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Multi-temperature neutron irradiation of pure beryllium and beryllides to 2.5–3 dpa in BR2 reactor
No full textThis paper reports the current status of neutron irradiation experiments designed to evaluate beryllide (BeV, BeTi, BeTi + 1 wt%BeV) and pure beryllium under controlled neutron flux conditions in the BR2 reactor. The target fluence corresponds to 2.5–3 dpa in Fe, achieved over three to four cycles, at four distinct temperatures (400, 600, 750, and 900◦ C) with using dedicated stainless-steel capsules, designed according to the BAMI (Basket for Material Irradiation) concept, which allows fast deployment and high neutron flux without active temperature control or gas flushing. To determine irradiation condition, thermal and neutronic calculations (FEM and MCNP) were conducted. Gadolinium (Gd) is selected as the thermal neutron shield to reduce thermal flux, with its burn-up and reactivity effects assessed for reactor safety. Eight capsules will accommodate different sample geometries (pebbles, disks, and cylinders), filled with helium to ensure inert conditions
Magnetic actuation of fungal pellets via immobilization of ferromagnetic particles
No full textMagnetic functionalization of fungal biomass via in situ immobilization of ferromagnetic particles enables non-contact manipulation and efficient magnetic separation for process intensification in biotechnological applications. In this study, Aspergillus oryzae was cultivated in the presence of magnetite or a magnetite-activated carbon composite to promote particle incorporation during pellet growth. Morphological analysis based on image processing revealed a concentration-dependent increase in pellet size, accompanied by internal particle agglomeration. Additionally, magnetic labelling was achieved post-cultivation by incubating mature pellets with suspended particles, allowing for flexible integration into existing processes. Both approaches yielded magnetically responsive fungal biocomposites that could be readily separated using external magnetic fields, highlighting their potential for biomass retention, recovery and process intensification
Dynamical system metrics and weather regimes explain the seasonally-varying link between European heatwaves and the large-scale atmospheric circulation
No full textGlobal warming is projected to increase the frequency and intensity of heatwaves in the extended summer period. To better predict heat extremes, it is important to explore the seasonal variations in their drivers.
Therefore, we analyze heatwaves in Central Europe using ERA5 reanalysis data over the historical period (1950–2023) for the extended summer months (May–September). We quantify atmospheric persistence, and the link between near-surface temperatures and large-scale atmospheric circulation patterns using dynamical system metrics. This approach is further contextualized by the consideration of weather regimes, which represent the lowfrequency variability of the atmosphere over the North Atlantic and Europe. Our results show a maximum in atmospheric persistence in July and August, associated with higher occurrence of Scandinavian Blocking, and relative minima in spring and autumn. The relationship between the large-scale atmospheric circulation and near-surface temperatures exhibits similar seasonal characteristics. For heatwave days, we find a statistically significant anomalous strong link between large-scale atmospheric circulation and surface temperatures from June to September. This relationship is generally not attributable to the occurrence of specific weather regimes. However, heatwaves in July and August are associated with higher atmospheric persistence due to an enhanced frequency of the persistent Scandinavian and European blocking weather regimes. Beyond atmospheric circulation, additional physical drivers of daily maximum temperature during heatwaves are analyzed: While surface net solar radiation shows a particularly strong link in June and July, soil moisture exhibits an anomalously high link in July and August. These findings highlight the critical role of intra-seasonal variations in shaping heatwave dynamics
A Detailed Investigation of the Onion Structure of Exchanged Coupled Magnetic FeO@CoFeO@FeO Nanoparticles
No full textNanoparticles that combine several magnetic phases offer wide perspectives for cutting edge applications because of the high modularity of their magnetic properties. Besides the addition of the magnetic characteristics intrinsic to each phase, the interface that results from core–shell and, further, from onion structures leads to synergistic properties such as magnetic exchange coupling. Such a phenomenon is of high interest to overcome the superparamagnetic limit of iron oxide nanoparticles which hampers potential applications such as data storage or sensors. In this manuscript, we report on the design of nanoparticles with an onion-like structure which has been scarcely reported yet. These nanoparticles consist of a FeO core covered by a first shell of CoFeO and a second shell of FeO, e.g., a FeO@CoFeO@FeO onion-like structure. They were synthesized through a multistep seed-mediated growth approach which consists consists in performing three successive thermal decomposition of metal complexes in a high-boiling-point solvent (about 300 °C). Although TEM micrographs clearly show the growth of each shell from the iron oxide core, core sizes and shell thicknesses markedly differ from what is suggested by the size increasing. We investigated very precisely the structure of nanoparticles in performing high resolution (scanning) TEM imaging and geometrical phase analysis (GPA). The chemical composition and spatial distribution of atoms were studied by electron energy loss spectroscopy (EELS) mapping and spectroscopy. The chemical environment and oxidation state of cations were investigated by Fe Mössbauer spectrometry, soft X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD). The combination of these techniques allowed us to estimate the increase of Fe content in the iron oxide core of the core@shell structure and the increase of the cobalt ferrite shell thickness in the core@shell@shell one, whereas the iron oxide shell appears to be much thinner than expected. Thus, the modification of the chemical composition as well as the size of the FeO core and the thickness of the cobalt ferrite shell have a high impact on the magnetic properties. Furthermore, the growth of the iron oxide shell also markedly modifies the magnetic properties of the core–shell nanoparticles, thus demonstrating the high potential of onion-like nanoparticles to accurately tune the magnetic properties of nanoparticles according to the desired applications
Experimental Observations on the CHF Performance of Cr/ CrN-Coated Zircaloy-4 in Low-Pressure Flow Boiling
No full textThe Dissolution-Dynamic Nuclear Polarization Experiment
No full textDissolution-Dynamic Nuclear Polarization (D-DNP) addresses the most pressing issue of nuclear magnetic resonance spectroscopy — low sensitivity. In D-DNP the analyte is mixed with a radical in a glass-forming matrix. This substrate is frozen and kept at low temperature (<100 K) and a magnetic field of several Tesla. By using microwave irradiation, polarization is transferred from electron spins to nuclear spins. The substrate is then liquefied, and the liquid-state signal of the nuclear spins is observed in a high-resolution nuclear magnetic resonance (NMR) magnet or a magnetic resonance imaging scanner. The D-DNP technique has enabled spectacular experiments, such as the in vivo observation of human metabolism. However, unlike other sensitivity enhancement methodologies, such as cryoprobes or magic angle spinning (MAS) DNP, D-DNP is not applied broadly in NMR spectroscopy at present. Here, we describe (i) the gains of an ideal D-DNP experiment for NMR spectroscopy, and contrast them with the real implementations of the D-DNP experiment available today, with a focus on applications in spectroscopy. We review principles of (ii) the dynamic nuclear polarization step and (iii) the sample transfer. We argue (iv) that stringent automation is essential for broader adaptation of the D-DNP experiment
Heterostructure‐Engineered TiO‐TiN Electrocatalyst Boosts Bidirectional Sulfur Redox Kinetics in Magnesium–Sulfur Batteries
No full textThe sluggish sulfur redox kinetics in magnesium–sulfur (Mg–S) batteries leads to low discharge voltage, poor sulfur utilization, and severe magnesium polysulfides (MgPS) shuttling, limiting their practical energy density. Herein, a heterostructure-engineered TiO-TiN electrocatalyst is rationally constructed and applied to separator modification to accelerate bidirectional sulfur conversion reactions. The TiO-TiN heterostructure induces charge redistribution, promoting electron/ion transport and providing strong chemical anchoring toward MgPS. Density functional theory calculations reveal that the heterostructure substantially lowers the energy barriers for MgPS and MgS dissociation, thereby enhancing the reversible MgPS ⇄ MgS conversion kinetics, which is corroborated by spectroscopic and electrochemical analyses. As a result, sulfur cathodes incorporated with the TiO-TiN-modified separator exhibit well-defined discharge plateaus and outstanding rate capability, delivering a high energy density of 1370 Wh kg at 0.1 C—three times higher than that of the cathode using the pristine separator. A reversible capacity of 254.8 mAh g at 1.0 C is achieved, far surpassing the pristine counterpart (38.3 mAh g) and outperforming most previously reported Mg–S systems. This work demonstrates a viable heterostructure-based catalytic strategy to boost sulfur redox kinetics and achieve high-rate Mg–S batteries
Cosolvent-Mediated Carbon Dots Aggregation in Microgel Microenvironments for Multicolor Dynamic Fluorescence Modulation
No full textDynamic fluorescent materials are attractive for tunable emission colors, but most multicolor systems are limited by a few switching states and complex modulation. To address these challenges, a composite system (MG-CDs) was designed by embedding aggregation-induced color-tuning carbon dots (CDs) into microgels. When respectively swollen in water (HO), ethanol (EtOH), or ethylene glycol (EG), MG-CDs formed distinct internal hydrogen-bonding networks, yielding varied CDs aggregation states and fluorescence emissions. In an HO-EtOH-EG cosolvent, MG-CDs established more complex hydrogen-bonding networks and heating-induced solvent volatilization driven hydrogen-bonds reorganization, which simultaneously tuned the CDs aggregation and polymer conformations, endowing diverse thermo-responsive fluorescence transitions and multiple programmable emission states within a unitary system. This mechanism highlighted that coupling solvent-responsive hydrogen-bond regulation in polymer microenvironments with emitter aggregation enables tunable dynamic fluorescence.Furthermore, MG-CDs were used as inks in which a cosolvent treatment and heating-driven printed patterns were used from monochromatic to polychromatic, achieving programmable color evolution for information storage
Excitonic effects and optical properties of CrO monolayer in 2H phases
No full textThe development and proposal of new 2D materials have been expanding the frontiers for new technologies in the field of photovoltaics and optoelectronics with ultra-thin materials, especially 2D semiconductor materials. As known in the literature, the CrO2 in 2H phase presents semiconductor characteristics, but the excitonic effects and optical properties have not yet been systematically investigated. In this sense, a significant gap in the understanding of its potential for optoelectronic applications needs to be overcome. Here, we performed a systematic investigation of its structural, electronic, excitonic, and optical properties. We identified it as dynamically stable, and quasi-harmonic phonon calculations indicate that the 2H phase is thermodynamically stabilized only for temperatures 660 K within our free-energy analysis. Also, it was determined to be an indirect band gap semiconductor (0.93 eV), with a direct band gap of 1.84 eV located in K/K′ valleys. Excitonic effects play an important role in the description of the linear optical response, with an exciton binding energy of 386 meV. Furthermore, these quasi-particle effects give rise to an indirect excitonic ground state, resulting in an optical band gap of 1.20 eV, which is significantly smaller than the direct electronic band gap. Consequently, high reflectivity is observed in the UV region with potential applications as a UV filter
