Enhanced quench propagation in 2G-HTS coils co-wound with stainless steel or anodised aluminium tapes

Early quench detection and thermal stability of superconducting coils are of great relevance for practical applications. Magnets made with second generation high temperature superconducting (2G-HTS) tapes present low quench propagation velocities and therefore slow voltage development and high local temperature rises, which may cause irreversible damage. Since quench propagation depends on the anisotropy of the thermal conductivity, this may be used to achieve an improvement of the thermal stability and robustness of 2G-HTS coils. On pancake type coils, the thermal conductivity along the tapes (coil's azimuthal direction) is mostly fixed by the 2G-HTS tape characteristics, so that the reduction of anisotropy relies on the improvement of the radial thermal conductivity, which depends on the used materials between superconducting tapes, as well as on the winding and impregnation processes. In this contribution, we have explored two possibilities for such anisotropy reduction: by using anodised aluminium or stainless steel tapes co-wound with the 2G-HTS tapes. For all the analysed coils, critical current distribution, minimum quench energy values and both tangential and radial quench propagation velocities at different temperatures and currents are reported and compared with the results of similar coils co-wound with polyimide (Kapton®) tapes.This work was supported by the Spanish Ministerio de Economía y Competitividad and the European FEDER Program (Projects MAT2011-22719 and ENE-2014-52105-R), and by the Gobierno de Aragón (research group T12).Peer reviewe

Evidence of strong antiferromagnetic coupling between localized and itinerant electrons in ferromagnetic Sr2FeMoO6

Magnetic dc susceptibility ($\chi$) and electron spin resonance (ESR) measurements in the paramagnetic regime, are presented. We found a Curie-Weiss (CW) behavior for $\chi$(T) with a ferromagnetic $\Theta = 446(5)$ K and $\mu_{eff} = 4.72(9) \mu_{B}/f.u.$, this being lower than that expected for either $Fe^{3+}(5.9\mu_{B})$ or $Fe^{2+}(4.9\mu_{B})$ ions. The ESR g-factor $g = 2.01(2)$, is associated with $Fe^{3+}$. We obtained an excellent description of the experiments in terms of two interacting sublattices: the localized $Fe^{3+}$ ($3d^{5}$) cores and the delocalized electrons. The coupled equations were solved in a mean-field approximation, assuming for the itinerant electrons a bare susceptibility independent on $T$. We obtained $\chi_{e}^{0} = 3.7$ $10^{-4}$ emu/mol. We show that the reduction of $\mu_{eff}$ for $Fe^{3+}$ arises from the strong antiferromagnetic (AFM) interaction between the two sublattices. At variance with classical ferrimagnets, we found that $\Theta$ is ferromagnetic. Within the same model, we show that the ESR spectrum can be described by Bloch-Hasegawa type equations. Bottleneck is evidenced by the absence of a $g$-shift. Surprisingly, as observed in CMR manganites, no narrowing effects of the ESR linewidth is detected in spite of the presence of the strong magnetic coupling. These results provide evidence that the magnetic order in $Sr_{2}FeMoO_{6}$ does not originates in superexchange interactions, but from a novel mechanism recently proposed for double perovskites

On the validity of the 630 nm Fe I nm lines for the magnetometry of the internetwork quiet Sun

The purpose of this work is to analyze the reliability of the magnetic field strengths inferred from the 630 nm pair of Fe I lines at internetwork quiet Sun regions. Some numerical experiments have been performed that demonstrate the inability of these lines to recover the magnetic field strength in such low flux solar regions. It is shown how different model atmospheres, with magnetic field strengths ranging from few hundred Gauss to kiloGauss, give rise to Stokes profiles that can not be distinguished. The reasons for this degeneracy are discussed.Comment: Accepted for publication in A&

Towards a better understanding of time-lags in karst aquifers by combining hydrological analysis tools and dye tracer tests. Application to a binary karst aquifer in southern Spain

The assessment of the response time of a karst aquifer is an important step towards the development of conceptual models from which tools for water resources planning and management could be applied. The aim of this work is to evaluate the applicability of the joint use of statistical time-lag evaluation and dye tracer tests techniques with a double objective: 1) the development of conceptual models on the hydrogeological functioning that include the duality in the aquifer recharge processes, as well as the particularities of the preferential drainage flowpaths respect to the global response of the aquifers; 2) to establish a reference frame to foresee with enough time in anticipation the potential affections derived from the concentrated recharge to the springs, required in the creation of water quality monitoring networks and early warning systems to water pollution. In the Ubrique karst aquifer (southern Spain), the empirical relationships between the intensity (I) of rainfall events (recharge) and the time-lag (T) observed in the springs that draining the aquifer have been quantified. The establishment of the curve (I-T) constitutes a reliable tool for the prediction of potential affections to the springs (intended for urban supply) derived from recharge events. On the other hand, the comparison of the values drawn in the I-T curve, characteristic of each spring, with those derived from three tracer tests, has allowed further advances in the understanding of the aquifer functioning and the influence of concentrated recharge on the global system behavior to be achieved.This research was supported by the European Project “Karst Aquifer Resources availability and quality in the Mediterranean Area (KARMA)” PRIMA, ANR-18-PRIM-0005. The associated project PCI2019-103675 was funded by the Spanish Research Agency through the scientific program “Programación Conjunta Internacional”. Additionally, it contributes to the project PID2019-111759RB-I00 supported by the Agencia Estatal de Investigación (AEI/https://doi.org/10.13039/501100 011033) of the Spanish Government. Funding for open access charge: University of Malaga / CBU

Momento Económico (38)

Temas de hoy. 2/ De la ganaderización de la agricultura a la desganaderización actual. Retos y perspectivas Rosario Pérez Espejo. 3/ El mejoramiento en el transporte colectivo. una necesidad insoslayable Bernardo Navarro Benitez. 8/ La reconversión industrial también afecta al sector educativo Leticia Campos, 10/ México y el marco internacional de la inflación Mario J. Zepeda M. 12/ El petróleo y el conflicto del Medio Oriente Arturo Bonilla. 13

Momento Económico (13)

En este número Temas de hoy, El desprendimiento de las paraestatales, 21 México: La coyuntura del susector paraestatal, Ramón Martínez Escamilla, 3/ Imperialismo y petróleo: una evocación de la leyenda de Transilvania, Isaac Palacios Solano, 6/ El mercado petrolero mundial y las perspectivas de recuperación de la economía mexicana, Raúl Gonzlllez Soriano, 9/ Presupuesto del D.F. para 1985: 6% menos que en 1984, Alejandro Méndez Rodriguez, 11/ El impacto de la política urbana del régimen actual en los sectores populares, Bernardo Navano y Jum Manuel Ramírez S., 1

Effect of Melatonin as an Antioxidant Drug to Reverse Hepatic Steatosis: Experimental Model

Introduction. The hepatic steatosis of the nonalcoholic origin or NAFLD is increasing at present, particularly in Western countries, parallel to the increase in obesity, constituting one of the most prevalent hepatic processes in the Western society. Melatonin has been successfully tested in experimental models in mice as a drug capable of reversing steatosis. The effect of melatonin on fat metabolism can be summarized as a decrease in lipid peroxidation and a decrease in oxidative stress, biochemical phenomena intimately related to fat deposition in the hepatocyte. There are hardly any studies in large animals. Objective. In this study, we investigate the effects of melatonin administered orally at a dose of 10 mg/kg/day to reverse established hepatic steatosis induced by a special diet in a porcine animal model. Materials and Methods. We analyze the parameters of oxidative stress: malondialdehyde (MDA), 4-hydroxyalkenals (4-HDA), and carbonyls, degree of fat infiltration (analyzed by direct vision by a pathologist and by means of a computer program of image treatment), and serological parameters of lipid metabolism and hepatic damage. These parameters were analyzed in animals to which hepatic steatosis was induced by means of dietary modifications. Results. We have not been able to demonstrate globally a beneficial effect of melatonin in the improvement or reversal of liver steatosis once established, induced by diet in a porcine animal model. However, we have found several signs of improvement at the histological level, at the level of lipid metabolism, and at the level of oxidative stress parameters. We have verified in our study that, in the histological analysis of the liver sample by means of the program image treatment (free of subjectivity) of the animals that continue with the diet, those that consume melatonin do not increase steatosis as much as those that do not consume it significantly (p=0.002). Regarding the parameters of oxidative stress, MDA modifies in a significant manner within the group of animals that continue with the diet and take melatonin (p=0.004). As for lipid metabolism, animals that maintain the steatotic diet and take melatonin lower total and LDL cholesterol levels and increase HDL levels, although these results do not acquire statistical significance. Conclusions. In this study, it has not been possible to demonstrate a beneficial effect of melatonin in the improvement or reversal of liver steatosis once established and induced by diet in the porcine model. It is true that signs of improvement have been found at the histological level, at the level of lipid metabolism, and at the level of oxidative stress phenomena, when comparing animals with established steatosis that are treated with melatonin with those who do not take it. This work is the first study conducted in a large animal model in which the effect of melatonin is studied as a treatment in the reversal of established hepatic steatosis

Model selection for spectro-polarimetric inversions

Inferring magnetic and thermodynamic information from spectropolarimetric observations relies on the assumption of a parameterized model atmosphere whose parameters are tuned by comparison with observations. Often, the choice of the underlying atmospheric model is based on subjective reasons. In other cases, complex models are chosen based on objective reasons (for instance, the necessity to explain asymmetries in the Stokes profiles) but it is not clear what degree of complexity is needed. The lack of an objective way of comparing models has, sometimes, led to opposing views of the solar magnetism because the inferred physical scenarios are essentially different. We present the first quantitative model comparison based on the computation of the Bayesian evidence ratios for spectropolarimetric observations. Our results show that there is not a single model appropriate for all profiles simultaneously. Data with moderate signal-to-noise ratios favor models without gradients along the line-of-sight. If the observations shows clear circular and linear polarization signals above the noise level, models with gradients along the line are preferred. As a general rule, observations with large signal-to-noise ratios favor more complex models. We demonstrate that the evidence ratios correlate well with simple proxies. Therefore, we propose to calculate these proxies when carrying out standard least-squares inversions to allow for model comparison in the future.Comment: 16 pages, 2 figures, 8 tables, accepted for publication in Ap

West Nile virus in the New World: potential impacts on bird species

The past five years have seen the arrival and extremely rapid expansion of West Nile virus (WNV) in the Western Hemisphere. The rapid sweep across North America has permitted little time for developing knowledge of the virus’s potential impacts on wildlife in the New World. Given this information gap, we here summarize for the ornithological community what is known or can be anticipated for WNV’s effect on bird communities in coming years. Our particular focus is on impacts of WNV on the conservation status of birds, the principal vertebrate reservoir for the virus