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  • Animals
  • Kinetics
  • Pregnancy
  • Springer  (21)
  • 1980-1984  (21)
  • 1925-1929
  • 1984  (11)
  • 1982  (10)
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  • 1980-1984  (21)
  • 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
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    Colloid & polymer science 262 (1984), S. 677-682 
    ISSN: 1435-1536
    Keywords: Kinetics ; methacrylamide ; reaction scheme ; viscosity ; additives
    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 The aqueous polymerization of methacrylamide initiated by potassiumpersulfate-L-cystein hydrochloride redox system has been studied at 35±0.01
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  • 3
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    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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  • 4
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    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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  • 5
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    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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  • 6
    ISSN: 1434-4475
    Keywords: Iodine monochloride ; Kinetics ; Solvent effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Kinetik der Addition von ICl zu einigen Vinylverbindungen in Nitrobenzol als Lösungsmittel wurde untersucht. In allen Fällen ist die Reaktion von zweiter Ordnung hinsichtlich ICl und von erster Ordnung hinsichtlich des Substrats, d. h. mit einer Gesamtordnung von drei. Geschwindigkeitskonstanten wurden für jedes Substrat bei 20°, 30°, 40° und 50°C gemessen. AusArrhenius-Diagrammen wurden Aktivierungsenergien ermittelt und auch andere kinetische und thermodynamische Parameter wurden bestimmt. Ein Mechanismus wird vorgeschlagen, wobei die verschiedenen Parameter diskutiert werden. Lösungsmitteleffekte werden ebenfalls diskutiert und die Daten mit Nitrobenzol und Essigsäure als Lösungsmittel miteinander verglichen.
    Notes: Abstract The kinetics of the addition of iodine monochloride (ICl) to some vinyl compounds in nitrobenzene solvent was investigated. In all cases the reaction follows second order dependence on ICl and first order on the substrate, making the total order three. Rate constants were measured for each substrate at 20°, 30°, 40° and 50°C.Arrhenius plots were made from which activation energies were evaluated. Other kinetic and thermodynamic parameters are reported. A suitable mechanism is proposed for the reaction and based on this, the various parameters are discussed. Solvent effects are discussed and the data with nitrobenzene and acetic acid solvents are compared.
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  • 7
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    Monatshefte für Chemie 115 (1984), S. 1185-1197 
    ISSN: 1434-4475
    Keywords: Mono and polycarboxylic esters ; Metal salt catalysis ; Kinetics ; Chromatographic analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The alcoholysis of various esters of aromatic carboxylic esters with octadecanol in the presence of lead stearate was investigated by chromatographic analysis of the reaction mixtures. The reactivity of the esters was found to be strongly affected by the substitution pattern of the aromatic nucleus as well as by the structure of the alkoxy group. Electron donating substituents in a suitable position lead to a remarkable increase in reactivity compared to the unsubstituted alkyl esters.
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  • 8
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    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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  • 9
    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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  • 10
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    Monatshefte für Chemie 115 (1984), S. 1385-1392 
    ISSN: 1434-4475
    Keywords: Periodate oxidation ; Solvent effect ; Reaction rate ; Kinetics ; Octacyanomolybdate (IV)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Kinetik der Oxidation von Mo(CN) 8 4− mit IO4/− wurde in Ethanol—Wasser über einen Temperaturbereich von 15–35 °C untersucht. Der Effekt der Lösungsmittelzusammensetzung auf die Reaktionsgeschwindigkeit und der Mechanismus der Reaktion werden diskutiert. Die Aktivierungsparameter sind angeführt. Es wird ein „Inner-Sphere“-Mechanismus vorgeschlagen, der mit den kinetischen Ergebnissen konsistent ist.
    Notes: Abstract The kinetics of the oxidation of Mo(CN) 8 4− by IO 4 − has been studied in ethanol—water solvent mixtures over a temperature range of 15–35 °C. The effect of solvent composition on the reaction rate and the mechanism has been investigated. Activation parameters are given. An inner-sphere mechanism, consistent with the kinetic results, is proposed.
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  • 11
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    Monatshefte für Chemie 115 (1984), S. 405-414 
    ISSN: 1434-4475
    Keywords: Kinetics ; Mechanism ; Oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wurde die Kinetik der Oxidation von Chinol mit Quecksilbernitrat in Gegenwart einer Mischung ausAcOH-H2O-HNO3 untersucht, um die aktive Species bei der Oxidation in diesem Medium aufzuklären. Die Reaktionsordnung ist sowohl bezüglich des Chinols als auch des Hg(II)-Ions erster Ordnung. Die Reaktionsgeschwindigkeit erhöht sich leicht mit der HNO3-Konzentration und auch mit abfallender Dielektrizitätskonstante des Mediums. Die Reaktionsgeschwindigkeit sinkt mit dem Zusatz von KNO3. Es ist keinerlei Hinweis auf eine Komplexbildung zwischen Chinol und Hg(II) festzustellen. Die Resultate der Untersuchungen legen HgNO + 3 als aktive Spezies nahe. Es wird ein möglicher Mechanismus mit einem Zweielektronen-Transfer im geschwindigkeitsbestimmenden Schritt vorgeschlagen. Das dabei produziertep-Benzochinon existiert nicht in freier Form, sondern es bildet einen stabilen 1 : 1-Komplex mit Quecksilbernitrat; dieser Komplex wurde mittels TLC und IR charakterisiert.
    Notes: Abstract The kinetics of oxidation of quinol by mercuric nitrate in presence ofAcOH-H2O-HNO3 mixture has been investigated in order to find the active species of mercuric nitrate involved in the oxidation in this medium. The order of reaction both with respect to quinol and Hg(II) is found to be one. The reaction rate slightly increases with the increase in [HNO3] and the decrease of the dielectric constant of the medium. The reaction rate retards on addition of KNO3. There is no evidence for complex formation between quinol and Hg(II). These results suggest that HgNO + 3 might be the active species in this medium. A probable mechanism involving a two electron transfer in the rate determining step has been suggested. The producedp-benzoquinone does not exist in free state but forms a stable (1 : 1) complex with mercuric nitrate which has been characterized by TLC and IR studies.
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  • 12
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    Monatshefte für Chemie 115 (1984), S. 697-704 
    ISSN: 1434-4475
    Keywords: Electrohydrodimerization ; Benzylidenemalononitriles ; Kinetics ; Electrohydrodimerization ; Benzylidenemalononitriles ; Kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Mittels derivativer cyclischer Voltammetrie wurden für die Titelreaktion Geschwindigkeitskonstanten und Aktivierungsparameter erhalten (Dimethylformamid als Lösungsmittel). Benzyliden-,p-Methyl- undp-Methoxybenzylidenmalonnitril reagieren ausschließlich über die Dimerisierung ihrer Anionenradikale (Radikal-Radikal-Kopplung), währenddessen die Dimerisierung vonp-Fluorbenzylidenmalonnitril zu 25% über die Kopplung des Anionenradikals mit dem Substrat erfolgt.
    Notes: Abstract Rate constants and activation parameters for the reductive dimerization of substituted benzylidenemalononitriles were obtained from derivate cyclic voltammetry measurements in dimethylformamide as solvent. Benzylidene-,p-methyl-andp-methoxybenzylidenemalononitrile react exclusively via dimerization of their anion radicals (radical-radical coupling) while forp-fluorobenzylidenemalononitrile 25% of the dimerization proceeds by coupling of the anion radical with the substrate.
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  • 13
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    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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  • 14
    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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  • 15
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    Calcified tissue international 36 (1984), S. 697-701 
    ISSN: 1432-0827
    Keywords: Endochondral osteogenesis ; Growth ; Pregnancy ; Lactation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The rates of endochondral bone elongation during pregnancy and lactation in rats have been studied. The rate of growth at the distal femoral epiphyseal growth plate was measured using fluorescent bone markers. Endochondral growth rates were substantially increased in pregnant animals when compared with age-matched, nonmated controls. There were also increases in growth plate thickness, hypertrophic cell lacunar height, and the calculated rate of cell production during pregnancy. At parturition, this growth trend was reversed and during lactation there were significant decreases in endochondral growth rates. There were also corresponding decreases in growth plate thickness, hypertrophic cell lacunar height, and the calculated rate of cartilage cell production. These results indicate that significant changes occur in maternal endochondral growth rates during the reproductive cycle in rats.
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  • 16
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    Calcified tissue international 36 (1984), S. 48-59 
    ISSN: 1432-0827
    Keywords: Salivary proteins ; Adsorption ; Thermodynamics ; Kinetics ; Hydroxyapatite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Equilibrium and kinetic experiments were conducted to investigate the factors determining the adsorption of salivary macromolecules onto hydroxyapatite. Using amino acids and other small adsorbates, it was determined that the carboxyl attached to the α carbon does not appear to adsorb onto HA and the affinities of side-chain carboxyls are much smaller than that of the phosphate group (phosphoserine). Hydroxyl (serine) displays an extremely high affinity, but its adsorption site on HA is different and the number of such sites is much smaller than found for the rest of the functional groups investigated. It is shown that the information obtained from small molecules cannot be readily applied to prediction of the adsorption behavior of salivary macromolecules and polypeptides. The kinetics of adsorption of the salivary phosphopeptide statherin, a polyaspartate, and the salivary prolinerich phosphoprotein PRP3 are consistent with the reversibility of the adsorption process; no conclusion was possible in the case of the protein PRP1. Apparent irreversibility cannot be explained on the basis of multipoint binding or the properties of the carboxyl versus phosphate group; it appears that secondary structure determines to a significant extent the adsorption properties of the macromolecules. Calculation of the thermodynamic molar quantities of adsorption of PRP1, PRP3, andl-ASP onto HA showed that the process is entropically driven. The functional relationship between partial molar entropy and adsorption coverage is similar for the two proteins, but quite different from that for aspartate. Explanations for these results are advanced on the bases of changes in structure configurations and displacement of water from the adsorbate and the adsorbent surface, the second factor being the dominant one in the adsorption of a small molecule such asl-ASP.
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  • 17
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    Environmental management 8 (1984), S. 309-324 
    ISSN: 1432-1009
    Keywords: Animals ; Indicators ; Air pollution ; Ecosystem responses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract With existing and proposed air-quality regulations, ecological disasters resulting from air emissions such as those observed at Copperhill, Tennessee, and Sudbury, Ontario, are unlikely. Current air-quality standards, however, may not protect ecosystems from subacute and chronic exposure to air emissions. The encouragement of the use of coal for energy production and the development of the fossil-fuel industries, including oil shales, tar sands, and coal liquification, point to an increase and spread of fossil-fuel emissions and the potential to influence a number of natural ecosystems. This paper reviews the reported responses of ecosystems to air-borne pollutants and discusses the use of animals as indicators of ecosystem responses to these pollutants. Animal species and populations can act as important indicators of biotic and abiotic responses of aquatic and terrestrial ecosystems. These responses can indicate long-term trends in ecosystem health and productivity, chemical cycling, genetics, and regulation. For short-term trends, fish and wildlife also serve as monitors of changes in community structure, signaling food-web contamination, as well as providing a measure of ecosystem vitality. Information is presented to show not only the importance of animals as indicators of ecosystem responses to air-quality degradation, but also their value as air-pollution indices, that is, as air-quality-related values (AQRV), required in current air-pollution regulation.
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  • 18
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    Archives of microbiology 139 (1984), S. 28-32 
    ISSN: 1432-072X
    Keywords: Cyanobacterium ; Phosphate ; Uptake ; Kinetics ; Regulation ; Pulse ; Steady state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In order to study phosphate uptake kinetics the cyanobacteriumOscillatoria agardhii was grown in continuous culture under a phosphorus limitation. The affinity of the uptake system reflected in the initial slope of the uptake rate versus external substrate concentration curve (dV/ds) was found to be unaffected by the growth wate. The maximum phosphate uptake rate (V m ) decreased as the growth rate was increased. Attempts were made to relate the decrease ofV m to the increase in phosphorus content of the cells that occurred a higher growth rates. Accumulation of phosphate during pulse experiments indeed resulted in a decrease ofV m . However feedback regulation ofV m by accumulated phosphorus was found to occur only to a small extent in steady state growing cells. The main part of the regulation of the activity of the phosphate uptake system seemingly is determined by a long term process that is, at least longer than 2 h. The presence of short term feedback inhibition by accumulated phosphorus on the activity of the uptake system provides an explanation of the phenomenon thatOscillatoria agardhii is not able to grow at nearμ max growth rates under a phosphorus limitation.
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  • 19
    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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  • 20
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    Journal of statistical physics 34 (1984), S. 399-426 
    ISSN: 1572-9613
    Keywords: Kinetics ; Becker-Doring equations ; clusters ; computer simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We make a quantitative comparison between the predictions of the Becker-Döring equations and computer simulations on a model of a quenched binary A-B alloy. The atoms are confined to the vertices of a simple cubic lattice, interact through attractive nearest neighbor interactions, and move by interchanges of nearest neighbor pairs (Kawasaki dynamics). We study in particular the time evolution of the number of clusters of A atoms of each size, at four different concentrations: ρA=0.035, 0.05, 0.075, and 0.1 atoms per lattice site. The temperature is 0.59 times the critical temperature. At this temperature the equilibrium concentration of A atoms in the B-rich phase is ρ A eq =0.0145 atoms/lattice site. The coefficients entering the Becker-Döring equations are obtained by extrapolation from previously published low-density calculations, leaving the time scale as the only adjustable parameter. We find good agreement at the three lower densities. At 10% density the agreement is, as might be expected, less satisfactory but still fairly good-indicating a quite wide range of utility for the Becker-Döring equations.
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  • 21
    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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