Search results for "Ciencias Naturales"
showing 10 items of 287 documents
Phase recovery by using optical fiber dispersion
2014
We propose a simple and fast procedure to retrieve the phase profile of arbitrary light pulses. It combines a first experimental stage, followed by a one-step numerical stage. To this end, it is necessary to perform a Fresnel transform, which is obtained just by propagating the light pulses through an optical fiber. We experimentally test this proposal recovering the phase profile in the light pulses provided by a passively mode-locked laser. The proposal is then compared with a temporal variation of the Gerchberg–Saxton recursive algorithm, which is specially modified for this purpose. Fil: Cuadrado Laborde, Christian Ariel. Universidad de Valencia; España. Consejo Nacional de Investigacio…
Valoración patrimonial de los yacimientos del Mioceno inferior del Barranco de Campisano de la Cuenca de Ribesalbes-Alcora (Araia d'Alcora, Castelló,…
2019
En el presente trabajo se realiza una valoración patrimonial del conjunto de yacimientos del Mioceno inferior del barranco de Campisano (cuenca de Ribesalbes-Alcora). Los resultados obtenidos al calcular los parámetros según la metodología del Inventario Español de Lugares de Interés Geológico (IELIG) ponen de manifi esto el alto valor científi co y didáctico de la zona, así como un valor turístico y recreativo medio. El riesgo de degradación es medio, por lo que debería ser tenido en cuenta para la protección de los yacimientos a corto plazo. En consonancia con estos datos, se propone la consideración de los yacimientos como LIG (Lugar de Interés Geológico) y su inclusión en el IELIG. In t…
The design of artificial nestboxes for the study of secondary hole-nesting birds: A review of methodological inconsistencies and potential biases
2010
The widespread use of artificial nestboxes has led to significant advances in our knowledge of the ecology, behaviour and physiology of cavity nesting birds, especially small passerines. Nestboxes have made it easier to perform routine monitoring and experimental manipulation of eggs or nestlings, and also repeatedly to capture, identify and manipulate the parents. However, when comparing results across study sites the use of nestboxes may also introduce a potentially significant confounding variable in the form of differences in nestbox design amongst studies, such as their physical dimensions, placement height, and the way in which they are constructed and maintained. However, the use of …
Leukoma antiqua (Bivalvia) - A high-resolution marine paleoclimate archive for southern South America?
2018
The Patagonian Sea in the SW Atlantic is one of the most productive marine ecosystems worldwide. Besides its economic relevance, this shelf sea serves as a major sink for atmospheric CO2 and thus plays a major role in global climate. Despite that, the marine climate dynamics in that region remain barely known. Instrumental records only cover the last 30 years or so and high-resolution climate archives are currently not available. Here, we explore the possibility to obtain seasonally to inter-annually resolved paleotemperature data from shells of the bivalve mollusk, Leukoma antiqua collected alive from the shallow subtidal zone of the San Jorge Gulf. Results demonstrate that this species gr…
Chemical and photochemical properties of chloroharmine derivatives in aqueous solutions
2015
Thermal and photochemical stability (ΦR), room temperature UV-vis absorption and fluorescence spectra, fluorescence quantum yields (ΦF) and lifetimes (τF), quantum yields of hydrogen peroxide (ΦH2O2) and singlet oxygen (ΦΔ) production, and triplet lifetimes (τT) have been obtained for the neutral and protonated forms of 6-chloroharmine, 8-chloroharmine and 6,8-dichloroharmine, in aqueous media. When it was possible, the effect of pH and oxygen concentration was evaluated. The nature of electronic transitions of protonated and neutral species of the three investigated chloroharmines was established using Time-Dependent Density Functional Theory (TD-DFT) calculations. The impact of all the fo…
Scanning electron microscopy of Antarctophthirus microchir (Phthiraptera: Anoplura: Echinophthiriidae): Studying morphological adaptations to aquatic…
2012
The members of the Family Echinophthiriidae (Phthiraptera: Anoplura) are unique among insects because they infest hosts with an amphibious lifestyle. During their evolution they developed morphological traits that are reflected in unique features. The SEM is a helpful tool to analyze them. Knowing in detail the external structure of these lice is the first step to understand the whole process that derived from the co-adaptation of lice and pinnipeds to the marine environment. For the first time, we studied the external structure of all stages of an echinophthiriid louse. The results are discussed in the light of their evolutionary, functional, and ecological implications. Fil: Leonardi, Mar…
Anti-inflammatory properties of hydroalcoholic extracts of Argentine Puna plants
2015
The aim of this study is to evaluate the activity of thirteen hydroalcoholic extracts obtained from aerial parts of plants from Argentina Puna on pro-inflammatory enzymes and inflammatory mediators. Eleven extracts were non-cytotoxic on RAW 264.7. Data obtained suggest the capacity of these Argentine Puna plant extracts to inhibit the production of inflammatory mediators (nitric oxide and prostaglandin) at different levels. The plant extracts can affect enzymes expression and/or enzymes activity, and they can also act by NO scavenging. Each extract exerts its anti-inflammatory effect through different mechanisms. The inhibitory ability on pro-inflammatory enzymes by these hydroalcoholic ext…
Third family of compact stars within a nonlocal chiral quark model equation of state
2019
A class of hybrid compact star equations of state is investigated that joins by a Maxwell construction a low-density phase of hadronic matter, modeled by a relativistic mean-field approach with excluded nucleon volume, with a high-density phase of color superconducting two-flavor quark matter, described within a nonlocal covariant chiral quark model. It is found that the occurrence of a stable branch of hybrid compact stars requires a nonvanishing vector meson coupling in the quark model that exceeds a minimal value which depends on the presence of a diquark condensate. It is shown that these hybrid stars do not form a third family disconnected from the second family of ordinary neutron sta…
Nuclear and partonic dynamics in the EMC effect
2013
It has been recently confirmed that the magnitude of the EMC effect measured in the electron deep inelastic scattering is linearly related to the short-range correlation scaling factor obtained from electron inclusive scattering. By using a x-rescaling approach we are able to understand the interplay between the quark-gluon and hadronic degrees of freedom in the discussion of the EMC effect.
Zero permeability and zero permittivity band gaps in 1D metamaterial photonic crystals
2007
We consider layered heterostructures combining ordinary positive index materials and dispersive metamaterials. We show that these structures can exhibit a new type of photonic gap around frequencies where either the magnetic permeability \mu or the electric permittivity \epsilon of the metamaterial is zero. Although the interface of a semi-infinite medium with zero refractive index (a condition attained either when \mu= 0 or when \epsilon= 0) is known to give full reflectivity for all incident polarizations, here we show that a gap corresponding to \mu = 0 occurs only for TE polarized waves, whereas a gap corresponding to \epsilon = 0 occurs only for TM polarized waves. These band gaps are …