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1

Chemical reactions at aqueous interfaces  

NASA Astrophysics Data System (ADS)

Interfaces or phase boundaries are a unique chemical environment relative to individual gas, liquid, or solid phases. Interfacial reaction mechanisms and kinetics are often at variance with homogeneous chemistry due to mass transfer, molecular orientation, and catalytic effects. Aqueous interfaces are a common subject of environmental science and engineering research, and three environmentally relevant aqueous interfaces are investigated in this thesis: 1) fluorochemical sonochemistry (bubble-water), 2) aqueous aerosol ozonation (gas-water droplet), and 3) electrolytic hydrogen production and simultaneous organic oxidation (water-metal/semiconductor). Direct interfacial analysis under environmentally relevant conditions is difficult, since most surface-specific techniques require relatively `extreme' conditions. Thus, the experimental investigations here focus on the development of chemical reactors and analytical techniques for the completion of time/concentration-dependent measurements of reactants and their products. Kinetic modeling, estimations, and/or correlations were used to extract information on interfacially relevant processes. We found that interfacial chemistry was determined to be the rate-limiting step to a subsequent series of relatively fast homogeneous reactions, for example: 1) Pyrolytic cleavage of the ionic headgroup of perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) adsorbed to cavitating bubble-water interfaces during sonolysis was the rate-determining step in transformation to their inorganic constituents carbon monoxide, carbon dioxide, and fluoride; 2) ozone oxidation of aqueous iodide to hypoiodous acid at the aerosol-gas interface is the rate-determining step in the oxidation of bromide and chloride to dihalogens; 3) Electrolytic oxidation of anodic titanol surface groups is rate-limiting for the overall oxidation of organics by the dichloride radical. We also found chemistry unique to the interface, for example: 1) Adsorption of dilute PFOS(aq) and PFOA(aq) to acoustically cavitating bubble interfaces was greater than equilibrium expectations due to high-velocity bubble radial oscillations; 2) Relative ozone oxidation kinetics of aqueous iodide, sulfite, and thiosulfate were at variance with previously reported bulk aqueous kinetics; 3) Organics that directly chelated with the anode surface were oxidized by direct electron transfer, resulting in immediate carbon dioxide production but slower overall oxidation kinetics. Chemical reactions at aqueous interfaces can be the rate-limiting step of a reaction network and often display novel mechanisms and kinetics as compared to homogeneous chemistry.

Vecitis, Chad David

2

Aqueous chemical wash compositions  

SciTech Connect

This patent describes an aqueous, substantially unfoamed chemical wash composition having properties making it suitable for use as a pre-flush in well cementing operations and/or for removal of drilling mud from a borehole at a temperature of from about 150/sup 0/F to about 270/sup 0/F, the wash a. being predominantly composed of water, b. containing an active surfactant component comprising a combination of (1) from about 0.1 to about 1.5 weight percent (total weight basis) of a water soluble anionic surfactant; (2) from about 0.1 to about 1.5 weight percent (total weight basis) of a nonionic surfactant; and (3) from about 0.05 to about 0.54 weight percent (total weight basis) of at least one water soluble amphoteric surfactant, and c. having dispersed therein a heterogeneous mixture of distinct particles comprising both a first particulate oil soluble resin which is friable and a second particulate oil soluble resin which is pliable and where the size of the friable resin particles ranges from about 0.5 to about 300 microns and the size of the pliable resin particles ranges from about 0.05 to about 30 microns. The amount of the friable-pliable resin mixture is sufficient to impart effective fluid loss control to the chemical wash composition.

Bannister, C.E.

1987-07-21

3

Chemical treatment of aqueous plutonium wastes  

Microsoft Academic Search

Chemical precipitation processes have been used for the removal of microconcentrations of Pu (approx. 4 nM to 4 ..mu..m) since the late 1940's; however, previous experiments have been empirically oriented. In order to provide a rational approach to the chemical treatment, aqueous Pu chemistry was reviewed to determine the species most likely to be present in alkaline conditions where chemical

Drago

1980-01-01

4

Plasmon-driven sequential chemical reactions in an aqueous environment  

PubMed Central

Plasmon-driven sequential chemical reactions were successfully realized in an aqueous environment. In an electrochemical environment, sequential chemical reactions were driven by an applied potential and laser irradiation. Furthermore, the rate of the chemical reaction was controlled via pH, which provides indirect evidence that the hot electrons generated from plasmon decay play an important role in plasmon-driven chemical reactions. In acidic conditions, the hot electrons were captured by the abundant H+ in the aqueous environment, which prevented the chemical reaction. The developed plasmon-driven chemical reactions in an aqueous environment will significantly expand the applications of plasmon chemistry and may provide a promising avenue for green chemistry using plasmon catalysis in aqueous environments under irradiation by sunlight. PMID:24958029

Zhang, Xin; Wang, Peijie; Zhang, Zhenglong; Fang, Yurui; Sun, Mengtao

2014-01-01

5

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...

6

Uranium dioxide dissolution under acidic aqueous conditions  

SciTech Connect

Understanding of the long-term dissolution of waste forms in groundwater is required for the safe disposal of high level nuclear waste in a geologic repository, because waste-form radionuclides could be released by dissolution and transported in groundwater. The dissolution of the uranium dioxide (UO{sub 2}) matrix in spent nuclear fuel is considered the rate-limiting step for release of radioactive fission products. The intrinsic UO{sub 2} dissolution rate sets an upper limit on the aqueous radionuclide release rate. Unsaturated spent fuel tests have shown that pH`s of leachates have decreased to a range of 4 to 6, presumably due to air radiolysis that oxidizes nitrogen, producing nitric acid. Dissolution rates under such acidic conditions may be different than those previously reported for alkaline groundwater conditions. No dissolution rate measurements of UO{sub 2} or spent fuel have been reported for acidic conditions possibly relevant to a geologic repository. The purpose of our work has been to measure the intrinsic dissolution rates of uranium dioxide under acidic conditions that are relevant to a repository and allow for modeling. Experiments have been completed at room-temperature and 75 C, pH`s of 4 and 6, and air and oxygen saturated aqueous solutions. These are compared with earlier work on spent fuel and UO{sub 2} using alkaline solutions.

Steward, S.A.; Mones, E.T.

1995-11-20

7

Aqueous Chemical Solution Deposition of Ferroelectric Thin Films  

Microsoft Academic Search

Thin films of various ferroelectric multimetal oxides such as (Bi 1 m x La x ) 4 Ti 3 O 12 (BLT), SrBi 2 Ta 2 O 9 (SBT) and PbZr 1 m x Ti x O 3 (PZT) have been prepared by an entirely aqueous chemical solution deposition (CSD) route. Two critical issues related with aqueous CSD have hereby

M. K. Van Bael; D. Nelis; A. Hardy; D. Mondelaers; K. Van Werde; J. DHaen; G. Vanhoyland; H. Van Den Rul; J. Mullens; L. C. Van Poucke; F. Frederix; D. J. Wouters

2002-01-01

8

Explosivity Conditions of Aqueous Solutions and L. Mercury2  

E-print Network

1 Explosivity Conditions of Aqueous Solutions R. Thiéry1 and L. Mercury2 Revised version February of explosive boiling and gas exsolution of aqueous solutions from a thermodynamic point of view. Indeed, the kinetic nature of these processes, hence their explosivity, can be assessed by considering their relation

Paris-Sud XI, Université de

9

Chemical Stability of Laponite in Aqueous Media  

E-print Network

In this work stability of Laponite against dissolution in its aqueous dispersions is investigated as a function of initial pH of water before mixing Laponite, and concentration of Laponite. Dissolution of Laponite is quantified in terms of concentration of leached magnesium in the dispersions. Interestingly the solvent pH is observed to play no role in dissolution of Laponite in dispersion over the explored range of 3 to 10. Furthermore, contrary to the usual belief that Laponite dissolves when pH of aqueous dispersion decreases below 9, dissolution of the same is observed even though dispersion pH is above 10 for low concentrations of Laponite (1 and 1.7 mass%). On the other hand, for dispersions having high concentration of Laponite (2.8 mass%) and pH in the similar range (>10) no dissolution is observed. Measurement of ionic conductivity of dispersion shows that concentration of sodium ions in dispersion increases with concentration of Laponite, which appears to have a role in preventing the dissolution of Laponite.

Shweta Jatav; Yogesh M Joshi

2014-07-06

10

CHEMICAL SYNTHESES IN AQUEOUS MEDIA USING MICROWAVES  

EPA Science Inventory

The development of efficient, selective and eco-friendly synthetic methods has remained a major focus of our research group. Microwave (MW) irradiation as alternative energy source in conjunction with water as reaction media has proven to be a successful 'greener' chemical appro...

11

Preparation of fine nickel powders in aqueous solution under wet chemical process  

Microsoft Academic Search

Ultrafine nickel powders have been prepared by chemical reduction of aqueous NiCl2 with hydrazine at various reaction conditions as wet chemical process. The reductive atmosphere was produced by the dissolution of hydrazine hydrate in basic solution. The nickel powders were characterized by the means of an X-ray diffractometry, a scanning electron microscopy, BET method, a thermo-gravimetry and an X-ray photoelectron

Kwang Ho Kim; Yoon Bok Lee; Sang Geun Lee; Seong Soo Park

2004-01-01

12

Aqueous Polymer Emulsions by Chemical Modifications of Thermosetting Alternating Polyketones  

Microsoft Academic Search

Aqueous polymer emulsions were prepared by chemical modifications of thermosetting alternating pol- yketones in a one-pot reaction. Polymeric amines derived from the polyketones can act as polymeric surfactants for the self-emulsification of polyketones. The stability and structure of the emulsions with respect to the storage time at room temperature (208C) at different experimental con- ditions were thoroughly studied by dynamic

Youchun Zhang; A. A. Broekhuis; F. Picchioni

2007-01-01

13

Establishing and maintaining specific pathogen free (SPF) conditions in aqueous solutions using ozone.  

PubMed

The paper discusses the use of ozone in space applications for the elimination of pathogens, and the enhancement of the oxidation potential of ozone using hydrogen peroxide and ultraviolet radiation. These combinations will be possible to set up in space conditions. The sterilizing effect versus free radical generation is an important equilibrium to establish when specific pathogen free conditions are wanted in aqueous solutions containing organic matter. In situ sterilization of plant roots in hydroponic systems, as well as the oxidation of root exudates, will be discussed. The paper will contain examples of the chemical interaction of ozone with some of the other compounds found in hydroponic systems. PMID:11540210

Vestergard, B

1994-11-01

14

Chemical Reactivity at Metal Oxide-Aqueous Solution Interfaces  

NASA Astrophysics Data System (ADS)

The chemical reactivity of metal oxide surfaces in contact with aqueous solutions, with respect to cations and anions, is controlled by the composition, structure, and charging properties of the surface, the dielectric properties of the bulk oxide, and the stability of the aqueous cation or anion complex versus its sorption complex. These points will be illustrated for selected cations, anions, and metal oxides using macroscopic uptake and EXAFS spectroscopy results, x-ray standing wave data, and crystal truncation rod diffraction data. The reactivity of metal oxide surfaces with respect to low molecular weight (LMW) carboxylic acids is also dependent on the types of ring structures formed between surface functional groups and the LMW organic molecules. These types of interactions will be illustrated using ATR-FTIR data and dissolution measurements as a function of pH for oxalate, maleate, phthalate, and pyromellitate interacting with boehmite (AlOOH). Co-Authors are Tae Hyun Yoon, Stephen B. Johnson, Dept. of Geological & Environmental Sciences, Stanford University, Stanford CA 94305-2115; Thomas P. Trainor, Dept. of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, AK 99775; Anne M. Chaka, National Institute of Standards and Technology, Gaithersburg, MD 20899

Brown, Gordon E., Jr.

2005-03-01

15

Hydrodefluorination and hydrogenation of fluorobenzene under mild aqueous conditions.  

PubMed

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

Baumgartner, Rebekka; McNeill, Kristopher

2012-09-18

16

Simulation of 59Co NMR chemical shifts in aqueous solution.  

PubMed

59Co chemical shifts were computed at the GIAO-B3LYP level for [Co(CN)6]3-, [Co(H2O)6]3+, [Co(NH3)6]3+, and [Co(CO)4]- in water. The aqueous solutions were modeled by Car-Parrinello molecular dynamics (CPMD) simulations, or by propagation on a hybrid quantum-mechanical/molecular-mechanical Born-Oppenheimer surface (QM/MM-BOMD). Mean absolute deviations from experiment obtained with these methods are on the order of 400 and 600 ppm, respectively, over a total delta(59Co) range of about 18,000 ppm. The effect of the solvent on delta(59Co) is mostly indirect, resulting primarily from substantial metal-ligand bond contractions on going from the gas phase to the bulk. The simulated solvent effects on geometries and delta(59Co) values are well reproduced by using a polarizable continuum model (PCM), based on optimization and perturbational evaluation of quantum-mechanical zero-point corrections. PMID:16196064

Bhl, Michael; Grigoleit, Sonja; Kabrede, Hendrik; Mauschick, Frank T

2005-12-23

17

'GREENER' CHEMICAL SYNTHESES USING ALTERNATE REACTION 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-alkylation t...

18

MINEQL-EIR. Chemical Equilibrium Composition of Aqueous Systems  

SciTech Connect

MINEQL is a subroutine package to calculate equilibrium composition of an aqueous system, accounting for mass transfer. MINEQL-EIR contains an additional base on enthalpy and heat capacity data and has the option to do calculations at temperatures different from 25 degrees C.

Westall, J.C.; Zachary, J.L.; Morel, F.M.M [Massachusetts Institute of Technology, Cambridge (United States); Schweingruber, M. [Eidgenoessisches Institut for Reaktorforschung, Wuerenlingen (Switzerland)

1986-11-21

19

SORPTION AND TRANSPORT OF HYDROPHOBIC ORGANIC CHEMICALS IN AQUEOUS AND MIXED SOLVENT SYSTEMS: MODEL DEVELOPMENT AND PRELIMINARY EVALUATION  

EPA Science Inventory

A theoretical approach, based upon the assumption of predominance of solvophobic interactions, was formulated to quantitatively describe the sorption and transport of hydrophobic organic chemicals (HOC) from aqueous and aqueous-organic-solvent mixtures. In the theoretical approac...

20

The Effect of Salt on Protein Chemical Potential Determined by Ternary Diffusion in Aqueous Solutions  

E-print Network

using the Onsager reciprocal relation and the equality of molal cross-derivatives of solute chemicalThe Effect of Salt on Protein Chemical Potential Determined by Ternary Diffusion in Aqueous Solutions Onofrio Annunziata,*, Luigi Paduano,, Arne J. Pearlstein,§ Donald G. Miller,,| and John G

Annunziata, Onofrio

21

Biosorption of heavy metal ions from aqueous solutions by short hemp fibers: Effect of chemical composition  

Microsoft Academic Search

Sorption potential of waste short hemp fibers for Pb2+, Cd2+ and Zn2+ ions from aqueous media was explored. In order to assess the influence of hemp fiber chemical composition on their heavy metals sorption potential, lignin and hemicelluloses were removed selectively by chemical modification. The degree of fiber swelling and water retention value were determined in order to evaluate the

Biljana Pejic; Marija Vukcevic; Mirjana Kostic; Petar Skundric

2009-01-01

22

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

NASA Astrophysics Data System (ADS)

CM chondrites have undergone prevailed aqueous alteration in the parent asteroids and the alteration changed mineralogical and isotope signatures of water-bearing C-type asteroids.[1,2] In the previous studies, classification schemes of CM chondrites by the alteration degree were proposed by )[3,4] In the present study, we have performed a mineralogical study of 9 CM chondrites found in Antarctica in order to estimatie the nature and extents of aqueous alteration reactions. At first, small pieces (200 microns in size) of matrix were picked up and analyzed by synchroton radiation X-ray diffraction to identify minerals and relative abundances. The results of the X-ray diffraction analysis and SEM observations indicate that serpentine is present in the matrix of all samples as a major phase, suggesting that all samples have undergone aqueous alteration and have not been heated to temperature enough to dehydrate serpentine. Two out of 9 samples (LEW85311 and LAP03178 hereafter GroupA) contain Fe-Ni metal grains in both chondrule and matrix and anhydrous silicates (olivine and pyroxene) in matrix. Five of 9 samples (GRA06172, MET01072, LEW87022, LAP02269 and GRO95566 hereafter GroupB) contain fine-grained PCPs and anhydrous silicates but no metallic phases in matrix. In addition their chondrules are altered only in glassy parts and in limited parts of anhydrous silicates. The rest two of 9 samples (LAP031166 and MAC88100 hereafter GroupC) don't contain Fe-Ni metal and PCPs and contain little anhydrous silicates in matrix. In addition chondrules are almost completely altered. Since metallic phases are more susceptible to aqueous alteration than anhydrous silicates, the results suggest that the alteration degree is in the order of GroupA< GrouB< GroupC. The EPMA analysis indicates that most data of matrix composition fall within the triangle area defined by [1]: the area is enclosed by the composition of PCPs and two serpentines (the serpentin compositions are defined by 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

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

2011-12-01

23

Quantum-chemical calculations of electronic-absorption spectra of aromatic amino acids in aqueous solution  

NASA Astrophysics Data System (ADS)

Quantum-chemical methods are used to calculate electronic-absorption spectra, dipole moments, and atomic-charge distributions of aromatic amino acids in aqueous solutions at various concentrations. The electronic-absorption spectra are analyzed and compared with the spectra that are calculated for gas phase. The bathochromic shift of the spectral position is shown for the long-wavelength absorption peak of the singlet-singlet transition for aqueous solutions of amino acids.

Migovich, M. I.; Kel'man, V. A.

2014-08-01

24

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

PubMed

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

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

2014-09-17

25

CHEMICAL ACCUMULATION IN PLANT TISSUES FROM AQUEOUS EXPOSURE  

EPA Science Inventory

Predictive models have been designed to investigate plant-water distribution coefficients and to study the dynamics of chemical accumulation in aquatic plant organs. nitial model testing has been completed in laboratory studies using two chlorinated benzenes and three species of ...

26

Optical techniques for nanoscale probing and chemical detection in aqueous environments  

NASA Astrophysics Data System (ADS)

We present an investigation of charge-dependent physical properties of water-soluble synthetic polymers and polymer-based layered structures, using optical detection methods in a visible range. We apply in situ nanoscale optical techniques to study response of polymer systems to changes in pH, polymer concentration, and concentration and type of counterions. This work describes three optical techniques and custom built instrumental setups for nanoscale polymer characterization in aqueous environment. Phase-modulated ellipsometry was applied to determine the refraction coefficient and the thickness of a hydrogel-like polymer layer on a substrate. The present study describes the sensitivity of the phase modulated ellipsometry to errors of measurement and determines conditions for decoupling film thickness and refraction index. It is shown that, for a certain range of film thickness, both the thickness and the refractive index can be determined from a single measurement with high precision. This optimal range of the film thickness is calculated for organic thin films, and the analysis is tested on crosslinked poly(methacrylic acid) polymer films in air and in water. Fluorescent correlation spectroscopy was used to investigate diffusion of a synthetic polyelectrolyte in aqueous solutions. Translational diffusion of Alexa-labeled poly(methacrylic acid) chains was studied in very dilute, 10-4 mg/ml, solutions as a function of polymer charge density and counterion concentration. The results illustrate the utility of the technique for studying hydrodynamic sizes of polyelectrolyte coils in response to variation in solution pH or concentration of salt and polyelectrolytes. We apply surface-enhanced Raman scattering (SERS) for studying of enhancement capabilities of individual silver nanoparticles attached to glass and silicon substrates. Nanoparticles were electrostatically bound to a self-assembled polyallylamine hydrochloride (PAH) monolayer, which was deposited on substrates from aqueous solution. We have shown that the coverage density of Ag nanoparticles on the glass substrates correlates with the amount of adsorbed PAH. The SERS-active substrates were robust and stable in 0.5 M NaCl solutions, as well in extreme acidic and basic conditions. Rhodamine 6G dye (R6G) was chosen as a model molecule for SERS spectra acquisition. The glass substrates with immobilized non-aggregated Ag nanoparticles exhibited SERS enhancement and provided in situ detection sensitivity of R6G at 5 ppt level, with estimated surface coverage of 2 to 4 R6G molecules per silver particle. The results will improve the design of SERS-active photonic crystal fibers for highly sensitive chemical and biological detection.

Pristinski, Denis

27

Adsorption of heavy metal ion from aqueous single metal solution by chemically modified sugarcane bagasse  

Microsoft Academic Search

This work describes the preparation of new chelating materials derived from sugarcane bagasse for adsorption of heavy metal ions in aqueous solution. The first part of this report deals with the chemical modification of sugarcane bagasse with succinic anhydride. The carboxylic acid functions introduced into the material were used to anchor polyamines, which resulted in two yet unpublished modified sugarcane

Osvaldo Karnitz; Leandro Vinicius Alves Gurgel; Jlio Csar Perin de Melo; Vagner Roberto Botaro; Tnia Mrcia Sacramento Melo; Rossimiriam Pereira de Freitas Gil; Laurent Frdric Gil

2007-01-01

28

Improving chemical aqueous based intervention methods for microorganism elimination from fresh produce surfaces  

E-print Network

iii ABSTRACT Improving Chemical Aqueous Based Intervention Methods for Microorganism Elimination from Fresh Produce Surfaces. (December 2004) Alex Frank Puerta-Gomez, B.S., Universidad Nacional Agraria La Molina Chair of Advisory Committee: Dr... Results and Discussion................................................................... 12 Survival of S. Typhimurium LT2 on different produce surfaces after different storage times .................. 12 Attachment of S...

Puerta-Gomez, Alex Frank

2006-04-12

29

A USER'S GUIDE FOR REDEQL.EPA. A COMPUTER PROGRAM FOR CHEMICAL EQUILIBRIA IN AQUEOUS SYSTEMS  

EPA Science Inventory

This user's guide explains the use of the computerized chemical equilibrium program REDEQL.EPA. This program computes aqueous equilibria for up to 20 metals and 30 ligands in a system. The metals and ligands are selected from a list of 35 metals and 59 ligands for which thermodyn...

30

Plasma treatment of aqueous solutes: Some chemical properties of a gliding arc in humid air  

Microsoft Academic Search

The chemical properties of the gaseous species generated in a humid air gliding arc discharge are investigated. Aqueous solutions are used as the targets exposed to the plasma, and this allows to evidence strong acid and oxidizing effects on various solutes by means of spectrometric or potentiometric methods. The influence of some working parameters such as the input gas flow,

B. Benstaali; D. Moussa; A. Addou; J.-L. Brisset

1998-01-01

31

Biosorption of Pb(II) from aqueous solutions using chemically modified Moringa oleifera tree leaves  

Microsoft Academic Search

Moringa oleifera leaves (MOL); an agro-waste material has been used as a precursor to prepare a new biosorbent. The leaves were washed with base and citric acid, and obtained new chemically modified MOL biosorbent (CAMOL) for sequestration of Pb(II) from aqueous solution. The biosorbent was characterized by SEM, FTIR spectral and elemental analyses. The effect of experimental parameters such as

D. Harikishore Kumar Reddy; Y. Harinath; K. Seshaiah; A. V. R. Reddy

2010-01-01

32

A Review on Chemical Effects in Aqueous Solution induced by Plasma with Glow Discharge  

NASA Astrophysics Data System (ADS)

Chemical effects in different aqueous solutions induced by plasma with glow discharge electrolysis (GDE) and contact glow discharge electrolysis (CGDE) are described in this paper. The experimental and discharge characteristics are also reviewed. These are followed by a discussion of their mechanisms of both anodic and cathodic CGDE..

Gao, Jin-zhang; Wang, Xiao-yan; Hu, Zhong-ai; Hou, Jing-guo; Lu, Quan-fang

2001-06-01

33

Chemical-equilibrium calculations for aqueous geothermal brines  

SciTech Connect

Results from four chemical-equilibrium computer programs, REDEQL.EPAK, GEOCHEM, WATEQF, and SENECA2, have been compared with experimental solubility data for some simple systems of interest with geothermal brines. Seven test cases involving solubilities of CaCO/sub 3/, amorphous SiO/sub 2/, CaSO/sub 4/, and BaSO/sub 4/ at various temperatures from 25 to 300/sup 0/C and in NaCl or HCl solutions of 0 to 4 molal have been examined. Significant differences between calculated results and experimental data occurred in some cases. These differences were traced to inaccuracies in free-energy or equilibrium-constant data and in activity coefficients used by the programs. Although currently available chemical-equilibrium programs can give reasonable results for these calculations, considerable care must be taken in the selection of free-energy data and methods of calculating activity coefficients.

Kerrisk, J.F.

1981-05-01

34

Aqueous alteration of VHTR fuels particles under simulated geological conditions  

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

35

Aqueous phase oligomerization of methyl vinyl ketone through photooxidation - Part 2: Development of the chemical mechanism and atmospheric implications  

NASA Astrophysics Data System (ADS)

We developed a chemical mechanism based on laboratory experiments that have shown efficient oligomerization from methyl vinyl ketone (MVK) in the bulk aqueous phase. Kinetic data are applied (if known) or fitted to the observed MVK decay and oligomer mass increase. The mechanism is then implemented into a multiphase box model that simulates (i) oligomer formation upon uptake of MVK from the gas phase, and (ii) SOA formation from isoprene, as a precursor of MVK and methacrolein (MACR) in the aqueous and gas phases. Model results show that under atmospheric conditions, the oligomer formation rate strongly depends on the availability of dissolved oxygen. If oxygen is consumed too quickly or its solubility is kinetically or thermodynamically limited, oligomerization is accelerated, in agreement with the laboratory studies. The comparison of predicted oligomer formation shows that for most model assumptions (e.g. depending on the assumed partitioning of MVK and MACR), SOA formation from isoprene in the gas phase exceeds aqueous SOA formation by a factor 3-4. However, at high aerosol liquid water content and potentially high partitioning of oligomer precursors into the aqueous phase, SOA formation in both phases might be equally efficient.

Ervens, B.; Renard, P.; Ravier, S.; Clment, J.-L.; Monod, A.

2014-08-01

36

FACILITATED CHEMICAL SYNTHESIS UNDER ALTERNATE REACTION CONDITIONS  

EPA Science Inventory

The chemical research in the late 1990's witnessed a paradigm shift towards "environmentally-friendly chemistry" more popularly known as "green chemistry" due to the increasing environmental concerns and legislative requirements to curb the release of chemical waste into the atmo...

37

Exploring Atmospheric Aqueous Chemistry (and Secondary Organic Aerosol Formation) through OH Radical Oxidation Experiments, Droplet Evaporation and Chemical Modeling  

NASA Astrophysics Data System (ADS)

Gas phase photochemistry fragments and oxidizes organic emissions, making water-soluble organics ubiquitous in the atmosphere. My group and others have found that several water-soluble compounds react further in the aqueous phase forming low volatility products under atmospherically-relevant conditions (i.e., in clouds, fogs and wet aerosols). Thus, secondary organic aerosol can form as a result of gas followed by aqueous chemistry (aqSOA). We have used aqueous OH radical oxidation experiments coupled with product analysis and chemical modeling to validate and refine the aqueous chemistry of glyoxal, methylglyoxal, glycolaldehyde, and acetic acid. The resulting chemical model has provided insights into the differences between oxidation chemistry in clouds and in wet aerosols. Further, we conducted droplet evaporation experiments to characterize the volatility of the products. Most recently, we have conducted aqueous OH radical oxidation experiments with ambient mixtures of water-soluble gases to identify additional atmospherically-important precursors and products. Specifically, we scrubbed water-soluble gases from the ambient air in the Po Valley, Italy using four mist chambers in parallel, operating at 25-30 L min-1. Aqueous OH radical oxidation experiments and control experiments were conducted with these mixtures (total organic carbon ? 100 ?M-C). OH radicals (3.5E-2 ?M [OH] s-1) were generated by photolyzing H2O2. Precursors and products were characterized using electrospray ionization mass spectrometry (ESI-MS), ion chromatography (IC), IC-ESI-MS, and ultra high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Chemical modeling suggests that organic acids (e.g., oxalate, pyruvate, glycolate) are major products of OH radical oxidation at cloud-relevant concentrations, whereas organic radical - radical reactions result in the formation of oligomers in wet aerosols. Products of cloud chemistry and droplet evaporation have effective vapor pressures that are orders of magnitude lower when ammonium hydroxide is present (pH 7) than without (at lower pH). In Po Valley experiments, nitrogen-containing organics were prominent precursors and intermediates. Pyruvate and oxalate were among the products. Importantly, formation of aqSOA helps to explain the high O/C ratios found in atmospheric aerosols. While uncertainties remain large, global modeling suggests that aqSOA is comparable in magnitude to SOA formed through gas phase chemistry and vapor pressure driven partitioning (gasSOA).

Turpin, B. J.; Kirkland, J. R.; Lim, Y. B.; Ortiz-Montalvo, D. L.; Sullivan, A.; Hkkinen, S.; Schwier, A. N.; Tan, Y.; McNeill, V. F.; Collett, J. L.; Skog, K.; Keutsch, F. N.; Sareen, N.; Carlton, A. G.; Decesari, S.; Facchini, C.

2013-12-01

38

Selection among aqueous and off-gas treatment technologies for synthetic organic chemicals  

SciTech Connect

A methodology for selecting the least-cost treatment technology for waters contaminated by organic wastes was developed using performance and cost models. This methodology simplifies the selection of the least expensive treatment process(es) for a given set of conditions. Two aqueous-phase treatment options were considered: air stripping and liquid-phase adsorption (granular activated carbon). When the off-gases from air stripping must be treated, four off-gas treatment options were considered: gas-phase adsorption (with both on- and off-site regeneration of the granular activated carbon), thermal incineration, and catalytic oxidation. Methodologies were developed for rapidly selecting the least-cost off-gas treatment option [for volatile organic compound (VOC) sources such as an air stripping tower], for selecting the least-cost overall (liquid and gas phase treatment) system, and for selecting the least-cost overall system for a multicomponent mixture. The comparison methodology is based on physical parameters of the target chemical: Henry`s constant and the solute distribution parameter. The results are a set of diagrams and heuristics for rapid identification of cases for which one treatment option is significantly less expensive than the other.

Dvorak, B.I. [Univ. of Nebraska, Lincoln, NE (United States). Dept. of Civil Engineering; Herbeck, C.J. [County Sanitation District of Los Angeles County, Whittier, CA (United States); Meurer, C.P. [Bee County Coll., Beeville, TX (United States); Lawler, D.F.; Speitel, G.E. Jr. [Univ. of Texas, Austin, TX (United States). Dept. of Civil Engineering

1996-07-01

39

Highly enantioselective Mukaiyama aldol reaction in aqueous conditions using a chiral iron(II) bipyridine catalyst.  

PubMed

A highly enantioselective method for the catalytic Mukaiyama aldol reaction of silyl enol ethers with aldehydes in aqueous conditions was developed. The desired aldol products were obtained in excellent yields, diastereo- and enantioselectivities. Structural evidence of the pre-catalyst revealed an unprecedented heptadentate Fe(II) complex with the chiral bipyridine ligand. PMID:22080154

Ollevier, Thierry; Plancq, Baptiste

2012-02-25

40

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

DOEpatents

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.

Giese, R.W.; Wang, P.

1996-04-30

41

Phytotoxic Activity and Chemical Composition of Aqueous Volatile Fractions from Eucalyptus Species  

PubMed Central

The essential oils from four Eucalyptus species (E. spathulata, E. salubris, E. brockwayii and E. dundasii) have been previously confirmed to have stronger inhibitory effects on germination and seedling growth of silverleaf nightshade (Solanum elaeagnifolium Cav.). The aqueous volatile fractions (AVFs) were the water soluble volatile fractions produced together with the essential oils (water insoluble fractions) during the steam distillation process. The aim of this study was to further assess the phytotoxicity of AVFs from the four Eucalyptus species and their chemical composition. The fresh leaves of the four Eucalyptus species were used for the extraction of AVFs. The AVFs were tested for their phytotoxic effects on the perennial weed, silverleaf nightshade under laboratory conditions. The chemical compositions of the AVFs were determined by gas chromatographmass spectrometry (GC-MS). Our results showed that the AVFs had strong inhibition on the germination and seedling growth of silverleaf nightshade. The inhibition index increased with the increasing concentrations of AVFs. The inhibitory effects of the AVFs varied between different Eucalyptus species. The AVF from E. salubris demonstrated the highest inhibitory activity on the weed tested, with complete inhibition on germination and seedling growth at a concentration of 75%. The GC-MS analysis revealed that 1,8-cineole, isopentyl isovalerate, isomenthol, pinocarvone, trans-pinocarveol, alpha-terpineol and globulol were the main compounds in the AVFs. These results indicated that all AVFs tested had differential inhibition on the germination and seedling growth of silverleaf nightshade, which could be due to the joint effects of compounds present in the AVFs as these compounds were present in different quantities and ratio between Eucalyptus species. PMID:24681490

Zhang, Jinbiao; An, Min; Wu, Hanwen; Liu, De Li; Stanton, Rex

2014-01-01

42

Chemical modification of amino acids by atmospheric-pressure cold plasma in aqueous solution  

NASA Astrophysics Data System (ADS)

Plasma medicine is an attractive new research area, but the principles of plasma modification of biomolecules in aqueous solution remain elusive. In this study, we investigated the chemical effects of atmospheric-pressure cold plasma on 20 naturally occurring amino acids in aqueous solution. High-resolution mass spectrometry revealed that chemical modifications of 14 amino acids were observed after plasma treatment: (i) hydroxylation and nitration of aromatic rings in tyrosine, phenylalanine and tryptophan; (ii) sulfonation and disulfide linkage formation of thiol groups in cysteine; (iii) sulfoxidation of methionine and (iv) amidation and ring-opening of five-membered rings in histidine and proline. A competitive reaction experiment using 20 amino acids demonstrated that sulfur-containing and aromatic amino acids were preferentially decreased by the plasma treatment. These data provide fundamental information for elucidating the mechanism of protein inactivation for biomedical plasma applications.

Takai, Eisuke; Kitamura, Tsuyoshi; Kuwabara, Junpei; Ikawa, Satoshi; Yoshizawa, Shunsuke; Shiraki, Kentaro; Kawasaki, Hideya; Arakawa, Ryuichi; Kitano, Katsuhisa

2014-07-01

43

Removal of Acid Dyes from Aqueous Solutions using Chemically Activated Carbon  

Microsoft Academic Search

Textile dyes (Acid Yellow 17 and Acid Orange 7) were removed from its aqueous solution in batch and continuous packed bed adsorption systems by using thermally activated Euphorbia macroclada carbon with respect to contact time, initial dye concentration, and temperature. The activated carbon was prepared using a cheap plant-based material called Euphorbia macroclada, which was chemically modified with K2CO3. Lagergren-first-order

zgl Gerel; H. Ferdi Gerel

2009-01-01

44

Chemical Treatment Effects on Si(111) Surfaces in Aqueous NaF Solution  

Microsoft Academic Search

Chemically treated Si(111) surfaces in aqueous NaF solution have been investigated using spectroscopic ellipsometry (SE), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and wettability measurements. The SE data indicate that the solution causes the removal of the native oxide upon immersing the sample in the solution. After the native oxide is etched away completely, the SE data yield the

Noriko Tomita; Sadao Adachi

2001-01-01

45

Chemically tuned anode with tailored aqueous hydrocarbon binder for direct methanol fuel cells.  

PubMed

An anode for direct methanol fuel cells was chemically tuned by tailoring an aqueous hydrocarbon catalyst (SPI-BT) binder instead of using a conventional perfluorinated sulfonic acid ionomer (PFSI). SPI-BT designed in triethylamine salt form showed lower proton conductivity than PFSI, but it was stable in the catalyst ink forming the aqueous colloids. The aqueous colloidal particle size of SPI-BT was much smaller than that of PFSI. The small SPI-BT colloidal particles contributed to forming small catalyst agglomerates and simultaneously reducing their pore volume. Consequently, the high filling level of binders in the pores, where Pt-Ru catalysts are mainly located on the wall and physically interconnected, resulted in increased electrochemical active surface area of the anode, leading to high catalyst utilization. In addition, the chemical affinity between the SPI-BT binder and the membrane material derived from their similar chemical structure induced a stable interface on the membrane-electrode assembly (MEA) and showed low electric resistance. Upon adding SPI-BT, the synergistic effect of high catalyst utilization, improved mass transfer behavior to Pt-Ru catalyst, and low interfacial resistance of MEA became greater than the influence of reduced proton conductivity in the electrochemical performance of single cells. The electrochemical performance of MEAs with SPI-BT anode was enhanced to almost the same degree or somewhat higher than that with PFSI at 90 degrees C. PMID:19485372

Lee, Chang Hyun; Lee, So Young; Lee, Young Moo; McGrath, James E

2009-07-21

46

KEMOD: A mixed chemical kinetic and equilibrium model of aqueous and solid phase geochemical reactions  

SciTech Connect

This report presents the development of a mixed chemical Kinetic and Equilibrium MODel in which every chemical species can be treated either as a equilibrium-controlled or as a kinetically controlled reaction. The reaction processes include aqueous complexation, adsorption/desorption, ion exchange, precipitation/dissolution, oxidation/reduction, and acid/base reactions. Further development and modification of KEMOD can be made in: (1) inclusion of species switching solution algorithms, (2) incorporation of the effect of temperature and pressure on equilibrium and rate constants, and (3) extension to high ionic strength.

Yeh, G.T.; Iskra, G.A. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Civil Engineering; Szecsody, J.E.; Zachara, J.M.; Streile, G.P. [Pacific Northwest Lab., Richland, WA (United States)

1995-01-01

47

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

PubMed Central

The chemical history of dust particles in the atmosphere is crucial for assessing their impact on both the Earths 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]

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

2010-01-01

48

Dermal absorption of chemicals: effect of application of chemicals as a solid, aqueous paste, suspension, or in volatile vehicle.  

PubMed

The purpose of this study was to investigate the dermal absorption of chemicals in different physical forms when applied to female F344 rats. Chemicals were applied either as a solid, aqueous paste, suspension, or dissolved in the volatile vehicle ethanol. The chemicals investigated were [14C]-2-sec-butyl-4,6-dinitrophenol (DNBP, 4.2 mumol), 2,4,5,2',4',5'-[14C]-hexachlorobiphenyl (HCB, 2.3 mumol), and 3,4,3',4'-[14C]-tetrachlorobiphenyl (TCB, 0.5 mumol). The chemicals were applied on the clipped mid-dorsal region of the rat over a 2.54-cm2 treatment area, which was then occluded. Urine and feces were collected and assayed for radioactivity. Twenty-four hours post-application, the treated skin was washed with a mixture (1:1) of soap and water, dried, and reoccluded. The animals were sacrificed at 120 h by exsanguination under ether anesthesia. Radioactivity in the blood, skin (treated and untreated), and carcass was assayed. Dermal absorption of DNBP-derived radioactivity was approximately 50% of the recovered dose after application in the four physical forms, and the major route of excretion was via the urine. Twelve percent of the absorbed dose of DNBP was retained in the body. Dermal penetration of HCB-derived radioactivity was 5-8% of the recovered dose after application in the four forms, and the major route of excretion was via the feces. Greater than 90% of the absorbed dose of HCB-derived radioactivity was retained in the body. Dermal penetration of TCB-derived radioactivity was 6-8% of the recovered dose in the four forms, and the major route of excretion was via the feces. Approximately 21% of the absorbed dose was retained in the body at 120 h. Absorption of each chemical applied either as solid, aqueous paste, or suspension was compared to the absorption of the same chemical in ethanol. Absorption of HCB applied as a solid was significantly higher (p less than or equal to .05) as compared to HCB applied in ethanol. There were no other significantly differences in the comparisons of absorption. The data indicate that the chemicals examined in this study can penetrate the skin as readily when applied either as a solid, aqueous paste, or suspension, as when applied in the volatile vehicle ethanol. PMID:1522614

Hughes, M F; Shrivastava, S P; Sumler, M R; Edwards, B C; Goodwin, J H; Shah, P V; Fisher, H L; Hall, L L

1992-09-01

49

Ammonium removal from aqueous solutions by zeolite adsorption together with chemical precipitation.  

PubMed

The aim of this study was to remove ammonium from aqueous solution and recycle ammonium. Ammonium removal from aqueous solution by natural and pretreated zeolites, breakthrough curve, chemical regeneration of pretreated zeolite, ammonium removal from regeneration solution by chemical precipitation and NH(4) (+) adsorption isotherms were investigated by conducting a series of batch and continuous experiments in this study. Morphologies and structures of zeolites were analyzed by Surface Area and Pore Size analysis, Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR) spectroscopy. The NH(4) (+)-N removal efficiencies by natural and NaCl-treated zeolite were 30.73% and 85.55% respectively at an initial concentration of 100 mg/L. Breakthrough and exhaustion capacities for adsorption of ammonium ions were 3.36 and 4.26 mg /g (NH(4) (+)-N/zeolite), respectively. After chemical regeneration, NH(4) (+)-N removal efficiency by NaCl-treated zeolite only reduced 9.95% than previously. NH(4) (+)-N concentration of the regeneration solution was reduced from 460 to 74.55 mg/L by chemical precipitation. The Freundlich isotherm provided a slightly more consistent fit to the experimental data of ammonium adsorption on NaCl-treated zeolite than Langmuir. Based on the results, it was concluded that the objective of this study had been well achieved. PMID:20388990

Wen, T; Zhang, X; Zhang, H Q; Liu, J D

2010-01-01

50

Stability of Lysozyme in Aqueous Extremolyte Solutions during Heat Shock and Accelerated Thermal Conditions  

PubMed Central

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 70C), betaine, trehalose, ectoin and firoin protected lysozyme against inactivation while hydroxyectoine, did not have a significant effect. During accelerated thermal conditions (4 weeks at 55C), 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

van Streun, Erwin L. P.; Frijlink, Henderik W.; Hinrichs, Wouter L. J.

2014-01-01

51

"Studying the electrochemical and chemical conditions of corrosion in  

E-print Network

inhibitors. � Developed improved accelerated salt spray laboratory corrosion test. Improved Accelerated"Studying the electrochemical and chemical conditions of corrosion in mission critical systems of Virginia Charlottesville, VA 434.982.5783 Center for Electrochemical Science & Engineering Corrosion

Acton, Scott

52

Solubility of platinum in aqueous solutions at 25C and pHs 4 to 10 under oxidizing conditions  

E-print Network

Solubility of platinum in aqueous solutions at 25°C and pHs 4 to 10 under oxidizing conditions to those found in such environments. The solubility of platinum metal was measured at 25°C in several strength of the aqueous solutions did not exceed 0.30 (molal scale). The interpretation of the solubility

Boyer, Edmond

53

Transformation nanostructured nickel hydroxide to nickel oxide film by aqueous chemical growth  

NASA Astrophysics Data System (ADS)

Nickel hydroxide, [Ni(OH)2] has been used extensively as the positive electrode material in rechargeable nickel-based batteries. Several approaches are known to be able for Ni(OH)2 growth including dc reactive magnetron sputtering, chemical spray pyrolysis, thermal evaporation, etc. This study discusses about nanostructured Ni(OH)2 film growth by aqueous chemical growth based technique. Ni(OH)2 film grown at 150 C has a coral-like morphology whereas converted to NiO film by oxidation of Ni(OH)2 at 400 C, confirmed by X-ray diffraction (XRD). Field Emission Scanning Electron Microscopy (FESEM) revealed a coral-like structure of Ni(OH)2 were grown on the glass substrates. Flake-like morphology was obtained for NiO film. The XRD pattern reveals that the intensity of observed peaks increased with the longer reaction time and film thickness which indicated an improvement in crystallinity. The optical band gap for Ni(OH)2 film calculated from transmission spectra increased from 3.72 eV to 3.91 eV with the increasing of reaction time. Higher optical band gap of 4.00 eV was obtained for NiO film. This result indicates that the Ni(OH)2/NiO films grown by aqueous chemical growth could to produce similar quality properties to other conventional methods either nanoparticle or bulk size.

Bakar, M. A.; Hamid, M. A. A.; Jalar, A.; Shamsudin, R.

2013-05-01

54

Homogeneous ice freezing temperatures and ice nucleation rates of aqueous ammonium sulfate and aqueous levoglucosan particles for relevant atmospheric conditions.  

PubMed

Homogeneous ice nucleation from micrometre-sized aqueous (NH4)2SO4 and aqueous levoglucosan particles is studied employing the optical microscope technique. A new experimental method is introduced that allows us to control the initial water activity of the aqueous droplets. Homogeneous ice freezing temperatures and ice melting temperatures of these aqueous solution droplets, 10 to 80 microm in diameter, are determined. Homogeneous ice nucleation from aqueous (NH4)2SO4 particles 5-39 wt% in concentration and aqueous levoglucosan particles with initial water activities of 0.85-0.99 yield upper limits of the homogeneous ice nucleation rate coefficients of up to 1x10(10) cm(-3) s(-1). The experimentally derived homogeneous ice freezing temperatures and upper limits of the homogeneous ice nucleation rate coefficients are compared with corresponding predictions of the water-activity-based ice nucleation theory [T. Koop, B. P. Luo, A. Tsias and T. Peter, Nature, 2000, 406, 611]. It is found that the water-activity-based ice nucleation theory can capture the experimentally derived ice freezing temperatures and homogeneous ice nucleation rate coefficients of the aqueous (NH4)2SO4 and aqueous levoglucosan particles. However, the level of agreement between experimentally derived and predicted values, in particular for homogeneous ice nucleation rate coefficients, crucially depends on the extrapolation method to obtain water activities at corresponding freezing temperatures. It is suggested that the combination of experimentally derived ice freezing temperatures and homogeneous ice nucleation rate coefficients can serve as a better validation of the water-activity-based ice nucleation theory than when compared to the observation of homogeneous ice freezing temperatures alone. The atmospheric implications with regard to the application of the water-activity-based ice nucleation theory and derivation of maximum ice particle production rates are briefly discussed. PMID:19727513

Knopf, Daniel Alexander; Lopez, Miguel David

2009-09-28

55

Validity conditions for moment closure approximations in stochastic chemical kinetics  

E-print Network

Approximations based on moment-closure (MA) are commonly used to obtain estimates of the mean molecule numbers and of the variance of fluctuations in the number of molecules of chemical systems. The advantage of this approach is that it can be far less computationally expensive than exact stochastic simulations of the chemical master equation. Here we numerically study the conditions under which the MA equations yield results reflecting the true stochastic dynamics of the system. We show that for bistable and oscillatory chemical systems with deterministic initial conditions, the solution of the MA equations can be interpreted as a valid approximation to the true moments of the CME, only when the steady-state mean molecule numbers obtained from the chemical master equation fall within a certain finite range. The same validity criterion for monostable systems implies that the steady-state mean molecule numbers obtained from the chemical master equation must be above a certain threshold. For mean molecule numbe...

Schnoerr, David; Grima, Ramon

2014-01-01

56

Chemical and Isotopic Study of Lab-formed Carbonates Under Cryogenic and Hydrothermal Conditions  

NASA Technical Reports Server (NTRS)

Aqueous environments on early Mars were probably relatively short-lived and localized, as evidenced by the lack of abundant secondary minerals detected by the TES instrument. In order to better understand the aqueous history of early Mars we need to be able to interpret the evidence preserved in secondary minerals formed during these aqueous events. Carbonate minerals, in particular, are important secondary minerals for interpreting past aqueous environments as illustrated by the carbonates preserved in ALH84001. Carbonates formed in short-lived, dynamic aqueous events often preserve kinetic rather than equilibrium chemical and isotopic processes, and predicting the behavior of such systems is facilitated by empirical data.

Niles, P. B.; Leshin, L. A.; Socki, R. A.; Guan, Y.; Golden, D. C.; Ming, D. W.; Gibson, E. K.

2004-01-01

57

Theoretical study of the dimerization of calcium carbonate in aqueous solution under natural water conditions  

NASA Astrophysics Data System (ADS)

First principles calculations have been used to investigate the condensation reactions of hydrated calcium bicarbonate monomers in a simulated aqueous environment. The reaction pathway for the calcium bicarbonate dimerization process has been computed at the density functional theory-PBE level with the COSMO dielectric continuum model to simulate the hydrated environment. The results indicate that calcium bicarbonate dimers form via an associative mechanism: the first step involves a sevenfold calcium bicarbonate intermediate followed by the loss of one water molecule from the first coordination shell of calcium. Both steps are characterised by a low energy barrier of approximately 2 kcal mol -1, suggesting that the dimerization process is not kinetically hindered in aqueous solution. However, the Gibbs free energies for the condensation reactions to form the calcium bicarbonate dimers and the species Ca(HCO 3) 2(H 2O) 4, Ca(HCO 3) 3(H 2O) 3- and Ca 2(HCO 3)(H 2O) 103+, computed using the PBE and mPW1B95 density functional theory levels for the gas-phase component and the UAHF-CPCM solvation model for the hydration contribution, are all positive, which indicates that the formation of these early calcium bicarbonate clusters is thermodynamically unfavourable in aqueous solutions. Our calculations therefore suggest that the oligomerization of calcium carbonate is not spontaneous in water, at the conditions considered in our simulations, i.e. T = 298 K and neutral pH, which indicates that the nucleation of calcium carbonate cannot occur through a homogeneous process when calcium-bicarbonate ion pairs are the major source of CaCO 3 in the aqueous environment.

Di Tommaso, Devis; de Leeuw, Nora H.

2009-09-01

58

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

PubMed

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 12gL(-1), 363K 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

Gonzlez, A; Moreno, N; Navia, R

2014-12-01

59

Carbon dioxide hydrate equilibrium conditions in aqueous solutions containing electrolytes and methanol using a new apparatus  

SciTech Connect

A knowledge of the gas hydrate formation conditions, i.e. pressure, temperature, and compositions, of the coexisting phases at equilibrium, is required in formulating processes to avoid their formation in natural gas transmission lines or processing equipment. Additives like methanol and electrolytes are often used to inhibit hydrate formation in industrial operations. Computation of the inhibition effects of these additives is necessary for the design of such operations. Development of thermodynamic methods to calculate the hydrate equilibria conditions requires accurate experimental data. In the present work experimental three-phase (aqueous liquid solution, vapor, and incipient hydrate) equilibrium conditions of CO{sub 2} hydrate formation in aqueous solutions of electrolytes and methanol are measured in the temperature range of 263--279 K and pressure range of 0.9--3.0 MPa. A new full view sapphire tube equilibrium cell and the associated equipment are designed, fabricated, and used for the measurements. The equipment details and the measured data are also reported here.

Dholabhai, P.D.; Parent, J.S.; Bishnoi, P.R. [Univ. of Calgary, Alberta (Canada). Dept. of Chemical and Petroleum Engineering] [Univ. of Calgary, Alberta (Canada). Dept. of Chemical and Petroleum Engineering

1996-03-01

60

Validity conditions for moment closure approximations in stochastic chemical kinetics  

NASA Astrophysics Data System (ADS)

Approximations based on moment-closure (MA) are commonly used to obtain estimates of the mean molecule numbers and of the variance of fluctuations in the number of molecules of chemical systems. The advantage of this approach is that it can be far less computationally expensive than exact stochastic simulations of the chemical master equation. Here, we numerically study the conditions under which the MA equations yield results reflecting the true stochastic dynamics of the system. We show that for bistable and oscillatory chemical systems with deterministic initial conditions, the solution of the MA equations can be interpreted as a valid approximation to the true moments of the chemical master equation, only when the steady-state mean molecule numbers obtained from the chemical master equation fall within a certain finite range. The same validity criterion for monostable systems implies that the steady-state mean molecule numbers obtained from the chemical master equation must be above a certain threshold. For mean molecule numbers outside of this range of validity, the MA equations lead to either qualitatively wrong oscillatory dynamics or to unphysical predictions such as negative variances in the molecule numbers or multiple steady-state moments of the stationary distribution as the initial conditions are varied. Our results clarify the range of validity of the MA approach and show that pitfalls in the interpretation of the results can only be overcome through the systematic comparison of the solutions of the MA equations of a certain order with those of higher orders.

Schnoerr, David; Sanguinetti, Guido; Grima, Ramon

2014-08-01

61

Guided shear-horizontal surface acoustic wave (SH-SAW) chemical sensors for detection of organic contaminants in aqueous environments  

Microsoft Academic Search

With the growing concern of the threat of the use of (bio) chemical weapons, and the ever-present environmental pollution, acoustic wave sensors attract considerable attention for the detection of various (bio) chemical compounds due to the need for real-time, stable and direct detection in aqueous environments. In this work, direct chemical sensing in liquid environments using polymer-guided shear horizontal surface

Zhonghui Li

2005-01-01

62

Aqueous fluid composition in CI chondritic materials: Chemical equilibrium assessments in closed systems  

NASA Astrophysics Data System (ADS)

Solids of nearly solar composition have interacted with aqueous fluids on carbonaceous asteroids, icy moons, and trans-neptunian objects. These processes altered mineralogy of accreted materials together with compositions of aqueous and gaseous phases. We evaluated chemistry of aqueous solutions coexisted with CI-type chondritic solids through calculations of chemical equilibria in closed water-rock-gas systems at different compositions of initial fluids, water/rock mass ratios (0.1-1000), temperatures (<350 C), and pressures (<2 kbars). The calculations show that fluid compositions are mainly affected by solubilities of solids, the speciation of chlorine in initial water-rock mixtures, and the occurrence of Na-bearing secondary minerals such as saponite. The major species in modeled alkaline solutions are Na+, Cl-, CO32-,HCO3-, K+, OH-, H2, and CO2. Aqueous species of Mg, Fe, Ca, Mn, Al, Ni, Cr, S, and P are not abundant in these fluids owing to low solubility of corresponding solids. Typical NaCl type alkaline fluids coexist with saponite-bearing mineralogy that usually present in aqueously altered chondrites. A common occurrence of these fluids is consistent with the composition of grains emitted from Enceladus. Na-rich fluids with abundant CO32-,HCO3-, and OH- anions coexist with secondary mineralogy depleted in Na. The Na2CO3 and NaHCO3 type fluids could form via accretion of cometary ices. NaOH type fluids form in reduced environments and may locally occur on parent bodies of CR carbonaceous chondrites. Supposed melting of accreted HCl-bearing ices leads to early acidic fluids enriched in Mg, Fe and other metals, consistent with signs of low-pH alteration in chondrites. Neutralization of these solutions leads to alkaline Na-rich fluids. Sulfate species have negligible concentrations in closed systems, which remain reduced, especially at elevated pressures created by forming H2 gas. Hydrogen, CO2, and H2O dominate in the gaseous phase, though the abundance of methane cannot be fairly estimated.

Zolotov, Mikhail Yu.

2012-08-01

63

Chemical characterization of the main products formed through aqueous-phase photonitration of guaiacol  

NASA Astrophysics Data System (ADS)

Guaiacol (2-methoxyphenol) and its derivatives can be emitted into the atmosphere by thermal degradation (i.e., burning) of wood lignins. Due to its volatility, guaiacol is predominantly distributed atmospherically in the gaseous phase. Recent studies have shown the importance of aqueous-phase reactions in addition to the dominant gas-phase and heterogeneous reactions of guaiacol, in the formation of secondary organic aerosol (SOA) in the atmosphere. The main objectives of the present study were to chemically characterize the main products of the aqueous-phase photonitration of guaiacol and examine their possible presence in urban atmospheric aerosols. The aqueous-phase reactions were carried out under simulated sunlight and in the presence of hydrogen peroxide and nitrite. The formed guaiacol reaction products were concentrated by solid-phase extraction and then purified with semi-preparative high-performance liquid chromatography (HPLC). The fractionated individual compounds were isolated as pure solids and further analyzed with liquid-state proton, carbon-13 and two-dimensional nuclear magnetic resonance (NMR) spectroscopy, and direct infusion negative ion electrospray ionization tandem mass spectrometry ((-)ESI-MS/MS). The NMR and product ion (MS2) spectra were used for unambiguous product structure elucidation. The main products of guaiacol photonitration are 4-nitroguaiacol (4NG), 6-nitroguaiacol (6NG), and 4,6-dinitroguaiacol (4,6DNG). Using the isolated compounds as standards, 4NG and 4,6DNG were unambiguously identified in winter PM10 aerosols from the city of Ljubljana (Slovenia) by means of HPLC/(-)ESI-MS/MS. Owing to the strong absorption of ultraviolet and visible light, 4,6DNG could be an important constituent of atmospheric "brown" carbon, especially in regions affected by biomass burning.

Kitanovski, Z.; ?usak, A.; Grgi?, I.; Claeys, M.

2014-08-01

64

Semiconducting Polymer Encapsulated Mesoporous Silica Particles with Conjugated Europium Complexes: Toward Enhanced Luminescence under Aqueous Conditions.  

PubMed

Immobilization of lanthanide organic complexes in meso-organized hybrid materials for luminescence applications have attracted immense interest due to the possibility of controlled segregation at the nanoscopic level for novel optical properties. Aimed at enhancing the luminescence intensity and stability of the hybrid materials in aqueous media, we developed polyvinylpyrrolidone (PVP) stabilized, semiconducting polymer (poly(9-vinylcarbazole), PVK) encapsulated mesoporous silica hybrid particles grafted with Europium(III) complexes. Monosilylated ?-diketonate ligands (1-(2-naphthoyl)-3,3,3-trifluoroacetonate, NTA) were first co-condensed in the mesoporous silica particles as pendent groups for bridging and anchoring the lanthanide complexes, resulting in particles with an mean diameter of ?450 nm and a bimodal pore size distribution centered at 3.5 and 5.3 nm. PVK was encapsulated on the resulted particles by a solvent-induced surface precipitation process, in order to seal the mesopores and protect Europium ions from luminescence quenching by producing a hydrophobic environment. The obtained polymer encapsulated MSN-EuLC@PVK-PVP particles exhibit significantly higher intrinsic quantum yield (?Ln = 39%) and longer lifetime (?obs = 0.51 ms), as compared with those without polymer encapsulation. Most importantly, a high luminescence stability was realized when MSN-EuLC@PVK-PVP particles were dispersed in various aqueous media, showing no noticeable quenching effect. The beneficial features and positive attributes of both mesoporous silica and semiconducting polymers as lanthanide-complex host were merged in a single hybrid carrier, opening up the possibility of using these hybrid luminescent materials under complex aqueous conditions such as biological/physiological environments. PMID:25289897

Zhang, Jixi; Prabhakar, Neeraj; Nreoja, Tuomas; Rosenholm, Jessica M

2014-11-12

65

Removal of methylene blue from aqueous solutions by chemically modified bamboo.  

PubMed

Chemically modified bamboo (CMB) was utilized for removing methylene blue (MB) from aqueous media in the present study. The adsorbent was characterized by Fourier transform infrared (FTIR) spectra and elemental analysis, which confirms that carboxyl groups and diethylenetriamine were successfully introduced into the surface of bamboo. The effects of initial MB concentration (100-900mgL(-1)), contact time (15-315min), the pH of the solution (3-10), temperature (298-318K), adsorbent dosage (0.4-2.6gL(-1)) and salt concentration on the adsorption efficiency of CMB towards MB were investigated. It was found that the adsorption of MB in CMB fits Langmuir mode well, and the maximum adsorption capacity of CMB achieved 606mgg(-1) at 298K, which is much higher than those obtained from previously investigated bioadsorbents. The adsorption kinetics can be described by pseudo-second-order kinetic model, and the adsorption of MB on CMB was an exothermic process. The results of the present study suggest that CMB is an effective biosorbent for removal of organic pollutants from aqueous solutions. PMID:24997922

Guo, Jian-Zhong; Li, Bing; Liu, Li; Lv, Kangle

2014-09-01

66

Chemical bonding in aqueous ferrocyanide: experimental and theoretical X-ray spectroscopic study.  

PubMed

Resonant inelastic X-ray scattering (RIXS) and X-ray absorption (XA) experiments at the iron L- and nitrogen K-edge are combined with high-level first-principles restricted active space self-consistent field (RASSCF) calculations for a systematic investigation of the nature of the chemical bond in potassium ferrocyanide in aqueous solution. The atom- and site-specific RIXS excitations allow for direct observation of ligand-to-metal (Fe L-edge) and metal-to-ligand (N K-edge) charge-transfer bands and thereby evidence for strong ?-donation and ?-backdonation. The effects are identified by comparing experimental and simulated spectra related to both the unoccupied and occupied molecular orbitals in solution. PMID:24450820

Engel, Nicholas; Bokarev, Sergey I; Suljoti, Edlira; Garcia-Diez, Raul; Lange, Kathrin M; Atak, Kaan; Golnak, Ronny; Kothe, Alexander; Dantz, Marcus; Khn, Oliver; Aziz, Emad F

2014-02-13

67

Secondary organic aerosol (trans)formation through aqueous phase guaiacol photonitration: chemical characterization of the products  

NASA Astrophysics Data System (ADS)

One of the largest primary sources of organic aerosol in the atmosphere is biomass burning (BB) (Laskin et al. 2009); in Europe its contribution to annual mean of PM10 is between 3 and 14 % (Maenhaut et al. 2012). During the process of wood burning many different products are formed via thermal degradation of wood lignin. Hardwood burning produces mainly syringol (2,6-dimetoxyphenol) derivatives, while softwood burning exclusively guaiacol (2-methoxyphenol) and its derivatives. Taking into account physical properties of methoxyphenols only, their concentrations in atmospheric waters might be underestimated. So, their aqueous phase reactions can be an additional source of SOA, especially in regions under significant influence of wood combustion. An important class of compounds formed during physical and chemical aging of the primary BBA in the atmosphere is nitrocatechols, known as strong absorbers of UV and Vis light (Claeys et al. 2012). Very recently, methyl-nitrocatechols were proposed as suitable markers for highly oxidized secondary BBA (Iinuma et al. 2010, Kitanovski et al. 2012). In the present work, the formation of SOA through aqueous phase photooxidation and nitration of guaiacol was examined. The key objective was to chemically characterize the main low-volatility products and further to check their possible presence in the urban atmospheric aerosols. The aqueous phase reactions were performed in a thermostated reactor under simulated sunlight in the presence of H2O2 and nitrite. Guaiacol reaction products were first concentrated by solid-phase extraction (SPE) and then subjected to semi-preparative liquid chromatography.The main product compounds were fractionated and isolated as pure solids and their structure was further elucidated by using nuclear magnetic resonance spectroscopy (1H, 13C and 2D NMR) and direct infusion negative ion electro-spray ionization tandem mass spectrometry (( )ESI-MS/MS). The main photonitration products of guaiacol (4-nitroguaiacol, 6-nitroguaiacol and 4,6-dinitroguaiacol) were examined for their presence in winter aerosol samples by using an optimized HPLC-(-)ESI-MS/MS. 4-nitroguaiacol and 4,6-dinitroguaiacol were unambiguously identified in winter PM10 from Ljubljana, Slovenia, whereas the absence of 6-nitroguaiacol was further explained with the help of long-term reaction monitoring. To our knowledge, our study represents the first report on the identification of 4,6-dinitroguaiacol in ambient aerosols. Laskin, A. et al. (2009) Environ. Sci. Technol. 43, 3764-3771. Maenhaut, W. et al. (2012) Sci. Tot. Environ. 437, 226-236. Claeys, M. et al. (2012) Environ. Chem. 9, 273-284. Iinuma, Y. et al. (2010) Environ. Sci. Technol. 44, 8453-8459. Kitanovski, Z. et al. (2012)J. Chromatogr. A 1268, 35-43.

Grgi?, Irena; Kitanovski, Zoran; Krofli?, Ana; ?usak, Alen

2014-05-01

68

Stieglitz rearrangement of N,N-dichloro-beta,beta-disubstituted taurines under mild aqueous conditions.  

PubMed

New topical anti-infectives comprised of N,N-dichloro-beta,beta-disubstituted taurines [Tetrahedron Lett.2008, 49, 2193; Biorg. Med. Chem. Lett. 2009, 19, 196] have been examined for structure-stability relationships (SSR) based upon various alkyl, heteroalkyl and cycloalkyl beta-substitutions. These substitutions affect order-of-magnitude changes in the aqueous stability of these N,N-dichloroamines which can undergo Stieglitz rearrangement of alkyl groups under extremely mild conditions (H(2)O, pH 4-7, 0-20 mM acetate or phosphate buffer, 20-40 degrees C). This process produces beta-ketosulfonic acids which function as substrates for chlorination by the N-chlorotaurines which leads to their further degradation. PMID:19167221

Shiau, Timothy P; Houchin, Ashley; Nair, Satheesh; Xu, Ping; Low, Eddy; Najafi, Ramin Ron; Jain, Rakesh

2009-02-15

69

Excess Chemical Potentials, Excess Partial Molar Enthalpies, Entropies, Volumes, and Isobaric Thermal Expansivities of Aqueous Glycerol at 25C  

Microsoft Academic Search

The vapor pressures p the excess partial molar enthalpies of glycerol HGlyE the densities d and the thermal expansivities ap of aqueous glycerol were measured at 25C. From the vapor pressure data, the excess chemical potential of H2O WE was calculated, assuming that the partial pressure of glycerol pGly is negligibly small. The excess chemical potential of glycerol GlyE

Eric C. H. To; James V. Davies; Michael Tucker; Peter Westh; Christa Trandum; Kennth S. H. Suh; Yoshikata Koga

1999-01-01

70

Corrosion of aluminium in the aqueous chemical environment of a loss-of-coolant accident at a nuclear power plant  

Microsoft Academic Search

Aluminium corrosion is a significant concern in the aqueous chemical environment of the reactor containment building following a hypothetical loss-of-coolant accident (LOCA) at a nuclear power plant. Aluminium corrosion may lead to the formation of precipitates that can, in combination with insulation debris, block the recirculation sump screens. This study investigated aluminium corrosion experimentally at both bench and pilot scale

Dong Chen; Kerry J. Howe; Jack Dallman; Bruce C. Letellier

2008-01-01

71

Temporal Changes in Aqu/C60 Physical-Chemical, Deposition, and Transport Characteristics in Aqueous Systems  

EPA Science Inventory

Little is known about how temporal changes in the physical?chemical properties of C60 aggregates formed in aqueous systems (termed aqu/C60) can impact transport pathways contributing to ecological exposures. In this study three aqu/C60 suspensions of short-term (100 days), interm...

72

pH effect on the morphology of ZnO nanostructures grown with aqueous chemical growth  

E-print Network

pH effect on the morphology of ZnO nanostructures grown with aqueous chemical growth D. Vernardou a Available online 1 April 2007 Abstract ZnO nanostructures were grown for various pH values on Corning 7059 hexahydrate) and C6H12N4 (HMTA; hexamethylenetetramine). It was indicated that the increasing of the pH

73

IMPROVED DECONTAMINATION: INTERFACIAL, TRANSPORT, AND CHEMICAL PROPERTIES OF AQUEOUS SURFACTANT CLEANERS  

EPA Science Inventory

This investigation is focused on decontamination using environmentally benign aqueous solutions, specifically the removal of organics and associated radionuclide and heavy metal contaminants by synthetic surfactants. Aqueous-based solutions promise several advantages for deconta...

74

Amphiphilic lauryl ester derivatives from aromatic amino acids: significance of chemical architecture in aqueous aggregation properties.  

PubMed

Lauryl esters of L-tyrosine (LET) and L-phenylalanine (LEP) were, in a previous interface adsorption study, found to adopt very different interfacial conformations. The present study is an investigation of their aqueous aggregation properties with the goal of elucidating the effects of the presence in LET and absence in LEP of the phenolic OH group on their aqueous aggregate structures and micellar conformations of the surfactant monomers. The measured properties included aggregation numbers from time-resolved fluorescence quenching (TRFQ), interface hydration index and microviscosity by electron spin resonance (ESR), chemical shifts of (1)H resonance lines by NMR, and Krafft temperatures and enthalpies of structural transitions by differential scanning calorimetry (DSC). The TRFQ, ESR, and NMR experiments were conducted at various temperatures from 23 to 70 degrees C for various surfactant concentrations from 0.050 to 0.200 M. Markedly different temperature dependences of aggregation number and (1)H NMR chemical shifts are exhibited by LET and LEP micelles. LET and LEP form ionic micelles. The aggregation number of LEP decreases as is characteristic of ionic micelles, but that of LET increases slightly with temperature. The changes with temperature in the NMR chemical shifts and width of the resonance lines are significantly greater for the various LEP protons than for those of LET. The differences in these properties and other fluorescence decay characteristics of fluorophores incorporated into the micelles could be attributed to the difference in the micellar conformations of LET and LEP which are postulated to be similar to that at oil-water interfaces. The phenolic group is hypothesized to be in the micelle-water interface as part of the headgroup in LET micelles, and its location does not change with temperature. On the other hand, in LEP micelles, the phenyl ring is folded into the core overlapping with the flexible hydrophobic chains. The resulting closer proximity between the phenyl ring and the flexible hydrocarbon chain causes interdependence of the phenyl ring and chain proton resonances, leading to the observed temperature dependence of the chemical shifts in LEP. The TRFQ and ESR data are combined together in a molecular space-filling model, referred to as the polar shell model, to derive the geometrical properties of the micelle. The DSC scans in the temperature range 10-55 degrees C showed the presence of distinctly different endotherms for LET and LEP. The Krafft temperatures, K(T), and the enthalpies were determined. The higher K(T) and broader peak of the DSC endotherm of LET as compared to LEP are attributed to the stabilization of fiberlike structures below the Krafft temperature due to its chirality and the hydrogen bonding capability of the phenolic OH and also to the ion-dipole interactions. Thus, all of the observed differences between LET and LEP could be attributed to the difference in their chemical architecture. PMID:19778004

Vijay, R; Singh, Jasmeet; Baskar, Geetha; Ranganathan, Radha

2009-10-22

75

Partitioning of Trace Elements Between Hydrous Minerals and Aqueous Fluids : a Contribution to the Chemical Budget of Subduction Zones  

NASA Astrophysics Data System (ADS)

Subduction zones are powerful chemical engines where the downgoing lithosphere reacts with asthenospheric mantle and produces magmas. Understanding this deep recycling system is a scientific challenge requiring multiple approaches. Among those, it appears that we lack basic information on the composition of the fluid that begins the process of material transfer in subduction zones. Indeed, no pristine fluid sample has yet been collected from this particular environment. Albeit challenging, the alternative would be experimental study of fluids under the appropriate conditions. Consequently, we developed an experimental protocol to measure the concentration of aqueous fluids equilibrated with minerals up to pressures (P) of 5 GPa, at least and temperatures (T) of 550 C. This includes syntheses at high-P and -T conditions, and determination of the fluid composition. Syntheses were performed in a large volume belt-type press at the conditions, 2-5 GPa and ca. 550 C. Oxides or minerals were loaded with water in a gold capsule sealed afterwards. Presence of free fluid during experiments could be confirmed by direct observation of fluid release from the sealed capsule upon puncturing. The composition in trace elements of the fluids that were equilibrated at high-P and -T with minerals was reconstructed from that of the precipitates deposited at the surface of minerals after evaporation of the capsule. The precipitates were dissolved and analyzed by a leaching technique detailed in Koga et al. (2005). Two hydrous minerals of prime interest for subductions were sofar investigated: the high-pressure variety of serpentine, antigorite, and talc. The partitioning coefficients of a series of trace-elements will be presented, as well as their evolution as a function of pressure. Consequences for the composition of the fluids released during the dehydration of hydrous metamorphic minerals will be drawn. Those measurements are unlikely to be feasible at pressures in excess of 5 GPa, since limited by the sample size. Hence, in order to gain similar data at higher pressures, we begun in situ measurements in an externally heated diamond anvil cell, that allows to reach 10 GPa. Composition of aqueous fluids could be measured at the ppm level by synchrotron X-ray fluorescence. The first results and the perspectives will be presented. Koga K.T., I. Daniel, B. Reynard (2005), Geochem. Geophys. Geosyst., 6, Q09014, doi:10.1029/2005GC000944

Daniel, I.; Koga, K. T.; Reynard, B.; Petitgirard, S.; Chollet, M.; Simionovici, A.

2006-12-01

76

Ciprofloxacin adsorption from aqueous solution onto chemically prepared carbon from date palm leaflets.  

PubMed

A chemically prepared carbon was synthesized from date palm leaflets via sulphuric acid carbonization at 160 degrees C. Adsorption of ciprofloxacin (CIP) from aqueous solution was investigated in terms of time, pH, concentration, temperature and adsorbent status (wet and dry). The equilibrium time was found to be 48 hr. The adsorption rate was enhanced by raising the temperature for both adsorbents, with adsorption data fitting a pseudo second-order model well. The activation energy, Ea, was found to be 17 kJ/mol, indicating a diffusion-controlled, physical adsorption process. The maximum adsorption was found at initial pH 6. The wet adsorbent showed faster removal with higher uptake than the dry adsorbent, with increased performance as temperature increased (25-45 degrees C). The equilibrium data were found to fit the Langmuir model better than the Freundlich model. The thermodynamic parameters showed that the adsorption process is spontaneous and endothermic. The adsorption mechanism is mainly related to cation exchange and hydrogen bonding. PMID:23520864

El-Shafey, El-Said Ibrahim; Al-Lawati, Haider; Al-Sumri, Asmaa Soliman

2012-01-01

77

Evaluation of an evanescent fiber optic chemical sensor for monitoring aqueous volatile organic compounds  

SciTech Connect

Linear chemometric algorithms were used to model the quantitative response of an evanescent fiber optic chemical sensor in aqueous mixtures with concentrations between 20 and 300 ppm. Four data sets were examined with two different experimental arrangements. Two data sets contained trichloroethene, 1,1,2 trichloroethane, and toluene. Partial Least Squares, PLS, and Principal Component Regression, PCR, algorithms performed comparably on these calibration sets with cross-validated root mean squared errors of prediction (RMSEP) for trichloroethene, 1,1,1 trichloroethane, and toluene of approximately 26, 29 and 22 ppm, respectively. The third data set contained trichloroethene, 1,1,2 trichloroethane, toluene, and chloroform and the fourth contained these four analytes as well as tetrachloroethene. Again, both chemometric algorithms performed comparably on a given data set with RMSEP for trichloroethene, 1,1,2 trichloroethane, toluene, and chloroform of approximately 6, 6, 9, and 16 ppm from the first set, and 7, 11, 13, and 31 ppm from the second set with tetrachloroethene RMSEP of 31 ppm. The decrease in the quantitative performance of the sensor for modeling toluene and chloroform upon addition of tetrachloroethene to the sample solutions is due to increased cladding absorption features in the spectral response matrix. These features overlap with the analyte absorption features of toluene and chloroform. These results suggest one of the limitations with this type of sensing format.

Blair, D.S.

1997-04-01

78

Relationship of fatigue-crack growth rate in an aqueous corrosive medium to the electrochemical conditions at the crack tip  

Microsoft Academic Search

p of this data with the fatiguecrack growth rate in samples of 40Kh13 steel in an aqueous solution with pH 8 was studied. The electrochemical investigations and cyclic crack resistance tests were made on i0 20 150 mm beam samples of rectangular cross section of 40Kh13 steel, the chemical composition, heat-treat cycles, and mechanical properties of which were

V. V. Panasyuk; L. V. Ratych; I. N. Dmytrakh

1984-01-01

79

Heteroepitaxial nucleation and oriented growth of manganese oxide islands on carbonate minerals under aqueous conditions.  

PubMed

Manganese redox cycling and the accompanying dissolution and precipitation reactions are important processes in natural waters. In the present study, Mn2+ (aq) is reacted with O2(aq) at circumneutral pH to form manganese oxide islands on the (1014) surface of MnCO3. The islands grow heteroepitaxially. The effects of the substrate surface morphology, the substrate atomic structure, and the aqueous concentration of Mn2+ are investigated. On terraces, rhombohedral oxide islands form with 90 degrees rotation relative to the crystallographic axis of the underlying carbonate substrate. Although the island heights self-limit between 2 and 3 nm depending on reaction conditions, the islands grow laterally to several square microns before separate islands collide and coalesce. The islands do not grow over substrate steps or down dissolution-pit edges. Comparison studies done with MgCO3 and CaCO3 show that the former also promotes heteroepitaxial growth whereas the latter does not. This difference is explained by the relative bond length mismatch between the structures of the carbonate substrates and the atomic structures of manganese oxides. A free energy model is also presented to explain why the heights of the manganese oxide islands self-limit. Our results provide an improved basis both for the development of predictive models of contaminant fate and transport and for the modeling of hydraulic flow through carbonate aquifers. PMID:15787362

Jun, Young-Shin; Kendall, Treavor A; Martin, Scot T; Friend, Cynthia M; Vlassak, Joost J

2005-03-01

80

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

NASA Astrophysics Data System (ADS)

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.

Albarrn, Guadalupe; Ramrez-Cahero, Fernando; Aliev, Roustam

2008-05-01

81

Biological and chemical phosphorus solubilization from pyrolytical biochar in aqueous solution.  

PubMed

Biochar, a massive byproduct of biomass pyrolysis during biofuel generation, is a potential P source for the mitigation of P depletion. However, the chemical and biological effect of the release of P from biochar is still unclear. In this study, two types of Lysinibacillus strains (Lysinibacillussphaericus D-8 and Lysinibacillus fusiformis A-5) were separated from a sediment and their P-solubilizing characteristics to biochar was first reported. Compared with the bacterial mixture W-1 obtained from a bioreactor, the introduction of A-5 and D-8 significantly improved P solubilization. The release of P from biochar by A-5 and D-8 reached 54% and 47%, respectively, which is comparable to that under rigorous chemical conditions. SEM images and XPS spectra demonstrated that the physicochemical properties of the biochar surface have changed in the process which may be caused by the activities of the microbes. PMID:25065807

He, Hui; Qian, Ting-Ting; Liu, Wu-Jun; Jiang, Hong; Yu, Han-Qing

2014-10-01

82

Modeling aqueous ozone/UV process using oxalic acid as probe chemical.  

PubMed

A kinetic model that describes the removal of organic pollutants by an ozone/UV process is described. Oxalic acid, which reacts with a very low rate constant with ozone and relatively high rate constant with hydroxyl radical (OH*), was used as the probe chemical to model the process. The model was verified by experimental data on concentrations of oxalic acid and hydrogen peroxide (H202) under various experimental conditions, i.e., ozone gas dosage, UV light intensity, and varying oxalic acid concentrations. PMID:16295862

Garoma, Temesgen; Gurol, Mirat D

2005-10-15

83

Chemical cleaning of Slovak brown coal by GACL (Grinding and Aqueous Caustic Leaching)  

SciTech Connect

The desulfuration of coal by chemical methods is accomplished by different reagents of acid or alkaline character. The study of the processes applying hot alkaline solutions to purification of coal is not a recent development. As early as during the second World War this process was used in Germany on purpose to prepare from coal a low-ash product suited to production of electrode carbon. It has been stated in a paper published by U.S. Bureau of Mines that one can reduce the content of ash in coal from original 98% to 0.7% by using 10% NaOH at increased pressure and temperature of 225 C. The application of NaOH solutions at increased temperatures (150--250 C) and pressures (0.6--2.5 MPa) were investigated in several laboratories. Another possibility of using alkaline medium for cleaning of coal involves atmospheric pressure. Molten NaOH (or its mixture with KOH) is used and the effective temperature is about 400 C. The ability of molten NaOH to desulfurate coal has been known for more than three decades. The liberation of the pyritic sulfur starts at temperatures above 150 C while the organic sulfur is released from the coal matrix at temperatures above 200 C. The process known as MCL (Molten Caustic Leaching) was for the first time tested by TRW in cooperation with US Department of Energy in the Seventies. The objective was to remove mineral components, pyritic and organic sulfur by using the reaction of coal with a mixture of molten sodium and potassium hydroxide. For leaching time of 60--180 min and temperatures of 370--400 C the effectiveness of MCL process of removal of individual components was as follows: 90--95% of pyritic sulfur, 70--90% of organic sulfur and 90--99% of ash. The MCL process was also effectively applied for treatment of Slovak brown coal in previous work. Because of the presence of sulfidic admixtures in coal and the fact that organic sulfur is built in the matrix of coal and from the view-point of chemical cleaning also exhibits refractory character, the possibility of verifying the principle of such pretreatment offers itself for coal as well. The aim of this work is to apply the new GACL process (Grinding and Aqueous Caustic Leaching) to brown coal Novaky, and to determine how effectively this process lowers ash, sulfur and arsenic levels.

Balaz, P.; Turcaniova, L. [Slovak Academy of Sciences, Kosice (Slovakia). Inst. of Geotechnics; Frommel, E.A.; Martello, D.V. [Dept. of Energy, Pittsburgh, PA (United States). Federal Energy Technology Center; Kern, D.G.; LaCount, R.B. [Virolac Industries, Waynesburg, PA (United States)

1998-12-31

84

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

NASA Astrophysics Data System (ADS)

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.

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

2009-08-01

85

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

SciTech Connect

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 ?-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 ?-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.

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

2006-04-20

86

Transdermal drug delivery using microemulsion and aqueous systems: influence of skin storage conditions on the in vitro permeability of diclofenac from aqueous vehicle systems.  

PubMed

The objective of this study was to evaluate the transdermal delivery potential of diclofenac-containing microemulsion system in vivo and in vitro. It was found that the transdermal administration of the microemulsion to rats resulted in 8-fold higher drug plasma levels than those obtained after application of Voltaren Emulgel. After s.c. administration (3.5 mg/kg), the plasma levels of diclofenac reached a peak of 0.94 microg/ml at t=1 h and decreased rapidly to 0.19 microg/ml at t=6 h, while transdermal administration of the drug in microemulsion maintained constant levels of 0.7-0.9 microg/ml for at least 8 h. The transdermal fluxes of diclofenac were measured in vitro using skin excised from different animal species. In three rodent species, penetration fluxes of 53.35+/-8.19 (furry mouse), 31.70+/-3.83 (hairless mouse), 31.66+/-4.45 (rat), and 22.89+/-6.23 microg/cm(2)/h (hairless guinea pig) were obtained following the application of the microemulsion. These fluxes were significantly higher than those obtained by application of the drug in aqueous solution. In contrast to these results, a 'flip-flop' phenomenon was observed when frozen porcine skin (but not fresh skin) was significantly more permeable to diclofenac-in-water than to the drug-in-microemulsion. In fact, the drug penetration from the microemulsion was not affected by the skin storage conditions, but it was increased when an aqueous solution was applied. However, this unusual phenomenon observed in non-freshly used porcine skin places a question mark on its relevancy for in vitro penetration studies involving aqueous vehicle systems. PMID:16431047

Sintov, Amnon C; Botner, Shafir

2006-03-27

87

Equilibrium hydrate formation conditions for hydrogen sulfide, carbon dioxide, and ethane in aqueous solutions of ethylene glycol and sodium chloride  

SciTech Connect

Natural gas components such as hydrogen sulfide, carbon dioxide, and ethane form gas hydrates of structure I under suitable temperature and pressure conditions. Information on such conditions is vital to the oil and gas industry in order to design and operate processing equipment and pipelines so that hydrate formation is avoided. Incipient equilibrium hydrate formation conditions for hydrogen sulfide, carbon dioxide, and ethane in aqueous solutions of ethylene glycol and sodium chloride were experimentally obtained in the temperature range 264--290 K and the pressure range 0.23--3.18 MPa. A variable-volume sapphire cell was used for the measurements.

Majumdar, A.; Mahmoodaghdam, E.; Bishnoi, P.R.

2000-02-01

88

PROJECT SUMMARY. IMPROVED DECONTAMINATION: INTERFACIAL, TRANSPORT, AND CHEMICAL PROPERTIES OF AQUEOUS SURFACTANT CLEANERS  

EPA Science Inventory

This investigation is focused on decontamination using environmentally benign aqueous solutions, specifically the removal of organics and associated radionuclide contaminants by synthetic surfactants. Facilities throughout DOE have need for removal of organics (oils, PCBs, etc.) ...

89

The characterisation of PbO 2-coated electrodes prepared from aqueous methanesulfonic acid under controlled deposition conditions  

Microsoft Academic Search

A series of PbO2 coatings on planar carbon substrates has been prepared by anodic deposition in aqueous methanesulfonic acid (MSA) under galvanostatic conditions. The effect of four experimental parameters, i.e., lead(II) methanesulfonate and MSA concentrations, current density, and temperature was analysed. Surface characterisation by XRD, SEM-EDX, and AFM has provided information about the structural (phase distribution, degree of crystallinity, and

I. Sirs; C. T. J. Low; C. Ponce-de-Len; F. C. Walsh

2010-01-01

90

Chemical extraction of arsenic from contaminated soil under subcritical conditions.  

PubMed

In this research, we investigated a chemical extraction process, under subcritical conditions, for arsenic (As)-contaminated soil in the vicinity of an abandoned smelting plant in South Korea. The total concentration of As in soil was 75.5 mg/kg, 68% of which was As(+III). X-ray photoelectron spectroscopy analysis showed that the possible As(+III)-bearing compounds in the soil were As(2)O(3) and R-AsOOH. At 20C, 100 mM of NaOH could extract 26% of the As from the soil samples. In contrast, 100 mM of ethylenediaminetetraacetic acid (EDTA) and citric acid showed less than 10% extraction efficiency. However, as the temperature increased to 250 and 300C, extraction efficiencies increased to 75-91% and 94-103%, respectively, regardless of the extraction reagent used. Control experiments with subcritical water at 300C showed complete extraction of As from the soil. Arsenic species in the solution extracted at 300C indicated that subcritical water oxidation may be involved in the dissolution of As(+III)-bearing minerals under given conditions. Our results suggest that subcritical water extraction/oxidation is a promising option for effective disposal of As-contaminated soil. PMID:21601910

Oh, Seok-Young; Yoon, Myong-Keun; Kim, Ick-Hyun; Kim, Ju Yup; Bae, Wookeun

2011-07-15

91

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

NASA Astrophysics Data System (ADS)

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 assemblage, our experiments most closely resemble alteration in the CI chondrites, although the degree of alteration of our experiments is much lower. CI chondrites contain serpentine/saponite intergrowths and veins of Ca-sulfate and Ca-carbonate as well as the Fe-oxyhydroxide, ferrihydrite. However, the phyllosilicate phases formed in our experiments are somewhat coarser-grained than the finest phyllosilicate fraction present in CI chondrites, suggesting that alteration of the CI chondrites occurred at lower temperatures. In terms of mineral assemblage, our experiments also appear to come close to matching CR chondrites, although we infer that CR alteration probably occurred at temperatures <100 C, based on the very fine-grained size of phyllosilicates in CR matrices.

Jones, Catherine L.; Brearley, Adrian J.

2006-02-01

92

Thermodynamics of carbon dioxide in aqueous piperazine/potassium carbonate systems at stripper conditions  

E-print Network

GHGT-8 1 Thermodynamics of carbon dioxide in aqueous piperazine/potassium carbonate systems thermodynamic models. The range in CO2 solubility measured from 100 � 120 o C for K+ /PZ mixtures was from (0 and Technology to expand the thermodynamic data of for potassium carbonate/piperazine/CO2 with measurements of CO

Rochelle, Gary T.

93

Arsenic mobility in soils contaminated with metallurgical wastes as a function of variable chemical conditions  

NASA Astrophysics Data System (ADS)

Arsenic is a pervasive contaminant of natural aqueous systems, such as groundwater and soils, its sources being both natural and anthropogenic. The present investigation was performed on soils contaminated with residues from ore processing activities and revealed the presence of arsenate [As(V)] species with a very low mobility, through natural attenuation processes. The stability of this attenuation was investigated by varying two specific equilibrium chemical conditions: pH and presence of bicarbonate ions. One-unit changes in equilibrium pH generally caused small increases in As mobility, whereas the presence of bicarbonate ions considerably increased this mobility. The results were compared to thermodinamic simulations of equilibrium conditions using the total elemental composition of each individual soil, but excluding sorption reactions. Close matches between experimental data and simulations revealed the predominance of solubility-controlled As mobility via heavy-metal arsenate solid formation. Bicarbonate ions were found to be highly unsuitable for extraction of sorbed arsenate fractions due to indirect As release from solid arsenates, via heavy-metal carbonate precipitation processes.

Garcia Payne, D. G.; Villalobos, M.; Ceniceros, A.; Lopez, J. L.; Gutierrez, M.

2008-12-01

94

CHEMICAL SYNTHESIS USING 'GREENER' ALTERNATIVE REACTION CONDITIONS AND MEDIA  

EPA Science Inventory

The chemical research during the last decade has witnessed a paradigm shift towards "environmentally-friendly chemistry" more popularly known as "green chemistry" due to the increasing environmental concerns and legislative requirements to curb the release of chemical waste into ...

95

Adsorptive removal of direct yellow 161dye from aqueous solution using bamboo charcoals activated with different chemicals  

Microsoft Academic Search

The adsorption of direct yellow 161 dye from aqueous solution on derived bamboo charcoals activated with orthophosphoric acid, nitric acid, potassium hydroxide and zinc chloride was investigated. Batch adsorption results showed that under optimal sorption condition including initial dye concentration 24.62mg\\/L, pH 1.0, contact time 21h, and temperature 298k the maximum and the minimum adsorption capacities were 2.401mg\\/g and 1.705mg\\/g

Liang-Gui Wang; Guo-Bing Yan

2011-01-01

96

Epoxidized natural rubber toughened aqueous resole type liquefied EFB resin: Physical and chemical characterization  

NASA Astrophysics Data System (ADS)

A preliminary study on the reaction between aqueous resole type resinified liquefied palm oil empty fruit bunches fibres (RLEFB) with epoxidized natural rubber (ENR). Liquefaction of empty fruit bunches (EFB) is carried out at different ratio of phenol to EFB (P:EFB). Resole type phenolic resin is prepared using sodium hydroxide (NaOH) as the catalyst with the ratio of liquefied EFB (LEFB) to formaldehyde (LEFB:F) of 1:1.8. 50% epoxidation of epoxidized natural rubber (ENR-50) is used to react with resole resin by mixing with ENR with aqueous resole resin. The cured resin is characterized with FT-IR and SEM. Aqueous system have been found to be unsuitable medium in the reaction between resin and ENR. This system produced a highly porous product when RLEFB/ENR resin is cured.

Amran, Umar Adli; Zakaria, Sarani; Chia, Chin Hua

2013-11-01

97

Mass spectrometric elucidation of triacylglycerol content of Brevoortia tyrannus (menhaden) oil using non-aqueous reversed-phase liquid chromatography under ultra high pressure conditions.  

PubMed

A non-aqueous reversed phase high performance liquid chromatography method was developed, and optimized for triacylglycerol analysis in a Brevoortia tyrannus (menhaden) oil sample. Four columns were serially coupled to tackle such a task, for a total length of 60 cm of shell-packed stationary phase, and operated under ultra high pressure conditions. As detection, positive-ion atmospheric pressure chemical ionization mass spectrometry was used to attain identification of the analyzed sample components. A number of 137 triacylglycerols containing up to 19 fatty acids, with 14-22 carbon atom alkyl chain length and 0-6 double bonds, were positively identified in the complex lipidic sample. This is the first work that reports an extensive characterization of the triacylglycerol fraction of menhaden oil. PMID:22503927

Dugo, Paola; Beccaria, Marco; Fawzy, Nermeen; Donato, Paola; Cacciola, Francesco; Mondello, Luigi

2012-10-12

98

Chemical speciation of metal complexes from chemical shift calculations: the interaction of 2-amino-N-hydroxypropanamide with V(V) in aqueous solution.  

PubMed

The chemical speciation of 2-amino-N-hydroxypropanamide (?-alaninohydroxamic acid, HL) and vanadium (V) in aqueous solution has been investigated through calculations of the thermodynamic properties and the (51)V nuclear magnetic resonance (NMR) chemical shifts of the species formed at equilibrium. The results have been compared directly with the experimental (51)V NMR data. The (51)V NMR chemical shifts have been calculated by using a density functional theory (DFT) approach accounting for relativistic corrections and solvent effects. All tautomers of the 1:1 and 1:2 VO2(+)/?-ala complexes with different degrees of protonation have been calculated and thermodynamic and structural properties are presented for the most stable species. The system is better modeled as tautomeric equilibria, and species lying down in the range of 10 kcalmol(-1) cannot be neglected at the BP/TZ2P/COSMO approach. In fact, the metal complex speciation in aqueous solution should not be investigated based solely on the thermodynamic analysis, but together with spectroscopic calculations such as NMR. PMID:23971999

Duarte, Hlio Anderson; Vankova, Nina; Ferreira, Isabella Pires; Paniago, Eucler B; Heine, Thomas

2013-10-01

99

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

PubMed

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

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

2013-03-21

100

CHEMICAL TRANSFORMATION MODULES FOR EULERIAN ACID DEPOSITION MODELS. VOLUME 2. THE AQUEOUS-PHASE CHEMISTRY  

EPA Science Inventory

This study focuses on the review and evaluation of mechanistic and kinetic data for aqueous-phase reactions that lead to the production of acidic substances in the environment. The intent of this research is to provide a framework that can be used to develop a state-of-the-art aq...

101

Waste treatment process for removal of contaminants from aqueous, mixed-waste solutions using sequential chemical treatment and crossflow microfiltration, followed by dewatering  

DOEpatents

In processes of this invention aqueous waste solutions containing a variety of mixed waste contaminants are treated to remove the contaminants by a sequential addition of chemicals and adsorption/ion exchange powdered materials to remove the contaminants including lead, cadmium, uranium, cesium-137, strontium-85/90, trichloroethylene and benzene, and impurities including iron and calcium. Staged conditioning of the waste solution produces a polydisperse system of size enlarged complexes of the contaminants in three distinct configurations: water-soluble metal complexes, insoluble metal precipitation complexes, and contaminant-bearing particles of ion exchange and adsorbent materials. The volume of the waste is reduced by separation of the polydisperse system by cross-flow microfiltration, followed by low-temperature evaporation and/or filter pressing. The water produced as filtrate is discharged if it meets a specified target water quality, or else the filtrate is recycled until the target is achieved.

Vijayan, Sivaraman (Deep River, CA); Wong, Chi F. (Pembroke, CA); Buckley, Leo P. (Deep River, CA)

1994-01-01

102

Waste treatment process for removal of contaminants from aqueous, mixed-waste solutions using sequential chemical treatment and crossflow microfiltration, followed by dewatering  

DOEpatents

In processes of this invention aqueous waste solutions containing a variety of mixed waste contaminants are treated to remove the contaminants by a sequential addition of chemicals and adsorption/ion exchange powdered materials to remove the contaminants including lead, cadmium, uranium, cesium-137, strontium-85/90, trichloroethylene and benzene, and impurities including iron and calcium. Staged conditioning of the waste solution produces a polydisperse system of size enlarged complexes of the contaminants in three distinct configurations: water-soluble metal complexes, insoluble metal precipitation complexes, and contaminant-bearing particles of ion exchange and adsorbent materials. The volume of the waste is reduced by separation of the polydisperse system by cross-flow microfiltration, followed by low-temperature evaporation and/or filter pressing. The water produced as filtrate is discharged if it meets a specified target water quality, or else the filtrate is recycled until the target is achieved. 1 fig.

Vijayan, S.; Wong, C.F.; Buckley, L.P.

1994-11-22

103

Quantum-Chemical Calculations of Carbon-Isotope Fractionation in CO2(g), Aqueous Carbonate Species, and Carbonate Minerals  

SciTech Connect

Quantum chemical calculations on large supermolecular carbonate-water and carbonate mineral clusters are used to predict equilibrium constants for 13,12C-isotope-exchange reactions between CO2(g), aqueous carbonate species, and the common carbonate minerals. For the aqueous species, we evaluate the influence of the size and conformational variability of the solvation shell, the exchange-correlation functional, and the basis set. The choice of exchange-correlation functional (PBE vs B3LYP), the basis set (6-31G* vs aug-cc-pVDZ), and solvation shell size (first shell only vs first shell and a partial second shell) each produce changes of ~5-10 per mil in the reduced partition function ratio. Conformational variability gives rise to a standard error of ~0.5 per mil using ~10 solute-solvent conformations. The best results are obtained with the B3LYP/ aug-cc-pVDZ combination, but because the improvements in the basis set and exchange correlation functional drive the reduced partition function ratios in opposite directions, reasonably good results are also obtained with the PBE/6-31G* combination. To construct molecular clusters representative of mineral environments, a new method is introduced on the basis of conservation of Pauling bond strength. Using these clusters as models for minerals, calculations of mineral-gas and mineral-aqueous carbon-isotope fractionation factors, are in good agreement with experimental measurements. Carbon-isotope fractionation factors for gas, aqueous, and mineral phases are thus integrated into a single theoretical/computational framework.

Rustad, James R.; Nelmes, Sierra L.; Jackson, Virgil E.; Dixon, David A.

2008-01-24

104

Control of Convective Dissolution by Chemical Reactions: General Classification and Application to CO2 Dissolution in Reactive Aqueous Solutions  

NASA Astrophysics Data System (ADS)

In partially miscible two-layer systems within a gravity field, buoyancy-driven convective motions can appear when one phase dissolves with a finite solubility into the other one. We investigate the influence of chemical reactions on such convective dissolution by a linear stability analysis of a reaction-diffusion-convection model. We show theoretically that a chemical reaction can either enhance or decrease the onset time of the convection, depending on the type of density profile building up in time in the reactive solution. We classify the stabilizing and destabilizing scenarios in a parameter space spanned by the solutal Rayleigh numbers. As an example, we experimentally demonstrate the possibility to enhance the convective dissolution of gaseous CO2 in aqueous solutions by a classical acid-base reaction.

Loodts, V.; Thomas, C.; Rongy, L.; De Wit, A.

2014-09-01

105

Control of Convective Dissolution by Chemical Reactions: General Classification and Application to CO_{2} Dissolution in Reactive Aqueous Solutions.  

PubMed

In partially miscible two-layer systems within a gravity field, buoyancy-driven convective motions can appear when one phase dissolves with a finite solubility into the other one. We investigate the influence of chemical reactions on such convective dissolution by a linear stability analysis of a reaction-diffusion-convection model. We show theoretically that a chemical reaction can either enhance or decrease the onset time of the convection, depending on the type of density profile building up in time in the reactive solution. We classify the stabilizing and destabilizing scenarios in a parameter space spanned by the solutal Rayleigh numbers. As an example, we experimentally demonstrate the possibility to enhance the convective dissolution of gaseous CO_{2} in aqueous solutions by a classical acid-base reaction. PMID:25259984

Loodts, V; Thomas, C; Rongy, L; De Wit, A

2014-09-12

106

On demand fusion and triggering of confined chemical reactions in femtoliter volume aqueous droplets controlled by interfacial tension  

NASA Astrophysics Data System (ADS)

Droplet-based microfluidic platforms offer many opportunities to confine chemical and biochemical reactants in discrete ultrasmall reaction volumes, and investigate the effects of increased confinement on reaction dynamics. Current state-of-the-art microfluidic sampling strategies for creating ultrasmall reaction volumes are predominately steady-state approaches, which result in difficulty in trapping reacting species with a well-defined time-zero for initiation of biochemical reactions in the confined space. This talk describes stepwise, on-demand generation and fusion of femtoliter aqueous droplets based on interfacial tension. Sub-millisecond reaction times from droplet fusion were demonstrated, as well as a reversible chemical toggle switch based on alternating fusion of droplets containing acidic or basic solution, monitored with the pH-dependent emission of fluorescein.

Collier, Pat; Jung, Seung-Yong; Retterer, Scott

2011-03-01

107

The direct catalytic asymmetric aldol reaction of ?-substituted nitroacetates with aqueous formaldehyde under base-free neutral phase-transfer conditions.  

PubMed

Enantioselective direct aldol reaction of ?-substituted nitroacetates with aqueous formaldehyde for the synthesis of ?-alkyl serines has been achieved under base-free neutral phase-transfer conditions with a bifunctional chiral phase-transfer catalyst. PMID:22349720

Shirakawa, Seiji; Ota, Kensuke; Terao, Shogo J; Maruoka, Keiji

2012-08-14

108

CHEMICAL AND BIOLOGICAL TREATMENT OF THERMALLY CONDITIONED SLUDGE RECYCLE LIQUORS  

EPA Science Inventory

The objective of this research project was to demonstrate and evaluate the feasibility of treating undiluted heat treatment liquor prior to its rerouting back to the head of the sewage treatment plant. Chemical and biological treatment processes were studied. Chemical treatment w...

109

Plant Cell Walls: Basics of Structure, Chemistry, Accessibility and the Influence on Conversion - Aqueous Pretreatment of Plant Biomass for Biological and Chemical Conversion to Fuels and Chemicals  

SciTech Connect

This book is focused on the pretreatment of biomass, a necessary step for efficient conversion of the plant cell wall materials to fuels and other products. Pretreatment is required because it is difficult to access, separate, and release the monomeric sugars comprising the biopolymers within the biomass that can be further upgraded to products through chemical processes such as aqueous phase reforming or biological routes such as fermentation of the sugars to ethanol This resistance to degradation or difficulty to release the monomers (mostly sugars) is commonly referred to as recalcitrance. There are many methods to overcome plant recalcitrance, but the underlying cause of the recalcitrance lies in the complex combination of chemical and structural features of the plant cell walls.

Davison, Brian H [ORNL; Davis, Dr. Mark F. [National Renewable Energy Laboratory (NREL); Parks, Jerry M [ORNL; Donohoe, Bryan [National Renewable Energy Laboratory (NREL)

2013-01-01

110

Chemical Speciation of Inorganic Compounds under Hydrothermal Conditions  

SciTech Connect

Measurements of oxidation. These spectra are to the best of our knowledge the first reported in situ spectroscopic observation of homogeneous aqueous redox chemistry at temperatures beyond the critical temperature of waste. We also observed a time-dependence for the growth of the Cr(VI) XANES peak and have therefore obtained both kinetic information as well as structural information on the reactants and products at the reaction temperature. We feel that these new techniques, when employed on actual waste components will elucidate the underlying chemistry.

Edward A Stern; John Fulton

2002-02-21

111

Chemical passivation of InSb (100) substrates in aqueous solutions of sodium sulfide  

SciTech Connect

The elemental composition and electronic structure of both native-oxide-covered InSb (100) substrates and substrates treated in aqueous solutions of sodium sulfide are analyzed by X-ray photoelectron spectroscopy. It is found that, as a result of treatment in a 1 M aqueous solution of Na{sub 2}S and subsequent annealing in vacuum at 150 Degree-Sign C, the surface layer consisting of complex antimony and indium oxides of nonstoichiometric composition is removed completely with the formation of a continuous layer of chemisorbed sulfur atoms coherently bound to indium atoms. According to atomic-force microscopy data, no etching of the host substrate material occurs during sulfide passivation. A shift (by 0.37 eV) of the In-Sb bulk photoemission towards higher binding energies is found, which indicates that the surface Fermi level shifts deeper into the conduction band.

Lvova, T. V., E-mail: tatyana.lvova.12@mail.ru; Dunaevskii, M. S.; Lebedev, M. V. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation); Shakhmin, A. L. [St. Petersburg State Polytechnical University (Russian Federation); Sedova, I. V.; Ivanov, S. V. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)

2013-05-15

112

Transformations of biomass-derived platform molecules: from high added-value chemicals to fuels via aqueous-phase processing.  

PubMed

Global warming issues and the medium-term depletion of fossil fuel reserves are stimulating researchers around the world to find alternative sources of energy and organic carbon. Biomass is considered by experts the only sustainable source of energy and organic carbon for our industrial society, and it has the potential to displace petroleum in the production of chemicals and liquid transportation fuels. However, the transition from a petroleum-based economy to one based on biomass requires new strategies since the petrochemical technologies, well-developed over the last century, are not valid to process the biomass-derived compounds. Unlike petroleum feedstocks, biomass derived platform molecules possess a high oxygen content that gives them low volatility, high solubility in water, high reactivity and low thermal stability, properties that favour the processing of these resources by catalytic aqueous-phase technologies at moderate temperatures. This tutorial review is aimed at providing a general overview of processes, technologies and challenges that lie ahead for a range of different aqueous-phase transformations of some of the key biomass-derived platform molecules into liquid fuels for the transportation sector and related high added value chemicals. PMID:21713268

Serrano-Ruiz, Juan Carlos; Luque, Rafael; Seplveda-Escribano, Antonio

2011-11-01

113

Morphology and Optical Properties of Zinc Oxide Films Grown on Metal Coated Glass Substrates by Aqueous Chemical Growth  

NASA Astrophysics Data System (ADS)

Zinc oxide films were deposited on three different metal coated substrates (gold, nickel and platinum) by aqueous chemical growth method. This paper discusses the effect of metal coated substrates on the morphology and optical properties of grown ZnO films. X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM) and UV-visible spectroscopy (UV-vis) were employed to characterize the samples. All the as-deposited ZnO films exhibit crystalline hexagonal wurzite structure. The crystallite size of the ZnO films were in the range of 29 to 32 nm. FESEM micrographs revealed hexagonal rod, oval-like and flower-like ZnO structures formed on all metal coated substrates. The Pt coated film contains higher density hexagonal rod as compared to others metal coated substrate. Most probably the Pt lattice parameter is the nearest to ZnO compared to nickel and gold. The optical band gap energy, Eg of ZnO films were estimated to be 3.30 eV which is near to bulk Eg, 3.37 eV. This indicates that the ZnO grown by aqueous chemical growth is able to produce similar quality properties to other conventional method either films or bulk size.

Bakar, M. A.; Hamid, M. A. A.; Jalar, A.; Shamsudin, R.

2013-04-01

114

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

SciTech Connect

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.

Rard, J.A.

1989-10-01

115

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

PubMed Central

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 M1 s1, in aqueous and lipidic environment, respectively, which makes dopamine a very good OOH, and presumably OOR, radical scavenger. PMID:21919526

2011-01-01

116

Condition prediction of chemical complex systems based on Multifractal and Mahalanobis-Taguchi system  

Microsoft Academic Search

Abnormal condition is hazardous which may lead to accidents in chemical industry and effective condition prediction methods are imperative for chemical complex system. Comparing with traditional techniques of condition prediction without concerning nonlinearity of complex system, multifractal analysis elaborately reveals scale-invariance or self-similarity properties of observed data, which is one of the intrinsic characteristics of complex system. To predict the

Yanqing Lv; Jianmin Gao

2011-01-01

117

Detection of aqueous phase chemical warfare agent degradation products by negative mode ion mobility time-of-flight mass spectrometry [IM(tof)MS  

Microsoft Academic Search

The use of negative ion monitoring mode with an atmospheric pressure ion mobility orthogonal reflector time-of-flight mass\\u000a spectrometer [IM(tof)MS] to detect chemical warfare agent (CWA) degradation products from aqueous phase samples has been determined.\\u000a Aqueous phase sampling used a traditional electrospray ionization (ESI) source for sample introduction and ionization. Certified\\u000a reference materials (CRM) of CWA degradation products for the detection

Wes E. Steiner; Charles S. Harden; Feng Hong; Steve J. Klopsch; Vincent M. McHugh

2006-01-01

118

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

SciTech Connect

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.

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

1994-12-01

119

Abiotic Formation of Hydrocarbons Under Hydrothermal Conditions: Constraints from Chemical and Isotope Data  

SciTech Connect

To understand reaction pathways and isotope systematics during mineral-catalyzed abiotic synthesis of hydrocarbons under hydrothermal conditions, experiments involving magnetite and CO{sub 2} and H{sub 2}-bearing aqueous fluids were conducted at 400 C and 500 bars. A robust technique for sample storage and transfer from experimental apparatus to stable isotope mass spectrometer provides a methodology for integration of both carbon and hydrogen isotope characterization of reactants and products generated during abiogenic synthesis experiments. Experiments were performed with and without pretreatment of magnetite to remove background carbon associated with the mineral catalyst. Prior to experiments, the abundance and carbon isotope composition of all carbon-bearing components were determined. Time-series samples of the fluid from all experiments indicated significant concentrations of dissolved CO and C{sub 1}-C{sub 3} hydrocarbons and relatively large changes in dissolved CO{sub 2} and H{sub 2} concentrations, consistent with formation of additional hydrocarbon components beyond C{sub 3}. The existence of relatively high dissolved alkanes in the experiment involving non-pretreated magnetite in particular, suggests a complex catalytic process, likely involving reinforcing effects of mineral-derived carbon with newly synthesized hydrocarbons at the magnetite surface. Similar reactions may be important mechanisms for carbon reduction in chemically complex natural hydrothermal systems. In spite of evidence supporting abiotic hydrocarbon formation in all experiments, an 'isotopic reversal' trend was not observed for {sup 13}C values of dissolved alkanes with increasing carbon number. This may relate to the specific mechanism of carbon reduction and hydrocarbon chain growth under hydrothermal conditions at elevated temperatures and pressures. Over time, significant {sup 13}C depletion in CH{sub 4} suggests either depolymerization reactions occurring in addition to synthesis, or reactions between the C{sub 1}-C{sub 3} hydrocarbons and carbon species absorbed on mineral surfaces and in solution.

Fu, Q. [University of Minnesota; Lollar, Barbara Sherwood [University of Toronto; Horita, Juske [ORNL; Lacrampe-Couloume, Georges [University of Toronto; Seyfried, W. E. [University of Minnesota

2007-01-01

120

Oxidative weathering chemical migration under variably saturated conditions and supergene copper enrichment  

SciTech Connect

Transport of oxygen gas from the land surface through an unsaturated zone has a strong influence on oxidative weathering processes. Oxidation of sulfide minerals such as pyrite (FeS{sub 2}), one of the most common naturally occurring minerals, is the primary source of acid drainage from mines and waste rock piles. Here we present a detailed numerical model of supergene copper enrichment that involves the oxidative weathering of pyrite (FeS{sub 2}) and chalcopyrite (CuFeS{sub 2}), and acidification that causes mobilization of metals in the unsaturated zone, with subsequent formation of enriched ore deposits of chalcocite (CuS) and covellite (Cu{sub 2}S) in the reducing conditions below the water table. We examine and identify some significant conceptual and computational issues regarding the oxidative weathering processes through the modeling tool. The dissolution of gaseous oxygen induced by the oxidation reduces oxygen partial pressure, as well as the total pressure of the gas phase. As a result, the gas flow is modified, then the liquid phase flow. Results indicate that this reaction effect on the fluid flow may not be important under ambient conditions, and gas diffusion can be a more important mechanism for oxygen supply than gas or liquid advection. Acidification, mobilization of metals, and alteration of primary minerals mostly take place in unsaturated zone (oxidizing), while precipitation of secondary minerals mainly occurs in saturated zone (reducing). The water table may be considered as an interface between oxidizing and reducing zones. Moving water table due to change of infiltration results in moving oxidizing zone and redistributing aqueous chemical constitutes and secondary mineral deposits. The oxidative weathering processes are difficult to model numerically, because concentrations of redox sensitive chemical species such as O{sub 2}(aq), SO{sub 4}{sup 2-} and HS{sup -} may change over tens of orders of magnitude between oxidizing and reducing conditions. In order to simulate substantial reaction progress over geologic time, one can benefit from the quasi-stationary state (QSS) approximation. A significant saving of computing time using QSS is demonstrated through the example. In addition, changes in porosity and permeability due to mineral dissolution and precipitation are also addressed in some degree. Even though oxidative weathering is sensitive to many factors, this work demonstrates that our model provides a comprehensive suite of process modeling capabilities, which could serve as a prototype for oxidative weathering processes with broad significance for geoscientific, engineering, and environmental applications.

Xu, Tianfu; Pruess, K.; Brimhall, G.

1999-04-01

121

Chemical Enrichment and Physical Conditions in IZw18*  

NASA Technical Reports Server (NTRS)

Low-metallicity star-forming dwarf galaxies are prime targets to understand the chemical enrichment of the interstellar medium. The H I region contains the bulk of the mass in blue compact dwarfs, and it provides important constraints on the dispersal and mixing of heavy elements released by successive star-formation episodes. The metallicity of the H I region is also a critical parameter to investigate the future star-formation history, as metals provide most of the gas cooling that will facilitate and sustain star formation. Aims. Our primary objective is to study the enrichment of the H I region and the interplay between star-formation history and metallicity evolution. Our secondary obje ctive is to constrain the spatial- and time-scales over which the HI and H II regions are enriched, and the mass range of stars responsible for the heavy element production. Finally, we aim to examine the gas heating and cooling mechanisms in the H I region. Methods. We observed the most metal-poor star-forming galaxy in the Local Universe, I Zw 18, with the Cosmic Origin Spectrograph onboard Hubble. The abundances in the neutral gas are derived from far-ultraviolet absorption-lines (H I, CIII, CIIi*, N I, OI,...) and are compared to the abundances in the H II region. Models are constructed to calculate the ionization structure and the thermal processes. We investigate the gas cooling in the HIi region through physical diagnostics drawn from the fine-structure level of C+. Results. We find that H I region abundances are lower by a factor of approx 2 as compared to the H II region. There is no differential depletion on dust between the H I and H II region. Using sulfur as a metallicity tracer, we calculate a metallicity of 1/46 Z(solar) (vs. 1/31 Z(solar) in the H II region). From the study of the C/O, [O/Fe], and N/O abundance ratios, we propose that C, N, O, and Fe are mainly produced in massive stars. We argue that the H I envelope may contain pockets of pristine gas with a metallicity essentially null. Finally, we derive the physical conditions in the H I region by investigating the C II* absorption line. The cooling rate derived from C II* is consistent with collisions with H(sup 0) atoms in the diffuse neutral gas. We calculate the star-formation rate from the CII* cooling rate assuming that photoelectric effect on dust is the dominant gas heating mechanism. Our determination is in good agreement with the values in the literature if we assume a low dust-to-gas ratio (approx 2000 times lower than the Milky Way value).

Lebouteiller, V.; Heap, S.; Hubeny, I.; Kunth, D.

2013-01-01

122

The aqueous root extract of Aristolochia ringens (Vahl.) Aristolochiaceae inhibits chemically-induced inflammation in rodents.  

PubMed

The potential of the aqueous root extract of Aristolochia ringens (AR) (10-100 mg/kg p.o) to inhibit inflammation induced by phlogistics was evaluated using the carrageenan and egg albumin induced rat paw oedema, formaldehyde induced arthritic inflammation and xylene induced mouse ear oedema models. AR (10-50 mg/kg) dose-dependently decreased rat paw oedema in the carrageenan and egg albumin induced inflammation, producing comparable inhibition of 57.1% and 65.6% to the 57.9% and 63.9% of indomethacin and diclofenac (10 mg/kg p.o) respectively at 50 mg/kg. AR (10-50 mg/kg) also dose dependently inhibited formaldehyde-induced arthritic paw oedema over the 10 day observation period, with a greater inhibition of 50% at 50 mg/kg than the 40.8% inhibition by diclofenac (10 mg/kg i.p). AR (50 mg/kg) also produced greater inhibition of 84.78% than the 65.21% by dexamethasone (1 mg/kg) in xylene-induced ear oedema. Results show that the aqueous root extract of Aristolochia ringens possesses antiinflammatory activity. PMID:25362593

Ruth, Aigbe Flora; Olaide, Adeyemi Olufunmilayo; Oluwatoyin, Sofidiya Margaret

2014-11-01

123

Chemical characterization of the main secondary organic aerosol (SOA) products formed through aqueous-phase photonitration of guaiacol  

NASA Astrophysics Data System (ADS)

Guaiacol (2-methoxyphenol) and its derivatives can be emitted into the atmosphere by thermal degradation (i.e. burning) of wood lignins. Due to its volatility, guaiacol is predominantly distributed in the atmospheric gaseous phase. Recent studies have shown the importance of aqueous-phase reactions in addition to the dominant gas-phase and heterogeneous reactions of guaiacol, in the formation of secondary organic aerosol (SOA) in the atmosphere. The main objectives of the present study were to chemically characterize the low-volatility SOA products of the aqueous-phase photonitration of guaiacol and examine their possible presence in urban atmospheric aerosols. The aqueous-phase reactions were carried out under simulated sunlight and in the presence of H2O2 and nitrite. The formed guaiacol reaction products were concentrated by using solid-phase extraction (SPE) and then purified by means of semi-preparative high-performance liquid chromatography (HPLC). The fractionated individual compounds were isolated as pure solids and further analyzed with liquid-state 1H, 13C and 2D nuclear magnetic resonance (NMR) spectroscopy and direct infusion negative ion electrospray ionization tandem mass spectrometry ((-)ESI-MS/MS). The NMR and product ion (MS2) spectra were used for unambiguous product structure elucidation. The main products of guaiacol photonitration are 4-nitroguaiacol (4NG), 6-nitroguaiacol (6NG), and 4,6-dinitroguaiacol (4,6DNG). Using the isolated compounds as standards, 4NG and 4,6DNG were unambiguously identified in winter PM10 aerosols from the city of Ljubljana (Slovenia) by means of HPLC/(-)ESI-MS/MS. Owing to the strong absorption of UV and visible light, 4,6DNG could be an important constituent of atmospheric "brown" carbon, especially in regions affected by biomass burning.

Kitanovski, Z.; ?usak, A.; Grgi?, I.; Claeys, M.

2014-04-01

124

EFFICIENT CHEMICAL TRANSFORMATIONS USING ALTERNATIVE REACTION CONDITIONS AND MEDIA  

EPA Science Inventory

The diverse nature of chemical entities requires various green' strategic pathways in our quest towards attaining sustainability. A solvent-free approach that involves microwave (MW) exposure of neat reactants (undiluted) catalyzed by the surfaces of less-expensive and recyclable...

125

Experimental analysis of the aqueous chemical environment following a loss-of-coolant accident  

Microsoft Academic Search

Five different 30-day tests were conducted to simulate the chemical environment in a pressurized water reactor containment water pool after a loss-of-coolant accident (LOCA). All chemical environments within the test apparatus included boric acid, lithium hydroxide, and hydrochloric acid. In addition, trisodium phosphate, sodium hydroxide, and sodium tetraborate were used to control pH in separate tests. Materials tested within this

Dong Chen; Kerry J. Howe; Jack Dallman; Bruce C. Letellier; Marc Klasky; Janet Leavitt; Bhagwat Jain

2007-01-01

126

Characterizing stability of ``click'' modified glass surfaces to common microfabrication conditions and aqueous electrolyte solutions  

E-print Network

, chemisorption arises due to the covalent attachment of a molecule through chemical bond formation.16 The main be adhered through two primary mechanisms, physisorption and covalent attachment or chemisorption.1 advantage of the covalent attachment of the surface layers over the physisorbed surface layers

127

Chemical analysis and aqueous solution properties of Charged Amphiphilic Block Copolymers PBA-b-PAA synthesized by MADIX  

E-print Network

We have linked the structural and dynamic properties in aqueous solution of amphiphilic charged diblock copolymers poly(butyl acrylate)-b-poly(acrylic acid), PBA-b-PAA, synthesized by controlled radical polymerization, with the physico-chemical characteristics of the samples. Despite product imperfections, the samples self-assemble in melt and aqueous solutions as predicted by monodisperse microphase separation theory. However, the PBA core are abnormally large; the swelling of PBA cores is not due to AA (the Flory parameter chiPBA/PAA, determined at 0.25, means strong segregation), but to h-PBA homopolymers (content determined by Liquid Chromatography at the Point of Exclusion and Adsorption Transition LC-PEAT). Beside the dominant population of micelles detected by scattering experiments, capillary electrophoresis CE analysis permitted detection of two other populations, one of h-PAA, and the other of free PBA-b-PAA chains, that have very short PBA blocks and never self-assemble. Despite the presence of these free unimers, the self-assembly in solution was found out of equilibrium: the aggregation state is history dependant and no unimer exchange between micelles occurs over months (time-evolution SANS). The high PBA/water interfacial tension, measured at 20 mN/m, prohibits unimer exchange between micelles. PBA-b-PAA solution systems are neither at thermal equilibrium nor completely frozen systems: internal fractionation of individual aggregates can occur.

M. Jacquin; P. Muller; R. Talingting-Pabalan; H. Cottet; J. -F. Berret; T. Futterer; O. Theodoly

2007-08-27

128

Measurements of aerosol chemical composition in boreal forest summer conditions  

NASA Astrophysics Data System (ADS)

Boreal forests are an important biome, covering vast areas of the northern hemisphere and affecting the global climate change via various feedbacks [1]. Despite having relatively few anthropogenic primary aerosol sources, they always contain a non-negligible aerosol population [2]. This study describes aerosol chemical composition measurements using Aerodyne Aerosol Mass Spectrometer (C-ToF AMS, [3]), carried out at a boreal forest area in Hyytil, Southern Finland. The site, Helsinki University SMEAR II measurement station [4], is situated at a homogeneous Scots pine (Pinus sylvestris) forest stand. In addition to the station's permanent aerosol, gas phase and meteorological instruments, during the HUMPPA (Hyytil United Measurements of Photochemistry and Particles in Air) campaign in July 2010, a very comprehensive set of atmospheric chemistry measurement instrumentation was provided by the Max Planck Institute for chemistry, Johannes Gutenberg-University, University of California and the Finnish Meteorological institute. In this study aerosol chemical composition measurements from the campaign are presented. The dominant aerosol chemical species during the campaign were the organics, although periods with elevated amounts of particulate sulfates were also seen. The overall AMS measured particle mass concentrations varied from near zero to 27 ?g/m observed during a forest fire smoke episode. The AMS measured aerosol mass loadings were found to agree well with DMPS derived mass concentrations (r2=0.998). The AMS data was also compared with three other aerosol instruments. The Marga instrument [5] was used to provide a quantitative semi-online measurement of inorganic chemical compounds in particle phase. Fourier Transform Infrared Spectroscopy (FTIR) analysis was performed on daily filter samples, enabling the identification and quantification of organic aerosol subspecies. Finally an Atmospheric Pressure Chemical Ionization Ion Trap Mass Spectrometer (APCI-IT-MS, [6]) was measuring gas and particle phase aerosol composition, offering additional information on molecular compositions. Overall, the availability of a variety of aerosol chemical characterization instruments provided a good opportunity for a comparison of the results obtained by these four very different measurement approaches. Overall the results were found to agree. The inorganic particulate masses measured with the AMS and Marga were found to correlate especially well for sulphates (r2=0.92) and ammonia compounds (r2=0.82). The organic mass seen by the AMS was correlated with the FTIR filter analysis (r2=0.87) and the APCI-IT-MS (r2=0.88).

?ijl, M.; Junninen, H.; Ehn, M.; Petj, T.; Vogel, A.; Hoffmann, T.; Corrigan, A.; Russell, L.; Makkonen, U.; Virkkula, A.; Mntykentt, J.; Kulmala, M.; Worsnop, D.

2012-04-01

129

Chemical and structural evaluation of activated carbon prepared from jute sticks for Brilliant Green dye removal from aqueous solution.  

PubMed

Activated carbons have been prepared from jute sticks by chemical activation using ZnCl(2) and physical activation using steam for the removal of Brilliant Green dye from aqueous solution. The activated carbons and charcoal prepared from jute sticks were characterized by evaluating the surface chemistry, structural features and surface morphology. The maximum BET surface area was obtained to be 2304 m(2)/g for chemical activated carbon (ACC) while it is 730 and 80 m(2)/g for steam activated carbon (ACS) and charcoal, respectively. The FT-IR spectra exhibited that the pyrolysis and steam activation of jute sticks resulted in the release of aliphatic and O-containing functional groups by thermal effect. However, the release of functional groups is the effect of chemical reaction in the ZnCl(2) activation process. A honeycomb-type carbon structure in ACC was formed as observed on SEM images. Although charcoal and ACC were prepared at 500 degrees C the ACC exhibited much lower Raman sensitivity due to the formation of condensed aromatic ring systems. Due to high surface area and high porous structure with abundance of functional groups, the ACC adsorbed dye molecules with much higher efficiency than those of ACS and charcoal. PMID:19815339

Asadullah, Mohammad; Asaduzzaman, Mohammad; Kabir, Mohammad Shajahan; Mostofa, Mohammad Golam; Miyazawa, Tomohisa

2010-02-15

130

Oligo-Glycine Synthesis in an Aqueous Solution of Glycine Under Oxidative Conditions  

NASA Astrophysics Data System (ADS)

Di-and tri-glycine were synthesized in 1M aqueous solution of glycine by bubbling for 90 hr with oxygen discharged in the path from an oxygen cylinder. The peptides were also produced by an incubation at 37C of 2M glycine solution prepared with 75% hydrogen peroxide, and the yields were traced for 200 days. The final yields were about 0.25% and 0.01% for di-and tri-glycine, respectively. The solution at 166 days of incubation was applied to a Sephadex G 10 column, and the fractions around the top of the chromatogram were found to increase the intensity of ninhydrin color about 45 times after hydrolysis, indicating an existence of oligo-glycine. The solutions of 1M glycine and 0.5M diglycine prepared with 30% hydrogen peroxide were incubated at 37C for 38 days, and di-and tetra-glycine were detected in the yields of 0.12% and 0.33%, respectively.

Yamagata, Yukio; Yamashita, Atsunori; Inomata, Katsuhiko

1980-03-01

131

Physical and chemical effects of direct aqueous advanced oxidation processing on green sand foundry mold materials  

NASA Astrophysics Data System (ADS)

Iron foundries using the common green sand molding process have increasingly been incorporating aqueous advanced oxidation (AO) systems to reduce the consumption of sand system bentonite clay and coal raw materials by and to decrease their volatile organic compound (VOC) emissions. These AO systems typically use a combination of sonication, ozone aeration, and hydrogen peroxide to treat and recycle slurries of sand system baghouse dust, which is rich in clay and coal. While the overall effects of AO on raw material consumption and organic emissions are known, the mechanisms behind these effects are not well understood. This research examined the effects of bench-scale direct aqueous AO processing on green sand mold materials at the micro level. Bench-scale AO processing, including acoustic sonication, ozone/oxygen aeration, and hydrogen peroxide dramatically decreased the particle sizes of both western bentonite and foundry sand system baghouse dust. Bench-scale AO processing was shown to effectively separate the clay material from the larger silica and coal particles and to extensively break up the larger clay agglomerates. The acoustic sonication component of AO processing was the key contributor to enhanced clay recovery. Acoustic sonication alone was slightly more effective than combined component AO in reducing the particle sizes of the baghouse dust and in the recovery of clay yields in the supernatant during sedimentation experiments. Sedimentation separation results correlated well with the increase in small particle concentrations due to AO processing. Clay suspension viscosity decreased with AO processing due to enhanced dispersion of the particles. X-ray diffraction of freeze-dried baghouse dust indicated that AO processing does not rehydrate calcined montmorillonite and does not increase the level of interlayer water hydration in the dry clays. Zeta potential measurements indicated that AO processing also does not produce any large changes in the surface charge of the small clay particles upon AO treatment.

Clobes, Jason Kenneth

132

"GREENER" CHEMICAL SYNTHESES USING AN ALTERNATE REACTION CONDITIONS OR AQUEOUS MEDIA  

EPA Science Inventory

A solvent-free approach that involves microwave (MW) exposure of neat reactants (undiluted) catalyzed by the surfaces of recyclable mineral supports such as alumina, silica, clay, or 'doped' surfaces is presented which is applicable to a wide range of cleavage, condensation, cycl...

133

'GREENER' CHEMICAL SYNTHESES USING MICROWAVES UNDER SOLVENT-FREE CONDITIONS OR AQUEOUS MEDIA  

EPA Science Inventory

A solvent-free approach that involves microwave (MW) exposure of neat reactants (undiluted) catalyzed by the surfaces of recyclable mineral supports such as alumina, silica, clay, or 'doped' surfaces is presented which is applicable to a wide range of cleavage, condensation, cycl...

134

Chemical Composition of Meridiani Sediments: Traces of Aqueous Past on Martian Surface  

NASA Astrophysics Data System (ADS)

Measurements of outcrop samples by the Alpha Particle X-Ray Spectrometer (APXS), onboard the NASA Mars Exploration Rover Opportunity at Meridiani, showed strong sulfur peaks in the x-ray spectra. Sulfur concentrations increased from natural (as is) rock surfaces over brushed to abraded rocks that turned out to be sulfur-loaded sediments. Along the 11-kilometer traverse of the rover many abraded surfaces could be measured by the APXS because the softness of the outcrops permitted grinding by the Rock Abrasion Tool (RAT) until today. All outcrop samples exhibited high sulfur concentrations of more than 6 weight percent; some samples exceeded 10 wt-% making S a major element and indicating a special history of these sediments. Element concentrations of all abraded rocks along the traverse were studied as function of sulfur content. A linear relationship with a negative slope was found for the silicon-sulfur pair. A similar relation holds for Al, Na, K, P, Ti, and Cr versus S. Iron shows a weak correlation with S (only a slight negative slope). Constant concentrations are exhibited by Mn and Ni. Calcium, Mg, and Zn, reveal a slight increase with increasing S contents (positive slope). During the first half of the traverse Mg and S are strongly correlated, later almost none. The formation of the sediments can be described by a two-component mixing model, where sulfur is mainly present in one component. The composition of the other component, the siliciclastic material, was extrapolated from above sample compositions to low S contents. The derived siliciclastic composition differs from encountered basaltic material, such as 'Bounce Rock' at Meridiani or the Adirondack Class rocks at Gusev crater, but, is similar to rocks discovered near Home Plate (Gusev). Best compositional matches are found for 'Masada Clod', 'Raquelme3', and others, which are significantly altered from an original basaltic composition. Apparently this composition type is wider spread on the Martian surface. The other mixing component contains various sulfates. Assuming large volcanic exhalations of sulfur, any original aqueous solution became very acidic. 'Normal' rocks were rapidly leached and gradually dissolved to form new compounds and large quantities of sulfates in an aqueous system. To bring the two components together, either wind and/or water did the transport. The small scatter of the concentration data points (mostly around a straight line) suggests that there was a concentration gradient in bodies of standing water on a kilometer-wide scale at least for a short period of time. The concentrations of many elements (Si, Al, Na, K, P, Ti, and Cr) are diluted by increasing sulfur contents. Hence, these elements were mainly part of the siliciclastic component. On the other hand, elements whose concentrations increase with increasing S (e.g. Ca, Mg, and Zn) were part of sulfates and of mafic minerals (in the siliciclastic component). Iron showing some dilution by sulfur was determined by Mssbauer spectroscopy to be present also as ferric sulfate. The above observations reveal that several elements formed sulfates in these sediments: Mg, Ca, Fe, and Zn. An aqueous system existed during the period of sediment formation and left unique traces in the sedimentary composition.

Brueckner, J.; Gellert, R.; D'Uston, C.; Treguier, E.; Squyres, S. W.

2007-12-01

135

Aqueous-based chemical route toward ambient preparation of multicomponent core-shell nanotubes.  

PubMed

Room-temperature synthesized V2O5@MnO2 core-shell nanotubes with tunable tunnel dimensions via a facile aqueous-based method are presented. The rational-designed tubular morphology endows them with good permeability of electrolyte ions for maximum utilization of the electroactive sites, while the epitaxial-grown MnO2 imposes mechanical support to V2O5 against structural collapse upon long-term cycling. Hence, specific capacitance as high as 694 F g(-1) is achieved at 1 A g(-1) accompanied by excellent cycling stability (preserved 92% of its initial specific capacitance after 5000 cycles). In addition, functionalization of the V2O5@MnO2 nanotubes with other transition metal oxides results in ternary composites, V2O5@MnO2/M nanotubes (M = Fe2O3, Co2O3/Co(OH)2, Ni(OH)2). The versatility of this synthetic protocol provides a platform to fabricate complex ternary nanocomposites in a more benign way. PMID:24645828

Tan, Hui Teng; Rui, Xianhong; Yu, Hong; Liu, Weiling; Xu, Chen; Xu, Zhichuan; Hng, Huey Hoon; Yan, Qingyu

2014-04-22

136

Crack size effects on the chemical driving force for aqueous corrosion fatigue  

NASA Astrophysics Data System (ADS)

Small crack size accelerates corrosion fatigue propagation through high strength 4130 steel in aqueous 3 pct NaCl. The size effect is attributed to crack geometry dependent mass transport and electrochemical reaction processes which govern embrittlement. For vacuum or moist air, growth rates are defined by stress intensity range independent of crack size (0.1 to 40 mm) and applied maximum stress (0.10 to 0.95 ?ys). In contrast small (0.1 to 2 mm) surface elliptical and edge cracks in saltwater grow up to 500 times faster than long (15 to 40 mm) cracks at constant ?K. Small cracks grow along prior austenite grain boundaries, while long cracks propagate by a brittle transgranular mode associated with tempered martensite. The small crack acceleration is maximum at low ?K levels and decreases with increasing crack length at constant stress, or with increasing stress at constant small crack size. Reductions in corrosion fatigue growth rate correlate with increased brittle transgranular cracking. Crack mouth opening, proportional to the crack solution volume to surface area ratio, determines the environmental enhancement of growth rate and the proportions of inter- and transgranular cracking. Small cracks grow at rapid rates because of enhanced hydrogen production, traceable to increased hydrolytic acidification and reduced oxygen inhibition within the occluded cell.

Gangloff, R. P.

1985-05-01

137

Ferrate(VI): a green chemical for the oxidation of cyanide in aqueous/waste solutions.  

PubMed

The higher oxidation state of iron, i.e. Fe(VI), was employed for the oxidation of the important toxic ion cyanide in aqueous/waste waters. Cyanide was oxidized to cyanate, which is 1,000 times less toxic than cyanide, and can often be accepted for its ultimate disposal. It was noted that Fe(VI) is a very powerful oxidizing agent, and can oxidize most of the cyanide within a few minutes, ca 5 minutes, of contact. The extent of the reduction of Fe(VI) was obtained using the UV-Visible measurements. Further, the UV-Visible data was used to explain the reaction kinetics involved in the redox reaction between ferrate(VI) and cyanide. The pseudo-first-order rate constant was calculated by maintaining the cyanide concentration in excess, with the overall second order rate constant values obtained for initial Fe(VI) concentrations of 1.0 and 0.1 mmol/L. The oxidation of cyanide was again confirmed using a cyanide probe. Fe(VI) was further employed for its possible application in the treatment of industrial wastewaters containing cyanide, along with some heavy metals, such as those obtained from electroplating industries. PMID:17474007

Tiwari, Diwakar; Kim, Hyoung-Uk; Choi, Bong-Jong; Lee, Seung-Mok; Kwon, Oh-Heung; Choi, Kyu-Man; Yang, Jae-Kyu

2007-05-01

138

Ion-pair solid-phase extraction and gas chromatographymass spectrometric determination of acidic hydrolysis products of chemical warfare agents from aqueous samples  

Microsoft Academic Search

The chemical warfare agents (CWA) degrade rapidly in aqueous samples and convert to acidic degradation products. Extraction and identification of the degradation products from complex matrices using simple sample preparation and sensitive detection and identification is the most important step in the off-site analysis of samples. In this present study, we report a simple sample preparation step based on ion-pair

U. V. R. Vijaya Saradhi; S. Prabhakar; T. Jagadeshwar Reddy; M. Vairamani

2006-01-01

139

SH-SAW Sensor Platform for Chemical Detection in Aqueous Solutions  

SciTech Connect

Chemically sensitive polymers coated on delay lines utilizing shear horizontal surface acoustic wave (SH-SAW) sensors are investigated for the detection of organic analytes in liquid environments. The SH-SAW sensor platform was designed and fabricated on 36{degree} rotated Y-cut LiTaO{sub 3}. By depositing a SiO{sub 2} dielectric layer over the entire device prior to applying the polymer film, partial electrical passivation of the interdigital transducers (IDT) is obtained while increasing the mass sensitivity of the device. Changes in the mechanical properties of the chemically sensitive polymer materials were clearly detectable through a frequency shift at least one order of magnitude larger than that of a coated-quartz crystal resonator (QCR) in a similar experiment.

Casalnuovo, Steve; Cernosek, Richard; Josse, Fabien; Ricco, Antonio; Zhou, Rongnong

1999-07-20

140

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

SciTech Connect

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%.

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

2000-02-01

141

Low temperature aqueous chemical growth, structural, and optical properties of Mn-doped ZnO nanowires  

NASA Astrophysics Data System (ADS)

Mn-doped ZnO nanowires were successfully synthesized by using the low temperature aqueous chemical growth (ACG) method. Field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), X-Ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectroscopy have been used to characterize the grown Zn1-xMnxO. The FESEM and the XRD measurements revealed that the grown of Mn-doped ZnO had wurtzite structure and the lattice parameters and the size of the crystal changed according to the change of concentration of the dopant. The chemical composition and charge states of the Mn ions doped in the ZnO nanowires was analyzed by the EDX and the XPS, respectively, indicated that the Mn ions is incorporated onto zinc sites in the ZnO nanowires. PL spectroscoCpy shows a strong ultraviolet (UV) emission peak at 378 nm (3.27 eV) from the Mn-doped ZnO nanowires, which is shifted 6 nm to the lower wavelength compared to ZnO nanowires grown by the same ACG method. The unique feature of our samples were the simple low temperature growth method which provides no clustering and the as-synthesized Mn-doped ZnO nanowires have shown good crystal quality. This capability to fabricate Mn-doped ZnO nanowires is of potential to develop new spintronic, photonic and sensor devices fabrication on any substrates.

Chey, Chan Oeurn; Nur, Omer; Willander, Magnus

2013-07-01

142

Removal of Cu2+ and Ag+ from aqueous solution on a chemically-carbonized sorbent from date palm leaflets.  

PubMed

A chemically-carbonized sorbent was prepared from date palm leaflets by sulphuric acid treatment at 170 degrees C. Carbonization took place via the dehydration effect of the hot sulphuric acid producing a carbon with reduction property. Sorption of Cu2+ and Ag+ from aqueous solution was investigated in terms of pH, contact time, metal concentration and temperature. A peculiar behaviour was found for the sorption of the two metals on the produced carbon. Sorption of Cu2+ was fast, reaching equilibrium within -2 h, whilst Ag+ sorption was slow and required -60 h to reach equilibrium. Activation energy (E(a)) for Cu2+ sorption was -16.1 kJ/mol indicating a diffusion-controlled ion exchange process; however, E(a) for Ag+ sorption was -44.3 kJ/mol indicating a chemically controlled process. Equilibrium sorption data were tested for the Langmuir and Freundlich equations. Sorption capacity appears to be much higher for Ag+ than for Cu2+ with increased uptake, for both metals, when increasing the temperature (25-45 degrees C). Ag+ was reduced to elemental silver on the sorbent surface and this was confirmed using scanning electron microscopy and x-ray powder diffraction; however, no reduction processes were involved in Cu2+ sorption. This paper discusses the sorption mechanism. PMID:23530353

El-Shafey, El-Said Ibrahim; Al-Kindy, Salma Muhammed Zahran

2013-01-01

143

Effect of the glass composition on the chemical durability of zinc-phosphate-based glasses in aqueous solutions  

NASA Astrophysics Data System (ADS)

The chemical durability of glasses with the composition 40P2O5-55ZnO-1Ga2O3-4Ag2O and 41P2O5-51ZnO-8Ga2O3 (mol%) was studied by measuring the rates of aqueous dissolution in neutral, acidic and alkaline aqueous solutions and discussed as a function of the glass composition. The change in the pH of the solutions as a function of the immersion time of the samples was used to study the dissolution mechanism. Using XRD and SEM/EDXA, we showed that the dissolution in deionized (DI) water and HCl consists of the leaching of the phosphate chains into the medium along with (i) the formation of a hydrated layer with the composition Zn2P2O73H2O and also of AgCl agglomerates when immersed in HCl and (ii) a leaching out of P, Ga and Ag when immersed for more than 180 min in DI water and for more than 60 min in HCl. The dissolution in NaOH-Na2CO3 consists of a net consumption of the OH- along with the formation of layers of Zn3(PO4)2(H2O)4 and Zn(H2PO2)2H2O with no apparent diffusion of P, Ga and Ag when immersed for as long as 240 min. Increasing the Ga2O3 concentration in zinc-phosphate glass at the expense of Ag2O lowers the dissolution rate when immersed in DI water, HCl and NaOH-Na2CO3 probably due to a reinforcement of the glass network.

Massera, J.; Bourhis, K.; Petit, L.; Couzi, M.; Hupa, L.; Hupa, M.; Videau, J. J.; Cardinal, T.

2013-01-01

144

Sorption of nickel (II) from aqueous system by chemically modified pungan (pongamia pinnata) seedpod carbon  

NASA Astrophysics Data System (ADS)

The adsorption of Ni (II) on chemically modified bicarbonate impregnated sulphuric acid treated pungan (pongamia pinnata) seedpod carbon (BSPAC) was investigated as a function of equilibrium time, solution pH and carbon dosage. The adsorption of nickel (II) was also studied by using Freundlich, Langmuir and Temkin isotherm models. Kinetic studies were conducted using reversible-first-order, pseudo-first-order and pseudo-second-order kinetic equations. The results obtained were compared with commercially available activated carbon (CAC) of same 20-50 ASTM mesh size.

Senthil, M.; Arulanantham, A.

2013-06-01

145

BLACK HOLE FORMATION IN PRIMORDIAL GALAXIES: CHEMICAL AND RADIATIVE CONDITIONS  

SciTech Connect

In massive primordial galaxies, the gas may directly collapse and form a single central massive object if cooling is suppressed. H{sub 2} line cooling can be suppressed in the presence of a strong soft-ultraviolet radiation field, but the role played by other cooling mechanisms is less clear. In optically thin gas, Ly{alpha} cooling can be very effective, maintaining the gas temperature below 10{sup 4} K over many orders of magnitude in density. However, the large neutral hydrogen column densities present in primordial galaxies render them highly optically thick to Ly{alpha} photons. In this paper, we examine in detail the effects of the trapping of these Ly{alpha} photons on the thermal and chemical evolution of the gas. We show that despite the high optical depth in the Lyman series lines, cooling is not strongly suppressed, and proceeds via other atomic hydrogen transitions. At densities larger than {approx}10{sup 9} cm{sup -3}, collisional dissociation of molecular hydrogen becomes the dominant cooling process and decreases the gas temperature to about 5000 K. The gas temperature evolves with density as T{proportional_to}{rho}{sup {gamma}{sub eff}}{sup -1}, with {gamma}{sub eff} = 0.97-0.98. The evolution is thus very close to isothermal, and so fragmentation is possible, but unlikely to occur during the initial collapse. However, after the formation of a massive central object, we expect that later-infalling, higher angular momentum material will form an accretion disk that may be unstable to fragmentation, which may give rise to star formation with a top-heavy initial mass function.

Schleicher, Dominik R. G. [ESO Garching, Karl-Schwarzschild-Str. 2, 85748 Garching bei Muenchen (Germany); Spaans, Marco [Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700 AV, Groningen (Netherlands); Glover, Simon C. O. [Zentrum fuer Astronomie der Universitaet Heidelberg, Institut fuer Theoretische Astrophysik, Albert-Ueberle-Str. 2, D-69120 Heidelberg (Germany)], E-mail: dschleic@eso.org

2010-03-20

146

Inhibitory Effect of Berberis vulgaris Aqueous Extract on Acquisition and Reinstatement Effects of Morphine in Conditioned Place Preferences (CPP) in Mice  

PubMed Central

Background: It has been elucidated that Berberis vulgaris (barberry) can alleviate morphine withdrawal syndrome. Also it has been reported that aqueous extract of barberry possibly have inhibitory effect on NMDA receptors. Objectives: In this study, we decided to evaluate the effects of aqueous extract of B. vulgaris fruit on morphine tendency in mice using conditioned place preference (CPP) method. Materials and Methods: In experiment 1 (acquisition phase), mice underwent morphine-induced conditioned place preference (CPP) training with injections of morphine (40 mg/kg). In experiment 2 (extinction and reinstatement phases), mice underwent the same CPP training as in experiment 1 and subsequent extinction training on day 16th a reinstatement by CPP was done by injection of reminding 10 mg/kg morphine. Results: The administration of morphine (40 mg/kg for four days) produced place preference. In the first method, the aqueous extract of barberry (200 mg/kg) prevented morphine tendency to white cell in CPP method. In the second method, after inter-peritoneal injection of aqueous extracts of barberry at 100 and 200 mg/kg, the animals tendency toward the white cells of CPP chamber on the sixteenth day (after a reminder injection of morphine 10 mg/kg) was significantly reduced. Conclusions: These results show that aqueous extract of barberry can reduce the acquisition and reinstatement of morphine-induced conditioned place preference.

Imenshahidi, Mohsen; Qaredashi, Reza; Hashemzaei, Mahmoud; Hosseinzadeh, Hossein

2014-01-01

147

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

SciTech Connect

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.

Boukis, N.; Kritzer, P. [Forschungszentrum Karlsruhe (Germany)

1997-08-01

148

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

SciTech Connect

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.

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

1993-01-01

149

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

SciTech Connect

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.

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

1993-01-01

150

Radiofluorination of diaryliodonium tosylates under aqueous-organic and cryptand-free conditions  

PubMed Central

Positron emission tomography (PET) has growing importance as a molecular imaging technique for clinical research and drug development. Methods for producing PET radiotracers utilizing cyclotron-produced [18F]fluoride ion (t1/2 = 109.7 min) without the need for complete removal of irradiated target [18O]water and addition of cryptand are keenly sought for practical convenience and efficiency. Several structurally diverse diaryliodonium tosylates, XArI+Ar?Y TsO? (X = H or p-MeO), were investigated in a microfluidic apparatus for their reactivity towards radiofluorination with high specific activity (no-carrier-added) [18F]fluoride ion in mixtures of DMF and irradiated target [18O]water in the absence of cryptand. Salts bearing a para or ortho electron-withdrawing group Y (e.g., Y = p-CN) reacted rapidly (~ 3 min) to give the expected major [18F]fluoroarene product, [18F]ArY, in useful moderate radiochemical yields even when the solvent had [18O]water content up to 28%. Salts bearing electron-withdrawing groups in meta position (e.g., Y = m-NO2), or an electron-donating substituent (Y = p-OMe), gave low radiochemical yields under the same conditions. PMID:23804017

Chun, Joong-Hyun; Telu, Sanjay; Pike, Victor W.

2013-01-01

151

Production of chemical alarm cues in convict cichlids: the effects of diet, body condition and ontogeny  

Microsoft Academic Search

While much is known regarding the role of chemical alarm cues in the mediation of predator-prey dynamics within aquatic ecosystems, little is known regarding the production of these critically important information sources. In a series of labora- tory experiments, we tested the possible effects of diet, body condition and ontogeny on the production of chemical alarm cues in juvenile convict

Grant E. Brown; Patricia E. Foam; Hilary E. Cowell; Palestina Guevara Fiore; Douglas P. Chivers

152

SIMULATION OF ECOLOGICALLY CONSCIOUS CHEMICAL PROCESSES: FUGITIVE EMISSIONS VERSUS OPERATING CONDITIONS: JOURNAL ARTICLE  

EPA Science Inventory

NRMRL-CIN-1531A Mata, T.M., Smith*, R.L., Young*, D., and Costa, C.A.V. "Simulation of Ecologically Conscious Chemical Processes: Fugitive Emissions versus Operating Conditions." Paper published in: CHEMPOR' 2001, 8th International Chemical Engineering Conference, Aveiro, Portu...

153

A study of the anatomical and chemical variations occuring in cottonseed grown under varying conditions  

E-print Network

different sections of the Cotton Belt vary in anatomical structure and chemical composition, ST Both c11matic and so11 conditions affect the structure and composition of the seed, with climate, perhaps~ the ma)or factori S Xerio conditions such as eu3... different sections of the Cotton Belt vary in anatomical structure and chemical composition, ST Both c11matic and so11 conditions affect the structure and composition of the seed, with climate, perhaps~ the ma)or factori S Xerio conditions such as eu3...

Latta, James Edwin

2012-06-07

154

Uniting Cheminformatics and Chemical Theory To Predict the Intrinsic Aqueous Solubility of Crystalline Druglike Molecules  

PubMed Central

We present four models of solution free-energy prediction for druglike molecules utilizing cheminformatics descriptors and theoretically calculated thermodynamic values. We make predictions of solution free energy using physics-based theory alone and using machine learning/quantitative structureproperty relationship (QSPR) models. We also develop machine learning models where the theoretical energies and cheminformatics descriptors are used as combined input. These models are used to predict solvation free energy. While direct theoretical calculation does not give accurate results in this approach, machine learning is able to give predictions with a root mean squared error (RMSE) of ?1.1 log S units in a 10-fold cross-validation for our Drug-Like-Solubility-100 (DLS-100) dataset of 100 druglike molecules. We find that a model built using energy terms from our theoretical methodology as descriptors is marginally less predictive than one built on Chemistry Development Kit (CDK) descriptors. Combining both sets of descriptors allows a further but very modest improvement in the predictions. However, in some cases, this is a statistically significant enhancement. These results suggest that there is little complementarity between the chemical information provided by these two sets of descriptors, despite their different sources and methods of calculation. Our machine learning models are also able to predict the well-known Solubility Challenge dataset with an RMSE value of 0.91.0 log S units. PMID:24564264

2014-01-01

155

Passivation of Zn{sub 3}P{sub 2} substrates by aqueous chemical etching and air oxidation  

SciTech Connect

Surface recombination velocities measured by time-resolved photoluminescence and compositions of Zn{sub 3}P{sub 2} surfaces measured by x-ray photoelectron spectroscopy (XPS) have been correlated for a series of wet chemical etches of Zn{sub 3}P{sub 2} substrates. Zn{sub 3}P{sub 2} substrates that were etched with Br{sub 2} in methanol exhibited surface recombination velocity values of 2.8 Multiplication-Sign 10{sup 4} cm s{sup -1}, whereas substrates that were further treated by aqueous HF-H{sub 2}O{sub 2} exhibited surface recombination velocity values of 1.0 Multiplication-Sign 10{sup 4} cm s{sup -1}. Zn{sub 3}P{sub 2} substrates that were etched with Br{sub 2} in methanol and exposed to air for 1 week exhibited surface recombination velocity values of 1.8 Multiplication-Sign 10{sup 3} cm s{sup -1}, as well as improved ideality in metal/insulator/semiconductor devices.

Kimball, Gregory M.; Bosco, Jeffrey P.; Mueller, Astrid M.; Tajdar, Syed F.; Brunschwig, Bruce S.; Atwater, Harry A.; Lewis, Nathan S. [Noyes Laboratory, Watson Laboratory, and Beckman Institute, California Institute of Technology, Pasadena, California 91125 (United States)

2012-11-15

156

A new method of reconstituting the P-T conditions of fluid circulation in an accretionary prism (Shimanto, Japan) from microthermometry of methane-bearing aqueous inclusions  

NASA Astrophysics Data System (ADS)

In paleo-accretionary prisms and the shallow metamorphic domains of orogens, circulating fluids trapped in inclusions are commonly composed of a mixture of salt water and methane, producing two types of fluid inclusions: methane-bearing aqueous and methane-rich gaseous fluid inclusions. In such geological settings, where multiple stages of deformation, veining and fluid influx are prevalent, textural relationships between aqueous and gaseous inclusions are often ambiguous, preventing the microthermometric determination of fluid trapping pressure and temperature conditions. To assess the P-T conditions of deep circulating fluids from the Hyuga unit of the Shimanto paleo-accretionary prism on Kyushu, Japan, we have developed a new computational code, applicable to the H2O-CH4-NaCl system, which allows the characterization of CH4-bearing aqueous inclusions using only the temperatures of their phase transitions estimated by microthermometry: Tmi, the melting temperature of ice; Thyd, the melting temperature of gas hydrate and Th,aq, homogenization temperature. This thermodynamic modeling calculates the bulk density and composition of aqueous inclusions, as well as their P-T isochoric paths in a P-T diagram with an estimated precision of approximatively 10%. We use this computational tool to reconstruct the entrapment P-T conditions of aqueous inclusions in the Hyuga unit, and we show that these aqueous inclusions cannot be cogenetic with methane gaseous inclusions present in the same rocks. As a result, we propose that pulses of a high-pressure, methane-rich fluid transiently percolated through a rock wetted by a lower-pressure aqueous fluid. By coupling microthermometric results with petrological data, we infer that the exhumation of the Hyuga unit from the peak metamorphic conditions was nearly isothermal and ended up under a very hot geothermal gradient. In subduction or collision zones, modeling aqueous fluid inclusions in the ternary H2O-CH4-NaCl system and not simply in the binary H2O-NaCl is necessary, as the addition of even a small amount of methane to the water raises significantly the isochores to higher pressures. Our new code provides therefore the possibility to estimate precisely the pressure conditions of fluids circulating at depth.

Raimbourg, Hugues; Thiry, Rgis; Vacelet, Maxime; Ramboz, Claire; Cluzel, Nicolas; Le Trong, Emmanuel; Yamaguchi, Asuka; Kimura, Gaku

2014-01-01

157

The direct agglutination test for diagnosis of visceral leishmaniasis under field conditions in Sudan: comparison of aqueous and freeze-dried antigens  

Microsoft Academic Search

The performance of the direct agglutination test (DAT) was evaluated under field conditions in an endemic area of visceral leishmaniasis in eastern Sudan, using aqueous (Aq) antigen which has to be kept refrigerated and a newly developed freeze-dried (FD) antigen which is stable at ambient temperature. Both antigens compared well, with 9298% of readings being identical or only with one

E. E. Zijlstra; O. F. Osman; H. W. Chr. Hofland; L. Oskam; H. W. Ghalib; A. M. El-Hassan; P. A. Kager; S. E. O. Meredith

1997-01-01

158

Polymerization of amino acids under high-pressure conditions: Implication to chemical evolution on the early Earth  

NASA Astrophysics Data System (ADS)

Prebiotic polymerization of amino acids is the most fundamental reaction to promote the chemical evolution for origin of life. Polymerization of amino acids is the dehydration reaction. This questions as to if submarine hydrothermal conditions, thus hydrated enironments, were appropreate for peptide formations. Our previous experiments implied that non-aqueous and high-pressure environments (more than 20 MPa) would be suitable for polymerization of amino acids (Ohara et al., 2006). This leads to the hypothesis that the first peptides may have formed in the Hadean oceanic crustal environments, where dehydration proceeded with availability of appropriate temperatures and pressures. In the present study, experiments simulating the crustal conditions were performed with various pressures (1-175 MPa) and temperatures (100- 200 C degree) using autoclaves. Purified powders (100 mg) of alanine, glycine, valine and aspartic acid were used in the experiments without mixing water in order to examine the solid-solid reactions. The products were analyzed using HPLC and LC-MS. Results indicate that: (1) longer time is required to form peptide compared to those of previous aqueous experiments; (2) pressure has a role to limit the production of melanoidine and cyclic amino acids, which are inhibitors for elongation of peptides; (3) glycine was polymerized up to 11-mer, which was not formed in any previous experiments without catalyses; (4) valine was polymerized up to 3-mer; and (5) aspartic acid was polymerized to 4-mer, accompanied with production of other amino acids. It is noteworthy that high-pressure environments favor all examined polymerization reactions. Such situations would have happened inside of deep oceanic crusts of the early Earth.

Kakegawa, T.; Ohara, S.; Ishiguro, T.; Abiko, H.; Nakazawa, H.

2008-12-01

159

XAFS measurements on zinc chloride aqueous solutions from ambient to supercritical conditions using the diamond anvil cell  

USGS Publications Warehouse

The structure and bonding properties of metal complexes in subcritical and supercritical fluids are still largely unknown. Conventional high pressure and temperature cell designs impose considerable limitations on the pressure, temperature, and concentration of metal salts required for measurements on solutions under supercritical conditions. In this study, we demonstrate the first application of the diamond anvil cell, specially designed for x-ray absorption studies of first-row transition metal ions in supercritical fluids. Zn K-edge XAFS spectra were measured from aqueous solutions of 1-2m ZnCl2 and up to 6m NaCl, at temperatures ranging from 25-660 ??C and pressures up to 800 MPa. Our results indicate that the ZnCl42- complex is predominant in the 1m ZnCl2/6m NaCl solution, while ZnCl2(H2O)2 is similarly predominant in the 2m ZnCl2 solution, at all temperatures and pressures. The Zn-Cl bond length of both types of chlorozinc(II) complexes was found to decrease at a rate of about 0.01 A??/100 ??C.

Mayanovic, R. A.; Anderson, A. J.; Bassett, W. A.; Chou, I. -M.

1999-01-01

160

Rare-earth metal oxide doped transparent mesoporous silica plates under non-aqueous condition as a potential UV sensor.  

PubMed

Transparent mesoporous silica plates doped with rare-earth metal oxide were prepared using solvent-evaporation method based on the self-organization between structure-directing agent and silicate in a non-aqueous solvent. A triblock copolymer, Pluronic (F127 or P123), was used as the structure-directing agent, while tetraethyl orthosilicate (TEOS) was used as a silica source. The pore diameter and the surface area of the mesoporous silica plate prepared with the optimized conditions were ca 40 A and 600 m2 g(-1), respectively, for both structure-directing agent. Rare-earth metal oxides (Eu, Tb, Tm oxide) in mesochannel were formed via one-step synthetic route based on the preparation method of a silica plate. Optical properties of rare-earth metal oxide-doped mesoporous silica plates were investigated by UV irradiation and photoluminescence (PL) spectroscopy. Under the exitation wavelength of 254 nm, the doped mesoporous silica plates emitted red, green and blue for Eu, Tb and Tm oxides, respectively. Rare-earth metal oxide-doped mesoporous silica plates showed enhanced PL intensity compared to that of the bulk rare-earth metal oxide. PMID:24245274

Lee, Sang-Joon; Park, Sung Soo; Lee, Sang Hyun; Hong, Sang-Hyun; Ha, Chang-Sik

2013-11-01

161

Conditions for defect-free solidification of aqueous ammonium chloride in a quasi two-dimensional directional solidification facility  

NASA Astrophysics Data System (ADS)

Experimental and theoretical approaches to the problem of the solidification of a binary melt are presented. We describe a series of experiments in which aqueous solutions of ammonium chloride of above eutectic composition are cooled from below in a Hele-Shaw cell that is translated downwards at a constant rate. A mushy layer of solid dendrites bathed in a salt-depleted interstitial fluid is formed. For certain combinations of initial concentration and translation speed, convection in the mush gives rise to chimneys which result in defects in the solidified material. Our experiments demonstrate that using a higher temperature gradient for solidification increases the range of conditions for which a mushy layer forms that is free from both chimneys and secondary nucleation. We present a mathematical model of the system, to which we derive an approximate analytical solution. Predictions of the height of the mushy layer given by this approximate solution are found to be in excellent agreement with full numerical predictions when the height is small. Both numerical and analytical predictions are a better match to experimental data when the temperature gradient is low.

Whiteoak, S. H.; Huppert, Herbert E.; Worster, M. Grae

2008-07-01

162

Radiation chemical experiments relevant to studies of cometary nuclei: remarks on working conditions.  

PubMed

We survey some obstacles that a chemist encounters in defining conditions for radiation chemical experiments relevant to cometary nuclei. The choice of working conditions is examined in the light to present knowledge about comets and the facilities available for routine work in radiation chemistry. PMID:11537764

Draganic, I G; Draganic, Z D

1984-01-01

163

Chemical changes in the non-volatile fraction of Brazilian honeys during storage under tropical conditions  

Microsoft Academic Search

The chemical transformations of the non-volatile fraction of Brazilian honeys during storage in tropical condition were monitored. Five systems, namely: 1 fresh samples; 2 and 3 samples heated for 3 and 6 months at 3540C; 4 and 5 samples left under similar conditions to systems 2 and 3, but containing sodium metabisulphite (120ppm), were tested. The major

Ricardo F. A. Moreira; Carlos A. B. De Maria; Mrcia Pietroluongo; Luiz C. Trugo

2007-01-01

164

CO-conditioning and dewatering of chemical sludge and waste activated sludge  

Microsoft Academic Search

The conditioning and dewatering behaviors of chemical and waste activated sludges from a tannery were studied. Capillary suction time (CST), specific resistance to filtration (SRF), and bound water content were used to evaluate the sludge dewatering behaviors. Zeta potentials were also measured. Experiments were conducted on each sludge conditioned and dewatered separately, and on the sludge mixed at various ratios.

G. R Chang; J. C Liu; D. J Lee

2001-01-01

165

An integrated approach to optimize the conditioning chemicals for enhanced sludge conditioning in a pilot-scale sludge dewatering process.  

PubMed

An integrated approach incorporating response surface methodology (RSM), grey relational analysis, and fuzzy logic analysis was developed to quantitatively evaluate the conditioning chemicals in sludge dewatering process. The polyacrylamide (PAM), ferric chloride (FeCl(3)) and calcium-based mineral powders were combined to be used as the sludge conditioners in a pilot-scale sludge dewatering process. The performance of conditioners at varied dosages was comprehensively evaluated by taking into consideration the sludge dewatering efficiency and chemical cost of conditioner. In the evaluation procedure, RSM was employed to design the experiment and to optimize the dosage of each conditioner. The grey-fuzzy logic was established to quantify the conditioning performance on the basis of grey relational coefficient generation, membership function construction, and fuzzy rule description. Based on the evaluation results, the optimal chemical composition for conditioning was determined as PAM at 4.62 g/kg DS, FeCl(3) at 55.4 g/kg DS, and mineral powders at 30.0 g/kg DS. PMID:22858481

Zhai, Lin-Feng; Sun, Min; Song, Wei; Wang, Gan

2012-10-01

166

Chemical Compositional Indications of Aqueous Alteration for Whitewater Lake Boxworks, Veneers and Veins at Cape York, Mars  

NASA Astrophysics Data System (ADS)

An area of partially-veneered, flat-lying rocks which also includes boxwork and linear veins contains a variety of compositions which are each indicative of minor to major aqueous alteration processes in the Cape York rim of Endeavour Crater. As analyzed by APXS x-ray fluorescence spectroscopy, the sets of unique elemental compositions correspond variously to Al-Si rich clays in boxwork veins, with Fe- and Cl-enriched salt veneers (Esperance samples); swarms of Ca sulfate veins (Ortiz samples); and, as indicated by remote sensing, mafic smectite alteration products in veneers (Chelmsford covering Azilda samples). Multiple offset analyses by APXS reveal clear trends and associations of certain elements, allowing inferences of mineralogies. In contrast to the acidic environment deduced for the genesis of the multiple-sulfate Burns formation sediments and shallow ferric-rich sulfate deposits beneath soils, these alteration products formed at more near-neutral pH, often with major chemical segregations and requiring high water-rock ratios comparable to a wide range of eminently habitable terrestrial environments. Several of these compositions are also rated high with respect to their potential for preservation of organic materials and biomarkers. Within distances of just tens of meters inside this so-called Whitewater Lake unit, this broad diversity exemplifies the tantalizing opportunities as well as challenges for future sample return missions to the red planet, which in this case could also be expanded to include nearby samples of Burns Fm sandstones, hematite concretions, light-toned spherules (Kirkwood), large gypsum veins (Homestake), martian global soils and surface dust.

Clark, Benton; Gellert, R.; Squyres, S.; Arvidson, R.; Yen, A.; Rice, J.; Athena Science Team

2013-10-01

167

Aqueous solution-chemical derived Nisbnd Al2O3 solar selective absorbing coatings. 2. Wetting agents and spreading of aqueous solutions on aluminum substrate  

NASA Astrophysics Data System (ADS)

Wettability of aluminum substrate by the aqueous solutions containing ethoxylated alcohol nonionic surfactants C12En- or Triton X-series was studied using dynamic contact angle measurements. The efficiency of wetting was found to strongly depend on the length of polyoxyethylene (POE) chain of C12En- or Triton X surfactants. For C12E4 that has a very short POE chain, it hardly made the aqueous solution spreading over aluminum. The others with a long POE chain were indeed very efficient in promoting the solution spreading. Moreover, all the spreading process could be completed within 10 s. The single-layer Nisbnd Al2O3 coatings were fabricated from the precursor solutions containing C12En- or Triton X surfactants and the reflectance spectra were measured by a UV/vis spectrophotometer equipped with an integrating sphere. The results indicated that the precursor solution with a long POE chain surfactant as wetting agent favored to fabricate a uniform film on the aluminum substrate and therefore to get a high solar absorptance.

Li, Zhenxiang; Zhao, Jianxi

2013-03-01

168

Variability of physico-chemical conditions in 950?N EPR diffuse flow vent habitats  

Microsoft Academic Search

The physico-chemical characteristics of habitats have been considered to be one of the prime determinants of animal distribution within hydrothermal vent sites. However, the relative importance of abiotic to biotic influences is still debated. The primary aim of this study is twofold. The first is to determine and compare the ranges of physico-chemical conditions that characterize mussel-dominated and tubeworm-dominated communities

N. Le Bris; B. Govenar; C. Le Gall; C. R. Fisher

2006-01-01

169

Variability of physico-chemical conditions in 9850VN EPR diffuse flow vent habitats  

Microsoft Academic Search

Abstract The physico-chemical characteristics of habitats have,been,considered to be one of the prime determinants,of animal distribution within hydrothermal vent sites. However, the relative importance of abiotic to biotic influences is still debated. The primary aim of this study is twofold. The first is to determine and compare,the ranges of physico-chemical conditions that characterize mussel-dominated and tubeworm-dominated communities,at different sites within

N. Le Bris; B. Govenar Supbs; C. Le Gall; C. r. Fisher

2006-01-01

170

Effects of physical conditioning on heat tolerance in chemical-defense gear. Master's thesis  

SciTech Connect

Today the threat of chemical warfare is real. The only effective defense is the use of chemical defense gear and gas masks. Since they render chemical-warfare gases and liquids impermeable to penetration, they also prohibit sweat evaporation in conditions of thermal stress and thus, contribute to heat illness development. Historically, it has been the hot, humid tropics where United Nation's peacekeeping forces have been called, thus the use of chemical-defense gear in these regions is a realistic possibility and heat illness could affect the outcome of any mission carried out there. The human body only operates within a narrow range of core temparatures, and heat illness is the result of a breakdown in homeostasis. Many factors influence heat tolerance, thus maintaining core temperature within a safe range. Adequate hydration, acclimitization to heat, low body weight, young age, low alcohol intake, and physical fitness all contribute to heat tolerance. This proposal attempts to look specifically at the effect of physical conditioning on heat tolerance in chemical-defense gear as a possible solution to the heat-stress problem noted in this gear. Trainee graduates attending technical training schools at Lackland AFB, Texas, will be tested for maximum oxygen uptake (VO/2max) and heat tolerance time (HTT) in chemical defense gear on bicycle ergometers at Brooks AFB, Texas. Half of these subjects will be physically conditioned for 12 weeks.

Nauss, M.M.

1986-06-01

171

Fabrication of core-shell structured nanoparticle layer substrate for excitation of localized surface plasmon resonance and its optical response for DNA in aqueous conditions  

Microsoft Academic Search

LSPR from nanostructured noble metals such as gold and silver offers great potential for biosensing applications. In this study, a core-shell structured nanoparticle layer substrate was fabricated and the localized surface plasmon resonance (LSPR) optical characteristics were investigated for DNA in aqueous conditions. Factors such as DNA length dependence, concentration dependence, and the monitoring of DNA aspects (ssDNA or dsDNA)

Tatsuro Endo; Daisuke Ikeda; Yukari Kawakami; Yasuko Yanagida; Takeshi Hatsuzawa

2010-01-01

172

QUANTITATIVE ANALYSIS OF AQUEOUS SPECIES USING RAMAN SPECTROMETRY AND EQUILIBRIUM MODEL CALCULATIONS  

EPA Science Inventory

An analytical approach of quantifying various chemical species, using Raman spectrometry in conjunction with equilibrium modeling, has been tested on aqueous solutions containing Nd, Cu, and dipicolinic acid. Equilibrium modeling was used to select optimum conditions in simple so...

173

ACCURACY OF PESTICIDE REFERENCE STANDARD SOLUTIONS. PART II. CHEMICAL STABILITY UNDER FOUR STORAGE CONDITIONS  

EPA Science Inventory

A study was undertaken to assess the long-term chemical stability of dilute standard pesticide solutions of 4 compound classes. The solutions were studied under 4 storage conditions: freezer at -15C; refrigerator at 3C; ambient temperature in the dark; and ambient temperature on ...

174

Conditions for defect-free solidification of aqueous ammonium chloride in a quasi two-dimensional directional solidification facility  

Microsoft Academic Search

Experimental and theoretical approaches to the problem of the solidification of a binary melt are presented. We describe a series of experiments in which aqueous solutions of ammonium chloride of above eutectic composition are cooled from below in a HeleShaw cell that is translated downwards at a constant rate. A mushy layer of solid dendrites bathed in a salt-depleted interstitial

S. H. Whiteoak; Herbert E. Huppert; M. Grae Worster

2008-01-01

175

Solubilization and desorption of PAHs in soil-aqueous system by biosurfactants produced from Pseudomonas aeruginosa P-CG3 under thermophilic condition.  

PubMed

Surface-active agents (surfactants) can enhance bioremediation of soils contaminated with PAHs by reducing sorption of PAHs or increasing desorption rates. The effectiveness of nonionic surfactant (Tween 80) and biosurfactants to enhance the solubilization and desorption of phenanthrene (Phe) and pyrene (Pyr) in soil-aqueous systems under thermophilic conditions was investigated using batch studies. Tween 80 and biosurfactants produced from Pseudomonas aeruginosa strain, ATCC 9027 and a strain isolated in our laboratory, P-CG3 were tested in this study. The results showed that all the surfactants could effectively enhance the solubility of both Phe and Pyr under thermophilic condition (55 degrees C), which was linearly proportional to the concentrations of surfactants at concentrations above their respective critical micelle concentration (CMC). When the surfactants' concentrations in aqueous phase were above their respective CMCs, substantial amounts of PAHs were desorbed from soil into the aqueous phase. Among the three surfactants used, the biosurfactant produced from our own isolate, P-CG3 was more effective in enhancing the solubilization and desorption of PAHs, implying that it might have the potential to be further applied in the bioremediation of PAH contaminated soils. PMID:15551830

Cheng, K Y; Zhao, Z Y; Wong, J W C

2004-10-01

176

Chemical Composition and Antimicrobial Potential of Aqueous Distillate Volatiles of Indian Peppermint (Mentha piperita) and Spearmint (Mentha spicata)  

Microsoft Academic Search

During the process of distillation, the hydrophilic part of the essential oil dissolves in the aqueous distillate that is generally considered waste and discarded. The decanted (main essential oil) and hydrophilic (recovered essential oil) fractions of peppermint (Mentha piperita cv Kukrail) and spearmint (Mentha spicata cv MSS-5) essential oils were investigated by gas chromatography and gas chromatographymass spectrometry. The decanted

Ram Swaroop Verma; Vandana Pandey; Rajendra Chandra Padalia; Dharmendra Saikia; Binay Krishna

2011-01-01

177

Supplementary Material for: A Comparison of the chemical sinks of atmospheric organics in the gas and aqueous  

E-print Network

value was predicted theoretically based on structure from (Kwok and Atkinson, 1995). Acid dissociation+09 Ervens 2003 4.38333E13 NIST Kinetics NAV acetic acid 64197 4.10E+03 6200 Sander, S.P. 2011 1.70E: List of aqueous and gas phase rate constants and their references. "NAV" indicates that data were

Nizkorodov, Sergey

178

Universal reaction mechanism of boronic acids with diols in aqueous solution: kinetics and the basic concept of a conditional formation constant.  

PubMed

To establish a detailed reaction mechanism for the condensation between a boronic acid, RB(OH)2, and a diol, H2L, in aqueous solution, the acid dissociation constants (Ka(BL)) of boronic acid diol esters (HBLs) were determined based on the well-established concept of conditional formation constants of metal complexes. The pKa values of HBLs were 2.30, 2.77, and 2.00 for the reaction systems, 2,4-difluorophenylboronic acid and chromotropic acid, 3-nitrophenylboronic acid and alizarin red?S, and phenylboronic acid and alizarin red?S, respectively. A general and precise reaction mechanism of RB(OH)2 with H2L in aqueous solution, which can serve as a universal reaction mechanism for RB(OH)2 and H2L, was proposed on the basis of (a)?the relative kinetic reactivities of the RB(OH)2 and its conjugate base, that is, the boronate ion, toward H2L, and (b)?the determined pKa values of HBLs. The use of the conditional formation constant, K', based on the main reaction: RB(OH)2 + H2L (K1)? RB(L)(OH)(-) + H3O(+) instead of the binding constant has been proposed for the general reaction of uncomplexed boronic acid species (B') with uncomplexed diol species (L') to form boronic acid diol complex species (esters, BL') in aqueous solution at pH?5-11: B' + L' (K')? BL'. The proposed reaction mechanism explains perfectly the formation of boronic acid diol ester in aqueous solution. PMID:25169423

Furikado, Yuki; Nagahata, Tomomi; Okamoto, Takuya; Sugaya, Tomoaki; Iwatsuki, Satoshi; Inamo, Masahiko; Takagi, Hideo D; Odani, Akira; Ishihara, Koji

2014-10-01

179

Use of pervaporation to separate butanol from dilute aqueous solutions: Effects of operating conditions and concentration polarization  

Microsoft Academic Search

This study deals with the separation of n-butanol from aqueous solutions by pervaporation. The effects of feed concentration, temperature, and membrane thickness on the separation performance were investigated. Over the low feed butanol concentration range (0.030.4wt%) studied, the butanol flux was shown to increase proportionally with an increase in the feed butanol concentration, whereas the water flux was relatively constant.

Elsayed A. Fouad; Xianshe Feng

2008-01-01

180

New aqueous magnetic fluids  

Microsoft Academic Search

New aqueous magnetic fluids constituted of nickel-zinc ferrite particles are synthesized using a soft chemical approach. Ferrofluids and solid particles are characterized using several techniques : chemical analysis, X-ray diffraction, transmission electron microscopy, infrared spectroscopy, and magnetization measurements.The stability of the aqueous magnetic fluids is studied as a function of pH and their magnetization is measured as a function of

D. Zins; V. Cabuil; R. Massart

1999-01-01

181

DETERMINATION OF STABLE VALENCE STATES OF CHROMIUM IN AQUEOUS AND SOLID WASTE MATRICES - EXPERIMENTAL VERIFICATION OF CHEMICAL BEHAVIOR  

EPA Science Inventory

The objective of the research effort was to experimentally assess the chemical behavior of the stable species of chromium during the preparation, chemical manipulation, and spectrophotometric analyses of simulated and authentic environmental samples for hexavalent chromium. The d...

182

Potential Usage of Aqueous Alum for Decomposition of Chemical Warfare Agents. Part 2: Reactions with VX and QL.  

National Technical Information Service (NTIS)

The destruction of chemical warfare agents (CWA's), particularly 0- ethyl- S- 2-(diisopropylamino)ethyl methyiphosponothiolate (VX), has been the focus of many articles in the popular media and in professional news journals such as Chemical and Engineerin...

D. J. Williams, V. L. Bevilacqua, W. R. Creasy, D. J. McGarvey, J. S. Rice

2006-01-01

183

Reduction of antitumour mitosenes in non-aqueous and aqueous environment. An electron spin resonance and cyclic voltammetry study  

Microsoft Academic Search

Chemical reduction of mitosenes under aerobic conditions in DMSO showed characteristic ESR signals of the mitosene derived semiquinone free radicals. However, these signals diminished strongly upon addition of water to the reaction mixture, indicating a short lifetime of the mitosene semiquinone free radicals under aqueous conditions. In addition, enzymatic one-electron reduction of these mitosenes with either xanthine oxidase or purified

Marc Maliepaard; Mol de Nico J; Lambert H. M. Janssen; Arnold R. Goeptar; Johan M. Te Koppele; Nico P. E. Vermeulen; Willem Verboom; David N. Reinhoudt

1995-01-01

184

Effect of cooling condition on chemical vapor deposition synthesis of graphene on copper catalyst.  

PubMed

Here, we show that chemical vapor deposition growth of graphene on copper foil is strongly affected by the cooling conditions. Variation of cooling conditions such as cooling rate and hydrocarbon concentration in the cooling step has yielded graphene islands with different sizes, density of nuclei, and growth rates. The nucleation site density on Cu substrate is greatly reduced when the fast cooling condition was applied, while continuing methane flow during the cooling step also influences the nucleation and growth rate. Raman spectra indicate that the graphene synthesized under fast cooling condition and methane flow on cool-down exhibit superior quality of graphene. Further studies suggest that careful control of the cooling rate and CH4 gas flow on the cooling step yield a high quality of graphene. PMID:25386721

Choi, Dong Soo; Kim, Keun Soo; Kim, Hyeongkeun; Kim, Yena; Kim, TaeYoung; Rhy, Se-Hyun; Yang, Cheol-Min; Yoon, Dae Ho; Yang, Woo Seok

2014-11-26

185

Studies of the condition of insulation in aged power transformers. 2. Fundamental electrical and chemical considerations  

Microsoft Academic Search

For pt.1 see ibid. vol.2, p.1116-19 (July 1991). The authors address the question of remanent life in the insulation of aged power transformers. After reviewing the current techniques available for studying the condition of such insulation, new techniques are proposed based on sensitive analytical instrumentation recently developed for the scientific study of the chemical and physical structure of degraded synthetic

M. Darveniza; D. Hill; T. Le; T. K. Saha

1991-01-01

186

Relative toxicity of pyrolysis gases from materials - Effects of chemical composition and test conditions  

NASA Technical Reports Server (NTRS)

Relative toxicity test data on 270 materials are presented, based on test procedures developed at the University of San Francisco. The effects of chemical composition, using data on 13 types of synthetic polymers and eight types of fabrics, are discussed. Selected materials were evaluated using nine test conditions with the USF method, and using methods developed at the FAA Civil Aeromedical Institute, Douglas Aircraft Company and San Jose State University.

Hilado, C. J.; Cumming, H. J.

1978-01-01

187

Effect of Rare Earth Oxide Content on Nanograined Base Metal Electrode Multilayer Ceramic Capacitor Powder Prepared by Aqueous Chemical Coating Method  

NASA Astrophysics Data System (ADS)

The aqueous chemical coating route is highly effective in preparing BaTiO3 nanoparticles uniformly coated with additives. Such nanoparticles can be used to produce nano-grained temperature stable BaTiO3 ceramics with core-shell structure, fulfilling the need of next-generation ultrathin layer base metal electrode (BME) multilayer ceramic capacitors (MLCCs). Rare earth oxides are an important class of additives owing to their ability to fulfill both donor and acceptor roles. In this paper, the effects of Y2O3 and Ho2O3 co-dopant content on dielectric and microstructural properties were investigated. By applying chemical coating, BaTiO3-based high performance temperature stabilized ceramics with the average grain size of about 130 nm, which met the requirement of next generation BME MLCCs, were obtained.

Zhang, Yichi; Wang, Xiaohui; Kim, Jinyong; Li, Longtu

2013-02-01

188

Quantum-chemical and experimental modeling of hydrogen peroxide generation in heterogenous aqueous surroundings, which contain dibenzo-p-dioxines or their analogues  

NASA Astrophysics Data System (ADS)

A hypothetical molecular mechanism of previously unknown way of toxic action of dibenzo-p-dioxin derivatives has been suggested and demonstrated on the basis of quantum-chemical investigations. The main stages of this process are as follows: protonization of oxygen atom of dioxin ring on the surface of biomembrane; interaction of dioxin with oxygen of oxidized cytochrome P-450; as a result, this xenobiotic becomes a catalyst in the generation of active forms of oxygen (H IIO II, O II -, 3O II, etc.). The process may become cyclic if the initial state of dibenzo-p-dioxin is restored. In this case dibenzo-p-dioxines can be considered as carriers of electrons. The hypothesis we are coming up with has been tested by means of comparatively simple experimental models based on the well-known chemical model of cytochrome P-450. Generation of hydrogen peroxide in heterogeneous aqueous media containing dioxanes derivatives has been experimentally proven.

Kuznetsova, Nina B.; Kuznetsov, Pavel E.; Vlasov, Igor A.; Mikhirev, Dmitry A.

2006-07-01

189

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

USGS Publications Warehouse

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.

Mayanovic, R.A.; Jayanetti, S.; Anderson, A.J.; Bassett, W.A.; Chou, I.-M.

2003-01-01

190

Laboratory studies of the aqueous-phase oxidation of polyols: submicron particles vs. bulk aqueous solution  

NASA Astrophysics Data System (ADS)

Oxidation in the atmospheric aqueous phase (cloud droplets and deliquesced particles) has received recent attention as a potential pathway for the formation of highly oxidized organic aerosol. Most laboratory studies of aqueous-phase oxidation, however, are carried out in bulk solutions rather than aqueous droplets. Here we describe experiments in which aqueous oxidation of polyols (water-soluble species with chemical formula CnH2n+2On) is carried out within submicron particles in an environmental chamber, allowing for significant gas-particle partitioning of reactants, intermediates, and products. Dark Fenton chemistry is used as a source of hydroxyl radicals, and oxidation is monitored using a high-resolution aerosol mass spectrometer (AMS). Aqueous oxidation is rapid, and results in the formation of particulate oxalate; this is accompanied by substantial loss of carbon to the gas phase, indicating the formation of volatile products. Results are compared to those from analogous oxidation reactions carried out in bulk solution. The bulk-phase chemistry is similar to that in the particles, but with substantially less carbon loss. This is likely due to differences in partitioning of early-generation products, which evaporate out of the aqueous phase under chamber conditions (in which liquid water content is low), but remain in solution for further aqueous processing in the bulk phase. This work suggests that the product distributions from oxidation in aqueous aerosol may be substantially different from those in bulk oxidation experiments. This highlights the need for aqueous oxidation studies to be carried out under atmospherically relevant partitioning conditions, with liquid water contents mimicking those of cloud droplets or aqueous aerosol.

Daumit, K. E.; Carrasquillo, A. J.; Hunter, J. F.; Kroll, J. H.

2014-05-01

191

Laboratory studies of the aqueous-phase oxidation of polyols: submicron particles vs. bulk aqueous solution  

NASA Astrophysics Data System (ADS)

Oxidation in the atmospheric aqueous phase (cloud droplets and deliquesced particles) has received recent attention as a potential pathway for the formation of highly oxidized organic aerosol. Most laboratory studies of aqueous-phase oxidation, however, are carried out in bulk solutions rather than aqueous droplets. Here we describe experiments in which aqueous oxidation of polyols (water-soluble species with chemical formula CnH2n+2On) is carried out within submicron particles in an environmental chamber, allowing for significant gas-particle partitioning of reactants, intermediates, and products. Dark Fenton chemistry is used as a source of hydroxyl radicals, and oxidation is monitored using a high-resolution aerosol mass spectrometer (AMS). Aqueous oxidation is rapid, and results in the formation of particulate oxalate; this is accompanied by substantial loss of carbon to the gas phase, indicating the formation of volatile products. Results are compared to those from analogous oxidation reactions carried out in bulk solution. The bulk-phase chemistry is similar to that in the particles, but with substantially less carbon loss. This is likely due to differences in partitioning of early-generation products, which evaporate out of the aqueous phase under chamber conditions (in which liquid water content is low), but remain in solution for further aqueous processing in the bulk phase. This work suggests that the product distributions from oxidation in aqueous aerosol may be substantially different from those in bulk oxidation experiments. This highlights the need for aqueous oxidation studies to be carried out under atmospherically relevant partitioning conditions, with liquid water contents mimicking those of cloud droplets or aqueous aerosol.

Daumit, K. E.; Carrasquillo, A. J.; Hunter, J. F.; Kroll, J. H.

2014-10-01

192

APPLICATION OF THE TRADESCANTIA MICRONUCLEUS ASSAY FOR THE GENETIC EVALUATION OF CHEMICAL MIXTURES IN SOIL AND AQUEOUS MEDIA  

EPA Science Inventory

Genotoxic evaluation of nine binary and one tertiary mixtures of arsenic trioxide, dieldrin, and lead tetraacetate were performed using the Tradescantia micronucleus (Trad-MN) assay. he chemical mixtures were either (I) mixed into soil, and chemical exposure to the target cells w...

193

Chemical kinetic modeling of chlorinated hydrocarbons under stirred-reactor conditions  

SciTech Connect

The combustin of chloroethane is modeled as a stirred reactor so that we can study critical emission characteristics of the reactor as a function of residence time. We examine important operating conditions such as pressure, temperature, and equivalence ratio and their influence on destructive efficiency of chloroethane and production of other chlorinated products. The model uses a detailed chemical kinetic mechanism that we have developed previously for C{sub 3} hydrocarbons. We have added to this mechanism the chemical kinetic mechanism for C{sub 2} chlorinated hydrocarbons developed by Senkan and coworkers. Some reactions have been added to Senkan's mechanism and some of the reaction-rate expressions have been updated to reflect recent developments in the literature. In the modeling calculations, sensitivity coefficients are determined to find which reaction-rate constants have the largest effect on destructive efficiency. 25 refs., 6 figs., 1 tab.

Pitz, W.J.; Westbrook, C.K.

1990-10-04

194

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

NASA Astrophysics Data System (ADS)

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.

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

2013-01-01

195

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

SciTech Connect

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.

Kritzer, P.; Boukis, N.; Dinjus, E. [Forschungszentrum Karlsruhe (Germany)

1998-12-31

196

Bake condition effect on hybrid lithography process for negative-tone chemically amplified resists  

NASA Astrophysics Data System (ADS)

This paper presents the process optimization study of negative tone Chemically Amplified Resists (CAR) under E-Beam exposure. The importance of post apply bake temperature choice on resolution is underlined. The process study determines the process window in which optimal conditions of both post apply and post exposure bake steps are defined and present a method to define more precisely the thermal cross-linking onset. Finally lithographic performances of CARs are studied and we show that resolution can be pushed down to 40 nm.

Pain, Laurent; Sala, F.; Higgins, C.; Dal'zotto, B.; Tedesco, Serge V.

2000-06-01

197

Indium adsorption on GaN under metal-organic chemical vapor deposition conditions  

NASA Astrophysics Data System (ADS)

Real-time synchrotron grazing-incidence x-ray fluorescence is employed to study indium adsorption on the GaN (0001) surface under typical process conditions for InGaN metal-organic chemical vapor deposition. An indium condensation boundary is mapped as a function of trimethylindium pressure, substrate temperature, and carrier gas composition. Below the condensation boundary, indium surface coverage reaches a maximum of 1/4 ML. The addition of 8% H2 to the carrier gas is found to have a significant effect on both condensation and adsorption of indium.

Jiang, F.; Wang, R.-V.; Munkholm, A.; Streiffer, S. K.; Stephenson, G. B.; Fuoss, P. H.; Latifi, K.; Thompson, Carol

2006-10-01

198

Aqueous-phase photooxidation of levoglucosan - a mechanistic study using aerosol time-of-flight chemical ionization mass spectrometry (Aerosol ToF-CIMS)  

NASA Astrophysics Data System (ADS)

Levoglucosan (LG) is a widely employed tracer for biomass burning (BB). Recent studies have shown that LG can react rapidly with hydroxyl (OH) radicals in the aqueous phase despite many mass balance receptor models assuming it to be inert during atmospheric transport. In the current study, aqueous-phase photooxidation of LG by OH radicals was performed in the laboratory. The reaction kinetics and products were monitored by aerosol time-of-flight chemical ionization mass spectrometry (Aerosol ToF-CIMS). Approximately 50 reaction products were detected by the Aerosol ToF-CIMS during the photooxidation experiments, representing one of the most detailed product studies yet performed. By following the evolution of mass defects of product peaks, unique trends of adding oxygen (+O) and removing hydrogen (-2H) were observed among the products detected, providing useful information for determining potential reaction mechanisms and sequences. Additionally, bond-scission reactions take place, leading to reaction intermediates with lower carbon numbers. We introduce a data analysis framework where the average oxidation state (OSc) is plotted against a novel molecular property: double-bond-equivalence-to-carbon ratio (DBE/#C). The trajectory of LG photooxidation on this plot suggests formation of polycarbonyl intermediates and their subsequent conversion to carboxylic acids as a general reaction trend. We also determined the rate constant of LG with OH radicals at room temperature to be 1.08 0.16 109 M-1 s-1. By coupling an aerosol mass spectrometer (AMS) to the system, we observed a rapid decay of the mass fraction of organic signals at mass-to-charge ratio 60 (f60), corresponding closely to the LG decay monitored by the Aerosol ToF-CIMS. The trajectory of LG photooxidation on a f44-f60 correlation plot matched closely to literature field measurement data. This implies that aqueous-phase photooxidation might be partially contributing to aging of BB particles in the ambient atmosphere.

Zhao, R.; Mungall, E. L.; Lee, A. K. Y.; Aljawhary, D.; Abbatt, J. P. D.

2014-09-01

199

Nanofiltration and sensing of picomolar chemical residues in aqueous solution using an optical porous resonator in a microelectrofluidic channel  

E-print Network

and livestock products were considered as the trace chemical analyte. The filtration process of the charged or biochemical analysis [7]. The transport through nanofiltration membranes is extremely complicated and numerous

Guo, Zhixiong "James"

200

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

Synchrotron X-ray spectroscopy experiments were made on the Gd(III) aqua and chloro complexes in low pH aqueous solutions at temperatures ranging from 25 to 500????C and at pressures up to 480??MPa using a hydrothermal diamond anvil cell. Analysis of fluorescence Gd L3-edge X-ray absorption fine structure (XAFS) spectra measured from a 0.006m Gd/0.16m HNO3 aqueous solution at temperatures up to 500????C and at pressures up to 260??MPa shows that the Gd-O distance of the Gd3+ aqua ion decreases steadily at a rate of ??? 0.007??A??/100????C whereas the number of coordinated H2O molecules decreases from 9.0 ?? 0.5 to 7.0 ?? 0.4. The loss of water molecules in the Gd3+ aqua ion inner hydration shell over this temperature range (a 22% reduction) is smaller than exhibited by the Yb3+ aqua ion (42% reduction) indicating that the former is significantly more stable than the later. We conjecture that the anomalous enrichment of Gd reported from measurement of REE concentrations in ocean waters may be attributed to the enhanced stability of the Gd3+ aqua ion relative to other REEs. Gd L3-edge XAFS measurements of 0.006m and 0.1m GdCl3 aqueous solutions at temperatures up to 500????C and pressures up to 480??MPa reveal that the onset of significant Gd3+-Cl- association occurs around 300????C. Partially-hydrated stepwise inner-sphere complexes most likely of the type Gd(H2O)??-nCln+3-n occur in the chloride solutions at higher temperatures, where ?? ??? 8 at 300????C decreasing slightly to an intermediate value between 7 and 8 upon approaching 500????C. This is the first direct evidence for the occurrence of partially-hydrated REE Gd (this study) and Yb [Mayanovic, R.A., Jayanetti, S., Anderson, A.J., Bassett, W.A., Chou, I-M., 2002a. The structure of Yb3+ aquo ion and chloro complexes in aqueous solutions at up to 500 ??C and 270 MPa. J. Phys. Chem. A 106, 6591-6599.] chloro complexes in hydrothermal solutions. The number of chlorides (n) of the partially-hydrated Gd(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.

Mayanovic, R.A.; Anderson, A.J.; Bassett, W.A.; Chou, I.-M.

2007-01-01

201

Process for the conversion of and aqueous biomass hydrolyzate into fuels or chemicals by the selective removal of fermentation inhibitors  

DOEpatents

A process of making a fuel or chemical from a biomass hydrolyzate is provided which comprises the steps of providing a biomass hydrolyzate, adjusting the pH of the hydrolyzate, contacting a metal oxide having an affinity for guaiacyl or syringyl functional groups, or both and the hydrolyzate for a time sufficient to form an adsorption complex; removing the complex wherein a sugar fraction is provided, and converting the sugar fraction to fuels or chemicals using a microorganism.

Hames, Bonnie R. (Westminster, CO); Sluiter, Amie D. (Arvada, CO); Hayward, Tammy K. (Broomfield, CO); Nagle, Nicholas J. (Broomfield, CO)

2004-05-18

202

Conversion of Japanese red pine wood (Pinus densiflora) into valuable chemicals under subcritical water conditions.  

PubMed

A comparative study on the decomposition of Japanese red pine wood under subcritical water conditions in the presence and absence of phosphate buffer was investigated in a batch-type reaction vessel. Since cellulose makes up more than 40-45% of the components found in most wood species, a series of experiments were also carried out using pure cellulose as a model for woody biomass. Several parameters such as temperature and residence time, as well as pH effects, were investigated in detail. The best temperature for decomposition and hydrolysis of pure cellulose was found around 270 degrees C. The effects of the initial pH of the solution which ranged from 1.5 to 6.5 were studied. It was found that the pH has a considerable effect on the hydrolysis and decomposition of the cellulose. Several products in the aqueous phase were identified and quantified. The conditions obtained from the subcritical water treatment of pure cellulose were applied for the Japanese red pine wood chips. As a result, even in the absence of acid catalyst, a large amount of wood sample was hydrolyzed in water; however, by using phosphate buffer at pH 2, there was an increase in the hydrolysis and dissolution of the wood chips. In addition to the water-soluble phase, acetone-soluble and water-acetone-insoluble phases were also isolated after subcritical water treatment (which can be attributed mainly to the degraded lignin, tar, and unreacted wood chips, respectively). The initial wood:acid ratio in the case of reactions catalyzed by phosphate buffer was also investigated. The results showed that this weight ratio can be as high as 3:1 without changing the catalytic activity. The size of the wood chips as one of the most important experimental parameters was also investigated. PMID:19892325

Asghari, Feridoun Salak; Yoshida, Hiroyuki

2010-01-11

203

Prebiotic chemistry: chemical evolution of organics on the primitive Earth under simulated prebiotic conditions.  

PubMed

A series of prebiotic mixtures of simple molecules, sources of C, H, N, and O, were examined under conditions that may have prevailed during the Hadean eon (4.6-3.8 billion years), namely an oxygen-free atmosphere and a significant UV radiation flux over a large wavelength range due to the absence of an ozone layer. Mixtures contained a C source (methanol, acetone or other ketones), a N source (ammonia or methylamine), and an O source (water) at various molar ratios of C : H : N : O. When subjected to UV light or heated for periods of 7 to 45 days under an argon atmosphere, they yielded a narrow product distribution of a few principal compounds. Different initial conditions produced different distributions. The nature of the products was ascertained by gas chromatographic-mass spectral analysis (GC-MS). UVC irradiation of an aqueous methanol-ammonia-water prebiotic mixture for 14 days under low UV dose (6 x 10(-2) Einstein) produced methylisourea, hexamethylenetetramine (HMT), methyl-HMT and hydroxy-HMT, whereas under high UV dose (45 days; 1.9 x 10(-1) Einstein) yielded only HMT. By contrast, the prebiotic mixture composed of acetone-ammonia-water produced five principal species with acetamide as the major component; thermally the same mixture produced a different product distribution of four principal species. UVC irradiation of the CH(3)CN-NH(3)-H(2)O prebiotic mixture for 7 days gave mostly trimethyl-s-triazine, whereas in the presence of two metal oxides (TiO(2) or Fe(2)O(3)) also produced some HMT; the thermal process yielded only acetamide. PMID:17973054

Dondi, Daniele; Merli, Daniele; Pretali, Luca; Fagnoni, Maurizio; Albini, Angelo; Serpone, Nick

2007-11-01

204

The use of chemically modified and unmodified cassava waste for the removal of Cd, Cu and Zn ions from aqueous solution.  

PubMed

The use of different chemically modified cassava waste biomass for the enhancement of the adsorption of three metal ions Cd, Cu and Zn from aqueous solution is reported in this paper. Treating with different concentrations of thioglycollic acid modified the cassava waste biomass. The sorption rates of the three metals were 0.2303 min(-1) (Cd(2+)), 0.0051 min(-1) (Cu(2+)), 0.0040 min(-1) (Zn(2+)) and 0.109 min(-1) (Cd(2+)), 0.0069 min(-1) (Cu(2+)), 0.0367 min(-1) (Zn(2+)) for 0.5 and 1.00 M chemically modified levels, respectively. The adsorption rates were quite rapid and within 20-30 min of mixing, about 60-80% of these ions were removed from the solutions by the biomass and that chemically modifying the binding groups in the biomass enhanced its adsorption capacity towards the three metals. The results further showed that increased concentration of modifying reagent led to increased incorporation, or availability of more binding groups, in the biomass matrix, resulting in improved adsorptivity of the cassava waste biomass. The binding capacity study showed that the cassava waste, which is a serious environmental nuisance, due to foul odour released during decomposition, has the ability to adsorb trace metals from solutions. PMID:14575960

Abia, A A; Horsfall, M; Didi, O

2003-12-01

205

Chemical and Structural Properties of Jordanian Zeolitic Tuffs and Their Admixtures with Urea and Thiourea: Potential Scavengers for Phenolics in Aqueous Medium.  

PubMed

Native Jordanian zeolitic tuffs, rich in phillipsite, were treated with urea and thiourea. The chemical and structural properties of the tuffs and their urea and thiourea admixtures were studied using SEM, XRF, XRD, and FTIR techniques, and their adsorption capacities were estimated by the methylene blue method. The urea and thiourea treatment has not affected the mineral constitution of the tuffs. The results revealed that urea and thiourea were linked by hydrogen bonding through the NH(2) moiety to the zeolite substrate, with urea showing the strongest effect. Experiments were carried out to investigate the possible use of the prepared materials for the removal of phenol and chlorinated phenols from aqueous solutions. Although thiourea caused a reduction in the relative surface area, both urea and thiourea admixtures were more effective than the free zeolitic tuff in the removal of phenol and chlorinated phenols from water, with urea admixture displaying the largest removal capacity. Copyright 1999 Academic Press. PMID:10421742

Yousef; Tutunji; Derwish; Musleh

1999-08-15

206

Adsorption of Trace Levels of Arsenic from Aqueous Solutions by Conditioned Layered Double Hydroxides: Batch and Flow  

E-print Network

calcined layered double hydroxide (LDH) adsorbents. Conditioning the adsorbent significantly reduced the dissolution observed with uncalcined and calcined LDH3. The adsorption rates and isotherms have been invariant with particle size4. The removal of As(V) on conditioned, calcined LDH adsorbents was also

Southern California, University of

207

Chemical boundary conditions for the classification of aerosol particles using computer controlled electron probe microanalysis.  

PubMed

A method for the classification of individual aerosol particles using computer controlled electron probe microanalysis is presented. It is based on chemical boundary conditions (CBC) and enables quick and easy processing of a large set of elemental concentration data (mass%), derived from the X-ray spectra of individual particles. The particles are first classified into five major classes (sea salt related, secondary inorganic, minerals, iron-rich and carbonaceous), after which advanced data mining can be performed by examining the elemental composition of particles within each class into more detail (e.g., by ternary diagrams). The CBC method is validated and evaluated by comparing its results with the output obtained with hierarchical cluster analysis (HCA) for well-known standard particles as well as real aerosol particles collected with a cascade impactor. The CBC method gives reliable results and has a major advantage compared to HCA. CBC is based on boundary conditions that are derived from chemical logical thinking and does not require a translation of a mathematical algorithm output as does HCA. Therefore, the CBC method is more objective and enables comparison between samples without intermediate steps. PMID:23158343

Anaf, Willemien; Horemans, Benjamin; Van Grieken, Ren; De Wael, Karolien

2012-11-15

208

Aqueous precursors for electrochromic tungsten oxide hydrates  

Microsoft Academic Search

Tungsten oxide hydrates WO3 nH2O are formed upon the acidification of tungstate aqueous solutions. Different amorphous or crystalline phases can be obtained depending on the experimental conditions (pH, concentration, temperature). The chemical mechanisms for the formation of these hydrates are discussed and the electrochromic properties of thin films deposited from these solutions are described. Hydrogen peroxide H2O2 reacts with

J. Livage; G. Guzman

1996-01-01

209

DETERMINATION OF PHTHALATES IN WATER AND SOIL BY TANDEM MASS SPECTROMETRY UNDER CHEMICAL IONIZATION CONDITIONS WITH ISOBUTANE AS REAGENT GAS  

EPA Science Inventory

Phthalate determination is important because phthalates often are major impurities in samples and can have significant health effects. Tandem mass spectrometry under chemical ionization mass spectrometry conditions with isobutane as the reagent gas was used to determine 11 phthal...

210

Stability of the Versatic 10decyl-4-pyridinecarboxylate system under continuous SX conditions: chemical analysis and phase disengagement studies  

Microsoft Academic Search

The chemical stability of n-decyl-4-pyridinecarboxylate ester (decyl-4PC) in a Versatic 10\\/decyl-4PC\\/aliphatic diluent system under conditions expected in a typical plant solvent extraction (SX) circuit has been assessed. This was achieved by monitoring phase disengagement properties and chemical composition of each organic solution with time when tested under the following conditions: continuous batch mixing over 12 weeks at 40 C and

K. R Barnard; M. G Davies; C. Y Cheng

2004-01-01

211

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

PubMed

A macromolecule, CML, was obtained by purifying and carboxy-methylating the lignin generated from acid hydrolysis of sugarcane bagasse during bioethanol production from biomass. The CMLs complexed with Al(3+) (CML-Al) and Mn(2+) (CML-Mn) were utilised for the removal of a textile dye, Procion Blue MX-R (PB), from aqueous solutions. CML-Al and CML-Mn were characterised using Fourier transform infrared spectroscopy (FTIR), scanning differential calorimetry (SDC), scanning electron microscopy (SEM) and pHPZC. The established optimum pH and contact time were 2.0 and 5h, respectively. The kinetic and equilibrium data fit into the general order kinetic model and Liu isotherm model, respectively. The CML-Al and CML-Mn have respective values of maximum adsorption capacities of 73.52 and 55.16mgg(-1) at 298K. Four cycles of adsorption/desorption experiments were performed attaining regenerations of up to 98.33% (CML-Al) and 98.08% (CML-Mn) from dye-loaded adsorbents, using 50% acetone+50% of 0.05molL(-1) NaOH. The CML-Al removed ca. 93.97% while CML-Mn removed ca. 75.91% of simulated dye house effluents. PMID:24462989

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

2014-03-15

212

Chemical relevance of the copper(II) L-carnosine system in aqueous solution: A thermodynamic and spectrophotometric study  

NASA Astrophysics Data System (ADS)

The copper(II) L-carnosine (L -) system has been re-investigated in aqueous solution, at I = 0.1 mol dm -1, different temperatures (5? t?45C) and with metal to ligand ratios ranging from 3:1 to 1:3. Both potentiometry and visible spectrophotometry were employed. From an overall consideration of all experiments, [CuLH] 2+, [CuL] +, [CuLH -1], [Cu 2L 2H -2] and [Cu 2LH -1] 2+ were recognized as the species which provide the best interpretation of experimental data. The complex formation constants, determined at different temperatures, allowed us to obtain reliable values of ? H and good estimates of ? C p. From visible spectrophotometric measurements, carried out at different pH and metal to ligand ratios, it was possible to calculate the electronic spectrum of each complex formed in solution. A structure is also proposed for each species, on the basis of thermodynamic and spectral results.

Daniele, Pier G.; Prenesti, Enrico; Zelano, Vincenzo; Ostacoli, Giorgio

1993-08-01

213

Iodine-xenon, chemical, and petrographic studies of Semarkona chondrules - Evidence for the timing of aqueous alteration  

NASA Technical Reports Server (NTRS)

The relationship of the I-Xe system of the Semarkona meteorite to other measured properties is investigated via INAA, petrographic, and noble-gas analyses on 17 chondrules from the meteorite. A range of not less than 10 Ma in apparent I-Xe ages is observed. The three latest apparent ages fall in a cluster, suggesting the possibility of a common event. It is argued that the initial I-129/I-127 ratio (R0) is related to chondrule type and/or mineralogy, with nonporphyritic and pyroxene-rich chondrules showing evidence for lower R0s than porphyritic and olivine-rich chondrules. Chondrules with sulfides on or near the surface have lower R0s than other chondrules. The He-129/Xe-132 ratio in the trapped Xe component anticorrelates with R0, consistent with the evolution of a chronometer in a closed system or in multiple systems. It is concluded that the variations in R0 represent variations in ages, and that later events, possibly aqueous alteration, preferentially affected chondrules with nonporphyritic textures and/or sulfide-rich exteriors about 10 Ma after the formation of the chondrules.

Swindle, T. D.; Grossman, J. N.; Olinger, C. T.; Garrison, D. H.

1991-01-01

214

Iodine-xenon, chemical, and petrographie studies of Semarkona chondrules: Evidence for the timing of aqueous alteration  

USGS Publications Warehouse

We have performed INAA, petrographie, and noble gas analyses on seventeen chondrules from the Semarkona meteorite (LL3.0) primarily to study the relationship of the I-Xe system to other measured properties. We observe a range of ???10 Ma in apparent I-Xe ages. The three latest apparent ages fall in a cluster, suggesting the possibility of a common event. The initial 129I/127I ratio (R0) is apparently related to chondrule type and/or mineralogy, with nonporphyritic and pyroxene-rich chondrules showing evidence for lower R0'S (later apparent I-Xe ages) than porphyritic and olivine-rich chondrules. In addition, chondrules with sulfides on or near the surface have lower R0S than other chondrules. The 129Xe/132Xe ratio in the trapped Xe component anticorrelates with R0, consistent with evolution of a chronometer in a closed system or in multiple similar systems. On the basis of these correlations, we conclude that the variations in R0 represent variations in ages, and that later event(s), possibly aqueous alteration, preferentially affected chondrules with nonporphyritic textures and/or sulfide-rich exteriors about 10 Ma after the formation of the chondrules. ?? 1991.

Swindle, T.D.; Grossman, J.N.; Olinger, C.T.; Garrison, D.H.

1991-01-01

215

Solubility of platinum in aqueous solutions at 25C and pHs 4 to 10 under oxidizing conditions  

Microsoft Academic Search

Platinum has been found to be mobile under supergene conditions, including placers and weathering profiles. To elucidate the nature of Pt mobility in supergene environments, the dissolution of platinum metal was investigated under physicochemical conditions similar to those found in such environments. The solubility of platinum metal was measured at 25C in several systems: Pt-K-HC8H4O4-H2O (pH 4.02), Pt-Na-HCO3-Cl-H2O (pH 6.40),

Mohamed Azaroual; Bruno Romand; Philippe Freyssinet; Jean-Robert Disnar

2001-01-01

216

Some physico-chemical properties of Moringa oleifera seed oil extracted using solvent and aqueous enzymatic methods  

Microsoft Academic Search

The physico-chemical properties of oil from Moringa oleifera seed were determined following extraction either with petroleum ether or 2% Neutrase 0.8L (a neutral bacterial protease from Bacillus amyloiquefaciens, Novozyme Bagsvaerd Denmark). The enzyme was chosen following a preliminary study conducted on the enzymatic extraction of M. oleifera seed oil using four commercial enzymes that showed Neutrase to be the best

S. M. Abdulkarim; K. Long; O. M. Lai; S. K. S. Muhammad; H. M. Ghazali

2005-01-01

217

Chemical evolution of RNA under hydrothermal conditions and the role of thermal copolymers of amino acids for the prebiotic degradation and formation of RNA  

NASA Technical Reports Server (NTRS)

The roles of thermal copolymers of amino acids (TCAA) were studied for the prebiotic degradation of RNA. A weak catalytic ability of TCAA consisted of Glu, L-Ala, L-Val, L-Glu, L-Asp, and optionally L-His was detected for the cleavage of the ribose phosphodiester bond of a tetranucleotide (5'-dCrCdGdG) in aqueous solution at 80 degees C. The rate constants of the disappearance of 5'-dCrCdGdG were determined in aqueous solutions using different pH buffer and TCAA. The degradation rates were enhanced 1.3-3.0 times in the presence of TCAA at pH 7.5 and 8.0 at 80 degrees C, while the hydrolysis of oligoguanylate (oligo(G)) was accelerated about 1.6 times at pH 8.0. A weak inhibitory activity for the cleavage of oligo(G) was detected in the presence of 0.055 M TCAA-Std. On the other hand, our recent study on the influences of TCAA for the template-directed reaction of oligo(G) on a polycytidylic acid template showed that TCAA has an acceleration activity for the degradation of the activated nucleotide monomer and an acceleration activity for the formation of G5' ppG capped oligo(G). This series of studies suggest that efficient and selective catalytic or inhibitory activities for either the degradation or formation of RNA under hydrothermal conditions could have hardly emerged from the simple thermal condensation products of amino acids. A scenario is going to be deduced on the chemical evolution of enzymatic activities and RNA molecules concerning hydrothermal earth conditions. c2005 COSPAR. Published by Elsevier Ltd. All rights reserved.

Kawamura, K.; Nagahama, M.; Kuranoue, K.

2005-01-01

218

Review and analysis of high temperature chemical reactions and the effect of non-equilibrium conditions  

NASA Technical Reports Server (NTRS)

Chemical reactions at high temperatures have been considered extensively because of their importance to the heating effects on re-entry of space vehicles. Data on these reactions however, are not abundant and even when found there are discrepancies in data collected by various investigators. In particular, data for recombination reactions are calculated from the dissociation reactions or vice versa through the equilibrium constant. This involves the use of the principle of detailed balancing. This principle is discussed in reference to conditions where it is valid as well as to those where it is not valid. Related topics that merit further study or for which applicable information was available are briefly mentioned in an appendix to this report.

Johnson, R. E.

1986-01-01

219

A Molecular Dynamics Study of Chemical Reactions of Solid Pentaerythritol Tetranitrate at Extreme Conditions  

SciTech Connect

We have carried out density functional based tight binding (DFTB) molecular dynamics (MD) simulation to study energetic reactions of solid Pentaerythritol Tetranitrate (PETN) at conditions approximating the Chapman-Jouguet (CJ) detonation state. We found that the initial decomposition of PETN molecular solid is characterized by uni-molecular dissociation of the NO{sub 2}groups. Interestingly, energy release from this powerful high explosive was found to proceed in several stages. The large portion of early stage energy release was found to be associated with the formation of H{sub 2}O molecules within a few picoseconds of reaction. It took nearly four times as long for majority of CO{sub 2} products to form, accompanied by a slow oscillatory conversion between CO and CO{sub 2}. The production of N{sub 2} starts after NO{sub 2} loses its oxygen atoms to hydrogen or carbon atoms to form H{sub 2}O or CO. We identified many intermediate species that emerge and contribute to reaction kinetics, and compared our simulation with a thermo-chemical equilibrium calculation. In addition, a detailed chemical kinetics of formation of H{sub 2}O, CO, and CO{sub 2} were developed. Rate constants of formations of H{sub 2}O, CO{sub 2} and N{sub 2} were reported.

Wu, C J; Manaa, M R; Fried, L E

2006-05-30

220

Effective dispersion in a chemically heterogeneous medium under temporally fluctuating flow conditions  

NASA Astrophysics Data System (ADS)

We investigate effective solute transport in a chemically heterogeneous medium subject to temporal fluctuations of the flow conditions. Focusing on spatial variations in the equilibrium adsorption properties, the corresponding fluctuating retardation factor is modeled as a stationary random space function. The temporal variability of the flow is represented by a stationary temporal random process. Solute spreading is quantified by effective dispersion coefficients, which are derived from the ensemble average of the second centered moments of the normalized solute distribution in a single disorder realization. Using first-order expansions in the variances of the respective random fields, we derive explicit compact expressions for the time behavior of the disorder induced contributions to the effective dispersion coefficients. Focusing on the contributions due to chemical heterogeneity and temporal fluctuations, we find enhanced transverse spreading characterized by a transverse effective dispersion coefficient that, in contrast to transport in steady flow fields, evolves to a disorder-induced macroscopic value (i.e., independent of local dispersion). At the same time, the asymptotic longitudinal dispersion coefficient can decrease. Under certain conditions the contribution to the longitudinal effective dispersion coefficient shows superdiffusive behavior, similar to that observed for transport in s stratified porous medium, before it decreases to its asymptotic value. The presented compact and easy to use expressions for the longitudinal and transverse effective dispersion coefficients can be used for the quantification of effective spreading and mixing in the context of the groundwater remediation based on hydraulic manipulation and for the effective modeling of reactive transport in heterogeneous media in general.

Zavala-Sanchez, Vanessa; Dentz, Marco; Sanchez-Vila, Xavier

2007-05-01

221

INITIAL CHEMICAL AND RESERVOIR CONDITIONS AT LOS AZUFRES WELLHEAD POWER PLANT STARTUP  

SciTech Connect

One of the major concerns of electric utilities in installing geothermal power plants is not only the longevity of the steam supply, but also the potential for changes in thermodynamic properties of the resource that might reduce the conversion efficiency of the design plant equipment. Production was initiated at Los Azufres geothermal field with wellhead generators not only to obtain electric energy at a relatively early date, but also to acquire needed information about the resource so that plans for large central power plants could be finalized. Commercial electric energy production started at Los Azufres during the summer of 1982 with five 5-MWe wellhead turbine-generator units. The wells associated with these units had undergone extensive testing and have since been essentially in constant production. The Los Azufres geothermal reservoir is a complex structural and thermodynamic system, intersected by at least 4 major parallel faults and producing geothermal fluids from almost all water to all steam. The five wellhead generators are associated with wells of about 30%, 60%, and 100% steam fraction. A study to compile existing data on the chemical and reservoir conditions during the first two years of operation has been completed. Data have been compiled on mean values of wellhead and separator pressures, steam and liquid flowrates, steam fraction, enthalpy, and pertinent chemical components. The compilation serves both as a database of conditions during the start-up period and as an initial point to observe changes with continued and increased production. Current plans are to add additional wellhead generators in about two years followed by central power plants when the data have been sufficiently evaluated for optimum plant design. During the next two years, the data acquired at the five 5-MWe wellhead generator units can be compared to this database to observe any significant changes in reservoir behavior at constant production.

Kruger, P.; Semprini, L.; Verma, S.; Barragan, R.; Molinar, R.; Aragon, A.; Ortiz, J.; Miranda, C.

1985-01-22

222

Permafrost conditions in peatlands regulate magnitude, timing, and chemical composition of catchment dissolved organic carbon export.  

PubMed

Permafrost thaw in peatlands has the potential to alter catchment export of dissolved organic carbon (DOC) and thus influence downstream aquatic C cycling. Subarctic peatlands are often mosaics of different peatland types, where permafrost conditions regulate the hydrological setting of each type. We show that hydrological setting is key to observed differences in magnitude, timing, and chemical composition of DOC export between permafrost and nonpermafrost peatland types, and that these differences influence the export of DOC of larger catchments even when peatlands are minor catchment components. In many aspects, DOC export from a studied peatland permafrost plateau was similar to that of a forested upland catchment. Similarities included low annual export (2-3g Cm(-2) ) dominated by the snow melt period (~70%), and how substantial DOC export following storms required wet antecedent conditions. Conversely, nonpermafrost fens had higher DOC export (7g Cm(-2) ), resulting from sustained hydrological connectivity during summer. Chemical composition of catchment DOC export arose from the mixing of highly aromatic DOC from organic soils from permafrost plateau soil water and upland forest surface horizons with nonaromatic DOC from mineral soil groundwater, but was further modulated by fens. Increasing aromaticity from fen inflow to outlet was substantial and depended on both water residence time and water temperature. The role of fens as catchment biogeochemical hotspots was further emphasized by their capacity for sulfate retention. As a result of fen characteristics, a 4% fen cover in a mixed catchment was responsible for 34% higher DOC export, 50% higher DOC concentrations and ~10% higher DOC aromaticity at the catchment outlet during summer compared to a nonpeatland upland catchment. Expansion of fens due to thaw thus has potential to influence landscape C cycling by increasing fen capacity to act as biogeochemical hotspots, amplifying aquatic C cycling, and increasing catchment DOC export. PMID:24753046

Olefeldt, David; Roulet, Nigel T

2014-10-01

223

Molecular Characterization of Corn Starch Using an Aqueous HPSEC-MALLS-RI System Under Various Dissolution and Analytical Conditions  

Microsoft Academic Search

Cereal Chem. 77(3):303-308 Molecular characteristics based on absolute weight-average molecular weight (Mw) and z-average radius of gyration ( Rg) of normal corn starch were analyzed by high-performance size-exclusion chromatography (HPSEC) attached to multiangle laser-light scattering (MALLS) and refractive index (RI) detectors under different starch dissolution and ana- lytical conditions. Autoclaving (121C, 20 min) or microwave heating (35 sec) provided better

SangGuan You; Seung-Taik Lim

2000-01-01

224

Study of CdS epitaxial films chemically deposited from aqueous solutions on InP single crystals  

SciTech Connect

Epitaxial growth of cadmium sulfide on InP single crystals is achieved by chemical bath deposition (CBD) in ammonia solutions at near room temperature. A better understanding of the correlations between the deposition parameters (temperature, bath composition) and the epitaxial quality is obtained by using electron diffraction and transmission techniques, x-ray diffraction, in combination with Raman spectroscopy. They are supplemented by electrochemical impedance and photocurrent experiments which give information on energetic structures between InP and CBD-CdS. Direct relations between the substrate properties and the growth habits of the CdS film (hexagonal vs. cubic, epitaxial vs. polycrystalline) are found.

Froment, M.; Bernard, M.C.; Cortes, R. [Univ. Pierre et Marie Curie, Paris (France). Physique des Liquides et Electrochimie; Mokili, B.; Lincot, D. [Ecole Nationale Superieure de Chimie de Paris (France). Lab. d`Electrochimie et de Chimie Analytique

1995-08-01

225

Surface studies of niobium chemically polished under conditions for superconducting radiofrequency cavity production  

SciTech Connect

The performance of niobium superconducting radiofrequency accelerator cavities is strongly impacted by the topmost several nanometers of the active (interior) surface, especially by the final surface conditioning treatments. We examined the effect of the most commonly employed treatment, buffered chemical polishing (BCP), on polycrystalline niobium sheet over a range of realistic solution flow rates using electron back scatter diffraction (EBSD), stylus profilometry, atomic force microscopy, laboratory XPS and synchrotron (variable photon energy) XPS, seeking to collect statistically significant data sets. We found that the predominant general surface orientation is (100), but others are also present and at the atomic-level details of surface plane orientation are more complex. The post-etch surface exhibits micron-scale roughness, whose extent does not change with treatment conditions. The outermost surface consists of a few-nm thick layer of niobium pentoxide, whose thickness increases with solution flow rate to a maximum of 1.3 - 1.4 times that resulting from static solution. The standard deviation of the roughness measurements is ?? 30% and that of the surface composition is ?? 5%.

Hui Tian; Michael Kelley; Charles Reece

2005-11-14

226

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

PubMed

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

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

2014-01-01

227

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

PubMed Central

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

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

2014-01-01

228

Accounting for natural organic matter in aqueous chemical equilibrium models: a review of the theories and applications  

NASA Astrophysics Data System (ADS)

Soil organic matter consists of a highly complex and diversified blend of organic molecules, ranging from low molecular weight organic acids (LMWOAs), sugars, amines, alcohols, etc., to high apparent molecular weight fulvic and humic acids. The presence of a wide range of functional groups on these molecules makes them very reactive and influential in soil chemistry, in regards to acid-base chemistry, metal complexation, precipitation and dissolution of minerals and microbial reactions. Out of these functional groups, the carboxylic and phenolic ones are the most abundant and most influential in regards to metal complexation. Therefore, chemical equilibrium models have progressively dealt with organic matter in their calculations. This paper presents a review of six chemical equilibrium models, namely N ICA-Donnan, E Q3/6, G EOCHEM, M INTEQA2, P HREEQC and W HAM, in light of the account they make of natural organic matter (NOM) with the objective of helping potential users in choosing a modelling approach. The account has taken various faces, mainly by adding specific molecules within the existing model databases (E Q3/6, G EOCHEM, and P HREEQC) or by using either a discrete (W HAM) or a continuous (N ICA-Donnan and M INTEQA2) distribution of the deprotonated carboxylic and phenolic groups. The different ways in which soil organic matter has been integrated into these models are discussed in regards to the model-experiment comparisons that were found in the literature, concerning applications to either laboratory or natural systems. Much of the attention has been focused on the two most advanced models, W HAM and N ICA-Donnan, which are able to reasonably describe most of the experimental results. Nevertheless, a better knowledge of the humic substances metal-binding properties is needed to better constrain model inputs with site-specific parameter values. This represents the main axis of research that needs to be carried out to improve the models. In addition to humic substances, more non-humic compounds should also be introduced in model databases, notably the ones that readily interact with the soil microorganisms. Thermodynamic data are generally available for most of these compounds, such as low molecular-weight organic acids. However, the more complex non-humic substances, exhibiting a ratio of hydrophobic versus hydrophilic bonds lower than humic substances, need to be further characterised for a comprehensive implementation in chemical equilibrium models.

Dudal, Yves; Grard, Frdric

2004-08-01

229

Analysis of chemical reactions of ?-radiolysis, hydrolysis and complex formation in alkali solutions of the object ``Shelter". Investigations of transfer coefficients of UO22+, PuO22+ ions in aqueous solutions (in Ukrainian)  

NASA Astrophysics Data System (ADS)

Chemical reactions of ?-radiolysis, hydrolysis and complex formation as well as oxidizing-reducing processes in alkali solutions of ions UO^{2+}_2, PuO^{2+}_2, AmO^{2+}_2 have been analyzed. It has been established that polyuranites and superuranites, phosphate, carbonate and nitrate precipitates of uraninite and plutoninite may arise in aqueous solutions, which are characteristic of the object ``Shelter". Hydrodynamic-fluctuation theory for calculation of bimolecular reactions is presented. Calculation of mutual diffusion and viscosity transfer coefficients for ions UO^{2+}_2, PuO^{2+}_2 and atomic hydrohen in aqueous solutions is carried out.

Yukhnovskii, I. R.; Tokarchuk, M. V.; Kobryn, O. E.; Dmytriv, G. S.; Humenyuk, Y. A.

230

Soil structure, colloids, and chemical transport as affected by short-term reducing conditions: a laboratory study  

NASA Astrophysics Data System (ADS)

Upland soils in the Midwestern US often undergo reducing conditions when soils are temporally flooded during the spring and remain water saturated for days or weeks. Short-term reducing conditions change the chemistry of the soil and may affect soil structure and solution chemical transport. The effects of short-term reducing conditions on chemical and physical properties of the soils, colloids, and associated chemical/nutrients transport are still not well understood and was the objective of our study. A biogeochemical reactor was built to achieve reducing conditions. Three cultivated and three uncultivated soils with different organic carbon contents were incubated in the reactor for 1 hour and 3 days under anaerobic conditions. Effects of the redox state on soil structure (pore size distribution) and drainable porosity, colloids mobility, and chemical transport were determined using high energy moisture characteristic and analytical methods. After each treatment, the soil solution was collected for redox potential (Eh), pH, and electrical conductivity (EC) measurements, and chemical analysis of metals (Ca, Mg, K), nutrients (N, P), and dissolved organic carbon. Strongly reducing conditions were achieved after 3 days of incubation and were followed by a decrease in soil porosity and an increase in pH, EC, clay dispersion, swelling, colloids mobility, and associated chemical transport. The trend for each soil depended on their initial structural stability and chemical properties. The structure of cultivated soils and the leaching of nutrients and carbon from uncultivated soils were more sensitive to the redox state. A strong correlation was found between changes in Eh and drainable porosity. The role of short-term reducing conditions on changes in redox sensitive elements, organic matter decomposition, pH, and EC and their influence on soil structure and soil particles or colloids/chemical transport for both soil groups are discussed in the paper. This study showed that short- term reducing conditions influence colloids/chemical transport and it should be taken into account for modeling because dissolved compounds and colloids facilitated nutrient and associated pollutant transport during coupled overland and soil-matrix flow conditions.

de-Campos, A. B.; Mamedov, A. I.; Huang, C.; Wagner, L. E.

2008-12-01

231

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

NASA Astrophysics Data System (ADS)

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 ?W. 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 acknowledged.

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

2012-12-01

232

Chemical interactions between Nano-ZnO and Nano-TiO2 in a natural aqueous medium.  

PubMed

The use of diverse engineered nanomaterials (ENMs) potentially leads to the release of multiple ENMs into the environment. However, previous efforts to understand the behavior and the risks associated with ENMs have focused on only one material at a time. In this study, the chemical interactions between two of the most highly used ENMs, nano-TiO2, and nano-ZnO, were examined in a natural water matrix. The fate of nano-ZnO in Lake Michigan water was investigated in the presence of nano-TiO2. Our experiments demonstrate that the combined effects of ZnO dissolution and Zn adsorption onto nano-TiO2 control the concentration of dissolved zinc. X-ray absorption spectroscopy was used to determine the speciation of Zn in the particulate fraction. The spectra show that Zn partitions between nano-ZnO and Zn2+ adsorbed on nano-TiO2. A simple kinetic model is presented to explain the experimental data. It integrates the processes of nano-ZnO dissolution with Zn adsorption onto nano-TiO2 and successfully predicts dissolved Zn concentration in solution. Overall, our results suggest that the fate and toxicity potential of soluble ENMs, such as nano-ZnO, are likely to be influenced by the presence of other stable ENMs, such as nano-TiO2. PMID:24918623

Tong, Tiezheng; Fang, Kaiqi; Thomas, Sara A; Kelly, John J; Gray, Kimberly A; Gaillard, Jean-Franois

2014-07-15

233

Kinetics of chemical degradation of isoxaflutole: influence of the nature of aqueous buffers (alkanoic acid/sodium salt vs phosphate).  

PubMed

A kinetic study of the chemical degradation of isoxaflutole (5-cyclopropyl-1,2-oxazol-4-yl alpha alpha alpha-trifluoro-2-mesyl-p-tolyl ketone) into its diketonitrile derivative (DKN), which is its active herbicide principle, in organic buffers at different pH values was carried out using a HPLC/UV detection method. The values of the pseudo-first-order rate constants Kobs for the reaction were calculated and compared with those previously obtained in inorganic buffers. In both cases, Kobs was found to be dependent on pH and temperature, but at pH 5.2 the degradation of isoxaflutole in CH3COOH/CH3COONa buffers was considerably faster than in KH2PO4/Na2HPO4 buffers, indicating that the compound was sensitive to the nature of the reagents used to prepare buffered solutions. The influence of phosphate and acetate concentrations and the influence of the R-substituent in RCOOH/RCOONa buffers were investigated. For the HA/A- buffers studied, the values of Kobs were linearly dependent on HA and A- concentrations, which meant that the degradation of isoxaflutole was subject to general catalysis. The values of Kobs were also found to be dependent on the number and the position of the CH3 groups of the R-substituent. The known degradation product of DKN (a benzoic acid derivative) was not detected throughout this study. PMID:11455816

Beltran, E; Fenet, H; Cooper, J F; Coste, C M

2001-04-01

234

Discharge characteristics of chemically prepared MnO 2 and electrolytic MnO 2 in non-aqueous electrolytes  

NASA Astrophysics Data System (ADS)

The discharge performance of chemically prepared MnO 2 (CMD) and electrolytic MnO 2 (EMD) is investigated in various electrolytes. LiPF 6, LiCF 3SO 3, and LiBF 4 are used as lithium salts in a mixed solvent of ethylene carbonate, propylene carbonate, and 1,2-dimethoxyethane (DME). The size and crystal structure of MnO 2 particles is observed by scanning electron microscope and X-ray diffraction, respectively. The particle size of CMD is smaller than that of EMD, but the crystal structures of the two materials are similar. The concentration of dissolved manganese ions from CMD and EMD particles is 148 and 23 mg l -1 in the same electrolyte, respectively. The interfacial electrochemistry of test cells is analyzed by impedance spectroscopy. The discharge performance is poor in the electrolyte containing LiCF 3SO 3 salt. The specific discharge capacity of CMD is superior to that of EMD at high discharge rate.

Kim, Hyung-Sun; Kim, Hyun-Joong; Cho, Won-Il; Cho, Byung-Won; Ju, Jeh-Beck

235

Improving the Survivability of High Speed Ball Bearings under Oil Shut-off Conditions by Chemical Modification of the Surface  

Microsoft Academic Search

Oil shut-off tests were performed using 150 mm bore M50-steel ball bearings under high speed rotation conditions. This investigation demonstrated that bearings that had received chemical modification of the surface were able to delay the onset of bearing seizure after lubricant shut-off Comparing the chemically modified surface, to a conventional bearing surface, this paper describes the differences and changes in

S. Ijuin; T. Yuruzume; Y. Shoda; K. Toma; H. Kawamura

1995-01-01

236

Stability of an aqueous quadrupole micro-trap  

NASA Astrophysics Data System (ADS)

The recently demonstrated functionality of an aqueous quadrupole micro- or nano-trap opens a new avenue for applications of Paul traps, like confinement of a charged biomolecule which requires a water environment for its chemical stability. Besides the strong viscosity forces, the motion of a charged particle in the aqueous trap is subject to dielectrophoretic and electrophoretic forces. In this study, we describe the general conditions for stability of a charged particle in an aqueous quadrupole trap. We find that for typical micro-trap parameters, the effects of both dielectrophoresis and electrophoresis significantly influence the trap stability. In particular, an aqueous quadrupole trap could play the role of a synthetic virtual nanopore for the third generation of DNA sequencing technology.

Park, Jae Hyun; Krsti?, Predrag S.

2012-04-01

237

Removal of Zn(II) and Hg(II) from aqueous solution on a carbonaceous sorbent chemically prepared from rice husk.  

PubMed

A carbonaceous sorbent was prepared from rice husk via sulfuric acid treatment. Sorption of Zn(II) and Hg(II) from aqueous solution was studied varying time, pH, metal concentration, temperature and sorbent status (wet and dry). Zn(II) sorption was found fast reaching equilibrium within approximately 2h while Hg(II) sorption was slow reaching equilibrium within approximately 120 h with better performance for the wet sorbent than for the dry. Kinetics data for both metals were found to follow pseudo-second order model. Sorption rate of both metals was enhanced with temperature rise. Activation energy, E(a), for Zn(II) sorption, was approximately 13.0 kJ/mol indicating a diffusion-controlled process ion exchange process, however, for Hg(II) sorption, E(a) was approximately 54 kJ/mol indicating a chemically controlled process. Sorption of both metals was low at low pH and increased with pH increase. Sorption was much higher for Hg(II) than for Zn(II) with higher uptake for both metals by rising the temperature. Hg(II) was reduced to Hg(I) on the sorbent surface. This was confirmed from the identification of Hg(2)Cl(2) deposits on the sorbent surface by scanning electron microscopy and X-ray diffraction. However, no redox processes were observed in Zn(II) sorption. Sorption mechanism is discussed. PMID:19883976

El-Shafey, E I

2010-03-15

238

Sodium Borohydride Reduction of Aqueous Silver-Iron-Nickel Solutions: a Chemical Route to Synthesis of Low Thermal Expansion-High Conductivity Ag-Invar Alloys  

NASA Astrophysics Data System (ADS)

Thermal management is a critical concern in the design and performance of electronics systems. If heat extraction and thermal expansion are not properly addressed, the thermal mismatch among dissimilar materials may give rise to high thermal stresses or interfacial shear strains, and ultimately to premature system failure. In this article, we present a chemical synthesis process that yields Ag-Invar (64Fe-36Ni) alloys with a range of attractive properties for thermal management applications. Sodium borohydride reduction of an aqueous Ag-Fe-Ni metal salt solution produces nanocrystalline powders, and conventional powder processing converts this powder to fine-grained alloys. The samples are characterized by X-ray diffraction (XRD), scanning electron microscopy, thermomechanical analysis, and electrical conductivity measurements; thermal conductivity is estimated using the Wiedemann-Franz law. Sintering of Ag-Fe-Ni powders leads to the formation of two-phase silver-Invar alloys with low coefficients of thermal expansion (CTEs) and relatively high electrical conductivities. A sample of 50Ag-50Invar exhibits a CTE of 8.76 ?m/(m C) and an estimated thermal conductivity of 236 W/(mK). The Ag-Invar alloys offer thermodynamic stability and tailorable properties, and they may help address the need for improved packaging materials.

Sterling, E. A.; Stolk, J.; Hafford, L.; Gross, M.

2009-07-01

239

Particle Emissions from a Marine Engine: Chemical Composition and Aromatic Emission Profiles under Various Operating Conditions.  

PubMed

The chemical composition of particulate matter (PM) emissions from a medium-speed four-stroke marine engine, operated on both heavy fuel oil (HFO) and distillate fuel (DF), was studied under various operating conditions. PM emission factors for organic matter, elemental carbon (soot), inorganic species and a variety of organic compounds were determined. In addition, the molecular composition of aromatic organic matter was analyzed using a novel coupling of a thermal-optical carbon analyzer with a resonance-enhanced multiphoton ionization (REMPI) mass spectrometer. The polycyclic aromatic hydrocarbons (PAHs) were predominantly present in an alkylated form, and the composition of the aromatic organic matter in emissions clearly resembled that of fuel. The emissions of species known to be hazardous to health (PAH, Oxy-PAH, N-PAH, transition metals) were significantly higher from HFO than from DF operation, at all engine loads. In contrast, DF usage generated higher elemental carbon emissions than HFO at typical load points (50% and 75%) for marine operation. Thus, according to this study, the sulfur emission regulations that force the usage of low-sulfur distillate fuels will also substantially decrease the emissions of currently unregulated hazardous species. However, the emissions of soot may even increase if the fuel injection system is optimized for HFO operation. PMID:25202837

Sippula, O; Stengel, B; Sklorz, M; Streibel, T; Rabe, R; Orasche, J; Lintelmann, J; Michalke, B; Abbaszade, G; Radischat, C; Grger, T; Schnelle-Kreis, J; Harndorf, H; Zimmermann, R

2014-10-01

240

Polar organic chemical integrative samplers for pesticides monitoring: impacts of field exposure conditions.  

PubMed

This study focuses on how Polar Organic Chemical Integrative Samplers (POCIS) work in real environmental conditions. A selection of 23 polar pesticides and 8 metabolites were investigated by exposure of triplicates of integrative samplers in two rivers in France for successive 14-day periods. The pesticides and metabolites were trapped not only in Oasis HLB sorbent but also in the polyethersulfone (PES) membrane of the POCIS. The distribution of pesticides depended on the molecular structure. The use of the Performance Reference Compound (PRC) is also discussed here. The impact of some environmental parameters and exposure setup on the transfer of pesticides in POCIS sorbent was studied: river flow rate, biofouling on membranes, sampler holding design and position in the stream. Results show a significant impact of river flow velocity on PRC desorption, especially for values higher than 4 cms(-1). Some fouling was observed on the PES membrane which could potentially have an impact on molecule accumulation in the POCIS. Finally, the positioning of the sampler in the river did not have significant effects on pesticide accumulation, when perpendicular exposures were used (sampler positioning in front of the water flow). The POCIS with PRC correction seems to be a suitable tool for estimating time-weighted average (TWA) concentrations, for all the molecules except for one of the nine pesticides analyzed in these two French rivers. PMID:24830931

Lissalde, Sophie; Mazzella, Nicolas; Mazellier, Patrick

2014-08-01

241

The aqueous and non-aqueous electrochemistry of polyacetylene: Application in high power density rechargeable batteries  

NASA Astrophysics Data System (ADS)

Polyacetylene can be doped either chemically or electrochemically in aqueous solution to the metallic regime. The characteristics of selected rechargeable batteries employing (CH) x electrodes in non-aqueous electrolytes are described.

MacDiarmid, A. G.; Kaner, R. B.; Mammone, R. J.; Heeger, A. J.

1983-01-01

242

DES-code: A metacode to aid calculation of the chemical potential of aqueous solutions at elevated temperatures and pressures  

NASA Astrophysics Data System (ADS)

The DH-ASF (Debye-Hckel-asymmetric formalism) model is a recently developed activity-composition model that can be used to calculate the thermodynamic effects of mixing in strong electrolyte and mixed solvent supercritical solutions at high pressures ( >3kbar) and temperatures ( >400C). The model uses a mole fraction concentration scale, and calculations are based on a pre-defined independent set of end-members that define speciation within the solution. This differs from the conventional use of molal concentration scales with sets of end-members that define the composition of the solution, but not the speciation (apparent end-members). This work presents DES (dual end-member sets)-code, a code that takes a conventional molal scale description of solution composition and implements the DH-ASF model for that solution. The code converts between apparent and independent end-member sets, and calculates standard state chemical potentials, ideal activities and activity coefficients using the DH-ASF model for molal and mole fraction concentration scales. The code runs in MathematicaTM 4.1 onwards, but it is written in a general meta-code form so that it can be implemented on a variety of platforms. Inputs to the code can be made manually, read from an auxiliary file, or presented to the input modules as passed variables. The code is provided with thermodynamic data from the Holland and Powell data set, but can be used with any data specified by the user. Outputs are designed to be modified by the user. Calculations on the systems NaCl- H2O, NaCl- CaCl2- H2O and NaCl- CO2- H2O are used to demonstrate the utility of the DES-code. Calculations predict that ion association increases with increasing temperature and concentration of salt and CO2, and with decreasing pressure. This is consistent with experimental observation and the results of molecular simulations. The DES-code is suitable for use as it stands, or for modification and incorporation into existing or new Gibbs energy minimisation or equilibrium solving thermodynamic codes.

Evans, Katy; Powell, Roger

2007-06-01

243

Thermo-chemical ablation of heat shields under Earth reentry conditions  

NASA Astrophysics Data System (ADS)

The process of ablation for earth atmospheric entry is modeled. The flowfield surrounding the ablator is modeled by an extended set of Navier-Stokes equations that include the effects of thermochemical nonequilibrium. This set of equations encompasses the conservation of mass for each chemical species, conservation of momentum, the conservation of vibrational energy, and the conservation of total energy. The heat conduction into the ablator material is modeled by using Fourier's Law of heat conduction and the heat equation. The flowfield and ablator are coupled by a thermochemical ablation model that includes a surface mass balance and a surface energy balance. The ablation model takes into account chemical reactions of the flowfield species with the surface material, surface material acting as a catalytic surface, and sublimation of the surface material. To solve the governing equations for the model, a computational fluid dynamics approach is used where the flowfield is solved using a modified Steger-Warming flux vector splitting scheme and the solid is solved using a centrally differenced scheme. A Gauss-Seidel line relaxation technique is implemented to speed numerical convergence. The flowfield model is verified by comparing to flowfield computations of other researchers and to experimental data. The ablator/heat shield model is validated by a direct comparison between an exact analytical solution and a numerical solution. The thermochemical ablation model is verified by comparing to the experimental results of the Passive Nosetip Technology (PANT) program. The model is used to calculate steady-state ablation data for sphere-cone reentry bodies. Two bodies with nose radii of 0.0127 m and 0.1270 m are tested at a velocity of 8 km/s. The ablator material is selected to be a commercial grade graphite. Due to the ablator selection, the flowfield is limited to 11 chemical species and two internal energy modes. A standard earth atmosphere is selected at altitudes ranging from 40 km to 80 km. The major results concern the thermochemical ablation model. Both oxidation and sublimation mechanisms are evident and are dependent on freestream conditions and the reentry body shape.

Keenan, James Anthony

1994-04-01

244

Greener Syntheses and Chemical Transformations: Sustainable Alternative Methods and Applications of Nano-Catalysts  

EPA Science Inventory

The presentation summarizes our sustainable chemical synthesis activity involving benign alternatives, such as the use of supported reagents, and greener reaction medium in aqueous or solvent-free conditions.1 The synthesis of heterocyclic compounds, coupling reactions, and a var...

245

Greener Syntheses and Chemical Transformations: Sustainable Alternative Methods and Applications of Nano-Catalysts. (Florence, Italy)  

EPA Science Inventory

The presentation summarizes our sustainable chemical synthesis activity involving benign alternatives, such as the use of supported reagents, and greener reaction medium in aqueous or solvent-free conditions. The synthesis of heterocyclic compounds, coupling reactions, and a vari...

246

Formation and maintenance of aggregations in walleye pollock, Theragra chalcogramma , larvae under laboratory conditions: role of visual and chemical stimuli  

Microsoft Academic Search

Although planktonic marine fish larvae are often distributed in aggregations, the role of behavioral responses to environmental factors in these aggregations is not well understood. This work examines, under laboratory conditions, the influence of visual and chemical stimuli in the formation and maintenance of aggregations in walleye pollock,Theragra chalcogramma, larvae. Larvae were exposed to a horizontal gradient of light (visual

Michael W. Davis; Bori L. Olla

1995-01-01

247

The Effect of Cooperative Learning Approach Based on Conceptual Change Condition on Students' Understanding of Chemical Equilibrium Concepts  

ERIC Educational Resources Information Center

The purpose of this study is to investigate the effects of the cooperative learning approach based on conceptual change conditions over traditional instruction on 10th grade students' conceptual understanding and achievement of computational problems related to chemical equilibrium concepts. The subjects of this study consisted of 87 tenth grade

Bilgin, Ibrahim; Geban, Omer

2006-01-01

248

Study of Chemical Surface Structure of Natural Sorbents Used for Removing of Pb2+ Ions from Model Aqueous Solutions (part Ii)  

NASA Astrophysics Data System (ADS)

This article presents the results of the chemical structure research of organic sorbent surface such as walnut shells, plums stones and sunflower hulls with using such methods as infrared spectrometry (FTIR) and elemental analysis. Based on the IR spectra identification of functional groups present on the surface of studied materials has been done as well as determination of their effect on the sorption mechanism of Pb2+ ions from aqueous model solutions W artykule przedstawiono wyniki bada? chemicznej struktury powierzchni sorbentw organicznych takich jak: ?upiny orzecha w?oskiego, pestki ?liwek oraz ?uski s?onecznika z wykorzystaniem metody spektrometrii w podczerwieni (FTIR) oraz analizy elementarnej. W oparciu o uzyskane widma IR dokonano identyfikacji grup funkcyjnych obecnych na powierzchni tych materia?w i okre?lono ich wp?yw na mechanizm sorpcji jonw Pb2+ z modelowych roztworw wodnych. Analiza elementarna wykaza?a, ?e spo?rd badanych sorbentw, najwi?ksz? zawarto?? w?gla (49,91%) i wodoru (5,93%) maj? pestki ?liwek. Najwi?cej azotu (1,59%) zawieraj? ?uszczyny s?onecznika (tabela 1). Zawarto?? siarki we wszystkich badanych materia?ach jest znikoma, dlatego nie uda?o si? jej oznaczy? t? metod?. Obecno?? pozosta?ych pierwiastkw mo?e ?wiadczy? o istnieniu zarwno alifatycznych jak i aromatycznych po??cze? organicznych. Potwierdzeniem tego s? rwnie? zarejestrowane widma IR (rysunki 1-3). W oparciu o uzyskane wyniki mo?na przypuszcza? tak?e, i? udzia? procesu wymiany jonowej w sorpcji o?owiu z roztworw wodnych jest znacz?cy. ?wiadcz? o tym m.in. intensywno?ci pasm na widmach IR dla prbek badanych materia?w po ich kontakcie z roztworami jonw Pb2+ (rysunki 4-6).

Bo??cka, Agnieszka; Bo??cki, Piotr; Sanak-Rydlewska, Stanis?awa

2014-03-01

249

Evaluation of meat and bone meal combustion residue as lead immobilizing material for in situ remediation of polluted aqueous solutions and soils: "chemical and ecotoxicological studies".  

PubMed

As a result of bovine spongiform encephalopathy (BSE) crisis, meat and bone meal (MBM) production can no longer be used to feed cattle and must be safely disposed of or transformed. MBM specific incineration remains an alternative that could offer the opportunity to achieve both thermal valorization and solid waste recovery as ashes are calcium phosphate-rich material. The aim of this work is to evaluate ashes efficiency for in situ remediation of lead-contaminated aqueous solutions and soils, and to assess the bioavailability of lead using two biological models, amphibian Xenopus laevis larvae and Nicotiana tabaccum tobacco plant. With the amphibian model, no toxic or genotoxic effects of ashes are observed with concentrations from 0.1 to 5 g of ashes/L. If toxic and genotoxic effects of lead appear at concentration higher than 1 mg Pb/L (1 ppm), addition of only 100 mg of ashes/L neutralizes lead toxicity even with lead concentration up to 10 ppm. Chemical investigations (kinetics and X-ray diffraction (XRD) analysis) reveals that lead is quickly immobilized as pyromorphite [Pb10(PO4)6(OH)2] and lead carbonate dihydrate [PbCO(3).2H2O]. Tobacco experiments are realized on contaminated soils with 50, 100, 2000 and 10000 ppm of lead with and without ashes amendment (35.3g ashes/kg of soil). Tobacco measurements show that plant elongation is bigger in an ashes-amended soil contaminated with 10000 ppm of lead than on the reference soil alone. Tobacco model points out that ashes present two beneficial actions as they do not only neutralize lead toxicity but also act as a fertilizer. PMID:17240054

Deydier, E; Guilet, R; Cren, S; Pereas, V; Mouchet, F; Gauthier, L

2007-07-19

250

Self-association of unconjugated bilirubin-IX alpha in aqueous solution at pH 10.0 and physical-chemical interactions with bile salt monomers and micelles.  

PubMed Central

Spectrophotometric measurements of bilirubin-IX alpha in water and in aqueous/organic solvent mixtures at pH 10.0 as a function of bilirubin-IX alpha concentration (approx. 0.6--400 microM) are consistent with the formation of dimers (KD - 1.5 microM) in dilute (less than 10 microM) aqueous solution and further self-aggregation to multimers at higher concentrations. Added urea (to 10M) and increases in temperature (to 62 degrees C) obliterate the dimer-multimer transition at 10 microM, but added NaCl (to 0.30 M) promotes strong aggregation of dimers over a narrow concentration range, suggesting a 'micellization' phenomenon. Concentrations of dioxan or ethanol greater than 60% (v/v) in water were required to obtain the absorption spectrum of bilirubin-IX alpha monomers, suggesting that both hydrophobic and electrostatic (pi-orbital) interactions are involved in stabilizing the dimeric state in water. Micellar concentrations of sodium dodecyl sulphate induced spectrophotometric shifts in the dimer absorption spectrum of bilirubin-IX alpha consistent with progressive partitioning of bilirubin-IX alpha monomers into a relatively non-polar region of the micelles and allowed a deduction of the apparent critical micellar concentration that closely approximated the literature values. The pattern of bilirubin IX alpha association with bile salts is complex, since the absorption spectrum shifts hypsochromically below and bathochromically above the critical micellar concentration of the bile salts. Consistent with these observations, bilirubin IX alpha appears to bind to the polar face of bile salt monomers and to the polar perimeter of small bile salt micelles. At higher bile salt concentrations some-bilirubin-IX alpha monomers partition into the hydrophobic interior of the bile salt micelles. Our results suggest that under physiological conditions the natural conjugates of bilirubin-IX alpha may exhibit similar physical chemical properties in bile, in that dimers, highly aggregated multimers and bile salt-associated monomers may co-exist. PMID:38779

Carey, M C; Koretsky, A P

1979-01-01

251

Journal of Chemical Ecology, Vol. 25, No. 12, 1999 CONDITIONED ALARM BEHAVIOR IN FATHEAD  

E-print Network

(Pimephales promelas) RESULTING FROM ASSOCIATION OF CHEMICAL ALARM PHEROMONE WITH A NONBIOLOGICAL VISUAL--Fathead minnows (Pimephales promelas) adopt antipredator (alarm) behavior when they detect alarm pheromone, Pimephales promelas, alarm pheromone, Schreckstoff, learned recognition of predation risk, red light. #12

Wisenden, Brian D.

252

Effect of chemical mechanical planarization processing conditions on polyurethane pad properties  

E-print Network

Chemical Mechanical Planarization (CMP) is a vital process used in the semiconductor industry to isolate and connect individual transistors on a chip. However, many of the fundamental mechanisms of the process are yet to ...

Ng, Grace Siu-Yee, 1980-

2003-01-01

253

Sensitivity of chemical exergy for atmospheric gases and gaseous fuels to variations in ambient conditions  

Microsoft Academic Search

The variations of chemical exergy with ambient temperature from ?30C to 45C, pressure from 0.6 to 1.1bar and relative humidity (RH) from 10% to 100% were investigated for gaseous fuels and atmospheric gases on the basis of Szarguts model. It was found that the variations are significant. At ambient pressure of 1atm and RH at 70%, the chemical exergy of

Ivar S. Ertesvg

2007-01-01

254

Maximizing productivity of CHO cell-based fed-batch culture using chemically defined media conditions and typical manufacturing equipment.  

PubMed

A highly productive chemically defined fed-batch process was developed to maximize titer and volumetric productivity for Chinese hamster ovary cell-based recombinant protein manufacturing. Two cell lines producing a recombinant antibody (cell line A) and an Fc-fusion protein (cell line B) were used for development. Both processes achieved product titers of 10 g/L on day 18 under chemically defined conditions. For cell line B, the use of plant derived hydrolysates combined with the optimized chemically defined medium increased the titer to 13 g/L. Volumetric productivities were increased from a base line of about 200 mg/L/d to about 500 mg/L/d under chemically defined conditions and as high as 700 mg/L/d with cell line B using plant derived hydrolysates. Peak cell densities reached greater than 20E6 vc/mL, and cell viabilities were maintained above 80% on day 18 without the use of antiapoptotic genes or temperature shift. A rapid compound screening method was developed to effectively test positive factors within 72 h. Peak volumetric oxygen uptake rates (OUR) more than tripled from the baseline condition. Oxygen demand continued to increase after maximum cell density was reached with a maximal OUR of 3.7 mmol/L/h. The new process format was scaled up and verified at 100 L pilot scale using reactor equipment of similar configuration as used at manufacturing scale. PMID:20945494

Huang, Yao-Ming; Hu, WeiWei; Rustandi, Eddie; Chang, Kevin; Yusuf-Makagiansar, Helena; Ryll, Thomas

2010-01-01

255

In vivo hepatoprotective activity of the aqueous extract of Artemisia absinthium L. against chemically and immunologically induced liver injuries in mice  

Microsoft Academic Search

Aim of the studyThis study aimed to evaluate in vivo hepatoprotective activity of the aqueous extract of Artemisia absinthium L. (AEAA), which has been used for the treatment of liver disorders in Traditional Uighur Medicine.

Nurmuhammat Amat; Halmurat Upur; Biljana Blaekovi?

2010-01-01

256

Clinical vocabulary as a boundary object in multidisciplinary care management of multiple chemical sensitivity, a complex and chronic condition  

PubMed Central

Background: Research has shown that accurate and timely communication between multidisciplinary clinicians involved in the care of complex and chronic health conditions is often challenging. The domain knowledge for these conditions is heterogeneous, with poorly categorized, unstructured, and inconsistent clinical vocabulary. The potential of boundary object as a technique to bridge communication gaps is explored in this study. Methods: A standardized and controlled clinical vocabulary was developed as a boundary object in the domain of a complex and chronic health condition, namely, multiple chemical sensitivity, to improve communication among multidisciplinary clinicians. A convenience sample of 100 patients with a diagnosis of multiple chemical sensitivity, nine multidisciplinary clinicians involved in the care of patients with multiple chemical sensitivity, and 36 clinicians in the community participated in the study. Results: Eighty-two percent of the multidisciplinary and inconsistent vocabulary was standardized using the Systematized Nomenclature of Medicine Clinical Terms (SNOMED CT as a reference terminology. Over 80% of the multidisciplinary clinicians agreed on the overall usefulness of having a controlled vocabulary as a boundary object. Over 65% of clinicians in the community agreed on the overall usefulness of the vocabulary. Conclusion: The results from this study are promising and will be further evaluated in the domain of another complex chronic condition, ie, chronic pain. The study was conducted as a preliminary analysis for developing a boundary object in a heterogeneous domain of knowledge. PMID:21594060

Sampalli, Tara; Shepherd, Michael; Duffy, Jack

2011-01-01

257

Chemical sludge conditioning in combination with different conventional and alternative dewatering devices: chamber filter press, decanter and Bucher press.  

PubMed

The Kemicond process for sludge conditioning consists of chemical treatment with sulphuric acid and hydrogen peroxide at a pH-value of approximately 4 followed by a dewatering unit. It is shown that chemical treatment can improve the dewaterability of ferruginous digested sludge. It is concluded that the Fenton process as well as the oxidation of organics and the formation of iron hydroxo complexes are important reaction mechanisms. Furthermore, the organic matter changes through the acidic oxidative process. With the improvement in dewaterability, it is possible to achieve an increase in TS concentration, which affects a reduction of the sludge volume. Cost savings for sludge disposal can amortize the additional investment and operational costs for chemical treatment. PMID:18821238

Schaum, Christian; Cornel, Peter; Faria, Pedro; Recktenwald, Michael; Norrlw, Olof

2008-11-01

258

Chemical conversion of cisplatin and carboplatin with histidine in a model protein crystallized under sodium iodide conditions  

PubMed Central

Cisplatin and carboplatin are platinum anticancer agents that are used to treat a variety of cancers. Previous X-ray crystallographic studies of carboplatin binding to histidine in hen egg-white lysozyme (HEWL) showed a partial chemical conversion of carboplatin to cisplatin owing to the high sodium chloride concentration used in the crystallization conditions. Also, the co-crystallization of HEWL with carboplatin in sodium bromide conditions resulted in the partial conversion of carboplatin to the transbromoplatin form, with a portion of the cyclobutanedicarboxylate (CBDC) moiety still present. The results of the co-crystallization of HEWL with cisplatin or carboplatin in sodium iodide conditions are now reported in order to determine whether the cisplatin and carboplatin converted to the iodo form, and whether this took place in a similar way to the partial conversion of carboplatin to cisplatin in NaCl conditions or to transbromoplatin in NaBr conditions as seen previously. It is reported here that a partial chemical transformation has taken place to a transplatin form for both ligands. The NaI-grown crystals belonged to the monoclinic space group P21 with two molecules in the asymmetric unit. The chemically transformed cisplatin and carboplatin bind to both His15 residues, i.e. in each asymmetric unit. The binding is only at the N? atom of His15. A third platinum species is also seen in both conditions bound in a crevice between symmetry-related molecules. Here, the platinum is bound to three I atoms identified based on their anomalous difference electron densities and their refined occupancies, with the fourth bound atom being a Cl atom (in the cisplatin case) or a portion of the CBDC moiety (in the carboplatin case). PMID:25195879

Tanley, Simon W. M.; Helliwell, John R.

2014-01-01

259

Low-thrust chemical propulsion system propellant expulsion and thermal conditioning study. Executive summary  

NASA Technical Reports Server (NTRS)

Preferred techniques for providing abort pressurization and engine feed system net positive suction pressure (NPSP) for low thrust chemical propulsion systems (LTPS) were determined. A representative LTPS vehicle configuration is presented. Analysis tasks include: propellant heating analysis; pressurant requirements for abort propellant dump; and comparative analysis of pressurization techniques and thermal subcoolers.

Merino, F.; Wakabayashi, I.; Pleasant, R. L.; Hill, M.

1982-01-01

260

Strontium and steady state chemical alteration of minerals under hydrothermal conditions  

Microsoft Academic Search

Hydrothermal systems, common feature of active collisional orogens, have a profound effect on the Sr fluxes and Sr isotopic composition of riverine waters through the direct input of Sr from hot springs and ground-waters and chemical weathering of hydrothermal calcite. In an effort to quantify the role of mineral weathering, we present experimental results that describe the relationship between rock

P. Zuddas

2006-01-01

261

Metal-free activation of H 2 O 2 by synergic effect of ionic liquid and microwave: chemoselective oxidation of benzylic alcohols to carbonyls and unexpected formation of anthraquinone in aqueous condition  

Microsoft Academic Search

H2O2 mediated oxidation of alcohols in ionic liquid is revisited, wherein, ionic liquids under the influence of microwave irradiation\\u000a have been found to facilitate activation of H2O2 without any metal catalyst in aqueous condition. The method utilizes a neutral ionic liquid [hmim]Br both as catalyst and\\u000a solvent for efficient and chemoselective oxidation of benzyl alcohol derivatives on aromatic (?, ?)

Rakesh Kumar; Nandini Sharma; Naina Sharma; Abhishek Sharma; Arun K. Sinha

262

The effect of chemicals released by Gammarus lacustris on the depth distribution of Arctodiaptomus salinus in laboratory conditions  

Microsoft Academic Search

The effect of treatment water containing chemicals released by Gammarus lacustris or crushed\\/injured Arctodiaptomus salinus induced changes in vertical distribution of Arctodiaptomus in laboratory conditions. With food concentration in the medium corresponding to the maximum of algae concentration in Shira lake, A.salinus in an experimental vessel was situated higher than in the control. Average population depth of A.salinus decreased as

Yegor S. Zadereev; Michael V. Gubanov

2002-01-01

263

Thermodynamic and quantum chemical study of the transformations and operation mechanism of molybdenum catalysts under hydrogenation conditions  

Microsoft Academic Search

Structural transformations and the mechanism of the operation of molybdenum-containing catalysts under hydrogenation conditions\\u000a have been studied by chemical thermodynamics and quantum chemistry methods, as well as the role of sulfur compounds in this\\u000a process. It has been shown that molybdenum disulfide, an effective hydrogenation catalyst, is produced via the reaction of\\u000a molybdenum oxide with hydrogen sulfide, not elemental sulfur.

Kh. M. Kadiev; A. M. Gyulmaliev; M. Ya. Shpirt; S. N. Khadzhiev

2010-01-01

264

Conditions required for citrate utilization during growth of Lactobacillus casei ATCC334 in chemically defined medium and Cheddar Cheese extract  

Microsoft Academic Search

Conditions required for citrate utilization by Lactobacillus casei ATCC334 were identified. Citrate was utilized by this microorganism in modified Chemically Defined Media (mCDM) as an energy source, solely in the presence of limiting concentrations of galactose. The presence of glucose inhibited citrate utilization by this microorganism even when added in limiting concentrations. Utilization of citrate occurred at pH 6.00.2 and

Ilenys Daz-Muiz; James L. Steele

2006-01-01

265

Transport and fate of bacteria in porous media: Coupled effects of chemical conditions and pore space geometry  

Microsoft Academic Search

(1) Experimental and theoretical studies were undertaken to explore the coupled effects of chemical conditions and pore space geometry on bacteria transport in porous media. The retention of Escherichia coli D21g was investigated in a series of batch and column experiments with solutions of different ionic strength (IS) and ultrapure quartz sand. Derjaguin-Landau-Verwey-Overbeek (DLVO) calculations and results from batch experiments

Saeed Torkzaban; Shiva S. Tazehkand; Sharon L. Walker; Scott A. Bradford

2008-01-01

266

Transport and fate of bacteria in porous media: Coupled effects of chemical conditions and pore space geometry  

Microsoft Academic Search

Experimental and theoretical studies were undertaken to explore the coupled effects of chemical conditions and pore space geometry on bacteria transport in porous media. The retention of Escherichia coli D21g was investigated in a series of batch and column experiments with solutions of different ionic strength (IS) and ultrapure quartz sand. DerjaguinLandauVerweyOverbeek (DLVO) calculations and results from batch experiments suggested

Saeed Torkzaban; Shiva S. Tazehkand; Sharon L. Walker; Scott A. Bradford

2008-01-01

267

Diurnal fluctuations in the physico-chemical conditions of the Shatt al-Arab and the Ashar Canal  

Microsoft Academic Search

Diel fluctuations of temperature, dissolved oxygen, carbon dioxide, pH, total alkalinity and chlorosity in the Shatt al-Arab\\u000a River and the Ashar Canal at Basrah, Iraq were studied. The study covered three 24-hour periods in three different months.\\u000a Appreciable diurnal changes in the physico-chemical conditions and considerable heterogeneity were noted at the three stations\\u000a selected. The ranges of diurnal differences between

A L Sarker; S K Al-Nasiri; S A Hussein

1980-01-01

268

One-electron reduction of tris(2,2 prime -bipyrimidine)ruthenium(2+) ion in aqueous solution. A photochemical, radiation chemical, and electrochemical study  

SciTech Connect

The reduction of Ru(bpm){sub 3}{sup 2+} in aqueous solution has been investigated by use of photochemical, radiation chemical, and electrochemical techniques. The luminescent excited state of the substrate, *Ru(bpm){sub 3}{sup 2+}, has a lifetime ({tau}{sub 0}) of 0.081 {mu}s and a standard reduction potential of {approximately} 1.2 V; it is quenched by electron donors (D) such as ethylenediaminetetraacetic acid (EDTA), triethanolamine (TEOA), ascorbate ion, deprotonated cysteine, and reduced glutathione with values of k{sub q} that depend on the pH of the solution and the reducing ability of the quencher. The one-electron-reduced species, Ru(bpm){sub 3}{sup +}, is formed in the quenching reaction; it is also produced electrochemically and from the reaction of radiolytically generated CO{sub 2}{sup {center dot}{minus}} with Ru(bpm){sub 3}{sup 2+} (k = 6.7 {times} 10{sup 9} M{sup {minus}1} s{sup {minus}1}). Ru(bpm){sub 3}{sup +} is a good reducing agent (E{sub ox}{sup 0} = 0.73 V) and reduces MV{sup 2+} (methylviologen) to MV{sup {center dot}+} (k = 1.0 {times} 10{sup 9} M{sup {minus}1} s{sup {minus}1}). Ru(bpm){sub 3}{sup +} also undergoes protonation; its acidic form (pK{sub a} 6.3) is a milder reducing agent (E{sub ox}{sup 0} = 0.50 V) but is still capable of reducing MV{sup 2+} (k = 1.0 {times} 10{sup 6} M{sup {minus}1} s{sup {minus}1}). Both forms of Ru(bpm){sub 3}{sup +} are unstable with respect to long-term storage; it is likely they engage in disproportionation and/or reaction with the solvent. The continuous photolysis of a solution containing Ru(bpm){sub 3}{sup 2+}, MV{sup 2+}, and a sacrificial reductive quencher (EDTA, TEOA) generates MV{sup {center dot}+}. Values of {eta}{sub ce} of 0.64 and {approximately}0.7 for TEOA and EDTA, respectively, in alkaline solution have been obtained.

Neshvad, G.; Hoffman, M.Z. (Boston Univ., MA (USA)); Mulazzani, Q.G.; Ciano, M.; D'Angelantonio, M. (Istituto di Fotochimica e Radiazioni d'Alta Energia, Bologna (Italy)); Venturi, M. (Istituto di Fotochimica e Radiazioni d'Alta Energia, Bologna (Italy) Univ. di Bologna (Italy))

1989-08-10

269

Effect of chemical structure on the biodegradation of polyurethanes under composting conditions  

Microsoft Academic Search

Polyesterpolyurethanes having different chemical structure were synthesized and their biodegradabilities were investigated. Average molecular weight of the synthesized polyurethanes ranged from 79106 to 161715(Mw) by gel permeation chromatography. Degradation experiments were conducted by: hydrolytic degradation in NaOH solution; enzymatic degradation by lipase; and composting. Hydrolytic and enzymatic degradation decreased with the increase of the diol carbon chains in polyol, and

Young Duk Kim; Sung Chul Kim

1998-01-01

270

Sensitivity of the chemical exergy for atmospheric gases and gaseous fuels to variations in ambient conditions  

Microsoft Academic Search

Variation of the chemical exergy with ambient temperature from ?30 C to 45 C, pressure from 0.6 to 1.1 bar, and relative humidity (RH) from 10% to 100% was investigated for gaseous fuels and atmospheric gases on the basis of Szargut's model. It was found that the variation is significant. At ambient pressure at 1 atm and RH at 70%,

Ivar S. Ertesvg

271

The effect of chemical composition and austenite conditioning on the transformation behavior of microalloyed steels  

SciTech Connect

In this investigation, by using continuous cooling torsion (CCT) testing, the transformation behavior of four microalloyed steels under two circumstances of austenite conditioning and non-conditioning was studied. A full scale hot-rolling schedule containing a 13-pass deformation was employed for the conditioning of the austenite. The CCT tests were then employed till temperature of {approx} 540 Degree-Sign C and the flow curves obtained from this process were analyzed. The initial and final microstructures of the steels were studied by optical and electron microscopes. Results show that alloying elements would decrease the transformation temperature. This effect intensifies with the gradual increase of Mo, Nb and Cu as alloying elements added to the microalloyed steels. As well, austenite conditioning increased the transformation start temperature due mainly to the promotion of polygonal ferrite formation that resulted from a pancaked austenite. The final microstructures also show that CCT alone would decrease the amount of bainite by inducing ferrite transformation in the two phase region. In addition, after the transformation begins, the deformation might result in the occurrence of dynamic recrystallization in the ferrite region. This could lead to two different ferrite grain sizes at the end of the CCT. Moreover, the Nb bearing steels show no sign of decreasing the strength level after the transformation begins in the non-conditioned situation and their microstructure is a mix of polygonal ferrite and bainite indicating an absence of probable dynamic recrystallization in this condition. In the conditioned cases, however, these steels show a rapid decrease of the strength level and their final microstructures insinuate that ferrite could have undergone a dynamic recrystallization due to deformation. Consequently, no bainite was seen in the austenite conditioned Nb bearing steels. The pancaking of austenite in the latest cases produced fully polygonal ferrite structures. - Highlights: Black-Right-Pointing-Pointer Adding alloying elements would decrease the transformation temperatures. Black-Right-Pointing-Pointer Austenite conditioning increases the transformation start temperature. Black-Right-Pointing-Pointer Deformation could induce the occurrence of dynamic recrystallization in ferrite region.

Mousavi Anijdan, S.H., E-mail: hashem.mousavi@mail.mcgill.ca [Department of Mining and Materials Engineering, McGill University, 3610 University Street, Montreal, Quebec, H3A 2B (Canada); Rezaeian, Ahmad [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Yue, Steve [Department of Mining and Materials Engineering, McGill University, 3610 University Street, Montreal, Quebec, H3A 2B (Canada)

2012-01-15

272

Impact of oxygen cut off and starvation conditions on biological activity and physico-chemical properties of activated sludge.  

PubMed

Physico-chemical and biological parameters were monitored both throughout different oxygen cut off and starvation (OCS) times (6 h-72 h) and after the restoration of normal operational conditions. Sludge apparent viscosity and soluble extracellular polymeric substances (EPS) characteristics were measured to determine the activated sludge (AS) properties. Oxygen transfer, biological activity with specific oxygen uptake rate (SOUR) measurements during endogenous/exogenous conditions (without any external substrate/with external substrate consumption) and chemical oxygen demand (COD) removal were measured to assess the AS performances. During the different stress times, AS deflocculated as a decrease of apparent viscosity was observed and microorganisms biodegraded the released EPS to survive. After aeration return, and under endogenous conditions, size exclusion chromatographic fingerprints of soluble EPS were modified and macromolecules probably of type humic-like substances appeared in significant quantities. These new macromolecules presumably acted as biosurfactants. Consequently, the liquid surface tension, as well as the oxygen transfer rate (OTR), decreased. Under exogenous conditions, high biological activity (SOUR = 11.8 +/- 2.1 mg(O2 x g(MLVSS)(-1) x h(-1)) compensated the decrease of oxygen transfer. Finally, AS biomass maintained a constant COD degradation rate (15.7 +/- 1.9 mg(O2) x g(MLVSS)(-1) x h(-1)) before and after the disturbances for all times tested. This work demonstrates that AS microorganisms can counteract concomitant oxygen and nutrients shortage when the duration of such a condition does not exceed 72 h. Dissociation of endogenous/exogenous conditions appears to offer an ideal laboratory model to study EPS and biomass activity effects on oxygen transfer. PMID:23837341

Villain, Maud; Clouzot, Ludiwine; Guibaud, Gilles; Marrot, Benoit

2013-01-01

273

Effect of pedoclimatic conditions on the chemical composition of the Sigoise olive cultivar.  

PubMed

The present work focused on the quality and the chemical composition of monovarietal virgin olive oil from the Sigoise variety grown in two different locations in Tunisia, viz., a sub-humid zone (Bjaoua, Tunis) and an arid zone (Boughrara, Sfax). In addition to the quality characteristics (acidity, peroxide value, and the spectrophotometric indices K232 and K270) and the chemical composition (content of fatty acids, antioxidants, and volatile compounds) of the oil, the fruit characteristics of the olives were studied. Except for the content of the majority of the fatty acids, there were significant differences observed in the oil composition of olives that were cultivated in different locations. The content of total phenols and lipoxygenase (LOX) oxidation products was higher for olives grown at the higher altitude, whereas that of alpha-tocopherol, carotenes, and chlorophylls was higher for olives from the Boughrara region (lower altitude). Moreover, olives produced at the higher altitude showed a higher ripeness index and oil content than those cultivated at the lower altitude. PMID:20397230

Dabbou, Samia; Sifi, Samira; Rjiba, Imed; Esposto, Sonia; Taticchi, Agnese; Servili, Maurizio; Montedoro, Gian Francesco; Hammami, Mohamed

2010-04-01

274

Disruption of biofilms from sewage pipes under physical and chemical conditioning.  

PubMed

Biofilms grown inside two sewage collecting pipes located in industrial and residential areas are studied. Bacterial biomass inside three layers of biofilms was evaluated. Biofilm cohesion under different mixing rate and ionic strength was also investigated. Effects of physical and chemical parameters in the biofilms were evaluated by monitoring turbidity, chemical and biochemical oxygen demands. Extracted organic matter from biofilms was partitioned to polar, aromatic and saturated fractions using activated silica column chromatography. Results revealed that bacterial biomass growth depending on biofilm thickness and stratification. The most loaded stratum in bacterial biomass was the sewage-biofilm interface stratum that represented 51% of the total bacterial biomass. Stirring rate and ionic strength of mono- and bivalent salts showed a major influence in biofilm disruption. The stirring time enhanced the exchange dynamic and matter capture between biofilm fragments at the critical stirring rate 90 r/min. Sodium chloride showed the dispersing effect on biofilms in suspension, and decreased the BOD5 (biochemical oxygen demand) beyond the physiological salt concentration. PMID:19402410

Mahfoud, Charbel; El Samrani, Antoine; Mouawad, Rita; Hleihel, Walid; El Khatib, Rim; Lartiges, Bruno S; Ouani, Nam

2009-01-01

275

THE JOURNAL OF CHEMICAL PHYSICS 134, 154503 (2011) pH-dependent x-ray absorption spectra of aqueous boron oxides  

E-print Network

-ray absorption fine structure (NEXAFS) spectra at the boron K-edge were measured for aqueous boric acid, borate reveal that water is arranged nearly isotrop- ically around boric acid and sodium borate) spectroscopy ex- periments to probe boric acid, borate, and polyborate ions in solution. We also compare

Cohen, Ronald C.

276

Conversion of Japanese red pine wood ( Pinus densiflora) into valuable chemicals under subcritical water conditions  

Microsoft Academic Search

A comparative study on the decomposition of Japanese red pine wood under subcritical water conditions in the presence and absence of phosphate buffer was investigated in a batch-type reaction vessel. Since cellulose makes up more than 4045% of the components found in most wood species, a series of experiments were also carried out using pure cellulose as a model for

Feridoun Salak Asghari; Hiroyuki Yoshida

2010-01-01

277

Properties of chemical bath deposited CdS films at different annealing conditions  

SciTech Connect

The preparation of cubic CdS thin films with low resistivity by Chemical Bath Deposition (CBD) technique and subsequent annealings in S{sub 2} and H{sub 2}+ In is reported. Low temperature photoluminescence, x-rays and transmission spectra support the assumption that sulfur annealings contribute to fill the vacancies in the as-deposited films leading to an enlargement of the CdS cubic cell. This fact is revealed by increase in interplanar distances, evanescence of the PL red broad band and decrease in band gap energies. Cubic phase remains after H{sub 2}+ In annealing at higher temperatures. A resistivity as low as 11 {Omega}-cm was obtained at an optimum annealing temperature of 350{degree}C. {copyright} {ital 1996 American Institute of Physics.}

de Melo, O.; Hernandez, L.; Zelaya-Angel, O.; Lozada-Morales, R. [Physics Department, CINVESTAV-IPN, Aptdo. 14-740, 07000 (Mexico) D.F.; Vasco, E.; Puron, E. [Physics Faculty, University of Havana, 10400 La Habana (Cuba)

1996-07-01

278

A review of catalytic issues and process conditions for renewable hydrogen and alkanes by aqueous-phase reforming of oxygenated hydrocarbons over supported metal catalysts  

Microsoft Academic Search

We have recently developed a single-step, low-temperature process for the catalytic production of fuels, such as hydrogen and\\/or alkanes, from renewable biomass-derived oxygenated hydrocarbons. This paper reviews our work in the development of this aqueous-phase reforming (APR) process to produce hydrogen or alkanes in high yields. First, the thermodynamic and kinetic considerations that form the basis of the process are

R. R. Davda; J. W. Shabaker; G. W. Huber; R. D. Cortright; J. A. Dumesic

2005-01-01

279

Low temperature nanostructured zinc titanate by an aqueous particulate solgel route: Optimisation of heat treatment condition based on Zn:Ti molar ratio  

Microsoft Academic Search

Nanocrystalline zinc titanate (ZnTiO3) thin films and powders with purity of 94% were produced at the low sintering temperature of 500C and the short sintering time of 1h by a straightforward aqueous particulate solgel route. The effect of Zn:Ti molar ratio was studied on the crystallisation behaviour of zinc titanates. The prepared sols showed a narrow particle size distribution in

M. R. Mohammadi; D. J. Fray

2010-01-01

280

Impact of engineering flow conditions on plasmid DNA yield and purity in chemical cell lysis operations.  

PubMed

Chemical lysis of bacterial cells using an alkaline solution containing a detergent may provide an efficient scalable means for selectively removing covalently closed circular plasmid DNA from high-molecular-weight contaminating cellular components including chromosomal DNA. In this article we assess the chemical lysis of E. coli cells by SDS in a NaOH solution and determine the impact of pH environment and shear on the supercoiled plasmid and chromosomal DNA obtained. Experiments using a range of plasmids from 6 kb to 113 kb determined that in an unfavorable alkaline environment, where the NaOH concentration during lysis is greater than 0.15 +/- 0.03 M (pH 12.9 +/- 0.2), irreversible denaturation of the supercoiled plasmid DNA occurs. The extent of denaturation is shown to increase with time of exposure and NaOH concentration. Experiments using stirred vessels show that, depending on NaOH concentration, moderate to high mixing rates are necessary to maximize plasmid yield. While NaOH concentration does not significantly affect chromosomal DNA contamination, a high NaOH concentration is necessary to ensure complete conversion of chromosomal DNA to single-stranded form. In a mechanically agitated lysis reactor the correct mixing strategy must balance the need for sufficient mixing to eliminate potential regions of high NaOH concentrations and the need to avoid excessive breakage of the shear sensitive chromosomal DNA. The effect of shear on chromosomal DNA is examined over a wide range of shear rates (10(1)-10(5) s(-1)) demonstrating that, while increasing shear leads to fragmentation of chromosomal DNA to smaller sizes, it does not lead to significantly increased chromosomal DNA contamination except at very high shear rates (about 10(4)-10(5) s(-1)). The consequences of these effects on the choice of lysis reactor and scale-up are discussed. PMID:15281104

Meacle, F J; Lander, R; Ayazi Shamlou, P; Titchener-Hooker, N J

2004-08-01

281

Aqueous chemical growth of free standing vertical ZnO nanoprisms, nanorods and nanodiskettes with improved texture co-efficient and tunable size uniformity  

NASA Astrophysics Data System (ADS)

Tuning the morphology, size and aspect ratio of free standing ZnO nanostructured arrays by a simple hydrothermal method is reported. Pre-coated ZnO seed layers of two different thicknesses (?350 nm or 550 nm) were used as substrates to grow ZnO nanostructures for the study. Various parameters such as chemical ambience, pH of the solution, strength of the Zn2+ atoms and thickness of seed bed are varied to analyze their effects on the resultant ZnO nanostructures. Vertically oriented hexagonal nanorods, multi-angular nanorods, hexagonal diskette and popcorn-like nanostructures are obtained by altering the experimental parameters. All the produced nanostructures were analysed by X-ray powder diffraction analysis and found to be grown in the (002) orientation of wurtzite ZnO. The texture co-efficient of ZnO layer was improved by combining a thick seed layer with higher cationic strength. Surface morphological studies reveal various nanostructures such as nanorods, diskettes and popcorn-like structures based on various preparation conditions. The optical property of the closest packed nanorods array was recorded by UV-VIS spectrometry, and the band gap value simulated from the results reflect the near characteristic band gap of ZnO. The surface roughness profile taken from the Atomic Force Microscopy reveals a roughness of less than 320 nm.

Ram, S. D. Gopal; Ravi, G.; Athimoolam, A.; Mahalingam, T.; Kulandainathan, M. Anbu

2011-12-01

282

Strength change and chemical reactivity of ceramic breeder materials near operation conditions  

NASA Astrophysics Data System (ADS)

Measurements of mechanical strength achieved on pellet samples of various ceramic breeder materials which had been irradiated in the COMPLIMENT experiment (1.8 dpa, 0.4-1.4% lithium burnup, 400-450C and 650-700C) indicated a general strength reduction. The Young's modulus decreased to 70-80%, and the compressive strength down to about 30% of the initial values. Concerning the fracture strength, increasing irradiation sensitivity was indicated in the order: LiAlO 2, Li 2ZrO 3 ? Li 2SiO 3, Li 4SiO 4. The largest irradiation effect seems to be due to coarse microstructure damage and could be advanced by the tritium production. The cladding attack observed in the sealed breeder rod samples was compared with the amount expected from tritium water production and, on the other hand, with that in annealing tests at 1 Pa H 2O. Such tests were found to be conservative. Major chemical attack of the steel cladding seemed to be connected with an unusual content of oxidizing impurities in the breeder material.

Dienst, W.; Zimmermann, H.

1994-09-01

283

Physico-chemical conditions for plankton in Lake Timsah, a saline lake on the Suez Canal  

NASA Astrophysics Data System (ADS)

Lake Timsah receives high salinity water from the Suez Canal, mainly from the south, and freshwater from a Nile canal and other sources, producing a salinity stratification with surface salinities of 20-40 and over 40 in deeper water. Water temperature at a depth of 50-70 cm fell to below 20 C in winter and rose to above 30 C in summer; oxygen concentration at the same depth ranged between 6-10 mg l -1 and the pH was 81-83, and at mid-day this water was supersaturated with oxygen through 6-8 months of the year. The main chemical nutrients reached their highest levels in winter (December-February) and their lowest levels in summer (May-August), silicate varying between 1-7 ? M, phosphate between 01 and 08 ? M and nitrate between 4-10 ? M; nitrite varied in a more complex manner, usually between 025 and 04 ? M. The atomic ratio of N/P was generally well above the Redfield ratio level, except for a few months in midwinter. These nutrient concentrations are high in comparison with those of unpolluted seas of the region, but are typical of the more eutrophic coastal waters in most parts of the world.

El-Serehy, H. A. H.; Sleigh, M. A.

1992-02-01

284

Direct density measurements under mantle and core conditions and chemical characterization of high-PT samples (Invited)  

NASA Astrophysics Data System (ADS)

We simulate the physical conditions of Earths interior in multi-anvil apparatus and diamond-anvil cell (DAC) that can routinely generate pressure(P)-temperature(T) conditions corresponding to the top of the lower mantle and the outer core, respectively. The challenges have been to obtain precious measurements of physical properties of mantle and core material under well-controlled simultaneous high P-T conditions and to obtain chemical information of the recovered high P-T diamond-anvil cell samples. We have developed a range of complementary high-PT devices to optimize sample environment and P-T stability. They include large-volume multi-anvil apparatus, externally heated DAC, internal-heating DAC, laser-heating DAC, combination of internal- and laser-heating DAC, and combination of externally heated and laser-heating DAC. The externally heated and laser-heating DACs are complementary in P-T range and heating stability, whereas the combination of externally heated and laser-heating DAC shows great promises to achieve stable simultaneous high P-T conditions. We have take the internal resistance heating of metallic sample in the diamond-anvil cell into a new level, generating stable heating up to 2100 K at 70 GPa with iron foil. Higher, stable temperatures were achieved by combination of internal- and laser-heating, a promise technique for studying conductive samples at high pressure and temperature. The combination of improved high-PT technique and advancement in synchrotron X-ray diffraction has significantly expanded our capability to investigate the physical properties of the Earths mantle and core. We have determined the densities of (Al,Fe)-bearing mantle perovskite and (Mg,Fe)O solid solutions, with high precision, up to 135 GPa and 2700 K, covering the entire lower mantle P-T conditions. I will also show density measurements of iron alloys at simultaneous high P-T, using internal- and laser-heating DACs and combination of internal- and laser-heating. Stable temperature generation in the DAC is a key to obtaining reproducible, reliable chemical information of the laser-heated samples. Use of micro- and nano-analytical tools such as FIB and FE-SEM to recover and analyze recovered DAC samples will be demonstrated. The complete characterization of chemical and physical properties of the mantle and core materials at high pressure and temperature will further advance our understanding of the Earths interior.

Fei, Y.

2009-12-01

285

Meteorites and the physico-chemical conditions in the early solar nebula  

E-print Network

Chondritic meteorites constitute the most ancient rock record available in the laboratory to study the formation of the solar system and its planets. Detailed investigations of their mineralogy, petrography, chemistry and isotopic composition and comparison with other primitive solar system samples such as cometary dust particles have allowed through the years to decipher the conditions of formation of their individual components thought to have once been free-floating pieces of dust and rocks in the early solar nebula. When put in the context of astrophysical models of young stellar objects, chondritic meteorites and cometary dust bring essential insights on the astrophysical conditions prevailing in the very first stages of the solar system. Several exemples are shown in this chapter, which include (1) high temperature processes and the formation of chondrules and refractory inclusions, (2) oxygen isotopes and their bearing on photochemistry and large scale geochemical reservoirs in the nebula, (3) organosynthesis and cold cloud chemistry recorded by organic matter and hydrogen isotopes, (4) irradiation of solids by flares from the young Sun and finally (5) large scale transport and mixing of material evidenced in chondritic interplanetary dust particles and samples returned from comet Wild2 by the Stardust mission.

Jerome Aleon

2008-09-10

286

Low-thrust chemical propulsion system propellant expulsion and thermal conditioning study  

NASA Technical Reports Server (NTRS)

Thermal conditioning systems for satisfying engine net positive suction pressure (NPSP) requirements, and propellant expulsion systems for achieving propellant dump during a return-to-launch site (RTLS) abort were studied for LH2/LO2 and LCH4/LO2 upper stage propellant combinations. A state-of-the-art thermal conditioning system employing helium injection beneath the liquid surface shows the lowest weight penalty for LO2 and LCH4. A technology system incorporating a thermal subcooler (heat exchanger) for engine NPSP results in the lowest weight penalty for the LH2 tank. A preliminary design of two state-of-the-art and two new technology systems indicates a weight penalty difference too small to warrant development of a LH2 thermal subcooler. Analysis results showed that the LH2/LO2 propellant expulsion system is optimized for maximum dump line diameters, whereas the LCH4/LO2 system is optimized for minimum dump line diameter (LCH4) and maximum dump line diameter (LO2). The primary uncertainty is the accurate determination of two-phase flow rates through the dump system; experimentation is not recommended because this uncertainty is not considered significant.

Merino, F.; Wakabayashi, I.; Pleasant, R. L.; Hill, M.

1982-01-01

287

Chemical and Physical Environmental Conditions Underneath Mat- and Canopy-Forming Macroalgae, and Their Effects on Understorey Corals  

PubMed Central

Disturbed coral reefs are often dominated by dense mat- or canopy-forming assemblages of macroalgae. This study investigated how such dense macroalgal assemblages change the chemical and physical microenvironment for understorey corals, and how the altered environmental conditions affect the physiological performance of corals. Field measurements were conducted on macroalgal-dominated inshore reefs in the Great Barrier Reef in quadrats with macroalgal biomass ranging from 235 to 1029 g DW m?2 dry weight. Underneath mat-forming assemblages, the mean concentration of dissolved oxygen was reduced by 26% and irradiance by 96% compared with conditions above the mat, while concentrations of dissolved organic carbon and soluble reactive phosphorous increased by 26% and 267%, respectively. The difference was significant but less pronounced under canopy-forming assemblages. Dissolved oxygen declined and dissolved inorganic carbon and alkalinity increased with increasing algal biomass underneath mat-forming but not under canopy-forming assemblages. The responses of corals to conditions similar to those found underneath algal assemblages were investigated in an aquarium experiment. Coral nubbins of the species Acropora millepora showed reduced photosynthetic yields and increased RNA/DNA ratios when exposed to conditions simulating those underneath assemblages (pre-incubating seawater with macroalgae, and shading). The magnitude of these stress responses increased with increasing proportion of pre-incubated algal water. Our study shows that mat-forming and, to a lesser extent, canopy-forming macroalgal assemblages alter the physical and chemical microenvironment sufficiently to directly and detrimentally affect the metabolism of corals, potentially impeding reef recovery from algal to coral-dominated states after disturbance. Macroalgal dominance on coral reefs therefore simultaneously represents a consequence and cause of coral reef degradation. PMID:20856882

Hauri, Claudine; Fabricius, Katharina E.; Schaffelke, Britta; Humphrey, Craig

2010-01-01

288

Chemical and physical environmental conditions underneath mat- and canopy-forming macroalgae, and their effects on understorey corals.  

PubMed

Disturbed coral reefs are often dominated by dense mat- or canopy-forming assemblages of macroalgae. This study investigated how such dense macroalgal assemblages change the chemical and physical microenvironment for understorey corals, and how the altered environmental conditions affect the physiological performance of corals. Field measurements were conducted on macroalgal-dominated inshore reefs in the Great Barrier Reef in quadrats with macroalgal biomass ranging from 235 to 1029 g DW m(-2) dry weight. Underneath mat-forming assemblages, the mean concentration of dissolved oxygen was reduced by 26% and irradiance by 96% compared with conditions above the mat, while concentrations of dissolved organic carbon and soluble reactive phosphorous increased by 26% and 267%, respectively. The difference was significant but less pronounced under canopy-forming assemblages. Dissolved oxygen declined and dissolved inorganic carbon and alkalinity increased with increasing algal biomass underneath mat-forming but not under canopy-forming assemblages. The responses of corals to conditions similar to those found underneath algal assemblages were investigated in an aquarium experiment. Coral nubbins of the species Acropora millepora showed reduced photosynthetic yields and increased RNA/DNA ratios when exposed to conditions simulating those underneath assemblages (pre-incubating seawater with macroalgae, and shading). The magnitude of these stress responses increased with increasing proportion of pre-incubated algal water. Our study shows that mat-forming and, to a lesser extent, canopy-forming macroalgal assemblages alter the physical and chemical microenvironment sufficiently to directly and detrimentally affect the metabolism of corals, potentially impeding reef recovery from algal to coral-dominated states after disturbance. Macroalgal dominance on coral reefs therefore simultaneously represents a consequence and cause of coral reef degradation. PMID:20856882

Hauri, Claudine; Fabricius, Katharina E; Schaffelke, Britta; Humphrey, Craig

2010-01-01

289

All-aqueous multiphase microfluidics  

PubMed Central

Immiscible aqueous phases, formed by dissolving incompatible solutes in water, have been used in green chemical synthesis, molecular extraction and mimicking of cellular cytoplasm. Recently, a microfluidic approach has been introduced to generate all-aqueous emulsions and jets based on these immiscible aqueous phases; due to their biocompatibility, these all-aqueous structures have shown great promises as templates for fabricating biomaterials. The physico-chemical nature of interfaces between two immiscible aqueous phases leads to unique interfacial properties, such as an ultra-low interfacial tension. Strategies to manipulate components and direct their assembly at these interfaces needs to be explored. In this paper, we review progress on the topic over the past few years, with a focus on the fabrication and stabilization of all-aqueous structures in a multiphase microfluidic platform. We also discuss future efforts needed from the perspectives of fluidic physics, materials engineering, and biology for fulfilling potential applications ranging from materials fabrication to biomedical engineering. PMID:24454609

Song, Yang; Sauret, Alban; Cheung Shum, Ho

2013-01-01

290

Physicochemical Properties of Secondary Organic Aerosol (soa) Particles Generated Under Laboratory Photooxidation Conditions  

NASA Astrophysics Data System (ADS)

The goal of this experiment is to investigate the chemical reactivity of secondary or- ganic aerosol particles (SOA) in the presence of NOx. of special interest is the ques- tion whether or not SOA enables the reduction of NO2 to HONO, an important photochemical OH precursor. We report the controlled production of SOA particles using 5ppm of toluene (C7H8) or limonene (C10H16) in the presence of O3 or NO2 at 60% r.h. at 1 atmosphere of air using a (filtered) 150W highpressure Xe arc lamp as a photon source. The particle production is taking place in an atmospheric pressure flow cell whose gas phase residence time was chosen to lie in the range of one to several seconds. The gas phase is monitored using a differentially pumped quadrupole mass spectrometer whereas the condensed phase has been characterized both by its total particle count using a Condensation Nucleation Counter (CNC) or a downstream Differential Mobility Analyzer (DMA) coupled to an additional CNC. Particle counts of several 105 particles cm-3 were routinely achieved. Both O3 and NO2 are removed immediately after the flow reactor using a diffusion denuder coated with either KI or NDA. The flow has been directed across a glass fiber filter during one to two hours at constant throughput. Subsequently the SOA particles supported on the glass fiber fil- ter, typically a few mg, have been investigated in a low-pressure Knudsen flow reactor using NO2 and H2O.

Demirdjian, B.; Rossi, M. J.

291

Fretting-wear prediction in heat exchanger tubes: The effect of chemical cleaning and modelling ill-defined support conditions  

SciTech Connect

Chemical cleaning of heat exchangers increases the clearances between tubes and their supports, which may lead to increased fretting-wear damage. This paper presents the results of a fretting-wear damage analysis of a U-bend tube at nominal and post-cleaning conditions. In multi-span heat exchanger tubes, the boundary conditions at the supports are ill-defined due to tube-support clearances. The fretting-wear rate at a support is a function of the gap (the distance between the tube and the support if the tube is not contacting the support) and preload (the contact force between the tube and the support if the tube is contacting the support). The configurations of gap/preload for a typical multi-span tube are numerous and not all possibilities can be analyzed. Instead, a randomly selected group of tube-to-support configurations that is representative of the whole set needs to be used. In this paper, results of simulations for 40 randomly chosen tube-to-support configurations are presented. These indicate that when random vibration is considered, on the average no significant increase in fretting-wear damage will occur after chemical cleaning.

Yetisir, M.; Fisher, N.J. [Atomic Energy of Canada Limited, Chalk River, Ontario (Canada). Chalk River Labs.

1996-12-01

292

Chemical profiling of Jatropha tissues under different torrefaction conditions: application to biomass waste recovery.  

PubMed

Gradual depletion of the world petroleum reserves and the impact of environmental pollution highlight the importance of developing alternative energy resources such as plant biomass. To address these issues, intensive research has focused on the plant Jatropha curcas, which serves as a rich source of biodiesel because of its high seed oil content. However, producing biodiesel from Jatropha generates large amounts of biomass waste that are difficult to use. Therefore, the objective of our research was to analyze the effects of different conditions of torrefaction on Jatropha biomass. Six different types of Jatropha tissues (seed coat, kernel, stem, xylem, bark, and leaf) were torrefied at four different temperature conditions (200C, 250C, 300C, and 350C), and changes in the metabolite composition of the torrefied products were determined by Fourier transform-infrared spectroscopy and nuclear magnetic resonance analyses. Cellulose was gradually converted to oligosaccharides in the temperature range of 200C-300C and completely degraded at 350C. Hemicellulose residues showed different degradation patterns depending on the tissue, whereas glucuronoxylan efficiently decomposed between 300C and 350C. Heat-induced depolymerization of starch to maltodextrin started between 200C and 250C, and oligomer sugar structure degradation occurred at higher temperatures. Lignin degraded at each temperature, e.g., syringyl (S) degraded at lower temperatures than guaiacyl (G). Finally, the toxic compound phorbol ester degraded gradually starting at 235C and efficiently just below 300C. These results suggest that torrefaction is a feasible treatment for further processing of residual biomass to biorefinery stock or fertilizer. PMID:25191879

Watanabe, Taiji; Shino, Amiu; Akashi, Kinya; Kikuchi, Jun

2014-01-01

293

Photolysis of oxyfluorfen in aqueous methanol.  

PubMed

Photolysis of oxyfluorfen, an herbicide of the nitrodiphenyl ether class, was studied in aqueous methanol under UV and sunlight. UV irradiation was carried out in a borosilicate glass photoreactor (containing 250ppm oxyfluorfen in 50% aqueous methanol) equipped with a quartz filter and 125 watt mercury lamp (maximum output 254 nm) at 25 1C. Sunlight irradiation was conducted at 28 1C in borosilicate Erlenmeyer flasks containing 250ppm oxyfluorfen in 50% aqueous methanol. The samples from both the irradiated conditions were withdrawn at a definite time interval and extracted to measure oxyfluorfen content by gas chromatography-flame ionization detector for rate study. The half-life values were 20hours and 2.7days under UV and sunlight exposure, respectively. Photolysis of oxyfluorfen yielded 13 photoproducts of which three were characterized by infrared spectrophotometer and (1)H NMR and (13)C NMR spectroscopy. The rest of the photoproducts were identified by gas chromatography-mass spectrometry (GC-MS) and thin layer chromatography (TLC). An ionization potential 70eV was used for electron impact-mass spectrometry (EI-MS) and methane was used as reagent gas for chemical ionization-mass spectrometry (CI-MS). Two of the photoproducts were also synthesized for comparison. The main phototransformation pathways of oxyfluorfen involved nitro reduction, dechlorination, and hydrolysis as well as nucleophiles displacement reaction. PMID:23998303

Chakraborty, Subhasish K; Chakraborty, Savitri; Bhattacharyya, Anjan; Chowdhury, Ashim

2013-01-01

294

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

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.

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

2006-01-01

295

Effects of Atmospheric Conditions and the Land/Atmospheric Interface on Transport of Chemical Vapors from Subsurface Sources  

NASA Astrophysics Data System (ADS)

Understanding the movement of chemical vapors and gas through variably saturated soil subjected to atmospheric thermal and mass flux boundary conditions at the land/atmospheric interface is important to many applications, including landmine detection, methane leakage during natural gas production from shale and CO2 leakage from deep geologic storage. New, advanced technologies exist to sense chemical signatures and gas leakage at the land/atmosphere interface, but interpretation of sensor signals remains a challenge. Chemical vapors are subject to numerous interactions while migrating through the soil environment, masking source conditions. The process governing movement of gases through porous media is often assumed to be Fickian diffusion through the air phase with minimal quantification of other processes, such as convective gas flow and temporal or spatial variation in soil moisture. Vapor migration is affected by atmospheric conditions (e.g. humidity, temperature, wind velocity), soil thermal and hydraulic properties and contaminant properties, all of which are physically and thermodynamically coupled. The complex coupling of two drastically different flow regimes in the subsurface and atmosphere is commonly ignored in modeling efforts, or simplifying assumptions are made to treat the systems as de-coupled. Experimental data under controlled laboratory settings are lacking to refine the theory for proper coupling and complex treatment of vapor migration through porous media in conversation with atmospheric flow and climate variations. Improving fundamental understanding and accurate quantification of these processes is not feasible in field settings due to lack of controlled initial and boundary conditions and inability to fully characterize the subsurface at all relevant scales. The goal of this work is to understand the influence of changes in atmospheric conditions to transport of vapors through variably saturated soil. We have developed a tank apparatus with a network of soil and atmospheric sensors and a head space for air flow to simulate the atmospheric boundary layer. Experiments were performed under varying temperature values at the soil surface bounded by the atmospheric boundary layer. The model of Smits et al. [2011], accounting for non-equilibrium phase change and coupled heat, water vapor and liquid water flux through soil, was amended to include organic vapor in the gas phase and migration mechanisms often overlooked in models (thermal and Knudsen diffusion, density driven advection). Experimental results show increased vapor mass flux across the soil/atmospheric interface due to heat applied from the atmosphere and coupling of heat and mass transfer in the shallow subsurface for both steady and diurnal temperature patterns. Comparison of model results to experimental data shows dynamic interactions between transport in porous media and boundary conditions. Results demonstrate the value of considering interactions of the atmosphere and subsurface to better understand chemical gas transport through unsaturated soils and the land/atmospheric interface.

Rice, A. K.; Smits, K. M.; Cihan, A.; Howington, S. E.; Illangasekare, T. H.

2013-12-01

296

Impact of operating conditions on the removal of endocrine disrupting chemicals by membrane photocatalytic reactor.  

PubMed

This study focuses on the performance of a submerged membrane photocatalytic reactor for the removal of 17beta-oestradiol (E2) in the presence of humic acid (HA). In addition to the impact of operating parameters, such as membrane pore size, ultraviolet (UV) intensity and hydraulic retention time (HRT), the influence of long-term operation was also assessed by advanced characterization of the fouling layer formed on the membrane. The tighter (0.04 microm) hollow fibre polyvinylydene fluoride (PVDF) membrane was found to exhibit not only higher HA removal than the (0.2 microm) module (85% and 75%, respectively), but also greater transmembrane pressure (TMP) values and higher irreversible fouling. Long-term operation conditions have been simulated by conducting an ageing catalyst process and demonstrated a decrease in performance obtained with time. The artificially aged TiO2 resulted in higher TMP values and lower HA removals (about 10-20% decrease) compared with the non-aged catalyst. For E2 removal in the presence of HA, the passive adsorption of the oestrogen onto the organic matter was found to be significant (40% of the E2 adsorbed after I h), demonstrating the importance of the nature of the water matrix for this type of treatment process. An increase in the UV light intensity was observed to favour the E2 elimination, leading to more than 90% removal when using 64 W combined with PVDF membrane and an HRT of 3 h. PMID:24956801

Lpez Fernndez, Raquel; Coleman, Heather M; Le-Clech, Pierre

2014-08-01

297

Conditioned Place Avoidance of Zebrafish (Danio rerio) to Three Chemicals Used for Euthanasia and Anaesthesia  

PubMed Central

Zebrafish are becoming one of the most used vertebrates in developmental and biomedical research. Fish are commonly killed at the end of an experiment with an overdose of tricaine methanesulfonate (TMS, also known as MS-222), but to date little research has assessed if exposure to this or other agents qualifies as euthanasia (i.e. a good death). Alternative agents include metomidate hydrochloride and clove oil. We use a conditioned place avoidance paradigm to compare aversion to TMS, clove oil, and metomidate hydrochloride. Zebrafish (n?=?51) were exposed to the different anaesthetics in the initially preferred side of a light/dark box. After exposure to TMS zebrafish spent less time in their previously preferred side; aversion was less pronounced following exposure to metomidate hydrochloride and clove oil. Nine of 17 fish exposed to TMS chose not to re-enter the previously preferred side, versus 2 of 18 and 3 of 16 refusals for metomidate hydrochloride and clove oil, respectively. We conclude that metomidate hydrochloride and clove oil are less aversive than TMS and that these agents be used as humane alternatives to TMS for killing zebrafish. PMID:24505365

Wong, Devina; von Keyserlingk, Marina A. G.; Richards, Jeffrey G.; Weary, Daniel M.

2014-01-01

298

Study of chemically induced pressure generation of hydrogels under isochoric conditions using a microfabricated device  

NASA Astrophysics Data System (ADS)

A method is proposed to study the behavior of stimulus-sensitive hydrogels under isochoric conditions. Freedom of swell movement of such a hydrogel was restricted in all directions by enclosing the hydrogel between a micropressure sensor and a porous cover. Water and external stimuli can be applied to the hydrogel through the pores of the cover to provoke swelling, which results in pressure generation measured by the pressure sensor. The method was put to the proof by examining the response of a pH-sensitive hydrogel to changes in pH, ionic strength, and buffer concentrations of the surrounding solution. Both equilibrium and dynamic pressure generation were observed. The results show that higher pressures are obtained by incorporating more ionizable groups into the hydrogel network or by lowering the ionic strength of the external solution. Furthermore it was proven that pressures reach equilibrium faster when less titratable groups are incorporated or at the presence of higher buffer concentrations in the surrounding solution. By using microfabrication techniques the dimensions of the hydrogel could be kept small with the advantage that responses are fast. A DMAEMA-co-HEMA hydrogel with 2.5% protonable groups and a thickness of 15 ?m generated a ?pressure of 0.67105 Pa in 12 min when a pH step from 9 to 6 was applied. The presented method is a simple and fast manner to characterize the static and dynamic stimulus-dependent behavior of hydrogels.

Herber, S.; Eijkel, J.; Olthuis, W.; Bergveld, P.; van den Berg, A.

2004-08-01

299

Influence of Aqueous-Salt Conditions on the Structure and Dynamics of the Monomeric and Novel Dimeric forms of the Alzheimer s ABeta21-30 protein fragment  

NASA Astrophysics Data System (ADS)

The behavior of the Alzheimer's related peptide Abeta is the subject of much study. In typical computational studies the environment local to the peptide is assumed to be pure water; however, in vivo the peptide is found in the extracellular space near the plasma membrane which is rich in ionic species. In this thesis, the hypothesis that the presence of group I/IIA salts will result in increased sampling of disordered structures as well as modify the dynamics of meta-stable structural motifs in the small folding nucleus of the Abeta peptide (Abeta21-30) is examined under a variety of ionic environments and was shown that of the tested salts, CaCl2 (and MgCl2, to a much lesser degree) did increase the propensity for disordered states; while, the group IA salts, KCl and NaCl, had little effect on the secondary structure of the peptide. Further, study of three familial mutations of this peptide region is also performed under aqueous salt-environments to elucidate further mechanistic details of how aqueous salts modify the region's behavior. Finally, as experimental results have highlighted that aggregation rates of the full-length peptide are modified by the presence of CaCl2, this work examines novel dimers states of Abeta21-30 and their stabilities when exposed to CaCl2.

Smith, Micholas Dean

300

Rapid screening procedures for the hydrolysis products of chemical warfare agents using positive and negative ion liquid chromatographymass spectrometry with atmospheric pressure chemical ionisation  

Microsoft Academic Search

Qualitative screening procedures have been developed for the rapid detection and identification of the hydrolysis products of chemical warfare agents in aqueous samples and extracts, using liquid chromatographymass spectrometry with positive and negative atmospheric pressure chemical ionisation (APCI). Previously reported screening procedures, which used positive APCI or electrospray ionisation (ESI), were modified by using LC conditions that allowed acquisition of

Robert W Read; Robin M Black

1999-01-01

301

Lithium intercalation from aqueous solutions  

SciTech Connect

Lithium can be intercalated into a wide variety of materials using nonaqueous electrochemical cells. The use of aqueous methods is less common because of the reactivity of many lithium intercalation compounds with water. Here the authors show that lithium can be intercalated into host compounds from aqueous LiOH solution, provided the chemical potential of the intercalated lithium is sufficiently lower than the chemical potential of lithium in lithium metal. Using LiMn[sub 2]O[sub 4] as the host, the authors formed Li[sub 2]Mn[sub 2]O[sub 4] by intercalating Li from LiOH solution in an aqueous cell. This method may prove to be an economical way of preparing lithium transition metal oxides with high lithium contents for lithium-ion cell cathodes.

Li, W.; Dahn, J.R. (Simon Fraser Univ., Burnaby, British Columbia (Canada). Dept. of Physics); McKinnon, W.R. (National Research Council of Canada, Ottawa, Ontario (Canada). Inst. of Microstructural Sciences)

1994-09-01

302

The IUPAC aqueous and non-aqueous experimental pKa data repositories of organic acids and bases.  

PubMed

Accurate and well-curated experimental pKa data of organic acids and bases in both aqueous and non-aqueous media are invaluable in many areas of chemical research, including pharmaceutical, agrochemical, specialty chemical and property prediction research. In pharmaceutical research, pKa data are relevant in ligand design, protein binding, absorption, distribution, metabolism, elimination as well as solubility and dissolution rate. The pKa data compilations of the International Union of Pure and Applied Chemistry, originally in book form, have been carefully converted into computer-readable form, with value being added in the process, in the form of ionisation assignments and tautomer enumeration. These compilations offer a broad range of chemistry in both aqueous and non-aqueous media and the experimental conditions and original reference for all pKa determinations are supplied. The statistics for these compilations are presented and the utility of the computer-readable form of these compilations is examined in comparison to other pKa compilations. Finally, information is provided about how to access these databases. PMID:24952470

Slater, Anthony Michael

2014-10-01

303

Chemical characterization of SOA formed from aqueous-phase reactions of phenols with the triplet excited state of carbonyl and hydroxyl radical  

NASA Astrophysics Data System (ADS)

Phenolic compounds, which are emitted in significant amounts from biomass burning, can undergo fast reactions in atmospheric aqueous phases to form secondary organic aerosol (aqSOA). In this study, we investigate the reactions of phenol and two methoxy-phenols (syringol and guaiacol) with two major aqueous phase oxidants - the triplet excited states of an aromatic carbonyl (3C*) and hydroxyl radical (\\centerdot OH). We thoroughly characterize the low-volatility species produced from these reactions and interpret their formation mechanisms using aerosol mass spectrometry (AMS), nanospray desorption electrospray ionization mass spectrometry (nano-DESI MS), and ion chromatography (IC). A large number of oxygenated molecules are identified, including oligomers containing up to six monomer units, functionalized monomer and oligomers with carbonyl, carboxyl, and hydroxyl groups, and small organic acid anions (e.g., formate, acetate, oxalate, and malate). The average atomic oxygen-to-carbon (O / C) ratios of phenolic aqSOA are in the range of 0.85-1.23, similar to those of low-volatility oxygenated organic aerosol (LV-OOA) observed in ambient air. The aqSOA compositions are overall similar for the same precursor, but the reactions mediated by 3C* are faster than \\centerdot OH-mediated reactions and produce more oligomers and hydroxylated species at the point when 50% of the phenol had reacted. Profiles determined using a thermodenuder indicate that the volatility of phenolic aqSOA is influenced by both oligomer content and O / C ratio. In addition, the aqSOA shows enhanced light absorption in the UV-vis region, suggesting that aqueous-phase reactions of phenols are likely an important source of brown carbon in the atmosphere, especially in regions influenced by biomass burning.

Yu, L.; Smith, J.; Laskin, A.; Anastasio, C.; Laskin, J.; Zhang, Q.

2014-08-01

304

Mastery of cultural conditions and physico-chemical properties improves the production and the catalytic efficiency of bglG.  

PubMed

Stachybotrys microspora is a filamentous fungus secreting multiple ?-glucosidases. Two of them were characterized. The third one, named bglG, was also characterized and used for various investigations. The current work undertakes the plausible role played by some cultural conditions and physico-chemical properties to improve bglG time course synthesis and also its catalytic efficiency. Indeed, bglG time course synthesis is slightly affected by light, but it is clearly affected by aeration and presence of baffle. On the same case, optimization of substrate and enzyme concentration contributes to the improvement of the catalytic efficiency of bglG. This biocatalyst tolerates a high ionic strength during its activity assay; ?-mercaptoethanol increases the enzymatic rate. BglG has the capacity to hydrolyse efficiently oleuropin, with a recovery of 88%. PMID:23700144

Saibi, Walid; Gargouri, Ali

2013-07-01

305

Optical properties and chemical bonding states with annealing conditions of ZnO nanofibers prepared by using the electrospinning method  

NASA Astrophysics Data System (ADS)

We have prepared ZnO nanofibers by using the electrospinning method and have analyzed the variations in their structure, optical properties, and chemical bonding states with the annealing temperature and the annealing conditions. After annealing at 500 C, the average diameter and the average grain size are determined to be approximately 170 nm and 50 nm, respectively. The ZnO nanofibers have a clearly visible dislocation-free crystal structure. The 2 p level of Zn caused Zn-O bonds and the O 1 s core level caused physisorbed O2. When the nanofibers are annealed at 700 C, both ions exhibit shifts of the binding energies compared with those annealed at 500 C. The observed band in the visible region shows a strong temperature dependence and a red-shift with the oxygen flow in annealing process, which is related to oxygen vacancies.

Hong, Kyong-Soo; Pak, Eun Sick; Bae, Jong Seong; Jeong, Euh Duck; Jin, Jong Sung; Ha, Myong Gyu; Kim, Jong-Pil

2012-05-01

306

Identification of morphological and chemical markers of dry- and wet-season conditions in female Anopheles gambiae mosquitoes  

PubMed Central

Background Increased understanding of the dry-season survival mechanisms of Anopheles gambiae in semi-arid regions could benefit vector control efforts by identifying weak links in the transmission cycle of malaria. In this study, we examined the effect of photoperiod and relative humidity on morphologic and chemical traits known to control water loss in mosquitoes. Methods Anopheles gambiae body size (indexed by wing length), mesothoracic spiracle size, and cuticular hydrocarbon composition (both standardized by body size) were examined in mosquitoes raised from eggs exposed to short photoperiod and low relative humidity, simulating the dry season, or long photoperiod and high relative humidity, simulating the wet-season. Results Mosquitoes exposed to short photoperiod exhibited larger body size and larger mesothoracic spiracle length than mosquitoes exposed to long photoperiod. Mosquitoes exposed to short photoperiod and low relative humidity exhibited greater total cuticular hydrocarbon amount than mosquitoes exposed to long photoperiod and high relative humidity. In addition, total cuticular hydrocarbon amount increased with age and was higher in mated females. Mean n-alkane retention time (a measure of cuticular hydrocarbon chain length) was lower in mosquitoes exposed to short photoperiod and low relative humidity, and increased with age. Individual cuticular hydrocarbon peaks were examined, and several cuticular hydrocarbons were identified as potential biomarkers of dry- and wet-season conditions, age, and insemination status. Conclusions Results from this study indicate that morphological and chemical changes underlie aestivation of Anopheles gambiae and may serve as biomarkers of aestivation. PMID:24970701

2014-01-01

307

Influence of chemical conditioning on the ion exchange capacity and on kinetic of zinc uptake by clinoptilolite.  

PubMed

Aim of this study was to evaluate the feasibility of the use of clinoptilolite as a barrier material to eliminate heavy metals from roof runoff. The effect of chemical conditioning with 1 M NaCl solution upon the ion exchange capacity and on kinetic of zinc uptake by clinoptilolite has been investigated. According to the batch experiments the modified clinoptilolite has up to 100% higher sorption capacity, regarding Zn than the natural material. The pre-treatment of clinoptilolite results in an acceleration of the ion exchange process up to 40% regarding zinc. In order to define the reasons of this behaviour, both materials, modified and natural, were analysed for: (i) chemical composition, (ii) density, (iii) pore size distribution and (iv) zeta potential. The clogging of the pores, the charge of the grain surface, the pH of the initial metal solution and the ion metal concentration are the factors which are mainly affecting the ion exchange capacity and the rate of zinc uptake by clinoptilolite. PMID:15878024

Athanasiadis, Konstantinos; Helmreich, Brigitte

2005-04-01

308

Studies on the phytoplankton populations and physico-chemical conditions of treated sewage discharged into Lake Manzala in Egypt.  

PubMed

Over a full year, the phytoplankton populations and physico-chemical conditions of treated sewage discharged into Lake Manzala in Egypt were investigated. Sixty-seven species of algae were identified, 18 Cyanophyta (Cyanobacteria), 19 Chlorophyta, 21 Bacillariophyta, 6 Euglenophyta, 2 Cryptophyta and one species Pyrrhophyta. Nitzschia (6 spp.), Scenedesmus (6 spp.), Navicula (4 spp.), Oscillatoria (4 spp.) and Euglena (4 spp.) were the most common genera. A remarkable seasonal variation in species composition and standing crop of the phytoplankton populations was noted during the study. The total phytoplankton standing crop appeared to be mainly dependent on the growth of certain species viz., Oscillatoria chalybea, O. princepes, O. tenuis, Microcystis aeruginosa, Anabaena constricta (Cyanophyta), Nitzschia obtusa, Bacillaria paradoxa, Cocconeis placentula, Cyclotella meneghiniana (Bacillariophyta), Pandorina morum, Volvox sp. (Chlorophyta) and Phacus curvicauda (Euglenophyta). The continuous presence of Anabaena constricta and Nitzschia palea was recorded in the treated sewage. The least represented algal divisions were Pyrrhophyta and Cryptophyta, both in terms of quality and quantity. The data indicate that the secondary effluents were unstable in their chemical features and grossly polluted. Therefore, the treatment systems must treat the discharged sewage to a tertiary level before discharging into Lake Manzala. PMID:9579343

el-Naggar, M E; Shaaban-Dessouki, S A; Abdel-Hamid, M I; Aly, E M

1998-04-01

309

Chemical Soil Physics Phenomena for Chemical Sensing of Buried UXO  

SciTech Connect

Technology development efforts are under way to apply chemical sensors to discriminate inert ordnance and clutter from live munitions that remain a threat to reutilization of military ranges. However, the chemical signature is affected by multiple environmental phenomena that can enhance or reduce its presence and transport behavior, and can affect the distribution of the chemical signature in the environment. For example, the chemical can be present in the vapor, aqueous, and solid phases. The distribution of the chemical among these phases, including the spatial distribution, is key in designing appropriate detectors, e.g., gas, aqueous or solid phase sampling instruments. A fundamental understanding of the environmental conditions that affect the chemical signature is needed to describe the favorable and unfavorable conditions of a chemical detector based survey to minimize the consequences of a false negative. UXO source emission measurements are being made to estimate the chemical flux from a limited set of ordnance items. Phase partitioning analysis has been completed to show what the expected concentrations of chemical analytes would be fi-om total concentrations measured in the soil. The soil moisture content in the dry region has been shown to be critical in the attenuation of soil gas concentrations by increased sorption to soil particles. Numerical simulation tools have been adapted to include surface boundary conditions such as solar radiation, surface boundary layer (which is a function of wind speed), precipitation and evaporation, and plant cover/root density to allow transport modeling and evaluate long term processes. Results of this work will provide performance targets for sensor developers and support operational decisions regarding field deployments.

Phelan, James, M.; Webb, Stephen W.

1999-06-14

310

Distribution of fish, benthic invertebrate, and algal communities in relation to physical and chemical conditions, Yakima River basin, Washington, 1990  

USGS Publications Warehouse

Biological investigations were conducted in the Yakima River Basin, Washington, in conjunction with a pilot study for the U.S. Geological Survey's National Water-Quality Assessment Program. Ecological surveys were conducted at 25 sites in 1990 to (1) assess water-quality conditions based on fish, benthic invertebrate, and algal communities; (2) determine the hydrologic, habitat, and chemical factors that affect the distributions of these organisms; and (3) relate physical and chemical conditions to water quality. Results of these investigations showed that land uses and other associated human activities influenced the biological characteristics of streams and rivers and overall water-quality conditions. Fish communities of headwater streams in the Cascades and Eastern Cascades ecoregions of the Yakima River Basin were primarily composed of salmonids and sculpins, with cyprinids dominating in the rest of the basin. The most common of the 33 fish taxa collected were speckled dace, rainbow trout, and Paiute sculpin. The highest number of taxa (193) was found among the inverte- brates. Insects, particularly sensitive forms such as mayflies, stoneflies, and caddisflies (EPT--Ephemeroptera, Plecoptera, and Trichoptera fauna), formed the majority of the invertebrate communities of the Cascades and Eastern Cascades ecoregions. Diatoms dominated algal communities throughout the basin; 134 algal taxa were found on submerged rocks, but other stream microhabitats were not sampled as part of the study. Sensitive red algae and diatoms were predominant in the Cascades and Eastern Cascades ecoregions, whereas the abundance of eutrophic diatoms and green algae was large in the Columbia Basin ecoregion of the Yakima River Basin. Ordination of physical, chemical, and biological site characteristics indicated that elevation was the dominant factor accounting for the distribution of biota in the Yakima River Basin; agricultural intensity and stream size were of secondary importance. Ordination identified three site groups and three community types. Site groups consisted of (1) small streams of the Cascades and Eastern Cascades ecoregions, (2) small streams of the Columbia Basin ecoregions, and (3) large rivers of the Cascades and Columbia Basin ecoregions. The small streams of the Columbia Basin could be further subdivided into two groups--one where agricultural intensity was low and one where agricultural intensity was moderate to high. Dividing the basin into these three groups removed much of the influence of elevation and facilitated the analysis of land-use effects. Community types identified by ordination were (1) high elevation, cold-water communities associated with low agricultural intensity; (2) lower elevation, warm-water communities associated with low agricultural intensity, and (3) lower elevation, warm-water communities associated with moderate to high agricultural intensity. Multimetric community condition indices indicated that sites in the Cascades and Eastern Cascades site group were largely unimpaired. In contrast, all but two sites in the Columbia Basin site group were impaired, some severely. Agriculture (nutrients and pesticides) was the primary factor responsible for this impairment, and all impaired sites were characterized by multiple indicators of impairment. Three sites (Granger Drain, Moxee Drain, and Spring Creek) had high levels of impairment. Sites in the large-river site group were moderately to severely impaired downstream from the city of Yakima. High levels of impairment at large-river sites corresponded with high levels of pesticides in fish tissues and the occurrence of external anomalies. The response exhibited by invertebrates and algae to a gradient of agricultural intensity suggested a threshold response for sites in the Columbia Basin site group. Community condition declined precipitously at agricultural intensities above 50 (non-pesticide agricultural intensity index) and showed little respon

Cuffney, T. F.; Meador, M. R.; Porter, S. D.; Gurtz, M. E.

1997-01-01

311

MODEL OF CHEMICAL REACTION EQUILIBRIUM OF SULFURIC ACID SALTS OF TRIOCTYLAMINE  

Microsoft Academic Search

The chemical reaction of trioctylamine (TOA) and sulfuric acid in organic solvent\\/aqueous solution was carried out. TOA salt products of various kinds were obtained based on different conditions of operation and organic solvents. An equilibrium model, based on the chemical reaction of sulfuric acid and trioctylamine, is proposed. The equilibrium constants of various reactions of trioctylamine and sulfuric acid were

MAW-LING WANG; KWAN-HUA HU

1993-01-01

312

The effect of variety and growing conditions on the chemical composition and nutritive value of wheat for broilers.  

PubMed

The aim of this study was to examine the effect of variety and growing conditions of wheat on broiler performance and nutrient digestibility. One hundred and sixty-four wheat samples, collected from a wide range of different sources, locations, varieties and years, were analyzed for a range of chemical and physical parameters. Chemical and physical parameters measured included specific weight, thousand grain weight (TG), in vitro viscosity, gross energy, N, NDF, starch, total and soluble non-starch polysaccharides (NSP), lysine, threonine, amylose, hardness, rate of starch digestion and protein profiles. Ninety-four of the wheat samples were selected for inclusion in four bird trials. Birds were housed in individual wire metabolizm cages from 7 to 28 d and offered water and feed ad libitum. Dry matter intake (DMI), live weight gain (LWG) and gain:feed were determined weekly. A balance collection was carried out from 14 to 21 d for determination of apparent metabolizable energy (AME), ME:gain, DM retention, oil and NDF digestibility. At 28 d the birds were sacrificed, the contents of the jejunum removed for determination of in vivo viscosity and the contents of the ileum removed for determination of ileal DM, starch and protein digestibility. The wheat samples used in the study had wide-ranging chemical and physical parameters, leading to bird DMI, LWG, gain:feed, ME:GE, AME content and ileal starch and protein digestibility being significantly (p<0.05) affected by wheat sample. A high level of N fertilizer application to the English and NI wheat samples tended to benefit bird performance, with increases of up to 3.4, 7.2 and 3.8% in DMI, LWG and gain:feed, respectively. Fungicide application also appeared to have a positive effect on bird performance, with fungicide treated (+F) wheat increasing bird DMI, LWG and gain:feed by 6.6, 9.3 and 2.7%, over the non-fungicide treated (-F) wheats. An increase (p<0.1) of 9.3% in gain:feed was also observed at the low seed rate of 40 compared to 640 seeds/m(2). It was concluded that the type of wheat sample and environmental growing conditions significantly affects bird performance when fed wheat-based diets. PMID:25049800

Ball, M E E; Owens, B; McCracken, K J

2013-03-01

313

Testing Insecticidal Activity of Novel Chemically Synthesized siRNA against Plutella xylostella under Laboratory and Field Conditions  

PubMed Central

Background Over the last 60 years, synthetic chemical pesticides have served as a main tactic in the field of crop protection, but their availability is now declining as a result of the development of insect resistance. Therefore, alternative pest management agents are needed. However, the demonstration of RNAi gene silencing in insects and its successful usage in disrupting the expression of vital genes opened a door to the development of a variety of novel, environmentally sound approaches for insect pest management. Methodology/Principal Findings Six small interfering RNAs (siRNAs) were chemically synthesized and modified according to the cDNA sequence of P. xylostella acetylcholine esterase genes AChE1 and AChE2. All of them were formulated and used in insecticide activity screening against P. xylostella. Bioassay data suggested that Si-ace1_003 and Si-ace2_001 at a concentration of 3 g cm?2 displayed the best insecticidal activity with 73.7% and 89.0%, mortality, respectively. Additional bioassays were used to obtain the acute lethal concentrations of LC50 and LC90 for Si-ace2_001, which were 53.66 g/ml and 759.71 g/ml, respectively. Quantitative Real-time PCR was used to confirm silencing and detected that the transcript levels of P. xylostella AChE2 (PxAChE2) were reduced by 5.7-fold compared to the control group. Consequently, AChE activity was also reduced by 1.7-fold. Finally, effects of the siRNAs on treated plants of Brassica oleracea and Brassica alboglabra were investigated with different siRNA doses. Our results showed that Si-ace2_001 had no negative effects on plant morphology, color and growth of vein under our experimental conditions. Conclusions The most important finding of this study is the discovery that chemically synthesized and modified siRNA corresponding to P. xylostella AChE genes cause significant mortality of the insect both under laboratory and field conditions, which provides a novel strategy to control P. xylostella and to develop bio-pesticides based on the RNA interference technology. PMID:23667556

Gong, Liang; Chen, Yong; Hu, Zhen; Hu, Meiying

2013-01-01

314

Laboratory insights into the chemical and kinetic evolution of several organic molecules under simulated Mars surface UV radiation conditions  

NASA Astrophysics Data System (ADS)

The search for organic carbon at the surface of Mars, as clues of past habitability or remnants of life, is a major science goal of Mars exploration. Understanding the chemical evolution of organic molecules under current martian environmental conditions is essential to support the analyses performed in situ. What molecule can be preserved? What is the timescale of organic evolution at the surface? This paper presents the results of laboratory investigations dedicated to monitor the evolution of organic molecules when submitted to simulated Mars surface ultraviolet radiation (190-400 nm), mean temperature (218 2 K) and pressure (6 1 mbar) conditions. Experiments are done with the MOMIE simulation setup (for Mars Organic Molecules Irradiation and Evolution) allowing both a qualitative and quantitative characterization of the evolution the tested molecules undergo (Poch, O. et al. [2013]. Planet. Space Sci. 85, 188-197). The chemical structures of the solid products and the kinetic parameters of the photoreaction (photolysis rate, half-life and quantum efficiency of photodecomposition) are determined for glycine, urea, adenine and chrysene. Mellitic trianhydride is also studied in order to complete a previous study done with mellitic acid (Stalport, F., Coll, P., Szopa, C., Raulin, F. [2009]. Astrobiology 9, 543-549), by studying the evolution of mellitic trianhydride. The results show that solid layers of the studied molecules have half-lives of 10-103 h at the surface of Mars, when exposed directly to martian UV radiation. However, organic layers having aromatic moieties and reactive chemical groups, as adenine and mellitic acid, lead to the formation of photoresistant solid residues, probably of macromolecular nature, which could exhibit a longer photostability. Such solid organic layers are found in micrometeorites or could have been formed endogenously on Mars. Finally, the quantum efficiencies of photodecomposition at wavelengths from 200 to 250 nm, determined for each of the studied molecules, range from 10-2 to 10-6 molecule photon-1 and apply for isolated molecules exposed at the surface of Mars. These kinetic parameters provide essential inputs for numerical modeling of the evolution of Mars current reservoir of organic molecules. Organic molecules adsorbed on martian minerals may have different kinetic parameters and lead to different endproducts. The present study paves the way for the interpretation of more complex simulation experiments where organics will be mixed with martian mineral analogs.

Poch, O.; Kaci, S.; Stalport, F.; Szopa, C.; Coll, P.

2014-11-01

315

Applicability of DLVO Approach to Predict Trends in Iron Oxide Colloid Mobility Under Various Physical And Chemical Soil Conditions  

NASA Astrophysics Data System (ADS)

In soil and groundwater, highly mobile iron oxide colloids can act as "shuttles" for transport of adsorbed contaminants such as heavy metals and radionuclides. Artificial iron oxide colloids are injected into polluted porous media to accelerate bacterial degradation of pollutants in the context of bioremediation purposes. The mobility of iron oxide colloids is strongly affected by the hydraulic, physical and chemical conditions of the pore space, the solid particle surface properties, the fluid phase, and the colloids themselves. Most pioneering studies focused on iron oxide colloid transport and retention in simplified model systems. The aim of this study is to investigate iron oxide colloid mobility under more complex, soil-typical conditions that have as yet only been applied for model microspheres, i.e. functionalized latex colloids. Among these conditions is the pivotal impact of organic matter, either dissolved or adsorbed onto solid particles, modifying wettability properties. Of particular importance was to determine if effective chemical surface parameters derived from contact angle and zeta potential measurements can be used as a tool to predict general tendencies for iron oxide colloid mobility in porous media. In column breakthrough experiments, goethite colloids (particle size: 200-900 nm) were percolated through quartz sand (grain size: 100-300 m) at pH 5. The impact of a multitude of conditions on colloid mobility was determined: dissolved organic matter (DOM) concentration, ionic strength, flow velocity, flow interruption, partial saturation, and drying with subsequent re-wetting. The solid matrix consisted of either clean sand, organic matter-coated sand, goethite-coated sand, or sand hydrophobized with dichlorodimethylsilane. Additionally, contact angles and zeta potentials of the materials applied in the column experiments were measured. By means of these surface parameters, traditional DLVO interaction energies based on zeta potential as well as extended DLVO energies including Lewis acid-base parameters based on contact angle measurements were estimated. The results elucidate that high mobility of goethite colloids was distinctly restricted to a narrow set of conditions: presence of DOM, sufficient flow velocity and constant flow, low ionic strength, full saturation as well as an uncoated and hydrophilic quartz sand matrix. Any deviation from these favorable transport conditions led from varying degrees of colloid retention up to complete immobilization. Results yielded by both traditional and extended DLVO interaction energy calculations demonstrated that increasing secondary minimum depth correlated well with higher colloid retention. Extended DLVO calculations revealed strong repulsive forces due to Lewis acid-base interactions at close distances that did not comply with experimental data. It is likely that Lewis acid-base interactions were limited due to surface roughness of the sand grains and colloids. It can be concluded that the impact of various soil and hydraulic conditions on goethite colloid mobility is in principle assessable with column flow experiments. Moreover, with restrictions for the interpretation of close-distance interactions, DLVO interaction energies are capable of predicting general trends of goethite colloid mobility.

Florian Carstens, Jannis; Bachmann, Jrg; Neuweiler, Insa

2014-05-01

316

Selective chemical protein modification.  

PubMed

Chemical modification of proteins is an important tool for probing natural systems, creating therapeutic conjugates and generating novel protein constructs. Site-selective reactions require exquisite control over both chemo- and regioselectivity, under ambient, aqueous conditions. There are now various methods for achieving selective modification of both natural and unnatural amino acids--each with merits and limitations--providing a 'toolkit' that until 20 years ago was largely limited to reactions at nucleophilic cysteine and lysine residues. If applied in a biologically benign manner, this chemistry could form the basis of true Synthetic Biology. PMID:25190082

Spicer, Christopher D; Davis, Benjamin G

2014-01-01

317

Synthetic Surface for Expansion of Human Mesenchymal Stem Cells in Xeno-Free, Chemically Defined Culture Conditions  

PubMed Central

Human mesenchymal stem cells (hMSCs) possess three properties of great interest for the development of cell therapies and tissue engineering: multilineage differentiation, immunomodulation, and production of trophic factors. Efficient ex vivo expansion of hMSCs is a challenging requirement for large scale production of clinical grade cells. Low-cost, robust, scalable culture methods using chemically defined materials need to be developed to address this need. This study describes the use of a xeno-free synthetic peptide acrylate surface, the Corning Synthemax Surface, for culture of hMSCs in serum-free, defined medium. Cell performance on the Corning Synthemax Surface was compared to cells cultured on biological extracellular matrix (ECM) coatings in xeno-free defined medium and in traditional conditions on tissue culture treated (TCT) plastic in fetal bovine serum (FBS) supplemented medium. Our results show successful maintenance of hMSCs on Corning Synthemax Surface for eight passages, with cell expansion rate comparable to cells cultured on ECM and significantly higher than for cells in TCT/FBS condition. Importantly, on the Corning Synthemax Surface, cells maintained elongated, spindle-like morphology, typical hMSC marker profile and in vitro multilineage differentiation potential. We believe the Corning Synthemax Surface, in combination with defined media, provides a complete synthetic, xeno-free, cell culture system for scalable production of hMSCs. PMID:23940553

Dolley-Sonneville, Paula J.; Romeo, Lori E.; Melkoumian, Zara K.

2013-01-01

318

Influence of annealing conditions on the crystallographic structure, chemical composition and luminescence of ZnO thin films  

NASA Astrophysics Data System (ADS)

ZnO thin films have many applications in semiconductor devices, such as semiconductor lasers, amplifiers, solar cells, chemical and ultraviolet sensors. We produced ZnO thin films on Si (4 0 0) substrates, using e-beam technique and subsequently annealed them under different conditions (i.e., temperature (200-800), time (60 min and 180 min) and environment (air and oxygen flow). The ZnO (0 0 2) preferred orientation which increases in intensity with annealing temperature and annealing time is deduced from X-ray diffraction (XRD) results. Dislocation density was higher for the films annealed in air which may be caused by the impurities (nitrogen and other species in the air) embedded in the film structure. No significant change in the nano-strain of each group of the samples (annealed under different conditions) was observed. The FESEM images showed a granular structure for annealed samples at 200 C and 800 C and a mixed structure of nanowires and nanosheets for samples annealed at 350 C and 500 C. Two peaks of UV emission and green emission were observed in the photoluminescence (PL) spectra of the produced samples. The UV emission increased with annealing temperature and annealing time showing higher crystal quality while the behavior of the green emission was opposite to that of the UV emission. The ZnO films resulted from annealing in the air showed stronger green emission than those annealed with flow of oxygen indicating higher impurity concentration and oxygen vacancies in the sample.

Khojier, K.; Savaloni, H.; Amani, E.

2014-01-01

319

Standard partial molar volumes of some aqueous alkanolamines and alkoxyamines at temperatures up to 325 degrees C: functional group additivity in polar organic solutes under hydrothermal conditions.  

PubMed

Apparent molar volumes of dilute aqueous solutions of monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), N,N-dimethylethanolamine (DMEA), ethylethanolamine (EAE), 2-diethylethanolamine (2-DEEA), and 3-methoxypropylamine (3-MPA) and their salts were measured at temperatures from 150 to 325 degrees C and pressures as high as 15 MPa. The results were corrected for the ionization and used to obtain the standard partial molar volumes, Vo2. A three-parameter equation of state was used to describe the temperature and pressure dependence of the standard partial molar volumes. The fitting parameters were successfully divided into functional group contributions at all temperatures to obtain the standard partial molar volume contributions. Including literature results for alcohols, carboxylic acids, and hydroxycarboxylic acids yielded the standard partial molar volume contributions of the functional groups >CH-, >CH2, -CH3, -OH, -COOH, -O-, -->N, >NH, -NH2, -COO-Na+, -NH3+Cl-, >NH2+Cl-, and -->NH+Cl- over the range (150 degrees C aqueous organic solutes composed of these groups at temperatures up to approximately 310 degrees C and pressures of 10-20 MPa to within a precision of +/-5 cm3 x mol(-1). The model could not be extended to higher temperatures because of uncertainties caused by thermal decomposition. At temperatures above approximately 250 degrees C, the order of the group contributions to Vo2 changes from that observed at 25 degrees C, to become increasingly consistent with the polarity of each functional group. The effect of the dipole moment of each molecule on the contribution to Vo2 from long-range solvent polarization was calculated from the multipole expansion of the Born equation using dipole moments estimated from restricted Hartree-Fock calculations with Gaussian 03 (Gaussian, Inc., Wallingford, CT) and the Onsager reaction-field approximation for solvent effects. Below 325 degrees C, the dipole contribution was found to be less than 2 cm3 x mol(-1) for all the solute molecules studied. At higher temperatures and pressures near steam saturation, the effect is much larger and may explain anomalies in functional group additivity observed in small, very polar solutes. PMID:18412415

Bulemela, E; Tremaine, Peter R

2008-05-01

320

Chemical equilibria model of strontium-90 adsorption and transport in soil in response to dynamic alkaline conditions.  

PubMed

Strontium-90 is a major hazardous contaminant of radioactive wastewater and its processing sludges at many Department of Energy (DOE) facilities. In the past, such contaminated wastewater and sludge have been disposed in soil seepage pits, lagoons, or cribs often under highly perturbed alkaline conditions (pH > 12) where 90Sr solubility is low and its adsorption to surrounding soil is high. As natural weathering returns these soils to near-neutral or slightly acidic conditions, the adsorbed and precipitated calcium and magnesium phases, in which 90Sr is carried, change significantly in both nature and amounts. No comprehensive computational method has been formulated previously to quantitatively simulate the dynamics of 90Sr in the soil-groundwater environment under such dynamic and wide-ranging conditions. A computational code, the Hydrologic Utility Model for Demonstrating Integrated Nuclear Geochemical Environmental Responses (HUMDINGER), was composed to describe the changing equilibria of 90Sr in soil based on its causative chemical reactions including soil buffering, pH-dependent cation-exchange capacity, cation selectivity, and the precipitation/dissolution of calcium carbonate, calcium hydroxide, and magnesium hydroxide in response to leaching groundwater characteristics including pH, acid-neutralizing capacity, dissolved cations, and inorganic carbonate species. The code includes a simulation of one-dimensional transport of 90Sr through a soil column as a series of soil mixing cells where the equilibrium soluble output from one cell is applied to the next cell. Unamended soil leaching and highly alkaline soil treatments, including potassium hydroxide, sodium silicate, and sodium aluminate, were simulated and compared with experimental findings using large (10 kg) soil columns that were leached with 90Sr-contaminated groundwater after treatment. HUMDINGER's simulations were in good agreement with dynamic experimental observations of soil exchange capacity, exchangeable cations, total 90Sr, and pH values of layers within the soil columns and of column effluents. PMID:11347611

Spalding, B P; Spalding, I R

2001-01-15

321

Halogen production from aqueous tropospheric particles.  

PubMed

Box model studies have been performed to study the role of aqueous phase chemistry with regard to halogen activation for marine and urban clouds and the marine aerosol as well. Different chemical pathways leading to halogen activation in diluted cloud droplets and highly concentrated sea salt aerosol particles are investigated. The concentration of halides in cloud droplets is significantly smaller than in sea-salt particles, and hence different reaction sequences control the overall chemical conversions. In diluted droplets radical chemistry involving OH, NO(3), Cl/Cl(2)(-)/ClOH(-), and Br/Br(2)(-)/BrOH(-) gains in importance and pH independent pathways lead to the release of halogens from the particle phase whereas the chemistry in aerosol particles with high electrolyte concentrations is controlled by non-radical reactions at high ionic strengths and relatively low pH values. For the simulation of halogen activation in tropospheric clouds and aqueous aerosol particles in different environments a halogen module was developed including both gas and aqueous phase processes of halogen containing species. This module is coupled to a base mechanism consisting of RACM (Regional Atmospheric Chemistry Mechanism) and the Chemical Aqueous Phase Radical Mechanism CAPRAM 2.4 (MODAC-mechanism). Phase exchange is described by the resistance model by Chemistry of Multiphase Atmospheric Systems, NATO ASI Series, 1986. It can be shown that under cloud conditions the bromine atom is mainly produced by OH initiated reactions, i.e. its concentration maximum is reached at noon. In contrast, the concentration level of chlorine atoms is linked to NO(3) radical chemistry leading to a smaller amplitude between day and night time concentrations. The contribution of radical processes to halogen atom formation in the particle phase is evident, e.g. by halogen atoms which undergo direct phase transfer. Furthermore, the application of the multiphase model for initial concentrations for sea-salt aerosols shows that the particle phase can act as a main source of halogen containing molecules (Cl(2), BrCl, Br(2)) which are photolysed in the gas phase to yield halogen atoms (about 70% of all Cl sources and more than 99% for Br). PMID:12738274

Herrmann, H; Majdik, Z; Ervens, B; Weise, D

2003-07-01

322

Synthesis Under 'Greener' Conditions: Role of Sustainable Nano-Catalysts  

EPA Science Inventory

The presentation summarizes our recent activity in chemical synthesis involving benign alternatives, such as the use of supported reagents, and greener reaction medium in aqueous or solvent-free conditions.1 The synthesis of heterocyclic compounds, coupling reactions, and a varie...

323

Effect of the water content on the retention and enantioselectivity of albendazole and fenbendazole sulfoxides using amylose-based chiral stationary phases in organic-aqueous conditions.  

PubMed

Four commercially available immobilized amylose-derived CSPs (Chiralpak IA-3, Chiralpak ID-3, Chiralpak IE-3 and Chiralpak IF-3) were used in the HPLC analysis of the chiral sulfoxides albendazole (ABZ-SO) and fenbendazole (FBZ-SO) and their in vivo sulfide precursor (ABZ and FBZ) and sulfone metabolite (ABZ-SO2 and FBZ-SO2) under organic-aqueous mode. U-shape retention maps, established by varying the water content in the acetonitrile- and ethanol-water mobile phases, were indicative of two retention mechanisms operating on the same CSP. The dual retention behavior of polysaccharide-based CSPs was exploited to design greener enantioselective and chemoselective separations in a short time frame. The enantiomers of ABZ-SO and FBZ-SO were baseline resolved with water-rich mobile phases (with the main component usually being 50-65% water in acetonitrile) on the IF-3 CSP and ethanol-water 100:5 mixture on the IA-3 and IE-3 CSPs. A simultaneous separation of ABZ (or FBZ), enantiomers of the corresponding sulfoxide and sulfone was achieved on the IA-3 using ethanol-water 100:60 (acetonitrile-water 100:100 for FBZ) as a mobile phase. PMID:24411094

Materazzo, Sabrina; Carradori, Simone; Ferretti, Rosella; Gallinella, Bruno; Secci, Daniela; Cirilli, Roberto

2014-01-31

324

Evidence for a Transient Interresidue Hydrogen Bond in Sucrose in Aqueous Solution Obtained by Rotating-Frame Exchange NMR Spectroscopy Under Supercooled Conditions  

Microsoft Academic Search

We have used the hydroxyl protons of sucrose dissolved in supercooled water as NMR probes for the detection of intramolecular hydrogen bonds. Neither the measured OH temperature shift coefficients, 3JHCOH scalar couplings, isotope-induced 13C chemical shifts (??COH\\/COD) nor OH exchange rates allowed us to single out any hydroxyl group in sucrose with characteristics indicative of involvement in strong hydrogen bonding.

S. Q. Sheng; H. Vanhalbeek

1995-01-01

325

Chemical immobilization of adult female Weddell seals with tiletamine and zolazepam: effects of age, condition and stage of lactation  

PubMed Central

Background Chemical immobilization of Weddell seals (Leptonychotes weddellii) has previously been, for the most part, problematic and this has been mainly attributed to the type of immobilizing agent used. In addition to individual sensitivity, physiological status may play an important role. We investigated the use of the intravenous administration of a 1:1 mixture of tiletamine and zolazepam (Telazol) to immobilize adult females at different points during a physiologically demanding 56 week lactation period. We also compared performance between IV and IM injection of the same mixture. Results The tiletamine:zolazepam mixture administered intravenously was an effective method for immobilization with no fatalities or pronounced apnoeas in 106 procedures; however, there was a 25 % (one animal in four) mortality rate with intramuscular administration. Induction time was slightly longer for females at the end of lactation (54.9 2.3 seconds) than at post-parturition (48.2 2.9 seconds). In addition, the number of previous captures had a positive effect on induction time. There was no evidence for effects due to age, condition (total body lipid), stage of lactation or number of captures on recovery time. Conclusion We suggest that intravenous administration of tiletamine and zolazepam is an effective and safe immobilizing agent for female Weddell seals. Although individual traits could not explain variation in recovery time, we suggest careful monitoring of recovery times during longitudinal studies (> 2 captures). We show that physiological pressures do not substantially affect response to chemical immobilization with this mixture; however, consideration must be taken for differences that may exist for immobilization of adult males and juveniles. Nevertheless, we recommend a mass-specific dose of 0.50 0.65 mg/kg for future procedures with adult female Weddell seals and a starting dose of 0.50 mg/kg for other age classes and other phocid seals. PMID:16469105

Wheatley, Kathryn E; Bradshaw, Corey JA; Harcourt, Robert G; Davis, Lloyd S; Hindell, Mark A

2006-01-01

326

Simulation of size-segregated aerosol chemical composition over northern Italy in clear sky and wind calm conditions  

NASA Astrophysics Data System (ADS)

The present article compares the outputs of the 3-D regional chemistry-transport model (CTM) CHIMERE against observations of the size-resolved aerosol chemical composition over northern Italy in clear sky and wind calm conditions. Two 4-day intensive field campaigns were carried out in July 2007 and February 2008 at three sites (urban, rural and mountain backgrounds) in the framework of the AEROCLOUDS project. Predicted levels are in reasonable agreement with observations for the urban and rural sites. Bias ranges from - 30%, for the rural site in winter, to + 38%, for the urban site during summer. In addition, the model is able to capture both the daily evolution of the bulk aerosol mass as well as its spatial gradients. Aerosol size distribution and chemical composition remain difficult to predict. The largest discrepancies were found for secondary organic aerosol (SOA) during summer and nitrates during the cold season. Compared with observations, modelled size distribution is shifted towards fine mode in winter, and towards coarse mode in summer. More accurate predictions can be achieved for both seasons by tuning the gas to particle absorption process. By reducing the SOA absorption rate by 25% at the urban sampling site in summer, the correlation between observed and simulated SOA size distributions increases from - 0.30 to + 0.70, and the bias is reduced from 200% to 0%. In winter, increasing the intra-sectional flux of particles from smaller to larger ones by a factor of 5, the Pearson correlation coefficient calculated over the nitrate size distribution goes up to + 0.85, compared to + 0.50 from CTRL, also resulting in a better agreement with the size distribution of PM10. As expected, the nitrate bulk mass concentration does not vary with respect to the base-case, and therefore nitrate overestimation remains present in the model.

Landi, T. C.; Curci, G.; Carbone, C.; Menut, L.; Bessagnet, B.; Giulianelli, L.; Paglione, M.; Facchini, M. C.

2013-05-01

327

Chemical and Structural Properties of Jordanian Zeolitic Tuffs and Their Admixtures with Urea and Thiourea: Potential Scavengers for Phenolics in Aqueous Medium  

Microsoft Academic Search

Native Jordanian zeolitic tuffs, rich in phillipsite, were treated with urea and thiourea. The chemical and structural properties of the tuffs and their urea and thiourea admixtures were studied using SEM, XRF, XRD, and FTIR techniques, and their adsorption capacities were estimated by the methylene blue method. The urea and thiourea treatment has not affected the mineral constitution of the

Rushdi I Yousef; Maha F Tutunji; Ghazi A. W Derwish; Salem M Musleh

1999-01-01

328

Chemical composition of rock-forming minerals in gold-related granitoid intrusions, southwestern New Brunswick, Canada: implications for crystallization conditions, volatile exsolution, and fluorine-chlorine activity  

Microsoft Academic Search

Chemical composition of rock-forming minerals in Appalachian Siluro-Devonian granitoid intrusions, southwestern New Brunswick,\\u000a was systematically determined by electron microprobe. The mineral chemical data together with petrographic examination was\\u000a used to test magmatic equilibration and to constrain crystallization conditions, volatile exsolution, and fluorine-chlorine\\u000a activity of fluids associated with these intrusions. Mineralogical distinction between Late Silurian to Early Devonian granodioritic\\u000a to monzogranitic

Xue-Ming Yang; David R. Lentz

2005-01-01

329

Predator-induced alarm responses in the common periwinkle, Littorina littorea: dependence on season, light conditions, and chemical labelling of predators  

Microsoft Academic Search

Chemically mediated alarm reactions of the common periwinkle, Littorina littorea (L.), were studied in laboratory experiments during two consecutive summers, and one intermediate autumn season. Responses\\u000a to chemical stimuli were detected as crawl-out responses, i.e. movements of snails out of the water. Snails were exposed to\\u000a extracts of injured conspecifics, extracts of the mussel Modiolus modiolus (L.), and water conditioned

H. P. Jacobsen; O. B. Stabell

1999-01-01

330

Impact of chemical and meteorological boundary and initial conditions on air quality modeling: WRF-Chem sensitivity evaluation for a European domain  

NASA Astrophysics Data System (ADS)

This study evaluates the impact of different chemical and meteorological boundary and initial conditions on the state-of-the-art Weather Research and Forecasting (WRF) model with its chemistry extension (WRF-Chem). The evaluation is done for July 2005 with 50 km horizontal resolution. The effect of monthly mean chemical boundary conditions derived from the chemical transport model LMDZ-INCA on WRF-Chem is evaluated against the effect of the preset idealized profiles. Likewise, the impact of different meteorological initial and boundary conditions (GFS and Reanalysis II) on the model is evaluated. Pearson correlation coefficient between these different runs range from 0.96 to 1.00. Exceptions exists for chemical boundary conditions on ozone and for meteorological boundary conditions on PM10, where coefficients of 0.90 were obtained. Best results were achieved with boundary and initial conditions from LMDZ-INCA and GFS. Overall, the European simulations show encouraging results for observed air pollutant, with ozone being the most and PM10 being the least satisfying.

Ritter, Mathias; Mller, Mathias D.; Jorba, Oriol; Parlow, Eberhard; Liu, L.-J. Sally

2013-01-01

331

Detection of component segregation in granules manufactured by high shear granulation with over-granulation conditions using near-infrared chemical imaging.  

PubMed

The objective of this study was to evaluate the high shear granulation process using near-infrared (NIR) chemical imaging technique and to make the findings available for pharmaceutical development. We prepared granules and tablets made under appropriate- and over-granulation conditions with high shear granulation and observed these granules and tablets using NIR chemical imaging system. We found an interesting phenomenon: lactose agglomeration and segregation of ingredients occurred in experimental tablets when over-granulation conditions, including greater impeller rotation speeds and longer granulation times, were employed. Granules prepared using over-granulation conditions were larger and had progressed to the consolidation stage; segregation between ethenzamide and lactose occurred within larger granules. The segregation observed here is not detectable using conventional analytical technologies such as high pressure liquid chromatography (HPLC) because the content of the granules remained uniform despite the segregation. Therefore, granule visualization using NIR chemical imaging is an effective method for investigating and evaluating the granulation process. PMID:23247019

Koide, Tatsuo; Nagato, Takuya; Kanou, Yoshiyuki; Matsui, Kou; Natsuyama, Susumu; Kawanishi, Toru; Hiyama, Yukio

2013-01-30

332

Efficient generation of lens progenitor cells and lentoid bodies from human embryonic stem cells in chemically defined conditions  

PubMed Central

The eye lens is an encapsulated avascular organ whose function is to focus light on the retina. Lens comprises a single progenitor cell lineage in multiple states of differentiation. Disruption of lens function leading to protein aggregation and opacity results in age-onset cataract. Cataract is a complex disease involving genetic and environmental factors. Here, we report the development of a new 3-stage system that differentiates human embryonic stem cells (hESCs) into large quantities of lens progenitor-like cells and differentiated 3-dimensional lentoid bodies. Inhibition of BMP signaling by noggin triggered differentiation of hESCs toward neuroectoderm. Subsequent reactivation of BMP and activation of FGF signaling stimulated formation of lens progenitor cells marked by the expression of PAX6 and ?-crystallins. The formation of lentoid bodies was most efficient in the presence of FGF2 and Wnt-3a, yielding ?1000 lentoid bodies/30-mm well. Lentoid bodies expressed and accumulated lens-specific markers including ?A-, ?B-, ?-, and ?-crystallins, filensin, CP49, and MIP/aquaporin 0. Collectively, these studies identify a novel procedure to generate lens cells from hESCs that can be applied for studies of lens differentiation and cataractogenesis using induced pluripotent stem (iPS) cells derived from various cataract patients.Yang, C., Yang, Y., Brennan, L., Bouhassira, E. E., Kantorow, M., and Cvekl, A. Efficient generation of lens progenitor cells and lentoid bodies from human embryonic stem cells in chemically defined conditions. PMID:20410439

Yang, Chunbo; Yang, Ying; Brennan, Lisa; Bouhassira, Eric E.; Kantorow, Marc; Cvekl, Ales

2010-01-01

333

NaNO2-mediated transformation of aliphatic secondary nitroalkanes into ketones or oximes under neutral, aqueous conditions: how the nitro derivative catalyzes its own transformation.  

PubMed

The nitrosation of secondary nitro derivatives into ketones or oximes depending on the nitro substituents has been reinvestigated. The reaction efficiently takes place under neutral conditions, thus allowing acid-sensitive substrates to be converted in very good yields. The generation of nitrosating species under such mild conditions is unprecedented. Mechanistic investigations strongly suggest that they result from the nucleophilic attack of the nitrite anion on the aci-nitro(nate) form of the secondary nitroalkane. The latter acts in turn as an autocatalyst for its own transformation by means of the nitrosating species generated in situ from it. PMID:15609931

Gissot, Arnaud; N'Gouela, Silvere; Matt, Christophe; Wagner, Alain; Mioskowski, Charles

2004-12-24

334

Sodium Borohydride Reduction of Aqueous Silver-Iron-Nickel Solutions: a Chemical Route to Synthesis of Low Thermal ExpansionHigh Conductivity Ag-Invar Alloys  

Microsoft Academic Search

Thermal management is a critical concern in the design and performance of electronics systems. If heat extraction and thermal\\u000a expansion are not properly addressed, the thermal mismatch among dissimilar materials may give rise to high thermal stresses\\u000a or interfacial shear strains, and ultimately to premature system failure. In this article, we present a chemical synthesis\\u000a process that yields Ag-Invar (64Fe-36Ni)

E. A. Sterling; J. Stolk; L. Hafford; M. Gross

2009-01-01

335

Chemical and operational aspects in running the polymer assisted ultrafiltration for separation of copper(II)citrate complexes from aqueous media  

Microsoft Academic Search

The polymer assisted ultrafiltration (PAUF) process for treatment of wastewaters containing metal ions chelated with citric acid has been studied giving particular attention to the chemical and operational aspects. The polyethylenimine (PEI) polymer bound quantitatively the copper(II)citrate chelate at pH 5.5 forming the ternary PEICucitrate complex as discussed considering the stability constants. The ternary complex was separated by UF membranes

Raffaele Molinari; Teresa Poerio; Pietro Argurio

2007-01-01

336

Effect of aqueous LiBr solutions on the corrosion resistance and galvanic corrosion of an austenitic stainless steel in its welded and non-welded condition  

Microsoft Academic Search

The corrosion resistance and galvanic behaviour of a highly alloyed austenitic stainless steel (UNS N08031) and a nickelbase alloy (UNS N06059) in its welded (GTAW) and non-welded condition were analysed in LiBr solutions by means of electrochemical measurements. Samples microstructure was studied by SEM and EDX analysis. The alloys considered showed passive behaviour and they were able to repassivate after

E. Blasco-Tamarit; A. Igual-Muoz; J. Garca Antn; D. Garca-Garca

2006-01-01

337

Aqueous cleaning design presentation  

NASA Technical Reports Server (NTRS)

The phase-out of CFC's and other ozone depleting chemicals has prompted industries to re-evaluate their present methods of cleaning. It has become necessary to find effective substitutes for their processes as well as to meet the new cleaning challenges of improved levels of cleanliness and to satisfy concerns about environmental impact of any alternative selected. One of the most popular alternatives being selected is aqueous cleaning. This method offers an alternative for removal of flux, grease/oil, buffing compound, particulates and other soils while minimizing environmental impact. What I will show are methods that can be employed in an aqueous cleaning system that will make it environmentally friendly, relatively simple to maintain and capable of yielding an even higher quality of cleanliness than previously obtained. I will also explore several drying techniques available for these systems and other alternatives along with recent improvements made in this technology. When considering any type of cleaning system, a number of variables should be determined before selecting the basic configuration. Some of these variables are: (1) Soil or contaminants being removed from your parts; (2) The level of cleanliness required; (3) The environmental considerations of your area; (4) Maintenance requirements; and (5) Operating costs.

Maltby, Peter F.

1995-01-01

338

Well aligned ZnO nanorods growth on the gold coated glass substrate by aqueous chemical growth method using seed layer of Fe3O4 and Co3O4 nanoparticles  

NASA Astrophysics Data System (ADS)

In this study, Fe3O4 and Co3O4 nanoparticles were prepared by co-precipitation method and sol-gel method respectively. The synthesised nanoparticles were characterised by X-ray diffraction [XRD] and Raman spectroscopy techniques. The obtained results have shown the nanocrystalline phase of obtained Fe3O4 and Co3O4 nanoparticles. Furthermore, the Fe3O4 and Co3O4 nanoparticles were used as seed layer for the fabrication of well-aligned ZnO nanorods on the gold coated glass substrate by aqueous chemical growth method. Scanning electron microscopy (SEM), high resolution transmission electron microscopy [HRTEM], as well as XRD and energy dispersive X-ray techniques were used for the structural characterisation of synthesised ZnO nanorods. This study has explored highly dense, uniform, well-aligned growth pattern along 0001 direction and good crystal quality of the prepared ZnO nanorods. ZnO nanorods are only composed of Zn and O atoms. Moreover, X-ray photoelectron spectroscopy was used for the chemical analysis of fabricated ZnO nanorods. In addition, the structural characterisation and the chemical composition study and the optical investigation were carried out for the fabricated ZnO nanorods and the photoluminescence [PL] spectrum have shown strong ultraviolet (UV) peak at 381 nm for Fe3O4 nanoparticles seeded ZnO nanorods and the PL spectrum for ZnO nanorods grown with the seed layer of Co3O4 nanoparticles has shown a UV peak at 382 nm. The green emission and orange/red peaks were also observed for ZnO nanorods grown with both the seed layers. This study has indicated the fabrication of well aligned ZnO nanorods using the one inorganic nanomaterial on other inorganic nanomaterial due to their similar chemistry.

Ibupoto, Z. H.; Khun, K.; Lu, Jun; Liu, Xianjie; AlSalhi, M. S.; Atif, M.; Ansari, Anees A.; Willander, M.

2013-04-01

339

Recovery of acetic acid from dilute aqueous solutions using catalytic dehydrative esterification with ethanol.  

PubMed

We have developed a direct esterification of aqueous acetic acid with ethanol (molar ratio=1:1) catalyzed by polystyrene-supported or homogeneous sulfonic acids toward the recovery of acetic acid from wastewater in chemical plants. The equilibrium yield was significantly increased by the addition of toluene, which had a high ability to extract ethyl acetate from the aqueous phase. It was shown that low-loading and alkylated polystyrene-supported sulfonic acid efficiently accelerated the reaction. These results suggest that the construction of hydrophobic reaction environments in water was critical in improving the chemical yield. Addition of inorganic salts was also effective for the reaction under not only biphasic conditions (toluene-water) but also toluene-free conditions, because the mutual solubility of ethyl acetate and water was suppressed by the salting-out effect. Among the tested salts, CaCl(2) was found to be the most suitable for this reaction system. PMID:23290939

Yagyu, Daisuke; Ohishi, Tetsuo; Igarashi, Takeshi; Okumura, Yoshikuni; Nakajo, Tetsuo; Mori, Yuichiro; Kobayashi, Sh?

2013-03-01

340

Aqueous alteration of kamacite in CM chondrites  

NASA Astrophysics Data System (ADS)

The study of aqueous alteration of kamacite in CM chondrites provides insight on the conditions, products, and relative timing of aqueous alteration. We studied unaltered, partially altered, and fully altered kamacite grains from Murray, Murchison, Cold Bokkeveld, and Nogoya using optical microscopy, electron microprobe analysis, scanning electron microscopy, and Raman spectroscopy. From textual evidence and chemical analysis, we established three separate microchemical environments. 1) In a microchemical environment with a high S activity, kamacite alters to form tochilinite, P-bearing sulfides, eskolaite, and schreibersite. Mass balance calculations show that 81% of the Fe in kamacite is removed from the alteration region, making it available for the formation of other minerals or Fe-rich aureoles. The release of Fe can alter the mesostasis of type-I chondrules forming cronstedtite. 2) In a microchemical environment with a high Si activity and a low S activity, kamacite alters to form cronstedtite with small accessory sulfide inclusions. 3) A microchemical environment with limited S and Si activity results in kamacite alteration forming magnetite. The resulting magnetite retains associated Ni that can distinguish it from precipitated magnetite. In addition, the accessory phases of pentlandite and apatite can be formed if S or Ca are present. Finally, we note that small tochilinite grains in the matrix lack typical Ni, P, and Co levels, suggesting that they did not form from kamacite but possibly by sulfidization of magnetite.

Palmer, Eric E.; Lauretta, Dante S.

2011-10-01

341

Corrosion problems with aqueous coolants, final report  

SciTech Connect

The results of a one year program to characterize corrosion of solar collector alloys in aqueous heat-transfer media are summarized. The program involved a literature review and a laboratory investigation of corrosion in uninhibited solutions. It consisted of three separate tasks, as follows: review of the state-of-the-art of solar collector corrosion processes; study of corrosion in multimetallic systems; and determination of interaction between different waters and chemical antifreeze additives. Task 1 involved a comprehensive review of published literature concerning corrosion under solar collector operating conditions. The reivew also incorporated data from related technologies, specifically, from research performed on automotive cooling systems, cooling towers, and heat exchangers. Task 2 consisted of determining the corrosion behavior of candidate alloys of construction for solar collectors in different types of aqueous coolants containing various concentrations of corrosive ionic species. Task 3 involved measuring the degradation rates of glycol-based heat-transfer media, and also evaluating the effects of degradation on the corrosion behavior of metallic collector materials.

Diegle, R B; Beavers, J A; Clifford, J E

1980-04-11

342

Reaction mechanism for the aqueous-phase mineral carbonation of heat-activated serpentine at low temperatures and pressures in flue gas conditions.  

PubMed

Mineral carbonation is known as one of the safest ways to sequester CO2. Nevertheless, the slow kinetics and low carbonation rates constitute a major barrier for any possible industrial application. To date, no studies have focused on reacting serpentinite with a relatively low partial pressure of CO2 (pCO2) close to flue gas conditions. In this work, finely ground and heat-treated serpentinite [Mg3Si2O5(OH)4] extracted from mining residues was reacted with a 18.2 vol % CO2 gas stream at moderate global pressures to investigate the effect on CO2 solubility and Mg leaching. Serpentinite dissolution rates were also measured to define the rate-limiting step. Successive batches of gas were contacted with the same serpentinite to identify surface-limiting factors using scanning electron microscopy (SEM) analysis. Investigation of the serpentinite carbonation reaction mechanisms under conditions close to a direct flue gas treatment showed that increased dissolution rates could be achieved relative to prior work, with an average Mg dissolution rate of 3.55 10(-11) mol cm(-2) s(-1). This study provides another perspective of the feasibility of applying a mineral carbonation process to reduce industrial greenhouse gas (GHG) emissions from large emission sources. PMID:24669999

Pasquier, Louis-Csar; Mercier, Guy; Blais, Jean-Franois; Cecchi, Emmanuelle; Kentish, Sandra

2014-05-01

343

The Effect of Chemical Composition and Heat Treatment Conditions on Stacking Fault Energy for Fe-Cr-Ni Austenitic Stainless Steel  

NASA Astrophysics Data System (ADS)

In order to establish more reliable formulae for calculating stacking fault energies (SFE) from the chemical compositions of austenitic stainless steels, SFE values were measured for 54 laboratory-melted heats and 2 commercial heats. The results were checked against those of a first-principle, atomistic calculation approach. More than ~20,000 data points for the width and angle of the Burgers vectors were determined from dark-field images of isolated extended dislocations in 56 heats of austenitic stainless steel using weak electron beams with g-3g diffraction conditions. Based on these numerous observations and on fundamental thermodynamic analyses, it is concluded that the SFE values for austenitic stainless steels are changed not only by chemical composition but also by heat treatment. In this paper, new formulae for calculating SFE values from the chemical compositions in three different heat treatment conditions have been proposed for austenitic stainless steels within given limited chemical composition ranges. In these formulae, the SFE values are calculated from the nickel, chromium, molybdenum, silicon, manganese, nitrogen, and carbon contents for the each heat treatment condition. The three heat treatment conditions studied were water cooling after solution heat treating (SHTWC), furnace cooling after solution heat treating, and aging after SHTWC.

Yonezawa, Toshio; Suzuki, Ken; Ooki, Suguru; Hashimoto, Atsushi

2013-12-01

344

Native chemical ligation of hydrophobic peptides in organic solvents.  

PubMed

The application of chemistry to hydrophobic peptides and membrane-spanning helices is hampered by the fact that they are only poorly soluble in aqueous buffers and that they have a tendency for aggregation. These properties lead to difficulties when purifying them after chemical synthesis and particularly interfere with native chemical ligation. Here, we describe native chemical ligation of model peptides in the organic solvent dimethylformamide (DMF) under anhydrous conditions. Best results concerning yields and complete solubility are obtained if thiophenole is used in the presence of LiCl. These conditions might be applicable also for the ligation of transmembrane helices. PMID:20814908

Dittmann, Marc; Sauermann, Jrg; Seidel, Ralf; Zimmermann, Wolfgang; Engelhard, Martin

2010-10-01

345

The chemical conditions on the parent body of the murchison meteorite: Some conclusions based on amino, hydroxy and dicarboxylic acids  

NASA Astrophysics Data System (ADS)

Amino and hydroxy acids have been identified in the Murchison meteorite. Their presence is consistent with a synthetic pathway involving aldehydes, hydrogen cyanide and ammonia in an aqueous environment (Strecker-cyanohydrin synthesis). From the various equilibrium and rate constants involved in this synthesis, four independent estimates of the ammonium ion concentrations on the parent body at the time of compound synthesis are obtained; all values are about 2 10-3 M. Succinic acid and ?-alanine have also been detected in the Murchison meteorite. Their presence is consistent with a synthesis from acrylonitrile, hydrogen cyanide and ammonia. Using the equilibrium and rate constants for this synthetic pathway, and the succinic acid/?-alanine ratio measured in the Murchison meteorite, an estimate of the hydrogen cyanide concentration of 10-3 to 10-2 M is obtained. Since hydrogen cyanide hydrolyzes relatively rapidly in an aqueous environment (t1/2 < 104 yrs) this high concentration implies a period of synthesis of organic compounds as short as 104 years on the Murchison meteorite parent body.

Peltzer, E. T.; Bada, J. L.; Schlesinger, G.; Miller, S. L.

346

Aqueous phase processing of secondary organic aerosols  

NASA Astrophysics Data System (ADS)

The aging of secondary organic aerosol (SOA) by photooxidation in the aqueous phase was experimentally investigated. To simulate multiphase processes, the following experiments were sequentially performed in a smog chamber and in an aqueous phase photoreactor: (1) Gas-phase photooxidation of three different volatile organic compounds (VOC): isoprene, ?-pinene, and 1,3,5-trimethylbenzene (TMB) in the presence of NOx, leading to the formation of SOA which was subjected to on-line physical and chemical analysis; (2) particle-to-liquid transfer of water soluble species of SOA using filter sampling and aqueous extraction; (3) aqueous-phase photooxidation of the obtained water extracts; and (4) nebulization of the solutions for a repetition of the on-line characterization. SOA concentrations in the chamber measured with a scanning mobility particle sizer (SMPS) were higher than 200 ?g m-3, as the experiments were conducted under high initial concentrations of volatile organic compounds (VOC) and NOx. The aging of SOA through aqueous phase processing was investigated by measuring the physical and chemical properties of the particles online before and after processing using a high resolution time-of-flight aerosol mass spectrometer (AMS) and a hygroscopicity tandem differential mobility analyzer (H-TDMA). It was shown that, after aqueous phase processing, the particles were significantly more hygroscopic, and contained more fragmentation ions at m/z = 44 and less ions at m/z = 43, thus showing a significant impact on SOA aging for the three different precursors. Additionally, the particles were analyzed with a thermal desorption atmospheric pressure ionization aerosol mass spectrometer (TD-API-AMS). Comparing the smog chamber SOA composition and non processed nebulized aqueous extracts with this technique revealed that sampling, extraction and/or nebulization did not significantly impact the chemical composition of SOA formed from isoprene and ?-pinene, whereas it affected that formed from TMB. For the two first precursors, the aqueous phase chemical composition of SOA was further investigated using offline measurements, i.e. ion chromatography coupled to a mass spectrometer (IC-MS) and an atmospheric pressure chemical ionization mass spectrometer (APCI-MS) equipped with high pressure liquid chromatography (HPLC-MS). These analyses showed that aqueous phase processing enhanced the formation of some compounds already present in the SOA, thus confirming the aging effect of aqueous phase processes. For isoprene experiments, additional new compounds, likely oligomers, were formed through aqueous phase photooxidation, and their possible origins are discussed.

Liu, Yao; Tritscher, T.; Praplan, A. P.; Decarlo, P. F.; Temime-Roussel, B.; Quivet, E.; Marchand, N.; Dommen, J.; Baltensperger, U.; Monod, A.

2011-07-01

347

Computer modeling of the mineralogy of the Martian surface, as modified by aqueous alteration  

NASA Technical Reports Server (NTRS)

Mineralogical constraints can be placed on the Martian surface by assuming chemical equilibria among the surface rocks, atmosphere and hypothesized percolating groundwater. A study was made of possible Martian surface mineralogy, as modified by the action of aqueous alteration, using the EQ3/6 computer codes. These codes calculate gas fugacities, aqueous speciation, ionic strength, pH, Eh and concentration and degree of mineral saturation for complex aqueous systems. Thus, these codes are also able to consider mineralogical solid solutions. These codes are able to predict the likely alteration phases which will occur as the result of weathering on the Martian surface. Knowledge of the stability conditions of these phases will then assist in the definition of the specifications for the sample canister of the proposed Martian sample return mission. The model and its results are discussed.

Zolensky, M. E.; Bourcier, W. L.; Gooding, J. L.

1988-01-01

348

Response to Chemical Alarm Cues under Weakly Acidic Conditions: A Graded Loss of Antipredator Behaviour in Juvenile Rainbow Trout  

Microsoft Academic Search

A wide variety of aquatic organisms, including juvenile salmonids, assess local predation risks using chemosensory cues. Such\\u000a chemical cues are typically released from injured conspecifics and their detection may lead to species-typical antipredator\\u000a behaviour, increasing the probability of prey to survive during predator encounters. Studies have demonstrated however, that\\u000a under weak acidification (pH ~6.0), the response towards these chemical alarm

Antoine O. H. C. Leduc; Fabien C. Lamaze; Lindsay McGraw; Grant E. Brown

2008-01-01

349

Zwitterionic, cationic, and anionic fluorinated chemicals in aqueous film forming foam formulations and groundwater from U.S. military bases by nonaqueous large-volume injection HPLC-MS/MS.  

PubMed

A new analytical method was developed to quantify 26 newly-identified and 21 legacy (e.g. perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, and fluorotelomer sulfonates) per and polyfluorinated alkyl substances (PFAS) in groundwater and aqueous film forming foam (AFFF) formulations. Prior to analysis, AFFF formulations were diluted into methanol and PFAS in groundwater were micro liquid-liquid extracted. Methanolic dilutions of AFFF formulations and groundwater extracts were analyzed by large-volume injection (900 ?L) high-performance liquid chromatography tandem mass spectrometry. Orthogonal chromatography was performed using cation exchange (silica) and anion exchange (propylamine) guard columns connected in series to a reverse-phase (C18) analytical column. Method detection limits for PFAS in groundwater ranged from 0.71 ng/L to 67 ng/L, and whole-method accuracy ranged from 96% to 106% for analytes for which matched authentic analytical standards were available. For analytes without authentic analytical standards, whole-method accuracy ranged from 78 % to 144 %, and whole-method precision was less than 15 % relative standard deviation for all analytes. A demonstration of the method on groundwater samples from five military bases revealed eight of the 26 newly-identified PFAS present at concentrations up to 6900 ng/L. The newly-identified PFAS represent a minor fraction of the fluorinated chemicals in groundwater relative to legacy PFAS. The profiles of PFAS in groundwater differ from those found in fluorotelomer- and electrofluorination-based AFFF formulations, which potentially indicates environmental transformation of PFAS. PMID:23590254

Backe, Will J; Day, Thomas C; Field, Jennifer A

2013-05-21

350

Synthesis, Chemical and Enzymatic Hydrolysis, and Aqueous Solubility of Amino Acid Ester Prodrugs of 3-Carboranyl Thymidine Analogues for Boron Neutron Capture Therapy of Brain Tumors  

PubMed Central

Various water-soluble L-valine-, L-glutamate-, and glycine ester prodrugs of two 3-Carboranyl Thymidine Analogues (3-CTAs), designated N5 and N5-2OH, were synthesized for Boron Neutron Capture Therapy (BNCT) of brain tumors since the water solubilities of the parental compounds proved to be insufficient in preclinical studies. The amino acid ester prodrugs were prepared and stored as hydrochloride salts. The water solubilities of these amino acid ester prodrugs, evaluated in phosphate buffered saline (PBS) at pH 5, pH 6 and pH 7.4, improved 48 to 6600 times compared with parental N5 and N5-2OH. The stability of the amino acid ester prodrugs was evaluated in PBS at pH 7.4, Bovine serum, and Bovine cerebrospinal fluid (CSF). The rate of the hydrolysis in all three incubation media depended primarily on the amino acid promoiety and, to a lesser extend, on the site of esterification at the deoxyribose portion of the 3-CTAs. In general, 3'-amino acid ester prodrugs were less sensitive to chemical and enzymatic hydrolysis than 5'-amino acid ester prodrugs and the stabilities of the latter decreased in the following order: 5'-valine > 5'-glutamate > 5'-glycine. The rate of the hydrolysis of the 5'-amino acid ester prodrugs in Bovine CSF was overall higher than in PBS and somewhat lower than in Bovine serum. Overall, 5'-glutamate ester prodrug of N5 and the 5'-glycine ester prodrugs of N5 and N5-2OH appeared to be the most promising candidates for preclinical BNCT studies. PMID:22889558

Hasabelnaby, Sherifa; Goudah, Ayman; Agarwal, Hitesh K.; Abd alla, Mosaad S. M.; Tjarks, Werner

2012-01-01

351

QD-antibody conjugates via carbodiimide-mediated coupling: a detailed study of the variables involved and a possible new mechanism for the coupling reaction under basic aqueous conditions.  

PubMed

A detailed study into the optimization of carbodiimide-mediated coupling of antibodies (Ab) and quantum dots (QD) for use in cellular imaging has been undertaken. This involved the grafting of commercially available carboxyl-modified QDs (Evident Technologies "Lake Placid Blue" Evitag and eBioscience's eflour nanocrystals) with anti-Cdc8 Abs to produce conjugates with specific affinity for fission yeast tropomyosin Cdc8 protein. The water-soluble carbodiimide 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) was used to activate the QDs prior to their incubation with antibody, and a range of QD-carboxyl/EDC/Ab mole ratios were used in the experiments in attempts to optimize fluorescence and bioaffinity of the conjugate products (EDC to QD-carboxyl-600 nmol/15 pmol to 0.12 nmol/15 pmol and QD to Ab 120 pmol/24 pmol to 120 pmol/1.2 pmol). It was observed that a specific "optimum" ratio of the three reactants was required to produce the most fluorescent and biologically active product and that it was generated at alkaline pH 10.8. Increasing the ratio of Ab to QD produced conjugate which was less fluorescent while reducing the ratio of EDC to QD in the activation step led to increased fluorescence of product. Conjugates were tested for their possession of antibody by measurement of their absorption at OD(280 nm) and for their fluorescence by assay ?(max(em)) at 495 nm. A quantitative assay of the bioactivity of the conjugates was developed whereby a standardized amount of Cdc8 antigen was spotted onto nylon membranes and reacted with products from conjugation reactions in a sandwich-type colormetric assay The "best" conjugate was used in intracellular imaging of yeast Cdc8 protein and produced brighter, higher definition images of fixed yeast cell actin structure than a fluorescein-Ab conjugate routinely produced in our laboratory. The QD-Ab conjugate was also significantly more resistant to photobleaching than the fluorescein-Ab conjugate. Results from other experiments involving EDC, the water-soluble carbodiimide 1-cyclohexyl-3-(2-morpholinoethyl)carbodiimide metho-p-toluenesulphonate (CMC), and EDC.HCl have suggested a new reaction mechanism for EDC coupling under basic aqueous conditions. In summary, a robust understanding of commercial QD-COOH surface chemistry and the variables involved in the materials' efficient conjugation with a bioligand using carbidiimide has been obtained along with an optimized approach for Ab-QD conjugate production. A novel assay has been developed for bioassay of QD-Ab conjugates and a new mechanism for EDC coupling under basic aqueous conditions is proposed. PMID:21970592

East, Daniel A; Mulvihill, Daniel P; Todd, Michael; Bruce, Ian J

2011-11-15

352

Cr(VI) removal from aqueous solution with bamboo charcoal chemically modified by iron and cobalt with the assistance of microwave.  

PubMed

Bamboo charcoal (BC) was used as starting material to prepare Co-Fe binary oxideloaded adsorbent (Co-Fe-MBC) through its impregnation in Co(NO3)2, FeCl3 and HNO3 solutions simultaneously, followed by microwave heating. The low-cost composite was characterized and used as an adsorbent for Cr(VI) removal from water. The results showed that a cobalt and iron binary oxide (CoFe2O4) was uniformly formed on the BC through redox reactions. The composite exhibited higher surface area (331 m2/g) than that of BC or BC loaded with Fe alone (Fe-MBC). The adsorption of Cr(VI) strongly depended on solution pH, temperature and ionic strength. The adsorption isotherms followed the Langmuir isotherm model well, and the maximum adsorption capacities for Cr(VI) at 288 K and pH 5.0 were 35.7 and 51.7 mg/g for Fe-MBC and Co-Fe-MBC, respectively. The adsorption processes were well fitted by the pseudo second-order kinetic model. Thermodynamic parameters showed that the adsorption of Cr(VI) onto both adsorbents was feasible, spontaneous, and exothermic under the studied conditions. The spent Co-Fe-MBC could be readily regenerated for reuse. PMID:24520714

Wang, Wei; Wang, Xuejiang; Wang, Xin; Yang, Lianzhen; Wu, Zhen; Xia, Siqing; Zhao, Jianfu

2013-09-01

353

Preparation conditions and optical properties of rare earth ion (Er{sup 3+} and Eu{sup 3+})-doped alumina films by the aqueous sol{endash}gel method  

SciTech Connect

Transparent alumina and rare earth ion (Er{sup 3+} and Eu{sup 3+}) highly doped alumina films (15 mol%) were prepared by the aqueous sol{endash}gel method, in order to examine the effects of various preparation conditions on the structure and optical properties of doped films. The results showed that when the gel was heat treated, it lost free and bound water and was converted into the oxide by way of a series of intermediate phases although the oxide as a whole remained structureless. The thermogravimetric analysis curve showed a marked weight loss in the temperature range of 100{endash}500{degree}C and the slow loss continuing at higher temperature of 800{degree}C. High doping may reflect noncrystalline structure of alumina. The fluorescence of Eu{sup 3+} sensitive of microstructure increased especially corresponding to this weight loss with treatment. The {Omega}{sub 2} indicative of the asymmetric environment of Er{sup 3+} showed a similar increase. Concentration quenching for doped films treated at 800{degree}C was not significant in this concentration range. Lifetimes increased with increasing treatment temperature, similar to above increase. {copyright} 2001 American Institute of Physics.

Ishizaka, T.; Kurokawa, Y.

2001-07-01

354

Mukaiyama Aldol Reactions in Aqueous Media  

PubMed Central

Mukaiyama aldol reactions in aqueous media have been surveyed. While the original Mukaiyama aldol reactions entailed stoichiometric use of Lewis acids in organic solvents under strictly anhydrous conditions, Mukaiyama aldol reactions in aqueous media are not only suitable for green sustainable chemistry but are found to produce singular phenomena. These findings led to the discovery of a series of water-compatible Lewis acids such as lanthanide triflates in 1991. Our understanding on these beneficial effects in the presence of water will be deepened through the brilliant examples collected in this review. 1 Introduction 2 Rate Enhancement by Water in the Mukaiyama Aldol Reaction 3 Lewis Acid Catalysis in Aqueous or Organic Solvents 3.1 Water-Compatible Lewis Acids 4 Lewis-Base Catalysis in Aqueous or Organic Solvents 5 The Mukaiyama Aldol Reactions in 100% Water 6 Asymmetric Catalysts in Aqueous Media and Water 7 Conclusions and Perspective PMID:24971045

Kitanosono, Taku; Kobayashi, Shu

2013-01-01

355

Silver nanoparticles for SERS-based ultrasensitive chemical detection in aqueous solutions: Role of binding affinity and surface oxidation in the detection limit  

NASA Astrophysics Data System (ADS)

Surface-enhanced Raman spectroscopy (SERS) in the presence of noble metal nanostructures holds significant promise for sensing and molecular fingerprinting down to single molecule level. This dissertation explores the effect of binding affinity and surface oxidation of Ag nanoparticles on SERS detection sensitivity of SO42-, CN-, SCN-, ClO4- and nitro-aromatic compounds in water. Specifically positively charged Ag nanoparticles (Ag [+]) were synthesized by UV-assisted reduction of silver nitrate using branched polyethyleneimine (BPEI) and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) solutions. Both primary amino and amide groups on the surface of Ag [+] allowed strong binding affinity with anions, critical for sensitive SERS measurements. For substrates with immobilized Ag [+] (30 nanoparticles/mum2), SERS sensitivity increased in the order of SO42- < CN- < SCN- ? ClO4 -, with respective binding constants of 105, 3.3 x 105, and 107 (for both SCN- and ClO4-) M-1. Significantly, substrates with Ag [+] exhibited limit of detection values of 8.0 x 10-8 M (8 ppb) and 2.7 x 10-7 M (7 ppb) for ClO 4- and CN-, respectively. We revealed for the first time that oxidation of negatively charged Ag nanoparticles (Ag [-]) produced by a modified Lee and Meisel procedure drastically altered adsorption and orientation of nitro-aromatic molecules and increased their SERS detection limit. This observation can be attributed to the hinderance of Ag-to-aromatic ring charge transfer by the resultant oxide layer. SERS detection of p-nitrophenol at 1 ppt was achieved through inhibition of oxidation of Ag [-] in argon gas. Finally, to extend our work for potential biosensing applications, we showed that BPEI coatings of high molecular weight were unique in their ability to provide avidin-resistant surfaces at physiological conditions due to steric hindrance from the branched architecture of adsorbed polymer chains. BPEI coated surfaces were also effective for suppression of smaller positively charged proteins such as lysozyme and ribonuclease A at pH 7 and 0.15 M NaCl and of negatively charged proteins such as BSA and fibrinogen at pH 7 and 0.75 M NaCl. Furthermore, using PEI-modified protein-repellent surfaces, selective binding of avidin was achieved to surface-bound Ag nanoparticles, thus providing a promising strategy for SERS-based bio-detection.

Erol, Melek

356

Effects of temperature and wave conditions on chemical dispersion efficacy of heavy fuel oil in an experimental flow-through wave tank.  

PubMed

The effectiveness of chemical dispersants (Corexit 9500 and SPC 1000) on heavy fuel oil (IFO180 as test oil) has been evaluated under different wave conditions in a flow-through wave tank. The dispersant effectiveness was determined by measuring oil concentrations and droplet size distributions. An analysis of covariance (ANCOVA) model indicated that wave type and temperature significantly (p<0.05) affected the dynamic dispersant effectiveness (DDE). At higher temperatures (16 degrees C), the test IFO180 was effectively dispersed under breaking waves with a DDE of 90% and 50% for Corexit 9500 and SPC 1000, respectively. The dispersion was ineffective under breaking waves at lower temperature (10 degrees C), and under regular wave conditions at all temperatures (10-17 degrees C), with DDE<15%. Effective chemical dispersion was associated with formation of smaller droplets (with volumetric mean diameters or VMD < or = 200 microm), whereas ineffective dispersion produced large oil droplets (with VMD > or = 400 microm). PMID:20483435

Li, Zhengkai; Lee, Kenneth; King, Thomas; Boufadel, Michel C; Venosa, Albert D

2010-09-01

357

Conditioned Alarm Behavior in Fathead Minnows ( Pimephales promelas ) Resulting from Association of Chemical Alarm Pheromone with a Nonbiological Visual Stimulus  

Microsoft Academic Search

Fathead minnows (Pimephales promelas) adopt antipredator (alarm) behavior when they detect alarm pheromone released from an injured conspecific. This is an adaptive response since alarm pheromone is generally released only in the context of a predation event. Alarm reactions may also occur in response to chemical and visual stimuli that minnows learn to associate with release of alarm pheromone. Here,

Warren K. Yunker; Dan E. Wein; Brian D. Wisenden

1999-01-01

358

Chemical immobilization of adult female Weddell seals with tiletamine and zolazepam: effects of age, condition and stage of lactation  

Microsoft Academic Search

BACKGROUND: Chemical immobilization of Weddell seals (Leptonychotes weddellii) has previously been, for the most part, problematic and this has been mainly attributed to the type of immobilizing agent used. In addition to individual sensitivity, physiological status may play an important role. We investigated the use of the intravenous administration of a 1:1 mixture of tiletamine and zolazepam (Telazol) to immobilize

Kathryn E Wheatley; Corey JA Bradshaw; Robert G Harcourt; Lloyd S Davis; Mark A Hindell; NJ Gales; M Haulena; RB Heath; GL Kooyman; MA Castellini; RW Davis; H Bornemann; J Pltz; R Woods; DJ Slip; IC Field; CJA Bradshaw; CR McMahon; J Harrington; HR Burton; S McLean; M Bester; Sepulveda; H Ochoa-Acua; GS McLaughlin; FR Engelhardt; Cline; DB Siniff; AW Erickson; JR Phelan; K Green; D Hammond; R Elsner; V Flyger; MSR Smith; R Damm; RS Peterson; H Kusagaya; K Sato; K Bodley; T van Polanen Petel; MJ Lynch; M Tahmindjis; H Gardner; WB Karesh; RA Cook; M Stetter; MM Uhart; A Hoogesteijn; MN Lewis; C Campagna; P Majluf; A Torres; C House; LA Thomas; WE Braselton; ES Dierenfeld; TS McNamara; P Duignan; S Raverty; M Linn; I Stirling; B Sjare; CH Tracy; CE Short; BC Clark; A Massolo; A Sforzi; S Lovari; G Samelius; S Lariviere; RT Alisauskas; JR Baker; M Fedak; SS Anderson; T Arnbom; R Baker; LJ Gage; KP Burnham; MF Cameron; S Nicol; DS Houser; DP Costa; CL Ortiz; BJ Le Boeuf; JR Reilly; E Mammen; S Van de Geer; P McCullagh; JA Nedler; JC Pinheiro; JM Bates; JD Lebreton; J Colbert; R Ihaka; R Gentleman; PJ Mitchell

1991-01-01

359

Effects of biological and chemical treatments on Botrytis stem canker and fruit yield of tomato under greenhouse conditions  

Microsoft Academic Search

Experiments were conducted to identify, by in vitro dual culture tests, potential biological control agents producing antibiotics and to evaluate selected biological and chemical agents for control of stem canker caused by Botrytis cinerea on tomato plants (Lycopersicon esculentum) grown in yellow cedar sawdust in a research greenhouse. Four strains of Bacillus subtilis and one each of Enterobacter agglomerans and

R. Utkhede; C. Bogdanoff; J. McNevin

2001-01-01

360

Surface Conditions of Nitinol Wires, Tubing, and AsCast Alloys. The Effect of Chemical Etching, Aging in Boiling Water, and Heat Treatment  

Microsoft Academic Search

The surface conditions of Nitinol wires and tubing were evaluated with the use of X-ray photoelectron spectroscopy, high-resolution Auger spectroscopy, electron backscatter- ing, and scanning-electron microscopy. Samples were studied in the as-received state as well as after chemical etching, aging in boiling water, and heat treatment, and compared to a mechanically polished 600-grit-finish Nitinol surface treated similarly. General regularities in

S. A. Shabalovskaya; J. Anderegg; F. Laab; P. A. Thiel; G. Rondelli

2003-01-01

361

The effects of deposition and test conditions on nanomechanical behaviour of ultrathin films produced by plasma-enhanced chemical vapour deposition process at atmospheric pressure  

Microsoft Academic Search

Nanometer thick films have been deposited on silicon substrate by plasma-enhanced chemical vapour deposition (PE-CVD) process using non-homogenous, filamentary dielectric-barrier discharge (DBD) at atmospheric pressure. This film deposition technique enables the introduction some organic fragments into the coating materialsilicon dioxide (or oxynitride)resulting in good properties for self-lubrication of micro-electro-mechanical systems (MEMS) devices. The effect of the deposition conditions and loading

Zygmunt Rymuza; Maciej Misiak; Zenobia Rzanek-Boroch; Krzysztof Schmidt-Sza?owski; Jadwiga Janowska

2004-01-01

362

A Study of the Development of Chemical Heterogeneity in Large Forging Ingots: Depending Upon the Configuration and Thermophysical Conditions of Casting  

NASA Astrophysics Data System (ADS)

The paper reports the findings in the development of "A" segregation streaks in large ingots which were cast under various solidification conditions: different bottom shapes of ingots and metal pouring using inoculated stream. It is shown that changed conditions bring about a decrease in the "A" segregation zones as well as reduced diameters and shorter lengths of "A" segregation streaks. A different design of the ingot bottom and smaller streaks reduce the chemical heterogeneity of ingots and improve the anisotropy of the forgings fabricated from the ingots.

Zyuban, Nikolai; Rutskii, Dmitrii; Konovalov, Sergei; Gamanyuk, Sergei

2014-09-01

363

Morphological and chemical stability of silicon nanostructures and their molecular overlayers under physiological conditions: towards long-term implantable nanoelectronic biosensors  

PubMed Central

Background The detection of biological and chemical species is of key importance to numerous areas of medical and life sciences. Therefore, a great interest exists in developing new, rapid, miniature, biocompatible and highly sensitive sensors, capable to operate under physiological conditions and displaying long-term stabilities (e.g. in-body implantable sensors). Silicon nanostructures, nanowires and nanotubes, have been extensively explored as building blocks for the creation of improved electrical biosensing devices, by virtue of their remarkably high surface-to-volume ratios, and have shown exceptional sensitivity for the real time label-free detection of molecular species adsorbed on their surfaces, down to the sensitivity of single molecules. Yet, till this date, almost no rigorous studies have been performed on the temporal morphological stability of these nanostructures, and their resulting electrical devices, under physiological conditions (e.g. serum, blood), as well as on the chemical stability of the molecular recognition over-layers covering these structures. Results Here, we present systematic time-resolved results on the morphological stability of bare Si nanowire building blocks, as well on the chemical stability of siloxane-based molecular over-layers, under physiological conditions. Furthermore, in order to overcome the observed short-term morpho-chemical instabilities, we present on the chemical passivation of the Si nanostructures by thin metal oxide nanoshells, in the range of 310nm. The thickness of the metal oxide layer influences on the resulting electrical sensitivity of the fabricated FETs (field effect transistors), with an optimum thickness of 34nm. Conclusions The core-shell structures display remarkable long-term morphological stability, preventing both, the chemical hydrolytic dissolution of the silicon under-structure and the concomitant loss of the siloxane-based chemical over-layers, for periods of at least several months. Electrical devices constructed from these nanostructures display excellent electrical characteristics and detection sensitivities, with exceptionally high morphological and functional stabilities. These results pave the road for the creation of long-term implantable biosensing devices in general, and nanodevices in particular. PMID:24606762

2014-01-01

364

Stability of metal oxide nanoparticles in aqueous solutions.  

PubMed

The application of nanoparticles in the processes of making commercial products has increased in recent years due to their unique physical and chemical properties. With increasing amount of commercial nanoparticles released into nature, their fate and effects on the ecosystem and human health are of growing concern. This study investigated the stability and morphology of three metal oxide nanoparticles in aqueous solutions. The commercially available nanoparticles, TiO(2), ZnO, SiO(2), aggregated quickly into micrometer-size particles in aqueous solutions, which may not threaten human health. Their changes in morphology and characteristics were further examined by dynamic light scattering (DLS) method and transmission electron microscopy (TEM). Among the several dispersion approaches, ultrasonication was found to be the most effective for disaggregating nanoparticles in water. For these three selected nanoparticles, ZnO could not remain stable in suspensions, presumably due to the dissolution of particles to form high concentration of ions, resulting in enhanced aggregation of particles. In addition, the existence of dissolved organic matters stabilized nanoparticles in lake water and wastewater for several hours in spite of the high concentration of cations in these real-water samples. The fate of metal oxide nanoparticles in natural water bodies would be determined by the type and concentration of cations and organic matters. Results obtained in this study revealed that the stability of nanoparticles changed under different aqueous conditions and so did their fate in the environment. PMID:20057098

Tso, Chih-ping; Zhung, Cheng-min; Shih, Yang-hsin; Tseng, Young-Ming; Wu, Shian-chee; Doong, Ruey-an

2010-01-01

365

Photodecomposition of anthracene in aqueous and heterogeneous media  

SciTech Connect

We have undertaken an in-depth study of the photodecomposition of PAHs in aqueous solutions and in heterogeneous environments with an emphasis on identifying the primary photoproducts and clarifying mechanistic aspects of the processes. Our initial studies have involved the photodecomposition of anthracene, 1, in aqueous solutions and in SiO{sub 2}/cyclohexane slurries. Results from these studies will be reported here and possible mechanistic similarities will be explored. Our experimental approach to investigations of the aqueous photochemistry of 1 has been to avoid the use of organic cosolvents. This practice necessitated the study of dilute, 10{sup {minus}7} M, solutions which complicated the isolation, identification, and quantification of photoproducts, however, it circumvented questions of selective solvation. Photolysis has been done through uranium glass tubes in a Rayonet RPR-208 photoreactor equipped with 350 nm bulbs, irradiance of 3.2 {times} 10{sup 16} photons sec{sup {minus}1} cm{sup {minus}2}. Oxygen purged, aerated, and oxygen-deficient solutions, prepared by purging with argon containing less than 0.5 ppm O{sub 2}m were examined. Products were analyzed by HPLC, GC, GC-MS, UV-Vis spectroscopy, chemical derivatization, independent synthesis and x-ray analysis. Anthracene in SiO{sub 2}/cyclohexane slurries was photolyzed under similar conditions to those described above. 6 refs., 2 figs.

Sigman, M.E.; Zingg, S.P.

1991-01-01

366

Influence of chemical extraction conditions on the physicochemical and functional properties of polysaccharide gum from durian (Durio zibethinus) seed.  

PubMed

Durian seed is an agricultural biomass waste of durian fruit. It can be a natural plant source of non-starch polysaccharide gum with potential functional properties. The main goal of the present study was to investigate the effect of chemical extraction variables (i.e., the decolouring time, soaking temperature and soaking time) on the physicochemical properties of durian seed gum. The physicochemical and functional properties of chemically-extracted durian seed gum were assessed by determining the particle size and distribution, solubility and the water- and oil-holding capacity (WHC and OHC). The present work revealed that the soaking time should be considered as the most critical extraction variable affecting the physicochemical properties of crude durian seed gum. PMID:22643356

Mirhosseini, Hamed; Amid, Bahareh Tabatabaee

2012-01-01

367

Kinetic analysis on formation of poly(3-hydroxybutyrate) from acetic acid by Ralstonia eutropha under chemically defined conditions  

Microsoft Academic Search

Batch cultures of Ralstonia eutropha in chemically defined media with acetic acid (HAc) as the sole carbon source were conducted to investigate acetate utilization,\\u000a formation of poly(3-hydroxybutyrate) (PHB) and growth of active biomass (ABM) under different carbon to nitrogen (C\\/N) weight\\u000a ratios. The specific acetate utilization rate based on ABM approached 0.16 g\\/g ABM h?1, which was not affected very

J Wang; J Yu

2001-01-01

368

Effects of Extrusion Variables and Chemicals on the Properties of Starch-Based Binders and Processing Conditions 1  

Microsoft Academic Search

Cereal Chem. 75(4):541-546 The effects of extrusion variables (moisture, screw speed, and temper- ature) and chemicals (urea and sodium bicarbonate) on the properties of starch-based binders (water absorption, bulk density, binder yield, expan- sion ratio, solubility, pH) and processing c onditions (die temperature and pressure, feed rate, and specific mechanical energy) were studied using a central composite design. All quadratic

Z. Pan; S. Zhang; J. Jane

1998-01-01

369

Corrosion inhibition of aqueous potassium carbonate gas treating systems  

Microsoft Academic Search

Union Carbide Corp.'s new chemical mixture inhibits corrosion of ferrous metals used in acid-gas treating plants that use aqueous potassium carbonate solutions to remove carbon dioxide and hydrogen sulfide from natural gases, flue gases, synthesis gas, etc. The new mixture consists of (1) about 9 to 1 parts by weight of a vanadium compound capable of ionizing in the aqueous

Mago

1976-01-01

370

Chemical synthesis of poly(aniline-co-o\\/m-toluidine)\\/V 2O 5 nano composites and their characterizations  

Microsoft Academic Search

Chemical oxidative polymerization of aniline (ANI) and o\\/m-toluidine (OT or MT) and their nano composites at different experimental conditions were performed using peroxydisulfate (PDS) as a lone chemical initiator and V2O5 as a host material in an aqueous HCl medium at 45C under nitrogen atmosphere. The nano composites were synthesized under different experimental conditions and were characterized by Fourier transform

J. Juliet Latha Jeyakumari; A. Yelilarasi; B. Sundaresan; V. Dhanalakshmi; R. Anbarasan

2010-01-01

371

Is an assessment factor of 10 appropriate to account for the variation in chemical toxicity to freshwater ectotherms under different thermal conditions?  

PubMed

Ecotoxicity tests are often conducted following standard methods, and thus carried out at a fixed water temperature under controlled laboratory conditions. Yet, toxicity of a chemical contaminant may vary in a temperature-dependent manner, depending on the physiology of the test organism and physicochemical properties of the chemical. Although an assessment factor of 10 (AF10) is commonly adopted to account for variability in toxicity data related to temperature in the development of water quality guidelines and/or ecological risk assessment, no one has ever rigorously assessed the appropriateness of AF10 to account for potential variation in temperature-dependent chemical toxicity to aquatic organisms. This study, therefore, aims to address this issue through a meta-analysis by comparing median lethal concentration data for nine chemicals (cadmium, copper, nickel, lead, silver, zinc, arsenic, selenium and DDT) on a range of freshwater ectothermic animal species at different temperatures, and to assess whether AF10 is under- or over-protective for tropical and temperate freshwater ecosystems. Our results reveal varying extents of interaction between temperature and different chemicals on organisms and the complexity of these interactions. Applying AF10 sufficiently protects 90% of the animal species tested over a range of temperatures for cadmium, copper, nickel, silver, zinc and DDT in the tropics, but it is insufficient to adequately encompass a larger temperature variation for most studied chemicals in temperate regions. It is therefore important to set specific AFs for different climatic zones in order to achieve the desired level of ecosystem protection. PMID:23640388

Lau, Edward Tak Chuen; Yung, Mana Man Na; Karraker, Nancy E; Leung, Kenneth Mei Yee

2014-01-01

372

Chemical Models for Aqueous Biodynamical Processes  

E-print Network

through a continuum, the processes of self-diffusion and viscous flow are inversely related as shown by equation 9: D = KI/ 6 TTTi r (9) At 298 K, D for H20 is 2.5 x 1(TS cm2see"""1 and for D20 2.0 x 1CT5 cm2sec The deuterium isotope effect on D... xii III-6. Pan-Hydronium Ion as a Catalytic Entity in the Neutral Hydrolysis of Carboxylic Esters. 74 CHAPTER IV I V-l. I V-2. IV-3. IV-4. CHAPTER V V-l. V-2. V-3. V-4. V-5. V-6. Determination of the Isotopic Fractionation Factor...

Mata-Segreda, Julio F.

1975-05-01

373

Chemical sensor  

NASA Technical Reports Server (NTRS)

A sensor for detecting a chemical substance includes an insertion element having a structure which enables insertion of the chemical substance with a resulting change in the bulk electrical characteristics of the insertion element under conditions sufficient to permit effective insertion; the change in the bulk electrical characteristics of the insertion element is detected as an indication of the presence of the chemical substance.

Rauh, R. David (Inventor)

1990-01-01

374

Low temperature aqueous desulfurization of coal  

DOEpatents

This invention describes a chemical process for desulfurizing coal, especially adaptable to the treatment of coal-water slurries, at temperatures as low as ambient, comprising treating the coal with aqueous titanous chloride whereby hydrogen sulfide is liberated and the desulfurized coal is separated with the conversion of titanous chloride to titanium oxides.

Slegeir, W.A.; Healy, F.E.; Sapienza, R.S.

1985-04-18

375

Adaptive plasticity of Laguncularia racemosa in response to different environmental conditions: integrating chemical and biological data by chemometrics.  

PubMed

Mangroves are dynamic environments under constant influence of anthropic contaminants. The correlation between environmental contamination levels and possible changes in the morphology of plants, evaluated by multivariate statistics helps to highlight matching between these variables. This study aimed to evaluate the uptake and translocation of metals and metalloids in roots and leaves as well as the changes induced in both anatomy and histochemistry of roots of Laguncularia racemosa inhabiting two estuaries of Esprito Santo (Brazil) with different pollution degrees. The analysis of 14 elements in interstitial water, sediments and plants followed by multivariate statistics, allowed the differentiation of studied sites, showing good match between levels of elements in the environment with the corresponding in plants. L. racemosa showed variations in their root anatomy in different collection areas, with highest values of cortex/vascular cylinder ratio, periderm thickness and air gap area in Vitria Bay, the most polluted sampling area. These three parameters were also important to differentiate the mangrove areas by linear discriminant analysis. The development stage of aerenchyma in roots reflected the oxygen availability in the water, being found a negative correlation between these variables. The combined use of chemical and biological analyses responded quite well to different pollution scenarios, matching morphological responses to physical and chemical parameters, measured at different partitions within the estuary. Thus, L. racemosa can be confirmed as a reliable sentinel plant for biomonitoring of estuaries impacted by anthropic pollution. PMID:24445776

da Souza, Iara; Bonomo, Marina Marques; Morozesk, Mariana; Rocha, Lvia Dorsch; Duarte, Ian Drumond; Furlan, Larissa Maria; Arrivabene, Hiulana Pereira; Monferrn, Magdalena Victoria; Matsumoto, Silvia Tamie; Milanez, Camilla Rozindo Dias; Wunderlin, Daniel Alberto; Fernandes, Marisa Narciso

2014-04-01

376

[Study of the effects of pectin substances under conditions of ontogenesis impairment by a complex of chemical factors].  

PubMed

In the experimental conditions the use of homogenized fruits and vegetables mashed potatoes with the addition of the water-extracted apple-pectin Classic AF-702 as a protector of a toxic action of xenobiotic for the conservation of reproductive ability of the organism and the optimum development of posterity. PMID:10943011

Seliutina, S N; Bebeshko, V V; Kozhin, A A; Afonin, A A

2000-01-01

377

Distribution of small dispersive coal dust particles and absorbed radioactive chemical elements in conditions of forced acoustic resonance in iodine air filter at nuclear power plant  

E-print Network

The physical features of distribution of the small dispersive coal dust particles and the adsorbed radioactive chemical elements and their isotopes in the absorber with the granular filtering medium with the cylindrical coal granules were researched in the case of the intensive air dust aerosol stream flow through the iodine air filter (IAF). It was shown that, at the certain aerodynamic conditions in the IAF, the generation of the acoustic oscillations is possible. It was found that the acoustic oscillations generation results in an appearance of the standing acoustic waves of the air pressure (density) in the IAF. In the case of the intensive blow of the air dust aerosol, it was demonstrated that the standing acoustic waves have some strong influences on both: 1) the dynamics of small dispersive coal dust particles movement and their accumulation in the IAF; 2) the oversaturation of the cylindrical coal granules by the adsorbed radioactive chemical elements and their isotopes in the regions, where the antin...

Ledenyov, Oleg P

2013-01-01

378

Drying kinetics and physico-chemical characteristics of Osmo- dehydrated Mango, Guava and Aonla under different drying conditions.  

PubMed

Mango (Mangiferra indica L), guava (Psiduim guajava L.) slices and aonla (Emblica officinalis L) segments were osmo-dried under four different dying conditions viz., cabinet drier (CD), vacuum oven drier (VOD), low temperature drier (LTD) and solar drier (SD) to evaluate the best drying condition for the fruits. It was found that vacuum oven drying was superior to other mode of drying as it holds maximum nutrients like acidity, ascorbic acid, sugar and water removal and moisture ratio of products. It was found through regression analysis that drying ratio and rehydration ratio was also superior in vacuum drying followed by cabinet drying. In addition, descriptive analysis on sensory score was also found best with vacuum drying while the Non-enzymatic browning (NEB), which is undesirable character on dried product, was more with solar drier. PMID:25114345

Kumar, P Suresh; Sagar, V R

2014-08-01

379

Nematode diversity, food web condition, and chemical and physical properties in different soil habitats of an organic farm  

Microsoft Academic Search

The aim of this paper was to assess biodiversity among different habitats of an organic farm and the relationships between\\u000a some soil properties, nematode taxonomic diversity, and soil food web condition. Eight habitats were studied in the farm:\\u000a ponds, ditches, a riparian corridor, hedgerows, and four agricultural fields (mustard, oats, fallow, and legumes). The undisturbed\\u000a riparian corridor had higher soil

Sara Snchez-Moreno; Sean Smukler; Howard Ferris; Anthony T. OGeen; Louise E. Jackson

2008-01-01

380

Chemical, physical and electrical properties of aged dodecylbenzene 3: thermal ageing of mixed isomers in nitrogen and under sealed conditions  

Microsoft Academic Search

Commercial dodecylbenzene cable fluid was aged at temperatures of 105 and 135degC in dry oxygen-free nitrogen. In addition, selected samples were aged at 135degC under sealed conditions where air was excluded from the headspace above the oil. A variety of analytical techniques, such as ultra-violet visible and infra-red spectroscopy, acid number and water content measurements, were then used to characterize

I. L. Hosier; A. S. Vaughan; S. J. Sutton; J. Cooper; F. J. Davis

2008-01-01

381

MECHANICAL AND CHEMICAL PROPERTIES OF CEMENTITIOUS MATERIALS USING ?-2CaO.SiO2 UNDER THE SEVERAL CONDITIONS IN ACCELERATED CARBONATION CURING  

NASA Astrophysics Data System (ADS)

The experiments have been conducted in order to investigate the mechanical and chemical properties of mortar with three different binders under the several conditions in accelerated carbonation curing. As the results, the depth of carbonation varied among each mix proportion. It is proven that by increasing CO2 density in the mortar having ?-2CaO.SiO2, the CaCO3 production will increase, which leads to the increase of filling ability in the pore of mortar. Furthermore, as a result from the calculation of Tritium permeation, it shows that the permeation decreases with an increase of CO2 density.

Watanabe, Kenzo; Yokozeki, Kosuke; Torichigai, Takeshi; Sakai, Etsuo

382

Influence of the experimental conditions on porosity and structure of adsorbents elaborated from Moroccan oil shale of Timahdit by chemical activation.  

PubMed

This study records experiments undertaken to determine the suitable conditions for the use of the oil shale of Timahdit, as an adsorbent for water treatment. A simple process was proposed based on chemical activation. The preparation has been carried out by carbonization after impregnation of the precursor with phosphoric acid. The effect of different conditions of preparation on the specific surface area is discussed. These parameters are H3PO4/shale weight ratio, carbonization temperature, carbonization time and concentration of H3PO4. The properties and surface structure of the adsorbent were investigated by XPS and FT-IR. Their total surface acidity and basicity were also determined. The retention process of methylene blue (MB) by adsorbents has been studied. It was found that MHP2 and MHP7 have relatively high retention ability as compared to activated carbons. PMID:15721527

Ichcho, S; Khouya, E; Fakhi, S; Ezzine, M; Hannache, H; Pallier, R; Naslain, R

2005-02-14

383

Exploring chemical variables in Ligustrum lucidum Ait. F. tricolor (rehd.) Rehd. in relation to air pollutants and environmental conditions  

SciTech Connect

A diagnostic study was done on Ligustrum lucidum Ait. f. tricolor (Rehd.) Rehd. in relation to atmospheric pollutants in Cordoba city, Argentina. The study area receives regional Pollutants and was categorized taking into account traffic level, industrial density, type of industry, location of the sample point in relation to the street corner, treeless condition, and topographic level. Dried weight/fresh weight ratio (DW/FW) and specific leaf area (SLA) were calculated, and concentrations of chlorophylls, carotenoids, total sulfur, soluble proteins, malondialdehyde (MDA), and hydroperoxy conjugated dienes (HPCD) were determined in leaf samples. Sulfur content correlates positively with traffic density and SLA correlates negatively with some combinations of the categorical variables; MDA correlates positively with topographic level and total protein concentration correlates negatively with treeless condition. On the basis of our results, traffic, location of trees, type of industry, situation of a tree with respect to others, and topographic level are the environmental variables to bear in mind when selecting analogous sampling points in a passive monitoring program. An approximation to predict tree injury may be obtained by measuring DW/FW ratio, proteins, pigments, HPCD, and MDA as they are responsible for the major variability of data.

Pignata, M.L.; Canas, M.S.; Carreras, H.A. [Universidad Nacional de Cordoba (Argentina)] [Universidad Nacional de Cordoba (Argentina); Orellana, L. [Universidad de Buenos Aires (Argentina)] [Universidad de Buenos Aires (Argentina)

1997-09-01

384

Aluminoborosilicate Waste Glass Dissolution under Alkaline Conditions at 40C: Implications for a Chemical Affinity-Based Rate Equation  

SciTech Connect

Single-pass flow-through (SPFT) experiments were conducted with aluminoborosilicate waste glasses to evaluate how changes in solution composition affect the dissolution rate (r) at 40C and pH(23C) = 9.0. The three prototypic low-activity waste (LAW) glasses; LAWE-1A, -95A, and -290A, used in these experiments span a wide range covering the expected processing composition of candidate immobilized low-activity waste (ILAW) glasses. Results suggest incongruent release of Al, B, Na, and Si at low flow-rate (q) to sample surface area (S) [log10 (q/S) < -8.9 (m s-1)] whereas congruent release was observed at high q/S [log10 (q/S) > -7.9 (m s-1)]. Dissolution rates increase from log10 (q/S) ? -9.3 to -8.0 (m s-1) and then become constant at log10 (q/S) > -7.9 (m s-1). Forward (maximum) dissolution rates, based on B release, are the same irrespective of glass composition, evident by the dissolution rates being within the experimental error of one another (r1A = 0.0301 0.0153 g m-2 d-1, r95A = 0.0248 0.0125 g m-2 d-1, and r290A = 0.0389 0.0197 g m-2 d-1). Finally these results support the use of a chemical affinity based rate law to describe glass dissolution as a function of solution composition.

Pierce, Eric M.; Richards, Emily L.; Davis, Aaron M.; Reed, Lunde R.; Cordova, Elsa A.

2008-02-25

385

Monolayer culturing and cloning of human pluripotent stem cells on laminin-521-based matrices under xeno-free and chemically defined conditions.  

PubMed

A robust method for culturing human pluripotent stem (hPS) cells under chemically defined and xeno-free conditions is an important tool for stem cell research and for the development of regenerative medicine. Here, we describe a protocol for monolayer culturing of Oct-4-positive hPS cells on a specific laminin-521 (LN-521) isoform, under xeno-free and chemically defined conditions. The cells are dispersed into single-cell suspension and then plated on LN-521 isoform at densities higher than 5,000 cells per cm, where they attach, migrate and survive by forming small monolayer cell groups. The cells avidly divide and expand horizontally until the entire dish is covered by a confluent monolayer. LN-521, in combination with E-cadherin, allows cloning of individual hPS cells in separate wells of 96-well plates without the presence of rho-associated protein kinase (ROCK) inhibitors or any other inhibitors of anoikis. Characterization of cells maintained for several months in culture reveals pluripotency with a minimal degree of genetic abnormalities. PMID:25211513

Rodin, Sergey; Antonsson, Liselotte; Hovatta, Outi; Tryggvason, Karl

2014-10-01

386

Aqueous SOA formation from radical oligomerization of methyl vinyl ketone (MVK) and methacrolein (MACR)  

NASA Astrophysics Data System (ADS)

It is now accepted that one of the important pathways of secondary organic aerosol (SOA) formation occurs through aqueous phase chemistry in the atmosphere. However, the chemical mechanisms leading to macromolecules are still not well understood. It was recently shown that oligomer production by OH radical oxidation in the aerosol aqueous phase from ?-dicarbonyl precursors, such as methylglyoxal and glyoxal, is irreversible and fast. We have investigated the aqueous phase photooxidation of MACR and MVK, which are biogenic organic compounds derived from isoprene. Aqueous phase photooxidation of MVK and MACR was investigated in a photoreactor using photolysis of H2O2 as OH radical source. Electrospray high resolution mass spectrometry analysis of the solutions brought clear evidence for the formation of oligomer systems having a mass range of up to 1800 Da within less than 15 minutes of reaction. Highest oligomer formation rates were obtained under conditions of low dissolved oxygen, highest temperature (T = 298 K) and highest precursor initial concentrations ([MVK]0 = 20 mM). A radical mechanism of oligomerization is proposed to explain the formation of the high molecular weight products. Furthermore, we quantified the total amount of carbon present in oligomers. Kinetic parameters of the proposed oligomerization mechanism are constrained by means of a box model that is able to reproduce the temporal evolution of intermediates and products as observed in the laboratory experiments. Additional model simulations for atmospherically-relevant conditions will be presented that show the extent to which these radical processes contribute to SOA formation in the atmospheric multiphase system as compared to other aqueous phase as well as traditional SOA sources. MVK time profile (as measured by UV Spectroscopy) and mass spectra (obtained using UPLC-ESI-MS for the retention time range 0-5 min in the positive mode) at 5, 10 and 50 min of reaction (MVK 20 mM, 25 C, under supersaturated O2 initial conditions).

Renard, P.; Siekmann, F.; Ravier, S.; Temime-Roussel, B.; Clment, J.; Ervens, B.; Monod, A.

2013-12-01

387

Distribution of small dispersive coal dust particles and absorbed radioactive chemical elements in conditions of forced acoustic resonance in iodine air filter at nuclear power plant  

E-print Network

The physical features of distribution of the small dispersive coal dust particles and the adsorbed radioactive chemical elements and their isotopes in the absorber with the granular filtering medium with the cylindrical coal granules were researched in the case of the intensive air dust aerosol stream flow through the iodine air filter (IAF). It was shown that, at the certain aerodynamic conditions in the IAF, the generation of the acoustic oscillations is possible. It was found that the acoustic oscillations generation results in an appearance of the standing acoustic waves of the air pressure (density) in the IAF. In the case of the intensive blow of the air dust aerosol, it was demonstrated that the standing acoustic waves have some strong influences on both: 1) the dynamics of small dispersive coal dust particles movement and their accumulation in the IAF; 2) the oversaturation of the cylindrical coal granules by the adsorbed radioactive chemical elements and their isotopes in the regions, where the antinodes of the acoustic waves are positioned. Finally, we completed the comparative analysis of the theoretical calculations with the experimental results, obtained for the cases of: 1) the experimental aerodynamic modeling of physical processes of the absorbed radioactive chemical elements and their isotopes distribution in the IAF; and 2) the gamma-activation spectroscopy analysis of the absorbed radioactive chemical elements and their isotopes distribution in the IAF. We made the innovative propositions on the necessary technical modifications with the purpose to improve the IAF technical characteristics and increase its operational time at the nuclear power plant (NPP), going from the completed precise characterization of the IAF parameters at the long term operation.

Oleg P. Ledenyov; Ivan M. Neklyudov

2013-06-14

388

Changes in fluid geochemistry and physico-chemical conditions of geothermal systems caused by magmatic input: The recent abrupt outgassing off the island of Panarea (Aeolian Islands, Italy)  

NASA Astrophysics Data System (ADS)

Hydrothermal systems and related vents can exhibit dramatic changes in their physico-chemical conditions over time as a response to varying activity in the feeding magmatic systems. Massive steam condensation and gas scrubbing processes of thermal fluids during their ascent and cooling cause further compositional changes that mask information regarding the conditions evolving at depth in the hydrothermal system. Here we propose a new stability diagram based on the CO 2-CH 4-CO-H 2 concentrations in vapor, which aims at calculating the temperatures and pressures in hydrothermal reservoirs. To filter gas scrubbing effects, we have also developed a model for selective dissolution of CO 2-H 2S-N 2-CH 4-He-Ne mixtures in fresh and/or air-saturated seawater. This methodology has been applied to the recent (November 2002) crisis that affected the geothermal field off the island of Panarea (Italy), where the fluid composition and fluxes have been monitored for the past two decades. The chemical and isotopic compositions of the gases suggest that the volatile elements originate from an active magma, which feeds a boiling saline solution having temperatures of up to 350C and containing ?12 mol% CO 2 in vapor. The thermal fluids undergo cooling and re-equilibration processes on account of gas-water-rock interactions during their ascent along fracture networks. Furthermore, steam condensation and removal of acidic species, partial dissolution in cold air-saturated seawater and stripping of atmospheric components, affect the composition of the geothermal gases at shallow levels. The observed geochemical variations are consistent with a new input of magmatic fluids that perturbed the geothermal system and caused the unrest event. The present-state evolution shows that this dramatic input of fluids is probably over, and that the system is now tending towards steady-state conditions on a time scale of months.

Caracausi, A.; Ditta, M.; Italiano, F.; Longo, M.; Nuccio, P. M.; Paonita, A.; Rizzo, A.

2005-06-01

389

Comparison of the Sensitivities of Noroviruses and Feline Calicivirus to Chemical Disinfection under Field-Like Conditions?  

PubMed Central

Noroviruses (NV), in the family Caliciviridae, are an important cause of gastroenteritis in humans worldwide. Measures for prevention and control of NV dissemination are therefore necessary to ensure public safety. The abilities of an organic acid (Venno Vet 1 Super), an aldehyde (Venno FF Super), a halogen compound (sodium hypochlorite solution), and a peroxide (Oxystrong FG) to inactivate feline calicivirus (FCV), a cultivable virus surrogate for NV, were studied. Molecular protocols were then used for the comparative evaluation of disinfectant efficacies against NV and FCV, which were tested by reproducing NV field conditions, using human fecal material as a protein load. Generally, disinfectant efficacy was strongly reduced by the organic impurities (feces) used during tests. All disinfectants, except the aldehyde, were effective on FCV, as measured by cell culture and reverse transcription-PCR (RT-PCR), with inactivation levels of ?99.9%. The glutaraldehyde-based compound failed to adequately inactivate FCV according to RT-PCR results, although the infectivity in cell culture was completely abolished. Similar inactivation levels were achieved with NV, but generally NV appeared more resistant than FCV, and consequently, the suitability of FCV as a model for NV should be considered with caution. In conclusion, according to RT-PCR results, 5% Venno Vet 1 Super, 1% Oxystrong FG, and not less than 2% Venno FF Super, with a contact time of 1 h, and 1% sodium hypochlorite, with 6,000 ppm of free chlorine and a contact time of 15 min, are required for safe disinfection when a calicivirus-related outbreak is suspected. PMID:17616619

Poschetto, Lorenza Ferrero; Ike, Anthony; Papp, Tibor; Mohn, Ulrich; Bhm, Reinhard; Marschang, Rachel E.

2007-01-01

390

Processes controlling aqueous concentrations for riverine spills.  

PubMed

The aqueous concentrations of sparingly soluble compounds resulting from oil, fuel, or chemical spills onto rivers predicted by numerical spill models contain an inherent degree of uncertainty due to the inaccuracies, or bias, of the user supplied rate coefficients. Methods for estimating the values of spreading, evaporation, dissolution, volatilization, and longitudinal dispersion coefficients for a small sheltered river are reviewed, and the uncertainties associated with each coefficient are estimated. The uncertainties in the predicted aqueous concentrations are then computed using a concurrently developed riverine spill model for a simulated spill of 10,000 kg of jet fuel. The resulting aqueous concentrations were found to be most sensitive to the saturation concentrations and the dissolution rates, moderately sensitive to the evaporation rates and longitudinal dispersion coefficient, and nearly completely insensitive to the volatilization coefficient. PMID:10337393

Hibbs, D E; Gulliver, J S

1999-01-01

391

Pretreatment of rice straw with combined process using dilute sulfuric acid and aqueous ammonia  

PubMed Central

Background Use of lignocellulosic biomass has received attention lately because it can be converted into various versatile chemical compounds by biological processes. In this study, a two-step pretreatment with dilute sulfuric acid and aqueous ammonia was performed efficiently on rice straw to obtain fermentable sugar. The soaking in aqueous ammonia process was also optimized by a statistical method. Results Response surface methodology was employed. The determination coefficient (R2) value was found to be 0.9607 and the coefficient of variance was 6.77. The optimal pretreatment conditions were a temperature of 42.75C, an aqueous ammonia concentration of 20.93%, and a reaction time of 48h. The optimal enzyme concentration for saccharification was 30 filter paper units. The crystallinity index was approximately 60.23% and the Fourier transform infrared results showed the distinct peaks of glucan. Ethanol production using Saccharomyces cerevisiae K35 was performed to verify whether the glucose saccharified from rice straw was fermentable. Conclusions The combined pretreatment using dilute sulfuric acid and aqueous ammonia on rice straw efficiently yielded fermentable sugar and achieved almost the same crystallinity index as that of ?-cellulose. PMID:23898802

2013-01-01

392

Reflectance of aqueous solutions  

NASA Technical Reports Server (NTRS)

The optical properties and optical constants of water and aqueous solutions were studied to develop an accurate tabulation of graphical representations of the optical constants through a broad spectrum. Manuscripts of articles are presented concerning extinction coefficients, relative specular reflectance, and temperature effect on the water spectrum. Graphs of absolute reflectance, phase shifts, index of refraction, and extinction coefficients for water, heavy water and aqueous solutions are included.

Querry, M. R.

1972-01-01

393

Comparison of alkaline industrial wastes for aqueous mineral carbon sequestration through a parallel reactivity study.  

PubMed

Thirty-one alkaline industrial wastes from a wide range of industrial processes were acquired and screened for application in an aqueous carbon sequestration process. The wastes were evaluated for their potential to leach polyvalent cations and base species. Following mixing with a simple sodium bicarbonate solution, chemistries of the aqueous and solid phases were analyzed. Experimental results indicated that the most reactive materials were capable of sequestering between 77% and 93% of the available carbon under experimental conditions in four hours. These materials - cement kiln dust, spray dryer absorber ash, and circulating dry scrubber ash - are thus good candidates for detailed, process-oriented studies. Chemical equilibrium modeling indicated that amorphous calcium carbonate is likely responsible for the observed sequestration. High variability and low reactive fractions render many other materials less attractive for further pursuit without considering preprocessing or activation techniques. PMID:24735991

Noack, Clinton W; Dzombak, David A; Nakles, David V; Hawthorne, Steven B; Heebink, Loreal V; Dando, Neal; Gershenzon, Michael; Ghosh, Rajat S

2014-10-01

394

Aqueous Alteration on Mars. Chapter 23  

NASA Technical Reports Server (NTRS)

Aqueous alteration is the change in composition of a rock, produced in response to interactions with H2O-bearing ices, liquids, and vapors by chemical weathering. A variety of mineralogical and geochemical indicators for aqueous alteration on Mars have been identified by a combination of surface and orbital robotic missions, telescopic observations, characterization of Martian meteorites, and laboratory and terrestrial analog studies. Mineralogical indicators for aqueous alteration include goethite (lander), jarosite (lander), kieserite (orbiter), gypsum (orbiter) and other Fe-, Mg-, and Ca-sulfates (landers), halides (meteorites, lander), phyllosilicates (orbiter, meteorites), hematite and nanophase iron oxides (telescopic, orbiter, lander), and Fe-, Mg-, and Ca-carbonates (meteorites). Geochemical indicators (landers only) for aqueous alteration include Mg-, Ca-, and Fe-sulfates, halides, and secondary aluminosilicates such as smectite. Based upon these indicators, several styles of aqueous alteration have been suggested on Mars. Acid-sulfate weathering (e.g., formation of jarosite, gypsum, hematite, and goethite), may occur during (1) the oxidative weathering of ultramafic igneous rocks containing sulfides, (2) sulfuric acid weathering of basaltic materials, and (3) acid fog (i.e., vapors rich in H2SO4) weathering of basaltic or basaltic-derived materials. Near-neutral or alkaline alteration occurs when solutions with pH near or above 7 move through basaltic materials and form phases such as phyllosilicates and carbonates. Very low water:rock ratios appear to have been prominent at most of the sites visited by landed missions because there is very little alteration (leaching) of the original basaltic composition (i.e., the alteration is isochemical or in a closed hydrologic system). Most of the aqueous alteration appears to have occurred early in the history of the planet (3 to 4.5 billion years ago); however, minor aqueous alteration may be occurring at the surface even today (e.g., in thin films of water or by acid fog).

Ming, Douglas W.; Morris, Richard V.; Clark, Benton C.

2007-01-01

395

Estimating pesticide sampling rates by the polar organic chemical integrative sampler (POCIS) in the presence of natural organic matter and varying hydrodynamic conditions  

USGS Publications Warehouse

The polar organic chemical integrative sampler (POCIS) was calibrated to monitor pesticides in water under controlled laboratory conditions. The effect of natural organic matter (NOM) on the sampling rates (Rs) was evaluated in microcosms containing -1 of total organic carbon (TOC). The effect of hydrodynamics was studied by comparing Rs values measured in stirred (SBE) and quiescent (QBE) batch experiments and a flow-through system (FTS). The level of NOM in the water used in these experiments had no effect on the magnitude of the pesticide sampling rates (p > 0.05). However, flow velocity and turbulence significantly increased the sampling rates of the pesticides in the FTS and SBE compared to the QBE (p < 0.001). The calibration data generated can be used to derive pesticide concentrations in water from POCIS deployed in stagnant and turbulent environmental systems without correction for NOM.

Charlestra, Lucner; Amirbahman, Aria; Courtemanch, David L.; Alvarez, David A.; Patterson, Howard

2012-01-01

396

Removal of Pb(II) ions from aqueous solution by using modified butea monosperma leaf  

NASA Astrophysics Data System (ADS)

In the present study, Butea monosperma leaf., a natural waste, was used for the preparation of an adsorbent by chemical activation using NaOH under optimized conditions. The optimum pH range for the maximum removal of lead ion is 2-9. Maximum uptake of the metal ions obtained at adsorbent dose of 10 mg 1-. Adsorption of Pb(II) ions as a function of temperature indicate that the adsorption was a spontaneous and an endothermic in nature. It is concluded that Butea monosperma leaf. can be used as an effective adsorbent for removing Pb(II) ions from aqueous solutions.

Sharma, Ashish; Joshi, Kushal; Mitra, Santosh; Soni, Gireesh; Gupta, Nitish

2012-06-01

397

Quantitative analysis of aqueous species using Raman spectrometry and equilibrium model calculations  

SciTech Connect

An analytical approach of quantifying various chemical species, using Raman spectrometry in conjunction with equilibrium modeling, has been tested on aqueous solutions containing Nd, Cu, and dipicolinic acid. Equilibrium modelling was used to select optimum conditions in simple solutions for the determination of concentration - Raman intensity relationships. These relationships were then used to interpret spectra from more complex solutions and to make comparisons with equilibrium modelling results from the same systems. Peak heights were determined through curve fitting of the spectra using nonlinear regression and were normalized using ClO/sub 4//sup -/ as an internal standard. 18 references, 2 figures, 4 tables.

Sorensen, J.A.; Thompson, L.C.; Glass, G.E.

1985-05-01

398

Sensory Profiles of Sweeteners in Aqueous Solutions  

Microsoft Academic Search

EDIV A., PANOVSK Z., POKORN J. (2006): Sensory profiles of sweeteners in aqueous solutions. Czech J. Food Sci., 24: 283-287. Sensory profiles of saccharin, acesulfame K, aspartame, and neotame were compared with that of sucrose in three different types of water (tap water, commerical Crystalis water, and distilled water) under the conditions of the respec- tive ISO standards.

JAN POKORN

399

Effect of process conditions and chemical composition on the microstructure and properties of chemically vapor deposited SiC, Si, ZnSe, ZnS and ZnS(x)Se(1-x)  

NASA Technical Reports Server (NTRS)

Subatmospheric pressure CVD processes have been developed to produce theoretically dense, highly pure, void-free and large area bulk materials, SiC, Si, ZnSe, ZnS and ZnS(x)Se(1-x). These materials are used for optical elements, such as mirrors, lenses and windows, over a wide spectral range from the VUV to the IR. We discuss the effect of CVD process conditions on the microstructure and properties of these materials, with emphasis on optical performance. In addition, we discuss the effect of chemical composition on the properties of the composite material ZnS(x)Se(1-x). We first present a general overview of the bulk CVD process and the relationship between process conditions, such as temperature, pressure, reactant gas concentration and growth rate, and the microstructure, morphology and properties of CVD-grown materials. Then we discuss specific results for CVD-grown SiC, Si, ZnSe, ZnS and ZnS(x)Se(1-x).

Pickering, Michael A.; Taylor, Raymond L.; Goela, Jitendra S.; Desai, Hemant D.

1992-01-01

400

Continuous environmental monitoring for aqueous effluents  

SciTech Connect

An aquatic environmental monitor has been developed that will continuously monitor aqueous waste streams from coal processing plants. The monitor contains three different instruments: a continuous chemical oxygen demand monitor and two continuous-flow fluorometers with different excitation-emission characteristics. A prototype instrument was fabricated and evaluated for several different applications. The details of the instrument design and results of its evaluation are presented in this report.

Pitt, Jr., W. W.; Jones, G. Jr.

1980-05-01

401

The research of Iodine pool pressure of chemical oxygen-iodine laser in non-equilibrium condition and its automatic control system design  

NASA Astrophysics Data System (ADS)

In the working process of chemical oxy-iodigenne laser(COIL), the change of iodine pool pressure is complicated. As a result, it causes some mis-judgements, such as the damage of heater and the leakage of iodine steam. Further more, when the heater electric circuit is in a single working status, and after the heater switch is on or off, there exists a buffer time for the stabilization of iodine pool pressure, which is a relatively long time, and the minimum buffer pressure exceeds to 19 torr . Of course, it increases the preparing time for steady operation of laser, and reduces the quality of laser beam. In this paper, we study the iodine pool pressure of COIL in non-equilibrium condition, and analyze the mutation and the serious buffer phenomenon of iodine steam pressure. At the same time, we design an automatic control system for iodine pool pressure, which consists of five modules, such as data collection, automatic control, manual control, heater electric circuit, and the setting and display of pressure. This system uses two kinds of heater electric circuits, in this way, the serious buffer phenomenon of iodine pool pressure is effectively avoided. As a result, the maximal buffer pressure reduces to 4 torr, this makes sure that the iodine steam pressure is suitable for the operation of COIL, which produces a good condition for the steady operation of laser system and an excellent laser output.

Zhou, Songqing; Qu, Pubo; Ren, Weiyan

2013-05-01

402

Surface chemical modification on hyper-cross-linked resin by hydrophilic carbonyl and hydroxyl groups to be employed as a polymeric adsorbent for adsorption of p-aminobenzoic acid from aqueous solution  

Microsoft Academic Search

In this study, a novel hyper-cross-linked HJ-Y10 resin was synthesized and its adsorption behaviors for p-aminobenzoic acid were investigated from aqueous solution. The results indicated that the skeleton surface of HJ-Y10 resin was modified by formaldehyde carbonyl, quinone carbonyl and phenolic hydroxyl groups, the unadjusted p-aminobenzoic acid solution was favorable for the adsorption, the isotherms could be fitted by Langmuir

Xiaomei Wang; Jianhan Huang; Kelong Huang

2010-01-01

403

The kinetics and mechanism of an aqueous phase isoprene reaction with hydroxyl radical  

NASA Astrophysics Data System (ADS)

Aqueous phase chemical processes of organic compounds in the atmosphere have recei