Broadband transverse susceptibility in multiferroic Y-type hexaferrite Ba0.5Sr1.5Zn2Fe12O22

Producción CientíficaNoncollinear spin systems with magnetically induced ferroelectricity from changes in spiral magnetic ordering have attracted significant interest in recent research due to their remarkable magnetoelectric effects with promising applications. Single phase multiferroics are of great interest for these new multifunctional devices, being Y-type hexaferrites good candidates, and among them the ZnY compounds due to their ordered magnetic behaviour over room temperature. Polycrystalline Y type hexaferrites with composition Ba0.5Sr1.5Zn2Fe2O22 (BSZFO) were sintered in 1050 °C–1250 °C temperature range. Transverse susceptibility measurements carried out on these BSZFO samples in the temperature range 80–350 K with DC fields up to ± 5000 Oe reveal different behaviour depending on the sintering temperature. Sample sintered at 1250 °C is qualitatively different, suggesting a mixed Y and Z phase like CoY hexaferrites. Sintering at lower temperatures produce single phase Y-type, but the transverse susceptibility behaviour of the sample sintered at 1150 °C is shifted at temperatures 15 K higher. Regarding the DC field sweeps the observed behaviour is a peak that shifts to lower values with increasing temperature, and the samples corresponding to single Y phase exhibit several maxima and minima in the 250 K–330 K range at low DC applied field as a result of the magnetic field induced spin transitions in this compound.Ministerio de Ciencia, Innovación y Universidades; Agencia Estatal de Investigación with FEDER (MAT2016-80784-P

The Effect of the Exchange Rates on Investment in Mexican Manufacturing Industry

This paper, considering revenue and cost exposure channels, investigates the effects of exchange rate behaviour on fixed capital investment in Mexican manufacturing sector over 1994-2002. We find that i) currency depreciation has a positive (negative) effect on fixed investment through the export (import) channel; ii) exchange rate volatility impacts mostly export oriented sectors ; iii) the sensitivity of investment to exchange rate movements is stronger in non-durable goods sectors and industries with low mark-up ratios.Exchange rate volatility ; investment ; external exposure ; market structure

Influence of the Compaction Pressure and Sintering Temperature on the Mechanical Properties of Porous Titanium for Biomedical Applications

In the present work, the use of porous titanium is proposed as a solution to the difference in stiffness between the implant and bone tissue, avoiding the bone resorption. Conventional powder metallurgical technique is an industrially established route for fabrication of this type of material. The results are discussed in terms of the influence of compaction pressure and sintering temperature on the porosity (volumetric fraction, size, and morphology) and the quality of the sintering necks. A very good agreement between the predicted values obtained using a simple 2D finite element model, the experimental uniaxial compression behavior, and the analytical model proposed by Nielsen, has been found for both the Young’s modulus and the yield strength. The porous samples obtained by the loose sintering technique and using temperatures between 1000 °C −1100 °C (about 40% of total porosity) are recommended for achieving a suitable biomechanical behavior for cortical bone partial replacement.Ministry of Economy and Competitiveness of the State General Administration of Spain grant MAT2015-71284-

Molecular dynamics simulations of complex shaped particles using Minkowski operators

The Minkowski operators (addition and substraction of sets in vectorial spaces) has been extensively used for Computer Graphics and Image Processing to represent complex shapes. Here we propose to apply those mathematical concepts to extend the Molecular Dynamics (MD) Methods for simulations with complex-shaped particles. A new concept of Voronoi-Minkowski diagrams is introduced to generate random packings of complex-shaped particles with tunable particle roundness. By extending the classical concept of Verlet list we achieve numerical efficiencies that do not grow quadratically with the body number of sides. Simulations of dissipative granular materials under shear demonstrate that the method complies with the first law of thermodynamics for energy balance.Comment: Submitted to Phys. Rev.

Price dynamics, informational efficiency and wealth distribution in continuous double auction markets

This paper studies the properties of the continuous double auction trading mechanishm using an artificial market populated by heterogeneous computational agents. In particular, we investigate how changes in the population of traders and in market microstructure characteristics affect price dynamics, information dissemination and distribution of wealth across agents. In our computer simulated market only a small fraction of the population observe the risky asset's fundamental value with noise, while the rest of agents try to forecast the asset's price from past transaction data. In contrast to other artificial markets, we assume that the risky asset pays no dividend, so agents cannot learn from past transaction prices and subsequent dividend payments. We find that private information can effectively disseminate in the market unless market regulation prevents informed investors from short selling or borrowing the asset, and these investors do not constitute a critical mass. In such case, not only are markets less efficient informationally, but may even experience crashes and bubbles. Finally, increased informational efficiency has a negative impact on informed agents' trading profits and a positive impact on artificial intelligent agents' profits

Porous Titanium for Biomedical Applications: Evaluation of the Conventional Powder Metallurgy Frontier and Space-Holder Technique

Titanium and its alloys are reference materials in biomedical applications because of their desirable properties. However, one of the most important concerns in long-term prostheses is bone resorption as a result of the stress-shielding phenomena. Development of porous titanium for implants with a low Young’s modulus has accomplished increasing scientific and technological attention. The aim of this study is to evaluate the viability, industrial implementation and potential technology transfer of different powder-metallurgy techniques to obtain porous titanium with stiffness values similar to that exhibited by cortical bone. Porous samples of commercial pure titanium grade-4 were obtained by following both conventional powder metallurgy (PM) and space-holder technique. The conventional PM frontier (Loose-Sintering) was evaluated. Additionally, the technical feasibility of two different space holders (NH4HCO3 and NaCl) was investigated. The microstructural and mechanical properties were assessed. Furthermore, the mechanical properties of titanium porous structures with porosities of 40% were studied by Finite Element Method (FEM) and compared with the experimental results. Some important findings are: (i) the optimal parameters for processing routes used to obtain low Young’s modulus values, retaining suitable mechanical strength; (ii) better mechanical response was obtained by using NH4HCO3 as space holder; and (iii) Ti matrix hardening when the interconnected porosity was 36–45% of total porosity. Finally, the advantages and limitations of the PM techniques employed, towards an industrial implementation, were discussed.Ministry of Economy and Competitiveness of Spain Grant MAT2015-71284-PJunta de Andalucía Grant P12-TEP-1401Comisión Nacional de Investigación, Científica y Tecnológica (CONICYT) of the Chilean government project FONDECYT 1116086

Objetividad y verdad. Sobre el vigor contemporáneo de la falacia objetivista

La influencia de la filosofía positivista ha propiciado que, en el mundo contemporáneo, se tienda a identificar verdad y objetividad. Este artículo se propone argumentar que: a) el concepto de objetividad es una reducción indebida del concepto clásico de verdad; b) las premisas en las que se basa la teoría de la objetividad no son axiomáticas, como parecen, y conducen a contradicciones; c) es necesaria una rehabilitación de la concepción realista de verdad, libre de las ataduras del pensamiento positivista.The influence of the positivist philosophy has fostered, in the contemporary world, an ecuation between truth and objectivity. This article intends to argue that: a) the concept of objectivity is an unjustified reduction of the realist concept of truth; b) the premises upon which the objectivity theory is based are not –as seem to be– evident, and they lead to blatant contradictions; c) the realist concept of truth should be restored, freed from the ties of positivism

Todavía sobre la objetividad periodística: hacia la superación de un paradigma fracturado

Since the end of the nineteenth century, the theory of objectivity has been creating what it would be the prevailing paradigm both in journalistic practice and in the scholarly reflection upon it. However, during the last decades of the twentieth century, an increasing number of communication scholars and practitioners began to contest the main notions embedded in this paradigm, which was put in crisis. Since then, no other concept has stimulated as much controversy as the concept of objectivity, which still gives origin to debates not only endless, but also inconclusive. This article addresses the topic from an often neglected perspective, namely, that of the philosophical underpinnings of the theory of objectivity and its bearing upon the positivist presumptions, dated back to the empiricist tradition. By putting those foundations into scrutiny, it is argued that the theory of objectivity stems from an ill-conceived question. This accounts why this is a fractured paradigm, which, nonetheless, still remains firmly entrenched in our minds. Lastly, some hints are suggested as to how to overcome and replace it.Desde finales del siglo XIX, la teoría de la objetividad fue generando el que llegaría a ser el paradigma dominante en el ejercicio periodístico, así como en la reflexión académica sobre él. Sin embargo, durante las últimas décadas del siglo XX, fue surgiendo un creciente número de académicos y periodistas que rebatieron las tesis fundamentales de este paradigma, hasta llegar a ponerlo en crisis. Desde entonces, ningún otro concepto ha suscitado tanta controversia como el concepto de objetividad, que todavía origina debates, no sólo interminables, sino inconcluyentes. En este artículo se aborda la cuestión desde una perspectiva habitualmente ignorada: la de los fundamentos filosóficos de la teoría objetivista y su relación con el positivismo, cuyas raíces se remontan al empirismo inglés. Analizando tales fundamentos, se argumenta que la teoría objetivista parte de una pregunta mal concebida, lo cual explica por qué estamos ante un paradigma fracturado, que, pese a ello, sigue todavía firmemente arraigado en nuestras mentes. Finalmente, se apuntan algunas vías hacia su posible superación