1,721,115 research outputs found
Denitrification potential of beech soils as influenced by the seasonal cycle.
No full textThe potential for nitrification is appreciable throughout the whole seasonal cycle, but nitrate is depleted at different rates during the year. The highest values of nitrate depletion occurred in late spring, early summer and at leaf-fall when readily available carbon substrates are released from root exudates or from litter decomposition. -from Author
Nitrogen mineralization in southern beech forests.
No full textNitrogen mineralization has been studied in the slightly acidic brown earth on limestone of a beech stand and a beech-fir stand, in the forests of Monte Taburno (Campania Apennines). NH4 is the predominant form of the mineral N in the soil of both stands. Yearly NO3- production is 42.4 kg ha-1 in the beech stand and 47.0 kg ha-1 in the beech-fir stand.-from Author
Assessment of nutritional status and trace element contamination of holm oak woodlands through analyses of leaves and surrounding soils.
No full textInterfacial tension of aqueous mixtures of Na-caseinate and Na-alginate by drop deformation in shear flow
No full textIn this work, the interfacial tension of biphasic aqueous mixtures of Na-caseinate and Na-alginate was measured by a methodology based on drop deformation in shear flow. The two phases coexisting at equilibrium in the mixtures were separated by ultracentrifugation. A drop of one phase was injected into the other phase and sheared in a sliding plate apparatus equipped with video-enhanced microscopy. A detailed quantitative characterization of drop shape in several flow conditions, including steady state shear and transient flows, was performed by image analysis techniques. All the results are well described by classical theories of drop deformation in shear flow (which were originally developed for immiscible fluids), the only fitting parameter being the interfacial tension. The methodology used in this work allowed the measurement of very low values of interfacial tension, of the order of 10-5 N/m, and can be applied in general to aqueous mixtures of proteins and polysaccharides
Phase diagram, rheology and interfacial tension of aqueous mixtures of Na-caseinate and Na-alginate
No full textIn this work, the system Na-alginate/Na-caseinate/water has been characterised in terms of phase diagram, rheological properties of the equilibrium phases, and interfacial tension as a function of tie-line position. In water, the two biopolymers are poorly miscible and the system separates in two phases, each highly enriched of only one of the two biopolymers. The rheological properties of the equilibrium phases are essentially determined by the biopolymer present to a larger extent. Thus, as for the aqueous solutions of each biopolymer, the Na-caseinate rich phases are Newtonian, while the Na-alginate rich phases show shear-thinning behaviour at shear rates larger than 1 s21. In the region close to the critical point, the Na-alginate rich phases are more viscous than the Na-caseinate rich ones. The opposite trend is found as the total amount of biopolymers increases. The interfacial tension between the equilibrium phases was measured by analysing drop retraction upon cessation of shear flow. The interfacial tension decreases as the tie-line approaches the critical point. A linear relation was found to hold between interfacial tension and tie-line length
Interfacial tension of aqueous mixtures of Na-caseinate and Na-alginate by drop deformation in shear flow
No full textIn this work, the interfacial tension of biphasic aqueous mixtures of Na-caseinate and Na-alginate was measured by a methodology based on drop deformation in shear flow. The two phases coexisting at equilibrium in the mixtures were separated by ultracentrifugation. A drop of one phase was injected into the other phase and sheared in a sliding plate apparatus equipped with video-enhanced microscopy. A detailed quantitative characterization of drop shape in several flow conditions, including steady state shear and transient flows, was performed by image analysis techniques. All the results are well described by classical theories of drop deformation in shear flow (which were originally developed for immiscible fluids), the only fitting parameter being the interfacial tension. The methodology used in this work allowed the measurement of very low values of interfacial tension, of the order of 10-5 N/m, and can be applied in general to aqueous mixtures of proteins and polysaccharides
Tropospheric ozone effects on chemical composition and decomposing rate of Quercus ilex L. leaves. Science of Total Environment, 409, 949-84
No full textWe determined the effects of tropospheric ozone on the chemical composition of Quercus ilex L. leaves and
their decomposition, with a view to assessing the influence of ozone on nutrient cycling and the sustainability
of Mediterranean holm oak forests. Forming one of the most widespread thermophilous vegetation
communities in the area, Q. ilex is a dominant and widespread evergreen oak in the Mediterranean, where
concentrations of tropospheric ozone are particularly high. The dynamics of carbon, nitrogen, lignin and
cellulose concentrations were monitored for six months during the decomposition of leaves from plants
subjected to controlled ozone exposure in open-top chambers. Ozone-exposed leaves, compared to
unexposed leaves, showed no significant differences in C, N, lignin and cellulose concentrations prior to
the incubation in mesocosms. However, during decomposition, leaves from plants exposed to ozone lost C
significantly more slowly and showed a higher C/N ratio than unexposed leaves. Ozone exposure significantly
slowed down the decomposition rate, indicating a negative effect of tropospheric ozone on nutrient cycling,
which may reduce long-term sustainability of the holm oak forest
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