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Sample records for modified aqueous buffer

  1. Direct extraction of genomic DNA from maize with aqueous ionic liquid buffer systems for applications in genetically modified organisms analysis.

    Science.gov (United States)

    Gonzalez García, Eric; Ressmann, Anna K; Gaertner, Peter; Zirbs, Ronald; Mach, Robert L; Krska, Rudolf; Bica, Katharina; Brunner, Kurt

    2014-12-01

    To date, the extraction of genomic DNA is considered a bottleneck in the process of genetically modified organisms (GMOs) detection. Conventional DNA isolation methods are associated with long extraction times and multiple pipetting and centrifugation steps, which makes the entire procedure not only tedious and complicated but also prone to sample cross-contamination. In recent times, ionic liquids have emerged as innovative solvents for biomass processing, due to their outstanding properties for dissolution of biomass and biopolymers. In this study, a novel, easily applicable, and time-efficient method for the direct extraction of genomic DNA from biomass based on aqueous-ionic liquid solutions was developed. The straightforward protocol relies on extraction of maize in a 10 % solution of ionic liquids in aqueous phosphate buffer for 5 min at room temperature, followed by a denaturation step at 95 °C for 10 min and a simple filtration to remove residual biopolymers. A set of 22 ionic liquids was tested in a buffer system and 1-ethyl-3-methylimidazolium dimethylphosphate, as well as the environmentally benign choline formate, were identified as ideal candidates. With this strategy, the quality of the genomic DNA extracted was significantly improved and the extraction protocol was notably simplified compared with a well-established method.

  2. 21 CFR 520.1696a - Buffered penicillin powder, penicillin powder with buffered aqueous diluent.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Buffered penicillin powder, penicillin powder with... FORM NEW ANIMAL DRUGS § 520.1696a Buffered penicillin powder, penicillin powder with buffered aqueous diluent. (a) Specifications. When reconstituted, each milliliter contains penicillin G procaine equivalent...

  3. Solvation consequences of polymer PVP with biological buffers MES, MOPS, and MOPSO in aqueous solutions

    International Nuclear Information System (INIS)

    Gupta, Bhupender S.; Chen, Bo-Ren; Lee, Ming-Jer

    2015-01-01

    Highlights: • Densities and viscosities data for aqueous solutions with PVP and/or buffer. • The studied buffers include MES, MOPS, and MOPSO. • DFT was used to estimate the binding energies of the (PVP + buffer) complexes. • The viscosity data were correlated with the Jones–Dole equation. • The investigated buffers behave as Kosmotropies. - Abstract: Densities and viscosities were measured for the aqueous buffer (MES, MOPS, or MOPSO) solutions containing different concentrations of polyvinylpyrrolidone (PVP) (5, 10, 15, 20 and 30) mass% at temperatures from (298.15 to 318.15) K under atmospheric pressure. The DFT calculations were also performed and the binding energies of the possible (PVP + buffer) complexes were obtained. The experimental and computational results reveal the interactions of the PVP with the constituent compounds in the aqueous buffer solutions. Additionally we have explored the solvation behavior of the buffers by measuring the densities and the viscosities data of the aqueous buffer solutions from (0.0 to 1.0) mol · kg"−"1 at temperatures from (298.15 to 318.15) K. The viscosity results were correlated with the Jones–Dole equation. The correlated results confirmed that all the investigated buffers behave as Kosmotropes (structure makers).

  4. Retention of ionisable compounds on high-performance liquid chromatography XVII. Estimation of the pH variation of aqueous buffers with the change of the methanol fraction of the mobile phase.

    Science.gov (United States)

    Subirats, Xavier; Bosch, Elisabeth; Rosés, Martí

    2007-01-05

    The use of methanol-aqueous buffer mobile phases in HPLC is a common election when performing chromatographic separations of ionisable analytes. The addition of methanol to the aqueous buffer to prepare such a mobile phase changes the buffer capacity and the pH of the solution. In the present work, the variation of these buffer properties is studied for acetic acid-acetate, phosphoric acid-dihydrogenphosphate-hydrogenphosphate, citric acid-dihydrogencitrate-hydrogencitrate-citrate, and ammonium-ammonia buffers. It is well established that the pH change of the buffers depends on the initial concentration and aqueous pH of the buffer, on the percentage of methanol added, and on the particular buffer used. The proposed equations allow the pH estimation of methanol-water buffered mobile phases up to 80% in volume of organic modifier from initial aqueous buffer pH and buffer concentration (before adding methanol) between 0.001 and 0.01 mol L(-1). From both the estimated pH values of the mobile phase and the estimated pKa of the ionisable analytes, it is possible to predict the degree of ionisation of the analytes and therefore, the interpretation of acid-base analytes behaviour in a particular methanol-water buffered mobile phase.

  5. Calculation of the equilibrium pH in a multiple-buffered aqueous solution based on partitioning of proton buffering: a new predictive formula.

    Science.gov (United States)

    Nguyen, Minhtri K; Kao, Liyo; Kurtz, Ira

    2009-06-01

    Upon the addition of protons to an aqueous solution containing multiple buffers, the final H+ concentration ([H+]) at equilibrium is determined by the partitioning of added H+ among the various buffer components. In the analysis of acid-base chemistry, the Henderson-Hasselbalch equation and the Stewart strong ion formulation can only describe (rather than predict) the equilibrium pH following a proton load since these formulas calculate the equilibrium pH only when the reactant concentrations at equilibrium(1) 1The term "equilibrium" refers to the steady state proton and reactant concentrations when the buffering of excess protons by the various buffers is complete. are already known. In this regard, it is simpler to directly measure the equilibrium pH rather than measure the equilibrium reactant concentrations to calculate the equilibrium pH. As these formulas cannot predict the final equilibrium [H+] following a proton load to a multiple-buffered aqueous solution, we developed a new quantitative approach for predicting the equilibrium [H+] that is based on the preequilibrium(2)2 The term "preequilibrium" refers to the initial proton and reactant concentrations immediately upon addition of protons and before the buffering of excess protons by the various buffers. concentrations of all buffers in an aqueous solution. The mathematical model used to derive our equation is based on proton transfer buffer equilibria without requiring the incorporation of electroneutrality considerations. The model consists of a quartic polynomial equation that is derived based solely on the partitioning of H+ among the various buffer components. We tested the accuracy of the model using aqueous solutions with various buffers and measured the equilibrium pH values following the addition of HCl. Our results confirmed the accuracy of our new equation (r2 = 1; measured pH vs. predicted pH), indicating that it quantitatively accounts for the underlying acid-base phenomenology.

  6. Calculation of the equilibrium pH in a multiple-buffered aqueous solution based on partitioning of proton buffering: a new predictive formula

    Science.gov (United States)

    Nguyen, Minhtri K.; Kao, Liyo; Kurtz, Ira

    2009-01-01

    Upon the addition of protons to an aqueous solution containing multiple buffers, the final H+ concentration ([H+]) at equilibrium is determined by the partitioning of added H+ among the various buffer components. In the analysis of acid-base chemistry, the Henderson-Hasselbalch equation and the Stewart strong ion formulation can only describe (rather than predict) the equilibrium pH following a proton load since these formulas calculate the equilibrium pH only when the reactant concentrations at equilibrium1 1The term “equilibrium” refers to the steady state proton and reactant concentrations when the buffering of excess protons by the various buffers is complete. are already known. In this regard, it is simpler to directly measure the equilibrium pH rather than measure the equilibrium reactant concentrations to calculate the equilibrium pH. As these formulas cannot predict the final equilibrium [H+] following a proton load to a multiple-buffered aqueous solution, we developed a new quantitative approach for predicting the equilibrium [H+] that is based on the preequilibrium22The term “preequilibrium” refers to the initial proton and reactant concentrations immediately upon addition of protons and before the buffering of excess protons by the various buffers. concentrations of all buffers in an aqueous solution. The mathematical model used to derive our equation is based on proton transfer buffer equilibria without requiring the incorporation of electroneutrality considerations. The model consists of a quartic polynomial equation that is derived based solely on the partitioning of H+ among the various buffer components. We tested the accuracy of the model using aqueous solutions with various buffers and measured the equilibrium pH values following the addition of HCl. Our results confirmed the accuracy of our new equation (r2 = 1; measured pH vs. predicted pH), indicating that it quantitatively accounts for the underlying acid-base phenomenology. PMID

  7. Retention of ionisable compounds on high-performance liquid chromatography. XV. Estimation of the pH variation of aqueous buffers with the change of the acetonitrile fraction of the mobile phase.

    Science.gov (United States)

    Subirats, Xavier; Bosch, Elisabeth; Rosés, Martí

    2004-12-03

    The most commonly used mobile phases in reversed-phase high-performance liquid chromatography (RP-HPLC) are hydro-organic mixtures of an aqueous buffer and an organic modifier. The addition of this organic solvent to buffered aqueous solutions involves a variation of the buffer properties (pH and buffer capacity). In this paper, the pH variation is studied for acetic acid-acetate, phosphoric acid-dihydrogenphosphate-hydrogenphosphate, citric acid-dihydrogencitrate-citrate, and ammonium-ammonia buffers. The proposed equations allow pH estimation of acetonitrile-water buffered mobile phases up to 60% (v/v) of organic modifier and initial aqueous buffer concentrations between 0.001 and 0.1 mol L(-1), from the initial aqueous pH. The estimated pH variation of the mobile phase and the pKa variation of the analytes allow us to predict the degree of ionisation of the analytes and from this and analyte hydrophobicities, to interpret the relative retention and separation of analyte mixtures.

  8. Effect of Buffers on Aqueous Solute-Exclusion Zones around Ion-Exchange Resins

    Science.gov (United States)

    Zheng, Jian-ming; Wexler, Adam

    2009-01-01

    Interaction between charged surfaces in aqueous solution is a fundamental feature of colloid science. Theoretically, surface potential falls to half its value at a distance equal to a Debye length, which is typically on the order of tens to hundreds of nanometers. This potential prevents colloids from aggregating. On the other hand, long-range surface effects have been frequently reported. Here we report additional long-range effects. We find that charged latex particles in buffer solutions are uniformly excluded from several-hundred-micron-thick shells surrounding ion-exchange beads. Exclusion is observed whether the beads are charged similarly or oppositely to the particles. Hence, electrostatic interactions between bead and microsphere do not cause particle exclusion. Rather, exclusion may be the consequence of water molecules re-orienting to produce a more ordered structure, which then excludes the particles. PMID:19185312

  9. Simultaneous determination of phenylethanoid glycosides and aglycones by capillary zone electrophoresis with running buffer modifier.

    Science.gov (United States)

    Dong, Shuqing; Gao, Ruibin; Yang, Yan; Guo, Mei; Ni, Jingman; Zhao, Liang

    2014-03-15

    Although the separation efficiency of capillary electrophoresis (CE) is much higher than that of other chromatographic methods, it is sometimes difficult to adequately separate the complex ingredients in biological samples. This article describes how one effective and simple way to develop the separation efficiency in CE is to add some modifiers to the running buffer. The suitable running buffer modifier β-cyclodextrin (β-CD) was explored to fast and completely separate four phenylethanoid glycosides and aglycones (homovanillyl alcohol, hydroxytyrosol, 3,4-dimethoxycinnamic acid, and caffeic acid) in Lamiophlomis rotata (Lr) and Cistanche by capillary zone electrophoresis with ultraviolet (UV) detection. It was found that when β-CD was used as running buffer modifier, a baseline separation of the four analytes could be accomplished in less than 20 min and the detection limits were as low as 10(-3) mg L(-1). Other factors affecting the CE separation, such as working potential, pH value and ionic strength of running buffer, separation voltage, and sample injection time, were investigated extensively. Under the optimal conditions, a successful practical application on the determination of Lr and Cistanche samples confirmed the validity and practicability of this method. Copyright © 2014 Elsevier Inc. All rights reserved.

  10. Simultaneous determination of flavonoids in chrysanthemum by capillary zone electrophoresis with running buffer modifiers.

    Science.gov (United States)

    Zhang, Shan; Dong, Shuqing; Chi, Langzhu; He, Pingang; Wang, Qingjiang; Fang, Yuzhi

    2008-08-15

    Despite the separation efficiency of capillary electrophoresis (CE) is much higher than other chromatographic methods, it is sometimes difficult to perfectly separate the complex ingredients in biological samples. One possible and simple way to develop the separation effect in CE is to add some modifiers in the running buffer. In this paper, the suitable running buffer modifiers were explored to simultaneously separate and detect six typical flavonoids (apigenin, luteolin, kaempferol, quercetin, (+)-catechin and (-)-epicatechin) which are the main active ingredients in chrysanthemum by capillary zone electrophoresis with amperometric detection (CZE-AD). It was found that when beta-cyclodextrin (beta-CD) and the mixture of methanol and ethanol were used as running buffer modifiers, a baseline separation of the six analytes could be accomplished in less than 20 min and the detection limits were as low as 10(-7) or 10(-8)gm l(-1). Other factors affecting the CZE separation, such as working potential, pH value and ionic strength of running buffer, separation voltage and sample injection time were extensively investigated. Under the optimum conditions, a successful practical application on the determination of chrysanthemum samples confirmed the validity and practicability of this method.

  11. Retention of ionisable compounds on high-performance liquid chromatography XVI. Estimation of retention with acetonitrile/water mobile phases from aqueous buffer pH and analyte pKa.

    Science.gov (United States)

    Subirats, Xavier; Bosch, Elisabeth; Rosés, Martí

    2006-07-21

    In agreement with our previous studies and those of other authors, it is shown that much better fits of retention time as a function of pH are obtained for acid-base analytes when pH is measured in the mobile phase, than when pH is measured in the aqueous buffer when buffers of different nature are used. However, in some instances it may be more practical to measure the pH in the aqueous buffer before addition of the organic modifier. Thus, an open methodology is presented that allows prediction of chromatographic retention of acid-base analytes from the pH measured in the aqueous buffer. The model presented estimates the pH of the buffer and the pKa of the analyte in a particular acetonitrile/water mobile phase from the pH and pKa values in water. The retention of the analyte can be easily estimated, at a buffer pH close to the solute pKa, from these values and from the retentions of the pure acidic and basic forms of the analyte. Since in many instances, the analyte pKa values in water are not known, the methodology has been also tested by using Internet software, at reach of many chemists, which calculates analyte pKa values from chemical structure. The approach is successfully tested for some pharmaceutical drugs.

  12. Stable Inverted Low-Bandgap Polymer Solar Cells with Aqueous Solution Processed Low-Temperature ZnO Buffer Layers

    Directory of Open Access Journals (Sweden)

    Chunfu Zhang

    2016-01-01

    Full Text Available Efficient inverted low-bandgap polymer solar cells with an aqueous solution processed low-temperature ZnO buffer layer have been investigated. The low-bandgap material PTB-7 is employed so that more solar light can be efficiently harvested, and the aqueous solution processed ZnO electron transport buffer layer is prepared at 150°C so that it can be compatible with the roll-to-roll process. Power conversion efficiency (PCE of the inverted device reaches 7.12%, which is near the control conventional device. More importantly, the inverted device shows a better stability, keeping more than 90% of its original PCE after being stored for 625 hours, while PCE of the conventional device is only 75% of what it was. In addition, it is found that the ZnO thin film annealed in N2 can obviously increase PCE of the inverted device further to 7.26%.

  13. Thermoacoustic model of a modified free piston Stirling engine with a thermal buffer tube

    International Nuclear Information System (INIS)

    Yang, Qin; Luo, Ercang; Dai, Wei; Yu, Guoyao

    2012-01-01

    This article presents a modified free-piston Stirling heat engine configuration in which a thermal buffer tube is added to sandwich between the hot and cold heat exchangers. Such a modified configuration may lead to an easier fabrication and lighter weight of a free piston. To analyze the thermodynamic performance of the modified free piston Stirling heat engine, thermoacoustic theory is used. In the thermoacoustic modelling, the regenerator, the free piston, and the thermal buffer tube are given at first. Then, based on linear thermoacoustic network theory, the thermal and thermodynamic networks are presented to characterize acoustic pressure and volume flow rate distributions at different interfaces, and the global performance such as the power output, the heat input and the thermal efficiency. A free piston Stirling heat engine with several hundreds of watts mechanical power output is selected as an example. The typical operating and structure parameters are as follows: frequency around 50 Hz, mean pressure around 3.0 MPa, and a diameter of free piston around 50 mm. From the analysis, it was found that the modified free-piston Stirling heat engine has almost the same thermodynamic performance as the original design, which indicates that the modified configuration is worthy to develop in future because of its mechanical simplicity and reliability.

  14. Removing Phosphorus from Aqueous Solutions Using Lanthanum Modified Pine Needles.

    Directory of Open Access Journals (Sweden)

    Xianze Wang

    Full Text Available The renewable pine needles was used as an adsorbent to remove phosphorus from aqueous solutions. Using batch experiments, pine needles pretreated with alkali-isopropanol (AI failed to effectively remove phosphorus, while pine needles modified with lanthanum hydroxide (LH showed relatively high removal efficiency. LH pine needles were effective at a wide pH ranges, with the highest removal efficiency reaching approximately 85% at a pH of 3. The removal efficiency was kept above 65% using 10 mg/L phosphorus solutions at desired pH values. There was no apparent significant competitive behavior between co-existing anions of sulfate, nitrate, and chloride (SO4(2-, NO3(- and Cl(-; however, CO3(2- exhibited increased interfering behavior as concentrations increased. An intraparticle diffusion model showed that the adsorption process occurred in three phases, suggesting that a boundary layer adsorption phenomena slightly affected the adsorption process, and that intraparticle diffusion was dominant. The adsorption process was thermodynamically unfavorable and non-spontaneous; temperature increases improved phosphorus removal. Total organic carbon (TOC assays indicated that chemical modification reduced the release of soluble organic compounds from 135.6 mg/L to 7.76 mg/L. This new information about adsorption performances provides valuable information, and can inform future technological applications designed to remove phosphorus from aqueous solutions.

  15. Adsorption of polynuclear aromatic hydrocarbons from aqueous solution: Agrowaste-modified kaolinite vs surfactant modified bentonite

    Directory of Open Access Journals (Sweden)

    E. I. Unuabonah

    2017-01-01

    Full Text Available The adsorption efficiency of a new hybrid clay adsorbent for polynuclear aromatic hydrocarbons (PAHs is compared with known modified clay adsorbents. The new hybrid clay adsorbent (HYCA showed far higher adsorption capacities for the adsorption of various PAH molecules compared with sodium dodecyl sulfate modified and humic acid modified Bentonite clay adsorbents. With the new hybrid clay adsorbent (HYCA, the adsorption of some of the larger PAH molecules was complete in the first 1 h as compared with ≈ 62% and ≈ 76% observed for both humic acid modified and sodium dodecyl sulfate modified Bentonite clay adsorbents respectively. In 24 h adsorption of the PAHs was complete for all adsorbents with HYCA adsorbent showing better efficiency in the removal of the PAH molecules from aqueous solutions. No significant change was observed with increase in time up to 48 h. The adsorption was observed to be more spontaneous with HYCA adsorbent than with either modified Bentonite adsorbents. The enthalpy of adsorption did not follow any specific order and were not consistent for all PAH molecules considered.

  16. Critical micelle concentration of surfactants in aqueous buffered and unbuffered systems

    International Nuclear Information System (INIS)

    Fuguet, Elisabet; Rafols, Clara; Roses, Marti; Bosch, Elisabeth

    2005-01-01

    Critical micelle concentration (CMC) of sodium dodecyl sulphate (SDS), lithium perfluorooctanesulfonate (LPFOS), hexadecyltrimethylammonium bromide (HTAB), tetradecyltrimethylammonium bromide (TTAB), and sodium cholate (SC), surfactants commonly used as pseudostationary phases in micellar electrokinetic chromatography (MEKC), have been determined by means of three different methods: MEKC, spectrophotometry, and conductometry. Determinations have been performed in water, and also in different concentrations of phosphate buffer at pH 7.0. CMC values ranging from 8.08 (water) to 1.99 (50 mM phosphate buffer) mM for SDS, from 7.16 (water) to 2,81 (30 mM phosphate buffer) mM for LPFOS, from 3.77 (water) to 1.93 (20 mM phosphate buffer) mM for TTAB, from 0.91 (water) to ∼0.34 (20 mM phosphate buffer) for HTAB, and around 13 mM (20 mM phosphate buffer) for SC, are obtained. The effect of the electrolyte concentration on the CMC, as well as the linear relationship between the electrolyte counter-ion concentration and the CMC are discussed. This linear relationship provides an easy way for users to estimate the CMC of a MEKC system, at a given electrolyte concentration. A comparison between experimental methods, as well as a discussion about the suitability of a given method for the determination of the CMC for a given surfactant system is also provided

  17. Comparing the acidities of aqueous, frozen, and freeze-dried phosphate buffers: Is there a "pH memory" effect?

    Science.gov (United States)

    Vetráková, Ľubica; Vykoukal, Vít; Heger, Dominik

    2017-09-15

    The concept of "pH memory" has been established in the literature for the correlation between the pH of a pre-lyophilization solution and the ionization state of freeze-dried powder (lyophile). In this paper, the concept of "pH memory" is explored for the system of an aqueous solution, a frozen solution, and a lyophile. Sodium and potassium phosphate buffers in the pH range of 5-9 were frozen and lyophilized with sulfonephthalein indicators as acidity probes, and their Hammett acidity functions were compared to the initial pH of the aqueous solution. The results show that the acidities of the lyophiles are somewhat changed compared to the initial pHs, but the acidities in the frozen state differ more substantially. The Hammett acidity functions of the frozen buffers were found to be markedly dissimilar from the initial pH, especially in the sodium phosphate frozen at 233K, where an increase in the initial pH led to a decrease in the Hammett acidity function of the frozen state at a certain pH range. The large acidification observed after freezing the sodium phosphate buffer was not detected in the lyophiles after the sample had been dried; the phenomenon is explained considering the formed crystals analyzed by X-ray powder diffraction. The results suggest that monitoring the final acidity of a lyophile is not sufficient to predict all the acidity changes throughout the whole lyophilization process. The importance of well-controlled freezing and lyophilization conditions follows from the results of the research. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Aspartate buffer and divalent metal ions affect oxytocin in aqueous solution and protect it from degradation

    DEFF Research Database (Denmark)

    Avanti, Christina; Oktaviani, Nur Alia; Hinrichs, Wouther L.J.

    2013-01-01

    Oxytocin is a peptide drug used to induce labor and prevent bleeding after childbirth. Due to its instability, transport and storage of oxytocin formulations under tropical conditions is problematic. In a previous study, we have found that the stability of oxytocin in aspartate buffered formulati...

  19. Aspartate buffer and divalent metal ions affect oxytocin in aqueous solution and protect it from degradation

    NARCIS (Netherlands)

    Avanti, Christina; Oktaviani, Nur Alia; Hinrichs, Wouter L J; Frijlink, Henderik W; Mulder, Frans A A

    2013-01-01

    Oxytocin is a peptide drug used to induce labor and prevent bleeding after childbirth. Due to its instability, transport and storage of oxytocin formulations under tropical conditions is problematic. In a previous study, we have found that the stability of oxytocin in aspartate buffered formulation

  20. Salicylimine-Based Colorimetric and Fluorescent Chemosensor for Selective Detection of Cyanide in Aqueous Buffer

    Energy Technology Data Exchange (ETDEWEB)

    Noh, Jin Young; Hwang, In Hong; Kim, Hyun; Song, Eun Joo; Kim, Kyung Beom; Kim, Cheal [Seoul National Univ., Seoul (Korea, Republic of)

    2013-07-15

    A simple colorimetric and fluorescent anion sensor 1 based on salicylimine showed a high selectivity and sensitivity for detection of cyanide in aqueous solution. The receptor 1 showed high selectivity toward CN{sup -} ions in a 1:1 stoichiometric manner, which induces a fast color change from colorless to orange and a dramatic enhancement in fluorescence intensity selectively for cyanide anions over other anions. Such selectivity resulted from the nucleophilic addition of CN{sup -} to the carbon atom of an electron-deficient imine group. The sensitivity of the fluorescence-based assay (0.06 μM) is below the 1.9 μM suggested by the World Health Organization (WHO) as the maximum allowable cyanide concentration in drinking water, capable of being a practical system for the monitoring of CN. concentrations in aqueous samples.

  1. Tandem organic light-emitting diodes with buffer-modified C60/pentacene as charge generation layer

    Science.gov (United States)

    Wang, Zhen; Zheng, Xin; Liu, Fei; Wang, Pei; Gan, Lin; Wang, Jing-jing

    2017-09-01

    Buffer-modified C60/pentacene as charge generation layer (CGL) is investigated to achieve effective performance of charge generation. Undoped green electroluminescent tandem organic light-emitting diodes (OLEDs) with multiple identical emissive units and using buffer-modified C60/pentacene organic semiconductor heterojunction (OHJ) as CGL are demonstrated to exhibit better current density and brightness, compared with conventional single-unit devices. The current density and brightness both can be significantly improved with increasing the thickness of Al. However, excessive thickness of Al seriously decreases the transmittance of films and damages the interface. As a result, the maximum current efficiency of 1.43 cd·A-1 at 30 mA·cm-2 can be achieved for tandem OLEDs with optimal thickness of Al. These results clearly demonstrate that Cs2CO3/Al is an effective buffer for C60/pentacene-based tandem OLEDs.

  2. modified bentonite clay for the removal of fluoride from aqueous ...

    African Journals Online (AJOL)

    NICOLAAS

    reagents and Total Ionic Solution Buffer (TISAB-III) were .... Equation 3 and it is used to describe liquid–solid phase adsorp- .... 0 and 1 indicating adsorption process was favourable at room temperature for all the adsorbate concentrations tested. 3.2.3. .... Marathe, Arsenic and fluoride contaminated groundwaters: a review.

  3. Modified band alignment effect in ZnO/Cu2O heterojunction solar cells via Cs2O buffer insertion

    Science.gov (United States)

    Eom, Kiryung; Lee, Dongyoon; Kim, Seunghwan; Seo, Hyungtak

    2018-02-01

    The effects of a complex buffer layer of cesium oxide (Cs2O) on the photocurrent response in oxide heterojunction solar cells (HSCs) were investigated. A p-n junction oxide HSC was fabricated using p-type copper (I) oxide (Cu2O) and n-type zinc oxide (ZnO); the buffer layer was inserted between the Cu2O and fluorine-doped tin oxide (FTO). Ultraviolet-visible (UV-vis) and x-ray and ultraviolet photoelectron spectroscopy analyses were performed to characterize the electronic band structures of cells, both with and without this buffer layer. In conjunction with the measured band electronic structures, the significantly improved visible-range photocurrent spectra of the buffer-inserted HSC were analyzed in-depth. As a result, the 1 sun power conversion efficiency was increased by about three times by the insertion of buffer layer. The physicochemical origin of the photocurrent enhancement was mainly ascribed to the increased photocarrier density in the buffer layer and modified valence band offset to promote the effective hole transfer at the interface to FTO on the band-alignment model.

  4. Electrical double layer modulation of hybrid room temperature ionic liquid/aqueous buffer interface for enhanced sweat based biosensing.

    Science.gov (United States)

    Jagannath, Badrinath; Muthukumar, Sriram; Prasad, Shalini

    2018-08-03

    We have investigated the role of kosmotropic anionic moieties and chaotropic cationic moieties of room temperature hydrophilic ionic liquids in enhancing the biosensing performance of affinity based immunochemical biosensors in human sweat. Two ionic liquids, 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM[BF 4 ]) and choline dihydrogen phosphate (Choline[DHP]) were investigated in this study with Choline[DHP] being more kosmotropic in nature having a more protein stabilizing effect based on the hofmeister series. Non-faradaic interfacial charge transfer has been employed as the mechanism for evaluating the formation and the biosensing of capture probe antibodies in room temperature ionic liquids (RTILs)/aqueous human sweat interface. The charge of the ionic moieties were utilized to form compact electrical double layers around the antibodies for enhancing the stability of the antibody capture probes, which was evaluated through zeta potential measurements. The zeta potential measurements indicated stability of antibodies due to electrostatic repulsion of the RTIL charged moieties encompassing the antibodies, thus preventing any aggregation. Here, we report for the first time of non-faradaic electrochemical impedance spectroscopy equivalent circuit model analysis for analyzing and interpreting affinity based biosensing at hybrid electrode/ionic liquid-aqueous sweat buffer interface guided by the choice of the ionic liquid. Interleukin-6 (IL-6) and cortisol two commonly occurring biomarkers in human sweat were evaluated using this method. The limit of detection (LOD) obtained using both ionic liquids for IL-6 was 0.2 pg mL -1 with cross-reactivity studies indicating better performance of IL-6 detection using Choline[DHP] and no response to cross-reactive molecule. The LOD of 0.1 ng/mL was achieved for cortisol and the cross-reactivity studies indicated that cortisol antibody in BMIM[BF 4 ] did not show any signal response to cross-reactive molecules

  5. The buffering-out effect and phase separation in aqueous solutions of EPPS buffer with 1-propanol, 2-propanol, or 2-methyl-2-propanol at T = 298.15 K

    International Nuclear Information System (INIS)

    Taha, Mohamed; Teng, Han-Lan; Lee, Ming-Jer

    2012-01-01

    Highlights: ► Buffering-out is a new liquid–liquid phase separation containing biological buffer. ► EPPS buffer-induced phase separation of aqueous solutions of aliphatic alcohols. ► Phase diagrams of EPPS + water + 1-propanol/2-propanol/2-methyl-2-propanol are studied. ► EPPS breaks the 1-propanol + water and 2-methyl-2-propanol + water azeotropes. ► The (liquid + liquid) equilibria can be well correlated by the NRTL model. - Abstract: Buffering-out is a new liquid–liquid phase separation phenomenon observed in mixtures containing a buffer as a mass separating agent. The (liquid + liquid) equilibrium (LLE) and (solid + liquid + liquid) equilibrium (SLLE) data were measured for the ternary systems {3-[4-(2-hydroxyethyl)piperazin-1-yl]propanesulfonic acid (EPPS) buffer + 1-propanol, 2-propanol, or 2-methyl-2-propanol + water} at T = 298.15 K under atmospheric pressure. The phase boundary data were fitted to an empirical equation relating to the concentrations of organic solvent and buffer. The effective excluded volume (EEV) values of EPPS were obtained from the phase boundary data. The phase-separation abilities of the investigated aliphatic alcohols were discussed. The reliability of the experimental tie-lines was satisfactorily confirmed by the Othmer–Tobias correlation. The experimental tie-lines data for the ternary systems have been correlated using the NRTL activity coefficient model. The separation of these aliphatic alcohols from their azeotropic aqueous mixtures is of particular interest to industrial process. The addition of the EPPS as an auxiliary agent breaks the (1-propanol + water) and (2-methyl-2-propanol + water) azeotropes. The possibility of using the new phase separation systems in the extraction process is demonstrated by using different dyestuffs.

  6. Effect of Alloy 625 Buffer Layer on Hardfacing of Modified 9Cr-1Mo Steel Using Nickel Base Hardfacing Alloy

    Science.gov (United States)

    Chakraborty, Gopa; Das, C. R.; Albert, S. K.; Bhaduri, A. K.; Murugesan, S.; Dasgupta, Arup

    2016-04-01

    Dashpot piston, made up of modified 9Cr-1Mo steel, is a part of diverse safety rod used for safe shutdown of a nuclear reactor. This component was hardfaced using nickel base AWS ER NiCr-B alloy and extensive cracking was experienced during direct deposition of this alloy on dashpot piston. Cracking reduced considerably and the component was successfully hardfaced by application of Inconel 625 as buffer layer prior to hardface deposition. Hence, a separate study was undertaken to investigate the role of buffer layer in reducing the cracking and on the microstructure of the hardfaced deposit. Results indicate that in the direct deposition of hardfacing alloy on modified 9Cr-1Mo steel, both heat-affected zone (HAZ) formed and the deposit layer are hard making the thickness of the hard layer formed equal to combined thickness of both HAZ and deposit. This hard layer is unable to absorb thermal stresses resulting in the cracking of the deposit. By providing a buffer layer of Alloy 625 followed by a post-weld heat treatment, HAZ formed in the modified 9Cr-1Mo steel is effectively tempered, and HAZ formed during the subsequent deposition of the hardfacing alloy over the Alloy 625 buffer layer is almost completely confined to Alloy 625, which does not harden. This reduces the cracking susceptibility of the deposit. Further, unlike in the case of direct deposition on modified 9Cr-1Mo steel, dilution of the deposit by Ni-base buffer layer does not alter the hardness of the deposit and desired hardness on the deposit surface could be achieved even with lower thickness of the deposit. This gives an option for reducing the recommended thickness of the deposit, which can also reduce the risk of cracking.

  7. Sedimentation behaviour and colloidal properties of porous, chemically modified silicas in non-aqueous solvents

    NARCIS (Netherlands)

    Vissers, J.P.C.; Laven, J.; Claessens, H.A.; Cramers, C.A.M.G.; Agterof, W.G.M.

    1997-01-01

    The sedimentation behaviour and colloidal properties of porous, chemically modified silicas dispersed in non-aqueous solvents have been studied. The free settling behaviour of non-aggregated silica suspensions could effectively be described with a modified Stokes equation that takes into account the

  8. Effects of buffer agents on hydrogen adsorption and desorption at/within activated carbon for the negative electrode of aqueous asymmetric supercapacitors

    International Nuclear Information System (INIS)

    Chien, Hsiu-Chuan; Wu, Tzu-Ho; Rajkumar, Muniyandi; Hu, Chi-Chang

    2016-01-01

    Highlights: • H adsorption causes local pH increase and negatively shifts the double-layer potential window. • The local pH variation at AC/electrolyte interface can be controlled via adding buffer agents. • H adsorption potential on AC in buffer electrolytes follows the Nernstian dependence. • The pseudocapacitive reversibility of H adsorption/desorption at/within AC is too poor. - Abstract: In this work, the effects of adding buffer agents into aqueous electrolytes on the hydrogen adsorption/desorption behaviour at/within activated carbon are systematically investigated for the negative electrode of asymmetric supercapacitors. Due to the poor electrochemical reversibility of hydrogen adsorption/desorption at/within activated carbon, the hydrogen responses at/within activated carbon are not suitable for pseudo-capacitive energy storage of high-performance asymmetric supercapacitor. The electrochemical adsorption of H atoms consumes protons and causes the local pH change at the activated carbon/electrolyte interface, leading to the negative shift in the H adsorption potential when weakly acidic, neutral, and weakly basic electrolytes without buffer agents are employed. The addition of buffer agents into electrolytes significantly improves the rate of proton supply and promotes the rate of hydrogen adsorption at/within AC. Interestingly, the onset potential of significant H adsorption obtained from the buffered electrolytes generally follows the Nernstian dependence, suggesting the Nerstian dependence of H"+/H_a_d_s on AC at all pH values. In order to obtain the energy storage devices with high coulombic and energy efficiencies, the onset potential of significant H adsorption obtained from the electrolyte containing buffer agents is a reliable lower potential limit of the AC-coated negative electrode for aqueous asymmetric supercapacitors.

  9. Large area flexible polymer solar cells with high efficiency enabled by imprinted Ag grid and modified buffer layer

    International Nuclear Information System (INIS)

    Lu, Shudi; Lin, Jie; Liu, Kong; Yue, Shizhong; Ren, Kuankuan; Tan, Furui; Wang, Zhijie; Jin, Peng; Qu, Shengchun; Wang, Zhanguo

    2017-01-01

    To take a full advantage of polymer semiconductors on realization of large-area flexible photovoltaic devices, herein, we fabricate polymer solar cells on the basis of polyethylene terephthalate (PET) with imprinted Ag grid as transparent electrode. The key fabrication procedure is the adoption of a modified PEDOT:PSS (PH1000) solution for spin-coating the buffer layer to form a compact contact with the substrate. In comparison with the devices with intrinsic PEDOT:PSS buffer layer, the advanced devices present a much higher efficiency of 6.51%, even in a large device area of 2.25 cm"2. Subsequent characterizations reveal that such devices show an impressive performance stability as the bending angle is enlarged to 180° and bending time is up to 1000 cycles. Not only providing a general methodology to construct high efficient and flexible polymer solar cells, this paper also involves deep insights on device working mechanism in bending conditions.

  10. Arsenic Removal from Aqueous Solutions Using Modified and Unmodified Oak Sawdust

    Directory of Open Access Journals (Sweden)

    Ali Reza Rahmani

    2016-01-01

    Full Text Available In this research, oak sawdust, in both modified and unmodified forms, was used as an economical and low-cost material for the removal of arsenic from aqueous solutions. For this purpose, arsenic synthetic samples were prepared using NaAsO2 in distilled water and the effects of pH, adsorbent dosage, contact time, and initial As(V concentration were investigated on As(V adsorption using the adsorbents prepared. The results showed that modified sawdust achieved the highest efficiency (>91% over a contact time of 60 min and at pH 7 when the adsorbent dosage was 4gr/L and the initial As(V concentration was 150 µg/L. The data from both adsorbents fitted well to the Langmuir isotherm. Under optimum conditions (an initial As(V concentration of 150 µg/L and optimal absorption pH, contact time, and adsorbent dosage, maximum As(V removal efficiencies were 93.85% and 91.034% with the modified  and unmodified sawdust adsorbents, respectively. Given the availability and low cost of the adsorbent used and the high removal efficiency obtained at  lower adsorbent dosages and contact times, the modified oak sawdust may be recommended as an effective adsorbent for the removal of arsenic (v from aqueous solutions, especially since it requires no need for pH modification.

  11. Kinetics and thermodynamics of Pb(II) adsorption onto modified spent grain from aqueous solutions

    International Nuclear Information System (INIS)

    Li Qingzhu; Chai Liyuan; Yang Zhihui; Wang Qingwei

    2009-01-01

    Spent grain, a main by-product of the brewing industry, is available in large quantities, but its main application has been limited to animal feeding. Nevertheless, in this study, spent grain modified with 1 M NaCl solution as a novel adsorbent has been used for the adsorption of Pb(II) in aqueous solutions. Isotherms, kinetics and thermodynamics of Pb(II) adsorption onto modified spent grain were studied. The equilibrium data were well fitted with Langmuir, Freundlich and Dubinin-Radushkevick (D-R) isotherm models. The kinetics of Pb(II) adsorption followed pseudo-second-order model, using the rate constants of pseudo-second-order model, the activation energy (E a ) of Pb(II) adsorption was determined as 12.33 kJ mol -1 according to the Arrhenius equation. Various thermodynamic parameters such as ΔG ads , ΔH ads and ΔS ads were also calculated. Thermodynamic results indicate that Pb(II) adsorption onto modified spent grain is a spontaneous and endothermic process. Therefore, it can be concluded that modified spent grain as a new effective adsorbent has potential for Pb(II) removal from aqueous solutions.

  12. Removal of Pb(II) from aqueous solution using modified and unmodified kaolinite clay

    International Nuclear Information System (INIS)

    Jiang Mingqin; Wang Qingping; Jin Xiaoying; Chen Zuliang

    2009-01-01

    Modified kaolinite clay with 25% (w/w) aluminium sulphate and unmodified kaolin were investigated as adsorbents to remove Pb(II) from aqueous solution. The results show that amount of Pb(II) adsorbed onto modified kaolin (20 mg/g) was more than 4.5-fold than that adsorbed onto unmodified kaolin (4.2 mg/g) under the optimized condition. In addition, the linear Langmuir and Freundlich models were used to describe equilibrium isotherm. It is observed that the data from both adsorbents fitted well to the Langmuir isotherm. The kinetic adsorption of modified and unmodified kaolinite clay fitted well to the pseudo-second-order model. Furthermore, both modified and unmodified kaolinite clay were characterized by X-ray diffraction, Fourier transform infrared (FT-IR) and scanning electron microscope (SEM). Finally, both modified and unmodified kaolinite clay were used to remove metal ions from real wastewater, and results show that higher amount of Pb(II) (the concentration reduced from 178 to 27.5 mg/L) and other metal ions were removed by modified kaolinite clay compared with using unmodified adsorbent (the concentration reduced from 178 to 168 mg/L).

  13. Sorption of Pb2+ from Aqueous Solution unto Modified Rice Husk: Isotherms Studies

    Directory of Open Access Journals (Sweden)

    A. O. Dada

    2013-01-01

    Full Text Available Investigation of the sorption potential of rice husk, an agricultural waste, as an adsorbent was carried out. The rice husk was modified with orthophosphoric acid and was used for adsorption of lead (II ions (Pb2+ from aqueous solution. Physicochemical properties of the modified rice husk were determined. Equilibrium sorption data were confirmed with Langmuir, Freundlich and Temkin adsorption isotherms. On the basis of adsorption isotherm graphs, R2 values were determined to be 0.995, 0.916, and 0.797 for Langmuir, Temkin, and Freundlich isotherms, respectively, indicating that the data fitted well into the adsorption isotherms, but Langmuir isotherm is a better model. The maximum monolayer coverage from Langmuir studies, Qmax=138.89 mg/g, Langmuir isotherm constant, KL=0.699 L/mg, and the separation factor, RL=1.41×10−2 at 100 mg/L of lead(II ions indicating that the sorption process, was favourable. The suitability of modified rice husk as an adsorbent for the removal of lead ions from aqueous solution and its potential for pollution control is established.

  14. Adsorption Efficiency of Iron Modified Carbons for Removal of Pb(II Ions from Aqueous Solution

    Directory of Open Access Journals (Sweden)

    Mohammad Hossein Salmani

    2016-06-01

    Full Text Available Abstract Introduction: The Lead causes severe damage to several systems of the body, especially to bony tissues. Until now, several low-cost biosorbents have been studied for removal of heavy metal ions from aqueous solutions. In the present study, carbonized pomegranate peels modified with Fe2+ and Fe3+ ions and then it was investigated for removal of Pb(II ions from aqueous solution. Materials and methods: the washed granola of pomegranate peel was separately socked with FeCl3 and FeCl2 solutions for 24 h. Then, the granules were carbonized at 400 ºC for 3 h in a programmable furnace in the atmosphere of nitrogen. The adsorption experiments were carried out for two types of iron-modified carbons by batch adsorption using one variable at a time procedures. Results: The optimum conditions were found as contact time 90 min, initial concentration 50 mg/l, and adsorbent dose, 1.00 g/100 ml solution. Maximum removal efficiency was calculated as 84% and 89% for Fe3+ and Fe2+ impregnated pomegranate peel carbons respectively. Conclusion: The iron treatment pomegranate peel carbons modified their surfaces for adsorption of heavy metals. The results showed that chemical modification of the low-cost adsorbents originating from agricultural waste has stood out for metal removal capabilities.

  15. Effects of TiO{sub 2} buffer layer on the photoelectrochemical properties of TiO{sub 2} Nano rods grown by modified chemical bath deposition method

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Tae-hyun; Ha, Jin-wook; Ryu, Hyukhyun [Inje University, Gimhae (Korea, Republic of); Lee, Won-Jae [Dong-Eui University, Busan (Korea, Republic of)

    2015-08-15

    In this study, we grew TiO{sub 2} nano rods on TiO{sub 2}-film buffered FTO substrate using modified chemical bath deposition (M-CBD). The TiO{sub 2} buffer layer was grown by spin coating method with different RPM (revolutions per minute) values and deposition cycles. We investigated the effects of the RPM values and the deposition cycles on the morphological, structural and photoelectrochemical properties of TiO{sub 2} nano rods. In this work, we have also found that the morphological and structural properties of TiO{sub 2} nano rods affected the photoelectrochemical properties of TiO{sub 2} nano rods. And the maximum photocurrent density of 0.34 mA/cm{sup 2} at 0.6V (vs.SCE) was obtained from the buffer layer deposition process condition of 4,000 RPM and two-times buffer layer depositions.

  16. Factors influencing hydroquinone degradation in aqueous solution using a modified microelectrolysis method.

    Science.gov (United States)

    Li, Tong; Li, Tingting; Xiong, Houfeng; Zou, Donglei

    2015-01-01

    The discharge of hydroquinone (HQ), an important chemical raw material, to natural waters poses different ecological threats to aquatic organisms. In this study, we investigated the removal performance of traditional and modified microelectrolysis methods in aqueous solutions. The traditional microelectrolysis packing was modified by adding manganese (Mn), zinc (Zn), and copper (Cu) powder as additives. The factors affecting the removal performance of HQ, such as catalytic metal type, mass fraction of additive, reaction time, and initial pH, were examined. The results showed that the Mn modified packing exhibited the best performance compared to Zn and Cu powder. The removal rate of HQ using Mn modified packing can reach 94% after 4 h. In addition, 9% of Mn packing has a higher removal rate than other mass fractions. The acidic solution pH shows a more favorable degradation than a neutral and alkaline solution. The intermediates of HQ degradation by modified microelectrolysis were identified and then the pathway of HQ degradation was proposed. Our result indicates that Mn as catalytic metal holds promising potential to enhance HQ removal in water using the microelectrolysis method.

  17. Removal of ammonium from aqueous solutions using alkali-modified biochars

    Directory of Open Access Journals (Sweden)

    Zhigang Liu

    2016-10-01

    Full Text Available Biochars converted from agricultural residuals can effectively remove ammonium from water. This work further improved the sorption ability of biochars to aqueous ammonium through alkali modification. Three modified biochars were prepared from agricultural residuals pre-treated with NaOH solution through low-temperature (300 °C slow pyrolysis. The modified biochars effectively removed ammonium ions from water under various conditions with relatively fast adsorption kinetics (reached equilibrium within 10 h and extremely high adsorption capacity (>200 mg/g. The Langmuir maximum capacity of the three modified biochars were between 313.9 and 518.9 mg/g, higher than many other ammonium adsorbents. Although the sorption of ammonium onto the modified biochar was affected by pH and temperature, it was high under all of the tested conditions. Findings from this work indicated that alkali-modified biochars can be used as an alternative adsorbent for the removal of ammonium from wastewater.

  18. Optimization of uranyl ions removal from aqueous solution by natural and modified kaolinites

    Energy Technology Data Exchange (ETDEWEB)

    Elhefnawy, O.A.; Elabd, A.A. [Nuclear and Radiological Regulatory Authority (NRRA), Cairo (Egypt). Nuclear Safeguards and Physical Protection Dept.

    2017-10-01

    The paper addresses the modifications of the most common mineral clay ''kaolinite'' for U(VI) removal from aqueous solutions. A new modified Egyptian natural kaolinite (Ca-MK) was prepared by coating kaolinite with calcium oxide. Another modification process was utilized by calcination and acid activation of kaolinite (E-MK). The Egyptian natural kaolinite (E-NK) and the two modified kaolinites were characterized by different techniques SEM, EDX, XRD, and FTIR. The removal process were investigated in batch experiments as a function of pH, contact time, initial U(VI) concentration, effect of temperature, and recovery of U(VI) were studied. The equilibrium stage was achieved after 60 min and the kinetic data was described well by pseudo-second order model. Isothermal data was better described by the Langmuir isotherm model, indicating the homogeneous removal process. Also the removal process was studied on different temperature 293, 313, and 323 K. The thermodynamic parameters ΔH , ΔS , and ΔG were calculated. The thermodynamic results pointed to the endothermic and favorable nature of the U(VI) removal process in the three kaolinite adsorbents. This study indicated that (Ca-MK) has higher CEC and can be used as a new adsorbent for highly efficient removal of U(VI) from aqueous solutions.

  19. Polyaniline (PANI) modified bentonite by plasma technique for U(VI) removal from aqueous solution

    International Nuclear Information System (INIS)

    Liu, Xinghao; Cheng, Cheng; Xiao, Chengjian; Shao, Dadong; Xu, Zimu; Wang, Jiaquan; Hu, Shuheng; Li, Xiaolong; Wang, Weijuan

    2017-01-01

    Highlights: • PANI/bentonie can be synthesized by simple plasma technique. • PANI/bentonie has an excellent adsorption capacity for trace uranium in solution. • U(VI) adsorption on PANI/bentonite is a spontaneous and endothermic process. - Abstract: Polyaniline (PANI) modified bentonite (PANI/bentonie) was synthesized by plasma induced polymerization of aniline on bentonite surface, and applied to uptake of uranium(VI) ions from aqueous solution. The as-synthesized PANI/bentonie was characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). Batch adsorption technique was utilized to investigate the adsorption of U(VI) on bentonite and PANI/bentonite. The adsorption of U(VI) (10 mg/L) on PANI/bentonite surface is fairly depend on solution pH, ionic strength, and temperature in solution. The modified PANI on PANI/bentonite surface significantly enhances its adsorption capability for U(VI). The presence of humic acid (HA) can sound enhance U(VI) adsorption on PANI/bentonite at pH 6.5. According to the thermodynamic parameters, the adsorption of U(VI) on PANI/bentonite surface is a spontaneous and endothermic process. The results highlight the application of PANI/bentonite composites as candidate material for the uptake of trace U(VI) from aqueous solution.

  20. Polyaniline (PANI) modified bentonite by plasma technique for U(VI) removal from aqueous solution

    Science.gov (United States)

    Liu, Xinghao; Cheng, Cheng; Xiao, Chengjian; Shao, Dadong; Xu, Zimu; Wang, Jiaquan; Hu, Shuheng; Li, Xiaolong; Wang, Weijuan

    2017-07-01

    Polyaniline (PANI) modified bentonite (PANI/bentonie) was synthesized by plasma induced polymerization of aniline on bentonite surface, and applied to uptake of uranium(VI) ions from aqueous solution. The as-synthesized PANI/bentonie was characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). Batch adsorption technique was utilized to investigate the adsorption of U(VI) on bentonite and PANI/bentonite. The adsorption of U(VI) (10 mg/L) on PANI/bentonite surface is fairly depend on solution pH, ionic strength, and temperature in solution. The modified PANI on PANI/bentonite surface significantly enhances its adsorption capability for U(VI). The presence of humic acid (HA) can sound enhance U(VI) adsorption on PANI/bentonite at pH 6.5. According to the thermodynamic parameters, the adsorption of U(VI) on PANI/bentonite surface is a spontaneous and endothermic process. The results highlight the application of PANI/bentonite composites as candidate material for the uptake of trace U(VI) from aqueous solution.

  1. Improved removal of malachite green from aqueous solution using chemically modified cellulose by anhydride.

    Science.gov (United States)

    Zhou, Yanmei; Min, Yinghao; Qiao, Han; Huang, Qi; Wang, Enze; Ma, Tongsen

    2015-03-01

    Cellulose modified with maleic (M) and phthalic (P) anhydride, to be named CMA and CPA, were tested as feasible adsorbents for the removal of malachite green from aqueous solution. At the same time, the uptake ability of natural cellulose was also studied for comparison. The structure of material was characterized by FT-IR and XRD. The effects of solution pH, initial dye concentration, contact time and temperature were investigated in detail by batch adsorption experiments. The kinetic and isotherm studies suggested that the adsorption followed the pseudo-second-order model and Langmuir isotherm. The maximum adsorption capacity on CMA and CPA were 370 mg g(-1) and 111 mg g(-1), respectively. Furthermore, the thermodynamics studies indicated the spontaneous nature of adsorption of malachite green on adsorbents. All the studied results showed that the modified cellulose could be used as effective adsorption material for the removal of malachite green from aqueous solutions. Copyright © 2014 Elsevier B.V. All rights reserved.

  2. Polyaniline (PANI) modified bentonite by plasma technique for U(VI) removal from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xinghao [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Intelligent Manufacturing Technology Research Institute, Hefei University of Technology, Hefei 230088 (China); Cheng, Cheng [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Xiao, Chengjian, E-mail: xiaocj@caep.cn [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Shao, Dadong, E-mail: shaodadong@126.com [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Xu, Zimu, E-mail: xzm@mail.ustc.edu.cn [Intelligent Manufacturing Technology Research Institute, Hefei University of Technology, Hefei 230088 (China); Wang, Jiaquan; Hu, Shuheng [Intelligent Manufacturing Technology Research Institute, Hefei University of Technology, Hefei 230088 (China); Li, Xiaolong; Wang, Weijuan [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China)

    2017-07-31

    Highlights: • PANI/bentonie can be synthesized by simple plasma technique. • PANI/bentonie has an excellent adsorption capacity for trace uranium in solution. • U(VI) adsorption on PANI/bentonite is a spontaneous and endothermic process. - Abstract: Polyaniline (PANI) modified bentonite (PANI/bentonie) was synthesized by plasma induced polymerization of aniline on bentonite surface, and applied to uptake of uranium(VI) ions from aqueous solution. The as-synthesized PANI/bentonie was characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). Batch adsorption technique was utilized to investigate the adsorption of U(VI) on bentonite and PANI/bentonite. The adsorption of U(VI) (10 mg/L) on PANI/bentonite surface is fairly depend on solution pH, ionic strength, and temperature in solution. The modified PANI on PANI/bentonite surface significantly enhances its adsorption capability for U(VI). The presence of humic acid (HA) can sound enhance U(VI) adsorption on PANI/bentonite at pH < 6.5 because of the strong complexation, and inhibits U(VI) adsorption at pH > 6.5. According to the thermodynamic parameters, the adsorption of U(VI) on PANI/bentonite surface is a spontaneous and endothermic process. The results highlight the application of PANI/bentonite composites as candidate material for the uptake of trace U(VI) from aqueous solution.

  3. Electrogenerated chemiluminescence of a cationic cyclometalated iridium complex–Nafion modified electrode in neutral aqueous solution

    International Nuclear Information System (INIS)

    Dong, YongPing; Ni, ZiYue; Zhang, Jing; Tong, BiHai; Chu, XiangFeng

    2013-01-01

    Electrogenerated chemiluminescence (ECL) of a cationic cyclometalated iridium complex, [(pqcm) 2 Ir(bpy)](PF 6 ) (1, pqcmH=2-phenyl-quinoline-4-carboxylic acid methyl ester, bpy=2,2′-bipyridine), was investigated at a bare glassy carbon electrode in CH 3 CN solution and 4 ECL peaks were observed. Then, the ECL of the iridium complex was studied in neutral phosphate buffer solution (PBS) by immobilizing it on a glassy carbon electrode. Two closely located ECL peaks were obtained at 1.07 and 1.40 V when the potential was scanned from −3.00 V to 2.20 V, while only one broad ECL peak located around −2.0 V was obtained when the potential was scanned from 2.20 V to −3.00 V. In the presence of oxalate, one ECL peak located around 1.22 V could be obtained except the broad ECL peak located at −2.00 V. The ECL peak at positive potential range was enhanced more than one magnitude in the presence of Nafion and was nearly 5-times higher than that of Ru(bpy) 3 2+ –Nafion modified electrode, suggesting that the synthesized iridium complex has great application potential in ECL detection. The ECL spectra of iridium complex were identical to its photoluminescence spectrum, indicating the same metal-to-ligand charge transfer (MLCT) excited states. The mechanisms of ECL were proposed based on the experimental results. The present ECL sensor gave a linear response for the oxalate concentration from 1.0×10 −6 to 1.0×10 −4 mol L −1 with a detection limit (S/N=3) of 9.1×10 −7 mol L −1 . -- Graphical abstract: Electrochemiluminescence (ECL) of immobilized novel cationic cyclometalated iridium complex in neutral phosphate buffer solution is reported for the first time. The intensity of iridium complex ECL is 5-times higher than that of Ru(bpy) 3 2+ ECL. Highlights: ► Cationic cyclometalated iridium complex was modified on a bare electrode. ► Electrochemiluminescence (ECL) of the modified electrode was studied. ► The ECL intensity is higher than that of Ru

  4. Adsorption properties of Congo Red from aqueous solution onto surfactant-modified montmorillonite

    International Nuclear Information System (INIS)

    Wang Li; Wang Aiqin

    2008-01-01

    A series of surfactant-modified montmorillonites (MMT) were prepared using octyltrimethylammonium bromide (OTAB), dodecyltrimethylammonium bromide (DTAB), cetyltrimethylammonium bromide (CTAB) and stearyltrimethylammonium bromide (STAB), and the organification of MMT was proved by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron micrographic (SEM) and transmission electron microscope (TEM). The adsorption of Congo Red (CR) anionic dye from aqueous solution onto surfactant-modified MMT was carried out. Compared with MMT, the adsorption capacity of surfactant-modified MMT for CR was greatly enhanced and MMT modified with CTAB (2.0 CEC) exhibited the higher adsorption capacity. The effects of pH value of the dye solution, adsorption temperature, adsorption time and the initial dye concentration on the adsorption capacity of CR on CTAB-MMT have been investigated. The results showed that the adsorption kinetic of CR on CTAB-MMT could be best described by the pseudo-second-order model and that the adsorption isotherm of CR was in good agreement with the Langmuir equation. The IR spectra and SEM analysis also revealed that the adsorption of CTAB-MMT was a chemical adsorption process between CTAB and the NH 2 , -N=N- and SO 3 groups of CR

  5. Adsorption of tannic acid from aqueous solution onto surfactant-modified zeolite

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Jianwei, E-mail: jwlin@shou.edu.cn [College of Marine Science, Shanghai Ocean University, No. 999 Hucheng Huan Road, Pudong District, Shanghai 201306 (China); Zhan, Yanhui; Zhu, Zhiliang [State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai 200092 (China); Xing, Yunqing [College of Marine Science, Shanghai Ocean University, No. 999 Hucheng Huan Road, Pudong District, Shanghai 201306 (China)

    2011-10-15

    Graphical abstract: Surfactant-modified zeolites (SMZs) with various loadings of cetylpyridinium bromide (CPB) were used as adsorbents to remove tannic acid (TA) from aqueous solution. Highlights: {yields} Surfactant modified zeolites (SMZs) have a good tannic acid (TA) adsorption capacity. {yields} Adsorption capacity for SMZ with bilayer was relatively high at solution pH 3.5-7.0. {yields} Adsorption was well described by pseudo-second-order kinetic model. {yields} Adsorption fitted well with Langmuir, Redlich-Peterson and Sips isotherm models. {yields} Coexisting Cu(II) in aqueous solution resulted in markedly enhanced TA adsorption. - Abstract: Surfactant-modified zeolites (SMZs) with various loadings of cetylpyridinium bromide (CPB) were used as adsorbents to remove tannic acid (TA) from aqueous solution. The TA adsorption efficiencies for natural zeolite and various SMZs were compared. SMZ presented higher TA adsorption efficiency than natural zeolite, and SMZ with higher loading amount of CPB exhibited higher TA adsorption efficiency. The adsorption of TA onto SMZ as a function of contact time, initial adsorbate concentration, temperature, ionic strength, coexisting Cu(II) and solution pH was investigated. The adsorbents before and after adsorption were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), thermogravimetric analysis (TGA), and Fourier transform infrared (FT-IR) spectroscopy. The adsorption kinetics of TA onto SMZ with CPB bilayer coverage (SMZ-CBC) followed a pseudo-second-order model. The equilibrium adsorption data of TA onto SMZ-CBC were well represented by Langmuir, Redlich-Peterson and Sips isotherm models. The calculated thermodynamic parameters indicated that TA adsorption onto SMZ-CBC was spontaneous and exothermic. The TA adsorption capacity for SMZ-CBC slightly decreased with increasing ionic strength but significantly increased with increasing Cu(II) concentration. The TA adsorption

  6. Effective Removal of Hexavalent Chromium from Aqueous Solutions Using Ionic Liquid Modified Graphene Oxide Sorbent

    Directory of Open Access Journals (Sweden)

    A. Nasrollahpour

    2017-10-01

    Full Text Available Ionic liquid modified reduced graphene oxide (IL-rGO was prepared and examined for chromate removal. The sorbent was characterized by N2 adsorption-desorption measurement (BET, transmission electron microscopy (TEM, powder X-ray diffraction (XRD, and X-ray photoelectron spectroscopy (XPS analysis. The sorption behavior of chromate on the ionic liquid modified reduced graphene oxide sorbent from an aqueous medium was studied by varying the parameters such as contact time, initial chromate concentration, pH, and agitation speed. The results showed that sorption kinetics of chromate by IL-rGO follows the pseudo second order, which indicates that the sorption mechanism is both chemical and physical interaction. The sorption isotherm studies revealed that Langmuir model provided the best fit to all the experimental data with an adsorption capacity of 232.55 mg g–1 for IL-rGO. Thermodynamic parameters, such as Gibbs free energy (–2.85 kJ mol–1 at 298 K, enthalpy (55.41 kJ mol–1, and entropy (11.64 J mol–1 K–1 of sorption of the chromate on ionic liquid modified reduced graphene oxide was evaluated, and it was found that the reaction was spontaneous and endothermic in nature.

  7. Sorption of Cr(III) ion from aqueous solution by two kinds of modified diatomite.

    Science.gov (United States)

    Li, Er; Zeng, Xiangying

    2012-01-01

    Raw diatomite modified by microemulsion (DMM) and manganese oxide (MnD) were used for the removal of Cr(III) ions from aqueous solution. The characteristics and performance of these two types of modified diatomite on Cr(III) ion adsorption were compared. The results indicate that the Cr(III) ion adsorption capacities of diatomite were considerably improved after modifications by manganese oxide (MnO) and microemulsion. The surface area of MnD was increased because of the formation of MnO on the diatomite surface, and that of DMM was promoted owing to the existence of the hydrolyzed aromatic acid. Because of the stronger surface ionized function, the adsorption performance of Cr(III) ions in DMM was better than that in MnD. Within the experimental range of pH (i.e. 2.2-6.3), the Cr(III) ion removal of DMM (35-70%) was higher than that of MnD (33-59%) owing to the different electrostatic forces between the Cr(III) ion and the surface of the modified diatomite. The Cr(III) ion removal in MnD and DMM was improved with the increase of synthetic solution concentration in volumes from 0 to 2,500 mL.

  8. Electrochemical Study of Modified Glassy Carbon Electrode with Carboxyphenyl Diazonium Salt in Aqueous Solutions

    Directory of Open Access Journals (Sweden)

    Mariem BOUROUROU

    2014-05-01

    Full Text Available The covalent grafting of carboxyphenyl functionalities to planar carbon substrates by reaction with 2-carboxybenezenediazonium salt has been studied in aqueous acid solution. The surface was characterized, before and after the functionnalization process, by cyclic voltammetry, electrochemical impedance spectroscopy and linear sweep voltammetry (LSV in order to control and to prove the formation of a coating on the carbon surface. The results indicate the presence of substituted phenyl groups on the investigated surface. Electrochemical impedance measurements show that the slowing down of the electron transfer kinetics was more evident by increasing the number of cycles resulting to higher DEp and RCT parameters. Besides, the effect of the pH on the electron transfer processes of the Fe(CN63-/4- at the modified electrode is studied. By changing the solution pH the terminal group’s charge state would vary, based on which the surface pKa value is estimated.

  9. Study on the adsorption of heavy metal ions from aqueous solution on modified SBA-15

    Directory of Open Access Journals (Sweden)

    Liliana Giraldo

    2013-01-01

    Full Text Available Amino-functionalized SBA-15 mesoporous silica was prepared, characterized, and used as an adsorbent for heavy metal ions. The organic - inorganic hybrid material was obtained by a grafting procedure using SBA-15 silica with 3-aminopropyl-triethoxysilane and bis(2,4,4-trimethylpentyl phosphinic acid (Cyanex 272, respectively. The structure and physicochemical properties of the materials were characterized by means of elemental analysis, X-ray diffraction (XRD, nitrogen adsorption - desorption, thermogravimetric analysis, FTIR spectroscopy and immersion calorimetry. The organic functional groups were successfully grafted onto the SBA-15 surface and the ordering of the support was not affected by the chemical modification. The behavior of the grafted solids was investigated for the adsorption of heavy metal ions from aqueous solutions. The hybrid materials showed high adsorption capacity and high selectivity for zinc ions. Other ions, such as cooper and cobalt were absorbed by the modified SBA-15 material.

  10. Removal of Parathion from Aqueous Media Through p-tert-Butylcalix[4]arene Based Modified Silica

    Directory of Open Access Journals (Sweden)

    Sibghatullah Memon

    2013-12-01

    Full Text Available This study explores, adsorption efficiency of p-tert-butylcalix[4]arene based modified silica to remove parathion from aqueous environment. The adsorption parameters, i.e. pH, concentration of pesticide solution, contact time and adsorbent dosage were optimized, as 10, 1 mg L-1, 40 min and 0.04 g, respectively. Langmuir, Freundlich and Dubinin-Radushkevich (D-R isotherm models were used to evaluate the adsorption mechanism. Adsorption constants values of these models suggest that the adsorption of parathion is favorable and were found to be best fit with Freundlich isotherm. From the kinetic study it can be predicted that adsorption of parathion follows Ho and McKay model (pseudo-second order. Thermodynamic parameters, enthalpy (ΔH, entropy (ΔS and Gibbs free energy (ΔG have also been evaluated and were found as -132.25, 0.45, -4.14 Jmol-1, respectively.

  11. Biosorption of strontium ions from aqueous solution using modified eggshell materials

    Energy Technology Data Exchange (ETDEWEB)

    Metwally, Sayed S.; Rizk, Hoda E.; Gasser, Mona S. [Atomic Energy Authority, Cairo (Egypt). Hot Laboratories Center

    2017-07-01

    Green composites emphasize renewable starting materials for better economy using biomass materials. Therefore, low-cost composite biosorbent was prepared by modification of eggshell material using heteropoly acid for removal of strontium ions from aqueous solution. The resulted composite was characterized and evaluated for the sorption process using the batch technique. Low concentration of strontium ions was used to evaluate the sorption sensitivity of the prepared composite. The obtained experimental results illustrated that the modification process of eggshell material enhanced the percent uptake from 49.9 to 95.7%. From kinetic studies, the sorption of strontium ions follows the pseudo-second-order kinetic model. The isotherm studies indicated that Langmuir is more applicable than Freundlich isotherm. Moreover, Dubinin-Radushkevich isotherm was studied. Thermodynamic studies revealed that the sorption process is spontaneous and has endothermic nature. Strontium ions can be desorbed from the modified eggshell using HNO{sub 3}, desorption percent was found to be 96.4%; the results revealed the reusability of the modified eggshell for further sorption.

  12. Morphology of modified biochar and its potential for phenol removal from aqueous solutions

    Directory of Open Access Journals (Sweden)

    Kostas A. Komnitsas

    2016-04-01

    Full Text Available In the present study, the efficiency of phenol removal from synthetic aqueous solutions by chemically modified biochar with the use of 1M KOH or 1M FeCl3 was investigated. Initially, biochar was produced after slow pyrolysis of three different agricultural wastes, namely pistachio (Pistacia vera L. shells, pecan (Carya illinoinensis shells and wood sawdust. The quality of biochar was assessed by evaluating its main properties, such as pH, surface area, porosity and C content. X-ray diffraction (XRD, Scanning Electron Microscopy (SEM and Fourier Transform Infrared Spectroscopy (FTIR were used for the identification of biochar’s structure. The efficiency of phenol removal from synthetic solutions was assessed with the use of kinetic and equilibrium experiments. The experimental results show that the KOH-modified biochar exhibited the highest phenol removal efficiency. Hydrophobic sorption on its surface is the main phenol removal mechanism. The pseudo-second order model fits best the kinetic data, while the Freundlich model, as deduced from an equilibrium study describes very well sorption of phenols on all biochars examined.

  13. The separation of uranium ions by natural and modified diatomite from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Sprynskyy, Myroslav, E-mail: sprynsky@yahoo.com [Department of Environmental Chemistry and Bioanalytics, Faculty of Chemistry, Nicolaus Copernicus University, 7 Gagarina Str., 87-100 Torun (Poland); Kovalchuk, Iryna [Department of Environmental Chemistry and Bioanalytics, Faculty of Chemistry, Nicolaus Copernicus University, 7 Gagarina Str., 87-100 Torun (Poland); Institute of Adsorption and Problem of Endoecology, National Academy of Sciences of Ukraine, 13 General Naumov Str., 03164 Kyiv (Ukraine); Buszewski, Boguslaw [Department of Environmental Chemistry and Bioanalytics, Faculty of Chemistry, Nicolaus Copernicus University, 7 Gagarina Str., 87-100 Torun (Poland)

    2010-09-15

    In this work the natural and the surfactant modified diatomite has been tested for ability to remove uranium ions from aqueous solutions. Such controlling factors of the adsorption process as initial uranium concentration, pH, contact time and ionic strength have been investigated. Effect of ionic strength of solution has been examined using the solutions of NaCl, Na{sub 2}CO{sub 3} and K{sub 2}SO{sub 4}. The pseudo-first order and the pseudo-second order models have been used to analyze the adsorption kinetic results, whereas the Langmuir and the Freundlich isotherms have been used to the equilibrium adsorption data. The effects of the adsorbent modification as well as uranium adsorption on the diatomite surface have been studied using X-ray powder diffraction, scanning electron microscopy and FTIR spectroscopy. The maximum adsorption capacities of the natural and the modified diatomite towards uranium were 25.63 {mu}mol/g and 667.40 {mu}mol/g, respectively. The desorptive solutions of HCl, NaOH, Na{sub 2}CO{sub 3}, K{sub 2}SO{sub 4}, CaCO{sub 3}, humic acid, cool and hot water have been tested to recover uranium from the adsorbent. The highest values of uranium desorption (86%) have been reached using 0.1 M HCl.

  14. The separation of uranium ions by natural and modified diatomite from aqueous solution.

    Science.gov (United States)

    Sprynskyy, Myroslav; Kovalchuk, Iryna; Buszewski, Bogusław

    2010-09-15

    In this work the natural and the surfactant modified diatomite has been tested for ability to remove uranium ions from aqueous solutions. Such controlling factors of the adsorption process as initial uranium concentration, pH, contact time and ionic strength have been investigated. Effect of ionic strength of solution has been examined using the solutions of NaCl, Na(2)CO(3) and K(2)SO(4). The pseudo-first order and the pseudo-second order models have been used to analyze the adsorption kinetic results, whereas the Langmuir and the Freundlich isotherms have been used to the equilibrium adsorption data. The effects of the adsorbent modification as well as uranium adsorption on the diatomite surface have been studied using X-ray powder diffraction, scanning electron microscopy and FTIR spectroscopy. The maximum adsorption capacities of the natural and the modified diatomite towards uranium were 25.63 micromol/g and 667.40 micromol/g, respectively. The desorptive solutions of HCl, NaOH, Na(2)CO(3), K(2)SO(4), CaCO(3), humic acid, cool and hot water have been tested to recover uranium from the adsorbent. The highest values of uranium desorption (86%) have been reached using 0.1M HCl. Copyright 2010 Elsevier B.V. All rights reserved.

  15. Pre-concentration and determination of tartrazine dye from aqueous solutions using modified cellulose nanosponges.

    Science.gov (United States)

    Shiralipour, Roohollah; Larki, Arash

    2017-01-01

    In this study, a new absorbent based on cellulose nanosponges modified with methyltrioctylammonium chloride (aliquat 336) was prepared and used for pre-concentration, removal and determination of tartrazine dye, using UV-vis spectrophotometry. This adsorbent was fully characterized using various instrumental techniques such as SEM, FTIR and XRD spectra. The pre-concentration and removal procedures were studied in column and batch modes, respectively. The effects of parameters such as pH of the aqueous medium, methyltrioctylammounium chloride dose, adsorbent amount, desorbing conditions and interfering ions on the adsorption of tartrazine were investigated and optimized. The fitting experimental data with conventional isotherm models revealed that the adsorption followed the Brunauer-Emmett-Teller (BET) model and the maximum adsorption capacity for tartrazine was 180mg/g with modified nanosponges. Under the optimized conditions, the calibration curve was linear over the range of 2-300ng/mL and the limit of detection was 0.15ng/mL. The relative standard deviation (RSD) for 20 and 100ng/mL of tartrazine were 3.1% and 1.5%, respectively. The proposed method was applied for pre-concentration and determination of tartrazine dye in different water samples. Copyright © 2016 Elsevier Inc. All rights reserved.

  16. Enhanced photocatalytic reduction of Hg(II) in aqueous medium by 2-aminothiazole-modified TiO2 particles

    OpenAIRE

    Cristante,Valtair M.; Araujo,Adriana B.; Jorge,Sônia M. A.; Florentino,Ariovaldo O.; Valente,José P. S.; Padilha,Pedro M.

    2006-01-01

    This work describes the synthesis and characterization of 2-aminothiazole-modified titania and its application on Hg (II) photoreduction in aqueous medium. Infrared spectroscopy confirmed the chemical modification of the titania matrix. The number of 2-aminothiazole groups attached to the titania was determined by Kjeldahl's method. The photocatalytic experiments were carried out in a cylindrical photoreactor thermostatted at 298 K. The resulting modified photocatalyst 2-aminothiazole titania...

  17. Kinetics Modeling and Isotherms for Adsorption of Phosphate from Aqueous Solution by Modified Clinoptilolit

    Directory of Open Access Journals (Sweden)

    Mohammad Malakootian

    2012-01-01

    Full Text Available The Phosphorous discharge into the surface water led to excessive growth of algae and eutrophication in lakes and rivers. Therefore the phosphorus removal is important due to negative effect on water resources. The aim of this study was to investigat the modification of clinoptilolite and application of modified clinoptilolite for phosphorous adsorption from aqueous solution and isotherms and kinetics modeling. Hexadecyl Trimethyl Ammonium bromide (HDTMA-Br, Hexadecyl trimethyl Ammonium Chloride (HDTMA-Cl, Sodium Decyl Sulphate (SDS and Cetrimide-C were used for modification of clinoptilolite. Experiments were conducted using jar apparatus and batch system. The effect of pH, adsorbent doses, contact time, phosphate initial concentration and particle size were studied surveyed on phosphate adsorption by modified clinoptilolite. The most common isotherms and the kinetics adsorption equations were used for determination of adsorption rate and dynamic reaction. The results showed that maximum phosphate adsorption was obtained in the pH of 7 and contact time 90min. Also it was found with the increasing of phosphate initial concentration, phosphate removal efficiency decreased significantly. Langmuir No 2 showed a good correlation compared to other isotherms (R2=0.997. Maximum adsorption capacity was obtained in 20g/L adsorbent dose (22.73mg/g. Also Interaparticle diffusion kinetics well fits with experimental data (R2=0.999 with constant rate of 3.84mg/g min0.5. The result showed that modified clinoptilolite can be used successfully as low cost and effective absorbent for phosphate removal.

  18. Textile Dye Removal from Aqueous Solution using Modified Graphite Waste/Lanthanum/Chitosan Composite

    Science.gov (United States)

    Kusrini, E.; Wicaksono, B.; Yulizar, Y.; Prasetyanto, EA; Gunawan, C.

    2018-03-01

    We investigated various pre-treatment processes of graphite waste using thermal, mechanical and chemical methods. The aim of this work is to study the performance of modified graphite waste/lanthanum/chitosan composite (MG) as adsorbent for textile dye removal from aqueous solution. Effect of graphite waste resources, adsorbent size and lanthanum concentration on the dye removal were studied in batch experiments. Selectivity of MG was also investigated. Pre-heated graphite waste (NMG) was conducted at 80°C for 1 h, followed by mechanical crushing of the resultant graphite to 75 μm particle size, giving adsorption performance of ˜58%, ˜67%, ˜93% and ˜98% of the model dye rhodamine B (concentration determined by UV-vis spectroscopy at 554 nm), methyl orange (464 nm), methylene blue (664 nm) and methyl violet (580 nm), respectively from aqueous solution. For this process, the system required less than ˜5 min for adsorbent material to be completely saturated with the adsorbate. Further chemical modification of the pre-treated graphite waste (MG) with lanthanum (0.01 – V 0.03 M) and chitosan (0.5% w/w) did not improve the performance of dye adsorption. Under comparable experimental conditions, as those of the ‘thermal-mechanical-pre-treated-only’ (NMG), modification of graphite waste (MG) with 0.03 M lanthanum and 0.5% w/w chitosan resulted in ˜14%, ˜47%, ˜72% and ˜85% adsorption of rhodamine B, methyl orange, methylene blue and methyl violet, respectively. Selective adsorption of methylene blue at most to ˜79%, followed by methyl orange, methyl violet and rhodamine B with adsorption efficiency ˜67, ˜38, and ˜9% sequentially using MG with 0.03 M lanthanum and 0.5% w/w chitosan.

  19. Removal of thorium(IV) from aqueous solution by biosorption onto modified powdered waste sludge. Experimental design approach

    International Nuclear Information System (INIS)

    Yunus Pamukoglu, M.; Mustafa Senyurt; Bulent Kirkan

    2017-01-01

    The biosorption of radioactive Th(IV) ions in the aqueous solutions onto the modified powdered waste sludge (MPWS) has been examined. In this context, the parameters affecting biosorption of Th(IV) from aqueous solutions has been examined by using MPWS biosorbent in Box Behnken statistical experimental design. The structure of MPWS biosorbent was characterized by using SEM and BET techniques. According to the experimental design results, MPWS and Th(IV) concentrations should be kept high to achieve the maximum efficiency in Th(IV) biosorption. On the other hand, MPWS, which is also used as a biosorbent, is an economical, effective and natural biosorbent. (author)

  20. Preparation of tetraethylenepentamine modified magnetic graphene oxide for adsorption of dyes from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Xiaosheng [Hubei Normal University (China); Tang, Ping; Liu, Liangliang, E-mail: liuliangliang@caas.cn [Chinese Academy of Agricultural Sciences, Changsha (China)

    2018-05-01

    In this study, tetraethylenepentamine modified magnetic graphene oxide nanomaterial (TMGO) was prepared and characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and vibration sample magnetometer (VSM). All the characterizations proved that the modification and preparation of TMGO were successful. The TMGO nanomaterial was used in the adsorption of Acid Red 18 (AR) in aqueous solution. The parameters like pH of solution, adsorption kinetics and isotherms were all investigated. The results indicated that the TMGO nanomaterial had satisfied adsorption ability and the maximum adsorption capacity was 524.2 mg g{sup -}'1 at 45 °C and pH 6. The adsorption capacity remained at 91.8% of the initial value after five cycles. The adsorption process with AR was found through fitting the pseudo-second-order kinetics equations and the Freundlich adsorption model. The experimental results demonstrated that the TMGO nanomaterial could be rapidly extracted from the medium and had a good adsorption ability to remove dyes in wastewater. (author)

  1. Uranium adsorption by non-treated and chemically modified cactus fibres in aqueous solutions

    International Nuclear Information System (INIS)

    Melpomeni Prodromou; Ioannis Pashalidis

    2013-01-01

    The adsorption efficiency of Opuntia ficus indica fibres regarding the removal of hexavalent uranium [U(VI)] from aqueous solutions has been investigated prior and after the chemical treatment (e.g. phosphorylation and MnO 2 -coating) of the biomass. The separation/removal efficiency has been studied as a function of pH, uranium concentration, adsorbent mass, ionic strength, temperature and contact time. Evaluation of the experimental data shows that biosorption is strongly pH-depended and that the MnO 2 -coated product presents the highest adsorption capacity followed by the phosphorylated and non-treated material. Experiments with varying ionic strength/salinity don't show any significant effect on the adsorption efficiency, indicating the formation of inner-sphere surface complexes. The adsorption reactions are in all cases exothermic and relatively fast, particularly regarding the adsorption on the MnO 2 -coated product. The results of the present study indicate that adsorption of uranium from waters is very effective by cactus fibres and particularly the modified treated fibres. The increased adsorption efficiency of the cactus fibres is attributed to their primary and secondary fibrillar structure, which result in a relative relative high specific surface available for sorption. (author)

  2. Removal of nitrate from aqueous solution using cetylpyridinium bromide (CPB) modified zeolite as adsorbent

    International Nuclear Information System (INIS)

    Zhan Yanhui; Lin Jianwei; Zhu Zhiliang

    2011-01-01

    Surfactant modified zeolites (SMZ) with different coverage types were prepared by loading the cetylpyridinium bromide (CPB) onto the surface of the natural zeolites. The adsorption behavior of nitrate on SMZ was investigated. Natural zeolite and SMZ with monolayer CPB coverage were inefficient for the removal of nitrate from aqueous solution. However, SMZ with patchy bilayer or bilayer CPB coverage was efficient in nitrate removal, and the nitrate adsorption capacity of SMZ increased with its CPB loading. For typical SMZ with bilayer CPB coverage, the nitrate adsorption process was well described by the pseudo-second-order kinetic model, and the experimental isotherm data fitted well with the Langmuir, Freundlich and Dubinin-Redushkevich isotherm models. Thermodynamic parameters such as Gibbs free energy change, enthalpy change and entropy change were calculated and the results showed that the adsorption of nitrate on SMZ was spontaneous and exothermic in nature. The presence of competing anions such as chloride, sulfate and bicarbonate ions slightly reduced the nitrate adsorption efficiency. Anionic exchange and electrostatic interaction were proven to be the main mechanisms that govern the adsorption of nitrate on SMZ.

  3. Removal of Reactive Orange 16 Dye from Aqueous Solution by Using Modified Kenaf Core Fiber

    Directory of Open Access Journals (Sweden)

    Maytham Kadhim Obaid

    2016-01-01

    Full Text Available Evaluated removal of reactive orange 16 (RO16 dye from aqueous solution was studied in batch mode by using kenaf core fiber as low-cost adsorbents. In this attempt, kenaf core fiber with size 0.25–1 mm was treated by using (3-chloro-2-hydroxypropyl trimethylammonium chloride (CHMAC as quaternization agent. Then effective parameters include adsorbent dose, pH, and contact time and initial dye concentration on adsorption by modified kenaf core fiber was investigated. In addition, isotherms and kinetics adsorption studies were estimated for determination of the equilibrium adsorption capacity and reactions dynamics, respectively. Results showed that the best dose of MKCF was 0.1 g/100 mL, the maximum removal of RO16 was 97.25 at 30°C, pH = 6.5, and agitation speed was 150 rpm. The results also showed that the equilibrium data were represented by Freundlich isotherm with correlation coefficients R2=0.9924, and the kinetic study followed the pseudo-second-order kinetic model with correlation coefficients R2=0.9997 for Co=100 mg/L. Furthermore, the maximum adsorption capacity was 416.86 mg/g. Adsorption through kenaf was found to be very effective for the removal of the RO16 dye.

  4. In situ characterization of organo-modified and unmodified montmorillonite aqueous suspensions by UV-visible spectroscopy.

    Science.gov (United States)

    Alin, Jonas; Rubino, Maria; Auras, Rafael

    2015-10-15

    UV-visible (UV-Vis) spectroscopy (Tyndall spectra) was applied and tested for its ability to measure organo-modified and unmodified montmorillonite (MMT) clays in aqueous suspensions. A full factorial design of experiments was used to study the influence of pH, NaCl and clay concentrations on the average particle size of the clay agglomerates. The methodology was evaluated by observing results that were consistent with previous research about the unmodified clay's behavior in aqueous suspensions. The results from this evaluation corresponded to accepted theories about the unmodified clay's behavior, indicating that the methodology is precise enough to distinguish the effects of the studied factors on these clay suspensions. The effect of clay concentration was related to the amount of ions per clay particle for the unmodified clay, but was not significant for the organo-modified MMT. The average particle size of the organo-modified MMT in suspension was significantly larger than that of the unmodified clay. Size of the organo-modified MMT agglomerates in suspension decreased in the presence of NaCl and at both high and low pH; this behavior was opposite to that of the unmodified clay. These results demonstrate that the UV-Vis methodology is well-suited for characterizing clay particle size in aqueous suspensions. The technique also is simple, rapid, and low-cost. Copyright © 2015 Elsevier Inc. All rights reserved.

  5. Development of polymer films by the coalescence of polymer particles in powdered and aqueous polymer-modified mortars

    International Nuclear Information System (INIS)

    Afridi, M.U.K.; Ohama, Y.; Demura, K.; Iqbal, M.Z.

    2003-01-01

    This paper evaluates and compares the coalescence of polymer particles (continuous polymer films formation) in powdered polymer-modified mortars (PPMMs) and aqueous polymer-modified mortars (APMMs). Polymer-modified mortars (PMMs) using various redispersible polymer powders (powdered cement modifiers) and polymer dispersions (aqueous cement modifiers) were prepared by varying the polymer-cement ratio (P/C) and were tested for the characterization of polymer films using a scanning electron microscope (SEM) after curing for 28 days. It is concluded from the test results that mortar constituents of unmodified mortar (UMM) are loosely joined with each other due to the absence of polymer films, thus having a structure with comparatively lower mechanical and durability characteristics. By contrast, mortar constituents in PPMMs and APMMs are compactly joined with each other due to the presence of interweaving polymer films, thereby forming a monolithic structure with improved mechanical and durability characteristics. However, the results make obvious the poor coalescence of polymer particles or development of inferior quality polymers films in PPMMs as compared to that observed in APMMs. Moreover, PPMMs show less uniform distribution of polymer films as compared to that in APMMs. Different powdered cement modifiers have different film-forming capabilities. However, such difference is hardly recognized in aqueous cement modifiers. The polymer films in PPMMs and APMMs may acquire different structures. They may appear as mesh-like, thread-like, rugged, dense or fibrous with fine or rough surfaces. Development of coherent polymer films is not well pronounced at a P/C of 5% in PPMMs, whereas sometimes coherent polymer films are observed at a P/C of 5% in APMMs. At a P/C of 10% or more, fully developed, coherent polymer films are observed in both PPMMs and APMMs

  6. Sodium sulfite pH-buffering effect for improved xylose-phenylalanine conversion to N-(1-deoxy-d-xylulos-1-yl)-phenylalanine during an aqueous Maillard reaction.

    Science.gov (United States)

    Cui, Heping; Duhoranimana, Emmanuel; Karangwa, Eric; Jia, Chengsheng; Zhang, Xiaoming

    2018-04-25

    The yield of the Maillard reaction intermediate (MRI), prepared in aqueous medium, is usually unsatisfactory. However, the addition of sodium sulfite could improve the conversion of xylose-phenylalanine (Xyl-Phe) to the MRI (N-(1-deoxy-d-xylulos-1-yl)-phenylalanine) in aqueous medium. Sodium sulfite (Na 2 SO 3 ) showed a significant pH-buffering effect during the Maillard reaction, which accounted for its facilitation of the N-(1-deoxy-d-xylulos-1-yl)-phenylalanine yield. The results revealed that the pH could be maintained at a relatively high level (above 7.0) for an optimized pH-buffering effect when Na 2 SO 3 (4.0%) was added before the reaction of Xyl-Phe. Thus, the conversion of Xyl-Phe to N-(1-deoxy-d-xylulos-1-yl)-phenylalanine increased from 47.23% to 74.86%. Furthermore, the addition moment of Na 2 SO 3 and corresponding solution pH were crucial factors in regulating the pH-buffering effect of Na 2 SO 3 on N-(1-deoxy-d-xylulos-1-yl)-phenylalanine yield. Based on the pH-buffering effect of Na 2 SO 3 and maintaining the optimal pH 7.4 relatively stable, the conversion of Xyl-Phe to N-(1-deoxy-d-xylulos-1-yl)-phenylalanine was successfully improved. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Application of modified multiwall carbon nanotubes as a sorbent for zirconium (IV) adsorption from aqueous solution

    International Nuclear Information System (INIS)

    Yavari, R.; Davarkhah, R.

    2013-01-01

    Modified multiwall carbon nanotubes (MWCNTs) by nitric acid solution were used to investigate the adsorption behavior of zirconium from aqueous solution. Pristine and oxidized MWCNTs were characterized using nitrogen adsorption/desorption isotherm, Boehm's titration method, thermogravimetry analysis, transmission electron microscopy and Fourier transform infrared spectroscopy. The results showed that the surface properties of MWCNTs such as specific surface area, total pore volume, functional groups and the total number of acidic and basic sites were improved after oxidation. These improvements are responsible for their hydrophobic properties and consequently an easy dispersion in water and suitable active sites for more adsorption of zirconium. The adsorption of Zr(IV) as a function of initial concentration of zirconium, contact time, MWCNTs dosage, HCl and HNO 3 concentration and also ionic strength was investigated using a batch technique under ambient conditions. The experimental results indicated that sorption of Zr(IV) was strongly influenced by zirconium concentrations, oxidized MWCNTs content and acid pH values. The calculated correlation coefficient of the linear regressions values showed that Langmuir model fits the adsorption equilibrium data better than the Freundlich model. Kinetic data of sorption indicated that equilibrium was achieved within 60 min and the adsorption process can be described by the pseudo second-order reaction rate model. Based on the experimental results, surface complexation is the major mechanism for adsorption of Zr(IV) onto MWCNTs. Also, Study on the desorption process of zirconium showed that the complete recovery can be obtained using nitric or hydrochloric acids of 4 M. (author)

  8. Control of Electrostatic Interactions Between F-Actin And Genetically Modified Lysozyme in Aqueous Media

    International Nuclear Information System (INIS)

    Sanders, L.K.; Xian, W.; Guaqueta, C.; Strohman, M.; Vrasich, C.R.; Luijten, E.; Wong, G.C.L.

    2009-01-01

    The aim for deterministic control of the interactions between macroions in aqueous media has motivated widespread experimental and theoretical work. Although it has been well established that like-charged macromolecules can aggregate under the influence of oppositely charged condensing agents, the specific conditions for the stability of such aggregates can only be determined empirically. We examine these conditions, which involve an interplay of electrostatic and osmotic effects, by using a well defined model system composed of F-actin, an anionic rod-like polyelectrolyte, and lysozyme, a cationic globular protein with a charge that can be genetically modified. The structure and stability of actin-lysozyme complexes for different lysozyme charge mutants and salt concentrations are examined by using synchrotron x-ray scattering and molecular dynamics simulations. We provide evidence that supports a structural transition from columnar arrangements of F-actin held together by arrays of lysozyme at the threefold interstitial sites of the actin sublattice to marginally stable complexes in which lysozyme resides at twofold bridging sites between actin. The reduced stability arises from strongly reduced partitioning of salt between the complex and the surrounding solution. Changes in the stability of actin-lysozyme complexes are of biomedical interest because their formation has been reported to contribute to the persistence of airway infections in cystic fibrosis by sequestering antimicrobials such as lysozyme. We present x-ray microscopy results that argue for the existence of actin-lysozyme complexes in cystic fibrosis sputum and demonstrate that, for a wide range of salt conditions, charge-reduced lysozyme is not sequestered in ordered complexes while retaining its bacterial killing activity.

  9. Solid-state mAbs and ADCs subjected to heat-stress stability conditions can be covalently modified with buffer and excipient molecules.

    Science.gov (United States)

    Valliere-Douglass, John F; Lewis, Patsy; Salas-Solano, Oscar; Jiang, Shan

    2015-02-01

    We report that a unique type of chemical modification occurs on lyophilized proteins. Freeze-dried mAbs and antibody-drug conjugates (ADCs) can be covalently modified with buffer and excipient molecules on the side chains of Glu, Asp, Thr, and Ser amino acids when subjected to temperature stress. The reaction occurs primarily via condensation of common buffers and excipients such as histidine, tris, trehalose and sucrose, with Glu and Asp carboxylates in the primary sequence of proteins. The reaction was also found to proceed through condensation of carboxylate containing buffers such as citrate, with Thr and Ser hydroxyls in the primary sequence of proteins. Based on the mass of the covalent adducts observed on mAbs and ADCs, it is apparent that the reaction produces water as a product and is thus favored in a low moisture environments such as a lyophilized protein cake. Herein, we present the evidence for the covalent modification of proteins drawn from case studies of in-depth characterization of heat-stressed mAbs and ADCs in the solid state. We also demonstrate how common charge variant assays such as imaged capillary isoelectric focusing and mass spectrometry can be used to monitor this specific class of protein modification. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

  10. Integration of carboxyl modified magnetic particles and aqueous two-phase extraction for selective separation of proteins.

    Science.gov (United States)

    Gai, Qingqing; Qu, Feng; Zhang, Tao; Zhang, Yukui

    2011-07-15

    Both of the magnetic particle adsorption and aqueous two-phase extraction (ATPE) were simple, fast and low-cost method for protein separation. Selective proteins adsorption by carboxyl modified magnetic particles was investigated according to protein isoelectric point, solution pH and ionic strength. Aqueous two-phase system of PEG/sulphate exhibited selective separation and extraction for proteins before and after magnetic adsorption. The two combination ways, magnetic adsorption followed by ATPE and ATPE followed by magnetic adsorption, for the separation of proteins mixture of lysozyme, bovine serum albumin, trypsin, cytochrome C and myloglobin were discussed and compared. The way of magnetic adsorption followed by ATPE was also applied to human serum separation. Copyright © 2011 Elsevier B.V. All rights reserved.

  11. Zirconium-modified materials for selective adsorption and removal of aqueous arsenic

    Science.gov (United States)

    Zhao, Hongting; Moore, Robert C.

    2004-11-30

    A method, composition, and apparatus for removing contaminant species from an aqueous medium comprising: providing a material to which zirconium has been added, the material selected from one or more of zeolites, cation-exchangeable clay minerals, fly ash, mesostructured materials, activated carbons, cellulose acetate, and like porous and/or fibrous materials; and contacting the aqueous medium with the material to which zirconium has been added. The invention operates on all arsenic species in the form of arsenate, arsenite and organometallic arsenic, with no pretreatment necessary (e.g., oxidative conversion of arsenite to arsenate).

  12. Chelate-Modified Fenton Reaction for the Degradation of Trichloroethylene in Aqueous and Two-Phase Systems

    Energy Technology Data Exchange (ETDEWEB)

    Lewis, Scott [Univ of KY, dept of chemical and materials engineering; lynch, Andrew [Univ of KY, dept of chemical and materials engineering; Bachas, Leonidas [Univ of KY, Dept of Chemistry; hampson, Steve [Univ of KY Center for Applied Energy Research - KY Research Consortium of Energy and Environment; Ormsbee, Lindelle [Univ of KY Center for Applied Energy Research - KY Research Consortium of Energy and Environment; Bhattacharyya, Dibakar [Univ of KY, dept of chemical and materials engineering

    2008-06-01

    The Standard Fenton reaction has been used for In-Situ Chemical Oxidation (ISCO) of toxic organics in groundwater. However, it requires low pH operating conditions, and thus has limitations for in situ applications. In addition, hydroxyl radicals are rapidly consumed by hydroxyl scavengers found in the subsurface. These problems are alleviated through the chelate-modified Fenton (hydroxyl radical) reaction, which includes the addition of nontoxic chelate (L) such as citrate or gluconic acid. This chelate allows the reaction to take place at bear neutral pH and control hydrogen peroxide consumption by binding to Fe(II), forming an FeL complex. The chelate also binds to Fe(III), preventing its precipitation as ferric hydroxide and thus prevents problems associated with injection well plugging. The rate of TCE dechlorination in chelate-modified Fenton systems is a function of pH, H2O2 concentration, and FE:L ratio. The primary objective of this research is to model and apply this process to the destruction of trichloroethylene (TCE) present in both the aqueous and organic (in the form of droplets) phases. Experimentation proved the chelate-modified Fenton reaction effectively dechlorinates TCE in both the aqueous and organic phases at near-neutral pH. Other focuses of this work include determining the effect of [L]:[Fe] ratios on H2O2 and TCE degradation as well as reusability of the FE citrate solution under repeated H2O2 injections. Generalized models were developed to predict the concentration of TCE in the aqueous phase and TCE droplet radius as a function of time using established hydroxyl radial kinetics and mass transfer relationships.

  13. Functional solid additive modified PEDOT:PSS as an anode buffer layer for enhanced photovoltaic performance and stability in polymer solar cells

    Science.gov (United States)

    Xu, Binrui; Gopalan, Sai-Anand; Gopalan, Anantha-Iyengar; Muthuchamy, Nallal; Lee, Kwang-Pill; Lee, Jae-Sung; Jiang, Yu; Lee, Sang-Won; Kim, Sae-Wan; Kim, Ju-Seong; Jeong, Hyun-Min; Kwon, Jin-Beon; Bae, Jin-Hyuk; Kang, Shin-Won

    2017-01-01

    Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is most commonly used as an anode buffer layer in bulk-heterojunction (BHJ) polymer solar cells (PSCs). However, its hygroscopic and acidic nature contributes to the insufficient electrical conductivity, air stability and restricted photovoltaic (PV) performance for the fabricated PSCs. In this study, a new multifunctional additive, 2,3-dihydroxypyridine (DOH), has been used in the PEDOT: PSS buffer layer to obtain modified properties for PEDOT: PSS@DOH and achieve high PV performances. The electrical conductivity of PEDOT:PSS@DOH films was markedly improved compared with that of PEDOT:PSS. The PEDOT:PSS@DOH film exhibited excellent optical characteristics, appropriate work function alignment, and good surface properties in BHJ-PSCs. When a poly(3-hexylthiohpene):[6,6]-phenyl C61-butyric acid methyl ester blend system was applied as the photoactive layer, the power conversion efficiency of the resulting PSCs with PEDOT:PSS@DOH(1.0%) reached 3.49%, outperforming pristine PEDOT:PSS, exhibiting a power conversion enhancement of 20%. The device fabricated using PEDOT:PSS@DOH (1.0 wt%) also exhibited improved thermal and air stability. Our results also confirm that DOH, a basic pyridine derivative, facilitates adequate hydrogen bonding interactions with the sulfonic acid groups of PSS, induces the conformational transformation of PEDOT chains and contributes to the phase separation between PEDOT and PSS chains. PMID:28338088

  14. Glassy carbon electrode modified by conductive polyaniline coating for determination of trace lead and cadmium ions in acetate buffer solution

    International Nuclear Information System (INIS)

    Wang Zhaomeng; Liu Erjia; Zhao Xing

    2011-01-01

    Polyaniline (PANI) coatings were electrodeposited on the surfaces of glassy carbon electrodes (GCEs) to form new electrodes, i.e. PANI/GCEs. It was found that with increased deposition time, the PANI coatings became more compact while the charge transfer resistance of the coatings became higher. The PANI/GCEs were used to detect Cd 2+ and Pb 2+ ions contained in 0.1 M acetate buffer solutions using square wave anodic stripping voltammetry (SWASV). It was found that the PANI/GCE had a highest anodic stripping peak current in a solution of pH 5.3. The study of the cleaning performance of the PANI/GCEs indicated that there were less remaining metals on the surfaces of the PANI/GCEs compared to the bare GCEs after cleaning at a potential of 0.4 V, which was probably due to that the PANI coatings could effectively prevent the deposition of the metals into the surface defects of the GCEs. The PANI coatings could also reduce the passivation effect of the GCEs, thus improving the repeatability of the electrodes.

  15. Iron and manganese oxides modified maize straw to remove tylosin from aqueous solutions.

    Science.gov (United States)

    Yin, Yongyuan; Guo, Xuetao; Peng, Dan

    2018-08-01

    Maize straw modified by iron and manganese oxides was synthesized via a simple and environmentally friendly method. Three maize straw materials, the original maize straw, maize straw modified by manganese oxides and maize straw modified by iron and manganese oxides, were detected by SEM, BET, XPS, XRD and FTIR. The results showed that maize straw was successfully modified and maize straw modified by iron and manganese oxides has a larger surface area than MS. According to the experimental data, the sorption trend could conform to the pseudo-second-order kinetic model well, and the sorption ability of tylosin on sorbents followed the order of original maize straw oxides iron and manganese oxides. The study indicated that manganese oxides and iron-manganese oxides could significantly enhance the sorption capacity of original maize straw. The sorption isotherm data of tylosin on original maize straw fit a linear model well, while Freundlich models were more suitable for maize straw modified by manganese oxides and maize straw modified by iron and manganese oxides. The pH, ionic strength and temperature can affect the sorption process. The sorption mechanisms of tylosin on iron and manganese oxides modified maize straw were attribute to the surface complexes, electrostatic interactions, H bonding and hydrophobic interactions. Copyright © 2018 Elsevier Ltd. All rights reserved.

  16. Solid phase extraction of uranium and thorium on octadecyl bonded silica modified with Cyanex 302 from aqueous solutions

    International Nuclear Information System (INIS)

    Nilchi, A.; Shariati Dehaghan, T.; Rasouli Garmarodi, S.

    2013-01-01

    A simple and reliable method for rapid extraction and determination of uranium and thorium using octadecyl-bonded silica modified with Cyanex 302 is presented. Extraction efficiency and the influence of various parameters such as aqueous phase pH, flow rate of sample solution and amount of extractant has been investigated. The study showed that the extraction of uranium and thorium increase with increasing pH value and was found to be quantitative at pH 6; and the retention of ions was not affected significantly by the flow rate of sample solution. The extraction percent were found to be 89.55 and 86.27 % for uranium and thorium, respectively. The maximal capacity of the cartridges modified by 30 mg of Cyanex 302 was found to be 20 mg of uranium and thorium. The method was successfully applied to the extraction and determination of uranium and thorium in aqueous solutions. The percentage recovery of uranium and thorium in a number of natural as well as seawater samples of Iran were also investigated and found to be in the range of 85-95%. (author)

  17. Adsorption of and acidic dye from aqueous solution by surfactant modified bentonite

    International Nuclear Information System (INIS)

    Bouberka, Z.; Khenifi, A.; Belkaid, N.; Ait Mahamed, H.; Haddou, B.; Derriche, Z.

    2009-01-01

    The aim of this paper is to study the adsorption of an acidic dye S. Y. 4 GL (i.e: Supranol yellow 4GL) from aqueous solution on inorgano-organo clay. Bentonite is a kind of natural clay with good exchanging ability. By exchanging its inter lamellar cations with Cetyltrimethylammonium bromide (CTAB) and hydroxy aluminic or chromium poly cations, the properties of natural bentonite can be greatly improved. (Author)

  18. Influence of pyrolysis temperature on lead immobilization by chemically modified coconut fiber-derived biochars in aqueous environments.

    Science.gov (United States)

    Wu, Weidong; Li, Jianhong; Niazi, Nabeel Khan; Müller, Karin; Chu, Yingchao; Zhang, Lingling; Yuan, Guodong; Lu, Kouping; Song, Zhaoliang; Wang, Hailong

    2016-11-01

    Biochar has received widespread attention as an eco-friendly and efficient material for immobilization of toxic heavy metals in aqueous environments. In the present study, three types of coconut fiber-derived biochars were obtained by pyrolyzing at three temperatures, i.e., 300, 500, and 700 °C. In addition, nine types of biochars were prepared by chemical modification with ammonia, hydrogen peroxide, and nitric acid, respectively, which were used to investigate changes in physico-chemical properties by inter alia, Fourier transformation infrared spectrophotometry (FTIR), scanning electron microscope (SEM), and BET specific surface area analysis. Batch sorption experiments were carried out to determine the sorption capacity of the biochars for lead (Pb) in aqueous solutions. Results showed that the cation exchange capacity of biochar pyrolyzed at 300 °C and modified with nitric acid increased threefold compared to the control. Loosely corrugated carbon surface and uneven carbon surface of the biochar pyrolyzed at 300 °C were produced during ammonia and nitric acid modifications. Removal rate of Pb by the coconut biochar pyrolyzed at 300 °C and modified with ammonia was increased from 71.8 to 99.6 % compared to the untreated biochar in aqueous solutions containing 100 mg L -1 Pb. However, chemical modification did not enhance adsorption of Pb of the biochars pyrolyzed at higher temperatures (e.g., 500 or 700 °C), indicating that resistance of biochars to chemical treatment increased with pyrolysis temperature.

  19. Experimental data for aluminum removal from aqueous solution by raw and iron-modified granular activated carbon

    Directory of Open Access Journals (Sweden)

    Mokhtar Mahdavi

    2018-04-01

    Full Text Available This dataset deals with the modification of granular activated carbon (GAC with FeCl3 under basic conditions (pH ≈ 12 for removal of aluminium (Al from aqueous solution. The structural properties and operational parameters including Al ion concentration (2.15 and 10.3 mg/L, pH solution (2–10, adsorbent dosage (0.1–5 g/L, and contact time (0–10 h was investigated for raw and modified GAC. This dataset provides information about Al removal by GAC and modified GAC at conditions including: pH = 8, contact time = 6 h, initial Al concentration = 2.15 mg/L. The characterization data of the adsorbents was analysed by Fourier transform infrared (FTIR spectroscopy, scanning electron microscopy (SEM and Brunauer, Emmett and Teller (BET test. The data showed that Freundlich isotherm with and Pseudo second order kinetic model were the best models for describing the Al adsorption reactions. The acquired data indicated that the maximum adsorption capacity of GAC and modified GAC to uptake Al (C0 = 10.3 mg/L was 3 and 4.37 mg/g respectively. Keywords: Aluminium removal, Adsorption, Iron-modified GAC, Water treatment

  20. Efficiency Comparison of Modified-Clay and Lime-Marlin the Adsorption of Fluoride from Aqueous Solution

    Directory of Open Access Journals (Sweden)

    Mohammad Taghi Samadi

    2016-06-01

    Full Text Available Background and purpose: Fluoride is one of the common anion in water that its concentration varies in different water supplies. Most of the body's requirement for fluoride is supplied through drinking water. Fluoride in low concentration is essential for human health but in high concentration is very hazardous for human health. The efficiency of modified-clay and lime-marl were investigated in this research as an adsorbent for the elimination of fluoride from aqueou solution.  Methods: In this study, the capability of modified-clay and lime-marl to adsorb fluoride ions was conducted using a series of batch tests in a shaker-incubator instrument. The effect of experimental parameters such as pH (4,7,10,  adsorbent dosage (1,5,10 g/L, initial fluoride concentration  (5,10,15 mg/L andcontact time (15-120 min were evaluated. The morphological and micro-structural character of  modified-clay and lime-marl have performed by using X-ray diffraction (XRD. The formation of the carboxylic functional groups was verified by Fourier transform infrared spectra (FT-IR.  Findings: results well demonstrate higher removal efficiency of fluoride was 95.23% and 28.71 by clay-modified and lime-marl, respectively; at 10 mg/L of fluoride concentration and 60 min contact time. The adsorption kinetics fitted well using the pseudo second-order kinetic model; however, equlibrium data were best fitted onto Langmiur isotherm model. The maximum adsorption capacities of modified-clay and lime-marl for fluoride were found to be 4.43 mg/g and 1.32 mg/g, respectively. Conclusion: According to our finding, it proposed that adsorption process by using modified clay is very efficient and economic process for fluoride removal from aqueous solution.

  1. Arsenic removal from aqueous solutions by sorption onto zirconium- and titanium-modified sorbents

    Directory of Open Access Journals (Sweden)

    Ignjatović Ljubiša

    2011-01-01

    Full Text Available Arsenic reduction in drinking water can include treatment by adsorption, switching to alternative water sources, or blending with water that has a lower arsenic concentration. Commercial sorbents MTM, Greensand and BIRM (Clack Corporation were modified with zirconium and titanium after activation. The modifications were performed with titanium tetrachloride and zirconium tetrachloride. The modified sorbents were dried at different temperatures. The sorption of arsenate and arsenite dissolved in drinking water (200μg L-1 onto the sorbents were tested using a batch procedure. After removal of the sorbent, the concentration of arsenic was determined by HG-AAS. Zirconium-modified BIRM showed the best performance for the removal of both arsenite and arsenate. Modification of the greensand did not affect arsenic sorption ability. Zirconium-modified BIRM diminished the concentration of total As to below 5 μg L-1.

  2. Chemically modified Moringa oleifera seed husks as low cost adsorbent for removal of copper from aqueous solution

    Science.gov (United States)

    Ghafar, Faridah; Mohtar, Aminullah; Sapawe, Norzahir; Hadi, Norulakmal Nor; Salleh, Marmy Roshaidah Mohd

    2017-12-01

    Moringa oleifera husks (MOH) are an agricultural byproduct that may have potential as adsorbent for removal of heavy metal ions in wastewater such as copper (Cu2+). The release of Cu2+ to the environment by the mining and electroplating industries cause a major problem because it is toxic and can cause liver and kidney problems. Hence, it is important to remove copper before the wastewater can be discharged to the environment. In order to increase the adsorption capacity, the MOH was chemically modified using citric acid. The raw and modified MOH were analyzed using Fourier Transform Infra-Red (FTIR) for identification of functional groups present at the adsorbent surface. The adsorption study was carried out using the batch technique in water bath shaker investigating different parameters; adsorbent dosage (30 - 70 g/L), initial concentration of copper (30 - 150 mg/L), contact time (2 - 90 min), temperature (27 - 60 °C) at constant agitation of 100 rpm. The concentrations of copper in aqueous solution before and after the adsorption process was analyzed using Atomic Absorption Spectrum (AAS). The highest percentage removal of copper was found at 10g/L of adsorbent dosage with 30 mg/L of initial concentration and temperature 30 °C. It was also observed that the adsorption of copper by MOH was approaching to equilibrium at 60 min of reaction time. From the FTIR analysis, it was found that the MOH contains hydroxyl, carboxyl and amine groups. The high adsorption capacity of modified MOH to remove copper from aqueous solution makes it preferable and attractive alternative to commercial adsorbent.

  3. Effective removal of hexavalent mercury from aqueous solution by modified polymeric nanoadsorbent

    Directory of Open Access Journals (Sweden)

    Lida Rahmanzadeh

    2016-07-01

    Full Text Available Mercury is one of the most toxic metals present in the environment. Adsorption has been proposed among the technologies for mercury adsorbent. The kinetics of adsorption depends on the adsorbent concentration, and the physical and chemical characteristics of adsorbent. In this study we were used a novel adsorbent, magnetite-polyrhodanine core- shell nanoparticles, for removing Hg(II from aqueous solution. The effect of pH, initial Hg(II concentration, initial adsorbent concentration and contact time on the efficiency of Hg(II removal were investigated systematically by batch experiments. The maximum adsorption capacity was obtained 29.14 mg g-1 at PH=6.5 and 25°C with 10 g L-1 nano adsorbent. The kinetic data of adsorption of Hg(II ion on the synthesized adsorbent were best described by a pseudo- second- order equation, indicating their chemical adsorption. The Freundlich, Langmuir and Temkin isotherms were used to modeling of mercury adsorption on Hg(II in aqueous medium which modeled best by the Freundlich isotherm is whole concentration rage.

  4. The Photocatalytic Removal of Ortho Chlorophenol from Aqueous Solution Using Modified Fly Ash - Titanium Dioxide

    Directory of Open Access Journals (Sweden)

    Mohamad Malakootian

    2016-05-01

    Full Text Available The photocatalytic process is a useful method for the effective removal of phenolic compounds. Conducted in the spring‒summer 2013 at the Engineering Research Center for Environmental Health, Kerman University of Medical Sciences, this experimental study used a modified fly ash‒TiO2 mixture to enhance the photocatalytic removal efficiency of ortho-chlorophenol. Fly ash obatined from the Thermal Power Plant in Zarand, Kerman, was initially washed with sulfuric acid before being oxidized with potassium permanganate. The mixture of modified fly ash and TiO2 was then used for the removal of ortho-chlorophenol in the presence of UV light and the factors involved in the removal process were optimized. It was found that the ortho-chlorophenol removal efficiency recorded by the mixture of modified fly ash and TiO2 was higher than that by each of the modified fly ash or TiO2/UV alone. It was, further, observed that removal efficiency with a modified fly ash to TiO2 ratio of 3:1 rose to 98.8% under optimum conditions (i.e., pH: 2; contact time: 2 h; room temperature (29±2˚C, and a catalyst dose of 0.6 g. The ortho-chlorophenol removal efficiency in real wastewater from the Coal Wash Plant in Zarand was recorded at 88.4%. Based on the results obtained from simultaneous use of modified fly ash and TiO2, the proposed method may be recommended for industrial applications.

  5. Removal of lead from aqueous solutions by using the natural and Fe(III)-modified zeolite

    International Nuclear Information System (INIS)

    Kragović, Milan; Daković, Aleksandra; Sekulić, Živko; Trgo, Marina; Ugrina, Marin; Perić, Jelena; Gatta, G. Diego

    2012-01-01

    In the present study, the sorption of lead by the natural and Fe(III)-modified zeolite (clinoptilolite) is described. The characterization of the natural zeolite-rich rock and the Fe(III)-modified form was performed by chemical analysis, point of the zero charge (pH pzc ), X-ray powder diffraction, applying the Rietveld/RIR method for the quantitative phase analysis, and scanning electron microscopy. The effects of sorbents dose and the initial lead concentrations on its sorption by two sorbents were investigated. For both sorbents, it was determined that at lower initial concentrations of lead, ion exchange of inorganic cations in zeolites with lead, together with uptake of hydrogen dominated, while at higher initial lead concentrations beside these processes, chemisorption of lead occurred. Significantly higher sorption of lead was achieved with Fe(III)-modified zeolite. From sorption isotherms, maximum sorbed amounts of lead, under the applied experimental conditions, were 66 mg/g for the natural and 133 mg/g for Fe(III)-modified zeolite. The best fit of experimental data was achieved with the Freundlich model (R 2 ≥ 0.94).

  6. Natural silica sand modified by calcium oxide as a new adsorbent for uranyl ions removal from aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Elhefnawy, O.A.; Elabd, A.A. [Nuclear and Radiological Regulatory Authority (NRRA), Cairo (Egypt). Nuclear Safeguards and Physical Protection Dept.

    2017-07-01

    Calcium oxide modified El-Zafarana silica sand (CMZS) was prepared as a new adsorbent for U(VI) removal from aqueous solutions in a series of batch experiments. The new adsorbent CMZS was characterized by different analysis techniques SEM, EDX, XRD, and FTIR. The influence of many parameters on the removal process like; effect of pH, contact time, U(VI) initial concentration and temperature on U(VI) removal were investigated. Kinetic experiments showed that U(VI) removal on CMZS followed pseudo-second-order kinetics model appropriately and the equilibrium data agreed well with the Langmuir isotherm model. Kinetics and isothermal data reveal the chemisorption process of U(VI) on CMZS. The thermodynamic parameters (ΔH {sup circle}, ΔS {sup circle}, ΔG {sup circle}) were evaluated from temperature dependent adsorption data and the U(VI) removal on CMZS was found to be endothermic and spontaneous in nature. U(VI) desorption from CMZS was studied by a simple acid treatment. The results indicate that CMZS is an effective adsorbent for U(VI) from aqueous solutions.

  7. Prediction of non-polar gas solubilities in water, alcohols and aqueous alcohol solutions by the modified ASOG method

    Energy Technology Data Exchange (ETDEWEB)

    Tochigi, K.; Kojima, K.

    1982-07-01

    This study evaluated a technique for predicting gas solubilities based on a modified ASOG group-contribution method, considering water, alcohols, and aqueous alcohol solutions as the solvents. The nonpolar gaseous solutes considered were oxygen, nitrogen, hydrogen, carbon dioxide, argon, methane, ethane, ethylene, propane, and butane. Gas solubilities were correlated and predicted for a partial gas pressure of 1 atm and a temperature range of 50/sup 0/-100/sup 0/F (10/sup 0/-40/sup 0/C) in pure solvents, and then predicted for the same pressure and temperature range in mixed solvents using only the solubility data for the pure solvents. The deviations between the observed and predicted solubilities averaged 6.0% in pure systems and 10.2% in mixed solvents.

  8. Zinc, nickel, and cobalt ions removal from aqueous solution and plating plant wastewater by modified Aspergillus flavus biomass: A dataset

    Directory of Open Access Journals (Sweden)

    Rauf Foroutan

    2017-06-01

    Full Text Available The biomass of Aspergillus flavus was modified by calcium chloride to achieve a bioadsorbent for treating nickel, cobalt, and zinc ions from aqueous solutions. The information of pH, bioadsorbent dose, contact time, and temperature effect on the removal efficiency are presented. The data of Freundlich and Langmuir isotherm and pseudo-first-order and pseudo-second-order kinetic models are also depicted. The data showed that the maximum bioadsorption capacity of nickel, cobalt, and zinc ions is 32.26, 31.06 and 27.86 mg/g, respectively. The suitability of the bioadsorbent in heavy metals removal at field condition was tested with a real wastewater sample collected from a plating plant in the final part of this dataset. Based on the findings, the bioadsorbent was shown to be an affordable alternative for the removal of metals in the wastewater.

  9. Rapid analysis of carbohydrates in aqueous extracts and hydrolysates of biomass using a carbonate-modified anion-exchange column.

    Science.gov (United States)

    Sevcik, Richard S; Mowery, Richard A; Becker, Christopher; Chambliss, C Kevin

    2011-03-04

    Quantitative liquid-chromatography techniques used to characterize carbohydrates present in biomass samples can suffer from long analysis times, limited analyte resolution, poor stability, or a combination of these factors. The current manuscript details a novel procedure enabling resolution of glucose, xylose, arabinose, galactose, mannose, fructose, and sucrose via isocratic elution in less than 5 min. Equivalent conditions also enable analysis of cellobiose and maltose with a minimal increase in chromatographic run time (ca. 3 and 6 min, respectively). Noted chromatographic performance requires that a commercially available anion-exchange column be modified with carbonate prior to analysis. Analytical performance of a modified column was assessed over a 5-day period via repeated analyses of 4 samples, resulting from aqueous extraction or quantitative saccharification of a potential biofuel feedstock (i.e., corn stover or switchgrass). A simple solid phase extraction procedure was utilized to clean up each sample prior to analysis. Analytical accuracy of the extraction protocol was assessed by evaluation of matrix spike recoveries which typically ranged from 84% to 98%. The instrumental variability of measured concentrations in real samples over the 5-day period was generally less than 5% RSD for all detected analytes, independent of sample type. Finally, it is important to note that the modified column exhibited exceptional stability over approximately 800 injections of biofeedstock-based samples. These data demonstrate that a carbonate-modified anion-exchange column can be employed for rapid determination of carbohydrates in biomass samples of lignocellulosic origin. Copyright © 2011 Elsevier B.V. All rights reserved.

  10. Elimination of reactive blue 4 from aqueous solutions using 3-aminopropyl triethoxysilane modified chitosan beads.

    Science.gov (United States)

    Vakili, Mohammadtaghi; Rafatullah, Mohd; Salamatinia, Babak; Ibrahim, Mahamad Hakimi; Abdullah, Ahmad Zuhairi

    2015-11-05

    The adsorption behavior of chitosan (CS) beads modified with 3-aminopropyl triethoxysilane (APTES) for the removal of reactive blue 4 (RB4) in batch studies has been investigated. The effects of modification conditions, such as the APTES concentration, temperature and reaction time on RB4 removal, were studied. The adsorbent prepared at a concentration of 2 wt% APTES for 8h at 50 °C was the most effective one for RB4 adsorption. The adsorption capacity of modified CS beads (433.77 mg/g) was 1.37 times higher than that of unmodified CS beads (317.23 mg/g). The isotherm data are adequately described by a Freundlich model, and the kinetic study revealed that the pseudo-second-order rate model was in better agreement with the experimental data. The negative values of the thermodynamic parameters, including ΔG° (-2.28 and -4.70 kJ/mol at 30 ± 2 °C), ΔH° (-172.18 and -43.82 kJ/mol) and ΔS° (-560.71 and -129.08 J/mol K) for CS beads and APTES modified beads, respectively, suggest that RB4 adsorption is a spontaneous and exothermic process. Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. Performance of Cationic Surfactant Modified Sepiolite and Bentonite in Lead Sorption from Aqueous Solutions

    Directory of Open Access Journals (Sweden)

    H.R. Rafiei

    2014-12-01

    Full Text Available The remediation of soils and water contaminated with heavy metals generate a great need to develop efficient adsorbents for these pollutants. This study reports the sorption of lead (Pb by bentonite (Bent, and sepiolite (Sep, that were modified with cetyltrimethyl ammonium (CTMA+ organic cations. The natural and surfactant modified clays (organo-clays were characterized with some instrumental techniques including XRF, XRD, FTIR and SEM. Sorption studies were performed in a batch system, and the effects of various experimental parameters including contact time and initial Pb concentration were evaluated upon the Pb sorption onto sorbents. Maximum sorption of Pb was found to be, 83.26, 71.36, 56.25 and 37 mg g-1 for Sep, CTMA-Sep, Bent and CTMA-Bent adsorbents, respectively. The Pb sorption data were fitted to both the Langmuir and Freundlich models. The Freundlich model represented the sorption process better than the Langmuir model. Lead sorption rate was found to be considerably slower for organo-clays than that for unmodified clays. Sorption kinetics was evaluated by pseudo-first order, pseudo-second order, Elovich and intraparticle diffusion models. The sorption processes of organo-clays followed intraparticle diffusion kinetics. The results showed that the cationic surfactant modified bentonite and sepiolite sorbed less Pb than the unmodified clays.

  12. Polyethylene imine modified hydrochar adsorption for chromium (VI) and nickel (II) removal from aqueous solution.

    Science.gov (United States)

    Shi, Yuanji; Zhang, Tao; Ren, Hongqiang; Kruse, Andrea; Cui, Ruofan

    2018-01-01

    An adsorbent hydrochar was synthesized from corn cobs and modified with polyethylene imine (PEI). The hydrochars before and after modification were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis. FTIR and XPS revealed that the PEI was grafted onto the hydrochar via ether and imine bonds formed with glutaraldehyde. The maximum adsorption capacities for Cr(VI) (33.663mg/g) and Ni(II) (29.059mg/g) on the modified hydrochars were 365% and 43.7% higher, respectively, than those on the unmodified hydrochar. A pseudo-second-order model described the adsorption of Ni(II) and Cr(VI) on all the adsorbents. The adsorption of Cr(VI) was endothermic, spontaneous, increased disorder, and obeyed the Langmuir model. By contrast, the adsorption of Ni(II) was exothermic, spontaneous, decreased disorder, and obeyed the Freundlich model. XPS confirmed that the adsorption sites and mechanisms for Ni(II) and Cr(VI) on the modified hydrochars were different. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. High-performance tandem organic light-emitting diodes based on a buffer-modified p/n-type planar organic heterojunction as charge generation layer

    Science.gov (United States)

    Wu, Yukun; Sun, Ying; Qin, Houyun; Hu, Shoucheng; Wu, Qingyang; Zhao, Yi

    2017-04-01

    High-performance tandem organic light-emitting diodes (TOLEDs) were realized using a buffer-modified p/n-type planar organic heterojunction (OHJ) as charge generation layer (CGL) consisting of common organic materials, and the configuration of this p/n-type CGL was "LiF/N,N'-diphenyl-N,N'-bis(1-napthyl)-1,1'-biphenyl-4,4'-diamine (NPB)/4,7-diphenyl-1,10-phenanthroline (Bphen)/molybdenum oxide (MoOx)". The optimized TOLED exhibited a maximum current efficiency of 77.6 cd/A without any out-coupling techniques, and the efficiency roll-off was greatly improved compared to the single-unit OLED. The working mechanism of the p/n-type CGL was discussed in detail. It is found that the NPB/Bphen heterojunction generated enough charges under a forward applied voltage and the carrier extraction was a tunneling process. These results could provide a new method to fabricate high-performance TOLEDs.

  14. Application of walnut shell modified with Zinc Oxide (ZnO nanoparticles in removal of natural organic matters (NOMs from aqueous solution

    Directory of Open Access Journals (Sweden)

    ali naghizadeh

    2015-10-01

    Full Text Available Background & Aims of the Study: Natural organic matters (NOMs are a mixture of chemically complex polyelectrolytes produced mainly from the decomposition of plant and animal residues that are present in all surface and groundwater resources. This paper evaluates the aqueous NOMs adsorption efficiency on walnut shell modified with Zinc Oxide (ZnO. Materials & Methods: This study examined the feasibility of removing NOMs from aqueous solutions using walnut shell modified with ZnO. The effects of NOMs concentration, modified walnut shell with ZnO dosage, and pH on adsorption of NOMs by modified walnut shell with ZnO were evaluated. Results: The adsorption capacities of modified walnut shell with ZnO in the best conditions were 37.93 mg/g. The results also demonstrated that adsorption capacity of NOMs on modified walnut shell with ZnO was higher in lower pHs due to significantly high electrostatic attraction exists between the positively charged surface of the adsorbent and negatively charged NOMs. And finally adsorption capacity decreases as adsorbent dose increase. Conclusion: Walnut shell modified with ZnO can be proposed as a natural adsorbent in the removal of NOMs from aqueous solutions

  15. Preparation of Magnetic Sorbent with Surface Modified by C18for Removal of Selected Organic Pollutants from Aqueous Samples

    Science.gov (United States)

    Kuráň, Pavel; Pilnaj, Dominik; Ciencialová, Lucie; Pšenička, Martin

    2017-12-01

    Magnetic sorbents have great potential in environmental applications due to their simple synthesis and separation in magnetic field, usability in heterogeneous systems and low toxicity. Possible syntheses, surface modifications and characteristics were described by Li et al 2013. This type of solid-phase extraction is being successfully used in various fields as health care, microbiology, biotechnologies or sample preconcentration in analytical chemistry. In this preliminary study we report on the preparation and application of magnetically separable sorbent with surface modified by C18 alkyl chain for purification of water contaminated by environmentally hazardous organic compounds. Magnetic cores were co-precipitated from Fe2+ and Fe3+ chlorides in alkalic aqueous solution. Surface of synthetized Fe3O4 was modified with SiO2 by tetraethylorthosilicate to assure physico-chemical stability. Furthermore, Fe3O4/SiO2 complex has been treated by C18 functional group, which provides good affinity towards hydrophobic substances in water. Efficiency of sorption under various conditions has been examined on benzene, toluene, ethylbenzene and xylenes (BTEX), compounds found in petroleum products which contaminate air, soil and groundwater near of store tanks. Sorption kinetics was followed by gas chromatography with mass spectrometry. The preliminary sorption kinetics data and efficiency of BTEX removal point at the possible application of prepared magnetic sorbent for BTEX removal, especially for ethylbenzene and xylenes.

  16. Self-assembly modified-mushroom nanocomposite for rapid removal of hexavalent chromium from aqueous solution with bubbling fluidized bed.

    Science.gov (United States)

    Xu, Fei; Liu, Xu; Chen, Yijiao; Zhang, Ke; Xu, Heng

    2016-05-18

    A self-assembled modified Pleurotus Cornucopiae material (SMPM) combined with improved Intermittent Bubbling Fluidized Bed (IBFB) was investigated to remove the hexavalent chromium ions in aqueous solution. After the modification, the powder-like raw material gradually self-assembled together to SMPM, which had crinkly porous structure, improved the Cr-accommodation ability in a sound manner. Optimized by Taguchi method, Cr(VI) removal efficiency was up to 75.91% and 48.01% for 100 mg/L and 500 mg/L initial concentration of Cr(VI), respectively. Results indicated that the metal removal was dependent on dosage of adsorbent, particle diameter and treatment time. The experimental data obtained from the biosorption process was successfully correlated with Freundlich isotherm model. Thermodynamic study indicated the endothermic nature of the process. The results confirmed that self-assembly modified Pleurotus Cornucopiae material could be applied for the removal of heavy metal from wastewater in continuous fluidized bed process.

  17. Removal of U(VI) from aqueous solution using TiO{sub 2} modified β-zeolite

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Peng; Yuan, Ni; Xiong, Wei; Wu, Hanyu; Pan, Duoqiang; Wu, Wangsuo [Lanzhou Univ. (China). Radiochemistry and Nuclear Environment Laboratory; Ministry of Education, Lanzhou (China). Key Laboratory of Special Function Materials and Structure Design

    2017-07-01

    β-Zeolite was synthesized and modified with TiO{sub 2}. The synthesized materials were characterized and used for removal of U(VI) from aqueous solutions. The influences of pH, contact time and temperature on U(VI) adsorption onto modified β-zeolite by TiO{sub 2} were studied by batch technique, and XPS was employed to analysed the experimental data. The dynamic process showed that the adsorption of U(VI) onto TiO{sub 2}/β-zeolite matched the pseudo-second-order kinetics model, and the adsorption of U(VI) were significantly dependent on pH values. Through simulating the adsorption isotherms by Langmuir, Freundlich and Dubini-Radushkevich (D-R) models, it could be seen, respectively that the adsorption patterns of U(VI) onto TiO{sub 2}/β-zeolite were mainly controlled by surface complexation, and the adsorption processes were endothermic and spontaneous. The modification of β-zeolite by TiO{sub 2} it shows a novel material for the removing of U(VI) from water environment for industrialized application.

  18. Use of a La(III)-modified bentonite for effective phosphate removal from aqueous media

    Energy Technology Data Exchange (ETDEWEB)

    Kuroki, Vivian; Bosco, Giulianna E. [Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Rua Santa Adélia, 166, Santo André CEP 09210-170, SP (Brazil); Fadini, Pedro S.; Mozeto, Antonio A. [Laboratório de Biogeoquímica Ambiental, Núcleo de Estudos, Diagnósticos e Intervenções Ambientais, Departamento de Química, Universidade Federal de São Carlos, Cx. Postal 676, São Carlos CEP 13565-905, SP (Brazil); Cestari, Antonio R. [Department of Chemistry/CCET, Universidade Federal de Sergipe, São Cristóvão CEP 49100-000, SE (Brazil); Carvalho, Wagner A., E-mail: wagner.carvalho@ufabc.edu.br [Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Rua Santa Adélia, 166, Santo André CEP 09210-170, SP (Brazil)

    2014-06-01

    Highlights: • A phosphate adsorbent was prepared from unpurified natural bentonite. • Physisorption was found to the main phosphate interaction mechanism. • The retention has reached 95% of the phosphate present in solution at room temperature. • The rate sorption was about 4 times faster than commercial phosphate adsorbents. - Abstract: A bentonite from the Northeast Brazilian region was modified with lanthanum (NT-25La) using an ion exchange process. Lanthanum incorporation in the natural clay, as well as the properties of the clay materials, were confirmed by X-ray diffraction, X-ray fluorescence, specific surface area and scanning electron microscopy (SEM/EDX). Phosphate adsorption equilibrium and kinetic tests were performed at different temperatures. The adsorption data have shown that NT-25La reaches equilibrium between modified clay and phosphate solution within 60 min of contact. The phosphate retention at room temperature reached 95%, when initial phosphate concentration in solution was 5 mg L{sup −1}. A kinetic-order variable model provided satisfactory fitting of the kinetic data. Adsorption of phosphate was best described by a Langmuir isotherm, with maximum phosphate sorption capacity of 14.0 mg g{sup −1}. Two distinct adsorption mechanisms were observed that may influence the adsorption processes. The investigation pointed out that the phosphate adsorption occurs via physisorption processes and that the use of NT-25La provides a maximum phosphate sorption capacity higher than many commercial adsorbents.

  19. Adsorption characteristics of N-nitrosodimethylamine from aqueous solution on surface-modified activated carbons

    Energy Technology Data Exchange (ETDEWEB)

    Xiaodong, Dai [Chemistry and Chemical Engineering School, China University of Petroleum, Dongying 257061, Shandong (China); Institute for Sustainability and Innovation, Victoria University, Melbourne, VIC 8001 (Australia); Zou, Linda [SA Water Centre for Water Management and Reuse, University of South Australia, Adelaide, SA5095 (Australia); Zifeng, Yan [Chemistry and Chemical Engineering School, China University of Petroleum, Dongying 257061, Shandong (China); Millikan, Mary [Institute for Sustainability and Innovation, Victoria University, Melbourne, VIC 8001 (Australia)

    2009-08-30

    This study investigated the removal of N-nitrosodimethylamine (NDMA) by an adsorption mechanism using commercially available activated carbons and surface-modified activated carbons. The effects of the modification on the properties of the activated carbon were studied by N{sub 2} adsorption/desorption, Diffuse Reflectance Infrared Fourier Transmission (DRIFT) analysis and X-Ray Photoelectron Spectroscopy (XPS). Adsorption experiments revealed that the activated carbons demonstrated a greater capacity for NDMA adsorption capacity than can be achieved using zeolite. The equilibrium data was fitted to the Freundlich equation and it was found that the adsorption capacity was significantly influenced by the micropore size, relative pore volume and surface characteristics. Adsorption experiments were conducted using unmodified and modified activated carbons. The results indicated that the adsorption capacity of NDMA can be significantly improved by heat treatment and doping of TiO{sub 2} particles. This was because the surface treatments yielded more hydrophobic sites and fewer oxygen-containing surface functional groups, and consequently an increased capacity for NDMA adsorption.

  20. Adsorption characteristics of N-nitrosodimethylamine from aqueous solution on surface-modified activated carbons

    International Nuclear Information System (INIS)

    Dai Xiaodong; Zou, Linda; Yan Zifeng; Millikan, Mary

    2009-01-01

    This study investigated the removal of N-nitrosodimethylamine (NDMA) by an adsorption mechanism using commercially available activated carbons and surface-modified activated carbons. The effects of the modification on the properties of the activated carbon were studied by N 2 adsorption/desorption, Diffuse Reflectance Infrared Fourier Transmission (DRIFT) analysis and X-Ray Photoelectron Spectroscopy (XPS). Adsorption experiments revealed that the activated carbons demonstrated a greater capacity for NDMA adsorption capacity than can be achieved using zeolite. The equilibrium data was fitted to the Freundlich equation and it was found that the adsorption capacity was significantly influenced by the micropore size, relative pore volume and surface characteristics. Adsorption experiments were conducted using unmodified and modified activated carbons. The results indicated that the adsorption capacity of NDMA can be significantly improved by heat treatment and doping of TiO 2 particles. This was because the surface treatments yielded more hydrophobic sites and fewer oxygen-containing surface functional groups, and consequently an increased capacity for NDMA adsorption.

  1. Modified granular activated carbon: A carrier for the recovery of nickel ions from aqueous wastes

    Energy Technology Data Exchange (ETDEWEB)

    Satapathy, D.; Natarajan, G.S.; Sen, R. [Central Fuel Research Inst., Nagpur (India)

    2004-07-01

    Granular Activated Carbon (GAC) is widely used for the removal and recovery of toxic pollutants including metals because of its low cost and high affinity towards the scavenging of metal ions. Activated carbon derived from bituminous coal is preferred for wastewater treatment due to its considerable hardness, a characteristic needed to keep down handling losses during re-activation. Commercial grade bituminous coal based carbon, viz. Filtrasorb (F-400), was used in the present work. The scavenging of precious metals such as nickel onto GAC was studied and a possible attempt made to recover the adsorbed Ni{sup 2+} ions through the use of some suitable leaching processes. As part of the study, the role of complexing agents on the surface of the carbon was also investigated. The use of organic complexing agents such as oxine and 2-methyloxine in the recovery process was found to be promising. In addition, the surface of the carbon was modified with suitable oxidising agents that proved to be more effective than chelating agents. Several attempts were made to optimise the recovery of metal ions by carrying out experiments with oxidising agents in order to obtain maximum recovery from the minimum quantity of carbon. Experiments with nitric acid indicated that not only was the carbon surface modified but such modification also helped in carbon regeneration.

  2. Removal of heavy metals from aqueous phases using chemically modified waste Lyocell fiber

    Energy Technology Data Exchange (ETDEWEB)

    Bediako, John Kwame; Wei, Wei; Kim, Sok; Yun, Yeoung-Sang, E-mail: ysyun@jbnu.ac.kr

    2015-12-15

    Highlights: • Waste Lyocell fiber was chemically modified into cellulose xanthate. • The sorbent showed high affinity for Pb(II), Cd(II) and Cu(II) ions. • The sorbent also showed strong Cu(II) selectivity in Pb(II)–Cd(II)–Cu(II) ternary metal solutions. - Abstract: In this study, an outstanding performance of chemically modified waste Lyocell for heavy metals treatment is reported. The sorbent, which was prepared by a simple and concise method, was able to bind heavy metals such as Pb(II), Cu(II) and Cd(II), with very high efficiencies. The binding mechanisms were studied through adsorption and standard characterization tests such as scanning electron microscopy, energy-dispersive spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction analyses. Adsorption kinetics was very fast and attained equilibrium within 5 min in all metals studied. The maximum single metal uptakes were 531.29 ± 0.28 mg/g, 505.64 ± 0.21 mg/g, and 123.08 ± 0.26 mg/g for Pb(II), Cd(II) and Cu(II), respectively. In ternary metal systems, Cu(II) selectivity was observed and the underlying factors were discussed. The sorbent by its nature, could be very effective in treating large volumes of wastewater with the contact of very little amount.

  3. Adsorption of lead and cadmium ions in aqueous solutions onto modified lignin from alkali glycerol delignication

    International Nuclear Information System (INIS)

    Demirbas, Ayhan

    2004-01-01

    Adsorptions of toxic metal ions (Pb(II) and Cd(II)) onto modified lignin from beech and poplar woods by alkali glycerol delignification are presented in this paper. The material exhibits good adsorption capacity and the adsorption data follow the Langmuir model. The maximum adsorption capacities are 8.2-9.0 and 6.7-7.5 mg/g of the modified lignin for Pb(II) and Cd(II), respectively. The maximum adsorption percentage is 95.8 for Pb(II) for 4 h at 330 K and is 95.0 for Cd(II) for 10 h at 290 K. The adsorption of both the metal ions increased with increasing temperature indicating endothermic nature of the adsorption process. The maximum adsorption percentages of Pb(II) and Cd(II) ions decrease with time till 48 and 42 h and then again increase slightly with time. The adsorption of both heavy metal ions increases with pH. The adsorption of Pb(II) ions reached a maximum at a 5.0 value of pH

  4. Adsorption of Nickel (II) from Aqueous Solution by Bicarbonate Modified Coconut Oilcake Residue Carbon.

    Science.gov (United States)

    Vijayakumari, N; Srinivasan, K

    2014-07-01

    The adsorption of Ni (II) on modified coconut oilcake residue carbon (bicarbonate treated coconut oilcake residue carbon-BCORC) was employed for the removal of Ni (II) from water and wastewater. The influence of various factors such as agitation time, pH and carbon dosage on the adsorption capacity has been studied. Adsorption isothermal data could be interpreted by Langmuir and Freundlich equations. In order to understand the reaction mechanism, kinetic data has been studied using reversible first order rate equation. Similar studies were carried out using commercially available activated carbon--CAC, for comparison purposes. Column studies were conducted to obtain breakthrough capacities of BCORC and CAC. Common anions and cations affecting the removal of Ni (II) on both the carbons were also studied. Experiments were also done with wastewater containing Ni (II), to assess the potential of these carbons.

  5. Rheological Properties in Aqueous Solution for Hydrophobically Modified Polyacrylamides Prepared in Inverse Emulsion Polymerization

    Directory of Open Access Journals (Sweden)

    Shirley Carro

    2017-01-01

    Full Text Available Inverse emulsion polymerization technique was employed to synthesize hydrophobically modified polyacrylamide polymers with hydrophobe contents near to feed composition. Three different structures were obtained: multisticker, telechelic, and combined. N-Dimethyl-acrylamide (DMAM, n-dodecylacrylamide (DAM, and n-hexadecylacrylamide (HDAM were used as hydrophobic comonomers. The effect of the hydrophobe length of comonomer, the initial monomer, and surfactant concentrations on shear viscosity was studied. Results show that the molecular weight of copolymer increases with initial monomer concentration and by increasing emulsifier concentration it remained almost constant. Shear viscosity measurements results show that the length of the hydrophobic comonomer augments the hydrophobic interactions causing an increase in viscosity and that the polymer thickening ability is higher for combined polymers.

  6. Removal of blue 1 dye of aqueous solutions with a modified clay with iron chloride

    International Nuclear Information System (INIS)

    Hernandez H, K. A.

    2012-01-01

    At the present time, several technologies have been proposed to remove dyes from water, adsorption is one of the most feasible methods and adsorbents with different properties, such as activated carbon, zeolites, clays and hydrogels among others. In this work, the sorption behavior of blue 1 dye by a natural clay from a site located in the Center-East of Mexico, and other modified with iron chloride were determined. The materials were characterized by X-ray diffraction to analyze its crystal structure, by scanning electron microscopy and elemental microanalysis of energy dispersive X-ray spectrometry to determine the composition and morphology, and the zero point charges were also determined to know the charge distribution on the surface of the clay. The ph effect, contact time, dye concentration and temperature were the parameters considered in this study. The results showed that clay does not suffer any important changes in its structure after the chemical treatments (modification with ferric chloride and contact with blue 1 solutions). The ph influences lightly the adsorption of the dye with natural clay, but the same effect is not observed in the ferric modified clay among the factor ph 6 and 8. The equilibrium time and the sorption capacity for natural clay were 48 hours and 6.16 mg/g, while for the ferric clay were 24 hours and 14.22 mg/g. Adsorption kinetics results were best adjusted to the pseudo first and pseudo second order models. Adsorption isotherms were best adjusted to the Langmuir model, indicating that both clays have a homogeneous surface. Thermodynamic parameters (E, ΔS and ΔG and ΔH) were calculated for the dye adsorption by the natural clay using data of the adsorption kinetics at temperatures between 20 and 50 C, indicating that the adsorption process is exothermic. For the case of ferric clay, it was not possible to calculate these thermodynamic parameters because the adsorption capacities were similar in the range of selected

  7. Enhanced analysis of triterpenes, flavonoids and phenolic compounds in Prunella vulgaris L. by capillary zone electrophoresis with the addition of running buffer modifiers.

    Science.gov (United States)

    Cheung, Hon-Yeung; Zhang, Qing-Feng

    2008-12-12

    A cyclodextrin-modified capillary zone electrophoresis method was developed for the separation and determination of three isomeric compounds (ursolic acid, oleanolic acid and betulinic acid), caffeic acid, p-coumaric acid, rosmarinic acid, rutin and quercetin. Without the addition of beta-cyclodextrin (beta-CD) and methanol, the separation of these analytes was poorly resolved. These eight compounds, however, were well separated from each other within 20 min with a borax running buffer (40 mM of borax, pH 9.4) containing 2mM beta-CD and 4% (v/v) methanol at the voltage of 25 kV, temperature of 25 degrees C and detection wavelength of 210 nm. The relative standard deviations (RSDs) of migration time ranged from 0.16 to 0.74% while those of the peak area ratios ranged from 2.17 to 4.61% for six determinations of the analytes at concentration of 10 and 25 microg mL(-1). The correlation coefficients of the calibration curves of the analytes were all >0.998, and the recoveries were from 96.8 to 103.6%. The method was successfully applied to determine these bioactive components in the samples of Prunella vulgaris L. and its beverage drink products. Our results reveal that only the isomeric compounds and rosmarinic acid could be detected in the spikes of P. vulgaris L.; other components were either too low to be detected or not present while only rosmarinic acid was detected in the beverage products.

  8. Gelation of covalently edge-modified laponites in aqueous media. 1. rheology and nuclear magnetic resonance.

    Science.gov (United States)

    Patil, Suhas P; Mathew, Renny; Ajithkumar, T G; Rajamohanan, P R; Mahesh, T S; Kumaraswamy, Guruswamy

    2008-04-17

    We describe the covalent modification of the edges of laponite with organic groups and the influence of this modification on gelation behavior. We compare three materials: an unmodified laponite, a laponite edge modified with a trimethyl moiety (MLap), and an octyldimethyl moiety (OLap). Gelation is investigated using rheology and NMR T1 relaxation measurements and nuclear Overhauser enhancement spectroscopy (NOESY). MLap and OLap show qualitatively different gelation. Gelation of MLap is very similar to laponite: MLap gels over the same time scale as laponite and has about the same solid modulus, and the MLap gel is almost as transparent as laponite. In contrast, OLap gels rapidly relative to laponite and forms a weak, turbid gel. We believe that gelation in laponite and MLap results from the formation of a network of well-dispersed platelets (or a few platelets), while in OLap, gelation results from a network of stacks of several platelets. NMR relaxation measurements indicate that gelation does not affect the average relaxation of water protons. However, T1 increases marginally for the protons in the organic moieties in MLap and decreases for protons in the organic moieties in OLap. Relaxation measurements, analyses of line width, and NOESY taken together suggest that, in OLap, gelation is a consequence of association of the organic moieties on the laponite edges, and that this association strengthens with time. Thus, the time-dependent changes in NMR suggest a structural origin for the time-dependent changes in the rheological behavior.

  9. Adsorption of sunset yellow FCF from aqueous solution by chitosan-modified diatomite.

    Science.gov (United States)

    Zhang, Y Z; Li, J; Li, W J; Li, Y

    2015-01-01

    Sunset yellow (SY) FCF is a hazardous azo dye pollutant found in food processing effluent. This study investigates the use of diatomaceous earth with chitosan (DE@C) as a modified adsorbent for the removal of SY from wastewater. Fourier transform infrared spectroscopy results indicate the importance of functional groups during the adsorption of SY. The obtained N2 adsorption-desorption isotherm values accord well with IUPAC type II. Our calculations determined a surface area of 69.68 m2 g(-1) for DE@C and an average pore diameter of 4.85 nm. Using response surface methodology, optimized conditions of process variables for dye adsorption were achieved. For the adsorption of SY onto DE@C, this study establishes mathematical models for the optimization of pH, contact time and initial dye concentration. Contact time plays a greater role in the adsorption process than either pH or initial dye concentration. According to the adjusted correlation coefficient (adj-R2>0.97), the models used here are suitable for illustration of the adsorption process. Theoretical experimental conditions included a pH of 2.40, initial dye concentration of 113 mg L(-1) and 30.37 minutes of contact time. Experimental values for the adsorption rate (92.54%) were close to the values predicted by the models (95.29%).

  10. Adsorption of ibuprofen from aqueous solution on chemically surface-modified activated carbon cloths

    Directory of Open Access Journals (Sweden)

    Hanen Guedidi

    2017-05-01

    Full Text Available This study aims to investigate the performance of an activated carbon cloth for adsorption of ibuprofen. The cloth was oxidized by a NaOCl solution (0.13 mol L−1 or thermally treated under N2 (700 °C for 1 hour. The raw and modified cloths were characterized by N2 adsorption–desorption measurement at 77 K, CO2 adsorption at 273 K, Boehm titrations, pHPZC measurements, X-ray Photoelectron Spectroscopy analysis, and by infrared spectroscopy. The NaOCl treatment increases the acidic sites, mostly creating phenolic and carboxylic groups and decreases both the specific surface area and slightly the micropore volume. However, the thermal treatment at 700 °C under N2 induced a slight increase in the BET specific surface area and yielded to the only increase in the carbonyl group content. Ibuprofen adsorption studies of kinetics and isotherms were carried out at pH = 3 and 7. The adsorption properties were correlated to the cloth porous textures, surface chemistry and pH conditions. The isotherms of adsorption were better reproduced by Langmuir–Freundlich models at 298, 313 and 328 K. The adsorption of ibuprofen on the studied activated carbon cloths at pH 3 was an endothermic process. The pore size distributions of all studied ibuprofen-loaded fabrics were determined by DFT method to investigate the accessible porosity of the adsorbate. Both treatments do not influence the kind of micropores where the adsorption of ibuprofen occurred.

  11. Design and characterization of sulfide-modified nanoscale zerovalent iron for cadmium(II) removal from aqueous solutions

    Science.gov (United States)

    Lv, Dan; Zhou, Xiaoxin; Zhou, Jiasheng; Liu, Yuanli; Li, Yizhou; Yang, Kunlun; Lou, Zimo; Baig, Shams Ali; Wu, Donglei; Xu, Xinhua

    2018-06-01

    Nanoscale zero-valent iron (nZVI) has high removal efficiency and strong reductive ability to organic and inorganic contaminants, but concerns over its stability and dispersity limit its application. In this study, nZVI was modified with sulfide to enhance Cd(II) removal from aqueous solutions. TEM and SEM analyses showed that sulfide-modified nZVI (S-nZVI) had a core-shell structure of nano-sized spherical particles, and BET results proved that sulfide modification doubled the specific surface area from 26.04 to 50.34 m2 g-1 and inhibited the aggregation of nZVI. Mechanism analysis indicated that Cd(II) was immobilized through complexation and precipitation. Cd(II) removal rate on nZVI was only 32% in 2 h, while complete immobilization could be achieved in 15 min on S-nZVI, and S-nZVI with an optimal S/Fe molar ratio of 0.3 offered a cadmium removal capacity of about 150 mg g-1 at pH 7 and 303 K. The process of Cd(II) immobilization on S-nZVI was fitted well with pseudo-second-order kinetic model, and the increase of temperature favored Cd(II) immobilization, suggesting an endothermic process. The presence of Mg2+ and Ca2+ hindered Cd(II) removal while Cu2+ did the opposite, which led to the order as Cu2+ > control > Mg2+ > Ca2+. The removal rate of 20 mg L-1 Cd(II) maintained a high level with the fluctuation of environmental conditions such as pH, ion strength and presence of HA. This study demonstrated that S-nZVI could be a promising adsorbent for Cd(II) immobilization from cadmium-contaminated water.

  12. Removal of blue indigo and cadmium present in aqueous solutions using a modified zeolitic material and an activated carbonaceous material

    International Nuclear Information System (INIS)

    Gutierrez S, E. E.

    2011-01-01

    In the last years the use of water has been increased substantially, it has been also altered its quality as a result of human activities such as mining, industrial activities and others. Water pollution caused by dyes and heavy metals has adverse effects on the environment, since both pollutants are very persisten even after conventional treatments. Denim blue and cadmium are not biodegradable. There is a growing interest in finding new, efficient and low cost alternative materials to remove such pollutants from the aqueous medium. The purpose of this work was to evaluate a modified zeolitic tuff and an activated carbonaceous material obtained from the pyrolysis of sewage sludge for the removal of denim blue and cadmium. The zeolitic material was modified with Na + and Fe 3+ solutions to improve its sorption properties for the removal of cadmium and denim blue, respectively. Carbonaceous material was treated with 10% HCl solution to remove ashes. Both materials were characterized by scanning electron microscopy and elemental analysis (EDS), specific surface areas (Bet), thermogravimetric analysis, infrared spectroscopy and X-ray diffraction. Simultaneously, the denim blue dye was characterized by infrared spectroscopy and its pKa value was determined, these data allowed the determination of its chemical properties and its acid-base behavior in solution. In the content of this work the term indigo blue was changed by denim blue, as it corresponds to the commercial name of the dye. To assess the sorption capacity of sorbents, the sorption kinetics and sorption isotherms in batch system were determined; the results were fitted to mathematical models such as the pseudo-first order, pseudo second order and second order to describe the sorption kinetics and the Langmuir, Freundlich and Langmuir-Freundlich isotherms to describe sorption processes. The results show that the most efficient material to remove denim blue from aqueous solutions is the carbonaceous material

  13. Effects of HCl and HNO3 on the oxidation of toluene to benzaldehyde by H2O2 over TS-1 modified with Al in aqueous phase

    Directory of Open Access Journals (Sweden)

    Paricha Pongjirawat

    2014-09-01

    Full Text Available This research studies effects of HCl and HNO3 in aqueous solution on the oxidation reaction between toluene and hydrogen peroxide to benzaldehyde over titanium silicalite-1 catalyst modified with Al. The reaction was carried out at reaction temperature 120°C in a pressurized autoclave reactor. The research found that the addition of HCl and HNO3 not only increases the concentration of toluene in the aqueous phase but also increases the formation of benzaldehyde as main product in the reaction.

  14. Cr(VI) and Cr(III) removal from aqueous solution by raw and modified lignocellulosic materials: a review.

    Science.gov (United States)

    Miretzky, P; Cirelli, A Fernandez

    2010-08-15

    In aqueous systems, chromium usually exists in both trivalent and hexavalent oxidation states, being Cr(VI) of particular importance and concern due to its great toxicity. Industrial sources of Cr(VI) are leather tanning, mining of chrome ore, production of steel and alloys, etc. The most common conventional method for Cr(VI) removal is reduction to Cr(III) at pH 2.0 and precipitation of Cr (OH)(3) with lime at pH 9-10. The disadvantage of precipitation is the disposal of the solid waste. Adsorption of Cr by different low cost materials seems to be a suitable choice for wastewater treatment. Many by-products of agriculture have proved to be suitable low cost adsorbents for Cr(VI) and Cr(III) removal from water. Lignocellulosic residues, which include both wood residues and agricultural residues, have adsorption capacity comparable to other natural sorbents, but they have the advantage of very low or no cost, great availability and simple operational process. This study is a review of the recent literature on the use of natural and modified lignocellulosic residues for Cr adsorption. The Cr maximum adsorption capacity and the adsorption mechanism under different experimental conditions are reported when possibly. Copyright 2010 Elsevier B.V. All rights reserved.

  15. Arsenic removal in aqueous solution by a novel Fe-Mn modified biochar composite: Characterization and mechanism.

    Science.gov (United States)

    Lin, Lina; Qiu, Weiwen; Wang, Di; Huang, Qing; Song, Zhengguo; Chau, Henry Wai

    2017-10-01

    The aim of this study was to develop a cost-effective method for As removal from aqueous systems. To this end, pristine biochar (BC) was impregnated with Fe-Mn oxides and a comparative analysis was conducted on the adsorption capacities of BC, Fe-Mn binary oxide (FMO), and Fe/Mn modified biochar (FMBC). The ferromanganese oxides increased the specific surface areas of BC. FMBC presented greater adsorption of As (Q max = 8.25mgg -1 ) than FMO and BC. Energy dispersive spectrometer analysis and electron microscope scanning revealed numerous pores of FMBC with the existence of Fe-Mn oxide using. Distinguished binding energy shifting of the As3d, Fe2p, O1s, and Mn2p3/2 regions after As sorption were found, indicating that Mn(III) oxidation and interaction of oxygen-containing function groups in the FMBC promoted the conversion of As(III) to As(V). Furthermore, chemisorption was found to be the main mechanism for As sorption on FMBC. Thus, the results suggest that FMBC could be used as an inexpensive and highly efficient adsorbent for As removal from water environment. Copyright © 2017 Elsevier Inc. All rights reserved.

  16. Preparation of carboxyl group-modified palladium nanoparticles in an aqueous solution and their conjugation with DNA

    Science.gov (United States)

    Wang, Zhifei; Li, Hongying; Zhen, Shuang; He, Nongyue

    2012-05-01

    The use of nanomaterials in biomolecular labeling and their corresponding detection has been attracting much attention, recently. There are currently very few studies on palladium nanoparticles (Pd NPs) due to their lack of appropriate surface functionalities for conjugation with DNA. In this paper, we thus firstly present an approach to prepare carboxyl group-modified Pd NPs (with an average size of 6 nm) by the use of 11-mercaptoundecanoic acid (MUDA) as a stabilizer in the aqueous solution. The effect of the various reducing reaction conditions on the morphology of the Pd NPs was investigated. The particles were further characterized by TEM, UV-vis, FT-IR and XPS techniques. DNA was finally covalently conjugated to the surface of the Pd NPs through the activation of the carboxyl group, which was confirmed by agarose gel electrophoresis and fluorescence analysis. The resulting Pd NPs-DNA conjugates show high single base pair mismatch discrimination capabilities. This work therefore sets a good foundation for further applications of Pd NPs in bio-analytical research.

  17. Electrocatalytic reduction of dioxygen by cobalt porphyrin-modified glassy carbon electrode with single-walled carbon nanotubes and nafion in aqueous solutions

    International Nuclear Information System (INIS)

    Choi, Ayoung; Jeong, Haesang; Kim, Songmi; Jo, Suhee; Jeon, Seungwon

    2008-01-01

    Cobalt porphyrin (CoP)-modified glassy carbon electrode (GCE) with single-walled carbon nanotubes (SWNTs) and Nafion demonstrated a higher electrocatalytic activity for the reduction of dioxygen in 0.1 M H 2 SO 4 solution. Cyclic and hydrodynamic voltammetry at the CoP-SWNTs/GCE-modified electrodes in O 2 -saturated aqueous solutions was used to study the electrocatalytic pathway. Compared with the CoP/GCE-modified electrodes, the reduction potential of dioxygen at the CoP-SWNTs/GCE-modified electrodes was shifted to the positive direction and the limiting current was greatly increased. Especially, the Co(TMPP)-SWNTs/GCE-modified electrode was catalyzed effectively by the 4e - reduction of dioxygen to water, because hydrodynamic voltammetry revealed the transference of approximately four electrons for dioxygen reduction and the minimal generation of hydrogen peroxide in the process of dioxygen reduction

  18. Synthesis, electrochemical, spectrophotometric and potentiometric studies of two azo-compounds derived from 4-amino-2-methylquinoline in ethanolic-aqueous buffered solutions

    Energy Technology Data Exchange (ETDEWEB)

    El-Attar, Mona A.; Ghoneim, Mohamed M. [Analytical Chemistry Research Unit, Chemistry Department, Tanta University (Egypt); Ismail, Iqbal M., E-mail: maema.2011@yahoo.com [Chemistry Department, Faculty of Science, King Abdul Aziz University, Jeddah (Saudi Arabia)

    2012-08-15

    Two azo-compounds, 2-methyl-4-(5-amino-2-hydroxy-phenylazo)-quinoline (2) and 2-methyl-4-(2-hydroxy-5-nitrophenylazo)-quinoline, derived from 4-amino-2-methylquinoline were synthesized. Their chemical structures were characterized and confirmed by means of elemental chemical analysis, infrared (IR) spectroscopy, {sup 1}H nuclear magnetic resonance (NMR) and mass spectrometry (MS). The electrochemical behavior of the starting compound (4-amino-2-methylquinoline) and of the two synthesized azo-derivatives was studied at the mercury electrode in the B-R universal buffer at various pH values (2-11.5) containing 40% (v/v) ethanol using dc-polarography, cyclic voltammetry and controlled-potential coulometry. Their electrode reaction pathways were elucidated and discussed. The dissociation constants (pKa) of the examined compounds, stability constants and stoichiometry of their complexes in solution with some transition metal ions (Co(II), Ni(II), Cu(II), La(III) and UO{sup 2+}{sub 2}) were determined. (author)

  19. Buffers Plus

    Science.gov (United States)

    Ramette, Richard W.

    1998-11-01

    In 1989 JCE Software published The Acid-Base Package: A Collection of Useful Programs for Proton Transfer Systems (Ramette, R. W. J. Chem. Educ. Software 1989, 2B No. 2). This DOS program has been fully upgraded by the same author to the world of Windows 95. Buffers Plus takes advantage of a modern user interface and offers many new options not possible in the original version.

  20. Buffer fluid

    Energy Technology Data Exchange (ETDEWEB)

    Mirzadzhanzade, A Kh; Dedusanko, G Ya; Dinaburg, L S; Markov, Yu M; Rasizade, Ya N; Rozov, V N; Sherstnev, N M

    1979-08-30

    A drilling fluid is suggested for separating the drilling and plugging fluids which contains as the base increased solution of polyacrylamide and additive. In order to increase the viscoelastic properties of the liquid with simultaneous decrease in the periods of its fabrication, the solution contains as an additive dry bentonite clay. In cases of the use of a buffer fluid under conditions of negative temperatures, it is necessary to add to it table salt or ethylene glycol.

  1. Cd(II) removal from aqueous solution by adsorption on α-ketoglutaric acid-modified magnetic chitosan

    International Nuclear Information System (INIS)

    Yang, Guide; Tang, Lin; Lei, Xiaoxia; Zeng, Guangming; Cai, Ye; Wei, Xue; Zhou, Yaoyu; Li, Sisi; Fang, Yan; Zhang, Yi

    2014-01-01

    The present study developed an α-ketoglutaric acid-modified magnetic chitosan (α-KA-Fe 3 O 4 /CS) for highly efficient adsorption of Cd(II) from aqueous solution. Several techniques, including transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and vibrating sample magnetometer (VSM), were applied to characterize the adsorbent. Batch tests were conducted to investigate the Cd(II) adsorption performance of α-KA-Fe 3 O 4 /CS. The maximum adsorption efficiency of Cd(II) appeared at pH 6.0 with the value of 93%. The adsorption amount was large and even reached 201.2 mg/g with the initial Cd(II) concentration of 1000 mg/L. The adsorption equilibrium was reached within 30 min and commendably described by pseudo-second-order model, and Langmuir model fitted the adsorption isotherm better. Furthermore, thermodynamic parameters, free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) of Cd(II) adsorption were also calculated and showed that the overall adsorption process was endothermic and spontaneous in nature because of positive ΔH values and negative ΔG values, respectively. Moreover, the Cd(II)-loaded α-KA-Fe 3 O 4 /CS could be regenerated by 0.02 mol/L NaOH solution, and the cadmium removal capacity could still be kept around 89% in the sixth cycle. All the results indicated that α-KA-Fe 3 O 4 /CS was a promising adsorbent in environment pollution cleanup.

  2. The study of furfural removal from aqueous solutions using activated carbon and bentonite modified with cetyltrimethylammonium bromide (CTAB), a cationic surfactant

    OpenAIRE

    M Leili; Gh Asgari; A. A Eskandari; L Borzoei; B Ramavandi

    2016-01-01

    Background and Objectives: Furfural is one of the toxic chemical compounds used in many industries such as petrochemical, food, paper products, pharmaceutical, etc., due to having some characteristics. Therefore, furfural could be found at different concentrations in the effluent from these industries and can enter the environment. Hence, the aim of this study was the assessment the efficiency of a low cost bentonite modified with cationic surfactant in the removal of furfural from aqueous so...

  3. Removal of Hexavalent Chromium from Aqueous Solution by Modified Holly Sawdust: A Study of Equilibrium and Kinetics

    Directory of Open Access Journals (Sweden)

    S. Azizian

    2010-01-01

    Full Text Available Introduction & Objective: Industrial wastewaters including heavy metals, are among the important sources of environmental pollution. Heavy metals such as chromium are found in plating wastewater and is harmful for human health and environment. The purpose of the present study was to investigate the absorption of heavy metals such as chromium onto modified holly sawdust as an cheaper absorbent. Materials & Methods: This study was a fundamental- application study done in Hamadan University of Medical Sciences, hygiene faculty water and wastewater chemistry laboratory. This study investigated the removal of hexavalent chromium by using modified holly sawdust with pH changes ,contact time ,absorbent dose and Cr(VI concentrations in batch system. Then the result was analyzed by Excel software.Results: The results showed that the removal efficiency decrease is accompanied by the increase of pH and initial chromium concentration. pH increase from 2 to 12(equilibrium time= 180 min, adsorbent dose= 0.6g/100CC, Cr(VI concentrations= 60 mg/L,leaded to the removal efficiency decrease from 99.67 % to 29.78 %. Also removal efficiency decreased from 99.37 % to 40.24 % after increasing the initial chromium concentrations from 20 mg/L to 100 mg/L. Moreover the results showed the removal efficiency increased after increasing the adsorbent dose and contact time. By increasing adsorbent dose from 0.2 g/100CC to 1 g/100CC, the removal efficiency increased from 34.65 % to 99.76 %.Additionally, the removal efficiency increased from 48.53%to 99.76% by increasing contact time from 5 mins to 180 mins. Experimental isotherms and kinetics models were assessed by Langmuir and Freundlich isotherms and pseudo-first-order and pseudo-second-order kinetics models. The results showed that the data were acceptably explained acceptably by Langmuir isotherms and pseudo-second-order kinetics models respectively.Conclusion: The results showed that the removal of hexavalent chromium

  4. Removal of Zn2+ from aqueous single metal solutions and electroplating wastewater with wood sawdust and sugarcane bagasse modified with EDTA dianhydride (EDTAD).

    Science.gov (United States)

    Pereira, Flaviane Vilela; Gurgel, Leandro Vinícius Alves; Gil, Laurent Frédéric

    2010-04-15

    This work describes the preparation of a new chelating material derived from wood sawdust, Manilkara sp., and not only the use of a new support, but also a chemically modified sugarcane bagasse synthesized in our previous work to remove Zn(2+) from aqueous solutions and electroplating wastewater. The first part describes the chemical modification of wood sawdust and sugarcane bagasse using ethylenediaminetetraacetic dianhydride (EDTAD) as modifying agent in order to introduce carboxylic acid and amine functional groups into these materials. The obtained materials such as the modified sugarcane bagasse, EB, and modified wood sawdust, ES were then characterized by infrared spectroscopy (IR) and CHN. The second part evaluates the adsorption capacity of Zn(2+) by EB and ES from aqueous single metal solutions and real electroplating wastewater, which concentration was determined through direct titration with EDTA and inductively coupled plasma (ICP-OES). Adsorption isotherms were developed using Langmuir model. Zn(2+) adsorption capacities were found to be 80 mg/g for ES and 105 mg/g for EB whereas for the industrial wastewater these values were found to be 47 mg/g for ES and 45 mg/g for EB. Zn(2+) adsorption in the wastewater was found to be lower than in Zn(2+) spiked solution due to the competition between other cations and/or interference of other ions, mainly Ca(2+) and Cl(-) that were present in the wastewater. 2009 Elsevier B.V. All rights reserved.

  5. Solid Phase Extraction of Trace Copper in Aqueous Samples Using C18 Membrane Disks Modified by Benzildithiosemicarbazone Prior to Flame Atomic Absorption Spectrometric (FAAS Determination

    Directory of Open Access Journals (Sweden)

    M. Mohammadhosseini

    2013-08-01

    Full Text Available A highly convenient, selective and sensitive procedure for pre-concentration, separation and determination of sub-ppm levels of Cu2+ in aqueous samples based on modification of octadecyl silica bonded phase membrane (OSBPM disks is described using benzildithiosemicarbazone  (BDSC as a powerful modifier. It was revealed that each loaded OSBPM disk with 6.0 mg of BDSC serves as excellent bead for trapping, enrichment and isolation of trace copper. The analyte was trapped during introduction the aqueous solutions through the surface of each modified membrane, quantitatively, while other interfering ions passed through the disk to drain. The adsorbed Cu2+ ions were then stripped by appropriate eluting agents followed by monitoring of the eluates by FAAS. The effects of sample pH, amount of the modifier, stripping agent types and sample flow-rates were also investigated. The described method permitted a pre-concentration factor of about 200. The detection limit of the procedure was predicted to be about 0.013 ng L-1. The method was successfully employed for recovery and quantification of trace copper in different water samples. 

  6. Removal of 2,4-Dichlorophenolyxacetic acid (2,4-D) herbicide in the aqueous phase using modified granular activated carbon

    OpenAIRE

    Dehghani, Mansooreh; Nasseri, Simin; Karamimanesh, Mojtaba

    2014-01-01

    Background Low cost 2,4-Dichlorophenolyxacetic acid (2,4-D) widely used in controlling broad-leafed weeds is frequently detected in water resources. The main objectives of this research were focused on evaluating the feasibility of using granular activated carbon modified with acid to remove 2,4-D from aqueous phase, determining its removal efficiency and assessing the adsorption kinetics. Results The present study was conducted at bench-scale method. The influence of different pH (3–9), the ...

  7. Efficient device for the benign removal of organic pollutants from aqueous solutions using modified mesoporous magnetite nanostructures

    Science.gov (United States)

    Vojoudi, H.; Badiei, A.; Amiri, A.; Banaei, A.; Ziarani, G. M.; Schenk-Joß, K.

    2018-02-01

    In this study, a home-made device comprising a column filled with magnetic mesoporous silica-coated nanostructures (MSCM-PA) as an adsorbent was constructed and used to remove organic pollutants from aqueous solutions. The MSCM-PA adsorbent was prepared and characterized using Fourier transform-infrared spectroscopy, ultraviolet-visible spectroscopy, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, vibrating sample magnetometry, Brunauer-Emmett-Teller, thermogravimetric analysis/differential thermal analysis, and powder X-ray diffraction techniques. The adsorption behavior of the MSCM-PA sorbent was studied based on the removal of Everzol blue dye from aqueous solutions. We investigated the effects of various parameters such as the solution pH, initial dye concentration, adsorbent dose, flow rate, and contact time on the adsorption of Everzol blue from aqueous solutions. The adsorption data were modeled using Langmuir and Freundlich isotherms, and a good fit was obtained with the Langmuir isotherm. The maximum Everzol blue adsorption capacity by MSCM-PA was 162 mg g-1. The results indicate that our device is capable of adsorbing anionic dyes from aqueous solutions.

  8. Buffer mass test - Buffer materials

    International Nuclear Information System (INIS)

    Pusch, R.; Boergesson, L.

    1982-08-01

    Commercial Na bentonite (MX-80) is the clay component of the buffer material in the heater holes as well of the tunnel backfill. Important characteristics are the clay content, liquid limit, X-ray diffraction pattern, water content, and degree of granulation. The ballast material consists of quartz-rich sand and feldspar-rich filler. The preparation of highly compacted bentonite for the near-field isolation of the canister was made by using isostatic compaction technique. The resulting dense bentonite core was cut into regularly shaped blocks which were arranged around each heater and lowered as one unit - heavily instrumented - in the respective deposition holes. For three of the six holes a narrow slot was left open between the bentonite stack and the rock; for the remaining ones a wider slot was chosen with a fill of soft bentonite powder. Both arrangements are expected to yield an ultimate bulk density which is sufficiently high to fulfil the requirement of a negligible permeability and a sufficient swelling pressure as well as heat conductivity, which are the essential parameters. The tunnel backfill, which consists of a mixture of suitably graded ballast material and MX-80 powder, has a considerably lower swelling pressure and heat conductivity, and a higher permeability, all these parameters still within the requirements of the KBS 2 concept. The various zones with different bentonite/sand ratios and the technique to apply them are described in the final part of the report. (Author)

  9. Use of Chitosan-modified Bentonite for Removal of Cu2+, Cl- and 2,4-Dichlorophenoxyacetic Acid (2,4-D from Aqueous Solution

    Directory of Open Access Journals (Sweden)

    Ba, K.

    2014-07-01

    Full Text Available Batch experiments were performed to investigate the removal of Cu2+ , Cl- , and 2,4-dichlorophe- noxyacetic acid (2,4-D from aqueous solution using chitosan-modified bentonite. When the chi-tosan was loaded on the bentonite, the inter-layer space of the montmorillonite increased and the adsorption efficiency enhanced, as chitosan contains large numbers of -NH2 and -OH functional groups that could serve as coordination sites to bind heavy metals. In this study, the bentonite that was prepared through three procedures: Na2CO3 treatment, thermal treatment and compound treatment, was modified by chitosan. Experimental results demonstrated that the average removal rates of Cu2+ , Cl-, and 2,4-D effectively were 94.87 %, 86.19 % and 91.06 %, respectively.

  10. Removal of As(V, Cr(VI and Pb(II from aqueous solution using surfactant-modified Sabzevar nanozeolite

    Directory of Open Access Journals (Sweden)

    Kourosh Razmgar

    2016-04-01

    Full Text Available The pollution of water environments is a challenging issue especially in developing countries. Contamination of drinking water with heavy metals has been reported in many parts of the world. Arsenic, chromium and lead are dangerous heavy metals and also common contaminants of drinking water. In this study, the capacity and performance of the surfactant-modified Sabzevar natural nanozeolite (SMSNZ on the removal of heavy metals from an aqueous solution was investigated. Initially, the appropriate concentration of hexadecyltrimethylammonium bromide HDTMA-Br solution for modification was investigated; it was found that it must be higher than the critical concentration micelle (CMC. Then, the removal of As (V, Cr (VI, and Pb(II from an aqueous solution was studied using SMSNZ. The results indicated that the removal efficiency was very high in different initial concentrations of heavy metals. The Linear, Langmuir and Freundlich isotherm models were used to investigate the adsorption equilibrium of the surfactant-modified natural zeolite for heavy metals adsorption. The results showed that the Linear isotherm is a better fit for the three studied heavy metals.

  11. Enhancement of sorption capacity of cocoa shell biomass modified with non-thermal plasma for removal of both cationic and anionic dyes from aqueous solution.

    Science.gov (United States)

    Takam, Brice; Acayanka, Elie; Kamgang, Georges Y; Pedekwang, Merlin T; Laminsi, Samuel

    2017-07-01

    Removal of cationic dye, Azur II, and anionic dye, Reactive Red 2 (RR-2) from aqueous solutions, has been successfully achieved by using a modified agricultural biomaterial waste: cocoa shell husk (Theobroma cacao) treated by gliding arc plasma (CPHP). The biomass in its natural form CPHN and modified form CPHP was characterized by infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and point of zero charge (pH pzc ). Experimental variables such as initial pH, contact time, and temperature were optimized for adsorptive characteristics of CPHN and CPHP. The results show that the removal of the Azur II dye was favorable in the basic pH region (pH 10) while the Reactive Red 2 dye was favorable in the acidic pH region (pH 2). The minimum equilibrium time for Azur II and RR-2 dye was obtained after 40 and 240 min, respectively. The adsorption kinetics and isotherm data obtained were best described by a pseudo-second-order kinetic rate model and a combination of Langmuir-Freundlich isotherm models. This work indicates that the plasma-treated raw materials are good alternative multi-purpose sorbents for the removal of many coexisting pollutants from aqueous solutions.

  12. Investigation of Pb(II Removal from Aqueous Solutions Using Modified Nano Zero-Valent Iron Particles

    Directory of Open Access Journals (Sweden)

    Amirhossein Ramezanpoor

    2014-05-01

    Full Text Available This research was conducted in experimental scale with the aim of investigation effect of polyacrylic acid-stabilized zero-valent iron nanoparticles (PAA-nZVI on lead removal from aqueous solution. In this regards, NZVI was synthesized with polyacrylic acid and their size and morphological characteristics were examined via X-ray diffraction (XRD, Scanning Electron Microscopy (SEM and Fourier Transmission Infrared Spectroscopy (FTIR. To study the effect of PAA-nZVI on lead removal, pH of aqueous solution, contact time, PAA-NZVI concentration  and initial Pb(II concentration were considered as variables. Furthermore, the experimental data of Pb(II  removal were fitted using three kinetic models, namely Zero-order, First-order and Second-order.The results of experiments showed that maximum Pb(II removal efficiency was observed at pH=5, 15 min contact time and 5 g/L PAA-nZVI concentration. Moreover, the results of kinetic studies indicated that among all applied kinetic models, First-order kinetic model had more better prediction than other kinetic models ofPb(II removal. Based on the results of present research, PAA-NZVI is an efficient agent to remove Pb(II from aqueous solutions.

  13. Removal of chromium (VI) ions from aqueous solutions using amine-impregnated TiO2 nanoparticles modified cellulose acetate membranes.

    Science.gov (United States)

    Gebru, Kibrom Alebel; Das, Chandan

    2018-01-01

    In this work, TiO 2 nanoparticles (NPs) were modified using tetraethylenepentamine (TEPA), ethylenediamine (EDA), and hexamethylenetetramine (HMTA) amines using impregnation process. The prepared amine modified TiO 2 samples were explored as an additive to fabricate ultrafiltration membranes with enhanced capacity towards the removal of chromium ions from aqueous solution. Modified membranes were prepared from cellulose acetate (CA) polymer blended with polyethylene glycol (PEG) additive, and amine modified TiO 2 by using phase inversion technique. Fourier transform infrared spectroscopy (FTIR), zeta potential (ζ), thermo gravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), water contact angle (WCA), and atomic absorption spectrophotometer (AAS) studies were done to characterize the membranes in terms of chemical structure, electric charge, thermal stability, morphology, hydrophilicity, and removal performance. The pure water permeability and Cr (VI) ion removal efficiency of the unmodified (i.e. CA/U-Ti) and the amine modified (CA/Ti-HMTA, CA/Ti-EDA, and CA/Ti-TEPA) membranes were dependent on pH and metal ion concentration. Incorporation of amine modified TiO 2 composite to the CA polymer was found to improve the fouling and removal characteristics of the membranes during the chromium ultrafiltration process. The maximum removal efficiency result of Cr (VI) ions at pH of 3.5 using CA/Ti-TEPA membrane was 99.8%. The washing/regeneration cycle results in this study described as an essential part for prospect industrial applications of the prepared membranes. The maximum Cr (VI) removal results by using CA/Ti-TEPA membrane for four washing/regeneration cycles are 99.6%, 99.5%, 98.6% and, 96.6%, respectively. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Simultaneous determination of oleanolic acid, ursolic acid, quercetin and apigenin in Swertia mussotii Franch by capillary zone electrophoresis with running buffer modifier.

    Science.gov (United States)

    Gao, Ruibin; Wang, Litao; Yang, Yan; Ni, Jingman; Zhao, Liang; Dong, Shuqing; Guo, Mei

    2015-03-01

    The method of capillary zone electrophoresis (CZE) with direct UV detection was developed for the determination of oleanolic acid, ursolic acid, quercetin and apigenin. and then for the first time successfully applied to the analysis of four analytes in Swertia mussotii Franch and its preparations. Various factors affecting the CZE procedure were investigated and optimized, and the optimal conditions were: 50 × 10(-3) mol/L borate-phosphate buffer (pH 9.5) with 5.0 × 10(-3) mol/L β-cyclodextrin, 15 kV separation voltage, 20 °C column temperature, 250 nm detection wavelength and 5 s electrokinetic injection time (voltage 20 psi). Under the conditions, oleanolic acid, ursolic acid, quercetin and apigenin could be determined within the test ranges with a good correlation coefficient (r(2) > 0.9991). The limits of detection for conditions, oleanolic acid, ursolic acid, quercetin and apigenin were 0.3415, 0.2003, 0.0062 and 0.2538 µg/mL, respectively, and the intra- and inter-day relative standard deviations were no more than 4.72%. This procedure provided a convenient, sensitive and accurate method for simultaneous determination of oleanolic acid, ursolic acid, quercetin and apigenin in S. mussotii Franch. Copyright © 2014 John Wiley & Sons, Ltd.

  15. The removal of Tartrazine dye by modified Alumina with sodium dodecyl sulfate from aqueous solutions: equilibrium and thermodynamic studies

    Directory of Open Access Journals (Sweden)

    A. Parchebaf Jadid

    2017-11-01

    Full Text Available Edible colors are materials which in the case of adding to food and drinks cause transferring color to them. Most of these colors are not acceptable in terms of applying in human food and underlies various diseases like gastrointestinal disorders, renal, liver and blood toxicity. The goal of this study was investigating the efficiency of improved alumina by sodium dodecyl sulfate (SDS in eliminating Tartrazine from aqueous environments. In this research, the impact of effective parameters such as initial concentration of Tartrazine, time, pH, alumina dose and SDS value were studied in order to approach an optimal condition for eliminating the color. Also, absorption behavior was evaluated by Freundlich and Langmuir isotherms. The highest efficiency of Tartrazine elimination in the solution resulted in optimal pH of 2, the amount of adsorbent 1.5 g/L, 16 min duration and value 0.04 SDS g/l which was obtained for dye concentration 5 mg/L about 94.13%. Also, results suggested that Tartrazine absorption follows Langmuir isotherm (R2 = 0.9867. Obtained results from thermodynamic studies such as Gibbs free energy (-5.728 Kj/mol and enthalpy (-85.86 Kj/mol and entropy (-271.102 J/mol.K also suggested that the absorption process was exothermic. The results of this research suggested that improved alumina by sodium dodecyl sulfate had a relative good capability in Tartrazine elimination from aqueous environments. Thus

  16. Phosphorus removal from aqueous solution in parent and aluminum-modified eggshells: thermodynamics and kinetics, adsorption mechanism, and diffusion process.

    Science.gov (United States)

    Guo, Ziyan; Li, Jiuhai; Guo, Zhaobing; Guo, Qingjun; Zhu, Bin

    2017-06-01

    Parent and aluminum-modified eggshells were prepared and characterized with X-ray diffraction, specific surface area measurements, infrared spectroscopy, zeta potential, and scanning electron microscope, respectively. Besides, phosphorus adsorptions in these two eggshells at different temperatures and solution pH were carried out to study adsorption thermodynamics and kinetics as well as the mechanisms of phosphorus adsorption and diffusion. The results indicated that high temperature was favorable for phosphorus adsorption in parent and aluminum-modified eggshells. Alkaline solution prompted phosphorus adsorption in parent eggshell, while the maximum adsorption amount was achievable at pH 4 in aluminum-modified eggshell. Adsorption isotherms of phosphorus in these eggshells could be well described by Langmuir and Freundlich models. Phosphorus adsorption amounts in aluminum-modified eggshell were markedly higher compared to those in parent eggshell. Adsorption heat indicated that phosphorus adsorption in parent eggshell was a typically physical adsorption process, while chemical adsorption mechanism of ion exchange between phosphorus and hydroxyl groups on the surface of eggshells was dominated in aluminum-modified eggshell. The time-resolved uptake curves showed phosphorus adsorption in aluminum-modified eggshell was significantly faster than that in parent eggshell. Moreover, there existed two clear steps in time-resolved uptake curves of phosphorus in parent eggshell. Based on pseudo-second order kinetic model and intraparticle diffusion model, we inferred more than one process affected phosphorus adsorption. The first process was the diffusion of phosphorus through water to external surface and the opening of pore channel in the eggshells, and the second process was mainly related to intraparticle diffusion.

  17. Determination of residual nonsteroidal anti-inflammatory drugs in aqueous sample using magnetic nanoparticles modified with cetyltrimethylammonium bromide by high performance liquid chromatography.

    Science.gov (United States)

    Khoeini Sharifabadi, Malihe; Saber-Tehrani, Mohammad; Waqif Husain, Syed; Mehdinia, Ali; Aberoomand-Azar, Parviz

    2014-01-01

    A simple and sensitive solid-phase extraction method for separation and preconcentration of trace amount of four nonsteroidal anti-inflammatory drugs (naproxen, indomethacin, diclofenac, and ibuprofen) using Fe3O4 magnetic nanoparticles modified with cetyltrimethylammonium bromide has been developed. For this purpose, the surface of MNPs was modified with cetyltrimethylammonium bromide (CTAB) as a cationic surfactant. Effects of different parameters influencing the extraction efficiency of drugs including the pH, amount of salt, shaking time, eluent type, the volume of solvent, amount of adsorbent, sample volume, and the time of desorption were investigated and optimized. Methanol has been used as desorption solvent and the extracts were analysed on a reversed-phase octadecyl silica column using 0.02 M phosphate-buffer (pH = 6.02) acetonitrile (65 : 35 v/v) as the mobile phase and the effluents were measured at 202 nm with ultraviolet detector. The relative standard deviation (RSD%) of the method was investigated at three concentrations (25, 50, and 200 ng/mL) and was in the range of 3.98-9.83% (n = 6) for 50 ng/mL. The calibration curves obtained for studied drugs show reasonable linearity (R (2) > 0.99) and the limit of detection (LODs) ranged between 2 and 7 ng/mL. Finally, the proposed method has been effectively employed in extraction and determination of the drugs in biological and environmental samples.

  18. The buffer effect in neutral electrolyte supercapacitors

    DEFF Research Database (Denmark)

    Thrane Vindt, Steffen; Skou, Eivind M.

    2016-01-01

    The observation that double-layer capacitors based on neutral aqueous electrolytes can have significantly wider usable potential windows than those based on acidic or alkaline electrolytes is studied. This effect is explained by a local pH change taking place at the electrode surfaces, leading...... potassium nitrate as the electrolyte and potassium phosphates as the buffer system....

  19. Effective removal of heavy metal ions Cd2+, Zn2+, Pb2+, Cu2+ from aqueous solution by polymer-modified magnetic nanoparticles

    International Nuclear Information System (INIS)

    Ge, Fei; Li, Meng-Meng; Ye, Hui; Zhao, Bao-Xiang

    2012-01-01

    We prepared novel Fe 3 O 4 magnetic nanoparticles (MNPs) modified with 3-aminopropyltriethoxysilane (APS) and copolymers of acrylic acid (AA) and crotonic acid (CA). The MNPs were characterized by transmission electron microscopy, X-ray diffraction, infra-red spectra and thermogravimetric analysis. We explored the ability of the MNPs for removing heavy metal ions (Cd 2+ , Zn 2+ , Pb 2+ and Cu 2+ ) from aqueous solution. We investigated the adsorption capacity of Fe 3 O 4 -APS-AA-co-CA at different pH in solution and metal ion uptake capacity as a function of contact time and metal ion concentration. Moreover, adsorption isotherms, kinetics and thermodynamics were studied to understand the mechanism of the synthesized MNPs adsorbing metal ions. In addition, we evaluated the effect of background electrolytes on the adsorption. Furthermore, we explored desorption and reuse of MNPs. Fe 3 O 4 -APS-AA-co-CA MNPs are excellent for removal of heavy metal ions such as Cd 2+ , Zn 2+ , Pb 2+ and Cu 2+ from aqueous solution. Furthermore, the MNPs could efficiently remove the metal ions with high maximum adsorption capacity at pH 5.5 and could be used as a reusable adsorbent with convenient conditions.

  20. High-Yield and Sustainable Production of Phosphatidylserine in Purely Aqueous Solutions via Adsorption of Phosphatidylcholine on Triton-X-100-Modified Silica.

    Science.gov (United States)

    Zhang, Xiaoli; Li, Binglin; Wang, Jiao; Li, Huanyu; Zhao, Binxia

    2017-12-13

    Triton X-100 was covalently bound to a surface of silica and acted as an anchor molecule to facilitate the adsorption of phosphatidylcholine (PC) in a purely aqueous solution. The silica-adsorbed PC obtained was successfully used for phospholipase D (PLD)-mediated transphosphatidylation in the production of phosphatidylserine (PS). Organic solvents were completely avoided in the whole production process. The PC loading and PS yield reached 98.9 and 99.0%, respectively. Two adsorption models were studied, and the relevant parameters were calculated to help us understand the adsorption and reaction processes deeply. In addition, the silica-adsorbed PC provides a promising way to continuously biosynthesize PS. A packed-bed reactor was employed to demonstrate the process flow of the continuous production of PS. The recyclability and stability of the Triton-X-100-modified silica were excellent, as demonstrated by its use 30 times during continuous operation without any loss of the productivity.

  1. Synthesis of novel amperometric urea-sensor using hybrid synthesized NiO-NPs/GO modified GCE in aqueous solution of cetrimonium bromide.

    Science.gov (United States)

    Parsaee, Zohreh

    2018-06-01

    In this study NiO nanostructures were synthesized via combinational synthetic method (ultrasound-assisted biosynthesis) and immobilized on the glassy carbon electrode (GCE) as a highly sensitive and selective enzyme-less sensor for urea detection. NiO-NPs were fully characterized using SEM, EDX, XRD, BET, TGA, FT-IR, UV-vis and Raman methods which revealed the formation of NiO nanostructures in the form of cotton like porous material and crystalline in nature with the average size of 3.8 nm. GCE was modified with NiO-NPs in aqueous solution of cetrimonium bromide(CTAB). Highly adhesive NiO/CTAB/GO nanocomposite membrane has been formed on GCE by immersing NiO/CTAB modified GCE in GO suspension. CTAB has a major role in the production and immobilization of the nanocomposites on the GCE surface and the binding NiO nanoparticles on GO plates. In addition, CTAB/GO composition made a highly adhesive surface on the GCE. The resulting NiO/CTAB/GO/GCE contains potently sensitive to urea in aqueous environments. The response of as developed amperometric sensor was linear in the range of 100-1200 µM urea with R 2 value of 0.991 and limit of detection (LOD), 8 µM. The sensor responded negligibly to various interfering species like glucose, uric acid and ascorbic acid. This sensor was applied successfully for determining urea in real water samples such as mineral water, tap water and river water with acceptable recovery. Copyright © 2018 Elsevier B.V. All rights reserved.

  2. Photocatalytic, antimicrobial activities of biogenic silver nanoparticles and electrochemical degradation of water soluble dyes at glassy carbon/silver modified past electrode using buffer solution.

    Science.gov (United States)

    Khan, Zia Ul Haq; Khan, Amjad; Shah, Afzal; Chen, Yongmei; Wan, Pingyu; Khan, Arif Ullah; Tahir, Kamran; Muhamma, Nawshad; Khan, Faheem Ullah; Shah, Hidayat Ullah

    2016-03-01

    In the present research work a novel, nontoxic and ecofriendly procedure was developed for the green synthesis of silver nano particle (AgNPs) using Caruluma edulis (C. edulis) extract act as reductant as well as stabilizer agents. The formation of AgNPs was confirmed by UV/Vis spectroscopy. The small and spherical sizes of AgNPs were conformed from high resolution transmission electron microscopy (HRTEM) analysis and were found in the range of 2-10nm, which were highly dispersion without any aggregation. The crystalline structure of AgNPs was conformed from X-ray diffraction (XRD) analysis. For the elemental composition EDX was used and FTIR helped to determine the type of organic compounds in the extract. The potential electrochemical property of modified silver electrode was also studied. The AgNPs showed prominent antibacterial motion with MIC values of 125 μg/mL against Bacillus subtilis and Staphylococcus aureus while 250 μg/mL against Escherichia coli. High cell constituents' release was exhibited by B. subtilis with 2 × MIC value of silver nanoparticles. Silver nanoparticles also showed significant DPPH free radical scavenging activity. This research would have an important implication for the synthesis of more efficient antimicrobial and antioxidant agent. The AgNP modified electrode (GC/AgNPs) exhibited an excellent electro-catalytic activity toward the redox reaction of phenolic compounds. The AgNPs were evaluated for electrochemical degradation of bromothymol blue (BTB) dyes which showed a significant activity. From the strong reductive properties it is obvious that AgNPs can be used in water sanitization and converting some organic perilous in to non-hazardous materials. The AgNPs showed potential applications in the field of electro chemistry, sensor, catalyst, nano-devices and medical. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. Removal of Disperse Blue 56 and Disperse Red 135 dyes from aqueous dispersions by modified montmorillonite nanoclay

    Directory of Open Access Journals (Sweden)

    Ahmadishoar Javad

    2017-01-01

    Full Text Available In this study modified montmorillonite was used as an adsorbent for the removal of two selected disperse dyes i.e., Disperse Blue 56 (DB and Disperse Red 135 (DR from dye dispersions. The adsorption equilibrium data of dyes adsorption were investigated by using Nernst, Freundlich and Langmuir isotherm models. The adsorption kinetics was analyzed by using different models including pseudo-first-order, pseudo-second-order, Elovich and Intraparticle diffusion model. The Freundlich isotherm was found to be the most appropriate model for describing the sorption of the dyes on modified nanoclay. The best fit to the experimental results was obtained by using the pseudo-second-order kinetic equation, which satisfactorily described the process of dye adsorption. Although different kinetic models may control the rate of the adsorption process, the results indicated that the main rate limiting step was the intraparticle diffusion. The results showed that the proposed modified montmorillonite could be used as an effective adsorbent for the removal of disperse dyes even from highly concentrated dispersions.

  4. Sorption of Lead (Pb from Aqueous Solutions by Sepiolite and Bentonite Modified with Chitosan Biopolymers: Isotherms and Kinetics

    Directory of Open Access Journals (Sweden)

    Hamid Reza Rafiei

    2016-07-01

    Full Text Available In this study, sepiolite and bentonite clay minerals were modified with a natural chitosan biopolymer and the modified-clays were characterized using XRF, XRD, FTIR, SEM, and TOC analyses. The isothermal and kinetic parameters of lead (Pb sorption by both the minerals and the modified-minerals were determined in a batch mode under various conditions such as different contact times and initial concentrations of Pb. It was found that the Freundlich model described well the isotherm experimental data of Pb sorption by the sorbents. Modification with chitosan, however, decreased the Pb adsorption capacity of sepiolite from 83 to 27 mg g-1 and that of bentonite from 56 to 29 mg g-1. Kinetic results showed that more than 24 hours was required for Pb sorption by the natural clays to reach equilibrium, while the equilibrium time reduced to 16 and 4 hours for Pb sorption on chitosan-sepiolite and chitosan–bentonite, respectively. The pseudo-second-order model well described the time-dependent Pb sorption data by sepiolite, chitosan-sepiolite, and chitosan-bentonite, suggesting that chemical sorption is the rate-limiting step of Pb adsorption mechanism. The Pb sorption data by bentonite showed the best fit with Elovich model.

  5. Adsorption of phosphate from aqueous solution using iron-zirconium modified activated carbon nanofiber: Performance and mechanism.

    Science.gov (United States)

    Xiong, Weiping; Tong, Jing; Yang, Zhaohui; Zeng, Guangming; Zhou, Yaoyu; Wang, Dongbo; Song, Peipei; Xu, Rui; Zhang, Chen; Cheng, Min

    2017-05-01

    Phosphate (P) removal is significant for the prevention of eutrophication in natural waters. In this paper, a novel adsorbent for the removal of P from aqueous solution was synthesized by loading zirconium oxide and iron oxide onto activated carbon nanofiber (ACF-ZrFe) simultaneously. The adsorbent was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The results showed that P adsorption was highly pH dependent and the optimum pH was found to be 4.0. The isotherm of adsorption could be well described by the Langmuir model and the maximum P adsorption capacity was estimated to be 26.3mgP/g at 25°C. The kinetic data were well fitted to the pseudo-second-order equation, indicating that chemical sorption was the rate-limiting step. Moreover, co-existing ions including sulfate (SO 4 2- ), chloride (Cl - ), nitrate (NO 3 - ) and fluoride (F - ) exhibited a distinct effect on P adsorption with the order of F - >NO 3 - >Cl - >SO 4 2- . Further investigations by FT-IR spectroscopy and pH variations associated with the adsorption process revealed that ligands exchange and electrostatic interactions were the dominant mechanisms for P adsorption. The findings reported in this work highlight the potential of using ACF-ZrFe as an effective adsorbent for the removal of P in natural waters. Copyright © 2017 Elsevier Inc. All rights reserved.

  6. Removal of chromium (VI from aqueous medium using chemically modified banana peels as efficient low-cost adsorbent

    Directory of Open Access Journals (Sweden)

    Ashraf Ali

    2016-09-01

    Full Text Available The adsorptive removal of hexavalent chromium Cr(VI from aqueous solutions was investigated by acrylonitrile grafted banana peels (GBPs. Banana peels were treated with 10% HCl, followed by alkaline hydrolysis with 10% NaOH, and washed thoroughly. The bleaching of alkali hydrolyzed peels was carried out with sodium chlorate (NaClO3 in the presence of hydrogen peroxide and glacial acetic acid. The grafting co-polymerization of acrylonitrile onto the bleached pulp was initiated by Fenton’s reagent (Fe+2/H2O2. The optimum conditions for adsorption of Cr(VI were found to be the following: pH 3, adsorbent dose 4 g/L, concentration 400 mg/L and contact time of 120 min. The surface morphology of adsorbent was characterized by scanning electron microscopy (SEM before and after the adsorption. The adsorption of Cr(VI onto grafted banana peels (GBPs was recorded to be 96%. The adsorption data were fully fitted with the Freundlich and Langmuir isotherm model and followed a pseudo-second order kinetic model. Thermodynamic study showed that the adsorption is exothermic and spontaneous. Owing to high efficiency and low cost, grafted banana peels (GBPs can be used as effective adsorbent for Cr(VI removal from wastewater.

  7. Implementation of chitosan inductively modified by γ-rays copolymerization with acrylamide in the decontamination of aqueous basic dye solution

    Directory of Open Access Journals (Sweden)

    R.O. Aly

    2017-02-01

    Full Text Available The modification induced by gamma rays for the natural polymer, chitosan, was established using the monomer acrylamide. The hydrogel obtained was characterized using Fourier transform infrared spectroscopy and the thermal properties were investigated by thermogravimetric analysis (TGA. The effect of absorbed dose (kGy and chitosan:acrylamide ratio on the gel % was studied. The impact of the polymerization variables was observed on the swelling % of the prepared hydrogel with water. The highest equilibrium degree of swelling of the prepared chitosan–AAm hydrogel, 380 g/g was predicted at 75% AAm and absorbed dose of 10 kGy for 97.7% gel. The removal of the basic blue dye (Astrazone Blue BG-200% from aqueous solutions was discussed. The adsorption capacity of basic dye on chitosan–AAm increased from 24.5 to 47.2 mg/g by increasing pH from 4.0 to 9.0. The effect of pH, absorbed dose, chitosan:AAm ratio and the concentration of the dye on the effectiveness of the adsorption process was studied.

  8. Internal Active Thermal Control System (IATCS) Sodium Bicarbonate/Carbonate Buffer in an Open Aqueous Carbon Dioxide System and Corollary Electrochemical/Chemical Reactions Relative to System pH Changes

    Science.gov (United States)

    Stegman, Thomas W.; Wilson, Mark E.; Glasscock, Brad; Holt, Mike

    2014-01-01

    The International Space Station (ISS) Internal Active Thermal Control System (IATCS) experienced a number of chemical changes driven by system absorption of CO2 which altered the coolant’s pH. The natural effects of the decrease in pH from approximately 9.2 to less than 8.4 had immediate consequences on system corrosion rates and corrosion product interactions with specified coolant constituents. The alkalinity of the system was increased through the development and implementation of a carbonate/bicarbonate buffer that would increase coolant pH to 9.0 – 10.0 and maintain pH above 9.0 in the presence of ISS cabin concentrations of CO2 up to twenty times higher than ground concentrations. This paper defines how a carbonate/bicarbonate buffer works in an open carbon dioxide system and summarizes the analyses performed on the buffer for safe and effective application in the on-orbit system. The importance of the relationship between the cabin environment and the IATCS is demonstrated as the dominant factor in understanding the system chemistry and pH trends before and after addition of the carbonate/bicarbonate buffer. The paper also documents the corollary electrochemical and chemical reactions the system has experienced and the rationale for remediation of these effects with the addition of the carbonate/bicarbonate buffer.

  9. Isotherm Studies of Equilibrium Sorption of Cu2+ and Cd2+ from Aqueous Solutions by Modified and Unmodified Breadfruit Seed Hull

    Directory of Open Access Journals (Sweden)

    Christopher Uchechukwu Sonde

    2015-09-01

    Full Text Available The ability of an economically cheap adsorbent material of natural origin, African breadfruit seed hull, was assessed for Cu(II and Cd(II ions’ adsorption from aqueous solutions. The effects of adsorbent dose, particle size and initial metal ion concentrations were investigated in a batch adsorption process. The experimental data were analyzed using five two-parameter isotherm equations (i.e., Langmuir, Freundlich, Temkin, Harkins-Jura and Halsey isotherm models. Freundlich and Halsey models provided the best description for the adsorption data while the other three models gave fairly good interpretation to the experimental adsorption data. The maximum adsorption capacity corresponding to saturation of sites (qmax, obtained from the Langmuir plots, were 7.76 and 8.06 mg g-1 for Cu(II and Cd(II onto the unmodified breadfruit seed hull (UBSH and 12.67 and 13.97 mg g-1, respectively for Cu(II and Cd(II adsorption onto the modified breadfruit seed hull (MBSH. The experimental results showed that there was an enhancement in the removal of the metal ions by the mercaptoacetic acid-modified breadfruit seed hull. DOI: http://dx.doi.org/10.17807/orbital.v7i3.625 

  10. Selective removal mercury (Ⅱ) from aqueous solution using silica aerogel modified with 4-amino-5-methyl-1,2,4-triazole-3(4H)-thion

    Energy Technology Data Exchange (ETDEWEB)

    Tadayon, Fariba; Saber-Tehrani, Mohammad; Motahar, Shiva [Islamic Azad University, Tehran (Iran, Islamic Republic of)

    2013-03-15

    Silica aerogel surface modifications with chelating agents for adsorption/removal of metal ions have been reported in recent years. This investigation reported the preparation of silica aerogel (SA) adsorbent coupled with metal chelating ligands of 4-amino-5-methyl-1,2,4-triazole-3(4H)-thion (AMTT) and its application for selective adsorption of Hg(Ⅱ) ion. The adsorbent was characterized by Fourier transform infrared spectra (FTIR) and thermo gravimetric analysis (TGA) measurements, nitrogen physisorption and scanning electron microscope (SEM). Optimal experimental conditions including pH, temperature, adsorbent dosage and contact time have been established. Langmuir and Freundlich isotherm models were applied to analyze the experimental data. The best interpretation for the experimental data given by the Langmuir isotherm equation and the maximum adsorption capacity of the modified silica gel and silica aerogel was 142.85 and 17.24mgg⌃(-1), respectively. Thermodynamic parameters such as Gibbs free energy (ΔG{sup o}), standard enthalpy (ΔH{sup o}) and entropy change (ΔS{sup o}) were investigated. The adsorbed Hg(Ⅱ) on the SA-AMTT adsorbents could be completely eluted by 1.0M KBr solution and recycled at least four times without the loss of adsorption capacity. The results of the present investigation illustrate that modified silica aerogel with AMTT could be used as an adsorbent for the effective removal of Hg(Ⅱ) ions from aqueous solution.

  11. Pb(II) and Cd(II) removal from aqueous solution, shipyard wastewater, and landfill leachate by modified Rhizopus oryzae biomass

    Science.gov (United States)

    Naeimi, Behrouz; Foroutan, Rauf; Ahmadi, Bahram; Sadeghzadeh, Farzaneh; Ramavandi, Bahman

    2018-04-01

    This study was designed to remove Pb(II) and Cd(II) from aqueous solution, shipyard wastewater, and sanitary landfill leachate using an alkaline-modified Rhizopus oryzae biomass. According to the Fourier transform infrared test, different functional groups like O–H, N–H, C=O, and P–O were detected in the bioadsorbent. The x-ray fluorescence (XRF) analysis showed that CaO, P2O3, and SO3 oxides have the highest content in the bioadsorbent. The surface area of modified Rhizopus oryzae was obtained as 20.32 m2 g‑1. The effect of initial pH, temperature, contact time, and bioadsorbent dose on the metals removal was discussed. At optimal conditions, maximum Pb(II) and Cd(II) removal was obtained 95.66% and 94.55%, respectively. Freundlich model was well- accurately described the equilibrium data. Among four studied models, the pseudo-second-order was better able to describe the kinetic behavior of the bioadsorption process. The amount of enthalpy, free energy of Gibbs, and entropy parameters indicated that the bioadsorption process of studied heavy metals is negative, exothermic, and spontaneous. The amount of heavy metals in a shipyard wastewater and sanitary landfill leachate was significantly decreased by using the developed bioadsorbent.

  12. Buffer Zone Fact Sheets

    Science.gov (United States)

    New requirements for buffer zones and sign posting contribute to soil fumigant mitigation and protection for workers and bystanders. The buffer provides distance between the pesticide application site and bystanders, reducing exposure risk.

  13. Adsorption of arsenic(III) into modified lamellar Na-magadiite in aqueous medium—Thermodynamic of adsorption process

    Science.gov (United States)

    Guerra, Denis Lima; Pinto, Alane Azevedo; Airoldi, Claudio; Viana, Rúbia Ribeiro

    2008-12-01

    Synthetic Na-magadiite sample was used for organofunctionalization process with N-propyldiethylenetrimethoxysilane and bis[3-(triethoxysilyl)propyl]tetrasulfide, after expanding the interlayer distance with polar organic solvents such as dimethylsulfoxide (DMSO). The resulted materials were submitted to process of adsorption with arsenic solution at pH 2.0 and 298±1 K. The adsorption isotherms were adjusted using a modified Langmuir equation with regression nonlinear; the net thermal effects obtained from calorimetric titration measurements were adjusted to a modified Langmuir equation. The adsorption process was exothermic (Δ intH=-4.15-5.98 kJ mol -1) accompanied by increase in entropy (Δ intS=41.32-62.20 J k -1 mol -1) and Gibbs energy (Δ intG=-22.44-24.56 kJ mol -1). The favorable values corroborate with the arsenic (III)/basic reactive centers interaction at the solid-liquid interface in the spontaneous process.

  14. Adsorption of Procion Blue MX-R dye from aqueous solutions by lignin chemically modified with aluminium and manganese

    International Nuclear Information System (INIS)

    Adebayo, Matthew A.; Prola, Lizie D.T.; Lima, Eder C.; Puchana-Rosero, M.J.; Cataluña, Renato; Saucier, Caroline; Umpierres, Cibele S.; Vaghetti, Julio C.P.; Silva, Leandro G. da; Ruggiero, Reinaldo

    2014-01-01

    Graphical abstract: - Highlights: • Complexes of carboxy-methylated lignin with Al and Mn were used as adsorbents. • The optimum adsorption conditions were achieved at pH 2 and 298 K. • Maximum adsorption capacities are 73.52 mg g −1 (CML-Al) and 55.16 mg g −1 (CML-Mn). • CML-Al could remove ca. 95.83% of dye-contaminated industrial effluents. • CML-Al and CML-Mn are effective for treatment of simulated dye-house effluents. - Abstract: A macromolecule, CML, was obtained by purifying and carboxy-methylating the lignin generated from acid hydrolysis of sugarcane bagasse during bioethanol production from biomass. The CMLs complexed with Al 3+ (CML-Al) and Mn 2+ (CML-Mn) were utilised for the removal of a textile dye, Procion Blue MX-R (PB), from aqueous solutions. CML-Al and CML-Mn were characterised using Fourier transform infrared spectroscopy (FTIR), scanning differential calorimetry (SDC), scanning electron microscopy (SEM) and pH PZC . The established optimum pH and contact time were 2.0 and 5 h, respectively. The kinetic and equilibrium data fit into the general order kinetic model and Liu isotherm model, respectively. The CML-Al and CML-Mn have respective values of maximum adsorption capacities of 73.52 and 55.16 mg g −1 at 298 K. Four cycles of adsorption/desorption experiments were performed attaining regenerations of up to 98.33% (CML-Al) and 98.08% (CML-Mn) from dye-loaded adsorbents, using 50% acetone + 50% of 0.05 mol L −1 NaOH. The CML-Al removed ca. 93.97% while CML-Mn removed ca. 75.91% of simulated dye house effluents

  15. Adsorption of Procion Blue MX-R dye from aqueous solutions by lignin chemically modified with aluminium and manganese

    Energy Technology Data Exchange (ETDEWEB)

    Adebayo, Matthew A. [Institute of Chemistry, Federal University of Rio Grande do Sul (UFRGS), Av. Bento Gonçalves 9500, Postal Box 15003, 91501-970 Porto Alegre, RS (Brazil); Department of Chemical Sciences, Ajayi Crowther University, PMB 1066 Oyo, Oyo State (Nigeria); Prola, Lizie D.T. [Institute of Chemistry, Federal University of Rio Grande do Sul (UFRGS), Av. Bento Gonçalves 9500, Postal Box 15003, 91501-970 Porto Alegre, RS (Brazil); Lima, Eder C., E-mail: eder.lima@ufrgs.br [Institute of Chemistry, Federal University of Rio Grande do Sul (UFRGS), Av. Bento Gonçalves 9500, Postal Box 15003, 91501-970 Porto Alegre, RS (Brazil); Puchana-Rosero, M.J.; Cataluña, Renato; Saucier, Caroline; Umpierres, Cibele S.; Vaghetti, Julio C.P. [Institute of Chemistry, Federal University of Rio Grande do Sul (UFRGS), Av. Bento Gonçalves 9500, Postal Box 15003, 91501-970 Porto Alegre, RS (Brazil); Silva, Leandro G. da; Ruggiero, Reinaldo [Institute of Chemistry, Federal University of Uberlândia (UFU), AV. João Naves de Ávila 2121 block 1D—Campus Santa Mônica, 38400-902 Uberlândia, MG (Brazil)

    2014-03-01

    Graphical abstract: - Highlights: • Complexes of carboxy-methylated lignin with Al and Mn were used as adsorbents. • The optimum adsorption conditions were achieved at pH 2 and 298 K. • Maximum adsorption capacities are 73.52 mg g{sup −1} (CML-Al) and 55.16 mg g{sup −1} (CML-Mn). • CML-Al could remove ca. 95.83% of dye-contaminated industrial effluents. • CML-Al and CML-Mn are effective for treatment of simulated dye-house effluents. - Abstract: A macromolecule, CML, was obtained by purifying and carboxy-methylating the lignin generated from acid hydrolysis of sugarcane bagasse during bioethanol production from biomass. The CMLs complexed with Al{sup 3+} (CML-Al) and Mn{sup 2+} (CML-Mn) were utilised for the removal of a textile dye, Procion Blue MX-R (PB), from aqueous solutions. CML-Al and CML-Mn were characterised using Fourier transform infrared spectroscopy (FTIR), scanning differential calorimetry (SDC), scanning electron microscopy (SEM) and pH{sub PZC}. The established optimum pH and contact time were 2.0 and 5 h, respectively. The kinetic and equilibrium data fit into the general order kinetic model and Liu isotherm model, respectively. The CML-Al and CML-Mn have respective values of maximum adsorption capacities of 73.52 and 55.16 mg g{sup −1} at 298 K. Four cycles of adsorption/desorption experiments were performed attaining regenerations of up to 98.33% (CML-Al) and 98.08% (CML-Mn) from dye-loaded adsorbents, using 50% acetone + 50% of 0.05 mol L{sup −1} NaOH. The CML-Al removed ca. 93.97% while CML-Mn removed ca. 75.91% of simulated dye house effluents.

  16. Removal of Hexavalent Chromium from Aqueous Solutions Using Magnetic Nanoparticles Coated with Alumina and Modified by Cetyl Trimethyl Ammonium Bromide

    Directory of Open Access Journals (Sweden)

    Mohammad Malakootian

    2015-12-01

    Full Text Available Introduction: The development of an effective method regarding chromium removal from the environment is of great importance. Therefore, the present study aimed to examiner magnetic nanoparticles coated with alumina modified by Cetyl Trimethyl Ammonium Bromide (CTAB in the removal of Cr6+ through magnetic solid phase extraction method. Materials & Methods: At first, iron oxide nanoparticles were synthesized, coated with alumina, modified with CTAB and characterized with suitable instruments. The factors affecting the process of chromium removal were investigated, including the concentration of CTAB, the pH, the amount of nanoparticles, the sample volume, a proper eluent, the adsorption and desorption time, and the effect of interfering ions. Moreover, the chromium concentration was determined by flame atomic absorption spectrometric (FAAS technique. The adsorption isotherm, adsorption capacity, and recoverability of the adsorbent were further examined. Results: The modified magnetic nanoparticles were demonstrated to be homogeneous, spherical, with a size lower than 20 nanometer having a magnetic property. The optimal conditions for chromium removal entailed 7*10-6 mol/L concentration of CTAB, pH range of 6-8, 0.1 g of the nanoparticles, 10 mL volume of the chromium sample (5 &mug mL-1, nitric acid 2 M as a suitable eluent, 15 minutes of adsorption and desorption, and no interference of interfering ions in the process of chromium separation. The process efficiency under optimal conditions was determined to be over 95%, which this process followed the Langmuir adsorption isotherm. The adsorption capacity proved to be 23.8 mg/g. Reusing after four times of adsorbent recovering was effective in the chromium removal (80%. The method accuracy for five measurement times was 4.155% and the method’s LOD was 0.081 mg/L. Conclusion: The method enjoys the benefits of convenient preparation of the adsorbent, high selectivity, high accuracy, short process

  17. Removal of reactive red-120 and 4-(2-pyridylazo) resorcinol from aqueous samples by Fe3O4 magnetic nanoparticles using ionic liquid as modifier

    International Nuclear Information System (INIS)

    Absalan, Ghodratollah; Asadi, Mozaffar; Kamran, Sedigheh; Sheikhian, Leila; Goltz, Douglas M.

    2011-01-01

    Highlights: → Ionic liquids modify the dye-adsorption characteristics of magnetic nanoparticles. → Modified nanoparticles improved the sensitivity of dye measurements. → Water-solubility is an important factor for choosing an ionic liquid as a modifier for nanoparticles. - Abstract: The nanoparticles of Fe 3 O 4 as well as the binary nanoparticles of ionic liquid and Fe 3 O 4 (IL-Fe 3 O 4 ) were synthesized for removal of reactive red 120 (RR-120) and 4-(2-pyridylazo) resorcinol (PAR) as model azo dyes from aqueous solutions. The mean size and the surface morphology of the nanoparticles were characterized by TEM, DLS, XRD, FTIR and TGA techniques. Adsorption of RR-120 and PAR was studied in a batch reactor at different experimental conditions such as nanoparticle dosage, dye concentration, pH of the solution, ionic strength, and contact time. Experimental results indicated that the IL-Fe 3 O 4 nanoparticles had removed more than 98% of both dyes under the optimum operational conditions of a dosage of 60 mg, a pH of 2.5, and a contact time of 2 min when initial dyes concentrations of 10-200 mg L -1 were used. The maximum adsorption capacity of IL-Fe 3 O 4 was 166.67 and 49.26 mg g -1 for RR-120 and PAR, respectively. The isotherm experiments revealed that the Langmuir model attained better fits to the equilibrium data than the Freundlich model. The Langmuir adsorption constants were 5.99 and 3.62 L mg -1 for adsorptions of RR-120 and PAR, respectively. Both adsorption processes were endothermic and dyes could be desorbed from IL-Fe 3 O 4 by using a mixed NaCl-acetone solution and adsorbent was reusable.

  18. Removal of 2,4-Dichlorophenolyxacetic acid (2,4-D) herbicide in the aqueous phase using modified granular activated carbon.

    Science.gov (United States)

    Dehghani, Mansooreh; Nasseri, Simin; Karamimanesh, Mojtaba

    2014-01-10

    Low cost 2,4-Dichlorophenolyxacetic acid (2,4-D) widely used in controlling broad-leafed weeds is frequently detected in water resources. The main objectives of this research were focused on evaluating the feasibility of using granular activated carbon modified with acid to remove 2,4-D from aqueous phase, determining its removal efficiency and assessing the adsorption kinetics. The present study was conducted at bench-scale method. The influence of different pH (3-9), the effect of contact time (3-90 min), the amount of adsorbent (0.1-0.4 g), and herbicide initial concentration (0.5-3 ppm) on 2,4-D removal efficiency by the granular activated carbon were investigated. Based on the data obtained in the present study, pH of 3 and contact time of 60 min is optimal for 2,4-D removal. 2,4-D reduction rate increased rapidly by the addition of the adsorbent and decreased by herbicide initial concentration (63%). The percent of 2,4-D reduction were significantly enhanced by decreasing pH and increasing the contact time. The adsorption of 2,4-D onto the granular activated carbon conformed to Langmuir and Freundlich models, but was best fitted to type II Langmuir model (R2 = 0.999). The second order kinetics was the best for the adsorption of 2,4-D by modified granular activated carbon with R2 > 0.99. Regression analysis showed that all of the variables in the process have been statistically significant effect (p granular activated carbon modified with acid is an appropriate method for reducing the herbicide in the polluted water resources.

  19. Synthesis and characterization of nanocomposites based on polyurethane in aqueous dispersions with non-modified hydrophilic clays

    International Nuclear Information System (INIS)

    Miranda, G.S.; Delpechi, M.C.; Santo, W.L.E.

    2010-01-01

    Several studies involving the formation of polyurethane nanocomposites employing clays of montmorillonite modified. This involves the presence of quaternary ammonium salts, the cation exchange needed to increase the interlayer space of clays that incorporate more than one step to the process, generates a higher cost. In this paper the synthesis of nanocomposite polyurethanes dispersed in water allowed not only the production of materials less harmful to the environment, but also the incorporation of hydrophilic clays, calcium and sodium in nature, without any modifications. Dispersions produced from 0.5, 1.0 and 2.5% clay (on the mass of prepolymer) were characterized in terms of total solids content, the films obtained by casting were evaluated for adhesiveness, diffraction X-rays, scanning electron microscopy. Most systems showed intercalated and partially exfoliated structures. (author)

  20. Novel Swelling-Resistant Sodium Alginate Membrane Branching Modified by Glycogen for Highly Aqueous Ethanol Solution Pervaporation.

    Science.gov (United States)

    Ji, Chen-Hao; Xue, Shuang-Mei; Xu, Zhen-Liang

    2016-10-12

    A novel carbohydrate chain cross-linking method of sodium alginate (SA) is proposed in which glycogen with the branched-chain structure is utilized to cross-link with SA matrix by the bridging of glutaraldehyde (GA). The active layer of SA composite ceramic membrane modified by glycogen and GA for pervaporation (PV) demonstrates great advantages. The branched structure increases the chain density of the active layer, which compresses the free volume between the carbohydrate chains of SA. Large amounts of hydroxyl groups are consumed during the reaction with GA, which reduces the hydrogen bond formation between water molecules and the polysaccharide matrix. The two factors benefit the active layer with great improvement in swelling resistance, promoting the potential of the active layer for the dehydration of an ethanol-water solution containing high water content. Meanwhile, the modified active layer is loaded on the rigid α-Al 2 O 3 ceramic membrane by dip-coating method with the enhancement of anti-deformation and controllable thickness of the active layer. Characterization techniques such as SEM, AFM, XRD, FTIR, XPS, and water contact angle are utilized to observe the composite structure and surface morphology of the composite membrane, to probe the free volume variation, and to determine the chemical composition and hydrophilicity difference of the active layer caused by the different glycogen additive amounts. The membrane containing 3% glycogen in the selective layer demonstrates the flux at 1250 g m -2 h -1 coupled with the separation factor of 187 in the 25 wt % water content feed solution at the operating temperature of 75 °C, reflecting superior pervaporation processing capacity compared with the general organic PV membranes in the same condition.

  1. Buffer-regulated biocorrosion of pure magnesium.

    Science.gov (United States)

    Kirkland, Nicholas T; Waterman, Jay; Birbilis, Nick; Dias, George; Woodfield, Tim B F; Hartshorn, Richard M; Staiger, Mark P

    2012-02-01

    Magnesium (Mg) alloys are being actively investigated as potential load-bearing orthopaedic implant materials due to their biodegradability in vivo. With Mg biomaterials at an early stage in their development, the screening of alloy compositions for their biodegradation rate, and hence biocompatibility, is reliant on cost-effective in vitro methods. The use of a buffer to control pH during in vitro biodegradation is recognised as critically important as this seeks to mimic pH control as it occurs naturally in vivo. The two different types of in vitro buffer system available are based on either (i) zwitterionic organic compounds or (ii) carbonate buffers within a partial-CO(2) atmosphere. This study investigated the influence of the buffering system itself on the in vitro corrosion of Mg. It was found that the less realistic zwitterion-based buffer did not form the same corrosion layers as the carbonate buffer, and was potentially affecting the behaviour of the hydrated oxide layer that forms on Mg in all aqueous environments. Consequently it was recommended that Mg in vitro experiments use the more biorealistic carbonate buffering system when possible.

  2. Determination of Residual Nonsteroidal Anti-Inflammatory Drugs in Aqueous Sample Using Magnetic Nanoparticles Modified with Cetyltrimethylammonium Bromide by High Performance Liquid Chromatography

    Directory of Open Access Journals (Sweden)

    Malihe Khoeini Sharifabadi

    2014-01-01

    Full Text Available A simple and sensitive solid-phase extraction method for separation and preconcentration of trace amount of four nonsteroidal anti-inflammatory drugs (naproxen, indomethacin, diclofenac, and ibuprofen using Fe3O4 magnetic nanoparticles modified with cetyltrimethylammonium bromide has been developed. For this purpose, the surface of MNPs was modified with cetyltrimethylammonium bromide (CTAB as a cationic surfactant. Effects of different parameters influencing the extraction efficiency of drugs including the pH, amount of salt, shaking time, eluent type, the volume of solvent, amount of adsorbent, sample volume, and the time of desorption were investigated and optimized. Methanol has been used as desorption solvent and the extracts were analysed on a reversed-phase octadecyl silica column using 0.02 M phosphate-buffer (pH = 6.02 acetonitrile (65 : 35 v/v as the mobile phase and the effluents were measured at 202 nm with ultraviolet detector. The relative standard deviation (RSD% of the method was investigated at three concentrations (25, 50, and 200 ng/mL and was in the range of 3.98–9.83% (n=6 for 50 ng/mL. The calibration curves obtained for studied drugs show reasonable linearity (R2>0.99 and the limit of detection (LODs ranged between 2 and 7 ng/mL. Finally, the proposed method has been effectively employed in extraction and determination of the drugs in biological and environmental samples.

  3. Kinetic and isotherm analyses for thorium (IV) adsorptive removal from aqueous solutions by modified magnetite nanoparticle using response surface methodology (RSM)

    Energy Technology Data Exchange (ETDEWEB)

    Karimi, Mohammad, E-mail: m.karimi407@alumni.ut.ac.ir [School of Chemical Engineering, College of Engineering, University of Tehran, P.O. Box: 11365-4563, Tehran (Iran, Islamic Republic of); Milani, Saeid Alamdar [Nuclear Fuel Cycle Research School, Nuclear Science and Technology Research Institute, AEOI, P.O. Box: 14893-836, Tehran (Iran, Islamic Republic of); Abolgashemi, Hossein [School of Chemical Engineering, College of Engineering, University of Tehran, P.O. Box: 11365-4563, Tehran (Iran, Islamic Republic of)

    2016-10-15

    In this study, the ability and the adsorption capacity of magnetite/aminopropyltriethoxysilane/glutaraldehyde (Fe{sub 3}O{sub 4}/APTES/GA) adsorbent were evaluated for the adsorption of thorium (IV) ions from aqueous solutions. The influence of the several variables such as pH (1–5), Th (IV) initial concentration (50–300 mg L{sup −1}) and adsorbent concentration (1–5 g L{sup −1}) on the Th (IV) adsorption were investigated by response surface methodology (RSM). The results showed that the highest absorption capacity (q) was 107.23 mg g{sup −1} with respect to pH = 4.5, initial concentration of 250 mg L{sup −1} and adsorbent concentration of 1 g L{sup −1} for 90 min. Modeling equilibrium sorption data with the Langmuir, Freundlich and Dubinin–Radushkevich models pointed out that the results were in good agreement with Langmuir model. The experimental kinetic data were well fitted to pseudo-second-order equation with R{sup 2} = 0.9739. Also thermodynamic parameters (ΔG{sup o}, ΔH{sup o}, ΔS{sup o}) declared that the Th (IV) adsorption was endothermic and spontaneous. - Highlights: • Thorium ions were removed from aqueous solutions by modified magnetite nanoparticle. • The effects of process variables on adsorption capacity were investigated by RSM. • Thermodynamic parameters showed that the adsorption was endothermic and spontaneous. • The equilibrium data for the adsorption of Thorium followed the Langmuir isotherm. • The experimental kinetic data were described by the pseudo-second-order equation.

  4. Visible light assisted photodecolorization of eosin-Y in aqueous solution using hesperidin modified TiO2 nanoparticles

    Science.gov (United States)

    Vignesh, K.; Suganthi, A.; Rajarajan, M.; Sakthivadivel, R.

    2012-03-01

    Hesperidin a flavanoid, modified TiO2 nanoparticles (Hes-TiO2) was synthesized to improve the visible light driven photocatalytic performance of TiO2. The synthesized nanoparticles were characterized by UV-visible diffuse reflectance spectroscopy (UV-vis-DRS), FT-IR, powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). The photocatalytic activity of Hes-TiO2 was investigated based on the decolorization of eosin-Y under visible light irradiation. Hes-TiO2 showed high efficiency for the decolorization of eosin-Y. The influences of various reaction parameters like effect of pH, catalyst dosage and initial dye concentration on the photocatalytic efficiency were investigated. The adsorption of eosin-Y on Hes-TiO2 was found favorable by the Langmuir approach. The removal percentage of chemical oxygen demand (COD) was determined to evaluate the mineralization of eosin-Y during photodecolorization. Based on the intermediates obtained in the GC-MS spectroscopic technique, a probable degradation mechanism has been proposed.

  5. Visible light assisted photodecolorization of eosin-Y in aqueous solution using hesperidin modified TiO2 nanoparticles

    International Nuclear Information System (INIS)

    Vignesh, K.; Suganthi, A.; Rajarajan, M.; Sakthivadivel, R.

    2012-01-01

    Hesperidin a flavanoid, modified TiO 2 nanoparticles (Hes-TiO 2 ) was synthesized to improve the visible light driven photocatalytic performance of TiO 2 . The synthesized nanoparticles were characterized by UV-visible diffuse reflectance spectroscopy (UV-vis-DRS), FT-IR, powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). The photocatalytic activity of Hes-TiO 2 was investigated based on the decolorization of eosin-Y under visible light irradiation. Hes-TiO 2 showed high efficiency for the decolorization of eosin-Y. The influences of various reaction parameters like effect of pH, catalyst dosage and initial dye concentration on the photocatalytic efficiency were investigated. The adsorption of eosin-Y on Hes-TiO 2 was found favorable by the Langmuir approach. The removal percentage of chemical oxygen demand (COD) was determined to evaluate the mineralization of eosin-Y during photodecolorization. Based on the intermediates obtained in the GC-MS spectroscopic technique, a probable degradation mechanism has been proposed.

  6. Visible light assisted photodecolorization of eosin-Y in aqueous solution using hesperidin modified TiO{sub 2} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Vignesh, K. [P.G. and Research Department of Chemistry, Thiagarajar College, Madurai, Tamilnadu 625009 (India); Suganthi, A., E-mail: suganthiphd09@gmail.com [P.G. and Research Department of Chemistry, Thiagarajar College, Madurai, Tamilnadu 625009 (India); Rajarajan, M., E-mail: rajarajan_1962@yahoo.com [Department of Chemistry, C.P.A. College, Bodinayakanur, Tamilnadu 626513 (India); Sakthivadivel, R. [P.G. and Research Department of Chemistry, Thiagarajar College, Madurai, Tamilnadu 625009 (India)

    2012-03-01

    Hesperidin a flavanoid, modified TiO{sub 2} nanoparticles (Hes-TiO{sub 2}) was synthesized to improve the visible light driven photocatalytic performance of TiO{sub 2}. The synthesized nanoparticles were characterized by UV-visible diffuse reflectance spectroscopy (UV-vis-DRS), FT-IR, powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). The photocatalytic activity of Hes-TiO{sub 2} was investigated based on the decolorization of eosin-Y under visible light irradiation. Hes-TiO{sub 2} showed high efficiency for the decolorization of eosin-Y. The influences of various reaction parameters like effect of pH, catalyst dosage and initial dye concentration on the photocatalytic efficiency were investigated. The adsorption of eosin-Y on Hes-TiO{sub 2} was found favorable by the Langmuir approach. The removal percentage of chemical oxygen demand (COD) was determined to evaluate the mineralization of eosin-Y during photodecolorization. Based on the intermediates obtained in the GC-MS spectroscopic technique, a probable degradation mechanism has been proposed.

  7. Catalytic oxidation of cyanides in an aqueous phase over individual and manganese-modified cobalt oxide systems

    International Nuclear Information System (INIS)

    Christoskova, St.; Stoyanova, M.

    2009-01-01

    The possibility for purification of wastewaters containing free cyanides by applying of a new method based on cyanides catalytic oxidation with air to CO 2 and N 2 at low temperature and atmospheric pressure was investigated. On this purpose, individual and modified with manganese Co-oxide systems as active phase of environmental catalysts were synthesized. The applied method of synthesis favours the preparation of oxide catalytic systems with high active oxygen content (total-O* and surface-O* s ) possessing high mobility, and the metal ions being in a high oxidation state and in an octahedral coordination-factors determining high activity in reactions of complete oxidation. The catalysts employed were characterized by powder X-ray diffraction, Infrared spectroscopy, and chemical analysis. The effect of pH of the medium and catalyst loading on the effectiveness of the cyanide oxidation process, expressed by the degree of conversion (α, %), by the rate constant (k, min -1 ), and COD was studied. The results obtained reveal that using catalysts investigated a high cyanide removal efficiency could be achieved even in strong alkaline medium. The higher activity of the manganese promoted catalytic sample could be explained on the basis of higher total active oxygen content and its higher mobility both depending on the conditions, under which the synthesis of catalyst is being carried out.

  8. Diatomite Modified Immobilized Delftia sp. for the Bio-Abiotic Removal of Antibiotics Amoxicillin in the Aqueous System

    Science.gov (United States)

    Gao, Lijuan; Sun, Jing; Guan, Kai; Shen, Tingting; Wang, Xikui

    2017-05-01

    Diatomite modified sodium alginate (Si/SA) immobilized Delftia sp. A2(2011) (STT01) was applied to degrade amoxicillin. The immobilized pellets provided a direct and visual probe for the degradation process due to their intrinsic bright colour. The results demonstrated that 100% of amoxicillin and 68.5% of CODcr removal were achieved after 72 h, comparing with the cases of sodium alginate (SA) system (81.2%, 46.9%) and the free cells system (60.5%, 35.5%). The degradation kinetics was in good agreement with Michaelis-Menten equation. The maximum rate (Vm ) and Michaelis constant (Km ) were calculated as 9.09 mg L-1 h-1 and 228 mg L-1, respectively. The results further revealed that diatomite not only acted as immobilization support to improve the mechanical strength and lifetime of the pellets but also as absorbent to promote the treatment efficiency. Therefore, both enzymatic catalysis and chemisorption were responsible for the removal of amoxicillin.

  9. Recognition of RNA by amide modified backbone nucleic acids: molecular dynamics simulations of DNA-RNA hybrids in aqueous solution.

    Science.gov (United States)

    Nina, Mafalda; Fonné-Pfister, Raymonde; Beaudegnies, Renaud; Chekatt, Habiba; Jung, Pierre M J; Murphy-Kessabi, Fiona; De Mesmaeker, Alain; Wendeborn, Sebastian

    2005-04-27

    Thermodynamic and structural properties of a chemically modified DNA-RNA hybrid in which a phosphodiester linkage is replaced by a neutral amide-3 linkage (3'-CH(2)-CONH-5') were investigated using UV melting experiments, molecular dynamics simulations in explicit water, and continuum solvent models. van't Hoff analysis of the experimental UV melting curves suggests that the significant increase of the thermodynamic stability of a 15-mer DNA-RNA with seven alternated amide-3 modifications (+11 degrees C) is mainly due to an increased binding enthalpy. To further evaluate the origin in the observed affinities differences, the electrostatic contribution to the binding free energy was calculated by solving the Poisson-Boltzmann equation numerically. The nonelectrostatic contribution was estimated as the product of a hydrophobic surface tension coefficient and the surface area that is buried upon double strand formation. Structures were taken from 10 ns molecular dynamics simulations computed in a consistent fashion using explicit solvent, counterions, and the particle-mesh Ewald procedure. The present preliminary thermodynamic study suggests that the favorable binding free energy of the amide-3 DNA single strand to the complementary RNA is equally driven by electrostatic and nonpolar contributions to the binding compared to their natural analogues. In addition, molecular dynamics simulations in explicit water were performed on an amide-3 DNA single strand and the corresponding natural DNA. Results from the conformations cluster analysis of the simulated amide-3 DNA single strand ensembles suggest that the 25% of the population sampled within 10 ns has a pre-organized conformation where the sugar C3' endo pucker is favored at the 3'-flanking nucleotides. These structural and thermodynamic features contribute to the understanding of the observed increased affinities of the amide-3 DNA-RNA hybrids at the microscopic level.

  10. Thermodynamics of inclusion complexes of natural and modified cyclodextrins with acetylsalicylic acid and ibuprofen in aqueous solution at 298 K

    Energy Technology Data Exchange (ETDEWEB)

    Castronuovo, Giuseppina, E-mail: giuseppina.castronuovo@unina.it [Department of Chemistry, University Federico II of Naples, Complesso Universitario a Monte S. Angelo, via Cintia, 80126 Naples (Italy); Niccoli, Marcella [Department of Chemistry, University Federico II of Naples, Complesso Universitario a Monte S. Angelo, via Cintia, 80126 Naples (Italy)

    2013-04-10

    Graphical abstract: Complexation forces acting in the association between natural and modified α- and β-cyclodextrins and acetylsalicylic acid (aspirin) or ibuprofen are examined through the analysis of the thermodynamic parameters obtained by isothermal calorimetry. Highlights: ► A calorimetric method is reported to study the association of natural and substituted cyclodextrins with acetylsalicylic acid and ibuprofen. ► The study aims to propose a hypothesis about the forces involved in the interaction. That can be useful for designing new cyclodextrins having suitable characteristics to include specific drugs. ► Enthalpic and entropic contributions on the association are discussed. The differences in the cavity dimensions of the cyclodextrins determine the values of the thermodynamic properties to be very different. - Abstract: Thermodynamic parameters for the association of natural and substituted α-, β-, and γ-cyclodextrins with acetylsalicylic acid, salicylic acid and ibuprofen have been determined by isothermal titration calorimetry. Analysis of the data shows that complexes form, all having 1:1 stoichiometry. The shape-matching between the host and guest is the factor determining the values of the thermodynamic quantities. In the case of the smallest cyclodextrin interacting with acetylsalicylic acid and salicylic acid, the parameters indicate that hydrophobic interactions play the major role. Association occurs through the shallow inclusion of the benzene ring into the cavity. In the case of substituted β-cyclodextrins, instead, inclusion of the benzene ring is deeper and the tight fitting of the guest molecule to the cavity makes the enthalpy and entropy to be both negative. Ibuprofen interacts through its isobutyl group: the values of the association constants are very high for β-cyclodextrins as determined by the large and positive entropies due to the relaxation of water molecules from the cavity and the hydration spheres of the interacting

  11. Adsorption of platinum(IV) and palladium(II) from aqueous solution by thiourea-modified chitosan microspheres

    International Nuclear Information System (INIS)

    Zhou Limin; Liu Jinhui; Liu Zhirong

    2009-01-01

    The chitosan microparticles were prepared using the inverse phase emulsion dispersion method and modified with thiourea (TCS). TCS was characterized by scanning electron microscope (SEM), the Fourier transform infrared (FT-IR) spectra, sulfur elemental analysis, specific surface area and pore diameter. The effects of various parameters, such as pH, contact time, initial concentration and temperature, on the adsorption of Pt(IV) and Pd(II) by TCS were investigated. The results showed that the maximum adsorption capacity was found at pH 2.0 for both Pt(IV) and Pd(II). TCS can selectively adsorb Pt(IV) and Pd(II) from binary mixtures with Cu(II), Pb(II), Cd(II), Zn(II), Ca(II), and Mg(II). The adsorption reaction followed the pseudo-second-order kinetics, indicating the main adsorption mechanism of chemical adsorption. The isotherm adsorption equilibrium was well described by Langmuir isotherms with the maximum adsorption capacity of 129.9 mg/g for Pt(IV) and 112.4 mg/g for Pd(II). The adsorption capacity of both Pt(IV) and Pd(II) decreased with temperature increasing. The negative values of enthalpy (ΔH o ) and Gibbs free energy (ΔG o ) indicate that the adsorption process is exothermic and spontaneous in nature. The adsorbent was stable without loss of the adsorption capacity up to at least 5 cycles and the desorption efficiencies were above 95% when 0.5 M EDTA-0.5 M H 2 SO 4 eluent was used. The results also showed that the preconcentration factor for Pt(IV) and Pd(II) was 196 and 172, respectively, and the recovery was found to be more than 97% for both precious metal ions.

  12. Thermodynamics of inclusion complexes of natural and modified cyclodextrins with acetylsalicylic acid and ibuprofen in aqueous solution at 298 K

    International Nuclear Information System (INIS)

    Castronuovo, Giuseppina; Niccoli, Marcella

    2013-01-01

    Graphical abstract: Complexation forces acting in the association between natural and modified α- and β-cyclodextrins and acetylsalicylic acid (aspirin) or ibuprofen are examined through the analysis of the thermodynamic parameters obtained by isothermal calorimetry. Highlights: ► A calorimetric method is reported to study the association of natural and substituted cyclodextrins with acetylsalicylic acid and ibuprofen. ► The study aims to propose a hypothesis about the forces involved in the interaction. That can be useful for designing new cyclodextrins having suitable characteristics to include specific drugs. ► Enthalpic and entropic contributions on the association are discussed. The differences in the cavity dimensions of the cyclodextrins determine the values of the thermodynamic properties to be very different. - Abstract: Thermodynamic parameters for the association of natural and substituted α-, β-, and γ-cyclodextrins with acetylsalicylic acid, salicylic acid and ibuprofen have been determined by isothermal titration calorimetry. Analysis of the data shows that complexes form, all having 1:1 stoichiometry. The shape-matching between the host and guest is the factor determining the values of the thermodynamic quantities. In the case of the smallest cyclodextrin interacting with acetylsalicylic acid and salicylic acid, the parameters indicate that hydrophobic interactions play the major role. Association occurs through the shallow inclusion of the benzene ring into the cavity. In the case of substituted β-cyclodextrins, instead, inclusion of the benzene ring is deeper and the tight fitting of the guest molecule to the cavity makes the enthalpy and entropy to be both negative. Ibuprofen interacts through its isobutyl group: the values of the association constants are very high for β-cyclodextrins as determined by the large and positive entropies due to the relaxation of water molecules from the cavity and the hydration spheres of the interacting

  13. Transport behaviors of anionic azo dyes at interface between surfactant-modified flax shives and aqueous solution: Synchrotron infrared and adsorption studies

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Wenxia [MOE Key Laboratory of Resources and Environmental Systems Optimization, Institute for Energy, Environment and Sustainability Research, UR-NCEPU, North China Electric Power University, Beijing, 102206 (China); Huang, Guohe, E-mail: huang@iseis.org [MOE Key Laboratory of Resources and Environmental Systems Optimization, Institute for Energy, Environment and Sustainability Research, UR-NCEPU, North China Electric Power University, Beijing, 102206 (China); An, Chunjiang; Xin, Xiaying [Institute for Energy, Environment and Sustainable Communities, University of Regina, Regina, S4S 0A2 (Canada); Zhang, Yan [MOE Key Laboratory of Resources and Environmental Systems Optimization, Institute for Energy, Environment and Sustainability Research, UR-NCEPU, North China Electric Power University, Beijing, 102206 (China); Liu, Xia [Canadian Light Source, Saskatoon, S7N 2V3 (Canada)

    2017-05-31

    Highlights: • Surfactant modified flax shives for removing anionic azo dyes. • The equilibrium and kinetic studies for the adsorption of anionic azo dyes. • The migration patterns of dye pollutants at flax shive-water interface. • New insights from synchrotron infrared-assisted characterization. • Potential as biomass adsorbent for the removal of dyes from wastewater. - Abstract: From the viewpoint of sustainability, biomass adsorbent has a high potential in pollution control and there is an emerging interest to investigate the behaviors of pollutants at the interface between biomass adsorbent and solution. This study investigated the performance of cetyltrimethylammonium bromide surfactant-modified flax shives (MFS) for removal of anionic azo dyes from aqueous solution. The equilibrium and kinetic analysis for the adsorption of Acid Orange 7 (AO-7), Acid Red 18 (AR-18) and Acid Black 1 (AB-1) on MFS were conducted. The surface of MFS was characterized by synchrotron infrared and SEM analysis. The absorbed amount of three anionic azo dyes varied with the change of adsorbent dosage, pH and ionic strength. The adsorption isotherm data well fit to the Langmuir model. The adsorption process followed the pseudo-second-order kinetics and the liquid film diffusion models. Thermodynamic studies indicated that the adsorption of three anionic azo dyes was spontaneous. The adsorption of AR-18 and AB-1 onto MFS was endothermic while the adsorption of AO-7 was exothermic. The results can help better understand the behaviors of organic pollutants at biomass adsorbent-water interface. They also present the potential of using MFS as a suitable adsorbent for the removal of anionic azo dyes from wastewater.

  14. Transport behaviors of anionic azo dyes at interface between surfactant-modified flax shives and aqueous solution: Synchrotron infrared and adsorption studies

    International Nuclear Information System (INIS)

    Wang, Wenxia; Huang, Guohe; An, Chunjiang; Xin, Xiaying; Zhang, Yan; Liu, Xia

    2017-01-01

    Highlights: • Surfactant modified flax shives for removing anionic azo dyes. • The equilibrium and kinetic studies for the adsorption of anionic azo dyes. • The migration patterns of dye pollutants at flax shive-water interface. • New insights from synchrotron infrared-assisted characterization. • Potential as biomass adsorbent for the removal of dyes from wastewater. - Abstract: From the viewpoint of sustainability, biomass adsorbent has a high potential in pollution control and there is an emerging interest to investigate the behaviors of pollutants at the interface between biomass adsorbent and solution. This study investigated the performance of cetyltrimethylammonium bromide surfactant-modified flax shives (MFS) for removal of anionic azo dyes from aqueous solution. The equilibrium and kinetic analysis for the adsorption of Acid Orange 7 (AO-7), Acid Red 18 (AR-18) and Acid Black 1 (AB-1) on MFS were conducted. The surface of MFS was characterized by synchrotron infrared and SEM analysis. The absorbed amount of three anionic azo dyes varied with the change of adsorbent dosage, pH and ionic strength. The adsorption isotherm data well fit to the Langmuir model. The adsorption process followed the pseudo-second-order kinetics and the liquid film diffusion models. Thermodynamic studies indicated that the adsorption of three anionic azo dyes was spontaneous. The adsorption of AR-18 and AB-1 onto MFS was endothermic while the adsorption of AO-7 was exothermic. The results can help better understand the behaviors of organic pollutants at biomass adsorbent-water interface. They also present the potential of using MFS as a suitable adsorbent for the removal of anionic azo dyes from wastewater.

  15. Hybrid molecularly imprinted poly(methacrylic acid-TRIM)-silica chemically modified with (3-glycidyloxypropyl)trimethoxysilane for the extraction of folic acid in aqueous medium

    Energy Technology Data Exchange (ETDEWEB)

    Midori de Oliveira, Fernanda; Gava Segatelli, Mariana [Departamento de Química, Universidade Estadual de Londrina, Rod. Celso Garcia Cid, PR 445 Km 380, Campus Universitário, Londrina, PR CEP 86051-990 (Brazil); Tarley, César Ricardo Teixeira, E-mail: ctarleyquim@yahoo.com.br [Departamento de Química, Universidade Estadual de Londrina, Rod. Celso Garcia Cid, PR 445 Km 380, Campus Universitário, Londrina, PR CEP 86051-990 (Brazil); Instituto Nacional de Ciência e Tecnologia (INCT) de Bioanalítica, Universidade Estadual de Campinas (UNICAMP), Instituto de Química, Departamento de Química Analítica, Cidade Universitária Zeferino Vaz s/n, CEP 13083-970 Campinas, SP (Brazil)

    2016-02-01

    In the present study a hybrid molecularly imprinted poly(methacrylic acid-trimethylolpropane trimethacrylate)-silica (MIP) was synthesized and modified with (3-glycidyloxypropyl)trimethoxysilane (GPTMS) with posterior opening of epoxy ring to provide hydrophilic properties of material in the extraction of folic acid from aqueous medium. The chemical and structural aggregates of hybrid material were characterized by means of Fourier Transform Infrared (FT-IR), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Thermogravimetric analysis (TGA) and textural data. Selectivity data of MIP were compared to non-imprinted polymer (NIP) through competitive sorption studies in the presence of caffeine, paracetamol or 4-aminobenzamide yielding relative selectivity coefficients (k′) higher than one unit, thus confirming the selective character of MIP even in the presence of structurally smaller compounds than the folic acid. The lower hydrophobic sorption by bovine serum albumin (BSA) in the MIP as compared to unmodified MIP proves the hydrophilicity of polymer surface by using GPTMS with opening ring. Under acid medium (pH 1.5) the sorption of folic acid onto MIP from batch experiments was higher than the one achieved for NIP. Equilibrium sorption of folic acid was reached at 120 min for MIP, NIP and MIP without GPTMS and kinetic sorption data were well described by pseudo-second-order, Elovich and intraparticle diffusion models. Thus, these results indicate the existence of different binding energy sites in the polymers and a complex mechanism consisting of both surface sorption and intraparticle transport of folic acid within the pores of polymers. - Highlights: • The molecularly imprinted hybrid polymer showed high adsorption capacity for folic acid. • The molecularly imprinted hybrid polymer showed high selectivity for folic acid. • The molecularly imprinted hybrid polymer modified with GPTMS excludes higher amount of BSA.

  16. Preparation, characterization and application of superparamagnetic iron oxide nanoparticles modified with natural polymers for removal of {sup 60}Co-radionuclides from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Sharaf El-Deen, Gehan E. [Atomic Energy Authority, Cairo (Egypt). Radioactive Waste Management Dept.; Imam, Neama G. [Atomic Energy Authority, Cairo (Egypt). Experimental Physics Dept.; Elettra, Sincrotrone, Trieste (Italy); Ayoub, Refaat R. [Atomic Energy Authority, Cairo (Egypt). Nuclear Chemistry Dept.

    2017-04-01

    Superparamagnetic iron oxide nanoparticles (IO-MNPs) coated with natural polymers, starch (IO-S MNPs) and dextrin (IO-D MNPs), were synthesized by modified co-precipitation method. IO and hybrid-IO-MNPs were characterized by XRD, SEM, HRTEM, FT-IR spectroscopy, vibrating sample magnetometer (VSM) and zeta potential (ZP). IO-S MNPs and IO-D MNPs have IO core-shell structure with core of 10.8 nm and 13.8 nm and shell of 7.5 nm and 5.9 nm, respectively. The efficiency of the hybrid IO-MNPs for sorption of {sup 60}Co(II)-radionuclides from aqueous solution was investigated under varying experimental conditions. Kinetic data were described well by pseudo-second-order mode, sorption isotherms were fitted quite with Freundlich model with maximum adsorption capacity 36.89 (mmol.g{sup -1})/(L.mmol{sup -1}){sup n} for IO-S MNPs and 24.9 (mmol.g{sup -1})/(L.mmol{sup -1}){sup n} for IO-D MNPs. Sorption of {sup 60}Co-radionuclides by IO-S MNPs was suppressed with salinity and most of the adsorbed {sup 60}Co onto IO-S MNPs could be remove with 0.1 M HCl solution. IO-S MNPs exhibits superparamagnetic properties, easier separation according to higher saturation magnetization (47 emu/g) and better adsorption for {sup 60}CO-radionuclides than IO-D MNPs.

  17. Determination of Uranium in Aqueous and Organic Medium From Product and Waste Processes by Potentiometric Titration Using Modified Davies Gray Method

    International Nuclear Information System (INIS)

    Putro, K.P; Suripto, A

    1998-01-01

    Determination of uranium in aqueous and organic solution generated from nuclear fuels production and liquid radioactive waste at Fuel Element Production Installation for Research Reactor, by modified Davies-Gray method using phosphoric acid as medium and vanadium as catalyst has been carried out. The performed at different concentration of phosphoric acid, vanadium and the effect of impurities, as Al, Fe, Si, Cl and F in sample are measurement. Determination of uranium in organic solvent are the sample volume, agitation time and the optimum concentration of uranium to measurement. It was observed that, the optimum conditions for uranium analysis were : 5 -400 mg uranium in 3.2 M phosphoric acid medium containing 220 mg/l vanadium as catalyst. The impurities of Al ≤ 40.5 μg/ml, Fe ≤ 67.6 μg/ml, Si ≤ 20.3 μg/ml, Cl ≤ 135.1 μg/ml and F 13.5 μg/ml have not effect, but the concentration of F ≥ 40.5 μg/ml have effect in analysis result. The uranium content detectable in organic medium has been found between 0.01 to 0.10 g/l and the reproducibility range between 0.09 to 0.15 as well as the sample volume should be in the range of 5 and 10 ml by the agitation time for 4 minute

  18. Kinetics of Cd2+ and Cr3+ Sorption from Aqueous Solutions Using Mercaptoacetic Acid Modified and Unmodified Oil Palm Fruit Fibre(Elaeis guineensis) Adsorbents

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The kinetics of the sorption of Cd2+ and Cr3+ from aqueous solutions by mercaptoacetic acid modified and unmodified oil palm fruit fibre adsorbents were investigated. The results indicate that sorption equilibrium was reached within 60 min for both metals. Also, the removal efficiency of the three adsorbents was observed to increase for both metals with stronger treatments with mercaptoacetic acid. This may be attributed to the influence of the thiolation of the adsorbents. Furthermore, Cr3+ had higher removal percentages than Cd2+ for all the adsorbents. The sorption mechanism based on the intraparticle diffusion model shows that Cd2+ sorption is better described than Cr3+. The intraparticle diffusion rate constants, K1d, for Cd2+are 62.04 min-1 (untreated), 67.01 min-1 (treated with 0.5 mol/L mercaptoacetic acid), and 71.43 min-1(treated with 1.0 mol/L mercaptocacetic acid) while those for Cr3+ are 63.41 min-1 (untreated), 65.79 min-1(0.5 mol/L acid treated), and 66.25 min-1 (1.0 mol/L acid treated).

  19. Shelf-life extension of semi-dried buckwheat noodles by the combination of aqueous ozone treatment and modified atmosphere packaging.

    Science.gov (United States)

    Bai, Yi-Peng; Guo, Xiao-Nao; Zhu, Ke-Xue; Zhou, Hui-Ming

    2017-12-15

    The present study investigated the combined effects of aqueous ozone treatment and modified atmosphere packaging (MAP) on prolonging the shelf-life of semi-dried buckwheat noodles [SBWN; moisture content (22.5±0.5%)] at 25°C. Firstly, the different concentrations of ozonated water were used to make SBWN. Subsequently, SBWN prepared with ozonated water were packaged under six different conditions and stored for 11days. Changes in microbial, chemical-physical, textural properties and sensorial qualities of SWBN were monitored during storage. Microbiological results indicated that adopting 2.21mg/L of ozonated water resulted in a 1.8 log 10 CFU/g reduction of the initial microbial loads in SBWN. In addition, MAP suppressed the microbial growth with a concomitant reduction in the rates of acidification and quality deteriorations of SBWN. Finally, the shelf-life of sample packed under N 2 :CO 2 =30:70 was extended to 9days, meanwhile textural and sensorial characteristics were maintained during the whole storage period. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Redox Buffer Strength

    Science.gov (United States)

    de Levie, Robert

    1999-04-01

    The proper functioning of enzymes in bodily fluids requires that the pH be maintained within rather narrow limits. The first line of defense against large pH fluctuations in such fluids is the passive control provided by the presence of pH buffers. The ability of pH buffers to stabilize the pH is indicated by the buffer value b introduced in 1922 by van Slyke. It is equally important for many enzymes that the redox potential is kept within a narrow range. In that case, stability of the potential is most readily achieved with a redox buffer. In this communication we define the redox buffer strength by analogy with acid-base buffer strength.

  1. Organellar Calcium Buffers

    Science.gov (United States)

    Prins, Daniel; Michalak, Marek

    2011-01-01

    Ca2+ is an important intracellular messenger affecting many diverse processes. In eukaryotic cells, Ca2+ storage is achieved within specific intracellular organelles, especially the endoplasmic/sarcoplasmic reticulum, in which Ca2+ is buffered by specific proteins known as Ca2+ buffers. Ca2+ buffers are a diverse group of proteins, varying in their affinities and capacities for Ca2+, but they typically also carry out other functions within the cell. The wide range of organelles containing Ca2+ and the evidence supporting cross-talk between these organelles suggest the existence of a dynamic network of organellar Ca2+ signaling, mediated by a variety of organellar Ca2+ buffers. PMID:21421925

  2. Phosphorus-modified poly(styrene-co-divinylbenzene)–PAMAM chelating resin for the adsorption of uranium(VI) in aqueous

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Qiong [College of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China); Liu, Yaochi, E-mail: liuyaochi72@163.com [College of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China); Wang, Chunzhi [Baling Company, China Petroleum and Chemical Corporation (China); Cheng, Jiashun [College of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China)

    2013-12-15

    Highlights: • A series of phosphorus-modified poly(styrene-co-divinylbenzene)–PAMAM chelating resins were synthesized. • The materials were commercially available and economic. • The new resins were high effective and selective adsorbents. • U(VI) adsorption is fitted with pseudo-second-order equation and Langmuir model. • The new resins can be regenerated. -- Abstract: Polyamidoamine (PAMAM) modified poly(styrene-co-divinylbenzene) absorbents carrying phosphorus functional groups (PS-PAMAM-PPA) were prepared and used as adsorbents for the adsorption of uranium(VI) from aqueous solution. Different generations of PAMAM were used for obtaining different chelating resins, PS-PPA, PS-1.0G PAMAM-PPA, PS-2.0G PAMAM-PPA, PS-3.0G PAMAM-PPA and PS-4.0G PAMAM-PPA. The synthesized resins were characterized by FTIR and XPS. The effects of many physio-chemical properties on metal ion adsorption to adsorbent phase, such as solution pH, kinetic studies, initial uranium concentration, temperature, were investigated using batch method. The results showed that the maximum adsorption capacity (99.89 mg/g) was observed at the pH 5.0 and 25 °C with initial U(VI) concentration 100 mg/L and adsorbent dose 1 g/L. PS-1.0G PAMAM-PPA had the largest adsorption capacity for U(VI) compared with other prepared adsorbents. The adsorption kinetics of U(VI) onto PS-1.0G PAMAM-PPA followed the mechanism of the pseudo-second-order equation, indicating that the chemical adsorption was a rate-limiting step. The calculated thermodynamic parameters (ΔG, ΔH, ΔS) stated that the adsorption of U(VI) onto PS-1.0G PAMAM-PPA were spontaneous, endothermic and feasible. The adsorption isotherms obeyed the Langmuir isotherm models. The desorption studies showed that PS-1.0G PAMAM-PPA could be used repeatedly and adsorption and desorption percentage did not have any noticeable loss after 27 cycles in a fixed bed.

  3. Aqueous solution dispersement of carbon nanotubes

    Science.gov (United States)

    Kim, Jae-Woo (Inventor); Park, Cheol (Inventor); Choi, Sang H. (Inventor); Lillehei, Peter T. (Inventor); Harrison, Joycelyn S. (Inventor)

    2011-01-01

    Carbon nanotubes (CNTs) are dispersed in an aqueous buffer solution consisting of at least 50 weight percent water and a remainder weight percent that includes a buffer material. The buffer material has a molecular structure defined by a first end, a second end, and a middle disposed between the first and second ends. The first end is a cyclic ring with nitrogen and oxygen heteroatomes, the middle is a hydrophobic alkyl chain, and the second end is a charged group.

  4. MIPs in Aqueous Environments.

    Science.gov (United States)

    Wan, Ying-chun; Ma, Hui-ting; Lu, Bin

    2015-01-01

    When organic solvent-compatible molecularly imprinted polymers (MIPs) are used in aqueous environment, how to reduce nonspecific binding is a major challenge. By modifying the binding solvents and introducing appropriate washing and elution steps, even relatively hydrophobic MIPs can gain optimal rebinding selectivity in aqueous conditions. Furthermore, water-compatible MIPs that can be used to treat aqueous samples directly have been prepared. The use of hydrophilic co-monomers, the controlled surface modification through controlled radical polymerization, and the new interfacial molecular imprinting methods are different strategies to prepare water-compatible MIPs. By combining MIPs with other techniques, both organic solvent-compatible and water-compatible MIPs can display better functional performances in aqueous conditions. Intensive studies on MIPs in aqueous conditions can provide new MIPs with much-improved compatibilities that will lead to more interesting applications in biomedicine and biotechnology.

  5. ZnS/Zn(O,OH)S-based buffer layer deposition for solar cells

    Science.gov (United States)

    Bhattacharya, Raghu N [Littleton, CO

    2009-11-03

    The invention provides CBD ZnS/Zn(O,OH)S and spray deposited ZnS/Zn(O,OH)S buffer layers prepared from a solution of zinc salt, thiourea and ammonium hydroxide dissolved in a non-aqueous/aqueous solvent mixture or in 100% non-aqueous solvent. Non-aqueous solvents useful in the invention include methanol, isopropanol and triethyl-amine. One-step deposition procedures are described for CIS, CIGS and other solar cell devices.

  6. Electrochemical detection of copper ions leached from CuO nanoparticles in saline buffers and biological media using a gold wire working electrode

    Energy Technology Data Exchange (ETDEWEB)

    Baldisserri, Carlo, E-mail: carlo.baldisserri@istec.cnr.it; Costa, Anna Luisa [ISTEC-CNR (Italy)

    2016-04-15

    We performed explorative cyclic voltammetry in phosphate-buffered saline buffers, Dulbecco’s modified Eagle’s medium (DMEM), and fetal bovine serum-added DMEM using Au wire as working electrode, both in the absence and in the presence of known nominal concentrations of Cu{sup 2+} ions or 15 nm CuO nanoparticles. Addition of either Cu{sup 2+} ions or aqueous suspension of CuO nanoparticles caused a single anodic peak to appear in the double-layer region of all three pristine media. The height of the anodic peak was found to increase in a monotonic fashion vs. Cu{sup 2+} concentration in Cu{sup 2+}-added media, and versus time since CuO addition in CuO-added media. Stepwise addition of glycine to Cu{sup 2+}-added phosphate-buffered saline buffer caused an increasing cathodic shift of the anodic peak accompanied by decreasing peak currents. Results indicate that preparing Cu{sup 2+}-free suspensions of CuO nanoparticles in such media is difficult, owing to the presence of leached copper ions. The implications on results of experiments in which CuO nanoparticle-added biological media are used as cell culture substrates are discussed. Literature data on the interactions between Cu{sup 2+} ions, dissolved carbon dioxide in aqueous CuO suspensions, and amino acids present in such media are compared to our results.

  7. Electrochemical detection of copper ions leached from CuO nanoparticles in saline buffers and biological media using a gold wire working electrode

    Science.gov (United States)

    Baldisserri, Carlo; Costa, Anna Luisa

    2016-04-01

    We performed explorative cyclic voltammetry in phosphate-buffered saline buffers, Dulbecco's modified Eagle's medium (DMEM), and fetal bovine serum-added DMEM using Au wire as working electrode, both in the absence and in the presence of known nominal concentrations of Cu2+ ions or 15 nm CuO nanoparticles. Addition of either Cu2+ ions or aqueous suspension of CuO nanoparticles caused a single anodic peak to appear in the double-layer region of all three pristine media. The height of the anodic peak was found to increase in a monotonic fashion vs. Cu2+ concentration in Cu2+-added media, and versus time since CuO addition in CuO-added media. Stepwise addition of glycine to Cu2+-added phosphate-buffered saline buffer caused an increasing cathodic shift of the anodic peak accompanied by decreasing peak currents. Results indicate that preparing Cu2+-free suspensions of CuO nanoparticles in such media is difficult, owing to the presence of leached copper ions. The implications on results of experiments in which CuO nanoparticle-added biological media are used as cell culture substrates are discussed. Literature data on the interactions between Cu2+ ions, dissolved carbon dioxide in aqueous CuO suspensions, and amino acids present in such media are compared to our results.

  8. Buffer design 2012

    International Nuclear Information System (INIS)

    Juvankoski, M.

    2013-08-01

    Posiva's spent nuclear fuel disposal is based on the KBS-3V concept and on the characteristics of the Olkiluoto site. In this concept single canisters containing spent nuclear fuel surrounded by a bentonite buffer are emplaced in individual vertical boreholes drilled in the floor of deposition tunnels in bedrock at about 420 m depth below ground level. Disk type bentonite blocks are installed at the bottom of the hole and on the top of the disposal canister. Ring type bentonite blocks surround the canisters. This report describes the detailed design of the buffer for a KBS-3V repository. The report presents the design basis, the reference design, and summarises the performance analyses carried out for the design. This report addresses aspects concerning the manufacture, quality control, mechanical strength, chemical resistance, thermal dimensioning, handling of buffer components and material ageing phenomena including the effect of radiation. Interaction of buffer and other engineered barriers are included in the study. The long-term evolution of the repository and its effective drivers are considered if they have an impact on the buffer performance but operational safety aspects are also included because they may affect long-term safety. (orig.)

  9. The SVT Hit Buffer

    International Nuclear Information System (INIS)

    Belforte, S.; Dell'Orso, M.; Donati, S.

    1996-01-01

    The Hit Buffer is part of the Silicon Vertex Tracker, a trigger processor dedicated to the reconstruction of particle trajectories in the Silicon Vertex Detector and the Central Tracking Chamber of the Collider Detector at Fermilab. The Hit Buffer is a high speed data-traffic node, where thousands of words are received in arbitrary order and simultaneously organized in an internal structured data base, to be later promptly retrieved and delivered in response to specific requests. The Hit Buffer is capable of processing data at a rate of 25 MHz, thanks to the use of special fast devices like Cache-Tag RAMs and high performance Erasable Programmable Logic Devices from the XILINX XC7300 family

  10. A parallel buffer tree

    DEFF Research Database (Denmark)

    Sitchinava, Nodar; Zeh, Norbert

    2012-01-01

    We present the parallel buffer tree, a parallel external memory (PEM) data structure for batched search problems. This data structure is a non-trivial extension of Arge's sequential buffer tree to a private-cache multiprocessor environment and reduces the number of I/O operations by the number of...... in the optimal OhOf(psortN + K/PB) parallel I/O complexity, where K is the size of the output reported in the process and psortN is the parallel I/O complexity of sorting N elements using P processors....

  11. Buffer Zone Sign Template

    Science.gov (United States)

    The certified pesticide applicator is required to post a comparable sign, designating a buffer zone around the soil fumigant application block in order to control exposure risk. It must include the don't walk symbol, product name, and applicator contact.

  12. Buffer Zone, Nicosia

    OpenAIRE

    Sorensen, Marie Louise

    2010-01-01

    Images of the United Nations Buffer Zone or Green Line which has partitioned Cyprus since 1974 The research leading to these results has received funding from the European Community's Seventh Framework Programme [FP7/2007-2013] under grant agreement n° 217411.

  13. Creep in buffer clay

    International Nuclear Information System (INIS)

    Pusch, R.; Adey, R.

    1999-12-01

    The study involved characterization of the microstructural arrangement and molecular forcefields in the buffer clay for getting a basis for selecting suitable creep models. It is concluded that the number of particles and wide range of the particle bond spectrum require that stochastical mechanics and thermodynamics will be considered and they are basic to the creep model proposed for predicting creep settlement of the canisters. The influence of the stress level on creep strain of MX-80 clay is not well known but for the buffer creep is approximately proportional to stress. Theoretical considerations suggest a moderate impact for temperatures up to 90 deg C and this is supported by model experiments. It is believed that the assumption of strain being proportional to temperature is conservative. The general performance of the stochastic model can be illustrated in principle by use of visco-elastic rheological models implying a time-related increase in viscosity. The shear-induced creep settlement under constant volume conditions calculated by using the proposed creep model is on the order of 1 mm in ten thousand years and up to a couple of millimeters in one million years. It is much smaller than the consolidation settlement, which is believed to be on the order of 10 mm. The general conclusion is that creep settlement of the canisters is very small and of no significance to the integrity of the buffer itself or of the canisters

  14. Synchrotron x-ray spectroscopy of EuHN O3 aqueous solutions at high temperatures and pressures and Nb-bearing silicate melt phases coexisting with hydrothermal fluids using a modified hydrothermal diamond anvil cell and rail assembly

    Science.gov (United States)

    Mayanovic, Robert A.; Anderson, Alan J.; Bassett, William A.; Chou, I.-Ming

    2007-01-01

    A modified hydrothermal diamond anvil cell (HDAC) rail assembly has been constructed for making synchrotron x-ray absorption spectroscopy, x-ray fluorescence, and x-ray mapping measurements on fluids or solid phases in contact with hydrothermal fluids up to ???900??C and 700 MPa. The diamond anvils of the HDAC are modified by laser milling grooves or holes, for the reduction of attenuation of incident and fluorescent x rays and sample cavities. The modified HDAC rail assembly has flexibility in design for measurement of light elements at low concentrations or heavy elements at trace levels in the sample and the capability to probe minute individual phases of a multiphase fluid-based system using focused x-ray microbeam. The supporting rail allows for uniform translation of the HDAC, rotation and tilt stages, and a focusing mirror, which is used to illuminate the sample for visual observation using a microscope, relative to the direction of the incident x-ray beam. A structure study of Eu(III) aqua ion behavior in high-temperature aqueous solutions and a study of Nb partitioning and coordination in a silicate melt in contact with a hydrothermal fluid are described as applications utilizing the modified HDAC rail assembly. ?? 2007 American Institute of Physics.

  15. Characterization of modified clinoptilolite

    International Nuclear Information System (INIS)

    Novosad, J.; Jandl, J.; Woollins, J.D.

    1992-01-01

    Samples of clinoptilolite were modified using insoluble hexacyanoferrate from aqueous solution. The modified samples were characterized by elemental analysis, powder X-ray diffraction, solid state NMR and vibrational spectroscopy. The sorption properties of modified clinoptilolite were studied, too. Higher affinity for 137 Cs sorption in comparison with the natural clinoptilolite has been proved. (author) 5 refs.; 3 figs.; 2 tabs

  16. Determination of Residual Nonsteroidal Anti-Inflammatory Drugs in Aqueous Sample Using Magnetic Nanoparticles Modified with Cetyltrimethylammonium Bromide by High Performance Liquid Chromatography

    OpenAIRE

    Khoeini Sharifabadi, Malihe; Saber-Tehrani, Mohammad; Waqif Husain, Syed; Mehdinia, Ali; Aberoomand-Azar, Parviz

    2014-01-01

    A simple and sensitive solid-phase extraction method for separation and preconcentration of trace amount of four nonsteroidal anti-inflammatory drugs (naproxen, indomethacin, diclofenac, and ibuprofen) using Fe3O4 magnetic nanoparticles modified with cetyltrimethylammonium bromide has been developed. For this purpose, the surface of MNPs was modified with cetyltrimethylammonium bromide (CTAB) as a cationic surfactant. Effects of different parameters influencing the extraction efficiency of dr...

  17. Characterization of sodium dodecyl sulfate modified iron pillared montmorillonite and its application for the removal of aqueous Cu(II) and Co(II)

    International Nuclear Information System (INIS)

    Li Shuzhen; Wu Pingxiao

    2010-01-01

    Anionic surfactant modified Fe-pillared montmorillonites were prepared by Fe-hydrate solution and sodium dodecyl sulfate (SDS) solution. These organo-inorgano complex montmorillonites were divided into three types (CM1, CM2 and CM3) depending on different intercalation processes. X-ray diffraction spectra, the Fourier transform infrared (FTIR) spectra were used to analyze the structure of the raw and modified montmorillonites. X-ray photoelectron spectra of the simples have been studied to determine spectral characteristics to allow the identification of Fe(III) hydroxide. The specific surface area of the host montmorillonite (M0) is 73.2 m 2 /g, while for the modified montmorillonites it is 114.0 m 2 /g, 117.2 m 2 /g, and 115.8 m 2 /g, respectively. The mesopore volumes of the montmorillonites decrease after modification. Ions of copper and cobalt were selected as adsorbates to evaluate the adsorption performance of each montmorillonite. The adsorption data was analyzed by both Freundlich and Langmuir isotherm models and the data was well fit by the Langmuir isotherm model. The adsorption was efficient and significantly influenced by metal speciation, metal concentration, contact time, and pH. Higher adsorption capacity of the modified montmorillonites were obtained at pH 5-6. The results of desorption indicated that the metal ions were covalently bound to the modified montmorillonites.

  18. The use of new modified poly(acrylamide chelating resin with pendent benzothiazole groups containing donor atoms in the removal of heavy metal ions from aqueous solutions

    Directory of Open Access Journals (Sweden)

    Semmedu Selvaraj Kalaivani

    2014-03-01

    Full Text Available The adsorption studies of poly(6-(ethoxybenzothiazole acrylamide (PEBTA, for Cu(II and Zn(II metal ions removal from an aqueous solution have been investigated, as a function of solution pH, adsorbent dose, contact time, initial metal ion concentration and temperature. The chemical and structural characteristics of the adsorbent were determined by the FT-IR, 1H-NMR, TGA, SEM, and EDAX analysis. The maximum adsorption capacities of the adsorbent for Cu(II and Zn(II ions, as calculated from the Langmuir isotherm model, were 273.5 and 216.4 mg/g, respectively. The adsorption kinetic studies show that the adsorption of Cu(II and Zn(II ions onto PEBTA follows the pseudo second order kinetic model. Thermodynamic parameters such as ΔG°, ΔH° and ΔS° were also evaluated, and it has been found that the adsorption process is feasible, spontaneous and exothermic in nature. Desorption studies were carried out using 0.3 N HCl, and it revealed that the adsorbed Cu(II and Zn(II ions can be easily removed. The adsorption–desorption process is reversible, and this indicates that PEBTA is an effective adsorbent for the removal of heavy metal ions from an aqueous medium.

  19. Buffered or under Scrutiny?

    DEFF Research Database (Denmark)

    Klopf, Patricia; Nell, Phillip C.; Puck, Jonas

    – they are to a stronger extent buffered from the external environment than small firms. Thus, this paper adds to previous research by disentangling the complex effects of size on the use of political strategies – a strand of literature which has been characterized by inconsistent findings in the past.......This paper investigates political strategies of MNE subsidiaries operating in emerging markets. Our findings support previous findings of more intense political strategies in the presence of stronger institutional pressures from public and private stakeholders. Furthermore, we hypothesize...

  20. Investigating the episodic buffer

    Directory of Open Access Journals (Sweden)

    Alan Baddeley

    2010-10-01

    Full Text Available A brief account is presented of the three-component working memory model proposed by Baddeley and Hitch. This is followed by an account of some of the problems it encountered in explaining how information from different subsystems with different codes could be combined, and how it was capable of communicating with long-term memory. In order to account for these, a fourth component was proposed, the episodic buffer. This was assumed to be a multidimensional store of limited capacity that can be accessed through conscious awareness. In an attempt to test and develop the concept, a series of experiments have explored the role of working memory in the binding of visual features into objects and verbal sequences into remembered sentences. The experiments use a dual task paradigm to investigate the role of the various subcomponents of working memory in binding. In contrast to our initial assumption, the episodic buffer appears to be a passive store, capable of storing bound features and making them available to conscious awareness, but not itself responsible for the process of binding.

  1. A comparative study for adsorption of lysozyme from aqueous samples onto Fe3O4 magnetic nanoparticles using different ionic liquids as modifier.

    Science.gov (United States)

    Kamran, Sedigheh; Absalan, Ghodratollah; Asadi, Mozaffar

    2015-12-01

    In this paper, nanoparticles of Fe3O4 as well as their modified forms with different ionic liquids (IL-Fe3O4) were prepared and used for adsorption of lysozyme. The mean size and the surface morphology of the nanoparticles were characterized by TEM, XRD and FTIR techniques. Adsorption studies of lysozyme were performed under different experimental conditions in batch system on different modified magnetic nanoparticles such as, lysozyme concentration, pH of the solution, and contact time. Experimental results were obtained under the optimum operational conditions of pH 9.0 and a contact time of 10 min when initial protein concentrations of 0.05-2.0 mg mL(-1) were used. The isotherm evaluations revealed that the Langmuir model attained better fits to the equilibrium data than the Freundlich model. The maximum obtained adsorption capacities were 370.4, 400.0 500.0 and 526.3 mg of lysozyme for adsorption onto Fe3O4 and modified magnetic nanoparticles by [C4MIM][Br], [C6MIM][Br] and [C8MIM][Br] per gram of adsorbent, respectively. The Langmuir adsorption constants were 0.004, 0.019, 0.024 and 0.012 L mg(-1) for adsorptions of lysozyme onto Fe3O4 and modified magnetic nanoparticles by [C4MIM][Br], [C6MIM][Br] and [C8MIM][Br], respectively. The adsorption capacity of lysozyme was found to be dependent on its chemical structure, pH of the solution, temperature and type of ionic liquid as modifier. The applicability of two kinetic models including pseudo-first order and pseudo-second order model was estimated. Furthermore, the thermodynamic parameters were calculated. Protein could desorb from IL-Fe3O4 nanoparticles by using NaCl solution at pH 9.5 and was reused.

  2. Bus Implementation Using New Low Power PFSCL Tristate Buffers

    Directory of Open Access Journals (Sweden)

    Neeta Pandey

    2016-01-01

    Full Text Available This paper proposes new positive feedback source coupled logic (PFSCL tristate buffers suited to bus applications. The proposed buffers use switch to attain high impedance state and modify the load or the current source section. An interesting consequence of this is overall reduction in the power consumption. The proposed tristate buffers consume half the power compared to the available switch based counterpart. The issues with available PFSCL tristate buffers based bus implementation are identified and benefits of employing the proposed tristate buffer topologies are put forward. SPICE simulation results using TSMC 180 nm CMOS technology parameters are included to support the theoretical formulations. The performance of proposed tristate buffer topologies is examined on the basis of propagation delay, output enable time, and power consumption. It is found that one of the proposed tristate buffer topology outperforms the others in terms of all the performance parameters. An examination of behavior of available and the proposed PFSCL tristate buffer topologies under parameter variations and mismatch shows a maximum variation of 14%.

  3. Effect of passivation on the sensitivity and stability of pentacene transistor sensors in aqueous media

    KAUST Repository

    Khan, Hadayat Ullah

    2011-06-01

    Charge-detecting biosensors have recently become the focal point of biosensor research, especially research onto organic thin-film transistors (OTFTs), which combine compactness, a low cost, and fast and label-free detection to realize simple and stable in vivo diagnostic systems. We fabricated organic pentacene-based bottom-contact thin-film transistors with an ultra-thin insulating layer of a cyclized perfluoro polymer called CYTOP (Asahi Glass Co., Tokyo, Japan) on SiO2 for operation in aqueous media. The stability and sensitivity of these transistor sensors were examined in aqueous buffer media with solutions of variable pH levels after the passivation of perfluoro polymers with thicknesses ranging from 50 to 300nm. These transistor sensors were further modified with an ultra-thin film (5nm) functional layer for selective BSA/antiBSA detection in aqueous buffer media, demonstrating a detection capability as low as 500nM of concentrated antiBSA. The dissociation constant from the antiBSA detection results was 2.1×10-6M. Thus, this study represents a significant step forward in the development of organic electronics for a disposable and versatile chemical and bio-sensing platform. © 2011 Elsevier B.V.

  4. Buffer moisture protection system

    International Nuclear Information System (INIS)

    Ritola, J.; Peura, J.

    2013-11-01

    With the present knowledge, bentonite blocks have to be protected from the air relative humidity and from any moisture leakages in the environment that might cause swelling of the bentonite blocks during the 'open' installation phase before backfilling. The purpose of this work was to design the structural reference solution both for the bottom of the deposition hole and for the buffer moisture protection and dewatering system with their integrated equipment needed in the deposition hole. This report describes the Posiva's reference solution for the buffer moisture protection system and the bottom plate on basis of the demands and functional requirements set by long-term safety. The reference solution with structural details has been developed in research work made 2010-2011. The structural solution of the moisture protection system has not yet been tested in practice. On the bottom of the deposition hole a copper plate which protects the lowest bentonite block from the gathered water is installed straight to machined and even rock surface. The moisture protection sheet made of EPDM rubber is attached to the copper plate with an inflatable seal. The upper part of the moisture protection sheet is fixed to the collar structures of the lid which protects the deposition hole in the disposal tunnel. The main function of the moisture protection sheet is to protect bentonite blocks from the leaking water and from the influence of the air humidity at their installation stage. The leaking water is controlled by the dewatering and alarm system which has been integrated into the moisture protection liner. (orig.)

  5. Buffer capacity of biologics--from buffer salts to buffering by antibodies.

    Science.gov (United States)

    Karow, Anne R; Bahrenburg, Sven; Garidel, Patrick

    2013-01-01

    Controlling pH is essential for a variety of biopharmaceutical process steps. The chemical stability of biologics such as monoclonal antibodies is pH-dependent and slightly acidic conditions are favorable for stability in a number of cases. Since control of pH is widely provided by added buffer salts, the current study summarizes the buffer characteristics of acetate, citrate, histidine, succinate, and phosphate buffers. Experimentally derived values largely coincide with values calculated from a model that had been proposed in 1922 by van Slyke. As high concentrated protein formulations become more and more prevalent for biologics, the self-buffering potential of proteins becomes of relevance. The current study provides information on buffer characteristics for pH ranges down to 4.0 and up to 8.0 and shows that a monoclonal antibody at 50 mg/mL exhibits similar buffer capacity as 6 mM citrate or 14 mM histidine (pH 5.0-6.0). Buffer capacity of antibody solutions scales linearly with protein concentration up to more than 200 mg/mL. At a protein concentration of 220 mg/mL, the buffer capacity resembles the buffer capacity of 30 mM citrate or 50 mM histidine (pH 5.0-6.0). The buffer capacity of monoclonal antibodies is practically identical at the process relevant temperatures 5, 25, and 40°C. Changes in ionic strength of ΔI=0.15, in contrast, can alter the buffer capacity up to 35%. In conclusion, due to efficient self-buffering by antibodies in the pH range of favored chemical stability, conventional buffer excipients could be dispensable for pH stabilization of high concentrated protein solutions. Copyright © 2013 American Institute of Chemical Engineers.

  6. Characterization and application of expanded graphite modified with phosphoric acid and glucose for the removal of Ni(II) from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Li [Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Jinan 250100 (China); Zhang, Jian, E-mail: zhangjian00@sdu.edu.cn [Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Jinan 250100 (China); Xu, Xiaoli [Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Jinan 250100 (China); Zhang, Jie [Shandong Experimental High School, Jinan 250100 (China); Liu, Hai; Guo, Zizhang; Kang, Yan; Li, Yiran [Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Jinan 250100 (China); Xu, Jingtao [School of Municipal and Environmental Engineering, Shandong Jianzhu University, Jinan 250100 (China)

    2015-12-01

    Highlights: • Glucose and H{sub 3}PO{sub 4}, single or together, were used to modify expanded graphite. • The modified condition was at a low temperature (150 °C). • The properties of EG and the highest adsorption ability modified EG were compared. • G-P-EG has the highest adsorption ability, which is much higher than that of EG. - Abstract: Three kinds of modified expanded graphite (EG), impregnated with phosphoric acid (H{sub 3}PO{sub 4}) (P-EG), impregnated with glucose (G-EG), and impregnated with H{sub 3}PO{sub 4} and glucose (G-P-EG), were prepared under a low temperature (150 °C). The adsorption capacity of G-P-EG (Q{sub m} = 7.016 mg/g) is much higher than original expanded graphite (EG Q{sub m} = 0.423 mg/g) and other two kinds of modified expanded graphite (P-EG Q{sub m} = 0.770 mg/g; G-EG Q{sub m} = 0.507 mg/g). The physicochemical properties of EG and G-P-EG were characterized by N{sub 2} adsorption/desorption, Boehm's titration and X-ray photoelectron spectroscopy (XPS). EG exhibited higher values of BET surface area (11.357 m{sup 2}/g) and total pore volume (0.0303 cm{sup 3}/g) than that of G-P-EG (4.808 m{sup 3}/g and 0.0109 cm{sup 3}/g). However, the results of Bohm's titration and XPS showed that G-P-EG contained more surface oxygen-containing functional groups. The Ni(II) adsorption equilibrium data agreed well with the Langmuir model. And the experimental data of EG and G-P-EG fitted better by pseudo-second order model. Based on the results of batch adsorption experiments and XPS analysis, there were several possible mechanisms for Ni(II) adsorption on the G-P-EG, including chemical adsorption, cation exchange, electrostatic attraction and surface complication.

  7. Characterization and application of expanded graphite modified with phosphoric acid and glucose for the removal of Ni(II) from aqueous solution

    International Nuclear Information System (INIS)

    Jiang, Li; Zhang, Jian; Xu, Xiaoli; Zhang, Jie; Liu, Hai; Guo, Zizhang; Kang, Yan; Li, Yiran; Xu, Jingtao

    2015-01-01

    Highlights: • Glucose and H 3 PO 4 , single or together, were used to modify expanded graphite. • The modified condition was at a low temperature (150 °C). • The properties of EG and the highest adsorption ability modified EG were compared. • G-P-EG has the highest adsorption ability, which is much higher than that of EG. - Abstract: Three kinds of modified expanded graphite (EG), impregnated with phosphoric acid (H 3 PO 4 ) (P-EG), impregnated with glucose (G-EG), and impregnated with H 3 PO 4 and glucose (G-P-EG), were prepared under a low temperature (150 °C). The adsorption capacity of G-P-EG (Q m = 7.016 mg/g) is much higher than original expanded graphite (EG Q m = 0.423 mg/g) and other two kinds of modified expanded graphite (P-EG Q m = 0.770 mg/g; G-EG Q m = 0.507 mg/g). The physicochemical properties of EG and G-P-EG were characterized by N 2 adsorption/desorption, Boehm's titration and X-ray photoelectron spectroscopy (XPS). EG exhibited higher values of BET surface area (11.357 m 2 /g) and total pore volume (0.0303 cm 3 /g) than that of G-P-EG (4.808 m 3 /g and 0.0109 cm 3 /g). However, the results of Bohm's titration and XPS showed that G-P-EG contained more surface oxygen-containing functional groups. The Ni(II) adsorption equilibrium data agreed well with the Langmuir model. And the experimental data of EG and G-P-EG fitted better by pseudo-second order model. Based on the results of batch adsorption experiments and XPS analysis, there were several possible mechanisms for Ni(II) adsorption on the G-P-EG, including chemical adsorption, cation exchange, electrostatic attraction and surface complication.

  8. Two-Buffer Simulation Games

    Directory of Open Access Journals (Sweden)

    Milka Hutagalung

    2016-07-01

    Full Text Available We consider simulation games played between Spoiler and Duplicator on two Büchi automata in which the choices made by Spoiler can be buffered by Duplicator in two different buffers before she executes them on her structure. Previous work on such games using a single buffer has shown that they are useful to approximate language inclusion problems. We study the decidability and complexity and show that games with two buffers can be used to approximate corresponding problems on finite transducers, i.e. the inclusion problem for rational relations over infinite words.

  9. Synthesis of titania modified silica-pillared clay (SPC) with highly ordered interlayered mesoporous structure for removing toxic metal ion Cr(VI) from aqueous state

    Energy Technology Data Exchange (ETDEWEB)

    Mao, Huihui, E-mail: maohuihui_beijing@126.com [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, Changzhou University, Changzhou, Jiangsu Province 213164 (China); Zhu, Kongnan [Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, Changzhou University, Changzhou, Jiangsu Province 213164 (China); Li, Baoshan, E-mail: bsli@mail.buct.edu.cn [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Yao, Chao; Kong, Yong [Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, Changzhou University, Changzhou, Jiangsu Province 213164 (China)

    2014-02-15

    Titanium-functionalized silica-pillared clays synthesized through post synthetic route was utilized as adsorbers for the removal of Cr(VI) ions from aqueous solutions under different temperatures and initial concentrations. The starting mesostructured silica-pillared clay is assembled by intragallery ammonia-catalyzed hydrolysis of tetraethoxysilane using cationic surfactant as gallery template, and subsequently, the formed interlayered pore walls were decorated with nano-sized TiO{sub 2} particle through organic titanium functionalization process. The kind of structural transformation has been confirmed by X-ray diffraction (XRD), nitrogen adsorption–desorption isotherms, Fourier transform infrared (FT-IR) analysis, UV–vis diffuse reflectance spectroscopy (DRS), elemental analysis (XRF), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Such results indicate that most of the grafted titanium species was combined with Si–OH on the surface of gallery pores. By changing the concentration of organic titanium source during synthesis, the porous structure system is effected. Under suitable conditions, these materials exhibit high adsorption capacity and efficiency. Qualitative estimates of the thermodynamic parameters showed that the overall adsorption process is spontaneous (ΔG° < 0) and endothermic (ΔH° > 0). The adsorption isotherms of Cr(VI) on titanium-functionalized silica-pillared clay were best fitted by Redlich–Peterson models. Detail results of thermodynamics and kinetics are also presented.

  10. Synthesis of titania modified silica-pillared clay (SPC) with highly ordered interlayered mesoporous structure for removing toxic metal ion Cr(VI) from aqueous state

    International Nuclear Information System (INIS)

    Mao, Huihui; Zhu, Kongnan; Li, Baoshan; Yao, Chao; Kong, Yong

    2014-01-01

    Titanium-functionalized silica-pillared clays synthesized through post synthetic route was utilized as adsorbers for the removal of Cr(VI) ions from aqueous solutions under different temperatures and initial concentrations. The starting mesostructured silica-pillared clay is assembled by intragallery ammonia-catalyzed hydrolysis of tetraethoxysilane using cationic surfactant as gallery template, and subsequently, the formed interlayered pore walls were decorated with nano-sized TiO 2 particle through organic titanium functionalization process. The kind of structural transformation has been confirmed by X-ray diffraction (XRD), nitrogen adsorption–desorption isotherms, Fourier transform infrared (FT-IR) analysis, UV–vis diffuse reflectance spectroscopy (DRS), elemental analysis (XRF), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Such results indicate that most of the grafted titanium species was combined with Si–OH on the surface of gallery pores. By changing the concentration of organic titanium source during synthesis, the porous structure system is effected. Under suitable conditions, these materials exhibit high adsorption capacity and efficiency. Qualitative estimates of the thermodynamic parameters showed that the overall adsorption process is spontaneous (ΔG° 0). The adsorption isotherms of Cr(VI) on titanium-functionalized silica-pillared clay were best fitted by Redlich–Peterson models. Detail results of thermodynamics and kinetics are also presented.

  11. Modified Rice Straw as Adsorbent Material to Remove Aflatoxin B1 from Aqueous Media and as a Fiber Source in Fino Bread

    OpenAIRE

    Sherif R. Mohamed; Tarek A. El-Desouky; Ahmed M. S. Hussein; Sherif S. Mohamed; Khayria M. Naguib

    2016-01-01

    The aims of the current work are in large part the benefit of rice straw to be used as adsorbent material and natural source of fiber in Fino bread. The rice straw was subjected to high temperature for modification process and the chemical composition was carried out and the native rice straw contained about 41.15% cellulose, 20.46% hemicellulose, and 3.91% lignin while modified rice straw has 42.10, 8.65, and 5.81%, respectively. The alkali number was tested and showed an increase in the alk...

  12. Use of bicarbonate buffer systems for dissolution characterization of enteric-coated proton pump inhibitor tablets.

    Science.gov (United States)

    Shibata, Hiroko; Yoshida, Hiroyuki; Izutsu, Ken-Ichi; Goda, Yukihiro

    2016-04-01

    The aim of this study was to assess the effects of buffer systems (bicarbonate or phosphate at different concentrations) on the in vitro dissolution profiles of commercially available enteric-coated tablets. In vitro dissolution tests were conducted using an USP apparatus II on 12 enteric-coated omeprazole and rabeprazole tablets, including innovator and generic formulations in phosphate buffers, bicarbonate buffers and a media modified Hanks (mHanks) buffer. Both omeprazole and rabeprazole tablets showed similar dissolution profiles among products in the compendial phosphate buffer system. However, there were large differences between products in dissolution lag time in mHanks buffer and bicarbonate buffers. All formulations showed longer dissolution lag times at lower concentrations of bicarbonate or phosphate buffers. The dissolution rank order of each formulation differed between mHanks buffer and bicarbonate buffers. A rabeprazole formulation coated with a methacrylic acid copolymer showed the shortest lag time in the high concentration bicarbonate buffer, suggesting varied responses depending on the coating layer and buffer components. Use of multiple dissolution media during in vitro testing, including high concentration bicarbonate buffer, would contribute to the efficient design of enteric-coated drug formulations. © 2016 Royal Pharmaceutical Society, Journal of Pharmacy and Pharmacology.

  13. Layer silicates modified with 1,4-bis(3-aminopropyl)piperazine for the removal of Th(IV), U(VI) and Eu(III) from aqueous media

    Energy Technology Data Exchange (ETDEWEB)

    Guerra, Denis L., E-mail: dlguerra@iqm.unicamp.br [Chemistry Institute, State University of Campinas, P.O. Box 6154, 13084-971 Campinas, Sao Paulo (Brazil); Pinto, Alane A. [Chemistry Institute, State University of Campinas, P.O. Box 6154, 13084-971 Campinas, Sao Paulo (Brazil); Viana, Rubia R. [Universidade Federal de Mato Grosso, UFMT, Centro de Recursos Minerais, Cuiaba, Mato Grosso 78060 900 (Brazil); Airoldi, Claudio [Chemistry Institute, State University of Campinas, P.O. Box 6154, 13084-971 Campinas, Sao Paulo (Brazil)

    2009-11-15

    Natural montmorillonite (M) and synthetic kanemite (K) have been functionalized with 1,4-bis(3-aminopropyl)piperazine reacted with methylacrylate to yield new inorganic-organic chelating materials. The original and modified materials were characterized by X-ray diffractometry, textural analysis, SEM and nuclear magnetic nuclei of carbon-13 and silicon-29. The chemically modified clay samples (M-APPMA and K-APPMA) showed modification of its physical-chemical properties including: specific area 45.0 m{sup 2} g{sup -1} (M) to 978.8 m{sup 2} g{sup -1} (M-APPMA) and 23.5 m{sup 2} g{sup -1} (K) to 898.9 m{sup 2} g{sup -1} (K-APPMA). The ability of these materials to remove thorium(IV), uranyl(VI) and europium(III) from aqueous solution was followed by a series of adsorption isotherms, which were fitted to non-linear Sips adsorption isotherm model. To achieve the best adsorption conditions the influence of pH and variation of metal concentration were investigated. The energetic effects ({Delta}{sub int}H{sup o}, {Delta}{sub int}G{sup o} and {Delta}{sub int}S{sup o}) caused by metal ions adsorption were determined through calorimetric titrations.

  14. Layer silicates modified with 1,4-bis(3-aminopropyl)piperazine for the removal of Th(IV), U(VI) and Eu(III) from aqueous media

    International Nuclear Information System (INIS)

    Guerra, Denis L.; Pinto, Alane A.; Viana, Rubia R.; Airoldi, Claudio

    2009-01-01

    Natural montmorillonite (M) and synthetic kanemite (K) have been functionalized with 1,4-bis(3-aminopropyl)piperazine reacted with methylacrylate to yield new inorganic-organic chelating materials. The original and modified materials were characterized by X-ray diffractometry, textural analysis, SEM and nuclear magnetic nuclei of carbon-13 and silicon-29. The chemically modified clay samples (M-APPMA and K-APPMA) showed modification of its physical-chemical properties including: specific area 45.0 m 2 g -1 (M) to 978.8 m 2 g -1 (M-APPMA) and 23.5 m 2 g -1 (K) to 898.9 m 2 g -1 (K-APPMA). The ability of these materials to remove thorium(IV), uranyl(VI) and europium(III) from aqueous solution was followed by a series of adsorption isotherms, which were fitted to non-linear Sips adsorption isotherm model. To achieve the best adsorption conditions the influence of pH and variation of metal concentration were investigated. The energetic effects (Δ int H o , Δ int G o and Δ int S o ) caused by metal ions adsorption were determined through calorimetric titrations.

  15. Database on gas migration tests through bentonite buffer material

    International Nuclear Information System (INIS)

    Tanai, Kenji

    2009-02-01

    Carbon steel is a candidate material for an overpack for geological disposal of high-level radioactive waste in Japan. The corrosion of the carbon steel overpack in aqueous solution under anoxic conditions will cause the generation of hydrogen gas, which may affect hydrological and mechanical properties of the bentonite buffer. To evaluate such an effect of gas generation, it is necessary to develop a model of gas migration through bentonite buffer material taking account of data obtained from experiments. The gas migration experiments under both unsaturated and saturated conditions have been carried out to clarify the fundamental characteristics of bentonite for gas migration. This report compiles the experimental data obtained from gas migration tests for buffer material which has been conducted by JAEA until December, 2007. A CD-ROM is attached as an appendix. (author)

  16. 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.

  17. Removal of reactive red-120 and 4-(2-pyridylazo) resorcinol from aqueous samples by Fe3O4 magnetic nanoparticles using ionic liquid as modifier.

    Science.gov (United States)

    Absalan, Ghodratollah; Asadi, Mozaffar; Kamran, Sedigheh; Sheikhian, Leila; Goltz, Douglas M

    2011-08-30

    The nanoparticles of Fe(3)O(4) as well as the binary nanoparticles of ionic liquid and Fe(3)O(4) (IL-Fe(3)O(4)) were synthesized for removal of reactive red 120 (RR-120) and 4-(2-pyridylazo) resorcinol (PAR) as model azo dyes from aqueous solutions. The mean size and the surface morphology of the nanoparticles were characterized by TEM, DLS, XRD, FTIR and TGA techniques. Adsorption of RR-120 and PAR was studied in a batch reactor at different experimental conditions such as nanoparticle dosage, dye concentration, pH of the solution, ionic strength, and contact time. Experimental results indicated that the IL-Fe(3)O(4) nanoparticles had removed more than 98% of both dyes under the optimum operational conditions of a dosage of 60mg, a pH of 2.5, and a contact time of 2min when initial dyes concentrations of 10-200mg L(-1) were used. The maximum adsorption capacity of IL-Fe(3)O(4) was 166.67 and 49.26mg g(-1) for RR-120 and PAR, respectively. The isotherm experiments revealed that the Langmuir model attained better fits to the equilibrium data than the Freundlich model. The Langmuir adsorption constants were 5.99 and 3.62L mg(-1) for adsorptions of RR-120 and PAR, respectively. Both adsorption processes were endothermic and dyes could be desorbed from IL-Fe(3)O(4) by using a mixed NaCl-acetone solution and adsorbent was reusable. Copyright © 2011 Elsevier B.V. All rights reserved.

  18. Using fractional order method to generalize strengthening generating operator buffer operator and weakening buffer operator

    OpenAIRE

    Wu, L.; Liu, S.; Yang, Yingjie

    2016-01-01

    Traditional integer order buffer operator is extended to fractional order buffer operator, the corresponding relationship between the weakening buffer operator and the strengthening buffer operator is revealed. Fractional order buffer operator not only can generalize the weakening buffer operator and the strengthening buffer operator, but also realize tiny adjustment of buffer effect. The effectiveness of GM(1,1) with the fractional order buffer operator is validated by six cases.

  19. Mechanisms of buffer therapy resistance.

    Science.gov (United States)

    Bailey, Kate M; Wojtkowiak, Jonathan W; Cornnell, Heather H; Ribeiro, Maria C; Balagurunathan, Yoganand; Hashim, Arig Ibrahim; Gillies, Robert J

    2014-04-01

    Many studies have shown that the acidity of solid tumors contributes to local invasion and metastasis. Oral pH buffers can specifically neutralize the acidic pH of tumors and reduce the incidence of local invasion and metastatic formation in multiple murine models. However, this effect is not universal as we have previously observed that metastasis is not inhibited by buffers in some tumor models, regardless of buffer used. B16-F10 (murine melanoma), LL/2 (murine lung) and HCT116 (human colon) tumors are resistant to treatment with lysine buffer therapy, whereas metastasis is potently inhibited by lysine buffers in MDA-MB-231 (human breast) and PC3M (human prostate) tumors. In the current work, we confirmed that sensitive cells utilized a pH-dependent mechanism for successful metastasis supported by a highly glycolytic phenotype that acidifies the local tumor microenvironment resulting in morphological changes. In contrast, buffer-resistant cell lines exhibited a pH-independent metastatic mechanism involving constitutive secretion of matrix degrading proteases without elevated glycolysis. These results have identified two distinct mechanisms of experimental metastasis, one of which is pH-dependent (buffer therapy sensitive cells) and one which is pH-independent (buffer therapy resistant cells). Further characterization of these models has potential for therapeutic benefit. Copyright © 2014 Neoplasia Press, Inc. Published by Elsevier Inc. All rights reserved.

  20. Unusual buffer action of free-standing nanoscopically confined water.

    Science.gov (United States)

    Liao, Kylin; Xu, Xiaozhou; Du, Xuezhong

    2010-01-15

    The acid-base properties of nanoscopic water confined in the black soap films (BSFs), which were prepared from aqueous solutions of sodium dodecylsulphate (SDS) with the dye neutral red (NR) as a pH probe, were investigated using a combination of UV-vis and FTIR spectroscopy. For the SDS micellar solutions at pH 1.0-9.5 adjusted with HCl/NaOH solutions and at pH 9.4 with ammonium buffered solution, the aqueous core thicknesses in the corresponding BSFs ranged from 2.7 to 6.2 nm, and the nanoscopically confined water exhibits unusual buffer action resistant not only to acidic/alkaline solutions but also to standard buffer solution. In the heavily water-depleted confined zones, it is most likely that charge pairs in proton-transfer reactions could not be formed effectively and proton transfer was prohibited in the absence of sufficient solvating ability. Theoretical analyzes indicated that the buffer action of the nanoscopic water originated from the confinement effect of two charged surfaces of the BSFs. These results might inspire deeper understanding and further studies of biobuffering, enzyme superactivity, acid-catalyzed reactions, and Nafion fuel cell membranes.

  1. Photodegradation of emamectin benzoate in aqueous solutions

    International Nuclear Information System (INIS)

    Mushtaq, M.; Chukwudebe, A.C.; Wrzesinski, C.; Allen, L.R.S.; Luffer-Atlas, D.; Arison, B.H.

    1998-01-01

    The half-life of [ 14 C]4'-deoxy-4'-(epi-methylamino)avermectin B1a (MAB1a) benzoate (1 ppm) photodegradation in buffer (pH 7), natural pond water, and sensitized buffer (1% acetone in pH 7 buffer) determined at Three Bridges, NJ (latitude approximately 40 degrees N) during the fall season under natural sunlight was 22, 7, and 1 days, respectively. The half-life of [ 14 C]MAB1a benzoate (10-12 ppm) photodegradation in buffer (pH 7) containing 1% (v/v) acetonitrile, ethanol, or acetone as cosolvent under continuous exposure with a xenon lamp was 64.5, 8.5, or 0.5 days, respectively. The photoisomer 8,9-Z-MAB1a, 8a-hydroxy-MAB1a, and unknown polar residues were found in light-exposed samples of MAB1a in buffer and natural pond water. In light-exposed sensitized buffer samples, 8a-oxo-MAB1a and MAB1a-10,11-14,15-diepoxide were additional products. Very polar residues found in the organic and aqueous phases after extraction increased with time, and their formation followed the order sensitized buffer natural pond water buffer. (author)

  2. Ce-Fe-modified zeolite-rich tuff to remove Ba(2+)-like (226)Ra(2+) in presence of As(V) and F(-) from aqueous media as pollutants of drinking water.

    Science.gov (United States)

    Olguín, María Teresa; Deng, Shuguang

    2016-01-25

    The sorption behavior of the Ba(2+)-like (226)Ra(2+) in the presence of H2AsO4(-)/HAsO4(2-) and F(-) from aqueous media using Ce-Fe-modified zeolite-rich tuff was investigated in this work. The Na-modified zeolite-rich tuff was also considered for comparison purposes. The zeolite-rich tuff collected from Wyoming (US) was in contact with NaCl and CeCl3-FeCl3 solutions to obtain the Na- and Ce-Fe-modified zeolite-rich tuffs (ZUSNa and ZUSCeFe). These zeolites were characterized by scanning electron microscopy and X-ray diffraction. The BET-specific surface and the points of zero charge were determined as well as the content of Na, Ce and Fe by neutron activation analysis. The textural characteristics and the point of zero charge were changed by the presence of Ce and Fe species in the zeolitic network. A linear model described the Ba(2+)-like (226)Ra(2+) sorption isotherms and the distribution coefficients (Kd) varied with respect to the metallic species present in the zeolitic material. The As(V) oxianionic chemical species and F(-) affected this parameter when the Ba(2+)-like (226)Ra(2+)-As(V)-F(-) solutions were in contact with ZUSCeFe. The H2AsO4(-)/HAsO4(2-) and F(-) were adsorbed by ZUSCeFe in the same amount, independent of the concentration of Ba(2+)-like (226)Ra(2+) in the initial solution. Copyright © 2015 Elsevier B.V. All rights reserved.

  3. Removal of reactive red-120 and 4-(2-pyridylazo) resorcinol from aqueous samples by Fe{sub 3}O{sub 4} magnetic nanoparticles using ionic liquid as modifier

    Energy Technology Data Exchange (ETDEWEB)

    Absalan, Ghodratollah, E-mail: gubsulun@yahoo.com [Professor Masoumi Laboratory, Department of Chemistry, College of Science, Shiraz University, Hafeziyeh, Fars, 71454 Shiraz (Iran, Islamic Republic of); Asadi, Mozaffar; Kamran, Sedigheh; Sheikhian, Leila [Professor Masoumi Laboratory, Department of Chemistry, College of Science, Shiraz University, Hafeziyeh, Fars, 71454 Shiraz (Iran, Islamic Republic of); Goltz, Douglas M. [Department of Chemistry, University of Winnipeg, Winnipeg, MB, R3B 2E9 Canada (Canada)

    2011-08-30

    Highlights: {yields} Ionic liquids modify the dye-adsorption characteristics of magnetic nanoparticles. {yields} Modified nanoparticles improved the sensitivity of dye measurements. {yields} Water-solubility is an important factor for choosing an ionic liquid as a modifier for nanoparticles. - Abstract: The nanoparticles of Fe{sub 3}O{sub 4} as well as the binary nanoparticles of ionic liquid and Fe{sub 3}O{sub 4} (IL-Fe{sub 3}O{sub 4}) were synthesized for removal of reactive red 120 (RR-120) and 4-(2-pyridylazo) resorcinol (PAR) as model azo dyes from aqueous solutions. The mean size and the surface morphology of the nanoparticles were characterized by TEM, DLS, XRD, FTIR and TGA techniques. Adsorption of RR-120 and PAR was studied in a batch reactor at different experimental conditions such as nanoparticle dosage, dye concentration, pH of the solution, ionic strength, and contact time. Experimental results indicated that the IL-Fe{sub 3}O{sub 4} nanoparticles had removed more than 98% of both dyes under the optimum operational conditions of a dosage of 60 mg, a pH of 2.5, and a contact time of 2 min when initial dyes concentrations of 10-200 mg L{sup -1} were used. The maximum adsorption capacity of IL-Fe{sub 3}O{sub 4} was 166.67 and 49.26 mg g{sup -1} for RR-120 and PAR, respectively. The isotherm experiments revealed that the Langmuir model attained better fits to the equilibrium data than the Freundlich model. The Langmuir adsorption constants were 5.99 and 3.62 L mg{sup -1} for adsorptions of RR-120 and PAR, respectively. Both adsorption processes were endothermic and dyes could be desorbed from IL-Fe{sub 3}O{sub 4} by using a mixed NaCl-acetone solution and adsorbent was reusable.

  4. Optimization of hexavalent chromium removal from aqueous solution using acid-modified granular activated carbon as adsorbent through response surface methodology

    International Nuclear Information System (INIS)

    Daoud, Waseem; Ebadi, Taghi; Fahimifar, Ahmad

    2015-01-01

    Response surface methodology (RSM) was applied to evaluate the effect of the main operational variables, including initial pH, initial chromium ion concentration, bulk density of GAC and time on the removal of hexavalent chromium Cr(Ⅵ) from contaminated groundwater by permeable reactive barriers (PRB) with acid-modified granular activated carbon (GAC) as an adsorbent material. The removal rates of Cr(Ⅵ) under different values of these parameters were investigated and results indicated high adsorption capacity at low pH and low initial metal ion concentration of Cr(Ⅵ), but the bulk density of GAC slightly influenced the process efficiency. According to the ANOVA (analysis of variance) results, the model presents high R 2 values of 94.35% for Cr(Ⅵ) removal efficiency, which indicates that the accuracy of the polynomial models was good. Also, quadratic regression models with estimated coefficients were developed to describe the pollutant removals

  5. Optimization of hexavalent chromium removal from aqueous solution using acid-modified granular activated carbon as adsorbent through response surface methodology

    Energy Technology Data Exchange (ETDEWEB)

    Daoud, Waseem; Ebadi, Taghi; Fahimifar, Ahmad [Amirkabir University of Technology (Tehran Polytechnic), Tehran (Iran, Islamic Republic of)

    2015-06-15

    Response surface methodology (RSM) was applied to evaluate the effect of the main operational variables, including initial pH, initial chromium ion concentration, bulk density of GAC and time on the removal of hexavalent chromium Cr(Ⅵ) from contaminated groundwater by permeable reactive barriers (PRB) with acid-modified granular activated carbon (GAC) as an adsorbent material. The removal rates of Cr(Ⅵ) under different values of these parameters were investigated and results indicated high adsorption capacity at low pH and low initial metal ion concentration of Cr(Ⅵ), but the bulk density of GAC slightly influenced the process efficiency. According to the ANOVA (analysis of variance) results, the model presents high R{sup 2} values of 94.35% for Cr(Ⅵ) removal efficiency, which indicates that the accuracy of the polynomial models was good. Also, quadratic regression models with estimated coefficients were developed to describe the pollutant removals.

  6. Characterization and application of expanded graphite modified with phosphoric acid and glucose for the removal of Ni(II) from aqueous solution

    Science.gov (United States)

    Jiang, Li; Zhang, Jian; Xu, Xiaoli; Zhang, Jie; Liu, Hai; Guo, Zizhang; Kang, Yan; Li, Yiran; Xu, Jingtao

    2015-12-01

    Three kinds of modified expanded graphite (EG), impregnated with phosphoric acid (H3PO4) (P-EG), impregnated with glucose (G-EG), and impregnated with H3PO4 and glucose (G-P-EG), were prepared under a low temperature (150 °C). The adsorption capacity of G-P-EG (Qm = 7.016 mg/g) is much higher than original expanded graphite (EG Qm = 0.423 mg/g) and other two kinds of modified expanded graphite (P-EG Qm = 0.770 mg/g; G-EG Qm = 0.507 mg/g). The physicochemical properties of EG and G-P-EG were characterized by N2 adsorption/desorption, Boehm's titration and X-ray photoelectron spectroscopy (XPS). EG exhibited higher values of BET surface area (11.357 m2/g) and total pore volume (0.0303 cm3/g) than that of G-P-EG (4.808 m3/g and 0.0109 cm3/g). However, the results of Bohm's titration and XPS showed that G-P-EG contained more surface oxygen-containing functional groups. The Ni(II) adsorption equilibrium data agreed well with the Langmuir model. And the experimental data of EG and G-P-EG fitted better by pseudo-second order model. Based on the results of batch adsorption experiments and XPS analysis, there were several possible mechanisms for Ni(II) adsorption on the G-P-EG, including chemical adsorption, cation exchange, electrostatic attraction and surface complication.

  7. Stacking and discontinuous buffers in capillary zone electrophoresis.

    Science.gov (United States)

    Shihabi, Z K

    2000-08-01

    Discontinuous buffers for capillary zone electrophoresis (CZE) can be used under less rigid conditions compared to those for isotachophoresis for stacking. They can be prepared simply by modifying the sample itself, either by addition of small inorganic ions, low conductivity diluents, or both, and also by adjusting its pH, meanwhile injecting a large volume on the capillary. Zwitterionic and organic-based buffers such as triethanolamine and tris(hydroxymethyl)aminomethane (Tris) are well suited for stacking due to their low conductivity, provided the buffer is discontinuous as demonstrated here. A simple mechanism based on discontinuous buffers is described to explain many of the observed stacking types in CZE, pointing out the many similarities to transient isotachophoresis.

  8. Study of the interaction of flavonoids with 3-mercaptopropionic acid modified CdTe quantum dots mediated by cetyltrimethyl ammonium bromide in aqueous medium

    Science.gov (United States)

    Aucelio, Ricardo Q.; Carvalho, Juliana M.; Real, Juliana T.; Maqueira-Espinosa, Luis; Pérez-Gramatges, Aurora; da Silva, Andrea R.

    2017-02-01

    Flavonoids are polyphenols that help the maintenance of health, aiding the prevention of diseases. In this work, CdTe QDs coated with 3-mercaptopropionic acid (3MPA), with an average size of 2.7 nm, were used as photoluminescence probe for flavonoids in different conditions. The interaction between 14 flavonoids and QDs was evaluated in aqueous dispersions in the absence and in the presence of cetyltrimethylammonium bromide (CTAB). To establish a relationship between photoluminescence quenching and the concentration of flavonoids, the Stern-Volmer model was used. In the absence of CTAB, the linear ranges for quercetin, morin and rutin were from 5.0 × 10- 6 mol L- 1 to 6.0 × 10- 5 mol L- 1 and from 1.0 × 10- 5 mol L- 1 to 6.0 × 10- 4 mol L- 1 for kaempferol. The sensibility of the Stern-Volmer curves (Ks) indicated that quercetin interacts more strongly with the probe: Ks quercetin > Ks kaempferol > Ks rutin > Ks morin. The conjugation extension in the 3 rings, and the acidic hydroxyl groups (positions 3ʹand 4ʹ) in the B-ring enhanced the interaction with 3MPA-CdTe QDs. The other flavonoids do not interact with the probe at 10- 5 mol L- 1 level. In CTAB organized dispersions, Ks 3-hydroxyflavone > Ks 7-hydroxyflavone > Ks flavona > Ks rutin in the range from 1.0 × 10- 6 mol L- 1 to 1.2 × 10- 5 mol L- 1 for flavones and of 1.0 × 10- 6 mol L- 1 to 1.0 × 10- 5 mol L- 1 for rutin. Dynamic light scattering, conductometric measurements and microenvironment polarity studies were employed to elucidate the QDs-flavonoids interaction in systems containing CTAB. The quenching can be attributed to the preferential solubility of hydrophobic flavonoid in the palisade layer of the CTAB aggregates adsorbed on the surface of the 3MPA CdTe QDs.

  9. Ce–Fe-modified zeolite-rich tuff to remove Ba{sup 2+}-like {sup 226}Ra{sup 2+} in presence of As(V) and F{sup −} from aqueous media as pollutants of drinking water

    Energy Technology Data Exchange (ETDEWEB)

    Olguín, María Teresa, E-mail: teresa.olguin@inin.gob.mx [Department of Chemical & Materials Engineering, New Mexico State University, P.O. Box 30001, MSC 3805, Las Cruces, NM 88003 (United States); Departamento de Química, Instituto Nacional de Investigaciones Nucleares, A.P. 18-1027, Col. Escandón, Delegación Miguel Hidalgo, C.P. 11801, México D.F. (Mexico); Deng, Shuguang [Department of Chemical & Materials Engineering, New Mexico State University, P.O. Box 30001, MSC 3805, Las Cruces, NM 88003 (United States)

    2016-01-25

    Graphical abstract: Ba{sup 2+}-like {sup 226}Ra{sup 2+}, As(V) and F{sup −} simultaneous removal from aqueous media by Ce–Fe-modified natural zeolites. - Highlights: • The metallic species which modified the zeolite change the textural properties. • The pH{sub pzc} is acid for ZUSCeFe and neutral for ZUSNa. • The Linear model describes the Ba{sup 2+}-like {sup 226}Ra{sup 2+} sorption by ZUSNa and ZUSCeFe. • K{sub d} is highest for Ba{sup 2+-} like {sup 226}Ra{sup 2+}-As(V)-F{sup -} solution in contact with ZUSCeFe. • The ZUSCeFe remove simultaneously Ba{sup 2+}-like {sup 226}Ra{sup 2+}, As(V) and F{sup −}. - Abstract: The sorption behavior of the Ba{sup 2+}-like {sup 226}Ra{sup 2+} in the presence of H{sub 2}AsO{sub 4}{sup −}/HAsO{sub 4}{sup 2−} and F{sup −} from aqueous media using Ce–Fe-modified zeolite-rich tuff was investigated in this work. The Na-modified zeolite-rich tuff was also considered for comparison purposes. The zeolite-rich tuff collected from Wyoming (US) was in contact with NaCl and CeCl{sub 3}–FeCl{sub 3} solutions to obtain the Na- and Ce–Fe-modified zeolite-rich tuffs (ZUSNa and ZUSCeFe). These zeolites were characterized by scanning electron microscopy and X-ray diffraction. The BET-specific surface and the points of zero charge were determined as well as the content of Na, Ce and Fe by neutron activation analysis. The textural characteristics and the point of zero charge were changed by the presence of Ce and Fe species in the zeolitic network. A linear model described the Ba{sup 2+}-like {sup 226}Ra{sup 2+} sorption isotherms and the distribution coefficients (K{sub d}) varied with respect to the metallic species present in the zeolitic material. The As(V) oxianionic chemical species and F{sup −} affected this parameter when the Ba{sup 2+}-like {sup 226}Ra{sup 2+}-As(V)-F{sup −} solutions were in contact with ZUSCeFe. The H{sub 2}AsO{sub 4}{sup −}/HAsO{sub 4}{sup 2−} and F{sup −} were adsorbed by ZUSCe

  10. Thermophysical properties of carboxylic and amino acid buffers at subzero temperatures: relevance to frozen state stabilization.

    Science.gov (United States)

    Sundaramurthi, Prakash; Suryanarayanan, Raj

    2011-06-02

    Macromolecules and other thermolabile biologicals are often buffered and stored in frozen or dried (freeze-dried) state. Crystallization of buffer components in frozen aqueous solutions and the consequent pH shifts were studied in carboxylic (succinic, malic, citric, tartaric acid) and amino acid (glycine, histidine) buffers. Aqueous buffer solutions were cooled from room temperature (RT) to -25 °C and the pH of the solution was measured as a function of temperature. The thermal behavior of frozen solutions was investigated by differential scanning calorimetry (DSC), and the crystallized phases were identified by X-ray diffractometry (XRD). Based on the solubility of the neutral species of each buffer system over a range of temperatures, it was possible to estimate its degree of supersaturation at the subambient temperature of interest. This enabled us to predict its crystallization propensity in frozen systems. The experimental and the predicted rank orderings were in excellent agreement. The malate buffer system was robust with no evidence of buffer component crystallization and hence negligible pH shift. In the citrate and tartrate systems, at initial pH pI. In the histidine buffer system, depending on the initial pH, either histidine or histidine HCl crystallized.

  11. Application of natural and modified hectorite clays as adsorbents to removal of Cr(VI) from aqueous solution-Thermodynamic and equilibrium study

    Energy Technology Data Exchange (ETDEWEB)

    Guerra, Denis L., E-mail: dlguerra@iqm.unicamp.br [Chemistry Institute, State University of Campinas, P. O. Box 6154, 13084-971, Campinas, Sao Paulo (Brazil); Viana, Rubia R. [Universidade Federal de Mato Grosso, UFMT, Centro de Recursos Minerais, Cuiaba, Mato Grosso, 768060 900 (Brazil); Airoldi, Claudio [Chemistry Institute, State University of Campinas, P. O. Box 6154, 13084-971, Campinas, Sao Paulo (Brazil)

    2009-12-15

    A hectorite (H) clay sample has been modified with 2-mercaptobenzimidazole (MBI) using homogeneous and heterogeneous routes. Both modification methodologies resulted in similar products, named H{sub HOM} and H{sub HET}, respectively. These materials were characterized by CO{sub 2} gas adsorption, elemental analysis, nuclear magnetic nuclei of carbon-13 and silicon-29. The effect of two variables (contact time and metal concentration) has been studied using batch technique at room temperature and pH 2.0. After achieving the best conditions for Cr(VI) adsorption, isotherms of this adsorbate on using the chosen adsorbents were obtained, which were fitted to non-linear Sips isotherm model. The maximum number of moles adsorbed was determined to be 11.63, 12.85 and 14.01 mmol g{sup -1} for H, H{sub HOM} and H{sub HET}, respectively, reflecting the maximum adsorption order of H{sub HET} > H{sub HOM} > H. The energetic effects ({Delta}{sub int}H{sup o}, {Delta}{sub int}G{sup o} and {Delta}{sub int}S{sup o}) caused by chromium ion adsorption were determined through calorimetric titrations.

  12. Application of natural and modified hectorite clays as adsorbents to removal of Cr(VI) from aqueous solution-Thermodynamic and equilibrium study

    International Nuclear Information System (INIS)

    Guerra, Denis L.; Viana, Rubia R.; Airoldi, Claudio

    2009-01-01

    A hectorite (H) clay sample has been modified with 2-mercaptobenzimidazole (MBI) using homogeneous and heterogeneous routes. Both modification methodologies resulted in similar products, named H HOM and H HET , respectively. These materials were characterized by CO 2 gas adsorption, elemental analysis, nuclear magnetic nuclei of carbon-13 and silicon-29. The effect of two variables (contact time and metal concentration) has been studied using batch technique at room temperature and pH 2.0. After achieving the best conditions for Cr(VI) adsorption, isotherms of this adsorbate on using the chosen adsorbents were obtained, which were fitted to non-linear Sips isotherm model. The maximum number of moles adsorbed was determined to be 11.63, 12.85 and 14.01 mmol g -1 for H, H HOM and H HET , respectively, reflecting the maximum adsorption order of H HET > H HOM > H. The energetic effects (Δ int H o , Δ int G o and Δ int S o ) caused by chromium ion adsorption were determined through calorimetric titrations.

  13. The oxygen-rich pentaerythritol modified multi-walled carbon nanotube as an efficient adsorbent for aqueous removal of alizarin yellow R and alizarin red S

    Science.gov (United States)

    Yang, Jia-Ying; Jiang, Xin-Yu; Jiao, Fei-Peng; Yu, Jin-Gang

    2018-04-01

    A contrastive work on the removal of two organic dyes, alizarin yellow R (AYR) and alizarin red S (ARS), was carried out by utilizing pentaerythritol modified multi-walled carbon nanotubes (ox-MWCNT-PER) as a highly efficient adsorbent. Various characterization methods such as scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, the Brunauer-Emmett-Teller (BET) analysis and X-ray photoelectron spectroscopy (XPS), were applied for revealing the physical and chemical properties of the as-prepared material. In addition, the adsorption kinetics, isotherms and thermodynamic parameters were also discussed. The results showed that the time required to achieve the adsorption equilibrium for both dyes was about 30 min, and the increase in temperature was not favorable to the adsorption process. It was worth noting that the adsorption capacity of ox-MWCNT-PER towards ARS dye was more significant than that towards AYR dye. And the maximum adsorption capacities for ARS and AYR were 257.73 mg g-1 and 45.39 mg g-1, respectively. The possible adsorption mechanism was also proposed, and the synergistic effects of the hydrogen bonding and the π-π electron stacking interactions between the adsorbents and adsorbates both contributed to the adsorption. It could be proposed that the ox-MWCNT-PER nanocomposite might have some positive effects in removing organic dyes from water treatment in the future.

  14. Electrodialysis operation with buffer solution

    Science.gov (United States)

    Hryn, John N [Naperville, IL; Daniels, Edward J [Orland Park, IL; Krumdick, Greg K [Crete, IL

    2009-12-15

    A new method for improving the efficiency of electrodialysis (ED) cells and stacks, in particular those used in chemical synthesis. The process entails adding a buffer solution to the stack for subsequent depletion in the stack during electrolysis. The buffer solution is regenerated continuously after depletion. This buffer process serves to control the hydrogen ion or hydroxide ion concentration so as to protect the active sites of electrodialysis membranes. The process enables electrodialysis processing options for products that are sensitive to pH changes.

  15. g-C{sub 3}N{sub 4} Modified biochar as an adsorptive and photocatalytic material for decontamination of aqueous organic pollutants

    Energy Technology Data Exchange (ETDEWEB)

    Pi, Liu, E-mail: 626956077@qq.com; Jiang, Rui, E-mail: jumrychem@163.com; Zhou, Wangchi, E-mail: 931860337@qq.com; Zhu, Hua, E-mail: zhuhua333@126.com; Xiao, Wei, E-mail: gabrielxiao@whu.edu.cn; Wang, Dihua, E-mail: wangdh@whu.edu.cn; Mao, Xuhui, E-mail: clab@whu.edu.cn

    2015-12-15

    Graphical abstract: - Highlights: • Composite material consisting of photo-responsive C{sub 3}N{sub 4} and biochar was studied. • Interconnection of C{sub 3}N{sub 4} and biochar was fulfilled via a condensation reaction. • The adsorption properties of composite were governed by the biochar. • The composite exhibited decontamination capability even after saturated. • Adsorption and photo-induced regeneration were mutual beneficial in composite. - Abstract: Converting the waste biomasses with high-carbon content into value-added materials is an environmental-friendly way for their utilization. In this study, a leaf-derived biochar is modified with graphitic C{sub 3}N{sub 4} to fulfill an affordable composite material capable of removing organic pollutants via adsorptive and photocatalytic processes simultaneously. The preparation process includes a carbonization process of chestnut leaf biomass and a followed condensation reaction of melamine at 520 °C. The characterization shows that biochar and C{sub 3}N{sub 4} existed in the composites in their pristine status, and the effective connection of C{sub 3}N{sub 4} and biochar was established. The adsorptive performance of the composites is governed by the biochar content in the composite, thus showing favorable performance for the removal of cationic dye methylene blue (MB). The condensation reaction of the melamine precursor has a coalescing effect on the dispersed biochar, resulting in the growth of particle size of composite. The composites prepared at different biochar/melamine ratios all show a photocatalytic activity on decolorization of MB. In terms of the specific photocatalytic activity of C{sub 3}N{sub 4} in the composite, biochar/melamine ratio of 0.5:1 is the best. Unlike the conventional adsorptive carbon materials which have saturated adsorption capacity, the composite in this study retain a sustaining decontamination capability due to the photocatalytic degradation of adsorbed organic

  16. Co-modified MCM-41 as an effective adsorbent for levofloxacin removal from aqueous solution: optimization of process parameters, isotherm, and thermodynamic studies.

    Science.gov (United States)

    Jin, Ting; Yuan, Wenhua; Xue, Yujie; Wei, Hong; Zhang, Chaoying; Li, Kebin

    2017-02-01

    Antibiotics are emerging contaminants due to their potential risks to human health and ecosystems. Poor biodegradability makes it necessary to develop effective physical-chemical methods to eliminate these contaminants from water. The cobalt-modified MCM-41 was prepared by a one-pot hydrothermal method and characterized by SAXRD, N 2 adsorption-desorption, SEM, UV-Vis DR, and FTIR spectroscopy. The results revealed that the prepared 3% Co-MCM-41 possessed mesoporous structure with BET surface areas at around 898.5 m 2 g -1 . The adsorption performance of 3% Co-MCM-41 toward levofloxacin (LVF) was investigated by batch experiments. The adsorption of LVF on 3% Co-MCM-41 was very fast and reached equilibrium within 2 h. The adsorption kinetics followed the pseudo-second-order kinetic model with the second-order rate constants in the range of 0.00198-0.00391 g mg -1  min -1 . The adsorption isotherms could be well represented by the Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm equations. Nevertheless, D-R isotherm provided the best fit based on the coefficient of determination and average relative error values. The mean free energy of adsorption (E) calculated from D-R model was about 11 kJ mol -1 , indicating that the adsorption was mainly governed by a chemisorption process. Moreover, the adsorption capacity was investigated as a function of pH, adsorbent dosage, LVF concentration, and temperature with help of respond surface methodology (RSM). A quadratic model was established, and an optimal condition was obtained as follows: pH 8.5, adsorbent dosage of 1 g L -1 , initial LVF concentration of 119.8 mg L -1 , and temperature of 31.6 °C. Under the optimal condition, the adsorption capacity of 3% Co-MCM-41 to LVF could reach about 108.1 mg g -1 . The solution pH, adsorbent dosage, LVF concentration, and a combination of adsorbent dose and LVF concentration were significant factors affecting the adsorption process. The adsorption

  17. Differentiation and characterization of isotopically modified silver nanoparticles in aqueous media using asymmetric-flow field flow fractionation coupled to optical detection and mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Gigault, Julien [National Institute of Standards and Technology, Material Measurement Laboratory, 100 Bureau Drive Stop 8520, Gaithersburg, MD 20899-8520 (United States); Hackley, Vincent A., E-mail: vince.hackley@nist.gov [National Institute of Standards and Technology, Material Measurement Laboratory, 100 Bureau Drive Stop 8520, Gaithersburg, MD 20899-8520 (United States)

    2013-02-06

    Highlights: ► Isotopically modified and unmodified AgNPs characterization by A4F-DAD-MALS–DLS-ICP-MS. ► Size-resolved characterization and speciation in simple or complex media. ► Capacity to detect stable isotope enriched AgNPs in a standard estuarine sediment. ► New opportunities to monitor and study fate and transformations of AgNPs. -- Abstract: The principal objective of this work was to develop and demonstrate a new methodology for silver nanoparticle (AgNP) detection and characterization based on asymmetric-flow field flow fractionation (A4F) coupled on-line to multiple detectors and using stable isotopes of Ag. This analytical approach opens the door to address many relevant scientific challenges concerning the transport and fate of nanomaterials in natural systems. We show that A4F must be optimized in order to effectively fractionate AgNPs and larger colloidal Ag particles. With the optimized method one can accurately determine the size, stability and optical properties of AgNPs and their agglomerates under variable conditions. In this investigation, we couple A4F to optical absorbance (UV–vis spectrometer) and scattering detectors (static and dynamic) and to an inductively coupled plasma mass spectrometer. With this combination of detection modes it is possible to determine the mass isotopic signature of AgNPs as a function of their size and optical properties, providing specificity necessary for tracing and differentiating labeled AgNPs from their naturally occurring or anthropogenic analogs. The methodology was then applied to standard estuarine sediment by doping the suspension with a known quantity of isotopically enriched {sup 109}AgNPs stabilized by natural organic matter (standard humic and fulvic acids). The mass signature of the isotopically enriched AgNPs was recorded as a function of the measured particle size. We observed that AgNPs interact with different particulate components of the sediment, and also self-associate to form

  18. Heat conductivity of buffer materials

    International Nuclear Information System (INIS)

    Boergesson, L.; Fredrikson, Anders; Johannesson, L.E.

    1994-11-01

    The report deals with the thermal conductivity of bentonite based buffer materials. An improved technique for measuring the thermal conductivity of buffer materials is described. Measurements of FLAC calculations applying this technique have led to a proposal of how standardized tests should be conducted and evaluated. The thermal conductivity of bentonite with different void ratio and degree of water saturation has been determined in the following different ways: * Theoretically according to three different investigations by other researchers. * Laboratory measurements with the proposed method. * Results from back-calculated field tests. Comparison and evaluation showed that these results agreed very well, when the buffer material was almost water saturated. However, the influence of the degree of saturation was not very well predicted with the theoretical methods. Furthermore, the field tests showed that the average thermal conductivity in situ of buffer material (compacted to blocks) with low degree of water saturation was lower than expected from laboratory tests. 12 refs, 29 figs, 11 tabs

  19. Buffers and vegetative filter strips

    Science.gov (United States)

    Matthew J. Helmers; Thomas M. Isenhart; Michael G. Dosskey; Seth M. Dabney

    2008-01-01

    This chapter describes the use of buffers and vegetative filter strips relative to water quality. In particular, we primarily discuss the herbaceous components of the following NRCS Conservation Practice Standards.

  20. Programmable pH buffers

    Science.gov (United States)

    Gough, Dara Van; Huber, Dale L.; Bunker, Bruce C.; Roberts, Mark E.

    2017-01-24

    A programmable pH buffer comprises a copolymer that changes pK.sub.a at a lower critical solution temperature (LCST) in water. The copolymer comprises a thermally programmable polymer that undergoes a hydrophobic-to-hydrophilic phase change at the LCST and an electrolytic polymer that exhibits acid-base properties that are responsive to the phase change. The programmable pH buffer can be used to sequester CO.sub.2 into water.

  1. Removal of blue indigo and cadmium present in aqueous solutions using a modified zeolitic material and an activated carbonaceous material; Remocion de azul indigo y cadmio presentes en soluciones acuosas empleando un material zeolitico modificado y un material carbonoso activado

    Energy Technology Data Exchange (ETDEWEB)

    Gutierrez S, E. E.

    2011-07-01

    In the last years the use of water has been increased substantially, it has been also altered its quality as a result of human activities such as mining, industrial activities and others. Water pollution caused by dyes and heavy metals has adverse effects on the environment, since both pollutants are very persisten even after conventional treatments. Denim blue and cadmium are not biodegradable. There is a growing interest in finding new, efficient and low cost alternative materials to remove such pollutants from the aqueous medium. The purpose of this work was to evaluate a modified zeolitic tuff and an activated carbonaceous material obtained from the pyrolysis of sewage sludge for the removal of denim blue and cadmium. The zeolitic material was modified with Na{sup +} and Fe{sup 3+} solutions to improve its sorption properties for the removal of cadmium and denim blue, respectively. Carbonaceous material was treated with 10% HCl solution to remove ashes. Both materials were characterized by scanning electron microscopy and elemental analysis (EDS), specific surface areas (Bet), thermogravimetric analysis, infrared spectroscopy and X-ray diffraction. Simultaneously, the denim blue dye was characterized by infrared spectroscopy and its pKa value was determined, these data allowed the determination of its chemical properties and its acid-base behavior in solution. In the content of this work the term indigo blue was changed by denim blue, as it corresponds to the commercial name of the dye. To assess the sorption capacity of sorbents, the sorption kinetics and sorption isotherms in batch system were determined; the results were fitted to mathematical models such as the pseudo-first order, pseudo second order and second order to describe the sorption kinetics and the Langmuir, Freundlich and Langmuir-Freundlich isotherms to describe sorption processes. The results show that the most efficient material to remove denim blue from aqueous solutions is the carbonaceous

  2. Photo-degradation behaviour of roseoflavin in some aqueous solutions

    International Nuclear Information System (INIS)

    Tyagi, A.; Penzkofer, A.; Mathes, T.; Hegemann, P.

    2010-01-01

    An absorption and emission spectroscopic characterization of roseoflavin (8-dimethylamino-8-demethyl-riboflavin, RoF) in aqueous solutions was carried out. The studies were concentrated on roseoflavin in pH 8 phosphate buffer. Absorption cross-section spectra, fluorescence excitation spectra, fluorescence quantum distributions, fluorescence quantum yields and fluorescence lifetimes were determined. The fluorescence of RoF is quenched by photo-induced intra-molecular charge-transfer at room temperature. The photo-degradation of RoF in un-buffered water, in Tris-HCl buffer, and in phosphate buffer was studied. Phosphate buffer and to a smaller extent Tris buffer catalyse the RoF photo-degradation. Photo-excitation of the primary photoproduct, 8-methylamino-riboflavin (8-MNH-RF), enhanced the RoF degradation by triplet 8-MNH-RF - singlet RoF excitation transfer with subsequent triplet-state RoF degradation.

  3. Photo-degradation behaviour of roseoflavin in some aqueous solutions

    Science.gov (United States)

    Tyagi, A.; Penzkofer, A.; Mathes, T.; Hegemann, P.

    2010-03-01

    An absorption and emission spectroscopic characterization of roseoflavin (8-dimethylamino-8-demethyl-riboflavin, RoF) in aqueous solutions was carried out. The studies were concentrated on roseoflavin in pH 8 phosphate buffer. Absorption cross-section spectra, fluorescence excitation spectra, fluorescence quantum distributions, fluorescence quantum yields and fluorescence lifetimes were determined. The fluorescence of RoF is quenched by photo-induced intra-molecular charge-transfer at room temperature. The photo-degradation of RoF in un-buffered water, in Tris-HCl buffer, and in phosphate buffer was studied. Phosphate buffer and to a smaller extent Tris buffer catalyse the RoF photo-degradation. Photo-excitation of the primary photoproduct, 8-methylamino-riboflavin (8-MNH-RF), enhanced the RoF degradation by triplet 8-MNH-RF - singlet RoF excitation transfer with subsequent triplet-state RoF degradation.

  4. Photo-degradation behaviour of roseoflavin in some aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Tyagi, A. [Institut II - Experimentelle und Angewandte Physik, Universitaet Regensburg, Universitaetsstrasse 31, D-93053 Regensburg (Germany); Penzkofer, A., E-mail: alfons.penzkofer@physik.uni-regensburg.de [Institut II - Experimentelle und Angewandte Physik, Universitaet Regensburg, Universitaetsstrasse 31, D-93053 Regensburg (Germany); Mathes, T.; Hegemann, P. [Institut fuer Biologie/Experimentelle Biophysik, Humboldt Universitaet zu Berlin, Invalidenstrasse 42, D-10115 Berlin (Germany)

    2010-03-24

    An absorption and emission spectroscopic characterization of roseoflavin (8-dimethylamino-8-demethyl-riboflavin, RoF) in aqueous solutions was carried out. The studies were concentrated on roseoflavin in pH 8 phosphate buffer. Absorption cross-section spectra, fluorescence excitation spectra, fluorescence quantum distributions, fluorescence quantum yields and fluorescence lifetimes were determined. The fluorescence of RoF is quenched by photo-induced intra-molecular charge-transfer at room temperature. The photo-degradation of RoF in un-buffered water, in Tris-HCl buffer, and in phosphate buffer was studied. Phosphate buffer and to a smaller extent Tris buffer catalyse the RoF photo-degradation. Photo-excitation of the primary photoproduct, 8-methylamino-riboflavin (8-MNH-RF), enhanced the RoF degradation by triplet 8-MNH-RF - singlet RoF excitation transfer with subsequent triplet-state RoF degradation.

  5. Comparison of Aqueous and 1-Octanol Solubility as well as Liquid?Liquid Distribution of Acyclovir Derivatives and Their Complexes with Hydroxypropyl-?-Cyclodextrin

    OpenAIRE

    Ko?bia?, Ma?gorzata; Gierycz, Pawe?

    2013-01-01

    The aim of the presented work is the comparison of aqueous and 1-octanol solubilities of different acyclovir derivatives and their hydroxypropyl-?-cyclodextrin inclusion complexes. The solubility measurements were carried out at different temperatures over the range 25?45??C using water, 1-octanol, water saturated with 1-octanol, 1-octanol saturated with water, buffered aqueous solutions (pH?=?5.5 and 7.0) and buffered aqueous solutions containing cyclodextrin as solvents. The aqueous solubil...

  6. Thermophysical tests of buffer materials

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, H. [ITC, Tokyo (Japan); Taniguchi, Wataru

    1999-03-01

    Thermodynamic properties of buffer materials were measured for putting in order thermodynamic constants to be used in the near-field thermal analysis. The thermal diffusivity and thermal conductivity were measured as functions of the water content and temperature to deduce the specific heat. The thermal conductivity and specific heat varied significantly as the water content changed. Obtained values of the specific heat agreed well the expected values calculated based on the constituents of the buffer material. Temperature dependence of the thermodynamic constants was found small below 90degC. From the findings, the thermal conductivity and specific heat of the buffer material were formulated as functions of the water content. Thermodynamic study of powdery bentonite was carried out as well with a purpose of use for filling apertures in the artificial barrier. (H. Baba)

  7. ACETIC ACID AND A BUFFER

    DEFF Research Database (Denmark)

    2009-01-01

    The present invention relates to a composition comprising : a) 0.01-20% wt/wt acetic acid and b) a physiologically tolerable buffer capable of maintaining acetic acid at a pH in the range of 2-7; and use of such a composition as an antimicrobial agent.......The present invention relates to a composition comprising : a) 0.01-20% wt/wt acetic acid and b) a physiologically tolerable buffer capable of maintaining acetic acid at a pH in the range of 2-7; and use of such a composition as an antimicrobial agent....

  8. A Capital Adequacy Buffer Model

    NARCIS (Netherlands)

    D.E. Allen (David); M.J. McAleer (Michael); R.J. Powell (Robert); A.K. Singh (Abhay)

    2013-01-01

    markdownabstract__Abstract__ In this paper, we develop a new capital adequacy buffer model (CABM) which is sensitive to dynamic economic circumstances. The model, which measures additional bank capital required to compensate for fluctuating credit risk, is a novel combination of the Merton

  9. Smoothing type buffer memory device

    International Nuclear Information System (INIS)

    Podorozhnyj, D.M.; Yashin, I.V.

    1990-01-01

    The layout of the micropower 4-bit smoothing type buffer memory device allowing one to record without counting the sequence of input randomly distributed pulses in multi-channel devices with serial poll, is given. The power spent by a memory cell for one binary digit recording is not greater than 0.15 mW, the device dead time is 10 mus

  10. The influence of bile salts on the distribution of simvastatin in the octanol/buffer system.

    Science.gov (United States)

    Đanić, Maja; Pavlović, Nebojša; Stanimirov, Bojan; Vukmirović, Saša; Nikolić, Katarina; Agbaba, Danica; Mikov, Momir

    2016-01-01

    Distribution coefficient (D) is useful parameter for evaluating drugs permeability properties across biological membranes, which are of importance for drugs bioavailability. Given that bile acids are intensively studied as drug permeation-modifying and -solubilizing agents, the aim of this study was to estimate the influence of sodium salts of cholic (CA), deoxycholic (DCA) and 12-monoketocholic acids (MKC) on distribution coefficient of simvastatin (SV) (lactone [SVL] and acid form [SVA]) which is a highly lipophilic compound with extremely low water solubility and bioavailability. LogD values of SVA and SVL with or without bile salts were measured by liquid-liquid extraction in n-octanol/buffer systems at pH 5 and 7.4. SV concentrations in aqueous phase were determined by HPLC-DAD. Chem3D Ultra program was applied for computation of physico-chemical properties of analyzed compounds and their complexes. Statistically significant decrease in both SVA and SVL logD was observed for all three studied bile salts at both selected pH. MKC exerted the most pronounced effect in the case of SVA while there were no statistically significant differences between observed bile salts for SVL. The calculated physico-chemical properties of analyzed compounds and their complexes supported experimental results. Our data indicate that the addition of bile salts into the n-octanol/buffer system decreases the values of SV distribution coefficient at both studied pH values. This may be the result of the formation of hydrophilic complexes increasing the solubility of SV that could consequently impact the pharmacokinetic parameters of SV and the final drug response in patients.

  11. Internal acid buffering in San Joaquin Valley fog drops and its influence on aerosol processing

    Science.gov (United States)

    Collett, Jeffrey L.; Hoag, Katherine J.; Rao, Xin; Pandis, Spyros N.

    Although several chemical pathways exist for S(IV) oxidation in fogs and clouds, many are self-limiting: as sulfuric acid is produced and the drop pH declines, the rates of these pathways also decline. Some of the acid that is produced can be buffered by uptake of gaseous ammonia. Additional internal buffering can result from protonation of weak and strong bases present in solution. Acid titrations of high pH fog samples (median pH=6.49) collected in California's San Joaquin Valley reveal the presence of considerable internal acid buffering. In samples collected at a rural location, the observed internal buffering could be nearly accounted for based on concentrations of ammonia and bicarbonate present in solution. In samples collected in the cities of Fresno and Bakersfield, however, significant additional, unexplained buffering was present over a pH range extending from approximately four to seven. The additional buffering was found to be associated with dissolved compounds in the fogwater. It could not be accounted for by measured concentrations of low molecular weight ( C1- C3) carboxylic acids, S(IV), phosphate, or nitrophenols. The amount of unexplained buffering in individual fog samples was found to correlate strongly with the sum of sample acetate and formate concentrations, suggesting that unmeasured organic species may be important contributors. Simulation of a Bakersfield fog episode with and without the additional, unexplained buffering revealed a significant impact on the fog chemistry. When the additional buffering was included, the simulated fog pH remained 0.3-0.7 pH units higher and the amount of sulfate present after the fog evaporated was increased by 50%. Including the additional buffering in the model simulation did not affect fogwater nitrate concentrations and was found to slightly decrease ammonium concentrations. The magnitude of the buffering effect on aqueous sulfate production is sensitive to the amount of ozone present to oxidize S

  12. The thermodynamic-buffer enzymes.

    Science.gov (United States)

    Stucki, J W

    1980-08-01

    Oxidative phosphorylation operates at optimal efficiency if and only if the condition of conductance matching L33/L11 = square root 1-q2 is fulfilled. In this relation L11 is the phenomenological conductance of phosphorylation, L33 the phenomenological conductance of the load, i.e. the irreversible ATP-utilizing processes in the cell, and q the degree of coupling of oxidative phosphorylation driven by respiration. Since during short time intervals L11 and q are constant whereas L33 fluctuates in the cell, oxidative phosphorylation would only rarely operate at optimal efficiency due to violation of conductance matching. This paper demonstrates that the reversible ATP-utilizing reaction catalyzed by adenylate kinase can effectively compensate deviations from conductance matching in the presence of a fluctuating L33 and hence allows oxidative phosphorylation to operate at optimal efficiency in the cell. Since the adenylate kinase reaction was found to buffer a thermodynamic potential, i.e. the phosphate potential, this finding was generalized to the concept of thermodynamic buffering. The thermodynamic buffering ability of the adenylate kinase reaction was demonstrated by experiments with incubated rat-liver mitochondria. Considerations of changes introduced in the entropy production by the adenylate kinase reaction allowed to establish the theoretical framework for thermodynamic buffering. The ability of thermodynamic buffering to compensate deviations from conductance matching in the presence of fluctuating loads was demonstrated by computer simulations. The possibility of other reversible ATP-utilizing reactions, like the ones catalyzed by creatine kinase and arginine kinase, to contribute to thermodynamic buffering is discussed. Finally, the comparison of the theoretically calculated steady-stae cytosolic adenine nucleotide concentrations with experimental data from perfused livers demonstrated that in livers from fed rats conductance matching is fulfilled on a

  13. Flow of Aqueous Humor

    Science.gov (United States)

    ... Home Flow of Aqueous Humor Flow of Aqueous Humor Most, but not all, forms of glaucoma are ... remains normal when some of the fluid (aqueous humor) produced by the eye's ciliary body flows out ...

  14. Urban Runoff: Model Ordinances for Aquatic Buffers

    Science.gov (United States)

    Aquatic Buffers serve as natural boundaries between local waterways and existing development. The model and example ordinaces below provide suggested language or technical guidance designed to create the most effective stream buffer zones possible.

  15. Buffer Zone Requirements for Soil Fumigant Applications

    Science.gov (United States)

    Updated pesticide product labels require fumigant users to establish a buffer zone around treated fields to reduce risks to bystanders. Useful information includes tarp testing guidance and a buffer zone calculator.

  16. Swelling characteristics of buffer material

    International Nuclear Information System (INIS)

    Suzuki, Hideaki; Fujita, Tomoo

    1999-12-01

    After emplacement of the engineered barrier system (EBS), it is expected that the near-field environment will be impacted by phenomena such as heat dissipation by conduction and other heat transfer mechanism, infiltration of groundwater from the surrounding rock into the EBS, generation of swelling pressure in the buffer due to water infiltration and the stress imposed by the overburden pressure. These phenomena are not all independent, but can be strongly influenced by, and coupled with, each other. Evaluating these coupled thermo-hydro-mechanical phenomena is important in order to clarify the initial transient behavior of the engineered barrier system within the near-field. This report describes the results on measurement of swelling amount and stress at boundary built up under restraint condition with water uptake. The following results are identified. (1) The swelling stress of buffer material at saturated condition tends to be independent of effects of pore water pressure and synthetic sea water, and to decrease with increasing temperature. The swelling stress can be explained by the effective dry density. (2) The strain due to swelling estimated from the results of the swelling amount of buffer material is proportional to swelling stress. (3) The swelling stress and strain under unsaturated condition increase with water uptake. (author)

  17. Buffer erosion in dilute groundwater

    International Nuclear Information System (INIS)

    Schatz, T.; Kanerva, N.; Martikainen, J.; Sane, P.; Olin, M.; Seppaelae, A.; Koskinen, K.

    2013-08-01

    One scenario of interest for repository safety assessment involves the loss of bentonite buffer material in contact with dilute groundwater flowing through a transmissive fracture interface. In order to examine the extrusion/erosion behavior of bentonite buffer material under such circumstances, a series of experiments were performed in a flow-through, 1 mm aperture, artificial fracture system. These experiments covered a range of solution chemistry (salt concentration and composition), material composition (sodium montmorillonite and admixtures with calcium montmorillonite), and flow velocity conditions. No erosion was observed for sodium montmorillonite against solution compositions from 0.5 g/L to 10 g/L NaCl. No erosion was observed for 50/50 calcium/sodium montmorillonite against 0.5 g/L NaCl. Erosion was observed for both sodium montmorillonite and 50/50 calcium/sodium montmorillonite against solution compositions ≤ 0.25 g/L NaCl. The calculated erosion rates for the tests with the highest levels of measured erosion, i.e., the tests run under the most dilute conditions (ionic strength (IS) < ∼1 mM), were well-correlated to flow velocity, whereas the calculated erosion rates for the tests with lower levels of measured erosion, i.e., the tests run under somewhat less dilute conditions (∼1 mM < IS < ∼4 mM), were not similarly correlated indicating that material and solution composition can significantly affect erosion rates. In every experiment, both erosive and non-erosive, emplaced buffer material extruded into the fracture and was observed to be impermeable to water flowing in the fracture effectively forming an extended diffusive barrier around the intersecting fracture/buffer interface. Additionally, a model which was developed previously to predict the rate of erosion of bentonite buffer material in low ionic strength water in rock fracture environments was applied to three different cases: sodium montmorillonite expansion in a vertical tube, a

  18. Direct electrochemistry and electrocatalysis of glucose oxidase on three-dimensional interpenetrating, porous graphene modified electrode

    International Nuclear Information System (INIS)

    Cui, Min; Xu, Bing; Hu, Chuangang; Shao, Hui Bo; Qu, Liangti

    2013-01-01

    Direct electrochemistry of glucose oxidase (GOD) on three-dimensional (3D) interpenetrating porous graphene electrodes has been reported, which have been fabricated by one-step electrochemical reduction of graphene oxide (GO) from its aqueous suspension. The electrochemically reduced GO (ERGO) modified electrodes exhibited excellent electron transfer properties for GOD and enhanced the enzyme activity and stability by the assistance of chitosan. The immobilized GOD shows a fast electron transfer with the rate constant (k s ) of 6.05 s −1 . It is worth mentioning that in the air-saturated phosphate buffer solution without any mediator, the resultant modified electrodes exhibited low detection limit of 1.7 μM with wide linear range of 0.02–3.2 mM and high sensitivity and high selectivity for measuring glucose. It would also be extended to various enzymes and bioactive molecules to develop the biosensor or other bio-electrochemical devices

  19. BUFFER CAPACITY IN HETEROGENEOUS MULTICOMPONENT SYSTEMS. REVIEW

    Directory of Open Access Journals (Sweden)

    Oxana Spinu

    2015-12-01

    Full Text Available The quantitative basis of the theory of buffer properties for two-phase acid-base buffer systems and for multicomponent heterogeneous systems has been derived. The analytical equations with respect to all components for diverse multicomponent systems were deduced. It has been established, that the buffer capacities of components are mutually proportional.

  20. Doped LZO buffer layers for laminated conductors

    Science.gov (United States)

    Paranthaman, Mariappan Parans [Knoxville, TN; Schoop, Urs [Westborough, MA; Goyal, Amit [Knoxville, TN; Thieme, Cornelis Leo Hans [Westborough, MA; Verebelyi, Darren T [Oxford, MA; Rupich, Martin W [Framingham, MA

    2010-03-23

    A laminated conductor includes a metallic substrate having a surface, a biaxially textured buffer layer supported by the surface of the substrate, the biaxially textured buffer layer comprising LZO and a dopant for mitigating metal diffusion through the LZO, and a biaxially textured conductor layer supported by the biaxially textured buffer layer.

  1. RESEARCH NEEDS IN RIPARIAN BUFFER RESTORATION

    Science.gov (United States)

    Riparian buffer restorations are used as management tools to produce favorable water quality impacts; moreover, the basis for riparian buffers as an instrument of water quality restoration rests on a relatively firm foundation. However, the extent to which buffers can restore rip...

  2. Comparison of zwitterionic N-alkylaminomethanesulfonic acids to related compounds in the Good buffer series

    Directory of Open Access Journals (Sweden)

    Robert D. Long

    2010-04-01

    Full Text Available Several N-alkyl and N,N-dialkylaminomethanesulfonic acids were synthesized (as zwitterions and/or sodium salts to be tested for utility as biological buffers at lower pH levels than existing Good buffer compounds (aminoalkanesulfonates with a minimum of two carbons between amine and sulfonic acid groups as originally described by Norman Good, and in common use as biological buffers. Our hypothesis was that a shorter carbon chain (one carbon between the amino and sulfonic acid groups should lower the ammonium ion pKa values. The alkylaminomethanesulfonate compounds were synthesized in aqueous solution by reaction of primary or secondary amines with formaldehyde/sodium hydrogensulfite addition compound. The pKa values of the ammonium ions of this series of compounds (compared to existing Good buffers was found to correlate well with the length of the carbon chain between the amino and sulfonate moeties, with a significant decrease in amine basicity in the aminomethanesulfonate compounds (pKa decrease of 2 units or more compared to existing Good buffers. An exception was found for the 2-hydroxypiperazine series which shows only a small pKa decrease, probably due to the site of protonation in this compound (as confirmed by X-ray crystal structure. X-ray crystallographic structures of two members of the series are reported. Several of these compounds have pKa values that would indicate potential utility for buffering at pH levels below the normal physiological range (pKa values in the range of 3 to 6 without aqueous solubility problems – a range that is problematic for currently available Good buffers. Unfortunately, the alkylaminomethanesulfonates were found to degrade (with loss of their buffering ability at pH levels below the pKa value and were unstable at elevated temperature (as when autoclaving – thus limiting their utility.

  3. Efficacy of egg-yolk citrate extender fortified with aqueous garlic ...

    African Journals Online (AJOL)

    An experiment was designed to harness the potential of aqueous fresh and dried garlic extracts supplement in egg yolk extender for rooster semen to improve fertility and hatchability of egg. Aqueous extract of fresh and dry garlic were obtained and supplemented into egg yolk-citrate buffer at 0,1, 2, 3, 4, 5, 6 and 7% for ...

  4. Improving Water Quality With Conservation Buffers

    Science.gov (United States)

    Lowrance, R.; Dabney, S.; Schultz, R.

    2003-12-01

    Conservation buffer technologies are new approaches that need wider application. In-field buffer practices work best when used in combination with other buffer types and other conservation practices. Vegetative barriers may be used in combination with edge-of-field buffers to protect and improve their function and longevity by dispersing runoff and encouraging sediment deposition upslope of the buffer. It's important to understand how buffers can be managed to help reduce nutrient transport potential for high loading of nutrients from manure land application sites, A restored riparian wetland buffer retained or removed at least 59 percent of the nitrogen and 66 percent of the phosphorus that entered from an adjacent manure land application site. The Bear Creek National Restoration Demonstration Watershed project in Iowa has been the site of riparian forest buffers and filter strips creation; constructed wetlands to capture tile flow; stream-bank bioengineering; in-stream structures; and controlling livestock grazing. We need field studies that test various widths of buffers of different plant community compositions for their efficacy in trapping surface runoff, reducing nonpoint source pollutants in subsurface waters, and enhancing the aquatic ecosystem. Research is needed to evaluate the impact of different riparian grazing strategies on channel morphology, water quality, and the fate of livestock-associated pathogens and antibiotics. Integrating riparian buffers and other conservation buffers into these models is a key objective in future model development.

  5. Buffered Communication Analysis in Distributed Multiparty Sessions

    Science.gov (United States)

    Deniélou, Pierre-Malo; Yoshida, Nobuko

    Many communication-centred systems today rely on asynchronous messaging among distributed peers to make efficient use of parallel execution and resource access. With such asynchrony, the communication buffers can happen to grow inconsiderately over time. This paper proposes a static verification methodology based on multiparty session types which can efficiently compute the upper bounds on buffer sizes. Our analysis relies on a uniform causality audit of the entire collaboration pattern - an examination that is not always possible from each end-point type. We extend this method to design algorithms that allocate communication channels in order to optimise the memory requirements of session executions. From these analyses, we propose two refinements methods which respect buffer bounds: a global protocol refinement that automatically inserts confirmation messages to guarantee stipulated buffer sizes and a local protocol refinement to optimise asynchronous messaging without buffer overflow. Finally our work is applied to overcome a buffer overflow problem of the multi-buffering algorithm.

  6. A THEORETICAL DISCUSSION OF THE ECONOMIC EFFECTS OF BUFFER STOCKS AND BUFFER FUNDS

    OpenAIRE

    Simmons, Phil

    1988-01-01

    It has been established that the absence of risk markets justifies market intervention in principle. The form of intervention that has been discussed most widely in the literature is the buffer stock. This paper points out that other forms of intervention, specifically buffer funds, are likely to perform better. The analysis shows that buffer funds are likely to outperform buffer stocks because they address market failure more directly. A sub-theme developed in this paper is that since buffer...

  7. Buffer capacity of the coelomic fluid in echinoderms.

    Science.gov (United States)

    Collard, Marie; Laitat, Kim; Moulin, Laure; Catarino, Ana I; Grosjean, Philippe; Dubois, Philippe

    2013-09-01

    The increase in atmospheric CO2 due to anthropogenic activity results in an acidification of the surface waters of the oceans. The impact of these chemical changes depends on the considered organisms. In particular, it depends on the ability of the organism to control the pH of its inner fluids. Among echinoderms, this ability seems to differ significantly according to species or taxa. In the present paper, we investigated the buffer capacity of the coelomic fluid in different echinoderm taxa as well as factors modifying this capacity. Euechinoidea (sea urchins except Cidaroidea) present a very high buffer capacity of the coelomic fluid (from 0.8 to 1.8mmolkg(-1) SW above that of seawater), while Cidaroidea (other sea urchins), starfish and holothurians have a significantly lower one (from -0.1 to 0.4mmolkg(-1) SW compared to seawater). We hypothesize that this is linked to the more efficient gas exchange structures present in the three last taxa, whereas Euechinoidea evolved specific buffer systems to compensate lower gas exchange abilities. The constituents of the buffer capacity and the factors influencing it were investigated in the sea urchin Paracentrotus lividus and the starfish Asterias rubens. Buffer capacity is primarily due to the bicarbonate buffer system of seawater (representing about 63% for sea urchins and 92% for starfish). It is also partly due to coelomocytes present in the coelomic fluid (around 8% for both) and, in P. lividus only, a compound of an apparent size larger than 3kDa is involved (about 15%). Feeding increased the buffer capacity in P. lividus (to a difference with seawater of about 2.3mmolkg(-1) SW compared to unfed ones who showed a difference of about 0.5mmolkg(-1) SW) but not in A. rubens (difference with seawater of about 0.2 for both conditions). In P. lividus, decreased seawater pH induced an increase of the buffer capacity of individuals maintained at pH7.7 to about twice that of the control individuals and, for those at pH7

  8. Buffered Electrochemical Polishing of Niobium

    Energy Technology Data Exchange (ETDEWEB)

    Ciovati, Gianluigi [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Tian, Hui [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); College of William and Mary, Williamsburg, VA (United States); Corcoran, Sean [Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States)

    2011-03-01

    The standard preparation of superconducting radio-frequency (SRF) cavities made of pure niobium include the removal of a 'damaged' surface layer, by buffered chemical polishing (BCP) or electropolishing (EP), after the cavities are formed. The performance of the cavities is characterized by a sharp degradation of the quality factor when the surface magnetic field exceeds about 90 mT, a phenomenon referred to as 'Q-drop.' In cavities made of polycrystalline fine grain (ASTM 5) niobium, the Q-drop can be significantly reduced by a low-temperature (? 120 °C) 'in-situ' baking of the cavity if the chemical treatment was EP rather than BCP. As part of the effort to understand this phenomenon, we investigated the effect of introducing a polarization potential during buffered chemical polishing, creating a process which is between the standard BCP and EP. While preliminary results on the application of this process to Nb cavities have been previously reported, in this contribution we focus on the characterization of this novel electrochemical process by measuring polarization curves, etching rates, surface finish, electrochemical impedance and the effects of temperature and electrolyte composition. In particular, it is shown that the anodic potential of Nb during BCP reduces the etching rate and improves the surface finish.

  9. Melatonin: Buffering the Immune System

    Directory of Open Access Journals (Sweden)

    Juan M. Guerrero

    2013-04-01

    Full Text Available Melatonin modulates a wide range of physiological functions with pleiotropic effects on the immune system. Despite the large number of reports implicating melatonin as an immunomodulatory compound, it still remains unclear how melatonin regulates immunity. While some authors argue that melatonin is an immunostimulant, many studies have also described anti-inflammatory properties. The data reviewed in this paper support the idea of melatonin as an immune buffer, acting as a stimulant under basal or immunosuppressive conditions or as an anti-inflammatory compound in the presence of exacerbated immune responses, such as acute inflammation. The clinical relevance of the multiple functions of melatonin under different immune conditions, such as infection, autoimmunity, vaccination and immunosenescence, is also reviewed.

  10. Melatonin: Buffering the Immune System

    Science.gov (United States)

    Carrillo-Vico, Antonio; Lardone, Patricia J.; Álvarez-Sánchez, Nuria; Rodríguez-Rodríguez, Ana; Guerrero, Juan M.

    2013-01-01

    Melatonin modulates a wide range of physiological functions with pleiotropic effects on the immune system. Despite the large number of reports implicating melatonin as an immunomodulatory compound, it still remains unclear how melatonin regulates immunity. While some authors argue that melatonin is an immunostimulant, many studies have also described anti-inflammatory properties. The data reviewed in this paper support the idea of melatonin as an immune buffer, acting as a stimulant under basal or immunosuppressive conditions or as an anti-inflammatory compound in the presence of exacerbated immune responses, such as acute inflammation. The clinical relevance of the multiple functions of melatonin under different immune conditions, such as infection, autoimmunity, vaccination and immunosenescence, is also reviewed. PMID:23609496

  11. Modelling of buffer material behaviour

    International Nuclear Information System (INIS)

    Boergesson, L.

    1988-12-01

    Some material models of smectite rich buffer material suited for nuclear waste isolation are accounted for in the report. The application of these models in finite element calculations of some scenarios and performance are also shown. The rock shear scenario has been closely studied with comparisons between calculated and measured results. Sensitivity analyses of the effect of changing the density of the clay and the rate of shear have been performed as well as one calculation using a hollow steel cylinder. Material models and finite element calculations of canister settlement, thermomechanical effects and swelling are also accounted for. The report shows the present state of the work to establish material models and calculation tools which can be used at the final design of the repository. (31 illustrations)

  12. Signature-based store checking buffer

    Science.gov (United States)

    Sridharan, Vilas; Gurumurthi, Sudhanva

    2015-06-02

    A system and method for optimizing redundant output verification, are provided. A hardware-based store fingerprint buffer receives multiple instances of output from multiple instances of computation. The store fingerprint buffer generates a signature from the content included in the multiple instances of output. When a barrier is reached, the store fingerprint buffer uses the signature to verify the content is error-free.

  13. SODR Memory Control Buffer Control ASIC

    Science.gov (United States)

    Hodson, Robert F.

    1994-01-01

    The Spacecraft Optical Disk Recorder (SODR) is a state of the art mass storage system for future NASA missions requiring high transmission rates and a large capacity storage system. This report covers the design and development of an SODR memory buffer control applications specific integrated circuit (ASIC). The memory buffer control ASIC has two primary functions: (1) buffering data to prevent loss of data during disk access times, (2) converting data formats from a high performance parallel interface format to a small computer systems interface format. Ten 144 p in, 50 MHz CMOS ASIC's were designed, fabricated and tested to implement the memory buffer control function.

  14. A Stable Metal-Organic Framework Featuring a Local Buffer Environment for Carbon Dioxide Fixation.

    Science.gov (United States)

    He, Hongming; Sun, Qi; Gao, Wenyang; Perman, Jason A; Sun, Fuxing; Zhu, Guangshan; Aguila, Briana; Forrest, Katherine; Space, Brian; Ma, Shengqian

    2018-04-16

    A majority of metal-organic frameworks (MOFs) fail to preserve their physical and chemical properties after exposure to acidic, neutral, or alkaline aqueous solutions, therefore limiting their practical applications in many areas. The strategy demonstrated herein is the design and synthesis of an organic ligand that behaves as a buffer to drastically boost the aqueous stability of a porous MOF (JUC-1000), which maintains its structural integrity at low and high pH values. The local buffer environment resulting from the weak acid-base pairs of the custom-designed organic ligand also greatly facilitates the performance of JUC-1000 in the chemical fixation of carbon dioxide under ambient conditions, outperforming a series of benchmark catalysts. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Biosorptive removal of cobalt (II) ions from aqueous solution by ...

    African Journals Online (AJOL)

    hope&shola

    2010-11-29

    Nov 29, 2010 ... chemical reaction, decay, adsorption and biodegradation. The presence of ... sted coffee (Dakiky et al., 2002), waste tea (Ahluwalia and Goyal, 2005) ..... green removal from aqueous solution by citric acid modified rice straw.

  16. An analysis of extrusion of buffer material into fracture behavior by diffusion model

    International Nuclear Information System (INIS)

    Matsumoto, Kazuhiro; Tanai, Kenji; Kanno, Takeshi; Iwata, Yumiko

    2005-06-01

    The buffer that will be used as a component of the engineered barriers system swells when saturated by groundwater. As a result of this swelling, buffer may penetrate into the surrounding rock zone through open fractures. It sustained for extremely long periods of time, the buffer extrusion could lead to reduction of buffer density, which may in turn degrade the assumed performance. In this report, the viscosity of bentonite was measured as one of the parameter of diffusion model. In addition, the simulation analysis was carried out to confirm the applicability of diffusion model. Moreover, an analytical evaluation on extrusion behavior of buffer into rock fractures was performed to estimate the long-term stability of buffer as reduction of density. (1) Measurement of the viscosity of bentonite. The viscosity of bentonite is measured by the Rheometer. The viscosity of bentonite indicated tendency to non-Newton flow. The viscosity of bentonite at water contents of 400-1000% was estimated. The evaluated value of the viscosity was modified based on this measurement. (2) Simulation analysis of an experiment results. The simulation analysis of the experimental result using diffusion model was performed to confirm applicability of this model. The results of the simulation reasonably agreed with obtained experimental result. (3) Example analysis of a long-term stability of buffer. The analysis of a long-term stability of buffer as reduction of density was performed to compare with the results in H12 report. In this analysis, the density of the buffer material decreased earlier than the results in H12 report. In addition, a long-term change in the density of the buffer material under seawater condition was preliminary calculated. As a result, it is indicated that extrusion behavior is not significant under seawater condition. (author)

  17. Temperature buffer test. Dismantling operation

    Energy Technology Data Exchange (ETDEWEB)

    Aakesson, Mattias [Clay Technology AB, Lund (Sweden)

    2010-12-15

    The Temperature Buffer Test (TBT) is a joint project between SKB/ANDRA and supported by ENRESA (modelling) and DBE (instrumentation), which aims at improving the understanding and to model the thermo-hydro-mechanical behavior of buffers made of swelling clay submitted to high temperatures (over 100 deg C) during the water saturation process. The test has been carried out in a KBS-3 deposition hole at Aespoe HRL. It was installed during the spring of 2003. Two heaters (3 m long, 0.6 m diameter) and two buffer arrangements have been investigated: the lower heater was surrounded by bentonite in the usual way, whereas the upper heater was surrounded by a ring of sand. The test was dismantled and sampled during a period from the end of October 2009 to the end of April 2010, and this report describes this operation. Different types of samples have been obtained during this operation. A large number of diameter 50 mm bentonite cores have been taken for analysis of water content and density. Large pieces, so-called big sectors, have been taken for hydro-mechanical and chemical characterizations. Finally, there has been an interest to obtain different types of interface samples in which bentonite were in contact with sand, iron or concrete. One goal has been to investigate the retrievability of the upper heater, given the possibility to remove the surrounding sand shield, and a retrieval test has therefore been performed. The sand in the shield was first removed with an industrial vacuum cleaner after loosening the material through mechanical means (with hammer drill and core machine). A front loader was subsequently used for applying a sufficient lifting force to release the heater from the bentonite underneath. The experiment has been documented in different aspects: measurements of the coordinate (height or radius) of different interfaces (between bentonite blocks and between bentonite and sand); verification of sensor positions and retrieval of sensors for subsequent

  18. Temperature buffer test. Dismantling operation

    International Nuclear Information System (INIS)

    Aakesson, Mattias

    2010-12-01

    The Temperature Buffer Test (TBT) is a joint project between SKB/ANDRA and supported by ENRESA (modelling) and DBE (instrumentation), which aims at improving the understanding and to model the thermo-hydro-mechanical behavior of buffers made of swelling clay submitted to high temperatures (over 100 deg C) during the water saturation process. The test has been carried out in a KBS-3 deposition hole at Aespoe HRL. It was installed during the spring of 2003. Two heaters (3 m long, 0.6 m diameter) and two buffer arrangements have been investigated: the lower heater was surrounded by bentonite in the usual way, whereas the upper heater was surrounded by a ring of sand. The test was dismantled and sampled during a period from the end of October 2009 to the end of April 2010, and this report describes this operation. Different types of samples have been obtained during this operation. A large number of diameter 50 mm bentonite cores have been taken for analysis of water content and density. Large pieces, so-called big sectors, have been taken for hydro-mechanical and chemical characterizations. Finally, there has been an interest to obtain different types of interface samples in which bentonite were in contact with sand, iron or concrete. One goal has been to investigate the retrievability of the upper heater, given the possibility to remove the surrounding sand shield, and a retrieval test has therefore been performed. The sand in the shield was first removed with an industrial vacuum cleaner after loosening the material through mechanical means (with hammer drill and core machine). A front loader was subsequently used for applying a sufficient lifting force to release the heater from the bentonite underneath. The experiment has been documented in different aspects: measurements of the coordinate (height or radius) of different interfaces (between bentonite blocks and between bentonite and sand); verification of sensor positions and retrieval of sensors for subsequent

  19. A Reversible Photoacid Functioning in PBS Buffer under Visible Light.

    Science.gov (United States)

    Abeyrathna, Nawodi; Liao, Yi

    2015-09-09

    A metastable-state photoacid that can reversibly release a proton in PBS buffer (pH = 7.4) under visible light is reported. The design is based on the dual acid-base property and tautomerization of indazole. The quantum yield was as high as 0.73, and moderate light intensity (10(2) μmol·m(2)·s(-1)) is sufficient for the photoreaction. Reversible pH change of 1.7 units was demonstrated using a 0.1 mM aqueous solution. This type of photoacid is promising for control of proton-transfer processes in physiological conditions and may find applications in biomedical areas.

  20. THE BUFFER CAPACITY OF AIRWAY EPITHELIAL SECRETIONS

    Directory of Open Access Journals (Sweden)

    Dusik eKim

    2014-06-01

    Full Text Available The pH of airway epithelial secretions influences bacterial killing and mucus properties and is reduced by acidic pollutants, gastric reflux, and respiratory diseases such as cystic fibrosis (CF. The effect of acute acid loads depends on buffer capacity, however the buffering of airway secretions has not been well characterized. In this work we develop a method for titrating micro-scale (30 µl volumes and use it to study fluid secreted by the human airway epithelial cell line Calu-3, a widely used model for submucosal gland serous cells. Microtitration curves revealed that HCO3- is the major buffer. Peak buffer capacity (β increased from 17 to 28 mM/pH during forskolin stimulation, and was reduced by >50% in fluid secreted by cystic fibrosis transmembrane conductance regulator (CFTR-deficient Calu-3 monolayers, confirming an important role of CFTR in HCO3- secretion. Back-titration with NaOH revealed non-volatile buffer capacity due to proteins synthesized and released by the epithelial cells. Lysozyme and mucin concentrations were too low to buffer Calu-3 fluid significantly, however model titrations of porcine gastric mucins at concentrations near the sol-gel transition suggest that mucins may contribute to the buffer capacity of ASL in vivo. We conclude that CFTR-dependent HCO3- secretion and epithelially-derived proteins are the predominant buffers in Calu-3 secretions.

  1. Shock buffer for nuclear control assembly

    International Nuclear Information System (INIS)

    Bevilacqua, F.

    1977-01-01

    A shock buffer is provided for the gradual deceleration of a rapidly descending control element assembly in a nuclear reactor. The interactive buffer components are associated respectively with the movable control element assembly and part of the upper guide structure independent of and spaced from the fuel assemblies of the reactor

  2. Dissolution properties of co-amorphous drug-amino acid formulations in buffer and biorelevant media.

    Science.gov (United States)

    Heikkinen, A T; DeClerck, L; Löbmann, K; Grohganz, H; Rades, T; Laitinen, R

    2015-07-01

    Co-amorphous formulations, particularly binary drug-amino acid mixtures, have been shown to provide enhanced dissolution for poorly-soluble drugs and improved physical stability of the amorphous state. However, to date the dissolution properties (mainly intrinsic dissolution rate) of the co-amorphous formulations have been tested only in buffers and their supersaturation ability remain unexplored. Consequently, dissolution studies in simulated intestinal fluids need to be conducted in order to better evaluate the potential of these systems in increasing the oral bioavailability of biopharmaceutics classification system class II drugs. In this study, solubility and dissolution properties of the co-amorphous simvastatin-lysine, gibenclamide-serine, glibenclamide-threonine and glibenclamide-serine-threonine were studied in phosphate buffer pH 7.2 and biorelevant media (fasted and fed state simulated intestinal fluids (FaSSIF and FeSSIF, respectively)). The co-amorphous formulations were found to provide a long-lasting supersaturation and improve the dissolution of the drugs compared to the crystalline and amorphous drugs alone in buffer. Similar improvement, but in lesser extent, was observed in biorelevant media suggesting that a dissolution advantage observed in aqueous buffers may overestimate the advantage in vivo. However, the results show that, in addition to stability advantage shown earlier, co-amorphous drug-amino acid formulations provide dissolution advantage over crystalline drugs in both aqueous and biorelevant conditions.

  3. Buffer sizing for multi-hop networks

    KAUST Repository

    Shihada, Basem

    2014-01-28

    A cumulative buffer may be defined for an interference domain in a wireless mesh network and distributed among nodes in the network to maintain or improve capacity utilization of network resources in the interference domain without increasing packet queuing delay times. When an interference domain having communications links sharing resources in a network is identified, a cumulative buffer size is calculated. The cumulative buffer may be distributed among buffers in each node of the interference domain according to a simple division or according to a cost function taking into account a distance of the communications link from the source and destination. The network may be monitored and the cumulative buffer size recalculated and redistributed when the network conditions change.

  4. Optimization of protein buffer cocktails using Thermofluor.

    Science.gov (United States)

    Reinhard, Linda; Mayerhofer, Hubert; Geerlof, Arie; Mueller-Dieckmann, Jochen; Weiss, Manfred S

    2013-02-01

    The stability and homogeneity of a protein sample is strongly influenced by the composition of the buffer that the protein is in. A quick and easy approach to identify a buffer composition which increases the stability and possibly the conformational homogeneity of a protein sample is the fluorescence-based thermal-shift assay (Thermofluor). Here, a novel 96-condition screen for Thermofluor experiments is presented which consists of buffer and additive parts. The buffer screen comprises 23 different buffers and the additive screen includes small-molecule additives such as salts and nucleotide analogues. The utilization of small-molecule components which increase the thermal stability of a protein sample frequently results in a protein preparation of higher quality and quantity and ultimately also increases the chances of the protein crystallizing.

  5. Probing Regenerative Potential of Moringa oleifera Aqueous Extracts Using In vitro Cellular Assays.

    Science.gov (United States)

    Fernandes, Evangeline E; Pulwale, Anubha V; Patil, Gauri A; Moghe, Alpana S

    2016-01-01

    effect on cancer cell lines. Abbreviations Used : ALT: Alanine transaminase, AST: Asparatate amino transferase, ATCC: American type culture collection, BMMSC: Bone marrow mesenchymal stem cells (used in this paper), CAM: Chick chorioallantoic membrane, CCl4: Carbon tetra chloride, DMEM: Dulbecco's modified Eagle medium, DMSO: Dimethyl sulfoxide, EDTA: Ethylene diamine tetraacetic acid, HBL 100: Human breast epithelial cell line, Mcf-7: Human breast adenocarcinoma cell line, aMEM: Minimum Essential Medium Eagle alpha modification, MOF: Moringa oleifera aqueous flower extract (used in this paper), MOL: Moringa oleifera aqueos leaf extract (Used in this paper), OD: Optical density, PBS: Phosphate buffered saline.

  6. Electrochemical immobilization of biomolecules on gold surface modified with monolayered L-cysteine

    Energy Technology Data Exchange (ETDEWEB)

    Honda, Mitsunori, E-mail: honda.mitsunori@jaea.go.jp; Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Hirao, Norie

    2014-04-01

    Immobilization of organic molecules on the top of a metal surface is not easy because of lattice mismatch between organic and metal crystals. Gold atoms bind to thiol groups through strong chemical bonds, and a self-assembled monolayer of sulfur-terminated organic molecules is formed on the gold surface. Herein, we suggested that a monolayer of L-cysteine deposited on a gold surface can act as a buffer layer to immobilize biomolecules on the metal surface. We selected lactic acid as the immobilized biomolecule because it is one of the simplest carboxyl-containing biomolecules. The immobilization of lactic acid on the metal surface was carried out by an electrochemical method in an aqueous environment under the potential range varying from − 0.6 to + 0.8 V. The surface chemical states before and after the electrochemical reaction were characterized using X-ray photoelectron spectroscopy (XPS). The N 1s and C 1s XPS spectra showed that the L-cysteine-modified gold surface can immobilize lactic acid via peptide bonds. This technique might enable the immobilization of large organic molecules and biomolecules. - Highlights: • Monolayer l-cysteine deposited on Au surface as a buffer layer to immobilize biomolecules. • Lactic acid as the immobilized biomolecule as it is simple carboxyl-containing biomolecule. • X-ray photoelectron spectroscopy (XPS) of surface chemical states, before and after. • L-cysteine-modified Au surface can immobilize lactic acid via peptide bonds.

  7. Electrochemical immobilization of biomolecules on gold surface modified with monolayered L-cysteine

    International Nuclear Information System (INIS)

    Honda, Mitsunori; Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Hirao, Norie

    2014-01-01

    Immobilization of organic molecules on the top of a metal surface is not easy because of lattice mismatch between organic and metal crystals. Gold atoms bind to thiol groups through strong chemical bonds, and a self-assembled monolayer of sulfur-terminated organic molecules is formed on the gold surface. Herein, we suggested that a monolayer of L-cysteine deposited on a gold surface can act as a buffer layer to immobilize biomolecules on the metal surface. We selected lactic acid as the immobilized biomolecule because it is one of the simplest carboxyl-containing biomolecules. The immobilization of lactic acid on the metal surface was carried out by an electrochemical method in an aqueous environment under the potential range varying from − 0.6 to + 0.8 V. The surface chemical states before and after the electrochemical reaction were characterized using X-ray photoelectron spectroscopy (XPS). The N 1s and C 1s XPS spectra showed that the L-cysteine-modified gold surface can immobilize lactic acid via peptide bonds. This technique might enable the immobilization of large organic molecules and biomolecules. - Highlights: • Monolayer l-cysteine deposited on Au surface as a buffer layer to immobilize biomolecules. • Lactic acid as the immobilized biomolecule as it is simple carboxyl-containing biomolecule. • X-ray photoelectron spectroscopy (XPS) of surface chemical states, before and after. • L-cysteine-modified Au surface can immobilize lactic acid via peptide bonds

  8. Electrochemical behaviour of silver in borate buffer solutions

    International Nuclear Information System (INIS)

    Zaky, Ayman M.; Assaf, Fawzi H.; Abd El Rehim, Sayed S.; Mohamed, Basheer

    2004-01-01

    The electrochemical behaviour of Ag in aqueous 0.15 M borax and 0.15 M boric acid buffer solution was studied under various conditions using cyclic voltammetry and potentiostatic techniques. It was found that the anodic polarization curve of Ag in borate buffer solution was characterized by the appearance of two potential regions, active and passive, prior to the oxygen evolution reaction. The active potential region was characterized by the appearance of three anodic peaks, the first two peaks A 1 and A 2 correspond to the oxidation of Ag and formation of [Ag(OH) 2 ] - soluble compound and a passive film of Ag 2 O on the electrode surface. The third anodic peak corresponds to the conversion of both [Ag(OH) 2 ] - and Ag 2 O to Ag 2 O 2 . X-ray diffraction patterns confirmed the existence of Ag 2 O and Ag 2 O 2 passive layers on the electrode surface potentiodynamically polarized up to 800 mV. Potentiostatic current transient measurements showed that the formation of Ag 2 O and Ag 2 O 2 involves a nucleation and growth mechanism under diffusion control

  9. COMBINATIONS OF BUFFER-STOCKS AND BUFFER-FUNDS FOR WOOL PRICE STABILISATION IN AUSTRALIA

    OpenAIRE

    Moir, Brian; Piggott, Roley R.

    1991-01-01

    In this paper a preliminary analysis is presented of a combined buffer-fund and buffer-stock as an alternative to a pure buffer-fund or a pure buffer stock for stabilising wool prices. The alternatives analysed are designed so that each provides the same prices to producers as did the Reserve Price Scheme over the period of analysis. Least-cost combinations of policy instruments are derived. The results show that there is considerable potential for cost savings to be made by combining buffer-...

  10. Buffer mass test - Site documentation

    International Nuclear Information System (INIS)

    Pusch, R.

    1983-10-01

    The purpose of this report is to compile test site data that are assumed to be of importance for the interpretation of the Buffer Mass Test. Since this test mainly concerns water uptake and migration processes in the integrated rock/backfill system and the development of temperature fields in this system, the work has been focused on the constitution and hydrology of the rock. The major constitutional rock feature of interest for the BMT is the frequency and distribution of joints and fractures. The development of models for water uptake into the highly compacted bentonite in the heater holes requires a very detailed fracture survey. The present investigation shows that two of the holes (no. 1 and 2) are located in richly fractured rock, while the others are located in fracture-poor to moderately fractured rock. The hydrological conditions of the rock in the BMT area are characterized by water pressures of as much as 100 m water head at a few meters distance from the test site. The average hydraulic conductivity of the rock that confines the BMT tunnel has been estimated at about 10 -10 m/s by Lawrence Laboratory. The actual distribution of the water that enters the tunnel has been estimated by observing the successive moistening after having switched off the ventilation, and this has offered basis of predicting the rate and uniformity of the water uptake in the tunnel backfill. As to the heater holes the detailed fracture patterns and various inflow measurements have yielded a similar basis. The report also gives major data on the rock temperature, gas conditions, mineralogy, rock mechanics, and groundwater chemistry for BMT purposes. (author)

  11. Temperature buffer test. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Aakesson, Mattias [Clay Technology AB, Lund (Sweden)

    2012-04-15

    The Temperature Buffer Test (TBT) is a joint project between SKB/ANDRA and supported by ENRESA (modelling) and DBE (instrumentation), which aims at improving the understanding and to model the thermo-hydro-mechanical behavior of buffers made of swelling clay submitted to high temperatures (over 100 deg C) during the water saturation process. The test has been carried out in a KBS-3 deposition hole at Aspo HRL. It was installed during the spring of 2003. Two steel heaters (3 m long, 0.6 m diameter) and two buffer arrangements have been investigated: the lower heater was surrounded by rings of compacted Wyoming bentonite only, whereas the upper heater was surrounded by a composite barrier, with a sand shield between the heater and the bentonite. The test was dismantled and sampled during the winter of 2009/2010. This report is the final report and a summary of all work performed within the TBT project. The design and the installation of the different components are summarized: the depositions hole, the heating system, the bentonite blocks with emphasis on the initial density and water content in these, the filling of slots with sand or pellets, the retaining construction with the plug, lid and nine anchor cables, the artificial saturation system, and finally the instrumentation. An overview of the operational conditions is presented: the power output from heaters, which was 1,500 W (and also 1,600 W) from each heater during the first {approx}1,700 days, and then changed to 1,000 and 2,000 W, for the upper and lower heater respectively, during the last {approx}600 days. From the start, the bentonite was hydrated with a groundwater from a nearby bore-hole, but this groundwater was replaced with de-ionized water from day {approx}1,500, due to the high flow resistance of the injections points in the filter, which implied that a high filter pressure couldn't be sustained. The sand shield around the upper heater was hydrated from day {approx}1,500 to day {approx}1

  12. Temperature buffer test. Final report

    International Nuclear Information System (INIS)

    Aakesson, Mattias

    2012-04-01

    The Temperature Buffer Test (TBT) is a joint project between SKB/ANDRA and supported by ENRESA (modelling) and DBE (instrumentation), which aims at improving the understanding and to model the thermo-hydro-mechanical behavior of buffers made of swelling clay submitted to high temperatures (over 100 deg C) during the water saturation process. The test has been carried out in a KBS-3 deposition hole at Aspo HRL. It was installed during the spring of 2003. Two steel heaters (3 m long, 0.6 m diameter) and two buffer arrangements have been investigated: the lower heater was surrounded by rings of compacted Wyoming bentonite only, whereas the upper heater was surrounded by a composite barrier, with a sand shield between the heater and the bentonite. The test was dismantled and sampled during the winter of 2009/2010. This report is the final report and a summary of all work performed within the TBT project. The design and the installation of the different components are summarized: the depositions hole, the heating system, the bentonite blocks with emphasis on the initial density and water content in these, the filling of slots with sand or pellets, the retaining construction with the plug, lid and nine anchor cables, the artificial saturation system, and finally the instrumentation. An overview of the operational conditions is presented: the power output from heaters, which was 1,500 W (and also 1,600 W) from each heater during the first ∼1,700 days, and then changed to 1,000 and 2,000 W, for the upper and lower heater respectively, during the last ∼600 days. From the start, the bentonite was hydrated with a groundwater from a nearby bore-hole, but this groundwater was replaced with de-ionized water from day ∼1,500, due to the high flow resistance of the injections points in the filter, which implied that a high filter pressure couldn't be sustained. The sand shield around the upper heater was hydrated from day ∼1,500 to day ∼1,800. The sensors data concerning

  13. Dynamic mechanical properties of buffer material

    International Nuclear Information System (INIS)

    Takaji, Kazuhiko; Taniguchi, Wataru

    1999-11-01

    The buffer material is expected to maintain its low water permeability, self-sealing properties, radionuclides adsorption and retardation properties, thermal conductivity, chemical buffering properties, overpack supporting properties, stress buffering properties, etc. over a long period of time. Natural clay is mentioned as a material that can relatively satisfy above. Among the kinds of natural clay, bentonite when compacted is superior because (i) it has exceptionally low water permeability and properties to control the movement of water in buffer, (ii) it fills void spaces in the buffer and fractures in the host rock as it swells upon water uptake, (iii) it has the ability to exchange cations and to adsorb cationic radioelements. In order to confirm these functions for the purpose of safety assessment, it is necessary to evaluate buffer properties through laboratory tests and engineering-scale tests, and to make assessments based on the ranges in the data obtained. This report describes the procedures, test conditions, results and examinations on the buffer material of dynamic triaxial tests, measurement of elastic wave velocity and liquefaction tests that aim at getting hold of dynamic mechanical properties. We can get hold of dependency on the shearing strain of the shearing modulus and hysteresis damping constant, the application for the mechanical model etc. by dynamic triaxial tests, the acceptability of maximum shearing modulus obtained from dynamic triaxial tests etc. by measurement of elastic wave velocity and dynamic strength caused by cyclic stress etc. by liquefaction tests. (author)

  14. Buffer protection in the installation phase

    International Nuclear Information System (INIS)

    Wimelius, Hans; Pusch, Roland

    2008-12-01

    The research and development of the design and construction of the SKB's repository for final disposal of spent reactor fuel is conducted along several paths ('lines'). Issues concerning the bedrock are dealt with in the 'rock line' and those related to buffer and backfill in deposition holes and tunnels are considered in the 'buffer line' and 'backfill line', respectively. These lines also deal with sub-activities that are coupled to several other lines. One of them includes development of techniques for protecting buffer blocks from moisture and water in the installation phase. Techniques and methods for placement and removal of the 'buffer protection sheet' are dealt with in the 'buffer line'. The removal is, however, considered as being part of the backfilling sequence. Since the performance of the sheet is of fundamental importance to the placement and function of the buffer it deserves particular attention. Thus, the removal of the rubber sheet that serves to protect the buffer blocks in the installation phase may be difficult and can cause significant problems that may require retrieval of already placed canister, buffer and backfill. These matters are in focus in the present report. Arrangements for protecting already placed buffer blocks from moist air and water have been tested in earlier large-scale experiments, i.e. the Prototype Repository project at Aespoe but the experience from them has called for more effective protection of the clay blocks as described in the present report. Focus is on the construction of foundation components at the bottom of the deposition holes required for establishing a tight seal between rock and buffer blocks, and on the protection sheet and arrangements for limiting water pressure on it. Special attention is paid to the drainage of the space between rock and protection sheet that is necessary for avoiding failure of the sheet and to systems for achieving this and for providing alarm signals if the allowed pressure is

  15. Buffer protection in the installation phase

    Energy Technology Data Exchange (ETDEWEB)

    Wimelius, Hans (Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden)); Pusch, Roland (Geodevelopment International AB, Lund (Sweden))

    2008-12-15

    The research and development of the design and construction of the SKB's repository for final disposal of spent reactor fuel is conducted along several paths ('lines'). Issues concerning the bedrock are dealt with in the 'rock line' and those related to buffer and backfill in deposition holes and tunnels are considered in the 'buffer line' and 'backfill line', respectively. These lines also deal with sub-activities that are coupled to several other lines. One of them includes development of techniques for protecting buffer blocks from moisture and water in the installation phase. Techniques and methods for placement and removal of the 'buffer protection sheet' are dealt with in the 'buffer line'. The removal is, however, considered as being part of the backfilling sequence. Since the performance of the sheet is of fundamental importance to the placement and function of the buffer it deserves particular attention. Thus, the removal of the rubber sheet that serves to protect the buffer blocks in the installation phase may be difficult and can cause significant problems that may require retrieval of already placed canister, buffer and backfill. These matters are in focus in the present report. Arrangements for protecting already placed buffer blocks from moist air and water have been tested in earlier large-scale experiments, i.e. the Prototype Repository project at Aespoe but the experience from them has called for more effective protection of the clay blocks as described in the present report. Focus is on the construction of foundation components at the bottom of the deposition holes required for establishing a tight seal between rock and buffer blocks, and on the protection sheet and arrangements for limiting water pressure on it. Special attention is paid to the drainage of the space between rock and protection sheet that is necessary for avoiding failure of the sheet and to systems for achieving

  16. Surface Water Protection by Productive Buffers

    DEFF Research Database (Denmark)

    Christen, Benjamin

    Vegetated riparian buffer zones are a widely recommended best management practice in agriculture for protecting surface and coastal waters from diffuse nutrient pollution. On the background of the EU funded research project NitroEurope (NEU; www.NitroEurope.eu), this study concentrates...... on the mitigation of nitrogen pollution in surface and groundwater, using riparian buffer zones for biomass production. The objectives are to map suitable areas for buffer implementation across the six NEU study landscapes, model tentative N-loss mitigation, calculate biomass production potential and economic...... designed for local conditions could be a way of protecting water quality attractive to many stakeholders....

  17. Macroprudential Policy, Countercyclical Bank Capital Buffers and Credit Supply : Evidence from the Spanish Dynamic Provisioning Experiments

    NARCIS (Netherlands)

    Jiménez, G.; Ongena, S.; Peydro, J.L.; Saurina, J.

    2012-01-01

    Abstract: We analyze the impact of the countercyclical capital buffers held by banks on the supply of credit to firms and their subsequent performance. Countercyclical ‘dynamic’ provisioning that is unrelated to specific loan losses was introduced in Spain in 2000, and modified in 2005 and 2008.

  18. Evaluation of buffer zone effectiveness in mitigating the risks associated with agricultural runoff in Prince Edward Island.

    Science.gov (United States)

    Dunn, A M; Julien, G; Ernst, W R; Cook, A; Doe, K G; Jackman, P M

    2011-02-01

    To minimize the risk posed by runoff from row crops, Prince Edward Island introduced buffer legislation in 2000. The legislation mandates 10-m and 20-m buffers, respectively, for moderate sloped (i.e. 5%) agricultural fields that border streams. Since 2001, Environment Canada has been evaluating the effectiveness of various buffer widths on operational farms in reducing toxicity and contaminant concentrations in runoff. Sample collectors, placed in 44 fields at the field edge (0m), 10m and at distances out to 30m, collected overland flow following rainfall-induced runoff events. Samples were collected within 24 hours of an event and analysed for seven pesticides (endosulfan, chlorothalonil, carbofuran, linuron, metribuzin, metalaxyl, mancozeb), water quality parameters and Daphnia magna toxicity. The 10-m buffer required for moderate sloped fields was effective at reducing contaminant concentrations but not always to less than lethal concentrations to Daphnia magna. Limited data beyond 10m for fields of both slope types precluded making recommendations on a suitable buffer width for shallow sloped fields and evaluating the effectiveness of 20-m buffers for steep sloped fields. When paired data were combined and statistically tested for all fields, the studied pesticides underwent a 52-98% and 68-100% reduction in aqueous and particulate concentrations within 10m and 30m, respectively. In addition, by 10m, soluble phosphorus, nitrate-nitrogen and total suspended solids were reduced by 34%, 38% and 64%, respectively. Results suggest buffer zones on operational farms are capable of achieving contaminant reductions comparable to those reported for controlled experiments. Inconsistent siting of sample collectors beyond 10m limited the evaluation of the effects of field slope and buffer width on buffer effectiveness on working farms. Future studies on buffer efficiency on operational farms should focus on building the data set beyond 10m and evaluating load reductions

  19. Electrogenerated chemiluminescence of tris(2,2' bipyridine)ruthenium(II) using common biological buffers as co-reactant, pH buffer and supporting electrolyte.

    Science.gov (United States)

    Kebede, Noah; Francis, Paul S; Barbante, Gregory J; Hogan, Conor F

    2015-11-07

    A series of aliphatic tertiary amines (HEPES, POPSO, EPPS and BIS-TRIS) commonly used to buffer the pH in biological experiments, were examined as alternative, non-toxic co-reactants for the electrogenerated chemiluminescence (ECL) of tris(2,2'-bipyridine)ruthenium(ii) ([Ru(bpy)3](2+)). These were found to be very attractive as "multi-tasking" reagents, serving not only as co-reactants, but also fulfiling the roles of pH buffer and supporting electrolyte within an aqueous environment; thus significantly simplifying the overall ECL analysis. Sub-nanomolar detection limits were obtained for [Ru(bpy)3](2+) in the presence of BIS-TRIS, making this species an valuable option for co-reactant ECL-based bioanalytical applications.

  20. Interaction Studies of Dilute Aqueous Oxalic Acid

    Directory of Open Access Journals (Sweden)

    Kiran Kandpal

    2007-01-01

    Full Text Available Molecular conductance λm, relative viscosity and density of oxalicacid at different concentration in dilute aqueous solution were measured at 293 K.The conductance data were used to calculate the value association constant.Viscosity and density data were used to calculate the A and B coefficient ofJone-Dole equation and apparent molar volume respectively. The viscosityresults were utilized for the applicability of Modified Jone-Dole equation andStaurdinger equations. Mono oxalate anion acts, as structure maker and thesolute-solvent interaction were present in the dilute aqueous oxalic acid.

  1. Non-aqueous slurries used as thickeners

    Energy Technology Data Exchange (ETDEWEB)

    Hatfield, J C

    1982-04-07

    A non-aqueous slurry is described that is suitable for use as a thickener or viscosifier in oil or gas drilling, fracturing, flow diversion completion or workover fluids. The slurry comprises a water-soluble cellulose ether polymer, a water-insoluble liquid hydrocarbon, a non-ionic surfactant having an HLB of from 7 to 14, and an organo modified clay. There also is described a process for thickening or viscosifying a drilling, fracturing, flow diversion, completion or workover fluid. The use of the slurry prevents bumping during addition to aqueous fluids. (27 claims)

  2. Buffer sizing for multi-hop networks

    KAUST Repository

    Shihada, Basem; Jamshaid, Kamran

    2014-01-01

    domain according to a simple division or according to a cost function taking into account a distance of the communications link from the source and destination. The network may be monitored and the cumulative buffer size recalculated and redistributed

  3. Moisture Buffer Value of Building Materials

    DEFF Research Database (Denmark)

    Rode, Carsten; Peuhkuri, Ruut; Time, Berit

    2007-01-01

    When building materials are in contact with indoor air they have some effect to moderate the variations of indoor humidity in occupied buildings. But so far there has been a lack of a standardized quantity to characterize the moisture buffering capability of materials. It has been the objective o...... is a test protocol which expresses how materials should be tested for determination of their Moisture Buffer Value. Finally, the paper presents some of the results of a Round Robin Test on various typical building materials that has been carried out in the project....... of a recent Nordic project to define such a quantity, and to declare it in the form of a NORDTEST method. The Moisture Buffer Value is the figure that has been developed in the project as a way to appraise the moisture buffer effect of materials, and the value is described in the paper. Also explained...

  4. Liquid growth hormone: preservatives and buffers

    DEFF Research Database (Denmark)

    Kappelgaard, Anne-Marie; Anders, Bojesen; Skydsgaard, Karen

    2004-01-01

    injection are dependent on the preservative used in the formulation and the concentration of GH. Injection pain may also be related to the buffer substance and injection volume. A liquid formulation of GH, Norditropi SimpleXx, has been developed that dispenses with the need for reconstitution before...... solution. More pain was also reported following large volume injections and following injections with solutions containing high protein concentrations. In summary, optimization of the preservative and buffer content of a liquid GH formulation may reduce injection pain and lead to improved patient...... administration. The formulation uses phenol (3 mg/ml) as a preservative (to protect product from microbial degradation or contamination) and histidine as a buffer. Alternative preservatives used in other GH formulations include m-cresol (9 mg/ml) and benzyl alcohol (3-9 mg/ml). Buffering agents include citrate...

  5. Calculating Buffer Zones: A Guide for Applicators

    Science.gov (United States)

    Buffer zones provide distance between the application block (i.e., edge of the treated field) and bystanders, in order to control pesticide exposure risk from soil fumigants. Distance requirements may be reduced by credits such as tarps.

  6. Buffer Strips for Riparian Zone Management

    National Research Council Canada - National Science Library

    1991-01-01

    This study provides a review of technical literature concerning the width of riparian buffer strips needed to protect water quality and maintain other important values provided by riparian ecosystem...

  7. [Meeting point Stewart. Buffer bases, base excess and strong ions].

    Science.gov (United States)

    Lang, W

    2007-04-01

    Development of a two-buffer model which simulates the acid-base properties of blood and allows comparison of the different acidbase concepts according to Stewart and to Siggaard-Andersen. The two-buffer model consisted of different aqueous solutions of bicarbonate/CO(2) (pCO(2), sCO(2), pK(1)), HEPES buffer (A(tot), pK(a)) and electrolytes. These were used to calculate the pH from the independent variables according to Stewart - strong ion difference (SID), pCO(2) and total concentration of the weak acids (A(tot)) - from which all other dependent variables (cHCO(3)(-), cA(-), BB, BE) were obtained and compared with the measured values. The normal pH (7.408) was calculated from the normal values for SID (48 mmol/l), pCO(2) (40 mmHg) and A(tot) (45.2 mmol/l) and agreed perfectly with the measured value (7.409+/-0.001). This was also valid for all calculated and measured pH values when the SID was varied: non-respiratory alkalosis ( upward arrow) or acidosis ( downward arrow), pCO(2):respiratory acidosis ( upward arrow) or alkalosis ( downward arrow) and A(tot):hyperproteinemic acidosis ( upward arrow) or hypoproteinemic alkalosis ( downward arrow) were varied and the sum of the buffer bases (BB) was always equal to the SID. All changes and hence BE were also equal, providing that A(tot) was normal. This was not the case, however, if A(tot) was outside the normal range, when BE was then the difference from the normal BB at the respective reference point. Whereas the deviation of the measured pCO(2) was acceptable (1.74+/-0.86 mmHg), this was not the case for the SID (-6.18+/-3.58 mmol/l) calculated from the measured ion concentrations (Na, K, Ca, Cl). Despite controversial discussions, both concepts are much closer than might be expected. Whereas in the Stewart approach the focus of analysis is on plasma, with the Siggaard-Andersen approach it is on blood. Hence, a combined analysis of the blood gases (pH, pCO(2), pO(2), sO(2), cHb, BE) and of the strong ion gap (SIG

  8. Lucas Heights buffer zone: plan of management

    International Nuclear Information System (INIS)

    1986-01-01

    This plan is being used by the Commission as a guide for its management of the Lucas Heights buffer zone, which is essentially a circular area having a 1-6 km radius around the HIFAR reactor. Aspects covered by this plan include past uses, current use, objectives for buffer zone land management, emergency evacuation, resource conservation, archaeology, fire, access, rehabilitation of disturbed areas, resource management and plan implementation

  9. Buffer regulation of calcium puff sequences

    International Nuclear Information System (INIS)

    Fraiman, Daniel; Dawson, Silvina Ponce

    2014-01-01

    Puffs are localized Ca 2+ signals that arise in oocytes in response to inositol 1,4,5-trisphosphate (IP 3 ). They are the result of the liberation of Ca 2+ from the endoplasmic reticulum through the coordinated opening of IP 3 receptor/channels clustered at a functional release site. The presence of buffers that trap Ca 2+ provides a mechanism that enriches the spatio–temporal dynamics of cytosolic calcium. The expression of different types of buffers along the cell's life provides a tool with which Ca 2+ signals and their responses can be modulated. In this paper we extend the stochastic model of a cluster of IP 3 R-Ca 2+ channels introduced previously to elucidate the effect of buffers on sequences of puffs at the same release site. We obtain analytically the probability laws of the interpuff time and of the number of channels that participate of the puffs. Furthermore, we show that under typical experimental conditions the effect of buffers can be accounted for in terms of a simple inhibiting function. Hence, by exploring different inhibiting functions we are able to study the effect of a variety of buffers on the puff size and interpuff time distributions. We find the somewhat counter-intuitive result that the addition of a fast Ca 2+ buffer can increase the average number of channels that participate of a puff. (paper)

  10. Buffer regulation of calcium puff sequences.

    Science.gov (United States)

    Fraiman, Daniel; Dawson, Silvina Ponce

    2014-02-01

    Puffs are localized Ca(2 +) signals that arise in oocytes in response to inositol 1,4,5-trisphosphate (IP3). They are the result of the liberation of Ca(2 +) from the endoplasmic reticulum through the coordinated opening of IP3 receptor/channels clustered at a functional release site. The presence of buffers that trap Ca(2 +) provides a mechanism that enriches the spatio-temporal dynamics of cytosolic calcium. The expression of different types of buffers along the cell's life provides a tool with which Ca(2 +) signals and their responses can be modulated. In this paper we extend the stochastic model of a cluster of IP3R-Ca(2 +) channels introduced previously to elucidate the effect of buffers on sequences of puffs at the same release site. We obtain analytically the probability laws of the interpuff time and of the number of channels that participate of the puffs. Furthermore, we show that under typical experimental conditions the effect of buffers can be accounted for in terms of a simple inhibiting function. Hence, by exploring different inhibiting functions we are able to study the effect of a variety of buffers on the puff size and interpuff time distributions. We find the somewhat counter-intuitive result that the addition of a fast Ca(2 +) buffer can increase the average number of channels that participate of a puff.

  11. Assessing critical source areas in watersheds for conservation buffer planning and riparian restoration.

    Science.gov (United States)

    Qiu, Zeyuan

    2009-11-01

    A science-based geographic information system (GIS) approach is presented to target critical source areas in watersheds for conservation buffer placement. Critical source areas are the intersection of hydrologically sensitive areas and pollutant source areas in watersheds. Hydrologically sensitive areas are areas that actively generate runoff in the watershed and are derived using a modified topographic index approach based on variable source area hydrology. Pollutant source areas are the areas in watersheds that are actively and intensively used for such activities as agricultural production. The method is applied to the Neshanic River watershed in Hunterdon County, New Jersey. The capacity of the topographic index in predicting the spatial pattern of runoff generation and the runoff contribution to stream flow in the watershed is evaluated. A simple cost-effectiveness assessment is conducted to compare the conservation buffer placement scenario based on this GIS method to conventional riparian buffer scenarios for placing conservation buffers in agricultural lands in the watershed. The results show that the topographic index reasonably predicts the runoff generation in the watershed. The GIS-based conservation buffer scenario appears to be more cost-effective than the conventional riparian buffer scenarios.

  12. ssDNA degradation along capillary electrophoresis process using a Tris buffer.

    Science.gov (United States)

    Ric, Audrey; Ong-Meang, Varravaddheay; Poinsot, Verena; Martins-Froment, Nathalie; Chauvet, Fabien; Boutonnet, Audrey; Ginot, Frédéric; Ecochard, Vincent; Paquereau, Laurent; Couderc, François

    2017-06-01

    Tris-Acetate buffer is currently used in the selection and the characterization of ssDNA by capillary electrophoresis (CE). By applying high voltage, the migration of ionic species into the capillary generates a current that induces water electrolysis. This phenomenon is followed by the modification of the pH and the production of Tris derivatives. By injecting ten times by capillary electrophoresis ssDNA (50 nM), the whole oligonucleotide was degraded. In this paper, we will show that the Tris buffer in the running vials is modified along the electrophoretic process by electrochemical reactions. We also observed that the composition of the metal ions changes in the running buffer vials. This phenomenon, never described in CE, is important for fluorescent ssDNA analysis using Tris buffer. The oligonucleotides are degraded by electrochemically synthesized species (present in the running Tris vials) until it disappears, even if the separation buffer in the capillary is clean. To address these issues, we propose to use a sodium phosphate buffer that we demonstrate to be electrochemically inactive. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Low noise buffer amplifiers and buffered phase comparators for precise time and frequency measurement and distribution

    Science.gov (United States)

    Eichinger, R. A.; Dachel, P.; Miller, W. H.; Ingold, J. S.

    1982-01-01

    Extremely low noise, high performance, wideband buffer amplifiers and buffered phase comparators were developed. These buffer amplifiers are designed to distribute reference frequencies from 30 KHz to 45 MHz from a hydrogen maser without degrading the hydrogen maser's performance. The buffered phase comparators are designed to intercompare the phase of state of the art hydrogen masers without adding any significant measurement system noise. These devices have a 27 femtosecond phase stability floor and are stable to better than one picosecond for long periods of time. Their temperature coefficient is less than one picosecond per degree C, and they have shown virtually no voltage coefficients.

  14. Buffer-free therapeutic antibody preparations provide a viable alternative to conventionally buffered solutions: from protein buffer capacity prediction to bioprocess applications.

    Science.gov (United States)

    Bahrenburg, Sven; Karow, Anne R; Garidel, Patrick

    2015-04-01

    Protein therapeutics, including monoclonal antibodies (mAbs), have significant buffering capacity, particularly at concentrations>50 mg/mL. This report addresses pH-related issues critical to adoption of self-buffered monoclonal antibody formulations. We evaluated solution conditions with protein concentrations ranging from 50 to 250 mg/mL. Samples were both buffer-free and conventionally buffered with citrate. Samples were non-isotonic or adjusted for isotonicity with NaCl or trehalose. Studies included accelerated temperature stability tests, shaking stability studies, and pH changes in infusion media as protein concentrate is added. We present averaged buffering slopes of capacity that can be applied to any mAb and present a general method for calculating buffering capacity of buffer-free, highly concentrated antibody liquid formulations. In temperature stability tests, neither buffer-free nor conventionally buffered solution conditions showed significant pH changes. Conventionally buffered solutions showed significantly higher opalescence than buffer-free ones. In general, buffer-free solution conditions showed less aggregation than conventionally buffered solutions. Shaking stability tests showed no differences between buffer-free and conventionally buffered solutions. "In-use" preparation experiments showed that pH in infusion bag medium can rapidly approximate that of self-buffered protein concentrate as concentrate is added. In summary, the buffer capacity of proteins can be predicted and buffer-free therapeutic antibody preparations provide a viable alternative to conventionally buffered solutions. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Static mechanical properties of buffer material

    International Nuclear Information System (INIS)

    Takaji, Kazuhiko; Suzuki, Hideaki

    1999-11-01

    The buffer material is expected to maintain its low water permeability, self-sealing properties, radionuclides adsorption and retardation properties, thermal conductivity, chemical buffering properties, overpack supporting properties, stress buffering properties, etc. over a long period of time. Natural clay is mentioned as a material that can relatively satisfy above. Among the kinds of natural clay, bentonite when compacted is superior because (i) it has exceptionally low water permeability and properties to control the movement of water in buffer, (ii) it fills void spaces in the buffer and fractures in the host rock as it swells upon water uptake, (iii) it has the ability to exchange cations and to adsorb cationic radioelements. In order to confirm these functions for the purpose of safety assessment, it is necessary to evaluate buffer properties through laboratory tests and engineering-scale tests, and to make assessments based on the ranges in the data obtained. This report describes the procedures, test conditions, results and examinations on the buffer material of unconfined compression tests, one-dimensional consolidation tests, consolidated-undrained triaxial compression tests and consolidated-undrained triaxial creep tests that aim at getting hold of static mechanical properties. We can get hold of the relationship between the dry density and tensile stress etc. by Brazilian tests, between the dry density and unconfined compressive strength etc. by unconfined compression tests, between the consolidation stress and void ratio etc. by one-dimensional consolidation tests, the stress pass of each effective confining pressure etc. by consolidated-undrained triaxial compression tests and the axial strain rate with time of each axial stress etc. by consolidated-undrained triaxial creep tests. (author)

  16. Defining the buffering process by a triprotic acid without relying on Stewart-electroneutrality considerations.

    Science.gov (United States)

    Nguyen, Minhtri K; Kao, Liyo; Kurtz, Ira

    2011-08-17

    Upon the addition of protons to an aqueous solution, a component of the H+ load will be bound i.e. buffered. In an aqueous solution containing a triprotic acid, H+ can be bound to three different states of the acid as well as to OH- ions that are derived from the auto-ionization of H2O. In quantifying the buffering process of a triprotic acid, one must define the partitioning of H+ among the three states of the acid and also the OH- ions in solution in order to predict the equilibrium pH value. However, previous quantitative approaches that model triprotic acid titration behaviour and used to predict the equilibrium pH rely on the mathematical convenience of electroneutrality/charge balance considerations. This fact has caused confusion in the literature, and has led to the assumption that charge balance/electroneutrality is a causal factor in modulating proton buffering (Stewart formulation). However, as we have previously shown, although charge balance can be used mathematically as a convenient tool in deriving various formulae, electroneutrality per se is not a fundamental physicochemical parameter that is mechanistically involved in the underlying buffering and proton transfer reactions. The lack of distinction between a mathematical tool, and a fundamental physicochemical parameter is in part a reason for the current debate regarding the Stewart formulation of acid-base analysis. We therefore posed the following question: Is it possible to generate an equation that defines and predicts the buffering of a triprotic acid that is based only on H+ partitioning without incorporating electroneutrality in the derivation? Towards this goal, we derived our new equation utilizing: 1) partitioning of H+ buffering; 2) conservation of mass; and 3) acid-base equilibria. In validating this model, we compared the predicted equilibrium pH with the measured pH of an aqueous solution consisting of Na2HPO4 to which HCl was added. The measured pH values were in excellent agreement

  17. Defining the buffering process by a triprotic acid without relying on stewart-electroneutrality considerations

    Directory of Open Access Journals (Sweden)

    Kao Liyo

    2011-08-01

    Full Text Available Abstract Upon the addition of protons to an aqueous solution, a component of the H+ load will be bound i.e. buffered. In an aqueous solution containing a triprotic acid, H+ can be bound to three different states of the acid as well as to OH- ions that are derived from the auto-ionization of H2O. In quantifying the buffering process of a triprotic acid, one must define the partitioning of H+ among the three states of the acid and also the OH- ions in solution in order to predict the equilibrium pH value. However, previous quantitative approaches that model triprotic acid titration behaviour and used to predict the equilibrium pH rely on the mathematical convenience of electroneutrality/charge balance considerations. This fact has caused confusion in the literature, and has led to the assumption that charge balance/electroneutrality is a causal factor in modulating proton buffering (Stewart formulation. However, as we have previously shown, although charge balance can be used mathematically as a convenient tool in deriving various formulae, electroneutrality per se is not a fundamental physicochemical parameter that is mechanistically involved in the underlying buffering and proton transfer reactions. The lack of distinction between a mathematical tool, and a fundamental physicochemical parameter is in part a reason for the current debate regarding the Stewart formulation of acid-base analysis. We therefore posed the following question: Is it possible to generate an equation that defines and predicts the buffering of a triprotic acid that is based only on H+ partitioning without incorporating electroneutrality in the derivation? Towards this goal, we derived our new equation utilizing: 1 partitioning of H+ buffering; 2 conservation of mass; and 3 acid-base equilibria. In validating this model, we compared the predicted equilibrium pH with the measured pH of an aqueous solution consisting of Na2HPO4 to which HCl was added. The measured pH values

  18. Defining the buffering process by a triprotic acid without relying on stewart-electroneutrality considerations

    Science.gov (United States)

    2011-01-01

    Upon the addition of protons to an aqueous solution, a component of the H+ load will be bound i.e. buffered. In an aqueous solution containing a triprotic acid, H+ can be bound to three different states of the acid as well as to OH- ions that are derived from the auto-ionization of H2O. In quantifying the buffering process of a triprotic acid, one must define the partitioning of H+ among the three states of the acid and also the OH- ions in solution in order to predict the equilibrium pH value. However, previous quantitative approaches that model triprotic acid titration behaviour and used to predict the equilibrium pH rely on the mathematical convenience of electroneutrality/charge balance considerations. This fact has caused confusion in the literature, and has led to the assumption that charge balance/electroneutrality is a causal factor in modulating proton buffering (Stewart formulation). However, as we have previously shown, although charge balance can be used mathematically as a convenient tool in deriving various formulae, electroneutrality per se is not a fundamental physicochemical parameter that is mechanistically involved in the underlying buffering and proton transfer reactions. The lack of distinction between a mathematical tool, and a fundamental physicochemical parameter is in part a reason for the current debate regarding the Stewart formulation of acid-base analysis. We therefore posed the following question: Is it possible to generate an equation that defines and predicts the buffering of a triprotic acid that is based only on H+ partitioning without incorporating electroneutrality in the derivation? Towards this goal, we derived our new equation utilizing: 1) partitioning of H+ buffering; 2) conservation of mass; and 3) acid-base equilibria. In validating this model, we compared the predicted equilibrium pH with the measured pH of an aqueous solution consisting of Na2HPO4 to which HCl was added. The measured pH values were in excellent agreement

  19. Temperature Buffer Test. Measurements of water content and density of the excavated buffer material

    Energy Technology Data Exchange (ETDEWEB)

    Johannesson, Lars-Erik [Clay Technology AB, Lund (Sweden)

    2010-12-15

    TBT (Temperature Buffer Test) is a joint project between SKB/ANDRA and supported by ENRESA (modeling) and DBE (instrumentation), which aims at understanding and modeling the thermo-hydromechanical behavior of buffers made of swelling clay submitted to high temperatures (over 100 deg C) during the water saturation process. The test was carried out at the - 420 m level in Aespoe HRL in a 8 meters deep and 1.76 m diameter deposition hole, with two heaters (3 m long, 0.6 m diameter), surrounded by a MX-80 bentonite buffer and a confining plug on top anchored with 9 rods. It was installed during spring 2003. The bentonite around upper heater was removed during the period October - December 2009 and the buffer around the lower heater was removed during January - Mars 2010. During dismantling of the buffer, samples were taken on which analyses were made. This report describes the work with the deteroemoeination of the water content and the density of the taken samples. Most of the samples were taken from the buffer by core drilling from the upper surface of each installed bentonite block. The cores had a diameter of about 50 mm and a maximum length equal to the original height of the bentonite blocks (about 500 mm). The water content of the buffer was determined by drying a sample at a temperature of 105 deg C for 24 h and the bulk density was determined by weighing a sample both in the air and immerged in paraffin oil with known density. The water content, dry density, degree of saturation and void ratio of the buffer were then plotted. The plots show that all parts of the buffer had taken up water and the degree of saturation of the buffer varied between 90 - 100%. Large variation in the dry density of the buffer was also observed.

  20. Effect of a data buffer on the recorded distribution of time intervals for random events

    Energy Technology Data Exchange (ETDEWEB)

    Barton, J C [Polytechnic of North London (UK)

    1976-03-15

    The use of a data buffer enables the distribution of the time intervals between events to be studied for times less than the recording system dead-time but the usual negative exponential distribution for random events has to be modified. The theory for this effect is developed for an n-stage buffer followed by an asynchronous recorder. Results are evaluated for the values of n from 1 to 5. In the language of queueing theory the system studied is of type M/D/1/n+1, i.e. with constant service time and a finite number of places.

  1. Scientific Applications Performance Evaluation on Burst Buffer

    KAUST Repository

    Markomanolis, George S.

    2017-10-19

    Parallel I/O is an integral component of modern high performance computing, especially in storing and processing very large datasets, such as the case of seismic imaging, CFD, combustion and weather modeling. The storage hierarchy includes nowadays additional layers, the latest being the usage of SSD-based storage as a Burst Buffer for I/O acceleration. We present an in-depth analysis on how to use Burst Buffer for specific cases and how the internal MPI I/O aggregators operate according to the options that the user provides during his job submission. We analyze the performance of a range of I/O intensive scientific applications, at various scales on a large installation of Lustre parallel file system compared to an SSD-based Burst Buffer. Our results show a performance improvement over Lustre when using Burst Buffer. Moreover, we show results from a data hierarchy library which indicate that the standard I/O approaches are not enough to get the expected performance from this technology. The performance gain on the total execution time of the studied applications is between 1.16 and 3 times compared to Lustre. One of the test cases achieved an impressive I/O throughput of 900 GB/s on Burst Buffer.

  2. Improved indexes for targeting placement of buffers of Hortonian runoff

    Science.gov (United States)

    M.G. Dosskey; Z. Qiu; M.J. Helmers; D.E. Eisenhauer

    2011-01-01

    Targeting specific locations within agricultural watersheds for installing vegetative buffers has been advocated as a way to enhance the impact of buffers and buffer programs on stream water quality. Existing models for targeting buffers of Hortonian, or infiltration-excess, runoff are not well developed. The objective was to improve on an existing soil survey–based...

  3. A buffer overflow detection based on inequalities solution

    International Nuclear Information System (INIS)

    Xu Guoai; Zhang Miao; Yang Yixian

    2007-01-01

    A new buffer overflow detection model based on Inequalities Solution was designed, which is based on analyzing disadvantage of the old buffer overflow detection technique and successfully converting buffer overflow detection to Inequalities Solution. The new model can conquer the disadvantage of the old technique and improve efficiency of buffer overflow detection. (authors)

  4. Formation of monofunctional cisplatin-DNA adducts in carbonate buffer.

    Science.gov (United States)

    Binter, Alexandra; Goodisman, Jerry; Dabrowiak, James C

    2006-07-01

    Carbonate in its various forms is an important component in blood and the cytosol. Since, under conditions that simulate therapy, carbonate reacts with cisplatin to form carbonato complexes, one of which is taken up and/or modified by the cell [C.R. Centerwall, J. Goodisman, D.J. Kerwood, J. Am. Chem. Soc., 127 (2005) 12768-12769], cisplatin-carbonato complexes may be important in the mechanism of action of cisplatin. In this report we study the binding of cisplatin to pBR322 DNA in two different buffers, using gel electrophoresis. In 23.8mM HEPES, N-(2-hydroxyethyl)-piperazine-N'-2-ethanesulfonic acid, 5mM NaCl, pH 7.4 buffer, cisplatin produces aquated species, which react with DNA to unwind supercoiled Form I DNA, increasing its mobility, and reducing the binding of ethidium to DNA. This behavior is consistent with the formation of the well-known intrastrand crosslink on DNA. In 23.8mM carbonate buffer, 5mM NaCl, pH 7.4, cisplatin forms carbonato species that produce DNA-adducts which do not significantly change supercoiling but enhance binding of ethidium to DNA. This behavior is consistent with the formation of a monofunctional cisplatin adduct on DNA. These results show that aquated cisplatin and carbonato complexes of cisplatin produce different types of lesions on DNA and they underscore the importance of carrying out binding studies with cisplatin and DNA using conditions that approximate those found in the cell.

  5. Stability of biodegradable waterborne polyurethane films in buffered saline solutions.

    Science.gov (United States)

    Lin, Ying Yi; Hung, Kun-Che; Hsu, Shan-Hui

    2015-09-21

    The stability of polyurethane (PU) is of critical importance for applications such as in coating industry or as biomaterials. To eliminate the environmental concerns on the synthesis of PU which involves the use of organic solvents, the aqueous-based or waterborne PU (WBPU) has been developed. WBPU, however, may be unstable in an electrolyte-rich environment. In this study, the authors reported the stability of biodegradable WBPU in the buffered saline solutions evaluated by atomic force microscopy (AFM). Various biodegradable WBPU films were prepared by spin coating on coverslip glass, with a thickness of ∼300 nm. The surface AFM images of poly(ε-caprolactone) (PCL) diol-based WBPU revealed nanoglobular structure. The same feature was observed when 20% molar of the PCL diol soft segment was replaced by polyethylene butylenes adipate diol. After hydration in buffered saline solutions for 24 h, the surface domains generally increased in sizes and became irregular in shape. On the other hand, when the soft segment was replaced by 20% poly(l-lactide) diol, a meshlike surface structure was demonstrated by AFM. When the latter WBPU was hydrated, the surface domains appeared to be disconnected. Results from the attenuated total reflectance infrared spectroscopy and x-ray photoelectron spectroscopy indicated that the surface chemistry of WBPU films was altered after hydration. These changes were probably associated with the neutralization of carboxylate by ions in the saline solutions, resulting in the rearrangements of soft and hard segments and causing instability of the WBPU.

  6. Moisture buffer capacity of different insulation materials

    DEFF Research Database (Denmark)

    Peuhkuri, Ruut Hannele; Rode, Carsten; Hansen, Kurt Kielsgaard

    2004-01-01

    . In the isothermal tests the material samples were exposed to the same change in the relative humidity of the ambient air on both sides, while the samples were exposed to variations in relative humidity only on the cold side in the non-isothermal tests. The results of these rather different measurement principles...... lead to more durable constructions. In this paper, a large range of very different thermal insulation materials have been tested in specially constructed laboratory facilities to determine their moisture buffer capacity. Both isothermal and nonisothermal experimental set-ups have been used...... are discussed, and different ways are presented how to determine the moisture buffer capacity of the materials using partly standard material parameters and partly parameters determined from the actual measurements. The results so far show that the determination of moisture buffer capacity is very sensitive...

  7. Buffer construction technique using granular bentonite

    International Nuclear Information System (INIS)

    Masuda, Ryoichi; Asano, Hidekazu; Toguri, Satohito; Mori, Takuo; Shimura, Tomoyuki; Matsuda, Takeshi; Uyama, Masao; Noda, Masaru

    2007-01-01

    Buffer construction using bentonite pellets as filling material is a promising technology for enhancing the ease of repository operation. In this study, a test of such technology was conducted in a full-scale simulated disposal drift, using a filling system which utilizes a screw conveyor system. The simulated drift, which contained two dummy overpacks, was configured as a half-cross-section model with a height of 2.22 m and a length of 6.0 m. The average dry density of the buffer obtained in the test was 1.29 Mg/m 3 , with an angle of repose of 35 to 40 degrees. These test results indicate that buffer construction using a screw conveyor system for pellet emplacement in a waste disposal drift is a promising technology for repositories for high level radioactive wastes. (author)

  8. Labview virtual instruments for calcium buffer calculations.

    Science.gov (United States)

    Reitz, Frederick B; Pollack, Gerald H

    2003-01-01

    Labview VIs based upon the calculator programs of Fabiato and Fabiato (J. Physiol. Paris 75 (1979) 463) are presented. The VIs comprise the necessary computations for the accurate preparation of multiple-metal buffers, for the back-calculation of buffer composition given known free metal concentrations and stability constants used, for the determination of free concentrations from a given buffer composition, and for the determination of apparent stability constants from absolute constants. As implemented, the VIs can concurrently account for up to three divalent metals, two monovalent metals and four ligands thereof, and the modular design of the VIs facilitates further extension of their capacity. As Labview VIs are inherently graphical, these VIs may serve as useful templates for those wishing to adapt this software to other platforms.

  9. Modified cyanobacteria

    Science.gov (United States)

    Vermaas, Willem F J.

    2014-06-17

    Disclosed is a modified photoautotrophic bacterium comprising genes of interest that are modified in terms of their expression and/or coding region sequence, wherein modification of the genes of interest increases production of a desired product in the bacterium relative to the amount of the desired product production in a photoautotrophic bacterium that is not modified with respect to the genes of interest.

  10. Developing suitable buffers to capture transport cycling behavior

    DEFF Research Database (Denmark)

    Madsen, Thomas; Schipperijn, Jasper; Christiansen, Lars Breum

    2014-01-01

    units (e.g., home-buffer-based neighborhoods) are not necessarily representative for environmental exposure. An increased understanding of appropriate neighborhoods is needed. GPS cycling tracks from 78 participants for 7 days form the basis for the development and testing of different neighborhood...... buffers for transport cycling. The percentage of GPS points per square meter was used as indicator of the effectiveness of a series of different buffer types, including home-based network buffers, shortest route to city center buffers, and city center-directed ellipse-shaped buffers. The results show...... center-directed ellipse-shaped buffers yielded better results than traditional home-based network buffer types. The ellipse-shaped buffer types could therefore be considered an alternative to more traditional buffers or administrative units in future studies of transport cycling behavior....

  11. Synthesis and characterization of nanocomposites based on polyurethane in aqueous dispersions with non-modified hydrophilic clays; Sintese e caracterizacao de nanocompositos a base de poliuretanos em dispersoes aquosas com argilas hidrofilicas nao-modificadas

    Energy Technology Data Exchange (ETDEWEB)

    Miranda, G.S.; Delpechi, M.C.; Santo, W.L.E., E-mail: mcd@uerj.b [Universidade do Estado do Rio de Janeiro (UERJ), RJ (Brazil)

    2010-07-01

    Several studies involving the formation of polyurethane nanocomposites employing clays of montmorillonite modified. This involves the presence of quaternary ammonium salts, the cation exchange needed to increase the interlayer space of clays that incorporate more than one step to the process, generates a higher cost. In this paper the synthesis of nanocomposite polyurethanes dispersed in water allowed not only the production of materials less harmful to the environment, but also the incorporation of hydrophilic clays, calcium and sodium in nature, without any modifications. Dispersions produced from 0.5, 1.0 and 2.5% clay (on the mass of prepolymer) were characterized in terms of total solids content, the films obtained by casting were evaluated for adhesiveness, diffraction X-rays, scanning electron microscopy. Most systems showed intercalated and partially exfoliated structures. (author)

  12. Buffer of Events as a Markovian Process

    International Nuclear Information System (INIS)

    Berdugo, J.; Casaus, J.; Mana, C.

    2001-01-01

    In Particle and Asro-Particle Physics experiments, the events which get trough the detectors are read and processes on-line before they are stored for a more detailed processing and future Physics analysis. Since the events are read and, usually, processed sequentially, the time involved in these operations can lead to a significant lose of events which is, to some extent, reduced by using buffers. We present an estimate of the optimum buffer size and the fraction of events lost for a simple experimental condition which serves as an introductory example to the use of Markow Chains.(Author)

  13. Buffer of Events as a Markovian Process

    Energy Technology Data Exchange (ETDEWEB)

    Berdugo, J.; Casaus, J.; Mana, C.

    2001-07-01

    In Particle and Asro-Particle Physics experiments, the events which get trough the detectors are read and processes on-line before they are stored for a more detailed processing and future Physics analysis. Since the events are read and, usually, processed sequentially, the time involved in these operations can lead to a significant lose of events which is, to some extent, reduced by using buffers. We present an estimate of the optimum buffer size and the fraction of events lost for a simple experimental condition which serves as an introductory example to the use of Markow Chains.(Author)

  14. Emplacement of small and large buffer blocks

    International Nuclear Information System (INIS)

    Saari, H.; Nikula, M.; Suikki, M.

    2010-05-01

    The report describes emplacement of a buffer structure encircling a spent fuel canister to be deposited in a vertical hole. The report deals with installability of various size blocks and with an emplacement gear, as well as evaluates the achieved quality of emplacement and the time needed for installing the buffer. Two block assembly of unequal size were chosen for examination. A first option involved small blocks, the use of which resulted in a buffer structure consisting of small sector blocks 200 mm in height. A second option involved large blocks, resulting in a buffer structure which consists of eight blocks. In these tests, the material chosen for both block options was concrete instead of bentonite. The emplacement test was a three-phase process. A first phase included stacking a two meter high buffer structure with small blocks for ensuring the operation of test equipment and blocks. A second phase included installing buffer structures with both block options to a height matching that of a canister-encircling cylindrical component. A third phase included testing also the installability of blocks to be placed above the canister by using small blocks. In emplacement tests, special attention was paid to the installability of blocks as well as to the time required for emplacement. Lifters for both blocks worked well. Due to the mass to be lifted, the lifter for large blocks had a more heavy-duty frame structure (and other lifting gear). The employed lifters were suspended in the tests on a single steel wire rope. Stacking was managed with both block sizes at adequate precision and stacked-up towers were steady. The stacking of large blocks was considerably faster. Therefore it is probably that the overall handling of the large blocks will be more convenient at a final disposal site. From the standpoint of reliability in lifting, the small blocks were safer to install above the canister. In large blocks, there are strict shape-related requirements which are

  15. Grass buffers for playas in agricultural landscapes: An annotated bibliography

    Science.gov (United States)

    Melcher, Cynthia P.; Skagen, Susan K.

    2005-01-01

    This bibliography and associated literature synthesis (Melcher and Skagen, 2005) was developed for the Playa Lakes Joint Venture (PLJV). The PLJV sought compilation and annotation of the literature on grass buffers for protecting playas from runoff containing sediments, nutrients, pesticides, and other contaminants. In addition, PLJV sought information regarding the extent to which buffers may attenuate the precipitation runoff needed to fill playas, and avian use of buffers. We emphasize grass buffers, but we also provide information on other buffer types.

  16. Analysis of the role of elution buffers on the separation capabilities of dielectrophoretic devices

    Directory of Open Access Journals (Sweden)

    Rossana Di Martino

    2016-03-01

    Full Text Available Field flow fractionation dielectrophoretic (FFF-DEP devices are currently used, among the others, for the separation of tumor cells from healthy blood cells. To this end specific suspension/elution buffers (EBs, with reduced conductivity (with respect to that of the cell cytoplasm are generally used. In this paper we investigate the long-term alterations of the cells and elution buffers. We find that the EB conductivity is critically modified within few minutes after cells suspension. In turn, this modification results in a change the ideal separation frequency of the FFF-DEP device. On the other hand we prove that DEP manipulation is preserved for more than three hours for cells suspended in the considered EBs. Keywords: Dielectrophoresis, Elution buffer, Circulating tumor cells, Cell motility

  17. Experimental measurements of U60 nanocluster stability in aqueous solution

    Science.gov (United States)

    Flynn, Shannon L.; Szymanowski, Jennifer E. S.; Gao, Yunyi; Liu, Tianbo; Burns, Peter C.; Fein, Jeremy B.

    2015-05-01

    In this study, the aqueous behavior of isolated U60 nanoclusters (K16Li25[UO2(O2)OH]60)-19 was studied under several pH conditions and nanocluster concentrations to determine if the nanoclusters exhibit solid phase buffering behavior or if they exhibit behavior more like aqueous complexes. U60 is a cage cluster consisting of 60 (UO2)(O2)2(OH)2 uranyl polyhedral which share OH and O2 groups with their neighboring uranyl polyhedral, resulting in negatively charged cage clusters whose charge is at least partially offset by K+ and Li+ in the aqueous phase. Batch experiments to monitor nanocluster stability were conducted for 16 days at pH 7.5, 8.0 and 8.5 at nanocluster suspension concentrations of 1.4, 2.8 and 6.0 g/L. The aqueous concentrations of U, Li, and K, determined after 10 kDa molecular weight filtration, achieved steady-state with the nanoclusters within 24 h. The steady-state aqueous U, Li, and K concentrations were independent of solution pH, however they increased with increasing nanocluster concentration, indicating that the nanoclusters do not buffer the aqueous activities as a bulk solid phase would, but exhibit behavior that is more characteristic of dissolved aqueous complexes. The ion activity product (I.A.P.) value was calculated using two approaches: (1) treating the nanoclusters as a solid phase with an activity of one, and (2) treating the nanoclusters as aqueous complexes with a non-unit activity equal to their concentration in solution. The I.A.P. values that were calculated with non-unit activity for the nanoclusters exhibited significantly less variation as a function of nanocluster concentration compared to the I.A.P. values calculated with a nanocluster activity of one. The results yield a calculated log dissociation constant for the U60 nanoclusters of 9.2 + 0.2/-0.3 (1σ). Our findings provide a better understanding of the thermodynamic stability and behavior of U60 nanoclusters in aqueous systems, and can be used to estimate the

  18. Aqueous lithium air batteries

    Science.gov (United States)

    Visco, Steven J.; Nimon, Yevgeniy S.; De Jonghe, Lutgard C.; Petrov, Alexei; Goncharenko, Nikolay

    2017-05-23

    Aqueous Li/Air secondary battery cells are configurable to achieve high energy density and prolonged cycle life. The cells include a protected a lithium metal or alloy anode and an aqueous catholyte in a cathode compartment. The aqueous catholyte comprises an evaporative-loss resistant and/or polyprotic active compound or active agent that partakes in the discharge reaction and effectuates cathode capacity for discharge in the acidic region. This leads to improved performance including one or more of increased specific energy, improved stability on open circuit, and prolonged cycle life, as well as various methods, including a method of operating an aqueous Li/Air cell to simultaneously achieve improved energy density and prolonged cycle life.

  19. Removal of blue 1 dye of aqueous solutions with a modified clay with iron chloride; Remocion de colorante azul 1 de soluciones acuosas con una arcilla modificada con cloruro de hierro

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez H, K. A.

    2012-07-01

    At the present time, several technologies have been proposed to remove dyes from water, adsorption is one of the most feasible methods and adsorbents with different properties, such as activated carbon, zeolites, clays and hydrogels among others. In this work, the sorption behavior of blue 1 dye by a natural clay from a site located in the Center-East of Mexico, and other modified with iron chloride were determined. The materials were characterized by X-ray diffraction to analyze its crystal structure, by scanning electron microscopy and elemental microanalysis of energy dispersive X-ray spectrometry to determine the composition and morphology, and the zero point charges were also determined to know the charge distribution on the surface of the clay. The ph effect, contact time, dye concentration and temperature were the parameters considered in this study. The results showed that clay does not suffer any important changes in its structure after the chemical treatments (modification with ferric chloride and contact with blue 1 solutions). The ph influences lightly the adsorption of the dye with natural clay, but the same effect is not observed in the ferric modified clay among the factor ph 6 and 8. The equilibrium time and the sorption capacity for natural clay were 48 hours and 6.16 mg/g, while for the ferric clay were 24 hours and 14.22 mg/g. Adsorption kinetics results were best adjusted to the pseudo first and pseudo second order models. Adsorption isotherms were best adjusted to the Langmuir model, indicating that both clays have a homogeneous surface. Thermodynamic parameters (E, {Delta}S and {Delta}G and {Delta}H) were calculated for the dye adsorption by the natural clay using data of the adsorption kinetics at temperatures between 20 and 50 C, indicating that the adsorption process is exothermic. For the case of ferric clay, it was not possible to calculate these thermodynamic parameters because the adsorption capacities were similar in the range of

  20. Buffer gas cooling and mixture analysis

    Science.gov (United States)

    Patterson, David S.; Doyle, John M.

    2018-03-06

    An apparatus for spectroscopy of a gas mixture is described. Such an apparatus includes a gas mixing system configured to mix a hot analyte gas that includes at least one analyte species in a gas phase into a cold buffer gas, thereby forming a supersaturated mixture to be provided for spectroscopic analysis.

  1. Buffer Overflow Period in a MAP Queue

    Directory of Open Access Journals (Sweden)

    Andrzej Chydzinski

    2007-01-01

    Full Text Available The buffer overflow period in a queue with Markovian arrival process (MAP and general service time distribution is investigated. The results include distribution of the overflow period in transient and stationary regimes and the distribution of the number of cells lost during the overflow interval. All theorems are illustrated via numerical calculations.

  2. Body Buffer Zone and Proxemics in Blocking.

    Science.gov (United States)

    Stockwell, John C.; Bahs, Clarence W.

    This paper investigates the effect of personal body buffer zones on compositional arrangements staged by novice directors. Relationships between directors' concepts of personal space and their projection of its dimensions into staging are studied through the use of a variety of proximity measures--distance, area angles of approach, and physical…

  3. Preformulation study of methazolamide for topical ophthalmic delivery: physicochemical properties and degradation kinetics in aqueous solutions.

    Science.gov (United States)

    Jiang, Sunmin; Wang, Fengzhen; Zhu, Shuning; Zhang, Xiumei; Guo, Zhigang; Li, Rui; Xu, Qunwei

    2013-05-20

    Methazolamide (MTZ) is an anti-glaucoma drug. The present paper aims to characterize the physicochemical properties and degradation kinetics of MTZ to provide a basis for topical ophthalmic delivery. With the increase in pH (pH 5.5-8.0) of aqueous solution, the solubility of the compound increased while the partition coefficient (Ko/w) which was estimated in the system n-octanol/aqueous solution decreased. The degradation of MTZ in aqueous solution followed pseudo-first-order kinetic. The degradation rate kpH is the rate in the absence of buffer catalysis. Plotting the natural logarithm of kpH versus the corresponding pH value gave a V-shaped pH-rate profile with a maximum stability at pH 5.0. The degradation rate constants as a function of the temperature obeyed the Arrhenius equation (R(2)=0.9995 at pH 7.0 and R(2)=0.9955 at pH 9.0, respectively). A decrease in ionic strength and buffer concentration displayed a stabilizing effect on MTZ. Buffer species also influenced the MTZ hydrolysis. Phosphate buffer system was more catalytic than tris and borate buffer systems. In brief, it is important to consider the physicochemical properties and the stability of MTZ during formulation. Copyright © 2013 Elsevier B.V. All rights reserved.

  4. Rapid synthesis of CdSe nanocrystals in aqueous solution at room ...

    Indian Academy of Sciences (India)

    Administrator

    Water-soluble thioglycolic acid-capped CdSe nanocrystals (NCs) were prepared in aqueous solu- tion at room temperature. We investigated the ... NCs dispersed in buffer solution (pH = 4⋅0). FTIR spectra were recorded on a ... the theory of acid-base equilibrium, the initial pH value of original solution determines the ...

  5. Peak distortion in the column liquid chromatographic determination of omeprazole dissolved in borax buffer.

    Science.gov (United States)

    Arvidsson, T; Collijn, E; Tivert, A M; Rosén, L

    1991-11-22

    Injection of a sample containing omeprazole dissolved in borax buffer (pH 9.2) into a reversed-phase liquid chromatographic system consisting of a mixture of acetonitrile and phosphate buffer (pH 7.6) as the mobile phase and a C18 surface-modified silica as the solid phase resulted under special conditions in split peaks of omeprazole. The degree of peak split and the retention time of omeprazole varied with the concentration of borax in the sample solution and the ionic strength of the mobile phase buffer as well as with the column used. Borax is eluted from the column in a broad zone starting from the void volume of the column. The retention is probably due to the presence of polyborate ions. The size of the zone varies with the concentration of borax in the sample injected. In the borax zone the pH is increased compared with the pH of the mobile phase, and when omeprazole (a weak acid) is co-eluting in the borax zone its retention is affected. In the front part and in the back part of the borax zone, pH gradients are formed, and these gradients can induce the peak splitting. When the dissolving medium is changed to a phosphate buffer or an ammonium buffer at pH 9 no peak distortion of omeprazole is observed.

  6. Buffering action of human dentin in vitro.

    Science.gov (United States)

    Camps, J; Pashley, D H

    2000-01-01

    The purpose of this study was to determine the relative contributions of the mineral and organic phases of dentin to its total buffering capacity and to compare the buffering abilities of normal and caries-affected dentin for acids used in adhesive dentistry. Disks of normal and caries-affected human coronal dentin 0.6 mm thick were prepared. Fifty microL of various acids were applied to the surface of mineralized or completely demineralized dentin for varying lengths of time. They were collected from the surface and combined with water rinses to permit titration of the total amount of acid applied, the amount recovered, the total amount that was taken up by the dentin, and the amount that diffused across dentin into 1 mL of water. Equal volumes of acids were applied to mineralized or demineralized dentin powder or hydroxyapatite powder. About 88% to 90% of applied acid was recovered from the surface; only 10% to 12% of the acid was taken up by dentin. Of the H+ that was taken up, only 1% to 2% actually diffused across 0.6 mm of dentin. Increasing the application time of 37% phosphoric acid did not increase the amount of H+ that diffused across dentin. Increasing the concentration of phosphoric acid from 10% to 65% produced only slight increases in H+ diffusion across dentin. There was no difference in the buffering capacity of normal vs caries-affected dentin disks. Almost all of the buffering capacity of dentin is due to its mineral phase. The high buffering capacity of dentin and the high reactivity of H+ insure that little H+ diffuses through dentin more than 0.6 mm thick.

  7. Semi-mechanistic partial buffer approach to modeling pH, the buffer properties, and the distribution of ionic species in complex solutions.

    Science.gov (United States)

    Dougherty, Daniel P; Da Conceicao Neta, Edith Ramos; McFeeters, Roger F; Lubkin, Sharon R; Breidt, Frederick

    2006-08-09

    In many biological science and food processing applications, it is very important to control or modify pH. However, the complex, unknown composition of biological media and foods often limits the utility of purely theoretical approaches to modeling pH and calculating the distributions of ionizable species. This paper provides general formulas and efficient algorithms for predicting the pH, titration, ionic species concentrations, buffer capacity, and ionic strength of buffer solutions containing both defined and undefined components. A flexible, semi-mechanistic, partial buffering (SMPB) approach is presented that uses local polynomial regression to model the buffering influence of complex or undefined components in a solution, while identified components of known concentration are modeled using expressions based on extensions of the standard acid-base theory. The SMPB method is implemented in a freeware package, (pH)Tools, for use with Matlab. We validated the predictive accuracy of these methods by using strong acid titrations of cucumber slurries to predict the amount of a weak acid required to adjust pH to selected target values.

  8. A magnetic trap for living cells suspended in a paramagnetic buffer

    Science.gov (United States)

    Winkleman, Adam; Gudiksen, Katherine L.; Ryan, Declan; Whitesides, George M.; Greenfield, Derek; Prentiss, Mara

    2004-09-01

    This manuscript describes the fabrication and use of a three-dimensional magnetic trap for diamagnetic objects in an aqueous solution of paramagnetic ions; this trap uses permanent magnets. It demonstrates trapping of polystyrene spheres, and of various types of living cells: mouse fibroblast (NIH-3T3), yeast (Saccharomyces cerevisiae), and algae (Chlamydomonas reinhardtii). For a 40mM solution of gadolinium (III) diethylenetriaminepentaacetic acid (Gd .DTPA) in aqueous buffer, the smallest cell (particle) that could be trapped had a radius of ˜2.5μm. The trapped particle and location of the magnetic trap can be translated in three dimensions by independent manipulation of the permanent magnets. This letter a1so characterizes the biocompatibility of the trapping solution.

  9. Ethylene glycol modified 2-(2′-aminophenyl)benzothiazoles at the amino site: the excited-state N-H proton transfer reactions in aqueous solution, micelles and potential application in live-cell imaging

    International Nuclear Information System (INIS)

    Liu, Bo-Qing; Tsai, Yi-Hsuan; Li, Yi-Jhen; Chao, Chi-Min; Liu, Kuan-Miao; Chen, Yi-Ting; Chen, Yu-Wei; Chung, Kun-You; Tseng, Huan-Wei; Chou, Pi-Tai

    2016-01-01

    Triethylene glycol monomethyl ether and poly(ethylene glycol) monomethyl ether modified 2-(2′-aminophenyl)benzothiazoles, namely ABT-P3EG, ABT-P7EG and ABT-P12EG varied by different chain length of poly(ethylene glycol) at the amino site, were synthesized to probe their photophysical and bio-imaging properties. In polar, aprotic solvents such as CH 2 Cl 2 ultrafast excited-state intramolecular proton transfer (ESIPT) takes place, resulting in a large Stokes shifted tautomer emission in the green-yellow (550 nm) region. In neutral water, ABT-P12EG forms micelles with diameters of 15  ±  3 nm under a critical micelle concentration (CMC) of ∼80 μM, in which the tautomer emission is greatly enhanced free from water perturbation. Cytotoxicity experiments showed that all ABT-PnEGs have negligible cytotoxicity against HeLa cells even at doses as high as 1 mM. Live-cell imaging experiments were also performed, the results indicate that all ABT-PnEGs are able to enter HeLa cells. While the two-photon excitation emission of ABT-P3EG in cells cytoplasm shows concentration independence and is dominated by the anion blue fluorescence, ABT-P7EG and ABT-P12EG exhibit prominent green tautomer emission at  >  CMC and in part penetrate to the nuclei, adding an additional advantage for the cell imaging. (paper)

  10. Atmospheric plasma generates oxygen atoms as oxidizing species in aqueous solutions

    International Nuclear Information System (INIS)

    Hefny, Mohamed Mokhtar; Pattyn, Cedric; Benedikt, Jan; Lukes, Petr

    2016-01-01

    A remote microscale atmospheric pressure plasma jet ( µ APPJ) with He, He/H 2 O, He/O 2 , and He/O 2 /H 2 O gas mixtures was used to study the transport of reactive species from the gas phase into the liquid and the following aqueous phase chemistry. The effects induced by the µ APPJ in water were quantitatively studied using phenol as a chemical probe and by measuring H 2 O 2 concentration and pH values. These results were combined with the analysis of the absolute densities of the reactive species and the modeling of convective/diffusion transport and recombination reactions in the effluent of the plasma jet. Additionally, modified plasma jets were used to show that the role of emitted photons in aqueous chemistry is negligible for these plasma sources. The fastest phenol degradation was measured for the He/O 2 plasma, followed by He/H 2 O, He/O 2 /H 2 O, and He plasmas. The modeled quantitative flux of O atoms into the liquid in the He/O 2 plasma case was highly comparable with the phenol degradation rate and showed a very high transfer efficiency of reactive species from the plasma into the liquid, where more than half of the O atoms leaving the jet nozzle entered the liquid. The results indicate that the high oxidative effect of He/O 2 plasma was primarily due to solvated O atoms, whereas OH radicals dominated the oxidative effects induced in water by plasmas with other gas mixtures. These findings help to understand, in a quantitative way, the complex interaction of cold atmospheric plasmas with aqueous solutions and will allow a better understanding of the interaction of these plasmas with water or buffered solutions containing biological macromolecules, microorganisms, or even eukaryotic cells. Additionally, the µ APPJ He/O 2 plasma source seems to be an ideal tool for the generation of O atoms in aqueous solutions for any future studies of their reactivity. (paper)

  11. Chemical buffering in natural and engineered barrier systems: Thermodynamic constraints and performance assessment consequences

    International Nuclear Information System (INIS)

    Arthur, R.C.; Wei Zhou

    2000-12-01

    Thermodynamic and kinetic constraints on the chemical buffering properties of natural and engineered-barrier systems are derived in this study from theoretical descriptions, incorporated in the reaction-path model, of reversible and irreversible mass transfer in multicomponent, multiphase systems. The buffering properties of such systems are conditional properties because they refer to a specific aqueous species in a system that is open with respect to a specific reactant. The solution to a mathematical statement of this concept requires evaluation of the dependence of the activity of the buffered species on incremental changes in the overall reaction-progress variable. This dependence can be represented by a truncated Taylor's series expansion, where the values of associated derivatives are calculated using finite-difference techniques and mass-balance, charge-balance and mass-action constraints. Kinetic constraints on buffering behavior can also be described if the relation between reactant flux and reaction rate is well defined. This relation is explicit for the important case of advective groundwater flow and water-rock interaction. We apply the theoretical basis of the chemical buffering concept to processes that could affect the performance of a deep geologic repository for nuclear waste. Specifically, we focus on the likelihood that an inverse relation must exist between the buffer intensity and the migration velocity of reaction fronts in systems involving advective or diffusive mass transport. A quantitative understanding of this relation would provide the basis for evaluating the potential role of chemical buffering in achieving the isolation and retardation functions, of the EBS and geosphere in a KBS-3 repository. Our preliminary evaluation of this role considers the effects of chemical buffering on the propagation velocity of a pH front in both the near- and far field. We use a geochemical modeling technique compatible with the reaction-path model to

  12. Estimation of aqueous solubility of TODGA using group contribution method

    International Nuclear Information System (INIS)

    Balasubramonian, S.; Kumar, Shekhar; Sampath, M.; Sivakumar, D.; Kamachi Mudali, U.

    2017-01-01

    The aqueous solubility of N, N, N', N'-tetraoctyl-3-oxapentanediamide normally referred as TODGA is experimentally measured. The aqueous solubility was also predicted using Marrero and Gani group contribution method. The modification of original Marrero and Gani method was proposed to accurately predict TODGA solubility. The predicted solubility of TODGA using original Marrero and Gani method, Modified Marrero and Gani method and UNIFAC Model was compared. The predicted solubility of TODGA using modified Marrero and Gani method is 0.0237 g/l against the experimentally measured value of 0.0226 g/l. (author)

  13. Fluorescence-based detection of nitric oxide in aqueous and methanol media using a copper(II) complex.

    Science.gov (United States)

    Mondal, Biplab; Kumar, Pankaj; Ghosh, Pokhraj; Kalita, Apurba

    2011-03-14

    The quenched fluorescent intensity of a copper(II) complex, 1, of a fluorescent ligand, in degassed methanol or aqueous (buffered at pH 7.2) solution, was found to reappear on exposure to nitric oxide. Thus, it can function as a fluorescence based nitric oxide sensor. It has been found that the present complex can be used to sense nanomolar quantities of nitric oxide in both methanol and pH 7.2 buffered-water medium.

  14. Coupled microrings data buffer using fast light

    Science.gov (United States)

    Scheuer, Jacob; Shahriar, Selim

    2013-03-01

    We present a theoretical study of a trap-door optical buffer based on a coupled microrings add/drop filter (ADF) utilizing the white light cavity (WLC). The buffer "trap-door" can be opened and closed by tuning the resonances of the microrings comprising the ADF and trap/release optical pulses. We show that the WLC based ADF yields a maximally flat filter which exhibits superior performances in terms of bandwidth and flatness compared to previous design approaches. We also present a realistic, Silicon-over-Insulator based, design and performance analysis taking into consideration the realistic properties and limitations of the materials and the fabrication process, leading to delays exceeding 850ps for 80GHz bandwidth, and a corresponding delay-bandwidth product of approximately 70.

  15. MOISTURE-BUFFERING CHARACTERISTICS OF BUILDING MATERIALS

    Directory of Open Access Journals (Sweden)

    Young Cheol Choi

    2016-05-01

    Full Text Available The humidity level of indoor air is an important factor influencing the air quality and energy consumption of buildings, as well as the durability of building components. Indoor humidity levels depend on several factors, such as moisture sources, air flow, and the adsorption/desorption properties of materials. The moisture-buffering characteristics of building materials that are in contact with indoor air may help moderate the variations of indoor humidity, especially in the summer and winter. In this study, the moisture adsorption/desorption properties of building materials were investigated experimentally and numerically. These properties can be used to characterize the ability of building materials to exchange moisture with the indoor environment. This study indicates that a building material surface resistivity was the main factor creating variations of moisture buffering.

  16. Chemical buffering capacity of clay rock

    International Nuclear Information System (INIS)

    Beaucaire, C.; Pearson, F.J.; Gautschi, A.

    2004-01-01

    The long-term performance of a nuclear waste repository is strongly dependent on the chemical properties of the host rock. The host rock establishes the chemical environment that determines such important performance attributes as radionuclide solubilities from the waste and the transport rates from the repository to the accessible environment. Clay-rich rocks are especially favourable host rocks because they provide a strong buffering capacity to resist chemical changes prompted either internally, by reactions of the waste itself and emplacement materials, or externally, by changes in the hydrologic systems surrounding the host rock. This paper will focus on three aspects of the stability of clay-rich host rocks: their ability to provide pCO 2 and redox buffering, and to resist chemical changes imposed by changes in regional hydrology and hydro-chemistry. (authors)

  17. Complexation of lysozyme with sodium caseinate and micellar casein in aqueous buffered solutions

    NARCIS (Netherlands)

    Antonov, Y.A.; Moldenaers, P.; Cardinaels, R.M.

    We present an extended structural and morphological study of the complexation of lysozyme (Lys) with sodium caseinate (SC) and micellar casein (MC) by means of turbidity measurements, phase analysis, dynamic, static and electrophoretic light scattering, bright-field and confocal laser scanning

  18. Role of buffer gases in optoacoustic spectroscopy

    International Nuclear Information System (INIS)

    Thomas III, L.J.; Kelly, M.J.; Amer, N.M.

    1978-01-01

    The dependence of an acoustically resonant optoacoustic signal on the molecular weight and thermodynamic and transport properpties of the buffer gas is reported. Our results show that careful selection of such gases can significantly increase the sensitivity and flexibility of optoacoustic spectroscopy. We also demonstrate that such thermodynamic quantities as γ (equivalentC/sub p//C/sub v/) and sound velocity can now be measured readily and accurately. Other potential applications are suggested

  19. Microbial activity in bentonite buffers. Literature study

    Energy Technology Data Exchange (ETDEWEB)

    Ratto, M.; Itavaara, M.

    2012-07-01

    The proposed disposal concept for high-level radioactive wastes involves storing the wastes underground in copper-iron containers embedded in buffer material of compacted bentonite. Hydrogen sulphide production by sulphate-reducing prokaryotes is a potential mechanism that could cause corrosion of waste containers in repository conditions. The prevailing conditions in compacted bentonite buffer will be harsh. The swelling pressure is 7-8 MPa, the amount of free water is low and the average pore and pore throat diameters are small. This literature study aims to assess the potential of microbial activity in bentonite buffers. Literature on the environmental limits of microbial life in extreme conditions and the occurrence of sulphatereducing prokaryotes in extreme environments is reviewed briefly and the results of published studies characterizing microbes and microbial processes in repository conditions or in relevant subsurface environments are presented. The presence of bacteria, including SRBs, has been confirmed in deep groundwater and bentonite-based materials. Sulphate reducers have been detected in various high-pressure environments, and sulphate-reduction based on hydrogen as an energy source is considered a major microbial process in deep subsurface environments. In bentonite, microbial activity is strongly suppressed, mainly due to the low amount of free water and small pores, which limit the transport of microbes and nutrients. Spore-forming bacteria have been shown to survive in compacted bentonite as dormant spores, and they are able to resume a metabolically active state after decompaction. Thus, microbial sulphide production may increase in repository conditions if the dry density of the bentonite buffer is locally reduced. (orig.)

  20. Isostatic compression of buffer blocks. Middle scale

    International Nuclear Information System (INIS)

    Ritola, J.; Pyy, E.

    2012-01-01

    Manufacturing of buffer components using isostatic compression method has been studied in small scale in 2008 (Laaksonen 2010). These tests included manufacturing of buffer blocks using different bentonite materials and different compression pressures. Isostatic mould technology was also tested, along with different methods to fill the mould, such as vibration and partial vacuum, as well as a stepwise compression of the blocks. The development of manufacturing techniques has continued with small-scale (30 %) blocks (diameter 600 mm) in 2009. This was done in a separate project: Isostatic compression, manufacturing and testing of small scale (D = 600 mm) buffer blocks. The research on the isostatic compression method continued in 2010 in a project aimed to test and examine the isostatic manufacturing process of buffer blocks at 70 % scale (block diameter 1200 to 1300 mm), and the aim was to continue in 2011 with full-scale blocks (diameter 1700 mm). A total of nine bentonite blocks were manufactured at 70 % scale, of which four were ring-shaped and the rest were cylindrical. It is currently not possible to manufacture full-scale blocks, because there is no sufficiently large isostatic press available. However, such a compression unit is expected to be possible to use in the near future. The test results of bentonite blocks, produced with an isostatic pressing method at different presses and at different sizes, suggest that the technical characteristics, for example bulk density and strength values, are somewhat independent of the size of the block, and that the blocks have fairly homogenous characteristics. Water content and compression pressure are the two most important properties determining the characteristics of the compressed blocks. By adjusting these two properties it is fairly easy to produce blocks at a desired density. The commonly used compression pressure in the manufacturing of bentonite blocks is 100 MPa, which compresses bentonite to approximately

  1. Nuclear Calcium Buffering Capacity Shapes Neuronal Architecture*

    Science.gov (United States)

    Mauceri, Daniela; Hagenston, Anna M.; Schramm, Kathrin; Weiss, Ursula; Bading, Hilmar

    2015-01-01

    Calcium-binding proteins (CaBPs) such as parvalbumin are part of the cellular calcium buffering system that determines intracellular calcium diffusion and influences the spatiotemporal dynamics of calcium signals. In neurons, CaBPs are primarily localized to the cytosol and function, for example, in nerve terminals in short-term synaptic plasticity. However, CaBPs are also expressed in the cell nucleus, suggesting that they modulate nuclear calcium signals, which are key regulators of neuronal gene expression. Here we show that the calcium buffering capacity of the cell nucleus in mouse hippocampal neurons regulates neuronal architecture by modulating the expression levels of VEGFD and the complement factor C1q-c, two nuclear calcium-regulated genes that control dendrite geometry and spine density, respectively. Increasing the levels of nuclear calcium buffers by means of expression of a nuclearly targeted form of parvalbumin fused to mCherry (PV.NLS-mC) led to a reduction in VEGFD expression and, as a result, to a decrease in total dendritic length and complexity. In contrast, mRNA levels of the synapse pruning factor C1q-c were increased in neurons expressing PV.NLS-mC, causing a reduction in the density and size of dendritic spines. Our results establish a close link between nuclear calcium buffering capacity and the transcription of genes that determine neuronal structure. They suggest that the development of cognitive deficits observed in neurological conditions associated with CaBP deregulation may reflect the loss of necessary structural features of dendrites and spines. PMID:26231212

  2. Nuclear Calcium Buffering Capacity Shapes Neuronal Architecture.

    Science.gov (United States)

    Mauceri, Daniela; Hagenston, Anna M; Schramm, Kathrin; Weiss, Ursula; Bading, Hilmar

    2015-09-18

    Calcium-binding proteins (CaBPs) such as parvalbumin are part of the cellular calcium buffering system that determines intracellular calcium diffusion and influences the spatiotemporal dynamics of calcium signals. In neurons, CaBPs are primarily localized to the cytosol and function, for example, in nerve terminals in short-term synaptic plasticity. However, CaBPs are also expressed in the cell nucleus, suggesting that they modulate nuclear calcium signals, which are key regulators of neuronal gene expression. Here we show that the calcium buffering capacity of the cell nucleus in mouse hippocampal neurons regulates neuronal architecture by modulating the expression levels of VEGFD and the complement factor C1q-c, two nuclear calcium-regulated genes that control dendrite geometry and spine density, respectively. Increasing the levels of nuclear calcium buffers by means of expression of a nuclearly targeted form of parvalbumin fused to mCherry (PV.NLS-mC) led to a reduction in VEGFD expression and, as a result, to a decrease in total dendritic length and complexity. In contrast, mRNA levels of the synapse pruning factor C1q-c were increased in neurons expressing PV.NLS-mC, causing a reduction in the density and size of dendritic spines. Our results establish a close link between nuclear calcium buffering capacity and the transcription of genes that determine neuronal structure. They suggest that the development of cognitive deficits observed in neurological conditions associated with CaBP deregulation may reflect the loss of necessary structural features of dendrites and spines. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  3. Isostatic compression of buffer blocks. Middle scale

    Energy Technology Data Exchange (ETDEWEB)

    Ritola, J.; Pyy, E. [VTT Technical Research Centre of Finland, Espoo (Finland)

    2012-01-15

    Manufacturing of buffer components using isostatic compression method has been studied in small scale in 2008 (Laaksonen 2010). These tests included manufacturing of buffer blocks using different bentonite materials and different compression pressures. Isostatic mould technology was also tested, along with different methods to fill the mould, such as vibration and partial vacuum, as well as a stepwise compression of the blocks. The development of manufacturing techniques has continued with small-scale (30 %) blocks (diameter 600 mm) in 2009. This was done in a separate project: Isostatic compression, manufacturing and testing of small scale (D = 600 mm) buffer blocks. The research on the isostatic compression method continued in 2010 in a project aimed to test and examine the isostatic manufacturing process of buffer blocks at 70 % scale (block diameter 1200 to 1300 mm), and the aim was to continue in 2011 with full-scale blocks (diameter 1700 mm). A total of nine bentonite blocks were manufactured at 70 % scale, of which four were ring-shaped and the rest were cylindrical. It is currently not possible to manufacture full-scale blocks, because there is no sufficiently large isostatic press available. However, such a compression unit is expected to be possible to use in the near future. The test results of bentonite blocks, produced with an isostatic pressing method at different presses and at different sizes, suggest that the technical characteristics, for example bulk density and strength values, are somewhat independent of the size of the block, and that the blocks have fairly homogenous characteristics. Water content and compression pressure are the two most important properties determining the characteristics of the compressed blocks. By adjusting these two properties it is fairly easy to produce blocks at a desired density. The commonly used compression pressure in the manufacturing of bentonite blocks is 100 MPa, which compresses bentonite to approximately

  4. META-ANALYSIS OF NITROGEN REMOVAL IN RIPARIAN BUFFERS

    Science.gov (United States)

    Riparian buffer zones, the vegetated region adjacent to streams and wetlands, are thought to be effective at intercepting and controlling nitrogen loads entering water bodies. Riparian buffer width may be positively related to nitrogen removal effectiveness by influencing nitrog...

  5. Methyl Bromide Commodity Fumigation Buffer Zone Lookup Tables

    Science.gov (United States)

    Product labels for methyl bromide used in commodity and structural fumigation include requirements for buffer zones around treated areas. The information on this page will allow you to find the appropriate buffer zone for your planned application.

  6. Success and failure with phthalate buffers in capillary zone electrophoresis

    NARCIS (Netherlands)

    Bocek, P.; Gebauer, P.; Beckers, J.L.

    2001-01-01

    Phthalate buffers are currently used in capillary electrophoresis as robust electrolyte systems for indirect detection. This contribution demonstrates that these buffers show regularly not only successful regions of mobilities of analytes (sample window) but also regions of failure where the

  7. Does good leadership buffer effects of high emotional demands at work on risk of antidepressant treatment?

    DEFF Research Database (Denmark)

    Madsen, Ida E H; Hanson, Linda L Magnusson; Rugulies, Reiner Ernst

    2014-01-01

    Emotionally demanding work has been associated with increased risk of common mental disorders. Because emotional demands may not be preventable in certain occupations, the identification of workplace factors that can modify this association is vital. This article examines whether effects of emoti...... of emotional demands on antidepressant treatment, as an indicator of common mental disorders, are buffered by good leadership.......Emotionally demanding work has been associated with increased risk of common mental disorders. Because emotional demands may not be preventable in certain occupations, the identification of workplace factors that can modify this association is vital. This article examines whether effects...

  8. International comparison of observation-specific spatial buffers

    DEFF Research Database (Denmark)

    Frank, Lawrence D; Fox, Eric H; Ulmer, Jared M

    2017-01-01

    the relative differences in resulting explanatory power on self-reported physical activity outcomes. BEMs were developed in five countries using 'sausage,' 'detailed-trimmed,' and 'detailed,' network buffers at a distance of 1 km around participant household addresses (n = 5883). RESULTS: BEM values were...... significantly different (p trimmed buffer comparisons and 89% of sausage versus detailed network buffer comparisons. Results showed that BEM coefficients in physical activity models did not differ significantly across buffering methods, and in most cases BEM...

  9. Complexation of buffer constituents with neutral complexation agents: part I. Impact on common buffer properties.

    Science.gov (United States)

    Riesová, Martina; Svobodová, Jana; Tošner, Zdeněk; Beneš, Martin; Tesařová, Eva; Gaš, Bohuslav

    2013-09-17

    The complexation of buffer constituents with the complexation agent present in the solution can very significantly influence the buffer properties, such as pH, ionic strength, or conductivity. These parameters are often crucial for selection of the separation conditions in capillary electrophoresis or high-pressure liquid chromatography (HPLC) and can significantly affect results of separation, particularly for capillary electrophoresis as shown in Part II of this paper series (Beneš, M.; Riesová, M.; Svobodová, J.; Tesařová, E.; Dubský, P.; Gaš, B. Anal. Chem. 2013, DOI: 10.1021/ac401381d). In this paper, the impact of complexation of buffer constituents with a neutral complexation agent is demonstrated theoretically as well as experimentally for the model buffer system composed of benzoic acid/LiOH or common buffers (e.g., CHES/LiOH, TAPS/LiOH, Tricine/LiOH, MOPS/LiOH, MES/LiOH, and acetic acid/LiOH). Cyclodextrins as common chiral selectors were used as model complexation agents. We were not only able to demonstrate substantial changes of pH but also to predict the general complexation characteristics of selected compounds. Because of the zwitterion character of the common buffer constituents, their charged forms complex stronger with cyclodextrins than the neutral ones do. This was fully proven by NMR measurements. Additionally complexation constants of both forms of selected compounds were determined by NMR and affinity capillary electrophoresis with a very good agreement of obtained values. These data were advantageously used for the theoretical descriptions of variations in pH, depending on the composition and concentration of the buffer. Theoretical predictions were shown to be a useful tool for deriving some general rules and laws for complexing systems.

  10. Further improvements in competitive guarantees for QoS buffering

    NARCIS (Netherlands)

    Bansal, N.; Fleischer, L.K.; Kimbrel, T.; Mahdian, M.; Schieber, B.; Sviridenko, M.; Diaz, J.; Karhumäki, J.; Lepistö, A.; Sannella, D.

    2004-01-01

    We study the behavior of algorithms for buffering packets weighted by different levels of Quality of Service (QoS) guarantees in a single queue. Buffer space is limited, and packet loss occurs when the buffer overflows. We describe a modification of the previously proposed ``preemptive greedy{''}

  11. Towards Optimal Buffer Size in Wi-Fi Networks

    KAUST Repository

    Showail, Ahmad J.

    2016-01-19

    Buffer sizing is an important network configuration parameter that impacts the quality of data traffic. Falling memory cost and the fallacy that ‘more is better’ lead to over provisioning network devices with large buffers. Over-buffering or the so called ‘bufferbloat’ phenomenon creates excessive end-to-end delay in today’s networks. On the other hand, under-buffering results in frequent packet loss and subsequent under-utilization of network resources. The buffer sizing problem has been studied extensively for wired networks. However, there is little work addressing the unique challenges of wireless environment. In this dissertation, we discuss buffer sizing challenges in wireless networks, classify the state-of-the-art solutions, and propose two novel buffer sizing schemes. The first scheme targets buffer sizing in wireless multi-hop networks where the radio spectral resource is shared among a set of con- tending nodes. Hence, it sizes the buffer collectively and distributes it over a set of interfering devices. The second buffer sizing scheme is designed to cope up with recent Wi-Fi enhancements. It adapts the buffer size based on measured link characteristics and network load. Also, it enforces limits on the buffer size to maximize frame aggregation benefits. Both mechanisms are evaluated using simulation as well as testbed implementation over half-duplex and full-duplex wireless networks. Experimental evaluation shows that our proposal reduces latency by an order of magnitude.

  12. Managing Multiuser Database Buffers Using Data Mining Techniques

    NARCIS (Netherlands)

    Feng, L.; Lu, H.J.

    2004-01-01

    In this paper, we propose a data-mining-based approach to public buffer management for a multiuser database system, where database buffers are organized into two areas – public and private. While the private buffer areas contain pages to be updated by particular users, the public

  13. Heed the head: buffer benefits along headwater streams

    Science.gov (United States)

    Rhonda Mazza; Deanna (Dede) Olson

    2015-01-01

    Since the Northwest Forest Plan implemented riparian buffers along non-fish bearing streams in 1994, there have been questions about how wide those buffers need to be to protect aquatic and riparian resources from upland forest management activities. The Density Management and Riparian Buffer Study of western Oregon, also initiated in 1994, examines the effects of...

  14. Concentrated flow paths in riparian buffer zones of southern Illinois

    Science.gov (United States)

    R.C. Pankau; J.E. Schoonover; K.W.J. Willard; P.J. Edwards

    2012-01-01

    Riparian buffers in agricultural landscapes should be designed to trap pollutants in overland flow by slowing, filtering, and infiltrating surface runoff entering the buffer via sheet flow. However, observational evidence suggests that concentrated flow is prevalent from agricultural fields. Over time sediment can accumulate in riparian buffers forming berms that...

  15. Stream water responses to timber harvest: Riparian buffer width effectiveness

    Science.gov (United States)

    Barton D. Clinton

    2011-01-01

    Vegetated riparian buffers are critical for protecting aquatic and terrestrial processes and habitats in southern Appalachian ecosystems. In this case study, we examined the effect of riparian buffer width on stream water quality following upland forest management activities in four headwater catchments. Three riparian buffer widths were delineated prior to cutting; 0m...

  16. Analysis of diffusive mass transport in a cracked buffer

    International Nuclear Information System (INIS)

    Garisto, N.C.; Garisto, F.

    1989-11-01

    In the disposal vault design for the Canadian Nuclear Fuel Waste Management Program, cylindrical containers of used nuclear fuel would be placed in vertical boreholes in rock and surrounded with a bentonite-based buffer material. The buffer is expected to absorb and/or retard radionuclides leaching from the fuel after the containers fail. There is some evidence, however, that the buffer may be susceptible to cracking. In this report we investigate numerically the consequences of cracking on uranium diffusion through the buffer. The derivation of the mass-transport equations and the numerical solution method are presented for the solubility-limited diffusion of uranium in a cracked buffer system for both swept-away and semi-impermeable boundary conditions at the rock-buffer interface. The results indicate that for swept-away boundary conditions the total uranium flux through the cracked buffer system is, as expected, greater than through the uncracked buffer. The effect of the cracks is strongly dependent on the ratio D/D eff , where D and D eff are the pore-water and the effective buffer diffusion coefficient, respectively. However, although a decrease in D eff enhances the effect of cracks on the total cumulative flux (relative to the uncracked buffer), it also decreases the total cumulative flux through the cracked buffer system (relative to a cracked buffer with a larger D eff value). Finally, for semi-impermeable boundary conditions, the effect of cracks on the total radionuclide flux is relatively small

  17. Exchangeability of bentonite buffer and backfill materials

    Energy Technology Data Exchange (ETDEWEB)

    Savage, D. [Savage Earth Associates Ltd, Bournemouth (United Kingdom); Arthur, R. [Intera Inc, Ottawa, ON, (Canada); Luukkonen, A.

    2012-08-15

    Clay-based buffer and tunnel backfill materials are important barriers in the KBS-3 repository concept for final disposal of spent nuclear fuel in Finland. One issue that is relevant to material properties is the degree to which different bentonite compositions can be regarded as interchangeable. In Posiva's current repository design, the reference bentonite composition is MX-80, a sodium montmorillonite dominated clay. Posiva would like to be able to use bentonite with Ca-montmorillonite as the dominant clay mineral. However, at this stage, it is not clear what supporting data need to be acquired/defined to be able to place the state of knowledge of Ca-bentonite at the same level as that of Na-bentonite. In this report, the concept of bentonite exchangeability has been evaluated through consideration of how bentonite behaviour may be affected in six key performance-relevant properties, namely (1) mineralogical composition and availability of materials, (2) hydraulic conductivity, (3) mechanical and rheological properties, (4) long-term alteration, (5) colloidal properties, and (6) swelling pressure. The report evaluates implications for both buffer and backfill. Summary conclusions are drawn from these sections to suggest how bentonite exchangeability may be addressed in regulatory assessments of engineered barrier design for a future geological repository for spent fuel in Finland. Some important conclusions are: (a) There are some fundamental differences between Ca- and Na-bentonites such as colloidal behaviour, pore structure and long-term alteration that could affect the exchangeability of these materials as buffer or backfill materials and which should be further evaluated; (b) Additional experimental data are desirable for some issues such as long-term alteration, hydraulic properties and swelling behaviour, (c) The minor mineral content of bentonites is very variable, both between different bentonites and within the same bentonite type, it is not clear

  18. Impact of solute concentration on the electrocatalytic conversion of dissolved gases in buffered solutions

    KAUST Repository

    Shinagawa, Tatsuya

    2015-04-24

    To maintain local pH levels near the electrode during electrochemical reactions, the use of buffer solutions is effective. Nevertheless, the critical effects of the buffer concentration on electrocatalytic performances have not been discussed in detail. In this study, two fundamental electrochemical reactions, oxygen reduction reaction (ORR) and hydrogen oxidation reaction (HOR), on a platinum rotating disk electrode are chosen as model gas-related aqueous electrochemical reactions at various phosphate concentrations. Our detailed investigations revealed that the kinetic and limiting diffusion current densities for both the ORR and HOR logarithmically decrease with increasing solute concentration (log|jORR|=-0.39c+0.92,log|jHOR|=-0.35c+0.73). To clarify the physical aspects of this phenomenon, the electrolyte characteristics are addressed: with increasing phosphate concentration, the gas solubility decrease, the kinematic viscosity of the solution increase and the diffusion coefficient of the dissolved gases decrease. The simulated limiting diffusion currents using the aforementioned parameters match the measured ones very well (log|jORR|=-0.43c+0.99,log|jHOR|=-0.40c+0.54), accurately describing the consequences of the electrolyte concentration. These alterations of the electrolyte properties associated with the solute concentration are universally applicable to other aqueous gas-related electrochemical reactions because the currents are purely determined by mass transfer of the dissolved gases. © 2015 The Authors.

  19. Aqueous polyethylene oxide solutions

    International Nuclear Information System (INIS)

    Breen, J.

    1987-01-01

    A number of aspects concerning the reorientation of polymer, water and ion hydration complexes have been studied in aqueous solution of polyethylene oxide (PEO). The polymer dynamics are investigated by 1 H-PEO and 13 C-PEO nuclear relaxation experiments. 162 refs.; 30 figs.; 19 tabs

  20. Progress in aqueous rechargeable batteries

    OpenAIRE

    Jilei Liu; Chaohe Xu; Zhen Chen; Shibing Ni; Ze Xiang Shen

    2018-01-01

    Over the past decades, a series of aqueous rechargeable batteries (ARBs) were explored, investigated and demonstrated. Among them, aqueous rechargeable alkali-metal ion (Li+, Na+, K+) batteries, aqueous rechargeable-metal ion (Zn2+, Mg2+, Ca2+, Al3+) batteries and aqueous rechargeable hybrid batteries are standing out due to peculiar properties. In this review, we focus on the fundamental basics of these batteries, and discuss the scientific and/or technological achievements and challenges. B...

  1. A Buffer Management Issue in Designing SSDs for LFSs

    Science.gov (United States)

    Kim, Jaegeuk; Seol, Jinho; Maeng, Seungryoul

    This letter introduces a buffer management issue in designing SSDs for log-structured file systems (LFSs). We implemented a novel trace-driven SSD simulator in SystemC language, and simulated several SSD architectures with the NILFS2 trace. From the results, we give two major considerations related to the buffer management as follows. (1) The write buffer is used as a buffer not a cache, since all write requests are sequential in NILFS2. (2) For better performance, the main architectural factor is the bus bandwidth, but 332MHz is enough. Instead, the read buffer makes a key role in performance improvement while caching data. To enhance SSDs, accordingly, it is an effective way to make efficient read buffer management policies, and one of the examples is tracking the valid data zone in NILFS2, which can increase the data hit ratio in read buffers significantly.

  2. Magnetorheological elastomer and its application on impact buffer

    International Nuclear Information System (INIS)

    Fu, J; Yu, M; Zhu, L X; Dong, X M

    2013-01-01

    In this study, a new magnetorheological elastomer (MRE) based buffer is proposed and its vibration isolation performance is investigated. The MRE buffer with a compact structure is first designed in order to accomplish the maximization of the variable stiffness range. The working characteristics of the MRE buffer are then measured and the model of MRE is established. On the basis of the experimental data, the control model of the MRE buffer is also formulated. A two-degree-of-freedom dynamic model with an MRE buffer is then developed. An intelligent control strategy, human simulated intelligent control (HSIC), is proposed to reduce the impact during the drop crash. Finally, the proposed MRE buffer and controller are validated numerically and experimentally. The results show that the proposed MRE buffer and the control strategy can reduce the impact acceleration effectively.

  3. Buffer layers and articles for electronic devices

    Science.gov (United States)

    Paranthaman, Mariappan P.; Aytug, Tolga; Christen, David K.; Feenstra, Roeland; Goyal, Amit

    2004-07-20

    Materials for depositing buffer layers on biaxially textured and untextured metallic and metal oxide substrates for use in the manufacture of superconducting and other electronic articles comprise RMnO.sub.3, R.sub.1-x A.sub.x MnO.sub.3, and combinations thereof; wherein R includes an element selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y, and A includes an element selected from the group consisting of Be, Mg, Ca, Sr, Ba, and Ra.

  4. Shock buffer for nuclear control element assembly

    International Nuclear Information System (INIS)

    Bevilacqua, F.

    1977-01-01

    A shock buffer for a control element assembly in a nuclear reactor is described, comprising a piston and a cylinder. The piston is affixed to and extends upward from the control rod guide structure; the cylinder is supported by the upper portion of the control element assembly and is vertically oriented with open end downward for receiving the piston. Coolant liquid normally has free access to the cylinder. The piston displaces liquid from the cylinder when inserted, thereby decelerating the control element assembly near its lower extent of travel. (LL)

  5. Lead (II) and nickel (II) adsorption kinetics from aqueous metal ...

    African Journals Online (AJOL)

    This paper discusses the kinetics of lead (II) and Nickel (II) ions adsorption from aqueous solutions using chemically modified and unmodified agricultural adsorbents at 28°C, pH 6.2 and 0.01M NaCl ionic strength. The removal of the two metals were found to increase with increase in chemical modification, the sequence ...

  6. Chemical buffering in natural and engineered barrier systems: Thermodynamic constraints and performance assessment consequences

    Energy Technology Data Exchange (ETDEWEB)

    Arthur, R.C.; Wei Zhou [Monitor Scientific, LLC, Denver, CO (United States)

    2000-12-01

    Thermodynamic and kinetic constraints on the chemical buffering properties of natural and engineered-barrier systems are derived in this study from theoretical descriptions, incorporated in the reaction-path model, of reversible and irreversible mass transfer in multicomponent, multiphase systems. The buffering properties of such systems are conditional properties because they refer to a specific aqueous species in a system that is open with respect to a specific reactant. The solution to a mathematical statement of this concept requires evaluation of the dependence of the activity of the buffered species on incremental changes in the overall reaction-progress variable. This dependence can be represented by a truncated Taylor's series expansion, where the values of associated derivatives are calculated using finite-difference techniques and mass-balance, charge-balance and mass-action constraints. Kinetic constraints on buffering behavior can also be described if the relation between reactant flux and reaction rate is well defined. This relation is explicit for the important case of advective groundwater flow and water-rock interaction. We apply the theoretical basis of the chemical buffering concept to processes that could affect the performance of a deep geologic repository for nuclear waste. Specifically, we focus on the likelihood that an inverse relation must exist between the buffer intensity and the migration velocity of reaction fronts in systems involving advective or diffusive mass transport. A quantitative understanding of this relation would provide the basis for evaluating the potential role of chemical buffering in achieving the isolation and retardation functions, of the EBS and geosphere in a KBS-3 repository. Our preliminary evaluation of this role considers the effects of chemical buffering on the propagation velocity of a pH front in both the near- and far field. We use a geochemical modeling technique compatible with the reaction-path model

  7. A hierarchical updating method for finite element model of airbag buffer system under landing impact

    Directory of Open Access Journals (Sweden)

    He Huan

    2015-12-01

    Full Text Available In this paper, we propose an impact finite element (FE model for an airbag landing buffer system. First, an impact FE model has been formulated for a typical airbag landing buffer system. We use the independence of the structure FE model from the full impact FE model to develop a hierarchical updating scheme for the recovery module FE model and the airbag system FE model. Second, we define impact responses at key points to compare the computational and experimental results to resolve the inconsistency between the experimental data sampling frequency and experimental triggering. To determine the typical characteristics of the impact dynamics response of the airbag landing buffer system, we present the impact response confidence factors (IRCFs to evaluate how consistent the computational and experiment results are. An error function is defined between the experimental and computational results at key points of the impact response (KPIR to serve as a modified objective function. A radial basis function (RBF is introduced to construct updating variables for a surrogate model for updating the objective function, thereby converting the FE model updating problem to a soluble optimization problem. Finally, the developed method has been validated using an experimental and computational study on the impact dynamics of a classic airbag landing buffer system.

  8. Kinetics of the methylparathion hydrolysis in aqueous medium

    International Nuclear Information System (INIS)

    Manzanilla, J.; Barcelo, M.; Reyes, O.

    1997-01-01

    The kinetics of alkaline hydrolysis of methylparathion was studied at different temperatures (0-50 Centigrade) in the p H range of 8-12 by ultraviolet-visible absorption spectroscopy. Optimum p H and wavelength conditions were defined to carry out the simultaneous determination of methylparathion and one of its hydrolysis product, paranitrophenol, in buffered aqueous medium. Based on the experimental data and the mathematical equation of the kinetics, a rate constant (k) of first-order and an activation energy (Ea) of 9.2 Kcal/mol, were estimated. (Author) activation energy (Ea) of 9.2 Kcal/mol, were estimated. (Author)

  9. Eco-friendly aqueous core surface-modified nanocapsules.

    Science.gov (United States)

    Carbone, C; Musumeci, T; Lauro, M R; Puglisi, G

    2015-01-01

    In this work, positively charged nanocapsules have been developed for potential ocular delivery exploiting the deposition of PLA onto the droplet surface of a W/O nanoemulsion prepared by the reversed procedure of the PIT method. PLA in combination with different amounts of various oils and surfactants have been studied in order to select the best formulation for polymeric nanocapsule preparation. The traditional visual observation together with the Turbiscan(®) technology were exploited in order to identify the best combination of polymer/oil for nanocapsule preparation. Two different primary surfactants (Span(®) 60 and Span(®) 80) have been tested to select their influence on the field of existence of the nanoemulsion by the construction of the pseudoternary phase diagrams. Cationic hybrid NC have been prepared by the addition of a coating layer of DDAB. The physico-chemical and morphological properties of all the prepared nanocapsules have been evaluated and compared by PCS, DSC and AFM. Therefore, positively charged nanocapsules can be easily prepared by a simple eco-friendly technique that exploits biocompatible materials avoiding a large input of mechanical energy as a potential ocular delivery systems for hydrophilic compounds or gene materials. Copyright © 2014 Elsevier B.V. All rights reserved.

  10. Lead ions removal from aqueous solution using modified carbon ...

    Indian Academy of Sciences (India)

    2018-02-02

    Feb 2, 2018 ... Recently, in Vietnam and many other countries, the pollution of water by ... ions in water, including copper (Cu2+), lead (Pb2+), cadmium. (Cd2+), zinc (Zn2+) and chromium (Cr3+), may be a potential hazard to human health ...

  11. Theoretical and practical aspects of aqueous solution sodium silicate modifying

    Directory of Open Access Journals (Sweden)

    Mizuryaev Sergey

    2016-01-01

    Full Text Available This research deals with the use of liquid glass in industry particularly for porous filler production. The aim of this paper is to show the necessity liquid glass modification for the purpose of its rheological characteristics change for raw granules formation and providing given structure after porization. Data on chemical liquid glass modification are provided by adding sodium chloride. Moreover, inert mineral additives influence on porous filler properties are shown in this paper. The basic principles of light concrete composition selection are specified. Test results of light concrete on the developed porous sodium silicate filler are given.

  12. Tunable aqueous virtual micropore.

    Science.gov (United States)

    Park, Jae Hyun; Guan, Weihua; Reed, Mark A; Krstić, Predrag S

    2012-03-26

    A charged microparticle can be trapped in an aqueous environment by forming a narrow virtual pore--a cylindrical space region in which the particle motion in the radial direction is limited by forces emerging from dynamical interactions of the particle charge and dipole moment with an external radiofrequency quadrupole electric field. If the particle satisfies the trap stability criteria, its mean motion is reduced exponentially with time due to the viscosity of the aqueous environment; thereafter the long-time motion of particle is subject only to random, Brownian fluctuations, whose magnitude, influenced by the electrophoretic and dielectrophoretic effects and added to the particle size, determines the radius of the virtual pore, which is demonstrated by comparison of computer simulations and experiment. The measured size of the virtual nanopore could be utilized to estimate the charge of a trapped micro-object. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Modified SEAGULL

    Science.gov (United States)

    Salas, M. D.; Kuehn, M. S.

    1994-01-01

    Original version of program incorporated into program SRGULL (LEW-15093) for use on National Aero-Space Plane project, its duty being to model forebody, inlet, and nozzle portions of vehicle. However, real-gas chemistry effects in hypersonic flow fields limited accuracy of that version, because it assumed perfect-gas properties. As a result, SEAGULL modified according to real-gas equilibrium-chemistry methodology. This program analyzes two-dimensional, hypersonic flows of real gases. Modified version of SEAGULL maintains as much of original program as possible, and retains ability to execute original perfect-gas version.

  14. Aqueous liquid redox desulfurisation

    Energy Technology Data Exchange (ETDEWEB)

    Reicher, M.; Niemiec, B.; Katona, T.

    1999-12-01

    The LO-CAT II process is an aqueous liquid redox process which uses ferric and ferrous iron catalysts to oxidise hydrogen sulfide (from sour gas) to elemental sulfur: the relevant chemical equations are given. Chelating agents keep the iron in solution. The system is described under the headings of (i) LO-CAT chemistry, (ii) design parameters, (iii) startup challenges, (iv) present situation and (v) anticipated future conditions. Further improvements to the system are anticipated.

  15. Clad buffer rod sensors for liquid metals

    International Nuclear Information System (INIS)

    Jen, C.-K.; Ihara, I.

    1999-01-01

    Clad buffer rods, consisting of a core and a cladding, have been developed for ultrasonic monitoring of liquid metal processing. The cores of these rods are made of low ultrasonic-loss materials and the claddings are fabricated by thermal spray techniques. The clad geometry ensures proper ultrasonic guidance. The lengths of these rods ranges from tens of centimeters to 1m. On-line ultrasonic level measurements in liquid metals such as magnesium at 700 deg C and aluminum at 960 deg C are presented to demonstrate their operation at high temperature and their high ultrasonic performance. A spherical concave lens is machined at the rod end for improving the spatial resolution. High quality ultrasonic images have been obtained in the liquid zinc at 600 deg C. High spatial resolution is needed for the detection of inclusions in liquid metals during processing. We also show that the elastic properties such as density, longitudinal and shear wave velocities of liquid metals can be measured using a transducer which generates and receives both longitudinal and shear waves and is mounted at the end of a clad buffer rod. (author)

  16. Unsaturated hydraulic property of buffer material

    International Nuclear Information System (INIS)

    Suzuki, Hideaki; Fujita, Tomoo

    1999-09-01

    After emplacement of the engineered barrier system (EBS), it is expected that the near-field environment will be impacted by phenomena such as heat dissipation by conduction and other heat transfer mechanism, infiltration of groundwater from the surrounding rock into the EBS, generation of swelling pressure in the buffer due to water infiltration and the stress imposed by the overburden pressure. These phenomena are not all independent, but can be strongly influenced by, and coupled with, each other. Evaluating these coupled thermo-hydro-mechanical phenomena is important in order to clarify the initial transient behavior of the engineered barrier system within the near-field. This report describes the results on measurement of chemical potential, water diffusivity, and thermal water diffusivity of bentonite that is considered as a candidate material of buffer and on comparison between measurements and theoretical studies for these properties. The following results are identified; (l) The hysteresis of chemical potential in wet and dry conditions for compacted bentonite is not shown clearly. The chemical potential depends on temperature and amount of montmorillonite. When chemical potential of compacted bentonite is zero, the specimen is saturated. The van Genuchten model is applicable to the measured chemical potential of compacted bentonite. (2) The Darcy's law and Philip and de Vries model are applicable to the measured water diffusivity and thermal water diffusivity of compacted bentonite. (author)

  17. Effect of organic carbon content of the domestic bentonite on the performance of buffer material in a high-level waste repository

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Won Jin; Lee, Jae Owan; Kang, Chul Hyung [Korea Atomic Energy Research Institute, Taejon (Korea)

    1999-12-01

    The organic carbon content of the domestic bentonite have been measured, and its effects on the performance of buffer are analyzed. The total carbon content and the organic carbon content were in the range of 3160 to 3600 and 2400 to 2800 ppm, respectively. The aqueous phase equilibrium concentrations of total carbon and organic carbon in bentonite-water mixture were in the range of 25 to 50 ppm and 4 to 18 ppm, respectively. The results indicate that the effect of organic matter in the domestic bentonite on the performance of buffer material were insignificant. 33 refs., 15 figs., 10 tabs. (Author)

  18. Corrosion in low dielectric constant Si-O based thin films: Buffer concentration effects

    International Nuclear Information System (INIS)

    Zeng, F. W.; Lane, M. W.; Gates, S. M.

    2014-01-01

    Organosilicate glass (OSG) is often used as an interlayer dielectric (ILD) in high performance integrated circuits. OSG is a brittle material and prone to stress-corrosion cracking reminiscent of that observed in bulk glasses. Of particular concern are chemical-mechanical planarization techniques and wet cleans involving solvents commonly encountered in microelectronics fabrication where the organosilicate film is exposed to aqueous environments. Previous work has focused on the effect of pH, surfactant, and peroxide concentration on the subcritical crack growth of these films. However, little or no attention has focused on the effect of the conjugate acid/base concentration in a buffer. Accordingly, this work examines the “strength” of the buffer solution in both acidic and basic environments. The concentration of the buffer components is varied keeping the ratio of acid/base and therefore pH constant. In addition, the pH was varied by altering the acid/base ratio to ascertain any additional effect of pH. Corrosion tests were conducted with double-cantilever beam fracture mechanics specimens and fracture paths were verified with ATR-FTIR. Shifts in the threshold fracture energy, the lowest energy required for bond rupture in the given environment, G TH , were found to shift to lower values as the concentration of the base in the buffer increased. This effect was found to be much larger than the effect of the hydroxide ion concentration in unbuffered solutions. The results are rationalized in terms of the salient chemical bond breaking process occurring at the crack tip and modeled in terms of the chemical potential of the reactive species

  19. The use of 0.01M phosphate buffered saline as detection buffer for ...

    African Journals Online (AJOL)

    Insufficient supply of manufacture's buffers/diluents in relation to the number of strips per kit has been found to have negative impact on patients' results. Some laboratories personnel tend to use diluents from other rapid tests manufacturers such as Bioline, Unigold as well as malaria rapid diagnostic test (MRDT). This study ...

  20. Vegetative buffer strips for reducing herbicide transport in runoff: effects of buffer width, vegetation, and season

    Science.gov (United States)

    The effect of vegetative buffer strip (VBS) width, vegetation, and season of the year on herbicide transport in runoff has not been well documented for runoff prone soils. A multi-year replicated plot-scale study was conducted on an eroded claypan soil with the following objectives: 1) assess the ef...

  1. Is buffer a good proxy for a crowded cell-like environment? A comparative NMR study of calmodulin side-chain dynamics in buffer and E. coli lysate.

    Directory of Open Access Journals (Sweden)

    Michael P Latham

    Full Text Available Biophysical studies of protein structure and dynamics are typically performed in a highly controlled manner involving only the protein(s of interest. Comparatively fewer such studies have been carried out in the context of a cellular environment that typically involves many biomolecules, ions and metabolites. Recently, solution NMR spectroscopy, focusing primarily on backbone amide groups as reporters, has emerged as a powerful technique for investigating protein structure and dynamics in vivo and in crowded "cell-like" environments. Here we extend these studies through a comparative analysis of Ile, Leu, Val and Met methyl side-chain motions in apo, Ca(2+-bound and Ca(2+, peptide-bound calmodulin dissolved in aqueous buffer or in E. coli lysate. Deuterium spin relaxation experiments, sensitive to pico- to nano-second time-scale processes and Carr-Purcell-Meiboom-Gill relaxation dispersion experiments, reporting on millisecond dynamics, have been recorded. Both similarities and differences in motional properties are noted for calmodulin dissolved in buffer or in lysate. These results emphasize that while significant insights can be obtained through detailed "test-tube" studies, experiments performed under conditions that are "cell-like" are critical for obtaining a comprehensive understanding of protein motion in vivo and therefore for elucidating the relation between motion and function.

  2. Buffer Sizing in 802.11 Wireless Mesh Networks

    KAUST Repository

    Jamshaid, Kamran; Shihada, Basem; Xia, Li; Levis, Philip

    2011-01-01

    We analyze the problem of buffer sizing for TCP flows in 802.11-based Wireless Mesh Networks. Our objective is to maintain high network utilization while providing low queueing delays. The problem is complicated by the time-varying capacity of the wireless channel as well as the random access mechanism of 802.11 MAC protocol. While arbitrarily large buffers can maintain high network utilization, this results in large queueing delays. Such delays may affect TCP stability characteristics, and also increase queueing delays for other flows (including real-time flows) sharing the buffer. In this paper we propose sizing link buffers collectively for a set of nodes within mutual interference range called the 'collision domain'. We aim to provide a buffer just large enough to saturate the available capacity of the bottleneck collision domain that limits the carrying capacity of the network. This neighborhood buffer is distributed over multiple nodes that constitute the network bottleneck; a transmission by any of these nodes fully utilizes the available spectral resource for the duration of the transmission. We show that sizing routing buffers collectively for this bottleneck allows us to have small buffers (as low as 2 - 3 packets) at individual nodes without any significant loss in network utilization. We propose heuristics to determine these buffer sizes in WMNs. Our results show that we can reduce the end-to-end delays by 6× to 10× at the cost of losing roughly 5% of the network capacity achievable with large buffers.

  3. Buffer Sizing in 802.11 Wireless Mesh Networks

    KAUST Repository

    Jamshaid, Kamran

    2011-10-01

    We analyze the problem of buffer sizing for TCP flows in 802.11-based Wireless Mesh Networks. Our objective is to maintain high network utilization while providing low queueing delays. The problem is complicated by the time-varying capacity of the wireless channel as well as the random access mechanism of 802.11 MAC protocol. While arbitrarily large buffers can maintain high network utilization, this results in large queueing delays. Such delays may affect TCP stability characteristics, and also increase queueing delays for other flows (including real-time flows) sharing the buffer. In this paper we propose sizing link buffers collectively for a set of nodes within mutual interference range called the \\'collision domain\\'. We aim to provide a buffer just large enough to saturate the available capacity of the bottleneck collision domain that limits the carrying capacity of the network. This neighborhood buffer is distributed over multiple nodes that constitute the network bottleneck; a transmission by any of these nodes fully utilizes the available spectral resource for the duration of the transmission. We show that sizing routing buffers collectively for this bottleneck allows us to have small buffers (as low as 2 - 3 packets) at individual nodes without any significant loss in network utilization. We propose heuristics to determine these buffer sizes in WMNs. Our results show that we can reduce the end-to-end delays by 6× to 10× at the cost of losing roughly 5% of the network capacity achievable with large buffers.

  4. Enumeration of sugars and sugar alcohols hydroxyl groups by aqueous-based acetylation and MALDI-TOF mass spectrometry

    Science.gov (United States)

    A method is described for enumerating hydroxyl groups on analytes in aqueous media is described, and applied to some common polyalcohols (erythritol, mannitol, and xylitol) and selected carbohydrates. The analytes were derivatized in water with vinyl acetate in presence of sodium phosphate buffer. ...

  5. Addressing a Common Misconception: Ammonium Acetate as Neutral pH "Buffer" for Native Electrospray Mass Spectrometry

    Science.gov (United States)

    Konermann, Lars

    2017-09-01

    Native ESI-MS involves the transfer of intact proteins and biomolecular complexes from solution into the gas phase. One potential pitfall is the occurrence of pH-induced changes that can affect the analyte while it is still surrounded by solvent. Most native ESI-MS studies employ neutral aqueous ammonium acetate solutions. It is a widely perpetuated misconception that ammonium acetate buffers the analyte solution at neutral pH. By definition, a buffer consists of a weak acid and its conjugate weak base. The buffering range covers the weak acid pKa ± 1 pH unit. NH4 + and CH3-COO- are not a conjugate acid/base pair, which means that they do not constitute a buffer at pH 7. Dissolution of ammonium acetate salt in water results in pH 7, but this pH is highly labile. Ammonium acetate does provide buffering around pH 4.75 (the pKa of acetic acid) and around pH 9.25 (the pKa of ammonium). This implies that neutral ammonium acetate solutions electrosprayed in positive ion mode will likely undergo acidification down to pH 4.75 ± 1 in the ESI plume. Ammonium acetate nonetheless remains a useful additive for native ESI-MS. It is a volatile electrolyte that can mimic the solvation properties experienced by proteins under physiological conditions. Also, a drop from pH 7 to around pH 4.75 is less dramatic than the acidification that would take place in pure water. It is hoped that the habit of referring to pH 7 solutions as ammonium acetate "buffer" will disappear from the literature. Ammonium acetate "solution" should be used instead. [Figure not available: see fulltext.

  6. Aqueous shunts for glaucoma.

    Science.gov (United States)

    Tseng, Victoria L; Coleman, Anne L; Chang, Melinda Y; Caprioli, Joseph

    2017-07-28

    Aqueous shunts are employed to control intraocular pressure (IOP) for people with primary or secondary glaucomas who fail or are not candidates for standard surgery. To assess the effectiveness and safety of aqueous shunts for reducing IOP in glaucoma compared with standard surgery, another type of aqueous shunt, or modification to the aqueous shunt procedure. We searched CENTRAL (which contains the Cochrane Eyes and Vision Trials Register) (2016, Issue 8), MEDLINE Ovid (1946 to August 2016), Embase.com (1947 to August 2016), PubMed (1948 to August 2016), LILACS (Latin American and Caribbean Health Sciences Literature Database) (1982 to August 2016), ClinicalTrials.gov (www.clinicaltrials.gov); searched 15 August 2016, and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en); searched 15 August 2016. We did not use any date or language restrictions in the electronic search for trials. We last searched the electronic databases on 15 August 2016. We also searched the reference lists of identified trial reports and the Science Citation Index to find additional trials. We included randomized controlled trials that compared various types of aqueous shunts with standard surgery or to each other in eyes with glaucoma. Two review authors independently screened search results for eligibility, assessed the risk of bias, and extracted data from included trials. We contacted trial investigators when data were unclear or not reported. We graded the certainty of the evidence using the GRADE approach. We followed standard methods as recommended by Cochrane. We included 27 trials with a total of 2099 participants with mixed diagnoses and comparisons of interventions. Seventeen studies reported adequate methods of randomization, and seven reported adequate allocation concealment. Data collection and follow-up times varied.Four trials compared an aqueous shunt (Ahmed or Baerveldt) with trabeculectomy, of which

  7. Experiments on thermal conductivity in buffer materials for geologic repository

    International Nuclear Information System (INIS)

    Kanno, T.; Yano, T.; Wakamatsu, H.; Matsushima, E.

    1989-01-01

    Engineered barriers for geologic disposal for HLW are planned to consist of canister, overpack and buffer elements. One of important physical characteristics of buffer materials is determining temperature profiles within the near field in a repository. Buffer materials require high thermal conductivity to disperse radiogenic heat away to the host rock. As the buffer materials, compacted blocks of the mixture of sodium bentonite and sand have been the most promising candidate in some countries, e.g. Sweden, Switzerland and Japan. The authors have been carrying out a series of thermal dispersion experiments to evaluate thermal conductivity of bentonite/quartz sand blocks. In this study, the following two factors considered to affect thermal properties of the near field were examined: effective thermal conductivities of buffer materials, and heat transfer characteristics of the gap between overpack and buffer materials

  8. Moisture buffering capacity of highly absorbing materials

    Energy Technology Data Exchange (ETDEWEB)

    Cerolini, S.; D' Orazio, M.; Stazi, A. [Department of Architecture, Construction and Structures (DACS), Faculty of Engineering, Polytechnic University of Marche, Via Brecce Bianche, 60100 Ancona (Italy); Di Perna, C. [Department of Energetics, Faculty of Engineering, Polytechnic University of Marche, Via Brecce Bianche, 60100 Ancona (Italy)

    2009-02-15

    This research investigates the possibility to use highly absorbing materials to dampen indoor RH% variations. The practical MBV of sodium polyacrylate, cellulose-based material, perlite and gypsum is evaluated for a daily cyclic exposure that alternates high (75%) and low (33%) RH% levels for 8 h and 16 h, respectively. The adjustment velocity to RH% variations and the presence of hysteretic phenomena are also presented. The cellulose-based material proves to be the most suitable for moisture buffering applications. Starting from this material's properties, the effect of thickness, vapour resistance factor ({mu}) and mass surface exchange coefficient (Z{sub v}) on sorption capacity is evaluated by the use of a numerical model. (author)

  9. A high capacity FASTBUS multiple event buffer

    International Nuclear Information System (INIS)

    Appel, J.A.; Farr, W.D.; Kaplan, D.M.; Levit, L.B.; Napier, T.M.

    1985-01-01

    We have developed a front-end data acquisition and event buffering memory. This single-width FASTBUS module has a capacity of 256K X 32 bits plus parity. The module is dual ported, and its front panel ECLport accepts data at up to 20 MB/sec. It may also be written to and read from as a standard FASTBUS Slave. The module records events as variable length records. Each record is accepted or rejected via front panel control signal. Circuitry to automate FASTBUS record readout and record skip is provided. In its ''linear'' mode, the module may be used as a single pass list. Alternatively, in the ''circular'' mode, the module's internal read pointer can follow its write pointer continuously around the memory. Circular mode is well suited to handling of a continuous data stream. Modules may be linked for larger memory capacity

  10. Buffer mass test - Heater design and operation

    International Nuclear Information System (INIS)

    Nilsson, J.; Ramqvist, G.; Pusch, R.

    1984-06-01

    The nuclear waste is assumed to be contained in cylindrical metal canisters which will be inserted in deposition holes. Heat is generated as a result of the continuing decay of the radioactive waste and in the Buffer Mass Test (BMT) the heat flux expected from such canisters was simulated by the use of six electric heaters. the heaters were constructed partly of aluminium and partly of stainless steel. They are 1520 mm in length and 380 mm in diameter, and give a maximum power output of 3000 W. The heater power can be monitored by panel meters coupled to a computer-based data acquisition system. Both the heater and the control system were manufactured with a high degree of redundancy in case of component failure. This report describes the design, construction, testing, installation and necessary tools for heater installation and dismantling operation. (author)

  11. SPARC: Demonstrate burst-buffer-based checkpoint/restart on ATS-1.

    Energy Technology Data Exchange (ETDEWEB)

    Oldfield, Ron A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Ulmer, Craig D. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Widener, Patrick [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Ward, H. Lee [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2018-01-01

    Recent high-performance computing (HPC) platforms such as the Trinity Advanced Technology System (ATS-1) feature burst buffer resources that can have a dramatic impact on an application’s I/O performance. While these non-volatile memory (NVM) resources provide a new tier in the storage hierarchy, developers must find the right way to incorporate the technology into their applications in order to reap the benefits. Similar to other laboratories, Sandia is actively investigating ways in which these resources can be incorporated into our existing libraries and workflows without burdening our application developers with excessive, platform-specific details. This FY18Q1 milestone summaries our progress in adapting the Sandia Parallel Aerodynamics and Reentry Code (SPARC) in Sandia’s ATDM program to leverage Trinity’s burst buffers for checkpoint/restart operations. We investigated four different approaches with varying tradeoffs in this work: (1) simply updating job script to use stage-in/stage out burst buffer directives, (2) modifying SPARC to use LANL’s hierarchical I/O (HIO) library to store/retrieve checkpoints, (3) updating Sandia’s IOSS library to incorporate the burst buffer in all meshing I/O operations, and (4) modifying SPARC to use our Kelpie distributed memory library to store/retrieve checkpoints. Team members were successful in generating initial implementation for all four approaches, but were unable to obtain performance numbers in time for this report (reasons: initial problem sizes were not large enough to stress I/O, and SPARC refactor will require changes to our code). When we presented our work to the SPARC team, they expressed the most interest in the second and third approaches. The HIO work was favored because it is lightweight, unobtrusive, and should be portable to ATS-2. The IOSS work is seen as a long-term solution, and is favored because all I/O work (including checkpoints) can be deferred to a single library.

  12. A study on manufacturing and construction method of buffer

    International Nuclear Information System (INIS)

    Chijimatsu, Masakazu; Sugita, Yutaka; Amemiya, Kiyoshi

    1999-09-01

    As an engineered barrier system in the geological disposal of high-level waste, multibarrier system is considered. Multibarrier system consists of the vitrified waste, the overpack and the buffer. Bentonite is one of the potential material as the buffer because of its low water permeability, self-sealing properties, radionuclides adsorption and retardation properties, thermal conductivity, chemical buffering properties, overpack supporting properties, stress buffering properties, etc. In order to evaluate the functions of buffer, a lot of experiments has been conducted. The evaluations of these functions are based on the assumption that the buffer is emplaced or constructed in the disposal tunnel (or disposal pit) properly. Therefore, it is necessary to study on the manufacturing / construction method of buffer. As the manufacturing / construction technology of the buffer, the block installation method and in-situ compaction method, etc, are being investigated. The block installation method is to emplace the buffer blocks manufactured in advance at the ground facility, and construction processes of the block installation method at the underground will be simplified compared with the in-situ compaction method. On the other hand, the in-situ compaction method is to introduce the buffer material with specified water content into the disposal tunnel and to make the buffer with high density at the site using a compaction machine. In regard to the in-situ compaction method, it is necessary to investigate the optimum finished thickness of one layer because it is impossible to construct the buffer at one time. This report describes the results of compaction property test and the summary of the past investigation results in connection with the manufacturing / construction method. Then this report shows the construction method that will be feasible in the actual disposal site. (J.P.N.)

  13. Aqueous radioactive waste bituminization

    International Nuclear Information System (INIS)

    Williamson, A.S.

    1980-08-01

    The bituminzation of decontamination and ion exchange resin stripping wastes with four grades of asphalt was investigated to determine the effects of asphalt type on the properties of the final products. All waste forms deformed readily under light loads indicating they would flow if not restrained. It was observed in all cases that product leaching rates increased as the hardness of the asphalt used to treat the waste increased. If bituminization is adopted for any Ontario Hydro aqueous radioactive wastes they should be treated with soft asphalt to obtain optimum leaching resistance and mechanical stability during interim storage should be provided by a corrosion resistant container

  14. A new capillary electrophoresis buffer for determining organic and inorganic anions in electroplating bath with surfactant additives.

    Science.gov (United States)

    Sun, H; Lau, K M; Fung, Y S

    2010-05-07

    Monitoring of trace impurities in electroplating bath is needed to meet EU requirements for WEEE and RoHS and for quality control of electrodeposits. Methods using IC and 100% aqueous CE buffer were found producing non-repeatable results attributed to interference of surfactants and major methanesulphonate anion. A new CE buffer containing 1.5mM tetraethylenepentaamine, 3mM 1,3,5-benzenetricarboxylic acid and 15 mM Tris in 20% (v/v) methanol at pH=8.4 was shown to enhance the separation window, reduce interaction between buffer and bath constituents, and give satisfactory repeatability with baseline separation for 14 organic and inorganic anions within 14 min, good repeatability for migration time (0.32-0.57% RSD), satisfactory peak area and peak height (2.9-4.5 and 3-4.7% respectively), low detection limit (S/N=2, 20-150 ppb), and wide working ranges (0.1-100 ppm). The CE buffer with 20% (v/v) methanol has demonstrated its capability for identifying anion impurities causing problem in aged tin bath and the use of only 10-fold dilution to produce reliable results for quality assessment in plating bath containing high surfactant additives. Copyright (c) 2010 Elsevier B.V. All rights reserved.

  15. Moisture Buffer Effect and its Impact on Indoor Environment

    DEFF Research Database (Denmark)

    Zhang, Mingjie; Qin, Menghao; Chen, Zhi

    2017-01-01

    The moisture buffer effect of building materials may have great influence on indoor hygrothermal environment. In order to characterize the moisture buffering ability of materials, the basic concept of moisture buffer value (MBV) is adopted. Firstly, a theoretical correction factor is introduced...... in this paper. The moisture uptake/release by hygroscopic materials can be calculated with the factor and the basic MBV. Furthermore, the validation of the correction factor is carried out. The impact of moisture buffering on indoor environment is assessed by using numerical simulations. The results show...

  16. Effects of node buffer and capacity on network traffic

    International Nuclear Information System (INIS)

    Ling Xiang; Ding Jian-Xun; Hu Mao-Bin

    2012-01-01

    In this paper, we study the optimization of network traffic by considering the effects of node buffer ability and capacity. Two node buffer settings are considered. The node capacity is considered to be proportional to its buffer ability. The node effects on network traffic systems are studied with the shortest path protocol and an extension of the optimal routing [Phys. Rev. E 74 046106 (2006)]. In the diagrams of flux—density relationships, it is shown that a nodes buffer ability and capacity have profound effects on the network traffic

  17. Back contact buffer layer for thin-film solar cells

    Science.gov (United States)

    Compaan, Alvin D.; Plotnikov, Victor V.

    2014-09-09

    A photovoltaic cell structure is disclosed that includes a buffer/passivation layer at a CdTe/Back contact interface. The buffer/passivation layer is formed from the same material that forms the n-type semiconductor active layer. In one embodiment, the buffer layer and the n-type semiconductor active layer are formed from cadmium sulfide (CdS). A method of forming a photovoltaic cell includes the step of forming the semiconductor active layers and the buffer/passivation layer within the same deposition chamber and using the same material source.

  18. Solubilization of proteins: the importance of lysis buffer choice.

    Science.gov (United States)

    Peach, Mandy; Marsh, Noelle; Miskiewicz, Ewa I; MacPhee, Daniel J

    2015-01-01

    The efficient extraction of proteins of interest from cells and tissues is not always straightforward. Here we demonstrate the differences in extraction of the focal adhesion protein Kindlin-2 from choriocarcinoma cells using NP-40 and RIPA lysis buffer. Furthermore, we demonstrate the use of a more denaturing urea/thiourea lysis buffer for solubilization, by comparing its effectiveness for solubilization of small heat-shock proteins from smooth muscle with the often utilized RIPA lysis buffer. Overall, the results demonstrate the importance of establishing the optimal lysis buffer for specific protein solubilization within the experimental workflow.

  19. How Do Stream Buffers Reduce the Offsite Impact of Pollution?

    OpenAIRE

    Easton, Zachary M.

    2012-01-01

    Summarizes the importance of buffers to reduce pollution and specifically examines where they can be used, how they work, their limitations, required maintenance, performance levels, and expected cost.

  20. Effect of Buffer Bow Structure in Ship-Ship Collision

    DEFF Research Database (Denmark)

    Yamada, Yasuhira; Endo, Hisayoshi; Pedersen, Preben Terndrup

    2008-01-01

    tankers, the introduction of buffer bulbous bows has been proposed. Relatively soft buffer bows absorb part of the kinetic energy of the striking ship before penetrating the inner hull of the struck vessel. The purpose of the present paper is to verify the effectiveness of a prototype buffer bulbous bow......) and the forward velocity of the struck ship on the collapse mode of the bow of the striking vessel are investigated. Collapse modes, contact forces and energy absorption capabilities of the buffer bows are compared with those of conventional bows....

  1. Biophysical characterization data on Aβ soluble oligomers produced through a method enabling prolonged oligomer stability and biological buffer conditions

    Directory of Open Access Journals (Sweden)

    Amanda C. Crisostomo

    2015-09-01

    Aβ1-40 soluble oligomers are produced that are suitable for biophysical studies requiring sufficient transient stability to exist in their “native” conformation in biological phosphate-saline buffers for extended periods of time. The production involves an initial preparation of highly monomeric Aβ in a phosphate saline buffer that transitions to fibrils and oligomers through time incubation alone, without added detergents or non-aqueous chemicals. This criteria ensures that the only difference between initial monomeric Aβ reactant and subsequent Aβ oligomer products is their degree of peptide assembly. A number of chemical and biophysical methods were used to characterize the monomeric reactants and soluble oligomer and amyloid fibril products, including chemical cross-linking, Western blots, fraction solubility, thioflvain T binding, size exclusion chromatography, transmission electron micrscopy, circular dichroism spectroscopy, and fluorescence resonance energy transfer.

  2. Comparison of extraction buffers for the detection of fumonisin B(1) in corn by immunoassay and high-performance liquid chromatography.

    Science.gov (United States)

    Kulisek, E S; Hazebroek, J P

    2000-01-01

    The Associatian of Official Analytical Chemists approved method for quantification of fumonisin B(1) (FB(1)) in corn meal or corn-based food products includes extraction into methanol (MeOH)/water (3:1, v/v). Disposal of the extraction medium can pose safety and environmental problems. To secure a rapid and inexpensive screen for FB(1) contamination, a sensitive competitive ELISA using a rabbit polyclonal antibody was developed. This assay was used in a comparative study measuring the extraction efficiency of FB(1) in aqueous or organic solvent buffers using 16 field corn samples. An aqueous phosphate buffer was found to be suitable for extracting FB(1), thus eliminating the need for organic solvents. HPLC and ELISA determinations compared well in fortified samples at known concentrations between 1 and 50 microg/mL of extract. Overestimation at levels >50 microg/mL were common. The characteristics and application of the ELISA for screening purposes are discussed.

  3. Temperature buffer test. Installation of buffer, heaters and instruments in the deposition hole

    Energy Technology Data Exchange (ETDEWEB)

    Johannesson, Lars-Erik; Sanden, Torbjoern; Aakesson, Mattias [Clay Technology AB, Lund (Sweden); Barcena, Ignacio; Garcia-Sineriz, Jose Luis [Aitemin, Madrid (Spain)

    2010-12-15

    During 2003 the Temperature Buffer Test was installed in Aespoe Hard Rock Laboratory. Temperature, water pressure, relative humidity, total pressure and displacements etc. are measured in numerous points in the test. Most of the cables from the transducers are led in the deposition hole through slots in the rock surface of the deposition hole in watertight tubes to the data collection system in a container placed in the tunnel close to the deposition hole. This report describes the work with the installations of the buffer, heaters, and instruments and yields a description of the final location of all instruments. The report also contains a description of the materials that were installed and the densities yielded after placement.

  4. Temperature buffer test. Installation of buffer, heaters and instruments in the deposition hole

    International Nuclear Information System (INIS)

    Johannesson, Lars-Erik; Sanden, Torbjoern; Aakesson, Mattias; Barcena, Ignacio; Garcia-Sineriz, Jose Luis

    2010-12-01

    During 2003 the Temperature Buffer Test was installed in Aespoe Hard Rock Laboratory. Temperature, water pressure, relative humidity, total pressure and displacements etc. are measured in numerous points in the test. Most of the cables from the transducers are led in the deposition hole through slots in the rock surface of the deposition hole in watertight tubes to the data collection system in a container placed in the tunnel close to the deposition hole. This report describes the work with the installations of the buffer, heaters, and instruments and yields a description of the final location of all instruments. The report also contains a description of the materials that were installed and the densities yielded after placement

  5. Mars aqueous chemistry experiment

    Science.gov (United States)

    Clark, Benton C.; Mason, Larry W.

    1994-06-01

    Mars Aqueous Chemistry Experiment (MACE) is designed to conduct a variety of measurements on regolith samples, encompassing mineral phase analyses, chemical interactions with H2O, and physical properties determinations. From these data, much can be learned or inferred regarding the past weathering environment, the contemporaneous soil micro-environments, and the general chemical and physical state of the Martian regolith. By analyzing both soil and duricrust samples, the nature of the latter may become more apparent. Sites may be characterized for comparative purposes and criteria could be set for selection of high priority materials on future sample return missions. The second year of the MACE project has shown significant progress in two major areas. MACE Instrument concept definition is a baseline design that has been generated for the complete MACE instrument, including definition of analysis modes, mass estimates and thermal model. The design includes multiple reagent reservoirs, 10 discrete analysis cells, sample manipulation capability, and thermal control. The MACE Measurement subsystems development progress is reported regarding measurement capabilities for aqueous ion sensing, evolved gas sensing, solution conductivity measurement, reagent addition (titration) capabilities, and optical sensing of suspended particles.

  6. Mars aqueous chemistry experiment

    Science.gov (United States)

    Clark, Benton C.; Mason, Larry W.

    1994-01-01

    Mars Aqueous Chemistry Experiment (MACE) is designed to conduct a variety of measurements on regolith samples, encompassing mineral phase analyses, chemical interactions with H2O, and physical properties determinations. From these data, much can be learned or inferred regarding the past weathering environment, the contemporaneous soil micro-environments, and the general chemical and physical state of the Martian regolith. By analyzing both soil and duricrust samples, the nature of the latter may become more apparent. Sites may be characterized for comparative purposes and criteria could be set for selection of high priority materials on future sample return missions. The second year of the MACE project has shown significant progress in two major areas. MACE Instrument concept definition is a baseline design that has been generated for the complete MACE instrument, including definition of analysis modes, mass estimates and thermal model. The design includes multiple reagent reservoirs, 10 discrete analysis cells, sample manipulation capability, and thermal control. The MACE Measurement subsystems development progress is reported regarding measurement capabilities for aqueous ion sensing, evolved gas sensing, solution conductivity measurement, reagent addition (titration) capabilities, and optical sensing of suspended particles.

  7. Sorption of fission nuclides on model milk components. I. Sorption of radiostrontium on hydroxyapatite in aqueous solutions

    International Nuclear Information System (INIS)

    Rosskopfova, O.; Kopunec, R.; Matel, L.; Macasek, F.; Kristin, J.

    1999-01-01

    Hydroxyapatite, Ca 10 (PO 4 ) 6 (OH) 2 is a mineral widely spread in nature as a main constituent of phosphate rocks, and also as the major inorganic component of bones and teeth. It was found that sorption process occurs by an ion exchange reaction mechanism between strontium ions in solution and calcium ions in apatite. Ca 2+ → Sr 2+ substitution in hydroxyapatite is important since it explains the mechanism of incorporation of beta-active Sr-90 of atomic debris into the human skeletal system. The strontium uptake at 100 grad C is done by adsorption and diffusion while at 25 grad C it is done by the process of adsorption only. The hydroxyapatite was prepared from aqueous solutions and characterized by standard analytical methods. Some samples of hydroxyapatite were modified by heating after its precipitation from aqueous solution. The sample obtained had characteristics of well crystallized stoichiometric hydroxyapatite. Also, commercial hydroxy-apatites were used. Sorption of strontium ions on synthetic hydroxyapatite was examined using batch method and sorption depends on the method of preparation of hydroxyapatite. In generally, sorption of strontium decreases with the increase in the particle size of hydroxyapatite and decreases with the increase in the pH ( hydroxyapatite surface is amphoteric and acts as a buffer in a wide pH range). The sorption of strontium increases with the increase in [Sr 2+ ] or [Ca 2+ ] in solution to ∼ 10 -5 mol · dm -3 for the hydroxyapatite prepared by heating. The experimental data for sorption of strontium has been fitted with Langmuir-adsorption isotherm. (authors)

  8. The buffer/container experiment: results, synthesis, issues

    International Nuclear Information System (INIS)

    Graham, J.; Chandler, N.A.; Dixon, D.A.; Roach, P.J.; To, T.; Wan, A.W.L.

    1997-12-01

    A large in-ground experiment has examined how heat affects the performance of the dense sand bentonite 'buffer' that has been proposed for use in the Canadian Nuclear Fuel Waste Management Program. The experiment was performed by Atomic Energy of Canada Limited at its Underground Research Laboratory, Lac du Bonnet, Manitoba between 1991 and 1994. The experiment placed a full-size heater representing a container of nuclear fuel waste in a 1.24-m diameter borehole filled with buffer below the floor of a room excavated at 240-m depth in granitic rock of the Canadian Shield. The buffer and surrounding rock were extensively instrumented for temperatures, total pressures, water pressures, suctions, and rock displacements. Power was provided to the heater for almost 900 days. The experiment showed that good rock conditions can be pre-selected, a borehole can be drilled, and buffer can be placed at controlled densities and water contents. The instrumentation generally worked well, and an extensive data base was successfully organized. Drying was observed in buffer close to the heater. This caused some desiccation cracking. However the cracks only extended approximately one third of the distance to the buffer-rock interface and did not form an advective pathway. Following sampling at the time of decommissioning, cracked samples of buffer were transported to the laboratory and given access to water. The hydraulic conductivities and swelling pressures of these resaturated samples were very similar to those of uncracked buffer. A good balance was achieved between the mass of water flowing into the experiment from the surrounding rock and the increased mass of water in the buffer. A good understanding was developed of the relationships between suctions, water contents, and total pressures in buffer near the buffer-rock interface. Comparisons between measurements and predictions of measured parameters show that a good understanding has been developed of the processes operating

  9. The buffer/container experiment: results, synthesis, issues

    Energy Technology Data Exchange (ETDEWEB)

    Graham, J. [Univ. of Manitoba, Dept. of Civil Engineering, Winnipeg, MB (Canada); Chandler, N.A.; Dixon, D.A.; Roach, P.J.; To, T.; Wan, A.W.L

    1997-12-01

    A large in-ground experiment has examined how heat affects the performance of the dense sand bentonite 'buffer' that has been proposed for use in the Canadian Nuclear Fuel Waste Management Program. The experiment was performed by Atomic Energy of Canada Limited at its Underground Research Laboratory, Lac du Bonnet, Manitoba between 1991 and 1994. The experiment placed a full-size heater representing a container of nuclear fuel waste in a 1.24-m diameter borehole filled with buffer below the floor of a room excavated at 240-m depth in granitic rock of the Canadian Shield. The buffer and surrounding rock were extensively instrumented for temperatures, total pressures, water pressures, suctions, and rock displacements. Power was provided to the heater for almost 900 days. The experiment showed that good rock conditions can be pre-selected, a borehole can be drilled, and buffer can be placed at controlled densities and water contents. The instrumentation generally worked well, and an extensive data base was successfully organized. Drying was observed in buffer close to the heater. This caused some desiccation cracking. However the cracks only extended approximately one third of the distance to the buffer-rock interface and did not form an advective pathway. Following sampling at the time of decommissioning, cracked samples of buffer were transported to the laboratory and given access to water. The hydraulic conductivities and swelling pressures of these resaturated samples were very similar to those of uncracked buffer. A good balance was achieved between the mass of water flowing into the experiment from the surrounding rock and the increased mass of water in the buffer. A good understanding was developed of the relationships between suctions, water contents, and total pressures in buffer near the buffer-rock interface. Comparisons between measurements and predictions of measured parameters show that a good understanding has been developed of the processes

  10. Aqueous electrolytes for redox flow battery systems

    Science.gov (United States)

    Liu, Tianbiao; Li, Bin; Wei, Xiaoliang; Nie, Zimin; Wang, Wei; Liu, Jun; Sprenkle, Vincent L.

    2017-10-17

    An aqueous redox flow battery system includes an aqueous catholyte and an aqueous anolyte. The aqueous catholyte may comprise (i) an optionally substituted thiourea or a nitroxyl radical compound and (ii) a catholyte aqueous supporting solution. The aqueous anolyte may comprise (i) metal cations or a viologen compound and (ii) an anolyte aqueous supporting solution. The catholyte aqueous supporting solution and the anolyte aqueous supporting solution independently may comprise (i) a proton source, (ii) a halide source, or (iii) a proton source and a halide source.

  11. Influence of temperature elevation on the sealing performance of a potential buffer material for a high-level radioactive waste repository

    International Nuclear Information System (INIS)

    Cho, W.-J.; Lee, J.-O.; Kang, C.-H.

    2000-01-01

    The sealing performance of buffer material in a high-level waste repository depends largely upon the hydraulic conductivity, the swelling pressure, and the dissolution of organic carbon in the buffer material. Temperature effects on these properties were evaluated. The hydraulic conductivity and the swelling pressure of compacted bentonite increase with increasing temperature, but the effect of temperature elevation is not large. The dissolution of organic carbon in bentonite also increases with increasing temperature, but the resultant aqueous concentrations of organic carbon in bentonite suspensions are less than those of deep groundwater in granite. Therefore, the organic carbon dissolved from the bentonite will not cause a significant increase in the organic carbon content of deep groundwater in the repository environment. Overall, temperature effects on the sealing performance of buffer material in a waste repository is not important, if the maximum temperature is maintained below 100 deg. C

  12. Estimation of presynaptic calcium currents and endogenous calcium buffers at the frog neuromuscular junction with two different calcium fluorescent dyes.

    Science.gov (United States)

    Samigullin, Dmitry; Fatikhov, Nijaz; Khaziev, Eduard; Skorinkin, Andrey; Nikolsky, Eugeny; Bukharaeva, Ellya

    2014-01-01

    At the frog neuromuscular junction, under physiological conditions, the direct measurement of calcium currents and of the concentration of intracellular calcium buffers-which determine the kinetics of calcium concentration and neurotransmitter release from the nerve terminal-has hitherto been technically impossible. With the aim of quantifying both Ca(2+) currents and the intracellular calcium buffers, we measured fluorescence signals from nerve terminals loaded with the low-affinity calcium dye Magnesium Green or the high-affinity dye Oregon Green BAPTA-1, simultaneously with microelectrode recordings of nerve-action potentials and end-plate currents. The action-potential-induced fluorescence signals in the nerve terminals developed much more slowly than the postsynaptic response. To clarify the reasons for this observation and to define a spatiotemporal profile of intracellular calcium and of the concentration of mobile and fixed calcium buffers, mathematical modeling was employed. The best approximations of the experimental calcium transients for both calcium dyes were obtained when the calcium current had an amplitude of 1.6 ± 0.08 pA and a half-decay time of 1.2 ± 0.06 ms, and when the concentrations of mobile and fixed calcium buffers were 250 ± 13 μM and 8 ± 0.4 mM, respectively. High concentrations of endogenous buffers define the time course of calcium transients after an action potential in the axoplasm, and may modify synaptic plasticity.

  13. Interfacial Modifiers

    Energy Technology Data Exchange (ETDEWEB)

    Martin, Ina; French, Roger H.

    2018-03-19

    Our project objective in the first and only Budget Period was to demonstrate the potential of nm-scale organofunctional silane coatings as a method of extending the lifetime of PV materials and devices. Specifically, the target was to double the lifetime performance of a laminated Cu(In,Ga)Se2 (CIGS) cell under real-world and accelerated aging exposure conditions. Key findings are that modification of aluminum-doped zinc oxide (AZO) films (materials used as transparent conductive oxide (TCO) top contacts) resulted in decreased degradation of optical and electrical properties under damp heat (DH) exposure compared to un-modified AZO. The most significant finding is that modification of the AZO top contact of full CIGS devices resulted in significantly improved properties under DH exposure compared to un-modified devices, by a factor of 4 after 1000 h. Results of this one-year project have demonstrated that surface functionalization is a viable pathway for extending the lifetime of state-of-the-art CIGS devices.

  14. Riparian ecosystems and buffers - multiscale structure, function, and management: introduction

    Science.gov (United States)

    Kathleen A. Dwire; Richard R. Lowrance

    2006-01-01

    Given the importance of issues related to improved understanding and management of riparian ecosystems and buffers, the American Water Resources Association (AWRA) sponsored a Summer Specialty Conference in June 2004 at Olympic Valley, California, entitled 'Riparian Ecosystems and Buffers: Multiscale Structure, Function, and Management.' The primary objective...

  15. Universal buffers for use in biochemistry and biophysical experiments

    Directory of Open Access Journals (Sweden)

    Dewey Brooke

    2015-08-01

    Full Text Available The use of buffers that mimic biological solutions is a foundation of biochemical and biophysical studies. However, buffering agents have both specific and nonspecific interactions with proteins. Buffer molecules can induce changes in conformational equilibria, dynamic behavior, and catalytic properties merely by their presence in solution. This effect is of concern because many of the standard experiments used to investigate protein structure and function involve changing solution conditions such as pH and/or temperature. In experiments in which pH is varied, it is common practice to switch buffering agents so that the pH is within the working range of the weak acid and conjugate base. If multiple buffers are used, it is not always possible to decouple buffer induced change from pH or temperature induced change. We have developed a series of mixed biological buffers for protein analysis that can be used across a broad pH range, are compatible with biologically relevant metal ions, and avoid complications that may arise from changing the small molecule composition of buffers when pH is used as an experimental variable.

  16. Social Buffering of Stress in Development: A Career Perspective

    Science.gov (United States)

    Gunnar, Megan R.

    2016-01-01

    This review provides a broad overview of my research group's work on social buffering in human development in the context of the field. Much of the focus is on social buffering of the hypothalamic-pituitary-adrenocortical (HPA) system, one of the two major arms of the mammalian stress system. This focus reflects the centrality of the HPA system in research on social buffering in the fields of developmental psychobiology and developmental science. However, buffering of the cardiovascular and autonomic nervous system is also discussed. The central developmental question in this area derives from attachment theory which argues that the infant's experience of stress and arousal regulation in the context of her early attachment relationships is not an immature form of social buffering experienced in adulthood, but rather the foundation out of which individual differences in the capacity to gain stress relief from social partners emerge. The emergence of social buffering in infancy, changes in social buffering throughout childhood and adolescence, the influence of early experience on later individual differences in social buffering, and critical gaps in our knowledge are described. PMID:28544861

  17. Dynamic Buffer Capacity in Acid-Base Systems.

    Science.gov (United States)

    Michałowska-Kaczmarczyk, Anna M; Michałowski, Tadeusz

    The generalized concept of 'dynamic' buffer capacity β V is related to electrolytic systems of different complexity where acid-base equilibria are involved. The resulting formulas are presented in a uniform and consistent form. The detailed calculations are related to two Britton-Robinson buffers, taken as examples.

  18. Molecular Buffers Permit Sensitivity Tuning and Inversion of Riboswitch Signals

    DEFF Research Database (Denmark)

    Rugbjerg, Peter; Genee, Hans Jasper; Jensen, Kristian

    2016-01-01

    transcription factor, while interacting DNA-binding domains mediate the transduction of signal and form an interacting molecular buffer. The molecular buffer system enables modular signal inversion through integration with repressor modules. Further, tuning of input sensitivity was achieved through perturbation...

  19. Reduction of buffering requirements: Another advantage of cooperative transmission

    KAUST Repository

    Bader, Ahmed

    2015-04-01

    Yet another advent of cooperative transmission is exposed in this letter. It is shown that cooperation lends itself to the reduction of buffer sizes of wireless sensor nodes. It is less likely to find the channel busy when cooperative transmission is employed in the network. Otherwise, in the lack of cooperation, the probability of build up of packet queues in transmission buffers increases.

  20. Dynamic Buffer Capacity in Acid?Base Systems

    OpenAIRE

    Micha?owska-Kaczmarczyk, Anna M.; Micha?owski, Tadeusz

    2015-01-01

    The generalized concept of ?dynamic? buffer capacity ? V is related to electrolytic systems of different complexity where acid?base equilibria are involved. The resulting formulas are presented in a uniform and consistent form. The detailed calculations are related to two Britton?Robinson buffers, taken as examples.

  1. Methods for improved growth of group III nitride buffer layers

    Science.gov (United States)

    Melnik, Yurity; Chen, Lu; Kojiri, Hidehiro

    2014-07-15

    Methods are disclosed for growing high crystal quality group III-nitride epitaxial layers with advanced multiple buffer layer techniques. In an embodiment, a method includes forming group III-nitride buffer layers that contain aluminum on suitable substrate in a processing chamber of a hydride vapor phase epitaxy processing system. A hydrogen halide or halogen gas is flowing into the growth zone during deposition of buffer layers to suppress homogeneous particle formation. Some combinations of low temperature buffers that contain aluminum (e.g., AlN, AlGaN) and high temperature buffers that contain aluminum (e.g., AlN, AlGaN) may be used to improve crystal quality and morphology of subsequently grown group III-nitride epitaxial layers. The buffer may be deposited on the substrate, or on the surface of another buffer. The additional buffer layers may be added as interlayers in group III-nitride layers (e.g., GaN, AlGaN, AlN).

  2. Sampling phase lock loop (PLL) with low power clock buffer

    NARCIS (Netherlands)

    Gao, X.; Bahai, A.; Bohsali, M.; Djabbari, A.; Klumperink, Eric A.M.; Nauta, Bram; Socci, G.

    2013-01-01

    A sampling phase locked loop (PLL) circuit includes a pull-up/down buffer configured to convert an oscillator reference clock into a square wave sampling control signal input to a sampling phase detector. The buffer circuit is configured to reduce power by controlling the switching of the pull-up

  3. Effects of riparian buffers on hydrology of northern seasonal ponds

    Science.gov (United States)

    Randall K. Kolka; Brian J. Palik; Daniel P. Tersteeg; James C. Bell

    2011-01-01

    Although seasonal ponds are common in northern, glaciated, forested landscapes, forest management guidelines are generally lacking for these systems. The objective of this study was to determine the effect of riparian buffer type on seasonal pond hydrology following harvest of the adjacent upland forest. A replicated block design consisting of four buffer treatments...

  4. The aqueous chemistry of oxides

    CERN Document Server

    Bunker, Bruce C

    2016-01-01

    The Aqueous Chemistry of Oxides is a comprehensive reference volume and special topics textbook that explores all of the major chemical reactions that take place between oxides and aqueous solutions. The book highlights the enormous impact that oxide-water reactions have in advanced technologies, materials science, geochemistry, and environmental science.

  5. Smooth Nb surfaces fabricated by buffered electropolishing

    International Nuclear Information System (INIS)

    Wu, Andy T.; Mammosser, John; Phillips, Larry; Delayen, Jean; Reece, Charles; Wilkerson, Amy; Smith, David; Ike, Robert

    2007-01-01

    It was demonstrated that smooth Nb surfaces could be obtained through buffered electropolishing (BEP) employing an electrolyte consisting of lactic, sulfuric, and hydrofluoric acids. Parameters that control the polishing process were optimized to achieve a smooth surface finish. The polishing rate of BEP was determined to be 0.646 μm/min which was much higher than 0.381 μm/min achieved by the conventional electropolishing (EP) process widely used in the superconducting radio frequency (SRF) community. Root mean square measurements using a 3D profilometer revealed that Nb surfaces treated by BEP were an order of magnitude smoother than those treated by the optimized EP process. The chemical composition of the Nb surfaces after BEP was analyzed by static and dynamic secondary ion mass spectrometry (SIMS) systems. SIMS results implied that the surface oxide structure of Nb might be more complicated than what usually believed and could be inhomogeneous. Preliminary results of BEP on Nb SRF single cell cavities and half-cells were reported. It was shown that smooth and bright surfaces could be obtained in 1800 s when the electric field inside a SRF cavity was uniform during a BEP process. This study showed that BEP is a promising technique for surface treatment on Nb SRF cavities to be used in particle accelerators

  6. Aqueous reprocessing - some dreams!

    International Nuclear Information System (INIS)

    Srinivasan, T.G.

    2015-01-01

    India has been pursuing a aqueous reprocessing based closed fuel cycle for both thermal and fast reactor fuels employing the PUREX process. Though the country has more than six decades of experience, the dreams or wish lists such as, a highly efficient process with textbook specifications of 99.9% recovery of U and Pu, a DF of more than 10 7 for both U and Pu from the fission products, operating with name plate capacity with high safety, low waste generation, recovery of useful fission products and minor actinides from high level waste are never ceasing and ever growing. The talk will cover safety precautions and actions to be taken in the steps listed below, to ensure a safe and successful process

  7. Buffers for biomass production in temperate European agriculture

    DEFF Research Database (Denmark)

    Christen, Benjamin; Dalgaard, Tommy

    2013-01-01

    , environmental pressures from intensive agriculture and policy developments. Use of conservation buffers by farmers outside of designated schemes is limited to date, but the increasing demand for bioenergy and the combination of agricultural production with conservation calls for a much wider implementation....... This paper reviews the biophysical knowledge on buffer functioning and associated ecosystem services. It describes how a three-zone buffer design, with arable fields buffered in combination by grassland, short rotation forestry (SRF) or coppice (SRC) and undisturbed vegetation along water courses, can...... be incorporated into farming landscapes as productive conservation elements and reflects on the potential for successful implementation. Land use plays a much greater role in determining catchment hydrology than soil type: shelterbelts or buffer strips have markedly higher infiltration capacity than arable...

  8. Evaluation on elution feature of bentonite buffer materials

    Energy Technology Data Exchange (ETDEWEB)

    Ishikawa, Hirohisa; Kanno, Takeshi; Matsumoto, Kazuhiro

    1997-09-01

    In order to evaluate long term physical stability of artificial barrier in land disposal of high level radioactive wastes, it is necessary to know quantitatively elution behavior of buffering materials from disposal road (or cavity) to circumferential rock crack. When elution of the buffer material occurs on large scale, amount of bentonite in the disposal road (or cavity) reduces and reduction of various functions expected to the buffer materials is presumed. According to specification examples of road transverse arrangement and disposal vertical arrangement systems, evaluation on elution amount of the buffer materials at disposal environment was conducted. Opening width of rock crack in the disposal environment was supposed to be 0.5 mm. As a result, obtained mass elution ratios of the buffer materials due to extrusion phenomenon were 0.04 to 0.2% after 10,000 year and 2 to 12% after 1,000,000 years. (G.K.)

  9. Thin film photovoltaic devices with a minimally conductive buffer layer

    Science.gov (United States)

    Barnes, Teresa M.; Burst, James

    2016-11-15

    A thin film photovoltaic device (100) with a tunable, minimally conductive buffer (128) layer is provided. The photovoltaic device (100) may include a back contact (150), a transparent front contact stack (120), and an absorber (140) positioned between the front contact stack (120) and the back contact (150). The front contact stack (120) may include a low resistivity transparent conductive oxide (TCO) layer (124) and a buffer layer (128) that is proximate to the absorber layer (140). The photovoltaic device (100) may also include a window layer (130) between the buffer layer (128) and the absorber (140). In some cases, the buffer layer (128) is minimally conductive, with its resistivity being tunable, and the buffer layer (128) may be formed as an alloy from a host oxide and a high-permittivity oxide. The high-permittivity oxide may further be chosen to have a bandgap greater than the host oxide.

  10. Multi-Buffer Simulations for Trace Language Inclusion

    Directory of Open Access Journals (Sweden)

    Milka Hutagalung

    2016-09-01

    Full Text Available We consider simulation games played between Spoiler and Duplicator on two Büchi automata in which the choices made by Spoiler can be buffered by Duplicator in several buffers before she executes them on her structure. We show that the simulation games are useful to approximate the inclusion of trace closures of languages accepted by finite-state automata, which is known to be undecidable. We study the decidability and complexity and show that the game with bounded buffers can be decided in polynomial time, whereas the game with one unbounded and one bounded buffer is highly undecidable. We also show some sufficient conditions on the automata for Duplicator to win the game (with unbounded buffers.

  11. Replenishing data descriptors in a DMA injection FIFO buffer

    Science.gov (United States)

    Archer, Charles J [Rochester, MN; Blocksome, Michael A [Rochester, MN; Cernohous, Bob R [Rochester, MN; Heidelberger, Philip [Cortlandt Manor, NY; Kumar, Sameer [White Plains, NY; Parker, Jeffrey J [Rochester, MN

    2011-10-11

    Methods, apparatus, and products are disclosed for replenishing data descriptors in a Direct Memory Access (`DMA`) injection first-in-first-out (`FIFO`) buffer that include: determining, by a messaging module on an origin compute node, whether a number of data descriptors in a DMA injection FIFO buffer exceeds a predetermined threshold, each data descriptor specifying an application message for transmission to a target compute node; queuing, by the messaging module, a plurality of new data descriptors in a pending descriptor queue if the number of the data descriptors in the DMA injection FIFO buffer exceeds the predetermined threshold; establishing, by the messaging module, interrupt criteria that specify when to replenish the injection FIFO buffer with the plurality of new data descriptors in the pending descriptor queue; and injecting, by the messaging module, the plurality of new data descriptors into the injection FIFO buffer in dependence upon the interrupt criteria.

  12. Buffer erosion: An overview of concepts and potential safety consequences

    International Nuclear Information System (INIS)

    Apted, Michael J.; Arthur, Randy; Bennett, David; Savage, David; Saellfors, Goeran; Wennerstroem, Haakan

    2010-11-01

    In its safety analysis SR-Can, SKB reported preliminary results and conclusions on the mechanisms of bentonite colloid formation and stability, with a rough estimate of the consequences of loss of bentonite buffer by erosion. With the review of SR-Can the authorities (SKI and SSI) commented that erosion of the buffer had the greatest safety significance, that the understanding of the mechanisms of buffer erosion was inadequate, and that more work would be required to arrive at robust estimates of the extent and impacts of buffer erosion. After the SR-Can report, SKB started a two-year research project on buffer erosion. The results from this two-year project have been reported in several SKB technical reports. SSM started this project to build up its own competence in the related scientific areas by a preliminary evaluation of SKB's research results

  13. Buffer erosion: An overview of concepts and potential safety consequences

    Energy Technology Data Exchange (ETDEWEB)

    Apted, Michael J.; Arthur, Randy (INTERA Incorporated, Denver, CO (United States)); Bennett, David (TerraSalus Limited, Rutland (United Kingdom)); Savage, David (Savage Earth Associates Limited, Bournemouth (United Kingdom)); Saellfors, Goeran (GeoForce AB, Billdal (Sweden)); Wennerstroem, Haakan (Dept. of Chemistry, Lund Univ., Lund (Sweden))

    2010-11-15

    In its safety analysis SR-Can, SKB reported preliminary results and conclusions on the mechanisms of bentonite colloid formation and stability, with a rough estimate of the consequences of loss of bentonite buffer by erosion. With the review of SR-Can the authorities (SKI and SSI) commented that erosion of the buffer had the greatest safety significance, that the understanding of the mechanisms of buffer erosion was inadequate, and that more work would be required to arrive at robust estimates of the extent and impacts of buffer erosion. After the SR-Can report, SKB started a two-year research project on buffer erosion. The results from this two-year project have been reported in several SKB technical reports. SSM started this project to build up its own competence in the related scientific areas by a preliminary evaluation of SKB's research results

  14. Aqueous chemical dosimetry

    International Nuclear Information System (INIS)

    Matthews, R.W.

    1982-01-01

    Aqueous chemical dosimetry based on ceric and ferrous sulfate solutions and on a number of fluorescence-induced systems is reviewed. Particular attention is given to the factors affecting the response of these dosimeters to radiation and the corrections necessary for more accurate dosimetry under various irradiation conditions. The effect of cerous and ceric ion, oxygen, and sulfuric acid concentration on the ceric dosimeter is discussed together with the effects of temperature, energy of radiation, degraded energy spectra, and peroxysulfuric acids. Practical aspects of ceric/cerous dosimetry are given. Although ferrous sulfate solution is the most important and widely studied reference dosimeter, general agreement has not been reached on the ''best'' value for the molar extinction coefficient of ferric ions nor on the correction necessary to the G(Fe 3 - ) value for irradiations at temperatures significantly different from 25 0 C. New data are presented which indicate that the larger temperature coefficients given in the literature are more accurate. The ferrous sulfate system has been of great importance in establishing the primary radiolytic yields for 0.4 M sulfuric acid solution; it is shown how the failure to take into account the effect of oxygen and ferrous sulfate concentrations has led to erroneously high estimates of the zero solute concentration values in acid solutions. Some of the methods for extending the dose ranges measurable with ferrous sulfate-based solutions are reviewed. Substances which on irradiation give highly fluorescent products are among the most sensitive aqueous chemical dosimeters. These include benzoate and terephthalate solutions and the more recent coumarin and trimesate solutions. Advantages and disadvantages system are discussed. (author)

  15. Volumetric properties of MES, MOPS, MOPSO, and MOBS in water and in aqueous electrolyte solutions

    International Nuclear Information System (INIS)

    Taha, Mohamed; Lee, Ming-Jer

    2010-01-01

    4-Morpholineethanesulfonic acid (MES), 4-morpholinepropanesulfonic acid (MOPS), 3-morpholino-2-hydroxypropanesulfonic acid (MOPSO), and 4-(N-morpholino)butanesulfonic acid (MOBS), are useful for pH control as standard buffers in the physiological region of 5.5-6.7 for MES, 6.5-7.9 for MOPS, 6.2-7.6 for MOPSO, and 6.9-8.3 for MOBS, respectively. On the basis of density measurements at 298.15 K, the apparent molar volumes, V φ , of the above-mentioned buffers in water and in (0.05, 0.16, and 0.25) mol kg -1 aqueous solutions of NaCl, KCl, KBr, and CH 3 COOK have been calculated. The partial molar volumes at infinite dilution, V φ o , obtained from V φ , have been used to calculate the volume of transfer, Δ tr V φ o , from water to aqueous electrolyte solutions. It was found that both V φ o and Δ tr V φ o vary linearly with increasing the number of carbon atoms in the alkyl group side chain of the zwitterionic buffers. These linear correlations have been utilized to estimate the contributions of the zwitterionic end group (morpholinium ion, -SO 3 - ) and -CH 2 - group to V φ o and Δ tr V φ o . The values of V φ o and Δ tr V φ o for some functional group contributions of the zwittierionic buffers with salts have also been reported.

  16. Assembly of Modified Ferritin Proteins on Carbon Nanotubes and its Electrocatalytic Activity for Oxygen Reduction

    Science.gov (United States)

    Kim, Jae-Woo; Lillehei, Peter T.; Park, Cheol

    2012-01-01

    Highly effective dispersions of carbon nanotubes (CNTs) can be made using a commercially available buffer solution. Buffer solutions of 3-(N-morpholino)-propanesulfonic acid (MOPS), which consists of a cyclic ring with nitrogen and oxygen heteroatoms, a charged group, and an alkyl chain greatly enhance the dispersibility and stability of CNTs in aqueous solutions. Additionally, the ability of biomolecules, especially cationized Pt-cored ferritins, to adhere onto the well-dispersed CNTs in the aqueous buffer solution is also improved. This was accomplished without the use of surfactant molecules, which are detrimental to the electrical, mechanical, and other physical properties of the resulting products. The assembled Pt-cored ferritin proteins on the CNTs were used as an electrocatalyst for oxygen reduction

  17. The role of social buffering on chronic disruptions in quality of care: evidence from caregiver-based interventions in foster children.

    Science.gov (United States)

    Flannery, Jessica E; Beauchamp, Kathryn G; Fisher, Philip A

    2017-02-01

    There is growing evidence that social support can buffer the physiological stress response, specifically cortisol reactivity. We use a developmental framework to review the importance of social buffering in early childhood, a period of heightened plasticity for programming of the hypothalamic-pituitary-adrenal (HPA) axis. The social environment, in which parents play the largest role in early life, is a critical agent in the developmental trajectory of the HPA axis. A prevailing model of social buffering primarily focuses on the role of social support in the context of acute stressors and cortisol response. This review expands this model to provide evidence of the mechanism of social buffering, or lack thereof, across periods of chronic stress by applying the social buffer model to children involved in the child welfare system. We also highlight current interventions that capitalize on the mechanism of social buffering to modify HPA axis functioning across childhood. Last, we synthesize our findings using the social buffering framework to inform future targeted interventions.

  18. Phosphorus retention in riparian buffers: review of their efficiency.

    Science.gov (United States)

    Hoffmann, Carl Christian; Kjaergaard, Charlotte; Uusi-Kämppä, Jaana; Hansen, Hans Christian Bruun; Kronvang, Brian

    2009-01-01

    Ground water and surface water interactions are of fundamental importance for the biogeochemical processes governing phosphorus (P) dynamics in riparian buffers. The four most important conceptual hydrological pathways for P losses from and P retention in riparian buffers are reviewed in this paper: (i) The diffuse flow path with ground water flow through the riparian aquifer, (ii) the overland flow path across the riparian buffer with water coming from adjacent agricultural fields, (iii) irrigation of the riparian buffer with tile drainage water from agricultural fields where disconnected tile drains irrigate the riparian buffer, and (iv) inundation of the riparian buffer (floodplain) with river water during short or longer periods. We have examined how the different flow paths in the riparian buffer influence P retention mechanisms theoretically and from empirical evidence. The different hydrological flow paths determine where and how water-borne P compounds meet and interact with iron and aluminum oxides or other minerals in the geochemical cycling of P in the complex and dynamic environment that constitutes a riparian buffer. The main physical process in the riparian buffer-sedimentation-is active along several flow paths and may account for P retention rates of up to 128 kg P ha(-1) yr(-1), while plant uptake may temporarily immobilize up to 15 kg P ha(-1) yr(-1). Retention of dissolved P in riparian buffers is not as pronounced as retention of particulate P and is often below 0.5 kg P ha(-1) yr(-1). Several studies show significant release of dissolved P (i.e., up to 8 kg P ha(-1) yr(-1)).

  19. CZE separation of strawberry anthocyanins with acidic buffer and comparison with HPLC.

    Science.gov (United States)

    Comandini, Patrizia; Blanda, Giampaolo; Cardinali, Andrea; Cerretani, Lorenzo; Bendini, Alessandra; Caboni, Maria Fiorenza

    2008-10-01

    Anthocyanins, the major colourants of strawberries, are polar pigments that are positively charged at low pH. Herein, we have assessed a new analytical method for the separation of anthocyanins using CZE. Acidic buffer solutions (pH pigments in the cation flavylium form and achieve high molar absorptivity at 510 nm. These spectral properties enabled us to identify strawberry anthocyanins in a preliminary stage by detection in the visible range, although the method was optimised at 280 nm to obtain the best S/N. The effects of buffer composition highlighted the necessity of adding an organic modifier to the running buffer to obtain a suitable separation. The electrophoretic method permitted the separation of the three main anthocyanins of strawberry extracts, namely pelargonidin 3-glucoside (Pg-glu), pelargonidin 3-rutinoside and cyanidin 3-glucoside. The electrophoretic results, expressed as retention time and separation efficiency of the major anthocyanin (Pg-glu), were compared to those achieved in HPLC, the analytical technique traditionally used for the investigation of anthocyanins in vegetable matrix. The content of Pg-glu in strawberries (cv. Camarosa), calculated with HPCE and HPLC methods, resulted respectively in 11.41 mg/L and 11.37 mg/L.

  20. Simultaneous determination of hydroquinone and catechol based on glassy carbon electrode modified with gold-graphene nanocomposite

    International Nuclear Information System (INIS)

    Ma, X.; Liu, Z.; Qiu, C.; Chen, T.; Ma, H.

    2013-01-01

    We have synthesized a virtually monodisperse gold-graphene (Au-G) nanocomposite by a single-step chemical reduction method in aqueous dimethylformamide solution. The nanoparticles are homogenously distributed over graphene nanosheets. A glassy carbon electrode was modified with this nanocomposite and displayed high electrocatalytic activity and extraordinary electronic transport properties due to its large surface area. It enabled the simultaneous determination of hydroquinone (HQ) and catechol (CC) in acetate buffer solution of pH 4.5. Two pairs of well-defined, quasi-reversible redox peaks are obtained, one for HQ and its oxidized form, with a 43 mV separation of peak potentials (ΔEp), the other for CC and its oxidized form, with a ΔEp of 39 mV. Due to the large separation of oxidation peak potentials (102 mV), the concentrations of HQ and CC can be easily determined simultaneously. The oxidation peak currents for both HQ and CC increase linearly with the respective concentrations in the 1.0 μM to 0.1 mM concentration range, with the detection limits of 0.2 and 0. 15 μM (S/N = 3), respectively. The modified electrode was successfully applied to the simultaneous determination of HQ and CC in spiked tap water, demonstrating that the Au-G nanocomposite may act as a high-performance sensing material in the selective detection of some environmental pollutants. (author)

  1. Visualization of Buffer Capacity with 3-D "Topo" Surfaces: Buffer Ridges, Equivalence Point Canyons and Dilution Ramps

    Science.gov (United States)

    Smith, Garon C.; Hossain, Md Mainul

    2016-01-01

    BufCap TOPOS is free software that generates 3-D topographical surfaces ("topos") for acid-base equilibrium studies. It portrays pH and buffer capacity behavior during titration and dilution procedures. Topo surfaces are created by plotting computed pH and buffer capacity values above a composition grid with volume of NaOH as the x axis…

  2. BENTO buffer development program in Finland - Key issues

    International Nuclear Information System (INIS)

    Autio, J.; Korkiala-Tanttu, L.; Vaehaenen, M.; Koskinen, K.; Korkeakoski, P.; Haapala, K.

    2010-01-01

    Document available in extended abstract form only. Posiva launched a programme, BENTO, to develop technology of using bentonite in spent nuclear fuel repositories. The main purpose of the BENTO programme is to produce buffer designs and verify that they fulfil the requirements, especially safety requirements. To achieve this objective, resources and the level of expertise and know-how has to be increased. There are several uncertainties related to the functioning of the buffer components at present. An issue is defined as being significant if there is sufficient uncertainty that the buffer system might not fulfil the requirements because of the issue. These significant issues need to be resolved in order to develop a proper design and to verify the fulfilment of the requirements. The list of significant issues may change with time. Therefore it is crucial to develop adequate expertise, know-how and laboratory facilities to manage the changes. Moreover, there is confidence that by solving the open issues a defendable construction license application can be submitted in 2012. The basic nature of the programme is a combination of material and process research with the design and manufacturing of buffer components to produce feasible buffer design with proven long-term functional properties. The development work carried out under BENTO-programme has been initially divided into four different projects. During the course of work the number of projects and their content can be adjusted. The four BENTO projects are: 1. Manufacturing (MANU); 2. Design (DESI); 3. Modelling (MODE); 4. Material and Process Research (MARE). BENTO programme aims at producing feasible buffer designs which fulfil the requirements specified in Posiva's requirement management system. The designs are produced in DESI-project by following the design development scheme which starts from specification of design basis and ends in documented detailed designs and therefore DESIgn is specified as one

  3. Photosynthetic activity buffers ocean acidification in seagrass meadows

    Science.gov (United States)

    Hendriks, I. E.; Olsen, Y. S.; Ramajo, L.; Basso, L.; Steckbauer, A.; Moore, T. S.; Howard, J.; Duarte, C. M.

    2014-01-01

    Macrophytes growing in shallow coastal zones characterised by intense metabolic activity have the capacity to modify pH within their canopy and beyond. We observed diel pH changes in shallow (5-12 m) seagrass (Posidonia oceanica) meadows spanning 0.06 pH units in September to 0.24 units in June. The carbonate system (pH, DIC, and aragonite saturation state (ΩAr)) and O2 within the meadows displayed strong diel variability driven by primary productivity, and changes in chemistry were related to structural parameters of the meadow, in particular, the leaf surface area available for photosynthesis (LAI). LAI was positively correlated to mean, max and range pHNBS and max and range ΩAr. In June, vertical mixing (as Turbulent Kinetic Energy) influenced max and min ΩAr, while in September there was no effect of hydrodynamics on the carbonate system within the canopy. Max and range ΩAr within the meadow showed a positive trend with the calcium carbonate load of the leaves, pointing to a possible link between structural parameters, ΩAr and carbonate deposition. Calcifying organisms, e.g. epiphytes with carbonate skeletons, may benefit from the modification of the carbonate system by the meadow. There is, however, concern for the ability of seagrasses to provide modifications of similar importance in the future. The predicted decline of seagrass meadows may alter the scope for alteration of pH within a seagrass meadow and in the water column above the meadow, particularly if shoot density and biomass decline, on which LAI is based. Organisms associated with seagrass communities may therefore suffer from the loss of pH buffering capacity in degraded meadows.

  4. Erosion of buffer caused by groundwater leakages

    International Nuclear Information System (INIS)

    Autio, J.; Hanana, K.; Punkkinen, O.; Koskinen, K.; Olin, M.

    2010-01-01

    Document available in extended abstract form only. In the Finnish HLW disposal concept the most important properties of the bentonite clay being considered for these isolation purposes are its thermal behaviour, low hydraulic conductivity, diffusion limited transport, rheology, plasticity, sufficient swelling potential, and exchange capacity. All of these properties depend critically on bentonite density; therefore, any potential mass loss or redistribution events must be well characterized. One such event or process is the erosion of bentonite by flowing groundwater and the groundwater flowing in newly formed channels, in special. Mechanical erosion during the operational phase, due to high groundwater pressure gradients in open excavations, has been identified as a critical issue in TKS-2006 and SR-Can. This work addresses the mechanical erosion of bentonite by fluid shear. In order for buffer erosion to occur three processes must take place: detachment, entrainment, and transport. These processes are followed by the settling of the material and redistribution of buffer mass. Erosion begins with the detachment of a particle from surrounding material, which requires the application of shear forces greater than the attractive force between the particle and parent structure. Entrainment is the process by which the eroding medium lifts the detached particle into the flow. The most important aspect in entrainment is transfer of fluid's inertial forces via surface friction to particles' inertial forces, which, in turn, must overcome the frictional resistance between the particle and its surroundings. Factors influencing frictional resistance include gravity, particle mass, saturation degree of parent structure, composition of water present in parent structure, particle size, and surface roughness. Recent erosion tests, whereby water flow was directed over compacted bentonite blocks or through a system of bentonite pellets, have indicated that bentonite erodes

  5. MANU. Instrumentation of Buffer Demo. Preliminary Study

    International Nuclear Information System (INIS)

    Laaksonen, R.

    2010-01-01

    The purpose of this work is to describe feasible measuring and monitoring alternatives which can be used, if needed, in medium to full scale nuclear waste repository deposition hole mock-up tests. The focus of the work was to determine what variables can actually be measured, how to achieve the measurements and what kind of demands comes from the modelling, scientific, and technical points of view. This project includes a review of the previous waste repository mock-up tests carried out in several European countries such as Belgium, Czech Republic, Spain and Sweden. Also information was gathered by interviewing domestic and foreign scientists specialized in the fields of measurement instrumentation and related in-situ and laboratory work. On the basis of this review, recommendations were developed for the necessary actions needed to be done from the instrumentation point of view for future tests. It is possible to measure and monitor the processes going on in a deposition hole in-situ conditions. The data received during a test in real repository conditions enables to follow the processes and to verify the hypothesis made on the behaviour of various components of the repository: buffer, canister, rock and backfill. Because full scale testing is expensive, the objectives and hypothesis must be carefully set and the test itself with its instrumentation must serve very specific objectives. The main purpose of mock-up tests is to verify that the conditions surrounding the canister are according to the design requirements. A whole mock-up test and demonstration process requires a lot of time and effort. The instrumentation part of the work must also start at early stages to ensure that the instrumentation itself will not become bottlenecked nor suffer from low quality solutions. The planning of the instrumentation work could be done in collaboration with foreign scientists which have participated to previous instrumentation projects. (orig.)

  6. Temperature Buffer Test. Final THM modelling

    International Nuclear Information System (INIS)

    Aakesson, Mattias; Malmberg, Daniel; Boergesson, Lennart; Hernelind, Jan; Ledesma, Alberto; Jacinto, Abel

    2012-01-01

    The Temperature Buffer Test (TBT) is a joint project between SKB/ANDRA and supported by ENRESA (modelling) and DBE (instrumentation), which aims at improving the understanding and to model the thermo-hydro-mechanical behavior of buffers made of swelling clay submitted to high temperatures (over 100 deg C) during the water saturation process. The test has been carried out in a KBS-3 deposition hole at Aespoe HRL. It was installed during the spring of 2003. Two heaters (3 m long, 0.6 m diameter) and two buffer arrangements have been investigated: the lower heater was surrounded by bentonite only, whereas the upper heater was surrounded by a composite barrier, with a sand shield between the heater and the bentonite. The test was dismantled and sampled during the winter of 2009/2010. This report presents the final THM modelling which was resumed subsequent to the dismantling operation. The main part of this work has been numerical modelling of the field test. Three different modelling teams have presented several model cases for different geometries and different degree of process complexity. Two different numerical codes, Code B right and Abaqus, have been used. The modelling performed by UPC-Cimne using Code B right, has been divided in three subtasks: i) analysis of the response observed in the lower part of the test, by inclusion of a number of considerations: (a) the use of the Barcelona Expansive Model for MX-80 bentonite; (b) updated parameters in the vapour diffusive flow term; (c) the use of a non-conventional water retention curve for MX-80 at high temperature; ii) assessment of a possible relation between the cracks observed in the bentonite blocks in the upper part of TBT, and the cycles of suction and stresses registered in that zone at the start of the experiment; and iii) analysis of the performance, observations and interpretation of the entire test. It was however not possible to carry out a full THM analysis until the end of the test due to

  7. Temperature Buffer Test. Final THM modelling

    Energy Technology Data Exchange (ETDEWEB)

    Aakesson, Mattias; Malmberg, Daniel; Boergesson, Lennart; Hernelind, Jan [Clay Technology AB, Lund (Sweden); Ledesma, Alberto; Jacinto, Abel [UPC, Universitat Politecnica de Catalunya, Barcelona (Spain)

    2012-01-15

    The Temperature Buffer Test (TBT) is a joint project between SKB/ANDRA and supported by ENRESA (modelling) and DBE (instrumentation), which aims at improving the understanding and to model the thermo-hydro-mechanical behavior of buffers made of swelling clay submitted to high temperatures (over 100 deg C) during the water saturation process. The test has been carried out in a KBS-3 deposition hole at Aespoe HRL. It was installed during the spring of 2003. Two heaters (3 m long, 0.6 m diameter) and two buffer arrangements have been investigated: the lower heater was surrounded by bentonite only, whereas the upper heater was surrounded by a composite barrier, with a sand shield between the heater and the bentonite. The test was dismantled and sampled during the winter of 2009/2010. This report presents the final THM modelling which was resumed subsequent to the dismantling operation. The main part of this work has been numerical modelling of the field test. Three different modelling teams have presented several model cases for different geometries and different degree of process complexity. Two different numerical codes, Code{sub B}right and Abaqus, have been used. The modelling performed by UPC-Cimne using Code{sub B}right, has been divided in three subtasks: i) analysis of the response observed in the lower part of the test, by inclusion of a number of considerations: (a) the use of the Barcelona Expansive Model for MX-80 bentonite; (b) updated parameters in the vapour diffusive flow term; (c) the use of a non-conventional water retention curve for MX-80 at high temperature; ii) assessment of a possible relation between the cracks observed in the bentonite blocks in the upper part of TBT, and the cycles of suction and stresses registered in that zone at the start of the experiment; and iii) analysis of the performance, observations and interpretation of the entire test. It was however not possible to carry out a full THM analysis until the end of the test due to

  8. The Interplay between Feedback and Buffering in Cellular Homeostasis.

    Science.gov (United States)

    Hancock, Edward J; Ang, Jordan; Papachristodoulou, Antonis; Stan, Guy-Bart

    2017-11-22

    Buffering, the use of reservoirs of molecules to maintain concentrations of key molecular species, and negative feedback are the primary known mechanisms for robust homeostatic regulation. To our knowledge, however, the fundamental principles behind their combined effect have not been elucidated. Here, we study the interplay between buffering and negative feedback in the context of cellular homeostasis. We show that negative feedback counteracts slow-changing disturbances, whereas buffering counteracts fast-changing disturbances. Furthermore, feedback and buffering have limitations that create trade-offs for regulation: instability in the case of feedback and molecular noise in the case of buffering. However, because buffering stabilizes feedback and feedback attenuates noise from slower-acting buffering, their combined effect on homeostasis can be synergistic. These effects can be explained within a traditional control theory framework and are consistent with experimental observations of both ATP homeostasis and pH regulation in vivo. These principles are critical for studying robustness and homeostasis in biology and biotechnology. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  9. Buffer lining manufacturing method for radioactive waste container

    International Nuclear Information System (INIS)

    Kawakami, Susumu; Sugino, Hiroyuki

    1998-01-01

    A recessed portion is formed on an upper surface of a filler layer made of a buffer powder filled into a container main body, the upper portion of the vessel main body is closed by a shrinkable liquid tight film. It is placed in a pressurizing container and pressed to mold a buffer lining base material integrated with the vessel main body. A flat upper surface and a containing space are formed by shaving to form a buffer lining. A disposing vessel containing radioactive wastes is inserted into the containing space, and the containing space is closed by a buffer block. The upper surface is sealed by a lid. With such a constitution, since a buffer lining integrated with the vessel main body can be formed easily inside the vessel main body, the disposing vessel can be contained in the containing vessel in a state surrounded by the buffer easily and stably without laying or piling over a large quantity of buffer blocks. (T.M.)

  10. Accelerating Science with the NERSC Burst Buffer Early User Program

    Energy Technology Data Exchange (ETDEWEB)

    Bhimji, Wahid [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Bard, Debbie [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Romanus, Melissa [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Rutgers Univ., New Brunswick, NJ (United States); Paul, David [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Ovsyannikov, Andrey [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Friesen, Brian [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Bryson, Matt [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Correa, Joaquin [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Lockwood, Glenn K. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Tsulaia, Vakho [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Byna, Suren [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Farrell, Steve [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Gursoy, Doga [Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS); Daley, Chris [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Beckner, Vince [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Van Straalen, Brian [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Trebotich, David [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Tull, Craig [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Weber, Gunther H. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Wright, Nicholas J. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Antypas, Katie [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Prabhat, none [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2016-01-01

    NVRAM-based Burst Buffers are an important part of the emerging HPC storage landscape. The National Energy Research Scientific Computing Center (NERSC) at Lawrence Berkeley National Laboratory recently installed one of the first Burst Buffer systems as part of its new Cori supercomputer, collaborating with Cray on the development of the DataWarp software. NERSC has a diverse user base comprised of over 6500 users in 700 different projects spanning a wide variety of scientific computing applications. The use-cases of the Burst Buffer at NERSC are therefore also considerable and diverse. We describe here performance measurements and lessons learned from the Burst Buffer Early User Program at NERSC, which selected a number of research projects to gain early access to the Burst Buffer and exercise its capability to enable new scientific advancements. To the best of our knowledge this is the first time a Burst Buffer has been stressed at scale by diverse, real user workloads and therefore these lessons will be of considerable benefit to shaping the developing use of Burst Buffers at HPC centers.

  11. pH variations during diafiltration due to buffer nonidealities.

    Science.gov (United States)

    Baek, Youngbin; Yang, Deyu; Singh, Nripen; Arunkumar, Abhiram; Ghose, Sanchayita; Li, Zheng Jian; Zydney, Andrew L

    2017-11-01

    Diafiltration is used for final formulation of essentially all biotherapeutics. Several studies have demonstrated that buffer/excipient concentrations in the final diafiltered product can be different than that in the diafiltration buffer due to interactions between buffer species and the protein product. However, recent work in our lab has shown variations in solution pH that are largely independent of the protein concentration during the first few diavolumes. Our hypothesis is that these pH variations are due to nonidealities in the acid-base equilibrium coefficient. A model was developed for the diafiltration process accounting for the ionic strength dependence of the pK a . Experimental results obtained using phosphate and histidine buffers were in excellent agreement with model predictions. A decrease in ionic strength leads to an increase in the pK a for the phosphate buffer, causing a shift in the solution pH, even under conditions where the initial feed and the diafiltration buffer are at the same pH. This effect could be eliminated by matching the ionic strength of the feed and diafiltration buffer. The experimental data and model provide new insights into the factors controlling the pH profile during diafiltration processes. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1555-1560, 2017. © 2017 American Institute of Chemical Engineers.

  12. Mars Aqueous Processing System

    Science.gov (United States)

    Berggren, Mark; Wilson, Cherie; Carrera, Stacy; Rose, Heather; Muscatello, Anthony; Kilgore, James; Zubrin, Robert

    2012-01-01

    The goal of the Mars Aqueous Processing System (MAPS) is to establish a flexible process that generates multiple products that are useful for human habitation. Selectively extracting useful components into an aqueous solution, and then sequentially recovering individual constituents, can obtain a suite of refined or semi-refined products. Similarities in the bulk composition (although not necessarily of the mineralogy) of Martian and Lunar soils potentially make MAPS widely applicable. Similar process steps can be conducted on both Mars and Lunar soils while tailoring the reaction extents and recoveries to the specifics of each location. The MAPS closed-loop process selectively extracts, and then recovers, constituents from soils using acids and bases. The emphasis on Mars involves the production of useful materials such as iron, silica, alumina, magnesia, and concrete with recovery of oxygen as a byproduct. On the Moon, similar chemistry is applied with emphasis on oxygen production. This innovation has been demonstrated to produce high-grade materials, such as metallic iron, aluminum oxide, magnesium oxide, and calcium oxide, from lunar and Martian soil simulants. Most of the target products exhibited purities of 80 to 90 percent or more, allowing direct use for many potential applications. Up to one-fourth of the feed soil mass was converted to metal, metal oxide, and oxygen products. The soil residue contained elevated silica content, allowing for potential additional refining and extraction for recovery of materials needed for photovoltaic, semiconductor, and glass applications. A high-grade iron oxide concentrate derived from lunar soil simulant was used to produce a metallic iron component using a novel, combined hydrogen reduction/metal sintering technique. The part was subsequently machined and found to be structurally sound. The behavior of the lunar-simulant-derived iron product was very similar to that produced using the same methods on a Michigan iron

  13. Bio resorbability of the modified hydroxyapatite in Tris-HCL buffer

    International Nuclear Information System (INIS)

    Golovanova, O A; Izmailov, R R; Ghyngazov, S A

    2016-01-01

    The solubility of carbonated hydroxyapatite powders and granulated carbonated hydroxyapatite produced from the synovial biofluid model solution has been studied. The kinetic characteristics of dissolution were determined. It was found that the solubility of carbonated hydroxyapatite is higher as compared to that of hydroxyapatite. The impact of the organic matrix on the rate of sample dissolution was revealed. For HA-gelatin composites, as the gelatin concentration grows, the dissolution rate becomes greater, and a sample of 6.0 g / L concentration has higher resorbability. The results of the research can be used to study the kinetics of dissolution and the biocompatibility of ceramic materials for medicine, namely for reconstructive surgery, dentistry, and development of drug delivery systems. (paper)

  14. Protein buffering in model systems and in whole human saliva.

    Directory of Open Access Journals (Sweden)

    Andreas Lamanda

    Full Text Available The aim of this study was to quantify the buffer attributes (value, power, range and optimum of two model systems for whole human resting saliva, the purified proteins from whole human resting saliva and single proteins. Two model systems, the first containing amyloglucosidase and lysozyme, and the second containing amyloglucosidase and alpha-amylase, were shown to provide, in combination with hydrogencarbonate and di-hydrogenphosphate, almost identical buffer attributes as whole human resting saliva. It was further demonstrated that changes in the protein concentration as small as 0.1% may change the buffer value of a buffer solution up to 15 times. Additionally, it was shown that there was a protein concentration change in the same range (0.16% between saliva samples collected at the time periods of 13:00 and others collected at 9:00 am and 17:00. The mode of the protein expression changed between these samples corresponded to the change in basic buffer power and the change of the buffer value at pH 6.7. Finally, SDS Page and Ruthenium II tris (bathophenantroline disulfonate staining unveiled a constant protein expression in all samples except for one 50 kDa protein band. As the change in the expression pattern of that 50 kDa protein band corresponded to the change in basic buffer power and the buffer value at pH 6.7, it was reasonable to conclude that this 50 kDa protein band may contain the protein(s belonging to the protein buffer system of human saliva.

  15. The stochastic nuclide transport model for buffer/backfill materials

    International Nuclear Information System (INIS)

    Ma Liping; Han Yongguo

    2014-01-01

    Currently, study on nuclide migration law in geological disposal repository of high level waste is assumed buffer/backfill layer to be continuous medium, utilized the continuity equation, equation of state, the equations of motion, etc, formed a set of theory and method to estimate nuclide concentration distribution in buffer/backfill layer, and provided an important basis for nuclide migration rules of repository. However, it is necessary to study the buffer/backfill layer microstructure and subtly describe the pore structure and fracture system of the buffer/backfill layer, and reflect the changes in connectivity and in different directions of the buffer/backfill layer. Through using random field theory, the nuclide transport for the buffer/backfill layer in geological disposal repository of nuclear waste is described in the paper. This paper mainly includes that, t represents the time, ξ t ⊂ Z d = d represents the integer lattice, Z represents collectivity integers, d = l, 2, 3, for instance, d = 2, Z d = {(m, n) : m, n ∈ Z} the state point of ξ t is typically considered to be occupied by the nuclide concentration values of the buffer/backfill layer, ξ t also represents random set in the diagram of two dimensional integer lattice, namely, t ∈ [0, T], {ξ t ,0 ≤ t ≤ ⊂ T} Consequently, according to the stochastic process obtained above, the changes of the nuclide concentration values of the buffer/backfill layer or the buffer/backfill laboratory materials in the repository with the time can be known. (authors)

  16. On Buffer-Aided Multiple-Access Relay Channel

    DEFF Research Database (Denmark)

    Liu, Rongkuan; Popovski, Petar; Wang, Gang

    2016-01-01

    This letter treats uplink scenario where M user equipments (UEs) send to a base station (BS), possibly via a common relay station (RS) that is equipped with a buffer. This is a multiple-access relay channel aided by a buffer. We devise a protocol in which the transmission mode is selected...... entirely at the BS, while simultaneously a number of UEs sends new messages to the BS. The results show that the adaptive selection of direct and buffer-aided relay transmissions leads to significant average throughput gains....

  17. Lean buffering in serial production lines with Bernoulli machines

    Directory of Open Access Journals (Sweden)

    A. B. Hu

    2006-01-01

    Full Text Available Lean buffering is the smallest buffer capacity necessary to ensure the desired production rate of a manufacturing system. In this paper, analytical methods for selecting lean buffering in serial production lines are developed under the assumption that the machines obey the Bernoulli reliability model. Both closed-form expressions and recursive approaches are investigated. The cases of identical and nonidentical machines are analyzed. Results obtained can be useful for production line designers and production managers to maintain the required production rate with the smallest possible inventories.

  18. Buffer-gas-induced absorption resonances in Rb vapor

    International Nuclear Information System (INIS)

    Mikhailov, Eugeniy E.; Novikova, Irina; Rostovtsev, Yuri V.; Welch, George R.

    2004-01-01

    We observe transformation of the electromagnetically induced transparency (EIT) resonance into an absorption resonance in a Λ interaction configuration in a cell filled with 87 Rb and a buffer gas. This transformation occurs as one-photon detuning of the coupling fields is varied from the atomic transition. No such absorption resonance is found in the absence of a buffer gas. The width of the absorption resonance is several times smaller than the width of the EIT resonance, and the changes of absorption near these resonances are about the same. Similar absorption resonances are detected in the Hanle configuration in a buffered cell

  19. Buffer layers for REBCO films for use in superconducting devices

    Science.gov (United States)

    Goyal, Amit; Wee, Sung-Hun

    2014-06-10

    A superconducting article includes a substrate having a biaxially textured surface. A biaxially textured buffer layer, which can be a cap layer, is supported by the substrate. The buffer layer includes a double perovskite of the formula A.sub.2B'B''O.sub.6, where A is rare earth or alkaline earth metal and B' and B'' are different transition metal cations. A biaxially textured superconductor layer is deposited so as to be supported by the buffer layer. A method of making a superconducting article is also disclosed.

  20. Stacking by electroinjection with discontinuous buffers in capillary zone electrophoresis.

    Science.gov (United States)

    Shihabi, Zak K

    2002-08-01

    The work presented here demonstrates that electroinjection can be performed using discontinuous buffers, which can result in better stacking than that obtained by hydrodynamic injection. The sample can be concentrated at the tip of the capillary leaving practically the whole capillary for sample separation. This results in several advantages, such as better sample concentration, higher plate number and shorter time of stacking. However, sample introduction by electromigration is suited for samples free or low in salt content. Samples, which are high in salt content, are better introduced by the hydrodynamic injection for stacking by the discontinuous buffers. Different simple methods to introduce the discontinuity in the buffer for electroinjection are discussed.

  1. Fabrication of electrochemical theophylline sensor based on manganese oxide nanoparticles/ionic liquid/chitosan nanocomposite modified glassy carbon electrode

    International Nuclear Information System (INIS)

    MansouriMajd, Samira; Teymourian, Hazhir; Salimi, Abdollah; Hallaj, Rahman

    2013-01-01

    In this study, the preparation of a glassy carbon (GC) electrode modified with chitosan/NH 2 -ionic liquid/manganese oxide nanoparticles (Chit/NH 2 -IL/MnO x ) was described for electrocatalytic detection of theophylline (TP). First, chitosan hydrogel (Chit) was electrodeposited on the GC electrode surface at a constant potential (−1.5 V) in acidic solution. Then, the previously synthesized amine-terminated 1-(3-Aminopropyl)-3-methylimidazolium bromide ionic liquid (NH 2 -IL) was covalently attached to the modified electrode via glutaraldehyde (GA) as linking agent. Finally, manganese oxide (MnO x ) nanoparticles were electrodeposited onto the Chit/NH 2 -IL film by potential cycling between −1.0 and 1.7 V in Mn(CH 3 COO) 2 ·4H 2 O neutral aqueous solution. Electrochemical behavior of the modified electrode was evaluated by cyclic voltammetry (CV) technique. The charge transfer coefficient (α) and electron transfer rate constant (k s ) for MnOOH/MnO 2 redox couple were calculated to be 0.35 and 1.62 s −1 , respectively. The resulting system brings new capabilities for electrochemical sensing through combining the advantages of IL and MnO x nanoparticles. The differential pulse voltammetric (DPV) results indicated the high ability of GC/Chit/NH 2 -IL/MnO x modified electrode to catalyze the oxidation of TP. DPV determination of TP in acetate buffer solution (pH 5) gave linear responses over the concentration range up to 120 μM with the detection limit of 50 nM and sensitivity of 804 nA μM −1 . Furthermore, the applicability of the sensor for TP analysis in pharmaceutical samples has been successfully demonstrated

  2. Aqueous chemistry of transactinides

    International Nuclear Information System (INIS)

    Schaedel, M.

    2001-01-01

    The aqueous chemistry of the first three transactinide elements is briefly reviewed with special emphasis given to recent experimental results. Short introductory remarks are discussing the atom-at-a-time situation of transactinide chemistry as a result of low production cross-sections and short half-lives. In general, on-line experimental techniques and, more specifically, the automated rapid chemistry apparatus, ARCA, are presented. Present and future developments of experimental techniques and resulting perspectives are outlined at the end. The central part is mainly focussing on hydrolysis and complex formation aspects of the superheavy group 4, 5, and 6 transition metals with F - and Cl - anions. Experimental results are compared with the behaviour of lighter homologous elements and with relativistic calculations. It will be shown that the chemical behaviour of the first superheavy elements is already strongly influenced by relativistic effects. While it is justified to place rutherfordium, dubnium and seaborgium in the Periodic Table of the Elements into group 4, 5 and 6, respectively, it is no more possible to deduce from this position in detail the chemical properties of these transactinide or superheavy elements. (orig.)

  3. Sorption of ochratoxin A from aqueous solutions using β-cyclodextrin-polyurethane polymer.

    Science.gov (United States)

    Appell, Michael; Jackson, Michael A

    2012-02-01

    The ability of a cyclodextrin-polyurethane polymer to remove ochratoxin A from aqueous solutions was examined by batch rebinding assays. The results from the aqueous binding studies were fit to two parameter models to gain insight into the interaction of ochratoxin A with the nanosponge material. The ochratoxin A sorption data fit well to the heterogeneous Freundlich isotherm model. The polymer was less effective at binding ochratoxin A in high pH buffer (9.5) under conditions where ochratoxin A exists predominantly in the dianionic state. Batch rebinding assays in red wine indicate the polymer is able to remove significant levels of ochratoxin A from spiked solutions between 1-10 μg·L(-1). These results suggest cyclodextrin nanosponge materials are suitable to reduce levels of ochratoxin A from spiked aqueous solutions and red wine samples.

  4. Assessing Anthropogenic Influence and Edge Effect Influence on Forested Riparian Buffer Spatial Configuration and Structure: An Example Using Lidar Remote Sensing Methods

    Science.gov (United States)

    Wasser, L. A.; Chasmer, L. E.

    2012-12-01

    Forested riparian buffers (FRB) perform numerous critical ecosystem services. However, globally, FRB spatial configuration and structure have been modified by anthropogenic development resulting in widespread ecological degradation as seen in the Gulf of Mexico and the Chesapeake Bay. Riparian corridors within developed areas are particularly vulnerable to disturbance given two edges - the naturally occurring stream edge and the matrix edge. Increased edge length predisposes riparian vegetation to "edge effects", characterized by modified physical and environmental conditions at the interface between the forested buffer and the adjacent landuse, or matrix and forest fragment degradation. The magnitude and distance of edge influence may be further influenced by adjacent landuse type and the width of the buffer corridor at any given location. There is a need to quantify riparian buffer spatial configuration and structure over broad geographic extents and within multiple riparian systems in support of ecologically sound management and landuse decisions. This study thus assesses the influence of varying landuse types (agriculture, suburban development and undeveloped) on forested riparian buffer 3-dimensional structure and spatial configuration using high resolution Light Detection and Ranging (LiDAR) data collected within a headwater watershed. Few studies have assessed riparian buffer structure and width contiguously for an entire watershed, an integral component of watershed planning and restoration efforts such as those conducted throughout the Chesapeake Bay. The objectives of the study are to 1) quantify differences in vegetation structure at the stream and matrix influenced riparian buffer edges, compared to the forested interior and 2) assess continuous patterns of changes in vegetation structure throughout the buffer corridor beginning at the matrix edge and ending at the stream within buffers a) of varying width and b) that are adjacent to varying landuse

  5. Progress in aqueous rechargeable batteries

    Directory of Open Access Journals (Sweden)

    Jilei Liu

    2018-01-01

    Full Text Available Over the past decades, a series of aqueous rechargeable batteries (ARBs were explored, investigated and demonstrated. Among them, aqueous rechargeable alkali-metal ion (Li+, Na+, K+ batteries, aqueous rechargeable-metal ion (Zn2+, Mg2+, Ca2+, Al3+ batteries and aqueous rechargeable hybrid batteries are standing out due to peculiar properties. In this review, we focus on the fundamental basics of these batteries, and discuss the scientific and/or technological achievements and challenges. By critically reviewing state-of-the-art technologies and the most promising results so far, we aim to analyze the benefits of ARBs and the critical issues to be addressed, and to promote better development of ARBs.

  6. aqueous root extract on spermatogenesis

    African Journals Online (AJOL)

    Four groups were gavaged with the whole plant or root aqueous extract in low or high doses. The male ... motility and morphology as well as chromatin integrity were evaluated. Results: Serum ... Treatment of disease began long ago with the.

  7. Towards Optimal Buffer Size in Wi-Fi Networks

    KAUST Repository

    Showail, Ahmad

    2016-01-01

    extensively for wired networks. However, there is little work addressing the unique challenges of wireless environment. In this dissertation, we discuss buffer sizing challenges in wireless networks, classify the state-of-the-art solutions, and propose two

  8. Studies of Latent Acidity and Neutral Buffered Chloroaluminate Ionic Liquids

    National Research Council Canada - National Science Library

    Osteryoung, Robert

    2000-01-01

    Studies on ionic liquids composed of aluminum chloride and 1-ethyl-3-methylimidazolium chloride were carried out, with emphasis on understanding and explaining acidity and latent acidity in "neutral buffered" melts...

  9. EnviroAtlas - Phoenix, AZ - Near Road Tree Buffer

    Data.gov (United States)

    U.S. Environmental Protection Agency — This EnviroAtlas dataset addresses the tree buffer along heavily traveled roads. The roads are interstates, arterials, and collectors within the EnviroAtlas...

  10. EnviroAtlas - Tampa, FL - Near Road Tree Buffer

    Data.gov (United States)

    U.S. Environmental Protection Agency — This EnviroAtlas dataset addresses the tree buffer along heavily traveled roads. The roads are interstates, arterials, and collectors within the EnviroAtlas...

  11. Full scale tests of moisture buffer capacity of wall materials

    DEFF Research Database (Denmark)

    Mortensen, Lone Hedegaard; Rode, Carsten; Peuhkuri, Ruut Hannele

    2005-01-01

    that are harmful such as growth of house dust mites, surface condensation and mould growth. Therefore a series of experiments has been carried out in a full scale test facility to determine the moisture buffer effect of interior walls of cellular concrete and plaster board constructions. For the cellular concrete......Moisture buffer capacity of hygroscopic materials can be used to moderate peaks in the relative humidity (RH) of indoor air as well as moisture content variations in building materials and furnishing. This can help to ensure healthier indoor environments by preventing many processes...... of the changes of moisture content in specimens of the wall composites exposed to the same environment. It was found that the finishes had a big impact on the buffer performance of the underlying materials. Even though the untreated cellular concrete had a very high buffer capacity, the effect was strongly...

  12. EnviroAtlas - Woodbine, IA - Near Road Tree Buffer

    Data.gov (United States)

    U.S. Environmental Protection Agency — This EnviroAtlas dataset addresses the tree buffer along heavily traveled roads. The roads are interstates, arterials, and collectors within the EnviroAtlas...

  13. Buffer management in wireless full-duplex systems

    KAUST Repository

    Bouacida, Nader; Showail, Ahmad; Shihada, Basem

    2015-01-01

    , we address the problem of buffer management in full-duplex networks by using Wireless Queue Management (WQM), which is an active queue management technique for wireless networks. Our solution is based on Relay Full-Duplex MAC (RFD

  14. Design and analysis of hybrid optical and electronic buffer based ...

    Indian Academy of Sciences (India)

    ARUNENDRA SINGH

    2018-03-10

    Mar 10, 2018 ... need and requirement of internet traffic is increasing in a very rapid pace. ... infrastructure of telecommunication and data networking. One of the significant .... packet loss rate, large buffer space would be required, and.

  15. EnviroAtlas - Paterson, NJ - Near Road Tree Buffer

    Data.gov (United States)

    U.S. Environmental Protection Agency — This EnviroAtlas dataset addresses the tree buffer along heavily traveled roads. The roads are interstates, arterials, and collectors within the EnviroAtlas...

  16. Swelling of the buffer of KBS-3V deposition hole

    International Nuclear Information System (INIS)

    Lempinen, A.

    2006-12-01

    At the time of the installation of spent nuclear fuel canister in the KBS-3V deposition hole, empty space is left around bentonite buffer for technical reasons. The gap between the buffer and the canister is about 10 mm, and the gap between the buffer and the rock is 30 to 35 mm. In this study, the swelling of the buffer to fill the gaps was simulated, when the gaps are initially filled with water and no external water is available. The model used here is a thermodynamical model for swelling clay, with parameters determined for bentonite. The simulations presented here were performed with Freefem++ software, which is a finite element application for partial differential equations. These equations come from the material model. The simulation results show that the swelling fills the outer gaps in few years, but no significant swelling pressure is generated. For swelling pressure, external water supply is required. (orig.)

  17. EnviroAtlas - New York, NY - Near Road Tree Buffer

    Data.gov (United States)

    U.S. Environmental Protection Agency — This EnviroAtlas dataset addresses the tree buffer along heavily traveled roads. The roads are interstates, arterials, and collectors within the EnviroAtlas...

  18. EnviroAtlas - Durham, NC - Near Road Tree Buffer

    Data.gov (United States)

    U.S. Environmental Protection Agency — This EnviroAtlas dataset addresses the tree buffer along heavily traveled roads. The roads are interstates, arterials, and collectors within the EnviroAtlas...

  19. EnviroAtlas - Austin, TX - Near Road Tree Buffer

    Data.gov (United States)

    U.S. Environmental Protection Agency — This EnviroAtlas dataset addresses the tree buffer along heavily traveled roads. The roads are interstates, arterials, and collectors within the EnviroAtlas...

  20. EnviroAtlas - Green Bay, WI - Near Road Tree Buffer

    Data.gov (United States)

    U.S. Environmental Protection Agency — This EnviroAtlas dataset addresses the tree buffer along heavily traveled roads. The roads are interstates, arterials, and collectors within the EnviroAtlas...