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  • chemisorption  (2)
  • Aerospace Medicine
  • 1995-1999  (3)
  • 1
    Electronic Resource
    Electronic Resource
    The effect of Mo on the catalytic and surface properties of Rh-Mo/ZrO2 catalysts (1995)
    Springer
    Catalysis letters 34 (1995), S. 331-341 
    Details
    ISSN: 1572-879X
    Keywords: rhodium ; molybdenum ; chemisorption ; TPR ; XPS ; hydrogenation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A series of Rh-Mo/ZrO2 catalysts with fixed Rh and different Mo loadings were prepared and characterized by H2 chemisorption, XRD, TPR, TEM and XPS. The catalysts were studied in two reactions: the hydrogenation of carbon monoxide and the hydrogenation of toluene. The results suggest that the increase in the Mo content produces a partial coverage of the support and the Rh particles. Moreover, at high Mo coverage, an increase of the MoO3 layer thickness is produced. After being treated in hydrogen, the molybdenum oxide remains as slightly reduced particles, while Rh is essentially as Rh0, with only a small contribution of Rh+ species. The Mo promotes the formation of oxygenates in the CO hydrogenation and it does not affect the activity in the hydrogenation of toluene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00806882
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Influence of the nature of the platinum precursor on the surface properties and catalytic activity of alumina-supported catalysts (1996)
    Springer
    Catalysis letters 37 (1996), S. 193-197 
    Details
    ISSN: 1572-879X
    Keywords: catalysts ; platinum ; alumina ; acetylacetonates ; chemisorption ; hydrogenation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The influence of the nature of the metal precursor — platinum acetylacetonates and chloroplatinic acid — on the surface properties and catalytic activity of Pt/Al2O3 catalysts is reported. The obtained results indicate that the catalysts prepared by the organometallic route present higher metal dispersion and lower acidity compared with those prepared from H2PtCl6. On the other hand, XPS results showed that the state of platinum is essentially Pt0 in the catalysts obtained from Pt(acac)2 while in the solids prepared by impregnation of H2PtCl6 there exists an important contribution of Ptδ+ species which plays a positive role in the hydrogenation of toluene. An additional hydrogen spillover due to the presence of more acidic support is also suggested as an explanation of the observed catalytic results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807753
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  • 3
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    Marked Exacerbation of Orthostatic Intolerance After Long vs. Short-Duration Spaceflight in Veteran Astronauts (1999)
    In:  Other Sources
    Details
    Publication Date: 2019-07-17
    Description: The incidence of postflight orthostatic intolerance following short-duration spaceflight is about 20%. However, the incidence following long-duration spaceflight is unknown. We performed tilt tests on six astronauts before and after their long-duration (129 - 190 days) spaceflights and compared these data to those obtained during stand tests before and after their previous short-duration missions and also to tilt test data from 20 different short-duration (8 - 16 days) flight astronauts. Five of these six became presyncopal during tilt testing after long-duration flights: only one had become presyncopal during stand testing after short-duration flights. Five of the twenty astronauts who flew on other short-duration flights, became presyncopal during upright tilt on landing day. Long-duration presyncopal subjects had lower stroke volumes, lower cardiac outputs and higher peripheral vascular resistance than short-duration presyncopal subjects, but their heart rate responses were not different. One subject had subnormal norepinephrine release with upright posture after a long but not short flight. Plasma volume losses were not greater after long flights. Long-duration spaceflight markedly increases orthostatic intolerance, probably related to altered autonomic function.
    Keywords: Aerospace Medicine
    Format: text
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    NASA TECHNICAL REPORTS
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