Superconducting and pseudogap phases from scaling near a Van Hove singularity

We study the quantum corrections to the Fermi energy of a two-dimensional electron system, showing that it is attracted towards the Van Hove singularity for a certain range of doping levels. The scaling of the Fermi level allows to cure the infrared singularities left in the BCS channel after renormalization of the leading logarithm near the divergent density of states. A phase of d-wave superconductivity arises beyond the point of optimal doping corresponding to the peak of the superconducting instability. For lower doping levels, the condensation of particle-hole pairs due to the nesting of the saddle points takes over, leading to the opening of a gap for quasiparticles in the neighborhood of the singular points.Comment: 4 pages, 6 Postscript figures, the physical discussion of the results has been clarifie

Morphological Variations of Wild Populations of Brycon dentex (Characidae, Teleostei) in the Guayas Hydrographic Basin (Ecuador). The Impact of Fishing Policies and Environmental Conditions

The Guayas, located in Ecuador, is the largest basin in the Pacific Ocean and has an inventory of 123 native freshwater species. Most of these are endemic species that are threatened or at-risk due to anthropogenic activity and the modification, fragmentation, and destruction of habitats. The aim of this study was to determine the morphometric variation in three wild populations of Brycon dentex in the Guayas basin rivers and their connections to fishing management and environmental conditions. A total of 200 mature fish were captured, and 26 morphometric parameters were measured. The fishing policies (Hypothesis 1) and environmental conditions (Hypothesis 2) were considered fixed factors and were validated by t-tests. The morphological variation among the three populations (Hypothesis 3) was validated through a discriminant analysis. Fishing policies and resource management were found to generate morphological differences associated with body development. In addition, the environmental conditions were found to influence the size and structure of Brycon dentex populations. The analyzed populations were discriminated by the generated morphometric models, which differentiated Cluster 1 (Quevedo and Mocache rivers) with high fishing pressure from Cluster 2 (Pintado river) with medium–low fishing pressure. Morphometric differentiation by discriminant analysis is a direct and economic methodology that can be applied as an indicator of diversity maintenance

Usefulness of Discriminant Analysis in the Morphometric Differentiation of Six Native Freshwater Species from Ecuador

The aim of this research was to find out the morphometric differentiation of six native freshwater species in the Guayas Hydrographic Basin (Ecuador) by means of discriminant analysis. A total of 1355 mature fishes (Cichlasoma festae, Andinoacara rivulatus, Dormitator latifrons, Bryncon dentex, Hoplias microlepis and Leporinus ecuadorensis) were captured and 27 morphometric measurements and 20 landmarks were used. Two-way analysis of variance with species and sex as fixed factors and discriminant analysis were applied. The selection of the most discriminant variables was made applying the F of Snedecor, Wilks’-Lambda and the 1-Tolerance. While sex within species had no significant effect on the morphology, differences among species were significant. Twenty-seven morphological variables showed highly significant differences among six native freshwater species. Nine biometric variables with high discriminant power were selected. The six species analyzed were discriminated by the morphometric models generated, thus showing that discriminant analysis was useful for differentiating species. The morphometric differentiation by discriminant analysis is a direct, simple and economic methodology to be applied in situ in rural communities. It favors the implementation of a livestock development program and it could be used with other native freshwater species in the Guayas Hydrographic Basin

Estructura poblacional del Podenco Andaluz

En nuestro país los libros genealógicos caninos están gestionados por la Real Sociedad de Razas Caninas en España, quien delega su mantenimiento y control en las distintas asociaciones de criadores afiliadas. En el caso de la raza Podenco Andaluz, la gestión del libro genealógico es especialmente compleja debido al aislamiento reproductivo entre las distintas variedades existentes que obliga el actual patrón racial. En el presente estudio analizamos la estructura genética de la población del Podenco Andaluz basándonos en los registros genealógicos de los cinco últimos años donde indagamos en los ratios por sexo, ratios por tallas, ratios por edades dentro de talla; su evolución durante este tiempo y su proyección el futuro. Asimismo, profundizamos en una análisis de los niveles de consanguinidad individuales de los ejemplares inscritos, así como del nivel de endogamia media de la población

Contribution to ehtno-genetic chatacterisation of anandalusian canine dog racial group

We are analysing a sample of 53 animals (16 males and 37 females) of Andalusian mouse hunter dogs or caves dog, with a view to obtain their ethnogenetic characterisation. From our results we have concluded that this population is a racial group presenting a great homogeneity in the variables and zoometric indexes studied, as in the phaneroptical aspects. Their morphology is as a small format, probably elipometrics, with proportional leg length, brevilineous cephalic and body proportions. This population present a three-coloured coat, generally white colour on the body and “black and tan” on the head; the hair is short and smooth, the mucosae is black and the iris brown. With respect the bite, the most frequent are the tweezers form and the scissors, also in few animals we have found the absence of premolars.Se analiza una muestra de perros ratoneros o bodegueros compuesta por 53 ejemplares de los cuales 16 eran machos y 37 hembras, con objeto de lograr una caracterización etnogenética. De los resultados obtenidos concluimos que se trata de una agrupación racial que presenta gran homogeneidad tanto en las variables e índices zoométricos estudiados como en los aspectos fanerópticos. Morfológicamente se trata de animales de formato pequeño, posiblemente elipométricos, ni lejos ni cerca de tierra, y de proporciones braquicéfalas y brevilíneas en cuanto a sus proporciones cefálicas y corporales respectivamente. Fanerópticamente esta población presenta una capa tricolor, generalmente blanco en el cuerpo y negro-fuego en la cabeza, el pelo corto y liso, la pigmentación de las mucosas negras y el iris castaño. En cuanto a la mordida los tipos más frecuentes son en tijera y pinza, y en un escaso número de ejemplares existe ausencia de premolares

Microscopic description of d-wave superconductivity by Van Hove nesting in the Hubbard model

We devise a computational approach to the Hubbard model that captures the strong coupling dynamics arising when the Fermi level is at a Van Hove singularity in the density of states. We rely on an approximate degeneracy among the many-body states accounting for the main instabilities of the system (antiferromagnetism, d-wave superconductivity). The Fermi line turns out to be deformed in a manner consistent with the pinning of the Fermi level to the Van Hove singularity. For a doping rate $\delta \sim 0.2$, the ground state is characterized by d-wave symmetry, quasiparticles gapped only at the saddle-points of the band, and a large peak at zero momentum in the d-wave pairing correlations.Comment: 4 pages, 2 Postscript figure

Hydrodynamic modelling and operational oceanography for oil-spill events in the andalusian coast: a real case study during the fedra accident (October 2008)

Peer Reviewe

Is tagging with visual implant elastomer a reliable technique for marking earthworms?

Visual implant elastomer (VIE) has recently been employed to investigate different aspects of earthworm ecology. However, a number of fundamental questions relating to the detection and positioning of the tag, its persistence and potential effects on earthworms remain unknown. Seven earthworm species belonging to three ecological groupings, with different pigmentation and burrowing behaviour, were tagged using different coloured VIE. External inspection after two days, one week and 1, 10 and 27 months were followed by preservation, dissection and internal inspection. Tags could be seen in living specimens to 27 months, and dissection revealed that in most cases they were lodged in the coelomic cavity, held in place by septa. However, over longer time periods (more than two years), the chlorogogenous tissue tended to bind to the tags and made external observation increasingly difficult. Migration of the VIE material towards the posterior of the earthworm and potential loss of the tag were only observed on rare occasions, and a recovery rate in excess of 98% was recorded. By introducing a reasonable amount of VIE into segments, just after the clitellum, this technique can become a valuable tool in earthworm ecology and life history studies, particularly in short-medium term laboratory and field experiments

Effect of Research Impact on Emerging Camel Husbandry, Welfare and Social-Related Awareness

The lack of applied scientific research on camels, despite them being recognized as production animals, compels the reorganization of emerging camel breeding systems with the aim of achieving successful camel welfare management strategies all over the world. Relevant and properly-framed research widely impacts dissemination of scientific contents and drives public willingness to enhance ethically acceptable conditions for domestic animals. Consumer perception of this livestock industry will improve and high-quality products will be obtained. This paper draws on bibliometric indicators as promoting factors for camel-related research advances, tracing historical scientific publications indexed in ScienceDirect directory from 1880–2019. Camel as a species did not affect Journal Citation Reports (JCR) impact (p > 0.05) despite the journal, author number, corresponding author origin, discipline and publication year affecting it (p < 0.001). Countries with traditionally well-established camel farming are also responsible for the papers with the highest academic impact. However, camel research advances may have only locally and partially influenced welfare related laws, so intentional harming acts and basic needs neglect may persist in these species. A sustainable camel industry requires those involved in camel research to influence business stakeholders and animal welfare advocacies by highlighting the benefits of camel wellbeing promotion, co-innovation partnership establishment and urgent enhancement of policy reform

Morphometric and Meristic Characterization of Native Chame Fish (Dormitator latifrons) in Ecuador Using Multivariate Analysis

Ecuador, a country exhibiting large developments in fish farming, has a great variety of freshwater native fish. Among these fish is the Dormitator latifrons or chame, which has characteristics that make its farming prone to occur at a quite-developed stage. However, morphological characterization is required to establish a conservation program. In this study, 300 chames were captured in the Manabi province (Ecuador) to analyze their morphostructural model and to evaluate the effects of sex and the production system through multivariant techniques. The fish from the farm presented morphological measurements that were statistically (p 0.05). The percentage of correct adscription was 84%, with larger errors in wild fish. The morphostructural model had a high homogeneity, with 89.95% significant correlations (p < 0.05), and wild male and female fish were more homogeneous. The farm fish were larger because of the higher food availability. Moreover, the species exhibited sexual dimorphism, although there were no great differences in the morphometric measurements. This study shows the great biodiversity that naturally exists in Ecuadorian rivers. Therefore, it is of great interest to develop a chame breeding and conservation program