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Les poèmes en français consacrés à la dernière grande campagne bourguignonne contre Liège — celle qui, de l’expédition contre Dinant en août 1466, aboutit à la destruction de la Cité en octobre 1468 — constituent un ensemble remarquable par l'unité de ses thèmes autant que par la diversité de ses formes. Les treize pièces dont il sera question dans ces pages totalisent 2.225 vers et peuvent, d’après la chronologie des événements, se répartir en quatre groupes. Le premier comprend trois poèmes...

International audience; Thiry M., Liron M.N., Dubreucq P., Polton J.-C., 2017, Curiosités géologiques du massif de Fontainebleau, Guide géologique, BRGM Editions., 115 p.

A histological analysis was undertaken on the gonad development ofLabeo parvus Boulenger 1902, a medium-sized cyprinid from the Ouémé River, Benin. Samples were collected monthly between April 2006 and March 2007 and were examined using routine macroscopic and histological techniques. Five macroscopic stages of gonad maturation were identified in the ovaries and testes and described histologically. Oocyte development was subdivided into five stages, based on the presence of chromatin nucleolus oocytes, perinucleolus oocytes, yolk vesicle oocytes, vitellogenic oocytes and mature oocytes. Four stages of spermatogenesis (spermatogonia, spermatocytes, spermatids and spermatozoa) were observed. Comparisons of macroscopic and histological observations revealed that the temporal patterns of maturation activity obtained from visual examination closely reflected the seasonal histological trend in gonad development. Histological characteristics of spent ovaries and testes were similar to those of immature fish, indicating thatL. parvus were synchronous iteroparous spawners.African Journal of Aquatic Science 2012, 37(2): 155–163

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A sediment core containing a yellowish-green clay bed was recovered from an area of extensive hydrothermal deposition at the SE slope of the Eolo Seamount, Tyrrhenian Sea. The clay bed is composed of pure nontronite (described for the first time in the Tyrrhenian Sea), which appears to be the most aluminous nontronite ever found among the seafloor hydrothermal deposits. The high Al content suggests precipitation from Al-containing hydrothermal solutions. The REE distribution of the Eolo nontronite has a V-shape pattern. The heavy REE enrichment is in part due to their preferential partitioning in the nontronite structure. This enrichment was possibly further enhanced by the HREE preferential sorption on bacterial cell walls. The light REE enrichment is the result of scavenging uptake by one of the nontronite precursors, i.e., poorly-ordered Fe-oxyhydroxides, from the hydrothermal fluids. Oxygen isotopic composition of the nontronite yields a formation temperature of 30 T, consistent with a low-temperature hydrothermal origin. The relatively radiogenic Nd isotopic signature of the nontronite compared to the present-day Mediterranean seawater indicates that approximately half of Nd, and presumably the rest of the LREE, are derived from local volcanic sources. On the other hand, Sr-87/Sr-86 is dominated by present-day seawater Sr. Scanning electron microscopy investigation revealed that the nontronite is composed of aggregates of lepispheres and tube-like filaments, which are indicative of bacteria assisted precipitation. Bacteria inhabiting this hydrothermal site likely acted as reactive geochemical surfaces on which poorly-ordered hydrothermal Fe-oxyhydroxides and silica precipitated. Upon aging, the interactions of these primary hydrothermal precipitates coating bacterial filaments and cell walls likely led to the formation of nontronite. Finally, the well-balanced interlayer and layer charges of the crystal lattice of seafloor hydrothermal nontronite decrease its sorption capacity to zero. Thus the ubiquitous nontronite precipitation along the active plate boundaries and around the hot spots has no significant impact on oceanic trace element chemistry.

Chromosome localization in the interphase nuclei of eukaryotes depends on gene replication and transcription. Little is known about chromosome localization in protozoan parasites such as trypanosomes, which have unique mechanisms for the control of gene expression, with most genes being posttranscriptionally regulated. in the present study, we examined where the chromosomes are replicated in Trypanosoma cruzi, the agent of Chagas' disease. the replication sites, identified by the incorporation of 5-bromodeoxyuridine, are located at the nuclear periphery in proliferating epimastigote forms in the early S phase of the cell cycle. When the S phase ends and cells progress through the cell cycle, 5-bromodeoxyuridine labeling is observed in the nuclear interior, suggesting that chromosomes move. We next monitored chromosome locations in different stages of the cell cycle by using a satellite DNA sequence as a probe in a fluorescence in situ hybridization assay. We found two distinct labeling patterns according to the cell cycle stage. the first one is seen in the G, phase, in hydroxyurea-arrested epimastigotes or in trypomastigotes, which are differentiated nondividing forms. in all of these forms the satellite DNA is found in dots randomly dispersed in the nucleus. the other pattern is found in cells from the S phase to the G, phase. in these cells, the satellite DNA is found preferentially at the nuclear periphery. the labeling at the nuclear periphery disappears only after mitosis. Also, DNA detected with terminal deoxynucleotidyl transferase is found distributed throughout the nuclear space in the G, phase but concentrated at the nuclear periphery in the S phase to the G, phase. These results strongly suggest that T. cruzi chromosomes move and, after entering the S phase, become constrained at the nuclear periphery, where replication occurs. Universidade Federal de São Paulo, Dept Microbiol Immunol & Parasitol, BR-04023062 São Paulo, Brazil Univ Fed Rio de Janeiro, Inst Biofis Carlos Chagas Filho, Lab Ultraestrutura Celular Hertha Meyer, BR-21941 Rio de Janeiro, Brazil Univ Liege, Lab Cellular & Tissue Biol, Liege, Belgium Universidade Federal de São Paulo, Dept Microbiol Immunol & Parasitol, BR-04023062 São Paulo, Brazil Web of Science

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Les tepetates de la Vallée de Mexico sont des horizons indurés de sols volcaniques à comportement de fragipan. Ce sont des tufs rhyo-dacitiques altérés à la base de paléosols, ceux-ci provenant de l'altération de cendres de même composition au-dessus du tuf. Dans le profil étudié il y a trois paléosols et trois horizons de tepetate, correspondant à trois séries de dépôts volcaniques datant de 12 à 35 ka, BP. L'argile d'altération des verres volcaniques s'accroît du tuf au tepetate, puis au sol. Mais sa composition varie peu du tepetate au sol, sinon qu'elle est un peu plus siliceuse et présente une meilleure orientation des feuillets d'argile dans le tepetate. L'argile est composée surtout d'interstratifiés irréguliers d'halloysite et de smectite, ainsi que d'un peu d'opale A, de gel de silice et d'oxyde de fer mal cristallisé. Les agrégats sont formés d'amas de plaquettes orientées face à face. Les coupes ultraminces montrent : - dans la matrice des amas en fuseau et quelques formes en tube et en sphère ; - dans les argilanes microlaminés un arrangement lité et compact. La microanalyse de particules d'argiles confirme une composition mixte d'argiles 1:1 et 2:1. La distance réticulaire entre feuillets varie de 0,7-0,8 à 1,0 nm environ. Des remplissages de silice non cristalline sont observés entre des paquets d'argiles. Il s'agit de très fines plaquettes et grains d'opale non cristalline, et très peu d'alumine et d'oxyde de fer. Il y a aussi des revêtements diffus de gel de silice dans les fissures. L'organisation compacte des argiles caractérise les tepetates, assure leur cohésion. La silice non cristalline renforce cette cohésion à l'état sec, ce qui explique le comportement de fragipan (plastique à l'état humide, dur à l'état sec). (Résumé d'auteur)