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10,561 results for “mechanics”
Decomposition disentangled: a test of the multiple mechanisms by which nitrogen enrichment alters litter decomposition
<ol> <li>Nitrogen (N) enrichment has direct effects on ecosystem functioning by altering soil abiotic conditions and indirect effects by reducing plant diversity and shifting plant functional composition from dominance by slow to fast growing species. Litter decomposition is a key ecosystem function and is affected by N enrichment either by a change in litter quality (the recalcitrance of the plant material) or through a change in soil quality (the abiotic and biotic components of the soil that affect decomposition). How the direct and indirect effects of N alter soil and litter quality remains poorly known.</li> <li>We designed a large grassland field experiment manipulating N enrichment, plant species richness and functional composition in a full factorial design. We used three complementary litterbag experiments, combined in a structural equation model (SEM), to quantify the effects of the treatments and various measures of functional composition and diversity on litter and soil quality and overall decomposition.</li> <li>Our results revealed multiple drivers of litter quality and showed that nutrient concentrations (N and calcium) were about twice as important as structural components (leaf dry matter content, fibres) in determining litter quality. Overall the experimental results suggest that N enrichment increases litter decomposition mostly indirectly through a shift in functional composition toward faster growing plant species, producing higher quality litter. N enrichment also altered soil quality and thereby litter decomposition, through its effects on vegetation cover.</li> <li>Our approach provides a mechanistic tool to test the drivers of litter decomposition across different ecosystems. Our results show that litter quality is determined by several nutrient and structure traits and highlight the importance of considering shifts in plant species composition when assessing the effects of N enrichment on decomposition.</li> </ol>
Data from: Underlying mechanisms and ecological context of variation in exploratory behavior of the Argentine ant, Linepithema humile
Uncovering how and why animals explore their environment is fundamental for understanding population dynamics, the spread of invasive species, species interactions, etc. In social animals, individuals within a group can vary in their exploratory behavior, and the behavioral composition of the group can determine its collective success. Workers of the invasive Argentine ant (Linepithema humile) exhibit individual variation in exploratory behavior, which affects the colony's collective nest selection behavior. Here, we examine the mechanisms underlying this behavioral variation in exploratory behavior and determine its implications for the ecology of this species. We first establish that individual variation in exploratory behavior is repeatable and consistent across situations. We then show a relationship between exploratory behavior and the expression of genes that have been previously linked with other behaviors in social insects. Specifically, we found a negative relationship between exploratory behavior and the expression of the foraging (Lhfor) gene. Finally, we determine how colonies allocate exploratory individuals in natural conditions. We found that ants from inside the nest are the least exploratory individuals, whereas workers on newly formed foraging trails are the most exploratory individuals. Furthermore, we found temporal differences throughout the year: in early-mid spring, when new resources emerge, workers are more exploratory than at the end of winter, potentially allowing the colony to find and exploit new resources. These findings reveal the importance of individual variation in behavior for the ecology of social animals.
Determinants of heart rate in Svalbard reindeer reveal mechanisms of seasonal energy management
<p>Seasonal energetic challenges may constrain an animal's ability to respond to changing individual and environmental conditions. Here we investigated variation in heart rate, a well-established proxy for metabolic rate, in Svalbard reindeer, a species with strong seasonal changes in foraging and metabolic activity. In 19 adult females we recorded heart rate, subcutaneous temperature and activity using biologgers. Mean heart rate more than doubled from winter to summer. Typical drivers of energy expenditure, such as reproduction and activity, explained a relatively limited amount of variation (2–6% in winter and 16–24% in summer), compared to seasonality which explained 75% of annual variation in heart rate. The relationship between heart rate and subcutaneous temperature depended on individual state via body mass, age and reproductive status, and the results suggested that peripheral heterothermy is an important pathway of energy management in both winter and summer. While the seasonal plasticity in energetics make Svalbard reindeer well-adapted to their highly seasonal environment, intraseasonal constraints on modulation of their heart rate may limit their ability to respond to severe environmental change. This study emphasizes the importance of encompassing individual state and seasonal context when studying energetics in free-living animals.</p>
A 3D multi-cellular tissue model of the human omentum to study mechanisms of ovarian cancer metastasis
<p>Here, the design of 3D multi-cellular tissue model of the human omentum is presented to study mechanisms of ovarian cancer metastasis.</p>
Springtail coloration at a finer scale: mechanisms behind vibrant Collembolan metallic colours
<p>The mechanisms and evolution of metallic structural colours are of both fundamental and applied interest, yet most work in arthropods has focused on derived butterflies and beetles with distinct hues. In particular, basal hexapods - groups with many scaled, metallic representatives – are currently poorly studied and controversial, with some recent studies suggesting either that thin- film (lamina thickness) or diffraction grating elements (longitudinal ridges, crossribs) produce these colors in early Lepidoptera and one springtail (Collembola) species. Especially the Collembolan basal scale design, consisting of a singlelamina and longitudinal ridges with smooth valleys lacking crossribs, makes them an interesting group to explore the mechanisms of metallic colouration. Using microspectroscopy, Raman spectroscopy, electron microscopy and FDTD optical modelling we investigated scale colour in seven springtail species that show clear metallic colouration. Reflectance spectra are largely uniform and exhibit a broadband metallic/golden colouration with peaks in the violet/blue region. Our simulations confirm the role of the longitudinal ridges, working in conjunction with thin-film effects to produce a broadband metallic colouration. Broadband colouration occurs through spatial colour mixing which likely results from nanoscale variation in scale thickness and ridge height and distance. These results provide crucial insights into the colour production mechanisms in a basal scale design and highlight the need for further investigation of scaled, basal arthropods.</p>
Bonding mechanism of cyanoacrylate on SiO2 and Au: Spectroscopic studies of the interface
<p>Cyanoacrylates form a highly reactive class of adhesives that develop significant adhesive strength to surfaces within a few seconds. Despite their commercial use, the exact bonding mechanism is virtually unknown. In the present work, we spin coat nm-thin films of ethyl cyanoacrylate on the two model substrates gold and silicon dioxide. The objective of the studies is to identify chemical interactions at the interface between adhesive and metal (oxide) which are possible reasons for film adhesion on the macroscopic scale. For this purpose, thin films of ethyl cyanoacrylate are investigated by X-Ray photoelectron spectroscopy.</p>
Mechanisms of Convergent Egg Provisioning in Poison Frogs
<p>Parental provisioning of offspring with physiological products (nursing) occurs in many animals, yet little is known about the neuroendocrine basis of nursing in non-mammalian species. Within amphibians, maternal provisioning has evolved multiple times, with mothers of some species feeding unfertilized eggs to their developing offspring until tadpoles complete metamorphosis. We conducted field studies in Ecuador and Madagascar to ask whether convergence at the behavioral level provides similar benefits to offspring and relies on shared neural mechanisms in dendrobatid and mantellid poison frogs. At an ecological level, we found that nursing allows poison frogs to provide chemical defenses to their tadpoles in both species. At the neural level, nursing was associated with increased activity in the lateral septum and preoptic area, demonstrating recruitment of shared brain regions in the convergent evolution of nursing within frogs and across vertebrates. In contrast, only mantellids showed increased oxytocin neuron activity akin to that in nursing mammals, suggesting evolutionary versatility in molecular mechanisms. Our findings demonstrate that maternal provisioning provides similar potential benefits to offspring and relies on similar brain regions in poison frog species with convergently evolved toxicity and maternal care.</p>
Supplemental material to 'A variational rigid-block modelling approach to nonlinear elastic and kinematic analysis of failure mechanisms in historic masonry structures subjected to lateral actions'
<p>This repository contains the data necessary to reproduce the content of the article:</p> <blockquote> <p>A variational rigid-block modelling approach to nonlinear elastic and kinematic analysis of failure mechanisms in historic masonry structures subjected to lateral actions (2021). Earthquake Engineering & Structural Dynamics, 1–23. <a href="https://onlinelibrary.wiley.com/doi/full/10.1002/eqe.3512">https://doi.org/10.1002/eqe.3512</a></p> </blockquote> <p>The file <strong>01_Dataset.zip</strong> contains the dataset. The companion document <strong>00_Dataset_description.pdf </strong>describes the content of the dataset, guiding the analyst to its use in order to (i) reproduce the article's results and (ii) compare the article's results to new results brought by the analyst, e.g. by comparison with other numerical models.</p> <p>Version history</p> <p>v2: updated references in 00_dataset description.pdf </p>
Legacy effects of seed dispersal mechanisms shape the spatial interaction network of plant species in Mediterranean forests
<p>1. Seed dispersal by frugivores plays a key role in structuring and maintaining tree diversity in forests. However, little is known about how the spatial legacy of seed dispersal and early recruitment shapes spatial patterns and the spatial interaction network of plant species in mature forest communities.</p> <p>2. We analysed two fully mapped mixed Pine-Oak forest communities using spatial point pattern analysis to determine (i) the detailed structure of the intraspecific spatial patterns of saplings and adults, (ii) the intra- and interspecific spatial interaction of saplings, adults, and saplings relative to adults, (iii) the spatial patterns of species richness at the community level, and (iv) whether seed dispersal mechanisms affect the plant-plant interaction networks and the ratio of adult to sapling neighbourhood densities used as surrogate for spatial self-thinning.</p> <p>3. The intraspecific spatial patterns of saplings and adults showed in general complex nested cluster structures that were similar for sapling and adult stages, despite of substantial self-thinning in some dry-fruited species. The spatial network of saplings was characterized by positive spatial interactions. Adults of several tree species facilitated saplings in their proximity; however, adults of dry-fruited species, but not those of fleshy-fruited ones, lost almost all positive interactions that occurred at the sapling stage. Besides, interaction strength between adults was positive and often significantly stronger if both species were fleshy-fruited. At the community level, the forests were structured into multispecies clumps across all life stages.</p> <p>4. Synthesis. Our analyses highlight the importance of the spatial legacy of seed dispersal and early recruitment in the assembly of plant communities. Particularly, animal seed dispersal can lead to multispecies clusters and positive spatial associations across life stages in Mediterranean forests, with surprisingly little signatures of negative interactions. Our analysis suggests that changes of the spatial structure across plant life stages are driven by seed dispersal mechanisms and subsequent spatial self-thinning, generating a spatial footprint at the sapling stage that conditions the long-term interactions between adult plants. Combining spatial point pattern analysis with network analysis and species traits is a promising way to disentangle the processes underlying observed patterns of local diversity. </p>
Mechanical MNIST crack path extended version
<p>The Mechanical MNIST Crack Path dataset contains Finite Element simulation results from phase-field models of quasi-static brittle fracture in heterogeneous material domains subjected to prescribed loading and boundary conditions. For all samples, the material domain is a square with a side length of 1. There is an initial crack of fixed length (0.25) on the left edge of each domain. The bottom edge of the domain is fixed in x (horizontal) and y (vertical), the right edge of the domain is fixed in x and free in y, and the left edge is free in both x and y. The top edge is free in x, and in y it is displaced such that, at each step, the displacement increases linearly from zero at the top right corner to the maximum displacement on the top left corner. Maximum displacement starts at 0.0 and increases to 0.02 by increments of 0.0001 (200 simulation steps in total). The heterogeneous material distribution is obtained by adding rigid circular inclusions to the domain using the Fashion MNIST bitmaps as the reference location for the center of the inclusions. Specifically, each center point location is generated randomly inside a square region defined by the corresponding Fashion MNIST pixel when the pixel has an intensity value higher than 10. In addition, a minimum center-to-center distance limit of 0.0525 is applied while generating these center points for each sample. The values of Young's Modulus (E), Fracture Toughness (G<sub>f</sub>), and Failure Strength (f<sub>t</sub>) near each inclusion are increased with respect to the background domain by a variable rigidity ratio r. The background value for E is 210000, the background value for G<sub>f</sub> is 2.7, and the background value for f<sub>t</sub> is 2445.42. The rigidity ratio throughout the domain depends on position with respect to all inclusion centers such that the closer a point is to the inclusion center the higher the rigidity ratio will be. We note that the full algorithm for constructing the heterogeneous material property distribution is included in the simulation scripts shared on GitHub. The following information is included in our dataset:</p> <p><span><span><span><span><span><span><span><span><span>(1) Locations of the center of the inclusions (the script to extract rigidity ratio matrices with the desired resolution is available on GitHub), (2) the displacement and damage fields every ten simulation step reported over a uniform 256×256 grid (3) the full resolution displacements and damage fields at both the final displacement step and the damage initiation state, and (4) the force-displacement curves for each simulation.</span></span></span></span></span></span></span></span></span></p> <p><span><span><span><span><span><span><span><span><span>All simulations are conducted with the FEniCS computing platform (FEniCS Project). The code to reproduce these simulations is hosted on GitHub (https://github.com/saeedmhz/phase-field).</span></span></span></span></span></span></span></span></span></p>
Dataset related to the article "Cardiac Biomarkers and Autoantibodies in Endurance Athletes: Potential Similarities with Arrhythmogenic Cardiomyopathy Pathogenic Mechanisms"
<p>This record contains raw data related to the article “Cardiac Biomarkers and Autoantibodies in Endurance Athletes: Potential Similarities with Arrhythmogenic Cardiomyopathy Pathogenic Mechanisms". </p> <p>The "Extreme Exercise Hypothesis" states that when individuals perform training beyond the ideal exercise dose, a decline in the beneficial effects of physical activity occurs. This is due to significant changes in myocardial structure and function, such as hemodynamic alterations, cardiac chamber enlargement and hypertrophy, myocardial inflammation, oxidative stress, fibrosis, and conduction changes. In addition, an increased amount of circulating biomarkers of exercise-induced damage has been reported. Although these changes are often reversible, long-lasting cardiac damage may develop after years of intense physical exercise. Since several features of the athlete's heart overlap with arrhythmogenic cardiomyopathy (ACM), the syndrome of "exercise-induced ACM" has been postulated. Thus, the distinction between ACM and the athlete's heart may be challenging. Recently, an autoimmune mechanism has been discovered in ACM patients linked to their characteristic junctional impairment. Since cardiac junctions are similarly impaired by intense physical activity due to the strong myocardial stretching, we propose in the present work the novel hypothesis of an autoimmune response in endurance athletes. This investigation may deepen the knowledge about the pathological remodeling and relative activated mechanisms induced by intense endurance exercise, potentially improving the early recognition of whom is actually at risk.</p>
Hearing sensitivity: An underlying mechanism for niche differentiation in gleaning bats
<p>Supplemental data, Auditory Brain Response (ABR) measurement files, measured echolocation call parameter, echolocation call sequences</p>
Progressive failure analysis of slip zone soils with strain-softening behavior and implications for landslide triggering mechanisms
<p>All figure for paper entitled “Progressive failure analysis of slip zone soils with strain-softening behavior and implications for landslide triggering mechanisms”</p>
Exercise and Sestrin mediate speed and lysosomal activity in Drosophila by partially overlapping mechanisms-source data
<p>Source data, Figures 1-7</p>
Epigenetic mechanisms of partial dosage compensation in an avian, female heterogametic system
The evolution of genetic sex determination is often accompanied by degradation of one of the proto sex chromosomes. Male heterogametic systems have evolved convergent, epigenetic mechanisms restoring the resulting imbalance in gene dosage between diploid autosomes (AA) and the hemizygous sex chromosome (X). Female heterogametic systems (AA<sub>f</sub> ZW<sub>f</sub>, AA<sub>m</sub> ZZ<sub>m</sub>) tend to only show partial dosage compensation (0.5 < Z<sub>f</sub>:AA<sub>f</sub> < 1) and dosage balance (0.5f:ZZ<sub>m</sub><1). The underlying mechanism remains largely elusive. Here, we quantified gene expression for a total of 15 male and female Eurasian crows (<em>Corvus (corone) spp</em>.) raised under common garden conditions. In addition, we characterized aspects of the regulatory landscape quantifying genome-wide ATAC-seq and 5mC methylation profiles. Partial dosage compensation was explained by female upregulation of Z-linked genes accompanied by increased chromatin accessibility on the female Z chromosome. 5mC methylation was strongly reduced in open chromatin-regions and GC islands and showed chromosome-, but no sex-specific variation. With the exception of the pseudo-autosomal region (PAR), female upregulation of gene expression was evenly spread across the Z chromosome without evidence for regional epigenetic regulation, as has for example been suggested for the male hypermethylated region (MHM) in chicken. Our results support the hypothesis that partial dosage compensation in female heterogametic systems is subject to chromosome-wide, epigenetic control mediated by differential chromatin accessibility between the sexes.
Quantum mechanical double slit for molecular scattering
<p>Interference observed in a double-slit experiment most conclusively demonstrates the wave properties of particles. We construct a quantum mechanical double-slit interferometer by rovibrationally exciting D2 (v=2, j=2) molecules in a biaxial state using Stark-induced adiabatic Raman passage. In D2(v=2, j=2)→D2(v=2, j'=0) rotational relaxation via a cold collision with ground state He, the entangled bond axis orientations in the biaxial state act as two slits generating two indistinguishable quantum mechanical pathways connecting initial and final states of the colliding system. The interference disappears when we decouple the two orientations of the bond axis by separately constructing the uniaxial states of D2, unequivocally establishing the double-slit action of the biaxial state. This double slit opens new possibilities in the coherent control of molecular collisions.</p>
Single-cell profiling of human bone marrow progenitors reveals mechanisms of failing erythropoiesis in Diamond-Blackfan anemia
<p>Ribosome dysfunction underlies the pathogenesis of many cancers and heritable ribosomopathies. Here we investigate how mutations in either ribosomal protein large (RPL) or ribosomal protein small (RPS) subunit genes selectively affect erythroid progenitor development and clinical phenotypes in Diamond-Blackfan anemia (DBA), a rare ribosomopathy with limited therapeutic options. Using single-cell assays of patient-derived bone marrow, we delineated two distinct cellular trajectories segregating with ribosomal protein genotypes: almost complete loss of erythroid specification were observed in <em>RPS</em>-DBA. In contrast, we observed relative preservation of qualitatively abnormal erythroid progenitors and precursors in <em>RPL</em>-DBA. Although both DBA genotypes exhibited a pro-inflammatory bone marrow milieu, <em>RPS</em>-DBA was characterized by erythroid differentiation arrest, whereas <em>RPL</em>-DBA was characterized by preserved GATA1 expression and activity. Compensatory stress erythropoiesis in <em>RPL</em>-DBA exhibited disordered differentiation underpinned by an altered glucocorticoid molecular signature, including reduced <em>ZFP36L2</em> expression<em>,</em> leading to milder anemia and improved corticosteroid response. This integrative analysis approach identified distinct pathways of erythroid failure and defined genotype-phenotype correlations in DBA. These findings may help facilitate therapeutic target discovery.</p> <p> </p>
Attenuating surface gravity waves with mechanical metamaterials
<p>Videos showing simulations of one or more submerged oscillators attenuating surface gravity waves, related to the publication </p> <p><a href="https://aip.scitation.org/author/de+Vita%2C+F">F. De Vita</a><em>, </em><a href="https://aip.scitation.org/author/de+Lillo%2C+F">F. De Lillo</a><em>, </em><a href="https://aip.scitation.org/author/Bosia%2C+F">F. Bosia</a><em>, and </em><a href="https://aip.scitation.org/author/Onorato%2C+M">M. Onorato</a>, "Attenuating surface gravity waves with mechanical metamaterials", Physics of Fluids 33, 047113 (2021) <a href="https://doi.org/10.1063/5.0048613">https://doi.org/10.1063/5.0048613</a></p> <p>Also included are Data relative to Figs. 3, 5, 6, 8 and gnuplot scripts to generate the figures.</p>
Conditional natal dispersal provides a mechanism for populations tracking resource pulses after fire
<p>Animals that persist in spatially structured populations face the challenge of tracking the rise and fall of resources across space and time. To combat these challenges, theory predicts that species should use conditional dispersal strategies that allow them to emigrate from patches with declining resources and colonize new resource patches as they appear. We studied natal dispersal movements in the black-backed woodpecker (<i>Picoides arcticus</i>), a species known for its strong association with recent post-fire forests in western North America. We radio-tracked juveniles originating from seven burned areas and tested hypotheses that environmental and individual factors influence dispersal distance and emigration rates – investigating emigration while additionally accounting for imperfect detection with a novel Bayesian model. We found that juveniles were more likely to leave natal areas and disperse longer distances if they were heavier or hatched in older burned areas where resources are increasingly scarce. Juveniles were also more likely to leave their natal burn if they hatched in a nest closer to the fire perimeter. While dispersing across the landscape, black-backed woodpeckers selected for burned forest relative to unburned available habitat. Together, these results strongly support the hypothesis that black-backed woodpecker populations track resource pulses across fire-prone landscapes, with conditional natal dispersal acting as a mechanism for locating and colonizing newly burned areas. Lending empirical support to theoretical predictions, our findings suggest that changes in resource distribution may shape dispersal patterns and, consequently, the distribution and persistence of spatially structured populations. </p>
FIGURE 1 in Resistance Mechanisms To Abamectin In Iranian Populations Of The Two-Spotted Spider Mite, Tetranychus Urticae Koch (Acari: Tetranychidae)
FIGURE 1: GST banding pattern in the susceptible GUS2 and resistant ISR populations of T. urticae. St: GUS2 mites treated with 1 ppm abamectin solution (using leaf dip method); Sc: GUS2 mites, control; Rt: ISR mites treated with 3000 ppm abamectin solution (using leaf dip method); Rc: ISR mites, control.
ScienceDex guides
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These curated guides explain access requirements, typical timelines, costs, and reuse considerations for widely used research datasets.
Allen Brain Atlas
Allen Brain Atlas is an Allen Institute collection of brain map atlases, datasets, APIs, and analysis tools covering mouse, human, and non-human primate brain resources.
Annotated Behaviour and Observability Dataset (ABODe)
ABODe is a University of Edinburgh DataShare dataset for behavior classification in group-housed mice using home-cage video, identities, bounding boxes, ground-plate positions, and annotator labels.
DANDI Archive for NWB datasets
DANDI is a BRAIN Initiative archive for publishing and sharing neurophysiology data, including electrophysiology, optophysiology, and behavioral data packaged as NWB and related standards.
International Brain Laboratory public data
The International Brain Laboratory public data releases expose standardized mouse decision-making experiments, including Neuropixels recordings, widefield calcium imaging, behavior, and session metadata accessed through the ONE API.
OpenNeuro
OpenNeuro is a free, open platform for sharing neuroimaging datasets, with public search, dataset pages, and download paths for web, S3, DataLad, and the OpenNeuro CLI.