Análisis de la diversidad de los sistemas de producción agrícolas: un caso de estudio en el suroeste de Francia

The huge changes in agricultural activities, which may be amplified by the forthcoming Common Agriculture Policy reform, call the future of crop-livestock systems into question and hence the impact of these changes on landscapes and biodiversity. We analyzed relationships between agriculture, landscape and biodiversity in south-western France. The study area covered about 4000 ha and included four villages. We conducted a survey of 56 farms. Multivariate analysis (multiple factor analysis and cluster analysis) were used to analyze relationships between 25 variables and to build a typology. The type of farming (beef and/or dairy cattle, cash crops), size (area and workforce) and cultivation practices, among others, were revealed as differentiating factors of farms. Six farming types were identified (1) hillside mixed crop-livestock farms, (2) large ‘corporate’ farms, (3) extensive cattle farms, (4) large intensive farms on the valley sides, (5) small multiple-job holdings, and (6) ‘hobby’ farms. The diversity of farming systems revealed the variable impact of the main drivers of change affecting agricultural development, particularly the enlargement and modernization of farms along with the demography of agricultural holdings.Los enormes cambios experimentados en las actividades agrícolas en Europa, que podrían ser amplificados por la próxima reforma de la política agrícola común de Europa, cuestionan el futuro de los sistemas agropecuarios y, por tanto, el impacto de estos cambios en el paisaje y en la biodiversidad. Para ello, se estudiaron las relaciones entre la agricultura, el paisaje y la biodiversidad en el suroeste de Francia (Cerros de Gascuña). El área de estudio cubre aproximadamente 4000 ha e incluye cuatro municipios. Los datos relacionados con las actividades agrícolas provienen de encuestas realizadas en 56 explotaciones. Para estudiar las relaciones entre 25 variables, se utilizaron análisis multivariados (análisis factorial múltiple y análisis de conglomerados) y se elaboró una tipología. Los factores de diferenciación identificados, entre otros, son: el tipo de producción (ganado de carne y/o lechero, cultivos herbáceos), tamaño (superficie y mano de obra) y prácticas de cultivo. Se distinguieron seis tipos de explotaciones: (1) explotaciones de ladera que combinan agricultura y ganadería, (2) grandes explotaciones corporativas, (3) explotaciones ganaderas extensivas, (4) grandes explotaciones intensivas en valles, (5) pequeñas fincas explotadas a tiempo parcial, y (6) explotaciones para ocio. La diversidad de los sistemas de producción reveló el impacto variable de las principales fuerzas de cambio que afectan al desarrollo de la agricultura, en particular a la ampliación y modernización de las explotaciones, junto con la demografía de la población agrícola

Laser and electron deflection from transverse asymmetries in laser-plasma accelerators.

We report on the deflection of laser pulses and accelerated electrons in a laser-plasma accelerator (LPA) by the effects of laser pulse front tilt and transverse density gradients. Asymmetry in the plasma index of refraction leads to laser steering, which can be due to a density gradient or spatiotemporal coupling of the laser pulse. The transverse forces from the skewed plasma wave can also lead to electron deflection relative to the laser. Quantitative models are proposed for both the laser and electron steering, which are confirmed by particle-in-cell simulations. Experiments with the BELLA Petawatt Laser are presented which show controllable 0.1-1 mrad laser and electron beam deflection from laser pulse front tilt. This has potential applications for electron beam pointing control, which is of paramount importance for LPA applications

fMRI visualization of transient activations in the rat olfactory bulb using short odor stimulations

International audienceOdor-evoked activity in the olfactory bulb displays both spatial and temporal organization. The difficulty when assessing spatio-temporal dynamics of olfactory representation is to find a method that reconciles the appropriate resolution for both dimensions. Imaging methods based on optical recordings can reach high temporal and spatial resolution but are limited to the observation of the accessible dorsal surface. Functional magnetic resonance imaging (fMRI) may be useful to overcome this limitation as it allows recording from the whole brain. In this study, we combined ultra fast imaging sequence and short stimulus duration to improve temporal resolution of odor-evoked BOLD responses. Short odor stimulations evoked high amplitude BOLD responses and patterns of activation were similar to those obtained in previous studies using longer stimulations. Moreover, short odor exposures prevented habituation processes. Analysis of the BOLD signal time course in the different areas of activation revealed that odorant response maps are not static entities but rather are temporally dynamic as reported by recent studies using optical imaging. These data demonstrated that fMRI is a non-invasive method which could represent a powerful tool to study not only the spatial dimension of odor representation but also the temporal dimension of information processing

Emittance preservation in a plasma-wakefield accelerator

Radio-frequency particle accelerators are engines of discovery, powering high-energy physics and photon science, but are also large and expensive due to their limited accelerating fields. Plasma-wakefield accelerators (PWFAs) provide orders-of-magnitude stronger fields in the charge-density wave behind a particle bunch travelling in a plasma, promising particle accelerators of greatly reduced size and cost. However, PWFAs can easily degrade the beam quality of the bunches they accelerate. Emittance, which determines how tightly beams can be focused, is a critical beam quality in for instance colliders and free-electron lasers, but is particularly prone to degradation. We demonstrate, for the first time, emittance preservation in a high-gradient and high-efficiency PWFA while simultaneously preserving charge and energy spread. This establishes that PWFAs can accelerate without degradation—an essential step toward energy boosters in photon science and multistage facilities for compact high-energy particle colliders

Reshaping of Bulbar Odor Response by Nasal Flow Rate in the Rat

The impact of respiratory dynamics on odor response has been poorly studied at the olfactory bulb level. However, it has been shown that sniffing in the behaving rodent is highly dynamic and varies both in frequency and flow rate. Bulbar odor response could vary with these sniffing parameter variations. Consequently, it is necessary to understand how nasal airflow can modify and shape odor response at the olfactory bulb level.To assess this question, we used a double cannulation and simulated nasal airflow protocol on anesthetized rats to uncouple nasal airflow from animal respiration. Both mitral/tufted cell extracellular unit activity and local field potentials (LFPs) were recorded. We found that airflow changes in the normal range were sufficient to substantially reorganize the response of the olfactory bulb. In particular, cellular odor-evoked activities, LFP oscillations and spike phase-locking to LFPs were strongly modified by nasal flow rate.Our results indicate the importance of reconsidering the notion of odor coding as odor response at the bulbar level is ceaselessly modified by respiratory dynamics

Semantic Knowledge Influences Prewired Hedonic Responses to Odors

Background Odor hedonic perception relies on decoding the physicochemical properties of odorant molecules and can be influenced in humans by semantic knowledge. The effect of semantic knowledge on such prewired hedonic processing over the life span has remained unclear. Methodology/Principal Findings The present study measured hedonic response to odors in different age groups (children, teenagers, young adults, and seniors) and found that children and seniors, two age groups characterized by either low level of (children) or weak access to (seniors) odor semantic knowledge, processed odor hedonics more on the basis of their physicochemical properties. In contrast, in teenagers and young adults, who show better levels of semantic odor representation, the role of physicochemical properties was less marked. Conclusions/Significance These findings demonstrate for the first time that the biological determinants that make an odor pleasant or unpleasant are more powerful at either end of the life span

Researchers in ecology and spatial planners confronted with landscape changes

Landscapes change continuously as a result of natural dynamics and human activity. These changes are intensified by global change i.e. a combination of the alteration in land use and climate change. Researchers in ecology and planners are encouraged to broaden their approaches to the various spatial scales so as to understand altered ecological processes, make provision for climate change and develop a concerted planning approach between the various players. Greater demands are being made on the farming and forestry sectors to increase their carbon sequestration function and the substitution of fossil energy by renewable carbon. These potential strategies however need to be evaluated in economic, ecological and social terms so as to provide solutions that are suited to spatial variability. Scientists and planners must compare their approaches and pool their efforts in pursuit of balanced development and shared land use that converge towards sustainable landscape management.Le paysage évolue en permanence au gré des dynamiques naturelles et des activités humaines. Cette évolution s’est accentuée avec le changement global, combinaison de la modification de l’occupation des terres et du changement climatique. Chercheurs en écologie et gestionnaires sont conduits à étendre leurs approches à l’échelle des territoires pour comprendre l’évolution des processus écologiques, organiser l’adaptation aux changements climatiques et développer une gestion concertée entre acteurs. Les secteurs agricoles et forestiers sont largement sollicités pour accroître la séquestration du carbone et la substitution de carbone renouvelable aux énergies fossiles, mais les stratégies possibles doivent être évaluées aux niveaux économique, écologique et social pour déboucher sur des solutions adaptées à la diversité des territoires. Scientifiques et gestionnaires doivent confronter leurs approches et mettre en commun leurs efforts pour permettre un développement équilibré et un usage partagé des territoires et pour tendre vers une gestion durable des paysages

Une méthode d'identification inverse à partir d'essais dynamiques comprenant des mesures incertaines

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