Spontaneous, collective coherence in driven, dissipative cavity arrays

We study an array of dissipative tunnel-coupled cavities, each interacting with an incoherently pumped two-level emitter. For cavities in the lasing regime, we find correlations between the light fields of distant cavities, despite the dissipation and the incoherent nature of the pumping mechanism. These correlations decay exponentially with distance for arrays in any dimension but become increasingly long ranged with increasing photon tunneling between adjacent cavities. The interaction-dominated and the tunneling-dominated regimes show markedly different scaling of the correlation length which always remains finite due to the finite photon trapping time. We propose a series of observables to characterize the spontaneous build-up of collective coherence in the system.Comment: 9 pages, 4 figures, including supplemental material (with 4 pages, 1 figure). This is a shorter version with some modifications in the supplemental material (a gap in the proof was closed and calculations significantly generalized and improved

Dissipative structures in optomechanical cavities

Motivated by the increasing interest in the properties of multimode optomechanical devices, here we study a system in which a driven mode of a large-area optical cavity is despersively coupled to a deformable mechanical element. Two different models naturally appear in such scenario, for which we predict the formation of periodic patterns, localized structures (cavity solitons), and domain walls, among other complex nonlinear phenomena. Further, we propose a realistic design based on intracavity membranes where our models can be studied experimentally. Apart from its relevance to the field of nonlinear optics, the results put forward here are a necessary step towards understanding the quantum properties of optomechanical systems in the multimode regime of both the optical and mechanical degrees of freedom.Comment: Updated version with a more general model and a specific implementation proposal. Comments and (constructive) criticism are welcom

The Bose–Hubbard model with squeezed dissipation

The stationary properties of the Bose–Hubbard model under squeezed dissipation are investigated. The dissipative model does not possess aU (1) symmetry but conserves parity. We find that 〈a j 〉 = 0 always holds, so no symmetry breaking occurs. Without the onsite repulsion, the linear case is known to be critical. At the critical point the system freezes to an EPR state with infinite two mode entanglement. We show here that the correlations are rapidly destroyed whenever the repulsion is switched on. As we increase the latter, the system approaches a thermal state with an effective temperature defined in terms of the squeezing parameter in the dissipators. We characterize this transition by means of a Gutzwiller ansatz and the Gaussian Hartree–Fock–Bogoliubov approximation

Active locking and entanglement in type II optical parametric oscillators

Type II optical parametric oscillators are amongst the highest-quality sources of quantum-correlated light. In particular, when pumped above threshold, such devices generate a pair of bright orthogonally-polarized beams with strong continuous-variable entanglement. However, these sources are of limited practical use, because the entangled beams emerge with different frequencies and a diffusing phase difference. It has been proven that the use of an internal wave-plate coupling the modes with orthogonal polarization is capable of locking the frequencies of the emerging beams to half the pump frequency, as well as reducing the phase-difference diffusion, at the expense of reducing the entanglement levels. In this work we characterize theoretically an alternative locking mechanism: the injection of a laser at half the pump frequency. Apart from being less invasive, this method should allow for an easier real-time experimental control. We show that such an injection is capable of generating the desired phase locking between the emerging beams, while still allowing for large levels of entanglement. Moreover, we find an additional region of the parameter space (at relatively large injections) where a mode with well defined polarization is in a highly amplitude-squeezed state

De los centros TIC al PRODIG: evolución de los planes de formación del profesorado

En el presente trabajo abordaremos parte de los resultados de una investigación en la que hemos analizado la evolución de los planes de formación de la Consejería de Educación de la Junta de Andalucía para favorecer la implementación de los distintos planes de introducción de las TIC en las aula desde la puesta en marcha de los llamados “centros TIC” hasta el Programa de Digitalización de Centro (PRODIG) iniciado en este curso 2018-2019. Desde que la Junta de Andalucía aprobó el Decreto 72/2003 de Medidas de Impulso de la Sociedad del Conocimiento, la apuesta de la administración por la formación del profesorado de enseñanzas obligatorias fue muy ambiciosa. En general el impacto en los centros por el proyecto TIC fue muy positivo en opinión de la mayoría de los docentes, destacando principalmente el aumento en la motivación del alumnado. A pesar de ello, la formación ofrecida por parte de la administración era una de las mejoras que se demandaban. El siguiente plan de introducción de tecnología en las aula fue el proyecto “Escuela TIC 2.0”, que dotó a los centros de aulas con pizarras digitales y conexión Wifi, así como de dispositivos portátiles para el alumnado. En este caso, el profesorado manifestó igualmente la necesidad de una formación más centrada en los pedagógico que en lo tecnológico y que diera prioridad a fomentar los cambios metodológicos que se demandaban en los procesos de enseñanza-aprendizaje. La última apuesta (PRODIG) se ha iniciado este curso 2018-2019 con el fin de fomentar el cambio metodológico en los centros educativos, partiendo de la base expuesta en diferentes estudios previos realizados que afirman que la mera dotación tecnológica de los centros docentes no implica cambios en los procesos de enseñanza-aprendizaje si no se sustenta en cambios pedagógicos profundos que surjan de las necesidades de cada uno de los centros educativos.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Sistema de programación y control automático de un riego por goteo subterráneo en un cultivo de olivar

En esta comunicación se presenta un nuevo sistema de programación y control automático del riego por goteo subterráneo para un cultivo de olivar ecológico de una finca situada en el T.M. de Tabernas en Almería (España) y propiedad de la empresa Rafael Alonso Aguilera S.L. La finca se riega mediante un novedoso sistema de riego subterráneo patentado por esta empresa. El sistema de control propuesto está basado en el establecimiento de un balance hídrico diario en el en el sistema suelo-planta a partir de la estimación de las necesidades de riego del cultivo en tiempo real a partir de los datos climáticos medidos en tiempo real a partir de una estación agroclimática. Se presentan también los resultados de la evaluación del funcionamiento del sistema a lo largo de un periodo de 5 años y se analiza el ahorro de agua proporcionado por la combinación del sistema de control del riego y del método de riego subterráneo

Throughflow Velocity Crossing the Dome of Erupting Bubbles in 2-D Fluidized Beds

A new non-intrusive method for measuring the throughflow velocity crossing the dome of erupting bubbles in freely bubbling 2-D fluidized beds is presented. Using a high speed video-camera, the dome acceleration, drag force and throughflow velocity profiles are obtained for different experiments, varying the superficial gas velocity. The acceleration profiles show greater values in the dome zone where the gravity component is negligible. The drag force and the throughflow velocity profiles show a uniform value in the central region of the dome (40 deg \u3c \u3c 140 deg) and the total throughflow increases with the superficial gas velocity

Spatial localization and pattern formation in discrete optomechanical cavities and arrays

We investigate theoretically the generation of nonlinear dissipative structures in optomechanical (OM) systems containing discrete arrays of mechanical resonators. We consider both hybrid models in which the optical system is a continuous multimode field, as it would happen in an OM cavity containing an array of micro-mirrors, and also fully discrete models in which each mechanical resonator interacts with a single optical mode, making contact with Ludwig and Marquardt (2013 Phys. Rev. Lett. 101, 073603). Also, we study the connections between both types of models and continuous OM models. While all three types of models merge naturally in the limit of a large number of densely distributed mechanical resonators, we show that the spatial localization and the pattern formation found in continuous OM models can still be observed for a small number of mechanical elements, even in the presence of finite-size effects, which we discuss. This opens new venues for experimental approaches to the subject

Hydrodynamic Characteristics of a Fluidized Bed with Rotating Distributor

The performance of a novel rotating distributor fluidized bed is presented. The pressure drop and the standard deviation of pressure fluctuations, σp, were used to find the minimum fluidization velocity, Umf, and to characterize the quality of fluidization at different rotational speeds of the distributor plate. Experiments were conducted in the freely bubbling regime in a 0.19 m i.d. fluidized bed, operating with Group B particles according to Geldart’s classification. A decrease in Umf is observed when the rotational speed increases. Frequency analysis of pressure fluctuations shows that fluidization can be controlled by the adjustable rotational speed, at several excess gas velocities

Effectiveness and safety of glimepiride and iDPP4, associated with metformin in second line pharmacotherapy of type 2 diabetes mellitus: systematic review and meta-analysis

Objective: Our review analyses the studies that have specifically compared the association iDPP4/metformin with glimepiride/metformin, both in second line pharmacotherapy of type 2 diabetes mellitus (DM2). Methods: Systematic literature review with a meta-analysis of clinical trials comparing glimepiride with any iDPP4, both used together with metformin as a second line treatment of DM2. The effectiveness variables used were as follows: %HbA1c variation, fasting plasma glucose variation, patients achieving the therapeutic objective of HbA1c <7%, treatment dropouts due to lack of effectiveness and rescue treatments needed. The safety variables included were as follows: weight variation at the end of treatment; presentation of any type of adverse event; presentation of serious adverse events; patients who experienced any type of hypoglycaemia; patients who experienced severe hypoglycaemia; treatments suspended due to adverse effects; and deaths for any reason. Results: Four studies met the inclusion criteria. The group treated with glimepiride showed better results in all effectiveness variables. Regarding safety variables, the main differences observed were in the greater number of cases with hypoglycaemia in the group treated with glimepiride, and the serious adverse events or treatment discontinuations due to these which occurred in slightly over 2% more cases in this group compared to the iDPP4 group. The remaining adverse events, including mortality, did not show any differences between both groups. The variation in the weight difference between groups (2.1 kg) is not considered clinically relevant. Conclusions: A greater effectiveness is seen in the glimepiride/metformin association, which should not be diminished by slight differences in adverse effects, with absence of severe hypoglycaemia in over 98% of patients under treatment. The association of glimepiride/metformin, both due to cost as well as effectiveness and safety, may be the preferential treatment for most DM2 patients, and it offers a potential advantage in refractory hyperglycemic populations, tolerant to treatment.S