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  • Animals
  • Kinetics
  • Pregnancy
  • Springer  (10)
  • 1980-1984  (10)
  • 1925-1929
  • 1982  (10)
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  • 1980-1984  (10)
  • 1925-1929
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 260 (1982), S. 641-642 
    ISSN: 1435-1536
    Keywords: Kinetics ; Nucleation ; Water ; Emulsion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 113 (1982), S. 1087-1092 
    ISSN: 1434-4475
    Keywords: Dissolution ; Kinetics ; Pyrrhotite ; Rotating disc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Auflösungsgeschwindigkeit von natürlichem monoklinen Pyrrhotin, FeS1.14, wurde in sauerstofffreien LösungenS([H+]=0.1, [Na+]=0.9, [ClO 4 − ]=1.0 mol kg−1) mit Hilfe der Methode der rotierenden Scheibe bestimmt. Im Temperaturbereich von 40–90° erfolgt die Auflösungsreaktion kinetisch kontrolliert, wobei eine Aktivierungsenergie von 14±1 kcal mol−1 (59±5 kJ mol−1) gefunden wurde.
    Notes: Abstract Using the rotating disc method, the rates of dissolution of natural monoclinic pyrrhotite, FeS1.14, in oxygen-free aqueous solutionsS([H+]=0.1, [Na+]=0.9, [ClO 4 − ]=1.0 mol kg−1) were determined. In the temperature range 40–90 °C the dissolution reaction occurs under kinetic control; the activation energy being 14±1 kcal mol−1 (50±5 kJ mol−1).
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 113 (1982), S. 1239-1244 
    ISSN: 1434-4475
    Keywords: Allyl alcohol ; Kinetics ; Mechanism ; Oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Kinetik der Oxidation von Allylalkohol mitN-Bromsuccinimid (NBS) wurde bei 35 °C in wäßrigem Medium untersucht. Die Reaktion zeigt erste Ordnung gegenüberNBS und Allylalkohol. Bei relativ hoher Säurekonzentration zeigt sich keine Änderung der Reaktionsgeschwindigkeit, bei niedriger Säurekonzentration wird die Reaktionsgeschwindigkeit beträchtlich erhöht. Es wurde kein primärer Salzeffekt festgestellt. Bei varriierender Quecksilberacetatkonzentration bleibt die Reaktionsgeschwindigkeit gleich, bei Abwesenheit von Quecksilberacetat wird jedoch die Geschwindigkeitskonstante erhöht. Die kinetischen Parameter,E a, derArrheniusfaktorA, ΔH ≠, ΔG ≠ und ΔS ≠ wurden bestimmt. Ein Geschwindigkeitsgesetz in Übereinstimmung mit den experimentellen Befunden wurde abgeleitet und ein Mechanismus vorgeschlagen.
    Notes: Abstract The kinetics of oxidation of allyl alcohol byN-bromosuccinimide (NBS) has been studied at 35 °C in aqueous medium. The reaction shows first order dependence on bothNBS and allyl alcohol. In fairly high acid concentration, there is no change in the rate of the reaction but at low acid concentration, the rate is considerably enhanced. There is no primary salt effect. At varying mercuric acetate concentrations, the rate constant remains the same. But in the absence of mercuric acetate, the rate is enhanced. The kinetic parameters,E a,Arrhenius factorA, ΔH≠, ΔG≠ and ΔS≠ have been calculated. A rate law in agreement with experimental results has been derived. A mechanism is proposed.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 113 (1982), S. 887-893 
    ISSN: 1434-4475
    Keywords: Diazotation ; Kinetics ; α-Naphthylamine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Optimal diazotation conditions were determined by means of extinction measurements at various experimental conditions. The optimal conditions found arep H=9,5, the amount of phenol is 1 250 times the amount of α-naphthylamine.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 113 (1982), S. 3-14 
    ISSN: 1434-4475
    Keywords: Graphite ; Kinetics ; Reduction ; Thoria ; Thoriumcarbide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Reduktion von Thoriumoxid mit Graphit im Überschuß wurde mittels einer Thermowaage zwischen 1620 und 1920 K im Vakuum untersucht. Ab ThO2:C=1:50 war die Reaktionsgeschwindigkeit vom Mischungsverhältnis unabhängig; das Endprodukt war immer ThC2. Der logarithmische Gewichtsverlust war direkt proportional der Zeit, und dieArrheniusgerade zeigte einen Knickpunkt bei 1710 K: unterhalb dieser Temperatur ergab sich eine Aktivierungsenergie von 440 kJ, oberhalb eine solche von 260 kJ. Die Temperatur des Knickpunkts entspricht der Umwandlungstemperatur von monoklinem in tetragonal raumzentriertes ThC2.
    Notes: Abstract The reduction of thoria with excess graphite was studied with a thermo-balance in vacuum between 1620 and 1920 K. From Th02:C=1:50 the rate of reaction was independent of the ratio of the reactants; the endproduct was always ThC2. The logarithmic weight loss was directly proportional to the time, and theArrhenius plot showed a break at 1710 K: below this temperature the activation energy was found to be 440 kJ, above 260 kJ. The temperature corresponding to the break coincides with the transition temperature of monoclinic to body-centered tetragonal ThC2.
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  • 6
    ISSN: 1434-4475
    Keywords: Kinetics ; Ligand-transfer ; Thallium (III)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The transfer of oxinate ions from thallium (III)oxinate to trivalent Fe(DMF) 6 3+ in propylenecarbonate takes place via rearrangements within a rapidly formed binuclear thallium(III)—iron(III) complex. In a last rapid step this rearranged complex reacts with excess reactants to the final products whose composition accordingly depends on the ratio of the reactant concentrations.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 34 (1982), S. 9-12 
    ISSN: 1432-0827
    Keywords: Parathyroid hormone ; Pregnancy ; Nephrogenous cAMP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Parathyroid hormone (PTH) metabolism in pregnancy has not been clearly defined. Studies have reported either increased or unchanged values of immunoreactive PTH (iPTH). However, iPTH levels do not necessarily correlate with hormonal bioactivity due to the presence of immunoreactive but nonbioactive PTH fragments. In this study we evaluated PTH metabolism in the third trimester of pregnancy by determining iPTH blood levels as well as the biological effects of PTH, assessed by tubular maximum phosphate reabsorption (TmP) and nephrogenous cAMP (ncAMP) excretion, in 10 young, healthy pregnant patients (mean gestational age 35 weeks) and 10 young, healthy age-matched female controls. Pregnancy was associated with a significant increase in creatinine clearance (146±13 vs 106±9 ml/min,P〈0.01), and a significant decrease in total fasting serum calcium (8.4±0.1 vs 9.0±0.1 mg/dl,P〈0.001) and serum albumin (3.6±0.1 vs 4.2±0.1 g/dl,P〈0.001). There was no significant difference in iPTH (3.7±0.4 vs 4.3±0.5 µlEq/ml), serum phosphorus (3.6±0.1 vs 3.8±0.2 mg/dl), TmP (3.61±0.13 vs 3.75±0.25 mg/100 ml GFR), or ncAMP (1.68±0.20 vs 1.88±0.23 nmoles/100 ml GFR) between the two groups. Pregnancy was attended by a significant increase in fasting urinary calcium to creatinine ratio (0.14±0.03 vs 0.06±0.01,P〈0.05), an index of bone resorption. The data suggest that the biological effects of PTH are unchanged in pregnancy, and that reported increments in 1,25(OH)2 vitamin D in pregnancy are not regulated by changes in either PTH, calcium, or phosphate.
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  • 8
    ISSN: 1432-0827
    Keywords: Vitamin D ; Vitamin D deficiency ; Bone ; Pregnancy ; Lactation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The effect of vitamin D on bone changes during the reproductive cycle in female rats has been investigated. One group of female rats was maintained on a vitamin D-deficient diet and another group on a vitamin D-replete diet from weaning. Both groups were mated with normal males and changes in their bones were determined histomorphometrically during pregnancy, lactation, and after weaning. All vitamin D-deficient rats had bone changes typical of rickets. Pregnancy caused significant reductions in mineralized tissue of trabecular and cortical bone in the vitamin D-deficient rats. Lactation caused further significant reductions in mineralized tissues of cortical and trabecular bone in both the vitamin D-deficient and vitamin D-replete animals, with the greatest changes seen at weaning. Some restoration of mineralized tissues occurred following weaning. There was an increase in tetracycline-labeled bone surface in the vitamin D-replete animals during lactation, likely due to an increase in bone formation rates. In the vitamin D-deficient animals during lactation, there was a decrease in tetracyclinelabeled bone surface, likely due to severely depressed bone mineralization. These results indicate that the mobilization of calcium from bone to maintain pregnancy and lactation occurs by a mechanism independent of vitamin D.
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  • 9
    ISSN: 1573-5036
    Keywords: Ammonification ; Cadmium ; Heavy metals ; Kinetics ; Lead ; Nitrification ; Perfusion incubations ; Polluted soils ; Selection ; Toxicity ; Zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The sensitivity of the mineralization of nitrogen by a range of soils contaminated with heavy metals (up to 340 μg Cd g−1, 7500 μg Pb g−1 and 34000 μg Zn g−1) to the addition of heavy metals in solution were studied using pot incubations (ammonification) and a soil perfusion technique (nitrification). The ammonification of peptone showed little correlation between treatments with Cd, Zn (1000 and 5000 μg g−1) and Pb (10000 and 20000 μg g−1) and origin of the soil. Nitrification was considerably more sensitive to heavy metals than ammonification. All the soils had active, often large, populations of ammonifying and nitrifying organisms which showed substantial similarities between the soils. The rate of nitrifying activity (NO3−N production) was logrithmic in most cases. The presence of tolerant populations of nitrifying organisms in the contaminated soils was demonstrated. Tolerance was also eventually acquired after a longer lag phase, by the non-contaminated soil populations although the rate of activity was often reduced. Metals added in solution were adsorbed by the soil within 4 hours. Differences in toxicity between metal salts (chlorides, sulphates and acetate) were attributed to the amount left in solution. However, in many instances, acetate was found to stimulate all the stages in the mineralisation of nitrogen.
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  • 10
    ISSN: 1432-0878
    Keywords: Uterus ; Epithelial cells ; Tight junctions ; Pregnancy ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ultrastructure of tight junctions between uterine luminal epithelial cells of the pregnant rat was studied by the freeze-fracture technique. On day 5 of pregnancy, the day of implantation, the region of tight junctions extended three times as far down the lateral cell membrane as on day 1 of pregnancy, and the strands of the complex interlinked more frequently. These observations suggest that tight junctions on day 5 may be more efficient in preserving the contents of the uterine lumen from dilution or escape than at earlier times of pregnancy.
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