Algunos ejemplos de relación entre agregación, capacidad de infiltración y erosión en suelos mediterráneos

[Resumen] Este trabajo tiene por objeto evaluar la influencia de la agregación sobre la capacidad de infiltración y la tendencia a la erosión de suelos mediterráneos sobre litología caliza. Se identifican algunas variables de agregación que influyen de una manera importante en la infiltración y la erosión, aunque es en combinación con otras características del suelo cuando estas variables explican mejor dichos parámetros. Se consiguen una serie de modelos de ecuaciones de regresión múltiple basadas en variables indicadoras de la agregación de los suelos y otras características (cobertura vegetal, materia orgánica, pedregosidad y humedad del suelo) que explican bastante bien la capacidad de infiltración, la concentración de sedimentos y la erosión de los suelos en las zonas de estudio.[Abstract] The objective of this work is to evaluate the influence of soil aggregation on soil infiltration capacity and erosion in mediterranean soils developed on limestones. Sorne key-variables related to soil aggregation which play an important role on soil infiltration capacity and erosion are identified. Especially the combination of these variables with other soil characterisitics give the most satisfactory results explaining soil infiltration and erosiono Sorne models of multiple regression equations based in variables related to aggregation and other soil characteristics (vegetation cover, organic matter, stoniness and soil moisture) are obtained. They explain quite well the infiltration capacity, the sediment concentration and the erosion in the study zones

Influencia de la estructura y usos del suelo en las características de retención hídrica de suelos mediterráneos sobre litología caliza

[Resumen] Se investigan las diferencias entre la capacidad de retención hídrica de suelos mediterráneos sobre litología caliza sometidos a diferentes usos: incendiados y bajo pastoreo intensivo. En estos mismos suelos se valoran las relaciones entre estructura del suelo y capacidad de retención hídrica a diversos puntos de la curva de retención. Agregados de pequeño tamaño y materia orgánica influyen positivamente y de manera considerable en la capacidad de retención en casi todos los puntos de la curva de retención determinados. Agregados de gran tamaño y microagregados estables en agua influyen negativamente. La combinación de agregados de tamaño 1-0,105 mm y el contenido en materia orgánica predicen bastante bien la capacidad de retención a niveles bajos de succión (pF 0,4 YpF 1).[Abstract] The differences between the water holding capacity of Mediterranean soils developed on limestones and under different land uses (burnt and overgrazed soils) are investigated. The relationships between soil structure and soil moisture characteristic at different levels of the water retention curve in these same soils are evaluated. Organic matter and small sized aggregates are positively related to the water holding capacity. Large sized aggregates and waterstable microaggregates are negatively related to the water holding capacity of the soils. The combination of aggregates at 1-0,105 mm and organic matter content predict quite well the water retention capacity at lower suction levels (pF 0,4 and pF 1)

Robustness of a model predicting drop-testing performance of fruit packs

In an earlier investigation a numerical model was defined which summarized the effects on apple packs of multiple drops from different heights. The results suggested that a given package-type could be associated with a "package constant", k, characteristic of the package and independent of the drop height and the number of drops. The effect on k of change in experimental conditions and material is investigated; it is shown that the model is remarkably robust under such changes, and is equally applicable to pears. The results suggest, however, that k may be affected by flesh firmness and state of maturity of the fruit, and this possibility requires further specific investigation. Two methods of calculating k are described and compared, and restrictions on the calculations noted; the methods are shown to be in good agreement

Two decades of numerical modelling to understand long term fluvial archives: Advances and future perspectives

The development and application of numerical models to investigate fluvial sedimentary archives has increased during the last decades resulting in a sustained growth in the number of scientific publications with keywords, 'fluvial models', 'fluvial process models' and 'fluvial numerical models'. In this context we compile and review the current contributions of numerical modelling to the understanding of fluvial archives. In particular, recent advances, current limitations, previous unexpected results and future perspectives are all discussed. Numerical modelling efforts have demonstrated that fluvial systems can display non-linear behaviour with often unexpected dynamics causing significant delay, amplification, attenuation or blurring of externally controlled signals in their simulated record. Numerical simulations have also demonstrated that fluvial records can be generated by intrinsic dynamics without any change in external controls. Many other model applications demonstrate that fluvial archives, specifically of large fluvial systems, can be convincingly simulated as a function of the interplay of (palaeo) landscape properties and extrinsic climate, base level and crustal controls. All discussed models can, after some calibration, produce believable matches with real world systems suggesting that equifinality - where a given end state can be reached through many different pathways starting from different initial conditions and physical assumptions - plays an important role in fluvial records and their modelling. The overall future challenge lies in the development of new methodologies for a more independent validation of system dynamics and research strategies that allow the separation of intrinsic and extrinsic record signals using combined fieldwork and modelling

Height and timing of growth spurt during puberty in young people living with vertically acquired HIV in Europe and Thailand.

OBJECTIVE: The aim of this study was to describe growth during puberty in young people with vertically acquired HIV. DESIGN: Pooled data from 12 paediatric HIV cohorts in Europe and Thailand. METHODS: One thousand and ninety-four children initiating a nonnucleoside reverse transcriptase inhibitor or boosted protease inhibitor based regimen aged 1-10 years were included. Super Imposition by Translation And Rotation (SITAR) models described growth from age 8 years using three parameters (average height, timing and shape of the growth spurt), dependent on age and height-for-age z-score (HAZ) (WHO references) at antiretroviral therapy (ART) initiation. Multivariate regression explored characteristics associated with these three parameters. RESULTS: At ART initiation, median age and HAZ was 6.4 [interquartile range (IQR): 2.8, 9.0] years and -1.2 (IQR: -2.3 to -0.2), respectively. Median follow-up was 9.1 (IQR: 6.9, 11.4) years. In girls, older age and lower HAZ at ART initiation were independently associated with a growth spurt which occurred 0.41 (95% confidence interval 0.20-0.62) years later in children starting ART age 6 to 10 years compared with 1 to 2 years and 1.50 (1.21-1.78) years later in those starting with HAZ less than -3 compared with HAZ at least -1. Later growth spurts in girls resulted in continued height growth into later adolescence. In boys starting ART with HAZ less than -1, growth spurts were later in children starting ART in the oldest age group, but for HAZ at least -1, there was no association with age. Girls and boys who initiated ART with HAZ at least -1 maintained a similar height to the WHO reference mean. CONCLUSION: Stunting at ART initiation was associated with later growth spurts in girls. Children with HAZ at least -1 at ART initiation grew in height at the level expected in HIV negative children of a comparable age

Platelets of patients with chronic kidney disease demonstrate deficient platelet reactivity in vitro

<p>Abstract</p> <p>Background</p> <p>In patients with chronic kidney disease studies focusing on platelet function and properties often are non-conclusive whereas only few studies use functional platelet tests. In this study we evaluated a recently developed functional flow cytometry based assay for the analysis of platelet function in chronic kidney disease.</p> <p>Methods</p> <p>Platelet reactivity was measured using flow cytometric analysis. Platelets in whole blood were triggered with different concentrations of agonists (TRAP, ADP, CRP). Platelet activation was quantified with staining for P-selectin, measuring the mean fluorescence intensity. Area under the curve and the concentration of half-maximal response were determined.</p> <p>Results</p> <p>We studied 23 patients with chronic kidney disease (9 patients with cardiorenal failure and 14 patients with end stage renal disease) and 19 healthy controls. Expression of P-selectin on the platelet surface measured as mean fluorescence intensity was significantly less in chronic kidney disease patients compared to controls after maximal stimulation with TRAP (9.7 (7.9-10.8) vs. 11.4 (9.2-12.2), P = 0.032), ADP (1.6 (1.2-2.1) vs. 2.6 (1.9-3.5), P = 0.002) and CRP (9.2 (8.5-10.8) vs. 11.5 (9.5-12.9), P = 0.004). Also the area under the curve was significantly different. There was no significant difference in half-maximal response between both groups.</p> <p>Conclusion</p> <p>In this study we found that patients with chronic kidney disease show reduced platelet reactivity in response of ADP, TRAP and CRP compared to controls. These results contribute to our understanding of the aberrant platelet function observed in patients with chronic kidney disease and emphasize the significance of using functional whole blood platelet activation assays.</p

Timing of gully development in a structurally controlled badland landscape, western Turkey

The development of badlands at a global scale has become an increasingly relevant research topic in various earth science disciplines with respect to climate change and extensive erosion over the past few decades. Not only understanding badland forming processes but also investigating the potential causes and timing of badlands at a spatio-temporal scale is of great importance to unravel the genesis of badlands. To address these key aspects, this work focuses on a multi-method study in a Mediterranean badland landscape, Kula Badlands, western Turkey, exposed in two tributary catchments of the Gediz river. The Kula Badlands is recognised with its dense gully network deeply incised into fine grain and weakly consolidated Miocene and Quaternary sediments. These badlands are known to have developed within the extensional tectonic regime of a mini-graben system. However, the genesis, timing and incision history of the gully and badland development of the Kula Badlands require further investigation. In this work, timing and behaviour of gully erosion and sedimentation are studied with age control using appropriate luminescence and radiocarbon dating methods combined with geological and geomorphological observations. Sedimentation pattern and age results demonstrate a staircase-like form resembling river terraces in badland gullies. Sediment burial ages of badland deposits show an estimated age range of 140 ka to 0.5 ka. An accelerated incision is observed during the mid-Holocene with alternating erosion and sedimentation waves in response to upstream erosion. This period coincides with increased human activity in the area. Although, an apparent link between the timing of the preserved deposition and climate change could not be observed. A volcanic damming and subsequent breaching, and an interplay between tectonics and climate are likely to have triggered and accelerated the badland erosion and sedimentation activity within the spatial gully network pattern along the fault lines

Evaluating the strength of evidence of elemental profiling of polymers with LA-ICP-MS

LA-ICP-MS is a powerful technique for obtaining a forensic elemental profile of polymer evidence materials. However, the lack of homogeneous polymer reference standards hampers database creation and reliably matching a sample to a specific source. Therefore, the current study aims to evaluate the strength of evidence of forensic polymer comparisons by applying a matrix-matched reference standard with known concentrations for elements of interest. Four datasets of tapes, electrical wires, tubing, and jerrycans were compiled using LA-ICP-MS. It was found that quantification with the new PVC standard or by simply using the response of one element as internal standard significantly reduced the between-run variation. For each class of polymeric materials, characteristic elements could be identified with PCA and LDA. To facilitate classification, elemental concentrations were found to be typical for specific colors and types of polymeric materials. For forensic comparison, a score-based Bayesian likelihood ratio model and the t-test overlap method performed better than the feature-based model and 4-sigma criterion, in terms of rates of misleading evidence. Normalization to 13C and quantification with the PVC standard with and without prior normalization to 13C slightly reduced rates of misleading evidence. The t-test method showed an overall average false inclusion rate of only 0.45% and a false exclusion rate of 2.4%. Maximum calibrated likelihood ratios of 0.014 to 1778 were found for the tape dataset. In conclusion, this study demonstrates that with the use of proper standards, quantitative elemental profiling with LA-ICP-MS is a promising tool for forensic classification and comparison of polymers