Les forces i els estiraments a segon d'ESO

Cadascun dels estiraments que fem consisteix en la deformació de la musculatura per l'acció d'una força. Aprofitem el concepte d'estirament, que esdevé de manera natural, per treballar de manera interdisciplinar el continguts de les forces a segon d'ESO. La introducció del concepte de la magnitud força, el seu caràcter vectorial, el newton (N) com a unitat de mesura i la representació de les forces utilitzant les escales, es relaciona d'una manera molt significativa i viva amb l'efecte de la deformació i amb el treball dels estiraments per a la prevenció de lesions muscular

Spectral properties of the two-dimensional Schrödinger Hamiltonian with various solvable confinements in the presence of a central point perturbation

We study three solvable two-dimensional systems perturbed by a point interaction centered at the origin. The unperturbed systems are the isotropic harmonic oscillator, a square pyramidal potential and a combination thereof. We study the spectrum of the perturbed systems. We show that, while most eigenvalues are not affected by the point perturbation, a few of them are strongly perturbed. We show that for some values of one parameter, these perturbed eigenvalues may take lower values than the immediately lower eigenvalue, so that level crossings occur. These level crossings are studied in some detail

La Rúbrica, instrument en l'avaluació per les Competències Bàsiques

El procés d'ensenyament-aprenentatge (E-A) de l'alumnat de secundària ha de respondre al repte d'incorporar el treball per competències a l'avaluació. La necessitat de concretar indicadors del nivell de competencialitat assolit per l'alumnat amb descriptors propis de cada competència és l'element de qualitat que incorpora la LOE. L'objectiu d'aconseguir a més la implicació i motivació de alumnat i de que prengui un rol actiu en el seu propi procés d'aprenentatge troba en la rúbrica un potent instrument. Les rúbriques contenen tres components: escales de qualificació, aspectes a avaluar i criteris o descriptors. Les rúbriques poden estar concebudes per a l'autoavaluació reflexiva que realitzarà l'alumne del propi procés d'aprenentatge i per a la co-avaluació amb la que el docent acompanya l'alumne; i des de aquesta perspectiva compleix la premissa que l'avaluació tingui una component formativa al llarg del procés d'E-A i que proporcioni informació del grau d'assoliment de les competències bàsiques. La rúbrica es presenta com a solució d'excel·lència per organitzar de manera conjunta criteris, àmbits i escala d'aprenentatge. Els autors fan una proposta de descriptors de diferents graus de competencialitat, observables a l'àmbit científic tecnològic, en el treball al laboratori, al taller, en la resolució de problemes i en la realització de dossiers de treball. A tots els àmbits

Simplified Microbial Mats: Unraveling a complex community one alga at a time.

Microbial mats are the oldest known ecosystems with an over 3.4 billion-year fossil record. Understanding their structure and function will help us better understand the biological evolution of life on early earth. They are rich in diversity (phylogenetically and physiologically) ranking amongst the most complex systems on earth. In this investigation, we aim to develop an effective method to study microbial mat organisms in relatively uncomplicated ecosystems that mimic the way they grow in nature. By growing “simplified microbial mats” on polypropylene cloth, we are able to observe the range of biogeochemical processes of a single species in a biogeochemical setting that approximates in situ conditions. We are measuring the rate of nutrient consumption, specifically nitrate and phosphate, and hydrogen production, in order to determine if these “simple mats” are behaving as they would in nature. Pulse amplitude modulation (PAM) fluorometer data is recorded daily for regular observations of photosynthetic efficiency of each sample. Overall growth is documented using a digital SLR camera. In addition, microscopic photographs are taken to observe exactly how these organisms are growing and using the polypropylene cloth as a substrate

Non-volatility of ferroelectric SBT thin fims, at 75ºC

[ES] El estudio de la no volatilidad de una memoria FeRAM de tantalato de bismuto y estroncio, SrBi2Ta2O9 (SBT) en condiciones reales de uso, requiere la caracterización ferroeléctrica del material en forma de lámina delgada a temperaturas por encima del ambiente. Para ello se han depositado láminas de SBT mediante un método sol-gel, sobre substratos de Pt/TiO2/SiO2/Si(100), seleccionándose condensadores de área 5.10-4 cm-2. Basándonos en las medidas de la variación de la polarización con el tiempo (retención) realizadas a temperatura ambiente y a 75ºC, analizamos la viabilidad del material como una FeRAM en condiciones reales de uso.[EN] The study of the non-volatility of Strontium bismuth tantalate SrBi2Ta2O9 (SBT) FeRAM memory, at real operating conditions, requires the ferroelectric characterisation of the material, as a thin film, above the room temperature.As a result, it has been deposited SBT films by the sol-gel method, onto Pt/TiO2/SiO2/Si (100) substrates, using capacitors of 5 x 10–4 cm-2 .In this work, we analysed the viability of this material as a FeRAM memory in real operating conditions, as a result of the variation of the polarisation measurements with time (retention), performed at room temperature and 75ºC.Este trabajo ha sido realizado con el apoyo del proyecto de la CICYT MAT98-1068.Peer reviewe

Feasibility of (Pb, Ca)TiO3 thin films deposited on Pt/TiO2/SiO2/Si(100) for switching applications

[ES] Se han depositado láminas delgadas de (Pb,Ca)TiO3 sobre substratos de Pt/TiO2/SiO2/Si(100) por centrifugación, partiendo de soluciones sintetizadas por sol -gel. La concentración de las soluciones y el contenido de PbO se seleccionaron para minimizar las tensiones de las láminas cristalizadas y obtener la adecuada estequiometria. La cristalización mediante un calentamiento rápido (RTP), conduce a láminas con orientaciones preferentes [001]/[001], reducida capa interfacial ferroeléctrico-Pt y composición deseada. Los parámetros ferroeléctricos obtenidos muestran una mejora de las propiedades. Estas láminas presentan una fatiga y envejecimiento mucho más moderados que otros materiales alternativos depositados sobre substratos iguales, lo que permite considerar al método descrito como muy valioso para conseguir materiales susceptibles de emplear en aplicaciones de conmutación.[EN] (Pb,Ca)TiO3 ferroelectric thin films have been spin-coated on Pt/TiO2/SiO2/Si(100) substrates from sol-gel synthesized solutions. Selecting the solution concentrations and the excess of PbO content, stoichiometric composicion with reduced strains are obtained. Crystallization process by rapid thermal treatment (RTP) promote preferred orientations [001]/[100] resulting a thiner ferroelectric-platinum interface layer, which causes the improvement of fatigue and retain behaviour, despite the use of platinum electrodes. These experimental finds let to cosider the described methode of processing very convenient to prepare thin films of this composition to use on switching applications such as non volatil RAM memories.Peer reviewe

Spinodally synthesized magnetoelectric

This is the publisher's version, also available electronically from http://scitation.aip.org/content/aip/journal/apl/91/8/10.1063/1.2767174.Lead zirconium titanate/nickel ferrite (PZT/NFO) composites have been produced by crystallizing and spinodally decomposing a gel in a magnetic field below the Curie temperature of NFO. The gel had been formed by spinning a sol onto a silicon substrate. The ensuing microstructure, characterized by atomic force microscopy, magnetic force microscopy, (Lorentz) transmission electron microscopy, and scanning electron microscopy, is nanoscopically periodic and, determined by the direction of magnetic annealing field, anisotropic. The wavelength of the PZT/NFO alternation, 25nm, agrees within a factor of 2 with the theoretically estimated value. The macroscopic ferromagnetic and magnetoelectric responses correspond qualitatively and semiquantitatively to the features of the nanostructure. The maximum of the field dependent magnetoelectric susceptibility equals 1.8V∕cmOe

Superintegrability and higher order polynomial algebras II

In an earlier article, we presented a method to obtain integrals of motion and polynomial algebras for a class of two-dimensional superintegrable systems from creation and annihilation operators. We discuss the general case and present its polynomial algebra. We will show how this polynomial algebra can be directly realized as a deformed oscillator algebra. This particular algebraic structure allows to find the unitary representations and the corresponding energy spectrum. We apply this construction to a family of caged anisotropic oscillators. The method can be used to generate new superintegrable systems with higher order integrals. We obtain new superintegrable systems involving the fourth Painleve transcendent and present their integrals of motion and polynomial algebras.Comment: 11 page

A parallel algorithm for solving the incompressible Navier-Stokes problems

AbstractWe introduce and analyze a parallel algorithm for solving the Navier-Stokes equations based on the splitting of the two main difficulties involved, the presence of nonlinear terms and the zero divergence condition. The numerical results obtained by using the proposed algorithm are quite consistent with those furnished by other known algorithms. Numerical results are discussed, as well as the advantages of this new algorithm