1,421 results match your criteria: "a Helmholtz-Zentrum Geesthacht; Institute of Materials Research; Structural Research on Macromolecules ; Geesthacht[Affiliation]"

Environmental changes are a growing concern, as they exert pressures on ecosystems. In some cases, such changes lead to shifts in ecosystem structure. However, species can adapt to changes through evolution, and it is unclear how evolution interacts with regime shifts, which restricts ecosystem management strategies.

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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.

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This work proposes a fuel cell power supply system for underwater applications (e.g., autonomous underwater vehicles), where artificial gills, based on a polymer membrane, harvest the required oxygen from the ambient water.

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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.

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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.

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Mercury (Hg) is a global pollutant with substantial risks to human and ecosystem health. By upward transport in tropical regions, mercury enters into the stratosphere, but the contribution of the stratosphere to global mercury dispersion and deposition remains unknown. We find that between 5 and 50% (passing through the 400-kelvin isentropic surface and tropopause, respectively) of the mercury mass deposited on Earth's surface is chemically processed in the lower stratosphere.

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Self-supervised denoising of grating-based phase-contrast computed tomography.

Sci Rep

December 2024

Research Group Biomedical Imaging Physics, Department of Physics, TUM School of Natural Sciences, Technical University of Munich, 85748, Garching, Germany.

Article Synopsis
  • GbPC-CT is gaining popularity for its ability to enhance soft-tissue contrast in imaging, but it struggles with resolution issues, especially at low doses commonly used in clinical settings.
  • The study introduces a self-supervised deep learning model called Noise2Inverse, which helps enhance image quality while reducing the required radiation dose.
  • The results show that Noise2Inverse outperforms traditional denoising methods, indicating that deep learning can improve the resolution of gbPC-CT images, making it a more viable option for medical applications.
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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.

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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.

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Assessment of fine-tuned large language models for real-world chemistry and material science applications.

Chem Sci

January 2025

Laboratory of Molecular Simulation (LSMO), Institut des Sciences et Ingénierie Chimiques, École Polytechnique Fédérale de Lausanne (EPFL) Rue de l'Industrie 17 CH-1951 Sion Switzerland

Article Synopsis
  • Large language models (LLMs) like GPT-J-6B, Llama-3.1-8B, and Mistral-7B can learn chemical properties effectively through fine-tuning without specialized features.
  • Fine-tuning these models often outperforms traditional machine learning methods in simple classification tasks, with potential success in more complex problems depending on dataset size and question type.
  • The ease of converting datasets for LLM training and the effectiveness of small datasets in generating predictive models suggest that LLMs could significantly streamline experimental processes in chemical research.
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The rapid melting of the Arctic cryosphere due to climate change will result in significant freshwater input into Arctic marine ecosystems. This might also cause the release of legacy mercury (Hg) stored in the cryosphere, increasing Hg concentration and its subsequent effects on the marine biota. However, there is scarce knowledge on the concentration of Hg in the lower trophic level organisms at the base of the Arctic pelagic food web.

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Gallium is classified as a technology metal as it is important for technological innovations. It is also referred to as a strategic metal, which emphasizes its economic relevance. In addition, gallium is a critical raw material that is strategically important but only available in limited quantities.

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A Complex Concentrated Alloy with Record-High Strength-Toughness at 77 K.

Adv Mater

December 2024

State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an, 710049, P. R. China.

High strength and large ductility, leading to a high material toughness (area under the stress-strain curve), are desirable for alloys used in cryogenic applications. Assisted by domain-knowledge-informed machine learning, here a complex concentrated FeCoNiAlTa alloy is designed, which uses L1 coherent nanoprecipitates in a high volume fraction (≈65 ± 3 vol.%) in a face-centered-cubic (FCC) solid solution matrix that undergoes FCC-to-body-centered-cubic (BCC) phase transformation upon tensile straining.

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A pioneering longterm experiment on mesophotic macrofouling communities in the North Atlantic.

Commun Biol

December 2024

MARE - Marine and Environmental Sciences Centre, ARNET - Aquatic Research Network, Agência Regional para o Desenvolvimento da Investigação Tecnologia e Inovação (ARDITI), Funchal, Madeira, Portugal.

The mesophotic zone represents one of our planet's largest and least explored biomes. An increasing number of studies evidence the importance of macrofouling species in marine ecosystems, but information on these communities and the factors influencing their structures at mesophotic depths remain poor. This lack of understanding limits our ability to predict anthropogenic impacts or conduct restoration operations in the mesophotic and the lower boundary of the euphotic zones.

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Article Synopsis
  • Phytoplankton in lakes capture atmospheric CO2 and convert it to organic carbon (OC), but most OC is recycled back to the atmosphere as CO and methane (CH), contributing to climate change.
  • * The research identifies a 3.1-fold increase in CO-equivalent emissions over the next century, exacerbated by climate warming.
  • * While climate change boosts phytoplankton growth in many lakes, it can also negatively impact their ability to sequester CO-eq, potentially weakening this feedback loop over time.
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Switchable 3D Photonic Crystals Based on the Insulator-to-Metal Transition in VO.

ACS Appl Mater Interfaces

December 2024

Center for Hybrid Nanostructures, Universität Hamburg, Luruper Chaussee 149, 22607 Hamburg, Germany.

Article Synopsis
  • Photonic crystals (PhCs) are optical structures that manipulate light by creating a photonic band gap (PBG) through their dielectric properties, traditionally fixed and static.
  • Recent advancements target switchable PhCs, especially using vanadium dioxide (VO), which changes its state and optical properties near room temperature, allowing for a reversible adjustment of the PBG.
  • This research introduces a fabrication method for 3D switchable VO photonic crystals, demonstrating significant control over PBG at specific wavelengths in the near-infrared region, paving the way for versatile photonic devices that can adapt their functionalities.
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This study evaluates deployment strategies for artificial oxygenation devices to mitigate coastal hypoxia, particularly in mariculture regions. Focusing on a typical mariculture region in the coastal waters of China, we examined the combined effects of topography, hydrodynamics, and biogeochemical processes. A high-resolution three-dimensional physical-biogeochemical coupled model, validated against observational data from three summer cruises in 2020, accurately captured key drivers of hypoxia.

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The compressive deformation of the extruded binary Mg-Gd with gadolinium in solid solution has been studied in situ by combining synchrotron diffraction and acoustic emission techniques during compression tests. These two techniques are useful in investigating the evolution of twinning in all its stages. The extruded bars develop a fiber texture with the basal plane parallel to the extrusion direction.

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Human population dynamics and their drivers are not well understood, especially over the long term and on large scales. Here, we estimate demographic growth trajectories from 9 to 3 ka BP across the entire globe by employing summed probability distributions of radiocarbon dates. Our reconstruction reveals multicentennial growth cycles on all six inhabited continents, which exhibited matching dominant frequencies and phase relations.

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Thin-film composite (TFC) membranes containing metal-polyphenol network (MPN) selective layers were fabricated using a supramolecular self-assembly between tannic acid (TA) and ferric ion (Fe). The TA-Fe thin film was coated on a porous polyacrylonitrile support using aqueous solutions of TA and FeCl via a layer-by-layer deposition technique. The pH of the TA solution was used as a tool to alter the membrane characteristics.

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The eastern Niger Delta region in Nigeria is a hotspot for reactive nitrogen pollution due to extensive animal husbandry, pit latrine usage, and agricultural practices. Despite the high level of human activity, the sources and processes affecting nitrogen in groundwater remain understudied. Groundwater nitrate (NO) concentrations are highly variable, with some areas recording values well above the safe drinking water threshold of 50 mg/L.

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High-entropy alloys (HEAs) have become pivotal materials in the field of catalysis, offering unique advantages due to their diverse elemental compositions and complex atomic structures. Recent advances in computational techniques, particularly density functional theory (DFT) and machine learning (ML), have significantly enhanced our understanding and design of HEAs for use in catalysis. These innovative atomistic simulations shed light on the properties of HEAs, enabling the discovery and optimization of catalysis materials for solid-solution structures.

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The field of bone regeneration has primarily focused on investigating fracture healing and nonunion in isolated musculoskeletal injuries. Compared to isolated fractures, which frequently heal well, fractures in patients with multiple bodily injuries (polytrauma) may exhibit impaired healing. While some papers have reported the overall cytokine response to polytrauma conditions, significant gaps in our understanding remain in how fractures heal differently in polytrauma patients.

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Article Synopsis
  • - Mg-Li alloys may serve as effective bioresorbable implants that release lithium (Li) for treating bipolar and neurodegenerative disorders, potentially offering advantages over traditional Li salts.
  • - In a study utilizing a neuroinflammation model, two Mg-Li alloys (Mg-1.6Li and Mg-9.5Li) were tested, showing that Li from these alloys enhanced the phosphorylation of GSK3β in glial cells more effectively than Li salts.
  • - The results indicate that Mg-Li alloys can improve the modulation of inflammation-related gene expression and support further exploration of their therapeutic potential in neurological treatments.
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