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1

Theoretical characterization of formamide on the inner surface of montmorillonite  

NASA Astrophysics Data System (ADS)

Density functional theory calculations were performed to characterize the low-lying structures of formamide (FA) and protonated formamide (FAH) in the interlayer space of montmorillonite (MMT). The interactions among FA/FAH, H2O, Na+, and the inner surface of MMT were systematically analyzed. The carbonyl-O of FA/FAH has strong coulomb interaction with Na+, while its amide-H forms hydrogen bonds (HBs) with water and MMT surface. The adsorption of FA is promoted by H2O, which exhibits a cooperative adsorption effect by enhancing the FA-Na+ coulomb interaction and by forming HBs with FA. Our study reveals the structural basis of FA/FAH as an intercalator for MMT splitting.

Shi, Jing; Lou, Zhaoyang; Yang, Mingli; Zhang, Yao; Liu, Houbin; Meng, Yingfeng

2014-06-01

2

Laser surface heat treating  

SciTech Connect

Laser surface heat treating is a proven process that increases strength, hardness, and fatigue life, and reduces wear. The process can be accurately controlled and heat can be precisely positioned. As a result, hardness and strength may be increased in specified areas with very little part distortion. This process has been proven in automotive and aircraft applications, as well as the pulp and paper industries. Treated parts include, but are not limited to gears, shuttles, punches, valves, valve guides, and locomotive cylinders. This article describes the process and presents fundamental criteria that help determine if a component is a viable candidate for laser surface heat treating.

Wollenweber, J. [Laser Applications Inc., Westminster, MD (United States)

1996-12-01

3

Surface area of montmorillonite from the dynamic sorption of nitrogen and carbon dioxide  

USGS Publications Warehouse

Surface area determinations were made on a montmorillonite with various cations emplaced on the exchangeable sites, utilizing nitrogen and carbon dioxide as adsorbates at 77 ??K and 195 ??K, respectively, in a dynamic system. From the fraction of a Mississippi montmorillonite less than about 1 ?? in size, samples were prepared by replacing the original exchangeable cations with Li+, Na+, K+, Rb+, Cs+, Mg++, Ca++, Ba++, and NH4+, forming a series of homoionic montmorillonite species. Surface areas from 3-point B.E.T. plots (half-hour adsorption points), with nitrogen as the adsorbate, ranged from 61 m2/g for Li-montmorillonite to 138 m2/g for Cs-montmorillonite, thus reflecting a certain degree of nitrogen penetration between layers. Complete penetration should theoretically result in a surface area of over 300 m2/g for this clay with a nitrogen monolayer between each pair of platelets. The experimental data indicate that the extent of penetration is time-dependent and is also a function of the interlayer forces as governed by the size and charge of the replaceable cation. This finding negates the generally accepted concept that nitrogen at 77 ??K does not penetrate the layers and provides a measure only of the external surface of expandable clay minerals. A further measure of the variation of interlayer forces is provided by the adsorption of carbon dioxide at 195 ??K. Surface area values ranged from 99 m2/g for Li-montmorillonite to 315 m2/g for Csmontmorillonite. Although the carbon dioxide molecule is larger than the nitrogen molecule, its greater penetration apparently is a result of its being kinetically more energetic (with a larger diffusion coefficient) at its higher adsorption temperature. Similar differences have been found with both adsorbates in the study of microporous substances, such as coal, where activated diffusion is of considerable significance. ?? 1968.

Thomas, J., Jr.; Bohor, B.F.

1968-01-01

4

Influence of the intercalated cations on the surface energy of montmorillonites: consequences for the morphology and gas barrier properties of polyethylene/montmorillonites nanocomposites.  

PubMed

Organically modified montmorillonites obtained by cation exchange from the same natural layered silicate were studied. The surface properties of the pristine and a series of organically modified clays were determined by inverse gas chromatography and the water adsorption mechanisms were studied by a gravimetric technique coupled with a microcalorimeter. A significant increase of the specific surface area, a decrease of the water adsorption, and a decrease of the dispersive component of the surface energy were observed when the sodium cations of the natural montmorillonite were exchanged for a quaternary ammonium. Slighter differences in surface properties were observed, on the other hand, between the different types of organically modified montmorillonites. Indeed, similar dispersive components of the surface energy were determined on the organoclays. Nevertheless, the specific surface area increased in the range 48-80 m(2)/g with increasing d-spacing values and the presence of specific groups attached to the quaternary ammonium, such as phenyl rings or hydroxyl groups, led to some specific behaviors, i.e., a more pronounced base character and a higher water adsorption at high activity, respectively. Differences in interlayer cation chain organization, denoted as crystallinity, were also observed as a function of the nature of the chains borne by the quaternary ammonium. In a later step, polyethylene-based nanocomposites were prepared with those organically modified montmorillonites. The clay dispersion and the barrier properties of the nanocomposites were discussed as a function of the montmorillonite characteristics and of the matrix/montmorillonite interactions expected from surface energy characterization. PMID:17222420

Picard, E; Gauthier, H; Gérard, J-F; Espuche, E

2007-03-15

5

Reflectance Spectroscopy of Palagonite and Iron-Rich Montmorillonite Clay Mixtures: Implications for the Surface Composition of Mars  

NASA Technical Reports Server (NTRS)

Mixtures of a Hawaiian palagonite and an iron-rich, montmorillonite clay (15.8 +/- 0.4 wt% Fe as Fe2O3) were evaluated as Mars surface spectral analogs from their diffuse reflectance spectra. The presence of the 2.2 microns absorption band in the reflectance spectrum of clays and its absence in the Mars spectrum have been interpreted as indicating that highly crystalline aluminous hydroxylated clays cannot be a major mineral component of the soil on Mars. The palagonite sample used in this study does not show this absorption feature in its spectrum. In mixtures of palagonite and iron-rich montmorillonite, the 2.2 microns Al-OH clay lattice band is not seen below 15 wt% montmorillonite. This suggests the possibility that iron-rich montmorillonite clay may be present in the soil of Mars at up to 15 wt% in combination with palagonite, and remain undetected in remotely sensed spectra of Mars.

Orenberg, James; Handy, Jonathan

1992-01-01

6

Surface characteristics of thermally treated titanium surfaces  

PubMed Central

Purpose The characteristics of oxidized titanium (Ti) surfaces varied according to treatment conditions such as duration time and temperature. Thermal oxidation can change Ti surface characteristics, which affect many cellular responses such as cell adhesion, proliferation, and differentiation. Thus, this study was conducted to evaluate the surface characteristics and cell response of thermally treated Ti surfaces. Methods The samples were divided into 4 groups. Control: machined smooth titanium (Ti-S) was untreated. Group I: Ti-S was treated in a furnace at 300? for 30 minutes. Group II: Ti-S was treated at 500? for 30 minutes. Group III: Ti-S was treated at 750? for 30 minutes. A scanning electron microscope, atomic force microscope, and X-ray diffraction were used to assess surface characteristics and chemical composition. The water contact angle and surface energy were measured to assess physical properties. Results The titanium dioxide (TiO2) thickness increased as the treatment temperature increased. Additional peaks belonging to rutile TiO2 were only found in group III. The contact angle in group III was significantly lower than any of the other groups. The surface energy significantly increased as the treatment temperature increased, especially in group III. In the 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, after 24 hours of incubation, the assessment of cell viability showed that the optical density of the control had a higher tendency than any other group, but there was no significant difference. However, the alkaline phosphatase activity increased as the temperature increased, especially in group III. Conclusions Consequently, the surface characteristics and biocompatibility increased as the temperature increased. This indicates that surface modification by thermal treatment could be another useful method for medical and dental implants. PMID:22803009

Lee, Yang-Jin; Cui, De-Zhe; Jeon, Ha-Ra; Chung, Hyun-Ju; Park, Yeong-Joon; Kim, Ok-Su

2012-01-01

7

Mobility of Na and Cs on montmorillonite surface under partially saturated conditions.  

PubMed

Cs migration in soils at contaminated sites or in clay-rich backfill of waste disposal sites can take place under partially saturated conditions. To understand the molecular mechanism of Cs migration in partially saturated clays, Grand Canonical Monte Carlo simulations were applied to model adsorption of water films onto external surfaces of Cs and Na montmorillonites as function of partial water pressure. The surface complexation and diffusivity of Cs and Na at different partial water pressure was obtained by molecular dynamics simulations. The results suggest that ion mobility in adsorbed water films on external basal surfaces of clay is similar to that in the near-surface water of a saturated pore as far as the thickness of the adsorbed water film is more than two water layers. At lower partial water pressure (i.e., in thinner water films) the ion mobility dramatically decreases. In contrast, the average water mobility in thin water film is higher than in the water-saturated system due to enhanced mobility of water molecules close to vapor-film interface. The results of the simulations were applied to interpret recent laboratory measurements of tritiated water and Cs diffusivity in Callovo-Oxfordian Claystones under partially saturated conditions. PMID:23909661

Churakov, Sergey V

2013-09-01

8

Sonogashira couplings on the surface of montmorillonite-supported Pd/Cu nanoalloys.  

PubMed

To explore the true identity of palladium-catalyzed Sonogashira coupling reaction, montmorillonite (MMT)-supported transition metal nanoparticles (MMT@M, M=Pd, Cu, Fe, and Ni) were prepared, characterized, and evaluated systematically. Among all MMT@M catalysts, MMT@Pd/Cu showed the highest activity, and it was successfully extended to 20 examples with 57%-97% yields. The morphology characterization of MMT@Pd/Cu revealed that the crystalline bimetallic particles were dispersed on a MMT layer as nanoalloy with diameters ranged from 10 to 11 nm. In situ IR analysis using CO as molecular probe and XPS characterization found that the surface of Pd/Cu particles consisted of both catalytic active sites of Pd(0) and Cu(I). The experiments on the catalytic activities of MMT@M found that Pd/Cu catalyst system exhibited high activity only in nanoalloy form. Therefore, the Pd/Cu nanoalloy was identified as catalyst, on which the interatom Pd/Cu transmetalation between surfaces was proposed to be responsible for its synergistic activity. PMID:25315209

Xu, Wei; Sun, Huaming; Yu, Bo; Zhang, Guofang; Zhang, Weiqiang; Gao, Ziwei

2014-11-26

9

Selective removal and inactivation of bacteria by nanoparticle composites prepared by surface modification of montmorillonite with quaternary ammonium compounds.  

PubMed

The purpose of the present study was to prepare new nanocomposites with antibacterial activities by surface modification of montmorillonite using quaternary ammonium compounds that are widely applied as disinfectants and antiseptics in food-processing environments. The intercalation of four quaternary ammonium compounds namely benzalkonium chloride, cetylpyridinium chloride monohydrate, hexadecyltrimethylammonium bromide, tetraethylammonium chloride hydrate into montmorillonite layers was confirmed by X-ray diffraction. The antibacterial influences of the modified clay variants against important foodborne pathogens differed based on modifiers quantities, microbial cell densities, and length of contact. Elution experiments through 0.1 g of the studied montmorillonite variants indicated that Staphylococcus aureus, Pseudomonas aeroginosa, and Listeria monocytogenes were the most sensitive strains. 1 g of hexadecyltrimethylammonium bromide intercalated montmorillonites demonstrated maximum inactivation of L. monocytogenes populations, with 4.5 log c.f.u./ml units of reduction. In adsorption experiments, 0.1 g of tetraethylammonium chloride hydrate montmorillonite variants significantly reduced the growth of Escherichia coli O157:H7, L. monocytogenes, and S. aureus populations by 5.77, 6.33, and 7.38 log units respectively. Growth of wide variety of microorganisms was strongly inhibited to undetectable levels (montmorillonite variants. This investigation highlights that reduction in counts of microbial populations adsorbed to the new nanocomposites was substantially different from that in elution experiments, where interactions of nanocomposites with bacteria were specific and more complex than simple ability to inactivate. Treatment columns packed with modified variants maintained their inactivation capacity to the growth of Salmonella Tennessee and S. aureus populations after 48 h of incubation at room temperature with maximum reductions of 6.3 and 5.0 log units respectively. New nanocomposites presented in this research may have potential applications in industrial scale for the control of foodborne pathogens by their incorporation into high-performance filters in food processing plant environments where selectivity in removal and/or inactivation of species in fluid flow streams is desirable. Nevertheless, extensive in vitro and in vivo studies of these new nanocomposites is essential to outpace the understanding of their potential impacts and consequences on human health and the environment if they will make an appearance in commercialized food packaging and containment food materials in the future. PMID:23709187

Khalil, Rowaida K S

2013-10-01

10

VERUCLAY – a new type of photo-adsorbent active in the visible light range: modification of montmorillonite surface with organic surfactant  

EPA Science Inventory

Montmorillonite K10 was treated with VeruSOL-3, a biodegradable and food-grade surfactant mixture of coconut oil, castor oil and citrus extracts, to manufacture a benign catalytic adsorbent that is active in the visible light. Veruclay was characterized by SEM, XRD, TGA, UVDRS, a...

11

Effect of surface modification of montmorillonite on the properties of rigid polyurethane foam composites  

Microsoft Academic Search

This study investigated the influence of various organically modified montmorillonites (organoclays) on the structure and\\u000a properties of rigid polyurethane foam (RPUF) nanocomposites. The organoclays were modified with cetyltrimethyl ammonium bromide\\u000a (CTAB), methyl tallow bis(2-hydroxyethyl) quaternary ammonium chloride (MT2ETOH) and tris(hydroxymethyl)aminomethane (THMA)\\u000a and denoted as CMMT, Cloisite 30B and OMMT, respectively. MT2ETOH and THMA contain hydroxyl groups, while THMA does not

Zhong-bin Xu; Wei-wei Kong; Ming-xing Zhou; Mao Peng

2010-01-01

12

Effect of interlayer cations of montmorillonite on the biodegradation and adsorption of crude oil polycyclic aromatic compounds.  

PubMed

Cation exchange capacity, surface acidity and specific surface area are surface properties of clay minerals that make them act as catalysts or supports in most biogeochemical processes hence making them play important roles in environmental control. However, the role of homoionic clay minerals during the biodegradation of polycyclic aromatic compounds is not well reported. In this study, the effect of interlayer cations of montmorillonites in the removal of some crude oil polycyclic aromatic compounds during biodegradation was investigated in aqueous clay/oil microcosm experiments with a hydrocarbon degrading microorganism community. The homoionic montmorillonites were prepared via cation exchange reactions by treating the unmodified montmorillonite with the relevant metallic chloride. The study indicated that potassium-montmorillonite and zinc-montmorillonite did not enhance the biodegradation of the polycyclic aromatic hydrocarbons whereas calcium-montmorillonite, and ferric-montmorillonite enhanced their biodegradation significantly. Adsorption of polycyclic aromatic hydrocarbons was significant during biodegradation with potassium- and zinc-montmorillonite where there was about 45% removal of the polycyclic aromatic compounds by adsorption in the experimental microcosm containing 5:1 ratio (w/w) of clay to oil. PMID:24813351

Ugochukwu, Uzochukwu C; Manning, David A C; Fialips, Claire I

2014-09-01

13

Mechanism of montmorillonite catalysis in the formation of RNA oligomers.  

PubMed

The montmorillonite clay-catalyzed reactions of nucleotides generate oligomers as long as 50-mers. The extent of catalysis depends on the magnitude of the negative charge on the montmorillonite lattice and the number of cations associated with it. When cations in raw montmorillonites are replaced by sodium ions, the resulting Na(+)-montmorillonite does not catalyze oligomer formation because they saturate the interlayers between the platelets of montmorillonites, which blocks the binding of the activated monomers. Treating the montmorillonite with dilute hydrochloric acid replaces the cations on the raw montmorillonite with protons. The protonated montmorillonite, titrated to pH 6-7, serves as a catalyst for the formation of RNA oligomers. The titration does not add sufficient sodium ions to the interlayers of the montmorillonite platelets to prevent the activated monomer from entering. It was noted that noncatalytic montmorillonites have a higher negative charge on their platelets that is due mainly to the natural substitution of the tetravalent and trivalent elements in the montmorillonite lattice with trivalent and divalent metal ions, respectively. The larger negative charge on these montmorillonites was demonstrated by the almost 2-fold greater amounts of sodium hydroxide needed to titrate noncatalytic montmorillonites as compared to the catalytic montmorillonites. Adsorption isotherms established that the equilibrium binding is strongest for ImpA and weakest for ImpU. Of the 22 montmorillonites investigated, 12 were catalysts. This research provides insight into the mechanism of the catalytic process. PMID:19719166

Joshi, Prakash C; Aldersley, Michael F; Delano, John W; Ferris, James P

2009-09-23

14

The adsorption of valine on cation-exchanged montmorillonites  

Microsoft Academic Search

The interfacial reaction of valine was systematically studied on the surface of different cation-exchanged montmorillonites, namely calcium-, copper-, zinc-montmorillonite, and montmorillonite KSF. The exchanged cations were selected on the basis of stability of their valine complexes. At first the interfacial acid\\/base properties of cation exchanged montmorillonites were studied: the stability constants of the ion exchange processes on the layer charges

Noémi M. Nagy; József Kónya

2004-01-01

15

Cadmium ion adsorption controls the growth of CdS nanoparticles on layered montmorillonite and calumit surfaces  

SciTech Connect

Adsorption isotherms have been determined for the intercalation of cadmium ions (Cd{sup 2+}) into layered hydrophobized montmorillonite (HDP-M) and calumit (DBS-C) sheets dispersed in ethanol (1)-cyclohexane (2) mixtures. The amount of Cd{sup 2+} adsorbed depended strongly on the composition of the binary liquid; at an ethanol mole fraction of 0.05 (x{sub 1} = 0.05), 95% of the added Cd{sup 2+} is located in the ethanolic nanoreactor at the HDP-M (or DBS-C) surface. CdS nanoparticles have been generated in situ in ethanolic nanoreactors at the HDP-M and DBS-C surfaces. Absorption spectrophotometric measurements provided information on the number of CdS nanoparticles formed and on their absorption edges, bandgaps, and mean diameters. Good correlations have been obtained between the adsorption isotherms and the size (and the amount) of the CdS formed. X-ray diffractometry established that CdS nanoparticles stretched the HDP-M and DBS-C lamellas unevenly upon intercalation.

Dekany, I.; Turi, L. [Hungarian Academy of Sciences (Hungary)] [Hungarian Academy of Sciences (Hungary); Galbacs, G. [Attila Jozsef Univ., Szeged (Hungary). Dept. of Inorganic and Analytical Chemistry] [Attila Jozsef Univ., Szeged (Hungary). Dept. of Inorganic and Analytical Chemistry; Fendler, J.H. [Clarkson Univ., Potsdam, NY (United States). Center for Advanced Materials Processing] [Clarkson Univ., Potsdam, NY (United States). Center for Advanced Materials Processing

1999-05-15

16

Control of Montmorillonite Surface Coatings on Quartz Grains in Bentonite by Precursor Volcanic Glass  

Microsoft Academic Search

The pathogenic tendencies of respirable-sized quartz grains may be dependent on inherent characteristics of the quartz as well as external factors. Surface coatings on quartz are of particular interest as they modify both physical and chemical properties of quartz grain surfaces and sequester the grain from contact with reactive lung fluids. Wendlandt et al. (Appl. Geochem. 22, 2007) investigated the

R. F. Wendlandt; W. J. Harrison

2008-01-01

17

Elaboration et caracterisation de nanocomposites polyethylene/montmorillonite  

NASA Astrophysics Data System (ADS)

This research project consists in preparing polyethylene/montmorillonite nanocomposites for film packaging applications. Montmorillonite is a natural clay with an exceptional aspect ratio. In recent years, its incorporation in polymer matrices has attracted great interest. The pioneer work from Toyota on polyamide-6/montmorillonite composites has shown that it was possible to disperse the clay at a nanometric scale. Such a structure, so-called exfoliated, leads to a significant increase in mechanical, barrier and fire retardant properties, even at low volumetric fractions of clay. This allows a valorization of the polymeric material at moderate cost. Due to its high polarity, montmorilloite exfoliation in polymeric matrices is problematic. In the particular case of polyolefin matrices, the platelets dispersion remains limited: most frequently, the composites obtained exhibit conventional structures (microcomposites) or intercalated structures. To solve this problem, two techniques are commonly employed: the surface treatment of the clay, which allows the expansion of the interfoliar gallery while increasing the affinity between the clay and the polymer, and the use of a polar compatibilizing agent (grafted polyolefin). The first part of this thesis deals with the preparation and the characterization of highly thermally stable organophilic montmorillonites. Commercial organophilic montmorillonites are treated with quaternary ammonium intercalating agents. However, those intercalating agents present a poor thermal stability and are susceptible to decompose upon processing, thus affecting the clay dispersion and the final properties of the nanocomposites. In this work, it was proposed to modify the clay with alkyl pyridinium, alkyl imidazolium and alkyl phosphonium intercalating agents, which are more stable than ammonium based cations. Organophilic montmorillonites with enhanced thermal stabilites compared to commercial organoclays (+20°C to +70°C) were prepared. The effect of the chemical structure of the intercalating agent on the capacity of the organoclay to be dispersed in polyethylene matrices was analyzed. In addition, the influence of the dispersion on the thermal stability of the nanocomposites prepared is discussed. In a second part, the effect of the compatibilizing agent characteristics on the quality of the clay dispersion in polyethylene/montmorillonite nanocomposites was analyzed. The mechanical properties and the oxygen permeability of the nanocomposites were evaluated and related to the level of clay delamination and to the strength of the polymer/clay interface, which was evaluated through surface tension measurements.

Stoeffler, Karen

18

Reflectance spectroscopy of ferric sulfate-bearing montmorillonites as Mars soil analog materials  

NASA Technical Reports Server (NTRS)

Spectroscopic analyses have shown that smectites enhanced in the laboratory with additional ferric species exhibit important similarities to those of the soils on Mars. Ferrihydrite in these chemically treated smectites has features in the visible to near-infrared region that resemble the energies and band strengths of features in reflectance spectra observed for several bright regions on Mars. New samples have been prepared with sulfate as well, because S was found by Viking to be a major component in the surface material on Mars. A suite of ferrihydrite-bearing and ferric sulfate-bearing montmorillonites, prepared with variable Fe3+ and S concentrations and variable pH conditions, has been analyzed using reflectance spectroscopy in the visible and infrared regions, Mossbauer spectroscopy at room temperature and 4 K, differential thermal analysis, and X-ray diffraction. These analyses support the formation of ferrihydrite of variable crystallinity in the ferrihydrite-bearing montmorillonites and a combination of schwertmannite and ferrihydrite in the ferric sulfate-bearing montmorillonites. Small quantities of poorly crystalline or nanophase forms of other ferric materials may also be present in these samples. The chemical formation conditions of the ferrihydrite-bearing and ferric sulfate-bearing montmorillonites influence the character of the low temperature Mossbauer sextets and the visible reflectance spectra. An absorption minimum is observed at 0.88-0.89 micrometers in spectra of the ferric sulfate-bearing samples, and at 0.89-0.92 micrometers in spectra of the ferrihydrate-bearing montmorillonites. Mossbauer spectra of the ferric sulfate-bearing montmorillonites indicate variable concentrations of ferrihydrite and schwertmannite in the interlaminar spaces and along grain surfaces. Dehydration under reduced atmospheric pressure conditions induces a greater effect on the adsorbed and interlayer water in ferrihydrite-bearing montmorillonite than on the water in ferric sulfate-bearing montmorillonite. Reflectance spectra of ferric sulfate-bearing montmorillonite include a strong 3-micrometers band that is more resistant to dry atmospheric conditions than the 3-micrometers band in spectra of similarly prepared ferrihydrite-bearing montmorillonites.

Bishop, J. L.; Pieters, C. M.; Burns, R. G.; Edwards, J. O.; Mancinelli, R. L.; Froschl, H.

1995-01-01

19

Ferric sulfate montmorillonites as Mars soil analogs  

NASA Technical Reports Server (NTRS)

Spectroscopic analyses have shown that Fe(3+)-doped smectites prepared in the laboratory exhibit important similarities to the soils on Mars. Ferrihydrite in these smectites has features in the visible to near-infrared region that resemble the energies and band-strengths of features in reflectance spectra observed for several bright regions on Mars. Ferric - sulfate - montmorillonite samples have been prepared more recently because they are a good compositional match with the surface material on Mars as measured by Viking. Reflectance spectra of montmorillonite doped with ferric sulfate in the interlayer regions include a strong 3 micron band that persists under dry conditions. This is in contrast to spectra of similarly prepared ferric-doped montmorillonites, which exhibit a relatively weaker 3 micron band under comparable dry environmental conditions. Presented here are reflectance spectra of a suite of ferric-sulfate exchanged montmorillonites prepared with variable ferric sulfate concentrations and variable pH conditions.

Bishop, J. L.; Pieters, C. M.; Burns, R. G.

1993-01-01

20

Development of Surface Complexation Models of Cr(VI) Adsorption on Soils, Sediments and Model Mixtures of Kaolinite, Montmorillonite, ?-Alumina, Hydrous Manganese and Ferric Oxides and Goethite  

SciTech Connect

Hexavalent chromium is a highly toxic contaminant that has been introduced into aquifers and shallow sediments and soils via many anthropogenic activities. Hexavalent chromium contamination is a problem or potential problem in the shallow subsurface at several DOE sites, including Hanford, Idaho National Laboratory, Los Alamos National Laboratory and the Oak Ridge Reservation (DOE, 2008). To accurately quantify the fate and transport of hexavalent chromium at DOE and other contaminated sites, robust geochemical models, capable of correctly predicting changes in chromium chemical form resulting from chemical reactions occurring in subsurface environments are needed. One important chemical reaction that may greatly impact the bioavailability and mobility of hexavalent chromium in the subsurface is chemical binding to the surfaces of particulates, termed adsorption or surface complexation. Quantitative thermodynamic surface complexation models have been derived that can correctly calculate hexavalent chromium adsorption on well-characterized materials over ranges in subsurface conditions, such pH and salinity. However, models have not yet been developed for hexavalent chromium adsorption on many important constituents of natural soils and sediments, such as clay minerals. Furthermore, most of the existing thermodynamic models have been developed for relatively simple, single solid systems and have rarely been tested for the complex mixtures of solids present in real sediments and soils. In this study, the adsorption of hexavalent chromium was measured as a function of pH (3-10), salinity (0.001 to 0.1 M NaNO3), and partial pressure of carbon dioxide(0-5%) on a suite of naturally-occurring solids including goethite (FeOOH), hydrous manganese oxide (MnOOH), hydrous ferric oxide (Fe(OH)3), ?-alumina (Al2O3), kaolinite (Al2Si2O5(OH)4), and montmorillonite (Na3(Al, Mg)2Si4O10(OH)2?nH2O). The results show that all of these materials can bind substantial quantities of hexavalent chromium, especially at low pH. Unexpectedly, experiments with the clay minerals kaolinite and montmorillonite suggest that hexavalent chromium may interact with these solids over much longer periods of time than expected. Furthermore, hexavalent chromium may irreversibly bind to these solids, perhaps because of oxidation-reduction reactions occurring on the surfaces of the clay minerals. More work should be done to investigate and quantify these chemical reactions. Experiments conducted with mixtures of goethite, hydrous manganese oxide, hydrous ferric oxide, ?-alumina, montmorillonite and kaolinite demonstrate that it is possible to correctly predict hexavalent chromium binding in the presence of multiple minerals using thermodynamic models derived for the simpler systems. Further, these models suggest that of the six solid considered in this study, goethite is typically the solid to which most of the hexavalent chromium will bind. Experiments completed with organic-rich and organic-poor natural sediments demonstrate that in organic-rich substrates, organic matter is likely to control uptake of the hexavalent chromium. The models derived and tested in this study for hexavalent chromium binding to ?-alumina, hydrous manganese oxide, goethite, hydrous ferric oxide and clay minerals can be used to better predict changes in hexavalent chromium bioavailability and mobility in contaminated sediments and soils.

Koretsky, Carla [Western Michigan University] [Western Michigan University

2013-11-29

21

Enantioselective photooxidation of a sulfide by a chiral ruthenium(II) complex immobilized on a montmorillonite clay surface: the role of weak interactions in asymmetric induction.  

PubMed

The present work pursued a possibility that enantioselectivity was achieved through weak intermolecular interactions between a catalyst and a substrate. For that purpose, we studied the photooxidation of alpha-ethylbenzyl phenyl sulfide catalyzed by a polypyridyl ruthenium(II) complex as a chiral photosensitizer. No covalent bonding was formed between a catalyst and a substrate, because the complexes used ([Ru(phen)(3)](2+) or [Ru(bpy(3))(2+)]) were coordinatively saturated. Enantiomer excess (ee) was attained to be 30% when a chiral photosensitizer was immobilized on montmorillonite clay. It was even improved to 43% in the presence of an additional chiral auxiliary, dibenzoyl-D(+)-tartaric acid. Notably, no enantioselectivity was achieved when the reaction took place in homogeneous solutions. The ab initio calculations were performed on the stability of an associate composed of a catalyst (metal complex) and a product (sulfoxide) to obtain a clue to reaction mechanisms. The calculations suggest that chiral discrimination is achieved even through noncovalent interactions between a substrate and a chiral sensitizer when the attacking direction by a substrate toward a catalyst is limited sterically on a solid surface. PMID:16471852

Fujita, Shuji; Sato, Hisako; Kakegawa, Norishige; Yamagishi, Akihiko

2006-02-16

22

Liquid Crystals of Montmorillonite  

Microsoft Academic Search

IF a section of a dry sodium montmorillonite film is placed in a solution of sodium chloride it will swell parallel to the c-axis, the swelling increasing as the salt concentration is reduced, until at a sufficiently low concentration (about N\\/100) complete dispersion occurs. This swelling has now been observed under a microscope. Fractions less than 2µ from samples of

W. W. Emerson

1956-01-01

23

40 CFR 721.10573 - Magnesium hydroxide surface treated with substituted alkoxysilanes (generic).  

Code of Federal Regulations, 2014 CFR

...2014-07-01 2014-07-01 false Magnesium hydroxide surface treated with substituted...Chemical Substances § 721.10573 Magnesium hydroxide surface treated with substituted...chemical substance identified generically as magnesium hydroxide surface treated with...

2014-07-01

24

40 CFR 721.10573 - Magnesium hydroxide surface treated with substituted alkoxysilanes (generic).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Magnesium hydroxide surface treated with substituted...Chemical Substances § 721.10573 Magnesium hydroxide surface treated with substituted...chemical substance identified generically as magnesium hydroxide surface treated with...

2013-07-01

25

EDDY CURRENT SPECTROSCOPY FOR NEAR-SURFACE RESIDUAL STRESS PROFILING IN SURFACE TREATED NONMAGNETIC ENGINE ALLOYS.  

E-print Network

??Recent research results indicated that eddy current conductivity measurements can be exploited for nondestructive evaluation of near-surface residual stresses in surface-treated nickel-base superalloy components. Most… (more)

ABU-NABAH, BASSAM ABDEL JABER

2007-01-01

26

Biocompatibility Evaluation of Nanosecond Laser Treated Titanium Surfaces  

NASA Astrophysics Data System (ADS)

We developed surface modification technologies for dental implants in this study. The study contributes to shortening the time required for adhesion between alveolar bone and fixtures which consist of dental implants. A Nd:YVO4 nanosecond laser was used to modify the surfaces of commercially pure titanium (CP Ti) disks, and their biocompatibility was evaluated cytocompatibility and bioactivity. First, rows of 200 µm spaced rectilinear laser treatments were performed on surfaces of CP Ti disks. Osteoblasts derived from rat mesenchymal stem cells were then cultured on the treated surfaces. Cytocompatibility on the laser treated area was evaluated by observing adhesion behavior of cells on these surfaces. The results indicated that the micro-order structure formed by the laser treatment promoted adhesion of osteoblasts and that traces of laser treatment without microstucture didn't affect the adhesion. Second, surfaces of CP Ti disks were completely covered by traces of laser treatment, which created complex microstructures of titania whose crystal structure is rutile and anatase. This phenomenon allowed the creation of hydroxyapatite on the surface of the disks in 1.5-times simulated body fluid (1.5SBF) while no hydroxyapatite was observed on conventional polished surfaces in the same conditions. This result indicates that bioactivity was enabled on CP Ti by the laser treatment. From these two results, laser treatment for CP Ti surfaces is an effective method for enhancing adhesion of osteoblasts and promoting bioactivity, which are highly appreciated properties for dental implants.

Honda, Ryo; Mizutani, Masayoshi; Ohmori, Hitoshi; Komotori, Jun

27

Utilization of surface-treated rubber particles from waste tires  

SciTech Connect

During a 12-month program, the author successfully demonstrated commercial applications for surface-treated rubber particles in two major markets: footwear (shoe soles and components) and urethane-foam carpet underlay (padding). In these markets, he has clearly demonstrated the ease of using R-4080 and R-4030 surface-treated rubber particles in existing manufacturing plants and processes and have shown that the material meets or exceeds existing standards for performance, quality, and cost-effectiveness. To produce R-4080 and R-4030, vulcanized rubber, whole-tire material is finely ground to particles of nominal 80 and mesh size respectively. Surface treatment is achieved by reacting these rubber particles with chlorine gas. In this report, the author describes the actual test and evaluations of the participant companies, and identifies other potential end uses.

Smith, F.G. [Argonne National Lab., IL (United States). Energy Systems Div.]|[Environmental Technologies Alternatives, Inc., Lima, OH (United States)

1994-12-01

28

Induced hydrophobic recovery of oxygen plasma-treated surfaces  

PubMed Central

Plasma treatment is a widely used method in microfabrication laboratories and the plasticware industry to functionalize surfaces for device bonding and preparation for mammalian cell culture. However, spatial control of plasma treatment is challenging because it typically requires a tedious masking step that is prone to alignment errors. Currently, there are no available methods to actively revert a surface from a treated hydrophilic state to its original hydrophobic state. Here, we describe a method that relies on physical contact treatment (PCT) to actively induce hydrophobic recovery of plasma-treated surfaces. PCT involves applying brushing and peeling processes with common wipers and tapes to reverse the wettability of hydrophilized surfaces while simultaneously preserving hydrophilicity of non-contacted surfaces. We demonstrate that PCT is a user-friendly method that allows 2D and 3D surface patterning of hydrophobic regions, and the protection of hydrophilic surfaces from unwanted PCT-induced recovery. This method will be useful in academic and industrial settings where plasma treatment is frequently used. PMID:22592853

Guckenberger, David J.; Berthier, Erwin; Young, Edmond W. K.; Beebe, David J.

2014-01-01

29

Method of treating the surface of a glass member  

NASA Technical Reports Server (NTRS)

A method is described of treating a surface of a glass member intended to abut a transparent element for disrupting the light interference fringes formed between the surfaces. The method involves the steps of grinding the surface to form irregularities thereon; bathing the surface with an aqueous solution containing between substantially 41.3 percent and 45.7 percent by volume of sulfuric acid and between substantially 54.3 percent and 58.7 percent by volume of hydrofluoric acid for a time sufficient to polish the irregularities until the glass member is about 90 percent light transmissive; and washing the glass member with a liquid having a temperature substantially lower than the temperature of the aqueous solution for preventing further reaction between the aqueous solution and the surface.

Rice, S. H.; Spencer, R. S. (inventors); Fleetwood, C. M., Jr.

1977-01-01

30

Aflatoxin toxicity reduction in feed by enhanced binding to surface-modified clay additives.  

PubMed

Animal feeding studies have demonstrated that clay additives, such as bentonites, can bind aflatoxins in ingested feed and reduce or eliminate the toxicity. Bentonite deposits are found throughout the world and mostly consist of expandable smectite minerals, such as montmorillonite. The surfaces of smectite minerals can be treated with organic compounds to create surface-modified clays that more readily bind some contaminants than the untreated clay. Montmorillonites treated with organic cations, such as hexadecyltrimethylammonium (HDTMA) and phenyltrimethylammonium (PTMA), more effectively remove organic contaminants, such as benzene and toluene, from water than untreated clay. Similarly, montmorillonite treated with PTMA (K(d) = 24,100) retained more aflatoxin B1 (AfB1) from aqueous corn flour than untreated montmorillonite (K(d) = 944). Feed additives that reduced aflatoxin toxicity in animal feeding studies adsorbed more AfB1 from aqueous corn flour than feed additives that were less effective. The organic cations HDTMA and PTMA are considered toxic and would not be suitable for clay additives used in feed or food, but other non-toxic or nutrient compounds can be used to prepare surface-modified clays. Montmorillonite (SWy) treated with choline (K(d) = 13,800) and carnitine (K(d) = 3960) adsorbed much more AfB1 from aqueous corn flour than the untreated clay (K(d) = 944). A choline-treated clay prepared from a reduced-charge, high-charge montmorillonite (K(d) = 20,100) adsorbed more AfB1 than the choline-treated high-charge montmorillonite (K(d) = 1340) or the untreated montmorillonite (K(d) = 293). Surface-modified clay additives prepared using low-charge smectites and nutrient or non-toxic organic compounds might be used to more effectively bind aflatoxins in contaminated feed or food and prevent toxicity. PMID:22069725

Jaynes, William F; Zartman, Richard E

2011-06-01

31

Aflatoxin Toxicity Reduction in Feed by Enhanced Binding to Surface-Modified Clay Additives  

PubMed Central

Animal feeding studies have demonstrated that clay additives, such as bentonites, can bind aflatoxins in ingested feed and reduce or eliminate the toxicity. Bentonite deposits are found throughout the world and mostly consist of expandable smectite minerals, such as montmorillonite. The surfaces of smectite minerals can be treated with organic compounds to create surface-modified clays that more readily bind some contaminants than the untreated clay. Montmorillonites treated with organic cations, such as hexadecyltrimethylammonium (HDTMA) and phenyltrimethylammonium (PTMA), more effectively remove organic contaminants, such as benzene and toluene, from water than untreated clay. Similarly, montmorillonite treated with PTMA (Kd = 24,100) retained more aflatoxin B1 (AfB1) from aqueous corn flour than untreated montmorillonite (Kd = 944). Feed additives that reduced aflatoxin toxicity in animal feeding studies adsorbed more AfB1 from aqueous corn flour than feed additives that were less effective. The organic cations HDTMA and PTMA are considered toxic and would not be suitable for clay additives used in feed or food, but other non-toxic or nutrient compounds can be used to prepare surface-modified clays. Montmorillonite (SWy) treated with choline (Kd = 13,800) and carnitine (Kd = 3960) adsorbed much more AfB1 from aqueous corn flour than the untreated clay (Kd = 944). A choline-treated clay prepared from a reduced-charge, high-charge montmorillonite (Kd = 20,100) adsorbed more AfB1 than the choline-treated high-charge montmorillonite (Kd = 1340) or the untreated montmorillonite (Kd = 293). Surface-modified clay additives prepared using low-charge smectites and nutrient or non-toxic organic compounds might be used to more effectively bind aflatoxins in contaminated feed or food and prevent toxicity. PMID:22069725

Jaynes, William F.; Zartman, Richard E.

2011-01-01

32

Treating ocular surface disease: new agents in development  

PubMed Central

This paper reviews recent advances and investigation in the treatment of ocular surface pathology. There is significant investment in this area, paralleling the growing demand for more effective alternatives to current treatments. Clinicians are becoming more aware of surface pathology, yet the ability to treat the most common forms of ocular pathology are still limited to the few medications approved by the US Food and Drug Administration. Medicines and devices currently under investigation are very promising. It is absolutely critical to understand the emerging options and think of their role in the treatment paradigm. PMID:21573093

Fahmy, Ahmad M; Hardten, David R

2011-01-01

33

Surface characterization of silica glass substrates treated by atomic hydrogen  

SciTech Connect

Silica glass substrates with very flat surfaces were exposed to atomic hydrogen at different temperatures and durations. An atomic force microscope was used to measure root-mean-square (RMS) roughness and two-dimensional power spectral density (PSD). In the treatment with atomic hydrogen up to 900 °C, there was no significant change in the surface. By the treatment at 1000 °C, the changes in the RMS roughness and the PSD curves were observed. It was suggested that these changes were caused by etching due to reactions of atomic hydrogen with surface silica. By analysis based on the k-correlation model, it was found that the spatial frequency of the asperities became higher with an increase of the treatment time. Furthermore, the data showed that atomic hydrogen can flatten silica glass surfaces by controlling heat-treatment conditions. - Highlights: • Silica glass surface was treated by atomic hydrogen at various temperatures. • Surface roughness was measured by an atomic force microscope. • Roughness data were analyzed by two-dimensional power spectral density. • Atomic hydrogen can flatten silica glass surfaces.

Inoue, Hiroyuki [Institute of Industrial Science, The University of Tokyo, Meguro-ku, Tokyo 153-8505 (Japan); Masuno, Atsunobu, E-mail: masuno@iis.u-tokyo.ac.jp [Institute of Industrial Science, The University of Tokyo, Meguro-ku, Tokyo 153-8505 (Japan); Ishibashi, Keiji [Canon ANELVA Corporation, Asao-ku, Kawasaki, Kanagawa 215-8550 (Japan); Tawarayama, Hiromasa [Kawazoe Frontier Technologies Corporation, Kuden 931-113, Sakae-ku, Yokohama, Kanagawa 247-0014 (Japan); Zhang, Yingjiu; Utsuno, Futoshi [Institute of Industrial Science, The University of Tokyo, Meguro-ku, Tokyo 153-8505 (Japan); Koya, Kazuo; Fujinoki, Akira [Shin Etsu Quartz Prod. Co., Ltd., Res and Applicat Lab, Fukushima 963-0725 (Japan); Kawazoe, Hiroshi [Kawazoe Frontier Technologies Corporation, Kuden 931-113, Sakae-ku, Yokohama, Kanagawa 247-0014 (Japan)

2013-12-15

34

Scanning electron microscopical analysis of laser-treated titanium implant surfaces—a comparative study  

Microsoft Academic Search

Design and surface qualities of titanium implants are of vital importance for long-term stability following implantation. Four different implant surfaces treated individually were analyzed with special attention focused on laser surface treatment. Surfaces with machine roughness, titanium spray coating, treated by aluminum oxide and treated by laser were examined individually. Evaluation of the surface was carried out by electron microscope

A Gaggl; G Schultes; W. D Müller; H Kärcher

2000-01-01

35

Peptide formation mechanism on montmorillonite under thermal conditions.  

PubMed

The oligomerization of amino acids is an essential process in the chemical evolution of proteins, which are precursors to life on Earth. Although some researchers have observed peptide formation on clay mineral surfaces, the mechanism of peptide bond formation on the clay mineral surface has not been clarified. In this study, the thermal behavior of glycine (Gly) adsorbed on montmorillonite was observed during heating experiments conducted at 150 °C for 336 h under dry, wet, and dry-wet conditions to clarify the mechanism. Approximately 13.9 % of the Gly monomers became peptides on montmorillonite under dry conditions, with diketopiperazine (cyclic dimer) being the main product. On the other hand, peptides were not synthesized in the absence of montmorillonite. Results of IR analysis showed that the Gly monomer was mainly adsorbed via hydrogen bonding between the positively charged amino groups and negatively charged surface sites (i.e., Lewis base sites) on the montmorillonite surface, indicating that the Lewis base site acts as a catalyst for peptide formation. In contrast, peptides were not detected on montmorillonite heated under wet conditions, since excess water shifted the equilibrium towards hydrolysis of the peptides. The presence of water is likely to control thermodynamic peptide production, and clay minerals, especially those with electrophilic defect sites, seem to act as a kinetic catalyst for the peptide formation reaction. PMID:24917118

Fuchida, Shigeshi; Masuda, Harue; Shinoda, Keiji

2014-02-01

36

Peptide Formation Mechanism on Montmorillonite Under Thermal Conditions  

NASA Astrophysics Data System (ADS)

The oligomerization of amino acids is an essential process in the chemical evolution of proteins, which are precursors to life on Earth. Although some researchers have observed peptide formation on clay mineral surfaces, the mechanism of peptide bond formation on the clay mineral surface has not been clarified. In this study, the thermal behavior of glycine (Gly) adsorbed on montmorillonite was observed during heating experiments conducted at 150 °C for 336 h under dry, wet, and dry-wet conditions to clarify the mechanism. Approximately 13.9 % of the Gly monomers became peptides on montmorillonite under dry conditions, with diketopiperazine (cyclic dimer) being the main product. On the other hand, peptides were not synthesized in the absence of montmorillonite. Results of IR analysis showed that the Gly monomer was mainly adsorbed via hydrogen bonding between the positively charged amino groups and negatively charged surface sites (i.e., Lewis base sites) on the montmorillonite surface, indicating that the Lewis base site acts as a catalyst for peptide formation. In contrast, peptides were not detected on montmorillonite heated under wet conditions, since excess water shifted the equilibrium towards hydrolysis of the peptides. The presence of water is likely to control thermodynamic peptide production, and clay minerals, especially those with electrophilic defect sites, seem to act as a kinetic catalyst for the peptide formation reaction.

Fuchida, Shigeshi; Masuda, Harue; Shinoda, Keiji

2014-02-01

37

SYNTHESIS OF IRON OXIDE-MONTMORILLONITE COMPOSITE AND STUDY OF ITS STRUCTURAL STABILITY AGAINTS SULFURIC ACID Sintesis Komposit Oksida-Besi Montmorillonit dan Uji Stabilitas Strukturnya Terhadap Asam Sulfat  

Microsoft Academic Search

The synthesis and characterization of iron oxide-montmorillonite and its structural stability test with various concentration of sulfuric acid were conducted. Synthesis was performed by treating Na- montmorillonite clay with oligocations of iron, followed by calcinating the intercalation compound of oligocations-montmorillonite at 200oC for 24 hours. Calcined product was then characterized to determine the iron content, basal spacing and its porosities

Karna Wijaya; Eko Sugiharto; Ika Liawati; Jurusan Kimia

38

Thermal analysis of hexadecyltrimethylammonium-montmorillonites  

Microsoft Academic Search

Na-montmorillonite (Na-MONT) was loaded with hexadecyltrimethylammonium cations (HDTMA) by replacing 41 and 90% of the exchangeable\\u000a Na with HDTMA. The organoclays were labeled OC-41 and OC-90, respectively. Freeze-dried Na-MONT, OC-41, and OC-90 were heated\\u000a in air at 150, 250, 360, 420, 550, 700, and 900 °C. The thermally treated samples were suspended in water, air-dried, and\\u000a desiccated over silica during 40 days.

Isaak Lapides; Mikhail Borisover; Shmuel Yariv

2011-01-01

39

Effect of in-situ bonding system and surface modification of montmorillonite on the properties of butyl rubber/MMT composites  

NASA Astrophysics Data System (ADS)

Isobutylene-isoprene rubber (IIR)/nanoclay composites were prepared by solution intercalation method. Cloisite Na+ nanoclays and organo-modified montmorillonite (OMT) Cloisite 10 A,.15 A and 20 A were used in this study. The effect of In-situ bonding system HRH (hexametylene tetramine: resorcinol: hydrated silica) on the dispersion of used nanoclays in the rubber matrix were examined by X-ray diffraction and atomic force microscopy (AFM). Characterization of the prepared composites was performed by studying the rheometeric and mechanical properties. The burning out behavior of the nanocomposites with and without the bonding system was also measured.

Halim, S. F.; Lawandy, S. N.; Nour, M. A.

2012-07-01

40

Preparation and characterization of zwitterionic surfactant-modified montmorillonites.  

PubMed

A series of zwitterionic surfactant-modified montmorillonites (ZSMMs) were synthesized using montmorillonite and three zwitterionic surfactants with different alkyl chain lengths at different concentrations [0.2-4.0 cation exchange capacity (CEC)]. These ZSMMs were characterized by X-ray diffraction (XRD), thermo-gravimetric analysis and differential thermo-gravimetric (TG/DTG) analyses. The zwitterionic surfactant could be intercalated into the interlayer spaces of montmorillonites and causing interlayer space-swelling. From XRD measurements, the amount of the surfactants loaded and the basal spacing increased with surfactant concentration and alkyl chain length. One endothermic DTG peak occurred at ~390 °C, which was assigned to the decomposition of the zwitterionic surfactant on the organo-montmorillonites from 0.2 to 0.6 CEC. When the surfactant loading was increased, a new endothermic peak appeared at ~340 °C. From the microstructures of these ZSMMs, the mechanism of zwitterionic surfactant adsorption was proposed. At relatively low loadings of the zwitterionic surfactant, most of surfactants enter the spacing by an ion-exchange mechanism and are adsorbed onto the interlayer cation sites. When the concentration of the zwitterionic surfactant exceeds the CEC of montmorillonite, the surfactant molecules then adhere to the surface-adsorbed surfactant. Some surfactants enter the interlayers, whereas the others are attached to the clay surface. When the concentration of surfactant increases further beyond 2.0 CEC, the surfactants may occupy the inter-particle space within the house-of-cards aggregate structure. PMID:21575956

Zhu, Jianxi; Qing, Yanhong; Wang, Tong; Zhu, Runliang; Wei, Jingming; Tao, Qi; Yuan, Peng; He, Hongping

2011-08-15

41

Alkylammonium montmorillonites as adsorbents for organic vapors from air  

SciTech Connect

Montmorillonite clays may be modified by the exchange of the inorganic interlayer cations with alkylammonium ions, resulting in a fixed internal porosity. The pore size and shape depend on the nature of the alkylammonium ion. A number of different ions were used to prepare adsorbents with varying properties, and these were examined for their potential application to sampling organic vapors in air. Characterization involved determination of nitrogen and water contents, surface area, interlayer spacing, thermal stability, and breakthrough volumes of organic vapors. The adsorbent that showed the most promise (tetramethylammonium montmorillonite (TMA)) was further evaluated for use as an adsorbent in both thermal- and solvent-desorable sampling systems.

Harper, M.; Purnell, C.J. (London School of Hygiene and Tropical Medicine (England))

1990-01-01

42

Adsorption of methyl green on montmorillonite  

NASA Astrophysics Data System (ADS)

Adsorption of the dye methyl green (MG) on Na -montmorillonite (Clay) takes place through a cation exchange mechanism. At low and high MG loads, each MG molecule replaces approximately two and one Na + ions, respectively. Interactions between MG and Clay were studied using visible absorption and FTIR spectroscopies, and the orientation of the adsorbed molecules were determined by infrared linear dichroism and X-ray powder diffraction. The dye molecules are preferentially oriented with their plane parallel to the clay surface. The influence of MG load on the adsorption of two additional organic molecules, benzyl benzoate and benzophenone, was also studied.

Margulies, Leon; Rozen, Harel

1986-03-01

43

Comparison of removal torques between laser-treated and SLA-treated implant surfaces in rabbit tibiae  

PubMed Central

PURPOSE The purpose of this study was to compare removal torques and surface topography between laser treated and sandblasted, large-grit, acid-etched (SLA) treated implants. MATERIALS AND METHODS Laser-treated implants (experimental group) and SLA-treated implants (control group) 8 mm in length and 3.4 mm in diameter were inserted into both sides of the tibiae of 12 rabbits. Surface analysis was accomplished using a field emission scanning electron microscope (FE-SEM; Hitachi S-4800; Japan) under ×25, ×150 and ×1,000 magnification. Surface components were analyzed using energy dispersive spectroscopy (EDS). Rabbits were sacrificed after a 6-week healing period. The removal torque was measured using the MGT-12 digital torque meter (Mark-10 Co., Copiague, NY, USA). RESULTS In the experimental group, the surface analysis showed uniform porous structures under ×25, ×150 and ×1,000 magnification. Pore sizes in the experimental group were 20-40 mm and consisted of numerous small pores, whereas pore sizes in the control group were 0.5-2.0 mm. EDS analysis showed no significant difference between the two groups. The mean removal torque in the laser-treated and the SLA-treated implant groups were 79.4 Ncm (SD = 20.4; range 34.6-104.3 Ncm) and 52.7 Ncm (SD = 17.2; range 18.7-73.8 Ncm), respectively. The removal torque in the laser-treated surface implant group was significantly higher than that in the control group (P=.004). CONCLUSION In this study, removal torque values were significantly higher for laser-treated surface implants than for SLA-treated surface implants. PMID:25177474

Kang, Nam-Seok; Li, Lin-Jie

2014-01-01

44

Montmorillonite-Alginate Composites as a Drug delivery System: Intercalation and In vitro Release of Diclofenac sodium  

PubMed Central

Diclofenac sodium and alginate was intercalated into montmorillonite to form uniform sized beads by gelation method. The structure and surface morphology of the synthesized composite beads were characterized by powdered X-ray diffraction, Fourier transform infrared spectroscopy, thermo gravimetric analysis and scanning electron microscopy. Diclofenac release kinetics of the composite in simulated intestinal fluid medium (pH 7.4) and effect of montmorillonite content on the in vitro release of diclofenac from diclofenac-montmorillonite-alginate composites bead was investigated by UV/Vis spectrophotometer. Diclofenac encapsulation efficiency in the montmorillonite-alginate composites bead increases with an increase in the montmorillonite content. The control release of diclofenac from diclofenac-montmorillonite-alginate composites beads was observed to be better as compared to diclofenac-alginate beads. PMID:21969745

Kevadiya, B. D.; Patel, H. A.; Joshi, G. V.; Abdi, S. H. R.; Bajaj, H. C.

2010-01-01

45

Method and system for treating an interior surface of a workpiece using a charged particle beam  

DOEpatents

A method and system of treating an interior surface on an internal cavity of a workpiece using a charged particle beam. A beam deflector surface of a beam deflector is placed within the internal cavity of the workpiece and is used to redirect the charged particle beam toward the interior surface to treat the interior surface.

Swenson, David Richard (Georgetown, MA)

2007-05-23

46

Molecular dynamics simulation of the intercalation behaviors of methane hydrate in montmorillonite.  

PubMed

The formation and mechanism of CH4 hydrate intercalated in montmorillonite are investigated by molecular dynamics (MD) simulation. The formation process of CH4 hydrate in montmorillonite with 1?~?8 H2O layers is observed. In the montmorillonite, the "surface H2O" constructs the network by hydrogen bonds with the surface Si-O ring of clay, forming the surface cage. The "interlayer H2O" constructs the network by hydrogen bonds, forming the interlayer cage. CH4 molecules and their surrounding H2O molecules form clathrate hydrates. The cation of montmorillonite has a steric effect on constructing the network and destroying the balance of hydrogen bonds between the H2O molecules, distorting the cage of hydrate in clay. Therefore, the cages are irregular, which is unlike the ideal CH4 clathrate hydrates cage. The pore size of montmorillonite is another impact factor to the hydrate formation. It is quite easier to form CH4 hydrate nucleation in montmorillonite with large pore size than in montmorillonite with small pore. The MD work provides the constructive information to the investigation of the reservoir formation for natural gas hydrate (NGH) in sediments. PMID:24906646

Yan, KeFeng; Li, XiaoSen; Xu, ChunGang; Lv, QiuNan; Ruan, XuKe

2014-06-01

47

Effect of pH in preparation and properties of mesoporous sieve from montmorillonite  

Microsoft Academic Search

Mesoporous material with dual mesoporous size distribution had been synthesized with montmorillonite as precursor. The materials\\u000a exhibited two kinds of mesopores: one is mesopore in interlayers of montmorillonite with mean sizes of 2.9 nm, the other is\\u000a mesopore out of layers of montmorillonite with mean sizes of 3.9 nm. With the increasing of pH values (8.0–11.0), the specific\\u000a surface area and pore

Maosheng Xia; Yinshan Jiang; Fangfei Li; Mengmeng Sun; Bing Xue

2010-01-01

48

Simulations of the Viking Gas Exchange Experiment using palagonite and Fe-rich montmorillonite as terrestrial analogs: implications for the surface composition of Mars.  

PubMed

Simulations of the Gas Exchange Experiment (GEX), one of the Viking Lander Biology Experiments, were run using palagonite and Fe-rich montmorillonite as terrestrial analogs of the Martian soil. These terrestrial analogs were exposed to a nutrient solution of the same composition as that of the Viking Landers under humid (no contact with nutrient) and wet (intimate contact) conditions. The headspace gases in the GEX sample cell were sampled and then analyzed by gas chromatography under both humid and wet conditions. Five gases were monitored: CO2, N2, O2, Ar, and Kr. It was determined that in order to simulate the CO2 gas changes of the Viking GEX experiment, the mixture of soil analog mineral plus nutrient medium must be slightly (pH = 7.4) to moderately basic (pH = 8.7). This conclusion suggests constraints upon the composition of terrestrial analogs to the Mars soil; acidic components may be present, but the overall mixture must be basic in order to simulate the Viking GEX results. PMID:11539578

Quinn, R; Orenberg, J

1993-10-01

49

Montmorillonite enhanced ciprofloxacin transport in saturated porous media with sorbed ciprofloxacin showing antibiotic activity.  

PubMed

Antibiotic ciprofloxacin (CIP) is immobile in the subsurface but it has been frequently detected in the aquatic system. Therefore it is important to investigate the factors impacting CIP's mobilization in aquifer. Laboratory columns packed with sand were used to test colloid-facilitated CIP transport by 1) using kaolinite or montmorillonite to mobilize presorbed-CIP in a column or 2) co-transporting with CIP by pre-mixing them before transport. The Langmuir model showed that CIP sorption by montmorillonite (23gkg(-1)) was 100 times more effective than sand or kaolinite. Even with strong CIP complexation ability to Fe/Al coating on sand surface, montmorillonite promoted CIP transport, but not kaolinite. All presorbed-CIP by sand was mobilized by montmorillonite after 3 pore volumes through co-transporting of CIP with montmorillonite. The majority of CIP was fixed onto the montmorillonite interlayer but still showed inhibition of bacteria growth. Our results suggested that montmorillonite with high CIP sorption ability can act as a carrier to enhance CIP's mobility in aquifer. PMID:25528132

Chen, Hao; Gao, Bin; Yang, Liu-Yan; Ma, Lena Q

2015-02-01

50

Montmorillonite enhanced ciprofloxacin transport in saturated porous media with sorbed ciprofloxacin showing antibiotic activity  

NASA Astrophysics Data System (ADS)

Antibiotic ciprofloxacin (CIP) is immobile in the subsurface but it has been frequently detected in the aquatic system. Therefore it is important to investigate the factors impacting CIP's mobilization in aquifer. Laboratory columns packed with sand were used to test colloid-facilitated CIP transport by 1) using kaolinite or montmorillonite to mobilize presorbed-CIP in a column or 2) co-transporting with CIP by pre-mixing them before transport. The Langmuir model showed that CIP sorption by montmorillonite (23 g kg- 1) was 100 times more effective than sand or kaolinite. Even with strong CIP complexation ability to Fe/Al coating on sand surface, montmorillonite promoted CIP transport, but not kaolinite. All presorbed-CIP by sand was mobilized by montmorillonite after 3 pore volumes through co-transporting of CIP with montmorillonite. The majority of CIP was fixed onto the montmorillonite interlayer but still showed inhibition of bacteria growth. Our results suggested that montmorillonite with high CIP sorption ability can act as a carrier to enhance CIP's mobility in aquifer.

Chen, Hao; Gao, Bin; Yang, Liu-Yan; Ma, Lena Q.

2015-02-01

51

XAS of uranium(VI) sorbed onto silica, alumina, and montmorillonite  

NASA Astrophysics Data System (ADS)

The purpose of this work is to determine the speciation (oxidation state and molecular structure) of uranium sorbed onto surfaces of silica, alumina, and montmorillonite, in order to investigate the modes of uranium sorption on these minerals. Characterization of actinide sorption onto silicates, aluminates, and aluminosilicates such as montmorillonite is vital for the prediction of the environmental impact and risk assessment of actinide migration from nuclear waste storage sites, underground test sites, and mining sites.

Sylwester, E. R.; Allen, P. G.; Hudson, E. A.

2000-07-01

52

Electrical and optical characteristics of surface treated ZnO nanotubes  

SciTech Connect

Highlights: ? ZnO nanotubes were formed onto an ITO glass and were surface treated. ? Photoluminescence and fluorescence imaging for ZnO nanotubes showed blue emission. ? Surface treated samples that showed green emissions. ? Lifetime measurements showed higher excitonic times in surface treated samples. ? Conductance measurements showed significant improvement for the treated samples. -- Abstract: Vertical ZnO nanotubes were electrochemically deposited onto an indium doped tin oxide glass substrate. These nanotubes were surface treated with zinc acetate and annealed at 450 °C, resulting in a nanotubes/nanoparticles composite layer. Scanning electron microscopy of the surface treated samples showed nanoparticles been dispersed uniformly along the ZnO tubular matrix, which was confirmed by X-ray diffractrometry. Photoluminescence and fluorescence microscopy showed untreated ZnO nanotubes exhibiting blue emission, while the treated samples exhibited green emissions. Ultra-violet spectroscopy of treated samples revealed lower band gap values compare to their untreated counterparts. Lifetime measurements showed higher excitonic lifetimes in treated samples. Conductance studies using atomic force microscopy showed significant improvement in the conductance values for the treated samples. A significant increase in photocurrent was observed in treated samples when used as photo-anodes in dye sensitized solar cells.

Ranjusha, R.; Sreeja, R.; Mini, P.A.; Subramanian, K.R.V. [Nano Solar Division, Amrita Center for Nanosciences, Kochi 682 041 (India)] [Nano Solar Division, Amrita Center for Nanosciences, Kochi 682 041 (India); Nair, Shantikumar V., E-mail: nairshanti@gmail.com [Nano Solar Division, Amrita Center for Nanosciences, Kochi 682 041 (India); Balakrishnan, Avinash, E-mail: avinash.balakrishnan@gmail.com [Nano Solar Division, Amrita Center for Nanosciences, Kochi 682 041 (India)] [Nano Solar Division, Amrita Center for Nanosciences, Kochi 682 041 (India)

2012-08-15

53

Assessing the protective qualities of treated and untreated concrete surfaces under cyclic wetting and drying  

Microsoft Academic Search

The cyclic wetting and drying characteristics of treated and untreated concrete substrates were studied. During the absorption cycle, specimens were exposed to both water and sodium chloride solution. The testing programme used relatively simple, non-destructive methods to quantify the efficacy of the treated surface; in particular, cumulative volume gain and surface resistivity measurements. Destructive testing was used to investigate the

W. J. McCarter

1996-01-01

54

Surface modification of polymers treated by various fluorinating media.  

PubMed

Fluorination processes of polymer surfaces are able to lead to drastic modifications of the surface properties without changing the bulk characteristics of the virgin material. In this paper, two types of polymers, i.e. ultrahigh molecular weight polyethylene (UHMWPE) and high density polyethylene (HDPE), are considered. The surface of these materials have been modified using two different fluorination routes, both carried out at room temperature: the direct fluorination with 10% F2 + 90% He gaseous mixtures and the radio-frequency plasma-enhanced fluorination (PEF) using either O2/CF4 mixtures or c-C4F8. The effect of these processes on the surface of the polymer samples are compared using mostly XPS results. The different components of the C1s spectra are assigned in term of CFx bonding, giving valuable information on the surface fluorination rate. PMID:24169703

Tressaud, Alain; Durand, Etienne; Labrugère, Christine; Kharitonov, Alexander P; Simbirtseva, Galina V; Kharitonova, Larisa N; Dubois, Marc

2013-01-01

55

Spectroscopic ellipsometry studies of HF treated Si (100) surfaces  

NASA Technical Reports Server (NTRS)

Both ex situ and in situ spectroscopic ellipsometry (SE) measurements were employed to investigate the effect of HF cleaning on Si surfaces. The hydrogen-terminated (H-terminated) Si surface was modeled as an equivalent dielectric layer, and monitored in real time by SE measurements. The SE analyses indicate that, after a 20-sec 9:1 HF dip without rinse, the Si (100) surface was passivated by the hydrogen termination and remained chemically stable. Roughness of the HF-etched bare Si (100) surface was observed, in an ultrahigh vacuum chamber (UHV), and analyzed by the in situ SE. Evidence for desorption of the H-terminated Si surface layer, after being heated to about 550 C in the UHV chamber, is presented and discussed. This is the first use of an ex situ and in situ real-time, nondestructive technique capable of showing state of passivation, the rate of reoxidation, and the surface roughness of the H-terminated Si surfaces.

Yao, Huade; Woollam, John A.; Alterovitz, Samuel A.

1993-01-01

56

Spectroscopic ellipsometry studies of HF treated Si (100) surfaces  

NASA Technical Reports Server (NTRS)

Both ex situ and in situ spectroscopic ellipsometry (SE) measurements were employed to investigate the effects of HF cleaning on Si surfaces. The hydrogen-terminated (H-terminated) Si surface was modeled as an equivalent dielectric layer, and monitored in real time by SE measurements. The SE analyses indicate that after a 20-s 9:1 HF dip without rinse, the Si(100) surface was passivated by the hydrogen termination and remained chemically stable. Roughness of the HF-etched bare Si(100) surface was observed, in an ultrahigh vacuum (UHV) chamber, and analyzed by the in situ SE. Evidence for desorption of the H-terminated Si surface-layer, after being heated to approximately 550 C in the UHV chamber, is presented and discussed. This is the first use of an ex situ and in situ real-time, nondestructive technique capable of showing state of passivation, the rate of reoxidation, and the surface roughness of the H-terminated Si surfaces.

Yao, Huade; Woollam, John A.; Alterovitz, Samuel A.

1993-01-01

57

Molecular dynamics simulation of methane in potassium montmorillonite clay hydrates  

NASA Astrophysics Data System (ADS)

We present molecular dynamics simulation results for molecular structure, density profile and radial distribution functions of water, cation and methane in hydrated potassium montmorillonite clays. The systems we have studied consist of eight Otay Montmorillonite unit cells forming a clay patch of 21.12 × 18.28 Å2 with a thickness of 6.56 Å, eight potassium interlayer cations, with 0.5, 1.0 and 2.25 CH4 per unit cell, corresponding to 11.5, 11.0 and 9.75 H2O per unit cell. The calculations are conducted in constant (N, V, T) ensembles at T = 300 K and with a layer spacing of 18 Å. Visualization of simulation results in the 1.0 CH4 per unit cell system indicated that the methane molecule is nested inside the hexagonal cavities of the clay surface oxygen due to the fact that the clay surfaces include neutral regions that are hydrophobic. The calculated CH4-O coordination number of around 20 for 0.5 and 1.0 CH4 per unit cell systems is consistent with previous simulations. Our simulations show that water in potassium montmorillonite formed stretched hydrogen bonds with either the clay surface or other water molecules.

Zhang, Junfang; Choi, S. K.

2006-09-01

58

Preparation and properties of montmorillonite modified asphalts  

Microsoft Academic Search

Modified asphalts were prepared by melt blending with different contents of montmorillonite (MMT) and organomodified montmorillonite (OMMT). The X-ray diffraction (XRD) results show that the MMT modified asphalt may form an intercalated structure, whereas the OMMT modified asphalt may form an exfoliated structure. The addition of MMT and OMMT to asphalt increases both the softening point and viscosity of the

Jianying Yu; Xuan Zeng; Shaopeng Wu; Lin Wang; Gang Liu

2007-01-01

59

Influence of ambient conditions on the ageing behaviour of plasma-treated PET surfaces  

Microsoft Academic Search

Plasma treatment is often used to modify the surface properties of polymer films, since it offers numerous advantages over the conventional surface modification techniques. However, plasma-treated polymer films have a tendency to revert back to the untreated state (ageing process). Therefore, the stability of plasma induced changes on polymer surfaces over a desired period of time is a very important

N. De Geyter; R. Morent; C. Leys

2008-01-01

60

Bone regeneration performance of surface-treated porous titanium.  

PubMed

The large surface area of highly porous titanium structures produced by additive manufacturing can be modified using biofunctionalizing surface treatments to improve the bone regeneration performance of these otherwise bioinert biomaterials. In this longitudinal study, we applied and compared three types of biofunctionalizing surface treatments, namely acid-alkali (AcAl), alkali-acid-heat treatment (AlAcH), and anodizing-heat treatment (AnH). The effects of treatments on apatite forming ability, cell attachment, cell proliferation, osteogenic gene expression, bone regeneration, biomechanical stability, and bone-biomaterial contact were evaluated using apatite forming ability test, cell culture assays, and animal experiments. It was found that AcAl and AnH work through completely different routes. While AcAl improved the apatite forming ability of as-manufactured (AsM) specimens, it did not have any positive effect on cell attachment, cell proliferation, and osteogenic gene expression. In contrast, AnH did not improve the apatite forming ability of AsM specimens but showed significantly better cell attachment, cell proliferation, and expression of osteogenic markers. The performance of AlAcH in terms of apatite forming ability and cell response was in between both extremes of AnH and AsM. AcAl resulted in significantly larger volumes of newly formed bone within the pores of the scaffold as compared to AnH. Interestingly, larger volumes of regenerated bone did not translate into improved biomechanical stability as AnH exhibited significantly better biomechanical stability as compared to AcAl suggesting that the beneficial effects of cell-nanotopography modulations somehow surpassed the benefits of improved apatite forming ability. In conclusion, the applied surface treatments have considerable effects on apatite forming ability, cell attachment, cell proliferation, and bone ingrowth of the studied biomaterials. The relationship between these properties and the bone-implant biomechanics is, however, not trivial. PMID:24811260

Amin Yavari, Saber; van der Stok, Johan; Chai, Yoke Chin; Wauthle, Ruben; Tahmasebi Birgani, Zeinab; Habibovic, Pamela; Mulier, Michiel; Schrooten, Jan; Weinans, Harrie; Zadpoor, Amir Abbas

2014-08-01

61

ESCA study of alkali-treated coal surfaces  

SciTech Connect

The surface interactions of alkali with coal and mineral matter have been studied by ESCA to establish a basis for predicting the relative reactivity of alkali with sulfur during coal beneficiation processes. The speciation of sulfur in several coals doped with various alkali salts was determined and quantified following heating of the samples to 375/degree/C in air or N/sub 2/ and after washing them with water. Organic and pyritic sulfur react with the alkali cation when heated, after which the sulfide or oxidized sulfur product can be washed from the coal. The extent of reaction between the alkali salt and sulfur is governed by the size of the cation and the electronic properties of the anion; larger alkali cations are more reactive, as are anions with stronger nucleophilic properties.

Baltrus, J.P.; Diehl, J.R.; D'Este, J.R.

1988-01-01

62

RESIDUAL STRESS ASSESSMENT IN SURFACE-TREATED NICKEL-BASE SUPERALLOYS  

Microsoft Academic Search

Experimental results are presented to illustrate that there exists a unique window of opportunity for eddy current NDE of residual stress in surface-treated nickel-base superalloys. In light of its frequency-dependent penetration depth, the measurement of eddy current conductivity has been suggested as a possible means to allow the nondestructive evaluation of subsurface residual stresses in surface-treated components. This technique is

M. P. Blodgett; P. B. Nagy

63

Helmholtz Fermi surface harmonics: an efficient approach for treating anisotropic problems involving Fermi surface integrals  

NASA Astrophysics Data System (ADS)

We present a new efficient numerical approach for representing anisotropic physical quantities and/or matrix elements defined on the Fermi surface (FS) of metallic materials. The method introduces a set of numerically calculated generalized orthonormal functions which are the solutions of the Helmholtz equation defined on the FS. Noteworthy, many properties of our proposed basis set are also shared by the FS harmonics introduced by Philip B Allen (1976 Phys. Rev. B 13 1416), proposed to be constructed as polynomials of the cartesian components of the electronic velocity. The main motivation of both approaches is identical, to handle anisotropic problems efficiently. However, in our approach the basis set is defined as the eigenfunctions of a differential operator and several desirable properties are introduced by construction. The method is demonstrated to be very robust in handling problems with any crystal structure or topology of the FS, and the periodicity of the reciprocal space is treated as a boundary condition for our Helmholtz equation. We illustrate the method by analysing the free-electron-like lithium (Li), sodium (Na), copper (Cu), lead (Pb), tungsten (W) and magnesium diboride (MgB_{2}).

Eiguren, Asier; Gurtubay, Idoia G.

2014-06-01

64

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

PubMed

Anionic surfactant modified Fe-pillared montmorillonites were prepared by Fe-hydrate solution and sodium dodecyl sulfate (SDS) solution. These organo-inorgano complex montmorillonites were divided into three types (CM1, CM2 and CM3) depending on different intercalation processes. X-ray diffraction spectra, the Fourier transform infrared (FTIR) spectra were used to analyze the structure of the raw and modified montmorillonites. X-ray photoelectron spectra of the samples have been studied to determine spectral characteristics to allow the identification of Fe(III) hydroxide. The specific surface area of the host montmorillonite (M0) is 73.2m(2)/g, while for the modified montmorillonites it is 114.0m(2)/g, 117.2m(2)/g, and 115.8m(2)/g, respectively. The mesopore volumes of the montmorillonites decrease after modification. Ions of copper and cobalt were selected as adsorbates to evaluate the adsorption performance of each montmorillonite. The adsorption data was analyzed by both Freundlich and Langmuir isotherm models and the data was well fit by the Langmuir isotherm model. The adsorption was efficient and significantly influenced by metal speciation, metal concentration, contact time, and pH. Higher adsorption capacity of the modified montmorillonites were obtained at pH 5-6. The results of desorption indicated that the metal ions were covalently bound to the modified montmorillonites. PMID:19748730

Li, Shu-Zhen; Wu, Ping-Xiao

2010-01-15

65

Montmorillonite: a multifunctional mineral catalyst for the prebiological formation of phosphate esters.  

PubMed

Reaction of diiminosuccinonitrile (DISN) with 3'-AMP in the presence of alkali- and alkaline earth-montmorillonites results in the formation of 2',3'-cAMP in aqueous solution. Little or no 2', 3'-cAMP is produced when metal ion concentrations equivalent to that of the metal ion associated with the homoionic clays are used instead of mobntmorillionite. Yields comparable to those obtained with DISN are obtained when diaminomaleonitrile (DAMN) is used in place of DISN as the condensing agent. DAMN, a compound which is more stable than DISN in aqueous solution, is oxidized to DISN on the surface of the clay by Fe+3 in the clay lattice. DISN, the true condensing agent, is thus generated in the presence of the bound 3'-AMP on the montmorillonite surface. The montmorillonite catalyzes the DISN-mediated formation of 2', 3'-cAMP and this product, which binds much less strongly than does the 3'-AMP, is desorbed from the clay surface. This research established that the montmorillonite performs four different functions in its role as catalyst: (1) Binding one of the substrate molecules (3'-AMP) (2) Activating the second substrate (DAMN) (3) Catalyzing the formation of 2', 3'-cAMP (4) Releasing the reaction product so another substrate molecules can bind to the montmorillonite. PMID:3368214

Ferris, J P; Huang, C H; Hagan, W J

1988-01-01

66

Montmorillonite: A multifunctional mineral catalyst for the prebiological formation of phosphate esters  

NASA Astrophysics Data System (ADS)

Reaction of diiminosuccinonitrile (DISN) with 3'-AMP in the presence of alkali- and alkaline earth-montmorillonites results in the formation of 2',3'-cAMP in aqueous solution. Little or no 2',3'-cAMP is produced when metal ion concentrations equivalent to that of the metal ion associated with the homoionic clays are used instead of mobntmorillionite. Yields comparable to those obtained with DISN are obtained when diaminomaleonitrile (DAMN) is used in place of DISN as the condensing agent. DAMN, a compound which is more stable than DISN in aqueous solution, is oxidized to DISN on the surface of the clay by Fe+3 in the clay lattice. DISN, the true condensing agent, is thus generated in the presence of the bound 3'-AMP on the montmorillonite surface. The montmorillonite catalyzes the DISN-mediated formation of 2',3'-cAMP and this product, which binds much less strongly than does the 3'-AMP, is desorbed from the clay surface. This research established that the montmorillonite performs four different functions in its role as catalyst: (1) Binding one of the substrate molecules (3'-AMP) (2) Activating the second substrate (DAMN) (3) Catalyzing the formation of 2',3'-cAMP (4) Releasing the reaction product so another substrate molecules can bind to the montmorillonite.

Ferris, James P.; Huang, Chun-Hsien; Hagan, William J.

1988-03-01

67

STRUCTURAL AND OPTICAL CHARACTERIZATION OF PMMA SURFACE TREATED IN LOW POWER NITROGEN AND OXYGEN RF PLASMAS  

Microsoft Academic Search

Oxygen and nitrogen plasmas are used to modify the Poly methyl methacrylate (PMMA) polymer surface and results are compared. Samples are treated in a plane parallel capacitively coupled RF discharge at 13.56 MHz frequency and 25 W power for different times. The modified surfaces are characterized by Fourier transform infrared spectrometer (ATR-FTIR) and atomic force microscopic (AFM) micrographs. By the

D. DORRANIAN; Z. ABEDINIa; A. HOJABRIa; M. GHORANNEVISS

68

Controlled Release of Agrochemicals Intercalated into Montmorillonite Interlayer Space  

PubMed Central

Periodic application of agrochemicals has led to high cost of production and serious environmental pollution. In this study, the ability of montmorillonite (MMT) clay to act as a controlled release carrier for model agrochemical molecules has been investigated. Urea was loaded into MMT by a simple immersion technique while loading of metalaxyl was achieved by a rotary evaporation method. The successful incorporation of the agrochemicals into the interlayer space of MMT was confirmed by several techniques, such as, significant expansion of the interlayer space, reduction of Barrett-Joyner-Halenda (BJH) pore volumes and Brunauer-Emmett-Teller (BET) surface areas, and appearance of urea and metalaxyl characteristic bands on the Fourier-transform infrared spectra of the urea loaded montmorillonite (UMMT) and metalaxyl loaded montmorillonite (RMMT) complexes. Controlled release of the trapped molecules from the matrix was done in water and in the soil. The results reveal slow and sustained release behaviour for UMMT for a period of 10 days in soil. For a period of 30 days, MMT delayed the release of metalaxyl in soil by more than 6 times. It is evident that MMT could be used to improve the efficiency of urea and metalaxyl delivery in the soil. PMID:24696655

2014-01-01

69

Investigation of Reoxidation and Phosphorus Behavior in HF-Treated Heavily Doped Silicon Surfaces  

NASA Astrophysics Data System (ADS)

The thermally stimulated desorption (TSD) from aqueous HF-treated heavily phosphorus-doped Si(100) and polycrystalline Si surfaces was studied by Auger electron spectroscopy (AES), electron energy loss spectroscopy (EELS) and mass spectroscopy. Desorption analyses indicated that reoxidation takes place slightly, to the same extent in the doped Si(100) and polycrystalline Si surfaces owing to hydrogen desorption. Moreover, a large quantity of phosphorus segregates to the top few layers in the desorption process of the oxides. It was clarified that the HF-treated polycrystalline silicon surface is terminated by hydrogen and resists oxidation similarly to a single-crystal one.

Kamiura, Yoshitomo; Mizokawa, Yusuke; Iida, Makio; Isobe, Yoshihiko; Kawamoto, Kazunori

1993-11-01

70

Detection of the adhesion events of dispersed single montmorillonite particles at a static mercury drop electrode  

Microsoft Academic Search

Montmorillonite particles suspended in aqueous electrolyte solutions give rise to adhesion events that can be detected by chronoamperometry using a static mercury drop electrode. The potential dependence of the adhesion signals allows determining the surface charge density of the adhering particle surfaces.

Fritz Scholz; Dirk Hellberg; Falk Harnisch; Anke Hummel; Ulrich Hasse

2004-01-01

71

Alteration of biotite by suspended montmorillonite  

Microsoft Academic Search

Summary Alteration of biotite flakes which were placed in suspensions of Na+ — and Mg++-montmorillonite for different contact periods at two different temperatures, were followed using X-ray and petrographic microscope.

Sh. I. Abdel-Aal; H. Bergseth

1975-01-01

72

Textural and hydration properties of a synthetic montmorillonite compared with a natural Na-exchanged clay analogue  

Microsoft Academic Search

An aluminous montmorillonite has been synthesized at hydrothermal conditions (623K, 120MPa) and compared to the natural Na-exchanged Wyoming montmorillonite (Na-SWy2). The synthetic product is characterized by a high cation exchange capacity (83meq\\/100g) and ethylene glycol specific surface area (764m2\\/g) similar to Na-SWy2 but with a higher purity with one crystalline phase. Compacted smectite samples were percolated with water by using

Lydie Le Forestier; Fabrice Muller; Frédéric Villieras; Manuel Pelletier

2010-01-01

73

Indium tin oxide exhibiting high poly-crystallinity on oxygen plasma-treated polyethylene terephthalate surface  

PubMed Central

Low-resistivity indium tin oxide [ITO] film was successfully deposited on oxygen plasma-treated polyethylene terephthalate [PET] surfaces at room temperature. X-ray diffraction [XRD] measurements demonstrated that the film deposited on the PET surface that had not been treated with oxygen plasma had an amorphous structure. In contrast, after the low-power oxygen plasma treatment of the PET surface, the ITO film deposited on the PET surface had a poly-crystalline structure due to interactions between electric dipoles on the PET surface and electric dipoles in the ITO film. The minimum resistivity of the poly-crystalline ITO was about 3.6 times lower than that of the amorphous ITO film. In addition, we found that the resistivity of ITO film is proportional to the intensity of the (400) line in the film's XRD spectra. PMID:22330878

2012-01-01

74

Evaluation of stability of surface-treated mini-implants in diabetic rabbits.  

PubMed

Introduction. The purpose of this study was to investigate effects of surface treatment of mini-implants in diabetes-induced rabbits by comparing osseointegration around mini-implants. Methods. Twelve New Zealand white rabbits were divided into two groups (alloxan-induced diabetic group and control group). A total of 48 mini-implants were placed after four weeks of diabetic induction. 24 mini-implants were surface-treated with SLA (sandblasted with large grit, and acid etched) and the remaining 24 mini-implants had smooth surfaces. Four weeks after placement, 32 mini-implants were removed from 4 control and 4 diabetic rabbits. Insertion and removal torques were measured. The remaining 16 mini-implants from the two groups were histomorphometrically analyzed. Results. Maximum insertion torque showed no difference between diabetic and control groups, but total insertion energy was higher in control group. In surface-treated mini-implants, maximum removal torque was higher in both diabetic and control groups. Bone-implant contact (BIC) was increased in the control group when compared to the diabetic group. Surface-treated group had higher BIC than smooth surface group in both control and diabetic groups. However, there was no significantly statistical difference. Conclusions. Type 1 diabetes mellitus and surface treatment method of mini-implant affected primary stability of mini-implants. In addition, the use of orthodontic mini-implants in a diabetic patient is likely to show results similar to the healthy patient. PMID:24971093

Oh, Nam-Hee; Kim, Eun-Young; Paek, Janghyun; Kook, Yoon-Ah; Jeong, Do-Min; Cho, Il-Sik; Nelson, Gerald

2014-01-01

75

Evaluation of Stability of Surface-Treated Mini-Implants in Diabetic Rabbits  

PubMed Central

Introduction. The purpose of this study was to investigate effects of surface treatment of mini-implants in diabetes-induced rabbits by comparing osseointegration around mini-implants. Methods. Twelve New Zealand white rabbits were divided into two groups (alloxan-induced diabetic group and control group). A total of 48 mini-implants were placed after four weeks of diabetic induction. 24 mini-implants were surface-treated with SLA (sandblasted with large grit, and acid etched) and the remaining 24 mini-implants had smooth surfaces. Four weeks after placement, 32 mini-implants were removed from 4 control and 4 diabetic rabbits. Insertion and removal torques were measured. The remaining 16 mini-implants from the two groups were histomorphometrically analyzed. Results. Maximum insertion torque showed no difference between diabetic and control groups, but total insertion energy was higher in control group. In surface-treated mini-implants, maximum removal torque was higher in both diabetic and control groups. Bone-implant contact (BIC) was increased in the control group when compared to the diabetic group. Surface-treated group had higher BIC than smooth surface group in both control and diabetic groups. However, there was no significantly statistical difference. Conclusions. Type 1 diabetes mellitus and surface treatment method of mini-implant affected primary stability of mini-implants. In addition, the use of orthodontic mini-implants in a diabetic patient is likely to show results similar to the healthy patient. PMID:24971093

Oh, Nam-Hee; Kim, Eun-Young; Paek, Janghyun; Kook, Yoon-Ah; Jeong, Do-Min; Cho, Il-Sik; Nelson, Gerald

2014-01-01

76

Investigation of Reoxidation and Phosphorus Behavior in HF-Treated Heavily Doped Silicon Surfaces  

Microsoft Academic Search

The thermally stimulated desorption (TSD) from aqueous HF-treated heavily phosphorus-doped Si(100) and polycrystalline Si surfaces was studied by Auger electron spectroscopy (AES), electron energy loss spectroscopy (EELS) and mass spectroscopy. Desorption analyses indicated that reoxidation takes place slightly, to the same extent in the doped Si(100) and polycrystalline Si surfaces owing to hydrogen desorption. Moreover, a large quantity of phosphorus

Yoshitomo Kamiura; Yusuke Mizokawa; Makio Iida; Yoshihiko Isobe; Kazunori Kawamoto

1993-01-01

77

Effect of washing on surface free energy of polystyrene plate treated by RF atmospheric pressure plasma  

Microsoft Academic Search

Low-temperature plasma can be generated at one atmospheric pressure by applying a radio frequency (RF, 13.56MHz) voltage between two parallel electrodes, and used for thin film deposition, chemical synthesis, etching, surface treatments and sterilization. The surface properties of a general purpose polystyrene (GPPS) plate treated with RF atmospheric pressure plasma (APP) can be modified by subsequent washing. In this paper,

Yan Zhao; Shen Tang; Sung-Woon Myung; Na Lu; Ho-Suk Choi

2006-01-01

78

Mechanism of stabilization of Na-montmorillonite clay with cement kiln dust  

Microsoft Academic Search

A study of the physicochemical interaction of a high free lime (CaO) content cement kiln dust (CKD) with expansive Na-montmorillonite clay is presented. Moist compacted specimens of the CKD-treated clay, the clay alone, the CKD alone, and (for comparison) the clay treated with 7% CaO were each cured for periods up to 90 days and examined by XRD, TGA, and SEM

Sulapha Peethamparan; Jan Olek; Sidney Diamond

2009-01-01

79

Thermal Stability and Flammability of Polypropylene/Montmorillonite Composites  

NASA Astrophysics Data System (ADS)

Smectite clays, such as montmorillonite, are a valuable class of mineral for industrial applications because of their high aspect ratio, plate morphology, and intercalative capacity. After preparation, smectite clays may be used as a nano-scalled inorganic fillers to prepare polymer/layered silicate nanocomposites, which has unique properties such as improved strength, modulus, heat resistance, surface scratch resistance and good barrier properties, at very low filler. In the present work, polypropylene/montmorillonite (PP/MMT) composites were prepared and their thermal stability and flammability were investigated. Regardless of the micro-dispersed or submicro-dispersed structure, the composites exhibit higher thermal stability and considerably reduced peak heat release rate (PHRR). It is likely caused by the physical-chemical adsorption of the volatile degradation products on the silicates. On the other hand, the addition of MMT can catalyze the initial decomposition of PP matrix and accelerate the ignition of PP matrix in combustion. It has been observed that a ceramic-like char formed on the surface of the composites during burning test. The characterization of the char surface before ignition indicates that it is an inorganic-rich surface, which provided a better barrier property, leading to the improvement of the thermal stability and reduction of flammability of the composites.

Yang, Ming-Shu; Qin, Huai-Li; Zhang, Shi-Min; Han, Charles C.

2004-03-01

80

Cellular Performance Comparison of Biomimetic Calcium Phosphate Coating and Alkaline-Treated Titanium Surface  

PubMed Central

The influence of biomimetic calcium phosphate coating on osteoblasts behavior in vitro is not well established yet. In this study, we investigated the behavior of osteoblastic rat osteosarcoma 17/2.8 cells (ROS17/2.8) on two groups of biomaterial surfaces: alkaline-treated titanium surface (ATT) and biomimetic calcium phosphate coated ATT (CaP). The cell attachment, proliferation, differentiation, and morphology on these surfaces were extensively evaluated to reveal the impact of substrate surface on osteoblastic cell responses. It was found that the ROS17/2.8 cells cultured on the ATT surface had higher attachment and proliferation rates compared to those on the CaP surface. Our results also showed that the calcium phosphate coatings generated in this work have an inhibiting effect on osteoblast adhesion and further influenced the proliferation and differentiation of osteoblast compared to the ATT surface in vitro. Cells on the ATT surface also exhibited a higher alkaline phosphatase activity than on the CaP surface after two weeks of culture. Immunofluorescence staining and scanning electron microscopy results showed that the cells adhered and spread faster on the ATT surface than on the CaP surface. These results collectively suggested that substrate surface properties directly influence cell adhesion on different biomaterials, which would result in further influence on the cell proliferation and differentiation. PMID:24455730

Wei, Mei

2013-01-01

81

Cytotoxicity of Ni from Surface-Treated Porous Nitinol (PNT) on Osteoblast Cells  

NASA Astrophysics Data System (ADS)

The leaching of nickel from the surface of porous Nitinol (PNT) is mainly dependent on its surface characteristics, which can be controlled by appropriate surface treatments. In this investigation, PNT was subjected to two surface treatments, namely, water-boiling and dry-heating passivations. Phosphate buffer saline (PBS) solutions obtained from cyclic potentiodynamic polarization tests on PNT were employed to assess the cytotoxicity of Ni contained therein on osteoblast cells by Sulforhodamine B (SRB) assay. In addition, similar concentrations of Ni were added exogenously to cell culture media to determine cytotoxic effects on osteoblast cells. The morphologies of the untreated and the surface-treated PNTs were examined using SEM and AFM. Furthermore, growth of human osteoblast cells was observed on the PNT surfaces.

Pulletikurthi, C.; Munroe, N.; Gill, P.; Pandya, S.; Persaud, D.; Haider, W.; Iyer, K.; McGoron, A.

2011-07-01

82

Role of surface fimbriae (fibrils) in the adsorption of Actinomyces species to saliva-treated hydroxyapatite surfaces.  

PubMed

We studied the adsorption, morphological, and serological characteristics of selected Actinomyces and related species. Evaluation of uranyl acetate-stained cells by electron microscopy revealed wide variations among strains in the frequency of surface fimbriae. These variations did not always correlate with the percent adsorption to saliva-treated hydroxyapatite of the various Actinomyces strains. However, two strains of Rothia dentocariosa possessing no surface fimbriae and five strains of A. israelii possessing very few surface fimbriae exhibited feeble adsorption to saliva-treated hydroxyapatite. Although the calculated number of adsorption sites on saliva-treated hydroxypatite did not vary widely among the strains tested, significant differences were observed in the affinities calculated for some species or serotypes. The mean affinities for strains of A. viscosus serotype 2 and A. naeslundii serotype 3 were similar, and these strains adsorbed well to saliva-treated hydroxyapatite. The mean adsorption and affinity for the A. naeslundii strain serotype 1 and all strains of A. israelii tested were significantly less than those determined for the A. viscosus serotype 2 or A. naeslundii serotype 3 strains. Adsorption inhibition activity of antiserum to strain T14V, previously shown to be solely related to antibodies in immune serum directed against the VA1 fimbria (fibril) antigen, was removed by preadsorption of the antiserum with most A. viscosus and A. naelundii strains, but not with A. israelii strains. This suggests some cross-reactivity among strains of A. viscosus and A. naeslundii but not A. israelii. Adsorption to saliva-treated hydroxyapatite of all A. viscosus and A. naeslundii strains tested was strongly inhibited by fimbriae isolated from A. viscosus strain T14V. Collectively, these data suggest that the adsorption of certain A. viscosus and A. naeslundii strains is mediated by surface fimbriae, many of which appear serologically cross-reactive with strain T14V fimbriae. PMID:6169645

Clark, W B; Webb, E L; Wheeler, T T; Fischlschweiger, W; Birdsell, D C; Mansheim, B J

1981-09-01

83

Role of Surface Fimbriae (Fibrils) in the Adsorption of Actinomyces Species to Saliva-Treated Hydroxyapatite Surfaces  

PubMed Central

We studied the adsorption, morphological, and serological characteristics of selected Actinomyces and related species. Evaluation of uranyl acetate-stained cells by electron microscopy revealed wide variations among strains in the frequency of surface fimbriae. These variations did not always correlate with the percent adsorption to saliva-treated hydroxyapatite of the various Actinomyces strains. However, two strains of Rothia dentocariosa possessing no surface fimbriae and five strains of A. israelii possessing very few surface fimbriae exhibited feeble adsorption to saliva-treated hydroxyapatite. Although the calculated number of adsorption sites on saliva-treated hydroxypatite did not vary widely among the strains tested, significant differences were observed in the affinities calculated for some species or serotypes. The mean affinities for strains of A. viscosus serotype 2 and A. naeslundii serotype 3 were similar, and these strains adsorbed well to saliva-treated hydroxyapatite. The mean adsorption and affinity for the A. naeslundii strain serotype 1 and all strains of A. israelii tested were significantly less than those determined for the A. viscosus serotype 2 or A. naeslundii serotype 3 strains. Adsorption inhibition activity of antiserum to strain T14V, previously shown to be solely related to antibodies in immune serum directed against the VA1 fimbria (fibril) antigen, was removed by preadsorption of the antiserum with most A. viscosus and A. naelundii strains, but not with A. israelii strains. This suggests some cross-reactivity among strains of A. viscosus and A. naeslundii but not A. israelii. Adsorption to saliva-treated hydroxyapatite of all A. viscosus and A. naeslundii strains tested was strongly inhibited by fimbriae isolated from A. viscosus strain T14V. Collectively, these data suggest that the adsorption of certain A. viscosus and A. naeslundii strains is mediated by surface fimbriae, many of which appear serologically cross-reactive with strain T14V fimbriae. Images PMID:6169645

Clark, William B.; Webb, Eldon L.; Wheeler, Timothy T.; Fischlschweiger, Werner; Birdsell, Dale C.; Mansheim, Bernard J.

1981-01-01

84

Adsorption of Salmonella enteritidis by cetylpyridinium-exchanged montmorillonite clays  

Microsoft Academic Search

Recent experiments in our laboratory have suggested that certain montmorillonite clays, when exchanged with the cationic surfactant cetylpyridinium (CP), may be useful in removing bacteria from aqueous solution. During an initial study, screening various CP-exchanged products for potential antibacterial activity, three CP-exchanged clays — CP*AAM (acid-activated montmorillonite), CP*STx-1 (Ca++-montmorillonite), and CP*SWy-2 (Na+-montmorillonite), proved to be the most effective. Binding studies

P. Herrera; R. C. Burghardt; T. D. Phillips

2000-01-01

85

Driving force for the hydration of the swelling clays: case of montmorillonites saturated with alkaline-earth cations.  

PubMed

Important structural modifications occur in swelling clays upon water adsorption. The multi-scale evolution of the swelling clay structure is usually evidenced by various experimental techniques. However, the driving force behind such phenomena is still not thoroughly understood. It appears strongly dependent on the nature of the interlayer cation. In the case of montmorillonites saturated with alkaline cations, it was inferred that the compensating cation or the layer surface could control the hydration process and thus the opening of the interlayer space, depending on the nature of the interlayer cation. In the present study, emphasis is put on the impact of divalent alkaline-earth cations compensating the layer charge in montmorillonites. Since no experimental technique offers the possibility of directly determining the hydration contributions related to interlayer cations and layer surfaces, an approach based on the combination of electrostatic calculations and immersion data is developed here, as already validated in the case of montmorillonites saturated by alkaline cations. This methodology allows to estimate the hydration energy for divalent interlayer cations and therefore to shed a new light on the driving force for hydration process occurring in montmorillonites saturated with alkaline-earth cations. Firstly, the surface energy values obtained from the electrostatic calculations based on the Electronegativity Equalization Method vary from 450 mJ m(-2) for Mg-montmorillonite to 1100 mJ m(-2) for Ba-montmorillonite. Secondly, considering both the hydration energy for cations and layer surfaces, the driving force for the hydration of alkaline-earth saturated montmorillonites can be attributed to the interlayer cation in the case of Mg-, Ca-, Sr-montmorillonites and to the interlayer surface in the case of Ba-montmorillonites. These results explain the differences in behaviour upon water adsorption as a function of the nature of the interlayer cation, thereby allowing the macroscopic swelling trends to be better understood. The knowledge of hydration processes occurring in homoionic montmorillonites saturated with both the alkaline and the alkaline-earth cations may be of great importance to explain the behaviour of natural clay samples where mixtures of the two types of interlayer cation are present and also provides valuable information on the cation exchange occurring in the swelling clays. PMID:23352873

Salles, Fabrice; Douillard, Jean-Marc; Bildstein, Olivier; Gaudin, Cedric; Prelot, Benedicte; Zajac, Jerzy; Van Damme, Henri

2013-04-01

86

Oxidation characteristics of the electron beam surface-treated Alloy 617 in high temperature helium environments  

NASA Astrophysics Data System (ADS)

The oxidation characteristics of the electron beam surface-treated Alloy 617, which has an Al-rich surface layer, were evaluated in high temperature helium environments. Isothermal oxidation tests were performed in helium (99.999% purity) and VHTR-helium (helium of prototypical VHTR chemistry containing impurities like CO, CO2, CH4, and H2) environments at 900 °C for up to 1000 h. The surface-treated Alloy 617 showed an initial transient oxidation stage followed by the steady-state oxidation in all test environments. In addition, the steady-state oxidation kinetics of the surface-treated Alloy 617 was 2-order of magnitude lower than that of the as-received Alloy 617 in both helium environments as well as in air. The improvement in oxidation resistance was primarily due to the formation of the protective Al2O3 layer on the surface. The weight gain was larger in the order of air, helium, and VHTR-helium, while the parabolic rate constants (kp) at steady-state were similar for all test environments. In both helium environments, the oxide structure consisted of the outer transition Al2O3 with a small amount of Cr2O3 and inner columnar structured Al2O3 without an internal oxide. In the VHTR-helium environment, where the impurities were added to helium, the initial transient oxidation increased but the steady state kinetics was not affected.

Lee, Ho Jung; Sah, Injin; Kim, Donghoon; Kim, Hyunmyung; Jang, Changheui

2015-01-01

87

Influence of ambient conditions on the ageing behaviour of plasma-treated PET surfaces  

NASA Astrophysics Data System (ADS)

Plasma treatment is often used to modify the surface properties of polymer films, since it offers numerous advantages over the conventional surface modification techniques. However, plasma-treated polymer films have a tendency to revert back to the untreated state (ageing process). Therefore, the stability of plasma induced changes on polymer surfaces over a desired period of time is a very important issue. The objective of this study is to examine the effect of storage conditions (relative humidity, temperature and pressure) on the ageing behaviour in air of plasma-treated polyethylene terephthalate (PET) films. Plasma treatment is performed using a dielectric barrier discharge (DBD) operating in air at medium pressure (5.0 kPa). Results show that the ageing process can be suppressed by storing the PET films at low temperature or by decreasing the relative humidity of the surrounding air. In this paper, it is also shown that decreasing pressure has no influence on the ageing process.

De Geyter, N.; Morent, R.; Leys, C.

2008-06-01

88

Fibroblastic response and surface characterization of O(2)-plasma-treated thermoplastic polyetherurethane.  

PubMed

Injection-molded samples of thermoplastic polyetherurethane (TPU) were treated with low-temperature oxygen plasma for different processing times in order to enhance cellular attachment for a gastric implant. Its effects were investigated by contact angle measurement, surface topography, cytotoxicity and cell colonization tests. No significant changes were found in the surface roughness of plasma treatment with plasma treatment time of less than 5 min. Longer treatment showed significantly higher surface roughness. It seems that there was a link between the changes in contact angle and enhanced cell growth on the treated surface, although only for the range up to plasma treatment times of 3 min. Prolonged treatment times did not cause any major changes in the water contact angle, but strongly improved the number of growing cells on the surface. Plasma treatment for 3-7 min led to a twofold increase in the number of cells compared to untreated samples and did not significantly alter the WST-1 nor worsened the lactate dehydrogenase activity compared to the control. Thus, it appears that O(2) plasma treatment is a suitable surface modification method for a gastric implant made of TPU in order to improve surface cell attachment where 3-7 min is the recommended treatment time. PMID:20208128

Schlicht, Henning; Haugen, Håvard J; Sabetrasekh, Roya; Wintermantel, Erich

2010-04-01

89

Surface functionalization, oxygen depth profiles, and wetting behavior of PET treated with different nitrogen plasmas.  

PubMed

Polyethylene terephthalate (PET) plates have been exposed to different nitrogen containing plasmas with the purpose of incorporating nitrogen functional groups on its surface. Results with a dielectric barrier discharge (DBD) at atmospheric pressure and a microwave discharge (MW) at reduced pressure and those using an atom source working under ultrahigh vacuum conditions have been compared for N(2) and mixtures Ar + NH(3) as plasma gases. The functional groups have been monitored by X-ray Photoemission Spectroscopy (XPS). Nondestructive oxygen and carbon depth profiles for the plasma treated and one month aged samples have been determined by means of the nondestructive Tougaard's method of XPS background analysis. The surface topography of the treated samples has been examined by Atomic Force Microscopy (AFM), while the surface tension has been determined by measuring the static contact angles of water and iodomethane. It has been found that the DBD with a mixture of Ar+NH(3) is the most efficient treatment for nitrogen and amine group functionalization as determined by derivatization by reaction with chlorobenzaldehyde. It is also realized that the nitrogen functional groups do not contribute significantly to the observed increase in surface tension of plasma treated PET. PMID:20423118

López-Santos, Carmen; Yubero, Francisco; Cotrino, José; González-Elipe, Agustín R

2010-04-01

90

Stability of the hydrophilic and superhydrophobic properties of oxygen plasma-treated poly(tetrafluoroethylene) surfaces.  

PubMed

Poly(tetrafluoroethylene) (PTFE) materials were exposed to low and high-energy oxygen plasma, and the stability of the materials' surface was evaluated using contact angle, surface roughness, and surface chemistry characterizations. Lower-energy oxygen plasma treatments exhibited hydrophilic behavior with contact angles as low as 87°, and the higher-energy oxygen plasma treatments exhibited superhydrophobic behavior with contact angles as high as 151°. The wettability of all the treated samples as stored in air and in water was found to be stable in time as evidenced by the statistically insignificant differences in the advancing, receding, and hysteresis contact angles. Low contact angle hysteresis (?H<5°) and low sliding angle (??4°) were exhibited by the superhydrophobic surface. The surface morphology was found to be responsible for the changes in the wettability of the PTFE samples since (1) there was an increase in the surface rms roughness as the plasma discharge energy was increased, and (2) there were no significant changes in the observed group frequencies of the FT-IR spectra of the treated PTFE from the untreated PTFE. PMID:23403114

Salapare, Hernando S; Guittard, Frédéric; Noblin, Xavier; Taffin de Givenchy, Elisabeth; Celestini, Franck; Ramos, Henry J

2013-04-15

91

Hydrophobic to hydrophilic transition of HF-treated Si surface during Langmuir-Blodgett film deposition  

NASA Astrophysics Data System (ADS)

HF-treated Si surface, which is hydrophobic in nature and quite stable in air and inside pure water, can become completely hydrophilic during nickel arachidate Langmuir-Blodgett film growth. Such transition is clearly evident from the structures of films deposited by different number of strokes and can be understood by considering partial oxidation of Si surface inside subphase water and further or complete oxidation in air, in presence of Ni head-groups. Attached Ni head-groups weaken the nearby Si-Si covalent bonding and easily oxidize those Si atoms. Depending upon the amount of those head-groups and its distribution, oxidation or transition can even complete.

Bal, J. K.; Kundu, S.; Hazra, S.

2010-11-01

92

Problems in laser repair-welding a surface-treated tool steel  

Microsoft Academic Search

A research work is described on the development of defects in laser repair welding of a surface-treated tool steel. Repair welding tests were carried out on plasma-nitrided and on chrome-plated type 1.2738 steel plates. Welding defects in the chrome-plated samples were mainly due to chrome and oxygen overalloying of the weld metal, leading to extensive hot cracking. Cracks of the

M. Vedani; B. Previtali; G. M. Vimercati; A. Sanvito; G. Somaschini

2007-01-01

93

A Gas Grain Model of Interstellar Cloud Cores with Moment Equations to Treat Surface Chemistry  

NASA Astrophysics Data System (ADS)

We have built a gas-grain model of homogeneous cold cloud cores with time-independent physical conditions. In this model, we use the full OSU gas phase network, which involves 458 gas phase species and more than 4000 reactions, and treat it by rate equations which is totally deterministic. A small surface reaction network accounts for the productions of stable molecules such as H_2O, CO, CO_2, H_2CO, CH_3OH, NH_3 and CH_4. The surface reactions are treated by a hybrid method of moment equations (Barzel & Biham 2007) and rate equations: when the abundance of a surface species is lower than a specific threshold, say one per grain, we use the "stochastic" moment equations to simulate the evolution; when its abundance goes above this threshold, we use the rate equations. A continuity technique is utilized to secure a smooth transition between these two methods. We have run chemical simulations for a time up to 108 yr at three temperatures: 10 K, 15 K, and 20 K. The results will be compared with those generated from (1) a completely deterministic model that uses rate equations for both gas phase and grain surface chemistry, and (2) modified rate equations (Garrod 2008) that partially take into account the stochastic effect for surface reactions. At 10 K, our model results agree with the above two methods, while discrepancies appear at higher temperatures and smaller grain sizes.

Pei, Yezhe; Herbst, Eric

2010-06-01

94

Force Field for Mica-Type Silicates and Dynamics of Octadecylammonium Chains Grafted to Montmorillonite  

SciTech Connect

Layered silicates are widely used in nanotechnology and composite materials. We describe a force field for phyllosilicates (mica, montmorillonite, and pyrophyllite) on the basis of physically justified atomic charges, van der Waals parameters, vibrational constants, and distributions of charge defects in agreement with solid state {sup 29}Si NMR data. Unit cell parameters deviate only {approx}0.5% relative to experimental X-ray measurements and surface (respectively cleavage) energies deviate less than 10% from experimental data, including the partition between Coulomb and van der Waals contributions. Reproduction of surface energies facilitates quantitative simulations of hybrid interfaces with water, organics, and biomolecules for which accurate force fields are available. Parameters are consistent with the force fields PCFF (polymer consistent force field), CVFF (consistent valence force field), CHARMM (chemistry at Harvard macromolecular mechanics), and GROMACS (Groningen machine for chemical simulations). As an example of interest, we investigate the structure and dynamics of octadecylammonium montmorillonite ('C{sub 18}'-montmorillonite, cation exchange capacity = 91 mmol/100 g) by molecular dynamics simulation. The surfactant chains assemble essentially as a bilayer with minimal interpenetration within the gallery while the ammonium headgroups are hydrogen-bonded to cavities in the montmorillonite surface. In contrast to quaternary ammonium ions, no rearrangements on the surface have been observed (cavity crossing barrier >5 kcal/mol). The alkyl chains are in a liquidlike state with approximately 30% gauche conformations, in agreement with previous Fourier-transform infrared and solid-state NMR measurements. Computed X-ray diffraction patterns of sodium and C18-montmorillonite agree very well with X-ray patterns from experiment, and the computational model can assist in the assignment of complex reflections.

Heinz,H.; Koerner, H.; Anderson, K.; Vaia, R.; Farmer, B.

2005-01-01

95

The effects of some laser parameters on the surface and near surface region of laser treated cast iron cylinder bore  

NASA Astrophysics Data System (ADS)

The environmental and pollution materials emission standards in Europe are going to be more and more strict. In order to keep the standards, a large European automotive manufacturer makes a laser treatment on the cast iron cylinder bores of the V-engine blocks. Samples of laser treated cast iron cylinder bore with lamellar graphite were investigated. Four samples were treated with Nd-YAG laser and Yb-fiber laser sources in three different configurations. Microhardness measurements were made to evaluate the hardness profile of the treated layer. In order to evaluate the microstructure and grain size of the laser treated layer, scanning electron microscopic (SEM) images were taken in cross section with a SEM/focused ion beam (FIB) dual beam electron microscope. The opened graphite area percent were also determined by image analysis method on the surface after laser treatment with a SEM in backscattered electron (BSE) mode, because the outburned graphite holes are the oil reservoirs for lubrication during operating conditions of the engine.

Májlinger, K.; Szabó, P. J.

2010-07-01

96

Heterogeneous freezing of water droplets containing kaolinite and montmorillonite particles  

NASA Astrophysics Data System (ADS)

Clouds composed of both ice particles and supercooled liquid water droplets, known as mixed phase clouds, exist at temperatures above ~236 K. These clouds, which strongly impact climate, are very sensitive to the presence of particles that can catalyse ice particle formation. In this paper we describe experiments to determine at which temperatures water droplets containing clay mineral particles froze. Water droplets containing a known amount of clay mineral were supported on a hydrophobic surface and the temperatures at which individual droplets froze, as they were cooled down, was determined by optical microscopy. The hydrophobic substrate does not significantly catalyse ice formation in droplets and pure water droplets freeze around 236 K. Droplets containing kaolinite and montmorillonite nucleate ice at warmer temperatures. The mean nucleation temperature increases from close to or at the homogeneous nucleation limit (236 K) to 240.8 ± 0.6 K as the kaolinite concentration is increased from 0.005 wt% to 1 wt%. In contrast, ice always nucleates at 245.8 ± 0.6 K when water droplets are contaminated with montmorillonite independent of mineral concentration. These results highlight the importance of understanding the ice nucleating properties of individual minerals rather than complex mixtures of minerals found in natural dusts and so-called test dusts. In addition we parameterise the results in a form suitable for modelling studies and also derive contact angles for kaolinite.

Murray, Benjamin J.; Broadley, Sarah; Wilson, Theodore; Bull, Sophia; Wills, Rebecca

2010-05-01

97

Preparation and characterization of antibacterial silver/vermiculites and silver/montmorillonites  

NASA Astrophysics Data System (ADS)

The reason for the preparation and characterization of the novel antibacterial silver/vermiculites (Ag/V) together with the silver/montmorillonites (Ag/M) was that the information on the vermiculite structure change and stability of Ag/V in water as well as its effect on bacteria are sporadic. The vermiculite (V), (Si 3.02Al 0.98) IV (Mg 2.27Al 0.12Fe0.283+Fe0.052+Ti 0.07) VI O 10(OH) 2 Ca 0.09Na 0.21K 0.50 from West China and montmorillonite (M), (Si 3.96Al 0.04) IV (Al 1.20Fe0.343+Mg 0.42Ti 0.02) VI O 10 (OH) 2Ca 0.15Na 0.14K 0.08 from Ivan?ice (Czech Republic), fraction <0.4 ?m were the starting clay materials for sample preparation. The samples V1 and M1 were prepared via reaction of the V and M with the 0.01 mol L -1 AgNO 3 aqueous solution. The samples V2 and M2 were treated with the aqueous solution of AgNO 3 for two times. The cation exchange and reduced metallic silver on M1 and V1 evoked the specific surface area (SSA) diminution, the mean particle-size diameter extension and appearance of micropores with radius (<0.4 nm). Repeated silver cation exchange in M2 and V2 reduced particle size, increased slightly SSA and micropores with radius of 0.4-0.5 nm. Samples Ag/V and Ag/M showed higher content of pores with radius 0.5-1.0 nm than original V and M. The Ag concentration was found higher in Ag/V than in Ag/M and higher in repeatedly treated samples: 0.9 wt.% Ag in V1, 1.4 wt.% Ag in V2, 0.6 wt.% Ag in M1 and 1.0 wt.% Ag in M2. Vermiculite structure consisting of the hydrated interstratified phases and the mica-like phase changed to the cation-one-zero layer hydrate interstratification structure in V1 and to the random of two-one layer hydrate interstratifications in V2. Infrared and Mössbauer spectroscopy revealed no changes in the structure of the clay minerals that could be related directly to the sorption and crystallization of silver. Transmission electron microscopy showed that the silver nanoparticles size distribution was much narrower for the samples Ag/M than for Ag/V. The mean size of the Ag particles was between 40 and 50 nm. Although the Ag nanoparticles did not adhere sufficiently at the clay minerals surface and migrated moderately into water, all samples under study were approved to be effective inhibitors of the bacterial growth persisting for the whole testing period of 6 days. Silver/vermiculite was antimicrobial more efficient against Klebsiella pneumoniae and Pseudomonas aeruginosa than silver/montmorillonite.

Valášková, Marta; Hundáková, Marianna; Kutláková, Kate?ina Mamulová; Seidlerová, Jana; ?apková, Pavla; Pazdziora, Erich; Mat?jová, Kate?ina; He?mánek, Martin; Klemm, Volker; Rafaja, David

2010-11-01

98

Synthesis and Characterizations of Hydroxy-aluminum Cross-Linked Montmorillonite  

Microsoft Academic Search

Cross-linked montmorillonite was prepared by reacting homoionic sodium form of bentonite (Na-M) from Istenmezeje (Hungary)\\u000a with high molecular weight polyhydroxy-aluminum complex. The complex was prepared by controlled hydrolysis of alumina macrocation.\\u000a The intercalated clay (Na-Al-M) was thermally treated to convert the hydroxy cations to oxide pillars. The pillared products\\u000a were characterized by X-ray powder diffraction (XRD), Fourie transform infrared spectroscopy

L. Pöppl; E. Tóth; M. Tóth; I. Pászli; V. Izvekov; M. Gábor

1998-01-01

99

Synthesis of Highly Microporous and Hydrophilic Alumina-Pillared Montmorillonite: Water-Sorption Properties  

Microsoft Academic Search

A montmorillonite exchanged with large hydroxy-A1 cations was thermally treated to convert the hydroxy cations to oxide pillars and to generate permanent microporosity in the interlayers. The pillared clay products were characterized by X-ray powder diffraction (XRD) and water-sorption mea- surements to delineate the effect of aging of the pillaring solutions, the methods of drying and concentration of clay-water suspensions,

P. B. Malla

1990-01-01

100

Preparation and surface characterization of plasma-treated and biomolecular-micropatterned polymer substrates  

NASA Astrophysics Data System (ADS)

A micropatterning process creates distinct microscale domains on substrate surfaces that differ from the surfaces' original chemical/physical properties. Numerous micropatterning methods exist, each having relative advantages and disadvantages in terms of cost, ease, reproducibility, and versatility. Polymeric surfaces micropatterned with biomolecules have many applications, but are specifically utilized in tissue engineering as cell scaffolds that attempt to controlled tissue generation in vivo and ex vivo. As the physical and chemical cues presented by micropatterned substrates control resulting cellular behavior, characterization of these cues via surface-sensitive analytical techniques is essential in developing cell scaffolds that mimic complex in vivo physicochemical environments. The initial focus of this thesis is the chemical and physical characterization of plasma-treated, microcontact-printed (muCP) polymeric substrates used to direct nerve cell behavior. Unmodified and oxygen plasma-treated poly(methyl methacrylate) (PMMA) substrates were analyzed by surface sensitive techniques to monitor plasma-induced chemical and physical modifications. Additionally, protein-micropattern homogeneity and size were microscopically evaluated. Lastly, poly(dimethylsiloxane) (PDMS) stamps and contaminated PMMA substrates were characterized by spectroscopic and microscopic methods to identify a contamination source during microcontact printing. The final focus of this thesis is the development of microscale plasma-initiated patterning (muPIP) as a versatile, reproducible micropatterning method. Using muPIP, polymeric substrates were micropatterned with several biologically relevant inks. Polymeric substrates were characterized following muPIP by surface-sensitive techniques to identify the technique's underlying physical and chemical bases. In addition, neural stem cell response to muPIP-generated laminin micropatterns was microscopically and biologically evaluated. Finally, enhanced versatility of muPIP in generating microscale poly-L-lysine gradients was demonstrated.

Langowski, Bryan Alfred

101

Surface properties of low alloy steel treated by plasma nitrocarburizing prior to laser quenching process  

NASA Astrophysics Data System (ADS)

Laser quenching (LQ) technique is used as a part of duplex treatments to improve the thickness and hardness of the surface layers of steels. The present study is to investigate the surface properties of low alloy steel treated by plasma nitrocarburizing (PNC) prior to a laser quenching process (PNC+LQ). The microstructure and properties of PNC+LQ layer determined are compared with those obtained by PNC and LQ processes. OM, XRD, SEM and EDS analyses are utilized for microstructure observation, phases identification, morphology observation and chemical composition detection, respectively. Microhardness tester and pin-on-disc tribometer are used to investigate the mechanical properties of the modified layers. Laser quenching of plasma nitrocarburized (PNC+LQ) steel results in much improved thickness and hardness of the modified layer in comparison with the PNC or LQ treated specimens. The mechanism is that the introduction of trace of nitrogen decreases the eutectoid point, that is, the transformation hardened region is enlarged under the same temperature distribution. Moreover, the layer treated by PNC+LQ process exhibits enhanced wear resistance, due to the lubrication effect and optimized impact toughness, which is contributed to the formation of oxide film consisting of low nitrogen compound (FeN0.076) and iron oxidation (mainly of Fe3O4).

Wang, Y. X.; Yan, M. F.; Li, B.; Guo, L. X.; Zhang, C. S.; Zhang, Y. X.; Bai, B.; Chen, L.; Long, Z.; Li, R. W.

2015-04-01

102

Formation and characterization of hydrophobic glass surface treated by atmospheric pressure He/CH4 plasma  

NASA Astrophysics Data System (ADS)

Atmospheric pressure helium plasmas, generated in the open air by 13.56 MHz rf power, were applied for the glass surface wettability modification. The plasma gas temperature, measured by the spectroscopic method, was under 400 K which is low enough to treat the samples without thermal damages. The hydrophobicity of the samples determined by the water droplet contact angle method was dependent on the methane gas content and the plasma exposure time. Adding the methane gas by a small amount of 0.25%, the contact angle was remarkably increased from 10° to 83° after the 10 s plasma treatment. From the analysis of the treated surface and the plasma, it was shown that the deposition of alkane functional groups such as C-H stretch, CH2 bend, and CH3 bend was one of the contributing factors for the hydrophobicity development. In addition, the hydrophobic properties lasted over 2 months even after the single treatment. From the results, the atmospheric pressure plasma treatment promises the fast and low-cost method for the thermally-weak surface modification.

Noh, Sooryun; Youn Moon, Se

2014-01-01

103

Surface Characterization and Platelet Adhesion Studies of Plasma-Treated Polyethylene  

NASA Astrophysics Data System (ADS)

Plasma modification and plasma polymerization were employed to incorporate chemical functional groups of interest onto low density polyethylene (LDPE) surfaces. ESCA, ATR-FTIR spectroscopy, contact angle measurements, profilometry and canine platelet adhesion studies in association with SEM were used to determine elemental compositions, functional group presence, surface hydrophilicity, film thickness and thromboresistance of the modified LDPE. Ten families of materials were synthesized using plasma treatment to introduce nitrogen-, oxygen- and/or sulfur-containing functional groups on their surfaces. The reactive gases and monomers included sulfur dioxide, carbon dioxide, ammonia, allyl phenyl sulfone, acrylic acid and allylamine. In addition, the ammonia and allylamine treated LDPE were subsequently chemically grafted with 1,3-propane sultone and beta-propiolactone. An increase of surface acidic oxygen- or sulfur-containing functional groups on the LDPE substrates usually resulted in an improvement of thromboresistance as measured by platelet adhesion and shape change. In contrast, an increase of surface basic nitrogen-containing functional groups produced a more thrombogenic material. The allyl phenyl sulfone and acrylic acid plasma modified LDPE were the two materials which showed improved thromboresistance. In general, low plasma excitation energies (5 W) resulted in the highest levels of surface derivatization. The surface hydrophilicity of most materials was found to decrease with time. ESCA results indicated that it was due to the diffusion of the hydrophilic functional groups into the bulk of material since the substrate/air interface is hydrophobic. Extensive post-plasma-treatment oxidation occurred on a few materials which increased their surface hydrophilicity. The diffusivity of the polar groups was smaller in the plasma polymerized materials than in the plasma grafted materials.

Ko, Tze-Man

104

Osteoclasts but not osteoblasts are affected by a calcified surface treated with zoledronic acid in vitro  

SciTech Connect

Bisphosphonates are potent inhibitors of osteoclast-mediated bone resorption. Recent interest has centered on the effects of bisphosphonates on osteoblasts. Chronic dosing of osteoblasts with solubilized bisphosphonates has been reported to enhance osteogenesis and mineralization in vitro. However, this methodology poorly reflects the in vivo situation, where free bisphosphonate becomes rapidly bound to mineralized bone surfaces. To establish a more clinically relevant cell culture model, we cultured bone cells on calcium phosphate coated quartz discs pre-treated with the potent nitrogen-containing bisphosphonate, zoledronic acid (ZA). Binding studies utilizing [{sup 14}C]-labeled ZA confirmed that the bisphosphonate bound in a concentration-dependent manner over the 1-50 {mu}M dose range. When grown on ZA-treated discs, the viability of bone-marrow derived osteoclasts was greatly reduced, while the viability and mineralization of the osteoblastic MC3T3-E1 cell line were largely unaffected. This suggests that only bone resorbing cells are affected by bound bisphosphonate. However, this system does not account for transient exposure to unbound bisphosphonate in the hours following a clinical dosing. To model this event, we transiently treated osteoblasts with ZA in the absence of a calcified surface. Osteoblasts proved highly resistant to all transitory treatment regimes, even when utilizing ZA concentrations that prevented mineralization and/or induced cell death when dosed chronically. This study represents a pharmacologically more relevant approach to modeling bisphosphonate treatment on cultured bone cells and implies that bisphosphonate therapies may not directly affect osteoblasts at bone surfaces.

Schindeler, Aaron [Department of Orthopaedic Research and Biotechnology, Children's Hospital at Westmead, Sydney (Australia) and Discipline of Paediatrics and Child Health, Faculty of Medicine, University of Sydney, Sydney (Australia)]. E-mail: AaronS@chw.edu.au; Little, David G. [Department of Orthopaedic Research and Biotechnology, Children's Hospital at Westmead, Sydney (Australia); Discipline of Paediatrics and Child Health, Faculty of Medicine, University of Sydney, Sydney (Australia)

2005-12-16

105

Adhesion strength measurements of excimer-laser-treated PTFE surfaces using liquid photoreagents  

NASA Astrophysics Data System (ADS)

The most known feature of polytetrafluoroethylene (PTFE) is its adhesion behavior: it is hydrophobic and oleophobic at the same time. This can cause serious problems and obstacles during the surface treatment and fixing of PTFE objects. During our experiments Teflon films were irradiated by an ArF excimer laser beam in presence of liquid photoreagents containing amine groups (aminoethanol, 1,2-diaminoethane, triethylene-tetramine). In consequence of the treatment the adhesion of the modified surfaces significantly increased, the samples could be glued and moistened. The adhesion strength of the glued surfaces was measured in the function of the applied laser fluence. The adhesion strength increased drastically between 0 - 1 mJ/cm2 and showed saturation above 1 mJ/cm2 at approximately 5 - 9 MPa values depending on the applied photoreagents. On the basis of our experiments it was found that the treatment with triethylene-tetramine was the most effective. The surface chemical modifications of the treated Teflon samples can be due to the incorporation of amine groups into the surface layer.

Hopp, Bela; Smausz, Tomi; Kresz, Norbert; Ignacz, Ferenc

2003-04-01

106

Montmorillonite, oligonucleotides, RNA and origin of life  

NASA Technical Reports Server (NTRS)

Na-montmorillonite prepared from Volclay by the titration method facilitates the self-condensation of ImpA, the 5'-phosphorimidazolide derivative of adenosine. As was shown by AE-HPLC analysis and selective enzymatic hydrolysis of products, oligo(A)s formed in this reaction are 10 monomer units long and contain 67% 3',5'-phosphodiester bonds (Ferris and Ertem, 1992a). Under the same reaction conditions, 5'-phosphorimidazolide derivatives of cytidine, uridine and guanosine also undergo self-condensation producing oligomers containing up to 12-14 monomer units for oligo(C)s to 6 monomer units for oligo(G)s. In oligo(C)s and oligo(U)s, 75-80% of the monomers are linked by 2',5'-phosphodiester bonds. Hexamer and higher oligomers isolated from synthetic oligo(C)s formed by montmorillonite catalysis, which contain both 3',5'- and 2',5'-linkages, serve as catalysts for the non-enzymatic template directed synthesis of oligo(G)s from activated monomer 2-MeImpG, guanosine 5'-phospho-2-methylimidazolide (Ertem and Ferris, 1996). Pentamer and higher oligomers containing exclusively 2',5'-linkages, which were isolated from the synthetic oligo(C)s, also serve as templates and produce oligo(G)s with both 2',5'- and 3',5'-phosphodiester bonds. Kinetic studies on montmorillonite catalyzed elongation rates of oligomers using the computer program SIMFIT demonstrated that the rate constants for the formation of oligo(A)s increased in the order of 2-mer < 3-mer < 4-mer ... < 7-mer (Kawamura and Ferris, 1994). A decameric primer, dA(pdA)8pA bound to montmorillonite was elongated to contain up to 50 monomer units by daily addition of activated monomer ImpA to the reaction mixture (Ferris, Hill and Orgel, 1996). Analysis of dimer fractions formed in the montmorillonite catalyzed reaction of binary and quaternary mixtures of ImpA, ImpC, 2-MeImpG and ImpU suggested that only a limited number of oligomers could have formed on the primitive Earth rather than equal amounts of all possible isomers (Ertem and Ferris, 2000). Formation of phosphodiester bonds between mononucleotides by montmorillonite catalysis is a fascinating discovery, and a significant step forward in efforts to find out how the first RNA-like oligomers might have formed in the course of chemical evolution. However, as has been pointed out in several publications, these systems should be regarded as models rather than a literal representation of prebiotic chemistry (Orgel, 1998; Joyce and Orgel, 1999; Schwartz, 1999).

Ertem, Gozen

2004-01-01

107

Corrosion behaviour of a surface-treated AISI H11 hot work tool steel in molten aluminium alloy  

Microsoft Academic Search

Immersion tests in a molten aluminium alloy of a surface-treated AISI H11 hot work tool steel were carried out in order to study the corrosion mechanisms and the effect of different surface treatments on the resistance of the material. The steel has a great reactivity with molten aluminium, which causes a generalised attack on the exposed surface. Plasma nitriding and

A. Molinari; M. Pellizzari; G. Straffelini; M. Pirovano

2000-01-01

108

Effects of methoxyfenozide-treated surfaces on the attractiveness and responsiveness of adult codling moth (Lepidoptera: Tortricidae).  

PubMed

The attractiveness and responsiveness of adult codling moth, Cydia pomonella (L.), exposed to surfaces treated with the ecdysteroid agonist methoxyfenozide was investigated in wind tunnel and orientation tube assays. When males were exposed to either water- or surfactant-treated surfaces for 48 h, and regardless of what treatment surfaces the females had been exposed to, the mean percent recaptures of such treated males in the wind tunnel assay were sometimes significantly greater than the recaptures of males that had been exposed to methoxyfenozide. Similarly, in the orientation tube assay, males exposed to methoxyfenozide-treated surfaces almost always had significantly lower mean levels of individuals exhibiting sexual excitability and the mean distances traveled upwind, regardless of female exposures. The two assays demonstrated that male codling moths exposed to methoxyfenozide-treated surfaces were not as responsive to calling females (treated and nontreated) as were the nontreated males. Conversely, females exposed to methoxyfenozide-treated surfaces were just as attractive to nontreated males as were nontreated females. It appears that a male's ability to respond to a calling female is more negatively affected by the ecdysone agonist than a female's ability to call and attract males. PMID:12852597

Hoelscher, Jennifer A; Barrett, Bruce A

2003-06-01

109

Surface and crystalline analysis of aluminum oxide single crystal treated by quasistationary compression plasma flow  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer The effects of treatment of Al{sub 2}O{sub 3} (0001) surface by CPF are analyzed. Black-Right-Pointing-Pointer Oriented low-dimensional structures are occurred for the treated Al{sub 2}O{sub 3} crystal. Black-Right-Pointing-Pointer The dimension of these ripples are 1 {mu}m and the distance between them is about 10 {mu}m. Black-Right-Pointing-Pointer The ripple-shaped structures contain a higher percentage of oxygen than the surroundings. Black-Right-Pointing-Pointer Results could promote CPF as a tool for producing organized oxygen-rich structures. -- Abstract: Material such as aluminum oxide (Al{sub 2}O{sub 3}) is important in electronics industry. On the other hand, plasma is one of the most efficient and sophisticated tools for materials processing. In this work a treatment of Al{sub 2}O{sub 3} (0001) surface by quasistationary compression plasma flow (CPF) is analyzed in detail. Offline metrology was performed using dielectric measurements, X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM). Oriented low-dimensional periodic structures are occurred for the plasma treated Al{sub 2}O{sub 3} single crystal. In the paper is reported that these oriented ripple-shaped structures contain a higher percentage of oxygen than the surrounding crystal surface. This could be the framework for usage of CPF as a tool in manufacturing of surfaces containing the highly organized oxygen-rich structures.

Maletic, S., E-mail: sslavica@ff.bg.ac.rs [University of Belgrade, Faculty of Physics, Studentski trg 12-14, 11000 Belgrade (Serbia); Popovic, D.M.; Cubrovic, V.; Zekic, A.A.; Dojcilovic, J. [University of Belgrade, Faculty of Physics, Studentski trg 12-14, 11000 Belgrade (Serbia)] [University of Belgrade, Faculty of Physics, Studentski trg 12-14, 11000 Belgrade (Serbia)

2012-04-15

110

Morphological structures of poly(vinylidene fluoride)\\/montmorillonite nanocomposites  

Microsoft Academic Search

Poly(vinylidene fluoride) (PVDF)\\/montmorillonite (MMT) nanocomposites were prepared by melt blending a kind of organically\\u000a modified montmorillonite with PVDF. The morphological structures of the nanocomposites were studied using X-ray diffraction\\u000a (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, and differential scanning calorimetry\\u000a (DSC). The results indicate that organically modified montmorillonites are in the form of intercalation, exfoliation, and\\u000a fragments

YuMing Song; ZhuDi Zhao; WenXue Yu; Bo Li; XinFang Chen

2007-01-01

111

Heterogeneous freezing of water droplets containing kaolinite and montmorillonite particles  

NASA Astrophysics Data System (ADS)

Clouds composed of both ice particles and supercooled liquid water droplets exist at temperatures above ~236 K. These mixed phase clouds, which strongly impact climate, are very sensitive to the presence of solid particles that can catalyse freezing. In this paper we describe experiments to determine the rate at which kaolinite and montmorillonite nucleate ice when immersed within water droplets. These are the first immersion mode experiments in which the ice nucleating ability of individual minerals has been determined quantitatively. Water droplets containing a known amount of clay mineral were supported on a hydrophobic surface and cooled at a rate of 10 K min-1. The temperatures at which individual 10-40 ?m diameter droplets froze were determined by optical microscopy. As the concentration of kaolinite in the droplets was increased from 0.005 wt% to 1 wt% the median nucleation temperature increased from close to the homogeneous nucleation limit (236 K) to 240.8±0.6 K. We go onto show that the probability of freezing scales with surface area of the kaolinite inclusions rather than, as is often assumed, the volume of the droplet. When droplets contained montmorillonite ice always nucleated at 245.8±0.6 K, independent of the mineral concentration. We report temperature dependent nucleation rates and present parameterisations for nucleation by these minerals which capture the surface area and cooling rate dependence of the nucleation rate. We show that our parameterisations produce significantly different results to parameterisations employed in global models. These results also highlight the importance of understanding the ice nucleating properties of individual minerals rather than complex mixtures of minerals found in natural dusts and so-called test dusts.

Murray, B. J.; Wilson, T. W.; Broadley, S. L.; Wills, R. H.

2010-04-01

112

Constructing covalent interface in rubber/clay nanocomposite by combining structural modification and interlamellar silylation of montmorillonite.  

PubMed

Strong interfacial interaction and nanodispersion are necessary for polymer nanocomposites with expectations on mechanical performance. In this work, montmorillonite (MMT) was first structurally modified by acid treatment to produce more silanol groups on the layer surface. This was followed by chemical modification of ?-methacryloxy propyl trimethoxysilane molecule (KH570) through covalent grafting with the silanol groups. (29)Si and (27)Al magic angle spinning (MAS) NMR results revealed the microstructural changes of MMT after acid treatment and confirmed the increase of silanol groups on acid-treated MMT surfaces. Thermogravimetric analysis indicated an increase in the grafted amount of organosilane on the MMT surface. X-ray diffraction (XRD) showed that the functionalization process changed the highly ordered stacking structure of the MMT mineral into a highly disordered structure, indicating successful grafting of organosilane to the interlayer surface of the crystalline sheets. The styrene-butadiene rubber (SBR)/MMT nanocomposites were further prepared by co-coagulating with SBR latex and grafted-MMT aqueous suspension. During vulcanization, a covalent interface between modified MMT and rubber was established through peroxide-radical-initiated reactions, and layer aggregation was effectively prevented. The SBR/MMT nanocomposites had highly and uniformly dispersed MMT layers, and the covalent interfacial interaction was finally achieved and exhibited high performance. PMID:25322875

Zha, Chao; Wang, Wencai; Lu, Yonglai; Zhang, Liqun

2014-11-12

113

Effect of Surface Treated Silicon Dioxide Nanoparticles on Some Mechanical Properties of Maxillofacial Silicone Elastomer  

PubMed Central

Current materials used for maxillofacial prostheses are far from ideal and there is a need for novel improved materials which mimic as close as possible the natural behavior of facial soft tissues. This study aimed to evaluate the effect of adding different concentrations of surface treated silicon dioxide nanoparticles (SiO2) on clinically important mechanical properties of a maxillofacial silicone elastomer. 147 specimens of the silicone elastomer were prepared and divided into seven groups (n = 21). One control group was prepared without nanoparticles and six study groups with different concentrations of nanoparticles, from 0.5% to 3% by weight. Specimens were tested for tear strength (ASTM D624), tensile strength (ASTM D412), percent elongation, and shore A hardness. SEM was used to assess the dispersion of nano-SiO2 within the elastomer matrix. Data were analyzed by one-way ANOVA and Scheffe test (? = 0.05). Results revealed significant improvement in all mechanical properties tested, as the concentration of the nanoparticles increased. This was supported by the results of the SEM. Hence, it can be concluded that the incorporation of surface treated SiO2 nanoparticles at concentration of 3% enhanced the overall mechanical properties of A-2186 silicone elastomer. PMID:25574170

Zayed, Sara M.; Alshimy, Ahmad M.; Fahmy, Amal E.

2014-01-01

114

High capacity mercury adsorption on freshly ozone-treated carbon surfaces  

PubMed Central

A set of carbon materials was treated by a choice of common oxidizers to investigate the mercury capture capacities at varying temperature conditions. It was found that ozone treatment dramatically increases the mercury capture capacity of carbon surfaces by factors up to 134, but the activity is easily destroyed by exposure to the atmosphere, to water vapor, or by mild heating. Freshly ozone-treated carbon surfaces are shown to oxidize iodide to iodine in solution and this ability fades with aging. FTIR analysis shows broad C–O stretch features from 950 to 1300 cm?1, which decay upon atmospheric exposure and are similar to the C-O-C asymmetric stretch features of ethylene secondary ozonide. The combined results suggest that the ultra-high mercury capture efficiency is due to a subset of labile C-O functional groups with residual oxidizing power that are likely epoxides or (epoxide-containing) secondary ozonides. The results open the possibility for in situ ozonolysis to create high-performance carbon-based Hg sorbents. PMID:19255621

Manchester, Shawn; Wang, Xuelei; Kulaots, Indrek; Gao, Yuming; Hurt, Robert H.

2008-01-01

115

Adhesive forces and surface properties of cold gas plasma treated UHMWPE.  

PubMed

Cold atmospheric plasma (CAP) treatment was used on ultra-high molecular weight polyethylene (UHMWPE), a common articulating counter material employed in hip and knee replacements. UHMWPE is a biocompatible polymer with low friction coefficient, yet does not have robust wear characteristics. CAP effectively cross-links the polymer chains of the UHMWPE improving wear performance (Perni et al., Acta Biomater. 8(3) (2012) 1357). In this work, interactions between CAP treated UHMWPE and spherical borosilicate sphere (representing model material for bone) were considered employing AFM technique. Adhesive forces increased, in the presence of PBS, after treatment with helium and helium/oxygen cold gas plasmas. Furthermore, a more hydrophilic surface of UHMWPE was observed after both treatments, determined through a reduction of up to a third in the contact angles of water. On the other hand, the asperity density also decreased by half, yet the asperity height had a three-fold decrease. This work shows that CAP treatment can be a very effective technique at enhancing the adhesion between bone and UHMWPE implant material as aided by the increased adhesion forces. Moreover, the hydrophilicity of the CAP treated UHMWPE can lead to proteins and cells adhesion to the surface of the implant stimulating osseointegration process. PMID:25431523

Preedy, Emily Callard; Brousseau, Emmanuel; Evans, Sam L; Perni, Stefano; Prokopovich, Polina

2014-10-20

116

Preparation and Characterization of Novel Montmorillonite Nanocomposites  

NASA Astrophysics Data System (ADS)

Clay minerals have historically played a consequential role in human health. While the beginnings were rooted in geophagy, a primitive act of consuming earth, the health-related uses of clay minerals have evolved and diversified over time.. As excipients in pharmaceutical formulations, clay minerals can attribute novel properties onto intercalated compounds. Intercalating oxybenzone, a UV filter, within the interlamellar space of montmorillonite is desirable in order to minimize direct contact with skin. Intercalating resveratrol, a compound known for attributing beneficial effects onto human health, may be advantageous since this compound is susceptible to cis-trans isomerisation. The strategy of using alkylammonium--modified clay was undertaken and proved successful for the intercalation of oxybenzone. The field of biopolymer/layered silicate nanocomposites is heavily researched for use in a multitude of applications. Novel montmorillonite nanocomposites were prepared with neutral guar gum and cationic guar gum, using an environmentally friendly process and are fully characterized.

Mansa, Rola

117

Preparation and characterization of microporous SiO{sub 2}-ZrO{sub 2} pillared montmorillonite  

SciTech Connect

SiO{sub 2}-ZrO{sub 2} pillared montmorillonite (SZM) was prepared by the reaction of Na-montmorillonite with colloidal silica-zirconia particles which were prepared by depositing zirconium hydroxy cations on silica particles. By pillaring with the colloidal particles, the basal spacing of montmorillonite was expanded to ca. 45 A and the calcined SZM samples showed large specific surface areas up to 320 m{sup 2}/g at 400 deg. C. In spite of large interlayer separation, adsorption results indicated the presence of micropores generated between the colloidal particles. The microporous structure was maintained at least up to 600 deg. C and exhibited specific shape selectivity for the adsorption of large organic molecules, especially between toluene and mesitylene. According to the temperature-programmed-desorption (TPD) spectra of ammonia, the calcined SZM showed weakly acidic sites.

Han, Yang-Su [Nanospace Co. Ltd., Business Incubator, Korea Institute of Ceramic Engineering and Technology, 233-5 Gasan-dong Guemcheon-Gu, Seoul 153-801 (Korea, Republic of)]. E-mail: yshan@inanospace.com; Yamanaka, Shoji [Department of Applied Chemistry, Faculty of Engineering, Hiroshima University, Higashi-Hiroshima 739 (Japan)

2006-04-15

118

Sorption of cadmium, nickel, and zinc by kaolinite and montmorillonite suspensions  

Microsoft Academic Search

Sorption is the predominant process governing metal ion movement in soils and includes the following physical and chemical mechanisms: adsorption, precipitation and absorption. This research attempts to use the hard-soft-acid-base principle to explain sorption selectivity of the metal cations Cd, Ni, and Zn by kaolinite and montmorillonite clays. The hard-soft character of the clay surfaces, which is due to their

R. W. Puls; H. L. Bohn

2009-01-01

119

Low-temperature InP /GaAs wafer bonding using sulfide-treated surface  

NASA Astrophysics Data System (ADS)

An approach for InP /GaAs wafer bonding based on thiourea treatment was presented. The bonding energy reaches the InP fracture energy by annealing at 360°C. An In0.53Ga0.47As/InP multiple quantum well (MQW) structure grown on InP was transferred onto GaAs substrate via the bonding process. X-ray diffraction and photoluminescence reveal that crystal quality of the bonded MQW was preserved. A thin sulfide layer with thickness of about 29nm at the bonding interface was detected. X-ray photoelectron spectroscopy analyses indicate that the formation of In-S and Ga-S bond at thiourea treated surface is responsible for the strong fusion obtained at such low temperature.

Huang, Hui; Ren, Xiaomin; Wang, Xinyan; Wang, Qi; Huang, Yongqing

2006-02-01

120

Optimization of electrocoagulation process to treat grey wastewater in batch mode using response surface methodology  

PubMed Central

Background Discharge of grey wastewater into the ecological system causes the negative impact effect on receiving water bodies. Methods In this present study, electrocoagulation process (EC) was investigated to treat grey wastewater under different operating conditions such as initial pH (4–8), current density (10–30 mA/cm2), electrode distance (4–6 cm) and electrolysis time (5–25 min) by using stainless steel (SS) anode in batch mode. Four factors with five levels Box-Behnken response surface design (BBD) was employed to optimize and investigate the effect of process variables on the responses such as total solids (TS), chemical oxygen demand (COD) and fecal coliform (FC) removal. Results The process variables showed significant effect on the electrocoagulation treatment process. The results were analyzed by Pareto analysis of variance (ANOVA) and second order polynomial models were developed in order to study the electrocoagulation process statistically. The optimal operating conditions were found to be: initial pH of 7, current density of 20 mA/cm2, electrode distance of 5 cm and electrolysis time of 20 min. Conclusion These results indicated that EC process can be scale up in large scale level to treat grey wastewater with high removal efficiency of TS, COD and FC. PMID:24410752

2014-01-01

121

Oxidation mechanism of the ammonium-fluoride-treated Si(100) surface  

SciTech Connect

High-resolution electron energy loss (HREEL) spectroscopy, Auger electron spectroscopy, and low-energy electron diffraction have been employed to examine the initial oxidation stage of ammonium-fluoride-treated Si(100) surfaces exposed to air. The NH{sub 4}F treatment results in a hydrogen-terminated surface, as shown by the presence of the Si{endash}H stretch (2100 cm{sup {minus}1}), SiH{sub 2} scissor (910 cm{sup {minus}1}), and SiH bend (650 cm{sup {minus}1}) in the HREEL spectra. Initial oxidation on this surface occurs through oxygen insertion in the silicon backbonds, as indicated by the presence of the asymmetric bridge-bonded oxygen stretch in the region between 1060 and 1160 cm{sup {minus}1}. Oxygen is observed in both surface and bulk bridge-bonding sites for even the shortest air exposures, suggesting that initial oxygen uptake is not taking place in a layer-by-layer fashion. Auger electron spectroscopy shows a slow uptake of oxygen over the first few days of air exposure, followed by more rapid oxidation. Over the first two weeks of air exposure, the Si{endash}H stretch at 2100 cm{sup {minus}1} gradually disappears, accompanied by the appearance of oxygen backbonded Si{endash}H peaks around 2250 cm{sup {minus}1}. This behavior indicates that, despite the increase in oxygen uptake, the hydrogen termination remains intact, and further confirms that oxygen uptake occurs through insertion in the silicon backbonds. Water is found to play a significant role in the initial oxidation. {copyright} {ital 1996 American Institute of Physics.}

Kluth, G.J.; Maboudian, R. [Department of Chemical Engineering, University of California, Berkeley, California 94720 (United States)] [Department of Chemical Engineering, University of California, Berkeley, California 94720 (United States)

1996-11-01

122

Influence of absorbed moisture on surface hydrophobization of ethanol pretreated and plasma treated ramie fibers  

NASA Astrophysics Data System (ADS)

The existence of moisture in the substrate material may influence the effect of atmospheric pressure plasma treatment. Our previous study has found that the employment of ethanol pretreatment and plasma treatment can effectively induce hydrophobic surface modification of cellulose fiber to enhance the compatibility to polypropylene (PP) matrix, and this study aims to investigate the influence of fiber moisture regain on the treatment effect of this technique. Ramie fibers with three different moisture regains (MR) (2.5, 6.1 and 23.5%) are pretreated with ethanol followed by atmospheric pressure plasma treatment. Scanning electron microscope (SEM) shows that the 2.5% MR group has the most significant plasma etching effect. X-ray photoelectron spectroscopy (XPS) analysis indicates an increase of Csbnd C and a decrease of Csbnd O bond in the plasma treated groups, and the largest raise of Csbnd C bond for the 2.5% MR group. The water contact angles of the 2.5 and 6.1% MR groups increase, whereas no significant change is showed in the 23.5% MR group. The interfacial shear strengths (IFSS) measured by microbond pull-out test are raised by 44 and 25% when moisture regains are 2.5 and 6.1%, while presented no apparent improvement at high moisture regain of 23.5%. Therefore, it can be concluded that moisture regain has negative influence on the surface hydrophobization of ramie fibers in the improvement of adhesion property to PP matrix.

Zhou, Zhou; Wang, Jilong; Huang, Xiao; Zhang, Liwen; Moyo, Senelisile; Sun, Shiyuan; Qiu, Yiping

2012-03-01

123

Blood compatibility of gas plasma-treated diamond-like carbon surface—Effect of physicochemical properties of DLC surface on blood compatibility  

Microsoft Academic Search

From the knowledge that zwitterion-type polymers show good blood compatibility, the introduction of both cationic and anionic functional groups onto diamond-like carbon (DLC) surface is expected to improve blood compatibility. Thus, DLC films were treated with oxygen and ammonia gas plasmas. The surfaces were characterized in terms of chemical composition by XPS, contact angle, and zeta potential. XPS analysis showed

Akira Mochizuki; Tatsuhisa Ogawa; Keishi Okamoto; Tatsuyuki Nakatani; Yuki Nitta

2011-01-01

124

Adsorption and reduction in bioactivity of polychlorinated biphenyl (Aroclor 1254) to redroot pigweed by soil organic matter and montmorillonite clay  

SciTech Connect

Aroclor 1254 polychlorinated biphenyl (PCB) applied to untreated (1.4% organic matter) and H/sub 2/O/sub 2/-treated (0.2% organic matter) Lakeland sand at rates of 0, 50,100, 150, and 200 ppm caused significant reductions in redroot pigweed (Amaranthus retroflexus L.) growth at the high rates of application. Polychlorinated biphenyl decreased plant height in the H/sub 2/O/sub 2/-treated soil much more than in the untreated soil. A greater decrease in dry weight also resulted in the H/sub 2/O/sub 2/-treated soil, but only at the 200 ppm rate. In one study, soil was amended with montmorillonite clay and organic matter (peaty muck) at rates of 0, 2.5, 5.0, and 10.0% by weight and treated with 200 ppm PCB. The organic matter proved to be much more effective than montmorillonite in reducing PCB toxicity to pigweed at the lower rates of addition (2.5 and 5.0%), but no differences were noted between the two adsorbents at the 10% rate. Adsorption of /sup 14/C-labeled PCB closely resembling Aroclor 1254 by the untreated and H/sub 2/O/sub 2/-treated soils, montmorillonite clay, organic matter, and activated carbon was measured. The order of highest to lowest adsorption was as follows: activated carbon >> organic matter > montmorillonite clay > Lakeland sand > H/sub 2/O/sub 2/-treated Lakeland sand. These experiments suggest that organic matter content of a soil, and clay content to a lesser extent, are involved in reducing the availability of soil-applied PCB to pigweed. Differences in reduction of PCB toxicity to pigweed are explained by differences in adsorption by the adsorbents.

Strek, H.J.; Weber, J.B.

1982-03-01

125

Influence of Montmorillonite on Nucleotide Oligomerization Reactions: A Molecular Dynamics Study  

NASA Astrophysics Data System (ADS)

We investigate a proposed origins of life scenario involving the clay montmorillonite and its catalytic role in forming oligonucleotides from activated mononucleotides. Clay and mineral surfaces are important for concentrating the reactants and for promoting nucleotide polymerization reactions. Using classical molecular dynamics methods we provide atomic details of reactant conformations prior to polynucleotide formation, lending insight into previously reported experimental observations of this phenomenon. The simulations clarify the catalytic role of metal ions, demonstrate that reactions leading to correct linkages take place primarily in the interlayer, and explain the observed sequence selectivity in the elongation of the chain. The study comparing reaction probabilities involving L- and D-chiral forms of the reactants has found enhancement of homochiral over heterochiral products when catalyzed by montmorillonite.

Mathew, Damien C.; Luthey-Schulten, Zaida

2010-03-01

126

Effects of pH on Dielectric Relaxation of Montmorillonite, Allophane, and Imogolite Suspensions.  

PubMed

Dielectric measurements were performed on montmorillonite, allophane, and imogolite suspensions under various pH conditions, using time domain reflectometry over the frequency range 10 kHz-20 GHz. A dielectric relaxation peak due to bound water could be observed for all the clays. Allophane has two peaks, indicating that its peaks are very similar to those of silica-alumina gels. Although imogolite has a similar chemical composition, only one peak was found. The relaxation strength of montmorillonite is greater than that of the other two clays. For all the clays, the relaxation strength depended on the pH. A change in the relaxation strength according to a change in pH is explained in terms of the different network structures of the clay particles. It is suggested that bound water influences the network structure formation. In montmorillonite, a great relaxation process detected at low frequency is caused by surface polarization of counterions. The change in measure of the structural unit with the pH, identified from Schwartz's theory, has a tendency similar to that postulated by other experimental techniques, and surface charge densities identified are close to those estimated from CEC. Copyright 1999 Academic Press. PMID:10072285

Ishida; Makino

1999-04-01

127

Enzymatic Modification of Bacterial Receptors on Saliva-Treated Hydroxyapatite Surfaces  

PubMed Central

Certain properties of experimental pellicles formed by the adsorption of salivary components on hydroxyapatite surfaces change over time. To determine whether enzymes likely to be present in the oral environment could induce such changes, pellicles were treated with saliva which had been incubated for 18 h at 35°C to promote the elaboration of microbial enzymes. This treatment markedly reduced the numbers of Streptococcus mutans MT3 and JBP and S. sanguis FC-1 and C5 cells which attached, but it had little or no effect on the attachment of S. mitis RE7, Actinomyces viscosus LY7 and CK-8, Bacteroides gingivalis 381, or B. melaninogenicus subsp. intermedius 581. Heating the incubated saliva at 60°C for 30 min partially reduced its pellicle-modifying activity, whereas heating at 80°C for 30 min or 100°C for 15 min completely eliminated such activity. This indicated that the saliva contained heat-labile substances, presumably enzymes, which could affect the pellicle receptors involved in the attachment of S. mutans and S. sanguis. Treatment of saliva-treated hydroxyapatite with commercially obtained enzyme preparations also affected bacterial attachment. Thus, treatment with galactose oxidase reduced the numbers of the S. mutans strains which attached, whereas treatment with neuraminidase reduced the adsorption of S. sanguis FC-1 but not that of S. sanguis C5. Treatment with ?-glucosidase preparations derived from almonds significantly reduced the attachment of all of the streptococcal strains studied, but, when subjected to isoelectric fractionation, the adherence-inhibiting activity did not correlate directly with ?-glucosidase activity. Treatment of the pellicles with trypsin or eight other glycosidases did not affect streptococcal attachment. Exposure of the enzymatically modified pellicles to fresh saliva did not restore the streptococcal receptors. Collectively, the data suggest that some bacterial receptors in the pellicle coating of teeth can be modified by enzymes likely to be present in the oral environment, and these interactions may affect oral bacterial ecology. PMID:6281193

Gibbons, R. J.; Etherden, I.

1982-01-01

128

The Effect of Surface Treated Nanoparticles on Single and Multi-Phase Flow in Porous Media  

NASA Astrophysics Data System (ADS)

Surface treated nanoparticles have been suggested to be an additive to CO2 storage scenarios. This is because 1) the nanoparticles have been shown to freely transport through permeable media, and 2) the nanoparticles can stabilize a CO2 in water foam by adhering to the surface of CO2 bubbles/droplets preventing their coalescence. In terms of storage, The formation of CO2 foam will limit the CO2 mobility which can potentially help limit the CO2 leakage. Here, we will show how nanoparticles in porous media can have many interesting properties in single and multi-phase flow. For multi-phase CO2, we have performed experiments where high pressure liquid CO2 displaces brine and vice versa with and without nanoparticles in the brine. We measure the displacement pattern and in-situ CO2 saturation using CT scanning and measure the pressure drop using pressure transducers. We find that the flow is less preferential and the pressure drop is greater than when nanoparticles are present. This suggest the formation of in-situ foam/emulsion. We also show that on a brine chase, the residual saturation of CO2 is greater in the presence of nanoparticles. In terms of nanoparticle transport, it is observed that nanoparticles accumulate at the front of a brine/octane displacement. We hypothesize that this occurs due to the nanoparticles being size excluded from portions of the pore-space. To determine if this occurs in single phase flow, we have also performed experiments single-phase flow with the nanoparticles and tracer. We find that the nanoparticles arrive roughly 5% faster than the tracer. This also has implications for the positioning of nanoparticles in the pore space and how this can change the effective viscosity of the nanoparticle suspension.

DiCarlo, D. A.; Aminzadeh, B.; Chung, D.; Zhang, X.; Wung, R.; Huh, C.; Bryant, S. L.

2013-12-01

129

Reduced reactivity to air on HF-treated YBa2Cu3O(7-x)surfaces  

NASA Technical Reports Server (NTRS)

Treatment of YBa2Cu3O(7-x) films with a nonaqueous solution of HF in absolute ethanol results in the formation of an oxyfluoride with relative Y:Ba:Cu concentrations of 1:4:3 on the surface, as determined by X-ray photoelectron spectroscopy. The passivation properties of chemically treated films were tested by monitoring the growth of the high binding energy O 1s peak, associated with nonsuperconducting surface species, as a function of air exposure time, for both HF-treated and untreated films. The native oxyfluoride is shown to reduce the reactivity of the superconductor to air.

Vasquez, R. P.; Hunt, B. D.; Foote, M. C.

1989-01-01

130

Phosphorus removal in a surface-flow constructed wetland treating agricultural runoff.  

PubMed

Agricultural runoff is a leading source of phosphorus (P) pollution to lakes and streams. The objective of this study was to evaluate P removal dynamics in a constructed treatment wetland (CTW) treating agricultural irrigation return flows. The CTW included a sedimentation basin (SB) followed by two surface-flow wetlands in parallel. Typical retention times and total P (TP) loading were 1.4 d and 50 to 110 g m yr P, respectively, for the SB and 5 to 6 d and 4 to 10 g m yr P, respectively, for wetlands. On the basis of this multiyear study, concentration removal efficiency in the SB averaged 21% for TP and 32% for reactive phosphorus (RP). Concentration removal efficiency in wetlands averaged 37 and 43% for TP and 22 and 33% for RP. Areal first-order removal rates for TP averaged 22 and 31 m yr in wetlands. Total P removal in wetlands exhibited a strong seasonal pattern, with minimum removal in the summer when high temperatures likely enhanced P release from decaying plant biomass. The performance of the CTW was stochastic, with removal unpredictably poorer in some years in part as a result of muskrat bioturbation and plant harvesting. In years before muskrat impacts, concentration removal efficiencies in wetlands were 50% for TP and 65% for RP. PMID:25602836

Beutel, Marc W; Morgan, Matthew R; Erlenmeyer, Jonathan J; Brouillard, Elaine S

2014-05-01

131

Analysis of oligonucleotide DNA binding and sedimentation properties of montmorillonite clay using ultraviolet light spectroscopy.  

PubMed

Smectite clays such as montmorillonite form complexes with a variety of biomolecules, including the nucleic acids DNA and RNA. Most previous studies of DNA adsorption onto clay have relied on spectrophotometric analysis after the separation of free nucleic acids from bound complexes by centrifugation. In the current work, we demonstrate that such studies produce a consistent error because of (a) incomplete sedimentation of montmorillonite and (b) strong absorbance of the remaining clay at 260 nm. Clay sedimentation efficiency was strongly dependent on cation concentration (Na+ or Mg2+) and on the level of dispersion of the original suspension. An improved clay-DNA adsorption assay was developed and utilized to assess the impact of metal counterions on the binding of single-stranded DNA to montmorillonite. X-ray diffraction demonstrated, for the first time, the formation of intercalated structures consistent with orientation of the DNA strands parallel to the clay surface. Observed gallery spacings were found to match values calculated using atomistic modeling techniques closely. PMID:19061334

Beall, Gary W; Sowersby, Drew S; Roberts, Rachel D; Robson, Michael H; Lewis, L Kevin

2009-01-12

132

Study of antibacterial activity of Ag and Ag2CO3 nanoparticles stabilized over montmorillonite  

NASA Astrophysics Data System (ADS)

Silver carbonate and silver nanoparticles (NPs) over of stabilizer montmorillonite (MMT) have been synthesized in aqueous and polyol solvent, respectively. Dispersions of silver nanoparticles have been prepared by the reduction of silver nitrate over of MMT in presence and absence of Na2CO3 compound in ethylene glycol. It was observed that montmorillonite was capable of stabilizing formed Ag nanoparticles through the reduction of Ag+ ions in ethylene glycol. Na2CO3 was used as carbonate source in synthesis of Ag2CO3 NPs in water solvent and also for controlling of Ag nanoparticles size in ethylene glycol medium. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and ultraviolet-visible diffuse reflectance spectroscopy (DRS). The TEM images showed that Ag NPs size in presence Na2CO3 salts was smaller than without that. The results indicated intercalation of Ag and Ag2CO3 nanoparticles into the montmorillonite clay layers. The diffuse reflectance spectra exhibited a strong surface plasmon resonance (SPR) adsorption peak in the visible region, resulting from Ag nanoparticles. The antibacterial testing results showed that the Ag2CO3-MMT nanocomposite exhibited an antibacterial activity higher than Ag-MMT sample against Escherichia coli.

Sohrabnezhad, Sh.; Pourahmad, A.; Mehdipour Moghaddam, M. J.; Sadeghi, A.

2015-02-01

133

Study of antibacterial activity of Ag and Ag2CO3 nanoparticles stabilized over montmorillonite.  

PubMed

Silver carbonate and silver nanoparticles (NPs) over of stabilizer montmorillonite (MMT) have been synthesized in aqueous and polyol solvent, respectively. Dispersions of silver nanoparticles have been prepared by the reduction of silver nitrate over of MMT in presence and absence of Na2CO3 compound in ethylene glycol. It was observed that montmorillonite was capable of stabilizing formed Ag nanoparticles through the reduction of Ag(+) ions in ethylene glycol. Na2CO3 was used as carbonate source in synthesis of Ag2CO3 NPs in water solvent and also for controlling of Ag nanoparticles size in ethylene glycol medium. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and ultraviolet-visible diffuse reflectance spectroscopy (DRS). The TEM images showed that Ag NPs size in presence Na2CO3 salts was smaller than without that. The results indicated intercalation of Ag and Ag2CO3 nanoparticles into the montmorillonite clay layers. The diffuse reflectance spectra exhibited a strong surface plasmon resonance (SPR) adsorption peak in the visible region, resulting from Ag nanoparticles. The antibacterial testing results showed that the Ag2CO3-MMT nanocomposite exhibited an antibacterial activity higher than Ag-MMT sample against Escherichia coli. PMID:25467663

Sohrabnezhad, Sh; Pourahmad, A; Mehdipour Moghaddam, M J; Sadeghi, A

2014-10-28

134

Stratified assemblies of magnetite nanoparticles and montmorillonite prepared by the layer-by-layer assembly  

SciTech Connect

Hybrid thin films are prepared from 8 to 10 nm Fe{sub 3}O{sub 4} nanoparticles and exfoliated montmorillonite clay by using layer-by-layer assembly on poly(diallyldimethylammonium bromide), PDDA. Distinct stratification of the Fe{sub 3}O{sub 4}/PDDA/clay films is obtained due to the sheetlike structure of the clay particles. This feature distinguishes these assemblies from their polyelectrolyte-polyelectrolyte analogues, where the layers of individual polyelectrolytes are strongly interdigitated. Being adsorbed on PDDA strictly parallel to the substrate surface, montmorillonite produces a dense layer of overlapping alumosilicate sheets, which virtually flawlessly separates one magnetite layer from another. The difference in magnetic properties between assemblies of various architectures is attributed to the insulation effect of clay layers inserted between magnetic layers. The montmorillonite sheets disrupt the electron exchange interactions between the magnetite nanoparticles in adjacent layers, thereby limiting the magnetization reversal to two dimensions. Some optical properties of Fe{sub 3}O{sub 4}/PDDA films are investigated as well. When they are deposited on thin plastic substrate, oscillations of optical density were observed in the red part of the UV-vis spectrum. This effect, which has never been observed for conventional, thick substrates such as glass slides, stems from the interference of the light beams passed through and reflected off of the assembled film.

Mamedov, A.; Ostrander, J.; Aliev, F.; Kotov, N.A.

2000-04-18

135

Sublethal exposure to methoxyfenozide-treated surfaces reduces the attractiveness and responsiveness in adult oriental fruit moth (Lepidoptera: Tortricidae).  

PubMed

The chemical communication (female attractiveness and male responsiveness) of adult oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), exposed to surfaces treated with the ecdysteroid agonist methoxyfenozide for 48 h were investigated in two laboratory wind tunnel assays. The recapture assay examined the ability of treated males to orient to a single cage of treated females, and the data gathered were mean percentage of males recaptured per treatment. The male sexual behavior assay examined some specific orientation behaviors (associated with sexual excitability) of treated males when they were given a choice of two competing pheromone sources (cages of treated females), and the data gathered were mean time males spent in upwind plume orientations and at source contact (female cage) per treatment. Data from the recapture assay suggests that exposure to methoxyfenozide impacts male responsiveness more than female attractiveness. In contrast, data from the sexual behavior assay strongly revealed that exposure to methoxyfenozide-treated surfaces does negatively impact both the ability of calling females to attract males and of aroused males to display sustained upwind flight behavior and time spent at the female cages. PMID:17370812

Reinke, Michael D; Barrett, Bruce A

2007-02-01

136

The characteristics of treated zone processed by pulsed Nd-YAG laser surface remelting on hot work steel  

NASA Astrophysics Data System (ADS)

In this study, the surface of H13 steel was treated using laser surface remelting. Some important characteristics of the treated zone (biomimetic strengthening units) were investigated, e.g. size, cross-sectional morphology, microstructure and hardness as functions of average peak power density and effective peak power density. The results indicate that different combinations of average peak power density and effective peak power density could vary the appearance of cross-sectional morphology, microstructure and hardness. An appropriate range of EPPD for preparing the treated zone was acquired: 595-1448 W/mm2. In this range, the depth/width ratio of 0.31-0.47 and microhardness of 559-667 HV were obtained.

Zhang, Zhihui; Lin, Pengyu; Cong, Dalong; Kong, Shuhua; Zhou, Hong; Ren, Luquan

2014-12-01

137

Eddy current residual stress profiling in surface-treated engine alloys Bassam A. Abu-Nabaha1  

E-print Network

Eddy current residual stress profiling in surface-treated engine alloys Bassam A. Abu-Nabaha1 version received 3 June 2008 ) Recent research results indicate that eddy current conductivity profile is calculated from the measured frequency-dependent apparent eddy current conductivity spectrum

Nagy, Peter B.

138

Surface characteristics and osteoblastic cell response of alkali-and heat-treated titanium-8tantalum-3niobium alloy  

PubMed Central

Purpose The aim of the present study was to evaluate the biological response of alkali- and heat-treated titanium-8tantalum-3niobium surfaces by cell proliferation and alkaline phosphatase (ALP) activity analysis. Methods Commercial pure titanium (group cp-Ti) and alkali- and heat-treated titanium-8tantalum-3niobium (group AHT) disks were prepared. The surface properties were evaluated using scanning electron microscopy, energy dispersed spectroscopy and X-ray photoelectron spectroscopy (XPS). The surface roughness was evaluated by atomic force microscopy and a profilometer. The contact angle and surface energy were also analyzed. The biological response of fetal rat calvarial cells on group AHT was assessed by cell proliferation and ALP activity. Results Group AHT showed a flake-like morphology microprofile and dense structure. XPS analysis of group AHT showed an increased amount of oxygen in the basic hydroxyl residue of titanium hydroxide groups compared with group cp-Ti. The surface roughness (Ra) measured by a profilometer showed no significant difference (P>0.05). Group AHT showed a lower contact angle and higher surface energy than group cp-Ti. Cell proliferation on group AHT surfaces was significantly higher than on group cp-Ti surfaces (P<0.05). In comparison to group cp-Ti, group AHT enhanced ALP activity (P<0.05). Conclusions These results suggest that group AHT stimulates osteoblast differentiation. PMID:23346470

Lee, Bo-Ah; Kang, Choong-Hee; Vang, Mong-Sook; Jung, Young-Suk; Piao, Xing Hui; Kim, Ok-Su; Chung, Hyun-Ju

2012-01-01

139

Disassembly of the cystovirus ?6 envelope by montmorillonite clay  

PubMed Central

Prior studies of clay–virus interactions have focused on the stability and infectivity of nonenveloped viruses, yielding contradictory results. We hypothesize that the surface charge distribution of the clay and virus envelope dictates how the components react and affect aggregation, viral stability, and infectivity. The bacteriophage Cystoviridae species ?6 used in this study is a good model for enveloped pathogens. The interaction between ?6 and montmorillonite (MMT) clay (the primary component of bentonite) is explored by transmission electron microscopy. The analyses show that MMT–?6 mixtures undergo heteroaggregation, forming structures in which virtually all the virions are either sequestered between MMT platelet layers or attached to platelet edges. The virions swell and undergo disassembly resulting in partial or total envelope loss. Edge-attached viral envelopes distort to increase contact area with the positively charged platelet edges indicating that the virion surface is negatively charged. The nucleocapsid (NCs) remaining after envelope removal also exhibit distortion, in contrast to detergent-produced NCs which exhibit no distortion. This visually discernible disassembly is a mechanism for loss of infectivity previously unreported by studies of nonenveloped viruses. The MMT-mediated sequestration and disassembly result in reduced infectivity, suggesting that clays may reduce infectivity of enveloped pathogenic viruses in soils and sediments. PMID:24357622

Block, Karin A; Trusiak, Adrianna; Katz, Al; Gottlieb, Paul; Alimova, Alexandra; Wei, Hui; Morales, Jorge; Rice, William J; Steiner, Jeffrey C

2014-01-01

140

Structure property and deformation analysis of polypropylene montmorillonite nanocomposites  

NASA Astrophysics Data System (ADS)

Nanocomposites with expandable smectites such as montmorillonite layered silicates (MLS) in polymer matrices have attracted extensive application interest. Numerous MLS concentrations have been used with no particular justification. Here, we investigate the effects of MLS dispersion within the matrix and on mechanical performance. The latter is resolved through a three-prong investigation on rate dependent tensile results, time dependent creep results and the influence of a sharp notch in polypropylene (PP) nanocomposites. A fixed concentration of maleated polypropylene (mPP) was utilized as a compatibilizer between the MLS and non-polar PP. Analysis of transmission electron micrographs and X-ray diffraction patterns on the surface and below the surface of our samples revealed a unique skin-core effect induced by the presence of clay. Differential scanning calorimetric and polarized optical microscopic examination of spherulites sizes showed changes in nucleation and growth resulting from both the maleated PP compatibilizer and the MLS. These structural changes resulted in a tough nanocomposite, a concept not reported before in the PP literature. Nonlinear creep analysis of the materials showed two concentrations 3 and 5% wt of PP, which reduced the compliance in the base PP. The use of thermal wave imaging allowed the identification of ductile failure among materials, but more important, aided the mapping of the elastic and plastic contributions. These are essential concepts in fracture analysis.

Hernandez-Luna, Alejandro

141

Disassembly of the cystovirus ?6 envelope by montmorillonite clay.  

PubMed

Prior studies of clay-virus interactions have focused on the stability and infectivity of nonenveloped viruses, yielding contradictory results. We hypothesize that the surface charge distribution of the clay and virus envelope dictates how the components react and affect aggregation, viral stability, and infectivity. The bacteriophage Cystoviridae species ?6 used in this study is a good model for enveloped pathogens. The interaction between ?6 and montmorillonite (MMT) clay (the primary component of bentonite) is explored by transmission electron microscopy. The analyses show that MMT-?6 mixtures undergo heteroaggregation, forming structures in which virtually all the virions are either sequestered between MMT platelet layers or attached to platelet edges. The virions swell and undergo disassembly resulting in partial or total envelope loss. Edge-attached viral envelopes distort to increase contact area with the positively charged platelet edges indicating that the virion surface is negatively charged. The nucleocapsid (NCs) remaining after envelope removal also exhibit distortion, in contrast to detergent-produced NCs which exhibit no distortion. This visually discernible disassembly is a mechanism for loss of infectivity previously unreported by studies of nonenveloped viruses. The MMT-mediated sequestration and disassembly result in reduced infectivity, suggesting that clays may reduce infectivity of enveloped pathogenic viruses in soils and sediments. PMID:24357622

Block, Karin A; Trusiak, Adrianna; Katz, Al; Gottlieb, Paul; Alimova, Alexandra; Wei, Hui; Morales, Jorge; Rice, William J; Steiner, Jeffrey C

2014-02-01

142

Photooxidation of Polypropylene/Montmorillonite Nanocomposites. 2. Interactions with Antioxidants  

E-print Network

Photooxidation of Polypropylene/Montmorillonite Nanocomposites. 2. Interactions with Antioxidants) nanocomposites exposed to UV light was studied. Two different stabilizers were used, a phenolic antioxidant and a redox antioxidant. A significant reduction in the induction period of oxidation was observed

Paris-Sud XI, Université de

143

Dissolution of alkaline earth sulfates in the presence of montmorillonite  

USGS Publications Warehouse

In a study of the effect of montmorillonite on the dissolution of BaSO4 (barite), SrSO4 (celestite), and 226Ra from U mill tailings, it was found that: (1) More of these substances dissolve in an aqueous system that contains montmorillonite than dissolve in a similar system without clay, due to the ion exchange properties of the clay; (2) Na-montmorillonite is more effective in aiding dissolution than is Ca-montmorillonite; (3) the amount of Ra that moves from mill tailings to an exchanger increases as solution sulfate activity decreases. Leaching experiments suggest that 226Ra from H2SO4-circuit U mill tailings from Edgemont, South Dakota, is not present as pure Ra sulfate or as an impurity in anhydrite or gypsum; it is less soluble, and probably occurs as a trace constituent in barite.

Eberl, D.D.; Landa, E.R.

1985-01-01

144

The structure of uranium (VI) sorption complexes on silica, alumina, and montmorillonite  

NASA Astrophysics Data System (ADS)

We have investigated the adsorption of the uranyl ion (UO 22+) in contact with amorphous silica (SiO 2), ?-alumina (Al 2O 3), and montmorillonite surfaces in the pH range of 3.1-6.5, using X-ray absorption fine structure (XAFS) spectroscopy to observe the local structure around the uranium atom. Analysis shows that in all samples the uranyl ion structure is preserved, with two axial oxygen atoms detected at ca. 1.8 Å. For the montmorillonite samples at low pH a single equatorial oxygen shell is observed at ca. 2.4 Å, with a coordination number of 6 ± 1. At near-neutral pH (6.41) and high ion concentration (0.1 M NaCl), two separate equatorial shells are observed with bond lengths of ca. 2.30 and 2.48 Å. The samples of uranyl on silica and ?-alumina are all observed to have two separate equatorial shells with bond lengths of ca. 2.30 Å and 2.49 Å. A uranium shell at ca. 4.0 Å is observed in the near-neutral pH (˜6.5) samples of uranyl on silica and on ?-alumina. A silicon shell at ca. 3.10 Å is observed in the sample of uranyl on silica at pH 6.5. These results suggest that adsorption of the uranyl ion onto montmorillonite at low pH occurs via ion exchange, leaving the inner-sphere uranyl aquo-ion structure intact. At near-neutral pH and in the presence of a competing cation, inner-sphere complexation with the surface predominates. Adsorption of the uranyl onto the silica and ?-alumina surfaces appears to occur via an inner-sphere, bidentate complexation with the surface, with the formation of polynuclear surface complexes occurring at near-neutral pH.

Sylwester, E. R.; Hudson, E. A.; Allen, P. G.

2000-07-01

145

Montmorillonite-induced Bacteriophage ?6 Disassembly  

NASA Astrophysics Data System (ADS)

It is estimated that there are 1031 virus particles on Earth making viruses an order of magnitude more prevalent in number than prokaryotes with the vast majority of viruses being bacteriophages. Clays are a major component of soils and aquatic sediments and can react with RNA, proteins and bacterial biofilms. The clays in soils serve as an important moderator between phage and their host bacteria, helping to preserve the evolutionary balance. Studies on the effects of clays on viral infectivity have given somewhat contradictory results; possibly a consequence of clay-virus interactions being dependent on the unique structure of particular viruses. In this work, the interaction between montmorillonite and the bacteriophage ?6 is investigated. ?6 is a member of the cystovirus family that infects Pseudomonas syringe, a common plant pathogen. As a member of the cystovirus family with an enveloped structure, ?6 serves as a model for reoviruses, a human pathogen. Experiments were conducted with ?6 suspended in dilute, purified homoionic commercial-grade montmorillonite over a range of virus:clay ratios. At a 1:100000 virus:clay ratio, the clay reduced viral infectivity by 99%. The minimum clay to virus ratio which results in a measurable reduction of P. syringae infection is 1:1. Electron microscopy demonstrates that mixed suspensions of smectite and virus co-aggregate to form flocs encompassing virions within the smectite. Both free viral particles as well as those imbedded in the flocs are seen in the micrographs to be missing the envelope- leaving only the nucleocapsid (NC) intact; indicating that smectite inactivates the virus by envelope disassembly. These results have strong implications in the evolution of both the ?6 virus and its P. syringae host cells. TEM of aggregate showing several disassembled NCs.

Trusiak, A.; Gottlieb, P.; Katz, A.; Alimova, A.; Steiner, J. C.; Block, K. A.

2012-12-01

146

Interactions of pendimethalin with organo-montmorillonite complexes  

Microsoft Academic Search

Pendimethalin (PM) is a dinitroaniline herbicide, highly hydrophobic and with a very low solubility in water. It is used for pre-emergence weed control, is usually applied before sowing, and mechanically incorporated into the soil. We tested sorption of PM on montmorillonite and on two different organo-montmorillonites in a mixed water–chloroform environment, to determine the feasibility of developing an environmentally oriented

Giora Rytwo; Yotam Gonen; Shmuel Afuta; Stefan Dultz

2005-01-01

147

Preparation of ZrO2/Al2O3-montmorillonite composite as catalyst for phenol hydroxylation  

PubMed Central

Zirconium dispersed in aluminum-pillared montmorillonite was prepared as a catalyst for phenol hydroxylation. The effects of varying the Zr content on the catalyst’s physicochemical character and activity were studied with XRD, BET surface area analysis, surface acidity measurements and scanning electron microscopy before investigating the performance for phenol conversion. The zirconia dispersion significantly affects the specific surface area, the total surface acidity and surface acidity distribution related to the formation of porous zirconia particles on the surface. The prepared samples exhibited excellent catalytic activity during phenol hydroxylation.

Fatimah, Is

2013-01-01

148

Nanoscale mechanical and tribological properties of fluorocarbon films grafted onto plasma-treated low-density polyethylene surfaces  

NASA Astrophysics Data System (ADS)

Fluorocarbon (FC) films were grafted onto Ar plasma-treated low-density polyethylene (LDPE) surfaces by plasma polymerization and deposition. The evolution of the surface morphology of the grafted FC films was investigated at different scales with an atomic force microscope. Nanoscale sliding experiments performed with a surface force microscope provided insight into the nanotribological properties of Ar plasma-treated LDPE, with and without grafted FC films, in terms of applied normal load and number of sliding cycles. The observed trends are explained in the context of microstructure models accounting for morphological and structure changes at the LDPE surface due to the effects of plasma treatment (e.g., selective etching of amorphous phase, chain crosslinking and FC film grafting) and surface sliding (e.g., crystalline lamellae alignment along the sliding direction). Nanoindentation experiments elucidated the effect of plasma treatment on surface viscoelasticity and global contact stiffness. The results of this study demonstrate that plasma-assisted grafting of FC films is an effective surface modification method for tuning the nanomechanical/tribological properties of polymers.

Cheng, Q.; Komvopoulos, K.

2012-03-01

149

Wastewater effects on montmorillonite suspensions and hydraulic properties of sandy soils  

SciTech Connect

Recycled wastewater effluent is an important source of irrigation water in arid and semiarid regions. In these regions, however, irrigation water quality is one of the main factors limiting plant growth. Wastewater effluents generally contain high concentrations of suspended and dissolved solids, both organic and inorganic. Inorganic dissolved solids are only minimally removed from the effluent during conventional sewage treatment. As a result, most of the salts added during domestic and industrial usage remain in the irrigation water and may eventually reach the soil. A number of researchers have reported reduced hydraulic conductivity for soils to which treated wastewater has been applied. In this research, the influence of dissolved organic matter (DOM) contained in reclaimed wastewater effluents on the flocculation of montmorillonite and on the hydraulic properties of soils was studied. Flocculation values (FVs) for Na-montmorillonite increased with increasing concentrations of DOM at all pH levels analyzed. Maximum FV levels were exhibited for Na-montmorillonite at the highest DOM concentrations. The effect of DOM on FV can be explained by the mechanisms of edge-charge reversal and mutual flocculation. The hydraulic conductivity (HC) of a sandy soil was determined in the laboratory by leaching columns with an electrolyte solution chemically similar to that of the wastewater effluent (but without DOM). In columns treated with wastewater effluent, the HC exhibited a sharp decrease to only 20% of its initial value. The adverse effect of DOM on HC was evident for this soil despite a relatively low exchangeable sodium percentage (ESP). The reduction in HC is likely to be the result of decreases soil pore-size, which reflects two processes: (1) retention of part of the DOM during water percolation; and (2) a change in pore-size distribution due to swelling and dispersion of clay particles. The latter may result from a higher percentage of adsorbed sodium combined with the presence of humic substances from the wastewater effluent.

Tarchitzky, J.; Golobati, Y.; Keren, R.; Chen, Y.

1999-06-01

150

Surface properties and hydrophobic recovery of polymers treated by atmospheric-pressure plasma  

NASA Astrophysics Data System (ADS)

This paper provides an analysis on the relation between plasma effects on polymers exposed to inert gas atmospheric-pressure plasma, polymer structure characteristics and surface recovery during post-processing ageing. Polymers offering variety of structure, functionality, degree of oxidation, polarity, crystallinity are tested, using contact angle, XPS, XRD and solvent absorption measurement, thus exploring the relationship linking the surface polarity, the chemical structure and composition contribution in the combined functionalization/crosslinking surface modification mechanisms of plasma-exposed polymers. The limiting level of modification attainable, the surface stability and the factors controlling these are examined, concluding on the plasma capacity to provide operational stability for modified polymer surfaces.

Borcia, C.; Punga, I. L.; Borcia, G.

2014-10-01

151

Influence of annealing on the metal/semiconductor contacts deposited on sulfur-treated n-GaAs surface  

SciTech Connect

Comparative analysis of the influence of thermal annealing on Ge/Au/Ni-, Ge/Au/Ti/Au-, and Ge/Au/Ni/Ti/Au-based ohmic contacts and Ti/Au-based Schottky contacts deposited on an n-GaAs (100) surface treated and nontreated in (NH{sub 4}){sub 2}S aqueous solution have been performed. Annealing conditions for ohmic contacts are found that lead to a decrease in the specific contact resistance of sulfur-treated samples by a factor of 2.5-15 in comparison with the nontreated samples. Optimal annealing conditions are also determined for sulfur-treated GaAs samples with Schottky contacts, which make it possible to reduce the ideality factor and increase the barrier height and the breakdown voltage with respect to the nontreated samples.

Erofeev, E. V. [Micran Research and Production Company (Russian Federation); Kagadei, V. A., E-mail: vak@micran.ru [OOO Submicron Technologies (Russian Federation)

2011-09-15

152

Topographic and surface chemical aspects of the adhesion of structural epoxy resins to phosphorus oxo acid-treated aluminum adherends  

NASA Astrophysics Data System (ADS)

Structural adhesive bonding offers several advantages over other types of joining. These include improved stress distribution and increased design flexibility. Adhesive bonding is important in aerospace, automotive, and packaging applications. However, the full potential of the technology has not been exploited because the understanding of the basic mechanisms of adhesion and adhesion failure is incomplete. This investigation elucidates the chemical and mechanical mechanisms responsible for durable adhesion of epoxy resins to phosphorus oxo acid treated aluminum alloys. By systematically altering the adherend surface chemistry, surface topography, and adhesive formulation, combined with accelerated testing, the chemical and mechanical factors that influence the properties of adhesively bonded aluminum are isolated and assessed. It is postulated that a combination of two factors determines the strength and environmental durability of epoxy-bonded aluminum. One is the formation of hydrolytically stable, primary bonds between the adhesive and the adherend, and the second is the hydrolytic stability of the surface oxide, which is always present on the surface of aluminum and aluminum alloys. These conditions can best be met by chemical pretreatment of the oxide surface, which renders the oxide insoluble and creates, at the same time, functional surface sites. These sites can form chemical bonds with reactive components of the adhesive. Morphological and mechanical alteration of the metal surface oxide through hydroxide formation requires liquid water. Liquid water can only form by capillary condensation in interfacial gaps from molecularly diffusing water. A hydrolytically stable oxide will prevent bond failure due to mechanical weakening of the substrate surface, while a high density of hydrolytically stable surface bonding sites will minimize the occurrence of capillary gaps at the interface, thus decreasing the formation of liquid water. It is shown that highly chemically active, although not inherently stable, oxide surfaces can provide environmentally stable adhesive bonds. Conversely, certain highly stable oxide surfaces with few chemically active sites provide no environmental stability to adhesive joints, regardless of the topography of the surface.

Nitowski, Gary Alan

153

Characterization of wet-chemically treated silicon interfaces by surface photovoltage measurements.  

PubMed

A non-destructive and surface-sensitive surface photovoltage (SPV) technique was employed to investigate the influence of important wet-chemical treatments on the electronic surface properties. The preparation-induced surface roughness as well as the hydrogen and oxide coverage were additionally determined by spectroscopic ellipsometry (SE). High values of interface charge and a high density of rechargeable interface states were observed on atomically rough surfaces and interfaces after HF-treatment and conventional wet-chemical oxidation. Both interface charge and density of rechargeable interface states could be reduced significantly by preparing an atomically flat Si surface and a well-ordered silicon/silicon oxide interface by applying special H-termination and hot-water oxidation procedures. PMID:12397491

Angermann, H

2002-10-01

154

Structure of tetraalkylammonium ionic liquids in the interlayer of modified montmorillonite  

NASA Astrophysics Data System (ADS)

We perform molecular dynamics simulations of tetraalkylammonium ionic liquids confined in the interlayer of montmorillonite (MMT). We study the structure and energetics of the systems, which consist of cations with two different alkyl chain lengths and several ionic liquid concentrations. The results we obtained for the structure, namely the presence of a strong layering in all systems and the formation of nonpolar domains with interdigitated alkyl chains in some cases, are largely consistent with previous surface force balance experiments performed on similar systems. Finally, we show that swelling of the organo-modified MMT by a large amount of ionic liquid seems energetically favorable in all cases.

Duarte, Daniel; Salanne, Mathieu; Rotenberg, Benjamin; Bizeto, Marcos A.; Siqueira, Leonardo J. A.

2014-07-01

155

Structure of tetraalkylammonium ionic liquids in the interlayer of modified montmorillonite.  

PubMed

We perform molecular dynamics simulations of tetraalkylammonium ionic liquids confined in the interlayer of montmorillonite (MMT). We study the structure and energetics of the systems, which consist of cations with two different alkyl chain lengths and several ionic liquid concentrations. The results we obtained for the structure, namely the presence of a strong layering in all systems and the formation of nonpolar domains with interdigitated alkyl chains in some cases, are largely consistent with previous surface force balance experiments performed on similar systems. Finally, we show that swelling of the organo-modified MMT by a large amount of ionic liquid seems energetically favorable in all cases. PMID:24920411

Duarte, Daniel; Salanne, Mathieu; Rotenberg, Benjamin; Bizeto, Marcos A; Siqueira, Leonardo J A

2014-07-16

156

Influence of laser surface treated on the characterization and corrosion behavior of Al-Fe aerospace alloys  

NASA Astrophysics Data System (ADS)

In this research laser surface remelting without protective coating with a 2 kW Yb-fiber laser (IPG YLR-2000S) was applied in the Al-1.5 wt.%Fe alloy in order to investigate the layer treated with different techniques of superficial characterization, thereby, the technique of optical microscopy, atomic force microscopy and low-angle X-ray diffraction were used. The present work mainly focuses on the corrosion study by diverse techniques in aggressive environment of the laser-treated area and the substrate material was carried out, thereby, at open circuit potential testing, the results have shown a displacement to more anodic values in the corrosion potential for the laser-treated specimen when compared to the untreated specimen; in potentiodynamic polarization tests have shown that as a result of the laser treatment, the corrosion current can be reduced by as much as ten times, and a passive region was obtained, which served as an effective barrier for reducing anodic dissolution and finally, the result in cyclic polarization curves of the untreated sample there was a greater area of the hysteresis loop, implying that it is more susceptible to corrosion. This study was complemented by other techniques mentioned above in order to elucidate this study. Laser surface remelting process has definitely modified the surface film, which results in higher corrosion resistance, a large range of passivation and a lower area of the hysteresis loop.

Pariona, Moisés Meza; Teleginski, Viviane; dos Santos, Kelly; de Lima, Angela A. O. C.; Zara, Alfredo J.; Micene, Katieli Tives; Riva, Rudimar

2013-07-01

157

Formation of OTS self-assembled monolayers at chemically treated titanium surfaces  

Microsoft Academic Search

Enhanced biocompatibility of titanium implants highly depends on the possibility of achieving high degrees of surface functionalization\\u000a for a low immune response and\\/or enhanced mineralization of bioactive minerals, such as hydroxyapatite. In this respect, surface\\u000a modification with Self Assembled Monolayers (SAMs) has a great potential in delivering artificial surfaces of improved biocompatibility.\\u000a Herein, the effectiveness of common chemical pre-treatments, i.e.

Elnaz Ajami; Kondo-Francois Aguey-Zinsou

2011-01-01

158

Biofilm formation on surfaces of glass and Teflon exposed to treated water  

Microsoft Academic Search

Biofilm formation on glass and Teflon cylinders, situated on top of each other in vertical glass columns exposed to different types of treated water at a flow rate of 0.2 m\\/s, was determined using ATP analysis and heterotrophic plate counts. Biofilm formation rates (BFR) of these water types, as calculated from the linear relationship between exposure time and biomass accumulated

Dick van der Kooij; Harm R. Veenendaal; Cynthia Baars-Lorist; Daan W. van der Klift; Yvonne C. Drost

1995-01-01

159

Effet de la dilution de suspensions de kaolinite et de montmorillonite sur l'adsorption de l'atrazine  

E-print Network

Effet de la dilution de suspensions de kaolinite et de montmorillonite sur l'adsorption de l'atrazine L'étude de l'adsorption d'une base faible organique, l'atrazine (pKBH + = 1,68), par une kaolinite fixation de l'atrazine est une protonation de la molécule au voisinage de la surface, suivie d

Paris-Sud XI, Université de

160

Functional attachment of horse radish peroxidase to plasma-treated surfaces  

Microsoft Academic Search

Controlling the interaction of surfaces with macromolecules, such as proteins and antibodies, is the key to producing biocompatible prosthetic devices, biosensors and diagnostic arrays. The development of technologies to control these interactions will result in the early detection of disease and have the potential to dramatically reduce costs associated with clinical treatment. For example, tethering functional anti-bodies to a surface

Marcela M. Bilek; David R. McKenzie; Neil Nosworthy; Kerrie Davies; Richard Morrow; Palli Thordarson; Bee K. Gan; Cristobal G. dos Remedios

2004-01-01

161

Coupled chemical processes at clay/electrolyte interface: a batch titration study of Na-montmorillonites.  

PubMed

The present work addresses the protolytic charge of montmorillonite, which occurs on the broken-bond sites at the particle edges. The purpose is to overcome the general difficulty arising in potentiometric titration due to coupled side reactions, which severely impede the titrant budget (partial dissolution of the clay and of secondary phases, hydrolysis and readsorption of dissolved species, cation exchange). Batch potentiometric titrations were carried out on the montmorillonite fractions extracted from two bentonites (MX80 and SWy2) to quantify their protolytic charge. The effects of equilibration time (24 h and 7 days), pH from 4 to 10, and ionic strength (0.1 and 0.01 mol L(-1)) were extensively studied for the MX80 sample. Quantification of dissolution was achieved by analysis of the equilibrium solutions for dissolved species and by La(3+) exchange of the readsorbed species. The results clearly show that secondary phases such as iron- or silica-rich minerals contribute to the dissolved species, according to the nature of the raw bentonite. Furthermore, readsorption affects significant amounts of dissolved species. The overconsumption of proton/hydroxide due to dissolution, readsorption, and hydrolysis of dissolved species was evaluated using a self-consistent thermodynamic calculation. The ability of such calculation to correct the raw titration curves in order to extract the titrable surface charge of montmorillonite was evaluated by comparison with the continuous titration procedure. Especially in the alkaline domain, correcting the raw batch titration curves for the measured side reactions failed to reproduce the continuous titration curves. These observations demonstrate the limitations of the batch titration method and the superiority of fast, continuous methods for quantifying the dissociable surface charge of clays. PMID:16777124

Duc, Myriam; Thomas, Fabien; Gaboriaud, Fabien

2006-08-15

162

Hydrogen bonding and mechanical properties in segmented montmorillonite\\/polyurethane nanocomposites of different hard segment ratios  

Microsoft Academic Search

Hydrogen bonding in the hard segments of the synthesized montmorillonite\\/polyurethane nanocomposites of various hard segment ratios was found to decrease with the increasing amount of montmorillonite regardless of the hard segment ratios, but reached plateau values at 5wt% montmorillonite concentration. The maximal reductions of the hydrogen bonding in the polyurethane nanocomposites ranged from 20 to 37%, depending on the hard

Y. I Tien; K. H Wei

2001-01-01

163

Arsenate adsorption and desorption kinetics on a Fe(III)-modified montmorillonite.  

PubMed

The adsorption-desorption kinetics of arsenate on a Fe(III)-modified montmorillonite (Fe-M) was studied at different arsenate concentrations, pH and stirring rates. The synthesized solid was a porous sample with Fe(III) present as a mix of monomeric and polymeric Fe(III) species in the interlayer and on the external surface. Adsorption took place in a two-step mechanism, with an initial fast binding of arsenate to Fe(III) species at the external surface (half-lives of 1 min or shorter) followed by a slower binding to less accessible Fe(III) species in pores and the interlayer (half-lives of around 1 h). Desorption kinetics also reflected the presence of externally and internally adsorbed arsenate. At pH 6 the maximum adsorbed arsenate was 52 ?mol/g, a value that is low as compared to adsorption on ferrihydrite (700 ?mol/g) and goethite (192-220 ?mol/g). However, since the Fe(III) content of Fe-M is much lower than that of ferrihydrite and goethite, Fe(III) species in Fe-M are more efficient in binding arsenate than in ferrihydrite or goethite (one As atom is attached every 8.95 iron atoms). This high binding efficiency indicates that Fe(III) species are well spread on montmorillonite, forming small oligomeric species or surface clusters containing just a few iron atoms. PMID:21242027

Luengo, Carina; Puccia, Virginia; Avena, Marcelo

2011-02-28

164

Speciation of uranyl sorbed at multiple binding sites on montmorillonite  

NASA Astrophysics Data System (ADS)

We have investigated the structures of U (VI) complexes as uranyl moieties sorbed onto a reference montmorillonite, SAz-1, using X-ray absorption fine structure spectroscopy (XAFS). The uranyl-loaded clays were prepared from aqueous solutions of uranyl nitrate in the pH range from 3.0 to 3.5. The U concentrations on the clay ranged from 1.7 to 34.6% of the reported cation exchange capacity (CEC = 1.2 meq/g) of the clay. For all samples, XAFS results indicate that there are two axial oxygen atoms at 1.78-1.80 Å, as expected for the uranyl moiety. The average numbers and distances of equatorial oxygen atoms about uranyl sorbed on the clay vary significantly as a function of surface coverage. At high coverage (34.6% CEC), the average number and distance of equatorial oxygen atoms are near those found for the fully hydrated uranyl species in aqueous solution. However, there are fewer equatorial oxygen atoms at a shorter average distance about uranyl sorbed at low coverage (1.7% CEC). At moderate coverage (7.3% CEC), the average number and distance of equatorial oxygen atoms are intermediate between those at higher and lower coverage. These changes suggest that sorbing U is reacting with at least three different sites on the clay as U concentration increases. The existence of multiple surface sites and sorption complexes which are structurally distinct from solution species need to be considered for rigorous modeling of sorption processes.

Chisholm-Brause, Catherine; Conradson, Steven D.; Buscher, C. T.; Eller, P. Gary; Morris, David E.

1994-09-01

165

Surface Characterization of Vulcanized Rubber Treated with Sulfuric Acid and its Adhesion to Polyurethane Adhesive  

Microsoft Academic Search

Modifications produced on a vulcanized styrene –butadiene rubber surface by treatment with sulfuric acid were studied and several experimental variables were considered.The treatment of R1 rubber with sulfuric acid produced a noticeable decrease in contact angle which was mainly ascribed to an increase in surface energy due to the formation of sulfonic acid moieties and C?O bonds, and the removal

Carmen M. Cepeda-Jiménez; M. Mercedes Pastor-blas; Teresa P. Ferrándiz-Gómez; José Miguel Martín-Martínez

2000-01-01

166

Surface stoichiometry of pulsed ultraviolet laser treated polycrystalline CdTe  

NASA Astrophysics Data System (ADS)

The effects of nanosecond pulsed ultraviolet laser annealing on the surface stoichiometry of close-space sublimated polycrystalline thin films are investigated using angle-resolved x-ray photoemission spectroscopy (XPS). The raw data suggest the formation of a Cd-rich surface layer, but this is counter to the expectation based on Cd and Te vapor pressures above CdTe that predicts a Te-rich layer and to direct observation of elemental Te at the surface. In order to explain this apparent discrepancy, we analyze our XPS data in the context of prior reports of lateral segregation of Cd and Te at the surface after pulsed laser treatments with a simple model of angular dependent XPS in the presence of surface roughness. This analysis reveals that a uniform Te layer cannot explain our results. Instead, our analysis suggests that Te enrichment occurs near grain boundaries and that a sub-monolayer Cd layer exists elsewhere. These complex yet repeatable results underscore the challenges in measuring surface stoichiometry to high precision on films relevant for polycrystalline CdTe devices. It also suggests that the Cd and Te vapor pressures above grain boundaries may differ from those above grain interiors and that ohmic contact may be made preferentially at the grain boundaries after pulsed laser annealing.

Simonds, Brian J.; Palekis, Vasilios; Van Devener, Brian; Ferekides, Christos; Scarpulla, Michael A.

2014-07-01

167

Electrostatic model for treating long-range lateral interactions between polar molecules adsorbed on metal surfaces  

NASA Astrophysics Data System (ADS)

A classical polarizable point-dipole model for the adsorption of polar molecules on metal surfaces is presented. The main usefulness of the model is that lattice sums are represented by simple functions in closed form. This allows a simple extrapolation of adsorption energies of polar molecules—as calculated by first-principles calculations employing periodic boundary conditions—to the zero-coverage limit. Such an extrapolation is rather important for the proper evaluation of adsorption energy of highly polar molecules, because their long-range lateral interactions can extend beyond the nearest-neighbor distances of 50 bohrs. Moreover, the dependence of the adsorption energy on the orientation and configuration of molecular dipoles can be straightforwardly analyzed. It is demonstrated that an accumulation of polar molecules on the surface is favored provided that the molecular dipoles point parallel to the surface in the adsorbed state, whereas adsorbed molecules displaying dipoles oriented perpendicular to the surface would prefer to stay well separated due to repulsive lateral interactions. Further, the model is used to analyze the density-functional theory (DFT) calculated data of two polar molecules, triazole and benzotriazole, adsorbed onto Cu(111) surface. The DFT-calculated adsorption energies are about -0.5 eV, and it is shown that the main contribution to the molecule-surface bonding comes from the dipole-dipole electrostatic interactions.

Kokalj, Anton

2011-07-01

168

Functional attachment of horse radish peroxidase to plasma-treated surfaces  

NASA Astrophysics Data System (ADS)

Controlling the interaction of surfaces with macromolecules, such as proteins and antibodies, is the key to producing biocompatible prosthetic devices, biosensors and diagnostic arrays. The development of technologies to control these interactions will result in the early detection of disease and have the potential to dramatically reduce costs associated with clinical treatment. For example, tethering functional anti-bodies to a surface in a patterned array allows the selection of specific proteins from a microlitre serum sample, immediately identifying diseases, well before the symptoms are manifested. Unfortunately, simple physical absorption of proteins onto most surfaces results in changes in their structure and loss of function. The use of ions from plasmas allows flexibility in surface modification by accessing a variety of ion energies and activated chemical species. In this paper we describe plasma based techniques which are being developed to modify the chemistry and morphology of surfaces in order to optimise their interaction with biomolecules. Early results of plasma processes to activate surfaces for non specific attachment of proteins by hydrophilic /hydrophobic interactions are presented, with particular attention to the time stability of such treatments, which is of special interest.

Bilek, Marcela M.; McKenzie, David R.; Nosworthy, Neil; Davies, Kerrie; Morrow, Richard; Thordarson, Palli; Gan, Bee K.; dos Remedios, Cristobal G.

2004-02-01

169

Investigation of surface properties of Ar-plasma treated polyethylene terephthalate (PET) films  

NASA Astrophysics Data System (ADS)

The effect of low energy argon plasma treatment on the surfaces of polyethylene terephthalate (PET) was investigated by means of contact angle measurement, X-ray photoelectron spectroscopy (XPS), Vickers' microhardness indentation and atomic force microscopy (AFM). It was observed that the surface free energy (SFE) changes from 42.1 mJ/m2 to 85.1 mJ/m2 with the increase of plasma treatment time and the corresponding contact angle changes from 60o to 15o. The increase in SFE after plasma treatment is attributed to the functionalization of the polymer surface with hydrophilic groups. The XPS analysis shows the increase in C-O and Cdbnd O groups after plasma treatment of the polymer surface. The microhardness of the film increases with the treatment time. This may be attributed to the cross linking effect at the surface. Atomic force microscopy (AFM) reveals that average surface roughness increases from 5.8 nm to 49.7 nm as treatment time increases.

Pelagade, S. M.; Singh, N. L.; Qureshi, Anjum; Rane, R. S.; Mukherjee, S.; Deshpande, U. P.; Ganesan, V.; Shripathi, T.

2012-10-01

170

Electrical characteristics of TMAH-surface treated Ni/Au/Al2O3/GaN MIS Schottky structures  

NASA Astrophysics Data System (ADS)

The electrical characteristics and reverse leakage mechanisms of tetramethylammonium hydroxide (TMAH) surface-treated Ni/Au/Al2O3/GaN metal-insulator-semiconductor (MIS) diodes were investigated by using the current-voltage ( I-V) and capacitance-voltage ( C-V) characteristics. The MIS diode was formed on n-GaN after etching the AlGaN in the AlGaN/GaN heterostructures. The TMAH-treated MIS diode showed better Schottky characteristics with a lower ideality factor, higher barrier height and lower reverse leakage current compared to the TMAH-free MIS diode. In addition, the TMAH-free MIS diodes exhibited a transition from Poole-Frenkel emission at low voltages to Schottky emission at high voltages, whereas the TMAH-treated MIS diodes showed Schottky emission over the entire voltage range. Reasonable mechanisms for the improved device-performance characteristics in the TMAH-treated MIS diode are discussed in terms of the decreased interface state density or traps associated with an oxide material and the reduced tunneling probability.

Reddy, M. Siva Pratap; Lee, Jung-Hee; Jang, Ja-Soon

2014-03-01

171

Speciation of uranium(VI) sorption complexes on montmorillonite  

SciTech Connect

Environmental contaminant releases that contain uranium are among the most serious problems that must be confronted by restoration programs. To facilitate restoration, information concerning the speciation of uranium is needed. Under oxidizing conditions, dissolved uranium is predominantly in the U(VI) (uranyl) form and is quite mobile in the environment, however sorption onto soils may retard its movement. In this study, we have investigated the effects of changes in solution speciation on the nature of uranyl sorption complexes on montmorillonite, a common soil constituent. Aqueous U(VI) solutions between pH 3 to 7 were batch-equilibrated with montmorillonite for several days; specific pH values were selected such that the solutions consisted of dominantly monomeric, oligomeric, or a mix of monomeric and oligomeric aqueous uranyl species. Emission spectroscopy was used to investigate the nature of U(VI) sorbed to montmorillonite.

Chisholm-Brause, C.J.; Morris, D.E. (Los Alamos National Lab., NM (United States)); Richard, R.E. (Fort Lewis Coll., Durango, CO (United States). Dept. of Chemistry)

1992-01-01

172

Speciation of uranium(VI) sorption complexes on montmorillonite  

SciTech Connect

Environmental contaminant releases that contain uranium are among the most serious problems that must be confronted by restoration programs. To facilitate restoration, information concerning the speciation of uranium is needed. Under oxidizing conditions, dissolved uranium is predominantly in the U(VI) (uranyl) form and is quite mobile in the environment, however sorption onto soils may retard its movement. In this study, we have investigated the effects of changes in solution speciation on the nature of uranyl sorption complexes on montmorillonite, a common soil constituent. Aqueous U(VI) solutions between pH 3 to 7 were batch-equilibrated with montmorillonite for several days; specific pH values were selected such that the solutions consisted of dominantly monomeric, oligomeric, or a mix of monomeric and oligomeric aqueous uranyl species. Emission spectroscopy was used to investigate the nature of U(VI) sorbed to montmorillonite.

Chisholm-Brause, C.J.; Morris, D.E. [Los Alamos National Lab., NM (United States); Richard, R.E. [Fort Lewis Coll., Durango, CO (United States). Dept. of Chemistry

1992-05-01

173

Iterative Inversion Method for Eddy Current Evaluation of Near-Surface Residual Stress Profile in Surface-Treated Metals  

SciTech Connect

Because of their frequency-dependent penetration depth, eddy current measurements are capable of mapping the near-surface depth profile of the electric conductivity. This technique can be used to nondestructively characterize the subsurface residual stress distribution in certain types of shot-peened metals, e.g., in nickel-base superalloys. To predict the depth-dependent, but frequency-independent, intrinsic electric conductivity from the frequency-dependent apparent eddy current conductivity (AECC), a highly convergent iterative inversion procedure is presented. The proposed technique exploits three specific features of the subsurface electric conductivity variation caused by near-surface residual stresses in shot-peened metals. First, compressive residual stresses are limited to a shallow surface region of depth much less than typical probe coil diameters. Second, the change in electric conductivity due to residual stresses is always very small, typically less than 1%. Third, the electric conductivity profile is fairly smooth and continuous. The accuracy of the proposed iterative inversion procedure is one order of magnitude better than that of the previously developed simpler method (J. Appl. Phys. 96, 1257 2004)

Abu-Nabah, Bassam A.; Nagy, Peter B. [Department of Aerospace Engineering and Engineering Mechanics, University of Cincinnati, Cincinnati, Ohio 45221-0070 (United States)

2007-03-21

174

Nanoscale evaluation of laser-based surface treated 12Ni maraging steel  

NASA Astrophysics Data System (ADS)

Maraging steels are used in several high-tech areas. Among them are highly thermo-mechanically loaded vital parts of die casting dies for pressure die casting of aluminium and magnesium alloys. From the economic point of view, the operation life of dies is extremely important to the price of the castings. Operational life can be successfully extended by a regular maintenance of die parts. Laser surfacing is a very promising process for rebuilding of worn out surfaces of vital die parts. In this research, the state in the maraging steel 1.2799 (DIN) after the application of laser surfacing process has been analysed using scanning electron microscope. The analysis revealed diverse microstructure through-depth of the laser-surfaced specimens. On the basis of the estimated size and volume fraction of the nano-precipitates in the individual microstructure zones located through-depth of the heat-affected zone, a through-depth variation of microhardness was predicted. The results are supported by Vickers microhardness tests. It was confirmed that the mechanical properties of the 1.2799 maraging steel strongly depend on the characteristic at the nano or micro level. Some of the results obtained can be also applied to laser surface heat treatment of maraging steels.

Grum, J.; Slabe, J. M.

2005-07-01

175

Analysis of the Release Characteristics of Cu-Treated Antimicrobial Implant Surfaces Using Atomic Absorption Spectrometry  

PubMed Central

New developments of antimicrobial implant surfaces doped with copper (Cu) ions may minimize the risk of implant-associated infections. However, experimental evaluation of the Cu release is influenced by various test parameters. The aim of our study was to evaluate the Cu release characteristics in vitro according to the storage fluid and surface roughness. Plasma immersion ion implantation of Cu (Cu-PIII) and pulsed magnetron sputtering process of a titanium copper film (Ti-Cu) were applied to titanium alloy (Ti6Al4V) samples with different surface finishing of the implant material (polished, hydroxyapatite and corundum blasted). The samples were submersed into either double-distilled water, human serum, or cell culture medium. Subsequently, the Cu concentration in the supernatant was measured using atomic absorption spectrometry. The test fluid as well as the surface roughness can alter the Cu release significantly, whereby the highest Cu release was determined for samples with corundum-blasted surfaces stored in cell medium. PMID:22162672

Zietz, Carmen; Fritsche, Andreas; Finke, Birgit; Stranak, Vitezslav; Haenle, Maximilian; Hippler, Rainer; Mittelmeier, Wolfram; Bader, Rainer

2012-01-01

176

A model expansion criterion for treating surface topography in ray path calculations using the eikonal equation  

NASA Astrophysics Data System (ADS)

Irregular surface topography has revolutionized how seismic traveltime is calculated and the data are processed. There are two main schemes for dealing with an irregular surface in the seismic first-arrival traveltime calculation: (1) expanding the model and (2) flattening the surface irregularities. In the first scheme, a notional infill medium is added above the surface to expand the physical space into a regular space, as required by the eikonal equation solver. Here, we evaluate the chosen propagation velocity in the infill medium through ray path tracking with the eikonal equation-solved traveltime field, and observe that the ray paths will be physically unrealistic for some values of this propagation velocity. The choice of a suitable propagation velocity in the infill medium is crucial for seismic processing of irregular topography. Our model expansion criterion for dealing with surface topography in the calculation of traveltime and ray paths using the eikonal equation highlights the importance of both the propagation velocity of the infill physical medium and the topography gradient.

Ma, Ting; Zhang, Zhongjie

2014-04-01

177

Nanofabrication via direct transfer of BOE treated PDMS stamp patterns onto SiO2 surfaces  

NASA Astrophysics Data System (ADS)

Various PDMS patterns with a few microns to sub-micron size and thickness of 20~30 nanometers were successfully transferred on the substrate via simple printing process of a buffered oxide etchant-treated PDMS stamp on the SiO2 substrate. The patterned PDMS layer acted as sacrificial layer for metal-film patterning and as chemical passivation layer for the selective adsorption of V2O5 nanowires. In particular, the electrical measurement of the patterned V2O5 nanowire network showed the semiconducting non-ohmic behavior in the channel.

Kim, Yong-Kwan; Park, Jae-Hyun; Shin, Gun-Chul; Ha, Jeong Sook; Park, So Jeong; Yi, Seong Min; Kim, Gyu Tae

2007-03-01

178

Surface free energy analysis for bipolar pulsed argon plasma treated polymer films  

NASA Astrophysics Data System (ADS)

The effect of low energy (300 eV) argon plasma treatment on the morphology of polycarbonate was studied by means of contact angle measurement, X-ray photoelectron spectroscopy (XPS), Vickers' micro hardness indentation and atomic force microscopy (AFM). The surface free energy (SFE) changes from 38.5 mJ/m2 to 74.9 mJ/m2 on increasing the treatment time and the corresponding contact angle was changed from 63° to 17°, which shows the enhancement in surface adhesion. The XPS analysis shows the increase of the C-O and C=O functional groups upon treatment. The Vickers' micro hardness was studied in the load range 10-500 gf. The micro hardness of the film increases with the treatment time. Atomic force microscopy (AFM) reveals that average surface roughness increases from 7.0 nm to 27.2 nm as treatment time increases.

Pelagade, S.; Singh, N. L.; Shah, Sejal; Qureshi, Anjum; Rane, R. S.; Mukherjee, S.; Deshpande, U. P.; Ganesan, V.; Shripathi, T.

2010-02-01

179

Hydrogen effect on zirconium alloy surface treated by pulsed electron beam  

NASA Astrophysics Data System (ADS)

Influence of modification by pulsed electron beam (PEB) and hydrogen adsorption in zirconium alloys have been investigated. Treatment of Zr-1Nb alloy by high-current PEB allows for a decrease in the amount of hydrogen absorbed by the samples during the hydrogenation process from gas atmosphere in the temperature range of (350-550 °?). The effect of the PEB surface treatment on the hydrogen adsorption connected with the formation of a protective oxide film after PEB irradiation and also by the formation of a specific hardening structure under the action of irradiation at temperatures exceeding the melting temperature from the subsequent high-speed surface cooling.

Pushilina, N. S.; Lider, A. M.; Kudiiarov, V. N.; Chernov, I. P.; Ivanova, S. V.

2015-01-01

180

Treated wastewater effluent as a source of microbial pollution of surface water resources.  

PubMed

Since 1990, more than 1.8 billion people have gained access to potable water and improved sanitation worldwide. Whilst this represents a vital step towards improving global health and well-being, accelerated population growth coupled with rapid urbanization has further strained existing water supplies. Whilst South Africa aims at spending 0.5% of its GDP on improving sanitation, additional factors such as hydrological variability and growing agricultural needs have further increased dependence on this finite resource. Increasing pressure on existing wastewater treatment plants has led to the discharge of inadequately treated effluent, reinforcing the need to improve and adopt more stringent methods for monitoring discharged effluent and surrounding water sources. This review provides an overview of the relative efficiencies of the different steps involved in wastewater treatment as well as the commonly detected microbial indicators with their associated health implications. In addition, it highlights the need to enforce more stringent measures to ensure compliance of treated effluent quality to the existing guidelines. PMID:24366046

Naidoo, Shalinee; Olaniran, Ademola O

2014-01-01

181

Treated Wastewater Effluent as a Source of Microbial Pollution of Surface Water Resources  

PubMed Central

Since 1990, more than 1.8 billion people have gained access to potable water and improved sanitation worldwide. Whilst this represents a vital step towards improving global health and well-being, accelerated population growth coupled with rapid urbanization has further strained existing water supplies. Whilst South Africa aims at spending 0.5% of its GDP on improving sanitation, additional factors such as hydrological variability and growing agricultural needs have further increased dependence on this finite resource. Increasing pressure on existing wastewater treatment plants has led to the discharge of inadequately treated effluent, reinforcing the need to improve and adopt more stringent methods for monitoring discharged effluent and surrounding water sources. This review provides an overview of the relative efficiencies of the different steps involved in wastewater treatment as well as the commonly detected microbial indicators with their associated health implications. In addition, it highlights the need to enforce more stringent measures to ensure compliance of treated effluent quality to the existing guidelines. PMID:24366046

Naidoo, Shalinee; Olaniran, Ademola O.

2013-01-01

182

Synthesis of an intercalated compound of montmorillonite and 6-polyamide  

Microsoft Academic Search

Natural montmorillonite, fractionated from bentonite produced in Yamagata, Japan, was ion-exchanged for NH3+-(CH2)11-COOH, NH3+-(CH2)5-COOH, Al3+, Cu2+, Mg2+, Co2+, Li+, K+ and H+. The mixtures of the ion-exchanged montmorillonite and e-caprolactam were heated at 263°C in glass ampoules for various periods. The intercalated compounds before and after the heating were examined by X-ray powder diffraction, DSC and GPC. Although e-caprolactam was

Yoshiaki Fukushima; Shinji Inagaki

1987-01-01

183

Mg ion implantation on SLA-treated titanium surface and its effects on the behavior of mesenchymal stem cell.  

PubMed

Magnesium (Mg) is one of the most important ions associated with bone osseointegration. The aim of this study was to evaluate the cellular effects of Mg implantation in titanium (Ti) surfaces treated with sand blast using large grit and acid etching (SLA). Mg ions were implanted into the surface via vacuum arc source ion implantation. The surface morphology, chemical properties, and the amount of Mg ion release were evaluated by scanning electron microscopy (SEM), Auger electron spectroscopy (AES), Rutherford backscattering spectroscopy (RBS), and inductively coupled plasma-optical emission spectrometer (ICP-OES). Human mesenchymal stem cells (hMSCs) were used to evaluate cellular parameters such as proliferation, cytotoxicity, and adhesion morphology by MTS assay, live/dead assay, and SEM. Furthermore, osteoblast differentiation was determined on the basis of alkaline phosphatase (ALP) activity and the degree of calcium accumulation. In the Mg ion-implanted disk, 2.3×10(16) ions/cm(2) was retained. However, after Mg ion implantation, the surface morphology did not change. Implanted Mg ions were rapidly released during the first 7 days in vitro. The MTS assay, live/dead assay, and SEM demonstrated increased cell attachment and growth on the Mg ion-implanted surface. In particular, Mg ion implantation increased the initial cell adhesion, and in an osteoblast differentiation assay, ALP activity and calcium accumulation. These findings suggest that Mg ion implantation using the plasma source ion implantation (PSII) technique may be useful for SLA-treated Ti dental implants to improve their osseointegration capacity. PMID:23827608

Kim, Beom-Su; Kim, Jin Seong; Park, Young Min; Choi, Bo-Young; Lee, Jun

2013-04-01

184

Mechanisms of CO2 Interaction with Montmorillonite  

NASA Astrophysics Data System (ADS)

Improved understanding of basic fluid-rock interactions can lead to more accurate models of the coupled fluid-flow and geomechanics in engineered geological systems. We studied carbon dioxide (CO2) interaction with source clay samples from The Clay Minerals Society. The manometric, infrared (IR) and X-ray diffraction (XRD) data indicated that montmorillonite can permanently trap CO2 molecules in its interlayer, after dynamic exposure to supercritical CO2. Such trapping is quite secure and appears to result in partial carbonate formation. Molecular dynamics simulations were carried out to investigate CO2 intercalation into the interlayer and its interaction with interlayer species. Previously reported results of simulations using simplified smectite models suggested that the experimentally observed red shift of the asymmetric-stretch vibrational mode for the trapped carbon dioxide can be attributed to induced polarization of the CO2 molecule by the interlayer water molecules. Modified smectite models were designed to account for the naturally occurring structural disorder that allows guest molecules to occupy localized interlamellar voids. In such models, energy dependences and structural rearrangements of the interlayer species are governed by rotational misalignment in turbostratically disordered clay. CO2 invasion in the interlayer disrupts the long-range ordering of water molecules and cations thus forcing the system to adopt energetically unfavorable configurations. New findings indicate that interaction between intercalated CO2 and H2O is limited and, with the increasing interlayer hydration, CO2 preferentially accumulates in interlamellar voids. The vibrational spectra produced by the new model, assuming that clay systems can exist in fractional hydration states, show either a combination of undisturbed and red-shifted asymmetric-stretch modes or a broad peak consistent with the multiple smeared peaks, which explain the multi-mode features that have appeared in experimental IR spectra.

Romanov, V.; Myshakin, E. M.; Howard, B.; Guthrie, G.

2013-12-01

185

Characterization of plasma treated surfaces for food safety by terahertz spectroscopy  

NASA Astrophysics Data System (ADS)

A physico-chemical approach to modify surfaces not only for use in medicine, but also for preservation of food is nowadays widely studied to lower the risks of increased number of bacterial pathogens that are in a direct contact with people. Food safety is very important part of preserving sustainability during crises, especially after the enterohaemorrhagic Escherichia coli outbreak in Europe in 2011. One of the possibility how we can protect food against various pathogens is the modification of packing materials that are directly in contact with preserved food. This contribution deals with the characterization of modified surfaces with antibacterial properties via Terahertz spectroscopy. For the purpose of this paper, three monomers were used for grafting onto air radiofrequency plasma activated low density polyethylene surface, which created a brush-like structure. Next, the antibacterial agents, Irgasan and Chlorhexidine, were anchored to these surfaces. These antibacterial agents were selected for supposed effect on two most frequently occurring bacterial strains - Escherichia coli and Staphylococcus aureus. Materials were further tested for the presence of antibacterial agent molecules, in our case by means of terahertz spectroscopy. Each material was tested on two spectroscopes - the SPECTRA and the OSCAT terahertz instruments.

Sulovská, Kate?ina; Lehocký, Marián.

2014-10-01

186

Surface chemistry, pore sizes and adsorption properties of activated carbon fibers and precursors treated with ammonia  

Microsoft Academic Search

A series of activated carbon fibers (ACFs) were produced by treatment with ammonia to yield a basic surface. The micropore sizes of these chemically modified fibers were determined with nitrogen adsorption experiments and they were shown to increase with increasing activation time and temperature. The types of groups present were analyzed by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy

Christian L Mangun; Kelly R Benak; James Economy; Kenneth L Foster

2001-01-01

187

First Low-Iron Materials on Mars and Possibility of a Major Montmorillonite Component  

NASA Astrophysics Data System (ADS)

During exploration of Columbia Hills at Gusev crater, the Spirit rover of the MER mission has discovered several separate occurrences of material with a unique elemental signature. As measured by x-ray fluorescence emission using the APXS instrument, these samples stand out for their low Fe content, accompanied by corresponding increases in Al and Si but without high concentrations of mineralogically important cations such as Ca, Mg, Na, or K. No previous martian samples, from five landed missions and numerous martian meteorites, have such low iron content. Chemical trends implicate Mg sulfates and Ca phosphates are important but minor accessory minerals. Moessbauer analysis indicates some or all Ti to be present as ilmenite. The remaining component has high Al and Si abundances in proportions within the range of classical montmorillonite compositions found at various locations on Earth, including their correspondingly low concentrations of major cations. Typically the result of weathering of basaltic ash and often associated with more arid environments, the formation of montmorillonite or its alteration-product precursor implies that significant aqueous activity to facilitate geochemical separations occurred. In addition, various of these samples contain trace element anomalies that are unique for martian materials, including enrichments in Cu, Ni, Y, Ga, Cr, and possibly Pb, Co, Sr, and Zn. Adsorption by high cation exchange minerals such as montmorillonite clays or other alteration materials (allophane, silica, imogolite) often bear similar fingerprints due to their high-area charged surfaces which confer affinities for multivalent metal ions in solution. Samples of this "Independence Class" of materials have been found at three separated sites in the upper portion of Husband Hill. The samples are disparate in form, including clods (or peds), an outcrop, and a "rock". Their lighter color and rugged morphology are a common feature. The latter may indicate susceptibility to fragmentation, with possible derivation from a deeper-lying layer of source material.

Clark, B. C.; Richter, L.; Gellert, R.; Farrand, W.; Ming, D. W.; Morris, R. V.; Yen, A.

2005-12-01

188

A comparative study and evaluation of sulfamethoxazole adsorption onto organo-montmorillonites.  

PubMed

Three organo-montmorillonites were prepared using surfactants, and their adsorption behaviors toward sulfamethoxazole (SMX) were investigated. The surfactants used were cetyltrimethyl ammonium bromide (CTMAB), 3-(N,N-dimethylhexadecylammonio) propane sulfonate (HDAPS) and 1,3-bis(hexadecyldimethylammonio)-propane dibromide (BHDAP). The properties of the organo-montmorillonites were characterized by X-ray diffraction, scanning electron microscopy and N2 adsorption-desorption isotherm measurements. Results showed that the interlayer spacing of montmorillonite was increased and the surface area as well as the morphology were changed. Batch adsorption experiments showed that the surfactant loading amount had a great effect on the adsorption of SMX. The adsorption process was pH dependent and the maximum adsorption capacity was obtained at pH3 for HDAPS-Mt, while CTMAB-Mt and BHDAP-Mt showed a high removal efficiency at 3-11. The adsorption capacity increased with the initial SMX concentration and contact time but decreased with increasing solution ionic strength. Kinetic data were best described by the pseudo second-order model. Equilibrium data were best represented by the Langmuir model, and the Freundlich constant (n) indicated a favorable adsorption process. The maximum adsorption capacity of SMX was 235.29mg/g for CTMAB-Mt, 155.28mg/g for HDAPS-Mt and 242.72mg/g for BHDAP-Mt. Thermodynamic parameters were calculated to evaluate the spontaneity and endothermic or exothermic nature. The adsorption mechanism was found to be dominated by electrostatic interaction, while hydrophobic interaction played a secondary role. PMID:25499502

Lu, Laifu; Gao, Manglai; Gu, Zheng; Yang, Senfeng; Liu, Yuening

2014-12-01

189

Hydrophobic recovery of UV/ozone treated poly(dimethylsiloxane): adhesion studies by contact mechanics and mechanism of surface modification  

NASA Astrophysics Data System (ADS)

Silicone elastomers (Sylgard 184 and 170), based on poly(dimethylsiloxane) (PDMS), were surface treated by a combined exposure to UV and ozone. The effects of the treatments were analyzed as a function of time elapsed after stopping the treatments using different standard surface characterization techniques, such as water contact angle measurements, XPS and atomic force microscopy (AFM). However, the primary focus of this study was to apply the Johnson-Kendall-Roberts (JKR) contact mechanics approach to investigate PDMS samples prior to and following UV/ozone surface treatment. A gradual formation of a hydrophilic, silica-like surface layer with increasing modulus was observed with increasing UV/ozone exposure. A subsequent hydrophobic recovery after UV/ozone exposure was observed, as indicated by increasing contact angles. This supports the hypothesis that the hydrophobic recovery is mainly caused by the gradual coverage of a permanent silica-like structure with free siloxanes and/or reorientation of polar groups. PDMS containing a homogenously dispersed filler (Sylgard 184), exhibited a decreasing surface roughness (by AFM) when the oxidized surface region "collapsed" into a smooth SiO x layer (final surface roughness <2 nm). PDMS containing heterogeneously distributed, aggregated filler particles (Sylgard 170), exhibited an increasing surface roughness with treatment dose, which was attributed to the "collapse" of the oxidized surface region thus exposing the contours of the underlying filler aggregates (final surface roughness ˜140 nm). A dedicated device was designed and built to study the contact mechanics behavior of PDMS prior to, and following surface treatment. The value of the combined elastic modulus obtained for PDMS lens and semi-infinite flat surface system showed an increase in full agreement with the formation of a silica-like layer exhibiting a high elastic modulus (compared with untreated PDMS). The work of adhesion observed in JKR experiments exhibited an increasing trend as a function of treatment done in agreement with contact angle data. JKR experiments showed hydrophobic recovery behavior as anticipated from contact angle measurements. Single pull-off force measurements by JKR and numerical analysis of full-approach JKR curves were in quantitative agreement regarding practical work of adhesion values.

Oláh, Attila; Hillborg, Henrik; Vancso, G. Julius

2005-01-01

190

Thermal Characteristics of ThermoBrachytherapy Surface Applicators (TBSA) for Treating Chestwall Recurrence  

PubMed Central

Purpose To study temperature and thermal dose distributions of ThermoBrachytherapy Surface Applicators (TBSA) developed for concurrent or sequential high dose rate (HDR) brachytherapy and microwave hyperthermia treatment of chest wall recurrence and other superficial disease. Methods A steady state thermodynamics model coupled with the fluid dynamics of water bolus and electromagnetic radiation of hyperthermia applicator is used to characterize the temperature distributions achievable with TBSA applicators in an elliptical phantom model of the human torso. Power deposited by 915 MHz conformal microwave array (CMA) applicators is used to assess the specific absorption rate (SAR) distributions of rectangular (500 cm2) and L-shaped (875 cm2) TBSA. The SAR distribution in tissue and fluid flow distribution inside the Dual-Input Dual-Output (DIDO) water bolus are coupled to solve the steady state temperature and thermal dose distributions of rectangular TBSA (R-TBSA) for superficial tumor targets extending 10–15 mm beneath the skin surface. Thermal simulations are carried out for a range of bolus inlet temperature (Tb=38–43°C), water flow rate (Qb=2–4 L/min) and tumor blood perfusion (?b=2–5 kg/m3/s) to characterize their influence on thermal dosimetry. Results Steady state SAR patterns of R- and L-TBSA demonstrate the ability to produce conformal and localized power deposition inside tumor target sparing surrounding normal tissues and nearby critical organs. Acceptably low variation in tissue surface cooling and surface temperature homogeneity was observed for the new DIDO bolus at 2 L/min water flow rate. Temperature depth profiles and thermal dose volume histograms indicate bolus inlet temperature (Tb) to be the most influential factor on thermal dosimetry. A 42 °C water bolus was observed to be the optimal choice for superficial tumors extending 10–15 mm from the surface even under significant blood perfusion. Lower bolus temperature may be chosen to reduce thermal enhancement ratio (TER) in the most sensitive skin where maximum radiation dose is delivered and to extend thermal enhancement of radiation dose deeper. Conclusion This computational study indicates that well-localized elevation of tumor target temperature to 40–44 °C can be accomplished by large surface-conforming TBSA applicators using appropriate selection of coupling bolus temperature. PMID:20224154

Arunachalam, K.; Maccarini, P. F.; Craciunescu, O. I.; Schlorff, J. L.; Stauffer, P. R.

2010-01-01

191

Effect of adsorbed iron on thermoluminescence and electron spin resonance spectra of Ca-Fe-exchanged montmorillonite  

NASA Technical Reports Server (NTRS)

The ESR spectra and the natural and gamma-induced thermoluminescence (TL) glow curves of a series of variably cation-exchanged Fe-Ca-clays prepared from SWy-1 montmorillonite were examined. The ESR signal intensity associated with surface Fe increased linearly with surface Fe content up to a nominal concentration of 50 percent exchangeable Fe. At above 50 percent exchangeable Fe, no appreciable increase in the signal was noted. The TL intensity decreased linearly with increasing surface Fe up to 50 percent nominal exchangeable Fe. At above 50 percent, the signal was not appreciably further diminished. Possible effects of Fe on quenching of TL are considered.

Coyne, Lelia M.; Banin, Amos

1986-01-01

192

Synthesis of silver/montmorillonite nanocomposites using ?-irradiation.  

PubMed

Silver nanoparticles (Ag-NPs) were synthesized into the interlamellar space of montmorillonite (MMT) by using the ?-irradiation technique in the absence of any reducing agent or heat treatment. Silver nitrate and ?-irradiation were used as the silver precursor and physical reducing agent in MMT as a solid support. The MMT was suspended in the aqueous AgNO(3) solution, and after the absorption of silver ions, Ag(+) was reduced using the ?-irradiation technique. The properties of Ag/MMT nanocomposites and the diameters of Ag-NPs were studied as a function of ?-irradiation doses. The interlamellar space limited particle growth (d-spacing [d(s)] = 1.24-1.42 nm); powder X-ray diffraction and transmission electron microscopy (TEM) measurements showed the production of face-centered cubic Ag-NPs with a mean diameter of about 21.57-30.63 nm. Scanning electron microscopy images indicated that there were structure changes between the initial MMT and Ag/MMT nanocomposites under the increased doses of ?-irradiation. Furthermore, energy dispersive X-ray fluorescence spectra for the MMT and Ag/ MMT nanocomposites confirmed the presence of elemental compounds in MMT and Ag-NPs. The results from ultraviolet-visible spectroscopy and TEM demonstrated that increasing the ?-irradiation dose enhanced the concentration of Ag-NPs. In addition, the particle size of the Ag-NPs gradually increased from 1 to 20 kGy. When the ?-irradiation dose increased from 20 to 40 kGy, the particle diameters decreased suddenly as a result of the induced fragmentation of Ag-NPs. Thus, Fourier transform infrared spectroscopy suggested that the interactions between Ag-NPs with the surface of MMT were weak due to the presence of van der Waals interactions. The synthesized Ag/MMT suspension was found to be stable over a long period of time (ie, more than 3 months) without any sign of precipitation. PMID:21170354

Shameli, Kamyar; Ahmad, Mansor Bin; Yunus, Wan Md Zin Wan; Ibrahim, Nor Azowa; Gharayebi, Yadollah; Sedaghat, Sajjad

2010-01-01

193

Synthesis of silver/montmorillonite nanocomposites using ?-irradiation  

PubMed Central

Silver nanoparticles (Ag-NPs) were synthesized into the interlamellar space of montmorillonite (MMT) by using the ?-irradiation technique in the absence of any reducing agent or heat treatment. Silver nitrate and ?-irradiation were used as the silver precursor and physical reducing agent in MMT as a solid support. The MMT was suspended in the aqueous AgNO3 solution, and after the absorption of silver ions, Ag+ was reduced using the ?-irradiation technique. The properties of Ag/MMT nanocomposites and the diameters of Ag-NPs were studied as a function of ?-irradiation doses. The interlamellar space limited particle growth (d-spacing [ds] = 1.24–1.42 nm); powder X-ray diffraction and transmission electron microscopy (TEM) measurements showed the production of face-centered cubic Ag-NPs with a mean diameter of about 21.57–30.63 nm. Scanning electron microscopy images indicated that there were structure changes between the initial MMT and Ag/MMT nanocomposites under the increased doses of ?-irradiation. Furthermore, energy dispersive X-ray fluorescence spectra for the MMT and Ag/ MMT nanocomposites confirmed the presence of elemental compounds in MMT and Ag-NPs. The results from ultraviolet-visible spectroscopy and TEM demonstrated that increasing the ?-irradiation dose enhanced the concentration of Ag-NPs. In addition, the particle size of the Ag-NPs gradually increased from 1 to 20 kGy. When the ?-irradiation dose increased from 20 to 40 kGy, the particle diameters decreased suddenly as a result of the induced fragmentation of Ag-NPs. Thus, Fourier transform infrared spectroscopy suggested that the interactions between Ag-NPs with the surface of MMT were weak due to the presence of van der Waals interactions. The synthesized Ag/MMT suspension was found to be stable over a long period of time (ie, more than 3 months) without any sign of precipitation. PMID:21170354

Shameli, Kamyar; Ahmad, Mansor Bin; Yunus, Wan Md Zin Wan; Ibrahim, Nor Azowa; Gharayebi, Yadollah; Sedaghat, Sajjad

2010-01-01

194

Treating Curved Surfaces in a 3D Finite Element Program for Parallel Computers  

Microsoft Academic Search

This paper provides both a simple and for many purposes sufficient method of definingand dealing with curved surfaces in a 3D Finite Element program ([1], [10], [12], [13]).Automatic mesh generation for three-dimensional problems, especially with respect tothe parallelization of computational algorithms, has become a research field of currentinterest where different approaches are applicable ([6], [7], [9]).In this paper we use

Matthias Pester

1997-01-01

195

Electrostatic model for treating long-range lateral interactions between polar molecules adsorbed on metal surfaces  

Microsoft Academic Search

A classical polarizable point-dipole model for the adsorption of polar molecules on metal surfaces is presented. The main usefulness of the model is that lattice sums are represented by simple functions in closed form. This allows a simple extrapolation of adsorption energies of polar molecules---as calculated by first-principles calculations employing periodic boundary conditions---to the zero-coverage limit. Such an extrapolation is

Anton Kokalj

2011-01-01

196

Investigation on oxygen controlled liquid lead corrosion of surface treated steels  

Microsoft Academic Search

A low alloyed martensitic steel Fe9Cr (OPTIFER IVc) and an austenitic steel 16Cr15Ni (1.4970) were exposed to liquid lead to examine their suitability as structural material for lead cooled accelerator driven subcritical actinide burners. The surface of part of the steel specimens was restructured and that of another part was alloyed with Al by treatment with high power pulsed electron

G. Muller; G Schumacher; F Zimmermann

2000-01-01

197

Surface and pore structure of deoiled acid-and heat-treated spent bleaching clays  

Microsoft Academic Search

Samples of spent bleaching clay were deoiled by hexane, methanol, hexane-methanol, and supercritical CO2 extractions. The deoiled clays were regenerated by acid and heat treatments. Nitrogen adsorption isotherms for these samples\\u000a are type IV with hysteresis loops corresponding to type H3, indicating slit-shaped pores. Used deoiled and dried samples have\\u000a smaller surface areas and pore volumes than unused clay. The

K. F. Ng; N. K. Nair; K. Y. Liew; Ahmad M. Noor

1997-01-01

198

Monte Carlo study of the adsorption and aggregation of alkyltrimethylammonium chloride on the montmorillonite-water interface.  

PubMed

Organically modified clays exhibit adsorption capacities for cations, anions, and nonpolar organic compounds, which make them valuable for various environmental technical applications. To improve the understanding of the adsorption processes, the molecular-scale characterization of the structures of organic aggregates assembled on the external basal surfaces of clay particles is essential. The focus of this Monte Carlo simulation study was on the effects of the surface coverage and the alkyl chain length n on the structures of alkyltrimethylammonium chloride ((C(n)TMA)Cl) aggregates assembled on the montmorillonite-water interface. We found that the amount of adsorbed C(n)TMA(+) ions is independent of the alkyl chain length and increases with the C(n)TMA(+) surface coverage. The C(n)TMA(+) ions predominantly adsorb as inner-sphere complexes; the fraction of outer-sphere adsorbed ions equals only about 10%. The conformational order of the C(n)TMA(+) alkyl chains substantially decreases with decreasing alkyl chain length. In agreement with previous experiments, the amount of C(n)TMA(+) ions that are aggregated at the mineral surface increases with increasing chain length. The maximum value of 0.66 C(n)TMA(+) adsorption complex per unit cell area of the clay surface considerably exceeds the amount of cations required to compensate the negative charge of the montmorillonite surface. Furthermore, in most of the studied systems, fractions of Na(+) surface cations remain adsorbed on montmorillonite. The resulting interfacial positive charge excess is counterbalanced by coadsorbed chloride ions forming ion pairs with both C(n)TMA(+) and Na(+). PMID:22894657

Klebow, Birthe; Meleshyn, Artur

2012-09-18

199

[Genotoxicity of surface water treated with different disinfectants using in situ plant tests].  

PubMed

Disinfection of surface drinking water, in particular water chlorination, produces many by-products with genotoxic and/or carcinogenic activity. The aim of this research was to evaluate the genotoxicity of surface water after treatment with different disinfectants by means of in situ plant genotoxicity assays. The study was carried out in a pilot plant using lake water after sedimentation and filtration, which supplied four stainless steel basins: three basins were disinfected with sodium hypochlorite, chlorine dioxide and peracetic acid, respectively, and the fourth basin contained untreated lake water and was used as a control. The study was carried out using water collected in different seasons over a period of about one year in order to assess the treatments under different physical and chemical lake water conditions. Plant genotoxicity tests were performed by exposing plant bioindicators directly to raw and disinfected water. The Tradescantia micronucleus test in pollen cells of the flowers of an hybrid of Tradescantia and the Allium cepa test, a chromosome aberration test in root cells of Allium cepa, showed genotoxic effects only in some disinfected samples and revealed genotoxicity also in raw water in one experiment. The Vicia faba test, a micronucleus test in root cells of Vicia faba, revealed genotoxicity in many samples of disinfected water. The results of the study indicated that the Vicia faba/MCN test was the most sensitive plant assay for disinfected water, and that peracetic acid disinfection produced lower genotoxicity than sodium hypochlorite or chlorine dioxide treatment. PMID:15049553

Alberti, A; Tizzoni, M; Zani, C; Feretti, D; Gustavino, B; Zerbini, I; Nardi, G; Monarca, S

2003-01-01

200

Genotoxicity of surface water treated with different disinfectants using in situ plant tests.  

PubMed

Disinfection of surface drinking water, in particular water chlorination, results in many by-products with potential genotoxic and/or carcinogenic activity. In the present study, we evaluated the genotoxicity of surface water after treatment with different disinfectants by means of in situ plant genotoxicity assays (micronucleus and chromosomal aberration tests) which can detect both clastogenic and aneugenic effects. The study was carried out at a pilot plant using lake water after sedimentation and filtration. This water supplied four stainless steel basins: three basins were disinfected with sodium hypochlorite, chlorine dioxide, and peracetic acid and the fourth basin containing untreated lake water was used as a control. Plants were exposed in situ in the basins. The study was carried out using water collected in different seasons over a period of about 1 year in order to assess the treatments in different physical and chemical lake water conditions. The micronucleus test in root cells of Vicia faba (Vicia faba/MCN test) revealed genotoxicity in many samples of disinfected water. The micronucleus test in Tradescantia pollen cells and the chromosome aberration test in root cells of Allium cepa showed genotoxic effects only in some disinfected samples, but also revealed genotoxicity in raw water. The results of the study indicated that the Vicia faba/MCN test was the most sensitive plant assay for disinfected water and that peracetic acid disinfection produced similar or lower genotoxicity than sodium hypochlorite or chlorine dioxide treatment. PMID:12802806

Monarca, S; Rizzoni, M; Gustavino, B; Zani, C; Alberti, A; Feretti, D; Zerbini, I

2003-01-01

201

Cation exchange interaction between antibiotic ciprofloxacin and montmorillonite  

Microsoft Academic Search

Exploring the interactions between antibiotics and soils\\/minerals is of great importance in resolving their fate, transport, and elimination in the environment due to their frequent detection in wastewater, river water, sewage sludge and soils. This study focused on determining the adsorption properties and mechanisms of interaction between antibiotic ciprofloxacin and montmorillonite (SAz-1), a swelling dioctahedral mineral with Ca2+ as the

Chih-Jen Wang; Zhaohui Li; Wei-Teh Jiang; Jiin-Shuh Jean; Chia-Chuan Liu

2010-01-01

202

Surface characterization of KMnO 4 treated carbon fiber precursors using X-ray photoelectron spectroscopy 1 IPCL communication no. 334. 1  

Microsoft Academic Search

X-ray photoelectron spectra (XPS) have been recorded for carbon fiber precursors treated for various durations with 5% KMnO4 solution at 85°C. A systematic change in surface functional groups has been observed with treatment time. The study has been used to identify opportunities for improvement in mechanical properties of carbon fiber produced from treated precursors.

Vijay Kumar Kaushik

2000-01-01

203

Voltammetric and impedance behaviours of surface-treated nano-crystalline diamond film electrodes  

NASA Astrophysics Data System (ADS)

The electrochemical performances of hydrogen- and oxygen-terminated nano-crystalline diamond film electrodes were investigated by cyclic voltammetry and AC impedance spectroscopy. In addition, the surface morphologies, phase structures, and chemical states of the two diamond films were analysed by scanning probe microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy, respectively. The results indicated that the potential window is narrower for the hydrogen-terminated nano-crystalline diamond film than for the oxygen-terminated one. The diamond film resistance and capacitance of oxygen-terminated diamond film are much larger than those of the hydrogen-terminated diamond film, and the polarization resistances and double-layer capacitance corresponding to oxygen-terminated diamond film are both one order of magnitude larger than those corresponding to the hydrogen-terminated diamond film. The electrochemical behaviours of the two diamond film electrodes are discussed.

Liu, F. B.; Jing, B.; Cui, Y.; Di, J. J.; Qu, M.

2015-04-01

204

Surface modifications of some nanocomposites containing starch  

NASA Astrophysics Data System (ADS)

Polymer-layered silicate nanocomposites have attracted strong interest in today's materials research, due to the possible impressive enhancements of material properties, comparatively with those of pure polymers. Several starch/poly(vinylalcohol)/montmorillonite nanocomposites have been subjected to surface modification by physical treatments such as dielectric barrier discharge (DBD) exposure and coating with proteins (albumin) or polysaccharides (chitosan), for improving their biocompatibility. Untreated and treated surfaces have been comparatively studied by contact angle measurements, FT-IR and 2D-FT-IR spectroscopy and optical microscopy. It has been established that enhancement of the surface characteristics depends on the type and number of incorporated nanoparticles as well as on the treatment applied. Coupling of DBD exposure and coating techniques appears to be highly efficient.

Pascu, M.-C.; Popescu, M.-C.; Vasile, C.

2008-09-01

205

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

PubMed

Sorption interaction of chlorimuron-ethyl with montmorillonite clays was investigated under varied types of exchangeable cation, pH, and ionic strength conditions. Chlorimuron-ethyl sorption on bentonites exhibited pronounced cation dependency, and the sorption ability increased as the sequence Ca(2+)- < Na(+)- < Al(3+)- < Fe(3+)-bentonite, due to different sorption mechanisms, whereas the cation dependency was influenced by the clay type and much weaker for montmorillonites. The decrease of pH at the range of 4.0-6.0 prominently increased sorption of chlorimuron-ethyl on all cation-exchanged montmorillonite clays, and nearly a neglected sorption (about 2 %) can be observed at pH over 7.0. In the presence of CaCl2, sorption of chlorimuron-ethyl on Fe(3+)-bentonite was promoted because of complexion of Ca(2+) and the surface of Fe(3+)-bentonite. However, as the concentration of CaCl2 increased, chlorimuron-ethyl sorption on Ca(2+)- and Fe(3+)-exchanged bentonite decreased, suggesting that Ca bridging was not the prevailing mechanism for sorption of chlorimuron-ethyl on these clays. Furthermore, chlorimuron-ethyl sorption was relatively sensitive to pH, and the change of pH may obscure effect of other factors on the sorption, so it was quite necessary to control pH at a constant value when the effect of other factor was being studied. PMID:25028319

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

2014-10-01

206

Hydrothermal interactions of cement or mortar with zeolites or montmorillonites  

SciTech Connect

Concretes, grouts, clays and/or zeolites are candidate borehole, shaft or tunnel plugging materials for any nuclear waste repository. Interactions between these plugging materials may take place under mild hydrothermal conditions during the life of a repository. Class H cement or motar (PSU/WES mixture) was reacted with one of two montmorillonites, clinoptilolite or mordenite at 100/sup 0/ and 200/sup 0/C for different periods under a confining pressure of 30 MPa. The solid reaction products were characterized by x-ray powder diffraction and scanning electron microscopy after the hydrothermal treatments. When zeolites were in contact (not intimate mixture) with class H cement, they did not seem to alter but clinoptilolite altered to analcime, and mordenite became poorly crystalline in the presence of mortar (containing NaCl) at both 100/sup 0/ and 200/sup 0/C. When cement or mortar was intimately mixed with zeolites or montmorillonites and reacted hydrothermally, the reaction resulted in the formation of Al substituted tobermorite (11A type) in all cases (this type of reaction is expected at the interface) at both 100/sup 0/ and 200/sup 0/C. The mechanism of tobermorite formation includes the decomposition of zeolites or montmorillonites in the presence of alkaline (pH approx. = 12) cement or mortar and recrystallization to form Al substituted tobermorite. Cesium sorption measurements in 0.01N CaCl/sub 2/ on the reaction products revealed that selective Cs sorption increased in most cases, even though little or none of the original zeolites and montmorillonites remained in the products. For example, Cs sorption K/sub d/ (mL/g) increased from 80 in the untreated mortar + Ca montmorillonite mixture to 1700 in the interaction product which is Al substituted tobermorite. Thus, we discover here that Al substituted tobermorite has good selectivity for Cs.

Komarneni, S.; Roy, D.M.

1983-01-01

207

Aggregation of rhodamine 3B adsorbed in Wyoming Montmorillonite aqueous suspensions.  

PubMed

The adsorption of Rhodamine 3B (R3B) molecules in Wyoming Montmorillonite (Mont) particles suspended in water was studied by electronic absorption spectroscopy. Several adsorbed R3B species in the Mont tactoids were characterized from the observed changes in the absorption spectra by increasing the relative dye/clay concentration and the stirring time of the samples. R3B molecules can be adsorbed as monomeric units both in the water/clay interface and in the interlayer space, and head-to-tail R3B dimers and trimers were present in the external surface of Mont. The formation of internally adsorbed R3B monomers by the migration of the externally adsorbed species to the interlayer space leads to the deaggregation of the dye molecules in the external surface. PMID:16290412

López Arbeloa, F; Chaudhuri, R; Arbeloa López, T; López Arbeloa, I

2002-02-15

208

Natural montmorillonite induced photooxidation of As(III) in aqueous suspensions: roles and sources of hydroxyl and hydroperoxyl/superoxide radicals.  

PubMed

Photooxidation of arsenite(As(III)) in a suspension of natural montmorillonite under the irradiation of metal halide lamp (? ? 313 nm)has been investigated. The results showed that the natural montmorillonite induced the photooxidation of As(III) by generating hydroxyl radicals (HO·) and hydroperoxyl/superoxide radicals (HO?·/O??·). HO· which was responsible for the As(III) photooxidation. Approximately 38% of HO· was generated by the photolysis of ferric ions, and the formation of the remaining 62% was strongly dependent on the HO?·/O??·. The presence of free ironions (Fe(2+) and Fe(3+)), made significant contributions to the photogeneration of these reactive oxygen species (ROS). The photooxidation of As(III) in natural montmorillonite suspensions was greatly influenced by the pH values. The photooxidation of As(III) by natural montmorillonite followed the Langmuir-Hinshelwood equation. In addition, the photooxidation of As(III) could be enhanced by the addition of humic acid. This work demonstrates that photooxidation may be an important environmental process for the oxidation of As(III) and may be a way to remove As(III) from acidic surface water containing iron-bearing clay minerals. PMID:23770489

Wang, Yajie; Xu, Jing; Li, Jinjun; Wu, Feng

2013-09-15

209

Radionuclide desorption kinetics on synthetic Zn/Ni-labeled montmorillonite nanoparticles  

NASA Astrophysics Data System (ADS)

Sorption/desorption kinetics for selected radionuclides (99Tc(VII), 232Th(IV), 233U(VI), 237Np(V), 242Pu and 243Am(III)) under Grimsel (Switzerland) ground water conditions (pH 9.7 and ionic strength of ?1 mM) in the presence of synthetic Zn or Ni containing montmorillonite nanoparticles and granodiorite fracture filling material (FFM) from Grimsel were examined in batch studies. The structurally bound Zn or Ni in the octahedral sheet of the synthetic colloids rendered them suitable as colloid markers. Only a weak interaction of the montmorillonite colloids with the fracture filling material occurs over the experimental duration of 10,000 h (?13 months). The tri- and tetravalent radionuclides are initially strongly associated with nanoparticles in contrast to 99Tc(VII), 233U(VI) and 237Np(V) which showed no sorption to the montmorillonite colloids. Radionuclide desorption of the nanoparticles followed by sorption to the fracture filling material is observed for 232Th(IV), 242Pu and 243Am(III). Based on the conceptual model that the driving force for the kinetically controlled radionuclide desorption from nanoparticles and subsequent association to the FFM is the excess in surface area offered by the FFM, the observed desorption kinetics are related to the colloid/FFM surface area ratio. The observed decrease in concentration of the redox sensitive elements 99Tc(VII), 233U(VI) and 237Np(V) may be explained by reduction to lower oxidation states in line with Eh-pH conditions prevailing in the experiments and thermodynamic considerations leading to (i) precipitation of a sparingly soluble phase, (ii) sorption to the fracture filling material, (iii) possible formation of eigencolloids and/or (iv) sorption to the montmorillonite colloids. Subsequent to the sorption/desorption kinetics study, an additional experiment was conducted investigating the potential remobilization of radionuclides/colloids attached to the FFM used in the sorption/desorption kinetic experiments by contacting this FFM with pure Grimsel groundwater for 7 days. A positive correlation of 242Pu, 232Th(IV) and 237Np was observed with the Zn and Ni concentrations in the desorption experiments indicating a remobilization of sorbed montmorillonite colloids. The results of the study in hand highlight (i) the novel use of structural labeled colloids to decrease the uncertainties in the determination of nanoparticle attachment providing more confidence in the derived radionuclide desorption rates. Moreover, the data illustrate (ii) the importance of radionuclide colloid desorption to be considered in the analysis and application of colloid facilitated transport both in laboratory or in-situ experiments and numerical model simulations and (iii) a possible remobilization of sorbed colloids and associated radionuclides by desorption from the matrix material (FFM) under non-equilibrium conditions.

Huber, F. M.; Heck, S.; Truche, L.; Bouby, M.; Brendlé, J.; Hoess, P.; Schäfer, T.

2015-01-01

210

Changes of cell-surface thiols and intracellular signaling in human monocytic cell line THP-1 treated with diphenylcyclopropenone.  

PubMed

Changes of cell-surface thiols induced by chemical treatment may affect the conformations of membrane proteins and intracellular signaling mechanisms. In our previous study, we found that a non-toxic dose of diphenylcyclopropene (DPCP), which is a potent skin sensitizer, induced an increase of cell-surface thiols in cells of a human monocytic cell line, THP-1. Here, we examined the influence of DPCP on intracellular signaling. First, we confirmed that DPCP induced an increase of cell-surface thiols not only in THP-1 cells, but also in primary monocytes. The intracellular reduced-form glutathione/oxidized-form glutathione ratio (GSH/GSSG ratio) was not affected by DPCP treatment. By means of labeling with a membrane-impermeable thiol-reactive compound, Alexa Fluor 488 C5 maleimide (AFM), followed by two-dimensional gel electrophoresis and analysis by liquid chromatography coupled with electrospray tandem mass spectrometry (LC/MS/MS), we identified several proteins whose thiol contents were modified in response to DPCP. These proteins included cell membrane components, such as actin and ?-tubulin, molecular chaperones, such as heat shock protein 27A and 70, and endoplasmic reticulum (ER) stress-inducible proteins. Next, we confirmed the expression in DPCP-treated cells of spliced XBP1, a known marker of ER stress. We also detected the phosphorylation of SAPK/JNK and p38 MAPK, which are downstream signaling molecules in the IRE1?-ASK1 pathway, which is activated by ER stress. These data suggested that increase of cell-surface thiols might be associated with activation of ER stress-mediated signaling. PMID:21139337

Hirota, Morihiko; Motoyama, Akira; Suzuki, Mie; Yanagi, Masashi; Kitagaki, Masato; Kouzuki, Hirokazu; Hagino, Shigenobu; Itagaki, Hiroshi; Sasa, Hitoshi; Kagatani, Saori; Aiba, Setsuya

2010-12-01

211

Surface degradation of CeO2 stabilized acrylic polyurethane coated thermally treated jack pine during accelerated weathering  

NASA Astrophysics Data System (ADS)

The thermally treated wood is a new value-added product and is very important for the diversification of forestry products. It drew the attention of consumers due to its attractive dark brown color. However, it loses its color when exposed to outside environment. Therefore, development of a protective coating for this value added product is necessary. In the present study, the efficiency of CeO2 nano particles alone or in combination with lignin stabilizer and/or bark extracts in acrylic polyurethane polymer was investigated by performing an accelerated weathering test. The color measurement results after accelerated weathering demonstrated that the coating containing CeO2 nano particles was the most effective whereas visual assessment suggested the coating containing CeO2 nano particles and lignin stabilizer as the most effective coating. The surface polarity changed for all the coatings during weathering and increase in contact angle after weathering suggested cross linking and reorientation of the polymer chain during weathering. The surface chemistry altered during weathering was evaluated by ATR-FTIR analysis. It suggested formation of different carbonyl byproducts during weathering. The chain scission reactions of the urethane linkages were not found to be significant during weathering.

Saha, Sudeshna; Kocaefe, Duygu; Boluk, Yaman; Pichette, Andre

2013-07-01

212

LIMITATIONS OF EDDY CURRENT RESIDUAL STRESS PROFILING IN SURFACE-TREATED ENGINE ALLOYS OF VARIOUS HARDNESS LEVELS  

SciTech Connect

Recent research results indicated that eddy current conductivity measurements might be exploited for nondestructive evaluation of subsurface residual stresses in surface-treated nickel-base superalloy components. This paper presents new results that indicate that in some popular nickel-base superalloys the relationship between the electric conductivity profile and the sought residual stress profile is more tenuous than previously thought. It is shown that in IN718 the relationship is very sensitive to the state of precipitation hardening and, if left uncorrected, could render the eddy current technique unsuitable for residual stress profiling in components of 36 HRC or harder, i.e., in most critical engine applications. The presented experimental results show that the observed dramatic change in the eddy current response of hardened IN718 to surface treatment is caused by very fine nanometer-scale features of the microstructure, such as gamma' and gamma'' precipitates, rather than micrometer-scale features, such as changing grain size or carbide precipitates.

Abu-Nabah, B. A. [General Electric Aviation, Cincinnati, OH 45221 (United States); Hassan, W. T. [Rolls-Royce Corporation, Indianapolis, IN 46241 (United States); Blodgett, M. P. [Air Force Research Laboratory, WPAFB, Dayton, OH 45433 (United States); Nagy, P. B. [University of Cincinnati, Cincinnati, OH 45221 (United States)

2010-02-22

213

Characterization of cell surface polypeptides of unfertilized, fertilized, and protease-treated zona-free mouse eggs  

SciTech Connect

The polypeptide composition of unfertilized, fertilized, and protease-treated zona-free mouse eggs was evaluated in this study. Zona-free eggs were radioiodinated by an Iodogen-catalyzed reaction. Light microscopic autoradiography of egg sections revealed that labeling was restricted to the cell surface. Labeled eggs were solubilized, and cell surface polypeptides were identified by one-dimensional SDS polyacrylamide gel electrophoresis and autoradiography. The unfertilized egg demonstrated 8-10 peptides that incorporated {sup 125}I, with major bands observed at approximately 145-150, 94, and 23 kilodaltons (kD). Zona-free eggs fertilized in vitro and then radiolabeled demonstrated several new bands in comparison to unfertilized eggs, with a major band appearing at approximately 36 kD. Treatment of radiolabeled unfertilized eggs with either trypsin or chymotrypsin (1 mg/ml for 5-20 min) caused enzyme-specific modifications in labeled polypeptides. Trypsin (T) treatment resulted in time-dependant modification of the three major peptides at 145-150, 94, and 23 kD. Chymotrypsin (CT) treatment, in contrast, was associated with loss or modification of the 94 kD band, with no apparent effect on either the 145-150 or 23 kD band. Taken together with previous data indicating that T or CT egg treatment interferes with sperm-egg attachment and fusion, these results suggest a possible role for the 94 kD protein in sperm-egg interaction.

Boldt, J.; Gunter, L.E.; Howe, A.M. (Medical College of Georgia, Augusta (USA))

1989-05-01

214

The role of fluoride in montmorillonite-catalyzed RNA synthesis.  

PubMed

The montmorillonite-catalyzed reactions of the 5'-phosphorimidazolide of adenosine in the presence of fluoride were investigated to complete our study on the effect of salts on this type of reaction. Both anions and cations have been found to influence the oligomerization reactions of the activated nucleotides, being used here as a model system for pre-biotic RNA synthesis. However, in total contrast to the behavior of the activated nucleotides in the presence of montmorillonite and other salts, alkali metal fluorides did not yield any detectable oligomerization products except in very dilute (<0.005 M) solutions of fluoride. Instead, 5'-phosphorofluoridates were formed. Their identity was confirmed by a combination of HPLC, mass spectrometry, synthesis, and NMR. PMID:24756181

Aldersley, Michael F; Joshi, Prakash C

2014-05-01

215

Tantalum pillard montmorillonite: II. Acidic and catalytic properties  

SciTech Connect

The acidic and catalytic properties of a series of Ta-PILCs synthesized with a different initial tantalum content were characterized by adsorption of gaseous probe molecules (TPD of ammonia and FTIR spectra of absorbed pyridine) and by the test reaction of 1-butanol dehydration. A large increase of acidity was noted in Ta-PILCs compared to Na-montmorillonite or tantalum oxide. Cross-linking pillars and silica layers of the clay induce stronger Lewis and new Bronsted sites. The lack of basic sites formation is evidenced by the dehydration of 1-butanol to butene selectivity (100%). The incorporation of the tantalum oxide between the montmorillonite sheets produce, within Ta-PILC, acid centers of the same nature as observed for the silicon-tantalum mixed oxides. 32 refs., 4 figs., 5 tabs.

Guiu, G.; Grange, P. [Universite Catholique de Louvain, Louvain-la-Neuve (Belgium)] [Universite Catholique de Louvain, Louvain-la-Neuve (Belgium)

1997-06-01

216

Do contaminants originating from state-of-the-art treated wastewater impact the ecological quality of surface waters?  

PubMed

Since the 1980s, advances in wastewater treatment technology have led to considerably improved surface water quality in the urban areas of many high income countries. However, trace concentrations of organic wastewater-associated contaminants may still pose a key environmental hazard impairing the ecological quality of surface waters. To identify key impact factors, we analyzed the effects of a wide range of anthropogenic and environmental variables on the aquatic macroinvertebrate community. We assessed ecological water quality at 26 sampling sites in four urban German lowland river systems with a 0-100% load of state-of-the-art biological activated sludge treated wastewater. The chemical analysis suite comprised 12 organic contaminants (five phosphor organic flame retardants, two musk fragrances, bisphenol A, nonylphenol, octylphenol, diethyltoluamide, terbutryn), 16 polycyclic aromatic hydrocarbons, and 12 heavy metals. Non-metric multidimensional scaling identified organic contaminants that are mainly wastewater-associated (i.e., phosphor organic flame retardants, musk fragrances, and diethyltoluamide) as a major impact variable on macroinvertebrate species composition. The structural degradation of streams was also identified as a significant factor. Multiple linear regression models revealed a significant impact of organic contaminants on invertebrate populations, in particular on Ephemeroptera, Plecoptera, and Trichoptera species. Spearman rank correlation analyses confirmed wastewater-associated organic contaminants as the most significant variable negatively impacting the biodiversity of sensitive macroinvertebrate species. In addition to increased aquatic pollution with organic contaminants, a greater wastewater fraction was accompanied by a slight decrease in oxygen concentration and an increase in salinity. This study highlights the importance of reducing the wastewater-associated impact on surface waters. For aquatic ecosystems in urban areas this would lead to: (i) improvement of the ecological integrity, (ii) reduction of biodiversity loss, and (iii) faster achievement of objectives of legislative requirements, e.g., the European Water Framework Directive. PMID:23593263

Stalter, Daniel; Magdeburg, Axel; Quednow, Kristin; Botzat, Alexandra; Oehlmann, Jörg

2013-01-01

217

Speciation of uranium in surface-modified, hydrothermally treated, (UO{sub 2}){sup 2+}-exchanged smectite clays  

SciTech Connect

A successful solution to the problem of disposal and permanent storage of water soluble radioactive species must address two issues: exclusion of the radionuclides from the environment and the prevention of leaching from the storage media into the environment. Immobilization of radionuclides in clay minerals has been studied. In addition to the use of clays as potential waste forms, information about the interactions of radionuclides with clays and how such interactions affect their speciations is crucial for successful modeling of actinide-migration. X-ray absorption spectroscopy (XAS) is used to determine the uranium speciation in exchanged and surface-modified clays. The XAS data from uranyl-loaded bentonite clay are compared with those obtained after the particle surfaces have been coated with alkylsilanes. These silane films, which render the surface of the clay hydrophobic, are added in order to minimize the ability of external water to exchange with the water in the clay interlayer, thereby decreasing the release rate of the exchanged-uranium species. Mild hydrothermal conditions are used in an effort to mimic potential geologic conditions that may occur during long-term radioactive waste storage. The XAS spectra indicate that the uranyl monomer species remain unchanged in most samples, except in those samples that were both coated with an alkylsilane and hydrothermally treated. When the clay was coated with an organic film, formed by the acidic deposition of octadecyltrimethoxysilane, hydrothermal treatment results in the formation of aggregated uranium species in which the uranium is reduced from U{sup VI} to U{sup IV}.

Giaquinta, D.M.; Soderholm, L.; Yuchs, S.E.; Wasserman, S.R. [Argonne National Lab., IL (United States). Chemistry Div.

1997-08-01

218

Do Contaminants Originating from State-of-the-Art Treated Wastewater Impact the Ecological Quality of Surface Waters?  

PubMed Central

Since the 1980s, advances in wastewater treatment technology have led to considerably improved surface water quality in the urban areas of many high income countries. However, trace concentrations of organic wastewater-associated contaminants may still pose a key environmental hazard impairing the ecological quality of surface waters. To identify key impact factors, we analyzed the effects of a wide range of anthropogenic and environmental variables on the aquatic macroinvertebrate community. We assessed ecological water quality at 26 sampling sites in four urban German lowland river systems with a 0–100% load of state-of-the-art biological activated sludge treated wastewater. The chemical analysis suite comprised 12 organic contaminants (five phosphor organic flame retardants, two musk fragrances, bisphenol A, nonylphenol, octylphenol, diethyltoluamide, terbutryn), 16 polycyclic aromatic hydrocarbons, and 12 heavy metals. Non-metric multidimensional scaling identified organic contaminants that are mainly wastewater-associated (i.e., phosphor organic flame retardants, musk fragrances, and diethyltoluamide) as a major impact variable on macroinvertebrate species composition. The structural degradation of streams was also identified as a significant factor. Multiple linear regression models revealed a significant impact of organic contaminants on invertebrate populations, in particular on Ephemeroptera, Plecoptera, and Trichoptera species. Spearman rank correlation analyses confirmed wastewater-associated organic contaminants as the most significant variable negatively impacting the biodiversity of sensitive macroinvertebrate species. In addition to increased aquatic pollution with organic contaminants, a greater wastewater fraction was accompanied by a slight decrease in oxygen concentration and an increase in salinity. This study highlights the importance of reducing the wastewater-associated impact on surface waters. For aquatic ecosystems in urban areas this would lead to: (i) improvement of the ecological integrity, (ii) reduction of biodiversity loss, and (iii) faster achievement of objectives of legislative requirements, e.g., the European Water Framework Directive. PMID:23593263

Stalter, Daniel; Magdeburg, Axel; Quednow, Kristin; Botzat, Alexandra; Oehlmann, Jörg

2013-01-01

219

Vis-NIR Spectroscopy of Mineral Mixtures with Montmorillonite and Silica: Implications for Detecting Alteration Products on Mars  

NASA Astrophysics Data System (ADS)

Introduction. A variety of secondary silicates have been identified on Mars using Vis-NIR spectroscopic data from the Observatoire pour la Mineralogie, l’Eau, les Glaces et l’Activite (OMEGA) on Mars Express and the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on Mars Reconnaissance Orbiter, including smectite, chlorite, kaolinite, and illite clay minerals and hydrous amorphous silica [1-4]. The detection of these materials is significant because they provide important information about past aqueous environments on Mars. Vis-NIR spectra of specific secondary silicates can be distinguished by the positions and shapes of hydration features. Here, we investigate the detection of secondary silicates by vis-NIR spectroscopy of mixtures with basaltic igneous minerals and either hydrous amorphous silica or montmorillonite. Experimental Procedure. Minor amounts of <2 ?m amorphous silica or montmorillonite clay (2.5, 5, 10, and 20 wt%) were physically mixed with augite, andesine, or olivine (75-106 ?m). A portion of each mixture was compressed into a pellet. Vis-NIR spectra (0.32-2.55 ?m) of particulate and pellet mixtures were measured at RELAB at Brown University, and each spectrum was visually inspected to determine detection limits of secondary silicates based on hydration features. Preliminary Results. Absorptions at 1.4 and 1.9 ?m (OH stretch overtone and H2O bend and stretch, respectively) occur in almost all mixture spectra; however, the strength, shape, and position are dependent on the igneous mineral and secondary silicate abundance in the mixture. The morphology of absorptions at ~2.2 ?m (from metal-OH bonds) differs between amorphous silica and montmorillonite [3,4], so we use these absorptions to determine the detection limits of amorphous silica and montmorillonite. The 2.2 ?m absorption is present in all montmorillonite-mixture spectra, indicating the montmorillonite detection limit is <2.5 wt%; however, the 2.2 ?m absorption is generally present in silica-mixture spectra that contain >10 wt% silica. Conclusions. Vis-NIR spectra of our mineral mixtures show that montmorillonite has a lower detection limit than amorphous silica, based on the presence of the ~2.2 ?m absorption. This indicates that chemically weathered surfaces on Mars that contain silica must have much more alteration material to be detected than surfaces with clay. Furthermore, the shape and position of the 1.4 and 1.9 ?m features changes with igneous mineral type and silica abundance, which adds to the difficulty in using vis-NIR to detect amorphous silica on Mars. Our study is consistent with a previous study that demonstrates the inability to detect thin silica coatings on basaltic particulates by vis-NIR spectroscopy [5], and suggests acidic chemical weathering and the precipitation of amorphous silica on Mars may be more pervasive and intense than vis-NIR spectroscopic data indicate. References. [1] J.-P. Bibring et al. (2006) Science, 312, 400-404. [2] F. Poulet et al. (2005) Nature, 438, 623-627. [3] J.F. Mustard et al. (2008) Nature, 454, 305-309. [4] R.E. Milliken et al. (2008) Geology, 36, 847-850. [5] M.D. Kraft et al. (2007) 7th Int. Conf. Mars, 3396.

Rampe, E. B.; Kraft, M. D.; Sharp, T. G.

2009-12-01

220

An X-ray photoelectron spectroscopy study of surface changes on brominated and sulfur-treated activated carbon sorbents during mercury capture: performance of pellet versus fiber sorbents.  

PubMed

This work explores surface changes and the Hg capture performance of brominated activated carbon (AC) pellets, sulfur-treated AC pellets, and sulfur-treated AC fibers upon exposure to simulated Powder River Basin-fired flue gas. Hg breakthrough curves yielded specific Hg capture amounts by means of the breakthrough shapes and times for the three samples. The brominated AC pellets showed a sharp breakthrough after 170-180 h and a capacity of 585 ?g of Hg/g, the sulfur-treated AC pellets exhibited a gradual breakthrough after 80-90 h and a capacity of 661 ?g of Hg/g, and the sulfur-treated AC fibers showed no breakthrough even after 1400 h, exhibiting a capacity of >9700 ?g of Hg/g. X-ray photoelectron spectroscopy was used to analyze sorbent surfaces before and after testing to show important changes in quantification and oxidation states of surface Br, N, and S after exposure to the simulated flue gas. For the brominated and sulfur-treated AC pellet samples, the amount of surface-bound Br and reduced sulfur groups decreased upon Hg capture testing, while the level of weaker Hg-binding surface S(VI) and N species (perhaps as NH4(+)) increased significantly. A high initial concentration of strong Hg-binding reduced sulfur groups on the surface of the sulfur-treated AC fiber is likely responsible for this sorbent's minimal accumulation of S(VI) species during exposure to the simulated flue gas and is linked to its superior Hg capture performance compared to that of the brominated and sulfur-treated AC pellet samples. PMID:24256554

Saha, Arindom; Abram, David N; Kuhl, Kendra P; Paradis, Jennifer; Crawford, Jenni L; Sasmaz, Erdem; Chang, Ramsay; Jaramillo, Thomas F; Wilcox, Jennifer

2013-12-01

221

Enthalpy changes accompanying the collapse of montmorillonite layers and the penetration of electrolyte into interlayer space  

SciTech Connect

The enthalpy changes, {Delta}H, in suspensions of Li-, Na-, and K-montmorillonite were determined as functions of the molal concentrations of LiCl, NaCl, and KCl, respectively, by microcalorimetry. These changes were compared with the corresponding changes in interlayer distance, {lambda}, as determined by X-ray diffraction. It was found that {Delta}H values accompanying the collapse of the montmorillonite layers from {lambda} > 14 nm to {lambda} {approx_equal} 1.0 nm were essentially negligible; however, {Delta}H values accompanying the collapse of layers of Li- and Na-montmorillonite from {lambda} {approx_equal} 1.0 nm to {lambda} {approx_equal} 0.6 nm, and the collapse of layers of K-montmorillonite from {lambda} {approx_equal} 0.6 nm, were not negligible. No additional collapse of Li- and Na-montmorillonite layers occurred after {lambda} {approx_equal} 0.6 nm, and for K-montmorillonite layers after {lambda} {approx_equal} 0.3 nm, but {Delta}H continued to change with increasing salt addition. This change was attributed to the penetration of electrolyte into the interlayer space. A notable observation was that the value of {Delta}H was positive for Li-montmorillonite, but negative for Na- and K-montmorillonite. These observations were interpreted to mean that {Delta}H changes in the montmorillonite suspension were largely attributable to reorganization of the interlayer space by the added electrolytes.

Yan, L.; Low, P.F.; Roth, C.B. [Purdue Univ., West Lafayette, IN (United States). Dept. of Agronomy] [Purdue Univ., West Lafayette, IN (United States). Dept. of Agronomy

1996-09-25

222

Oxidative dissolution of hydroxy-cr interlayers from montmorillonite  

Microsoft Academic Search

Expandable layer silicates can sorb considerable amounts of hydrolyzed Cr(III). This study was conducted to determine the effect of the interlayer environment on the oxidative dissolution of intercalated hydroxy-Cr polymers. Seven montmorillonite clays with pure hydroxy-Cr interlayers and three with coprecipitated hydroxy-Cr and -Al interlayers were suspended in dilute NaOCI. The supernatant Cr concentrations of each were monitored over time.

W. E. Dubbin; Tee Boon Goh

1997-01-01

223

Homoionic inorganic montmorillonites as fillers for polyamide 6 nanocomposites  

Microsoft Academic Search

The homoionic montmorillonites Ca-MMT, Mg-MMT, Ba-MMT and Ca-MMT intercalated with ?-caprolactam – Ca-MMT·CL were prepared from commercial Na-MMT and characterized by WAXS and TGA. They were used as fillers for nanocomposites of polyamide 6 synthesized either by anionic polymerization of ?-caprolactam (monomer casting) or by melt blending. WAXS analysis showed that the intercalation of MMT by the polyamide was complete

Zuzana Kadlecová; Rudolf Puffr; Josef Baldrian; Pavel Schmidt; Jan Roda; Ji?í Brožek

2008-01-01

224

Preparation and characterization of flame retardant ABS\\/montmorillonite nanocomposite  

Microsoft Academic Search

Flame retardant acrylonitrile–butadiene–styrene (ABS)\\/montmorillonite (MMT) nanocomposites were prepared by direct melt intercalation of ABS, organophilic clay and conventional fire retardants (decabromodiphenyl oxide (DB) and antimony oxide (AO)). Morphology and flammability properties were characterized by X-ray power diffractionmeter (XRD), high resolution electron microscopy (HREM), transmission electron microscopy (TEM), scanning electron microscopy (SEM), limiting oxygen index (LOI) test, UL-94 test and cone

Shaofeng Wang; Yuan Hu; Ruowen Zong; Yong Tang; Zuyao Chen; Weicheng Fan

2004-01-01

225

Characterization of Aminopropyltriethoxysilane-functionalized Polycaprolactone-Montmorillonite Beads for Heavy Metal Biosorption  

NASA Astrophysics Data System (ADS)

The study focuses on the fabrication of montmorillonite (MMT) based composites via functionalization with polycaprolactone (PCL) and aminopropyltriethoxysilane (APTS) for adsorption of divalent metal ions Cu2+ and Fe2+. Surface morphology of the composites revealed that the PCL-APTS-MMT beads have finer particle size compared to PCL-MMT. Infrared spectroscopy analyses confirmed the covalent interaction of the PCL to the MMT matrix and the APTS-PCL-MMT composite. Thermogravimetric analysis showed a decrease in thermal stability for the composite powders. Analyses with Langmuir and Freundlich isotherm models revealed greater maximum adsorption capacity for the PCL-APTS-MMT composite compared to PCL-MMT. The divalent ions could be removed by the obtained composite material through the possible mechanisms of ion exchange and chelation.

Magdaluyo, E., Jr.; Dayhon, E.; delos Angeles, M.; dela Cruz, Rj; de Sales-Papa, L.

2011-10-01

226

Environmental ageing of irradiated polypropylene/montmorillonite nanocomposites obtained in molten state  

NASA Astrophysics Data System (ADS)

Nanocomposites of High Melt Strength Polypropylene (HMSPP) were obtained in organoclay concentrations of 0.1, 5 and 10 wt% using the montmorillonite (MMT). The clay was dispersed through the melting intercalation technique using a twin-screw extruder. The dumbbell samples were manufactured and settled in device for natural ageing assay. The mechanical properties (elongation and rupture strength) were evaluated and the thermal behavior was investigated by differential scanning calorimetry (DSC). The morphology of the nanocomposites was observed by scanning electron microscopy (SEM). Nanocomposites HMSPP/MMT showed intense cracks at the surface after 3 months of environmental ageing but not as deeply as in the HMSPP. The carbonyl index (CI) was calculated using infrared spectroscopy (FT-IR) technique in which the nanocomposites showed CI values lower than the HMSPP.

Komatsu, L. G. H.; Oliani, W. L.; Lugao, A. B.; Parra, D. F.

2014-04-01

227

Relevance of Pore Structure and Diffusion-Accessible Porosity for Calcium-Bromide Diffusion in Na-Montmorillonite  

NASA Astrophysics Data System (ADS)

Bentonite is an important hydraulic barrier material in many geotechnical applications, such as geosynthetic clay liners at solid waste landfills, or as proposed backfill material in engineered barrier systems at nuclear waste repositories. The limited permeability of bentonite is at least partially the result of its low porosity and the swelling of Na-montmorillonite, its major mineralogical component, in water. Due to these characteristics, the transport of contaminants through bentonite layers is expected to be limited and dominated by diffusion processes. In bentonite, the majority of the connected porosity is associated with montmorillonite particles, which consist of stacks of negatively-charged smectite layers. As a result, compacted smectite has two types of porosities: (1) large pores between clay particles, where diffusion is less affected by electric-double-layer forces, and (2) very thin interlayer spaces within individual clay particles, where diffusion is strongly impacted by surface charge and ionic strength. As diffusion is expected to take place differently in these two volumes, this essentially creates two 'small-scale diffusion pathways', where each may become dominant under different system conditions. Furthermore, for surface-reactive solutes, these two porous regimes differ with regards to surface complexation reactions. Electrostatic and hydration forces only are thought to govern interlayer binding, whereas chemical bonding with surface ligands is dominant for reactions at edge sites of layered clay particles and for iron oxide nanoparticles on outer basal planes. In this presentation, we will demonstrate the relevance of clay pore structure and diffusion-accessible porosity for solute diffusion rates, and hence, contaminant mobility in bentonites. First, we will discuss the effects of chemical solution conditions on montmorillonite properties, such as clay surface charge, diffusion-accessible porosity, clay tortuosity and constrictivity, and evaluate the implications for metal diffusion coefficients. Furthermore, we will highlight the importance of solute charge for solute diffusion rates based on results from a calcium-bromide (CaBr2) through-diffusion experiment in Na-montmorillonite. In this experiment, dry, purified Na-montmorillonite (SWy-2, Clay Minerals Society) was packed into a diffusion cell, allowed to equilibrate with the background electrolyte (pH=7, I=0.1 M NaCl), and then exposed to a constant CaBr2 concentration gradient between two solution reservoirs. After reaching steady-state conditions for the diffusive fluxes of Ca and Br, cumulative mass data could be used to compute effective and apparent Ca and Br diffusion coefficients. Furthermore, the diffusion data for an uncharged, non-reactive tracer (tritiated water) allowed us to calculate the clay porosity in the system, and to determine Ca and Br sorption distribution coefficients (Kd values). Our results indicate that Ca diffusion in Na-montmorillonite is slower than for the non-reactive tracer, most likely due to Ca exchange reactions within the clay interlayers. In contrast, rates of Br diffusion are faster than for an uncharged tracer, indicating solute-specific differences in diffusion-accessible porosities and/or effective concentration gradients in pore spaces.

Tinnacher, R. M.; Davis, J. A.

2013-12-01

228

In Vitro Evaluation of the Effect of Different Laser Irradiations on the Enamel Surfaces of Teeth Treated with Home Bleach Procedure  

PubMed Central

Introduction: The aim of this study was to evaluate the effect of dental surface treatment with Erbium-Doped Yttrium Aluminum Garnet(Er: YAG), Neodymium-Doped Yttrium Aluminium Garnet(Nd: YAG) and Carbon Dioxide Laser (CO2) lasers and sodium ascorbate to recently home bleached enamel by scanning electron microscope (SEM). Methods: Thirty extracted human third molars were selected for this in vitro study. The teeth were randomly divided in two groups including home bleached group and control group (non-bleached). In group 1, the samples were bleached by home bleach technique. No bleaching procedure was done in second the group which served as control group.Then , the samples of two groups were divided to five subgroups as follow: Subgroup 1: treated using Nd:YAG laser with output power of 1 W, Subgroup 2: treated using Er:YAG laser with output power of 0.5 W, Subgroup 3: treated using CO2 laser with output power of 0.5 W, Subgroup 4: sodium ascorbate 10%, Subgroup 5: no treatment. After treatments, the surfaces were evaluated using Scanning Electron Microscope (SEM) analysis. Results: The surfaces treated by Nd:YAG laser showed some melting and recrystallized areas and in some area droplet pattern was observed. But the surface treated by Er:YAG laser showed irregular and micro porous surface with flake pattern. CO2 laser treatment of home-bleached surfaces resulted in melting area and cracks. Sodium ascorbate did not change the home-bleached surface. Conclusion: Among different surface treatments used in this study, it seems that Er:YAG laser can best interact with home-bleached teeth.

Mohammadi Bassir, Mahshid; Rezvani, Mohammad Bagher; Chiniforush, Nasim; Moradi, Zohreh

2013-01-01

229

Antibacterial effect of Cu2+-exchanged montmorillonite on Aeromonas hydrophila and discussion on its mechanism.  

PubMed

Montmorillonite (MMT) and its Cu2+-exchanged montmorillonite (Cu-MMT) were used to study the antibacterial activity on Aeromonas hydrophila. The results indicated that MMT had no antibacterial activity. The minimum inhibitory concentration (MIC) and bactericidal concentration (MBC) of Cu-MMT on A. hydrophila are found to be 150 and 600 mg/L, respectively. The continuance of the antibacterial activity of Cu-MMT was much longer than copper sulfate. In order to reveal the mechanism of the antibacterial activity of Cu-MMT, the Cu release from Cu-MMT in tryptic soy broth (TSB) was investigated. In the first 2 h, Cu concentration in the supernatant reaches saturated value, about 1.22-2.27% of the overall Cu in Cu-MMT suspended in the medium. The washed Cu-MMT in TSB for 24 h retained their full antibacterial activity; whereas, the supernatants from the washed pellets showed very little antibacterial activity. These findings suggested that the antibacterial activity of Cu-MMT was mainly localized on the clay surface, and not due to the release of Cu2+ into solution. The excessive positive charge of Cu-MMT would make Cu-MMT attract A. hydrophila with negatively charged cellular wall. In this case, the copper cation would act directly on the bacteria adsorbed on the surface of Cu-MMT, instead of into the medium. The mechanism for the antibacterial activity of Cu-MMT may involve the enhanced affinity of Cu-MMT for A. hydrophila and the antibacterial activity of Cu2+. PMID:15939555

Hu, C H; Xu, Z R; Xia, M S

2005-08-10

230

Correlation Between the Extent of Catalytic Activity and Charge Density of Montmorillonites  

NASA Astrophysics Data System (ADS)

The clay mineral montmorillonite is a member of the phyllosilicate group of minerals, which has been detected on martian soil. Montmorillonite catalyzes the condensation of activated monomers to form RNA-like oligomers. Extent of catalysis, that is, the yield of oligomers, and the length of the longest oligomer formed in these reactions widely varies with the source of montmorillonite (i.e., the locality where the mineral is mined). This study was undertaken to establish whether there exists a correlation between the extent of catalytic property and the charge density of montmorillonites. Charge density was determined by saturating the montmorillonites with alkyl ammonium cations that contained increasing lengths of alkyl chains, [CH3-(CH2)n-NH3]+, where n = 3-16 and 18, and then measuring d(001), interlayer spacing of the resulting montmorillonite-alkyl ammonium-montmorillonite complex by X-ray diffractometry (XRD). Results demonstrate that catalytic activity of montmorillonites with lower charge density is superior to that of higher charge density montmorillonite. They produce longer oligomers that contain 9 to 10 monomer units, while montmorillonite with high charge density catalyzes the formation of oligomers that contain only 4 monomer units. The charge density of montmorillonites can also be calculated from the chemical composition if elemental analysis data of the pure mineral are available. In the next mission to Mars, CheMin (Chemistry and Mineralogy), a combined X-ray diffraction/X-ray fluorescence instrument, will provide information on the mineralogical and elemental analysis of the samples. Possible significance of these results for planning the future missions to Mars for the search of organic compounds and extinct or extant life is discussed.

Ertem, Gözen; Steudel, Annett; Emmerich, Katja; Lagaly, Gerhard; Schuhmann, Rainer

2010-09-01

231

Correlation between the extent of catalytic activity and charge density of montmorillonites.  

PubMed

The clay mineral montmorillonite is a member of the phyllosilicate group of minerals, which has been detected on martian soil. Montmorillonite catalyzes the condensation of activated monomers to form RNA-like oligomers. Extent of catalysis, that is, the yield of oligomers, and the length of the longest oligomer formed in these reactions widely varies with the source of montmorillonite (i.e., the locality where the mineral is mined). This study was undertaken to establish whether there exists a correlation between the extent of catalytic property and the charge density of montmorillonites. Charge density was determined by saturating the montmorillonites with alkyl ammonium cations that contained increasing lengths of alkyl chains, [CH?-(CH?)(n)-NH?](+), where n?=?3-16 and 18, and then measuring d(???), interlayer spacing of the resulting montmorillonite-alkyl ammonium-montmorillonite complex by X-ray diffractometry (XRD). Results demonstrate that catalytic activity of montmorillonites with lower charge density is superior to that of higher charge density montmorillonite. They produce longer oligomers that contain 9 to 10 monomer units, while montmorillonite with high charge density catalyzes the formation of oligomers that contain only 4 monomer units. The charge density of montmorillonites can also be calculated from the chemical composition if elemental analysis data of the pure mineral are available. In the next mission to Mars, CheMin (Chemistry and Mineralogy), a combined X-ray diffraction/X-ray fluorescence instrument, will provide information on the mineralogical and elemental analysis of the samples. Possible significance of these results for planning the future missions to Mars for the search of organic compounds and extinct or extant life is discussed. PMID:20854214

Ertem, Gözen; Steudel, Annett; Emmerich, Katja; Lagaly, Gerhard; Schuhmann, Rainer

2010-09-01

232

Polyimide-Silica Hybrids Containing Novel Phenylethynyl Imide Silanes as Coupling Agents for Surface-Treated Titanium Alloy  

NASA Technical Reports Server (NTRS)

Polyimide-silica hybrids composed of an organic precursor containing a novel phenylethynyl imide silane and an inorganic precursor were evaluated as an adhesion-promoting interphase between surface-treated titanium alloy and a phenylethynyl-containing imide adhesive. The phenylethynyl groups present in the organic precursor, either as a pendent or end group, can bond chemically with a phenylethynyl-containing imide adhesive during processing, while the silane groups of the organic precursor would react chemically with the inorganic precursor. In addition, the inorganic precursor is able to react with the titanium alloy to form a stable bond with the metal oxide. Bond strength and durability were evaluated by single lap shear tests at various conditions. Lap shear specimens exhibited predominantly cohesive failure after a 3-d water boil with 92% retention of the initial room temperature strength. Morphology and chemical composition of the hybrid interphase were investigated with scanning electron microscopy, X-ray photoelectron spectroscopy, and Auger electron spectroscopy, which revealed development of a silicon-gradient, hybrid structure between the metal substrate and the adhesive.

Park, C.; Lowther, S. E.; Smith, J. G., Jr.; Connell, J. W.; Hergenrother, P. M.; SaintClair, T. L.

2000-01-01

233

Anopheline and culicine mosquitoes are not repelled by surfaces treated with the entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana  

PubMed Central

Background Entomopathogenic fungi, Metarhizium anisopliae and Beauveria bassiana, are promising bio-pesticides for application against adult malaria mosquito vectors. An understanding of the behavioural responses of mosquitoes towards these fungi is necessary to guide development of fungi beyond the 'proof of concept' stage and to design suitable intervention tools. Methods Here we tested whether oil-formulations of the two fungi could be detected and avoided by adult Anopheles gambiae s.s., Anopheles arabiensis and Culex quinquefasciatus. The bioassays used a glass chamber divided into three compartments (each 250 × 250 × 250 mm): release, middle and stimulus compartments. Netting with or without fungus was fitted in front of the stimulus compartment. Mosquitoes were released and the proportion that entered the stimulus compartment was determined and compared between treatments. Treatments were untreated netting (control 1), netting with mineral oil (control 2) and fungal conidia formulated in mineral oil evaluated at three different dosages (2 × 1010, 4 × 1010 and 8 × 1010 conidia m-2). Results Neither fungal strain was repellent as the mean proportion of mosquitoes collected in the stimulus compartment did not differ between experiments with surfaces treated with and without fungus regardless of the fungal isolate and mosquito species tested. Conclusion Our results indicate that mineral-oil formulations of M. anisopliae and B. bassiana were not repellent against the mosquito species tested. Therefore, both fungi are suitable candidates for the further development of tools that aim to control host-seeking or resting mosquitoes using entomopathogenic fungi. PMID:20799937

2010-01-01

234

Mineral catalysis of the formation of the phosphodiester bond in aqueous solution: The possible role of montmorillonite clays  

NASA Astrophysics Data System (ADS)

The binding of adenosine to Na+-montmorillonite 22A is greater than 5'-AMP, at neutral pH. Adenine derivatives bind more strongly to the clay than the corresponding uracil derivatives. These data are consistent with the protonation of the adenine by the acidic clay surface and a cationic binding of the protonated ring to the anionic clay surface. Other forces must be operative in the binding of uracil derivatives to the clay since the uracil ring system is not basic. The reaction of the 5'-AMP with water soluble carbodiimide in the presence of Na+-montmorillonite results in the formation of 2',5'-pApA (18.9%), 3',5'-pApA (11%), and AppA (4.8%). When poly(U) is used in place of the clay the product yields are 2',5',-pApA (15.5%), 3',5'-pApA (3.7%) and AppA (14.9%). The cyclic nucleotide, c(pA)2 is also formed when poly(U) is used. AppA is the principal reaction product when neither clay nor poly(U) is present in the reaction mixture. When 2'-deoxy-5'-AMP reacts with carbodiimide in the presence of Na+-montmorillonite 22A the products are dpApA (4.8%), dAppApA (4.5%) and dAppA (17.4%). Cyclic 3',5'-dAMP is the main product (14%) of the reaction of 2'-deoxy-3'-AMP.

Ferris, James P.; Ertem, Gözen; Kamaluddin; Agarwal, Vipin; Hua, Lu Lin

235

Kinetic study of citrate effects on orthophosphate solubility in an acidic, montmorillonitic soil  

Microsoft Academic Search

Previous studies on the effects of pH, organic acids, ionic strength, and Ca on residual orthophosphate solubility in an acidic montmorillonitic soil were extended to include the variation of reaction time. The objective of the experiments was to determine the time dependence of the reactions and to elucidate further the mechanism of orthophosphate solubility in a montmorillonitic soil separate containing

S. J. Traina; G. Sposito; G. R. Bradford; U. Kafkafi

2008-01-01

236

Cation exchange capacities of safranin, toluidine and alizarin complexes with montmorillonite  

Microsoft Academic Search

To obtain information about the cation exchange capacity (CEC) of montmorillonite as affected by the sorption of charged organic molecules, montmorillonite samples were loaded with different amounts of positively charged molecules of safranin, toluidine blue, and negatively charged alizarin red S. Dye sorption by the clay was carried out by equilibrating samples with different concentrations of the dye. The adsorbed

N. Peinemann; A. K. Helmy

1999-01-01

237

High-Frequency Eddy Current Conductivity Spectroscopy for Near-Surface Residual Stress Profiling in Surface-Treated Nickel-Base Superalloys  

SciTech Connect

Recent research indicated that eddy current conductivity measurements can be exploited for nondestructive evaluation of subsurface residual stress in surface-treated components. This technique is based on the so-called piezoresistive effect, i.e., the stress-dependence of electric conductivity. Previous experimental studies were conducted on excessively peened (Almen 10-16A peening intensity levels) nickel-base superalloy specimens that exhibited harmful cold work in excess of 30% plastic strain. The main reason for choosing peening intensities above recommended normal levels was that the eddy current penetration depth could not be decreased below 0.2 mm without conducting accurate measurements above 10 MHz, which is beyond the operational range of most commercially available eddy current instruments. In this paper we report the development of a new high-frequency eddy current conductivity measuring system that offers an extended inspection frequency range up to 80 MHz with a single probe coil. In addition, the new system offers better reproducibility, accuracy, and measurement speed than the previously used conventional system.

Abu-Nabah, Bassam A.; Nagy, Peter B. [Department of Aerospace Engineering and Engineering Mechanics, University of Cincinnati, Cincinnati, Ohio 45221-0070 (United States)

2007-03-21

238

Insecticide-Treated Bed Nets Reduce Plasma Antibody Levels and Limit the Repertoire of Antibodies to Plasmodium falciparum Variant Surface Antigens  

Microsoft Academic Search

The use of insecticide-treated bed nets (ITN) has been documented to reduce malaria morbidity and mortality in areas with endemic malaria, but concerns have been raised that ITN usage could affect the acquisition of malaria immunity. Several lines of evidence have indicated that antibodies against variant surface antigens (VSA) are important in the development of naturally acquired immunity to Plasmodium

NIKOLAJ ASKJAER; CAROLINE MAXWELL; WILLIAM CHAMBO; TRINE STAALSOE; MORTEN NIELSEN; LARS HVIID; CHRIS CURTIS; THOR G. THEANDER

2001-01-01

239

Behavior of Listeria monocytogenes on frankfurters surface treated with lauric arginate and/or a liquid smoke extract delivered using the Sprayed Lethality in Container (SLIC®) technology  

Technology Transfer Automated Retrieval System (TEKTRAN)

The objective of this study was to determine the viability of Listeria monocytogenes (LM) on commercially-produced frankfurters prepared without lactates that were surface treated with 0 or 4 mL of a blend of LAE (CytoGuard; 1.0% LAE final concentration) diluted in a concentrated liquid smoke extrac...

240

Nitrogen behavior in a free water surface constructed wetland used as posttreatment for anaerobically treated swine wastewater effluent.  

PubMed

The aim of this study was to evaluate the behavior of total nitrogen (TN) in its different forms in a Free Water Surface constructed wetland (FWS) used as posttreatment for anaerobically treated swine wastewater. The experiment was conducted in a glasshouse from July 2010 to November 2011. The system consists in a FWS mesocosm inoculated with Typha angustifolia L. using as pretreatment an UASB reactor (upflow anaerobic sludge blanket). The operation are based on the progressive increase of the nitrogen loading rate (NLR) (2.0-30.2 kg TN/ha·d) distributed in 12 loads, with an operational time of 20 d. The results indicate that the behavior of the TN in the FWS, mainly depends on the NLR applied, the amount of dissolved oxygen available and the seasonality. The FWS operated with an NLR between 2.0-30.2 kg TN/ha·d, presents average removal efficiency for TN of 54.8%, with a maximum removal (71.7%) between spring-summer seasons (17.3-21.7°C). The availability of dissolved oxygen hinders the nitrification/denitrification processes in the FWS representing a 0.3-5.6% of TN removed.The main route of TN removal is associated with ammonia volatilization processes (2.6-40.7%), mainly to NLR over 25.8 kg TN/ha· d and with temperatures higher than 18°C. In a smaller proportion, the incorporation of nitrogen via plant uptake was 10.8% whereas the TN accumulated in the sediments was a 5.0% of the TN applied during the entire operation (550 d). An appropriate control of the NLR applied, can reduce the ammonia volatilization processes and the phytotoxicity effects expressed as growth inhibition in 80.0% from 496.0 mg NH(+) 4-N/L (25.8 kg TN/ha·d). PMID:24171422

De Los Reyes, Catalina Plaza; Pozo, Guillermo; Vidal, Gladys

2014-01-01

241

Evaluation of Subsurface Flow and Free-water Surface Wetlands Treating NPR-3 Produced Water - Year No. 1  

SciTech Connect

This paper is a summary of some of the activities conducted during the first year of a three-year cooperative research and development agreement (CRADA) between the Department of Energy (DOE) Rocky Mountain Oilfield Testing Center (RMOTC) and Texaco relating to the treatment of produced water by constructed wetlands. The first year of the CRADA is for design, construction and acclimation of the wetland pilot units. The second and third years of the CRADA are for tracking performance of pilot wetlands as the plant and microbial communities mature. A treatment wetland is a proven technology for the secondary and tertiary treatment of produced water, storm water and other wastewaters. Treatment wetlands are typically classified as either free-water surface (FWS) or subsurface flow (SSF). Both FWS and SSF wetlands work well when properly designed and operated. This paper presents a collection of kinetic data gathered from pilot units fed a slipstream of Wyoming (NPR-3) produced water. The pilot units are set up outdoors to test climatic influences on treatment. Monitoring parameters include evapotranspiration, plant growth, temperature, and NPDES discharge limits. The pilot wetlands (FWS and SSF) consist of a series of 100-gal plastic tubs filled with local soils, gravel, sharp sand and native wetland plants (cattail (Typha spp.), bulrush (Scirpus spp.), dwarf spikerush (Eleocharis)). Feed pumps control hydraulic retention time (HRT) and simple water control structures control the depth of water. The treated water is returned to the existing produced water treatment system. All NPDES discharge limits are met. Observations are included on training RMOTC summer students to do environmental work.

Myers, J. E.; Jackson, L. M.

2001-10-13

242

Oligomerization reactions of deoxyribonucleotides on montmorillonite clay - The effect of mononucleotide structure, phosphate activation and montmorillonite composition on phosphodiester bond formation  

NASA Technical Reports Server (NTRS)

The 2(prime)-d-5(prime)-GMP and 2(prime)-d-5(prime)-AMP bind 2 times more strongly to montmorillonite 22A than do 2(prime)-d-5(prime)-CMP and 5(prime)-TMP. The dinucleotide d(pG)2 forms in 9.2 percent yield and the cyclic dinucleotide c(dpG)2 in 5.4 percent yield in the reaction of 2(prime)-d-5(prime)-GMP with EDAC in the presence of montmorillonite 22A. The yield of dimers which contain the phosphodiester bond decreases as the reaction medium is changed from 0.2 M NaCl to a mixture of 0.2 M NaCl and 0.075 M MgCl2. A low yield of d(pA)2 was observed in the condensation reaction of 5(prime)-ImdpA on montmorillonite 22A. The yield of d(pA)2 obtained when EDAC is used as the condensing agent increases with increasing iron content of the Na(+)-montmorillonite used as catalyst. Evidence is presented which shows that the acidity of the Na(+)-montmorillonite is a necessary but not sufficient factor for the montmorillonite catalysis of phosphodiester bond formation.

Ferris, James P.; KAMALUDDIN; Ertem, Gozen

1990-01-01

243

Oligomerization reactions of deoxyribonucleotides on montmorillonite clay: the effect of mononucleotide structure, phosphate activation and montmorillonite composition on phosphodiester bond formation.  

PubMed

2'-d-5'-GMP and 2'-d-5'-AMP bind 2 times more strongly to montmorillonite 22A than do 2'-d-5'-CMP and 5'-TMP. The dinucleotide d(pG)2 forms in 9.2% yield and the cyclic dinucleotide c(dpG)2 in 5.4% yield in the reaction of 2'-d-5'-GMP with EDAC in the presence of montmorillonite 22A. The yield of d(pC)2 (2.0%) is significantly lower but comparable to that obtained from 5'-TMP. The yield of dimers which contain the phosphodiester bond decreases as the reaction medium is changed from 0.2 M NaCl to a mixture of 0.2 M NaCl and 0.075 M MgCl2. A low yield of d(pA)2 was observed in the condensation reaction of 5'-ImdpA on montmorillonite 22A. The cyclic nucleotide (3',5'-cdAMP) was obtained in 14% yield from 3'-ImdpA. The yield of d(pA)2 obtained when EDAC is used as the condensing agent increases with increasing iron content of the Na(+)-montmorillonite used as a catalyst. Evidence is presented which shows that the acidity of the Na(+)-montmorillonite is a necessary but not sufficient factor for the montmorillonite catalysis of phosphodiester bond formation. PMID:11537409

Ferris, J P; Kamaluddin; Ertem, G

1990-01-01

244

Electrospun novel super-absorbent based on polysaccharide-polyvinyl alcohol-montmorillonite clay nanocomposites.  

PubMed

A novel super-absorbent material was fabricated by electrospinning the natural polysaccharide pullulan (PULL) with polyvinyl alcohol (PVA) and montmorillonite (MMT) clay to form nonwoven webs, which were then heat treated. Transmission electron microscopy (TEM) micrographs, X-ray diffraction (XRD) patterns, and Fourier transform infrared (FTIR) analysis of the novel super-absorbent nanofibers suggest the coexistence of PULL, PVA, and MMT through the exfoliation of MMT layers in the super-absorbent nanofiber composite. The heat-treated PULL/PVA/MMT webs loaded with 5 wt% MMT electrospun nanofibers exhibited a water absorbency of 143.42gg(-1) in distilled water and a water absorbency of 39.75gg(-1) in a 0.9 wt% NaCl solution. Under extremely dry conditions, the PULL/PVA/MMT webs exhibited the ability to retain 43% distilled water and 38% saline water after being exposed to the atmosphere for one week. The heat treatment improved the crystallinity of the electrospun PULL/PVA/MMT super-absorbent webs and thus made the webs highly stable in aqueous environments. Overall, the addition of MMT resulted in improved thermal stability and mechanical properties and increased the water absorbency of the PULL/PVA/MMT composite. PMID:25439870

Islam, Md Shahidul; Rahaman, Md Saifur; Yeum, Jeong Hyun

2015-01-22

245

Interpretation of small-angle x-ray scattering data from dilute montmorillonite suspensions using a modified Guinier approximation  

NASA Astrophysics Data System (ADS)

Smectites are a group of 2:1-layer phyllosilicate minerals that have been extensively studied by small-angle x-ray scattering (SAXS) because of their industrial and environmental significance. In previous studies, a Guinier plot has been used to obtain the radius of gyration of the clay particles, from which geometric information of the particle structure is derived. Using an indirect Fourier transform to treat SAXS data from a dilute montmorillonite suspension, a negative electron contrast at the clay-water interface is observed. This electron inhomogeneity has violated the assumption underlying the application of the Guinier plot, which requires particles to have a uniform electron density. The presence of this inhomogeneity explains the inability of previous studies to correctly determine particle dimensions using the Guinier plot. Using this model of the clay-water interface, a modified Guinier plot has been derived and was experimentally verified. The calculation shows the presence of negative electron contrast at montmorillonite-water interfaces, which is in accordance with the results from the indirect Fourier transform method. This approximation has the potential to predict the geometric information for similar colloids studied by small-angle scattering.

Shang, C.; Rice, J. A.

2001-08-01

246

Evidence for the nucleation and epitaxial growth of Zn phyllosilicate on montmorillonite  

NASA Astrophysics Data System (ADS)

Zinc uptake in suspensions (?3.7 g L -1) of MX80 montmorillonite was investigated at pH 4.0 and 7.3, a total Zn concentration ([Zn] total) of 500 ?M, and dissolved Si concentrations ([Si] aq) of ˜70 and ˜500 ?M in 0.5 M NaCl, by kinetics experiments and polarized extended X-ray absorption fine structure (P-EXAFS) spectroscopy. Differential thermogravimetric analysis verified the cis-vacant character of the montmorillonite. No Zn uptake occurred at pH 4.0, confirming that cation exchange was hampered by the high ionic strength of the suspension. At pH 7.3 and low [Si] aq (˜70 ?M), Zn uptake occurred rapidly during the first hour of reaction, and then leveled off to 50 ?mol/g montmorillonite at 168 h. The uptake rate is consistent with Zn sorption on pH-dependent edge sites. At pH 7.3 and high [Si] aq (˜500 ?M), the initial sorption rate was similar, but Zn sorption continued, reaching 130 ?mol/g at 168 h, and was paralleled by Si uptake with a Si/Zn uptake ratio of 1.51(10), suggesting formation of a Zn (hydrous) silicate. P-EXAFS data indicated that the first oxygen coordination shell of sorbed Zn is split into two subshells at 1.97(2) and 2.08(3)-2.12(2) Å for all EXAFS samples. These two distances are assigned to a mixture of tetrahedral ( IVZn) and octahedral ( VIZn) Zn complexes. The proportion of IVZn was lower in the high [Si] aq samples and decreased with reaction time. Al low [Si] aq and 216 h of reaction, nearest cationic shells of 0.6(4) Al in the film plane and 0.5(4) Si out of the film plane were detected at 3.00(2) and 3.21(2) Å, respectively, and were interpreted as the formation of IVZn and VIZn mononuclear complexes at the edges of montmorillonite platelets, in structural continuity to the (Al, Mg) octahedral sheets. At high [Si] aq, in-plane Zn and Al and out-of-plane Si neighbors were detected at 4 h, indicating the formation of Zn phyllosilicate nuclei at the layer edges. At 313 h, Zn-Al pairs were no longer detected, and Zn atoms were surrounded on average by 3.4(5) in-plane Zn at 3.10(1) Å and 1.7(9) out-of-plane Si at 3.30(2) Å, supporting the precipitation of a Zn phyllosilicate. Thus, dioctahedral Al phyllosilicate may act as a nucleating surface for the heterogeneous formation of trioctahedral Zn phyllosilicate at [Si] aq relevant to natural systems.

Schlegel, Michel L.; Manceau, Alain

2006-02-01

247

Montmorillonite-based porous clay heterostructures (PCHs) intercalated with silica-titania pillars-synthesis and characterization  

SciTech Connect

Porous clay heterostructures (PCHs) were synthesized using natural montmorillonite as a raw material. Apart from pure silica pillars also silica-titania pillars were intercalated into the interlayer space of the parent clay. The detailed studies of the calcination process of the as-prepared PCH samples as well as thermal stability of the pillared structure of these materials were performed. The pillared structure of PCHs intercalated with both silica and silica-titania clusters was found to be thermally stable up to temperatures exceeding 600 deg. C. It was found that titanium incorporated into the silica pillars was present mainly in the form of separated tetracoordinated cations. For the samples with the higher Ti loading also small contribution of titanium in the form of the polymeric oxide species was detected. Titanium incorporated into the PCH materials significantly increased their surface acidity forming mainly Bronsted acid sites. - Graphical abstract: Synthesis of the montmorillonite based porous clay heterostructures (PCHs) intercalated with silica-titania pillars has been performed. The mechanism of the thermal degradation of organic templates in the pore system of PCHs was studied. PCHs were characterized with respect to structure, texture, composition, surface acidity, thermal stability and form of introduced titanium.

Chmielarz, Lucjan, E-mail: chmielar@chemia.uj.edu.p [Jagiellonian University, Faculty of Chemistry, Ingardena 3, 30-060 Krakow (Poland); Gil, Barbara; Kustrowski, Piotr; Piwowarska, Zofia; Dudek, Barbara [Jagiellonian University, Faculty of Chemistry, Ingardena 3, 30-060 Krakow (Poland); Michalik, Marek [Jagiellonian University, Institute of Geological Sciences, Oleandry 2a, 30-063 Krakow (Poland)

2009-05-15

248

Mineral catalysis of the formation of the phosphodiester bond in aqueous solution - The possible role of montmorillonite clays  

NASA Technical Reports Server (NTRS)

The possible role of montmorillonite clays in the spontaneous formation on the primitive earth of the phosphodiester bond in the presence of water was investigated in experiments measuring the binding of various nucleosides and nucleotides with Na(+)-montmorillonite 22A and the reactions of these compounds with a water-soluble carbodiimide. It was found that, at neutral pH, adenine derivatives bind stronger than the corresponding uracil derivatives, consistent with the protonation of the adenine by the acidic clay surface and a cationic binding of the protonated ring to the anionic clay surface. The reaction of the 5-prime-AMP with carbodiimide resulted in the formation of 2-prime,5-prime-pApA (18.9 percent), 3-prime,5-prime-pApA (11 percent), and AppA (4.8 percent). The yields of these oligomers obtained when poly(U) was used in place of the clay were 15.5 percent, 3.7 percent, and 14.9 percent AppA, respectively.

Ferris, James P.; Ertem, Gozen; KAMALUDDIN; Agarwal, Vipin; Hua, Lu Lin

1989-01-01

249

U(VI) sorption on montmorillonite in the absence and presence of carbonate: A macroscopic and microscopic study  

NASA Astrophysics Data System (ADS)

The mechanism of U(VI) sorption on montmorillonite (Na-SWy-1) in the absence and presence of carbonate was investigated through a combination of different approaches: macroscopic sorption experiments, surface complexation modelling using the 2 Site Protolysis Non Electrostatic Surface Complexation and Cation Exchange sorption model and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. U(VI) sorption measurements were performed in the absence of carbonate at fixed ionic strength (0.1 M NaClO4) as a function of pH at U(VI) trace concentration (˜9 × 10-8 M) and as a function of U(VI) concentration (˜10-7-10-4 M) at a fixed pH (5, 6.8 and 8). In the presence of carbonate, experiments were carried out in equilibrium with atmospheric pCO2 and in 1, 3 and 5 mM NaHCO3. The pH dependent sorption measurements at trace concentration in the absence of carbonate were modelled by considering the formation of the following surface species, tbnd SOUO2+, tbnd SOUOOH, tbnd SOUO(OH)2- and tbnd SOUO(OH)32- on the strong sites. From the isotherms the formation of tbnd SOUO2+ and tbnd SOUOOH on the weak sites was inferred. Two additional surface complexes on the strong sites, tbnd SOUOCO3- and tbnd SOUO(CO)23- and one surface complex on the weak sites, SOUOCO3-, were necessary to reproduce the sorption data obtained in the presence of carbonate. The EXAFS measurements did not allow to verify the formation of ternary uranyl-carbonate complexes on the montmorillonite surface. However, the obtained fit results, i.e. splitting of the equatorial oxygen shell, one Si/Al shell at ˜3.09 Å and one Si/Al at ˜3.29 Å or one Fe shell at ˜3.42 Å, clearly indicate that under the given experimental conditions (pH, U(VI) loading) U(VI) forms inner-sphere surface complexes on montmorillonite edge sites via binding to aluminum octahedra and/or silicon tetrahedra.

Marques Fernandes, M.; Baeyens, B.; Dähn, R.; Scheinost, A. C.; Bradbury, M. H.

2012-09-01

250

Study on the surface of fluorosilicone acrylate RGP contact lens treated by low-temperature nitrogen plasma  

NASA Astrophysics Data System (ADS)

In order to improve the surface hydrophilicity of fluorosilicone acrylate rigid gas permeable (RGP) contact lens, low temperature nitrogen plasma was used to modify the lens surface. Effects of plasma conditions on the surface structures and properties were investigated. Results indicated that the surface hydrophilicity of RGP contact lens was significantly improved after treatment. X-ray photoelectron spectroscopy (XPS) results showed that the nitrogen element was successfully incorporated into the surface. Furthermore, some new bonds such as N sbnd C dbnd O, F - and silicate were formed on the lens surface after nitrogen plasma treatment, which could result in the improvement of the surface hydrophilicity. Scanning electronic microscope (SEM) results indicated that nitrogen plasma with moderate power could make the surface smoother in some degree, while plasma with higher power could etch the surface.

Ren, Li; Yin, Shiheng; Zhao, Lianna; Wang, Yingjun; Chen, Hao; Qu, Jia

2008-11-01

251

Electrorheological Behaviors of Polyaniline-Montmorillonite Clay Nanocomposite  

NASA Astrophysics Data System (ADS)

Polyanilline-montmorillonite nanocomposite (PANI-MMT) particles were synthesized by an emulsion intercalation method and characterized by IR, XRD and TEM spectrometry. TEM showed that the particle's size of MMT-PANI particles was about 100 mm. The dielectric constant of PANI-MMT nanocomposite was increased 2.4 times than that of MMT and 7 times than PANI, the conductivity of PANI-MMT particles was increased was increased 10 times than that of MMT. Meanwhile, the dielectric loss tangent was also increased about 1.36 times than that of PANI. The electrorheological behaviors of the suspensions of PANI-MMT nanocomposite in silicone oil with a 30% weight fraction were investigated under DC electric fields. In 3 kV/mm DC field at room temperature, the yield stress was 8.26 kPa (shear 5 s-1). In 4 kV/mm DC field, the shear strength was 8.30 kPa (? = 103.1 s-1, T = 20°C), and much higher than that of pure polyaniline (PANI), montmorillonite (MMT) and mixture of polyaniline with clay (MMT + PANI). The sedimentation experiment showed that the PANI-MMT nanocomposite particles did not deposit during about two months. The relevant influential factors between shear stress and electric fields, between shear stress and shear rate, between shear stress and temperature was also discussed preliminarily. The results showed that the MMT-PANI ER fluid displays a notable ER effect under DC electric field.

Lu, Jun; Zhao, Xiaopeng

252

Promethazine-montmorillonite inclusion complex to enhance drug photostability.  

PubMed

The capability of montmorillonite as a matrix (MONT) to improve the photostability of photolabile drugs has been recently reported. Herein promethazine (PRO), which was chosen as a model drug because of its photodegradation mechanism, was intercalated into this inorganic matrix, and the effects on drug photoprotection were evaluated as well. The hybrid material (MONT-PRO) was successfully prepared with high drug loading and then was characterized by X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC), and FTIR spectroscopy. The spectrophotometric measurements as a function of light exposure time showed that PRO intercalation into montmorillonite markedly improved the drug photostability because a 5-fold-slower degradation rate was determined compared to that measured for PRO in homogeneous solutions; nanosecond transient absorption measurements highlighted that the interaction with the inorganic matrix made negligible the photoionization process of the drug, and its efficiency in producing singlet oxygen was strongly reduced. The MONT-PRO intercalation compound could be easily formulated in gel or ointment media without losing its photostability. PMID:25407703

Ambrogi, Valeria; Nocchetti, Morena; Latterini, Loredana

2014-12-01

253

Heterostructured nanohybrid of zinc oxide-montmorillonite clay.  

PubMed

We have synthesized heterostructured zinc oxide-aluminosilicate nanohybrids through a hydrothermal reaction between the colloidal suspension of exfoliated montmorillonite nanosheets and the sol solution of zinc acetate. According to X-ray diffraction, N2 adsorption-desorption isotherm, and field emission-scanning electron microscopic analyses, it was found that the intercalation of zinc oxide nanoparticles expands the basal spacing of the host montmorillonite clay, and the crystallites of the nanohybrids are assembled to form a house-of-cards structure. From UV-vis spectroscopic investigation, it becomes certain that calcined nanohybrid contains two kinds of the zinc oxide species in the interlayer space of host lattice and in mesopores formed by the house-of-cards type stacking of the crystallites. Zn K-edge X-ray absorption near-edge structure/extended X-ray absorption fine structure analyses clearly demonstrate that guest species in the nanohybrids exist as nanocrystalline zinc oxides with wurzite-type structure. PMID:16471722

Hur, Su Gil; Kim, Tae Woo; Hwang, Seong-Ju; Hwang, Sung-Ho; Yang, Jae Hun; Choy, Jin-Ho

2006-02-01

254

Effects of Dextrose and Lipopolysaccharide on the Corrosion Behavior of a Ti-6Al-4V Alloy with a Smooth Surface or Treated with Double-Acid-Etching  

PubMed Central

Diabetes and infections are associated with a high risk of implant failure. However, the effects of such conditions on the electrochemical stability of titanium materials remain unclear. This study evaluated the corrosion behavior of a Ti-6Al-4V alloy, with a smooth surface or conditioned by double-acid-etching, in simulated body fluid with different concentrations of dextrose and lipopolysaccharide. For the electrochemical assay, the open-circuit-potential, electrochemical impedance spectroscopy, and potentiodynamic test were used. The disc surfaces were characterized by scanning electron microscopy and atomic force microscopy. Their surface roughness and Vickers microhardness were also tested. The quantitative data were analyzed by Pearson's correlation and independent t-tests (??=?0.05). In the corrosion parameters, there was a strong lipopolysaccharide correlation with the Ipass (passivation current density), Cdl (double-layer capacitance), and Rp (polarization resistance) values (p<0.05) for the Ti-6Al-4V alloy with surface treatment by double-acid-etching. The combination of dextrose and lipopolysaccharide was correlated with the Icorr (corrosion current density) and Ipass (p<0.05). The acid-treated groups showed a significant increase in Cdl values and reduced Rp values (p<0.05, t-test). According to the topography, there was an increase in surface roughness (R2?=?0.726, p<0.0001 for the smooth surface; R2?=?0.405, p?=?0.036 for the double-acid-etching-treated surface). The microhardness of the smooth Ti-6Al-4V alloy decreased (p<0.05) and that of the treated Ti-6Al-4V alloy increased (p<0.0001). Atomic force microscopy showed changes in the microstructure of the Ti-6Al-4V alloy by increasing the surface thickness mainly in the group associated with dextrose and lipopolysaccharide. The combination of dextrose and lipopolysaccharide affected the corrosion behavior of the Ti-6Al-4V alloy surface treated with double-acid-etching. However, no dose-response corrosion behavior could be observed. These results suggest a greater susceptibility to corrosion of titanium implants in diabetic patients with associated infections. PMID:24671257

Faverani, Leonardo P.; Assunção, Wirley G.; de Carvalho, Paulo Sérgio P.; Yuan, Judy Chia-Chun; Sukotjo, Cortino; Mathew, Mathew T.; Barao, Valentim A.

2014-01-01

255

Effects of dextrose and lipopolysaccharide on the corrosion behavior of a Ti-6Al-4V alloy with a smooth surface or treated with double-acid-etching.  

PubMed

Diabetes and infections are associated with a high risk of implant failure. However, the effects of such conditions on the electrochemical stability of titanium materials remain unclear. This study evaluated the corrosion behavior of a Ti-6Al-4V alloy, with a smooth surface or conditioned by double-acid-etching, in simulated body fluid with different concentrations of dextrose and lipopolysaccharide. For the electrochemical assay, the open-circuit-potential, electrochemical impedance spectroscopy, and potentiodynamic test were used. The disc surfaces were characterized by scanning electron microscopy and atomic force microscopy. Their surface roughness and Vickers microhardness were also tested. The quantitative data were analyzed by Pearson's correlation and independent t-tests (??=?0.05). In the corrosion parameters, there was a strong lipopolysaccharide correlation with the Ipass (passivation current density), Cdl (double-layer capacitance), and Rp (polarization resistance) values (p<0.05) for the Ti-6Al-4V alloy with surface treatment by double-acid-etching. The combination of dextrose and lipopolysaccharide was correlated with the Icorr (corrosion current density) and Ipass (p<0.05). The acid-treated groups showed a significant increase in Cdl values and reduced Rp values (p<0.05, t-test). According to the topography, there was an increase in surface roughness (R2?=?0.726, p<0.0001 for the smooth surface; R2?=?0.405, p?=?0.036 for the double-acid-etching-treated surface). The microhardness of the smooth Ti-6Al-4V alloy decreased (p<0.05) and that of the treated Ti-6Al-4V alloy increased (p<0.0001). Atomic force microscopy showed changes in the microstructure of the Ti-6Al-4V alloy by increasing the surface thickness mainly in the group associated with dextrose and lipopolysaccharide. The combination of dextrose and lipopolysaccharide affected the corrosion behavior of the Ti-6Al-4V alloy surface treated with double-acid-etching. However, no dose-response corrosion behavior could be observed. These results suggest a greater susceptibility to corrosion of titanium implants in diabetic patients with associated infections. PMID:24671257

Faverani, Leonardo P; Assunção, Wirley G; de Carvalho, Paulo Sérgio P; Yuan, Judy Chia-Chun; Sukotjo, Cortino; Mathew, Mathew T; Barao, Valentim A

2014-01-01

256

Anti-graffiti nanocomposite materials for surface protection of a very porous stone  

NASA Astrophysics Data System (ADS)

The preservation of stone substrates from defacement induced by graffiti represents a very challenging task, which can be faced by applying suitable protective agents on the surface. Although different anti-graffiti materials have been developed, it is often found that their effectiveness is unsatisfactory, most of all when applied on very porous stones, e.g. Lecce stone. The aim of this work was to study the anti-graffiti behaviour of new nanocomposite materials obtained by dispersing montmorillonite nanoparticles (layered aluminosilicates with a high-aspect ratio) into a fluorinated polymer matrix (a fluorinated polyurethane based on perfluoropolyether blocks). Polymeric structure was modified by inducing a cross-linking process, in order to produce a durable anti-graffiti coating with enhanced barrier properties. Several composites were prepared using a naturally occurring and an organically modified montmorillonite clay (1, 3, and 5 % w/w concentrations). Materials were applied on Lecce stone specimens, and then their treated surfaces were soiled by a black ink permanent marker or by a black acrylic spray paint. Several repeated staining/cleaning cycles were performed in order to evaluate anti-graffiti effectiveness. Colorimetric measurements were selected to assess the anti-graffiti performance. It was found that the presence of 3 % w/w organically modified montmorillonite in the polymer coating is enough to induce a durable anti-graffiti effect when the stone surface is stained by acrylic paint. Less promising results are obtained when staining by permanent marker is considered as all the investigated treatments afford a reasonable protection from ink only for the first staining/cleaning cycle.

Licchelli, Maurizio; Malagodi, Marco; Weththimuni, Maduka; Zanchi, Chiara

2014-09-01

257

Comparison of the protection effectiveness of acrylic polyurethane coatings containing bark extracts on three heat-treated North American wood species: Surface degradation  

NASA Astrophysics Data System (ADS)

High temperature heat-treatment of wood is a very valuable technique which improves many properties (biological durability, dimensional stability, thermal insulating characteristics) of natural wood. Also, it changes the natural color of wood to a very attractive dark brown color. Unfortunately, this color is not stable if left unprotected in external environment and turns to gray or white depending on the wood species. To overcome this problem, acrylic polyurethane coatings are applied on heat-treated wood to delay surface degradations (color change, loss of gloss, and chemical modifications) during aging. The acrylic polyurethane coatings which have high resistance against aging are further modified by adding bark extracts and/or lignin stabilizer to enhance their effectiveness in preventing the wood aging behavior. The aging characteristic of this coating is compared with acrylic polyurethane combined with commercially available organic UV stabilizers. In this study, their performance on three heat-treated North American wood species (jack pine, quaking aspen and white birch) are compared under accelerated aging conditions. Both the color change data and visual assessment indicate improvement in protective characteristic of acrylic polyurethane when bark extracts and lignin stabilizer are used in place of commercially available UV stabilizer. The results showed that although acrylic polyurethane with bark extracts and lignin stabilizer was more efficient compared to acrylic polyurethane with organic UV stabilizers in protecting heat-treated jack pine, it failed to protect heat-treated aspen and birch effectively after 672 h of accelerated aging. This degradation was not due to the coating adhesion loss or coating degradation during accelerated aging; rather, it was due to the significant degradation of heat-treated aspen and birch surface beneath this coating. The XPS results revealed formation of carbonyl photoproducts after aging on the coated surfaces and chain scission of Csbnd N of urethane linkages.

Kocaefe, Duygu; Saha, Sudeshna

2012-04-01

258

Influence of operating parameters on surface properties of RF glow discharge oxygen plasma treated TiO?/PET film for biomedical application.  

PubMed

In this paper, a thin transparent titania (TiO2) film was coated on the surface of flexible poly(ethylene terephthalate) (PET) film using the sol-gel method. The surface properties of the obtained TiO2/PET film were further improved by RF glow discharge oxygen plasma as a function of exposure time and discharge power. The changes in hydrophilicity of TiO2/PET films were analyzed by contact angle measurements and surface energy. The influence of plasma on the surface of the TiO2/PET films was analyzed by atomic force microscopy (AFM) as well as the change in chemical state and composition that were investigated by X-ray photo electron spectroscopy (XPS). The cytotoxicity of the TiO2/PET films was analyzed using human osteoblast cells and the bacterial eradication behaviors of TiO2/PET films were also evaluated against Staphylococcus bacteria. It was found that the surface roughness and incorporation of oxygen containing polar functional groups of the plasma treated TiO2/PET films increased substantially as compared to the untreated one. Moreover the increased concentration of Ti(3+) on the surface of plasma treated TiO2/PET films was due to the transformation of chemical states (Ti(4+)?Ti(3+)). These morphological and chemical changes are responsible for enhanced hydrophilicity of the TiO2/PET films. Furthermore, the plasma treated TiO2/PET film exhibited no citotoxicity against osteoblast cells and antibacterial activity against Staphylococcus bacteria which can find application in manufacturing of biomedical devices. PMID:24433917

Pandiyaraj, K Navaneetha; Deshmukh, R R; Mahendiran, R; Su, Pi-G; Yassitepe, Emre; Shah, Ismat; Perni, Stefano; Prokopovich, Polina; Nadagouda, Mallikarjuna N

2014-03-01

259

Preparation and characterization of silver loaded montmorillonite modified with sulfur amino acid  

NASA Astrophysics Data System (ADS)

The Na+ montmorillonite (MMT) was modified with sulfur containing amino acid (L-cystine, L-cysteine or L-methionine) and characterized by energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and Fourier transform infrared spectrum (FT-IR). The results showed the modification was smooth and the surface condition of MMT was changed with sulfur containing groups. Then silver was loaded on the modified MMTs via ion-exchange reaction under microwave irradiation, the spectra of X-ray photoelectron spectroscopy (XPS), EDS and FT-IR confirmed the successful loading of massive silver and the strong interaction between sulfur and silver, the silver loaded L-cystine modified MMT (Ag@AA-MMT-3) with a silver content of 10.93 wt% was the highest of all. Further more, the Ag@AA-MMT-3 was under the irradiation of a UV lamp to turn silver ions to silver nano particles (Ag NPs). The XPS, specific surface area (SSA), transmission electron microscopy (TEM), XRD patterns and UV-vis spectra proved the existence of uniform nano scaled metallic Ag NPs. By contrast, the UV irradiated Ag@AA-MMT-3 (Ag@AA-MMT-UV) showed a much better slow release property than Ag@AA-MMT-3 or Ag@MMT. The Ag@AA-MMT-UV showing a large inhibition zone and high inhibition ratio presented very good antibacterial property.

Li, Tian; Lin, Oulian; Lu, Zhiyuan; He, Liuimei; Wang, Xiaosheng

2014-06-01

260

Modification of a Ca-montmorillonite with ionic liquids and its application for chromate removal.  

PubMed

Ionic liquids (ILs), due to their low vapor pressure, have been explored as green solvents for organic synthesis. In this study, the uptake of ILs on a high charge Ca-montmorillonite (MMT) and the use of the IL-modified MMT for the removal of anionic contaminants from water were systematically studied. Uptake of ILs by MMT was exclusively resulted from a cation exchange mechanism when the initial IL concentrations were less than the critical micelle concentration (CMC) and the sorbed ILs formed a monolayer conformation on the surface of MMT. When the initial IL concentrations were greater than the CMC, both cation exchange and hydrophobic interactions were responsible for the IL uptake. The IL molecules formed admicelles and the surface charge was reversed to positive balanced by counterion Cl(-) when the IL loading was higher than the cation exchange capacity of the mineral. The modified MMT could remove chromate from water instantaneously, with an adsorption capacity of 190 mmol/kg and a 99.5% removal efficiency at an initial chromate concentration of 2.6 mmol/L. These features could further expand the application of ILs and enable IL-modified MMT to be used as inexpensive sorbents for the removal of chromate and other oxyanions from water. PMID:24572273

Li, Zhaohui; Jiang, Wei-Teh; Chang, Po-Hsiang; Lv, Guocheng; Xu, Shangping

2014-04-15

261

Adsorption of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and related compounds onto montmorillonite clay.  

PubMed

Sodium montmorillonite clay (Na-MMT) was modified using 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS). The objective of this study was to determine which chemical group is the 'driving force' leading to the adsorption of AMPS inside the clay galleries. AMPS has been reported to be a good candidate as a clay modifier for the preparation of polymer-clay nanocomposites by in situ free radical polymerization in emulsion. However, the way in which AMPS interacts with the surface of MMT has not yet been studied. The type of interaction between organic modifiers and clay plays a determining role in the successful preparation of polymer-clay nanocomposite materials. The adsorption ability of three other organic compounds similar to AMPS, namely sodium 1-allyloxy-2-hydroxypropyl sulfonate (Cops), N-isopropylacrylamide (NIPA) and methacryloyloxyundecan-1-yl sulfate (MET), was also evaluated. These selected compounds also have functional groups potentially able to interact with the clay surface (i.e., a sulfonate group, an amido group, or a sulfate group, respectively). Results of FT-IR, TGA and SAXS analyses showed that AMPS, NIPA, Cops and MET all interacted with clay, but to various extents. PMID:17996883

Greesh, Nagi; Hartmann, Patrice C; Cloete, Valeska; Sanderson, Ronald D

2008-03-01

262

Pharmaceuticals and personal care products (PPCPs) in surface and treated waters of Louisiana, USA and Ontario, Canada  

Microsoft Academic Search

A newly developed analytical method was used to measure concentrations of nine pharmaceuticals and personal care products (PPCPs) in samples from two surface water bodies, a sewage treatment plant effluent and various stages of a drinking water treatment plant in Louisiana, USA, and from one surface water body, a drinking water treatment plant and a pilot plant in Ontario, Canada.

Glen R. Boyd; Helge Reemtsma; Deborah A. Grimm; Siddhartha Mitra

2003-01-01

263

Influence of a zirconia sandblasting treated surface on peri-implant bone healing: An experimental study in sheep.  

PubMed

A sandblasting process with round zirconia (ZrO(2)) particles might be an alternative surface treatment to enhance the osseointegration of titanium dental implants. Our previous study on sheep compared smooth surface titanium implants (control) with implant surfaces sandblasted with two different granulations of ZrO(2). As the sandblasted surfaces proved superior, the present study further compared the ZrO(2) surface implant with other surface treatments currently employed: machined titanium (control), titanium oxide plasma sprayed (TPS) and alumina sandblasted (Al-SL) at different times after insertion (2, 4 and 12weeks). Twelve sheep were divided into three groups of four animals each and underwent implant insertion in tibia cortical bone under general anaesthesia. The implants with surrounding tissues were subjected to histology, histomorphometry, scanning electron microscopy and microhardness tests. The experimentation indicated that at 2weeks Zr-SL implants had the highest significant bone ingrowth (p<0.05) compared to the other implant surfaces, and a microhardness of newly formed bone inside the threads significantly higher than that of Ti. The present work shows that the ZrO(2) treatment produces better results in peri-implant newly formed bone than Ti and TPS processing, whereas its performance is similar to the Al-SL surface treatment. PMID:19233751

Bacchelli, Beatrice; Giavaresi, Gianluca; Franchi, Marco; Martini, Désirée; De Pasquale, Viviana; Trirè, Alessandra; Fini, Milena; Giardino, Roberto; Ruggeri, Alessandro

2009-07-01

264

Eco-Friendly Magnetic Iron Oxide Pillared Montmorillonite for Advanced Catalytic Degradation of Dichlorophenol  

EPA Science Inventory

Eco-friendly pillared montmorillonites, in which the pillars consist of iron oxide are expected to have interesting and unusual magnetic properties that are applicable for environmental decontamination. Completely ?green? and effective composite was synthesized using mild reactio...

265

Bioavailability of labile and desorption-resistant phenanthrene sorbed to montmorillonite clay containing humic fractions  

SciTech Connect

The biodegradation of {sup 14}C-labeled phenanthrene in the presence of particles of montmorillonite and fulvic and humic acid-montmorillonite complexes was studied in a batch system. A mathematical model that takes into account the contribution to mineralization by the slowly desorbing compound was used to calculate the initial mineralization rates. Sorption of phenanthrene to the particles was determined in sorption isotherms, and desorption was measured during successive water extractions. Mineralization rates in equilibrated suspensions were higher than predicted from aqueous equilibrium concentrations, and in some cases, montmorillonite and fulvic acid-montmorillonite complexes stimulated the phenanthrene transformation rates. In contrast with the high bioavailability exhibited by phenanthrene sorbed as a labile form, biodegradation of the desorption-resistant phenanthrene occurred slowly and followed zero-order kinetics, which indicated a limitation caused by slow desorption. The results suggest that the mechanism of sorption may cause a differential bioavailability of the sorbed compound.

Lahlou, M.; Ortega-Calvo, J.J.

1999-12-01

266

Variation of arsenic concentration on surfaces of in-service CCA-treated wood planks in a park and its influencing field factors.  

PubMed

Wood preservatives can protect wood from dry rot, fungi, mould and insect damage, and chromated copper arsenate (CCA) has been used as an inorganic preservative for many years. However, wood treated with CCA has been restricted from residential uses in the EU from June 30, 2004, due to its potential toxicity. Such a regulation is not in place in China yet, and CCA-treated wood is widely used in public parks. A portable XRF analyser was used to investigate arsenic (As) concentration on surfaces of in-service CCA-treated wood planks in a popular park as well as the influencing field factors of age in-service, immersion and human footfall. With a total of 1207 readings, the observed As concentrations varied from below the detection limit (<10 mg/kg) to 15,746 mg/kg with a median of 1160 mg/kg. Strong variation of As concentrations were observed in different wood planks of the same age, on the surface of the same piece of wood, inside the same piece of wood, and different surfaces of walkway planks, hand rails and poles in the field. The oldest planks exhibited high As concentrations, which was related to its original treatment with high retention of CCA preservative. The effect of immersion in the field for about 4 months was insignificant for As concentration on the surfaces. However, a significant reduction of As was observed for immersion combined with human footfall (wiping by shoes). Human traffic in general caused slightly reduced and more evenly distributed As concentrations on the wood surfaces. The strong variation, slow aging and relatively weak immersion effects found in this study demonstrate that the in-service CCA-treated wood poses potential health risks to the park users, due to easy dermal contact especially when the wood is wet after rainfall. It is suggested that further comprehensive investigations and risk assessments of CCA-treated wood in residential areas in China are needed, and precautionary measures should be considered to reduce the potential risks to residents and visitors, especially children. PMID:25512245

Tang, Ya; Gao, Wei; Wang, Xiuli; Ding, Shiming; An, Taicheng; Xiao, Weiyang; Wong, Ming H; Zhang, Chaosheng

2015-01-01

267

Novel wet SEM imaging of organically modified montmorillonite clay dispersions  

NASA Astrophysics Data System (ADS)

Rheology and a novel application of wet scanning electron microscopy (WSEM) are performed on organically modified montmorillonite clay dispersions differing in free surfactant content. The dispersion without free surfactant exhibits a higher yield stress and strongly hysteretic rheology. WSEM imaging shows the influence of free surfactant on the quiescent distribution of nano- and microscale organoclay domains. Spatially resolved elemental analysis using energy dispersive X-ray spectroscopy defines regions consisting primarily of clay silicate versus those that are dominantly solvent. The contrasting images suggest that free surfactant screens attractive van der Waals forces between domains, leading to a more homogeneously distributed but structurally weaker mesoscopic network. WSEM is shown to be a valuable complementary technique in characterizing the network morphology of organoclay dispersions. More broadly, WSEM demonstrates great potential for the direct imaging of the microstructure of other classes of suspensions and particulate gels.

Li, J.; Fitz-Gerald, J. M.; Oberhauser, J. P.

2007-04-01

268

Intergrown mica and montmorillonite in the Allende carbonaceous chondrite  

NASA Technical Reports Server (NTRS)

High resolution transmission electron microscopy (HRTEM) observations were made of a mixture of mica and montmorillonite from fine-grained calcium, aluminum inclusions (CAI) in the Allende C3(V) meteorite. A petrographic thin section having a diameter of 4 mm contained CAI fragments ranging from less than 1 to 50 microns. The observed textural and chemical characteristics placed the inclusion in the fine-grained alkali-rich spinel aggregate category of Warks' (1979) classifications of CAIs and as type 3 in Kornacki's classifications of fine grains in Allende. Chemical analyses were performed on the phyllosilicate grains observed in the TEM scan by means of an X ray observed, and the proximity to the matrix boundary suggests a metamorphism which included aqueous alteration at a relatively low temperature.

Tomeoka, K.; Buseck, P. R.

1982-01-01

269

Effect of Montmorillonite Clay upon the polycondensation of Lactic Acid  

NASA Astrophysics Data System (ADS)

The development of synthetic biodegradable polymers, such as poly(?-hydroxy acid), is particularly important for constructing medical devices, drug delivery systems, including scaffolds and sutures, and has attracted growing interest in the biomedical field. Here, we report a novel approach to preparing poly(D, L-lactic acid) (PDLA) as a biodegradable polymer. We investigated in detail the reaction conditions for the simple direct polycondensation of lactic acid, including the reaction times, temperatures, and catalyst. The molecular weight of synthesized PLA is dependent on both the reaction temperature and time. The optimum reaction condition to obtain PDLA by direct polycondensation using Maghnite-H+, a proton exchanged Montmorillonite clay, as catalyst was thus determined to be 120 °C for 28h with a molecular weight of 7970. The method for PDLA synthesis established here will facilitate production of PDLA of various molecular weights, which may have a potential utility as biomaterials.

El Amine, Belaouedj Mohammed; Mohammed, Belbachir

2008-08-01

270

Characterization of synthesized polyurethane/montmorillonite nanocomposites foams  

NASA Astrophysics Data System (ADS)

Nanophased hybrid composites based on polyurethane/montmorillonite (PU/MMT) have been fabricated. The nanocomposite which was formed by the addition of a polyol premix with 4,4'-diphenylmethane diisocyanate to obtain nanophased polyurethane foams which were then used for fabrication of nanocomposite panels has been shown to have raised strength, stiffness and thermal insulation properties. The nanophased polyurethane foam was characterized by means of scanning electron microscope (SEM), transmission electron microscope (TEM) measurements and X-ray diffraction (XRD). TEM and SEM analysis indicated that nanophased particles are dispersed homogeneously in the polyurethane matrix on the nanometer scale indicating that PU/MMT is an intercalated nanocomposite with a 2-3 nm nanolayer thickness.

Ansari, Farahnaz; Sachse, Sophia; Michalowski, S.; Kavosh, Masoud; Pielichowski, Krzysztof; Njuguna, James

2014-08-01

271

Antibacterial effect of Cu 2+-exchanged montmorillonite on Aeromonas hydrophila and discussion on its mechanism  

Microsoft Academic Search

Montmorillonite (MMT) and its Cu2+-exchanged montmorillonite (Cu-MMT) were used to study the antibacterial activity on Aeromonas hydrophila. The results indicated that MMT had no antibacterial activity. The minimum inhibitory concentration (MIC) and bactericidal concentration (MBC) of Cu-MMT on A. hydrophila are found to be 150 and 600mg\\/L, respectively. The continuance of the antibacterial activity of Cu-MMT was much longer than

C. H. Hu; Z. R. Xu; M. S. Xia

2005-01-01

272

Infrared Spectroscopic Study of Adsorbed Water on Reduced-Charge Na\\/Li-Montmorillonites  

Microsoft Academic Search

Infrared (IR) spectra in the fundamental and near-IR regions were obtained for Na-saturated Wyoming montmoriUonite and reduced-charge Na\\/Li-saturated Wyoming montmorillonites hydrated un- der water vapor at 50% RH and dehydrated under vacuum. For the Na-montmorillonite, changes in the intensities of the structural OH-bending modes, particularly that of the MgA1OH group, were observed as the clay was dehydrated. This result was

Garrison Sposito; R. PROST; J.-P. GAULTIER

1983-01-01

273

Antimicrobial silver-montmorillonite nanoparticles to prolong the shelf life of fresh fruit salad  

Microsoft Academic Search

In this work, silver-montmorillonite (Ag-MMT) antimicrobial nanoparticles have been obtained by allowing silver ions from nitrate solutions to replace the Na+ of natural montmorillonite and then to be reduced by a thermal treatment. Ag-MMT were used as active antimicrobial compounds to improve the shelf life of fresh fruit salad. In order to assess their influence on product shelf life, sensorial

C. Costa; A. Conte; G. G. Buonocore; M. A. Del Nobile

2011-01-01

274

Morphology, structure and properties of a poly(1-butene)\\/montmorillonite nanocomposite  

Microsoft Academic Search

A specifically formulated nanocomposite based on isotactic poly(1-butene) (PB) and montmorillonite was studied, by wide angle X-ray diffraction (WAXD), small angle X-ray scattering (SAXS), transmission electron microscopy (TEM) and polarized light optical microscopy, investigating the polymorphism of the polymer, and examining the interaction between PB and the silicate. Montmorillonite was found to disrupt the ordered morphology of the polymer, determining

Valerio Causin; Carla Marega; Antonio Marigo; Giuseppe Ferrara; Gulnaz Idiyatullina; Fabiana Fantinel

2006-01-01

275

Characterization of montmorillonite doped PVA/SA blends using X-ray diffraction  

SciTech Connect

PVA films doped with Montmorillonite was prepared by slow evaporation technique. These films have been used to record X-ray patterns at room temperature. Correlation lengths and microstructural parameters were computed using in-house program employing X-ray data. Results show that correlation lengths as well as crystallite size increases with increase in the concentration of Montmorillonite which is inconformity with the conductivity studies.

Hemalatha, K.; Somashekarappa, H. [Department of Physics, Yuvaraja's College, University of Mysore, Manasagangotri, Mysore-570005 (India); Mahadevaiah,; Somashekar, R., E-mail: rs@physics.uni-mysore.ac.in [Department of Studies in Physics, University of Mysore, Manasagangotri, Mysore-570006 (India)

2014-04-24

276

Polypropylene\\/Montmorillonite Nanocomposites. Review of the Synthetic Routes and Materials Properties  

Microsoft Academic Search

The synthetic routes and materials properties of polypropylene\\/montmorillonite nano- composites are reviewed. The nanocomposite formation is achieved in two ways: either by using functionalized polypropylenes and common organo-montmorillonites, or by using neat\\/ unmodified polypropylene and a semi-fluorinated organic modification for the silicates. All the hybrids can be formed by solventless melt-intercalation or extrusion, and the resulting polymer\\/inorganic structures are characterized

E. Manias; A. Touny; L. Wu; K. Strawhecker; B. Lu; T. C. Chung

2001-01-01

277

Designing of a wheat gluten\\/montmorillonite based system as carvacrol carrier: Rheological and structural properties  

Microsoft Academic Search

An antimicrobial delivery system was designed from film-forming solutions containing wheat gluten 20% (wt\\/vol) (WG) as matrix, montmorillonites (Mmt) as structuring agent and carvacrol as active agent (15% wt\\/wt dry WG). The objectives of this work were to understand how the addition of montmorillonites (0–10% wt\\/wt dry WG) affects the carvacrol retention capacity of both the film forming solution and the resulting

E. Mascheroni; P. Chalier; N. Gontard; E. Gastaldi

2010-01-01

278

Significant long-term reduction in n-channel MESFET subthreshold leakage using ammonium-sulfide surface treated gates  

NASA Technical Reports Server (NTRS)

Ammonium-sulfide (NH4)2S treated gates have been employed in the fabrication of GaAs MESFETs that exhibit a remarkable reduction in subthreshold leakage current. A greater than 100-fold reduction in drain current minimum is observed due to a decrease in Schottky gate leakage. The electrical characteristics have remained stable for over a year during undesiccated storage at room temperature, despite the absence of passivation layers.

Neudeck, P. G.; Carpenter, M. S.; Melloch, Michael R.; Cooper, James A., Jr.

1991-01-01

279

Influence of gas and treatment time on the surface modification of EPDM rubber treated at afterglow microwave plasmas  

NASA Astrophysics Data System (ADS)

The ethylene propylene diene monomer (EPDM) rubber possesses excellent physical/chemical bulk properties, is cost-effective, and has been used in the mechanical and aerospace industry. However, it has an inert surface and needs a surface treatment in order to improve its adhesion properties. Plasma modification is the most accepted technique for surface modification of polymers without affecting the properties of the bulk. In this study, an afterglow microwave plasma reactor was used to generate the plasma species responsible for the EPDM surface modification. The plasma modified surfaces were analyzed by means of contact angle measurement, adhesion tests, attenuated total reflection-infrared spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy. Two experimental variables were analyzed: type of the plasma gases and exposure time were considered. The predominant failure mode was adhesive, for long treatment times a mixture of adhesive and cohesive failure can be observed and the best conditions tested there was an increase of the rupture strength of about 27%, that can be associated mainly with the creation of oxygen containing functional groups on the rubber surface (CO, COC and CO) identified by spectroscopic methods. The predominant failure mode was adhesive, for long treatment times a mixture of adhesive and cohesive failure can be observed. In various conditions tested the contact angles easily decreased more than 500%. What can be concluded that high wettability is a necessary condition to obtain good adhesion, but this is not a sufficient condition.

da Maia, J. V.; Pereira, F. P.; Dutra, J. C. N.; Mello, S. A. C.; Becerra, E. A. O.; Massi, M.; Sobrinho, A. S. da Silva

2013-11-01

280

Comparative evaluation of effect of acidic beverage on enamel surface pre-treated with various remineralizing agents: An In vitro study  

PubMed Central

Aim: This study aimed at quantitatively evaluating the effect of colabased beverage on the calcium loss of enamel surface pre-treated with fluorideenriched casein phosphopeptideamorphous calcium phosphate (CPP-ACPF) and ?eta-ricalcium phosphate (?-TCP) using energy dispersive X-ray analysis (EDX). Materials and Methods: 24 enamel specimens were prepared from the buccal and palatal surfaces of extracted intact human premolars and were randomly assigned to study groups and control group. Specimens of Group II were pre-treated with CPP-ACPF and Group III treated with ?-TCP twice daily for 4 for 28 days, followed by storage in artificial saliva. All specimens were evaluated for mineral (calcium and phosphorus) content (wt%) after pre-treatment using SEM-EDAX. The specimens were then placed in the acidic beverages for 4 days for 10 Mineral content was again measured using SEM-EDAX. Results: Statistical analysis using one-way ANOVA followed by Tukey's HSD test was applied to compare the re-mineralization and de-mineralization of the samples. Conclusion: The present study concluded that both the remineralizing agents tested were found to be effective in inhibiting the de-mineralization caused by colabased beverage. Among the remineralizing agents tested, ?-TCP was found to be more effective than CPP-ACPF. PMID:23112483

Hegde, Mithra N; Devadiga, Darshana; Jemsily, Prince A

2012-01-01

281

The effect of NaOH concentration on the steam-hydrothermally treated bioactive microarc oxidation coatings containing Ca, P, Si and Na on pure Ti surface.  

PubMed

The microarc oxidation (MAO) coating covered pure Ti plates are steam-hydrothermally treated in autoclaves containing NaOH solutions with different concentrations of 0, 0.001, 0.01, 0.1 and 1mol·L(-1). Due to the composition of Ti, O, Ca, P, Si and Na elements in the MAO coating, anatase and hydroxyapatite (HA) crystals are generated from the previously amorphous MAO coating after the steam-hydrothermal treatment. Meanwhile, it is noticed that the amount of HA crystals increases but showing a decline trend in aspect ratio in morphologies with the increasing of NaOH concentration. Interestingly, the steam-hydrothermally treated MAO coatings exhibit better bonding strength with Ti substrate (up to 43.8±1.1MPa) than that of the untreated one (20.1±3.1MPa). In addition, benefiting from the corrosive attack of the dissolved NaOH in water vapor on the MAO coating, Ti-OH is also formed on the steam-hydrothermally treated MAO coating surface, which can trigger apatite nucleation. Thus, the steam-hydrothermally treated MAO coatings exhibit good apatite-inducing ability. PMID:25686996

Zhou, Rui; Wei, Daqing; Cao, Jianyun; Feng, Wei; Cheng, Su; Du, Qing; Li, Baoqiang; Wang, Yaming; Jia, Dechang; Zhou, Yu

2015-04-01

282

Surface-enhanced Raman scattering study of the healing of radial fractures treated with or without Huo–Xue–Hua–Yu decoction therapy  

NASA Astrophysics Data System (ADS)

This study aimed to assess, through surface-enhanced Raman scattering (SERS) spectroscopy, the incorporation of calcium hydroxyapatite (CHA ~960?cm?1) and other biochemical substances in the repair of complete radial fractures in rabbits treated with or without Huo–Xue–Hua–Yu decoction (HXHYD) therapy. A total of 18 rabbits with complete radial fractures were randomly divided into two groups; one group was treated with HXHYD therapy and the other without therapy acted as a control. The animals were sacrificed at 15, 30 and 45?d after surgery. Specimens were routinely prepared for SERS measurement and high quality SERS spectra from a mixture of bone tissues and silver nanoparticles were obtained. The mineral-to-matrix ratios from the control and treated groups were calculated. Results showed that both deposition content of CHA measured by SERS spectroscopy and the mineral-to-matrix ratio in the treated group were always greater than those of the control group during the experiment, demonstrating that HXHYD therapy is effective in improving fracture healing and that SERS spectroscopy might be a novel tool to assess fracture healing.

Chen, Weiwei; Huang, Hao; Chen, Rong; Feng, Shangyuan; Yu, Yun; Lin, Duo; Lin, Jia

2014-11-01

283

Particle configuration and mechanical properties of poly(vinyl chloride)\\/montmorillonite nanocomposites via in situ suspension polymerization  

Microsoft Academic Search

Poly(vinyl chloride)\\/montmorillonite (PVC\\/MMT) nanocomposites were synthesized via in situ intercalative polymerization and their microstructure, particle characteristics and mechanical properties were investigated. The montmorillonite layers were almost exfoliated into nanoscale layers and an exfoliated nanostructure was obtained. The mean particle size of the nanocomposites decreased and the degree of porosity of the particles increased with increasing organic modified montmorillonite (OMMT) content.

Fangling Gong; Meng Feng; Chungui Zhao; Shimin Zhang; Mingshu Yang

2004-01-01

284

Effects of exchanged cation and layer charge on the sorption of water and EGME vapors on montmorillonite clays  

USGS Publications Warehouse

The effects of exchanged cation and layer charge on the sorption of water and ethylene glycol monoethyl ether (EGME) vapors on montmorillonite have been studied on SAz-1 and SWy-1 source clays, each exchanged respectively with Ca, Na, K, Cs and tetramethylammonium (TMA) cations. The corresponding lattice expansions were also determined, and the corresponding N2 adsorption data were provided for comparison. For clays exchanged with cations of low hydrating powers (such as K, Cs and TMA), water shows a notably lower uptake than does N2 at low relative pressures (P/P0). By contrast, EGME shows higher uptakes than N2 on all exchanged clays at all P/P0. The anomaly for water is attributed to its relatively low attraction for siloxane surfaces of montmorillonite because of its high cohesive energy density. In addition to solvating cations and expanding interlayers, water and EGME vapors condense into small clay pores and interlayer voids created by interlayer expansion. The initial (dry) interlayer separation varies more significantly with cation type than with layer charge; the water-saturated interlayer separation varies more with cation type than the EGME-saturated interlayer separation. Because of the differences in surface adsorption and interlayer expansion for water and EGME, no general correspondence is found between the isotherms of water and EGME on exchanged clays, nor is a simple relation observed between the overall uptake of either vapor and the cation solvating power. The excess interlayer capacities of water and of EGME that result from lattice expansion of the exchanged clays are estimated by correcting for amounts of vapor adsorption on planar clay surfaces and of vapor condensation into intrinsic clay pores. The resulting data follow more closely the relative solvating powers of the exchanged cations.

Chiou, C.T.; Rutherford, D.W.

1997-01-01

285

Tribological characterization of surface-treated commercially pure titanium for femoral heads in total hip replacement: a feasibility study.  

PubMed

Most noncemented total hip replacements combine a titanium alloy stem, a CoCrMo femoral head and an ultra-high molecular weight polyethylene (UHMWPE) acetabular cup. In spite of its nickel content of up to 1% and the resulting biocompatibility issues in some clinical situations, the higher cost and some difficulties in machining, CoCrMo alloy is preferred to titanium alloys thanks to its outstanding tribological properties, higher hardness and elastic modulus. Nowadays most of the heads of hip prostheses use CoCrMo as bearing material. The present study investigates the effect of various surface treatments and combinations of treatments, such as electrochemical oxidation (anodization), laser surface melting and barrel polishing, on the tribological properties of commercially pure grade 2 titanium. The aim of the study was to characterize surface treatments capable of improving the tribological properties of titanium surface to the same extent as CoCrMo. The tribological properties were characterized by multidirectional pin-on-flat screening wear tests, using UHMWPE pins as bearing surface. The experiments showed the possibility of improving the wear resistance of titanium to the degree of CoCrMo. Although further efforts will be required to optimize the treatments studied, the results are encouraging enough to warrant pursuing this direction of investigation. PMID:17219358

Cotogno, G; Holzwarth, U; Franchi, M; Rivetti, S; Chiesa, R

2006-12-01

286

Corrosion Behavior of Surface-Treated Implant Ti-6Al-4V by Electrochemical Polarization and Impedance Studies  

NASA Astrophysics Data System (ADS)

Implant materials for orthopedic and heart surgical services demand a better corrosion resistance material than the presently used titanium alloys, where protective oxide layer breaks down on a prolonged stay in aqueous physiological human body, giving rise to localized corrosion of pitting, crevice, and fretting corrosion. A few surface treatments on Ti alloy, in the form of anodization, passivation, and thermal oxidation, followed by soaking in Hank solution have been found to be very effective in bringing down the corrosion rate as well as producing high corrosion resistance surface film as reflected from electrochemical polarization, cyclic polarization, and Electrochemical Impedance Spectroscopy (EIS) studies. The XRD study revealed the presence of various types of oxides along with anatase and rutile on the surface, giving rise to high corrosion resistance film. While surface treatment of passivation and thermal oxidation could reduce the corrosion rate by 1/5th, anodization in 0.3 M phosphoric acid at 16 V versus stainless steel cathode drastically brought down the corrosion rate by less than ten times. The mechanism of corrosion behavior and formation of different surface films is better understood from the determination of EIS parameters derived from the best-fit equivalent circuit.

Paul, Subir; Yadav, Kasturi

2011-04-01

287

Improved performance of dye-sensitized solar cells with surface-treated TiO{sub 2} as a photoelectrode  

SciTech Connect

We report on the effects of surface-modified TiO{sub 2} on the performance of dye-sensitized solar cells (DSSCs). TiO{sub 2} surface was modified with Na{sub 2}CO{sub 3} via a simple dip coating process and the modified TiO{sub 2} was applied to photoelectrodes of DSSCs. By dipping of TiO{sub 2} layer into aqueous Na{sub 2}CO{sub 3} solution, the DSSC showed a power conversion efficiency of 9.98%, compared to that (7.75%) of the reference device without surface treatment. The UV–vis absorption spectra, the impedance spectra and the dark current studies revealed that the increase of all parameters was attributed to the enhanced dye adsorption, the prolonged electron lifetime and the reduced interfacial resistance.

Park, Su Kyung; Chung, Chinkap [Department of Chemistry, Keimyung University, Daegu 704-701 (Korea, Republic of)] [Department of Chemistry, Keimyung University, Daegu 704-701 (Korea, Republic of); Kim, Dae-Hwan; Kim, Cham; Lee, Sang-Ju [Green Energy Research Division, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 711-873 (Korea, Republic of)] [Green Energy Research Division, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 711-873 (Korea, Republic of); Han, Yoon Soo, E-mail: yshancu@cu.ac.kr [Department of Advanced Energy Material Science and Engineering, Catholic University of Daegu, Gyeongbuk 712-702 (Korea, Republic of)

2012-10-15

288

Modified montmorillonite clay microparticles for stable oil-in-seawater emulsions.  

PubMed

Environmentally benign clay particles are of great interest for the stabilization of Pickering emulsions. Dodecane-in-synthetic seawater (SSW) emulsions formed with montmorillonite (MMT) clay microparticles modified with bis(2-hydroxyethyl)oleylamine were stable against coalescence, even at clay concentrations down to 0.1% w/v. Remarkably, as little as 0.001% w/v surfactant lowered the hydrophilicity of the clay to a sufficient level for stabilization of oil-in-SSW emulsions. The favorable effect of SSW on droplet size reduction and emulsion stability enhancement is hypothesized to be due to reduced electrostatic repulsion between adsorbed clay particles and a consequent increase in the continuous phase (an aqueous clay suspension) viscosity. Water/oil (W/O) emulsions were inverted to O/W either by decreasing the mass ratio of surfactant-to-clay (transitional inversion) or by increasing the water volume fraction (catastrophic inversion). For both types of emulsions, coalescence was minimal and the sedimentation or creaming was highly correlated with the droplet size. For catastrophic inversions, the droplet size of the emulsions was smaller in the case of the preferred curvature. Suspensions of concentrated clay in oil dispersions in the presence of surfactant were stable against settling. The mass transfer pathways during emulsification of oil containing the clay particles were analyzed on the droplet size/stability phase diagrams to provide insight for the design of dispersant systems for remediating surface and subsurface oceanic oil spills. PMID:24932773

Dong, Jiannan; Worthen, Andrew J; Foster, Lynn M; Chen, Yunshen; Cornell, Kevin A; Bryant, Steven L; Truskett, Thomas M; Bielawski, Christopher W; Johnston, Keith P

2014-07-23

289

Bisphenol A sorption by organo-montmorillonite: implications for the removal of organic contaminants from water.  

PubMed

Remediation of bisphenol A (BPA) from aqueous solutions by adsorption using organoclays synthesized from montmorillonite (MMT) with different types of organic surfactant molecules was demonstrated. High adsorption capacities of the organoclays for the uptake of BPA were observed and these demonstrated their potential application as strong adsorbents for noxious organic water contaminants. The adsorption of BPA was significantly influenced by pH, with increased adsorption of BPA in acidic pH range. However, the organoclays intercalated with highly loaded surfactants and/or large surfactant molecules were less influenced by the pH of the environment and this was thought to be due to the shielding the negative charge from surfactant molecules and the development of more positive charge on the clay surface, which leads to the attraction of anionic BPA even at alkaline pH. The hydrophobic phase created by loaded surfactant molecules contributed to a partitioning phase, interacting with BPA molecules strongly through hydrophobic interaction. Pseudo-second order kinetic model and Langmuir isotherm provided the best fit for the adsorption of BPA onto the organoclays. In addition, the adsorption process was spontaneous and exothermic with lower temperature facilitating the adsorption of BPA onto the organoclays. The described process provides a potential pathway for the removal of BPA from contaminated waters. PMID:24412097

Park, Yuri; Sun, Zhiming; Ayoko, Godwin A; Frost, Ray L

2014-07-01

290

Activity of Laccase Immobilized on TiO2-Montmorillonite Complexes.  

PubMed

The TiO2-montmorillonite (TiO2-MMT) complex was prepared by blending TiO2 sol and MMT with certain ratio, and its properties as an enzyme immobilization support were investigated. The pristine MMT and TiO2-MMT calcined at 800 °C (TiO2-MMT800) were used for comparison to better understand the immobilization mechanism. The structures of the pristine MMT, TiO2-MMT, and TiO2-MMT800 were examined by HR-TEM, XRD and BET. SEM was employed to study different morphologies before and after laccase immobilization. Activity and kinetic parameters of the immobilized laccase were also determined. It was found that the TiO2 nanoparticles were successfully introduced into the MMT layer structure, and this intercalation enlarged the "d value" of two adjacent MMT layers and increased the surface area, while the calcination process led to a complete collapse of the MMT layers. SEM results showed that the clays were well coated with adsorbed enzymes. The study of laccase activity revealed that the optimum pH and temperature were pH = 3 and 60 °C, respectively. In addition, the storage stability for the immobilized laccase was satisfactory. The kinetic properties indicated that laccase immobilized on TiO2-MMT complexes had a good affinity to the substrate. It has been proved that TiO2-MMT complex is a good candidate for enzyme immobilization. PMID:23771020

Wang, Qingqing; Peng, Lin; Li, Guohui; Zhang, Ping; Li, Dawei; Huang, Fenglin; Wei, Qufu

2013-01-01

291

Activity of Laccase Immobilized on TiO2-Montmorillonite Complexes  

PubMed Central

The TiO2-montmorillonite (TiO2-MMT) complex was prepared by blending TiO2 sol and MMT with certain ratio, and its properties as an enzyme immobilization support were investigated. The pristine MMT and TiO2-MMT calcined at 800 °C (TiO2-MMT800) were used for comparison to better understand the immobilization mechanism. The structures of the pristine MMT, TiO2-MMT, and TiO2-MMT800 were examined by HR-TEM, XRD and BET. SEM was employed to study different morphologies before and after laccase immobilization. Activity and kinetic parameters of the immobilized laccase were also determined. It was found that the TiO2 nanoparticles were successfully introduced into the MMT layer structure, and this intercalation enlarged the “d value” of two adjacent MMT layers and increased the surface area, while the calcination process led to a complete collapse of the MMT layers. SEM results showed that the clays were well coated with adsorbed enzymes. The study of laccase activity revealed that the optimum pH and temperature were pH = 3 and 60 °C, respectively. In addition, the storage stability for the immobilized laccase was satisfactory. The kinetic properties indicated that laccase immobilized on TiO2-MMT complexes had a good affinity to the substrate. It has been proved that TiO2-MMT complex is a good candidate for enzyme immobilization. PMID:23771020

Wang, Qingqing; Peng, Lin; Li, Guohui; Zhang, Ping; Li, Dawei; Huang, Fenglin; Wei, Qufu

2013-01-01

292

Surface-Treated versus Untreated Large-Bore Catheters as Vascular Access in Hemodialysis and Apheresis Treatments  

PubMed Central

Background. Catheter-related infections, thrombosis, and stenosis are among the most frequent complications associated with catheters, which are inserted in vessels. Surface treatment processes of the outer surface, such as ion-beam-assisted deposition, can be used to mitigate such complications. Methods. This retrospective study (1992–2007) evaluated silver-coated (54 patients) and noncoated (105 patients) implanted large-bore catheters used for extracorporeal detoxification. The catheters were inserted into the internal jugular or subclavian veins. After removal, the catheters were cultured for bacterial colonization using standard microbiologic assays. They also were examined using scanning electron microscope. Results. The silver coated catheters showed a tendency towards longer in situ time. The microbiologic examinations of the catheter tips were in both catheter types high positive, but not significant. Conclusion. The silver-coated catheters showed no significantly reduction in infection rate by evaluation of all collected data in this retrospective study. There was no association between both catheters in significantly reducing savings in treatment costs and in reducing patient discomfort. Other new developed catheter materials such as the microdomain-structured inner and outer surface are considered more biocompatible because they mimic the structure of natural biological surface. PMID:22577548

Bambauer, Rolf; Schiel, Ralf; Bambauer, Carolin; Latza, Reinhard

2012-01-01

293

A bioluminescence ATP assay for estimating surface hydrophobicity and membrane damage of Escherichia coli cells treated with pulsed electric fields  

Technology Transfer Automated Retrieval System (TEKTRAN)

Pulse Electric Field (PEF) treatments, a non-thermal process have been reported to injure and inactivate bacteria in liquid foods. However, the effect of this treatment on bacterial cell surface charge and hydrophobicity has not been investigated. Apple juice (AJ, pH 3.8) purchased from a wholesale ...

294

Mechanical properties of nitrogen-rich surface layers on SS304 treated by plasma immersion ion implantation  

NASA Astrophysics Data System (ADS)

The formation of hard and wear resistant surface regions for austenitic stainless steel through different nitriding and nitrogen implantation processes at intermediate temperatures is an established technology. As the inserted nitrogen remains in solid solution, an expanded austenite phase is formed, accounting for these surface improvements. However, experiments on long-term behavior and exact wear processes within the expanded austenite layer are still missing. Here, the modified layers were produced using plasma immersion ion implantation with nitrogen gas and had a thickness of up to 4 ?m, depending on the processing temperature. Thicker layers or those with higher surface nitrogen contents presented better wear resistance, according to detailed microscopic investigation on abrasion, plastic deformation, cracking and redeposition of material inside the wear tracks. At the same time, cyclic fatigue testing employing a nanoindenter equipped with a diamond ball was carried out at different absolute loads and relative unloadings. As the stress distribution between the modified layer and the substrate changes with increasing load, additional simulations were performed for obtaining these complex stress distributions. While high nitrogen concentration and/or thicker layers improve the wear resistance and hardness, these modifications simultaneously reduce the surface fatigue resistance.

Fernandes, B. B.; Mändl, S.; Oliveira, R. M.; Ueda, M.

2014-08-01

295

Microstructure and electrochemical behavior of laser treated Fe?Cr and Fe?Cr?Si?N surface alloyed layers on carbon steel  

Microsoft Academic Search

Laser surface alloyed Fe?Cr and Fe?Cr?Si?N layers on carbon steel were produced by laser irradiation involving preplaced Fe\\/Cr and Fe\\/Cr\\/Si3N4 powders, respectively. The effects of Cr content (13–25 wt.%) and microstructure on the corrosion behavior of the laser treated Fe?Cr and Fe?Cr?Si?N alloys in deaerated neutral 3.5 wt.% NaCl solution were studied. Potentiodynamic polarization tests and electrochemical impedance spectroscopy measurements

Chong-Cheng Huang; Wen-Ta Tsai; Ju-Tung Lee

1995-01-01

296

Surface and interfacial reaction study of half cycle atomic layer deposited HfO{sub 2} on chemically treated GaSb surfaces  

SciTech Connect

An in situ half-cycle atomic layer deposition/X-ray photoelectron spectroscopy (XPS) study was conducted in order to investigate the evolution of the HfO{sub 2} dielectric interface with GaSb(100) surfaces after sulfur passivation and HCl etching, designed to remove the native oxides. With the first pulses of tetrakis(dimethylamido)hafnium(IV) and water, a decrease in the concentration of antimony oxide states present on the HCl-etched surface is observed, while antimony sulfur states diminished below the XPS detection limit on sulfur passivated surface. An increase in the amount of gallium oxide/sulfide is seen, suggesting oxygen or sulfur transfers from antimony to gallium during antimony oxides/sulfides decomposition.

Zhernokletov, D. M. [Department of Physics, University of Texas at Dallas, Richardson, Texas 75080 (United States)] [Department of Physics, University of Texas at Dallas, Richardson, Texas 75080 (United States); Dong, H.; Brennan, B.; Kim, J. [Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080 (United States)] [Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080 (United States); Yakimov, M.; Tokranov, V.; Oktyabrsky, S. [College of Nanoscale Science and Engineering, University at Albany - SUNY, Albany, New York 12203 (United States)] [College of Nanoscale Science and Engineering, University at Albany - SUNY, Albany, New York 12203 (United States); Wallace, R. M. [Department of Physics, University of Texas at Dallas, Richardson, Texas 75080 (United States) [Department of Physics, University of Texas at Dallas, Richardson, Texas 75080 (United States); Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080 (United States)

2013-04-01

297

Optimization of magnetic and dielectric properties of surface-treated magnetite-filled epoxy composites by factorial design  

NASA Astrophysics Data System (ADS)

The effect of surface modification parameters such as 3-aminopropyl triethoxysilane (3APTES) coupling agent concentration (5, 10, and 20 wt%) and treatment duration (3, 5, and 7 h) were studied using design of experiment (DOE) approach. A quadratic model was developed based on response surface analysis. Analysis of variance (ANOVA), R-squared (R-Sq), and normal plot of residuals were applied to determine the accuracy of the models. Multiple responses were simultaneously analyzed by optimization. Magnetic and dielectric properties were used as composite system responses. Solution 1 with 16.66 wt% silane and 7 h treatment time was selected for optimum response. Confirmation study showed that predicted response values match the experimental results.

Boon, M. S.; Mariatti, M.

2014-04-01

298

Effects of Graded Levels of Montmorillonite on Performance, Hematological Parameters and Bone Mineralization in Weaned Pigs  

PubMed Central

The aim of this study was to investigate the effects of graded levels of montmorillonite, a constituent of clay, on performance, hematological parameters and bone mineralization in weaned pigs. One hundred and twenty, 35-d-old crossbred pigs (Duroc×Large White×Landrace, 10.50±1.20 kg) were used in a 28-d experiment and fed either an unsupplemented corn-soybean meal basal diet or similar diets supplemented with 0.5, 1.0, 2.5 or 5.0% montmorillonite added at the expense of wheat bran. Each treatment was replicated six times with four pigs (two barrows and two gilts) per replicate. Feed intake declined (linear and quadratic effect, p< 0.01) with increasing level of montmorillonite while feed conversion was improved (linear and quadratic effect, p<0.01). Daily gain was unaffected by dietary treatment. Plasma myeloperoxidase declined linearly (p = 0.03) with increasing dietary level of montmorillonite. Plasma malondialdehyde and nitric oxide levels were quadratically affected (p<0.01) by montmorillonite with increases observed for pigs fed the 0.5 and 1.0% levels which then declined for pigs fed the 2.5 and 5.0% treatments. In bone, the content of potassium, sodium, copper, iron, manganese and magnesium were decreased (linear and quadratic effect, p<0.01) in response to an increase of dietary montmorillonite. These results suggest that dietary inclusion of montmorillonite at levels as high as 5.0% does not result in overt toxicity but could induce potential oxidative damage and reduce bone mineralization in pigs. PMID:25049749

Duan, Q. W.; Li, J. T.; Gong, L. M.; Wu, H.; Zhang, L. Y.

2013-01-01

299

Electron microscopic observations on the alterations of tegumental surface of Raillietina echinobothrida treated with root-peel extract of Potentilla fulgens.  

PubMed

Potentilla fulgens, a member of the family Rosaceae, has been known since ancient times in Northeast India for its antiparasitic, antitumour and antidiabetic properties. The crude ethanolic extract of the plant was assayed against Raillietina echinobothrida, the intestinal cestode parasite of domestic fowl to authenticate the putative anthelmintic efficacy and cestocidal potential in particular of the plant. Treatment of the worm in-vitro with 25, 50 and 100 mg of crude extract per ml of phosphate buffered saline caused paralysis leading to death taking 4.02-4.20, 3.05-3.75 and 2.05-2.83 h respectively. Scanning electron microscopic observations on treated worms revealed deformation of surface architecture, particularly in scolex and surface microtriches. Severe distortion and disorganization of the tegumental and subtegumental layer along with cytoplasmic organelle was also observed under transmission electron microscope. The possible use of the plant as a potential anthelmintic against cestode parasite is discussed. PMID:22407728

Roy, Bishnupada; Dasgupta, Shyamashree; Giri, Bikash Ranjan

2012-07-01

300

Improvement of GaN light-emitting diodes with surface-treated Al-doped ZnO transparent Ohmic contacts by holographic photonic crystal  

NASA Astrophysics Data System (ADS)

This letter presents a holographic photonic crystal (H-PhC) Al-doped ZnO (AZO) transparent Ohmic contact layer on p-GaN to increase the light output of GaN-based LEDs without destroying the p-GaN. The operating voltage of the PhC LEDs at 20 mA was almost the same as that of the typical planar AZO LEDs. While the resultant PhC LED devices exhibited significant improvements in light extraction, up to 1.22 times that of planar AZO LEDs without PhC integration. Temperature dependence of the integrated photoluminescence intensity indicates that this improvement can be attributed to the increased extraction efficiency due to the surface modification. These results demonstrate that the surface-treated AZO layer by H-PhCs is suitable for fabricating high-brightness GaN-based LEDs.

Yang, W. F.; Liu, Z. G.; Xie, Y. N.; Cai, J. F.; Liu, S.; Gong, H.; Wu, Z. Y.

2012-06-01

301

Surface and internalized Escherichia coli O157:H7 on field-grown spinach and lettuce treated with spray-contaminated irrigation water.  

PubMed

Numerous field studies have revealed that irrigation water can contaminate the surface of plants; however, the occurrence of pathogen internalization is unclear. This study was conducted to determine the sites of Escherichia coli O157:H7 contamination and its survival when the bacteria were applied through spray irrigation water to either field-grown spinach or lettuce. To differentiate internalized and surface populations, leaves were treated with a surface disinfectant wash before the tissue was ground for analysis of E. coli O157:H7 by direct plate count or enrichment culture. Irrigation water containing E. coli O157:H7 at 10(2), 10(4), or 10(6) CFU/ml was applied to spinach 48 and 69 days after transplantation of seedlings into fields. E. coli O157:H7 was initially detected after application on the surface of plants dosed at 10(4) CFU/ml (4 of 20 samples) and both on the surface (17 of 20 samples) and internally (5 of 20 samples) of plants dosed at 10(6) CFU/ml. Seven days postspraying, all spinach leaves tested negative for surface or internal contamination. In a subsequent study, irrigation water containing E. coli O157:H7 at 10(8) CFU/ml was sprayed onto either the abaxial (lower) or adaxial (upper) side of leaves of field-grown lettuce under sunny or shaded conditions. E. coli O157:H7 was detectable on the leaf surface 27 days postspraying, but survival was higher on leaves sprayed on the abaxial side than on leaves sprayed on the adaxial side. Internalization of E. coli O157:H7 into lettuce leaves also occurred with greater persistence in leaves sprayed on the abaxial side (up to 14 days) than in leaves sprayed on the adaxial side (2 days). PMID:20537256

Erickson, Marilyn C; Webb, Cathy C; Diaz-Perez, Juan Carlos; Phatak, Sharad C; Silvoy, John J; Davey, Lindsey; Payton, Alison S; Liao, Jean; Ma, Li; Doyle, Michael P

2010-06-01

302

Exposure to methoxyfenozide-treated surfaces reduces the responsiveness of adult male codling moth (Lepidoptera: Tortricidae) to codlemone and pear ester lures in a wind tunnel.  

PubMed

The responsiveness of male codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), exposed to surfaces treated with the ecdysteroid agonist methoxyfenozide, toward lures loaded with the synthetic sex pheromone codlemone and/or the pear ester kairomone were investigated in wind tunnel experiments. Five different kinds of commercially available codling moth monitoring lures (obtained from Tr6c6 Inc., Adair, OK) were used in the bioassay: Pherocon CM Standard lure (loaded with 1 mg of codlemone), Pherocon CM Long-Life L2 (loaded with 3.5 mg of codlemone), Pherocon CM 10X (loaded with 10 mg of codlemone), Pherocon CM-DA Combo (loaded with 3.0 mg of codlemone and 3.0 mg of pear ester), and Pherocon DA (loaded with 3.0 mg of pear ester). Results from the study revealed that male codling moth exposed to surfaces treated with methoxyfenozide and the surfactant exhibited a significant decline in responsiveness toward lures loaded with either codlemone or pear ester. The full impact of how this negative effect might alter current moth monitoring procedures in orchards receiving ecdysone agonist sprays requires further investigation. PMID:21061970

Barrett, Bruce A

2010-10-01

303

Soil surface colonization by phototrophic indigenous organisms, in two contrasted soils treated by formulated maize herbicide mixtures.  

PubMed

Soil phototrophic microorganisms, contributors to soil health and food webs, share their particular metabolism with plants. Current agricultural practices employ mixtures of pesticides to ensure the crops yields and can potentially impair these non-target organisms. However despite this environmental reality, studies dealing the susceptibility of phototrophic microorganisms to pesticide mixtures are scarce. We designed a 3 months microcosm study to assess the ecotoxicity of realistic herbicide mixtures of formulated S-metolachlor (Dual Gold Safeneur(®)), mesotrione (Callisto(®)) and nicosulfuron (Milagro(®)) on phototrophic communities of two soils (Limagne vertisol and Versailles luvisol). The soils presented different colonizing communities, with diatoms and chlorophyceae dominating communities in Limagne soil and cyanobacteria and bryophyta communities in Versailles soil. The results highlighted the strong impairment of Dual Gold Safeneur(®) treated microcosms on the biomass and the composition of both soil phototrophic communities, with no resilience after a delay of 3 months. This study also excluded any significant mixture effect on these organisms for Callisto(®) and Milagro(®) herbicides. We strongly recommend carrying on extensive soil studies on S-metolachlor and its commercial formulations, in order to reconsider its use from an ecotoxicological point of view. PMID:25129149

Joly, Pierre; Misson, Benjamin; Perrière, Fanny; Bonnemoy, Frédérique; Joly, Muriel; Donnadieu-Bernard, Florence; Aguer, Jean-Pierre; Bohatier, Jacques; Mallet, Clarisse

2014-11-01

304

Determination of pharmaceuticals, personal care products, and pesticides in surface and treated waters: method development and survey.  

PubMed

Water is fundamental to the existence of life since it is essential to a series of activities, such as agriculture, power generation, and public and industrial supplies. The residual water generated by these activities is released into the environment, reaches the water systems, and becomes a potential risk to nontarget organisms. This paper reports the development and validation of a quantitative method, based on solid-phase extraction and liquid chromatography tandem mass spectrometry, for the simultaneous analysis of 18 pharmaceuticals and personal care products (PPCPs) and 33 pesticides in surface and drinking waters. The accuracy of the method was determined by calculating the recoveries, which ranged from 70 to 120 % for most pesticides and PPCPs, whereas limits of quantification ranged from 0.8 to 40 ng/L. After the validation step, the method was applied to drinking and surface waters. Pesticides and PPCPs were found in concentrations lower than 135.5 ng/L. The evaluation of different water sources with regard to contamination by pesticides and PPCPs has been quite poor in southern Brazil. PMID:23539208

Caldas, Sergiane Souza; Bolzan, Cátia Marian; Guilherme, Juliana Rocha; Silveira, Maria Angelis Kisner; Escarrone, Ana Laura Venquiaruti; Primel, Ednei Gilberto

2013-08-01

305

Isotretinoin Increases Skin Surface Levels of Neutrophil Gelatinase-Associated Lipocalin in Patients Treated for Severe Acne  

PubMed Central

Background A clear-cut need exists for safe and effective alternatives to the use of isotretinoin in severe acne. Lack of data regarding the specifics of isotretinoin’s mechanism of action has hampered progress in this area. Recently the protein neutrophil gelatinase-associated lipocalin (NGAL) has been identified as a mediator of the apoptotic effect of isotretinoin on sebocytes. The goal of this paper is to further establish the clinical relevance of NGAL and to elucidate the factors that induce NGAL expression in sebocytes. Methods/Results Methods were developed to isolate and quantify skin surface levels of NGAL from normal subjects and acne patients undergoing treatment with isotretinoin. Acne patients were found to have higher skin levels of NGAL compared to normal subjects. Studies in SEB-1 sebocytes indicate that NGAL expression is increased in response to P. acnes and IL-1?. In patients, isotretinoin increases NGAL levels by 2.4-fold on the skin surface and this increase precedes decreases in sebum and P. acnes counts. Conclusions These data support the hypothesis that NGAL is an important mediator of the early effects of isotretinoin on the sebaceous glands and provide insights into the mechanisms that regulate NGAL expression in the skin. PMID:21466536

Lumsden, K.R.; Nelson, A.M.; Dispenza, M.C.; Gilliland, K.L.; Cong, Z.; Zaenglein, A.L.; Thiboutot, D.M.

2011-01-01

306

Plan-view and cross-sectional characterization of thiourea-treated phosphorus-added steel surface.  

PubMed

The galvanizing reaction is retarded when phosphorus-added steel is used as a substrate. We have found that both the galvanizing and the galvannealing reactions are highly promoted when thiourea solution is coated on the cold-rolled steel surface before the annealing process. Both a plan-view and cross-sectional characterization of thiourea-coated steel was performed using low-voltage scanning electron microscopy and a focused ion beam. A fine grain structure is formed in the surface region of approximately 1 microm in thickness. In this region, (Mn, Fe)S particles are formed by the reaction between sulphur from thiourea and manganese from steel. These (Mn, Fe)S particles have a pinning effect on the cold-rolled steel grains and greatly retard recrystallization when the steel is annealed. It is concluded that the promotion of the galvannealing reaction is due to the increased diffusion paths of zinc and iron materialized by the fine grain structure of the thiourea-coated steel. PMID:15582964

Sato, Kaoru; Sakurai, Michitaka; Taira, Shoichiro; Hamada, Etsuo

2004-01-01

307

Polymer-encapsulated liquid crystals comprising montmorillonite clay  

NASA Astrophysics Data System (ADS)

The morphologies of polymer-dispersed liquid crystals (PDLCs) and holographic PDLC (HPDLC) composites consisting of nematic liquid crystals filled with inorganic nanoparticles of either pristine montmorillonite (MMT) clay or organically modified MMT (OMMT) clay in polymer matrices are described. Different curing processes with ultraviolet irradiation and an Ar+ laser were applied to make the PDLCs and HPDLCs, respectively. In order to gain some prior knowledge of the dispersion of the inorganic nanoparticles in the polymer-encapsulated systems, wide-angle x-ray diffraction patterns from an MMT clay suspension in liquid crystal were observed at variable temperatures. Differential scanning photocalorimetry was carried out to observe the monomer conversion. The morphology of liquid-crystal droplets of the PDLCs was investigated by optical polarizing microscopy. The holographic nature of the HPDLCs was confirmed by both scanning electron microscopy and atomic force microscopy. It was found that the diffraction efficiency is markedly enhanced by doping a small amount of pristine clay platelets in the HPDLC. This preliminary study demonstrates the potential of a new optical device, which is made of MMT clay hybridized with liquid crystal in a PDLC system.

Chang, Yun-Min; Tsai, Tsung-Yen; Huang, Yuan-Pin; Cheng, Wei-Sheng; Lee, Wei

2009-02-01

308

Dielectrophoretic alignment of montmorillonite nanoplatelet suspensions in an organic matrix  

NASA Astrophysics Data System (ADS)

High orientational alignment of pseudo-two-dimensional inorganic platelets in an organic matrix is achieved by external AC electric fields (˜0.5V/?m, rms). Namely, montmorillonite alumino-silicate platelets are organically modified by alkyl-ammonium surfactants and dispersed in an uncrosslinked epoxy. Orientation is quantified through wide angle 2D X-Ray diffraction under an AC electric field (˜0.05-4V/?m), following the reorientation of inorganic stacks (tactoids), resulting in Hermans orientation factors of 0.7--0.9 even at moderate field strengths. The degree of orientation dependence on the electric field frequency and strength is presented. The electrophoretic motion of the cationic surfactants as a possible mechanism to produce alignment is delineated via broadband (10-2-10^7 Hz) dielectric relaxation spectroscopy, and dipole moment theoretical analyses. The cationic electrophoretic motion does not have any major contribution for the platelet alignment, suggesting that the primary cause is due to induced dipoles (image charges) on the dielectric inorganic platelets.

Manias, Evangelos; Polizos, Georgios; Koerner, Hilmar; Vaia, Richard

2006-03-01

309

The effect of dispersion technique of montmorillonite on polyisocyanurate nanocomposites  

NASA Astrophysics Data System (ADS)

The biomass represents an abundant, renewable, competitive and low cost resource that can play an alternative role to petrochemical resources. The central topic of the research activity reported is the use of rape seed oil (RO) as a raw material for the production of rigid polyisocyanurate foams (PIR). The content of the renewable resource-derived polymers achieved in ready foams is up to 20%. By using biopolymers as a matrix, a prospective way is to reinforce them with nanoparticles, organically modified clays, for improvement of mechanical properties while, at the same time, replacing petrochemical raw materials. Organoclay Cloisite® 15A was tested as a filler of PIR foams. Three different techniques - ultrasonification, mixing by three-roll mills, and high-pressure homogenization were used for dispergation of nanoclays in polyols. Composite polyisocyanurate foams and solid polymer samples were produced and tested for stiffness and strength. This paper discusses the studies into the use of RO as a renewable source in rigid PIR foams filled with organomodified montmorillonite clay with loadings from 1 to 5% by weight.

Cabulis, U.; Fridrihsone, A.; Andersons, J.; Vlcek, T.

2014-05-01

310

Synthesis of silver nanoparticles in montmorillonite and their antibacterial behavior  

PubMed Central

Silver nanoparticles (Ag NPs) were synthesized by the chemical reducing method in the external and interlamellar space of montmorillonite (MMT) as a solid support at room temperature. AgNO3 and NaBH4 were used as a silver precursor and reducing agent, respectively. The most favorable experimental conditions for synthesizing Ag NPs in the MMT are described in terms of the initial concentration of AgNO3. The interlamellar space limits changed little (d-spacing = 1.24–1.47 nm); therefore, Ag NPs formed on the MMT suspension with d-average = 4.19–8.53 nm diameter. The Ag/MMT nanocomposites (NCs), formed from AgNO3/MMT suspension, were characterizations with different instruments, for example UV-visible, PXRD, TEM, SEM, EDXRF, FT-IR, and ICP-OES analyzer. The antibacterial activity of different sizes of Ag NPs in MMT were investigated against Gram-positive, ie, Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) and Gram-negative bacteria, ie, Escherichia coli, Escherichia coli O157:H7, and Klebsiella pneumoniae, by the disk diffusion method using Mueller-Hinton agar (MHA). The smaller Ag NPs were found to have significantly higher antibacterial activity. These results showed that Ag NPs can be used as effective growth inhibitors in different biological systems, making them applicable to medical applications. PMID:21674015

Shameli, Kamyar; Ahmad, Mansor Bin; Zargar, Mohsen; Yunus, Wan Md Zin Wan; Rustaiyan, Abdolhossein; Ibrahim, Nor Azowa

2011-01-01

311

Intercalation behavior of poly(ethylene glycol) in organically modified montmorillonite  

NASA Astrophysics Data System (ADS)

In this paper, two kinds of organically modified montmorillonite (OMMT) were prepared using alkylammonium surfactants with different alkyl chain numbers. XRD results showed the interlayer spacing of OMMT increased with low concentration surfactants. With further increasing the surfactants concentration, the interlayer spacing of OMMT was unchanged. Meanwhile, FTIR was used to characterize the local environments of surfactants in the interlayer space of OMMT. The results suggested that the double chain surfactant D-18 preferred to adopt highly ordered conformation compared with single chain surfactant S-18 in interlayer space of OMMT. It indicated that the surface property of the OMMT is affected by the concentration and configuration of the intercalated surfactants. Moreover, the effect of the OMMT type, or more particularly the chemical nature of the organic modifier in the interlayer spacing and the poly(ethylene glycol) (PEG) concentration onintercalation behavior of PEG chains in OMMT were investigated with XRD and DSC.The results indicated that PEG chains could not intercalate into Na-MMT when the surfactants were saturated in interlayer space of Na-MMT. PEG chains could intercalate into the interlayer space of SM when the S-18 concentration was lower than 2.00CEC, implying that the low surfactant concentration modified SM provided a better environment (presumably through the balanced hydrophobic and hydrophilic surfaces) for the PEG intercalation as well. However, PEG did not intercalate into the interlayer space of DM when the D-18 concentration was higher than 1.00CEC. It could be attributed to the hydrophobic double alkyl chains of DM increased with D-18. The increased hydrophobic properties in the interlayer space of 1.50DM hybrids can prevent the intercalation of hydrophilic PEG.

Zhu, Shipeng; Peng, Hongmei; Chen, Jinyao; Li, Huilin; Cao, Ya; Yang, Yunhua; Feng, Zhihai

2013-07-01

312

Crystal structure and nanotopographical features on the surface of heat-treated and anodized porous titanium biomaterials produced using selective laser melting  

NASA Astrophysics Data System (ADS)

Porous titanium biomaterials manufactured using additive manufacturing techniques such as selective laser melting are considered promising materials for orthopedic applications where the biomaterial needs to mimic the properties of bone. Despite their appropriate mechanical properties and the ample pore space they provide for bone ingrowth and osseointegration, porous titanium structures have an intrinsically bioinert surface and need to be subjected to surface bio-functionalizing procedures to enhance their in vivo performance. In this study, we used a specific anodizing process to build a hierarchical oxide layer on the surface of porous titanium structures made by selective laser melting of Ti6Al4V ELI powder. The hierarchical structure included both nanotopographical features (nanotubes) and micro-features (micropits). After anodizing, the biomaterial was heat treated in Argon at different temperatures ranging between 400 and 600 °C for either 1 or 2 h to improve its bioactivity. The effects of applied heat treatment on the crystal structure of TiO2 nanotubes and the nanotopographical features of the surface were studied using scanning electron microscopy and X-ray diffraction. It was shown that the transition from the initial crystal structure, i.e. anatase, to rutile occurs between 500 and 600 °C and that after 2 h of heat treatment at 600 °C the crystal structure is predominantly rutile. The nanotopographical features of the surface were found to be largely unchanged for heat treatments carried out at 500 °C or below, whereas they were partially or largely disrupted after heat treatment at 600 °C. The possible implications of these findings for the bioactivity of porous titanium structures are discussed.

Amin Yavari, S.; Wauthle, R.; Böttger, A. J.; Schrooten, J.; Weinans, H.; Zadpoor, A. A.

2014-01-01

313

Ocular surface evaluation in patients treated with a fixed combination of prostaglandin analogues with 0.5% timolol maleate topical monotherapy: a randomized clinical trial  

PubMed Central

OBJECTIVES: To compare ocular surface changes induced via glaucoma treatment in patients using fixed combinations of prostaglandin analogues (travoprost, latanoprost and bimatoprost) with 0.5% timolol maleate METHODS: A prospective, multicenter, randomized, parallel group, single-blind clinical trial was performed in 33 patients with ocular hypertension or open angle glaucoma who had not been previously treated. The ocular surface was evaluated prior to and three months after treatment, with a daily drop instillation of one of the three medications. The main outcome measurements included the tear film break-up time, Schirmer's test, Lissamine green staining, the Ocular Surface Disease Index questionnaire, impression cytology using HE and PAS and immunocytochemistry for interleukin-6 and HLA-DR. Ensaiosclinicos.gov.br: UTN - U1111-1129-2872 RESULTS: All of the drugs induced a significant reduction in intraocular pressure. Decreases in the Schirmer's test results were observed with all of the drugs. Decreases in tear-film break-up time were noted with travoprost/timolol and latanoprost/timolol. An increase in the Lissamine green score was noted with travoprost/timolol and bimatoprost/timolol. The Ocular Surface Disease Index score increased after treatment in the travoprost/timolol group. Impression cytology revealed a significant difference in cell-to-cell contact in the same group, an increase in cellularity in all of the groups and an increase in the number of goblet cells in all of the groups. The fixed combinations induced an increase in IL-6 expression in the travoprost/timolol group, in which there was also an increase in HLA-DR expression. CONCLUSIONS: All of the fixed combinations induced a significant reduction in intraocular pressure, and the travoprost/timolol group showed increased expression of the inflammatory markers HLA-DR and interleukin-6. All three tested medications resulted in some degree of deterioration in the ocular surface after three months of glaucoma treatment. PMID:24212838

Russ, Heloisa Helena; Nogueira-Filho, Pedro Antônio; de Nadai Barros, Jeison; de Faria, Nubia Vanessa Lima; Montiani-Ferreira, Fabiano; Gomes, José Álvaro Pereira; Mello, Paulo Augusto Arruda

2013-01-01

314

Synthesis and characterization of silver/montmorillonite/chitosan bionanocomposites by chemical reduction method and their antibacterial activity.  

PubMed

Silver nanoparticles (AgNPs) of a small size were successfully synthesized using the wet chemical reduction method into the lamellar space layer of montmorillonite/chitosan (MMT/Cts) as an organomodified mineral solid support in the absence of any heat treatment. AgNO3, MMT, Cts, and NaBH4 were used as the silver precursor, the solid support, the natural polymeric stabilizer, and the chemical reduction agent, respectively. MMT was suspended in aqueous AgNO3/Cts solution. The interlamellar space limits were changed (d-spacing = 1.24-1.54 nm); therefore, AgNPs formed on the interlayer and external surface of MMT/Cts with d-average = 6.28-9.84 nm diameter. Characterizations were done using different methods, ie, ultraviolet-visible spectroscopy, powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray fluorescence spectrometry, and Fourier transform infrared spectroscopy. Silver/montmorillonite/chitosan bionanocomposite (Ag/MMT/Cts BNC) systems were examined. The antibacterial activity of AgNPs in MMT/Cts was investigated against Gram-positive bacteria, ie, Staphylococcus aureus and methicillin-resistant S. aureus and Gram-negative bacteria, ie, Escherichia coli, E. coli O157:H7, and Pseudomonas aeruginosa by the disc diffusion method using Mueller Hinton agar at different sizes of AgNPs. All of the synthesized Ag/MMT/Cts BNCs were found to have high antibacterial activity. These results show that Ag/MMT/Cts BNCs can be useful in different biological research and biomedical applications, including surgical devices and drug delivery vehicles. PMID:21499424

Shameli, Kamyar; Bin Ahmad, Mansor; Zargar, Mohsen; Yunus, Wan Md Zin Wan; Ibrahim, Nor Azowa; Shabanzadeh, Parvaneh; Moghaddam, Mansour Ghaffari

2011-01-01

315

Synthesis and characterization of silver/montmorillonite/chitosan bionanocomposites by chemical reduction method and their antibacterial activity  

PubMed Central

Silver nanoparticles (AgNPs) of a small size were successfully synthesized using the wet chemical reduction method into the lamellar space layer of montmorillonite/chitosan (MMT/Cts) as an organomodified mineral solid support in the absence of any heat treatment. AgNO3, MMT, Cts, and NaBH4 were used as the silver precursor, the solid support, the natural polymeric stabilizer, and the chemical reduction agent, respectively. MMT was suspended in aqueous AgNO3/Cts solution. The interlamellar space limits were changed (d-spacing = 1.24–1.54 nm); therefore, AgNPs formed on the interlayer and external surface of MMT/Cts with d-average = 6.28–9.84 nm diameter. Characterizations were done using different methods, ie, ultraviolet-visible spectroscopy, powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray fluorescence spectrometry, and Fourier transform infrared spectroscopy. Silver/montmorillonite/chitosan bionanocomposite (Ag/MMT/Cts BNC) systems were examined. The antibacterial activity of AgNPs in MMT/Cts was investigated against Gram-positive bacteria, ie, Staphylococcus aureus and methicillin-resistant S. aureus and Gram-negative bacteria, ie, Escherichia coli, E. coli O157:H7, and Pseudomonas aeruginosa by the disc diffusion method using Mueller Hinton agar at different sizes of AgNPs. All of the synthesized Ag/MMT/Cts BNCs were found to have high antibacterial activity. These results show that Ag/MMT/Cts BNCs can be useful in different biological research and biomedical applications, including surgical devices and drug delivery vehicles. PMID:21499424

Shameli, Kamyar; Ahmad, Mansor Bin; Zargar, Mohsen; Yunus, Wan Md Zin Wan; Ibrahim, Nor Azowa; Shabanzadeh, Parvaneh; Moghaddam, Mansour Ghaffari

2011-01-01

316

On the reactivity of plasma-treated photo-catalytic TiO2 surfaces for oxidation of C2H2 and CO  

NASA Astrophysics Data System (ADS)

The objective of this study is to understand fundamental aspects of interactions of plasmas with catalytic surfaces. Based on this approach the reactivity of plasma treated and stimulated catalytic surfaces of TiO2 is studied by analysing the oxidation (i) of C2H2 to CO and CO2 and (ii) of CO to CO2. The inner surface of a Pyrex discharge tube is coated with TiO2 films impregnated with TiO2 nanoparticles, which provides a surface area of about 4 m2. In addition to the exposure of the TiO2 surface by low-pressure radio-frequency plasmas using O2, Ar or N2 (f = 13.56 MHz, p = 0.53 mbar, P = 17 W) the surfaces are stimulated by heating and UV radiation treatment. The temporal development of the concentrations of the precursor gases C2H2 or CO and of the reaction products is monitored using quantum cascade laser absorption spectroscopy, which provides multi-component detection in the mid-infrared spectral range. The C2H2 concentration was found to be nearly constant over time after a pre-treatment with Ar or N2 discharges using an initial gas mixture of 1% C2H2 in Ar. However, a strong decay of the concentration of C2H2 is observed for pure O2 plasma pre-treatment. In general, the decay is found to be nearly exponential with time constant in the order of about 10 min. The reactive adsorption of C2H2 molecules on the inner surface of the tube reactor showed a density of about 7.5 × 1012 C2H2 molecules cm-2. This behaviour demonstrates that the reaction (O_{ads} +C_{2} H_{2})_{{TiO}_{2}} produces some adsorbed intermediates, which can be thermally or photo-catalytically oxidized to CO2. In contrast, when 1% CO in Ar is used as an initial gas mixture no adsorption processes on the TiO2 surface could be detected. An effective destruction of CO took part via photo-catalytic oxidation.

Lopatik, D.; Marinov, D.; Guaitella, O.; Rousseau, A.; Röpcke, J.

2013-06-01

317

Utilization of near infrared spectroscopy for studying solvation properties of Cu-montmorillonites.  

PubMed

The benefit of near infrared (NIR) spectroscopy to follow the adsorption of dimethylsulfoxide and acetonitrile on reduced-charge Cu-montmorillonites differing in their chemical composition is presented. A NIR UpDRIFT accessory enabling measurement of spectra directly in closed glass vials was used to determine the amounts of adsorbed solvents. The area of the complex 2?CH band correlated very well with gravimetric analysis confirming that the UpDRIFT technique is suitable for studies of total content of organic solvents adsorbed on montmorillonites. Changes of the 2?OH band revealed that acetonitrile with a lower dipole moment (DP) and Gutmann donor number (GDN) fully solvated all samples heated up to 200°C and only partially those heated at 300°C, while DMSO with a higher DP and GDN completely solvated all the samples. These results indicate that fixation of Cu(2+) cations in montmorillonites upon heating is a partially reversible process. PMID:24412792

Brtá?ová, Anna; Madejová, Jana; Bizovská, Valéria; Komadel, Peter

2014-04-01

318

Dynamics of sulphur compounds in horizontal sub-surface flow laboratory-scale constructed wetlands treating artificial sewage.  

PubMed

The knowledge regarding the dynamics of sulphur compounds inside constructed wetlands is still insufficient. Experiments in planted (Juncus effusus) and unplanted horizontal sub-surface-flow laboratory-scale constructed wetlands fed with artificial wastewater were carried out to evaluate the sulphate reduction, the composition and dynamics of generated sulphur compounds, as well as the influence of carbon load and plants on processes of sulphur transformation. In planted and unplanted wetlands, the addition of organic carbon (TOC of about 120 mg L(-1)) immediately affected the transformation of up to 90% of the incoming sulphate (150 mg L(-1)), directing it mainly towards elemental sulphur (30%) and sulphide (8%). During this experimental period, nearly 52% of the transformed sulphate-sulphur was calculated to be immobilized inside the planted wetland and 66% inside the unplanted one. In subsequent experiments, the deficiency of organic carbon inside the planted wetlands favoured the decrease of elemental sulphur in the pore water coupled to retransformation of depot-sulphur to dissolved sulphate. Nearly 90% of the deposited and reduced sulphur was found to be reoxidized. In principle, the results indicate a substantial improvement of this reoxidation of sulphur by oxygen released by the helophytes. Surplus of organic carbon promotes the ongoing sulphate reduction and the stability of deposed and dissolved reduced sulphur compounds. In contrast, inside the unplanted control wetland, a relative stability of the formed sulphur depots and the generated amount of dissolved sulphur compounds including elemental sulphur could be observed independently of the different loading conditions. PMID:20692006

Wiessner, A; Rahman, K Z; Kuschk, P; Kästner, M; Jechorek, M

2010-12-01

319

Effect of Organic Matter on the Flocculation of Colloidal Montmorillonite: A Modeling Approach  

NASA Astrophysics Data System (ADS)

The effect of organic matter (OM) on the flocculation of colloidal montmorillonite was investigated through a complementary use of laboratory experiments and computational flocculation modeling. The model, based on Smoluchowski's coagulation model and population balance equation (PEB), was established with two key flocculation parameters, sticking efficiency and breakup parameter. The laboratory flocculation experiments tracked the temporal evolution of the floc sizes for aqueous systems with colloidal bare montmorillonite as well as those with montmorillonite and OM (humic acid, chitin or xanthan gum). The key flocculation parameters were calibrated through the interactive optimization of the model results against the laboratory results. The calibrated flocculation parameter values revealed that OM has a complex influence on the flocculation behavior of montmorillonite. They also showed that the effect of OM on flocculation depends on the types of OM. For example, xanthan gum does not significantly modify the flocculation behavior of montmorillonite that is primarily determined by the electrical double layer repulsion (i.e., zeta-potential) and van der Waals attraction (i.e., DLVO interaction energies), whereas chitin modifies both the sticking efficiency and breakup parameter. This study illustrates that there is no universally predictive correlation between DLVO energies or zeta-potential and flocculation parameters, as some OM has little effect on the DLVO interaction of montmorillonite colloids whereas other types of OM exert non-DLVO interactions such as repulsive hydration, steric repulsion and polymer bridging. Further understanding of the physical-chemical properties of OM is needed in order to predict the flocculation behaviors of estuarine and coastal suspended colloids.

Furukawa, Y.

2011-12-01

320

Hydrophobic and electrostatic interaction chromatography for estimating changes in cell surface charge of Escherichia coli cells treated with pulsed electric fields.  

PubMed

Pulsed electric field (PEF) treatments, a nonthermal process, have been reported to injure and inactivate bacteria in liquid foods. However, the effect of this treatment on bacterial cell surface charge and hydrophobicity has not been investigated. Apple juice (pH 3.8) purchased from a wholesale distributor was inoculated with cocktail of Escherichia coli O157:H7 at 7.4 log CFU/mL, processed with a PEF at a field strength of 18.4 kV/cm and 32.2?kV/cm at 25°C, 35°C, and 45°C with a treatment time of 160 ?s and a flow rate of 120 mL/min. Bacterial cell surface charge and hydrophobicity of untreated and PEF-treated E. coli O157:H7 were determined immediately and after storage at 5°C and 23°C using hydrophobic and electrostatic interaction chromatography. Similarly, the populations surviving the PEF treatments including injured cells were determined by plating 0.1 mL of the sample on sorbitol MacConkey agar and tryptic soy agar (TSA) plates. The surviving populations of E. coli cells after PEF treatment varied depending on field strength and treatment temperature used. Percent injury in the surviving populations was high immediately after PEF treatment and varied among treatment temperatures. Cell surface charge of E. coli bacteria before PEF treatment averaged 32.10±8.12. PEF treatments at 25°C, 35°C, and 45°C reduced the above surface charge to 26.34±1.24, 14.24±3.30, and 6.72±2.82, respectively. Similarly, the surface hydrophobicity of untreated E. coli cells at 0.194±0.034 was increased to an average of 0.268±0.022, 0.320±0.124, and 0.586±0.123 after PEF treatments at 25°C, 35°C, and 45°C, respectively. The results of this study indicate that PEF treatment affects the outer cell envelope of E. coli bacteria as evidenced by the changes in surface hydrophobicity and cell surface charge leading to injury and subsequent inactivation of the cells. PMID:21668373

Ukuku, Dike O; Yuk, Hyun-Gyun; Zhang, Howard

2011-10-01

321

FT-IR study of montmorillonite-chitosan nanocomposite materials  

NASA Astrophysics Data System (ADS)

Bone defect is one of the most frequent problems in bone tissue reconstruction in which application of a biomaterial filling is necessary. It creates a still rising demand of biomaterials for bone surgery. Polymer-ceramic nanocomposites (e.g. based on chitosan matrix) is a group of novel materials whose properties such as strength, Young's modulus, bioactivity and controlled degradation time make them suitable materials for filling bone defects. Investigations of nanocomposite foils which consisted of biopolymer-chitosan (CS) matrix and montmorillonite (MMT) as a nano-filler was the subject of the work. The nanocomposite materials were produced by a two-step dispersion of the nanoparticles in the biopolymer matrix. The first stage involved mechanical stirring and the second one - ultrasonic agitation. Mechanical tests were performed on the nanocomposites and their Young's modulus was estimated. Significant improvement of mechanical properties of the nanocomposites in comparison with the pure polymer (CS) was observed. The nanocomposite foils (CS/MMT) were subjected to FT-IR spectroscopy investigations whose objective was to explain the reason of the change in mechanical characteristics of the nanocomposites. Transmission and ATR techniques operating in MIR range were used to study the nanocomposites. The FT-IR techniques were used to determine interactions at nanoparticle-biopolymer matrix interface. A pure unmodified CS foil was used as a reference material for FT-IR studies. It was proven that application of FT-IR techniques allows not only to identify phases, but also to explain structural changes in the systems studied.

Paluszkiewicz, C.; Stodolak, E.; Hasik, M.; Blazewicz, M.

2011-08-01

322

Adsorption of aniline and toluidines on montmorillonite: Implications for the disposal of shale oil production wastes  

SciTech Connect

Bentonite clay liners are commonly employed to mitigate the movement of contaminants from waste disposal sites. Solid and liquid waste materials that arise from the production of shale oil contain a vast array of organic compounds. Common among these compounds are the aromatic amines. in order to assess the ability of clay liner material to restrict organic compound mobility, the adsorption of aniline and o-, m-, and p-toluidine on Ca[sup 2+] - and K[sup +]-saturated Wyoming bentonite was investigated. Adsorption experiments were performed under conditions of varied pH, ionic strength, and dominate electrolyte cation and anion. organic adsorption on Ca[sup 2+] - and K[sup +]-saturated montmorillonite is pH dependent. For any given organic compound, maximum adsorption increases with decreasing ionic strength. organic compound adsorption is inhibited in the presence of sulfate and is greater in the Ca[sup 2+] systems than in the K[sup +] systems at any given ionic strength. High salt content and K[sup +] collapse the bentonite layers and limit access to and compete for adsorption sites. The K[sup +] ion is also more difficult to displace than Ca[sup 2+] from interlayer positions. Fourier transform infrared spectroscopic data show that the aniline compounds are adsorbed on bentonite through the hydrogen bonding of an amine hydrogen to a surface silica oxygen. Sulfate reduces amine adsorption by removing positively charged anilinium species from solution to form negatively charge sulfate complexes. Although adsorption of the substituted amines on bentonite is observed, aniline and toluidine adsorption is minimal in saline systems and not detected in alkaline systems. Thus, in shale oil process waste disposal sites, the mobility of the anilines through bentonite liners will not be mitigated by sorption processes, as spent oil shale leachates are both highly alkaline and saline.

Essington, M.E.; Bowen, J.M.; Wills, R.A.; Hart, B.K.

1992-01-01

323

Adsorption of aniline and toluidines on montmorillonite: Implications for the disposal of shale oil production wastes  

SciTech Connect

Bentonite clay liners are commonly employed to mitigate the movement of contaminants from waste disposal sites. Solid and liquid waste materials that arise from the production of shale oil contain a vast array of organic compounds. Common among these compounds are the aromatic amines. in order to assess the ability of clay liner material to restrict organic compound mobility, the adsorption of aniline and o-, m-, and p-toluidine on Ca{sup 2+} - and K{sup +}-saturated Wyoming bentonite was investigated. Adsorption experiments were performed under conditions of varied pH, ionic strength, and dominate electrolyte cation and anion. organic adsorption on Ca{sup 2+} - and K{sup +}-saturated montmorillonite is pH dependent. For any given organic compound, maximum adsorption increases with decreasing ionic strength. organic compound adsorption is inhibited in the presence of sulfate and is greater in the Ca{sup 2+} systems than in the K{sup +} systems at any given ionic strength. High salt content and K{sup +} collapse the bentonite layers and limit access to and compete for adsorption sites. The K{sup +} ion is also more difficult to displace than Ca{sup 2+} from interlayer positions. Fourier transform infrared spectroscopic data show that the aniline compounds are adsorbed on bentonite through the hydrogen bonding of an amine hydrogen to a surface silica oxygen. Sulfate reduces amine adsorption by removing positively charged anilinium species from solution to form negatively charge sulfate complexes. Although adsorption of the substituted amines on bentonite is observed, aniline and toluidine adsorption is minimal in saline systems and not detected in alkaline systems. Thus, in shale oil process waste disposal sites, the mobility of the anilines through bentonite liners will not be mitigated by sorption processes, as spent oil shale leachates are both highly alkaline and saline.

Essington, M.E.; Bowen, J.M.; Wills, R.A.; Hart, B.K.

1992-01-01

324

Effect of organic matters on CO2 hydrate phase equilibrium conditions in Na-montmorillonite clay  

NASA Astrophysics Data System (ADS)

Formation of gas hydrates provides an attractive idea for storing greenhouse gases in a long-term stable geological formation. Since the phase equilibrium conditions of gas hydrates indicate the stability of hydrates, estimation of the phase equilibrium conditions of gas hydrates in marine geological conditions is necessary. In this study, we have identified the effects of organic matters (glycine, glucose, and urea) and solid surface (montmorillonite (MMT)) on the three-phase (liquid-hydrate-vapor) equilibrium conditions of CO2 hydrate. CO2 phase equilibrium experiments were conducted using 0.5mol% organic matter solutions with and without 10g soil mineral were experimentally conducted. Addition of organic matters shifted the phase equilibrium conditions of CO2 hydrate to the higher pressure or lower pressure region because of higher competition of water molecules due to the dissolved organic matters. Presence of MMT also leaded to the higher equilibrium pressure due to the interaction of cations with water molecules. By addition of organic matters to the clay suspension, the hydrate phase equilibrium conditions were less inhibited compared to those of MMT and organic matters independently. The diminished magnitudes by addition of organic matters to the clay suspension (MMT > MMT+urea > MMT+glycine > MMT+glucose > DIW) were different to the order of inhibition degree without MMT (Glucose > glycine > urea > DIW). X-ray diffraction (XRD), scanning electron microscope (SEM), and ion chromatography (IC) analysis were conducted to support the hypothesis that the organic matters interact with cations in MMT interlayer space, and leads to the less inhibition of phase equilibrium conditions. The present study provides basic information for the formation and dissociation of CO2 hydrates in the geological formation when sequestering CO2 as a form of CO2 hydrate.

Park, T.; Kyung, D.; Lee, W.

2013-12-01

325

Intestinal toxicity evaluation of TiO2 degraded surface-treated nanoparticles: a combined physico-chemical and toxicogenomics approach in caco-2 cells  

PubMed Central

Background Titanium dioxide (TiO2) nanoparticles (NPs) are widely used due to their specific properties, like UV filters in sunscreen. In that particular case TiO2 NPs are surface modified to avoid photocatalytic effects. These surface-treated nanoparticles (STNPs) spread in the environment and might release NPs as degradation residues. Indeed, degradation by the environment (exposure to UV, water and air contact …) will occur and could profoundly alter the physicochemical properties of STNPs such as chemistry, size, shape, surface structure and dispersion that are important parameters for toxicity. Although the toxicity of surface unmodified TiO2 NPs has been documented, nothing was done about degraded TiO2 STNPs which are the most likely to be encountered in environment. The superoxide production by aged STNPs suspensions was tested and compared to surface unmodified TiO2 NPs. We investigated the possible toxicity of commercialized STNPs, degraded by environmental conditions, on human intestinal epithelial cells. STNPs sizes and shape were characterized and viability tests were performed on Caco-2 cells exposed to STNPs. The exposed cells were imaged with SEM and STNPs internalization was researched by TEM. Gene expression microarray analyses were performed to look for potential changes in cellular functions. Results The production of reactive oxygen species was detected with surface unmodified TiO2 NPs but not with STNPs or their residues. Through three different toxicity assays, the STNPs tested, which have a strong tendency to aggregate in complex media, showed no toxic effect in Caco-2 cells after exposures to STNPs up to 100??g/mL over 4?h, 24?h and 72?h. The cell morphology remained intact, attested by SEM, and internalization of STNPs was not seen by TEM. Moreover gene expression analysis using pangenomic oligomicroarrays (4x 44000 genes) did not show any change versus unexposed cells after exposure to 10??g/ mL, which is much higher than potential environmental concentrations. Conclusions TiO2 STNPs, degraded or not, are not harmful to Caco-2 cells and are unlikely to penetrate the body via oral route. It is likely that the strong persistence of the aluminium hydroxide layer surrounding these nanoparticles protects the cells from a direct contact with the potentially phototoxic TiO2 core. PMID:22650444

2012-01-01

326

Consequences of treated water recycling as regards pharmaceuticals and drugs in surface and ground waters of a medium-sized Mediterranean catchment.  

PubMed

In Mediterranean regions where the population is rapidly growing, the risk of water resource contamination by wastewater is likely to increase. This is the case of the Hérault watershed (south of France), where the presence of treated wastewater in surface and ground waters has been shown in a previous study. To assess the consequence of these wastewater contaminations as regards pharmaceuticals and other organic compounds, 16 common pharmaceuticals (amitryptilin, acetylsalicylic acid, carbamazepine, clenbuterol, diazepam, diclofenac, doxepin, gemfibrozil, ibuprofen, imipramine, ketoprofen, naproxen, nordiazepam, paracetamol, salbutamol, and terbutalin) as well as wastewater related pollutants (caffeine, gadolinium anomaly, and boron) were analyzed in wells pumped for potable water supply and in two wastewater treatment plant (WWTP) effluents. In addition, a monitoring along the Lergue River (the main tributary of the Hérault River) was achieved to assess pharmaceutical behavior in surface waters. Pharmaceuticals and other wastewater-related contaminants are present in several reservoirs tapped for drinking water, confirming wastewater contamination; paracetamol, caffeine, and diclofenac are the most frequently detected. Paracetamol is present at rather high concentrations (up to 11 microg/L and 211 ng/L, respectively, in a wastewater effluent and in a drinking water sample). Though degradable in WWTP, caffeine is commonly encountered in surface waters and detected in highly polluted groundwater. On the contrary, acetylsalicylic acid concentrations are generally low despite a large consumption in France; this is related to its metabolism in humans and rapid degradation in the aquatic environment. The monitoring of pharmaceuticals along the Lergue River shows that dilution is sufficient to decrease pharmaceutical values. PMID:16999100

Rabiet, Marion; Togola, Anne; Brissaud, Francois; Seidel, Jean-Luc; Budzinski, Helene; Elbaz-Poulichet, Françoise

2006-09-01

327

The viscosity of a dilute suspension of sodium montmorillonite in an alkaline state  

Microsoft Academic Search

The viscosity of a suspension of sodium montmorillonite (at pH 10) was measured using a capillary viscometer as a function of electrolyte (NaCl) concentration. The concentration of clay was made sufficiently low so that the effective volume fraction could be analysed on the basis of viscosity equations. The solvent condition was maintained in an alkaline condition such that the electrostatic

K. Miyahara; Y. Adachi; K. Nakaishi

1998-01-01

328

Rheology of Na-Rich Montmorillonite Suspension as Affected by Electrolyte Concentration and Shear Rate  

Microsoft Academic Search

Rheolo gical measurements were used to evaluate the particle-particle associations of Na-rich montmorillonite in suspensions, under various electrolyte concentrations. A 2% free electrolyte clay sus- pension showed pseudoplastic flow behavior and had a high apparent viscosity, attributed at low shear rates to the high volume fraction of the suspended clay platelets, the flexibility of the platelets, and the presence of

Hadar Heller; RAMI KEREN

2001-01-01

329

OXIDATION OF ALCOHOLS OVER FE3+/MONTMORILLONITE-K10 USING HYDROGEN PEROXIDE  

EPA Science Inventory

Oxidation of various primary and secondary alcohols is studied in liquid phase at atmospheric pressure over Fe3+/montmorillonite-K10 catalyst prepared by ion-exchange method at a pH of 4 in an environmentally friendly protocol using hydrogen peroxide. The catalyst and the method ...

330

Preparation and characterisation of montmorillonite-supported palladium hydrogenation catalysts possessing molecular sieving properties  

SciTech Connect

Highly dispersed palladium metal has been deposited in the interlayer space of montmorillonite clay by the reduction of intercalated palladium complexes. The use of the highly electrophilic Pd(II) precursor complexes [Pd(PPh[sub 3])(NCMe)[sub 3

Crocker, M.; Herold, R.H.M.; Buglass, J.G.; Companje, P. (Koninklijke/Shell-Laboratorium, Amsterdam (Netherlands))

1993-06-01

331

Peptide chain elongation: A possible role of montmorillonite in prebiotic synthesis of protein precursors  

NASA Astrophysics Data System (ADS)

Several studies have proven the ability of montmorillonite to catalyse amino acid condensation under assumed prebiotic conditions, simulating wetting-drying cycles. In this work, the oligomerization of short peptides gly2, gly3, gly4 and ala2 on Ca-and Cu-montmorillonite in drying-wetting cycles at 80 °C was studied. The catalytic effect of montmorillonite was found to be much higher than in the case of glycine oligomerization. From gly2 after 3 weeks, 10% oligomers (up to gly6, with gly3 as main products) are formed. Gly3 and gly4 give higher oligomers even after 1 cycle. Ala2 produces both ala3 and ala4, whereas ala does not produce any oligomers under these conditions. Heteroologomerization was observed: ala-gly-gly is formed from ala and gly2. Much higher yields are obtained using Ca-montmorillonite, because copper (II) oxidizes organic molecules. The influence of the reaction mechanism on the preferential oligomerization of oligopeptides is discussed.

Bujdák, Juraj; Faybíková, Katarína; Eder, Artur; Yongyai, Yongyos; Rode, Bernd M.

1995-10-01

332

Hydrodynamic and Chemical Factors in Clogging by Montmorillonite in Porous Media  

PubMed Central

Clogging by colloid deposits is important in water treatment filters, groundwater aquifers, and petroleum reservoirs. The complexity of colloid deposition and deposit morphology preclude models based on first principles, so this study extends an empirical approach to quantify clogging using a simple, one-parameter model. Experiments were conducted with destabilized suspensions of sodium- and calcium-montmorillonite to quantify the hydrodynamic and chemical factors important in clogging. Greater clogging is observed at slower fluid velocity, consistent with previous investigations. However, calcium-montmorillonite causes one order of magnitude less clogging per mass of deposited particles compared to sodium-montmorillonite or a previously published summary of clogging in model granular media. Steady state conditions, in which the permeability and the quantity of deposited material are both constant, were not observed, even though the experimental conditions were optimized for that purpose. These results indicate that hydrodynamic aspects of clogging by these natural materials are consistent with those of simplified model systems, and they demonstrate significant chemical effects on clogging for fully destabilized montmorillonite clay. PMID:17874771

Mays, David C.; Hunt, James R.

2008-01-01

333

Sorption Speciation of Nickel(II) onto Ca-Montmorillonite: Batch, EXAFS Techniques and Modeling  

E-print Network

and modeling. The pH and temperature at the aqueous-montmorillonite interface affects both the extent of Ni time scales at pH levels undersaturated with respect to pure metal hydroxide solubility, and pH, the study reveals that the majority of Ni(II) is adsorbed in the interlayers of Ca

Paris-Sud XI, Université de

334

Inactivation of cadmium induced immunotoxicological alterations in rats by Tunisian montmorillonite clay  

Microsoft Academic Search

Cadmium (Cd2+) is a heavy metal that is dispersed throughout the modern environment mainly as a result of pollution from a variety of sources. The aims of the current study were to investigate the efficacy of purified Tunisian montmorillonite clay (TMC) to adsorb Cd, to test the stability of the resulting complex under different conditions in vitro, and to utilize

Samir Abbès; Jalila Ben Salah-Abbès; Kais Nahdi; Ridha Ben Younes; Mona M. Hetta; Ahmed A. El-Kady; Mosaad A. Abdel-Wahhab; Ridha Oueslati

2007-01-01

335

Iron changes in natural and Fe(III) loaded montmorillonite during carbon nanotube growth  

NASA Astrophysics Data System (ADS)

A detailed elaboration of the transformations of iron species, present in natural and Fe(NO3)3 loaded montmorillonite, during carbon deposition and carbon nanotube growth is described. According to transmission electron microscopy results, deposited carbon atoms form fibres in the case of pristine montmorillonite and multiwalled carbon nanotubes in the case of Fe(III) loaded montmorillonite. Mössbauer and x-ray diffraction analysis results point to an extensive reduction of structural and intercalated Fe(III) cations to Fe(II) with the latter migrating from the interlayer space to the vacant octahedral sites of the mineral's lattice. Such migration of the non-structural iron catalyst prohibits extensive contamination of the final composite with various metal catalyst impurities. The crucial role of the active catalytic centres in the formation of carbon nanotubes is ascribed to a minor quantity of iron, found entrapped in the carbon nanostructures, which, at the end of the reaction, is identified as iron carbide. The interesting formation of a nanometric ?-iron precipitate is also detected, which is probably stabilized through strong interactions with the lattice of montmorillonite. Finally, it is demonstrated that iron-rich natural clay minerals can serve as direct catalysts for carbon nanotube growth.

Bakandritsos, Aristides; Simopoulos, Athanasios; Petridis, Dimitris

2006-02-01

336

Iron changes in natural and Fe(III) loaded montmorillonite during carbon nanotube growth.  

PubMed

A detailed elaboration of the transformations of iron species, present in natural and Fe(NO(3))(3) loaded montmorillonite, during carbon deposition and carbon nanotube growth is described. According to transmission electron microscopy results, deposited carbon atoms form fibres in the case of pristine montmorillonite and multiwalled carbon nanotubes in the case of Fe(III) loaded montmorillonite. Mössbauer and x-ray diffraction analysis results point to an extensive reduction of structural and intercalated Fe(III) cations to Fe(II) with the latter migrating from the interlayer space to the vacant octahedral sites of the mineral's lattice. Such migration of the non-structural iron catalyst prohibits extensive contamination of the final composite with various metal catalyst impurities. The crucial role of the active catalytic centres in the formation of carbon nanotubes is ascribed to a minor quantity of iron, found entrapped in the carbon nanostructures, which, at the end of the reaction, is identified as iron carbide. The interesting formation of a nanometric ?-iron precipitate is also detected, which is probably stabilized through strong interactions with the lattice of montmorillonite. Finally, it is demonstrated that iron-rich natural clay minerals can serve as direct catalysts for carbon nanotube growth. PMID:21727389

Bakandritsos, Aristides; Simopoulos, Athanasios; Petridis, Dimitris

2006-02-28

337

Adsorption of Benzyltrimethylammonium and Benzyltriethylammonium on Montmorillonite: Experimental Studies and Model Calculations  

Microsoft Academic Search

The adsorption of the monovalent organic cations benzyltrimethylammonium (BTMA) and benzyltriethylammonium (BTEA) to montmorillonite was studied as a function of their concentrations and ionic strength. At low ionic strength the adsorbed amounts of BTMA and BTEA reached values of the cation exchange capacity (CEC) of the clay. An increase in the ionic strength resulted in reduction in the adsorbed amounts

Tamara Polubesova; GIORA RYTWO; SHLOMO NIR; CARINA SERBAN; LEON MARGULIES

1997-01-01

338

Structure of cationic dyes assemblies intercalated in the films of montmorillonite  

Microsoft Academic Search

Hybrid materials based on cationic organic dyes intercalated in oriented clay mineral films were prepared via dye adsorption from aqueous solutions on the films having been prepared by a spin-coating method. The films with four thiazine dyes thionine, azure A, azure B and methylene blue and one representative xanthene dye, pyronin Y (Py), were investigated. Four reduced charge montmorillonites (RCM)

Juraj Bujdák; Adriana Czímerová; Nobuo Iyi

2008-01-01

339

Calcium montmorillonite clay reduces urinary biomarkers of fumonisin B1 exposure in rats and humans  

Technology Transfer Automated Retrieval System (TEKTRAN)

Background: Fumonisin B1 (FB1) is often a co-contaminant with aflatoxin (AF) in grains and may enhance AF’s carcinogenicity by acting as a cancer promoter. An oral dose of calcium montmorillonite clay (i.e. NovaSil, NS) was able to reduce aflatoxin exposure in a Ghanaian population at risk. In vitro...

340

Melt-intercalation studies of polystyrene ionomers in pristine montmorillonite  

NASA Astrophysics Data System (ADS)

The main objective of this study was to examine the use of ionomers, specifically alkylamine-neutralized sulfonated polystyrene (SPS) for promoting intercalation into unmodified sodium montmorillonite clay and its use as a compatabilizer for intercalating another polymer into unmodified silicate clay. The processing parameters and chemical structure of polymers which led to the formation of partially intercalated/exfoliated morphologies were investigated. Melt-intercalated polymer layered silicate nanocomposites (PLSNs) are made by mixing polymers and organically modified silicates by the application of shear forces. However, the thermal decomposition temperatures of the organic modifications are usually comparable to the processing temperatures of most of the polymers. Hence, in this work modification of the polymer, rather than the clay, for promoting melt intercalation, specifically the introduction of alkyl ammonium salt groups along the polymer chain was considered. In this study the effects of viscosity, shear rates and mixing times on the morphology of nanocomposites were investigated. The effect of ionic content in the polymer chain of SPS in the batch mixtures of SPS and PS was researched. We also compared the effect on the extent of intercalation in these silicate clay galleries as a function of size of the counter-ions by varying the alkyl chain length and as a function of basicity of these counter-ions by varying the number of alkyl substituents that are attached on the N of the amine. The melt mixing of pristine Na-Mmt with alkyl ammonium and quaternary ammonium salts of SPS ionomers, resulted in an increase in the silicate gallery spacing consistent with intercalation. Mixtures of the ionomer with PS exhibited similar gallery spacing increases, indicating that the ionomer is an effective compatibilizing agent for the melt-intercalation of hydrophobic polymers into the clay. The extent of intercalation was independent of the melt processing conditions employed in this study and also did not change as the molecular weight of ionomer was varied. Intercalation appeared to be dependent on the charge ratio between the ionomer and the clay. The increase in gallery spacing achieved was a function of size of the alkylamine counter-ions used. The nanocomposites containing ionomers exhibited higher storage moduli compared to nanocomposites without the compatibilizer.

Bhiwankar, Nikhil N.

341

Competitive and synergistic effects between excimer VUV radiation and O radicals on the etching mechanisms of polyethylene and fluoropolymer surfaces treated by an atmospheric He-O2 post-discharge  

NASA Astrophysics Data System (ADS)

Among various surface modification techniques, plasma can be used as a source for tailoring the surface properties of diverse materials. HDPE and fluoropolymer surfaces have been treated by the post-discharge of an atmospheric RF-plasma torch supplied with helium and oxygen gases. The plasma-treated surfaces were characterized by measurements of mass losses, water contact angles, x-ray photoelectron spectroscopy and atomic force microscopy. This experimental approach correlated with an optical characterization of the plasma phase allowed us to propose etching mechanisms occurring at the post-discharge/polymer interface. We discuss how competitive and synergistic effects can result from the oxidation and/or the roughening of the surface but also from the excimer VUV radiation, the He metastable species and the O radicals reaching the plasma-polymer interface.

Dufour, T.; Hubert, J.; Vandencasteele, N.; Viville, P.; Lazzaroni, R.; Reniers, F.

2013-08-01

342

Adsorption of PolyCarboxylate Poly(ethylene glycol) (PCP) esters on Montmorillonite (Mmt): Effect of exchangeable cations (Na(+), Mg(2+) and Ca(2+)) and PCP molecular structure.  

PubMed

This study deals with the adsorption of PolyCarboxylate Poly(ethylene glycol) esters (PCP) superplasticizers on Na-, Mg- and Ca-saturated Montmorillonite (Mmt) clays. The interactions have been examined through different experimental methods: adsorption isotherms, zeta potential measurements and sedimentation experiments. It was found that PCP adsorption depends both on the architecture of PCP molecules and the nature of cation located on the interlayer exchange sites of the Montmorillonite. Whatever the PCP, a larger amount was adsorbed on Na-Mont than on Mg-Mont or Ca-Mont. This indicates the occurrence of two adsorption mechanisms: (i) a superficial adsorption via electrostatic interactions between the carboxylate groups of PCP and positively charged sites on clay surfaces, (ii) intercalation of ether units of the PCP grafts in the interlayer space by displacement of water molecules coordinated to the exchangeable cations. Furthermore, despite the weak negative values of the zeta potential, the addition of PCP promotes the stability of the suspensions which is attributed to steric repulsion acting between particles. PMID:25313488

Ait-Akbour, Rachid; Boustingorry, Pascal; Leroux, Fabrice; Leising, Frédéric; Taviot-Guého, Christine

2015-01-01

343

Monomeric metal aqua complexes in the interlayer space of montmorillonites as strong Lewis acid catalysts for heterogeneous carbon-carbon bond-forming reactions.  

PubMed

Montmorillonite-enwrapped copper and scandium catalysts (Cu(2+)- and Sc(3+)-monts) were easily prepared by treating Na(+)-mont with the aqueous solution of the copper nitrate and scandium triflate, respectively. The resulting Cu(2+)- and Sc(3+)-monts showed outstanding catalytic activities for a variety of carbon-carbon bond-forming reactions, such as the Michael reaction, the Sakurai-Hosomi allylation, and the Diels-Alder reaction, under solvent-free or aqueous conditions. The remarkable activity of the mont catalysts is attributable to the negatively charged silicate layers that are capable of stabilizing metal cations. Furthermore, these catalysts were reusable without any appreciable loss in activity and selectivity. The Cu(2+)-mont-catalyzed Michael reaction proceeds via a ternary complex in which both the 1,3-dicarbonyl compound and the enone are coordinated to a Lewis acid Cu(2+) center. PMID:15551316

Kawabata, Tomonori; Kato, Masaki; Mizugaki, Tomoo; Ebitani, Kohki; Kaneda, Kiyotomi

2004-12-17

344

Ultra-violet protection and water repellency of polyester fabrics treated by surface deposition of nickel under the effect of low temperature plasma  

NASA Astrophysics Data System (ADS)

This paper is aimed at understanding the textile properties of nickel-deposited polyester fabric after treating with low temperature plasma treatment. Low temperature plasma treatment with oxygen gas was employed in this paper to activate a hydrophilic surface for the polyester fabrics and hence facilitate the nickel deposition through an electroless plating process. The textile properties of plasma-induced electroless nickel-plated polyester fabrics were evaluated by different standard testing methods in terms of both physical and chemical performances. The electroless nickel plating with plasma treatment improved significantly the performance of nickel-plated polyester fabrics as reflected by the scanning electron microscopy, tensile strength, ultraviolet protection as well as fabric weight. On the contrary, it also enhanced the fabric thickness and colour fastness to crocking. In addition, there was no influence on the performance of colour fastness to light and colourfastness to laundering. Moreover, the application of plasma treatment adversely affected slightly the performance of contact angle and wrinkle recovery property.

Kan, C. W.; Yuen, C. W. M.

2007-12-01

345

Treating Meningitis  

MedlinePLUS

... ways to treat bacterial meningitis. 1 They compared steroids (dexamethasone) with placebo. The doctors gave medication (or ... al. compared antibiotics by themselves with antibiotics plus steroids. Dr. Fritz and colleagues compared the mortality (deaths) ...

346

Use of X-ray Absorption Spectroscopy to Distinguish Between Inner And Outer-sphere Pb Adsorption Complexes on Montmorillonite  

E-print Network

Use of X-ray Absorption Spectroscopy to Distinguish Between Inner And Outer-sphere Pb Adsorption on the functional groups at the edges of the montmorillonite. At I = 0.002 M Pb absorption was less dependent

Sparks, Donald L.

347

Effect of functionalized montmorillonite addition on the thermal properties and ionic conductivity of PVDF–PEG polymer electrolyte  

Microsoft Academic Search

Composite microporous polymer electrolyte membranes comprising poly(vinylidene fluoride), PVDF, poly(ethylene glycol), PEG, and 1-ethyl-3-methylimidazolium tetrafluoroborate functionalized montmorillonite (EMIm-MMT) were prepared by a phase inversion method. The EMIm-MMT was subjected to FTIR, WXRD, TGA and element analysis in order to better understand the intercalation of imidazolium cations in sodium montmorillonite (Na-MMT) through exchange with intermellar sodium ions and improved thermal stability

Yun-Pu Wang; Xiang-Hu Gao; Rong-Min Wang; Han-Gong Liu; Chao Yang; Yu-Bing Xiong

2008-01-01

348

Polyvinyl Alcohol\\/Na-Montmorillonite Nanocomposite Hydrogels Prepared by Freezing–Thawing Method: Structural, Mechanical, Thermal, and Swelling Properties  

Microsoft Academic Search

Physically crosslinked nanocomposite hydrogels based on polyvinyl alcohol (PVA) containing Na-montmorillonite were prepared by the cyclic freezing–thawing method. The primarily exfoliated morphology of prepared nanocomposite hydrogels was confirmed by X-ray diffractometry (XRD) and transmission electron microscopy (TEM) as complementary techniques. It is shown that some interactions developed between the hydroxyl groups of PVA chains and Na-montmorillonite silicate layers in the

M. Sirousazar; M. Kokabi; Z. M. Hassan; A. R. Bahramian

2012-01-01

349

Polyvinyl Alcohol \\/Na-Montmorillonite Nanocomposite Hydrogels Prepared by Freezing-Thawing Method: Structural, Mechanical, Thermal and Swelling Properties  

Microsoft Academic Search

Physically crosslinked nanocomposite hydrogels based on polyvinyl alcohol (PVA) containing Na-montmorillonite were prepared by the cyclic freezing-thawing method. The primarily exfoliated morphology of prepared nanocomposite hydrogels was confirmed by X-ray diffractometry (XRD) and transmission electron microscopy (TEM) as complementary techniques. It is shown that some interactions developed between the hydroxyl groups of PVA chains and Na-montmorillonite silicate layers in the

M. SIROUSAZAR; M. KOKABI; Z. M. HASSAN; A. R. BAHRAMIAN

2012-01-01

350

The role of heat of immersion calorimetry and gas adsorption in determining the surface areas of a thermally treated lignite and supercritically solvent extracted low-rank coal residues  

Microsoft Academic Search

Comparative surface area data can be obtained from the exothermic heat liberated when a solid substance is immersed in a suitable liquid penetrant. The surface areas determined by this method provide an explanation of results of thermal treatment and supercritical solvent extraction of low-rank coal. The thermally treated samples were prepared by drying Indian Head (North Dakota) lignite at 330°C

C. Tye; D. J. Maas; M. L. Swanson

1987-01-01

351

Oligomerization reactions of ribonucleotides - The reaction of the 5'-phosphorimidazolide of nucleosides on montmorillonite and other minerals  

NASA Technical Reports Server (NTRS)

The reaction of ImpA in the presence of Na(+)-montmorillonite 22A or Na(+)-Volclay in aqueous, pH 8 solution gives a 50-60 percent yield of dimers and trimers (pA)2 and (pA)3. The ratio of 3',5'-phosphodiester bond formation is twice as great as 2',5'-bond formation. The reaction requires the presence of Mg2+ and is inhibited by 0.4 M imidazole. N-methylimidazole enhances the rate of the reaction but does not cause major changes in yield or product composition. Higher yields were obtained when Li+- or Ca2+-montmorillonites were used in place of Na+-montmorillonite. Little or no phosphodiester bond formation was observed with Mg2+- or Al3+-montmorillonite. Montmorillonites other than 22A and Volclay exhibited litle or no catalysis. In addittion, little or no catalysis was exhibited in ferrugenous smectite, nontronite, allophane, imogolite or sepiolite. Oligomers were also formed by the reaction of ImpG, 2-methylImpG, ImpC and ImpU in the presence of Na+-montmorillonite. The pyrimidine nucleotides gave significantly lower yields of oligomers.

Ferris, James P.; Ertem, Gozen

1992-01-01

352

Oligomerization reactions of ribonucleotides: The reaction of the 5'-phosphorimidazolide of nucleosides on montmorillonite and other minerals  

NASA Astrophysics Data System (ADS)

The reaction of ImpA in the presence of Na+-montmorillonite 22A or Na+-Volclay in aqueous, pH 8 solution gives a 50 60% yield of dimers and trimers (pA)2 and (pA)3. The ratio of 3',5'-phosphodiester bond formation is twice as great as 2',5'-bond formation. The reaction requires the presence of Mg2+ and is inhibited by 0.4 M imidazole. N-methylimidazole enhances the rate of the reaction but does not cause major changes in yield or product composition. Higher yields were obtained when Li+- or Ca2+-montmorillonites were used in place of Na+-montmorillonite. Little or no phosphodiester bond formation was observed with Mg2+- or Al3+-montmorillonite. Montmorillonites other than 22A and Volclay exhibited little or no catalysis. In addition, little or no catalysis was exhibited in ferrugenous smectite, nontronite, allophane, imogolite or sepiolite. Oligomers were also formed by the reaction of ImpG, 2-methylImpG, ImpC and ImpU in the presence of Na+-montmorillonite. The pyrimidine nucleotides gave significantly lower yields of oligomers.

Ferris, James P.; Ertem, Gözen

1992-11-01

353

Oligomerization reactions of ribonucleotides: the reaction of the 5'-phosphorimidazolide of nucleosides on montmorillonite and other minerals.  

PubMed

The reaction of ImpA in the presence of Na+ -montmorillonite 22A or Na+ -Volclay in aqueous, pH 8 solution gives a 50-60% yield of dimers and trimers (pA)2 and (pA)3. The ratio of 3',5'-phosphodiester bond formation is twice as great as 2',5'-bond formation. The reaction requires the presence of Mg2+ and is inhibited by 0.4 M imidazole. N-methylimidazole enhances the rate of the reaction but does not cause major changes in yield or product composition. Higher yields were obtained when Li+ -or Ca2+ -montmorillonites were used in place of Na+ -montmorillonite. Little or no phosphodiester bond formation was observed with Mg2+ - or Al3+ -montmorillonite. Montmorillonites other than 22A and Volclay exhibited little or no catalysis. In addition, little or no catalysis was exhibited in ferrugenous smectite, nontronite, allophane, imogolite or sepiolite. Oligomers were also formed by the reaction of ImpG, 2-methylImpG, ImpC and ImpU in the presence of Na+ -montmorillonite. The pyrimidine nucleotides gave significantly lower yields of oligomers. PMID:11536512

Ferris, J P; Ertem, G

1992-01-01

354

Calcium montmorillonite clay reduces urinary biomarkers of fumonisin B1 exposure in rats and humans  

PubMed Central

Fumonisin B1 (FB1) is often a co-contaminant with aflatoxin (AF) in grains and may enhance AF’s carcinogenicity by acting as a cancer promoter. Calcium montmorillonite (i.e. NovaSil, NS) is a possible dietary intervention to help decrease chronic aflatoxin exposure where populations are at risk. Previous studies show that an oral dose of NS clay was able to reduce AF exposure in a Ghanaian population. In vitro analyses from our laboratory indicated that FB1 (like aflatoxin) could also be sorbed onto the surfaces of NS. Hence, our objectives were to evaluate the efficacy of NS clay to reduce urinary FB1 in a rodent model and then in a human population highly exposed to AF. In the rodent model, male Fisher rats were randomly assigned to either, FB1 control, FB1 + 2% NS or absolute control group. FB1 alone or with clay was given as a single dose by gavage. For the human trial, participants received NS (1.5 or 3 g day?1) or placebo (1.5 g day?1) for 3 months. Urines from weeks 8 and 10 were collected from the study participants for analysis. In rats, NS significantly reduced urinary FB1 biomarker by 20% in 24 h and 50% after 48 h compared to controls. In the humans, 56% of the urine samples analyzed (n = 186) had detectable levels of FB1. Median urinary FB1 levels were significantly (p < 0.05) decreased by > 90% in the high dose NS group (3 g day?1) compared to the placebo. This work indicates that our study participants in Ghana were exposed to FB1 (in addition to AFs) from the diet. Moreover, earlier studies have shown conclusively that NS reduces the bioavailability of AF and the findings from this study suggest that NS clay also reduces the bioavailability FB1. This is important since AF is a proven dietary risk factor for hepatocellular carcinoma (HCC) in humans and FB1 is suspected to be a dietary risk factor for HCC and esophageal cancer in humans. PMID:22324939

Robinson, A.; Johnson, N.M.; Strey, A.; Taylor, J.F.; Marroquin-Cardona, A.; Mitchell, N.J.; Afriyie-Gyawu, E.; Ankrah, N.A.; Williams, J.H.; Wang, J.S.; Jolly, P.E.; Nachman, R.J.; Phillips, T.D.

2012-01-01

355

Effect of Repulsive Force on the Visco-elastic Properties of a Montmorillonite Suspension  

NASA Astrophysics Data System (ADS)

The effect of salt concentration on the visco-elastic properties of a montmorillonite suspension was clarified by applying the Maxwell model to the measured flow curves. Based on the sheet-like shape and measured size of montmorillonite, the suspended particles at a 1.1×10-2 volume concentration (experimental condition) were found to orient in the same direction. In this configuration of the particles, the repulsive force was calculated from the balk salt concentration on the basis of the two flat-plates model. The relative repulsive force at various salt concentrations was defined as the increasing ratio of this force to the force at critical coagulation concentration (C. C. C). The effect of the relative repulsive force computed from the salt concentration on the visco-elastic properties (such as viscosity, elastic modulus and relaxation time) was examined and it was found that the fluidity decreases and the solidity increases almost linearly with the increase in the repulsive force.

Nakaishi, Katsuya; Ooi, Setsuo

356

Chitosan-montmorillonite biocomposite as an adsorbent for copper (II) cations from aqueous solutions.  

PubMed

Chitosan-montmorillonite (KSF-CTS) beads were prepared by crosslinking with pentasodium tripolyphosphate (TPP). Montmorillonite (KSF-Na), CTS and KSF-CTS biocomposite were used to remove Cu(II) from aqueous solutions. These materials were characterized before and after copper adsorption by XRD, FTIR and thermogravimetry (TG). The data indicated that the adsorption process proceeds kinetically according to a pseudo-second-order model. The adsorption processes were adjusted to the Langmuir model for KSF-Na and CTS and to the Temkin model for KSF-CTS. The maximum adsorption capacity followed the order CTS>KSF-CTS>KSF-Na. Percentages desorption of copper ions from the KSF-CTS composite after three desorption cycles were 86%, 85% and 84%, respectively, using EDTA as regeneration agents. PMID:23973496

Pereira, F A R; Sousa, K S; Cavalcanti, G R S; Fonseca, M G; de Souza, Antônio G; Alves, A P M

2013-10-01

357

Engineering New Layered Solids from Exfoliated Inorganics: a Periodically Alternating Hydrotalcite - Montmorillonite Layered Hybrid  

NASA Astrophysics Data System (ADS)

Two-dimensional (2D) nanosheets obtained by exfoliating inorganic layered crystals have emerged as a new class of materials with unique attributes. One of the critical challenges is to develop robust and versatile methods for creating new nanostructures from these 2D-nanosheets. Here we report the delamination of layered materials that belonging to two different classes - the cationic clay, montmorillonite, and the anionic clay, hydrotalcite - by intercalation of appropriate ionic surfactants followed by dispersion in a non-polar solvent. The solids are delaminated to single layers of atomic thickness with the ionic surfactants remaining tethered to the inorganic and consequently the nanosheets are electrically neutral. We then show that when dispersions of the two solids are mixed the exfoliated sheets self-assemble as a new layered solid with periodically alternating hydrotalcite and montmorillonite layers. The procedure outlined here is easily extended to other layered solids for creating new superstructures from 2D-nanosheets by self-assembly.

Chalasani, Rajesh; Gupta, Amit; Vasudevan, Sukumaran

2013-12-01

358

Radiolysis of aqueous solutions of acetic acid in the presence of Na-montmorillonite  

NASA Technical Reports Server (NTRS)

The gamma-irradiation of 0.8 mol dm-3 aqueous, oxygen-free acetic acid solutions was investigated in the presence or absence of Na-montmorillonite. H2, CH4, CO, CO2, and several polycarboxylic acids were formed in all systems. The primary characteristics observed in the latter system were: (1) Higher yield of the decomposition of acetic acid; (2) Lower yield of the formation of polycarboxylic acids; (3) No effect on the formation of methane; (4) Higher yield of the formation of carbon dioxide; and (5) The reduction of Fe3+ in the octahedral sites of Na-montmorillonite. A possible reaction scheme was proposed to account for the observed changes. The results are important in understanding heterogeneous processes in radiation catalysis and might be significant to prebiotic chemistry.

Navarro-Gonzalez, R.; Negron-Mendoza, A.; Ramos, S.; Ponnamperuma, C.

1990-01-01

359

Preparation and properties of poly HTBN-based urethane-urea/organo reactive montmorillonite nanocomposites  

NASA Astrophysics Data System (ADS)

With ultrasonic assistant mixing way, an intercalated mixture of polyol/organo reactive montmorillonite (ORMMT) was pretreated. The prepolymer composed MMT clay was prepared by reaction of polyol/ORMMT mixture with toluene diisocyanate (TDI). The resultant prepolymer reacted with extender (DMTDA) and then the polyurethane-urea/organo reactive montmorillonite (PUU/ORMMT) nanocomposites were obtained. The structure, morphology and properties of PUU/ORMMT nanocomposites were characterized by FT-IR, TEM, AFM, strain-stress machine, TGA, and dynamic mechanical analysis (DMA). The results showed that when the OMMT content is 3%, the PUU/ORMMT nanocomposities performed super mechanical properties. Because of the presence of ORMMT, both T g of the soft segment and tan ? of the PUU increased, and the decomposition temperature for the first step and the second step increased respectively. TEM images showed that the organophilic MMT particles in the PUU composite exhibit a high degree of intercalation and exfoliation.

Li, Zai-Feng; Wu, Yuan; Zhang, Fu-Tao; Cao, Yu-Yang; Wu, Shou-Peng; Wang, Ting

2012-12-01

360

Multifunctional chitosan nanocomposites: The effect of silver supported on montmorillonite platelets on barrier and mechanical properties  

NASA Astrophysics Data System (ADS)

Multifunctional bionanocomposites have been prepared by loading chitosan matrix with silver-montmorillonite antimicrobial nanoparticles obtained by replacing Na+ ions of natural montmorillonite with silver ions followed by thermal reduction to metallic nanoparticles. This filler has been chosen for its twofold advantage to serve as silver supporting material and to confer new and better performance to the obtained material. It has been proved that the ultrasound-assisted procedure resulted in an efficient tool for the chitosan macromolecules to intercalate into the silicate galleries. The achievement of the intercalation as well as the interaction between chitosan and silver nanoparticles lead to an enhancement of barrier properties of the bionanocomposites and to an improvement of their mechanical strengths mainly due to a better load transfer between matrix and fillers.

Lavorgna, M.; Buonocore, G. G.; Tescione, F.; Capezzuto, F.; Yan, N.; Amendola, E.

2014-05-01

361

Amine functionalized K10 montmorillonite: a solid acid-base catalyst for the Knoevenagel condensation reaction.  

PubMed

Different amine functionalized K10 montmorillonites were hydrothermally fabricated by a simple method of treatment of the neat clay with different amine solutions and used as heterogeneous catalysts towards the Knoevenagel condensation reaction. Catalytic results show that the di-amine functionalized K10 montmorillonite exhibits high efficacy for promoting this reaction at room temperature and in the absence of a solvent. The solid catalyst was characterized using a variety of different techniques; including Fourier transform infrared spectroscopy (FT-IR), nitrogen physisorption measurements, (29)Si CP MAS NMR spectroscopy, NH3-temperature programmed desorption (NH3-TPD), X-ray powder diffraction (XRD), and field emission scanning electron microscopy (FESEM). The catalyst could be recycled and reused for several runs without any loss of inherent catalytic activity. PMID:23400041

Varadwaj, G Bishwa Bidita; Rana, Surjyakanta; Parida, K M

2013-04-14

362

Treating Sludges  

ERIC Educational Resources Information Center

Discussed are some of the ways to handle municipal and industrial wastewater treatment sludge presented at the 1978 American Chemical Society meeting. Suggestions include removing toxic materials, recovering metals, and disposing treated sewage sludge onto farm land. Arguments for and against land use are also given. (MA)

Josephson, Julian

1978-01-01

363

An electron paramagnetic resonance (EPR) study of the adsorption of copper complexes on montmorillonite and imogolite  

NASA Astrophysics Data System (ADS)

The adsorption of three copper species, the hydrated cupric ion, bisglycine Cu(II) and a Cu(II)-humic acid complex, on montmorillonite and imogolite at pH 7 was investigated by electron paramagnetic resonance (EPR) spectroscopy. The spectra of the supernatant solutions indicated that adsorption of the glycine complexes was very much less than that of the uncomplexed ion for both minerals and that montmorillonite adsorbed significantly more Cu from the humic acid solution than did imogolite. In every case the adsorbed Cu was characterized by more than one type of chemical environment and the spectral parameters show differences between the adsorbed species depending on their freedom of movement and their mode and site of adsorption. Qualitatively similar spectra were obtained when the uncomplexed ion was adsorbed on either of the mineral species and it is suggested that simple Cu(II) ions were involved and that their coordination environments comprised water molecules and hydroxyl groups. With the bisglycine Cu(II) complexes, the spectra were characterized by two components which may be accounted for by adsorption at two different types of site in the structures. In each case one component had parameters that are similar to those of the bisglycine Cu(II) in the solid state, but the second component in the spectra of the montmorillonite sample was quite different to that obtained with imogolite. The Cu(II)-humic acid complex with montmorillonite gave spectra that were similar to that from copper humate, but with imogolite the spectra from the Cu(II)-humic acid system were similar to those obtained with the uncomplexed Cu(II) ion, indicating that imogolite is able to extract copper from humic acid.

Goodman, B. A.; Green, H. L.; Mcphail, D. B.

1984-10-01

364

Preparation and properties of compatibilized LDPE\\/organo-modified montmorillonite nanocomposites  

Microsoft Academic Search

Nanocomposites based on low density polyethylene, containing of 3 or 6wt.% of organo-modified montmorillonite nanoclay (MMT-ODA) and maleic anhydride grafted low density polyethylene as a compatibilizer were prepared by melt mixing and characterized. Exfoliation of silicate layers was achieved, as confirmed by X-ray diffraction and transmission electron microscopy. The compatibilized nanocomposites exhibit improved thermal stability in air as compared to

J. Morawiec; A. Pawlak; M. Slouf; A. Galeski; E. Piorkowska; N. Krasnikowa

2005-01-01

365

Cross-Linked Hydroxy-Al-Montmorillonite as a Stationary Phase in Liquid Chromatography  

Microsoft Academic Search

Quasi-spherical particles (7-tzm mean diameter) were prepared from cross-linked hydroxy-A1- montmorillonite (basal spacing = 15.3 and 18.6 A) by spray-drying. These particles (SP-CLM) were used as a packing material for columns in high-pressure liquid chromatography (HPLC). Aromatic phosphate esters, chlorosubstituted phenyl-ureas, monosubstituted benzenes, and the o-, m-, and p-isomers of di- substituted benzenes were separated on the columns, using isopropanol

Faina Tsvetkov; U. MINGELGRIN; N. LAHAV

1990-01-01

366

Aggregation of Rhodamine 3B Adsorbed in Wyoming Montmorillonite Aqueous Suspensions  

Microsoft Academic Search

The adsorption of Rhodamine 3B (R3B) molecules in Wyoming Montmorillonite (Mont) particles suspended in water was studied by electronic absorption spectroscopy. Several adsorbed R3B species in the Mont tactoids were characterized from the observed changes in the absorption spectra by increasing the relative dye\\/clay concentration and the stirring time of the samples. R3B molecules can be adsorbed as monomeric units

F. López Arbeloa; R. Chaudhuri; T. Arbeloa López; I. López Arbeloa

2002-01-01

367

Enhancing mechanical and thermal properties of PLLA ligaments with fumed silica nanoparticles and montmorillonite  

Microsoft Academic Search

Nanocomposites of poly(l-lactic acid) (PLLA) containing 2.5 wt% of fumed silica nanoparticles (SiO2) and organically modified montmorillonite (OMMT) were prepared by solved evaporation method. From SEM micrographs it was\\u000a observed that both nanoparticles were well dispersed into PLLA matrix. All nanocomposites exhibited higher mechanical properties\\u000a compared to neat PLLA, except elongation at break, indicating that nanoparticles can act as efficient

K. Chrissafis; E. Pavlidou; K. M. Paraskevopoulos; T. Beslikas; N. Nianias; D. Bikiaris

2011-01-01

368

Hindered ion diffusion in polyelectrolyte/montmorillonite multilayers: Toward compartmentalized films  

NASA Astrophysics Data System (ADS)

This report describes the construction of multicomposite ultrathin films using the layer-by-layer assembly technique. The films are built-up with two different architectures: with and without a layer composed of the inorganic nanosheets of the clay mineral montmorillonite. Using two techniques of characterization, neutron reflectometry (for deuterated polyelectrolytes) and absorbance spectroscopy (for ion-sensitive dyes), it is demonstrated that the mineral layer acts as a barrier for the transport of ions along the film normal.

Struth, B.; Eckle, M.; Decher, G.; Oeser, R.; Simon, P.; Schubert, D. W.; Schmitt, J.

369

The hydrometallurgical extraction of lithium from egyptian montmorillonite-type clay  

NASA Astrophysics Data System (ADS)

The processing of El-Fayoum montmorillonite-type clay deposits is attained through leaching with commercial sulfuric acid using a ball-mill-type autoclave. This process yields lithium sulfate, which can be used either for the production of lithium carbonate or to produce lithium metal. The effects of temperature, grain size, and sulfuric acid concentration and leaching on lithium recovery as well as the kinetics of the leaching process have been studied.

Amer, A. M.

2008-10-01

370

Artificial neural networks approach for zeta potential of Montmorillonite in the presence of different cations  

NASA Astrophysics Data System (ADS)

In this study, the zeta potential of montmorillonite in the presence of different chemical solutions was modeled by means of artificial neural networks (ANNs). Zeta potential of the montmorillonite was measured in the presence of salt cations, Na+, Li+ and Ca2+ and metals Zn2+, Pb2+, Cu2+, and Al3+ at different pH values, and observed values pointed to a different behavior for this mineral in the presence of salt and heavy metal cations. Artificial neural networks were successfully developed for the prediction of the zeta potential of montmorillonite in the presence of salt and heavy metal cations at different pH values and ionic strengths. Resulting zeta potential of montmorillonite shows different behavior in the presence of salt and heavy metal cations, and two ANN models were developed in order to be compared with experimental results. The ANNs results were found to be close to experimentally measured zeta potential values. The performance indices such as coefficient of determination, root mean square error, mean absolute error, and variance account for were used to control the performance of the prediction capacity of the models developed in this study. These indices obtained make it clear that the predictive models constructed are quite powerful. The constructed ANN models exhibited a high performance according to the performance indices. This performance has also shown that the ANNs seem to be a useful tool to minimize the uncertainties encountered during the soil engineering projects. For this reason, the use of ANNs may provide new approaches and methodologies.

Yukselen, Yeliz; Erzin, Yusuf

2008-05-01

371

Structural characterization and transport properties of organically modified montmorillonite\\/polyurethane nanocomposites  

Microsoft Academic Search

Samples of polyurethane and organically modified montmorillonite (OMont) were prepared, covering a wide range of inorganic composition, up to 40wt%. They were obtained by a three step process using diphenylmethane diisocyanate, poly(?-caprolactone), di(ethylene glycol) and poly(?-caprolactone)–OMont (NPCL) nanocomposites. The NPCL nanocomposites were used as soft segments for a partial replacement of the di(ethylene glycol) in the hard-segment of the polymeric

Mariarosaria Tortora; Giuliana Gorrasi; Vittoria Vittoria; Giancarlo Galli; Stefano Ritrovati; Emo Chiellini

2002-01-01

372

Regio- and diastereo-selectivity of montmorillonite-catalyzed oligomerization of racemic adenosine 5'-phosphorimidazolide.  

PubMed

Clay is a possible candidate for an effective catalyst in prebiotic chemical evolution of biomolecules. Montmorillonite was reported to effectively catalyze oligomerization of racemic adenosine 5'-phosphorimidazolide (DL-ImpA). In the oligomerization reaction, considerable amounts of cyclic dimers as well as linear dimers were produced in the oligomerization reactions. To assess the regio- and diastereo-selectivities of the oligomerization reaction, the dimer products including cyclic dimers were completely identified by means of enzymatic degradation reactions of the products. PMID:18404575

Urata, Hidehito; Fujimori, Mami; Aono, Chie; Yamakawa, Tomomi; Harada, Emi; Akagi, Masao

2008-04-01

373

Adsorption Characteristics and the Kinetics of the Cation Exchange of Rhodamine6G with Na +Montmorillonite  

Microsoft Academic Search

The adsorption and the kinetics of the cation exchange of rhodamine-6G (Rh-6G) with Na+-montmorillonite (Na+-MMT) have been studied. The binding parameters of Rh-6G have been determined by applying Freundlich and D–R isotherms. The enthalpy and the entropy of adsorption have been determined. The isosteric heat of adsorption has also been determined and decreases with increasing the concentration of Rh-6G. Increasing

Ali H. Gemeay

2002-01-01

374

Diphosphonium ion-exchanged montmorillonite for Telon dye removal from aqueous media  

Microsoft Academic Search

Diphosphonium-intercalated montmorillonites were prepared via ion exchange using para, meta and ortho-bis(triphenyl phosphonium methylene)-benzene-dichloride (p-, m- and o-TPhPMB) in quantities not exceeding the cation exchange capacity. Adsorption tests applied to Telon dyes (Red, blue and orange) revealed a significant increase of the maximum adsorption capacity from ca. 11-26 to 110-160mg.g-1 after intercalation. This improvement was explained by an increased organophilic

B. Makhoukhi; M. A. Didi; H. Moulessehoul; A. Azzouz; D. Villemin

2010-01-01

375

Preparation of porous PMMA\\/Na +–montmorillonite cation-exchange membranes for cationic dye adsorption  

Microsoft Academic Search

Porous PMMA\\/Na+–montmorillonite (MMT) cation-exchange membranes were successfully prepared by entrapment method in this study. One approach (simple mixing) was to mix commercial PMMA polymer with Na+–MMT clays in solvent for membrane preparation (Membrane A). The other approach (emulsion polymerization) was to synthesize the PMMA\\/Na+–MMT polymer composite via emulsion polymerization first, followed by membrane casting (Membrane B for Kunipia F clays

Ray-Yi Lin; Bang-Shuo Chen; Guan-Liang Chen; Jeng-Yue Wu; Hsin-Cheng Chiu; Shing-Yi Suen

2009-01-01

376

Thermogravimetric study of n -alkylammonium-intercalated montmorillonites of different cation exchange capacity  

Microsoft Academic Search

Three n-alkylammonium salts of varying alkyl chain length were ion exchanged with montmorillonites (MMT) of different cation exchange\\u000a capacity (CEC). The intercalated MMTs were characterized by thermogravimetry (TG), XRD, FTIR to acquire an insight into the\\u000a intergallery structural arrangement of the organic alkylammonium cations (AAC). The increment in the intergallery spacing\\u000a from XRD pattern was correlated with chain length and

Kausik Dana; Sankar Ghatak

2010-01-01

377

Studying nanostructure gradients in injection-molded polypropylene/montmorillonite composites by microbeam small-angle x-ray scattering  

NASA Astrophysics Data System (ADS)

The core-shell structure in oriented cylindrical rods of polypropylene (PP) and nanoclay composites (NCs) from PP and montmorillonite (MMT) is studied by microbeam small-angle x-ray scattering (SAXS). The structure of neat PP is almost homogeneous across the rod showing regular semicrystalline stacks. In the NCs the discrete SAXS of arranged crystalline PP domains is limited to a skin zone of 300 ?m thickness. Even there only frozen-in primary lamellae are detected. The core of the NCs is dominated by diffuse scattering from crystalline domains placed at random. The SAXS of the MMT flakes exhibits a complex skin-core gradient. Both the direction of the symmetry axis and the apparent perfection of flake-orientation are varying. Thus there is no local fiber symmetry, and the structure gradient cannot be reconstructed from a scan across the full rod. To overcome the problem the rods are machined. Scans across the residual webs are performed. For the first time webs have been carved out in two principal directions. Comparison of the corresponding two sets of SAXS patterns demonstrates the complexity of the MMT orientation. Close to the surface (< 1 mm) the flakes cling to the wall. The variation of the orientation distribution widths indicates the presence of both MMT flakes and grains. The grains have not been oriented in the flowing melt. An empirical equation is presented which describes the variation from skin to core of one component of the inclination angle of flake-shaped phyllosilicate filler particles.

Stribeck, Norbert; Schneider, Konrad; Zeinolebadi, Ahmad; Li, Xuke; Sanporean, Catalina-Gabriela; Vuluga, Zina; Iancu, Stela; Duldner, Monica; Santoro, Gonzalo; Roth, Stephan V.

2014-02-01

378

Montmorillonite-alginate nanocomposite as a drug delivery system--incorporation and in vitro release of irinotecan.  

PubMed

The scope of the present study was the preparation and characterization of irinotecan nanocomposite beads based on montmorillonite (Mt) and sodium alginate (AL) as drug carriers. After irinotecan (I) incorporation into Mt, the resulting hybrid was compounded with alginate, and I-Mt-AL nanocomposite beads were obtained by ionotropic gelation technique. The structure and surface morphology of the hybrid and composite materials were established by means of X-ray diffraction (XRD), IR spectroscopy (FT-IR), thermal analysis (TG-DTA) and scanning electron microscopy (SEM). Irinotecan incorporation efficiency in Mt and in alginate beads was determined both by UV-vis spectroscopy and thermal analysis and was found to be high. The hybrid and composite materials were tested in vitro in simulated intestinal fluid (pH 7.4, at 37 °C) in order to establish if upon administering the beads at the site of a resected colorectal tumor, the delivery of the drug is sustained and can represent an alternative to the existing systemic chemotherapy. The in vitro drug release test results clearly suggested that Mt, and Mt along with AL were able to control the release of irinotecan by making it sustained, without any burst effect, and by reducing the released amount and the release rate. The nanocomposite beads may be a promising drug delivery system in chemotherapy. PMID:23998956

Iliescu, Ruxandra Irina; Andronescu, Ecaterina; Ghitulica, Cristina Daniela; Voicu, Georgeta; Ficai, Anton; Hoteteu, Mihai

2014-03-25

379

Spectral properties of mixtures of montmorillonite and dark grains - Implications for remote sensing minerals containing chemically and physically adsorbed water  

NASA Technical Reports Server (NTRS)

The spectral properties from 0.4 to 3 microns of montmorillonite plus dark carbon grains (called opaques) of various sizes are studied as a function of the weight fraction of opaques present. The reflectance level and band depths of the 1.4-, 1.9-, 2.2-, and 2.8-micron water and/or OH absorption features are analyzed using derived empirical relationships and scattering theory. It is found that the absorption band depths and reflectance level are a very nonlinear function of the weight fraction of opaques present but can be predicted in many cases by simple scattering theory. The 2.8-micron bound water fundamental band is the most difficult absorption feature to suppress. The overtone absorptions are suppressed a greater amount than the fundamental but are still apparent even when 10-20 wt pct opaques are present. The relationships observed and the simple scattering theory presented show that quantitative compositional remote sensing studies are feasible for surfaces containing complex mineral mixtures.

Clark, R. N.

1983-01-01

380

Experimental study of the effect of pH on the kinetics of montmorillonite dissolution at 25 °C  

NASA Astrophysics Data System (ADS)

The effect of pH on the kinetics of smectite (K-montmorillonite) dissolution was investigated at 25 °C in batch and stirred flow-through reactors over the pH range of 1-13.5, in KNO 3 solutions. Dissolution rates were obtained based on the release of Si and Al at steady-state under far from equilibrium conditions. Dissolution was non-stoichiometric between pH 5 and 10, due to adsorption/precipitation of Al. Dissolution rates computed from batch and flow-through experiments were consistent, irrespective of the Si and Al concentrations. Sample pre-treatment and the interlayer cation do not affect the steady-state dissolution rate or stoichiometry of cation release. The rate dependence on pH can be described by: R(molm-2s-1)=10-12.30aH0.40+10-14.37+10-13.05aOH0.27 The experimental results are consistent with a dissolution mechanism involving inward movement of a dissolution front from crystal edges. Consequently, normalization of the dissolution rates should take into account the reactive surface located on the smectite edges.

Rozalén, M. Luisa; Huertas, F. Javier; Brady, Patrick V.; Cama, Jordi; García-Palma, Susana; Linares, José

2008-09-01

381

The structure of montmorillonites modified with zwitterionic surfactants and their sorption ability  

NASA Astrophysics Data System (ADS)

In this work, a novel organo-clays, zwitterionic surfactant modified montmorillonites (ZSMMs) were synthesized by using sulphobetaine and montmorillonites. The structures of ZSMMs were characterized by X ray diffraction (XRD) methods; the surfactant loading levels were measured by Total organic carbon (TOC) analysis, and their sorptive characteristics toward p-nitrophenol and nitrobenzene were investigated. XRD and TOC measurements indicated that the amount of adsorbed surfactants and the basal spacing of the ZSMMs increase with alkyl chain length and surfactant concentration. Sorption experiments showed that the capacity of p-nitrophenol to sorb onto the ZSMMs is higher than that of nitrobenzene. Both capacities increase with surfactant loading level; However, sorption capacity decreases when the surfactant concentration is higher than 2.0 CEC. Under the same surfactant loading level, the sorption capacities of p-nitrophenol and nitrobenzene increase with alkyl chain length. Under this experimental condition, the longer alkyl chain leads to a higher sorption capacity for hydrophobic organic compounds. On the basis of the ability of p-nitrophenol and nitrobenzene to sorb onto the montmorillonites, we conclude that the contaminant sorption coefficients, normalized with organic carbon content, highly depend on surfactant loading levels.

Zhu, Jianxi; Qing, Yanhong; Ma, Lingya; Zhu, Runliang; He, Hongping

2014-08-01

382

Copper and nitrophenol pollutants removal by Na-montmorillonite/alginate microcapsules.  

PubMed

The use of renewable bioresources allows the development of low cost adsorbents that are versatile. In the present paper, the affinity and the removal capacity of montmorillonite/alginate microcapsules for a hydrophobic organic pollutant (4-nitrophenol) and an inorganic pollutant (copper) were evaluated. The physicochemical processes through sorption and kinetic experiments under different ratios of montmorillonite vs. alginate and initial contaminant concentrations were investigated. The total weight loss and diameter decrease during the drying process were 90-96% and 64%, respectively. A significant decrease in beads diameter, related to water elimination, has been observed during the first 24h. Structural modifications that occur during the drying process were evaluated using thermal analysis. From correlation coefficients, the second-order equation depicts properly the adsorption of copper by the microbeads adsorption capacity increases to saturation with time; 3 and 6h were needed to reach equilibrium on wet and dry mixed microcapsules. The pseudo-second order model properly depicts the adsorption process of 4-NP onto Na-mont and (Na-mont/SA) mixed microcapsules but failed to reproduce the data observed for the alginate beads. Isotherms data were fitted with good correlation using the Langmuir model; alginate and montmorillonite adsorption capacities (q(m)/wet beads) agree with those obtained by various studies. PMID:19604638

Ely, Abdellahi; Baudu, Michel; Basly, Jean-Philippe; Kankou, Mohamed Ould Sid'Ahmed Ould

2009-11-15

383

Acid activated montmorillonite as catalysts in methyl esterification reactions of lauric acid.  

PubMed

The catalytic activity of acid activated montmorillonite in the esterification of free fatty acids (FFA) is reported. Standard Montmorillonite (MMT) type STx-1 provided by the Clay Mineral Society repository was activated using phosphoric, nitric and sulphuric acids under different conditions and the resulting materials were characterized and evaluated as catalysts in the methyl esterification of lauric acid. Blank reactions carried out in the absence of any added catalyst presented conversions of 32.64, 69.79 and 79.23%, for alcohol:lauric acid molar ratios of 60:1, 12:1 and 6:1, respectively. In the presence of the untreated clay and using molar ratios of 12:1 and 6:1 with 12% of catalyst, conversions of 70.92 and 82.30% were obtained, respectively. For the acid activated clays, conversions up to 93.08% of lauric acid to methyl laurate were obtained, much higher than those observed for the thermal conversion or using untreated montmorillonite. Relative good correlations were observed between the catalytic activity and the development of acid sites and textural properties of the resulting materials. Therefore, a simple acid activation was able to improve the catalytic activity and produce clay catalysts that are environmental friendly, cost effective, noncorrosive and reusable. PMID:22975784

Zatta, Leandro; Ramos, Luiz Pereira; Wypych, Fernando

2012-01-01

384

Adsorption of Adenine, Cytosine, Thymine, and Uracil on Sulfide-Modified Montmorillonite: FT-IR, Mössbauer and EPR Spectroscopy and X-Ray Diffractometry Studies  

NASA Astrophysics Data System (ADS)

In the present work the interactions of nucleic acid bases with and adsorption on clays were studied at two pHs (2.00, 7.00) using different techniques. As shown by Mössbauer and EPR spectroscopies and X-ray diffractometry, the most important finding of this work is that nucleic acid bases penetrate into the interlayer of the clays and oxidize Fe2+ to Fe3+, thus, this interaction cannot be regarded as a simple physical adsorption. For the two pHs the order of the adsorption of nucleic acid bases on the clays was: adenine ? cytosine > thymine > uracil. The adsorption of adenine and cytosine on clays increased with decreasing of the pH. For unaltered montmorillonite this result could be explained by electrostatic forces between adenine/cytosine positively charged and clay negatively charged. However for montmorillonite modified with Na2S, probably van der Waals forces also play an important role since both adenine/cytosine and clay were positively charged. FT-IR spectra showed that the interaction between nucleic acid bases and clays was through NH+ or NH{2/+} groups. X-ray diffractograms showed that nucleic acid bases adsorbed on clays were distributed into the interlayer surface, edge sites and external surface functional groups (aluminol, silanol) EPR spectra showed that the intensity of the line g ? 2 increased probably because the oxidation of Fe2+ to Fe3+ by nucleic acid bases and intensity of the line g = 4.1 increased due to the interaction of Fe3+ with nucleic acid bases. Mössbauer spectra showed a large decreased on the Fe2+ doublet area of the clays due to the reaction of nucleic acid bases with Fe2+.

Carneiro, Cristine E. A.; Berndt, Graciele; de Souza Junior, Ivan G.; de Souza, Cláudio M. D.; Paesano, Andrea; da Costa, Antonio C. S.; di Mauro, Eduardo; de Santana, Henrique; Zaia, Cássia T. B. V.; Zaia, Dimas A. M.

2011-10-01

385

Adsorption of adenine, cytosine, thymine, and uracil on sulfide-modified montmorillonite: FT-IR, Mössbauer and EPR spectroscopy and X-ray diffractometry studies.  

PubMed

In the present work the interactions of nucleic acid bases with and adsorption on clays were studied at two pHs (2.00, 7.00) using different techniques. As shown by Mössbauer and EPR spectroscopies and X-ray diffractometry, the most important finding of this work is that nucleic acid bases penetrate into the interlayer of the clays and oxidize Fe(2+) to Fe(3+), thus, this interaction cannot be regarded as a simple physical adsorption. For the two pHs the order of the adsorption of nucleic acid bases on the clays was: adenine???cytosine?>?thymine?>?uracil. The adsorption of adenine and cytosine on clays increased with decreasing of the pH. For unaltered montmorillonite this result could be explained by electrostatic forces between adenine/cytosine positively charged and clay negatively charged. However for montmorillonite modified with Na(2)S, probably van der Waals forces also play an important role since both adenine/cytosine and clay were positively charged. FT-IR spectra showed that the interaction between nucleic acid bases and clays was through NH(+) or NH (2) (+) groups. X-ray diffractograms showed that nucleic acid bases adsorbed on clays were distributed into the interlayer surface, edge sites and external surface functional groups (aluminol, silanol) EPR spectra showed that the intensity of the line g???2 increased probably because the oxidation of Fe(2+) to Fe(3+) by nucleic acid bases and intensity of the line g?=?4.1 increased due to the interaction of Fe(3+) with nucleic acid bases. Mössbauer spectra showed a large decreased on the Fe(2+) doublet area of the clays due to the reaction of nucleic acid bases with Fe(2+). PMID:21717172

Carneiro, Cristine E A; Berndt, Graciele; de Souza Junior, Ivan G; de Souza, Cláudio M D; Paesano, Andrea; da Costa, Antonio C S; di Mauro, Eduardo; de Santana, Henrique; Zaia, Cássia T B V; Zaia, Dimas A M

2011-10-01

386

Plasmon-assisted degradation of methylene blue with Ag/AgCl/montmorillonite nanocomposite under visible light  

NASA Astrophysics Data System (ADS)

Metal-semiconductor compounds, such as Ag/AgX (X = Cl, Br, I), enable visible light absorption and separation of photogenerated electron-hole through surface plasmon resonance (SPR) effect. However, the electron-hole generated and separated by light are vulnerable in Ag/AgX phase because of the occurrence of secondary recombined. In order to more effectively utilize the SPR photocatalytic effect, nanoparticles are located in a matrix. In this article, Ag/AgCl nanoparticles were synthesized in montmorillonite (MMT) matrix using dispersion method and light irradiation. The structure, composition and optical properties of such material were investigated by transmission electron microscopy (TEM), UV-visible diffuse reflectance spectroscopy (UV-Vis DRS), X-ray diffraction (XRD) and FTIR. Powder X-ray diffraction showed intercalation of Ag/AgCl nanoparticles into the clay layers. The as-prepared plasmonic photocatalyst exhibited an enhanced and stable photoactivity for the degradation of methylene blue (MB) under visible light. The high activity was attributed to the surface plasmon resonance (SPR) exhibited by Ag nanoparticles on the surface of AgCl. The detection of reactive species by radical scavengers displays that rad O2- and rad OH- are the main reactive species for the degradation of MB under visible light irradiation. The studies showed that 20 min illumination under visible light can complete degradation of methylene blue (MB), and indicate a high stability of photocatalytic degradation. The mechanism of separation of the photo-generated electrons and holes at the Ag/AgCl-MMT nanocomposite was discussed.

Sohrabnezhad, Sh.; Zanjanchi, M. A.; Razavi, M.

2014-09-01

387

Plasmon-assisted degradation of methylene blue with Ag/AgCl/montmorillonite nanocomposite under visible light.  

PubMed

Metal-semiconductor compounds, such as Ag/AgX (X=Cl, Br, I), enable visible light absorption and separation of photogenerated electron-hole through surface plasmon resonance (SPR) effect. However, the electron-hole generated and separated by light are vulnerable in Ag/AgX phase because of the occurrence of secondary recombined. In order to more effectively utilize the SPR photocatalytic effect, nanoparticles are located in a matrix. In this article, Ag/AgCl nanoparticles were synthesized in montmorillonite (MMT) matrix using dispersion method and light irradiation. The structure, composition and optical properties of such material were investigated by transmission electron microscopy (TEM), UV-visible diffuse reflectance spectroscopy (UV-Vis DRS), X-ray diffraction (XRD) and FTIR. Powder X-ray diffraction showed intercalation of Ag/AgCl nanoparticles into the clay layers. The as-prepared plasmonic photocatalyst exhibited an enhanced and stable photoactivity for the degradation of methylene blue (MB) under visible light. The high activity was attributed to the surface plasmon resonance (SPR) exhibited by Ag nanoparticles on the surface of AgCl. The detection of reactive species by radical scavengers displays that O2- and OH- are the main reactive species for the degradation of MB under visible light irradiation. The studies showed that 20 min illumination under visible light can complete degradation of methylene blue (MB), and indicate a high stability of photocatalytic degradation. The mechanism of separation of the photo-generated electrons and holes at the Ag/AgCl-MMT nanocomposite was discussed. PMID:24769384

Sohrabnezhad, Sh; Zanjanchi, M A; Razavi, M

2014-09-15

388

Investigation of nano-size montmorillonite on electron beam irradiated flame retardant polyethylene and ethylene vinyl acetate blends  

NASA Astrophysics Data System (ADS)

This study aims at investigating the effects of montmorillonite (MMT) and electron beam irradiation on alumina trihydrate (ATH) added low density polyethylene and ethylene vinyl acetate (LDPE-EVA) blends. The nano-size MMT was used to improve the flammability and mechanical properties of the ATH added LDPE-EVA blends. The samples were irradiated at the dosage range 0-250 kGy using electron beam accelerator. The limiting oxygen index test (LOI) revealed that the incorporation of MMT into ATH added LDPE-EVA blends could improve the flammability up to 28.4 LOI%. The application of irradiation effect also improved the flame retardancy of the blends for ˜2 LOI% compared to un-irradiated samples. The addition of MMT loading levels from 10 to 20 phr exhibited reinforcing effect for 10.3-14.6% in tensile strength. On the other hand, the increasing of MMT loading levels has gradually decreased the surface and volume resistance of ATH added LDPE-EVA blends. The increase in irradiation dosages from 0 to 150 kGy was found to slightly decrease the surface and volume resistivity of the ATH added LDPE-EVA samples especially at high loading of MMT. The enhancement of mobility of MMT ionic in polymer matrix could lead to the reduction of the surface and volume resistivity. Consequently, this study has demonstrated that addition of MMT and electron beam irradiation to ATH added LDPE-EVA blends have resulted better flammability, mechanical and electrical properties of ATH added LDPE-EVA blends.

Bee, Soo-Tueen; Hassan, A.; Ratnam, C. T.; Tee, Tiam-Ting; Sin, Lee Tin

2013-03-01

389

Effects of monovalent, exchangeable cations and electrolytes on the relation between swelling pressure and interlayer distance in montmorillonite  

SciTech Connect

An oriented gel of homoionic montmorillonite was supported on a porous filter in a metal environmental chamber fitted with beryllium windows for the transmission of X-rays. Beneath the filter was a shallow reservoir connected to the outside atmosphere. Solution was expressed from the gel into the reservoir by admitting nitrogen gas to the environmental chamber at successively higher pressures. At each pressure the expressed solution in the reservoir was allowed to equilibrate through the filter with the gel and then the distance between the superimposed layers of montmorillonite in the gel was measured by X-ray diffraction. The swelling pressure of the montmorillonite equals the applied pressure at equilibrium. Thus, the relation between the swelling pressure and interlayer distance of the montmorillonite was determined when it was saturated with different exchangeable cations and equilibrated with electrolyte solutions of different concentration. The experimental results showed that, at relatively low concentrations of electrolyte, neither the species of exchangeable cation nor the electrolyte concentration had any effect on the relation between the swelling pressure and the interlayer distance. However, at relatively high concentrations of electrolyte, both of these factors affected this relation. Since the effect of the electrolyte concentration was not described quantitatively by electric double-layer theory, it was assumed that this theory was not applicable and that the added electrolyte reduced swelling by disrupting the hydration shells surrounding the montmorillonite particles.

Zhang, F.; Low, P.F.; Roth, C.B. [Purdue Univ., West Lafayette, IN (United States). Agronomy Dept.] [Purdue Univ., West Lafayette, IN (United States). Agronomy Dept.

1995-07-01

390

Effect of N{sub 2} + H{sub 2} gas mixtures in plasma nitriding on tribological properties of duplex surface treated steels  

SciTech Connect

Thermo-reactive diffusion chromizing followed by pulsed plasma nitriding were carried out on AISI 52100 and 8620 bearing steels. The chromized samples were pulse-plasma nitrided for 5 h at 500 deg. C in various N{sub 2}-H{sub 2} gas mixtures. The coated steels were characterized using scanning electron microscopy, X-ray diffraction and microhardness testing. The unlubricated wear behaviors of only chromized and duplex treated steels were investigated in ball-on-disc system tests at room temperature. X-ray diffraction patterns of the duplex treated samples containing H{sub 2} indicated the formation of dominant CrN and Cr{sub 2}N nitrides as well as the formation of Cr{sub 3}C{sub 2} and Cr{sub 7}C{sub 3} carbides. Gas mixtures in the plasma nitriding, which was performed after chromizing, have a significant influence on the wear rate of the duplex treated steels. The wear and friction tests showed that the lowest friction coefficient and wear rates were observed for the samples duplex treated in a 50%N{sub 2} +50%H{sub 2} plasma. Conversely, the lowest wear resistance was observed on the samples duplex treated in a gas mixture of 75%N{sub 2} + 25%H{sub 2}, probably due to formation of a hard and brittle layer.

Taktak, Sukru [Afyon Kocatepe University, Technical Education Faculty, Department of Metal Education, Afyonkarahisar (Turkey)], E-mail: taktak@aku.edu.tr; Gunes, Ibrahim; Ulker, Sukru; Yalcin, Yilmaz [Afyon Kocatepe University, Technical Education Faculty, Department of Metal Education, Afyonkarahisar (Turkey)

2008-12-15

391

Heat treating of manufactured components  

DOEpatents

An apparatus for heat treating manufactured components using microwave energy and microwave susceptor material is disclosed. The system typically includes an insulating vessel placed within a microwave applicator chamber. A moderating material is positioned inside the insulating vessel so that a substantial portion of the exterior surface of each component for heat treating is in contact with the moderating material.

Ripley, Edward B. (Knoxville, TN)

2012-05-22

392

Green synthesis of silver/montmorillonite/chitosan bionanocomposites using the UV irradiation method and evaluation of antibacterial activity  

PubMed Central

In this study, silver nanoparticles (Ag-NPs) were synthesized using a green physical synthetic route into the lamellar space of montmorillonite (MMT)/chitosan (Cts) utilizing the ultraviolet (UV) irradiation reduction method in the absence of any reducing agent or heat treatment. Cts, MMT, and AgNO3 were used as the natural polymeric stabilizer, solid support, and silver precursor, respectively. The properties of Ag/MMT/Cts bionanocomposites (BNCs) were studied as the function of UV irradiation times. UV irradiation disintegrated the Ag-NPs into smaller sizes until a relatively stable size and size distribution were achieved. Meanwhile, the crystalline structure and d-spacing of the MMT interlayer, average size and size distribution, surface morphology, elemental signal peaks, functional groups, and surface plasmon resonance of Ag/MMT/Cts BNCs were determined by powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray fluorescence, Fourier transform infrared, and UV-visible spectroscopy. The antibacterial activity of Ag-NPs in MMT/Cts was investigated against Gram-positive bacteria, ie, Staphylococcus aureus and methicillin-resistant S. aureus and Gram-negative bacteria (ie, Escherichia coli) by the disk diffusion method on Muller–Hinton Agar at different sizes of Ag-NPs. All of the synthesized Ag/MMT/Cts BNCs were found to have high antibacterial activity. These results show that Ag/MMT/Cts BNCs can be useful in different biologic research and biomedical applications, such as surgical devices and drug delivery vehicles. PMID:21116328

Shameli, Kamyar; Ahmad, Mansor Bin; Yunus, Wan Md Zin Wan; Rustaiyan, Abdolhossein; Ibrahim, Nor Azowa; Zargar, Mohsen; Abdollahi, Yadollah

2010-01-01

393

Montmorillonite Poly-L-Lactide Microcomposites of Procainamide for controlled drug delivery: In vitro and In vivo evaluation  

PubMed Central

The research work reported in this paper is extension of our previous findings related to intercalation of procainamide hydrochloride, an antiarrythmia drug in interlayer gallery of Na+-clay (montmorillonite). The microcomposite particles prepared from procainamide-montmorillonite hybrid and poly L-lactide were characterised by scanning electron microscope and atomic force microscopy analysis. In vitro drug release study in simulated intestinal fluid showed controlled release pattern up to ~72 h and significant reduction in the drug release in gastric environment. In vivo pharmacokinetics and biodistribution in rats showed that the plasma/tissue drug levels were within therapeutic window as compared with free drug. The data from toxicity biomarker estimations and clinical biochemistry/haematological parameters showed significant reduction in drug toxicity when formulated in montmorillonite/poly L-lactide as compared with free drug, which is of considerable value in achieving improved therapy with reduced side effects. PMID:24591748

Kevadiya, B. D.; Patel, T. K.; Patel, Parvati B.; Rajkumar, Shalini; Tripathi, C. B.; Bajaj, H. C.

2013-01-01

394

Oligomerization of uridine phosphorimidazolides on montmorillonite: a model for the prebiotic synthesis of RNA on minerals  

NASA Technical Reports Server (NTRS)

The 5'-phosphorimidazolide of uridine reacts on Na(+)-montmorillonite 22A in aqueous solution to give oligomers as long as 7 mers. The maximum chain length increases to 9 mers and the overall oligomer yield increases when 9:1 ImpU, A5' ppA mixtures react under the same conditions. The oligomer yield and maximum chain length decreases with the structure of the added pyrophosphate in the order A5' ppA > A5' ppU > U5' ppU. Structure analysis of individual oligomer fractions was performed by selective enzymatic hydrolyses followed by HPLC analysis of the products. The regioselectivity for 3',5'-bond formation is 80-90% in the 9:1 ImpU, A5' ppA reaction, a percentage comparable to that observed in the 9:1 ImpA, A5' ppA reaction. Oligomerization of ImpU is inhibited by addition of dA5' ppdA, and MeppA. No oligomers containing A5' ppU were products of the 9:1 ImpU,A5' ppA reaction, a finding consistent with the simple addition of the ImpU to the A5' ppA and not the rearrangement of an ImpU-A5' ppA adduct. Concentrations of lysine or arginine which were close to that of the ImpU did not inhibit oligomer formation. Treatment of Na(+)-montmorillonite with 1 M arginine yielded arginine-montmorillonite, an amino acid-mineral adduct which did not catalyze ImpU oligomerization. Neither the 4-9 mers formed in the 9:1 ImpU, A5' ppA reaction nor the 4-9 mers formed by the base hydrolysis of poly(U) served as templates for the formation of oligo(A)s.

Ding, P. Z.; Kawamura, K.; Ferris, J. P.

1996-01-01

395

Sequence- and regio-selectivity in the montmorillonite-catalyzed synthesis of RNA.  

PubMed

The six binary montmorillonite clay-catalyzed reactions of the 5'-phosphorimidazolides of adenosine, cytidine, guanosine and uridine were performed and the eight dimers from each reaction were separated and analyzed by HPLC. A 16-51-fold higher yield of the 5'-purine-pyrimidine dimers over that of the 5'-pyrimidine-purines was observed. The total yield of the 5'-purine-pyrimidine dimers was in the 50-70% range while that of the 5'-pyrimidine-purine dimers was 1.3-7.0%. Less sequence selectivity was observed in the homodimers formed. Regioselectivity for the formation of 3', 5'-phosphodiester bonds over that found in the absence of clay was observed. The 5'-purine-pyrimidine, 5'-pyrimidine-pyrimidine and 5'-purine-purine dimers had 3', 5'-links in about half of their phosphodiester bonds. The percent phosphodiester links in the 5'-pyrimidine-pyrimidine dimers was 18%, a value close to that observed in the absence of the montmorillonite catalyst. The montmorillonite-catalyzed reaction of all four activated nucleotides was performed and the 24 products were separated and analyzed. The trends observed in the binary reactions were confirmed and the results also showed that the relative reactivity of the activated monomers was A > G > C > U in the ratio 8.2:4.8:1.3:1 respectively. No 5'-pyrimidine-purines with a 5'-U and pG3' pU, pC3' pA and pC3' pG were detected. These studies suggest that a limited population of RNAs would have formed in catalyzed prebiotic reactions. PMID:11002887

Ertem, G; Ferris, J P

2000-10-01

396

Adsorption of Ba2+ by Ca-exchange clinoptilolite tuff and montmorillonite clay.  

PubMed

The adsorption of barium by Ca-exchanged clinoptilolite and montmorillonite is presented. The kinetics of adsorption of Ba(2+) were evaluated contacting 1g portion of each adsorber with 100mL 0.1N BaCl(2) for 200 h. Adsorption by Ca-clinoptilolite is defined by second-order kinetics of rate constant K(v) 8.232 x 10(-2) g mg(-1)h(-1) and maximum removal of 71.885 mg g(-1). It is a two-stage process initiated by a rapid uptake of Ba(2+) followed by more moderate kinetics. The adsorption isotherms were determined contacting 0.2g of each adsorber with 10 mL 0.1-0.005N BaCl(2)+CaCl(2) solution, Ba(2+)/Ca(2+) ratio 1, for periods of 7 days for the tuff and 2 days for the clay. The equilibrium adsorption is described by the Langmuir model, of equilibrium constant K 0.0151 L mg(-1) and maximum adsorption of 15.29 mg g(-1). The adsorption of Ba(2+) by Ca-exchanged montmorillonite also follows a second-order reaction of rate constant K(v) 3.179 x 10(-2) g mg(-1)h(-1), and calculated separation of 36.74 mg g(-1); the Langmuir isotherm is defined by the constant K 0.034 L mg(-1) and maximum adsorption of 15.29 mg g(-1). X-ray diffraction shows that the exchange of Ba(2+) modifies the d(001) of Ca-montmorillonite from 15.4 to 12.4A. PMID:19926210

Chávez, M L; de Pablo, L; García, T A

2010-03-15

397

Kinetic and mechanistic analysis of dinucleotide and oligonucleotide formation from the 5'-phosphorimidazolide of adenosine on Na(+)-montmorillonite  

NASA Technical Reports Server (NTRS)

The rate constants for the condensation reaction of the 5'-phosphorimidazolide of adenosine (ImpA) to form dinucleotides and oligonucleotides have been measured in the presence of Na(+)-volclay (a Na(+)-montmorillonite) in pH 8 aqueous solution at 25 degrees C. The rates of the reaction of ImpA with an excess of adenosine 5'-monophosphoramidate (NH2pA), P1,P2-diadenosine 5',5'-pyrophosphate (A5'ppA), or adenosine 5'-monophosphate (5'-AMP or pA) in the presence of the montmorillonite to form NH2pA3'pA, A5'ppA3'pA, and pA3'pA, respectively, were measured. Only 3',5'-linked products were observed. The magnitude of the rate constants decrease in the order NH2pA3'pA > A5'-ppA3'pA > pA3'pA. The binding of ImpA to montmorillonite was measured, and the adsorption isotherm was determined. The binding of ImpA to montmorillonite and the formation of higher oligonucleotides is not observed in the absence of salts. Mg2+ enhances binding and oligonucleotide formation more than Ca2+ and Na+. The rate constants for the oligonucleotide formation were determined from the reaction products formed from 10 to 40 mM ImpA in the presence of Na(+)-montmorillonite using the computer program SIMFIT. The magnitudes of the rate constants for the formation of oligonucleotides increased in the order 2-mer < 3-mer < 4-mer ... 7-mer. The rate constants for dinucleotide and trinucleotide formation are more than 1000 times larger than those measured in the absence of montmorillonite. The rate constants for the formation of dinucleotide, trinucleotide, and tetranucleotide are 41,2.6, and 3.7 times larger than those for the formation of oligo(G)s with a poly(C) template. The hydrolysis of ImpA was accelerated 35 times in the presence of the montmorillonite. The catalytic ability of montmorillonite to form dinucleotides and oligonucleotides is quantitatively evaluated and possible pathways for oligo(A) formation are proposed.

Kawamura, K.; Ferris, J. P.

1994-01-01

398

Montmorillonite K-10 promoted synthesis of chiral dioxa-caged compounds derived from levoglucosenone.  

PubMed

A short and efficient methodology for the synthesis of chiral dioxa-caged compounds from levoglucosenone, a biomass-derived enone, is herein presented. The key transformation, that involves a cascade 3-step cationic cyclization, was efficiently carried out in high yields and selectivities by Montmorillonite K-10 catalysis. The usefulness of K-10 in related semi-pinacol rearrangements to obtain pyran-3-ones is also shown. Interesting differences in the reactivity pattern was found for epimeric alcohols, and the origins of these findings were determined by DFT calculations. PMID:25497334

Zurita, Mariano A; Avila, Aylén; Spanevello, Rolando A; Suárez, Alejandra G; Sarotti, Ariel M

2015-01-30

399

Solid state characterisation of silver sulfadiazine loaded on montmorillonite/chitosan nanocomposite for wound healing.  

PubMed

Biopolymer chitosan/montmorillonite nanocomposites loaded with silver sulfadiazine for wound healing purposes were prepared via intercalation solution technique. Structure and morphology of loaded nanocomposites were studied and compared with pure components and unloaded nanocomposites. X-ray diffraction, Fourier transformed infrared spectroscopy, high resolution transmission electron microscopy coupled with energy-dispersion X-ray analysis, thermal and elemental analysis were employed for the characterisation. The results confirmed that the drug was effectively loaded in the three-dimensional nanocomposite structures, in which chitosan chains were adsorbed in monolayers into the clay mineral interlayer spaces. PMID:24077113

Aguzzi, Carola; Sandri, Giuseppina; Bonferoni, Cristina; Cerezo, Pilar; Rossi, Silvia; Ferrari, Franca; Caramella, Carla; Viseras, César

2014-01-01

400

Preparation of poly(oxybutyleneoxymaleoyl) catalyzed by a proton exchanged montmorillonite clay.  

PubMed

The polycondensation of tetrahydrofuran with maleic anhydride catalyzed by Maghnite-H+ (Mag-H) was investigated. Maghnite is a montmorillonite sheet silicate clay that is exchanged with protons to produce Maghnite-H [1]. It was found that the polymerization in bulk is initiated by Mag-H in the presence of acetic anhydride at 40 degrees C. The effects of the amounts of Mag-H and acetic anhydride were studied. The polymerization yield increased as the proportions of catalyst and acetic anhydride were increased. PMID:18007497

Ferrahi, Mohammed Issam; Belbachir, Mohammed

2004-01-01

401

Water adsorption constrained Frenkel-Halsey-Hill adsorption activation theory: Montmorillonite and illite clays  

NASA Astrophysics Data System (ADS)

Recently, fresh, unprocessed mineral aerosol has been found to contribute to the number of available cloud condensation nuclei (CCN) and cloud droplets in the atmosphere due to the effect of water adsorption on CCN activation. The work described here uses experimental water adsorption measurements on montmorillonite and illite clay to determine empirical adsorption parameters for a recently derived theoretical framework (Frenkel-Halsey-Hill Activation Theory, FHH-AT) used to calculate CCN activities of clay minerals. Upon fitting the Frenkel-Halsey-Hill (FHH) adsorption model to experimental water adsorption measurements, we find FHH adsorption parameters, AFHH and BFHH, to be 98×22 and 1.79×0.11 for Na-montmorillonite and 75×17 and 1.77×0.11 for illite, respectively. The AFHH and BFHH values obtained for these clays are significantly different from FHH adsorption parameters derived from CCN activation measurements reported previously for similar clay minerals. Differences in FHH adsorption parameters were attributed to the different approaches used, the hydratable nature of the clays and the relative difficulty in measuring CCN activation of hydratable clays due to relatively long adsorption and desorption equilibration times. However, despite these differences, the calculated CCN activities of montmorillonite and illite are quite similar and are in excellent agreement with experimental CCN activation measurements reported previously for similar clays. The different FHH adsorption parameters, however, translate to lower sc-Ddry CCN activation curve exponents (xFHH = -0.61 and -0.64 for montmorillonite and illite, respectively) than have been reported previously. The lower exponent suggests that the CCN activity of hydratable clay aerosol is less sensitive to changes in dry particle diameter (Ddry) and the hygroscopicity parameter exhibits a broader variability with Ddry compared to more soluble aerosols. This study illustrates that FHH-AT using adsorption pa