Enhancing power factor of SnSe sheet with grain boundary by doping germanium or silicon
NPJ COMPUTATIONAL MATERIALS
Authors: Sun, Jie; Yu, Jiabing; Guo, Yaguang; Wang, Qian
Abstract
Grain boundaries (GBs) widely exist in two-dimensional (2D) and three-dimensional (3D) materials in experiment, which significantly affect the thermoelectric performance because of the scattering effect on the transport of both electron and phonon. Motivated by the research progress in 3D SnSe, we have systematically studied the GBs in a SnSe monolayer including their stable geometric configurations, the effect of GBs on power factor and Seebeck coefficient, and the strategies to improve the performance by using first principles calculations combined with semiclassical Boltzmann theory. We find that the GBs increase the potential energy barrier of carriers and decrease the valley degeneracy of the conducting bands, leading to the reduction of Seebeck coefficient, as compared to that of the pristine SnSe sheet. We further demonstrate that the trapping gap states are effectively eliminated or reduced by doping germanium or silicon, leading to the enhanced electrical conductivity, power factor, and Seebeck coefficient. These findings shed lights on developing practical strategies for modulating the thermoelectric performance of 2D polycrystalline sheets.
A Reason of Facial Diplegia: Guillain-Barre Syndrome
MEANDROS MEDICAL AND DENTAL JOURNAL
Authors: Arikan, Zehra; Akyol, Ali; Kiylioglu, Nefati
Abstract
Guillain-Barre syndrome (GBS), an acute demyelinating inflammatory poliradiculopathy, is characterised by rapidly progressive, symmetrical, ascending weakness and areflexia. The disease usually occurs after 1-3 weeks of infection, vaccinations, trauma, surgical interventions and immunosuppression. Facial diplegia and paraesthesia which is a rare GBS variant has no weakness whereas, GBS is present with weakness which usually begins from lower extremities. In this article, three cases were presented to emphasise the importance of GBS in patients with facial diplegia.