Search results for "670"

Modelling nitrous oxide emissions from cropland at the regional scale

2006

Arable soils are a large source of nitrous oxide (N2O) emissions, making up half of the biogenic emissions worldwide. Estimating their source strength requires methods capable of capturing the spatial and temporal variability of N2O emissions, along with the effects of crop management. Here, we applied a process-based model, CERES, with geo-referenced input data on soils, weather, and land use to map N2O emissions from wheat-cropped soils in three agriculturally intensive regions in France. Emissions were mostly controlled by soil type and local climate conditions, and only to a minor extent by the doses of fertilizer nitrogen applied. As a result, the direct emission factors calculated at …

Social process of adaptation to environmental changes: How eastern african societies intervene between crops and climate

2014

Abstract Studies on climate change can only be conducted on a long time scale, and observing how societies adapt their sowing practices to climate variability is challenging and costly. As an alternative, a space and time substitution design was used, changes in space corresponding to that induced in time by environmental change. On the eastern slope of Mount Kenya, the Tharaka community, originating from the lowlands (750 m), moved up to the midlands (950 m) with their lowland-adapted resources, whereas the Mwimbi, originating from wetter upland (1100 m), moved down to the midlands with their highland-adapted genetic resources. A weather station was installed at 950 and 1100 m, and a logis…

A preliminary approach for modelling the effects of cropping systems on the dynamics of broomrape ( Phelipanche ramosa) in interaction with the non-p…

2011

International audience; The current decrease in herbicide use may increase and diversify weed flora in crops as well as companion bioagressors spreading via weeds. Among these bioagressors is Phelipanche ramosa (L.) Pomel, a parastic plant which is very harmful on oilseed rape. The objective of the present work was to develop a new model (called PheraSys) of the effects of cropping systems on parasite dynamics, in interaction with non-parasitic weed hosts. The structure of this first model version was based on models developed for other parasitic plants and on FlorSys which quantifies the effects of cropping systems on non-parasitic weed flora. PheraSys was parametrized with preliminary val…

Using the GENESYS model quantifying the effect of cropping systems on gene escape from GM rape varieties to evaluate and design cropping systems.

2004

Gene flow in rapeseed is a process taking place both in space and over the years and cannot be studied exclusively by field trials. Consequently, the GENESYS model was developed to quantify the effects of cropping systems on transgene escape from rapeseed crops to rapeseed volunteers in neighbour plots and in the subsequent crops. In the present work, this model was used to evaluate the risk of rape harvest contamination by extraneous genes in various farming systems in case of co-existing GM, conventional and organic crops. When 50 % of the rape varieties in the region were transgenic, the rate of GM seeds in non-GM crop harvests on farms with large fields was lower than the 0.9 % purity t…

Assessing the indirect and long-term ecological impacts of innovation in agriculture is a real challenge: the GM example

2003

All innovation in agriculture constitutes a significant and complex ecological disturbance, even if limited to a single and simple action. Indeed, whatever the nature and objective of the action, a large number of ecological processes are affected and numerous discontinuities may occur within the agro-ecosystem, in both time and space. As the GMO example illustrates, it is not sufficient to focus on direct effect of innovation, it is necessary to forecast mid- and long-term impacts of innovation with respect to the environment. Modelling phenomena appear then to be a key element to achieve this goal.

Intestinal microbiota mediates the beneficial effects of n-3 polyunsaturated fatty acids during dietary obesity,

2021

Obesity, now considered as a real worldwide epidemic affecting more than 650 million people, is complex and mainly associated with excessive energy intake and changes in eating habits favoring the consumption of diets rich in saturated fat and sugar. This multifactorial pathology is linked to chronic low grade systemic inflammation. Indeed, a high fat diet (HFD) leads to intestinal microbiota dysbiosis increasing gut permeability (partly attributed to a downregulation of genes encoding tight junction proteins) leading to an increase in bacterial lipopolysaccharides (LPS) levels so-called metabolic endotoxemia. Studies have shown that n-3 polyunsaturated fatty acids (PUFAs) are involved in t…

« Nez et langues électroniques » : bilan et perspectives pour les huiles alimentaires

2003

Le « Nez electronique », et plus recemment la « Langue electronique » ont ete fort mediatises durant la derniere decennie. Aussi est-il necessaire, avec le recul, de faire le point sur les benefices que ces technologies peuvent apporter dans le domaine des produits alimentaires, et en particulier pour huiles vegetales. On trouve une litterature relativement abondante dans ce domaine, mais les applications qui ont reussi a franchir le cap de l’utilisation industrielle sont extremement restreintes. S’agit-il d’une frilosite des industriels pour des investissements de controle-qualite ou d’un manque de fiabilite des resultats de laboratoire ? Pourtant, la demande en outils rapides de controle-…

The implication of omega-3 polyunsaturated fatty acids in retinal physiology

2007

International audience; Neuronal tissues such as the retina and the brain are characterized by their high content in phospholipids. In the retina, phospholipids can account for until 80% of total lipids and are mainly composed by species belonging to phosphatidyl-choline and phosphatidyl-ethanolamine sub-classes. Within fatty acids esterified on retinal phospholipids, omega-3 PUFAs are major components since docosahexaenoic acid (DHA) can represent until 50% of total fatty acids in the photoreceptor outer segments.For long time, DHA is known to play a major role in membrane function and subsequently in visual processes by affecting permeability, fluidity, thickness and the activation of mem…

Vēsture: Latvijas Universitātes Žurnāls, Nr.11/12

2021

Señor. El Real Convento de San Miguèl de los Reyes del Orden de San Geronimo ... dize: que aviendo sido servido vuestra Magestad de hazer merced al…

1717

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