State-of-the-art techniques for calculating spectral functions in models for correlated materials

The dynamical mean field theory (DMFT) has become a standard technique for the study of strongly correlated models and materials overcoming some of the limitations of density functional approaches based on local approximations. An important step in this method involves the calculation of response functions of a multiorbital impurity problem which is related to the original model. Recently there has been considerable progress in the development of techniques based on the density matrix renormalization group (DMRG) and related matrix product states (MPS) implying a substantial improvement to previous methods. In this article we review some of the standard algorithms and compare them to the newly developed techniques, showing examples for the particular case of the half-filled two-band Hubbard model.Comment: 8 pages, 4 figures, to be published in EPL Perspective

Seagrasses of Costa Rica: from the mighty Caribbean to the dynamic meadows of the Eastern Tropical Pacific

Seagrass meadows are declining worldwide, mostly attributed to anthropogenic disturbances. Understanding the dynamics of these meadows is urgent in order to establish adequate management and conservation strategies. Here, we analyzed the current knowledge on the seagrass meadows in the Caribbean and Pacific coasts of Costa Rica, Central America. Current knowledge was based on literature searches, herbarium collections, informal interviews, and personal observations. We report a total of five genera and seven species for Costa Rica: Thalassia testudinum, Syringodium filiforme, Halophila decipiens, Halophila baillonis, Halodule wrightii, Halodule beaudettei, and Ruppia maritima. Six species are reported for the Caribbean, and four species for the Pacific. Thalassia testudinum, S. filiforme, and H. decipiens have only been reported for the Caribbean. Halodule beaudettei has only been reported for the Pacific coast. Halophila baillonis, H. wrightii and R. maritima have been reported for both coasts. Seagrasses were found at a total of 31 locations in Costa Rica, most from the Pacific coast; 16 of which are reported here for the first time. Seagrass meadows from both coasts are vastly different. Along the Caribbean coast, meadows are often dominated by the robust T. testudinum, they are extensive and stable, persisting for decades. In contrast, the meadows along the Pacific coast are more dynamic and are dominated by pioneer and smaller ephemeral species, such as H. baillonis and H. beaudettei. The number of studies on Costa Rican seagrasses is scarce but has been increasing over time, and mostly concern taxonomic reports and basic descriptions of the dynamics of T. testudinum meadows from the Caribbean. Research, conservation and management efforts on Costa Rican seagrass meadows would benefit from continued monitoring and research on associated fauna and flora, incorporating ecosystem resilience and services.Universidad de Costa Rica/[808-B6-170]/UCR/Costa RicaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Ciencias del Mar y Limnología (CIMAR)UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí

Reproducción sexual sincronizada del pasto marino Syringodium filiforme (Cymodoceaceae) en la laguna de un arrecife tropical en la costa Caribe de Costa Rica

There has been an increasing effort to understand the mechanisms of sexual reproduction in seagrasses, which is usually synchronized. Synchronization is caused by environmental cues, such as temperature and light availability, and most likely occurs to maximize pollination success. At higher latitudes where seagrass reproductive seasons are clearly marked, intraannual variability of environmental triggers is significant. Our aim was to identify the period and frequency of sexual reproduction for the manatee grass Syringodium filiforme in a tropical coral reef lagoon, where the above-mentioned environmental triggers are homogenous all year round. The reproductive state and frequency and shoot length of S. filiforme were measured non-destructively in a monospecific patch on the tropical Caribbean coast of Costa Rica. The meadow was surveyed at 1 to 4-month intervals between May 2010 and May 2012. Water turbidity, temperature, and salinity were measured in situ. During the surveyed period, sexual reproduction of S. filiforme was detected in February and May, while seagrass shoot length showed no variation. The moment of seagrass sexual reproduction was not fully explained by the environmental parameters studied. Regardless of the limited environmental variability compared to previous studies at higher latitudes, synchronization of seagrass sexual reproduction at this tropical location is interesting and requires further studies on mechanisms and its possible adaptive advantage.Ha habido un incremento en los esfuerzos por entender los mecanismos de reproducción sexual en pastos marinos, la cual usualmente ocurre de manera sincronizada. Se considera que esta sincronización se da para maximizar el éxito de la polinización. Esta sincronización en la reproducción sexual de pastos marinos es inducida por señales ambientales, como la temperatura y disponibilidad de luz. A mayores latitudes, donde los pastos marinos tienen períodos de reproducción estacional marcados, la variabilidad interanual de estas señales ambientales es significativa. Nuestro objetivo fue identificar el período de tiempo y frecuencia de reproducción sexual del pasto de manatí, Syringodium filiforme, en una laguna de arrecife tropical, donde los factores ambientales mencionados son homogéneos a lo largo del año. El estado y frecuencia reproductiva, así como la longitud de los haces, de S. filiforme se midieron de manera no destructiva en un parche monoespecífico de una pradera en la costa Caribe de Costa Rica. Esta pradera se muestreó en intervalos de 1 a 4 meses entre mayo del 2010 y mayo del 2012. La turbidez del agua, temperatura y salinidad se midieron in situ. Nuestro estudio identificó reproducción sexual durante el período de muestreo para S. filiforme en febrero y mayo en el sitio de estudio; mientras que la longitud de haces no evidenció variación. El momento de reproducción sexual de pasto marino no fue explicado de lleno por los parámetros ambientales estudiados. Su sincronización en esta ubicación tropical, a pesar de contar con variabilidad ambiental limitada en comparación con estudios previos a mayores latitudes, es interesante y amerita más investigación sobre los mecanismos y la posible ventaja adaptativa de la reproducción sexual sincronizada en pastos marinos.Centro de Investigación del Mar y Limnología/[808-96-298]/CIMAR/Costa RicaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Ciencias del Mar y Limnología (CIMAR)UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí

Identification of Natural and Anthropogenic Geochemical Processes Determining the Groundwater Quality in Port del Comte High Mountain Karst Aquifer (SE, Pyrenees)

The Port del Comte Massif (SE, Pyrenees) contains one of the most important vulnerable and strategic karst aquifers for supplying freshwater to the city of Barcelona (Spain). It is a fragile system, whose possible environmental impact is highly conditioned by land use. To improve the hydrogeological knowledge of the system, between September 2013 and October 2015, a detailed fieldwork was carried out for the revision of the geological model, the inventory of water points, and the in situ physico-chemical characterization on major elements and isotopes of up to a total of 43 springs, as well as precipitation water. This paper focuses on the characterization of the geochemical processes that allow explanation of the observed chemical variability of groundwater drained by the pristine aquifer system to determine the origin of salinity. The results show that the main process is the dissolution of calcite and dolomite, followed by gypsum and halite, and a minor cation exchange-like process. Sulfur and oxygen isotopes from dissolved sulfate in the studied springs point out a geogenic origin related to the dissolution of gypsum from Triassic and Tertiary materials, and that the contribution from anthropogenic sources, like fertilizers, is lower. Nitrate in groundwater is not an important issue, with a few localized cases related with agricultural activities. The multidisciplinary approach has allowed the development of a consistent hydrogeological conceptual model of the functioning of the aquifer system, which can be replicated in other places to understand the geogenic character of the hydrogeochemistry

Els dos telescopis refractors més grans de Catalunya

[cat] Entre 1886 i 1904 varen aparèixer a Catalunya dos telescopis refractors dobles (amb dos tubs, un visual i un altre fotogràfic) de grans dimensions. El primer fou un telescopi de la firma francesa Mailhat amb una obertura de 22 cm en ambdós tubs, que finalment va ser donat a la Facultat de Ciències de la Universitat de Barcelona. L'altre telescopi refractor fou també doble, de la mateixa firma, però amb 38 cm d'obertura, i va anar a l'Observatori Fabra. Aquesta comunicació, fa un estudi històric i tècnic d'aquestos telescopis.[eng] Two double refracting large telescopes (with two tubes, one for observations and another for photography) appeared in Catalonia between 1886 and 1904. The first was from the French firm Mailhat, a telescope with an aperture of 22 cm in both tubes that eventually was given to the Faculty of Sciences of the University of Barcelona in 1923 as a donation. The other refractor telescope was also made by the same firm but with an aperture of 38 cm and was designed for the Fabra Observatory project. In this communication a historical and technical study of these telescopes is carried out

Optical Photometric Monitoring of LS i +61 303

Three gamma-ray binaries, namely PSR B1259 63, HESS J0632+057 and LS I +61 303, contain compact objects orbiting around massive Be stars. Around periastron passage the compact objects should produce significant changes in the structure of the Be disks due to gravitational forces and eventually by ram pressure from the putative pulsar wind. Indeed, variability in the Hα emission line has been detected in all these systems, and optical periodic variability has been detected in one of them. However, there is lack of a systematic monitoring with accurate photometry, which could be used to constrain the shape of the disk during the periastron passage. This information is important to build accurate physical models to explain the broadband spectral energy distribution of these sources. Here we present an ongoing program to monitor the optical photometry of gamma-ray binaries and show preliminary results for the case of LS I +61 303

Contribution of isotopic research techniques to characterize highmountain-Mediterranean karst aquifers: The Port del Comte (Eastern Pyrenees) aquifer.

Water resources in high mountain karst aquifers are usually characterized by high rainfall, recharge and discharge that leads to the sustainability of the downstream ecosystems. Nevertheless, these hydrological systems are vulnerable to the global change impact. The mean transit time (MTT) is a key parameter to describe the behavior of these hydrologic systems and also to assess their vulnerability. This work is focused on estimating MTT by using water stable isotopes in the framework of high-mountain karst systems with a very thick unsaturated zone (USZ). To this end, it is adapted to alpine zones an existing methodology that combines in a row a semi-distributed rainfall-runoff model used to estimate recharge time series, and a lumped-parameter model to obtain through a convolution integral. The methodology has been applied to the Port del Comte Massif (PCM) hydrological system (Southeastern Pyrenees, NE Spain), a karst aquifer system with an overlying1000 m thick USZ. Six catchment areas corresponding to most important springs of the system are considered. The obtained results show that hydrologically the behavior of the system can be described by an exponential flow model (EM), with MTT ranging between 1.9 and 2.9 years. These values are shorter than those obtained by considering a constant recharge rate along time, which is the easiest and most applied aquifer recharge hypothesis when estimating through lumped-parameter models. This methodology can be useful to improve the characterization and understanding of other high mountain karst aquifers with an overlying thick USZ that are common in many alpine zones elsewhere the globe

Evidence of coupling between the thermal and nonthermal emission in the gamma-ray binary LS I +61 303

The gamma-ray binary LS I +61 303 is composed of a Be star and a compact companion orbiting in an eccentric orbit. Variable flux modulated with the orbital period of ~26.5 d has been detected from radio to very high-energy gamma rays. In addition, the system presents a superorbital variability of the phase and amplitude of the radio outbursts with a period of ~4.6 yr. We present optical photometric observations of LS I +61 303 spanning ~1.5 yr and contemporaneous Hα equivalent width (EWHα) data. The optical photometry shows, for the first time, that the known orbital modulation suffers a positive orbital phase shift and an increase in flux for data obtained 1-yr apart. This behavior is similar to that already known at radio wavelengths, indicating that the optical flux follows the superorbital variability as well. The orbital modulation of the EWHα presents the already known superorbital flux variability but shows, also for the first time, a positive orbital phase shift. In addition, the optical photometry exhibits a lag of ~0.1-0.2 in orbital phase with respect to the EWHα measurements at similar superorbital phases, and presents a lag of ~0.1 and ~0.3 orbital phases with respect noncontemperaneous radio and X-ray outbursts, respectively. The phase shifts detected in the orbital modulation of thermal indicators, such as the optical flux and the EWHα, are in line with the observed behavior for nonthermal indicators, such as X-ray or radio emission. This shows that there is a strong coupling between the thermal and nonthermal emission processes in the gamma-ray binary LS I +61 303. The orbital phase lag between the optical flux and the EWHα is naturally explained considering different emitting regions in the circumstellar disk, whereas the secular evolution might be caused by the presence of a moving one-armed spiral density wave in the disk

Proyecto de diseño de un condensador con fuente eólica para obtención de agua

This document deals with the description of a project to obtain a vital resource, water. Water is the most important resource in the daily life of humanity. This project attempts to compensate for the lack of access to this resource by vapor condensation present in the air. The need to do this work was seen, given that, due to earthquakes, coastal areas were affected, destroying buildings and distribution pipes of this vital product; which left the affected areas in very precarious conditions. The objective of this work is to show how to condense water, clean and of quality for human consumption, by means of a condensation device, to cover the most vital needs, which are daily hydration, disease prevention and food preparation. In this way, the temperature differential between the air and the ground is the key factor in the design, since it occurs naturally without any extra energy contribution. In history, different mechanisms of condensation have been generated, the most efficient do not take into account the relative humidity of the air, but reach the dew point by changing the temperature. This is the mechanism of operation of the project. This work was designed for the mountain area of the country and from this, work can be extrapolated to a warmer area.Este documento aborda a descrição de um projeto para obter um recurso vital, a água. A água é o recurso mais importante no cotidiano da humanidade. Este projeto procura compensar a falta de acesso a este recurso por condensação de vapor presente no ar. A necessidade de fazer este trabalho foi vista, dado que, devido a terremotos, as áreas costeiras foram afetadas, destruindo edifícios e tubos de distribuição deste produto vital; que deixou as áreas afetadas em condições muito precárias. O objetivo deste trabalho é mostrar como condensar água, limpar e de qualidade para consumo humano, por meio de um dispositivo de condensação, para cobrir as necessidades mais vitais, que são hidratação diária, prevenção de doenças e preparação de alimentos. Desta forma, o diferencial de temperatura entre o ar eo solo é o fator chave no projeto, pois ocorre naturalmente sem qualquer contribuição de energia extra. Na história, foram gerados diferentes mecanismos de condensação, os mais eficientes não levam em conta a umidade relativa do ar, mas atingem o ponto de orvalho alterando a temperatura. Este é o mecanismo de operação do projeto. Este trabalho foi projetado para a região montanhosa do país, e disso, o trabalho pode ser extrapolado para uma área mais quente.Este documento trata la descripción de un proyecto para conseguir un recurso vital, el agua. El agua es el recurso más importante en la vida diaria de la humanidad. Este proyecto intenta compensar la falta de acceso a este recurso mediante condensación de vapor presente en el aire. Se vio la necesidad de hacer este trabajo, dado que, por terremotos, zonas costeras se vieron afectadas, destruyendo edificaciones y tuberías de distribución de este producto vital; lo cual dejó en muy precarias condiciones las zonas afectadas. El objetivo de este trabajo es mostrar cómo condensar agua, limpia y de calidad para el consumo humano, mediante un dispositivo de condensación, para cubrir las necesidades más vitales, que son hidratación diaria, prevención de enfermedades y preparación de alimentos. De esta manera, el diferencial de temperatura entre el aire y el suelo, es el factor clave en el diseño, ya que se da de manera natural sin ningún aporte energético extra. En la historia se han generado distintos mecanismos de condensación, los más eficientes no toman en cuenta la humedad relativa del aire, sino alcanzar el punto de rocío cambiando la temperatura. Este es el mecanismo de funcionamiento del proyecto. Este trabajo fue diseñado para la zona serrana del país, y a partir de este, se puede extrapolar el trabajo para una zona más cálida