Pressure-induced Jahn-Teller suppression in Rb2CuCl4( H2O )2: Pseudo-Jahn-Teller effect

In this work we investigate the variation of the local structure around Cu2+ as well as the crystal structure in Rb2CuCl4(H2O)2 through x-ray absorption spectroscopy (XAS) and x-ray diffraction (XRD) as a function of pressure. We show that the application of pressure induces a local structural change in the Jahn-Teller (JT) CuCl4(H2O)22− complex from an axially elongated complex to a compressed one, yielding disappearance of the JT distortion related to the four in-plane Cl− ligands, which are responsible for the antiferrodistortive structure displayed by the crystal at ambient pressure. According to the Pseudo-Jahn-Teller (PJT) theory (electron-phonon coupling E⊗e), the presence of water ligands enhances the JT release at pressures well below the metallization pressure. The results are compared with recent pressure experiments on A2CuCl4 layered perovskites and heteronuclear CuCl4L2 complex series, L :Cl→H2O→NH3, and explained on the basis of the PJT model

High-resolution optical imaging of the core of the globular cluster M15 with FastCam

We present high-resolution I-band imaging of the core of the globular cluster M15 obtained at the 2.5 m Nordic Optical Telescope with FastCam, a low readout noise L3CCD based instrument. Short exposure times (30 ms) were used to record 200000 images (512 x 512 pixels each) over a period of 2 hours 43 min. The lucky imaging technique was then applied to generate a final image of the cluster centre with FWHM ~ 0".1 and 13" x 13" FoV. We obtained a catalogue of objects in this region with a limiting magnitude of I=19.5. I-band photometry and astrometry are reported for 1181 stars. This is the deepest I-band observation of the M15 core at this spatial resolution. Simulations show that crowding is limiting the completeness of the catalogue. At shorter wavelengths, a similar number of objects has been reported using HST/WFPC observations of the same field. The cross-match with the available HST catalogues allowed us to produce colour-magnitude diagrams where we identify new Blue Straggler star candidates and previously known stars of this class.Comment: 11 pages, 15 figures. Accepted for publication in Monthly Notices of the Royal Astronomical Societ

The field high-amplitude SX Phe variable BL Cam: results from a multisite photometric campaign. II. Evidence of a binary - possibly triple - system

Short-period high-amplitude pulsating stars of Population I ($\delta$ Sct stars) and II (SX Phe variables) exist in the lower part of the classical (Cepheid) instability strip. Most of them have very simple pulsational behaviours, only one or two radial modes being excited. Nevertheless, BL Cam is a unique object among them, being an extreme metal-deficient field high-amplitude SX Phe variable with a large number of frequencies. Based on a frequency analysis, a pulsational interpretation was previously given. aims heading (mandatory) We attempt to interpret the long-term behaviour of the residuals that were not taken into account in the previous Observed-Calculated (O-C) short-term analyses. methods heading (mandatory) An investigation of the O-C times has been carried out, using a data set based on the previous published times of light maxima, largely enriched by those obtained during an intensive multisite photometric campaign of BL Cam lasting several months. results heading (mandatory) In addition to a positive (161 $\pm$ 3) x 10$^{-9}$ yr$^{-1}$ secular relative increase in the main pulsation period of BL Cam, we detected in the O-C data short- (144.2 d) and long-term ($\sim$ 3400 d) variations, both incompatible with a scenario of stellar evolution. conclusions heading (mandatory) Interpreted as a light travel-time effect, the short-term O-C variation is indicative of a massive stellar component (0.46 to 1 M_{\sun}) with a short period orbit (144.2 d), within a distance of 0.7 AU from the primary. More observations are needed to confirm the long-term O-C variations: if they were also to be caused by a light travel-time effect, they could be interpreted in terms of a third component, in this case probably a brown dwarf star ($\geq$ 0.03 \ M_{\sun}), orbiting in $\sim$ 3400 d at a distance of 4.5 AU from the primary.Comment: 7 pages, 5 figures, accepted for publication in A&

CURRENT DISTRIBUTION, HABITAT USE, AND BREEDING RECORDS OF THE HOUSE SPARROW (PASSER DOMESTICUS) IN VENEZUELA

ABSTRACT ∙ The House Sparrow (Passer domesticus, Passeridae), native to Eurasia and northern Africa, was introduced to the Americas and Australia where it inhabits mainly urban environments. The objective of this study was to determine the distribution of the House Sparrow in Venezuela from our own observations and data reported in personal communications, published material, and eBird records. House Sparrows were recorded for first time in Venezuela in 1996 at the port of La Guaira. Since then, records have increased, and we found 133 records of the House Sparrow until July 2015, in the states of Falcón, Zulia, Vargas, Miranda, Carabobo, Anzoátegui, and Los Roques Archipelago. The states of Falcón and Vargas included the greatest number of records, and 2015 was the year with the most records. Most sightings occurred in urban areas of coastal Venezuela. House Sparrows were recorded within three protected areas: Refugio de Fauna Silvestre de Cuare (Falcón), Refugio de Fauna Silvestre y Reserva de Pesca Ciénaga de los Olivitos (Zulia), and Parque Nacional Archipiélago Los Roques. Two records for Caracas, one for Barquisimeto and another for Margarita Island, need confirmation. Breeding was confirmed in five states where the House Sparrow is currently present, and records indicated that the nesting season extends from February to November. Most nests (84%) were located in man‐made structures, but two breeding records included a nesting colony in cavities of an exotic palm (Phoenix sp.) in Falcón and a nest under a pile of dead coral fragments in Los Roques Archipelago. We found evidence of foraging on new food items from two coastal trees (Conocarpus erectus and Coccoloba uvifera). Formal research and long‐term surveys are required to assess the functional ecological role of this exotic species in the avian communities of Venezuela.  RESUMEN ∙ Distribución actual, uso de hábitat y registros reproductivos del Gorrión Común (Passer domesticus) en Venezuela El Gorrión Común (Passer domesticus, Passeridae), nativo de Eurasia y el norte de África, fue introducido en gran parte de América y Australia, donde ocupa principalmente hábitats urbanos. El objetivo de este trabajo consistió en determinar la distribución del Gorrión Común en Venezuela con base en nuestras observaciones y datos reportados en comunicaciones personales, material publicado y registros en eBird. Los Gorriones Comunes se registraron por primera vez en Venezuela en 1996 en el puerto de La Guaira. Desde entonces, el número de registros se ha incrementado y nosotros encontramos 133 registros de Gorrión Común fechados hasta el julio de 2015 para los estados Falcón, Zulia, Vargas, Miranda, Carabobo, Anzoátegui y el Archipiélago de Los Roques. Los estados con mayor número de registros fueron Falcón y Vargas, y el año con el mayor número de registros fue 2015. La mayor parte de los avistamientos se realizaron dentro de áreas urbanas en la costa de Venezuela. Se registraron gorriones en tres áreas protegidas: el Refugio de Fauna Silvestre de Cuare (Falcón), el Refugio de Fauna Silvestre y Reserva de Pesca Ciénaga de los Olivitos (Zulia) y el Parque Nacional Archipiélago Los Roques. Dos reportes de avistamientos para Caracas, uno para Barquisimeto y otro para la Isla de Margarita requieren confirmación. La reproducción fue confirmada en cinco de los estados donde el Gorrión Común está presente actualmente, y los registros indican que la época reproductiva se extiende de febrero a noviembre. La mayoría de los nidos (84%) se ubicaron en estructuras hechas por el hombre, pero dos registros reproductivos incluyen una colonia de anidación en cavidades de una palma exótica (Phoenix sp.) en Falcón, y un nido bajo una pila de fragmentos de coral muerto en el Archipiélago de Los Roques. Encontramos nueva evidencia de alimentación con ítems de dos árboles costeros (Conocarpus erectus y Coccoloba uvifera). Estudios formales y monitoreo a largo plazo son necesarios para evaluar el rol ecológico funcional de esta especie exótica en las comunidades de aves en Venezuela

Effects of the herbicide Roundup on freshwater microbial communities: a mesocosm study

The impact of the widely used herbicide glyphosate has been mainly studied in terrestrial weed control, laboratory bioassays, and field studies focusing on invertebrates, amphibians, and fishes. Despite the importance of phytoplankton and periphyton communities at the base of the aquatic food webs, fewer studies have investigated the effects of glyphosate on freshwater microbial assemblages. We assessed the effect of the commercial formulation Roundup using artificial earthen mesocosms. The herbicide was added at three doses: a control (without Roundup) and two treatments of 6 and 12 mg/L of the active ingredient (glyphosate). Estimates of the dissipation rate (k) were similar in the two treatments (half-lives of 5.77 and 7.37 d, respectively). The only two physicochemical parameters showing statistically significant differences between treatments and controls were the downward vertical spectral attenuation coefficient kd(k), where k is wavelength, and total phosphorus concentration (TP). At the end of the experiment, the treated mesocosms showed a significant increase in the ratio kd(490 nm)/kd(550 nm) and an eightfold increase in TP. Roundup affected the structure of phytoplankton and periphyton assemblages. Total micro- and nanophytoplankton decreased in abundance in treated mesocosms. In contrast, the abundance of picocyanobacteria increased by a factor of about 40. Primary production also increased in treated mesocosms (roughly by a factor of two). Similar patterns were observed in the periphytic assemblages, which showed an increased proportion of dead : live individuals and increased abundances of cyanobacteria (about 4.5-fold). Interestingly, the observed changes in the microbial assemblages were captured by the analysis of the pigment composition of the phytoplankton, the phytoplankton absorption spectra, and the analysis of the optical properties of the water. The observed changes in the structure of the microbial assemblages are more consistent with a direct toxicological effect of glyphosate rather than an indirect effect mediated by phosphorus enrichment.Facultad de Ciencias Naturales y Muse

Studies of micronuclei and other nuclear abnormalities in red blood cells of Colossoma macropomum exposed to methylmercury

The frequencies of micronuclei (MN) and morphological nuclear abnormalities (NA) in erythrocytes in the peripheral blood of tambaqui (Colossoma macropomum), treated with 2 mg.L−1 methylmercury (MeHg), were analyzed. Two groups (nine specimens in each) were exposed to MeHg for different periods (group A - 24 h; group B - 120 h). A third group served as negative control (group C, untreated; n = 9). Although, when compared to the control group there were no significant differences in MN frequency in the treated groups, for NA, the differences between the frequencies of group B (treated for 120 h) and the control group were extremely significant (p < 0.02), thus demonstrating the potentially adverse effects of MeHg on C. macropomum erythrocytes after prolonged exposure

Investigaciones en ciencias humanas y sociales : del ABC disciplinar a la reflexión metodológica

Diversidad de objetos, variedad de enfoques, prácticas disciplinares y multidisciplinares, y ejemplos de ejecución de proyectos de investigación y desarrollo son los rasgos distintivos de los siete capítulos que integran esta obra. En ellos se recoge el material desplegado en los Seminarios-Talleres de Metodología de la Investigación en Humanidades que se realizaron en el marco de las V Jornadas de Investigación de la Facultad de Filosofía y Letras de la Universidad Nacional de Cuyo en setiembre de 2004: estudios sobre procesos sociales, cuestiones educativas, geográficas, históricas, lingüísticas y literarias. Algunos capítulos han mantenido el estilo y formato característicos del contexto de los seminarios-talleres, a veces con ligeras modificaciones; otros han sido enteramente reescritos para la convocatoria de esta publicación. Este libro refleja entonces abordajes disciplinares y pluridisciplinares diversos a problemáticas igualmente variadas. Por tratarse de propuestas orientadas a y/o basadas en seminarios-talleres, está claro que los autores involucrados no pueden abarcar todos los aspectos de los objetos de estudio respectivos. Sin embargo, la idea es al menos brindar algún punto de vista sobre el estadio de desarrollo de algunas de las investigaciones actualmente en ejecución en nuestra Facultad

The E-ELT first light spectrograph HARMONI: capabilities and modes

Trabajo presentado en SPIE Astronomical Telescopes, celebrado en San Diego (California), del 26 de junio al 1 de julio de 2016HARMONI is the E-ELT's first light visible and near-infrared integral field spectrograph. It will provide four different spatial scales, ranging from coarse spaxels of 60 × 30 mas best suited for seeing limited observations, to 4 mas spaxels that Nyquist sample the diffraction limited point spread function of the E-ELT at near-infrared wavelengths. Each spaxel scale may be combined with eleven spectral settings, that provide a range of spectral resolving powers (R 3500, 7500 and 20000) and instantaneous wavelength coverage spanning the 0.5 - 2.4 ¿m wavelength range of the instrument. In autumn 2015, the HARMONI project started the Preliminary Design Phase, following signature of the contract to design, build, test and commission the instrument, signed between the European Southern Observatory and the UK Science and Technology Facilities Council. Crucially, the contract also includes the preliminary design of the HARMONI Laser Tomographic Adaptive Optics system. The instrument's technical specifications were finalized in the period leading up to contract signature. In this paper, we report on the first activity carried out during preliminary design, defining the baseline architecture for the system, and the trade-off studies leading up to the choice of baseline