Search results for "Water content"
showing 10 items of 380 documents
Visualizing pectin polymer-polymer entanglement produced by interfacial water movement.
2020
In this report, we investigated the physical conditions for creating pectin polymer-polymer (homopolymer) entanglement. The potential role of water movement in creating pectin entanglement was investigated by placing water droplets-equivalent to the water content of two gel phase films-between two glass phase films and compressing the films at variable probe velocities. Slow probe velocity (0.5 mm/sec) demonstrated no significant debonding. Corresponding videomicroscopy demonstrated an occasional water bridge, but no evidence of stranding or polymer entanglement. In contrast, fast probe velocity (5 mm/sec) resulted in 1) an increase in peak adhesion strength, 2) a progressive debonding curv…
Olive yield as a function of soil moisture dynamics
2011
This study introduces a water-driven crop model aiming to quantitatively link olive yield to climate and soil moisture dynamics using an ecohydrological approach. A mathematical model describing soil moisture, evapotranspiration and assimilation dynamics of olive orchards is developed here. The model is able to explicitly reproduce two different hydroclimatic phases in Mediterranean areas: the well-watered conditions in which evapotranspiration and assimilation assume their maximum values and the real conditions where the limitations induced by soil moisture availability are taken into account. Annual olive yield is obtained by integrating the carbon assimilation during the growing season, …
SMAP Multi-Temporal vegetation optical depth retrieval as an indicator of crop yield trends and crop composition
2017
Vegetation Optical Depth (VOD) is related to Vegetation Water Content (VWC). This provides new and highly valuable information for ecological and agricultural studies. In this work, VOD from the Soil Moisture Active-Passive (SMAP) satellite has been retrieved with the new Multi-Temporal Dual-Channel Algorithm (MT-DCA). Then, it has been applied to the study of crop yield trends and crop composition. The increase on VOD (¿VOD) during crop development has been compared to yield data in two selected regions located in the United States. The first region presents a heterogeneous crop composition and weak ¿VOD-yield relationship (r2=0.21). The second region presents a highly homogenous cover and…
The relationship between the Sahelian and previous 2nd Guinean rainy seasons: a monsoon regulation by soil wetness?
2002
The correlation of 0.61 found between observed July–September Sahelian rainfall in year 0 and September–November Guinean rainfall in year - 1, led us to explore the statistical relationships between precipitation, soil moisture and near surface Moist Static Energy (MSE) gradients in West Africa. These analyses were performed over successive 30-year periods and specifically, the most recent period between 1968–1998. It is shown from observations, National Centers for Environmental Predictions and National Center for Atmospheric Research (NCEP/NCAR) reanalyses and from the Global Soil Wetness Project (GSWP) database, that wet Sahelian rainy seasons are preceded by abnormally wet soils over th…
A HS-SPME-GC-MS analysis of IR heated wood: Impact of the water content on the depth profile of oak wood aromas extractability
2013
http://www.sciencedirect.com/science/article/pii/S0963996913003736; International audience; Controlled and reproducible IR heat treatments were applied to oak wood surfaces in order to establish a depth-profiled picture of the extractability of volatile compounds, with particular emphasis on the impact of the initial water content. Headspace-solid phase microextraction-gas chromatography coupled to mass spectrometry (HS-SPME-GC-MS) has been used to compare the concentrations of six aroma compounds (vanillin, furfural, eugenol; guaiacol and cis- and trans-whisky lactones) in hydroalcoholic extracts of series of slices representative of the first 8 mm of the wood facing the IR source. Results…
Dry vs soaked wood: Modulating the volatile extractible fraction of oak wood by heat treatments
2012
The aim of this study was to analyze the impact of the water content of wood on the concentrations of volatile compounds which can be extracted after heat treatments. Head Space-Solid Phase Micro Extraction Gas Chromatography coupled to Mass Spectrometry (HS-SPME GC-MS) has been used to compare the concentrations of six aroma compounds (vanillin, furfural, eugenol, guaiacol and cis- and trans-whisky lactones) in hydroalcoholic extracts of heated oak wood samples either previously soaked in hot water or not. Except for eugenol, concentrations of extracted aromas appeared to be lower in soaked woods than in dry woods for temperatures up to 200 °C. If a delaying effect of water could explain s…
A method for the preparation of repacked soil cores with homogeneous aggregates for studying microbial nitrogen transformations under highly controll…
1998
International audience; he feasibility of studies on nitrate transformations during incubation in controlled conditions of air-filled porosity using a method of soil core preparation was investigated. Repacked cores were obtained by uniaxial confined compression in a cylindrical mould of a mass of calibrated and conveniently wet aggregates with a water content selected to saturate the textural porosity of the soil aggregates, imposing structural porosity and thereby producing controlled conditions of aeration. The principle and the descrip- tion of the incubation method are explained and some denitrification and respiration data obtained with low and increasing OZ partial pressures are pres…
Évolution du bilan hydrique à l'échelle de bassins versants en contexte de changement climatique – mise place d’une méthodologie
2014
Assessment of hydric balance at the catchment scale, under climate change scenario Face to climate change, public policies must implement adaptation strategies. This implies that the effects of climate change are plainly identified on territories. However, in the current state, data and knowledge at the local level are limited or not available to decision makers. This work proposes to well characterize the local impacts of climate change and to develop synergies between researchers and territorial actors to prepare the public decision.
Ultrathin Tropical Tropopause Clouds (UTTCs): II. Stabilization mechanisms
2003
Abstract. Mechanisms by which subvisible cirrus clouds (SVCs) might contribute to dehydration close to the tropical tropopause are not well understood. Recently Ultrathin Tropical Tropopause Clouds (UTTCs) with optical depths around 10-4 have been detected in the western Indian ocean. These clouds cover thousands of square kilometers as 200-300 m thick distinct and homogeneous layer just below the tropical tropopause. In their condensed phase UTTCs contain only 1-5% of the total water, and essentially no nitric acid. A new cloud stabilization mechanism is required to explain this small fraction of the condensed water content in the clouds and their small vertical thickness. This work sugges…
A priori parameterisation of the CERES soil-crop models and tests against several European data sets
2002
Mechanistic soil-crop models have become indispensable tools to investigate the effect of management practices on the productivity or environmental impacts of arable crops. Ideally these models may claim to be universally applicable because they simulate the major processes governing the fate of inputs such as fertiliser nitrogen or pesticides. However, because they deal with complex systems and uncertain phenomena, site-specific calibration is usually a prerequisite to ensure their predictions are realistic. This statement implies that some experimental knowledge on the system to be simulated should be available prior to any modelling attempt, and raises a tremendous limitation to practica…