Navegando por Autor "Silva, E.F."
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Artigo Effects of graphene on light transmission spectra in Dodecanacci photonic quasicrystals(Elsevier, 2019) Silva, E.F.; Vasconcelos, Manoel Silva de; Costa, C.H.; Anselmo, Dory Hélio Aires de Lima; Mello, V.D.We make a theoretical study of light waves, for both TE and TM polarization with oblique incidence. The light waves propagate on SiO2/TiO2 multilayers, organized by Dodecanacci sequence, where we consider a graphene monolayer at the interfaces between distinct layers. We also calculate numerically the optical transmissivity spectrum, by using the transfer matrix method, for the cases with a graphene sheet and without a graphene sheet at the interfaces. Our results indicate that the whole optical spectrum becomes affected by the presence of graphene in the interfaces. Among these effects, we can highlight the shift of bandgaps to high-frequency regions, the emergence of a graphene induced bandgap at low-frequency regions, and the decreasing of transmittance in the whole frequency range considered here. The self-similarity, which is a property that indicates a fractal spectrum, keeps essentially unchanged when we consider graphene sheets between the layers. Our studies can be applied to electromagnetic filters, where an input gate voltage, applied on the graphene sheets, can control the bandgaps which arise on these structuresArtigo Lithium and valproate prevent methylphenidate-induced mania-like behaviors in the hole board test(Elsevier, 2016-08-26) Souza, L.S.; Soares, Bruno Lobão; Silva, E.F.; Santos, W.B.; Asth, L.; Soares-Rachetti, V.P.; Medeiros, I.U.; Gavioli, E.C.Manic bipolar is diagnosed by psychomotor agitation, increased goal-directed activity, insomnia, grandiosity, excessive speech, and risky behavior. Animal studies aimed to modeling mania are commonly based in psychostimulants-induced hyperlocomotion. The exploration of other behaviors related with mania is mandatory to investigate this phase of bipolar disorder in animals. In this study, the hole board apparatus was suggested for evaluating mania-like behaviors induced by the psychostimulant methylphenidate. The treatment with methylphenidate (10 mg/kg, ip) increased locomotion in the open field test. The pretreatment with lithium (50 mg/kg, ip) and valproate (400 mg/kg, ip) significantly prevented the hyperlocomotion. In the hole-board test, methylphenidate increased interactions with the central and peripheral holes and the exploration of central areas. Lithium was more effective than valproate in preventing all the behavioral manifestations induced by the psychostimulant. These findings were discussed based on the ability of methylphenidate-treated mice mimicking two symptoms of mania in the hole board test: goal-directed action and risk-taking behavior. In conclusion, the results point to a new approach to study mania through the hole board apparatus. The hole board test appears to be a sensitive assay to detect the efficacy of antimanic drugs.Artigo Transmission spectra in graphene-based octonacci one-dimensional photonic quasicrystals(Elsevier, 2019) Silva, E.F.; Costa, C.H.; Vasconcelos, Manoel Silva de; Anselmo, Dory Hélio Aires de LimaIn this work, we have studied theoretically the optical transmissivity spectra in graphene-based quasiperiodic dielectric multilayers made of SiO2 and TiO2 which are juxtaposed in accordance with the Octonacci sequence, with a graphene monolayer between them. Our results show that all the optical spectra are affected, and their band gaps are slightly displaced for high frequencies. We also show that the properties of fractality and self-similarity of the spectra are maintained for high frequencies. We have also analyzed the influence of the incident angle and the chemical potential, and shown that when one changes the chemical potential, there is not an appreciable difference between TE and TM transmission spectra for angles close to the normal incidence. The absorption is also calculated as a function of the frequency, and is shown that sharp peaks will appear at the edges of the allowed band frequencies when we increase the Octonacci generation number. Our model can be used in the study of polarizing filters based on photonic crystals, in order to perform an angular selectivity in the incident light. Also, it is possible to tune the chemical potential of graphene layers and set up an angular selective filter using these phenomena