Suchergebnisse

Es un ensayo en el que se intenta indagar razones en pro y en contra de permitir la entrada de símbolos islámicos en las aulas de las ecuelas españolas. Este ensayo está motivado por el reciente caso de exclusión de una alumna musulmana de un instituto de Pozuelo de Alarcón (Madrid) por llevar un hijab.

Se trata de una adaptación curricular diseñada para estudiantes con dificultades cognitivas debidas al síndrome de Down que ocasiona un retraso mental leve. De acuerdo a la legislacióin vigente se proponen medidas para que estos estudiantes tengan un acceso adecuado al currículo de matemáticas.

We report on the fabrication and operation of a multi-element vibrational structure consisting of two graphene mechanical resonators coupled by a nanotube beam. The whole structure is suspended. Each graphene resonator is clamped by two metal electrodes. The structure is fabricated using a combination of electron-beam lithography and atomic-force microscopy nano-manipulation. This layout allows us to detect the mechanical vibrations electrically. The measured eigenmodes are localized in either one of the graphene resonators. The coupling due to the nanotube is studied by measuring the shift of the resonance frequency of one graphene resonator as a function of the vibration amplitude of the other resonator. Coupled graphene resonators hold promise for the study of nonlinear dynamics, the manipulation of mechanical states, and quantum non-demolition measurements. © 2013 AIP Publishing LLC. ; We acknowledge support from the European Union through the RODIN-FP7 project, the ERC-carbonNEMS project, and a Marie Curie Grant (271938), the Spanish state (FIS2009-11284), the Catalan Government (AGAUR and SGR), and by the MINAHE4 project (TEC2011-29140-C03-01). ; Peer Reviewed

6 p.-4 fig.Torras, Núria et al. ; A novel suspended planar-array chips technology is described, which effectively allows molecular multiplexing using a single suspended chip to analyze extraordinarily small volumes. The suspended chips are fabricated by combining silicon-based technology and polymer-pen lithography, obtaining increased molecular pattern flexibility, and improving miniaturization and parallel production. The chip miniaturization is so dramatic that it permits the intracellular analysis of living cells. ; This work was supported by the EU ERDF (FEDER) funds and the Spanish Government grants TEC2011-29140-C03-01/02 and TEC2014-51940-C2-1/2. ; Peer reviewed

7 pages, 5 figures, 1 table. ; Thermomechanical noise determines the lowest detection limits of microcantilever-based devices for measuring forces and surface stress variations. In this work, arrays of 334-nm-thick single-crystalline silicon microcantilevers with dissimilar lengths and widths from 50 to 500 µm and 20 to 200 µm, respectively, have been fabricated to calculate the minimal detectable force and surface stress on the basis of the measurement of the spring constant, resonance frequency, and quality factor. The calculated minimal detectable force and surface stress are of the orders of 10–15 N Hz–1/2 and 10–7 N m–1 Hz–1/2, respectively, and both follow a nonintuitive dependence on the dimensions. The minimal detectable force decreases as the cantilevers are shorter and narrower, whereas the minimal detectable surface stress decreases by making the cantilevers shorter and wider. Theoretical expressions of the minimal detectable force and surface stress are provided as a function of the material properties, cantilever dimensions, and quality factor, which allow us to interpret the results. Both force and surface stress noises follow the same dependence on the quality factor and material properties, however, exhibit striking differences in the dimension dependences. The force and surface stress noises enhance with the quality factor. If the quality factor is kept constant, the force noise enhances as the cantilever is longer and wider, whereas the surface stress noise enhances by making the cantilever shorter and wider. The observed increase of the force noise with the length is attributed to the strong decrease of the quality factor. The results imply that the design of cantilevers for surface stress measurements in general should be different than for atomic force microscopy probes. ; The authors would like to acknowledge the European Union (IST-2001-37239) and the Spanish Ministry of Science (GEN2001-4856-C13-11 and TIC2002-10473-E) for the financial support. ; Peer reviewed

Se trata de un estudio exploratorio y descriptivo llevado a cabo con estudiantes del primer curso de bachillerato de un instituto de la provincia de Granada con el objetivo de describir los significados del concepto de límite finito de una función en un punto que ponen de manifiesto al enfrentarse con tareas que vinculan varios sistemas de representación, tanto en formato de respuesta abierta como de elección múltiple cerrada. El instrumento utilizado fue un cuestionario que incluían tareas provenientes de investigaciones previas como propuestas por los investigadores. El análisis de las respuestas abiertas fundamentado en el análisis conceptual previo de los términos claves "aproximar", "tender", "alcanzar", "rebasar" y "límite" que emergen de las respuestas de los estudiantes concluyendo con que los escolares hacen uso de un lenguaje poco elaborado y con persistencia de significados coloquiales informados ya por Cornu, Monaghan y Tall, si bien el apoyo gráfico es un aliciente para una argumentación más fluida y precisa de los escolares. El análisis de las respuestas de elección múltiple refleja la existencia de contradicciones establecidas por los escolares cuando asignan propiedades simbólicas a diferentes tipos de gráficas, de hecho, las frecuencias asociadas a los distintos casos se corresponden con la complejidad que a priori pueden tener dichas gráficas.

Stimuli-responsive materials undergo physicochemical and/or structural changes when a specific actuation is applied. They are heterogeneous composites, consisting of a non-responsive matrix where functionality is provided by the filler. Surprisingly, the synthesis of polydimethylsiloxane (PDMS)-based stimuli-responsive elastomers (SRE) has seldomly been presented. Here, we present the structural, biological, optical, magnetic, and mechanical properties of several magnetic SRE (M-SRE) obtained by combining PDMS and isoparafin-based ferrofluid (FF). Independently of the FF concentration, results have shown a similar aggregation level, with the nanoparticles mostly isolated (>60%). In addition to the superparamagnetic behavior, the samples show no cytotoxicity except the sample with the highest FF concentration. Spectral response shows FF concentrations where both optical readout and magnetic actuation can simultaneously be used. The Young's modulus increases with the FF concentration until the highest FF concentration is used. Our results demonstrate that PDMS can host up to 24.6% FF (corresponding to 2.8% weight of Fe3O4 nanoparticles concentration). Such M-SRE are used to define microsystems – also called soft microsystems due to the use of soft materials as main mechanical structures. In that scenario, a large displacement for relatively low magnetic fields (<0.3 T) is achieved. The herein presented M-SRE characterization can be used for a large number of disciplines where magnetic actuation can be combined with optical detection, mechanical elements, and biological samples. ; The research leading to these results has received funding from the European Research Council under the European Community's Seventh Framework Programme (FP7/2007-2013) ERC grant agreement no. 209243. Partial financial support from the 2014SGR-1015 (DGU) is acknowledged. Dr. XM-B was supported by the "Ramón y Cajal" program from the Spanish Government. MINAHE4:TEC2011-29140-C03-01. ; Peer reviewed ; Peer Reviewed

Local electric stimulation of tissues and cells has gained importance as therapeutic alternative in the treatment of many diseases. These alternatives aim to deliver a less invasively stimuli in liquid media, making imperative the development of versatile micro- and nanoscale solutions for wireless actuation. Here, a simple microfabrication process to produce suspended silicon microphotodiodes that can be activated by visible light to generate local photocurrents in their surrounding medium is presented. Electrical characterization using electrical probes confirms their diode behavior. To demonstrate their electrochemical performance, an indirect test is implemented in solution through photoelectrochemical reactions controlled by a white-LED lamp. Furthermore, their effects on biological systems are observed in vitro using mouse primary neurons in which the suspended microphotodiodes are activated periodically with white-LED lamp, bringing out observable morphological changes in neuronal processes. The results demonstrate a simplified and cost-effective wireless tool for photovoltaic current generation in liquid media at the microscale. ; This research was supported by a Spanish government through the project MINAHE 5 (TEC2014-51940-C2), EU ERDF (FEDER), the predoctoral FPI grant (BES-2012-052105) to C.V.-E. and the TRANSMECAD grant to C.A.S. (SAF2013-43900-R) from the Ministerio de Economía, Industria y Competitividad of Spain. ; Peer reviewed

20 p.4 fig. ; The ability to measure pressure changes inside different components of a living cell is important, because it offers an alternative way to study fundamental processes that involve cell deformation1. Most current techniques such as pipette aspiration2, optical interferometry3 or external pressure probes4 use either indirect measurement methods or approaches that can damage the cell membrane. Here we show that a silicon chip small enough to be internalized into a living cell can be used to detect pressure changes inside the cell. The chip, which consists of two membranes separated by a vacuum gap to form a Fabry–Pérot resonator, detects pressure changes that can be quantified from the intensity of the reflected light. Using this chip, we show that extracellular hydrostatic pressure is transmitted into HeLa cells and that these cells can endure hypo-osmotic stress without significantly increasing their intracellular hydrostatic pressure. ; This work was supported by the Spanish Government grants TEC2009-07687-E, TEC2011-29140-C03-01 and SAF2010-21879-C02-01. ; Peer reviewed

9 p.-4 fig. ; Current microtechnologies have shown plenty of room inside a living cell for silicon chips. Microchips as barcodes, biochemical sensors, mechanical sensors and even electrical devices have been internalized into living cells without interfering their cell viability. However, these technologies lack from the ability to trap and preconcentrate cells in a specific region, which are prerequisites for cell separation, purification and posterior studies with enhanced sensitivity. Magnetic manipulation of microobjects, which allows a non-contacting method, has become an attractive and promising technique at small scales. Here, we show intracellular Ni-based chips with magnetic capabilities to allow cell enrichment. As a proof of concept of the potential to integrate multiple functionalities on a single device of this technique, we combine coding and magnetic manipulation capabilities in a single device. Devices were found to be internalized by HeLa cells without interfering in their viability. We demonstrated the tagging of a subpopulation of cells and their subsequent magnetic trapping with internalized barcodes subjected to a force up to 2.57 pN (for magnet-cells distance of 4.9 mm). The work opens the venue for future intracellular chips that integrate multiple functionalities with the magnetic manipulation of cells. ; This study was financed by the Spanish Government through project MINAHE6 (TEC2017-85059-C3), MINAHE7 (PID2020-115663GB-C3) and FEDER funding. M.I.A. thanks the MCIU for the pre-doctoral Grant (BES-2015-075932) and the University of Granada for the guidance and support within the doctoral program. ; Peer reviewed

Remote microactuators are of great interest in biology and medicine as minimally-invasive tools for cellular stimulation. Remote actuation can be achieved by active magnetostrictive transducers which are capable of changing shape in response to external magnetic fields thereby creating controlled displacements. Among the magnetostrictive materials, Galfenol, the multifaceted iron-based smart material, offers high magnetostriction with robust mechanical properties. In order to explore these capabilities for biomedical applications, it is necessary to study the feasibility of material miniaturization in standard fabrication processes as well as evaluate the biocompatibility. Here we develop a technology to fabricate, release, and suspend Galfenol-based microparticles, without affecting the integrity of the material. The morphology, composition and magnetic properties of the material itself are characterized. The direct cytotoxicity of Galfenol is evaluated in vitro using human macrophages, osteoblast and osteosarcoma cells. In addition, cytotoxicity and actuation of Galfenol microparticles in suspension are evaluated using human macrophages. The biological parameters analyzed indicate that Galfenol is not cytotoxic, even after internalization of some of the particles by macrophages. The microparticles were remotely actuated forming intra- and extracellular chains that did not impact the integrity of the cells. The results propose Galfenol as a suitable material to develop remote microactuators for cell biology studies and intracellular applications. ; This study was supported by the Spanish Government through the project MINAHE 5 (No. TEC2014-51940-C1) and ENVBIOPORAL (No. MAT2014-57960-C3-3-R), the predoctoral FPI grant (No. BES- 2012-052105), the NANONEURO project PIE201350E110 (CSIC) and the Generalitat de Catalunya (2014-SGR-524). A.B. was supported by a predoctoral grant from the Universitat Aut onoma de Barcelona. We wish to thank as well the IMB-CNM Clean Room (Barcelona, Spain), Prof. William P. Robbins of University of Minnesota (Minneapolis, USA) for his support to perform the magnetostrictive measurements and the Institute for Rock Magnetism (Minneapolis, USA) for its facilities. ; Peer reviewed

Microcantilever-based biosensors are a promising tool to detect biomolecular interactions in a direct way with high accuracy. We show the development of a portable biosensor microsystem able to detect nucleic acid hybridization with high sensitivity. The microsystem comprises an array of 20 micromechanical cantilevers produced in silicon technology, a polymer microfluidic system for delivery of the samples, an array of 20 vertical cavity surface emitting lasers (VCSELs) with collimated beams thanks to an integrated microlens array, an optical coupling element to provide the optical path required, and chips with the photodetectors and the CMOS circuitry for signal acquisition and conditioning, capable of measuring the cantilever deflection with sub-nanometer resolution. Robust immobilization and regeneration procedures have been implemented for the oligonucleotide receptor sequences. In a further innovation, an optical waveguide cantilever transducer has been also developed in order to improve the final performance of the device. This has a number of advantages in terms of a simple optical geometry and improved sensitivity. ; European Union IST-2001-37239 ; Gobierno de España TIC2002-10473-E