1,865 research outputs found

    Contribución al atlas palinológico de Andalucía Occidental, VI. Caprifoliaceae

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    En el presente trabajo se l leva a cabo un estudio morfológico de los granos de pol en de Lonicera etrusca G. Santi , L. i mplexa Ai ton , L. pericl ymenum L. , L. splendida Boiss ., Sambucus ebulus L. , S.. nigra L. y Viburnum tinus L., tanto en microscopía óptica como electr ónica de barrido . Se reconocen tres t ipos de polen diferentes , para cuya separación han servido fundamenta lmente las aperturas y la ornamentación.The polleo morphology of Lonicera etrusca G. San t i, L. implexa Ai to'n , L. periclymenum L. , L. splendida Boiss . , Sacumbus ebul us L. , S. nigra L. and Viburnum tinus L. have benn s t udied by light and scanning electron mi croscopy . Three types of pollen are recognized using the apertures a nd the ornamenta ti e

    Air gap influence on the vibro-acoustic response of Solar Arrays during launch

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    One of the primary elements on the space missions is the electrical power subsystem, for which the critical component is the solar array. The behaviour of these elements during the ascent phase of the launch is critical for avoiding damages on the solar panels, which are the primary source of energy for the satellite in its final configuration. The vibro-acoustic response to the sound pressure depends on the solar array size, mass, stiffness and gap thickness. The stowed configuration of the solar array consists of a multiple system composed of structural elements and the air layers between panels. The effect of the air between panels on the behaviour of the system affects the frequency response of the system not only modifying the natural frequencies of the wings but also as interaction path between the wings of the array. The usual methods to analyze the vibro-acoustic response of structures are the FE and BE methods for the low frequency range and the SEA formulation for the high frequency range. The main issue in the latter method is, on one hand, selecting the appropriate subsystems, and, on the other, identifying the parameters of the energetic system: the internal and coupling loss factors. From the experimental point of view, the subsystems parameters can be identified by exciting each subsystem and measuring the energy of all the subsystems composing the Solar Array. Although theoretically possible, in practice it is difficult to apply loads on the air gaps. To analyse this situation, two different approaches can be studied depending on whether the air gaps between the panels are included explicitly in the problem or not. For a particular case of a solar array of three wings in stowed configuration both modelling philosophies are compared. This stowed configuration of a three wing solar arrays in stowed configuration has been tested in an acoustic chamber. The measured data on the solar wings allows, in general, determining the loss factors of the configuration. The paper presents a test description and measurements on the structure, in terms of the acceleration power spectral density. Finally, the performance of each modelling technique has been evaluated by comparison between simulations with experimental results on a spacecraft solar array and the influence on the apparent properties of the system in terms of the SEA loss factors has been analyse

    The kinematics of the quadrupolar nebula M 1–75 and the identification of its central star

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    8 páginas, 5 figuras, 3 tablas.-- El Pdf del artículo es la versión pre-print: arXiv:1006.2398v1.-- et al.[Context]: The link between how bipolar planetary nebulae are shaped and their central stars is still poorly understood. [Aims]: This paper investigates the kinematics and shaping of the multipolar nebula M 1–75, and briefly discusses the location and nature of its central star. [Methods]: Fabry-Perot data from GHαFAS on the WHT that samples the Doppler shift of the [Nii] 658.3 nm line are used to study the dynamics of the nebula by means of a detailed 3D spatio-kinematical model. Multi-wavelength images and spectra from the WFC and IDS on the INT, as well as from ACAM on the WHT, allowed us to constrain the parameters of the central star. [Results]: The two pairs of lobes, angularly separated by ~22°, were ejected simultaneously approx. ~3500–5000 years ago, at the adopted distance range from 3.5 to 5.0 kpc. The larger lobes show a slight degree of point symmetry. The formation of the nebula could be explained by wind interaction in a system consisting of a post-AGB star surrounded by a disc warped by radiative instabilities. This requires the system to be a close binary or a single star that engulfed a planet as it died. On the other hand, we present broad- and narrow-band images and a low S/N optical spectrum of the highly-reddened, previously unnoticed star that is likely the nebular progenitor. Its estimated V–I colour allows us to derive a rough estimate of the parameters and nature of the central star.Peer reviewe

    Role of Tetraspanins CD9 and CD151 in Primary Melanocyte Motility

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    Tetraspanins CD9 and CD151 have been implicated in cellular motility and intercellular adhesion in several cellular types. Here, we have studied the subcellular localization and the functional role of these molecules in primary melanocytes. We found that endogenous tetraspanins preferentially clustered in areas of melanocyte homotypic intercellular contacts and at the tips of dendrites. These observations were further confirmed using time-lapse fluorescence confocal microscopy of melanocytes transfected with CD9– and CD151–GFP (green fluorescent protein) constructs, suggesting an involvement of these proteins in cellular contacts and migration. Cell adhesion and migration assays performed using blocking monoclonal antibodies against CD9 and CD151 showed no significant effect on cell–extracellular matrix adhesion, whereas the migration of melanocytes was significantly enhanced. The regulation of the migratory capacity of melanocytes by CD9 and CD151 was further confirmed knocking down the endogenous expression of these tetraspanins with small interference RNA oligonucleotides. Therefore, tetraspanin molecules are localized at motile structures in primary human melanocytes regulating the migratory capacity of these cells

    In vitro hydrolytic degradation of polyester-based scaffolds under static and dynamic conditions in a customized perfusion bioreactor

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    Creating biofunctional artificial scaffolds could potentially meet the demand of patients suffering from bone defects without having to rely on donors or autologous transplantation. Three-dimensional (3D) printing has emerged as a promising tool to fabricate, by computer design, biodegradable polymeric scaffolds with high precision and accuracy, using patient-specific anatomical data. Achieving controlled degradation profiles of 3D printed polymeric scaffolds is an essential feature to consider to match them with the tissue regeneration rate. Thus, achieving a thorough characterization of the biomaterial degradation kinetics in physiological conditions is needed. Here, 50:50 blends made of poly(e-caprolactone)–Poly(D, L-lactic-co-glycolic acid (PCL-PLGA) were used to fabricate cylindrical scaffolds by 3D printing (Ø 7 × 2 mm). Their hydrolytic degradation under static and dynamic conditions was characterized and quantified. For this purpose, we designed and in-house fabricated a customized bioreactor. Several techniques were used to characterize the degradation of the parent polymers: X-ray Photoelectron Spectroscopy (XPS), Gel Permeation Chro-matography (GPC), Scanning Electron Microscopy (SEM), evaluation of the mechanical properties, weigh loss measurements as well as the monitoring of the degradation media pH. Our results showed that flow perfusion is critical in the degradation process of PCL-PLGA based scaffolds implying an accelerated hydrolysis compared to the ones studied under static conditions, and up to 4 weeks are needed to observe significant degradation in polyester scaffolds of this size and chemical composition. Our degradation study and characterization methodology are relevant for an accurate design and to tailor the physicochemical properties of polyester-based scaffolds for bone tissue engineering

    Neutron-Capture elements in planetary nebulae: first detections of near-Infrared [Te III] and [Br V] emission lines

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    We have identified two new near-infrared emission lines in the spectra of planetary nebulae (PNe) arising from heavy elements produced by neutron capture reactions: [Te III] 2.1019 μ\mum and [Br V] 1.6429 μ\mum. [Te III] was detected in both NGC 7027 and IC 418, while [Br V] was seen in NGC 7027. The observations were obtained with the medium-resolution spectrograph EMIR on the 10.4m Gran Telescopio Canarias at La Palma, and with the high-resolution spectrograph IGRINS on the 2.7m Harlan J. Smith telescope at McDonald Observatory. New calculations of atomic data for these ions, specifically A-values and collision strengths, are presented and used to derive ionic abundances of Te2+^{2+} and Br4+^{4+}. We also derive ionic abundances of other neutron-capture elements detected in the near-infrared spectra, and estimate total elemental abundances of Se, Br, Kr, Rb, and Te after correcting for unobserved ions. Comparison of our derived enrichments to theoretical predictions from AGB evolutionary models shows reasonable agreement for solar metallicity progenitor stars of \sim2 - 4 M_{\odot}. The spectrally-isolated [Br V] 1.6429 μ\mum line has advantages for determining nebular Br abundances over optical [Br III] emission lines that can be blended with other features. Finally, measurements of Te are of special interest because this element lies beyond the first peak of the s-process, and thus provides new leverage on the abundance pattern of trans-iron species produced by AGB stars.Comment: 9 pages, 1 figure, 4 tables. Accepted for publication in ApJ Letter

    Caracterización geoquímica y estudio comparativo de plagiogranitos de las Zonas Surportuguesa y Ossa-Morena (SO del Macizo Ibérico, España)

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    Plagiogranites and albitic rocks belonging to contrasted magmatic associations of different ages and geodynamic environments outcrop in Ossa-Morena (OMZ) and Surportuguese (SPZ) Zones. OMZ plagiogranites are related with Cambrian-Ordovician rifting and represent a part of the felsic members of a bimodal magmatic suite and show oceanic plagiogranites affinities. SPZ plagiogranites are related with a Carboniferous volcano-plutonic calc-alkaline suite related with Variscan Orogeny. Both plagiogranites show many similar petrological and geochemical characteristics but display some different immobile elements ratios as La/Nb, Th/Nb, Th/La that are unaltered by metamorphism, magmatic differentiation and alteration processes and prove differences in their sources. SPZ plagiogranites show a more compositional homogeneity than OMZ ones. This is interpreted as a proof of cogenetic origin for SPZ plagiogranites and heterogeneous origin for OMZ plagiogranites, derived from the mix of different sources (astenospheric, lithospheric and crustal).En la Zona de Ossa-Morena (ZOM) y en la Zona Surportuguesa (ZSP) se encuentran plagiogranitos pertenecientes a asociaciones magmáticas y ambientes geodinámicos muy contrastados. Los primeros pertenecen a una asociación bimodal máfica-félsica relacionada con el rifting cámbrico-ordovícico y presentan bastantes afinidades con plagiogranitos oceánicos. Los segundos forman parte de una asociación volcánico-plutónica calcoalcalina carbonífera relacionada con la Orogenia Varisca. Ambos plagio-granitos son semejantes en diversos aspectos petrológicos y geoquímicos pero muestran diferencias en algunas relaciones de elementos inmóviles tales como La/Nb, Th/Nb, Th/La poco sensibles a los procesos de evolución magmática, metamorfismo y alteración y que son reflejo de la composición de las fuentes. Los plagiogranitos de la ZSP presentan una mayor homogeneidad composicional que los de la ZOM. Esto se interpreta como que los primeros tienen un origen cogenético, mientras que los segundos se derivan de diferentes fuentes (astenosféricas, litosféricas y crustales)

    Development and Initial testing of a Virtual Laboratory for the Build-up and Testing of Microgrid Management Algorithms

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    In a bid of facilitating the increasing penetration of intermittent and random renewable energies, microgrids along with their management algorithms are becoming crucial assets. To prove their effectiveness, these algorithms need to be tested in real environments and/or laboratories, which can be very difficult in many cases, especially at the initial development stages. To solve this issue, this article proposes the use of a laboratory digital twin, i.e., a virtual laboratory with a behaviour that is similar to that of real installations, aimed at facilitating the development, testing and debugging of microgrids management algorithms. The proposed solution is demonstrated to be safe and complete when it comes to test these algorithms.Acknowledgement This publication is part of the Sistemas energéticos aislados 100% renovables ENERISLA (exp. CER-20191002) Project which has received a grant from the Centre for Industrial Technological Development (CDTI, Centro para el Desarrollo Tecnológico Industrial in Spanish) under the Ministry of Science and Innovation in the call Acreditación y Concesión de Ayudas destinadas a Centros Tecnológicos de Excelencia “Cervera” in 2019. This research has received funding from the European Union’s Horizon 2020 Framework Program for Research and Innovation under grant agreement no. 893857
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