866 research outputs found
Problemática de la taxonomía del género cannabis
Se considera el cáñamo como una de las plantas más extendidas, sin embargo existe
hoy un consenso entre los botánicos que están de acuerdo con una sola especie Cannabis
sativa L. Hay que reconocer qué variedades de otros epititos específicos están todavía
usadas por algunos autores, especialmente C. ruderalis Janisch. y C. indica Lam.Hemp is considered as one of the widespread plants. Although a consensus of
botanists today agree that only one species, Cannabis sativa L. It should be reconized,
that a variety of other specific epithets, specially C. ruderalis Janisch. and C. indica
Lam., are still used by sorne authors
The evolution of Lithium: Implications of a universal Spite plateau
The cosmological 7Li problem consists in explaining why the primordial Li abundance, as predicted by the standard Big Bang nucleosynthesis theory with constraints from WMAP and Planck, is a factor of 3 larger than the Li abundance measured in the stars of the Spite plateau defined by old, warm dwarf stars of the Milky Way halo. Several explanations have been proposed to explain this difference, including various Li depletion processes as well as non-standard Big Bang nucleosynthesis, but the main question remains unanswered. In this paper, we present detailed chemical evolution models for dwarf spheroidal and ultra faint galaxies, compute the galactic evolution of 7Li abundance in these objects, and compare it with observations of similar objects. In our models, Li is mainly produced by novae and cosmic rays, and to a minor extent, by low and intermediate mass stars. We adopt the yield combination that best fits the Li abundances in the Milky Way stars. It is evident that the observations of dwarf objects define a Spite plateau, identical to that observed in the Milky Way, thus suggesting that the Spite plateau could be a universal feature and its meaning should be discussed. The predictions of our models for dwarf galaxies are obtained by assuming as Li primordial abundance either the one detected in the atmospheres of the oldest halo stars (Spite plateau; A(Li) ~ 2.2 dex), or the one from cosmological observations (WMAP; A(Li) ~ 2.66 dex). Finally, we discuss the implications of the universality of the Spite plateau results
Validation positive behaviors questionnaire in educative dance
El objetivo de la presente investigación era adaptar y validar al contexto de la danza educativa, el Cuestionario de Comportamientos Positivos en Educación Física. La muestra estuvo formada por 921 alumnos, de sexo femenino (n = 421) y masculino (n = 500), con edades comprendidas entre los 11 y los 17 años, pertenecientes a cuatro escuelas en México. Esta investigación estaba organizada por ConArte (Consorcio Internacional de Arte y Escuela). Los resultados obtenidos mostraron que el instrumento presentaba una adecuada validez factorial y consistencia interna. Asimismo, el instrumento se mostró invariante en cuanto al género y la edad de los participantes. De esta manera, este trabajo aporta evidencias científicas de que el cuestionario de comportamientos positivos en la danza educativa se muestra válido y fiable para analizar dichos comportamientos durante este tipo de clasesThe aim of the current research was to validate into the educative dance in Mexican secondary school, the questionnaire of positive behaviors in physical education. The sample was formed by 921 students, both female (n = 421) and male (n = 500) participants, ranging in age from 11 to 17 years old, belonged to four schools from Mexico. This research was organized by ConArte (International Consortium of Art and School). The results showed that the instrument had an adequate factorial validity and internal consistency. Furthermore, the instrument was invariant regarding individuals´ gender and age. Thus, this work gives empiric evidences that the questionnaire of positive behaviors in educative dance is valid and reliable to assess these behavior
El orden Lygeo Spartii-Stipelia Tenacissimae en el sector malacitano-Almijarense de Sierra Nevada (Granada, España)
A study of the order Lygeo-Stipetalia in the Malacitano-Almijarense sector of the Sierra Nevada is realized. Seven new syntaxa as proposed: PhlomidiBrachypodietum ramosi thymetosum baetici subass. nov., Helictotricho sarracenori (velutini)-Brachypodietum boissieri ass. nov., Thymo gracile-Stipetum tenacissimae ass. nov. and helianthemetosum squamati subass. nov., Helictotricho filifolii-Festucetum scariosae brachypodietosum boissieri subass. nov. ,festucetosum elegantis subass. nov. and festucetosum indigestae subass. nov.Se realiza un estudio fitosociológico del orden Lygeo-Stipetalia en el sector Malacitano-Almijarense de Sierra Nevada. Se proponen por vez primera los siguientes sintaxones: Phlomidi-Brachypodietum ramosi thymetosum baetici subass. nov., Helictotricho sarracenori (velutini)-Brachypodietum boissieri ass. nov., Thymo gracile-Stipetum tenacissimae ass. nov. y helianthemetosum squamati subass. nov., Helictotricho filifolii-Festucetum scariosae brachypodietosum boissieri subass. nov., festucetosum elegantis subass. nov. y festucetosum indigestae subass. nov
Time-periodic Metallic Metamaterials defined by Floquet Circuits
In this paper, we study the scattering and diffraction phenomena in
time-modulated metamaterials of metallic nature by means of Floquet equivalent
circuits. Concretely, we focus on a time-periodic screen that alternates
between "metal" and "air" states. We generalize our previous approaches by
introducing the concepts of "macroperiod" and "duty cycle" to the time
modulation. This allows to analyze time-periodic metallic metamaterials whose
modulation ratios are, in general, rational numbers. Furthermore, with the
introduction of the duty cycle, perfect temporal symmetry is broken within the
time modulation as the time screen could remain a different amount of time in
metal and air states. Previous statements lead to an enrichment of the
diffraction phenomenon and to new degrees of freedom that can be exploited in
engineering to control the reflection and transmission of electromagnetic
waves. Finally, we present some analytical results that are validated with a
self-implemented finite-difference time-domain (FDTD) approach. Results show
that the scattering level and diffraction angles can be controlled
independently by means of the duty cycle and the modulation ratio,
respectively. Thus, novel time-based pulsed sources and beamformers can be
efficiently designe
Diffraction Phenomena in Time-Varying Metal-Based Metasurfaces
This paper presents an analytical framework for the analysis of time-varying metal-based metamaterials.
Specifically, we particularize the study to time-modulated metal-air interfaces embedded between two
different semi-infinite media that are illuminated by monochromatic plane waves of frequency ω0. The
formulation is based on a Floquet-Bloch modal expansion, which takes into account the time periodicity
of the structure (Ts = 2π/ωs) and integral-equation techniques. It allows us to extract the reflection and
transmission coefficients as well as to derive nontrivial features about the dynamic response and dispersion
curves of time-modulated metal-based screens. In addition, the proposed formulation has an associated
analytical equivalent circuit that gives a physical insight into the diffraction phenomenon. Similarities
and differences between space- and time-modulated metamaterials are discussed via the proposed circuit
model. Finally, some analytical results are presented to validate the present framework. Good agreement
is observed with numerical computations provided by a self-implemented finite-difference time-domain
(FDTD) method. Interestingly, the present results suggest that time-modulated metal-based screens can be
used as pulsed sources (when ωs ω0), beam formers (ωs ∼ ω0) to redirect energy in specific regions of
space, and analog samplers (ωs ω0).Spanish Government ID2020-112545RB-C54
RTI2018-102002-A-I00Junta de Andalucia B-TIC-402-UGR18
A-TIC-608- UGR20
PYC20-RE-012-UGR
P18.RT.4830Leonardo Grant of the BBVA FoundationBBVA Foundatio
Total safety by design: Increased safety and operability of supply chain of inland terminals for containers with dangerous goods
[EN] In recent years, there has been a considerable increase in the international transport of containers with dangerous goods, increasing the risk of seaports and surrounding cities together with the introduction of inherent environmental and security disaster risks. Therefore, there is an increasing interest in seaports that are more socially inclusive, addressing the storage of containers of hazardous goods to safe inland terminals. An appropriate design of inland terminals for containers with dangerous goods (ITDGs) may contribute to the achievement of a sustainable development and the minimization of risks, avoiding disasters such as Tianjin. The objective of this study was the analysis of the criteria used for the design of safe, secure, cost efficient and greener ITDGs by applying the multicriteria decision theory AHP (analytic hierarchy process). Criteria regarding safety and security, environmental care, productivity and information and communication technologies (ICT) have been considered simultaneously into a total performance management system. (C) 2016 Elsevier Ltd. All rights reserved.Public funding entity: Generalitat Valenciana.Molero Prieto, GD.; Santarremigia Rosaleny, FE.; Aragonés-Beltrán, P.; Pastor-Ferrando, J. (2017). Total safety by design: Increased safety and operability of supply chain of inland terminals for containers with dangerous goods. Safety Science. 100(B):168-182. https://doi.org/10.1016/j.ssci.2016.10.007S168182100
Analytical Equivalent Circuits for Three-dimensional Metamaterials and Metagratings
In recent times, three-dimensional (3D) metamaterials have undergone a
revolution driven mainly by the popularization of 3D-printing techniques, which
has enabled the implementation of modern microwave and photonic devices with
advanced functionalities. However, the analysis of 3D metamaterials is complex
and computationally costly in comparison to their 1D and 2D counterparts due to
the intricate geometries involved. In this paper, we present a fully-analytical
framework based on Floquet-Bloch modal expansions of the electromagnetic fields
and integral-equation methods for the analysis of 3D metamaterials and
metagratings. Concretely, we focus on 3D configurations formed by periodic
arrangements of rectangular waveguides with longitudinal slot insertions. The
analytical framework is computationally efficient compared to full-wave
solutions and also works under oblique incidence conditions. Furthermore, it
comes associated with an equivalent circuit that allows to gain physical
insight into the scattering and diffraction phenomena. The analytical
equivalent circuit is tested against full-wave simulations in commercial
software CST. Simulation results show that the proposed 3D structures provide
independent polarization control of the two orthogonal polarizations states.
This key property is of potential interest for the production of full-metal
polarizers, such as the one illustrated
Developing documents for practical sessions in Zoology
La implantación del sistema unificado de créditos (E.C.T.S.) implica
nuevos planteamientos por parte del profesorado al elaborar la programación
teórico-práctica de las diferentes asignaturas. Con la elaboración de los
protocolos prácticos de zoología pretendemos alcanzar los objetivos siguientes:
1. Proveer a los alumnos de material didáctico básico y complementario a la
información impartida en las sesiones prácticas. 2. Proporcionar una perspectiva
amplia de diferentes aspectos prácticos de la zoología. 3. Familiarizar a los
alumnos con las fuentes (complementarias) de información y los procedimientos
de acceso a diferentes tipos de material biológico. 4. Favorecer el trabajo
personal y de grupo, enfatizando diferentes aspectos biológicos necesarios para
la asimilación de los contenidos prácticos de la asignatura. 5. Facilitar la
preparación de las pruebas prácticas que los alumnos han de realizar. En el curso
académico 2003/2004 nos fue concedido un primer proyecto docente que nos
permitió preparar contenidos correspondientes a la práctica “Introducción a las
técnicas de campo y de laboratorio en Zoología”. A partir de esta primera
experiencia hemos desarrollado varios proyectos docentes que nos han permitido
preparar materiales y contenidos prácticos de los principales taxones de animales
invertebrados: Poríferos y Cnidarios. Platelmintos, Nematodos y Anélidos.
Artrópodos. Moluscos. Equinodermos. La preparación de estos contenidos nos
ha obligado a realizar desplazamientos así como a solicitar colaboraciones de
diversas instituciones, por ejemplo, al Museo Nacional de Ciencias Naturales de
Madrid. Los protocolos están diseñados de forma que fomentan la labor
individual y auto-formativa del alumnado, así como el estudio en grupo. Todo
está encaminado hacia una completa preparación y correcta adecuación al nuevo
sistema educativo. Las presentaciones multimedia están a disposición del
alumnado gracias a las posibilidades que ofrece la web de la Universidad de
Córdoba.The implementation of the unified credit system (ECTS) involves new
approaches by teachers in the development of both theoretical and practical
curricula of different subjects. With the development of practical zoology
documents we aim to achieve the following objectives: 1. To provide the
students with basic educational materials, and complementary information to the
practical sessions. 2. To provide a broad overview of different practical aspects
of zoology. 3. To familiarize students with additional sources of information and
procedures for access to different types of biological material. 4. To encourage
personal and group work, emphasizing different biological aspects, which are
necessary for the understanding of the practical contents of the subjects. 5. To
assist in the preparation of exams that students must perform. In the academic
course 2003/2004 we were awarded with a first educational project that allowed
us to prepare content for the practice "Introduction to field and lab techniques in
Zoology". From this first experience we have developed several educational
projects that have allowed us to prepare materials and practical content of the
main taxa of invertebrates: Sponges and Cnidarians. Flatworms, Nematodes and
Annelids. Arthropods. Molluscs. Echinoderms. The preparation of these
materials has lead us to make trips and to request contributions from various
institutions, for example, the Museo Nacional de Ciencias Naturales in Madrid.
The protocols are designed in ways that encourage individual work and selftraining
of students, and study groups. Everything is aimed to the complete
preparation and fair adaptation to the new educational system. Multimedia
presentations are available to students thanks to the possibilities offered by the
website of the University of Cordoba
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