Syntheses of ternary oxyhydrates and oxides in the calcium-uranium system: Stoichiometric influences on their structural affinity, precipitation mechanisms, and solid-state transformations

Calcium uranyl(VI) oxyhydrates and uranates are structurally related U(VI)-phases featuring uranium oxo-polyhedral sheets, with calcium ions occupying the interlayer. Both coordination environments appear throughout the nuclear fuel-cycle as alteration products, colloids, and sorption complexes. However, concerted studies spanning the aqueous precipitation mechanisms of uranyl(VI) oxyhydrates, their solid-state transformations, and structural relationships with uranates, have hitherto remained largely unexplored. A series of calcium-based uranyl(VI) oxyhydrates were precipitated via alkalisation of aqueous precursor solutions in titration and batch reactions. The bulk stoichiometric ratio of calcium to uranium (Ca/U) of precipitates was varied by modifying precursor stoichiometry, reaction temperature, or extraction pH. The rate of precipitation and its dependency on temperature was quantified in-situ using a quartz crystal microbalance. Novel insight was revealed on the mechanisms influencing nucleation and growth, by determining associated kinetic barriers as a function of precursor-Ca/U. Remarkably, as the bulk precipitate Ca/U increased from ~⅛ to unity, there was a transition from crystalline Becquerelite to primary or secondary amorphous phases, with uranate-like coordination environments. Formation of the latter was driven by solution alkalinity, and comprises a poorly-ordered matrix with occlusions of Ca2+-rich nano-clusters. A congruency limit lies Ca/U of ~1.5 Ca/U, whereupon discrete Portlandite crystallises. Solid-state transformation of all Ca2+-U(VI)-phases studied involved dehydration, dehydroxylation-decarbonation, and desorption processes. Associated kinetic barriers were catalysed by higher Ca2+-contents, and was reflected by reaction enthalpies for dehydration and desorption. Crystalline Becquerelite (~⅛ Ca/U) underwent amorphisation-crystallisation via partial egress of interlayer calcium, followed by reduction of β-UO3 to form a novel intercalation compound Ca0.18.α-U3O8. The endmember uranates Ca3U11O36, CaU2O7, Ca2U3O11, and CaUO4 crystallised from amorphous precursors with higher bulk Ca/U (~⅓, ~½, ~⅔, ~1), where Ca3U11O36 is a novel compound that is isostructural to (Pb/Sr)3U11O36. Nucleation and growth became predominant in the presence of Ca2+-rich occlusions. A higher Ca2+-loading facilitated the progressive ingress of interlayer-Ca2+, inducing a concerted axial compression in uranyl(VI) oxo-polyhedra towards the uranate-like coordination environment

Association of the Porcine Cluster of Differentiation 4 Gene with T Lymphocyte Subpopulations and Its Expression in Immune Tissues

Cluster of differentiation 4 (CD4) is mainly expressed on CD4+ T cells, which plays an important role in immune response. The aim of this study was to detect the association between polymorphisms of the CD4 gene and T lymphocyte subpopulations in pigs, and to investigate the effects of genetic variation on the CD4 gene expression level in immune tissues. Five missense mutations in the CD4 gene were identified using DNA pooling sequencing assays, and two main haplotypes (CCTCC and AGCTG) in strong linkage disequilibrium (with frequencies of 50.26% and 46.34%, respectively) were detected in the population of Large White pigs. Our results indicated that the five SNPs and the two haplotypes were significantly associated with the proportions of CD4−CD8−, CD4+CD8+, CD4+CD8−, CD4+ and CD4+/CD8+ in peripheral blood (p0.05). These results indicate that the CD4 gene may influence T lymphocyte subpopulations and can be considered as a candidate gene affecting immunity in pigs

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Identifying Priority Conservation Areas in Shennongjia National Park Based on Monetary Costs and Zonation Model

Identifying priority conservation areas (PCAs) for national parks is critical for improving the cost-effectiveness and viability of conservation efforts, given the multiplicity of conservation values, the complexity of human activities, and the limited financial resources available. Assessing conservation costs is central to systematic conservation planning (SCP). To compensate for the limitations of the alternative cost method in small-scale case studies and accurately reflect the cost differences due to specific land use, tenure, and management strategies, conservation costs are quantified and spatialized in this study using monetization methods. Taking Shennongjia National Park (SNP) as an example, we considered the core conservation values of species, ecosystems, and geological heritage, using the Zonation 5 model to identify PCAs under three different targets: 17%, 30%, and 50%. The results indicated that, as the conservation targets increased, PCAs expanded from the central and southern high-altitude areas to the northwest and northeast. Conservation gaps are primarily concentrated in the western part of Songluo and the northern parts of Hongping and Songba. Conservation costs exhibit clear spatial heterogeneity, increasing gradually from the central high mountains towards the surrounding areas. Among these, ecological compensation cost was the primary factor driving the sharp increase in total costs, while opportunity cost remained consistently low with minimal fluctuations. Compared to the alternative method, our study clarified the spatial distribution and types of costs in the process of national park construction, providing a quantitative basis and scientific guidance for future fiscal investment directions, methods, and responsible entities. At the administrative division level, we revealed the main cost challenges faced by townships in balancing resource conservation with community development, leading to more targeted, timely, and actionable community governance strategies. These findings further illustrate the significant advantages of using monetary costs in optimizing the boundaries of individual national parks and enhancing funding allocation efficiency, while promoting effective unified management of natural resource assets within spatial planning

Numerical study of ballast-flight caused by dropping snow/ice blocks in high-speed railways using Discontinuous Deformation Analysis (DDA)

International audienc

CFD/DEM coupled approach for the stability of caisson-type breakwater subjected to violent wave impact

International audienc