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  • Aluminophosphate molecular sieves  (1)
  • Kidney  (1)
  • isomerization of 1-butene  (1)
  • 1990-1994  (2)
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  • 1990-1994  (2)
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  • 1
    ISSN: 1572-879X
    Keywords: Aluminophosphate molecular sieves ; Si and/or Mn modification ; isomerization of 1-butene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Molecular sieve AlPO4-31 and substituted analogues (MnAPO-31,SAPO-31, MnAPSO-31) have been tested for their catalytic properties in the isomerization of 1-butene over 6 h time on stream at 743 K. The conversion of 1-butene proceeds selectively by either double bond or skeletal isomerization. MnAPSO-31 with a molar MnO/P2O5 ratio adjusted to 0.01 yields the highest percentage of isobutene whereas the parent AlPO4-31 leads almost completely to a double bond shift with only minor skeletal isomerization. The results are related to the acidity characteristics that were determined by ammonia thermodesorption. Deactivation is accompanied by a loss of selectivity for the skeletal isomerization.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1440
    Keywords: Kidney ; Calcium ; Phosphate ; Sodium ; Caries
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Clearance studies were performed for 2 days in two groups of age-matched young female volunteers: those with low caries prevalence and those with high caries prevalence. Both groups were kept on a low-calcium diet for 1 week and received 0.5 g calcium at the beginning of the second day. In both groups, glomerular filtration rate, urinary flow rate and renal excretions of sodium, calcium, and phosphate were subject to significant circadian variations. In both groups the administration of calcium led to a significant increase in renal excretion of sodium and calcium and a significant decrease in that of phosphate. On the first day, calcium excretion was significantly greater in those with low caries prevalence than in those with high caries prevalence, pointing to altered calcium homeostasis in this group.
    Type of Medium: Electronic Resource
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