PubMed · 5444033
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C W Laymon. 1970. Hemangiomas.. https://pubmed.ncbi.nlm.nih.gov/5444033/
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The oxidation of pyrite (FeS2) contained in unsaturated aquifer sediment was studied by sediment incubation in gas impermeable polymer laminate bags. Reaction progress was followed over a period of nearly 2 months by monitoring the gas composition within the laminate bag. The gas phase in the incubation bags became depleted in O2 and enriched in CO2 and N2 and was interpreted as due to pyrite oxidation in combination with calcite dissolution. Sediment incubation provides a new method to estimate low rates of pyrite oxidation in unsaturated zone aquifer sediments. Oxidation rates of up to 9.4 x 10(-10) mol FeS2/g x s are measured, and the rates are only weakly correlated with the sediment pyrite content. The reactivity of pyrite, including the inhibition by FeOOH layers formed on its surface, apparently has a major effect on the rate of oxidation. The code PHREEQC 2.0 was used to calculate the reaction stoichiometry and partitioning of gases between the solution and the gas phase. Pyrite oxidation with concurrent calcite dissolution was found to be consistent with the experimental data while organic carbon oxidation was not. The reaction involves changes in the total volume of the gas phase. The reaction scheme predicts the volume of O2 gas consumed to be larger than of CO2 produced. In addition the solubility of CO2 in water is about 30 times larger than of O2 causing a further decrease in total gas volume. The change in total gas volume therefore also depends on the gas/water volume ratio and the lower the ratio the more pronounced the loss of volume will be. Under field conditions the change in total volume may amount up to 20% in the absence of calcite and over 10% in the presence of calcite. Such changes in gas volume during the oxidation of pyrite are expected to result in pressure gradients causing advective transport of gaseous oxygen.
Three groups of carambola fruits (Averrhoa carambola L.) were stored at 2 and 10 degrees C (85-90% relative humidity). The major physicochemical, physiological, and enzymatic responses of fruit were measured in each group over a 30-day period: chilling injury index (CII), decay (%), intracuticular waxes, cuticle permeability, pulp firmness, weight loss, sucrose, fructose and glucose contents, ion electrolyte leakage in pulp (%), ethylene and carbon dioxide production rates, and the activities of peroxidase (POD), polyphenol oxidase (PPO), and phenylalanine ammonia-lyase (PAL) enzymes. CII values were statistically different at 2 and 10 degrees C, showing high significance with respect to sucrose content and weight loss (P < 0.05). Chilling injury included darkened ribs and skin desiccation. According to the CI symptom development, a possible relationship of POD and PPO activities was found at 2 degrees C. A significant sucrose content increase was observed at 10 degrees C. CI symptoms were associated with POD and PAL activities.