3,106 research outputs found
Current-driven skyrmion motion along disordered magnetic tracks
The motion of skyrmions along ferromagnetic strips driven by current pulses
is theoretically analyzed by means of micromagnetic simulations. Analytical
expressions describing the skyrmion dynamics during and after the current pulse
are obtained from an extended rigid skyrmion model, and its predictions are
compared with full micromagnetic simulations for perfect samples with a
remarkable agreement. The dynamics along realistic samples with random disorder
is also studied by both models. Our analysis describes the relevant ingredients
behind the current-driven skyrmion dynamics, and it is expected to be useful to
understand recent and future experimental.Comment: Micromagnetic simulations and analytical expressions describing the
dynamics of skyrmions under current-pulses along realistic strip
Tectonic evolution of Variscan Iberia: Gondwana–Laurussia
An integrated interpretation of the late Paleozoic structural and geochronological record of the Iberian Massif is
presented and discussed under the perspective of a Gondwana-Laurussia collision giving way to the Variscan
orogen. Compressional and extensional structures developed during the building of the Variscan orogenic crust
of Iberia are linked together into major tectonic events operating at lithosphere scale. A review of the
tectonometamorphic and magmatic evolution of the IberianMassif reveals backs and forths in the overall conver-
gence between Gondwana and Laurussia during theamalgamation of Pangea in late Paleozoic times. Stages dom-
inated by lithosphere compression are characterized by subduction, both oceanic and continental, development
of magmatic arcs, (over- and under-) thrusting of continental lithosphere, and folding. Variscan convergence re-
sulted in the eventual transference of a large allochthonous set of peri-Gondwanan terranes, the Iberian
Allochthon, onto the Gondwana mainland. The Iberian Allochthon bears the imprint of previous interaction be-
tween Gondwana and Laurussia, including their juxtaposition after the closure of the Rheic Ocean in Lower De-
vonian times. Stages governed by lithosphere extension are featured by the opening of two short-lived oceanic
basins that dissected previous Variscan orogenic crust, first in the Lower-Middle Devonian, following the closure
of the Rheic Ocean, and then in the early Carboniferous, following the emplacement of the peri-Gondwanan
allochthon. An additional, major intra-orogenic extensional event in the early-middle Carboniferous dismem-
bered the Iberian Allochthon into individual thrust stacks separated by extensional faults and domes. Lateral tec-
tonics played an important role through the Variscan orogenesis, especially during the creation of new tectonic
blocks separated by intracontinental strike-slip shear zones in the late stages of continental convergence
Estradiol regulates brown adipose tissue thermogenesis via hypothalamic AMPK
Copyright © 2014 Elsevier Inc. All rights reserved.Peer reviewedPublisher PD
En la costa aún sin mar
Los trabajos que conforman este volumen son una muestra de la presencia y actualidad de la obra de César Vallejo. Su poesía aún da lugar a nuevas y diversas interpretaciones; también a ciertas reconsideraciones. Asimismo, la narrativa del escritor peruano, poco atendida, está presente y exige estudio además de revalorización. La persona y obra de César Vallejo, en fin, son actuales incluso como un fenómeno metapoético.César Vallejo es un escritor esencial en el ámbito de la literatura contemporánea. Su obra literaria, escrita a principios del siglo pasado, sigue vigente. En su poesía, en particular, captó la sensibilidad de toda una época. Asimismo, supo traducir lo que él llamaba “el ritmo interior y el espíritu que se desprende de la realidad actual”. En cuanto a su obra en prosa, los estudios recientes dan muestra de su importancia, valor social y artístico. A casi cien años de la publicación de libros como Trilce y Los heraldos negros, la obra de César Vallejo sigue siendo fuente de goce estético y, por su complejidad, de búsqueda de conocimiento profundo de la realidad social y humana
Algunas evidencias de aplicación
Libro temático especializadoLa sustentabilidad también debe aplicarse al sistema de producción, buscando impulsar transformaciones graduales de los estilos y modelos productivos tradicionales a unas de mayor eficiencia. Y donde se incorpore la dimensión ambiental y geográfico-espacial, para crear estructuras productivas más progresivas y equitativas en las sociedades. Todo esto, como alternativa para revertir las tendencias de escasez y agotamiento de los recursos naturales, así como de los desequilibrios globales, cuyos costos permean todos los tejidos humanos. De esta manera, la “sustentabilidad productiva” se concibe como la generación de bienes y servicios con ciertos estándares de calidad, bajo un esquema de eficiencia, rendimiento y de organización inclusiva e integrada, con baja presión al ambiente y uso racional de los recursos, garantizando la estadía y permanencia de los insumos y materiales en el tiempo. Desde esta perspectiva, la producción sustentable y el crecimiento de largo plazo pueden ser explicados por la capacidad que tienen las economías para generar e incorporar conocimientos y tecnologías. De ahí que, la educación y las cualificaciones del capital humano, los cambios en la organización de la producción y la calidad institucional, sean elementos nodales para avanzar en la consolidación de este ambiente productivo
Differences in clinical features and mortality in very old unvaccinated patients (≥ 80 years) hospitalized with COVID-19 during the first and successive waves from the multicenter SEMI-COVID-19 Registry (Spain)
Background: Old age is one of the most important risk factors for severe COVID-19. Few studies have analyzed changes in the clinical characteristics and prognosis of COVID-19 among older adults before the availability of vaccines. This work analyzes differences in clinical features and mortality in unvaccinated very old adults during the first and successive COVID-19 waves in Spain. Methods This nationwide, multicenter, retrospective cohort study analyzes unvaccinated patients >= 80 years hospitalized for COVID-19 in 150 Spanish hospitals (SEMI-COVID-19 Registry). Patients were classified according to whether they were admitted in the first wave (March 1-June 30, 2020) or successive waves (July 1-December 31, 2020). The endpoint was all-cause in-hospital mortality, expressed as the case fatality rate (CFR). Results Of the 21,461 patients hospitalized with COVID-19, 5,953 (27.7%) were >= 80 years (mean age [IQR]: 85.6 [82.3-89.2] years). Of them, 4,545 (76.3%) were admitted during the first wave and 1,408 (23.7%) during successive waves. Patients hospitalized in successive waves were older, had a greater Charlson Comorbidity Index and dependency, less cough and fever, and met fewer severity criteria at admission (qSOFA index, PO2/FiO2 ratio, inflammatory parameters). Significant differences were observed in treatments used in the first (greater use of antimalarials, lopinavir, and macrolides) and successive waves (greater use of corticosteroids, tocilizumab and remdesivir). In-hospital complications, especially acute respiratory distress syndrome and pneumonia, were less frequent in patients hospitalized in successive waves, except for heart failure. The CFR was significantly higher in the first wave (44.1% vs. 33.3%; -10.8%; p = 95 years (54.4% vs. 38.5%; -15.9%; p < 0.001). After adjustments to the model, the probability of death was 33% lower in successive waves (OR: 0.67; 95% CI: 0.57-0.79). Conclusions Mortality declined significantly between the first and successive waves in very old unvaccinated patients hospitalized with COVID-19 in Spain. This decline could be explained by a greater availability of hospital resources and more effective treatments as the pandemic progressed, although other factors such as changes in SARS-CoV-2 virulence cannot be ruled out
Energy Estimation of Cosmic Rays with the Engineering Radio Array of the Pierre Auger Observatory
The Auger Engineering Radio Array (AERA) is part of the Pierre Auger
Observatory and is used to detect the radio emission of cosmic-ray air showers.
These observations are compared to the data of the surface detector stations of
the Observatory, which provide well-calibrated information on the cosmic-ray
energies and arrival directions. The response of the radio stations in the 30
to 80 MHz regime has been thoroughly calibrated to enable the reconstruction of
the incoming electric field. For the latter, the energy deposit per area is
determined from the radio pulses at each observer position and is interpolated
using a two-dimensional function that takes into account signal asymmetries due
to interference between the geomagnetic and charge-excess emission components.
The spatial integral over the signal distribution gives a direct measurement of
the energy transferred from the primary cosmic ray into radio emission in the
AERA frequency range. We measure 15.8 MeV of radiation energy for a 1 EeV air
shower arriving perpendicularly to the geomagnetic field. This radiation energy
-- corrected for geometrical effects -- is used as a cosmic-ray energy
estimator. Performing an absolute energy calibration against the
surface-detector information, we observe that this radio-energy estimator
scales quadratically with the cosmic-ray energy as expected for coherent
emission. We find an energy resolution of the radio reconstruction of 22% for
the data set and 17% for a high-quality subset containing only events with at
least five radio stations with signal.Comment: Replaced with published version. Added journal reference and DO
Measurement of the Radiation Energy in the Radio Signal of Extensive Air Showers as a Universal Estimator of Cosmic-Ray Energy
We measure the energy emitted by extensive air showers in the form of radio
emission in the frequency range from 30 to 80 MHz. Exploiting the accurate
energy scale of the Pierre Auger Observatory, we obtain a radiation energy of
15.8 \pm 0.7 (stat) \pm 6.7 (sys) MeV for cosmic rays with an energy of 1 EeV
arriving perpendicularly to a geomagnetic field of 0.24 G, scaling
quadratically with the cosmic-ray energy. A comparison with predictions from
state-of-the-art first-principle calculations shows agreement with our
measurement. The radiation energy provides direct access to the calorimetric
energy in the electromagnetic cascade of extensive air showers. Comparison with
our result thus allows the direct calibration of any cosmic-ray radio detector
against the well-established energy scale of the Pierre Auger Observatory.Comment: Replaced with published version. Added journal reference and DOI.
Supplemental material in the ancillary file
Measurement of the cosmic ray spectrum above eV using inclined events detected with the Pierre Auger Observatory
A measurement of the cosmic-ray spectrum for energies exceeding
eV is presented, which is based on the analysis of showers
with zenith angles greater than detected with the Pierre Auger
Observatory between 1 January 2004 and 31 December 2013. The measured spectrum
confirms a flux suppression at the highest energies. Above
eV, the "ankle", the flux can be described by a power law with
index followed by
a smooth suppression region. For the energy () at which the
spectral flux has fallen to one-half of its extrapolated value in the absence
of suppression, we find
eV.Comment: Replaced with published version. Added journal reference and DO
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