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Sample records for mild aqueous conditions

  1. Hydrodefluorination and hydrogenation of fluorobenzene under mild aqueous conditions.

    PubMed

    Baumgartner, Rebekka; McNeill, Kristopher

    2012-09-18

    Fluorinated organic compounds are increasingly used in many applications, and their release to the environment is expected. It is therefore important to find suitable methods for degradation of fluorinated compounds under environmentally relevant conditions. In this study, a simple heterogeneous rhodium-based catalytic system (Rh/Al(2)O(3) and H(2)) for hydrodefluorination and hydrogenation of fluorobenzene under mild aqueous conditions (1 atm of H(2), ambient temperature) was developed and the underlying reaction mechanism was investigated. Fluorobenzene degraded rapidly (t(1/2) ≈ 0.2 h) to form cyclohexane and fluoride (F(-)) as the stable end products, with benzene and cyclohexene observed as intermediates. Cyclohexadiene intermediates were not observed but were expected to form during the hydrogenation of benzene. Three postulated but unobserved fluorinated intermediates were subjected to the catalytic reaction conditions, and it was concluded that they most likely do not form during the fluorobenzene degradation reaction. Isotope labeling experiments showed that the unsaturated intermediates undergo rapid and reversible hydrogenation/dehydrogenation under the reaction conditions and also that fully saturated compounds are unreactive in the catalytic system. Both molecular hydrogen and water were sources of hydrogen in the final cyclohexane product. Kinetic fitting indicated that sorption/desorption of fluorobenzene onto the catalyst surface plays an important role in the mechanism. PMID:22871102

  2. Sulfur removal from Gediz lignite using aqueous sodium hydroxide solutions under mild oxidative conditions

    SciTech Connect

    Yaman, S.; Kuecuekbayrak, S.

    1999-11-01

    Sulfur removal from a high-sulfur Turkish lignite (Gediz) using aqueous sodium hydroxide solutions having dissolved oxygen was investigated under mild oxidative conditions. Effects of the parameters such as sodium hydroxide/lignite weight ratio, temperature, and partial pressure of oxygen were investigated within the ranges of 0.05--0.8, 423--498 K, and 1--2 MPa, respectively. Optimum values of these parameters were determined regarding sulfur removal and coal recovery. Influences of dry oxidation of the lignite sample as a pretreatment at 573 K and subsequent washing of some treated lignite samples with 1 N HCl were investigated.

  3. Promoted oxidation of phenol in aqueous solution using molecular oxygen at mild conditions

    SciTech Connect

    Vogel, F.; Harf, J.; Hug, A.; Rohr, P.R. von

    1999-05-01

    Wet oxidation with molecular oxygen at mild conditions (temperature < 200 C, pressure {le} 2 MPa) is an economically attractive pretreatment step for non-biodegradable aqueous waste streams. In order to overcome the low reactivity of molecular oxygen towards organic molecules at these mild process conditions, an initiator was used in combination with ferrous ions in the acidic range. The promoted oxidation of phenol in aqueous solution was investigated in a 4 liters stirred autoclave. It was possible to degrade the phenol at temperatures as low as 100 C without observing an induction time. The remaining solution contained mainly acetic and formic acid and was well biodegradable. The oxidative behavior of the oxygen/phenol system could be explained using the well-known autoxidation mechanism for aliphatic molecules. 4-hydroperoxy-phenol is suggested as a key intermediate. Measured products are p-benzoquinone, hydroquinone, catechol, maleic, oxalic, pyruvic, formic, and acetic acid. Dimers could also be identified in sample extracts. A global pathway including all identified products is presented.

  4. Kinetics of organic transformations under mild aqueous conditions: implications for the origin of life and its metabolism

    NASA Technical Reports Server (NTRS)

    Weber, Arthur L.

    2004-01-01

    The rates of thermal transformation of organic molecules containing carbon, hydrogen, and oxygen were systematically examined in order to identify the kinetic constraints that governed origin-of-life organic chemistry under mild aqueous conditions. Arrhenius plots of the kinetic data were used to estimate the reaction of half-lifes at 50 degrees C. This survey showed that hydrocarbons and organic substances containing a single oxygenated group were kinetically the most stable; whereas organic substances containing two oxygenated groups in which one group was an alpha- or beta-positioned carbonyl group were the most reactive. Compounds with an alpha- or beta-positioned carbonyl group (aldehyde or ketone) had rates of reaction that were up to 10(24)-times faster than rates of similar molecules lacking the carbonyl group. This survey of organic reactivity, together with estimates of the molecular containment properties of lipid vesicles and liquid spherules, indicates that an origins process in a small domain that used C,H,O-intermediates had to be catalytic and use the most reactive organic molecules to prevent escape of its reaction intermediates.

  5. Kinetics of Organic Transformations Under Mild Aqueous Conditions: Implications for the Origin of Life and Its Metabolism

    NASA Technical Reports Server (NTRS)

    Weber, Arthur L.

    2003-01-01

    The rates of thermal transformation of organic molecules containing carbon, hydrogen, and oxygen were systematically examined in order to identify the kinetic constraints that governed origin-of-life organic chemistry under mild aqueous conditions. Arrhenius plots of the kinetic data were used to estimate the reaction half-life at 50 C, and to reveal the effect of functional groups on reactivity. This survey showed that hydrocarbons and organic substances containing a single oxygenated group were kinetically the most stable (i. e. acetate decarboxylation half-life was l0(exp 18) years at 50 C); whereas, organic substances containing two oxygenated groups in which one group was a beta-positioned carbonyl group were the most reactive (i. e. acetoacetate decarboxylation half-life was l0(exp-2) years at 50 C). Of all functional groups the beta-positioned carbonyl group (aldehyde or ketone) was the strongest activating group, giving rates of reaction that were up to 10(exp 24)-times faster than rates of similar molecules lacking the beta-carbonyl group. From this knowledge of organic reactivity and the inherent constraints of autocatalytic processes, we concluded that an origins-of-life process based on autocatalytic transformation of C,H,O-substrates was constrained to using the most reactive organic molecules that contain alpha- or beta-carbonyl groups, since small autocatalytic domains of plausible catalytic power that used less reactive substrates could not carry out chemical transformations fast enough to prevent catastrophic efflux (escape) of reaction intermediates. Knowledge of the kinetics of organic transformations is useful, not only in constraining the chemistry of the earliest autocatalytic process related to the origin of life, but also in establishing the relative reactivity of organic molecules on the early Earth and other planets that may or may not be related to the origin of life.

  6. Chemical Constraints Governing the Origin of Metabolism: The Thermodynamic Landscape of Carbon Group Transformations under Mild Aqueous Conditions

    NASA Astrophysics Data System (ADS)

    Weber, Arthur L.

    2002-08-01

    The thermodynamics of organic chemistry under mild aqueous conditions was examined in order to begin to understand its influence on the structure and operation of metabolism and its antecedents. Free energies (ΔG) were estimated for four types of reactions of biochemical importance - carbon-carbon bond cleavage and synthesis, hydrogen transfer between carbon groups, dehydration of alcohol groups, and aldo-keto isomerization. The energies were calculated for mainly aliphatic groups composed of carbon, hydrogen, and oxygen. The energy values showed (1) that generally when carbon-carbon bond cleavage involves groups from different functional group classes (i.e., carboxylic acids, carbonyl groups, alcohols, and hydrocarbons), the transfer of the shared electron-pair to the more reduced carbon group is energetically favored over transfer to the more oxidized carbon group, and (2) that the energy of carbon-carbon bond transformation is primarily determined by the functional group class of the group that changes oxidation state in the reaction (i.e., the functional group class of the group that donates the shared electron-pair during cleavage, or that accepts the incipient shared electron-pair during synthesis). In contrast, the energy of hydrogen transfer between carbon groups is determined by the functional group class of both the hydrogen-donor group and the hydrogen-acceptor group. From these and other observations we concluded that the chemistry involved in the origin of metabolism (and to a lesser degree modern metabolism) was strongly constrained by (1) the limited redox-based transformation energy of organic substrates that is readily dissipated in a few energetically favorable irreversible reactions; (2) the energy dominance of a few transformation half-reactions that determines whether carbon-carbon bond transformation (cleavage or synthesis) is energetically favorable (ΔG < -3.5 kcal/mol), reversible (ΔG between +/-3.5 kcal/mol), or unfavorable (ΔG > +3

  7. Chemical constraints governing the origin of metabolism: the thermodynamic landscape of carbon group transformations under mild aqueous conditions

    NASA Technical Reports Server (NTRS)

    Weber, Arthur L.

    2002-01-01

    The thermodynamics of organic chemistry under mild aqueous conditions was examined in order to begin to understand its influence on the structure and operation of metabolism and its antecedents. Free energies (deltaG) were estimated for four types of reactions of biochemical importance carbon-carbon bond cleavage and synthesis, hydrogen transfer between carbon groups, dehydration of alcohol groups, and aldo-keto isomerization. The energies were calculated for mainly aliphatic groups composed of carbon, hydrogen, and oxygen. The energy values showed (1) that generally when carbon-carbon bond cleavage involves groups from different functional group classes (i.e., carboxylic acids, carbonyl groups, alcohols, and hydrocarbons), the transfer of the shared electron-pair to the more reduced carbon group is energetically favored over transfer to the more oxidized carbon group, and (2) that the energy of carbon-carbon bond transformation is primarily determined by the functional group class of the group that changes oxidation state in the reaction (i.e., the functional group class of the group that donates the shared electron-pair during cleavage, or that accepts the incipient shared electron-pair during synthesis). In contrast, the energy of hydrogen transfer between carbon groups is determined by the functional group class of both the hydrogen-donor group and the hydrogen-acceptor group. From these and other observations we concluded that the chemistry involved in the origin of metabolism (and to a lesser degree modern metabolism) was strongly constrained by (1) the limited redox-based transformation energy of organic substrates that is readily dissipated in a few energetically favorable irreversible reactions; (2) the energy dominance of a few transformation half-reactions that determines whether carbon-carbon bond transformation (cleavage or synthesis) is energetically favorable (deltaG < -3.5 kcal/mol), reversible (deltaG between +/-3.5 kcal/mol), or unfavorable (delta

  8. Aqueous hydrodechlorination of 4-chlorophenol over an Rh/reduced graphene oxide synthesized by a facile one-pot solvothermal process under mild conditions.

    PubMed

    Ren, Yanlin; Fan, Guangyin; Wang, Chenyu

    2014-06-15

    Reduced graphene oxide (RGO) supported rhodium nanoparticles (Rh-NPs/RGO) was synthesized through one-pot polyol co-reduction of graphene oxide (GO) and rhodium chloride. The catalytic property of Rh-NPs/RGO was investigated for the aqueous phase hydrodechlorination (HDC) of 4-chlorophenol (4-CP). A complete conversion of 4-CP into high valued products of cyclohexanone (selectivity: 23.2%) and cyclohexanol (selectivity: 76.8%) was successfully achieved at 303K and balloon hydrogen pressure in a short reaction time of 50 min when 1.5 g/L of 4-CP was introduced. By comparing with Rh-NPs deposited on the other supports, Rh-NPs/RGO delivered the highest initial rate (111.4 mmol/gRh min) for 4-CP HDC reaction under the identical conditions. The substantial catalytic activity of Rh-NPs/RGO can be ascribed to the small and uniform particle size of Rh (average particle size was 1.7 ± 0.14 nm) on the surface of the RGO sheets and an electron-deficient state of Rh in the catalyst as a result of the strong interaction between the active sites and the surface function groups of RGO. PMID:24762698

  9. Flocculation performance of a cationic biopolymer derived from a cellulosic source in mild aqueous solution.

    PubMed

    Liimatainen, Henrikki; Sirviö, Juho; Sundman, Ola; Visanko, Miikka; Hormi, Osmo; Niinimäki, Jouko

    2011-10-01

    The flocculation behavior of cationic, quaternary ammonium groups containing cellulosic biopolymers, CDACs, synthesized by cationizing dialdehyde cellulose in mild aqueous solution was studied in a kaolin suspension. In particular, the role of CDAC dosage and solution pH, NaCl concentration, and temperature were clarified. In addition, the initial apparent charge densities (CDs), particle sizes, ζ-potential, and stability of CDs were determined. CDACs possessed a high flocculation activity in neutral and acidic solutions, but a significant decrease was observed in alkaline solutions (pH >9). This was also seen as a decline in the apparent CD and particle size of the CDACs in alkaline conditions. The measurements also indicated that the apparent CD decreased to a constant level of 3 mmol/g in aqueous solutions. However, no notable decrease in flocculation performance was obtained after several days of storage. Moreover, the variation of NaCl concentration and temperature did not affect the flocculation activity. PMID:21862324

  10. Cyclodextrin-promoted Diels Alder reactions of a polycyclic aromatic hydrocarbon under mild reaction conditions

    PubMed Central

    Chaudhuri, Sauradip; Phelan, Tyler; Levine, Mindy

    2015-01-01

    Reported herein is the effect of cyclodextrins on the rates of aqueous Diels Alder reactions of 9-anthracenemethanol with a variety of N-substituted maleimides. These reactions occurred under mild reaction conditions (aqueous solvent, 40 °C), and were most efficient for the reaction of N-cyclohexylmaleimide with a methyl-β-cyclodextrin additive (94% conversion in 24 hours). These results can be explained on the basis of a model wherein the cyclodextrins bind the hydrophobic substituents on the maleimides and activate the dienophile via electronic modulation of the maleimide double bond. The results reported herein represent a new mechanism for cyclodextrin-promoted Diels Alder reactions, and have significant potential applications in the development of other cyclodextrin-promoted organic transformations. Moreover, the ability to deplanarize polycyclic aromatic hydrocarbons (PAHs) under mild conditions, as demonstrated herein, has significant applications for PAH detoxification. PMID:26692588

  11. Solvolytic liquefaction of wood under mild conditions

    SciTech Connect

    Yu, S.M.

    1982-04-01

    Conversion of wood to liquid products requires cleavage of bonds which crosslink the wood structure. This study examines a low-severity wood solubilization process utilizing a solvent medium consisting of a small amount of sulfuric acid and a potentially wood-derivable alcohol. In one half hour of reaction time at 250/sup 0/C under 15 psia starting nitrogen pressure, over 95% of the wood (maf) was rendered acetone-soluble. The product is a soft, black, bitumen-like solid at room temperature but readily softens at 140/sup 0/C. Between 25 and 50% of the original wood oxygen, depending on alcohol used, was removed as water. Approximately 2 to 17% of the alcohols were retained in the product. Gel permeation chromatography showed that the product's median molecular weight is around 300. Based on experimental and literature results, a mechanism for wood solubilization is proposed. This involves protonation of the etheric oxygen atoms, leading to subsequent bond scission to form carbonium ions which are stabilized by solvent alkoxylation. At severe conditions, polymerization and condensation reactions result in acetone-insoluble materials.

  12. Chronoamperometric study of mild steel pitting in sodium sulfide aqueous solution

    SciTech Connect

    Otero, T.F.; Achucarro, C. . Dept. de Ciencia y Tecnologia de Polimeros)

    1994-08-01

    Mild steel samples were studied by chronoamperometry in sodium sulfide (Na[sub 2]S) aqueous solution. Pit nucleation and growth also were monitored by optical microscopy. The influence of variables such as temperature, polarization potential, surface roughness, the presence of electrochemically generated oxide layers, and the simultaneous presence of potassium hydroxide (KOH) was studied. The influence of each parameter on pit shape and growth was reviewed. Different reactions and competitive processes were proposed based on the experimental results.

  13. The rapid formation of functional monolayers on silicon under mild conditions.

    PubMed

    Ciampi, Simone; Luais, Erwann; James, Michael; Choudhury, Moinul H; Darwish, Nadim A; Gooding, J Justin

    2014-05-01

    We report on an exceedingly mild chemical functionalization of hydrogen-terminated Si(100) with unactivated and unprotected bifunctional α,ω-dialkynes. Monolayer formation occurs rapidly in the dark, and at room temperature, from dilute solutions of an aromatic-conjugated acetylene. The method addresses the poor reactivity of p-type substrates under mild conditions. We suggest the importance of several factors, including an optimal orientation for electron transfer between the adsorbate and the Si surface, conjugation of the acetylenic function with a π-system, as well as the choice of a solvent system that favors electron transfer and screens Coulombic interactions between surface holes and electrons. The passivated Si(100) electrode is amenable to further functionalization and shown to be a viable model system for redox studies at non-oxide semiconductor electrodes in aqueous solutions. PMID:24647452

  14. An Iron Catalyst for Ketone Hydrogenations Under Mild Conditions

    SciTech Connect

    Bullock, R. Morris

    2007-10-01

    Casey and Guan reported a homogeneous catalyst for ketone hydrogenation that does not require a precious metal, but instead is based on iron. Excellent yields and chemoselectivity for hydrogenation are found under mild conditions (25 °C, 3 atm H2). An ionic hydrogenation mechanism allows the delivery of a proton from the OH and a hydride from the metal. RMB gratefully acknowledges funding from the Division of Chemical Sciences, Office of Basic Energy Sciences, US Department of Energy, and from a grant from the Laboratory Directed Research and Development Program. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

  15. Telomerization of butadiene with starch under mild conditions.

    PubMed

    Mesnager, Julien; Quettier, Claude; Lambin, Anne; Rataboul, Franck; Pinel, Catherine

    2009-01-01

    The design of industrial products based on bioresources is a challenging issue. Modification of starch, by hydrophobic chemical substituents, results in an innovative hydrophobic material. Herein, the hydrophobic part of the derivative, comprised of octadienyl chains, is introduced through catalytic butadiene telomerization. The process is efficiently conducted on starch in its granular form in an aqueous medium using hydrosoluble palladium complexes. After optimization, a turnover number (TON) of up to 550 was achieved in the presence of [(pi-allyl)PdCl](2) catalyst and, unusually, by using dimethylisosorbide as a cosolvent. PMID:19856380

  16. Integration of advanced oxidation processes at mild conditions in wet scrubbers for odourous sulphur compounds treatment.

    PubMed

    Vega, Esther; Martin, Maria J; Gonzalez-Olmos, Rafael

    2014-08-01

    The effectiveness of different advanced oxidation processes on the treatment of a multicomponent aqueous solution containing ethyl mercaptan, dimethyl sulphide and dimethyl disulphide (0.5 mg L(-1) of each sulphur compound) was investigated with the objective to assess which one is the most suitable treatment to be coupled in wet scrubbers used in odour treatment facilities. UV/H2O2, Fenton, photo-Fenton and ozone treatments were tested at mild conditions and the oxidation efficiency obtained was compared. The oxidation tests were carried out in magnetically stirred cylindrical quartz reactors using the same molar concentration of oxidants (hydrogen peroxide or ozone). The results show that ozone and photo-Fenton are the most efficient treatments, achieving up to 95% of sulphur compounds oxidation and a mineralisation degree around 70% in 10 min. Furthermore, the total costs of the treatments taking into account the capital and operational costs were also estimated for a comparative purpose. The economic analysis revealed that the Fenton treatment is the most economical option to be integrated in a wet scrubber to remove volatile organic sulphur compounds, as long as there are no space constraints to install the required reactor volume. In the case of reactor volume limitation or retrofitting complexities, the ozone and photo-Fenton treatments should be considered as viable alternatives. PMID:24873715

  17. Preparation and Characterization of Colloidal Silica Particles under Mild Conditions

    ERIC Educational Resources Information Center

    Neville, Frances; Zin, Azrinawati Mohd.; Jameson, Graeme J.; Wanless, Erica J.

    2012-01-01

    A microscale laboratory experiment for the preparation and characterization of silica particles at neutral pH and ambient temperature conditions is described. Students first employ experimental fabrication methods to make spherical submicrometer silica particles via the condensation of an alkoxysilane and polyethyleneimine, which act to catalyze…

  18. Biomineralization of arsenate to arsenic sulfides is greatly enhanced at mildly acidic conditions.

    PubMed

    Rodriguez-Freire, Lucia; Sierra-Alvarez, Reyes; Root, Robert; Chorover, Jon; Field, James A

    2014-12-01

    Arsenic (As) is an important water contaminant due to its high toxicity and widespread occurrence. Arsenic-sulfide minerals (ASM) are formed during microbial reduction of arsenate (As(V)) and sulfate (SO4(2-)). The objective of this research is to study the effect of the pH on the removal of As due to the formation of ASM in an iron-poor system. A series of batch experiments was used to study the reduction of SO4(2-) and As(V) by an anaerobic biofilm mixed culture in a range of pH conditions (6.1-7.2), using ethanol as the electron donor. Total soluble concentrations and speciation of S and As were monitored. Solid phase speciation of arsenic was characterized by x-ray adsorption spectroscopy (XAS). A marked decrease of the total aqueous concentrations of As and S was observed in the inoculated treatments amended with ethanol, but not in the non-inoculated controls, indicating that the As-removal was biologically mediated. The pH dramatically affected the extent and rate of As removal, as well as the stoichiometric composition of the precipitate. The amount of As removed was 2-fold higher and the rate of the As removal was up to 17-fold greater at pH 6.1 than at pH 7.2. Stoichiometric analysis and XAS results confirmed the precipitate was composed of a mixture of orpiment and realgar, and the proportion of orpiment in the sample increased with increasing pH. The results taken as a whole suggest that ASM formation is greatly enhanced at mildly acidic pH conditions. PMID:25222328

  19. Biomineralization of Arsenate to Arsenic Sulfides is Greatly Enhanced at Mildly Acidic Conditions

    PubMed Central

    Rodriguez-Freire, Lucia; Sierra-Alvarez, Reyes; Root, Robert; Chorover, Jon; Field, James A.

    2014-01-01

    Arsenic (As) is an important water contaminant due to its high toxicity and widespread occurrence. Arsenic-sulfide minerals (ASM) are formed during microbial reduction of arsenate (AsV) and sulfate (SO42−). The objective of this research is to study the effect of the pH on the removal of As due to the formation of ASM in an iron-poor system. A series of batch experiments was used to study the reduction of SO42− and AsV by an anaerobic biofilm mixed culture in a range of pH conditions (6.1–7.2), using ethanol as the electron donor. Total soluble concentrations and speciation of S and As were monitored. Solid phase speciation of arsenic was characterized by x-ray adsorption spectroscopy (XAS). A marked decrease of the total aqueous concentrations of As and S was observed in the inoculated treatments amended with ethanol, but not in the non-inoculated controls, indicating that the As-removal was biologically mediated. The pH dramatically affected the extent and rate of As removal, as well as the stoichiometric composition of the precipitate. The amount of As removed was 2-fold higher and the rate of the As removal was up to 17-fold greater at pH 6.1 than at pH 7.2. Stoichiometric analysis and XAS results confirmed the precipitate was composed of a mixture of orpiment and realgar, and the proportion of orpiment in the sample increased with increasing pH. The results taken as a whole suggest that ASM formation is greatly enhanced at mildly acidic pH conditions. PMID:25222328

  20. The Formation of Fe/Mg Smectite Under Mildly Acidic Conditions on Early Mars

    NASA Technical Reports Server (NTRS)

    Sutter, B.; Golden, D. C.; Ming, Douglas W.; Niles, P. B.

    2011-01-01

    The detection of Fe/Mg smectites and carbonate in Noachian and early Hesperian terrain of Mars suggests that neutral to mildly alkaline conditions prevailed during the early history of Mars. If early Mars surface geochemical conditions were neutral to moderately alkaline with a denser CO2 atmosphere than today, then large carbonates deposits should be more widely detected in Noachian terrain. Why have so few carbonate deposits been detected compared to Fe/Mg smectites? Fe/Mg smectites on early Mars formed under mildly acidic conditions, which would preclude the extensive formation of carbonate deposits. The goal of the proposed work is to evaluate the formation of Fe/Mg smectites under mildly acidic conditions.

  1. Metal-Free Markovnikov-Type Alkyne Hydration under Mild Conditions.

    PubMed

    Liu, Wenbo; Wang, Haining; Li, Chao-Jun

    2016-05-01

    A Markovnikov-type alkyne hydration protocol is presented using 20% CF3SO3H (TfOH) as the catalyst under unprecedented mild conditions applicable to various alkynes, including terminal arylalkynes, terminal nonfunctionalized aliphatic alkynes, and internal alkynes with excellent regioselectivity in good to excellent yields (average yields >85%). The reaction procedure operates under mild conditions (25-70 °C), with broad functional group compatibility, and uses only slightly more than a stoichiometric amount of water in the absence of any transition metal. The success of this protocol hinges upon the utilization of trifluoroethanol as the solvent. PMID:27082159

  2. Timescales and conditions for the aqueous alteration of chondrites

    NASA Astrophysics Data System (ADS)

    Jilly, Christine E.

    It has become well-recognized that water played a critical role in the early geological evolution of materials through observation of hydrated phases in chondritic meteorites. However, details about the mechanism, timing, and conditions of aqueous alteration are poorly constrained. This dissertation investigates water-driven processes in Renazzo-like (CR) carbonaceous chondrites, with some comparison to the heavily altered and Mighei-like (CM) chondrites. CR chondrites were chosen as the focus of this study, as they are the only chondrite group to range from practically anhydrous to completely hydrated, providing petrographic context for the aqueous alteration process. The central goal of the thesis is to elucidate the complete mechanism of aqueous alteration, from primary anhydrous components to secondary minerals. This research uses a variety of micro-analytical techniques to address three main objectives: 1) to detail the petrographic context, 2) to quantify the onset and duration of alteration using radiometric dating, and 3) to constrain the fluid chemistry and conditions for aqueous alteration. On a microscopic scale, fine-grained matrices and glassy mesostases were the first phases to become altered, allowing for elemental transport over short distances (< 100 microns). As alteration progressed, the iron-metal was oxidized, and silicate phenocrysts were pseudomorphically replaced. 53Mn-53 Cr radiometric dating of secondary carbonates in CR chondrites show that aqueous alteration began quickly after accretion of the parent body, ~4 Myr after the beginning of the Solar System. This is contemporaneous with dolomite formation in the CM chondrite Sutter's Mill and with carbonate formation in other CM chondrites. However, the calcite age from a heavily hydrated CR lithology indicates that late-stage alteration occurred ~12 Myr after the beginning of the Solar System. The oxygen isotopic compositions of magnetite and carbonate minerals reveal that altering fluid

  3. Mild Transient Hypercapnia as a Novel Fear Conditioning Stimulus Allowing Re-Exposure during Sleep

    PubMed Central

    Balbir, Alex; Germain, Anne; O’Donnell, Christopher P.

    2013-01-01

    Introduction Studies suggest that sleep plays a role in traumatic memories and that treatment of sleep disorders may help alleviate symptoms of posttraumatic stress disorder. Fear-conditioning paradigms in rodents are used to investigate causal mechanisms of fear acquisition and the relationship between sleep and posttraumatic behaviors. We developed a novel conditioning stimulus (CS) that evoked fear and was subsequently used to study re-exposure to the CS during sleep. Methods Experiment 1 assessed physiological responses to a conditioned stimulus (mild transient hypercapnia, mtHC; 3.0% CO2; n = 17)+footshock for the purpose of establishing a novel CS in male FVB/J mice. Responses to the novel CS were compared to tone+footshock (n = 18) and control groups of tone alone (n = 17) and mild transient hypercapnia alone (n = 10). A second proof of principle experiment re-exposed animals during sleep to mild transient hypercapnia or air (control) to study sleep processes related to the CS. Results Footshock elicited a response of acute tachycardia (30–40 bpm) and increased plasma epinephrine. When tone predicted footshock it elicited mild hypertension (1–2 mmHg) and a three-fold increase in plasma epinephrine. When mtHC predicted footshock it also induced mild hypertension, but additionally elicited a conditioned bradycardia and a smaller increase in plasma epinephrine. The overall mean 24 hour sleep–wake profile was unaffected immediately after fear conditioning. Discussion Our study demonstrates the efficacy of mtHC as a conditioning stimulus that is perceptible but innocuous (relative to tone) and applicable during sleep. This novel model will allow future studies to explore sleep-dependent mechanisms underlying maladaptive fear responses, as well as elucidate the moderators of the relationship between fear responses and sleep. PMID:23840700

  4. A mild, near-surface aqueous environment on Noachian Mars preserved in ALH84001

    NASA Astrophysics Data System (ADS)

    Halevy, I.; Fischer, W. W.; Eiler, J. M.

    2011-12-01

    Despite widespread evidence for liquid water at the surface of Mars during parts of the Noachian epoch, the temperature of early aqueous environments has been impossible to establish, raising questions of whether Mars' surface was ever warmer than today. This has hindered insight into aqueous alteration processes, which, on the basis of orbital spectroscopy, appear to have been prevalent on Noachian Mars. It is important to understand such processes, as they link the observed secondary mineral assemblages to interactions between primary igneous silicates and the surface environment (atmosphere-hydrosphere). We have addressed this problem by determining the precipitation temperatures of secondary carbonate minerals preserved in the oldest known sample of Mars' crust-the meteorite Allan Hills 84001 (ALH84001). Using carbonate 'clumped' isotope thermometry we have found that the carbonates in ALH84001, which are 3.9-4.0 billion years old, formed at a temperature of ~18±4°C. With temperature known, we used the carbon and oxygen isotopic composition of the carbonates, as constrained by both our measurements and previous acid digestion and ion microprobe studies, to develop a model for their formation process and environment. The observed isotopic variation is best explained by carbonate precipitation out of a gradually evaporating, shallow subsurface aqueous solution (e.g. a regolith aquifer) at near-constant temperatures. Furthermore, on the basis of the isotopic composition of the earliest precipitated carbonates in ALH84001, the volatiles from which they formed (H2O and CO2) came not from depth, but from the early Martian surface. The occurrence of carbonates in other SNC meteorites and as a minor component of Martian dust implies that environments analogous to the one we studied may have been important in generating some of the observed secondary mineral assemblages by interaction between Mars' igneous crust and its atmosphere-hydrosphere.

  5. The Formation of Fe/Mg Smectite Under Mildly Acidic Conditions on Early Mars

    NASA Astrophysics Data System (ADS)

    Sutter, B.; Golden, D. C.; Ming, D.; Niles, P. B.

    2011-12-01

    The detection of Fe/Mg smectites and carbonate in Noachian and early Hesperian terrain of Mars has been used to suggest that neutral to mildly alkaline conditions prevailed during the early history of Mars. However, if early Mars was neutral to moderately alkaline with a denser CO2 atmosphere than today, then "large" carbonates deposits should be more widely detected in Noachian terrain. The critical question is: Why have so few carbonate deposits been detected compared to Fe/Mg smectites? We suggest that Fe/Mg smectites on early Mars formed under mildly acidic conditions, which would inhibit the extensive formation of carbonate deposits. The goal of this work is to evaluate the formation of Fe/Mg smectites under mildly acidic conditions. The stability of smectites under mildly acidic conditions is attributed to elevated Fe/Mg activities that inhibit smectite dissolution. Beidelite and saponite have been shown to form from hydrothermal alteration of basaltic glass at pH 3.5-4.0 in seawater solutions. Nontronite is also known to be stable in mildly acidic systems associated with mafic and ultramafic rock. Nontronite was shown to form in acid sulfate soils in the Bangkok Plain, Thailand due to oxidation of Fe-sulfides that transformed saponite to nontronite. Smectite is known to transform to kaolinite in naturally acid soils due to selective leaching of Mg. However, if Mg removal is limited, then based on equilibrium relationships, the dissolution of smectite should be minimized. If Fe and Mg solution activities are sufficiently high, such as might be found in a low water/rock ratio system that is poorly drained, smectite could form and remain stable under mildly acidic conditions on Mars. The sources of mild acidity on early Mars includes elevated atmospheric CO2 levels, Fe-hydrolysis reactions, and the presence of volcanic SO2 aerosols. Equilibrium calculations dictate that water equilibrated with an early Mars CO2 atmosphere at 1 to 4 bar yields a pH of 3.6 to 3

  6. The Formation of Fe/Mg Smectite Under Mildly Acidic Conditions on Early Mars

    NASA Technical Reports Server (NTRS)

    Sutter, Brad; Golden, D. C.; Ming, Douglas W.; Niles, P. B.

    2011-01-01

    The detection of Fe/Mg smectites and carbonate in Noachian and early Hesperian terrain of Mars has been used to suggest that neutral to mildly alkaline conditions prevailed during the early history of Mars. However, if early Mars was neutral to moderately alkaline with a denser CO2 atmosphere than today, then large carbonates deposits should be more widely detected in Noachian terrain. The critical question is: Why have so few carbonate deposits been detected compared to Fe/Mg smectites? We suggest that Fe/Mg smectites on early Mars formed under mildly acidic conditions, which would inhibit the extensive formation of carbonate deposits. The goal of this work is to evaluate the formation of Fe/Mg smectites under mildly acidic conditions. The stability of smectites under mildly acidic conditions is attributed to elevated Fe/Mg activities that inhibit smectite dissolution. Beidelite and saponite have been shown to form from hydrothermal alteration of basaltic glass at pH 3.5-4.0 in seawater solutions. Nontronite is also known to be stable in mildly acidic systems associated with mafic and ultramafic rock. Nontronite was shown to form in acid sulfate soils in the Bangkok Plain, Thailand due to oxidation of Fe-sulfides that transformed saponite to nontronite. Smectite is known to transform to kaolinite in naturally acid soils due to selective leaching of Mg. However, if Mg removal is limited, then based on equilibrium relationships, the dissolution of smectite should be minimized. If Fe and Mg solution activities are sufficiently high, such as might be found in a low water/rock ratio system that is poorly drained, smectite could form and remain stable under mildly acidic conditions on Mars. The sources of mild acidity on early Mars includes elevated atmospheric CO2 levels, Fe-hydrolysis reactions, and the presence of volcanic SO2 aerosols. Equilibrium calculations dictate that water equilibrated with an early Mars CO2 atmosphere at 1 to 4 bar yields a pH of 3.6 to 3

  7. Self-assembled monolayers of flufenaminate anions on mild steel surface formed in aqueous solution

    NASA Astrophysics Data System (ADS)

    Kazansky, Leonid P.; Kuznetsov, Yuri I.; Andreeva, Nina P.; Bober, Yana G.

    2010-12-01

    Adsorption of derivative of phenylanthranilic acid - flufenamic acid (FFA) on the "oxide-free" and oxidized surface of mild steel in neutral borate buffer solution was studied by ellipsometry and XPS. Anodic polarization curves reveal that complete suppression of the anodic dissolution of iron is achieved at FFA concentration Cin = 3.8 mM. Besides, adding FFA substantially shifts the pitting potential from 0.06 V to 0.67 V. Ellipsometric studies have shown that at the applied potential -0.65 V, when the surface is free from the oxide layer, FFA forms monomolecular layer. To characterize the surface layers formed after exposing the sample in 5 mM FFA solution the XPS was used to assess the composition and the thickness of the layers. Using the intensities of the Fe 2p, Fe 3p, N 1s, F 1s, O 1s and C 1s and analyzing the angle resolved XPS data the FFA molecules have been shown to form monomolecular layer in which FFA is (vertically or slightly inclined) anchored by iron cations through oxygen atoms of carboxyl group to the surface and the fluorine atoms of CF 3 groups form the utmost layer. Similar orientation is also assumed for FFA molecules adsorbed on the oxidized iron surface. It seems that the layer formed by FFA or similar molecules may serve a robust interface for grafting other substances on such a functionalized surface.

  8. Mild and selective Et2Zn-catalyzed reduction of tertiary amides under hydrosilylation conditions.

    PubMed

    Kovalenko, Oleksandr O; Volkov, Alexey; Adolfsson, Hans

    2015-02-01

    Diethylzinc (Et2Zn) can be used as an efficient and chemoselective catalyst for the reduction of tertiary amides under mild reaction conditions employing cost-effective polymeric silane (PMHS) as the hydride source. Crucial for the catalytic activity was the addition of a substoichiometric amount of lithium chloride to the reaction mixture. A series of amides containing different additional functional groups were reduced to their corresponding amines, and the products were isolated in good-to-excellent yields. PMID:25587664

  9. Critical conditions for initiation of localized corrosion of mild steels in contact with bentonite used in geological disposal packages of nuclear waste

    SciTech Connect

    Nakayama, Guen; Akashi, Masatsune

    1993-12-31

    In the current design of geological disposal of high-level nuclear waste, the use of bentonite to stand as an artificial barrier-cum-buffer between the host rock and the packages made of mild steel is being investigated. Although mild steels commonly have been considered to be passivity in alkaline environments, under certain circumstances, they become liable to localized corrosion, e.g., pitting corrosion and crevice corrosion. Since bentonite can turn the environment alkaline to a pH of approximately 10 when it is mixed with groundwater, critical conditions for the initiation of localized corrosion of mild steel must be known to evaluate the extremely long time integrity of disposal packages serving in such an environment. This paper presents and discusses the observations and results acquired in a series of critical conditions for the initiation of localized corrosion of mild steels in various groundwater-bentonite environments at 20C, with a deaerated aqueous solution of 1 mMol/L [HCO{sub 3}{sup -}] + 10 ppm [Cl{sup -}], simulating the natural groundwater and varying the bentonite content.

  10. Effects of surface condition on aqueous corrosion and environmental embrittlement of iron aluminides

    SciTech Connect

    Perrin, R.L.; Buchanan, R.A.

    1996-08-01

    Effects of retained high-temperature surface oxides, produced during thermomechanical processing and/or heat treatment, on the aqueous-corrosion and environmental-embrittlement characteristics of Fe{sub 3}Al-based iron aluminides (FA-84, FA-129 and FAL-Mo), a FeAl-based iron aluminide (FA-385), and a disordered low-aluminum Fe-Al alloy (FAPY) were evaluated. All tests were conducted at room temperature in a mild acid-chloride solution. In cyclic-anodic-polarization testing for aqueous-corrosion behavior, the surface conditions examined were: as-received (i.e., with the retained high-temperature oxides), mechanically cleaned and chemically cleaned. For all materials, the polarization tests showed the critical pitting potentials to be significantly lower in the as-received condition than in the mechanically-cleaned and chemically-cleaned conditions. These results indicate detrimental effects of the retained high-temperature oxides in terms of increased susceptibilities to localized corrosion. In 200-hour U-bend stress-corrosion-cracking tests for environmental-embrittlement behavior, conducted at open-circuit corrosion potentials and at a hydrogen-charging potential of {minus}1500 mV (SHE), the above materials (except FA-385) were examined with retained oxides and with mechanically cleaned surfaces. At the open-circuit corrosion potentials, none of the materials in either surface condition underwent cracking. At the hydrogen-charging potential, none of the materials with retained oxides underwent cracking, but FA-84, FA-129 and FAL-Mo in the mechanically cleaned condition did undergo cracking. These results suggest beneficial effects of the retained high-temperature oxides in terms of increased resistance to environmental hydrogen embrittlement.

  11. Production of Retrovirus-Based Vectors in Mildly Acidic pH Conditions.

    PubMed

    Holic, Nathalie; Fenard, David

    2016-01-01

    Gene transfer vectors based on retroviridae are increasingly becoming a tool of choice for biomedical research and for the development of biotherapies in rare diseases or cancers. To meet the challenges of preclinical and clinical production, different steps of the production process of self-inactivating γ-retroviral (RVs) and lentiviral vectors (LVs) have been improved (e.g., transfection, media optimization, cell culture conditions). However, the increasing need for mass production of such vectors is still a challenge and could hamper their availability for therapeutic use. Recently, we observed that the use of a neutral pH during vector production is not optimal. The use of mildly acidic pH conditions (pH 6) can increase by two- to threefold the production of RVs and LVs pseudotyped with the vesicular stomatitis virus G (VSV-G) or gibbon ape leukemia virus (GALV) glycoproteins. Here, we describe the production protocol in mildly acidic pH conditions of GALVTR- and VSV-G-pseudotyped LVs using the transient transfection of HEK293T cells and the production protocol of GALV-pseudotyped RVs produced from a murine producer cell line. These protocols should help to achieve higher titers of vectors, thereby facilitating experimental research and therapeutic applications. PMID:27317171

  12. MICROWAVE-ASSISTED PREPARATION OF 1-BUTYL-3-METHYLIMIDAZOLIUM TETRACHLOROGALLATE AND ITS CATALYTIC USE IN ACETAL FORMATION UNDER MILD CONDITIONS

    EPA Science Inventory

    1-Butyl-3-methylimidazolium tetrachlorogallate, [bmim][GaCl4], prepared via microwave-assisted protocol, is found to be an active catalyst for the efficient acetalization of aldehydes under mild conditions.

  13. Degradation of textile dyes using immobilized lignin peroxidase-like metalloporphines under mild experimental conditions

    PubMed Central

    2012-01-01

    Background Synthetic dyes represent a broad and heterogeneous class of durable pollutants, that are released in large amounts by the textile industry. The ability of two immobilized metalloporphines (structurally emulating the ligninolytic peroxidases) to bleach six chosen dyes (alizarin red S, phenosafranine, xylenol orange, methylene blue, methyl green, and methyl orange) was compared to enzymatic catalysts. To achieve a green and sustainable process, very mild conditions were chosen. Results IPS/MnTSPP was the most promising biomimetic catalyst as it was able to effectively and quickly bleach all tested dyes. Biomimetic catalysis was fully characterized: maximum activity was centered at neutral pH, in the absence of any organic solvent, using hydrogen peroxide as the oxidant. The immobilized metalloporphine kept a large part of its activity during multi-cycle use; however, well-known redox mediators were not able to increase its catalytic activity. IPS/MnTSPP was also more promising for use in industrial applications than its enzymatic counterparts (lignin peroxidase, laccase, manganese peroxidase, and horseradish peroxidase). Conclusions On the whole, the conditions were very mild (standard pressure, room temperature and neutral pH, using no organic solvents, and the most environmental-friendly oxidant) and a significant bleaching and partial mineralization of the dyes was achieved in approximately 1 h. Therefore, the process was consistent with large-scale applications. The biomimetic catalyst also had more promising features than the enzymatic catalysts. PMID:23256784

  14. Thermodynamics of Water and Aqueous Solutions under Mantle Conditions

    NASA Astrophysics Data System (ADS)

    Brown, J. M.; Vance, S.; Bollengier, O.; Shaw, G. H.; Abramson, E.

    2014-12-01

    Interactions between aqueous solutions and rocks extending from the surface and through the deep mantle control the state and evolution of Earth. The accurate representation of the fluid chemical energy as a function of pressure, temperature and composition over a wide range of conditions is prerequisite in understanding phase equilibria and solubilities in multicomponent systems. End-member thermodynamic properties of water (densities, specific heats, sound speeds, and more) have been extensively explored in a regime below about 100 MPa and an available complex formulation for the Helmholtz free energy (IAPWS-95) accurately represents these data and a smaller number of measurements extending to 1 GPa. However, this parameterization systematically misfits higher pressure data and is not easily adjusted to provide a better description. To address these points, we developed a flexible framework for the acquisition and description of Gibbs' free energy of water and aqueous solutions. Through use of local basis functions, the thermodynamic state surface can be adjusted to account for improved experimental constraints or for results in new regimes of pressure and temperature. Based on our experimental work on pure water, MgSO4(aq), Na2SO4(aq), and ammonia-water mixtures, new insights are provided on the volumetric behavior of fluids at high pressure. For the ionic solutions, where the partial molar volume at infinite dilution, Vo, is dominated by electrostriction at low pressure, the initial pressure derivative of Vo is large. At high pressure, where Vo is more related to the "size" of the ions, it is only weakly pressure dependent. The non-ideal behavior of these ionic solutions over an extended range of pressures and temperatures is successfully described using a standard three-term parameterization representing solvent (Debye-Hückel), solvent-ion, and ion-ion interactions. The solvent-ion and ion-ion interaction parameters show less dependence on pressure and

  15. Pretreatment combining ultrasound and sodium percarbonate under mild conditions for efficient degradation of corn stover.

    PubMed

    Nakashima, Kazunori; Ebi, Yuuki; Kubo, Masaki; Shibasaki-Kitakawa, Naomi; Yonemoto, Toshikuni

    2016-03-01

    Ultrasound (US) can be used to disrupt microcrystalline cellulose to give nanofibers via ultrasonic cavitation. Sodium percarbonate (SP), consisting of sodium carbonate and hydrogen peroxide, generates highly reactive radicals, which cause oxidative delignification. Here, we describe a novel pretreatment technique using a combination of US and SP (US-SP) for the efficient saccharification of cellulose and hemicellulose in lignocellulosic corn stover. Although US-SP pretreatment was conducted under mild condition (i.e., at room temperature and atmospheric pressure), the pretreatment greatly increased lignin removal and cellulose digestibility. We also determined the optimum US-SP treatment conditions, such as ultrasonic power output, pretreatment time, pretreatment temperature, and SP concentration for an efficient cellulose saccharification. Moreover, xylose could be effectively recovered from US-SP pretreated biomass without the formation of microbial inhibitor furfural. PMID:26547502

  16. Osmium(0) nanoclusters stabilized by zeolite framework; highly active catalyst in the aerobic oxidation of alcohols under mild conditions.

    PubMed

    Zahmakiran, Mehmet; Akbayrak, Serdar; Kodaira, Tetsuya; Ozkar, Saim

    2010-08-28

    Osmium(0) nanoclusters stabilized by zeolite-Y framework were reproducibly prepared by a simple two step procedure involving the incorporation of osmium(III) cations into the zeolite matrix by ion-exchange, followed by their reduction within the cavities of zeolite with sodium borohydride in aqueous solution all at room temperature. The composition and morphology of osmium(0) nanoclusters stabilized by zeolite framework, as well as the integrity and crystallinity of the host material were investigated by using ICP-OES, XRD, XPS, SEM, TEM, HRTEM, TEM/EDX, mid-IR, far-IR spectroscopies, and N(2)-adsorption/desorption technique. The results of the multiprong analysis reveal the formation of osmium(0) nanoclusters within the cavities of zeolite-Y without causing alteration in the framework lattice, formation of mesopores, or loss in the crystallinity of the host material. More importantly, far-IR studies showed that after the reduction of Os(3+) cations by sodium borohydride the Na(+) cations reoccupy their authentic cation sites restoring the integrity of zeolite-Y. The catalytic activity of osmium(0) nanoclusters stabilized by zeolite framework was tested in the aerobic oxidation of activated, unactivated and heteroatom containing alcohols to carbonyl compounds and was found to provide high activity and selectivity even under mild conditions (80 degrees C and 1 atm O(2) or air). Moreover, they were found to be stable enough to be isolated and bottled as solid material, which can be reused as active catalyst under the identical conditions of the first run. PMID:20614055

  17. Efficient and selective degradation of polyethylenes into liquid fuels and waxes under mild conditions

    PubMed Central

    Jia, Xiangqing; Qin, Chuan; Friedberger, Tobias; Guan, Zhibin; Huang, Zheng

    2016-01-01

    Polyethylene (PE) is the largest-volume synthetic polymer, and its chemical inertness makes its degradation by low-energy processes a challenging problem. We report a tandem catalytic cross alkane metathesis method for highly efficient degradation of polyethylenes under mild conditions. With the use of widely available, low-value, short alkanes (for example, petroleum ethers) as cross metathesis partners, different types of polyethylenes with various molecular weights undergo complete conversion into useful liquid fuels and waxes. This method shows excellent selectivity for linear alkane formation, and the degradation product distribution (liquid fuels versus waxes) can be controlled by the catalyst structure and reaction time. In addition, the catalysts are compatible with various polyolefin additives; therefore, common plastic wastes, such as postconsumer polyethylene bottles, bags, and films could be converted into valuable chemical feedstocks without any pretreatment. PMID:27386559

  18. Mild solutions to a measure-valued mass evolution problem with flux boundary conditions

    NASA Astrophysics Data System (ADS)

    Evers, Joep H. M.; Hille, Sander C.; Muntean, Adrian

    2015-08-01

    We investigate the well-posedness and approximation of mild solutions to a class of linear transport equations on the unit interval [ 0, 1 ] endowed with a linear discontinuous production term, formulated in the space M ([ 0, 1 ]) of finite Borel measures. Our working technique includes a detailed boundary layer analysis in terms of a semigroup representation of solutions in spaces of measures able to cope with the passage to the singular limit where thickness of the layer vanishes. We obtain not only a suitable concept of solutions to the chosen measure-valued evolution problem, but also derive convergence rates for the approximation procedure and get insight in the structure of flux boundary conditions for the limit problem.

  19. Efficient and selective degradation of polyethylenes into liquid fuels and waxes under mild conditions.

    PubMed

    Jia, Xiangqing; Qin, Chuan; Friedberger, Tobias; Guan, Zhibin; Huang, Zheng

    2016-06-01

    Polyethylene (PE) is the largest-volume synthetic polymer, and its chemical inertness makes its degradation by low-energy processes a challenging problem. We report a tandem catalytic cross alkane metathesis method for highly efficient degradation of polyethylenes under mild conditions. With the use of widely available, low-value, short alkanes (for example, petroleum ethers) as cross metathesis partners, different types of polyethylenes with various molecular weights undergo complete conversion into useful liquid fuels and waxes. This method shows excellent selectivity for linear alkane formation, and the degradation product distribution (liquid fuels versus waxes) can be controlled by the catalyst structure and reaction time. In addition, the catalysts are compatible with various polyolefin additives; therefore, common plastic wastes, such as postconsumer polyethylene bottles, bags, and films could be converted into valuable chemical feedstocks without any pretreatment. PMID:27386559

  20. Effects of aqueous extract of Hibiscus sabdariffa on the renin-angiotensin-aldosterone system of Nigerians with mild to moderate essential hypertension: A comparative study with lisinopril

    PubMed Central

    Nwachukwu, Daniel Chukwu; Aneke, Eddy Ikemefuna; Obika, Leonard Fidelis; Nwachukwu, Nkiru Zuada

    2015-01-01

    Objectives: The present study investigated the effects of aqueous extract of Hibiscus sabdariffa (HS) on the three basic components of renin-angiotensin-aldosterone system: Plasma renin, serum angiotensin-converting enzyme (ACE), and plasma aldosterone (PA) in mild to moderate essential hypertensive Nigerians and compared with that of lisinopril, an ACE inhibitor. Materials and Methods: A double-blind controlled randomized clinical study was used. Seventy-eight newly diagnosed but untreated mild to moderate hypertensive subjects attending Medical Outpatients Clinic of Enugu State University Teaching Hospital, Enugu were recruited for the study. Those in Group A received placebo (150 mg/kg/day), Group B were given lisinopril (10 mg once daily) while those in Group C received aqueous extract of HS (150 mg/kg/day). After 4 weeks of treatment, the levels of plasma renin, serum ACE, and PA were determined. Results: HS and lisinopril significantly (P < 0.001) reduced PA compared to placebo by 32.06% and 30.01%, respectively. Their effects on serum ACE and plasma renin activity (PRA) were not significant compared to placebo; they reduced ACE by 6.63% and 5.67% but increased plasma PRA by 2.77% and 5.36%, respectively. Conclusion: HS reduced serum ACE and PA in mild to moderate hypertensive Nigerians with equal efficacy as lisinopril. These actions are possibly due to the presence of anthocyanins in the extract. PMID:26600645

  1. Hetropolyacid-Catalyzed Oxidation of Glycerol into Lactic Acid under Mild Base-Free Conditions.

    PubMed

    Tao, Meilin; Yi, Xiaohu; Delidovich, Irina; Palkovits, Regina; Shi, Junyou; Wang, Xiaohong

    2015-12-21

    Lactic acid (LA) is a versatile platform molecule owing to the opportunity to transform this compound into useful chemicals and materials. Therefore, efficient production of LA based on inexpensive renewable feedstocks is of utmost importance for insuring its market availability. Herein, we report the efficient conversion of glycerol into LA catalyzed by heteropolyacids (HPAs) under mild base-free conditions. The catalytic performance of molecular HPAs appears to correlate with their redox potential and Brønsted acidity. Namely, H3 PMo(12)O(40) (HPMo) exhibits the best selectivity towards LA (90 %) with 88 % conversion of glycerol. Loading of HPMo onto a carbon support (HPMo/C) further improves LA productivity resulting in 94 % selectivity at 98 % conversion under optimized reaction conditions. The reaction takes place through the formation of dihydroxyacetone/glyceraldehyde and pyruvaldehyde as intermediates. No leaching of HPMo was observed under the applied reaction conditions and HPMo/C could be recycled 5 times without significant loss of activity. PMID:26611678

  2. Effect of surface condition on the aqueous corrosion behavior of iron aluminies

    SciTech Connect

    Buchanan, R.A.; Perrin, R.L.

    1995-08-01

    The effects of retained high-temperature surface oxides, produced during thermomechanical processing and/or heat treatment, on the aqueous-corrosion characteristics of Fe-Al-based alloys were evaluated by electrochemical methods. Cyclic anodic polarization evaluations were conducted at room temperature in a mild acid-chloride solution (pH = 4,200 ppm Cl{sup {minus}}) on the Fe{sub 3}Al-based iron aluminides, FA-84 (Fe-28Al-2Cr-0.05B, at %), FA-129 (Fe-28Al-5Cr-0.5Nb-0.2C, at %), and FAL-Mo (Fe-28Al-5Cr-1Mo-0.04B-0.08Zr, at %), on the FeAl-based iron aluminide, FA-385 (Fe-35.65Al-0.20Mo-0.05Zr-0.11C, at %). The surface conditions evaluated were: As received (i.e. with the retained high-temperature oxides), mechanically cleaned (ground through 600-grit SiC paper), and chemically cleaned (10% HNO{sub 3}, 2%HF, at 43 {degree}C). The principal electrochemical parameter of interest was the critical putting potential with lower values indicating less resistance to chloride-induced localized corrosion. For all materials evaluated, the critical pitting potential was found to be significantly lower in the as-received condition than in the mechanically-cleaned and chemically-cleaned conditions. Mechanisms responsible for the detrimental high-temperature-oxide effect are under study.

  3. Flow-Assisted Synthesis of [10]Cycloparaphenylene through Serial Microreactions under Mild Conditions.

    PubMed

    Kim, Heejin; Lee, Hyune-Jea; Kim, Dong-Pyo

    2016-01-22

    Cycloparaphenylene (CPP) has been recognized as an attractive template for the bottom-up synthesis of carbon nanotubes with uniform diameter, and is important for the chemistry of graphitic as well as ring-shaped macromolecules. However, the reported routes from halogenated benzenes have suffered from low yields even under time- and labor-consuming multistep conditions. Herein we report a flow-assisted synthesis of [10]CPP in four steps under mild conditions. For the synthesis, a selective nucleophilic addition of the unprotected diketone without the double-added byproduct was achieved within 3 s in high yield. Subsequently, the obtained compound was reacted with dilithiated benzene at 25 °C to form a U-shaped precursor for CPP in a separate microreactor, which was finally dimerized and aromatized to obtain [10]CPP by a two-step in-flask reaction. Precise control of time and flow facilitated by the flow-assisted system enabled the development of an efficient synthetic route for [10]CPP. PMID:26661931

  4. Chemoselective Oxidation of Benzyl, Amino, and Propargyl Alcohols to Aldehydes and Ketones under Mild Reaction Conditions

    PubMed Central

    Reddy, C B Rajashekar; Reddy, Sabbasani Rajasekhara; Naidu, Shivaji

    2015-01-01

    Catalytic oxidation reactions often suffer from drawbacks such as low yields and poor selectivity. Particularly, selective oxidation of alcohols becomes more difficult when a compound contains more than one oxidizable functional group. In order to deliver a methodology that addresses these issues, herein we report an efficient, aerobic, chemoselective and simplified approach to oxidize a broad range of benzyl and propargyl alcohols containing diverse functional groups to their corresponding aldehydes and ketones in excellent yields under mild reaction conditions. Optimal yields were obtained at room temperature using 1 mmol substrate, 10 mol % copper(I) iodide, 10 mol % 4-dimethylaminopyridine (DMAP), and 1 mol % 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) in acetonitrile, under an oxygen balloon. The catalytic system can be applied even when sensitive and oxidizable groups such as alkynes, amines, and phenols are present; starting materials and products containing such groups were found to be stable under the developed conditions. PMID:25969806

  5. Chemoselective Oxidation of Benzyl, Amino, and Propargyl Alcohols to Aldehydes and Ketones under Mild Reaction Conditions.

    PubMed

    Reddy, C B Rajashekar; Reddy, Sabbasani Rajasekhara; Naidu, Shivaji

    2015-04-01

    Catalytic oxidation reactions often suffer from drawbacks such as low yields and poor selectivity. Particularly, selective oxidation of alcohols becomes more difficult when a compound contains more than one oxidizable functional group. In order to deliver a methodology that addresses these issues, herein we report an efficient, aerobic, chemoselective and simplified approach to oxidize a broad range of benzyl and propargyl alcohols containing diverse functional groups to their corresponding aldehydes and ketones in excellent yields under mild reaction conditions. Optimal yields were obtained at room temperature using 1 mmol substrate, 10 mol % copper(I) iodide, 10 mol % 4-dimethylaminopyridine (DMAP), and 1 mol % 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) in acetonitrile, under an oxygen balloon. The catalytic system can be applied even when sensitive and oxidizable groups such as alkynes, amines, and phenols are present; starting materials and products containing such groups were found to be stable under the developed conditions. PMID:25969806

  6. Synthesis of boron suboxide from boron and boric acid under mild pressure and temperature conditions

    SciTech Connect

    Jiao, Xiaopeng; Jin, Hua; Ding, Zhanhui; Yang, Bin; Lu, Fengguo; Zhao, Xudong; Liu, Xiaoyang; Peng, Liping

    2011-05-15

    Graphical abstract: Well-crystallized and icosahedral B{sub 6}O crystals were prepared by reacting boron and boric acid at milder reaction conditions (1 GPa and 1300 {sup o}C for 2 h) as compared to previous work.. Research highlights: {yields} Well-crystallized icosahedral B{sub 6}O was synthesized by reacting boric acid and boron. {yields} The synthesis conditions (1 GPa and 1300 {sup o}C for 2 h) are milder in comparison with previous work. {yields} The more practical synthesis method may make B{sub 6}O as a potential substitute for diamond in industry. -- Abstract: Boron suboxide (B{sub 6}O) was synthesized by reacting boron and boric acid (H{sub 3}BO{sub 3}) at pressures between 1 and 10 GPa, and at temperatures between 1300 and 1400 {sup o}C. The B{sub 6}O samples prepared were icosahedral with diameters ranging from 20 to 300 nm. Well-crystallized and icosahedral crystals with an average size of {approx}100 nm can be obtained at milder reaction conditions (1 GPa and 1300 {sup o}C for 2 h) as compared to previous work. The bulk B{sub 6}O sample was stable in air at 600 {sup o}C and then slowly oxidized up to 1000 {sup o}C. The relatively mild synthetic conditions developed in this study provide a more practical synthesis of B{sub 6}O, which may potentially be used as a substitute for diamond in industry as a new superhard material.

  7. Sterically-controlled intermolecular Friedel-Crafts acylation with twisted amides via selective N-C cleavage under mild conditions.

    PubMed

    Liu, Yongmei; Meng, Guangrong; Liu, Ruzhang; Szostak, Michal

    2016-05-21

    Highly chemoselective Friedel-Crafts acylation with twisted amides under mild conditions is reported for the first time. The reaction shows high functional group tolerance, obviating the need for preformed sensitive organometallic reagents and expensive transition metal catalysts. The high reactivity of amides is switched on by ground-state steric distortion to disrupt the amide bond nN→πCO* resonance as a critical design feature. Conceptually, this new acid-promoted mechanism of twisted amides provides direct access to bench-stable acylating reagents under mild, metal-free conditions. PMID:27139813

  8. Evolutionary optimization for conditions of variable BHF for springback reduction in AHSS-mild steel TWB

    NASA Astrophysics Data System (ADS)

    Nguyen, N.-T.; Chakraborti, N.; Barlat, F.

    2013-12-01

    In this study, the advanced high strength steels (AHSS)/mild steel TWB sheet is applied to the U-draw bending springback under non-constant blank holding force (BHF). On both sides of the blank, two different BHF-punch stroke are applied. A systematic approach to obtain optimal BHF-stroke profiles is proposed. The optimal condition would require satisfying two conflicting objectives simultaneously: (1) minimize springback deformation and (2) minimize the forming severity, leading to a Pareto-optimal problem. The optimization procedure consists of the following steps: sampling design, finite element (FE) simulations, metamodeling, and finally the calculation of a Pareto-frontier. PAM-STAMP® FE software is employed in this study. The generated outputs of FE simulations on some statistically significant sampling points are then used for the construction of metamodels of optimum accuracy and complexity, which, in turn, were used to evaluate the output for any set of inputs, replacing the computing intensive FE simulations. A novel genetic algorithms based multi-objective optimization technique is applied for optimization. Yet far to be completely removed, springback in TWB can be appreciably reduced using the proposed approach of variable BHF control.

  9. Examination of the interaction of different lighting conditions and chronic mild stress in animal model.

    PubMed

    Muller, A; Gal, N; Betlehem, J; Fuller, N; Acs, P; Kovacs, G L; Fusz, K; Jozsa, R; Olah, A

    2015-09-01

    We examined the effects of different shift work schedules and chronic mild stress (CMS) on mood using animal model. The most common international shift work schedules in nursing were applied by three groups of Wistar-rats and a control group with normal light-dark cycle. One subgroup from each group was subjected to CMS. Levels of anxiety and emotional life were evaluated in light-dark box. Differences between the groups according to independent and dependent variables were examined with one- and two-way analysis of variance, with a significance level defined at p < 0.05. Interaction of lighting regimen and CMS was proved to be significant according to time spent in the light compartment and the average number of changes between the light and dark compartments. Results of our examination confirm that the changes of lighting conditions evocate anxiety more prominently than CMS. No significant differences were found between the results of the low rotating group and the control group, supposing that this schedule is the least harmful to health. Our results on the association between the use of lighting regimens and the level of CMS provide evidence that the fast rotating shift work schedule puts the heaviest load on the organism of animals. PMID:26551746

  10. Facile one-step fabrication of magnetite particles under mild hydrothermal conditions

    NASA Astrophysics Data System (ADS)

    Keerthana, D. Shanthini; Namratha, K.; Byrappa, K.; Yathirajan, H. S.

    2015-03-01

    Hydrophilic magnetite particles for biological applications were synthesized by hydrothermal method in the presence of D-Glucose as both reducing and capping agent in a facile, one-step, low energy and environmentally friendly route. The role of D-Glucose as a reducing agent in the formation of magnetite particles under mild hydrothermal conditions has been investigated. The absence of D-Glucose results in the formation of hematite. The magnetite particles synthesized were characterized using powder X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR) Spectroscopy, High Resolution Scanning Electron Microscopy (HR-SEM), Dynamic Light Scattering (DLS) and Vibrating Sample Magnetometery (VSM). The influence of the quantity of D-Glucose used and the reaction duration on the formation of magnetite were studied. DLS and HR-SEM results show that the size of the particles was in nano- to micron range. The antioxidant potency of the particles was confirmed using DPPH assay, where 2,2- Diphenyl-1-picrylhydrazyl was used as a source of free radicals. Hence the magnetite particles obtained could be considered for the use in various biological applications.

  11. Transition-Metal-Mediated Cleavage of Fluoro-Silanes under Mild Conditions.

    PubMed

    Kameo, Hajime; Kawamoto, Tatsuya; Sakaki, Shigeyoshi; Bourissou, Didier; Nakazawa, Hiroshi

    2016-02-12

    Si-F bond cleavage of fluoro-silanes was achieved by transition-metal complexes under mild and neutral conditions. The Iridium-hydride complex [Ir(H)(CO)(PPh3 )3 ] was found to readily break the Si-F bond of the diphosphine- difluorosilane {(o-Ph2 P)C6 H4 }2 Si(F)2 to afford a silyl complex [{[o-(iPh2 P)C6 H4 ]2 (F)Si}Ir(CO)(PPh3 )] and HF. Density functional theory calculations disclose a reaction mechanism in which a hypervalent silicon species with a dative Ir→Si interaction plays a crucial role. The Ir→Si interaction changes the character of the H on the Ir from hydridic to protic, and makes the F on Si more anionic, leading to the formation of H(δ+) ⋅⋅⋅F(δ-) interaction. Then the Si-F and Ir-H bonds are readily broken to afford the silyl complex and HF through σ-bond metathesis. Furthermore, the analogous rhodium complex [Rh(H)(CO)(PPh3 )3 ] was found to promote the cleavage of the Si-F bond of the triphosphine-monofluorosilane {(o-Ph2 P)C6 H4 }3 Si(F) even at ambient temperature. PMID:26836576

  12. Merging Photoredox with Palladium Catalysis: Decarboxylative ortho-Acylation of Acetanilides with α-Oxocarboxylic Acids under Mild Reaction Conditions.

    PubMed

    Zhou, Chao; Li, Pinhua; Zhu, Xianjin; Wang, Lei

    2015-12-18

    A room temperature decarboxylative ortho-acylation of acetanilides with α-oxocarboxylic acids has been developed via a novel Eosin Y with Pd dual catalytic system. This dual catalytic reaction shows a broad substrate scope and good functional group tolerance, and an array of ortho-acylacetanilides can be afforded in high yields under mild conditions. PMID:26646667

  13. Biocatalysis in semi-aqueous and nearly anhydrous conditions.

    PubMed

    Hudson, Elton P; Eppler, Ross K; Clark, Douglas S

    2005-12-01

    In the past few years there have been prolific advances in activating enzymes for nonaqueous biocatalysis. Molecular dynamics simulations complement recent experimental results and offer new insights into the deleterious effects of organic solvents, such as water stripping and active-site penetration. Methods for activating enzymes in semi-aqueous or nonaqueous media include protein engineering, chemical modification, and co-lyophilization with non-buffer salts. Enzyme immobilization on novel polymeric supports and the use of zeolite molecular sieves can also increase solvent tolerance, enhance activity, and improve enantioselectivity. The recent implementation of enzymes in ionic liquids has also led to better long-term stability relative to traditional organic solvents and the simultaneous solubilization of enzymes, cofactors and substrates. PMID:16256329

  14. Optical spectroscopy of simple aqueous solutions under extreme conditions

    NASA Astrophysics Data System (ADS)

    Vass, H.; Edington, D.; Crain, J.

    2003-06-01

    We report the results of an extensive series of Brillouin scattering experiments on simple aqueous solutions with a view to exploring their dynamical properties over a wide range of temperatures and pressures. For all solutes studied that inhibit freezing and allow access to temperatures far below the normal supercooling limit of water, we find clear spectroscopic evidence of GHz-range viscoelastic behavior below ≈-40 °C. This is manifested by a dramatic rise in the Brillouin mode frequencies accompanied by initial broadening and subsequent narrowing of the spectral linewidths on cooling. We find similar behavior in pure compressed (to between 2 and 4 kbar) supercooled water. This suggests that the low-temperature viscoelastic dynamics of these solutions is dominated by the behavior of the aqueous component which evidently exhibits a pronounced decrease in relaxation time though the temperature range over which it occurs is inaccessible unless freezing is suppressed either by pressure or the presence of solutes. No firm conclusion can be drawn concerning the proposed second critical point at these very low temperatures though it is not required for a consistent interpretation of the data. In the high-temperature regime, where the hydrogen bond structure is disrupted, we find considerable chemical sensitivity (even among the three chloride salts NaCl, CsCl, and CaCl2) in the dynamics especially in the vicinity of the liquid-gas critical point. This is in contrast to the low-temperature case where the cooperative dynamics of the water network dominates and appears to remain intact in the presence of a wide variety of solutes.

  15. X-ray photoelectron spectroscopic study of surface chemistry of dibenzyl disulfide on steel under mild and severe wear conditions

    NASA Technical Reports Server (NTRS)

    Wheeler, D. R.

    1978-01-01

    X-ray photoelectron spectroscopy was used to characterize the chemical composition of 304 stainless steel surfaces run in oil containing dibenzyl disulfide under both mild and severe wear conditions. In severe wear a sulfide was formed at the expense of the normal oxide. This was due to either chemical attack on the oxide or reaction with clean metal exposed by the wear process. In the mild wear scars there was no evidence of either sulfide or mercaptide. The oxide, however, was approximately twice as thick as the normal oxide on an unworn surface. The change in surface chemistry was primarily a function of wear rate rather than load.

  16. Green Catalytic Process for Cyclic Carbonate Synthesis from Carbon Dioxide under Mild Conditions.

    PubMed

    Lang, Xian-Dong; He, Liang-Nian

    2016-06-01

    As a renewable and abundant C1 resource possessing multiple attractive characteristics, such as low cost, nontoxicity, non-flammability, and easy accessibility, CO2 conversion into value-added chemicals and fuels can contribute to green chemistry and sustainable development. Since CO2 is a thermodynamically inert molecule, the activation of CO2 is pivotal for its effective conversion. In this regard, the formation of a transition-metal CO2 complex through direct coordination is one of the most powerful ways to induce the inert CO2 molecule to undergo chemical reactions. To date, numerous processes have been developed for efficient synthesis of cyclic carbonates from CO2 . On the basis of mechanistic understanding, we have developed efficient metal catalysts and green processes, including heterogeneous catalysis, and metal-free systems, such as ionic liquids, for cyclic carbonate synthesis. The big challenge is to develop catalysts that promote the reaction under low pressure (preferably at 1 bar). In this context, bifunctional catalysis is capable of synergistic activation of both the substrate and CO2 molecule, and thus, could render CO2 conversion smoothly under mild conditions. Alternatively, converting CO2 derivatives, that is, the captured CO2 as an activated species, would more easily take place at low pressure in comparison with gaseous CO2 . The aim of this Personal Account is to summarize versatile catalytic processes for cyclic carbonate synthesis from CO2 , including epoxide/CO2 coupling reaction, carboxylation of 1,2-diol with CO2 , oxidative cyclization of olefins with CO2 , condensation of vicinal halohydrin with CO2 , carboxylative cyclization of propargyl alcohols with CO2 , and conversion of the CO2 derivatives. PMID:27121768

  17. TOPEX/El Nino Watch - Mild La Nina Conditions Developing, November 12, 1999

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Unusually warm ocean temperatures off Asia and cool waters in the eastern and equatorial Pacific are signaling La Nina's mild return, according to the latest sea-surface heights observed by the joint NASA-French space agency's TOPEX/Poseidon satellite.

    Lower than normal sea-surface heights in the eastern North Pacific and abnormally high sea-surface heights in the western and mid-latitude Pacific are expected to drive storms coming out of the Pacific this winter, the mission data indicate. Those conditions will most likely steer storms north into the Pacific Northwest and keep the southwestern United States dryer than normal.

    The latest measurements, processed after a 10-day data cycle November 4-13 at NASA's Jet Propulsion Laboratory, Pasadena, CA, are available at http://www.jpl.nasa.gov/elnino . Sea-surface height is shown relative to normal (green) and reveals cooler water(blue and purple) measuring between 8 and 24 centimeters (3 to 9 inches) lower than average in the eastern North Pacific, from the Gulf of Alaska to central Alaska, and along the equator.

    Unusual conditions persist in the western and mid-latitude Pacific Ocean as well, with higher than average sea-surface heights(red and white) of between 8 and 24 centimeters (3 to 9 inches). These areas of increased sea-surface height and unusually warm water were present last year, but the increase in height has surpassed last year's measurements.

    The TOPEX/Poseidon satellite's measurements over the last seven and a half years have provided scientists with a comprehensive record of the 1997-1999 El Nino/La Nina climate pattern by measuring changing sea-surface heights to within 4centimeters (1.5 inches) precision.

    The U.S./French mission is managed by the Jet Propulsion Laboratory for NASA's Earth Sciences Enterprise, Washington, DC. JPL is a division of the California Institute of Technology, Pasadena, CA.

    For more information, please visit the TOPEX/Poseidon project web page at http://topex-www.jpl.nasa.gov/

  18. Investigation of acyl migration in mono- and dicaffeoylquinic acids under aqueous basic, aqueous acidic, and dry roasting conditions.

    PubMed

    Deshpande, Sagar; Jaiswal, Rakesh; Matei, Marius Febi; Kuhnert, Nikolai

    2014-09-17

    Acyl migration in chlorogenic acids describes the process of migration of cinnamoyl moieties from one quinic acid alcohol group to another, thus interconverting chlorogenic acid regioisomers. It therefore constitutes a special case of transesterification reaction. Acyl migration constitutes an important reaction pathway in both coffee roasting and brewing, altering the structure of chlorogenic acid initially present in the green coffee bean. In this contribution we describe detailed and comprehensive mechanistic studies comparing inter- and intramolecular acyl migration involving the seven most common chlorogenic acids in coffee. We employe aqueous acidic and basic conditions mimicking the brewing of coffee along with dry roasting conditions. We show that under aqueous basic conditions intramolecular acyl migration is fully reversible with basic hydrolysis competing with acyl migration. 3-Caffeoylquinic acid was shown to be most labile to basic hydrolysis. We additionally show that the acyl migration process is strongly pH dependent with increased transesterification taking place at basic pH. Under dry roasting conditions acyl migration competes with dehydration to form lactones. We argue that acyl migration precedes lactonization, with 3-caffeoylquinic acid lactone being the predominant product. PMID:25116442

  19. Elephant Moraine 96029, a very mildly aqueously altered and heated CM carbonaceous chondrite: Implications for the drivers of parent body processing

    NASA Astrophysics Data System (ADS)

    Lee, Martin R.; Lindgren, Paula; King, Ashley J.; Greenwood, Richard C.; Franchi, Ian A.; Sparkes, Robert

    2016-08-01

    Elephant Moraine (EET) 96029 is a CM carbonaceous chondrite regolith breccia with evidence for unusually mild aqueous alteration, a later phase of heating and terrestrial weathering. The presence of phyllosilicates and carbonates within chondrules and the fine-grained matrix indicates that this meteorite was aqueously altered in its parent body. Features showing that water-mediated processing was arrested at a very early stage include a matrix with a low magnesium/iron ratio, chondrules whose mesostasis contains glass and/or quench crystallites, and a gehlenite-bearing calcium- and aluminium-rich inclusion. EET 96029 is also rich in Fe,Ni metal relative to other CM chondrites, and more was present prior to its partial replacement by goethite during Antarctic weathering. In combination, these properties indicate that EET 96029 is one of the least aqueously altered CMs yet described (CM2.7) and so provides new insights into the original composition of its parent body. Following aqueous alteration, and whilst still in the parent body regolith, the meteorite was heated to ∼400-600 °C by impacts or solar radiation. Heating led to the amorphisation and dehydroxylation of serpentine, replacement of tochilinite by magnetite, loss of sulphur from the matrix, and modification to the structure of organic matter that includes organic nanoglobules. Significant differences between samples in oxygen isotope compositions, and water/hydroxyl contents, suggests that the meteorite contains lithologies that have undergone different intensities of heating. EET 96029 may be more representative of the true nature of parent body regoliths than many other CM meteorites, and as such can help interpret results from the forthcoming missions to study and return samples from C-complex asteroids.

  20. Oxygen Tension in the Aqueous Humor of Human Eyes under Different Oxygenation Conditions

    PubMed Central

    Sharifipour, Farideh; Idani, Esmaeil; Zamani, Mitra; Helmi, Toktam; Cheraghian, Bahman

    2013-01-01

    Purpose To measure oxygen tension in the aqueous humor of human eyes under different oxygenation conditions. Methods This prospective comparative interventional case series consisted of two parts. In the first part, 120 consecutive patients scheduled for cataract surgery were randomized into group I (control group) in which surgery was performed under local anesthesia inhaling 21% oxygen; group II in whom general anesthesia using 50% oxygen was employed; and group III receiving general anesthesia with 100% oxygen. After aspirating 0.2 ml aqueous humor under sterile conditions, the aqueous sample and a simultaneously drawn arterial blood sample were immediately analyzed using a blood gas analyzer. In part II the same procedures were performed in 10 patients after fitting a contact lens and patching the eye for 20 minutes (group IV) and in 10 patients after transcorneal delivery of oxygen at a flow rate of 5 L/min (group V). Results Mean aqueous PO2 in groups I, II and III was 112.3±6.2, 141.1±20.4, and 170.1±27 mmHg, respectively (P values <0.001) and mean arterial PO2 was 85.7±7.9, 184.6±46, and379.1±75.9 mmHg, respectively (P values <0.001). Aqueous PO2 was 77.2±9.2 mmHg in group IV and 152.3±10.9 mmHg in group V (P values <0.001). There was a significant correlation between aqueous and blood PO2 (r=0.537, P<0.001). The contribution of atmospheric oxygen to aqueous PO2 was 23.7%. Conclusion Aqueous oxygen tension is mostly dependent on the systemic circulation and in part on the atmosphere. Increasing inspiratory oxygen and transcorneal oxygen delivery both increase aqueous PO2 levels. PMID:23943686

  1. Pursuit Rotor Learning of Mildly Retarded Children under Supplementary Feedback Conditions.

    ERIC Educational Resources Information Center

    Horgan, James S.

    1980-01-01

    The purpose of this study was to determine if performance and learning of mildly retarded children on a rotary pursuit task was facilitated by various types of supplementary, concurrent sensory feedback and if supplementary feedback presented during either correct or incorrect responding differentially affected motor learning. (Author/SJL)

  2. Aqueous alteration of VHTR fuels particles under simulated geological conditions

    NASA Astrophysics Data System (ADS)

    Ait Chaou, Abdelouahed; Abdelouas, Abdesselam; Karakurt, Gökhan; Grambow, Bernd

    2014-05-01

    Very High Temperature Reactor (VHTR) fuels consist of the bistructural-isotropic (BISO) or tristructural-isotropic (TRISO)-coated particles embedded in a graphite matrix. Management of the spent fuel generated during VHTR operation would most likely be through deep geological disposal. In this framework we investigated the alteration of BISO (with pyrolytic carbon) and TRISO (with SiC) particles under geological conditions simulated by temperatures of 50 and 90 °C and in the presence of synthetic groundwater. Solid state (scanning electron microscopy (SEM), micro-Raman spectroscopy, electron probe microanalyses (EPMA) and X-ray photoelectron spectroscopy (XPS)) and solution analyses (ICP-MS, ionique chromatography (IC)) showed oxidation of both pyrolytic carbon and SiC at 90 °C. Under air this led to the formation of SiO2 and a clay-like Mg-silicate, while under reducing conditions (H2/N2 atmosphere) SiC and pyrolytic carbon were highly stable after a few months of alteration. At 50 °C, in the presence and absence of air, the alteration of the coatings was minor. In conclusion, due to their high stability in reducing conditions, HTR fuel disposal in reducing deep geological environments may constitute a viable solution for their long-term management.

  3. Ionic-liquid-catalyzed efficient transformation of γ-valerolactone to methyl 3-pentenoate under mild conditions.

    PubMed

    Zeng, Fan-Xin; Liu, Hai-Feng; Deng, Li; Liao, Bing; Pang, Hao; Guo, Qing-Xiang

    2013-04-01

    Green nylons! Acidic ionic-liquid catalysis for the transformation of γ-valerolactone into methyl 3-pentenoate (M3P) is shown to be performed efficiently under mild conditions. M3P is obtained selectively from a reaction at 170 °C for 3.5 h in the presence of an acidic ionic liquid that has a low vapor pressure, high thermal stability, and excellent catalytic performance. A possible reaction pathway for this conversion is also presented. PMID:23468313

  4. High selective delignification using oxidative ionic liquid pretreatment at mild conditions for efficient enzymatic hydrolysis of lignocellulose.

    PubMed

    Pang, Zhiqiang; Lyu, Wenkang; Dong, Cuihua; Li, Hongxing; Yang, Guihua

    2016-08-01

    Herein, the oxidative ionic liquid (IL) pretreatment for overcoming recalcitrance of lignocellulose with selective delignification was investigated, and the subsequent enzymatic hydrolysis was evaluated. IL pretreatment incorporating oxygen delignification could enhance lignin extraction with high selectivity at low carbohydrate loss. The dual-action of oxidative decomposition and dissolution by 1-butyl-3-methlimidazolium chloride (BmimCl) on biomass were synergistically acted, accounting for efficient recalcitrance removal. In addition, the mild oxidative IL treatment only slightly converted crystalline cellulose into amorphous structure, and the extensive extraction of the amorphous lignin and carbohydrate resulted to the expose of cellulose with high susceptibility. Correspondingly, the enzymatic hydrolysis of the pretreated lignocellulose was greatly enhanced. The oxidative IL treatment at mild conditions, collaborating BmimCl treatment with oxygen delignification is a promising and effective system for overcoming the robust structure of lignocellulose. PMID:27128194

  5. Ionic Liquid Promoted Diazenylation of N-Heterocyclic Compounds with Aryltriazenes under Mild Conditions.

    PubMed

    Cao, Dawei; Zhang, Yonghong; Liu, Chenjiang; Wang, Bin; Sun, Yadong; Abdukadera, Ablimit; Hu, Haiyan; Liu, Qiang

    2016-05-01

    An efficient, mild, and metal-free approach to direct diazenylation of N-heterocyclic compounds with aryltriazenes using Brønsted ionic liquid as a promoter has been developed for the first time. Many N-heterocyclic azo compounds were synthesized in good to excellent yields at room temperature under an open atmosphere. Notably, the promoter 1,3-bis(4-sulfobutyl)-1H-imidazol-3-ium hydrogen sulfate could be conveniently recycled and reused with the same efficacies for at least four cycles. PMID:27096379

  6. Corrosion inhibition of aminated hydroxyl ethyl cellulose on mild steel in acidic condition.

    PubMed

    Sangeetha, Y; Meenakshi, S; Sairam Sundaram, C

    2016-10-01

    Aminated hydroxyethyl cellulose (AHEC) was synthesized, characterized using Fourier Transform Infrared spectroscopy (FTIR) and the corrosion inhibition of AHEC on mild steel in 1M HCl was studied using chemical and electrochemical studies. Results obtained in weight loss method showed that inhibition efficiency increased with increase in concentration of AHEC. The adsorption of the inhibitor on metal surface followed Frumkin isotherm. Polarization studies revealed that the AHEC inhibits through mixed mode. Thermodynamic parameters and activation energy were calculated and discussed. FTIR and X-ray diffraction studies (XRD) confirmed the adsorption of the inhibitor. The surface morphology was studied using Scanning Electron Microscope (SEM) and Atomic Force Microscopy (AFM). PMID:27312608

  7. Single step signal group-imidazole labeling of organic phosphate groups under aqueous conditions

    DOEpatents

    Giese, R.W.; Wang, P.

    1996-04-30

    Compounds and methods for single step, covalent labeling of the phosphate group of an organic substance under aqueous conditions are described. The labeling compound includes any kind of detectable signal group covalently bound to an imidazole moiety, which can be imidazole or a substituted imidazole. A preferred labeling compound has the formula shown in the accompanying diagram. 4 figs.

  8. Single step signal group-imidazole labeling of organic phosphate groups under aqueous conditions

    DOEpatents

    Giese, Roger W.; Wang, Poguang

    1996-01-01

    Compounds and methods for single step, covalent labeling of the phosphate group of an organic substance under aqueous conditions are described. The labeling compound includes any kind of detectable signal group covalently bound to an imidazole moiety, which can be imidazole or a substituted imidazole. A preferred labeling compound has the formula ##STR1##

  9. Efficient conversion of brown grease produced by municipal wastewater treatment plant into biofuel using aluminium chloride hexahydrate under very mild conditions.

    PubMed

    Pastore, Carlo; Lopez, Antonio; Mascolo, Giuseppe

    2014-03-01

    Wastes produced by oil/water separation at the wastewater treatment plant of Bari West (Southern Italy) were taken, characterized and converted. About 12% of this material was composed of greases, mainly made of free fatty acids (50%) and soaps (34%), and was easily separable by the aqueous phase through a hot centrifugation. After chemical activation of this fatty fraction, a direct esterification was carried out under very mild conditions (320K and atmospheric pressure), converting more than 90% of the original free fatty acids into the respective methyl esters in less than 4h, by using AlCl3·6H2O. The activation energy correlated to the use of this catalyst was also calculated (Eaest=43.9kJmol(-1)). The very low cost of the biodiesel produced (0.45€L(-1)) and the associated relevant specific energy (5.02MJ kgFAMEs(-1)) make such a process a really sustainable and effective example of valorization of a waste. PMID:24434702

  10. Production of starch nanoparticles using normal maize starch via heat-moisture treatment under mildly acidic conditions and homogenization.

    PubMed

    Park, Eun Young; Kim, Min-Jung; Cho, MyoungLae; Lee, Ju Hun; Kim, Jong-Yea

    2016-10-20

    Normal maize starch was subjected to heat-moisture treatment (HMT) under mildly acidic conditions (0.000, 0.050, or 0.075M H2SO4) for various treatment times (3, 5, or 8h) followed by homogenization up to 60min to prepare nanoparticles. The combination of HMT (0.075M, for 8h) and homogenization (60min) produced nanoparticles with diameters of less than 50nm at a yield higher than 80%. X-ray diffractometry and size-exclusion chromatography revealed that HMT under mildly acidic conditions selectively hydrolyzed the starch chains (especially amylose and/or long chains of amylopectin) in the amorphous region of the granules without significant damage to the crystalline structure, however, modification of the molecular structure in the amorphous region increased fragility of the granules during homogenization. Homogenization for 60min caused obvious damage in the long-range crystalline structure of the HMT starch (0.15N, for 8h), while the short-range chain associations (FT-IR) remained intact. PMID:27474568

  11. Reversible hydrogen storage using CO2 and a proton-switchable iridium catalyst in aqueous media under mild temperatures and pressures

    NASA Astrophysics Data System (ADS)

    Hull, Jonathan F.; Himeda, Yuichiro; Wang, Wan-Hui; Hashiguchi, Brian; Periana, Roy; Szalda, David J.; Muckerman, James T.; Fujita, Etsuko

    2012-05-01

    Green plants convert CO2 to sugar for energy storage via photosynthesis. We report a novel catalyst that uses CO2 and hydrogen to store energy in formic acid. Using a homogeneous iridium catalyst with a proton-responsive ligand, we show the first reversible and recyclable hydrogen storage system that operates under mild conditions using CO2, formate and formic acid. This system is energy-efficient and green because it operates near ambient conditions, uses water as a solvent, produces high-pressure CO-free hydrogen, and uses pH to control hydrogen production or consumption. The extraordinary and switchable catalytic activity is attributed to the multifunctional ligand, which acts as a proton-relay and strong π-donor, and is rationalized by theoretical and experimental studies.

  12. Reversible hydrogen storage using CO2 and a proton-switchable iridium catalyst in aqueous media under mild temperatures and pressures.

    PubMed

    Hull, Jonathan F; Himeda, Yuichiro; Wang, Wan-Hui; Hashiguchi, Brian; Periana, Roy; Szalda, David J; Muckerman, James T; Fujita, Etsuko

    2012-05-01

    Green plants convert CO(2) to sugar for energy storage via photosynthesis. We report a novel catalyst that uses CO(2) and hydrogen to store energy in formic acid. Using a homogeneous iridium catalyst with a proton-responsive ligand, we show the first reversible and recyclable hydrogen storage system that operates under mild conditions using CO(2), formate and formic acid. This system is energy-efficient and green because it operates near ambient conditions, uses water as a solvent, produces high-pressure CO-free hydrogen, and uses pH to control hydrogen production or consumption. The extraordinary and switchable catalytic activity is attributed to the multifunctional ligand, which acts as a proton-relay and strong π-donor, and is rationalized by theoretical and experimental studies. PMID:22522258

  13. Reversible Hydrogen Storage using CO2 and a Proton-Switchable Iridium Catalyst in Aqueous Media under Mild Temperatures and Pressures

    SciTech Connect

    Hull J. F.; Himeda, Y.; Wang, W.-H.; Hashiguchi, B.; Szalda, D.J.; Muckerman, J.T.; Fujita, E.

    2012-05-01

    Green plants convert CO{sub 2} to sugar for energy storage via photosynthesis. We report a novel catalyst that uses CO{sub 2} and hydrogen to store energy in formic acid. Using a homogeneous iridium catalyst with a proton-responsive ligand, we show the first reversible and recyclable hydrogen storage system that operates under mild conditions using CO{sub 2}, formate and formic acid. This system is energy-efficient and green because it operates near ambient conditions, uses water as a solvent, produces high-pressure CO-free hydrogen, and uses pH to control hydrogen production or consumption. The extraordinary and switchable catalytic activity is attributed to the multifunctional ligand, which acts as a proton-relay and strong {pi}-donor, and is rationalized by theoretical and experimental studies.

  14. Zero-valent iron removal rates of aqueous Cr(VI) measured under flow conditions

    SciTech Connect

    Kaplan, Daniel I.; Gilmore, Tyler J.

    2004-06-30

    The rates of Cr(VI) removal from the aqueous phase by zero-valent iron Fe(0) was measured under flow conditions. The intent of this work was to generate removal rate coefficients that would be applicable to the Reactive Well Technology, a gournwater remediation technology that replaces the sand in a filter pack of a conventioanl well with a reactive material, such as Fe(0).

  15. An econometric model of an episode of mental health care for patients with mild conditions: implications for caregiver substitution.

    PubMed

    Cross, J G; Knesper, D J; De Rooij, J P

    1990-01-01

    This article presents a model of the number of hours of mental health care, the concurrent improvement in the patient's condition, the probability the patient will receive medications, and the reasons for treatment termination. The variables related to these aspects of mental health care are analyzed separately for patients of psychiatrists, psychologists, and social workers. Estimates of the average length of treatment, the average price and income elasticities, and the average cost of treatment are obtained from the model. The major conclusions from this study are that psychiatrists do not have a benefit-cost advantage in the treatment of relatively mild conditions, and that consumer responsiveness to variations in price appear to be largely confined to the decision to seek treatment. These and other findings provide a basis for making tentative recommendations about personnel substitution and reimbursement policies in mental health. PMID:10113416

  16. Synthesis of graphene-based Pt nanoparticles by a one-step in situ plasma approach under mild conditions

    SciTech Connect

    Wang Qi; Song Mingming; Chen Changlun; Wei Yu; Zuo Xiao; Wang Xiangke

    2012-07-16

    Herein, a one-step in situ plasma approach to synthesize the highly dispersed Pt nanoparticles on graphene under mild conditions is reported. The graphene oxide (GO) was transformed into graphene and H{sub 2}PtCl{sub 6} was simultaneously transformed into Pt nanoparticles under argon plasma conditions. The synthesized graphene-based Pt nanoparticles were characterized by scanning electron microscopy, atomic force microscopy, x-ray diffraction, and Fourier transform infrared spectroscopy. The analysis showed that the Pt nanoparticles were deposited on graphene as a form of face-centered cubical structure and the oxygen groups on graphene oxide were partially removed. The results of x-ray photoelectron spectroscopy analysis further confirmed the results.

  17. Stability of lysozyme in aqueous extremolyte solutions during heat shock and accelerated thermal conditions.

    PubMed

    Avanti, Christina; Saluja, Vinay; van Streun, Erwin L P; Frijlink, Henderik W; Hinrichs, Wouter L J

    2014-01-01

    The purpose of this study was to investigate the stability of lysozyme in aqueous solutions in the presence of various extremolytes (betaine, hydroxyectoine, trehalose, ectoine, and firoin) under different stress conditions. The stability of lysozyme was determined by Nile red Fluorescence Spectroscopy and a bioactivity assay. During heat shock (10 min at 70°C), betaine, trehalose, ectoin and firoin protected lysozyme against inactivation while hydroxyectoine, did not have a significant effect. During accelerated thermal conditions (4 weeks at 55°C), firoin also acted as a stabilizer. In contrast, betaine, hydroxyectoine, trehalose and ectoine destabilized lysozyme under this condition. These findings surprisingly indicate that some extremolytes can stabilize a protein under certain stress conditions but destabilize the same protein under other stress conditions. Therefore it is suggested that for the screening extremolytes to be used for protein stabilization, an appropriate storage conditions should also be taken into account. PMID:24465983

  18. Mild hydrothermal conditioning prior to torrefaction and slow pyrolysis of low-value biomass.

    PubMed

    Van Poucke, R; Nachenius, R W; Agbo, K E; Hensgen, F; Bühle, L; Wachendorf, M; Ok, Y S; Tack, F M G; Prins, W; Ronsse, F; Meers, E

    2016-10-01

    The aim of this research was to establish whether hydrothermal conditioning and subsequent thermochemical processing via batch torrefaction or slow pyrolysis may improve the fuel quality of grass residues. A comparison in terms of fuel quality was made of the direct thermochemical processing of the feedstock versus hydrothermal conditioning as a pretreatment prior to thermochemical processing. Hydrothermal conditioning reduced ash content, and particularly nitrogen, potassium and chlorine contents in the biomass. The removal of volatile organic matter associated with thermochemical processes can increase the HHV to levels of volatile bituminous coal. However, slow pyrolysis only increased the HHV of biomass provided a low ash content (<6%) feedstock was used. In conclusion, hydrothermal conditioning can have a highly positive influence on the efficiency of thermochemical processes for upgrading low-value (high-ash) biomass to a higher quality fuel. PMID:26976062

  19. Apomorphine induced conditioned place preference and sensitization is greater in rats exposed to unpredictable chronic mild stress.

    PubMed

    Kanwal, Sumera; Ikram, Huma; Farhan, Muhammad; Haleem, Darakhshan Jabeen

    2015-11-01

    CNS stimulants are the class of the drugs that may be used to get relief from depression. Apomorphine is a D1 and D2 receptor agonist with a CNS stimulatory effect used for the treatment of Parkinson's disease is also abused. Although many drugs of abuse produce tolerance and dependence. Long term use of pshycostimulants produce reverse tolerance described as sensitization. These drugs also have a number of other beneficial effects but their therapeutic use is limited because of abuse potential. Conditioned place preference (CPP) test is used to monitor the reinforcing effect of drugs of abuse. Stress is an important factor that precipitates and potentiates addictive effects of different drugs of abuse. The present study was designed to investigate the addictive effect of apomorphine (1mg/kg) in rats previously exposed to repeated unpredictable chronic mild stress for 10 days (animal model of depression). Results from present study illustrate that unpredictable chronic mild stress potentiates the reinforcing effects of apomorphine as the number of entries and the time spent in the CPP compartment associated with drug administration is increased. Motor activity was taken as a parameter for behavioral sensitization which is induced by repeated administration of apomorphine, monitored as the number of cage crossings in light compartment of the CPP apparatus, also increased. PMID:26639488

  20. Intrinsic formation of nanocrystalline neptunium dioxide under neutral aqueous conditions relevant to deep geological repositories.

    PubMed

    Husar, Richard; Hübner, René; Hennig, Christoph; Martin, Philippe M; Chollet, Mélanie; Weiss, Stephan; Stumpf, Thorsten; Zänker, Harald; Ikeda-Ohno, Atsushi

    2015-01-25

    The dilution of aqueous neptunium carbonate complexes induces the intrinsic formation of nanocrystalline neptunium dioxide (NpO2) particles, which are characterised by UV/Vis and X-ray absorption spectroscopies and transmission electron microscopy. This new route of nanocrystalline NpO2 formation could be a potential scenario for the environmental transport of radionuclides from the waste repository (i.e. under near-field alkaline conditions) to the geological environment (i.e. under far-field neutral conditions). PMID:25479067

  1. Alumino-silicate speciation in aqueous fluids at deep crustal conditions

    NASA Astrophysics Data System (ADS)

    Mookherjee, M.; Keppler, H.; Manning, C. E.

    2014-12-01

    Alumina and silica are major oxides in most crustal rocks. While SiO2 is quite soluble in aqueous fluids at metamorphic conditions, behavior of Al2O3 in crustal metamorphic fluids has been poorly understood. It is known that alumina is dramatically less soluble in aqueous fluids and hence it is difficult to explain the common occurrence of quartz with aluminous minerals in metamorphic veins. In order to understand this complex behavior of alumina, we investigated aluminum speciation in aqueous fluids in equilibrium with corundum using in situ Raman spectroscopy in hydrothermal diamond anvil cells to 20 kbar and 1000 oC. In order to better understand the spectral features of the aqueous fluids, we used first principles simulations based on density functional theory to calculate and predict the energetics and vibrational spectra for various aluminum species that are likely to be present in aqueous solutions. The Raman spectra of pure water in equilibrium with Al2O3 are devoid of any characteristic spectral features. In contrast, aqueous fluids with KOH solution in equilibrium with Al2O3 show a sharp band at ~620 cm-1 which could be attributed to the [Al(OH)4]1- species. The band grows in intensity with temperature along an isochore. In the limited pressure, temperature and density explored in the present study, we do not find any evidence for the polymerization of the [Al(OH)4]1- species to dimers [(OH)2-Al-O2-Al(OH)2]2- or [(OH)3-Al-O-Al(OH)3]2-. This is likely due to the relatively low concentration of Al in the solutions and does not rule out significant polymerization at higher pressures and temperatures. We are also investigating the effect of SiO2 on the solubility of Al2O3 and the relative energetics of formation of pure alumina dimer [(OH)3-Al-O-Al(OH)3]2- vs. the aluminosilicate dimers, [(OH)3-Al-O-Si(OH)3]2- at deep crustal conditions. Acknowledgement- MM is supported by the US National Science Foundation grant (EAR-1250477).

  2. The effect of certain biochemical factors on well clogging under suboxic and mildly anoxic conditions.

    PubMed

    Dimkić, M; Pušić, M; Obradović, V; Kovačević, S

    2012-01-01

    Research conducted at the Belgrade Groundwater Source in Serbia has shown that significant well screen clogging processes take place under reduced oxic and initial anoxic conditions. Criteria for the prevention, or deceleration, of clogging are becoming more relevant to well ageing, compared with classical, mechanical clogging criteria and the permissible entrance velocities derived from them. The research project was later expanded to encompass other alluvial sources, which feature distinct oxic conditions. This paper presents some of the outcomes of this project, which shed light on the correlation between certain important indicators of well screen clogging (such as the redox potential and iron concentration) and the rate of increase in local hydraulic resistance at the wells. PMID:22643417

  3. Cannabinoid modulation of chronic mild stress-induced selective enhancement of trace fear conditioning in adolescent rats.

    PubMed

    Reich, Christian G; Iskander, Anthony N; Weiss, Michael S

    2013-10-01

    History of stress is considered a major risk factor for the development of major depression and posttraumatic stress disorder (PTSD). Elucidating the neurobiological mechanisms of Pavlovian fear conditioning may provide insight into the etiology of PTSD. In the current study, adolescent male Sprague-Dawley rats were exposed to 3 weeks of a chronic-mild-unpredictable stress (CMS) protocol. Immediately following the CMS, the animals were subjected to hippocampal-dependent (trace and contextual) and hippocampal-independent (delay) fear conditioning. CMS exposure enhanced trace freezing behavior compared to non-stress controls. This effect was not observed in contextual or delay conditioned animals. Given that the endocannabinoid system is negatively affected by CMS procedures, separate groups of stressed rats were administered the CB1 receptor agonist, ACEA (0.1 mg/kg), prior to trace fear conditioning or a memory-recall test. Regardless of administration time, ACEA significantly reduced freezing behavior in stressed animals. Furthermore, when administered during the first memory recall test, ACEA enhanced long-term extinction in both stress and non-stress groups. The results demonstrate that chronic unpredictable stress selectively enhances hippocampal-dependent episodic fear memories. Pathologies of the episodic memory and fear response may increase the susceptibility of developing PTSD. Reduction in fear responses via exogenous activation of the CB1 receptor suggests that a deficiency in the endocannabinoid system contributes to this pathology. PMID:23926242

  4. A New Biarylphosphine Ligand for the Pd-Catalyzed Synthesis of Diaryl Ethers Under Mild Conditions

    PubMed Central

    Salvi, Luca; Davis, Nicole R.; Ali, Siraj Z.; Buchwald, Stephen L.

    2011-01-01

    A new bulky biarylphosphine ligand (L8) has been developed that allows the Pd-catalyzed C–O cross-coupling of a wide range of aryl halides and phenols under milder conditions than previously possible. A direct correlation between the size of the ligand substituents in the 2′, 4′ and 6′ positions of the non-phosphine containing ring and the reactivity of the derived catalyst system was observed. Specifically, the rate of coupling increased with the size of these substituents. PMID:22182186

  5. Hydrolysis of Indole-3-Acetic Acid Esters Exposed to Mild Alkaline Conditions 1

    PubMed Central

    Baldi, Bruce G.; Maher, Barbara R.; Cohen, Jerry D.

    1989-01-01

    Ester conjugates of indole-3-acetic acid are hydrolyzed easily in basic solutions; however, quantitative data have not been available on the relationship between pH and rate of hydrolysis of the known ester conjugates. The use of basic conditions during extraction or purification of IAA by several laboratories suggested that a more systematic analysis of this process was needed. In this report we present data indicating: (a) that measurable hydrolysis of IAA-glucose (from standard solutions) and IAA-esters (from maize kernel extracts) occurs with only a few hours of treatment at pH 9 or above; (b) that the lability of some ester conjugates is even greater than that of IAA-glucose; and (c) that ester hydrolysis of standard compounds, IAA-glucose and IAA-p-nitrophenol, occurs in the `three phase extraction system' proposed by Liu and Tillberg ([1983] Physiol Plant 57: 441-447). These data indicate that the potential for problems with inadvertent hydrolysis of ester conjugates of IAA exists even at moderate pH values and in the multiphase system where exposure to basic conditions was thought to be limited. PMID:16667049

  6. Electrocatalytic Hydrogenation of Oxygenates using Earth-Abundant Transition-Metal Nanoparticles under Mild Conditions.

    PubMed

    Carroll, Kyler J; Burger, Thomas; Langenegger, Lukas; Chavez, Steven; Hunt, Sean T; Román-Leshkov, Yuriy; Brushett, Fikile R

    2016-08-01

    Electrocatalytic hydrogenation (ECH) is a sustainable pathway for the synthesis of value-added organic compounds, provided affordable catalysts with high activity, selectivity and durability are developed. Here, we synthesize Cu/C, Ni/C, and CuNi/C nanoparticles and compare their performance to Pt/C, Ru/C, PtRu/C for the ECH of hydroxyacetone, a bio-derived feedstock surrogate containing a carbonyl and a hydroxyl functional group. The non-precious metal electrocatalysts show promising conversion-time behavior, product selectivities, and Faradaic efficiencies. Ni/C forms propylene glycol with a selectivity of 89 % (at 80 % conversion), while Cu/C catalyzes ECH (52 % selectivity) and hydrodeoxygenation (HDO, 48 % selectivity, accounting for evaporation). CuNi/C shows increased turnover frequencies but reduced ECH selectivity (80 % at 80 % conversion) as compared to the Ni/C catalyst. Importantly, stability studies show that the non-precious metal catalysts do not leach at operating conditions. PMID:27337680

  7. Solvothermal synthesis of perovskites and pyrochlores: crystallisation of functional oxides under mild conditions.

    PubMed

    Modeshia, Deena R; Walton, Richard I

    2010-11-01

    In this critical review we consider the large literature that has accumulated in the past 5-10 years concerning solution-mediated crystallisation of complex oxide materials using hydrothermal, or more generally solvothermal, reaction conditions. The aim is to show how the synthesis of dense, mixed-metal oxide materials, usually prepared using the high temperatures associated with solid-chemistry, is perfectly feasible from solution in one step reactions, typically at temperatures as low as 200 °C, and that important families of oxide materials have now been reported to crystallise using such synthetic approaches. We will focus on two common structures seen in oxide chemistry, ABO(3) perovskites and A(2)B(2)O(6)O' pyrochlores, and include a systematic survey of the variety of chemical elements now included in these two prototypical structure types, from transition metals, in families of materials that include titanates, niobates, manganites and ferrites, to main-group elements in stannates, plumbates and bismuthates. The significant advantages of solution-mediated crystallisation are well illustrated by the recent literature: examples are provided of elegant control of crystal form from the nanometre to the micron length scale to give thin films, anisotropic crystal morphologies, or hierarchical structures of materials with properties desirable for many important contemporary applications. In addition, new metastable materials have been reported, not stable once high temperatures and pressures are applied and hence not amenable using conventional synthesis. We critically discuss the possible control offered by solvothermal synthesis from crystal chemistry to crystal form and how the discovery of new materials may be achieved. Computer simulation, combinatorial synthesis approaches and in situ methods to follow crystallisation will be vital in providing the predictability in synthesis that is needed for rational design of new materials (232 references). PMID

  8. CO₂ carbonation under aqueous conditions using petroleum coke combustion fly ash.

    PubMed

    González, A; Moreno, N; Navia, R

    2014-12-01

    Fly ash from petroleum coke combustion was evaluated for CO2 capture in aqueous medium. Moreover the carbonation efficiency based on different methodologies and the kinetic parameters of the process were determined. The results show that petroleum coke fly ash achieved a CO2 capture yield of 21% at the experimental conditions of 12 g L(-1), 363°K without stirring. The carbonation efficiency by petroleum coke fly ash based on reactive calcium species was within carbonation efficiencies reported by several authors. In addition, carbonation by petroleum coke fly ash follows a pseudo-second order kinetic model. PMID:25000300

  9. Corrosion detection of mild steel in a two phase hydrocarbon-electrolyte system under flow conditions using electrochemical noise

    SciTech Connect

    Male, J.M.; Uruchurtu, J.; Coron, O.

    1998-12-31

    Electrochemical current noise (ECN) measurements were carried out in mixtures of 3% NaCl electrolyte in diesel under stirred conditions (0 to 2,000 rpm) using a Rotating Electrodes System (RES) which includes three mild steel concentric electrodes embedded in activated polyester resin. Chemical activation of the resin allowed electrochemical measurements in the water in oil emulsion system. A 0.2 to 15% in volume range of 3% NaCl electrolyte additions was studied. Three distinctive noise patterns were obtained from electrochemical current noise (ECN) time-series: (a) a low noise baseline for diesel in absence of electrolyte, diesel with small additions of electrolyte and/or low flow rates, (b) a low noise signal with current bursts superimposed obtained from relatively small additions of electrolyte and high rotation rates and (c) a high amplitude signal for high rotation rates and relatively high additions of electrolyte. For case b, the number and intensity of current bursts is indicative of proximity to cases a or c. These results contrast with experiments carried out with a conventional non-activated resin which is insensitive to the range of electrolyte additions or to stirring conditions. This method can be implemented for water in oil systems where early corrosion detection is desirable.

  10. Alcohol‐Selective Oxidation in Water under Mild Conditions via a Novel Approach to Hybrid Composite Photocatalysts

    PubMed Central

    Abd‐Elaal, Ali; Ciriminna, Rosaria; Loddo, Vittorio

    2015-01-01

    Abstract The oxidation of alcohols to carbonyl compounds in a clean fashion (i.e., with water as a solvent or under solvent‐free conditions, and using O2 or H2O2 as the primary oxidant) is the subject of considerable research efforts. A new approach for the selective oxidation of soluble aromatic alcohols in water under mild conditions via a novel composite photocatalyst has been developed. The catalyst is synthesized by grafting 4‐(4‐(4‐hydroxyphenylimino)cyclohexa‐2,5dienylideneamino)phenol and silver nanoparticles onto the surface of moderately crystalline titanium dioxide. The titanium dioxide‐based composite was first extensively characterized and then employed in the catalytic oxidation of 4‐methoxybenzyl alcohol to 4‐methoxybenzaldehyde under UV irradiation in water at room temperature. The corresponding aldehyde was obtained with unprecedented high selectivity (up to 86 %). The method is general and opens the route to fabrication of photocatalytic composites based on titanium dioxide functionalized with shuttle organic molecules and metal nanoparticles for a variety of oxidative conversions. PMID:27308204

  11. Conditions of aqueous alteration of 9 CM chondrites estimated from mineralogy and compositional variations of matrix

    NASA Astrophysics Data System (ADS)

    Yoshioka, K.; Nakamura, T.; Fujimaki, H.

    2011-12-01

    those from Murry and Nogoya meteorites) in a Mg-Fe-Si ternary diagram. Nine samples have different compositional trends and PCP/(PCP+serpentine) ratios, suggesting that these 9 samples have suffered various extents of aqueous alteration. The matrix compositions reflect the conditions of aqueous alteration, because of its fine-grained nature. Therefore, it is expected that, for instance, GroupA samples show compositional trends similar within the Group, but different from other Groups. However, GroupA sample (LAP03178) has the same trend as GroupB sample (GRO95566), and GroupB sample (MET01072) has the same trend as GroupC sample (MAC88100).This suggests that aqueous alteration process is very complex: the starting matrix compositions are variable, and the resultant matrix compositions are also different. This indicates that matrix chemical composition alone is not enough to define the alteration degree. [1]McSween (1986), GCA 51, 2469-2477 [2]Clayton and Mayeda (1984) Earth and Planetary Science Letters 67, 151-161 [3]Zolensky et.al (1997) GCA 61, 5099-5115 [4]Rubin et al. (2007) GCA 71, 2361-2382

  12. On hematite as a target for dating aqueous conditions on Mars

    NASA Astrophysics Data System (ADS)

    Kula, Joseph; Baldwin, Suzanne L.

    2012-07-01

    Hematite spherules, identified by the Opportunity Mars Exploration Rover (MER), have been interpreted as in situ evidence for past aqueous conditions on the Martian surface. Hematite has also been demonstrated as a reliable (U-Th)/He chronometer, although it is not widely used. In the absence of post-formational diffusive He loss, (U-Th)/He ages measured from Martian hematite spherules should yield the time since water was present on Mars. Using published morphologic constraints and He diffusion kinetics for hematite we model He diffusive loss to assess whether Martian hematite spherules will retain original (U-Th)/He ages during long residence times (4.0 Ga) at surface conditions (22 °C). Fractional loss calculations predict <2% diffusive loss at 22 °C over 4.0 Ga, indicating Martian hematite will preserve ages within analytical precision of the (U-Th)/He technique. If present Mars conditions persisted since the Noachian (e.g. 4.0 Ga), hematite spherules likely record ages reflecting the timing of aqueous mineralization. For the 'wetting-upwards' Burn Formation at Meridiani Planum, hematite from the lower eolian dune subunit would be postdepositional providing a minimum age on deposition, while hematite from the upper interdune/playa unit may be syndepositional thus yielding the age of the deposit. Therefore (U-Th)/He hematite ages obtained from samples collected along a vertical profile could potentially constrain the timing and rates of water saturation of the rock column, and the timing of the transition from wet to dry conditions at Meridiani Planum. Determining an absolute paleohydrologic timescale on Mars may reveal if water was available for sufficient durations required for the development of life.

  13. Anticompulsive Activity of a New Pyrazolo[C]Pyridine Derivative GIZh-72 under Conditions of Unpredictable Chronic Mild Stress.

    PubMed

    Kudryashov, N V; Kalinina, T S; Zhmurenko, L A; Voronina, T A

    2016-07-01

    Anticompulsive activity of a novel compound GIZh-72 (4,6-dimethyl-2-(4-chlorphenyl)-2,3-dihydro-1H-pyrazolo[4,3-C]Pyridine-3-on, chloral hydrate) in a dose of 20 mg/kg (single, subchronic, and chronic administration) in comparison with fluvoxamine (25 mg/kg) was studied in the marble burying test in the model of unpredictable chronic mild stress on BALB/c mice. GIZh-72 produced an anticompulsive effect that increased with increasing treatment duration under stress conditions in contrast to fluvoxamine that induced inversion of this effect after long-term administration. Neuroleptic activity of GIZh-72 in doses of 20 and 40 mg/kg was studied on the model of apomorphine-induced climbing in C57Bl/6 mice. In contrast to haloperidol (0.5 mg/kg), GIZh-72 exhibited no neuroleptic properties. Our results indicate that GIZh-72 holds much promise for pharmacotherapy of obsessive-compulsive disorder. PMID:27502699

  14. Catalytic oxidative treatment of diluted black liquor at mild conditions using copper oxide/cerium oxide catalyst.

    PubMed

    Garg, Anurag; Mishra, Indra M; Chand, Shri

    2008-02-01

    Wet-air oxidation of diluted black liquor (chemical oxygen demand [COD] approximately 3250 to 14 500 mg/L) was performed at mild operating conditions (temperature = 388 to 423 K and total pressure = 0.6 MPa) in the presence of heterogeneous 60% copper oxide (CuO)/ 40% cerium oxide (CeO2) catalyst. Maximum COD reduction of 77.3% was obtained at 423 K at pH 3.0, which was marginally higher than that obtained at 413 K temperature (77.1%). In the acidic environment (pH < or = 3), most of the COD was removed in the form of settleable solids during the transient heating of the wastewater from room temperature to the desired one. The solid residue obtained after the reaction has a heating value of 20.1 MJ/kg, which is comparable with that of Indian coal. Thermal degradation kinetic determination suggested that thermal characteristics of the solid residue are well represented by a power law model with Agarwal and Sivasubramanian approximation (Safi et al., 2004). PMID:18330223

  15. ZERO-VALENT IRON REMOVAL RATES OF AQUEOUS Cr(VI) MEASURED UNDER FLOW CONDITIONS

    SciTech Connect

    Kaplan, Daniel I.; Gilmore, Tyler J.

    2004-06-01

    The rates of Cr(VI) removal from the aqueous phase by zero-valent iron, Fe(0), was measured under flow conditions. The intent of this work was to generate removal rate coefficients that would be applicable to the Reactive Well Technology, a groundwater remediation technology that replaces the sand in a filter pack of a conventional well with a reactive material, such as Fe(0). Dissolved Cr(VI) concentration, dissolved O2 concentration, and Eh data indicated that Cr(VI) removal from the aqueous phase was mass-transfer limited. All pseudo-first-order regression fits to the data were significant (P≤0.05), however, they did not capture many of the salient aspects of the data, including that the removal rate often decreased as contact time increased. As such, application of these rate coefficients to predict long-term Cr(VI) removal were compromised. The rate coefficients measured under flow conditions were comparable to those measured previously under batch conditions with significantly greater solution:solid ratios. Between the range of 20 and 100 wt-% Fe(0) in the column, there was little measurable change in the reaction kinetics. Thus, it may be possible to include sand into the reactive filter packs in the event it is necessary to increase filter pack porosity or to decrease the accumulation of secondary reaction products that may lead to filter pack plugging. Background water chemistry (0.2 M NaHCO3, distilled water, and a carbonate-dominated groundwater) had only marginal, if any, effects on reaction rate coefficients. The reaction rates measured in this study indicated that an Fe(0) filter pack could be used to lower Cr(VI) concentrations by several orders of magnitude in a once-through mode of operation of the Reactive Well Technology.

  16. The Formation of Seven-Membered Heterocycles under Mild Pictet-Spengler Conditions: A Route to Pyrazolo[3,4]benzodiazepines.

    PubMed

    Katte, Timothy A; Reekie, Tristan A; Jorgensen, William T; Kassiou, Michael

    2016-06-01

    Reported is a method for the synthesis of seven-membered heterocycles via a Pictet-Spengler condensation reaction under very mild conditions. High substrate scope allows for use of aldehydes using catalytic amounts of acetic acid yielding 39-90% and ketones using catalytic amounts of trifluoroacetic acid yielding 25-83%. PMID:27159074

  17. Cementation and Aqueous Alteration of a Sandstone Unit Under Acidic Conditions in Gale Crater, Mars

    NASA Technical Reports Server (NTRS)

    Yen, A. S.; Blake, D. F.; Ming, D. W.; Morris, R. V.; Gellert, R.; Clark, B.; Vaniman, D. T.; Chipera, S. J.; Thompson, L. M.; Bristow, T. F.; Rampe, E. B.; Crisp, J. A.

    2016-01-01

    The Curiosity rover landed on Mars in August 2012 to explore the sedimentary history and to assess the habitability of Gale Crater. After 1200 sols of surface operations and over 12 km of traverse distance, the mineralogy of 10 samples has been determined by the CheMin X-ray diffractometer (XRD) and the chemical composition of nearly 300 targets has been established by the Alpha Particle X-ray Spectrometer (APXS). Light-toned fracture zones containing elevated concentrations of silica have been studied by Curiosity's instruments to determine the nature of the fluids that resulted in the enrichment of SiO2. Multiple fluid exposures are evident, and the chemistry and mineralogy data indicate at least two aqueous episodes may have occurred under acidic conditions.

  18. Aqueous Dissolution of Silver Iodide and Associated Iodine Release Under Reducing Conditions with Sulfide

    SciTech Connect

    Yaohiro Inagaki; Toshitaka Imamura; Kazuya Idemitsu; Tatsumi Arima; Osamu Kato; Hidekazu Asano; Tsutomu Nishimura

    2007-07-01

    Aqueous dissolution tests of silver iodide (AgI) were performed in Na{sub 2}S solutions in order to evaluate, empirically, dissolution of AgI to release iodine under reducing conditions with sulfide. The results indicated that AgI dissolves to release iodine being controlled by mainly precipitation of Ag{sub 2}S. However, the dissolution of AgI can be depressed to proceed, and the thermodynamic equilibrium cannot be attained easily. Solid phase analysis for the reacted AgI suggested that a thin layer of solid silver forming at AgI surface may evolve to be protective against transportation of reactant species, which can lead to the depression in the dissolution of AgI. (authors)

  19. Removal Rates of Aqueous Cr(VI) by Zero-Valent Iron Measured Under Flow Conditions

    SciTech Connect

    Kaplan, D.I.

    2002-05-10

    Studies were undertaken to measure the rate of Cr(VI) removal from the aqueous phase by zero-valent iron, Fe(0), under flow conditions. The intent of this work was to generate removal rate coefficients that would be applicable to the Reactive Well Technology, a groundwater remediation technology that replaces the sand in a filter pack of a conventional well with a reactive material, such as Fe(0). The pseudo-first-order rate coefficients measured under flow conditions were comparable to those previously measured under batch conditions that had significantly greater ratios of solution volume to Fe(0) surface area. Between the range of 20 and 100 weight percent Fe(0), there was little measurable change in the reaction kinetics. Thus, it may be possible to include sand into the reactive filter packs in the event it is necessary to increase filter pack porosity or to decrease the accumulation of secondary reaction products that may lead to filter pack plugging. Background water chemistry had only marginal effects on reaction rate coefficients. The reaction rates measured in this study indicated that an Fe(0) filter pack could be used to lower Cr(VI) concentrations by several orders of magnitude in a once-through mode of operation of the Reactive Well Technology.

  20. Mechanics and mechanisms of surface damage in Al-Si alloys under ultra-mild wear conditions

    NASA Astrophysics Data System (ADS)

    Chen, Ming

    Al-Si alloys intended for use in engine components must operate under ultra-mild wear (UMW) conditions to fit an acceptable amount of wear during a typical vehicle life. This study simulated surface damage in a UMW regime on five chemically etched Al-Si alloy surfaces using a pin-on-disc tribometer at low loads (0.5-2.0 N) under boundary lubricated conditions. The five alloys contained 11 to 25 wt.% Si and differed in matrix hardness, silicon particle morphology, and size. The mechanisms leading to the UMW damage and the role that the matrix hardness and microstructure play on said mechanisms were studied. Quantitative measurement methods based on statistical analysis of particle height changes and material loss from elevated aluminum using a profilometer technique were developed and used to assess UMW. The Greenwood and Tripp's numerical model was adapted to analyze the contact that occurred between Al-Si alloys with silicon particles protruding above the aluminum and steel balls. The estimation of the real contact pressure applied to the silicon particles was used to rationalize the damage mechanisms. The UMW mechanisms consisted of (i) abrasive wear on the top of the silicon particle surfaces; (ii) sinking-in of the silicon particles; (iii) piling-up of the aluminium around sunken-in particles and (vi) wear of the aluminium by the counterface, which eventually led to the initiation of UMW-II. Increasing the size or areal density of silicon particles with small aspect ratios delayed the onset of UMW-II by providing resistance against the silicon particles sinking-in and the aluminum piling-up. The UMW wear rates, however, began to decrease after long sliding cycles once an oil residue layer supported by hardened ultra-fine subsurface grains formed on the deformed aluminium matrix. The layer formation depended on the microstructure and applied load. Overall experimental observations suggested that Al-11% Si with small silicon particles exhibited optimal long

  1. Neutron Diffraction of Aqueous Tetramethylammonium Chloride (TMA) Solutions and TMA Intercalated Swelling Clays Under Burial Conditions

    NASA Astrophysics Data System (ADS)

    Patel, R.; Howard, C. A.; Greenwell, C.; Youngs, T.; Soper, A. K.; Skipper, N. T.

    2014-12-01

    There is a need for the improvement and optimisation of clay swelling inhibitors for the enhancement of oil and gas exploration. The hydration region of both ions and the possibility of ion pairing in 1 molar aqueous solution of clay swelling inhibitor, tetramethylammonium chloride (TMACl), in D2O, under elevated hydrostatic-pressures and temperatures has been determined with unprecedented detail using a combination of neutron diffraction and small-angle scattering in conjunction with hydrogen/deuterium isotopic labeling. The O-H correlation function (H-bonds) for the water in the 1.0M solution is measured and compared with that for pure D2O. Also investigated is the effect of burial conditions on the d-spacing of TMA-intercalated vermiculite. Contrary to expectations, no aggregation of TMA ions due to hydrophobic interactions is observed, nor are any ionic pairs of TMA+ and Cl- at these burial conditions. The data revealed a more ordered water-water structure with the addition of TMACl from bulk D2O. There is no change in the hydration structure measured at the applied elevated conditions. This is in remarkable contrast to pure water at the same conditions which is well known to be compressible. The dry d-spacing of the TMA-exchanged Eucatex vermiculite is measured at 13.66 Å which increases to 14.03 Å with the addition of D2O. Beyond this, there is no change in d-spacing with increasing pressure and temperature indicating the strength of the TMA ions binding to the clay interlayers and therefore its performance as a clay-swelling inhibitor.

  2. Radiolysis of pyridoxine (vitamin B 6) in aqueous solution under different conditions

    NASA Astrophysics Data System (ADS)

    Albarrán, Guadalupe; Ramírez-Cahero, Fernando; Aliev, Roustam

    2008-05-01

    Aqueous solutions of pyridoxine (1 mM) without or with additive of K 3[Fe(CN) 6] (2.5 mM) were gamma-irradiated at different doses and dose rate of 2.16 kGy/h in the absence of air, in the presence of air or by their saturation with N 2O. The radiolytic products were analyzed with HPLC, mass spectrometry and UV spectroscopy. 2,4,5-Trihydroxymethyl-3-pyridinol, pyridoxal, isopyridoxal and 6-hydroxypyridoxine were formed by radiolysis in the absence of K 3[Fe(CN) 6], and their concentrations were much higher in samples saturated with N 2O. Pyridoxi-3,6-quinone was found by radiolysis under all the above-mentioned conditions but only in the presence of K 3[Fe(CN) 6]. Besides, the pyridoxal formation increased in the presence of this oxidizing agent. G values of pyridoxal formation and pyridoxine degradation were quantified. Some details of the radiolytic product formation were discussed.

  3. Human Serum Albumin Increases the Stability of Green Tea Catechins in Aqueous Physiological Conditions.

    PubMed

    Zinellu, Angelo; Sotgia, Salvatore; Scanu, Bastianina; Forteschi, Mauro; Giordo, Roberta; Cossu, Annalisa; Posadino, Anna Maria; Carru, Ciriaco; Pintus, Gianfranco

    2015-01-01

    Epicatechin (EC), epigallocatechin (EGC), epicatechingallate (ECG) and epigallocatechingallate (EGCG) are antioxidants present in the green tea, a widely used beverage whose health benefits are largely recognized. Nevertheless, major physicochemical limitations, such as the high instability of catechins, pose important questions concerning their potential pharmacological use. Recent studies indicate that binding of catechins with plasmatic proteins may modulate their plasma concentration, tissue delivery and biological activity. After 5 minutes of incubation with HSA both ECG and EGCG were fully bound to HSA, while after 48h incubation only 41% of EC and 70% of EGC resulted linked. HSA had a strong stabilizing effect on all catechins, which could be found in solution between 29 and 85% even after 48h of incubation. In the absence of HSA, EGC and EGCG disappeared in less than 24h, while ECG and EC were found after 48h at 5 and 50%, respectively. The stabilizing effect of HSA toward EGCG, obtained in aqueous physiological conditions, resulted stronger in comparison to cysteine and HCl, previously reported to stabilize this polyphenol. Because of the multitude of contradictory data concerning in vivo and in vitro antioxidant-based experimentations, we believe our work may shed some light on this debated field of research. PMID:26230943

  4. Protection of moisture-sensitive drugs with aqueous polymer coatings: importance of coating and curing conditions.

    PubMed

    Bley, O; Siepmann, J; Bodmeier, R

    2009-08-13

    The aim of this study was to better understand the importance of coating and curing conditions of moisture-protective polymer coatings. Tablets containing freeze-dried garlic powder were coated with aqueous solutions/dispersions of hydroxypropyl methylcellulose (HPMC), poly(vinyl alcohol), ethyl cellulose and poly(methacrylate-methylmethacrylates). The water content of the tablets during coating and during storage at different temperatures and relative humidities (RH) was determined gravimetrically. In addition, changes in the allicin (active ingredient in garlic powder) content were monitored. During the coating process, the water uptake was below 2.7% and no drug degradation was detectable. Thermally induced drug degradation occurred only at temperatures above the coating temperatures. Different polymer coatings effectively decreased the rate, but not the extent of water uptake during open storage at room temperature and 75% RH. Tablets coated with poly(vinyl alcohol) and poly(methacrylate-methylmethacrylates) showed the lowest moisture uptake rates (0.49 and 0.57%/d, respectively). Curing at elevated temperature after coating did not improve the moisture-protective ability of the polymeric films, but reduced the water content of the tablets. Drug stability was significantly improved with tablets coated with poly(vinyl alcohol) and poly(methacrylate-methylmethacrylates). PMID:19477253

  5. Photooxidation of methylhydroperoxide and ethylhydroperoxide in the aqueous phase under simulated cloud droplet conditions

    NASA Astrophysics Data System (ADS)

    Monod, A.; Chevallier, E.; Durand Jolibois, R.; Doussin, J. F.; Picquet-Varrault, B.; Carlier, P.

    The photooxidation of methylhydroperoxide (MHP) and ethylhydroperoxide (EHP) was studied in the aqueous phase under simulated cloud droplet conditions. The kinetics and the reaction products of direct photolysis and OH-oxidation were studied for both compounds. The photolysis frequencies obtained were JMHP=4.5 (±1.0)×10 -5 s -1 and JEHP=3.8 (±1.0)×10 -5 s -1 for MHP and EHP respectively at 6 °C. The rate constants of OH-oxidation of MHP at 6 °C were 6.3 (±2.6)×10 8 M -1 s -1 and 5.8 (±1.9)×10 8 M -1 s -1 relative to ethanol and 2-propanol respectively, and the rate constant of OH-oxidation of EHP was 2.1 (±0.6)×10 9 M -1 s -1 relative to 2-propanol at 6 °C. The reaction products obtained were not only the corresponding aldehydes, but also the corresponding acids, and hydroxyhydroperoxides as primary reaction products. The yields for these products were sensitive to the pH value. The carbon balance was higher than 85% for all experiments, showing that most reaction products were detected. A chemical mechanism was proposed for each reaction, and the atmospheric implications were discussed.

  6. Human Serum Albumin Increases the Stability of Green Tea Catechins in Aqueous Physiological Conditions

    PubMed Central

    Zinellu, Angelo; Sotgia, Salvatore; Scanu, Bastianina; Forteschi, Mauro; Giordo, Roberta; Cossu, Annalisa; Posadino, Anna Maria; Carru, Ciriaco; Pintus, Gianfranco

    2015-01-01

    Epicatechin (EC), epigallocatechin (EGC), epicatechingallate (ECG) and epigallocatechingallate (EGCG) are antioxidants present in the green tea, a widely used beverage whose health benefits are largely recognized. Nevertheless, major physicochemical limitations, such as the high instability of catechins, pose important questions concerning their potential pharmacological use. Recent studies indicate that binding of catechins with plasmatic proteins may modulate their plasma concentration, tissue delivery and biological activity. After 5 minutes of incubation with HSA both ECG and EGCG were fully bound to HSA, while after 48h incubation only 41% of EC and 70% of EGC resulted linked. HSA had a strong stabilizing effect on all catechins, which could be found in solution between 29 and 85% even after 48h of incubation. In the absence of HSA, EGC and EGCG disappeared in less than 24h, while ECG and EC were found after 48h at 5 and 50%, respectively. The stabilizing effect of HSA toward EGCG, obtained in aqueous physiological conditions, resulted stronger in comparison to cysteine and HCl, previously reported to stabilize this polyphenol. Because of the multitude of contradictory data concerning in vivo and in vitro antioxidant-based experimentations, we believe our work may shed some light on this debated field of research. PMID:26230943

  7. Mild Cognitive Impairment

    MedlinePlus

    ... other people their age. This condition is called mild cognitive impairment, or MCI. People with MCI can take care of themselves and do their normal activities. MCI memory problems may include Losing things often Forgetting ...

  8. Mild Cognitive Impairment

    MedlinePlus

    ... Research Portfolio (IADRP) AMP-AD Detecting Cognitive Impairment Database ... Mild cognitive impairment (MCI) is a condition in which people have more memory or other thinking problems than normal for their ...

  9. Diverse Aqueous Conditions on Mars from New Orbital Detections of Carbonate and Sulfate

    NASA Astrophysics Data System (ADS)

    Wray, James J.; Squyres, S. W.

    2010-10-01

    Diverse aqueous environments on ancient Mars have been a key inference from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on NASA's Mars Reconnaissance Orbiter, which has identified many alteration minerals in a range of settings [e.g., 1-4]. Here we report two new minerals detected using CRISM. In the southern highlands northwest of the Hellas basin, a mid-sized crater exposes carbonate in its central uplift. Spectral absorptions at 1, 2.33, and 2.53 microns are most consistent with Fe-carbonate, distinct from the Mg-carbonates identified from orbit by [5]. Fe-carbonate is associated with Mg-phyllosilicate in fractured materials formerly buried kilometers beneath the surface, and--like the Mg/Fe-carbonate found by the Spirit rover [6]--suggests a reducing, neutral-to-alkaline alteration environment. One of the largest phyllosilicate exposures on Mars occurs in the Mawrth Vallis region [e.g., 7]. We identify bassanite (Ca-sulfate hemihydrate) in layers underlying the phyllosilicate-bearing beds [8], a stratigraphy distinct from that predicted by global models of martian aqueous history [9]. Bassanite could have formed via acid-sulfate alteration of Ca-carbonate, through dehydration of gypsum, or under hydrothermal conditions [10]. These detections expand the known mineralogic diversity of Mars and the range of environments to explore for past habitability. [1] Mustard, J. F. et al. (2008) Nature 454, 305-309. [2] Murchie, S. L. et al. (2009) J. Geophys. Res. 114, E00D06. [3] Ehlmann, B. L. et al. (2009) J. Geophys. Res. 114, E00D08. [4] Wray, J. J. et al. (2009) Geology 37, 1043-1046. [5] Ehlmann, B. L. et al. (2008) Science 322, 1828-1832. [6] Morris, R. V. et al. Science, in press, doi:10.1126/science.1189667. [7] Poulet, F. et al. (2005) Nature 438, 623-627. [8] Wray, J. J. et al. Icarus, in press, doi:10.1016/j.icarus.2010.06.001. [9] Bibring, J.-P. et al. (2006) Science 312, 400-404. [10] Vaniman, D. T. et al. (2009) LPSC 40, 1654.

  10. The Aqueous Complexation of Thorium with Citrate under Neutral to Basic Conditions

    SciTech Connect

    Felmy, Andrew R; Cho, Herman M; Dixon, David A; Xia, Yuanxian; Hess, Nancy J; Wang, Zheming

    2006-04-20

    The aqueous complexation of thorium with citrate was investigated under neutral to basic conditions and over a broad range of ionic strengths. The solubility data for ThO2(am) as a function of citrate concentration indicate the presence of stable species with citrate-to-metal ratios of between two to three. The dependence of the ThO2(am) solubilities on hydrogen ion concentration can also be readily explained by the classical assumption of hydrolysis of the central Th(IV) ion to form mixed thorium-hydroxide-citrate complexes. 13C NMR spectra of the species in solution confirm that the citrate-to-metal ratio of the species in solution is between two and three and show that the citrate attaches to the metal in a bidentate fashion through oxygens on the -carboxylate and -alkoxyl groups, rather than through the carboxylate groups. The 13C NMR spectra, as well as a density functional theory (DFT) electronic structure study of the presumptive complexes, suggests that the associated α-hydroxyl proton can be displaced during complex formation. These findings indicate an alternative explanation for the observed changes in solubility as a function of hydrogen ion concentration, the displacement of protons from the citrate alkoxyl groups via metal binding. Removal of protons from the alkoxyl groups or hydrolysis of the central Th(IV) cannot be distinguished by thermodynamic measurements, however the species with the α-hydroxyl proton removed (i.e., ThOH(Cit)25- and Th(Cit)38-) would appear to better represent the microscopic binding. Apparent equilibrium constants for the solution phase reactions of these species and the hydrous thorium oxide have been calculated as a function of ionic strength.

  11. Experimental reduction of aqueous sulphate by hydrogen under hydrothermal conditions: Implication for the nuclear waste storage

    NASA Astrophysics Data System (ADS)

    Truche, Laurent; Berger, Gilles; Destrigneville, Christine; Pages, Alain; Guillaume, Damien; Giffaut, Eric; Jacquot, Emmanuel

    2009-08-01

    Sulphate reduction by hydrogen, likely to occur in deep geological nuclear waste storage sites, was studied experimentally in a two-phase system (water + gas) at 250-300 °C and under 4-16 bars H 2 partial pressure in hydrothermal-vessels. The calculated activation energy is 131 kJ/mol and the half-life of aqueous sulphate in the presence of hydrogen and elemental sulphur ranges from 210,000 to 2.7 × 10 9 years at respective temperatures of 90 °C, the thermal peak in the site and 25 °C, the ambient temperature far from the site. The features and rate of the sulphate reduction by H 2 are close to those established for TSR in oil fields. The experiments also show that the rate of sulphate reduction is not significantly affected in the H 2 pressure range of 4-16 bars and in the pH range of 2-5, whereas a strong increase is measured at pH below 2. We suggest that the condition for the reaction to occur is the speciation of sulphate dominated by non symmetric species ( HSO4- at low pH), and we propose a three steps reaction, one for each intermediate-valence sulphur species, the first one requiring H 2S as electron donor rather than H 2. We distinguish two possible reaction pathways for the first step, depending on pH: reduction of sulphate into sulphur dioxide below pH 2 or into thiosulphate or sulphite + elemental sulphur in the pH range 2-5.

  12. Asian dust particles converted into aqueous droplets under remote marine atmospheric conditions

    PubMed Central

    Tobo, Yutaka; Zhang, Daizhou; Matsuki, Atsushi; Iwasaka, Yasunobu

    2010-01-01

    The chemical history of dust particles in the atmosphere is crucial for assessing their impact on both the Earth’s climate and ecosystem. So far, a number of studies have shown that, in the vicinity of strong anthropogenic emission sources, Ca-rich dust particles can be converted into aqueous droplets mainly by the reaction with gaseous HNO3 to form Ca(NO3)2. Here we show that other similar processes have the potential to be activated under typical remote marine atmospheric conditions. Based on field measurements at several sites in East Asia and thermodynamic predictions, we examined the possibility for the formation of two highly soluble calcium salts, Ca(NO3)2 and CaCl2, which can deliquesce at low relative humidity. According to the results, the conversion of insoluble CaCO3 to Ca(NO3)2 tends to be dominated over urban and industrialized areas of the Asian continent, where the concentrations of HNO3 exceed those of HCl ([HNO3/HCl] >  ∼ 1). In this regime, CaCl2 is hardly detected from dust particles. However, the generation of CaCl2 becomes detectable around the Japan Islands, where the concentrations of HCl are much higher than those of HNO3 ([HNO3/HCl] <  ∼ 0.3). We suggest that elevated concentrations of HCl in the remote marine boundary layer are sufficient to modify Ca-rich particles in dust storms and can play a more important role in forming a deliquescent layer on the particle surfaces as they are transported toward remote ocean regions. PMID:20921372

  13. Rh-Catalyzed Direct Amination of Unactivated C(sp(3) )-H bond with Anthranils Under Mild Conditions.

    PubMed

    Tang, Conghui; Zou, Miancheng; Liu, Jianzhong; Wen, Xiaojin; Sun, Xiang; Zhang, Yiqun; Jiao, Ning

    2016-08-01

    C-N Bond formation is of great significance due to the ubiquity of nitrogen-containing compounds. Here, a mild and efficient Rh(III) -catalyzed C(sp(3) )-H aryl amination reaction is reported. Anthranil is employed as the nitrogen source with 100 % atom efficiency. This C-H amination reaction exhibits broad substrate scope without using any external oxidants. Mechanistic studies including rhodacycle intermediates, H-D exchange, kinetic isotope effect (KIE) experiments, and in situ IR are presented. PMID:27258824

  14. Kinetics of carbonate dissolution in CO2-saturated aqueous system at reservoir conditions

    NASA Astrophysics Data System (ADS)

    Peng, Cheng; Crawshaw, John P.; Maitland, Geoffrey; Trusler, J. P. Martin

    2014-05-01

    In recent years, carbon capture and storage (CCS) has emerged as a key technology for limiting anthropogenic CO2 emissions while allowing the continued utilisation of fossil fuels. The most promising geological storage sites are deep saline aquifers because the capacity, integrity and injection economics are most favourable, and the environmental impact can be minimal. Many rock-fluid chemical reactions are known to occur both during and after CO2 injection in saline aquifers. The importance of rock-fluid reactions in the (CO2 + H2O) system can be understood in terms of their impact on the integrity and stability of both the formation rocks and cap rocks. The chemical interactions between CO2-acidified brines and the reservoir minerals can influence the porosity and permeability of the formations, resulting in changes in the transport processes occurring during CO2 storage. Since carbonate minerals are abundant in sedimentary rocks, one of the requirements to safely implement CO2 storage in saline aquifers is to characterise the reactivity of carbonate minerals in aqueous solutions at reservoir conditions. In this work, we reported measurements of the intrinsic rate of carbonate dissolution in CO2-saturated water under high-temperature high-pressure reservoir conditions extending up to 373 K and 14 MPa. The rate of carbonate dissolution in CO2-free HCl(aq) was also measured at ambient pressure at temperatures up to 353 K. Various pure minerals and reservoir rocks were investigated in this study, including single-crystals of calcite and magnesite, and samples of dolomite, chalks and sandstones. A specially-designed batch reactor system, implementing the rotating disc technique, was used to obtain the intrinsic reaction rate at the solid/liquid interface, free of mass transfer effects. The effective area and mineralogy of the exposed surface was determined by a combination of surface characterisation techniques including XRD, SEM, EDX and optical microscopy. The

  15. High areal capacitance three-dimensional Ni@Ni(OH)2 foams via in situ oxidizing Ni foams in mild aqueous solution

    NASA Astrophysics Data System (ADS)

    Zhou, Qingfeng; Cui, Mangwei; Tao, Keyu; Yang, Yongzhen; Liu, Xuguang; Kang, Litao

    2016-03-01

    In this work, commercial Ni foams are directly oxidized into Ni@Ni(OH)2 foams in a mild NH4NO3 solution at 80 °C. When used as binder-free electrodes, these Ni@Ni(OH)2 electrodes demonstrate a high areal capacitance of 6.4 F/cm2 at a current density of 2.5 mA/cm2, or 1.62 F/cm2 at a high current density of 30 mA/cm2. Nevertheless, they show a poor cycling ability with 70.4% (or 42%) capacitance retention after 2000 (or 5000) cycles at 30 mA/cm2. This kind of electrodes has a promising application in low-cost, high-performance supercapacitor, if an effective strategy is found to improve their cycling ability.

  16. The distribution of methane in groundwater in Alberta (Canada) and associated aqueous geochemistry conditions

    NASA Astrophysics Data System (ADS)

    Humez, Pauline; Mayer, Bernhard; Nightingale, Michael; Becker, Veith; Kingston, Andrew; Taylor, Stephen; Millot, Romain; Kloppmann, Wolfram

    2016-04-01

    Development of unconventional energy resources such as shale gas and coalbed methane has generated some public concern with regard to the protection of groundwater and surface water resources from leakage of stray gas from the deep subsurface. In terms of environmental impact to and risk assessment of shallow groundwater resources, the ultimate challenge is to distinguish: (a) natural in-situ production of biogenic methane, (b) biogenic or thermogenic methane migration into shallow aquifers due to natural causes, and (c) thermogenic methane migration from deep sources due to human activities associated with the exploitation of conventional or unconventional oil and gas resources. We have conducted a NSERC-ANR co-funded baseline study investigating the occurrence of methane in shallow groundwater of Alberta (Canada), a province with a long record of conventional and unconventional hydrocarbon exploration. Our objective was to assess the occurrence and sources of methane in shallow groundwaters and to also characterize the hydrochemical environment in which the methane was formed or transformed through redox processes. Ultimately our aim was to determine whether methane was formed in-situ or whether it migrated from deeper formations into shallow aquifers. Combining hydrochemical and dissolved and free geochemical gas data from 372 groundwater samples obtained from 186 monitoring wells of the provincial groundwater observation well network (GOWN) in Alberta, it was found that methane is ubiquitous in groundwater in Alberta and is predominantly of biogenic origin. The highest concentrations of dissolved biogenic methane (> 0.01 mM or > 0.2 mg/L), characterized by δ13CCH4 values < -55‰, occurred in anoxic Na-Cl, Na-HCO3 and Na-HCO3-Cl type groundwater with negligible concentrations of nitrate and sulfate suggesting that methane was formed in-situ under methanogenic conditions consistent with the redox ladder concept. Despite quite variable gas concentrations and a

  17. Experimental aqueous alteration of the Allende meteorite under oxidizing conditions: Constraints on asteroidal alteration

    NASA Astrophysics Data System (ADS)

    Jones, Catherine L.; Brearley, Adrian J.

    2006-02-01

    We have performed an experimental study of the aqueous alteration of the Allende CV3 carbonaceous chondrite under highly oxidizing conditions, in order to examine the alteration behavior of Allende's anhydrous mineralogy. The experiments were carried out at temperatures of 100, 150, and 200 °C, for time periods between 7 and 180 days, with water/rock ratios ranging from 1:1 to 9:1. Uncrushed cubes of Allende were used so that the spatial relationships between reactant and product phases could be examined in detail. Scanning electron microscope studies show that in all the experiments, even those of short duration (7 days), soluble salts of Ca and Mg (CaSO 4, CaCO 3, and MgSO 4) precipitated on the sample surface, indicating that these elements are rapidly mobilized during alteration. In addition, iron oxides and hydroxides formed on the sample surfaces. The sulfates, carbonates, and the majority of the iron-bearing secondary minerals are randomly distributed over the surface of samples. In some instances the iron oxides and hydroxides are constrained to the boundaries of altering mineral grains. Transmission electron microscope studies show that the FeO-rich olivine in the interior of the samples has altered to form interlayered serpentine/saponite and Fe-oxyhydroxides. The degree of alteration increases significantly with increasing water/rock ratio, and to a lesser extent with increasing duration of heating. The serpentine/saponite forms both by direct replacement of the olivine in crystallographically oriented intergrowths, and by recrystallization of an amorphous Si-rich phase that precipitates in pore space between the olivine grains. The alteration assemblage bears many similarities to those found in altered carbonaceous chondrites, although in detail there are important differences, which we attribute to (a) the relatively high temperatures of our experiments and (b) comparatively short reaction times compared with the natural examples. In terms of mineral

  18. Pd/Nb2O5/SiO2 catalyst for the direct hydrodeoxygenation of biomass-related compounds to liquid alkanes under mild conditions.

    PubMed

    Shao, Yi; Xia, Qineng; Liu, Xiaohui; Lu, Guanzhong; Wang, Yanqin

    2015-05-22

    A simple Pd-loaded Nb2 O5 /SiO2 catalyst was prepared for the hydrodeoxygenation of biomass-related compounds to alkanes under mild conditions. Niobium oxide dispersed in silica (Nb2 O5 /SiO2 ) as the support was prepared by the sol-gel method and characterized by various techniques, including N2 adsorption, XRD, NH3 temperature-programmed desorption (TPD), TEM, and energy-dispersive X-ray spectroscopy (EDAX) atomic mapping. The characterization results showed that the niobium oxide species were amorphous and well dispersed in silica. Compared to commercial Nb2 O5 , Nb2 O5 /SiO2 has significantly more active niobium oxide species exposed on the surface. Under mild conditions (170 °C, 2.5 MPa), Pd/10 %Nb2 O5 /SiO2 was effective for the hydrodeoxygenation reactions of 4-(2-furyl)-3-buten-2-one (aldol adduct of furfural with acetone), palmitic acid, tristearin, and diphenyl ether (model compounds of microalgae oils, vegetable oils, and lignin), which gave high yields (>94 %) of alkanes with little CC bond cleavage. More importantly, owing to the significant promotion effect of NbOx species on CO bond cleavage and the mild reaction conditions, the CC cleavage was considerably restrained, and the catalyst showed an excellent activity and stability for the hydrodeoxygenation of palmitic acid with almost no decrease in hexadecane yield (94-95 %) in a 150 h time-on-stream test. PMID:25876904

  19. Hydrodefluorination of fluorobenzene and 1,2-difluorobenzene under mild conditions over rhodium pyridylphosphine and bipyridyl complexes tethered on a silica-supported palladium catalyst

    SciTech Connect

    Yang, H.; Gao, H.; Angelici, R.J.

    1999-06-07

    The C-F bond, which is the strongest bond that carbon can form, is extremely reluctant to coordinate to metal centers and is resistant to chemical attack. Although this lack of fluorocarbon reactivity has frequently been exploited in technological and medical applications, this chemical inertness also translates into environmental persistence since these compounds are quite difficult to degrade. Fluorobenzene and 1,2-difluorobenzene are defluorinated under very mild conditions by H{sub 2}(4 atm) at 70 C in the presence of NaOAc. The heterogeneous catalysts for these reactions contain the rhodium pyridylphosphine and bipyridyl complexes tethered to heterogeneous Pd-SiO{sub 2}.

  20. Iron-promoted C-C bond cleavage of 1,3-diketones: a route to 1,2-diketones under mild reaction conditions.

    PubMed

    Huang, Lehao; Cheng, Kai; Yao, Bangben; Xie, Yongju; Zhang, Yuhong

    2011-07-15

    A conceptual method for the preparation of 1,2-diketones is reported. The selective C-C bond cleavage of 1,3-diketones affords the 1,2-diketones in high yields under mild reaction conditions in air by the use of FeCl(3) as the catalyst and tert-butyl nitrite (TBN) as the oxidant without the use of solvent. The possible reaction mechanism is discussed. This protocol provides an expeditious route to the useful 1,2-diketones. PMID:21627329

  1. Effect of condensation agents and minerals for oligopeptide formation under mild and hydrothermal conditions in related to chemical evolution of proteins

    NASA Astrophysics Data System (ADS)

    Kawamura, Kunio; Takeya, Hitoshi; Kushibe, Takao

    2009-07-01

    The role of condensation agents and minerals for oligopeptide formation was inspected to see whether minerals possess catalytic activity under mild and hydrothermal conditions. Under mild conditions, oligopeptide formation from negatively charged amino acids (Asp and Glu) using different minerals and the elongation of alanine oligopeptides ((Ala) 2-(Ala) 5) were attempted using apatite minerals. Oligo(Asp) up to 10 amino acid units from Asp were observed in the presence of 1-ethyl-3-(3-dimethylaminopropyl carbodiimide (EDC). Notable influence of minerals was not detected for the oligo(Asp) formation. Oligo(Asp) was gradually degraded by the further incubation in the presence of EDC in both the absence and presence of minerals. The formation of oligo(Glu) was less efficient in the presence of carbonyldiimidazole. The elongation from (Ala) 3, (Ala) 4, and (Ala) 5 and the formation of diketopiperazine from (Ala) 2 proceeded immediately in the presence of EDC in the meantime of the sample preparations. In addition, it was unexpected that the disappearance of the products and the reformation of the reactants occurred by the further incubation for 24 h; for instance, (Ala) 5 decreased but (Ala) 4 increased with increasing the reaction time in the reaction of (Ala) 4 with EDC. These facts suggest that the activation of the reactant amino acids or peptides immediately occurs. Under the simulated hydrothermal conditions, EDC did not enhance the formation of oligopeptides from Asp, Glu or Ala nor the spontaneous formation of (Ala) 5 from (Ala) 4.

  2. Delamination of layered zeolite precursors under mild conditions: synthesis of UCB-1 via fluoride/chloride anion-promoted exfoliation.

    PubMed

    Ogino, Isao; Nigra, Michael M; Hwang, Son-Jong; Ha, Jeong-Myeong; Rea, Thomas; Zones, Stacey I; Katz, Alexander

    2011-03-16

    New material UCB-1 is synthesized via the delamination of zeolite precursor MCM-22 (P) at pH 9 using an aqueous solution of cetyltrimethylammonium bromide, tetrabutylammonium fluoride, and tetrabutylammonium chloride at 353 K. Characterization by powder X-ray diffraction, transmission electron microscopy, and nitrogen physisorption at 77 K indicates the same degree of delamination in UCB-1 as previously reported for delaminated zeolite precursors, which require a pH of greater than 13.5 and sonication in order to achieve exfoliation. UCB-1 consists of a high degree of structural integrity via (29)Si MAS NMR and Fourier transform infrared spectroscopies, and no detectable formation of amorphous silica phase via transmission electron microscopy. Porosimetry measurements demonstrate a lack of hysteresis in the N(2) adsorption/desorption isotherms and macroporosity in UCB-1. The new method is generalizable to a variety of Si:Al ratios and leads to delaminated zeolite precursor materials lacking amorphization. PMID:21341663

  3. Complexes of earth-abundant metals for catalytic electrochemical hydrogen generation under aqueous conditions.

    PubMed

    Thoi, V Sara; Sun, Yujie; Long, Jeffrey R; Chang, Christopher J

    2013-03-21

    Growing global energy demands and climate change motivate the development of new renewable energy technologies. In this context, water splitting using sustainable energy sources has emerged as an attractive process for carbon-neutral fuel cycles. A key scientific challenge to achieving this overall goal is the invention of new catalysts for the reductive and oxidative conversions of water to hydrogen and oxygen, respectively. This review article will highlight progress in molecular electrochemical approaches for catalytic reduction of protons to hydrogen, focusing on complexes of earth-abundant metals that can function in pure aqueous or mixed aqueous-organic media. The use of water as a reaction medium has dual benefits of maintaining high substrate concentration as well as minimizing the environmental impact from organic additives and by-products. PMID:23034627

  4. Immiscible Hydrocarbon and Aqueous Fluids Under Subduction Zone Conditions and Implications for the Deep Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Huang, F.; Daniel, I.; Cardon, H.; Montagnac, G.; Sverjensky, D. A.

    2015-12-01

    Subducting slabs recycle rocks into the deep Earth releasing fluids which may cause partial melting and possible oxidation of the mantle wedge. Recent theoretical studies1 indicate that at pressures greater than about 3.0 GPa these fluids could contain high concentrations of organic and inorganic C-species with a wide range of C-oxidation states at equilibrium. If so, such fluids could play an important role in the deep carbon cycle, including the formation of diamond. However, direct experimental observations of the speciation in the fluids are needed. We studied 1.0 M aqueous Na-formate and 1.0 M Na-acetate solutions in the diamond anvil cell using Raman spectroscopy at 300 ºC and 3.0 GPa for up to 60 hours. Our preliminary results indicate that formate rapidly decomposed to bicarbonate/carbonate species and methane, with no detectable H2. Acetate decomposed much more slowly. Within the first two hours of heating, crystals of Na2CO3 precipitated in the fluid, and kept growing while immiscible droplets of hydrocarbon appeared and persisted throughout the experiments at elevated temperature and pressure. In the aqueous fluid, acetate and HCO3- were present during the first 6 hours, and then CO32- and acetate after 20 hours of heating. The final HCO3- /CO32- ratio was constant indicating a constant pH. This is the first in situ observation of persistent immiscible fluid hydrocarbons formed from an aqueous precursor at upper mantle pressures. Our results suggest that Earth's subduction zone fluids at high pressures might involve fluid hydrocarbon species as well as inorganic and organic aqueous C-species, which considerably broadens the picture of deep carbon sources, cycles and sinks. [1] Sverjensky et at. (2014), Nat. Geosci. 7, 909-913.

  5. Tertiary recovery process. [conditioning the research with a solution of a vinylpyrrolidone polymer, then an aqueous surfactant is injected and then waterflooding

    SciTech Connect

    Haltmar, W.C.; Lacey, E.S.

    1980-06-17

    A process for recovering hydrocarbons from a hydrocarbon-bearing formation penetrated by an injection well and a production well which comprises injecting an aqueous solution of a vinylpyrrolidone polymer into the formation to condition the reservoir, in a first step injecting an aqueous surfactant solution into the formation and recovering hydrocarbons via the said production well. The pretreatment of the formation with the vinylpyrrolidone polymer reduces the consumption or loss of surfactant and thus improves the efficiency of the process. Optionally, after the injection of the aqueous surfactant solution an aqueous drive fluid is injected into the formation.

  6. Dissolution of Columbia River Basalt Under Mildly Acidic Conditions as a Function of Temperature: Experimental Results Relevant to the Geological Sequestration of Carbon Dioxide

    SciTech Connect

    Schaef, Herbert T.; McGrail, B. Peter

    2009-05-01

    Increasing attention is being focused on the rapid rise of carbon dioxide levels in the atmosphere, which many believe to be the major contributing factor to global climate change. Sequestering CO2 in deep geological formations has been proposed as a long-term solution to help stabilize CO2 levels. However, before such technology can be developed and implemented, a basic understanding of H2O-CO2 systems and the chemical interactions of these fluids with the host formation must be obtained. Important issues concerning mineral stability, reaction rates, and carbonate formation are all controlled or at least significantly impacted by the kinetics of rock-water reactions in mildly acidic, CO2-saturated solutions. Basalt has recently been identified as a potentially important host formation for geological sequestration. Dissolution kinetics of the Columbia River Basalt (CRB) were measured for a range of temperatures (25° to 90°C) under mildly acidic to neutral pH conditions using the single-pass flow-through test method. Under anaerobic conditions, the normalized dissolution rates for CRB decrease with increasing pH (3≤pH≤7) with a slope, η, of -0.12 ± 0.02. An activation energy, Ea, has been estimated at 30.3 ± 2.4 kJ mol-1. Dissolution kinetics measurements like these are essential for modeling the rate at which the CO2 reacts with basalt and ultimately converted to carbonate minerals in situ.

  7. Superparamagnetic iron oxide coated on the surface of cellulose nanospheres for the rapid removal of textile dye under mild condition

    NASA Astrophysics Data System (ADS)

    Qin, Yunfeng; Qin, Zongyi; Liu, Yannan; Cheng, Miao; Qian, Pengfei; Wang, Qian; Zhu, Meifang

    2015-12-01

    Magnetic composite nanoparticles (MNPs) were prepared by anchoring iron oxide (Fe3O4) on the surface of carboxyl cellulose nanospheres through a facile chemical co-precipitation method. The as-prepared MNPs were characterized by atomic force microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, wide-angle X-ray diffraction measurement, thermal gravity analysis and vibrating sample magnetometry. These MNPs were of a generally spherical shape with a narrow size distribution, and exhibited superparamagnetic behaviors with high saturation magnetization. High efficient removal of Navy blue in aqueous solution was demonstrated at room temperature in a Fenton-like system containing the MNPs and H2O2, which benefited from small particle size, large surface area, high chemical activity, and good dispersibility of the MNPs. The removal efficiency of Navy blue induced by the MNPs prepared at a weight ratio of cellulose to iron of 1:2 were 90.6% at the first minute of the degradation reaction, and 98.0% for 5 min. Furthermore, these MNPs could be efficiently recycled and reused by using an external magnetic field. The approach presented in this paper promotes the use of renewable natural resources as templates for the preparation and stabilization of various inorganic nanomaterials for the purpose of catalysis, magnetic resonance imaging, biomedical and other potential applications.

  8. Enzyme mediated silicon-oxygen bond formation; the use of Rhizopus oryzae lipase, lysozyme and phytase under mild conditions.

    PubMed

    Abbate, Vincenzo; Bassindale, Alan R; Brandstadt, Kurt F; Lawson, Rachel; Taylor, Peter G

    2010-10-21

    The potential for expanding the variety of enzymic methods for siloxane bond formation is explored. Three enzymes, Rhizopus oryzae lipase (ROL), lysozyme and phytase are reported to catalyse the condensation of the model compound, trimethylsilanol, formed in situ from trimethylethoxysilane, to produce hexamethyldisiloxane in aqueous media at 25 °C and pH 7. Thermal denaturation and reactant inhibition experiments were conducted to better understand the catalytic role of these enzyme candidates. It was found that enzyme activities were significantly reduced following thermal treatment, suggesting a potential key-role of the enzyme active sites in the catalysis. Similarly, residue-specific modification of the key-amino acids believed to participate in the ROL catalysis also had a significant effect on the silicon bio-catalysis, indicating that the catalytic triad of the lipase may be involved during the enzyme-mediated formation of the silicon-oxygen bond. E. coli phytase was found to be particularly effective at catalysing the condensation of trimethylsilanol in a predominantly organic medium consisting of 95% acetonitrile and 5% water. Whereas the use of enzymes in silicon chemistry is still very much a developing and frontier activity, the results presented herein give some grounds for optimism that the variety of enzyme mediated reactions will continue to increase and may one day become a routine element in the portfolio of the synthetic silicon chemist. PMID:20683529

  9. Guiding functional connectivity estimation by structural connectivity in MEG: an application to discrimination of conditions of mild cognitive impairment.

    PubMed

    Pineda-Pardo, José Angel; Bruña, Ricardo; Woolrich, Mark; Marcos, Alberto; Nobre, Anna C; Maestú, Fernando; Vidaurre, Diego

    2014-11-01

    Whole brain resting state connectivity is a promising biomarker that might help to obtain an early diagnosis in many neurological diseases, such as dementia. Inferring resting-state connectivity is often based on correlations, which are sensitive to indirect connections, leading to an inaccurate representation of the real backbone of the network. The precision matrix is a better representation for whole brain connectivity, as it considers only direct connections. The network structure can be estimated using the graphical lasso (GL), which achieves sparsity through l1-regularization on the precision matrix. In this paper, we propose a structural connectivity adaptive version of the GL, where weaker anatomical connections are represented as stronger penalties on the corresponding functional connections. We applied beamformer source reconstruction to the resting state MEG recordings of 81 subjects, where 29 were healthy controls, 22 were single-domain amnestic Mild Cognitive Impaired (MCI), and 30 were multiple-domain amnestic MCI. An atlas-based anatomical parcellation of 66 regions was obtained for each subject, and time series were assigned to each of the regions. The fiber densities between the regions, obtained with deterministic tractography from diffusion-weighted MRI, were used to define the anatomical connectivity. Precision matrices were obtained with the region specific time series in five different frequency bands. We compared our method with the traditional GL and a functional adaptive version of the GL, in terms of log-likelihood and classification accuracies between the three groups. We conclude that introducing an anatomical prior improves the expressivity of the model and, in most cases, leads to a better classification between groups. PMID:25111472

  10. The effect of precipitation conditions and aging upon characteristics of particles precipitated from aqueous solutions

    SciTech Connect

    Rard, J.A.

    1989-10-01

    Precipitation of a dissolved species from aqueous solutions is one of the techniques used to grow particles with certain size or composition characteristics. Various factors affecting the particle properties for sparingly soluble substances are briefly discussed here, including homogeneous versus heterogeneous nucleation, the effect of relative supersaturation on the number of nuclei and their relative size, particle growth by way of Ostwald Ripening, the Ostwald Step Rule and nucleation of metastable phases, diffusion-controlled versus surface reaction-controlled growth, incorporation of dopants into the precipitate, and dendritic growth. 13 refs.

  11. ROS Initiated Oxidation of Dopamine under Oxidative Stress Conditions in Aqueous and Lipidic Environments

    PubMed Central

    2011-01-01

    Dopamine is known to be an efficient antioxidant and to protect neurocytes from oxidative stress by scavenging free radicals. In this work, we have carried out a systematic quantum chemistry and computational kinetics study on the reactivity of dopamine toward hydroxyl (•OH) and hydroperoxyl (•OOH) free radicals in aqueous and lipidic simulated biological environments, within the density functional theory framework. Rate constants and branching ratios for the different paths contributing to the overall reaction, at 298 K, are reported. For the reactivity of dopamine toward hydroxyl radicals, in water at physiological pH, the main mechanism of the reaction is proposed to be the sequential electron proton transfer (SEPT), whereas in the lipidic environment, hydrogen atom transfer (HAT) and radical adduct formation (RAF) pathways contribute almost equally to the total reaction rate. In both environments, dopamine reacts with hydroxyl radicals at a rate that is diffusion-controlled. Reaction with the hydroperoxyl radical is much slower and occurs only by abstraction of any of the phenolic hydrogens. The overall rate coefficients are predicted to be 2.23 × 105 and 8.16 × 105 M–1 s–1, in aqueous and lipidic environment, respectively, which makes dopamine a very good •OOH, and presumably •OOR, radical scavenger. PMID:21919526

  12. Oxidation of 1,4-dichloro-2-butene by aqueous sodium hypochlorite under phase transfer conditions

    SciTech Connect

    Grigoryan, G.S.; Karoyan, I.L.; Malkhasyan, A.Ts.; Martirosyan, G.T.; Artamkina, G.A.; Beletskaya, I.P.

    1987-11-10

    In the industrial process for the production of chloroprene from butadiene, the problem of reducing the organic impurities in the waste water to 2000 mg/liter has not yet been solved. A method has been patented for the oxidation of organic compounds by sodium hypochlorite at high temperatures and high pressure but this method is limited by the oxidation of soluble organic compounds. The oxidation of 1,4-dichloro-2-butene by aqueous sodium hypochlorite was studied. A sharp increase in the reaction rate was found in the presence of phase transfer catalysts and surfactants. The involvement of oxygen as a cooxiant and the effect of surfactants on the absorption of atmospheric oxygen by the reaction system were demonstrated.

  13. Composition and freezing of aqueous H2SO4/HNO3 solutions under polar stratospheric conditions

    NASA Technical Reports Server (NTRS)

    Beyer, K. D.; Seago, S. W.; Chang, H. Y.; Molina, M. J.

    1994-01-01

    The results of laboratory investigations of the freezing behavior of aqueous acid solutions indicate that in the stratosphere H2SO/H2O aerosol droplets would not freeze at temperatures above the ice frost point in the absence of HNO3; however, in the presence of typical levels of HNO3 liquid sulfuric acid aerosols take up significant amounts of HNO3 and H2O vapors and freeze much more readily. This is a consequence of the very rapid change in composition of the liquid droplets as the temperature drops to within two to three degrees of the equilibrium temperature at which HNO3 and H2O vapors would co-condense to form a liquid solution. In the high latitude stratosphere this HNO3/H2O 'dew point' is typically around 192-194 K at 100 mbar.

  14. Molecular engineering of a cobalt-based electrocatalytic nanomaterial for H₂ evolution under fully aqueous conditions.

    PubMed

    Andreiadis, Eugen S; Jacques, Pierre-André; Tran, Phong D; Leyris, Adeline; Chavarot-Kerlidou, Murielle; Jousselme, Bruno; Matheron, Muriel; Pécaut, Jacques; Palacin, Serge; Fontecave, Marc; Artero, Vincent

    2013-01-01

    The viability of a hydrogen economy depends on the design of efficient catalytic systems based on earth-abundant elements. Innovative breakthroughs for hydrogen evolution based on molecular tetraimine cobalt compounds have appeared in the past decade. Here we show that such a diimine-dioxime cobalt catalyst can be grafted to the surface of a carbon nanotube electrode. The resulting electrocatalytic cathode material mediates H(2) generation (55,000 turnovers in seven hours) from fully aqueous solutions at low-to-medium overpotentials. This material is remarkably stable, which allows extensive cycling with preservation of the grafted molecular complex, as shown by electrochemical studies, X-ray photoelectron spectroscopy and scanning electron microscopy. This clearly indicates that grafting provides an increased stability to these cobalt catalysts, and suggests the possible application of these materials in the development of technological devices. PMID:23247177

  15. Copper-catalyzed direct amination of quinoline N-oxides via C-H bond activation under mild conditions.

    PubMed

    Zhu, Chongwei; Yi, Meiling; Wei, Donghui; Chen, Xuan; Wu, Yangjie; Cui, Xiuling

    2014-04-01

    A highly efficient and concise one-pot strategy for the direct amination of quinoline N-oxides via copper-catalyzed dehydrogenative C-N coupling has been developed. The desired products were obtained in good to excellent yields for 22 examples starting from the parent aliphatic amines. This methodology provides a practical pathway to 2-aminoquinolines and features a simple system, high efficiency, environmental friendliness, low reaction temperature, and ligand, additives, base, and external oxidant free conditions. PMID:24628081

  16. New iridium catalysts for the selective alkylation of amines by alcohols under mild conditions and for the synthesis of quinolines by acceptor-less dehydrogenative condensation.

    PubMed

    Ruch, Susanne; Irrgang, Torsten; Kempe, Rhett

    2014-10-01

    A novel family of iridium catalysts stabilised by P,N-ligands have been introduced. The ligands are based on imidazo[1,5-b]pyridazin-7-amines and can be synthesised with a broad variety of substitution patterns. The catalysts were synthesised quantitatively from the protonated ligands and a commercially available iridium precursor. The catalysts mediate the alkylation of amines by alcohols under mild conditions (70 °C). In addition, the synthesis of quinolines from secondary or primary alcohols and amino alcohols is reported. This sustainable synthesis proceeds through the liberation of two equivalents of water and two equivalents of dihydrogen. The investigations indicate that catalysts suitable for hydrogen autotransfer or borrowing hydrogen chemistry might also be suitable for acceptor-less dehydrogenative condensation reactions. PMID:25186522

  17. Growth of La{sub 2}CuO{sub 4} nanofibers under a mild condition by using single walled carbon nanotubes as templates

    SciTech Connect

    Gao Lizhen . E-mail: lizhen@mech.uwa.edu.au; Wang Xiaolin; Chua, H.T.; Kawi, Sibudjing

    2006-07-15

    La{sub 2}CuO{sub 4} nanofibers (ca. 30 nm in diameter and 3 {mu}m in length) have been grown in situ by using single walled carbon nanotubes (SWNTs; ca. 2 nm in inner diameter; made via cracking CH{sub 4} over the catalyst of Mg{sub 0.8}Mo{sub 0.05}Ni{sub 0.10}Co{sub 0.05}O {sub x} at 800 deg. C) as templates under mild hydrothermal conditions and a temperature around 60 deg. C. During synthesis, the surfactant poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) and H{sub 2}O{sub 2} were added to disperse SWNTs and oxidize the reactants, respectively. The structure of La{sub 2}CuO{sub 4} nanofibers was confirmed by powder X-ray diffraction (XRD) and their morphologies were observed with field emission scanning electron microscope (FESEM) at the hydrothermal synthesis lasting for 5, 20 and 40 h, respectively. The La{sub 2}CuO{sub 4} crystals grew from needle-like (5 h) through stick-like (20 h) and finally to plate-like (40 h) fibers. Twenty hours is an optimum reaction time to obtain regular crystal fibers. The La{sub 2}CuO{sub 4} nanofibers are probably cubic rather than round and may capsulate SWNTs. - Graphical abstract: La{sub 2}CuO{sub 4} nanofibers have been grown in situ by using single walled carbon nanotubes as templates under mild hydrothermal conditions and a temperature around 60 deg. C. The La{sub 2}CuO{sub 4} crystals grew from needle-like (5 h) through stick-like (20 h) and finally to plate-like (40 h) fibers. The La{sub 2}CuO{sub 4} nanofibers are probably cubic rather than round and may capsulate SWNTs.

  18. Diffusion behavior of lysozyme in aqueous ammonium sulfate solutions under varying solution conditions as determined by dynamic light scattering

    SciTech Connect

    Fornefeld, U.M.; Kuehner, D.E.; Blanch, H.W.; Prausnitz, J.M. . Dept. of Chemical Engineering Lawrence Berkeley Lab., CA . Chemical Sciences Div.)

    1994-12-01

    As proteins gain significance in commercial applications such as pharmaceuticals, detergents, organic waste management and cosmetics, efficient and economical recovery of these valuable biomolecules is of increasing importance. the salting-out process has found widespread application in the area of protein separations. To date, salt-induced precipitation of proteins from complex aqueous solutions remains largely an empirical process; no comprehensive model exists to predict salting-out phase equilibria in protein solutions. Rational predictive models for salt-induced precipitation will therefore be of great value in protein purification, both on the preparative and the analytical scale. Any attempt to model theoretically salt-induced protein precipitation must include the known physics of protein interactions in aqueous solution. With this in mind, it is crucial to acknowledge that protein precipitation is fundamentally an aggregation process. In order to incorporate aggregation effects into ongoing efforts to model salting out of proteins, it is necessary to quantify the degree of aggregation as a function of solution conditions. Therefore, dynamic light scattering measurements were performed with a well-studied protein, hen-egg-white lysozyme, under several solution conditions.

  19. Polyurethane foam loaded with sodium dodecylsulfate for the extraction of 'quat' pesticides from aqueous medium: Optimization of loading conditions.

    PubMed

    Vinhal, Jonas O; Lima, Claudio F; Cassella, Ricardo J

    2016-09-01

    The cationic herbicides paraquat, diquat and difenzoquat are largely used in different cultures worldwide. With this, there is an intrinsic risk of environmental contamination when these herbicides achieve natural waters. The goal of this work was to propose a novel and low-cost sorbent for the removal of the cited herbicides from aqueous medium. The proposed sorbent was prepared by loading polyurethane foam with sodium dodecylsulfate. The influence of several parameters (SDS concentration, HCl concentration and shaking time) on the loading process was investigated. The results obtained in this work demonstrated that all studied variables influenced the loading process, having significant effect on the extraction efficiency of the resulted PUF-SDS. At optimized conditions, the PUF was loaded by shaking 200mg of crushed foam with 200mL of a solution containing 5.0×10(-3)molL(-1) SDS and 0.25molL(-1) HCl, for 30min. The obtained PUF-SDS was efficient for removing the three herbicides from aqueous medium, achieving extraction percentages higher than 90%. The sorption process followed a pseudo second-order kinetics, which presented excellent predictive capacity of the amount of herbicide retained with time. PMID:27213562

  20. Mild balanoposthitis.

    PubMed Central

    Fornasa, C V; Calabrŏ, A; Miglietta, A; Tarantello, M; Biasinutto, C; Peserico, A

    1994-01-01

    AIM--To identify and study cases of mild balanoposthitis (MBP) with penile pathology among patients observed at a dermatology clinic over an 18-month period. MATERIALS--The study included 321 patients with penile pathology. The term MBP was used to describe balanoposthitis of a localised, inflammatory nature with few, non-specific symptoms and a tendency to become chronic or recur. Two hundred and seventy had diseases clearly identifiable by clinical examination or laboratory tests; 51 cases were diagnosed as MBP and these patients had blood tests (to evaluate immune status) and microbiological examination; when these proved negative, a series of patch tests was also used. RESULTS--Of the 51 patients diagnosed as having MBP, the cause was ascertained in 34 cases (infection, mechanical trauma, contact irritation, contact allergy, etc.), whereas no specific aetiological factor was detected to explain the symptoms in the remaining 17 cases. PMID:8001949

  1. Pd-loaded magnetic mesoporous nanocomposites: A magnetically recoverable catalyst with effective enrichment and high activity for DDT and DDE removal under mild conditions.

    PubMed

    Tian, Hua; Chen, Jun; He, Junhui; Liu, Feng

    2015-11-01

    1,1,1-Trichloro-2,2-bis(4-chlorophenyl) ethane (DDT), an organochlorine pollutant, is highly persistent in environment and responsible for many ecological and health damages. Although remediation and degradation of DDT and its metabolites in soil and water by microorganisms and abiotic techniques can be accomplished, success is often accompanied by rigorous reaction conditions, such as anaerobic system, explosive gases, high pressure or temperature, and illumination. Here a triple-functional nanocomposite was prepared by integrating superparamagnetic Fe3O4 and palladium (Pd) nanoparticles onto mesoporous Fe3O4@nSiO2@mSiO2 nanospheres. These magnetic mesoporous materials display excellent capabilities of capturing and catalytically degrading DDT in water. Over these nanocomposites, DDT and its metabolite, 1,1-dichloro-2,2-bis(4-chlorophenyl) ethylene (DDE) could be quickly enriched and completely degraded at as low as 150 °C. The nanocomposites can be magnetically separated from the dispersion after adsorption, and then be easily regenerated which is accompanied by catalytic reaction. The whole treatment process is convenient, energy-saving, and just requires ambient pressure and mild reaction conditions. PMID:26188725

  2. Optimization of Aqueous Extraction Conditions for Recovery of Phenolic Content and Antioxidant Properties from Macadamia (Macadamia tetraphylla) Skin Waste

    PubMed Central

    Dailey, Adriana; Vuong, Quan V.

    2015-01-01

    The macadamia is native to Australia and is now grown commercially around the world. Macadamia skin, known as waste, has been generated abundantly, but this ample source has had limited uses as a byproduct. The aim of this study was to develop optimal aqueous extraction conditions for the recovery of phenolic compounds and antioxidant properties from macadamia skin using Response Surface Methodology (RSM). Water was selected for optimizing the extraction conditions because it is a cheap, safe, and environmentally friendly solvent. The results showed that the RSM models were reliable for the prediction and evaluation of the tested variables. Within the tested ranges, temperature (°C), time (min), and sample-to-solvent ratio (g/100 mL), and their interactions, did not significantly affect phenolic compound (TPC), flavonoid, proanthocyanidin, CUPRAC, and FRAP contents. However, the time and the sample-to-solvent ratio significantly affected DPPH antioxidant activity and the ratio significantly affected ABTS antioxidant capacity. The optimal extraction conditions for the recovery of phenolic compounds and antioxidant properties were predicted and validated at a temperature of 90 °C, a time of 20 min, and a sample-to-solvent ratio of 5 g/100 mL. At these conditions, an extract with TPC of 86 mg GAE/g, flavonoids of 30 mg RUE/g, and proanthocyanidins of 97 mg CAE/g could be prepared with potent antioxidant capacity. PMID:26783954

  3. X-ray absorption spectroscopy studies of ionic association in aqueous solutions of zinc bromide from normal to critical conditions

    NASA Astrophysics Data System (ADS)

    Simonet, V.; Calzavara, Y.; Hazemann, J. L.; Argoud, R.; Geaymond, O.; Raoux, D.

    2002-08-01

    Ion-pairing and dehydration phenomena occurring in ZnBr2 aqueous solutions from normal to critical T, P conditions were investigated by x-ray absorption spectroscopy. The respective influences of temperature, pressure, and concentration were studied. The evolution of the density of solute ions, probed by the height of the absorption edge, allowed us to get information on phase diagrams and salt precipitation. The average structural evolution deduced from extended x-ray absorption fine structure was related to the formation of complexes identified from x-ray absorption near edge structure analysis. Consequently, in noncritical conditions, an increase of temperature or concentration produces dehydration and ion-pairing, while a rise of pressure destroys the ion-pairs. In contrast, concentration and pressure have weaker effects on the local order in high P, T conditions. Moreover, ion pairing formation is found not to be specifically enhanced when the fluid is close to supercritical conditions as it also occurs at lower temperatures. In a discussion, the modifications induced by a variation of the different structural parameters are related to the macroscopic properties of the solvent.

  4. Optimization of Aqueous Extraction Conditions for Recovery of Phenolic Content and Antioxidant Properties from Macadamia (Macadamia tetraphylla) Skin Waste.

    PubMed

    Dailey, Adriana; Vuong, Quan V

    2015-01-01

    The macadamia is native to Australia and is now grown commercially around the world. Macadamia skin, known as waste, has been generated abundantly, but this ample source has had limited uses as a byproduct. The aim of this study was to develop optimal aqueous extraction conditions for the recovery of phenolic compounds and antioxidant properties from macadamia skin using Response Surface Methodology (RSM). Water was selected for optimizing the extraction conditions because it is a cheap, safe, and environmentally friendly solvent. The results showed that the RSM models were reliable for the prediction and evaluation of the tested variables. Within the tested ranges, temperature (°C), time (min), and sample-to-solvent ratio (g/100 mL), and their interactions, did not significantly affect phenolic compound (TPC), flavonoid, proanthocyanidin, CUPRAC, and FRAP contents. However, the time and the sample-to-solvent ratio significantly affected DPPH antioxidant activity and the ratio significantly affected ABTS antioxidant capacity. The optimal extraction conditions for the recovery of phenolic compounds and antioxidant properties were predicted and validated at a temperature of 90 °C, a time of 20 min, and a sample-to-solvent ratio of 5 g/100 mL. At these conditions, an extract with TPC of 86 mg GAE/g, flavonoids of 30 mg RUE/g, and proanthocyanidins of 97 mg CAE/g could be prepared with potent antioxidant capacity. PMID:26783954

  5. Computational Study of the Cation-Modified GSH Peptide Interactions With Perovskite-Type BFO-(111) Membranes Under Aqueous Conditions.

    PubMed

    Bian, Liang; Dong, Fa-Qin; Song, Mian-Xin; Xu, Jin-Bao; Zhang, Xiao-Yan

    2015-12-01

    We elucidated a number of facets regarding glutathione (GSH)-bismuth ferrite (BiFeO3, BFO) interactions and reactivity that have previously remained unexplored on a molecular level. In this approach, the cation-modified reduced GSH (or oxidised glutathione (GS·)) formed on the (111)-oriented BiFeO3 membrane (namely BFO-(111)) can serve as an efficient quencher, and the luminescence mechanism is explained in aqueous conditions. Notably, we suggest the use of Fe(2+)↓ ion as an electron donor and K(+) ion as an electron acceptor to exert a "gluing" effect on the glutamic acid (Glu) and glycine (Gly) side chains, producing an exposed sulfhydryl (-SH) configuration. This method may enable the rational design of a convenient platform for biosensors. PMID:26061445

  6. Computational Study of the Cation-Modified GSH Peptide Interactions With Perovskite-Type BFO-(111) Membranes Under Aqueous Conditions

    NASA Astrophysics Data System (ADS)

    Bian, Liang; Dong, Fa-qin; Song, Mian-xin; Xu, Jin-bao; Zhang, Xiao-yan

    2015-06-01

    We elucidated a number of facets regarding glutathione (GSH)-bismuth ferrite (BiFeO3, BFO) interactions and reactivity that have previously remained unexplored on a molecular level. In this approach, the cation-modified reduced GSH (or oxidised glutathione (GS·)) formed on the (111)-oriented BiFeO3 membrane (namely BFO-(111)) can serve as an efficient quencher, and the luminescence mechanism is explained in aqueous conditions. Notably, we suggest the use of Fe2+↓ ion as an electron donor and K+ ion as an electron acceptor to exert a "gluing" effect on the glutamic acid (Glu) and glycine (Gly) side chains, producing an exposed sulfhydryl (-SH) configuration. This method may enable the rational design of a convenient platform for biosensors.

  7. Hydrothermal diamond anvil cell for XAFS studies of first-row transition elements in aqueous solutions up to supercritical conditions

    USGS Publications Warehouse

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

    2000-01-01

    A hydrothermal diamond anvil cell (HDAC) has been modified by drilling holes with a laser to within 150 ??m of the anvil face to minimize the loss of X-rays due to absorption and scatter by diamond. This modification enables acquisition of K-edge X-ray absorption fine structure (XAFS) spectra from first-row transition metal ions in aqueous solutions at temperatures ranging from 25??C to 660??C and pressures up to 800 MPa. These pressure-temperature (P-T) conditions are more than sufficient for carrying out experimental measurements that can provide data valuable in the interpretation of fluid inclusions in minerals found in ore-forming hydrothermal systems as well as other important lithospheric processes involving water. (C) 2000 Elsevier Science B.V. All rights reserved.

  8. CHEMICAL TRANSFORMATIONS USING NON-TRADITIONAL APPROACHES: MICROWAVE-ASSISTED GREENER SYNTHESES IN AQUEOUS MEDIA OR UNDER SOLVENT-FREE CONDITIONS

    EPA Science Inventory

    Microwave (MW) irradiation in conjunction with water as reaction media has proven to be a 'greener' chemical approach for expeditious N-alkylation reactions of amines and hydrazines wherein the reactions under mildly basic conditions afford tertiary amines and double N<...

  9. Coordinating Chiral Ionic Liquids: Design, Synthesis, and Application in Asymmetric Transfer Hydrogenation under Aqueous Conditions

    PubMed Central

    Vasiloiu, Maria; Gaertner, Peter; Zirbs, Ronald; Bica, Katharina

    2015-01-01

    Hydrophilic coordinating chiral ionic liquids with an amino alcohol substructure were developed and efficiently applied to the asymmetric reduction of ketones. Their careful design and adaptability to the desired reaction conditions allow for these chiral ionic liquids to be used as the sole source of chirality in a ruthenium-catalyzed transfer hydrogenation reaction of aromatic ketones. When used in this reaction system, these chiral ionic liquids afforded excellent yields and high enantioselectivities. PMID:26279638

  10. Determination of the optimum conditions for boric acid extraction with carbon dioxide gas in aqueous media from colemanite containing arsenic

    SciTech Connect

    Ata, O.N.; Colak, S.; Copur, M.; Celik, C.

    2000-02-01

    The Taguchi method was used to determine optimum conditions for the boric acid extraction from colemanite ore containing As in aqueous media saturated by CO{sub 2} gas. After the parameters were determined to be efficient on the extraction efficiency, the experimental series with two steps were carried out. The chosen experimental parameters for the first series of experiments and their ranges were as follows: (1) reaction temperature, 25--70 C; (2) solid-to-liquid ratio (by weight), 0.091 to 0.333; (3) gas flow rate (in mL/min), 66.70--711; (4) mean particle size, {minus}100 to {minus}10 mesh; (5) stirring speed, 200--600 rpm; (6) reaction time, 10--90 min. The optimum conditions were found to be as follows: reaction temperature, 70 C; solid-to-liquid ratio, 0.091; gas flow rate, 711 (in mL/min); particle size, {minus}100 mesh; stirring speed, 500 rpm; reaction time, 90 min. Under these optimum conditions, the boric acid extraction efficiency from the colemanite containing As was approximately 54%. Chosen experimental parameters for the second series of experiments and their ranges were as follows: (1) reaction temperature, 60--80 C; (2) solid-to-liquid ratio (by weight), 0.1000 to 0.167; (3) gas pressure (in atm), 1.5; 2.7; (4) reaction time, 45--120 min. The optimum conditions were found to be as follows: reaction temperature, 70 C; solid-to-liquid ratio, 0.1; gas pressure, 2.7 atm; reaction time, 120 min. Under these optimum conditions the boric acid extraction efficiency from the colemanite ore was approximately 75%. Under these optimum conditions, the boric acid extraction efficiency from calcined colemanite ore was approximately 99.55%.

  11. Immobilization of selenate by iron in aqueous solution under anoxic conditions and the influence of uranyl

    NASA Astrophysics Data System (ADS)

    Puranen, Anders; Jonsson, Mats; Dähn, Rainer; Cui, Daqing

    2009-08-01

    In proposed high level radioactive waste repositories a large part of the spent nuclear fuel (SNF) canisters are commonly composed of iron. Selenium is present in spent nuclear fuel as a long lived fission product. This study investigates the influence of iron on the uptake of dissolved selenium in the form of selenate and the effect of the presence of dissolved uranyl on the above interaction of selenate. The iron oxide, and selenium speciation on the surfaces was investigated by Raman spectroscopy. X-ray Absorption Spectroscopy was used to determine the oxidation state of the selenium and uranium on the surfaces. Under the simulated groundwater conditions (10 mM NaCl, 2 mM NaHCO 3, <0.1 ppm O 2) the immobilized selenate was found to be reduced to oxidation states close to zero or lower and uranyl was found to be largely reduced to U(IV). The near simultaneous reduction of uranyl was found to greatly enhance the rate of selenate reduction. These findings suggest that the presence of uranyl being reduced by an iron surface could substantially enhance the rate of reduction of selenate under anoxic conditions relevant for a repository.

  12. Stimuli-sensitive hydrogel based on N-isopropylacrylamide and itaconic acid for entrapment and controlled release of Candida rugosa lipase under mild conditions.

    PubMed

    Milašinović, Nikola; Knežević-Jugović, Zorica; Milosavljević, Nedeljko; Lučić Škorić, Marija; Filipović, Jovanka; Kalagasidis Krušić, Melina

    2014-01-01

    Stimuli responsive pH- and temperature-sensitive hydrogel drug delivery systems, as those based on N-isopropylacrylamide (NiPAAm) and itaconic acid (IA), have been attracting much of the attention of the scientific community nowadays, especially in the field of drug release. By adjusting comonomer composition, the matrix is enabled to protect the incorporated protein in the highly acidic environment of upper gastrointestinal tract and deliver it in the neutral or slightly basic region of the lower intestine. The protein/poly(NiPAAm-co-IA) hydrogels were synthetized by free radical crosslinking copolymerization and were characterized concerning their swelling capability, mechanical properties, and morphology. The pore structure and sizes up to 1.90 nm allowed good entrapment of lipase molecules. Model protein, lipase from Candida rugosa, was entrapped within hydrogels upon mild conditions that provided its protection from harmful environmental influences. The efficiency of the lipase entrapment reached 96.7%, and was dependent on the initial concentration of lipase solution. The swelling of the obtained hydrogels in simulated pH and temperature of gastrointestinal tract, the lipase entrapment efficiency, and its release profiles from hydrogels were investigated as well. PMID:24982870

  13. Stimuli-Sensitive Hydrogel Based on N-Isopropylacrylamide and Itaconic Acid for Entrapment and Controlled Release of Candida rugosa Lipase under Mild Conditions

    PubMed Central

    Milašinović, Nikola; Knežević-Jugović, Zorica; Milosavljević, Nedeljko; Lučić Škorić, Marija; Filipović, Jovanka; Kalagasidis Krušić, Melina

    2014-01-01

    Stimuli responsive pH- and temperature-sensitive hydrogel drug delivery systems, as those based on N-isopropylacrylamide (NiPAAm) and itaconic acid (IA), have been attracting much of the attention of the scientific community nowadays, especially in the field of drug release. By adjusting comonomer composition, the matrix is enabled to protect the incorporated protein in the highly acidic environment of upper gastrointestinal tract and deliver it in the neutral or slightly basic region of the lower intestine. The protein/poly(NiPAAm-co-IA) hydrogels were synthetized by free radical crosslinking copolymerization and were characterized concerning their swelling capability, mechanical properties, and morphology. The pore structure and sizes up to 1.90 nm allowed good entrapment of lipase molecules. Model protein, lipase from Candida rugosa, was entrapped within hydrogels upon mild conditions that provided its protection from harmful environmental influences. The efficiency of the lipase entrapment reached 96.7%, and was dependent on the initial concentration of lipase solution. The swelling of the obtained hydrogels in simulated pH and temperature of gastrointestinal tract, the lipase entrapment efficiency, and its release profiles from hydrogels were investigated as well. PMID:24982870

  14. Syntheses and crystal structures of benzene-sulfonate and -carboxylate copper polymers and their application in the oxidation of cyclohexane in ionic liquid under mild conditions.

    PubMed

    Hazra, Susanta; Ribeiro, Ana P C; Guedes da Silva, M Fátima C; Nieto de Castro, Carlos A; Pombeiro, Armando J L

    2016-09-21

    The syntheses, crystal structures and catalytic activities of the polymers derived from 2-(2-pyridylmethyleneamino)benzenesulfonic acid (HL), viz. [CuL(H2tma)]n (1) and [{Cu2L2(H2pma)}·(8H2O)]n (2) [H3tma = benzene-1,3,5-tricarboxylic (trimesic) acid and H4pma = benzene-1,2,4,5-tetracarboxylic (pyromellitic) acid], are presented. Despite the comparable combinations and compositions of ligands (sulfonate and carboxylate) in these two polymers the bridging moiety in 1 is sulfonate while in 2 it is carboxylate. Complexes 1 and 2 act as catalysts in the peroxidative oxidation of cyclohexane under mild conditions using either the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate [bmim][PF6] or acetonitrile as the solvent. The ionic liquid medium leads to increases in the yields and in the turnover numbers, achieved in shorter reaction times in comparison with those when using the conventional acetonitrile solvent. A simple recycling of the catalysts in the ionic liquid medium is achieved without loss of activity and selectivity. PMID:27529408

  15. Reversible thermal switching of aqueous dispersibility of multiwalled carbon nanotubes.

    PubMed

    O'Driscoll, Luke J; Welsh, Daniel J; Bailey, Steven W D; Visontai, David; Frampton, Harry; Bryce, Martin R; Lambert, Colin J

    2015-03-01

    Easily reversible aqueous dispersion/precipitation of multiwalled carbon nanotubes (MWNTs) has been demonstrated using small-molecule non-ionic pyrene-based surfactants, which exhibit lower critical solution temperature (LCST) phase behaviour. The MWNTs are dispersed by means of non-covalent interactions. The dispersibility can be switched "off" (i.e., MWNTs precipitated) upon heating and switched "on" (i.e., MWNTs re-dispersed) upon cooling and merely swirling the sample at room temperature, that is, under very mild conditions. This effect is also observed under high ionic strength conditions with NaCl in the aqueous phase. PMID:25639258

  16. Physical properties of rocks and aqueous fluids at conditions simulating near- and supercritical reservoirs

    NASA Astrophysics Data System (ADS)

    Kummerow, Juliane; Raab, Siegfried

    2016-04-01

    The growing interest in exploiting supercritical geothermal reservoirs calls for a thorough identification and understanding of physico-chemical processes occuring in geological settings with a high heat flow. In reservoir engineering, electrical sounding methods are common geophysical exploration and monitoring tools. However, a realistic interpretation of field measurements is based on the knowledge of both, the physical properties of the rock and those of the interacting fluid at defined temperature and pressure conditions. Thus, laboratory studies at simulated in-situ conditions provide a link between the field data and the material properties in the depth. The physico-chemical properties of fluids change dramatically above the critical point, which is for pure water 374.21 °C and 221.2 bar. In supercritical fluids mass transfer and diffusion-controlled chemical reactions are enhanced and cause mineral alterations. Also, ion mobility and ion concentration are affected by the change of physical state. All this cause changes in the electrical resistivity of supercritical fluids and may have considerable effects on the porosity and hydraulic properties of the rocks they are in contact with. While there are some datasets available for physical and chemical properties of water and single component salt solutions above their critical points, there exist nearly no data for electrical properties of mixed brines, representing the composition of natural geothermal fluids. Also, the impact of fluid-rock interactions on the electrical properties of multicomponent fluids in a supercritical region is scarcely investigated. For a better understanding of fluid-driven processes in a near- and supercritical geological environment, in the framework of the EU-funded FP7 program IMAGE we have measured (1) the electrical resistivity of geothermal fluids and (2) physical properties of fluid saturated rock samples at simulated in-situ conditions. The permeability and electrical

  17. Transparent ZnO Films Deposited by Aqueous Solution Process Under Various pH Conditions

    NASA Astrophysics Data System (ADS)

    Hong, Jeong Soo; Wagata, Hajime; Ohashi, Naoki; Katsumata, Ken-ichi; Okada, Kiyoshi; Matsushita, Nobuhiro

    2015-08-01

    ZnO films were deposited using a spin-spray method with the source solution containing zinc nitrate and an oxidizing solution containing trisodium citrate onto glass substrates under various pH conditions. A ZnO film with a columnar structure was obtained at pH higher than 7.0, while no ZnO film was formed at a mixed solution pH of 6.7. The transparent and conductive ZnO film obtained from a mixed solution with pH 10.7 exhibited the lowest resistivity of 9.9 × 10-3 Ω cm with a high transmittance above 90%.

  18. Diffusion and polymerization of styrene in an aqueous solution of potassium persulfate under static conditions

    SciTech Connect

    Oganesyan, A.A.; Boyadzhyan, V.G.; Gritskova, I.A.; Gukasyan, A.V.; Matsoyan, S.G.; Pravednikov, A.N.

    1985-10-01

    The potassium persulfate-initiated polymerization of styrene in a mechanically agitated mixture of water and monomer leads to the formation of a stable, monodisperse latex. In order to explain the mechanism of the stabilization of the latex particles in this system, the authors present a detailed investigation of the polymerization of styrene in a specially constructed electrochemical cell under static conditions. A schematic of the cell is shown. Results show that the capacity of the electrical double layer on the platinum electrode remains constant with time in a system containing only a solution of electrolyte, either K/sub 2/SO/sub 4/ or K/sub 2/S/sub 2/O/sub 8/.

  19. Flow and morphological conditions associated with the directional solidification of aqueous ammonium chloride. Annual performance report

    SciTech Connect

    Magirl, C.S.; Incropera, F.P.

    1993-01-01

    Using 27% aq. NH{sub 4}Cl solutions as transparent analog, shadowgraphy and dye injection were used to observe flow and morphology in unidirectional solidification (UDS) from below. Dendritic crystals that form at the cold surface reject lighter, solute-deficient fluid, and instability is shown by finger-type double-diffusive convection. As the mushy two-phase region grows, perturbations at the liquidus interface cause localized remelting and downward development of channels. Solsutal plumes emanate from the channels, and in time, double-diffusive convection layers also form in the melt. When the solution is chilled at the sides as well as at the bottom, conditions are influenced by detachment and settling of crystals from the sidewall and by plumes from slanted channels. When a slow, oscillatory rocking motion is imposed on UDS, the freckle-type segregates in the final cast is suppressed. Within the melt, plumes and double-diffusive convection are eliminated. Inertially induced convection mixes the melt and produces a dense slurry. Although channels are eliminated from the bottom mushy region, overall heat transfer and macrosegregation in the cavity are unaffected by the slow rocking. Numerical simulations qualitatively predict trends in the field variables and provide insights on interdendritic flows and macrosegregation (freckle-, A-type segregates), although its quantitative predictions are hampered by simplifying assumptions.

  20. Flow and morphological conditions associated with the directional solidification of aqueous ammonium chloride

    SciTech Connect

    Magirl, C.S.; Incropera, F.P.

    1993-01-01

    Using 27% aq. NH[sub 4]Cl solutions as transparent analog, shadowgraphy and dye injection were used to observe flow and morphology in unidirectional solidification (UDS) from below. Dendritic crystals that form at the cold surface reject lighter, solute-deficient fluid, and instability is shown by finger-type double-diffusive convection. As the mushy two-phase region grows, perturbations at the liquidus interface cause localized remelting and downward development of channels. Solsutal plumes emanate from the channels, and in time, double-diffusive convection layers also form in the melt. When the solution is chilled at the sides as well as at the bottom, conditions are influenced by detachment and settling of crystals from the sidewall and by plumes from slanted channels. When a slow, oscillatory rocking motion is imposed on UDS, the freckle-type segregates in the final cast is suppressed. Within the melt, plumes and double-diffusive convection are eliminated. Inertially induced convection mixes the melt and produces a dense slurry. Although channels are eliminated from the bottom mushy region, overall heat transfer and macrosegregation in the cavity are unaffected by the slow rocking. Numerical simulations qualitatively predict trends in the field variables and provide insights on interdendritic flows and macrosegregation (freckle-, A-type segregates), although its quantitative predictions are hampered by simplifying assumptions.

  1. Corrosion phenomena on alloy 625 in aqueous solutions containing hydrochloric acid and oxygen under subcritical and supercritical conditions

    SciTech Connect

    Boukis, N.; Kritzer, P.

    1997-08-01

    Supercritical Water Oxidation (SCWO) is a very effective process to destroy hazardous aqueous wastes containing organic contaminants. The main target applications in the USA are the destruction of DOD and DOE wastes such as rocket fuels and explosives, warfare agents and organics present in low level radioactive liquid wastes. Alloy 625 is frequently used as reactor material for Supercritical Water Oxidation (SCWO) applications. This is due to the favorable combination of mechanical properties, corrosion resistance, price and availability. Nevertheless, the corrosion of alloy 625 like the corrosion of other Ni-base alloys during oxidation of hazardous organic waste containing chloride proceeds too fast and is a major problem in SCWO applications. In these experiments high pressure, high-temperature resistant tube reactors made of alloy 625 were used as specimens. They were exposed to SCWO conditions, without organics, at temperatures up to 500 C and pressures up to 37 MPa for up to 150 h. Simultaneously, coupons also made from alloy 625 are exposed inside the test tubes. The most important corrosion problem for alloy 625 is pitting and intercrystalline corrosion at temperatures near the critical temperature, i.e. in the preheater and cooling sections of the test tubes. Under certain conditions, stress corrosion cracking appears and leads to premature failure of the test reactors. The corrosion products were insoluble in supercritical water and formed thick layers in the supercritical part of the reactor. Under these layers only minor corrosion occurred. 33 refs.

  2. Chronic Mild Cold Conditioning Modulates the Expression of Hypothalamic Neuropeptide and Intermediary Metabolic-Related Genes and Improves Growth Performances in Young Chicks

    PubMed Central

    Nguyen, Phuong; Greene, Elizabeth; Ishola, Peter; Huff, Geraldine; Donoghue, Annie; Bottje, Walter; Dridi, Sami

    2015-01-01

    Background Low environmental temperatures are among the most challenging stressors in poultry industries. Although landmark studies using acute severe cold exposure have been conducted, still the molecular mechanisms underlying cold-stress responses in birds are not completely defined. In the present study we determine the effect of chronic mild cold conditioning (CMCC) on growth performances and on the expression of key metabolic-related genes in three metabolically important tissues: brain (main site for feed intake control), liver (main site for lipogenesis) and muscle (main site for thermogenesis). Methods 80 one-day old male broiler chicks were divided into two weight-matched groups and maintained in two different temperature floor pen rooms (40 birds/room). The temperature of control room was 32°C, while the cold room temperature started at 26.7°C and gradually reduced every day (1°C/day) to reach 19.7°C at the seventh day of the experiment. At day 7, growth performances were recorded (from all birds) and blood samples and tissues were collected (n = 10). The rest of birds were maintained at the same standard environmental condition for two more weeks and growth performances were measured. Results Although feed intake remained unchanged, body weight gain was significantly increased in CMCC compared to the control chicks resulting in a significant low feed conversion ratio (FCR). Circulating cholesterol and creatine kinase levels were higher in CMCC chicks compared to the control group (P<0.05). CMCC significantly decreased the expression of both the hypothalamic orexigenic neuropeptide Y (NPY) and anorexigenic cocaine and amphetamine regulated transcript (CART) in chick brain which may explain the similar feed intake between the two groups. Compared to the control condition, CMCC increased the mRNA abundance of AMPKα1/α2 and decreased mTOR gene expression (P<0.05), the master energy and nutrient sensors, respectively. It also significantly decreased the

  3. Increased Cortical Gamma-Aminobutyric Acid Precedes Incomplete Extinction of Conditioned Fear and Increased Hippocampal Excitatory Tone in a Mouse Model of Mild Traumatic Brain Injury.

    PubMed

    Schneider, Brandy L; Ghoddoussi, Farhad; Charlton, Jennifer L; Kohler, Robert J; Galloway, Matthew P; Perrine, Shane A; Conti, Alana C

    2016-09-01

    Mild traumatic brain injury (mTBI) contributes to development of affective disorders, including post-traumatic stress disorder (PTSD). Psychiatric symptoms typically emerge in a tardive fashion post-TBI, with negative effects on recovery. Patients with PTSD, as well as rodent models of PTSD, demonstrate structural and functional changes in brain regions mediating fear learning, including prefrontal cortex (PFC), amygdala (AMYG), and hippocampus (HC). These changes may reflect loss of top-down control by which PFC normally exhibits inhibitory influence over AMYG reactivity to fearful stimuli, with HC contribution. Considering the susceptibility of these regions to injury, we examined fear conditioning (FC) in the delayed post-injury period, using a mouse model of mTBI. Mice with mTBI displayed enhanced acquisition and delayed extinction of FC. Using proton magnetic resonance spectroscopy ex vivo, we examined PFC, AMYG, and HC levels of gamma-aminobutyric acid (GABA) and glutamate as surrogate measures of inhibitory and excitatory neurotransmission, respectively. Eight days post-injury, GABA was increased in PFC, with no significant changes in AMYG. In animals receiving FC and mTBI, glutamate trended toward an increase and the GABA/glutamate ratio decreased in ventral HC at 25 days post-injury, whereas GABA decreased and GABA/glutamate decreased in dorsal HC. These neurochemical changes are consistent with early TBI-induced PFC hypoactivation facilitating the fear learning circuit and exacerbating behavioral fear responses. The latent emergence of overall increased excitatory tone in the HC, despite distinct plasticity in dorsal and ventral HC fields, may be associated with disordered memory function, manifested as incomplete extinction and enhanced FC recall. PMID:26529240

  4. Hydrogenation of arenes under mild conditions using rhodium pyridylphosphine and bipyridyl complexes tethered to a silica-supported palladium heterogeneous catalyst

    SciTech Connect

    Yang, H.; Gao, H.; Angelici, R.J.

    2000-02-21

    The rhodium complexes [Rh(COD)(1)]BF{sub 4} (RH(N-P)) and [Rh(COD)(2)]BF{sub 4} (Rh(N-N)), containing the new pyridylphosphine and bipyridyl ligands (1 and 2) with alkoxysilane groups, were tethered on the silica-supported palladium heterogeneous catalyst Pd-SiO{sub 2} to give the TCSM (tethered complex on supported metal) catalysts Rh(N-P)/Pd-SiO{sub 2} and Rh(N-N)/Pd-SiO{sub 2}. Under the mild conditions of 70 C and 4 atm of H{sub 2}, the two TCSM catalysts are very active for the hydrogenation of arenes (PhCO{sub 2}Me, PhOH, toluene, PhOCH{sub 3}, PhCO{sub 2}Et, 4-CH{sub 3}C{sub 6}H{sub 4}CO{sub 2}Et, dimethyl terephthalate) to cyclohexanes; the activities are higher than those of the separate homogeneous Rh(N-P) and Rh(N-N) complex catalysts, the silica-supported palladium catalyst Pd-SiO{sub 2}, or the rhodium complex catalysts tethered on just SiO{sub 2}. The catalysts are easily separated from the reaction mixtures and can be recycled several times without losing activity. Of the two TCSM catalysts, the higher activity for the hydrogenation of anisole to methyl cyclohexyl ether was observed for Rh(N-N)/Pd-SiO{sub 2}, which gives a TOF value of 3060 mol of substrate converted/((mol of Rh)h) and a TO value of 14500 mol of substrate converted/(mol of Rh) in 6 h. Reactions of acetophenone lead to hydrogenation of the arene ring, the carbonyl group, or both, depending on the catalyst (Rh(N-P)/Pd-SiO{sub 2} or Rh(N-N)/Pd-SiO{sub 2}) and the solvent (heptane or ethanol).

  5. Effect of core body temperature, time of day, and climate conditions on behavioral patterns of lactating dairy cows experiencing mild to moderate heat stress.

    PubMed

    Allen, J D; Hall, L W; Collier, R J; Smith, J F

    2015-01-01

    Cattle show several responses to heat load, including spending more time standing. Little is known about what benefit this may provide for the animals. Data from 3 separate cooling management trials were analyzed to investigate the relationship between behavioral patterns in lactating dairy cows experiencing mild to moderate heat stress and their body temperature. Cows (n=157) were each fitted with a leg data logger that measured position and an intravaginal data logger that measures core body temperature (CBT). Ambient conditions were also collected. All data were standardized to 5-min intervals, and information was divided into several categories: when standing and lying bouts were initiated and the continuance of each bout (7,963 lying and 6,276 standing bouts). In one location, cows were continuously subjected to heat-stress levels according to temperature-humidity index (THI) range (THI≥72). The THI range for the other 2 locations was below and above a heat-stress threshold of 72 THI. Overall and regardless of period of day, cows stood up at greater CBT compared with continuing to stand or switching to a lying position. In contrast, cows lay down at lower CBT compared with continuing to lie or switching to a standing position, and lying bouts lasted longer when cows had lower CBT. Standing bouts also lasted longer when cattle had greater CBT, and they were less likely to lie down (less than 50% of lying bouts initiated) when their body temperature was over 38.8°C. Also, cow standing behavior was affected once THI reached 68. Increasing CBT decreased lying duration and increased standing duration. A CBT of 38.93°C marked a 50% likelihood a cow would be standing. This is the first physiological evidence that standing may help cool cows and provides insight into a communally observed behavioral response to heat. PMID:25468707

  6. Unprecedented Selective Oxidation of Styrene Derivatives using a Supported Iron Oxide Nanocatalyst in Aqueous Medium

    EPA Science Inventory

    Iron oxide nanoparticles supported on mesoporous silica-type materials have been successfully utilized in the aqueous selective oxidation of alkenes under mild conditions using hydrogen peroxide as a green oxidant. Catalysts could be easily recovered after completion of the reac...

  7. Detection of native protein ions in aqueous solution under ambient conditions by electrospray laser desorption/ionization mass spectrometry.

    PubMed

    Shiea, Jentaie; Yuan, Cheng-Hui; Huang, Min-Zong; Cheng, Sy-Chyi; Ma, Ya-Lin; Tseng, Wei-Lung; Chang, Hui-Chiu; Hung, Wen-Chun

    2008-07-01

    Liquid electrospray laser desorption/ionization (ELDI) mass spectrometry allows desorption and ionization of proteins directly from aqueous solutions and biological fluids under ambient conditions. Native protein ions such as those of myoglobin, cytochrome c, and hemoglobin were obtained. A droplet (ca. 5 microL) containing the protein molecules and micrometer-sized particles (e.g., carbon graphite powder) is irradiated with a pulsed UV laser. The laser energy adsorbed by the inert particles is transferred to the surrounding solvent and protein molecules, leading to their desorption; the desorbed gaseous molecules are then postionized within an electrospray (ESI) plume to generate the ESI-like protein ions. With the use of this technique, we detected only the protonated protein ions in various biological fluids (including human tears, cow milk, serum, and bacterial extracts) without interference from their corresponding sodiated or potassiated adduct ions. In addition, we rapidly quantified the levels of glycosylated hemoglobin present in drops of whole blood obtained from diabetic patients without the need of sample pretreatment. PMID:18510347

  8. Weathering and dissolution rates among Pb shot pellets of differing elemental compositions exposed to various aqueous and soil conditions.

    PubMed

    Takamatsu, Takejiro; Murata, Tomoyoshi; Koshikawa, Masami K; Watanabe, Mirai

    2010-07-01

    The present study was performed to investigate the weathering and dissolution rates of Pb shot pellets differing in elemental composition (Pb, Sb, and As) exposed under various aqueous and soil conditions using five commercial shot pellet preparations. Upon immersion in distilled water, the dissolution rates of shot pellets, calculated from the difference in weight before versus after immersion, decreased with increasing Sb + As contents and the dominant precipitate was hydrocerussite. These subsidiary ingredients may be related to the difficulty of metallic Pb oxidation (transformation to PbO). Weight losses standardized by the amount of rainfall upon exposure to rainfall on open grassland and under canopies of Japanese cedar (Cryptomeria japonica) and bamboo-leafed oak (Quercus myrsinaefolia) were 1.11, 1.07, and 7.35 mg g pellets(-1) year(-1) L(-1), respectively, and was also related to Sb + As contents in shot pellets. However, annual dissolution rates of Pb standardized by the amount of rainfall as the soluble fraction at the same sites were 0.72, 0.33, and 0.40 mg Pb g pellets(-1) year(-1) L(-1) in the same order. These trends seemed to be related to the rainfall pH, which induces precipitation of Pb dissolved as PbCO(3) under conditions of higher pH at the Q. myrsinaefolia site or organic matter released from leaves, etc., which can form metal complexes. Dissolution rates of shot pellets buried in soils (Cambisol, Fluvisol, Regosol, Andosol) also seemed to be related to the soil pH and dissolved organic matter contents but were about sixfold faster than those with exposure to rainfall. PMID:20039167

  9. X-ray photoelectron spectroscopic study of surface chemistry of dibenzyl-disulfide on steel under mild and severe wear conditions

    NASA Technical Reports Server (NTRS)

    Wheeler, D. R.

    1977-01-01

    Wear tests were performed on 304 stainless steel lubricated with pure mineral oil with and without dibenzyl-disulfide. Both mild and severe wear were observed. The type of wear was distinguished by a marked change in wear rate, friction coefficient, and wear scar appearance. The chemical composition of the wear scar surface was examined with X-ray photoelectron spectroscopy in conjunction with argon ion sputter etching. In severe wear scars, a sulfide was formed at the expense of the normal oxide layer. In mild wear scars, there were only superficial sulfur compounds, but there was a substantial increase in the oxide thickness.

  10. Conductive polymer coatings for anodes in aqueous electrowinning

    NASA Astrophysics Data System (ADS)

    Alfantazi, A. M.; Moskalyk, R. R.

    2003-07-01

    This article discusses the potential application of electrically conductive polymers as protective coatings for permanent lead anodes employed in aqueous electrowinning processes. Also presented are results from a preliminary study of the performance of two intrinsically conductive polymers (polyaniline and poly 3,4,5-trifluorophenylthiophene [TFPT]) under mild copper electrowinning conditions as conductive and protective coatings on anodic surfaces. The laboratory results indicated that using lead alloy anodes coated with TFPT merits continued research.

  11. Serpentinization, iron oxidation, and aqueous conditions in an ophiolite: Implications for hydrogen production and habitability on Mars

    NASA Astrophysics Data System (ADS)

    Greenberger, Rebecca N.; Mustard, John F.; Cloutis, Edward A.; Pratt, Lisa M.; Sauer, Peter E.; Mann, Paul; Turner, Kathryn; Dyar, M. Darby; Bish, David L.

    2015-04-01

    weathering, and isotopic trends are consistent with kinetic fractionation. The extensive presence of tetrahedral Fe3+ in serpentine shows the system liberally produced H2 while the isotope systematics have implications for preservation of indicators of the aqueous conditions that formed serpentinites on Mars and their habitability.

  12. Facile stabilization of cyclodextrin metal-organic frameworks under aqueous conditions via the incorporation of C60 in their matrices.

    PubMed

    Li, Haiqing; Hill, Matthew R; Huang, Runhong; Doblin, Christian; Lim, Seng; Hill, Anita J; Babarao, Ravichandar; Falcaro, Paolo

    2016-05-21

    A facile method to improve the stability of γ-cyclodextrin metal-organic frameworks (γ-CD-MOFs) in an aqueous environment has been developed through the incorporation of hydrophobic C60 in their matrices, and the resulting hybrid materials were exploited for drug delivery applications. PMID:27055670

  13. Sample preparation followed by HPLC under harmless 100% aqueous conditions for determination of oxytetracycline in milk and eggs.

    PubMed

    Furusawa, Naoto

    2004-05-01

    A simple and hazardous chemical-free method for the high-performance liquid chromatographic determination of oxytetracycline (OTC) residues in milk and eggs has been developed. Sample preparation consists in homogenization with an aqueous solution by means of a handheld ultrasonic homogenizer followed by centrifugal ultrafiltration. HPLC is performed with an isocratic aqueous mobile phase and a photodiode array detector. Average recoveries of OTC (0.05, 0.1, and 0.2 microg mL(-1) for milk; 0.1, 0.2, and 0.4 microg mL(-1) for eggs) were > or =84% with relative standard deviations of < or =2.3%. The total time required for the analysis of one sample and LOQs were <30 min and <0.1 microg mL(-1), respectively. In all the processes, no organic solvents or hazardous reagents were used. PMID:15335039

  14. Treatment of rheumatoid arthritis and other related conditions by provoking a mild infection to be controlled by the immune system itself.

    PubMed

    Halabe Bucay, Alberto

    2007-01-01

    When rheumatoid arthritis presents, the immune system overcompensates and acts attacking the joints and the body in general, the same thing occurs with other autoimmune diseases; the immunological mechanisms that manifest in these diseases have been identified, but there is still no explanation as to why this occurs. This article will present a hypothesis that is based on provoking a mild infection in patients with rheumatoid arthritis, and other related autoimmune diseases, an infection that does not result in serious consequences to the health of the patients, but does generate an immunological response, in this manner, the immune system itself, which is overcompensating, will fight the provoked infection instead of causing damage to the body itself. PMID:17280795

  15. The facile construction of the phthalazin-1(2H)-one scaffold via copper-mediated C–H(sp2)/C–H(sp) coupling under mild conditions

    PubMed Central

    Zhu, Wei; Wang, Bao; Zhou, Shengbin

    2015-01-01

    Summary A novel strategy for the construction of the phthalazin-1(2H)-one scaffold has been developed by means of a copper-mediated cascade C–H/C–H coupling and intramolecular annulations and a subsequent facile hydrazinolysis. This C–H activation transformation proceeds smoothly with wide generality, good functional tolerance and high stereo- and regioselectivity under mild conditions. Through the removal of the directing group, the resulting moiety could easily be transformed into the phthalazin-1(2H)-one scaffold, which is known to be a privileged moiety and a bioactive nucleus in pharmaceuticals. PMID:26664581

  16. Relaxation of the structure of simple metal ion complexes in aqueous solutions at up to supercritical conditions

    USGS Publications Warehouse

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

    2003-01-01

    Recently x-ray absorption fine structure (XAFS) studies of various ions in aqueous solutions showed a variation of cation-ligand bond lengths, often coupled with other structure changes, with increasing temperatures. Thus, the variations of the structure of several metal ion complexes with temperature based on observations from the X-ray absorption fine structure (XAFS) studies in the hope that it will stimulate the development of either first- principles theory or molecular dynamics simulations that might adequately describes these results are discussed.

  17. Kinetics of OH-initiated oxidation of some oxygenated organic compounds in the aqueous phase under tropospheric conditions

    NASA Astrophysics Data System (ADS)

    Poulain, L.; Grubert, S.; François, S.; Monod, A.; Wortham, H.

    2003-04-01

    The interest for multiphase interactions of Volatile Organic Compounds (VOCs) in the troposphere has increased for a few years. Inside the clouds water droplets, soluble VOCs can be oxidized by free radicals thus modifying the droplet composition. This reactivity has an impact on the tropospheric oxidizing capacity as well as the aerosols' properties. In the present work, we measured aqueous phase OH-initiated oxidation rate constants of several oxygenated organic compounds relevant to the atmosphere or chosen as test compounds (ethanol, t-butanol, 1-butanol, iso-propanol, 1-propanol, acetaldehyde, propionaldehyde, butyraldehyde, valeraldehyde, phenol, ethyl ter-butyl ether (ETBE), n-propyl acetate, acetone, methyl ethyl ketone (MEK), methyl iso-butyl ketone (MIBK), ethyl formate). Experiments took place in an aqueous phase photoreactor. The rate constants were determinated using the relative kinetic method. Different OH-radical sources were tested, as well as different reference compounds in order to detect any artifact. The results have shown validation of the experimental protocol on test compounds. The overall results allowed to propose a structure reactivity method in order to predict OH-oxidation rate constant of new compounds. Finally, tropospheric life times of the studied compounds were compared inside and outside a cloud.

  18. Oxalic acid mediated synthesis of WO{sub 3}.H{sub 2}O nanoplates and self-assembled nanoflowers under mild conditions

    SciTech Connect

    Li Linzhi; Zhao Jingzhe; Wang Yi; Li Yunling; Ma Dechong; Zhao Yan; Hou Shengnan; Hao Xinli

    2011-07-15

    Tungsten oxide hydrate (WO{sub 3}.H{sub 2}O) nanoplates and flower-like assemblies were successfully synthesized via a simple aqueous method. The effects of reaction parameters in solution on the preparation were studied. Nanoplates and nanoflowers can be selectively prepared by changing the amount of H{sub 2}C{sub 2}O{sub 4}. In-situ assembly of nanoplates to nanoflowers was also proposed for the formation of assembled nanostructures. In addition, the reaction time and temperature have important effects on the sizes of the as-obtained samples. Crystal structure, morphology, and composition of final nanostructures were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Optical properties of the synthesized samples and the growth mechanism were studied by UV-vis detection. Degradation experiments of Rhodamine B (RhB) were also performed on samples of nanoplates and nanoflowers under visible light illumination. Nanoflower sample exhibited preferable photocatalytic property to nanoplate sample. - Graphical abstract: The oxalic acid has a key role for the structure of WO{sub 3}.H{sub 2}O evolution from plates to flowers and the dehydration process of WO{sub 3}.2H{sub 2}O to WO{sub 3}.H{sub 2}O. Highlights: > Tungsten oxides hydrate was synthesized via a simple aqueous method. > The size of WO{sub 3}.H{sub 2}O was controlled by the reaction time and temperature. > The assembly of WO{sub 3}.H{sub 2}O nanoplates to nanoflowers was achieved with higher H{sub 2}C{sub 2}O{sub 4}/Na{sub 2}WO{sub 4} ratio. > Oxalic acid has a key role in the dehydration process of WO{sub 3}.2H{sub 2}O to WO{sub 3}.H{sub 2}O.

  19. In situ X-ray absorption spectroscopy study of Si(1-x)Ge(x)O2 dissolution and germanium aqueous speciation under hydrothermal conditions.

    PubMed

    Ranieri, V; Haines, J; Cambon, O; Levelut, C; Le Parc, R; Cambon, M; Hazemann, J-L

    2012-01-01

    The dissolution of Si(1-x)Ge(x)O(2) solid solutions under hydrothermal conditions was studied by in situ X-ray absorption spectroscopy. Experiments were performed at the Ge K-edge using a high-pressure cell mounted on the FAME beamline of the European Synchrotron Radiation Facility. Spectra in both transmission and fluorescence mode were collected in isobaric conditions (100 and 150 MPa) up to 475 °C. The local atomic structure around the Ge atom was investigated as a function of the temperature and in pure water and sodium hydroxide solutions. In pure water, the solubility of the cristobalite-type Si(0.8)Ge(0.2)O(2) increases with the temperature and the Ge atom is in 4-fold coordination. In a sodium hydroxide aqueous solution, a complex between Ge and Na atoms forms and gives rise to precipitation of sodium germanates. Under these conditions, the Ge content in the solution decreases with increasing temperature. These results show that a sodium hydroxide aqueous solution, usually used for quartz crystal growth, is not suitable for Ge-containing crystals. The dissolution kinetics and phase transformation of the solid solution were studied as a function of the atomic fraction of Ge. Ge-rich solid solutions dissolve and transform to stable phases faster than Ge-poorer composition, giving rise to important variations of the Ge content in solution. PMID:22175278

  20. Microbiologically mediated reduction in the pitting of mild steel overlaid with plywood

    SciTech Connect

    Soracco, R J; Berger, L R; Berger, J A; Mayack, L A; Pope, D H; Wilde, E W

    1984-01-01

    Laboratory experiments were conducted to determine the role of microorganisms in the pitting of mild steel flooring, which had been overlaid with plywood. The experimental setups consisted of 4.8 mm (3/16 in.) mild steel plates covered with 12.7 mm (1/2 in.) thick pieces of plywood which were exposed to several different aqueous media supplemented with various combinations of a soil suspension and selected inorganic and organic compounds. Half of the replicate metal-wood-water setups were sterilized and aseptically maintained during incubation after which they were checked for the presence of viable microorganisms and pitting of the mild steel. Results of the first set of experiments showed that pitting of the mild steel specimens in many of these setups occurred after a reasonably short incubation period (3 to 6 months). However, the method used to exclude microorganisms by sterilizing the components separately was unsuccessful. In a second set of experiments, setups were sterilized by exposure to gamma irradiation after they had been assembled. The sterilized setups remained sterile after incubation while those which were not originally sterile still contained viable microorganisms. Pitting of the mild steel specimens was more severe when they were exposed to sterile conditions than when viable microorganisms were present. These experiments showed that while microorganisms are known to enhance corrosion processes in some circumstances, their presence can reduce corrosion in others.

  1. MIPs in Aqueous Environments.

    PubMed

    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. PMID:25796623

  2. Corrosion phenomena of alloy 625 in aqueous solutions containing sulfuric acid and oxygen under subcritical and supercritical conditions

    SciTech Connect

    Kritzer, P.; Boukis, N.; Dinjus, E.

    1998-12-31

    Corrosion phenomena of alloy 625 pressure tubes were investigated in aqueous solutions containing up to 0.2 mol/kg sulfuric acid and up to 1.44 mol/kg oxygen. Applied maximum temperatures and pressures were 500 C, and 38 MPa, respectively. Corrosion started at temperatures around 150 C with intergranular attack. Above 250 C, the whole surface of the alloy was attacked, shallow pits and deep intergranular attack appeared. This behavior can be explained by transpassive dissolution of the protecting Cr(III) oxide layer and leads to severe material loss. The upper temperature limit of severe corrosion at an experimental pressure of 24 MPa was about 390 C. As temperature was increased further and the density of the solution dropped to low values, only slight corrosion was detected.

  3. Molecular engineering of a cobalt-based electrocatalytic nanomaterial for H2 evolution under fully aqueous conditions

    NASA Astrophysics Data System (ADS)

    Andreiadis, Eugen S.; Jacques, Pierre-André; Tran, Phong D.; Leyris, Adeline; Chavarot-Kerlidou, Murielle; Jousselme, Bruno; Matheron, Muriel; Pécaut, Jacques; Palacin, Serge; Fontecave, Marc; Artero, Vincent

    2013-01-01

    The viability of a hydrogen economy depends on the design of efficient catalytic systems based on earth-abundant elements. Innovative breakthroughs for hydrogen evolution based on molecular tetraimine cobalt compounds have appeared in the past decade. Here we show that such a diimine-dioxime cobalt catalyst can be grafted to the surface of a carbon nanotube electrode. The resulting electrocatalytic cathode material mediates H2 generation (55,000 turnovers in seven hours) from fully aqueous solutions at low-to-medium overpotentials. This material is remarkably stable, which allows extensive cycling with preservation of the grafted molecular complex, as shown by electrochemical studies, X-ray photoelectron spectroscopy and scanning electron microscopy. This clearly indicates that grafting provides an increased stability to these cobalt catalysts, and suggests the possible application of these materials in the development of technological devices.

  4. On the formation and structure of rare-earth element complexes in aqueous solutions under hydrothermal conditions with new data on gadolinium aqua and chloro complexes

    USGS Publications Warehouse

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

    2007-01-01

    (III) chloro complexes increases steadily with temperature from 0.4 ?? 0.2 to 1.7 ?? 0.3 in the 0.006m chloride solution and from 0.9 ?? 0.7 to 1.8 ?? 0.7 in the 0.1m GdCl3 aqueous solution in the 300-500????C range. Conversely, the number of H2O ligands of Gd(H2O)??-nCln+3-n complexes decreases steadily from 8.9 ?? 0.4 to 5.8 ?? 0.7 in the 0.006m GdCl3 aqueous solution and from 9.0 ?? 0.5 to 5.3 ?? 1.0 in the 0.1m GdCl3 aqueous solution at temperatures from 25 to 500????C. Analysis of our results shows that the chloride ions partially displace the inner-shell water molecules during Gd(III) complex formation under hydrothermal conditions. The Gd-OH2 bond of the partially-hydrated Gd(III) chloro complexes exhibits slightly smaller rates of length contraction (??? 0.005??A??/100????C) for both solutions. The structural aspects of chloride speciation of Gd(III) as measured from this study and of Yb(III) as measured from our previous experiments are consistent with the solubility of these and other REE in deep-sea hydrothermal fluids. ?? 2006 Elsevier B.V. All rights reserved.

  5. Formation of carboxylic acids from alcohols and olefins in zeolite H-ZSM-5 under mild conditions via trapping of alkyl carbenium ions with carbon monoxide: An in situ {sup 13}C solid state NMR study

    SciTech Connect

    Stepanov, A.G.; Luzgin, M.V.; Romannikov, V.N.; Sidelnikov, V.N.; Zamaraev K.I.

    1996-12-01

    Using in situ {sup 13}C solid state MAS NMR (for some reagents in combination with ex situ GC-MS), it is shown that butyl alcohols and olefins (ethene, isobutene, octene-1) undergo carbonylation to form carboxylic acids (the Koch reaction) with high conversion on zeolite H-ZSM-5 at 296-373 K. The reactions proceed without application of pressurized conditions, just upon coadsorption of CO and alcohols or CO, H{sub 2}O, and olefins on zeolite. The observed Koch reaction under mild conditions provides strong evidence for the formation of alkyl carbenium ions from alcohols and olefins on the zeolites as crucial reaction intermediates. Of the family of carbenium ions, CO reacts selectively with tertiary cations to produce tertiary carboxylic acids, unless the carbonylated molecule is too large for more bulky tertiary moieties to be accommodated and carbonylated in the narrow pores of H-ZSM05. Thus, t-BuOH, i-BuOH, and isobutene produce trimethylacetic acid with high selectivity and conversion, while ethene transforms selectively into 2-methyl-2-ethyl butyric acid. Reaction of octene-1 molecules with CO and H{sub 2}O results in acids of the C{sub 8}H{sub 17}COOH and C{sub 16}H{sub 33}COOH families with predominantly linear hydrocarbon chains. The data obtained may open up new possibilities in using solid acids in organic synthesis as carbonylation catalysts under mild conditions i.e., low temperature and normal atmospheric pressure. 55 refs., 8 figs.

  6. The secondary formation of inorganic aerosols in the droplet mode through heterogeneous aqueous reactions under haze conditions

    NASA Astrophysics Data System (ADS)

    Wang, Xinfeng; Wang, Wenxing; Yang, Lingxiao; Gao, Xiaomei; Nie, Wei; Yu, Yangchun; Xu, Pengju; Zhou, Yang; Wang, Zhe

    2012-12-01

    Secondary inorganic aerosols play important roles in visibility reduction and in regional haze pollution. To investigate the characteristics of size distributions of secondary sulfates and nitrates as well as their formation mechanisms under hazes, size-resolved aerosols were collected using a Micro-Orifice Uniform Deposit Impactor (MOUDI) at an urban site in Jinan, China, in all four seasons (December 2007-October 2008). In haze episodes, the secondary sulfates and nitrates primarily formed in fine particles, with elevated concentration peaks in the droplet mode (0.56-1.8 μm). The fine sulfates and nitrates were completely neutralized by ammonia and existed in the forms of (NH4)2SO4 and NH4NO3, respectively. The secondary formation of sulfates, nitrates and ammonium (SNA) was found to be related to heterogeneous aqueous reactions and was largely dependent on the ambient humidity. With rising relative humidity, the droplet-mode SNA concentration, the ratio of droplet-mode SNA to the total SNA, the fraction of SNA in droplet-mode particles and the mass median aerodynamic diameter of SNA presented an exponential, logarithmic or linear increase. Two heavily polluted multi-day haze episodes in winter and summer were analyzed in detail. The secondary sulfates were linked to heterogeneous uptake of SO2 followed by the subsequent catalytic oxidation by oxygen together with iron and manganese in winter. The fine nitrate formation was strongly associated with the thermodynamic equilibrium among NH4NO3, gaseous HNO3 and NH3, and showed different temperature-dependences in winter and summer.

  7. Silver-Catalyzed Decarboxylative Allylation of Aliphatic Carboxylic Acids in Aqueous Solution.

    PubMed

    Cui, Lei; Chen, He; Liu, Chao; Li, Chaozhong

    2016-05-01

    Direct decarboxylative radical allylation of aliphatic carboxylic acids is described. With K2S2O8 as the oxidant and AgNO3 as the catalyst, the reactions of aliphatic carboxylic acids with allyl sulfones in aqueous CH3CN solution gave the corresponding alkenes in satisfactory yields under mild conditions. This site-specific allylation method is applicable to all primary, secondary, and tertiary alkyl acids and exhibits wide functional group compatibility. PMID:27065060

  8. Fabrication of Thin Films of α-Fe2O3 via Atomic Layer Deposition Using Iron Bisamidinate and Water under Mild Growth Conditions.

    PubMed

    Avila, Jason R; Kim, Dong Wook; Rimoldi, Martino; Farha, Omar K; Hupp, Joseph T

    2015-08-01

    Atomic layer deposition (ALD) has been shown to be an excellent method for depositing thin films of iron oxide. With limited iron precursors available, the methods widely used require harsh conditions such as high temperatures and/or the use of oxidants such as ozone or peroxide. This letter aims to show that bis(N,N'-di-t-butylacetamidinato) iron(II) (iron bisamidinate or FeAMD) is an ideal ALD precursor because of its reactivity with water and relative volatility. Using in situ QCM analysis, we show outstanding conformal self-limiting growth of FeOx using FeAMD and water at temperatures lower than 200 °C. By annealing thin films of FeOx at 500 °C, we observe the formation of α-Fe2O3, confirming that we can use FeAMD to fabricate thin films of catalytically promising iron oxide materials using moderate growth conditions. PMID:26192606

  9. Racemisation of N-Fmoc phenylglycine under mild microwave-SPPS and conventional stepwise SPPS conditions: attempts to develop strategies for overcoming this.

    PubMed

    Elsawy, Mohamed A; Hewage, Chandralal; Walker, Brian

    2012-05-01

    We have been engaged in the microwave-solid phase peptide synthesis (SPPS) synthesis of the phenylglycine (Phg)-containing pentapeptide H-Ala-Val-Pro-Phg-Tyr-NH(2) (1) previously demonstrated to bind to the so-called BIR3 domain of the anti-apoptotic protein XIAP. Analysis of the target peptide by a combination of RP-HPLC, ESI-MS, and NMR revealed the presence of two diastereoisomers arising out of the racemisation of the Phg residue, with the percentage of the LLLDL component assessed as 49%. We performed the synthesis of peptide (1) using different microwave and conventional stepwise SPPS conditions in attempts to reduce the level of racemisation of the Phg residue and to determine at which part of the synthetic cycle the epimerization had occurred. We determined that racemisation occurred mainly during the Fmoc-group removal and, to a much lesser extent, during activation/coupling of the Fmoc-Phg-OH residue. We were able to obtain the desired peptide with a 71% diastereomeric purity (29% LLLDL as impurity) by utilizing microwave-assisted SPPS at 50 °C and power 22 Watts, when the triazine-derived coupling reagent DMTMM-BF(4) was used, together with NMM as an activator base, for the incorporation of this residue and 20% piperidine as an Fmoc-deprotection base. In contrast, the phenylalanine analogue of the above peptide, H-Ala-Val-Pro-Phe-Tyr-NH(2) (2), was always obtained as a single diastereoisomer by using a range of standard coupling and deprotection conditions. Our findings suggest that the racemisation of Fmoc-Phg-OH, under both microwave-SPPS and stepwise conventional SPPS syntheses conditions, is very facile but can be limited through the use of the above stated conditions. PMID:22451378

  10. Template Catalysis by Metal-Ligand Cooperation. C-C Bond Formation via Conjugate Addition of Non-activated Nitriles under Mild, Base-free Conditions Catalyzed by a Manganese Pincer Complex.

    PubMed

    Nerush, Alexander; Vogt, Matthias; Gellrich, Urs; Leitus, Gregory; Ben-David, Yehoshoa; Milstein, David

    2016-06-01

    The first example of a catalytic Michael addition reaction of non-activated aliphatic nitriles to α,β-unsaturated carbonyl compounds under mild, neutral conditions is reported. A new de-aromatized pyridine-based PNP pincer complex of the Earth-abundant, first-row transition metal manganese serves as the catalyst. The reaction tolerates a variety of nitriles and Michael acceptors with different steric features and acceptor strengths. Mechanistic investigations including temperature-dependent NMR spectroscopy and DFT calculations reveal that the cooperative activation of alkyl nitriles, which leads to the generation of metalated nitrile nucleophile species (α-cyano carbanion analogues), is a key step of the mechanism. The metal center is not directly involved in the catalytic bond formation but rather serves, cooperatively with the ligand, as a template for the substrate activation. This approach of "template catalysis" expands the scope of potential donors for conjugate addition reactions. PMID:27164437

  11. Electrochemical efficacy of a carboxylated multiwalled carbon nanotube filter for the removal of ibuprofen from aqueous solutions under acidic conditions.

    PubMed

    Bakr, Ahmed Refaat; Rahaman, Md Saifur

    2016-06-01

    This study provides insight into the efficiency of a functionalized multiwalled carbon nanotube filter for the removal of an anti-inflammatory drug, ibuprofen, through conventional filtration and electrochemical filtration processes. A comparison was made between carboxylated multiwalled carbon nanotubes (MWNTs-COOH) and pristine multiwalled carbon nanotubes (MWNTs) in order to emphasize the enhanced performance of MWNTs-COOH for the removal of ibuprofen using an electrochemical filtration process under acidic conditions. Ibuprofen-removal trials were evaluated based on absorbance values obtained using a UV/Vis spectrophotometer, and possible degradation products were identified using liquid chromatography mass spectrometry (LC-MS). The results exhibited near complete removal of ibuprofen by MWNTs-COOH at lower applied potentials (2 V), at lower flow rates, and under acidic conditions, which can be attributed to the generation of superoxides and their active participation in simultaneous degradation of ibuprofen, and its by-products, under these conditions. At higher applied potential (3 V), the possible participation of both bulk indirect oxidation reactions, and direct electron transfer were hypothesized for the removal behavior over time (breakthrough). At 3 V under acidic conditions, near 100% removal of the target molecule was achieved and was attributed to the enhanced generation of electroactive species toward bulk chemical reactions and a possible contribution from direct electron transfer under these conditions. The degradation by-products of ibuprofen were effectively removed by allowing longer residence time during the filtration process. Moreover, the effect of temperature was studied, yet showed a non-significant effect on the overall removal process. PMID:27035389

  12. Unprecedented one-pot sequential thiolate substitutions under mild conditions leading to a red emissive BODIPY dye 3,5,8-tris(PhS)-BODIPY.

    PubMed

    Roacho, Robinson I; Metta-Magaña, Alejandro; Peña-Cabrera, Eduardo; Pannell, Keith

    2015-01-28

    The simple reaction of phenylthiol with 8-MeS-BODIPY (1) in dichloromethane was readily accomplished to form 8-PhS-BODIPY (2). If the reaction is performed in THF 3,8-bis(phenylthio)-BODIPY (3) and 3,5,8-tris(phenylthio)-BODIPY (4) are sequentially formed in an unprecedented reaction. This provides a simple new methodology for the introduction of the phenylthio-moiety in the 3- and 5-positions. Alkyl thiols do not form multi-thiolated products under identical conditions, as exemplified using EtSH, where only 8-EtS-BODIPY (5) is formed. PMID:25429697

  13. A study of X100 pipeline steel passivation in mildly alkaline bicarbonate solutions using electrochemical impedance spectroscopy under potentiodynamic conditions and Mott-Schottky

    NASA Astrophysics Data System (ADS)

    Gadala, Ibrahim M.; Alfantazi, Akram

    2015-12-01

    The key steps involved in X100 pipeline steel passivation in bicarbonate-based simulated soil solutions from the pre-passive to transpassive potential regions have been analyzed here using a step-wise anodizing-electrochemical impedance spectroscopy (EIS) routine. Pre-passive steps involve parallel dissolution-adsorption in early stages followed by clear diffusion-adsorption control shortly before iron hydroxide formation. Aggressive NS4 chlorides/sulfate promote steel dissolution whilst inhibiting diffusion in pre-passive steps. Diffusive and adsorptive effects remain during iron hydroxide formation, but withdraw shortly thereafter during its removal and the development of the stable iron carbonate passive layer. Passive layer protectiveness is evaluated using EIS fitting, current density analysis, and correlations with semiconductive parameters, consistently revealing improved robustness in colder, bicarbonate-rich, chloride/sulfate-free conditions. Ferrous oxide formation at higher potentials results in markedly lower impedances with disordered behavior, and the involvement of the iron(III) valence state is observed in Mott-Schottky tests exclusively for 75 °C conditions.

  14. Basalt and olivine dissolution under cold, salty, and acidic conditions: What can we learn about recent aqueous weathering on Mars?

    NASA Astrophysics Data System (ADS)

    Hausrath, E. M.; Brantley, S. L.

    2010-12-01

    To test which variables may be important for weathering on Mars, the effects of temperature (22°C, 6°C, and -19°C), high ionic strength, and oxygen concentrations were investigated in batch dissolution experiments containing forsterite, fayalite, and basalt glass. CaCl2-NaCl-H2O brine can remain liquid to temperatures of -55°C and thus may be liquid in the cold, dry climate that currently characterizes Mars. To understand weathering under such conditions, dissolution rates were measured in experiments in distilled water with and without CaCl2 and NaCl. As observed by others, dissolution rates increased with temperature, and only fayalite dissolution was significantly affected by the presence or absence of oxygen. Enhanced fayalite dissolution under anoxic conditions suggests that Fe-rich olivine would dissolve more rapidly than Mg-rich olivine on Mars. Dissolution in the two most dilute experimental solutions (deionized water and CaCl2-NaCl-H2O solution of ionic strength = 0.7 m) were the same within uncertainty, but apparent dissolution rate constants in CaCl2-NaCl-H2O brines were significantly slower. Steady silica concentrations are decreased in the brines, consistent with other work, and precipitation rates of silica decrease with decreasing temperatures. These results suggest that enhanced silica precipitation could be an indicator of high ionic strength solutions on Mars. Consistent with these observations, weathering of basalt has been observed to sometimes be accompanied by precipitated layers of silica in cold, dry environments on Earth. If dissolution on Mars occurs or occurred under conditions similar to our experiments, cation leaching would be expected to be accompanied by silica precipitates on weathering surfaces.

  15. Partial complex I deficiency due to the CNS conditional ablation of Ndufa5 results in a mild chronic encephalopathy but no increase in oxidative damage

    PubMed Central

    Peralta, Susana; Torraco, Alessandra; Wenz, Tina; Garcia, Sofia; Diaz, Francisca; Moraes, Carlos T.

    2014-01-01

    Deficiencies in the complex I (CI; NADH-ubiquinone oxidoreductase) of the respiratory chain are frequent causes of mitochondrial diseases and have been associated with other neurodegenerative disorders, such as Parkinson's disease. The NADH-ubiquinone oxidoreductase 1 alpha subcomplex subunit 5 (NDUFA5) is a nuclear-encoded structural subunit of CI, located in the peripheral arm. We inactivated Ndufa5 in mice by the gene-trap methodology and found that this protein is required for embryonic survival. Therefore, we have created a conditional Ndufa5 knockout (KO) allele by introducing a rescuing Ndufa5 cDNA transgene flanked by loxP sites, which was selectively ablated in neurons by the CaMKIIα-Cre. At the age of 11 months, mice with a central nervous system knockout of Ndufa5 (Ndufa5 CNS-KO) showed lethargy and loss of motor skills. In these mice cortices, the levels of NDUFA5 protein were reduced to 25% of controls. Fully assembled CI levels were also greatly reduced in cortex and CI activity in homogenates was reduced to 60% of controls. Despite the biochemical phenotype, no oxidative damage, neuronal death or gliosis were detected in the Ndufa5 CNS-KO brain at this age. These results showed that a partial defect in CI in neurons can lead to late-onset motor phenotypes without neuronal loss or oxidative damage. PMID:24154540

  16. Ruthenium(0) nanoclusters stabilized by a Nanozeolite framework: isolable, reusable, and green catalyst for the hydrogenation of neat aromatics under mild conditions with the unprecedented catalytic activity and lifetime.

    PubMed

    Zahmakiran, Mehmet; Tonbul, Yalçin; Ozkar, Saim

    2010-05-12

    The hydrogenation of aromatics is a ubiquitous chemical transformation used in both the petrochemical and specialty industry and is important for the generation of clean diesel fuels. Reported herein is the discovery of a superior heterogeneous catalyst, superior in terms of catalytic activity, selectivity, and lifetime in the hydrogenation of aromatics in the solvent-free system under mild conditions (at 25 degrees C and 42 +/- 1 psig initial H(2) pressure). Ruthenium(0) nanoclusters stabilized by a nanozeolite framework as a new catalytic material is reproducibly prepared from the borohydride reduction of a colloidal solution of ruthenium(III)-exchanged nanozeolites at room temperature and characterized by using ICP-OES, XRD, XPS, DLS, TEM, HRTEM, TEM/EDX, mid-IR, far-IR, and Raman spectroscopy. The resultant ruthenium(0) nanoclusters hydrogenate neat benzene to cyclohexane with 100% conversion under mild conditions (at 25 degrees C and 42 +/- 1 psig initial H(2) pressure) with record catalytic activity (initial TOF = 5430 h(-1)) and lifetime (TTO = 177 200). They provide exceptional catalytic activity not only in the hydrogenation of neat benzene but also in the solvent-free hydrogenation of methyl substituted aromatics such as toluene, o-xylene, and mesitylene under otherwise identical conditions. Moreover, they are an isolable, bottleable, and reusable catalyst in the hydrogenation of neat aromatics. When the isolated ruthenium(0) nanoclusters are reused, they retain 92% of their initial catalytic activity even for the third run in the hydrogenation of neat benzene under the same conditions as those of the first run. The work reported here also includes (i) far-infrared spectroscopic investigation of nanozeolite, ruthenium(III)-exchanged-nanozeolite, and ruthenium(0) nanoclusters stabilized by a nanozeolite framework, indicating that the host framework remains intact after the formation of a nanozeolite framework stabilized ruthenium(0) nanoclusters; (ii) the

  17. [Adsorption of calcium ion from aqueous solution using Na(+)-conditioned clinoptilolite for hot-water softening].

    PubMed

    Zhang, Shuo; Wang, Dong; Chen, Yuan-Chao; Zhang, Xing-Wen; Chen, Gui-Jun

    2015-02-01

    This work investigated adsorptive removal of calcium ion (Ca2+) by virtue of Na(+) -conditioned clinoptilolite simulating the process of softening for industrial hot-water system. Influential factors such as the activation/regeneration of sorbent and solution pH were tested. The kinetics/thermodynamics for adsorption of Ca2+ were analyzed and discussed. Results showed that: (1) The adsorption rate was in good agreement with the pseudo-second order kinetic models, and the process of adsorption better followed the Langmuir model; (2) Higher solution temperature allowed an enhanced efficiency on Ca2+ removal, albeit the maximum adsorption capacity of Na(+)-conditioned clinoptilolite was hardly affected; (3) The process of adsorption was dominated by chemisorption, and also characterized by entropy increase with spontaneous/endothermic nature; (4) Solution temperature was suggested to be controlled within the range of 6 to 10, and more than 9 times of sorbent regeneration could be ensured for an effective adsorption towards Ca2+ with initial concentration less than 20 mg x L(-1). It was demonstrated that the activated clinoptilolite should be a promising alternative adsorbent for industrial hot-water softening. PMID:26031107

  18. Application of Zero-Valent Iron Nanoparticles for the Removal of Aqueous Zinc Ions under Various Experimental Conditions

    PubMed Central

    Liang, Wen; Dai, Chaomeng; Zhou, Xuefei; Zhang, Yalei

    2014-01-01

    Application of zero-valent iron nanoparticles (nZVI) for Zn2+ removal and its mechanism were discussed. It demonstrated that the uptake of Zn2+ by nZVI was efficient. With the solids concentration of 1 g/L nZVI, more than 85% of Zn2+ could be removed within 2 h. The pH value and dissolved oxygen (DO) were the important factors of Zn2+ removal by nZVI. The DO enhanced the removal efficiency of Zn2+. Under the oxygen-contained condition, oxygen corrosion gave the nZVI surface a shell of iron (oxy)hydroxide, which could show high adsorption affinity. The removal efficiency of Zn2+ increased with the increasing of the pH. Acidic condition reduced the removal efficiency of Zn2+ by nZVI because the existing H+ inhibited the formation of iron (oxy)hydroxide. Adsorption and co-precipitation were the most likely mechanism of Zn2+ removal by nZVI. The FeOOH-shell could enhance the adsorption efficiency of nZVI. The removal efficiency and selectivity of nZVI particles for Zn2+ were higher than Cd2+. Furthermore, a continuous flow reactor for engineering application of nZVI was designed and exhibited high removal efficiency for Zn2+. PMID:24416439

  19. Mild Hypertransaminasemia in Primary Care

    PubMed Central

    Al-Busafi, Said A.; Hilzenrat, Nir

    2013-01-01

    The liver enzymes, alanine transaminase (ALT) or aspartate transaminase (AST), are commonly used in clinical practice as screening as well as diagnostic tests for liver diseases. ALT is more specific for liver injury than AST and has been shown to be a good predictor of liver related and all-cause mortality. Asymptomatic mild hypertransaminasemia (i.e., less than five times normal) is a common finding in primary care and this could be attributed to serious underlying condition or has transient and benign cause. Unfortunately, there are no good literatures available on the cost-effectiveness of evaluating patients with asymptomatic mild hypertransaminasemia. However, if the history and physical examination do not suggest a clear cause, a stepwise approach should be initiated based on pretest probability of the underlying liver disease. Nonalcoholic fatty liver disease is becoming the most common cause of mild hypertransaminasemia worldwide. Other causes include alcohol abuse, medications, and hepatitis B and C. Less common causes include hemochromatosis, α1-antitrypsin deficiency, autoimmune hepatitis, and Wilson's disease. Nonhepatic causes such as celiac disease, thyroid, and muscle disorders should be considered in the differential diagnosis. Referral to a specialist and a possible liver biopsy should be considered if persistent hypertransaminasemia for six months or more of unclear etiology.

  20. Initial results from dissolution rate testing of N-Reactor spent fuel over a range of potential geologic repository aqueous conditions

    SciTech Connect

    Gray, W.J.; Einziger, R.E.

    1998-04-01

    Hanford N-Reactor spent nuclear fuel (HSNF) may ultimately be placed in a geologic repository for permanent disposal. To determine whether the engineered barrier system that will be designed for emplacement of light-water-reactor (LWR) spent fuel will also suffice for HSNF, aqueous dissolution rate measurements were conducted on the HSNF. The purpose of these tests was to determine whether HSNF dissolves faster or slower than LWR spent fuel under some limited repository-relevant water chemistry conditions. The tests were conducted using a flowthrough method that allows the dissolution rate of the uranium matrix to be measured without interference by secondary precipitation reactions that would confuse interpretation of the results. Similar tests had been conducted earlier with LWR spent fuel, thereby allowing direct comparisons. Two distinct corrosion modes were observed during the course of these 12 tests. The first, Stage 1, involved no visible corrosion of the test specimen and produced no undissolved corrosion products. The second, Stage 2, resulted in both visible corrosion of the test specimen and left behind undissolved corrosion products. During Stage 1, the rate of dissolution could be readily determined because the dissolved uranium and associated fission products remained in solution where they could be quantitatively analyzed. The measured rates were much faster than has been observed for LWR spent fuel under all conditions tested to date when normalized to the exposed test specimen surface areas. Application of these results to repository conditions, however, requires some comparison of the physical conditions of the different fuels. The surface area of LWR fuel that could potentially be exposed to repository groundwater is estimated to be approximately 100 times greater than HSNF. Therefore, when compared on the basis of mass, which is more relevant to repository conditions, the HSNF and LWR spent fuel dissolve at similar rates.

  1. Application of zero-valent iron nanoparticles for the removal of aqueous zinc ions under various experimental conditions.

    PubMed

    Liang, Wen; Dai, Chaomeng; Zhou, Xuefei; Zhang, Yalei

    2014-01-01

    Application of zero-valent iron nanoparticles (nZVI) for Zn²⁺ removal and its mechanism were discussed. It demonstrated that the uptake of Zn²⁺ by nZVI was efficient. With the solids concentration of 1 g/L nZVI, more than 85% of Zn²⁺ could be removed within 2 h. The pH value and dissolved oxygen (DO) were the important factors of Zn²⁺ removal by nZVI. The DO enhanced the removal efficiency of Zn²⁺. Under the oxygen-contained condition, oxygen corrosion gave the nZVI surface a shell of iron (oxy)hydroxide, which could show high adsorption affinity. The removal efficiency of Zn²⁺ increased with the increasing of the pH. Acidic condition reduced the removal efficiency of Zn²⁺ by nZVI because the existing H⁺ inhibited the formation of iron (oxy)hydroxide. Adsorption and co-precipitation were the most likely mechanism of Zn²⁺ removal by nZVI. The FeOOH-shell could enhance the adsorption efficiency of nZVI. The removal efficiency and selectivity of nZVI particles for Zn²⁺ were higher than Cd²⁺. Furthermore, a continuous flow reactor for engineering application of nZVI was designed and exhibited high removal efficiency for Zn²⁺. PMID:24416439

  2. Exceedingly Low Freezing Rates of Aqueous Hno3 and Hno3/h2so4 Droplets Under Polar Stratospheric Conditions

    NASA Astrophysics Data System (ADS)

    Knopf, D. A.; Koop, T.; Luo, B.; Weers, U. G.; Peter, T.

    In the Arctic winter 1999/2000 large particles containing nitric acid were observed during in situ field measurements. These large particles are important for the deni- trification of the Arctic stratosphere. It has been proposed that such particles form by homogeneous nucleation of nitric acid hydrates from liquid stratospheric aerosol droplets. Homogeneous nucleation rates of NAT (Nitric Acid Trihydrate) and NAD (Nitric Acid Dihydrate) have been determined in laboratory experiments for binary HNO3/H2O solutions only at supersaturations much larger than observed in the stratosphere. Therefore, an extrapolation of such laboratory data is required for the modelling of stratospheric particle formation and subsequent denitrification. We will present new laboratory data of homogeneous nucleation rates of NAT and NAD from droplets consisting of both binary HNO3/H2O as well as ternary HNO3/H2O/H2SO4 solutions. Optical microscopy has been used to deduce the droplet freezing tempera- tures. The nature of the crystallized solids was identified by Raman spectroscopy. The freezing data have been analyzed within the framework of classical nucleation theory. Our results are consistent with previously published laboratory aerosol data. However, for stratospheric conditions, we infer homogeneous nucleation rates to be lower by orders of magnitude than the extrapolation currently in use. We conclude that homo- geneous nucleation of NAT and NAD is not sufficient to explain the observed number concentrations of large nitric acid containing particles in the stratosphere.

  3. Chemical Reactions of Portland Cement with Aqueous CO2 and Their Impacts on Cement's Mechanical Properties under Geologic CO2 Sequestration Conditions.

    PubMed

    Li, Qingyun; Lim, Yun Mook; Flores, Katharine M; Kranjc, Kelly; Jun, Young-Shin

    2015-05-19

    To provide information on wellbore cement integrity in the application of geologic CO2 sequestration (GCS), chemical and mechanical alterations were analyzed for cement paste samples reacted for 10 days under GCS conditions. The reactions were at 95 °C and had 100 bar of either N2 (control condition) or CO2 contacting the reaction brine solution with an ionic strength of 0.5 M adjusted by NaCl. Chemical analyses showed that the 3.0 cm × 1.1 cm × 0.3 cm samples were significantly attacked by aqueous CO2 and developed layer structures with a total attacked depth of 1220 μm. Microscale mechanical property analyses showed that the hardness and indentation modulus of the carbonated layer were 2-3 times greater than for the intact cement, but those in the portlandite-dissolved region decreased by ∼50%. The strength and elastic modulus of the bulk cement samples were reduced by 93% and 84%, respectively. The properties of the microscale regions, layer structure, microcracks, and swelling of the outer layers combined to affect the overall mechanical properties. These findings improve understanding of wellbore integrity from both chemical and mechanical viewpoints and can be utilized to improve the safety and efficiency of CO2 storage. PMID:25893278

  4. Experimental investigation and planetary implications of the stability of clathrate hydrates in aqueous solution at icy satellite conditions

    NASA Astrophysics Data System (ADS)

    Dunham, M.; Choukroun, M.; Barmatz, M.; Hodyss, R. P.; Smythe, W. D.

    2012-12-01

    Clathrate hydrates consist of hydrogen-bonded water molecules forming cages in which gas molecules are trapped individually. They are among the favored volatile reservoirs in solar system bodies, and are expected to play an important role in many processes: accretion of volatiles in planetesimals, outgassing on Titan, Enceladus, and comets. Their insulating thermal properties and high mechanical strength also bear important implications for understanding the evolution of icy satellites like Europa. However, the conditions allowing for their formation and/or their dissociation and the release of volatiles to the atmosphere (Titan) or the plumes (Enceladus) are still poorly understood. This is mainly because of a lack of knowledge on the stability of mixed clathrate hydrates in presence of anti-freeze agents such as ammonia. We have developed a high-pressure cryogenic calorimeter to address this deficiency in the literature. This liquid nitrogen - cooled Setaram BT2.15 calorimeter is located at the JPL Ice Physics Laboratory. The temperature range achievable with this instrument is 77-473 K. This calorimeter uses Calvet elements (3D arrays of thermocouples) to measure the heat flow required to follow a predefined heating rate within a sample and a reference cell with a resolution of 0.1 μW. A gas handling system has been designed and fabricated in house to reach pressures up to 100 bars, corresponding to several km depth in icy satellites. The thermodynamic properties of CO2 and CH4 clathrates with ammonia are under investigation, and the results will be used to constrain a statistical thermodynamic model of clathrates for applications to planetary environments. Preliminary results will be shown at the meeting. This work has been conducted at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA. Support from the Minnesota Space Grant Consortium, the NASA Outer Planets Research program, and government sponsorship are gratefully

  5. Molecular dynamics simulation study of ionic hydration and ion association in dilute and 1 molal aqueous sodium chloride solutions from ambient to supercritical conditions

    NASA Astrophysics Data System (ADS)

    Driesner, T.; Seward, T. M.; Tironi, I. G.

    1998-09-01

    The increasing demand for accurate equations of state of fluids under extreme conditions and the need for a detailed microscopic picture of aqueous fluids in some areas of geochemistry (e.g., mineral dissolution/precipitation kinetics) potentially make molecular dynamics (MD) simulations a powerful tool for theoretical geochemistry. We present MD simulations of infinitely dilute and 1 molal aqueous NaCl solutions that have been carried out in order to study the systematics of hydration and ion association over a wide range of conditions from ambient to supercritical and compare them to the available experimental data. In the dilute case, the hydration number of the Na + ion remains essentially constant around 5.5 from ambient to supercritical temperatures when the density is kept constant at 1 g cm -3 but decreases to below 5 along the liquid-vapor curve. In both cases, the average ion-first shell water distance decreases by about 0.03 Å from ambient to near critical temperatures. The Cl - ion shows a slight expansion of the first hydration shell by about 0.02 Å from ambient to near critical temperatures. The geometric definition of the first hydration shell becomes ambiguous due to a shift of the position of the first minimum of the Cl-O radial distribution function. In the case of the 1 molal solution, the contraction of the Na + first hydration shell is similar to that in the dilute case whereas the hydration number decreases drastically from 4.9 to 2.8 due to strong ion association. The released waters are replaced on a near 1:1 basis by chloride ions. Polynuclear clusters as predicted by Oelkers and Helgeson (1993b) are observed in the high temperature systems. The hydration shell of the Cl --ion shows significant deviation from the behavior in dilute systems, that is, at near vapor saturated conditions, the expansion of the hydration shell is significantly larger (0.12 Å from ambient to near critical temperatures). Due to a very large shift of the first

  6. Multianalyte determination of 24 cytostatics and metabolites by liquid chromatography-electrospray-tandem mass spectrometry and study of their stability and optimum storage conditions in aqueous solution.

    PubMed

    Negreira, Noelia; Mastroianni, Nicola; López de Alda, Miren; Barceló, Damià

    2013-11-15

    A multianalyte liquid chromatography-electrospray-tandem mass spectrometry (LC-ESI-MS/MS) method for determination of 19 cytostatics and 5 metabolites, from 6 different therapeutic families, has been developed, and the structures of the main characteristic fragment ions have been proposed. Instrumental limits of detection and quantification are in the range 0.1-10.3 and 1.0-34.3 ng mL(-1), respectively. Moreover, the stability of the compounds in aqueous solution was investigated in order to establish the best conditions for preparation and storage of both calibration standards and water samples. Dimethylsulphoxide (DMSO) was selected as solvent for preparation of the stock solutions. At room temperature (25 °C), 11 of the 24 target compounds were shown to be unstable in water (percentage of organic solvent 4%), with concentration losses greater than 20% in less than 24 h. At 4 °C (typical storage temperature for water samples) all compounds, except MTIC and chlorambucil, were stable for 24h, but the number of stable compounds decreased to 10 after 9 days. Freezing of the aqueous solutions improved considerably the stability of various compounds: after 3 months of storage at -20 °C, 10 compounds, namely, 5-fluorouracil, carboplatin, gemcitabine, temozolomide, vincristine, vinorelbine, ifosfamide, cyclophosphamide, etoposide, and capecitabine, remained stable (in contrast to only carboplatin and capecitabine at 4 °C). The addition of acid improved the stability of methotrexate and its metabolite hydroxy-methotrexate but not that of the rest of compounds. The addition of organic solvent (50% methanol or DMSO) prevented the degradation at 4 °C of the otherwise unstable compounds oxaliplatin, methotrexate, erlotinib, doxorubicin, tamoxifen, and paclitaxel. To the authors' knowledge, five of the analytes investigated have never been searched for in the aquatic environment (imatinib, 6α-hydroxypaclitaxel, endoxifen, (Z)4-hydroxytamoxifen, and temozolomide), and for

  7. Aqueous Conditions and Habitability Associated with Formation of a Serpentinite: Using Analyses of Ferric Iron and Stable Carbon Isotopes to Reconstruct Hydrogen Production

    NASA Astrophysics Data System (ADS)

    Greenberger, R. N.; Mustard, J. F.; Cloutis, E.; Pratt, L. M.; Sauer, P. E.; Mann, P.; Turner, K.; Dyar, M. D.

    2014-12-01

    Serpentine deposits on Mars have generated significant interest because byproducts of serpentinization, H2 and CH4, can be important energy sources for subsurface microbial communities. H2 is produced through Fe2+ oxidation to form magnetite and Fe3+-bearing serpentine. In serpentine, Fe3+ goes into octahedral sites first, then tetrahedral sites [Marcaillou et al., 2011, EPSL]. We use Fe oxidation state and coordination in an Early Ordovician serpentinite in Norbestos, Quebec, as proxies for H2 production and stable isotopes of carbonates to understand past aqueous conditions at the Canadian Space Agency's 2012 Mars Methane Analogue Mission site. Rock outcrops were imaged with a visible hyperspectral imager (420-720 nm), and samples were imaged in the laboratory with the same imager and a near infrared imager (650-1100 nm). Other analyses determined major element chemistry (ICP-AES and C analyses), mineralogy (XRD), Fe phases (Mössbauer spectroscopy), and stable isotopes of carbonates. Fe oxidation state and coordination (tetrahedral vs octahedral) were mapped in samples and outcrops using imaging data. We focused on locations with tetrahedral Fe3+ in serpentine as these are the most serpentinized sites with maximum H2 production. Carbonate samples from ~100-200 m south of a shear zone are enriched in 13C (δ13C up to +16.12‰ vs VPDB) resulting from production of CH4 depleted in 13C in a system closed to C addition but open to CH4 escape. This alteration occurred at elevated temperatures and low water/rock ratios. In the shear zone, lower δ13C values (most < +2‰) positively correlated with δ18O likely result from kinetic fractionation under recent low temperature conditions. Spectroscopy suggests that much of this deposit underwent advanced serpentinization to produce significant H2. Isotopic signatures of carbonates precipitated during serpentinization outside the shear zone illuminate the temperatures (elevated) and chemistries of fluids (high Ca2+, low CO

  8. Myocardial protection with mild hypothermia.

    PubMed

    Tissier, Renaud; Ghaleh, Bijan; Cohen, Michael V; Downey, James M; Berdeaux, Alain

    2012-05-01

    Mild hypothermia, 32-35° C, is very potent at reducing myocardial infarct size in rabbits, dogs, sheep, pigs, and rats. The benefit is directly related to reduction in normothermic ischaemic time, supporting the relevance of early and rapid cooling. The cardioprotective effect of mild hypothermia is not limited to its recognized reduction of infarct size, but also results in conservation of post-ischaemic contractile function, prevention of no-reflow or microvascular obstruction, and ultimately attenuation of left ventricular remodelling. The mechanism of the anti-infarct effect does not appear to be related to diminished energy utilization and metabolic preservation, but rather to survival signalling that involves either the extracellular signal-regulated kinases and/or the Akt/phosphoinositide 3-kinase/mammalian target of rapamycin pathways. Initial clinical trials of hypothermia in patients with ST-segment elevation myocardial infarction were disappointing, probably because cooling was too slow to shorten normothermic ischaemic time appreciably. New approaches to more rapid cooling have recently been described and may soon be available for clinical use. Alternatively, it may be possible to pharmacologically mimic the protection provided by cooling soon after the onset of ischaemia with an activator of mild hypothermia signalling, e.g. extracellular signal-regulated kinase activator, that could be given by emergency medical personnel. Finally, the protection afforded by cooling can be added to that of pre- and post-conditioning because their mechanisms differ. Thus, myocardial salvage might be greatly increased by rapidly cooling patients as soon as possible and then giving a pharmacological post-conditioning agent immediately prior to reperfusion. PMID:22131353

  9. Defect formation in aqueous environment: Theoretical assessment of boron incorporation in nickel ferrite under conditions of an operating pressurized-water nuclear reactor (PWR)

    NASA Astrophysics Data System (ADS)

    Rák, Zs.; Bucholz, E. W.; Brenner, D. W.

    2015-06-01

    A serious concern in the safety and economy of a pressurized water nuclear reactor is related to the accumulation of boron inside the metal oxide (mostly NiFe2O4 spinel) deposits on the upper regions of the fuel rods. Boron, being a potent neutron absorber, can alter the neutron flux causing anomalous shifts and fluctuations in the power output of the reactor core. This phenomenon reduces the operational flexibility of the plant and may force the down-rating of the reactor. In this work an innovative approach is used to combine first-principles calculations with thermodynamic data to evaluate the possibility of B incorporation into the crystal structure of NiFe2O4 , under conditions typical to operating nuclear pressurized water nuclear reactors. Analyses of temperature and pH dependence of the defect formation energies indicate that B can accumulate in NiFe2O4 as an interstitial impurity and may therefore be a major contributor to the anomalous axial power shift observed in nuclear reactors. This computational approach is quite general and applicable to a large variety of solids in equilibrium with aqueous solutions.

  10. Conditions and mechanisms for the formation of nano-sized Delafossite (CuFeO2) at temperatures ≤90 °C in aqueous solution

    NASA Astrophysics Data System (ADS)

    John, Melanie; Heuss-Aßbichler, Soraya; Ullrich, Aladin

    2016-02-01

    In this study, we present the mechanism of CuFeO2 formation in aqueous solution at low temperatures ≤90 °C, using sulfate salts as reactants. Furthermore, we demonstrate the influence of experimental conditions (alkalization, reaction and ageing temperature and time) on the synthesized nanoparticles. In all cases, GR-SO4, a Fe(II-III) layered double hydroxysulphate Fe2+4 Fe3+2 (Fe2+4Fe3+2(OH)12·SO4) and Cu2O precipitate first. During further OH- supply GR-SO4 oxidizes and forms Fe10O14(OH)2, Cu2O and CuFeO2 crystals. Due to the high pH furtherCuFeO2 crystals grow at the cost of the unstable intermediate products. The reaction rate increases with increasing ageing temperature, reaction pH and, in particular, NaOH concentrations in the solution. As a result, highly crystalline CuFeO2 (3R and 2H polytypes) nanoparticles showing hexagonal morphology can be synthesized at 70 °C within 10 h or at 50 °C within 1 week. The formation of 2H polytype is favored by additional OH- supply during the pH-stat time and rather low temperatures.

  11. Aqueous production.

    PubMed

    Krupin, T; Wax, M; Moolchandani, J

    1986-01-01

    The formation of aqueous humour by the ciliary body is a complex process. Active transport of solutes by the ciliary process epithelium is an energy-dependent mechanism that selectively transports substances against an electrochemical gradient across the cell membranes. Water passively follows the active solute transport. In addition to these active transport processes, ultrafiltration contributes to the formation of aqueous humour. The ciliary epithelium contains enzyme systems that function in the production of aqueous humour. The enzymes sodium-potassium-activated adenosine triphosphatase [(Na+:K+)ATPase] and carbonic anhydrase participate in the active transport across this epithelium. Inhibition of these enzymes lowers intraocular pressure (IOP) by decreasing aqueous humour production. the ciliary epithelium contains both alpha- and beta-adrenergic receptors. Electrophysiologic studies on the isolated iris-ciliary body (I-CB) preparation provide a means to study direct effects of the adrenergic agents on transepithelial properties of the ciliary epithelium. This paper will discuss the enzymatic and adrenergic properties of the ciliary epithelium as they relate to active transport and thereby aqueous humour production. PMID:3026067

  12. Self-assembled dicopper(II) diethanolaminate cores for mild aerobic and peroxidative oxidation of alcohols.

    PubMed

    Figiel, Paweł J; Kirillov, Alexander M; Guedes da Silva, M Fátima C; Lasri, Jamal; Pombeiro, Armando J L

    2010-11-01

    The new dicopper(ii) complexes [Cu(2)(μ-Hmdea)(2)(NCS)(2)] (1) and [Cu(2)(μ-Hedea)(2)(N(3))(2)]·(H(2)O)(0.25) (2) with the {Cu(2)(μ-O)(2)} diethanolaminate cores have been easily generated by aqueous medium self-assembly reactions of copper(ii) nitrate with N-methyl- or N-ethyldiethanolamine (H(2)mdea or H(2)edea, respectively), in the presence of sodium thiocyanate (for 1) or sodium azide (for 2) as ancillary ligands sources. They have been isolated as air-stable crystalline solids and fully characterized by IR and UV-vis spectroscopies, ESI-MS(+), elemental and single-crystal X-ray diffraction analyses. The latter complex also features a fourfold linkage of neighbouring dimeric units via strong intermolecular O-HO hydrogen bonds, giving rise to the formation of tetracopper aggregates. The catalytic activity of compounds 1 and 2 has been studied for the mild (50-80 °C) and selective oxidations of alcohols, namely for (i) the aerobic aqueous medium oxidation of benzyl alcohols to benzaldehydes, mediated by TEMPO radical, and for (ii) the solvent-free oxidation of secondary alcohols to ketones by t-BuOOH under microwave (MW) irradiation. Complex 2 shows the highest efficiency in both oxidation systems, resulting in up to 99% molar yields (based on the alcohol substrate) of products. In addition, remarkably high values of TON (1020) and TOF (4080 h(-1)) have been achieved in the MW-assisted peroxidative oxidation of 1-phenylethanol to acetophenone (model reaction). Attractive green features of these catalytic systems include the operation in aqueous or solvent-free reaction medium, under mild conditions and with high yields and selectivities, using Cu catalyst precursors that are readily available by self-assembly in water of simple chemicals. PMID:20844801

  13. Staudinger ligation towards cyclodextrin dimers in aqueous/organic media. Synthesis, conformations and guest-encapsulation ability

    PubMed Central

    Manouilidou, Malamatenia D; Lazarou, Yannis G; Mavridis, Irene M

    2014-01-01

    Summary β-Cyclodextrin (β-CD) dimers have been prepared using the bioorthogonal Staudinger ligation for the first time. In addition to a known linker, methyl 2-(diphenylphosphanyl)terephthalate, a doubly active linker was specifically developed that enabled connection of two β-CD units in a single step and in aqueous/organic media, under mild conditions and with good yields. A three-carbon spacer between the β-CD torus and the azido group was required for facile dimer formation. The products, as studied by NMR spectroscopy, were found to adopt closed conformations by intramolecular self-inclusion. On the other hand, association via intermolecular binding was also observed in aqueous solution, confirmed by DOSY NMR experiments. Despite self-inclusion, the β-CD cavities were capable of guest encapsulation, as shown by titration experiments: the binding constant with 1-adamantylamine was similar to that of natural β-CD. Theoretical calculations for isolated molecules (PM3 level of theory) and in the presence of solvent [water, PM3(COSMO)] as well as DFT calculations suggested that the compounds prefer to adopt conformations which bring the phenyl groups either inside the β-CD cavity (inclusion) or over its narrow side (vicinal). Thus, Staudinger ligation could be the method of choice for linking CDs exhibiting (i) ease of preparation in aqueous media, in short steps, under mild conditions and in good yields, (ii) satisfactory aqueous solubility and independent binding capacity of the cavities. PMID:24778732

  14. Staudinger ligation towards cyclodextrin dimers in aqueous/organic media. Synthesis, conformations and guest-encapsulation ability.

    PubMed

    Manouilidou, Malamatenia D; Lazarou, Yannis G; Mavridis, Irene M; Yannakopoulou, Konstantina

    2014-01-01

    β-Cyclodextrin (β-CD) dimers have been prepared using the bioorthogonal Staudinger ligation for the first time. In addition to a known linker, methyl 2-(diphenylphosphanyl)terephthalate, a doubly active linker was specifically developed that enabled connection of two β-CD units in a single step and in aqueous/organic media, under mild conditions and with good yields. A three-carbon spacer between the β-CD torus and the azido group was required for facile dimer formation. The products, as studied by NMR spectroscopy, were found to adopt closed conformations by intramolecular self-inclusion. On the other hand, association via intermolecular binding was also observed in aqueous solution, confirmed by DOSY NMR experiments. Despite self-inclusion, the β-CD cavities were capable of guest encapsulation, as shown by titration experiments: the binding constant with 1-adamantylamine was similar to that of natural β-CD. Theoretical calculations for isolated molecules (PM3 level of theory) and in the presence of solvent [water, PM3(COSMO)] as well as DFT calculations suggested that the compounds prefer to adopt conformations which bring the phenyl groups either inside the β-CD cavity (inclusion) or over its narrow side (vicinal). Thus, Staudinger ligation could be the method of choice for linking CDs exhibiting (i) ease of preparation in aqueous media, in short steps, under mild conditions and in good yields, (ii) satisfactory aqueous solubility and independent binding capacity of the cavities. PMID:24778732

  15. A Rootstock Provides Water Conservation for a Grafted Commercial Tomato (Solanum lycopersicum L.) Line in Response to Mild-Drought Conditions: A Focus on Vegetative Growth and Photosynthetic Parameters

    PubMed Central

    Nilsen, Erik T.; Freeman, Joshua; Grene, Ruth; Tokuhisa, James

    2014-01-01

    The development of water stress resistant lines of commercial tomato by breeding or genetic engineering is possible, but will take considerable time before commercial varieties are available for production. However, grafting commercial tomato lines on drought resistant rootstock may produce drought tolerant commercial tomato lines much more rapidly. Due to changing climates and the need for commercial production of vegetables in low quality fields there is an urgent need for stress tolerant commercial lines of vegetables such as tomato. In previous observations we identified a scion root stock combination (‘BHN 602’ scion grafted onto ‘Jjak Kkung’ rootstock hereafter identified as 602/Jjak) that had a qualitative drought-tolerance phenotype when compared to the non-grafted line. Based on this initial observation, we studied photosynthesis and vegetative above-ground growth during mild-drought for the 602/Jjak compared with another scion-rootstock combination (‘BHN 602’ scion grafted onto ‘Cheong Gang’ rootstock hereafter identified as 602/Cheong) and a non-grafted control. Overall above ground vegetative growth was significantly lower for 602/Jjak in comparison to the other plant lines. Moreover, water potential reduction in response to mild drought was significantly less for 602/Jjak, yet stomatal conductance of all plant-lines were equally inhibited by mild-drought. Light saturated photosynthesis of 602/Jjak was less affected by low water potential than the other two lines as was the % reduction in mesophyll conductance. Therefore, the Jjak Kkung rootstock caused aboveground growth reduction, water conservation and increased photosynthetic tolerance of mild drought. These data show that different rootstocks can change the photosynthetic responses to drought of a high yielding, commercial tomato line. Also, this rapid discovery of one scion-rootstock combination that provided mild-drought tolerance suggests that screening more scion

  16. A rootstock provides water conservation for a grafted commercial tomato (Solanum lycopersicum L.) line in response to mild-drought conditions: a focus on vegetative growth and photosynthetic parameters.

    PubMed

    Nilsen, Erik T; Freeman, Joshua; Grene, Ruth; Tokuhisa, James

    2014-01-01

    The development of water stress resistant lines of commercial tomato by breeding or genetic engineering is possible, but will take considerable time before commercial varieties are available for production. However, grafting commercial tomato lines on drought resistant rootstock may produce drought tolerant commercial tomato lines much more rapidly. Due to changing climates and the need for commercial production of vegetables in low quality fields there is an urgent need for stress tolerant commercial lines of vegetables such as tomato. In previous observations we identified a scion root stock combination ('BHN 602' scion grafted onto 'Jjak Kkung' rootstock hereafter identified as 602/Jjak) that had a qualitative drought-tolerance phenotype when compared to the non-grafted line. Based on this initial observation, we studied photosynthesis and vegetative above-ground growth during mild-drought for the 602/Jjak compared with another scion-rootstock combination ('BHN 602' scion grafted onto 'Cheong Gang' rootstock hereafter identified as 602/Cheong) and a non-grafted control. Overall above ground vegetative growth was significantly lower for 602/Jjak in comparison to the other plant lines. Moreover, water potential reduction in response to mild drought was significantly less for 602/Jjak, yet stomatal conductance of all plant-lines were equally inhibited by mild-drought. Light saturated photosynthesis of 602/Jjak was less affected by low water potential than the other two lines as was the % reduction in mesophyll conductance. Therefore, the Jjak Kkung rootstock caused aboveground growth reduction, water conservation and increased photosynthetic tolerance of mild drought. These data show that different rootstocks can change the photosynthetic responses to drought of a high yielding, commercial tomato line. Also, this rapid discovery of one scion-rootstock combination that provided mild-drought tolerance suggests that screening more scion-rootstock combination for

  17. Hexacoordinate Ru-based olefin metathesis catalysts with pH-responsive N-heterocyclic carbene (NHC) and N-donor ligands for ROMP reactions in non-aqueous, aqueous and emulsion conditions.

    PubMed

    Balof, Shawna L; Nix, K Owen; Olliff, Matthew S; Roessler, Sarah E; Saha, Arpita; Müller, Kevin B; Behrens, Ulrich; Valente, Edward J; Schanz, Hans-Jörg

    2015-01-01

    Three new ruthenium alkylidene complexes (PCy3)Cl2(H2ITap)Ru=CHSPh (9), (DMAP)2Cl2(H2ITap)Ru=CHPh (11) and (DMAP)2Cl2(H2ITap)Ru=CHSPh (12) have been synthesized bearing the pH-responsive H2ITap ligand (H2ITap = 1,3-bis(2',6'-dimethyl-4'-dimethylaminophenyl)-4,5-dihydroimidazol-2-ylidene). Catalysts 11 and 12 are additionally ligated by two pH-responsive DMAP ligands. The crystal structure was solved for complex 12 by X-ray diffraction. In organic, neutral solution, the catalysts are capable of performing standard ring-opening metathesis polymerization (ROMP) and ring closing metathesis (RCM) reactions with standard substrates. The ROMP with complex 11 is accelerated in the presence of two equiv of H3PO4, but is reduced as soon as the acid amount increased. The metathesis of phenylthiomethylidene catalysts 9 and 12 is sluggish at room temperature, but their ROMP can be dramatically accelerated at 60 °C. Complexes 11 and 12 are soluble in aqueous acid. They display the ability to perform RCM of diallylmalonic acid (DAMA), however, their conversions are very low amounting only to few turnovers before decomposition. However, both catalysts exhibit outstanding performance in the ROMP of dicyclopentadiene (DCPD) and mixtures of DCPD with cyclooctene (COE) in acidic aqueous microemulsion. With loadings as low as 180 ppm, the catalysts afforded mostly quantitative conversions of these monomers while maintaining the size and shape of the droplets throughout the polymerization process. Furthermore, the coagulate content for all experiments stayed <2%. This represents an unprecedented efficiency in emulsion ROMP based on hydrophilic ruthenium alkylidene complexes. PMID:26664616

  18. Hexacoordinate Ru-based olefin metathesis catalysts with pH-responsive N-heterocyclic carbene (NHC) and N-donor ligands for ROMP reactions in non-aqueous, aqueous and emulsion conditions

    PubMed Central

    Balof, Shawna L; Nix, K Owen; Olliff, Matthew S; Roessler, Sarah E; Saha, Arpita; Müller, Kevin B; Behrens, Ulrich; Valente, Edward J

    2015-01-01

    Summary Three new ruthenium alkylidene complexes (PCy3)Cl2(H2ITap)Ru=CHSPh (9), (DMAP)2Cl2(H2ITap)Ru=CHPh (11) and (DMAP)2Cl2(H2ITap)Ru=CHSPh (12) have been synthesized bearing the pH-responsive H2ITap ligand (H2ITap = 1,3-bis(2’,6’-dimethyl-4’-dimethylaminophenyl)-4,5-dihydroimidazol-2-ylidene). Catalysts 11 and 12 are additionally ligated by two pH-responsive DMAP ligands. The crystal structure was solved for complex 12 by X-ray diffraction. In organic, neutral solution, the catalysts are capable of performing standard ring-opening metathesis polymerization (ROMP) and ring closing metathesis (RCM) reactions with standard substrates. The ROMP with complex 11 is accelerated in the presence of two equiv of H3PO4, but is reduced as soon as the acid amount increased. The metathesis of phenylthiomethylidene catalysts 9 and 12 is sluggish at room temperature, but their ROMP can be dramatically accelerated at 60 °C. Complexes 11 and 12 are soluble in aqueous acid. They display the ability to perform RCM of diallylmalonic acid (DAMA), however, their conversions are very low amounting only to few turnovers before decomposition. However, both catalysts exhibit outstanding performance in the ROMP of dicyclopentadiene (DCPD) and mixtures of DCPD with cyclooctene (COE) in acidic aqueous microemulsion. With loadings as low as 180 ppm, the catalysts afforded mostly quantitative conversions of these monomers while maintaining the size and shape of the droplets throughout the polymerization process. Furthermore, the coagulate content for all experiments stayed <2%. This represents an unprecedented efficiency in emulsion ROMP based on hydrophilic ruthenium alkylidene complexes. PMID:26664616

  19. Cognitive Processing in Mild Disabilities.

    ERIC Educational Resources Information Center

    Al-Hilawani, Yasser A.; Poteet, James A.

    Research regarding the cognitive processing of students with learning disabilities, mild mental handicap, and emotional handicap is reviewed. In considering cognitive processing for students with mild mental handicap, research attention has been directed to the issues of memory and learning, acquisition and retrieval deficits, inefficient…

  20. Experimental studies of a single-effect absorption refrigerator using aqueous lithium-bromide: Effect of operating condition to system performance

    SciTech Connect

    Aphornratana, Satha; Sriveerakul, Thanarath

    2007-11-15

    This paper describes an experimental investigation of a single-effect absorption using aqueous lithium-bromide as working fluid. A 2 kW cooling capacity experimental refrigerator was tested with various operating temperatures. It was found that the solution circulation ratio (SCR) has a strong effect on the system performance. The measured SCR was 2-5 times greater than the theoretical prediction. This was due to the low performance of the absorber. The use of solution heat exchanger could increase the COP by up to 60%. (author)

  1. Determination of formal kinetic constants of thermal decomposition of aqueous hydrogen peroxide solution in a mixture of magnetic powder, based on experimental thermogram, obtained in adiabatic conditions

    NASA Astrophysics Data System (ADS)

    Zaripov, Jamshed; Borisov, Boris; Bondarchuk, Sergey

    2014-08-01

    Process of thermal decomposition of hydrogen peroxide aqueous solution with the addition of magnetic powder in the form of toner for printers and lanthanum manganite were considered. Obtained resulting from an experiment in the Dewar container conducted thermogram analyzed using mass balance equations and heat. Formal kinetic parameters determined, and conclude that the magnetic powder in the mixture does not have catalytic properties. The described technique is recommended as a rapid analysis of the kinetics of the various reactions to substances having predefined thermal and thermodynamic properties.

  2. In situ study of mass transfer in aqueous solutions under high pressures via Raman spectroscopy: A new method for the determination of diffusion coefficients of methane in water near hydrate formation conditions

    USGS Publications Warehouse

    Lu, W.J.; Chou, I.-Ming; Burruss, R.C.; Yang, M.Z.

    2006-01-01

    A new method was developed for in situ study of the diffusive transfer of methane in aqueous solution under high pressures near hydrate formation conditions within an optical capillary cell. Time-dependent Raman spectra of the solution at several different spots along the one-dimensional diffusion path were collected and thus the varying composition profile of the solution was monitored. Diffusion coefficients were estimated by the least squares method based on the variations in methane concentration data in space and time in the cell. The measured diffusion coefficients of methane in water at the liquid (L)-vapor (V) stable region and L-V metastable region are close to previously reported values determined at lower pressure and similar temperature. This in situ monitoring method was demonstrated to be suitable for the study of mass transfer in aqueous solution under high pressure and at various temperature conditions and will be applied to the study of nucleation and dissolution kinetics of methane hydrate in a hydrate-water system where the interaction of methane and water would be more complicated than that presented here for the L-V metastable condition. ?? 2006 Society for Applied Spectroscopy.

  3. Shellac-coated iron oxide nanoparticles for removal of cadmium(II) ions from aqueous solution.

    PubMed

    Gong, Jilai; Chen, Long; Zeng, Guangming; Long, Fei; Deng, Jiuhua; Niu, Qiuya; He, Xun

    2012-01-01

    This study describes a new effective adsorbent for cadmium removal from aqueous solution synthesized by coating a shellac layer, a natural biodegradable and renewable resin with abundant hydroxyl and carboxylic groups, on the surface of iron oxide magnetic nanoparticles. Transmission Electron Microscopy (TEM) imaging showed shellac-coated magnetic nanoparticle (SCMN) adsorbents had a core-shell structure with a core of 20 nm and shell of 5 nm. Fourier Transform Infrared Spectroscopic analysis suggested the occurrence of reaction between carboxyl groups on the SCMN adsorbent surface and cadmium ions in aqueous solution. Kinetic data were well described by pseudo second-order model and adsorption isotherms were fitted with both Langmuir and Freundlich models with maximum adsorption capacity of 18.80 mg/g. SCMN adsorbents provided a favorable adsorption capacity under high salinity conditions, and cadmium could easily be desorbed using mild organic acid solutions at low concentration. PMID:23513435

  4. A localized tolerance in the substrate specificity of the fluorinase enzyme enables "last-step" 18F fluorination of a RGD peptide under ambient aqueous conditions.

    PubMed

    Thompson, Stephen; Zhang, Qingzhi; Onega, Mayca; McMahon, Stephen; Fleming, Ian; Ashworth, Sharon; Naismith, James H; Passchier, Jan; O'Hagan, David

    2014-08-18

    A strategy for last-step (18)F fluorination of bioconjugated peptides is reported that exploits an "Achilles heel" in the substrate specificity of the fluorinase enzyme. An acetylene functionality at the C-2 position of the adenosine substrate projects from the active site into the solvent. The fluorinase catalyzes a transhalogenation of 5'-chlorodeoxy-2-ethynyladenosine (ClDEA) to 5'-fluorodeoxy-2-ethynyladenosine (FDEA). Extending a polyethylene glycol linker from the terminus of the acetylene allows the presentation of bioconjugation cargo to the enzyme for (18)F labelling. The method uses an aqueous solution (H2(18)O) of [(18)F]fluoride generated by the cyclotron and has the capacity to isotopically label peptides of choice for positron emission tomography (PET). PMID:24989327

  5. Is vanadate reduced by thiols under biological conditions? Changing the redox potential of V(V)/V(IV) by complexation in aqueous solution.

    PubMed

    Crans, Debbie C; Zhang, Boyan; Gaidamauskas, Ernestas; Keramidas, Anastasios D; Willsky, Gail R; Roberts, Chris R

    2010-05-01

    Although dogma states that vanadate is readily reduced by glutathione, cysteine, and other thiols, there are several examples documenting that vanadium(V)-sulfur complexes can form and be observed. This conundrum has impacted life scientists for more than two decades. Investigation of this problem requires an understanding of both the complexes that form from vanadium(IV) and (V) and a representative thiol in aqueous solution. The reactions of vanadate and hydrated vanadyl cation with 2-mercaptoethanol have been investigated using multinuclear NMR, electron paramagnetic resonance (EPR), and UV-vis spectroscopy. Vanadate forms a stable complex of 2:2 stoichiometry with 2-mercaptoethanol at neutral and alkaline pH. In contrast, vanadate can oxidize 2-mercaptoethanol; this process is favored at low pH and high solute concentrations. The complex that forms between aqueous vanadium(IV) and 2-mercaptoethanol has a 1:2 stoichiometry and can be observed at high pH and high 2-mercaptoethanol concentration. The solution structures have been deduced based on coordination induced chemical shifts and speciation diagrams prepared. This work demonstrates that both vanadium(IV) and (V)-thiol complexes form and that redox chemistry also takes place. Whether reduction of vanadate takes place is governed by a combination of parameters: pH, solute- and vanadate-concentrations and the presence of other complexing ligands. On the basis of these results it is now possible to understand the distribution of vanadium in oxidation states (IV) and (V) in the presence of glutathione, cysteine, and other thiols and begin to evaluate the forms of the vanadium compounds that exert a particular biological effect including the insulin-enhancing agents, antiamoebic agents, and interactions with vanadium binding proteins. PMID:20359175

  6. Mild pretreatment and enzymatic saccharification of cellulose with recycled ionic liquids towards one-batch process.

    PubMed

    Auxenfans, Thomas; Buchoux, Sébastien; Djellab, Karim; Avondo, Carine; Husson, Eric; Sarazin, Catherine

    2012-10-01

    The development of second-generation bioethanol involves minimizing the energy input throughout the processing steps. We report here that efficient ionic liquid pretreatments of cellulose can be achieved with short duration times (20 min) at mild temperature (45°C) with [Emim](+)[MeO(H)PO(2)](-) and at room temperature (25 °C) with [Emim](+)[CH(3)COO](-). In these conditions, yields of glucose were increased by a factor of 3. In addition, the recycling of these two imidazolium-based ILs can be performed in maintaining their efficiency to pretreat cellulose. The short time and mild temperature of cellulose solubilization allowed a one-batch processing of [Emim](+)[MeO(H)PO(2)](-) IL-pretreatment and saccharification. In the range from 0 to 100% IL in an aqueous enzymatic medium, the glucose yields were improved at IL proportions between 10 and 40%. The maximum yield at 10% IL is very promising to consider one batch process as efficient as two-step process. PMID:22840005

  7. Mortality associated with mild, untreated xerophthalmia.

    PubMed Central

    Sommer, A

    1983-01-01

    The high mortality rate among children with severe corneal xerophthalmia is well recognized. The present study investigates, for the first time, mortality among the very much larger number of otherwise healthy free-living children with mild xerophthalmia (night blindness and Bitot's spots). An average of 3481 children (under 6 years of age) living in six Indonesian villages were reexamined by an ophthalmologist, pediatrician, and nutritionist every 3 months for 18 months. The overall prevalence of mild xerophthalmia was 4.9%. During the 18 months of observation, 132 children died. Of these, 24 had mild xerophthalmia and 108 had normal eyes at the 3-monthly examination preceding their death. Mortality rates were calculated for each 3-month interval by classifying all children by their ocular status at the start of the interval, and then dividing the number of deaths within the interval by the number of children of the same ocular status followed up for that interval. Mortality rates for the six 3-month intervals were then added together, and the results expressed as deaths per 1000 "child-intervals" of follow-up. Overall mortality rates for children with mild xerophthalmia and for children with normal eyes were 23.3 and 5.3, respectively, a ratio of 4 to 1. Excess mortality among the mildly xerophthalmic children increased with the severity of their xerophthalmia. Mortality rates for children with night blindness, with Bitot's spots, and with the two conditions concurrently were 2.7, 6.6, and 8.6 times the mortality rate of non-xerophthalmic children. This direct, almost linear relation between mortality and the severity of mild xerophthalmia was still present after standardizing for age and for the presence or absence of respiratory infection and protein-energy malnutrition. In the population studied, 16% of all deaths in children 1 to 6 years of age were directly related to vitamin A deficiency identified by the presence of mild xerophthalmia. These results

  8. Tannin (Polyphenol) Stability in Aqueous Solutions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Understanding the chemical stability of tannins (polyphenolics) in soils is critical to understanding their biological activities and fate. We examined the stability of chemically defined tannins in aqueous solutions under conditions simulating natural and laboratory conditions. We evaluated tanni...

  9. Mars aqueous chemistry experiment

    NASA Technical Reports Server (NTRS)

    Clark, Benton C.; Mason, Larry W.

    1993-01-01

    The 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. Progress for the first year MACE PIDDP is reported in two major areas of effort: (1) fluids handling concepts, definition, and breadboard fabrication and (2) aqueous chemistry ion sensing technology and test facility integration. A fluids handling breadboard was designed, fabricated, and tested at Mars ambient pressure. The breadboard allows fluid manipulation scenarios to be tested under the reduced pressure conditions expected in the Martian atmosphere in order to validate valve operations, orchestrate analysis sequences, investigate sealing integrity, and to demonstrate efficacy of the fluid handling concept. Additional fluid manipulation concepts have also been developed based on updated MESUR spacecraft definition. The Mars Aqueous Chemistry Experiment Ion Selective Electrode (ISE) facility was designed as a test bed to develop a multifunction interface for measurements of chemical ion concentrations in aqueous solution. The interface allows acquisition of real time data concerning the kinetics and heats of salt dissolution, and transient response to calibration and solubility events. An array of ion selective electrodes has been interfaced and preliminary calibration studies performed.

  10. Hematite Spherules in Basaltic Tephra Altered Under Aqueous, Acid-Sulfate Conditions on Mauna Kea Volcano, Hawaii: Possible Clues for the Occurrence of Hematite-Rich Spherules in the Burns Formation at Meridiani Planum, Mars

    NASA Technical Reports Server (NTRS)

    Morris, R. V.; Ming, D. W.; Graff, T. G.; Arvidson, R. E.; Bell, J. F., III; Squyres, S. W.; Mertzman, S. A.; Gruener, J. E.; Golden, D. C.; Robinson, G. A.

    2005-01-01

    Iron-rich spherules (>90% Fe2O3 from electron microprobe analyses) approx.10-100 microns in diameter are found within sulfate-rich rocks formed by aqueous, acid-sulfate alteration of basaltic tephra on Mauna Kea volcano, Hawaii. Although some spherules are nearly pure Fe, most have two concentric compositional zones, with the core having a higher Fe/Al ratio than the rim. Oxide totals less than 100% (93-99%) suggest structural H2O and/or /OH. The transmission Moessbauer spectrum of a spherule-rich separate is dominated by a hematite (alpha-Fe2O3) sextet whose peaks are skewed toward zero velocity. Skewing is consistent with Al(3+) for Fe(3+) substitution and structural H2O and/or /OH. The grey color of the spherules implies specular hematite. Whole-rock powder X-ray diffraction spectra are dominated by peaks from smectite and the hydroxy sulfate mineral natroalunite as alteration products and plagioclase feldspar that was present in the precursor basaltic tephra. Whether spherule formation proceeded directly from basaltic material in one event (dissolution of basaltic material and precipitation of hematite spherules) or whether spherule formation required more than one event (formation of Fe-bearing sulfate rock and subsequent hydrolysis to hematite) is not currently constrained. By analogy, a formation pathway for the hematite spherules in sulfate-rich outcrops at Meridiani Planum on Mars (the Burns formation) is aqueous alteration of basaltic precursor material under acid-sulfate conditions. Although hydrothermal conditions are present on Mauna Kea, such conditions may not be required for spherule formation on Mars if the time interval for hydrolysis at lower temperatures is sufficiently long.

  11. Ionic liquid-aqueous solution ultrasonic-assisted extraction of three kinds of alkaloids from Phellodendron amurense Rupr and optimize conditions use response surface.

    PubMed

    Wang, Wenchao; Li, Qingyong; Liu, Yuhui; Chen, Binbin

    2015-05-01

    In this paper, we chose diffident kinds of ionic liquids to optimal selection an optimal one to extract alkaloids from Phellodendron amurense Rupr. Four ionic liquids with diffident carbon chains or anions have been investigated and 1-butyl-3-methylimidazolium bromide with best productivity. Then, selections have been optimized in different conditions, including concentration of ionic liquid, time for ultrasonic treatment, ultrasonic power and solid-liquid ratio. Moreover, three conditions have been comprehensively assessment by response surface methodology, the optimal conditions were determined as follows ultrasonic power 100 W, extraction time 75 min and ratio of solvent to raw material 1:14. Under these conditions, the yield% (MIX) was 106.7% (extracted by heat reflux being defined 100%). Comparing with other methods, the advantages are saving conserving, time saving, high yield% and especially pollution-free. PMID:25443277

  12. Bioenhanced dissolution of dense non-aqueous phase of trichloroethylene as affected by iron reducing conditions: model systems and environmental samples.

    PubMed

    Paul, Laiby; Smolders, Erik

    2015-01-01

    The anaerobic biotransformation of trichloroethylene (TCE) can be affected by competing electron acceptors such as Fe (III). This study assessed the role of Fe (III) reduction on the bioenhanced dissolution of TCE dense non-aqueous phase liquid (DNAPL). Columns were set up as 1-D diffusion cells consisting of a lower DNAPL layer, a layer with an aquifer substratum and an upper water layer that is regularly refreshed. The substrata used were either inert sand or sand coated with 2-line ferrihydrite (HFO) or two environmental Fe (III) containing samples. The columns were inoculated with KB-1 and were repeatedly fed with formate. In none of the diffusion cells, vinyl chloride or ethene was detected while dissolved and extractable Fe (II) increased strongly during 60 d of incubation. The cis-DCE concentration peaked at 4.0 cm from the DNAPL (inert sand) while it was at 3.4 cm (sand+HFO), 1.7 cm and 2.5 cm (environmental samples). The TCE concentration gradients near the DNAPL indicate that the DNAPL dissolution rate was larger than that in an abiotic cell by factors 1.3 (inert sand), 1.0 (sand+HFO) and 2.2 (both environmental samples). This results show that high bioavailable Fe (III) in HFO reduces the TCE degradation by competitive Fe (III) reduction, yielding lower bioenhanced dissolution. However, Fe (III) reduction in environmental samples was not reducing TCE degradation and the dissolution factor was even larger than that of inert sand. It is speculated that physical factors, e.g. micro-niches in the environmental samples protect microorganisms from toxic concentrations of TCE. PMID:25460750

  13. Degradation of the biocide 4-chloro-3,5-dimethylphenol in aqueous medium with ozone in combination with ultraviolet irradiation: operating conditions influence and mechanism.

    PubMed

    Song, Shuang; Liu, Zhiwu; He, Zhiqiao; Li, Yu; Chen, Jianmeng; Li, Chaolin

    2009-11-01

    Biocides usually persist during municipal sewage treatment and are subsequently distributed into aquatic environments. To explore the capability of advanced oxidation processes for the rapid removal of biocides, we examined the total organic carbon (TOC) reduction of 4-chloro-3,5-dimethylphenol (PCMX) with a combination of UV/O(3). Moreover, the related important parameters, including the mass transfer coefficient and light utilization efficiency, in PCMX degradation were determined. The UV/O(3) experimental results showed a pronounced synergistic effect, leading to the nearly complete elimination of TOC within 75 min. Thus, the effect of operating variables was investigated as a function of pH, ozone dosage, bulk temperature and the initial concentration of PCMX. The efficiency of PCMX mineralization increased with an increase in ozone dose up to 3.1 gh(-1), and a decrease in the initial concentration from 250 to 100mg L(-1). The optimal pH value was 4.0, and the preferred bulk temperature was 20 degrees C on the basis of the influence of temperature on reaction rate and ozone solubility. The major aromatic intermediates identified by gas chromatography/mass spectrometry were 2,6-dimethylbenzene-1,4-diol, 2,6-dimethylbenzo-1,4-quinone, 2,6-bis(hydroxymethyl)benzo-1,4-quinone, and 2,6-dimethylbenzo-1,4-aldehyde. Quantitative determination of related carboxylic acid and inorganic anions was done by ion chromatography. On the basis of the identified reaction products, a possible degradation pathway for the UV/O(3) oxidation of PCMX in aqueous media is proposed. PMID:19818989

  14. Thermal behavior of aqueous iron oxide nano-fluid as a coolant on a flat disc heater under the pool boiling condition

    NASA Astrophysics Data System (ADS)

    Salari, E.; Peyghambarzadeh, S. M.; Sarafraz, M. M.; Hormozi, F.; Nikkhah, V.

    2016-04-01

    This paper experimentally focuses on the pool boiling heat transfer characteristics of gamma Fe3O4 aqueous nano-fluids on a flat disc heater. The nano-fluid used in this research was prepared using two-step method and was stabilized using nonylphenol ethoxylate nonionic surfactant, pH setting, and sonication process as well. Influence of different operating parameters such as heat flux (0-1546 kW/m2), mass concentration of nano-fluids (weight concentration 0.1-0.3 %), bubble formation, critical heat flux (1170 kW/m2 for water, 1230 kW/m2 (wt% = 0.1), 1320 kW/m2 (wt% = 0.2), 1450 kW/m2 (wt% = 0.3) and fouling on pool boiling heat transfer coefficient of nano-fluid as a thermal performance index were experimentally investigated and briefly discussed. Results demonstrated that the pool boiling heat transfer coefficient increases with increasing the mass concentration and the applied heat flux. In addition, the rate of bubble formation is significantly intensified at higher heat fluxes and subsequently, larger bubbles detach the surface due to the intensification of bubble coalescence. In terms of fouling formation, it can be stated that fouling of nano-fluids is a strong function of time and rate of deposition is increased over the extended time while the pool boiling heat transfer coefficient was not decreased over the time, as porous deposited layer on the surface are detached from the surface by bubble interactions. In terms of critical heat flux, capillary action of the deposited layer was found to be the main reason responsible for increasing the critical heat flux as liquid is stored inside the porous deposited layer, which enhances the surface toleration against the critical heat flux crisis.

  15. From a Sequential to a Concurrent Reaction in Aqueous Medium: Ruthenium-Catalyzed Allylic Alcohol Isomerization and Asymmetric Bioreduction.

    PubMed

    Ríos-Lombardía, Nicolás; Vidal, Cristian; Liardo, Elisa; Morís, Francisco; García-Álvarez, Joaquín; González-Sabín, Javier

    2016-07-18

    The ruthenium-catalyzed redox isomerization of allylic alcohols was successfully coupled with the enantioselective enzymatic ketone reduction (mediated by KREDs) in a concurrent process in aqueous medium. The overall transformation, formally the asymmetric reduction of allylic alcohols, took place with excellent conversions and enantioselectivities, under mild reaction conditions, employing commercially and readily available catalytic systems, and without external coenzymes or cofactors. Optimization resulted in a multistep approach and a genuine cascade reaction where the metal catalyst and biocatalyst coexist from the beginning. PMID:27258838

  16. Educating Students with Mild Disabilities.

    ERIC Educational Resources Information Center

    Meyen, Edward L., Ed.; And Others

    The book contains 19 papers from the journal, "Focus on Exceptional Children," that discuss new perspectives and practices in educating students with mild disabilities. The first half of the book is titled "New Perspectives" and includes the following articles: "Beyond the Regular Education Initiative/Inclusion and the Resource Room Controversy"…

  17. "White Privilege": A Mild Critique

    ERIC Educational Resources Information Center

    Blum, Lawrence

    2008-01-01

    White privilege analysis has been influential in philosophy of education. I offer some mild criticisms of this largely salutary direction--its inadequate exploration of its own normative foundations, and failure to distinguish between "spared injustice", "unjust enrichment" and "non-injustice-related" privileges; its inadequate exploration of the…

  18. Anthemis xylopoda flowers aqueous extract assisted in situ green synthesis of Cu nanoparticles supported on natural Natrolite zeolite for N-formylation of amines at room temperature under environmentally benign reaction conditions.

    PubMed

    Nasrollahzadeh, Mahmoud; Sajadi, S Mohammad; Hatamifard, Arezo

    2015-12-15

    Zeolites, which are nontoxic, abundant, and cheap, are very promising supports for the design and preparation of new and environmentally benign catalysts. In this study, Cu nanoparticles (NPs) were immobilized on the surface of natural Natrolite zeolite by Anthemis xylopoda flowers aqueous extract as a reducing and stabilizing agent. Afterward, the catalytic performance of the prepared catalyst was investigated for N-formylation of amines at room temperature under environmentally benign reaction conditions. The catalyst could be reused at least 5 times without any decrease in activity. The advantages of the present protocol include the use of green catalyst, easy isolation of the products, reusability of catalyst, absence of nontoxic reagents, and excellent yield of the products. PMID:26319331

  19. Photo-Fenton degradation of the herbicide 2,4-D in aqueous medium at pH conditions close to neutrality.

    PubMed

    Conte, Leandro O; Schenone, Agustina V; Alfano, Orlando M

    2016-04-01

    A theoretical and experimental study of the photo-Fenton degradation of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) in water is presented. A kinetic model derived from a reaction sequence is proposed using the ferrioxalate complex as iron source for conditions of pH = 5. The kinetic model was employed to predict the concentrations of 2,4-D, 2,4-dichlorophenol (2,4-DCP), hydrogen peroxide (HP) and oxalate (Ox) in a flat plate laboratory reactor irradiated with a solar simulator. Two types of incident irradiation levels were tested by different combinations of attenuation filters. The effects of the oxalate/Fe(+3) molar ratio (Ox/Fe), the reaction temperature (T) and the 2,4-D/HP molar ratio (R) on the photo-Fenton process were also investigated. For low radiation level and operating conditions of R = 50 and T = 50 °C, a 2,4-D conversion of 95.6% was obtained after 180 min. Moreover, the 2,4-D conversion was almost 100% in only 120 min when the system was operated under the same operating conditions and high radiation level. From the proposed model and the experimental data, the corresponding kinetic parameters were estimated applying a nonlinear regression method. A good agreement between the kinetic model and experimental data, for a wide range of simulated solar operating conditions, was observed. For 2,4-D, 2,4-DCP, HP and Ox concentrations, the calculated RMSE were 1.21 × 10(-2), 5.45 × 10(-3), 2.86 × 10(-1) and 2.65 × 10(-2) mM, respectively. PMID:26800432

  20. Aqueous foam toxicology evaluation and hazard review

    SciTech Connect

    Archuleta, M.M.

    1995-10-01

    Aqueous foams are aggregates of bubbles mechanically generated by passing air or other gases through a net, screen, or other porous medium that is wetted by an aqueous solution of surface-active foaming agents (surfactants). Aqueous foams are important in modem fire-fighting technology, as well as for military uses for area denial and riot or crowd control. An aqueous foam is currently being developed and evaluated by Sandia National Laboratories (SNL) as a Less-Than-Lethal Weapon for the National Institute of Justice (NIJ). The purpose of this study is to evaluate the toxicity of the aqueous foam developed for the NIJ and to determine whether there are any significant adverse health effects associated with completely immersing individuals without protective equipment in the foam. The toxicity of the aqueous foam formulation developed for NIJ is determined by evaluating the toxicity of the individual components of the foam. The foam is made from a 2--5% solution of Steol CA-330 surfactant in water generated at expansion ratios ranging from 500:1 to 1000:1. SteoI CA-330 is a 35% ammonium laureth sulfate in water and is produced by Stepan Chemical Company and containing trace amounts (<0.1%) of 1,4-dioxane. The results of this study indicate that Steol CA-330 is a non-toxic, mildly irritating, surfactant that is used extensively in the cosmetics industry for hair care and bath products. Inhalation or dermal exposure to this material in aqueous foam is not expected to produce significant irritation or systemic toxicity to exposed individuals, even after prolonged exposure. The amount of 1,4-dioxane in the surfactant, and subsequently in the foam, is negligible and therefore, the toxicity associated with dioxane exposure is not significant. In general, immersion in similar aqueous foams has not resulted in acute, immediately life-threatening effects, or chronic, long-term, non-reversible effects following exposure.

  1. Tannin bark Melalauca cajuputi powell (gelam) as green corrosion inhibitor of mild steel

    NASA Astrophysics Data System (ADS)

    Talib, Nur Atiqah Abu; Zakaria, Sarani; Hua, Chia Chin; Othman, Norinsan Kamil

    2014-09-01

    Tannin was extracted from gelam bark and used to produce corrosion inhibitor for mild steel. Tannin was extracted from gelam bark using 70% aqueous acetone for 6 hour. Tannin powder was characterization using fourier transform infrared spectroscopy to analyse chemical component in tannin and Scanning electron microscope (SEM) for tannin physical structure. The tannin effect on the corrosion inhibition of mild steel has been investigated in 1Mol HCl solution for 6 hour followed ASTM. The weight loss method were applied to study the mild steel corrosion behavior in the present and absend of different concentration of tannin (250, 300, 350)ppm. Tannin act good inhibitor as corrosion inhibitor for mild steel in acid medium. Surface morphology of carbon steel with and without inhibitor was investigated by scanning electron microscopy.

  2. Tannin bark Melalauca cajuputi powell (gelam) as green corrosion inhibitor of mild steel

    SciTech Connect

    Talib, Nur Atiqah Abu; Zakaria, Sarani; Hua, Chia Chin; Othman, Norinsan Kamil

    2014-09-03

    Tannin was extracted from gelam bark and used to produce corrosion inhibitor for mild steel. Tannin was extracted from gelam bark using 70% aqueous acetone for 6 hour. Tannin powder was characterization using fourier transform infrared spectroscopy to analyse chemical component in tannin and Scanning electron microscope (SEM) for tannin physical structure. The tannin effect on the corrosion inhibition of mild steel has been investigated in 1Mol HCl solution for 6 hour followed ASTM. The weight loss method were applied to study the mild steel corrosion behavior in the present and absend of different concentration of tannin (250, 300, 350)ppm. Tannin act good inhibitor as corrosion inhibitor for mild steel in acid medium. Surface morphology of carbon steel with and without inhibitor was investigated by scanning electron microscopy.

  3. Development of mild gasification process

    SciTech Connect

    Chu, C.I.C.; Derting, T.M.

    1988-07-01

    Under a previous contract with Morgantown Energy Technology Center (METC), Department of Energy (DOE) Contract No. AC21-84MC21108, UCC Research Corporation (UCCRC) built and tested a 1500 lb/day Mild Gasification Process Development Unit (MGU). The MGU, as tested under the previous contract, is shown in Figure 1. Testing completed under the previous contract showed that good quality hydrocarbon liquids and good quality char can be produced in the MGU. However, the MGU is not optimized. The primary objectives of the current project are to optimize the MGU and determine the suitability of char for several commercial applications. The program consists of four tasks; Task 1 -- Test Plan; Task 2 -- Optimization of Mild Gasification Process; Task 3 -- Evaluation of Char and Char/Coal Blends as a Boiler/Blast Furnace Fuel; and Task 4 -- Analysis of Data and Preparation of Final Report. Task 1 has been completed while work continued on Task 2.

  4. Development of mild gasification process

    SciTech Connect

    Chu, C.I.C.; Gillespie, B.L.

    1988-02-01

    Under a previous contract with Morgantown Energy Technology Center (METC), Department of Energy (DOE) Contract No. DE-AC21-84MC21108, UCC Research Corporation (UCCRC) built and tested a 1500 lb/day Mild Gasification Process Development Unit (MGU). The MGU, as tested under the previous contract, is shown in Figure 1. Testing completed under the previous contract showed that good quality hydrocarbon liquids and good quality char can be produced in the MGU. However, the MGU is not optimized. The primary objectives of the current project are to optimize the MGU and determine the suitability of char for several commercial applications. The program consists of four tasks; Task 1-Test Plan; Task 2-Optimization of Mild Gasification Process; Task 3-Evaluation of Char and Char/Coal Blends as a Boiler/Blast Furnace Fuel; and Task 4-Analysis of Data and Preparation of Final Report. Task 1 has been completed while work continued on Task 2.

  5. Development of mild gasification process

    SciTech Connect

    Chu, C.I.C.; Williams, S.W.

    1989-01-01

    Under a previous contract with Morgantown Energy Technology Center (METC), Department of Energy (DOE) Contract No. AC21-84MC21108, UCC Research Corporation (UCCRC) built and tested a 1500 lb/day Mild Gasification Process Development Unit (MGU). The MGU, as tested under the previous contract, is shown in Figure 1. Testing completed under the previous contract showed that good quality hydrocarbon liquids and good quality char can be produced in the MGU. However, the MGU is not optimized. The primary objectives of the current project are to optimize the MGU and determine the suitability of char for several commercial applications. The program consists of four tasks; Task 1 -- Test Plan; Task 2 -- Optimization of Mild Gasification Process; Task 3 -- Evaluation of Char and Char/Coal Blends as a Boiler/Blast Furnace Fuel; and Task 4 -- Analysis of Data and Preparation of Final Report. Task 1 has been completed while work continued on Task 2.

  6. Development of mild gasification process

    SciTech Connect

    Chu, C.I.C.; Gillespie, B.L.

    1987-11-01

    Under a previous contract with Morgantown Energy Technology Center (METC), Department of Energy (DOE) Contract No. AC21-84MC21108, UCC Research Corporation (UCCRC) built and tested a 1500 lb/day Mild Gasification Process Development Unit (MGU). The MGU, as tested under the previous contract, is shown in Figure 1. Testing completed under the previous contract showed that good quality hydrocarbon liquids and good quality char can be produced in the MGU. However, the MGU is not optimized. The primary objectives of the current project are to optimize the MGU and determine the suitability of char for several commercial applications. The program consists of four tasks; Task 1 -- Test Plan; Task 2 -- Optimization of Mild Gasification Process; Task 3 -- Evaluation of Char and Char/Coal Blends as a Boiler/Blast Furnace Fuel; and Task 4 -- Analysis of Data and Preparation of Final Report. Task 1 has been completed while work continued on Task 2.

  7. Mild coal gasification: Product separation

    SciTech Connect

    Wallman, P.H.; Singleton, M.F.

    1992-08-04

    Our general objective is to further the development of efficient continuous mild coal gasification processes. The research this year has been focused on product separation problems and particularly the problem of separating entrained ultra-fine particles from the chemically reactive environment of the product gas stream. Specifically, the objective of the present work has been to study candidate barrier filters for application to mild coal gasification processes. Our approach has been to select the most promising existing designs, to develop a design of our own and to test the designs in our bench-scale gasification apparatus. As a first step towards selection of the most promising barrier filter we have determined coking rates on several candidate filter media.

  8. In-situ observation of a dendrite growth in an aqueous condition and a uranium deposition into a liquid cadmium cathode in an electrowinning system

    NASA Astrophysics Data System (ADS)

    Kim, Si-Hyung; Yoon, Dal-Seong; You, Young-Jae; Paek, Seungwoo; Shim, Joon-Bo; Kwon, Sang-Woon; Kim, Kwang-Rag; Chung, Hong-Suk; Ahn, Do-Hee; Lee, Han-Soo

    2009-03-01

    A zinc-gallium system was setup to observe the growth process of dendrites and to compare the performance of the stirrers which would prevent a dendrite formation. In a no-stirring condition, zinc was easily deposited on a liquid gallium cathode in the form of dendrites. It was difficult for a paddle stirrer to directly fracture the zinc dendrites to fine particles. However, a harrow stirrer was observed to fracture the dendrite to some extent at high speeds. Not only their rotation speed but also the length of their blades needed to be properly adjusted to enhance their performance. In the uranium-cadmium experiment, the diffusion coefficient of the uranium species was obtained by the cyclic voltammetry method, which is around 1 × 10 -5 cm 2/s. In a no-stirring condition, most of the uranium deposited at the current densities of 35, 100 and 200 mA/cm 2 did not sink into the liquid cadmium cathode.

  9. Removal of aqueous rinsable flux residues in a batch spray dishwater

    SciTech Connect

    Slanina, J.T.

    1992-02-01

    An alkaline detergent solution used in an industrial dishwasher was evaluated to remove aqueous rinsable flux residues on printed wiring boards (PWBs) after hot air solder leveling and hot oil solder dip and leveling. The dishwasher, a batch cleaning process, was compared to an existing conveyorized aqueous cleaning process. The aqueous soluble flux residues from both soldering processes were removed with a solution of a mild alkaline detergent dissolved in hot deionized (DI) water.

  10. Memory dysfunction in mild aphasics.

    PubMed

    Rönnberg, J; Larsson, C; Fogelsjöö, A; Nilsson, L G; Lindberg, M; Angquist, K A

    1996-03-01

    The effect of mild aphasia (n = 9), as a result of subarachnoid haemorrhage (SAH), was evaluated against one matched (sex, age, and education) control group suffering from SAH of unknown origin without aphasia, and against one matched healthy control group. According to aphasia testing (Reinvang & Engvik, 1980), criteria for a classical diagnosis were not met. Therefore, the patients were characterized as mild aphasics: They generally displayed intact audo-verbal comprehension and repetition abilities, and they demonstrated a fluent, spontaneous speech. However, they showed phonemic and semantic paraphasias, with self-corrections; a few patients displayed alexia and agraphia. Memory performance of these three groups was evaluated by a neuropsychological test battery, designed to tap various components of verbal memory function. From the results it was concluded that: (a) Short-term memory is impaired, as regards the phonological loop and the central executive in working memory, whereas maintenance rehearsal is unaffected, given that the demands on phonological coding is minimized, (b) long-term memory is also generally impaired, whereas long-term learning and forgetting by means of subject-performed tasks proceeds within a normal range. Impairments were hypothesized to reflect less efficient central executive functions of working memory, involving generation of less appropriate semantic codes and phonological representations, (c) mildly aphasic patients are not subjectively aware of their own memory deficits, and (d) aphasia classification by means of standard procedures do not sufficiently characterize the nature of a mildy aphasic patient's memory problems. PMID:8900819