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  • 1
    ISSN: 1573-4846
    Keywords: SiO2 ; microporous ; ceramic membrane ; gas separation ; microstructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Microporous SiO2 and SiO2/MO2 (M=Ti, Zr, Al; 10 mol% MOx) materials for gas separation membrane applications have been prepared from polymeric sols. Characterization of these sols with SAXS showed that the mean fractal dimension of the SiO2 sols is 1.3–1.4 with a radius of gyration of approximately 2.5 nm. The dried and calcined films are microporous and the pore size distribution was bimodal with maxima at diameters of 0.5 nm and 0.75 nm. For the SiO2/TiO2, SiO2/ZrO2 and SiO2/Al2O3 systems, much milder reaction conditions proved to be necessary to obtain sols with comparable fractal dimensions due to the high reactivity of the Ti/Zr/Al-alkoxides. Microporous supported membranes with molecular sieve-like gas transport properties can be prepared from a relatively wide range of sol structures: from polymers too small to characterize with SAXS to structures with fractal dimensions: 1〈d f〈2.04.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of porous materials 2 (1995), S. 141-149 
    ISSN: 1573-4854
    Keywords: sorption ; microporous ; ceramic membranes ; gas separation ; gas transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Sorption experiments with H2, CO2, CH4 and iso-C4H10 were performed on microporous SiO2 and SiO2/TiO2 (30 mol% TiO2) non-supported membrane top-layers using volumetric and gravimetric techniques. For silica, the sorption capacity decreases in the order CO2〉iso-C4H10〉CH4〉H2 at temperatures 〈373 K. The isosteric heat of adsorption q st is 23, 24, 10 and 6 kJ·mol−1 for respectively CO2, iso-C4H10, CH4 and H2. The sub-atmospheric adsorption isotherms are of Henry-type for temperatures equal and higher than 348 K for CO2, temperatures higher than 373 K for iso-C4H10, temperatures equal and higher than 194 K for H2 and for temperatures equal and higher than 273 K for CH4. The sorption capacity for the SiO 2/TiO 2 sample was only slightly lower than for silica, as may be expected due to the lower porosity.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2011-08-24
    Description: The changes in erythropoiesis in astronauts caused by weightlessness was experimentally studied during the Spacelab 1 flight. Immediately after landing showed a mean decrease of 9,3 percent in the four astronauts. Neither hyperoxia nor an increase in blood phosphate caused the decrease. Red cell survival time and iron incorporation postflight were not significantly different from their preflight levels. Serum haptoglobin did not decrease, indicating that intravascular hemolysis was not a major cause of red cell mass change. An increase in serum ferritin after the second day of flight may have been caused by red cell breakdown early in flight. The space flight-induced decrease in red cell mass may result from a failure of erythropoesis to replace cells destroyed by the spleen soon after weightlessness is attained.
    Keywords: AEROSPACE MEDICINE
    Format: text
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  • 4
    Publication Date: 2019-06-28
    Description: An experiment conducted on the 10-day Spacelab 1 mission aboard the ninth Space Shuttle flight in November to December 1983 was designed to measure factors involved in the control of erythrocyte turnover that might be altered during weightlessness. Blood samples were collected before, during, and after the flight. Immediately after landing, red cell mass showed a mean decrease of 9.3 percent in the four astronauts. Neither hyperoxia nor an increase in blood phosphate was a cause of the decrease. Red cell survival time and iron incorporation postflight were not significantly different from their preflight levels. Serum haptoglobin did not decrease, indicating that intravascular hemolysis was not a major cause of red cell mass change. An increase in serum ferritin after the second day of flight may have been caused by red cell breakdown early in flight. Erythropoietin levels decreased during and after flight, but preflight levels were high and the decrease was not significant. The space flight-induced decrease in red cell mass may result from a failure of erythropoiesis to replace cells destroyed by the spleen soon after weightlessness is attained.
    Keywords: AEROSPACE MEDICINE
    Type: NASA-TM-58268 , S-548 , NAS 1.15:58268
    Format: application/pdf
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