Mechanisms Contributing to the Emergence of Ranavirus in Ectothermic Vertebrate Communities

Ranaviruses have been linked to amphibian die-off events in ectothermic vertebrates worldwide. Differences in susceptibility and capacity of transmission among and within classes are poorly understood. My goal was to determine possible mechanisms influencing susceptibility to ranavirus infection in amphibian species and other aquatic vertebrate taxa, as well as the capacity of transmission between classes and the effects of amphibian community composition on ranavirus transmission. I tested 16 amphibian species from USA, Europe, and the pet trade, expanding an existing database developed by the Center for Wildlife Health to 35 amphibian species from 9 families. I also tested the susceptibility of 5 fish and 3 turtle species by exposure to a panel of ranaviruses from amphibian, fish and reptilian hosts under laboratory conditions. I used outdoor aquatic mesocosms to explore if certain species functioned as amplification hosts in a semi-natural environment. All vertebrate classes tested (amphibian, reptile, and fish) presented variability in susceptibility. Amphibians were most susceptible to ranavirus, but no phylogenetic relationship with susceptibility was detected. Susceptibility was related to life history characteristics of amphibian hosts. Fast-developing species that bred in temporary wetlands during spring showed higher susceptibility to ranavirus. Further, for one of the isolates, pathogenicity increased as distance between host population and isolate location increased. Fish and turtle species showed low susceptibility to ranavirus, but could function as reservoirs for ranavirus due to documentation of subclinical infections. Transmission experiments demonstrated that ranavirus could be transmitted between classes, with greatest mortality when infected turtles or fish transmitted the virus to amphibians. Finally, I showed that community composition affects ranavirus transmission and mortality in larval amphibians. Wood frog larvae functioned as amplification hosts to spotted salamander (Ambystoma maculatum) and caused an outbreak in chorus frog (Pseudacris feriarum). My results demonstrate that ranaviruses can infect multiple hosts from different classes with different susceptibilities, contributing to its persistence in the environment and recurrent outbreaks. My results can be used to identify potential species of high risk to ranaviral disease and highlight the need to understand host community to predict ranavirus outbreaks and develop conservation strategies to mitigate emergence of ranaviral disease

Energy-based model of a solar-powered pumped-hydro storage system

This document presents a port-Hamiltonian model of a pumped-hydro storage system, using Photo Voltaic energy as the primary source. MATLAB simulation results show that the model is functional under ideal conditions of constant solar radiation. It also graphically demonstrate the relationship between input solar power and the accumulation of energy at the upper reservoir. This work is a fundamental step towards a tool for the analysis and design of optimized and fully automated system

State-of-the-Art Perovskite Solar Cells Benefit from Photon Recycling at Maximum Power Point

Photon recycling is required for a solar cell to achieve an open-circuit voltage ($V_{OC}$) and power conversion efficiency (PCE) approaching the Shockley-Queisser theoretical limit. In metal halide perovskite solar cells, the achievable performance gains from photon recycling remain uncertain due to high variability in perovskite material quality and the non-radiative recombination rate ($k_{1}$). In this work, we study state-of-the-art $\textrm{Cs}_{0.05}(\textrm{MA}_{0.17}\textrm{FA}_{0.83})_{0.95}\textrm{Pb}(\textrm{I}_{0.83}\textrm{Br}_{0.17})_{3}$ films and analyze the impact of varying non-radiative recombination rates on photon recycling and device performance. Importantly, we predict the impact of photon recycling at the maximum power point (MPP), demonstrating an absolute PCE increase of up to 2.0% in the radiative limit, primarily due to a 77 mV increase in $V_{MPP}$. Even with finite non-radiative recombination, benefits from photon recycling can be achieved when non-radiative lifetimes and external LED electroluminescence efficiencies measured at open-circuit, $Q_{e}^{LED}(\textrm{V}_{OC})$, exceed 2 $\mu$s and 10%, respectively. This analysis clarifies the opportunity to fully exploit photon recycling to push the real-world performance of perovskite solar cells toward theoretical limits.Comment: Main text: 16 pages and 6 figures, SI: 22 pages and 21 figure

Current-Sensorless Control Strategy for the MPPT of a PV Cell:An Energy-Based Approach

A novel energy-based modelling and control strategy is developed and implemented to solve the maximum power point tracking problem when a photovoltaic cell array is connected to consumption loads. A mathematical model that contains key characteristic parameters of an energy converter stage connected to a photovoltaic cell array is proposed and recast using the port-Hamiltonian framework. The system consists of input-output power port pairs and storage and dissipating elements. Then, a current-sensorless control loop for a maximum power point tracking is designed, acting over the energy converter stage and following an interconnection and damping assignment passivity-based strategy. The performance of the proposed strategy is compared to a (classical) sliding mode control law. Our energy-based strategy is implemented in a hardware platform with a sampling rate of 122 Hz, resulting in lower dynamic power consumption compared to other maximum power point tracking control strategies. Numerical simulations and experimental results validate the performance of the proposed energy-based modelling and the novel control law approach

A Reversible Hydropump–Turbine System

Water-pumped storage systems have become an ideal alternative to regulate the intermittent power delivered by renewable energy sources. For small-scale operations, a type of centrifugal pump coupled to asynchronous machines represents an adequate solution due to their techno-economic feasibility in addition to their ability to operate as reversible systems. This work provides a novel port-Hamiltonian modelling approach to an integrated reversible hydropump–turbine system, that can be switched from motor pump to turbine-generator by employing a conventional hydraulic switch. Our modelling strategy provides a clear physical interpretation of the energy flow from the mechanical to electrical domains. Then, the model was built with multi-domain storing and dissipating elements and the interconnection of well-defined input–output port pairs. The system’s internal energy, i.e., Hamiltonian function, can be exploited for energy-shaping control strategies. The performance of our modelling approach is validated via numerical simulations

ALGUNAS REFLEXIONES SOBRE EL PERIÓDICO "EL SHEIK" EN COSTA RICA

Con la segunda generación de inmigrantes libaneses en Costa Rica se despertó un marcado interés por el rescate de la cultura árabe. Por esta razón los descendientes de inmigrantes libaneses, así como los inmigrantes de la primera etapa que arribó al país hacia finales del siglo XIX y en la primeras décadas del siglo XX, fundaron la Sociedad Libanesa. En esta, se in- formaba sobre aconteceres en el Líbano y con gran añoranza los descendientes de inmigrantes libaneses se proponían resucitar la música, las danzas, la gastronomía del país de origen de sus antepasados.Â

Política en educación para el desarrollo sostenible del Ministerio de Educación Pública de Costa Rica

Education for Sustainable Development (ESD) has been integrated into numerous global frameworks and conventions. Currently, there is growing international recognition that considers ESD as an integral element of quality education, since it provides people with skills that allow them to face the challenges posed by  changes regarding environmental- alteration,  which in turn manifest themselves as social fractures. In this sense, the Education policy and action plan for Sustainable Development, approved by the Higher Council of Education in 2020, formalize the route for the implementation of such a model as an axis that can permeate the curriculum of the different subjects in the public school system, and in response to the commitment acquired by the country for sustainable development achievement goals (SDGs.)La educación para el desarrollo sostenible (EDS) se ha integrado en numerosos marcos y convenciones mundiales. Existe ahora un creciente reconocimiento internacional como elemento integral de una educación de calidad que forma personas con habilidades para enfrentar los desafíos que plantean los cambios provocados por las alteraciones en el ambiente y que, a su vez, se manifiestan en fracturas sociales. En ese sentido, la Política y Plan de Acción de Educación para el Desarrollo Sostenible, aprobada por el Consejo Superior de Educación en el año 2020, formaliza la ruta para la implementación del modelo como un eje que impregna el currículo en las diferentes asignaturas; en respuesta al compromiso adquirido por el país en el logro de los objetivos para el desarrollo sostenible (ODS)