993 resultados para Placer deposits
Resumo:
Seamounts, submarine banks, volcanoes and undercurrent channels are prominent geomorphic features that have become an important target for minerals research and exploration with the goal of future exploitation. Polymetallic ferromanganese deposits are common types of mineralization on these settings. Co-rich ferromanganese crusts are important as potential resources of Mn and Co, but also Ti, Ni, Tl, REEs, PGEs, and other metals. Many seamounts and channels along the Atlantic Spanish continental margin are known to hold mineral deposits but are poorly studied. This work presents and briefly describes the most recent activities of the Spanish Geological Survey (IGME) on exploration and investigation of ferromanganese deposits along the Atlantic Spanish continental margin. Different submarine areas from the northwestern margin of the Iberian Peninsula to the west off Canary Islands have been surveyed by geophysical, sampling and underwater observations from 89 to 4000 m water depth. The mineral deposits cover a large diversity of submarine geological and geomorphical features: mud volcanoes and diapirs related to hydrocarbon seeps, seamounts associated with hot spot volcanism, hydrothermal vents in active magmatic volcanoes, structural basement highs and banks or contourite channels. Considering the collected dataset, we present the preliminary results of the study of these mineral deposits, including ferromanganese nodules and crusts and phosphate pavements and nodules, which can be considered as potential sources of raw materials.
Resumo:
Megalin (gp330), an epithelial endocytic receptor, is a major target antigen of Heymann nephritis (HN), an autoimmune disease in rats. To elucidate the mechanisms of HN, we have mapped a pathogenic epitope in megalin that binds anti-megalin antibodies. We focused our attention on four clusters of cysteine-rich, low density lipoprotein receptor (LDLR) ligand binding repeats in the extracellular domain of megalin because they represent putative ligand binding regions and therefore would be expected to be exposed in vivo and to be able to bind circulating antibodies. Rat megalin cDNA fragments I through IV encoding the first through fourth clusters of ligand-binding repeats, respectively, were expressed in a baculovirus system. All four expression products were detected by immunoblotting with two antisera capable of inducing passive HN (pHN). When antibodies eluted from glomeruli of rats with pHN were used for immunoblotting, only the expression product encoded by fragment II was detected. This indicates that the second cluster of LDLR ligand binding repeats is directly involved in binding anti-megalin antibodies and in the induction of pHN. To narrow the major epitope in this domain, fragment II was used to prepare proteins sequentially truncated from the C- and N-terminal ends by in vitro translation. Analysis of the truncated translation products by immunoprecipitation with anti-megalin IgG revealed that the fifth ligand-binding repeat (amino acids 1160-1205) contains the major epitope recognized. This suggests that a 46-amino acid sequence in the second cluster of LDLR ligand binding repeats contains a major pathogenic epitope that plays a key role in pHN. Identification of this epitope will facilitate studies on the pathogenesis of HN.
Resumo:
La tesis tiene por objeto el estudio de los usos y funciones que tuvo el palacio del Buen Retiro durante los siglos XVII y XVIII, y cuál fue el proceso de formación, disposición y dispersión de las colecciones de obras de arte que alhajaban sus estancias, y en especial de las pinturas. Para llevarlo a cabo, hemos revisado la amplia bibliografía disponible, y consultado numerosas fuentes relativas al real sitio, a los artistas que trabajaron en él o realizaron obras que formaron parte de su decoración, y a la visión que tuvieron del Retiro los representantes diplomáticos y los viajeros a lo largo de los siglos XVII y XVIII. De este modo, hemos creado un sólido corpus documental que nos ha permitido reconstruir la serie de inventarios que se realizaron de las obras de arte que decoraban el Retiro, y también fechar las distintas marcas que fueron recibiendo las pinturas. La combinación de ambos datos ha resultado ser de enorme importancia para poder individualizar los principales espacios del palacio, los programas decorativos que albergó, y localizar con ciertas garantías buena parte de las obras de arte pertenecientes al Retiro. El amplio capítulo dedicado al siglo XVII, indispensable para poder comprender qué usos tenía el real sitio y verificar cuáles fueron los cambios que experimentó la colección a lo largo del siglo XVIII, ha permitido comprobar y documentar cómo, con la decisión de ampliar el cuarto real de San Jerónimo en 1632, se puso en marcha uno de los proyectos más interesantes de la historia del coleccionismo europeo del siglo XVII. Gracias a distintos documentos inéditos hemos podido precisar cómo y cuándo se produjeron los encargos destinados a alhajar el palacio, entre los que destacan las series de pinturas de paisajes con eremitas, la de escenas de la Antigua Roma, y la de san Juan Bautista...
Resumo:
Bacteria are able to induce carbonate precipitation although the participation of microbial or chemical processes in speleothem formation remains a matter of debate. In this study, the origin of carbonate depositions such as moonmilk, an unconsolidated microcrystalline formation with high water content, and the consolidation of carbonate precipitates into hard speleothems were analyzed. The utilized methods included measurements of the composition of stable isotopes in these precipitates, fluorimetric determinations of RNA/DNA ratios and respirometric estimations in Altamira Cave. Results from isotope composition showed increases of the δ18O and δ13C ratios from moonmilk in the very first stages of formation toward large speleothems. Estimates of RNA/DNA ratios suggested an inactivation of microorganisms from incipient moonmilk toward consolidated deposits of calcium carbonate. Respiratory activity of microorganisms also showed a significant decrease in samples with accumulated calcite. These results suggest that bacterial activity induces the conditions required for calcium carbonate precipitation, initiating the first stages of deposition. Progressive accumulation of carbonate leads towards a less favorable environment for the development of bacteria. On consolidated speleothems, the importance of bacteria in carbonate deposition decreases and chemical processes gain importance in the deposition of carbonates.
Resumo:
v.6:no.2 (1878)
Resumo:
Aristóteles afirma en la Ética a Nicómaco que el placer acompaña a la actividad perfecta, haciéndola más deseable, y que la actividad contemplativa es la más divina y placentera. Por otro lado, en la Metafísica dice que la actividad de Dios es sumo placer, porque su actividad es perfecta. En este artículo trato de estudiar la conexión entre placer y actividad en la contemplación y su relación con la actividad de Dios, para poder entender el agrado intelectual: ¿es posible hablar de un placer “espiritual”? ¿Hay sensaciones desligadas de los órganos materiales?
Resumo:
The cores described in this report were taken on AMPHITRITE Expedition in Decenber 1963 - February 1964 by Scripps Institution of Oceanography from, the R/V Argo. A total of 148 cores were recovered and are available at Scripps for sampling and study. The coring sites, all in the tropical central Pacific. The AMPHITRITE cores are here briefly described to identify visually distinct units based on lithology, color, texture, or other characteristic unique to an interval of sediment. For determination of lithology, the slides prepared from samples of the cores were examined microscopically in conjuction with the visual examination.
Resumo:
A sediment core obtained from the northeastern Philippine Sea Basin was analyzed for 232Th, 230Th, 226Ra and 210Pb. Three sheets of Ferro-manganese oxide in a matrix of red clay were included in the 73 m core. Although the concentration of 232Th of land origin is normal as compared with that of the usual red clay or of the sediment obtained at the neighboring station, the concentration of radiogenic 230Th is extremely low and does not decrease with increasing depth. The radioactivity of rather soluble 226Ra at the station is not less than that of 230Th in the surface sediment, showing a tendency different from that observed in usual cores. Some enrichment in the comparatively short-lived 210Pb activity relative to 226Ra activity was found in the top sediment and in the first ferro-manganese sheet at the station. If the excess 210Pb in the ferro-manganese sheet is not due to contamination of the surface sediment, lead should migrate through the sheet. These facts suggest that the core has not been accumulating during the past few hundred thousand years or more.
Resumo:
In this volume, Agassiz gives a detailed account of the results of the cruise the steamer "Amra" chartered from the British India Steam Navigation Company. The cruise covered the attols of the Maldives archipelago. The deep sea formations are described in detail.
Resumo:
The Danish Expedition of the "Galathea II" around the world brought important results concerning the marine organisms in the deep sea. The "Galathea II" showed not only different organisms of the Abyssal but for the first time of the deepest trenches of the western Pacific. Anton Bruun coined the term Hadal for the region below the Abyssal under 6000 m. Although the "Galathea II" aimed to investigate new deep sea regions beside the routes of former expeditions and to widen the horizon of knowledge relating marine organisms the technical equipment and the methodological approach had partly been developed earlier. The expedition of the "Galathea II" is part of a long tradition of cruises such as that of the British "Challenger", the German "Valdivia" and the Swedish "Albatross" and especially the Danish cruises of the "Dana I" and "Dana II" which happened some years before.
Resumo:
The McMurdo Dry Valleys, Antarctica (MDV) are among the oldest landscapes on Earth, and some landforms there present an intriguing apparent contradiction such that millions of years old surface deposits maintain their meter-scale morphology despite the fact that measured erosion rates are 0.1-4 m/Ma. We analyzed the concentration of cosmic ray-produced 10Be and 26Al in quartz sands from regolith directly above and below two well-documented ash deposits in the MDV, the Arena Valley ash (40Ar/39Ar age of 4.33 Ma) and the Hart ash (K-Ar age of 3.9 Ma). Measured concentrations of 10Be and 26Al are significantly less than expected given the age of the in situ air fall ashes and are best interpreted as reflecting the degradation rate of the overlying sediments. The erosion rate of the material above the Arena Valley ash that best explains the observed isotope profiles is 3.5 ± 0.41 x 10**-5 g/cm**2/yr (~0.19 m/Ma) for the past ~4 Ma. For the Hart ash, the erosion rate is 4.8 ± 0.21 x 10**-4 g/cm**2/yr (~2.6 m/Ma) for the past ~1 Ma. The concentration profiles do not show signs of mixing, creep, or deflation caused by sublimation of ground ice. These results indicate that the slow, steady lowering of the surface without vertical mixing may allow landforms to maintain their meter-scale morphology even though they are actively eroding.
Resumo:
The cores and dredges described in this report were taken on the DODO Expedition in May 1964 until December 1964 by the Scripps Institution of Oceanography from the R/V Argo. A total of 290 cores and dredges were recovered and are available at Scripps for sampling and study.