The ArDM experiment

The aim of the ArDM project is the development and operation of a one ton double-phase liquid argon detector for direct Dark Matter searches. The detector measures both the scintillation light and the ionization charge from ionizing radiation using two independent readout systems. This paper briefly describes the detector concept and presents preliminary results from the ArDM R&D program, including a 3 l prototype developed to test the charge readout system.Comment: Proceedings of the Epiphany 2010 Conference, to be published in Acta Physica Polonica

First results on light readout from the 1-ton ArDM liquid argon detector for dark matter searches

ArDM-1t is the prototype for a next generation WIMP detector measuring both the scintillation light and the ionization charge from nuclear recoils in a 1-ton liquid argon target. The goal is to reach a minimum recoil energy of 30\,keVr to detect recoiling nuclei. In this paper we describe the experimental concept and present results on the light detection system, tested for the first time in ArDM on the surface at CERN. With a preliminary and incomplete set of PMTs, the light yield at zero electric field is found to be between 0.3-0.5 phe/keVee depending on the position within the detector volume, confirming our expectations based on smaller detector setups.Comment: 14 pages, 10 figures, v2 accepted for publication in JINS

Análisis de la aplicabilidad del modelo de Bohr acerca de la predicción de las líneas de emisión del átomo de helio en el marco del dictado de Física Moderna en la Facultad de Ingeniería de la UNLP

El dictado de la materia Física IIIA de las carreras de Ingeniería Electrónica (IE1), Electricista (IE2) y Química (IQ) dictadas en la Facultad de Ingeniería (FI) de la Universidad Nacional de La Plata (UNLP) abarca dos módulos bimestrales. En el segundo de ellos se abordan temas de Física Moderna y entre las actividades de laboratorio establecidas, los alumnos deben realizar un experimento destinado a determinar las líneas características de emisión de una lámpara de gas de He a baja presión utilizando un espectrómetro portátil. En el presente trabajo se describe el instrumental utilizado, la metodología experimental adoptada, se presentan las mediciones realizadas de las líneas características emitidas por el átomo He (HeI) y se las compara con las líneas publicadas en la literatura. A partir del uso del modelo de Bohr para el caso del átomo de He+1 simplemente ionizado (HeII), se estiman las longitudes de onda emitidas por el ión HeII y se las compara con las líneas características del HeII publicadas. También en el marco del modelo de Bohr, se calculan las longitudes de onda emitidas por el átomo HeI despreciando la repulsión entre los electrones y se las compara con las líneas observadas en el laboratorio. Finalmente, se analiza la aplicabilidad del modelo de Bohr en la descripción de los sistemas HeI y HeII.The Physic IIIA course of the Electronic, Electric and Chemical Engineering degrees of La Plata University includes two modules of two months each. The second teaching module includes Modern Physic topics. In special, in the laboratory activities, students carry out an experiment to determine the characteristic emission lines of an He lamp using a didactic spectrometer. In the present work, we describe the approach used in the laboratory and the experimental methodology. We present the emission lines measured and we compare these measurements with the He emission lines reported in the literature. From the Bohr model, we estimate the emitted wave length for the case of the He+1 ion (The He atom without an electron) and we compare these wave lengths with the lines published. In this sense, we also calculate the emitted lines of the He atom in the frame of the Bohr model and we compare these calculations with the lines measured in the laboratory. Finally, we analyze the potential application of the Bohr model in the description of the He atom and of the He+1 ion.Trabajo presentado en la 96A Reunión Nacional de Física y II Reunión Conjunta Sociedad Uruguaya de Física - AsociacióN Física Argentin

Saberes y poder en un espacio escolar conflictivo : un estudio etnográfico

Este texto se presentó como comunicación al II Congreso Internacional de Etnografía y Educación: Migraciones y Ciudadanías. Universidad Autónoma de Barcelona, Barcelona, 5-8 Septiembre 2008.El sector público en Europa se encuentra desde los finales de los años 70 en una fase de reestructuración (Castells 1998; Esping-Anderson, 1990, 1996; Norrie & Goodson 2005). En ese contexto, la educación y la sanidad pública, en tanto que ejes principales del Estado de Bienestar, sufren las consecuencias de discursos neoliberales que promueven su descentralización y mercantilización (Beach 2005). Estos procesos afectan de forma directa el trabajo y el conocimiento profesional de docentes y enfermeros, que ven su práctica y su autonomía cada más amenazadas por dinámicas de mercado que promueven la desprofesionalización y el control de la eficiencia por parte de las autoridades públicas. (Goodson & Hargreaves, 1996; Troman, 2000).El proyecto de investigación europeo Profknow: Professional Knowledge - Restructuring work and life between state and citizens in Europe, tiene como principal objetivo analizar los efectos de estos procesos de reestructuración en la vida profesional de aquellas personas que trabajan en el sector público. Concretamente, propone prestar atención al conocimiento profesional, las condiciones laborales y las experiencias que se generan en la profesión docente y de enfermería en Europa en la actualidad, teniendo en cuenta los cambios habidos en el Estado de Bienestar. Este estudio, en el que participan investigadores del campo de la educación de siete países (Finlandia, Suecia, Irlanda, Reino Unido, Grecia, Portugal y España) ha sido financiado por el VI Programa Marco de la Unión Europea, y se encuentra actualmente en su fase final de ejecución (2004-2007). Nuestro propósito con esta comunicación es presentar parte de la investigación realizada en España. En concreto proponemos compartir algunos de los resultados del estudio etnográfico que llevamos a cabo en un Centro de Actuación Educativa Preferente (CAEP), de la ciudad de Barcelona. La experiencia de esta escuela y sus maestras nos han permitido reflexionar en torno a las múltiples dimensiones y facetas de las relaciones que se tejen en un espacio escolar considerado difícil y conflictivo, y sobre cómo las diversas situaciones ahí vividas - en el aula, en el claustro, en el barrio - pueden llegar a ser generadoras de conocimientos y saberes profesionales y personales

DM: a ton-scale LAr detector for direct Dark Matter searches

The Argon Dark Matter (ArDM-1t) experiment is a ton-scale liquid argon (LAr) double-phase time projection chamber designed for direct Dark Matter searches. Such a device allows to explore the low energy frontier in LAr with a charge imaging detector. The ionization charge is extracted from the liquid into the gas phase and there amplified by the use of a Large Electron Multiplier in order to reduce the detection threshold. Direct detection of the ionization charge with fine spatial granularity, combined with a measurement of the amplitude and time evolution of the associated primary scintillation light, provide powerful tools for the identification of WIMP interactions against the background due to electrons, photons and possibly neutrons if scattering more than once. A one ton LAr detector is presently installed on surface at CERN to fully test all functionalities and it will be soon moved to an underground location. We will emphasize here the lessons learned from such a device for the design of a large LAr TPC for neutrino oscillation, proton decay and astrophysical neutrinos searches

Autocracy-Sustaining Versus Democratic Federalism:Explaining the Divergent Trajectories of Territorial Politics in Russia and Western Europe

This article provides a comparative assessment of territorial politics in Russia and Western Europe. The consolidation or deepening of regional autonomy in Western Europe contrasts with the transformation of Russia from a segmented and highly centrifugal state into a centralized authoritarian state in the course of just two decades. The consolidation of territorial politics in Western Europe is linked to the presence of endogenous safeguards that are built into their territorial constitutional designs and most importantly to the dynamics that emanate from multi-level party competition in the context of a liberal and multi-level democracy. In contrast, in Russia, neither endogenous safeguards nor multi-level party democracy play an important role in explaining the dynamics of Russian federalism, but who controls key state resources instead. We argue that under Putin power dependencies between the Russian center and the regions are strongest where regional democracy is at its weakest, thus producing ‘autocracy-sustaining’ instead of a democratic federation. By studying the relationship between federalism and democracy in cases where both concepts are mutually reinforcing (as in Western Europe) with the critical case of Russia where they are not, we question the widely held view that democracy is a necessary pre-condition for federalism.Peer reviewe

The 'PUCE CAFE' Project: the First 15K Coffee Microarray, a New Tool for Discovering Candidate Genes correlated to Agronomic and Quality Traits

Background: Understanding the genetic elements that contribute to key aspects of coffee biology will have an impact on future agronomical improvements for this economically important tree. During the past years, EST collections were generated in Coffee, opening the possibility to create new tools for functional genomics. Results: The "PUCE CAFE" Project, organized by the scientific consortium NESTLE/IRD/CIRAD, has developed an oligo-based microarray using 15,721 unigenes derived from published coffee EST sequences mostly obtained from different stages of fruit development and leaves in Coffea Canephora (Robusta). Hybridizations for two independent experiments served to compare global gene expression profiles in three types of tissue matter (mature beans, leaves and flowers) in C. canephora as well as in the leaves of three different coffee species (C. canephora, C. eugenoides and C. arabica). Microarray construction, statistical analyses and validation by Q-PCR analysis are presented in this study. Conclusion: We have generated the first 15 K coffee array during this PUCE CAFE project, granted by Genoplante (the French consortium for plant genomics). This new tool will help study functional genomics in a wide range of experiments on various plant tissues, such as analyzing bean maturation or resistance to pathogens or drought. Furthermore, the use of this array has proven to be valid in different coffee species (diploid or tetraploid), drastically enlarging its impact for high-throughput gene expression in the community of coffee research

Systemic IL-12 Administration Alters Hepatic Dendritic Cell Stimulation Capabilities

The liver is an immunologically unique organ containing tolerogenic dendritic cells (DC) that maintain an immunosuppressive microenvironment. Although systemic IL-12 administration can improve responses to tumors, the effects of IL-12-based treatments on DC, in particular hepatic DC, remain incompletely understood. In this study, we demonstrate systemic IL-12 administration induces a 2–3 fold increase in conventional, but not plasmacytoid, DC subsets in the liver. Following IL-12 administration, hepatic DC became more phenotypically and functionally mature, resembling the function of splenic DC, but differed as compared to their splenic counterparts in the production of IL-12 following co-stimulation with toll-like receptor (TLR) agonists. Hepatic DCs from IL-12 treated mice acquired enhanced T cell proliferative capabilities similar to levels observed using splenic DCs. Furthermore, IL-12 administration preferentially increased hepatic T cell activation and IFNγ expression in the RENCA mouse model of renal cell carcinoma. Collectively, the data shows systemic IL-12 administration enables hepatic DCs to overcome at least some aspects of the inherently suppressive milieu of the hepatic environment that could have important implications for the design of IL-12-based immunotherapeutic strategies targeting hepatic malignancies and infections

Flexibility of a biotinylated ligand in artificial metalloenzymes based on streptavidin—an insight from molecular dynamics simulations with classical and ab initio force fields

In the field of enzymatic catalysis, creating activity from a non catalytic scaffold is a daunting task. Introduction of a catalytically active moiety within a protein scaffold offers an attractive means for the creation of artificial metalloenzymes. With this goal in mind, introduction of a biotinylated d6-piano-stool complex within streptavidin (SAV) affords enantioselective artificial transfer-hydrogenases for the reduction of prochiral ketones. Based on an X-ray crystal structure of a highly selective hybrid catalyst, displaying significant disorder around the biotinylated catalyst [η6-(p-cymene)Ru(Biot-p-L)Cl], we report on molecular dynamics simulations to shed light on the protein–cofactor interactions and contacts. The results of these simulations with classical force field indicate that the SAV-biotin and SAV-catalyst complexes are more stable than ligand-free SAV. The point mutations introduced did not affect significantly the overall behavior of SAV and, unexpectedly, the P64G substitution did not provide additional flexibility to the protein scaffold. The metal-cofactor proved to be conformationally flexible, and the S112K or P64G mutants proved to enhance this effect in the most pronounced way. The network of intermolecular hydrogen bonds is efficient at stabilizing the position of biotin, but much less at fixing the conformation of an extended biotinylated ligand. This leads to a relative conformational freedom of the metal-cofactor, and a poorly localized catalytic metal moiety. MD calculations with ab initio potential function suggest that the hydrogen bonds alone are not sufficient factors for full stabilization of the biotin. The hydrophobic biotin-binding pocket (and generally protein scaffold) maintains the hydrogen bonds between biotin and protein