Aménagement forestier et participation : quelles leçons tirer des forêts communales du Cameroun?

Outre l'aménagement forestier de grandes concessions et celui de forêts communautaires de taille réduite, certaines communes du Cameroun se lancent depuis peu dans l'aménagement durable de forêts qui leur sont rétrocédées par l'État. Ces Forêts Communales représentent un aménagement forestier intermédiaire entre ces deux types de concessions. Un plan d'aménagement est élaboré et une gestion participative doit obligatoirement être réalisée afin de tenir compte des usages et des intérêts des populations locales, lesquelles peuvent voter à l'encontre du maire. L'article cherche à définir si ce nouveau modèle d'aménagement, contribuant à accroître les capacités d'investissement de la commune et au transfert de pouvoir d'un niveau central vers un niveau local, peut constituer un cadre d'une gestion durable et participative de la forêt du Bassin du Congo. (Résumé d'auteur

Hole and Electron Contributions to the Transport Properties of Ba(Fe_(1-x)Ru_x)_2As_2 Single Crystals

We report a systematic study of structural and transport properties in single crystals of Ba(Fe_(1-x)Ru_x)_2As_2 for x ranging from 0 to 0.5. The isovalent substitution of Fe by Ru leads to an increase of the a parameter and a decrease of the c parameter, resulting in a strong increase of the AsFeAs angle and a decrease of the As height above the Fe planes. Upon Ru substitution, the magnetic order is progressively suppressed and superconductivity emerges for x > 0.15, with an optimal Tc ~ 20K at x = 0.35 and coexistence of magnetism and superconductivity between these two Ru contents. Moreover, the Hall coefficient RH which is always negative and decreases with temperature in BaFe2As2, is found to increase here with decreasing T and even change sign for x > 0.15. For x_Ru = 0.35, photo-emission studies have shown that the number of holes and electrons are similar with n_e = n_h ~ 0.11, that is twice larger than found in BaFe2As2 [1]. Using this estimate, we find that the transport properties of Ba(Fe_0.65Ru_0.35)_2As_2 can be accounted for by the conventional multiband description for a compensated semi-metal. In particular, our results show that the mobility of holes is strongly enhanced upon Ru addition and overcomes that of electrons at low temperature when x_Ru > 0.15.Comment: new version with minor correction

Venous obstruction of thyroid malignancy origin: the Antoine Lacassagne Institute experience

<p>Abstract</p> <p>Background and aims</p> <p>To show the benefits of Ultrasonography in the diagnosis of great vein involvement in the neck and mediastinum in thyroid malignancies (primary or secondary) in our experience and to report patient outcomes.</p> <p>Methods</p> <p>Clinical data were collected from the thyroid unit database of the Antoine Lacassagne Institute.</p> <p>Results</p> <p>Of 1171 patients with thyroid cancer treated at our institution over the last 18 years, we retrospectively identified nine patients (0.8%), three women and six men, aged 34–81 years (median age: 70 years) presenting with malignant thyroid tumor of median diameter 45 mm (range: 23–87) having venous obstruction of thyroid malignancy origin. Two patients underwent multimodal therapy. All other patients underwent external beam radiation therapy alone ± chemotherapy or palliative care. Ultrasound (US) provided particularly useful information on venous involvement characteristics. Median survival was 7 months and median progression-free survival was 6 months. Survival in our series was worse than that of previously reported series despite diagnosis of vein involvement at an early stage in 2/3 cases using US.</p> <p>Conclusion</p> <p>Despite small numbers of patients, it seems that aggressive treatment modalities including surgery are required to improve survival. In our experience, US was a useful non-invasive method to describe tumor extensions to great veins of the neck (invasion versus compression, tumor thrombus versus blood clot) and should be recommended to depict early venous invasion in cases of suspected thyroid malignancy.</p

The chronology of adipose tissue appearance and distribution in the human fetus

Timing of first appearance and subsequent distribution of adipose tissue were assessed in 488 normal-for-age human fetuses. The sample represented each of the three trimesters of normal pregnancies. Light microscopy showed that adipose tissue first appears and progressively develops from the 14th to 24th week of gestation (100-216 mm crown-rump length) in those areas where it characteristically accumulates after birth. No significant sex differences were found in patterns of early fat deposition. It is suggested that the second trimester of gestation is the critical or key period in fat adipogenesis.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24701/1/0000120.pd

Growth and development of human adipose tissue during early gestation

805 normal-for-age human embryos and fetuses were used to study early prenatal fat development. The investigation included observations on stages of fat morphogenesis at the light microscopic level and computerized image analyses of fat lobule size and number. The buccal fat pad was selected as a model system for the analyses. Fat tissue differentiates between the 14th and the 16th weeks: there are five morphogenic phases in adipose tissue formation, strongly associated with the formation of blood vessels. Fat lobules are the earliest structures to be identified before typical vacuolated fat cells appear. Concerning fat lobule size and number, we show that after the 23rd week the total number of fat lobules remains approximately constant, while from the 23rd to 29th week the growth of adipose tissue is determined mainly by an increase in size of the lobules. These results suggest that the 14th through the 23rd week is a sensitive period in fat lobule development, and that disturbances of normal adipogenesis during this period may play a role in the etiology of obesity in later life.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25267/1/0000710.pd

Influence de la teneur en oxygène sur la microstructure et le comportement mécanique de la phase « ex bêta » résultant de l'oxydation à haute température (1000-1200°C) du zircaloy 4

International audienceL'étude ici illustrée s'intéresse au comportement thermo - métallurgique - mécanique des alliages de Zr des tubes de gainage du combustible des Réacteurs nucléaires à Eau Pressurisée (REP), lors de transitoires à hautes températures (HT) en ambiance vapeur d'eau, simulant des conditions hypothétiques accidentelles (dites APRP). Il apparaît intéressant d'approfondir la connaissance des phénomènes métallurgiques et thermomécaniques mis en jeu lors de tels transitoires, en particulier vis-à-vis du comportement mécanique résiduel « post oxydation trempe ». Différentes teneurs en oxygène ont été incorporées dans l'alliage étudié, pour simuler la diffusion de cet élément dans le substrat métallique qui intervient lors de l'oxydation HT. Des caractérisations microstructurales par EBSD, MET, MEB... et des caractérisations mécaniques par essai de traction, mesures de constantes physiques... ont permis de décrire la microstructure et le comportement mécanique de la phase résiduelle la plus ductile – phase dite « ex-bêta » - résultant de l'oxydation HT des gaines en zircaloy-4