Efficiency enhancement in existing biomass organic Rankine cycle plants by means of thermoelectric systems integration

This work investigates, from a thermodynamic point of view, the possibility of integrating thermoelectric systems (TES) in existing solid biomass-fuelled ORC CHP plants in a cost-effective way. Thus, a simple plant layout was proposed. The benefits achieved in the overall plant performance, constrained by several technical parameters of the subsystems involved, are assessed in terms of the Second Law efficiency and other characteristic parameters such as the First Law efficiency and the Primary Energy Savings Ratio. The main conclusion obtained is anticipating the fact that exists a certain optimal TES driving temperature value leading to the maximisation of the plant''s performance. According to the specific results extracted from the examples evaluated (TES integrated in Toluene and MDM ORC CHP plants), this temperature is about 245°C and 210°C, respectively, which leads to an increase in the overall Second Law efficiency of the plant up to 7–8%. Hence, it is clear that thermoelectric systems can contribute to the enhancement of the performance and to do so, there are guidelines to be considered prior to the detailed design of such systems to be integrated in existing ORC CHP plants

Generation of entangled photon pairs in optical cavity-QED: Operating in the bad cavity limit

We propose an optical cavity-QED scheme for the deterministic generation of polarization entangled photon pairs that operates with high fidelity even in the bad cavity limit. The scheme is based on the interaction of an excited four-level atom with two empty optical cavity modes via an adiabatic passage process. Monte-Carlo wave function simulations are used to evaluate the fidelity of the cavity-QED source and its entanglement capability in the presence of decoherence. In the bad cavity limit, fidelities close to one are predicted for state-of-the-art experimental parameter values.Comment: 9 pages and 5 figure

Stabilization of the Peregrine soliton and Kuznetsov-Ma breathers by means of nonlinearity and dispersion management

We demonstrate a possibility to make rogue waves (RWs) in the form of the Peregrine soliton (PS) and Kuznetsov-Ma breathers (KMBs) effectively stable objects, with the help of properly defined dispersion or nonlinearity management applied to the continuous-wave (CW) background supporting the RWs. In particular, it is found that either management scheme, if applied along the longitudinal coordinate, making the underlying nonlinear Schr\"odinger equation (NLSE) selfdefocusing in the course of disappearance of the PS, indeed stabilizes the global solution with respect to the modulational instability of the background. In the process, additional excitations are generated, namely, dispersive shock waves and, in some cases, also a pair of slowly separating dark solitons. Further, the nonlinearity-management format, which makes the NLSE defocusing outside of a finite domain in the transverse direction, enables the stabilization of the KMBs, in the form of confined oscillating states. On the other hand, a nonlinearity-management format applied periodically along the propagation direction, creates expanding patterns featuring multiplication of KMBs through their cascading fission.Comment: Physics Letters A, on pres

A deterministic cavity-QED source of polarization entangled photon pairs

We present two cavity quantum electrodynamics proposals that, sharing the same basic elements, allow for the deterministic generation of entangled photons pairs by means of a three-level atom successively coupled to two single longitudinal mode high-Q optical resonators presenting polarization degeneracy. In the faster proposal, the three-level atom yields a polarization entangled photon pair via two truncated Rabi oscillations, whereas in the adiabatic proposal a counterintuitive Stimulated Raman Adiabatic Passage process is considered. Although slower than the former process, this second method is very efficient and robust under fluctuations of the experimental parameters and, particularly interesting, almost completely insensitive to atomic decay.Comment: 5 pages, 5 figure

Hydrodynamics and two-dimensional dark lump solitons for polariton superfluids

We study a two-dimensional incoherently pumped exciton-polariton condensate described by an open-dissipative Gross-Pitaevskii equation for the polariton dynamics coupled to a rate equation for the exciton density. Adopting a hydrodynamic approach, we use multiscale expansion methods to derive several models appearing in the context of shallow water waves with viscosity. In particular, we derive a Boussinesq/Benney-Luke–type equation and its far-field expansion in terms of Kadomtsev-Petviashvili-I (KP-I) equations for right- and left-going waves. From the KP-I model, we predict the existence of vorticity-free, weakly (algebraically) localized two-dimensional dark-lump solitons. We find that, in the presence of dissipation, dark lumps exhibit a lifetime three times larger than that of planar dark solitons. Direct numerical simulations show that dark lumps do exist, and their dissipative dynamics is well captured by our analytical approximation. It is also shown that lumplike and vortexlike structures can spontaneously be formed as a result of the transverse “snaking” instability of dark soliton stripes.Europe Union project AEI/FEDER: MAT2016-79866-

A survey of recent introduction events, spread and mitigation efforts of mynas (Acridotheres sp.) in Spain and Portugal

Un estudio sobre los recientes episodios de introducción, la propagación y las iniciativas de mitigación de los minás (Acridotheres sp.) en España y Portugal El miná común, Acridotheres tristis, está catalogado entre las 100 especies más invasoras del mundo. En el presente artículo combinamos las observaciones ya existentes con un estudio de campo para determinar los procesos de invasión de tres especies de minás en España y Portugal. Los resultados sugieren que hubo al menos 22 introducciones accidentales e independientes desde comienzos de los años 90 en la península ibérica y en tres archipiélagos. Si bien el miná oscuro (A. ginginianus) no ha llegado a establecerse, hay poblaciones reproductoras de miná común en cuatro islas. Las iniciativas de erradicación permitieron eliminar esas poblaciones insulares, pero la especie se mantiene en el estuario del Tajo (Portugal). En esta región existe también una población reproductora de miná crestado (A. cristatellus), que ha crecido exponencialmente en la última década. Es necesario combinar las campañas de erradicación con acciones preventivas, cuyo objetivo sea detener el comercio de estas especies en Europa, para evitar nuevas introducciones accidentales.The common myna Acridotheres tristis is listed among the world’s 100 worst invasive alien species. We combined previous records with a field survey to update the extent and fate of myna introductions in Spain and Portugal. Results suggest that there have been at least 22 independent accidental introductions of three myna species throughout the Iberian peninsula and three archipelagos since the early 1990s. While bank mynas (A. ginginianus) did not become established elsewhere, common mynas reached breeding populations on four islands. Eradication efforts allowed the extirpation of these breeding island populations, but common mynas continue to breed in the Tagus Estuary (continental Portugal). In this region, there is also a breeding population of crested mynas (A. cristatellus), which was undergone an exponential population growth in the last decade. To avoid further accidental introductions, eradication campaigns should be combined with preventive actions aiming to stop the trade of these species in Europe.Un estudio sobre los recientes episodios de introducción, la propagación y las iniciativas de mitigación de los minás (Acridotheres sp.) en España y Portugal El miná común, Acridotheres tristis, está catalogado entre las 100 especies más invasoras del mundo. En el presente artículo combinamos las observaciones ya existentes con un estudio de campo para determinar los procesos de invasión de tres especies de minás en España y Portugal. Los resultados sugieren que hubo al menos 22 introducciones accidentales e independientes desde comienzos de los años 90 en la península ibérica y en tres archipiélagos. Si bien el miná oscuro (A. ginginianus) no ha llegado a establecerse, hay poblaciones reproductoras de miná común en cuatro islas. Las iniciativas de erradicación permitieron eliminar esas poblaciones insulares, pero la especie se mantiene en el estuario del Tajo (Portugal). En esta región existe también una población reproductora de miná crestado (A. cristatellus), que ha crecido exponencialmente en la última década. Es necesario combinar las campañas de erradicación con acciones preventivas, cuyo objetivo sea detener el comercio de estas especies en Europa, para evitar nuevas introducciones accidentales

Nonlinear Beam Propagation in a Class of Complex Non-PT -Symmetric Potentials

The subject of PT-symmetry and its areas of application have been blossoming over the past decade. Here, we consider a nonlinear Schr\"odinger model with a complex potential that can be tuned controllably away from being PT-symmetric, as it might be the case in realistic applications. We utilize two parameters: the first one breaks PT-symmetry but retains a proportionality between the imaginary and the derivative of the real part of the potential; the second one, detunes from this latter proportionality. It is shown that the departure of the potential from the PT -symmetric form does not allow for the numerical identification of exact stationary solutions. Nevertheless, it is of crucial importance to consider the dynamical evolution of initial beam profiles. In that light, we define a suitable notion of optimization and find that even for non PT-symmetric cases, the beam dynamics, both in 1D and 2D -although prone to weak growth or decay- suggests that the optimized profiles do not change significantly under propagation for specific parameter regimes

Interactions and scattering of quantum vortices in a polariton fluid

Quantum vortices, the quantized version of classical vortices, play a prominent role in superfluid and superconductor phase transitions. However, their exploration at a particle level in open quantum systems has gained considerable attention only recently. Here we study vortex pair interactions in a resonant polariton fluid created in a solid-state microcavity. By tracking the vortices on picosecond time scales, we reveal the role of nonlinearity, as well as of density and phase gradients, in driving their rotational dynamics. Such effects are also responsible for the split of composite spin-vortex molecules into elementary half-vortices, when seeding opposite vorticity between the two spinorial components. Remarkably, we also observe that vortices placed in close proximity experience a pull-push scenario leading to unusual scattering-like events that can be described by a tunable effective potential. Understanding vortex interactions can be useful in quantum hydrodynamics and in the development of vortex-based lattices, gyroscopes, and logic devices.Comment: 12 pages, 7 figures, Supplementary Material and 5 movies included in arXi

A Microphysiological System for Studying Nonalcoholic Steatohepatitis

Nonalcoholic steatohepatitis (NASH) is the most severe form of nonalcoholic fatty liver disease (NAFLD), which to date has no approved drug treatments. There is an urgent need for better understanding of the genetic and molecular pathways that underlie NAFLD/NASH, and currently available preclinical models, be they in vivo or in vitro, do not fully represent key aspects of the human disease state. We have developed a human in vitro co‐culture NASH model using primary human hepatocytes, Kupffer cells and hepatic stellate cells, which are cultured together as microtissues in a perfused three‐dimensional microphysiological system (MPS). The microtissues were cultured in medium containing free fatty acids for at least 2 weeks, to induce a NASH‐like phenotype. The co‐culture microtissues within the MPS display a NASH‐like phenotype, showing key features of the disease including hepatic fat accumulation, the production of an inflammatory milieu, and the expression of profibrotic markers. Addition of lipopolysaccharide resulted in a more pro‐inflammatory milieu. In the model, obeticholic acid ameliorated the NASH phenotype. Microtissues were formed from both wild‐type and patatin‐like phospholipase domain containing 3 (PNPLA3) I148M mutant hepatic stellate cells. Stellate cells carrying the mutation enhanced the overall disease state of the model and in particular produced a more pro‐inflammatory milieu. Conclusion: The MPS model displays a phenotype akin to advanced NAFLD or NASH and has utility as a tool for exploring mechanisms underlying the disease. Furthermore, we demonstrate that in co‐culture the PNPLA3 I148M mutation alone can cause hepatic stellate cells to enhance the overall NASH disease phenotype