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R. Balossino G. Pennati F. Migliavacca L. Formaggia A. Veneziani M. Tuveri 《Computer methods in biomechanics and biomedical engineering》2013,16(1):113-123
This work addresses the problem of prescribing proper boundary conditions at the artificial boundaries that separate the vascular district from the remaining part of the circulatory system. A multiscale (MS) approach is used where the Navier–Stokes equations for the district of interest are coupled to a non-linear system of ordinary differential equations which describe the circulatory system. This technique is applied to three 3D models of a carotid bifurcation with increasing stenosis resembling three phases of a plaque growth. The results of the MS simulations are compared to those obtained by two stand-alone models. The MS shows a great flexibility in numerically predicting the haemodynamic changes due to the presence of a stenosis. Nonetheless, the results are not significantly different from a stand-alone approach where flows derived by the MS without stenosis are imposed. This is a consequence of the dominant role played by the outside districts with respect to the stenosis resistance. 相似文献
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Min Zhang;Helin Wang;Ahu Shao;Zhiqiao Wang;Xiaoyu Tang;Shaowen Li;Jiacheng Liu;Yue Ma; 《Liver Transplantation》2024,14(14):2303932
The implementation of solid polymer electrolytes (SPEs) in energy-dense batteries faces severe challenges including sluggish ionic diffusion, oxidation tendency at the cathode interface, dendrite protrusion from the metallic anode, as well as the technological incompatibility with the layer stack-up cell assembly. Herein, an in-situ polymerization strategy is presented to deal with above dilemma for the solid battery prototyping. The in situ cross-linked poly(ethylene glycol) diglycidyl ether is embedded within the nanocellulose framework, endowing SPE membrane with the reinforced mechanical strength (11.31 MPa) at the thickness of 10 µm as well as superior ionic conductance (150 mS). After a rigorous selection, the sacrificial triphenylphosphine additive preferentially oxidizes on the LiNi0.8Mn0.1Co0.1O2 (NCM811) cathode to form the cathode electrolyte interface during the formation charging. Concurrently, the solvated zinc(II) bis(trifluoromethylsulfonyl)imide constructs the polyether/LiZn mosaic layer on the Li foil, which effectively promotes interfacial cation diffusion and horizontal deposits propagation. By pairing the polymerized SPE with the thin-layer Li foil (50 µm) and the NCM811 cathode (25 mg cm−2), the 94 mAh pouch-format cell can realize a gravimetric/volumetric energy density of 397.5 Wh kg−1 and 1197.6 Wh L−1, high-voltage tolerance till 4.5 V, and robust cyclability (95.1% capacity retention for 200 cycles). 相似文献
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Studies addressing the variation of mating system between plant populations rarely account for the variability of these parameters between individuals within populations, although this variability is often non‐negligible. Here, we propose a new direct method based on paternity analyses (Mixed Effect Mating Model) to estimate individual migration (mi) and selfing rates (si) together with the pollen dispersal kernel. Using this method and the KINDIST approach, we investigated the variation of mating system parameters within and between three populations of Fagus sylvatica along an elevational gradient. Among the mother trees, si varied from 0% to 48%, mi varied from 12% to 86% and the effective number of pollen donors (Nepi) varied from 2 to 364. The mating patterns differed along the gradient, the top population showing higher m and lower s, and a trend to higher Nep than the bottom populations. The phenological lag shaped long‐distance pollen flow both within population (by increasing mi at mother‐tree level) and between populations (by increasing m at high elevation). Rather than the mate density, the canopy density was detected as a major mating system determinant within population; it acted as a barrier to pollen flow, decreasing the proportion of long‐distance pollen flow and increasing si. Overall, the effects of ecological factors on mating system were not the same within vs. between populations across the gradient, and these factors also differed from those traditionally found to shape variation at range‐wide scale, highlighting the interest of multiscale approaches. 相似文献
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PEDRO P. OLEA 《Ibis》2011,153(4):832-845
Animals can select breeding sites using non‐social information (habitat characteristics) and social information (conspecific presence or abundance). The availability of both types of information is expected to vary over time during the colonization of a new area, conditioning their use by colonizers. However, if and how both types of information are exploited during the colonization process remains unclear. We hypothesized that non‐social information should be predominant at the beginning of a colonization episode (when conspecific presence is low) and that social information should gain in importance as the colonization progresses. We tested this hypothesis by studying habitat selection by the Griffon Vulture Gyps fulvus, a long‐lived colonial raptor, during a natural colonization process spanning 40 years. In NW Spain, the population showed a sharp increase from 15 breeding pairs in three colonies in the 1970s to 586 breeding pairs in 120 colonies in 2008, expanding its range from 90 km2 in the 1970s to 6403 km2 in 2008, with directions of expansion following areas rich in nesting cliffs. The main determinants of habitat selection varied over time. Livestock density and the characteristics of nesting cliffs were the main predictors of settlement at the onset of colonization. Breeding density of conspecifics increased its importance over time, having the greatest relative weight in habitat selection later in the colonization process. Our results indicated a prevalent use of non‐social information during the early stages of the colonization and an increasing role of social information as the expansion progressed. 相似文献
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Jens Dauber Tobias Purtauf reas Allspach Johannes Frisch Karin Voigtländer Volkmar Wolters 《Global Ecology and Biogeography》2005,14(3):213-221
Aim A better understanding of the processes driving local species richness and of the scales at which they operate is crucial for conserving biodiversity in cultivated landscapes. Local species richness may be controlled by ecological processes acting at larger spatial scales. Very little is known about the effect of landscape variables on soil biota. The aim of our study was to partly fill this gap by relating the local variation of surface‐dwelling macroarthropod species richness to factors operating at the habitat scale (i.e. land use and habitat characteristics) and the landscape scale (i.e. composition of the surrounding matrix). Location An agricultural landscape with a low‐input farming system in Central Hesse, Germany. Methods We focused on five taxa significantly differing in mobility and ecological requirements: ants, ground beetles, rove beetles, woodlice, and millipedes. Animals were caught with pitfall traps in fields of different land use (arable land, grassland, fallow land) and different habitat conditions (insolation, soil humidity). Composition of the surrounding landscape was analysed within a radius of 250 m around the fields. Results Factors from both scales together explained a large amount of the local variation in species richness, but the explanatory strength of the factors differed significantly among taxa. Land use particularly affected ground beetles and woodlice, whereas ants and rove beetles were more strongly affected by habitat characteristics, namely by insolation and soil characteristics. Local species richness of diplopods depended almost entirely on the surrounding landscape. In general, the composition of the neighbouring landscape had a lower impact on the species richness of most soil macroarthropod taxa than did land use and habitat characteristics. Main conclusions We conclude that agri‐environment schemes for the conservation of biodiversity in cultivated landscapes have to secure management for both habitat quality and heterogeneous landscape mosaics. 相似文献
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Annie S. Guillaume;Kevin Leempoel;Aude Rogivue;Felix Gugerli;Christian Parisod;Stéphane Joost; 《Evolutionary Applications》2024,17(7):e13737
Landscape genomic analyses associating genetic variation with environmental variables are powerful tools for studying molecular signatures of species' local adaptation and for detecting candidate genes under selection. The development of landscape genomics over the past decade has been spurred by improvements in resolutions of genomic and environmental datasets, allegedly increasing the power to identify putative genes underlying local adaptation in non-model organisms. Although these associations have been successfully applied to numerous species across a diverse array of taxa, the spatial scale of environmental predictor variables has been largely overlooked, potentially limiting conclusions to be reached with these methods. To address this knowledge gap, we systematically evaluated performances of genotype–environment association (GEA) models using predictor variables at multiple spatial resolutions. Specifically, we used multivariate redundancy analyses to associate whole-genome sequence data from the plant Arabis alpina L. collected across four neighboring valleys in the western Swiss Alps, with very high-resolution topographic variables derived from digital elevation models of grain sizes between 0.5 m and 16 m. These comparisons highlight the sensitivity of landscape genomic models to spatial resolution, where the optimal grain sizes were specific to variable type, terrain characteristics, and study extent. To assist in selecting variables at appropriate spatial resolutions, we demonstrate a practical approach to produce, select, and integrate multiscale variables into GEA models. After generalizing fine-grained variables to multiple spatial resolutions, a forward selection procedure is applied to retain only the most relevant variables for a particular context. Depending on the spatial resolution, the relevance for topographic variables in GEA studies calls for integrating multiple spatial scales into landscape genomic models. By carefully considering spatial resolutions, candidate genes under selection by a more realistic range of pressures can be detected for downstream analyses, with important applied implications for experimental research and conservation management of natural populations. 相似文献
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Huarong Peng Bin Yao Xijun Wei Tianyu Liu Tianyi Kou Peng Xiao Yunhuai Zhang Yat Li 《Liver Transplantation》2019,9(19)
Carbonaceous materials are attractive supercapacitor electrode materials due to their high electronic conductivity, large specific surface area, and low cost. Here, a unique hierarchical porous N,O,S‐enriched carbon foam (KNOSC) with high level of structural complexity for supercapacitors is reported. It is fabricated via a combination of a soft‐template method, freeze‐drying, and chemical etching. The carbon foam is a macroporous structure containing a network of mesoporous channels filled with micropores. It has an extremely large specific surface area of 2685 m2 g?1. The pore engineered carbon structure is also uniformly doped with N, O, and S. The KNOSC electrode achieves an outstanding capacitance of 402.5 F g?1 at 1 A g?1 and superior rate capability of 308.5 F g?1 at 100 A g?1. The KNOSC exhibits a Bode frequency at the phase angle of ?45° of 18.5 Hz, which corresponds to a time constant of 0.054 s only. A symmetric supercapacitor device using KNOSC as electrodes can be charged/discharged within 1.52 s to deliver a specific energy density of 15.2 W h kg?1 at a power density of 36 kW kg?1. These results suggest that the pore and heteroatom engineered structures are promising electrode materials for ultrafast charging. 相似文献
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Lili X. Peng Anthony Ivetac Akshay S. Chaudhari Sang Van Gang Zhao Lei Yu Stephen B. Howell J. Andrew McCammon David A. Gough 《Biopolymers》2010,93(11):936-951
The molecular conformation of certain therapeutic agents has been shown to affect the ability to gain access to target cells, suggesting potential value in defining conformation of candidate molecules. This study explores how the shape and size of poly‐γ‐glutamyl‐glutamate paclitaxel (PGG‐PTX), an amphiphilic polymer‐drug with potential chemotherapeutic applications, can be systematically controlled by varying hydrophobic and hydrophilic entities. Eighteen different formulations of PGG‐PTX varying in three PTX loading fractions (fPTX) of 0.18, 0.24, and 0.37 and six spatial arrangements of PTX (‘clusters’, ‘ends’, ‘even’, ‘middle’, ‘random’, and ‘side’) were explored. Molecular dynamics (MD) simulations of all‐atom (AA) models of PGG‐PTX were run until a statistical equilibrium was reached at 100 ns and then continued as coarse‐grained (CG) models until a statistical equilibrium was reached at an effective time of 800 ns. Circular dichroism spectroscopy was used to suggest initial modeling configurations. Results show that a PGG‐PTX molecule has a strong tendency to form coil shapes, regardless of the PTX loading fraction and spatial PTX arrangement, although globular shapes exist at fPTX = 0.24. Also, less uniform PTX arrangements such as ‘ends’, ‘middle’, and ‘side’ produce coil geometries with more curvature. The prominence of coil shapes over globules suggests that PGG‐PTX may confer a long circulation half‐life and high propensity for accumulation to tumor endothelia. This multiscale modeling approach may be advantageous for the design of cancer therapeutic delivery systems. © 2010 Wiley Periodicals, Inc. Biopolymers 93: 936–951, 2010. 相似文献