Onset voltage shift due to non-zero Landau ground state level in coherent magnetotransport

Coherent electron transport in double-barrier heterostructures with parallel electric and magnetic fields is analyzed theoretically and with the aid of a quantum simulator accounting for 3-dimensional transport effects. The onset-voltage shift induced by the magnetic field in resonant tunneling diodes, which was previously attributed to the cyclotron frequency $w_c$ inside the well is found to arise from an upward shift of the non-zero ground (lowest) Landau state energy in the entire quantum region where coherent transport takes place. The spatial dependence of the cyclotron frequency is accounted for and verified to have a negligible impact on resonant tunneling for the device and magnetic field strength considered. A correction term for the onset-voltage shift arising from the magnetic field dependence of the chemical potential is also derived. The Landau ground state with its nonvanishing finite harmonic oscillator energy $\hbar w_c /2$ is verified however to be the principal contributor to the onset voltage shift at low temperatures.Comment: 13 pages, and 3 figures. Accepted for publication in Phys. Rev.

Resonant Magnetic Vortices

By using the complex angular momentum method, we provide a semiclassical analysis of electron scattering by a magnetic vortex of Aharonov-Bohm-type. Regge poles of the $S$-matrix are associated with surface waves orbiting around the vortex and supported by a magnetic field discontinuity. Rapid variations of sharp characteristic shapes can be observed on scattering cross sections. They correspond to quasibound states which are Breit-Wigner-type resonances associated with surface waves and which can be considered as quantum analogues of acoustic whispering-gallery modes. Such a resonant magnetic vortex could provide a new kind of artificial atom while the semiclassical approach developed here could be profitably extended in various areas of the physics of vortices.Comment: 6 pages, 7 figure

Constraining scalar fields with stellar kinematics and collisional dark matter

The existence and detection of scalar fields could provide solutions to long-standing puzzles about the nature of dark matter, the dark compact objects at the centre of most galaxies, and other phenomena. Yet, self-interacting scalar fields are very poorly constrained by astronomical observations, leading to great uncertainties in estimates of the mass $m_\phi$ and the self-interacting coupling constant $\lambda$ of these fields. To counter this, we have systematically employed available astronomical observations to develop new constraints, considerably restricting this parameter space. In particular, by exploiting precise observations of stellar dynamics at the centre of our Galaxy and assuming that these dynamics can be explained by a single boson star, we determine an upper limit for the boson star compactness and impose significant limits on the values of the properties of possible scalar fields. Requiring the scalar field particle to follow a collisional dark matter model further narrows these constraints. Most importantly, we find that if a scalar dark matter particle does exist, then it cannot account for both the dark-matter halos and the existence of dark compact objects in galactic nucleiComment: 23 pages, 8 figures; accepted for publication by JCAP after minor change

Escala de evaluación de habilidades tecnológicas para futuros docentes con alumnos con necesidades educativas especiales

En los últimos años ha habido un desarrollo importante de las nuevas tecnologías en nuestra sociedad: aparición de software y hardware para PC, programas de estimulación cognitiva, dispositivos táctiles, etc. que han permitido los alumnos que presentan necesidades educativas especiales pueda acceder al mundo de la información. Del mismo modo, los profesionales de la educación se han validado de estas nuevas tecnologías como elemento motivador para estimular diferentes habilidades en el alumno. El objetivo de este estudio es analizar las diferencias en habilidades tecnológicas de una muestra de alumnos con necesidades educativas especiales tras implantar un programa para el aprendizaje de habilidades informáticas. Para la evaluación de estas capacidades ideamos una escala de Evaluación de las habilidades informáticas que será muy útil a los docentes. Dicha escala fue cumplimentada por el tutor antes y después de implementar el programa. La escala permite obtener una puntuación global y de dos sub-escalas: habilidades en el dominio del PC y habilidades relacionadas con el dominio de Internet. Futuros estudios tendrán que estudiar las propiedades psicométricas de esta escala con una muestra mayor de alumnos

Evidencias arqueológicas de desplomes paramentales traumáticos en las Termas Marítimas de Baelo Claudia. Reflexiones arqueosismológicas

Durante los años 2011 a 2013 se han localizado, identificado y excavado parcialmente los restos de un nuevo complejo termal en la ciudad hispanorromana de Baelo Claudia (Tarifa, Cádiz), situado en el suburbium occidental de la ciudad, junto a la línea de costa. Denominadas Termas Marítimas, construidas en la primera mitad del s. II d.C. y abandonadas en época de Diocleciano/Constantino han sido excavadas estratigráficamente con detalle, habiéndose detectado la existencia de fases anteriores (que se remontan al s. II a.C.) y una continuidad de uso del ambiente en época tardorromana y moderna, vinculada con la explotación de los recursos marinos. Especialmente singular ha sido la constatación del desplome traumático de parte de los paramentos de las habitaciones del edificio en dos momentos concretos: por un lado en la Antigüedad Tardía (500 d.C. circa), ya que una unidad muraria de una de las habitaciones (H-3), anexa a la natatio, se localizó completamente derrumbada sobre el suelo, conexionada; y por otro, el desplome del muro oeste de la natatio y el oriental de la cisterna, estructuras de más de seis metros de longitud y cuatro de altura mínima conservada, desplomadas sobre los niveles de abandono del asentamiento en época bajomedieval o moderna (ss. XIV-XV d.C.). Se trata en ambas ocasiones de colapsos estructurales no habituales en circunstancias normales en los procesos de sedimentación arqueológica, por lo que es muy probable que su desplome se pueda vincular con eventos sísmicos u otras causas naturales similare

Pulmonary long-term consequences of COVID-19 infections after hospital discharge

Objectives: COVID-19 survivors are reporting residual abnormalities after discharge from the hospital. Limited information is available about this stage of recovery or the lingering effects of the virus on pulmonary function and inflammation. The aim of this study was to describe lung function and to identify biomarkers in serum and induced sputum samples from patients recovering from COVID-19 hospitalisation. Methods: Patients admitted to Spanish hospitals with laboratory-confirmed COVID-19 infection by a real-time PCR (RT-PCR) assay for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) were recruited for this study. Each hospital screened their lists of discharged patients at least 45 days after symptom onset. SARS-CoV-2-infected patients were divided into mild/moderate and severe disease groups according to the severity of their symptoms during hospitalisation. Patients’ epidemiological and medical histories, comorbidities, chronic treatments, and laboratory parameters were evaluated. Pulmonary function tests, the standardised 6-minute walk test (6 MWT) and chest computed tomography (CT) were also performed. The levels of proteases, their inhibitors, and shed receptors were measured in serum and induced sputum samples. Results: A total of 100 patients with respiratory function tests were included in this study. The median number of days after the onset of symptoms was 104 (IQR 89.25, 126.75). COVID-19 was severe in 47% (47/100) of patients. CT was normal in 48% (48/100) of patients. Lung function was normal (FEV1 ≥80%, FVC ≥80%, FEV1/FVC ≥0.7, and diffusing capacity for carbon monoxide [DLCO] ≥80%) in 92% (92/100), 94% (94/100), 100% (100/100) and 48% (48/100) of patients, respectively. Multivariate analysis showed that a DLCO <80% (OR 5.92; 95%CI 2.28-15.37; p <0.0001) and a lower serum LDH level (OR 0.98; 95%CI 0.97-0.99) were associated with the severe disease group of SARS-CoV-2 during hospital stay. Conclusions: A diffusion deficit (DLCO <80%) was still present after hospital discharge and was associated with the most severe SARS-CoV-2 cases

Ginzburg-Landau functional for nearly antiferromagnetic perfect and disordered Kondo lattices

Interplay between Kondo effect and trends to antiferromagnetic and spin glass ordering in perfect and disordered bipartite Kondo lattices is considered. Ginzburg-Landau equation is derived from the microscopic effective action written in three mode representation (Kondo screening, antiferromagnetic correlations and spin liquid correlations). The problem of local constraint is resolved by means of Popov-Fedotov representation for localized spin operators. It is shown that the Kondo screening enhances the trend to a spin liquid crossover and suppresses antiferromagnetic ordering in perfect Kondo lattices and spin glass ordering in doped Kondo lattices. The modified Doniach's diagram is constructed, and possibilities of going beyond the mean field approximation are discussed.Comment: 18 pages, RevTeX, 7 EPS figures include

Galactic-Centre Gamma Rays in CMSSM Dark Matter Scenarios

We study the production of gamma rays via LSP annihilations in the core of the Galaxy as a possible experimental signature of the constrained minimal supersymmetric extension of the Standard Model (CMSSM), in which supersymmetry-breaking parameters are assumed to be universal at the GUT scale, assuming also that the LSP is the lightest neutralino chi. The part of the CMSSM parameter space that is compatible with the measured astrophysical density of cold dark matter is known to include a stau_1 - chi coannihilation strip, a focus-point strip where chi has an enhanced Higgsino component, and a funnel at large tanb where the annihilation rate is enhanced by the poles of nearby heavy MSSM Higgs bosons, A/H. We calculate the total annihilation rates, the fractions of annihilations into different Standard Model final states and the resulting fluxes of gamma rays for CMSSM scenarios along these strips. We observe that typical annihilation rates are much smaller in the coannihilation strip for tanb = 10 than along the focus-point strip or for tanb = 55, and that the annihilation branching ratios differ greatly between the different dark matter strips. Whereas the current Fermi-LAT data are not sensitive to any of the CMSSM scenarios studied, and the calculated gamma-ray fluxes are probably unobservably low along the coannihilation strip for tanb = 10, we find that substantial portions of the focus-point strips and rapid-annihilation funnel regions could be pressured by several more years of Fermi-LAT data, if understanding of the astrophysical background and/or systematic uncertainties can be improved in parallel.Comment: 33 pages, 12 figures, comments and references added, version to appear in JCA

2. Cambios climáticos del Holoceno

Existe una variabilidad natural del clima. Se debe tanto a factores externos (como el cambio de la órbita de la Tierra) como internos (como erupciones volcánicas o movimientos tectónicos entre otros). Los paleo-climatólogos estudian los cambios del clima del pasado a través de complejos análisis de sedimentos de lagos, de testigos de hielo de los glaciares o también de estalagmitas de las cavernas. Estos registros son como libros donde está escrita la historia del clima de la Tierra. Usando estos marcadores ambientales y gracias a los modelos climáticos a diferentes escalas espaciales y de tiempo, los investigadores buscan discriminar cual es la parte natural del cambio climático actual de la parte debida a la actividad humana y disminuir las incertidumbres en las proyecciones futuras del clima.Il existe une variabilité climatique naturelle. Elle est due aussi bien à des facteurs externes (comme le changement d’orbite de la Terre) qu’internes (comme les éruptions volcaniques ou les mouvements tectoniques entre autres). Les paléo-climatologues étudient les changements du climat du passé en réalisant des analyses complexes de sédiments de lacs, de carottes glaciaires ou encore de stalagmites des grottes. Ces registres sont comme des livres où est écrite l’histoire du climat de la Terre. A partir de ces marqueurs environnementaux et des modelés climatiques à différentes échelles d’espace et de temps, les chercheurs cherchent à connaître quelle part du changement climatique actuel est naturelle et quelle part est liée à l’activité humaine et réduire les incertitudes dans les projections climatiques.There is natural climate variability. It ¡s due to both external factors (such as changes in Earth’s orbit) as well as internal factors (such as volcanic eruptions and tectonic movements among others). Paleoclimatologists study historic climate changes performance by complex analysis of lake sediments, ice cores or stalagmite caves. These records are like books in where the history of Earth’s climate has been written. Thanks to these environmental markers and the climate models at different scales of space and time, researchers seek to differentiate which part of the current climate change is natural and which part is due to human activity, in order to reduce uncertainties in future climate projections