Enhancement of the spin-gap in fully occupied two-dimensional Landau levels

Polarization-resolved magneto-luminescence, together with simultaneous magneto-transport measurements, have been performed on a two-dimensional electron gas (2DEG) confined in CdTe quantum well in order to determine the spin-splitting of fully occupied electronic Landau levels, as a function of the magnetic field (arbitrary Landau level filling factors) and temperature. The spin splitting, extracted from the energy separation of the \sigma+ and \sigma- transitions, is composed of the ordinary Zeeman term and a many-body contribution which is shown to be driven by the spin-polarization of the 2DEG. It is argued that both these contributions result in a simple, rigid shift of Landau level ladders with opposite spins.Comment: 4 pages, 3 figure

Medical students learning styles in Latin American and Spanish universities: relation with geographical and curricular contexts

Objetivo. Determinar si los estilos de aprendizaje (EA) de los estudiantes de medicina se correlacionan con el contexto geográfico, con el contexto curricular o con el nivel de la carrera. Sujetos y métodos. El estudio se realizó en 490 estudiantes de las Escuelas de Medicina de las Universidades de Chile (Santiago, Chile), Nacional de Cuyo (Mendoza, Argentina), San Francisco Xavier (Sucre, Bolivia), Zaragoza y País Vasco (España). Se aplicó el cuestionario Honey-Alonso, que valora la preferencia por cada uno de cuatro EA: activo, reflexivo, teórico y pragmático. También se evaluó el EA de acuerdo al modelo de Kolb. Resultados. Al relacionar el EA con el contexto geográfico se observó que mientras los estudiantes de universidades españolas muestran un estilo preferentemente asimilador, siguiendo la denominación de Kolb, para Chile fue el acomodador y para Bolivia los estudiantes se distribuyen entre los estilos asimilador y divergente. Al comparar la distribución de los EA durante el tercer curso de medicina en dos facultades que poseen diferente currículo, no se observaron diferencias significativas. Los EA en una Facultad de Medicina con un currículo basado en asignaturas (Chile) no mostraron diferencias en los tres cursos del estudio (1.o, 3.o y 5.o), siendo preferentes los estilos reflexivo y teórico. Conclusiones. El estudio permitió establecer diferencias significativas entre los estilos de aprendizaje de los estudiantes de Medicina en relación con el contexto geográfico, más que con los diferentes currículos, o a lo largo de los distintos cursos de la carrera.Aim. To establish a correlation between medical student learning styles (LS) and the geographical context, the curricular context and different academic levels. Subjects and methods. The study was performed in 490 undergraduate students from Medical Schools of the Universities of Chile (Santiago, Chile), Nacional de Cuyo (Mendoza, Argentina), San Francisco Xavier (Sucre, Bolivia), Zaragoza and País Vasco (Spain). The instrument used was the Honey-Alonso learning style questionnaire that assesses the student preference for one of four LS: active, reflexive, theoretic and pragmatic. In addition, LS according to the Kolb inventory were also assessed. Results. Using the Kolb inventory, significant differences were found when the LS were correlated with the geographical context. While Spanish students showed a high preference for the assimilator style of learning, Chilean students resulted to be mainly accommodators, and Bolivian students were both assimilators and divergent. Comparing the LS distribution during the third course in two universities with different curricula (problem and lecture based learning), there were no significant differences. LS of medical students from a Medical School with a lecture based curriculum (University of Chile) were not significantly different during the first, the third and the fifth level of their undergraduate students. They showed a significant preference for reflexive and theoretic styles of learning. Conclusions. The present study allowed demonstrating that significant differences among the styles of learning of medical students correlated with the geographical context more than with the different curricula, or along the different courses of the career.Fil: Diaz Veliz, G.. Universidad de Chile; ChileFil: Mora, S.. Universidad Nacional de Cuyo. Facultad de Ciencias Médicas; ArgentinaFil: Lafuente Sanchez, J. V.. Universidad del País Vasco; EspañaFil: Gargiulo, Pascual Angel. Universidad Nacional de Cuyo. Facultad de Ciencias Médicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; ArgentinaFil: Bianchi, R.. Universidad Nacional de Cuyo. Facultad de Ciencias Médicas; ArgentinaFil: Teran, C.. Universidad Andina Simón Bolívar; BoliviaFil: Gorena, D.. Universidad Andina Simón Bolívar; BoliviaFil: Arce, J.. Universidad San Francisco Xavier; BoliviaFil: Escanero Marcen, J. F.. Universidad de Zaragoza; Españ

Designing healthy communities: A walkability analysis of LEED-ND

AbstractPrevailing city design in many countries has created sedentary societies that depend on automobile use. Consequently, architects, urban designers, and land planners have developed new urban design theories, which have been incorporated into the Leadership in Energy and Environmental Design for Neighborhood Development (LEED-ND) certification system. The LEED-ND includes design elements that improve human well-being by facilitating walking and biking, a concept known as walkability. Despite these positive developments, relevant research findings from other fields of study have not been fully integrated into the LEED-ND. According to Zuniga-Teran (2015), relevant walkability research findings from multiple disciplines were organized into a walkability framework (WF) that organizes design elements related to physical activity into nine categories, namely, connectivity, land use, density, traffic safety, surveillance, parking, experience, greenspace, and community. In this study, we analyze walkability in the LEED-ND through the lens of the nine WF categories. Through quantitative and qualitative analyses, we identify gaps and strengths in the LEED-ND and propose potential enhancements to this certification system that reflects what is known about enhancing walkability more comprehensively through neighborhood design analysis. This work seeks to facilitate the translation of research into practice, which can ultimately lead to more active and healthier societies

Stability of trions in strongly spin-polarized two-dimensional electron gases

Low-temperature magneto-photoluminescence studies of negatively charged excitons (X- trions) are reported for n-type modulation-doped ZnSe/Zn(Cd,Mn)Se quantum wells over a wide range of Fermi energy and spin-splitting. The magnetic composition is chosen such that these magnetic two-dimensional electron gases (2DEGs) are highly spin-polarized even at low magnetic fields, throughout the entire range of electron densities studied (5e10 to 6.5e11 cm^-2). This spin polarization has a pronounced effect on the formation and energy of X-, with the striking result that the trion ionization energy (the energy separating X- from the neutral exciton) follows the temperature- and magnetic field-tunable Fermi energy. The large Zeeman energy destabilizes X- at the nu=1 quantum limit, beyond which a new PL peak appears and persists to 60 Tesla, suggesting the formation of spin-triplet charged excitons.Comment: 5 pages (RevTex), 4 embedded EPS figs. Submitted to PRB-R

Spintronics: Fundamentals and applications

Spintronics, or spin electronics, involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. This article reviews the current status of this subject, including both recent advances and well-established results. The primary focus is on the basic physical principles underlying the generation of carrier spin polarization, spin dynamics, and spin-polarized transport in semiconductors and metals. Spin transport differs from charge transport in that spin is a nonconserved quantity in solids due to spin-orbit and hyperfine coupling. The authors discuss in detail spin decoherence mechanisms in metals and semiconductors. Various theories of spin injection and spin-polarized transport are applied to hybrid structures relevant to spin-based devices and fundamental studies of materials properties. Experimental work is reviewed with the emphasis on projected applications, in which external electric and magnetic fields and illumination by light will be used to control spin and charge dynamics to create new functionalities not feasible or ineffective with conventional electronics.Comment: invited review, 36 figures, 900+ references; minor stylistic changes from the published versio

Potential therapeutic implications of new insights into respiratory syncytial virus disease

Viral bronchiolitis is the most common cause of hospitalization in infants under 6 months of age, and 70% of all cases of bronchiolitis are caused by respiratory syncytial virus (RSV). Early RSV infection is associated with respiratory problems such as asthma and wheezing later in life. RSV infection is usually spread by contaminated secretions and infects the upper then lower respiratory tracts. Infected cells release proinflammatory cytokines and chemokines, including IL-1, tumor necrosis factor-α, IL-6, and IL-8. These activate other cells and recruit inflammatory cells, including macrophages, neutrophils, eosinophils, and T lymphocytes, into the airway wall and surrounding tissues. The pattern of cytokine production by T lymphocytes can be biased toward 'T-helper-1' or 'T-helper-2' cytokines, depending on the local immunologic environment, infection history, and host genetics. T-helper-1 responses are generally efficient in antiviral defense, but young infants have an inherent bias toward T-helper-2 responses. The ideal intervention for RSV infection would be preventive, but the options are currently limited. Vaccines based on protein subunits, live attenuated strains of RSV, DNA vaccines, and synthetic peptides are being developed; passive antibody therapy is at present impractical in otherwise healthy children. Effective vaccines for use in neonates continue to be elusive but simply delaying infection beyond the first 6 months of life might reduce the delayed morbidity associated with infantile disease

De novo insertions and deletions of predominantly paternal origin are associated with autism spectrum disorder

Whole-exome sequencing (WES) studies have demonstrated the contribution of de novo loss-of-function single-nucleotide variants (SNVs) to autism spectrum disorder (ASD). However, challenges in the reliable detection of de novo insertions and deletions (indels) have limited inclusion of these variants in prior analyses. By applying a robust indel detection method to WES data from 787 ASD families (2,963 individuals), we demonstrate that de novo frameshift indels contribute to ASD risk (OR= 1.6; 95% CI= 1.0-2.7; p= 0.03), are more common in female probands (p= 0.02), are enriched among genes encoding FMRP targets (p= 6× 10-9), and arise predominantly on the paternal chromosome (p< 0.001). On the basis of mutation rates in probands versus unaffected siblings, we conclude that de novo frameshift indels contribute to risk in approximately 3% of individuals with ASD. Finally, by observing clustering of mutations in unrelated probands, we uncover two ASD-associated genes: KMT2E (MLL5), a chromatin regulator, and RIMS1, a regulator of synaptic vesicle release