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171.
Bjarne W. Strobel Flemming Kristensen Hans Christian B. Hansen 《International journal of environmental analytical chemistry》2013,93(12):909-917
Oxalate in soils may enhance phosphate availability, promote mineral dissolution, and increase the mobility of aluminium and heavy metal cations by complexation. Rhubarb (Rheum rhaponticum L.) has very high content of oxalate in leaves and petioles, and therefore the topsoil under rhubarb might have elevated contents of oxalate. Soil samples were collected at depths of 0–2.5 and 2.5–5?cm from 10?cm sections along 100?cm transects from rhubarb plants at four locations in Denmark, and from seven layers in a soil profile to 80?cm depth at one location. Oxalate was extracted from the soil with 0.2?M phosphate at pH 2 by reciprocal shaking for 24?h and then determined by a new fast capillary zone electrophoresis method with 300?mM KH2PO4 and 0.30?mM TTAB electrolyte adjusted to pH 7, developed and tested to analyse high-ionic-strength soil extracts. Rhubarb increases the oxalate content in soil under the leaves slightly. The average content of oxalate in the upper 0–5?cm soil was 444?µmol/kg at the Kaldred site, and 111–333?µmol/kg at the three other locations. In the soil profile, the content of oxalate decreased from 500?µmol/kg in 0–5?cm depth to 110?µmol/kg at 75–80?cm depth. No significant seasonal changes in oxalate contents were observed, while an annual variation of 100?µmol/kg could be observed at 0–2.5?cm depth. During plant decay in autumn, a slight increase in oxalate content was observed at 30?cm soil depth. In conclusion, the role of oxalate in weathering and metal transport appears to be limited in soils under rhubarb. Oxalate might stimulate microbiological growth and phosphate mobilisation in the rhizosphere, but concentrations observed are too low to impose any toxic effects to organisms. 相似文献
172.
The properties of water‐in‐toluene emulsions stabilized solely by hydrophobized microfibrillated cellulose (MFC) were investigated. By varying the degree of surface substitution (DSS), the wettability of the MFC was altered. All emulsions prepared with MFC displayed excellent stability to coalescence. The stability to gravity‐induced sedimentation increased with increasing MFC concentration, the highest stability being obtained with MFC of moderate hydrophobicity. Drop sizes increased with increasing DSS, with a corresponding decrease in stability to sedimentation. An increase in the toluene:water ratio at constant MFC concentration resulted in a decrease in the average drop size. For all emulsions, the polydispersity in drop size decreased with decreasing average drop diameter. 相似文献
173.
Bjarne S. Pedersen Sten Scheibye Sven-Olov Lawesson 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):235-236
Abstract Recent studies on thiation of carbonyl compounds with organic P,S-compounds have shown that p-methoxyphenyl-thionophosphinsulfide (1) is the most effective thiation reagent for ketones, carboxamides, esters, and thioloesters hitherto known. 相似文献
174.
Jacques H. Van Boom Bjarne Dahl Otto Dahl John E. Marugg John Nielsen Michael Taagaard 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4)
Abstract 2-Cyanoethyl bis(diisopropylamino) phosphorodiamidite (1) is a stable and easily obtainable compound1 which, when activated with 0.5 eq. tetrazole, gives solutions of deoxyribonucleoside 2-cyano-ethyl phosphoramidites (2) useful for the synthesis of deoxyoligo-nucleotides. 2 Our results applying these in-situ prepared phosphoramidites for polymer-supported syntheses of a variety of deoxyoligonucleotides (DNA fragments) will be presented. 相似文献
175.
176.
Andresen LC Konestabo HS Maraldo K Holmstrup M Ambus P Beier C Michelsen A 《Rapid communications in mass spectrometry : RCM》2011,25(11):1485-1496
The rising atmospheric CO(2) concentration, increasing temperature and changed patterns of precipitation currently expose terrestrial ecosystems to altered environmental conditions. This may affect belowground nutrient cycling through its intimate relationship with the belowground decomposers. Three climate change factors (elevated CO(2), increased temperature and drought) were investigated in a full factorial field experiment at a temperate heathland location. The combined effect of biotic and abiotic factors on nitrogen and carbon flows was traced in plant root → litter → microbe → detritivore/omnivore → predator food-web for one year after amendment with (15)N(13)C(2)-glycine. Isotope ratio mass spectrometry (IRMS) measurement of (15)N/(14)N and (13)C/(12)C in soil extracts and functional ecosystem compartments revealed that the recovery of (15)N sometimes decreased through the chain of consumption, with the largest amount of bioactive (15)N label pool accumulated in the microbial biomass. The elevated CO(2) concentration at the site for 2 years increased the biomass, the (15)N enrichment and the (15)N recovery in detritivores. This suggests that detritivore consumption was controlled by both the availability of the microbial biomass, a likely major food source, and the climatic factors. Furthermore, the natural abundance δ(13)C of enchytraeids was significantly altered in CO(2)-fumigated plots, showing that even small changes in δ(13)C-CO(2) can be used to detect transfer of carbon from primary producers to detritivores. We conclude that, in the short term, the climate change treatments affected soil organism activity, possibly with labile carbohydrate production controlling the microbial and detritivore biomass, with potential consequences for the decomposition of detritus and nutrient cycling. Hence, there appears to be a strong coupling of responses in carbon and nitrogen cycling at this temperate heath. 相似文献
177.
Dr. Bjarne Kreitz Dr. Patrick Lott Prof. Dr. Felix Studt Prof. Dr. Andrew J. Medford Prof. Dr. Olaf Deutschmann Prof. Dr. C. Franklin Goldsmith 《Angewandte Chemie (International ed. in English)》2023,62(39):e202306514
The study presents an ab-initio based framework for the automated construction of microkinetic mechanisms considering correlated uncertainties in all energetic parameters and estimation routines. 2000 unique microkinetic models were generated within the uncertainty space of the BEEF-vdW functional for the oxidation reactions of representative exhaust gas emissions from stoichiometric combustion engines over Pt(111) and compared to experiments through multiscale modeling. The ensemble of simulations stresses the importance of considering uncertainties. Within this set of first-principles-based models, it is possible to identify a microkinetic mechanism that agrees with experimental data. This mechanism can be traced back to a single exchange-correlation functional, and it suggests that Pt(111) could be the active site for the oxidation of light hydrocarbons. The study provides a universal framework for the automated construction of reaction mechanisms with correlated uncertainty quantification, enabling a DFT-constrained microkinetic model optimization for other heterogeneously catalyzed systems. 相似文献