Browse Articles

Observing the mechanism of delayed collapse in colloidal gels: Yielding while becoming stronger

The delayed collapse of colloidal gels is a vexing problem. Although the equilibrium behavior of colloid-polymer mixtures is well understood, that of far-from-equilibrium gels is surprisingly complex. As the gels age, they become stronger due to coarsening but exhibit no other macroscopic change. Quite counterintuitively for a material whose strength increases with time, gels may undergo sudden, catastrophic collapse under gravity, sometimes weeks or even years after preparation. An understanding of such delayed collapse has long remained elusive. Here, we probe delayed collapse using a variety of techniques across a range of length scales, from time-lapse imaging, particle-image velocimetry, and in situ vane rheology at the macroscopic scale to multiscale confocal microscopy, with which we image a complete sample with a microscopic level of detail. The insight obtained enables us to identify a mechanism for delayed collapse: increased heterogeneity at the top of the gel leads to droplets of solvent-rich material which are denser than the gel. Upon reaching a sufficient size, these droplets overcome the yield stress of the gel, creating channels in the gel as they fall. When they reach the bottom of the gel, these channels then enable rapid solvent flow and sudden, catastrophic collapse.

Graph guided multiscale cross attention for multilabel chest X ray classification

Refining the mechanism of heme acquisition from free hemoglobin by <i> <i>Staphylococcus aureus</i> </i> IsdH

Staphylococcus aureus is a human pathogen whose virulence depends on iron acquisition. The bacterium expresses the hemophores IsdB and IsdH that enable heme capture from host hemoglobin (Hb). Unlike IsdB, IsdH can bind both free Hb and Hb:haptoglobin (Hb:Hp) complexes. Here, we present a comprehensive structural analysis of full-length IsdH in complex with free Hb, overcoming the limitations of previous studies based on truncated IsdH constructs. Cryo-EM revealed a previously unobserved oligomeric state and a unique binding pose of the N-terminal Hb-binding domain, likely representing the initial step of Hb engagement. Time-resolved and single-molecule force spectroscopy experiments delineated the sequential steps and mechanical aspects of Hb binding and heme extraction. Together, these findings provide an integrated structural and functional view of the IsdH–Hb interaction in the absence of Hp, as may occur during hemolysis, and offer insights into S. aureus heme scavenging and potential avenues for therapeutic inhibition.

Neurocognitive effects of postbiotics from Lactobacillus and Bifidobacterium strains in a mouse model of chronic variable stress

Reply to Zhang: Causal identification, social networks, and biological aging

Comparative analysis of ABC, LTP, and WAK families in non-specific immunity of wheat and sunflower

Correction for Kuhlisch et al., Mapping of the viral shunt across widespread coccolithophore blooms using metabolic biomarkers

Adaptive schedule deviation correction for complex information system projects: a graph neural network approach with knowledge distillation

A multinational megastudy of the effects of gratitude practices on subjective well-being

Scholars have observed people from a variety of cultures using a variety of gratitude-related practices to change their emotions, outlooks, and social relationships. Across 34 countries purposively sampled to cover a broad set of cross-cultural differences (total N = 10,696), we experimentally tested the effects of 6 brief gratitude interventions on subjective moods, life outlooks, and social evaluations. Compared to 3 control tasks, gratitude practices immediately produced theorized improvements in positive affect ( d = 0.37), negative affect ( d = −0.22), optimism ( d = 0.24), life satisfaction ( d = 0.12), indebtedness ( d = 0.15), and envy ( d = −0.16). Notably, these effects varied across different gratitude practices (0.00 &lt; τ practice &lt; 0.08) and countries (0.10 &lt; τ country &lt; 0.19). For instance, based on existing evidence, stakeholders can expect gratitude interventions deployed in a randomly selected country to improve positive affect—but not our other measured outcomes. To guide future inquiry into why this might be the case, we provide exploratory Bayesian estimates of the importance of 12 cross-cultural differences.

A hybrid deep fuzzy clustering framework with fusion-based learning for robust SAR change detection

Synovial fibroblasts modulate endothelial activation in an acute injury-on-a-chip model

Most patients who sustain an acute joint injury develop degenerative joint disease or osteoarthritis (OA). Animal models have informed the design of OA therapeutics; however, no disease-modifying therapy has successfully translated to human patients. Thus, there is a strong motivation to develop humanized in vitro platforms to fill a critical gap in knowledge of disease progression postinjury. Here, we develop an acute injury-on-a-chip model of the synovium, a vascularized, joint-lining tissue that has been implicated in OA progression and as a key driver of joint disease. We apply this chip-based system to investigate the crosstalk between endothelial cells, lining an engineered vessel, and synovial fibroblasts, embedded within an extracellular matrix hydrogel. Our data indicate that synovial fibroblasts, rather than initiating disease, attempt to support and maintain vascular function in the presence of acute inflammation (i.e., interleukin-1β). Such knowledge may provide new targets for OA therapeutics, preventing the progression from joint injury to disease in patients.

Geochemical mechanisms of fluorine migration and transformation during deep geological sequestration of high-salinity coal mine water in the ordos basin

Anoxic photo-oxidation of Mn(II)-bearing carbonates on Mars and early Earth

Manganese oxides, thought to form almost exclusively through reactions between Mn 2+ and O 2 , catalyze oxidative transformations among redox-sensitive metals. Thus, the occurrence of Mn oxides, either observed or inferred from sedimentary geochemical data, has formed the basis for multiple hypotheses concerning the evolution of the atmospheric redox state on the early Earth and Mars. Here, using theory and experiments, we report that the band gap of common Ca/Mg carbonate minerals (including calcite, magnesite, and aragonite) is significantly lowered by trace incorporation (0.8 wt% or lower) of Mn(II) into their bulk structure or surface, conferring photochemical reactivity under ultraviolet conditions relevant to early Earth and Mars (200 to 400 nm). Moreover, we show that surface incorporation of Mn(II) reduces the fundamental band gap much more effectively (by &gt;1 eV) than bulk incorporation. Our results suggest that photo-oxidation of Mn(II)-bearing carbonates could have occurred widely on planetary surfaces, resulting in the abiotic formation of manganese oxides without free molecular oxygen. Photochemically driven redox cycling of manganese could help sustain redox disequilibria for microbial metabolisms, but compromises the use of manganese oxides as oxygen barometers.

Radiolabeled Ag2S quantum dots for the detection of breast cancer tumours

A molecular lattice reinforces the sperm head–tail junction

Combining glycine with thymoquinone offers a promising strategy for diabetes treatment

Abstract Diabetes is increasing globally, and current treatments are frequently associated with high costs and harmful side effects. Researchers are exploring safer, natural alternatives as thymoquinone and glycine. Glycine, the simplest proteinogenic amino acid, and thymoquinone, the active compound in Nigella sativa , have shown promising hypoglycemic, antioxidant, and anti-inflammatory properties. A combination of glycine and thymoquinone for treating diabetes was not investigated before. This work studies the biochemical and histopathological effects of thymoquinone and glycine administered in combination in a diabetic rat model. Diabetes mellitus was induced by streptozotocin (STZ). Five rat groups were used: control healthy, diabetes, diabetic rats treated with glycine (G) or thymoquinone (Q), or the combination (Q + G) groups. Rat body weight changes, water and food intake, fasting blood glucose (FBG), hemoglobin (Hb), glycated Hb (HbA1C), insulin, HOMA-IR, HOMA %B and HOMA %S, QUICKI, albumin, amylase, creatine kinase, TNF-α, IL-10, glucose-6-phosphatase, fructose 1,6-bisphosphatase, glucose-6-phosphat dehydrogenase, oxidative stress portrait, and pancreas histopathology were investigated. Treatment with glycine or thymoquinone or both significantly decreased FBG, oxidative stress, and inflammation and improved metabolic dysfunction compared to untreated diabetic group. It also, revealed cytoprotection to pancreas tissue and reduced inflammatory infiltration. Effects of thymoquinone and glycine treatments were appreciated, however effects of thymoquinone combined with glycine were much better. In conclusion, thymoquinone and glycine combination, can effectively reduce both blood sugar and diabetic-associated complications through their synergistic, strong antioxidant and anti-inflammatory properties, which support the body’s natural cytoprotective ability.

Temperature-dependent feedbacks drive the pattern of Antarctic temperature change

Antarctica is an important component of the Earth’s climate system. Here we investigate temperature change in Antarctica across a range of timescales, from millennial to orbital, over the last 4 × 10 5 y, using a compilation of ice-core water-isotope records. We identify a persistent pattern of change in which the temperature variability of an Antarctic site increases with its mean surface temperature. When the entire continent warms, the warmest parts of Antarctica warm more; when the entire continent cools, the warmest parts cool more. This pattern is inconsistent with the Planck response, the simplest possible null hypothesis for Antarctic temperature change. However, a temperature-dependent feedback explains the fundamental pattern of temperature change. The feedback arises from a nonlinearity of the greenhouse effect, evident only at the cold surface temperatures of the Antarctic. This feedback may be initiated by any mean energetic forcing and thus manifests across all timescales. Local deviations from the expected pattern of temperature change indicate regional forcing such as changes in ice-sheet elevation. We reconstruct the surface elevation of the main ice divide in West Antarctica over the last deglaciation, finding a history that is supported by geological and glaciological evidence and consistent with ice-sheet modeling.

Illuminating the black box of reservoir computing

Abstract Reservoir computers, using recurrent neural networks with fixed random connections, are known to perform a wide range of information-processing tasks. Yet the transformations taking place within the reservoir, the interaction between input matrix, reservoir, and readout layer, and the influence of key design parameters remain insufficiently understood. Here, we shift the focus from performance maximization to the identification of minimal computational requirements for different model tasks. We investigate how many neurons and how much nonlinearity are needed to solve specific tasks, including cases with non-sigmoidal activation functions. Our results show that the division of labor between input matrix, reservoir, and readout layer depends strongly on the task. In many cases, a weakly coupled and only minimally nonlinear reservoir proves sufficient. In addition, features often considered secondary, such as the structure of the input matrix or the steepness of the activation functions, can become decisive for performance.

MHC-I diversity enables rapid adaptation during a viral pandemic in wild rabbit populations

Emerging diseases can have devastating consequences for wild species, with long-term effects depending on the ability of the host to evolve resistance. Here, we show that major histocompatibility complex (MHC) genes provided standing genetic variation that enabled rabbits to mount a rapid evolutionary response to the myxoma virus pandemic that began in the 1950s. Using historical and modern specimens starting in 1865 and spanning the pandemic, we found strong parallel shifts in MHC-I allele frequencies across Australia, Britain, and France, alongside population-specific signals. These evolutionary shifts are predicted to alter the peptides presented to T cells. Our results provide evidence that MHC-I is under strong selection in natural populations during a pandemic and that the high polymorphism of MHC may have contributed to the recovery of these populations.

Machine learning surrogate for the leaf PROSPECT-D model and its applications across plant species

Abstract Leaf hyperspectral reflectance (HSR) data have gained increasing attention due to their usage in predicting a range of leaf physiological, biochemical, structural, and photosynthetic traits using machine learning (ML) models. The PROSPECT family of models offers a complementary, mechanistic means to estimate leaf traits from HSR data using model inversion. However, a comprehensive evaluation of the accuracy and transferability of the PROSPECT model across a large set of species is hindered by the limited availability of ground truth data sets. Here, we employed a combination of inversion and forward simulation of the PROSPECT-D model across a broad range of species and identified four narrow wavebands linked to environmental effects. We also introduced a novel framework using partial least squares regression to enable the analysis of the transferability of the machine learning models trained base on the PROSPECT-D across species. This analysis revealed trait-specific patterns of transferability for the machine learning surrogate based on the PROSPECT-D forward model. We then extended this analysis to PROSPECT-D inversion using neural networks and developed a fast, accurate deep-learning-based surrogate inversion approach to estimate leaf traits from measured HSR data. Our data-driven framework paves the way for improving the accuracy of PROSPECT and similar mechanistic models.