Sample size considerations for stepped wedge designs with subclusters

The stepped wedge cluster randomized trial (SW-CRT) is an increasingly popular design for evaluating health service delivery or policy interventions. An essential consideration of this design is the need to account for both within-period and between-period correlations in sample size calculations. Especially when embedded in health care delivery systems, many SW-CRTs may have subclusters nested in clusters, within which outcomes are collected longitudinally. However, existing sample size methods that account for between-period correlations have not allowed for multiple levels of clustering. We present computationally efficient sample size procedures that properly differentiate within-period and between-period intracluster correlation coefficients in SW-CRTs in the presence of subclusters. We introduce an extended block exchangeable correlation matrix to characterize the complex dependencies of outcomes within clusters. For Gaussian outcomes, we derive a closed-form sample size expression that depends on the correlation structure only through two eigenvalues of the extended block exchangeable correlation structure. For non-Gaussian outcomes, we present a generic sample size algorithm based on linearization and elucidate simplifications under canonical link functions. For example, we show that the approximate sample size formula under a logistic linear mixed model depends on three eigenvalues of the extended block exchangeable correlation matrix. We provide an extension to accommodate unequal cluster sizes and validate the proposed methods via simulations. Finally, we illustrate our methods in two real SW-CRTs with subclusters.     

Characterisation of soil potassium supply as derived from sorption–desorption experiments

PlantK uptake depends on soil K supply and this can be modelled using the K concentration in the soil solution (C _K), the soil K buffer power (S _K) and the effective K diffusion coefficient. With the appropriate sorption–desorption curve, the parameters C _K and S _K can be estimated from the equilibrium K concentration (C _K,0) and from the slope of the curve at C _K,0 (S _K,0). However, buffer power is frequently estimated by the ratio of the soil exchangeable K content (E _K) to C _K. Up to now, S _K,0 had not been compared with this ratio, nor had C _K,0 been compared with any C _K estimate from soil solution extract measurements. To address this question, we collected 45 soil samples from 15 K fertilisation trials in France. The soils differed widely in their physicochemical characteristics, soil solution K concentration and buffer power. For each soil sample, a sorption–desorption curve was established from 16-h experiments performed at the estimated Ca concentration of the soil solution. The C _K,0 estimates were compared with the K concentrations measured in the soil solution obtained either by direct centrifugation (^C C _K) or by centrifugation with 1,1,2-trichlorotrifluoroethane (^TFE C _K). On average, ^C C _K values were 16% higher than ^TFE C _K values, whereas C _K,0 values were intermediate between the two. The K buffer power increased when CEC increased and when C _K decreased. Multiple linear regressions using either CEC at the soil pH and ^TFE C _K ^–1 or E _K and ^TFE C _K ^–1 as independent variables accounted for more than 98 or 95% of the variability of S _K,0. The buffer power estimated by the ratio of E _K to ^TFE C _K overestimated by 100% the S _K,0 value obtained from the sorption–desorption curves.     

The effect of aluminum in soft water at low pH on oxygen consumption by the dragonfly Libellula julia Uhler

When subjected to a series of elevated Al and H⁺ concentrations spanning environmentally relevant levels, the dragonfly Libellula julia respired at a rate lower than the controls. This trend was consistent at all levels but only attained significance (p < 0.05) at pH 4.0 with A1 levels of 3.0 and 30 mg 1^–1. Low pH alone does not depress respiratory rates as greatly as Al and low pH combined. The authors speculate on some apparent inconsistencies found in the literature.     

Risk Assessment as a Decision-Making Tool for Treatment of Emissions at a New Aluminum Smelter in Iceland: 1. Background and Introduction

Protection of human health and ecosystems is gaining importance in corporate decision- making regarding industrial development. During the design phase for an aluminum smelter in East Iceland, it became necessary to determine whether a wet scrubber system should be installed to reduce sulfur dioxide emissions. Predictive risk assessment was used to determine whether there would be a consequential difference in the level of risk to human and ecological receptors from constituents in air emissions from the aluminum smelter, either with or without wet scrubbers. Benchmark exposure concentrations were established for avian, mammalian, and plant receptors and were compared to air modeling predictions to develop risk estimates. Benchmark concentrations were derived using plant uptake models for fluoride and polycyclic aromatic hydrocarbons (PAHs), and food-web modeling for birds and mammals. Exposure models were developed for all receptors, and population-level effects were modeled for plant, bird, and mammal receptors. Results indicated that exposures under both scenarios are lower than risk thresholds, and overall risk was lower for a smelter without wet scrubbers. Thus, although mass loading of sulfur dioxide (and other constituents) would be reduced using wet scrubbers, the corresponding risk to ecological receptors would actually be higher because of higher exposure-point concentrations in air.     

How much sorting is required for a circular low carbon aluminum economy?

Aluminum recycling follows a downcycling dynamic where wrought alloys are transformed into cast alloys, accumulating tramp elements at every cycle. With the saturation of stocks of aluminum and the reduction of the demand for cast alloy due to electrification of transport, improvement in the recycling system must be made to avoid a surplus of unused recycled aluminum, reduce the overall environmental impacts of the industry, and move toward a circular economy. We aim to evaluate the potential environmental benefits of improving sorting efforts by combining operations research, prospective material flow analysis, and life cycle assessment. An optimization defines the optimal sorting to minimize climate change impacts according to different sorting efforts, dismantling conditions, and collection rates. Results show how the improvement of sorting can reduce by around 30% the greenhouse gas emissions of the industry, notably by reducing unused scrap generation and increasing the recycled content of the flows that supply the demand of aluminum. The best performance is achievable with four different sorting pathways. Further improvements occur with a better dismantling and an increase of collection rates, but it requires more sorting pathways. Results point to different closed-loop recycling initiatives that should be promoted on priority in specific sectors, like the building and construction sector and the aluminum cans industry. To implement a better material circularity, the mobilization of different stakeholders is needed. From a wider perspective, the article shows how operations research can be used to project a circular future in a specific industry. This article met the requirements for a Gold–Gold JIE data openness badge described at http://jie.click/badges .      

The novel combinations of CTB,CpG, and aluminum hydroxide significantly enhanced the immunogenicity of clumping factor A 221-550 of Staphylococcus aureus

ABSTRACT

Here, we prepared the novel combined adjuvants, CTB as intra-molecular adjuvant, CpG and aluminum hydroxide (Alum) to strengthen the immunogenicity of clumping factor A_221-550 of Staphylococcus aureus (S. aureus). The protein-immunoactive results showed CTB-ClfA_221-550 elicited the strong immune responses to serum from mice immunized with CTB and ClfA_221-550, respectively. The mice immunized with CTB-ClfA_221-550 plus CpG and Alum adjuvant exhibited significantly stronger CD4⁺ T cell responses for IFN-γ, IL-2, IL-4, and IL-17 and displayed the higher proliferation response of splenic lymphocytes than the control groups, in addition, these mice generated the strongest humoral immune response against ClfA_221-550 among all groups. Our results also showed CTB-ClfA_221-550 plus CpG and Alum adjuvant obviously increased the survival percentage of the mice challenged by S. aureus. These data suggested that the novel combined adjuvants, CTB, CpG, and Alum, significantly enhance the immune responses triggered with ClfA_221-550, and could provide a new approach against infection of S. aureus.     

Potential effect of land-leveling on soil fertility in a Brazilian rice soil

Land-leveling to improve water management in lowland rice (Oryza sativa L.) production is becoming common in many countries. This technique exposes subsoil by removal and deposition of surface soil from high- to low-lying areas. The potential effect of land-leveling on soil fertility was studied in samples from an alluvial soil at depths of 0- to 5-, 5- to 15-, and 15- to 25-cm. Levels of soil cation exchange capacity; dilute acid-fluoride extractable P; DTPA extractable Cu, Mn, and Zn; exchangeable K; hot-water soluble B; and organic matter decreased with soil depth; whereas, soil pH increased with depth. Relatively low amounts of dilute acid-fluoride extractable P, exchangeable K, and DTPA extractable Zn occurred in the 15- to 25-cm layer of the soil. These data indicate the high likelihood that K, P, and Zn deficiencies would occur in rice grown on the subsoil that was exposed by land-leveling.