Coherent carrier dynamics in semiconductor superlattices

We investigate the coherent dynamics of carriers in semiconductor superlattices driven by ac-dc electric fields. We solve numerically the time-dependent effective-mass equation for the envelope function. We find that carriers undergo Rabi oscillations when the driving frequency is close to the separation between minibands.Comment: REVTEX (6 pages) and 3 figures (PostScript). Accepted in Physics Letters

Rabi oscillations in semiconductor superlattices

We investigate the dynamics of a semiconductor superlattice driven by an ac electric field by solving numerically the one-dimensional time-dependent Schro¨dinger equation including interface roughness effects. Rabi oscillations between minibands are clearly identified under resonant conditions, but we show that their lifetime is controlled by a characteristic time that depends on the superlattice deviation from perfection and is independent of the electric field. Experiments for the observation of the predicted effects are proposed.Work at Legane´s and Madrid was supported by CICYT ~Spain! under Projects Nos. MAT95-0325 and PB96-0199. E.D. gratefully acknowledges partial support from Fundacio´n Universidad Carlos III de Madrid. G.P.B. gratefully acknowledges partial support by the Defense Advanced Research Projects Agency.Publicad

Asimov: programa de robótica Tecnoparque Rionegro

El libro describe el programa de robótica ASIMOV del Tecnoparque nodo Rionegro, subs objetivos, antecedentes, metodología, eventos, infraestructura y talento humanoThe book describes the robotics program ASIMOV of the Tecnoparque node Rionegro, subs objectives, background, methodology, events, infrastructure and human talentPrograma de Robótica “Asimov” Antecedentes y contexto -- Qué es el programa ASIMOV? -- bjetivos -- Portafolio -- Metodología -- Público objetivo -- Infraestructura y Talento humano -- Transferencias de conocimientos -- Cómo hacer robótica sin robots -- La Robótica educativa en el mundo -- Avances tecnológicos en Robóticana32 página

The AMPA receptor positive allosteric modulator S 47445 rescues in vivo CA3-CA1 long-term potentiation and structural synaptic changes in old mice

Positive allosteric modulators of cc-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) are small molecules that decrease deactivation of AMPARs via an allosteric site. These molecules keep the receptor in an active state. Interestingly, this type of modulator has been proposed for treating cognitive decline in ageing, dementias, and Alzheimer's disease (AD). S 47445 (8-cyclopropyl-3[2-(3-fluorophenyflethy1]-7,8-dihydro-3H-[1,3]oxazino[6,5-g][1,2,3]benzotriazine-4,9-dione) is a novel AMPAR positive allosteric modulator (AMPA-PAM). Here, the mechanisms by which S 47445 could improve synaptic strength and connectivity were studied and compared between young and old mice. A single oral administration of S 47445 at 10 mg/kg significantly increased long-term potentiation (LTP) in CA3-CA1 hippocampal synapses in alert young mice in comparison to control mice. Moreover, chronic treatment with S 47445 at 10 mg/kg in old alert animals significantly counteracted the deficit of LTP due to age. Accordingly, chronic treatment with S 47445 at 10 mg/kg seems to preserve synaptic cytoarchitecture in old mice as compared with young control mice. It was shown that the significant decreases in number and size of pre-synaptic buttons stained for VGlutl, and post-synaptic dendritic spines stained for spinophilin, observed in old mice were significantly prevented after chronic treatment with 10 mg/kg of S 47445. Altogether, by its different effects on LTP, VGlutl-positive particles, and spinophilin, S 47445 is able to modulate both the structure and function of hippocampal excitatory synapses known to be involved in learning and memory processes. These results open a new window for the treatment of specific age-dependent cognitive decline and dementias such as AD. (C) 2017 The Authors. Published by Elsevier Ltd

Hyperosmolar myelinolysis

The central pontine myelinolysis is a metabolic disorder that affects the central nervous system; it is considered that a quick correction of hyponatremia leads to pontine and extra-pontine demyelination. This article briefly discusses some interesting aspects of this condition which is often diagnosed and should be known by the medical body that manages critical patients. (MED.UIS. 2010;23(2):120-5).   Key words: Mielinolisis hiperosmolar. Hyponatremia. Coma.    La mielinolisis osmótica es una patología metabólica que repercute sobre el sistema nervioso central; se considera que ocurre por la rápida corrección de una hiponatremia, lo que conduce a la desmielinización pontina y extrapontina. En este artículo se comentaran brevemente algunos aspectos de esta interesante patología que muchas veces no es diagnosticada y debe ser conocida por el cuerpo médico que maneja paciente críticos. (MED.UIS. 2010;23(2):120-5).   Palabras clave: Mielinolisis hiperosmolar. Hiponatremia. Coma.         &nbsp

Clonal chromosomal mosaicism and loss of chromosome Y in elderly men increase vulnerability for SARS-CoV-2

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, COVID-19) had an estimated overall case fatality ratio of 1.38% (pre-vaccination), being 53% higher in males and increasing exponentially with age. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, we found 133 cases (1.42%) with detectable clonal mosaicism for chromosome alterations (mCA) and 226 males (5.08%) with acquired loss of chromosome Y (LOY). Individuals with clonal mosaic events (mCA and/or LOY) showed a 54% increase in the risk of COVID-19 lethality. LOY is associated with transcriptomic biomarkers of immune dysfunction, pro-coagulation activity and cardiovascular risk. Interferon-induced genes involved in the initial immune response to SARS-CoV-2 are also down-regulated in LOY. Thus, mCA and LOY underlie at least part of the sex-biased severity and mortality of COVID-19 in aging patients. Given its potential therapeutic and prognostic relevance, evaluation of clonal mosaicism should be implemented as biomarker of COVID-19 severity in elderly people. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, individuals with clonal mosaic events (clonal mosaicism for chromosome alterations and/or loss of chromosome Y) showed an increased risk of COVID-19 lethality

Mutual coupling of antennas with overlapping minimum spheres based on the transformation between spherical and plane vector waves

Mutual coupling in finite arrays of antennas with strongly overlapping minimum spheres is quickly calculated by computing the general translation matrix between spherical modes. This matrix is obtained by using the transformation properties of spherical and plane vector waves. Although this approach is less efficient than the classical one, which is based on addition theorems, it allows to overcome the well-known limitation of addition theorems that requires nonintersecting minimum spheres. Symmetry relations are provided for the translation coefficients that greatly increase the speed of computation of the general translation matrix. By computing the reflection and the transmission submatrices of the generalized scattering matrix of a finite antenna array, accurate results are obtained for the Sparameters and the radiation patterns of arrays, in comparison with commercial software or a purely numerical in-house fullwave method. For this purpose, different types of antennas with strongly overlapping hemispheres in an array environment on a ground plane are used, such as apertures, monopoles, cavitybacked patch antennas, or dielectric resonator antennas.This work was supported in part by Ministerio de Economía y Competitividad (MINECO)/Agencia Estatal de Investigación (AEI)/Fondo Europeo de Desarrollo Regional (FEDER), Unión Europea (UE), Spain, under Project TEC2017-83352-C2-2-P and Project TEC2017-83352-C2-1-P and in part by the Junta de Extremadura and the FEDER Program (European Union) under Project GR18055.peerReviewe

Multistep transitions from microstrip and GCPW lines to SIW in 5G 26 GHz band

Las guías de onda integradas en sustrato (SIW) son un tema de interés para muchos investigadores, debido a su manejo de potencia y compatibilidad con las técnicas de procesamiento planar. Estas ventajas hacen de esta tecnología una candidata atractiva para las aplicaciones en la quinta generación de redes celulares (5G). Así, las transiciones desde tecnologías planares más comunes a SIW se han diseño para obtener un buen rendimiento. En estas transiciones se han empleado diversas técnicas, desde el uso de agujeros a sondas para la inclusión de elementos concentrados. Nosotros proponemos el uso de disminuciones graduales multipaso para obtener un rendimiento mejor, optimizando los diseños para la banda 5G n258. Como resultado, se han optimizado, medido y comparado con las simulaciones, varias configuraciones de transiciones. El proceso de diseño se realiza utilizando una aproximación heurística, simplemente aumentanto el número de iteraciones. La optimización de dieciseis topologías de transiciones (cuatro configuraciones diferentes, con cuatro números diferentes de pasos) se lleva a cabo mediante simulación electromagnética en CST Microwave Studio. Se presenta una comparación entre la respuesta de los diferentes diseños, el número de iteraciones y el número de iteraciones utilizadas para obtenerlas. Se han realizado simulaciones con un método de resolución propio de onda completa para validar las transiciones. Todas las transiciones se han fabricado en una placa de tecnología de circuito impreso de bajo coste en Rogers 4003C. Una configuración de microtira a SIW en 4 pasos, testeada como un prototipo de extremo a extremo, presenta una pérdida de inserción entre 2.0 dB y 2.2 dB y una pérdida de retorno mejor que 20 dB, desde 24.25 GHz a 26.5 GHz, incluyendo el efecto de los conectores terminación. Otra configuración GCPW a SIW de tres pasos, testada también como un prototipo de extremo a extremo, muestra una pérdida de retorno experimental de 13 dB de 24 GHz a 26.5 GHz y una pérdida de inserción entre 2.6 dB y 2.9 dB. El rendimiento general de las dieciseis configuraciones valida la utilidad del proceso de diseño propuesto.Substrate integrated waveguides (SIW) are a topic of interest for many researchers, due to their power handling capabilities and compatibility with planar processing techniques. These advantages make this technology an attractive candidate for fth generation of cellular networks applications (5G). Thus, transitions from more common planar technologies to SIW have been designed to obtain a good performance. Several techniques have been used in these transitions, from the use of via holes as probes to the inclusion of lumped elements. We propose the use of cascaded linear tapers as a multistep transition in order to obtain a better performance, optimizing the designs for the 5G n258 band. As result, several transition con gurations are optimized, measured and compared to simulations. The design process is performed using an heuristic approach, by just increasing the number of iterations. The optimization of sixteen transition topologies (four different con gurations, with four different numbers of steps), is carried out by electromagnetic simulation in CST Microwave Studio. A comparison between the response of the different designs, and the number of iterations used to obtain them, is also presented. Simulations with an in-house full-wave solver are performed to validate the transitions. All the transitions have been manufactured in a low-cost single-layer printed circuit board technology on Rogers 4003C. A microstrip-to-SIW 4-step con guration, tested as a back-to-back prototype, exhibits an insertion loss between 2:0 dB and 2:2 dB and a return loss better than 20 dB dB, from 24:25 GHz to 26:5 GHz, including the effect of the end-launch connectors. Another GCPW-to-SIW 3-step con guration, tested also as a back-to-back prototype, experimentally shows from 24 GHz to 26:5 GHz a minimum return loss of 13 dB, and an insertion loss between 2:6 dB and 2:9 dB. The overall performance of the sixteen con gurations validates the usefulness of the proposed design process.MINECO/AEI/FEDER, European Union, Spain, under Project TEC2017-83352-C2-2-P, and in part by the Junta de Extremadura and FEDER Program (European Union) under Project GR18055. The work of Alfonso Gómez García was supported by the Spanish Ministry of Education, Culture and Sport (MECD) through a Ph.D. Grant under Grant FPU17/00825peerReviewe