Quantum deformed magnon kinematics

The dispersion relation for planar N=4 supersymmetric Yang-Mills is identified with the Casimir of a quantum deformed two-dimensional kinematical symmetry, E_q(1,1). The quantum deformed symmetry algebra is generated by the momentum, energy and boost, with deformation parameter q=e^{2\pi i/\lambda}. Representing the boost as the infinitesimal generator for translations on the rapidity space leads to an elliptic uniformization with crossing transformations implemented through translations by the elliptic half-periods. This quantum deformed algebra can be interpreted as the kinematical symmetry of a discrete integrable model with lattice spacing given by the BMN length a=2\pi/\sqrt{\lambda}. The interpretation of the boost generator as the corner transfer matrix is briefly discussed

A new formulation of compartmental epidemic modelling for arbitrary distributions of incubation and removal times

The paradigm for compartment models in epidemiology assumes exponentially distributed incubation and removal times, which is not realistic in actual populations. Commonly used variations with multiple exponentially distributed variables are more flexible, yet do not allow for arbitrary distributions. We present a new formulation, focussing on the SEIR concept that allows to include general distributions of incubation and removal times. We compare the solution to two types of agent-based model simulations, a spatially homogeneous one where infection occurs by proximity, and a model on a scale-free network with varying clustering properties, where the infection between any two agents occurs via their link if it exists. We find good agreement in both cases. Furthermore a family of asymptotic solutions of the equations is found in terms of a logistic curve, which after a non-universal time shift, fits extremely well all the microdynamical simulations. The formulation allows for a simple numerical approach; software in Julia and Python is provided.Comment: 21 pages, 11 figures. v2 matches published version: improved presentation (including title, abstract and references), results and conclusions unchange

Modeling dust emission in PN IC 418

We investigated the infrared (IR) dust emission from PN IC 418, using a detailed model controlled by a previous determination of the stellar properties and the characteristics of the photoionized nebula, keeping as free parameters the dust types, amounts and distributions relative to the distance of the central star. The model includes the ionized region and the neutral region beyond the recombination front (Photodissociation region, or PDR), where the [OI] and [CII] IR lines are formed. We succeeded in reproducing the observed infrared emission from 2 to 200~\mm. The global energy budget is fitted by summing up contributions from big grains of amorphous carbon located in the neutral region and small graphite grains located in the ionized region (closer to the central star). Two emission features seen at 11.5 and 30~\mm are also reproduced by assuming them to be due to silicon carbide (SiC) and magnesium and iron sulfides (Mg$_x$Fe$_{1-x}$S), respectively. For this, we needed to consider ellipsoidal shapes for the grains to reproduce the wavelength distribution of the features. Some elements are depleted in the gaseous phase: Mg, Si, and S have sub-solar abundances (-0.5 dex below solar by mass), while the abundance of C+N+O+Ne by mass is close to solar. Adding the abundances of the elements present in the dusty and gaseous forms leads to values closer to but not higher than solar, confirming that the identification of the feature carriers is plausible. Iron is strongly depleted (3 dex below solar) and the small amount present in dust in our model is far from being enough to recover the solar value. A remaining feature is found as a residue of the fitting process, between 12 and 25~\mm, for which we do not have identification.Comment: Accepted for publication in Astronomy & Astrophysics. V2: adding reference

Can solar tower plants withstand the operational flexibility of combined cycle plants?

The aim of this work is to investigate the level of reliability of a 100 MWe solar tower plant operating as a load-following plant using actual operational data of combined cycle power plants. Despite the low cost, the steam generator has been identified as the main cause of unavailability of solar tower plants due to fatigue failures of tube-to-tubesheet joints, which can lead to steam/water leakage into the heat transfer fluid circuit, putting the plant performance at risk. A methodology based on the ASME code and EN standards is proposed to predict the fatigue failures of critical welded points of the steam generator, such as tube-to-tubesheet joints and other T-joints. The results show that the forced outages due to failures of the steam generator lead to an energy penalty that ranges over 230-453 GWh over the plant lifetime. The associated annual degradation rate ranges over 0.123-0.244%. Three tube leakage repair strategies are compared: tube-to-tubesheet weld crack repair, tube plugging and tube plugging with steam generator replacement. The latter strategy was shown to be the best practice because the lowest levelized cost of energy was obtained. In addition, the design of heat exchangers with a minimum of 20% extra area is highly recommended to not compromise the plant operation due to tube plugging. Last, the load-following operation of the solar tower plant increases the levelized cost of energy by approximately 1.6% in the case of tube repair and approximately 0.8% in the case of tube plugging with steam generator replacement.This research is partially funded by the Spanish government under the project RTI2018-096664-B-C21 (MICINN/FEDER, UE) and the fellowship "Programa de apoyo a la realización de proyectos interdisciplinares de I + D para jóvenes investigadores de la Universidad Carlos III de Madrid 2019-2020" under the project ZEROGASPAIN-CM-UC3M (2020/00033/001)

Residual Forage and Animal Performance from a Kikuyo Pasture under Mixed Grazing and Supplementation

Five grazing strategies were compared: grazing by ewes only and mixed grazing (ewes + heifers), in mixed grazing heifers received no supplement or one of three supplements. Ruminal undegradable protein (RUP) varied among supplement: 4.25, 9.11 and 9.13%, the supplement with the highest RUP included protected methionine. All supplements were 21% crude protein and 3.0 Mcal/kg of metabolizable energy. Grazing was on kikuyu, ratio was 30 kg of ewe per 100 kg of heifer in the mixed grazing treatments. Experimental grazing lasted 84 days. Variables measured were residual forage, proline content in residual forage and liveweight gains per animal and per hectare. Experimental design was a completely random with two replicates. Residual forage was the highest (P\u3c 0.05) in mixed grazing and RUP in supplement was above 4.25%. The highest (P\u3c 0.05) proline content was found in grazing by ewes only, 52% above the proline content found in mixed grazing without supplement, when heifers received supplement proline content decreased (P\u3c 0.05) further. Grazing by ewes only and mixed grazing with heifersreceiving the highest RUP in supplement showed the highest (P\u3c 0.05) daily liveweight gain per ewe of 134 g. Mixed grazing in which heifers received no supplement gave a 100% increase (P\u3c 0.05) in liveweight gain per hectare compared to grazing by ewes only. In mixed grazing offering a supplement with 9.13% RUP and protected methionine gave both the highest liveweight gains per animal and per hectare. It was concluded that mixed grazing allowed a lower stress level on kikuyu due to defoliation and a higher liveweight gain per hectare than grazing by ewes only

La ficción en la televisión generalista norteamericana y la representación de (nuevas) masculinidades

The text offers a tour through different representations of male characters in American generalist television that are beyond the classical representation of the male characters that were depicted as traditionally strong characters, courageous and machos. Considering how American television fiction has a maximum expan­sion –not only in the US but, also for its strong presence in all Western television, in Spain– we could see the impact that these representations can make in the public in order to build new identitarian points of referen­ce of the masculine, masculinity and virility.En el texto se hace un recorrido por diferentes representaciones de personajes masculinos en la televi­sión generalista norteamericana que se escapan a la representación clásica de los personajes masculi­nos que tradicionalmente eran representados como personajes fuertes, valerosos y machos. Teniendo en cuenta cómo la ficción televisiva norteamericana cuenta con una máxima expansión –no solamente en Estados Unidos sino también, por su gran presencia en todas las televisiones occidentales, en España– podríamos ver la repercusión que dichas representaciones pueden tener en los públicos en orden a cons­truir nuevos imaginarios y nuevas referencias identitarias de lo masculino, la masculinidad y la virilidad

The exergy costs of electrical power, cooling, and waste heat from a hybrid system based on a solid oxide fuel cell and an absorption refrigeration system

This paper applies the Exergy Cost Theory (ECT) to a hybrid system based on a 500 kWe solid oxide fuel cell (SOFC) stack and on a vapor-absorption refrigeration (VAR) system. To achieve this, a model comprised of chemical, electrochemical, thermodynamic, and thermoeconomic equations is developed using the software, Engineering Equation Solver (EES). The model is validated against previous works. This approach enables the unit exergy costs (electricity, cooling, and residues) to be computed by a productive structure defined by components, resources, products, and residues. Most importantly, it allows us to know the contribution of the environment and of the residues to the unit exergy cost of the product of the components. Finally, the simulation of different scenarios makes it possible to analyze the impact of stack current density, fuel use, temperature across the stack, and anode gas recirculation on the unit exergy costs of electrical power, cooling, and residues