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Thermal and Pressure-Dependent Lattice Dynamics of TlBiSe and Its Chromium-Doped Variants
No full textTopological insulator (TI) materials, which are conductive at the surface but insulate in bulk, have drawn significant attention in the past decade due to their fascinating properties and potential applications in spintronics, quantum computing, and topological superconductivity. Among three-dimensional TIs, thallium (Tl)-based III–V–VI2 chalcogenides stand out due to their simple electronic band structure near the Fermi level. The study of lattice dynamic properties is crucial for the practical application of any material. In this work, we report the synthesis and lattice dynamics of TlBiSe2 and Cr-doped TlBiSe2. The long- and short-range ordering of the materials was investigated upon Cr doping by powder X-ray diffraction (XRD), X-ray absorption spectra (XAS), and Raman scattering. Temperature-dependent XRD (123–500 K) and Raman scattering (100–500 K), as well as pressure-dependent XRD up to 15 GPa, were carried out to understand lattice dynamics. Both pristine TlBiSe2 and Cr0.06TlBi0.94Se2 show structural stability across the entire temperature and pressure ranges. However, long-range ordering in Cr0.02TlBi0.98Se2 changes above 300 K. Additionally, Cr0.02TlBi0.98Se2 undergoes a monoclinic phase transition at a lower pressure (∼5.0 GPa) compared to that of pristine TlBiSe2 (∼6.8 GPa). This anomalous behavior regarding local structural distortion in Se atoms upon Cr doping at the Bi atomic site is understood
Chemically Boosting Intercalation Voltage and Cycling Stability of Layered Na–Fe–Mn–O Cathode for Na-Ion Batteries through Li/Cu Cosubstitution
No full textIron–manganese-based layered Na-ion cathodes are appealing for building low-cost Na-ion batteries. However, their practical realization is hindered by the lower intercalation voltage (3.2 V, thanks to the introduction of Cu3+/Cu2+ redox and enhanced Fe–O bond ionicity. Na0.80(Li0.10Cu0.10Fe0.30Mn0.50)O2 displays extraordinary cycling stability (98 and 60% at 1C after 500 cycles in the window of 4.0–2.0 and 4.0–1.5 V, respectively) compared to the unsubstituted cathode (58 and 24% at 1C after 500 cycles in the window of 4.0–2.0 and 4.0–1.5 V, respectively). The enhanced stability is attributed to the retention of the O3-type structure and suppressed Jahn–Teller MnO6 distortion during deep sodiation, as revealed by X-ray diffraction and X-ray absorption spectroscopy measurements and DFT calculations. This study highlights the importance of chemical substitution strategies in the development of advanced layered oxide cathodes with higher energy densities and cycling stabilities
Evidence of Ferroelectric Distortions in Topological Crystalline Insulators via Transverse Thermoelectric Measurements
No full textThe transverse thermoelectric (Nernst) effect is a powerful probe for studying the electronic and structural properties of materials. In this study, we employ transverse thermoelectric measurements to investigate the ferroelectric distortion in the topological crystalline insulator (TCI) Pb0.60Sn0.40Te, a compound derived from PbTe and SnTe, known for their exceptional thermoelectric performance and distinct ferroelectric properties. By leveraging Nernst measurements, we provide direct evidence of ferroelectric distortion in this TCI, corroborated by Shubnikov–de Haas quantum oscillations that confirm the presence of two topologically nontrivial Fermi pockets. Density functional theory calculations show that these pockets originate from the L and T points in the Brillouin zone of the distorted structure within the TCI phase. Raman spectroscopy further identifies a structural phase transition below 50 K, consistent with the quantum oscillation observations. This observation is further substantiated by temperature-dependent synchrotron X-ray pair distribution function analysis and transmission electron microscopy, which confirm the local off-centering of cations at low temperature. These findings underscore the potential of transverse thermoelectric measurements in unveiling ferroelectric distortions and their role in modulating topological quantum states, opening new directions for research into the synergy between ferroelectricity and topological phases
Discovering Perovskite-Derived Tungsten Bronzes from In Situ Diffraction of Electrochemical Rubidium and Cesium Intercalation
No full textPerovskite-derived tungsten bronzes are formed from tungsten oxide by electrochemical intercalation of all alkali metals from aqueous solutions. In two steps, we yield two different polymorphs, where the first step is reversible and the second step is irreversible. The electrochemical approach affords precise control of the composition, while ex situ X-ray diffraction and particularly in situ X-ray diffraction allow the analysis of the atomic structure. For the heavy alkali metals, rubidium and cesium, the in situ synchrotron X-ray diffraction experiments reveal in sum four new structures and their formation process. The irreversible deintercalation step yields at room temperature, the α-WO3 phase, a tungsten oxide polymorph which is thermodynamically only stable above 1073 K. Finally, analyzing the full alkali metal series allows us to conclude that the symmetry and structure of the formed bronzes are dictated by the electron count on the tungsten oxide network and the size of the ions plays a negligible role
Adenovirus maturation establishes the transcription competent packaging of its genome
No full textAdenoviruses are human pathogens that more recently have gathered interest as tools for human gene therapy and vaccination. The maturation of the viral genome with associated proteins (core) remains largely unexplored. Here, we show that adenovirus core maturation is guided by features embedded in the viral DNA sequence, which primes the genome for transcription. Using DMS-seq to compare the accessibility of the nucleoprotein core structure before and after maturation (using the maturation deficient ts1 mutant), we identified five genomic regions that become specifically decompacted during maturation. These regions are characterized by low GC-content and are evolutionarily conserved across different adenovirus species, independent of protein-coding constraints. Adenoviral DNA packaging is guided by a distinct 6.1-bp dinucleotide periodicity pattern that helps position viral chromatin proteins. Core maturation serves a dual purpose: (i) it contributes to capsid uncoating by increasing internal pressure while (ii) simultaneously preparing the viral chromatin structure for rapid transcription upon nuclear entry. These findings reveal how sequence-encoded structural information guides adenoviral genome organization and suggest new approaches for optimizing therapeutical adenoviral vectors
Observation of tWZ production at the CMS experiment
No full textThe first observation of single top quark production in association with a W and a Z boson in proton-proton collisions is reported. The analysis uses data at center-of-mass energies of 13 and 13.6 TeV recorded with the CMS detector at the CERN LHC, corresponding to a total integrated luminosity of 200 fb. Events with three or four charged leptons, which can be electrons or muons, are selected. Advanced machine-learning algorithms and improved reconstruction methods, compared to an earlier analysis, result in an unprecedented sensitivity to tWZ production. The measured cross sections for tWZ production are 248 52 fb and 244 74 fb for =13 and 13.6 TeV, respectively. The signal is established with a statistical significance of 5.8 standard deviations, with 3.5 expected, compared to the background-only hypothesis
Search for dijet resonances with data scouting in proton-proton collisions at = 13 TeV
No full textA search is presented for narrow resonances, with a mass between 0.6 and 1.8 TeV, decaying to pairs of jets, in proton-proton collisions at = 13 TeV. The search is performed using dijets that are reconstructed, selected, and recorded in a compact form by the high-level trigger in a technique referred to as 'data scouting', from data collected in 20162018 corresponding to an integrated luminosity of 177 fb. The dijet mass spectra are well described by a smooth parameterization, and no significant evidence for the production of new particles is observed. Model-independent upper limits are presented on the product of the cross section, branching fraction, and acceptance for the individual cases of narrow quark-quark, quark-gluon, and gluon-gluon resonances, and are compared to the predictions from a variety of models of narrow dijet resonance production. The upper limit on the coupling of a dark matter mediator to quarks is presented as a function of the mediator mass. The sensitivity of this search goes beyond what is expected from statistical scaling with the integrated luminosity alone, as a consequence of the use of fewer parameters in the background function within a more robust statistical procedure
Integrating radio detectors of cosmic-ray air showers into the open-source NuRadio framework
No full textNuRadio is an open-source, Python-based software package for the simulation, analysis and reconstruction of the radio emission from ultra-high-energy (UHE) neutrinos and cosmic rays. While NuRadio has so far mainly been used for in-ice radio neutrino detectors, such as ARIANNA, RNO-G and the future IceCube-Gen2 radio array, its modularity, provision of standard data processing steps for radio detectors, extensive documentation, and continuous integration system have allowed the LOFAR and SKA experiments to readily adopt NuRadio for the analysis of cosmic-ray air showers.This contribution will provide a brief overview of NuRadio, covering its new features and improvements to performance and usability in the past several years. The main focus will be on the application to the reconstruction of UHE cosmic-ray air showers, including both radio emission as well as particle data. We argue that using an open, collaborative framework benefits the entire radio community by reducing the software development overhead involved in duplicating, maintaining, or refactoring code, while the open review and continuous integration processes help to ensure accuracy and reliability. We therefore invite other cosmic-ray air-shower experiments to use and contribute to NuRadio
Femtosecond Three-Dimensional Imaging of Single-Protein with Hard X-ray Laser
No full textSingle-particle diffractive imaging is one of the key foundational goals behind the establishment of X-ray Free-Electron Laser (XFEL) facilities. Outrunning radiation damage, extremely intense femtosecond XFEL pulses open up the possibility of imaging uncrystallized aperiodic single-particles frozen in time at room-temperature at the timescales of atomic and electronic motions and thus enabling the capturing of complete energy landscape of molecules both at ground and excited states with sufficiently large data. Despite the current sample-delivery and background scattering challenges, there has been a steady progress in XFEL-single-particle imaging (XFEL-SPI), especially with large viruses. As a significant-step towards XFEL imaging of the structure and dynamics of uncrystallized single-macromolecules, in this presentation, we report the demonstration of three-dimensional diffractive imaging of an uncrystallized single-protein for the first time using hard-x-ray laser pulses at the European X-ray Free-Electron Laser (EuXFEL)—a highly-significant and much-awaited milestone in biological XFEL-SPI. This opens up several new exciting avenues including, but not limited to, ultrafast time-resolved imaging of dynamics in uncrystallized single-proteins.Funding acknowledgementHuman Frontier Science Program (RGP0010/2017) European Research Council: Frontiers in Attosecond X-ray Science Imaging and Spectroscopy (AXSIS) (ERC-2013-SyG 609920) Joachim Herz Stiftun
Effect of competition between swelling and dye adsorption on the performance and selectivity of graphene oxide membranes
No full textThe performance of graphene oxide (GO) based nanofiltration membranes is strongly influenced by their interlayer spacing, governed by two competing factors: GO swelling in the liquid phase and penetrant adsorption. In this work, the structure of GO membranes was optimized via H2O2 treatment, and their performance was evaluated during nanofiltration of cationic and anionic dyes. For anionic dyes, the permeate flux remained stable, whereas cationic dyes caused a significant and irreversible flux decline. To clarify this behavior, dye adsorption experiments and in situ diffraction analyses of the GO interlayer distance were performed. The highest adsorption capacity was recorded for cationic methylene blue (MnB) at 643 mg g−1 (GO), compared to 97 mg g−1 (GO) for anionic methyl orange (MO). In the case of MO, the occupation of the interlayer space by dye molecules was compensated by slight structural expansion, maintaining flux stability. Conversely, the filtration of even a small amount of MnB solution caused a reduction in d-spacing from 12.1 ± 0.1 Å to 11.7 ± 0.1 Å, followed by further shrinkage to 11.4 ± 0.1 Å due to the electrostatic compression of the negatively charged GO with the positively charged dye molecules. Combined with physical blockage by dye molecules, this led to a rapid decline in membrane permeance described well by Poiseuille-based permeance trends. These results show that adsorption, particularly at low penetrant concentrations, can affect measured rejection rates and that adsorption can substantially alter the membrane permeance. Considering the roles of adsorption and electrostatic interactions, charged dyes are unsuitable for permeation tests intended to assess the intrinsic size-exclusion properties of two-dimensional lamellar membranes