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Margaret A. Tolbert - One of the best experts on this subject based on the ideXlab platform.

  • Heterogeneous uptake of the C1 to C4 organic acids on a swelling clay mineral
    Atmospheric Chemistry and Physics, 2007
    Co-Authors: C. D. Hatch, R. V. Gough, Margaret A. Tolbert
    Abstract:

    Mineral aerosol is of interest due to its physiochemical impacts on the Earth's atmosphere. However, adsorbed organics could influence the chemical and physical properties of atmospheric mineral particles and alter their impact on the biosphere and climate. In this work, the heterogeneous uptake of a series of small organic acids on the swelling clay, Na-montmorillonite, was studied at 212 K as a function of relative humidity (RH), organic acid pressure and clay mass. A high vacuum chamber equipped with a quadrupole mass spectrometer and a transmission Fourier transform infrared spectrometer was used to detect the gas and condensed phases, respectively. Our results show that while the initial uptake efficiency was found to be independent of organic acid pressure, it increased linearly with increasing clay mass. Thus, the small masses studied allow access to the entire surface area of the clay sample with minimal effects due to surface saturation. Additionally, results from this study show that the initial uptake efficiency for butanoic (butyric) acid on the clay increases by an order of magnitude as the RH is raised from 0% to 45% RH at 212 K while the initial uptake efficiency of formic, acetic and propanoic (propionic) acids increases only slightly at higher humidities. However, the initial uptake efficiency decreases significantly in a short amount of time due to surface saturation effects. Thus, although the initial uptake efficiencies are appropriate for initial times, the fact that the uptake efficiency will decrease over time as the surface saturates should be considered in atmospheric models. Surface saturation results in sub-monolayer coverage of organic acid on montmorillonite under dry conditions and relevant organic acid pressures that increases with increasing humidity for all organic acids studied. Additionally, the presence of large organic acids may slightly enhance the water content of the clay above 45% RH. Our results indicate that heterogeneous uptake of organic acids on swelling clay minerals provides an important irreversible heterogeneous sink for these species.

  • Heterogeneous uptake of the C1 to C4 organic acids on a swelling clay mineral
    Atmospheric Chemistry and Physics Discussions, 2007
    Co-Authors: C. D. Hatch, R. V. Gough, Margaret A. Tolbert
    Abstract:

    Mineral aerosol is of interest due to its physiochemical impacts on the Earth's atmosphere. However, adsorbed organics could influence the chemical and physical properties of atmospheric mineral particles and alter their impact on the biosphere and climate. In this work, the heterogeneous uptake of a series of small organic acids on the swelling clay, Na-montmorillonite, was studied at 212 K as a function of relative humidity (RH), organic acid pressure and clay mass. A high vacuum chamber equipped with a quadrupole mass spectrometer and a transmission Fourier transform infrared spectrometer was used to detect the gas and condensed phases, respectively. Sub-monolayer coverage of organic acid on montmorillonite was observed under dry conditions and relevant organic acid pressures. However, the organic acid content increased significantly with increasing humidity. Additionally, while the initial uptake efficiency was found to be independent of organic acid pressure, it increased linearly with increasing clay mass. Thus, the small masses studied allow access to the entire surface area of the clay sample with minimal effects due to surface saturation. Results from this study show that the initial uptake efficiency for n-butyric acid on the clay increases by an order of magnitude as the RH is raised from 0% to 45% RH at 212 K while the uptake of formic, acetic and propionic acids increase only slightly at higher humidities. Additionally, the presence of organic acids was found to slightly enhance the water content of the clay above 45% RH. Our results indicate that heterogeneous uptake of organic acids on swelling clay minerals provides an important heterogeneous sink for these species and may modify the cloud forming potential of the clay particles.

C. D. Hatch - One of the best experts on this subject based on the ideXlab platform.

  • Heterogeneous uptake of the C1 to C4 organic acids on a swelling clay mineral
    Atmospheric Chemistry and Physics, 2007
    Co-Authors: C. D. Hatch, R. V. Gough, Margaret A. Tolbert
    Abstract:

    Mineral aerosol is of interest due to its physiochemical impacts on the Earth's atmosphere. However, adsorbed organics could influence the chemical and physical properties of atmospheric mineral particles and alter their impact on the biosphere and climate. In this work, the heterogeneous uptake of a series of small organic acids on the swelling clay, Na-montmorillonite, was studied at 212 K as a function of relative humidity (RH), organic acid pressure and clay mass. A high vacuum chamber equipped with a quadrupole mass spectrometer and a transmission Fourier transform infrared spectrometer was used to detect the gas and condensed phases, respectively. Our results show that while the initial uptake efficiency was found to be independent of organic acid pressure, it increased linearly with increasing clay mass. Thus, the small masses studied allow access to the entire surface area of the clay sample with minimal effects due to surface saturation. Additionally, results from this study show that the initial uptake efficiency for butanoic (butyric) acid on the clay increases by an order of magnitude as the RH is raised from 0% to 45% RH at 212 K while the initial uptake efficiency of formic, acetic and propanoic (propionic) acids increases only slightly at higher humidities. However, the initial uptake efficiency decreases significantly in a short amount of time due to surface saturation effects. Thus, although the initial uptake efficiencies are appropriate for initial times, the fact that the uptake efficiency will decrease over time as the surface saturates should be considered in atmospheric models. Surface saturation results in sub-monolayer coverage of organic acid on montmorillonite under dry conditions and relevant organic acid pressures that increases with increasing humidity for all organic acids studied. Additionally, the presence of large organic acids may slightly enhance the water content of the clay above 45% RH. Our results indicate that heterogeneous uptake of organic acids on swelling clay minerals provides an important irreversible heterogeneous sink for these species.

  • Heterogeneous uptake of the C1 to C4 organic acids on a swelling clay mineral
    Atmospheric Chemistry and Physics Discussions, 2007
    Co-Authors: C. D. Hatch, R. V. Gough, Margaret A. Tolbert
    Abstract:

    Mineral aerosol is of interest due to its physiochemical impacts on the Earth's atmosphere. However, adsorbed organics could influence the chemical and physical properties of atmospheric mineral particles and alter their impact on the biosphere and climate. In this work, the heterogeneous uptake of a series of small organic acids on the swelling clay, Na-montmorillonite, was studied at 212 K as a function of relative humidity (RH), organic acid pressure and clay mass. A high vacuum chamber equipped with a quadrupole mass spectrometer and a transmission Fourier transform infrared spectrometer was used to detect the gas and condensed phases, respectively. Sub-monolayer coverage of organic acid on montmorillonite was observed under dry conditions and relevant organic acid pressures. However, the organic acid content increased significantly with increasing humidity. Additionally, while the initial uptake efficiency was found to be independent of organic acid pressure, it increased linearly with increasing clay mass. Thus, the small masses studied allow access to the entire surface area of the clay sample with minimal effects due to surface saturation. Results from this study show that the initial uptake efficiency for n-butyric acid on the clay increases by an order of magnitude as the RH is raised from 0% to 45% RH at 212 K while the uptake of formic, acetic and propionic acids increase only slightly at higher humidities. Additionally, the presence of organic acids was found to slightly enhance the water content of the clay above 45% RH. Our results indicate that heterogeneous uptake of organic acids on swelling clay minerals provides an important heterogeneous sink for these species and may modify the cloud forming potential of the clay particles.

R. V. Gough - One of the best experts on this subject based on the ideXlab platform.

  • Heterogeneous uptake of the C1 to C4 organic acids on a swelling clay mineral
    Atmospheric Chemistry and Physics, 2007
    Co-Authors: C. D. Hatch, R. V. Gough, Margaret A. Tolbert
    Abstract:

    Mineral aerosol is of interest due to its physiochemical impacts on the Earth's atmosphere. However, adsorbed organics could influence the chemical and physical properties of atmospheric mineral particles and alter their impact on the biosphere and climate. In this work, the heterogeneous uptake of a series of small organic acids on the swelling clay, Na-montmorillonite, was studied at 212 K as a function of relative humidity (RH), organic acid pressure and clay mass. A high vacuum chamber equipped with a quadrupole mass spectrometer and a transmission Fourier transform infrared spectrometer was used to detect the gas and condensed phases, respectively. Our results show that while the initial uptake efficiency was found to be independent of organic acid pressure, it increased linearly with increasing clay mass. Thus, the small masses studied allow access to the entire surface area of the clay sample with minimal effects due to surface saturation. Additionally, results from this study show that the initial uptake efficiency for butanoic (butyric) acid on the clay increases by an order of magnitude as the RH is raised from 0% to 45% RH at 212 K while the initial uptake efficiency of formic, acetic and propanoic (propionic) acids increases only slightly at higher humidities. However, the initial uptake efficiency decreases significantly in a short amount of time due to surface saturation effects. Thus, although the initial uptake efficiencies are appropriate for initial times, the fact that the uptake efficiency will decrease over time as the surface saturates should be considered in atmospheric models. Surface saturation results in sub-monolayer coverage of organic acid on montmorillonite under dry conditions and relevant organic acid pressures that increases with increasing humidity for all organic acids studied. Additionally, the presence of large organic acids may slightly enhance the water content of the clay above 45% RH. Our results indicate that heterogeneous uptake of organic acids on swelling clay minerals provides an important irreversible heterogeneous sink for these species.

  • Heterogeneous uptake of the C1 to C4 organic acids on a swelling clay mineral
    Atmospheric Chemistry and Physics Discussions, 2007
    Co-Authors: C. D. Hatch, R. V. Gough, Margaret A. Tolbert
    Abstract:

    Mineral aerosol is of interest due to its physiochemical impacts on the Earth's atmosphere. However, adsorbed organics could influence the chemical and physical properties of atmospheric mineral particles and alter their impact on the biosphere and climate. In this work, the heterogeneous uptake of a series of small organic acids on the swelling clay, Na-montmorillonite, was studied at 212 K as a function of relative humidity (RH), organic acid pressure and clay mass. A high vacuum chamber equipped with a quadrupole mass spectrometer and a transmission Fourier transform infrared spectrometer was used to detect the gas and condensed phases, respectively. Sub-monolayer coverage of organic acid on montmorillonite was observed under dry conditions and relevant organic acid pressures. However, the organic acid content increased significantly with increasing humidity. Additionally, while the initial uptake efficiency was found to be independent of organic acid pressure, it increased linearly with increasing clay mass. Thus, the small masses studied allow access to the entire surface area of the clay sample with minimal effects due to surface saturation. Results from this study show that the initial uptake efficiency for n-butyric acid on the clay increases by an order of magnitude as the RH is raised from 0% to 45% RH at 212 K while the uptake of formic, acetic and propionic acids increase only slightly at higher humidities. Additionally, the presence of organic acids was found to slightly enhance the water content of the clay above 45% RH. Our results indicate that heterogeneous uptake of organic acids on swelling clay minerals provides an important heterogeneous sink for these species and may modify the cloud forming potential of the clay particles.

Kazutoshi Haraguchi - One of the best experts on this subject based on the ideXlab platform.

  • control of cell cultivation and cell sheet detachment on the surface of polymer clay nanocomposite hydrogels
    Biomacromolecules, 2006
    Co-Authors: Kazutoshi Haraguchi, Toru Takehisa, Makiko Ebato
    Abstract:

    Cell cultivation on the surface of a novel poly(N-isopropylacrylamide) (PNIPA) hydrogel (N-NC gel), consisting of a specific type of organic (PNIPA)/inorganic (clay) network, was studied using three cell types; HepG2 human hepatoma cells, human dermal fibroblasts, and human umbilical vein endothelial cells. For the first time, it was found that cells could be cultured to be confluent on the surfaces of PNIPA hydrogels using N-NC gels, regardless of gel thickness. Cell adhesion and proliferation on N-NC gels exhibit strong dependencies on clay concentration (Cclay), and the numbers of cultured cells are maximum at about Cclay = 6 × 10-2 mol (45.72 g)/1 L of H2O. On the contrary, it was almost impossible to culture cells on conventional, chemically crosslinked PNIPA hydrogels, regardless of their cross-linker concentration. The reasons why cells cultured only on the surfaces of N-NC gels with their specific network structure and composition were discussed in terms of water content, protein adsorption, surfa...

  • mechanical properties and structure of polymer clay nanocomposite gels with high clay content
    Macromolecules, 2006
    Co-Authors: Kazutoshi Haraguchi
    Abstract:

    The mechanical properties and structures of nanocomposite gels (NC gels), consisting of poly(N-isopropylacrylamide) (PNIPA) and inorganic clay (hectorite), prepared using a wide range of clay concentration (∼25 mol % against water) were investigated. All NC gels were uniform and transparent, almost independent of the clay content, Cclay. The tensile modulus (E) and the strength (σ) were controlled without sacrificing extensibility by changing Cclay. The E, σ, and fracture energy observed for as-prepared NC gels attained 1.1 MPa, 453 kPa, and 3300 times that of a conventional chemically cross-linked gel, respectively, and σ increased to 3.0 MPa for a once-elongated NC25 gel. From the tensile and compression properties, in addition to optical transparency, it was concluded that a unique organic/inorganic network structure was retained regardless of Cclay. The effects of Cclay on the tensile mechanical properties on the first and second cycles, the time-dependent recovery from the first large elongation and ...

S. Shahaboddin Yasrobi - One of the best experts on this subject based on the ideXlab platform.

  • Volume change behavior of compacted clay due to organic liquids as permeant
    Applied Clay Science, 2008
    Co-Authors: Mohammad H. Moavenian, S. Shahaboddin Yasrobi
    Abstract:

    To investigate the influence of organic fluids on volume change behavior of compacted clays, two organic chemicals with low and intermediate dielectric constant permeated through compacted specimens of montmorillonite and vermiculite. Swelling and osmotic consolidation tests were performed. Soil index tests were modified to evaluate the effect of organic liquids on clay soils. Results of the investigation showed that pure organic chemicals caused less heaving in comparison with distilled water. Organic liquids caused osmotic consolidation in clay. The plasticity of soil reduced and the settlement time decreased when exposed to organic liquids.