Rapport scientifique de l'expédition belge à la Grande Barrière d'Australie en 1967. Sédimentologie 1: noircissement par pyritisation des tests de grands foraminifères benthiques actuels

This work tends to approach and define the earliest phases of fossilisation by pyritisation of the tests of two large benthic foraminifera coming from the south end of the Great Barrier Reef Australia

Polycyclic aromatic hydrocarbons (PAHs) in the atmospheres of two French alpine valleys: sources and temporal patterns

International audienceAlpine valleys represent some of the most important crossroads for international heavy-duty traffic in Europe, but the full impact of this traffic on air quality is not known due to a lack of data concerning these complex systems. As part of the program "Pollution des Vallées Alpines" (POVA), we performed two sampling surveys of polycyclic aromatic hydrocarbons (PAHs) in two sensitive valleys: the Chamonix and Maurienne Valleys, between France and Italy. Sampling campaigns were performed during the summer of 2000 and the winter of 2001, with both periods taking place during the closure of the "Tunnel du Mont-Blanc". The first objective of this paper is to describe the relations between PAH concentrations, external parameters (sampling site localization, meteorological parameters, sources), and aerosol characteristics, including its carbonaceous fraction (OC and EC). The second objective is to study the capacity of PAH profiles to accurately distinguish the different emission sources. Temporal evolution of the relative concentration of an individual PAH (CHR) and the PAH groups BghiP+COR and BbF+BkF is studied in order to differentiate wood combustion, gasoline, and diesel emissions, respectively. The results show that the total particulate PAH concentrations were higher in the Chamonix valley during both seasons, despite the cessation of international traffic. Seasonal cycles, with higher concentrations in winter, are also stronger in this valley. During winter, particulate PAH concentration can reach very high levels (up to 155 ng.m-3) in this valley during cold anticyclonic periods. The examination of sources shows the impact during summer of heavy-duty traffic in the Maurienne valley and of gasoline vehicles in the Chamonix valley. During winter, Chamonix is characterized by the strong influence of wood combustion in residential fireplaces, even if the temporal evolution of specific PAH ratios are difficult to interpret. Information on sources given by PAH profiles can only be considered in qualitative terms

A combination of particle filtering and deterministic approaches for multiple kernel tracking.

International audienceColor-based tracking methods have proved to be efficient for their robustness qualities. The drawback of such global representation of an object is the lack of information on its spatial configuration, making difficult the tracking of more complex motions. This issue is overcome by using several kernels weighting pixels locations. In this paper a multiple kernels configuration is proposed and developed in both probabilistic and deterministic frameworks. The advantages of both approaches are combined to design a robust tracker allowing to track location, size and orientation of the object. A visual servoing application in tracking a moving object validates the proposed approach

Flexible quota constraints in positive mathematical programming models

To explain over- and underuse of available quota, Buysse et al. (2007) have integrated the shadow cost of the quota constraint in a quota flexibility function in a positive mathematical programming model. This method and central hypothesis, formulated and tested for the case of Belgian sugar beet farms, is in current paper extended and confirmed for the cases of Flemish dairy quota and manure emission rights. Despite the different organisation, objectives and implementations of the diverse quota systems, the results are similar. A higher utilisation of quota is significantly driven by the quota rent, but farm characteristics are also important and the effect declines with increasing quota rent. Regardless the quota, the dairy quota flexibility behaviour of the sample of Flemish farms results in an output price elasticity of 0.6%. The quota flexibility functions can be used for policy analysis, model sophistication and farm advisory instrument.Quota, flexibility, Positive Mathematical Programming, farm model, Common Agricultural Policy, Agricultural and Food Policy, Demand and Price Analysis, Research Methods/ Statistical Methods,

Fertilization: trade-offs between manure abatement and plant productivity

In 2005, 30% of the Flemish farms faced a manure excess, while at aggregated level still 9.7% of the emission rights were unused. This means that, despite the various possibilities, Flemish farmers do not succeed in an effective exchange of manure between farms. In current paper is shown how inorganic fertilizer use influences the use and exchange of organic nitrogen. Because of the mutual interdependency between organic and inorganic nitrogen emission rights (or quota), inorganic nitrogen use limits the emission rights for organic nitrogen. Utilisation of these emission rights are analysed as a trade-offs choice between plant productivity (use of inorganic nitrogen) and manure disposal, as the major abatement alternative of manure production. Farmers still prefer inorganic fertilizers because of their effect on plant productivity and income. However, by changing the quota rent of organic nitrogen, the fertilization behaviour can be influenced. A higher quota rent of organic nitrogen would increase the use of manure. This trade-off behaviour seriously influences effectiveness of policies. When the objective is to lower the total nitrogen use, a mere reduction of organic quota can partially be counteracted by a higher inorganic nitrogen use. When the objective is to better spread the manure, increasing the quota rent for deficit farms will increase their acceptance of manure.manure abatement, nutrient emission rights, Tobit model, Crop Production/Industries,

A FARM LEVEL ANALYSIS OF THE RELATION BETWEEN CAP REFORMS AND LOCAL ENVIRONMENTAL LEGISLATIONS: HOW AND IN WHICH EXTENT FLEMISH DAIRY FARMERS CAN FILL UP EXTRA MILK QUOTA?

The agricultural policies shift gradually from EU-level organised market interventions to local organised environmental policies. This paper explores the growth possibilities of the Flemish dairy sector with the outlook of a quota abolishment as a case study of this policy shift. The dairy quota policy seems very restrictive for the highly profitable Flemish dairy sector, but the environmental restrictions from the manure regulation can limit the growth of the dairy sector as well. The paper uses a spatial multi-agent simulation model applied to a sample of 40.000 farms to estimate price development of emission rights and their possible impact on the growth of the dairy production. The results show that a higher milk production leads to higher prices for emission rights. However, the increased cost of manure emission rights is not expected to impede dairy farm growth because the current milk quota rent estimates go far beyond the cost of manure emission rights.milk quota, manure emission rights, mathematical programming, Flanders, Agricultural and Food Policy, Industrial Organization, Research Methods/ Statistical Methods, C02, C61, L11, Q18,

Effects of a flat rate introduction: shifts in farm activity and impact on farmers' income

Current thoughts on CAP changes, e.g. the "Health Check", emphasize the necessity to move away from payments based on historical receipts towards a "flatter rate" system. The aim of current research is to simulate the impact of a flat rate system (equal payments per hectare of cultivated land) compared to the current historical system (payments based on individual historic entitlements). Impact on production and income of arable, dairy and cattle farms of two different flat rate scenario's, is assessed with a farm-based sector model for Flanders. The model maximizes income at farm level, calibrated to observed farming behavior in 2001-2003. Farm data can be selected by farm type, size and region, simulations could be run for specific sub sectors, size classes or regions. In the two simulated flat rate scenario's subsectors will gain subsidies at the expense of other subsectors. However, farms can compensate a substantial part of their income loss by changing activity choice.Positive Mathematical Programming, farm model, Common Agricultural Policy, Payment Entitlements., Agricultural and Food Policy, Agricultural Finance, Farm Management, Research Methods/ Statistical Methods,

Variations in water use by a mature mangrove of Avicennia germinans, French Guiana

In the tropical intertidal zones, little is known on water uptake by mangroves. Transpiration rates are generally measured at leaf level, but few studies exist on water use at tree or stand levels. The objective of this study was to measure sap flow in trees of different sizes to appreciate the range of variation in water use that may exist in a site dominated by 80% mature Avicennia germinans. The results showed that from the dry to the wet season the mean water use increased from 3.2 to 5.3 dm3 d−1 in small trees (DBH ∼ 13 cm), from 11.5 to 30.8 dm3 d−1 in medium trees (∼24 cm) and from 40.8 to 64.1 dm3 d−1 in large ones (∼45 cm). Sapwood remained active up to a depth of 8 cm with radial variations within the stem. Weak correlations were obtained with VPD and net radiation. This study confirmed that transpiration was larger under low levels of salinity. Water use at stand level (∼1900 living stems ha−1) was estimated to be in the range of 5.8 to 11.8 m3 ha−1 d−1 according to the season

Magnetic Field scaling of Relaxation curves in Small Particle Systems

We study the effects of the magnetic field on the relaxation of the magnetization of small monodomain non-interacting particles with random orientations and distribution of anisotropy constants. Starting from a master equation, we build up an expression for the time dependence of the magnetization which takes into account thermal activation only over barriers separating energy minima, which, in our model, can be computed exactly from analytical expressions. Numerical calculations of the relaxation curves for different distribution widths, and under different magnetic fields H and temperatures T, have been performed. We show how a \svar scaling of the curves, at different T and for a given H, can be carried out after proper normalization of the data to the equilibrium magnetization. The resulting master curves are shown to be closely related to what we call effective energy barrier distributions, which, in our model, can be computed exactly from analytical expressions. The concept of effective distribution serves us as a basis for finding a scaling variable to scale relaxation curves at different H and a given T, thus showing that the field dependence of energy barriers can be also extracted from relaxation measurements.Comment: 12 pages, 9 figures, submitted to Phys. Rev.