Excitatory Amino Acids Contribute to the Pathogenesis of Perinatal Hypoxic-Ischemic Brain Injury

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75512/1/j.1750-3639.1992.tb00697.x.pd

Integrated assessment of changes in flooding probabilities due to climate change

An approach to considering changes in flooding probability in the integrated assessment of climate change is introduced. A reduced-form hydrological model for flood prediction and a downscaling approach suitable for integrated assessment modeling are presented. Based on these components, the fraction of world population living in river basins affected by changes in flooding probability in the course of climate change is determined. This is then used as a climate impact response function in order to derive emission corridors limiting the population affected. This approach illustrates the consideration of probabilistic impacts within the framework of the tolerable windows approach. Based on the change in global mean temperature, as calculated by the simple climate models used in integrated assessment, spatially resolved changes in climatic variables are determined using pattern scaling, while natural variability in these variables is considered using twentieth century deviations from the climatology. Driven by the spatially resolved climate change, the hydrological model then aggregates these changes to river basin scale. The hydrological model is subjected to a sensitivity analysis with regard to the water balance, and the uncertainty arising through the different projections of changes in mean climate by differing climate models is considered by presenting results based on different models. The results suggest that up to 20% of world population live in river basins that might inevitably be affected by increased flood events in the course of global warming, depending on the climate model used to estimate the regional distribution of changes in climate

Soil test measures of available P (Colwell, resin and DGT) compared with plant P uptake using isotope dilution

Background and aims: Recent research has demonstrated the high accuracy of a new method for assessment of plant available P in soil called diffusive gradients in thin-films (DGT). The process of P released by additions of bicarbonate to soil samples simulating common soil P tests is yet to be assessed by the new method (DGT). The aim of this study was to identify the pools of soil P extracted by soil test methods (DGT, Colwell and resin) by comparing, in 32P-labelled soils, the specific activity (SA) of phosphorus extracted by common soil test extracts with the SA of wheat plants grown in a range of agricultural soils from southern Australia. Methods: Wheat (cv. Frame) was grown for 4 weeks in 14 soils that were labelled uniformly with carrier-free 32P. The specific activity (SA) of P (MBq 32P kg 31P-1) in each soil test extract was compared to the SA of P in the wheat plants. Results: The SA of P in plants were similar to P extracted by the Colwell extractant in only 4 of the 14 soils; while SA in plants and extractants corresponded in 10 of the soils for the resin method and in 12 of the soils for the DGT method. Phosphorus in the Colwell and resin extract solutions had significantly lower SAs compared to P in the plants for 10 and 4 of the soils, respectively, indicating greater extraction of non-labile P sources (unlabelled 31P). Phosphorus in the DGT extractant had significantly lower SA than the plants for 1 soil and in 1 soil the SA was higher. Overall, across all soils, 25 % of P extracted by the Colwell method was non labile compared to 9 % and 2 % for the resin and DGT methods, respectively. Conclusion: The new DGT method for extraction of soil P has the potential to accurately predict occurrences of P deficiency because it generally extracts the same pool of labile soil P accessed by wheat plants, while methods using bicarbonate solution (e.g. Colwell, Olsen) or water (resin) at wide soil:solution ratios are more likely to measure more non-labile forms of P in soil. © 2013 Springer Science+Business Media Dordrecht.Sean D. Mason, Mike J. McLaughlin, Caroline Johnston, Ann McNeil

Prediction of wheat response to an application of phosphorus under field conditions using diffusive gradients in thin-films (DGT) and extraction methods

The ability of the Diffusive Gradients in Thin Films (DGT) technique and two other established testing methods (Colwell, resin) to predict wheat responsiveness to applied P from 35 field trials across southern Australia was investigated. Regression analysis of relative early dry matter production and grain yield responses demonstrated that the DGT method predicted plant responsiveness to applied P more accurately than Colwell P and resin P at sites where maximum yields were reached with P rates used (20 out of 35). The measured concentration in soils at the DGT surface, C-DGT, explained 74% of the variation in response for both early dry matter and grain, compared to 7% for early dry matter and 35% for grain using the resin P method. No significant relationships could be obtained for Colwell P although modifying the Colwell test data using Phosphorus Buffering Index resulted in a correct response prediction for 11 of the 20 field sites compared to 18 for DGT and 14 for resin P. These observations suggest that the DGT technique can assess plant available P in soils with significantly greater accuracy than traditional soil P testing methods. The critical P threshold, expressed as C-DGT, was 255 mu g L-1 for early dry matter and 66 mu g L-1 for grain