Transparent photovoltaic technologies: Current trends towards upscaling

The world energy scenario is now living significant contributions coming from the photovoltaic field: new organic/inorganic hybrid materials have emerged in recent years, and in some cases these emerging strategies have exceeded the performance of traditional crystalline silicon. The next step concerns the integration of these technologies in smart buildings, in order to maximize the active surface capable of producing electricity and to contain the costs of air conditioning without affecting the amount of light needed. This review focuses on some of the most recent strategies developed to this purpose. Following an initial background on solar cells and figures of merit to characterize a transparent photovoltaic panel, the manuscript deals with a thorough analysis of wavelength-selective and non-wavelength selective devices, mentioning the main outcomes in the recent years. This distinction is proposed for both solar cells and solar concentrators, two areas in rapid evolution in academia and company worlds. A newly proposed case study and the example of a pre-industrial reality that has just started to scale-up this technology conclude this review, leaving to the reader a rich background on this highly-in-vogue field

Green synthetic fuels: Renewable routes for the conversion of non-fossil feedstocks into gaseous fuels and their end uses

Innovative renewable routes are potentially able to sustain the transition to a decarbonized energy economy. Green synthetic fuels, including hydrogen and natural gas, are considered viable alternatives to fossil fuels. Indeed, they play a fundamental role in those sectors that are di cult to electrify (e.g., road mobility or high-heat industrial processes), are capable of mitigating problems related to flexibility and instantaneous balance of the electric grid, are suitable for large-size and long-term storage and can be transported through the gas network. This article is an overview of the overall supply chain, including production, transport, storage and end uses. Available fuel conversion technologies use renewable energy for the catalytic conversion of non-fossil feedstocks into hydrogen and syngas. We will show how relevant technologies involve thermochemical, electrochemical and photochemical processes. The syngas quality can be improved by catalytic CO and CO2 methanation reactions for the generation of synthetic natural gas. Finally, the produced gaseous fuels could follow several pathways for transport and lead to different final uses. Therefore, storage alternatives and gas interchangeability requirements for the safe injection of green fuels in the natural gas network and fuel cells are outlined. Nevertheless, the effects of gas quality on combustion emissions and safety are considered

UNEXPECTED LACK OF EFFECT OF THE INVASIVE AMERICAN MINK ON NESTING SURVIVAL OF FOREST BIRDS

Nest predation by invasive mammalian predators can cause major impacts on native bird populations. The American mink (Neovison vison) was recently introduced on Navarino Island in southern Chile. The mink established as a new terrestrial mesopredator on the island with documented impacts on waterfowl breeding success. However, little is known about mink effects on forest bird’s reproduction. Here, we investigated nest-predation rate by native predators and the invasive mink on open-cup nesting forest birds by using artificial and natural nests. In six different plots, we deployed a grid (7 x 2) of 14 artificial nests spaced by 50 m and at random heights from the ground. We used camera traps in each nest to identify predators. At each plot, we estimated predator relative abundance using camera traps, Sherman traps, and bird point counts. We estimated nest survival probability as a function of nest age, concealment, distance to the river, and nest height. Additionally, we monitored 43 natural nests of five open-cup nesting bird species. Contrary to expected, mink was not a main predator of nests, depredating only one natural nest. The native raptor Chimango Caracara (Milvago chimango) was the main nest predator, preying on 39.8% artificial nests and 27.0% natural nests. We also found evidence that Chimango Caracara learned to associate the artificial nests with the egg reward. We argue that the lower abundance of mink in the forest and a mismatch between mink peak activity patterns and bird breeding phenology can result in low depredation. Mink impacts, however, may be more pervasive in summer months and on fledglings when mink activity peaks, and more research should be conducted to assess these questions. Our results are valuable to better understand mink impacts on biodiversity and to prioritize conservation actions on species more severely affected

Stability of Dirac cone in artificial graphene

Trabajo presentado al 18th ETSF Workshop celebrado en Luxemburgo del 1 al 4 de Octubre de 2013.ETSF - European Theoretical Spectroscopy Facility I3 (211956).Peer Reviewe

Daily patterns of activity of passerine birds in a Magellanic sub-Antarctic forest at Omora Park (55°S), Cape Horn Biosphere Reserve, Chile

Abstract Ecosystems in the sub-Antarctic region can be subjected to extreme weather conditions year-round. Little data exist that show any relationship between climatic variables and activity patterns of passerine birds, despite the fact that weather patterns can have a dramatic influence on the foraging strategies of these birds in different seasons. Passerine birds must balance the risk of starvation and the risk of predation in accordance with variation in environmental variables. The goal of this study was to determine the relationship of season, habitat type and weather patterns with the daily activity patterns of three diurnal passerine bird species from different trophic guilds. Unlike most low-latitude passerine species, the three passerine bird species in Omora Park on Navarino Island do not show strict adherence to a bimodal activity pattern; instead, these birds show a variety of activity patterns throughout the year that differ by trophic guild and habitat type. These modifications in activity patterns may be an adaptation to minimize the risk of predation and starvation in the face of temperature-dependent food availability

Invasive expansion of the American Mink (Neovison vison) in the Cape Horn Biosphere Reserve, Chile

This article reports the continued expansion of the American mink to new sites in the Cape Horn Biosphere Reserve

Electron-Electron Interactions in Artificial Graphene

Recent advances in the creation and modulation of graphene-like systems are introducing a science of "designer Dirac materials". In its original definition, artificial graphene is a man-made nanostructure that consists of identical potential wells (quantum dots) arranged in a adjustable honeycomb lattice in the two-dimensional electron gas. As our ability to control the quality of artificial graphene samples improves, so grows the need for an accurate theory of its electronic properties, including the effects of electron-electron interactions. Here we determine those effects on the band structure and on the emergence of Dirac points

Terahertz plasmons in coupled two-dimensional semiconductor resonators

Advances in theory are needed to match recent progress in measurements of coupled semiconductor resonators supporting terahertz plasmons. Here, we present a field-based model of plasmonic resonators that comprise gated and ungated two-dimensional electron systems. The model is compared to experimental measurements of a representative system, in which the interaction between the gated and ungated modes leads to a rich spectrum of hybridized resonances. A theoretical framework is thus established for the analysis and design of gated low-dimensional systems used as plasmonic resonators, underlining their potential application in the manipulation of terahertz frequency range signals

Modal Analysis and Coupling in Metal-Insulator-Metal Waveguides

This paper shows how to analyze plasmonic metal-insulator-metal waveguides using the full modal structure of these guides. The analysis applies to all frequencies, particularly including the near infrared and visible spectrum, and to a wide range of sizes, including nanometallic structures. We use the approach here specifically to analyze waveguide junctions. We show that the full modal structure of the metal-insulator-metal (MIM) waveguides--which consists of real and complex discrete eigenvalue spectra, as well as the continuous spectrum--forms a complete basis set. We provide the derivation of these modes using the techniques developed for Sturm-Liouville and generalized eigenvalue equations. We demonstrate the need to include all parts of the spectrum to have a complete set of basis vectors to describe scattering within MIM waveguides with the mode-matching technique. We numerically compare the mode-matching formulation with finite-difference frequency-domain analysis and find very good agreement between the two for modal scattering at symmetric MIM waveguide junctions. We touch upon the similarities between the underlying mathematical structure of the MIM waveguide and the PT symmetric quantum mechanical pseudo-Hermitian Hamiltonians. The rich set of modes that the MIM waveguide supports forms a canonical example against which other more complicated geometries can be compared. Our work here encompasses the microwave results, but extends also to waveguides with real metals even at infrared and optical frequencies.Comment: 17 pages, 13 figures, 2 tables, references expanded, typos fixed, figures slightly modifie