8 resultados para SENSITIVE K CHANNELS
em Universidade do Minho
Resumo:
This work demonstrates the role of defects generated during rapid thermal annealing of pulsed laser deposited ZnO/Al2O3 multilayer nanostructures in presence of vacuum at different temperatures (Ta) (500900 C) on their electrical conductance and optical characteristics. Photoluminescence (PL) emissions show the stronger green emission at Ta 600 C and violetblue emission at TaP800 C, and are attributed to oxygen vacancies and zinc related defects (zinc vacancies and interstitials) respectively. Currentvoltage (IV) characteristics of nanostructures with rich oxygen vacancies and zinc related defects display the electroforming free resistive switching (RS) characteristics. Nanostructures with rich oxygen vacancies exhibit conventional and stable RS behavior with high and low resistance states (HRS/LRS) ratio 104 during the retention test. Besides, the dominant conduction mechanism of HRS and LRS is explained by trap-controlled-space-charge limited conduction mechanism, where the oxygen vacancies act as traps. On the other hand, nanostructures with rich zinc related defects show a diode-like RS behavior. The rectifying ratio is found to be sensitive on the zinc interstitials concentration. It is assumed that the rectifying behavior is due to the electrically formed interface layer ZnAl2O4 at the Zn defects rich ZnO crystals Al2O3 x interface and the switching behavior is attributed to the electron trapping/de-trapping process at zinc vacancies.
Resumo:
Measurements of the total and differential cross sections of Higgs boson production are performed using 20.3 fb1 of pp collisions produced by the Large Hadron Collider at a center-of-mass energy of s=8 TeV and recorded by the ATLAS detector. Cross sections are obtained from measured H and HZZ4 event yields, which are combined accounting for detector efficiencies, fiducial acceptances and branching fractions. Differential cross sections are reported as a function of Higgs boson transverse momentum, Higgs boson rapidity, number of jets in the event, and transverse momentum of the leading jet. The total production cross section is determined to be ppH=33.05.3(stat)1.6(sys)pb. The measurements are compared to state-of-the-art predictions.
Resumo:
A measurement of W boson production in lead-lead collisions at sNN=2.76 TeV is presented. It is based on the analysis of data collected with the ATLAS detector at the LHC in 2011 corresponding to an integrated luminosity of 0.14 nb1 and 0.15 nb1 in the muon and electron decay channels, respectively. The differential production cross-sections and lepton charge asymmetry are each measured as a function of the average number of participating nucleons Npart and absolute pseudorapidity of the charged lepton. The results are compared to predictions based on next-to-leading-order QCD calculations. These measurements are, in principle, sensitive to possible nuclear modifications to the parton distribution functions and also provide information on scaling of W boson production in multi-nucleon systems.
Resumo:
Gold nanoparticles were dispersed in two different dielectric matrices, TiO2 and Al2O3, using magnetron sputtering and a post-deposition annealing treatment. The main goal of the present work was to study how the two different host dielectric matrices, and the resulting microstructure evolution (including both the nanoparticles and the host matrix itself) promoted by thermal annealing, influenced the physical properties of the films. In particular, the structure and morphology of the nanocomposites were correlated with the optical response of the thin films, namely their localized surface plasmon resonance (LSPR) characteristics. Furthermore, and in order to scan the future application of the two thin film system in different types of sensors (namely biological ones), their functional behaviour (hardness and Young's modulus change) was also evaluated. Despite the similar Au concentrations in both matrices (~ 11 at.%), very different microstructural features were observed, which were found to depend strongly on the annealing temperature. The main structural differences included: (i) the early crystallization of the TiO2 host matrix, while the Al2O3 one remained amorphous up to 800 C; (ii) different grain size evolution behaviours with the annealing temperature, namely an almost linear increase for the Au:TiO2 system (from 3 to 11 nm), and the approximately constant values observed in the Au:Al2O3 system (45 nm). The results from the nanoparticle size distributions were also found to be quite sensitive to the surrounding matrix, suggesting different mechanisms for the nanoparticle growth (particle migration and coalescence dominating in TiO2 and Ostwald ripening in Al2O3). These different clustering behaviours induced different transmittance-LSPR responses and a good mechanical stability, which opens the possibility for future use of these nanocomposite thin film systems in some envisaged applications (e.g. LSPR-biosensors).
Resumo:
A measurement of the inclusive cross section for top quark pair production in pp collisions using events with an isolated lepton (muon or electron) and a lepton decaying to hadrons (had) is reported. Measurements of the branching ratios of top quark decays into leptons and jets using events with tt (top antitop) pairs are also reported. Events were recorded with the ATLAS detector at the LHC in pp collisions at a center-of-mass energy of 7 TeV. The collected data sample corresponds to an integrated luminosity of 4.6 fb1. The inclusive cross section measured using events with an isolated lepton and a had is tt=1839(stat.)23(syst.)3(lumi.)pb. The measured top quark branching ratios agree with the Standard Model predictions within the measurement uncertainties of a few percent.
Resumo:
Searches for both resonant and non-resonant Higgs boson pair production are performed in the hhbb,WW final states using 20.3 fb1 of pp collision data at a center-of-mass energy of 8 TeV recorded with the ATLAS detector at the Large Hadron Collider. No evidence of their production is observed and 95% confidence level upper limits on the production cross sections are set. These results are then combined with the published results of the hhbb,bbbb analyses. An upper limit of 0.69 (0.47) pb on the non-resonant Standard Model like hh production is observed (expected), corresponding to 70 (48) times of the SM gghh cross section. For production via narrow resonances, cross section limits of hh production from a heavy Higgs boson decay are set as a function of the heavy Higgs boson mass. The observed (expected) limits range from 2.1 (1.1) pb at 260 GeV to 0.011 (0.018) pb at 1000 GeV. These results are interpreted in the context of two simplified scenarios of the Minimal Supersymmetric Standard Model.
Resumo:
Supplementary data associated with this article can be found, in the online version, at: http://dx.doi.org/10.1016/j.electacta.2015.09.169.
Resumo:
This article argues for a cultural perspective to be brought to bear on studies of climate change risk perception. Developing the circuit of culture model, the article maintains that the producers and consumers of media texts are jointly engaged in dynamic, meaning-making activities that are context-specific and that change over time. A critical discourse analysis of climate change based on a database of newspaper reports from three U.K. broadsheet papers over the period 19852003 is presented. This empirical study identifies three distinct circuits of climate change19851990, 19911996, 19972003which are characterized by different framings of risks associated with climate change. The article concludes that there is evidence of social learning as actors build on their experiences in relation to climate change science and policy making. Two important factors in shaping the U.K.s broadsheet newspapers discourse on dangerous climate change emerge as the agency of top political figures and the dominant ideological standpoints in different newspapers.
