Weyl nodal ring states and Landau quantization with very large magnetoresistance in square-net magnet EuGa4

Magnetic topological semimetals allow for an effective control of the topological electronic states by tuning the spin configuration. Among them, Weyl nodal line semimetals are thought to have the greatest tunability, yet they are the least studied experimentally due to the scarcity of material candidates. Here, using a combination of angle-resolved photoemission spectroscopy and quantum oscillation measurements, together with density functional theory calculations, we identify the square-net compound EuGa4 as a magnetic Weyl nodal ring semimetal, in which the line nodes form closed rings near the Fermi level. The Weyl nodal ring states show distinct Landau quantization with clear spin splitting upon application of a magnetic field. At 2 K in a field of 14 T, the transverse magnetoresistance of EuGa4 exceeds 200,000%, which is more than two orders of magnitude larger than that of other known magnetic topological semimetals. Our theoretical model suggests that the non-saturating magnetoresistance up to 40 T arises as a consequence of the nodal ring state.

Associations of physical activity with muscular fitness in adolescents

The aim of this study was to examine the associations between objectively assessed physical activity (PA) and muscular fitness (MF) in adolescents, and to determine whether only resistance training exercise is associated with the increase of MF. A sample of 211 Spanish adolescents (105 girls) wore the ActiGraph monitor for 7 days. Participants also completed a fitness evaluation including three MF tests (handgrip strength, a 60-s abdominal test and a standing broad jump), a cardiorespiratory fitness assessment and anthropometric measures. A standardized MF score was computed using the three muscular tests. Adolescent participation in resistance training was self-reported. Linear regression showed that only vigorous PA was significantly (P=0.041) and positively (β=0.133) associated with MF after adjustment by gender, age, pubertal status, BMI, and cardiorespiratory fitness. Significant differences in MF were found between youth in the lowest and upper tertiles of vigorous PA. Moreover, adolescents who were involved in resistance training had significantly higher MF scores compared with youth in low and medium tertiles of vigorous PA, but no significant differences were found when compared with non-lifters from the highest tertile of vigorous PA (P=0.356). These findings suggest that vigorous activity may be associated with indicators of MF in adolescents.