Asymptotic decay under nonlinear and noncoercive dissipative effects for electrical conduction in biological tissues

We consider a nonlinear model for electrical conduction in biological tissues. The nonlinearity appears in the interface condition prescribed on the cell membrane. The purpose of this paper is proving asymptotic convergence for large times to a periodic solution when time-periodic boundary data are assigned. The novelty here is that we allow the nonlinearity to be noncoercive. We consider both the homogenized and the non-homogenized version of the problem

Labradores y vecinos en la campaña bonaerense a mediados del siglo XIX

Avanzado el siglo XIX y consolidado el modelo agroexportador en la Pampa argentina, la gran estancia, la ganadería extensiva y una distribución inequitativa de la tierra opacaron otras alternativas de desarrollo que se tuvieron en cuenta en los momentos de génesis de la modernización. Este artículo trata de recuperar el rol protagónico que los vecinos tuvieron en los pueblos bonaerenses a mediados del siglo xix, mostrando cómo los gobiernos de la época necesitaron de las redes existentes en la frontera para propiciar la gobernabilidad. A partir de la movilización de labradores de un partido eminentemente triguero, exigiendo el loteo y venta de las tierras públicas a los productores directos, se tratará de poner en evidencia que estadistas de la talla de Mitre y Sarmiento —los primeros presidentes de la Argentina unificada— no solo utilizaron las redes de poder ya existentes sino que evaluaron la posibilidad de considerar que la agricultura, la sociedad campesina y por ende una distribución equitativa de la tierra podían ser alternativas posibles para el desarrollo de la región pampeanaWell into the 19th century, and once the agro-export model had been consolidated in the Argentine pampas, the big estancia (ranch), extensive livestock farming and unequal distribution of land overshadowed other alternatives for development which had been taken into account at the moment of the genesis of modernization. This article aims to describe the leading role that the residents of the province of Buenos Aires played towards the middle of the 19th century, showing how the government needed the existing networks on the borders to build government. Taking as our starting point the mobilization of farmers from a prominent wheatproducing county demanding the subdivision and sale of public lands to the direct producers, we will attempt to demonstrate that important statesmen such as Mitre and Sarmiento —the first presidents of a unified Argentina— not only used these existing networks of power, but also evaluated the possibility of considering that agriculture, rural society and therefore a fair distribution of the land could be a possible alternative to the development of the pampas regio

Variable Support Control for the Wave Equation: A Multiplier Approach

We study the controllability of the multidimensional wave equation in a bounded domain with Dirichlet boundary condition, in which the support of the control is allowed to change over time. The exact controllability is reduced to the proof of the observability inequality, which is proven by a multiplier method. Besides our main results, we present some applications

Multianalytical provenance analysis of Eastern Ross Sea LGM till sediments (Antarctica): Petrography, geochronology, and thermochronology detrital data

In order to reveal provenance of detrital sediments supplied by West Antarctic Ice Sheet (WAIS), 19 glaciomarine cores of Last Glacial Maximum age were analyzed from Eastern Ross Sea and Sulzberger Bay. Analytical techniques included petrographic analysis of gravel-sized clasts, geochronology (zircon U-Pb: Zrn-UPb) and thermochronology (apatite fission track: AFT) of sand-sized fractions. Petrographic analysis revealed a similarity with the lithologies presently exposed in western Marie Byrd Land (MBL), with major roles played by low-grade metamorphic rocks and granitoids. Furthermore Zrn-UPb and AFT data allowed to identify the ages of formation and cooling of sedimentary source area, consisting of Cambrian-Precambrian basement (i.e., Swanson Formation in western MBL) which underwent at least two episodes of magma intrusion, migmatization and cooling during Devonian-Carboniferous and Cretaceous-Paleocene times. Scarcity of volcanic clasts in the region of Ross Sea along the front of West Antarctica Ice Streams in association with the occurrence of AFT Oligocene-Pliocene dates suggests a localized tectonic exhumation of portions of MBL, as already documented for the opposite side of West Antarctic Rift System in the Transantarctic Mountains. Furthermore, a Zrn-UPb and AFT population of Late Triassic-Jurassic age indicates the presence of unexposed rocks that formed or metamorphosed at that time in the sedimentary source area, which could be identified in McAyeal Ice Stream and Bindschadler Ice Stream catchment areas

Alternating and variable controls for the wave equation

The present article discusses the exact observability of the wave equation when the observation subset of the boundary is variable in time. In the one-dimensional case, we prove an equivalent condition for the exact observability, which takes into account only the location in time of the observation. To this end we use Fourier series. Then we investigate the two specific cases of single exchange of the control position, and of exchange at a constant rate. In the multi-dimensional case, we analyse sufficient conditions for the exact observability relying on the multiplier method. In the last section, the multi-dimensional results are applied to specific settings and some connections between the one and multi-dimensional case are discussed; furthermore some open problems are presented.Comment: The original publication is available at www.esaim-cocv.org. The copyright of this article belongs to ESAIM-COC

Un schéma vaut-il mieux qu'un long discours ?

International audienceThis research focuses on written language and systems of signs to study the learning of scientific concepts. It proposes to show that students (Grade 10 [aged 15]) mobilize ideas about gas in different ways in regard to the semiotic registers (text or picture) proposed during an assessment. Our study adopts a socio-constructivist approach of learning and develops a theoretical framework, articulating elements from the didactic of physics with semiotics concepts of Duval (1995). We give a test with questions (using simultaneously text and diagram) to approximately 90 students just after a teaching sequence on gas. We categorize with the software Sphinx students’ answers and diagram. This analysis has excellent intra-analyst reliability of our coding with the best level of reproducibility (Cohen’s Kappa test) and all our results are statistically significant (test of Khi2). Our results show that : (I) situations affect the mobilization of students’ ideas in regard to the semiotics registers involved in the assessment, (II) the semiotics registers have an effect on the mobilization of students’ ideas according to the facets of knowledge. Students are much more efficient in the register of : (a) schema to use facets about particles contained in gas and it homogeneous distribution and (b) text to mobilize their ideas about the action of gas, (III) the semiotic registers used in the tasks of the teaching sequence on gas could possibly be related to the mobilization of students’ ideas in the semiotics registers involved during the assessment. The implications of this work in teaching and research in didactic of physics are important. It allows to have a better consideration of the semiotic register to assess students’ knowledge.Cette recherche s’intéresse à l’importance du langage écrit et des systèmes de signes dans l’apprentissage de concepts scientifiques. Elle propose de montrer que la mobilisation des idées des élèves de seconde sur les gaz diffère selon les registres sémiotiques (texte ou schéma) proposés dans une évaluation. Notre étude adopte une approche socioconstructiviste de l’apprentissage et développe un cadre théorique mixte, articulant des éléments issus de la didactique de la physique avec les travaux de Duval (1995) sur la sémiotique. À partir d’une évaluation (utilisant simultanément du texte et du schéma) passée auprès d’environ 90 élèves de seconde juste après une séquence d’enseignement du groupe SESAMES sur les gaz, nous avons catégorisé à l’aide du logiciel Sphinx leurs réponses écrites et leurs schémas. La fiabilité de cette catégorisation a été éprouvée à l’aide du test de Cohen’s Kappa dont les résultats ont montré une excellente reproductibilité intra codeur. Nos résultats montrent par ailleurs que : (I) les situations influencent la mobilisation des idées des élèves en fonction des registres sémiotiques sollicités dans l’évaluation ; (II) les registres sémiotiques influencent différemment la mobilisation des idées des élèves en fonction des facettes du savoir mises en jeu. En effet, les productions des élèves sont beaucoup plus pertinentes : (a) dans le registre du schéma pour rendre compte des facettes aspect particulaire et répartition homogène du gaz et (b) dans le registre du texte en langage naturel pour mobiliser leurs idées relatives à l’action du gaz ; (III) les registres sémiotiques utilisés dans les tâches de la séquence d’enseignement sur les gaz pourraient éventuellement avoir un lien avec la mobilisation des idées des élèves dans les registres sémiotiques proposés par l’évaluation. Les implications de ces travaux dans l’enseignement de la physique, ainsi que la recherche en didactiques sont importantes. Elles devraient permettre une meilleure prise en compte des registres sémiotiques dans l’évaluation des connaissances des élèves