Mechanisms Shaping Research Articles

A 3D modelling approach to measuring structural characteristics of bird nest interiors

Abstract Nests are considered extended phenotypes of animals with potentially serious fitness consequences for the survival of offspring. Therefore, nest characteristics may contain valuable information about the underlying ecological and evolutionary mechanisms shaping animal reproduction. However, we currently lack efficient tools to archive nests and measure their characteristics, particularly concerning enclosed nests. Here we developed a step‐by‐step protocol of a 3D modelling approach to measure structural characteristics of nest interiors using the enclosed, dome‐shaped nests of Asian house martins as a test system. We first created the replicas of nest interiors using polyurethane (‘physical replicas’), from which 3D models were constructured using Metashape software (‘digital replicas’). We then estimated the volume and entrance area size of the digital replicas of nest interior using Metashape. To verify that the digital replicas preserve the structural characteristics of the physical replicas, we measured the volume and entrance area size of the physical replicas with Archimedes' drainage method and ImageJ, respectively. We then compared the manual measurements of the physical replicas to the values estimated from digital replicas. The estimates on the interior volume and entrance area size of 50 Asian house martin nests were nearly identical between physical and digital replicas. These results verified that the digital replicas are as reliable as the physical replicas for measuring structural characteristics of nest interior. Our 3D modelling approach allows for easy archiving as digital replicas of nest interiors endure preservation over time much better than actual nest specimens. Furthermore, digital replicas can be shared via internet and analysed for different aspects of morphometrics at any time by anyone. Overall, this tool should facilitate research on the ecology and evolution of animals in relation to nest construction.

Whole-Genome Resequencing Reveals Polygenic Signatures of Directional and Balancing Selection on Alternative Migratory Life Histories.

Migration in animals and associated adaptations to contrasting environments are underpinned by complex genetic architecture. Here, we explore the genomic basis of facultative anadromy in brown trout (Salmo trutta), wherein some individuals migrate to sea while others remain resident in natal rivers, to better understand how alternative migratory tactics (AMTs) are maintained evolutionarily. To identify genomic variants associated with AMTs, we sequenced whole genomes for 194 individual trout from five anadromous-resident population pairs, situated above and below waterfalls, in five different Irish rivers. These waterfalls act as natural barriers to upstream migration and hence we predicted that loci underpinning AMTs should be under similar divergent selection across these replicate pairs. A sliding windows based analysis revealed a highly polygenic adaptive divergence between anadromous and resident populations, encompassing 329 differentiated genomic regions. These regions were associated with 292 genes involved in various processes crucial for AMTs, including energy homeostasis, reproduction, osmoregulation, immunity, circadian rhythm and neural function. Furthermore, examining patterns of diversity we were able to link specific genes and biological processes to putative AMT trait classes: migratory-propensity, migratory-lifestyle and residency. Importantly, AMT outlier regions possessed higher genetic diversity than the background genome, particularly in the anadromous group, suggesting balancing selection may play a role in maintaining genetic variation. Overall, the results from this study provide important insights into the genetic architecture of migration and the evolutionary mechanisms shaping genomic diversity within and across populations.

Effect of Structural Configurations on Mechanical and Shape Recovery Properties of NiTi Triply Periodic Minimal Surface Porous Structures

Based on the advantages of triply periodic minimal surface (TPMS) porous structures, extensive research on NiTi shape memory alloy TPMS scaffolds has been conducted. However, the current reports about TPMS porous structures highly rely on the implicit equation, which limited the design flexibility. In this work, novel shell-based TPMS structures were designed and fabricated by laser powder bed fusion. The comparisons of manufacturability, mechanical properties, and shape recovery responses between traditional solid-based and novel shell-based TPMS structures were evaluated. Results indicated that the shell-based TPMS porous structures possessed larger Young’s moduli and higher compressive strengths. Specifically, Diamond shell structure possessed the highest Young’s moduli of 605.8±24.5 MPa, while Gyroid shell structure possessed the highest compressive strength of 43.90±3.32 MPa. In addition, because of the larger specific surface area, higher critical stress to induce martensite transformation, and lower austenite finish temperature, the Diamond shell porous structure exhibited much higher shape recovery performance (only 0.1% residual strain left at pre-strains of 6%) than other porous structures. These results substantially uncover the effects of structural topology on the mechanical properties and shape recovery responses of NiTi shape memory alloy scaffolds, and confirm the effectiveness of this novel structural design method. This research can provide guidance for the structural design application of NiTi porous scaffolds in bone implants.

A quantitative analysis of bestrophin 1 cellular localization in mouse cerebral cortex.

Calcium-activated ligand-gated chloride channels, beyond their role in maintaining anion homeostasis, modulate neuronal excitability by facilitating nonvesicular neurotransmitter release. BEST1, a key member of this family, is permeable to γ-aminobutyric acid (GABA) and glutamate. While astrocytic BEST1 is well-studied and known to regulate neurotransmitter levels, its distribution and role in other brain cell types remain unclear. This study aimed to reassess the localization of BEST1 in the mouse cerebral cortex. We examined the localization and distribution of BEST1 in the mouse parietal cortex using light microscopy, confocal double-labeling with markers for astrocytes, neurons, microglia, and oligodendrocyte precursor cells, and 3D reconstruction techniques. In the cerebral cortex, BEST1 is more broadly distributed than previously thought. Neurons are the second most abundant BEST1+ cell type in the cerebral cortex, following astrocytes. BEST1 is diffusely expressed in neuronal somatic and neuropilar domains and is present at glutamatergic and GABAergic terminals, with a prevalence at GABAergic terminals. We also confirmed that BEST1 is expressed in cortical microglia and identified it in oligodendrocyte precursor cells, albeit to a lesser extent. Together, these findings suggest that BEST1's role in controlling neurotransmission may extend beyond astrocytes to include other brain cells. Understanding BEST1's function in these cells could offer new insights into the molecular mechanisms shaping cortical circuitry. Further research is needed to clarify the diverse roles of BEST1 in both normal and pathophysiological conditions.

Tailoring smart hydrogels through manipulation of heterogeneous subdomains

The mechanical interactions among integrated cellular structures in soft tissues dictate the mechanical behaviors and morphogenetic deformations observed in living organisms. However, replicating these multifaceted attributes in synthetic soft materials remains a challenge. In this work, we develop a smart hydrogel system featuring engineered stiff cellular patterns that induce strain-driven heterogeneous subdomains within the hydrogel film. These subdomains arise from the distinct mechanical responses of the pattern and film domains under applied mechanical forces. Unlike previous studies that incorporate reinforced inclusions into soft matrices to tailor material properties, our method manipulates the localization, integration, and interaction of these subdomain building blocks within the soft film. This enables extensive tuning of both local and global behaviors. Notably, we introduce a subdomain-interface mechanism that allows for the concurrent customization and decoupling of mechanical properties and shape transformations within a single material system—an achievement rarely accomplished with current synthetic soft materials. Additionally, our use of in-situ imaging characterizations, including full-field strain mapping via digital imaging correlation and reciprocal-space patterns through fast Fourier transform analysis of real-space pattern domains, provides rapid real-time monitoring tools to uncover the underlying principles governing tailored multiscale heterogeneities and intricate behaviors.

Synthesis of a gallic acid-based self-healing waterborne polyurethane with a thermo-responsive dynamic phenol-carbamate network for enhanced mechanical strength, antimicrobial activity, and shape memory properties

To expedite the advancement of multifunctional next-generation smart materials, it is imperative to create polymers derived from renewable, green bio-based resources. This paper presents a direct synthesis of thermo-responsive aqueous polyurethanes by combining gallic acid (GA) with isocyanate groups to form a dynamic phenol-carbamate crosslinked network and the incorporation of the metal-organic framework Cu-MOF-2 for synergistic effects. The resulting GA-based polyurethane (MOF-GWPU) exhibits excellent thermal stability and mechanical properties, achieving an ideal balance between mechanical strength and self-healing efficiency. The MOF-GWPU film demonstrates strong antimicrobial efficacy against Escherichia coli and Staphylococcus aureus, highlighting its exceptional antibacterial performance. The thermo-responsive dynamic covalent bonds enable the MOF-GWPU film to rapidly revert from a temporary shape back to its original form. Post-processing experiments further indicate that the crosslinked GA-PU polymer can be efficiently recycled through solution casting and hot-pressing techniques. This design offers a novel approach and valuable insights for advancing the development of multifunctional smart polymers derived from bio-based resources.

Nanovibrational Stimulation of Escherichia coli Mitigates Surface Adhesion by Altering Cell Membrane Potential.

Mechanical forces shape living matter from the macro- to the microscale as both eukaryotic and prokaryotic cells are force wielders and sensors. However, whereas such forces have been used to control mechanically dependent behaviors in mammalian cells, we lack the same level of understanding in bacteria. Surface adhesion, the initial stages of biofilm formation and surface biofouling, is a mechanically dependent process, which makes it an ideal target for mechano-control. In this study, we employed nanometer surface vibrations to mechanically stimulate bacteria and investigate their effect on adhesion. We discovered that vibrational stimulation at the nanoscale consistently reduces surface adhesion by altering cell membrane potential. Our findings identify a link between bacteria electrophysiology and surface adhesion and provide evidence that the nanometric mechanical "tickling" of bacteria can inhibit surface adhesion.

Comparative Genomics of the World's Smallest Mammals Reveals Links to Echolocation, Metabolism, and Body Size Plasticity.

Originating 30 million years ago, shrews (Soricidae) have diversified into around 400 species worldwide. Shrews display a wide array of adaptations, with some species having developed distinctive traits such as echolocation, underwater diving, and venomous saliva. Accordingly, these tiny insectivores are ideal to study the genomic mechanisms of evolution and adaptation. We conducted a comparative genomic analysis of four shrew species and 16 other mammals to identify genomic variations unique to shrews. Using two existing shrew genomes and two de novo assemblies for the maritime (Sorex maritimensis) and smoky (Sorex fumeus) shrews, we identified mutations in conserved regions of the genomes, also known as accelerated regions, gene families that underwent significant expansion, and positively selected genes. Our analyses unveiled shrew-specific genomic variants in genes associated with the nervous, metabolic, and auditory systems, which can be linked to unique traits in shrews. Notably, genes suggested to be under convergent evolution in echolocating mammals exhibited accelerated regions in shrews, and pathways linked to putative body size plasticity were detected. These findings provide insight into the evolutionary mechanisms shaping shrew species, shedding light on their adaptation and divergence over time.

Females drive postmating reproductive trait evolution across Drosophila species, but not via remating rate.

While traits that contribute to premating sexual interactions are known to be wildly diverse, much less is known about the diversity of postmating (especially female) reproductive traits and the mechanisms shaping this diversity. To assess the rate, pattern, and potential drivers of postmating reproductive trait evolution, we analyzed male and female traits across up to 30 Drosophila species within a phylogenetic comparative framework. In addition to postmating reproductive morphology (e.g., sperm length, reproductive tract length and mass), we also quantified mating behaviors including female remating rate-a common proxy for the strength of postmating sexual selection. We found evidence for strong coevolution between male and female postmating traits (specifically sperm length and sperm storage organ size). However, remating rate was not associated with the rate of evolution or exaggeration of either male or female postmating reproductive morphology, once phylogenetic relatedness was accounted for. We infer that female-mediated and intersexual selection predominantly drive the evolution of our postmating morphological traits, including via divergent male and female interests in controlling paternity. In comparison, remating rate has a complex and likely secondary role in shaping this evolution, in part because this trait can be both a driver and a product of postmating selection.

Racialized Decoupling and Race-Neutral School Integration Policies From the Implementers’ Perspective

Today’s school integration policies in the United States are often “race neutral.” Scholarship on these race-neutral school integration policies finds they do not change the racial and ethnic composition of schools or do so under very specific conditions. Yet, we know relatively little about the mechanisms explaining these outcomes. Building on 2 years of qualitative data collection in two public elementary schools in a New York City implementing a voluntary, race-neutral integration policy, I find school leaders experience a racialized decoupling of their commitment to racial equity from the policy’s race-neutral design, its choice-based design, and the implementation context. I show how school leaders navigated this decoupling and how it led to racialized outcomes. I contribute to our understanding of the mechanisms shaping the outcomes of race-neutral policies, a point of growing importance given recent Supreme Court decisions on higher education.

Programmable Truncated Cuboctahedral Origami Metastructures Actuated by Shape Memory Polymer Hinges

AbstractOver the past few decades, origami‐inspired structures have attracted great attention across various engineering fields due to their unique geometric and mechanical characteristics. Additionally, combining origami structures with active materials is employed to achieve programmable mechanical properties and self‐reconfigurability under external stimuli. In this work, a novel family of truncated cuboctahedral origami metastructures is proposed. These designs integrate shape memory polymers (SMPs) to actively achieve programmable mechanical properties and shape memory behavior. By utilizing SMPs for the creases and stiff materials for the panels, this approach enables deformation along the creases while enhancing the overall structural robustness. The mechanical properties and shape memory processes of these structures are investigated in detail. The proposed origami metastructures exhibit a negative Poisson's ratio and demonstrate excellent energy storage capabilities. Notably, their mechanical properties can be programmed by controlling both temperature and geometric parameters. More particularly, their Poisson's ratio can be tuned within a range of zero to −1. As a result, these truncated cuboctahedral origami metastructures hold significant potential for applications across various engineering domains, particularly in composite structures and active metamaterials.

Above‐ and belowground plant pathogens along elevational gradients: patterns and potential mechanisms

Plant pathogens are important for community assembly and ecosystem functioning and respond to a variety of abiotic and biotic factors, which may change along elevational gradients. Thus, elevational gradients are a valuable model system for exploring how environmental, plant community and soil factors influence pathogen communities. Yet, how these factors influence pathogens in natural ecosystems remains poorly understood. We examined the dynamics of plant fungal pathogens along elevational gradients, as well as the mechanisms shaping these dynamics, by combining a field survey on the Tibetan Plateau with a global meta‐analysis. In the field survey, increasing elevation was associated with a decrease in soil fungal pathogen richness but not in foliar fungal disease symptoms. Elevation was primarily related to soil fungal pathogen richness through abiotic factors, whereas no association was found between elevation and foliar fungal diseases. The meta‐analysis confirmed the generality of our field survey results: elevation was associated with a decrease in soil fungal pathogen richness, but it had no consistent relationship with foliar fungal diseases or pathogens. Thus, above‐ and belowground plant pathogen communities showed distinct elevational patterns, providing new insights into underlying mechanisms.

Development of Higher-Level Vision: A Network Perspective.

Most studies on the development of the visual system have focused on the mechanisms shaping early visual stages up to the level of primary visual cortex (V1). Much less is known about the development of the stages after V1 that handle the higher visual functions fundamental to everyday life. The standard model for the maturation of these areas is that it occurs sequentially, according to the positions of areas in the adult hierarchy. Yet, the existing literature reviewed here paints a different picture, one in which the adult configuration emerges through a sequence of unique network configurations that are not mere partial versions of the adult hierarchy. In addition to studying higher visual development per se to fill major gaps in knowledge, it will be crucial to adopt a network-level perspective in future investigations to unravel normal developmental mechanisms, identify vulnerabilities to developmental disorders, and eventually devise treatments for these disorders.

Comparative single-cell multiome identifies evolutionary changes in neural progenitor cells during primate brain development.

Understanding the cellular and genetic mechanisms driving human-specific features of cortical development remains a challenge. We generated a cell-type resolved atlas of transcriptome and chromatin accessibility in the developing macaque and mouse prefrontal cortex (PFC). Comparing with published human data, our findings demonstrate that although the cortex cellular composition is overall conserved across species, progenitor cells show significant evolutionary divergence in cellular properties. Specifically, human neural progenitors exhibit extensive transcriptional rewiring in growth factor and extracellular matrix (ECM) pathways. Expression of the human-specific progenitor marker ITGA2 in the fetal mouse cortex increases the progenitor proliferation and the proportion of upper-layer neurons. These transcriptional divergences are primarily driven by altered activity in the distal regulatory elements. The chromatin regions with human-gained accessibility are enriched with human-specific sequence changes and polymorphisms linked to intelligence and neuropsychiatric disorders. Our results identify evolutionary changes in neural progenitors and putative gene regulatory mechanisms shaping primate brain evolution.

The species diversity and phylogenetic structure patterns of desert plant communities in the Turpan-Hami region, Xinjiang

Desert plant communities play a crucial role in enhancing desert ecosystem productivity and stability but are highly susceptible to environmental changes owing to their limited resilience and resistance to disturbances, making it essential to understand the factors influencing their diversity patterns and community structure, particularly under the threat of climate change and intensifying droughts. This study focused on the Turpan-Hami desert region, a typical desert ecosystem in which diversity patterns and community structures remain unclear. We established 101 sampling sites ranging from elevations of -134 to 2056m and recorded community information, including species composition, height, coverage, and density, using the sample plot method. The diversity patterns were analyzed using regression analysis, and the phylogenetic structure was assessed. Additionally, Canonical Correspondence Analysis, Mantel tests, and General Linear Models were used to identify the key factors affecting community structure. Our results demonstrated that the species richness and phylogenetic diversity of plant communities exhibited a monotonic increase with elevation, and the phylogenetic structure exhibited low clustering and high dispersion along the elevational gradient. The annual mean temperature emerged as the most significant factor influencing diversity patterns, with soil nutrients, such as total potassium and available phosphorus, also affecting the spatial distribution of diversity. Notably, no significant correlations were found between community phylogenetic structure and abiotic factors, highlighting the complex interactions that drive diversity in the Turpan-Hami region. This study offers valuable insights into the mechanisms shaping desert plant community diversity and is essential for biodiversity conservation efforts in fragile desert ecosystems amid climate change.

Functionalized cellulose nanocrystals-MoS2 nanosheets to tailor brick–mortar architecture of green composite for next-generation electronic packaging

Thermally conductive green composites are an attractive solution for addressing the escalating heat generation in miniaturized microelectronic devices. They offer simplicity in processing, cost-effectiveness, and the ability to potentially degrade, making them well-suited for overcoming heat-related challenges in next-generation electronics and 5G communication applications. Here, innovative work focuses on developing heat dissipation films by imitating artificial brick–mortar architecture. This approach incorporates cellulose nanocrystals-molybdenum disulfide (CNC-M) nanosheets as bifunctional fillers in polypropylene carbonate (PPC) via straightforward casting technology. This novel composite system leverages CNC-M nanosheets “brick” as oriented bonding and thermal linkers within the PPC “mortar,” significantly enhancing heat transfer across the film, enabling efficient heat propagation and overall thermal conductivity to 3.1 W·m−1·K−1, which is 4450.7 % higher than that of pure PPC. The superior heat dissipation capability enables these composite films to efficiently cool smartphone CPUs, shells, and high-power LED modules. When applying the composite film containing 8 wt% CNC-M to smartphone CPUs and cell phone shells, temperatures decrease by 17.9 °C and 8.3 °C, respectively. Notably, LED modules experience a significant temperature reduction of 22.6 °C. This distinctive “brick–mortar” architecture creates a homogeneous trapezoidal layered architecture that significantly enhances strong hydrogen bonding interactions within a composite film, resulting in exceptional mechanical properties, aging durability, and shape memory. The composite film with 5 wt% CNC-M exhibited impressive increases in tensile strength and Young’s modulus of 152.6 % and 1322.2 %, respectively. Furthermore, the composite film exhibited enhanced UV resistance and based materials. This study advances high-performance thermal conductive materials for electronics thermal management, paving the way for more efficient and sustainable solutions in electronics.

Sustainable three-dimensional printing of waste paper-based functional materials and constructs

Three-dimensional (3D) printing is a prominent technology across various industrial sectors, and its increasing popularity urgently calls for sustainable 3D printing materials. However, the availability of such materials remains under exploit. Here, we present a low-cost strategy to harnesses waste papers as a feedstock to develop sustainable 3D printing inks. This approach offers a remarkable printability and circular utilisation of biodegradable paper wastes to produce 3D printed constructs, with desired mechanical properties and shape stability for high temperature applications. Our constructs can be efficiently recycled into inks for reprinting, and our method can be applied to various types of waste papers. By employing multi-material printing, our approach can be extended to produce multi-coloured constructs, security information printings, and mechanically appealing designs. This strategy offers an innovative and sustainable solution that addresses the need for repurposing paper wastes, which would otherwise end up in landfills, while concurrently reducing the reliance on virgin plastics for 3D printing.

Boundary Spanning and Isomorphism Interactions

This study explores the relationship between isomorphism, boundary-spanning, institutional restrictions, and procedural congruence. Using fuzzy (set-theoretic) logic and concepts of causal dependence, we aim to clarify the presence of isomorphism on firms designated as protected origins and boundary-spanning. Employing fuzzy (set-theoretic) logic, we analyse the interactions between isomorphism, institutional restrictions, procedural congruence, and boundary-spanning. By investigating causal dependencies, we uncover the underlying mechanisms shaping firms’ interactions within diverse contexts. Our study reveals that isomorphism interactions can be examined through causal (counterfactual) dependence, emphasising their significance. Furthermore, causal dependence can occur without explicit causation, indicating a transitive relationship involving interactions. Isomorphism can serve as a counterexample to causal dependence, maintaining a boundary interaction between contextual factors and institutional constraints. Additionally, causal dependence involving interactions may not necessarily constrain isomorphism, suggesting an intransitive relationship. Isomorphism may also present a facade of conformity when analysed through causal (counterfactual) dependence, highlighting the complexity of these interactions. This research contributes to the literature by examining the relationship between isomorphism and institutional constraints, providing original insights into boundary-spanning and isomorphism. Moreover, our study advances understanding of causal dependence in explaining firm interactions, with implications for international business.

Effect of adding dune sand to bituminous concrete intended for wearing courses

The 20th century was marked by the development of road infrastructure around the world, which necessitated a great need for pavement materials which in turn had to meet certain geotechnical criteria such as hardness, grain size and cleanliness. A traditional pavement body generally includes gravel, but unfortunately these materials are not available in some areas. From there was born the need to use local materials, such as tuff and dune sand, which exist in abundance and which are inexpensive and which have proven their effectiveness in road construction. The semi grained bituminous concrete SGBC intended for wearing layers, known by the name BC 0/14, generally is prepared by mixing two components: aggregates and bitumen. The design of this material considers several criteria related to one hand to the aggregates, namely mechanical characteristics, shape, and cleanliness of stones, the blue value of the fine, the particle size of the mixture (% passing through), the choice of the bitumen grade and mechanical performance as well the water resistance of asphalt concrete 0/14. The present work aims to study the influence of the substitution of the fraction 0/3 mm of the crushed sand (usually used in this type of materials) by fine dune sand, on the mechanical performance including Duriez and Marshall Stability and water resistance.

Elucidating Supercrystal Mechanics and Nanoparticle Size and Shape Effects under High Pressure

Elucidating Supercrystal Mechanics and Nanoparticle Size and Shape Effects under High Pressure