Search results for "Rite"
showing 10 items of 2726 documents
Mineralogy and chemistry of cobbles at Meridiani Planum, Mars, investigated by the Mars Exploration Rover Opportunity
2010
Numerous loose rocks with dimensions of a few centimeters to tens of centimeters and with no obvious physical relationship to outcrop rocks have been observed along the traverse of the Mars Exploration Rover Opportunity. To date, about a dozen of these rocks have been analyzed with Opportunity’s contact instruments, providing information about elemental chemistry (Alpha Particle X‐ray Spectrometer), iron mineralogy and oxidation states (Mossbauer Spectrometer) and texture (Microscopic Imager). These "cobbles" appear to be impact related, and three distinct groups can be identified on the basis of chemistry and mineralogy. The first group comprises bright fragments of the sulfate‐rich bedroc…
New insights into the mineralogy and weathering of the Meridiani Planum meteorite, Mars
2011
– Meridiani Planum is the first officially recognized meteorite find on the surface of Mars. It was discovered at and named after the landing site of the Mars Exploration Rover Opportunity. Based on its composition, it was classified as a IAB complex iron meteorite. Mossbauer spectra obtained by Opportunity are dominated by kamacite (α-Fe-Ni) and exhibit a small contribution of ferric oxide. Several small features in the spectra have been neglected to date. To shed more light on these features, five iron meteorite specimens were investigated as analogs to Meridiani Planum with a laboratory Mossbauer setup. Measurements were performed on (1) their metallic bulk, (2) troilite (FeS) inclusions…
Geochemical modeling of evaporation processes on Mars: Insight from the sedimentary record at Meridiani Planum
2005
New data returned from the Mars Exploration Rover (MER) mission have revealed abundant evaporites in the sedimentary record at Meridiani Planum. A working hypothesis for Meridiani evaporite formation involves the evaporation of fluids derived from the weathering of martian basalt and subsequent diagenesis. On Earth, evaporite formation in exclusively basaltic settings is rare. However, models of the evaporation of fluids derived from experimentally weathering synthetic martian basalt provide insight into possible formation mechanisms. The thermodynamic database assembled for this investigation includes both Fe2+ and Fe3+ in Pitzer's ion interaction equations to evaluate Fe redox disequilibr…
Provenance and diagenesis of the evaporite-bearing Burns formation, Meridiani Planum, Mars
2005
Abstract Impure reworked evaporitic sandstones, preserved on Meridiani Planum, Mars, are mixtures of roughly equal amounts of altered siliciclastic debris, of basaltic provenance (40 ± 10% by mass), and chemical constituents, dominated by evaporitic minerals (jarosite, Mg-, Ca-sulfates ± chlorides ± Fe-, Na-sulfates), hematite and possibly secondary silica (60 ± 10%). These chemical constituents and their relative abundances are not an equilibrium evaporite assemblage and to a substantial degree have been reworked by aeolian and subaqueous transport. Ultimately they formed by evaporation of acidic waters derived from interaction with olivine-bearing basalts and subsequent diagenetic alterat…
Origin of metazoan stem cell system in sponges: first approach to establish the model (Suberites domuncula).
2003
Abstract It is established that Porifera (sponges) represent the earliest phylum which branched off from the common ancestor of all multicellular animals, the Urmetazoa. In the present study, the hypothesis is tested if, during this transition, pluripotent stem cells were formed which are provided—similar to the totipotent cells (archaeocytes/germ cells)—with a self-renewal capacity. As a model system, primmorphs from the sponge Suberites domuncula were used. These 3D-cell aggregates were cultivated in medium (RPMI 1640/seawater) either lacking silicate and ferric iron or in medium which was supplemented with these ‘morphogenetic’ factors. As molecular markers for the potential existence of…
Solidification microstructure during selective laser melting of Ni based superalloy: experiment and mesoscopic modelling
2019
International audience; A set of single track laser melting experiments was performed in a selective laser melting (SLM). The tracks were done on an Inconel 718 plate with various laser scan velocities at a constant laser power of 150 W. The geometries of the molten pool (MP), as well as the solidified dendrite structures, i.e., primary and secondary dendrite arm spacing (PDAS and SDAS), in the cross sections of the molten path were characterized to evaluate the effect of the laser scan velocity during SLM. Moreover, the local solidification thermal conditions (cooling rate R*, tip growth velocity V* and temperature gradient G*) at the MP bottom were deduced from the SDAS and the geometries…
Geometric aspects of synkinematic granite intrusion into a ductile shear zone — an example from the Yunmengshan core complex, northern China
2005
The Cretaceous Yungmengshan core complex in northern China contains a large syntectonic granodiorite batholith that intrudes a slightly older diorite intrusion. A major gently dipping ductile decollement shear zone is developed along the contact of the diorite and granodiorite. The shear zone is invaded by a large volume of granitic and pegmatite veins associated with the main granodiorite batholith during activity of the shear zone under high-grade metamorphic conditions. Progressively older veins are more strongly deformed into tight cylindrical fold structures rotated into parallelism with the lineation and foliation in the shear zone. Parallelism of veins to the foliation is partly due …
A Dutch contribution to early interpretations of Meteor Crater, Arizona, USA – Marten Edsge Mulder’s ignored 1911 paper
2018
Abstract Following the first scientific descriptions in the late nineteenth century, the origin of the curious structure currently known as Meteor Crater (or Barringer Crater) in Arizona (USA) remained controversial until well into the twentieth century. Within the context of commercial mining, Daniel Moreau Barringer’s view that it recorded a substratum-penetrative meteorite impact (with the cosmic body still preserved) was commonly discarded. Marten Edsge Mulder (1847–1928), Dutch professor of medicine, found fault with Barringer’s non-explosive model. In 1911, Mulder advanced, in an ignored paper written in Dutch, a novel model of an explosive meteorite (‘meteor’ in Mulder’s terminology)…
Boundary Issues in New Metropolitan Cities
2012
In the last decade, the focus of Italian politics aimed at the definition of metropolitan cities and independent associations of municipalities has become increasingly important. With regard to legislation, the issue has been considered since the 1990s, but despite several debates and legislative reforms there have been no real results. The only approach used was political-institutional, anchored in obsolete patterns and unable to deal with existing realities.Urban Planning and Urban Studies materialize the political choices in operational programs and control the evolution of urban and territorial transformations. These disciplines represent the starting point to reflect upon the process o…
Effect of triterpenoids on the inflammation induced by protein kinase C activators, neuronally acting irritants and other agents.
2000
In order to establish the mode of the anti-inflammatory activity of triterpenoids, 11 naturally occurring compounds were assayed on mouse ear oedema induced by the protein kinase C activators, mezerein, 12-O-tetradecanoylphorbol-13-acetate (TPA), two 12-deoxyphorbol-13-monoesters (13-tetradecanoate (DPT) and 13-phenylacetate (DPP)) and bryostatin 1, and by resiniferatoxin, xylene and arachidonic acid. The effects on bradykinin-induced paw oedema and on the rat skin inflammation caused by hydrogen peroxide were also examined. The oedema induced by mezerein and DPT was reduced to different extents by the triterpenoids administered epicutaneously (0.5 mg per ear). Against DPT-induced oedema, l…