Oxygen adsorption effect on magnetic properties of graphite

Both experimental and theoretical studies of the magnetic properties of micrographite and nanographite indicate a crucial role of the partial oxidation of graphitic zigzag edges in ferromagnetism. In contrast to total and partial hydrogenation, the oxidation of half of the carbon atoms on the graphite edges transforms the antiferromagnetic exchange interaction between graphite planes and over graphite ribbons to the ferromagnetic interaction. The stability of the ferromagnetism is discussed.Comment: 14 pages, 6 figure

Bed and suspended sediment-associated rare earth element concentrations and fluxes in a polluted Brazilian river system

Rare earth elements (REEs) have been recently recognized as emergent pollutants in rivers. However, data regarding REE fluxes in association with either bed or suspended are scarce. To address this knowledge gap, we determined the concentrations and fluxes of La, Ce, Pr, Nd, Sm, Eu, Gd, Yb, Lu, Dy, Er, Ho, Tb, and Tm in bed and suspended sediment samples of a representative polluted Brazilian River. Sediment-associated data on REEs were placed in the context of corresponding background concentrations in soils under natural conditions along the Ipojuca watershed. Light rare earth elements (LREEs) comprised more than 94% of the total REEs associated with bed and suspended sediments. Suspended sediments accounted for more than 95% of the total REE flux. The Ce and Nd fluxes of about 7 t year−1 underscore the importance of including REEs in future estimations of global suspended sediment-associated element fluxes. In contrast, bedload often transported less than 0.0007 t year−1 of each REE. The main sources of pollution in the Ipojuca River are anthropogenic, likely due to domestic effluent and waste water from industrial and agricultural operations—major causes of sediment-associated Gd transport in polluted streams

Poster: Reengineering legacy systems for supporting SOA: A case study on the brazilian's secretary of state for taxation

© 2018 Authors. The migration of legacy systems to a service-oriented architecture (SOA) allows to deal with the demand for interoperability and the need to provide a robust high-Available service interface. However, such migration presents a considerable risk, as it often involves the use of different techniques on systems with elevated technical debt and high maintenance costs. For this purpose, a process is instantiated to provide an appropriate set of techniques that will minimize risks and at the same time ensure quality improvement of the systems throughout the migration process. In this sense, this work reports on a case study of the application of a process for the reengineering of legacy systems to support the implementation of SOA project. This study has been applied to the evolution of legacy systems of the Secretariat of State for Taxation of Rio Grande do Norte (SET/RN), Brazil, providing significant results regarding the achievement of important quality goals

Universal Magnetic-Field-Driven Metal-Insulator-Metal Transformations in Graphite and Bismuth

Applied magnetic field induces metal - insulator and re-entrant insulator-metal transitions in both graphite and rhombohedral bismuth. The corresponding transition boundaries plotted on the magnetic field - temperature (B - T) plane nearly coincide for these semimetals and can be best described by power laws T ~ (B - B_c)^k, where B_c is a critical field at T = 0 and k = 0.45 +/- 0.05. We show that insulator-metal-insulator (I-M-I) transformations take place in the Landau level quantization regime and illustrate how the IMT in quasi-3D graphite transforms into a cascade of I-M-I transitions, related to the quantum Hall effect in quasi-2D graphite samples. We discuss the possible coupling of superconducting and excitonic correlations with the observed phenomena, as well as the signatures of quantum phase transitions associated with the M-I and I-M transformations.Comment: 23 pages including 14 figure

Reentrant Metallic Behavior of Graphite in the Quantum Limit

Magnetotransport measurements performed on several well-characterized highly oriented pyrolitic graphite and single crystalline Kish graphite samples reveal a reentrant metallic behavior in the basal-plane resistance at high magnetic fields, when only the lowest Landau levels are occupied. The results suggest that the quantum Hall effect and Landau-level-quantization-induced superconducting correlations are relevant to understand the metallic-like state(s) in graphite in the quantum limit.Comment: 4 pages, 5 figure

Protocolo de análise para determinação da atividade antioxidante total em hortaliças no sistema beta-caroteno / ácido linoléico.

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