Magnetic transitions in Pr2NiO4 single crystal

The magnetic properties of a stoichiometric Pr2NiO4 single crystal have been examined by means of the temperature dependence of the complex ac susceptibility and the isothermal magnetization in fields up to 200 kOe at T=4.2 K. Three separate phases have been identified and their anisotropic character has been analyzed. A collinear antiferromagnetic phase appears first between TN = 325 K and Tc1 = 115 K, where the Pr ions are polarized by an internal magnetic field. At Tc1 a first modification of the magnetic structure occurs in parallel with a structural phase transition (Bmab to P42/ncm). This magnetic transition has a first‐order character and involves both the out‐of‐plane and the in‐plane spin components (magnetic modes gx and gxcyfz, respectively). A second magnetic transition having also a first‐order character is also clearly identified at Tc2 = 90 K which corresponds to a spin reorientation process (gxcyfz to cxgyaz magnetic modes). It should be noted as well that the out‐of‐phase component of χac shows a peak around 30 K which reflects the coexistence of both magnetic configurations in a wide temperature interval. Finally, two field‐induced transitions have been observed at 4.2 K when the field is directed along the c axis. We propose that the high‐field anomaly arises from a metamagnetic transition of the weak ferromagnetic component, similarly to La2CuO4

3D high definition video coding on a GPU-based heterogeneous system

H.264/MVC is a standard for supporting the sensation of 3D, based on coding from 2 (stereo) to N views. H.264/MVC adopts many coding options inherited from single view H.264/AVC, and thus its complexity is even higher, mainly because the number of processing views is higher. In this manuscript, we aim at an efficient parallelization of the most computationally intensive video encoding module for stereo sequences. In particular, inter prediction and its collaborative execution on a heterogeneous platform. The proposal is based on an efficient dynamic load balancing algorithm and on breaking encoding dependencies. Experimental results demonstrate the proposed algorithm's ability to reduce the encoding time for different stereo high definition sequences. Speed-up values of up to 90× were obtained when compared with the reference encoder on the same platform. Moreover, the proposed algorithm also provides a more energy-efficient approach and hence requires less energy than the sequential reference algorith

An improved model for fast and reliable harbour wave agitation assessment

ABSTRACT: This study presents the new advances achieved in the field of harbour agitation climate assessment. Based on the improvement of an elliptic mild-slope model (MSP), which realistically reconstructs waves inside any-sized basin, represented by high-detailed unstructured meshes, and forced by real-shaped outer spectral data. A new solver is proposed for high performance runs, which allow fast agitation hindcast for statistical downtime analysis within an iterative and multi-scenario approach. Also, a realistic assimilation of partial reflection processes in quays/docks/wharfs/breakwaters is proposed. The model has been successfully validated in several harbours of special relevance in Spain with in situ measurements, through the assimilation of the hybrid downscaling (Camus et al., 2011) technique combined with monochromatic-based wave spectral reconstruction.This work has been also partially funded under the RETOS program of the Spanish Ministry of Science, Innovation and Universities (BIA2017-87213-R). We would like to thank Puertos del Estado of Spain for providing spectral outer wave spectral forcing and wave agitation measurements, for gather/organize each Port Authority base data required

Real-time moving object segmentation in H.264 compressed domain based on approximate reasoning

AbstractThis paper presents a real-time segmentation algorithm to obtain moving objects from the H.264 compressed domain. The proposed segmentation works with very little information and is based on two features of the H.264 compressed video: motion vectors associated to the macroblocks and decision modes. The algorithm uses fuzzy logic and allows to describe position, velocity and size of the detected regions in a comprehensive way, so the proposed approach works with low level information but manages highly comprehensive linguistic concepts. The performance of the algorithm is improved using dynamic design of fuzzy sets that avoids merge and split problems. Experimental results for several traffic scenes demonstrate the real-time performance and the encouraging results in diverse situations

Los depósitos de ceniza volcánica del Pleistoceno Superior-Holoceno de la región de Tafí del Valle-Cafayate, noroeste de Argentina

[EN]We identified volcanic ash deposits, whose thickness can exceed sometimes the 4 m, in the southeastern margin of La Puna and neighbouring areas (Provinces of Tucuman and Salta, Argentina). These Late Pleistocene and Holocene deposits show the existence of a highly explosive volcanism only some few thousand years ago, without comparison with any historical volcanic episode in northwestern Argentina. We have characterized the size distribution of ash (laser diffraction), morphology of particles (SEM), mineralogy (XRD) and the geochemistry of major and trace elements in bulk sample using mass spectrometry (HR-ICP-MS). The information provided by these deposits is of great interest to size adequately the geochemical impact models of ashfall in future volcanic eruptions in the Central Volcanic Zone of the Andes, quantifying the contribution of volcanic ash to the regional geochemical balances, both with respect to nutrients (e.g., Ca and Fe) and potentially toxic elements (e.g., As and F), among other elements of interest.[ES] Se han localizado diversos depósitos de ceniza volcánica, cuyos espesores llegan a superar en ocasiones los 4 m al suroeste de La Puna y áreas limítrofes (Provincias de Tucumán y Salta, Argentina). Estos depósitos son de edad Pleistoceno Superior y Holoceno y muestran la existencia hace pocos miles de años de volcanismo altamente explosivo, sin comparación con ningún episodio volcánico histórico en el noroeste de Argentina. Se han caracterizado la distribución granulométrica de la ceniza (difracción laser), la morfología de las partículas (microscopía electrónica de barrido), mineralogía (difracción de rayos X) y la geoquímica de elementos mayores y trazas en muestra total mediante espectrometría de masas (HR-ICP-MS). La información suministrada por estos depósitos tiene gran interés a la hora de dimensionar los modelos de impacto geoquímico de la caída de ceniza de futuras erupciones volcánicas en la Zona Volcánica Central de los Andes, cuantificando la contribución de la ceniza volcánica a los balances geoquímicos regionales, tanto por lo que respecta a nutrientes (p. ej., Ca y Fe), como de elementos potencialmente tóxicos (p. ej., As y F), entre otros elementos de interés.Agradecemos el apoyo técnico del labGEOTOP (infraestructura cofinanciada por FEDER, CSIC08-4E-001) del ICTJA-CSIC; de los Grupos PEGEFA (2009-SGR-972) y GEOVOL y fue financiado por el Proyecto QUECA (CGL2011-23307).Peer reviewe

Effect of chemical structure on the sonochemical degradation of perfluoroalkyl and polyfluoroalkyl substances (PFASs)

Perfluoroalkyl surfactants include chemicals characterized by a fully fluorinated carbon chain (hydrophobic and oleophobic tail) bound to a hydrophilic head (a carboxyl or sulfonic group). These compounds are toxic and highly resistant to chemical/biological attack, and some are known to be bio-accumulative. This study investigates the sonochemical degradation at 500 kHz of different carboxylic and sulfonic perfluoroalkyl and polyfluoroalkyl substances (PFASs, 1.7 mM total organic fluorine) to assess the effect of chain length, functional head group, and substituents (–CH2–CH2– moiety and ether group) on the degradation rate. Under these conditions, the rates of defluorination determined for two widely used perfluoroalkyl substances, perfluorooctanesulfonate (PFOS) and perfluorooctanoic acid (PFOA), were 3.5 to 3.7 μM F− min−1, respectively. The degradation rate of perfluoroalkyl sulfonates decreased with the perfluorocarbon chain length as indicated by the 1.3 and 1.9-fold lower defluorination rates for perfluorohexane- and perfluorobutane sulfonate than that of PFOS. A similar trend was observed during the sonolysis of perfluoroalkyl carboxylate analogs with 6, 5 or 3 carbon atoms which had 1.1-, 1.8-, and 2.3-fold lower defluorination rates, respectively, than that of PFOA. Furthermore, perfluoroalkyl compounds appeared more amenable to sonolysis than the polyfluoroalkyl analogues with the same number of C atoms (defluorination rate of PFOS/6 : 2 fluorotelomer sulfonate ≈ 2.3). The results demonstrate that sonolysis is a promising approach to treat PFASs in aqueous streams. Furthermore, they underscore that the chemical structure of PFASs has a marked effect on the rate at which they undergo sonochemical degradation

Chloroform conversion into ethane and propane by catalytic hydrodechlorination with Pd supported on activated carbons from lignin

Conversion of chloroform (TCM) by gas-phase catalytic hydrodechlorination (HDC) has been addressed to maximize the selectivity to ethane and propane. Several own-made Pd (1 wt%) catalysts have been tested. The catalysts were prepared by incipient wetness impregnation of five different activated carbons. These carbons were obtained by chemical activation of lignin with different activating agents, namely, H3PO4, ZnCl2, FeCl3, NaOH and KOH. The catalysts were fully characterized by N2 adsorption–desorption at −196 °C, CO2 adsorption at 0 °C, TPR, NH3-TPD, XRD, XPS and TEM. The activating agents provided important differences in the characteristics of activated carbon supports, and hence in the resulting catalysts, in terms of their porous texture, surface acidity, Pd oxidation state and Pd particle size distribution. NaOH and KOH activation led to carbons with the highest surface areas (2158 and 2991 m2 g−1 , respectively) and low Pd0 / Pdn+ ratios, while ZnCl2- and H3PO4-activated carbons yielded the highest surface acidity and mean Pd particle sizes. The analysis of the TOF values revealed that the HDC of TCM on these catalysts is a structure-sensitive reaction, increasing TOF values with Pd particle size. The best results, in terms of selectivity to ethane and propane, were obtained with the catalysts supported on KOH- and NaOH-activated carbons. The former allowed 80% selectivity to the target compounds at almost complete dechlorination (>99%) at 300 °C. The KOH-based catalyst showed fairly good stability at a reaction temperature of 200 °CThe authors gratefully acknowledge financial support from the Spanish Ministerio de Economía y Competitividad (MINECO) through the project CTM 2014-5300