Coexistence Theory Research Articles

A phosphorus distribution prediction model for CaO–SiO2–MgO–FeO–Fe2O3–Al2O3–P2O5 slags based on the IMCT

ABSTRACT A thermodynamic model for predicting the phosphorus distribution ratio L P of CaO–SiO2–MgO–FeO–Fe2O3–Al2O3–P2O5 slags was developed by considering the mass action concentration of ion couples or structural units in slags based on the ion-molecule coexistence theory (IMCT) and is referred to as the IMCT-L P model. Compared with the equilibrium mole number or mass percentage of the slag components, the mass action concentration for structural units of CaO–SiO2–MgO–FeO–Fe2O3–Al2O3–P2O5 slags used in HIsmelt smelting reduction ironmaking can characterize the reaction ability of the components. The mass action concentration of the iron oxides may characterize the oxidizing ability of the slag. The dephosphorization reactions in the HIsmelt smelting reduction vessel are jointly controlled by basic oxides and the oxidizing ability of the slag. The IMCT model can not only accurately predict the total phosphorus distribution ratio of metallurgical slags but also forecast the respective phosphorus distribution ratio of basic oxides in the slag, i.e. the dephosphorization contribution rates of 3CaO·P2O5, 4CaO·P2O5 and 2CaO·P2O5 were 99.7%, 0.227% and 0.033%, respectively. Moreover, to more conveniently predict the phosphorus distribution ratio, the empirical formulas of the phosphorus distribution ratio considering slag composition and temperature were determined by mathematical regression.

Coexistence theory as a tool to understand biological invasions in species interaction networks: Implications for the study of novel ecosystems

Abstract Questions related to understanding which characteristics of the recipient communities make them vulnerable to invasion (i.e. invasibility) are commonly formulated in such a way that they consider ecological communities as whole entities. Yet, species within recipient communities have specific responses to the introduction of exotic species. As a consequence, little is known about the role of species interaction networks within and between trophic levels in determining the invasion likelihood of exotics introduced in previously uninvaded communities and the temporal dynamics of invaded communities. To obtain a mature understanding of invasion processes and their impacts, I propose here to apply a structural stability approach of species coexistence to the field of biological invasions. The main aim here is to distinguish how direct and indirect species’ responses to invasion in competitive and trophic networks translate to the mechanisms determining the maintenance and stability of species diversity in multispecies and multitrophic assemblages. This approach brings the further opportunity to integrate the field of biological invasions within a broader perspective about the study of novel ecosystems, that is, ecosystems that contain exotic species and face new introductions sometimes under abrupt environmental changes. Moreover, it can help to target specific mechanisms separating winners from losers in novel ecosystems. Synthesis. A solid framework to predict biological invasions and understand community assembly along temporal scales under novel ecosystems can be obtained by framing species’ responses to invasion within recent theoretical and methodological advances stemming from coexistence theory, which seeks to determine how diversity is maintained. A plain language summary is available for this article.

Give chance a chance: from coexistence to coviability in biodiversity theory

AbstractA large part of biodiversity theory is driven by the basic question of what allows species to coexist in spite of a confined number of niches. A substantial theoretical background to this question is provided by modern coexistence theory (MCT), which rests on mathematical approaches of invasion analysis to categorize underlying mechanisms into factors that reduce either niche overlap (stabilizing mechanisms) or the average fitness differences of species (equalizing mechanisms). While MCT has inspired biodiversity theory in the search for these underlying mechanisms, we feel that the strong focus on coexistence causes a bias toward the most abundant species and neglects the plethora of species that are less abundant and often show high local turnover. Given the more stochastic nature of their occurrence, we advocate a complementary cross‐level approach that links individuals, small populations, and communities and explicitly takes into account (1) a more complete inclusion of environmental and demographic stochasticity affecting small populations, (2) intraspecific trait variation and behavioral plasticity, and (3) local heterogeneities, interactions, and feedbacks. Focusing on mechanisms that drive the temporary coviability of species rather than infinite coexistence, we suggest a new approach that could be dubbed coviability analysis (CVA). From a modeling perspective, CVA builds on the merged approaches of individual‐based modeling and population viability analysis but extends them to the community level. From an empirical viewpoint, CVA calls for a stronger integration of spatiotemporal data on variability and noise, changing drivers, and interactions at the level of individuals. The resulting large volumes of data from multiple sources could be strongly supported by novel techniques tailored to the discovery of complex patterns in high‐dimensional data. By complementing MCT through a stronger focus on the coviability of less common species, this approach can help make modern biodiversity theory more comprehensive, predictive, and relevant for applications.

Effects of Mineral Nitrogen Partitioning on Tree–Grass Coexistence in West African Savannas

Coexistence between trees and grasses in savannas is generally assumed to be due to a combination of partial niche separation for water acquisition and disturbances impacting the demography of trees and grasses. We propose a mechanism of coexistence solely based on the partitioning of the two dominant forms of mineral nitrogen (N), ammonium (NH4+) and nitrate (NO3−). We built a mean-field model taking into account the capacity of grasses and trees to alter nitrification fluxes as well as their relative preferences for NH4+ versus NO3−. Two models were studied and parameterized for the Lamto savanna (Cote d’Ivoire): In the first model, the nitrification only depends on the quantity of available NH4+, and in the second model the nitrification rate is also controlled by tree and grass biomass. Consistent with coexistence theories, our results show that taking these two forms of mineral N into account can allow coexistence when trees and grasses have contrasting preferences for NH4+ and NO3−. Moreover, coexistence is more likely to occur for intermediate nitrification rates. Assuming that grasses are able to inhibit nitrification while trees can stimulate it, as observed in the Lamto savanna, the most likely case of coexistence would be when grasses prefer NH4+ and trees NO3−. We propose that mineral N partitioning is a stabilizing coexistence mechanism that occurs in interaction with already described mechanisms based on disturbances by fire and herbivores. This mechanism is likely relevant in many N-limited African savannas with vegetation composition similar to the one at the Lamto site, but should be thoroughly tested through empirical studies and new models taking into account spatiotemporal heterogeneity in nitrification rates.

Applying modern coexistence theory to priority effects

Modern coexistence theory is increasingly used to explain how differences between competing species lead to coexistence versus competitive exclusion. Although research testing this theory has focused on deterministic cases of competitive exclusion, in which the same species always wins, mounting evidence suggests that competitive exclusion is often historically contingent, such that whichever species happens to arrive first excludes the other. Coexistence theory predicts that historically contingent exclusion, known as priority effects, will occur when large destabilizing differences (positive frequency-dependent growth rates of competitors), combined with small fitness differences (differences in competitors' intrinsic growth rates and sensitivity to competition), create conditions under which neither species can invade an established population of its competitor. Here we extend the empirical application of modern coexistence theory to determine the conditions that promote priority effects. We conducted pairwise invasion tests with four strains of nectar-colonizing yeasts to determine how the destabilizing and fitness differences that drive priority effects are altered by two abiotic factors characterizing the nectar environment: sugar concentration and pH. We found that higher sugar concentrations increased the likelihood of priority effects by reducing fitness differences between competing species. In contrast, higher pH did not change the likelihood of priority effects, but instead made competition more neutral by bringing both fitness differences and destabilizing differences closer to zero. This study demonstrates how the empirical partitioning of priority effects into fitness and destabilizing components can elucidate the pathways through which environmental conditions shape competitive interactions.

Longitudinal and microhabitat distributions of fishes, amphibians, and reptiles and the environmental characteristics in the upper Yura River, Kyoto, Japan

AbstractQuantitative data on the distribution of aquatic vertebrate species along environmental gradients at multiple spatial scales are useful for assessing habitat quality, understanding habitat selection, and predicting the population structures of focal species. In addition, comparable datasets for multiple species enable the examination of the interspecific differences in habitat niches and their differentiation or aggregation patterns in a stream assemblage, as well as the theory of species coexistence. The distributions of aquatic vertebrates and environmental characteristics on longitudinal and microhabitat scales were investigated at 21 sites in a temperate stream, the Yura River, Kyoto, Japan, during the day and at night from August to September 2009. The sites were located from the headwaters to about 40 km downstream along the main channel of the river. Snorkeling observations were conducted using the line‐transect method following a standardized procedure at each sampling site with a detailed description of the spatial structure of aquatic vertebrate habitats. The microhabitat environments (water depth, current velocity, substratum characteristics, and presence/absence of vegetation cover) could be determined for all observed individuals. A total of 11,724 individuals belonging to 28 fish, 2 amphibian, and 1 reptile species were observed. The data can be used to examine the spatial patterns of focal aquatic vertebrate species and assemblages, and interspecific differences in habitat use among sympatric aquatic vertebrate species at multiple spatial scales.

Coexistence of Cryptocurrencies and Central Bank Issued Fiat Currencies - A Systematic Literature Review

Since the amount of simultaneously circulating cryptocurrencies is increasing rapidly worldwide, this study aims to question the effects on competition between privately issued cryptocurrencies and central bank issued fiat currencies by postulating a coexistence theory despite extreme scenarios. This systematic literature review provides a comprehensive, detailed overview and analysis of the relevant contributions on currency competition and coexistence and develops a theoretical framework of the main ideas and functions of cryptocurrencies as well as a brief summary of the currency approach. Furthermore, it categorises current findings in finance literature into major categories to introduce further research on coexistence. To proof a lack of research, we conducted a systematic literature review to outline previous research and highlight its gaps. We find that the literature reveals convergence towards the hypothesis of a lack of research in coexistence and competition concerning the inter-market situation of privately issued cryptocurrencies and central bank issued fiat currencies.

Thermodynamic properties prediction of Mg-Al-Zn melts based on the atom and molecule coexistence theory

A developed and verified thermodynamic model based on the atom and molecule coexistence theory (AMCT) is employed to predict activities relative to pure liquids in standard state in Mg-Al, Mg-Zn, Al-Zn and Mg-Al-Zn melts through the calculated mass action concentrations of structural units, i.e., Ni. According to AMCT, Ni can be extrapolated and calculated by the chemical equilibrium constant of a structural molecule, i.e., Ki, in the Mg-Al-Zn ternary system and binary subsystems. In this paper, the standard Gibbs free energy function, for reported activities and mixing thermodynamic properties in Mg-Al, Mg-Zn and Al-Zn melts, was regressed and optimized. The results showed that Ki and Ni were deduced by Gibbs free energy function at the studied temperature. The results of calculating thermodynamic properties in the full composition range for liquid Mg-Al-Zn from 880 to 1100 K, as well as Mg-Al from 923 to 1073 K, Mg-Zn from 880 to 973 K and Al-Zn from 1000 to 1073 K, are presented in the paper by coupling with Ni and AMCT. An excellent agreement is noticed between the calculated values of this study and measured thermodynamic data from the references, suggesting that the AMCT can be well applied to describe and predict the activities of the Mg-Al-Zn system and its subsystems.

Research on the oxygen content in 304L stainless steel during VOD-LF-CC process based on IMCT

The total oxygen in 304L stainless steel produced by the VOD-LF-CC process is investigated in this research. The equilibrium oxygen content in the molten steel during the smelting process is calculated based on the ion-molecule coexistence theory. The results show that it is feasible to use the developed thermodynamic model for calculating the equilibrium oxygen content in CaO–SiO2–Al2O3–MgO–FeO–Cr2O3 slags equilibrated with 304L molten steel. The variation law for total oxygen is in good agreement with the equilibrium oxygen content. The oxygen content of the oxide-inclusion decreases with the number density of inclusions, which decrease at different stages in the process. The content of FeO and Cr2O3 in the slag has no obvious effect on the equilibrium oxygen content when the basicity of the slag remains constant. Combining the proposed method with industrial practice, the optimum VOD process parameters for obtaining a low equilibrium oxygen content are as follows: 1600–1650 °C of the temperature after the VOD stage, 0.4–0.5% of the Si content after reduction, and 2.2–2.5 of the slag basicity.

Mutualists Stabilize the Coexistence of Congeneric Legumes.

Coexistence requires that stabilizing niche differences, which cause species to limit themselves more than others, outweigh relative fitness differences, which cause competitive exclusion. Interactions with shared mutualists, which can differentially affect host fitness and change in magnitude with host frequency, can satisfy these conditions for coexistence, yet empirical tests of mutualist effects on relative fitness and stabilizing niche differences are largely lacking within the framework of coexistence theory. Here, we show that N-fixing rhizobial mutualists mediate coexistence in four naturally co-occurring congeneric legume (Trifolium) species. Using experimental greenhouse communities, we quantified relative fitness and stabilizing niche differences for each species in the presence of rhizobia originating from conspecific or congeneric hosts. Rhizobia stabilized coexistence by increasing the self-limitation of Trifolium species grown with rhizobia isolated from conspecifics, thus allowing congeners to increase when rare. Greenhouse-measured invasion growth rates predicted natural, unmanipulated coexistence dynamics of Trifolium species over 2 years at our field sites. Our results demonstrate that interactions with shared mutualists can stabilize the coexistence of closely related species.

A Further Evaluation of the Coupling Relationship between Dephosphorization and Desulfurization Abilities or Potentials for CaO-based Slags: Influence of Slag Chemical Composition

The coupling relationships between dephosphorization and desulfurization abilities or potentials for CaO–FeO–Fe2O3–Al2O3–P2O5 slags over a large variation range of slag oxidization ability during the secondary refining process of molten steel have been proposed by the present authors as log L P + 5 log L S or log C PO 4 3 − + log C S 2 − in the reducing zone and as log L P + log L S − 5 log N Fe t O or log C PO 4 3 − + log C S 2 − − log N FeO in the oxidizing zone based on the ion and molecule coexistence theory (IMCT). In order to further verify the validation and feasibility of the proposed coupling relationships, the effects of chemical composition of the CaO-based slags are provided. The chemical composition of slags was described by three group parameters including reaction abilities of components represented by the mass action concentrations N i , two kinds of slag basicity as simplified complex basicity ( % CaO ) / [ ( % P 2 O 5 ) + ( % Al 2 O 3 ) ] and optical basicity Λ , and the comprehensive effect of iron oxides FetO and basic oxide CaO. Comparing with the strong effects of chemical composition of the CaO-based slags on dephosphorization and desulfurization abilities or potentials, the proposed coupling relationships have been confirmed to not only be independent of slag oxidization ability as expected but also irrelevant to the aforementioned three groups of parameters for representing the chemical composition of the CaO-based slags. Increasing temperature from 1811 to 1927 K (1538 to 1654 °C) can result in a decreasing tendency of the proposed coupling relationships. In terms of the proposed coupling relationships, chemical composition of slags or fluxes with assigned dephosphorization ability or potential can be theoretically designed or optimized from its desulfurization ability or potential, and vice versa. Considering the large difference of magnitude between phosphate capacity C PO 4 3 − and sulfide capacity C S 2 − , the proposed coupling relationships between dephosphorization and desulfurization abilities for CaO-based slags are recommended to design or optimize chemical composition of slags.

‘Estrangement’ in aesthetics and beyond: Russian formalism and phenomenological method

We investigate the parallelism between aesthetic experience and the practice of phenomenology using Viktor Shklovsky’s theory of “estrangement” (ostranenie). In his letter to Hugo von Hofmannsthal, Husserl claims that aesthetic and phenomenological experiences are similar; in the perception of a work of art we change our attitude in order to concentrate on how the things appear to us instead of what they are. A work of art “forces us into” the aesthetic attitude in the same way as the phenomenological epoche drives us into the phenomenological one. The change of attitudes is a condition of possibility of aesthetic and/or phenomenological experience. Estrangement is an artistic device that breaks the routinized forms of perception: one sees the thing as new and does not just “recognize” it automatically. Shklovsky insists that it is possible if one experiences or feels the form of the work of art—in an affective and even sensuous way. We claim that this is similar to the phenomenological seeing, or intuition, which, according to Husserl, should be devoid of all understanding. Phenomenological epoche can also be described as a philosophical technique that aims to arrest the “ready-made,” “taken for granted,” “pre-given” meanings in order to access a new meaning which is not yet stabilized, the “meaning-in-formation.” It is not enough to turn from what appears to how it appears; one has to oscillate between these conflicting attitudes, or rather to keep them both at the same time thus gaining a kind of a 3D-vision of meaning in its becoming. This double life in two different attitudes (or, following a Husserlian metaphor, “double bookkeeping”) can be clarified in terms of Roman Jakobson’s theory of antinomic coexistence between the poetic and communicative functions of language. The notion of “double life in two attitudes” uncovers the role that ostranenie can play in the philosophical transformation of the subject based on variety and essential mobility of the affective components involved. Proposing a phenomenological interpretation of a passage from Samuel Beckett we show how the radicalization of ostranenie can lead even to “meta-estrangement”: to estrangement of the everyday “lack of estrangement.” We conclude with a remark on the productivity of this form of estrangement in the phenomenological context.

The type of nutrient limitation affects the plant species richness–productivity relationship: Evidence from dry grasslands across Eurasia

Abstract The species richness–productivity relationship is one of the most debated patterns in ecology. Species coexistence theory suggests that it could be tightly linked to the type of nutrient limitation (no limitation, single‐nutrient limitation, colimitation by several nutrients). Yet, the effects of nutrient limitation on the species richness–productivity relationship have been rarely studied at the regional and continental scales. Combining the predictions of the humped‐back model and the niche dimension hypothesis, we hypothesized that an increase in plant species richness with the number of different limiting nutrients is detectable only at higher productivity levels, at which competition for nutrients is more intense. Therefore, we expected the shape of the diversity–productivity relationship to differ between sites colimited by nitrogen (N) and phosphorus (P), sites limited by a single nutrient (either N or P), and sites not limited by any of these nutrients. To test this hypothesis, we used species richness data collected in 10 m × 10 m plots at 694 temperate dry grassland sites across eight regions in northern Eurasia. Productivity ranged from 10 to ~500 g/m2 of above‐ground standing biomass. The type of nutrient limitation was identified by critical nutrient ratios alone and their combination with critical nutrient concentrations measured in the plant tissue. Relationships were analysed using generalized linear and mixed‐effect models. In line with our expectations, species richness of Eurasian temperate dry grasslands increased more steeply and peaked higher under higher productivity levels at N&P‐colimited sites. When nutrient limitation was assessed by both ratios and concentrations, species richness at N&P‐colimited sites continued to increase monotonically until the maximum productivity sampled in this study. In contrast, at sites with a single‐nutrient limitation or no limitation, the peak in species richness was lower and occurred at a lower productivity of about 300–400 g/m2. Synthesis. We provide the first evidence that the species richness–productivity relationship may depend on the type of nutrient limitation as predicted by the species coexistence theory. To generalize these findings, the role of nutrient limitation needs to be tested in other ecosystems, including more productive plant communities.

Critical Assessment of Activities of Structural Units in Fe–Al Binary Melts Based on the Atom and Molecule Coexistence Theory

AbstractA thermodynamic model for calculating the mass action concentrations{N_i}of structural units in Fe–Al binary melts based on the atom–molecule coexistence theory,i. e., AMCT–{N_i}model, has been developed and verified to be valid by comparing with reported activities{a_{{\rm{R, }}i}}of both Al and Fe relative to pure liquid as standard state in Fe–Al binary melts over a temperature range from 1823 to 1973 K (1550 to 1700 °C). Furthermore, Raoultian activity coefficients\gamma _i^0of both Al and Fe in the Fe-rich corner or Al-rich corner of Fe–Al binary melts as well as the standard molar Gibbs-free energy changes{\Delta _{{\rm{sol}}}}G_{{\rm{m, }}i{\rm{(l)}} \to {{{\rm{[}}i{\rm{]}}}_{{\rm{ [ \% }}i]{\rm{ = 1}}{\rm{. 0}}}}}^{\Theta {\rm{, \% }}}of dissolved Al or Fe for forming [% Al] or [% Fe] as 1.0 in Fe–Al binary melts have also been determined by the developed AMCT–{N_i}model and verified to be accurate.The reported activities{a_{{\rm{R, }}i}}of both Al and Fe from the literature can be well reproduced by calculated mass action concentrations{N_i}of free Al and free Fe in Fe–Al binary melts. A small effect of changing temperature from 1823 to 1973 K (1550 to 1700 °C) on reaction abilities of both Al and Fe from the available literature is also confirmed by calculated mass action concentrations{N_i}of free Al and free Fe in Fe–Al binary melts. The obtained activity coefficients{\gamma _i}of both Al and Fe in Fe–Al binary melts can be described by a quadratic polynomial function and a cubic polynomial function, respectively. Furthermore, accurate expressions of Raoultian activity coefficients\gamma _i^0of both Al and Fe in Fe-rich corner or Al-rich corner of Fe–Al binary melts are also obtained as\ln \gamma _{{\rm{Al}}}^0 = - {\rm{9, 646}}{\rm{. 5}}/T{\rm{ + 2}}{\rm{. 196}}and\ln \gamma _{{\rm{Fe}}}^0 = - {\rm{6, 799}}{\rm{. 1}}/T - {\rm{0}}{\rm{. 01367}}, respectively. In addition, expressions of the first-order activity interaction coefficients\varepsilon _i^iore_i^iorh_i^iof both Al and Fe coupled with three activity coefficients\gamma _i^{}orf_{ \% {\rm{, }}i}^{}orf_{{\rm{H, }}i}^{}relative to three standard states are also obtained from the developed AMCT–{N_i}model for Fe–Al binary melts.

Release from intraspecific competition promotes dominance of a non-native invader

Species can coexist through equalizing (similar fitness abilities) and stabilizing (unique niche requirements) mechanisms—assuming that intraspecific competition imposes more limitation than interspecific competition. Non-native species often de-stabilize coexistence, suggesting that they bring either a fitness advantage or a distinct niche requirement. We tested whether greater fitness or unique niche requirements best explained a successful North American invasion by the European Myrmica rubra ant. North American invaded-range M. rubra aggressively sting and occur in enormous numbers (suggesting a fitness advantage), yet our study site has a history of anthropogenic disturbance that might favor M. rubra (suggesting a unique niche). We compared M. rubra to native ants, principally the dominant North American woodland ant Aphaenogaster picea, using physiological health (lipids and size), monthly bait station surveys and aggression assays to assess fitness abilities, and we used nest surveys and isotope analysis to assess niche characteristics. We confirmed the field observations with laboratory experiments that tested colony aggression (direct competition) and food retrieval (indirect competition). In both the observational and experimental investigations, we found little evidence of M. rubra interspecific competitive advantage (aggression or food retrieval) or niche differentiation. Instead, M. rubra violated the basic assumption of coexistence theory: intraspecific competition consistently was less than interspecific competition. Freed up from the costs and limitations of territorial competition, some non-native species may outcompete native species by not competing with themselves. This ‘friendly release’ from intraspecific competition provides an ecological mechanism for some successful invasions.

An expanded modern coexistence theory for empirical applications.

Understanding long-term coexistence of numerous competing species is a longstanding challenge in ecology. Progress requires determining which processes and species differences are most important for coexistence when multiple processes operate and species differ in many ways. Modern coexistence theory (MCT), formalised by Chesson, holds out the promise of doing that, but empirical applications remain scarce. We argue that MCT's mathematical complexity and subtlety have obscured the simplicity and power of its underlying ideas and hindered applications. We present a general computational approach that extends our previous solution for the storage effect to all of standard MCT's spatial and temporal coexistence mechanisms, and also process-defined mechanisms amenable to direct study such as resource partitioning, indirect competition, and life history trade-offs. The main components are a method to partition population growth rates into contributions from different mechanisms and their interactions, and numerical calculations in which some mechanisms are removed and others retained. We illustrate how our approach handles features that have not been analysed in the standard framework through several case studies: competing diatom species under fluctuating temperature, plant-soil feedbacks in grasslands, facilitation in a beach grass community, and niche differences with independent effects on recruitment, survival and growth in sagebrush steppe.

Coexistence theory and the frequency-dependence of priority effects.

Priority effects are commonly used to describe a broad suite of phenomena capturing the influence of species arrival order on the diversity, composition and function of ecological communities. Several studies have suggested reframing priority effects around the stabilizing and equalizing concepts of coexistence theory. We show that the only compatible priority effects are those characterized by positive frequency-dependence, irrespective of whether they emerge in equilibrium or non-equilibrium systems.

Niche and fitness differences determine invasion success and impact in laboratory bacterial communities

There is increasing awareness of invasion in microbial communities worldwide, but the mechanisms behind microbial invasions remain poorly understood. Specifically, we know little about how the evolutionary and ecological differences between invaders and natives regulate invasion success and impact. Darwin’s naturalization hypothesis suggests that the phylogenetic distance between invaders and natives could be a useful predictor of invasion, and modern coexistence theory proposes that invader-native niche and fitness differences combine to determine invasion outcome. However, the relative importance of phylogenetic distance, niche difference and fitness difference for microbial invasions has rarely been examined. By using laboratory bacterial microcosms as model systems, we experimentally assessed the roles of these differences for the success of bacterial invaders and their impact on native bacterial community structure. We found that the phylogenetic distance between invaders and natives failed to explain invasion success and impact for two of three invaders at the phylogenetic scale considered. Further, we found that invasion success was better explained by invader-native niche differences than relative fitness differences for all three invaders, whereas invasion impact was better explained by invader-native relative fitness differences than niche differences. These findings highlight the utility of considering modern coexistence theory to gain a more mechanistic understanding of microbial invasions.

Investigation of fluoride vaporization from CaF2[sbnd]CaO[sbnd]Al2O3 slag for vacuum electroslag remelting

In this study, five types of CaF2CaOAl2O3 slags with varying CaO/Al2O3 mass ratio and CaF2 content were selected for investigating the vaporization behavior of slag bearing high CaF2 content by thermo gravimetry and ion and molecule coexistence theory. The results show that the volatile product of slag is the AlF3. The vaporization rate is affected by the vapor pressure of AlF3, mole number of complex molecules and the viscosity of slag. For all slags, the vaporization rate of slag bearing approximately 70 wt% CaF2 and 30 wt% Al2O3 is the fastest due to the ultra-high vapor pressure of AlF3. In the test of slags containing 70 wt% CaF2, vaporization rate firstly decreases, then increases with CaO/Al2O3 mass ratio increasing from 0.05 to 1.10 and 2.00. In the case of slags containing same CaO/Al2O3 mass ratio, vaporization rate firstly increases, then decreases with CaF2 content decreasing from 68.9 wt% to 48.1 wt% and 28.7 wt%. Slag T5 bearing approximately 30 wt% CaF2, 33.9 wt% CaO and 36.1 wt % Al2O3 has lower electrical conductivity, slower vaporization rate and larger sulfide capacity, which will be economical, environmentally friendly and suitable for vacuum electroslag remelting.

Prediction and application of Si[sbnd]Ca and Si[sbnd]Ca[sbnd]Fe alloy solutions by co-existence theory model

Based on the atom and molecule co-existence theory (AMCT), the activity models of SiCa and SiCaFe alloy solutions were established. The self-interaction coefficient and infinitely diluted activity coefficient of Ca, along with the interaction coefficient of CaFe in silicon alloy solutions, were calculated at a temperature range of 1723–1873K. The calculated data agree well with the experimental values and indicate that the atom and molecule co-existence theory is reliable for predicting the activity of SiCa and SiCaFe solutions. In addition, an iso-activity phase diagram of SiCaFe solution at 1723 K was plotted. The established activity model of SiCaFe shows that the activities of CaSi2 and FeSi2 in silicon solution are high. The activities of CaSi2 and FeSi2 are equal at xCa/xFe = 1.1. The activity of CaSi2 is 9.91 times greater than that of FeSi2 at xCa/xFe = 10. The effect of xCa/xFe on acid leaching was further discussed based on thermodynamics.