Strained graphene structures: from valleytronics to pressure sensing

Due to its strong bonds graphene can stretch up to 25% of its original size without breaking. Furthermore, mechanical deformations lead to the generation of pseudo-magnetic fields (PMF) that can exceed 300 T. The generated PMF has opposite direction for electrons originating from different valleys. We show that valley-polarized currents can be generated by local straining of multi-terminal graphene devices. The pseudo-magnetic field created by a Gaussian-like deformation allows electrons from only one valley to transmit and a current of electrons from a single valley is generated at the opposite side of the locally strained region. Furthermore, applying a pressure difference between the two sides of a graphene membrane causes it to bend/bulge resulting in a resistance change. We find that the resistance changes linearly with pressure for bubbles of small radius while the response becomes non-linear for bubbles that stretch almost to the edges of the sample. This is explained as due to the strong interference of propagating electronic modes inside the bubble. Our calculations show that high gauge factors can be obtained in this way which makes graphene a good candidate for pressure sensing.Comment: to appear in proceedings of the NATO Advanced Research Worksho

Antioxidant pathways are up-regulated during biological nitrogen fixation to prevent ROS-induced nitrogenase inhibition in Gluconacetobacter diazotrophicus

Gluconacetobacter diazotrophicus, an endophyte isolated from sugarcane, is a strict aerobe that fixates N2. This process is catalyzed by nitrogenase and requires copious amounts of ATP. Nitrogenase activity is extremely sensitive to inhibition by oxygen and reactive oxygen species (ROS). However, the elevated oxidative metabolic rates required to sustain biological nitrogen fixation (BNF) may favor an increased production of ROS. Here, we explored this paradox and observed that ROS levels are, in fact, decreased in nitrogen-fixing cells due to the up-regulation of transcript levels of six ROS-detoxifying genes. A cluster analyses based on common expression patterns revealed the existence of a stable cluster with 99.8% similarity made up of the genes encoding the α-subunit of nitrogenase Mo–Fe protein (nifD), superoxide dismutase (sodA) and catalase type E (katE). Finally, nitrogenase activity was inhibited in a dose-dependent manner by paraquat, a redox cycler that increases cellular ROS levels. Our data revealed that ROS can strongly inhibit nitrogenase activity, and G. diazotrophicus alters its redox metabolism during BNF by increasing antioxidant transcript levels resulting in a lower ROS generation. We suggest that careful controlled ROS production during this critical phase is an adaptive mechanism to allow nitrogen fixation

Fatores de risco e complicações em hipertensos/diabéticos de uma regional sanitária do nordeste brasileiro

Objetivou-se com este estudo identificar os fatores de risco e a complicações associadas em usuários com hipertensão/diabetes, cadastrados no HIPERDIA da Secretaria Executiva Regional VI em Fortaleza, CE. O estudo documental analítico abordou 2.691 pessoas. Do total, 73,6% eram mulheres; 44,6% tinham 60-79 anos, com média de 60,8 anos; 87,4% eram brancos, amarelos ou pardos; 63,7% tinham até oito anos de estudo; 79,7% não eram fumantes; 56,6% sedentários; 59,6% apresentavam sobrepeso/obesidade; 48,4% possuíam antecedente familiar de doença cardiovascular. Verificou-se associação entre sedentarismo e sobrepeso/obesidade com diabéticos e diabéticos hipertensos; antecedente familiar de doença cardiovascular com os hipertensos e diabéticos hipertensos; acidente vascular encefálico, doença arterial coronariana e insuficiência renal crônica com hipertensos e diabéticos hipertensos; infarto e acidente vascular encefálico com diabéticos. O antecedente familiar cardiovascular associou-se com doença arterial coronariana e infarto. Evidenciou-se a presença relevante de fatores de risco e complicações, destacando a necessidade da educação em saúde com os usuários