According to the “miracle of aggregation” principle, in the absence of systematic biases, errors in individual judgments within a population should cancel each other out and lead to a correct decision at the aggregate level. This article explores potential individual- and group-level correlates of the accuracy of citizens’ electoral expectations and investigates how potential markers of political sophistication—namely, educational attainment and political interest—could be used to improve upon the raw aggregation of citizens’ forecasts using massive survey datasets collected during six Canadian national and provincial election campaigns between 2011 and 2022 (n = 279,003). We find that while educational attainment and interest increase the probability of a correct forecast at the individual level, delegating the forecasting task based on these variables does not necessarily lead to improvements in the accuracy of aggregate-level predictions. At the group level, we fail to uncover any evidence that sociological or informational diversity increases forecasting accuracy.

We discuss the emerging technology of digital twins (DTs) and the expected demands as they scale to represent increasingly complex, interconnected systems. Several examples are presented to illustrate core use cases, highlighting a progression to represent both natural and engineered systems. The forthcoming challenges are discussed around a hierarchy of scales, which recognises systems of increasing aggregation. Broad implications are discussed, encompassing sensing, modelling, and deployment, alongside ethical and privacy concerns. Importantly, we endorse a modular and peer-to-peer view for aggregate (interconnected) DTs. This mindset emphasises that DT complexity emerges from the framework of connections (Wagg et al. [2024, The philosophical foundations of digital twinning, Preprint]) as well as the (interpretable) units that constitute the whole.

Public health emergencies sometimes require the restriction of civil liberties through social distancing: lockdowns, quarantines, the closure of public spaces and institutions, and so on. Social distancing measures can decrease mortality and morbidity, but they also cause social and economic harm. Policymakers have to make trade-offs between “lives and livelihoods,” while introducing only minimally necessary restrictions on civil liberties. Traditionally, cost-benefit analysis has played a central role in formulating these trade-offs. Recently, however, some philosophers have argued that the trade-offs should instead be made on the basis of contractualist moral theory. In this essay, I argue against the use of contractualism for this purpose.

Theories of aggregated legislative intent posit that the legislative intent of parliament is what a significant enough proportion of legislators intended (e.g., legislative intent is p if a majority intend that p). After all, many think the same way about democracy (‘votes reveal the will of the people’) and about courts (‘a court decision is based on judicial voting’). The existing literature on aggregated legislative intent, however, tends to make two undefended assumptions: (i) Informed Assumption: all legislators have policy intentions; and (ii) Group Intent Assumption: the existence of an aggregated intent entails the existence of a group intent. Despite these assumptions being subject to great scrutiny, they largely remain undefended. This paper defends the Group Intent Assumption and shows that aggregated theories can survive with a weaker version of the Informed Assumption.

The effect of pH on the flocculation-dispersion behavior of noncrystalline aluminum and iron oxides, kaolinite, montmorillonite, and various mixtures of these materials was investigated. The clays were Na- or Ca-saturated and freeze-dried before use. Critical coagulation concentrations (CCC) of all materials and mixtures were found to be pH dependent. The Al oxide was flocculated at pH >9.5 and the iron oxide was flocculated between pH 6.0 and 8.2; i.e., flocculation occurred at pHs near the point of zero charge (PZC). The CCC of both the Na- and Ca-clay systems increased with increasing pH. The effect of pH was greater for the Na-kaolinite (flocculated at pH 5.8 and having a CCC of 55 meq/liter at pH 9.1) than the Na-montmorillonite system (having a CCC of 14 meq/liter at pH 6.4 and a CCC of 28 meq/liter at pH 9.4). A 50/50 mixture of Na-kaolinite and Na-montmorillonite behaved more like montmorillonite (having CCCs of 13 and 33 meq/liter at pH 6.2 and pH 9.0, respectively). The presence of either noncrystalline oxide decreased the CCC over that of the clay(s) alone; the decrease occurred at pHs >7 for Al oxide and at pHs >6.5 for Fe oxide. Aluminum oxide produced a greater decrease in CCC than Fe oxide, especially at pHs >8. The effect of each oxide on CCC was greatest near the PZC, 9.5 and 7.2 for Al and Fe oxide, respectively.

The influence of added sodium and calcium nitrate electrolyte on the particle aggregates in the colloid fraction of natural bentonite and kaolin was studied. Clays were flocculated in distilled water and various electrolyte concentrations. Aggregate size was studied by sedimentation analysis; the mean radius of the aggregates was plotted against the concentrations of Na+ and Ca2+. For bentonite, the mean radii decreased with an increase of Na+ and Ca2+ concentration, reaching a minimum; and further increases in concentration led to an increase of the mean radii of the aggregates. For kaolin, an increase in Na+ and Ca2+ concentration gave rise to an increase in the mean radii of aggregates.

Scanning electron micrographs showed different types of aggregates, depending on the physico-chemical conditions of a sedimentation process. In bentonite and kaolin sediments formed from a distilled water slurry, the dominant aggregate was an edge-face type. The small addition of salts to a bentonite slurry led to the formation of edge-edge-type aggregates; for kaolin edge-face-type aggregates formed, although within the microaggregate face-face associations were observed. The highest concentrations of electrolytes for sediments of both clays led to formation of compact, face-face-type aggregates.

The effect of electrolyte concentration, exchangeable sodium percentage (ESP), sodium adsorption ratio (SAR), and pH on the flocculation-dispersion behavior of 50/50 mixtures of reference illite with reference kaolinite or reference montmorillonite was investigated. The clays were Na- or Ca-saturated and freeze-dried before use. Critical coagulation concentrations (CCCs) were investigated in the range of pH 5.9 to 9.6, percent Na-clay 0, 10, 20, 40, 60, 80, and 100 and SAR 0, 10, 20, 40, 60, 80, and ∞. CCC values increased with increasing ESP, increasing SAR, and increasing pH. The pH dependence of illite/kaolinite was greater than that of illite/montmorillonite especially at high ESP and SAR. The presence of illite did not play a dominant role in determining flocculation-dispersion behavior of the 50/50 clay mixtures. The CCCs of illite/kaolinite resembled reference illite more than reference kaolinite for SAR 0 to SAR 60. Illite/montmorillonite exhibited CCCs more similar to reference illite than reference montmorillonite at SAR 40 and SAR 60. At the agriculturally desirable ESP and SAR values of 0 to 15, all the 2:1 clays and 2:1 clay mixtures demonstrated similar CCC values.

The influence of tartaric acid and pH on chemical composition, morphology, surface area, and porosity of short-range ordered Al precipitation products was studied. Samples were prepared (1) at pH 8.0 and at the tartaric acid/Al molar ratios (R) ranging from 0 to 0.25 and (2) at R = 0.1 and in the pH range of 4.7 to 10.0. In Al precipitation products formed at pH 8.0, the organic C content increased from 8 g/kg (R = 0.01) to 93 g/kg (R = 0.25), whereas the Al content decreased from 363 g/kg (R = 0.01) to 271 g/kg (R = 0.25). The specific surface of the materials was particularly high (>400 m2/g) when samples were prepared at R < 0.1, but drastically decreased when samples were prepared at R > 0.1 (e.g., 78.6 m2/g at R = 0.25). When the C content was relatively high (>45 g/kg), aggregation between the particles was promoted, and the specific surface, thus, decreased. Electron optical observations showed that such samples were strongly aggregated. In the materials prepared at R = 0.1, but at different initial pH values, the C content decreased from 90 g/kg (pH = 4.7) to 25 g/kg (pH = 10.0). As a consequence, the lower the initial pH, the lower was the specific surface of the Al precipitation products. Tartaric acid plays an important role in both Pertubation of crystallization of Al hydroxides and promotion of aggregation of the reaction products. The two processes counteract in influencing the specific surface and pore volume of Al hydroxides.

Heating treatments greatly affected the specific surface and porosity of Al precipitation products. The specific surface and porosity of the samples generally increased by increasing the temperature up to 400°C and then decreased. Small amounts of C still remained after heating some samples for 12 hr at 600°C.

Clay particle aggregation affects a number of environmental processes, such as contaminant sorption/desorption, particle movement/deposition, and sediment structure and stability, yet factors that control clay aggregation are not well understood. This study was designed to investigate how microbial reduction of Fe(III) in clay structure, a common process in soils and sediments, affects clay-particle aggregation. Microbial Fe(III) reduction experiments were conducted with Shewanella putrefaciens CN32 in bicarbonate buffer with structural Fe (III) in nontronite as the sole electron acceptor, lactate as the sole electron donor, and AQDS as an electron shuttle. Four size fractions of nontronite (D5–D95 of 0.12–0.22 µm, 0.41–0.69 µm, 0.73–0.96 µm and 1.42–1.78 µm) were used to evaluate size-dependent aggregation kinetics. The extent of Fe(III) bioreduction and the amount of exopolysaccharide (EPS), a major biopolymer secreted by CN32 cells during Fe(III) bioreduction, were measured with chemical methods. Nontronite particle aggregation was determined by photon correlation spectroscopy and scanning electron microscopy. The maximum extent of Fe(III) bioreduction reached 36% and 24% for the smallest and the largest size fractions, respectively. Within the same time duration, the effective diameter, measured at 95% percentile (D95), increased by a factor of 43.7 and 7.7 for these two fractions, respectively. Because there was production of EPS by CN32 cells during Fe(III) reduction, it was difficult to assess the relative role of Fe(III) bioreduction and EPS bridging in particle aggregation. Thus, additional experiments were performed. Reduction of Fe(III) by dithionite was designed to examine the effect of Fe(III) reduction, and pure EPS isolated from CN32 cells was used to examine the effect of EPS. The data showed that both Fe(III) reduction and EPS were important in promoting clay mineral aggregation. In natural environments, the relative importance of these two factors may be dependent on local conditions. These results have important implications for understanding factors in controlling clay particle aggregation in natural environments.

To control a vast spectrum of applications and processes, an understanding of the morphologies of clay mineral assemblies dispersed in aqueous or non-aqueous media is important. As such, the objective of this study was to verify the relationship between dispersion medium type and the size and morphology of the clay aggregates that are formed, which can increase knowledge on the assembly formation process. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared (FTIR) spectroscopy were used in an attempt to describe kaolinite platelet organization in non-aqueous media and to compare it to the organization in aqueous media or in media with or without a selection of dissolved organic polymers. The SEM images indicated that the kaolinite platelet assembly process occurs during slow evaporation of the solvent. Because the experimental procedure was rigorously identical for all cases in this study, the SEM images compared how the effects of various media and environments on kaolinite platelet interactions can lead to different morphologies. Quite spectacular morphological differences were indeed observed between samples dispersed in aqueous and non-aqueous media, particularly when the kaolinite platelets were dispersed in an organic solvent with dissolved organic polymers. For kaolinite dispersed in water, only small aggregates were observed after slow evaporation. In contrast, large kaolinite booklets or vermiform aggregates were formed by slow solvent evaporation when kaolinite was first dispersed into some organic solvents. The aggregates were particularly large when an organic polymer was dissolved in the organic solvent. For example, kaolinite aggregates dispersed in a binary cyclohexane/toluene mixture with dissolved ethyl cellulose (EC) had top apparent surface areas (i.e. stacking length × width) of more than 3,000 µm2. Other dissolved polymers, such as polystyrene or the polysaccharide, guar gum, gave similar results. Kaolinite platelet aggregation resulted from face-to-face interactions as well as edge-to-face and edge-to-edge interactions. The XRD results showed that ethyl cellulose led to the formation of smaller kaolinite platelets with an increased tendency to form larger aggregates, which is due to the ability of EC to chemically interact with silanol and/or the aluminol groups of kaolinite.

Recently, significant advances have been made in the theory and application of acoustic and electroacoustic spectroscopies for measuring the particle-size distribution (PSD) and zeta potential (ζ potential) of colloidal suspensions, respectively. These techniques extend or replace other techniques, such as light-scattering methods, particularly in concentrated suspensions. In this review, we summarize acoustic and electroacoustic theory and published results on clay mineral suspensions, detail theoretical constraints, and indicate potential applications for the study of environmentally significant clay mineral suspensions. Using commercially available instrumentation and suspension concentrations up to 45 vol.%, acoustic spectroscopy can characterize particle sizes from 10 nm to 10 µm, or greater. Electroacoustic spectroscopy can determine the ζ potential of a suspension with a precision and accuracy in the mV range. Despite the clear potential for their use in environmental settings, to date, acoustic methods have been used mainly on clay mineral colloids with industrial application, typically combined with similar measurements such as isoelectric point (IEP) determined from shear yield stress or ζ potential from electrophoretic mobility measurements. Potential applications in environmentally relevant suspension concentrations are significant, as PSD and ζ potential are important factors influencing the transport of mineral colloids and associated contaminants through porous media. Applications include determining the effects of suspension concentration, surfactants, electrolyte strength, pH and solution composition on soil clay properties and colloidal interactions, and determining changes in PSD, aggregation and ζ potential due to adsorption or variations in the clay mineralogy.

Study of the behavior of landfill lining materials (clays) in organic solvents is important because, in waste management, lining prevents groundwater contamination by the adsorption of various pollutants such as chemicals and organic solvents. Although scaling behavior and the self-association property of clays in water-alcohol binary solvents have been studied by many researchers, the anomalous behavior of Laponite XLG in binary solvents requires investigation as suggested by previous studies. In the present study, Laponite® RD, which is structurally similar to Laponite XLG, was used to gain further insight into the reasons for the anomalous viscosity, aggregation, and non-ergodic behavior of clay in a water–methanol binary solvent. Dynamic light scattering (DLS) revealed the emergence of the non-ergodic phase of 3% w/v Laponite® RD in the water–methanol binary solvent, which increased in the presence of a large methanol content as well as with aging time in the binary solvent. Viscosity measurements further indicated that aggregation was responsible for the non-ergodic behavior, and small-angle X-ray scattering (SAXS) revealed that a large methanol content enhanced the aggregation. Moreover, SAXS data also revealed that the surface charge was responsible for anomalous viscosity fluctuations in the binary solvent due to interparticle repulsion within aggregates. Rheological studies showed that the large methanol content in the binary solvent led to frequency-independent behavior of the storage modulus of Laponite® RD.

River-dominated delta areas are primary sites of active biogeochemical cycling, with productivity enhanced by terrestrial inputs of nutrients. Particle aggregation in these areas primarily controls the deposition of suspended particles, yet factors that control particle aggregation and resulting sedimentation in these environments are poorly understood. This study was designed to investigate the role of microbial Fe(III) reduction and solution chemistry in aggregation of suspended particles in the Mississippi Delta. Three representative sites along the salinity gradient were selected and sediments were collected from the sediment-water interface. Based on quantitative mineralogical analyses 88–89 wt.% of all minerals in the sediments are clays, mainly smectite and illite. Consumption of ${\text{SO}}_4^{2-}$\$\end{document} and the formation of H2S and pyrite during microbial Fe(III) reduction of the non-sterile sediments by Shewanella putrefaciens CN32 in artificial pore water (APW) media suggest simultaneous sulfate and Fe(III) reduction activity. The pHPZNPC of the sediments was ⩽3.5 and their zeta potentials at the sediment-water interface pH (6.9–7.3) varied from −35 to −45 mV, suggesting that both edges and faces of clay particles have negative surface charge. Therefore, high concentrations of cations in pore water are expected to be a predominant factor in particle aggregation consistent with the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Experiments on aggregation of different types of sediments in the same APW composition revealed that the sediment with low zeta potential had a high rate of aggregation. Similarly, addition of external Fe(II) (i.e. not derived from sediments) was normally found to enhance particle aggregation and deposition in all sediments, probably resulting from a decrease in surface potential of particles due to specific Fe(II) sorption. Scanning and transmission electron microscopy (SEM, TEM) images showed predominant face-to-face clay aggregation in native sediments and composite mixtures of biopolymer, bacteria, and clay minerals in the bioreduced sediments. However, a clear need remains for additional information on the conditions, if any, that favor the development of anoxia in deep- and bottom-water bodies supporting Fe(III) reduction and resulting in particle aggregation and sedimentation.

The Five Domains model is influential in contemporary studies of animal welfare. It was originally presented as a conceptual model to understand the types of impact that procedures may impose on experimental animals. Its application has since broadened to cover a wide range of animal species and forms of animal use. However, it has also increasingly been applied as an animal welfare assessment tool, which is the focus of this paper. Several critical limitations associated with this approach have not been widely acknowledged, including that: (1) it relies upon expert or stakeholder opinion, with little transparency around the selection of these individuals; (2) quantitative scoring is typically attempted despite the absence of clear principles for aggregation of welfare measures and few attempts to account for uncertainty; (3) there have been few efforts to measure the repeatability of findings; and (4) it does not consider indirect and unintentional impacts such as those imposed on non-target animals. These deficiencies lead to concerns surrounding testability, repeatability and the potential for manipulation. We provide suggestions for refinement of how the Five Domains model is applied to partially address these limitations. We argue that the Five Domains model is useful for systematic consideration of all sources of possible welfare compromise and enhancement, but is not, in its current state, fit-for-purpose as an assessment tool. We argue for wider acknowledgment of the operational limits of using the model as an assessment tool, prioritisation of the studies needed for its validation, and encourage improvements to this approach.