Correlation functions by Cluster Variation Method for Ising model with NN, NNN and Plaquette interactions

We consider the procedure for calculating the pair correlation function in the context of the Cluster Variation Methods. As specific cases, we study the pair correlation function in the paramagnetic phase of the Ising model with nearest neighbors, next to the nearest neighbors and plaquette interactions in two and three dimensions. In presence of competing interactions, the so called disorder line separates in the paramagnetic phase a region where the correlation function has the usual exponential behavior from a region where the correlation has an oscillating exponentially damped behavior. In two dimensions, using the plaquette as the maximal cluster of the CVM approximation, we calculate the phase diagram and the disorder line for a case where a comparison is possible with results known in literature for the eight-vertex model. In three dimensions, in the CVM cube approximation, we calculate the phase diagram and the disorder line in some cases of particular interest. The relevance of our results for experimental systems like mixtures of oil, water and surfactant is also discussed.Comment: 31 pages, LaTeX file, 7 figure

Fabrication methods for a quantum cascade photonic crystal surface emitting laser

Conventional quantum cascade (QC) lasers are intrinsically edge-emitting devices with mode confinement achieved via a standard mesa stripe configuration. Surface emission in edge emitting QC lasers has therefore necessitated redirecting the waveguided laser emission using a second order grating. This paper describes the methods used to fabricate a 2D photonic crystal (PC) structure with or without a central defect superimposed on an electrically pumped QC laser structure with the goal of achieving direct surface emission. A successful systematic study of PC hole radius and spacing was performed using e-beam lithography. This PC method offers the promise of a number of interesting applications, including miniaturization and integration of QC lasers

Scoping the potential usefulness of seasonal climate forecasts for solar power management

Solar photovoltaic energy is widespread worldwide and particularly in Europe, which became in 2016 the first region in the world to pass the 100 GW of installed capacity. As with all the renewable energy sources, for an effective management of solar power, it is essential to have reliable and accurate information about weather/climate conditions that affect the production of electricity. Operations in the solar energy industry are normally based on daily (or intra-daily) forecasts. Nevertheless, information about the incoming months can be relevant to support and inform operational and maintenance activities. This paper discusses a methodology to assess whether a seasonal climate forecast can provide a useful prediction for a specific sector, in this paper the European solar power industry. After evaluating the quality of the forecasts in providing probabilistic information for solar radiation, we describe how to assess their potential usefulness for a generic user by proposing an approach that takes into account not only their accuracy but also other potentially relevant factors. This approach is called index of opportunity and is then illustrated by presenting an example for the European solar power sector. The index of opportunity provides indications about where and when seasonal climate forecasts can benefit the decision-making in the photovoltaic sector. Even more importantly, it suggests an approach on how to evaluate their usefulness for the user's decision-making. This approach has the advantage of not limiting the definition of the usefulness only to the quality of the forecasts but rather considering, in an explicit way, all the factors that must be combined with the forecast's quality to define what is useful or not for the user

Quantum cascade photonic crystal surface emitting injection laser

A surface emitting quantum cascade injection laser is presented. Direct surface emission is obtained by using a 2D photonic-band-gap structure that simultaneously acts as a microcavity. The approach may allow miniaturization and on-chip-integration of the devices

Fabrication technologies for quantum cascade photonic-crystal microlasers

In this paper we describe the technological and fabrication methods necessary to incorporate both photonic and electronic-band engineering in order to create novel surface-emitting quantum cascade microcavity laser sources. This technology offers the promise of several innovative applications such as the miniaturization of QC lasers, and multi-wavelength two-dimensional laser arrays for spectroscopy, gas-sensing and imaging. This approach is not limited to light-emitting devices, and may be efficiently applied to the development of mid- and far-infrared normal-incidence detectors

Using ERA-Interim reanalysis for creating datasets of energy-relevant climate variables

The construction of a bias-adjusted dataset of climate variables at the near surface using ERA-Interim reanalysis is presented. A number of different, variable-dependent, bias-adjustment approaches have been proposed. Here we modify the parameters of different distributions (depending on the variable), adjusting ERA-Interim based on gridded station or direct station observations. The variables are air temperature, dewpoint temperature, precipitation (daily only), solar radiation, wind speed, and relative humidity. These are available on either 3 or 6 h timescales over the period 1979–2016. The resulting bias-adjusted dataset is available through the Climate Data Store (CDS) of the Copernicus Climate Change Data Store (C3S) and can be accessed at present from ftp://ecem.climate.copernicus.eu. The benefit of performing bias adjustment is demonstrated by comparinginitial and bias-adjusted ERA-Interim data against gridded observational fields

Lasing mode pattern of a quantum cascade photonic crystal surface-emitting microcavity laser

The identification of the lasing mode within a quantum cascade photonic crystal microcavity laser emitting at λ ~8 µm is presented. The symmetry of the lasing mode is determined by the position of nodal lines within micro-bolometer camera measurements of its polarized spatial distribution. Full three-dimensional finite-difference time-domain simulations are also performed, and the resulting vertically emitted radiation field pattern is seen to follow the experimental results closely

Ecología trófica del lenguado patagónico Paralichthys patagonicus (Jordan, 1889) en el Ecosistema Costero Argentino-Uruguayo

Food habits and diet composition of Patagonian flounder Paralichthys patagonicus (Jordan, 1889) were studied on the basis of stomach content analyses from 828 specimens (512 females, 304 males, 12 unsexed) collected during 16 commercial cruises between February 2009 and April 2010 in the Argentine-Uruguayan Coastal Ecosystem (34° S-41° S). A total of 272 stomachs (32.9%) contained food (184 females and 84 males), among which 20 prey taxa were identified. The most important prey category was pelagic fish, primarily Argentine anchovy (Engraulis anchoita), followed by rough scad (Trachurus lathami). Evidence showed that females consumed a higher total wet weight of prey compared to males. Results also suggested a specialised diet over E. anchoita, across all sex and size groups. The estimated trophic level for the population of P. patagonicus was 4.16. This study suggests that P. patagonicus is a tertiary piscivorous consumer of the trophic food web in the region, and reveals changes in the prey consumption compared with previous studies.Se estudiaron los hábitos alimentarios y la composición de la dieta del lenguado patagónico Paralichthys patagonicus (Jordan, 1889) sobre la base del análisis del contenido estomacal de 828 especímenes (512 hembras, 304 machos, 12 indeterminados) recolectados durante 16 cruceros comerciales entre febrero de 2009 y abril de 2010 en el Ecosistema Costero Argentino-Uruguayo (34° S-41° S). Un total de 272 estómagos (32,9%) contenían alimento (184 hembras y 84 machos), entre los que se identificaron 20 taxones de presas. La categoría de presa más importante fue los peces pelágicos, principalmente la anchoíta argentina (Engraulis anchoita), seguida por el surel (Trachurus lathami). La evidencia mostró que las hembras consumieron un mayor peso húmedo total de presa en comparación con los machos. Los resultados también sugirieron una dieta especializada sobre E. anchoita para todos los sexos y tamaños. El nivel trófico estimado para toda la población de P. patagonicus fue 4,16. Este estudio sugiere que P. patagonicus es un consumidor piscívoro terciario de la trama trófica en la región, y revela cambios importantes en el consumo de presas en comparación con estudios previos.

Coherent instabilities in a semiconductor laser with fast gain recovery

We report the observation of a coherent multimode instability in quantum cascade lasers (QCLs), which is driven by the same fundamental mechanism of Rabi oscillations as the elusive Risken-Nummedal-Graham-Haken (RNGH) instability predicted 40 years ago for ring lasers. The threshold of the observed instability is significantly lower than in the original RNGH instability, which we attribute to saturable-absorption nonlinearity in the laser. Coherent effects, which cannot be reproduced by standard laser rate equations, can play therefore a key role in the multimode dynamics of QCLs, and in lasers with fast gain recovery in general.Comment: 5 pages, 4 figure