Extraordinary transverse magneto-optical Kerr effect in a superlens

It has been shown that a slab of a negative index material can behave as a superlens enhancing the imaging resolution beyond the wavelength limit. We show here that if such a slab possesses in addition some magneto-optical activity, it could act as an ideal optical filter and exhibit an extraordinary transverse magneto-optical Kerr effect. Moreover, we show that losses, which spoil the imaging resolution of these lenses, are a necessary ingredient to observe this effect.Comment: 5 pages, 6 figure

Efectos espaciales en la formación de precios de oferta en mercados spot de generación eléctrica

El mecanismo de fijación del precio de oferta en el mercado eléctrico colombiano exhibe comportamientos estratégicos inherente a la estructura oligopólica de este mercado, no solo por su alto porcentaje hidrológico, aproximadamente 80%, sino también debido a la localización geográfica de las plantas de generación eléctrica cercanas a la Región Andina. En esta investigación se diseña una matriz de pesos espaciales, que recoge características de la localización geográfica de las plantas de generación eléctrica, la cual se incorpora en un panel espacial de tipo Durbin para identificar dichos comportamientos de la geografía económica, además de las variables fundamentales que explican la formación del precio en este mercado.The price bid mechanism in the Colombian electricity market exhibits a strategic behavior, inherent in their oligopolistic market structure, not only for its high hydrological percentage, about 80%, but also because the power plants geographical location, near to the Andean Region. This research designs a spatial weights matrix reflecting characteristics the power plants geographical location, who is incorporated into a spatial Durbin panel to identify the economic geography behaviors, in addition to the fundamentals that explain the prices formation in this market

Precios y desempeño regulatorio en el pool eléctrico español

Este trabajo examina la relación entre el Gap del precio marginal del sistema y otras variables típicas del mercado, organización industrial y cambios regulatorios en el pool eléctrico español. Se estima un modelo de panel de datos largo, en el cual la dimensión temporal es mayor al número de empresas consideradas. Los resultados indican que tanto la alta concentración del mercado como la posibilidad de ser pivote generaron efectos nocivos sobre la determinación del precio. Además, los cambios regulatorios implementados por las autoridades no indujeron los efectos esperados, creando distorsión e incentivos incorrectos en este mercado.This study examines the relation between the gap of the system marginal price and other common variables in the market such as industrial organization and regulatory changes in the Spanish electricity pool. We estimate a long panel model where the time is larger than the number of firms. Our findings show that high market concentration and the possibility of being a pivot agent generate adverse effects on price determination. In addition, regulatory changes did not generate the expected effects, creating distortion and incorrect incentives in the market

Magnetic-field control of near-field radiative heat transfer and the realization of highly tunable hyperbolic thermal emitters

We present a comprehensive theoretical study of the magnetic field dependence of the near-field radiative heat transfer (NFRHT) between two parallel plates. We show that when the plates are made of doped semiconductors, the near-field thermal radiation can be severely affected by the application of a static magnetic field. We find that irrespective of its direction, the presence of a magnetic field reduces the radiative heat conductance, and dramatic reductions up to 700% can be found with fields of about 6 T at room temperature. We show that this striking behavior is due to the fact that the magnetic field radically changes the nature of the NFRHT. The field not only affects the electromagnetic surface waves (both plasmons and phonon polaritons) that normally dominate the near-field radiation in doped semiconductors, but it also induces hyperbolic modes that progressively dominate the heat transfer as the field increases. In particular, we show that when the field is perpendicular to the plates, the semiconductors become ideal hyperbolic near-field emitters. More importantly, by changing the magnetic field, the system can be continuously tuned from a situation where the surface waves dominate the heat transfer to a situation where hyperbolic modes completely govern the near-field thermal radiation. We show that this high tunability can be achieved with accessible magnetic fields and very common materials like n-doped InSb or Si. Our study paves the way for an active control of NFRHT and it opens the possibility to study unique hyperbolic thermal emitters without the need to resort to complicated metamaterials.Comment: 21 pages, 10 figure

Acute Effect of Resistance Training on Cognitive Function of Costa Rican Older Adults

Different types of exercise interventions have shown to improve cognitive performance; however, there is scarce evidence on the acute effect of resistance training (RT) on cognitions in older adults. The purpose of this study is to determine the acute effect of RT on cognitive performance in healthy older adults. 45 adults (Mean age = 65.3 ± 3.7 yr.) were randomly allocated to one of three groups: high-intensity RT (G1), low-intensity RT (G2), or inactive control (G3). Participants completed cognitive tests assessing processing speed, visuospatial processing, executive function, and cognitive control, working memory and immediate memory. The RT protocol for G1 and G2 consisted of six exercises. A 3x2 ANCOVA was performed with education as a covariate. Significant improvements were found on visuospatial processing in G1 (Pre = 61.6 ± 2.1 vs. Post = 69.7 ± 2.4; 95%CI = 4.8, 11.4; p ≤ 0.001) and G2 (Pre = 62.4 ± 2.2 vs. Post = 67.0 ± 2.5; 95%CI = 1.2, 8.1; p = 0.009). Other tested cognitive abilities were unchanged by acute exercise or rest. Acute RT enhanced or maintained cognitive performance in older adults. It was possible to successfully perform 1RM tests with older adults. Additional evidence is needed to determine effective protocols to improve cognition in older adulthood

The Association Between Abdominal Fat, Cardiorespiratory Fitness, and Clinical Markers of Metabolic Syndrome

Our purpose was to determine the association between abdominal fat and cardiorespiratory fitness (CRF) on markers of metabolic syndrome (MetS) total cholesterol (TC), high-density lipoprotein (HDL-C), low-density lipoprotein (LDL-C), triglycerides (TG), glucose, and blood pressure. We conducted a retrospective study on 165 adults (108 men) in which correlations between waist girth (WG), CRF and blood variables were determined. The cohort was partitioned by gender into quartiles and again by WG and differences in markers of MetS were compared across quartiles by ANOVA and by ANCOVA to determine the influence of CRF. Males in the lowest WG quartile exhibited greater HDL-C and lower diastolic blood pressure vs. the highest quartile (p < 0.05). TG were lower in the lowest vs. the third and highest quartile (p < 0.05), and glucose was greater in the highest vs. the first and second quartiles (p < 0.05). Females in the second WG quartile exhibited higher HDL-C vs. the highest quartile, and TG, glucose, systolic and diastolic blood pressure were lower in the lowest vs. the highest quartile (p < 0.05). After adjusting for CRF, diastolic blood pressure across WG in males were no longer significant, and    HLD-C and TG quartile differences were no longer significant in females. We confirm WG as an important correlate of clinical markers of MetS in adults. CRF mitigates relationships between WG and clinical markers of cardio-metabolic risk in men and women