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Micro-environment regulation for strong metal–support interaction in -doped barium cerate for boosting photocatalytic ammonia production
No full textModulating the local microenvironment via strong metal-support interaction (SMSI) approach in Ru-based photocatalyst for improving photocatalytic ammonia production is poorly understood. Herein, we investigate the mechanism of the SMSI effect of RuO on barium cerate (BC) by forming Ru-O-Ce electron transfer channel to enhance the photocatalytic ammonium (NH) production. Among the prepared photocatalysts, BC-Ru showed the highest NH formation rate of 3.533 mmol g h with a 5.464 % apparent quantum efficiency (AQE), which was 5.17-fold higher than BC. In-situ X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES) analyses revealed that RuO doping on BC promoted the formation of Ru-O-Ce bonds and degenerate barium 3d orbitals, creating an asymmetric coordination environment that improved N interaction. Additionally, the formation of a Ru-O-Ce electron channel on BC prolonged the electron decay time and improved spatial separation, resulting in higher nitric oxide (NO) radical formation due to the promotion of hydroxyl radical generation from photoexcited holes. Notably, in-situ surface-enhanced Raman spectroscopy (SERS) analysis revealed that RuO loading on BC altered the electronic state of Ba owing to the SMSI effect, improved N interaction on the Ba-O bonds, and facilitated the NH production. Density functional theory (DFT) calculations showed that RuO-doping of BC can result in Ba-N bonding and promote the nitric oxide reduction reaction (NORR) by reducing the energy barrier of the rate-determining step and accelerating the protonation process. This study demonstrates the SMSI effects via the strategy of a Ru-based dopant on NH photocatalytic production
Search for exotic Higgs boson decays H with in events with a semi-merged topology in proton-proton collisions at = 13 TeV
No full textA search for exotic Higgs boson decays H , with is presented, using events with a semi-merged topology. One of the hypothetical particles, , is assumed to decay promptly into a semi-merged diphoton system reconstructed as a single photon-like object, while the other decays into two resolved photons. The search is performed using proton-proton collision data collected by the CMS experiment at = 13 TeV, corresponding to an integrated luminosity of 138 fb. The data agree with the standard model background expectation. Upper limits are set on the product of the Higgs boson production cross section and the branching fraction, (pp H)(H 4), which range from 0.264 to 0.005 pb at 95% confidence level, for masses in the range 1 15 GeV. These limits are the most stringent to date in the 15 GeV range
Structural and Electromechanical Insights into Thermoplastic Polyurethane/3D Hybrid Carbon Nanocomposites for Strain Sensor Applications
No full textIncorporation of carbon allotropes of different dimensions within elastomeric matrices has been established as an effective strategy to fabricate functional conductive polymer nanocomposites (PNCs). In this work, higher-dimensional 3D hybrid carbon nanofillers, comprising synergistically integrated multiwalled carbon nanotubes immobilized onto few-layer graphene, were incorporated into the thermoplastic polyurethane (TPU) matrix to demonstrate their effectiveness as strain sensors. The conductive films were fabricated through a simple solution casting technique, in which the mechanical, electrical, and strain-sensing characteristics were studied in view of filler distribution, structural confinement, and interfacial interactions. Analyses using wide-angle X-ray scattering, Raman spectroscopy, and tensile testing revealed a higher degree of filler reinforcement within the TPU moieties, indicating pronounced interfacial interactions. Further, the tensile modulus increased significantly with filler loading above its percolation threshold (363% for 20 wt % loading). The structural features of dispersed filler aggregates were explored through an iterative model fitting of the ultra-small-angle X-ray scattering (USAXS) data, along with scanning electron microscopy (SEM). As a strain sensor, the films displayed a superior working-strain Gauge Factor (GF = 123, up to 8%), with exceptional stability under both unidirectional and cyclic strain. The findings provide a fundamental understanding while validating the potential of hybrid carbonaceous fillers for the fabrication of PNCs with futuristic applications
Stainless magnesium alloy based on self-healing amorphous surface
No full textUltra-lightweight magnesium alloys characterized by high specific strength are highly sought after for applications in the automotive and aerospace industries. However, conventional magnesium alloys behave poor corrosion resistance when exposed to moisture, which significantly reduces their service life, thus limiting their applications and hindering effective realization of their lightweight advantages. Here, we develop a novel stainless Mg-2Sc-0.5Al alloy, which exhibits the lowest corrosion rate of 0.027 mm/year among all reported magnesium alloys and behaves insensitivity of Fe impurity content. More remarkably, the surface film of this stainless magnesium alloy possesses the ability to fully self-heal within hours of being scratched, which gives superior and long-term protection. The superior corrosion resistance of the stainless Mg-2Sc-0.5Al alloy origins from the rapid formation and stabilization of a compact amorphous surface film facilitated by the addition of Al and Sc. The stable amorphous surface film effectively and rapidly shields the magnesium matrix from the corrosive media, thereby significantly enhancing the corrosion resistance. This work offers an efficient design strategy to form the protective amorphous surface film and further inspires the development of stainless magnesium alloys across various systems
High-temperature oxygen-assisted molecular beam epitaxy of BaWO on W(110): growth mechanism and structural characterization
No full textWe have studied the growth of barium tungstate, BaWO, by high-temperature oxygen-assisted molecular beam epitaxy on W(110). Barium tungstate grows in the form of isosceles triangular-shaped islands, tens of micrometers wide and tens of nanometers in height. The growth was monitored in real time by low-energy electron microscopy and characterized in situ by low-energy electron diffraction, X-ray absorption and X-ray photoelectron spectroscopies. Further ex situ characterization was performed by optical and atomic force microscopies and Raman spectroscopy. Barium tungstate growth on W(110) was performed by dosing only barium in a molecular oxygen atmosphere due to incorporation of W atoms from the W(110) substrate. The islands correspond to the BaWO (011) crystallographic orientation and their sides are aligned along the [001] and [11] directions of the BaWO crystal
From Detector Development to New Physics Searches: CMS HGCAL Validation and Search for Top-Philic Resonances Using Variable-Radius Jet Tagging
No full textThis thesis presents two research works carried out within the Compact Muon Solenoid (CMS) experiment at the CERN Large Hadron Collider (LHC): the system validation of the scintillator section of the High Granularity Calorimeter (HGCAL), and a search for a heavy resonance coupling to top quarks and produced in association with top quark pairs in proton–proton collisions at center-of-mass energies of 13 and 13.6 TeV. For the High-Luminosity LHC (HL-LHC) phase, the endcap calorimeters of CMS will be replaced by the HGCAL, a high-precision sampling calorimeter designed to cope with the extreme radiation and pileup conditions expected at the HL-LHC. In regions where radiation levels remain moderate, the hadronic section employs scintillator tiles coupled to silicon photomultipliers (SiPM-on-tile) as active materials. Each HGCAL tilemodule, the basic detector unit of this region, accommodates up to 144 SiPM-on-tile channels read out by dedicated front-end electronics. The performance of several tilemodules was evaluated during test-beam campaigns at the DESY-II facility using 3 GeV electron beams. The measurements serve to validate the response and uniformity of the detector components and to confirm that they meet the design specifications for HL-LHC operation. A search for a new heavy resonance that couples exclusively to top quarks and is produced in association with a top quark pair is presented. The analysis uses proton–proton collision data collected with the CMS detector at center-of-mass energies of 13 TeV (2016–2018) and 13.6 TeV (2022). The search targets the final state with two oppositely charged leptons from the W boson decays of the nonresonant top quarks, and two high-energy jets reconstructing the hadronically decaying resonant top quarks. In this scenario, the two top quarks from the resonance decay are expected to be highly Lorentz-boosted. Their hadronic decays are reconstructed using jets clustered with a variable-radius algorithm and identified with a dedicated top quark tagger based on a boosted decision tree (BDT). Events are selected in a final state containing opposite-sign leptons and b-tagged jets, and the resonance mass is reconstructed from pairs of tagged top jets. The analysis probes resonance masses between 500 GeV and 4 TeV and searches for local excesses in the reconstructed mass spectrum. The results are interpreted in the context of models with vector-like, scalar and pseudoscalar resonances produced in association with top quarks, representing the first such interpretation performed with CMS data
New species of Lechytia Balzan, 1892 (Arachnida: Pseudoscorpiones) from Burmese amber highlights 99 million years of morphological stasis
No full textThe pseudoscorpion genus Lechytia Balzan, 1892 (Chthoniidae Daday, 1889: Lechytiinae Chamberlin, 1929) includes 27 extant species that are distributed across all continents except Antarctica, and a single extinct species from Dominican amber of Miocene age. We document the first record of Lechytia from Burmese amber (Cenomanian: ∼99 Ma), Lechytia finniae sp. nov., making it the oldest fossil record for Lechytia and extending the known temporal range of this group by more than 70 million years into the Mesozoic. The new species differs from most extant Lechytia species due to the distance between trichobothria sb and b that are separated by at least one areolar diameter, and by the absence of eyes. Since there is a close morphological resemblance between L. finniae sp. nov. and extant Lechytia species, the new fossil is placed in an extant genus and represents yet another example of morphological stasis in pseudoscorpions. The presence of Lechytia in Burmese amber implies that this genus was present on the Burma Terrane in the Cretaceous although no extant species are known from this landmass today. The ecology of extant species may lend support to a tropical forest environment on the Burma Terrane
Charge–Discharge Mechanisms in O3-NaFeMnO Na-Ion Battery Electrodes-Unraveling the Structure of the X-Phase
No full textLayered sodium transition metal oxides, NaTMO, based on abundant transition metals such as Fe and Mn, are promising low-cost and sustainable cathode materials for Na-ion batteries. However, their route to application is hampered by a limited understanding of the complex structural transformations entailing severe disordering during electrochemical cycling. In particular, lack of insight into the structure and formation mechanisms of the disordered high-potential phases poses a challenge, as these have been associated with rapid deterioration of electrochemical performance. In this work, we elucidate, for the first time, the structures of the high-voltage OP2- and X-phases in O3-type Na0.95Fe0.5Mn0.5O2, which are archetypical high-potential phases in layered NaTMO2 materials. The unprecedented structural insight allows us to unravel the charge–discharge mechanism, hereunder showing that the first-to-second cycle asymmetry, common to layered NaTMO2 materials, is caused by changes to the overlap between Fe3+/Fe4+ oxidation and oxygen redox processes. This promotes the migration of Fe-ions to tetrahedral sites in the NaO2 slabs, which effectively “pins” the O-type layers, thus obstructing the O3 → P3 transition while it is ongoing and leading to formation of the highly disordered X-phase consisting primarily of O3-type stacking disordered by large domains of P3- and OP2-type stacking
Flexible End‐Group Triggered Temporal Supramolecular Reordering on Substrate Surfaces and Its Impact on Electron Transport
No full textThe temporal stability of domain microstructure and morphologies is critical in regulating charge transport in organic field effect transistors (OFETs), ensuring consistent device performance and long-term reliability. Overcoming stability challenges in small molecular weight n-type materials, particularly in solution-processed active layers, necessitates careful molecular design. While flexible end groups or side chains enhance solution processability, they also introduce temporal disorder, or temporal reordering compromising device endurance. This study examines the trade-offs between rigid and flexible end groups in n-type molecular semiconductors, emphasizing their influence on morphological reordering in active layer films. As representative materials, -HexNDI, with flexible end groups, is compared to BCyHNDI, which features rigid end groups. Films containing flexible side chains exhibit pronounced sensitivity to thermal annealing, significantly modifying the molecular and supramolecular arrangement and the crystallinity of -HexNDI. Moreover, these flexible chains reduce current-voltage hysteresis, indicating enhanced structural order at elevated temperatures. Conversely, BCyHNDI demonstrates minimal temporal disorder at the molecular level organization, maintaining stable optical properties and negligible changes in current-voltage hysteresis upon annealing
Single mutations to tyrosine or glutamate improve the crystallizability and crystal diffraction properties of a flexible two-domain protein
No full textThis case report describes single surface substitutions that improve the crystallizability and diffraction properties of a flexible two-domain protein. InlB392 comprises the internalin domain and the B repeat of the Listeria monocytogenes invasion protein InlB. The InlB392 wild type yielded very few poorly reproducible hits in crystallization screens and the crystals had a diffraction limit of worse than 3.0 Å. It seems reasonable to assume that this crystallization bottleneck is caused by interdomain flexibility, given that crystals of the isolated internalin domain or B repeat diffract to high resolution. A previously identified variant, T332E, showed improved crystallization and diffraction. Here, two additional InlB392 variants are described with single threonine-to-tyrosine or valine-to-glutamate substitutions that produced crystals directly in initial screens and, without optimization, diffracted to 1.6 and 1.45 Å resolution, respectively. The mutated residues do not participate in intramolecular interdomain interactions but mediate crystal contacts, indicating that specific surface properties, rather than interdomain flexibility per se, impede the crystallization of wild-type InlB392. Notably, the beneficial glutamate substitutions contrast with the generally recognized underrepresentation of glutamate in crystal contacts and the high entropic cost of fixing an otherwise flexible side chain with many rotatable bonds in a crystal contact. The reported results suggest that surface mutations can help crystallization even if they increase the entropy of the respective residue. More broadly, the observations are consistent with the hypothesis that negative evolutionary design limits fortuitous lattice formation of proteins and the resulting expectation that random mutations of surface residues are likely to improve crystallizability