Application of multivariate statistical analyses to Itrax core scanner data for the identification of deep-marine sedimentary facies: a case study in the Galician Continental Margin

The validity and usefulness of multivariate statistical tools for the facies characterization in deep-marine environments have been applied on the geochemical, sedimentological and magnetic data from a piston core extracted from the Transitional Zone in the Galician Continental Margin. The combination of geochemical profiles of Fe, Mn, Ti, Ba and Ca and magnetic susceptibility (MS) obtained using the ItraxTM Core Scanner at the University of Vigo, together with the grain-size, grey level and R (red) G (green) B (blue) colour analyses have allowed characterizing and classifying the sediments of the core PC13-3 using SPSS package v. 23. Cluster Analysis (CA) displays, in the first level of the hierarchy, two major groups that correspond with clay-silt and sand facies. In a second level, it is possible to observe six subfacies that match de visu preliminary classification and allowed us to complete and improve the characterization and the facies limits in the whole core. Discriminant Analysis (DA) confirmed the validity of the cluster analyses and enhanced the results of the classification. The Principal Component Analysis (PCA) shows four principal components: coarse lithogenic fraction (PC1), fine lithogenic fraction (PC2), high density fraction (PC3) and biogenic fraction (PC4). These results are in concordance with the Pearson correlation coefficient and the SEM observations. In general terms, the results confirm the utility of the multivariate statistical methods applied on high resolution geochemical and magnetic data acquired with ItraxTM corer scanner, as a quick and complementary tool in sedimentary facies analysis and description in deep marine environments.publishe

Late Quaternary tectono-sedimentary processes on an isolated offshore high marginal platform (NW Iberian Continental Margin)

Studies of the most surficial sedimentary record from passive continental margins provide crucial knowledge about sedimentary dynamics and its changes through recent geological times. These studies allow understanding in detail the influence of both tectonic activity and long-term bottom-current circulation over the Late Quaternary sedimentary dynamics. Using a large dataset of multibeam bathymetry, chirp and multi-channel seismic (MCS) records, ROV seabed direct observations and a magneto-chemical facies characterisation, we provide a well-dated record of the tectono-sedimentary processes on an isolated high marginal platform over the Late Quaternary. Our results display several structural and geomorphological features and tectonic pulses that indicate intense faulting, folding, and deformation of the most recent sedimentary cover. Furthermore, we document four main sedimentary systems acting at the study area and controlled by different water masses (MOW, LSW and NADW): the (hemi)pelagic, bottom current-controlled (hemi)pelagic, contourite and downslope sedimentary systems; as well as a new typology of contourite associated to giant depressions, named as pockmarks-related drift. The record also shows erosive features and extremely low sedimentation rates for the last 172 cal ka BP. Results suggest that the topographic configuration of the high marginal platform and reorganizations of the water masses associated to climate changes causes a constriction of the water masses that induce an enhancement of the bottom-current activity, favouring erosion, winnowing and redistribution of sediments. Therefore, this study provides new insight into the tectonic control and bottom current activity effect over the Late Quaternary sedimentary cover from an isolated and elevate offshore morphostructural province, located at the Galician Continental Margin.publishe

Influence of microroughness on the frictional behavior and wear response of planar saw-cut rock surfaces

Saw-cut rock surfaces, classically utilized to estimate basic friction angle of discontinuities by means of tilt test and other procedures, may seem planar to the naked eye. Nevertheless, they actually present roughness at a micrometric scale. Aiming at characterizing some of these saw-cut rock surfaces and assessing the possible implications between their microscale topography and the resulting tribological behavior, the authors of this study resorted to the 3D focus-variation technique to analyze different surface-texture parameters. Tilt tests were carried out on specimens cut on three rock types, and the involved sliding surfaces were evaluated at a microscale for different testing stages (prior to any test and after two series of repeated tests). An apparently logical inverse correlation between repeated testing and friction angle has been observed, more marked for the smoother surfaces. Higher roughness at the scale of the analysis tends to produce lower friction-angle values, as otherwise observed for mismatched natural rock surfaces. In addition, saw-cut rock surfaces present systematically negative skewness and high values of kurtosis for their height distributions, indicating the occurrence of narrow and deep pits or valleys. Directional hybrid parameters and, in particular, the root mean square (RMS) of the gradient of the surface in the direction of sliding correlates rather well with the measured sliding angle. The authors concluded that the 3D focus-variation technique represents a powerful tool to assess surface-texture parameters of saw-cut rock surfaces, in addition to being useful for understanding some features of the tribological, or wear and frictional, behavior of these type of surfaces.Agencia Estatal de Investigación | Ref. RTI2018-093563-B-I0

Evaluation experiment of ontology tools’ interoperability with the WebODE ontology engineering workbench

This paper presents the results of the interoperability experiment proposed in EON2003, using the following ontology tools: Protégé-2000 and WebODE. We will show which knowledge is preserved and which knowledge is lost in the import/export processes between tools when using RDF(S) as an intermediate language

Anisotropic Pressures in Very Dense Magnetized Matter

The problem of anisotropic pressures arising as a consequence of the spatial symmetry breaking introduced by an external magnetic field in quantum systems is discussed. The role of the conservation of energy and momentum of external fields as well as of systems providing boundary conditions in quantum statistics is considered. The vanishing of the average transverse momentum for an electron-positron system in its Landau ground state is shown, which means the vanishing of its transverse pressure. The situation for neutron case and Strange Quark Matter (SQM) in $\beta$-equilibrium is also briefly discussed. Thermodynamical relations in external fields as well as the form of the stress tensor in a quantum relativistic medium are also discussed. The ferromagnetic symmetry breaking is briefly discussed.Comment: 10 page

Non-renormalization of next-to-extremal correlators in N=4 SYM and the AdS/CFT correspondence

We show that next-to-extremal correlators of chiral primary operators in N=4 SYM theory do not receive quantum corrections to first order in perturbation theory. Furthermore we consider next-to-extremal correlators within AdS supergravity. Here the exchange diagrams contributing to these correlators yield results of the same free-field form as obtained within field theory. This suggests that quantum corrections vanish at strong coupling as well.Comment: 21 pages, LaTex, 9 eps figures, typos corrected and references adde

Peculiarities in the electrical and magnetic properties of cobalt perovskites Ln1−xMxCoO3 (Ln3+: La3+, M2+: Ca2+, Sr2+, Ba2+; Ln3+: Nd3+, M2+: Sr2+)

This is the accepted manuscript of the following article: Señarís-Rodríguez, M. et al. (1999). Peculiarities in the electrical and magnetic properties of cobalt perovskites Ln1−xMxCoO3 (Ln3+: La3+, M2+: Ca2+, Sr2+, Ba2+; Ln3+: Nd3+, M2+: Sr2+). International Journal Of Inorganic Materials, 1(3-4), 281-287. doi: 10.1016/s1466-6049(99)00042-2We refer here to the electrical and magnetic properties of the Ln1−xMxCoO3 systems (Ln3+: La3+, M2+: Ca2+, Sr2+, Ba2+; Ln3+: Nd3+, M2+: Sr2+), paying special attention to those ferromagnetic compounds that display M–I transitions as temperature rises: La1−xMxCoO3 (M2+: Ca2+, Sr2+, Ba2+) in the compositional interval x=0.2–0.3, and Nd1−xSrxCoO3, with x=0.40. The magneto-transport properties of such materials are peculiar and interesting: they show diodic behavior and large relaxation effects — these latter being specially important in the Nd compound — they display magnetoresistive effects specially at the M–I transition temperatures, and they age with time. All these results are discussed on the basis of the inhomogeneous electronic structure of these doped cobalt perovskites and taking into account the influence of the lanthanide ion on their magnetic and electrical propertiesWe thank the Spanish DGICYT for financial support under project MAT98-0416-C03-02S

GadCap: A GADGET multispecies model for the Flemish Cap cod, redfish and shrimp.

Since late 1980s, the demersal community of Flemish Cap (NAFO area 3M) has experienced large variations (including the collapse) in the abundance and population structure of its main fishing resources: cod Gadus morhua, redfish Sebastes sp. and shrimp Pandalus borealis, with alternation in their dominant role in the ecosystem. GadCap is an EU project dealing with the development of a GADGET multispecies model for the Flemish Cap cod, redfish and shrimp, as part of the NAFO roadmap for the EAF. The effect of fishing, trophic interactions (including cannibalism) and water temperature in the dynamic of these three major fishing resources has been modeled. The results highlight the interdependent dynamic of these stocks, and reveals strong interactions between recruitment, fishing and predation (including cannibalism), with marked changes in their relative importance by species-age-length over time. The multispecies model shows that disregarding the species interactions would lead to serious underestimates of natural mortality, overestimations of the exploitable biomass, and highlights the need to move beyond single-species management in this highly coupled ecosystem. Preliminary estimates of total SSB and MSY, under different combinations of fishing mortality for all the three stocks, are also presented.Postprint0,000

Effects of land use on nocturnal birds in a Mediterranean agricultural landscape.

Abstract. Knowledge on the effects of land use on community composition and species abundance is crucial for designing realistic conservation strategies, particularly in highly dynamic systems such as Mediterranean agricultural mosaics that are subjected to intensive cultivation. We investigated these effects on the nocturnal bird species occurring in the study area (Stone Curlew Burhinus oedicnemus, Red-necked Nightjar Caprimulgus ruficollis, Barn Owl Tyto alba, Eurasian Scops Owl Otus scops, Little Owl Athene noctua, Tawny Owl Strix aluco, Long-eared Owl Asio otus, Short-eared Owl Asio flammeus and Eagle Owl Bubo bubo) across an agricultural-natural habitat mosaic in Central Spain for three consecutive years. Shares of vineyards, scrubland, herbaceous cropland, water bodies, and roads significantly affected the composition of the nocturnal bird community. Herbaceous cropland and olive groves, which covered 50% of the study area, proved to be neutral for all species. Remnant patches of natural and semi-natural scrubland (around 10% of the study area) and water bodies (only 1.5% of the study area) showed a positive effect on Eagle Owls, Eurasian Scops Owls, Long-eared Owls, and Red-necked Nightjars. Vineyard (35% of the study area) had a negative influence on Eagle Owls, Long-eared Owls, and Eurasian Scops Owls. Our results indicate, first, that the relative extent of land use types was apparently not related with the presence of nocturnal bird species and, second, that natural scrublands and water bodies are key habitats for assuring the persistence of nocturnal birds in agricultural Mediterranean landscapes. Current land planning focused toward land use intensification will likely increase the areas of habitats that are neutral or have adverse effects on nocturnal birds

Geologic carbon sources may confound ecosystem carbon balance estimates: Evidence from a semiarid steppe in the southeast of Spain

At a semiarid steppe site located in the SE of Spain, relatively large CO2 emissions were measured that could not be attributed to the ecosystem activity alone. Since the study site was located in a tectonically active area, it was hypothesized that a part of the measured CO2 was of geologic origin. This investigation included a survey of soil CO2 efflux, together with carbon isotope analyses of the CO2 in the soil atmosphere, soil CO2 efflux (ie, Keeling plots), groundwater and local thermal springs. These measurements confirmed the ... Articoli in Schola