ABSTRACT
We present a detailed study of the Li+ ion adsorption on two different hydrogenated carbon nanostructures, namely as pristine graphene (PG) and topologic Stone-Wales defective graphene (SWG) using the density functional theory (DFT). The studies are focused to analyze the structure-stability relationship with the estimated electronic and electrical properties for lithium-ion batteries (LIB) formed with an anode based on the Li/Li+#PG and Li/Li+#SWG systems. In addition, the electronic effects induced due to Li+ adsorption and the presence of SW defect on the graphene models were analyzed by the frontier molecular orbitals, ChelpG charges, Raman and UV-Vis spectra. It was verified that Li+ is more stably adsorbed on the edges on both graphene structures through an electrostatic interaction between cation and more negatively charged edges of nanostructures. TD-DFT calculations showed that the metallic nature of isolated graphene is disturbed after the adsorption of Li+, and this was demonstrated from the calculated HOMO-LUMO gap. The same Li+-Graphene geometries were optimized by introducing neutral charge in order to enable the calculation of ionization potentials. I was also found that such systems potentially contributed to the modeling of graphene-based anodes with reasonable electrical voltage responses estimated for a LIB. The simulation of Raman and UV-Vis spectra revealed significant variations in intensity and shifts the typical bands of graphene due to the presence of the Li+ ion that can contribute to point out new experiments to the spectroscopic characterization of these systems. Our results suggest that these carbon nanostructures are potential candidates for efficient applications in electrochemical systems, mainly dealing with LIB.
Subject(s)
Graphite , Lithium , Adsorption , Electric Power Supplies , ElectrodesABSTRACT
Two cases of cerebral venous thrombosis are reported. Patients were apparently healthy 39 and 28-year old females with non-specific presenting features. Image findings were characteristic of cerebral sinus thrombosis. The younger patient received progesterone to treat placental abruption eight years previously; she had cerebral venous thrombosis while using oral contraception. Both patients had used contraceptive pills for a long time. Oral hormonal contraceptives may increase the risk of vascular events, even in people without personal or family history of venous thrombosis. Modern imaging methods have contributed to early diagnosis, but the possibility of under diagnosis still persists. This report aims to increase the awareness of health-workers about cerebral venous thrombosis in women, an entity often misdiagnosed, under diagnosed and under-reported.
Subject(s)
Contraceptives, Oral, Hormonal/therapeutic use , Sinus Thrombosis, Intracranial/diagnosis , Adult , Female , Humans , Magnetic Resonance Angiography , Risk Factors , Tomography, X-Ray ComputedABSTRACT
The morphology and anatomy of the fruit development of Ocotee puberula (Rich.) Nees and Nectandra megapotamica (Spreng.) Mez (Lauraceae) was studied in flowers and fruits collected in secondary forests of Maringa, Parana State, Brazil. The fruits of the species are drupes, with epidermic exocarp, parenchymatous mesocarp and endocarp which consists of macrosclereids. The origin of endocarp is the internal epidermis of ovary. The exalbuminous seeds develop from the anatropous ovules and they have testa and tegmen with parenchymatous cells frequently compressed. In the hilum region these teguments show sciereids in radial arrangement. The straight embryo has thick cotyledons which contain reserve substances such as starch and oil. The plumule and hypocotyl-radicle axis are reduced.