Search

International audience

Aim: Our aim was to evaluate the extent to which we can predict and map tree alpha diversity across broad spatial scales either by using climate and remote sensing data or by exploiting spatial autocorrelation patterns.Location: Tropical rain forest, West Africa and Atlantic Central Africa.Methods: Alpha diversity estimates were compiled for trees with diameter at breast height ≥ 10 cm in 573 inventory plots. Linear regression (ordinary least squares, OLS) and random forest (RF) statistical techniques were used to project alpha diversity estimates at unsampled locations using climate data and remote sensing data [Moderate Resolution Imaging Spectroradiometer (MODIS), normalized difference vegetation index (NDVI), Quick Scatterometer (QSCAT), tree cover, elevation]. The prediction reliabilities of OLS and RF models were evaluated using a novel approach and compared to that of a kriging model based on geographic location alone.Results: The predictive power of the kriging model was comparable to that of OLS and RF models based on climatic and remote sensing data. The three models provided congruent predictions of alpha diversity in well-sampled areas but not in poorly inventoried locations. The reliability of the predictions of all three models declined markedly with distance from points with inventory data, becoming very low at distances ≥ 50 km. According to inventory data, Atlantic Central African forests display a higher mean alpha diversity than do West African forests.Main conclusions: The lower tree alpha diversity in West Africa than in Atlantic Central Africa may reflect a richer regional species pool in the latter. Our results emphasize and illustrate the need to test model predictions in a spatially explicit manner. Good OLS or RF model predictions from inventory data at short distance largely result from the strong spatial autocorrelation displayed by both the alpha diversity and the predictive variables rather than necessarily from causal relationships. Our results suggest that alpha diversity is driven by history rather than by the contemporary environment. Given the low predictive power of models, we call for a major effort to broaden the geographical extent and intensity of forest assessments to expand our knowledge of African rain forest diversity.

International audience

PURPOSE Modulated electron radiotherapy (MERT) promises sparing of organs at risk for certain tumor sites. Any implementation of MERT treatment planning requires an accurate beam model. The aim of this work is the development of a beam model which reconstructs electron fields shaped using the Millennium photon multileaf collimator (MLC) (Varian Medical Systems, Inc., Palo Alto, CA) for a Varian linear accelerator (linac). METHODS This beam model is divided into an analytical part (two photon and two electron sources) and a Monte Carlo (MC) transport through the MLC. For dose calculation purposes the beam model has been coupled with a macro MC dose calculation algorithm. The commissioning process requires a set of measurements and precalculated MC input. The beam model has been commissioned at a source to surface distance of 70 cm for a Clinac 23EX (Varian Medical Systems, Inc., Palo Alto, CA) and a TrueBeam linac (Varian Medical Systems, Inc., Palo Alto, CA). For validation purposes, measured and calculated depth dose curves and dose profiles are compared for four different MLC shaped electron fields and all available energies. Furthermore, a measured two-dimensional dose distribution for patched segments consisting of three 18 MeV segments, three 12 MeV segments, and a 9 MeV segment is compared with corresponding dose calculations. Finally, measured and calculated two-dimensional dose distributions are compared for a circular segment encompassed with a C-shaped segment. RESULTS For 15 × 34, 5 × 5, and 2 × 2 cm(2) fields differences between water phantom measurements and calculations using the beam model coupled with the macro MC dose calculation algorithm are generally within 2% of the maximal dose value or 2 mm distance to agreement (DTA) for all electron beam energies. For a more complex MLC pattern, differences between measurements and calculations are generally within 3% of the maximal dose value or 3 mm DTA for all electron beam energies. For the two-dimensional dose comparisons, the differences between calculations and measurements are generally within 2% of the maximal dose value or 2 mm DTA. CONCLUSIONS The results of the dose comparisons suggest that the developed beam model is suitable to accurately reconstruct photon MLC shaped electron beams for a Clinac 23EX and a TrueBeam linac. Hence, in future work the beam model will be utilized to investigate the possibilities of MERT using the photon MLC to shape electron beams.

Resume But de l'etude Le but de cette etude etait de rapporter les resultats d'une serie de 50 transplantations du rein et du pancreas realisees dans le meme centre, pour insuffisance renale chronique chez des patients diabetiques insulinodependants. Patients et methode De 1989 a 1999, 50 transplantations pancreatiques ont ete realisees de facon consecutive dont 48 combinees a une transplantation renale et deux chez des patients deja porteurs d'un greffon renal fonctionnel. Le pancreas entier a ete transplante dans la fosse iliaque droite par voie sous-peritoneale, avec derivation duodenovesicale de la secretion exocrine. Le rein a ete transplante dans la fosse iliaque gauche par une voie sous-peritoneale distincte. L'immunosuppression a ete realisee avec Azathioprine® remplacee par Mycophenolate Mofetil® depuis 1996, associee a la corticotherapie et a la cyclosporine remplacee depuis 1997 par FK 506. Les receveurs etaient 32 femmes et 18 hommes (âge moyen : 37 ± 5 ans), traites par l'insuline depuis 23 ± 6 ans et recevant 35 ± 10 unites d'insuline par jour. Le peptide C etait a 0,33 ± 0,35 mg/mL et la creatinine plasmatique a 726 ± 260 nmol/L. Resultats Un patient est decede a j10 d'une thrombose des arteres pulmonaires liee a une drepanocytose meconnue. Les complications postoperatoires les plus frequentes ont ete la fistulisation de l'anastomose duodenovesicale (n = 9) qui a necessite une reintervention avec conservation du greffon pancreatique dans tous les cas et la thrombose veineuse du transplant pancreatique (n = 5) qui a abouti a la perte du greffon dans tous les cas. Cinq patients sont decedes tardivement a 24, 36, 48, 50 et 72 mois dont deux qui avaient des greffons fonctionnels. Avec un recul moyen de cinq ans, 44 patients etaient vivants soit 88 % de l'ensemble des patients, dont 34 avec deux gref-fons fonctionnels, soit 68 % de l'ensemble des patients. Seize greffons pancreatiques ont ete perdus : trois par deces du patient, huit de complications chirurgicales, quatre de rejet et un par transplantectomie d'un organe fonctionnel. Conclusion Les resultats de la greffe combinee rein et pancreas sont satisfaisants chez le diabetique insulinodependant en insuffisance renale. La transplantation d'un pancreas total par voie sous peritoneale nous semble actuellement la technique la plus sure. Une selection rigoureuse des donneurs comme des receveurs est indispensable.

During a meeting on chronic lymphocytic leukaemia (CLL) in Brussels in May 2010, experts from the main departments of Haematology in Belgium met to discuss and create guidelines concerning the use of alemtuzumab (MabCampath®) in the treatment of CLL. The moderator of the meeting was Professor Dominique Bron. The objective of the meeting was to answer the following four questions with respect to the Belgian situation: 1) The place of alemtuzumab in the treatment of CLL. 2) The dose and route of administration of alemtuzumab. 3) Duration of treatment with alemtuzumab. 4) Patient management issues linked to the use of alemtuzumab.

Aim Our aim was to evaluate the extent to which we can predict and map tree alpha diversity across broad spatial scales either by using climate and remote sensing data or by exploiting spatial autocorrelation patterns. Location Tropical rain forest, West Africa and Atlantic Central Africa. Methods Alpha diversity estimates were compiled for trees with diameter at breast height = 10 cm in 573 inventory plots. Linear regression (ordinary least squares, OLS) and random forest (RF) statistical techniques were used to project alpha diversity estimates at unsampled locations using climate data and remote sensing data [Moderate Resolution Imaging Spectroradiometer (MODIS), normalized difference vegetation index (NDVI), Quick Scatterometer (QSCAT), tree cover, elevation]. The prediction reliabilities of OLS and RF models were evaluated using a novel approach and compared to that of a kriging model based on geographic location alone. Results The predictive power of the kriging model was comparable to that of OLS and RF models based on climatic and remote sensing data. The three models provided congruent predictions of alpha diversity in well-sampled areas but not in poorly inventoried locations. The reliability of the predictions of all three models declined markedly with distance from points with inventory data, becoming very low at distances > 50 km. According to inventory data, Atlantic Central African forests display a higher mean alpha diversity than do West African forests. Main conclusions The lower tree alpha diversity in West Africa than in Atlantic Central Africa may reflect a richer regional species pool in the latter. Our results emphasize and illustrate the need to test model predictions in a spatially explicit manner. Good OLS or RF model predictions from inventory data at short distance largely result from the strong spatial autocorrelation displayed by both the alpha diversity and the predictive variables rather than necessarily from causal relationships. Our results suggest that alpha diversity is driven by history rather than by the contemporary environment. Given the low predictive power of models, we call for a major effort to broaden the geographical extent and intensity of forest assessments to expand our knowledge of African rain forest diversity.

International audience; Dans cet article, un système d'extraction d'information par analyseur statistique de surface dans des documents manuscrits faiblement contraints est introduit. Contrairement aux principales approches de la littérature que sont le keyword spotting et la reconnaissance complète de documents, l'originalité du système mis en oeuvre réside dans l'attention portée à la modélisation globale de l'écriture. En effet, la ligne de texte est considérée comme une entité indivisible et est modélisée de manière duale à l'aide de modèles de Markov cachés. Ainsi, une analyse surfacique de l'écriture permet d'isoler rapidement l'information pertinente recherchée dans un texte quelconque et ce, en une seule passe. Les premiers résultats sont encourageants et illustrent le potentiel de l'approche en terme d'extraction d'information.

The potential benefit of adjuvant cytotoxic chemotherapy after radical surgical or radiation treatment of prostate cancer is discussed in the light of available reported studies. It is concluded that the effect of such treatment must still be regarded as uncertain and that further trials are needed.

A key problem for conservation is the coincidence of regions of high biodiversity with regions of high human impact. Twenty-five of the most threatened centers of plant diversity were identified by Myers et al., and these "hotspots" play a crucial role in international conservation strategies. The primary goal of the hotspots is to cover the most threatened centers of plant diversity, but their efficacy has not yet been tested empirically. For sub-Saharan Africa, our study evaluates the hotspots postulated by Myers and compares them to a set of redefined hotspots proposed on the basis of mapped distribution data for 5985 plant species. The two sets of hotspots overlap by 48%. Our redefined hotspots include 80% of the species and 66% of the range-restricted species of the sub-Saharan flora in areas under high human impact, whereas these values are 15% and 11% lower for Myers's hotspots. Despite having equal size and a considerable spatial overlap with Myers's hotspots, our redefined hotspots include further highly threatened centers of plant diversity in the Maputaland Pondoland Region, in Katanga, the East African Afromontane region, the Lower Guinea Region, and the Albertine Rift. Many of these redefined hotspots are poorly protected centers of plant and animal diversity. Their conservation is essential for a comprehensive coverage of Africa's centers of biodiversity.

We consider random q-state Potts models for $3\le q \le 8$ on the square lattice where the ferromagnetic couplings take two values $J_1>J_2$ with equal probabilities. For any q the model exhibits a continuous phase transition both in the bulk and at the boundary. Using Monte Carlo techniques the surface and the bulk magnetizations are studied close to the critical temperature and the critical exponents $\beta_1$ and $\beta$ are determined. In the strip-like geometry the critical magnetization profile is investigated with free-fixed spin boundary condition and the characteristic scaling dimension, $\beta_1/\nu$, is calculated from conformal field theory. The critical exponents and scaling dimensions are found monotonously increasing with q. Anomalous dimensions of the relevant scaling fields are estimated and the multifractal behaviour at criticality is also analyzed., Comment: LaTeX2e file with EPJB, 12 pages, 14 eps figures, 10 tables

National audience