Archaeological chert artifacts from Atapuerca sites (Burgos, Spain): characterization, causes of decay and selection of compatible consolidating products

Chert tools from Galería and Gran Dolina Caves, located in the Sierra de Atapuerca site complex (Burgos, Spain), were characterized (macro-visual inspection, mineralogical phases, degree of crystallinity, soluble salts, surface morphology and optical surface roughness) and compared to chert samples collected from the surrounding Atapuerca mountain range. The chert tools were studied to determine their causes of decay and for selecting the most compatible conso lidation treatments. It was found that samples solely containing quartz were not significantly altered and required little conservation treatment compared to those that contained quartz and moganite, which were more weathered and powdery, requiring consolidation. The effi cacy of the consolidating products traditionally used by conservators (acrylic resin and ethyl silicate) to preserve these chert remains, together with novel nanoparticle-based products (SiO2 and a mixture of SiO2 and Ca(OH)2 nanoparticles) were assessed in this study. Changes produced by these consolidating products in the physical (surface morphology and cohesion) and aesthetic properties of the chert tools were evaluated using non-destructive techniques (peeling test, spectrophotometry and optical surface roughness), followed by destructive techniques, such as SEM and XRD.This research work was carried out at the Instituto de Geociencias (CSIC-UCM) and was founded by predoctoral fellowship JAE-PreDoc 2010-2014 (CSIC) and the Adaptability and Employment Programme of The European Social Fund (FSE 2007-2013). The characterization analyses and tests were funded by Rafael Fort under Geomaterials Programme (S2009/MAT1629). Research of López-Polín is founded by MINECO-FEDER Project “Comportamiento ecosocial de los homínidos de la Sierra de Atapuerca durante el Cuaternario IV” (CGL2015-65387-C3-1-P); SGR 1040 (AGAUR); 2016PFR-URV-B2-17

Propiedades mecánicas de membranas de grafeno: consecuencias de la inducción controlada de defectos

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física de la Materia Condensada. Fecha de lectura: 22-09-201

Improved graphene blisters by ultrahigh pressure sealing

Graphene is a very attractive material for nanomechanical devices and membrane applications. Graphene blisters based on silicon oxide micro-cavities are a simple but relevant example of nanoactuators. A drawback of this experimental set up is that gas leakage through the graphene-SiO2 interface contributes significantly to the total leak rate. Here we study the diffusion of air from pressurized graphene drumheads on SiO2 micro-cavities and propose a straightforward method to improve the already strong adhesion between graphene and the underlying SiO2 substrate, resulting in reduced leak rates. This is carried out by applying controlled and localized ultrahigh pressure (> 10 GPa) with an Atomic Force Microscopy diamond tip. With this procedure, we are able to significantly approach the graphene layer to the SiO2 surface around the drumheads, thus enhancing the interaction between them allowing us to better seal the graphene-SiO2 interface, which is reflected in up to ~ 4 times lower leakage rates. Our work opens an easy way to improve the performance of graphene as a gas membrane on a technological relevant substrate such as SiO2.Comment: pages 19, 4 figures + supplementary informatio

Preparation of Pleistocene Human Bones with an Ultrasonic Scaler: The Case of Mandible ATD6-112 from Atapuerca (Spain)

The preparation of recently recovered fossil bones often consists of removing sediment by means of mechanical cleaning. A variety of tools are commonly employed in this process (hammers and chisels, air abrasion devices, pneumatic engraving pens, etc). Another tool, however, has received less attention in the literature: the ultrasonic scaler. An ultrasonic scaler is an ultrasonic device used by dentists to remove hard calculus deposits and stains from the teeth. In this article, we describe the preparation of the human mandible ATD6-112 from the Pleistocene site of Gran Dolina (Atapuerca, Spain) with an ultrasonic scaler. This article aims to describe the advantages and drawbacks of this tool for use in some cleaning processes.La préparation des ossements fossiles récemment découvert dans les sites archéologiques, consiste souvent à enlever le sédiment par nettoyage mécanique. Pour cela, une variété d’outils a été largement utilisée (marteaux et burins, dispositifs d’abrasion d’air, stylos pneumatiques). Moins rapportée, est l’utilisation d’un détartreur ultrasonique (un appareil à ultrasons utilisé par les dentistes pour enlever le tartre et les taches des dents). Dans cet article, nous décrivons la préparation réussie de la mandibule humaine ATD-112 du site archéologique pléistocène de Gran Dolina (Atapuerca, Espagne) par détartreur ultrasonique. Cet article vise à exposer les avantages et les inconvénients de cet outil à des fins de nettoyage

Exfoliated graphite flakes as soft-electrodes for precisely contacting nanoobjects

This is the post-peer reviewed version of the following article: P. ares et al. “Exfoliated graphite flakes as soft-electrodes for precisely contacting nanoobjects”. 2D Matererials, 2015, 2(3): 035008. Which has been published in final form at:http://dx.doi.org/10.1088/2053-1583/2/3/035008We introduce a simple, clean and reliable method to transfer exfoliated graphite flakes as soft-electrodes for the electrical contacts of nano-objects. The microelectrodes thus produced exhibit extremely well-defined and thin edges and can be placed at any sample location with sub-micrometer precision. The procedure is carried out under ambient conditions and does not require chemical agents. We present electrical characterization of relevant examples including carbon nanotubes, metal-organic MMX nanoribbons, reduced graphene sheets and damaged circuit repair. The quality of the electrical contacts thus obtained is as good as those fabricated with conventional techniques. This technique is particularly relevant for conductive atomic force microscopy (AFM) studiesThis work was supported by Consolider CSD2010-0024, MAD2D-CM, S2013/MIT-3007 and MAT2013-46753-C2-1 and

El interfaz de usuario. El caso de campus extens.

Con esta comunicación pretendemos revisar algunas teorías sobre el interfaz de usuario que han aparecido en los últimos años, analizando la interacción hombre-máquina, los estilos de aprendizaje, los factores que influyen en los procesos cognitivos, el aprendizaje situado, y recalcando los principios y tendencias del interfaz de usuario y el papel del diseño educativo en los ordenadores. Finalmente, describiremos un caso práctico: el modelo educativo Campus Extens.With this communication we seek to revise some theories on user's interface that have appeared in the last years, analyzing the interaction human-computer, the learning styles, the factors that influence in the cognitive processes, the located learning, and emphasizing the principles and tendencies of user's interface and the paper of the educational design in the computers. Finally, we will check if the theory, previously studied, is adjusted a practical case: the pattern educational Campus Extens

Neutral and charged excitons interplay in non-uniformly strain-engineered WS2

We investigate the response of excitons in two-dimensional semiconductors to nonuniformity of mechanical strain. In our approach to non-uniform strain-engineering, a WS2 monolayer is suspended over a triangular hole. Large (>2%), strongly non-uniform (>0.28% µm–1), and in-situ tunable strain is induced in WS2 by pressurizing it with inert gas. We observe a pronounced shift of the spectral weight from neutral to charged excitons at the center of the membrane, in addition to well-known strain-dependent bandgap modification. We show that the former phenomenon is a signature of a new effect unique for non-uniform strain: funneling of free carriers towards the region of high strain followed by neutral to charged exciton conversion. Our result establishes non-uniform strain engineering as a novel and useful experimental 'knob' for tuning optoelectronic properties of 2D semiconductors

La Cova de Dalt del Tossal de la Font (Vilafamés, Castellón): conclusiones preliminares de las intervenciones arqueológicas (1982-1987 / 2004-2012)

Las excavaciones llevadas a cabo en el yacimiento de la Cova de Dalt del Tossal de la Font en la década de 1980 pusieron al descubierto un importante relleno kárstico del Pleistoceno Superior. Entre el registro recuperado destacan, además de diversas especies de herbívoros y carnívoros, así como de un reducido conjunto litotécnico, tres fósiles humanos adscritos en términos generales al grupo de los neandertales. Entre 2004 y 2012, en el marco de un convenio entre la Universitat Jaume I de Castelló (UJI), el Servei d¿Investigacions Arqueològiques i Prehistòriques (SIAP) de la Diputació de Castelló y el Institut Català de Paleoecologia Humana i Evolució Social (IPHES), se ha desarrollado una segunda época de intervenciones en el yacimiento. En este artículo ofrecemos un estado de la cuestión de la información disponible hasta la fecha sobre el yacimiento, especialmente en lo que se refiere a los aspectos tafonómicos y a la formación del depósito