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Honey bees are unintentionally exposed to a wide range of chemicals through various routes in their natural environment, yet research on the cumulative effects of multi-chemical and sublethal exposures on important caste members, including the queen bee and brood, is still in its infancy. The hive's social structure and food-sharing (trophallaxis) practices are important aspects to consider when identifying primary and secondary exposure pathways for residential hive members and possible chemical reservoirs within the colony. Secondary exposures may also occur through chemical transfer (maternal offloading) to the brood and by contact through possible chemical diffusion from wax cells to all hive members. The lack of research on peer-to-peer exposures to contaminants and their metabolites may be in part due to the limitations in sensitive analytical techniques for monitoring chemical fate and dispersion. Combined application of automated honey bee monitoring and modern chemical trace analysis techniques could offer rapid progress in quantifying chemical transfer and accumulation within the hive environment and developing effective mitigation strategies for toxic chemical co-exposures. To enhance the understanding of chemical fate and toxicity within the entire colony, it is crucial to consider both the intricate interactions among hive members and the potential synergistic effects arising from combinations of chemical and their metabolites.

Impact glasses are abundant in the lunar regolith, and Mg isotopes have the potential to trace components from various lunar crustal reservoirs, which have recently been shown to exhibit large Mg isotopic fractionations. However, it remains unclear whether Mg isotopic fractionation occurs during the formation of impact glasses. In this study, we report in situ Mg isotopic and elemental compositional data for agglutinatic glasses returned by the Chang'e 5 mission and obtained using the laser ablation split stream technique. Vesicular textures, Fe–Ni alloys, tiny Fe droplets, and high Ni contents suggest the studied agglutinatic glasses had an impact origin. The agglutinatic glasses exhibit large Mg isotopic fractionation, with δ26Mg values ranging from −1.36 ‰ to −0.01 ‰. The lack of correlations between δ26Mg values, Ni contents, and ratios between volatile and relatively refractory elements (K/La, Rb/Sr, and Ce/Pb) indicate the addition of a meteoritic component and evaporation was not the major process responsible for the measured Mg isotopic variations. In fact, the MgO profiles and correlations between δ26Mg and MgO, Na 2 O, Sc, Sr, CaO/Al 2 O 3 , and δEu reflect Mg isotopic fractionation caused by Mg diffusion from a region with high Mg contents (i.e., more melted pyroxene) to one with lower contents (i.e., more melted plagioclase). Diffusion modeling shows that the duration of diffusion was less than a fraction of a second. Our results indicate that chemical diffusion can produce large Mg isotopic fractionation in impact glasses on a scale of at least tens of microns, and that isotopic fractionation driven by chemical diffusion needs to be considered when the Mg isotopic compositions of impact glasses are used to identify different lunar rock reservoirs. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the impact of magneto hydrodynamic Powell–Eyring fluid on double-diffusive phenomena, with a specific focus on employing the Cattaneo–Christov model. The purpose is to enhance the study's scope by incorporating a heat sink and chemical reactions, thereby analyzing the intricate interplay between heat transfer and chemical processes within the MHD fluid system. To achieve this aim, the study utilizes similarity variables to convert PDEs into ODEs. The primary objective is to gain insights into mass and heat transmission dynamics, placing a particular emphasis on understanding the influence of chemical reactions in the system. For numerical solutions during the analysis, MATLAB's BVP4C solver and the shooting technique are employed. The research further aims to explore various physical constraints, including the fluid Nusselt number and skin friction coefficient. By doing so, the study provides a comprehensive understanding of how the MHD fluid system responds to different conditions. The notable outcomes, presented through graphical representations and tables, include a discernible decrease in fluid velocity with a higher magnetic field parameter and an observable increase in fluid temperature with greater heat source constraints. In summary, this exploration subsidizes significantly to our considerate of complex fluid behavior and holds practical applicability in various scientific and engineering contexts. The novel and physical insights from the study offer valuable understanding into the impact of magneto hydrodynamic Powell–Eyring fluid, particularly concerning double-diffusive phenomena and the intricate interplay between heat transfer and chemical processes.

We develop a numerical model coupling heat and chemical transfers in the building envelope to predict human exposure to pollutants and heating load as affected by changes in temperature and building design. We characterize the effect of temperature variation by season and location on chemical emission dynamics from building materials and the resulting human exposure. Peak concentrations of organics are sensitive to temperatures, and increasing indoor temperature by 10°C doubles the maximum indoor air concentration reached by both VOCs and SVOCs contained in a vinyl flooring. SVOCs mean concentration over the flooring lifetime increases by a factor of 2, and, as a result, the fraction of chemical taken in by the occupants increases by 50%. Occupants' exposure to SVOCs emission in the city of Lille is likely to increase by 20% in 2050 because of temperature increase induced by climate change. [ABSTRACT FROM AUTHOR]

Diffusion in Ni-V solid-solution of A1 structure and Ni3V of D022 structure has been studied by interdiffusion experiments using single-phase (A1/A1 and D022/D022) and two-phase (A1/D022) diffusion couples. Concentration profiles in diffusion-annealed couples were measured by electron-probe microanalysis, and the chemical diffusion coefficient has been evaluated by Boltzmann-Matano analysis. The diffusion coefficient in the A1 phase agrees well with the data in the literature over the ranges of temperature from 900 to 1300 °C and composition from 0 to 25 mol.% V. The diffusion coefficient at 25 mol.% V in the ordered D022 phase, which exists below 1045 °C, is found to be smaller than the extrapolation from the A1 phase toward this temperature range. The much faster diffusion in the D022 phase reported by Khlomov et al. (Phys Met Metall 46(1): 173-175, 1978; Phys Met Metall 46(3):188-191, 1978) could have been caused by transient microstructural evolution - formation of new phases and grains - in their reaction diffusion experiments. [ABSTRACT FROM AUTHOR]

In this study, an incompressible, steady, and magnetohydrodynamic flow of Buongiorno nanofluid through a stretchable surface has been analyzed by adopting a theoretical and numerical approach. This paper involves the impacts of buoyancy forces, thermal conductivity, chemically diffusion, and Arrhenius activation energy. Moreover, the influence of the suspension of gyrotactic microorganisms in the nanofluids is also a part of this study. It is assumed that the behavior of viscosity varies as a function of time and the suspension of microorganisms remain consistent throughout the study. A system of PDEs is reduced to a solvable system of ODEs by applying a suitable similarity transformation. For the sake of numerical solutions, the shooting method has been employed. Wolfram Mathematica has been used to deal with the BVP. In addition, the behaviors of different emerging parameters comprising velocity outline, temperature outline, concentration distribution, the density outline of gyrotactic microorganisms have also been demonstrated by graphical illustrations. From the extracted results, it has been observed that the rising values of viscosity of fluid produce a decline in the velocity parameter. Also, an increment has been noticed in the temperature profile for the growing behavior of the mixed convective factor. [ABSTRACT FROM AUTHOR]

The paper presents the experimental results on ionic conductivity and chemical diffusion in nonstoichiometric nanocrystalline superionic materials NaxCu1.75S (x = 0.1, 0.15, 0.2, 25). High values of the coefficient of conjugated chemical diffusion of cations and electronic holes (1.1∙10−3 and 1.65∙10−3 cm2/s at 410 °C) were observed in the studied electron-ionic conductors Na0.10Cu1.75S and Na0.20Cu1.75S. Activation energies of the total ionic conductivity are measured as 0.30 and 0.40 eV for superionic Na0.10Cu1.75S and Na0.15Cu1.75S phases respectively. In the superionic phases, the measured values of the total ionic conductivity are 2.8, 1.5, and 2.0 S/cm for Na0.10Cu1.75S, Na0.15Cu1.75S, and Na0.20Cu1.75S at 410 °C respectively. Thus, insertion of sodium to copper sulfide did not lead to worse of high ionic conductivity in the superionic phase. [ABSTRACT FROM AUTHOR]

Abstract Background Contemporary biological observations have revealed a large variety of mechanisms acting during the expansion of a tumor. However, there are still many qualitative and quantitative aspects of the phenomenon that remain largely unknown. In this context, mathematical and computational modeling appears as an invaluable tool providing the means for conducting in silico experiments, which are cheaper and less tedious than real laboratory experiments. Results This paper aims at developing an extensible and computationally efficient framework for in silico modeling of tumor growth in a 3-dimensional, inhomogeneous and time-varying chemical environment. The resulting model consists of a set of mathematically derived and algorithmically defined operators, each one addressing the effects of a particular biological mechanism on the state of the system. These operators may be extended or re-adjusted, in case a different set of starting assumptions or a different simulation scenario needs to be considered. Conclusion In silico modeling provides an alternative means for testing hypotheses and simulating scenarios for which exact biological knowledge remains elusive. However, finer tuning of pertinent methods presupposes qualitative and quantitative enrichment of available biological evidence. Validation in a strict sense would further require comprehensive, case-specific simulations and detailed comparisons with biomedical observations.

Mixed conducting cobaltites PrBaCo2−xFexO6−δ (x = 0–0.6) with a double perovskite structure are promising materials for ceramic semi-permeable membranes for oxygen separation and purification due to their fast oxygen exchange and diffusion capability. Here, we report the results of the detailed study of an interplay between the defect chemistry, oxygen nonstoichiometry and oxygen transport in these materials as a function of iron doping. We show that doping leads to a systematic variation of both the thermodynamics of defect formation reactions and oxygen transport properties. Thus, iron doping can be used to optimize the performance of mixed conducting oxygen-permeable double perovskite membrane materials.

The ~2.05 Ga Bushveld Igneous Complex (BIC) in the Kaapvaal Craton, South Africa, with an areal extent of ~65,000 km2, represents one of the largest bimodal A‐type granitoid suites in the world. The igneous activity of this complex begun with the Rooiberg Group of basalt–rhyolite bimodal volcanism, followed by the emplacement of the ultramafic–mafic Rustenburg Layered Suite (RLS), and finally the granitoid rocks of the Rashoop Granophyre (RG) and Lebowa Granite Suite (LGS). In this study, we present our new borehole description and whole‐rock chemical data on the LGS from the relatively unknown western BIC to constrain the origin of the LGS and try to evaluate their geochemical relationship to the Rooiberg Group felsic volcanics. In the western BIC, the LGS is locally represented by the hydrothermally altered Paalkraal Granite and the Kenkelbos Granite that together form a central dome‐like feature. The Veekraal Granite forms the peripheral part of the dome. These granitoids are, in general, coarse‐grained, porphyritic, or equigranular, showing granophyric intergrowth, and consist of quartz, perthitic microcline, and albitic plagioclase with minor opaque and interstitial hornblende/biotite. Our whole‐rock chemical data on western LGS, along with those from the Groblersdal area, eastern BIC (taken as reference), form a cluster in the 'granite' field in the normative Ab–An–Or diagram with mean Or/(Ab+Or) ~0.5 (0.11), and are peralkaline to weakly peraluminous in composition. These A‐type granitoids are strictly 'ferroan' and calc‐alkalic to alkali‐calcic in nature, and evolved through partial melting as evident mainly in process identification plots. In bulk chemical composition, the LGS and high‐SiO2 Rooiberg Group rhyolites overlap with the experimental melts generated during dehydration melting of tonalite–granodiorite, indicating the Archaean Kaapvaal TTG as their possible source. Constraints from experimental petrology further suggest the pressure and temperature of this relatively anhydrous (≤1 wt% H2O) melting were 2–1 kbar (i.e., ≤7.5 km crustal depth) and ~920°C, respectively. As suggested before, the parent magma of the voluminous mafic–ultramafic body (RLS) of the BIC, forming a voluminous magma chamber in shallow crustal depth, provided the heat for this partial melting event. The following igneous event as evident from field description in the literature, our new borehole description and whole‐rock chemical data, were a limited chemical mixing between the parent basaltic magma of the Rooiberg Group and the parent LGS magma under anorogenic condition to generate the metaluminous felsic magma represented by the Rooiberg Group dacite at present. This anorogenic mixing, perhaps guided by chemical diffusion and lasted for ≤950 ka, modified the major oxide compositions (except Na), and/or transitional elements (Sc, V, Co, and Ni), LILEs (Rb, Sr, and Ba), REEs, HFSE (Y, Zr, Nb, and Ta), actinide (Th and U), and possibly Sr‐isotopic compositions of both the parent LGS and Rooiberg Group basaltic magmas. The petrogenetic model observed for the BIC is perhaps unique in explaining geochemical and isotopic variations observed in bimodal A‐type granitoid/volcanic suites like the Karoo Igneous Province. [ABSTRACT FROM AUTHOR]

The ~183 Ma Karoo Continental Flood Basalt (CFB), southern Africa, formed during a period of major crustal extension prior to Gondwana breakup. To explain the 'lithospheric contamination' observed in its whole‐rock chemical and isotopic data various models have been proposed, such as different subcontinental lithospheric mantle (SCLM) sources or interaction between a mantle plume and SCLM or subducted material. A re‐assessment of data in the literature from the Northern Karoo Province, combined with new petrographic, whole‐rock chemical and Sr‐Nd isotopic data of basaltic and dacite/trachydacite samples from the southern Lebombo suggest that chemical diffusion between low‐Ti basaltic/picritic magmas and high‐SiO2 rhyolite parent melt may have caused this 'lithospheric contamination'. Such slow chemical diffusion, which is posited to have developed during formation of this CFB, can explain the bimodal Karoo basalt‐rhyolite association, the wide variation in SiO2 content (~62–78 wt%) in the dacite/rhyolites, and variable 87Sr/86Sr (183 Ma) and ɛNd (183 Ma) isotope ratios of the Karoo picrites and basalts (0.7037 to 0.7102; 3.58 to −33.52, respectively) and dacites/rhyolites (0.7032 to 0.7152; 0.44 to −17.19). The intermediate incompatible trace element and isotopic compositions of the Karoo high‐Ti basalt/picrite suggest that these rocks could have evolved by magma mixing through chemical diffusion. Our geochemical model for the northern Karoo CFB province involves existence of a voluminous hot (>1,000°C) low‐Ti basaltic magma chamber with remnant picritic melts at shallow crustal depth (~4 km) during major crustal extension. Magma storage was relatively protracted, resulting in significant volumes of partial melt of the surrounding granitoids of the Kaapvaal Craton under relatively anhydrous condition, leading to generation of A‐type high‐SiO2 rhyolite parent magma at pressure of ~1.5 kbar and temperature of ~930°C. This was followed by chemical diffusion of selected elements [LREE, HFSE, and some LILE (K, Rb, Ba, Pb)] and self‐diffusion of Sr and Nd isotopes in these two melts, which generated the observed litho‐type variations in Karoo CFB. [ABSTRACT FROM AUTHOR]

To better understand the role and extent of inter-mineral diffusion during subsolidus processes, we investigated the iron and magnesium isotopic compositions of olivine, orthopyroxene, and chromite separates from the Peridotite Zone of the Stillwater Complex. Olivine and orthopyroxene show limited Mg isotopic variations, with δ26Mg values ranging from −0.40 to −0.26‰ and from −0.29 to −0.22‰, respectively. In contrast, chromite displays extremely large Mg isotopic variations, with δ26Mg values ranging from −0.05 to +0.84‰. The δ56Fe values of olivine and orthopyroxene range from 0.00 to +0.17‰ and −0.04 to +0.06‰, respectively, whereas those of chromite range from −0.09 to +0.13‰. Most olivine-orthopyroxene pairs in our samples show no clear Fe-Mg isotopic differences, whereas silicate and coexisting chromite pairs plot away from theoretically predicted equilibrium lines, indicating disequilibrium inter-mineral fractionation. Higher δ56Fe values in silicates than in chromite and significantly higher δ26Mg values in chromite than in silicates indicate that subsolidus re-equilibration is responsible for the observed disequilibrium Fe-Mg isotope fractionation. We develop a quantitative model based on the investigated olivine and chromite to reproduce the observed kinetic Fe-Mg isotope fractionations. Our model results indicate a systematic difference between the Fe and Mg isotope fractionation factors, β , of olivine (β Fe ≈ 0.27 and β Mg ≈ 0.16) and chromite (0.03 < β Fe < 0.08 and 0.05 < β Mg < 0.16). This study demonstrates that combined investigations of the Fe-Mg isotopic compositions of cumulus minerals provide more recognizable and more reliable information on inter-mineral diffusion among igneous minerals in magma chambers than elemental analyses alone. [ABSTRACT FROM AUTHOR]

To investigate the petrogenesis of Fe-Ti oxide ore deposits, we report Mg and Fe isotopic compositions for coexisting olivine, clinopyroxene and ilmenite in Fe-Ti oxide ores, magnetite-bearing gabbros and gabbros from the Panzhihua Fe-Ti-oxide-bearing layered mafic intrusion, Southwest China. Olivine and clinopyroxene have δ26Mg values ranging from −0.47 to −0.32‰ and −0.40 to −0.18‰, and δ57Fe values from −0.21 to +0.23‰ and −0.16 to +0.20‰, respectively. Most of these mineral pairs display disequilibrium inter-mineral fractionation as they fall off the theoretically predicted equilibrium fractionation lines. Ilmenites from oxide ores and magnetite-bearing gabbros (Group 1) have mantle-like or lower δ26Mg values of −0.80 to −0.13‰ and δ57Fe values of −0.33 to −0.23‰, and those from gabbros (Group 2) display slightly to extremely higher δ26Mg values of +0.48 to +23.10‰ and much lower δ57Fe values of −0.59 to −0.33‰. The δ26Mg negatively correlates with δ57Fe in all ilmenites, which cannot be explained by simple extensive fractional crystallization or Soret diffusion. Instead, the negative correlations between δ26Mg and δ57Fe and between MgO and FeO in ilmenites result from Mg-Fe inter-diffusion among ilmenite, silicate minerals and high-Ti basaltic melts. The extremely large isotopic variations were produced by the large Mg activity gradient between different types of ilmenites and melts, which was enhanced by interstitial liquid immiscibility process. Our study therefore demonstrates that combined Mg-Fe isotopes can be used to trace the genesis of Fe-Ti-oxide-bearing ore. [ABSTRACT FROM AUTHOR]

We consider a simplified chemotaxis model of tumor angiogenesis, described by a Keller-Segel system on the two dimensional infinite cylindrical domain (x , y) ∈ R × S λ , where S λ is the circle of perimeter λ > 0. The domain models a virtual channel where newly generated blood vessels toward the vascular endothelial growth factor will be located. The system is known to allow planar traveling wave solutions of an invading type. In this paper, we establish the nonlinear stability of these traveling invading waves when chemical diffusion is present if λ is sufficiently small. The same result for the corresponding system in one-dimension was obtained by Li-Li-Wang (2014) [17]. Our result solves the problem remained open in Chae-Choi-Kang-Lee (2018) [3] at which only linear stability of the planar traveling waves was obtained under certain artificial assumption. [ABSTRACT FROM AUTHOR]

Diffusion coefficients of electrode materials are often determined using galvanostatic (GITT) or potentiostatic intermittent titration technique (PITT), electrochemical impedance spectroscopy (EIS) or cyclic voltammetry (CV). However, these methods require special care as for each, their formal derivations use quite restrictive assumptions. As an alternative, a machine learning model is developed to extend a previously proposed optical method of studying lithium transport by operando microscopy. The herein reported model enables the measurement of concentration-dependent diffusion coefficients. For this purpose, a python code is developed that determines concentration profiles from RGB images using support vector regression (SVR), a flexible machine learning tool. To evaluate the diffusion coefficient, an inverse Boltzmann-Matano concept is applied. Representing the diffusion coefficient with generalized Redlich-Kister polynomials, concentration profiles are predicted and fit to the measured data. The method is demonstrated here on the example of delithiation of LiMn 2 O 4 , but it can, in-principle, be extended to any other battery material showing significant optical response on lithiation, which most of them do. [Display omitted] [ABSTRACT FROM AUTHOR]

The oxygen exchange process between the gas phase and a mixed conducting solid oxide was simulated by application of finite element modeling (FEM). The solid oxide was covered by inert surface particles of different shape and size. The effect of spherical, ellipsoidal, rectangular, and dendritic surface particles on the oxygen exchange kinetics was elaborated in detail. Relaxation curves for the total amount of exchanged oxygen upon an instantaneous change of the oxygen activity (partial pressure) of the surrounding atmosphere were calculated. One-dimensional analytical solutions of the diffusion equations were fitted to the numerically calculated relaxation curves, yielding apparent chemical diffusivities and surface exchange coefficients. The FEM simulations of the oxygen exchange process were carried out as a function of surface coverage for the various particle types. The apparent surface exchange coefficient decreased with increasing surface coverage. In case of small spherical and ellipsoidal particles with a fairly small extension of the shorter axis (large aspect ratio) the surface exchange coefficient decreased almost linearly with increasing surface coverage caused by the reduction of the active (uncovered) surface area. An additional decrease of the surface exchange coefficient (non-linear variation with surface coverage) was observed with respect to dendritic particles. This peculiar behavior could be interpreted in terms of flux constriction effects, i.e. lateral diffusion processes underneath the inert surface particles. The surface area blocked for the exchange reaction seems to be significantly larger than the cross-section of the dendritic surface particles. • Modeling the effect of inert surface particles on oxygen exchange kinetics • Finite element simulations of oxygen exchange relaxation curves • Remarkable decrease of surface exchange coefficient by dendritic surface particles • Lateral diffusion processes underneath the particles cause flux constriction effect. • Additional decrease of surface reaction rate by flux constriction [ABSTRACT FROM AUTHOR]

Interdiffusion coefficients are key parameters for the solidification process of liquid alloys. However, the determination of interdiffusion coefficients in liquid metals at high temperatures is a challenging and extensive task, due to a variety of potential systematic errors. In recent years we have developed an X-ray in situ shear cell method for the measurement of interdiffusion coefficients in binary metallic melts. This technique enables the monitoring of the experiment in order to exclude fatal errors. Utilizing X-ray contrast, the method also provides a time-resolved concentration distribution. Such an in situ data set contains significantly more information than ex situ evaluated experiments. Available analyzing strategies do not fully exploit this potential yet. We present three new analyzing approaches that are able to retrieve a concentration-dependent interdiffusion coefficient from only one in situ data set. In that way, larger concentration differences become accessible for an experiment, which considerably decreases efforts. Using simulations, the approaches are checked for robustness. Furthermore, the approaches are run on real in situ data from a binary (0 to 9 at% Au-content) Al–Au alloy at 1000 °C which results in a concentration-dependent interdiffusion coefficient within the measured concentration range.

Abstract Controlled cooling‐rate experiments were conducted on olivine‐hosted melt inclusions to characterize the development of compositional zoning observed in natural inclusions. All of the experimentally cooled inclusions are zoned due to olivine crystallization on the inclusion wall and diffusive exchange between the boundary layer adjacent to the growing olivine and the inclusion centers. Experimentally cooled inclusions are characterized by lower MgO and FeO and higher SiO2, Al2O3, and Na2O (and other incompatible oxides) near the inclusion wall relative to the inclusion center. The compositions at the centers of inclusions are susceptible to modification by diffusion, particularly for small inclusions and those subjected to low cooling rates. Uphill diffusion is evident in every oxide and is recognized by local extrema along a diffusion profile. CaO exhibits the most extreme manifestation of uphill diffusion, and a model attributes the diffusion behavior in CaO to solution nonideality in the boundary layer liquid. MgO profiles from experimentally cooled inclusions were fit with a diffusion model by varying the cooling rate. The cooling rates that resulted in the best fit models were always within a factor of 2 and typically within ±10% of the experimental cooling rates, which ranged from 70 to 50,000 °C/hr. The model was applied to MgO profiles across natural glassy olivine‐hosted melt inclusions from Hawaii and the shergottite Yamato 980459. Cooling rates from zoned melt inclusions in Yamato 980459 range from 85 to 1,047 °C/hr (mean = 383±43 °C/hr, 1σ, n=8) and support the hypothesis that the sample erupted at or near the Martian surface.

Molecular diffusion of chemical species in subsurface environments─rock formations, soil sediments, marine, river, and lake sediments─plays a critical role in a variety of dynamic processes, many of which affect water chemistry. We investigate and demonstrate the occurrence of anomalous (non-Fickian) diffusion behavior, distinct from classically assumed Fickian diffusion. We measured molecular diffusion through a series of five chalk and dolomite rock samples over a period of about two months. We demonstrate that in all cases, diffusion behavior is significantly different than Fickian. We then analyze the results using a continuous time random walk framework that can describe anomalous diffusion in heterogeneous porous materials such as rock. This methodology shows extreme long-time tailing of tracer advance as compared to conventional Fickian diffusion processes. The finding that distinct anomalous diffusion occurs ubiquitously implies that diffusion-driven processes in subsurface zones should be analyzed using tools that account for non-Fickian diffusion.

Extended diffusion layers of the cubic C15 and hexagonal C14 and C36 NbCo 2 Laves phases with concentration gradients covering their entire homogeneity ranges were produced by the diffusion couple technique. Single-phase and single-crystalline micropillars of the cubic and hexagonal NbCo 2 Laves phases were prepared in the diffusion layers by focused ion beam (FIB) milling. The influence of chemical composition, structure type, orientation and pillar size on the deformation behavior and the critical resolved shear stress (CRSS) was studied by micropillar compression tests. The pillar orientation influences the activated slip systems, but the deformation behavior and the CRSS are independent of orientation. The deformation of the smallest NbCo 2 micropillars (0.8 µm in top diameter) appears to be dislocation nucleation controlled and the CRSS approaches the theoretical shear stress for dislocation nucleation. The CRSS of the 0.8 µm-sized NbCo 2 micropillars is nearly constant from 26 to 34 at.% Nb where the C15 structure is stable. It decreases as the composition approaches the Co-rich and Nb-rich boundaries of the homogeneity range where the C15 structure transforms to the C36 and the C14 structure, respectively. The decrease in the CRSS at these compositions is related to the reduction of shear modulus and stacking fault energy. As the pillar size increases, stochastic deformation behavior and large scatter in the CRSS values occur and obscure the composition effect on the CRSS. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Controlled cooling‐rate experiments were conducted on olivine‐hosted melt inclusions to characterize the development of compositional zoning observed in natural inclusions. All of the experimentally cooled inclusions are zoned due to olivine crystallization on the inclusion wall and diffusive exchange between the boundary layer adjacent to the growing olivine and the inclusion centers. Experimentally cooled inclusions are characterized by lower MgO and FeO and higher SiO2, Al2O3, and Na2O (and other incompatible oxides) near the inclusion wall relative to the inclusion center. The compositions at the centers of inclusions are susceptible to modification by diffusion, particularly for small inclusions and those subjected to low cooling rates. Uphill diffusion is evident in every oxide and is recognized by local extrema along a diffusion profile. CaO exhibits the most extreme manifestation of uphill diffusion, and a model attributes the diffusion behavior in CaO to solution nonideality in the boundary layer liquid. MgO profiles from experimentally cooled inclusions were fit with a diffusion model by varying the cooling rate. The cooling rates that resulted in the best fit models were always within a factor of 2 and typically within ±10% of the experimental cooling rates, which ranged from 70 to 50,000 °C/hr. The model was applied to MgO profiles across natural glassy olivine‐hosted melt inclusions from Hawaii and the shergottite Yamato 980459. Cooling rates from zoned melt inclusions in Yamato 980459 range from 85 to 1,047 °C/hr (mean = 383±43 °C/hr, 1σ, n=8) and support the hypothesis that the sample erupted at or near the Martian surface. Plain Language Summary: Melt inclusions, which are small amounts of magma that become trapped within a growing crystal, are widely used by geologists as snapshots of the chemical evolution of magmas as they cool and crystallize. We performed a set of experiments that simulated the cooling of magmas by subjecting olivine crystals containing melt inclusions to a range of cooling rates. We then exposed the melt inclusions and measured the chemical zonation that developed during cooling. The experiments demonstrate that on the relatively short timescales of eruptions, the compositions of melt inclusions can be drastically changed. The diffusion equation, which was modified in a numerical code to describe a melt inclusion, was used to model the experimental zonation data. The cooling rates that resulted in the best fit model matched the known experimental rates to within a factor of 2, which is very accurate given that the experimental rates ranged from 70 to 50,000 °C/hr. The model was used to calculate the cooling rates of natural inclusions with unknown cooling histories from Hawaii and a meteorite from Mars. The results for the Martian meteorite support the hypothesis that the sample represents a magma that cooled rapidly, likely as a lava flow on the Martian surface. Key Points: A model of MgO diffusion across olivine‐hosted melt inclusions can be used to calculate eruptive cooling rates to within a factor of 2Chemical diffusion in melt inclusions is complicated by multicomponent effects due to the development of steep compositional gradientsThe model was used to calculate eruptive cooling rates for zoned glassy inclusions from Hawaii and Mars [ABSTRACT FROM AUTHOR]

Summary: An analytical model for contaminant transport in multilayered capped contaminated sediments including the degradation of organic contaminant is presented. The effect of benthic boundary layer was treated as a Robin‐type boundary condition. The results of the proposed analytical model agree well with experimental data. The biodegradation of contaminant in bioturbation layer shows a significant influence on the flux at the surface of system. The maximum flux for the case with t1/2,bio = 0.07 year can be 4.5 times less than that of the case without considering the effect of biodegradation. The thickness of bioturbation layer has a significant effect on the performance of the capped contaminated sediment. The maximum flux for the case with lbio = 15 cm can be 17 times larger than that of the case without bioturbation layer. This may be because the effective diffusion coefficient of sand cap can be 28 times lower than Dbio. The mass transfer coefficient should be considered for the design of the capping system as the contaminant concentration at the top of system for the case with kbl = 2.5 × 10−5 cm/s can be 13 times greater than that of the case with kbl = 10−4 cm/s. The proposed analytical model can be used for verification of complicated numerical methods, evaluation of experimental data, and design of the capping contaminated sediment systems with reactive cap layers. [ABSTRACT FROM AUTHOR]

The diffusive mass exchange of eight major elements (Si, Ti, Al, Fe, Mg, Ca, Na, and K) between natural, nominally dry shoshonitic and rhyolitic melts was studied at atmospheric pressure and temperatures between 1230 and 1413 °C using the diffusion couple method. For six elements, effective binary diffusion coefficients were calculated by means of a concentration-dependent method to obtain an internally consistent data set. Among these components, the range in diffusivities is restricted, pointing to a coupling of their diffusive fluxes. We find that the calculated diffusivities fit well into the Arrhenius relation, with activation energies (Ea) ranging from 258 to 399 kJ/mol in rhyolitic (70 wt% SiO2) melt and from 294 to 426 kJ/mol in the latitic melt (58 wt% SiO2). Ti shows the lowest Ea, while Si, Fe, Mg, Ca, and K have a similar value. A strong linear correlation is observed between logD0 and Ea, confirming the validity of the compensation law for this system. Uphill diffusion is observed in Al in the form of a concentration minimum in the rhyolitic side of the couple, (at ca. 69 wt% SiO2), and in Na indicated by a maximum in the shoshonitic side (ca. 59 wt% SiO2). Fe shows weak signs of uphill diffusion, possibly due to the contribution of ferric iron. The data presented here extend the database of previously published diffusivities in the shoshonite-rhyolite system (González-García et al. 2017) toward the water-free end and allows us to better constrain the water-dependence of major element diffusion at very low water concentrations. Combining both data sets, we find that logD is proportional to the square root of water concentration for a range between 0 and 2 wt% H2O. These results are of particular interest in the study of mass transfer phenomena in alkaline volcanic systems. [ABSTRACT FROM AUTHOR]

The effect of lithium salt on dynamics in highly cross-linked poly(ethylene oxide) (PEO) has been investigated. The elaboration uses results of dielectric relaxation studies. It turns out that competition of electric and structural relaxation coins conductivity mechanism. Neat cross-linked PEO with low mesh size can be transferred in super-cooled liquid state. Then, cross-linked PEO behaves like a hydrogen-bonded liquid since crystallization is strongly suppressed. As a result, one observes slow Debye-like relaxation at low temperature. It disappears after addition of salt since interaction of salt with polymer chains is stronger than the hydrogen-bonded network in the neat polymer. Analysis of tangent-loss spectra shows: Particle density governing dc conductivity does not depend on temperature at low concentration of added salt. It increases with temperature for neat cross-linked PEO and PEO loaded with sufficiently high concentration of salt. Prevention of crystallization requires a tight network of cross-links. Scaled representations of relevant impedance data for neat cross-linked PEO over extended ranges of frequency and temperature reveal that electric and structural relaxations are independent of temperature to good approximation at low and high frequency. There is a range of damped network oscillations, sandwiched between these limits, where relaxation becomes dependent on temperature. This range lessens with temperature. It does not occur at all in salt-comprising cross-linked PEO. [ABSTRACT FROM AUTHOR]

The impact of inert particles located at the surface of mixed ionically/electronically conducting oxide ceramics on the oxygen exchange properties has been studied by numerical modeling of the underlying transport processes. In particular, the phenomenological transport equations have been solved by application of the finite element method. Relaxation curves of the total amount of exchanged oxygen upon an instantaneous change of the oxygen activity in the surrounding atmosphere have been simulated as a function of surface coverage as well as particle size. Both thick samples (thickness, 0.05 cm) and thin samples (thickness, 5 μm) have been investigated. Apparent kinetic parameters, viz. chemical diffusion coefficient and chemical surface exchange coefficient, have been extracted from the simulated relaxation curves by means of nonlinear least squares fitting of appropriate analytical solutions. Basically, the surface exchange reaction is blocked by the inert surface particles, leading to pronounced flux constriction effects. Moreover, in the case of thin samples, relaxation curves can be found which consist of two separate relaxation times. The first time constant is related to the fast relaxation process at free (uncovered) surface regions (usually surface reaction controlled kinetics), while the second relaxation time is caused by two-dimensional diffusion in the thin sample underneath the blocking surface particles. [ABSTRACT FROM AUTHOR]

• Incremental variational formulation is developed for chemomechanical problem of heterogeneous composites. • Computation Homogenization-based FE2 solving algorithm is realized for heterogeneous composite. • Chemomechanical properties of composites are solved by two-scale consistent tangential solving algorithm. • The 'moment of mass concentration' is discussed for heterogeneous composites under mass diffusion. The chemomechanical properties of heterogeneous composites under mass diffusion are of significance in modern advanced technology and engineering applications. A homogenization-based two-scale chemomechanical model is developed for heterogeneous composites undergoing chemical mass diffusion. A two-scale incremental variational formulation is established for heterogeneous composites consisting of multiconstituents featuring local dissimilar diffusion-deformation properties. The minimization problems for coupled chemomechanical behaviors are solved for both macrostructure and microstructure contexts, where the macroscopic material properties are extracted from the results of local boundary value problem on the nested representative volume elements (RVEs). Through a staggered finite element method (FEM) implementation procedure, the proposed homogenization-based two-scale solution algorithm is implemented in the FEM package ABAQUS (V6.14). The developed variational model and tangential algorithm is checked by solving chemomechanical properties of particles enforced composite, where several numerical examples are conducted applying two-scale solution algorithm and validated by full-scale simulations. Parametric studies are carried out on the size effects of RVEs, with respect to the 'inertia effect' associated with 'moment of mass concentration', and the coupling mechanisms are discussed for mechanical and chemical solutions. To the end, the inelastic dissipations are solved on subscale BVPs and their effects on the mechanical deformation and chemical mass diffusion are checked. The contributions of this work are mainly two-folds. One is the theoretical advance for self-consistent homogenization modeling of the coupled multi-physics of heterogeneous composites, and a rigorous FE2 solution procedure. The other is providing numerical reference for evaluation of approximation algorithm as well as advanced data-driven method, which is needed for high-efficient material design. [ABSTRACT FROM AUTHOR]

Abstract The link between multicomponent diffusion and crystal growth has been investigated in a sodium borosilicate glass of interest to the nuclear industry. The growth rate of cristobalite, the principal crystal formed in this system, was studied between 700 °C and 900 °C. The growth rate was found to be linear with time and had an activation energy of 60 ± 12 kJ.mol−1 which is close to the activation energy of sodium self-diffusion. Analysis of compositions around crystals and in the bulk of the glass revealed compositional gradients assigned to multicomponent diffusion. A diffusive mechanism involving exchange between silicon and boron appears to drive melt compositions near the crystals while in the bulk of the glass, another diffusive mechanism is predominant, consisting of exchange of silicon and sodium, justifying the value calculated for the activation energy of crystal growth. These results were then used for modeling growth rates in our glass. Highlights • A borosilicate glass with molar composition 68SiO 2 -18B 2 O 3 -14Na 2 O mainly crystallizes cristobalite between 700 °C and 900 °C. • The linear cristobalite growth has an activation energy close to the activation energy for sodium self-diffusion. • The evolution of compositions around crystals during crystal growth is driven by chemical diffusion. • The growth rate can be modeled using the dominant eigenvalue of the diffusion matrix as a diffusion coefficient. [ABSTRACT FROM AUTHOR]

A NiV2O6-25 wt % V2O5 molten-oxide material has been prepared and characterized, and its transport properties (electrical conductivity, oxygen ion transport number, and oxygen permeability) have been studied in the temperature range 680-700°C. The results demonstrate that the molten-oxide membrane material obtained possesses high selective oxygen permeability (KO2 = (2.5-5.6) × 10-10 mol/(cm s) in the range 680-740°C and jO2jN2 ~ 1500) and can be used in separators for the preparation of extrapure oxygen from air. [ABSTRACT FROM AUTHOR]

Abstract Compositional profiles and mapping of selected mafic microgranular enclaves (MMEs) in Muchen quartz monzonite in eastern South China give constraints on the interaction between mingling mafic and felsic magmas. The intrusion is a typical I-type MME-bearing magnetite-series granitoid in western Pacific. The MMEs and host quartz monzonite are not deformed and have similar magnetic fabrics, which does not support the MMEs are restites or earlier solidified mafic rocks but implies mafic magma globules flowed with felsic magma. The two MMEs represent mafic magma interacting with felsic magma at early and late stage, respectively. The late-stage MME has a Hbl-Bt-Kfs-Pl-Mag assemblage. The early-stage MME has a Cpx-Bt-Kfs-Pl-Mag assemblage with a rim similar to the late-stage MME. Acicular apatite implies rapid cooling of the mafic magmas; however, the similar isotopic ratios and mafic silicate compositions of the MME and quartz monzonite indicate partial equilibrium during magma interactions. Al-in-hornblende estimates the pluton emplacement at ~3.1–3.6 km and therefore the magma mingling-mixing still worked at shallow levels. Most trace element Harker diagrams do not produce linear variation trends and magma mixing cannot solo explain such a pattern. Enrichments of Na 2 O, REE, Y, Nb, Ta, Ga, Fe3+ and depletions of K 2 O, Rb, Ba, Sr in the MMEs through diffusion caused noticeable chemical differentiation of both mafic and felsic magmas. Therefore, mass transfer during magma mingling is an important mechanism influencing petrography and chemical compositions of I-type granitoids. Such processes may also extensively occur in the deep hot zones of the continental arc environments. Highlights • In-situ sampling and analyses were conducted on the MME-quartz monzonite pairs. • High-level mass transfer significantly changed the mingled magmas. • The A-type granite likely escaped strong interactions with mafic magmas. [ABSTRACT FROM AUTHOR]

We develop an acousto-thermo-mechanical theory for nonlinear (large) deformation of temperaturesensitive hydrogels subjected to temperature and ultrasonic inputs, with diffusion mass transport driven by osmotic pressure accounted for. On the basis of the strain energy due to network stretching, the mixing energy of polymers and small molecules, the Cauchy stress of the deformed hydrogel can be obtained. The acoustic radiation stress generated by the ultrasonic inputs is incorporated into the Cauchy stress to give the constitutive equations of the acousto-thermal-mechanical hydrogel. The mixing energy contains an interaction parameter as a function of temperature and polymer concentration so that hydrogel deformation is temperature dependent. By employing the incompressible condition of polymers and molecules, both the temperature and acoustic radiation stress contribute to osmotic pressure, inducing hydrogel swelling (or shrinking). Specifically, for a temperature-sensitive hydrogel layer immersed in solvent, its acoustic-triggered large deformation is comprehensively analysed under different boundary conditions (e.g. free swelling, uniaxial constraint and biaxial constraint). [ABSTRACT FROM AUTHOR]

Abstract: Composites of ion and electron conducting phases allow for interfacial storage of a neutral component via space charge effects. The present contribution considers the rate of transport‐controlled incorporation and excorporation in such artificial mixed conductors. The upper limit of the relaxation time is determined by interfacial job‐sharing diffusion which is analyzed in greater detail. In general cases bulk phases assist by migration processes (dual phase transport). For more complex morphological situations, the considerations are complemented by numerical calculations. Thus the treatment also offers a pertinent approach with respect to the kinetics of solid state supercapacitors. Selected experimental results are included in the discussion. [ABSTRACT FROM AUTHOR]

Magnesium isotopic compositions of olivine, clinopyroxene, and ilmenite from the Baima intrusion, SW China, for the first time, are investigated to constrain the magnitude and mechanisms of Mg isotope fractionation among cumulus minerals in layered mafic intrusions and to evaluate their geological implications. Olivine and clinopyroxene have limited Mg isotope variations, with δ 26 Mg ranging from −0.33 to +0.05‰ and from −0.29 to −0.13‰, respectively, similar to those of mantle xenolithic peridotites. By contrast, ilmenites display extremely large Mg isotopic variation, with δ 26 Mg ranging from −0.50 to +1.90‰. The large inter-mineral fractionations of Mg isotopes between ilmenite and silicates may reflect both equilibrium and kinetic processes. A few ilmenites have lighter Mg isotopic compositions than coexisting silicates and contain high MgO contents without compositional zoning, indicating equilibrium fractionation. The implication is that the light Mg isotopic compositions of lunar high-Ti basalts may result from an isotopically light source enriched in cumulate ilmenites. On the other hand, most ilmenites have heavy Mg isotopic compositions, coupled with high MgO concentration and chemical zoning, which can be quantitatively modeled by kinetic Mg isotope fractionations induced by subsolidus Mg–Fe exchange between ilmenite and ferromagnesian silicates during the cooling of the Baima intrusion. The extensive occurrence of kinetic Mg isotope fractionation in ilmenites implies the possibility of widespread compositional disequilibrium among igneous minerals in magma chambers. Consequently, disequilibrium effects need to be considered in studies of basaltic magma evolution, magma chamber processes, and magmatic Fe–Ti oxide ore genesis. [ABSTRACT FROM AUTHOR]

Conductivity relaxation of disk-shaped ceramic samples upon a sudden change of the oxygen partial pressure of the surrounding gas phase has been simulated by application of a three-dimensional finite element model. The geometry is based on a homogeneous cylindrical specimen with a diameter of 10 mm and a thickness of 0.1 mm, where four peripheral line contacts are attached to the sample in accordance with the van der Pauw method. Both the chemical diffusion coefficient and the chemical surface exchange coefficient are assumed to vary with the oxygen non-stoichiometry during the oxygen exchange reaction (oxidation or reduction). The alteration of the oxygen non-stoichiometry as well as the relaxation of the electrical conductivity are calculated simultaneously. The modeling of conductivity relaxation curves is applied to the SOFC cathode material La 0.4 Sr 0.6 FeO 3 − δ (LSF) at 900 °C. The simulation of conductivity relaxation curves can be performed for arbitrary oxygen partial pressure changes. The present modeling approach allows the interpretation of significant differences between oxidation and reduction steps owing to the concentration (non-stoichiometry) dependence of the kinetic parameters. [ABSTRACT FROM AUTHOR]