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Analysis of the XENON100 dark matter search data
Aprile, E.; Alfonsi, M.; Arisaka, K.; Arneodo, F.; Balan, C.; Baudis, L.; Behrens, A.; Beltrame, P.; Bokeloh, K.; Brown, E.; Bruno, G.; Budnik, R.The XENON100 experiment, situated in the Laboratori Nazionali del Gran Sasso, aims at the direct detection of dark matter in the form of weakly interacting massive particles (WIMPs), based on their interactions with xenon nuclei in an ultra low background dual-phase time projection chamber. This paper describes the general methods developed for the analysis of the XENON100 data. These methods have been used in ...
Scattering by linear defects in graphene : a tight-binding approach
Rodrigues, J. N. B.; Peres, N. M. R.; Santos, J. M. B. Lopes dosWe develop an analytical scattering formalism for computing the transmittance through periodic defect lines within the tight-binding model of graphene. We first illustrate the method with a relatively simple case, the pentagon-only defect line. Afterwards, more complex defect lines are treated, namely the zz(558) and the zz(5757) ones. The formalism developed, only uses simple tight-binding concepts, reducing t...
Continuum model of the twisted bilayer
Santos, J. M. B. Lopes dos; Peres, N. M. R.; Castro Neto, A. H.The continuum model of the twisted graphene bilayer (Phys. Rev. Lett. 99, 256802, 2007) is extended to include all types of commensurate structures. The essential ingredient of the model, the Fourier components of the spatially modulated hopping amplitudes, can be calculated analytically, for any type of commensurate structures in the low twist angle limit. We show that the Fourier components that could give ri...
Scattering by linear defects in graphene : a continuum approach
Rodrigues, J. N. B.; Peres, N. M. R.; Santos, J. M. B. Lopes dosWe study the low-energy electronic transport across periodic extended defects in graphene. In the continuum low-energy limit, such defects act as infinitesimally thin stripes separating two regions where Dirac Hamiltonian governs the low-energy phenomena. The behavior of these systems is defined by the boundary condition imposed by the defect on the massless Dirac fermions. We demonstrate how this low-energy bo...
X-ray fluorescence (conventional and 3D) and scanning electron microscopy for t...
Guilherme, A.; Coroado, J.; Santos, J. M. F. dos; Lühl, L.; Wolff, T.; Kanngießee, B.; Carvalho, M. L.This work shows the first analytical results obtained by X-Ray Fluorescence (XRF) (conventional and 3D) and Scanning Electron Microscopy with Energy Dispersive System (SEM-EDS) on original Portuguese ceramic pieces produced between the 16th and 18th centuries in Coimbra and Lisbon. Experts distinguished these productions based only on the color, texture and brightness, which originates mislabeling in some cases...
Characterization of an energy dispersive X-ray fluorescence imaging system base...
Silva, A. L. M.; Azevedo, C. D. R.; Oliveira, C. A. B.; Santos, J. M. F. dos; Carvalho, M. L.; Veloso, J. F. C. A.An Energy Dispersive X-ray Fluorescence (EDXRF) imaging system based on a Micropattern Gas Detector has already shown good results for di erent applications. An X-ray tube, a pinhole camera and a Micro-Hole and Strip Plate (MHSP) based detector are the main components of the experimental system. The detector uses an MHSP in a Xe atmosphere at 1 bar, acting as a photon counting device, i.e., it is capable to rec...
Coulomb drag and high resistivity behavior in double layer graphene
Peres, N. M. R.; Santos, J. M. B. Lopes dos; Castro Neto, A. H.We show that Coulomb drag in ultra-clean graphene double layers can be used for controlling the on/o ratio for current ow by tunning the external gate voltage. Hence, although graphene remains semi-metallic, the double layer graphene system can be tuned from conductive to a highly resistive state. We show that our results explain previous data of Coulomb drag in double layer graphene samples in disordered SiO...
Zigzag graphene nanoribbon edge reconstruction with stone-wales defects
Rodrigues, João N. B.; Gonçalves, P. A. D.; Rodrigues, N. F. G.; Ribeiro, R. M.; Santos, J. M. B. Lopes dos; Peres, N. M. R.In this paper, we study zigzag graphene nanoribbons with edges reconstructed with Stone-Wales defects, by means of an empirical (first-neighbor) tight-binding method, with parameters determined by ab initio calculations of very narrow ribbons. We explore the characteristics of the electronic band structure with a focus on the nature of edge states. Edge reconstruction allows the appearance of a new type of edge ...
A qualidade das bases de dados como factor crucial em estudos ambientais: condi...
Oliveira, J.; Cortes, R.; Teixeira, Amílcar; Santos, J.M.; Pinheiro, P.J.; Ferreira, Maria T.; Bochechas, Jorge; Ferreira, J.; Pádua, J.Com base num conjunto superior a 1000 amostragens piscícolas em rios portugueses (troços vadeáveis) realizadas por diversas entidades nacionais nos últimos 10 anos, seleccionou-se um grupo de 459 locais que cumprem critérios de normalização de amostragem, procedimentos no terreno, e acuidade nas identificações taxonómicas. Estes locais representam a diversidade de condições naturais e de impactos humanos em Por...
A qualidade das bases de dados como factor crucial em estudos ambientais: Condi...
Oliveira, J.M.; Cortes, R.; Teixeira, Amílcar; Santos, J.M.; Pinheiro, P.J.; Ferreira, Maria T.; Bochechas, Jorge; Ferreira, Jorge; Pádua, J.Com base num conjunto superior a 1000 amostragens piscícolas em rios portugueses (troços vadeáveis) realizadas por diversas entidades nacionais nos últimos 10 anos, seleccionou-se um grupo de 459 locais que cumprem critérios de normalização de amostragem, procedimentos no terreno, e acuidade nas identificações taxonómicas. Estes locais representam a diversidade de condições naturais e de impactos humanos em Por...
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