ALBERT

Description: Mullite is certainly one of the most important oxide materials for both conventional and advanced ceramics. Mullite belongs to the compositional series of orthorhombic aluminosilicates with the general composition Al 2 (Al 2+2 x Si 2-2 x )O 10- x . Main members are sillimanite ( x = 0), stoichiometric 3/2-mullite ( x = 0.25), 2/1-mullite ( x = 0.40), and the SiO 2 -free phase ι-alumina ( x = 1, crystal structure not known). This study gives an overview on the present state of research regarding single crystal mullite. Following a short introduction, the second part of the review focuses on the crystal structure of mullite. In particular, the characteristic mullite-type structural backbone of parallel chains consisting of edge-sharing MO 6 octahedra and their specific cross-linkage by TO 4 tetrahedra is explained in detail, the role of cation disorder and structural oxygen vacancies is addressed, and the possibility of cation substitution on different sites is discussed. The third part of the study deals with physical properties being relevant for technical applications of mullite and includes mechanical properties (e.g., elasticity, compressibility, strength, toughness, creep), thermal properties (e.g., thermal expansion, heat capacity, atomic diffusion, thermal conductivity), electrical conductivity, and optical properties. Special emphasis is put on structure–property relationships which allow for interpretation of corresponding experimental data and offer in turn the possibility to tailor new mullite materials with improved properties. Finally, the reported anomalies and discontinuities in the evolution of certain physical properties with temperature are summarized and critically discussed.

Description: The new polymorph of sodium tetraborate HP-Na 2 B 4 O 7 was synthesized under high-pressure / high-temperature conditions of 6 GPa and 1000 °C in a multianvil apparatus with a Walker-type module. HP-Na 2 B 4 O 7 crystallizes with nine formula units per cell in the trigonal chiral space groups P 3 2 21 or P 3 1 21 . The parameters are a = 765.5(2), c = 2142.3(4) pm, V = 1.0872(3) nm 3 , R 1 = 0.0581, and wR 2 = 0.0809 (all data). The crystal structure of HP-Na 2 B 4 O 7 is built up from interconnected “sechser” rings of alternating corner-sharing BO 3 and BO 4 groups.

Description: Although previous findings support an origin of the Shatsky Rise igneous plateau (Northwest Pacific) through interaction of a mantle plume with a mid-ocean ridge triple junction, the evidence for the involvement of a mantle plume is equivocal. The identification of an intraplate hotspot track emanating from the plateau could solve this controversy. Here we present major and trace element geochemical data from two different bathymetric features that emanate from the youngest end of Shatsky Rise: Papanin Ridge and the Ojin Rise Seamount province. Combining our results with plate tectonic reconstructions, we conclude that Papanin Ridge represents a hotspot track formed by plume-ridge interaction. Whereas the southwestern part was formed along the path of the retreating Pacific-Farallon-Izanagi triple junction, the northeastern part was built by preferential drainage into its Pacific-Farallon branch. In contrast, the Ojin Rise Seamounts formed as a true intraplate hotspot track of the Shatsky plume tail. Our wide-ranging study reveals systematic spatial geochemical variations, consistent with a lithospheric thickness control on magma composition derived from melting a heterogeneous plume source. The recognition of two hotspot tracks and in particular of the Ojin Rise Seamounts as an intraplate hotspot track that is directly linked to Shatsky plateau volcanism both in terms of geochemistry and plate tectonic reconstructions confirms the long-disputed involvement of a mantle plume for the formation of Shatsky Rise.

Description: The majority of M〉8.5 active plate boundary earthquakes has hypocenters located beneath the oceans in subduction zones. Post-hoc analysis shows that most of the surface deformation related to co-seismic stress release takes place on the seafloor, in many cases unleashing major tsunamis. The structure and morphology of the seafloor and shallow subbottom thus stores crucial information on sub-seafloor processes, such as permanent deformation by seismic slip or aseismic creep within the overriding plate and earthquake and tsunami generation. We have mapped the seafloor seaward of the Northern Chilean coast between about 19°S and 22°S down to the Northern Chile deep sea trench, using the ship-based Multibeam Echosounder EM122, Parasound, and AUV (autonomous underwater vehicle) – in selected subareas - at sufficient resolution to identify active tectonic fault structures and submarine mass wasting structures, to quantitatively assess young and active deformation of the overriding plate in the area, and quantify the extent of recent catastrophic downslope mass movements of sediment. Furthermore, the investigations serve as a site survey for the deployment of the GeoSEA seafloor geodetic array, to be installed immediately after completion of this cruise. The investigations were made timely by the 1st April 2014 Pisagua M=8.2 earthquake, that ruptured the plate interface in the northern part of the area of investigation. The central and southern parts are located in the last remaining locked seimotectonic segment along the Chilean active margin. In addition to providing the first data base for geomorphological and tectonic interpretation of geo-processes at the seafloor, the bathymetric mapping done during SO244 Leg 1 will provide an important data reference for possible post-earthquake surveys once this seismotectonic segment will have broken in the future.

Description: In the marine environment elevated electrical conductivities may be caused by sulfide mineralizations within the seafloor as well as hot saline pore fluids. Such conductive targets may be studied with suitable electromagnetic systems like the novel coil-system MARTEMIS1, which we previously used to investigate a known zone of sediment covered mineralization at the Palinuro Seamount (cruises POS483 & POS509) and in the vicinity of the TAG hydrothermal mound at the Mid Atlantic Ridge (cruise JC138). Both the Palinuro site as well as the sites in the vicinity of the TAG hydrothermal mound (Shinkai, Double Mound, MIR) are hydrothermally inactive and, thus, allowed to study, how the responses of an inductive EM system is influenced and shaped by mineralizations within the seafloor without having to consider the effect of of heated pore fluids. In the interpretation of the collected data at these inactive sites we learned that the MARTEMIS system is able to detect conductivity anomalies in the vicinity of mineralizations. (...)

Description: Absolule and relative values of brain weight are now available for 1174 species of fishes, representing 45 taxonomic orders. The original FishBase "Brains" data was assembled by the research team of Bauchot and colleagues, to which the present report adds data for species representing several additional major taxonomic groups. This database is part of the FíshBase 97 package which provides researchers with a tool to explore lhe functional meaning of absolute and relative brain size díversily, in comparison with phylogenetic position, life history mode, locomotion, habitat, and other behavioral parameters. Several results are provided as an example of the use of these data. Galeomorph sharks and batoid rays possess the largest brains among fishes. and elongate forms with anguilliform locomotion (e.g.. hagfishes. lampreys, lrue eels, carapids, zoarcids) possess the smallest relative brain sizes. Among teleost fishes, Osteoglossomorphs possess the largest relative brain sizes. Brain size correlations with oxygen consumption suggest that larger brains consume proportionately more oxygen, or that active fish with higher metabolic rates have larger brains