Helmholtz-Zentrum Hereon

Coherent phase transformations in interstitial solid solutions or intercalation compounds with a miscibility gap are of practical relevance for energy storage materials and specifically for metal hydride or lithium-ion compound nanoparticles. Different conclusions on the size-dependence of the transformation conditions are reached by modeling or theory focusing on the impact of either one (internal, solid-state-) critical-point wetting of the nanoparticle surface or coherency constraints from solute-saturated surface layers. We report a hybrid numerical approach, combining atomistic grand canonical Monte Carlo simulation with a continuum mechanics analysis of coherency stress and modeling simultaneously wetting and mechanical constraints. When the ratio between chemical and misfit-strain-related contributions to the solute-solute interaction energy takes values realistic for interstitial solutions—which are typical for energy storage materials—we find that the impact of solid-state wetting is weak and that of coherency stress is dominant. Specifically, mechanical interaction can act to reduce the phase transformation hysteresis at small system size, and it can make the solid more binding for solute, thereby reducing the “plateau” chemical potential at phase coexistence. We present equations for the impact of coherency stress on the size-dependence of upper consolute temperature, plateau chemical potential, and charging/discharging hysteresis.

Computational models are complex scientific constructs that have become essential for us to better understand the world. Many models are valuable for peers within and beyond disciplinary boundaries. However, there are no widely agreed-upon standards for sharing models. This paper suggests 10 simple rules for you to both (i) ensure you share models in a way that is at least “good enough,” and (ii) enable others to lead the change towards better model-sharing practices.

The study aimed to assess the impact of climate change on the crop suitability index (CSI) of selected staple crops for current (1981–2010) and future (2021–2050 and 2051–2080) climates across Africa. Precipitation and mean temperature data from gridded observations, and 10 Global Climate Models (GCMs) were utilized to calculate the CSI for maize, soybean, wheat, plantain, cassava, rice, millet, sorghum, and yam. The Ecocrop model implemented in R, utilizing the FAO‐Ecocrop database alongside climatic variables for different climatic zones across the continent, was employed to compute the CSI. The results indicate that all crops, except rain‐fed rice, are suitable in parts of West and Central African regions, with wheat being inclusive in some parts of the Guinea Coast. The northern, eastern, and southern African regions are identified as the least suitable for any crop production based on the balance between the base climate parameters over the historical period. Analysis over this historical period reveals an increasing trend for major crops in most regions, except for wheat crop production, which demonstrates a decreasing trend in most areas. Projection analysis reveals that the Sahel region is expected to be the most affected by climate change, with a significant reduction in the suitability index for most crops. Conversely, the Southeastern Africa and the Guinea Coast regions are likely to be the least affected, as the suitability index increases for the considered crops. This analysis provides crucial information for effective agricultural planning and resource allocation, optimizing land use by identifying crops aligned with prevailing environmental conditions, including soil type, climate, and water availability. Such information enhances the understanding of crop suitability, contributing to improved agricultural productivity and sustainability.

This case study of Kongsfjorden, western coastal Svalbard, provides insights on how freshwater runoff from marine‐ and land‐terminating glaciers influences the biogeochemical cycles and distribution patterns of carbon, nutrients, and trace elements in an Arctic fjord system. We collected samples from the water column at stations along the fjord axis and proglacial river catchments, and analyzed concentrations of dissolved trace elements, together with dissolved nutrients, as well as alkalinity and dissolved inorganic carbon. Statistical tools were applied to identify and quantify biogeochemical processes within the fjord that govern the constituent distributions. Our results suggest that the glacier type affects nutrient availability and, therefore, primary production. Glacial discharge from both marine‐terminating glaciers and riverine discharge from land‐terminating glaciers are important sources of dissolved trace elements (dAl, dMn, dCo, dNi, dCu, and dPb) that are involved in biological and scavenging processes within marine systems. We identified benthic fluxes across the sediment‐water interface to supply fjord waters with silicate, dFe, dCu, and dZn. Our data show that intensive carbonate weathering in proglacial catchments supplies fjord waters with additional dissolved carbonates and, therefore, attenuates reduced buffering capacities caused by glacial runoff. Our study provides valuable insight into biogeochemical processes and carbon cycling within a climate‐sensitive, high‐latitude fjord region, which may help predict Arctic ecosystem changes in the future.

African easterly waves significantly influence regional hydroclimate, making it crucial to understand how global warming will impact their activity. Here, we investigate future changes in wave activity and assess the underlying mechanisms using an ensemble of Earth system models. We find a robust increase in wave activity over the Sahel–Sahara region by the end of the 21st century under two emission scenarios. This intensification is linked to increased baroclinicity associated with a strengthening of the meridional temperature gradient between the Guinea Coast and the Sahara. Our results also indicate that low-level warming enhances the waves by reinforcing monsoon flow, leading to increased convergence and vertical motion along the intertropical discontinuity. These energetic alterations significantly modify the conditions that currently produce these waves. Overall, our findings suggest that changes in wave activity could impact the transport of Saharan dust and mesoscale convective activity over the Sahel.

In the last decade, grating-based phase-contrast computed tomography (gbPC-CT) has received growing interest. It provides additional information about the refractive index decrement in the sample. This signal shows an increased soft-tissue contrast. However, the resolution dependence of the signal poses a challenge: its contrast enhancement is overcompensated by the low resolution in low-dose applications such as clinical computed tomography. As a result, the implementation of gbPC-CT is currently tied to a higher dose. To reduce the dose, we introduce the self-supervised deep learning network Noise2Inverse into the field of gbPC-CT. We evaluate the behavior of the Noise2Inverse parameters on the phase-contrast results. Afterward, we compare its results with other denoising methods, namely the Statistical Iterative Reconstruction, Block Matching 3D, and Patchwise Phase Retrieval. In the example of Noise2Inverse, we show that deep learning networks can deliver superior denoising results with respect to the investigated image quality metrics. Their application allows to increase the resolution while maintaining the dose. At higher resolutions, gbPC-CT can naturally deliver higher contrast than conventional absorption-based CT. Therefore, the application of machine learning-based denoisers shifts the dose-normalized image quality in favor of gbPC-CT, bringing it one step closer to medical application.

Additive manufacturing (AM) by powder bed fusion electron beam (PBF-EB) is a state-of-the-art method for processing titanium-based alloys, especially due to the high inherent oxygen affinity of the material. Ti-Nb-Ta-Zr alloys provide, dependent on composition and manufacturing, a versatile property profile and are of increasing interest as structural materials as AM eases their production. Enhancing sustainability through reduced purity requirements, alongside improved material performance, could lead to more efficient and environmentally-friendly material design. This study explores the feasibility of producing dense β-TNTZ alloys with an elevated oxygen content of 2800 ppm through PBF-EB, achieving up to 99.7% density and notable mechanical properties such as a hardness of 330HV0.3. The microstructure was found to be single-β in all samples with low segregation of constitutional elements. Indications of a fiber texture switch, depending on the chosen process parameters, were found.

Antimicrobial resistance (AMR) is a major cause of death worldwide. This urges the search for alternatives to antibiotics, and antimicrobial polymers hold promise due to their reduced susceptibility to AMR. The topology of such macromolecules has a strong impact on their activity, with bottlebrush architectures outperforming their linear counterparts significantly. Consequently, understanding the specific behavior of macromolecules featuring a confined conformation of linear subunits is pertinent. This study focusses on revealing fundamental differences between architectures regarding properties as well as interaction with biological membranes. Various analytical techniques (using membrane mimics and spectroscopic methods) are used to generate insights revealing the following trends: A) The reduction of degrees of freedom in bottle brushes reduces their tendencies for self‐assembly and undesired protein interaction. B) When compared to linear polymers, bottlebrushes attach to membranes faster and more efficiently as well as in a unimolecular fashion. Their multivalent presentation of linear subunits also leads to aggregation between liposomes, which is not induced by linear polymers. C) Neutron reflectometry measurements show an increased tendency of bottle brushes to insert into the hydrophobic tails of phospholipid monolayers. The knowledge about these features will fuel the future development of even more efficient antimicrobial polymers.

Room temperature operation of Na-S batteries with liquid electrolytes is plagued by fundamental challenges stemming from polysulfide solubility and their shuttle effects. Inorganic solid electrolytes offer a promising solution by acting as barriers to polysulfide migration, mitigating capacity loss. While the sequential formation of cycling products in molten-electrode and liquid electrolytes-based Na-S batteries generally aligns with the expectations from the Na-S phase diagram, their presence, stability, and transitory behavior in systems with inorganic solid electrolytes at room temperature, remain poorly understood. To address this, we employed operando scanning micro-beam X-ray diffraction and ex-situ X-ray absorption spectroscopy to investigate the sulfur conversion mechanisms in Na-S cells with Na3PS4 and Na4(B10H10)(B12H12) electrolytes. Our findings reveal the formation of crystalline and amorphous polysulfides, including those predicted by the Na-S phase diagram (e.g., Na2S5, Na2S4, Na2S2, Na2S), high-order polysulfides observed in liquid-electrolyte systems (e.g., Na2Sx, where x = 6–8), and phases like Na2S3 typically stable only under high-temperature or high-pressure conditions. We demonstrate that these transitions are governed by diffusion-limited kinetics and localized stress concentrations, emphasizing the critical role of pressure, which serves as both a thermodynamic variable, as well as a design parameter, for optimizing solid-state Na-S battery performance necessary for pushing these cells closer to the commercial frontier.

Extreme freeze events (EFEs) represent a rapid and intense fall of environmental temperature in a constrained area due to low-pressure systems at mid-levels of the atmosphere during winter. The semiarid region of Northwestern Mexico is frequently impacted by EFEs, causing damage to crops, livestock, economy, infrastructure, among other productive sectors. Hence, forecasting and prediction tools to reproduce the phenomenon accurately is crucial to minimize costs and the potential development of an early warning system for this kind of natural phenomena. This study evaluates the Weather Research and Forecasting (WRF) model performance to simulate three relevant freeze events in Northwestern Mexico. Different WRF physics parameterization arrangements were applied, and the results were evaluated using in-situ observations from a local network to measure the model performance through statistical errors. Thus, the aim is to find the key WRF model schemes to reproduce hazardous freezes in Northwestern Mexico. The analyses showed that WRF simulations reproduced the spatial distribution of minimum temperatures during each episode, mainly in the north, northeastern, and close to the steep slopes of the domain. The general model performance shows a negative bias of daily minimum temperatures. The scale of errors was strongly influenced by the temporal resolution (hourly/daily) of in-situ observations. All configurations for short– and long–wave radiation using Dudhia and RRTM schemes provided a better performance in the tested EFEs. A turbulent kinetic energy model was used as the planetary boundary layer scheme proved to enhance WRF model performance.

We utilize the 50-member MPI-ESM-LR Earth System model to investigate the projected changes in Arctic marine heatwaves’ (MHWs) characteristics caused by an additional 0.5 ∘C increase in global warming, from 1.5 ∘C to 2 ∘C, with respect to pre-industrial levels. Our results indicate that this 0.5 ∘C increase in global warming triggers an intensified reaction in both the Arctic’s mean sea surface temperature (SST) and variability. In a 2 ∘C warmer world, one out of every four summer months would be warmer than the current climate. We detect a nonlinear increase of MHW intensity in a 2 ∘C world, which is characterized by a break in slope occurring around the year 2042 ± 2 (across 50 ensemble members of the SSP5-8.5 scenario). At the estimated post-break dates, the intensity rate roughly doubles, leading to MHWs in a 2 ∘C world with average cumulative heat intensity 100 ∘C*days higher than in a 1.5 ∘C world. Further results reveal that an extremely rare MHW with an intensity of 3.19 ∘C, classified as a 1-in-100-year event in a 1.5 ∘C world, is expected to transform into a 1-in-7-year event in a 2 ∘C world. This transition signifies a ∼15-fold increase in the likelihood of such events occurring due to a 0.5 ∘C increase in global warming. Likewise, a rare occurrence of years featuring 125 MHW days in a 1.5 ∘C world is projected to become a 1-in-10-year event in a 2 ∘C world, resulting in a 10-fold increase in occurrence probability. The main contributor to these changes is predominantly the rise in mean SST, with enhanced SST variability playing a minor role. These findings highlight that a 2 ∘C world could lead to a substantial escalation of the frequency and intensity of MHWs in the Arctic compared to a 1.5 ∘C world, transforming what are currently rare extreme events into more common events, with significant implications for global climate dynamics and the well-being of Arctic ecosystems and communities.

Optimizing electrochemical kinetics by regulation ion/charge transfer efficiency and stabilizing the electrode structure of electrode materials is crucial to maximize the rapid charging and long cycling sodium‐ion storage. Herein, VS2/Bi2S3 spring‐type heterointerfaces hollow microspheres with spatial confinement and sulfur vacancy defects are synthesized as a fast‐charging anode for sodium‐ion hybrid capacitors (SIHCs). The experimental studies coupled with density functional theory calculations verify that the strong coupling between VS2 and Bi2S3 induces a stable built‐in electric field, largely promoting the charge and sodium‐ion transfer efficiency. Sulfur vacancy defects at the heterointerfaces produce additional sodium‐ion pseudocapacitive storage, which improves the reversible capacity and large‐rate fast charge performance of the VS2/Bi2S3 electrode. Finite element analysis and in situ expansion test confirm that the spring‐type heterostructured hollow microspheres formed by flat‐morphology VS2 and zigzag‐morphology Bi2S3 stacking mitigate the lattice expansion and contraction during sodium‐ion insertion/extraction, accommodate the mechanical stresses, and maintain the integrity of the heterojunction interface. When employed in coin SIHC, it achieves a high energy/power density of 135 Wh kg⁻¹/22 kW kg⁻¹, and an ultralong life of 50 000 cycles; the assembled pouch SIHC (1 Ah) demonstrates a high specific energy of 120 Wh kg⁻¹ with fast‐charging at 10 C, and 95.5% capacity retention after 1000 cycles.

Osteoarthritis (OA) is a significant condition that profoundly impacts synovial joints, including cartilage and subchondral bone plate. Biomaterials that can impede OA progression are a promising alternative or supplement to anti‐inflammatory and surgical interventions. Magnesium (Mg) alloys known for bone regeneration potential were assessed in the form of Mg microparticles regarding their impact on tissue regeneration and prevention of OA progression. In vitro assays based on mesenchymal stem cells (SCP‐1) were applied to evaluate the Mg microparticle's compatibility and function. Biocompatibility documented through live‐dead staining and lactate dehydrogenase assay revealed a 90% cell viability at a concentration below 10 mM after 3 days of exposure. An in vitro OA model based on the supplementation of the cytokines IL‐1β, and TNF‐α was established and disclosed the effect of Mg degradation products in differentiating SCP‐1 cells. Sustained differentiation was confirmed through extracellular matrix staining and increased gene marker expression. The Mg supplementation reduced the release of inflammatory cytokines (IL‐6 and IL‐8) while promoting the expression of proteins such as collagen X, collagen I, and osteopontin in a time‐dependent manner. The in vitro study suggests that Mg microparticles hold a therapeutic potential for OA treatment with their ability to support bone and cartilage repair mechanisms even under inflammatory conditions.

Changes in compound extreme events are a hallmark of global warming, posing significant risks to human well-being. This study investigates projected changes in compound extreme hot & humid and wet & windy events across Africa by the end of the 21st century (2069–2098). Using the multi-model ensemble mean from the regional climate projections from the coordinated regional climate downscaling experiment-coordinated output for regional evaluations project, we examined both low/high representative concentration pathway (RCP2.6/8.5) emission scenarios. We estimated population exposure to these joint events by combining climate projections with low/high shared socioeconomic pathway (SSP1/SSP3) population growth scenarios. Broadly, changes are regionally-dependent. In some subregions, we found a substantial increase in the frequency and duration of compound extreme hot & humid events, rising by approximately 100%/600% under RCP2.6/RCP8.5, associated with a rise in extremely hot univariate events. Conversely, compound extreme wet & windy events are projected to weaken, particularly under RCP8.5, with reductions up to 64%, driven in most regions, by declines in extreme wet-only events. Global warming expands historical equatorial hotspots for heat events into eastern and southern Africa, which is less severe under RCP2.6. These changes significantly increase exposed populations to these hazards, affecting up to 668 million person-events across various IPCC reference subregions, especially in West, Central, Northeast, and Southeast Africa, as well as most of West and East South Africa, and Madagascar (MDG). In subregions like the Sahara and West Africa, population growth is the primary driver of exposure to hot & humid events, while in Central, North-East, South-East, West-South, East-South and MDG, climate and interaction effects are more influential. We stress the need to enhance climate adaptation policies, especially in West, Central, Northeast, Southeast Africa and MDG, to address these risks, as they could exacerbate climate refugee migration, heat-related illnesses, food insecurity, and societal instability. We also advocate for disseminating climate services, particularly in low-income countries, to support research for sustainable development.

Suspended matter (SPM) was sampled in a grid off the Pearl River mouth in the northern South China Sea (SCS). SPM concentrations and the content of total organic carbon (TOC), total nitrogen (TN), amino acids (AA) and hexosamines (HA) and derived biogeochemical indicators were used to study organic matter sources on the shelf and slope. A surface SPM maximum curtailed the water mass of mixed riverine and marine origin off the Pearl River mouth with salinities <30. SPM in this river plume was rich in organic matter of fresh planktic origin. In areas outside the river plume chlorophyll (Chl‐a) maxima were found at the subsurface nutricline. The AA composition shows that the degradation state of organic matter is very similar in all samples except in bottom water samples. Rather than degradation indicators, an indicator of SPM residence time in the ocean shows differences between samples from the upper 200 m and the deeper SPM samples. On the shelf and the shelf break a distinct SPM maximum was found above the sea floor. AA and HA spectra revealed that its organic matter was more degraded than the other SPM samples and that part of the organic matter in the bottom water turbidity maximum originated from the fine fraction of sediments. The state of organic matter implies that degradation of this resuspended material possibly adds to bottom water hypoxia; furthermore, contaminants originally deposited in shelf sediments can be redistributed into distal areas of the South China Sea.

Kelps (Laminariales, Phaeophyceae) are foundation species along Arctic rocky shores, providing the basis for complex ecosystems and supporting a high secondary production. Due to ongoing climate change glacial and terrestrial run-off are currently accelerating, drastically changing physical and chemical water column parameters, e.g., water transparency for photosynthetically active radiation or dissolved concentrations of (harmful) elements. We investigated the performance and functioning of Arctic kelp holobionts in response to run-off gradients, with a focus on the effect of altered element concentrations in the water column. We found that the kelp Saccharina latissima accumulates harmful elements (e.g., cadmium, mercury) originating from coastal run-off. As kelps are at the basis of the food web, this might lead to biomagnification, with potential consequences for high-latitude kelp maricultures. In contrast, the high biosorption potential of kelps might be advantageous in monitoring environmental pollution or potentially extracting dissolved rare earth elements. Further, we found that the relative abundances of several kelp-associated microbial taxa significantly responded to increasing run-off influence, changing the kelps functioning in the ecosystem, e.g., the holobionts nutritional value and elemental cycling. The responses of kelp holobionts to environmental changes imply cascading ecological and economic consequences for Arctic kelp ecosystems in future climate change scenarios.

This study investigates cold‐season characteristics and the occurrence of ice episodes for a target region in northern Germany. Additionally, it identifies the characteristic atmospheric patterns associated with ice episodes using reanalysis data. A pattern‐matching method is developed, which uses the structural similarity index to determine whether regional climate models (RCMs) can reproduce the ice‐episode specific atmospheric patterns identified from the reanalysis data. The results show that the frequency of ice days is overestimated, but not the frequency of frost days. This suggests a daytime cold bias in the RCMs in this region, as maximum temperatures are too low. Moreover, most of the analysed RCMs simulate too many ice episodes (>$>$ 5 consecutive ice days). The developed pattern‐matching demonstrates, based on reanalysis data, that ice episodes in the target region can be associated with a variety of different atmospheric patterns. Specifically, longer ice episodes (lasting 14–29 consecutive ice days) in the target region are associated with a blocking pattern over Iceland/the British Isles. This is the most frequent pattern observed during ice episodes in the target region. The least frequent patterns show a system of low GPH over the European continent and are associated with shorter ice episodes (6–8 consecutive ice days) in the target region. The RCMs can reproduce these patterns and their frequency well, regardless of their forcing, and these patterns are also associated with ice episodes in the RCMs. Furthermore, it can be concluded that the “typical” blocking pattern is not a reliable indicator for ice episodes in the target region.