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Observation of X-ray transition radiation from a relativistic electron passing a stack of plates
No full textThe results of experimental observations of resonant transition radiation (RTR) with energies ranging from 8 to 200 keV using stacks of thin aluminium foils (thickness a = 10 μm) separated by layers of either air (radiator no. 1) or Teflon (radiator no. 2) (thickness b = 100 μm). Period of both radiators was fixed (d = a + b = 110 μm). For the studied energy interval, a radiation formation length was larger than period for radiator 1 and was less for radiator 2. For the previous one we observed a reasonable agreement between experiment and theory, but for the latter one we observed some discrepancy
Design of Rigid Compounds to Enhance Selectivity for Carbonic Anhydrase IX
No full textHigh affinity and selectivity for intended targets is an important goal of small molecule design in drug discovery, yet balancing molecular flexibility and rigidity remains a challenge. While flexible compounds can increase target affinity, they often result in non-specific interactions and reduced selectivity. In contrast, rigid compounds may recognize their target more precisely and have lower off-target effects. In this study, we incorporated a 1,1-dioxido-1,4-thiazine ring into fluorinated benzenesulfonamide derivatives with bulky meta-substituents to enhance selectivity for human carbonic anhydrase IX (CAIX), an important cancer-associated target. Due to the structural similarities of CAIX with other carbonic anhydrase isozymes, selective inhibition remains a significant challenge. A series of 3,4-substituted trifluorobenzenesulfonamides containing oxidized thiazine rings were synthesized using a novel synthetic pathway. Although the potency against CAIX was modestly reduced compared to more flexible analogs, selectivity increased significantly, with lead compounds 7 d and 7 e exhibiting over 1000-fold selectivity for CAIX over most other isozymes. X-ray crystallography revealed the structural basis for this selectivity, confirming the advantageous positioning of rigidified compounds within some CA isozyme active sites. These findings highlight the potential of molecular rigidity in the design of highly selective inhibitors for therapeutic applications
Interface-driven electrocatalysis: Highlighting the role of NdNiO₃-NiO heterointerface in urea electro-oxidation
No full textEnhancing the activity of Ni-based catalysts for the electrochemical urea oxidation reaction (UOR) through the construction of heterojunctions or by heteroatom doping primarily involves the generation of polarized and/or high-valent Ni sites. However, systematic investigations of the impact of this strategy on the formation of UOR-active NiOOH species and its influence on UOR activity are scarce. Herein, we have chosen NdNiO-NiO catalysts to systematically vary the average oxidation of Ni from + 2 to + 3 by adjusting the stoichiometric ratio of NdNiO to NiO. Detailed electrochemical analysis and in situ X-ray absorption spectroscopy have revealed that the catalyst systems rich in NdNiO-NiO heterointerfaces exhibit more favourable formation of NiOOH species and, subsequently, better UOR activity. Interestingly, this enhanced UOR activity does not show an obvious positive correlation with the increase in the average oxidation state of Ni. The UOR current density follows the trend NNONO (20 % NdNiO and 80 % NiO) > NNONO > NNONO > NNONO > NiO > NdNiO. The higher UOR activity of NNONO and NNONO is attributed to the more effective formation of surface-exposed heterointerfaces, thereby establishing the dependence of UOR activity on these active heterointerfaces. In situ Raman spectroscopy substantiates the formation and sustained presence of NiOOH in NdNiO-NiO heterointerface during UOR. Theoretical studies indicate that the modulation of electronic structure through charge redistribution at the heterointerface optimizes hydroxylation, urea adsorption, and CO₂ desorption, consequently leading to enhanced UOR performance. These insights bring attention to the importance of heterointerface engineering in enhancing Ni-based UOR electrocatalysts
Search for heavy neutral leptons in decays of W bosons produced in 13 TeV collisions using prompt signatures in the ATLAS detector
No full textThe existence of right-handed neutrinos with Majorana masses below the electroweak scale could help address the origins of neutrino masses, the matter–antimatter asymmetry, and dark matter. In this paper, leptonic decays of W bosons from 140 fb of 13 TeV proton–proton collisions at the LHC, reconstructed in the ATLAS experiment, are used to search for heavy neutral leptons produced through their mixing with muon or electron neutrinos in a scenario with lepton number violation. The search is conducted using prompt leptonic decay signatures. The considered final states require two same-charge leptons or three leptons, while vetoing three-lepton same-flavour topologies. No significant excess over the expected Standard Model backgrounds is found, leading to constraints on the heavy neutral lepton’s mixing with muon and electron neutrinos for heavy-neutral-lepton masses. The analysis excludes values above and values above in the full mass range of 8–65 GeV. The strongest constraints are placed on heavy-neutral-lepton masses in the range 15–30 GeV of and
Tuning the upper cut-off voltage for enabling Co/Co redox in a P2/P3/spinel composite cathode material for sodium-ion batteries: An in operando study
No full textRecently, research developments on layered-spinel composite cathodes have surfaced as a promising approach to improving the electrochemical performance of cathode materials for sodium-ion batteries (SIBs). Here, a P2/P3 layered-spinel composite, (P2/P3-LS-Na1/2Mn2/3Ni1/6Co1/6O2 (LS-NMNC)), has been synthesized and evaluated as a promising cathode material for SIBs. The material exhibited distinct electrochemical characteristics across different voltage ranges of 1.50–4.00 V and 1.50–4.50 V. In operando X-ray diffraction and X-ray absorption spectroscopy were employed to investigate the remarkable charge capacity and rapid capacity degradation observed in broader voltage range. It was determined that material undergoes various electrochemical mechanisms when adjusting the upper cut-off voltage. A unique Co3+/Co2+ redox process was activated during the intercalation of sodium ions at a potential of 1.94 V within 1.50–4.00 V range, accompanied by a phase transition from P2/P3 to P′2/O′3. This phase transition, in conjunction with the Co3+/Co2+ redox process, is likely responsible for the enhanced structural stability and capacity exhibited by the material when upper cut-off voltage is restricted. Additionally, presence of an anionic redox couple and strain in the structure was noted with the increase in the upper cut-off to 4.50 V, which leads to instability and diminished electrochemical performance
Synthesis of luminescent dinaphthopentacene isomers and their application in OLEDs
No full textHere we report the straightforward synthesis of a novel nanographene, syn-dinaphthopentacene. This new compound was prepared along with its isomer anti-dinaphthopentacene to compare how small structural differences may affect properties such as crystal packing, photostability, and device performance. syn-Dinaphthopentacene has a twisted, chiral structure, and assembles in enantiomerically pure π-stacked columns in the solid state, while the anti-isomer is rigid and planar and forms a slip-stacked packing structure. anti-Dinaphthopentacene quickly undergoes light-induced [4+2] cycloaddition with singlet oxygen when exposed to ambient light and air, but the twisted syn-dinaphthopentacene exhibits remarkable stability under the same conditions. The two isomers have notably different UV-Vis absorbance and emission profiles, and upon probing the efficacy of these compounds as OLED emitters, the anti-isomer was found to be the better fluorophore, achieving luminance values exceeding 2000 cd m at peak efficiencies of almost 1%, as compared to the syn-counterpart which only reached 250 cd m
As-built microstructure and mechanical behavior of Inconel 718 processed via directed energy deposition with laser beam
No full textInconel 718 (IN718) is a Ni–Cr–Mo-based superalloy widely used in aerospace applications due to its excellent mechanical properties and corrosion resistance at high temperatures. Its high strength, however, presents challenges for conventional manufacturing of complex geometries due to its poor machinability. Additive manufacturing (AM), mainly directed energy deposition with laser beam (DED-LB), has emerged as a promising solution, offering precision, reduced material waste, and design flexibility. The microstructural evolution of IN718, primarily influenced by the precipitation of secondary phases such as γʹ, γʺ, Laves phases, and carbides, is critical for its performance. This study successfully developed a process window for DED-LB, producing high-density samples with minimal defects. Microstructural analysis revealed the role of grain size, second phases and Laves phases. At the same time, mechanical testing demonstrated a balance between strength and ductility, attributed to precipitation hardening and the predominance of screw-type dislocations. This work investigates the as-built condition of IN718 to evaluate the direct impact of process parameters on microstructure and mechanical properties without the influence of post-processing treatments. Key findings include the correlation of grain morphology and defects to the mechanical behavior of as-built samples. The results provide insights into the microstructural evolution and mechanical performance of DED-LB IN718 in the as-built condition
Copper-Rich PdCu Alloy Nanoparticles as Catalyst for Electrochemical Reduction of CO
No full textCopper is uniquely able to catalyze the formation of hydrocarbon-derived molecules through the electrochemical carbon dioxide reduction reaction (CO2RR) in aqueous media. Here, we investigate the change of selectivity and/or activity in CO2RR by alloying Cu with palladium by using PdxCu1–x nanoparticles as electrocatalysts. In situ powder X-ray diffraction reveals a much lowered reduction temperature of the Cu-precursor upon alloying and establishes the importance of high heating rates during synthesis to ensure homogeneous Pd alloying into copper-rich PdxCu1–x nanoparticles. Two different synthetic approaches were used to obtain PdxCu1–x nanoparticles with a composition range of x = 0.025–0.20, and the complex nanostructures of the particles were highlighted using four-dimensional Scanning Transmission Electron Microscopy (4D-STEM). The activity and selectivity toward electrochemical CO2RR in 0.1 M KHCO3 were assessed for increasing Pd contents, and a systematic decrease in faradaic efficiency toward hydrocarbon products was found coupled with an increase in faradaic efficiency toward primarily H2. The results do not support PdxCu1–x alloying as a viable method for increasing selectivity toward specific hydrocarbon products in electrochemical CO2RR
Olivine‐Ahrensite Phase Relations in the MgSiO‐FeSiO System as a Function of Temperature
No full textOlivine and ahrensite are the primary components of the interiors of Fe-rich terrestrial planets and meteorites, making their phase relations crucial for planetary science. Moreover, their phase relations can be used for calibrating large-volume high-pressure devices such as multi-anvil apparatus. Here we defined the olivine–ahrensite phase relations in the MgO-FeO-SiO system at 7.5–12.0 GPa at 1,530 and 1,950 K using a multi-anvil apparatus. Combining the current results with our previously determined binary loop at 1,740 K, we re-estimated the shock parameters of several L5 and L6-types meteorites. Also, we determined the olivine-ahrensite phase ratio and compositions along cold and warm Mars aerotherms for Mg/(Mg + Fe) ratios of 0.75 and 0.80. Using this mineralogical model, we estimated and compared seismic wave velocity profiles in Mars' interior to data from the InSight geophysical mission
CaloChallenge 2022: a community challenge for fast calorimeter simulation
No full textWe present the results of the ‘Fast Calorimeter Simulation Challenge 2022’—the CaloChallenge. We study state-of-the-art generative models on four calorimeter shower datasets of increasing dimensionality, ranging from a few hundred voxels to a few tens of thousand voxels. The 31 individual submissions span a wide range of current popular generative architectures, including variational autoencoders (VAEs), generative adversarial networks (GANs), normalizing flows, diffusion models, and models based on conditional flow matching. We compare all submissions in terms of quality of generated calorimeter showers, as well as shower generation time and model size. To assess the quality we use a broad range of different metrics including differences in one-dimensional histograms of observables, KPD/FPD scores, AUCs of binary classifiers, and the log-posterior of a multiclass classifier. The results of the CaloChallenge provide the most complete and comprehensive survey of cutting-edge approaches to calorimeter fast simulation to date. In addition, our work provides a uniquely detailed perspective on the important problem of how to evaluate generative models. As such, the results presented here should be applicable for other domains that use generative AI and require fast and faithful generation of samples in a large phase space.Report Numbers: HEPHY-ML-24-05, FERMILAB-PUB-24-0728-CMS, TTK-24-43