Search

Non-Hermitian physics, studying systems described by non-Hermitian Hamiltonians, reveals unique phenomena not present in Hermitian systems. Unlike Hermitian systems, non-Hermitian systems have complex eigenvalues, making their effects less directly observable. Recently, significant efforts have been devoted to incorporating the non-Hermitian effects into condensed matter physics. However, progress is hindered by the absence of a viable experimental approach. Here, the discovery of the surface-selectively spontaneous reconstructed Weyl semimetal NdAlSi provides a feasible experimental platform for studying non-Hermitian physics. Utilizing angle-resolved photoemission spectroscopy (ARPES) measurements, surface-projected density functional theory (DFT) calculations, and scanning tunneling microscopy (STM) measurements, it is demonstrated that surface reconstruction in NdAlSi alters surface Fermi arc (SFA) connectivity and generates new isolated non-topological SFAs (NTSFAs) by introducing non-Hermitian terms. The surface-selective spontaneous reconstructed Weyl semimetal NdAlSi can be viewed as a Hermitian bulk - non-Hermitian boundary system. The isolated non-topological SFAs on the reconstructed surface act as a loss mechanism and open boundary condition (OBC) for the topological electrons and bulk states, serving as non-Hermitian boundary states. This discovery provides a good experimental platform for exploring new physical phenomena and potential applications based on boundary non-Hermitian effects, extending beyond purely mathematical concepts. Furthermore, it provides important enlightenment for constructing topological photonic crystals with surface reconstruction and studying their topological properties., (© 2025 The Author(s). Advanced Materials published by Wiley‐VCH GmbH.)

Background: There are few reported outcomes of treatment of acute cholecystitis incorporating current guidelines for gallbladder dissection techniques and use of percutaneous tube cholecystostomy (PCT). The authors hypothesize PCT allows regression of peritoneal inflammation, but infundibular inflammation is increased at interval cholecystectomy, resulting in greater requirement for advanced dissection techniques., Methods: Between December 2009 and July 2023, 1222 patients were admitted with acute cholecystitis and ultimately underwent cholecystectomy. Of these 1222 patients, there were 876 patients that underwent urgent (within 10 days) cholecystectomy (UrgSurg), 170 patients underwent interval cholecystectomy (10 or more days) after antibiotic therapy (IntMed), and 175 patients that underwent PCT and interval cholecystectomy (IntTube). Minimally invasive operation was attempted in all patients. Patient demographics, comorbidities, surgical techniques (Critical View of Safety (CVS), infundibulum down, fundus-down, subtotal fenestrating, subtotal reconstituting, and conversion to open operation), and surgical outcomes were reviewed retrospectively. Multivariate logistic regression was performed to identify if interval cholecystectomy was independently associated with more advanced dissection techniques or reinterventions., Results: Compared to the UrgSurg and IntMed patients, IntTube patients were significantly older (Median: 60 vs 66 vs 68, P < 0.001) and more often male (41.7% vs 47.6% vs 72.2%, P < 0.001). Additionally, IntTube patients were more likely to have medical comorbidities. Establishment of CVS was significantly less frequent in IntTube patients (61%) compared to UrgSurg patients (86%) and IntMed patients (85.9%) in unadjusted analysis (OR 0.26, P < 0.001) and in multivariable analysis after adjusting for potential confounders (OR 0.31, P < 0.001). There was no incidence of biliary injury, and no difference in rates of biliary reintervention among groups., Conclusion: Interval Cholecystectomy after PCT is independently associated with a lower rate of achieving CVS, and higher rate of requirement for advanced cholecystectomy dissection techniques. We report a low rate of complications using current guidelines for minimally invasive surgery for both urgent and interval cholecystectomy for acute cholecystitis., Competing Interests: Declarations. Disclosures: Steven P. Bowers, MD: Chief Medical Officer, Suture Shield LLC, medical device company which has not initiated the governmental review/approval process, and is not relevant to this manuscript. Teaching faculty, BK Medical, developed educational materials, not relevant to the manuscript. Mohammad Alomari, Courtland Polley, Michael Edwards, John Stauffer, and Charles Ritchie have no competing interest or financial ties to disclose., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)