Multiscale Investigation of Sodium-Ion Battery Anodes: Analytical Techniques and Applications

The anode/electrolyte interface behavior, and by extension, the overall cell performance of sodium-ion batteries is determined by a complex interaction of processes that occur at all components of the electrochemical cell across a wide range of size- and timescales. Single-scale studies may provide incomplete insights, as they cannot capture the full picture of this complex and intertwined behavior. Broad, multiscale studies are essential to elucidate these processes. Within this perspectives article, several analytical and theoretical techniques are introduced, and described how they can be combined to provide a more complete and comprehensive understanding of sodium-ion battery (SIB) performance throughout its lifetime, with a special focus on the interfaces of hard carbon anodes. These methods target various length- and time scales, ranging from micro to nano, from cell level to atomistic structures, and account for a broad spectrum of physical and (electro)chemical characteristics. Specifically, how mass spectrometric, microscopic, spectroscopic, electrochemical, thermodynamic, and physical methods can be employed to obtain the various types of information required to understand battery behavior will be explored. Ways are then discussed how these methods can be coupled together in order to elucidate the multiscale phenomena at the anode interface and develop a holistic understanding of their relationship to overall sodium-ion battery function.     

Ecological determinants of mating system within and between three Fagus sylvatica populations along an elevational gradient

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 (m_i) and selfing rates (s_i) 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, s_i varied from 0% to 48%, m_i varied from 12% to 86% and the effective number of pollen donors (Nep_i) 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 m_i 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 s_i. 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.     

Local vs. landscape controls on diversity: a test using surface-dwelling soil macroinvertebrates of differing mobility

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.     

Characterization of a clinical polymer‐drug conjugate using multiscale modeling

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 (f_PTX) 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 f_PTX = 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.     

A single species of plant predicts territory occupancy in a population of Peruvian Plantcutters

Habitat selection assessments at multiple spatial scales provide a more complete understanding of the habitat requirements of a species, a matter that is especially useful for managing endangered wildlife. Studies of the diet and population distribution of threatened Peruvian Plantcutters (Phytotoma raimondii) suggest that the presence of Prosopis spp. trees, and the shrubs Grabowskia boerhaaviaefolia and Scutia spicata could explain the scattered distribution of their remnant subpopulations. However, our overall understanding of this remains unclear and incomplete because plantcutters are often absent in areas dominated by Prosopis spp., and other species of plants have largely been overlooked in distribution models. One way to address this issue is to also investigate spatial distribution patterns at finer scales within subpopulations. We modeled the probability of territory occupancy at one of their last strongholds, the Pómac Forest Historical Sanctuary in Peru. Our predictors were defined by biotic interactions using data collected in 2015 and 2016, and previous studies of their diet. We found that Peruvian Plantcutters consumed the leaves, fruits, and flowers of at least nine species of plants, but only G. boerhaaviaefolia shrubs, and the trees Prosopis spp. and Colicodendron scabridum were used more than expected based on availability. We did not observe consumption of S. spicata, but this plant was rare. Territory occupancy was positively influenced only by the availability of G. boerhaaviaefolia, a plant used by Peruvian Plantcutters both as a source of food and nest material. Our results suggest that, despite their diverse diet, Peruvian Plantcutters can be particularly dependent on the availability of G. boerhaaviaefolia. Accordingly, this may explain why both co-occur in most subpopulations. Lastly, although we found that Prosopis spp. did not explain territory occupancy, previous research shows that it does explain their distribution on a broader scale (across subpopulations). This inconsistency across spatial scales suggests a potential key role of Prosopis spp. in guaranteeing dispersal between and connectivity among subpopulations.     

Heterogeneous animal group models and their group-level alignment dynamics: an equation-free approach

We study coarse-grained (group-level) alignment dynamics of individual-based animal group models for heterogeneous populations consisting of informed (on preferred directions) and uninformed individuals. The orientation of each individual is characterized by an angle, whose dynamics are nonlinearly coupled with those of all the other individuals, with an explicit dependence on the difference between the individual's orientation and the instantaneous average direction. Choosing convenient coarse-grained variables (suggested by uncertainty quantification methods) that account for rapidly developing correlations during initial transients, we perform efficient computations of coarse-grained steady states and their bifurcation analysis. We circumvent the derivation of coarse-grained governing equations, following an equation-free computational approach.     

A multiscale theoretical model for diffusive mass transfer in cellular biological media

An integrated methodology is developed for the theoretical analysis of solute transport and reaction in cellular biological media, such as tissues, microbial flocs, and biofilms. First, the method of local spatial averaging with a weight function is used to establish the equation which describes solute conservation at the cellular biological medium scale, starting with a continuum-based formulation of solute transport at finer spatial scales. Second, an effective-medium model is developed for the self-consistent calculation of the local diffusion coefficient in the cellular biological medium, including the effects of the structural heterogeneity of the extra-cellular space and the reversible adsorption to extra-cellular polymers. The final expression for the local effective diffusion coefficient is: D(Abeta)=lambda(beta)D(Aupsilon), where D(Aupsilon) is the diffusion coefficient in water, and lambda(beta) is a function of the composition and fundamental geometric and physicochemical system properties, including the size of solute molecules, the size of extra-cellular polymer fibers, and the mass permeability of the cell membrane. Furthermore, the analysis sheds some light on the function of the extra-cellular hydrogel as a diffusive barrier to solute molecules approaching the cell membrane, and its implications on the transport of chemotherapeutic agents within a cellular biological medium. Finally, the model predicts the qualitative trend as well as the quantitative variability of a large number of published experimental data on the diffusion coefficient of oxygen in cell-entrapping gels, microbial flocs, biofilms, and mammalian tissues.     

A complete categorization of multiscale models of infectious disease systems

Modelling of infectious disease systems has entered a new era in which disease modellers are increasingly turning to multiscale modelling to extend traditional modelling frameworks into new application areas and to achieve higher levels of detail and accuracy in characterizing infectious disease systems. In this paper we present a categorization framework for categorizing multiscale models of infectious disease systems. The categorization framework consists of five integration frameworks and five criteria. We use the categorization framework to give a complete categorization of host-level immuno-epidemiological models (HL-IEMs). This categorization framework is also shown to be applicable in categorizing other types of multiscale models of infectious diseases beyond HL-IEMs through modifying the initial categorization framework presented in this study. Categorization of multiscale models of infectious disease systems in this way is useful in bringing some order to the discussion on the structure of these multiscale models.