132,941 research outputs found
Uncertainty in the determination of soil hydraulic parameters and its influence on the performance of two hydrological models of different complexity
No full textData of soil hydraulic properties forms often a limiting factor in unsaturated zone modelling, especially at the larger scales. Investigations for the hydraulic characterization of soils are time-consuming and costly, and the accuracy of the results obtained by the different methodologies is still debated. However, we may wonder how the uncertainty in soil hydraulic parameters relates to the uncertainty of the selected modelling approach. We performed an intensive monitoring study during the cropping season of a 10 ha maize field in Northern Italy. The data were used to: i) compare different methods for determining soil hydraulic parameters and ii) evaluate the effect of the uncertainty in these parameters on different variables (i.e. evapotranspiration, average water content in the root zone, flux at the bottom boundary of the root zone) simulated by two hydrological models of different complexity: SWAP, a widely used model of soil moisture dynamics in unsaturated soils based on Richards equation, and ALHyMUS, a conceptual model of the same dynamics based on a reservoir cascade scheme. We employed five direct and indirect methods to determine soil hydraulic parameters for each horizon of the experimental profile. Two methods were based on a parameter optimization of: a) laboratory measured retention and hydraulic conductivity data and b) field measured retention and hydraulic conductivity data. The remaining three methods were based on the application of widely used Pedo-Transfer Functions: c) Rawls and Brakensiek, d) HYPRES, and e) ROSETTA. Simulations were performed using meteorological, irrigation and crop data measured at the experimental site during the period June – October 2006. Results showed a wide range of soil hydraulic parameter values generated with the different methods, especially for the saturated hydraulic conductivity <i>K</i><sub>sat</sub> and the shape parameter &alpha; of the van Genuchten curve. This is reflected in a variability of the modeling results which is, as expected, different for each model and each variable analysed. The variability of the simulated water content in the root zone and of the bottom flux for different soil hydraulic parameter sets is found to be often larger than the difference between modeling results of the two models using the same soil hydraulic parameter set. Also we found that a good agreement in simulated soil moisture patterns may occur even if evapotranspiration and percolation fluxes are significantly different. Therefore multiple output variables should be considered to test the performances of methods and models
Warum - Don Mus.Ms. 2351 : V, pf; D|b
No full textLudwig Bechstein: 1801-1860Julie von Baroni-CavalcabòText: Ludwig Bechstein. - Quelle: probably autograph. - Provenienz: Fürstlich Fürstenbergische Hofbibliothek, DonaueschingenWarum? | Gedicht von Ludwig Bechstein | In Musik gesetzt | für eine Singstimme mit Begleitung | des | Pianoforte | von | Julie Baroni- Cavalcab
The structure and phase stability of CO adsorbates on Rh(110)
No full textThe structure of CO adsorbates on the Rh(110) surface is studied at full coverage using first-principles techniques. The relative energies of different adsorbate geometries are determined by means of accurate structure optimizations. In agreement with experiments. we find that a p2mg(2 x 1)-2CO structure is the most stable. The CO molecules sit on the short-bridge site (carbon below) with the molecular asis slightly tilted off the surface normal, along the (001) direction. Configurations corresponding iv different distributions of tilt angles are mapped onto an anisotropic two-dimensional Ising model whose parameters are extracted from our ab initio calculations. We find that an order-disorder phase-transition occurs at a temperature T-c approximate to 300 K. (C) 1997 Elsevier Science B.V
Spatial distribution and ecological risk of potentially toxic elements in peri-urban soils of a historically industrialised area
No full textThe spatial distribution and ecological risk of potentially toxic elements (PTEs) were investigated in the topsoil of a peri-urban area surrounding a historical industrial complex in the Scarlino Plain in southwestern Tuscany, Italy. Superficial (0-5 cm) soil samples from 44 sites within a 1.5-km radius of the industrial district were analysed for As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Sb, Sn, Tl, V and Zn concentrations after microwave-assisted acid digestion with HNO3 and H2O2. The results revealed significant contamination exceeding regulatory thresholds, predominantly caused by historical pyrite roasting and natural geochemical anomalies. The enrichment of As, Mn, Cu and Zn compared to European baselines was widespread, with As and Zn levels exceeding the Italian screening values in several samples. Principal component analysis identified distinct contamination patterns linked to land use, with the first component (PC1, 49.2% of the variance) associated with pyrite-derived PTEs (As, Cu, Cd, Pb and Zn), whereas PC2 represented geogenic inputs. Despite their combined contribution to soil contamination, this analysis effectively differentiated industrial signatures from those of natural sources. Ecological risk assessment indicated that As and Cd are major concerns in agricultural soils, where anthropogenic and natural sources overlap. These findings underscore the importance of distinguishing between natural and anthropogenic contributions to inform realistic mitigation targets and protect environmental and human health in historically impacted peri-urban areas
Leaves and Tree Rings as Biomonitoring Archives of Atmospheric Mercury Deposition: An Ecophysiological Perspective
No full textTrees mediate critical biogeochemical cycles involving nutrients, pollutants, water, and energy at the interface between terrestrial biosphere and atmosphere. Forest ecosystems significantly influence the global cycling of mercury (Hg), serving as important sinks and potential sources of re-emission through various biotic and abiotic processes. Anthropogenic Hg emissions, predominantly from industrial activities, mining, and fossil fuel combustion, have substantially altered the natural Hg cycle, intensifying ecotoxicological concerns and establishing forests as primary routes for atmospheric Hg deposition into terrestrial reservoirs. This perturbation profoundly affects global atmospheric Hg concentrations, residence times, and spatial distribution patterns. While early investigations focused on forest stands near heavily polluted areas, contemporary research has expanded to diverse ecosystems, revealing that trees provide tissues that function as temporal archives for atmospheric-terrestrial Hg exchange. Leaves capture high-resolution records of contemporary Hg dynamics at sub-annual timescales, whereas annual growth rings preserve multi-decadal chronologies of historical atmospheric exposure. Incorporating this dual temporal perspective is crucial for analysing Hg deposition trends and assessing the efficacy of environmental policies designed to control and mitigate Hg pollution. This review critically evaluates recent developments concerning the ecophysiological determinants of Hg accumulation in trees, highlighting how combined foliar and dendrochemical analytical methods strengthen our mechanistic understanding of vegetation-atmosphere Hg exchange. To enhance biomonitoring approaches, we emphasised the need for methodological standardisation, deeper integration of ecophysiological variables, and consideration of climate change implications as priority research areas. Furthermore, integrating Hg measurements with functional markers (δ13C and δ18O) and Hg isotope analyses strengthens the capacity to differentiate between physiological and environmental influences on Hg accumulation, thereby refining the mechanistic framework underlying effective tree-based Hg biomonitoring
Identification of an intra-molecular disulfide bond in the sodium channel β1-subunit.
No full textThe sodium channel β1 subunit is non-covalently associated with the pore-forming α-subunits, and has been proposed to act as a modulator of channel activity, regulator of channel cell surface expression and cell adhesion molecule. Its importance is evident since mutations of the β1 subunit cause neurologic and cardiovascular disorders. The first described β1 subunit mutation is the C121W, that is related to generalized epilepsy with febrile seizures plus (GEFS+), a childhood genetic epilepsy syndrome. This mutation changed a conserved cysteine residue in position 121 into a tryptophan, putatively disrupting a disulfide bridge that should normally maintain the β1 extracellular immunoglobulin-like fold. Using the 2-D-diagonal-SDS-PAGE technique, we demonstrated the existence of this putative disulfide bridge in the Ig-like extracellular domain of the β1 subunit and its disruption in the epileptogenic C121W mutant
Independent association of hypovitaminosis d with non-alcoholic fatty liver disease in people with chronic spinal cord injury: a cross-sectional study
No full textPurposeNon-alcoholic fatty liver disease (NAFLD) and hypovitaminosis D are highly prevalent in people with spinal cord injury (SCI) and could exert an unfavorable influence on cardiovascular profile and rehabilitation outcomes. We aimed to assess the independent association between low 25-hydroxy vitamin D (25(OH)D) levels and NAFLD in people with chronic (> 1 year) SCI.MethodsOne hundred seventy-three consecutive patients with chronic SCI (132 men and 41 women) admitted to a rehabilitation program underwent clinical/biochemical evaluations and liver ultrasonography.ResultsNAFLD was found in 105 patients (60.7% of the study population). They were significantly older and exhibited a poorer leisure time physical activity (LTPA) and functional independence in activities of daily living, a greater number of comorbidities and a higher prevalence of metabolic syndrome (MetS) and its correlates, including lower HDL and higher values of body mass index (BMI), systolic blood pressure, HOMA-index of insulin resistance and triglycerides. 25(OH)D levels were significantly lower in NAFLD (median: 10.6 ng/ml, range: 2.0-31.0) than in non-NAFLD group (22.5 ng/ml, 4.2-51.6). When all these variables were included in a multiple logistic regression analysis, a significant independent association with NAFLD only persisted for lower 25(OH)D levels, a greater number of comorbidities and a poorer LTPA. The ROC analysis revealed that 25(OH)D levels < 18.25 ng/ml discriminated patients with NAFLD with a sensitivity of 89.0% and a specificity of 73.0% (AUC: 85.7%; 95%CI: 79.6-91.7%). NAFLD was exhibited by 83.9% of patients with 25(OH)D levels < 18.25 ng/ml and by 18% of those with 25(OH)D levels >= 18.25 ng/ml (p < 0.0001).ConclusionIn people with chronic SCI, 25(OH)D levels < 18.25 ng/ml may represent a marker of NAFLD independent of MetS-related features. Further studies are warranted to define the cause-effect relationships of this association
Intrigue artificielle, intrigue naturelle et schèmes cognitifs. Entretien avec Raphaël Baroni
No full textParmi les nombreux sujets du débat contemporain à propos de la théorie narrative et de la narratologie, deux paradigmes fondamentaux ont récemment été mis en évidence : le paradigme mimétique ou référentiel, et le paradigme anti-mimétique ou constructiviste. Les différences et les tensions apparues entre les deux portent encore une fois sur la conception du récit et de ses éléments : comment fait-on pour théoriser les relations entre fabula et sujet ? Quel rapport y a-t-il entre les éléments de la séquence, les effets de la narration et nos capacités cognitives ? Pour éclaircir ces problèmes, Raphaël Baroni répond à certaines questions fondamentales de la théorie narrative. L’auteur de La tension narrative et de L’œuvre du temps, discerne tout d’abord le plan sur lequel reposent les difficultés, à savoir la définition de « séquence » ou d’« intrigue ». Il esquisse, ensuite, une perspective théorique apte à surmonter de tels obstacles. En examinant les relations entre discordance narrative et virtualité du récit, il est finalement amené à concevoir le récit non seulement comme un acte interactif, mais aussi comme une forme de perturbation des normes ordinaires de la communication
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