RESUMO
The electrical and chemical properties of graphene (C(24)H(12)), graphane (C(24)H(24)) and graphene oxide (C(54)H(17)+O+(OH)(3)+COOH) were studied through the density functional theory (DFT) at level of Local Density Approximation (LDA) using a model C(n)H(m) like. The optimized geometry, energy gap and chemical reactivity for the proposed carbon 2D models are reported. It was found that while the graphene and graphane structures have semiconductor behavior, the graphene oxide behaves as semi-metal. However, a transition from semi-mental to semiconductor is predicted if the carboxyl group (COOH) is removed from such structure. The chemically active sites are analyzed on the basis of the electrophilic Fukui functions for each structure.
Assuntos
Condutividade Elétrica , Grafite/química , Óxidos/química , Elétrons , Modelos Químicos , Teoria Quântica , SemicondutoresRESUMO
A postmenopausic woman referred continuous bleeding during seven days, which suddenly started after she was swimming in the river. She didn't have a general symptoms. A gynecological examination showed that the cause of the bleeding was a leech bite on the vaginal wall. The worm was gave away by means of surgical forceps without complications. We described the clinical and pathological features of this unusual parasite attack.