A cluster model with random anisotropy for hysteresis jumps in CeNi1−x_{1-x}Cux_{x} alloys

Some Cerium compounds exhibit hysteresis cycles with sharp macroscopic jumps in the magnetization at very low temperatures. This effect is attributed to the formation of clusters in which the anisotropy competes with the applied magnetic field. Here, we present a simple model where a lattice of ferromagnetically coupled spins is separated in clusters of random sizes and with random anisotropy. Within this model, we obtain hysteresis cycles presenting jumps that behave in a similar way that the experimental ones, and that disappear when increasing the temperature. The results are in good agreement with the hysteresis cycles measured at very low temperatures in CeNi$_{1-x}$Cu$_{x}$ and the comparison with these experimental results allows to discriminate the relative importance of the mechanisms driving the thermal evolution of the cycles.Comment: Accepted in PR

Influencia del proceso de fritura en profundidad sobre el perfil lipídico de la grasa contenida en patatas tipo “french”, empleando oleina de palma

The aim of this investigation was to evaluate the influence of certain variables of the process of deep fat frying on the lipid profile of the fat fraction of the potato type “french” (Solanum tuberosum) using palm oil. This marked the first fat fraction of both the processing type and the oil used, through the evaluation of various physicochemical parameters, using the method of AOAC and the Standard COVENIN. We identified variables that influenced the process during frying of potatoes, using an experimental design of type 3 * 22, evaluating factors such as the reuse of the matrix fat (1st, the 4th and the 8th fry), temperature (150° and 180 °C) and method of food peeling (chemical and manual), studying the content of polar compounds as an indicator of the deterioration of the fat present in the potato, finding that oil reuse and peeling method significantly influenced in a positive manner, and that the temperature has a negative influence on the absorption of polar compounds in potato chips (α: 0.05).El objetivo de la presente investigación fue evaluar la influencia de ciertas variables del proceso de fritura en profundidad sobre el perfil lipídico de la fracción grasa de la patata tipo “french” (Solanum tuberosum), empleando oleína de palma. Para ello se caracterizó inicialmente la fracción grasa tanto de la patata como de la oleína utilizada, a través de la evaluación de diferentes parámetros fisicoquímicos, empleando para ello métodos de la A.O.A.C. y las Normas COVENIN. Se identificó las variables del proceso que más influían durante la fritura de las patatas, aplicando un diseño experimental del tipo 3*22, evaluando como factores; la reutilización de la matriz grasa (1ra, 4ta y 8va fritura), la temperatura (150° y 180 °C) y tipo de pelado del alimento (químico y manual), estudiando el contenido de compuestos polares como indicador de deterioro de la grasa presente en la patata, encontrando que la reutilización y el tipo de pelado influyen significativamente de manera positiva, y que la temperatura tiene una influencia negativa en la absorción de compuestos polares en las patatas fritas (α: 0.05)

Role of the surface states in the magnetotransport properties of ultrathin bismuth films

We have investigated the magnetotransport properties of ultrathin films of Bi grown on thermally oxidized Si(001) substrates with thickness ranging from 10 to 100 nm at temperatures down to 2 K and in magnetic fields up to 90 kOe. Remarkable differences both in temperature and field dependence of the Hall resistivity are found for the films with thickness above and below 20 nm. These observations can be explained due to the presence of surface states, which play an important role in determining the electronic transport properties of the thinnest films. The estimated surface carrier density 4 x 10^(13) cm^(-2) at room temperature correlates well with that recently reported from angle-resolved photoemission spectroscopy on ultrathin Bi(001) films

Transport and Thermodynamic Evidence for a Marginal Fermi Liquid State in ZrZn2_2

Measurements of low temperature transport and thermodynamic properties have been used to characterize the non-Fermi liquid state of the itinerant ferromagnet ZrZn$_2$. We observe a $T^{5/3}$ temperature dependence of the electrical resistivity at zero field, which becomes $T^2$ like in an applied field of 9 T. In zero field we also measured the thermal conductivity, and we see a novel linear in $T$ dependence of the difference between the thermal and electrical resistivities. Heat capacity measurements, also at zero field, reveal an upturn in the electronic contribution at low temperatures when the phonon term is subtracted. Taken together, we argue that these properties are consistent with a marginal Fermi liquid state which is predicted by a mean-field model of enhanced spin fluctuations on the border of ferromagnetism in three dimensions. We compare our data to quantitative predictions and establish this model as a compelling theoretical framework for understanding ZrZn$_2$.Comment: 10 pages, 10 figure

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

Neorealism and the Organization of American States (OAS): an examination of CARICOM rationality toward Venezuela and the United States

Since 2017, CARICOM member states have been divided in the positions they take on Organization of American States (OAS) resolutions addressing political instability in Venezuela. This article uses a neorealism framework to determine whether or not the provision of energy investments by Venezuela and the United States to CARICOM member countries is an attempt on their part to skew the OAS voting mechanism in their national interests. The article also examines the extent to which CARICOM member states’ response to Venezuela’s and United States’ interest in the OAS demonstrates a pattern of rationality. The findings suggest that though the OAS provides a medium for states to negotiate mutually beneficial solutions, states are rational actors and even where they do corporate, dominant states may try to manifest their self-interest

Metamodel-based model conformance and multiview consistency checking

Model-driven development, using languages such as UML and BON, often makes use of multiple diagrams (e.g., class and sequence diagrams) when modeling systems. These diagrams, presenting different views of a system of interest, may be inconsistent. A metamodel provides a unifying framework in which to ensure and check consistency, while at the same time providing the means to distinguish between valid and invalid models, that is, conformance. Two formal specifications of the metamodel for an object-oriented modeling language are presented, and it is shown how to use these specifications for model conformance and multiview consistency checking. Comparisons are made in terms of completeness and the level of automation each provide for checking multiview consistency and model conformance. The lessons learned from applying formal techniques to the problems of metamodeling, model conformance, and multiview consistency checking are summarized

Spin-phonon coupling in epitaxial Sr0.6Ba0.4MnO3 thin films

Spin-phonon coupling is investigated in epitaxially strained Sr1-xBaxMnO3 thin films with perovskite structure by means of microwave (MW) and infrared (IR) spectroscopy. In this work we focus on the Sr0.6Ba0.4MnO3 composition grown on (LaAlO3)0.3(Sr2AlTaO6)0.7 substrate. The MW complex electromagnetic response shows a decrease in the real part and a clear anomaly in the imaginary part around 150 K. Moreover, it coincides with a 17% hardening of the lowest-frequency polar phonon seen in IR reflectance spectra. In order to further elucidate this phenomenon, low-energy muon-spin spectroscopy was carried out, signaling the emergence of antiferromagnetic order with Néel temperature (TN) around 150 K. Thus, our results confirm that epitaxial Sr0.6Ba0.4MnO3 thin films display strong spin-phonon coupling below TN, which may stimulate further research on tuning the magnetoelectric coupling by controlling the epitaxial strain and chemical pressure in the Sr1-xBaxMnO3 system