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  • Fourier Transform Infrared Spectroscopy (FT-IR)  (1)
  • INORGANIC AND PHYSICAL CHEMISTRY  (1)
  • drug delivery  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Evidence that Oleic Acid Exists in a Separate Phase Within Stratum Corneum Lipids (1991)
    Springer
    Pharmaceutical research 8 (1991), S. 350-354 
    Details
    ISSN: 1573-904X
    Keywords: oleic acid ; penetration enhancer ; Fourier Transform Infrared Spectroscopy (FT-IR) ; lipid phase-separation transport mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Oleic acid is known to be a penetration enhancer for polar to moderately polar molecules. A mechanism related to lipid phase separation has been previously proposed by this laboratory to explain the increases in skin transport. In the studies presented here, Fourier transform infrared spectroscopy (FT-IR) was utilized to investigate whether or not oleic acid exists in a separate phase within stratum corneum (SC) lipids. Per-deuterated oleic acid was employed allowing the conformational phase behavior of the exogenously added fatty acid and the endogenous SC lipids to be monitored independently of each other. The results indicated that oleic acid exerts a significant effect on the SC lipids, lowering the lipid transition temperature (T m) in addition to increasing the conformational freedom or flexibility of the endogenous lipid alkyl chains above their T m. At temperatures lower than T m, however, oleic acid did not significantly change the chain disorder of the SC lipids. Similar results were obtained with lipids isolated from the SC by chloroform:methanol extraction. Oleic acid, itself, was almost fully disordered at temperatures both above and below the endogenous lipid T m in the intact SC and extracted lipid samples. This finding suggested that oleic acid does exist as a liquid within the SC lipids. The coexistence of fluid oleic acid and ordered SC lipids, at physiological temperatures, is consistent with the previously proposed phase-separation transport mechanism for enhanced diffusion. In this mechanism, the enhanced transport of polar molecules across the SC can be explained by the formation of permeable interfacial defects within the SC lipid bilayers which effectively decrease either the diffusional path length or the resistance, without necessarily invoking the formation of frank pores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015845632280
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The Influence of an Electric Field on Ion and Water Accessibility to Stratum Corneum Lipid Lamellae (1996)
    Springer
    Pharmaceutical research 13 (1996), S. 1168-1173 
    Details
    ISSN: 1573-904X
    Keywords: iontophoresis ; passive diffusion ; ion transport ; drug delivery ; fluorescence spectroscopy ; stratum corneum lipid lamellae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To study ion transport through stratum corneum (SC) lipid lamellae under passive and iontophoretic conditions. Methods. Iodide ion transport was measured by fluorescence quenching. Since the process involves diffusion of an iodide ion to the fluorophore located within the SC lamellae, the accessibility of iodide ions was measured. Moreover, the use of anthroyloxy fatty acid probes, provided information as a function of depth within the lamellae. Results. Fluorescence quenching by iodide ions increased with iontophoretic current density, suggesting increased ion accessibility within the SC lamellae. In addition, at constant current, quenching decreased as the fluorophore was located deeper within the lamellae. This gradient in ion accessibility suggests that more iodide is found near the head-group than near the core of the SC lipid lamellae. Results obtained in the absence of iodide also show increased water accessibility during iontophoresis. Conclusions. These results show that in the presence of an applied electric field the SC lipid lamellae interior becomes more accessible to water and ions. These results imply that during iontophoresis, ion and water transport through human skin is associated, at least in part, with the SC lipid lamellae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016099800770
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  • 3
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    Steady state composition with low Fe(2+) concentrations for efficient O2 production by 'magma' electrolysis of lunar soils (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: Parameters are estimated for a hypothetical, well stirred, continuous-feed electrolytic cell that converts 20 percent of a lunar soil feedstock to O2 gas, 26 percent to Fe-Si metal, 13 percent to spinel, and 41 percent to slag. Advantages of a molten Fe-Si cathode for trapping metal on reduction, a relatively conductive steady-state composition in equilibrium with spinel (a proposed container material), and close electrodes (less than 1 cm cathode-anode distance) are discussed. To produce 1 ton of O2, about 6 MHW of energy are required for the electrolysis and IR heating within the melt, and another about 6 MHW may be introduced as waste heat through internal resistance of the electrodes. Thus, to produce 1 ton of O2 per 24 hours, about 0.5 MW of power delivered to the cell would be required.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: In: Engineering, construction, and operations in space - III: Space '92; Proceedings of the 3rd International Conference, Denver, CO, May 31-June 4, 1992. Vol. 1 (A93-41976 17-12); p. 651-665.
    Format: text
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    NASA TECHNICAL REPORTS
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