The Experts below are selected from a list of 87 Experts worldwide ranked by ideXlab platform
Justyna Grabska - One of the best experts on this subject based on the ideXlab platform.
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spectra structure correlations of saturated and Unsaturated Medium chain fatty acids near infrared and anharmonic dft study of hexanoic acid and sorbic acid
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2017Co-Authors: Justyna Grabska, Mika Ishigaki, Marek J Wojcik, Yukihiro OzakiAbstract:Quantum chemical reproduction of entire NIR spectra is a new trend, enabled by contemporary advances in the anharmonic approaches. At the same time, recent increase of the importance of NIR spectroscopy of biological samples raises high demand for gaining deeper understanding of NIR spectra of biomolecules, i.e. fatty acids. In this work we investigate saturated and Unsaturated Medium-chain fatty acids, hexanoic acid and sorbic acid, in the near-infrared region. By employing fully anharmonic density functional theory (DFT) calculations we reproduce the experimental NIR spectra of these systems, including the highly specific spectral features corresponding to the dimerization of fatty acids. Broad range of concentration levels from 5·10-4M in CCl4 to pure samples are investigated. The major role of cyclic dimers can be evidenced for the vast majority of these samples. A highly specific NIR feature of fatty acids, the elevation of spectral baseline around 6500-4000cm-1, is being explained by the contributions of combination bands resulting from the vibrations of hydrogen-bonded OH groups in the cyclic dimers. Based on the high agreement between the calculated and experimental NIR spectra, a detailed NIR band assignments are proposed for hexanoic acid and sorbic acid. Subsequently, the correlations between the structure and NIR spectra are elucidated, emphasizing the regions in which clear and universal traces of specific bands corresponding to saturated and Unsaturated alkyl chains can be established, thus demonstrating the wavenumber regions highly valuable for structural identifications.
Ping Ping - One of the best experts on this subject based on the ideXlab platform.
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nonmonotonic traveling waves in an Unsaturated Medium induced by a solid force and fluid mass sources
Advances in Water Resources, 2020Co-Authors: Yu Zhang, Ping PingAbstract:Abstract The traveling wave responses in an Unsaturated Medium induced by a solid force and fluid mass sources are derived in 3D Green's functions using the Dirac Delta function decompositions. The wave behaviors are described in pore fluid pressures and solid frame displacement along with fluctuations of capillary pressure in response to time variant fluid injections and solid force loadings. These solutions are numerically calculated and analyzed for unconsolidated sands as a function of water saturation as representative examples. Our results reveal and validate four wave modes, a fast compressional wave (P1), two slow compressional waves (P2 and P3), and a shear wave. The P1 wave and shear wave can be effectively observed. The slow waves with diffusive characters bear low amplitudes and low velocities. The traveling waves in the pore fluid pressures and solid displacement are sensitive to the different sources and the water saturation. The solid force induces the total stress perturbation while the fluid mass sources directly make the volume strains in the fluid phases. This fluid-solid coupling difference causes the distinct traveling wave signature contrasts in the pore-fluid and solid-frame response amplitudes and tendencies with water retention. For the variation of water saturation, the traveling wave shows a nonmonotonic feature. The fluctuation of capillary pressure exhibits a concave upward relationship, which can further interpret the changes of wave amplitude with water saturation. A solid force may enhance the fluctuation. However, for high water saturation, the interactive fluid-solid effect by the solid force may break the fluid contact due to the extremely compressible air.
Yukihiro Ozaki - One of the best experts on this subject based on the ideXlab platform.
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spectra structure correlations of saturated and Unsaturated Medium chain fatty acids near infrared and anharmonic dft study of hexanoic acid and sorbic acid
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2017Co-Authors: Justyna Grabska, Mika Ishigaki, Marek J Wojcik, Yukihiro OzakiAbstract:Quantum chemical reproduction of entire NIR spectra is a new trend, enabled by contemporary advances in the anharmonic approaches. At the same time, recent increase of the importance of NIR spectroscopy of biological samples raises high demand for gaining deeper understanding of NIR spectra of biomolecules, i.e. fatty acids. In this work we investigate saturated and Unsaturated Medium-chain fatty acids, hexanoic acid and sorbic acid, in the near-infrared region. By employing fully anharmonic density functional theory (DFT) calculations we reproduce the experimental NIR spectra of these systems, including the highly specific spectral features corresponding to the dimerization of fatty acids. Broad range of concentration levels from 5·10-4M in CCl4 to pure samples are investigated. The major role of cyclic dimers can be evidenced for the vast majority of these samples. A highly specific NIR feature of fatty acids, the elevation of spectral baseline around 6500-4000cm-1, is being explained by the contributions of combination bands resulting from the vibrations of hydrogen-bonded OH groups in the cyclic dimers. Based on the high agreement between the calculated and experimental NIR spectra, a detailed NIR band assignments are proposed for hexanoic acid and sorbic acid. Subsequently, the correlations between the structure and NIR spectra are elucidated, emphasizing the regions in which clear and universal traces of specific bands corresponding to saturated and Unsaturated alkyl chains can be established, thus demonstrating the wavenumber regions highly valuable for structural identifications.
Dani Or - One of the best experts on this subject based on the ideXlab platform.
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scaling of capillary gravity and viscous forces affecting flow morphology in Unsaturated porous media
Advances in Water Resources, 2008Co-Authors: Dani OrAbstract:Interplay between capillary, gravity and viscous forces in Unsaturated porous media gives rise to a range of complex flow phenomena affecting morphology, stability and dynamics of wetting and drainage fronts. Similar average phase contents may result in significantly different fluid distribution and patterns affecting macroscopic transport properties of the Unsaturated Medium. The formulation of general force balance within simplified pore spaces yields scaling relationships for motion of liquid elements in which gravitational force in excess of capillary pinning force scales linearly with viscous force. Displacement fluid front morphology is described using dimensionless force ratios expressed as Bond and Capillary numbers. The concise representations of a wide range of flow regimes with scaling relations, and predictive capabilities of front morphology based on dimensionless numbers lend support to certain generalizations. Considering available experimental data, we are able to define conditions for onset of unstable and intermittent flows leading to enhanced liquid and gas entrapment. These results provide a basis for delineation of a tentative value of Bo ∼ 0.05 as an upper limit of applicability of the Richards equation (at pore to sample scales) and related continuum-based flow models.
Edwin G Walsh - One of the best experts on this subject based on the ideXlab platform.
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efficacious intestinal permeation enhancement induced by the sodium salt of 10 undecylenic acid a Medium chain fatty acid derivative
Aaps Journal, 2014Co-Authors: David J Brayden, Edwin G WalshAbstract:10-undecylenic acid (UA) is an OTC antifungal therapy and a nutritional supplement. It is an Unsaturated Medium chain fatty acid (MCFA) derivative, so our hypothesis was that its 11-mer sodium salt, uC11, would improve intestinal permeation similar to the established enhancer, sodium caprate (C10), but without the toxicity of the parent saturated MCFA, decylenic acid (C11). MTT assay and high-content screening (HCS) confirmed a cytotoxicity ranking in Caco-2 cells: C11 > C10 = uC11. Five to ten millimolars of the three agents reduced TEER and increased the Papp of [14C]-mannitol across Caco-2 monolayers and rat intestinal mucosae, a concentration that matched increases in plasma membrane permeability seen in HCS. Although C11 was the most efficacious enhancer in vitro, it damaged monolayers and tissue mucosae more than the other two agents at similar concentrations and exposure times and was therefore not pursued further. Rat jejunal and colonic in situ intestinal instillations of 100 mM C10 or uC11 with FITC-dextran 4000 (FD4) solutions yielded comparable regional enhancement ratios of ~10 and 30%, respectively, for each agent with acceptable tissue histology. Mini-tablets of uC11 and FD4 however delivered more FD4 compared to C10-FD-4 mini-tablets in both regions, as reflected by a statistically higher AUC, and with no evidence of membrane perturbation. The Unsaturated bond in uC11 therefore confers a reduction in lipophilicity and cytotoxicity compared to C11, and the resulting permeation enhancement is on a par with or superior to that of C10, a key component of formulations in current phase II oral peptide clinical trials.
