1,453 research outputs found
Recent sediments of the Eume river: mineralogical and textural composition
[Resumen] Se analiza la granulometría, textura y mineralogía de sedimentos recogidos en los fondos de la ría de Ares, estuario y tramo final del río Eume. Texturalmente, las muestras se agrupan en francolimosas o francoarenosas y su distribución está defmida según las características dinámicas de la ría y las modificaciones realizadas por las obras de infraestructura. La mineralogía de la fracción arcilla es muy homogénea, con caolinita y filosilicatos 2: 1 dominantes, junto con pequeñas antidades de cuarzo y feldespato. El contenido en carbonatos es bajo, siempre menor del 30 %, destacando los porcentajes encontrados en el sondeo de la cola del embalse del Eume, de origen claramente antrópico. Textura y mineralogía son coherentes con el marco geológico del que proceden, excepto en la presencia de carbonatos y exceso de partículas finas con caolinita cristalina existentes en la cola del embalse del Eume. La distribución de las partículas, según su tamaño, obedece fundamentalmente a causas naturales, pero existen imponantes modificaciones relacionadas con el papel de barrera del embalse y las obras de infraestructura que han alterado la circulaci6n original en algunas zonas del estuario y desembocadura.[Abstract] A textural and mineralogical analysis is made to sediments sampled at the bottom of the Ría de Ares, estuarine and Eume river. Clay mineralogy is very similar for all the samples and consists of kaolinite and 2: 1 phyllosilicates with small amounts of quartz and fe'ldspar. The percentage of carbonates is small, always less than 30 o/o. There should be pointed out the values found in the Eume reservoir core, with a clear antropic origino Texture and mineralogy are coherent with the geology of the basin they come from, excepting the carbonates and fine particle excess with cristaline caolinite in the Eume reservoir core. Size grain distribution is due to the dinamic characteristics of the ría, but there are important rnodifications related to the reservoir, that acts as a barrier, and the constructions in the lower part of the river that have changed the original circulation in sorne areas of the ría
Meteorización de las granulitas de Cabo Ortegal
[Resumen] Se realiza el estudio químico y mineralógico del proceso de alteración, en medios sustractivos, de las granuli tas de Cabo Ortegal, la precipi tación media anual supera los 1.300 mm. y las temperaturas medias mensuales extremas son 23ºC y 4,7ºC. Durante el proceso de meteorizaciór se origina una fuerte pérdida de Ca, Na y Mg y,en menor proporción, de Si con acumulación relativa de Fe y Al. Como productos de alteración aparecen filosilicatos 1:1 dioctaédricos, gibbsita, oxihidróxidos de hierro y micas y cloritas degradadas. La edafogénesis es de tipo fermonosialítico con una tendencia ferralítica, al menos en sus fases iniciales.[Abstract] This paper is a chemical and mineralogical study about the weathering process, in subtr&ctive environments, of the granul i tes in Cabo Ortegal. The mean annual precipitation is over 1.300 mm. and the mean monthly extreme temperatures are 23ºC and 4,7ºC . In the process of weathering there is an intense 10S8 of Ca, Na and Mg and, in a minar level , of Si, with a relative accumulation of Fe and Al. Proqucts of the weathering are 1: 1 dioctahedral phyllosilicates, gibbsi teiron oxyhydroxides and degraded micas and chlorites. The pedogenesis is of fermonosialli tic type wi th a ferrallitic tendence, in the first phases at least
Mineralogía de la fracción arcilla de suelos y sedimentos de la Cuenca de Maceda
[Resumen] Se estudia la mineralogía de la fracción arcilla de los sedimentos terciarios y cuaternarios que rellenan la depresión de Maceda,así como de las rocas que constituyen el marco y sus productos de alteración. Las rocas que rodean la cuenca están sometidas actual mente a un proceso de alteración de tipo hidrólisis ácida (caolinita, gibbsita y oxihidróxidos de hierro son los productos de alteración más significativos) Los sedimentos terciarios presentan en su fracción arcilla un filosilicato 1:1 dioctaédrico(haloisítico o caolinítico) como mineral más ahlndante, micas, micas degradadas, goethita y, ocasionalmente, hematita,observándose la presencia de vermiculitas de baja carga en las capas mas profundas. Los depósitos más recientes contienen abundante filo silicato 1:1 dioctaédrico de bajo grado de orden y gibbsita, micas degradadas en cantidades variables y goethita.[Abstract] The igneous and metamorphic rocks that surround the Maceda depressian are subjected to a weathering of acidic hydrolysis type (kaol inite, gibbsite and Fe-oxihydroxides are the more repl'esenta"LJ.ve weathering products). The tertiary sediments have as principal component a 1:1 diocthaedral phyllosilicate (halloysite or kaolini te) associated wi th micas, degradated micas, goethita-:occasionally hematite and in the deepest layers, low charge vermiculites • - The newest deposits have disordered 1:1 diocthaedral phyllosilicate and gibbsite, changing proportions of degradated micas and goethit
Volume elements of spacetime and a quartet of scalar fields
Starting with a `bare' 4-dimensional differential manifold as a model of
spacetime, we discuss the options one has for defining a volume element which
can be used for physical theories. We show that one has to prescribe a scalar
density \sigma. Whereas conventionally \sqrt{|\det g_{ij}|} is used for that
purpose, with g_{ij} as the components of the metric, we point out other
possibilities, namely \sigma as a `dilaton' field or as a derived quantity from
either a linear connection or a quartet of scalar fields, as suggested by
Guendelman and Kaganovich.Comment: 7 pages RevTEX, submitted to Phys. Rev.
Influence of geological material and about content of heavy metals in superficial horizons of L:1 Coruñ:1 soils
[Resumen] Los contenidos totales de Cr, Ni, Cu, Zn, Pb, Co y Mn en horizontes superficiales de suelos desarrollados sobre diferentes materiales geológicos de la provincia de La Coruña, ponen de manifiesto la importancia del factor litológico respecto a los aportes de origen antrópico. Los suelos sobre rocas ultramáficas y máficas muestran contenidos de Cr, Ni YCu que superan en muchas ocasiones los umbrales considerados de fitotoxicidad por diferentes autores. Le siguen los esquistos
ricos en biotita, mientras que sobre granitos y pizarras se obtienen los valores medios más bajos. Los resultados obtenidos permiten realizar una primera aproximación acerca de la «aptitud» de los suelos de cultivo como receptores de lodos residuales..[Abstract] The total contents of Cr, Ni, Cu, Zn, Pb, Co and Mn in superficial horizons of soils that are developed on different geological materials of La Coruña region (Spain), reveal the importance of the lithologic factor with respect to the contribution of anthropic. origino The soils on ultramafic and mafic rocks show contents of Cr, Ni and Cu that are many times higher than threshold considered phytotoxic by different authors. These are followed by the schists, rich in biotite, while the lowest average values are obtained on granites and slates. The obtained results allow a first approach about the «attitude» of the cultivable soils as receptore of waste sludge
NIKEL_AMC: Readout electronics for the NIKA2 experiment
The New Iram Kid Arrays-2 (NIKA2) instrument has recently been installed at
the IRAM 30 m telescope. NIKA2 is a state-of-art instrument dedicated to
mm-wave astronomy using microwave kinetic inductance detectors (KID) as
sensors. The three arrays installed in the camera, two at 1.25 mm and one at
2.05 mm, feature a total of 3300 KIDs. To instrument these large array of
detectors, a specifically designed electronics, composed of 20 readout boards
and hosted in three microTCA crates, has been developed. The implemented
solution and the achieved performances are presented in this paper. We find
that multiplexing factors of up to 400 detectors per board can be achieved with
homogeneous performance across boards in real observing conditions, and a
factor of more than 3 decrease in volume with respect to previous generations.Comment: 21 pages; 16 figure
Hemiquantal treatment of low energy p+H2 collisions
We present calculations of charge exchange and vibrational excitation cross sections in low energy p+H2 collisions. These cross sections are obtained by means of an hemiquantal treatment which uses Diatomics In Molecules (DIM) diabatic wavefunctions of the H3+ molecule. The hemiquantal approach allows to distinguish the nonreactive, dissociative and nuclear exchange contributions to the electronic reaction path
Submillimetre point sources from the Archeops experiment: Very Cold Clumps in the Galactic Plane
Archeops is a balloon-borne experiment, mainly designed to measure the Cosmic
Microwave Background (CMB) temperature anisotropies at high angular resolution
(~ 12 arcminutes). By-products of the mission are shallow sensitivity maps over
a large fraction of the sky (about 30 %) in the millimetre and submillimetre
range at 143, 217, 353 and 545 GHz. From these maps, we produce a catalog of
bright submillimetre point sources. We present in this paper the processing and
analysis of the Archeops point sources. Redundancy across detectors is the key
factor allowing to sort out glitches from genuine point sources in the 20
independent maps. We look at the properties of the most reliable point sources,
totalling 304. Fluxes range from 1 to 10,000 Jy (at the frequencies covering
143 to 545 GHz). All sources are either planets (2) or of galactic origin.
Longitude range is from 75 to 198 degrees. Some of the sources are associated
with well-known Lynds Nebulae and HII compact regions in the galactic plane. A
large fraction of the sources have an IRAS counterpart. Except for Jupiter,
Saturn, the Crab and Cas A, all sources show a dust-emission-like modified
blackbody emission spectrum. Temperatures cover a range from 7 to 27 K. For the
coldest sources (T<10 K), a steep nu^beta emissivity law is found with a
surprising beta ~ 3 to 4. An inverse relationship between T and beta is
observed. The number density of sources at 353 GHz with flux brighter than 100
Jy is of the order of 1 per degree of Galactic longitude. These sources will
provide a strong check for the calibration of the Planck HFI focal plane
geometry as a complement to planets. These very cold sources observed by
Archeops should be prime targets for mapping observations by the Akari and
Herschel space missions and ground--based observatories.Comment: Version matching the published article (English improved). Published
in Astron. Astrophys, 21 pages, 13 figures, 4 tables Full article (with
complete tables) can be retrieved at
http://www.archeops.org/Archeops_Publicatio
- …