Strain-induced coupling of electrical polarization and structural defects in SrMnO3 films

Letter.-- et al.Local perturbations in complex oxides, such as domain walls, strain and defects, are of interest because they can modify the conduction or the dielectric and magnetic response, and can even promote phase transitions. Here, we show that the interaction between different types of local perturbations in oxide thin films is an additional source of functionality. Taking SrMnO 3 as a model system, we use nonlinear optics to verify the theoretical prediction that strain induces a polar phase, and apply density functional theory to show that strain simultaneously increases the concentration of oxygen vacancies. These vacancies couple to the polar domain walls, where they establish an electrostatic barrier to electron migration. The result is a state with locally structured room-temperature conductivity consisting of conducting nanosized polar domains encased by insulating domain boundaries, which we resolve using scanning probe microscopy. Our 'nanocapacitor' domains can be individually charged, suggesting stable capacitance nanobits with a potential for information storage technology.M.F., D.M. and M.L. acknowledge funding from grant ‘ETH-06 12-2’ and from SNF proposal no. 200021-149192. The authors acknowledge funding through the SNF R’equip Program (no. 206021-144988). Financial support from Spanish Ministerio de Economía y Competitividad through projects MAT2011-27553-C02, MAT2012-38213-C02-01, MAT2014-51982-C2 and from Regional Gobierno de Aragón through project E26 is acknowledged.Peer Reviewe

Nature of antiferromagnetic order in epitaxially strained multiferroic SrMnO3 thin films

et al.Epitaxial films of SrMnO3 and bilayers of SrMnO3/La0.67Sr0.33MnO3 have been deposited by pulsed laser deposition on different substrates, namely, LaAlO3 (001), (LaAlO3)0.3(Sr2AlTaO6)0.7 (001), and SrTiO3 (001), allowing us to perform an exhaustive study of the dependence of antiferromagnetic order and exchange bias field on epitaxial strain. The Néel temperatures (TN) of the SrMnO3 films have been determined by low-energy muon spin spectroscopy. In agreement with theoretical predictions, TN is reduced as the epitaxial strain increases. From the comparison with first-principles calculations, a crossover from G-type to C-type antiferromagnetic orders is proposed at a critical tensile strain of around 1.6±0.1%. The exchange bias (coercive) field, obtained for the bilayers, increases (decreases) by increasing the epitaxial strain in the SrMnO3 layer, following an exponential dependence with temperature. Our experimental results can be explained by the existence of a spin-glass (SG) state at the interface between the SrMnO3 and La0.67Sr0.33MnO3 films. This SG state is due to the competition between the different exchange interactions present in the bilayer and favored by increasing the strain in the SrMnO3 layer.This work was supported by the Spanish Ministerio de Economía y Competitividad through Project Nos. MAT2011-28532-C03-02, MAT2011-27553-C02, MAT2012- 38213-C02-01, and MAT2014-51982-C2 including FEDER funding, by the Aragon Regional Government through projects E26 and CTPP4/11 and by the European Union under the Seventh Framework Programme under a contract for an Integrated Infrastructure Initiative Reference 312483-ESTEEM2. N. Marcano acknowledges the support of the Centro Universitario de la Defensa en Zaragoza (through Project 2013-03).Peer Reviewe

Growth and structural characterization of strained epitaxial Hf0.5Zr0.5O2 thin films

Ferroelectricity was recently reported in thin films with several compositions in the HfO2-ZrO2 system with orthorhombic crystal structure. In the present paper we study the growth by pulsed laser deposition and the structural characterization of strained epitaxial Hf0.5 Zr0.5 O2 films on (001)-oriented yttria-stabilized zirconia (YSZ) substrates. We have determined the conditions for the coherent growth and correlated the deposition parameters with the films structure and microstructure studied through a combination of x-ray diffraction, electron backscatter diffraction, and scanning transmission electron microscopy. In the range of experimental parameters explored, all the films show monoclinic structure with distorted lattice parameters relative to bulk

Cold-induced growth arrest in gilthead sea bream Sparus aurata: metabolic reorganisation and recovery

There are currently no standard diets or practices to counteract or ameliorate the growth arrest and extremely poor feed conversion rates (FCR) in gilthead sea bream Sparus aurata caused by low water temperatures. The present study analysed the effects of reducing dietary lipid content from 18 to 14 % during a temperature fluctuation period. Temperature was gradually reduced from 22 degrees to 14 degrees C over a period of 5 d, and maintained at this low temperature for a further 45 d before gradual recovery over 7 d to 22 degrees C under controlled conditions, avoiding other stressors often present in cage culture conditions. Decreasing dietary lipid content at an elevated temperature (22 degrees C) did not significantly affect the standard growth rate or FCRs of the sea bream, indicating a possibility to reduce the dietary energy during the months before winter. Although cold-induced growth arrest and metabolic depression were unavoidable, a well-formulated, low-lipid diet adequately met the low energy demands at low temperatures. Analysis of plasma metabolites and liver enzyme activities demonstrated a reorganisation of liver metabolism, mainly in fish on a low-lipid diet. Recovery from low temperatures was delayed, with a higher dietary lipid content required for optimal liver condition, and mineral supplementation to maintain osmoregulation and bone formation. Our results provide useful information for fish producers and researchers, suggesting that dietary lipid contents should be reduced to allow fish to better cope with low temperatures, and that improved diets with higher lipid content are required for recovery from low temperatures.Spanish government - AGL2011-29873; Erasmus Turkish Programinfo:eu-repo/semantics/publishedVersio

Equivalent circuit and calculation of unbalanced power in three-wire three-phase linear networks

[EN] For analysis of three-wire three-phase linear systems, the transformations wye-delta and delta-wye from theorem of Kennelly are used. These transformations can be applied to balanced systems but not to unbalanced systems. This is due to the fact that zero-sequence voltages or zero-sequence currents are present in these types of connections. This modifies the value of the unbalance power in the load with respect to the generator. These zero-sequence voltages and currents that appear in generators and loads are not transferred over the network. The zero-sequence voltage in a delta-connected load and the zero-sequence current that is obtained using theorem of Kennelly in a star-connected load, or vice versa, cause different imbalance effects. Here, the equivalent circuit for any point of the system is developed. The impedances of the equivalent circuit in any node are calculated using line-to-line voltages and line currents. This equivalent circuit incorporates all energetic phenomena, including the unbalance of all downstream loads. For its verification, the phasor unbalance power is used.Montoya-Mira, R.; Diez-Aznar, J.; Blasco Espinosa, PA.; Montoya Villena, R. (2018). Equivalent circuit and calculation of unbalanced power in three-wire three-phase linear networks. IET Generation Transmission & Distribution. 12(7):1466-1473. https://doi.org/10.1049/iet-gtd.2017.0670S14661473127Emanuel, A. E. (1993). On the definition of power factor and apparent power in unbalanced polyphase circuits with sinusoidal voltage and currents. IEEE Transactions on Power Delivery, 8(3), 841-852. doi:10.1109/61.252612Jeon, S.-J. (2005). Definitions of Apparent Power and Power Factor in a Power System Having Transmission Lines With Unequal Resistances. IEEE Transactions on Power Delivery, 20(3), 1806-1811. doi:10.1109/tpwrd.2005.848658Czarnecki, L. S. (1994). Misinterpretations of some power properties of electric circuits. IEEE Transactions on Power Delivery, 9(4), 1760-1769. doi:10.1109/61.329509Willems, J. L. (2004). Reflections on Apparent Power and Power Factor in Nonsinusoidal and Polyphase Situations. IEEE Transactions on Power Delivery, 19(2), 835-840. doi:10.1109/tpwrd.2003.823182Emanuel, A. E. (1999). Apparent power definitions for three-phase systems. IEEE Transactions on Power Delivery, 14(3), 767-772. doi:10.1109/61.772313Jayatunga, U., Ciufo, P., Perera, S., & Agalgaonkar, A. P. (2015). Deterministic methodologies for the quantification of voltage unbalance propagation in radial and interconnected networks. IET Generation, Transmission & Distribution, 9(11), 1069-1076. doi:10.1049/iet-gtd.2014.0661Von Jouanne, A., & Banerjee, B. (2001). Assessment of voltage unbalance. IEEE Transactions on Power Delivery, 16(4), 782-790. doi:10.1109/61.956770Viswanadha Raju, G. K., & Bijwe, P. R. (2008). Efficient reconfiguration of balanced and unbalanced distribution systems for loss minimisation. IET Generation, Transmission & Distribution, 2(1), 7. doi:10.1049/iet-gtd:20070216Kersting, W. H. (2001). Causes and effects of unbalanced voltages serving an induction motor. IEEE Transactions on Industry Applications, 37(1), 165-170. doi:10.1109/28.903142Pillay, P., & Manyage, M. (2006). Loss of Life in Induction Machines Operating With Unbalanced Supplies. IEEE Transactions on Energy Conversion, 21(4), 813-822. doi:10.1109/tec.2005.853724Emanuel, A. E. (1998). The Buchholz-Goodhue apparent power definition: the practical approach for nonsinusoidal and unbalanced systems. IEEE Transactions on Power Delivery, 13(2), 344-350. doi:10.1109/61.660900Leon-Martinez, V., Montanana-Romeu, J., & Palazon-Garcia, J. M. (2011). Unbalance Compensator for Three-Phase Industrial Installations. IEEE Latin America Transactions, 9(5), 808-814. doi:10.1109/tla.2011.6030993Reginatto, R., & Ramos, R. A. (2014). On electrical power evaluation in dq coordinates under sinusoidal unbalanced conditions. IET Generation, Transmission & Distribution, 8(5), 976-982. doi:10.1049/iet-gtd.2013.0532Diez, J. M., Blasco, P. A., & Montoya, R. (2016). Formulation of phasor unbalance power: application to sinusoidal power systems. IET Generation, Transmission & Distribution, 10(16), 4178-4186. doi:10.1049/iet-gtd.2016.0730Marzband, M., Moghaddam, M. M., Akorede, M. F., & Khomeyrani, G. (2016). Adaptive load shedding scheme for frequency stability enhancement in microgrids. Electric Power Systems Research, 140, 78-86. doi:10.1016/j.epsr.2016.06.03

Strained SrMnO3 thin films: engineering multiferroic properties

Resumen del trabajo presentado al "European Congress and Exhibition on Advanced Materials Processes" celebrado en Sevilla (España) del 8 al 13 de septiembre de 2013.-- et al.Multiferroic materials showing simultaneous magnetic and ferroelectric ordering have become the subject of intensive research in recent years. The scarcity of these materials due to the different phenomena responsible for both properties [1], and also, the weak magnetoelectric coupling in most of them force to develop new methods to avoid the excluding mechanisms of ferroelectricity and magnetism. Recent theoretical predictions suggested that epitaxially strained SrMnO3 should become multiferroic [2] by means of the interplay of spins, lattice phonons and strain of the perovskite unit cell. In this system, Mn4+ (d3 ion) is expected to drive both the magnetic order (Mn-O-Mn magnetic superexchange interaction) and the required non-centrosymmetric distortion for ferroelectric order (Mn4+ off-centers from MnO6 octahedra), and therefore a strong magnetoelectric coupling with similar ordering temperatures is expected. Here, we have investigated the effect of epitaxial strain on the structure, electrical and magnetic properties of SrMnO3 (SMO) thin films. Pulsed laser deposition technique was used to grow strained SMO thin films onto different substrates ranging from -1% compressive to 4% tensile mismatch. Coherent cube-on-cube growth is borne out by X-ray diffraction measurements, which also show that under appropriate deposition conditions and substrate selection the perovskite pseudo-cubic phase is stabilized in thin films. The growth of the samples has been monitored by in situ RHEED measurements. Selected films were observed by scanning transmission electron microscopy, which prove the homogeneity and defect-free crystal quality of films. Chemical composition mapping, stoichiometry and 4+ oxidation state of Mn were corroborated by electron energy loss spectroscopy. Nonlinear optics measurements reveal that SMO films, under epitaxial stress, emitt optical second harmonic generation signal, pointing to inversion symmetry being broken (necessary condition for ferroelectricity). Electric measurements were carried out to further investigate the ferroelectric nature of SMO films, thus assessing the possibility of non-d0 cations off-centring.Peer Reviewe

Neuronal p38α mediates age‐associated neural stem cell exhaustion and cognitive decline

[EN] Neuronal activity regulates cognition and neural stem cell (NSC) function. The molecular pathways limiting neuronal activity during aging remain largely unknown. In this work, we show that p38MAPK activity increases in neurons with age. By using mice expressing p38α-lox and CamkII-Cre alleles (p38α∆-N), we demonstrate that genetic deletion of p38α in neurons suffices to reduce age-associated elevation of p38MAPK activity, neuronal loss and cognitive decline. Moreover, aged p38α∆-N mice present elevated numbers of NSCs in the hippocampus and the subventricular zone. These results reveal novel roles for neuronal p38MAPK in age-associated NSC exhaustion and cognitive decline

Surface distribution of dissolved trace metals in the oligotrophic ocean and their influence on phytoplankton biomass and productivity

Pinedo-González, Paulina ... et. al.-- 19 pages, 10 figures, 2 tables, supporting information http://dx.doi.org/10.1002/2015GB005149The distribution of bioactive trace metals has the potential to enhance or limit primary productivity and carbon export in some regions of the world ocean. To study these connections, the concentrations of Cd, Co, Cu, Fe, Mo, Ni, and V were determined for 110 surface water samples collected during the Malaspina 2010 Circumnavigation Expedition (MCE). Total dissolved Cd, Co, Cu, Fe, Mo, Ni, and V concentrations averaged 19.0 ± 5.4 pM, 21.4 ± 12 pM, 0.91 ± 0.4 nM, 0.66 ± 0.3 nM, 88.8 ± 12 nM, 1.72 ± 0.4 nM, and 23.4 ± 4.4 nM, respectively, with the lowest values detected in the Central Pacific and increased values at the extremes of all transects near coastal zones. Trace metal concentrations measured in surface waters of the Atlantic Ocean during the MCE were compared to previously published data for the same region. The comparison revealed little temporal changes in the distribution of Cd, Co, Cu, Fe, and Ni over the last 30 years. We utilized a multivariable linear regression model to describe potential relationships between primary productivity and the hydrological, biological, trace nutrient and macronutrient data collected during the MCE. Our statistical analysis shows that primary productivity in the Indian Ocean is best described by chlorophyll a, NO3, Ni, temperature, SiO4, and Cd. In the Atlantic Ocean, primary productivity is correlated with chlorophyll a, NO3, PO4, mixed layer depth, Co, Fe, Cd, Cu, V, and Mo. The variables salinity, temperature, SiO4, NO3, PO4, Fe, Cd, and V were found to best predict primary productivity in the Pacific Ocean. These results suggest that some of the lesser studied trace elements (e.g., Ni, V, Mo, and Cd) may play a more important role in regulating oceanic primary productivity than previously thought and point to the need for future experiments to verify their potential biological functionsThis research was partially supported by U.S. National Science Foundation (OCE 1435666), the USC Graduate School Dissertation Completion Fellowship, the Spanish Ministry of Economy and Competitiveness through the Malaspina 2010 expedition project (Consolider-Ingenio 2010, CSD2008-00077) and the project CTM2014-59244-C3-3-RPeer Reviewe

Enfermedad del hígado graso no alcohólico, asociación con la enfermedad cardiovascular y tratamiento (I). Enfermedad del hígado graso no alcohólico y su asociación con la enfermedad cardiovascular

La enfermedad del hígado graso no alcohólico (EHGNA) comprende una serie de lesiones hepáticas histológicamente similares a las inducidas por el alcohol, en personas con un consumo del mismo muy escaso o nulo. La importancia de la EHGNA radica en su alta prevalencia en el mundo occidental y, desde el punto de vista hepático, en su progresiva evolución desde esteatosis a esteatohepatitis, cirrosis y cáncer de hígado. Durante la última década se ha observado que la EHGNA da lugar a un incremento del riesgo cardiovascular con aceleración de la arteriosclerosis y de los eventos a ella vinculados, principal causa de su morbimortalidad. Esta revisión actualizada a enero de 2016 consta de dos partes, analizando en esta primera parte la asociación de la EHGNA con la enfermedad cardiovascular. Non-alcoholic fatty liver disease (NAFLD) comprises a series of histologically lesions similar to those induced by alcohol consumption in people with very little or no liver damage. The importance of NAFLD is its high prevalence in the Western world and, from the point of view of the liver, in its gradual progression from steatosis to steatohepatitis, cirrhosis, and liver cancer. During the last decade it has been observed that NAFLD leads to an increased cardiovascular risk with acceleration of arteriosclerosis and events related to it, being the main cause of its morbidity and mortality. This review, updated to January 2016, consists of two parts, with the first part analysing the association of NAFLD with cardiovascular disease

Ocean Circulation over North Atlantic underwater features in the path of the Mediterranean Outflow Water: Ormonde and Formigas seamounts, and the Gazul mud volcano

Seamounts constitute an obstacle to the ocean circulation, modifying it. As a result, a variety of hydrodynamical processes and phenomena may take place over seamounts, among others, flow intensification, current deflection, upwelling, Taylor caps, and internal waves. These oceanographic effects may turn seamounts into very productive ecosystems with high species diversity, and in some cases, are densely populated by benthic organisms, such corals, gorgonians, and sponges. In this study, we describe the oceanographic conditions over seamounts and other underwater features in the path of the Mediterranean Outflow Water (MOW), where populations of benthic suspensions feeders have been observed. Using CTD, LADPC and biochemical measurements carried out in the Ormonde and Formigas seamounts and the Gazul mud volcano (Northeast Atlantic), we show that Taylor caps were not observed in any of the sampled features. However, we point out that the relatively high values of the Brunt–Väisälä frequency in the MOW halocline, in conjunction with the slope of the seamount flanks, set up conditions for the breakout of internal waves and amplification of the currents. This may enhance the vertical mixing, resuspending the organic material deposited on the seafloor and, therefore, increasing the food availability for the communities dominated by benthic suspension feeders. Thus, we hypothesize that internal waves could be improving the conditions for benthic suspension feeders to grow on the slope of seamounts.En prens