High-pressure transformation in the cobalt spinel ferrites

We report high pressure angle-dispersive x-ray diffraction measurements on CoxFe3−xO4 (x=1, 1.5, 1.75) spinels at room temperature up to 34 GPa. The three samples show a similar structural phase transformation from the cubic spinel structure to an analogous post-spinel phase at around 20 GPa. Spinel and post-spinel phases coexist in a wide pressure range (~20–25 GPa) and the transformation is irreversible. The equation of state of the three cubic spinel ferrites was determined and our results agree with the data obtained in related oxide spinels showing the role of the pressure-transmitting medium for the accurate determination of the equation of state. Measurements releasing pressure revealed that the post-spinel phase is stable down to 4 GPa when it decomposes yielding a new phase with poor crystallinity. Later compression does not recover either the spinel or the post-spinel phases. This phase transformation induced by pressure explains the irreversible lost of the ferrimagnetic behavior reported in these spinels.Financial support from the Spanish Ministerio de Economía y Competitividad (MINECO) (Projects no. MAT2012-38213-C02-01) and Diputación General de Aragón (DGA-CAMRADS) is acknowledged.Peer Reviewe

Trend analysis of water quality series based on regression models with correlated errors

This work proposes a methodology for characterizing the time evolution of water quality time series taking into consideration the inherent problems that often appear in this type of data such as non-linear trends, series having missing data, outliers, irregular measurement patterns, seasonal behavior, and serial correlation. The suggested approach, based on regression models with a Gaussian autoregressive moving average (ARMA) error, provides a framework where those problems can be dealt with simultaneously. Also the model takes into account the effect of influential factors, such as river flows, water temperature, and rainfall. The proposed approach is general and can be applied to different types of water quality series. We applied the modeling framework to four monthly conductivity series recorded at the Ebro river basin (Spain). The results show that the model fits the data reasonably well, that time evolution of the conductivity series is non-homogeneous over the year and, in some cases, non-monotonic. In addition, the results compared favorably over those obtained using simple linear regression, pre-whitening, and trend-free-pre-whitening techniques

Characterization of competing distortions in YFe2O4

We report the structural changes of three YFe2O4-δ (δ<0.1) specimens using high resolution synchrotron x-ray powder diffraction between 80 and 300 K. All samples adopt a rhombohedral cell at room temperature (space group R3m). This cell becomes unstable for the three samples on cooling, and the oxygen-poor specimen (δ∼0.1) shows a single transition at 240 K. The nearly stoichiometric (δ≤0.03) compounds exhibit two structural transitions with decreasing temperature at about 240 and 200 K. Each transition is revealed by an anomaly in the heat capacity measurements and a jump in the electric resistivity. Below 240 K, a strong splitting of some diffraction peaks is accompanied by the occurrence of superstructure peaks that follow the propagation vector k=(1/7,-2/7,9/7). The cell symmetry is then triclinic, and the structural transition is characterized by an expansion of the c axis coupled to a contraction of the other two lattice parameters. There are 49 nonequivalent sites for Fe atoms with a maximum charge disproportionation of ∼0.5e-. Upon cooling at 200 K, the previous superstructure peaks begin to vanish, and finally they are replaced by a new set of superstructure peaks following the propagation vector k=(1/4,1/2,1/4) with respect to the rhombohedral cell. The transition is also reflected in sudden changes in the lattice parameters that seem to smooth the changes observed in the previous transition. The new cell is also triclinic, and there are 48 nonequivalent Fe sites with a maximum charge disproportionation of ∼0.7e-. Both phases coexist in a wide temperature range because this second transition is not completed at 80 K. A symmetry mode analysis indicates a complicated pattern for the charge distribution in the Fe sublattice of both distorted structures but clearly discard any bimodal distribution of only two types of Fe cations. Therefore, the sharp jumps in the electric resistivity at the phase transitions are clearly correlated with two different structural changes. Finally, the oxygen stoichiometry seems to be a key factor in the stabilization of the different distorted structures.We are thankful for financial support from the Spanish Ministerio de Economía y Competitividad (MINECO) (Projects No. MAT2012-38213-C02-1-2 and No. MAT2015-68760-C2-1-2, cofunded by the European Regional Development Fund [ERDF] allocated by the European Union) and Diputacion General de Aragón (DGA, project E69).Peer Reviewe

Prescripción de antibióticos en pediatría de atención primaria: una responsabilidad compartida

Se publica en este número de Anales de PediatrÍa, un artículo que relaciona la hiperfrecuentación con la tasa de prescripción de antibióticos. Se trata de un buen estudio de base poblacional, realizado desde la red de pediatras investigadores de la Asociación Española de Pediatría de Atención Primaria (PAP.en.RED, http://www.aepap.org/grupos/papenred ) y promovido por su Grupo de Investigación. Con datos de 2.726 pacientes, la tasa de prescripción de antibióticos es signicativamente mayor en los hiperfrecuentadores respecto a los no hiperfrecuentadores, en todos los grupos de edad pediátrica. Siendo la accesibilidad a la atención pediátrica en nuestro sistema público sanitario una de sus grandes fortalezas, también puede ser una de las debilidades respecto al adecuado uso de recursos y el uso prudente de antibióticos. No son pocos los pacientes pediátricos que ante un proceso febril consultan repetidamente (en el sistema público y privado) en busca de una solución diferente al tratamiento sintomático inicialmente prescrito. En comparación con países de nuestro entorno, la prescripción antibiótica en pediatría de atención primaria (AP) es sensiblemente superior a la de países del norte y centro..

Structural effects of Sc doping on the multiferroic TbMnO3

9 páginas, 8 figuras, 4 tablas.-- PACS number(s): 75.85.+t, 61.05.cp, 61.05.fm, 61.05.cjThe new TbMn1−xScxO3 series has been synthesized and the structural properties have been characterized by x-ray diffraction, neutron diffraction, and x-ray absorption spectroscopy. The whole series belongs to the family of ABO3 perovskites. All of the samples are isostructural to the parent compound TbMnO3, crystallizing in an orthorhombic cell with space-group Pbnm symmetry. The homovalent substitution of Mn3+ with the larger Sc3+ ion leads to an increase in both the unit-cell volume and the BO6 octahedra tilting. The analysis of neutron and x-ray diffraction patterns suggest a continuous evolution from a Jahn-Teller distorted BO6 octahedron in TbMnO3 into a nearly regular one in TbScO3. However, x-ray absorption measurements at the Mn K edge reveal that the local geometry around the Mn3+ cation remains distorted in the series even for high values of x. This result is in opposition to previous findings in similar compounds such as LaMn1−x(Ga/Sc)xO3 and suggests that the strong orthorhombic distortion of the unit cell due to the small Tb3+ cation size favors the stability of the distorted MnO6 octahedron in diluted systems. Long-range magnetic ordering is not found for x≥0.3 samples and there is not sign of ferromagnetism for x=0.5 in opposite to the behavior observed in the La-based compounds. Since Sc substitution induces a minor perturbation on the local structure of the Mn sublattice but magnetic ordering of both Mn and Tb sublattices disappear for a small degree of substitution, we conclude that the involved magnetic interactions should have a strong directional anisotropy and the Tb magnetic ordering strongly depends on the existence of a long-range coherent Mn ordering.Financially supported by the Spanish MICINN (Projects No. FIS08-03951 and No. MAT2007-61621) and DGA (Camrads).Peer reviewe

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

Mesozoic palaeogeographic evolution of the External Zones of the Betic Cordillera

14 páginas, 8 figuras.The main events characterizing the Mesozoic palaeogeographic evolution of the External Zones of the Betic Cordillera are outlined. The Triassic sediments show a 'germanic' type lacies over the entire region, ending with Late Triassic evaporites and variegated clays of Keuper facies. At the beginning of the Jurassic a transgression takes place, and a broad shallow-marine carbonate-platform environment appears. During the Carixian (180 Ma) the carbonate platform breaks down leading to the differentiation of two large palaeogeographic units: the Prebetic Zone where shallow-water environments prevailed throughout the Mesozoic, and the Subbetic Zone where the sediments are clearly pelagic. Within the Prebetic Zone, two palaeogeographic realms are differentiated: the External Prebetic ,showing important stratigraphic gaps in the Jurassic and Early Cretaceous sequence, and the Internal Prebetic with a thicker and more continuous stratigraphic sequence. Between the Prebetic and Subbetic Zones, a palaeogeographic realm is distinguished (Intermediate units) where turbiditic and pelagic materials were deposited. This zone corresponds approximately to a slope environment during most of Mesozoic times. In the Subbetic Zone a marked differential subsidence occurs during the Jurassic, leading to trough (Median Subbetic) and swells (External and Internal Subbetic). In the Median Subbetic, the deposits consist mainly of marls, pelagic limestones, radiolarites and calcareous turbidites, with mafic volcanic hand subvolcanic rocks. During the Cretaceous pelagic marls and marty limestones were laid down. Mesozoic sedimentation took place along the southern margin of the European plate, in an Atlantic-type continental margin underlain by continental crust. Three-dimensional schemes, explaining the main palaeogcographic events are included.Peer reviewe

Distortion of the QRS in elderly patients with myocardial infarction

Background: Distortion of the terminal portion of the QRS in the initial electrocardiogram (ECG) is a strong predictor of adverse outcome in myocardial infarction. Our purpose is to assess the relationship of distortion of QRS and other ECG characteristics with older age. Methods and results: We analysed 634 consecutive patients (age 62.6 &#177; 13.7, 77% male) admitted in the first 12 hours of ST-elevation myocardial infarction. Two groups of age were defined: < 75 years-old and &#8805; 75 years-old. Additionally, we defined two ECG groups according to the presence of ST segment elevation with distortion of the terminal portion of the QRS in two or more adjacent leads (QRS+) or the absence of this pattern (QRS&#8211;). Older people had more often QRS+ (30% vs. 20%, p = 0.023). The older group with QRS+ had an in-hospital mortality of 18%, vs. 7% with QRS&#8211; (p = 0.04), and an incidence of major adverse events of 40% vs. 14% (p = 0.002). In the multivariate analysis, age &#8805; 75 years was an independent predictor of distortion of the QRS (odds ratio 2.1, 1.2&#8211;4.9, p = 0.016). Conclusions: The distortion of the terminal portion of the QRS in myocardial infarction is more frequent in elderly people, and is significantly related to adverse prognosis. This ECG finding can be helpful to promptly stratify the risk in elderly patient

Simulation model for the study of overhead rail current collector systems dynamics, focused on the design of a new conductor rail

Overhead rigid conductor arrangements for current collection for railway traction have some advantages compared to other, more conventional, energy supply systems. They are simple, robust and easily maintained, not to mention their flexibility as to the required height for installation, which makes them particularly suitable for use in subway infrastructures. Nevertheless, due to the increasing speeds of new vehicles running on modern subway lines, a more efficient design is required for this kind of system. In this paper, the authors present a dynamic analysis of overhead conductor rail systems focused on the design of a new conductor profile with a dynamic behaviour superior to that of the system currently in use. This means that either an increase in running speed can be attained, which at present does not exceed 110 km/h, or an increase in the distance between the rigid catenary supports with the ensuing saving in installation costs. This study has been carried out using simulation techniques. The ANSYS programme has been used for the finite element modelling and the SIMPACK programme for the elastic multibody systems analysis