382 research outputs found

    Stability and Regularity for Double Wall Carbon Nanotubes Modeled as Timoshenko Beams with Thermoelastic Effects and Intermediate Damping

    Full text link
    This research studies two systems composed by the Timoshenko beam model for double wall carbon nanotubes, coupled with the heat equation governed by Fourier's law. For the first system, the coupling is given by the speed the rotation of the vertical filament in the beam βψt\beta\psi_t from the first beam of Tymoshenko and the Laplacian of temperature δθxx\delta\theta_{xx}, where we also consider the damping terms fractionals γ1(xx)τ1ϕt\gamma_1(-\partial_{xx})^{\tau_1}\phi_t, γ2(xx)τ2yt\gamma_2(-\partial_{xx})^{\tau_2} y_t and γ3(xx)τ3zt\gamma_3(-\partial_{xx})^{\tau_3} z_t, where (τ1,τ2,τ3)[0,1]3(\tau_1, \tau_2, \tau_3) \in [0,1]^3. For this first system we proved that the semigroup S1(t)S_1(t) associated to system decays exponentially for all (τ1,τ2,τ3)[0,1]3(\tau_1 , \tau_2 , \tau_3 ) \in [0,1]^3. The second system also has three fractional damping γ1(xx)β1ϕt\gamma_1(-\partial_{xx})^{\beta_1}\phi_t, γ2(xx)β2yt\gamma_2(-\partial_{xx})^{\beta_2} y_t and γ3(xx)β3zt\gamma_3(-\partial_{xx})^{\beta_3} z_t, with (β1,β2,β3)[0,1]3(\beta_1, \beta_2, \beta_3) \in [0,1]^3. Furthermore, the couplings between the heat equation and the Timoshenko beams of the double wall carbon nanotubes for the second system is given by the Laplacian of the rotation speed of the vertical filament in the beam βψxxt\beta\psi_{xxt} of the first beam of Timoshenko and the Lapacian of the temperature δθxx\delta\theta_{xx}. For the second system, we prove the exponential decay of S2(t)S_2(t) for (β1,β2,β3)[0,1]3(\beta_1, \beta_2, \beta_3) \in [0,1]^3 and also show that S2(t)S_2(t) admits Gevrey classes s>(ϕ+1)/(2ϕ)s>(\phi+1)/(2\phi) for ϕ=min{β1,β2,β3},(β1,β2,β3)(0,1)3\phi=\min\{\beta_1,\beta_2,\beta_3\}, \forall (\beta_1,\beta_2,\beta_3)\in (0,1)^3, and proving that S2(t)S_2(t) is analytic when the parameters (β1,β2,β3)[1/2,1]3(\beta_1, \beta_2, \beta_3) \in [1/2,1]^3. One of the motivations for this research was the work; Ramos et al. \cite{Ramos2023CNTs}, whose partial results are part of our results obtained for the first system for (τ1,τ2,τ3)=(0,0,0)(\tau_1, \tau_2, \tau_3) = (0, 0, 0).Comment: 27 pages, 4 figures. arXiv admin note: text overlap with arXiv:2210.1257

    Angular emission properties of a layer of rare-earth based nanophosphors embedded in one-dimensional photonic crystal coatings

    Get PDF
    The angular properties of light emitted from rare-earth based nanophosphors embedded in optical resonators built in one-dimensional photonic crystal coatings are herein investigated. Strong directional dependence of the photoluminescence spectra is found. Abrupt angular variations of the enhancement caused by the photonic structure and the extraction power are observed, in good agreement with calculated polar emission patterns. Our results confirm that the optical cavity favors the extraction of different wavelengths at different angles and that integration of nanophosphors within photonic crystals provides control over the directional emission properties that could be put into practice in phosphorescent displays.Ministerio de Ciencia e Innovación MAT2008- 02166, CSD2007-00007Junta de Andalucía FQM3579, FQM524

    Variations in water use by a mature mangrove of Avicennia germinans, French Guiana

    Get PDF
    In the tropical intertidal zones, little is known on water uptake by mangroves. Transpiration rates are generally measured at leaf level, but few studies exist on water use at tree or stand levels. The objective of this study was to measure sap flow in trees of different sizes to appreciate the range of variation in water use that may exist in a site dominated by 80% mature Avicennia germinans. The results showed that from the dry to the wet season the mean water use increased from 3.2 to 5.3 dm3 d−1 in small trees (DBH ∼ 13 cm), from 11.5 to 30.8 dm3 d−1 in medium trees (∼24 cm) and from 40.8 to 64.1 dm3 d−1 in large ones (∼45 cm). Sapwood remained active up to a depth of 8 cm with radial variations within the stem. Weak correlations were obtained with VPD and net radiation. This study confirmed that transpiration was larger under low levels of salinity. Water use at stand level (∼1900 living stems ha−1) was estimated to be in the range of 5.8 to 11.8 m3 ha−1 d−1 according to the season

    The Lift Pool Method for Isolation of cDNA Clones from Lambda Phage Libraries

    Get PDF
    A PCR based strategy was developed to screen a Xenopus oocyte λgt10 cDNA library. The PCR-based lift pool (LP) method follows the same two tiered strategy as conventional screening of phage libraries by filter hybridization. Two rounds of plating, one at high density to detect the clone, and one at low density to purify the clone to homogeneity, are performed. In the first round, lysates from high density plates, termed plate pools (PP), serve as template for PCR. In the second round, phage particles adhering to plaque lifts of low density plates are washed off nitrocellulose filters to create LPs, which are used as template for PCR. The integrity of the plaques on the low-density plates is preserved. Once a positive LP has been identified, plaques on the corresponding plate are screened individually by PCR. Using isoform specific primer pairs for Xenopus myosin 7a and myosin 1d, two lambda clones were isolated. Subsequent DNA sequence analysis confirmed their identities as myosin isoforms (GenBank accession numbers: DQ100353 and AF540952). This method offers a time saving, cost-effective alternative to other hierarchical pooling strategies for the repeated screening by PCR of an arrayed lambda phage library

    Borreria (Rubiaceae) from Paraguay: occurrences, richness, geographical distribution, and nomenclatural novelties

    Get PDF
    Borreria is a genus into the Spermacoce clade with ca 80 native species in the Americas, from southem EE.UU. to center of Argentina. In South America, taxonomic and floristic contributions were performed in the genus to Bolivian, Brazilian, and Argentinian floras. In this context, nomenclatural changes, new records, and new species have been published in the last decades for Paraguay, but until now there is no comprehensive taxonomic treatment. In addition, this country has a great diversity of ecoregions as the Atlantic Forest, Cerrado, “Cordillera de los Altos”, Dry and Humid Chaco, Pantanal, and “Sabanas Mesopotámicas”. Our goal is to present an overview of Borreria in Paraguay, its geographical distribution, and the association of its occurrences in diíferent ecoregions. We studied collections deposited in BM, CTES, F, FACEN, FCQ, G, HUEFS, MO, P, SI, and SP. Coordinates were taken from the labels on each specimen, and when these were absent, the point was georeferenced using Google Earth according the locality ñames. A total of 503 datapoints were obtained corresponding to 21 species of Borreria. Each occurrence and ecoregions were mapped using QGIS. A map o f known richness was generated with this information and was quantified with 5 x 5 km cells using the Biodiverse software. As result, B. verticillata is the widest distribution species, whereas B. viridiflora is the only endemic species for Paraguay. Besides that, the ecoregion with the higher richness is the Atlantic Forest since it has 20 species, with B. diacrodonta, B. remota, and/i. runkii exclusive for it. In contrast, Pantanal and Dry Chaco have only one species each, B. cupularis and B. spinosa, respectively. Borreria alata is registered as a new record for the country, lectotypes for three varietal ñames are chosen, and five new synonyms for B. argéntea, B. orinocensis, and B. verticillata are proposed

    Stability and Regularity the MGT-Fourier Model with Fractional Coupling

    Full text link
    In this work, we study the stability and regularity of the system formed by the third-order vibration equation in Moore-Gilson-Thompson time coupled with the classical heat equation with Fourier's law. We consider fractional couplings. He then fractional coupling is given by: ηAϕθ,αηAϕutt\eta A^\phi\theta, \alpha\eta A^\phi u_{tt} and ηAϕut\eta A^\phi u_t, where the operator AϕA^\phi is self-adjoint and strictly positive in a complex Hilbert space HH and the parameter ϕ\phi can vary between 00 and 11. When ϕ=1\phi=1 we have the MGT-Fourier physical model, previously investigated, see; 2013\cite{ABMvFJRSV2013} and 2022\cite{DellOroPata2022}, in these works, the authors respectively showed that the semigroup S(t)=etBS(t) = e^{t\mathbb{B}} associated with the MGT-Fourier model are exponentially stable and analytical. The model abstract of this research is given by: \eqref{Eq1.1}--\eqref{Eq1.3}, we show directly that the semigroup S(t)S(t) is exponentially stable for ϕ[0,1]\phi \in [0,1], we also show that for ϕ=1\phi=1, S(t)S(t) is analytic and study of the Gevrey classes of S(t)S(t). We show that for ϕ(12,1)\phi\in (\frac{1}{2}, 1) there are two families of Gevrey classes: s1>2s_1>2 when ϕ(1/2,2/3]\phi\in(1/2,2/3] and s2>ϕ2ϕ1s_2>\frac{\phi}{2\phi-1} when ϕ[2/3,1)\phi\in[2/3,1), in the last part of our investigation using spectral analysis we tackled the study of the non-analyticity and lack of Gevrey classes of S(t)S(t) when ϕ[0,1/2]\phi \in[0,1/2]. For the study of the existence, stability, and regularity, semigroup theory is used together with the techniques of the frequency domain, multipliers, and spectral analysis of a system, using the property of the fractional operator AϕA^\phi for ϕ[0,1]\phi\in[0,1].Comment: 26 pages. arXiv admin note: text overlap with arXiv:2208.0148

    Competencias éticas de los consejeros de orientación

    Get PDF
    El objetivo general de este trabajo es presentar el análisis de las competencias éticas de los Consejeros de Orientación a través de una experiencia de un Proyecto Europeo sobre formación basada en las Habilidades TIC: Herramientas y Formación de éstas y cuyo propósito principal es alcanzar un amplio desarrollo profesional para una extensa comunidad de profesionales de la educación y orientación a lo largo de la vida así como desenvolver un perfil estándar del Consejero de la Carrera. En este artículo se presenta el diseño evaluativo y los resultados de un Seminario de 28 horas del currículo formativo para los profesionales de la Orientación centrado en las TIC, especialmente en el ámbito de sus competencias éticas: honestidad, confidencialidad, responsabilidad, respeto, etc.Facultad de Psicologí

    Competencias éticas de los consejeros de orientación

    Get PDF
    El objetivo general de este trabajo es presentar el análisis de las competencias éticas de los Consejeros de Orientación a través de una experiencia de un Proyecto Europeo sobre formación basada en las Habilidades TIC: Herramientas y Formación de éstas y cuyo propósito principal es alcanzar un amplio desarrollo profesional para una extensa comunidad de profesionales de la educación y orientación a lo largo de la vida así como desenvolver un perfil estándar del Consejero de la Carrera. En este artículo se presenta el diseño evaluativo y los resultados de un Seminario de 28 horas del currículo formativo para los profesionales de la Orientación centrado en las TIC, especialmente en el ámbito de sus competencias éticas: honestidad, confidencialidad, responsabilidad, respeto, etc

    Competencias éticas de los consejeros de orientación

    Get PDF
    El objetivo general de este trabajo es presentar el análisis de las competencias éticas de los Consejeros de Orientación a través de una experiencia de un Proyecto Europeo sobre formación basada en las Habilidades TIC: Herramientas y Formación de éstas y cuyo propósito principal es alcanzar un amplio desarrollo profesional para una extensa comunidad de profesionales de la educación y orientación a lo largo de la vida así como desenvolver un perfil estándar del Consejero de la Carrera. En este artículo se presenta el diseño evaluativo y los resultados de un Seminario de 28 horas del currículo formativo para los profesionales de la Orientación centrado en las TIC, especialmente en el ámbito de sus competencias éticas: honestidad, confidencialidad, responsabilidad, respeto, etc.Facultad de Psicologí

    Angular emission properties of a layer of rare-earth based nanophosphors embedded in one-dimensional photonic crystal coatings

    Get PDF
    The angular properties of light emitted from rare-earth based nanophosphors embedded in optical resonators built in one-dimensional photonic crystal coatings are herein investigated. Strong directional dependence of the photoluminescence spectra is found. Abrupt angular variations of the enhancement caused by the photonic structure and the extraction power are observed, in good agreement with calculated polar emission patterns. Our results confirm that the optical cavity favors the extraction of different wavelengths at different angles and that integration of nanophosphors within photonic crystals provides control over the directional emission properties that could be put into practice in phosphorescent displays.Fil: Sánchez Sobrado, O.. Universidad de Sevilla. Consejo Superior de Investigaciones Cientificas. Instituto de Ciencia de Materiales de Sevilla; EspañaFil: Yacomotti, A. M.. No especifíca;Fil: Calvo, M. E.. Universidad de Sevilla. Consejo Superior de Investigaciones Cientificas. Instituto de Ciencia de Materiales de Sevilla; EspañaFil: Martinez, Oscar Eduardo. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ocaña, M.. Universidad de Sevilla. Consejo Superior de Investigaciones Cientificas. Instituto de Ciencia de Materiales de Sevilla; EspañaFil: Núñez, N.. Universidad de Sevilla. Consejo Superior de Investigaciones Cientificas. Instituto de Ciencia de Materiales de Sevilla; EspañaFil: Levenson, J. A.. No especifíca;Fil: Míguez, H.. Universidad de Sevilla. Consejo Superior de Investigaciones Cientificas. Instituto de Ciencia de Materiales de Sevilla; Españ
    corecore