM at continental sites were attributed to increased winter combustion and summertime surface emissions, and monsoons in Asia, while those in GOM were controlled by GEM oxidation, free tropospheric transport, anthropogenic emissions, and wet deposition. Increased PBM at continental sites during winter was primarily due to local/regional coal and wood combustion emissions. Long-term TGM measurements from the MBL and continental sites indicated an overall declining trend. Limited measurements suggested TGM

  13. Understanding treatment effect mechanisms of the CAMBRA randomized trial in reducing caries increment.

    Science.gov (United States)

    Cheng, J; Chaffee, B W; Cheng, N F; Gansky, S A; Featherstone, J D B

    2015-01-01

    The Caries Management By Risk Assessment (CAMBRA) randomized controlled trial showed that an intervention featuring combined antibacterial and fluoride therapy significantly reduced bacterial load and suggested reduced caries increment in adults with 1 to 7 baseline cavitated teeth. While trial results speak to the overall effectiveness of an intervention, insight can be gained from understanding the mechanism by which an intervention acts on putative intermediate variables (mediators) to affect outcomes. This study conducted mediation analyses on 109 participants who completed the trial to understand whether the intervention reduced caries increment through its action on potential mediators (oral bacterial load, fluoride levels, and overall caries risk based on the composite of bacterial challenge and salivary fluoride) between the intervention and dental outcomes. The primary outcome was the increment from baseline in decayed, missing, and filled permanent surfaces (ΔDMFS) 24 mo after completing restorations for baseline cavitated lesions. Analyses adjusted for baseline overall risk, bacterial challenge, and fluoride values under a potential outcome framework using generalized linear models. Overall, the CAMBRA intervention was suggestive in reducing the 24-mo DMFS increment (reduction in ΔDMFS: -0.96; 95% confidence interval [CI]: -2.01 to 0.08; P = 0.07); the intervention significantly reduced the 12-mo overall risk (reduction in overall risk: -19%; 95% CI, -7 to -41%;], P = 0.005). Individual mediators, salivary log10 mutans streptococci, log10 lactobacilli, and fluoride level, did not represent statistically significant pathways alone through which the intervention effect was transmitted. However, 36% of the intervention effect on 24-mo DMFS increment was through a mediation effect on 12-mo overall risk (P = 0.03). These findings suggest a greater intervention effect carried through the combined action on multiple aspects of the caries process rather than

  14. The effect of MWCNT treatment by H2O2 and/or UV on fulvic acids sorption.

    Science.gov (United States)

    Czech, Bożena

    2017-05-01

    The carbon nanotubes (CNT) present in the wastewater subjected to treatment will possess altered physico-chemical properties. The changed properties will result in the unknown behavior of CNT in the environment after disposal; and it is expected to differ from their pristine analogues. In the present paper the effect of sorption of dissolved organic matter with fulvic acids (FA) as representatives onto UV and/or H 2 O 2 treated CNT was tested. Both kinetics and mechanism of sorption was estimated. The chemical adsorption was a rate limiting step and a pseudo-second order kinetics described the sorption of FA onto UV and/or H 2 O 2 treated CNT. The treating increased affinity towards FA and treating by UV and H 2 O 2 simultaneously possessed greater impact on k 2 than UV and H 2 O 2 separately. The greatest effect on CNT sorption capacity revealed H 2 O 2 . The sorption mechanism was described by Temkin (CNT-H 2 O 2 ) and Dubinin-Radushkevich model. The increase in CNT surface disorder caused by UV and/or H 2 O 2 treatment favored sorption of FA via π-π interactions (exfoliated surface and disordered CNT walls). FA sorption occurred between aromatic rings of FA and CNT and hydrogen bonds formed with the oxygen functional groups. The results indicate that UV and/or H 2 O 2 treatment affected the sorption capacity and affinity of CNT towards FA. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. Understanding and Exploration of the Biomineralization Mechanisms for the Controllable Synthesis of Nanomaterials

    Science.gov (United States)

    Xiao, Junwu

    This thesis is mainly concerned with understanding the biomineralization mechanisms, and further extrapolating them for the controllable synthesis of transition metal compound nanomaterials on graphene sheets for energy storage applications in electrochemical capacitors and lithium ion batteries (LIB). Firstly, we have studied the mimetic biomineralization process of CaCO 3 on a stearic acid or 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) Langmuir monolayer at the air-water interface by in-situ Brewster angle microscopy (BAM) and ex-situ electron microscopy. Amorphous calcium carbonate (ACC) precursors are directly nucleated from solvated ions prior to the crystal nuclei on a Langmuir monolayer. On a DPPC monolayer, numerous fresh ACC nanoparticles heterogeneously and continuously nucleated at the air-water interface are transformed into the metastable vaterite nanocrystals. Driven by the trend to decrease surface energy, the vaterite nanocrystals self-aggregate and grow into the loose-packed hollow ellipsoidal vaterite polycrystals. These nanocrystals in vaterite polycrystals are then gradually orientated in the same direction to evolve into tight-packed ellipsoidal mesocrystals. As the crystallization time is further increased, the metastable vaterite mesocrystals are eventually transformed into the most thermodynamically stable calcite crystals. Secondly, organic and inorganic additives control over the shapes, sizes and phases of inorganic nanocrystals and arrange them into ordered structures from amorphous precursors in the organisms. This interesting phenomenon has galvanized many attempts to mimic the biomineralization process for synthesizing novel materials. We have studied the crystallization processes from small citrate molecules stabilized ACC precursors under cetyltrimethyl ammonium bromide (CTAB) micellar structures. Amorphous precursors, with a hydrated and disordered structure, are easily transformed and molded into CaCO 3 crystals with

  16. The low FODMAP diet: recent advances in understanding its mechanisms and efficacy in IBS.

    Science.gov (United States)

    Staudacher, Heidi M; Whelan, Kevin

    2017-08-01

    There is an intensifying interest in the interaction between diet and the functional GI symptoms experienced in IBS. Recent studies have used MRI to demonstrate that short-chain fermentable carbohydrates increase small intestinal water volume and colonic gas production that, in those with visceral hypersensitivity, induces functional GI symptoms. Dietary restriction of short-chain fermentable carbohydrates (the low fermentable oligosaccharide, disaccharide, monosaccharide and polyol (FODMAP) diet) is now increasingly used in the clinical setting. Initial research evaluating the efficacy of the low FODMAP diet was limited by retrospective study design and lack of comparator groups, but more recently well-designed clinical trials have been published. There are currently at least 10 randomised controlled trials or randomised comparative trials showing the low FODMAP diet leads to clinical response in 50%-80% of patients with IBS, in particular with improvements in bloating, flatulence, diarrhoea and global symptoms. However, in conjunction with the beneficial clinical impact, recent studies have also demonstrated that the low FODMAP diet leads to profound changes in the microbiota and metabolome, the duration and clinical relevance of which are as yet unknown. This review aims to present recent advances in the understanding of the mechanisms by which the low FODMAP diet impacts on symptoms in IBS, recent evidence for its efficacy, current findings regarding the consequences of the diet on the microbiome and recommendations for areas for future research. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

  17. Phosphorus sorption isotherms and external phosphorus ...

    African Journals Online (AJOL)

    Information on P sorption characteristics of soils is important for making profitable P fertiliser recommendations and designing appropriate P management strategies for improving crop productivity. An experiment was conducted to determine the P sorption capacities and external P requirements (EPR) of some soils of ...

  18. New composite materials to metal sorption

    International Nuclear Information System (INIS)

    Annenkov, V.V.; Danilovtseva, E.N.; Filina, E.A.; Trofimov, B.A.

    2002-01-01

    Complexing-active polymers are promising substances for detoxication of radioactive elements from the polluted soils and natural waters. Tis work is devoted to searching of new polymeric compositions for detoxication of soils and waters from heavy metals. Three systems (azole-carboxylic polyampholytes, polymer-polymer complexes of poly(1-vinylimidazole) (PVI), Ai- and Al-based organo/inorganic composites) were discussed. Sorption properties of new composites were studied using Cu 2+ ions as an example. The sorption equilibrium range time is equals to 20-60 min, sorption capacity attains 280 mg/g. The most effective sorbents are composites on the basis of PVI, poly(4-vinylpyridine) decrease sorption capacity due to hydrophobia of this polymer. Thus, composites on the basis of nitrogen-containing polymers are promising systems for heavy materials sorption. Introduction of Si-, Al-hydroxides into composites allows to decrease cost of the materials and increase their nature-compatibility

  19. Sorption of mercury on chemically synthesized polyaniline

    International Nuclear Information System (INIS)

    Remya Devi, P.S.; Verma, R.; Sudersanan, M.

    2006-01-01

    Sorption of inorganic mercury (Hg 2+ ) and methyl mercury, on chemically synthesized polyaniline, in 0.1-10N HCl solutions has been studied. Hg 2+ is strongly sorbed at low acidities and the extent of sorption decreases with increase in acidity. The sorption of methyl mercury is very low in the HCl concentration range studied. Sorption of Hg 2+ on polyaniline in 0.1-10N LiCl and H 2 SO 4 solutions has also been studied. The analysis of the data indicates that the sorption of Hg 2+ depends on the degree of protonation of polyaniline and the nature of mercury(II) chloride complexes in solution. X-ray photoelectron spectroscopy analysis (XPS) of polyaniline sorbed with mercury show that mercury is bound as Hg 2+ . Sorbed mercury is quantitatively eluted from polyaniline with 0.5N HNO 3 . Polyaniline can be used for separation and pre-concentration of inorganic mercury from aqueous samples. (author)

  20. Cobalt sorption onto Savannah River Plant soils

    International Nuclear Information System (INIS)

    Hoeffner, S.L.

    1985-06-01

    A laboratory study of cobalt-60 sorption was conducted using Savannah River Plant soil and groundwater from the low-level waste burial ground. Systematic variation of soil and water composition indicates that cobalt sorption is most strongly a function of pH. Over a pH range of 2 to 9, the distribution coefficient ranged from 2 to more than 10,000 mL/g. Changes in clay content and in K + , Ca 2+ , or Mg 2+ concentrations influence cobalt sorption indirectly through the slight pH changes which result. The ions Na + , Cl - , and NO 3 - have no effect on cobalt sorption. Ferrous ion, added to groundwater to simulate the condition of water at the bottom of the waste trenches, accounts for part of the decrease in cobalt sorption observed with trench waters. 17 refs., 3 figs., 4 tabs

  1. Chemical equilibria in bio sorption

    International Nuclear Information System (INIS)

    Romero, A.; Gonzalez, F.; Ballester, A.; Blazquez, M. L.; Munoz, J.A.

    2007-01-01

    An experimental study of bio sorption was carried out using six different kinds of algae and five different heavy metals (cadmium, copper, nickel, lead and zinc). Experimental data fitted very well to langmuir's model and this allowed to predict the behaviour of the biomass under specific working conditions. Using the equations of the model under different initial assumptions, a series of mathematical calculations were done for mono metallic, bimetallic and tri metallic systems. the most complicated calculation is that in which, knowing the initial metal concentration (C 0 ), it is necessary to calculate the conditions reached at the equilibrium, this is, q e and C e . This assumption is of great interest from the point of view of the actual applicability of the process. However, in this case, it is necessary to solve very complex mathematical equations which, for multi metallic systems, are of degree n+1, where n is the number of ions present in solution. The excellent correlation between experimental and theoretical data demonstrates that the bio sorption process can be modelling. (Author) 18 refs

  2. Understanding the mechanisms that change the conductivity of damaged ITO-coated polymeric films: A micro-mechanical investigation

    KAUST Repository

    Nasr Saleh, Mohamed

    2014-11-01

    Degradation from mechanical loading of transparent electrodes made of indium tin oxide (ITO) endangers the integrity of any material based on these electrodes, including flexible organic solar cells. However, how different schemes of degradation change the conductivity of ITO devices remains unclear. We propose a systematic micro-mechanics-based approach to clarify the relationship between degradation and changes in electrical resistance. By comparing experimentally measured channel crack densities to changes in electrical resistance returned by the different micro-mechanical schemes, we highlight the key role played by the residual conductivity in the interface between the ITO electrode and its substrate after delamination. We demonstrate that channel cracking alone does not explain the experimental observations. Our results indicate that delamination has to take place between the ITO electrode and the substrate layers and that the residual conductivity of this delaminated interface plays a major role in changes in electrical resistance of the degraded device. © 2014 Elsevier B.V.

  3. Pressure impact of autoclave treatment on water sorption and pectin composition of flax cellulosic-fibres.

    Science.gov (United States)

    Alix, S; Colasse, L; Morvan, C; Lebrun, L; Marais, S

    2014-02-15

    The tensile properties of flax fibres might permit them to be used in composites as reinforcement in organic resin, as long as their mechanical properties are reproducible and their water sorption are reduced. In this study, to minimise the variability of mechanical properties, several samples of flax fibres were blended as a non-woven fabric. In order to reduce the water absorption of this non-woven technical fibres, an autoclave treatment was performed which was expected to remove the pectins and then to reduce the water sorption on their negative charges. The impact of autoclave pressure (0.5, 1 and 2 bars) on water sorption was investigated by using a gravimetric static equilibrium method. The Park model based on the three sorption modes: Langmuir, Henry's law and clustering, was successfully used to simulate the experimental sorption data. The lowest pressure treatments impacted only the Langmuir contribution while the 2 bar autoclave-treatment positively impacted the water resistance in the core of fibres by reducing Henry's absorption rate. This was shown to be related to the chemical modifications at the surface and in the core of fibres. A schematic model is presented relating the water sorption and the pectic composition of the fabric. Copyright © 2013 Elsevier Ltd. All rights reserved.

  4. Synthesis, properties and effect of ionizing radiation on sorption behavior of iron silico-antimonate

    International Nuclear Information System (INIS)

    Ali, I.M.; Zakaria, E.S.; El-Naggar, I.M.; Shama, S.A.

    2010-01-01

    Incorporation of iron oxide into silico-antimonate of different Si/Sb molar ratios introduced a class of dual salts ion exchangers with advanced ion exchange properties. Physicochemical and equilibrium studies have been carried out to understand the ion exchange properties of these materials. Apparent investigation indicated that iron incorporation into silico-antimonate yields materials having excellent mechanical properties. On the basis of distribution studies, the materials were found to be highly selective for Sr 2+ or Ce 3+ depending on their Si/Sb molar ratios. Diffractogram, thermogram, IR spectra and sorption performance of crystalline FeSiSb (114) indicated that no detectable structural changes after an exposure up to 100 kGy of γ-rays. Effect of reaction temperature on the exchange process was investigated and the respective thermodynamic parameters were calculated. (author)

  5. Effects of humic acid and heavy metals on the sorption of polar and apolar organic pollutants onto biochars.

    Science.gov (United States)

    Wang, Fei; Sun, Hongwen; Ren, Xinhao; Liu, Yarui; Zhu, Hongkai; Zhang, Peng; Ren, Chao

    2017-12-01

    The effects of humic acid (HA) and heavy metals (Cu 2+ and Ag + ) on the sorption of polar and apolar organic pollutants onto biochars that were produced at temperatures of 200 °C (BC200) and 700 °C (BC700) were studied. Due to the plentiful polar functional groups on BC200, cationic propranolol exhibited higher levels of sorption than naphthalene on BC200 while naphthalene and propranolol showed similar sorption capacities on BC700. HA changed the characteristics of biochars and generally inhibited the sorption of target organic pollutants on biochars; however, enhancement occurred in some cases depending on the pollutants involved and their concentrations, biochars used and the addition sequences and concentrations of HA. On BC200, HA modifications mainly influenced sorption by decreasing its polarity and increasing its aromaticity, while on BC700, the surface area and pore volume greatly decreased due to the pore-blocking effects of HA. Residue dissolved HA in solution may also contribute to sorption inhibition. Complexation between polar functional groups on BC200 and heavy metals slightly enhanced the sorption of neutral naphthalene and significantly enhanced that of anionic 4-nitro-1-naphtol, while limited the sorption of cationic propranolol. Heavy metals together with their associated water molecules decreased the sorption of target chemicals on BC700 via pore-filling or pore-mouth-covering. Inhibition of heavy metals for 4-nitro-1-naphthol was found to be the weakest due to the bridge effects of heavy metals between 4-nitro-1-naphtol and BC700. The higher polarizability of Ag + led to the increase of its sorption on biochars in the presence of organic aromatic pollutants. The results of the present study shed light on the sorption mechanisms of bi-solute systems and enable us to select suitable biochar sorbents when chemicals co-exist. Copyright © 2017. Published by Elsevier Ltd.

  6. U(VI) sorption on granite: prediction and experiments

    International Nuclear Information System (INIS)

    Nebelung, C.; Brendler, V.

    2010-01-01

    One widely accepted approach - component additivity (CA) - to describe the sorption of contaminants onto complex materials such as rocks or soils is based on the assumption that the surface of a complex mineral assemblage is composed of a mixture of mineral constituents whose surface properties are known from independent studies. An internally consistent SCM (surface complexation model) database can be developed that describes the adsorption reactions of solutes to each phase. Here, the capability of such a methodology was tested, using the code MINTEQA2 including thermodynamic data of the NEA-TDB, and literature data for SCM, namely the DDL model. The sorption characteristics of U(VI) on granite (from Eibenstock, Saxony, Germany, with the main components quartz, albite, orthoclase, and muscovite) was predicted and then compared to batch experiments. Granite plays an important role in the remediation of former uranium ore mining and milling sites, but is also one of the host rocks considered for final disposal of nuclear materials. Safety assessment requires a detailed understanding of this system and its retention potential with regard to hazardous components. Namely the sorption of uranium in this complex rock is not fully understood yet. The experiments thus also provided a better understanding of the far-field behaviour in granitic geological nuclear repositories. The robustness of the prediction was tested by variation of the granite composition and the variation of the specific surface area (SSA) - first all components were predicted with a uniform granite SSA, second with a distinct SSA for each granite component (determined on pure minerals for the same grain size fractions). Changes in compositions yielded only marginal differences in the prediction. Different approaches to SSA showed somewhat larger deviations. In conclusion, the CA methodology is a valid and robust approach to U(VI) sorption onto complex substrates such as granite, provided sufficient

  7. Dynamic design of gas sorption J-T refrigerator

    International Nuclear Information System (INIS)

    Chan, C.K.

    1986-01-01

    A long-life Joule-Thomson refrigerator which is heat powered, involves no sealing, and has few mechanical parts and is desirable for longterm sensor cooling in space. In the gas-sorption J-T refrigerator, cooling is achieved by gas sorption (either adsorption or absorption) processes. Currently, a modular, single-stage refrigerator is being designed and built to be operated at 20 K. The design was analyzed using a dynamic model, which is described here. The model includes the kinetics of the compressors and the heat switches, the heat transfer of the pre-coolers and the heat exchangers, the on/off ratio of the check valves, and the impedance of the J-T valve. The cooling power, the cycle time, and the operating conditions were obtained in terms of the power input, the heat sink temperature, and the J-T impedance

  8. Dynamic design of gas sorption J-T refrigerator

    Science.gov (United States)

    Chan, C. K.

    1986-01-01

    A long-life Joule-Thomson refrigerator which is heat powered, involves no sealing, and has few mechanical parts is desirable for long-term sensor cooling in space. In the gas-sorption J-T refrigerator, cooling is achieved by gas sorption (either adsorption or absorption) processes. Currently, a modular, single-stage refrigerator is being designed and built to be operated at 20 K. The design was analyzed using a dynamic model, which is described here. The model includes the kinetics of the compressors and the heat switches, the heat transfer of the pre-coolers and the heat exchangers, the on/off ratio of the check valves, and the impedance of the J-T valve. The cooling power, the cycle time, and the operating conditions were obtained in terms of the power input, the heat sink temperature, and the J-T impedance.

  9. Laboratory experiments for understanding mechanical properties of fractured granite under supercritical conditions

    Science.gov (United States)

    Kitamura, M.; Takahashi, M.; Takagi, K.; Hirano, N.; Tsuchiya, N.

    2017-12-01

    To extract geothermal energy effectively and safely from magma and/or adjacent hot rock, we need to tackle many issues which require new technology development, such as a technique to control a risk from induced-earthquakes. On a development of induced-earthquake mitigation technology, it is required to understand roles of factors on occurrences of the induced-earthquake (e.g., strength, crack density, and fluid-rock reaction) and their intercorrelations (e.g., Asanuma et al., 2012). Our purpose of this series of experiments is to clarify a relationship between the rock strength and the crack density under supercritical conditions. We conducted triaxial deformation test on intact granite rock strength under high-temperature (250 - 750°C), high-pressure (104 MPa) condition at a constant load velocity (0.1 μm/sec) using a gas-rig at AIST. We used Oshima granite, which has initially stress drop became smaller at higher temperature. Young's modulus increased with decreasing the temperature from 32.3 GPa at 750°C to 57.4 GPa at 250°C. At 400 °C, the stress drop accelerated the deformation with 98 times faster velocity than that at load-point. In contrast, at 650°C and 750°C, the velocity during stress drop kept the same order of the load-point velocity. Therefore, the deformation mechanism may start to be changed from brittle to ductile when the temperature exceeds 650°C. Highly dense cracked granite specimens were formed by a rapid decompression test (RDT) using an autoclave settled at Tohoku University (Hirano et al., 2016JpGU), caused by a reduction of fluid pressure within 1-2 sec from vapor/supercritical state (10 - 48 MPa, 550 °C) to ambient pressure. The specimens after RDT show numerous microcracks on X-ray CT images. The RDT imposed the porosity increasing towards 3.75 % and Vp and Vs decreasing towards 1.37±0.52 km/s and 0.97±0.25 km/s. The Poisson's ratio shows the negative values in dry and 0.5 in wet. In the meeting, we will present results of

  10. Toward Understanding Mechanisms Controlling Urea Delivery in a Coastal Plain Watershed

    Science.gov (United States)

    Tzilkowski, S. S.; Buda, A. R.; Boyer, E. W.; Bryant, R. B.; May, E. B.

    2012-12-01

    Improved understanding of nutrient mobilization and delivery to surface waters is critical to protecting water quality in agricultural watersheds. Urea, a form of organic nitrogen, is a common nutrient found in fertilizers, manures, and human waste, and is gaining recognition as an important driver of coastal eutrophication, particularly through the development of harmful algal blooms. While several studies have documented elevated urea concentrations in tributaries draining to the Chesapeake Bay, little is known about the potential sources and flow pathways responsible for urea delivery from the landscape to surface waters, as well as how these sources and pathways might vary with changing seasons, antecedent conditions, and storm types. In this study, we investigated hydrologic controls on urea delivery in the Manokin River watershed through the analysis of urea concentration dynamics and hysteresis patterns during seven storm events that occurred in 2010 and 2011. The Manokin River is a Coastal Plain watershed (11.1 km2) on the Delmarva Peninsula that drains directly to the Chesapeake Bay and is characterized by extensive rural development coupled with intensive agriculture, particularly poultry production. Sampling was conducted through monthly grab sampling at baseflow conditions and by time-weighted, automated (Sigma) samplers during stormflow events. Monitored storms were chosen to represent a spectrum of antecedent conditions based on precipitation and groundwater levels in the area. Flushing from the landscape during events was found to be the predominant urea delivery mechanism, as urea concentrations increased 3-9 times above baseflow concentrations during storms. The timing and number of flushes, as well as the degree of increased concentrations were dependent on antecedent conditions and the characteristics of the storm event. For instance, during an intense (13.7 mm hr-1), short-duration (4 hrs) storm in August of 2010 when antecedent conditions were

  11. Sorption behavior of cesium onto bentonite colloid

    International Nuclear Information System (INIS)

    Iijima, Kazuki; Masuda, Tsuguya; Tomura, Tsutomu

    2004-01-01

    It is considered that bentonite colloid might be generated from bentonite which will be used as buffer material in geological disposal system, and can facilitate the migration of radionuclides by means of sorption. In order to examine this characteristic, sorption and desorption experiments of Cs onto bentonite colloid were carried out to obtain its distribution coefficient (Kd) and information on the reversibility of its sorption. In addition, particle size distribution and shape of colloid were investigated and their effect on the sorption behavior was discussed. Kds for Cs were around 20 m 3 /kg for sorption and 30 m 3 /kg for desorption, in which sorbed Cs was desorbed by 8.4x10 -4 mol/l of NaCl solution. These values did not show any dependencies on Cs concentration and duration of sorption and desorption. The first 20% of sorbed Cs was desorbed reversibly at least. Most of colloidal particles were larger than 200 nm and TEM micrographs showed they had only several sheets of the clay crystal. Obtained Kds for colloidal bentonite were larger than those for powdered bentonite. This can be caused by difference of competing ions in the solution, characteristics of contained smectite, or sorption site density. (author)

  12. Thermodynamic study of uranyl sorption onto lanthanum monophosphate (LaPO4) and magnetite (Fe3O4)

    International Nuclear Information System (INIS)

    Felix, Olivia

    2012-01-01

    The migration of radio-toxic elements in the geosphere is mainly regulated by chemical parameters which control the partitioning of the elements between mineral phases and aqueous solutions. Variation in temperature may affect the retention properties of a mineral surface and requires a careful investigation in order to understand the radionuclides behavior in the geosphere. In this way, the interaction mechanisms between uranium(VI) and two minerals (LaPO 4 and Fe 3 O 4 ) have been studied. In a first step, the monazite (LaPO 4 ) has been chosen as methodological solid in order to clearly define all the different stages needed to completely characterize the influence of temperature on the sorption phenomena. To reach that goal, three media, more or less complexants towards aqueous uranyl and the mineral surface, have been considered. Physico-chemical as well as surface acid-base properties of the solid surface have been studied by considering three electrolytes (NaClO 4 , NaNO 3 and Na 2 SO 4 ) and temperatures ranged from 25 C to 95 C. The point of zero charge has been found to be identical for perchlorate and nitrate media (pH PZC =2.1) but it was found to be one pK unit higher for the sulfate medium indicating a sorption of the background electrolyte ions. The reaction heats associated to the hydration of the solid have been measured by using microcalorimetry and the nature of the reactive surface sites has been determined by carrying out Time-Resolved Laser-Induced Fluorescence Spectroscopy (TRLFS). On the basis of these experimental constraints, the titration curves obtained for the monazite suspensions were fitted by using the Constant Capacitance Model and the 1-pK model was preferred to characterize the surface charge evolution, due to the limited number of adjustable parameters. The surface protonation constants being determined, the behavior of U(VI) towards the monazite surface in the three electrolytes has been investigated. On the basis of both U

  13. SITE-94. Adaptation of mechanistic sorption models for performance assessment calculations

    International Nuclear Information System (INIS)

    Arthur, R.C.

    1996-10-01

    Sorption is considered in most predictive models of radionuclide transport in geologic systems. Most models simulate the effects of sorption in terms of empirical parameters, which however can be criticized because the data are only strictly valid under the experimental conditions at which they were measured. An alternative is to adopt a more mechanistic modeling framework based on recent advances in understanding the electrical properties of oxide mineral-water interfaces. It has recently been proposed that these 'surface-complexation' models may be directly applicable to natural systems. A possible approach for adapting mechanistic sorption models for use in performance assessments, using this 'surface-film' concept, is described in this report. Surface-acidity parameters in the Generalized Two-Layer surface complexation model are combined with surface-complexation constants for Np(V) sorption ob hydrous ferric oxide to derive an analytical model enabling direct calculation of corresponding intrinsic distribution coefficients as a function of pH, and Ca 2+ , Cl - , and HCO 3 - concentrations. The surface film concept is then used to calculate whole-rock distribution coefficients for Np(V) sorption by altered granitic rocks coexisting with a hypothetical, oxidized Aespoe groundwater. The calculated results suggest that the distribution coefficients for Np adsorption on these rocks could range from 10 to 100 ml/g. Independent estimates of K d for Np sorption in similar systems, based on an extensive review of experimental data, are consistent, though slightly conservative, with respect to the calculated values. 31 refs

  14. Heavy metal sorption by microalgae

    Energy Technology Data Exchange (ETDEWEB)

    Sandau, E. [IGV - Inst. fuer Getreideverarbeitung GmbH, Bergholz-Rehbruecke (Germany); Sandau, P. [IGV - Inst. fuer Getreideverarbeitung GmbH, Bergholz-Rehbruecke (Germany); Pulz, O. [IGV - Inst. fuer Getreideverarbeitung GmbH, Bergholz-Rehbruecke (Germany)

    1996-12-31

    Viable microalgae are known to be able to accumulate heavy metals (bioaccumulation). Against a background of the increasing environmental risks caused by heavy metals, the microalgae Chlorella vulgaris and Spirulina platensis and their potential for the biological removal of heavy metals from aqueous solutions were taken as an example for investigation. Small-scale cultivation tests (50 l) with Cd-resistant cells of Chlorella vulgaris have shown that approx. 40% of the added 10 mg Cd/l was removed from the solution within seven days. At this heavy metal concentration sensitive cells died. Non-viable microalgae are able to eliminate heavy metal ions in a short time by biosorption in uncomplicated systems, without any toxicity problems. Compared with original biomasses, the sorption capacity of microalgal by-products changes only insignificantly. Their low price makes them economical. (orig.)

  15. Towards a neurobiological understanding of pain in chronic pancreatitis: mechanisms and implications for treatment

    Directory of Open Access Journals (Sweden)

    Søren S. Olesen

    2017-12-01

    Conclusion:. Chronic pancreatitis is associated with abnormal processing of pain at the peripheral and central level of the pain system. This neurobiological understanding of pain has important clinical implications for treatment and prevention of pain chronification.

  16. Metal Sorption to Dolomite Surfaces

    International Nuclear Information System (INIS)

    Brady, P.V.; Papenguth, H.W.; Kelly, J.W.

    1999-01-01

    Potential human intrusion into the Waste Isolation Pilot Plant (WIPP) might release actinides into the Culebra Dolomite where sorption reactions will affect of radiotoxicity from the repository. Using a limited residence time reactor the authors have measured Ca, Mg, Nd adsorption/exchange as a function of ionic strength, P CO2 , and pH at 25 C. By the same approach, but using as input radioactive tracers, adsorption/exchange of Am, Pu, U, and Np on dolomite were measured as a function of ionic strength, P CO2 , and pH at 25 C. Metal adsorption is typically favored at high pH. Calcium and Mg adsorb in near-stoichiometric proportions except at high pH. Adsorption of Ca and Mg is diminished at high ionic strengths (e.g., 0.5M NaCl) pointing to association of Na + with the dolomite surface, and the possibility that Ca and Mg sorb as hydrated, outer-sphere complexes. Sulfate amplifies sorption of Ca and Mg, and possibly Nd as well. Exchange of Nd for surface Ca is favored at high pH, and when Ca levels are low. Exchange for Ca appears to control attachment of actinides to dolomite as well, and high levels of Ca 2+ in solution will decrease Kds. At the same time, to the extent that high P CO2 increase Ca 2+ levels, JK d s will decrease with CO 2 levels as well, but only if sorbing actinide-carbonate complexes are not observed to form (Am-carbonate complexes appear to sorb; Pu-complexes might sorb as well; U-carbonate complexation leads to desorption). This indirect CO 2 effect is observed primarily at, and above, neutral pH. High NaCl levels do not appear to affect to actinide K d s

  17. Sorption of methylxanthines by different sorbents

    Science.gov (United States)

    Dmitrienko, S. G.; Andreeva, E. Yu.; Tolmacheva, V. V.; Terent'eva, E. A.

    2013-05-01

    Sorption of caffeine, theophylline, theobromine, diprophylline, and pentoxyphylline on different sorbents (supercross-linked polystyrene, surface-modified copolymer of styrene and divinylbenzene Strata-X, and carbon nanomaterials Taunit and Diasorb-100-C16T) was studied in a static mode in an effort to find new sorbents suitable for sorption isolation and concentration of methylxanthines. The peculiarities of sorption of methylxanthines were explained in relation to the solution acidity, the nature of the sorbates and their concentration, the nature of the solvent, and the structural characteristics of the sorbents.

  18. Advances in understanding of soil biogeochemical cycles: the mechanism of HS entry into the root interior

    Science.gov (United States)

    Aleksandrova, Olga

    2017-04-01

    Humic substances represent the major reservoir of carbon (C) in ecosystems, and their turnover is crucial for understanding the global C cycle. As shown by some investigators [1-2], the phenomenon of the uptake of the whole humic particles by plant roots is a significant step of biogeochemical cycle of carbon in soils. The mechanism of HS entry the root interior remained unknown for a long time. However recently, the last one was discovered [3]. An advanced model [3] includes two hypotheses. These hypotheses are as follows: (1) each nano-size particle possesses a quantum image that can be revealed as a packet of electromagnetic waves; (2) the interaction of nano-size particle with the membrane (plasma membrane) of living cells, on which it is adsorbed, occurs via the development of the Rayleigh-Taylor (RT) instability on the membrane surface. An advanced model allows us to look insight some into some phenomena that were observed by experiments but remained not understood [2]. The authors [2] applied tritium autoradiography to wheat seedlings cultivated with tritium-labeled HS to consider the uptake of humic particles by plant roots. They found a significant increase in the content of some polar (monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), sulfoquinovosyl diacylglycerol (SQDG) and phosphatidylcholine (PC)) and neutral (free fatty acids, FFA) lipids which were detected in the wheat seedlings treated with humic particles. Authors [2] pointed that lipids MGDG, DGDG, SQDG are crucial for functional and structural integrity of the photosystem complex. Therefore, a stimulating action of adsorbed humic particles evoked phenomena like photosynthesis in root cells that can be interpreted using an advanced model: humic particles being nano-size particles become adsorbed on the plant roots in soils, and influence their micro environment, where they are located, with the specific electromagnetic exposure. Another finding of authors consisted in the

  19. Isotherms and thermodynamics for the sorption of heavy metal ions onto functionalized sporopollenin

    Energy Technology Data Exchange (ETDEWEB)

    Gubbuk, Ilkay Hilal, E-mail: ihilalg@gmail.com [Selcuk University, Department of Chemistry, Campus, 42031 Konya (Turkey)

    2011-02-15

    In this study, sporopollenin of Lycopodium clavatum spores was used for the sorption experiment. Glutaraldehyde (GA) immobilized sporopollenin (Sp), is employed as a sorbent in sorption of selected heavy metal ions. The sorbent prepared by sequential treatment of sporopollenin by silanazing compound and glutaraldehyde is suggested for sorption of Cu(II), Zn(II) and Co(II) from aqueous solutions. Experimental conditions for effective sorption of heavy metal ions were optimized with respect to different experimental parameters using batch method in detail. Optimum pH range of Cu(II) has occurred at pH {>=} 5.5 and Zn(II), Co(II) at pH {>=} 5.0, for the batch method. All of the metal ions can be desorbed with 10 cm{sup 3} of 0.5 mol dm{sup -3} of ethylenediaminetetraacetic acid (EDTA) solution. Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm equations were applied to the experimental data. Thermodynamic parameters such as free energy ({Delta}G{sup o}), entropy ({Delta}S{sup o}) and enthalpy ({Delta}H{sup o}) were also calculated from the sorption results used to explain the mechanism of the sorption. The results indicated that this sorbent is successfully employed in the separation of trace Cu(II), Zn(II) and Co(II) from the aqueous solutions.

  20. Sorption of atrazine, acetochlor, and 2,4-D by hardwood-derived biochar

    Science.gov (United States)

    Gonzalez, J. M.; Shipitalo, M. J.

    2016-12-01

    Offsite transport of herbicides and other agricultural pesticides to streams and other bodies of water can adversely impact drinking water supplies and aquatic ecology. Atrazine, acetochlor, and 2,4-D are herbicides commonly used to control weeds in maize (Zea mays) and soybean (Glycine max), the dominant crops in the U.S. Midwest. Unfortunately, these materials are frequently detected at high concentrations in surface runoff and subsurface drainage, especially when rainstorms occur shortly after their application. Thus, edge-of-field technologies employing effective sorbents to remove pesticides in water are needed to reduce this concern. In this study, we investigated the sorption of atrazine, acetochlor, and 2,4-D by a hardwood-derived biochar. Sorption kinetics and isotherms were determined for each pesticide using concentrations ranging from 5 to 100 ug L-1. The results from the kinetic sorption studies were fitted to pseudo first- and second-order reaction models and demonstrated that sorption was fast; in less than an hour > 90% of the added pesticides were sorbed and after 24 hours up to 100% was removed. The pH of the suspensions after the sorption kinetic and isotherm studies was 8.26 ± 0.51. Thus, because of the nature of the biochar and the pesticides used in this study, hydrophobic interactions appear to be the main mechanism of sorption. Furthermore, since the sorption was fast, we hypothesize that sorption occurred on the surface of biochar. The information from this study can be used to develop agricultural best management practices to remove pesticides in water.

  1. Sorption and diffusion of phenols onto well-defined ordered nanoporous monolithic silicas.

    Science.gov (United States)

    El-Safty, S A

    2003-04-01

    The sorption of phenol, and o-, m-, and p-aminophenol (o-, m-, and p-AP) onto highly ordered mesoporous silicas (HOM) with cubic Im3m (HOM-1), hexagonal H(I) (HOM-2), 3-D hexagonal p6(3)/mmc (HOM-3), cubic Ia3d (HOM-5), lamellar L( infinity ) (HOM-6), and solid phase S (HOM-8) materials has been investigated kinetically. Nanostructured silica molecular sieves have been prepared at 25 and 60 degrees C with lyotropic liquid-crystalline phases of the nonionic surfactant (Brij 76) that was used as a structure-directing agent. Such nanostructured silicas have been studied by 29Si nuclear magnetic resonance (29Si NMR), powder X-ray diffraction (XRD), the Brunauer-Emmett-Teller (BET) method for nitrogen adsorption and surface area measurements, and transmission electron microscopy (TEM) techniques after synthesis and sorption. It was found that all materials exhibit well-defined long-range porous architectures without significant loss of the ordered texture during phenol sorption. The kinetics of phenol sorption has been studied spectrophotometrically at different temperatures (25-40 degrees C; +/-0.1 range). The sorption rate is zero order in all phenols sorbed, and increases directly in the pattern P >m-AP > o-AP > p-AP, which reflects the mobility of the phenol compounds on the particle pores. The isothermal sorption and the kinetic parameters were discussed and it was established that a diffusion-controlled process characterizes phenol sorption. Furthermore, the mechanism of phenol sorption was deduced to be predominantly particle diffusion. The diffusion coefficients were determined using Fick's equation. The trend of diffusion of all phenols onto nanoporous silica was HOM-8 > HOM-2 > HOM-6 > HOM-5 > HOM-1 > HOM-3, reflecting the effect of the uniform pore size distribution and the internal surface area of the nanostructured silicas on the diffusion process.

  2. Oxide nanoparticle EUV resists: toward understanding the mechanism of positive and negative tone patterning

    KAUST Repository

    Chakrabarty, Souvik

    2013-04-01

    DUV, EUV and e-beam patterning of hybrid nanoparticle photoresists have been reported previously by Ober and coworkers. The present work explores the underlying mechanism that is responsible for the dual tone patterning capability of these photoresist materials. Spectroscopic results correlated with mass loss and dissolution studies suggest a ligand exchange mechanism responsible for altering the solubility between the exposed and unexposed regions. © 2013 SPIE.

  3. Using realist synthesis to understand the mechanisms of interprofessional teamwork in health and social care.

    Science.gov (United States)

    Hewitt, Gillian; Sims, Sarah; Harris, Ruth

    2014-11-01

    Realist synthesis offers a novel and innovative way to interrogate the large literature on interprofessional teamwork in health and social care teams. This article introduces realist synthesis and its approach to identifying and testing the underpinning processes (or "mechanisms") that make an intervention work, the contexts that trigger those mechanisms and their subsequent outcomes. A realist synthesis of the evidence on interprofessional teamwork is described. Thirteen mechanisms were identified in the synthesis and findings for one mechanism, called "Support and value" are presented in this paper. The evidence for the other twelve mechanisms ("collaboration and coordination", "pooling of resources", "individual learning", "role blurring", "efficient, open and equitable communication", "tactical communication", "shared responsibility and influence", "team behavioural norms", "shared responsibility and influence", "critically reviewing performance and decisions", "generating and implementing new ideas" and "leadership") are reported in a further three papers in this series. The "support and value" mechanism referred to the ways in which team members supported one another, respected other's skills and abilities and valued each other's contributions. "Support and value" was present in some, but far from all, teams and a number of contexts that explained this variation were identified. The article concludes with a discussion of the challenges and benefits of undertaking this realist synthesis.

  4. Detection of tritium sorption on four soil materials

    International Nuclear Information System (INIS)

    Teng Yanguo; Zuo Rui; Wang Jinsheng; Hu Qinhong; Sun Zongjian; Zeng Ni

    2011-01-01

    In order to measure groundwater age and design nuclear waste disposal sites, it is important to understand the sorption behavior of tritium on soils. In this study, batch tests were carried out using four soils from China: silty clays from An County and Jiangyou County in Sichuan Province, both of which could be considered candidate sites for Very Low Level Waste disposal; silty sand from Beijing; and loess from Yuci County in Shanxi Province, a typical Chinese loess region. The experimental results indicated that in these soil media, the distribution coefficient of tritium is slightly influenced by adsorption time, water/solid ratio, initial tritium specific activity, pH, and the content of humic and fulvic acids. The average distribution coefficient from all of these influencing factors was about 0.1-0.2 mL/g for the four types of soil samples. This relatively modest sorption of tritium in soils needs to be considered in fate and transport studies of tritium in the environment. - Research highlights: → In this study, batch sorption tests validate the adsorption of tritium on all of the four tested soil samples collected in China, and the distribution coefficient is found to be non-zero and less than 0.4 mL/g. The experimental results indicated that in these soil media, the distribution coefficient of tritium is slightly influenced by adsorption time, water/solid ratio, initial tritium specific activity, pH, and the content of humic and fulvic acids. This relatively modest sorption of tritium in soils needs to be considered in fate and transport studies of tritium in the environment.

  5. Understanding User Preferences and Awareness: Privacy Mechanisms in Location-Based Services

    Science.gov (United States)

    Burghardt, Thorben; Buchmann, Erik; Müller, Jens; Böhm, Klemens

    Location based services (LBS) let people retrieve and share information related to their current position. Examples are Google Latitude or Panoramio. Since LBS share user-related content, location information etc., they put user privacy at risk. Literature has proposed various privacy mechanisms for LBS. However, it is unclear which mechanisms humans really find useful, and how they make use of them. We present a user study that addresses these issues. To obtain realistic results, we have implemented a geotagging application on the web and on GPS cellphones, and our study participants use this application in their daily lives. We test five privacy mechanisms that differ in the awareness, mental effort and degree of informedness required from the users. Among other findings, we have observed that in situations where a single simple mechanism does not meet all privacy needs, people want to use simple and sophisticated mechanisms in combination. Further, individuals are concerned about the privacy of others, even when they do not value privacy for themselves.

  6. Combating mutations in genetic disease and drug resistance: understanding molecular mechanisms to guide drug design.

    Science.gov (United States)

    Albanaz, Amanda T S; Rodrigues, Carlos H M; Pires, Douglas E V; Ascher, David B

    2017-06-01

    Mutations introduce diversity into genomes, leading to selective changes and driving evolution. These changes have contributed to the emergence of many of the current major health concerns of the 21st century, from the development of genetic diseases and cancers to the rise and spread of drug resistance. The experimental systematic testing of all mutations in a system of interest is impractical and not cost-effective, which has created interest in the development of computational tools to understand the molecular consequences of mutations to aid and guide rational experimentation. Areas covered: Here, the authors discuss the recent development of computational methods to understand the effects of coding mutations to protein function and interactions, particularly in the context of the 3D structure of the protein. Expert opinion: While significant progress has been made in terms of innovative tools to understand and quantify the different range of effects in which a mutation or a set of mutations can give rise to a phenotype, a great gap still exists when integrating these predictions and drawing causality conclusions linking variants. This often requires a detailed understanding of the system being perturbed. However, as part of the drug development process it can be used preemptively in a similar fashion to pharmacokinetics predictions, to guide development of therapeutics to help guide the design and analysis of clinical trials, patient treatment and public health policy strategies.

  7. Laboratory Activities to Support Student Understanding of the Molecular Mechanisms of Mutation & Natural Selection

    Science.gov (United States)

    Hubler, Tina; Adams, Patti; Scammell, Jonathan

    2015-01-01

    The molecular basis of evolution is an important and challenging concept for students to understand. In a previous article, we provided some of the scientific background necessary to teach this topic. This article features a series of laboratory activities demonstrating that molecular events can alter the genomes of organisms. These activities are…

  8. Sorption of metaldehyde using granular activated carbon

    Directory of Open Access Journals (Sweden)

    S. Salvestrini

    2017-09-01

    Full Text Available In this work, the ability of granular activated carbon (GAC to sorb metaldehyde was evaluated. The kinetic data could be described by an intra-particle diffusion model, which indicated that the porosity of the sorbent strongly influenced the rate of sorption. The analysis of the equilibrium sorption data revealed that ionic strength and temperature did not play any significant role in the metaldehyde uptake. The sorption isotherms were successfully predicted by the Freundlich model. The GAC used in this paper exhibited a higher affinity and sorption capacity for metaldehyde with respect to other GACs studied in previous works, probably as a result of its higher specific surface area and high point of zero charge.

  9. Radionuclide sorption on granitic drill core material

    International Nuclear Information System (INIS)

    Eriksen, T.E.; Locklund, B.

    1987-11-01

    Distribution ratios were determined for Sr-85, Cs-134 and Eu-152 on crushed granite and fissure coating/filling material from Stripa mines. Measurements were also carried out on intact fissure surfaces. The experimental data for Sr-85, Cs-134 on crushed material can be accomodated by a sorption model based on the assumption that the crushed material consists of porous spheres with outer and inner surfaces available for sorption. In the case of Eu-152 only sorption on the outer surfaces of the crushed material was observed. The absence of sorption on inner surfaces is most probably due to high depletion of the more strongly sorbed Eu-152 in the water phase and very low diffusivity of Eu-152 in the sorbed state. (orig./HP)

  10. Phenanthrene sorption on biochar-amended soils

    DEFF Research Database (Denmark)

    Kahawaththa Gamage, Inoka Damayanthi Kumari; Moldrup, Per; Paradelo Pérez, Marcos

    2014-01-01

    Biochar, a byproduct resulting from the pyrolysis of biomass, is considered to be an anthropogenic carbonaceous sorbent. Despite a worldwide increase in the application of biochar on agricultural fields to improve crop productivity over the past few decades, there have been few studies...... on their influences on the sorption of environmental contaminants. In a field-based study at two experimental sites in Denmark, we investigated the effect of birch wood-derived biochar (Skogans kol) on the sorption of phenanthrene in soils with different properties. The soil sorption coefficient, Kd (L kg-1......), of phenanthrene was measured on sandy loam and loamy sand soils which have received from zero up to 100 t ha-1 of biochar. Results show that birch wood biochar had a higher Kd compared to soils. Furthermore, the application of birch wood biochar enhanced the sorption of phenanthrene in agricultural soils...

  11. Towards an understanding of hot carrier cooling mechanisms in multiple quantum wells

    Science.gov (United States)

    Conibeer, Gavin; Zhang, Yi; Bremner, Stephen P.; Shrestha, Santosh

    2017-09-01

    Multiple quantum wells have been shown significantly reduced hot carrier cooling rates compared to bulk material and are thus a promising candidate for hot carrier solar cell absorbers. However, the mechanism(s) by which hot carrier cooling is restricted is not clear. A systematic study of carrier cooling rates in GaAs/AlAs multiple quantum wells (MQWs) with either varying barrier thickness or varying well thickness is presented in this paper. These allow an investigation as to whether the mechanisms of either a modification in hot carrier diffusion or a localisation of phonons emitted by hot carriers are primarily responsible for reduced carrier cooling rates. With the conclusion that for the structures investigated the situation is rather more complex with both carrier mobility to modify hot carrier diffusion, different diffusion rates for electrons and holes and reflection and localisation of phonons to enhance phonon bottleneck all playing their parts in modulating phonon reabsorption and hot carrier behaviour.

  12. The contribution of experimental in vivo models to understanding the mechanisms of adaptation to mechanical loading in bone

    Directory of Open Access Journals (Sweden)

    Lee B Meakin

    2014-10-01

    Full Text Available Changing loading regimens by natural means such as exercise, with or without interference such as osteotomy, has provided useful information on the structure:function relationship in bone tissue. However, the greatest precision in defining those aspects of the overall strain environment that influence modeling and remodeling behavior has been achieved by relating quantified changes in bone architecture to quantified changes in bones’ strain environment produced by direct, controlled artificial bone loading.Jiri Heřt introduced the technique of artificial loading of bones in vivo with external devices in the 1960s using an electromechanical device to load rabbit tibiae through transfixing stainless steel pins. Quantifying natural bone strains during locomotion by attaching electrical resistance strain gauges to bone surfaces was introduced by Lanyon, also in the 1960s. These studies in a variety of bones in a number of species demonstrated remarkable uniformity in the peak strains and maximum strain rates experienced.Experiments combining strain gauge instrumentation with artificial loading in sheep, pigs, roosters, turkeys, rats and mice has yielded significant insight into the control of strain-related adaptive (remodeling. This diversity of approach has been largely superseded by non-invasive transcutaneous loading in rats and mice which is now the model of choice for many studies. Together such studies have demonstrated that; over the physiological strain range, bone’s mechanically-adaptive processes are responsive to dynamic but not static strains; the size and nature of the adaptive response controlling bone mass is linearly related to the peak loads encountered; the strain-related response is preferentially sensitive to high strain rates and unresponsive to static ones; is most responsive to unusual strain distributions; is maximized by remarkably few strain cycles and that these are most effective when interrupted by short periods of

  13. The Contribution of Experimental in vivo Models to Understanding the Mechanisms of Adaptation to Mechanical Loading in Bone

    Science.gov (United States)

    Meakin, Lee B.; Price, Joanna S.; Lanyon, Lance E.

    2014-01-01

    Changing loading regimens by natural means such as exercise, with or without interference such as osteotomy, has provided useful information on the structure:function relationship in bone tissue. However, the greatest precision in defining those aspects of the overall strain environment that influence modeling and remodeling behavior has been achieved by relating quantified changes in bone architecture to quantified changes in bones’ strain environment produced by direct, controlled artificial bone loading. Jiri Hert introduced the technique of artificial loading of bones in vivo with external devices in the 1960s using an electromechanical device to load rabbit tibiae through transfixing stainless steel pins. Quantifying natural bone strains during locomotion by attaching electrical resistance strain gages to bone surfaces was introduced by Lanyon, also in the 1960s. These studies in a variety of bones in a number of species demonstrated remarkable uniformity in the peak strains and maximum strain rates experienced. Experiments combining strain gage instrumentation with artificial loading in sheep, pigs, roosters, turkeys, rats, and mice has yielded significant insight into the control of strain-related adaptive (re)modeling. This diversity of approach has been largely superseded by non-invasive transcutaneous loading in rats and mice, which is now the model of choice for many studies. Together such studies have demonstrated that over the physiological strain range, bone’s mechanically adaptive processes are responsive to dynamic but not static strains; the size and nature of the adaptive response controlling bone mass is linearly related to the peak loads encountered; the strain-related response is preferentially sensitive to high strain rates and unresponsive to static ones; is most responsive to unusual strain distributions; is maximized by remarkably few strain cycles, and that these are most effective when interrupted by short periods of rest between them

  14. Experimental methodology to study radionuclide sorption and migration in geological formations and engineered barriers of waste repositories

    International Nuclear Information System (INIS)

    Rojo Sanz, H.

    2010-01-01

    In Spain, the waste management options include either the possibility of a final storage in a deep geological repository (DGR) or the centralized temporal surface disposal (CTS). DGRs are based in a multi-barrier concept with the geological barrier and including the vitrified waste, the metal containers and engineered barriers such as compacted bentonite and cement-based materials. On the other hand, CTS mainly considers concrete and cement to confine the metal canisters containing the waste. Radionuclide migration will mainly take place by the existence of chemical concentration gradients being thus diffusion the main transport mechanism or by the existence of hydraulic gradients due to the existence of water-conductive fractures. Radionuclide sorption/retention on the materials composing the natural and engineered barriers is the fundamental process controlling contaminant migration. The evaluation of sorption parameters and the understanding of the different mechanisms leading to radionuclide retention are very important issues. The study of diffusion processes is very relevant as well. This paper describes the main experimental methodologies applied to analyse radionuclide transport in the different barriers of radioactive repositories. Particularly we focused on obtaining of retention parameters as distribution coefficients, kd, or retardation factors, Rf, and diffusion coefficients of radionuclides. (Author) 6 refs.

  15. Understanding the mechanism of nanotube synthesis for controlled production of specific (n,m) structures

    Energy Technology Data Exchange (ETDEWEB)

    Resasco, Daniel E.

    2010-02-11

    This report shows the extensive research on the mechanism responsible for the formation of single walled carbon nanotubes in order to get control over their structural parameters (diameter and chirality). Catalyst formulations, pre-treatment conditions, and reaction conditions are described in detail as well as mechanisms to produce nanotubes structures of specific arrays (vertical forest, nanotube pillars). Applications of SWNT in different fields are also described in this report. In relation to this project five students have graduated (3 PhD and 2 MS) and 35 papers have been published.

  16. Sorption of fomesafen in Brazilian soils

    OpenAIRE

    Silva,G.R.; D'Antonino,L.; Faustino,L.A.; Silva,A.A.; Ferreira,F.A.; Texeira,C.C.

    2013-01-01

    The study of the dynamics of a herbicide in the soil focus on the interactions with environmental components to obtain agronomic efficiency, ensuring selectivity to the culture and risk reduction of environmental impact. This study evaluated the sorption process of fomesafen in the Brazilian soils Ultisol, Cambisol, and Organosol. Besides soil, washed sand was used as an inert material for determination of the sorption ratio of fomesafen in the soil. The bioassay method was applied, using Sor...

  17. Sorption and Transport of Sildenafil in Natural Soils

    Science.gov (United States)

    Boudinot, F. G.; Vulava, V. M.

    2013-12-01

    glass chromatography columns, homogenously packed with soil, saturated with 5 mM CaCl2 solution, and injected with 100 mg/L sildenafil. The effluent solution concentrations were plotted as a function of time to plot breakthrough curves. Sildenafil was significantly retarded in clay-rich soil column experiments confirming trends observed in sorption experiments. Overall data indicate very strong sorption of sildenafil to both organic- rich and clay-rich soils, but stronger sorption to clay-rich soils. Strong soil sorption acts as a filter for water, leaving the PC behind in the soils. These results suggest that little sildenafil will reside in groundwater once exposed to natural soils. Further research is needed to better understand how sildenafil's metabolites respond in ecosystems. Given the high metabolic rate and long shelf life of sildenafil, these metabolites may be more prevalent in natural soils.

  18. A mathematical model towards understanding the mechanism of neuronal regulation of wake-NREMS-REMS states.

    Directory of Open Access Journals (Sweden)

    Rupesh Kumar

    Full Text Available In this study we have constructed a mathematical model of a recently proposed functional model known to be responsible for inducing waking, NREMS and REMS. Simulation studies using this model reproduced sleep-wake patterns as reported in normal animals. The model helps to explain neural mechanism(s that underlie the transitions between wake, NREMS and REMS as well as how both the homeostatic sleep-drive and the circadian rhythm shape the duration of each of these episodes. In particular, this mathematical model demonstrates and confirms that an underlying mechanism for REMS generation is pre-synaptic inhibition from substantia nigra onto the REM-off terminals that project on REM-on neurons, as has been recently proposed. The importance of orexinergic neurons in stabilizing the wake-sleep cycle is demonstrated by showing how even small changes in inputs to or from those neurons can have a large impact on the ensuing dynamics. The results from this model allow us to make predictions of the neural mechanisms of regulation and patho-physiology of REMS.

  19. The Mediated MIMIC Model for Understanding the Underlying Mechanism of DIF

    Science.gov (United States)

    Cheng, Ying; Shao, Can; Lathrop, Quinn N.

    2016-01-01

    Due to its flexibility, the multiple-indicator, multiple-causes (MIMIC) model has become an increasingly popular method for the detection of differential item functioning (DIF). In this article, we propose the mediated MIMIC model method to uncover the underlying mechanism of DIF. This method extends the usual MIMIC model by including one variable…

  20. Understanding the antimicrobial mechanism of TiO2-based nanocomposite films in a pathogenic bacterium

    NARCIS (Netherlands)

    Kubacka, A.; Suarez Diez, M.; Rojo, D.; Bargiela, R.; Ciordia, S.; Zapico, I.; Albar, J.P.; Barbas, C.; Martins Dos Santos, V.A.P.; Fernández-García, M.; Ferrer, M.

    2014-01-01

    Titania (TiO2)-based nanocomposites subjected to light excitation are remarkably effective in eliciting microbial death. However, the mechanism by which these materials induce microbial death and the effects that they have on microbes are poorly understood. Here, we assess the low dose

  1. Understanding the mechanism of action of triazine-phosphonate derivatives as flame retardants for cotton fabrics

    Science.gov (United States)

    Countless hours of research and studies on triazine, phosphonate and their combination have provided insightful information into their flame retardant properties on polymeric systems. However, only limited number of studies shed light on the mechanism of flame retardant cotton fabrics. The purpose...

  2. Investigating and improving student understanding of quantum mechanics in the context of single photon interference

    Science.gov (United States)

    Marshman, Emily; Singh, Chandralekha

    2017-06-01

    Single photon experiments involving a Mach-Zehnder interferometer can illustrate the fundamental principles of quantum mechanics, e.g., the wave-particle duality of a single photon, single photon interference, and the probabilistic nature of quantum measurement involving single photons. These experiments explicitly make the connection between the abstract quantum theory and concrete laboratory settings and have the potential to help students develop a solid grasp of the foundational issues in quantum mechanics. Here we describe students' conceptual difficulties with these topics in the context of Mach-Zehnder interferometer experiments with single photons and how the difficulties found in written surveys and individual interviews were used as a guide in the development of a Quantum Interactive Learning Tutorial (QuILT). The QuILT uses an inquiry-based approach to learning and takes into account the conceptual difficulties found via research to help upper-level undergraduate and graduate students learn about foundational quantum mechanics concepts using the concrete quantum optics context. It strives to help students learn the basics of quantum mechanics in the context of single photon experiment, develop the ability to apply fundamental quantum principles to experimental situations in quantum optics, and explore the differences between classical and quantum ideas in a concrete context. We discuss the findings from in-class evaluations suggesting that the QuILT was effective in helping students learn these abstract concepts.

  3. Improving Student Understanding of Addition of Angular Momentum in Quantum Mechanics

    Science.gov (United States)

    Zhu, Guangtian; Singh, Chandralekha

    2013-01-01

    We describe the difficulties advanced undergraduate and graduate students have with concepts related to addition of angular momentum in quantum mechanics. We also describe the development and implementation of a research-based learning tool, Quantum Interactive Learning Tutorial (QuILT), to reduce these difficulties. The preliminary evaluation…

  4. A Changing Landscape of Advanced Prostate Cancer: Understanding Mechanisms of Resistance to Potent Hormonal Therapies

    Science.gov (United States)

    2016-10-01

    mechanisms of NEPC progression using deep sequencing techniques of metastatic tumor biopsies and non-invasively using liquid biopsies including...from each site. (b) AR signaling (right) based on abundance of mRNA transcripts included in the AR signaling signature described in ref 19. Violin

  5. Recent advances in understanding the reinforcing ability and mechanism of carbon nanotubes in ceramic matrix composites

    International Nuclear Information System (INIS)

    Estili, Mehdi; Sakka, Yoshio

    2014-01-01

    Since the discovery of carbon nanotubes (CNTs), commonly referred to as ultimate reinforcement, the main purpose for fabricating CNT–ceramic matrix composites has been mainly to improve the fracture toughness and strength of the ceramic matrix materials. However, there have been many studies reporting marginal improvements or even the degradation of mechanical properties. On the other hand, those studies claiming noticeable toughening measured using indentation, which is an indirect/unreliable characterization method, have not demonstrated the responsible mechanisms applicable to the nanoscale, flexible CNTs; instead, those studies proposed those classical methods applicable to microscale fiber/whisker reinforced ceramics without showing any convincing evidence of load transfer to the CNTs. Therefore, the ability of CNTs to directly improve the macroscopic mechanical properties of structural ceramics has been strongly questioned and debated in the last ten years. In order to properly discuss the reinforcing ability (and possible mechanisms) of CNTs in a ceramic host material, there are three fundamental questions to our knowledge at both the nanoscale and macroscale levels that need to be addressed: (1) does the intrinsic load-bearing ability of CNTs change when embedded in a ceramic host matrix?; (2) when there is an intimate atomic-level interface without any chemical reaction with the matrix, could one expect any load transfer to the CNTs along with effective load bearing by them during crack propagation?; and (3) considering their nanometer-scale dimensions, flexibility and radial softness, are the CNTs able to improve the mechanical properties of the host ceramic matrix at the macroscale when individually, intimately and uniformly dispersed? If so, how? Also, what is the effect of CNT concentration in such a defect-free composite system? Here, we briefly review the recent studies addressing the above fundamental questions. In particular, we discuss the new

  6. Understanding NOx SCR Mechanism and Activity on Cu/Chabazite Structures throughout the Catalyst Life Cycle

    Energy Technology Data Exchange (ETDEWEB)

    Ribeiro, Fabio; Delgass, Nick; Gounder, Rajmani; Schneider, William F.; Miller, Jeff; Yezerets, Aleksey; McEwen, Jean-Sabin; Peden, Charles HF; Howden, Ken

    2014-12-09

    Oxides of nitrogen (NOx) compounds contribute to acid rain and photochemical smog and have been linked to respiratory ailments. NOx emissions regulations continue to tighten, driving the need for high performance, robust control strategies. The goal of this project is to develop a deep, molecular level understanding of the function of Cu-SSZ-13 and Cu-SAPO-34 materials that catalyze the SCR of NOx with NH3.

  7. Progress in understanding the mechanical behavior of pressure-vessel materials at elevated temperatures

    International Nuclear Information System (INIS)

    Swindeman, R.W.; Brinkman, C.R.

    1981-01-01

    Progress during the 1970's on the production of high-temperature mechanical properties data for pressure vessel materials was reviewed. The direction of the research was toward satisfying new data requirements to implement advances in high-temperature inelastic design methods. To meet these needs, servo-controlled testing machines and high-resolution extensometry were developed to gain more information on the essential behavioral features of high-temperature alloys. The similarities and differences in the mechanical response of various pressure vessel materials were identified. High-temperature pressure vessel materials that have received the most attention included Type 304 stainless steel, Type 316 stainless steel, 2 1/4 Cr-1 Mo steel, alloy 800H, and Hastelloy X

  8. Understanding reaction mechanisms in organic chemistry from catastrophe theory applied to the electron localization function topology.

    Science.gov (United States)

    Polo, Victor; Andres, Juan; Berski, Slawomir; Domingo, Luis R; Silvi, Bernard

    2008-08-07

    Thom's catastrophe theory applied to the evolution of the topology of the electron localization function (ELF) gradient field constitutes a way to rationalize the reorganization of electron pairing and a powerful tool for the unambiguous determination of the molecular mechanisms of a given chemical reaction. The identification of the turning points connecting the ELF structural stability domains along the reaction pathway allows a rigorous characterization of the sequence of electron pair rearrangements taking place during a chemical transformation, such as multiple bond forming/breaking processes, ring closure processes, creation/annihilation of lone pairs, transformations of C-C multiple bonds into single ones. The reaction mechanism of some relevant organic reactions: Diels-Alder, 1,3-dipolar cycloaddition and Cope rearrangement are reviewed to illustrate the potential of the present approach.

  9. Understanding the Acute Skin Injury Mechanism Caused by Player-Surface Contact During Soccer

    Science.gov (United States)

    van den Eijnde, Wilbert A.J.; Peppelman, Malou; Lamers, Edwin A.D.; van de Kerkhof, Peter C.M.; van Erp, Piet E.J.

    2014-01-01

    Background: Superficial skin injuries are considered minor, and their incidence is probably underestimated. Insight into the incidence and mechanism of acute skin injury can be helpful in developing suitable preventive measures and safer playing surfaces for soccer and other field sports. Purpose: To gain insight into the incidence and severity of skin injuries related to soccer and to describe the skin injury mechanism due to player-surface contact. Study Design: Systematic review; Level of evidence, 4. Methods: The prevention model by van Mechelen et al (1992) combined with the injury causation model of Bahr and Krosshaug (2005) were used as a framework for the survey to describe the skin injury incidence and mechanism caused by player-surface contact. Results: The reviewed literature showed that common injury reporting methods are mainly based on time lost from participation or the need for medical attention. Because skin abrasions seldom lead to absence or medical attention, they are often not reported. When reported, the incidence of abrasion/laceration injuries varies from 0.8 to 6.1 injuries per 1000 player-hours. Wound assessment techniques such as the Skin Damage Area and Severity Index can be a valuable tool to obtain a more accurate estimation of the incidence and severity of acute skin injuries. Conclusion: The use of protective equipment, a skin lubricant, or wet surface conditions has a positive effect on preventing abrasion-type injuries from artificial turf surfaces. The literature also shows that essential biomechanical information of the sliding event is lacking, such as how energy is transferred to the area of contact. From a clinical and histological perspective, there are strong indications that a sliding-induced skin lesion is caused by mechanical rather than thermal injury to the skin. PMID:26535330

  10. Understanding the Personality and Behavioral Mechanisms Defining Hypersexuality in Men Who Have Sex With Men.

    Science.gov (United States)

    Miner, Michael H; Romine, Rebecca Swinburne; Raymond, Nancy; Janssen, Erick; MacDonald, Angus; Coleman, Eli

    2016-09-01

    Hypersexuality has been conceptualized as sexual addiction, compulsivity, and impulsivity, among others, in the absence of strong empirical data in support of any specific conceptualization. To investigate personality factors and behavioral mechanisms that are relevant to hypersexuality in men who have sex with men. A sample of 242 men who have sex with men was recruited from various sites in a moderate-size mid-western city. Participants were assigned to a hypersexuality group or a control group using an interview similar to the Structured Clinical Interview for the Diagnostic and Statistical Manual for Mental Disorders, Fourth Edition. Self-report inventories were administered that measured the broad personality constructs of positive emotionality, negative emotionality, and constraint and more narrow constructs related to sexual behavioral control, behavioral activation, behavioral inhibition, sexual excitation, sexual inhibition, impulsivity, attention-deficit/hyperactivity disorder, and sexual behavior. Hierarchical logistic regression was used to determine the relation between these personality and behavioral variables and group membership. A hierarchical logistic regression controlling for age showed a significant positive relation between hypersexuality and negative emotionality and a negative relation with constraint. None of the behavioral mechanism variables entered this equation. However, a hierarchical multiple regression analysis predicting sexual behavioral control indicated that lack of such control was positively related to sexual excitation and sexual inhibition owing to the threat of performance failure and negatively related to sexual inhibition owing to the threat of performance consequences and general behavioral inhibition Hypersexuality was found to be related to two broad personality factors that are characterized by emotional reactivity, risk taking, and impulsivity. The associated lack of sexual behavior control is influenced by sexual

  11. The effects of bariatric surgery – will understanding its mechanism render the knife unnecessary?

    OpenAIRE

    Browning, Kirsteen N; Hajnal, Andras

    2013-01-01

    The incidence of obesity is increasing worldwide at a dramatic rate, accompanied by an associated increase in comorbid conditions. Bariatric surgery is the most effective treatment for severe obesity with, until recently, Roux-en-Y gastric bypass (RYGB) being the most commonly performed procedures, yet the underlying mechanisms by which it induces a wide-array of beneficial effects remains obscure. From both basic science as well as clinical standpoints, there are several areas of current int...

  12. Understanding Freshness Perception from the Cognitive Mechanisms of Flavor: The Case of Beverages

    Science.gov (United States)

    Roque, Jérémy; Auvray, Malika; Lafraire, Jérémie

    2018-01-01

    Freshness perception has received recent consideration in the field of consumer science mainly because of its hedonic dimension, which is assumed to influence consumers’ preference and behavior. However, most studies have considered freshness as a multisensory attribute of food and beverage products without investigating the cognitive mechanisms at hand. In the present review, we endorse a slightly different perspective on freshness. We focus on (i) the multisensory integration processes that underpin freshness perception, and (ii) the top–down factors that influence the explicit attribution of freshness to a product by consumers. To do so, we exploit the recent literature on the cognitive underpinnings of flavor perception as a heuristic to better characterize the mechanisms of freshness perception in the particular case of beverages. We argue that the lack of consideration of particular instances of flavor, such as freshness, has resulted in a lack of consensus about the content and structure of different types of flavor representations. We then enrich these theoretical analyses, with a review of the cognitive mechanisms of flavor perception: from multisensory integration processes to the influence of top–down factors (e.g., attentional and semantic). We conclude that similarly to flavor, freshness perception is characterized by hybrid content, both perceptual and semantic, but that freshness has a higher-degree of specificity than flavor. In particular, contrary to flavor, freshness is characterized by specific functions (e.g., alleviation of oropharyngeal symptoms) and likely differs from flavor with respect to the weighting of each sensory contributor, as well as to its subjective location. Finally, we provide a comprehensive model of the cognitive mechanisms that underlie freshness perception. This model paves the way for further empirical research on particular instances of flavor, and will enable advances in the field of food and beverage cognition

  13. Investigating and improving student understanding of quantum mechanical observables and their corresponding operators in Dirac notation

    Science.gov (United States)

    Marshman, Emily; Singh, Chandralekha

    2018-01-01

    In quantum mechanics, for every physical observable, there is a corresponding Hermitian operator. According to the most common interpretation of quantum mechanics, measurement of an observable collapses the quantum state into one of the possible eigenstates of the operator and the corresponding eigenvalue is measured. Since Dirac notation is an elegant notation that is commonly used in upper-level quantum mechanics, it is important that students learn to express quantum operators corresponding to observables in Dirac notation in order to apply the quantum formalism effectively in diverse situations. Here we focus on an investigation that suggests that, even though Dirac notation is used extensively, many advanced undergraduate and PhD students in physics have difficulty expressing the identity operator and other Hermitian operators corresponding to physical observables in Dirac notation. We first describe the difficulties students have with expressing the identity operator and a generic Hermitian operator corresponding to an observable in Dirac notation. We then discuss how the difficulties found via written surveys and individual interviews were used as a guide in the development of a quantum interactive learning tutorial (QuILT) to help students develop a good grasp of these concepts. The QuILT strives to help students become proficient in expressing the identity operator and a generic Hermitian operator corresponding to an observable in Dirac notation. We also discuss the effectiveness of the QuILT based on in-class evaluations.

  14. Radionuclides sorption in clay soils

    International Nuclear Information System (INIS)

    Siraky, G.; Lewis, C.; Hamlat, S.; Nollmann, C.E.

    1987-01-01

    The sorption behaviour of clay soils is examined through a parametric study of the distribution coefficient (Kd) for the radionuclides of interest, Cs and Sr. This work is a preliminary stage of the migration studies of these nuclides in a porous medium (ground of Ezeiza, Argentina) and the evaluation of radiologic impact of the removal of low and intermediate activity wastes in shallow trenches. The determination of Kd is performed by a static technique or batch. The phases are separated by centrifugation at 20000 g during 1 hour. The activity of supernatant solution of Cs-137 and Sr-85 is measured in a detecting system of I Na(Tl) well-type. Two types of parameters were changed: a) those related to the determination method: phase separation (centrifugation vs. centrifugation plus filtration); equilibrium period, ratio solid/liquid; b) those related to the geochemical system: pH of contact solution, carrier concentration, competitive ions, ionic strength, desorption. It was observed that the modification of parameters in the Kd-measurement does not change the order of magnitude of results. (Author)

  15. Marine phospholipids: The current understanding of their oxidation mechanisms and potential uses for food fortification

    DEFF Research Database (Denmark)

    Lu, Henna Fung Sieng; Nielsen, Nina Skall; Baron, Caroline P.

    2017-01-01

    and storage of marine PL. For example, nonenzymatic browning reactions may occur between lipid oxidation products and primary amine group from phosphatidylethanolamine or amino acid residues that are present inmarine PL. Therefore, marine PL contain products from nonenzymatic browning and lipid oxidation...... reactions, namely, Strecker aldehydes, pyrroles, oxypolymers, and other impurities that may positively or negatively affect the oxidative stability and quality of marine PL. This review was undertaken to provide the industry and academia with an overview of the current understanding of the quality changes...... taking place in PL during their production and their storage as well as with regards to their utilization for food fortification....

  16. Understanding the Atomic Scale Mechanisms that Control the Attainment of Ultralow Friction and Wear in Carbon-Based Materials

    Science.gov (United States)

    2016-01-16

    2015. 15. Invited. New Insights into Friction and Wear through In-Situ Nanotribology. Joint Symposium of the Surface Science Society of Japan and...and Carpick, R.W. Influence of Surface Passivation on the Friction and Wear Behavior of Ultrananocrystalline Diamond and Tetrahedral Amorphous Carbon...AFRL-AFOSR-JP-TR-2016-0053 Understanding the Atomic Scale Mechanism that controls the attainment of ultralow friction and wear in carbon based

  17. The effects of students' reasoning abilities on conceptual understandings and problem-solving skills in introductory mechanics

    International Nuclear Information System (INIS)

    Ates, S; Cataloglu, E

    2007-01-01

    The purpose of this study was to determine if there are relationships among freshmen/first year students' reasoning abilities, conceptual understandings and problem-solving skills in introductory mechanics. The sample consisted of 165 freshmen science education prospective teachers (female = 86, male = 79; age range 17-21) who were enrolled in an introductory physics course. Data collection was done during the fall semesters in two successive years. At the beginning of each semester, the force concept inventory (FCI) and the classroom test of scientific reasoning (CTSR) were administered to assess students' initial understanding of basic concepts in mechanics and reasoning levels. After completing the course, the FCI and the mechanics baseline test (MBT) were administered. The results indicated that there was a significant difference in problem-solving skill test mean scores, as measured by the MBT, among concrete, formal and postformal reasoners. There were no significant differences in conceptual understanding levels of pre- and post-test mean scores, as measured by FCI, among the groups. The Benferroni post hoc comparison test revealed which set of reasoning levels showed significant difference for the MBT scores. No statistical difference between formal and postformal reasoners' mean scores was observed, while the mean scores between concrete and formal reasoners and concrete and postformal reasoners were statistically significantly different

  18. Understanding of bonding and mechanical characteristics of cementitious mineral tobermorite from first principles.

    Science.gov (United States)

    Tunega, Daniel; Zaoui, Ali

    2011-01-30

    This paper reports density functional theory study of the structural and mechanical properties of tobermorite mineral (9 Å phase) as one of the main component of cementitious materials in a concrete chemistry. Calculated bulk modulus and elastic constants reflect a relatively high resistance of the tobermorite structure with respect to external isostatic compression. Moreover, the elastic constants proved the anisotropic character of the tobermorite structure. The directions parallel to the axb plane are more resistant to the compression than the perpendicular direction. The largest contribution to this resistance comes from the "dreierketten" silicate chains. The bonding analysis linked macroscopic mechanical properties and the atomic structure of the tobermorite. It was found that polar covalent Si-O bonds are stiffer than iono-covalent Ca-O bonds. The SiO(4) tetrahedra are resistant with respect to the compression and the effect of external pressure is reflected by the large mutual tilting of these tetrahedra as it is shown by changes of the Si-O-Si bridging angles. Polyhedra with the seven-fold coordinated Ca(2+) cations undergo large structural changes. Especially, axial Ca-O bonds perpendicular to the axb plane are significantly shortened. Besides, it was shown that structural parameters, more or less in parallel orientation to the axb plane, are mainly responsible for the high resistance of the tobermorite structure to external pressure. The main mechanism of a dissipation of energy entered to the structure through the compression is proceeded by the tilting of the tetrahedra of the silicate chains and by large shortening of the axial Ca-O distances. Copyright © 2010 Wiley Periodicals, Inc.

  19. Understanding flocculation mechanism of graphene oxide for organic dyes from water: Experimental and molecular dynamics simulation

    Directory of Open Access Journals (Sweden)

    Jun Liu

    2015-11-01

    Full Text Available Flocculation treatment processes play an important role in water and wastewater pretreatment. Here we investigate experimentally and theoretically the possibility of using graphene oxide (GO as a flocculant to remove methylene blue (MB from water. Experimental results show that GO can remove almost all MB from aqueous solutions at its optimal dosages and molecular dynamics simulations indicate that MB cations quickly congregate around GO in water. Furthermore, PIXEL energy contribution analysis reveals that most of the strong interactions between GO and MB are of a van der Waals (London dispersion character. These results offer new insights for shedding light on the molecular mechanism of interaction between GO and organic pollutants.

  20. Understanding organometallic reaction mechanisms and catalysis experimental and computational tools computational and experimental tools

    CERN Document Server

    Ananikov, Valentin P

    2014-01-01

    Exploring and highlighting the new horizons in the studies of reaction mechanisms that open joint application of experimental studies and theoretical calculations is the goal of this book. The latest insights and developments in the mechanistic studies of organometallic reactions and catalytic processes are presented and reviewed. The book adopts a unique approach, exemplifying how to use experiments, spectroscopy measurements, and computational methods to reveal reaction pathways and molecular structures of catalysts, rather than concentrating solely on one discipline. The result is a deeper

  1. Sorption of a diverse set of organic chemical vapors onto XAD-2 resin: Measurement, prediction and implications for air sampling

    Science.gov (United States)

    Hayward, Stephen J.; Lei, Ying D.; Wania, Frank

    2011-01-01

    The wide-spread use of styrene-divinylbenzene-copolymeric resin (XAD-2) in air sampling necessitates a quantitative understanding of its sorption characteristics for organic chemicals. Inverse Gas Chromatography (IGC) was used to measure the sorption of a diverse set of 52 organic chemicals to XAD-2 at temperatures between 40 °C and 100 °C and at relative humidities between 0 and 87%. Even though relative humidity has been shown to influence sorption to other sorbents, it did not significantly influence most chemicals' sorption to XAD-2, indicating that water does not form a strong physical barrier to sorption on XAD-2 at high relative humidity. The resin-air partition coefficients ( KXAD) determined by IGC and the enthalpies of sorption derived from them were regressed against solute descriptors to derive poly-parameter Linear Free Energy Relationships (ppLFERs) which allow the estimation of KXAD for chemicals which are not sufficiently volatile to be amenable to IGC and for temperatures outside the experimental range. KXAD values at 20 °C estimated for a set of 296 chemicals for which solute descriptors are available, including polychlorinated biphenyls, polycyclic aromatic hydrocarbons, and pesticides, indicate that for many of the substances commonly found in the atmosphere sorption is higher to XAD-2 than to poly-urethane foam, another popular air sampling sorbent.

  2. A Multiscale Understanding of the Thermodynamic and Kinetic Mechanisms of Laser Additive Manufacturing

    Directory of Open Access Journals (Sweden)

    Dongdong Gu

    2017-10-01

    Full Text Available Selective laser melting (SLM additive manufacturing (AM technology has become an important option for the precise manufacturing of complex-shaped metallic parts with high performance. The SLM AM process involves complicated physicochemical phenomena, thermodynamic behavior, and phase transformation as a high-energy laser beam melts loose powder particles. This paper provides multiscale modeling and coordinated control for the SLM of metallic materials including an aluminum (Al-based alloy (AlSi10Mg, a nickel (Ni-based super-alloy (Inconel 718, and ceramic particle-reinforced Al-based and Ni-based composites. The migration and distribution mechanisms of aluminium nitride (AlN particles in SLM-processed Al-based nanocomposites and the in situ formation of a gradient interface between the reinforcement and the matrix in SLM-processed tungsten carbide (WC/Inconel 718 composites were studied in the microscale. The laser absorption and melting/densification behaviors of AlSi10Mg and Inconel 718 alloy powder were disclosed in the mesoscale. Finally, the stress development during line-by-line localized laser scanning and the parameter-dependent control methods for the deformation of SLM-processed composites were proposed in the macroscale. Multiscale numerical simulation and experimental verification methods are beneficial in monitoring the complicated powder-laser interaction, heat and mass transfer behavior, and microstructural and mechanical properties development during the SLM AM process.

  3. Understanding the differing governance of EU emissions trading and renewable: feedback mechanisms and policy entrepreneurs

    Energy Technology Data Exchange (ETDEWEB)

    Boasson, Elin Lerum; Wettestad, Joergen

    2010-04-15

    This paper presents a comparative study of two central EU climate policies: the revised Emissions Trading System (ETS), and the revised Renewable Energy Directive (RES). Both were originally developed in the early 2000s and revised policies were adopted in December 2008. While the ETS from 2013 on will have a quite centralized and market-streamlined design, the revised RES stands forward as a more decentralized and technology-focused policy. Differing institutional feed-back mechanisms and related roles of policy entrepreneurs can shed considerable light on these policy differences. Due to member states' cautiousness and contrary to the preferences of the Commission, the initial ETS was designed as a rather decentralized and 'politicized' market system, creating a malfunctioning institutional dynamic. In the revision process, the Commission skillfully highlighted this ineffective dynamic to win support for a much more centralized and market-streamlined approach. In the case of RES, national technology-specific support schemes and the strong links between the renewable industry and member states promoted the converse outcome: decentralization and technology development. Members of the European Parliament utilized these mechanisms through policy networking, while the Commission successfully used developments within the global climate regime to induce some degree of centralization. (Author)

  4. Understanding the Mechanisms of Gold Shell Growth onto Polymer Microcapsules to Control Shell Thickness.

    Science.gov (United States)

    Tasker, Alison L; Hitchcock, James; Baxter, Elaine A; Cayre, Dr Olivier J; Biggs, Simon

    2017-07-04

    Polymer microcapsules have been used commercially for decades, however they have an inherent flaw which renders them impractical as a carrier of small, volatile molecules. The porous nature of the polymer shell allows for diffusion of the encapsulated molecules into the bulk. The use of metal shells is an innovative way to prevent undesired loss of small molecules from the core of microcapsules, however it is important, particularly when using expensive metals to ensure that the resulting shell is as thin as possible. Here we investigate the fundamental mechanisms controlling the gold shell thickness when a fragrance oil is encapsulated in a poly(methyl methacrylate) shell. We consider the distribution of the nanoparticles on the capsule surface, and from quantification of the adsorbed nanoparticle (NP) density and resulting shell thickness, we propose mechanisms to describe the gold shell growth for systems with high and low NP surface coverage. We suggest from our observations that the gold grows to fill in the gaps between NPs. At low NP concentrations, thicker metal shells form. We postulate that this is due to the low NP density on the surface, forcing the gold clusters to grow larger before they meet the adjacent ones. Thus, to grow the thinnest possible shells a densely packed monolayer of platinum nanoparticles is required on the capsule surface. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Understanding of carbon-based supercapacitors ageing mechanisms by electrochemical and analytical methods

    Science.gov (United States)

    Liu, Yinghui; Soucaze-Guillous, Benoît; Taberna, Pierre-Louis; Simon, Patrice

    2017-10-01

    In order to shed light on ageing mechanisms of Electrochemical Double Layer Capacitor (EDLC), two kinds of activated carbons are studied in tetraethyl ammonium tetrafluoroborate (Et4NBF4) in acetonitrile. In floating mode, it turns out that two different ageing mechanisms are observed, depending on the activated carbon electrode materials used. On one hand, carbon A exhibits a continuous capacitance and series resistance fall-off; on the other hand, for carbon B, only the series resistance degrades after ageing while the capacitance keeps unchanged. Additional electrochemical characterizations (Electrochemical Impedance Spectroscopy - EIS - and diffusion coefficient calculations) were carried out showing that carbon A's ageing behavior is suspected to be primarily related to the carbon degradation while for carbon B a passivation occurs leading to the formation of a Solid Electrolyte Interphase-Like (SEI-L) film. These hypotheses are supported by TG-IR and Raman spectroscopy analysis. The outcome forms the latter is an increase of carbon defects on carbon A on positive electrode.

  6. Atmospheric Compensation of Variations in Tropical Ocean Heat Transport: Understanding Mechanisms and Implications on Tectonic Timescales

    Science.gov (United States)

    Rencurrel, M. C.; Rose, B. E. J.

    2015-12-01

    The poleward transport of energy is a key aspect of the climate system, with surface ocean currents presently dominating the transport out of deep tropics. A classic study by Stone (1978) proposed that the total heat transport is determined by astronomical parameters and is highly insensitive to the detailed atmosphere-ocean dynamics. On the other hand, previous modeling work has shown that past continental configurations could have produced substantially different tropical ocean heat transport (OHT). How thoroughly does the atmosphere compensate for changes in ocean transport in terms of the top-of-atmosphere (TOA) radiative budget, what are the relevant mechanisms, and what are the consequences for surface temperature and climate on tectonic timescales? We examine these issues in a suite of aquaplanet GCM simulations subject to large prescribed variations in OHT. We find substantial but incomplete compensation, in which adjustment of the atmospheric Hadley circulation plays a key role. We then separate out the dynamical and thermodynamical components of the adjustment mechanism. Increased OHT tends to warm the mid- to high latitudes without cooling the tropics due asymmetries in radiative feedback processes. The warming is accompanied by hydrological cycle changes that are completely different from those driven by greenhouse gases, suggesting that drivers of past global change might be detectable from combinations of hydroclimate and temperature proxies.

  7. Psychosomatic medicine in the 21st century: understanding mechanisms and barriers to utilization.

    Science.gov (United States)

    Wise, Thomas N; Balon, Richard

    2015-01-01

    The psychosomatic approach arose in antiquity as mankind looked for explanations for illness and death. With the rise of modern medicine, the links between emotions and medical conditions, such as cardiac disease and diabetes, were described by astute clinical observers, but the mechanisms for these conditions were based on correlation from observations rather than on experimental design. Psychoanalytic theory was often utilized to explain many common diseases. For example, peptic ulcer disease was blamed upon anger and stress, but scientific methodology discovered Helicobacter pylori to be the significant causal factor of this disease and resulted in the development of more effective treatments. Nevertheless emotional factors are still linked to disease states and morbidity; for example, depression is a risk factor for mortality following myocardial infarction. Advances in neuroscience demonstrate that the reduction of telomere length by anxiety and stress leads to more rapid aging and potential disease vulnerability. Thus, neuroscientific probes may allow for the elucidation of psychosomatic mechanisms. Sadly, clinical barriers, in terms of time pressure upon physicians and the current separation of mental health services from primary care settings, continue the dualistic treatment of many conditions where psychological factors are important. It is not clear whether a mandate for the integration of behavioral health into primary care will remedy this partition and finally maximize a psychosomatic approach to medical care. © 2015 S. Karger AG, Basel.

  8. A New Alkali-Stable Phosphonium Cation Based on Fundamental Understanding of Degradation Mechanisms.

    Science.gov (United States)

    Zhang, Bingzi; Kaspar, Robert B; Gu, Shuang; Wang, Junhua; Zhuang, Zhongbin; Yan, Yushan

    2016-09-08

    Highly alkali-stable cationic groups are a critical component of hydroxide exchange membranes (HEMs). To search for such cations, we studied the degradation kinetics and mechanisms of a series of quaternary phosphonium (QP) cations. Benzyl tris(2,4,6-trimethoxyphenyl)phosphonium [BTPP-(2,4,6-MeO)] was determined to have higher alkaline stability than the benchmark cation, benzyl trimethylammonium (BTMA). A multi-step methoxy-triggered degradation mechanism for BTPP-(2,4,6-MeO) was proposed and verified. By replacing methoxy substituents with methyl groups, a superior QP cation, methyl tris(2,4,6-trimethylphenyl)phosphonium [MTPP-(2,4,6-Me)] was developed. MTPP-(2,4,6-Me) is one of the most stable cations reported to date, with <20 % degradation after 5000 h at 80 °C in a 1 m KOD in CD3 OD/D2 O (5:1 v/v) solution. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Predicting sorption of organic acids to a wide range of carbonized sorbents

    Science.gov (United States)

    Sigmund, Gabriel; Kah, Melanie; Sun, Huichao; Hofmann, Thilo

    2016-04-01

    Many contaminants and infochemicals are organic acids that undergo dissociation under environmental conditions. The sorption of dissociated anions to biochar and other carbonized sorbents is typically lower than that of neutral species. It is driven by complex processes that are not yet fully understood. It is known that predictive approaches developed for neutral compounds are unlikely to be suitable for organic acids, due to the effects of dissociation on sorption. Previous studies on the sorption of organic acids to soils have demonstrated that log Dow, which describes the decrease in hydrophobicity of acids upon dissociation, is a useful alternative to log Kow. The aim of the present study was to adapt a log Dow based approach to describe the sorption of organic acids to carbonized sorbents. Batch experiments were performed with a series of 9 sorbents (i.e., carbonized wood shavings, pig manure, and sewage sludge, carbon nanotubes and activated carbon), and four acids commonly used for pesticidal and biocidal purposes (i.e., 2,4-D, MCPA, 2,4-DB, and triclosan). Sorbents were comprehensively characterized, including by N2 and CO2 physisorption, Fourier transform infrared spectroscopy, and elemental analysis. The wide range of sorbents considered allows (i) discussing the mechanisms driving the sorption of neutral and anionic species to biochar, and (ii) their dependency on sorbate and sorbent properties. Results showed that the sorption of the four acids was influenced by factors that are usually not considered for neutral compounds (i.e., pH, ionic strength). Dissociation affected the sorption of the four compounds, and sorption of the anions ranged over five orders of magnitude, thus substantially contributing to sorption in some cases. For prediction purposes, most of the variation in sorption to carbonized sorbents (89%) could be well described with a two-parameter regression equation including log Dow and sorbent specific surface area. The proposed model

  10. Understanding the evolution of the windlass mechanism of the human foot from comparative anatomy: Insights, obstacles, and future directions.

    Science.gov (United States)

    Griffin, Nicole L; Miller, Charlotte E; Schmitt, Daniel; D'Août, Kristiaan

    2015-01-01

    Humans stand alone from other primates in that we propel our bodies forward on a relatively stiff and arched foot and do so by employing an anatomical arrangement of bones and ligaments in the foot that can operate like a "windlass." This is a significant evolutionary innovation, but it is currently unknown when during hominin evolution this mechanism developed and within what genera or species it originated. The presence of recently discovered fossils along with novel research in the past two decades have improved our understanding of foot mechanics in humans and other apes, making it possible to consider this question more fully. Here we review the main elements thought to be involved in the production of an effective, modern human-like windlass mechanism. These elements are the triceps surae, plantar aponeurosis, medial longitudinal arch, and metatarsophalangeal joints. We discuss what is presently known about the evolution of these features and the challenges associated with identifying each of these specific components and/or their function in living and extinct primates for the purpose of predicting the presence of the windlass mechanism in our ancestors. In some cases we recommend alternative pathways for inferring foot mechanics and for testing the hypothesis that the windlass mechanism evolved to increase the speed and energetic efficiency of bipedal gait in hominins. © 2014 Wiley Periodicals, Inc.

  11. Effect of organic carbon chemistry on sorption of atrazine and metsulfuron-methyl as determined by (13)C-NMR and IR spectroscopy.

    Science.gov (United States)

    Dutta, Anirban; Mandal, Abhishek; Manna, Suman; Singh, S B; Berns, Anne E; Singh, Neera

    2015-10-01

    Soil organic matter (SOM) content is the major soil component affecting pesticide sorption. However, recent studies have highlighted the fact that it is not the total carbon content of the organic matter, but its chemical structure which have a profound effect on the pesticide's sorption. In the present study, sorption of atrazine and metsulfuron-methyl herbicides was studied in four SOM fractions viz. commercial humic acid, commercial lignin, as well as humic acid and humin extracted from a compost. Sorption data was fitted to the Freundlich adsorption equation. In general, the Freundlich slope (1/n) values for both the herbicides were <1. Except for atrazine sorption on commercial humic acid, metsulfuron-methyl was more sorbed. Desorption results suggested that atrazine was more desorbed than metsulfuron-methyl. Lignin, which showed least sorption of both the herbicides, showed minimum desorption. Sorption of atrazine was best positively correlated with the alkyl carbon (adjusted R (2) = 0.748) and carbonyl carbon (adjusted R (2) = 0.498) but, their effect was statistically nonsignificant (P = 0.05). Metsulfuron-methyl sorption showed best positive correlation with carbonyl carbon (adjusted R (2) = 0.960; P = 0.05) content. Sorption of both the herbicides showed negative correlation with O/N-alkyl carbon. Correlation of herbicide's sorption with alkyl and carbonyl carbon content of SOM fractions suggested their contribution towards herbicide sorption. But, sorption of metsulfuron-methyl, relatively more polar than atrazine, was mainly governed by the polar groups in SOM. IR spectra showed that H-bonds and charge-transfer bonds between SOM fraction and herbicides probably operated as mechanisms of adsorption.

  12. Understanding the mechanisms of thermal disintegrating treatment in the reduction of sludge production.

    Science.gov (United States)

    Camacho, P; Ginestet, P; Audic, J-M

    2005-01-01

    Among the technologies aimed at reducing sludge production, the combination of thermal treatment at 95 degrees C of sludge and the activated sludge process is a promising route. The feasibility of such a combined process is demonstrated (up to 60% sludge reduction) and the impacts of operating conditions on its efficiency are presented. Major emphasis was put on understanding the complex phenomena occurring within the thermal treatment: release and biodegradability of sludge organic matter, impact on the biological activity (decay, maintenance requirements, etc.). These effects were taken into account for the development of an ASM1-based model. Comparison between the modeling approach and experimental data (continuous and batch) showed that thermal treatment had three major issues partly explaining the reduction of sludge production: (i) a low release of organics; (ii) an immediate and reversible biological inactivation associated with additional maintenance energy requirements; and (iii) a potential inert production.

  13. Understanding mechanisms of solid-state phase transformations by probing nuclear materials

    Science.gov (United States)

    Banerjee, Srikumar; Donthula, Harish

    2018-04-01

    In this review a few examples will be cited to illustrate that a study on a specific nuclear material sometimes lead to a better understanding of scientific phenomena of broader interests. Zirconium alloys offer some unique opportunities in addressing fundamental issues such as (i) distinctive features between displacive and diffusional transformations, (ii) characteristics of shuffle and shear dominated displacive transformations and (iii) nature of mixed-mode transformations. Whether a transformation is of first or higher order?" is often raised while classifying it. There are rare examples, such as Ni-Mo alloys, in which during early stages of ordering the system experiences tendencies for both first order and second order transitions. Studies on the order-disorder transitions under a radiation environment have established the pathway for the evolution of ordering. These studies have also identified the temperature range over which the chemically ordered state remains stable in steady state under radiation.

  14. Polyaromatic hydrocarbons (PAHs) sorption behavior unaffected by the presence of multi-walled carbon nanotubes (MWNTs) in a natural soil system.

    Science.gov (United States)

    Li, Shibin; Anderson, Todd A; Green, Micah J; Maul, Jonathan D; Cañas-Carrell, Jaclyn E

    2013-06-01

    The batch equilibrium approach was used to examine the influence of multi-walled carbon nanotubes (MWNTs) on the sorption behaviors of polyaromatic hydrocarbons (PAHs) in soil. To the knowledge of the authors, this is the first study of PAH sorption to MWNTs in real natural soil systems. The sorption behavior of three PAHs (naphthalene, fluorene, and phenanthrene) in the presence of commercially available MWNTs in two natural soils (a sandy loam and a silt loam) and Ottawa sand was evaluated. Adsorption of PAHs by MWNTs in this study was three orders of magnitude higher than that of natural soils. Sorption coefficients of PAHs (Kd and Koc) were unchanged in the presence of 2 mg g(-1) MWNTs in soil (p > 0.05). A micro-mechanics approach, termed 'the rule of mixtures' was used for predicting PAH sorption behaviors in mixtures based on sorption coefficients derived from single sorbents. The equation, KT = KMα + KN(1 - α) (K, sorption coefficients, Kd or Koc), predicted sorption coefficients in a mixture based on mixture component sorption coefficients and mass fractions. Data presented in this study could be used to fill data gaps related to the environmental fate of carbon nanotubes in soil.

  15. Sorption-desorption properties of saponite-containing material

    Science.gov (United States)

    Morozova, M. V.; Frolova, M. A.; Makhova, T. A.

    2017-11-01

    The sorption mechanism of the mineral additive showed that self-saturation of the saponite-containing material with water vapors has a long-term nature (12 days). The nature of desorption differs from adsorption isotherm, i.e. the adsorption/desorption hysteresis is observed. Saponite-containing material samples studied after moisture desorption using infrared spectroscopy demonstrated that chemical compounds in the material have the ability to form calcium silicate hydrates when saturated with water. This fact along with the additive capability to control the water-cement ratio during concrete curing contributes to significantly better physical and chemical properties (strength, frost resistance) of the concrete composite.

  16. Different effects of copper (II), cadmium (II) and phosphate on the sorption of phenanthrene on the biomass of cyanobacteria

    Energy Technology Data Exchange (ETDEWEB)

    Tao, Yuqiang, E-mail: yqtao@niglas.ac.cn [State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008 (China); Li, Wei [Delaware Environmental Institute and Department of Plant and Soil Sciences, University of Delaware, Newark, DE 19717-1303 (United States); Xue, Bin; Zhong, Jicheng; Yao, Shuchun; Wu, Qinglong [State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008 (China)

    2013-10-15

    Highlights: • Low level of Cu{sup 2+} inhibited but high level of Cu{sup 2+} facilitated the sorption of Phe. • Cation–π interaction between Cu{sup 2+} and PAH facilitated the sorption of Phe. • Phenanthrene sorption rebounding did not occur in the presence of high level Cd{sup 2+}. • Both Cd{sup 2+} and PO{sub 4}{sup 3−} inhibited the sorption of Phe, but had various mechanisms. -- Abstract: Due to the large surface area and high organic carbon content of cyanobacteria, organic contaminants can be readily sorbed on cyanobacteria during algal blooms, and then be transferred to the food web. This process is likely to be affected by the coexisting metals and nutrients, however, the possible impacts remain unclear. Effects of Cu{sup 2+}, Cd{sup 2+}, and phosphate on the sorption of phenanthrene on cyanobacterial biomass collected from an algal bloom were therefore studied. Continuous decrease in phenanthrene sorption was observed in the presence of low concentrations of Cu{sup 2+}, and Cd{sup 2+} (<0.04 mmol L{sup −1}), because Cu{sup 2+} and Cd{sup 2+} were coadsorbed with phenanthrene on the surface of cyanobacteria as suggested by scanning electron microscopy-energy dispersive X-ray (SEM-EDX) and Fourier transform infrared (FTIR) analyses. Phenanthrene sorption began to increase with the further increase in Cu{sup 2+} concentration, but remained lower than that in the absence of Cu{sup 2+}. This increase in sorption was ascribed to the cation–π interaction between Cu{sup 2+} and phenanthrene, as suggested by the enhanced ultraviolet absorbance at 251 nm. In contrast, sorption rebounding of phenanthrene did not occur in the presence of higher concentrations of Cd{sup 2+}. The different effects of Cu{sup 2+} and Cd{sup 2+} on phenanthrene sorption were attributed to that Cd{sup 2+} required much more energy than Cu{sup 2+} to form cation–π complexes with phenanthrene in the solutions. Phenanthrene sorption decreased continuously with the increase

  17. Equilibrium, kinetic and thermodynamic studies for sorption of Ni (II from aqueous solution using formaldehyde treated waste tea leaves

    Directory of Open Access Journals (Sweden)

    Jasmin Shah

    2015-05-01

    Full Text Available The sorption characteristic of Ni (II from aqueous solution using formaldehyde treated waste tea leaves as a low cost sorbent has been studied. The effect of pH, contact time, sorbent dose, initial metal ion concentration and temperature were investigated in batch experiments. The equilibrium data were fitted into four most common isotherm models; Freundlich, Langmuir, Tempkin and Dubinin–Radushkevich (D–R. The Langmuir model described the sorption isotherm best with maximum monolayer sorption capacity of 120.50 mg g−1. Four kinetic models, pseudo-first-order, pseudo-second-order, intraparticle diffusion and Elovich were employed to explain the sorption mechanism. The kinetics of sorption data showed that the pseudo-second-order model is the best with correlation coefficient of 0.9946. The spontaneous and exothermic nature of the sorption process was revealed from thermodynamic investigations. The effect of some common alkali and alkaline earth metal ions were also studied which showed that the presence of these ions have no effect on the sorption of Ni (II. The results showed that waste tea leaves have the potential to be used as a low cost sorbent for the removal of Ni (II from aqueous solutions.

  18. Understanding the desensitizing mechanism of olefin in explosives: shear slide of mixed HMX-olefin systems.

    Science.gov (United States)

    Zhang, Chaoyang; Cao, Xia; Xiang, Bin

    2012-04-01

    We simulated the shear slide behavior of typical mixed HMX-olefin systems and the effect of thickness of olefin layers (4-22 Å) on the behavior at a molecular level by considering two cases: bulk shear and interfacial shear. The results show that: (1) the addition of olefin into HMX can reduce greatly the shear sliding barriers relative to the pure HMX in the two cases, suggesting that the desensitizing mechanism of olefin is controlled dominantly by its good lubricating property; (2) the change of interaction energy in both systoles of shear slide is strongly dominated by van der Waals interaction; and (3) the thickness of olefin layers in the mixed explosives can influence its desensitizing efficiency. That is, the excessive thinness of olefin layers in the mixed explosive systems, for example, several angstroms, can lead to very high sliding barriers.

  19. Heat and mass transfer models to understand the drying mechanisms of a porous substrate.

    Science.gov (United States)

    Songok, Joel; Bousfield, Douglas W; Gane, Patrick A C; Toivakka, Martti

    2016-02-01

    While drying of paper and paper coatings is expensive, with significant energy requirements, the rate controlling mechanisms are not currently fully understood. Two two-dimensional models are used as a first approximation to predict the heat transfer during hot air drying and to evaluate the role of various parameters on the drying rates of porous coatings. The models help determine the structural limiting factors during the drying process, while applying for the first time the recently known values of coating thermal diffusivity. The results indicate that the thermal conductivity of the coating structure is not the controlling factor, but the drying rate is rather determined by the thermal transfer process at the structure surface. This underlines the need for ensuring an efficient thermal transfer from hot air to coating surface during drying, before considering further measures to increase the thermal conductivity of porous coatings.

  20. Understanding the neural mechanisms involved in sensory control of voice production.

    Science.gov (United States)

    Parkinson, Amy L; Flagmeier, Sabina G; Manes, Jordan L; Larson, Charles R; Rogers, Bill; Robin, Donald A

    2012-05-15

    Auditory feedback is important for the control of voice fundamental frequency (F0). In the present study we used neuroimaging to identify regions of the brain responsible for sensory control of the voice. We used a pitch-shift paradigm where subjects respond to an alteration, or shift, of voice pitch auditory feedback with a reflexive change in F0. To determine the neural substrates involved in these audio-vocal responses, subjects underwent fMRI scanning while vocalizing with or without pitch-shifted feedback. The comparison of shifted and unshifted vocalization revealed activation bilaterally in the superior temporal gyrus (STG) in response to the pitch shifted feedback. We hypothesize that the STG activity is related to error detection by auditory error cells located in the superior temporal cortex and efference copy mechanisms whereby this region is responsible for the coding of a mismatch between actual and predicted voice F0. Published by Elsevier Inc.

  1. The effects of bariatric surgery: will understanding its mechanism render the knife unnecessary?

    Science.gov (United States)

    Browning, Kirsteen N; Hajnal, Andras

    2014-01-01

    The incidence of obesity is increasing worldwide at a dramatic rate, accompanied by an associated increase in comorbid conditions. Bariatric surgery is the most effective treatment for morbid obesity with Roux-en-Y gastric bypass being the most commonly performed procedure, yet the underlying mechanisms by which it induces a wide-array of beneficial effects remains obscure. From basic science as well as clinical standpoints, there are several areas of current interest that warrant continued investigation. Several major focus areas have also emerged in current research that may guide future efforts in this field, particularly with regards to using novel, non-surgical approaches to mimic the success of bariatric surgery while minimizing its adverse side effects.

  2. Metal Oxide Nanomaterial QNAR Models: Available Structural Descriptors and Understanding of Toxicity Mechanisms

    Directory of Open Access Journals (Sweden)

    Jiali Ying

    2015-10-01

    Full Text Available Metal oxide nanomaterials are widely used in various areas; however, the divergent published toxicology data makes it difficult to determine whether there is a risk associated with exposure to metal oxide nanomaterials. The application of quantitative structure activity relationship (QSAR modeling in metal oxide nanomaterials toxicity studies can reduce the need for time-consuming and resource-intensive nanotoxicity tests. The nanostructure and inorganic composition of metal oxide nanomaterials makes this approach different from classical QSAR study; this review lists and classifies some structural descriptors, such as size, cation charge, and band gap energy, in recent metal oxide nanomaterials quantitative nanostructure activity relationship (QNAR studies and discusses the mechanism of metal oxide nanomaterials toxicity based on these descriptors and traditional nanotoxicity tests.

  3. Oxide Nanoparticle EUV (ONE) Photoresists: Current Understanding of the Unusual Patterning Mechanism

    KAUST Repository

    Jiang, Jing

    2015-01-01

    © 2015 SPST. In the past few years, industry has made significant progress to deliver a stable high power EUV scanner and a 100 W light source is now being tested on the manufacuring scale. The success of a high power EUV source demands a fast and high resolution EUV resist. However, chemcially amplied resists encounter unprecedented challenges beyond the 22 nm node due to resolution, roughness and sensitivity tradeoffs. Unless novel solutions for EUV resists are proposed and further optimzed, breakthroughs can hardly be achieved. Oxide nanoparticle EUV (ONE) resists stablized by organic ligands were originally proposed by Ober et al. Recently this work attracts more and more attention due to its extraordinanry EUV sensitivity. This new class of photoresist utilizes ligand cleavage with a ligand exchange mechanism to switch its solubilty for dual-tone patterning. Therefore, ligand selection of the nanoparticles is extremely important to its EUV performance.

  4. Towards a better understanding of the therapeutic applications and corresponding mechanisms of action of honey.

    Science.gov (United States)

    Khan, Rifat Ullah; Naz, Shabana; Abudabos, Alaeldein M

    2017-12-01

    Honey is a bee-derived supersaturated solution composed of complex contents mainly glucose, fructose, amino acids, vitamins, and minerals. Composition of honey may vary due to the difference in nectar, season, geography, and storage condition. Honey has been used since times immemorial in folk medicine and has recently been rediscovered as an excellent therapeutic agent. In the past, honey was used for a variety of ailments without knowing the scientific background and active ingredients of honey. Today, honey has been scientifically proven for its antioxidant, regulation of glycemic response, antitumor, antimicrobial, anti-inflammatory, and cardiovascular potentiating agent. It can be used as a wound dressing and healing substance. Honey is different in color, flavor, sensory perception, and medical response. Apart from highlighting the nutritional facts of honey, we collected the finding of the published literature to know the mechanism of action of honey in different diseases. This review covers the composition, physiochemical characteristics, and some medical uses.

  5. Understanding Central Mechanisms of Acupuncture Analgesia Using Dynamic Quantitative Sensory Testing: A Review

    Directory of Open Access Journals (Sweden)

    Jiang-Ti Kong

    2013-01-01

    Full Text Available We discuss the emerging translational tools for the study of acupuncture analgesia with a focus on psychophysical methods. The gap between animal mechanistic studies and human clinical trials of acupuncture analgesia calls for effective translational tools that bridge neurophysiological data with meaningful clinical outcomes. Temporal summation (TS and conditioned pain modulation (CPM are two promising tools yet to be widely utilized. These psychophysical measures capture the state of the ascending facilitation and the descending inhibition of nociceptive transmission, respectively. We review the basic concepts and current methodologies underlying these measures in clinical pain research, and illustrate their application to research on acupuncture analgesia. Finally, we highlight the strengths and limitations of these research methods and make recommendations on future directions. The appropriate addition of TS and CPM to our current research armamentarium will facilitate our efforts to elucidate the central analgesic mechanisms of acupuncture in clinical populations.

  6. Understanding the Broad Substrate Repertoire of Nitroreductase Based on Its Kinetic Mechanism*

    Science.gov (United States)

    Pitsawong, Warintra; Hoben, John P.; Miller, Anne-Frances

    2014-01-01

    The oxygen-insensitive nitroreductase from Enterobacter cloacae (NR) catalyzes two-electron reduction of nitroaromatics to the corresponding nitroso compounds and, subsequently, to hydroxylamine products. NR has an unusually broad substrate repertoire, which may be related to protein dynamics (flexibility) and/or a simple non-selective kinetic mechanism. To investigate the possible role of mechanism in the broad substrate repertoire of NR, the kinetics of oxidation of NR by para-nitrobenzoic acid (p-NBA) were investigated using stopped-flow techniques at 4 °C. The results revealed a hyperbolic dependence on the p-NBA concentration with a limiting rate of 1.90 ± 0.09 s−1, indicating one-step binding before the flavin oxidation step. There is no evidence for a distinct binding step in which specificity might be enforced. The reduction of p-NBA is rate-limiting in steady-state turnover (1.7 ± 0.3 s−1). The pre-steady-state reduction kinetics of NR by NADH indicate that NADH reduces the enzyme with a rate constant of 700 ± 20 s−1 and a dissociation constant of 0.51 ± 0.04 mm. Thus, we demonstrate simple transient kinetics in both the reductive and oxidative half-reactions that help to explain the broad substrate repertoire of NR. Finally, we tested the ability of NR to reduce para-hydroxylaminobenzoic acid, demonstrating that the corresponding amine does not accumulate to significant levels even under anaerobic conditions. Thus E. cloacae NR is not a good candidate for enzymatic production of aromatic amines. PMID:24706760

  7. Sorption interactions of biochars and pyrogenic carbonaceous materials with anionic contaminants

    Science.gov (United States)

    Fristak, Vladimir; Moreno-Jimenez, Eduardo; Micháleková-Richveisová, Barbora; Schmidt, Hans-Peter; Bucheli, Thomas; Soja, Gerhard

    2016-04-01

    Biochar as a highly porous and carbon-rich material with a large surface area is a new player in the system of environmental remediation techniques. A wide range of valuable sorption properties of this carbonaceous pyrolysis product provides new options to solve contaminant problems in soil and water and thus may reduce the number of contaminated sites. The sorption capacity of agricultural wastes and wood processing-derived biochars has been found to be excellent due to high surface area, pore volume, and surface functional groups. However, sorption interactions and separation of xenobiotics from waste water, soil solutions or polluted surface water is very often affected by the concentration of contaminant, contact time, effects of competitive substances and mainly by the chemical form of the respective contaminant. The negative surface charge of biochar-based sorption materials supports significant sorption in particular for cationic forms of pollutants. On the other hand many environmentally critical substances occur in anionic forms (e.g. As, P, Mo, Tc). Therefore their retention and immobilization by biochar is frequently considered as problematic or limited. Besides, details about the mechanism of biochar interactions with anionic compounds and the options for surface modification are largely unexplored. This contribution presents a comparative study about production and characterization of unmodified, chemically pre-treated and post-treated biochars with respect to sorption processes of model anionic compounds (PO43-, AsO43-). The obtained results confirmed the crucial role of altering biochar properties (pH) and of surface modification for improving biochar sorption efficiency for anionic contaminants.

  8. Contribution of transcranial magnetic stimulation to the understanding of cortical mechanisms involved in motor control.

    Science.gov (United States)

    Reis, Janine; Swayne, Orlando B; Vandermeeren, Yves; Camus, Mickael; Dimyan, Michael A; Harris-Love, Michelle; Perez, Monica A; Ragert, Patrick; Rothwell, John C; Cohen, Leonardo G

    2008-01-15

    Transcranial magnetic stimulation (TMS) was initially used to evaluate the integrity of the corticospinal tract in humans non-invasively. Since these early studies, the development of paired-pulse and repetitive TMS protocols allowed investigators to explore inhibitory and excitatory interactions of various motor and non-motor cortical regions within and across cerebral hemispheres. These applications have provided insight into the intracortical physiological processes underlying the functional role of different brain regions in various cognitive processes, motor control in health and disease and neuroplastic changes during recovery of function after brain lesions. Used in combination with neuroimaging tools, TMS provides valuable information on functional connectivity between different brain regions, and on the relationship between physiological processes and the anatomical configuration of specific brain areas and connected pathways. More recently, there has been increasing interest in the extent to which these physiological processes are modulated depending on the behavioural setting. The purpose of this paper is (a) to present an up-to-date review of the available electrophysiological data and the impact on our understanding of human motor behaviour and (b) to discuss some of the gaps in our present knowledge as well as future directions of research in a format accessible to new students and/or investigators. Finally, areas of uncertainty and limitations in the interpretation of TMS studies are discussed in some detail.

  9. Accelerating Our Understanding of Supernova Explosion Mechanism via Simulations and Visualizations with GenASiS

    Energy Technology Data Exchange (ETDEWEB)

    Budiardja, R. D. [University of Tennessee, Knoxville (UTK); Cardall, Christian Y [ORNL; Endeve, Eirik [ORNL

    2015-01-01

    Core-collapse supernovae are among the most powerful explosions in the Universe, releasing about 1053 erg of energy on timescales of a few tens of seconds. These explosion events are also responsible for the production and dissemination of most of the heavy elements, making life as we know it possible. Yet exactly how they work is still unresolved. One reason for this is the sheer complexity and cost of a self-consistent, multi-physics, and multi-dimensional core-collapse supernova simulation, which is impractical, and often impossible, even on the largest supercomputers we have available today. To advance our understanding we instead must often use simplified models, teasing out the most important ingredients for successful explosions, while helping us to interpret results from higher fidelity multi-physics models. In this paper we investigate the role of instabilities in the core-collapse supernova environment. We present here simulation and visualization results produced by our code GenASiS.

  10. The NEA sorption data base (SDB)

    International Nuclear Information System (INIS)

    Ruegger, B.; Ticknor, K.

    1992-01-01

    The current NEA Sorption Data Base is developed to replace the former International Sorption Information Retrieval System (ISIRS) initiated at Pacific Northwest Laboratory and contains about 11,000 distribution coefficients with corresponding experimental condition parameters describing sorption of key nuclides for a large variety of solid and liquid phases. The SDB is designed to run on a micro-computer using the commercially available database software dBASE III Plus. For each recorded sorption experiment, the SDB provides a bibliographical reference, the most complete characterization of the solid and liquid phases available, a description of the experimental conditions and the distribution coefficient or retardation factor for each element studied. When available, parameters such as temperature, initial radionuclide concentration, pH, Eh, contact time, solid to solution ratio, sample origin, oxidation state and type of solution are included. The SDB provides information for a wide variety of rocks or geological materials, buffer backfill candidates, concretes/cements, elements (Am, Cs, Co, I, Np, Pu, Ra, Sr, Se, Tc, U and, to a lesser extent, Ag, Ba, C, Ce, Eu, Fe, Mn, Mo, Na, Nb, Ni, Pd, Pm, Ru, Sb, Sn, Y, Zn, and Zr), or radioisotopes. A compilation of sorption data like SDB provide a readily available source of data for radioactive waste repository performance assessments when site specific data are not available or essential, for example, during a site selection phase. 2 appendices

  11. Radionuclide sorption from the safety evaluation perspective

    International Nuclear Information System (INIS)

    1992-01-01

    Research and development directed towards the assessment of the long-term performance of radioactive waste disposal systems has been recognised as a priority area with a strong need for international co-operation and co-ordination. The ultimate aims is to promote the quality and credibility of safety assessment techniques for radioactive waste disposal. Sorption in the geosphere is one of the key processes for retarding the transport of radionuclide from the underground disposal facility to the biosphere. In many cases, sorption in the near field and in the biosphere is also important. A workshop, organised to favor discussion around a small number of invited papers, was held in October 1991: - to evaluate critically the way sorption processes are incorporated in performance assessment models; - to identify open issues of high priority, and; - to propose future activities to resolve these issues. These proceedings reproduce the invited papers and the conclusions and recommendations adopted by the workshop. Eight papers are in the INIS SCOPE. The main subjects studied are: sorption database comparison, sorption database development and three case studies, experimental techniques, adsorption models

  12. Sorption of Organophosphorus Flame Retardants (OPFRs) on ...

    Science.gov (United States)

    Organophosphorus flame retardants (OPFRs) are widely used as additives in industrial and consumer products such as electrical and electronic products, furniture, plastics, textiles, and building/construction materials. Due to human exposure and potential health effects, OPFRs including tris(2-chloroethyl) phosphate (TCEP), tris(1-chloro-2-propyl) phosphate (TCPP), and tris(1,3-dichloro-2-propyl) phosphate (TDCPP) are EPA Action Plan chemicals for chemical assessments under the Toxic Substances Control Act (TSCA). This work investigated the sorption of these three compounds from the air to settled Arizona Test Dust (ATD) and house dust (HD) in a dual small chamber system. The OPFR exposed dust was analyzed to determine the sorption concentration and sorption rate of OPFRs on the dust. The effect of the composition of the dust on OPFR sorption was evaluated. The results showed that ATD and HD have varied sorption capacity for OPFRs from air. This work explores the relationship between OPFR concentrations in settled dust and air. The data can be used to determine partitioning of OPFRs between the gas phase and settled dust indoors and to inform strategies to reduce exposure and risk.

  13. Sorption of tylosin on clay minerals.

    Science.gov (United States)

    Zhang, Qian; Yang, Chen; Huang, Weilin; Dang, Zhi; Shu, Xiaohua

    2013-11-01

    The equilibrium sorption of tylosin (TYL) on kaolinite and montmorillonite was measured at different solution pH using batch reactor systems. The results showed that all the sorption isotherms were nonlinear and that the nonlinearity decreased as the solution pH increased for a given clay. At a specific aqueous concentration, the single-point sorption distribution coefficient (KD) of TYL decreased rapidly as the solution pH increased. A speciation-dependent sorption model that accounted for the contributions of the cationic and neutral forms of TYL fit the data well, suggesting that the sorption may be dominated by both ion exchange and hydrophobic interactions. The isotherm data also fit well to a dual mode model that quantifies the contributions of a site-limiting Langmuir component (ion exchange) and a non-specific linear partitioning component (hydrophobic interactions). X-ray diffraction analyses revealed that the interlayers of montmorillonite were expanded due to the uptake of TYL. TYL molecules likely form a monolayer surface coverage. Copyright © 2013 Elsevier Ltd. All rights reserved.

  14. Understanding the growth mechanism of graphene on Ge/Si(001) surfaces

    Science.gov (United States)

    Dabrowski, J.; Lippert, G.; Avila, J.; Baringhaus, J.; Colambo, I.; Dedkov, Yu S.; Herziger, F.; Lupina, G.; Maultzsch, J.; Schaffus, T.; Schroeder, T.; Kot, M.; Tegenkamp, C.; Vignaud, D.; Asensio, M.-C.

    2016-01-01

    The practical difficulties to use graphene in microelectronics and optoelectronics is that the available methods to grow graphene are not easily integrated in the mainstream technologies. A growth method that could overcome at least some of these problems is chemical vapour deposition (CVD) of graphene directly on semiconducting (Si or Ge) substrates. Here we report on the comparison of the CVD and molecular beam epitaxy (MBE) growth of graphene on the technologically relevant Ge(001)/Si(001) substrate from ethene (C2H4) precursor and describe the physical properties of the films as well as we discuss the surface reaction and diffusion processes that may be responsible for the observed behavior. Using nano angle resolved photoemission (nanoARPES) complemented by transport studies and Raman spectroscopy as well as density functional theory (DFT) calculations, we report the direct observation of massless Dirac particles in monolayer graphene, providing a comprehensive mapping of their low-hole doped Dirac electron bands. The micrometric graphene flakes are oriented along two predominant directions rotated by 30° with respect to each other. The growth mode is attributed to the mechanism when small graphene “molecules” nucleate on the Ge(001) surface and it is found that hydrogen plays a significant role in this process. PMID:27531322

  15. Study and understanding of the ageing mechanisms in lead-calcium alloys

    International Nuclear Information System (INIS)

    Rossi, F.

    2006-12-01

    The data available in the literature about ageing and over-ageing of lead-calcium alloys are often incomplete and inconsistent. It is undoubtedly due to the experimental difficulties encountered to observe the structure transformations which are numerous. As a result there is a certain confusion among the results of the different authors. Moreover, small variations in the process parameters and chemical composition may have some influence on the alloy behaviour. This work enabled us to obtain a set of TTT diagrams, more realistic and accurate than the ones available in the literature. Experimental techniques developed (particularly the preservation of the cold chain with is essential for the guaranty of the results repeatability), enabled particularly the study of the first transformations and better control the five stages of ageing and over-ageing. Our work have enabled to determine precisely the kinetics and the mechanisms of the transformations. This work constitutes a thorough analysis of the ageing and over-ageing of theses alloys. (author)

  16. ARHGEF9 mutations in epileptic encephalopathy/intellectual disability: toward understanding the mechanism underlying phenotypic variation.

    Science.gov (United States)

    Wang, Jing-Yang; Zhou, Peng; Wang, Jie; Tang, Bin; Su, Tao; Liu, Xiao-Rong; Li, Bing-Mei; Meng, Heng; Shi, Yi-Wu; Yi, Yong-Hong; He, Na; Liao, Wei-Ping

    2018-01-01

    ARHGEF9 resides on Xq11.1 and encodes collybistin, which is crucial in gephyrin clustering and GABA A receptor localization. ARHGEF9 mutations have been identified in patients with heterogeneous phenotypes, including epilepsy of variable severity and intellectual disability. However, the mechanism underlying phenotype variation is unknown. Using next-generation sequencing, we identified a novel mutation, c.868C > T/p.R290C, which co-segregated with epileptic encephalopathy, and validated its association with epileptic encephalopathy. Further analysis revealed that all ARHGEF9 mutations were associated with intellectual disability, suggesting its critical role in psychomotor development. Three missense mutations in the PH domain were not associated with epilepsy, suggesting that the co-occurrence of epilepsy depends on the affected functional domains. Missense mutations with severe molecular alteration in the DH domain, or located in the DH-gephyrin binding region, or adjacent to the SH3-NL2 binding site were associated with severe epilepsy, implying that the clinical severity was potentially determined by alteration of molecular structure and location of mutations. Male patients with ARHGEF9 mutations presented more severe phenotypes than female patients, which suggests a gene-dose effect and supports the pathogenic role of ARHGEF9 mutations. This study highlights the role of molecular alteration in phenotype expression and facilitates evaluation of the pathogenicity of ARHGEF9 mutations in clinical practice.

  17. Understanding physiological and degenerative natural vision mechanisms to define contrast and contour operators.

    Directory of Open Access Journals (Sweden)

    Jacques Demongeot

    Full Text Available BACKGROUND: Dynamical systems like neural networks based on lateral inhibition have a large field of applications in image processing, robotics and morphogenesis modeling. In this paper, we will propose some examples of dynamical flows used in image contrasting and contouring. METHODOLOGY: First we present the physiological basis of the retina function by showing the role of the lateral inhibition in the optical illusions and pathologic processes generation. Then, based on these biological considerations about the real vision mechanisms, we study an enhancement method for contrasting medical images, using either a discrete neural network approach, or its continuous version, i.e. a non-isotropic diffusion reaction partial differential system. Following this, we introduce other continuous operators based on similar biomimetic approaches: a chemotactic contrasting method, a viability contouring algorithm and an attentional focus operator. Then, we introduce the new notion of mixed potential Hamiltonian flows; we compare it with the watershed method and we use it for contouring. CONCLUSIONS: We conclude by showing the utility of these biomimetic methods with some examples of application in medical imaging and computed assisted surgery.

  18. Comprehensive Understanding of Ductility Loss Mechanisms in Various Steels with External and Internal Hydrogen

    Science.gov (United States)

    Takakuwa, Osamu; Yamabe, Junichiro; Matsunaga, Hisao; Furuya, Yoshiyuki; Matsuoka, Saburo

    2017-11-01

    Hydrogen-induced ductility loss and related fracture morphologies are comprehensively discussed in consideration of the hydrogen distribution in a specimen with external and internal hydrogen by using 300-series austenitic stainless steels (Types 304, 316, 316L), high-strength austenitic stainless steels (HP160, XM-19), precipitation-hardened iron-based super alloy (A286), low-alloy Cr-Mo steel (JIS-SCM435), and low-carbon steel (JIS-SM490B). External hydrogen is realized by a non-charged specimen tested in high-pressure gaseous hydrogen, and internal hydrogen is realized by a hydrogen-charged specimen tested in air or inert gas. Fracture morphologies obtained by slow-strain-rate tensile tests (SSRT) of the materials with external or internal hydrogen could be comprehensively categorized into five types: hydrogen-induced successive crack growth, ordinary void formation, small-sized void formation related to the void sheet, large-sized void formation, and facet formation. The mechanisms of hydrogen embrittlement are broadly classified into hydrogen-enhanced decohesion (HEDE) and hydrogen-enhanced localized plasticity (HELP). In the HEDE model, hydrogen weakens interatomic bonds, whereas in the HELP model, hydrogen enhances localized slip deformations. Although various fracture morphologies are produced by external or internal hydrogen, these morphologies can be explained by the HELP model rather than by the HEDE model.

  19. Understanding the mechanism of iron sulfide-induced fouling in upgrading

    Energy Technology Data Exchange (ETDEWEB)

    Panchal, C.B. [United States Dept. of Energy, Chicago, IL (United States). Argonne National Laboratory

    2006-07-01

    This presentation investigated the underlying mechanisms of iron sulfide-induced fouling and coking in upgrading processes. Experiments to determine the effects of dissolved metals on the rate of fouling were reviewed. It was noted that the presence of species such as active sulfur and diolefins can enhance the effect of dissolved metals. An investigation of a high temperature fouling unit was then conducted to investigate the effect of iron acetate and theiphenol additions to stable heavy gas oil. The deposition rate became strongly dependent on temperature in the presence of the dissolved metals. Fouling deposit analyses from various parts of the refining process consistently showed high concentrations of iron and sulfur. It was observed that the threshold tube-wall temperature corresponded to the decomposition temperature of iron salts. A review of current literature indicated that there is little information on the interactive effects of the thermal stability of dissolved organo-metallic compounds and the reactivity of organic species in generating fouling precursors. The creation of a predictive model of threshold fouling and coking conditions was recommended. It was suggested that the model should be used during the design phases of furnaces and heat exchangers. Other recommendations included the use of on-line sensors to detect iron sulfide formulation; and the monitoring of coking furnaces. Blending guidelines to minimize the interactive effects of dissolved metals and active sulfur compounds were also presented. refs., tabs., figs.

  20. Toward understanding the mechanics of hovering in insects, hummingbirds and bats

    Science.gov (United States)

    Vejdani, Hamid; Boerma, David; Swartz, Sharon; Breuer, Kenneth

    2016-11-01

    We present results on the dynamical characteristics of two different mechanisms of hovering, corresponding to the behavior of hummingbirds and bats. Using a Lagrangian formulation, we have developed a dynamical model of a body (trunk) and two rectangular wings. The trunk has 3 degrees of freedom (x, z and pitch angle) and each wing has 3 modes of actuation: flapping, pronation/supination, and wingspan extension/flexion (only present for bats). Wings can be effectively massless (hummingbird and insect wings) or relatively massive (important in the case of bats). The aerodynamic drag and lift forces are calculated using a quasi-steady blade-element model. The regions of state space in which hovering is possible are computed by over an exhaustive range of parameters. The effect of wing mass is to shrink the phase space available for viable hovering and, in general, to require higher wingbeat frequency. Moreover, by exploring hovering energy requirements, we find that the pronation angle of the wings also plays a critical role. For bats, who have relatively heavy wings, we show wing extension and flexion is critical in order to maintain a plausible hovering posture with reasonable power requirements. Comparisons with biological data show good agreement with our model predictions.

  1. Recent advances in understanding the molecular mechanism of chloroplast photorelocation movement.

    Science.gov (United States)

    Kong, Sam-Geun; Wada, Masamitsu

    2014-04-01

    Plants are photosynthetic organisms that have evolved unique systems to adapt fluctuating environmental light conditions. In addition to well-known movement responses such as phototropism, stomatal opening, and nastic leaf movements, chloroplast photorelocation movement is one of the essential cellular responses to optimize photosynthetic ability and avoid photodamage. For these adaptations, chloroplasts accumulate at the areas of cells illuminated with low light (called accumulation response), while they scatter from the area illuminated with strong light (called avoidance response). Plant-specific photoreceptors (phototropin, phytochrome, and/or neochrome) mediate these dynamic directional movements in response to incident light position and intensity. Several factors involved in the mechanisms underlying the processes from light perception to actin-based movements have also been identified through molecular genetic approach. This review aims to discuss recent findings in the field relating to how chloroplasts move at molecular levels. This article is part of a Special Issue entitled: Dynamic and ultrastructure of bioenergetic membranes and their components. Copyright © 2013 Elsevier B.V. All rights reserved.

  2. Different approaches, one target: understanding cellular mechanisms of Parkinson's and Alzheimer's diseases.

    Science.gov (United States)

    Torrão, Andréa S; Café-Mendes, Cecilia C; Real, Caroline C; Hernandes, Marina S; Ferreira, Ana F B; Santos, Taisa O; Chaves-Kirsten, Gabriela P; Mazucanti, Caio H Y; Ferro, Emer S; Scavone, Cristoforo; Britto, Luiz R G

    2012-10-01

    Neurodegenerative disorders are undoubtedly an increasing problem in the health sciences, given the increase of life expectancy and occasional vicious life style. Despite the fact that the mechanisms of such diseases are far from being completely understood, a large number of studies that derive from both the basic science and clinical approaches have contributed substantial data in that direction. In this review, it is discussed several frontiers of basic research on Parkinson's and Alzheimer's diseases, in which research groups from three departments of the Institute of Biomedical Sciences of the University of São Paulo have been involved in a multidisciplinary effort. The main focus of the review involves the animal models that have been developed to study cellular and molecular aspects of those neurodegenerative diseases, including oxidative stress, insulin signaling and proteomic analyses, among others. We anticipate that this review will help the group determine future directions of joint research in the field and, more importantly, set the level of cooperation we plan to develop in collaboration with colleagues of the Nucleus for Applied Neuroscience Research that are mostly involved with clinical research in the same field.

  3. Sorption of hydrophobic organic compounds to plastics in marine environments: Equilibrium

    NARCIS (Netherlands)

    Endo, S.; Koelmans, A.A.

    2016-01-01

    Marine plastics have shown to contain various environmental chemicals. For evaluating the potential of plastics to influence regional and global dynamics of these chemicals and to serve as a vector to marine biota, understanding of sorption and desorption of chemicals by plastics is important. In

  4. Final Report: Improving the understanding of the coupled thermal-mechanical-hydrologic behavior of consolidating granular salt

    Energy Technology Data Exchange (ETDEWEB)

    Stormont, John [Univ. of New Mexico, Albuquerque, NM (United States); Lampe, Brandon [Univ. of New Mexico, Albuquerque, NM (United States); Mills, Melissa [Univ. of New Mexico, Albuquerque, NM (United States); Paneru, Laxmi [Univ. of New Mexico, Albuquerque, NM (United States); Lynn, Timothy [Univ. of New Mexico, Albuquerque, NM (United States); Piya, Aayush [Univ. of New Mexico, Albuquerque, NM (United States)

    2017-09-09

    The goal of this project is to improve the understanding of key aspects of the coupled thermal-mechanical-hydrologic response of granular (or crushed) salt used as a seal material for shafts, drifts, and boreholes in mined repositories in salt. The project is organized into three tasks to accomplish this goal: laboratory measurements of granular salt consolidation (Task 1), microstructural observations on consolidated samples (Task 2), and constitutive model development and evaluation (Task 3). Task 1 involves laboratory measurements of salt consolidation along with thermal properties and permeability measurements conducted under a range of temperatures and stresses expected for potential mined repositories in salt. Testing focused on the role of moisture, temperature and stress state on the hydrologic (permeability) and thermal properties of consolidating granular salt at high fractional densities. Task 2 consists of microstructural observations made on samples after they have been consolidated to interpret deformation mechanisms and evaluate the ability of the constitutive model to predict operative mechanisms under different conditions. Task 3 concerns the development of the coupled thermal-mechanical-hydrologic constitutive model for granular salt consolidation. The measurements and observations in Tasks 1 and 2 were used to develop a thermal-mechanical constitutive model. Accomplishments and status from each of these efforts is reported in subsequent sections of this report

  5. Reactive transport modeling at uranium in situ recovery sites: uncertainties in uranium sorption on iron hydroxides

    Science.gov (United States)

    Johnson, Raymond H.; Tutu, Hlanganani; Brown, Adrian; Figueroa, Linda; Wolkersdorfer, Christian

    2013-01-01

    Geochemical changes that can occur down gradient from uranium in situ recovery (ISR) sites are important for various stakeholders to understand when evaluating potential effects on surrounding groundwater quality. If down gradient solid-phase material consists of sandstone with iron hydroxide coatings (no pyrite or organic carbon), sorption of uranium on iron hydroxides can control uranium mobility. Using one-dimensional reactive transport models with PHREEQC, two different geochemical databases, and various geochemical parameters, the uncertainties in uranium sorption on iron hydroxides are evaluated, because these oxidized zones create a greater risk for future uranium transport than fully reduced zones where uranium generally precipitates.

  6. Lanthanides and actinides sorption on to alumina with simple organic ligands. Thermodynamic and spectroscopic approaches

    International Nuclear Information System (INIS)

    Alliot, C.

    2003-01-01

    This work comes within studies of nuclear waste disposal. The sorption of radionuclide onto mineral is very important to understand their migration. So this work deals with the influence of ligands like oxalic, acetic and carbonic acids on lanthanides and actinides sorption onto alumina. Two complementary approaches were carried out: thermodynamic (determination of chemical reactions and associated constants). So we obtain a thermodynamic database for the ternary systems metal/ligand/alumina which we use to define the experimental conditions to observe by spectroscopy sorbed species. Then the identification of surface complexes was carried out using two spectroscopies, XPS and TRLIFS. (author)

  7. Sorption kinetics of toluene in humin under two different levels of relative humidity.

    Science.gov (United States)

    Shih, Yang-hsin; Wu, Shian-chee

    2002-01-01

    To identify any resistant fraction for desorption of toluene from humin and to quantify the sorption-desorption rates, the time courses of toluene sorption to compressed humin disks and to a thin humin film were investigated. The apparent diffusivity of toluene with humin disks ranges from 10(-8) to 10(-9) cm2/s and increases with temperature, based on the weight change of humin disks mounted on a microbalance and on the results simulated by use of a diffusion model. No detectable level of residual toluene was found after desorption, as revealed either by the gravimetric analysis or by the Fourier transform infrared (FTIR) spectrum obtained at either low or high humidity. The time scale for intrinsic vapor sorption without mass transfer hindrance is less than a few minutes with the thin film. All the results indicate that the sorption of toluene to humin is reversible and mainly diffusion controlled. This finding helps to better understand the sorption kinetics associated with humin and soil organic matter.

  8. Sorption of Triton X-100 on soil organic matter fractions: kinetics and isotherms.

    Science.gov (United States)

    Zhang, Guangzhi; Hu, Hao; Sun, Weiling; Ni, Jinren

    2009-01-01

    Kinetics and isotherms of Triton X-100 sorption on soil, base-extracted soil (BE), humic acid (HA) and humin (HM) were investigated respectively to get better understanding on characteristics of the surfactant sorption onto different soil organic matters (SOMs). It was demonstrated that the kinetics results could be satisfactorily described by the pseudo-second order model. The half of the time to reach equilibrium (t1/2) for different sorbents followed the sequence of soil > HA > BE > HM. Furthermore, the calculated equilibrium sorption capacity (C(eq)) was found in the sequence of HA > BE > HM > soil, which agreed well with the experimental results. The isotherms of Triton X-100 sorption on soil and HA could be well described by the S-type isotherm, but BE and HM by the L-type. The isotherms of all the four sorbents were found reasonably fitted to the Langmuir equation. The K(d) value, defined as the ratio of Triton X-100 in sorbent and in the equilibrium solution for given concentrations, generally followed the order of HM > HA > soil > BE. Separated HM and HA showed high affinity for Triton X-100, but the HA and HM in soil and BE were tightly bounded by the minerals. Thus, the HA on the soil surface might dominate the sorption, whereas the bounded HM would play a key role upon the surfactants being penetrated inside the soil.

  9. Partitioning CO2 fluxes with isotopologue measurements and modeling to understand mechanisms of forest carbon sequestration

    Energy Technology Data Exchange (ETDEWEB)

    Saleska, Scott [Univ. of Arizona, Tucson, AZ (United States); Davidson, Eric [Univ. of Arizona, Tucson, AZ (United States); Finzi, Adrien [Boston Univ., MA (United States); Wehr, Richdard [Harvard Univ., Cambridge, MA (United States); Moorcroft, Paul [Harvard Univ., Cambridge, MA (United States)

    2016-01-28

    1. Objectives This project combines automated in situ observations of the isotopologues of CO2 with root observations, novel experimental manipulations of belowground processes, and isotope-enabled ecosystem modeling to investigate mechanisms of below- vs. aboveground carbon sequestration at the Harvard Forest Environmental Measurements Site (EMS). The proposed objectives, which have now been largely accomplished, include: A. Partitioning of net ecosystem CO2 exchange (NEE) into photosynthesis and respiration using long-term continuous observations of the isotopic composition of NEE, and analysis of their dynamics ; B. Investigation of the influence of vegetation phenology on the timing and magnitude of carbon allocated belowground using measurements of root growth and indices of belowground autotrophic vs. heterotrophic respiration (via trenched plots and isotope measurements); C. Testing whether plant allocation of carbon belowground stimulates the microbial decomposition of soil organic matter, using in situ rhizosphere simulation experiments wherein realistic quantities of artificial isotopically-labeled exudates are released into the soil; and D. Synthesis and interpretation of the above data using the Ecosystem Demography Model 2 (ED2). 2. Highlights Accomplishments: • Our isotopic eddy flux record has completed its 5th full year and has been used to independently estimate ecosystem-scale respiration and photosynthesis. • Soil surface chamber isotopic flux measurements were carried out during three growing seasons, in conjunction with a trenching manipulation. Key findings to date (listed by objective): A. Partitioning of Net Ecosystem Exchange: 1. Ecosystem respiration is lower during the day than at night—the first robust evidence of the inhibition of leaf respiration by light (the “Kok effect”) at the ecosystem scale. 2. Because it neglects the Kok effect, the standard NEE partitioning approach overestimates ecosystem photosynthesis (by ~25%) and

  10. Recent Advances in Understanding Amino Acid Sensing Mechanisms that Regulate mTORC1

    Directory of Open Access Journals (Sweden)

    Liufeng Zheng

    2016-09-01

    Full Text Available The mammalian target of rapamycin (mTOR is the central regulator of mammalian cell growth, and is essential for the formation of two structurally and functionally distinct complexes: mTORC1 and mTORC2. mTORC1 can sense multiple cues such as nutrients, energy status, growth factors and hormones to control cell growth and proliferation, angiogenesis, autophagy, and metabolism. As one of the key environmental stimuli, amino acids (AAs, especially leucine, glutamine and arginine, play a crucial role in mTORC1 activation, but where and how AAs are sensed and signal to mTORC1 are not fully understood. Classically, AAs activate mTORC1 by Rag GTPases which recruit mTORC1 to lysosomes, where AA signaling initiates. Plasma membrane transceptor L amino acid transporter 1 (LAT1-4F2hc has dual transporter-receptor function that can sense extracellular AA availability upstream of mTORC1. The lysosomal AA sensors (PAT1 and SLC38A9 and cytoplasmic AA sensors (LRS, Sestrin2 and CASTOR1 also participate in regulating mTORC1 activation. Importantly, AAs can be sensed by plasma membrane receptors, like G protein-coupled receptor (GPCR T1R1/T1R3, and regulate mTORC1 without being transported into the cells. Furthermore, AA-dependent mTORC1 activation also initiates within Golgi, which is regulated by Golgi-localized AA transporter PAT4. This review provides an overview of the research progress of the AA sensing mechanisms that regulate mTORC1 activity.

  11. Understanding the mechanisms of cobalt-catalyzed hydrogenation and dehydrogenation reactions.

    Science.gov (United States)

    Zhang, Guoqi; Vasudevan, Kalyan V; Scott, Brian L; Hanson, Susan K

    2013-06-12

    Cobalt(II) alkyl complexes of aliphatic PNP pincer ligands have been synthesized and characterized. The cationic cobalt(II) alkyl complex [(PNHP(Cy))Co(CH2SiMe3)]BAr(F)4 (4) (PNHP(Cy) = bis[(2-dicyclohexylphosphino)ethyl]amine) is an active precatalyst for the hydrogenation of olefins and ketones and the acceptorless dehydrogenation of alcohols. To elucidate the possible involvement of the N-H group on the pincer ligand in the catalysis via a metal-ligand cooperative interaction, the reactivities of 4 and [(PNMeP(Cy))Co(CH2SiMe3)]BAr(F)4 (7) were compared. Complex 7 was found to be an active precatalyst for the hydrogenation of olefins. In contrast, no catalytic activity was observed using 7 as a precatalyst for the hydrogenation of acetophenone under mild conditions. For the acceptorless dehydrogenation of 1-phenylethanol, complex 7 displayed similar activity to complex 4, affording acetophenone in high yield. When the acceptorless dehydrogenation of 1-phenylethanol with precatalyst 4 was monitored by NMR spectroscopy, the formation of the cobalt(III) acetylphenyl hydride complex [(PNHP(Cy))Co(III)(κ(2)-O,C-C6H4C(O)CH3)(H)]BAr(F)4 (13) was detected. Isolated complex 13 was found to be an effective catalyst for the acceptorless dehydrogenation of alcohols, implicating 13 as a catalyst resting state during the alcohol dehydrogenation reaction. Complex 13 catalyzed the hydrogenation of styrene but showed no catalytic activity for the room temperature hydrogenation of acetophenone. These results support the involvement of metal-ligand cooperativity in the room temperature hydrogenation of ketones but not the hydrogenation of olefins or the acceptorless dehydrogenation of alcohols. Mechanisms consistent with these observations are presented for the cobalt-catalyzed hydrogenation of olefins and ketones and the acceptorless dehydrogenation of alcohols.

  12. Understanding the mechanism of DNA deactivation in ion therapy of cancer cells: hydrogen peroxide action*

    Science.gov (United States)

    Piatnytskyi, Dmytro V.; Zdorevskyi, Oleksiy O.; Perepelytsya, Sergiy M.; Volkov, Sergey N.

    2015-11-01

    Changes in the medium of biological cells under ion beam irradiation has been considered as a possible cause of cell function disruption in the living body. The interaction of hydrogen peroxide, a long-lived molecular product of water radiolysis, with active sites of DNA macromolecule was studied, and the formation of stable DNA-peroxide complexes was considered. The phosphate groups of the macromolecule backbone were picked out among the atomic groups of DNA double helix as a probable target for interaction with hydrogen peroxide molecules. Complexes consisting of combinations including: the DNA phosphate group, H2O2 and H2O molecules, and Na+ counterion, were considered. The counterions have been taken into consideration insofar as under the natural conditions they neutralise DNA sugar-phosphate backbone. The energy of the complexes have been determined by considering the electrostatic and the Van der Waals interactions within the framework of atom-atom potential functions. As a result, the stability of various configurations of molecular complexes was estimated. It was shown that DNA phosphate groups and counterions can form stable complexes with hydrogen peroxide molecules, which are as stable as the complexes with water molecules. It has been demonstrated that the formation of stable complexes of H2O2-Na+-PO4- may be detected experimentally by observing specific vibrations in the low-frequency Raman spectra. The interaction of H2O2 molecule with phosphate group of the double helix backbone can disrupt DNA biological function and induce the deactivation of the cell genetic apparatus. Thus, the production of hydrogen peroxide molecules in the nucleus of living cells can be considered as an additional mechanism by which high-energy ion beams destroy tumour cells during ion beam therapy. Contribution to the Topical Issue "COST Action Nano-IBCT: Nano-scale Processes Behind Ion-Beam Cancer Therapy", edited by Andrey Solov'yov, Nigel Mason, Gustavo García, Eugene

  13. Toward an understanding of the molecular mechanisms of barnacle larval settlement: A comparative transcriptomic approach

    KAUST Repository

    Chen, Zhang-Fan

    2011-07-29

    Background: The barnacle Balanus amphitrite is a globally distributed biofouler and a model species in intertidal ecology and larval settlement studies. However, a lack of genomic information has hindered the comprehensive elucidation of the molecular mechanisms coordinating its larval settlement. The pyrosequencing-based transcriptomic approach is thought to be useful to identify key molecular changes during larval settlement. Methodology and Principal Findings: Using 454 pyrosequencing, we collected totally 630,845 reads including 215,308 from the larval stages and 415,537 from the adults; 23,451 contigs were generated while 77,785 remained as singletons. We annotated 31,720 of the 92,322 predicted open reading frames, which matched hits in the NCBI NR database, and identified 7,954 putative genes that were differentially expressed between the larval and adult stages. Of these, several genes were further characterized with quantitative real-time PCR and in situ hybridization, revealing some key findings: 1) vitellogenin was uniquely expressed in late nauplius stage, suggesting it may be an energy source for the subsequent non-feeding cyprid stage; 2) the locations of mannose receptors suggested they may be involved in the sensory system of cyprids; 3) 20 kDa-cement protein homologues were expressed in the cyprid cement gland and probably function during attachment; and 4) receptor tyrosine kinases were expressed higher in cyprid stage and may be involved in signal perception during larval settlement. Conclusions: Our results provide not only the basis of several new hypotheses about gene functions during larval settlement, but also the availability of this large transcriptome dataset in B. amphitrite for further exploration of larval settlement and developmental pathways in this important marine species. © 2011 Chen et al.

  14. Sorption of Europium in zirconium silicate; Sorcion de Europio en silicato de circonio

    Energy Technology Data Exchange (ETDEWEB)

    Garcia R, G. [ININ, Carretera Mexico-Toluca Km. 36.5, 52045 Estado de Mexico (Mexico)

    2004-07-01

    Some minerals have the property of sipping radioactive metals in solution, that it takes advantage to manufacture contention barriers that are placed in the repositories of nuclear wastes. The more recent investigations are focused in the development of new technologies guided to the sorption of alpha emissors on minerals which avoid their dispersion in the environment. In an effort to contribute to the understanding of this type of properties, some studies of sorption of Europium III are presented like homologous of the americium, on the surface of zirconium silicate (ZrSiO{sub 4}). In this work the results of sorption experiences are presented as well as the interpretation of the phenomena of the formation of species in the surface of the zirconium silicate. (Author)

  15. Understanding the mechanisms of solid-water reactions through analysis of surface topography.

    Science.gov (United States)

    Bandstra, Joel Z; Brantley, Susan L

    2015-12-01

    The topography of a reactive surface contains information about the reactions that form or modify the surface and, therefore, it should be possible to characterize reactivity using topography parameters such as surface area, roughness, or fractal dimension. As a test of this idea, we consider a two-dimensional (2D) lattice model for crystal dissolution and examine a suite of topography parameters to determine which may be useful for predicting rates and mechanisms of dissolution. The model is based on the assumption that the reactivity of a surface site decreases with the number of nearest neighbors. We show that the steady-state surface topography in our model system is a function of, at most, two variables: the ratio of the rate of loss of sites with two neighbors versus three neighbors (d(2)/d(3)) and the ratio of the rate of loss of sites with one neighbor versus three neighbors (d(1)/d(3)). This means that relative rates can be determined from two parameters characterizing the topography of a surface provided that the two parameters are independent of one another. It also means that absolute rates cannot be determined from measurements of surface topography alone. To identify independent sets of topography parameters, we simulated surfaces from a broad range of d(1)/d(3) and d(2)/d(3) and computed a suite of common topography parameters for each surface. Our results indicate that the fractal dimension D and the average spacing between steps, E[s], can serve to uniquely determine d(1)/d(3) and d(2)/d(3) provided that sufficiently strong correlations exist between the steps. Sufficiently strong correlations exist in our model system when D>1.5 (which corresponds to D>2.5 for real 3D reactive surfaces). When steps are uncorrelated, surface topography becomes independent of step retreat rate and D is equal to 1.5. Under these conditions, measures of surface topography are not independent and any single topography parameter contains all of the available mechanistic

  16. Zinc and copper sorption and fixation by an acid soil clay: effect of selective dissolutions

    Energy Technology Data Exchange (ETDEWEB)

    Cavallaro, N.; McBride, M.B.

    Copper and zinc sorption-desorption studies were carried out over a range of pH values using clay fractions separated from two horizons of an acid soil from New York. In the pH range of high sorption, as much as 95% of the sorbed metal could not be desorbed and thus was considered fixed. Sorption and fixation of Cu and Zn increased rapidly above pH 4 and 5, respectively, for the whole soil clays. Following removal of the oxide fraction by oxalate and citrate-dethionite extractions, sorption and fixation were reduced considerably at pH values below the onset of hydrolysis of the metals in bulk solution. Citrate-dithionite extraction was more effective than oxalate in reducing Zn sorption and fixation. These extraction procedures had less effect on the ability of the clays to sorb and fix Cu. It is concluded that microcrystalline and noncrystalline oxides in the clay fraction of this soil, representing < 20% off the clay by weight, provide reactive surfaces for the chemisorption of Cu and Zn. At low pH, adsorption at these surfaces may be the dominant mechanism of heavy metal immobilization, especially in the subsoil horizons.

  17. Nonequilibrium sorption and transport of volatile petroleum hydrocarbons in surfactant-modified zeolite

    Science.gov (United States)

    Simpson, Joshua A.; Bowman, Robert S.

    2009-08-01

    We characterized the nonequilibrium sorption and transport of benzene, toluene, ethylbenzene, and xylenes (BTEX) by surfactant-modified zeolite (SMZ) in batch and column tests. The SMZ was shown in previous studies to be an effective sorbent for removal of BTEX from oilfield wastewaters prior to disposal or reuse. A two-site, first-order chemical nonequilibrium model was used to determine sorption parameters from the batch results. Individual BTEX linear sorption coefficients, Kd, ranged from 7.5 to 37 L kg - 1 and were independent of BTEX concentration or competing solutes, suggesting that partitioning was the mechanism of sorption. The Kd values were the same whether the zeolite was covered by a monolayer or bilayer of the surfactant hexadecyltrimethylammonium (HDTMA). Batch rate coefficients and the fraction of "instantaneous" sorption sites decreased with BTEX hydrophobicity and with total BTEX concentration. The fraction of "instantaneous" sites was 3-11 times greater for the monolayer as compared to the bilayer SMZ. These observations are consistent with a conceptual model in which BTEX are rapidly partitioned into hydrophobic monolayer surfaces and more slowly partitioned to hydrophilic bilayer surfaces. Results from the batch experiments were used to predict BTEX transport through columns of SMZ. Batch-derived rate and site-distribution parameters accurately described the transport dynamics, but the batch-derived Kds significantly underestimated BTEX retardation. Excess dissolved HDTMA in the batch experiments likely led to anomalously low Kd values for those determinations.

  18. Equilibrium and kinetic studies for the sorption of 3-methoxybenzaldehyde on activated kaolinites

    Energy Technology Data Exchange (ETDEWEB)

    Koyuncu, Huelya [Forensic Medicine Foundation, Nasuhpasa Bath Street, No. 12, 16010 Heykel, Bursa (Turkey)]. E-mail: hkoyuncu@yyu.edu.tr; Kul, Ali Riza [Yuzuncu Yil University, Faculty of Art and Science, Department of Chemistry, 65080 Van (Turkey)]. E-mail: alirizakul@yyu.edu.tr; Yildiz, Nuray [Ankara University, Faculty of Engineering, Department of Chemical Engineering, 06100 Tandogan, Ankara (Turkey)]. E-mail: nyildiz@eng.ankara.edu.tr; Calimli, Ayla [Ankara University, Faculty of Engineering, Department of Chemical Engineering, 06100 Tandogan, Ankara (Turkey)]. E-mail: calimli@eng.ankara.edu.tr; Ceylan, Hasan [Yuzuncu Yil University, Faculty of Art and Science, Department of Chemistry, 65080 Van (Turkey)]. E-mail: hceylan@yyu.edu.tr

    2007-03-06

    The sorption of 3-methoxybenzaldehyde on activated kaolinites has been investigated at different temperatures. Two types of activation tests were performed. The sorption equilibrium was studied by sorption isotherms in the temperature range 303-333 K for natural (untreated), thermally and acid activated kaolinites. It was shown that the isotherm shapes were not affected by temperature and activation types of kaolinite. The absorbance data at 312 nm were fitted reasonably well with the Langmuir and Freundlich isotherm models and the model parameters were determined for different temperatures. Thermodynamic quantities such as Gibbs free energy ({delta}G), the enthalpy ({delta}H) and the entropy change of sorption ({delta}S) were determined for natural, thermally and acid activated kaolinites. It was shown that the sorption processes were an endothermic reactions, controlled by physical mechanisms and spontaneously. Adsorption capacity of acid activated kaolinite for 3-methoxybenzaldehyde was higher compared to that of natural and thermally activated kaolinites at various temperatures. The adsorption and desorption rate constants (k {sub a} and k {sub d}) were obtained separately by applying a geometric approach to the first order Langmuir model. This method provided good conformity between the K from Langmuir parameters and K {sub geo} (k {sub a}/k {sub d}) from geometric approach.

  19. Equilibrium and kinetic studies for the sorption of 3-methoxybenzaldehyde on activated kaolinites

    International Nuclear Information System (INIS)

    Koyuncu, Huelya; Kul, Ali Riza; Yildiz, Nuray; Calimli, Ayla; Ceylan, Hasan

    2007-01-01

    The sorption of 3-methoxybenzaldehyde on activated kaolinites has been investigated at different temperatures. Two types of activation tests were performed. The sorption equilibrium was studied by sorption isotherms in the temperature range 303-333 K for natural (untreated), thermally and acid activated kaolinites. It was shown that the isotherm shapes were not affected by temperature and activation types of kaolinite. The absorbance data at 312 nm were fitted reasonably well with the Langmuir and Freundlich isotherm models and the model parameters were determined for different temperatures. Thermodynamic quantities such as Gibbs free energy (ΔG), the enthalpy (ΔH) and the entropy change of sorption (ΔS) were determined for natural, thermally and acid activated kaolinites. It was shown that the sorption processes were an endothermic reactions, controlled by physical mechanisms and spontaneously. Adsorption capacity of acid activated kaolinite for 3-methoxybenzaldehyde was higher compared to that of natural and thermally activated kaolinites at various temperatures. The adsorption and desorption rate constants (k a and k d ) were obtained separately by applying a geometric approach to the first order Langmuir model. This method provided good conformity between the K from Langmuir parameters and K geo (k a /k d ) from geometric approach

  20. The Effect of Ventilation, Filtration and Passive Sorption on Indoor Air Quality in Museum Storage Rooms

    DEFF Research Database (Denmark)

    Ryhl-Svendsen, M.; Clausen, Geo

    2009-01-01

    and filtration units. Passive sorption was initiated by hanging sheets of sorptive materials oil walls. The control strategies were evaluated in terms of their ability to lower the concentration of internally, generated pollutants, and the indoor-to-outdoor concentration ratio of outdoor pollutants. The overall...... environmental impact for each method was evaluated by the use of material dosimeters. It was found that passive sorption performed better in a small room compared to a large room. Mechanical ventilation and filtration with activated charcoal gave a high protection against ozone, but were less effective...

  1. Water sorption and transport in dry crispy bread crust

    NARCIS (Netherlands)

    Meinders, M.B.J.; Nieuwenhuijzen, van N.H.; Tromp, R.H.; Hamer, R.J.; Vliet, van T.

    2010-01-01

    Water sorption and dynamical properties of bread crust have been studied using gravimetric sorption experiments. Water uptake and loss were followed while relative humidity (RH) was stepwise in- or decreased (isotherm experiment) or varied between two adjusted values (oscillatory experiment).

  2. Molecular simulation of polycyclic aromatic hydrocarbon sorption to black carbon

    NARCIS (Netherlands)

    Haftka, J.J.H.; Parsons, J.R.; Govers, H.A.J.

    2009-01-01

    Strong sorption of hydrophobic organic contaminants to soot or black carbon (BC) is an important environmental process limiting the bioremediation potential of contaminated soils and sediments. Reliable methods to predict BC sorption coefficients for organic contaminants are therefore required. A

  3. Tritium sorption on protective coatings for concrete

    International Nuclear Information System (INIS)

    Miller, J.M.; Senohrabek, J.A.; Allsop, P.A.

    1992-11-01

    Because of the high sorption level of tritium on unprotected concrete, a program to examine the effectiveness of various concrete coatings and sealants in reducing tritium sorption was undertaken, and various exposure conditions were examined. Coatings of epoxy, polyurethane, bituminous sealant, bituminous sealant covered with polyvinylidene chloride wrap, alkyd paint, and sodium silicate were investigated with tritium (HTO) vapor concentration, humidity and contact time being varied. An exposure to HT was also carried out, and the effect of humidity on the tritium desorption rate was investigated. The relative effectiveness of the coatings was in the order of bituminous sealant + wrap > bituminous sealant > solvent-based epoxy > 100%-solids epoxy > alkyd paint > sodium silicate. The commercially available coatings for concrete resulted in tritium sorption being reduced to less than 7% of unprotected concrete. This was improved to ∼0.1% with the use of the Saran wrap (polyvinylidene chloride). The amount of tritium sorbed was proportional to tritium concentration. The total tritium sorbed decreased with an increase in humidity. A saturation effect was observed with increasing exposure time for both the coated and unprotected samples. Under the test conditions, complete saturation was not achieved within the maximum 8-hour contact time, except for the solvent-based epoxy. The desorption rate increased with a higher-humidity air purge stream. HT desorbed more rapidly than HTO, but the amount sorbed was smaller. The experimental program showed that HTO sorption by concrete can be significantly reduced with the proper choice of coating. However, tritium sorption on concrete and proposed coatings will continue to be a concern until the effects of the various conditions that affect the adsorption and desorption of tritium are firmly established for both chronic and acute tritium release conditions. Material sorption characteristics must also be considered in

  4. SORPTION OF LEAD ON A RUTHENIUM COMPOUND: A MACROSCOPIC AND MICROSCOPIC STUDY

    Science.gov (United States)

    The objective of this study was to elucidate the sorption mechanism of Pb on the high-affinity ruthenium compound with time at pH 6 employing batch methods and X-ray absorption fine structure (XAFS) and X-ray diffraction (XRD) spectroscopies. For the spectroscopic studies, Pb so...

  5. Sorption of testosterone on partially-dispersed soil particles of different size fractions: Methodology and implications.

    Science.gov (United States)

    Qi, Yong; Zhang, Tian C

    2016-04-01

    Sorption of hormones to soil particles of different size fractions (DSFs) has been studied to understand their fate and transport (F/T) in soils. Conventional studies fractionated the soil particles into DSFs by using the high speed stirring method and/or adding surfactants to fully disperse the bulk soil. However, the natural processes (e.g., soil erosion, irrigation) often are relatively mild, and many soil particles may be still in the aggregate form. In this study, a method was developed for conducting the sorption test of a representative hormone (i.e., testosterone) to bulk soils first and then analyzing the results against DSFs. Results indicated the particle size distribution (PSD) of the two representative soils tested with partially-dispersed and fully-dispersed methods was significantly different due to the attachment of clay particles on sand and silt. Testosterone was sorbed mainly by the dominant aggregates even though they might have relatively lower sorption affinity than that of clays. However, the small particles (soil, contributed more than 30% of sorbed testosterone in the "whole" soils. The partially-dispersed soil particles of DSFs should be used to understand the transport of hormone in runoff, because using the fully-dispersed soil particles will overestimate while the whole soil method will underestimate the transport potential. With the methodology developed in this study, the sorption tests will not compromise soil's original properties (e.g., aggregates) or the competition (e.g., sorption) among soil particles, and the contribution of DSFs (particularly the partially-dispersed aggregates) to the sorption of the "whole" soil can be determined. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Understanding dental CAD/CAM for restorations - dental milling machines from a mechanical engineering viewpoint. Part A: chairside milling machines.

    Science.gov (United States)

    Lebon, Nicolas; Tapie, Laurent; Duret, Francois; Attal, Jean-Pierre

    2016-01-01

    The dental milling machine is an important device in the dental CAD/CAM chain. Nowadays, dental numerical controlled (NC) milling machines are available for dental surgeries (chairside solution). This article provides a mechanical engineering approach to NC milling machines to help dentists understand the involvement of technology in digital dentistry practice. First, some technical concepts and definitions associated with NC milling machines are described from a mechanical engineering viewpoint. The technical and economic criteria of four chairside dental NC milling machines that are available on the market are then described. The technical criteria are focused on the capacities of the embedded technologies of these milling machines to mill both prosthetic materials and types of shape restorations. The economic criteria are focused on investment costs and interoperability with third-party software. The clinical relevance of the technology is assessed in terms of the accuracy and integrity of the restoration.

  7. Perspectives for application of moulded sorption materials based on peat and mineral compositions

    Science.gov (United States)

    Misnikov, Oleg

    2017-11-01

    The paper discusses scientific and technological grounds for using peat, its wastes and processing products as sorption materials for liquidation of pollutions on water and oil basis. A negative effect on the hydro-physical properties of peat by hysteresis phenomena occurring during drying is noted. Use of optimal concentrations of mineral hydrophilic additives in peat matrix allows to increase speed and capacity of sorption. A working hypothesis is proposed that explains the physical and chemical mechanism for increasing quality of composite sorbents. A principal technological scheme for obtaining sorption materials based on peat is developed. It allows to take into account possible transitions between stages of the technological process, which reduce its cost.

  8. Sorption of Pu(IV) from nitric acid by bifunctional anion-exchange resins

    International Nuclear Information System (INIS)

    Bartsch, R.A.; Zhang, Z.Y.; Elshani, S.; Zhao, W.; Jarvinen, G.D.; Barr, M.E.; Marsh, S.F.; Chamberlin, R.M.

    1999-01-01

    Anion exchange is attractive for separating plutonium because the Pu(IV) nitrate complex is very strongly sorbed and few other metal ions form competing anionic nitrate complexes. The major disadvantage of this process has been the unusually slow rate at which the Pu(IV) nitrate complex is sorbed by the resin. The paper summarizes the concept of bifunctional anion-exchange resins, proposed mechanism for Pu(IV) sorption, synthesis of the alkylating agent, calculation of K d values from Pu(IV) sorption results, and conclusions from the study of Pu(IV) sorption from 7M nitric acid by macroporous anion-exchange resins including level of crosslinking, level of alkylation, length of spacer, and bifunctional vs. monofunctional anion-exchange resins

  9. Polyvinyl chloride Waste as an Adsorbent for the Sorption of Pb2+ from Aqueous Solution

    Directory of Open Access Journals (Sweden)

    Donbebe Wankasi

    2014-01-01

    Full Text Available The sorption of Pb2+ from solution by polyvinyl chloride waste was investigated. The morphological features of the polymer sample were studied using the energy dispersive X-ray spectroscopy (EDX, scanning electron microscopy (SEM, X-ray diffraction spectroscopy (XRD, and the Fourier transform infrared spectroscopy (FTIR. Equilibrium, kinetic, and thermodynamic batch adsorption experiments were carried out by the concentration, time, and temperature effects, respectively. The morphological image of the polymer showed irregular small size particles which indicated a high surface area and porosity that facilitated sorption. The adsorption studies recorded relatively rapid uptake of Pb2+ by the polymer which was mainly diffusion controlled and followed a second order kinetic process. The thermodynamic studies suggested relatively low temperature (low energy favoured sorption which was exothermic with a physisorption mechanism.

  10. A study of sorption of cadmium by goethite in aqueous solution

    Directory of Open Access Journals (Sweden)

    N. Salami

    2002-06-01

    Full Text Available Investigation has been carried out on the potential of a locally sourced goethite for the removal of cadmium ion from aqueous solutions using batch equilibration technique. The maximum uptake of cadmium is 6.4  10-2 mg/g-goethite. The sorption kinetics appears to be rapid as equilibrium was attained within a period of 1 hour. The highest sorption capacity was obtained for particle size with diameter (Φ 0.09 mm. Both infrared spectrophotometric and X-ray diffraction (XRD techniques have also provided evidence for cadmium fixation on to the surface of the goethite. The sorption mechanism appears to follow Langmuir adsorption isotherm model. The Langmuir constants K and Xm (mass of Cd2+ required to form monolayer on the entire surface of the goethite were 0.096 mg/g-goethite and 0.075 mg/g-goethite, respectively.

  11. Quantum interactive learning tutorial on the double-slit experiment to improve student understanding of quantum mechanics

    Directory of Open Access Journals (Sweden)

    Ryan Sayer

    2017-05-01

    Full Text Available Learning quantum mechanics is challenging, even for upper-level undergraduate and graduate students. Research-validated interactive tutorials that build on students’ prior knowledge can be useful tools to enhance student learning. We have been investigating student difficulties with quantum mechanics pertaining to the double-slit experiment in various situations that appear to be counterintuitive and contradict classical notions of particles and waves. For example, if we send single electrons through the slits, they may behave as a “wave” in part of the experiment and as a “particle” in another part of the same experiment. Here we discuss the development and evaluation of a research-validated Quantum Interactive Learning Tutorial (QuILT which makes use of an interactive simulation to improve student understanding of the double-slit experiment and strives to help students develop a good grasp of foundational issues in quantum mechanics. We discuss common student difficulties identified during the development and evaluation of the QuILT and analyze the data from the pretest and post test administered to the upper-level undergraduate and first-year physics graduate students before and after they worked on the QuILT to assess its effectiveness. These data suggest that on average, the QuILT was effective in helping students develop a more robust understanding of foundational concepts in quantum mechanics that defy classical intuition using the context of the double-slit experiment. Moreover, upper-level undergraduates outperformed physics graduate students on the post test. One possible reason for this difference in performance may be the level of student engagement with the QuILT due to the grade incentive. In the undergraduate course, the post test was graded for correctness while in the graduate course, it was only graded for completeness.

  12. Quantum interactive learning tutorial on the double-slit experiment to improve student understanding of quantum mechanics

    Science.gov (United States)

    Sayer, Ryan; Maries, Alexandru; Singh, Chandralekha

    2017-06-01

    Learning quantum mechanics is challenging, even for upper-level undergraduate and graduate students. Research-validated interactive tutorials that build on students' prior knowledge can be useful tools to enhance student learning. We have been investigating student difficulties with quantum mechanics pertaining to the double-slit experiment in various situations that appear to be counterintuitive and contradict classical notions of particles and waves. For example, if we send single electrons through the slits, they may behave as a "wave" in part of the experiment and as a "particle" in another part of the same experiment. Here we discuss the development and evaluation of a research-validated Quantum Interactive Learning Tutorial (QuILT) which makes use of an interactive simulation to improve student understanding of the double-slit experiment and strives to help students develop a good grasp of foundational issues in quantum mechanics. We discuss common student difficulties identified during the development and evaluation of the QuILT and analyze the data from the pretest and post test administered to the upper-level undergraduate and first-year physics graduate students before and after they worked on the QuILT to assess its effectiveness. These data suggest that on average, the QuILT was effective in helping students develop a more robust understanding of foundational concepts in quantum mechanics that defy classical intuition using the context of the double-slit experiment. Moreover, upper-level undergraduates outperformed physics graduate students on the post test. One possible reason for this difference in performance may be the level of student engagement with the QuILT due to the grade incentive. In the undergraduate course, the post test was graded for correctness while in the graduate course, it was only graded for completeness.

  13. Sorption Properties of Some Romanian Gingerbread

    Directory of Open Access Journals (Sweden)

    Tulbure Anca

    2014-06-01

    Full Text Available Water activity of gingerbread is very important for keeping the product freshness and shelf life. Water activity is influenced by composition, water content and temperature. The water content of gingerbread could vary according with storage condition. i.e. rH. 11 gingerbread samples were analysed. The water content and water activity lies between 7.0 and 12.6% and respectively 0.590 and 0.715. The sorption isotherms were determined at 30°C by gravimetric method. The moisture sorption is influenced by composition, especially sweeteners and humectants. Honey and invert sugar have the same impact on gingerbread higroscopicity.

  14. Deoxyribonucleic Acid Damage and Repair: Capitalizing on Our Understanding of the Mechanisms of Maintaining Genomic Integrity for Therapeutic Purposes

    Directory of Open Access Journals (Sweden)

    Jolene Michelle Helena

    2018-04-01

    Full Text Available Deoxyribonucleic acid (DNA is the self-replicating hereditary material that provides a blueprint which, in collaboration with environmental influences, produces a structural and functional phenotype. As DNA coordinates and directs differentiation, growth, survival, and reproduction, it is responsible for life and the continuation of our species. Genome integrity requires the maintenance of DNA stability for the correct preservation of genetic information. This is facilitated by accurate DNA replication and precise DNA repair. DNA damage may arise from a wide range of both endogenous and exogenous sources but may be repaired through highly specific mechanisms. The most common mechanisms include mismatch, base excision, nucleotide excision, and double-strand DNA (dsDNA break repair. Concurrent with regulation of the cell cycle, these mechanisms are precisely executed to ensure full restoration of damaged DNA. Failure or inaccuracy in DNA repair contributes to genome instability and loss of genetic information which may lead to mutations resulting in disease or loss of life. A detailed understanding of the mechanisms of DNA damage and its repair provides insight into disease pathogeneses and may facilitate diagnosis and the development of targeted therapies.

  15. Sorption of indigo carmine by a Fe-zeolitic tuff and carbonaceous material from pyrolyzed sewage sludge

    Energy Technology Data Exchange (ETDEWEB)

    Gutierrez-Segura, E. [Facultad de Quimica, Universidad Autonoma del Estado de Mexico, Paseo Colon y Tollocan s/n., C.P. 50000 Toluca (Mexico); Departamento de Quimica, Instituto Nacional de Investigaciones Nucleares, A.P. 18-1027, Col. Escandon, Delegacion Miguel Hidalgo, C.P. 11801 Mexico, D.F. (Mexico); Solache-Rios, M., E-mail: marcos.solache@inin.gob.mx [Departamento de Quimica, Instituto Nacional de Investigaciones Nucleares, A.P. 18-1027, Col. Escandon, Delegacion Miguel Hidalgo, C.P. 11801 Mexico, D.F. (Mexico); Colin-Cruz, A. [Facultad de Quimica, Universidad Autonoma del Estado de Mexico, Paseo Colon y Tollocan s/n., C.P. 50000 Toluca (Mexico)

    2009-10-30

    Indigo carmine removal from aqueous solution has been evaluated using Fe-zeolitic tuff and carbonaceous material from pyrolyzed sewage sludge treated with HCl (CM). The adsorbents were characterized by scanning electron microscopy, BET surface area and X-ray diffraction. Sorption kinetics and isotherms were determined and the adsorption behaviors analyzed. Kinetic pseudo-second order and Langmuir-Freundlich models were successfully applied to the experimental results obtained with the Fe-zeolitic material, while kinetic first order and Langmuir-Freundlich models were applied to the results from the carbonaceous materials. This indicates mechanisms of chemisorption and physic sorption, respectively, on the heterogeneous materials. The results indicate that the carbonaceous material from the pyrolysis of sewage sludge (sorption capacity 92.83 mg/g) is a better adsorbent of indigo carmine than the zeolitic material (sorption capacity 32.83 mg/g).

  16. Sorption of indigo carmine by a Fe-zeolitic tuff and carbonaceous material from pyrolyzed sewage sludge

    International Nuclear Information System (INIS)

    Gutierrez-Segura, E.; Solache-Rios, M.; Colin-Cruz, A.

    2009-01-01

    Indigo carmine removal from aqueous solution has been evaluated using Fe-zeolitic tuff and carbonaceous material from pyrolyzed sewage sludge treated with HCl (CM). The adsorbents were characterized by scanning electron microscopy, BET surface area and X-ray diffraction. Sorption kinetics and isotherms were determined and the adsorption behaviors analyzed. Kinetic pseudo-second order and Langmuir-Freundlich models were successfully applied to the experimental results obtained with the Fe-zeolitic material, while kinetic first order and Langmuir-Freundlich models were applied to the results from the carbonaceous materials. This indicates mechanisms of chemisorption and physic sorption, respectively, on the heterogeneous materials. The results indicate that the carbonaceous material from the pyrolysis of sewage sludge (sorption capacity 92.83 mg/g) is a better adsorbent of indigo carmine than the zeolitic material (sorption capacity 32.83 mg/g).

  17. Competitive sorption and desorption behavior for three fluoroquinolone antibiotics in a wastewater treatment wetland soil.

    Science.gov (United States)

    Conkle, Jeremy L; Lattao, Charisma; White, John R; Cook, Robert L

    2010-09-01

    Significant amounts of pharmaceuticals are discharged into the environment through wastewater effluent. Sorption has been shown to be a significant aqueous removal pathway for many of these compounds. Competition between ciprofloxacin (CIP), ofloxacin (OFL) and norfloxacin (NOR) and their sorption to, and desorption from, a surrogate Louisiana wastewater treatment wetland soil were investigated to gain insight into the fate and transport of the pollutants within wastewater treatment wetlands. This study was undertaken in the context of a treatment wetland that continuously receives pharmaceuticals. Therefore it is important to understand the total capacity of this soil to sorb these compounds. Sorption to this treatment wetland soil was found to provide a major and potentially long-term removal pathway for these antibiotics from wastewater. LogK(F) values for all three compounds were between 4.09 and 3.90 for sorption and 4.24 and 4.05 microg(1-1/)(n)(cm(3))(1/)(n)g(-1) for desorption. The compounds were sorbed in amounts ranging from 60% to 90% for high and low loading, respectively. The majority of the compounds were sorbed to the soil within the first 20h, indicating that treatment wetland may not need long retention times (weeks to months) in order to remove these compounds. Sorption K(D) values for competition (20 ppm of each compound for 60 ppm of total fluoroquinolones) ranged from 2300 to 3800 cm(3)g(-1) which is between both the 20 (4300-5800 cm(3)g(-1)) and 60 (1300-3000 cm(3)g(-1)) ppm single compound K(D) values, indicating that there is competition between these three compound for sorption sites. Sorption and desorption data (single component and mixture) collectively provide the following evidence: (1) NOR and, to a lesser extent, CIP outcompete OFL for sorption sites, (2) OFL sorbes to its share of "quality" sorption sites, and (3) competition only occurs for lesser "quality" binding sites. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

  18. Attenuation of polychlorinated biphenyl sorption to charcoal by humic acids

    NARCIS (Netherlands)

    Koelmans, A.A.; Meulman, B.; Meijer, T.; Jonker, M.T.O.

    2009-01-01

    Strong sorption to black carbon may limit the environmental risks of organic pollutants, but interactions with cosorbing humic acid (HA) may interfere. We studied the attenuative effect of HA additions on the sorption of polychlorinated biphenyls (PCBs) to a charcoal. "Intrinsic" sorption to

  19. Suitability of Moshi Pumice for Phosphorus Sorption in Constructed ...

    African Journals Online (AJOL)

    The study of Moshi Pumice's phosphorus sorption behaviours and properties was carried out in laboratory scale where by 1-2 mm, 2-4 mm and 4-8 mm grains were tested using batch experiments. The results show that Moshi Pumice has high phosphorus sorption capacity. The sorption capacity for the Moshi Pumice was ...

  20. Phosphorus sorption in relation to soil grain size and geochemical ...

    African Journals Online (AJOL)

    By using stepwise regression, the combination of Al, Fe, clay and Ca predicted more than 94% of the variation in the P sorption capacity of soils samples from Simiyu and Kagera basins. These four soil properties, which are strongly related to P sorption, could therefore be used as quick tests for predicting the P sorption ...

  1. suitability of murram for phosphorus sorption in constructed wetlands

    African Journals Online (AJOL)

    Mimi

    ABSTRACT: The study of Moshi Pumice's phosphorus sorption behaviours and properties was carried out in laboratory scale where by 1-2 mm, 2-4 mm and 4-8 mm grains were tested using batch experiments. The results show that Moshi Pumice has high phosphorus sorption capacity. The sorption capacity for the Moshi ...

  2. Sorption of perfluorooctane sulfonate to carbon nanotubes in aquatic sediments

    NARCIS (Netherlands)

    Kwadijk, C.J.A.F.; Velzeboer, I.; Koelmans, A.A.

    2013-01-01

    To date, sorption of organic compounds to nanomaterials has mainly been studied for the nanomaterial in its pristine state. However, sorption may be different when nanomaterials are buried in sediments. Here, we studied sorption of Perfluorooctane sulfonate (PFOS) to sediment and to sediment with 4%

  3. Attenuation of polychlorinated biphenyl sorption to charcoal by humic acids.

    NARCIS (Netherlands)

    Koelmans, A.A.; Meulman, B.; Meijer, T.; Jonker, M.T.O.

    2009-01-01

    Strong sorption to black carbon may limit the environmental risks of organic pollutants, but interactions with cosorbing humic acid (HA) may interfere. We studied the attenuative effect of HA additions on the sorption of polychlorinated biphenyls (PCBs) to a charcoal. "Intrinsic" sorption to

  4. Phenanthrene sorption to Chinese coal: Importance of coal's geochemical properties

    International Nuclear Information System (INIS)

    Yan Caixia; Yang Yi; Liu Min; Nie Minghua; Zhou, John L.

    2011-01-01

    Highlights: → Phen was chosen as the probe compound for determining the sorption of PAHs to a series of different Chinese coal samples. → The combined partition and adsorption model yielded a better fit than the Freundlich isotherm. → Compared to total carbon, BC might play more important role in the sorption of Phen to coal samples. → Relationships between aromatic and aliphatic carbon contents and sorption parameters indicated the significance of aromatic and aliphatic carbon in the coal sorption behavior. - Abstract: Phenanthrene (Phen) was chosen as the probe compound for determining the sorption of PAHs to a series of different coal samples from China. Based on elemental analysis and nuclear magnetic resonance (NMR) spectra analysis, coal samples were characterized with different metamorphic evolutional degrees. The experimental sorption data were fitted well by the Freundlich model, suggesting enhanced sorption capacity and strong nonlinearity of coal samples. The combined partition and adsorption model yielded a better fit than the Freundlich isotherm, indicating that adsorption dominated the sorption at low aqueous concentrations. Correlations between coal properties and sorption capacity values indicated that C%, H/C and O/C atomic ratios were the key factors controlling the sorption behavior. Compared to total carbon, BC might play more important role in the sorption of Phen to coal samples. Moreover, there existed nonlinear relationships between combined carbon, aromatic and aliphatic carbon contents and log K Fr and n values, respectively, indicating the significance of aromatic and aliphatic carbon in the coal sorption behavior.

  5. Sorption of caesium and strontium onto calcium silicate hydrate in saline groundwater

    International Nuclear Information System (INIS)

    Sugiyama, D.; Fujita, T.

    2005-01-01

    Full text of publication follows: In the concept for radioactive waste disposal in Japan, cement is a potential waste packaging and backfilling material and is expected to provide chemical containment. The sorption of radionuclides onto cement materials, which controls the aqueous concentrations of elements in the pore-water, is a very important parameter when considering the release of radionuclides from the near field of a cementitious radioactive waste repository. Many safety assessment calculations currently assume radionuclide retardation as linear sorption equilibrium and describe it with a distribution ratio (R d value). In this study, the sorption mechanism is discussed by measuring the sorption isotherm of caesium, strontium (10 -5 ∼ 10 -2 mol dm -3 ) and sodium (10 -4 ∼ 10 -1 mol dm -3 ) onto Calcium Silicate Hydrate (C-S-H gel, Ca/Si 0.65 ∼ 1.2) at a liquid:solid ratio of 100:1, to support the assumption. In addition, the competitive sorption between caesium or strontium, and sodium is studied by sorption measurements using a range of sodium chloride concentration to simulate different ionic strengths in saline groundwater. The initial and equilibrated aqueous compositions were measured in the sorption experiments and it was found that caesium, strontium and sodium were sorbed by substitution for Ca in C-S-H phases by examining the mass balance. Based on the experimental results, we propose a modelling approach in which the ion-exchange model is employed and the presence of some calcium sites with different ion-exchange log K values in C-S-H is assumed by considering the composition and the structure of C-S-H. The modelling calculation results predict the measured Rd values well and also describe the competition of sorption of caesium or strontium, and sodium in the experiments. The log K values for sorption of each cation element decreased as Ca/Si ratio of C-S-H gel increased. This agrees with the trend that C-S-H gel is negatively charged at low

  6. Sorption interactions of heavy metals with biochar in soil remediation studies

    Science.gov (United States)

    Fristak, Vladimir; Friesl-Hanl, Wolfgang; Wawra, Anna; Soja, Gerhard

    2015-04-01

    study of sorption mechanisms showed differences in the sorption of the targeted heavy metals in relation to the contribution of ion-exchange and precipitation processes. We confirmed the effectivity of physico-chemical artificial aging on sorption capacity of biochar in terms of changes in surface structure. Based on these results, the application potential of biochar as sorption material for stabilizing heavy metals in soils is discussed.

  7. Fluoride ions sorption of the water using natural and modified hematite with aluminium hydroxide

    International Nuclear Information System (INIS)

    Teutli S, E. A.

    2011-01-01

    sorbent, increased when using from 0.02 to 0.14 g of hematite. The results showed that the Elovich model described the process of sorption kinetics, and Langmuir, Freundlich and Langmuir-Freundlich models the sorption isotherm. These results indicated that the mechanism of sorption was the chemisorption. Also, desorption studies were carried out, and it was observed that the fluoride ions can be removed from the modified hematite using NaCl or NaOH solutions, desorption was more efficient using NaOH solution. (Author)

  8. Pyrolysis temperature and steam activation effects on sorption of phosphate on pine sawdust biochars in aqueous solutions

    Directory of Open Access Journals (Sweden)

    Kangyi Lou

    2016-10-01

    Full Text Available Biochar can be used as an adsorbent for phosphate removal in aquatic environments to treat eutrophication problems. Designing biochars that have large phosphate adsorption capacity through altering pyrolysis conditions and applying activation techniques will improve phosphate removal efficiency. In this study, four pine sawdust biochars were produced at 300 and 550 °C with and without steam activation. Batch sorption experiments including isotherm and kinetic studies were conducted to understand how phosphate removal capabilities and adsorption mechanisms of biochars were affected by pyrolysis temperature and steam activation. Our results showed that the steam activation and pyrolysis temperature did not affect phosphate adsorption by the biochars. The four biochars removed <4% of phosphate from the aqueous solution, which were not affected by the pH of the solution and biochar application rate. The repulsion forces between biochar surfaces and phosphate ions were likely the cause of the low adsorption.

  9. Kinetic, equilibrium and thermodynamic studies on sorption of uranium and thorium from aqueous solutions by a selective impregnated resin containing carminic acid

    Energy Technology Data Exchange (ETDEWEB)

    Rahmani-Sani, Abolfazl [Wastewater Division, Faculty of Health, Sabzevar University of Medical Sciences, PO Box 319, Sabzevar (Iran, Islamic Republic of); Hosseini-Bandegharaei, Ahmad, E-mail: ahoseinib@yahoo.com [Wastewater Division, Faculty of Health, Sabzevar University of Medical Sciences, PO Box 319, Sabzevar (Iran, Islamic Republic of); Department of Engineering, Kashmar Branch, Islamic Azad University, PO Box 161, Kashmar (Iran, Islamic Republic of); Hosseini, Seyyed-Hossein [Department of Engineering, Kashmar Branch, Islamic Azad University, PO Box 161, Kashmar (Iran, Islamic Republic of); Kharghani, Keivan [Water Division, Department of Engineering, Torbat-e-Hydarieh Branch, Islamic Azad University, PO Box 121, Torbat-e-Hydarieh (Iran, Islamic Republic of); Zarei, Hossein [Department of Engineering, Kashmar Branch, Islamic Azad University, PO Box 161, Kashmar (Iran, Islamic Republic of); Rastegar, Ayoob [Wastewater Division, Faculty of Health, Sabzevar University of Medical Sciences, PO Box 319, Sabzevar (Iran, Islamic Republic of); Department of Engineering, Kashmar Branch, Islamic Azad University, PO Box 161, Kashmar (Iran, Islamic Republic of)

    2015-04-09

    Highlights: • The objective of the study is to investigate the potential application of a selective EIR for sorption of U(VI) and Th(IV) ions. • The effects of several physiochemical parameters were investigated. • The sorption kinetics and sorption isotherms were used to explain the sorption mechanism. • The thermodynamic studies showed the feasibility of sorption process. • The EIR beads showed a great potential for effective removal of U(VI) and Th(IV) ions. - Abstract: In this work, the removal of uranium and thorium ions from aqueous solutions was studied by solid–liquid extraction using an advantageous extractant-impregnated resin (EIR) prepared by loading carminic acid (CA) onto Amberlite XAD-16 resin beads. Batch sorption experiments using CA/XAD-16 beads for the removal of U(VI) and Th(IV) ions were carried out as a function of several parameters, like equilibration time, metal ion concentration, etc. The equilibrium data obtained from the sorption experiments were adjusted to the Langmuir isotherm model and the calculated maximum sorption capacities in terms of monolayer sorption were in agreement with those obtained from the experiments. The experimental data on the sorption behavior of both metal ions onto the EIR beads fitted well in both Bangham and intra-particle diffusion kinetic models, indicating that the intra-particle diffusion is the rate-controlling step. The thermodynamic studies at different temperatures revealed the feasibility and the spontaneous nature of the sorption process for both uranium and thorium ions.

  10. Kinetic, equilibrium and thermodynamic studies on sorption of uranium and thorium from aqueous solutions by a selective impregnated resin containing carminic acid

    International Nuclear Information System (INIS)

    Rahmani-Sani, Abolfazl; Hosseini-Bandegharaei, Ahmad; Hosseini, Seyyed-Hossein; Kharghani, Keivan; Zarei, Hossein; Rastegar, Ayoob

    2015-01-01

    Highlights: • The objective of the study is to investigate the potential application of a selective EIR for sorption of U(VI) and Th(IV) ions. • The effects of several physiochemical parameters were investigated. • The sorption kinetics and sorption isotherms were used to explain the sorption mechanism. • The thermodynamic studies showed the feasibility of sorption process. • The EIR beads showed a great potential for effective removal of U(VI) and Th(IV) ions. - Abstract: In this work, the removal of uranium and thorium ions from aqueous solutions was studied by solid–liquid extraction using an advantageous extractant-impregnated resin (EIR) prepared by loading carminic acid (CA) onto Amberlite XAD-16 resin beads. Batch sorption experiments using CA/XAD-16 beads for the removal of U(VI) and Th(IV) ions were carried out as a function of several parameters, like equilibration time, metal ion concentration, etc. The equilibrium data obtained from the sorption experiments were adjusted to the Langmuir isotherm model and the calculated maximum sorption capacities in terms of monolayer sorption were in agreement with those obtained from the experiments. The experimental data on the sorption behavior of both metal ions onto the EIR beads fitted well in both Bangham and intra-particle diffusion kinetic models, indicating that the intra-particle diffusion is the rate-controlling step. The thermodynamic studies at different temperatures revealed the feasibility and the spontaneous nature of the sorption process for both uranium and thorium ions

  11. Development of a Composite Non-Electrostatic Surface Complexation Model Describing Plutonium Sorption to Aluminosilicates

    Energy Technology Data Exchange (ETDEWEB)

    Powell, B A; Kersting, A; Zavarin, M; Zhao, P

    2008-10-28

    Due to their ubiquity in nature and chemical reactivity, aluminosilicate minerals play an important role in retarding actinide subsurface migration. However, very few studies have examined Pu interaction with clay minerals in sufficient detail to produce a credible mechanistic model of its behavior. In this work, Pu(IV) and Pu(V) interactions with silica, gibbsite (Aloxide), and Na-montmorillonite (smectite clay) were examined as a function of time and pH. Sorption of Pu(IV) and Pu(V) to gibbsite and silica increased with pH (4 to 10). The Pu(V) sorption edge shifted to lower pH values over time and approached that of Pu(IV). This behavior is apparently due to surface mediated reduction of Pu(V) to Pu(IV). Surface complexation constants describing Pu(IV)/Pu(V) sorption to aluminol and silanol groups were developed from the silica and gibbsite sorption experiments and applied to the montmorillonite dataset. The model provided an acceptable fit to the montmorillonite sorption data for Pu(V). In order to accurately predict Pu(IV) sorption to montmorillonite, the model required inclusion of ion exchange. The objective of this work is to measure the sorption of Pu(IV) and Pu(V) to silica, gibbsite, and smectite (montmorillonite). Aluminosilicate minerals are ubiquitous at the Nevada National Security Site and improving our understanding of Pu sorption to aluminosilicates (smectite clays in particular) is essential to the accurate prediction of Pu transport rates. These data will improve the mechanistic approach for modeling the hydrologic source term (HST) and provide sorption Kd parameters for use in CAU models. In both alluvium and tuff, aluminosilicates have been found to play a dominant role in the radionuclide retardation because their abundance is typically more than an order of magnitude greater than other potential sorbing minerals such as iron and manganese oxides (e.g. Vaniman et al., 1996). The sorption database used in recent HST models (Carle et al., 2006

  12. Hydration and sorption characteristics of a polyfunctional weak-base anion exchanger after the sorption of vanillin and ethylvanillin

    Science.gov (United States)

    Rodionova, D. O.; Voronyuk, I. V.; Eliseeva, T. V.

    2016-07-01

    Features of the sorption of substituted aromatic aldehydes by a weak-base anion exchanger under equilibrium conditions are investigated using vanillin and ethylvanillin as examples. Analysis of the sorption isotherms of carbonyl compounds at different temperatures allows us to calculate the equilibrium characteristics of their sorption and assess the entropy and enthalpy contributions to the energy of the process. Hydration characteristics of the macroporous weak-base anion exchanger before and after the sorption of aromatic aldehydes are compared.

  13. Radionuclide sorption and migration studies of getters for backfill barriers

    International Nuclear Information System (INIS)

    Nowak, E.J.

    1980-07-01

    Bentonite and hectorite clay minerals were chosen for study and development as potential backfill materials for testing in the proposed Waste Isolation Pilot Plant (WIPP), a radioactive waste repository and test facility in bedded salt. This choice of materials was based on initial screening results which are presented and on the predicted physical properties of these materials. These properties were verified experimentally in concentrated brines specific to the WIPP site. Distribution coefficients, K/sub d/, were calculated from batch sorption measurements on bentonite and hectorite in the nearly saturated brines A and B. The resulting K/sub d/ values were in the range of (1 to 5) x 10 3 ml/g for europium; (2 to 40) x 10 3 ml/g for plutonium(IV); and (4 to 16) x 10 3 ml/g for americium(III). A silica- and calcite-containing sand mixed with bentonite and hectorite acted as a sorber of americium(III) but was merely an inert diluent for plutonium(IV). Pertechnetate anions (TcO 4 - ) sorbed on activated charcoal with K/sub d/ values in the range of (0.2 to 0.4) x 10 3 ml/g. Pertechnetate, cesium, and strontium ions in brine were not sorbed appreciably by bentonite or hectorite. Although experimental evidence is given for a possible role of solubility in the sorption of europium on getters, other data presented here and evidence from the literature are inconsistent with a simple single reaction sorption mechanism. It is concluded that a backfill containing bentonite on hectorite and activated charcoal is potentially an effective barrier to the migration of Eu(III), Pu(IV), and Am(III) cations and, with further development, to the migration of TcO 4 - anions as well

  14. Influence of Fulvic Acid Coatings on Plutonium Sorption to Goethite Colloids

    Science.gov (United States)

    Tinnacher, R. M.; Begg, J.; Powell, B. A.; Zavarin, M.; Kersting, A. B.

    2011-12-01

    underlying mechanisms of FA effects on Pu sorption behavior. First results for pre-complexed Pu-FA systems show an increase in the Pu fractions sorbed onto goethite in the presence of fulvic acid relative to binary Pu-goethite controls. Furthermore, in ternary systems the rates of overall metal sorption reactions appear to be faster and very similar to those for FA sorption. The latter suggests the potential formation of ternary Pu-FA surface complexes on goethite, either by direct sorption of Pu-FA solution complexes or after the rapid creation of an initial organic matter surface coating. In this presentation, results will be further compared to Pu sorption behavior in systems with initially FA-coated goethite. In addition, we will discuss potential differences in Pu desorption behavior in these three systems. Prepared by LLNL under Contract DE-AC52-07NA27344.

  15. A suggested approach toward measuring sorption and applying sorption data to repository performance assessment

    International Nuclear Information System (INIS)

    Rundberg, R.S.

    1991-01-01

    The sorption of radioisotopes in relation to geologic disposal of radioactive wastes is discussed. Properties of the radioactive materials, rocks, and minerals, and the chemistry involved are described. 51 refs., 12 figs. CBS

  16. Application potential of grapefruit peel as dye sorbent: Kinetics, equilibrium and mechanism of crystal violet adsorption

    International Nuclear Information System (INIS)

    Saeed, Asma; Sharif, Mehwish; Iqbal, Muhammad

    2010-01-01

    This study reports the sorption of crystal violet (CV) dye by grapefruit peel (GFP), which has application potential in the remediation of dye-contaminated wastewaters using a solid waste generated by the citrus fruit juice industry. Batch adsorption of CV was conducted to evaluate the effect of initial pH, contact time, temperature, initial dye concentration, GFP adsorbent dose, and removal of the adsorbate CV dye from aqueous solution to understand the mechanism of sorption involved. Sorption equilibrium reached rapidly with 96% CV removal in 60 min. Fit of the sorption experimental data was tested on the pseudo-first and pseudo-second-order kinetics mathematical equations, which was noted to follow the pseudo-second-order kinetics better, with coefficient of correlation ≥0.992. The equilibrium process was well described by the Langmuir isotherm model, with maximum sorption capacity of 254.16 mg g -1 . The GFP was regenerated using 1 M NaOH, with up to 98.25% recovery of CV and could be reused as a dye sorbent in repeated cycles. GFP was also shown to be highly effective in removing CV from aqueous solution in continuous-flow fixed-bed column reactors. The study shows that GFP has the potential of application as an efficient sorbent for the removal of CV from aqueous solutions.

  17. Sorption of fission nuclides on model milk components. II. Sorption of radiostrontium on hydroxyapatite in milk and whey

    International Nuclear Information System (INIS)

    Rosskopfova, O.; Kopunec, R.; Matel, L.; Macasek, F.

    1999-01-01

    In this work the whey was chosen as a model solution of liquid phase for sorption study of strontium on hydroxyapatite. The whey was obtained using two methods - ultracentrifugation and precipitation of casein. The sorption was studied at a different pH and at a different concentration of calcium. The sorption of strontium on hydroxyapatite from milk was studied, too. (authors)

  18. Acquisition of sorption isotherms for modified woods by the use of dynamic vapour sorption instrumentation. Principles and Practice

    DEFF Research Database (Denmark)

    Engelund, Emil Tang; Klamer, Morten; Venås, Thomas Mark

    2010-01-01

    for obtaining sorption isotherms are very time consuming. With new dynamic vapour sorption (DVS) instrumentation, the acquisition of data for constructing sorption isotherms is suddenly dramatically lowered. Where the traditional methods often required months, data can now be obtained in a matter of days...

  19. Influence of mineral characteristics on the retention of low molecular weight organic compounds: a batch sorption-desorption and ATR-FTIR study.

    Science.gov (United States)

    Yeasmin, Sabina; Singh, Balwant; Kookana, Rai S; Farrell, Mark; Sparks, Donald L; Johnston, Cliff T

    2014-10-15

    Batch experiments were conducted to evaluate the sorption-desorption behaviour of (14)C-labelled carboxylic acids (citric and oxalic) and amino acids (glutamic, alanine, phenylalanine and lysine) on pure minerals (kaolinite, illite, montmorillonite, ferrihydrite and goethite). The sorption experiments were complemented by ATR-FTIR spectroscopy to gain possible mechanistic insight into the organic acids-mineral interactions. In terms of charge, the organic solutes ranged from strongly negative (i.e., citric) to positively charged solutes (i.e., lysine); similarly the mineral phases also ranged from positively to negatively charged surfaces. In general, sorption of anionic carboxylic and glutamic acids was higher compared to the other compounds (except lysine). Cationic lysine showed a stronger affinity to permanently charged phyllosilicates than Fe oxides. The sorption of alanine and phenylalanine was consistently low for all minerals, with relatively higher sorption and lower desorption of phenylalanine than alanine. Overall, the role of carboxylic functional groups for the sorption and retention of these carboxylic and amino acids on Fe oxides (and kaolinite) and of amino group on 2:1 phyllosilicates was noticeable. Mineral properties (surface chemistry, specific surface area), chemistry of the organic compounds (pKa value, functional groups) and the equilibrium pH of the system together controlled the differences in sorption-desorption patterns. The results of this study aid to understand the effects of mineralogical and chemical factors that affect naturally occurring low molecular weight organic compounds sorption under field conditions. Copyright © 2014 Elsevier Inc. All rights reserved.

  20. Understanding the Mechanism of the Hydrogen Abstraction from Arachidonic Acid Catalyzed by the Human Enzyme 15-Lipoxygenase-2. A Quantum Mechanics/Molecular Mechanics Free Energy Simulation.

    Science.gov (United States)

    Suardíaz, Reynier; Jambrina, Pablo G; Masgrau, Laura; González-Lafont, Àngels; Rosta, Edina; Lluch, José M

    2016-04-12

    . Overall, a different binding mode from the one accepted for 15-LOX-1 is proposed, which provides a molecular basis for 15-LOX-2 exclusive 15-HPETE production in front of the double (although highly 15-) 12/15 regiospecificity of 15-LOX-1. Understanding how these different isoenzymes achieve their regiospecificity is expected to help in specific inhibitor design.

  1. From observation to understanding: Approach to analysis of wear mechanisms, Case of RCCAs and CRDM latch arms

    International Nuclear Information System (INIS)

    Hertz, D.

    2004-01-01

    Component wear can affect the ability of a component to fulfill its required function. For a designer or user, it is reasonable to expect possible wear occurrence as soon as parts are in relative motion. It