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1

Monomers of cutin biopolymer: sorption and esterification on montmorillonite surfaces  

NASA Astrophysics Data System (ADS)

One of the important precursors for soil organic matter is plant cuticle, a thin layer of predominantly lipids that cover all primary aerial surfaces of vascular plants. In most plant species cutin biopolymer is the major component of the cuticle (30-85% weight). Therefore cutin is the third most abundant plant biopolymer (after lignin and cellulose). Cutin is an insoluble, high molecular weight bio-polyester, which is constructed of inter-esterified cross linked hydroxy-fatty acids and hydroxyepoxy-fatty acids. The most common building blocks of the cutin are derivatives of palmitic acid, among them 9(10),16 dihydroxy palmitic acid (diHPA) is the main component. These fatty acids and their esters are commonly found in major organo-mineral soil fraction-humin. Hence, the complexes of cutin monomers with minerals may serve as model of humin. Both cutin and humin act as adsorption efficient domains for organic contaminants. However, only scarce information is available about the interactions of cutin with soil mineral surfaces, in particular with common soil mineral montmorillonite. The main hypothesize of the study is that adsorbed cutin monomers will be reconstituted on montmorillonite surface due to esterification and oligomerization, and that interactions of cutin monomers with montmorillonite will be affected by the type of exchangeable cation. Cutin monomers were obtained from the fruits of tomato (Lycopersicon esculentum). Adsorption of monomers was measured for crude Wyoming montmorillonites and montmorillonites saturated with Fe3+ and Ca2+. To understand the mechanism of monomer-clay interactions and to evaluate esterification on the clay surface, XRD and FTIR analyses of the montmorillonite-monomers complexes were performed. Our results demonstrated that the interactions of cutin monomers with montmorillonite are affected by the type of exchangeable cation. Isotherms of adsorption of cutin monomers on montmorillonites were fitted by a dual mode model of sorption, which combines site specific adsorption mechanism (Langmuir) and partitioning mechanism. Adsorption of monomers by Fe3+-montmorillonite was higher than for Ca2+ and crude -montmorillonites. XRD measurements showed expansion of d-spacing of montmorillonite samples with the increase in diHPA loading from 12.32, 12.66 and 12.17 Å for Fe3+- Ca2+- and crude-montmorillonite up to 16.84, 16.62 and 16.79 Å for organo-clay complexes of Fe3+-, Ca2+- and crude-montmorillonites respectively. This significant expansion of d-spacing suggests interlayer, and probably, multilayer diHPA adsorption by montmorillonite. Based on FTIR data we suggest that diHPA forms inner-sphere complexes with Fe3+-montmorillonite surface but not with Ca2+ and crude-montmorillonites. However all montmorillonite samples induce esterification and oligomerization of the monomers, which was demonstrated by FTIR spectra of the organo-montmorillonite complexes and by LC-MS analysis of the organic material extracted from organo-clay complexes. These results confirmed our hypothesis about oligomerization of cuticular monomers on mineral surfaces. We assume that esterification and oligomerization of monomers on montmorillonite surfaces simulate similar soil processes, which result in the formation of soil organo-mineral complexes and humin.

Olshansky, Yaniv; Polubesova, Tamara; Chefetz, Benny

2013-04-01

2

Silylation of montmorillonite surfaces: dependence on solvent nature.  

PubMed

Silylation of clay mineral surfaces has attracted much attention due to their extensive applications in materials science and environmental engineering. Silylation of montmorillonite surfaces with 3-aminopropyltriethoxysilane was carried out in polar-protic and nonpolar solvents. The swelling property of the silylated montmorillonites was investigated by intercalating with cetyltrimethylammonium bromide. Silylated montmorillonites prepared in nonpolar solvents showed a larger amount of loaded silane and a higher extent of condensation among different silane molecules, comparing with those prepared in polar-protic solvents with high dielectric constant. Meanwhile, the silylated montmorillonites prepared in nonpolar solvents displayed poor swelling property due to the linkage between silane oligomers and clay layers, that is, the neighboring clay layers were locked by the silane oligomers. The present study demonstrated that the polarity of the solvents used had an important influence on the extent of grafting, interlayer structure, and swelling property of the silylated products. This is of high importance for synthesis and application of silylated clay minerals. PMID:23123026

Su, Linna; Tao, Qi; He, Hongping; Zhu, Jianxi; Yuan, Peng; Zhu, Runliang

2013-02-01

3

Reflectance spectroscopy of palagonite and iron-rich montmorillonite clay mixtures - Implications for the surface composition of Mars  

NASA Technical Reports Server (NTRS)

The diffuse reflectance spectra of Hawaiian palagonite mixtures with an Fe-rich montmorillonite have prompted their present use as spectral analogs of the Martian surface. Like the Mars spectrum and unlike clays, the 2.2-micron reflectance spectrum absorption band is not present in the palagonite sample; neither is the 2.2-micron Al-OH clay lattice band seen in palagonite-montmorillonite mixtures, where the latter component remains below 15 wt pct. Fe-rich montmorillonite clay may therefore be present in Mars, in combination with palagonite, while remaining undetected in remotely sensed spectra.

Orenberg, James; Handy, Jonathan

1992-01-01

4

Modification of montmorillonite surfaces using a novel class of cationic gemini surfactants  

Microsoft Academic Search

A novel class of cationic gemini surfactants were prepared and used as modifiers for sodium montmorillonite (MMT-Na). The modified montmorillonites were characterized by X-ray diffraction (XRD), thermal analysis (TG), Fourier transform infrared spectroscopy (FTIR), dispersibility measurement, and scanning electron microscopy (SEM). The results show that the surfactants have been intercalated into the montmorillonite layers successfully. XRD measurements indicate that the

Limei Zhou; Hua Chen; Xiaohui Jiang; Fang Lu; Yafen Zhou; Wenmin Yin; Xiaoyang Ji

2009-01-01

5

Surface Area of Homoionic Illite and Montmorillonite Clay Minerals as Measured by the Sorption of Nitrogen and Carbon Dioxide  

Microsoft Academic Search

The surface areas obtained by application of the B.E.T. theory to adsorption isotherms of nitrogen and carbon dioxide gases at 77~ and 195~ respectively on homoionic samples of illite and montmorillonite clays have been examined. The isotherms were obtained using a standard volumetric adsorption system and the results are compared with those obtained by Thomas and Bohor (1968) using a

L. A. G. Aylmore; I. D. SILLS; J. P. QUIRK

1970-01-01

6

The Effects of Moisture on the Surface and Pore Areas of Kaolinite, Montmorillonite and Silica Gel  

NASA Astrophysics Data System (ADS)

A key factor in the uptake and release of contaminants in soils is the amount of water adsorbed on the surfaces of the soil particles. It is hypothesized that the surface and pore areas of porous solids will decrease because of the presence of this adsorbed water layer. In our experiments, we incubated four different solids (2 silica gels, kaolinite, and montmorillonite) in three different controlled environments (relative humidity (RH) values of 16%, 76%, and 86%) at ambient temperatures for over 440 days. Our results indicate that moisture significantly affects the surface areas of all solids except kaolinite. The surface areas of one of the silica gel samples incubated at 16%, 76%, and 86% were 271.1 m2/g, 237.5 m2/g, and 218.1 m2/g, respectively. Contrary to this, the surface areas of montmorrillonite increased with increasing RH because of the expansion of the clay layers. However, long-term incubation of montmorrillonite at 86% humidity resulted in a decrease in surface areas (surface areas of montmorrillonite at 76% RH increase from 2.95 to 7.10 m2/g while at 86% RH, they increase to 6.03 m2/g)), probably because more moisture was available at 86% RH to condense inside the pores and between the layers of the clay, reducing surface areas. This study is important because it will allow us to quantify the effects of moisture on the physical properties of particles and, hence improve our current understanding of contaminant distribution and fate in soils. These results are also important because they enhance our understanding of the swelling of clays such as montmorrillonite.

Monterrosa, A.

2004-12-01

7

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

8

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

9

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...

10

Free energies of absorption of alkali ions onto beidellite and montmorillonite surfaces from constrained molecular dynamics simulations  

NASA Astrophysics Data System (ADS)

Ab initio Molecular dynamics have been performed to study the free energy of adsorption of alkali atoms onto smectite clay surfaces and to identify the most favourable region in the interlayer for the cations. This is achieved by potential of mean force calculations using a constraint method to determine the lowest free energy configurations of lithium, potassium and sodium beidellite and sodium montmorillonite clays with a monolayer and bilayer of water present in the interlayer region. The constraint method has allowed us to examine the changes in the lowest free energy configuration for each ion with increasing hydration. From this, we can interpret the likelihood of clay swelling from the monolayer to bilayer coverage and compare with experimental observations. We find, that with a bilayer of water present, both lithium beidellite and sodium montmorillonite have their free energy minimum in the centre of the interlayer. For monolayer coverage, the free energy minimum for lithium, sodium and potassium beidellite is approximately the mid-point of the interlayer. Na-beidellite has a lowest free energy region at 6.1 Å from the centre of the clay layer for both mono- and bi-layer coverage, while for the potassium counter-ion, commonly used as swelling inhibitor, the free energy profile for K-beidellite shows peaks close to both surfaces at approximately 6.2 and 8.6 Å. We find that for systems where the free energy minimum remains in the middle of the interlayer when the hydration levels increase from monolayer to bilayer, it is known experimentally that these systems will swell in contact with water. The move to the middle of the interlayer with increasing hydration is associated with the full hydration sphere of the ion being composed purely of water oxygen atoms, and no clay surface oxygen atoms.

Suter, James L.; Sprik, Michiel; Boek, Edo S.

2012-08-01

11

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

12

Reflectance spectroscopy and GEX simulation of palagonite and iron-rich montmorillonite clay mixtures: Implications for the surface composition of Mars  

NASA Technical Reports Server (NTRS)

Because of the power of remote sensing reflectance spectroscopy in determining mineralogy, it has been used as the major method of identifying a possible mineral analogue of the martian surface. A summary of proposed martian surface compositions from reflectance spectroscopy before 1979 was presented by Singer et al. Since that time, iron-rich montmorillonite clay, nanocrystalline or nanophase hematite, and palagonite have been suggested as Mars soil analogue materials. Palagonite in petrological terms is best described as an amorphous, hydrated, ferric iron, silica gel. Montmorillonite is a member of the smectite clay group, and its structure is characterized by an octahedral sheet in coordination with two tetrahedral sheets in which oxygen atoms are shared. The crystal unity of montmorillonite is well defined in contrast to palagonite where it is considered amorphous or poorly crystalline at best. Because of the absence of the diagnostic strong 2.2-micron reflectance band characteristic of clays in the near-infrared (NIR) spectrum of Mars and palagonite and based upon a consideration of wide wavelength coverage (0.3-50 microns), Roush et al. concluded that palagonite is a more likely Mars surface analogue. In spite of the spectral agreement of palagonite and the Mars reflectance spectrum in the 2.2-micron region, palagonite shows poor correspondence with the results of the Viking LR experiment. In contrast, iron-rich montmorillonite clays show relatively good agreement with the results of the Viking LR experiment. This spectral study was undertaken to evaluate the spectral properties of mixtures of palagonite and Mars analogue iron-rich montmorillonite clay (16-18 wt. percent Fe as Fe2O3) as a Mars surface mineralogical model. Mixtures of minerals as Mars surface analogue materials have been studied before, but the mixtures were restricted to crystalline clays and iron oxides.

Orenberg, J. B.; Handy, J.; Quinn, R.

1992-01-01

13

Adsorption of low molecular weight halocarbons by montmorillonite  

SciTech Connect

Montmorillonite clay from Clay Spur, WY, was found to adsorb several low molecular weight, hydrophobic halocarbons from aqueous solution at sub-parts-per-million levels. The halocarbons studied were trichloroethylene, tetrachloroethylene, hexachloroethane, and dibromochloropropane. When the montmorillonite was treated with sodium citrate-bicarbonate-dithionite (CBD), it adsorbed higher levels of halocarbons than the untreated clay. In addition, the CBD-treated clay exhibited a maximum in halocarbon adsorption around pH 4, while untreated clay showed little variation in adsorption over the pH range 2-10. Adsorption of trichloroethylene was inhibited by low concentrations of sodium chloride (0.01 M or greater) in solution. Aging the CBD-treated clay in water decreased its capacity to adsorb trichloroethylene. Desorption studies showed that the sorption of tetrachloroethylene to CBD-treated clay is an irreversible process when compared to sorption by fumed silica. The ability of montmorillonite to adsorb halocarbons and the instability of the clay in water are postulated to involve changes in the oxide surface coating on the clay.

Estes, T.J.; Shah, R.V.; Vilker, V.L. (Univ. of California, Los Angeles (USA))

1988-04-01

14

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

15

NANOFILTRATION FOULANTS FROM A TREATED SURFACE WATER  

EPA Science Inventory

The foulant from pilot nanofiltration membrane elements fed conventionally-treated surface water for 15 months was analyzed for organic, inorganic, and biological parameters. The foulant responsible for flux loss was shown to be a film layer 20 to 80 um thick with the greatest de...

16

Dispersibility of Amphibious Montmorillonite  

NASA Astrophysics Data System (ADS)

The objective of this study is to develop a suitable method to convert hydrophilic montmorillonite into amphibious montmorillonite by replacing the sodium ions normally found in clay with poly(oxyethylene) (POE)-amide chlorite cations. Amphibious montmorillonite has a high d-spacing and good dispersion characteristics in many different types of solutions, including those having an intermediate hydrophilic lipophilic balance (HLB) value. Four different modifying cations are tested and X-ray diffraction analysis is performed to measure the resulting changes in the d-spacing of the MMT. Scanning electron microscopy is employed to investigate the morphology of the modified clays. A laser-doppler particle analyzer is used to measure the particle size of the clays in various solutions. Dobrat’s method is applied to calculate the dispersibility of each clay and Stoke’s law is used to evaluate the settling rate. The results indicate that the d-spacing of the POE-amide chlorite cation modified montmorillonite increases from 1.28 to 3.51 nm. The amphibious montmorillonite demonstrates good dispersion characteristics in eight commonly employed coating solutions with intermediate HLB values.

Yeh, Meng-Heng; Hwang, Weng-Sing; Kuo, Wuei-Jueng

2005-09-01

17

Surface properties of low-temperature plasma treated wool fabrics  

Microsoft Academic Search

Induced surface properties of wool fabrics created by the sputtering of low-temperature plasma treatment, such as surface lustre, wettability, surface electrostatic and dyeability, have been investigated. After the low-temperature plasma treatment, the treated wool fabric specimens exhibited better hydrophilicity and surface electrostatic properties at room temperature, together with improved dyeing rate. Study of the surfaces of the specimens showed that

C. W. Kan; K. Chan; C. W. M. Yuen; M. H. Miao

1998-01-01

18

Effect of modified montmorillonites on the biodegradation and adsorption of biomarkers such as hopanes, steranes and diasteranes.  

PubMed

The effect of modified montmorillonites on the biodegradation and adsorption of selected steranes, diasteranes and hopanes was investigated in aqueous clay/oil microcosm experiments with a hydrocarbon degrading microorganism community. The unmodified montmorillonite was treated with didecyldimethylammonium bromide, hydrochloric acid and the relevant metallic chloride to produce organomontmorillonite, acid activated montmorillonite and homoionic montmorillonite respectively which were used in this study. The study indicated that organomontmorillonite, acid activated montmorillonite and potassium montmorillonite did not support the biodegradation of the selected steranes, diasteranes and hopanes as alteration of the biomarkers via biodegradation varied from a paltry 2-6 %. The adsorption of the selected biomarkers on acid activated montmorillonite and organomontmorillonite was also poor. However, adsorption of the biomarkers on potassium montmorillonite was relatively high. Sodium montmorillonite and unmodified montmorillonite appear to stimulate the biodegradation of the selected biomarkers moderately (30-35 %) with adsorption occurring at low level. Calcium montmorillonite and ferric montmorillonite effected significant biodegradation (51-60 %) of the selected biomarkers. PMID:23749373

Ugochukwu, Uzochukwu C; Head, Ian M; Manning, David A C

2013-12-01

19

Surface characterization of plasma-treated polypropylene fibers  

Microsoft Academic Search

Plasma treatment is increasingly being used for surface modification of different materials in many industries. In this study, different techniques were employed to characterize the surface properties of plasma treated polypropylene fibers. The chemical nature of the fiber sufaces has been investigated by X-ray photoelectron spectroscopy (XPS). The XPS examination indicated the presence of oxygen-containing functional groups on fiber surfaces

Q. F Wei

2004-01-01

20

The acid-base titration of montmorillonite  

NASA Astrophysics Data System (ADS)

Proton binding to clay minerals plays an important role in the chemical reactivity of soils (e.g., acidification, retention of nutrients or pollutants). If should also affect the performance of clay barriers for waste disposal. The surface acidity of clay minerals is commonly modelled empirically by assuming generic amphoteric surface sites (>SOH) on a flat surface, with fitted site densities and acidity constant. Current advances in experimental methods (notably spectroscopy) are rapidly improving our understanding of the structure and reactivity of the surface of clay minerals (arrangement of the particles, nature of the reactive surface sites, adsorption mechanisms). These developments are motivated by the difficulty of modelling the surface chemistry of mineral surfaces at the macro-scale (e.g., adsorption or titration) without a detailed (molecular-scale) picture of the mechanisms, and should be progressively incorporated into surface complexation models. In this view, we have combined recent estimates of montmorillonite surface properties (surface site density and structure, edge surface area, surface electrostatic potential) with surface site acidities obtained from the titration of alpha-Al2O3 and SiO2, and a novel method of accounting for the unknown initial net proton surface charge of the solid. The model predictions were compared to experimental titrations of SWy-1 montmorillonite and purified MX-80 bentonite in 0.1-0.5 mol/L NaClO4 and 0.005-0.5 mol/L NaNO3 background electrolytes, respectively. Most of the experimental data were appropriately described by the model after we adjusted a single parameter (silanol sites on the surface of montmorillonite were made to be slightly more acidic than those of silica). At low ionic strength and acidic pH the model underestimated the buffering capacity of the montmorillonite, perhaps due to clay swelling or to the interlayer adsorption of dissolved aluminum. The agreement between our model and the experimental data illustrates the complementarity of molecular and macro-scale descriptions of the clay reactivity.

Bourg, I. C.; Sposito, G.; Bourg, A. C.

2003-12-01

21

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

22

Material, Mechanical, and Tribological Characterization of Laser-Treated Surfaces  

NASA Astrophysics Data System (ADS)

Laser treatment under nitrogen assisting gas environment of cobalt-nickel-chromium-tungsten-based superalloy and high-velocity oxygen-fuel thermal spray coating of nickel-chromium-based superalloy on carbon steel was carried out to improve mechanical and tribological properties. Superalloy surface was preprepared to include B4C particles at the surface prior to the laser treatment process. Material and morphological changes in the laser-treated samples were examined using scanning electron microscopy, energy-dispersive spectroscopy, and x-ray diffraction (XRD) analysis. Residual stresses present at the surface region of the laser-treated layer were determined from the XRD data. The microhardness of the laser-treated surface was measured by indentation tests. Fracture toughness of the coating surfaces before and after laser treatment were also measured using overload indentation tests. Macrowear and macrofriction characterization were carried out using pin-on-disk tests.

Yilbas, Bekir Sami; Kumar, Aditya; Bhushan, Bharat; Aleem, B. J. Abdul

2014-10-01

23

Acidbase characteristics of silane-treated E glass fiber surfaces  

Microsoft Academic Search

Acid-base properties of E glass fiber surfaces treated with various commercial organosilane coupling agents were studied with angle dependent X-ray photoelectron spectroscopy (XPS), electrolytic thermodesorption analysis of water (ETA), inverse gas chromatography (IGC) and programmed thermal desorption (PTD). XPS analysis indicates that ?-aminopropyltriethoxysilane and ?-chloropropyltrimethoxysilane show some preference for inverted surface orientation. Monolayer isotherms using Lewis acids and bases as

Sheldon P. Wesson; James S. Jen; Gary M. Nishioka

1992-01-01

24

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

25

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

26

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

27

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

28

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

29

40 CFR 721.10222 - Styrenyl surface treated manganese ferrite (generic).  

Code of Federal Regulations, 2012 CFR

...2012-07-01 false Styrenyl surface treated manganese ferrite (generic). 721.10222...721.10222 Styrenyl surface treated manganese ferrite (generic). (a) Chemical...generically as styrenyl surface treated manganese ferrite (PMN P-09-581) is...

2012-07-01

30

40 CFR 721.10222 - Styrenyl surface treated manganese ferrite (generic).  

Code of Federal Regulations, 2011 CFR

...2011-07-01 false Styrenyl surface treated manganese ferrite (generic). 721.10222...721.10222 Styrenyl surface treated manganese ferrite (generic). (a) Chemical...generically as styrenyl surface treated manganese ferrite (PMN P-09-581) is...

2011-07-01

31

40 CFR 721.10223 - Styrenyl surface treated manganese ferrite with acrylic ester polymer (generic).  

Code of Federal Regulations, 2012 CFR

...2012-07-01 false Styrenyl surface treated manganese ferrite with acrylic ester polymer...721.10223 Styrenyl surface treated manganese ferrite with acrylic ester polymer...generically as styrenyl surface treated manganese ferrite with acrylic ester...

2012-07-01

32

40 CFR 721.10223 - Styrenyl surface treated manganese ferrite with acrylic ester polymer (generic).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Styrenyl surface treated manganese ferrite with acrylic ester polymer...721.10223 Styrenyl surface treated manganese ferrite with acrylic ester polymer...generically as styrenyl surface treated manganese ferrite with acrylic ester...

2013-07-01

33

40 CFR 721.10223 - Styrenyl surface treated manganese ferrite with acrylic ester polymer (generic).  

...2014-07-01 false Styrenyl surface treated manganese ferrite with acrylic ester polymer...721.10223 Styrenyl surface treated manganese ferrite with acrylic ester polymer...generically as styrenyl surface treated manganese ferrite with acrylic ester...

2014-07-01

34

40 CFR 721.10222 - Styrenyl surface treated manganese ferrite (generic).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Styrenyl surface treated manganese ferrite (generic). 721.10222...721.10222 Styrenyl surface treated manganese ferrite (generic). (a) Chemical...generically as styrenyl surface treated manganese ferrite (PMN P-09-581) is...

2013-07-01

35

40 CFR 721.10222 - Styrenyl surface treated manganese ferrite (generic).  

...2014-07-01 false Styrenyl surface treated manganese ferrite (generic). 721.10222...721.10222 Styrenyl surface treated manganese ferrite (generic). (a) Chemical...generically as styrenyl surface treated manganese ferrite (PMN P-09-581) is...

2014-07-01

36

Surface characterisation of low temperature plasma-treated wool fibre  

Microsoft Academic Search

Previous investigation results revealed that after the low temperature plasma (LTP) treatment, the hydrophilicity of wool fibres was improved significantly. Such improvement enhances the wool dyeing and finishing processes which might be due to the changes of the wool surface to a more reactive one. In this paper, wool fibres were treated with LTP with different gases, namely oxygen, nitrogen

C. W. Kan; C. W. M. Yuen

2006-01-01

37

Surface characterization of plasma-treated polypropylene fibers  

SciTech Connect

Plasma treatment is increasingly being used for surface modification of different materials in many industries. In this study, different techniques were employed to characterize the surface properties of plasma treated polypropylene fibers. The chemical nature of the fiber sufaces has been investigated by X-ray photoelectron spectroscopy (XPS). The XPS examination indicated the presence of oxygen-containing functional groups on fiber surfaces after plasma treatment. The Atomic Force Microscopy (AFM) scans revealed the evolution of surface morphology under different experimental conditions. A Philips Environmental Scanning Electron Microscopy (ESEM) was also used to study the wetting behavior of the fibers. In the ESEM, relative humidity can be raised to 100% to facilitate the water condensation onto fiber surfaces for wetting observation. The ESEM observation revealed that the plasma treatment significantly altered the surface wettability of polypropylene fibers.

Wei, Q.F

2004-06-15

38

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

39

The mechanism of montmorillonite catalysis in RNA synthesis  

NASA Astrophysics Data System (ADS)

The formation of complex prebiotic molecules on the early Earth is likely to have involved a component of mineral catalysis. Amongst the variety of clay minerals that have been investigated by us for their ability to catalyze the formation of RNA oligomers is montmorillonite. These are 2:1 layer silicates that have a wide range of chemical compositions [(Na,Ca)0.33(Al,Fe,Mg)2(Si,Al)4O10(OH)2.nH2O]. They are commonly produced by the weathering of silicic volcanic ashes to form Bentonite. Once formed, montmorillonites gradually transform to Illites at a modest pressure and temperature. Of the many samples of montmorillonite that we have experimentally examined, a selected subset has been observed to be catalytic for RNA synthesis (Joshi et. al., 2009; Aldersley et al., 2011). Those that have been observed to be excellent catalysts come from a restricted range of elemental compositions. The recent identification of phyllosilicates including montmorillonite on Mars (Bishop et al., 2008) raises the possibility that such processes may have taken place there too. The extent of catalysis depended not only upon the magnitude of the negative charge on the montmorillonite lattice and the number of cations associated with it, but also on the pH at which the reaction is promoted. The isotherm and catalysis studies were extended to provide binding information and catalytic outcomes over a wide pH range. When cations in raw montmorillonite are completely replaced by sodium ions, the resulting Na+-montmorillonite does not catalyze oligomer formation because the ions saturate the interlayer between the platelets of montmorillonite, which blocks the binding of the activated monomers. Acid washed montmorillonite titrated to pH 6-8 with alkali metal ions, serves as the model catalyst for this RNA synthesis (Aldersley et. al., 2011). The optimal binding occurred in the region of maximal oligomer formation. X-ray diffraction studies revealed changes in layer separations of montmorillonite as reaction occurs. The application of the Scherer equation to the X-ray diffraction data showed differences in domain size. Modeling of the size of the activated nucleotide monomers and the charge on the montmorillonite surface provided an interpretation of how these factors influence adsorption. This research provides a basis for further understanding of the physical processes in the mechanism of this catalysis in prebiotic reactions. This research was supported by NASA Astrobiology Institute Grant NNA09DA80A. References: Aldersley, M.F., Joshi, P.C., Price, J.D., Ferris, J.P. The role of montmorillonite in its catalysis of RNA synthesis. Appl. Clay Sci. 54,1-14, 2011. Bishop, J.L., Dobrea, E.J.N., Mckeown, N.K., Parenta, M. Phyllos- ilicate diversity and past aqueous activity revealed at Mawrth Vallis, Mars. Science 321, 830-833, 2008. Joshi, P.C., Aldersley, M.F., Delano, J.W., Ferris, J.P., Mechanism of montmorillonite catalysis in the formation of RNA oligomers, J. Am. Chem. Soc., 131, 13369-13374, 2009.

Joshi, Prakash

40

Artefacts in RBS analysis of laser treated surfaces  

NASA Astrophysics Data System (ADS)

Laser treatment of deposited films often result in globules on the surface which may influence the solute depth profiles, as measured by Rutherford backscattering spectrometry (RBS). We show that the globules generally have poor adhesion to the substrate and can be easily removed using techniques commonly employed for testing adhesion of thin films, such as a scotch tape test, or mild abrasion test using a cotton bud or tip of a soft wooden piece. The effectiveness of this approach is demonstrated for Zn films on Al (treated with a 12 ns fwhm Nd: glass laser pulse) and Sb films on Al (treated with a 100 ns fwhm CO 2 laser pulse). The solute depth profiles, both before and after removal of globules from the laser treated surfaces, have been measured by employing RBS of He + ions and dramatic differences between the two cases have been observed. Laser treated surfaces are also characterized by optical microscopy and the topography is correlated with the RBS depth profiles. Results are presented for laser heating and liquid phase diffusion analysis of the solute depth profiles obtained after scotch tape and abrasion tests.

Kuldeep; Jain, Animesh K.

1986-04-01

41

Activity of tyrosinase immobilized on hydroxyaluminum-montmorillonite complexes  

Microsoft Academic Search

Montmorillonite was coated with varying levels of hydroxyaluminum, and the influence of degree of coatings on the adsorption, immobilization and activity of tyrosinase (Cu-containing polyphenoloxidase) was investigated in the absence of buffers. Tyrosinase was considered immobilized on the clay surfaces when after repeated washings with deionized distilled water no protein was detected in the supernatant. The immobilization of tyrosinase on

A. Naidja; P. M. Huang; J.-M. Bollag

1997-01-01

42

Transformation of montmorillonite to kaolinite during weathering  

USGS Publications Warehouse

Extensive deposits of kaolinite in Florida are formed by transformation of montmorillonite during low-temperature supergene weathering. The transformation occurs by intracrystalline leaching of interlayer cations and tetrahedral silica layers. Interposition of stripped layers within montmorillonite creates a regular 1:1 mixed-layered montmorillonite-kaolinite, a new clay structure. Kaolin-like layers are nourished by lateral epitaxy, as the iron-rich montmorillonite decomposes. Hexagonal outgrowths of new kaolinite develop at the edges of montmorillonite flakes and nucleate new vertical growth. Kaolinitic sands impregnated with goethite are ultimately formed, and the released silica enriches groundwater and forms secondary chert.

Altschuler, Z. S.; Dwornik, E. J.; Kramer, H.

1963-01-01

43

The effect of pillaring montmorillonite and beidellite on the conversion of trimethylbenzenes  

SciTech Connect

Natural montmorillonite, synthetic mica-montmorillonite (SMM), and Ni-substituted SMM were treated with hydroxy-Al solutions and the activities of the respective unpillared and pillared clays were tested using 1,2 4-trimethylbenzene as a reactant. Pillaring montmorillonite and, to a lesser extent, synthetic beidellite gave the largest % increase in the conversion level. The selectivity to 1,2,4,5-tetramethylbenzene, the smallest of the tetramethylbenzene isomers, was found to be a function not of the extent of pillaring, but rather of the extent of isomerization of the alkylbenzenes.

Kojima, M.; Hartford, R.; O'Connor, C.T. (Univ. of Cape Town, Rondebosch (South Africa))

1991-04-01

44

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

PubMed

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

2010-11-01

45

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

46

Wear behavior of different surface treated cam spindles  

Microsoft Academic Search

In this study wear behavior of cam spindles made of five different surface treated nodular cast iron (GGG50) and induction hardened CK45 steels was investigated. In the experiments; PVD–TiN-coated, both borided and PVD–TiN-coated, only hardened, both hardened and PVD–TiN-coated and only borided spherical graphite cast iron and induction hardened CK45 were used. The wear behavior of two type of steel

H. Sert; A. Can; H. Ar?kan; B. Selcuk; H. Toprak

2006-01-01

47

Surface characterization of low temperature plasma treated wool fiber  

Microsoft Academic Search

Previous investigation results revealed that after the Low Temperature Plasma (LTP) treatment, the hydrophilicity of wool\\u000a fiber was improved significantly. Such improvement enhances the wool dyeing and finishing processes which might be due to\\u000a the changes of the wool surface to a more reactive one. In this paper, wool fibers were treated with LTP with different gases,\\u000a namely, oxygen, nitrogen

C. W. Kan; K. Chan; C. W. M. Yuen

2004-01-01

48

The Stabiliy of Radio-Frequency Plasma Treated Polydimethylsiloxane Surface  

PubMed Central

Polydimethylsiloxane (PDMS) is a widely used material for manufacturing lab-on-chip devices. However, the hydrophobic nature of PDMS is a disadvantage in micro-fluidic systems. To transform the hydrophobic PDMS surface to hydrophilic it has been treated with radio frequency (RF) air plasma at 150, 300 and 500 mtorr pressure for up to 30 minutes. Following the surface treatment, the PDMS specimens were stored in air, deionized water or 0.14 M NaCl solution at 4 °C, 20 °C, and 70 °C. The change in the hydrophilicity (wettability) of the PDMS surfaces has been followed by contact angle measurements and Fourier Transform Infrared Attenuated Total Reflectance (FTIR-ATR) Spectroscopy as a function of time. As an effect of the RF plasma treatment the contact angles measured on PDMS surfaces dropped from 113±4 degrees to 9±3 degrees. The chamber pressure and the treatment time had no or negligible effect on the results. However, the PDMS surface gradually lost its hydrophilic properties in time. The rate of this process is influenced by the difference in the dielectric constants of the PDMS and its ambient environment. It has been the smallest at low temperatures in deionized water and largest at high temperatures in air. Apparently, the OH groups generated on the PDMS surface during the plasma treatment tend towards a more hydrophilic/less hydrophobic environment during the relaxation processes. The correlation between FTIR–ATR spectral information and contact angle data supports this interpretation. PMID:17279784

Chen, I-Jane

2008-01-01

49

Adsorption of basic dyes onto montmorillonite  

Microsoft Academic Search

Ca-montmorillonite (Ca-Mont) was exchanged with titanium cations and the adsorption equilibrium and kinetics of Basic Green 5 (BG5) and Basic Violet 10 (BV10) on these montmorillonites were measured to examine the ion-exchange effects on the basic dyes adsorption. The relationship between the dye adsorption and the alteration of pore structures of montmorillonite induced by ion-exchange processes was discussed. Moreover, the

Cheng-Cai Wang; Lain-Chuen Juang; Ting-Chu Hsu; Chung-Kung Lee; Jiunn-Fwu Lee; Fu-Chuang Huang

2004-01-01

50

Lead, cadmium, and calcium selectivity coefficients on a montmorillonite, illite, and kaolinite  

Microsoft Academic Search

Selectivity coefficients for Pb\\/sup 2 +\\/, Cd\\/sup 2 +\\/, and Ca\\/sup 2 +\\/ exchange adsorption with montmorillonite, illite, and kaolinite clays were determined over a wide range of clay surface concentration and found constant. The average selectivity coefficients describing the ion distributions for montmorillonite, illite, and kaolinite, respectively, were 0.60, 0.44, 0.34 for Pb-Ca exchange, 1.04, 1.01, 0.89 for Cd-Ca

J. E. Bittell; Raymond J. Miller

1974-01-01

51

Structural properties of reduced Upton montmorillonite  

NASA Astrophysics Data System (ADS)

Reduction of octahedral Fe in the crystalline structure of smectites influences, possibly controls, surface-sensitive physical and chemical properties. The purpose of this study was to investigate if reduction of structural Fe by Na-dithionite or bacteria affects the chemical environment of constituent cations in montmorillonite, employing solid state multinuclear (29Si and 27Al) magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. Reduction of structural Fe resulted in a positive (down field) chemical shift of the main Si Q3 (Q3(0Al)) site which was strongly correlated with Fe(II) content and inferred that distortions in Si-OT (T=Si, Al) bond angles and Si-O bond lengths occur with increasing layer charge. The line width (W) of the 29Si Q3 signal also increased with increasing levels of reduction. No change occurred in the position of the peak maximum for the octahedral Al (27AlVI) signal; however, an increased W was observed for this peak with increasing Fe(II) content. These results are attributed to decreases in Si-O-T bond angles and Si-O bond distances, corresponding to a better fit between the tetrahedral and octahedral sheets brought about by the presence of Fe(II) in the clay structure. The increased 27AlVI signal width (W) may also be due to a lessening of the paramagnetic influence of Fe(III) nuclei and enhancement of 27AlVI signals with different quadrupole coupling constants (QCC). Multinuclear MAS NMR analyses of dithioniteand microbially-reduced montmorillonite indicate that reduction of structural Fe caused reversible changes in the smectite structure, at least as far as this method could discern.

Gates, W. P.; Stucki, J. W.; Kirkpatrick, R. J.

1996-12-01

52

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

53

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

54

Octachlorodibenzodioxin formation on Fe(III)-montmorillonite clay.  

PubMed

Polychlorinated dibenzo-p-dioxins (PCDDs) are ubiquitous and highly toxic environmental contaminants found in surface and subsurface soils and in clay deposits. Interestingly, the congener profiles of such PCDDs are inexplicably dissimilar to those of known anthropogenic (e.g., pesticide manufacture, waste incineration) or natural (e.g., forest fire) sources. Characteristic features of soil or clay-associated PCDDs are the dominance of octachlorodibenzo-p-dioxin (OCDD) as the most abundant congener and very low levels of polychlorinated dibenzofurans (PCDFs). These propensities led to the hypothesis of in situ PCDD formation in soils and geologic clay deposits. In this study, we demonstrate the formation of OCDD on the naturally occurring and widely distributed clay mineral montmorillonite under environmentally relevant conditions. When pentachlorophenol (PCP)was mixed with Fe(III)-montmorillonite, significant amounts of OCDD were rapidly (minutes to days) formed (approximately 5 mg OCDD/kg clay) at ambient temperature in the presence of water. This reaction is initiated by single electron transfer from PCP to Fe(III)-montmorillonite thereby forming the PCP radical cation. Subsequent dimerization, dechlorination, and ring closure reactions result in formation of OCDD. This study provides the first direct evidence for clay-catalyzed formation of OCDD supporting the plausibility of its in situ formation in soils. PMID:18678002

Gu, Cheng; Li, Hui; Teppen, Brian J; Boyd, Stephen A

2008-07-01

55

Grafting Silane onto Silicate Glass Surface Treated by DBD in Air  

Microsoft Academic Search

Dielectric barrier discharge plasma in air was used to modify glass surface to induce the graft of silane onto the treated surface to increase the possibility of biomolecule immobilization. The plasma treated glass had been characterized by scanning electron microscopy (SEM), Fourier transform infrared attenuated total reflection spectroscopy, X-ray photoelectron spec-troscopy (XPS) and surface water contact angle measurement. The validity

Chunsheng Ren; Dezhen Wang; Younian Wang

2008-01-01

56

Tribological Properties of Laser Surface Texturing and Molybdenizing Duplex-Treated Ni-Base Alloy  

Microsoft Academic Search

Laser surface texturing (LST) and surface molybdenizing duplex-treatment was performed on Ni-base alloy in order to improve its wear resistance at high temperature. Surface molybdenizing was performed on the laser surface textured Ni-base alloy by a double glow plasma surface alloying technology. The friction and wear properties of the duplex-treated, the single-treated, and the untreated alloys were tested on a

JIANLIANG LI; DANGSHENG XIONG; HONGYAN WU; ZHONGJIA HUANG; JIHUI DAI; RAJNESH TYAGI

2010-01-01

57

Comparative studies on montmorillonite-supported zero-valent iron nanoparticles produced by different methods: reactivity and stability.  

PubMed

To mitigate the aggregation and enhance the reactivity of nanosized zero-valent iron (nZVI), montmorillonite is employed as a template-supporting matrix to prepare nZVI through two different pathways: heterogeneous nucleation and homogeneous nucleation processes. Dispersed sub-nanosized ZVI clusters with an average size around 0.5 nm (perpendicular to the clay layers) are intercalated in clay interlayers when using montmorillonite as a template in preparation via heterogeneous nucleation process. However, the particle sizes spanned from 0.62 nm (perpendicular to the clay layers) for the ZV1 intercalated in montmorillonite interlayers to 1-50 nm for the ZVI residing on an external surface when using montmorillonite as a dispersion agent in the preparation via homogeneous nucleation. Furthermore, parallel batch experiments have been conducted with nZVIs synthesized by the two different methods in solutions of nitrobenzene and their reactivity is evaluated via response of nZVI to nitrobenzene remediation. As a result, the reactivity of ZVI synthesized by heterogeneous nucleation is greater than that by homogeneous nucleation, which is inversely correlated to the size of ZVI supported by montmorillonite clay. Evaluation of the stability of montmorillonite-supported ZVI showed that ZVI intercalated in the interlayers of montmorillonite is more stable than that located on the external surface, which can be attributed to the protective effect of montmorillonite layers on ZVI from oxidation. These results suggest that the great reactivity and high stability of montmorillonite-intercalated ZVI synthesized through heterogeneous nucleation process warrants its significant potential in developing in situ remediation and treatment technologies for organic contaminants. PMID:23530312

Jia, Hanzhong; Wang, Chuanyi

2013-01-01

58

Montmorillonite nanodevices for the colon metronidazole delivery.  

PubMed

The adsorption profiles of the antibiotic metronidazole (MNE) into the K10-montmorillonite (MMT-K10) clay and the subsequent release have been investigated as a function of pH and MNE/MMT-K10 ratio, in order to evaluate the potential of the MNE/MMT-K10 hybrids as controlled drug delivery system. The adsorption mechanism has been first elucidated by performing complementary equilibrium and kinetic studies and through the X-ray diffractometry (XRD) characterization of the obtained composite materials. The gathered results allowed us to propose a mechanism consisting of a multi-step pathway involving the neutral and the cationic form of the drug, which interact with different sites of the clay surfaces, i.e. the interlayer region and the faces of the lamella. In a second step the drug release kinetics has been studied under physiological pH mimicking conditions simulating the oral drug administration and delivery. For the sake of comparison the commercial formulation has also been employed for the release studies. The investigation of the release profiles and the comparison with the commercial formulation of the drug reveal that the new-tailor made formulation could be fruitful exploited for successfully prolonged the action of drug in the desired site. PMID:24076230

Calabrese, Ilaria; Cavallaro, Gennara; Scialabba, Cinzia; Licciardi, Mariano; Merli, Marcello; Sciascia, Luciana; Turco Liveri, Maria Liria

2013-11-30

59

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

60

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

61

Surface characterizations of mono-, di-, and tri-aminosilane treated glass substrates  

Microsoft Academic Search

The surface properties and structure of mono-, di-, and tri-aminosilane treated glass surfaces were investigated using surface analytical techniques including X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, atomic force microscopy (AFM), and streaming potential. An optimized dip-coating process was demonstrated to produce roughly silane monolayer coverage on the glass surface. The surface charge measurements indicated that aminosilanization converts the glass surface

E. Metwalli; D. Hainesc; O. Becker; S. Conzone; C. G. Pantanoa

2006-01-01

62

Michaelis constant (K m ) of acid phospatase as affected by montmorillonite, illite, and kaolinite clay minerals.  

PubMed

The influence of Ca homoionic clay minerals (montmorillonite, illite, and kaolinite) on the activity,K m , andV m values of acid phosphatase was examined in model experiments. At each substrate (p-nitrophenyl phosphate) level tested, the addition of increasing amounts of clays (50, 100, and 150 mg, respectively) decreased the activity and increased theK m value from 1.43×10(-3) M PNP (in the soluble state) to 82.3×10(-3)M (montmorillonite), 8.02×10(-3) M (kaolinite), and 7.65×10(-3) M (illite) at the 150 mg level. The maximum enzyme reaction velocity (V m ) remained nearly constant at different amounts of kaolinite and illite, but increased remarkably with rising quantities of montmorillonite. Apparently, the substrate affinity of sorbed acid phosphatase is significantly lower with montmorillonite than with kaolinite or illite. This may be ascribed to an intensive sorption of both substrate and enzyme to the surface as well as to interlattice sites of montmorillonite. PMID:24232494

Makboul, H E; Ottow, J C

1979-09-01

63

Fractionation of humic acids upon adsorption on montmorillonite and palygorskite  

NASA Astrophysics Data System (ADS)

The adsorption of three humic acid (HA) preparations by clays—montmorillonite (Wyoming, USA) and palygorskite (Kolomenskoe district, Moscow oblast)—has been studied. The HA preparations were isolated from samples of the humus-accumulative horizons of a leached chernozem (Voronezh) and a chestnut soil (Volgograd), and a commercial preparation of sodium humate (Aldrich) was also used. The solid-state 13C NMR spectroscopy and IR spectroscopy revealed the selective adsorption of structural HA fragments (alkyls, O-alkyls (carbohydrates), and acetal groups) on these minerals. As a result, the aromaticity of the organic matter (OM) in the organic-mineral complexes (OMCs) and the degree of its humification have been found to be lower compared to the original HA preparations. The fractionation of HAs is controlled by the properties of the mineral surfaces. The predominant enrichment of OMCs with alkyls has been observed for montmorillonite, as well as an enrichment with O-alkyls (carbohydrates) for palygorskite. A decrease in the C : N ratio has been noted in the elemental composition of the OM in complexes, which reflected its more aromatic nature and (or) predominant sorption of N-containing structural components of HA molecules. The adsorption of HA preparations by montmorillonite predominantly occurs on the external surface of mineral particles, and the interaction of nonpolar alkyl groups of HAs with this mineral belongs to weak (van der Waals, hydrophobic) interactions. The adsorption of HA preparations by palygorskite is at least partly of chemical nature: Si-OH groups of minerals are involved in the adsorption process. The formation of strong bonds between the OM and palygorskite explains the long-term (over 300 million years) retention of fossil fulvate-type OM in its complex with palygorskite, which we revealed previously.

Alekseeva, T. V.; Zolotareva, B. N.

2013-06-01

64

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

65

SURFACE PROPERTIES AND ADSORPTION BREAKTHROUGH CURVES OF PLASMA-TREATED SILICA GELS  

Microsoft Academic Search

Plasma treatments are used widely in surface modification of thin films and membranes. A similar treatment method was used for granular silica gel by using both argon and oxygen plasma. The surface properties, such as contact angle of water, pore diameter, and BET surface area, and the adsorption breakthrough curves for water were obtained on the plasma-treated silica gel. The

WEI-HAN TAO; KUEI-SEN CHANG; TSAIR-WANG CHUNG; YAW-NAN CHANG

2004-01-01

66

Electronic States of Chemically Treated SiC Surfaces Shu Nie and R. M. Feenstra  

E-print Network

report on the electronic properties of electro-polished p-type 4H-SiC, both C-face and Si-face (these1 Electronic States of Chemically Treated SiC Surfaces Shu Nie and R. M. Feenstra Dept. of Physics SiC surfaces have been studied by scanning tunneling spectroscopy. Charge accumulation on the surface

Feenstra, Randall

67

Synthesis and Characterization of the Hybrid Clay- Based Material Montmorillonite-Melanoidin: A Potential Soil Model  

SciTech Connect

The study of the interactions among metals, minerals, and humic substances is essential in understanding the migration of inorganic pollutants in the geosphere. A considerable amount of organic matter in the environment is associated with clay minerals. To understand the role of organic matter in the environment and its association with clay minerals, a hybrid clay-based material (HCM), montmorillonite (STx-1)-melanoidin, was prepared from L-tyrosine and L-glutamic acid by the Maillard reaction. The HCM was characterized by elemental analysis, nuclear magnetic resonance, x-ray photoelectron spectroscopy (XPS), scanning transmission x-ray microscopy (STXM), and thermal analysis. The presence of organic materials on the surface was confirmed by XPS and STXM. The STXM results showed the presence of organic spots on the surface of the STx-1 and the characterization of the functional groups present in those spots. Thermal analysis confirmed the existence of organic materials in the montmorillonite interlayer, indicating the formation of a composite of melanoidin and montmorillonite. The melanoidin appeared to be located partially between the layers of montmorillonite and partially at the surface, forming a structure that resembles the way a cork sits on the top of a champagne bottle.

V Vilas; B Matthiasch; J Huth; J Kratz; S Rubert de la Rosa; P Michel; T Schäfer

2011-12-31

68

Laser surface hardening of AISI 420 stainless steel treated by pulsed Nd:YAG laser  

Microsoft Academic Search

The AISI 420 martensitic stainless steel was surface-hardened by a pulsed Nd:YAG laser. The influences of process parameters (laser pulse energy, duration time and travel speed) on the depth and hardness of laser treated area and its corrosion behavior were Investigated. In the optimum process parameters, maximum hardness (490VHN) in the laser surface treated area was achieved. The pitting corrosion

B. Mahmoudi; M. J. Torkamany; A. R. Sabour Rouh Aghdam; J. Sabbaghzade

2010-01-01

69

The Effect of Dissolved Ligands on the Sorption of Cu(II) by Ca-Montmorillonite  

Microsoft Academic Search

The effects of three organic ligands on the adsorption of copper on Ca-montmorillonite were studied. The results indicate that these effects include three different processes: l) Enhanced uptake of positively charged copper-ligand complexes by ion-exchange. 2) Formation of ternary surface complexes involving surface aluminol groups. 3) Inhibited uptake due to competition between the surface ligands and the dissolved ligands for

Markus Stadler; PAUL W. SCHINDLER

1994-01-01

70

Investigation on surface structure of potassium permanganate/nitric acid treated poly(tetrafluoroethylene)  

NASA Astrophysics Data System (ADS)

In the previous articles concerning the treatment of poly(tetrafluoroethylene) (PTFE) with potassium permanganate/nitric acid mixture, the conversion of a hydrophobic to a hydrophilic surface was partially assigned to the defluorination of PTFE and then the introduction of carbonyl and hydroxyl groups into the defluorinated sites. In the present work, PTFE sheets were treated with potassium permanganate/nitric acid, and the surfaces before and after treatment were comparatively characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The surface sediments of the treated PTFE were also determined by atomic absorption spectroscopy (AAS). The results indicate that the conversion of the hydrophobicity to the hydrophilicity on the modified PTFE surface is mainly due to the deposition of hydrophilic manganese oxides which covered the fluorocarbon surface, and no detectable chemical reactions of PTFE occur in the treating process.

Fu, Congli; Liu, Shuling; Gong, Tianlong; Gu, Aiqun; Yu, Zili

2014-10-01

71

Apparent diffusion coefficients and chemical species of neptunium (V) in compacted Na-montmorillonite.  

PubMed

Diffusion of neptunium (V) in compacted Na-montmorillonite was studied through the non-steady state diffusion method. In this study, two experimental attempts were carried out to understand the diffusion mechanism of neptunium. One was to establish the diffusion activation energy, which was then used to determine the diffusion process in the montmorillonite. The other was the measurement of the distribution of neptunium in the montmorillonite by a sequential batch extraction. The apparent diffusion coefficients of neptunium in the montmorillonite at a dry density of 1.0 Mg m-3 were from 3.7 x 10(-12) m2 s-1 at 288 K to 9.2 x 10(-12) m2 s-1 at 323 K. At a dry density of 1.6 Mg m-3, the apparent diffusion coefficients ranged between 1.5 x 10(-13) m2 s-1 at 288 K and 8.7 x 10(-13) m2 s-1 at 323 K. The activation energy for the diffusion of neptunium at a dry density of 1.0 Mg m-3 was 17.5 +/- 1.9 kJ mol-1. This value is similar to those reported for diffusion of other ions in free water, e.g., 18.4 and 17.4 kJ mol-1 for Na+ and Cl-, respectively. At a dry density of 1.6 Mg.m-3, the activation energy was 39.8 +/- 1.9 kJ mol-1. The change in the activation energy suggests that the diffusion process changes depending on the dry density of the compacted montmorillonite. A characteristic distribution profile was obtained by the sequential extraction procedure for neptunium diffused in compacted montmorillonite. The estimated fraction of neptunium in the pore water was between 3% and 11% at a dry density of 1.6 Mg m-3 and at a temperature of 313 K. The major fraction of the neptunium in the montmorillonite was identified as neptunyl ions sorbed on the outer surface of the montmorillonite. These findings suggested that the activation energy for diffusion and the distribution profile of the involved nuclides could become powerful parameters in understanding the diffusion mechanism. PMID:11288572

Kozai, N; Inada, K; Kozaki, T; Sato, S; Ohashi, H; Banba, T

2001-02-01

72

Dynamics of Polymeric Solid Surfaces Treated with Oxygen Plasma: Effect of Aging Media after Plasma Treatment  

Microsoft Academic Search

The dynamic behavior of functional groups on polymer surfaces was studied with regard to the effects of aging media on the work of adhesion (WA) and the surface free energy of the polymeric solid (?s). Films of polystyrene (PS), polydimethylsiloxane (PDMS), and a cured phenol–formaldehyde resin (PFR) were exposed to oxygen plasma. The plasma-treated samples were washed with methanol to

Tatsunosuke Murakami; Shin-ichi Kuroda; Zenjiro Osawa

1998-01-01

73

An investigation on surface properties of treated low carbon and alloyed steels (boriding and carburizing)  

Microsoft Academic Search

In this study, the wear behaviour of the borided and carburized AISI 1020 and 5115 steels are investigated. Some of the samples prepared from test materials are carburized and some borided. The microstructure, worn surface and hardness distribution of the samples are examined. After and before wear testing, the surface phases of the treated samples are determined by X-ray diffraction

B Selçuk; R Ipek; M. B Karami?; V Kuzucu

2000-01-01

74

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

75

Extending a transonic small disturbance code to treat swept vertical surfaces  

NASA Technical Reports Server (NTRS)

A flexible-swept vertical surface capability has been developed and implemented within the CAP-TSD transonic small disturbance (TSD) code. The new capability required a modification to the TSD equation and a grid transformation for swept vertical surfaces. Modifications to the vertical surface boundary conditions allow it to be treated as a flexible surface. The new capability extends the range of problems which the code can treat. In order to assess the accuracy of the modifications, calculations were performed for a rectangular T-tail configuration and an AGARD T-tail configuration. Unsteady forces and moments are presented for the rectangular T-tail oscillating in yaw for a range of reduced frequencies. Comparisons are presented with linear theory and experiment. Steady and unsteady surface pressures are presented for the AGARD T-tail along with generalized aerodynamic forces. Comparisons are made with linear theory. The comparisons demonstrate the accuracy of the vertical surface modifications.

Gibbons, Michael D.

1992-01-01

76

Influence of montmorillonite tactoid size on Na-Ca cation exchange reactions.  

PubMed

The spatial organisation of swelling clay platelets in a suspension depends on the chemical composition of the equilibration solution. Individual clay platelets can be well dispersed, with surfaces entirely in contact with the external solution, or be stacked in tactoids, where part of the surfaces forms parallel alignments embedding interlayer water and cations. External and interlayer surfaces do not exhibit similar affinities for cations having different hydration and charge properties and the clay platelet stacking arrangement influences the clay affinity for these cations. This paper aims to establish the link between exchange properties and clay tactoid size and organisation for Na-Ca exchange on montmorillonite. Different montmorillonite samples behave differently with regards to Na-Ca exchange, from ideal to non-ideal exchange behaviour. A simple model coupling the tactoid stacking size to different Na/Ca relative affinities of the external and interlayer clay surfaces enables these differences to be reproduced. PMID:21920529

Tournassat, Christophe; Bizi, Mohamed; Braibant, Gilles; Crouzet, Catherine

2011-12-15

77

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

78

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

79

Enhanced pH and thermal stabilities of invertase immobilized on montmorillonite K-10  

Microsoft Academic Search

Invertase was adsorbed onto micro-porous acid-activated montmorillonite clay (K-10) by two procedures, namely adsorption and covalent binding. The immobilized enzymes were characterized by XRD, surface area measurements and 27Al NMR. XRD measurements revealed an expansion of clay layers due to immobilization which suggests that intercalation had taken place. Surface area measurements also support this observation. 27Al NMR showed that interaction

G. Sanjay; S. Sugunan

2006-01-01

80

Biocidal action of ozone-treated polystyrene surfaces on vegetative and sporulated bacteria  

NASA Astrophysics Data System (ADS)

Surfaces of materials can be modified to ensure specific interaction features with microorganisms. The current work discloses biocidal properties of polystyrene (PS) Petri-dish surfaces that have been exposed to a dry gaseous-ozone flow. Such treated PS surfaces are able to inactivate various species of vegetative and sporulated bacteria on a relatively short contact time. Denaturation of proteins seems likely based on a significant loss of enzymatic activity of the lysozyme protein. Characterization of these surfaces by atomic-force microscopy (AFM), Fourier-transform infra-red (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) reveals specific structural and chemical modifications as compared to untreated PS. Persistence of the biocidal properties of these treated surfaces is observed. This ozone-induced process is technically simple to achieve and does not require active precursors as in grafting.

Mahfoudh, Ahlem; Barbeau, Jean; Moisan, Michel; Leduc, Annie; Séguin, Jacynthe

2010-03-01

81

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

82

Formation and characterization of OH–Al–humate–montmorillonite complexes  

Microsoft Academic Search

We studied the formation of OH–Al–humate–montmorillonite complexes as affected by the nature of the humic acid and the sequence of addition of montmorillonite, humic acid and hydrolytic species of Al. Complexes were prepared at pH 7.0 by different addition sequences of montmorillonite, 3 or 6 mmol Al and 5, 10 or 20 mg of humic acid per g of clay.

A Violante; M Arienzo; F Sannino; C Colombo; A Piccolo; L Gianfreda

1999-01-01

83

Oxygen plasma-treated thermoresponsive polymer surfaces for cell sheet engineering.  

PubMed

Although cell sheet tissue engineering is a potent and promising method for tissue engineering, an increase of mechanical strength of a cell sheet is needed for easy manipulation of it during transplantation or 3D tissue fabrication. Previously, we developed a cell sheet-polymer film complex that had enough mechanical strength that can be manipulated even by tweezers (Fujita et al., 2009. Biotechnol Bioeng 103(2): 370-377). We confirmed the polymer film involving a temperature sensitive polymer and extracellular matrix (ECM) proteins could be removed by lowering temperature after transplantation, and its potential use in regenerative medicine was demonstrated. However, the use of ECM proteins conflicted with high stability in long-term storage and low cost. In the present study, to overcome these drawbacks, we employed the oxygen plasma treatment instead of using the ECM proteins. A cast and dried film of thermoresponsive poly-N-isopropylacrylamide (PNIPAAm) was fabricated and treated with high-intensity oxygen plasma. The cells became possible to adhere to the oxygen plasma-treated PNIPAAm surface, whereas could not to the inherent surface of bulk PNIPAAm without treatment. Characterizations of the treated surface revealed the surface had high stability. The surface roughness, wettability, and composition were changed, depending on the plasma intensity. Interestingly, although bulk PNIPAAm layer had thermoresponsiveness and dissolved below lower critical solution temperature (LCST), it was found that the oxygen plasma-treated PNIPAAm surface lost its thermoresponsiveness and remained insoluble in water below LCST as a thin layer. Skeletal muscle C2C12 cells could be cultured on the oxygen plasma-treated PNIPAAm surface, a skeletal muscle cell sheet with the insoluble thin layer could be released in the medium, and thus the possibility of use of the cell sheet for transplantation was demonstrated. PMID:20091737

Shimizu, Kazunori; Fujita, Hideaki; Nagamori, Eiji

2010-06-01

84

Immobilization of Bone Morphogenetic Protein on DOPA- or Dopamine-Treated Titanium Surfaces to Enhance Osseointegration  

PubMed Central

Titanium was treated with 3,4-dihydroxy-L-phenylalanine (DOPA) or dopamine to immobilize bone morphogenetic protein-2 (BMP2), a biomolecule. DOPA and dopamine solutions turned into suspensions, and precipitates were produced at high pH. Both treatments produced a brown surface on titanium that was thicker at high pH than low pH. Dopamine produced a thicker layer than DOPA. The hydrophobicity of the surfaces increased after treatment with dopamine independent of pH. Furthermore, there were more amino groups in the layers formed at pH 8.5 than pH 4.5 in both treatments. Dopamine treatment produced more amino groups in the layer than DOPA. BMP2 was immobilized on the treated surfaces via a coupling reaction using carbodiimide. More BMP2 was immobilized on surfaces treated at pH 8.5 than pH 4.5 in both treatments. The immobilized BMP induced specific signal transduction and alkali phosphatase, a differentiation marker. Thus, the present study demonstrates that titanium treated with DOPA or dopamine can become bioactive via the surface immobilization of BMP2, which induces specific signal transduction. PMID:24459666

Kang, Jeonghwa; Tada, Seiichi; Kitajima, Takashi; Son, Tae Il; Aigaki, Toshiro; Ito, Yoshihiro

2013-01-01

85

Samarium Ion Exchanged Montmorillonite for High Temperature Cumene Cracking Reaction  

NASA Astrophysics Data System (ADS)

Montmorillonite clay is cation exchanged with samarium and its catalytic influence in cumene cracking reaction is investigated. Effect of exchange with sodium ions on further exchange with samarium ions is also noted. Acidity measurements are done using Temperature Programmed Desorption (TPD) of ammonia. The retention of basic structure is proved from FTIR spectra and XRD patterns. Elemental analysis result shows that samarium exchange has occurred, which is responsible for the higher catalytic activity. Surface area and pore volume remains more or less unaffected upon exchange. Thermogravimetric analysis indicates the enhanced thermal stability on exchanging. Cumene cracking reaction is carried out at atmospheric pressure in a fixed bed glass reactor at 673 K. The predominance of Brønsted acidity is confirmed from high selectivity to benzene.

Binitha, N. N.; Silija, P. P.; Suraj, V.; Yaakob, Z.; Sugunan, S.

2011-02-01

86

Permethrin transfer from treated cloth to the skin surface: Potential for exposure in humans  

Microsoft Academic Search

Permethrin is an agricultural insecticide of great interest to the military because of its repellency toward disease?bearing insects when impregnated into uniforms. However, migration of the substance from clothing to the skin surface is of toxicological importance. To quantitate leaching from treated clothing, studies were performed in which swatches of fabric impregnated with C?labeled permethrin were applied to the backs

Hubert L. Snodgrass

1992-01-01

87

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

PubMed

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. PMID:21666866

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

2011-07-01

88

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

89

Study of Np(V) Sorption by Ionic Exchange on Na, K, Ca and Mg-Montmorillonite  

NASA Astrophysics Data System (ADS)

The transport behavior of actinides in soil and ground water are highly influenced by clay minerals due to their ubiquity in the environment, reactivity and colloidal properties. Neptunium(V) has been introduced in the environment as a result of nuclear weapons testing [e.g. 1, 2] and is a radionuclide of potential interest for safety assessment of high level radioactive waste disposal because its long half-life and high toxicity [3]. Surface complexation and ionic exchange have been identified as Np(V) sorption mechanisms onto montmorillonite. At pH below 5, Np(V) sorption is mainly attributed to ionic exchange. This study examines Np(V) ion exchange on Na, K, Ca and Mg forms of montmorillonite. Experiments were carried out using 237Np concentrations between 2 x 10-8 M and 5 x 10-6 M at three different ionic strengths 0.1, 0.01 and 0.001M. The pH was maintained at 4.5. Np(V) sorption to montmorillonite homoionized with monovalent cations (Na and K) demonstrated a markedly different behavior to that observed for montmorillonite homoionized with divalent cations (Ca and Mg). Np sorption to Na and K-montmorillonite was greater than Np sorption to Ca and Mg-montmorillonite. Isotherms with Na and K-montmorillonite showed a strong dependence on ionic strength: the percentage of Np adsorbed was near zero at 0.1M ionic strength, but increased to 30% at 0.001 M ionic strength. This suggests ionic exchange is the main Np adsorption mechanism under the experimental conditions investigated. Dependence on ionic strength was not observed in the Np sorption isotherms for Ca and Mg-montmorillonite indicating a low exchange capacity between Np and divalent cations. Modeling of the sorption experimental data will allow determination of the Na+?NpO2+ and K+?NpO2+ ionic exchange constants on montmorillonite. References: [1] A. R. Felmy; K. J. Cantrell; S. D. Conradson, Phys. Chem. Earth 2010, 35, 292-297 [2] D. K. Smith; D. L. Finnegan; S. M. Bowen, J. Environ. Radioact. 2003, 67, (1), 35-51 [3] N. Kozai; T. Ohnuki; S. Muraoka, J. Nucl. Sci. Technol. 1993, 30, (11), 1153-1159 This work was funded by U. S. DOE Office of Biological & Environmental Sciences, Subsurface Biogeochemistry Research Program, and performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Security, LLC under Contract DE-AC52-07NA27344. A. Benedicto was supported by a Spanish Ministry of Science and Innovation 'FPI' pre-doctoral contract in CIEMAT (Spain). LLNL-ABS-570160

Benedicto, A.; Begg, J.; Zhao, P.; Kersting, A. B.; Zavarin, M.

2012-12-01

90

Abiotic transformation of TNT in montmorillonite and soil suspensions under reducing conditions  

Microsoft Academic Search

Abiotic reduction of nitrobenzenes by Fe+2 adsorbed to various surfaces has been demonstrated by others. The objective of this study was to describe abiotic TNT transformation as a function of pH and confirm the possibility of an abiotic Fe+2 reduction pathway in reduced soils.Effects of pH on abiotic transformations of TNT were examined in buffered batch tests with montmorillonite and

James M. Brannon; Cynthia B. Price; Charolett Hayes

1998-01-01

91

Prebiotic RNA Synthesis by Montmorillonite Catalysis  

PubMed Central

This review summarizes our recent findings on the role of mineral salts in prebiotic RNA synthesis, which is catalyzed by montmorillonite clay minerals. The clay minerals not only catalyze the synthesis of RNA but also facilitate homochiral selection. Preliminary data of these findings have been presented at the “Horizontal Gene Transfer and the Last Universal Common Ancestor (LUCA)” conference at the Open University, Milton Keynes, UK, 5–6 September 2013. The objective of this meeting was to recognize the significance of RNA in LUCA. We believe that the prebiotic RNA synthesis from its monomers must have been a simple process. As a first step, it may have required activation of the 5'-end of the mononucleotide with a leaving group, e.g., imidazole in our model reaction (Figure 1). Wide ranges of activating groups are produced from HCN under plausible prebiotic Earth conditions. The final step is clay mineral catalysis in the presence of mineral salts to facilitate selective production of functional RNA. Both the clay minerals and mineral salts would have been abundant on early Earth. We have demonstrated that while montmorillonite (pH 7) produced only dimers from its monomers in water, addition of sodium chloride (1 M) enhanced the chain length multifold, as detected by HPLC. The effect of monovalent cations on RNA synthesis was of the following order: Li+ > Na+ > K+. A similar effect was observed with the anions, enhancing catalysis in the following order: Cl? > Br? > I?. The montmorillonite-catalyzed RNA synthesis was not affected by hydrophobic or hydrophilic interactions. We thus show that prebiotic synthesis of RNA from its monomers was a simple process requiring only clay minerals and a small amount of salt.

Jheeta, Sohan; Joshi, Prakash C.

2014-01-01

92

Thermalanalysis of tributylammonium montmorillonite and laponite  

Microsoft Academic Search

Montmorillonite and Laponite loaded with\\u000a different amounts of tributylammonium cations (TBAH+),\\u000a up to 40 and 30 mmol, respectively, per 100 g clay, were studied by thermo-XRD-analysis.\\u000a TBAH-smectites heated at 300 and 420°C exhibited basal spacings of 1.30\\u000a and 1.24 nm, attributed to smectite tactoids with low- and high-temperature-stable\\u000a monolayer charcoals, respectively in the interlayers. DTA-EGA and TG of the\\u000a TBAH-smectites

D. Ovadyahu; I. Lapides; S. Yariv

2007-01-01

93

Structural analysis of heat-treated birch (Betule papyrifera) surface during artificial weathering  

NASA Astrophysics Data System (ADS)

Effect of artificial weathering on the surface structural changes of birch (Betule papyrifera) wood, heat-treated to different temperatures, was studied using the fluorescence microscopy and the scanning electron microscopy (SEM). Changes in the chemical structure of wood components were analyzed by FTIR in order to understand the mechanism of degradation taking place due to heat treatment and artificial weathering. The results are compared with those of the untreated (kiln-dried) birch. The SEM analysis results show that the effect of weathering on the cell wall of the untreated birch surface is more than that of heat-treated samples. The FTIR spectroscopy results indicate that lignin is the most sensitive component of heat-treated birch to the weathering degradation process. Elimination of the amorphous and highly crystallised cellulose is observed for both heat-treated and untreated wood during weathering. It is also observed that heat treatment increases the lignin and crystallised cellulose contents, which to some extent protects heat-treated birch against degradation due to weathering.

Huang, Xianai; Kocaefe, Duygu; Kocaefe, Yasar; Boluk, Yaman; Krause, Cornélia

2013-01-01

94

Laser restoring the glass surface treated with acid-based paint  

NASA Astrophysics Data System (ADS)

The modern city facilities are often being attacked by graffiti artists, and increasingly vandals leave "tags" using paints, which compound based on acids, hydrofluoric or acetic commonly. These paints not only ink the surface, but also increase the surface roughness, and such impact can not be corrected by conventional cleaning. Thus, it was requested to develop technology that would not only clean the surface, but also to restore its structure by smoothing out irregularities and roughness formed after exposure in acid. In this work we investigated the effect of restoring the surface of the glass, spoiled by acid-based paint and then treated with CO2-laser. During the experiments, it was found that it is real to create the single-step laser surface restoring technology.

Strusevich, Anastasia V.; Poltaev, Yuriy A.; Sinev, Dmitrii A.

2013-11-01

95

Spectra investigation on surface characteristics of graphene oxide nanosheets treated with tartaric, malic and oxalic acids.  

PubMed

The surface characteristics of graphene oxide nanosheets (GO) treated respectively with tartaric acid, malic acid and oxalic acid, have been investigated by mainly using optical spectroscopic methods including Fourier transform infrared spectroscopy (FT-IR), Ultraviolet-visible (UV-Vis) absorption and Raman spectroscopy. Additionally, the electrochemical property of the products has also been studied. The data revealed that oxygen-containing groups such as OH, COOH and CO on the GO surface have been almost removed and thus reduced graphene oxide nanosheets (RGN) were obtained. Interestingly, the number of sp(2) domains of RGN increases as treated by tartaric acidtreated with tartaric, malic and oxalic acids, respectively. This finding agrees well with the spectra result of the tendency of surface conjugated degree alteration. We claim that the difference in both SH and IC among these acids is the main reason for the diverse surface characteristics as well as the improved Cs of the RGN. PMID:24161864

Teng, Xiyao; Yan, Manqing; Bi, Hong

2014-01-24

96

Research on cell behavior related to anodized and hydrothermally treated titanium surface  

NASA Astrophysics Data System (ADS)

In vitro cell response is believed related to the physical and chemical properties of substrate. In this study, the cell adhesion affected by mechanical stimulation from substrate was evaluated by culturing the MG-63 osteoblast-like cells on Ti plates with different chemical composition and surface topography. Three types of surface, surface with machined grooves, with pores, and with pillars, was fabricated by mechanically abraded (control), anodized (AO) and anodized following with hydrothermally treated (HYT) Ti plates, individually. Cells exhibited earlier spreading on the AO and HYT surface after 5 h culturing, resulted from chemical factor, i.e., calcium and phosphate containing on the surface. After 24 h cells completely flattened on the HYT surface but not on the AO surface; this improved cell adhesion behavior was primarily attributed to physical factor that is specific surface topography provides cell relatively large mechanical stimulation. The finite element method was used to evaluate the stress distributions which cells were suffered. For the HYT group, analyzed data indicated that cell received larger stress stimulation than control group (P > 0.01); therefore it can explain the fact that the superior cell adhesion resulted from the specific geometry of HYT coated-surface.

Chen, Chin-Sung; Tsao, Yuan-Li; Wang, Duen-Jeng; Ou, Shih-Fu; Cheng, Han-Yi; Chiang, Yi-Chen; Ou, Keng-Liang

2013-04-01

97

Sorption/Desorption Interactions of Plutonium with Montmorillonite  

NASA Astrophysics Data System (ADS)

Plutonium (Pu) release to the environment through nuclear weapon development and the nuclear fuel cycle is an unfortunate legacy of the nuclear age. In part due to public health concerns over the risk of Pu contamination of drinking water, predicting the behavior of Pu in both surface and sub-surface water is a topic of continued interest. Typically it was assumed that Pu mobility in groundwater would be severely restricted, as laboratory adsorption studies commonly show that naturally occurring minerals can effectively remove plutonium from solution. However, evidence for the transport of Pu over significant distances at field sites highlights a relative lack of understanding of the fundamental processes controlling plutonium behavior in natural systems. At several field locations, enhanced mobility is due to Pu association with colloidal particles that serve to increase the transport of sorbed contaminants (Kersting et al., 1999; Santschi et al., 2002, Novikov et al., 2006). The ability for mineral colloids to transport Pu is in part controlled by its oxidation state and the rate of plutonium adsorption to, and desorption from, the mineral surface. Previously we have investigated the adsorption affinity of Pu for montmorillonite colloids, finding affinities to be similar over a wide range of Pu concentrations. In the present study we examine the stability of adsorbed Pu on the mineral surface. Pu(IV) at an initial concentration of 10-10 M was pre-equilibrated with montmorillonite in a background electrolyte at pH values of 4, 6 and 8. Following equilibration, aliquots of the suspensions were placed in a flow cell and Pu-free background electrolyte at the relevant pH was passed through the system. Flow rates were varied in order to investigate the kinetics of desorption and hence gain a mechanistic understanding of the desorption process. The flow cell experiments demonstrate that desorption of Pu from the montmorillonite surface cannot be modeled as a simple first order process. Furthermore, a pH dependence was observed, with less desorbed at pH 4 compared to pH 8. We suggest the pH dependence is likely controlled by reoxidation of Pu(IV) to Pu(V) and aqueous speciation. We will present models used to describe desorption behavior and discuss the implications for Pu transport. References: Kersting, A.B.; Efurd, D.W.; Finnegan, D.L.; Rokop, D.J.; Smith, D.K.; Thompson J.L. (1999) Migration of plutonium in groundwater at the Nevada Test Site, Nature, 397, 56-59. Novikov A.P.; Kalmykov, S.N.; Utsunomiya, S.; Ewing, R.C.; Horreard, F.; Merkulov, A.; Clark, S.B.; Tkachev, V.V.; Myasoedov, B.F. (2006) Colloid transport of plutonium in the far-field of the Mayak Production Association, Russia, Science, 314, 638-641. Santschi, P.H.; Roberts, K.; Guo, L. (2002) The organic nature of colloidal actinides transported in surface water environments. Environ. Sci. Technol., 36, 3711-3719. This work was funded by U. S. DOE Office of Biological & Environmental Sciences, Subsurface Biogeochemistry Research Program, and performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Security, LLC under Contract DE-AC52-07NA27344. LLNL-ABS-570161

Begg, J.; Zavarin, M.; Zhao, P.; Kersting, A. B.

2012-12-01

98

Biocompatible, smooth, plasma-treated nickel-titanium surface--an adequate platform for cell growth.  

PubMed

High nickel content is believed to reduce the number of biomedical applications of nickel-titanium alloy due to the reported toxicity of nickel. The reduction in nickel release and minimized exposure of the cell to nickel can optimize the biocompatibility of the alloy and increase its use in the application where its shape memory effects and pseudoelasticity are particularly useful, e.g., spinal implants. Many treatments have been tried to improve the biocompatibility of Ni-Ti, and results suggest that a native, smooth surface could provide sufficient tolerance, biologically. We hypothesized that the native surface of nickel-titanium supports cell differentiation and insures good biocompatibility. Three types of surface modifications were investigated: thermal oxidation, alkali treatment, and plasma sputtering, and compared with smooth, ground surface. Thermal oxidation caused a drop in surface nickel content, while negligible chemistry changes were observed for plasma-modified samples when compared with control ground samples. In contrast, alkali treatment caused significant increase in surface nickel concentration and accelerated nickel release. Nickel release was also accelerated in thermally oxidized samples at 600 °C, while in other samples it remained at low level. Both thermal oxidation and alkali treatment increased the roughness of the surface, but mean roughness R(a) was significantly greater for the alkali-treated ones. Ground and plasma-modified samples had 'smooth' surfaces with R(a)=4 nm. Deformability tests showed that the adhesion of the surface layers on samples oxidized at 600 °C and alkali treatment samples was not sufficient; the layer delaminated upon deformation. It was observed that the cell cytoskeletons on the samples with a high nickel content or release were less developed, suggesting some negative effects of nickel on cell growth. These effects were observed primarily during initial cell contact with the surface. The most favorable cell responses were observed for ground and plasma-sputtered surfaces. These studies indicated that smooth, plasma-modified surfaces provide sufficient properties for cells to grow. PMID:21862513

Chrzanowski, W; Szade, J; Hart, A D; Knowles, J C; Dalby, M J

2012-02-01

99

Genotoxicity and inflammatory investigation in mice treated with magnetite nanoparticles surface coated with polyaspartic acid  

NASA Astrophysics Data System (ADS)

In this study, some biological tests were carried out with a magnetic fluid (MF) sample based on magnetite nanoparticles (MNPs) surface coated with polyaspartic acid (PAMF). The tests were performed from 1 to 30 days after injection of 50 ?L of PAMF in Swiss mice. The PAMF biocompatibility/toxicity was evaluated through cytometry, micronuclei assay, and morphology of several organs. All observed results were time and dose dependent. The data indicate that MNPs surface-treated with polyaspartic acid may be considered as a potential precursor of anticancer drugs.

Sadeghiani, N.; Barbosa, L. S.; Silva, L. P.; Azevedo, R. B.; Morais, P. C.; Lacava, Z. G. M.

2005-03-01

100

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

101

Surface Characterization of Plasma Treated Carbon Fibers and Adhesion to Polyethersulfone.  

NASA Astrophysics Data System (ADS)

A series of RF plasmas was chosen to modify the surface chemical composition of Hercules IM7 carbon fibers. A two-liquid tensiometric method was used to determine the surface energy parameters gamma_sp {rm s}{rm d} and I_sp{rm sf}{rm p} of the fibers. An XPS analysis of air and argon plasma treated fibers indicated a significant surface oxidation of the fibers which translated into low gamma_sp{rm s}{ rm d} values and high I_sp {rm sf}{rm p} values. An ammonia plasma was shown to remove an outer layer from the surface of the fibers. It also increased gamma_sp{rm s}{rm d}, compared to as-received fibers, without affecting the non-dispersion term (I_sp {rm sf}{rm p}). XPS results indicated that methane and ethylene plasmas deposited a layer of low surface energy hydrocarbon on the fiber surface. A trifluoromethane plasma and a tetrafluoromethane plasma introduced a significant amount of fluorine containing groups in the fiber surface in the form of a fluorinated plasma polymer in the first case and through direct attack of the fiber surface by fluorine atoms in the second case. The surface chemical composition and the surface energy parameters of two series of commercially treated carbon fibers were also determined and compared to the results on IM7 carbon fibers. The adhesion of carbon fibers to polyethersulfone (PES) was measured by using the microbond pull-out test, and compared to the adhesion of the same fibers to an epoxy resin. The load required to debond the microdroplet was used as a measure of the bond strength. The data were also analyzed in terms of interfacial fracture energy according to the model developed by Jiang and Penn (1992). The microbond pull-out test results showed no significant relation between the fiber surface chemical composition or the fiber surface energy, and the adhesion to PES. However, plasmas which have a strong ablative character such as the ammonia and the tetrafluoromethane plasmas did improve the fiber-PES adhesion, when compared to as-received fibers. The study of the fiber-epoxy systems revealed that a chemical effect contributed to the adhesion improvement but to a lesser extent than the "cleaning" effect of the surface treatment. The results support the two part mechanism proposed by Drzal and extend its application to carbon fiber-thermoplastic systems, but in this case the chemical effect is minimal.

Commercon, Pascal

102

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

103

Analysis of Oligonucleotide DNA Binding and Sedimentation Properties of Montmorillonite Clay Using Ultraviolet Light Spectroscopy  

PubMed Central

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 upon spectrophotometric analysis after separation of free nucleic acids from bound complexes by centrifugation. In the current work we demonstrate that such studies produce a consistent error due to (a) incomplete sedimentation of montmorillonite and (b) strong absorbance of the remaining clay at 260 nm. Clay sedimentation efficiency was strongly dependent upon 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 binding of single-stranded DNA to montmorillonite. X-ray diffraction demonstrated, for the first time, formation of intercalated structures consistent with orientation of the DNA strands parallel to the clay surface. Observed gallery spacings were found to closely match values calculated utilizing atomistic modeling techniques. PMID:19061334

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

2009-01-01

104

Fe(II) uptake on natural montmorillonites. I. Macroscopic and spectroscopic characterization.  

PubMed

Iron is an important redox-active element that is ubiquitous in both engineered and natural environments. In this study, the retention mechanism of Fe(II) on clay minerals was investigated using macroscopic sorption experiments combined with Mössbauer and extended X-ray absorption fine structure (EXAFS) spectroscopy. Sorption edges and isotherms were measured under anoxic conditions on natural Fe-bearing montmorillonites (STx, SWy, and SWa) having different structural Fe contents ranging from 0.5 to 15.4 wt % and different initial Fe redox states. Batch experiments indicated that, in the case of low Fe-bearing (STx) and dithionite-reduced clays, the Fe(II) uptake follows the sorption behavior of other divalent transition metals, whereas Fe(II) sorption increased by up to 2 orders of magnitude on the unreduced, Fe(III)-rich montmorillonites (SWy and SWa). Mössbauer spectroscopy analysis revealed that nearly all the sorbed Fe(II) was oxidized to surface-bound Fe(III) and secondary Fe(III) precipitates were formed on the Fe(III)-rich montmorillonite, while sorbed Fe is predominantly present as Fe(II) on Fe-low and dithionite-reduced clays. The results provide compelling evidence that Fe(II) uptake characteristics on clay minerals are strongly correlated to the redox properties of the structural Fe(III). The improved understanding of the interfacial redox interactions between sorbed Fe(II) and clay minerals gained in this study is essential for future studies developing Fe(II) sorption models on natural montmorillonites. PMID:24930689

Soltermann, Daniela; Marques Fernandes, Maria; Baeyens, Bart; Dähn, Rainer; Joshi, Prachi A; Scheinost, Andreas C; Gorski, Christopher A

2014-08-01

105

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

106

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

107

Electrochemical analysis of the UV treated bactericidal Ti6Al4V surfaces.  

PubMed

This research investigates in detail the bactericidal effect exhibited by the surface of the biomaterial Ti6Al4V after being subjected to UV-C light. It has been recently hypothesized that small surface currents, occurring as a consequence of the electron-hole pair recombination taking place after the excitation process, are behind the bactericidal properties displayed by this UV-treated material. To corroborate this hypothesis we have used different electrochemical techniques, such as electrochemical impedance spectroscopy (EIS), potentiodynamic polarization plots and Mott-Schottky plots. EIS and Mott-Schottky plots have shown that UV-C treatment causes an initial increase on the surface electrical conduction of this material. In addition, EIS and polarization plots demonstrated that higher corrosion currents occur at the UV treated than at the non-irradiated samples. Despite this increase in the corrosion currents, EIS has also shown that such currents are not likely to affect the good stability of this material oxide film since the irradiated samples completely recovered the control values after being stored in dark conditions for a period not longer than 24h. These results agree with the already-published in vitro transitory behavior of the bactericidal effect, which was shown to be present at initial times after the biomaterial implantation, a crucial moment to avoid a large number of biomaterial associated infections. PMID:23827637

Pacha-Olivenza, Miguel A; Gallardo-Moreno, Amparo M; Vadillo-Rodríguez, Virginia; González-Martín, M Luisa; Pérez-Giraldo, Ciro; Galván, Juan C

2013-04-01

108

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

109

Montmorillonite-levan nanocomposites with improved thermal and mechanical properties.  

PubMed

This work reports on the structure and properties of novel nanocomposites composed of exfoliated montmorillonite clay blended with levan, a polysaccharide produced by Bacillus sp. Dry levan is very brittle, making it difficult to obtain stand-alone films. MMT-levan composites were prepared by solution blending in water, coating on plastic surfaces, partial drying at 50°C, and conditioning in air at 50-60% relative humidity. This process results in freestanding, transparent, and flexible films of pure levan and MMT-levan composites plasticized by 10-15 wt% water. XRD patterns from levan-MMT composites indicate an MMT interlayer spacing 0.62 nm greater than that of the starting MMT, suggesting re-stacking of MMT platelets coated by adsorbed, uncoiled levan molecules. FTIR results suggest that levan adheres to MMT via water-mediated hydrogen bonding between the levan's hydroxyl groups and MMT surface oxygens. MMT-levan composites have improved thermal stability and a well-defined glass transition temperature that increases with MMT loading. The tensile moduli of levan-MMT composites increase by as much as 480% relative to pure levan. The XRD and mechanical property results suggest that MMT reinforces levan through a filler network structure composed of MMT platelets bridged by adsorbed levan molecules, enhanced when the MMT loading becomes high enough (5-10wt% MMT) to induce an isotropic-nematic transition in MMT platelet orientation. PMID:24299812

Chen, Xiaoming; Gao, Hongsheng; Ploehn, Harry J

2014-01-30

110

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

111

Effect of montmorillonite on drug release from polymeric matrices.  

PubMed

Drug release from matrices of polyvinyl alcohol was affected by molecular weight and solubility of the drugs (either sodium salicylate or papaverine hydrochloride), and by the matrix loading. - Montmorillonite addition to the matrix formulation modified only the release constant of papaverine hydrochloride owing to drug interaction with the clay by an ionic exchange process. The kinetics exponent was affected a little bit by interaction of the drug with montmorillonite, whereas the influence of the matrix loading was more remarkable. PMID:2624524

Forni, F; Iannuccelli, V; Coppi, G; Bernabei, M T

1989-11-01

112

Homogeneous and heterogeneous asymmetric reactions. Part X: Enantioselective hydrogenations over K-10 montmorillonite supported noble metal catalysts with immobilized modifier 1 Part IX: B. Török, J. Wölfling, Gy. Schneider, M. Bartók, Asymmetric transfer hydrogenation of steroid 17-ketones in the presence of rhodium(I) complexes, React. Kinet. Catal. Lett. 64 (1998) 35. 1  

Microsoft Academic Search

The preparation, characterization and application of new K-10 montmorillonite supported noble metal catalysts containing immobilized chiral modifier are described. The active contents of the catalysts were Pt, Pd and Rh, while cinchonidine was used as chiral modifier. The preparation was carried out by two methods. Method I consists of the modification of the parent K-10 montmorillonite by direct surface reaction

Katalin Balázsik; Béla Török; Gerda Szakonyi; Mihály Bartók

1999-01-01

113

Influence of montmorillonite on antimicrobial activity of tetracycline and ciprofloxacin  

NASA Astrophysics Data System (ADS)

Antibiotics are used not only to fight infections and inhibit bacterial growth, but also as growth promotants in farm livestock. Farm runoff and other farm-linked waste have led to increased antibiotic levels present in the environment, the impact of which is not completely understood. Soil, more specifically clays, that the antibiotic contacts may alter its effectiveness against bacteria. In this study a swelling clay mineral montmorillonite was preloaded with antibiotics tetracycline and ciprofloxacin at varying concentrations and bioassays were conducted to examine whether the antibiotics still inhibited bacterial growth in the presence of montmorillonite. Escherichia coli was incubated with montmorillonite or antibiotic-adsorbed montmorillonite, and then the number of viable bacteria per mL was determined. The antimicrobial activity of tetracycline was affected in the presence of montmorillonite, as the growth of non-resistant bacteria was still found even when extremely high TC doses were used. Conversely, in the presence of montmorillonite, ciprofloxacin did inhibit E. coli bacterial growth at high concentrations. These results suggest that the effectiveness of antimicrobial agents in clayey soils depends on the amount of antibiotic substance present, and on the interactions between the antibiotic and the clays in the soil, as well.

Lv, Guocheng; Pearce, Cody W.; Gleason, Andrea; Liao, Libing; MacWilliams, Maria P.; Li, Zhaohui

2013-11-01

114

A nanomedicine to treat ocular surface inflammation: performance on an experimental dry eye murine model.  

PubMed

MUC5AC is a glycoprotein with gel-forming properties, whose altered expression has been implicated in the pathogenesis of dry eye disease. The aim of our study was to achieve an efficient in vivo transfection of MUC5AC, restore its normal levels in an inflamed ocular surface and determine whether restored MUC5AC levels improve ocular surface inflammation. Cationized gelatin-based nanoparticles (NPs) loaded with a plasmid coding a modified MUC5AC protein (pMUC5AC) were instilled in healthy and experimental dry eye (EDE) mice. MUC5AC expression, clinical signs, corneal fluorescein staining and tear production were evaluated. Ocular specimens were processed for histopathologic evaluation, including goblet cell count and CD4 immunostaining. Neither ocular discomfort nor irritation was observed in vivo after NP treatment. Expression of modified MUC5AC was significantly higher in ocular surface tissue of pMUC5AC-NP-treated animals than that of controls. In healthy mice, pMUC5AC-NPs had no effect on fluorescein staining or tear production. In EDE mice, both parameters significantly improved after pMUC5AC-NP treatment. Anterior eye segment of treated mice showed normal architecture and morphology with lack of remarkable inflammatory changes, and a decrease in CD4+ T-cell infiltration. Thus, pMUC5AC-NPs were well tolerated and able to induce the expression of modified MUC5A in ocular surface tissue, leading to reduction of the inflammation and, consequently improving the associated clinical parameters, such as tear production and fluorescein staining. These results identify a potential application of pMUC5AC-NPs as a new therapeutic modality for the treatment of dry eye disease. PMID:22809996

Contreras-Ruiz, L; Zorzi, G K; Hileeto, D; López-García, A; Calonge, M; Seijo, B; Sánchez, A; Diebold, Y

2013-05-01

115

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

Microsoft Academic Search

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

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

1989-01-01

116

Adhesive forces and surface properties of cold gas plasma treated UHMWPE  

PubMed Central

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.

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

2014-01-01

117

Surface properties of indium tin oxide treated by Cl2 inductively coupled plasma  

NASA Astrophysics Data System (ADS)

The effects of Cl2 inductively coupled plasma (ICP) treatment on the time dependence of work function (WF) and surface properties of indium tin oxide (ITO) were investigated. Kelvin probe (KP) measurements show that the WF after Cl2 ICP treatment is close to 5.9 eV. The WF decrease curve of Cl2 plasma treated ITO is fitted with double exponential functions with an adjusted R-square of 0.99. The mechanism under the decrease process is discussed by X-ray photoelectron spectroscopy (XPS). The ITO WF decrease after Cl2 ICP treatment performs much better than that after O2 ICP treatment and the chlorinated ITO keeps a WF increment of 0.3 eV compared with that without plasma treatment after 100 days. Other properties of chlorinated ITO surface such as morphology and transmittance change slightly. The results are significant for the understanding of degradation of Cl2 plasma treated ITO and the fabrication of organic semiconductor devices.

He, Kongduo; Yang, Xilu; Yan, Hang; Gong, Junyi; Zhong, Shaofeng; Ou, Qiongrong; Liang, Rongqing

2014-10-01

118

Behavior of codling moth (Lepidoptera: Tortricidae) neonate larvae on surfaces treated with microencapsulated pear ester.  

PubMed

Codling moth, Cydia pomonella (L.), larvae cause severe internal feeding damage to apples, pears, and walnuts worldwide. Research has demonstrated that codling moth neonate first instar larvae are attracted to a pear-derived kairomone, ethyl (2E,4Z)-2,4-decadienoate, the pear ester (PE). Reported here are the behavioral activities of neonate codling moth larvae to microencapsulated pear ester (MEC-PE) applied in aqueous solutions to both filter paper and apple leaf surfaces that were evaluated over a period of up to 20 d of aging. In dual-choice tests the MEC-PE treatment elicited attraction to and longer time spent on treated zones of filter papers relative to water-treated control zones for up to 14 d of aging. A higher concentration of MEC-PE caused no preferential response to the treated zone for the first 5 d of aging followed by significant responses through day 20 of aging, suggesting sensory adaptation as an initial concentration factor. Estimated emission levels of PE from treated filter papers were experimentally calculated for the observed behavioral thresholds evident over the aging period. When applied to apple leaves, MEC-PE changed neonate walking behavior by eliciting more frequent and longer time periods of arrestment and affected their ability to find the leaf base and stem or petiole. Effects of MEC-PE on extended walking time and arrestment by codling moth larvae would increase temporal and spatial exposure of neonates while on leaves; thereby potentially disrupting fruit or nut finding and enhancing mortality by increasing the exposure to insecticides, predation, and abiotic factors. PMID:22732619

Light, Douglas M; Beck, John J

2012-06-01

119

Adsorption of HCN onto sodium montmorillonite dependent on the pH as a component to chemical evolution  

NASA Astrophysics Data System (ADS)

The aim of this work is to study the behaviour of hydrogen cyanide (HCN) adsorbed onto mineral surfaces (sodium montmorillonite, a clay mineral) in different pH environments as a possible prebiotic process for complexation of organics. Our experimental results show that specific sites on the surface of the clay increased the concentration of HCN molecules dependent on the pH values. Moreover, this adsorption can occur through physical and chemical interactions enhanced by the channel structure of the sodium montmorillonite. The three-dimensional channelling structure of the clay accumulates the organics, hindering the releasing (desorption) of the organic molecules. A molecular model developed here also confirms the role of the pH as a regulating factor in the adsorption of HCN onto the inorganic surfaces and the possibility for further reactions forming more complex molecules, as an abiotic mechanism important in prebiotic chemical evolution processes.

Colin-Garcia, M.; Heredia, A.; Negron-Mendoza, A.; Ortega, F.; Pi, T.; Ramos-Bernal, S.

2014-10-01

120

Surface treated titanium dioxide nanoparticles as inorganic UV filters in sunscreen products.  

PubMed

TiO(2) nanoparticles were used in this research as an inorganic UV absorber for preparation of a sunscreen that ensures optically transparent films with adequate SPF. TiO(2) nanoparticles in rutile crystal form, produced in Cinkarna Celje, were used in this research. The elementary principle of the nanograde TiO(2) production is the sulphate synthesis process, which is upgraded for the synthesis of final nano product. TiO(2) nanoparticles were subsequently surface modified by coating with sodium silicate as the source of silica. The resulting silica coated TiO(2) nanoparticles were examined by scanning (SEM) and transmission electron microscopy (TEM). Uniform particles distribution and homogeneous amorphous coatings, formed in heterogeneous nucleation of silica molecules on the surface of TiO(2) nanoparticles, were observed. Sun-protection factor (SPF) of 28 was determined for sunscreen with incorporated 9.0 wt. % TiO(2) nanoparticles, surface treated with 5.0 wt. % silica according to the "Method for the In Vitro Determination of UVA Protection Provided by Sunscreen Products". PMID:25286215

Veronovski, Nika; Lešnik, Maja; Lubej, Andrej; Verhovšek, Dejan

2014-01-01

121

Plasma surface modification of aluminum alloy samples treated with argon discharge conditioning  

SciTech Connect

The study of change in surface properties of metals and their alloys under plasma processing has a wide range of applications. It affords range, flexibility, ease and accuracy of process control at low cost as compared to other techniques. All the applications of non-equilibrium plasmas involve processes like sputtering, etching, polymerization, surface modification, etc. It is expected for industries to get a final product with specific properties with high reliability and repeatability. Stainless steel is used to construct UHV chambers. A comparative study of outgassing rates show that SS can be replaced by aluminium alloy for UHV chambers. Turbomoleculer Pumping Unit evacuates a cylindrical discharge chamber of SS304 with various ports on it. A hollow cathode DC glow discharge in argon for different discharge pressures and for different discharge current densities respectively, is used for treating chemically cleaned ASA6063 aluminium alloy samples, keeping all other parameters constant. TMP unit evacuates SS304 chamber to a base pressure 3 x 10{sup {minus}7}mbar. The processing gas argon is introduced through a leak valve and with the help of a throttling valve the pressure in the discharge chamber is adjusted to the operating pressure 10{sup {minus}2}mbar. The wall temperature and discharge time were the same in all treatments. The Scanning Electron Microscope (SEM) is used to examine processed surfaces and to study topographical features.

Karandikar, S.J.; Samant, C.C.; Gogawale, S.V.

1999-07-01

122

40 CFR 721.10223 - Styrenyl surface treated manganese ferrite with acrylic ester polymer (generic).  

Code of Federal Regulations, 2011 CFR

...treated manganese ferrite with acrylic ester polymer (generic). 721.10223 Section...treated manganese ferrite with acrylic ester polymer (generic). (a) Chemical substance...treated manganese ferrite with acrylic ester polymer (PMN P-09-582) is subject to...

2011-07-01

123

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

124

The origin of the pozzolanic activity of calcined clay minerals: A comparison between kaolinite, illite and montmorillonite  

SciTech Connect

This paper investigates the decomposition of three clayey structures (kaolinite, illite and montmorillonite) when thermally treated at 600 {sup o}C and 800 {sup o}C and the effect of this treatment on their pozzolanic activity in cementitious materials. Raw and calcined clay minerals were characterized by the XRF, XRD, {sup 27}Al NMR, DTG and BET techniques. Cement pastes and mortars were produced with a 30% substitution by calcined clay minerals. The pozzolanic activity and the degree of hydration of the clinker component were monitored on pastes using DTG and BSE-IA, respectively. Compressive strength and sorptivity properties were assessed on standard mortars. It was shown that kaolinite, due to the amount and location of OH groups in its structure, has a different decomposition process than illite or montmorillonite, which results in an important loss of crystallinity. This explains its enhanced pozzolanic activity compared to other calcined clay-cement blends.

Fernandez, Rodrigo, E-mail: fernandezrod@gmail.co [Laboratory of Construction Materials, IMX, Ecole Polytechnique Federale de Lausanne, 1015 Lausanne (Switzerland); Martirena, Fernando [Centro de Investigacion y Desarrollo de Estructuras y Materiales (CIDEM), Universidad Central 'Marta Abreu' de Las Villas, 54830 Santa Clara (Cuba); Scrivener, Karen L. [Laboratory of Construction Materials, IMX, Ecole Polytechnique Federale de Lausanne, 1015 Lausanne (Switzerland)

2011-01-15

125

Interaction of sodium dodecylsulfate (SDS) with homoionic montmorillonites: adsorption isotherms and metal-ion release  

Microsoft Academic Search

The interaction of dodecylsulfate anions (DS-) with homoionic Ca-, Mg-, Ni-, Cu-, Cd-, Pb- and Fe-montmorillonites were investigated. Mg- and Cd-montmorillonite do not adsorb DS-, and an anion exchange at the edges of the clay mineral does not take place. Three different adsorption processes are identified on the other montmorillonites: i) Fe-montmorillonite is covered with amorphous iron hydroxide, and DS--anions

M. Ilic; J. González; A. Pohlmeier; H. D. Narres; M. J. Schwuger

1996-01-01

126

The structure of chiral phenylethylammonium montmorillonites in ethanol-toluene mixtures  

Microsoft Academic Search

Chiral phenylethyl alkylammonium montmorillonites were prepared by ion exchange of Na montmorillonite (from Wyoming). The\\u000a structure of chiral montmorillonite organocomplexes was studied in the dry state by X-ray diffraction, IR spectroscopy and\\u000a 13C cross-polarized MAS NMR and after swelling by X-ray diffraction. The phenylethylammonium ions are intercalated in montmorillonite\\u000a in a monolayer structure, while higher derivatives containing alkyl chains with

B. Török; M. Bartók; I. Dékány

1999-01-01

127

The Performance of Ce Surface Treated Ferritic Stainless Steels for Solid Oxide Fuel Cell Interconnects  

SciTech Connect

This research deals with the effect of a Ce surface treatment on the behavior of Fe-Cr-Mn ferritic stainless steels which may have application in SOFC technology. This treatment consisted of applying a slurry of CeO2 and a halide activator to the surface of coupons. After the slurry dried the coupons were heated to 900C in a controlled atmosphere furnace for 12 hours. The effectiveness of the treatment on commercial (Type 409 (12Cr), Type 430 (18Cr), Crofer 22APU (22Cr), Type 446(26Cr)) and experimental (NETL F9 (12Cr) and NETL F5 (22Cr)) alloys as a function of Cr content will be presented. The oxidation behavior of the alloys was assessed by exposing coupons (untreated and treated) to moist air at 800C. Area specific resistance (ASR) was measured at 800C. In general, the rare earth treatment effectively reduced the oxidation rate, resulting in thinner oxide scales and less internal oxidation.

Alman, D.E.; Jablonski, P.D.

2007-09-01

128

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

129

[Joint prostheses components of warm-forged and surface treated Ti-6Al-7Nb alloy].  

PubMed

In 1978 development of a TiAl alloy with the inert alloying element niobium was initiated. In 1984, the optimal composition was found to be Ti-6Al-7Nb (Protasul-100). This custom-made alloy for implants has the same alpha/beta micro-structure and equally good mechanical properties as Ti-6Al-4V. The corrosion resistance of Ti-6Al-7Nb is better than that of pure titanium and Ti-6Al-4V, due to the very dense and stable passive layer. Since 1985, highly stressed anchoring stems of various hip prosthesis designs have been manufactured from hot-forged Ti-6Al-7Nb/Protasul-100. Polished surfaces of hip, knee or wrist joints made of Ti-6Al-7Nb intended to articulate with polyethylene are surface-treated by the application of a very hard, 3-5 microns thick titanium nitride coating (Tribosul-TiN), or by oxygen diffusion hardening (Tribosul-ODH) to a depth of 30 microns. PMID:1859861

Semlitsch, M; Weber, H; Streicher, R M; Schön, R

1991-05-01

130

Modified montmorillonite as vector for gene delivery.  

PubMed

Currently, gene delivery systems can be divided into two parts: viral or non-viral vectors. In general, viral vectors have a higher efficiency on gene delivery. However, they may sometimes provoke mutagenesis and carcinogenesis once re-activating in human body. Lots of non-viral vectors have been developed that tried to solve the problems happened on viral vectors. Unfortunately, most of non-viral vectors showed relatively lower transfection rate. The aim of this study is to develop a non-viral vector for gene delivery system. Montmorillonite (MMT) is one of clay minerals that consist of hydrated aluminum with Si-O tetrahedrons on the bottom of the layer and Al-O(OH)2 octahedrons on the top. The inter-layer space is about 12 A. The room is not enough to accommodate DNA for gene delivery. In the study, the cationic hexadecyltrimethylammonium (HDTMA) will be intercalated into the interlayer of MMT as a layer expander to expand the layer space for DNA accommodation. The optimal condition for the preparation of DNA-HDTMA-MMT is as follows: 1 mg of 1.5CEC HDTMA-MMT was prepared under pH value of 10.7 and with soaking time for 2 h. The DNA molecules can be protected from nuclease degradation, which can be proven by the electrophoresis analysis. DNA was successfully transfected into the nucleus of human dermal fibroblast and expressed enhanced green fluorescent protein (EGFP) gene with green fluorescence emission. The HDTMA-MMT has a great potential as a vector for gene delivery in the future. PMID:16488006

Lin, Feng-Huei; Chen, Chia-Hao; Cheng, Winston T K; Kuo, Tzang-Fu

2006-06-01

131

Formation of RNA oligomers on montmorillonite: site of catalysis  

NASA Technical Reports Server (NTRS)

Certain montmorillonites catalyze the self condensation of the 5'-phosphorimidazolide of nucleosides in pH 8 aqueous electrolyte solutions at ambient temperatures leading to formation of RNA oligomers. In order to establish the nature of the sites on montmorillonite responsible for this catalytic activity, oligomerization reactions were run with montmorillonites which had been selectively modified (I) at the edges by (a) fluoride treatment, (b) silylation, (c) metaphosphate treatment of the anion exchange sites (II) in the interlayer by (a) saturation with quaternary alkylammonium ions of increasing size, (b) aluminum polyoxo cations. High pressure liquid chromatography, HPLC, analysis of condensation products for their chain lengths and yields indicated that modification at the edges did not affect the catalytic activity to a significant extent, while blocking the interlayer strongly inhibited product formation.

Ertem, G.; Ferris, J. P.

1998-01-01

132

Adsorptive property of Cu2+-ZnO/cetylpyridinium-montmorillonite complexes for pathogenic bacterium in vitro.  

PubMed

Cu(2+)-ZnO/cetylpyridinium-montmorillonite (Cu(2+)-ZnO/CP-MMT) complexes were prepared using montmorillonite (MMT), Cu(2+), Zn(2+), and cetylpyridinium (CP). The goal was to assess comparatively the adsorption properties of Cu(2+)-ZnO/CP-MMT in vitro using pathogenic Escherichia coli. The results showed that Cu(2+)-ZnO/CP-MMT adsorbed significantly (P<0.05) more E. coli compared with the parent clay. The adsorption process of bacterial cells occurring on the modified MMT surface reached equilibrium after 90 min. The percentages of E. coli adsorbed onto the surfaces of Cu(2+)-ZnO/CP-MMT and MMT in adsorption equilibrium were 84.66% and 47.01%, respectively. Adsorption data from the bacteria-clay systems followed the Langmuir and Freundlich isotherms, but not the BET isotherm. Adsorption of E. coli in acidic medium was higher than in alkaline medium. The extent of bacteria adsorption onto the modified MMT increased with decreasing ionic strength, and with increasing temperature. The processes of E. coli adsorption onto the tested adsorbents were endothermic and spontaneous at the experimental temperature. The mechanism of adsorption of bacteria on Cu(2+)-ZnO/CP-MMT may involve enhanced hydrophobicity and the reversal of surface charge from negative to positive. PMID:20554164

Ma, Yu-Long; Yang, Bo; Xie, Li

2010-09-01

133

Possible selective adsorption of enantiomers by Na-montmorillonite  

NASA Technical Reports Server (NTRS)

Racemic amino acids including (D,L) alpha-alamine, (D,L) alpha-aminobutyric acid, (D,L) valine, and (D,L) norvaline were incubated with Na-montmorillonite at 100% CEC at three hydrogen ion concentrations, and amino acid adsorption was determined by ion exchange chromatography. Enantiomers were analyzed by gas chromatography. Differences in the quantities of D and L enantiomers in any of the fractions was no larger than a few percent. Although a large difference in the adsorption of the amino acid enantiomers was not observed, the analysis may indicate a small preferential adsorption (0.5-2%) of L-amino acids by Na-montmorillonite.

Friebele, E.; Shimoyama, A.; Ponnamperuma, C.

1981-01-01

134

Chitosan intercalated montmorillonite: Preparation, characterization and cationic dye adsorption  

Microsoft Academic Search

Chitosan intercalated montmorillonite (Chi-MMT) was prepared by dispersing sodium montmorillonite (Na+-MMT) into chitosan solution at 60 °C for 24 h. The Chi-MMT was characterized by XRD, XRF and FT-IR. The intercalation was accomplished via the ion-exchange of Na+ ions with –NH3+ of chitosan, resulting in the expansion of d001 from 1.42 nm of Na+-MMT to 2.21 nm of Chi-MMT. The chitosan content in the

Pathavuth Monvisade; Punnama Siriphannon

2009-01-01

135

Treating of produced water for surface discharge at the Arun gas condensate field  

SciTech Connect

Mobil`s Arun Field in northern Sumatra produces natural gas, hydrocarbon liquids and water condensate. Purification of the water for surface disposal is the subject of this paper. The Arun waste water contains about 2,000 ppm of liquid hydrocarbons in the form of a very stable oil-in-water emulsion. Stability of the emulsion is enhanced by the small diameters of the oil droplets, low salt content of the water and low pH. The water is saturated with carbon dioxide and hydrocarbon gases which bubble from the water when pressure is released. Returns of acids, surfactants, emulsifying agents and corrosion inhibitors from acid fracturing operations also contribute to the composition of Arun waste water. Increases in waste water production, now about 32,000 BPD, and relatively high concentrations of BOD, phenols and ammonia have prompted Mobil to upgrade the Arun waste water treating facilities to protect the receiving bodies of water from contamination. The upgrade focused on two areas of water treating: (1) removal of suspended liquid hydrocarbons from the water; and (2) biological oxidation of dissolved organics. Demulsifier chemical and a skim tank were added to the oil removal facility; the decarbonator and caustic addition before air flotation were eliminated. Without added caustic, the gas flotation units remove acid gases from the water very effectively. The new skim tank removes over 90% of the suspended hydrocarbons. The biological oxidation ponds were upgraded by adding barriers to improved plug flow, increasing dispersed air flow, increasing sludge recycle volume, lowering the oil input and by adding nutrients and biological seeding. Results of the biological pond upgrades are not yet available because increased sludge recirculation and the optimization of biological seeding are not yet completed. Tests of the use of locally-produced biological sludge are planned.

Madian, E.S.; Moelyodihardjo, T.; Snavely, E.S.; Jan, R.J.

1995-11-01

136

Properties of thermo-chemically surface treated carbon fibers and of their epoxy and vinyl ester composites  

SciTech Connect

High strength carbon fibers were surface treated by a continuous gas phase thermo-chemical surface treatment. The surface and the mechanical properties of the fibers were investigated before and after treatment and compared to the properties obtained with a conventional industrial electro-chemical surface treatment. An increase of the oxygen atomic content from 3 % to 20 % with a preferential generation of carboxylic acid functionalities and hydroxyl groups was highlighted after the thermo-chemical surface treatment, compared to an oxygen atomic content of 7 % and a wide variety of oxygen moieties with the electro-chemical surface treatment. The tensile strength of the fibers increased slightly after the thermo-chemical surface treatment and remained the same after the electro-chemical surface treatment. Short beam shear and 90 flexural tests of composites revealed that the improvement of interfacial adhesion with a vinyl ester matrix was limited, revealing that oxidation of the carbon fiber surface alone cannot tremendously improve the mechanical properties of carbon fiber-vinyl ester composites. Atomic force microscopy showed that the creation of roughness with both surface treatments at a nanometric scale. Although the surface is slightly rougher after the electro-chemical surface treatment and is expected to lead to higher adhesion due to mechanical interlocking between the fiber surface and the matrix, the effect of covalent bonding coming from the high concentration of chemical groups on the surface results in higher adhesion strength, as obtained with the thermo-chemical surface treatment.

Vautard, Frederic [ORNL; Ozcan, Soydan [ORNL; Meyer III, Harry M [ORNL

2012-01-01

137

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

138

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

139

Surface chemistry and optical property of TiO{sub 2} thin films treated by low-pressure plasma  

SciTech Connect

The low temperature RF plasma treatment was used to control the surface chemistry and optical property of TiO{sub 2} thin films deposited by RF magnetron sputtering with a very good uniformity at 300 deg. C substrate heating temperature. The XRD pattern indicates the crystalline structure of the film could be associated to amorphous structure of TiO{sub 2} in thin film. The plasma treatment of TiO{sub 2} film can increase the proportion of Ti{sup 3+} in Ti2p and decrease in carbon atoms as alcohol/ether group in C1s at the surface. The optical transmittance of the film was enhanced by 50% after the plasma treatment. The surface structure and morphology remain the same for untreated and low-pressure plasma-treated films. Therefore, increase in the optical transmission could be due to change in surface chemistry and surface cleaning by plasma treatment. - Graphical abstract: The surface chemistry and surface states of TiO{sub 2} films was modified using low-pressure RF plasma treatment. The surface roughness and crystalline structure remain unchanged for low-pressure plasma-treated films. There was an increase in the Ti{sup 3+} surface states of Ti2p at the surface and this can be useful to increase the photocatalytic activities of TiO{sub 2} films. The proportion of carbon atoms as carboxyl group in C1s was also increased after plasma treatment. All the plasma-treated films show a higher optical transmittance when untreated and it was increased when the power was increased. The increase in the optical transmission could be due to surface cleaning of films by plasma treatment and possibly due to change in the surface chemistry.

Dhayal, Marshal [Liquid Crystal and Self Assembled Monolayer Section, Engineering Material Division, National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi 110012 (India)], E-mail: marshaldhayal@yahoo.com; Jun, Jin [Department of Environmental Engineering, Dongshin University, 252 Deaho-dong, Naju, Chonnam (Korea, Republic of); Gu, Hal Bon; Hee Park, Kyung [Department of Electrical Engineering, Chonnam National University, 300 Yongbong-dong, Buk-gu, Gwangju (Korea, Republic of)

2007-10-15

140

Polymorphism of spray-dried microencapsulated sulfamethoxazole with cellulose acetate phthalate and colloidal silica, montmorillonite, or talc.  

PubMed

Sulfamethoxazole was microencapsulated with cellulose acetate phthalate and talc, colloidal silica, or montmorillonite clay by a spray-drying technique. The surface topography of the products varied with the type of excipient used and the pH of the suspending medium. The products without the excipient were coated with flake-like crusts, while the products containing the excipient tended to become well-rounded spheres. In addition, the crystalline form of sulfamethoxazole converted from Form I to an amorphism and Form II during the spray-drying process. This polymorphic transformation was attributed to the interaction of cellulose acetate phthalate with sulfamethoxazole. Increasing the concentration of cellulose acetate phthalate in the formulation increased the attainment of amorphism. Form II was also obtained by freeze and vacuum drying. Talc was the only excipient that contributed to polymorphism, which occurred in the alkaline suspension medium. Montmorillonite products prepared from the acidic medium exhibited an exothermic differential scanning calorimetry thermogram, which might be interpreted in terms of adsorption of the fused sulfamethoxazole with the internal surface of montmorillonite, PMID:6271946

Takenaka, H; Kawashima, Y; Lin, S Y

1981-11-01

141

Sol–gel transitions of sodium montmorillonite dispersions  

Microsoft Academic Search

The flow behavior of sodium montmorillonite dispersions at salt concentrations below the critical coagulation concentration is determined by the influence of the ionic double layers on the mobility of the particles (secondary electroviscous effect). At solid contents above 3% the dispersions became gel-like with the appearance of a yield value and viscoelastic properties. Increasing salt concentration reduced the thickness of

S. Abend; G. Lagaly

2000-01-01

142

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

143

Establishment and Evaluation of the Vegetative Community in A Surface Flow Constructed Wetland Treating Industrial Park Contaminants  

Microsoft Academic Search

A surface flow constructed wetland, designed to curve in a kidney shape in order to increase the length to width ratio to 5:1 was used to treat runoff from an industrial park. A natural wetland system located approximately 200 m downstream of the constructed wetland was selected to act as the vegetative community model for the constructed wetland. The selected

C. C. Galbrand; A. M. Snow; A. E. Ghaly; R. Côté

2008-01-01

144

Influences of surface chemistry and swelling of salt-treated polyelectrolyte multilayers on migration of smooth muscle cells  

PubMed Central

The cell migration plays a crucial role in a variety of physiological and pathological processes and can be regulated by the cell–substrate interactions. We found previously that the poly(sodium 4-styrenesulphonate) (PSS)/poly(diallyldimethylammonium) chloride (PDADMAC) multilayers post-treated in 1–5 M NaCl solutions result in continuous changes of their physico-chemical properties such as thickness, chemical composition, surface charge, swelling ratio and wettability. In this study, the responses of human smooth muscle cells (SMCs) on these salt-treated multilayers, particularly the governing factors of cellular migration that offer principles for designing therapeutics and implants, were disclosed. The cell migration rate was slowest on the 3 M NaCl-treated multilayers, which was comparable with that on tissue culture plates, but it was highest on 5 M NaCl-treated multilayers. To elucidate the intrinsic mechanisms, cell adhesion, proliferation, adhesion and related gene expressions were further investigated. The SMCs preferred to attach, spread and proliferate on the PSS-dominated surfaces with well-organized focal adhesion and actin fibres, especially on the 3 M NaCl-treated multilayers, while were kept round and showed low viability on the PDADMAC-dominated surfaces. The relative mRNA expression levels of adhesion-related genes such as fibronectin, laminin and focal adhesion kinase, and migration-related genes such as myosin IIA and Cdc42 were compared to explain the different cellular behaviours. These results reveal that the surface chemistry and the swelling of the salt-treated multilayers govern the cell migration behaviours. PMID:22896570

Han, Lulu; Mao, Zhengwei; Wu, Jindan; Zhang, Yuying; Gao, Changyou

2012-01-01

145

A comparative study of the acidity toward the aqueous phase and adsorptive properties of Al{sub 13}-pillared montmorillonite and Al{sub 13}-pillared saponite  

SciTech Connect

The selectivity of an Al{sub 13}-pillared saponite and an Al{sub 13}-pillared montmorillonite for Cd{sup 2+} and Cu{sup 2+} adsorption was studied. The quantity of metal adsorbed on both pillared clays depends on the pH of the solution and the pillars density. Adsorption equilibria are regulated by the protonation equilibria of the amphoteric sites on the pillars. Pillared clays adsorb more cadmium and copper than classic aluminum hydroxides which is simply attributable to a higher density of surface aluminum groups. Significant differences in behavior are observed between pillared montmorillonite and pillared saponite. Pillared montmorillonite appears to be more acidic, which is correlated with a more advanced degree of structural modification of the pillars on calcination. The authors propose a tentative, partial structural model of pillar transformation compatible with these differences. At the same time, both pillared clays have similar affinities for cadmium II at low pH (5--6), but pillared montmorillonite seems to be a more efficient cadmium trap at pH = 8 when its surface groups are negatively ionized. Thus, the nature of the clay layers conditions the structural modifications of the intercalated [Al{sub 13}] polycations, which in turn determine adsorptive behavior.

Bergaoui, L.; Mrad, I.; Ghorbel, A. [Faculte des Sciences de Tunis (Tunisia). Lab. de Chimie des Materiaux et Catalyse] [Faculte des Sciences de Tunis (Tunisia). Lab. de Chimie des Materiaux et Catalyse; Lambert, J.F. [Univ. Pierre et Marie Curie, Paris (France). Lab. de Reactivite de Surface] [Univ. Pierre et Marie Curie, Paris (France). Lab. de Reactivite de Surface

1999-04-15

146

Removal of hexavalent chromium from aqueous solution using exfoliated polyaniline/montmorillonite composite.  

PubMed

Exfoliated polyaniline/montmorillonite (PANI/MMT) composites with nanosheet structure were successfully prepared by in situ chemical oxidation polymerization with MMT platelets as the scaffold. Amphoteric polymer, (2-methacryloyloxyethyl)trimethyl ammonium chloride and methacrylate acid copolymer, was used to modify montmorillonite and a large number of carboxylic acids were introduced on the surface of the clay platelets, which can be used as a dopant of PANI and play a 'bridge' role to combine PANI with clay. Adsorption experiments were carried out to study the effects of pH, contact time, Cr(VI) concentration, adsorbent dose and temperature. The adsorption of Cr(VI) on the PANI/MMT was highly pH dependent and the adsorption kinetics followed a pseudo-second-order model. The Langmuir isothermal model described the adsorption isotherm data well and the maximum adsorption capacity increased with the increase in temperature. Thermodynamic investigation indicated that the adsorption process is spontaneous, endothermic and marked with an increase in randomness at the adsorbent - liquid interface. The maximum adsorption capacity of the PANI/MMT composites for Cr(VI) was 308.6 mg/g at 25 °C. The excellent adsorption characteristic of exfoliated PANI/MMT composites will render it a highly efficient and economically viable adsorbent for Cr(VI) removal. PMID:25116498

Chen, Jun; Hong, Xiaoqin; Zhao, Yongteng; Zhang, Qianfeng

2014-01-01

147

Adsorption and degradation of model volatile organic compounds by a combined titania-montmorillonite-silica photocatalyst.  

PubMed

A series of adsorptive photocatalysts, combined titania-montmorillonite-silica were synthesized. The resultant photocatalysts consisted of more and more spherically agglomerated TiO(2) particles with increasing of TiO(2) content, and anatase was the only crystalline phase with nano-scale TiO(2) particles. With increasing of the cation exchange capacity to TiO(2) molar ratio, specific surface area and pore volume increased very slightly. In a fluidized bed photocatalytic reactor by choosing toluene, ethyl acetate and ethanethiol as model pollutants, all catalysts had relatively high adsorption capacities and preferred to adsorb higher polarity pollutants. Langmuir isotherm model better described equilibrium data compared to Freundlich model. Competitive adsorptions were observed for the mixed pollutants on the catalysts, leading to decrease adsorption capacity for each pollutant. The combined titania-montmorillonite-silica photocatalyst exhibited excellent photocatalytic removal ability to model pollutants of various components. Almost 100% of degradation efficiency was achieved within 120 min for each pollutant with about 500 ppb initial concentration, though the efficiencies of multi-component compounds slightly decreased. All photocatalytic reactions followed the Langmuir-Hinshelwood model. Degradation rate constants of multi-component systems were lower than those for single systems, following the order of toluene

Chen, Jiangyao; Li, Guiying; He, Zhigui; An, Taicheng

2011-06-15

148

Adsorption of cationic monomeric and gemini surfactants on montmorillonite and adsolubilization of vitamin E.  

PubMed

Adsorption of a cationic gemini surfactant (1,2-bis(dodecyldimethylammonio) ethane dibromide, 12-2-12) and the corresponding monomeric surfactant (dodecyltrimethylammonium bromide, DTAB) on montmorillonite has been characterized with a combination of adsorption isotherm, interlayer spacing and FT-IR spectroscopic data. Adsolubilization of vitamin E into the adsorbed surfactant layers has also been studied. The adsorption isotherm data reveal that the adsorption of the two surfactants is driven by the two factors: one is the cation exchange that occurs on the interlayer basal planes and the other is the hydrophobic interaction between hydrocarbon chains of the surfactants. Although the adsorbed amount measured in the saturation region (in mol g(-1)) is almost identical for the two surfactants, the conformation of the intercalated surfactant molecules differs significantly from each other. The adsorption of DTAB results in a lateral bilayer arrangement in the limited interlayer space, whereas 12-2-12 gives a normal bilayer arrangement in the expanded interlayer space. Adsolubilization of vitamin E takes place into the adsorbed surfactant layers, and interestingly, all the vitamin E molecules added in the montmorillonite suspensions are hybridized at lower surfactant concentrations due to the great specific surface area of the clay material. Since the maximum adsolubilization amount is usually obtained just below the critical micelle concentration, the gemini surfactant is deemed to be more efficient than the corresponding monomeric one to achieve the great adsolubilization amount. PMID:18622125

Sakai, Kenichi; Nakajima, Erimi; Takamatsu, Yuichiro; Sharma, Suraj C; Torigoe, Kanjiro; Yoshimura, Tomokazu; Esumi, Kunio; Sakai, Hideki; Abe, Masahiko

2008-01-01

149

Surface analytical characterisation of Nd:YAG-laser pre-treated Al Mg3 as a preparation for bonding  

NASA Astrophysics Data System (ADS)

The contribution summarises results of the surface pre-treatment of Al Mg3 (EN-AW-5754) for bonding applications. Mainly the sheet samples were irradiated with a pulsed solid-state laser in different atmospheres. Afterwards the pre-treated surfaces were analysed by quantitative topographic measurements, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and electrochemical impedance spectroscopy (EIS). The effect of surface pre-treatment on the strength of adhesively bonded specimens was evaluated by tensile lap-shear strength tests. The results were compared with conventional pre-treatment methods, such as anodic oxidation and others.

Langer, M.; Rechner, R.; Thieme, M.; Jansen, I.; Beyer, E.

2012-07-01

150

Evaluation of surface roughness of a plasma treated polymeric membrane by wavelet analysis and quantification of its enhanced performance  

NASA Astrophysics Data System (ADS)

The change in roughness of polyethersulfone (PES) ultrafiltration membranes by plasma treatment is quantified by atomic force microscopy (AFM). A wavelet-based analysis of surface morphology images from AFM is used to evaluate the surface roughness changes of polymeric membranes. Discrete wavelet transform with 3D image analysis is used to capture patterns at all relevant frequency scales — which are not possible with other traditional techniques of image analysis. The hydrophilic nature and roughness of the membrane surfaces are related to fouling over the membrane surfaces with associated change in solvent flux. The changes in flux of the plasma treated membranes are quantified by measuring the enhancement in flux of a model solution of bovine serum albumin (BSA). The results clearly demonstrate that a PES membrane being more hydrophilic and having smoother surface by optimal treatment of cold CO 2 plasma is easier to clean and the augmented permeability can be retained in successive use.

Pal, S.; Ghatak, S. K.; De, S.; DasGupta, S.

2008-12-01

151

Hydration and hydrolysis of samarium (III) in montmorillonite clay: a neutron diffraction study  

NASA Astrophysics Data System (ADS)

Neutron diffraction with isotopic substitution was carried out at room temperature on hydrated samples of Sm montmorillonite, prepared at pH = 4 and 8, in order to find out whether Sm is present as aqueous Sm(OH)3o, Sm3+, or intermediate hydrolyzed species, and how it is linked to the clay surface. It was found that the number of hydrogen atoms (5.5 ± 2.0) nearest to Sm3+ at pH = 4 is equal to or even slightly smaller than that of oxygen atoms (7.5 ± 1.0). This means that Sm3+ is bound to the clay surface and it is probably partially hydrolyzed. This result is very close to those obtained earlier for Yb3+ and Nd3+, despite the different methods of sample preparation and the different mineralogy of the samples.

Sobolev, O.; Charlet, L.; Cuello, G. J.; Gehin, A.; Brendle, J.; Geoffroy, N.

2008-03-01

152

PARAMETERS OF TREATED STAINLESS STEEL SURFACES IMPORTANT FOR RESISTANCE TO BACTERIAL CONTAMINATION  

EPA Science Inventory

Use of materials that are resistant to bacterial contamination could enhance food safety during processing. Common finishing treatments of stainless steel surfaces used for components of poultry processing equipment were tested for resistance to bacterial attachment. Surface char...

153

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

Microsoft Academic Search

The leaching of nickel from the surface of porous Nitinol (PNT) is mainly dependent on its surface characteristics, which\\u000a can be controlled by appropriate surface treatments. In this investigation, PNT was subjected to two surface treatments, namely,\\u000a water-boiling and dry-heating passivations. Phosphate buffer saline (PBS) solutions obtained from cyclic potentiodynamic polarization\\u000a tests on PNT were employed to assess the cytotoxicity

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

2011-01-01

154

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

155

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

156

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

157

Mechanisms of pore water organic matter adsorption to montmorillonite  

Microsoft Academic Search

The extent and mechanisms of adsorption of marine pore water organic matter to montmorillonite were studied in a series of batch and sequential adsorption experiments. Pore water natural organic matter (pNOM) and easily extracted natural organic matter (eNOM) were collected from Liberty Bay (Puget Sound, WA, USA) sediments. The pNOM and eNOM were each divided into two size fractions using

Thorarinn S. Arnarson; Richard G. Keil

2000-01-01

158

Effect of the intercalation conditions of a montmorillonite with octadecylamine  

Microsoft Academic Search

Intercalation of montmorillonite with octadecylamine under several conditions is reported. Octadecylamine was protonated in situ with HCl to obtain octadecylammonium cations. Water and water\\/ethanol mixtures were used as reaction medium, and the ratios amine\\/clay and HCl\\/amine were also varied. Intercalation was successful when the amine\\/clay ratio was in the range 1–3 mmol\\/g; optimal results were obtained for an amine\\/clay ratio

A. Pérez-Santano; R. Trujillano; C. Belver; A. Gil; M. A. Vicente

2005-01-01

159

Modeling Arsenate Competitive Adsorption on Kaolinite, Montmorillonite and Illite  

Microsoft Academic Search

The adsorption of arsenate (As(V)) on kaolinite, montmorillonite and illite was investigated at varying pH and competing anion concentration while holding As(V) concentration (6.7 x 10 7 M), clay suspension density (2.5 g L 1) and ionic strength (0.1 M NaC1) constant. The effects of 2 concen- trations of phosphate (P) or molybdate (Mo) (6.7 X 10 -7 and 6.7

Bruce A. Manning; S. GOLDBERG

1996-01-01

160

Interlayer water structure in Na- and Li-montmorillonite clays  

NASA Astrophysics Data System (ADS)

We measured the neutron diffraction patterns of dry Li-montmorillonite and its D2O hydrate at an incident wavelength of 1.057 Å. We used a difference method to obtain the diffraction pattern due to the interlayer water. Comparison with data for liquid D2O shows that the interlayer water has a liquid-type structure, although water molecules may be associated with specific crystallographic sites.

Powell, D. H.; Tongkhao, Kowut; Kennedy, Shane J.; Slade, Phillip G.

1998-04-01

161

A quantitative model for the surface restructuring of repeatedly plasma treated silicone rubber  

Microsoft Academic Search

Surface restructuring in ambient air of medical grade silicone rubber surfaces modified by repeated RF plasma treatments using\\u000a various discharge gases including oxygen, argon, carbon dioxide and ammonia, was studied quantitatively. From advancing and\\u000a receding water contact angle data, the fraction of the surface covered by mobile and immobile polar groups, and a characteristic\\u000a time constant of the restructuring process

Emmanuel P. Everaert; Ronald C. Chatelier; Henny C. van der Mei; Henk J. Busscher

1997-01-01

162

The effect of cerium surface treated ferritic stainless steel current collectors on the performance of solid oxide fuel cells (SOFC)  

SciTech Connect

Laboratory scale solid oxide fuel cells (“button” cells) were operated with untreated or cerium surface treated Fe–22Cr–0.5Mn composition by weight percent, wt%) ferritic stainless steel current collectors attached to the cathode. After a brief stabilization (or “burn-in”) period, the power density of a cell with the untreated current collector rapidly decreased. By contrast, there was little degradation in power density during testing of cells with the cerium surface treated current collectors. The difference in degradation was attributed to differences in Cr build-up within the cathode. It should be emphasized that the duration of the tests were quite short and longer duration testing is required, however, this initial assessment indicates the treatment may benefit the performance of SOFC with steel interconnects.

Alman, D.E.; Johnson, C.D.; Collins, W.K.; Jablonski, P.D.

2007-06-01

163

Morphology of enamel surfaces treated with topical fluoride agents: SEM considerations.  

PubMed

Three topical fluoride agents deposited surface coatings of different morphology and thickness on intact human enamel surfaces. The agents studied were an acidic silane fluoride lacquer, a neutral NaF lacquer, and an APF gel. Each agent reacted with the enamel surface differently, producing its own distinctive etching pattern. The smallest particles observed in the surface coatings were from 20 to 30 nm in diameter and appeared to have indistinct morphologies. They often agglomerated into spherical globules ranging from 1-3 micron in diameter. PMID:6581197

Nelson, D G; Jongebloed, W L; Arends, J

1983-12-01

164

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

165

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

166

Plasma surface modification of aluminium alloy samples treated with argon discharge conditioning  

Microsoft Academic Search

Summary form only given. The study of change in surface properties of metals and their alloys under plasma processing has a wide range of applications. It affords range, flexibility, ease and accuracy of process control at low cost as compared to other techniques. All the applications of non-equilibrium plasmas involve processes like sputtering, etching, polymerization, surface modification, etc. It is

S. J. Karandikar; C. C. Samant; S. V. Gogawale

1999-01-01

167

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

168

Susceptibility of the bedbug, Cimex lectularius, to selected insecticides and various treated surfaces  

Microsoft Academic Search

Adult bedbugs, Cimex lectularius, were exposed for 24h (25°C) to filter paper treated with various dilutions of the technical grade of nine insecticides dissolved in acetone to determine the concentration-response relationships. The order of toxicity, from most to least based on the LCso's was: dichlorvos, pirimiphos methyl, lambda-cyhalothrin, bendiocarb, permethrin, malathion, carbaryl, tetrachlorvinphos, and fenvalerate. The residual toxicities of commercial

M. G. FLETCHER; R. C. AXTELL

1993-01-01

169

Grain structure and homogeneity of pulsed laser treated surfaces on Al-aerospace alloys and FSWs  

Microsoft Academic Search

The effect of pulsed excimer laser surface treatment, on typical Al-aerospace alloys and friction stir weld substrates, has been studied. A thin <10?m deep surface layer can be achieved, where the majority of the re-solidified material does not exhibit phase separation, and has a higher level of homogeneity relative to the substrate material. However, due to the extremely short melt

P. Ryan; P. B. Prangnell

2008-01-01

170

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

171

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

172

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

173

Surface structure and corrosion resistance of short-time heat-treated NiTi shape memory alloy  

NASA Astrophysics Data System (ADS)

NiTi alloys are attractive materials that are used for medicine, however, Ni-release may cause allergic reactions in an organism. The Ni-release rate is strongly affected by the surface state of the NiTi alloy that is mainly determined by its processing route. In this study, a NiTi shape memory alloy (50.9 at.% Ni) was heat-treated by several regimes simulating the shape setting procedure, the last step in the manufacture of implants. Heating temperatures were between 500 and 550 °C and durations from 5 to 10 min. Heat treatments were performed in air at normal and low pressure and in a salt bath. The purpose of the treatments was to obtain and compare different surface states of the Ni-Ti alloy. The surface state and chemistry of heat-treated samples were investigated by electron microscopy, X-ray photoelectron spectroscopy and Raman spectrometry. The amount of nickel released into a model physiological solution of pH 2 and into concentrated HCl was taken as a measure of the corrosion rate. It was found that the heat treatments produced surface TiO 2 layers measuring 15-50 nm in thickness that were depleted in nickel. The sample covered by the 15-nm thick oxide that was treated at 500 °C/5 min in a low pressure air showed the best corrosion performance in terms of Ni-release. As the oxide thickness increased, due to either temperature or oxygen activity change, Ni-release into the physiological solution accelerated. This finding is discussed in relation to the internal structure of the oxide layers.

Vojt?ch, D.; Vod?rová, M.; Fojt, J.; Novák, P.; Kubásek, T.

2010-12-01

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

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

177

Surface Morphological Study of Low Temperature Plasma Treated Wool - A Time Dependence Study  

Microsoft Academic Search

Due to the ecological and economic restrictions, which are increasingly imposed on the textile industry, the development of environmentally friendly and economic processes is required. In wool processes such as printing, dyeing and anti-felting finishing, the wool surface morphology plays an important role. A number of investigations revealed that low temperature plasma (LTP) provided an alternative way, as an environmentally

C. W. Kan

178

Apparent diffusion coefficients and chemical species of neptunium (V) in compacted Na-montmorillonite  

Microsoft Academic Search

Diffusion of neptunium (V) in compacted Na-montmorillonite was studied through the non-steady state diffusion method. In this study, two experimental attempts were carried out to understand the diffusion mechanism of neptunium. One was to establish the diffusion activation energy, which was then used to determine the diffusion process in the montmorillonite. The other was the measurement of the distribution of

Naofumi Kozai; Koichi Inada; Tamotsu Kozaki; Seichi Sato; Hiroshi Ohashi; Tsunetaka Banba

2001-01-01

179

Organo-montmorillonite as substitute of carbon black in natural rubber compounds  

Microsoft Academic Search

The use of octadecylamine modified montmorillonite as substitute of carbon black in natural rubber (NR) compounds is studied. Rubber with 10 parts per hundred resin (phr) of pristine (clay) and octadecylamine modified montmorillonite (organoclay) were compared with 10 and 40phr carbon black as filler. The modified silicate is analysed by X-ray, FTIR and thermogravimetric analysis. Vulcametric curves show that the

M Arroyo; M. A López-Manchado; B Herrero

2003-01-01

180

Electrical treeing in EVA-Boehmite and EVA-Montmorillonite nanocomposites  

Microsoft Academic Search

The present experimental work focuses on the growth of electrical treeing inside different Ethylene-vinyl acetate (EVA) nanocomposites containing Bohemite (an aluminum oxide hydroxide) and Montmorillonite (a phyllosilicate clay mineral) nanoparticles. Bohemite and Montmorillonite particles have different aspect ratios: the first one has a nanometric cube-like symmetry, while the latter has a typical layered structure. The results evidence that the growth

F. Guastavino; A. Dardano; G. C. Montanari; L. Testa; F. Bellucci

2009-01-01

181

Removal of basic dye from water onto pristine and HCl-activated montmorillonite in fixed beds  

Microsoft Academic Search

The removal of a basic dye from water onto pristine montmorillonite and HCl-activated montmorillonites in fixed beds was investigated. Experiments were carried out as a function of liquid flow rate, influent dye concentration, and column length. The adsorption capacity of basic dye onto pristine clay could be largely improved when the clay is activated by HCl. The mathematical models that

Min-Yu Teng; Su-Hsia Lin

2006-01-01

182

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

183

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

PubMed

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. PMID:11537376

Ferris, J P; Ertem, G; Kamaluddin; Agarwal, V; Hua, L L

1989-01-01

184

Ca/Na montmorillonite: structure, forces and swelling properties.  

PubMed

Ca/Na montmorillonite and natural Wyoming bentonite (MX-80) have been studied experimentally and theoretically. For a clay system in equilibrium with pure water, Monte Carlo simulations predict a large swelling when the clay counterions are monovalent, while in presence of divalent counterions a limited swelling is obtained with an aqueous layer between the clay platelets of about 10 A. This latter result is in excellent agreement with X-ray scattering data, while dialysis experiments give a significantly larger swelling for Ca montmorillonite in pure water. Obviously, there is one "intra-lamellar" and a second "extra-lamellar" swelling. Montmorillonite in contact with a salt reservoir containing both Na(+) and Ca(2+) counterions will only show a modest swelling unless the Na(+) concentration in the bulk is several orders of magnitude larger than the Ca(2+) concentration. The limited swelling of clay in presence of divalent counterions is a consequence of ion-ion correlations, which reduce the entropic repulsion as well as give rise to an attractive component in the total osmotic pressure. Ion-ion correlations also favor divalent counterions in a situation with a competition with monovalent ones. A more fundamental result of ion-ion correlations is that the osmotic pressure as a function of clay sheet separation becomes nonmonotonic, which indicates the possibility of a phase separation into a concentrated and a dilute clay phase, which would correspond to the "extra-lamellar" swelling found in dialysis experiments. This idea also finds support in the X-ray scattering spectra, where sometimes two peaks corresponding to different lamellar spacings appear. PMID:20235552

Segad, M; Jönsson, Bo; Akesson, T; Cabane, B

2010-04-20

185

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

186

Remediation studies of trace metals in natural and treated water using surface modified biopolymer nanofibers  

NASA Astrophysics Data System (ADS)

In this study, remediation results of trace metals in natural water and treated water using three functionalized nanofiber mats of cellulose and chitosan are reported. The nanofiber materials, packed in mini-columns, were employed for the remediation of five toxic trace metals (Cd, Pb, Cu, Cr and Ni) from natural water samples. Trace metals in real water samples were undetectable as the concentrations were lower than the instrument’s detection limits of 0.27 × 10-3 (Cd) and 4.2 × 10-2 (Pb) ?g mL-1, respectively. However, after percolation through the functionalised biosorbents in cartridges, detectability of the metal ions was enhanced. The starting volume of the natural water sample was 100 mL, which was passed through a column containing the nanofibers sorbent and the retained metals eluted with 5 mL of 2.0 M nitric acid. The eluate was analyzed for metals concentrations. An enrichment factor of 20 for the metals was realized as a result of the pre-concentration procedure applied to handle the determination of the metals at trace levels. The order of remediation of the studied metals using the nanofibers was as follows: chitosan/PAM-g-furan-2,5-dione < cellulose-g-furan-2,5-dione < cellulose-g-oxolane-2,5-dione. The modified biopolymer nanofibers were able to adsorb trace metals from the river water and treated water, thereby confirming their capability of water purification. These materials are proposed as useful tools and innovative approach for improving the quality of drinking for those consumers in small scale households.

Musyoka, Stephen Makali; Ngila, Jane Catherine; Mamba, Bhekie B.

187

Surface Investigation of Bone Tissue Treated with Non-thermal Plasmas  

NASA Astrophysics Data System (ADS)

Plasma treatment of bio-materials is a technique directly derived from material surface processing. In future it may lead to a plasma-based cure for various skin and bone diseases. Non-thermal atmospheric plasmas for medical treatment have been developed. In this work we use a low-pressure discharge as a model case to study plasma interactions with bone tissue. The samples have been exposed to the plasma, using different gases (argon, krypton, helium, and oxygen in mixture) and analyzed using infrared spectroscopic ellipsometry. This technique gives accurate information on the chemical composition of the surface of the tissue. Results have been compared with EDX, environmental scanning electron microscopy (ESEM), and nano-indentation. We have also performed some ion beam diagnostics like RBS and ERDA. These complementary experiments allow us to determine the element composition of the bone tissue. The particular effects of plasma treatment on the tissue can be related to the plasma parameters.

Cigal, J.-C.; Maurice, C. Y. M.; Wagenaars, E.; van Ijzendoorn, L. J.; Baede, A. H. F. M.; Stoffels, E.; Huiskes, R.; Kroesen, G. M. W.

2002-10-01

188

Occurrence of pharmaceuticals and hormones in drinking water treated from surface waters  

Microsoft Academic Search

The levels of a wide variety of pharmaceuticals and hormones, in source and potable-water supplies of French drinking water\\u000a treatment plants, were assessed. In surface waters, 27 of the 51 target compounds were determined at least once. Paracetamol,\\u000a salicylic acid and carbamazepine were quantified in more than 80% of samples. The highest concentration of 71 ng\\/L was observed\\u000a for paracetamol. Twelve other substances

Emmanuelle Vulliet; Cécile Cren-Olivé; Marie-Florence Grenier-Loustalot

2011-01-01

189

Synthesis and properties of polystyrene-organoammonium montmorillonite hybrid  

Microsoft Academic Search

Summary  \\u000a Styrene monomer was mixed with quaternary ammonium montmorillonites(org-MMTs) and polymerized in the presence of radical initiator.\\u000a The resulting materials showed an expansion of interlayer distance. These hybrid materials exhibited higher thermal stability\\u000a compared with the virgin polystyrene(PS) or PS\\/pristine-MMT microcomposite. PS\\/Bz-MMT, containing benzyl-unit similar to styrene\\u000a in org-MMT, exhibited higher decomposition temperature even for MMT loading as low as

Jae Goo Doh; Iwhan Cho

1998-01-01

190

Monte Carlo molecular simulation of the hydration of K-montmorillonite at 353 K and 625 bar.  

PubMed

Monte Carlo molecular simulations of the hydration of K-saturated Wyoming-type montmorillonite at constant stress in the NPzzT ensemble and at constant chemical potential in the grand canonical muVT ensemble, under basin-like conditions of 353 K and 625 bar, show a strong tendency of the K+ ions to adhere to the siloxane surface, forming predominant inner-sphere complexes with tetrahedral oxygen atoms and adsorbed water molecules. Simulations in the grand canonical ensemble predict that none of the K-montmorillonite hydrates, the one-, two-, and three-layer hydrates, are stable in this environment of high depth, temperature, and pressure. The most nearly stable configuration corresponds to the one-layer hydrate, characterized by a d001 spacing of 12.75 A, the adsorbed water being 60 molecules/layer or 180.83 mg of H2O/g of clay, an internal energy of -22.73 kcal/mol, an interlayer density of 0.365 g/mL, and a pressure tensor, Pzz, of 1999.9 bar. The interlayer structure consists of two close layers of water molecules 0.50 A from the midplane, with broad shoulders on the sides, the protons oriented toward the midplane and the siloxane surfaces, and the K+ ions close to the clay surfaces and on the interlayer midplane. PMID:15544414

Chávez, M de Lourdes; de Pablo, Liberto; de Pablo, Juan J

2004-11-23

191

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

192

Surface Analytical Study of CuInSe2 Treated in Cd-Containing Partial Electrolyte Solution  

SciTech Connect

Junction formation in CuInSe2 (CIS) has been studied by exposing thin films and single-crystal samples to solutions containing NH4OH and CdSO4. The treated samples were analyzed by secondary ion mass spectrometry to determine the amount and distribution of Cd deposited on the surface of the films. Cadmium is found to react with the surface for all the solution exposure times and temperatures studied. The reaction rapidly approaches the endpoint and remains relatively unchanged for subsequent solution exposure. Cadmium in-diffusion, as measured by secondary ion mass spectrometry, is obscured by topography effects in the thin-film samples and by ion-beam mixing and topography in the single-crystal sample.

Asher, S. E.; Ramanathan, K.; Wiesner H.; Moutinho, H. (National Renewable Energy Laboratory); Niles, D. W. (Hewlett-Packard Corporation)

1998-11-19

193

pH profile of the adsorption of nucleotides onto montmorillonite. II - Adsorption and desorption of 5-prime-AMP in iron-calcium montmorillonite systems  

NASA Technical Reports Server (NTRS)

The interaction of 5-prime-AMP with montmorillonite saturated with various ratios of two metals found ubiquitously on the surface of earth, that is, iron and calcium, is investigated. Adsorption and desorption of the nucleotide were studied in the pH range of 2-12 at three levels of addition: 0.080, 0.268 and 0.803 mmole 5-prime-AMP per gram of clay. Two desorption stages were employed - H2O wash and NaOH extraction (pH = 12.0). 5-prime-AMP was preferentially adsorbed on the Fe-containing clays relative to the Ca clay. The nucleotide was fully recovered by the two desorption stages, mostly by the NaOH extraction. The evidence at hand indicates that 5-prime-AMP reaction with clay is affected by electrostatic interactions involving both attraction and repulsion forces. Some specific adsorption, possibly the result of covalent bonding and complex formation with the adsorbed ion, cannot be ruled out for iron but does not appear to operate for calcium. Changes in pH cause varying degrees of attaction and repulsion of 5-prime-AMP and may have been operating on the primitive earth, leading to sequences of adsorption and release of this biomolecule.

Banin, A.; Lawless, J. G.; Mazzurco, J.; Church, F. M.; Margulies, L.; Orenberg, J. B.

1985-01-01

194

Comprehensive study of hydrostatic pressure treated human umbilical cord blood cells via response surface method.  

PubMed

Amelioration of the survival parameters of cryopreserved samples after thawing has already been addressed through several techniques including vitrification to avoid the formation of ice cores. However, this approach cannot be followed in the case of samples with higher volumes. Hydrostatic pressure (HP) treatment has been proven to increase some qualifying parameters (e.g., motility, insemination efficiency) of certain biological samples. Accordingly, the preparation of umbilical cord blood (UCB) samples through an active (mechanical) pre-stressing process to increase the survival rate of cryopreserved samples can be regarded as a novel strategy that calls for basic experimental studies. The goal of our study was to assess the effects of HP treatment on the qualifying parameters (DNA fragmentation by agarose gel electrophoresis and capillary electrophoresis, Total Nucleotide Cell (TNC) count, CD34+/CD45+ count, and superoxide dismutase activity (SOD) of human umbilical cord blood (UCB) derived cells). The experimental arrangement was set to provide data for response-surface analysis to take into account the common effects of the individual variables of pressure and time exposure. 3D visualization of experimental data revealed that 50-min long HP treatment at 12.5MPa can significantly (?=0.05) enhance white blood cell (WBC) and CD34+/CD45+ cell counts. However no DNA fragmentation was observed even at higher pressures, SOD activity was triggered over 15.0MPa. As a conclusion, HP treatment may contribute to the optimal cryopreservation of UCB cells by significantly increasing WBC and CD34+/CD45+ cell counts without adverse effects neither on DNA stability nor on triggering SOD activity. PMID:25106745

Száraz, Leonóra; Szénási, Dóra; Oldak, Tomasz; Balogh, István

2014-10-01

195

Greenhouse gas emissions from surface flow and subsurface flow constructed wetlands treating dairy wastewater.  

PubMed

Agricultural wastewater treatment is important for protecting water quality in rural ecosystems, and constructed wetlands are an effective treatment option. During treatment, however, some C and N are converted to CH(4), N(2)O, respectively, which are potent greenhouse gases (GHGs). The objective of this study was to assess CH(4), N(2)O, and CO(2) emissions from surface flow (SF) and subsurface flow (SSF) constructed wetlands. Six constructed wetlands (three SF and three SSF; 6.6 m(2) each) were loaded with dairy wastewater in Truro, Nova Scotia, Canada. From August 2005 through September 2006, GHG fluxes were measured continuously using transparent steady-state chambers that encompassed the entire wetlands. Flux densities of all gases were significantly (p < 0.01) different between SF and SSF wetlands changed significantly with time. Overall, SF wetlands had significantly (p < 0.01) higher emissions of CH(4) N(2)O than SSF wetlands and therefore had 180% higher total GHG emissions. The ratio of N(2)O to CH(4) emissions (CO(2)-equivalent) was nearly 1:1 in both wetland types. Emissions of CH(4)-C as a percentage of C removal varied seasonally from 0.2 to 27% were 2 to 3x higher in SF than SSF wetlands. The ratio of N(2)O-N emitted to N removed was between 0.1 and 1.6%, and the difference between wetland types was inconsistent. Thus, N(2)O emissions had a similar contribution to N removal in both wetland types, but SSF wetlands emitted less CH(4) while removing more C from the wastewater than SF wetlands. PMID:20176819

VanderZaag, A C; Gordon, R J; Burton, D L; Jamieson, R C; Stratton, G W

2010-01-01

196

Ammonia emissions from surface flow and subsurface flow constructed wetlands treating dairy wastewater.  

PubMed

Agricultural wastewater treatment is important for maintaining water quality, and constructed wetlands (CW) can be an effective treatment option. However, some of the N that is removed during treatment can be volatilized to the atmosphere as ammonia (NH(3)). This removal pathway is not preferred because it negatively impacts air quality. The objective of this study was to assess NH(3) volatilization from surface flow (SF) and subsurface flow (SSF) CWs. Six CWs (3 SF and 3 SSF; 6.6 m(2) each) were loaded with dairy wastewater ( approximately 300 mg L(-1) total ammoniacal nitrogen, TAN = NH(3)-N + NH(4)(+)-N) in Nova Scotia, Canada. From June through September 2006, volatilization of NH(3) during 12 or 24 h periods was measured using steady-state chambers. No differences (p > 0.1) between daytime and nighttime fluxes were observed, presumably due in part to the constant airflow inside the chambers. Changes in emission rates and variability within and between wetland types coincided with changes in the vegetative canopy (Typha latifolia L.) and temperature. In SSF wetlands, the headspace depth also appeared to affect emissions. Overall, NH(3) emissions from SF wetlands were significantly higher than from SSF wetlands. The maximum flux densities were 974 and 289 mg NH(3)-N m(-2) d(-1) for SF and SSF wetlands, respectively. Both wetland types had similar TAN mass removal. On average, volatilization contributed 9 to 44% of TAN removal in SF and 1 to 18% in SSF wetlands. Results suggest volatilization plays a larger role in N removal from SF wetlands. PMID:18948455

VanderZaag, A C; Gordon, R J; Burton, D L; Jamieson, R C; Stratton, G W

2008-01-01

197

Sorption and Fractionation of a Peat Derived Humic Acid by Kaolinite, Montmorillonite, and Goethite *1 *1 Project supported by the Federal Hatch Program, USA (No. MAS 8532); the Cheung Kong Scholar Program, Ministry of Education of China; and the CSREES, USDA National Research Initiative Competitive Grants Program, USA (No. 2005-35107-15278)  

Microsoft Academic Search

Sorption of humic acid (HA) on mineral surfaces has a profound interest regarding the fate of hydrophobic organic contaminants (HOCs) and carbon sequestration in soils. The objective of our study is to determine the fractionation behavior of HA upon sorption on mineral surfaces with varying surface properties. HA was coated sequentially on kaolinite (1:1 clay), montmorillonite (2:1 clay), and goethite

S. GHOSH; Zhen-Yu WANG; S. KANG; P. C. BHOWMIK; B. S. XING

2009-01-01

198

Characterization and corrosion protection properties of polypyrrole \\/ montmorillonite electropolymerized onto aluminium alloy 1100  

Microsoft Academic Search

Films of Polypyrrole\\/Montmorillonite (PPy\\/MT) clays were electropolymerized potentiostatically on aluminium alloy 1100, using\\u000a sodium dodecylbenzenesulfonate (SDBS) as a dopant. Two clay species were used: Na+-Montmorillonite (MT-Na) and modified-Montmorillonite (MT-M). The characterization of the PPy\\/MT films performed by XRD and\\u000a TEM shows that the exfoliation method employed, as well the electrochemical polymerization method used in this work, allow\\u000a nanocomposite materials to

Kátia R. L. Castagno; Viviane Dalmoro; Raquel S. Mauler; Denise S. Azambuja

2010-01-01

199

Oligomerization reactions of deoxyribonucleotides on montmorillonite clay - The effect of mononucleotide structure on phosphodiester bond formation  

NASA Technical Reports Server (NTRS)

The formation of oligomers from deoxynucleotides, catalyzed by Na(+)-montmorillonite, was investigated with special attention given to the effect of the monomer structure on the phosphodiester bond formation. It was found that adenine deoxynucleotides bind more strongly to montmorillonite than do the corresponding ribonucleotides and thymidine nucleotides. Tetramers of 2-prime-dpA were detected in the reaction of 2-prime-d-5-prime-AMP with a water-soluble carbodiimide EDAC in the presence of Na(+)-montmorillonite, illustrating the possible role of minerals in the formation of biopolymers on the primitive earth.

Ferris, James P.; KAMALUDDIN

1989-01-01

200

Detect-to-treat: development of analysis of bacilli spores in nasal mucus by surfaced-enhanced Raman spectroscopy  

NASA Astrophysics Data System (ADS)

As the war on terrorism in Afghanistan and Iraq continue, future attacks both abroad and in the U.S.A. are expected. In an effort to aid civilian and military personnel, we have been investigating the potential of using a surface-enhanced Raman spectroscopy (SERS) sampling device to detect Bacillus anthracis spores in nasal swab samples. Such a device would be extremely beneficial to medical responders and management in assessing the extent of a bioterrorist attack and making detect-to-treat decisions. The disposable sample device consists of a glass capillary filled with a silver-doped sol-gel that is capable of extracting dipicolinic acid (DPA), a chemical signature of Bacilli, and generating SERS spectra. The sampling device and preliminary measurements of DPA extracted from spores and nasal mucus will be presented.

Inscore, Frank E.; Gift, Alan D.; Farquharson, Stuart

2004-12-01

201

Development of chitosan/montmorillonite nanocomposites with encapsulated ?-tocopherol.  

PubMed

Nanocomposites of chitosan (CS) were developed and characterized in a full factorial design with varying levels of montmorillonite (MMTNa) and encapsulated tocopherol (toc-encap). The structural properties (XRD, FTIR), morphology (TEM), hygroscopic properties (water vapour permeability, hydrophobicity, sorption isotherms) and optical properties (haze, CIELab parameters) of the resulting materials were evaluated. Toc-encap contents up to 10% influenced the intercalation of MMTNa in the CS matrix, resulting in films with reduced water vapour permeability (3.48×10(-11)(g/msPa)), increased hydrophobicity (?GHydroph |7.93-59.54|mJm(-2)) and lower equilibrium moisture content (EMC), thus showing potential for active food packaging materials. At levels above 10%, toc-encap agglomerates occurred, which deteriorated the properties of the resulting films, as shown with the TEM. As the toc-encap content increased, the films became slightly more yellow, more irregular and less transparent, with a higher haze index. PMID:25038682

Dias, Marali Vilela; Machado Azevedo, Viviane; Borges, Soraia Vilela; Soares, Nilda de Fátima Ferreira; de Barros Fernandes, Regiane Victória; Marques, João José; Medeiros, Eber Antonio Alves

2014-12-15

202

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

203

Removal of 8-quinolinecarboxylic acid pesticide from aqueous solution by adsorption on activated montmorillonites.  

PubMed

Sodium montmorillonite (Na-M), acidic montmorillonite (H-M), and organo-acidic montmorillonite (Org-H-M) were applied to remove the herbicide 8-quinolinecarboxylic acid (8-QCA). The montmorillonites containing adsorbed 8-QCA were investigated by transmission electron microscopy, FT-IR spectroscopy, X-ray diffraction analysis, X-ray fluorescence thermogravimetric analysis, and physical adsorption of gases. Experiments showed that the amount of adsorbed 8-QCA increased at lower pH, reaching a maximum at pH 2. The adsorption kinetics was found to follow the pseudo-second-order kinetic model. The Langmuir model provided the best correlation of experimental data for adsorption equilibria. The adsorption of 8-QCA decreased in the order Org-H-M > H-M > Na-M. Isotherms were also used to obtain the thermodynamic parameters. The negative values of ?G indicated the spontaneous nature of the adsorption process. PMID:23925862

Mekhloufi, M; Zehhaf, A; Benyoucef, A; Quijada, C; Morallon, E

2013-12-01

204

Preparation, Characterization and Application of K-10 Montmorillonite Modified with Chiral Ammonium Halides  

Microsoft Academic Search

Chiral modification of K-10 montmorillonite was carried out with chiral amine salts. The ion-exchanged K-10 samples were characterized by CHN analysis, XRD, FT-IR and Si NMR spectroscopies and tested in catalytic reactions.

Béla Török; György Szöllösi; Mária Rózsa-Tarjáni; Mihály Bartók

1998-01-01

205

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...

206

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

207

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, Jorg

2013-01-01

208

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

209

The effects of mixed quartz-montmorillonite gouge on the frictional sliding of Tennessee sandstone  

E-print Network

THE EFFECTS OF MIXED QUARTZ-MONTMORILLONITE GOUGE ON THE FRICTIONAL SLIDING OP TENNESSEE SANDSTONE A Thesis KIM ANN RAUENZAHN Submitted to the Graduate College of Tesas ASM University in partial fulfillment of the requirements for the degree... oi' MASTER OF SCIENCE December 1985 Major Subject: Geophysics THE EFFECTS OF MIXED QUARTZ-MONTMORILLONITE GOUGE ON THE FRICTIONAL SLIDING OF TENNESSEE SANDSTONE A Thesis KIM ANN RAUENZAHN Approved as to style and content by: r. ohn M. Logan...

Rauenzahn, Kim Ann

2012-06-07

210

Nanoporous Nanocomposite Hydrogels Composed of Polyvinyl Alcohol and Na-montmorillonite  

Microsoft Academic Search

Polyvinyl alcohol nanoporous nanocomposite hydrogels containing various levels of Na-montmorillonite were prepared by a cyclic freezing-thawing technique. An exfoliated morphology of silicate layers was observed for the nanocomposite hydrogels. The uniaxial tensile test indicated that the tensile modulus and tensile strength of the nanocomposite hydrogels increased with increasing Na-montmorillonite content, while their elongation-at-break values decreased. The results showed that by

M. SIROUSAZAR; M. KOKABI; Z. M. HASSAN; A. R. BAHRAMIAN

2012-01-01

211

Influence of clay exfoliation on the physical properties of montmorillonite\\/polyethylene composites  

Microsoft Academic Search

Melt compounding was used to prepare conventional composites of montmorillonite clay and polyethylene (PE) as well as nanocomposites of exfoliated montmorillonite platelets dispersed in a maleated polyethylene (PE-g-MAn) matrix. The extent of clay platelet exfoliation in the PE-g-MAn nanocomposites was confirmed by X-ray diffraction and resulted in a significant reduction of the degree of crystallinity and increased polymer crystallization rates.

T. G. Gopakumar; J. A. Lee; M. Kontopoulou; J. S. Parent

2002-01-01

212

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

213

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

214

Effect of alkyl quaternary ammonium on processing discoloration of melt-intercalated PVC-montmorillonite composites  

Microsoft Academic Search

The effects of alkyl quaternary ammonium on the processing thermal stability of poly (vinyl chloride)\\/alkyl quaternary ammonium modified montmorillonite (PVC\\/OMMT) composites were investigated. PVC\\/sodium montmorillonite (MMT) composites were prepared for comparison. The intercalated PVC\\/OMMT composites exhibited a non-terminal rheological behavior, and showed better mechanical properties and higher thermal degradation stability than the PVC\\/MMT composites. However, under identical melt processing conditions,

Chaoying Wan; Yong Zhang; Yinxi Zhang

2004-01-01

215

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

216

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

217

Optimization by Response Surface Methodology of the adsorption of Coomassie Blue dye on natural and acid-treated clays.  

PubMed

The effect of acid treatment on natural agalmatolite (AN) and natural kaolinite (KN) was investigated, together with the influence of those modifications on the removal of Coomassie Blue (CB) dye. The process was optimized using the Response Surface Methodology (RSM) developed by the application of the quadratic model associated with the Central Composite Design. Adsorption was promoted by initial CB concentration of 25 mg L(-1), pH 2 and adsorbent mass of 0.1 g. The adsorption kinetics study carried out in optimized conditions established that the equilibrium times were 1 h for AN and AA (treated agalmatolite), 4 h for KN and 2 h for KA (treated kaolinite). The kinetics data for AN, KN and KA were best fitted to the pseudo second order model, whilst for AA, the result pointed to the pseudo first order model. In the isotherm of adsorption the maximum quantities were obtained with reference to 11.29 mg g(-1), 9.84 mg g(-1), 22.89 mg g(-1) and 30.08 mg g(-1) for the samples AN, AA, KN and KA respectively. The data fitting showed that the Sips model was the most satisfactory for all the adsorbents. The calculated thermodynamic parameters showed that the process was spontaneous in all the adsorbents, endothermic for the KN and KA samples, exothermic for AN and AA, involved the disorganization of the adsorption system for the KN and KA and its organization for the AN and AA samples. The results showed that the KN and KA samples were more appropriate for use as adsorbents. PMID:24141066

de Sales, Priscila F; Magriotis, Zuy M; Rossi, Marco A L S; Resende, Ricardo F; Nunes, Cleiton A

2013-11-30

218

Effects of Surface Morphology on the Wear and Corrosion Resistance of Post-Treated Nitrided and Nitrocarburized 42CrMo4 Steel  

NASA Astrophysics Data System (ADS)

The surface of alloyed carbon steel was subjected to thermochemical modification by nitrocarburizing and nitriding with or without postoxidation in order to improve its mechanical properties, corrosion, and wear resistance. Treated samples were characterized by testing their basic properties (compound layer thickness, nitriding, nitrocarburizing depth, and surface hardness) according to standards. Detailed estimation of the modified metal surface was performed by additional testing: X-ray diffraction, microstructure, surface roughness and topography, and wear and corrosion resistance. The surface layer obtained after nitrocarburizing treatment consists mainly of ?-Fe2-3(N,C) and ?'-Fe4(N,C); similarly, the nitrided surface is formed by ?-Fe2-3N and ?'-Fe4N iron nitrides. The surface layer after postoxidation contains additionally Fe3O4. The results obtained show that nitrocarburization, nitridation, and postoxidation result in better mechanical, wear, and corrosion resistance of 42CrMo4 steel, and postoxidized sample properties are influenced by surface morphology.

Sola, Ramona; Poli, Giorgia; Veronesi, Paolo; Giovanardi, Roberto

2014-06-01

219

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

220

Comparison of nutrient cycling in a surface-flow constructed wetland and in a facultative pond treating secondary effluent.  

PubMed

There is a growing interest in the possibilities offered by combinations of waste stabilisation ponds (WSP) and constructed wetlands (CW). The purpose of our study was to compare treatment performances and nutrient cycling in a surface-flow wetland (SFW) and in a WSP treating secondary effluent. In the period between 2000 and 2003, a pilot SFW and a pilot WSP were constructed at the outlet of the wastewater treatment plant and their performance monitored while both were active under the same conditions. The SFW was planted with Phragmites australis and Eichhornia crassipes, while in the WSP development of algae was spontaneous. Performance efficiency was monitored by means of evaluation of physical and chemical parameters in water, by measurement of plant productivity and by analysis of N and P contents in biomass. The SFW with macrophytes proved more efficient in decreasing the suspended solids (64.6%), settleable solids (91.8%), organic N (59.3%), total N (38%), COD (67.2%) and BOD5 (72.1%) than the WSP. The WSP with algae was more efficient in treatment of ammonia nitrogen (48.9%) and ortho-phosphate (43.9%). The results of this study provide data that are of help in optimising combinations of SFW and WSP. PMID:16114697

Sajn Slak, A; Bulc, T G; Vrhovsek, D

2005-01-01

221

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

222

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

223

Removal of herbicides from aqueous solutions by modified forms of montmorillonite.  

PubMed

This investigation for the removal of agricultural pollutants, imazaquin and atrazine was conducted using montmorillonite (MMT) exchanged with organic cations through ion exchange. The study found that the adsorption of the herbicides was affected by the degree of organic cation saturations, the size of organic cations and the different natures of the herbicides. The modified clays intercalated with the larger surfactant molecules at the higher concentrations tended to enhance the adsorption of imazaquin and atrazine. In particular, the organoclays were highly efficient for the removal of imazaquin while the adsorption of atrazine was minimal due to the different hydrophobicities. Both imazaquin and atrazine were influenced by the changes of pH. The amphoteric imazaquin exists as an anion at the pH 5-7 and the anionic imazaquin was protonated to a neutral and further a cationic form when the pH is lower. The weak base, atrazine was also protonated at lower pH values. The anionic imazaquin had a strong affinity to the organoclays on the external surface as well as in the interlayer space of the MMT through electrostatic and hydrophobic interactions. In this study, the electrostatic interaction can be the primary mechanism involved during the adsorption process. This study also investigated a comparative adsorption for the imazaquin and atrazine and the lower adsorption of atrazine was enhanced and this phenomenon was due to the synergetic effect. This work highlights a potential mechanism for the removal of specific persistence herbicides from the environment. PMID:24267339

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

2014-02-01

224

Poly(D,?L-lactide-co-glycolide)/montmorillonite nanoparticles for improved oral delivery of exemestane.  

PubMed

The aim of this study was to develop poly(D,L-lactide-co-glycolide)/montmorillonite (PLGA/MMT) nanoparticles formulations for improved oral delivery of exemestane. Exemestane-loaded PLGA nanoparticles and PLGA/MMT nanoparticles were prepared by a modified solvent extraction/evaporation technology with vitamin E succinated polyethylene glycol 1000 (TPGS) as emulsifier. The content of MMT was estimated by thermal gravimetric analysis. The drug encapsulation efficiency and in vitro drug release kinetics were measured by high-performance liquid chromatography. The size, size distribution, surface charge and morphology of the exemestane-loaded nanoparticles were characterized using a Zetasizer Nano ZS and field emission scanning electron microscopy. The physical status of exemestane in the nanoparticles was characterized by differential scanning calorimetry. In vitro cellular uptake of coumarin-6-loaded nanoparticles was investigated by confocal laser scanning microscope, demonstrating that the fluorescence nanoparticles were internalized by Caco-2 cells (as an in vitro gastrointestinal model). The results of in vitro cytotoxicity experiment on MCF-7 cells (as a model of breast cancer cells) showed the exemestane-loaded nanoparticles resulted in lower cell viability versus the pure exemestane solution. The cytotoxicity against MCF-7 cells for exemestane-loaded nanoparticles and pure exemestane solution was dependent on the drug concentration and incubation time. In conclusion, this study indicates the capability of PLGA nanoparticles and PLGA/MMT nanoparticles in enhancing the oral delivery of exemestane. PMID:23517067

Li, Zhen; Liu, Kexin; Sun, Pengyuan; Mei, Lin; Hao, Tangna; Tian, Yan; Tang, Zeyao; Li, Lei; Chen, Dawei

2013-01-01

225

Transparent films based on PLA and montmorillonite with tunable oxygen barrier properties.  

PubMed

Polylactide (PLA) is viewed as a potential material to replace synthetic plastics (e.g., poly(ethylene terephthalate) (PET)) in food packaging, and there have been a number of developments in this direction. However, for PLA to be competitive in more demanding uses such as the packaging of oxygen-sensitive foods, the oxygen permeability coefficient (OP) needs to be reduced by a factor of ~10. To achieve this, a layer-by-layer (Lbl) approach was used to assemble alternating layers of montmorillonite clay and chitosan on extruded PLA film surfaces. When 70 bilayers were applied, the OP was reduced by 99 and 96%, respectively, at 20 and 50% RH. These are, to our knowledge, the best improvements in oxygen barrier properties ever reported for a PLA/clay-based film. The process of assembling such multilayer structures was characterized using a quartz crystal microbalance with dissipation monitoring. Transmission electron microscopy revealed a well-ordered laminar structure in the deposited multilayer coatings, and light transmittance results demonstrated the high optical clarity of the coated PLA films. PMID:22229499

Svagan, Anna J; Åkesson, Anna; Cárdenas, Marité; Bulut, Sanja; Knudsen, Jes C; Risbo, Jens; Plackett, David

2012-02-13

226

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

227

Imazaquin adsorbed on pillared clay and crystal violet-montmorillonite complexes for reduced leaching in soil.  

PubMed

Ground water pollution due to herbicide leaching has become a serious environmental problem. Imazaquin [2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)quinoline-3-carboxylic acid] is an herbicide used to control broadleaf weeds in legume crops. Imazaquin is negatively charged at the basic pH of calcareous soils and exhibits high leaching potential in soils. Our aim was to design formulation of imazaquin to reduce herbicide leaching. Imazaquin sorption on pillared clay (PC) and crystal violet (CV)-montmorillonite complexes was studied. The CV-montmorillonite complexes become positively charged with adsorption of CV above the cation exchange capacity (CEC) of montmorillonite, and thus can sorb imazaquin. The Langmuir equation provides a good fit to isotherms of imazaquin sorption on PC and CV-montmorillonite complexes, but for charged complexes an equation that combines electrostatics with specific binding was preferred. Maximal imazaquin sorption was 17.3 mmol kg-1 for PC and 22.2 mmol kg-1 for CV-montmorillonite complexes. The extents of imazaquin desorption into water were 21% for PC and 5% for CV-clay complexes. The presence of anions decreased imazaquin sorption on both sorbents in the sequence phosphate > acetate > sulfate. Reduction of imazaquin sorption by the anions and the extent of its desorption in electrolyte solutions were higher for PC than for CV-clay complexes. Leaching of imazaquin from CV-montmorillonite formulations through soil (Rhodoxeralf) columns was two times less than from PC formulations and four times less than that of technical imazaquin. The CV-montmorillonite complexes at a loading above the CEC appear to be suitable for preparation of organo-clay-imazaquin formulations that may reduce herbicide leaching significantly. PMID:12371183

Polubesova, Tamara; Nir, Shlomo; Gerstl, Zev; Borisover, Mikhail; Rubin, Baruch

2002-01-01

228

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

229

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

230

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

231

Mechanism of amitriptyline adsorption on Ca-montmorillonite (SAz-2).  

PubMed

The uptake of amitriptyline (AMI) from aqueous environment by Ca-montmorillonite (SAz-2) was studied in a batch system under different physicochemical conditions. The adsorbent was characterized by X-ray diffraction and Fourier transform infrared (FTIR) analyses. The AMI adsorption on SAz-2 obeyed the Langmuir isotherm with a capacity of 330mg/g (1.05mmol/g) at pH 6-7. The adsorption kinetics was fast, almost reaching equilibrium in 2h, and followed a pseudo-second-order kinetic model. Desorption of exchangeable cations correlated with the AMI adsorption well, indicating that cation exchange was the major mechanism. X-ray diffraction patterns showing significant expansions of the d001 spacing and characteristic FTIR band shifts toward higher frequencies after AMI adsorption onto SAz-2 indicated that the adsorbed AMI molecules were intercalated into the interlayers of the mineral. Thermodynamic parameters based on partitioning coefficients suggested that the AMI adsorption was an endothermic physisorption at high adsorption levels. At low and higher AMI adsorption levels, the intercalated AMI molecules take a horizontal monolayer and bilayer conformation, respectively. The higher adsorption capacity suggested that SAz-2 could be a good candidate to remove AMI from wastewater and would be an important environmental sink for the fate and transport of AMI in soils and groundwater. PMID:24373983

Chang, Po-Hsiang; Jiang, Wei-Teh; Li, Zhaohui; Kuo, Chung-Yih; Jean, Jiin-Shuh; Chen, Wan-Ru; Lv, Guocheng

2014-07-30

232

Transport mechanisms of small molecules through polyamide 12/montmorillonite nanocomposites.  

PubMed

The aim of this work is to study the transport of small molecules through the hybrid systems polyamide 12 (PA12)/organo-modified montmorillonite (Cloisite 30B, C30B) prepared by melt blending, using two blending conditions. The transport mechanisms were investigated by using three probe molecules: nitrogen, water, and toluene. While a barrier effect appears clearly with nitrogen, this effect changes with the amount of fillers for water and disappears for toluene. The reduction of permeability for nitrogen is mainly due to the increase of tortuosity. For water and toluene, the permeation kinetics reveals many concomitant phenomena responsible for the permeation behavior. Despite the tortuosity effect, the toluene permeability of nanocomposites increases with C30B fraction. The water and toluene molecules interact differently with fillers according to their hydrophilic/hydrophobic character. Moreover, the plasticization effect of water and toluene in the matrix, involving a concentration-dependent diffusion coefficient, is correctly described by the law D = D(0)e(gammaC). On the basis of Nielsen's tortuosity concept, we suggest a new approach for relative permeability modeling, not only based on the geometrical parameters (aspect ratio, orientation, recovery) but also including phenomenological parameters deduced from structural characterization and permeation kinetics. PMID:20568802

Alexandre, B; Colasse, L; Langevin, D; Médéric, P; Aubry, T; Chappey, C; Marais, S

2010-07-15

233

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

234

Correlation between primary stability and bone healing of surface treated titanium implants in the femoral epiphyses of rabbits.  

PubMed

The aim of this study was to analyse the stability and osseointegration of surface treated titanium implants in rabbit femurs. The implants were either grit-blasted and acid-etched (BE Group), calcium phosphate (CaP) coated by using the electrodeposition technique, or had bioactive molecules incorporated into the CaP coatings: either cyclic adenosine monophosphate (cAMP) or dexamethasone (Dex). Twenty four cylindrical titanium implants (n = 6/group) were inserted bilaterally into the femoral epiphyses of New Zealand White, female, adult rabbits for 4 weeks. Implant stability was measured by resonance frequency analysis (RFA) the day of implantation and 4 weeks later, and correlated to histomorphometric parameters, bone implant contact (BIC) and bone growth around the implants (BS/TS 0.5 mm). The BIC values for the four groups were not significantly different. That said, histology indicated that the CaP coatings improved bone growth around the implants. The incorporation of bioactive molecules (cAMP and Dex) into the CaP coatings did not improve bone growth compared to the BE group. Implant stability quotients (ISQ) increased in each group after 4 weeks of healing but were not significantly different between the groups. A good correlation was observed between ISQ and BS/TS 0.5 mm indicating that RFA is a non-invasive method that can be used to assess the osseointegration of implants. In conclusion, the CaP coating enhanced bone formation around the implants, which was correlated to stability measured by resonance frequency analysis. Furthers studies need to be conducted in order to explore the benefits of incorporating bioactive molecules into the coatings for peri-implant bone healing. PMID:24818874

Rozé, Julie; Hoornaert, Alain; Layrolle, Pierre

2014-08-01

235

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

236

XPS analysis of down stream plasma treated wool: Influence of the nature of the gas on the surface modification of wool  

Microsoft Academic Search

A microwave plasma treatment in a down stream configuration was used to modify the natural hydrophobocity of untreated wool fibers. This property is a consequence of the presence of a Fatty acid monolayer (F-layer) on the outermost part of the fiber surface. The wool fibers treated with plasma were analyzed by means of X-ray photoelectron spectroscopy (XPS) without previous exposure

R. Molina; J. P. Espinós; F. Yubero; P. Erra; A. R. González-Elipe

2005-01-01

237

Study of individual Na-montmorillonite particles size, morphology, and apparent charge.  

PubMed

Size, morphology, and apparent charge of individual Na-montmorillonite particles of natural MX-80 sodium montmorillonite were investigated in the present study by the use of three coupling methods. In the first part of this work, natural and synthetic montmorillonite clays were studied with atomic force microscopy (AFM) and photo-correlation spectroscopy (PCS). Both techniques exhibit the presence of two clay populations with a high dispersion of the length distribution. Microscopic analysis of the system revealed that clay particles could be reasonably approximated at low concentrations to ellipsoidal tactoids about 1.2 nm high. Average dimensions of the first population were typically 320-400 nm long/250 nm wide and 200-250 nm long/120 nm wide for natural and synthetic clays, respectively. The second population exhibits smaller sizes: 65 and 50 nm long and 35 and 25 nm wide for natural and synthetic clays, respectively. The statistics obtained for natural clay were then verified by PCS experiments on sodium montmorillonite suspensions. Both techniques reveal an important length dispersion. However, the relative proportions of the two kinds of particles could not be established properly because of both lack of statistics and limitations of the employed techniques. In the following part, conductivity measurements were performed on dilute montmorillonite clay suspensions. Raw data were then interpreted with the sizes and morphological information gained in the first part of the present work. The apparent charge of the clay sheets was found to be 8% of the structural charge. PMID:15837491

Cadene, A; Durand-Vidal, S; Turq, P; Brendle, J

2005-05-15

238

Protective effect of montmorillonite on plasmid DNA in oral gene delivery into small intestine.  

PubMed

Montmorillonite, a bioinert clay mineral, was examined as a novel vector for an oral gene-delivery system. The complex of montmorillonite and plasmid DNA encoding the enhanced green fluorescent protein (EGFP) gene was prepared at various weight ratios, and then transfected into cultured intestinal epithelial cells (IEC-6) in vitro. The EGFP gene was clearly transcribed when the transfection was performed using the montmorillonite-plasmid complex at a weight ratio of 0.05:1. In contrast, no gene expression was detected by reverse transcription-polymerase chain reaction (RT-PCR) analysis when the transfection was performed with naked plasmid. Various plasmid preparations were given orally to mice, and the gene expression in the stomach and small intestine was examined by RT-PCR. Although no gene expression was detected in the mice receiving an oral administration of naked plasmid or polyethyleneimine-plasmid complex, the EGFP gene complexed with montmorillonite was expressed in the small intestine. These results indicate that montmorillonite protected the plasmid DNA from the acidic environment in the stomach and DNA-degrading enzymes in the intestine, and successfully delivered it into cells of the small intestine. PMID:15577232

Kawase, Masaya; Hayashi, Yuka; Kinoshita, Fumie; Yamato, Eiji; Miyazaki, Jun-Ichi; Yamakawa, Junji; Ishida, Tomoyuki; Tamura, Manabu; Yagi, Kiyohito

2004-12-01

239

Oligomerization reactions of deoxyribonucleotides on montmorillonite clay: the effect of mononucleotide structure on phosphodiester bond formation.  

PubMed

Adenine deoxynucleotides bind more strongly to Na(+)-montmorillonite than do the corresponding ribonucleotides. Thymidine nucleotides binds less strongly to Na(+)-montmorillonite than do the corresponding adenine deoxynucleotides. Oligomers of 2'-dpA up to the tetramer were detected in the reaction 2'-d-5'-AMP with EDAC (a water-soluble carbodiimide) in the presence of Na(+)-montmorillonite. Reaction of 3'-d-5'-AMP with EDAC on Na(+)-montmorillonite yields 3'-d-2',5'-pApA while the reaction of 2'-d-3'-AMP yields almost exclusively 3',5'-cdAMP. The reaction of 5'-TMP under the same reaction conditions give 3',5'-cpTpT and 3',5'-pTpT while 3'-TMP gives mainly 3',5'-cpT. The yield of dinucleotide products (dpNpN) containing the phosphodiester bond is 1% or less when Na(+)-montmorillonite is omitted from the reaction mixture. PMID:11538680

Ferris, J P; Kamaluddin

1989-01-01

240

Low-temperature atomic layer deposition of Al{sub 2}O{sub 3} on blown polyethylene films with plasma-treated surfaces  

SciTech Connect

In this study, a layer of Al{sub 2}O{sub 3} was deposited on blown polyethylene films by atomic layer deposition (ALD) at low temperatures, and the surface characteristics of these Al{sub 2}O{sub 3}-coated blown polyethylene films were analyzed. In order to examine the effects of the plasma treatment of the surfaces of the blown polyethylene films on the properties of the films, both untreated and plasma-treated film samples were prepared under various processing conditions. The surface characteristics of the samples were determined by x-ray photoelectron spectroscopy, as well as by measuring their surface contact angles. It was confirmed that the surfaces of the plasma-treated samples contained a hydroxyl group, which helped the precursor and the polyethylene substrate to bind. ALD of Al{sub 2}O{sub 3} was performed through sequential exposures to trimethylaluminum and H{sub 2}O at 60 Degree-Sign C. The surface morphologies of the Al{sub 2}O{sub 3}-coated blown polyethylene films were observed using atomic force microscopy and scanning electron microscopy/energy-dispersive x-ray spectroscopy. Further, it was confirmed that after ALD, the surface of the plasma-treated film was covered with alumina grains more uniformly than was the case for the surface of the untreated polymer film. It was also confirmed via the focused ion beam technique that the layer Al{sub 2}O{sub 3} conformed to the surface of the blown polyethylene film.

Beom Lee, Gyeong; Sik Son, Kyung; Won Park, Suk; Hyung Shim, Joon; Choi, Byoung-Ho [School of Mechanical Engineering, Korea University, Seoul 136-707 (Korea, Republic of)

2013-01-15

241

Nano-scale structure of Geofluids in Porous Silica and Montmorillonite Clay  

NASA Astrophysics Data System (ADS)

Earth's crust, composed of different rocks with varying degrees of nm- micron scale porosity, is source and reservoir of geofluids, and target for geologic carbon storage (GCS). The specific fluid-rock interactions control formation of fluid deposits, subsurface fluid mobility and mixing, and enhanced recovery processes. Rock pore characterization includes surface chemical identity, pore size distribution, ratio of connected to unconnected porosity and surface roughness. The properties of fluids confined in these pores are altered from bulk due to surface-fluid interactions and confined geometry effects. Changes in density, freezing temperature, and diffusion properties of pore fluids have been observed. Using a combination of neutron scattering and excess sorption measurements the physical properties of pore fluids can be quantified. We study both model systems with well-defined pore morphologies and natural rocks with fractal pore characteristics. Synthetic Porous silica glasses possessing tunable pore sizes of 8 - 50 nm serve as proxies for quartz-rich rocks, including sandstones. Natural rocks studied are sandstone, limestone, and shale. Excess sorption isotherms to silica aerogel and mesoporous CPG10 were measured using a high-pressure sorption balance and a vibrating tube densimeter. Strong adsorption of CO2 to the silica surfaces was found at low fluid pressure, followed by formation of a maximum in the excess sorption isotherm. The excess sorption took small and finally even negative values at high pressure. An inverse temperature dependence of the sorption strength was found in the adsorption region at low and intermediate pressure, while the excess sorption showed little temperature dependence at high pressure. A shift of the excess sorption maximum to higher fluid density was observed with increasing pore width. From small-angle neutron scattering data the density and volume of the sorption phase of pore CO2 was calculated using the Adsorbed Phase Model. The sorption behaviour was modelled using Grand Canonical Monte Carlo simulation, which exactly reproduced the excess sorption isotherm data under the assumption of a weakly attractive solid-fluid interaction potential. Caprocks overlying the porous reservoir rock serve to retain buoyant plumes of CO2. Caprocks can be comprised of thick layers of clay or mudstones, thought to be impenetrable to CO2. To quantify the interactions of caprock with CO2, we measured the excess sorption of supercritical CO2 at Na-montmorillonite clay, a proxy for cap rock materials. Very limited amounts of CO2 adsorbed to this clay mineral at low fluid densities. Using neutron diffraction, the change of the clay interlayer spacing was measured as a function of the CO2 density. A jump-like increase of the interlayer spacing upon CO2 addition was found at low pressures, and remained constant with further additions of CO2. These results indicate suitability of montmorillonite clay for carbon storage caprock applications.

Rother, G.; Gruszkiewicz, M. S.; Vlcek, L.; Cole, D. R.

2012-12-01

242

Photoinduced catalytic adsorption of model contaminants on Bi/Cu pillared montmorillonite in the visible light range  

EPA Science Inventory

Montmorillonite K10 clay was pillared with BiCl3 and Cu(NO3)2 to extend its applicability as catalytic adsorbent to degrade aqueous solution of anionic azo-dye Methyl Orange (MO) in the presence of visible light irradiation. The preparation of Bi/Cu-montmorillonite utilized benig...

243

Competitive Fe(II)-Zn(II) uptake on a synthetic montmorillonite.  

PubMed

The interaction of Fe(II) with clay minerals is of particular relevance in global geochemical processes controlling metal and nutrient cycles and the fate of contaminants. In this context, the influence of competitive sorption effects between Fe(II) and other relevant transition metals on their uptake characteristics and mobility remains an important issue. Macroscopic sorption experiments combined with surface complexation modeling and extended X-ray absorption fine structure (EXAFS) spectroscopy were applied to elucidate competitive sorption processes between divalent Fe and Zn at the clay mineral-water interface. Sorption isotherms were measured on a synthetic iron-free montmorillonite (IFM) under anoxic conditions (O2 <0.1 ppm) for the combinations of Zn(II)/Fe(II) and Fe(II)/Zn(II), where the former metal in each pair represents the trace metal (<10(-7) M) and the latter the competing metal at higher concentrations (10(-7) to 10(-3) M). Results of the batch sorption and EXAFS measurements indicated that Fe(II) is competing with trace Zn(II) for the same type of strong sites if Fe(II) is present in excess, whereas no competition between trace Fe(II) and Zn(II) was observed if Zn(II) is present at high concentrations. The noncompetitive behavior suggests the existence of sorption sites which have a higher affinity for Fe(III), where surface-induced oxidation of the sorbed Fe(II) to Fe(III) occurred, and which are not accessible for Zn(II). The understanding of this competitive uptake mechanism between Fe(II) and Zn(II) is of great importance to assess the bioavailability and mobility of transition metals in the natural environment. PMID:24289476

Soltermann, Daniela; Marques Fernandes, Maria; Baeyens, Bart; Miehé-Brendlé, Jocelyne; Dähn, Rainer

2014-01-01

244

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

245

The microbiological and clinical outcome of guide wire exchanged versus newly inserted antimicrobial surface treated central venous catheters  

PubMed Central

Introduction The management of suspected central venous catheter (CVC)-related sepsis by guide wire exchange (GWX) is not recommended. However, GWX for new antimicrobial surface treated (AST) triple lumen CVCs has never been studied. We aimed to compare the microbiological outcome of triple lumen AST CVCs inserted by GWX (GWX-CVCs) with newly inserted triple lumen AST CVCs (NI-CVCs). Methods We studied a cohort of 145 consecutive patients with GWX-CVCs and contemporaneous site-matched control cohort of 163 patients with NI-CVCs in a tertiary intensive care unit (ICU). Results GWX-CVC and NI-CVC patients were similar for mean age (58.7 vs. 62.2 years), gender (88 (60.7%) vs. 98 (60.5%) male) and illness severity on admission (mean Acute Physiology and Chronic Health Evaluation (APACHE) III: 71.3 vs. 72.2). However, GWX patients had longer median ICU lengths of stay (12.2 vs. 4.4 days; P < 0.001) and median hospital lengths of stay (30.7 vs. 18.0 days; P < 0.001). There was no significant difference with regard to the number of CVC tips with bacterial or fungal pathogen colonization among GWX-CVCs vs. NI-CVCs (5 (2.5%) vs. 6 (7.4%); P = 0.90). Catheter-associated blood stream infection (CA-BSI) occurred in 2 (1.4%) GWX patients compared with 3 (1.8%) NI-CVC patients (P = 0.75). There was no significant difference in hospital mortality (35 (24.1%) vs. 48 (29.4%); P = 0.29). Conclusions GWX-CVCs and NI-CVCs had similar rates of tip colonization at removal, CA-BSI and mortality. If the CVC removed by GWX is colonized, a new CVC must then be inserted at another site. In selected ICU patients at higher central vein puncture risk receiving AST CVCs GWX may be an acceptable initial approach to line insertion. PMID:24004883

2013-01-01

246

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

247

Nanoclays reinforced glass ionomer cements: dispersion and interaction of polymer grade (PG) montmorillonite with poly(acrylic acid).  

PubMed

Montmorillonite nanoclays (PGV and PGN) were dispersed in poly(acrylic acid) (PAA) for utilization as reinforcing filler in glass ionomer cements (GICs). Chemical and physical interaction of PAA and nanoclay (PGV and PGN) was studied. PAA–PGV and PAA–PGN solutions were prepared in different weight percent loadings of PGV and PGN nanoclay (0.5-8.0 wt%) via exfoliation-adsorption method. Characterization was carried out by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and fourier transform infrared (FTIR) spectroscopy. XRD results of PAA–PGN demonstrated that the interlayer space expanded from 12.83 to 16.03 Å indicating intercalation whereas the absence of the peak at d(001) in PAA–PGV indicated exfoliation. XPS scans of PGV and PGN nanoclays depicted the main peak of O 1s photoelectron due to Si–O–M (M = Mg, Al, Fe) whereas, Si–O–Al linkages were identified by Si 2p or Si 2s and Al 2p or Al 2s peaks. The disappearance of the Na peak confirmed that PAA molecules exchanged sodium ions present on surface of silicate layers and significantly reduced the electrostatic van-der-Waals forces between silicate plates resulting in intercalation or exfoliation. FTIR spectra of PAA–nanoclay suspensions demonstrated the presence of a new peak at 1,019 cm(-1) associated with Si–O– stretching vibrations which increased with increasing nanoclays concentration. Information concerning the dispersion of nanoclay in PAA aqueous solutions, chemical reaction and increase interlayer space in montmorillonite nanoclay is particularly useful regarding dispersion and reinforcement of nanoclay in PAA. PMID:24077996

Fareed, Muhammad A; Stamboulis, Artemis

2014-01-01

248

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

249

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

250

Surface characterisation of ultraviolet-ozone treated PET using atomic force microscopy and X-ray photoelectron spectroscopy  

NASA Astrophysics Data System (ADS)

The effects of ultraviolet-ozone (UVO) oxidation of polyethyleneterephthalate (PET) surfaces have been studied using atomic force microscopy and X-ray photoelectron spectroscopy. Surface oxygen increases from 26 at.% (untreated) to 37 at.% for the most oxidised surfaces produced and an increase in mean surface roughness and grain size is also observed. The larger grains appear to result from the formation of low molecular weight oxidised species by PET chain scission at the ester group and the material formed is therefore COOH/COOR rich. These species are mobile on the polymer surface and coalesce to form 200 nm grains which can be partially removed by water washing. The surface beneath is still rougher and more highly oxidised than untreated PET but the increase in stable oxygen is due to the formation of COH/COR groups.

Ton-That, C.; Teare, D. O. H.; Campbell, P. A.; Bradley, R. H.

1999-08-01

251

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

252

Montmorillonite Clay Catalyzed Tosylation of Alcohols and Selective Monotosylation of Diols with p-Toluenesulfonic Acid: An Enviro-Economic Route  

Microsoft Academic Search

An enviro-economic route for tosylation of alcohols and selective monotosylation of diols in good yield directly using p-toluenesulfonic acid together with metal-exchanged montmorillonite instead of p-toluenesulfonyl chloride or p-toluenesulfonic anhydride is described. The Fe3+-montmorillonite clay is the most effective catalyst among metal-exchanged montmorillonites for such tosylation reactions. The activity follows the sequence Fe3+>Zn2+>Cu2+>Al3+-montmorillonite>K10 montmorillonite. Regioselective tosylation of diols to monotosylated

Boyapati M. Choudary; Naidu S. Chowdari; Mannepalli L. Kantam

2000-01-01

253

Surface passivation and morphology of GaAs(1 0 0) treated in HCl-isopropanol solution  

Microsoft Academic Search

A promising chemical surface preparation technique, which consists in the treatment of GaAs(100) in HCl-isopropyl alcohol (HCl-iPA) solution under nitrogen atmosphere, is further developed. It was shown earlier [Tereshchenko et al., J. Vac. Sci. Technol. A 17 (1999) 2655] that HCl-iPA treatment and subsequent anneals in vacuum yielded atomically clean GaAs(100) surface with the whole range of surface reconstructions characteristic

V. L. Alperovich; O. E. Tereshchenko; N. S. Rudaya; D. V. Sheglov; A. V. Latyshev; A. S. Terekhov

2004-01-01

254

Analysis of microscopic modifications and macroscopic surface properties of polystyrene thin films treated under DC pulsed discharge conditions.  

E-print Network

1 Analysis of microscopic modifications and macroscopic surface properties of polystyrene thin. These results composed of macroscopic and microscopic studies on polystyrene surfaces may allow to establish a macroscopic interpretation of the interaction between polymer and the DC pulsed plasma. Keywords : Polystyrene

Paris-Sud XI, Université de

255

Effect of Nature of Gas on Some Surface PhysicoChemical Properties of Plasma-Treated Wool Fiber  

Microsoft Academic Search

The wool scale present on the fiber surface gives rise to certain unwanted effects in textile wet processing. The effects, for example, include felting and poor wettability. In the past, the removal of scale was done either by surface modification through physical\\/chemical degradation of scale or by deposition of a polymer on the scale. In modern treatment, combination of both

C. W. Kan; C. W. M. Yuen

2010-01-01

256

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

257

PLASMA ETCHING RATES AND SURFACE COMPOSITION OF BULK NIOBIUM TREATED IN Ar/Cl2 MICROWAVE DISCHARGE  

SciTech Connect

To achieve theoretically predicted values of the accelerating fields in superconducting radiofrequency (SRF) cavities, their inside surface should be fairly smooth and free of impurities. Thus, surface preparation is the critical step in production of SRF cavities. Plasma etching process is a dry chemistry technique that can be used to achieve these requirements. It is based on interaction between reactive halogen species produced in the glow discharge and the surface. During this process, volatile Nb halides are evaporated from the surface of Nb, removing the mechanically damaged and contaminated layer. We present a treatment of bulk Nb samples in the Ar/Cl2 microwave discharge. We have shown that etching rates of bulk Nb as high as 1.5 mm/min can be achieved without introducing impurities in Nb. The rate dependence on various discharge parameters and reactive gas composition is presented. Surface composition and topology measurements were carried out before and after plasma treatment

Raskovic, Marija; Upadhyay, Janardan; Valente, Anne-Marie; Phillips, H.

2008-07-01

258

Effect Of Clay-Water Interactions On Swelling In Montmorillonite Clay  

Microsoft Academic Search

This paper describes effect of clay-water interactions on swelling of montmorillonite using a new controlled uniaxial swelling (CUS) cell developed by the authors. Using the CUS cell, a simultaneous measurement of swelling and swelling pressure is done. Undisturbed clay samples at well defined swelling (0%-75%) were removed from the CUS cell and analyzed using scanning electron microscopy and fourier transform

Kalpana Katti; Dinesh Katti

259

Mixed-layer kaolinite-montmorillonite from the Yucatan Peninsula, Mexico  

USGS Publications Warehouse

Clay beds 1-2 m thick and interbedded with marine limestones probably of early Eocene age are composed of nearly pure mixed-layer kaolinite-montmorillonite. Particle size studies, electron micrographs, X-ray diffraction studies, chemical analyses, cation exchange experiments, DTA, and TGA indicate that clays from three different localities contain roughly equal proportions of randomly interlayered kaolinite and montmorillonite layers. The montmorillonite structural formulas average K0??2Na0??2Ca0??2Mg0??2(Al2??5Fe1??03+Mg0??5)(Al0??75Si7??25)O20+(OH)4-, with a deficiency of structural (OH) in either the montmorillonite or kaolinite layers. Nonexchangeable K+ indicates that a few layers are mica-like. Crystals are mostly round plates 1 10 to 1 20 ?? across. The feature most diagnostic of the mixed-layer character is an X-ray reflection near 8 A?? after heating at 300 ??C. The clays are inferred to have developed by weathering of volcanic ash and subsequent erosion and deposition in protected nearshore basins. ?? 1971.

Schultz, L. G.; Shepard, A. O.; Blackmon, P. D.; Starkey, H. C.

1971-01-01

260

Static Sorption of Phenol and 4-Nitrophenol onto Composite Geomaterials based on Montmorillonite, Activated Carbon and  

E-print Network

and 4-nitrophenol (4NP) onto solid sorbents derived from mixtures of montmorillonite, activated carbon by batch testing on geomaterials with various X1 values at 20 �C and at different pH values (from 3 to 8 degradation processes, chemical oxidation and biological digestion, in which sorption onto activated carbon

Paris-Sud XI, Université de

261

Polymer–clay nanocomposites: exfoliation of organophilic montmorillonite nanolayers in polystyrene  

Microsoft Academic Search

A polymerizable cationic surfactant, vinylbenzyldimethyldodecylammonium chloride (VDAC) was synthesized for functionalization of montmorillonite (MMT) and preparation of exfoliated polystyrene–clay nanocomposites. Organophilic MMT was prepared by cationic exchange between inorganic ions of MMT and ammonium cations of VDAC in an aqueous medium. Dispersions of intercalated clay (VDAC–MMT) in styrene monomer formed gels. Shear thinning behavior of the gels was observed via

X Fu; S Qutubuddin

2001-01-01

262

Montmorillonite K10 catalyzed efficient synthesis of amidoalkyl naphthols under solvent free conditions  

Microsoft Academic Search

An efficient green protocol for the preparation of amidoalkyl naphthols, employing a three-component one-pot condensation reaction of ?-naphthol, aromatic aldehyde, amides or urea in the presence of montmorillonite K10 clay under solvent free conditions has been described. The present procedure offers advantages such as shorter reaction time (<2h), simple workup, excellent yields, recovery and reusability of catalyst.

Srinivas Kantevari; Srinivasu V. N. Vuppalapati; Lingaiah Nagarapu

2007-01-01

263

Near-infrared (0.67–4.7 ?m) optical constants estimated for montmorillonite  

Microsoft Academic Search

Optical constants are estimated from near-infrared reflectance spectra of the smectite clay montmorillonite using an iterative combination of particulate scattering theory and Kramers–Kronig analysis. The final results provide wavelength dependent imaginary indices of refraction similar to previous studies, but in addition produce wavelength dependent real indices of refraction, unlike most previous studies. A comparison of the values derived here to

Ted L. Roush

2005-01-01

264

Near-infrared (0.67 4.7 mum) optical constants estimated for montmorillonite  

Microsoft Academic Search

Optical constants are estimated from near-infrared reflectance spectra of the smectite clay montmorillonite using an iterative combination of particulate scattering theory and Kramers Kronig analysis. The final results provide wavelength dependent imaginary indices of refraction similar to previous studies, but in addition produce wavelength dependent real indices of refraction, unlike most previous studies. A comparison of the values derived here

Ted L. Roush

2005-01-01

265

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 ...

266

Frictional strength and the effective pressure law of montmorillonite and illite clays  

Microsoft Academic Search

Abstract Low-strength clay minerals are a common constituent of fault gouges, and are often cited as a possible explanation for the low ambient shear stresses along the San Andreas fault inferred from heat flow constraints and in situ stress measurements. Montmorillonite, the weakest of the clay minerals, undergoes a gradual phase transition to illite with depth. In order to compare

C. Morrow; B. Radney; J. D. Byerlee

1992-01-01

267

Adsorption of uranium and thorium from aqueous solutions by the clay minerals montmorillonite and vermiculite  

Microsoft Academic Search

The adsorption of uranium and thorium from aqueous solutions by montomorillonite and vermiculite has been studied. The uranium and thorium concentration of the solutions varied between 100 and 2000 ppm. The behaviour of vermiculite as adsorbent of uranyl ions was found to be identical to montmorillonite, whereas the quantity of the adsorbed hydroxy?Th ions was much lower than its theoretical

C. A. Sikalidis; C. Alexiades; P. Misaelides

1989-01-01

268

Hydroesterification of olefins catalyzed by Pd(OAc){sub 2} immobilized on montmorillonite  

SciTech Connect

Palladium acetate immobilized on montmorillonite is an efficient catalyst for the hydroesterification of olefins with carbon monoxide and methanol, in the presence of triphenylphosphine and an acid promoter, affording branched chain esters. The reaction is regiospecific for aryl olefins as well as vinyl benzoate and regioselective for aliphatic olefins. 4 tabs.

Lee, Chul Woo; Alper, H. [Univ. of Ottawa, Ontario (Canada)

1995-01-13

269

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

Microsoft Academic Search

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

Myriam Duc; Fabien Thomas; Fabien Gaboriaud

2006-01-01

270

The research about the time-effect of the wettability on the wool surface treated by the Ar plasma jet in the atmospheric pressure  

NASA Astrophysics Data System (ADS)

A facility which is called atmospheric pressure and normal temperature plasma jet was introduced in this paper. After the wool surface was treated by this kind of facility with Ar in different irradiating times, the time-effect of the fabric wettability has been weakened, and if the parameters of the irradiating time and the voltage of the facility are appropriate, the time-effect of wettability can be effectively inhibited. With the stable wettability, the fabric can be dressed without PVA (polyvinyl alcohol) which can cause lager pollution in the textile field, so the method without the time-effect of the textile wettability will be useful in the field of clean textile production. Undoubtedly, the stable wettability of textile surface was caused by the stable hydrophilic molecules on the textile surface. Thus, the reaction process and results on the textile surface treated by plasma needs to be studied to optimize the parameters of the irradiating time and the voltage of the plasma jet. So the initial experimental studies on the optimization of the parameters of the plasma jet were discussed in this paper, and the authors believe that the method without the time-effect also can be used in other fields of plasma application.

Yu, Wu; Shouguo, Wang

2009-09-01

271

Characteristics of Ni–Ir and Pt–Ir hard coatings surface treated by pulsed Nd:YAG laser  

Microsoft Academic Search

The subjects of the presented paper are to develop a laser surface treatment technology for the protective coatings of glass-molding dies and to better understand the interaction between laser beam and materials coated on the die surface. A variety of alloy films, including Ir-25 at.% Pt, Ir-50 at.% Pt, Ir-75 at.% Pt, Ir-25 at.% Ni, Ir-50 at.% Ni, and Ir-75

Shih-Feng Tseng; Wen-Tse Hsiao; Kuo-Cheng Huang; Ming-Fei Chen; Chao-Te Lee; Chang-Pin Chou

2010-01-01

272

Thermal fatigue resistance of H13 steel treated by selective laser surface melting and CrNi alloying  

NASA Astrophysics Data System (ADS)

In this study, the selective laser surface melting and laser surface alloying technologies were adopted to improve the thermal fatigue resistance of medium carbon hot-work die steel (H13) by a CO2 laser. Two kinds of mixed chromium (Cr) and nickel (Ni) powders were used as the laser alloying materials, and the effects of the mixing ratio on the thermal fatigue resistance were investigated thoroughly. Some important results such as cross-sectional morphology, phases, hardness and thermal fatigue behavior were analyzed and evaluated. It indicates that the laser surface alloying technique using mixed powder with ratio of 75%Cr-25%Ni can considerably enhance the thermal fatigue resistance of the H13 steel. The laser alloyed zone has excellent properties such as preventing crack initiation and oxidation corrosion compared with original H13. Thermal cracking and oxidation corrosion that occurred at substrate surface can be surrounded and intercepted by a gridded laser strengthened structure. Therefore, the naturally developed cracks could be effectively prevented. Theses results and analysis show that laser surface technique can be positively used to improve surface mechanical properties of H13 dies.

Tong, Xin; Dai, Ming-jiang; Zhang, Zhi-hui

2013-04-01

273

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

274

The role of Fe(III) modified montmorillonite on fluoride mobility: adsorption experiments and competition with phosphate.  

PubMed

Fluoride adsorption onto Fe(III) modified montmorillonite was investigated using batch experiments. The effect of reaction time, pH, ionic strength and phosphate, as a competitive anion, was evaluated. Kinetics indicated that adsorption obeys a pseudo-first-order rate law which involves two steps. The fast one (bulk transport/surface reaction) occurs instantaneously. The slower (diffusion in pores) takes hours to complete. The adsorption rate increases by increasing the fluoride concentration and by decreasing pH. The presence of phosphate reduces fluoride adsorption and reveals that both ions are in competition for surface sites. The reduction in fluoride adsorption when phosphate is present depends on the order of adsorbate addition. The higher fluoride adsorption occurs when both anions are added simultaneously, whereas when either fluoride or phosphate is added first, the fluoride adsorption is lower. The presence of fluoride does not have a measurable effect on phosphate adsorption. The results obtained contribute to our understanding of the mobility of fluoride in surface water which has naturally high levels of fluoride, in both the presence and absence of phosphate. PMID:22343612

Bia, Gonzalo; De Pauli, Carlos P; Borgnino, Laura

2012-06-15

275

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

276

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

277

Improvement on Hydrophilic and Hydrophobic Properties of Glass Surface Treated by Nonthermal Plasma Induced by Silent Corona Discharge  

Microsoft Academic Search

A fundamental study was conducted to investigate the improvement of the hydrophilic and hydrophobic properties of the glass surface using the atmospheric-pressure nonthermal plasma. The plasma was induced between the two parallel electrodes with a dielectric barrier using an AC 60Hz high voltage power supply. The objective is to demonstrate the possibility of the elimination of the windshield wiper from

Toshiaki Yamamoto; Masaaki Okubo; Norikazu Imai; Yasunao Mori

2004-01-01

278

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

279

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

280

Effect of Lithium Absorption at Tetrahedral Site and Isomorphic Substitution on Montmorillonite Properties: A Density Functional Theory Study  

NASA Astrophysics Data System (ADS)

This study deals with the effect of the isomorphic substitution on the sorption of two Li atoms on montmorillonite using density functional theory (DFT). The isomorphic substitution is carried out by modifying the atomic composition of the upper tetrahedral layer of the montmorillonite by replacing one Si atom with one Al atom on the said position. Note that in the conventional structure, Si atom is located at the upper tetrahedral layer of montmorillonite. Results show that one Li atom is likely to be situated in the vacant tetrahedral site and the other one is in the vacant octahedral site, for both of the two montmorillonite systems (isomorphic substitution and conventional structure). The sorption energy was found to be -6.31 eV at the most stable configuration, that is for the isomorphic substitution.

Wungu, Triati Dewi Kencana; Diño, Wilson Agerico; Dipojono, Hermawan Kresno; Kasai, Hideaki

2011-05-01

281

Efficacy of a Brazilian calcium montmorillonite against toxic effects of dietary aflatoxins on broilers reared to market weight.  

PubMed

1. The protective effect of a natural Brazilian calcium montmorillonite (CaMont) against aflatoxins was studied in broiler chickens. 2. A total of 1056-d-old Cobb male broilers were housed in experimental pens (22 chickens per pen) for 42 d. Three levels of CaMont (0, 2.5 and 5 g/kg) and two levels of aflatoxins (0 and 3 mg/kg) were assayed. Each treatment had 8 replicate pens of 22 broiler chickens each. 3. Of all the chickens tested in the experiment, the ones treated with aflatoxins were the most adversely affected. CaMont treatment at concentrations of 2.5 and 5 g/kg improved body weight of chickens at 42 d of age by 13.3% and 22.7%, increased daily feed intake by 9.7% and 24.7%, and improved the productive efficiency index of chickens by 53% and 66.5%, respectively. 4. Dietary CaMont positively affected parameters such as weight of liver, heart and gizzard; however, serum potassium concentration decreased by 15.3% compared with that of chickens given only the aflatoxin-contaminated diet. 5. CaMont did not cause adverse effects in chickens that did not receive aflatoxins. 6. CaMont at pH 8.5 partially reduced the toxic effects of aflatoxins in broilers when included at levels of 2.5 and 5 g/kg in the diet. PMID:24423730

Eckhardt, J C; Santurio, J M; Zanette, R A; Rosa, A P; Scher, A; Dal Pozzo, M; Alves, S H; Ferreiro, L

2014-01-01

282

Surface Electrical Stimulation for Treating Swallowing Disorders after Stroke: A Review of the Stimulation Intensity Levels and the Electrode Placements  

PubMed Central

Neuromuscular electrical stimulation (NMES) for treating dysphagia is a relatively new therapeutic method. There is a paucity of evidence about the use of NMES in patients with dysphagia caused by stroke. The present review aimed to introduce and discuss studies that have evaluated the efficacy of this method amongst dysphagic patients following stroke with emphasis on the intensity of stimulation (sensory or motor level) and the method of electrode placement on the neck. The majority of the reviewed studies describe some positive effects of the NMES on the neck musculature in the swallowing performance of poststroke dysphagic patients, especially when the intensity of the stimulus is adjusted at the sensory level or when the motor electrical stimulation is applied on the infrahyoid muscles during swallowing. PMID:24804147

Poorjavad, Marziyeh; Talebian Moghadam, Saeed; Daemi, Mostafa

2014-01-01

283

Lymphocytes of haemophilia patients treated with clotting factor concentrates display activation-linked cell-surface antigens.  

PubMed Central

Peripheral blood lymphocytes from 30 patients with haemophilia A were investigated for the expression of six activation-linked cell surface antigens as well as with regard to the relative proportions and total numbers of Leu-3a and Leu-2a positive cells. Twenty-nine of the haemophilia patients showed no clinical symptoms of immunodeficiency or infection whereas one patient presented the typical symptomatology of the acquired immunodeficiency syndrome (AIDS). The proportions and total numbers of circulating lymphocytes displaying Ia antigens, the p45 protein and/or the two recently defined surface antigens VIP-4 and VIP-5 were significantly increased in haemophilia patients when compared to healthy individuals of the same age group. No such increases could be observed for transferrin receptor and IL-2 receptor expression. After the observation of depressed helper/suppressor T-cell ratios in many haemophiliacs, the expression of activation linked surface antigens represents a further lymphocyte abnormality which resembles the findings in AIDS and its prodromal stages and can also be found in certain viral and parasitic diseases. PMID:3921299

Koller, U; Majdic, O; Liszka, K; Stockinger, H; Pabinger-Fasching, I; Lechner, K; Knapp, W

1985-01-01

284

Newly developed surface modification punches treated with alloying techniques reduce sticking during the manufacture of ibuprofen tablets.  

PubMed

Sticking is a serious problem during the manufacturing process of tablets. In order to prevent this, we used alloying techniques to prepare metal hardening (MH) and electron beam processing infinite product (EIP) punches with rougher asperity of surfaces than a hard chrome plated (HCr) punch. This study evaluated the anti-sticking properties of the MH and EIP punches compared to the HCr punch, using quantitative scraper force measurements and visual observation, for the manufacture of ibuprofen (Ibu) tablets. The anti-sticking property mechanism of the MH and EIP punches was also confirmed. The amount of Ibu adhering to the punch surface was 66% lower for the MH and EIP punches than for the HCr punch, suggesting a superior anti-sticking property of the MH and EIP punches. The scraper force of the HCr punch was 2.60-4.28 N, while that for the MH and EIP punches was 0.54-1.64 N and 0.42-1.33 N, respectively. The result of X-ray photoelectron spectroscopy suggested that the anti-sticking property of the EIP punch was attributed by the rough asperity as well as existence of low friction substance carbon fluoride on the punch surface. In conclusion, this study provides new evidence for the mechanisms behind the superior anti-sticking property of the MH and EIP punches. PMID:23247020

Uchimoto, Takeaki; Iwao, Yasunori; Yamamoto, Tatsuya; Sawaguchi, Kazuo; Moriuchi, Toshiaki; Noguchi, Shuji; Itai, Shigeru

2013-01-30

285

An atmospheric-pressure plasma-treated titanium surface potentially supports initial cell adhesion, growth, and differentiation of cultured human prenatal-derived osteoblastic cells.  

PubMed

An atmospheric-pressure plasma (APP) treatment was recently reported to render titanium (Ti) surfaces more suitable for osteoblastic cell proliferation and osteogenesis. However, the mechanism of action remains to be clearly demonstrated. In this study, we focused on cell adhesion and examined the effects of the APP treatment on the initial responses of human prenatal-derived osteoblastic cells incubated on chemically polished commercially pure Ti (CP-cpTi) plates. In the medium containing 1% fetal bovine serum, the initial cell adhesion and the actin polymerization were evaluated by scanning electron microscopy and fluorescence microscopy. The expression of cell adhesion-related molecules and osteoblast markers at the messenger RNA level was assessed by real-time quantitative polymerase chain reaction. Although the cells on the APP-treated CP-cpTi surface developed fewer cytoskeletal actin fibers, they attached with higher affinity and consequently proliferated more actively (1.46-fold over control at 72 h). However, most of the cell adhesion molecule genes were significantly downregulated (from 40 to 85% of control) in the cells incubated on the APP-treated CP-cpTi surface at 24 h. Similarly, the osteoblast marker genes were significantly downregulated (from 49 to 63% of control) at 72 h. However, the osteoblast marker genes were drastically upregulated (from 197 to 296% of control) in these cells by dexamethasone and ?-glycerophosphate treatment. These findings suggest that the APP treatment improves the ability of the CP-cpTi surface to support osteoblastic proliferation by enhancing the initial cell adhesion and supports osteoblastic differentiation when immature osteoblasts begin the differentiation process. PMID:24449377

Kawase, Tomoyuki; Tanaka, Takaaki; Minbu, Hiromi; Kamiya, Mana; Oda, Masafumi; Hara, Toshiaki

2014-08-01

286

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

287

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

288

Properties of M40J Carbon/PMR-II-50 Composites Fabricated with Desized and Surface Treated Fibers. Characterization of M40J Desized and Finished Fibers  

NASA Technical Reports Server (NTRS)

To increase performance and durability of high temperature composites for potential rocket engine components, it is necessary to optimize wetting and interfacial bonding between high modulus carbon fibers and high temperature polyimide resins. It has been previously demonstrated that the electro-oxidative shear treatments used by fiber manufacturers are not effective on higher modulus fibers that have fewer edge and defect sites in the surface crystallites. In addition, sizings commercially supplied on most carbon fibers are not compatible with polyimides. This study was an extension of prior work characterizing the surface chemistry and energy of high modulus carbon fibers (M40J and M60J, Torray) with typical fluorinated polyimide resins, such as PMR-II-50. A continuous desizing system which utilizes environmentally friendly chemical- mechanical processes was developed for tow level fiber and the processes were optimized based on weight loss behavior, surface elemental composition (XPS) and morphology (FE-SEM) analyses, and residual tow strength of the fiber, and the similar approaches have been applied on carbon fabrics. Both desized and further treated with a reactive finish were investigated for the composite reinforcement. The effects of desizing and/or subsequent surface retreatment on carbon fiber on composite properties and performance including fiber-matrix interfacial mechanical properties, thermal properties and blistering onset behavior will be discussed in this presentation.

Allred, Ronald E.; Gosau, Jan M.; Shin, E. Eugene; McCorkle, Linda S.; Sutter, James K.; OMalley, Michelle; Gray, Hugh R. (Technical Monitor)

2002-01-01

289

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

290

Concentration effect of dicamba on adsorption in soils, montmorillonite, bayerite, and silica gel  

Microsoft Academic Search

The process of adsorption?desorption of the dicamba herbicide (3,6?dichloro?2?methoxybenzoic acid) by 10 soils southwest of Buenos Aires (Argentine) and by calcium (Ca)?montmorillonite, bayerite, and silica gel, was studied as a function of the applied concentration. Only two of soils studied readily adsorbed dicamba. The most important parameters in the soil with greater adsorption are low pH (5.15) and high organic

S. G. de Bussctti; E. A. Ferreiro

1999-01-01

291

Migration of Cations in Copper(II)-Exchanged Montmorillonite and Laponite upon Heating  

Microsoft Academic Search

Two clay minerals, a dioctahedral, Na-montmorillonite from Wyoming and a trioctahedral, synthetic Na-laponite, were exchanged by cupric (Cu(II)) ions and subsequently heated at 100 ~ intervals up to 500 ~ The resulting materials were analyzed by chemical analysis, X-ray diffraction (XRD), cation exchange capacity (CEC) measurements, combined thermogravimetric and differential thermal analysis (TGA-DTA), infrared (IR) spectroscopy, electron paramagnetic resonance (EPR)

C. Mosser; L. J. MICHOT; E VILLIERAS; M. ROMEO

1997-01-01

292

Michaelis constant ( K m ) of acid phospatase as affected by montmorillonite, illite, and kaolinite clay minerals  

Microsoft Academic Search

The influence of Ca homoionic clay minerals (montmorillonite, illite, and kaolinite) on the activity,Km, andVm values of acid phosphatase was examined in model experiments. At each substrate (p-nitrophenyl phosphate) level tested, the addition of increasing amounts of clays (50, 100, and 150 mg, respectively) decreased the activity and increased theKm value from 1.43×10?3m PNP (in the soluble state) to 82.3×10?3M

H. E. Makboul; J. C. G. Ottow

1979-01-01

293

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

294

Preparation, characterization and mechanical properties of the polylactide\\/perlite and the polylactide\\/montmorillonite composites  

Microsoft Academic Search

In this study polylactide (PLA)\\/perlite and PLA\\/montmorillonite (MMT) composites were prepared by melt extrusion and solvent\\u000a dissolution methods. The effects of organic\\/inorganic ratios and the kind of inorganic compounds on the characterization of\\u000a the composite materials were investigated. The thermal stability of the organic–inorganic composite materials was evaluated\\u000a by TGA and DSC, and the morphology of these composites was measured

Hongyan Tian; Hideyuki Tagaya

2007-01-01

295

The catalytic conversion of n -pentanol to dialkylether by some cation-exchanged montmorillonite catalysts  

Microsoft Academic Search

The heterogeneous catalytic conversion ofn-pentanol to dialkylether was carried out using untreated cation-exchanged montmorillonites and using samples which had been preheated at 300°C in an atmosphere of air, hydrogen or nitrogen. The catalyst has been characterized by applying thermogravimetric analysis, X-ray diffraction and cation exchange capacity tests. Gas-chromatographic analysis of the products showed that the catalytic reactivity of the exchanged

A. M. Habib; M. F. Abd-El-Megeed; A. Saafan; R. M. Issa

1986-01-01

296

Heavy metal removal from water by sorption using surfactant-modified montmorillonite  

Microsoft Academic Search

Removal of Cu2+ and Zn2+ from aqueous solutions by sorption on the montmorillonite modified with sodium dodecylsulfate (SDS) was investigated. Experiments were carried out as a function of solution pH, solute concentration, and temperature (25–55°C). The Dubinin–Kaganer–Radushkevick model was adopted to describe the single-solute sorption isotherms. Also, the binary-solute sorption equilibria could be reasonably predicted by the competitive Langmuir model,

Su-Hsia Lin; Ruey-Shin Juang

2002-01-01

297

Physicochemical characterization of a Texas montmorillonite pillared with polyoxocations of aluminum. II. NMR and microcalorimetry results  

Microsoft Academic Search

Solid state magic angle spinning nuclear magnetic resonance (MAS NMR), together with microcalorimetry and XRD data, have been used to characterize a pillared interlayered clay (PILC) containing 1.3×10?4 mol Keggin ion\\/g PILC. The clay catalyst (Al13-PILC) was prepared by reacting a Texas Na-montmorillonite with Keggin ions, [Al13(O)4(OH)24(H2O)12 ]7+, from an aluminum chlorhydroxide (ACH) solution. Initially, Keggin ions H-bond with the

M. L Occelli; A Auroux; G. J Ray

2000-01-01

298

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

299

Characterization of Cinchonidine Doped Montmorillonite Supported Noble Metal Catalysts by Thermoanalytical Methods  

Microsoft Academic Search

The characterization of new cinchonidine doped K-10 montmorillonite supported noble metal catalysts is described. Our aim\\u000a was the mapping of thermal stability of these new catalytic materials by thermogravimetry (TG), differential thermogravimetry\\u000a (DTG) and differential thermoanalysis (DTA) methods accompanied by X-ray diffraction (XRD) measurements.\\u000a \\u000a The catalysts were prepared by various methods including conventional, microwave and ultrasonic treatments. They were characterized

K. Balázsik; B. Török; M. Bartók; I. Kiricsi; I. Dékány

1999-01-01

300

Mechanistic study on the oxidative coupling of amines to imines on K-10 montmorillonite  

Microsoft Academic Search

A mechanistic study of the K-10 montmorillonite-catalyzed microwave-assisted oxidative self-coupling of benzylamine and cross coupling of benzylamines with anilines and aliphatic amines is described. The coupling of benzylamines readily produced benzylidene benzylamines, while reactions of benzylamine with aliphatic amines and anilines resulted in benzylidene alkylamines and benzylidene anilines. The mechanism of the reaction has been investigated by varying reaction conditions,

Valentina Atanassova; Kristen Ganno; Aditya Kulkarni; Shainaz M. Landge; Steven Curtis; Michelle Foster; Béla Török

2011-01-01

301

Fabrication and characterization of montmorillonite clay-filled SC15 epoxy  

Microsoft Academic Search

In the present investigation, we have developed a novel technique to fabricate nanocomposite materials containing SC-15 epoxy resin and K-10 montmorillonite clay. A high-intensity ultrasonic liquid processor was used to obtain a homogeneous molecular mixture of epoxy resin and nano-clay. The clays were infused into the part A of SC-15 (Diglycidylether of Bisphenol A) through sonic cavitations and then mixed

Yuanxin Zhou; Farhana Pervin; Mohammad A. Biswas; Vijaya K. Rangari; Shaik Jeelani

2006-01-01

302

Poly( d, l-lactide-co-glycolide)\\/montmorillonite nanoparticles for oral delivery of anticancer drugs  

Microsoft Academic Search

This research developed a novel bioadhesive drug delivery system, poly(d,l-lactide-co-glycolide)\\/montmorillonite (PLGA\\/MMT) nanoparticles, for oral delivery of paclitaxel. Paclitaxel-loaded PLGA\\/MMT nanoparticles were prepared by the emulsion\\/solvent evaporation method. MMT was incorporated in the formulation as a matrix material component, which also plays the role of a co-emulsifier in the nanoparticle preparation process. Paclitaxel-loaded PLGA\\/MMT nanoparticles were found to be of spherical

Yuancai Dong; Si-Shen Feng

2005-01-01

303

Chemical effects of cationic surfactant and anionic surfactant used in organically modified montmorillonites on degradation and fire retardancy of polyamide 12 nanocomposites  

Microsoft Academic Search

Three kinds of organically modified Na+-montmorillonites (OMMTs), including two kinds of octadecylammonium modified montmorillonite with different contents of octadecylammonium and a kind of sodium dodecylsulfonate (SDSo) modified montmorillonite, were used to prepare polyamide 12 (PA12)\\/OMMT nanocomposites. Effects of the modifiers on degradation and fire retardancy of PA12\\/OMMT nanocomposites were investigated. Acid sites formed in cationic surfactant modified MMT via Hoffman

Zhe Wang; Xiaohua Du; Rongjun Song; Xiaoyu Meng; Zhiwei Jiang; Tao Tang

2007-01-01

304

Preparation and performance of a Nafion ®/montmorillonite nanocomposite membrane for direct methanol fuel cell  

NASA Astrophysics Data System (ADS)

Direct methanol fuel cells (DMFC) have major technical problems, e.g. slow methanol oxidation kinetics and high methanol crossover, to use as power sources for several applications. To overcome these problems it has been proposed to increase the fuel cell operating temperature to over 100-150 °C and to reduce the methanol permeability. In this work, we made Nafion ®/montmorillonite (MMT) nanocomposite membranes and carried out diverse tests. The nanocomposite membranes were produced by direct melt intercalation of perfluorosulfonylfluoride copolymer resin (Nafion ® resin) into the montmorillonite and modified montmorillonite (m-MMT) which was organized by dodecylamine. The membrane-electrode assembly (MEA) has been made using a hot pressing method and the electrode prepared using PtRu black and Pt black catalysts for anode and cathode, respectively. The morphology of the nanocomposite membranes has been investigated using SEM and TEM. The nanocomposite membranes and MMT and m-MMT were analyzed using by FT-IR and X-ray diffraction (XRD). The thermal and mechanical properties of those membranes were also investigated and the methanol permeability was measured by gas chromatography (GC). The performance of the MEA using the nanocomposite membrane was evaluated by single cell test. The results show that the performance of the MEA using the nanocomposite membrane was higher than that of a commercial Nafion ® membrane at high operating temperature.

Jung, D. H.; Cho, S. Y.; Peck, D. H.; Shin, D. R.; Kim, J. S.

305

Structure and rheology of mixed suspensions of montmorillonite and silica nanoparticles.  

PubMed

We present a study of the structure and rheology of mixed suspensions of montmorillonite clay platelets and Ludox TMA silica spheres at pH 5, 7, and 9. Using cryogenic transmission electron microscopy (cryo-TEM), we probe the changes in the structure of the montmorillonite suspensions induced by changing the pH and by adding silica particles. Using oscillatory and transient rheological measurements, we examine the changes in storage modulus and yield stress of the montmorillonite suspensions upon changing the pH and adding silica particles. Cryo-TEM images reveal that changes in pH have a significant effect on the structure of the suspensions, which can be related to the change in charge of the edges from positive at pH 5 to negative at higher pH. Furthermore, at pH 7, the cryo-TEM images show indications of a microphase separation between clay and silica particles. The addition of silica leads to lowering of the storage modulus and yield stress, which we connect to the structural changes of the suspension. PMID:25232927

Hilhorst, Jan; Meester, Vera; Groeneveld, Esther; Dhont, Jan K G; Lekkerkerker, Henk N W

2014-10-01

306

Adsorption of Gemini and Conventional Cationic Surfactants onto Montmorillonite and the Removal of Some Pollutants by the Clay.  

PubMed

The adsorption of a series of gemini surfactants, [C(n)H(2n+1)N(+) (CH(3))(2)-CH(2)CH(2)](2).2Br(-), where n = 10, 12, 14, and 16, on clay (Na-montmorillonite) from their aqueous solution in 0.01 M KBr and the effect of this adsorption on the removal of 2-naphthol and 4-chlorophenol have been studied. Compared to those of conventional cationic surfactants with similar single hydrophilic and hydrophobic groups (C(n)H(2n+1)N(+)(CH(3))(3).Br(-), where n = 10, 12, 14, and 16), the molar adsorptions of the gemini and conventional surfactants are almost identical. This indicates that only one of the hydrophilic groups in the gemini molecule is adsorbed onto the clay and that the second hydrophilic is presumably oriented toward the aqueous phase, in contrast to the adsorption of the conventional surfactants, where the hydrophobic group is oriented toward the aqueous phase. Stability studies on dispersions of clay treated with the two types of surfactants confirm this. The slight increase in the moles of surfactant to values above the CEC of the clay with an increase in the carbon number of the hydrophobic chain indicates that adsorption through hydrophobic group interaction occurs in addition to the major ion exchange. Adsorption studies of the pollutants onto the clay treated by either the gemini or the conventional surfactants show that the former are both more efficient and more effective at removing the pollutants from the aqueous phase. Copyright 2000 Academic Press. PMID:10727337

Li; Rosen

2000-04-15

307

Adsorption of gemini and conventional cationic surfactants onto montmorillonite and the removal of some pollutants by the clay  

SciTech Connect

The adsorption of a series of gemini surfactants, [C{sub n}H{sub 2n+1}N{sup +}(CH{sub 3}){sub 2}-CH{sub 2}CH{sub 2}]{sub 2}{center_dot}2Br{sup {minus}}, where n = 10, 12, 14, and 16, on clay (Na-montmorillonite) from their aqueous solution in 0.01 M KBr and the effect of this adsorption on the removal of 2-naphthol and 4-chlorophenol have been studied. Compared to those of conventional cationic surfactants with similar single hydrophilic and hydrophobic groups (C{sub n}H{sub 2n+1}N{sup +}(CH{sub 3}){sub 3}{center_dot}Br{sup {minus}}, where n = 10, 12, 14, and 16), the molar adsorptions of the gemini and conventional surfactants are almost identical. This indicates that only one of the hydrophilic groups in the gemini molecule is adsorbed onto the clay and that the second hydrophilic is presumably oriented toward the aqueous phase, in contrast to the adsorption of the conventional surfactants, where the hydrophobic group is oriented toward the aqueous phase. Stability studies on dispersions of clay treated with the two types of surfactants confirm this. The slight increase in the moles of surfactant to values above the CEC of the clay with an increase in the carbon number of the hydrophobic chain indicates that adsorption through hydrophobic group interaction occurs in addition to the major ion exchange. Adsorption studies of the pollutants onto the clay treated by either the gemini or the conventional surfactants show that the former are both more efficient and more effective at removing the pollutants from the aqueous phase.

Li, F.; Rosen, M.J.

2000-04-15

308

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

309

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

310

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

311

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 Antonio; de Nadai Barros, Jeison; de Faria, Nubia Vanessa Lima; Montiani-Ferreira, Fabiano; Gomes, Jose Alvaro Pereira; Mello, Paulo Augusto Arruda

2013-01-01

312

Interaction of CO2 and brines with montmorillonite to 400 bars and 45oC  

NASA Astrophysics Data System (ADS)

Carbon Capture and Storage (CCS) from large stationary CO2 point sources is considered a promising option to reduce anthropogenic CO2 emissions in short- to medium time scales. Besides a storage reservoir allowing for large storage capacity at reasonable injection rates, an impermeable caprock overlying the reservoir is indispensable to guarantee safe long-term storage. In this context, understanding the behavior of clay systems with aqueous fluids and CO2 is an essential aspect of site selection and design of CO2 storage projects. Therefore, montmorillonite was studied using an X-ray, high-pressure environmental chamber (HPEC) developed at the University of Illinois at Chicago. Two series of experiments include: (a) dry montmorillonite at various relative humidity with supercritical CO2, and (b) montmorillonite immersed in brines as slurries with supercritical CO2. Changes in the layer-to-layer spacing [d(001)] of montmorillonite under conditions of elevated pressure (P) and temperature (T) were monitored. Samples of dry montmorillonite (Clay Minerals Society Source Clay, SWy-2) were prepared and loaded in the HPEC and allowed to equilibrate with small amounts of water. Initial amounts of interlayer H2O (i.e., various relative humidity) were monitored by the d-value of the (001) diffraction peak, then CO2 was added to the HPEC. The position and shape of the (001) peak changed for most samples under low CO2 pressures (40-50 bars, 40 - 45oC). Response to CO2 by the d(001) is strongly related to the initial H2O content. For samples with an initial d(001) of ~ 10.5 Å, the peak position changed by a maximum shift of ~ 1.75 Å to higher values. Very dry (10.10 Å) and very hydrated (16.5 Å) samples did not exhibit detectable changes of the (001) peak position or shape. Experiments to P = 400 bars showed similar results to those at P = 40-50 bars. Aqueous brine (0.5 M NaCl) slurries of SWy-2 were examined also under CO2 pressure. Initially, the d(001) was at 19.5 - 20 Å. Over 36 hours at 135 - 200 bars of CO2 pressure (T = 27oC), a peak formed at ~ 28 Å. The peak remained nearly unchanged after ~150 hours. Financial support from Shell Exploration and Production B.V. and the National Science Foundation is gratefully acknowledged.

Koster van Groos, A. F.; Giesting, P. A.; Guggenheim, S.; Busch, A.

2010-12-01

313

Influence of a Cerium Surface Treatment on the Oxidation Behavior of Cr2O3-Forming Alloys (title on slides varies: Oxidation Behavior of Cerium Surface Treated Chromia Forming Alloys)  

SciTech Connect

Current goals of the U.S. Department of Energy’s Advanced Power Systems Initiatives include coal generation at 60% efficiency, which would require steam temperatures of up to 760°C. This temperature will require the construction of boiler and turbine components from austenitic stainless steels and nickel alloys. Many of the alloys being considered for use are primarily Cr2O3 forming alloys [1-4]. It is well known that the addition of a small amount of reactive elements, such as the rare earths elements Ce, La, and Y, can significantly improve the high temperature oxidation resistance of both iron- and nickel- base alloys. A list of the benefits of the reactive element effect include: (i) slowing scale growth, (ii) enhancing scale adhesion; and (iii) stabilizing Cr2O3 formation at lower Cr levels. The incorporation of the reactive element can be made in the melt or through a surface infusion or surface coating. Surface modifications allow for the concentration of the reactive element at the surface where it can provide the most benefit. This paper will detail a Ce surface treatment developed at NETL that improves the high temperature oxidation resistance of Cr2O3 forming alloys. The treatment consists of painting, dip coating, or spraying the alloy surface with a slurry containing CeO2 and a halide activator followed by a thermal treatment in a mild (x10-3 Torr) vacuum. During treatment the CeO2 reacts with the alloy to for a thin CrCeO3-type scale on the alloy surface. Upon subsequent oxidation, scale growth occurs at a reduced rate on alloys in the surface treated condition compared to those in the untreated condition.

Alman, D.E.; Holcomb, G.R.; Adler, T.A.; Jablonski, P.D.

2007-04-01

314

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

315

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

316

Patterning Method for Silver Nanoparticle Electrodes in Fully Solution-Processed Organic Thin-Film Transistors Using Selectively Treated Hydrophilic and Hydrophobic Surfaces  

NASA Astrophysics Data System (ADS)

Fully solution-processed organic thin-film transistor (OTFT) devices have been fabricated with simple patterning process at a relatively low process temperature of 100 °C. In the patterning process, a hydrophobic amorphous fluoropolymer material, which was used as the gate dielectric layer and the underlying base layer, was treated with an oxygen plasma to selectively change its surface wetting properties from hydrophobic to hydrophilic. Silver source and drain electrodes were successfully formed in the treated areas with highly uniform line widths and without residues between the electrodes. Nonuniformities in the thickness of the silver electrodes originating from the “coffee-ring” effect were suppressed by optimizing the blend of solvents used with the silver nanoparticles, such that the printed electrodes are appropriate for bottom-gate OTFT devices. A fully solution-processed OTFT device using a polymer semiconductor material (PB16TTT) exhibited good electrical performance with no hysteresis in its transfer characteristics and with good linearity in its output characteristics. A relatively high carrier mobility of 0.14 cm2 V-1 s-1 and an on/off ratio of 1×105 were obtained with the fabricated TFT device.

Fukuda, Kenjiro; Takeda, Yasunori; Kobayashi, Yu; Shimizu, Masahiro; Sekine, Tomohito; Kumaki, Daisuke; Kurihara, Masato; Sakamoto, Masatomi; Tokito, Shizuo

2013-05-01

317

XPS analysis of down stream plasma treated wool: Influence of the nature of the gas on the surface modification of wool  

NASA Astrophysics Data System (ADS)

A microwave plasma treatment in a down stream configuration was used to modify the natural hydrophobocity of untreated wool fibers. This property is a consequence of the presence of a Fatty acid monolayer (F-layer) on the outermost part of the fiber surface. The wool fibers treated with plasma were analyzed by means of X-ray photoelectron spectroscopy (XPS) without previous exposure to the air. Experiments have been carried out with air, water vapor, oxygen and nitrogen as plasma gas. The "in situ" analysis of the treated samples has permitted to differentiate between the plasma effects and those other linked to the exposure of the fibers to the air after their treatment. The results have evidenced the effects induced by the different active species generated by plasma from the different components of the air. In general, the intensity of C sbnd C peaks decreases and that of the C sbnd O, C dbnd O and O sbnd C dbnd O increases when using a gas containing oxygen species. Simultaneously, the intensity of the S sbnd S groups decreases and that of the sulphonate (SO 3-) increases. Other changes are also detected in the intensity of the N 1s level. The extent and characteristics of the oxidation and functionalisation of the hydrocarbon chains of the F-layer depend on the nature of gas. Thus, whereas treatments with plasmas of air and water vapor strongly affect the hydrocarbon chains of the F-layer, oxygen is less effective in the oxidation process. It has been also noted that the active species formed in the nitrogen plasma do not induce any significant change in the surface composition of the wool fibers.

Molina, R.; Espinós, J. P.; Yubero, F.; Erra, P.; González-Elipe, A. R.

2005-12-01

318

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

319

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

320

Investigation of the different binding edge sites for Zn on montmorillonite using P-EXAFS - The strong/weak site concept in the 2SPNE SC/CE sorption model  

NASA Astrophysics Data System (ADS)

The 2 site protolysis non electrostatic surface complexation and cation exchange (2SPNE SC/CE) sorption model has been used over the past decade or so to quantitatively describe the uptake of metals with oxidation states from II to VI on 2:1 clay minerals; montmorillonite and illite. One of the main features in this model is that there are two broad categories of amphoteric edge sorption sites; the so called strong ( tbnd S SOH) and weak ( tbnd S W1OH) sites. Because of their different sorption characteristics, it was expected that the coordination environments of the surface complexes on the two site types would be different. Zn isotherm data on two montmorillonites, Milos and STx-1, were measured and modelled using the 2SPNE SC/CE sorption model. The results were used to define the most favourable experimental conditions under which Zn sorption was either dominated by the strong ( tbnd S SOH, ˜2 mmol kg -1) or by the weak sites ( tbnd S W1OH, ˜40 mmol kg -1). Highly oriented self-supporting films were prepared for polarised extended X-ray absorption fine structure (P-EXAFS) investigations. Montmorillonites often contain Zn incorporated in the clay matrix. The Zn bound in this form was quantified and the results from the analysis of the P-EXAFS spectra were taken into account in the interpretation of the spectra measured at low Zn loadings (˜2 mmol kg -1) and medium Zn loadings (˜30 mmol kg -1). The Zn spectra on the "strong sites" exhibited a pronounced angular dependency and formed surface complexes in the continuity of the Al-octahedral sheets at the montmorillonite edges. In contrast, the Zn "weak site" spectra showed only a weak angular dependency. The spectroscopic evidence indicates the existence of two distinct groups of edge surface binding sites which is consistent with a multi-site sorption model and in particular with the strong/weak site concept intrinsic to the 2SPNE S/CE sorption model.

Dähn, Rainer; Baeyens, Bart; Bradbury, Michael H.

2011-09-01

321

Preparation and evaluation of composites from montmorillonite and some heterocyclic polymers: 3. A water dispersible nanocomposite from pyrrole-montmorillonite polymerization system  

SciTech Connect

Montmorillonite (MMT)-based nanocomposites of polypyrrole (PPY) were prepared through the polymerization of pyrrole with MMT and FeCl{sub 3}-impregnated MM in bulk and in aqueous medium. The composites were characterized by IR, X-ray diffraction (XRD), and scanning electron microscopy (SEM) studies. XRD analyses revealed no change in d{sub 001} spacing in MMT (9.8 {angstrom}), suggesting no intercalation of PPY into MMT lamellae. TEM analysis indicated the particle size to be 25 {+-} 7 nm. The bulk conductivity of the composites was in the range of (1.3 to 26) x 10{sup {minus}5} S/cm, depending on the FeCl{sub 3}-impregnation level and on the PPY loading in the composites. Suitable procedures were developed for obtaining a stable aqueous dispersion and a reversible dispersion of these composites.

SinhaRay, S.; Biswas, M.

1999-06-01

322

Interaction of Phenol and Aniline with Montmorillonite and llliti. D.L. SPARKS and P.C. ZHANG*. Univ. of Delaware.  

E-print Network

*. Univ. of Delaware. The interaction of phenol and aniline with montmorillonite ' and illite at low and illite was observed in a one h period. Phenol adsorption was observed on montmorillonite if the organic matter was not removed. but illite did not have detectable organic matter and thus no phenol adsorption

Sparks, Donald L.

323

Surfaces  

E-print Network

Surfaces is a collection of four individual essays which focus on the characteristics and tactile qualities of surfaces within a variety of perceived landscapes. Each essay concentrates on a unique surface theme and purpose; ...

DeMaio, Ernest Vincent, 1964-

1989-01-01

324

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

325

Montmorillonite Poly-L-Lactide Microcomposites of Procainamide for controlled drug delivery: In vitro and In vivo evaluation.  

PubMed

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

2013-11-01

326

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

327

Montmorillonite KSF as catalyst for degradation of acetaminophen with heterogeneous Fenton reactions  

Microsoft Academic Search

The degradation of acetaminophen (APAP) in aqueous solutions with heterogeneous Fenton reactions was investigated with montmorillonite\\u000a KSF as catalyst. The influencing factors of the initial APAP concentration, initial pH value, initial KSF dosage and H2O2 dosage were studied. The results showed that APAP could be effectively degraded under the conditions of pH 4.0, KSF 0.2 g\\/L\\u000a and H2O2 0.5 mM, and the

Chunyan Deng; Cong Ren; Feng Wu; Nansheng Deng; Evgeni M. Glebov; Ivan P. Pozdnyakov; Victor F. Plyusnin

2010-01-01

328

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

329

Water adsorption constrained Frenkel-Halsey-Hill adsorption activation theory: Montmorillonite and illite  

NASA Astrophysics Data System (ADS)

Fresh mineral aerosol has recently been found to be effective cloud condensation nuclei (CCN) and contribute to the number of 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 Na-montmorillonite and illite clay to determine empirical adsorption parameters that can be used in a recently derived theoretical framework (Frenkel-Halsey-Hill Activation Theory, FHH-AT) that accounts for the effect of water adsorption on CCN activation. Upon fitting the Frenkel-Halsey-Hill (FHH) adsorption model to water adsorption measurements, we find FHH adsorption parameters, AFHH and BFHH, to be 98 ± 22 and 1.79 ± 0.11 for montmorillonite and 75 ± 17 and 1.77 ± 0.11 for illite, respectively. The AFHH and BFHH values obtained from water adsorption measurements differ from values reported previously determined by applying FHH-AT to CCN activation measurements. Differences in FHH adsorption parameters were attributed to different methods used to obtain them and the hydratable nature of the clays. FHH adsorption parameters determined from water adsorption measurements were then used to calculate the critical super-saturation (sc) for CCN activation using FHH-AT. The relationship between sc and the dry particle diameter (Ddry) gave CCN activation curve exponents (xFHH) of -0.61 and -0.64 for montmorillonite and illite, respectively. The xFHH values were slightly lower than reported previously for mineral aerosol. The lower exponent suggests that the CCN activity of hydratable clays is less sensitive to changes in Ddry and the hygroscopicity parameter exhibits a broader variability with Ddry compared to more soluble aerosols. Despite the differences in AFHH, BFHH and xFHH, the FHH-AT derived CCN activities of montmorillonite and illite are quite similar to each other and in excellent agreement with experimental CCN measurements resulting from wet-generated clay aerosol. This study illustrates that FHH-AT using adsorption parameters constrained by water adsorption is a simple, valid method for predicting CCN activation of fresh clay minerals and provides parameters that can be used in atmospheric models to study the effect of mineral dust aerosol on cloud formation and climate.

Hatch, Courtney D.; Greenaway, Ann L.; Christie, Matthew J.; Baltrusaitis, Jonas

2014-04-01

330

Oligomerization of mononucleotides on montmorillonite: A potential approach to the prebiotic synthesis of RNA. [Abstract only  

NASA Technical Reports Server (NTRS)

The condensation of the 5'-phosphorimidazolide of adenosine (ImpA) on montmorillonite in a pH 8 aqueous solution yields oligomers containing up to 10 monomer units. The regiospecificity of 3',5'-phosphodiester bond formation is enhanced by addition of 10% diadenosine pyrophosphate (AppA) to the reaction mixture. A series of activated derivatives of 5'-AMP was prepared to investigate the effect of the leaving group on oligomer formation. The benzimidazole and p-dimethylamino-pyridine derivatives gave the best yields of oligomers. Factors important for oligomer formation is discussed.

Ferris, James P.; Ertem, Goezen; Ding, Zi Ping; Prabahar, Joseph

1994-01-01

331

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 parameters constrained by water adsorption measurements is a simple, valid method for predicting CCN activation of fresh, unprocessed clay minerals and provides parameters that can be used in atmospheric models to study cloud formation and climate.

Hatch, C. D.; Greenaway, A.; Christie, M. J.; Baltrusaitis, J.

2013-12-01

332

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

333

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

334

Considering the risk of infection by cryptosporidium via consumption of municipally treated drinking water from a surface water source in a Southwestern Ontario community.  

PubMed

Through the use of case-control analyses and quantitative microbial risk assessment (QMRA), relative risks of transmission of cryptosporidiosis have been evaluated (recreational water exposure vs. drinking water consumption) for a Canadian community with higher than national rates of cryptosporidiosis. A QMRA was developed to assess the risk of Cryptosporidium infection through the consumption of municipally treated drinking water. Simulations were based on site-specific surface water contamination levels and drinking water treatment log?? reduction capacity for Cryptosporidium. Results suggested that the risk of Cryptosporidium infection via drinking water in the study community, assuming routine operation of the water treatment plant, was negligible (6 infections per 10¹³ persons per day--5th percentile: 2 infections per 10¹? persons per day; 95th percentile: 3 infections per 10¹² persons per day). The risk is essentially nonexistent during optimized, routine treatment operations. The study community achieves between 7 and 9 log?? Cryptosporidium oocyst reduction through routine water treatment processes. Although these results do not preclude the need for constant vigilance by both water treatment and public health professionals in this community, they suggest that the cause of higher rates of cryptosporidiosis are more likely due to recreational water contact, or perhaps direct animal contact. QMRA can be successfully applied at the community level to identify data gaps, rank relative public health risks, and forecast future risk scenarios. It is most useful when performed in a collaborative way with local stakeholders, from beginning to end of the risk analysis paradigm. PMID:22443194

Pintar, K D M; Fazil, A; Pollari, F; Waltner-Toews, D; Charron, D F; McEwen, S A; Walton, T

2012-07-01

335

Surfactant immobilized interlayer species bonded to montmorillonite as recyclable adsorbent for lead ions.  

PubMed

Removal of lead ( Pb2+ ) ions from aqueous solution by adsorption onto surfactant-immobilized interlayer species bonded to montmorillonite clay (SIIS-clay) was investigated. Surfactant-immobilized interlayer chromate bound to clay (SIICr-clay) was prepared by treatment of montmorillonite clay with hexadecyltrimethylammonium (HDTMA) bromide followed by chromate adsorption at the intergallery framework of the clay. Experiments were carried out as a function of solution pH, solute concentration, and temperature (5-45 degrees C). The Dubinin-Kaganer-Radushkevich (DKR) model was adopted to describe the single-solute adsorption isotherms. Adsorption energy for lead ions on SIICr-clay computed from the DKR equation shows that a precipitation mechanism was operative. The thermodynamic parameters ( Delta G 0, Delta H 0, and Delta S 0) for lead ion adsorption on SIICr-clay were also determined from the temperature dependence. The kinetics of metal ion adsorption was examined and the first-order rate constant was finally evaluated. Adsorbed lead ions could be recovered completely on leaching with the disodium salt of ethylenediamine tetraacetic acid (EDTA) solution and the adsorbent was found to readsorb lead ions repeatedly after leaching. Thus, surfactant-modified smectite clays offer an effective method for designing a recyclable adsorbent for lead ions. PMID:14972602

Krishna, B S; Mahadevaiah, N; Murty, D S R; Prakash, B S Jai

2004-03-15

336

A revision of the Biginelli reaction under solid acid catalysis. Solvent-free synthesis of dihydropyrimidines over montmorillonite KSF  

Microsoft Academic Search

The reaction of aldehydes, ?-dicarbonyl compounds and urea (Biginelli reaction) has been performed over solid acid catalysis, under solventless conditions or in water affording dihydropyrimidines in good yield and selectivity.Dihydropyrimidines4 were obtained in good yield and selectivity by reacting aldehydes, ?-dicarbonyl compounds and ureas in the presence of montmorillonite KSF under solventless conditions.

Franca Bigi; Silvia Carloni; Bettina Frullanti; Raimondo Maggi; Giovanni Sartori

1999-01-01

337

Synthesis and surfactant modification of clinoptilolite and montmorillonite for the removal of nitrate and preparation of slow release nitrogen fertilizer.  

PubMed

This article introduces the synthesis of clinoptilolite and montmorillonite, and their surfactant modification by using solutions of hexadecyltrimethylammonium bromide (CH(3)(CH(2))(15)N(Br)(CH(3))(3), HDTMAB) and dioctadecyldimethylammonium bromide ((CH(3)(CH(2))(17))(2)N(Br)(CH(3))(2), DODMAB). The feasibility of using surfactant modified silicates (SMSs) as a potential adsorbent for nitrate and for slow release of nutrient has been investigated. Adsorption isotherms of NO(3)(-) on SMSs have been measured at aqueous concentration of 160-280 mg L(-1). The SMSs show much higher adsorption capacity than the unmodified materials as determined by Langmuir adsorption isotherm. The surfactant modification and increased surfactant loading concentration enhance the nitrate anion retaining capacity of silicates (montmorillonite (16.05 mg g(-1))montmorillonite (76.92 mg g(-1))montmorillonite (80.65 mg g(-1))

Bhardwaj, Deepesh; Sharma, Monika; Sharma, Pankaj; Tomar, Radha

2012-08-15

338

Sorption and Desorption of Acetonitrile on Montmorillonite from Aqueous Solutions Z. Z. Zhang,* D. L. Sparks, and R. A. Pease  

E-print Network

Sorption and Desorption of Acetonitrile on Montmorillonite from Aqueous Solutions Z. Z. Zhang,* D. L. Sparks, and R. A. Pease ABSTRACT The sorption and desorption of acetonitrile on K, Na, Ca, and Mg. The infrared spectra of the clay-water- organic systems wererecordedon a Fourier-transforminfrared spec

Sparks, Donald L.

339

Infrared characterization of water uptake by low-temperature Na-montmorillonite: Implications for Earth and Mars  

Microsoft Academic Search

A large fraction of atmospheric mineral aerosol is composed of clays, such as smectites. Smectites are known to expand upon addition of water, and thus their properties in the atmosphere may vary strongly with relative humidity (RH). Here we report on the adsorption of water to Na-montmorillonite, a smectite clay. We probe the water uptake under conditions representative of the

E. K. Frinak; C. D. Mashburn; M. A. Tolbert; O. B. Toon

2005-01-01

340

Effects of Water and pH on the Oxidative Oligomerization of Chloro an Methoxyphenol by a Montmorillonite Clay  

Microsoft Academic Search

This study focussed on the capacity of a montmorillonite clay to oxidize organic contaminants having activating (methoxyphenol) and deactivating (chlorophenol) substituent groups when pH and water conditions are changing. The amount and strength of Lewis and Brønsted acidity of the clay was measured using organic indicator and titration methods. Water plays two distinct roles in the oxidation of such contaminants

S. Desjardins; J. A. Landry; J. P. Farant

1999-01-01

341

Assessment of Salinity Variations in TBT Adsorption onto Kaolinite and Montmorillonite at Different pH Levels  

Microsoft Academic Search

Adsorption onto solid phases is an important process in controlling the distribution of toxic tributyltin (TBT) compounds in aqueous systems. In the present study, the TBT adsorption onto two types of clay, kaolinite (KGa) and montmorillonite (SWy), as a function of salinity (0, 8, 16, 24, 32‰) was investigated using the conventional batch technique. Experiments were carried out under different

Marion Hoch

2004-01-01

342

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) ...

343

Biodegradable poly(propylene carbonate)/montmorillonite nanocomposites prepared by direct melt intercalation  

SciTech Connect

Intercalation-exfoliated nanocomposites derived from poly(propylene carbonate) (PPC) and organo-modified montmorillonite (OMMT) were prepared by direct melt blending in an internal mixer. The nano-scale dispersion of the OMMT layers within the PPC matrix was verified using wide angle X-ray scattering and transmission electron microscopy technologies. Static mechanical properties were determined by using a tensile tester. The PPC/OMMT nanocomposites with lower OMMT content showed an increase in thermal decomposition temperature when compared with both pure PPC and the composites prepared from un-modified MMT. Dynamic mechanical analysis indicated that nano-scale OMMT dispersed well within PPC matrix and therefore enhanced the storage modulus of the composites.

Xu, J. [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Li, R.K.Y. [Department of Physics and Materials Sciences, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong (China)]. E-mail: RKYLi@cityu.edu.hk; Meng, Y.Z. [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China)]. E-mail: stdpmeng@zsu.edu.cn; Mai, Y-.W. [Centre for Advanced Materials Technology, School of Aerospace, Mechanical and Mechatronic Engineering, University of Sydney, Sydney, NSW 2006 (Australia)

2006-02-02

344

Oligomerization of ribonucleotides on montmorillonite: reaction of the 5'-phosphorimidazolide of adenosine.  

PubMed

The regiospecific formation of oligomers from unblocked monomers in aqueous solution is one of the central tenets in research on the origins of life on earth. Direct experimental support for this hypothesis has been obtained in studies of the condensation of the 5'-phosphorimidazolide of adenosine (ImpA) with itself and with P1,P2-diadenosine-5',5'-pyrophosphate (AppA) in water in the presence of a montmorillonite clay. Oligomers of up to ten nucleotides in length are formed. Analysis of the trimers, tetramers, and pentamers formed from a 9:1 ImpA:AppA mixture has shown that 85% of the bonds formed are 3',5'-linked and that any 2',5'-linkages present are at the phosphodiester bond next to the 3'-terminus of the oligomers. PMID:1529338

Ferris, J P; Ertem, G

1992-09-01

345

Application of Modified Nanonaturally Montmorillonite in Monochlorobenzene Remediation in River Water  

NASA Astrophysics Data System (ADS)

As the inland waterway transportation developed rapidly in China, the frequency of hazardous chemical leakage accidents is increasing every year. Such pollution to inland river environment has become a world-wide issue. Montmorillonite (Mont) is typical 2:1 layer type silicate clay and due to their special structure, it has been used in organic pollution removal process. In order to improve their ability in pollution adsorption, the pillared Mont was made in this work. Since the common toxic structure in most chemical pollutants is the halogen atom-benzene ring part, we select a typical compound Monochlorobenzene (MCB) as the aim contaminant. In this research, the original Mont, Na-Mont, TiO2 and TiO2-Mont were prepared and used in MCB degradation experiment as catalysts. The influence of catalyst amount, promoter (H2O2) amount, MCB concentration and reaction time to MCB removal rate were studied, respectively in detail.

Liu, Chen; Chen, Jun-Feng; Li, Yun; Chen, Rong-Chang; Asaoka, Sachio; Yuan, Guo-Li

2012-12-01

346

Effect of leaving group on the oligomerization of 5'-AMP on montmorillonite. [Abstract only  

NASA Technical Reports Server (NTRS)

The oligomerization of imidazole derivative of 5'-AMP (ImpA) in the presence of montmorillonite clay yields oligomers containing up to 10 monomer units. In these reactions, the heterocyclic base, imidazole is the leaving group. In our present study, we synthesized a series of activated nucleotides of 5'AMP using other leaving groups such as pyrazole, 1,2,4-triazole, piperidine, morpholine, 4-aminopyridine, 4-methylaminopyridine, 4-dimethylaminopyridine, 2-aminobenzimidazole etc. to determine the effect of amine leaving group on the products of the oligomerization reaction. Earlier results from our laboratory showed that the presence AppA in the clay reaction of ImpA enhances the oligomerization reaction to yield higher oligomers. We also studied the effect of AppA in the clay mediated oligomerization reaction of the activated nucleotides. Oligomerization of 2-amino-benzimidazole derivative of 5'-AMP gave higher oligomers containing up to nine monomer units in the presence of AppA.

Prabahar, K. Joseph; Ferris, James P.

1994-01-01

347

Sulfonated Styrene-(ethylene-co-butylene)-styrene/Montmorillonite Clay Nanocomposites: Synthesis, Morphology, and Properties  

PubMed Central

Sulfonated styrene-(ethylene-butylene)-styrene triblock copolymer (SSEBS) was synthesized by reaction of acetyl sulfate with SEBS. SSESB-clay nanocomposites were then prepared from hydrophilic Na-montmorillonite (MT) and organically (quaternary amine) modified hydrophobic nanoclay (OMT) at very low loading. SEBS did not show improvement in properties with MT-based nanocomposites. On sulfonation (3 and 6 weight%) of SEBS, hydrophilic MT clay-based nanocomposites exhibited better mechanical, dynamic mechanical, and thermal properties, and also controlled water–methanol mixture uptake and permeation and AC resistance. Microstructure determined by X-ray diffraction, atomic force microscopy, and transmission electron microscopy due to better dispersion of MT nanoclay particles and interaction of MT with SSEBS matrix was responsible for this effect. The resulting nanocomposites have potential as proton transfer membranes for Fuel Cell applications.

2008-01-01

348

Synthesis and Electrorheological Characterization of Polyaniline and NA+-MONTMORILLONITE Clay Nanocomposite  

NASA Astrophysics Data System (ADS)

Polyaniline-Na+-montmorillonite nanocomposite particles were synthesized using an emulsion intercalation method, and electrorheological (ER) fluids were produced by dispersing the synthesized nanocomposite particles in an electrically-insulating silicone oil. The emulsion of an aniline monomer with dodecyl benzenesulfonic acid was inserted into the layers of clay, and polymerization was processed by adding the oxidant initiator solution. DBSA as a emulsifier and a dopant took a important role for polyaniline clay nanocomposite. This insertion of polyaniline was confirmed by X-ray diffraction. To observe its ER properties, we measured the shear viscosity and the shear stress by controlling shear rate. Furthermore, we conducted dynamic tests to investigate the viscoelastic properties of the ER fluid under an electric field in the linear viscoelastic region.

Kim, J. W.; Kim, S. G.; Choi, H. J.; Suh, M. S.; Shin, M. J.; Jhon, M. J.

349

The oxidative polymerization of aromatic molecules in the interlayer of montmorillonites studied by resonance Raman spectroscopy  

NASA Astrophysics Data System (ADS)

The adsorption and reaction of aromatic molecules in the interlayer of transition-metal ion(Cu 2+, Fe 3+, Ru 3+)-exchanged montmorillonites have been investigated by resonance Raman spectroscopy. Some mono-substituted benzenes are found to form cation radicals of 4,4'-substituted biphenyl together with those having the composition of the parent molecules. Benzene, biphenyl and p-terphenyl polymerize to form the poly-p-phenylene cation. Thus, the cation radicals or cations may remain stable when para-positions of the benzene ring are occupied by a stable substituent, or undergo polymerization when the para-position is open. Phenols behave differently in that the polymerization via the ortho-position also occurs and the reaction is faster in aerobic than in anearobic conditions.

Soma, Y.; Soma, M.; Harada, I.

1986-02-01

350

DIFFERENCES IN APPARENT INTERSTRATIFICAT ION OF AN ORGANO-MONTMORILLONITE DISPERSED IN VARIOUS ORGANIC SOLVENTS I. X-RAY DIFFRACTION STUDY  

Microsoft Academic Search

The degree and tlpe of interstratification of a dimethyldioctadeclamine montmorillonite after dispersion in various organic solvents were studied by X-ray diffraction methods. Diffraction data from oriented films of the specimens were obtained at temperatures of 35\\

Janos L. McArnn

351

Direct electrochemical determination of methyl jasmonate in wheat spikelet at a nano-montmorillonite film modified electrode by derivative square wave voltammetry.  

PubMed

The direct electrochemical determination of methyl jasmonate (MeJA) at a nano-montmorillonite modified glassy carbon electrode (nano-MMT/GCE) is reported. The modified electrode, prepared by a simple casting-drying method and characterized by scanning electron microscope (SEM) and electrochemical impedance spectra (EIS), was proved to process a uniform nanostructured surface with a large surface area and a fast electron transfer rate. This electrode exhibited a sensitive electrochemical response for the direct oxidation of MeJA in 0.1 mol L(-1) HClO4, which could be further improved by using a derivative square wave voltammetry technique. Thus, a simple and fast electrochemical method for the determination of MeJA is proposed. Under optimal working conditions, the oxidation current of MeJA linearly increased with its concentration in the range of 7.0 × 10(-7)-1.0 × 10(-3) mol L(-1) with a detection limit of 5.0 × 10(-7) mol L(-1). This method had been applied to the determination of MeJA content in wheat spikelet samples. PMID:23654231

Gan, Tian; Hu, Chengguo; Chen, Zilin; Hu, Shengshui

2010-08-25

352

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

353

Modification of a Na-montmorillonite with quaternary ammonium salts and its application for organics removal from TNT red water.  

PubMed

Na-montmorillonite (Na-Mont) and organic montmorillonite modified by cetyltrimethylammonium bromide (CTAB-Mont) and tetramethylammonium bromide (TMAB-Mont) were prepared as adsorbents to remove organic contaminants from 2,4,6-trinitrotoluene (TNT) red water. The characterizations of the samples were performed with X-ray diffraction and Fourier transform infrared spectroscopy. The adsorption capacity of CTAB-Mont (15.9 mg/g) was much larger than Na-Mont (0.26 mg/g) and TMAB-Mont (1.7 mg/g). Langmuir isotherm and the pseudo-second-order kinetic models fitted the experimental results well. The main factor in the adsorption promotion was the distribution phase in the interlayer of CTAB-Mont. The arrangement of molecules analyzed by molecular simulation corresponded to the experimental data and supported the adsorption mechanism. PMID:24804652

Zhang, Qian; Meng, Zilin; Zhang, Yihe; Lv, Guocheng; Lv, Fengzhu; Wu, Limei

2014-01-01

354

Debromination of decabromodiphenyl ether by organo-montmorillonite-supported nanoscale zero-valent iron: preparation, characterization and influence factors.  

PubMed

An organo-montmorillonite-supported nanoscale zero-valent iron material (M-NZVI) was synthesized to degrade decabromodiphenyl ether (BDE-209). The results showed that nanoscale zero-valent iron had good dispersion on organo-montmorillonite and was present as a core-shell structure with a particle size range of nanoscale iron between 30-90 nm, characterized by XRD, SEM, TEM, XRF, ICP-AES, and XPS. The results of the degradation of BDE-209 by M-NZVI showed that the efficiency of M-NZVI in removing BDE-209 was much higher than that of NZVI. The efficiency of M-NZVI in removing BDE-209 decreased as the pH and the initial dissolved oxygen content of the reaction solution increased, but increased as the proportion of water in the reaction solution increased. PMID:25076541

Pang, Zhihua; Yan, Mengyue; Jia, Xiaoshan; Wang, Zhenxing; Chen, Jianyu

2014-02-01

355

Alkanolamine treating  

SciTech Connect

In this paper the chemistry, engineering and operational aspects of the primary and secondary amines utilized in syngas purification are explored. The gas treating chemistry is followed by the analysis of reactivity of chemicals involved with H/sub 2/S and CO/sub 2/ which constitute main impurities in gas streams. Other topics discussed include - capacity versus corrosivity; heat of reaction; reboiler duty, metallurgy; chemical degradation of amines; solvent purification; hydrocarbon solubility; mercaptane removed; freezing point of amine solutions. 27 refs.

Butwell, K.F.; Kubek, D.J.; Sigmund, P.W.

1982-03-01

356

Intestinal morphology, brush border and digesta enzyme activities of broilers fed on a diet containing Cu-loaded montmorillonite  

Microsoft Academic Search

1.?A total of 320 1-d-old Arbor Acres broiler chicks were used to investigate the effect of Cu-loaded montmorillonite (CM) on the growth performance, intestinal morphology and activities of brush border enzyme in the intestinal mucosa and digestive enzyme in the intestinal digesta of broilers.2.?The chicks were assigned randomly into 4 groups with 80 chicks per treatment. The 4 dietary treatments

Y. L. Ma; T. Guo

2008-01-01

357

Effect of Saturating Cation, pH, and Aluminum and Iron Oxide on the Flocculation of Kaolinite and Montmorillonite  

Microsoft Academic Search

The effect of pH on the flocculation-dispersion behavior of noncrystalline aluminum and iron oxides, kaolinite, montmorillonite, and various mixtures of these materials was investigated. The clays were Na- or Ca-saturated and freeze-dried before use. Critical coagulation concentrations (CCC) of all materials and mixtures were found to be pH dependent. The A1 oxide was flocculated at pH >9.5 and the iron

Sabine Goldberg; ROBERT A. GLAUBIG

1987-01-01

358

An investigation of some of the effects of anhydrous ammonia on the clay minerals montmorillonite and illite  

E-print Network

AN INVESTIGATION OF SOME OF THE EFFECTS OF ANHYDROUS AMMONIA ON THE CIAY MINERALS MONTMORILLONITE AND ILLITE A Dissertation By Ell Lamar Whiteley Submitted to the Graduate School of the Agricultural and Mechanical College of Texas in Partial... Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY January, 1959 Major Subject* Soil Physics AN INVESTIGATION OF SOME OF THE EFFECTS OF ANHYDROUS AMMONIA ON THE CLAY MINERALS MGNTMORILLONITE AND ILLITE A Dissertation By Eli Lamar...

Whiteley, Eli Lamar

2013-10-04

359

Changes in the Properties of a Montmorillonite-Water System during the Adsorption and Desorption of Water: Hysteresis1  

Microsoft Academic Search

Abstract--Samples of Na-saturated, Upton montmorillonite were prepared with different contents of water (H20 or D20) by: (1) adsorption of water from the vapor phase at a specific value of p\\/p*, the relative humidity, (2) adsorption of water from the vapor phase at p\\/p* = 1.0 followed by desorption of the water into the vapor phase at a specific p\\/p* <

M. H. Fu; Z. Z. Zhang; P. F. Low

1990-01-01

360

Clay-catalyzed organic reactions: The dimerization of 3,4- dimethoxypropenylbenzene with K-10 montmorillonite clay  

SciTech Connect

Interest in the use of montmorillonite clay as a catalyst in organic synthesis has recently increased, encouraged in part by the availability of the clay, its low cost, and propensity to intercalate organic molecules. Research in this laboratory has recently focused on the reactivity of 3,4-dimethoxypropenylbenzene (1) with K-10, a montmorillonite clay whose interlayer cations have been exchanged for protons. These efforts have been directed toward several related goals. First, through a detailed analysis of product mixtures and comparison with previously reported results of clay reactions with 1, a number of new products have been observed. Second, this montmorillonite has a complex aluminosilicate structure containing both Lewis and Broensted acid sites, and sites capable of generating radical cations from intercalated organic substrates. Therefore, the mechanisms by which these produts might be formed have been studied in an effort to gain a better understanding of the interactions of these sites with organic substrates. In this paper we report our initial observations in this area.

Wilson, R.M.; Orchin, M.; Green, J.V.; Dietz, J.G.

1989-01-01

361

Geochemical studies of clay minerals III. The determination of free silica and free alumina in montmorillonites  

USGS Publications Warehouse

Determination of free silica by the method proposed made possible the derivation of logical formulas for several specimens of montmorillonites for which the formulas could not be derived from the analyses alone. Other montmorillonites, for which logical formulas could be derived from their analyses, were found to contain small amounts of free silica or free alumina. Others were found to contain neither free silica nor free alumina. The method consists of the following steps: (1) digestion of 1 g of the specimen with 0.5 N NaOH solution in a covered platinum crucible or dish on a steam bath for 4 hrs, stirring the mixture at 30-min intervals, (2) filtration of the undissolved material, followed by washing several times with 1% NaOH solution, (3) neutralization of the filtrate with HCl, addition of 5 ml HCl in excess and determination of SiO and Al2O3 in the usual way and (4) calculation of the amount of free SiO2 or free Al2O3 if any and the amount of attack of the clay structure by the treatment from the ratio of SiO2 to Al2O3 dissolved and the ratio of SiO2 to Al2O3 obtained on analysis. Tests with 5% Na2CO3 solution, the reagent formerly used for the solution of free SiO2 in rocks and minerals, showed that solution of opal by this reagent is always fractional, never complete, no matter how small the amount present or how long the period of treatment. Re-treatment of the sample results in 90-95% solution if 10 mg or less of opal is present, but for larger amounts of opal the percentage dissolved decreases as the amount present increases. On the other hand, 75 ml of 0.5 N NaOH completely dissolves as much as 400 mg of opal in 4 hrs digestion in a covered platinum crucible or dish, on a steam bath. However, a weaker solution or a shorter period of digestion does not effect complete solution. The same amount (75 ml) of 0.5 N NaOH also dissolves 90 mg of cristobalite and 57 mg of quartz having a grain size of less than 2 microns. Use of NaOH also permits determination of the amount of alumina dissolved, and estimation of the extent to which the clay structure was attacked by the treatment. ?? 1953.

Foster, M.D.

1953-01-01

362

The characteristic of the ZnO nanowire morphology grown by the hydrothermal method on various surface-treated seed layers  

Microsoft Academic Search

ZnO nanowires with various density and diameters were obtained by altering the wetting properties of aluminum doped ZnO (AZO) seed layers. AZO seed layers deposited on glass substrates were treated by inductor coupled plasmas (ICP) or atmospheric pressure plasma (APP) systems in order to control wettability before ZnO nanowire growth. Morphology of ZnO nanowires grown by the hydrothermal method was

Joon-Yub Kim; Jin Woo Cho; Sung Hyun Kim

2011-01-01

363

Evidence for montmorillonite or its compositional equivalent in Columbia Hills, Mars  

NASA Astrophysics Data System (ADS)

During its exploration of the Columbia Hills, the Mars Exploration Rover ``Spirit'' encountered several similar samples that are distinctly different from Martian meteorites and known Gusev crater soils, rocks, and sediments. Occurring in a variety of contexts and locations, these ``Independence class'' samples are rough-textured, iron-poor (equivalent FeO ~ 4 wt%), have high Al/Si ratios, and often contain unexpectedly high concentrations of one or more minor or trace elements (including Cr, Ni, Cu, Sr, and Y). Apart from accessory minerals, the major component common to these samples has a compositional profile of major and minor elements which is similar to the smectite montmorillonite, implicating this mineral, or its compositional equivalent. Infrared thermal emission spectra do not indicate the presence of crystalline smectite. One of these samples was found spatially associated with a ferric sulfate-enriched soil horizon, possibly indicating a genetic relationship between these disparate types of materials. Compared to the nearby Wishstone and Watchtower class rocks, major aqueous alteration involving mineral dissolution and mobilization with consequent depletions of certain elements is implied for this setting and may be undetectable by remote sensing from orbit because of the small scale of the occurrences and obscuration by mantling with soil and dust.

Clark, B. C.; Arvidson, R. E.; Gellert, R.; Morris, R. V.; Ming, D. W.; Richter, L.; Ruff, S. W.; Michalski, J. R.; Farrand, W. H.; Yen, A.; Herkenhoff, K. E.; Li, R.; Squyres, S. W.; Schröder, C.; Klingelhöfer, G.; Bell, J. F.

2007-04-01

364

Short-Term Safety and Efficacy of Calcium Montmorillonite Clay (UPSN) in Children.  

PubMed

Recently, an association between childhood growth stunting and aflatoxin (AF) exposure has been identified. In Ghana, homemade nutritional supplements often consist of AF-prone commodities. In this study, children were enrolled in a clinical intervention trial to determine the safety and efficacy of Uniform Particle Size NovaSil (UPSN), a refined calcium montmorillonite known to be safe in adults. Participants ingested 0.75 or 1.5 g UPSN or 1.5 g calcium carbonate placebo per day for 14 days. Hematological and serum biochemistry parameters in the UPSN groups were not significantly different from the placebo-controlled group. Importantly, there were no adverse events attributable to UPSN treatment. A significant reduction in urinary metabolite (AFM1) was observed in the high-dose group compared with placebo. Results indicate that UPSN is safe for children at doses up to 1.5 g/day for a period of 2 weeks and can reduce exposure to AFs, resulting in increased quality and efficacy of contaminated foods. PMID:25135766

Mitchell, Nicole J; Kumi, Justice; Aleser, Mildred; Elmore, Sarah E; Rychlik, Kristal A; Zychowski, Katherine E; Romoser, Amelia A; Phillips, Timothy D; Ankrah, Nii-Ayi

2014-10-01

365

Structure-property relationships in heterophasic thermoplastic elastomers filled with montmorillonite.  

PubMed

Polypropylene (PP)/ethylene-propylene rubber (EPR)/Montmorillonite ternary nanocomposites with a phase separated morphology were studied in this work. Wide angle X-ray diffraction (WAXD), small angle X-ray scattering (SAXS), atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to investigate the samples. One of the aim of this work was to separate the effects of rubber and clay content on the structure, morphology and mechanical properties of the samples. The presence of clay favored the formation of gamma phase and disrupted the lamellar framework. Clay had moreover a major role in shaping the phase separated morphology of the samples. Atomic Force Microscopy showed that the shear exerted by the clay layers was key for inducing a shish kebab morphology in the polymer matrix. Rubber content decreased the degree of crystallinity at a crystalline cell level and induced the formation of a double population of lamellar stacks. The mechanical properties of the samples primarily depended on rubber content, and they were secondarily tuned by the effect of clay. This synergistic effect allowed to obtain composites with increased stiffness, ductility and toughness, oppositely to what is frequently found. PMID:22754991

Causin, Valerio; Marega, Carla; Saini, Roberta; Neppalli, Ramesh; Ferrara, Giuseppe; Adhikari, Rameshwar; Marigo, Antonio

2012-03-01

366

Modifying the structure and flow behaviour of aqueous montmorillonite suspensions with surfactant.  

PubMed

Colloidal suspensions of plate-like particles undergo a variety of phase transitions. The predicted isotropic/nematic transition is often pre-empted by a sol/gel transition, especially in suspensions of the most commonly used natural swelling clay montmorillonite (MMT). A number of factors, including charge interactions, flexibility and salt concentration, may contribute to this competition. In this study, the effect of surfactant adsorption on suspensions of MMT was studied using rheology, small-angle X-ray scattering, static light scattering and optical microscopy. The addition of a polyetheramine surfactant reduced the moduli of the system and shifted the sol/gel transition to a much higher clay concentration, compared with suspensions of bare clay particles. Yet, scattering data revealed no change in suspension structure on length scales up to around a micrometre. Primary aggregates remain at this length scale and no nematic phase is formed. There is, however, a change in structure at large length scales (of order 20??m) where light scattering indicates the presence of string-like aggregates that disappear on addition of surfactant. Microscope images of dried suspensions also revealed a string-like structure. The dried strings show strong birefringence and may consist of concentric cylinders, self-assembled from clay sheets. PMID:23459964

Cui, Yannan; Pizzey, Claire L; van Duijneveldt, Jeroen S

2013-04-13

367

Adsorption property of Rhodamine 6G onto chitosan-g-(N-vinyl pyrrolidone)/montmorillonite composite.  

PubMed

A series of chitosan-g-(N-vinyl pyrrolidone)/montmorillonite hydrogel composites were synthesized by in situ intercalative polymerization. The properties of the composites were investigated by FTIR, XRD, scanning electron microscopy and differential scanning calorimetry. The morphologies of the hydrogel composites were sponge like with a homogeneous structure. The effects of clay on the swelling, morphology, glass transition (Tg), and water structure were studied. The swelling of the hydrogel composites formed was found to be affected by the pH of the medium and the electrolyte. Maximum swelling was observed in the hydrogel containing low percentage of clay (H-0.2) and was used to investigate the adsorption of a water soluble cationic dye Rhodamine 6G (Rh6G). The results show that the adsorption capacity for the dye increased with increase in dose, contact time but there was no change observed with respect to increase in temperature. The adsorption kinetics of Rh6G followed Pseudo second order model and the equilibrium data was found to fit Freundlich model. PMID:24950308

Vanamudan, Ageetha; Bandwala, Khusbu; Pamidimukkala, Padmaja

2014-08-01

368

Template properties of oligocytidylates formed in the montmorillonite catalyzed condensation of ImpC. [Abstract only  

NASA Technical Reports Server (NTRS)

In an attempt to investigate the prebiotic formation of phosphodiester bond in RNA, we have studied the self condensation of 5'-phosphorimidazolide of adenosine (ImpA), in aqueous solutions containing 0.2 M sodium chloride and 0.075 M magnesium chloride at pH 8 using clay minerals as catalyst. In the presence of certain montmorillonites, oligomers containing up to ten monomer units in their chain were formed, while in control experiments, where no catalyst was added, the major product was 5',5'-diadenosine diphosphate, A(sup 5')ppA. In reactions carried out with ImpA: A(sup 5')ppA mixtures at 9:1 mole ratio, oligomers of the type A(sup 5')p(pA)(sub n) and (A(sup 5')p)(sub n)A(sup 5')ppA(pA)(sub n) formed at the expense of (pA)(sub n) type oligomers. Addition of A(sup 5')ppA to the reaction mixture increased the regiospecifity of 3',5'-link formation from 67% to 79%. The condensation of the 5'-phosphorimidazolide of cytidine, ImpC, was also carried out in the presence and absence of A(sup 5')ppA under the same conditions and oligomers containing up to twelve monomer units were obtained.

Ferris, James P.; Ertem, Goezen

1994-01-01

369

Evidence for montmorillonite or its compositional equivalent in Columbia Hills, Mars  

USGS Publications Warehouse

During its exploration of the Columbia Hills, the Mars Exploration Rover "Spirit" encountered several similar samples that are distinctly different from Martian meteorites and known Gusev crater soils, rocks, and sediments. Occurring in a variety of contexts and locations, these "Independence class" samples are rough-textured, iron-poor (equivalent FeO ??? 4 wt%), have high Al/Si ratios, and often contain unexpectedly high concentrations of one or more minor or trace elements (including Cr, Ni, Cu, Sr, and Y). Apart from accessory minerals, the major component common to these samples has a compositional profile of major and minor elements which is similar to the smectite montmorillonite, implicating this mineral, or its compositional equivalent. Infrared thermal emission spectra do not indicate the presence of crystalline smectite. One of these samples was found spatially associated with a ferric sulfate-enriched soil horizon, possibly indicating a genetic relationship between these disparate types of materials. Compared to the nearby Wishstone and Watchtower class rocks, major aqueous alteration involving mineral dissolution and mobilization with consequent depletions of certain elements is implied for this setting and may be undetectable by remote sensing from orbit because of the small scale of the occurrences and obscuration by mantling with soil and dust. Copyright 2007 by the American Geophysical Union.

Clark, III, B. C.; Arvidson, R. E.; Gellert, R.; Morris, R. V.; Ming, D. W.; Richter, L.; Ruff, S. W.; Michalski, J. R.; Farrand, W. H.; Yen, A. S.; Herkenhoff, K. E.; Li, R.; Squyres, S. W.; Schroder, C.; Klingelhofer, G.; Bell, III, J. F.

2007-01-01

370

A novel material of cross-linked styrylpyridinium salt intercalated montmorillonite for drug delivery  

NASA Astrophysics Data System (ADS)

A facile synthesis of a styrylpyridinium salt (SbQ)/montmorillonite (MMT) via cationic exchange interactions between styrylpyridinium species (specifically SbQ) and MMT platelets is reported in this work. The SbQ-MMT solutions were irradiated under ultraviolet (UV) light for a specific time to obtain the cross-linked SbQ-MMT materials. Scanning electron microscopy and atomic force microscopy analyses revealed the structures and morphologies of MMT and modified MMT. X-ray diffraction and transmission electron microscope analyses indicated that the basal spacing increased from 1.24 to 1.53 nm compared with the pristine MMT, which proved that SbQ had interacted with MMT. Thermal gravimetric analysis curves showed that the amount of SbQ in the MMT interlayers was 35.71 meq/100 g. Fourier transform infrared spectroscopy also confirmed the intercalation of SbQ species into MMT interlayers, and UV spectroscopy was used to follow up the cross-linking of SbQ-MMT. This novel material has potential applications in drug delivery, and it can also be used as an additive to improve the mechanical properties of polymers.

Cui, Jing; Wang, Qingqing; Chen, Xiaodong; Wei, Qufu

2014-08-01

371

Work-function changes of treated indium-tin-oxide films for organic light-emitting diodes investigated using scanning surface-potential microscopy  

SciTech Connect

Local surface work-function (WF) measurement on indium-tin-oxide (ITO) films prepared by different cleaning methods for use as anode materials in organic light-emitting diodes were studied using scanning surface-potential microscopy. The ITO WF changes with standard wet-cleaning treatment correspond directly to asperities on the film surface. The maximum difference value (MDV) in the local WF reached 0.41 eV. However, after wet-cleaning ITO with the ultraviolet ozone or O-plasma treatment, the WF distribution is more uniform than the original distribution. Owing to the sufficient ITO surface oxidization, the mean local WF value increases effectively to more than 5.00 eV and the MDV is less than 0.05 eV. Furthermore, the changes in roughness and conductivity on the ITO surface at different treatment times are also discussed. The proper exposure time for the O-plasma treatment can thereby be determined.

Chen, S.-H. [Department of Materials Engineering, Mingchi University of Technology, Taishan, Taipei Hsien 243, Taiwan (China)

2005-04-01

372

The Adsorption of Gemini and Conventional Surfactants onto Some Soil Solids and the Removal of 2-Naphthol by the Soil Surfaces.  

PubMed

The adsorption of two cationic gemini surfactants, [C(n)H(2n+1) N(+)(CH(3))(2)-CH(2)CH(2)](2).2Br(-), where n=12 and 14, on limestone, sand, and clay (Na-montmorillonite) from their aqueous solution in double-distilled water and the effect of this adsorption on the removal of 2-naphthol have been studied. Compared to those of conventional cationic surfactants with similar single hydrophilic and hydrophobic groups (C(n)H(2n+1)N(+)(CH(3))(3).Br(-), where n=12 and 14), the molar adsorptions of the gemini and the conventional surfactants on Na-montmorillonite are almost identical and very close to their cation exchange capacities. On sand and limestone, the molar adsorption of the cationic gemini surfactants is much larger than that of their corresponding conventional surfactants. Adsorption studies of the pollutants onto the three kinds of solids treated by either the gemini or the conventional surfactants show that the former are both more efficient and more effective at removing 2-naphthol from the aqueous phase. On all three soil solids, the addition of KBr increases the efficiency of the adsorption of both types of cationics and for most cases increases also the maximum amount adsorbed, but decreases slightly the efficiency of removal of 2-naphthol. On limestone, the anionic gemini adsorbs with one hydrophilic group oriented toward the Ca(2+) sites on the surface and its second hydrophilic group oriented toward the aqueous phase. The conventional anionic surfactant forms a double layer. The gemini anionic is more efficient and more effective than the conventional anionic in the removal of 2-naphathol from the aqueous phase. Both anionic conventional and gemini surfactants have no adsorption on sand. The adsorption mechanisms for all the surfactants on the three soil solid surfaces are discussed. Copyright 2001 Academic Press. PMID:11161529

Rosen, M. J.; Li, Fang

2001-02-15

373

Inflammatory Cytokines and Cell Death in BEAS-2B Lung Cells Treated with Soil Dust, Lipopolysaccharide, and Surface-Modified Particles  

PubMed Central

Cultured human lung epithelial cells (BEAS-2B) were treated in vitro with PM2.5-enriched particles of soil-derived mineral dust from nine sites in the western United States. The particle samples simulate windblown dust and vehicle-generated emissions from unpaved roads. Five of the sites yielded relatively benign dust. Particles from three sites caused IL-6 release when cells were treated for 24 h at doses from 20 to 80 ?g/cm2, and particles from one site were highly cytotoxic. The particle components or characteristics that caused the IL-6 release were stable at temperatures below 150°C, but were inactivated by treatment at 300–550°C. The active factors were also associated predominantly with the insoluble fraction, and were partially attenuated by leaching with aqueous and organic solvents. The IL-6 release caused by the particles was much greater than the cytokine response to either lipopolysaccharide (LPS) or to surrogate particles of titanium dioxide mixed with LPS, suggesting that endotoxin was not a major factor in the inflammatory response. The release of IL-8 in response to particle treatment was qualitatively similar to the IL-6 response, but release of TNF-? was not detected at the 24-h time point. The combined results support the hypothesis that some ambient dusts from geological sources can cause cell death and cytokine release in a lung cell line that is widely used as an in vitro model to study mechanisms of environmental respiratory injury. PMID:15310859

Veranth, John M.; Reilly, Christopher A.; Veranth, Martha M.; Moss, Tyler A.; Langelier, Charles R.; Lanza, Diane L.; Yost, Garold S.

2008-01-01

374

Vibrio cholerae non-O1: production of cell-associated hemagglutinins and in vitro adherence to mucus coat and epithelial surfaces of the villi and lymphoid follicles of human small intestines treated with formalin.  

PubMed Central

Clinically isolated Vibrio cholerae non-O1 strains produced more cell-associated hemagglutinins (HAs) on colonization factor antigen agar after ca. 3 h than after ca. 20 h of incubation at 37 degrees C. A high cell-associated HA producer variant of strain TVN-318, grown for 3 h at 37 degrees C, was entrapped in a native mucus coat covering the human ileal mucosa and displayed a striking ability to adhere to the surface of a Formalin-treated mucus coat, in contrast to a poor cell-associated HA producer variant of TVN-318, grown for 20 h at 37 degrees C. Adherence to the Formalin-treated human mucus coat was confirmed with all of the strains tested. V. cholerae non-O1 strains also possessed the ability to adhere to the epithelial surfaces of Formalin-treated human and rabbit ileal or jejunal villi, as well as human lymphoid follicles, in proportion to cell-associated HA levels. The epithelial surface of the lymphoid follicles provided most of the adherence sites for V. cholerae non-O1 strains under the test conditions. We conclude that a mucus coat covering the human small intestinal mucosa is a primary adherence target for V. cholerae non-O1 strains in human intestinal infections and that cell-associated HAs have at least a partial role in the adherence of V. cholerae non-O1 strains to the human small intestine, suggesting a potential role for V. cholerae non-O1 strains in an oral live vaccine. Images PMID:2903173

Yamamoto, T; Yokota, T

1988-01-01

375

Coordinate up-regulation of TMEM97 and cholesterol biosynthesis genes in normal ovarian surface epithelial cells treated with progesterone: implications for pathogenesis of ovarian cancer  

Microsoft Academic Search

BACKGROUND: Ovarian cancer (OvCa) most often derives from ovarian surface epithelial (OSE) cells. Several lines of evidence strongly suggest that increased exposure to progesterone (P4) protects women against developing OvCa. However, the underlying mechanisms of this protection are incompletely understood. METHODS: To determine downstream gene targets of P4, we established short term in vitro cultures of non-neoplastic OSE cells from

Cathy B Wilcox; Grace O Feddes; Joan E Willett-Brozick; Lih-Ching Hsu; Julie A DeLoia; Bora E Baysal

2007-01-01

376

Granular sludge growth under different reactor liquid surface tensions in lab-scale upflow anaerobic sludge blanket reactors treating wastewater from sugar-beet processing  

Microsoft Academic Search

The formation of anaerobic granular sludge on wastewater from sugar-beet processing was examined in upflow anaerobic sludge blanket reactors. Two strategies were investigated: addition of high-energy substrate, i.e. sugars, and varying the reactor liquid surface tension. When there were insufficient amounts of sugars i.e. less than 7% of the chemical O2 demand of the influent, no granulation was observed; moreover

J. Thaveesri; B. Liessens; W. Verstraete

1995-01-01

377

Antimicrobial hyperbranched poly(ester amide)/polyaniline nanofiber modified montmorillonite nanocomposites.  

PubMed

There has been growing interest in the use of nanomaterials featuring potent of antimicrobial activity in the biomedical domain. It still remains a challenge for the researchers to develop an efficient nanocomposite possessing antimicrobial efficacy against broad spectrum microbes including bacteria, fungi as well as algal consortium, posing serious challenges for the human survival. In addressing the above problem, we report the fabrication of bio-based hyperbranched poly(ester amide) (HBPEA)/polyaniline nanofiber modified montmorillonite (MMT) nanocomposites by an ex-situ polymerization technique at varied weight percentages (1, 2.5, 5 wt.%) of the modified MMT (nanohybrid). The Fourier transform infrared spectroscopy confirmed the structural changes upon interaction of the nanohybrid with HBPEA. A probable mechanism is proposed for the formation of nanocomposites with partially exfoliated nanoplatelet structure, which was further confirmed from the high resolution transmission electron microscopic analyses. The prepared nanocomposites exhibited potent efficacy against gram positive bacteria like Bacillus subtilis and Staphylococcus aureus as compared to the gram negative ones like Pseudomonas aeruginosa and Escherichia coli. The nanocomposites showed significant antifungal activity against Aspergillus niger, Fusarium oxysporum and Coleotricum capcii and antialgal activity against algal consortium comprising of Chlorella, Hormidium and Cladophorella species. The formation of thermosetting nanocomposites resulted in the acceptable improvement of desired physico-chemical and mechanical properties including thermostability. Thus pronounced antimicrobial activity of the nanocomposites against a spectrum of bacterial and fungal strains as well as a consortium of algal species along with other desired performance vouched them as potent antimicrobial materials in the realm of health and biomedical industry. PMID:24411352

Pramanik, Sujata; Bharali, Pranjal; Konwar, B K; Karak, Niranjan

2014-02-01

378

Montmorillonite catalysis of RNA oligomer formation in aqueous solution. A model for the prebiotic formation of RNA  

NASA Technical Reports Server (NTRS)

Oligomers of adenylic acid of up to the 11-mer in length are formed by the reaction of the phosphorimidazolide of adenosine (ImpA) in pH 8 aqueous solution at room temperature in the presence of Na(+)-montmorillonite. These oligomers are joined by phosphodiester bonds in which the 3',5'-linkage predominates over the 2',5'-linkage by a 2:1 ratio. Reaction of a 9:1 mixture of ImpA, A5'ppA results in the formation of oligomers with a 3:1 ratio of 3',5'- to 2',5'-linked phosphodiester bonds. A high proportion of these oligomers contain the A5'ppA grouping. A5'ppA reacts much more rapidly with ImpA than does 5'-ADP (ppA) or 5'-ATP (pppA). The exchangeable cation associated with the montmorillonite effects the observed catalysis with Li+, Na+, NH4+, and Ca2+ being the more effective while Mg2+ and Al3+ are almost ineffective catalysts. 2',5'-Linked oligomers, up to the tetramer in length, are formed using UO2(2+)-montmorillonite. The structure analysis of individual oligomer fractions was performed by selective enzymatic and KOH hydrolytic studies followed by HPLC analysis of the reaction products. It is concluded from the composition of the oligomers that the rate of addition ImpA to a 3'-terminus containing a 2',5'-linkage is slower than the addition to a nucleoside joined by a 3',5'-linked phosphodiester bond. The potential importance of mineral catalysis of the formation of RNA and other oligomers on primitive Earth is discussed.

Ferris, J. P.; Ertem, G.

1993-01-01

379

In situ study of CO? and H?O partitioning between Na-montmorillonite and variably wet supercritical carbon dioxide.  

PubMed

Shale formations play fundamental roles in large-scale geologic carbon sequestration (GCS) aimed primarily to mitigate climate change and in smaller-scale GCS targeted mainly for CO2-enhanced gas recovery operations. Reactive components of shales include expandable clays, such as montmorillonites and mixed-layer illite/smectite clays. In this study, in situ X-ray diffraction (XRD) and in situ infrared (IR) spectroscopy were used to investigate the swelling/shrinkage and H2O/CO2 sorption of Na(+)-exchanged montmorillonite, Na-SWy-2, as the clay is exposed to variably hydrated supercritical CO2 (scCO2) at 50 °C and 90 bar. Measured d001 values increased in stepwise fashion and sorbed H2O concentrations increased continuously with increasing percent H2O saturation in scCO2, closely following previously reported values measured in air at ambient pressure over a range of relative humidities. IR spectra show H2O and CO2 intercalation, and variations in peak shapes and positions suggest multiple sorbed types of H2O and CO2 with distinct chemical environments. Based on the absorbance of the asymmetric CO stretching band of the CO2 associated with the Na-SWy-2, the sorbed CO2 concentration increases dramatically at sorbed H2O concentrations from 0 to 4 mmol/g. Sorbed CO2 then sharply decreases as sorbed H2O increases from 4 to 10 mmol/g. With even higher sorbed H2O concentrations as saturation of H2O in scCO2 was approached, the concentration of sorbed CO2 decreased asymptotically. Two models, one involving space filling and the other a heterogeneous distribution of integral hydration states, are discussed as possible mechanisms for H2O and CO2 intercalations in montmorillonite. The swelling/shrinkage of montmorillonite could affect solid volume, porosity, and permeability of shales. Consequently, the results may aid predictions of shale caprock integrity in large-scale GCS as well as methane transmissivity in enhanced gas recovery operations. PMID:24810708

Loring, John S; Ilton, Eugene S; Chen, Jeffrey; Thompson, Christopher J; Martin, Paul F; Bénézeth, Pascale; Rosso, Kevin M; Felmy, Andrew R; Schaef, Herbert T

2014-06-01

380

Silver nanoparticle-treated filter paper as a highly sensitive surface-enhanced Raman scattering (SERS) substrate for detection of tyrosine in aqueous solution.  

PubMed

Highly sensitive SERS substrates based on deposition of silver nanoparticles on commercially available filter paper were prepared in this work, and used to overcome problems found in analyses of aqueous samples. To prepare silver nanoparticle- (AgNP) doped filter substrates, a silver mirror reaction was used. The procedures for substrate preparation were systematically optimized. Pretreatment of filter paper, reaction time, temperature, and concentration of reagents for silver mirror reactions were studied. The morphologies of the resulting substrates were characterized by field-emission scanning electron microscopy (FE-SEM) and correlated with the SERS signals by probing with p-nitrothiophenol (pNTP). Filter papers with different pretreatments were found to have different sizes and distributions of AgNPs. The best performance was found when filter paper was pre-treated with ammonia solution before growth of AgNPs. Based on the SEM images, the resulting AgNPs had roughly spherical shape with a high degree of uniformity. The silver-coated filter paper substrates provide much higher SERS signals compared to glass substrates and the reproducibility was improved significantly. Based on statistical analyses, the relative standard deviations for substrate-to-substrate and spot-to-spot were both were less than 8% and the enhancement factors for the substrates were, in general, higher than 107. The SERS substrates were used to selectively detect tyrosine in aqueous solution. Results indicate that filter-based SERS substrates are highly suited to detection of tyrosine. Compared to glass-based SERS substrates, 50 times more SERS signal was observed in detection of tyrosine. The linear range can be up to 100 ?M with a detection limit of 625 nM (SN(-1)=3). PMID:22093349

Cheng, Min-Liang; Tsai, Bo-Chan; Yang, Jyisy

2011-12-01

381

Montmorillonite catalysis of 30-50 mer oligonucleotides: laboratory demonstration of potential steps in the origin of the RNA world.  

PubMed

Elongation of the primer 32pdA(pdA)8pA proceeds by the reaction of the 5'-phosphorimidazolides of adenosine and uridine in the presence of montmorillonite clay. Daily addition of the activated nucleotides for up to 14 days results in the formation of 40-50 mers using the 5'-phosphorimidazolide of adenosine (ImpA) and 25-30 mers using the 5'-phosphorimidazolide of uridine (ImpU). The limitation on the lengths of the chains formed is not due to the inhibitors formed since the same chain lengths were formed using 2-3 times the amount of montmorillonite catalyst. The shorter oligomers formed by the addition of U monomers is not due to its greater rate of decomposition since it was found that both the A and the U adducts decompose at about the same rates. Alkaline phosphatase hydrolysis studies revealed that some of the oligomers are capped at the 5'-end to form, with ImpA, Ap32pdA(pdA)8pA(pA)n. The extent of capping depends on the reaction time and the purine or pyrimidine base in the activated mononucleotide. Hydrolysis with ribonuclease T2 followed by alkaline phosphatase determined the sites of the 3', 5'- and 2', 5'-phosphodiester bonding to the primer. The potential significance of the mineral catalyzed formation of 50 mer oligonucleotides to the origin of life based on RNA (the RNA world scenario) is discussed. PMID:12458736

Ferris, James P

2002-08-01

382

Comparison of In Situ Polymerization and Solution-Dispersion Techniques in the Preparation of Polyimide/Montmorillonite (MMT) Nanocomposites  

PubMed Central

In this paper, Polyimide/Montmorillonite Nanocomposites (PI/MMT NCs), based on aromatic diamine (4-Aminophenyl sulfone) (APS) and aromatic dianhydride (3,3?,4,4?-benzophenonetetracarboxylic dianhydride) (BTDA) were prepared using in situ polymerization and solution-dispersion techniques. The prepared PI/MMT NCs films were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). The XRD results showed that at the content of 1.0 wt % Organo Montmorillonite (OMMT) for two techniques and 3.0 wt % OMMT for the in situ polymerization technique, the OMMT was well-intercalated, exfoliated and dispersed into polyimide matrix. The OMMT agglomerated when its amount exceeded 10 wt % and 3.0 wt % for solution-dispersion and in situ polymerization techniques respectively. These results were confirmed by the TEM images of the prepared PI/MMT NCs. The TGA thermograms indicated that thermal stability of prepared PI/MMT NCs were increased with the increase of loading that, the effect is higher for the samples prepared by in situ polymerization technique. PMID:22016643

Ahmad, Mansor Bin; Gharayebi, Yadollah; Salit, Mohd. Sapuan; Hussein, Mohd. Zobir; Shameli, Kamyar

2011-01-01

383

Comparison between the removal of phenol and catechol by modified montmorillonite with two novel hydroxyl-containing Gemini surfactants.  

PubMed

Na-montmorillonites were modified with two novel hydroxyl-containing Gemini surfactants, 1,3-bis(hexadecyldimethylammonio)-2-hydroxypropane dichloride (BHHP) and 1,3-bis(octyldimethylammonio)-2-hydroxypropane dichloride (BOHP), via ion-exchange reaction in this study. The modified samples were characterized by X-ray diffraction (XRD) and Fourier Transform Infrared (FT-IR) spectroscopy. Phenol and catechol were removed from aqueous solution by these two kinds of organo-montmorillonites in a batch system. Important parameters have been investigated, which affect the adsorption efficiency, such as the amount of modifier, temperature, pH and contact time. The adsorption kinetics of phenol and catechol were discussed using pseudo-first-order, pseudo-second-order and intra-particle diffusion model. It indicated that the experimental data fitted very well with the pseudo-second-order kinetic model, and the equilibrium adsorption data was proved in good agreement with the Langmuir isotherm. The result also showed the adsorption capacity of catechol was higher than that of phenol in the same conditions, which might result from the extra hydroxyl in the structure of catechol. Thermodynamic quantities such as Gibbs free energy (?G°), the enthalpy (?H°), and the entropy change of sorption (?S°) were also determined. These parameters suggested the adsorption of phenol was a spontaneous and exothermic process, while the sorption of catechol was endothermic. PMID:24413053

Liu, Yuening; Gao, Manglai; Gu, Zheng; Luo, Zhongxin; Ye, Yage; Lu, Laifu

2014-02-28

384

Morphological and Functional Analysis of Hepatocyte Spheroids Generated on Poly-HEMA-Treated Surfaces under the Influence of Fetal Calf Serum and Nonparenchymal Cells  

PubMed Central

Poly (2-hydroxyethyl methacrylate) (HEMA) has been used as a clinical material, in the form of a soft hydrogel, for various surgical procedures, including endovascular surgery of liver. It is a clear liquid compound and, as a soft, flexible, water-absorbing material, has been used to make soft contact lenses from small, concave, spinning molds. Primary rat hepatocyte spheroids were created on a poly-HEMA-coated surface with the intention of inducing hepatic tissue formation and improving liver functions. We investigated spheroid formation of primary adult rat hepatocyte cells and characterized hepatic-specific functions under the special influence of fetal calf serum (FCS) and nonparencymal cells (NPC) up to six days in different culture systems (e.g., hepatocytes + FCS, hepatocytes – FCS, NPC + FCS, NPC – FCS, co-culture + FCS, co-culture – FCS) in both the spheroid model and sandwich model. Immunohistologically, we detected gap junctions, Ito cell/Kupffer cells, sinusoidal endothelial cells and an extracellular matrix in the spheroid model. FCS has no positive effect in the sandwich model, but has a negative effect in the spheroid model on albumin production, and no influence in urea production in either model. We found more cell viability in smaller diameter spheroids than larger ones by using the apoptosis test. Furthermore, there is no positive influence of the serum or NPC on spheroid formation, suggesting that it may only depend on the physical condition of the culture system. Since the sandwich culture has been considered a “gold standard” in vitro culture model, the hepatocyte spheroids generated on the poly-HEMA-coated surface were compared with those in the sandwich model. Major liver-specific functions, such as albumin secretion and urea synthesis, were evaluated in both the spheroid and sandwich model. The synthesis performance in the spheroid compared to the sandwich culture increases approximately by a factor of 1.5. Disintegration of plasma membranes in both models was measured by lactate dehydrogenase (LDH) release in both models. Additionally, diazepam was used as a substrate in drug metabolism studies to characterize the differences in the biotransformation potential with metabolite profiles in both models. It showed that the diazepam metabolism activities in the spheroid model is about 10-fold lower than the sandwich model. The poly-HEMA-based hepatocyte spheroid is a promising new platform towards hepatic tissue engineering leading to in vitro hepatic tissue formation. PMID:24970167

Acikgoz, Ali; Giri, Shibashish; Cho, Man-Gi; Bader, Augustinus

2013-01-01

385

Direct probing of the folding/unfolding event of bovine hemoglobin at montmorillonite clay modified electrode by adsorptive-transfer voltammetry.  

PubMed

An efficient way was proposed for probing the folding/unfolding event of bovine hemoglobin (Hb) through adsorptive-transfer voltammetry. Hb molecules in native and pre-unfolded in different urea conditions for 23 h were adsorbed onto the montmorillonite clay modified glassy carbon electrode (Hb/clay/GCE and uHb/clay/GCE, respectively). Cyclic voltammograms of Hb/clay/GCE and uHb/clay/GCE showed that the unfolding of Hb caused great change in the direct electron transfer between the heme irons within Hb and electrode surface, which was facilitated on clay film. From the amount of the electroactive Hb (W(Hbe)) and the adsorbed Hb (?) on clay per unit mass, the minimal electroactive portion (MEP) of the adsorbed Hb was calculated to assess the unfolding state of Hb. With the increase of urea concentration, MEP showed a sigmoid curve. Thermodynamic parameters related to the unfolding event of Hb were also obtained based on the linear free energy model (LEM), including the free energy of folding in water (?G(U)(water)), the slope of the Santoro-Bolen equation (m), and the urea concentration required in for achieving half of the total change (S(m)) in the unfolding curves. This work gave the first try for investigating protein unfolding at nano-materials modified electrode using adsorptive-transfer voltammetry, which improved the sensitivity of analysis and avoided the disadvantages involved in the existing electrochemical methods for protein unfolding. The proposed method will benefit the electrochemical studies of protein. PMID:21315912

Zhao, Xiaojuan; Mai, Zhibin; Dai, Zong; Zou, Xiaoyong

2011-03-15

386

Montmorillonite as a Conductivity Enhancer in (PEO)9LiCF3SO3 Polymer Electrolyte  

NASA Astrophysics Data System (ADS)

The solid polymer electrolyte systems, based on poly(ethylene oxide) (PEO) and lithium ions have attracted much attentions as a potential electrolyte medium in secondary energy sources and electrochromic devises. They show a characteristic property of an enhanced ionic conductivity when a plastizier is added. In this research work, PEO and lithium triflate have been taken as the electrolyte medium and an attempt was paid to improve the ionic conductivity of (PEO)9LiCF3SO3 polymer electrolyte system by choosing montmorillonite (MMT) as the plastisizer. The ionic conductivity, thermal transitions, crystallinity, and bonding of the complex system of (PEO)9LiCF3SO3 + x wt.% MMT (x = 0, 3, 4, 5, 6, 10, 15, 20) were systematically characterized by ac-impedance spectroscopy, differential scanning calorimetry (DSC), X-ray diffraction (XRD) spectroscopy and fourier transformed infrared (FTIR) spectroscopy, respectively. The ac-impedance data reveal that the ionic conductivity of (PEO)9LiCF3SO3 system is changed with the concentration of MMT, maximum conductivity of 4.14857 × 10-7 S cm-1 at room temperature was observed for the system of (PEO)9LiCF3SO3 + 5 wt.% MMT. However, the ionic conductivity of the above system was increased with the increase of temperature, and the highest conductivity of 2.63 × 10-4 S cm-1 was observed at 80°C. The DSC and XRD data clearly show that the crystalline nature of PEO is reduced when MMT is added. The glass transition temperature (-46.37°C) and melting temperature (53.72°C) of the above system is reduced compared to those of other systems. This supports to the conductivity enhancement in an amorphous environment. The FTIR spectra obtained for MMT, PEO, (PEO)9LiCF3SO3, and (PEO)9LiCF3SO3 + 5 wt.% MMT clearly indicative that the interactions take place between these constituents, as the intensities of typical stretching vibrational modes of 916 cm-1 ? (Al-O-H), 1040 cm-1 ? (Si-O) and 3300-3700 cm-1 ? (O-H) in MMT, and the vibrational modes of CH2 rocking at 948 and 840 cm-1 and C-O stretching at 1149 and 1090 cm-1 in PEO are shifted. The change of symmetric bending mode of CF3 [?s (CF3)] at 752 cm-1 in lithium triflate has altogether supported the bonding characteristics in the electrolyte system and the corresponding conductivity enhancements.

Manoratne, C. H.; Rajapakse, R. M. G.; Dissanayake, M. A. K. L.; Bandara, W. M. A. T.; Tennakoon, D. T. B.

2006-06-01

387

Ion equilibrium between montmorillonite interlayer space and an external solution—Consequences for diffusional transport  

NASA Astrophysics Data System (ADS)

Bentonite clay is proposed as buffer material in several concepts of High Level Radioactive Waste repositories, and a correct description of ion diffusion in this material is of vital importance for any quantification of the chemical evolution of the repository near field. This study investigates the importance of ion equilibrium between montmorillonite interlayer space and an external solution for the diffusional behavior of bentonite. Two distinct and well established mechanisms govern this type of ion equilibrium: Donnan equilibrium and ion exchange equilibrium. Donnan equilibrium influences both cations and anions in a symmetric manner, while ion exchange only is relevant in systems of more than one type of cations. Both mechanisms generate ion concentration discontinuities across the bentonite/external solution interface. A general theoretical framework for describing through-diffusion is developed. An expression for the effective diffusion coefficient, D, is derived, taking into account also the influence of filters typically present in these types of experiments D=??{?}/{2+?}D, where ? is total clay porosity, D is the diffusion coefficient in the clay, ? describes the influence of filters and ? is a general ion equilibrium coefficient. The above expression is valid for both cations and anions. The theory has been applied to one laboratory study concerning cation (Na +) and two independent laboratory studies concerning anion (Cl -) diffusion in Na-bentonite. The commonly observed different transport behavior for anions and cations in bentonite is principally explained by the concentration discontinuities: ? is large for tracer cations at low electrolyte concentrations, but approaches zero for anions in the same concentration limit. The presented theory implies that effective diffusion coefficients evaluated from tracer through-diffusion experiments do not describe diffusive mass transfer in bentonite in general. Furthermore, it shows that ion diffusion in compacted bentonite is principally explained without the commonly used concepts of anion porosity and sorption mechanisms. The striking explanatory power of this basic approach shows the necessity to consider interlayer ion equilibrium in compacted bentonite, and that these considerations must be at the core of any type of modeling (transport, pore water chemistry, mechanics etc.) of bentonite exerting swelling pressure.

Birgersson, Martin; Karnland, Ola

2009-04-01

388

Reflectance and Mossbauer spectroscopy of ferrihydrite-montmorillonite assemblages as Mars soil analog materials  

NASA Technical Reports Server (NTRS)

Spectroscopic analyses show that Fe(3+)-doped smectites prepared in the laboratory exhibit important similarities to the soils on Mars. Ferrihydrite has been identified as the interlayer ferric component in Fe(3+)-doped smectites by a low quadrupole splitting and magnetic field strength of approximately 48 tesla in Mossbauer spectra measured at 4.2 K, as well as a crystal field transition at 0.92 micrometer. Ferrihydrite in these smectites explains features in the visible-near infrared region that resemble the energies and band strengths of features in reflectance spectra observed for several bright regions on Mars. Clay silicates have met resistance in the past as Mars soil analogs because terrestrial clay silicates exhibit prominent hydrous spectral features at 1.4, 1.9, and 2.2 micrometers; and these are observed weakly, if at all, in reflectance spectra of Mars. However, several mechanisms can weaken or compress these features, including desiccation under low-humidity conditions. The hydration properties of the interlayer cations also effect band strengths, such that a ferrihydrite-bearing smectite in the Martian environment would exhibit a 1.9 micrometers H2O absorption that is even weaker than the 2.2 micrometers structural OH absorption. Mixing experiments demonstrate that infrared spectral features of clays can be significantly suppressed and that the reflectance can be significantly darkened by mixing with only a few percent of a strongly absorbing opaque material. Therefore, the absolute reflectance of a soil on Mars may be disproportionately sensitive to a minor component. For this reason, the shape and position of spectral features and the chemical composition of potential analogs are of utmost importance in assessing the composition of the soil on Mars. Given the remarkable similarity between visible-infrared reflectance spectra of soils in bright regions on Mars and Fe(3+)-doped montmorillonites, coupled with recent observations of smectites in SNC meteorites and a weak 2.2 micrometers absorption in some Mars soils, ferrihydrite-bearing smectites warrant serious consideration as a Mars soil analog.

Bishop, J. L.; Pieters, C. M.; Burns, R. G.; Chang, S. (Principal Investigator)

1993-01-01

389

One?Pot, Three?Component Synthesis of 2,3?Dihydro?4(1H)?quinazolinones by Montmorillonite K?10 as an Efficient and Reusable Catalyst  

Microsoft Academic Search

A wide range of mono? and disubstituted dihydroquinazolinones were synthesised via condensation of isatoic anhydride, primary amines, or ammonium salts with aromatic aldehydes in the presence of montmorillonite K?10. The catalyst is reusable and could be recycled for several runs without any decrease in its efficiency.

Peyman Salehi; Minoo Dabiri; Mostafa Baghbanzadeh; Mahboobeh Bahramnejad

2006-01-01

390

Investigation of montmorillonite alteration and form of iron corrosion products in compacted bentonite in contact with carbon steel for ten years  

NASA Astrophysics Data System (ADS)

In high-level radioactive waste disposal, the alteration of montmorillonite due to the corrosion of carbon steel possibly affects the swelling and self-healing capacity of compacted bentonite used as a buffer material. The nature of the corrosion products in compacted bentonite is also important to evaluate not only the diffusion and sorption behavior of radionuclides but also the chemical composition and redox potential of pore water. In this study, the alteration of montmorillonite in compacted bentonite due to the interaction with carbon steel was analyzed by X-ray diffraction (XRD). The possibility of montmorillonite alteration was also investigated from the cation exchange capacity (CEC) of compacted bentonite and scanning electron microscopy (SEM) observation. The corrosion products distributed in the compacted bentonite were investigated by selective dissolution analysis, which can estimate the crystallinity of Fe-bearing compounds. The valence of Fe in the corrosion products was spectrophotometrically determined. From the XRD analysis, newly formed phyllosilicates resulting from the alteration of montmorillonite could not be identified in compacted bentonite. CEC of compacted bentonite adjacent to the carbon steel, in which high concentration of Fe was extracted, was hardly decreased. No significant differences of clay particles were observed with SEM. Thus, the alteration of montmorillonite was scarcely detected in compacted bentonite in contact with carbon steel for ten years. The selective dissolution and valence analyses suggest that most of the corrosion products of carbon steel existed in Kunipia F, which consists of over 95 wt% montmorillonite, was amorphous, non-crystalline or poorly ordered Fe(OH) 2. This means that Fe(OH) 2 distributed into compacted bentonite was scarcely crystallized within ten years at 80 oC. From the XRD analysis, small amount of green rust one containing Cl - at the interlayers (GR1(Cl -)) and lepidocrocite were also identified in Kunipia F. Therefore, under this experimental condition, Fe(OH) 2 formed in Kunipia F due to the corrosion of carbon steel was oxidized to GR1(Cl -) as intermediates, and then GR1(Cl -) was possibly oxidized to lepidocrocite. On the other hand, GR1(Cl -) was hardly detected in Kunigel V1, which contains 46-49 wt% montmorillonite, from the XRD analysis.

Ishidera, Takamitsu; Ueno, Kenichi; Kurosawa, Seiichi; Suyama, Tadahiro

391

Effect of treatment with acids on the state of the surface of natural clay minerals  

Microsoft Academic Search

The state of the surface of natural clay minerals containing montmorillonite (lamellar structure), clinoptilolite (rigid skeleton\\u000a structure), and palygorskite (lamellar-banded structure) and of the same minerals modified with a 17% solution of sulfuric\\u000a acid was examined. It was established that the modification affected the specific surface area and porosity of the minerals\\u000a studied. It was found that the degree of

L. A. Novikova; L. I. Bel’chinskaya; F. Roessner

2006-01-01

392

Amino acid similarities and divergences in the small surface proteins of genotype C hepatitis B viruses between nucleos(t)ide analogue-naïve and lamivudine-treated patients with chronic hepatitis B.  

PubMed

Entire C-genotype small hepatitis B surface (SHBs) sequences were isolated from 139 nucleos(t)ide analogues (NA)-naïve and 74 lamivudine (LMV)-treated chronic hepatitis B (CHB) patients. The conservation and variability of total 226 amino acids (AAs) within the sequences were determined individually, revealing significant higher mutant isolate rate and mutation frequency in LMV-treated cohort than those in the NA-naïve one (P=0.009 and 0.0001, respectively). Three absolutely conserved fragments (s16-s19, s176-s181 and s185-s188) and seven moderately conserved regions (a few AA sites acquiring increased variability after LMV-treatment) were identified. The significant mutation rate increase after LMV-treatment occurred primarily in major hydrophilic region (except 'a' determinant) and transmembrane domain 3/4, but not in other upstream functional regions of SHBs. With little influence on immune escape-associated mutation frequencies within 'a' determinant, LMV-monotherapy significantly induced classical LMVr-associated mirror changes sE164D/rtV173L, sI195M/rtM204V and sW196L/S/rtM204I, as well as non-classical ones sG44E/rtS53N, sT47K/A/rtH55R/Q and sW182stop/rtV191I outside 'a' determinant. Interestingly, another newly-identified truncation mutation sC69stop/rtS78T decreased from 7.91% (11/139) in NA-naïve cohort to 2.70% (2/74) in LMV-treated one. Altogether, the altered AA conservation and diversity in SHBs sequences after LMV-treatment in genotype-C HBV infection might shed new insights into how LMV-therapy affects the SHBs variant evolution and its antigenicity. PMID:24316031

Ding, Hai; Liu, Baoming; Zhao, Chengyu; Yang, Jingxian; Yan, Chunhui; Yan, Ling; Zhuang, Hui; Li, Tong

2014-02-01

393

Detection of Soluble and Fixed NH4+ in Clay Minerals by DTA and IR Reflectance Spectroscopy : A Potential Tool for Planetary Surface Exploration  

NASA Technical Reports Server (NTRS)

Nitrogen is an essential element for life. It is the only element among the six major biogenic elements, C, O, S, O, P, H, whose presence in the Martian soil has not been positively and directly established. We describe here a study assessing the ability to detect NH4 in soils by two methods: differential thermal analysis (DTA) and infrared (IR) reflectance spectroscopy. Four standard clay minerals (kaolinite, montmorillonite, illite and attapulgite) and an altered tephra sample from Mauna Kea were treated with NH4 in this study. Samples of the NH4-treated and leached clays were analyzed by DTA and infrared (IR) reflectance spectroscopy to quantify the delectability of soluble and sorbed/fixed NH4. An exotherm at 270-280 C was clearly detected in the DTA curves of NH4-treated (non-leached) samples. This feature is assigned to the thermal decomposition reaction of NH4. Spectral bands observed at 1.56, 2.05, 2.12, 3.06, 3.3, 3.5, 5.7 and 7.0 microns in the reflectance spectra of NH4-treated and leached samples are assigned to the sorbed/fixed ammonium in the clays. The montmorillonite has shown the most intense absorbance due to fixed ammonium among the leached samples in this study, as a result of its high cation sorption capacity. It is concluded that the presence of sorbed or fixed NH4 in clays may be detected by infrared (IR) reflectance or emission spectroscopy. Distinction between soluble and sorbed NH4 may be achieved through the presence or absence of several spectral features assigned to the sorbed NH4 moietyi and, specifically, by use of the 4.2 micrometer feature assigned to solution NH4. Thermal analyses furnish supporting evidence of ammonia in our study through detection of N released at temperatures of 270-330 C. Based on these results it is estimated that IR spectra measured from a rover should be able to detect ammonia if present above 20 mg NH4/g sample in the surface layers. Orbital IR spectra and thermal analyses measured on a rover may be able to detect ammonia in soils as well but at higher abundances. The spectral features at 3.06 and 7.0 microns due to bound NH4 in clays and altered Hawaiian tephra appear to be the most promising for detection by orbital spectrometers. If N species are present on Mars the sedimentary deposits may be the best regions to look for them.

Janice, Bishop; Banin, A.; Mancinelli, R. L.; Klovstad, M. R.; DeVincenzi, Donald L. (Technical Monitor)

2001-01-01

394

Effect of phosphate activating group on oligonucleotide formation on montmorillonite: the regioselective formation of 3',5'-linked oligoadenylates  

NASA Technical Reports Server (NTRS)

The effects of amine structure on the montmorillonite-catalyzed oligomerization of the 5'-phosphoramidates of adenosine are investigated. 4-Aminopyridine derivatives yielded oligoadenylates as long as dodecamers with a regioselectivity for 3',5'-phosphodiester bond formation averaging 88%. Linear and cyclic oligomers are obtained and no A5'ppA-containing products are detected. Oligomers as long as the hexanucleotide are obtained using 2-aminobenzimidazole as the activating group. A predominance of pA2'pA is detected in the dimer fraction along with cyclic 3',5'-trimer; no A5'ppA-containing oligomers were detected. Little or no oligomer formation was observed when morpholine, piperidine, pyrazole, 1,2,4-triazole, and 2-pyridone are used as phosphate-activating groups. The effects of the structure of the phosphate activating group on the oligomer structure and chain lengths are discussed.

Prabahar, K. J.; Cole, T. D.; Ferris, J. P.

1994-01-01

395

Simple and novel electrochemical sensor for the determination of tetracycline based on iron/zinc cations-exchanged montmorillonite catalyst.  

PubMed

A simple and novel electrochemical sensor for the determination of tetracycline (TC), a kind of antibiotic that may induce residue in the food chain, was developed by the modification of iron/zinc cation-exchanged montmorillonite (Fe/Zn-MMT) catalyst on glassy carbon electrode (GCE). The morphology and the structure of the Fe/Zn-MMT nanomaterial were characterized by scanning electron microscopy and X-ray diffraction, respectively. The results of electrochemical experiments demonstrated that the sensor exhibited excellent electrocatalytic activity to the oxidation of TC in the presence of sodium dodecyl sulfate. The sensor displayed a wide linear range from 0.30 to 52.0 ?M and a low detection limit of 0.10 ?M by using the derivative differential pulse voltammetry. Moreover, the electrochemical sensor was applied to the detection of TC in feedstuff and meat samples. PMID:24607125

Gan, Tian; Shi, Zhaoxia; Sun, Junyong; Liu, Yanming

2014-04-01

396

Effects of preparation methods on the structure and mechanical properties of wet conditioned starch/montmorillonite nanocomposite films.  

PubMed

TPS/Na-montmorillonite nanocomposite films were prepared by solution and melt blending. Clay content changed between 0 and 25wt% based on the amount of dry starch. Structure, tensile properties, and water content of wet conditioned films were determined as a function of clay content. Intercalated structure and VH-type crystallinity of starch were found for all the nanocomposites independently of clay and plasticizer content or preparation method, but at larger than 10wt% clay content nanocomposites prepared by melt intercalation contained aggregated particles as well. In spite of the incomplete exfoliation clay reinforces TPS considerably. Preparation method has a strong influence on mechanical properties of wet conditioned films. Mechanical properties of the conditioned samples prepared by solution homogenization are much better than those of nanocomposites prepared by melt blending. Water, which was either adsorbed or bonded in the composites in conditioning or solution mixing process, respectively, has different effect on mechanical properties. PMID:25256520

Müller, Péter; Kapin, Eva; Fekete, Erika

2014-11-26

397

Oligomerization reactions of ribonucleotides - The reaction of the 5'-phosphorimidazolide of adenosine with diadenosine pyrophosphate on montmorillonite and other minerals  

NASA Technical Reports Server (NTRS)

The overall regiospecificity of the 3',5'-phosphodiester bond formation is shown to be increased from 64 to 83 percent when a 9:1 ratio of ImpA to A5'ppA instead of ImpA alone is reacted in the presence of Na(+)-montmorillonite. The major factor in the regiospecificity increase is the formation of 3',5'-linked A5'ppA3'pA and A5'pp-A3'pA3'pA. The results obtained show that ImpA reacts more readily with A5'ppA than it does with another ImpA molecule and that A5'ppA plays a central role in directing the formation of 3',5'-phosphodiester bonds.

Ferris, James P.; Ertem, Gozen

1993-01-01

398

Cooperative coadsorption of 4-nitrophenol and basic yellow 28 dye onto an iron organo-inorgano pillared montmorillonite clay.  

PubMed

Sorption properties of an iron surfactant-modified pillared montmorillonite (Fe-SMPM) toward two organic pollutants, basic yellow 28 dye (BY28) and 4-nitrophenol (4-NP), were studied at different pH values in both single component and binary pollutant systems. The pseudo-first-order model fits well with the kinetic data obtained in single component studies and sorption capacities of both BY28 and 4-NP increased with the pH value. A sorption synergetic mechanism was observed in binary systems; 4-nitrophenol adsorption was enhanced by the presence of BY28 in the mixture and increased with dye concentrations. Isotherms were described using the Freundlich model in single component systems and the Sheindorf-Rebhun-Sheintuch (SRS) model, an extended Freundlich model, in binary mixtures systems. Hydrophobic interactions between the surfactant-modified pillared clay and the pollutants were suggested to explain the sorption mechanisms. PMID:20638666

Zermane, Faiza; Bouras, Omar; Baudu, Michel; Basly, Jean-Philippe

2010-10-01

399

Montmorillonite-catalysed formation of RNA oligomers: the possible role of catalysis in the origins of life  

PubMed Central

Large deposits of montmorillonite are present on the Earth today and it is believed to have been present at the time of the origin of life and has recently been detected on Mars. It is formed by aqueous weathering of volcanic ash. It catalyses the formation of oligomers of RNA that contain monomer units from 2 to 30–50. Oligomers of this length are formed because this catalyst controls the structure of the oligomers formed and does not generate all possible isomers. Evidence of sequence-, regio- and homochiral selectivity in these oligomers has been obtained. Postulates on the role of selective versus specific catalysts on the origins of life are discussed. An introduction to the origin of life is given with an emphasis on reaction conditions based on the recent data obtained from zircons 4.0–4.5?Ga. PMID:17008218

Ferris, James P

2006-01-01

400

Diffusion of 22Na and 85Sr in montmorillonite: evidence of interlayer diffusion being the dominant pathway at high compaction.  

PubMed

A mechanistic understanding of transport phenomena in compacted clays is essential for the use of such materials as engineered barrier systems for the safe geological disposal of radioactive wastes. The present contribution is a first step in the development of an integrative treatment of the properties of tracer cations in compacted bentonites with respect to diffusion and sorption. The diffusion of 22Na and 85Sr in highly compacted montmorillonite and kaolinite is investigated as a function of the "external salt concentration" (NaClO4), i.e., of the solution in equilibrium with the clay. Consistent results were obtained from through-diffusion experiments and tracer profile analysis. Knowledge of genuine diffusion coefficients of the filter plates turned out to be crucial in cases where the diffusive resistance of the filter plates was similar to that of the clay. Diffusion coefficients formally calculated on the basis of the tracer concentration gradient in the external aqueous phase, and the sorption distribution ratios were found to decrease with increasing external salt concentration in the case of montmorillonite. In a logarithmic representation of these data, a slope of -1 was obtained for the monovalent 22Na, whereas the slope was -2 for the divalent 85Sr. In the case of kaolinite, diffusion coefficients were independent of the external salt concentration. It is postulated that the diffusion of the tracer cation through the interlayer water is the dominant pathway in compacted swelling clays under the experimental conditions tested. Effective diffusion coefficients, based on a tracer concentration gradient in the interlayer water of the clay, were found to be independent of the composition of the external aqueous phase. The latter gradient is assumed to be a function of the external salt concentration, according to a calculated distribution of the tracer cation between free pore water and the interlayer water via cation exchange. PMID:17310710

Glaus, Martin A; Baeyens, Bart; Bradbury, Michael H; Jakob, Andreas; Van Loon, Luc R; Yaroshchuk, Andriy

2007-01-15

401

Adenine derivatives as phosphate-activating groups for the regioselective formation of 3',5'-linked oligoadenylates on montmorillonite: possible phosphate-activating groups for the prebiotic synthesis of RNA  

NASA Technical Reports Server (NTRS)

Methyladenine and adenine N-phosphoryl derivatives of adenosine 5'-monophosphate (5'-AMP) and uridine 5'-monophosphate (5'-UMP) are synthesized, and their structures are elucidated. The oligomerization reactions of the adenine derivatives of 5'-phosphoramidates of adenosine on montmorillonite are investigated. 1-Methyladenine and 3-methyladenine derivatives on montmorillonite yielded oligoadenylates as long as undecamer, and the 2-methyladenine and adenine derivatives on montmorillonite yielded oligomers up to hexamers and pentamers, respectively. The 1-methyladenine derivative yielded linear, cyclic, and A5'ppA-derived oligonucleotides with a regioselectivity for the 3',5'-phosphodiester linkages averaging 84%. The effect of pKa and amine structure of phosphate-activating groups on the montmorillonite-catalyzed oligomerization of the 5'-phosphoramidate of adenosine are discussed. The binding and reaction of methyladenine and adenine N-phosphoryl derivatives of adenosine are described.

Prabahar, K. J.; Ferris, J. P.

1997-01-01

402

REVIEW: Liquid surfaces: theory of surface tension  

Microsoft Academic Search

The theory of equilibrium liquid surfaces is reviewed from the macroscopic (thermodynamic) and microscopic (statistical) points of view. Although emphasis is placed on the surface tension, other surface thermodynamic quantities are treated, especially the contact angle and work of adhesion. The Gibbs scheme is used to describe the surface thermodynamics. The equivalent hydrostatic approach, the curvature dependence of the surface

G. Navascues

1979-01-01

403

Sorption of lambda-cyhalothrin, cypermethrin, deltamethrin and fenvalerate to quartz, corundum, kaolinite and montmorillonite  

Microsoft Academic Search

Sorption to mineral surfaces may be important for retention and degradation of hydrophobic pesticides in subsoils and aquifers poor in organic matter. In this work the title pyrethroids have been used to investigate selective interactions with the surfaces of four minerals. Sorption of the four pyrethroids was quantified in batch experiments with initial pyrethroid concentrations of 1–100 ?g\\/l. Sorption to

H Chaaieri Oudou; H. C Bruun Hansen

2002-01-01

404