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Probing the semiconductor-Dirac-semimetal transition in Na-Sb-Bi alloys with x-ray Compton scattering
(2025) Pulkkinen, Aki Ismo Olavi; Kothalawala, Veenavee Nipunika; Suzuki, Kosuke; Barbiellini, Bernardo; Nokelainen, Johannes; Chiu, Wei-Chi; Singh, Bahadur; Lin, Hsin; Pandey, Alok K.; Yabuuchi, Naoaki; Tsuji, Naruki; Sakurai, Yoshiharu; Sakurai, Hiroshi; Minár, Jan; Bansil, Arun
We discuss electron redistribution during the semiconductor-to-Dirac semimetal transition in Na-Sb-Bi alloys using x-ray Compton scattering experiments combined with first-principles electronic structure modeling. A robust signature of the semiconductor-to-Dirac semimetal transition is identified in the spherically averaged Compton profile. We demonstrate how the number of electrons involved in this transition can be estimated to provide a novel descriptor for quantifying the strength of spin-orbit coupling responsible for driving the transition. The associated theoretical deviation of the Born charge of Na in Na3Bi from the expected ionic charge of +1 is found to be consistent with the corresponding experimental value of about 10%. Our study also shows the sensitivity of the Compton scattering technique toward capturing the spillover of Bi 6p relativistic states onto Na sites.
Evolution-based tool path and motion planning optimization for 5-axis CNC machining of free-form surfaces
(2026) Chichell, Juan Zaragoza; Bizzarri, Michal; Ibarra, Judith Echevarrieta; Perez, Aritz; Bartoň, Michael
Manufacturing of free-form geometries using 5-axis Computer Numerically Controlled (CNC) machining brings challenges in path-and motion-planning as one typically wants to minimize the manufacturing time of the object under consideration, while keeping the machining error within fine machining tolerances that ranges in tens of microns. We propose an optimization-based pipeline that, for a given toroidal and/or cylindrical flat-end cutter, simultaneously optimizes its milling paths together with its local positioning represented by the rotation and tilt functions. The proposed strategy is validated on a variety of benchmark surfaces, with different hyperparameters for the objective function and initial conditions, showing that our results provide high-quality approximations of free-form geometries using by-construction non-colliding motions of the given tool.
Accessory Spleen: An Anatomical Variation or Developmental Defect? Surgical, Anatomical and Embryological Perspectives
(2025) Mayer, Alexander; Varga, Ivan; Kachlík, David; Voller, Jaroslav; Fuljer, Ivan; Jackuliak, Peter
As the spleen is a morphologically highly variable organ, radiologists and surgeons frequently encounter normal variants which might be misinterpreted. Accessory spleen is quite a common anatomical variation and generally does not causes any symptoms. However, the finding of an accessory spleen located outside its usual position—the splenic hilum or surrounding. peritoneal folds—is relatively rare in clinical practice and can cause serious diagnostic and/or therapeutic complications: It may mimic a solid tumour or an enlarged lymph. In the review, we summarise the possible anatomical localisations of the accessory spleens (from the thoracic cavity to lesser pelvis and scrotum in males), as well as the diagnostic problems and challenges that the atypical anatomical localisation often causes. We also summarise recent knowledge about the embryological background of accessory spleen formation and address the classification of such a finding—is it a harmless anatomical variation, a developmental defect or a pathological condition of the spleen? According to the recent scientific literature and based the modern imaging techniques, the frequency of accessory spleens is so high that it should be considered rather an anatomical variation than a developmental defect.
Trimetallic Alloys as an Electrocatalyst for Fuel Cells: The Case of Methyl Formate on Pt3Pd3Sn2
(2024) Yadav, Radhey Shyam; Kashyap, Diwakar; Pitussi, Itay; Gebru, Medhanie Gebremedhin; Teller, Hanan; Schechter, Alexander; Kornweitz, Haya
The shift toward renewable energy sources plays a central role in the quest for a circular economy. In this context, methyl formate (MF) has garnered attention as a compelling hydrogen carrier and alternative fuel, because of its remarkable characteristics (energy density, ease of storage and transport, and low boiling point). In this study, DFT calculations supported by online electrochemical mass spectroscopy (OE-MS) were performed to investigate the MF electro-oxidation (MFEO) on Pt3Pd3Sn2 (111). The DFT calculations provide insight into the role of Pt, Pd, and Sn atoms in MFEO. Pt and Pd together provide a preferred active site for initiating MFEO through the O-H bond scission, and Sn plays an essential role in the mitigation of CO through oxygenation or water activation. By comparing the reaction energies and activation barriers for all possible reactions in MFEO, the suggested path necessitates a minimum energy of 0.14 eV to initiate the MFEO. This value was supported by the experimental results, showing that the oxidation wave of MF starts at 0.15 V (70 degrees C). Density functional theory (DFT) results, supported by OE-MS, indicate that the hydrolysis of MF prior to MFEO is not preferred on Pt3Pd3Sn2 (111) surfaces, although the formation of methanol is plausible via a CH3O intermediate. Among the three small organic molecules (SOMs) studied-MF, methanol, and formic acid-MF has the lowest activation energy for the initial bond breaking that starts the whole oxidation process (0.13 eV), compared to formic acid (0.45 eV) and methanol (0.61 eV); thus, MF is the preferred fuel on Pt3Pd3Sn2 (111).
Kramers nodal lines in intercalated TaS2 superconductors
(2025) Zhang, Yichen; Gao, Yuxiang; Pulkkinen, Aki Ismo Olavi; Guo, Xingyao; Huang, Jianwei; Guo, Yucheng; Yue, Ziqin; Oh, Ji Seop; Moon, Alex; Oudah, Mohamed; Gao, Xue-Jian; Marmodoro, Alberto; Fedorov, Alexei; Mo, Sung-Kwan; Hashimoto, Makoto; Lu, Donghui; Rajapitamahuni, Anil; Vescovo, Elio; Kono, Junichiro; Hallas, Alannah M.; Birgeneau, Robert J.; Balicas, Luis; Minár, Jan; Hosur, Pavan; Law, Kam Tuen; Morosan, Emilia; Yi, Ming
Kramers degeneracy is one fundamental embodiment of the quantum mechanical nature of particles with half-integer spin under time reversal symmetry. Under the chiral and noncentrosymmetric achiral crystalline symmetries, Kramers degeneracy emerges respectively as topological quasiparticles of Weyl fermions and Kramers nodal lines (KNLs), anchoring the Berry phase-related physics of electrons. However, an experimental demonstration for ideal KNLs well isolated at the Fermi level is lacking. Here, we establish a class of noncentrosymmetric achiral intercalated transition metal dichalcogenide superconductors with large Ising-type spin-orbit coupling, represented by InxTaS2, to host an ideal KNL phase. We provide evidence from angle-resolved photoemission spectroscopy with spin resolution, angle-dependent quantum oscillation measurements, and ab-initio calculations. Our work not only provides a realistic platform for realizing and tuning KNLs in layered materials, but also paves the way for exploring the interplay between KNLs and superconductivity, as well as applications pertaining to spintronics, valleytronics, and nonlinear transport.