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Results of the Stacy project Towards Safe Storage and Transportation of Cryogenic Hydrogen
No full textExclusion of a diquark–anti-diquark structure for the lightest positive-parity charmed mesons
No full textThe nature of low-lying scalar and axial-vector charmed mesons has been debated for decades, with hadronic molecular and compact tetraquark models being prominent candidates. These two models predict quite different features for the accessible SU(3) multiplets in the scalar and axial-vector sectors, which can be tested through lattice calculations at SU(3) symmetric points. In this work, we perform lattice calculations for both scalar and axial-vector charmed mesons with an SU(3) symmetric pion mass about 613 MeV for the SU(3) [6] and [15] multiplets. We find that the [6] multiplet exhibits attractive interactions in both scalar and axial-vector sectors, while the [15] multiplet shows repulsive interactions in both sectors. The energy shifts in the scalar and axial-vector sectors are compatible with each other within uncertainties. These results are fully consistent with the hadronic molecular picture, while challenging the compact tetraquark model, which predicts the existence of low-lying [15] states in the axial-vector sector but not in the scalar sector
A novel perspective on accelerated degradation studies of proton exchange membranes
No full textAccelerated degradation studies are widely applied in research on proton exchangemembranes (PEMs) for the investigation of the origins and mechanisms of performance lossfor electrolysis or fuel cell applications. In a nutshell, it is reported in literature thatdegradation in PEMs commonly occurs following Fenton-like reactions, where in situ formedH2O2 reacts with transition metal cations to produce radicals. These radicals then alter theionomer on a chemical level by attacking particularly its polar side chains, causing a loss offunctional moieties for proton transport [1]. Fast degradation studies mimic and promotethese conditions by subjecting PEMs to high concentrations of H2O2 and Fe2+ cations atelevated temperatures. However, these studies often exhibit discrepancies when comparedto degradation occurring during long-term operation [2].The presented work attempts to elucidate these discrepancies by i) addressinginconsistencies in accelerated degradation and testing procedures, ii) studying thedependence of degradation on PEM chemistry and structure and iii) utilizing both NMRspectroscopy and SEM microscopy among other techniques for a comprehensive picture.Hereby, solid-state magic angle spinning (MAS) NMR spectroscopy provides information onboth chemical and local structural transformations of the PEM, while SEM offers concreteinsights into structural changes on a microscopic scale.The Fenton-like accelerated degradation experiments were optimized for homogeneity andeffectiveness by introducing the catalytic iron centers into the PEMs. Additionally,interferences in the analytical techniques were minimized by careful removal of excessreactants after accelerated degradation. The combined analytical techniques reveal thatchemical degradation in PEMs is significantly less pronounced than suggested in literature,although differences were observed depending on the type of PEM material. Moreover,organic radicals that form during Fenton-like reactions could not be detected by EPRspectroscopy. However, all samples experienced significant changes in the local structure,as indicated by NMR relaxometry, and microscopic structure, as illustrated by SEMtechniques. Thus, instead of chemical degradation, the PEM may be affected on a structurallevel by mechanical stress due to microscopic gas pockets and macroscopic bubblesforming inside the gas impermeable material.[1] L. Ghassemzadeh et al., J. Am. Chem. Soc. 135, 8181–8184 (2013).[2] J. Mališ et al., Int. J. Hydrogen Energy 41, 2177–2188 (2016)
SERGHEI v2.1: a Lagrangian Model for Passive Particle Transport using a 2D Shallow Water Model (SERGHEI-LPT)
No full textBIOMAC-BP: Organization and scope
No full textIntroductory presentation about the MSCA doctoral network BIOMAC-BP, its andminstrative structure and scientific goals
Multi-stress interaction effects on BVOC emission fingerprints from oak and beech: A cross-investigation using Machine Learning and Positive Matrix Factorization
No full textUnderstanding the effects of heat stress and herbivory feeding on BVOC emissions in beech and oak trees
No full textIntercomparison and validation of first GLORIA-B measurements of stratospheric and upper tropospheric long-lived tracers and photochemically active species
No full textAccurate observations of the vertical distribution and variability of atmospheric trace gases are essential for understanding chemical processes, validating atmospheric models, and monitoring the impact of anthropogenic emissions on climate and ozone. The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) is a limb-imaging Fourier-Transform Spectrometer (iFTS) designed to provide high-resolution mid-infrared spectra in the 780–1400 cm−1 wavenumber range. Originally developed for aircraft, the instrument has now been adapted for stratospheric balloon deployment (GLORIA-B) to extend its observational range from the middle troposphere to the middle stratosphere. GLORIA-B completed its first flight from Kiruna (Sweden) in August 2021 and a second from Timmins (Canada) in August 2022 as part of the EU Research Infrastructure HEMERA (Integrated access to balloon-borne platforms for innovative research and technology). The main objectives of these flights were technical qualification and the provision of a first imaging hyperspectral limb-emission dataset from 5 to 36 km altitude. Here, we present a characterization and validation of GLORIA-B performance using vertical volume mixing ratio (VMR) profiles retrieved from the August 2021 flight. Comparisons with in-situ measurements (ozonesonde, MegaAirCore, and cryosampler) show agreement within 10 % for O3, CH4, SF6, and CFC-12, and within 10 %–20 % for CFC-11, HCFC-22, and CFC-113 up to 18 km, with larger deviations above this altitude. Another objective is analyzing diurnal changes in photochemically active species (N2O5, NO2, ClONO2, BrONO2). Observed VMR variations align well with simulations from the EMAC (ECHAM5/MESSy Atmospheric Chemistry) chemistry-climate model, though absolute concentrations differ to a certain extent. Nighttime BrONO2 measurements allowed an estimate of lower stratospheric Bry (20.4 ± 2.5 pptv). These results demonstrate the suitability of balloon-borne limb-imaging spectroscopy for providing high-quality vertical trace gas profiles, offering valuable new data to improve our understanding of stratospheric composition and to support the validation of atmospheric models
Energy Landscape and Kinetic Analysis of Molecular Dynamics Simulations for Intrinsically Disordered Proteins
No full textUnderstanding the conformational dynamics of biomolecules requires methods that go beyond structural sampling and provide a quantitative description of thermodynamics and kinetics. For intrinsically disordered proteins (IDPs), energy landscape characterization is particularly crucial to unravel their complex conformational behavior. Here, we present a comprehensive protocol for analyzing molecular dynamics (MD) simulations in terms of energy landscapes, metastable states, and transition pathways. Our approach is based on the distribution of reciprocal interatomic distances (DRID) for dimensionality reduction, followed by clustering and kinetic modeling. Free energy surfaces and transition state barriers are computed directly from the simulation data and visualized using disconnectivity graphs. The method integrates two Python packages, DRIDmetric and freenet, with standard energy landscape tools based on kinetic transition networks, including PATHSAMPLE and disconnectionDPS. We demonstrate this workflow for simulations of the intrinsically disordered, aggregation-prone Alzheimer’s amyloid-β peptide in physiologically relevant environments. This modular framework offers a robust and interpretable way to extract thermodynamic and kinetic insights from MD data and is especially valuable for characterizing the diverse conformational states of IDPs