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A comparison of porous sandstone fracturing induced by increasing fluid pressure or decreasing confining pressure: Stress-path and rate-dependence effects
No full textWhen a porous rock is subjected to overall compressive loading, either increasing pore pressure or decreasing confining pressure could result in rock failure. The stress path and the applied pressure change rate may affect the initiation and propagation of fractures within brittle materials. Understanding the physical mechanisms leading to failure is crucial for underground engineering applications and geo-energy exploration and storage. We conducted triaxial compression experiments on porous Bentheim sandstone samples at different stress paths and pressure change rates. First, at a constant confining pressure of 35 MPa and pore pressure of 5 MPa, intact cylindrical samples were axially loaded up to about 85% of the peak strength. Subsequently, the axial piston position was fixed, and then either the pore pressure was increased or the confining pressure was decreased at two different rates (0.5 MPa/min or 2 MPa/min), leading to final catastrophic failure. The mechanical results revealed that samples subjected to higher rates of decreasing effective confining pressure exhibited larger stress drop rates, higher slip rates, higher total breakdown work, higher rates of acoustic emissions (AEs) before failure, and higher post-failure AE decay rates. In contrast, the applied stress path did not significantly affect rock failure characteristics. Comparison of located AE events with post-mortem microstructures of deformed samples shows a good agreement. The AE source type determined from the P-wave first-motion polarity shows that shear failure dominated the fracture process when approaching failure. Gutenberg-Richter b-values revealed a significant decrease before failure in all tests. Our results indicate that, in contrast to the stress path, the rate of effective stress change strongly affects fracturing behavior and AE rate changes
Proteomic profiling of equine airway mucus reveals compositional changes in asthmatic phenotypes
No full textMucus hypersecretion and accumulation are hallmark features of equine asthma (EA), a meaningful respiratory disorder in horses occurring in mild to moderate (MEA) and severe (SEA) forms. Changes of the proteomic composition of airway mucus in EA are poorly understood. Using label-free quantitative liquid chromatography-mass spectrometry, we analyzed airway mucus from SEA ( n = 10), MEA ( n = 6), and healthy ( n = 8) horses. We identified and quantified 2,275 proteins including gel-forming mucins MUC5AC and MUC5B and membrane-bound mucins MUC1 and MUC4. Compared with healthy controls, 130 proteins (SEA) and 103 (MEA) were significantly increased. 38 were elevated in SEA relative to MEA, 10 were higher in MEA. MUC4 was markedly increased in both, correlated with bronchoalveolar lavage neutrophils (ρ = 0.790, p = 4.9E-06), and distinguished excellently between healthy and asthmatics (AUC = 1.0, 95% CI: 1–1), similar to 23 other proteins. MUC5AC was elevated in both, whereas MUC5B only in SEA. MUC1 did not differ between groups. Changes in mucus-modifying proteins, including glycosyltransferases and aquaporins, suggest altered mucus properties in EA. Functional enrichment analyses revealed inflammation-, tissue remodeling- and coagulation-linked GO terms and pathways in EA. The distinct proteomic profiles add to the understanding of EA and may offer novel targets for phenotype-specific biomarkers and therapy
Diversity of DNA viruses in the atmosphere of sub-Antarctic South Georgia
No full textStudying airborne viruses in remote environments like the sub-Antarctic island of South Georgia offers key insights into viral ecology, diversity, and their role in shaping ecosystems through microbial and nutrient interactions. We analyzed airborne viral community composition at two sites in South Georgia. Sampling took place using multiple methodologies, with the data produced subjected to viral metagenomics. The Coriolis μ device (wet collection) was the most effective, yielding 30 viral scaffolds. Two-thirds of the scaffolds were only obtained from the coastal location, indicating that location influences airborne viral diversity. Protein-based clustering of 39 viral operational taxonomic units (vOTUs) revealed similarities of 15 with known marine viruses, suggesting oceanic influence on the airborne viral community. Protein homologs related to UV damage protection and photosynthesis from two airborne vOTUs were widely distributed across major oceans, suggesting their potential role in supporting the resilience of marine microorganisms under changing climate conditions. Some vOTUs had protein similarities to viruses infecting extremophiles, indicating viral adaptations to harsh environments. This study provides a baseline for understanding the complexity and sustainability of airborne viral communities in remote ecosystems. It underscores the need for continued monitoring to assess how these communities respond to shifting atmospheric and ecological conditions
Tunneling spectroscopy of the spinon-Kondo effect in one-dimensional Mott insulators
No full textWe study the tunneling density of states (TDOS) in one-dimensional (1D) Mott insulators at energies below the charge gap. By employing nonlinear Luttinger liquid theory and density-matrix renormalization group (DMRG) simulations, we predict that in the presence of a magnetic impurity at the boundary, characteristic Fermi-edge singularity features can appear at subgap energies in the TDOS near the boundary. In contrast to the Kondo effect in a metal, these resonances are strongly asymmetric and of power-law form. The power-law exponent is universal and determined by the spinon-Kondo effect
Investigating the core microbiome concept: Daphnia as a case study
No full textBackground
Host-associated microbiomes play an important role in the ecology and fitness of organisms. Given their significance, it is much debated to what extent these associations are widespread and even obligatory. Such frequent associations are captured by the concept of the core microbiome. The cladoceran Daphnia is a pivotal genus in freshwater ecosystems occupying a central position in the food webs of standing waters. With its unique standing in pelagic waters, Daphnia serves as a key grazer, regulating algal populations and nutrient cycling, making its microbiome essential to understanding ecosystem function and stability. In recent years, Daphnia has become an increasingly popular study system for exploring host‒microbiota interactions. There is, however, limited knowledge on the baseline taxa that consistently inhabit this host and potentially contribute to its fitness. Identifying whether such a host-associated “core microbiome” exists for Daphnia and, if so, which microbial taxa it comprises is important both for enhancing our ecological understanding of this genus and its ecosystem function and for interpreting future experiments.
Results
We compiled a dataset on Daphnia magna microbiome based on 12 published studies, comprising gut and whole microbiome samples of both laboratory-cultured and field-grown animals across five countries spanning three continents. To identify core taxa, we employ quantification metrics based on prevalence and a combination of prevalence and relative abundance. Our analysis demonstrates that the D. magna microbiome is highly variable, yet, a consistent association with specific taxa, notably Limnohabitans planktonicus, is observed especially under laboratory conditions. However, this pattern is tempered by the observation that field-grown animals exhibit a more diverse microbiome with a weaker presence of L. planktonicus, challenging its status as a core member.
Conclusions
Our analysis suggests that the D. magna microbiome is defined by its high variability and few conserved associations, with L. planktonicus being the most stable taxon in laboratory settings but not necessarily a core member in natural environments. These findings underscore the need for caution when using laboratory results to interpret natural microbiome compositions and emphasize the need for further research on field-grown animals to better understand the structuring of microbial communities under natural settings
Spin Matters: A Multidisciplinary Roadmap to Understanding Spin Effects in Oxygen Evolution Reaction During Water Electrolysis
No full textA central challenge in water electrolysis lies with the oxygen evolution reaction (OER) where the formation of molecular oxygen (O2) is hindered by the constraint of angular momentum conservation. While the reactants OH− or H2O are diamagnetic (DM), the O2 product has a paramagnetic (PM) triplet ground state, requiring a change in spin configuration when being formed. This constraint has prompted interest in spin-selective catalysts as a means to facilitate OER. In this context, the roles of magnetism and chirality-induced spin selectivity (CISS) in promoting the OER reaction have recently been investigated through both theoretical and experimental studies. However, pinpointing the key principles and their relative contribution in mediating spin-enhancement remains a significant challenge. This roadmap offers a forward-looking perspective on current experimental trends and theoretical developments in spin-enhanced OER electrocatalysis and outlines strategic directions for integrating incisive experiments and operando approaches with computational modeling to disentangle key mechanisms. By providing a conceptual framework and identifying critical knowledge gaps, this perspective aims to guide researchers toward dedicated experimental and computational studies that will deepen the understanding of spin-induced OER enhancement and accelerate the development of next-generation catalysts
Soda-Anthraquinone-Catalyzed Delignification of Coconut Husk Waste
No full textThis study investigates the role of anthraquinone (AQ) in decomposing coconut husk waste, specifically collected from Banten, to produce pure α-cellulose pulp. The process used sodium hydroxide (NaOH) at 10%, 15%, and 20% concentrations, with 0.1 g of AQ added as a catalyst, and a waste-to-liquid ratio of 1:8 throughout. The goal is to accelerate lignin degradation while protecting cellulose in the material, thereby yielding higher-quality pulp. The Banten coconut husk analysis showed an α-cellulose content of 30.38%. Higher NaOH concentrations reduced pulp yield but increased lignin removal, indicated by lower kappa numbers. AQ addition enhanced lignin removal and preserved cellulose compared to the absence of AQ. The optimal outcome was achieved with 15% NaOH and 0.1 g AQ, balancing lignin removal and cellulose preservation. These findings indicate that anthraquinone can support sustainable pulp production from agricultural waste
De Novo Design of Glycan Foldamers with Programmable Tertiary Structure
No full textDe novo molecular design has yielded proteins and peptides with structures and functions beyond those found in nature. Despite the potential for glycans to form a broader scope of well-defined tertiary architectures, owing to the numerous conjugation sites and stereocenters, no one has yet built glycans with targeted structures and functions from scratch. Here, we designed glycan sequences that fold into programmable 3D architectures. Starting from first-principles, we create a linear glycan that spontaneously adopts a rigid tertiary structure not reported for natural glycans. Considering stereochemical and spatial orientation, we identify a rigid trisaccharide turn unit that programs backbone directionality, driving folding into antiparallel geometry. The combination of this turn unit with multiple cellulose-like strands completes our design, stabilizing a tertiary sheet-like folding, as confirmed by nuclear magnetic resonance spectroscopy and small-angle X-ray scattering (SAXS). To quantitatively evaluate the conformational landscape of our glycans in aqueous solution, we built a semiautomated protocol that integrates SAXS data with molecular dynamics simulations, demonstrating further the effectiveness of our design principles. This is an important step to design and control conformation populations, not just single structures in the solid state or of unknown prevalence in the solution phase. Together, these results show that glycans can be programmed to adopt rigid tertiary structures on demand, opening new avenues for de novo glycan-based architectures in synthetic glycobiology, catalysis, and materials science
Local PI(4,5)P2 synthesis by septin-associated PIPKIγ isoforms controls centralspindlin association with the midbody during cytokinesis
No full textCytokinesis critically depends on phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2]. Synthesis of PI(4,5)P2 is crucial for several stages of cytokinesis, including actomyosin ring assembly and constriction, membrane tethering of spindle microtubules, and midbody organization. How these activities of PI(4,5)P2 are spatiotemporally controlled is unknown. Here we unravel a crucial function for local PI(4,5)P2 synthesis at the ingressed cleavage furrow by septin-binding isoforms of PIPKIγ to control midbody formation. We demonstrate that loss of PIPKIγ isoforms perturbs cytokinesis by impairing septin association with microtubules, and anillin and septin deposition at the intercellular bridge and at the midbody. This mechanism requires the ability of PIPKIγ isoforms to synthesize PI(4,5)P2 and to associate with septins. Septins and PIPKIγ further synergize to promote centralspindlin recruitment to the midbody. Our findings establish septin-associated PIPKIγ isoforms as spatiotemporal controllers of midbody organization during cytokinesis that act through generating a local pool of PI4,5P2 at the ingressed cleavage furrow