Tipos y niveles de lectura de tablas estadísticas en libros de texto de primeros cursos: un estudio en el contexto chileno

En este trabajo presentamos resultados parciales de una investigación sobre el tratamiento de las tablas estadísticas de los libros de texto chilenos de Educación Primaria. Concretamente se han analizado cuatro libros de texto de primer y segundo año de Educación Primaria editados por el Ministerio de Educación y la editorial Santillana. El objetivo de este reporte va enfocado a examinar los tipos de tablas estadísticas y los niveles de lectura que exigen las actividades en las cuales interviene este objeto matemático. El estudio se ha llevado a cabo bajo una metodología cualitativa, de nivel descriptivo y mediante análisis de contenido. Los resultados evidencian un predominio de las tablas de conteo y del nivel de lectura “leer dentro de los datos” que lleva asociada el desarrollo de cálculos y/o comparaciones. El estudio revela la existencia de diferencias relacionadas con la cantidad y variedad de actividades entre los libros de texto, situaciones que deben ser consideras para un adecuado proceso de instrucción y para la mejora de los libros de texto. Entre las proyecciones inmediatas de esta investigación se tiene: a) ampliar el estudio a otros cursos de Educación Primaria y; b) diseñar, validar y aplicar un instrumento para evaluar la compresión que alcanzan los niños sobre este objeto matemático

A Comparative Electrochemical-Ozone Treatment for Removal of Phenolphthalein

The degradation of aqueous solutions containing phenolphthalein was carried out using ozone and electrochemical processes; the two different treatments were performed for 60 min at pH 3, pH 7, and pH 9. The electrochemical oxidation using boron-doped diamond electrodes processes was carried out using three current density values: 3.11 mA⋅cm −2 , 6.22 mA⋅cm −2 , and 9.33 mA⋅cm −2 , whereas the ozone dose was constantly supplied at 5 ± 0.5 mgL −1 . An optimal degradation condition for the ozonation treatment is at alkaline pH, while the electrochemical treatment works better at acidic pH. The electrochemical process is twice better compared with ozonation

Adaptation, reliability and validity of a Brief Multicomponent AIDS Phobia Scale (MAPS) in Colombian adolescents

La fobia al sida consiste en un miedo persistente, anormal e injustificado a contraer el VIH. Uno de los instrumentos disponibles para evaluar la fobia al sida es la Multicomponent AIDS Phobia Scale (MAPS). El objetivo de este estudio fue adaptar y validar la MAPS en adolescentes colombianos. Participaron 859 estudiantes entre 14-19 años respondiendo a la MAPS y otros autoinformes para analizar su validez (conocimientos sobre las ITS, actitud hacia el VIH y ansiedad por la salud). El análisis factorial confirmó la estructura bifactorial (F1: miedo a la infección y F2: miedo a otros), de acuerdo con la versión original. Se obtuvo evidencias de fiabilidad y validez consistentes con la teoría. La aplicación de la MAPS es idónea para evaluar miedo al VIH/sida y estudiar su relación con factores de riesgo sexual (uso de condón, múltiples parejas sexuales) a nivel investigador y comunitario en Colombia. También puede ser útil para evaluar el impacto de campañas sociales para reducir el estigma hacia el VIH y programas de prevención dirigidos a promover una sexualidad saludable en adolescentes mediante la transmisión de conocimientos adecuados y actitudes más tolerantes hacia las personas que viven con VIH.The AIDS phobia is a persistent, abnormal and unjustified fear of contracting HIV. The objective of this study was to adapt and validate MAPS in Colombian adolescents. Participants included 856 students aged 14-19 years who responded to the MAPS and other self-reports to analyze its validity (including knowledge about STIs, attitude towards HIV and health anxiety). Factor analysis confirmed the bifactorial structure (F1: fear of infection and F2: fear of others), according to the original version. Evidence of reliability and validity was obtained consistently with the theory. The application of MAPS is appropriate for assessing fear of HIV/AIDS and to study its relationship with sexual risk factors (e.g. condom use, multiple sexual partners) at research and community levels in Colombia. It also can be useful for assessing the impact of social campaigns to reduce stigma towards HIV and prevention programs aimed at promoting healthy sexuality in adolescents through the transmission of adequate knowledge and more favorable attitudes toward people living with HI

Standalone vertex finding in the ATLAS muon spectrometer

A dedicated reconstruction algorithm to find decay vertices in the ATLAS muon spectrometer is presented. The algorithm searches the region just upstream of or inside the muon spectrometer volume for multi-particle vertices that originate from the decay of particles with long decay paths. The performance of the algorithm is evaluated using both a sample of simulated Higgs boson events, in which the Higgs boson decays to long-lived neutral particles that in turn decay to bbar b final states, and pp collision data at √s = 7 TeV collected with the ATLAS detector at the LHC during 2011

Measurements of Higgs boson production and couplings in diboson final states with the ATLAS detector at the LHC

Measurements are presented of production properties and couplings of the recently discovered Higgs boson using the decays into boson pairs, H →γ γ, H → Z Z∗ →4l and H →W W∗ →lνlν. The results are based on the complete pp collision data sample recorded by the ATLAS experiment at the CERN Large Hadron Collider at centre-of-mass energies of √s = 7 TeV and √s = 8 TeV, corresponding to an integrated luminosity of about 25 fb−1. Evidence for Higgs boson production through vector-boson fusion is reported. Results of combined fits probing Higgs boson couplings to fermions and bosons, as well as anomalous contributions to loop-induced production and decay modes, are presented. All measurements are consistent with expectations for the Standard Model Higgs boson

Measurement of the top quark pair cross section with ATLAS in pp collisions at √s=7 TeV using final states with an electron or a muon and a hadronically decaying τ lepton

A measurement of the cross section of top quark pair production in proton-proton collisions recorded with the ATLAS detector at the Large Hadron Collider at a centre-of-mass energy of 7 TeV is reported. The data sample used corresponds to an integrated luminosity of 2.05 fb -1. Events with an isolated electron or muon and a τ lepton decaying hadronically are used. In addition, a large missing transverse momentum and two or more energetic jets are required. At least one of the jets must be identified as originating from a b quark. The measured cross section, σtt-=186±13(stat.)±20(syst.)±7(lumi.) pb, is in good agreement with the Standard Model prediction

Measurement of the top quark-pair production cross section with ATLAS in pp collisions at \sqrt{s}=7\TeV

A measurement of the production cross-section for top quark pairs(\ttbar) in $pp$ collisions at \sqrt{s}=7 \TeV is presented using data recorded with the ATLAS detector at the Large Hadron Collider. Events are selected in two different topologies: single lepton (electron $e$ or muon $\mu$) with large missing transverse energy and at least four jets, and dilepton ($ee$, $\mu\mu$ or $e\mu$) with large missing transverse energy and at least two jets. In a data sample of 2.9 pb-1, 37 candidate events are observed in the single-lepton topology and 9 events in the dilepton topology. The corresponding expected backgrounds from non-\ttbar Standard Model processes are estimated using data-driven methods and determined to be $12.2 \pm 3.9$ events and $2.5 \pm 0.6$ events, respectively. The kinematic properties of the selected events are consistent with SM \ttbar production. The inclusive top quark pair production cross-section is measured to be \sigmattbar=145 \pm 31 ^{+42}_{-27} pb where the first uncertainty is statistical and the second systematic. The measurement agrees with perturbative QCD calculations.Comment: 30 pages plus author list (50 pages total), 9 figures, 11 tables, CERN-PH number and final journal adde

Hunt for new phenomena using large jet multiplicities and missing transverse momentum with ATLAS in 4.7 fb−1 of √s=7 TeV proton-proton collisions

Results are presented of a search for new particles decaying to large numbers of jets in association with missing transverse momentum, using 4.7 fb−1 of pp collision data at s√=7TeV collected by the ATLAS experiment at the Large Hadron Collider in 2011. The event selection requires missing transverse momentum, no isolated electrons or muons, and from ≥6 to ≥9 jets. No evidence is found for physics beyond the Standard Model. The results are interpreted in the context of a MSUGRA/CMSSM supersymmetric model, where, for large universal scalar mass m 0, gluino masses smaller than 840 GeV are excluded at the 95% confidence level, extending previously published limits. Within a simplified model containing only a gluino octet and a neutralino, gluino masses smaller than 870 GeV are similarly excluded for neutralino masses below 100 GeV

Measurement of the inclusive isolated prompt photon cross-section in pp collisions at sqrt(s)= 7 TeV using 35 pb-1 of ATLAS data

A measurement of the differential cross-section for the inclusive production of isolated prompt photons in pp collisions at a center-of-mass energy sqrt(s) = 7 TeV is presented. The measurement covers the pseudorapidity ranges |eta|<1.37 and 1.52<=|eta|<2.37 in the transverse energy range 45<=E_T<400GeV. The results are based on an integrated luminosity of 35 pb-1, collected with the ATLAS detector at the LHC. The yields of the signal photons are measured using a data-driven technique, based on the observed distribution of the hadronic energy in a narrow cone around the photon candidate and the photon selection criteria. The results are compared with next-to-leading order perturbative QCD calculations and found to be in good agreement over four orders of magnitude in cross-section.Comment: 7 pages plus author list (18 pages total), 2 figures, 4 tables, final version published in Physics Letters

Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio