1,158 research outputs found
Turbiditas carbonatadas del Cretácico inferior en el Arroyo Bercho, Prebético de Jaén: Interpretación genética e implicaciones paleogeográficas
[ES] El análisis de las características sedimentarias de las turbiditas
carbonatadas permite precisar la interpretación paleogeográfica del
Prebético de Jaén, durante el Cretácico. Se pueden distinguir dos
asociaciones de facies: a) Turbiditas de estatificación fina, intercaladas
en abundante sedimento pelágico, e interpretadas como facies
de borde de lóbulo. b) Cuerpos turbidíticos lenticulares interpretados
como lóbulos de depósito formados por agradación. Aparecen
asociadas a una serie depositada en una cuenca que progresivamente
se fue haciendo más somera y que terminó con la implantación de
una plataforma carbonatada en el Cenomanense. Se calcula que el
depósito de las turbidítas debió realizarse a unos pocos centenares
de metros de profundidad.[EN] The analysis of the sedimentary characteristics of the carbonate
turbidites allows to accurate the paleogeographic interpretation of
the Prebetie of laen. Two types of facies associations can be distinguished: a) Thin bedded turbidites> as intercalations into mainly hemipelapic
sediments, interpreted as lobe fringe facies, b) Lents like
turbiditie bodies corresponding to agradational depositional lobes.
They occur associated to an shallowing upward sequence ending
with Cenomanian carbonated platform facies. The turbiditic deposit
supodselly took place in a few hundreds meters deep sedimentary
basin.Trabajo patrocinado por la C.A.I.C.Y.T.,
dentro del proyecto «El Mesozoico de las Cordilleras Béticas» realizado
en este centro del C.S.I.C.Peer reviewe
Desarrollo de Materiales para Aplicaciones Marítimas, Fluviales y Militares
A platform to design composite materials of a polymeric matrix, that are specifically for military applications on fluvial and naval navigation, has been developed using energy dissipation and storage mechanisms. Our composites are designed to generate synergy between the dissipation capacities of ceramics and high-performance fibers, which are used as the reinforced material in the lightweight laminates. The composite design is combined with processing tools and advanced characterization techniques that result in laminates with reliability, traceability and quality. The platform begins with the identification of energy dissipation mechanisms and the detailed characterization of the polymeric resin. It includes the Time – Temperature – Transformation Diagram (TTT- Diagram) that supplies the optimal processing conditions. Our designs open new paths for military applications including a wide spectrum of protective systems together with geometric versatility, high mechanical resistance and reliabilityUtilizando los múltiples mecanismos de disipación de la energía de impacto a alta velocidad, hemos desarrollado una plataforma de diseño de materiales compuestos de matriz polimérica, especiales para aplicaciones militares en navegación fluvial y marítima. Nuestros compuestos pretenden hacer sinergia entre las capacidades de disipación de cerámicos y fibras de alto desempeño, los cuales son utilizados como los elementos de refuerzo en los laminados de bajo peso. El diseño del material es combinado con herramientas de procesamiento y técnicas avanzadas de caracterización que resultan en laminados consistentes de alta repetibilidad, trazabilidad y alta calidad. La plataforma parte de la identificación de los mecanismos de disipación y de una caracterización detallada de la resina polimérica, el cual incluye un diagrama de Tiempo-Temperatura-Transformación que provee las condiciones óptimas de procesamiento. Nuestros diseños abren rutas novedosas para aplicaciones militares, los cuales incluyen amplios portafolios de protección, versatilidad geométrica, resistencia mecánica y confiabilida
Scalable design of an IMS cross-flow micro-generator/ion detector
Ion-mobility spectrometry (IMS) is an analytical technique used to separate
and identify ionized gas molecules based on their mobility in a carrier buffer
gas. Such methods come in a large variety of versions that currently allow ion
identification at and above the millimeter scale. Here, we present a design for
a cross-flow-IMS method able to generate and detect ions at the sub-millimeter
scale. We propose a novel ion focusing strategy and tested it in a prototype
device using Nitrogen as a sample gas, and also with simulations using four
different sample gases. By introducing an original lobular ion generation
localized to a few ten of microns and substantially simplifying the design, our
device is able to keep constant laminar flow conditions for high flow rates. In
this way, it avoids the turbulences in the gas flow, which would occur in other
ion-focusing cross-flow methods limiting their performance at the
sub-millimeter scale. Scalability of the proposed design can contribute to
improve resolving power and resolution of currently available cross-flow
methods.Comment: 14 pages, 10 figures, revised regular paper, minor correction
Linear algebra and optimization based controller design for trajectory tracking of typical chemical process
This paper presents a new controller design to tracking trajectory of a typical chemical process. The plant model is represented by numerical methods and, from this approach, the control actions for an optimal operation of the system are obtained. Its main advantage is that the condition for the tracking error tends to zero and the calculation of control actions, are obtained solving a system of linear equations. The proofs of convergence to zero of the tracking error are presented. Simulation results show the good performance of the proposed control system.Fil: Serrano, Mario Emanuel. Universidad Nacional de San Juan. Facultad de Ingenieria. Instituto de Ingenieria Quimica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Scaglia, Gustavo Juan Eduardo. Universidad Nacional de San Juan. Facultad de Ingenieria. Instituto de Ingenieria Quimica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Aballay, P.. Universidad Nacional de San Juan. Facultad de Ingenieria. Instituto de Ingenieria Quimica; ArgentinaFil: Ortiz, O. A.. Universidad Nacional de San Juan. Facultad de Ingenieria. Instituto de Ingenieria Quimica; ArgentinaFil: Mut, Vicente Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Juan. Instituto de Automática; Argentin
Glauconite and phosphate peloids in Mesozoic carbonate sediments (eastern Subbetic Zone, Betic Cordilleras, SE Spain)
13 páginas, 4 figuras, 3 tablas.Glauconite and Ca phosphate peloids occur in Jurassic and Cretaceous bioclastic carbonate rocks from pelagic swell sequences of the Algayat-Crevillente Unit (Subbetic Zone). The size and morphology of the peloids are controlled by the bioclasts. The glauconite in both stratigraphic positions is K rich (>0.69 atoms p.f.u.) and shows well-defined 10 Aa lattice fringes. Poorly crystalline areas with a composition of Fe-smectite are found within the peloids, indicating the nature of the glauconitic precursor. This precursor would be formed in the shielded microenvironments of the bioclast and later transformed to glauconite by equilibration of peloids with sea water that culminated with the crystallization of a phosphatic phase. The greater presence of smectite areas in the Jurassic peloids and the lower K contents (0.69-0.81) of these glauconites, compared with the Cretaceous glauconites (0.81-0.89) can be explained by the calcitic early diagenetic cementation which stopped the process of glauconitization.Financial support was
provided by the Research Groups 4065 and 4135 of
the Junta de Andalucía and the Projects PB92-0961 and
PB93-1150-CO2 of DGICYT.Peer reviewe
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Controlled deformation of vesicles by flexible structured media
Liquid crystalline (LC) materials, such as actin or tubulin networks, are known to be capable of deforming the shape of cells. Here, elements of that behavior are reproduced in a synthetic system, namely, a giant vesicle suspended in a LC, which we view as a first step toward the preparation of active, anisotropic hybrid systems that mimic some of the functionality encountered in biological systems. To that end, we rely on a coupled particle-continuum representation of deformable networks in a nematic LC represented at the level of a Landau–de Gennes free energy functional. Our results indicate that, depending on its elastic properties, the LC is indeed able to deform the vesicle until it reaches an equilibrium, anisotropic shape. The magnitude of the deformation is determined by a balance of elastic and surface forces. For perpendicular anchoring at the vesicle, a Saturn ring defect forms along the equatorial plane, and the vesicle adopts a pancake-like, oblate shape. For degenerate planar anchoring at the vesicle, two boojum defects are formed at the poles of the vesicle, which adopts an elongated, spheroidal shape. During the deformation, the volume of the topological defects in the LC shrinks considerably as the curvature of the vesicle increases. These predictions are confirmed by our experimental observations of spindle-like shapes in experiments with giant unilamellar vesicles with planar anchoring. We find that the tension of the vesicle suppresses vesicle deformation, whereas anchoring strength and large elastic constants promote shape anisotropy
Origin of Small Barriers in Jahn–Teller Systems:Quantifying the Role of 3d–4s Hybridization in the Model System NaCl:Ni<sup>+</sup>
Despite its relevance, the microscopic origin of the energy barrier, B, between the compressed and elongated geometries of Jahn–Teller (JT) systems is not well understood yet because of a lack of quantitative data about its various contributions. Seeking to clear up this matter, we have carried out both periodic and cluster ab initio calculations on the model system NaCl:Ni+. This system is particularly puzzling because, according to experimental data, its barrier is much smaller than that for other d9 and d7 ions in similar lattices. All calculations performed on the model system lead, in fact, to values |B| ≤ 160 cm–1, which are certainly smaller than B = 500 cm–1 derived for NaCl:M2+ (M = Ag, Rh) or B = 1024 cm–1 obtained for KCl:Ag2+. As a salient feature, analysis of calculations carried out as a function of the Qθ (3z2 – r2) coordinate unveils the microscopic origin of the barrier. It is quantitatively proven that the elongated geometry observed for NaCl:Ni+ is due to the 3d–4s vibronic admixture, which is slightly larger than the anharmonicity in the eg JT mode that favors a compressed geometry. The existence of these two competing mechanisms explains the low value of B for the model system, contrary to cases where the complex formed by d9 or d7 ions is elastically decoupled from the host lattice. Although the magnitude of B for NaCl:Ni+ is particularly small, the tunneling splitting, 3Γ, is estimated to be below 9 cm–1, thus explaining why the coherence is easily destroyed by random strains and thus a static JT effect is observed experimentally. As a main conclusion, the barrier in JT systems cannot be understood neglecting the tiny changes of the electronic density involved in small distortions. The present calculations reasonably explain the experimental g tensor of NaCl:Ni+, pointing out that the d–d transitions in NiCl65– are much smaller than those for CuCl64– and the optical electronegativity of Ni+ is only around 1.</p
A new tool based on artificial intelligence and GIS for preventive conservation of heritage buildings
This paper describes a new predictive model for preventive conservation of buildings. It allows for multiscenarios of several hazards, assessments of environmental risks, and the use level of buildings together with cultural val-ues of monuments. This modeling approach is based on fuzzy logic and geographic information system available to organizations dedicated to the restoration and rehabilitation in Spain. This system has a transversal development that includes urban, architectural, cultural heritage value, and the analysis of environmental and sociodemographic situations around the monuments. This new tool allows for decision making based on scientific criteria and minimizes risklosses of cultural asset
Pseudopotential study of binding properties of solids within generalized gradient approximations: The role of core-valence exchange-correlation
In ab initio pseudopotential calculations within density-functional theory
the nonlinear exchange-correlation interaction between valence and core
electrons is often treated linearly through the pseudopotential. We discuss the
accuracy and limitations of this approximation regarding a comparison of the
local density approximation (LDA) and generalized gradient approximations
(GGA), which we find to describe core-valence exchange-correlation markedly
different. (1) Evaluating the binding properties of a number of typical solids
we demonstrate that the pseudopotential approach and namely the linearization
of core-valence exchange-correlation are both accurate and limited in the same
way in GGA as in LDA. (2) Examining the practice to carry out GGA calculations
using pseudopotentials derived within LDA we show that the ensuing results
differ significantly from those obtained using pseudopotentials derived within
GGA. As principal source of these differences we identify the distinct behavior
of core-valence exchange-correlation in LDA and GGA which, accordingly,
contributes substantially to the GGA induced changes of calculated binding
properties.Comment: 13 pages, 6 figures, submitted to Phys. Rev. B, other related
publications can be found at http://www.rz-berlin.mpg.de/th/paper.htm
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