4,446 research outputs found

    Consideraciones sobre Statice dianiae Pau (Plumbaginaceae)

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    An apomictic Limonium with a single pollen-stigma combination (B type), Limonium interjectum, is proposed as a new species to replace the invalid name Statice dianiae Pau. The new species has a restricted distribution on the sea costs of eastern Spain (Alicante Province). It shows a striking morphological similarity to L. virgatum (Willd.) Fourr. and L. girardianum (Guss.) Girard; on this basis it is suggested that L. interjectum is a hybrid derived from the two species.Se describe Limonium interjectum como especie nueva del Levante peninsular español, el cual había sido previamente denominado con el nombre ilegítimo de Statice dianiae Pau. L. interjectum es una especie apomíctica que presenta una sola combinación polínico estigmática (tipo B). Sus afinidades morfológicas son próximas a L. virgatum (Willd.) Fourr. Y L. girardianum (Guss.) Girard, y se sugiere que L. interjectum es un taxon hibridógeno que pudo haberse originado a partir de ambas especies

    Flora pteridofítica de la Marina Alta (Alacant)

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    A partir de material d'herbari i referències bibliogràfiques es revisa i actualitza el catàleg de pteridòfits de la comarca de la Marina Alta (Alacant). Asplenium trichomanes L. subsp. inexpectans Lovis constitueix novetat per a la flora del País Valencià.A partir de material de herbario y de la recopilación de referencias bibliograficas se revisa y actualiza el catálogo de pteridófitos de la Marina Alta (Alicante). Asplenium trichomanes L. subsp. inexpectans Lovis supone novedad para la flora del País Valenciano.On the basis of herbarium material and bibliographic references, we have made a revision of the catalogue of Pteridophyta from Marina Alta (SE Iberian Peninsula). Asplenium trichomanes L. subsp. inexpectans Lovis is recorded for the first time in the Valencian Communit

    Dimensional crossover of thermal conductance in graphene nanoribbons: A first-principles approach

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    First-principles density-functional calculations are performed to investigate the thermal transport properties in graphene nanoribbons (GNRs). The dimensional crossover of thermal conductance from one to two dimensions (2D) is clearly demonstrated with increasing ribbon width. The thermal conductance of GNRs in a few nanometer width already exhibits an approximate low-temperature dependence of T1.5T^{1.5}, like that of 2D graphene sheet which is attributed to the quadratic nature of dispersion relation for the out-of-plane acoustic phonon modes. Using a zone-folding method, we heuristically derive the dimensional crossover of thermal conductance with the increase of ribbon width. Combining our calculations with the experimental phonon mean-free path, some typical values of thermal conductivity at room temperature are estimated for GNRs and for 2D graphene sheet, respectively. Our findings clarify the issue of low-temperature dependence of thermal transport in GNRs and suggest a calibration range of thermal conductivity for experimental measurements in graphene-based materials.Comment: 18 pages, 4 figure

    Interplay between excitation kinetics and reaction-center dynamics in purple bacteria

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    Photosynthesis is arguably the fundamental process of Life, since it enables energy from the Sun to enter the food-chain on Earth. It is a remarkable non-equilibrium process in which photons are converted to many-body excitations which traverse a complex biomolecular membrane, getting captured and fueling chemical reactions within a reaction-center in order to produce nutrients. The precise nature of these dynamical processes -- which lie at the interface between quantum and classical behaviour, and involve both noise and coordination -- are still being explored. Here we focus on a striking recent empirical finding concerning an illumination-driven transition in the biomolecular membrane architecture of {\it Rsp. Photometricum} purple bacteria. Using stochastic realisations to describe a hopping rate model for excitation transfer, we show numerically and analytically that this surprising shift in preferred architectures can be traced to the interplay between the excitation kinetics and the reaction center dynamics. The net effect is that the bacteria profit from efficient metabolism at low illumination intensities while using dissipation to avoid an oversupply of energy at high illumination intensities.Comment: 21 pages, 13 figures, accepted for publication in New Journal of Physic

    A physiological Plant Growth Simulation Engine Based on Accurate Radiant Energy Transfer

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    We present a new model for plant growth simulation, taking into account the eco-physiological processes driving plant development with unprecedented fidelity. The growth model, based on a physiological analysis, essentially simulates the internal function of the plant, and has been validated against measured biological data with excellent results. We show how to account for the influence of light through photosynthesis, and thereby incorporate the effects of a given plant's immediate environment on its architecture, shape and size. Since biological matter is controlled by water transpiration and received radiant enery, the model requires efficient and accurate simulation of radiant energy exchanges. We describe a complete lighting simulation system tailored for the difficult case of plants, by adapting state-of-the-art techniques such as hierarchical instanciation for radiosity and general BRDF modeling. Our results show that (a) our lighting simulation system efficiently provides the required information at the desired level of accuracy, and (b) the plant growth model is extremely well calibrated against real plants and (c) the combined system can simulate many interesting growth situations with direct feedback from the environment on the plant's characteristics. Applications range from landscape simulation to agronomical and agricultural studies, and to the design of virtual plants responding to their environment

    Personalized and adaptive learning: educational practice and technological impact

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    Education Technology advances many aspects of learning. More and more learning is taking place online. Learners’ learning behaviors, style, and performance can be easily profiled through learning analytics which collects their online learning footage. It enables and encourages educational research, learning software application development, and online education practices towards personalized and adaptive learning. As we continue to see personalized and adaptive learning progress, we must also pay attention to the negative impacts that feed into our research. In this paper, we will present our introspection of personalized and adaptive learning and argue that it is the social and moral responsibility of educators and institutions to apply personalized and adaptive learning wisely in their education practice. Educators and institutions should also recognize the realistic diversities of individual students’ learning styles and variable learning progress, contextually dependent learning accessibility, and their correspondent support needs for the fine-grained learning activities. We argue that the strategically balanced practices and innovated learning technology are crucial towards an optimized learning experience for the learners. A Tecnologia da Educação avança muitos aspectos da aprendizagem. Cada vez mais aprendizagem está ater lugar online. Os comportamentos de aprendizagem, estilo e desempenho dos aprendentes podem serfacilmente perfilados através de análises de aprendizagem que recolhem as suas filmagens de aprendizagemon-line. Permite e encoraja a investigação educacional, o desenvolvimento de aplicações de software deaprendizagem, e práticas de educação em linha para uma aprendizagem personalizada e adaptativa. À medidaque continuamos a ver progressos na aprendizagem personalizada e adaptativa, devemos também prestaratenção aos impactos negativos que alimentam a nossa investigação. Neste documento, apresentaremos anossa introspecção de aprendizagem personalizada e adaptativa e argumentaremos que é da responsabilidade social e moral dos educadores e instituições aplicar sabiamente a aprendizagem personalizada e adaptativa nasua prática educativa. Os educadores e as instituições devem também reconhecer as diversidades realistas dosestilos de aprendizagem dos estudantes individuais e o progresso variável da aprendizagem, a acessibilidade àaprendizagem contextualmente dependente, e as suas necessidades de apoio correspondente para as actividadesde aprendizagem de grão fino. Argumentamos que as práticas estrategicamente equilibradas e a tecnologiade aprendizagem inovadora são cruciais para uma experiência de aprendizagem optimizada para os alunos

    An approach to identify urban groundwater recharge

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    Evaluating the proportion in which waters from different origins are mixed in a given water sample is relevant for many hydrogeological problems, such as quantifying total recharge, assessing groundwater pollution risks, or managing water resources. Our work is motivated by urban hydrogeology, where waters with different chemical signature can be identified (losses from water supply and sewage networks, infiltration from surface runoff and other water bodies, lateral aquifers inflows, ...). The relative contribution of different sources to total recharge can be quantified by means of solute mass balances, but application is hindered by the large number of potential origins. Hence, the need to incorporate data from a large number of conservative species, the uncertainty in sources concentrations and measurement errors. We present a methodology to compute mixing ratios and end-members composition, which consists of (i) Identification of potential recharge sources, (ii) Selection of tracers, (iii) Characterization of the hydrochemical composition of potential recharge sources and mixed water samples, and (iv) Computation of mixing ratios and reevaluation of end-members. The analysis performed in a data set from samples of the Barcelona city aquifers suggests that the main contributors to total recharge are the water supply network losses (22%), the sewage network losses (30%), rainfall, concentrated in the non-urbanized areas (17%), from runoff infiltration (20%), and the Besòs River (11%). Regarding species, halogens (chloride, fluoride and bromide), sulfate, total nitrogen, and stable isotopes (<sup>18</sup>O, <sup>2</sup>H, and <sup>34</sup>S) behaved quite conservatively. Boron, residual alkalinity, EDTA and Zn did not. Yet, including these species in the computations did not affect significantly the proportion estimations

    Effect of fibrous diet and vitamin C inclusion on uniformity, carcass traits, skeletal strength, and behavior of broiler breeder pullets

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    This experiment studied the effect of broiler breeder nutritional strategies on uniformity, carcass traits, tibia parameters, and behavior during rearing and prebreeder periods (up to 22 wk of age). One-day-old pullets (n = 384) were randomly assigned to 4 treatments arranged as a 2 × 2 factorial, with 2 fiber levels (control vs. fibrous diet, 15% diluted in AMEn and nutrient content) and 2 vitamin C feed inclusions (0 vs. 200 mg/kg). At 6, 15, and 22 wk, blood sampling was carried out (4 birds/replicate) to determine serum alkaline phosphatase (ALP) levels, and behavior was observed by visual scan sampling. At 22 wk, carcass traits, tibia parameters, and intestinal morphology were assessed (2 birds/replicate), and tail- and wing-feather integrity of all birds were scored. Fibrous diet did not modify BW uniformity, mortality, or tibia growth when compared with control diet. Pullets fed the fibrous diet had lower tibia breaking strength, elastic modulus, and ash content values (P < 0.05). They also had lower ALP serum level at 6 and 22 wk (P < 0.05), their breast muscle was less developed (18.5 vs. 19.8%, P < 0.05), and their abdominal fat deposition was higher (1.14 vs. 0.87%, P < 0.05). At 15 and 22 wk, they performed, on average, 97% less grasping feather pecking and 45% less non-food object pecking behaviors, and their wing-feather score was lower (P < 0.05) at 22 wk. Tail- and wing-feather scores of the control treatments were reduced by vitamin C inclusion (tail: 0.30 vs. 1.15, P < 0.05; wing: 0.98 vs. 1.26, P < 0.05) at 22 wk. In conclusion, fibrous diet improves carcass traits (reduces breast muscle and increases abdominal fat deposition), deteriorates bone mineral deposition and thus skeletal strength, and reduces stereotypic behaviors, improving wing-feather integrity. Vitamin C inclusion improves tail- and wing-feather integrity of lower in feed allowance

    Flora pteridofítica de la Marina Alta (Alacant)

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    A partir de material d'herbari i referències bibliogràfiques es revisa i actualitza el catàleg de pteridòfits de la comarca de la Marina Alta (Alacant). Asplenium trichomanes L. subsp. inexpectans Lovis constitueix novetat per a la flora del País Valencià.A partir de material de herbario y de la recopilación de referencias bibliograficas se revisa y actualiza el catálogo de pteridófitos de la Marina Alta (Alicante). Asplenium trichomanes L. subsp. inexpectans Lovis supone novedad para la flora del País Valenciano.On the basis of herbarium material and bibliographic references, we have made a revision of the catalogue of Pteridophyta from Marina Alta (SE Iberian Peninsula). Asplenium trichomanes L. subsp. inexpectans Lovis is recorded for the first time in the Valencian Communit
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