Anisotropic magnetoresistance and electronic features of the candidate topological compound praseodymium monobismuthide.

PrBi, a sister member of the rare-earth monopnictide family, is an excellent candidate for studying extreme magnetoresistance and nontrivial topological electronic states. In this study, we perform angular magnetoresistance measurements as well as bulk and surface band structure calculations on this compound. PrBi's magnetoresistance is revealed to be significantly angle-dependent and shows a fourfold symmetry as always observed in the nonmagnetic isostructural counterparts, including LaSb, LaBi, and LuBi. Its angular magnetoresistance can be reproduced well using the semiclassical two-band model. The deduced parameters suggest that PrBi hosts an elongated electron pocket with a mobility anisotropy of ∼3.13 and is slightly uncompensated in its carrier concentration. Our bulk and surface band structure calculations confirm the anisotropic electronic features. Moreover, we reveal that a nodal-line-shaped surface state appears at the X̄ point, and is associated with the quadratic dispersion along the -X̄ direction, and the linear type-I Dirac dispersion along the X̄-M̄ direction. Owing to the type-I Dirac dispersion feature, PrBi could serve as a promising material platform for studying many unexpected physical properties, such as the highly anisotropic transport and valley polarization of electrons.

[Influencing factors for trauma-induced tibial infection in underground coal mine].

Objective: To investigate the influencing factors for trauma-induced tibial infection in underground coal mine. Methods: A retrospective analysis was performed for the clinical data of 1 090 patients with tibial fracture complicated by bone infection who were injured in underground coal mine and admitted to our hospital from January 1995 to August 2015, including the type of trauma, injured parts, severity, and treatment outcome. The association between risk factors and infection was analyzed. Results: Among the 1 090 patients, 357 had the clinical manifestations of acute and chronic bone infection, 219 had red and swollen legs with heat pain, and 138 experienced skin necrosis, rupture, and discharge of pus. The incidence rates of tibial infection from 1995 to 2001, from 2002 to 2008, and from 2009 to 2015 were 31%, 26.9%, and 20.2%, respectively. The incidence rate of bone infection in the proximal segment of the tibia was significantly higher than that in the middle and distal segments (42.1% vs 18.9%/27.1%, P<0.01) . As for patients with different types of trauma (Gustilo typing) , the patients with type III fracture had a significantly higher incidence rate of bone infection than those with type I/II infection (52.8% vs 21.8%/24.6%, P<0.01) . The incidence rates of bone infection after bone traction, internal fixation with steel plates, fixation with external fixator, and fixation with intramedullary nail were 20.7%, 43.5%, 21.4%, and 26.1%, respectively, suggesting that internal fixation with steel plates had a significantly higher incidence rate of bone infection than other fixation methods (P<0.01) . The multivariate logistic regression analysis showed that the position of tibial fracture and type of fracture were independent risk factors for bone infection. Conclusion: There is a high incidence rate of trauma-induced tibial infection in workers in underground coal mine. The position of tibial fracture and type of fracture are independent risk factors for bone infection. Vacuum sealing drainage and Ilizarov technique can achieve a satisfactory therapeutic effect.