Coordinates: 45°12′22″N 5°41′34″E / 45.206239°N 5.692774°E / 45.206239; 5.692774The Institut Laue–Langevin (ILL) is an internationally financed scientific facility, situated on the Polygone Scientifique in Grenoble, France. It is one of the world centres for research using neutrons. Founded in 1967 and honouring the physicists Max von Laue and Paul Langevin, the ILL provides one of the most intense neutron sources in the world and the most intense continuous neutron flux in the world in the moderator region: 1.5×1015 neutrons per second per cm2, with a thermal power of typically 58.3 MW.The ILL neutron scattering facilities allow the analysis of the structure of conducting and magnetic materials for future electronic devices, the measurement of stresses in mechanical materials. It also allows investigations into macromolecular assemblies, particularly protein dynamics and biomolecular structure. It is a world-renowned centre for nanoscale science.
The effective electron neutrino mass can be determined by analyzing the end-point region of the ^{163}Ho electron capture spectrum, provided a measurement with high-energy resolution and high statistics using calorimetric techniques. Here, the Electron Capture in ^{163}Ho Collaboration (ECHo) presents an analysis of the most precise ^{163}Ho spectrum currently available, obtained with the ECHo-1k experiment and comprising about 200 million events. A very low background rate of b_{const}=9.1(1.3)×10^{-6} eV/pixel/day was achieved allowing for a reliable analysis of the end-point region. The derived end-point energy Q=2862(4) eV is in excellent agreement with the one independently determined via Penning-trap mass spectrometry of Q=2863.2(6) eV [Ch. Schweiger et al., Nat. Phys. 226, 921 (2024)NPAHAX1745-247310.1038/s41567-024-02461-9]. The upper limit of the effective electron neutrino mass is improved by almost a factor of 2 compared to the lowest current value [B. K. Alpert et al., Phys. Rev. Lett. 135, 141801 (2025)PRLTAO0031-900710.1103/s9vl-7n24], reaching m_{ν_{e}}<15 eV/c^{2} (90% credible interval).
This research focuses on the impact of Co and Fe dopants on the crystal structure and magnetic properties of a NiMn-Ga alloy. The aim is to enable control over the possible magnetostrictive actuation temperature range through tuning the Curie temperature, TC, and the martensitic transformation temperature, TM. As these parameters are strongly influenced by the structural characteristics, Powder Neutron Diffraction was used to unravel the crystal structure and atomic site occupancies. As a result, a clear correlation was observed between the dopant content and the transition temperatures as well as the magnetic behavior. The Fe and Co dopants induce atomic disorder in the structure, which enhances ferromagnetic interactions as evidenced by noticeable higher values of TC and saturating magnetic moment, mu sat. Unlike Co, which remarkably increases TM, Fe doping leads to slightly lower martensitic transformation temperatures. Furthermore, the crystal structure of the martensitic phase only changes upon Co doping, becoming tetragonal and non-modulated, whereas the structure remains monoclinic 7 M modulated, similar to the non-doped alloy, upon Fe doping.
While fluids near a solid surface are at the core of applications in energy storage/conversion, electrochemistry/electrowetting and adsorption/catalysis, their nanoscale behavior remains only partially deciphered. Beyond conventional effects (e.g. adsorption/reaction, interfacial transport, phase transition shifts), recent experimental and theoretical studies on metallic surfaces have unraveled exotic peculiarities such as complex electrostatic screening, unexpected wetting transition, and interfacial quantum friction. These novel features require developing and embarking new tools to tackle the coupling between charge relaxation in the metal and molecular behavior in the vicinal fluid. Here, using the concept of Virtual Thomas-Fermi fluids, we employ a molecular simulation approach to investigate interfacial transport of fluid molecules and metal charge carriers at their interface–including the underlying electrostatically-driven dynamic friction and the coupling between charge current/hydrodynamic flow (the so-called electrohydrodynamic drag). While conventional numerical techniques consider either insulating materials or metallic materials described as polarizable, non-conducting media, our atom-scale strategy provides an effective yet realistic description of the solid excitation spectrum–including charge relaxation modes and conductivity. By applying this approach to water near metallic surfaces of various electrostatic screening lengths, we unveil a non-monotonous dependence of the fluid/solid friction on the metallicity with a maximum occurring as the charge dynamic structure factors of the solid and fluid strongly overlap. Moreover, we report a direct observation of the electrohydrodynamic drag which arises from the momentum transfer between the solid and liquid through dynamic electrostatic interactions and the underlying interfacial friction.
Lytic polysaccharide monooxygenases (LPMOs) are redox enzymes that bind to and oxidize insoluble carbohydrate substrates such as chitin or cellulose. This class of enzymes has attracted considerable attention due to their ability to convert biomaterials of high abundance into oligosaccharides that can be useful for producing biofuels and bioplastics. However, processes at the interface between solution and insoluble substrates represent a major challenge to biochemical and structural characterization. Here, we investigated the four-domain LPMO from Vibrio cholerae, N-acetyl glucosamine binding protein A (GbpA), to elucidate how it docks onto its insoluble substrate with its two terminal domains. First, we developed a protocol that allowed GbpA and chitin to form a stable complex in suspension, overcoming incompatibilities of the two binding partners with respect to pH. After determining the small-angle neutron scattering (SANS) contrast match point for chitin (47% D2O), we characterized the mesoscale structure of GbpA in complex with chitin by SANS and complemented the results with negative-stain electron microscopy. We found that GbpA binds rapidly to chitin, where it coats the chitin fibers and smooths their surface. In some locations, GbpA binding induces the formation of protein-chitin clumps containing a large number of GbpA molecules. Together, this suggests how the secretion of GbpA efficiently prepares the ground for microcolony formation by the bacteria.
Magnetocrystalline anisotropy is a key parameter governing the performance of magnetic nanoparticles in many applications. However, disentangling its intrinsic contribution from other sources of effective anisotropy, such as surface effects, dipolar interactions or shape anisotropy, remains highly challenging. Here, we report a novel approach to qualitatively estimate the magnetocrystalline anisotropy of two CoxFe3-xO4 nanoparticles with different Co contents (x = 0.11 and 0.61) using polarized neutron powder diffraction (PNPD). The off-diagonal elements of the susceptibility tensors and degree of asymmetry of the magnetization ellipsoids obtained from the PNPD refinements reveal that the sample with x = 0.61 presents a larger magnetocrystalline anisotropy than the sample with x = 0.11, which is consistent with the effective anisotropy derived from magnetometry. Moreover, comparison of the PNPD-derived magnetization ellipsoids across materials with varying anisotropies confirms the direct relationship between the ellipsoid asymmetry and magnetocrystalline anisotropy. These findings establish PNPD as a powerful tool for qualitatively probing intrinsic anisotropies in nanoparticle systems, paving the way for the rational design and optimization of magnetic nanoparticles for advanced applications.
