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  • 1
    Electronic Resource
    Electronic Resource
    Cycloadditions of nitrones with fluoroallene (1987)
    s.l. : American Chemical Society
    The @journal of organic chemistry 52 (1987), S. 2196-2201 
    Details
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jo00387a015
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  • 2
    Electronic Resource
    Electronic Resource
    Stereochemistry of cycloadditions of fluoroallene (1985)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 107 (1985), S. 7183-7184 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00310a075
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  • 3
    Electronic Resource
    Electronic Resource
    Hydrogen turnover by psychrotrophic homoacetogenic and mesophilic methanogenic bacteria in anoxic paddy soil and lake sediment (1989)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 62 (1989), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The effect of temperature on CH4 production, turnover of dissolved H2, and enrichment of H2-utilizing anaerobic bacteria was studied in anoxic paddy soil and sediment of Lake Constance. When anoxic paddy soil was incubated under an atmosphere of H2/CO2, rates of CH4 production increased 25°C, but decreased at temperatures lower than 20°C. Chloroform completely inhibited methano-genesis in anoxic paddy soil and lake sediment, but did not or only partially inhibit the turnover of dissolved H2, especially at low incubation temperatures. Cultures with H2 as energy source resulted in the enrichment of chemolithotrophic homoacetogenic bacteria whenever incubation temperatures were lower than 20°C. Hydrogenotrophic methanogens could only be enriched at 30°C from anoxic paddy soil. A homoacetogen
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1989.tb03382.x
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  • 4
    Electronic Resource
    Electronic Resource
    Microbial production and uptake of nitric oxide in soil (1989)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 62 (1989), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Fluxes of NO from three different soils have been studied by a flow-through system in the laboratory as a function of gas flow rate, of NO mixing ratio, and of incubation conditions. The dependence of net NO fluxes on gas flow rates and on NO mixing ratios could be described by a simple model of simultaneous NO production and NO uptake. By using this model, rates of gross NO production, rate constants of NO uptake, and NO compensation mixing ratios could be determined as function of the soil type and the incubation condition. Gross NO production rates were one to two orders of magnitude larger under anaerobic than under aerobic conditions. NO uptake rate constants, on the other hand, were only 5–8 times larger so that the compensation mixing ratios of NO were in a range of about 1600–2200 ppbv under anaerobic and of about 50–600 ppbv under aerobic conditions. The different soils exhibited similar NO uptake rate constants, but the gross NO production rate and compensation mixing ratio was significantly higher in an acidic (pH 4.7) sandy clay loam than in other less acidic soils. Experiments with autoclaved soil samples showed that both NO production and NO uptake was mainly due to microbial metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1989.tb03696.x
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  • 5
    Electronic Resource
    Electronic Resource
    Thermodynamics of H2-consuming and H2-producing metabolic reactions in diverse methanogenic environments under in situ conditions (1986)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 38 (1986), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract In situ concentrations of hydrogen and other metabolites involved in H2-consuming and H2-producing reactions were measured in anoxic methanogenic lake sediments, sewage sludge and fetid liquid of cottonwood. The data were used to calculate the Gibbs free energies of the metabolic reactions under the conditions prevailing in situ. The thermodynamics of most of the reactions studied were exergonic with Gibbs free energies being more negative for H2-dependent sulfate reduction methanogenesis acetogenesis and for H2-producing lactate fermentation ethanol fermentation. Butyrate and propionate fermentation, on the other hand, were endergonic under in situ conditions. This observation is interpreted by suggesting that butyrate and propionate is degraded within microbial clusters which shield the fermentating bacteria from the outside H2 (and acetate) pool.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1986.tb01748.x
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  • 6
    Electronic Resource
    Electronic Resource
    Hydrogen metabolism during methanogenesis from acetate by Methanosarcina barkeri (1987)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 40 (1987), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A tritium exchange assay and a sensitive gas chromatographic technique were used to demonstrate that hydrogenase was active and that hydrogen was produced by Methanosarcina barkeri strain MS grown on acetate. Both methane and hydrogen production rates were dependent on the concentration of acetate in the medium. H2 was produced at 0.5–2% of the rate of CH4 formation. Chloroform and potassium cyanide, inhibitors of methanogenesis from acetate, inhibited H2 production but not hydrogenase activity. The addition of hydrogen gas to cell suspensions did not inhibit CH4 or carbon dioxide production from the methyl group of acetate. H2 production appears to be linked to several intracellular redox processes which follow the cleavage of acetate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1987.tb02024.x
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  • 7
    Electronic Resource
    Electronic Resource
    Thermodynamics of hydrogen metabolism in methanogenic cocultures degrading ethanol or lactate (1988)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 55 (1988), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Pure cultures of Desulfovibrio vulgaris or Pelobacter acetylenicus do not grow with lactate or ethanol, respectively, under obligately proton- reducing conditions. However, a small part of these substrates was oxidized and molecular hydrogen was produced up to 4.2 and 3.2 kPa, respectively. During growth in syntrophic methanogenic cocultures with Methanospirillum hungatei as partner, maximum hydrogen partial pressures were significantly lower (0.7 to 2.5 kPa) than in the corresponding pure cultures. Calculation of Gibbs free energies for the prevailing culture conditions showed that H2 partial pressures were kept in a range at which both, H2-producing and H2-consuming reactions, were thermodynamically permissive in pure as well as in syntrophic mixed cultures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1988.tb13918.x
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  • 8
    Electronic Resource
    Electronic Resource
    Hydrogen metabolism in a mildly acidic lake sediment (Knaack Lake) (1987)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 45 (1987), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Hydrogen metabolism was studied in anoxic Knaack Lake sediments by measuring the in situ concentrations of dissolved H2, as well as the Vmax, turnover rate constant, and Km for H2. The results show that the relatively low rate of H2/CO2-dependent methanogenesis is paralleled by a low turnover of the dissolved H2 pool. H2-dependent acetate formation did not appear to be of importance based on the discrepancy of the Km for H2 consumption between the sediment and the prevalent homoacetogenic microbial population. In this mildly acidic lake sediment, H2 turnover apparently was limited by H2 production from organic matter. During incubation of sediment under a gaseous headspace, H2 escaped from the aqueous phase, and steady state concentrations of dissolved H2 were significantly lower than under in situ conditions. H2 concentrations increased upon addition of various organic substrates. H2 turnover within the sediment appeared unrelated to the concentration of H2 detected in the water column, especially in the epilimnetic water layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1987.tb02362.x
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of vegetation on the emission of methane from submerged paddy soil (1986)
    Springer
    Plant and soil 92 (1986), S. 223-233 
    Details
    ISSN: 1573-5036
    Keywords: CH4 emission ; CH4 oxidation ; Ebullition ; Laboratory and field studies ; Methanogenesis ; Paddy soil ; Rice ; Weeds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Methane emission rates from rice-vegetated paddy fields followed a seasonal pattern different to that of weed-covered or unvegetated fields. Presence of rice plants stimulated the emission of CH4 both in the laboratory and in the field. In unvegetated paddy fields CH4 was emitted almost exclusively by ebullition. By contrast, in rice-vegetated fields more than 90% of the CH4 emission was due to plant-mediated transport. Rice plants stimulated methanogenesis in the submerged soil, but also enhanced the CH4 oxidation rates within the rhizosphere so that only 23% of the produced CH4 was emitted. Gas bubbles in vegetated paddy soils contained lower CH4 mixing ratios than in unvegetated fiels. Weed plants were also efficient in mediating gas exchnage between submerged soil and atmosphere, but did not stimulate methanogenesis. Weed plants caused a relatively high redox potential in the submerged soil so that 95% of the produced CH4 was oxidized and did not reach the atmosphere. The emission of CH4 was stimulated, however, when the cultures were incubated under gas atmospheres containing acetylene or consisting of O2-free nitrogen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02372636
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  • 10
    Electronic Resource
    Electronic Resource
    Emission of hydrogen from deep and shallow freshwater environments (1988)
    Springer
    Biogeochemistry 5 (1988), S. 295-311 
    Details
    ISSN: 1573-515X
    Keywords: lake water ; lake sediments ; paddy fields ; ebullition ; plant-mediated gas flux ; atmospheric H2 budget
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract In-situ partial pressures of hydrogen in anoxic profundal lake sediments reached values of up to 5 Pa which were more than 5 orders of magnitude lower than the partial pressures of methane. Analysis of gas bubbles collected from anoxic submerged paddy soil showed H2 partial pressures in the range of 1.8 ± 1.3 Pa being ca. 4 orders of magnitude lower than the CH4 partial pressures. H2 emission rates, on the other hand, were less than 3 orders of magnitude lower than the CH4 emission rates indicating that H2 and CH4 were oxidized to a different extent in the rhizosphere of the soil before they reached the atmosphere, or that H2 was produced by the plants. More than 70% of the emitted H2 reached the atmosphere via plant-mediated flux. The rest was emitted via ebullition from the anoxic soil and, in addition, was produced in the paddy water. A significant amount of H2 was indeed found to be produced in the water under conditions where thallic algae and submerged parts of the rice plants produced oxygen by photosynthesis. Very little H2 was emitted via molecular diffusion through the paddy water; in addition, this amount was less than expected from the degree of supersaturation and the diffusional emission rate of CH4 indicating a relatively high rate of H2 consumption in the surface film of the paddy water. The total H2 source strength of rice paddies and other freshwater environments was estimated to be less than 1 Tg yr-1, being negligible in the atmospheric budget of H2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02180069
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