Characterization of goethites from surficial environments of Galicia and estimates of the substitution of Fe by Al

[Resumen] Se examinan cincuenta muestras ricas en goetita y de morfología y génesis variada (placas en sedimentos, suelos ricos en sesquióxidos, costras y menas de Fe), caracterizando su mineralogía y composición química por medio de diversas técnicas instrumentales y extractantes selectivas. Se estima el grado de sustitución isomorfa de Fe por Al mediante análisis químico y por el desplazamiento de las líneas de difracción de RX de la goetita. Por ambos métodos se obtienen resultados similares, dando porcentajes de sustitución que no sobrepasan en general el 15 O/o molar, lo que se considera un bajo grado de reemplazamiento y se explica en función de las condiciones de formación de estas concentraciones de hierro.[Abstract] Fifty samples with high goethite contents, differing in their morphology and formed in diverse environments are examined. They include ironpans, crusts, soils high in sesquioxides and iron ores. Several instrumental techniques are used for their mineralogical characterization, together with selective extractants of cristaBine and amorphous iron. The extent of the isomorphus replacement ofFe by Al in goethite is estimated by chemical analyses and by the shift ofXRD diffraction línes. Both methods give similar results, showing porcentages of substitution that not exceed in general 15 mole O/o. This can be considered a low degree of replacement and is discussed in sight of the formatíon conditions of these iron accumulations

Distribution and Origin of Iron Oxides in Soils over Limestone

[Resumen] Se pretende conocer la distribuci6n y el origen de los compuestos de hierro en suelos formados sobre calizas en Galicia. Predominan las formas minerales de hierro, encontrando en la fracción arena magnetita, goethita y/o hematites y excepcionalmente ilmenita, que se consideran heredadas del material de partida. En lámina delgada se observaron goethita y hematites como granos aislados, constituyendo nódulos e integrados en fragmentos de caliza. En la arcilla, trazas de goethita están presentes en casi todos los perfiles; s610 en uno de ellos la hematites es el único 6xido de hierro. La goethita puede haberse formado tanto por neoformaci6n como por microdivisi6n a partir de las fracciones gruesas, siendo este último fen6meno el que ha originado la hematites de la fracci6n arcilla. En dos perfiles la goethita va acompañada de magnetita y se discute la posible existencía y formaci6n de maghemita.[Abstract] Iron distribution in soils formed over limestone of Galicia is studied an the origin of the different iron forms is established. Organic iron is very scarce and mineral iron components dominate. Magnetite, goethite and / or hematite, less cornmonly ilmenite, are found in the sand fraction; they are considered as interited from the parent material. In polished sections goethite an hematite appear as single grains, nodules and il1corporated into limestone fragments. In the clay fraction, traces of goethite are present in aH except one of the profiles where only traces of hematite are indentified. Neoformation and microdivision from coarse fractions can act in the genesis of goethite; only microdivision is considered as the origin of hematite. Magnetite accompanies goethite in two profiles; the possible presence of maghemite and its origin is also discusse

Aplicación de la exoscopia del cuarzo a la caracterización de diversos ambientes en Galicia

[Abstract] Only one of the studied pegmatites shows a symmetrical-zoned structure: a border zone wi th spodumene and a central zone wi th lepidolite. In the other pegmatites there not zoned structures but rather a centimetric bedding of whi te and pink zones (albite and lfpidolite). All sam plesare mineralized in Tin (about 200-1000 ppm) and Tantalum (40-70 ppmT. The geochemical study shows significant contents of Ba, Y, Zr, Rb and Cs. There is also infil tration of Li, Rb, Cs and Sn in the wall-rocks. The study of polymorphism and composi tion of the Li-micas shows the existence of two internaly, intergrown, distintic structures (1M and 2M ): The first one is Li-rich (lepidoli te) and the second is poor in Li (Li-1 -muscovite). It is shown a genetical hypothesis and a evolutionary diagram of the micas formation[Résumé] Par les microformes superficielles des arenes de quartz on peut reconstruire les caracteristiques chimiques , mechaniques et biologiques des ambiances oú elles ont evolué. Au moyen de la technique d' Exoscopie des Quartz, qui permet l'observation, au microscope electronique de balayage, de la morphologie superficielle des grains de ce mineral,on éxamine des quartz provenant de diverssoIs et sédiments de la Galice,en identifiant les caracteres phénomorphiques correspondantes a chacun de cesambiances. - Cette techique se montra particulierement utile a la reconnaissance des horizons Edaphiques aloctones et a l'interprétation de l'histoire géologique des sédiment

Estudio sedimentológico de un depósito arenoso de la rasa cantábrica: aplicación de la exoscopia del cuarzo

[Resumen] Mediante la técnica de Exoscopía del Cuarzo se estudia un sedimento arenoso de la Rasa Cantábrica, en las proximidades de S.Miguel de Reinante (Lugo), contrastando los resultados de este estudio con los obtenidos por las metodologías clásicas de granulometría y morfoscopía. De la aplicación conjunta de estas técnicas se puede deducir que aún siendo las arenas depositadas en un mismo episodio final de sedimentación, cuya naturaleza se discute, tienen orígenes diversos cuya evolución intenta reconstruirse con ayuda de la técnica de Exoscopia del Cuarzo.[Résumé] Al' aide de la technique d' Exoscopie des Quartz on étude un sédiment sableux de la "Rasa Cantabrica" aux environs de S.Miguel de Reinante (Lugo). Les résultats de cet étude sont confrontés avec ceux issus des méthodes clasiques de granulometrie et morphoscopie. L'application conjointe de ces techniques permet déduire que, bien que déposées dans une meme épisode finale de sédimentation, dont la nature se discute, les s~bles de ce dépot ont des origines diverses dont l' evolution on tente de reconstruire par l'Exoscopie des Quart

Non-uniqueness of ergodic measures with full Hausdorff dimension on a Gatzouras-Lalley carpet

In this note, we show that on certain Gatzouras-Lalley carpet, there exist more than one ergodic measures with full Hausdorff dimension. This gives a negative answer to a conjecture of Gatzouras and Peres

Detritic deposits of periglacial origin under coluvial organic soil on a slope in Serra da Loba. (Galicia. Spain): characterization and genesis

[Resumen] En ciertas posiciones de las partes media e inferior de la ladera aparece bajo el suelo orgánico un material detrítico muy fragmentado y ordenado en lechos estratificados. Se estudian dos perfiles con estas características, se canografía su extensión en la ladera, y se interpreta su génesis. Estos derrubios tienen poca fracci6n fina entre ellos, son bastante frescos, yaparecen ordenados según la pendiente y dispuestos en lechos en los que se alternan fragmentos de pequeño tamaño con otros más gruesos con más escaso contenido en fracción fina. Los estudios morfológicos y granulométricos revelan claras discontinuidades en los perfiles, así como una baja clasificaci6n de este material detrítico. La composición mineralógica es menos reveladora por su escasa evolución, prácticamente la heredada del material de partida, con predominio de minerales poco alterables. Se hace una correspondencia estratigráfica de episodios de deposici6n en ambos perfiles y se interpreta el origen de este material detrítico como ligado al accionamiento periglaciar. La localizaci6n en la ladera de estos depósitos y su potencia están relacionados con el menor espesor de las líneas de piedras, indicativas de procesos de erosión posterior. Sin embargo estos depósitos están ausentes en las partes más bajas de la ladera que, en cambio, muestran ser las más propicias a la deposición, ya que presentan un mayor engrosamiento de los horizontes orgánicos de acumulaci6n y en ellas no aparecen indicios erosivos. Esta ausencia se interpreta por ser también estas zonas, bajas y abrigadas, las que podrían ser más favorables a una mayor cobertura vegetal en las condiciones periglaciares, que impediría la deposición de los derrubios.[Abstract] Stratified beds of highly fragmented detritic material under organic soil occur on medium and low parts ofthe slope. Two profiles with these features are studied, their extent on the slope is mapped and their genesis interpreted. Debris are quite fresh, with little fine fraction between them; they are arranged according to the slope and consist of alternating beds of little size fragments and others coarser and poor in fine fraction. Morphological and granulometric studies reveal clear discontinuities in the profiles and a poor soning of the detritic Ínaterials. Mineralogical composition is less meaningful because of its little evolution, almost inherited from parent material, with a predominance of hardly weatherable minerals. A stratigraphic correspondence is established of deposition episodes between both profiles, and the origin of the detritic material is related to periglacial dynamics. The position of these deposits on the slope and their thickness are inversely related to the thickness of stonelines which are indicative of subsequent erosive processes. Detritic deposits are absent in the lowest part of the slope, which on the other hand appear to be the most favourable to deposition as showed by the greatest thickness of organic horizons of accumulation, and the no occurrence of erosive signs. This absence is' interpreted as being caused by the presence of a more extensive vegetal cover, under periglacial conditions, in the lowest and more protected slope, so preventing debris deposition

Balance of IL-10 and Interferon-γ plasma levels in human visceral leishmaniasis: Implications in the pathogenesis

BACKGROUND: Leishmaniasis remains a serious public health problem in several parts of the developing world. Effective prophylactic measurements are hampered by imprecise comprehension of different aspects of the disease, including its immunoregulation. A better comprehension of immunoregulation in human VL may be useful both for designing and evaluating immunoprophylaxis. METHODS: To explore immunoregulatory mechanisms, 20 visceral leishmaniasis (VL) patients were evaluated during active disease and at different periods up to one year after treatment determining their plasma cytokine levels, clinical parameters (palpable spleen and liver) and antibody levels. RESULTS: Elevated plasma levels of IFN-γ and of IL-12 p40 were observed during active disease, significantly decreasing after treatment whereas in vitro Leishmania antigen-stimulated IFN-γ production by PBMC exhibited an inverse pattern being low during disease and increasing steadily thereafter. Absence of IFN-γ activity is a hallmark of VL. The main candidate for blunting IFN-γ activity is IL-10, a cytokine highly elevated in plasma with sharp decrease after treatment. Activity of IL-10 is inferred by high levels of anti-Leishmania specific IgG1 and IgG3. TGF-β had elevated total, but not of active, levels lessening the likelihood of being the IFN-γ counterpart. Spleen or liver size presented a steady decrease but return to normal values at only 120 days after treatment. Anti-Leishmania IgG (total and subclasses) levels and DTH or Leishmania-stimulated lymphocyte proliferation conversion to positive also present a slow decrease after treatment. IL-6 plasma levels were elevated in only a few patients. CONCLUSION: Taken together our results suggest that IFN-γ and IL-10 are the molecules most likely involved in determining fate of disease. After treatment, there is a long delay before the immune profile returns to normal what precludes using plasma cytokine levels as criteria of cure as simpler clinical evaluations, as a palpable spleen or liver, can be used

Wavelets techniques for pointwise anti-Holderian irregularity

In this paper, we introduce a notion of weak pointwise Holder regularity, starting from the de nition of the pointwise anti-Holder irregularity. Using this concept, a weak spectrum of singularities can be de ned as for the usual pointwise Holder regularity. We build a class of wavelet series satisfying the multifractal formalism and thus show the optimality of the upper bound. We also show that the weak spectrum of singularities is disconnected from the casual one (denoted here strong spectrum of singularities) by exhibiting a multifractal function made of Davenport series whose weak spectrum di ers from the strong one

Three-dimensional CFD simulations with large displacement of the geometries using a connectivity-change moving mesh approach

This paper deals with three-dimensional (3D) numerical simulations involving 3D moving geometries with large displacements on unstructured meshes. Such simulations are of great value to industry, but remain very time-consuming. A robust moving mesh algorithm coupling an elasticity-like mesh deformation solution and mesh optimizations was proposed in previous works, which removes the need for global remeshing when performing large displacements. The optimizations, and in particular generalized edge/face swapping, preserve the initial quality of the mesh throughout the simulation. We propose to integrate an Arbitrary Lagrangian Eulerian compressible flow solver into this process to demonstrate its capabilities in a full CFD computation context. This solver relies on a local enforcement of the discrete geometric conservation law to preserve the order of accuracy of the time integration. The displacement of the geometries is either imposed, or driven by fluid–structure interaction (FSI). In the latter case, the six degrees of freedom approach for rigid bodies is considered. Finally, several 3D imposed-motion and FSI examples are given to validate the proposed approach, both in academic and industrial configurations