Fontes alternativas: um debate sobre regulação e geração de energia
Eventos
USPITEC-2012: 1ª Feira USP de Inovação & Empreendedorismo
Dias 23, 24 e 25 de agosto – EACH-USP – Zona Leste – São Paulo
Seminário da Biofotônica
Titulo: Characteristic of the human eye aberrations and its applications in the refractive surgery
Palestrante: Wei Wang (Jining University, Qufu, Chandong, China)
Resumo:
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The wave-front aberrations on the postoperative eyes with two different type of excimer laser surgery have been measured by a Hartmann–Shack wave-front sensor. We have calculated the aberrations for both 3 and 6 mm pupils, and with which to acquire the MTF of the eye. There are no significant differences in wave-front aberrations postoperatively (P40.05) for 3 mm pupil size, but with 6 mm pupil, LASIK-treated eyes exhibit significant higher aberrations than LASEK-treated eyes for 4th and 5th-order aberrations. For individual Zernike terms, there are significant difference in C33, C-44, and C04. The MTF for 6 mm pupil is much lower than those for 3 mm pupil across all spatial frequencies. The LASEK curve shows higher than that with LASIK at spatial frequencies less than 60 c/d, which means that the optical quality in LASEK-treated eyes showed better than in LASIK-treated eyes. |
Wei Wang é graduada em física pela Qufu Normal University (2001) e mestre em Óptica (2004) pela mesma Instituição. É doutora pela Nankai University. Atualmente, seus principais interesses são óptica de polarização, produção de prismas de polarização, óptica visual e aberrações do olho humano.
Assessoria de Comunicação
“School on Theoretical High Energy Physics – Introduction and current research”
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Assessoria de Comunicação
Café com Física: “Studies of graphene by Raman spectroscopy”
Palestrante: Denise Nakabayashi (IFSC-USP)
Título: Studies of graphene by Raman spectroscopy
Resumo:
Graphene is described as a monolayer of carbon atoms arranged in a two-dimensional honeycomb lattice. One of the most interesting properties of this material is related to its electronic band structure which permits carriers to behave as massless Dirac fermions with vanishing density of states at the Fermi level. If two graphene layers are stacked in Bernal AB configuration these properties are destroyed as the electronic dispersion curve is no more linear but parabolic. However, for a misoriented stacking in graphene bilayer, the dispersion curve reverts back from parabolic to linear as on monolayers. The graphene monolayers and bilayers can thus be viewed as two different materials with high interest for both fundamental and applied physics.
Raman spectroscopy is a nondestructive and quick technique largely applied to characterize graphene samples. The spectral signature of second order peak (2D) is used to identify graphene monolayers and few layers. In this work, we studied by resonant Raman spectroscopy the dependence of 2D frequency and lineshape on the laser excitation energy for monolayers, Bernal bilayers, and misoriented bilayers. The comparison between the Raman response of monolayers and bilayers on different substrates was also investigated.
Maiores informações em: http://www.ifsc.usp.br/~cafecomfisica/index.html
