Éric Maire

Impacts of Public Policies and Farmer Preferences on Agroforestry Practices in Kerala, India

Agroforestry systems are fundamental features of the rural landscape of the Indian state of Kerala. Yet these mixed species systems are increasingly being replaced by monocultures. This paper explores how public policies on land tenure, agriculture, forestry and tree growing on private lands have interacted with farmer preferences in shaping land use dynamics and agroforestry practices. It argues that not only is there no specific policy for agroforestry in Kerala, but also that the existing sectoral policies of land tenure, agriculture, and forestry contributed to promoting plantation crops, even among marginal farmers. Forest policies, which impose restrictions on timber extraction from farmers’ fields under the garb of protecting natural forests, have often acted as a disincentive to maintaining tree-based mixed production systems on farmlands. The paper argues that public policies interact with farmers’ preferences in determining land use practices.

Long-term denudation rates from the Central Andes (Chile) estimated from a Digital Elevation Model using the Black Top Hat function and Inverse Distance Weighting: implications for the Neogene climate of the Atacama Desert

A methodology for determining long-term denudation rates from morphologic markers in a Digital Eleva- tion Model (DEM) is checked by a comparative study of two drainage basins in the Precordillera of the Central Andes. In both cases the initial confi guration of an incised pediment surface has been restored by using two different methods: the Black Top Hat (BTH) function and the Inverse Distance Weighting (IDW) interpolation. Where vertical incision and hillslope erosion are recorded, the IDW appears to be the most adequate to reconstitute the pediment surfaces. Conversely, where only vertical incision is observed, the BTH describes more precisely the former pediment surfaces and it is easier to solve. By subtracting the DEM from the reconstructed marker we calculated an eroded volume, and estimated its uncertainty by considering Root Mean Square Error (RMSE) and DEM grid error. For the last ~10 Myr we obtained long-term denudation rates of 7.33±1.6 m/Myr in the San Andres drainage basin and 13.59±1.9 m/Myr in the El Salado drainage basin. These estimations are largely in agreement with other reported estimates of long-term denudation rates in the Atacama Desert. Comparison with long-term denudation rates reported in a wide range of climatic regimes suggests that our estimates cannot be explained by the current rainfall in the Precordillera. However they could be explained by a rainfall similar to that reported 40 km to the east in the Puna. This suggests that during the time span concerned the geomorphologic evolution of the study area, this evolution is dominated by an orographically controlled rainfall pattern. The preserved pediment surface and the small long term denudation rates determined in this study also indicate that the Precordillera was never reached by humid tropical air masses and precipitation as currently observed in the Altiplano during the summer months.

Télédétection de la trame verte arborée en haute résolution par morphologie mathématique

Cet article pointe dabord les causes et/es enjeux des verrous cartographiques dans !a mise en oeuvre de la politique de la trame verte et bleue (TVB). Une connaissance de lemprise precise de la trame verte arboree par les acteurs locaux apparait incontournable. Nous proposons ensuite une methode de teledetection associee a des algorithmes de morphologie mathematique pour extraire la trame verte arboree a lechelle metrique a partir dune image a tres haute resolution spatiale. La methode proposee est une sequence de quatre etapes : 1) analyse en composantes principales (ACP), 2) segmentation par la transformation chapeau haut de forme, 3) elimination du bruit morphologique, 4) restauration des contours arbores par dilatation geodesique. Enfin, une discussion sur les perspectives en termes de consequences sur les methodologies de teledetection et sur les politiques publiques environnementales termine larticle.

L'arbre hors forêt en France : diversité, usages et perspectives

Difficile a definir, souvent percu comme genant dans les zones de grande culture, larbre hors foret nen est pas moins un element omnipresent dans les paysages francais, tellement que lon ne lui accorde pas toujours la place quil merite. La diversite des structures arborees peut fournir cependant de nombreuses ressources en termes economiques. En outre, ces structures sont de plus en plus reconnues pour leurs fonctions ecologiques. Larbre hors foret constitue egalement un important marqueur socioculturel et un atout a developper pour lamelioration des productions agricoles. Les paysages darbres hors foret (AHF), souvent mis en avant pour valoriser des produits de terroir, sont pourtant encore insuffisamment pris en compte par les pouvoirs publics en termes damenagement du territoire, et le volontarisme des politiques locales de preserver les arbres hors foret est confronte au manque de reconnaissance juridique et de statut de ces arbres champetres.

Damage assessment of Al alloys using in situ tensile tests in x-ray tomography

This paper presents recent results by using in situ tensile experiments. Two axisymmetric samples (one smooth and the other one with a notch) where machined out of a standard 5741 aluminium alloy. In both cases, the different damage steps (initiation, growth and coalescence) have been clearly visualised during interrupted in situ tensile tests in synchrotron X ray tomography with a voxel size of 1.6 microns. The X ray tomography technique can be used like a simple microscopy technique with a slightly lower resolution than conventional ones and provides a different type of information in the form of three dimensional (3D) non destructive images of the bulk of the observed material. The method also describes precisely the outer shape of the sample and its change during deformation. This allows calculating precisely the true strain true stress curve of the sample and also an approximation of the stress triaxiality by the Bridgeman formula. The results show that damage can be visualised and that the early fracture of the notched sample is due to the higher triaxiality.

Image analysis applied to luminescence microscopy

We have developed a novel approach to study luminescent light emission during migration of living cells by low-light imaging techniques. The equipment consists in an anti-vibration table with a hole for a direct output under the frame of an inverted microscope. The image is directly captured by an ultra low- light level photon-counting camera equipped with an image intensifier coupled by an optical fiber to a CCD sensor. This installation is dedicated to measure in a dynamic manner the effect of SF/HGF (Scatter Factor/Hepatocyte Growth Factor) both on activation of gene promoter elements and on cell motility. Epithelial cells were stably transfected with promoter elements containing Ets transcription factor-binding sites driving a luciferase reporter gene. Luminescent light emitted by individual cells was measured by image analysis. Images of luminescent spots were acquired with a high aperture objective and time exposure of 10 - 30 min in photon-counting mode. The sensitivity of the camera was adjusted to a high value which required the use of a segmentation algorithm dedicated to eliminate the background noise. Hence, image segmentation and treatments by mathematical morphology were particularly indicated in these experimental conditions. In order to estimate the orientation of cells during their migration, we used a dedicated skeleton algorithm applied to the oblong spots of variable intensities emitted by the cells. Kinetic changes of luminescent sources, distance and speed of migration were recorded and then correlated with cellular morphological changes for each spot. Our results highlight the usefulness of the mathematical morphology to quantify kinetic changes in luminescence microscopy.

Three-dimensional reconstruction of fluorescent lymphocyte cells

The complete process, image acquisition, deblurring, 3D reconstruction and analysis has been tested on 160 normal T lymphoid cells marked with monoclonal antibodies CD4-CD8. The images are acquired from a conventional optical microscope illuminated by a mercury vapor lamp. A set of 16 serial image cuts is first grabbed by a high sensitivity Silicon Intensified Target (SIT) camera fitted on the microscope. The 2D image cuts are then deblurred using an original deconvolution method developed in the laboratory. The 3D reconstruction is processed slice by slice using a variant of the 2D Delaunay triangulation. To get a correct triangulation in the case of our specific application the following stringent requirements must be met. First, we exclude the possibility of joining two contours if we meet an empty cut between them, and secondly we must avoid branching points and finally, we state that reconstructed shapes may not have holes. The 3D reconstruction highlights some qualitative characteristics of the cells. So we can show that the fluorescent spots are either scattered on the membrane surface and present a regular radial arrangement or on the contrary are confined in a restricted area. Accordingly we propose to introduce a spatial coefficient in order to characterize such a volume distribution. In a further development we plan to obtain discriminant descriptors of the immunological status of hematopoietic cells.

Laser-cytofluorescence microscopic image restoration by iterative deconvolution

The aim of our study is to improve the performances of an optical microscope by image deconvolution technique to attain that of a confocal one in the field of laser cytofluorescence. The fluorescence of antigen lymphocyte sites marked by rhodamine is induced by a laser ((lambda) equals 543 nm) or a mercury vapor lamp. A set of scanned fluorescence images is acquired at different focal planes by a SIT camera, fitted on an optical ZEISS microscope (N.A. 1.25, X100). The entire system is controlled by a PC equipped with a MATROX-MVP-AT image processing card. Since an optical microscope has a more important focal depth than a confocal one, an improved iterative deconvolution algorithm of Van Citterts has been used to artificially reduce the focal depth. In order to ensure the convergence of such an iterative algorithm, a new criterion for relaxation coefficient is defined through a theoretical study. The experiments show an improvement of 50% in the spatial x-y resolution of 30% in optical z axis gain. As regards our application, this processing brings our system to a comparable performance level as a confocal microscope.

IMAGE CYTOMETRY OF MEMBRANE SURFACE ANTIGENS EXPRESSION: A NEW APPROACH FOR IMMUNOLOGICAL PHENOTYPING

Induction of differentiation is another way in cancer research. Moreover. cell differentiation, usually associated with cell growth inhibition. can be related to apoptosis. Aclacinomycin (ACM) induced in K562 cells a growth inhibition, a differentiation assessed by benzidine staining and glyeophorin A expression, and a quiescence assessed by the loss of Ki-67 expression. In function of time, these effects are somewhat intricate ; the study of apoptosis on these cells could help in the understanding of ACM action. Concerning apoptosis, preliminary results obtained with K562 cells were disappointing, they led us to study differentiation and apoptosis induction in a more susceptible cell line, i.e. H1.60. HL60 cells were incubated continuously (cont) or Ih with ACM, cell death was assessed by trypan blue exclusion, differentiation was assessed by NBT reduction determined by microscopic and flow cytometric (FCM) analyses, apoptosis was determined by May-Gr~nwald-Giemsa (MGG) staining and by FCM using PI-Hoechst 33342 staining. After a 3 days i~ubation with 45 nM ACM, cell death reached about 50%, NBT reduction was observed only by FCM (80 % vs 1%) ; similarly, a higher rate of apoptosis was displayed according to FCM (25 %) than to MGG (I 5 %). Comparing cont and lh ACM incubations, lethality appeared in cont at 24 h and increased thereafter, when a plateau was observed with Ih ACM at about 30 % ; circa 75 % of cells were NBT positive with both methods from 3 days for I h ACM and in this case, apoptosis was still higher from 18 to 72h by FCM (about 15 %) than by MGG (<10 %). ACM effects on cell growth and differentiation were nearly similar with K562 and H]..60 cells. Results on differentiation and apoptosis varied according to the method used, this can be explained by a different level of sensitivity. It is of interest to notice that Ih incubation with ACM is sufficient to induce these pharmacological effects. Q U A N T I F I C A T I O N BY C Y T O F L U O R O M E T R Y OF G L U C O C O R T I C O I D I N D U C E D APOFTOSIS : STRUCTUREACTIVITY RELATIONSHIP.