Magnetic-field-induced electronic instability of Weyl-like fermions in compressed black phosphorus

Revealing the role of Coulomb interaction in topological semimetals with Dirac/Weyl-like band dispersion shapes a new frontier in condensed matter physics. Topological node-line semimetals (TNLSMs), anticipated as a fertile ground for exploring electronic correlation effects due to the anisotropy associated with their node-line structure, have recently attracted considerable attention. In this study, we report an experimental observation for correlation effects in TNLSMs realized by black phosphorus (BP) under hydrostatic pressure. By performing a combination of nuclear magnetic resonance measurements and band calculations on compressed BP, a magnetic-field-induced electronic instability of Weyl-like fermions is identified under an external magnetic field parallel to the so-called nodal ring in the reciprocal space. Anomalous spin fluctuations serving as the fingerprint of electronic instability are observed at low temperatures, and they are observed to maximize at approximately 1.0 GPa. This study presents compressed BP as a realistic material platform for exploring the rich physics in strongly coupled Weyl-like fermions.Comment: 10 pages, 4 figure

Perioperative management with biologics on severe aortic valve regurgitation caused by Behçet syndrome: the experience from a single center

Background: To investigate the efficacy and safety of biologics in the perioperative management of severe aortic valve regurgitation (AR) caused by Behçet syndrome (BS). Methods: We retrospectively analyzed 20 patients with severe AR caused by BS who were all treated with biologics during the perioperative period of cardiac surgeries in our center between February 2016 and October 2020. Results: A total of 20 patients with severe AR were enrolled, including 19 males and 1 female, with a mean age of 39.1 ± 8.8 years and a median course of 8 [interquartile range (IQR) 5.25–10.00] years. Before biologic administration, 92.9% of the patients who underwent aortic valve replacement had failed conventional therapy and developed postoperative paravalvular leakage (PVL) at a median interval of 4 months. Biologics were administered with background glucocorticoids (GCs) and immunosuppressants during the perioperative period for 22 aortic valve surgeries, including preoperatively with a median interval of 3.5 (IQR 2.75–4.25) months in 13 cases and within 3 months postoperatively in 9 cases. After a median follow up of 21 (IQR 15–32) months, 2 out of 13 cases (15.4%) preoperatively, and 1 out of 9 cases (11.1%) postoperatively treated with biologics developed PVL, and the rest were event free. The Behçet’s Disease Current Activity Form score improved significantly (7 versus 0, median, p  < 0.0001). Decrease of erythrocyte sedimentation rate [25.0 (IQR 11.00–36.25) mm/h versus 6.5 (IQR 4.0–8.8) mm/h, p  < 0.001], and C-reactive protein [20.77 (IQR 7.19–29.58) mg/l versus 1.53 (IQR 0.94–2.92) mg/l, p  = 0.001] were achieved rapidly and effectively. The GC dosage tapered from 40 (IQR 30–60) mg/d to 10 (IQR 5–11.25) mg/d, p  < 0.0001. Immunosuppressants were tapered in number and dosage in 6 (30%) and 20 patients (100%), respectively. No serious adverse event was observed. Conclusion: Our study suggests that biologics were effective and well tolerated for the perioperative management of severe and refractory AR caused by BS, which significantly reduced the occurrence of postoperative PVL and had favorable GC- and immunosuppressant-sparing effect

The response of diazotrophs to nutrient amendment in the South China Sea and western North Pacific

The availability of iron (Fe) and phosphorus (P) has been shown to be a key factor regulating rates of nitrogen fixation in the western subtropical Pacific. However, the relative importance of Fe and P at finer spatial scales between the northern South China Sea (NSCS) and the western boundary of the North Pacific is poorly constrained. Furthermore, nutrient limitation of specific diazotroph types has not yet been assessed. Here we investigated these unknowns by (i) carrying out measurements of finer-scale spatial variabilities in N2 fixation rates and diazotroph nifH gene abundances throughout these regions and (ii) conducting eight additional Fe and phosphate addition bioassay experiments where both changes in N2 fixation rates and the nifH gene abundances of specific diazotrophs were measured. Overall, nitrogen fixation rates and nifH gene abundances were lower in the NSCS than around the Luzon Strait and the western North Pacific. The nutrient addition bioassay experiments demonstrated that N2 fixation rates in the central NSCS were co-limited by Fe and P, whereas at the western boundary of the North Pacific they were P-limited. Changes in the abundances of nifH in response to nutrient addition varied in how well they correlated with changes in N2 fixation rates, and in six out of eight experiments the largest responses in nifH gene abundances were dominated by either Trichodesmium or UCYN-B (unicellular diazotrophic cyanobacteria group B). In general, nutrient addition had a relatively restricted impact on the composition of the six phylotypes that we surveyed apart from on UCYN-B. This unicellular cyanobacterium group showed increased contribution to the total nifH gene abundance following P addition at sites where N2 fixation rates were P-limited. Our study provides comprehensive evidence of nutrient controls on N2 fixation biogeography in the margin of the western North Pacific. Future research that more accurately constrains nutrient supply rates to this region would be beneficial for resolving what controls diazotroph community structure