Curved Graphene Nanoribbons: Structure and Dynamics of Carbon Nanobelts

Carbon nanoribbons (CNRs) are graphene (planar) structures with large aspect ratio. Carbon nanobelts (CNBs) are small graphene nanoribbons rolled up into spiral-like structures, i. e., carbon nanoscrolls (CNSs) with large aspect ratio. In this work we investigated the energetics and dynamical aspects of CNBs formed from rolling up CNRs. We have carried out molecular dynamics simulations using reactive empirical bond-order potentials. Our results show that similarly to CNSs, CNBs formation is dominated by two major energy contribution, the increase in the elastic energy due to the bending of the initial planar configuration (decreasing structural stability) and the energetic gain due to van der Waals interactions of the overlapping surface of the rolled layers (increasing structural stability). Beyond a critical diameter value these scrolled structures can be even more stable (in terms of energy) than their equivalent planar configurations. In contrast to CNSs that require energy assisted processes (sonication, chemical reactions, etc.) to be formed, CNBs can be spontaneously formed from low temperature driven processes. Long CNBs (length of $\sim$ 30.0 nm) tend to exhibit self-folded racket-like conformations with formation dynamics very similar to the one observed for long carbon nanotubes. Shorter CNBs will be more likely to form perfect scrolled structures. Possible synthetic routes to fabricate CNBs from graphene membranes are also addressed

Shades of red and blue: Political ideology and sustainable development

We study the effect of political ideology on sustainable development, measured as investment in genuine wealth, in a dynamic panel of 79 countries between 1981 and 2013. We find that a switch from a left-wing or centrist government to a right-wing government has a robust positive and statistically significant effect on investment in genuine wealth. We find no evidence of opportunistic cycles in these investments

Aplicação da PCAM e da análise de agrupamento em clones de cupuaçuzeiro.

O objetivo deste trabalho foi estudar a divergência genética de 50 clones de cupuaçuzeiro, por meio da PCAM e da Análise de Agrupament