The development of ceramic bone graft substitutes that combine mechanical strength, biocompatibility, and interconnected porosity remains a challenge, particularly for injectable applications. Mullite (Al6Si2O13) is a ceramic of particular interest due to its biocompatibility, chemical stability, and moderate mechanical properties; however, its use as a loose-fill implant has not yet been well explored. In this study, Al2O3-SiO2 macrospheres were fabricated via ionotropic gelcasting, using sodium alginate as the binder and colloidal silica as the silica source. Three compositions were investigated: Al2O3-rich, stoichiometric mullite, and SiO2-rich. Thermal treatments at 1500 degrees C yielded mullite, cristobalite, and residual alumina in different ratios. All samples exhibited high sphericity and inter-sphere macroporosity, favorable for loose-fill bone graft applications. The stoichiometric mullite macrospheres demonstrated the most balanced combination of specific surface area, microhardness, abrasion resistance, and compressive strength. In vitro assays confirmed the absence of cytotoxic and hemolytic effects and demonstrated support for osteoblast adhesion, proliferation, and alkaline phosphatase activity. These findings indicate that Al2O3-SiO2 macrospheres, particularly stoichiometric mullite, are promising candidates for granular bone graft substitutes, offering a combination of structural integrity and biological performance suitable for bone tissue regeneration.

Aqueous dispersions of colloidal silica (CS) are commonly employed in high-alumina refractory castables to prepare in situ mullite, behaving simultaneously as a liquid medium, binder, and SiO2-source. Despite such technological interest, CS was not explored as a uniaxial pressing additive to replace organic binders and promote earlier strengthening during sintering. This study mixed alumina particles with varying amounts of CS to compare structures composed of the same raw materials, shaped by different processing techniques. Such compositions were pressed as bars or cast into cylinders, and their microstructure and physical properties evolution were assessed during sintering (700-1500ºC). Cast samples developed a homogeneous microstructure comprised of alumina particles surrounded by a gelled CS phase; in contrast, the pressed samples generated SiO2-rich spherical clusters, originating from the original CS droplets, surrounded by alumina. Such a heterogeneous microstructure persisted during sintering, when the silica nanoparticles crystallized before forming mullite. Directly cast samples developed a granular microstructure of alumina-mullite, with traces of cristobalite. In pressed samples, regions with higher SiO2 concentration developed acicular mullite crystals, imbibed in a matrix of alumina and cristobalite. Increasing the CS content in both cases enhanced porosity and decreased strength after sintering at temperatures above 1100 °C.

Ionotropic gelation (GI) is a versatile technique for producing ceramic macrospheres with tailored properties, compatible with a wide range of particle sizes, including colloidal systems. However, the microstructural evolution of silica-based colloidal systems under heat treatment remains poorly understood due to their processing difficulties and the behavior of nanoparticles during crystallization and sintering. This study produced macrospheres combining an aqueous dispersion of colloidal silica (D-50 = 50 nm) with a sodium alginate solution in an IG system using a 0.1 M Ca(NO3)(2) as a coagulating agent. After drying, the samples were thermally treated at 500-1300 degrees C for 3 h. The morphology was analyzed using image analysis software, whereas the microstructure by SEM. Their total porosity, specific surface area, and crystalline phases were characterized by Hg intrusion, N-2 adsorption, and XRD, respectively. The spheres showed a narrow diameter distribution (D-50 = 2.42 +/- 0.17 mm) and high sphericity (>90%). They exhibited properties that depended on the applied thermal treatment, including high specific surface area and mesoporosity, as well as high mechanical strength, chemical inertness, and microporosity. After thermal treatment, all samples showed a total porosity of approximately 50 %, whereas the amount of mesopores and SSA ranged from 35 % to 57.62 m(2)/g in the dried green sample, to 1 % and 1.41 m(2)/g in the sintered ones. Such variation in properties resulted from the crystallization of initially amorphous colloidal silica particles into cristobalite above 800 degrees C. These results contribute to the development of porous ceramic materials for high-performance applications.

MgO-bricks for steelmaking require thermoset resin-based binders and pre-sintering steps above 1400 degrees C before installation to ensure strength and dimensional stability. Replacing resins with aqueous-based binders and employing shorter sintering schedules would save energy. An authors' study combined MgO particles and aqueous dispersion of silanized colloidal silica in a self-flowing suspension, reducing hydroxylation damages and improving strength before and after sintering. This study evaluated the same combination of raw materials in a pressed system. Fine MgO was sprayed with colloidal silica (0-0.04 SiO2-MgO molar ratio) and shaped by conventional uniaxial pressing. A thin magnesium silicate hydrate (4MgO.5SiO2 center dot H2O) coating formed at the surfaces of MgO particles and prevented hydroxylation damage. During sintering, it softened and became a mixture of amorphous silica and Forsterite (Mg2SiO4). Compared to the silica-free reference, samples containing colloidal silica showed a two-to-three-fold green strength increase and higher densification levels after sintering at lower temperatures.

Wood density is a critical control on tree biomass, so poor understanding of its spatial variation can lead to large and systematic errors in forest biomass estimates and carbon maps. The need to understand how and why wood density varies is especially critical in tropical America where forests have exceptional species diversity and spatial turnover in composition. As tree identity and forest composition are challenging to estimate remotely, ground surveys are essential to know the wood density of trees, whether measured directly or inferred from their identity. Here, we assemble an extensive dataset of variation in wood density across the most forested and tree-diverse continent, examine how it relates to spatial and environmental variables, and use these relationships to predict spatial variation in wood density over tropical and sub-tropical South America. Our analysis refines previously identified east-west Amazon gradients in wood density, improves them by revealing fine-scale variation, and extends predictions into Andean, dry, and Atlantic forests. The results halve biomass prediction errors compared to a naïve scenario with no knowledge of spatial variation in wood density. Our findings will help improve remote sensing-based estimates of aboveground biomass carbon stocks across tropical South America.

Understanding how the traits of lineages are related to diversification is key for elucidating the origin of variation in species richness. Here, we test whether traits are related to species richness among lineages of trees from all major biogeographical settings of the lowland wet tropics. We explore whether variation in mortality rate, breeding system and maximum diameter are related to species richness, either directly or via associations with range size, among 463 genera that contain wet tropical forest trees. For Amazonian genera, we also explore whether traits are related to species richness via variation among genera in mean species-level range size. Lineages with higher mortality rates—faster life-history strategies—have larger ranges in all biogeographic settings and have higher mean species-level range sizes in Amazonia. These lineages also have smaller maximum diameters and, in the Americas, contain dioecious species. In turn, lineages with greater overall range size have higher species richness. Our results show that fast life-history strategies influence species richness in all biogeographic settings because lineages with these ecological strategies have greater range sizes. These links suggest that dispersal has been a key process in the evolution of the tropical forest flora.

Zirconia-toughened alumina (ZTA) is a promising material for dentistry; however, its current formulation exhibits a mauve coloration. This study aimed to synthesize a white ZTA ceramic by doping it with 0.7 wt% magnesium oxide (MgO). Specimens (1.2 mm in thickness x 12 mm in diameter) were divided into 3 groups (n = 15): ZTA doped with chromium oxide (ZTA-Cr2O3), ZTA doped with MgO (ZTA-MgO) and ICE-Zirkon (control group). The materials were analyzed using X-ray diffraction, energy-dispersive X-ray fluorescence spectrometer, scanning electron microscopy, and spectrophotometer. Biaxial flexural strength was conducted, and the Weibull modulus (m) and probability of failure were calculated. ZTA-MgO group had a white color, showing the pattern for alumina and zirconia grains in ZTA with a typical composition of the materials. It demonstrated superior BFS (915 ±41 MPa) and higher reliability than the ZTA-Cr2O3. ZTA-MgO proved to be able to produce white ZTA for future use in dentistry.

Plants cope with the environment by displaying large phenotypic variation. Two spectra of global plant form and function have been identified: a size spectrum from small to tall species with increasing stem tissue density, leaf size, and seed mass; a leaf economics spectrum reflecting slow to fast returns on investments in leaf nutrients and carbon. When species assemble to communities it is assumed that these spectra are filtered by the environment to produce community level functional composition. It is unknown what are the main drivers for community functional composition in a large area such as Amazonia. We use 13 functional traits, including wood density, seed mass, leaf characteristics, breeding system, nectar production, fruit type, and root characteristics of 812 tree genera (5211 species), and find that they describe two main axes found at the global scale. At community level, the first axis captures not only the 'fast-slow spectrum', but also most size-related traits. Climate and disturbance explain a minor part of this variance compared to soil fertility. Forests on poor soils differ largely in terms of trait values from those on rich soils. Trait composition and soil fertility exert a strong influence on forest functioning: biomass and relative biomass production.

Climate change and increasing availability of resources such as carbon dioxide are modifying forest functioning worldwide, but the effects of these changes on forest structure are unclear. As additional resources become available, for example, through CO2 fertilization or nitrogen deposition, large trees, with greater access to light, may be expected to gain further advantages. Conversely, smaller light-suppressed trees might benefit more if their light compensation point changes, while bigger trees may be the most negatively impacted by increasing heat and drought. We assessed recent changes in the structure of Earth's largest tropical forest by analysing 30 years of Amazonian tree records across 188 mature forest plots. We find that, at a stand level, trees have become larger over time, with mean tree basal area increasing by 3.3% per decade (95% CI 2.4; 4.1). Larger trees have increased in both number and size, yet we observed similar rates of relative size gain in large and small trees. This evidence is consistent with a resource-driven boost for larger trees but also a reduction in suppression among smaller trees. These results, especially the persistence and consistency of tree size increases across Amazonian forest plots, communities and regions, indicate that any negative impacts of climate change on forests and large trees here have so far been mitigated by the positive effects of increased resources.

Unlike most rivers globally, nearly all lowland Amazonian rivers have unregulated flow, supporting seasonally flooded floodplain forests. Floodplain forests harbor a unique tree species assemblage adapted to flooding and specialized fauna, including fruit-eating fish that migrate seasonally into floodplains, favoring expansive floodplain areas. Frugivorous fish are forest-dependent fauna critical to forest regeneration via seed dispersal and support commercial and artisanal fisheries. We implemented linear mixed effects models to investigate drivers of species richness among specialized frugivorous fishes across the ~6,000,000 km 2 Amazon Basin, analyzing 29 species from 9 families (10,058 occurrences). Floodplain predictors per subbasin included floodplain forest extent, tree species richness (309,540 occurrences for 2,506 species), water biogeochemistry, flood duration, and elevation, with river order controlling for longitudinal positioning along the river network. We observed heterogeneous patterns of frugivorous fish species richness, which were positively correlated with floodplain forest extent, tree species richness, and flood duration. The natural hydrological regime facilitates fish access to flooded forests and controls fruit production. Thus, the ability of Amazonian floodplain ecosystems to support frugivorous fish assemblages hinges on extensive and diverse seasonally flooded forests. Given the low functional redundancy in fish seed dispersal networks, diverse frugivorous fish assemblages disperse and maintain diverse forests; vice versa, diverse forests maintain more fish species, underscoring the critically important taxonomic interdependencies that embody Amazonian ecosystems. Effective management strategies must acknowledge that access to diverse and hydrologically functional floodplain forests is essential to ensure the long-term survival of frugivorous fish and, in turn, the long-term sustainability of floodplain forests.

1. Leaf and wood functional traits of trees are related to growth, reproduction, and survival, but the degree of phylogenetic conservatism in these relationships is largely unknown. In this study, we describe the variability of strategies involving leaf, wood and demographic characteristics for tree genera distributed across the Amazon Region, and quantify phylogenetic signal for the characteristics and their relationships. 2. Leaf and wood traits are aligned with demographic variables along two main axes of variation. The first axis represents the coordination of leaf traits describing resource uptake and use, wood density, seed mass, and survival. The second axis represents the coordination between size and growth. Both axes show strong phylogenetic signal, suggesting a constrained evolution influenced by ancestral values, yet the second axis also has an additional, substantial portion of its variation that is driven by functional correlations unrelated to phylogeny, suggesting simultaneously higher evolutionary lability and coordination. 3. Synthesis. Our results suggest that life history strategies of tropical trees are generally phylogenetically conserved, but that tree lineages may have some capability of responding to environmental changes by modulating their growth and size. Overall, we provide the largest-scale synopsis of functional characteristics of Amazonian trees, showing substantial nuance in the evolutionary patterns of individual characteristics and their relationships.

Amazonia's floodplain system is the largest and most biodiverse on Earth. Although forests are crucial to the ecological integrity of floodplains, our understanding of their species composition and how this may differ from surrounding forest types is still far too limited, particularly as changing inundation regimes begin to reshape floodplain tree communities and the critical ecosystem functions they underpin. Here we address this gap by taking a spatially explicit look at Amazonia-wide patterns of tree-species turnover and ecological specialization of the region's floodplain forests. We show that the majority of Amazonian tree species can inhabit floodplains, and about a sixth of Amazonian tree diversity is ecologically specialized on floodplains. The degree of specialization in floodplain communities is driven by regional flood patterns, with the most compositionally differentiated floodplain forests located centrally within the fluvial network and contingent on the most extraordinary flood magnitudes regionally. Our results provide a spatially explicit view of ecological specialization of floodplain forest communities and expose the need for whole-basin hydrological integrity to protect the Amazon's tree diversity and its function.

Calcium hexaluminate (CA6) presents a wide application in high-temperature thermal insulation. Despite the high porosity levels achieved, the use of carbonated precursors in its synthesis inevitably produces CO2 as a by-product. CA6 was produced by combining different sources of alumina (alpha-Al2O3 and rho-Al2O3) and lime (CaCO3, Ca(OH)2, and CaO) in aqueous suspensions that were cast and sintered to evaluate these routes on its physical properties. The products attained after sintering at 1550 and 1600 degrees C were characterized for crystal phases, real density, particle morphology, uniaxial compressive strength, apparent porosity, and pore size distribution. Part of the samples sintered at 1600 degrees C was subjected to a thermal shock test and was then evaluated for residual strength under diametrical compression, apparent porosity, pore size distribution, and flexural elastic modulus. The CA6 samples produced from alpha-Al2O3 presented lower pore fraction and higher mechanical strength and modulus of elasticity. The superior properties of the materials produced with alpha-alumina were maintained after thermal shock. The acicular geometry of the CA6 particles is related to their excellent thermal shock resistance and mechanical performance. The results indicated a more environmentally friendly system produced from alpha-Al2O3-CaO for industrial applications of high-temperature thermal insulation resistant to thermal shock damage.

This study used an aqueous dispersion of silanized colloidal silica (SCS), whose particles’ surfaces were modified with an epoxysilane-based coupling agent, as the liquid medium and binder for MgO-Al2O3-containing suspensions. Fine calcined alumina and magnesia sinter particles were dispersed in SCS to form a 65 vol% solids suspension. Equivalent silica-free compositions containing calcium aluminate cement or unsilanized colloidal silica were tested as references. After mixing, the SCS-suspension showed low viscosity and suitable workability and, after curing, a thin protective coating of magnesium silicate hydrate (MSH) was formed, thus preventing MgO hydroxylation and improving bonding strength, generating green-dried structures of significant flexural strength (8 MPa). During initial heating, the decomposition of MSH and the softening of amorphous silica particles reduced the overall expansion of spinel (MgAl2O4) formation. After sintering at 1600ºC, the structure showed intense densification (total porosity of 8%) high flexural strength (73 MPa) and large spinel crystals surrounded by a thin layer of amorphous silica and magnesium silicates.

We describe the geographical variation in tree species composition across Amazonian forests and show how environmental conditions are associated with species turnover. Our analyses are based on 2023 forest inventory plots (1 ha) that provide abundance data for a total of 5188 tree species. Within-plot species composition reflected both local environmental conditions (especially soil nutrients and hydrology) and geographical regions. A broader-scale view of species turnover was obtained by interpolating the relative tree species abundances over Amazonia into 47,441 0.1-degree grid cells. Two main dimensions of spatial change in tree species composition were identified. The first was a gradient between western Amazonia at the Andean forelands (with young geology and relatively nutrient-rich soils) and central-eastern Amazonia associated with the Guiana and Brazilian Shields (with more ancient geology and poor soils). The second gradient was between the wet forests of the northwest and the drier forests in southern Amazonia. Isolines linking cells of similar composition crossed major Amazonian rivers, suggesting that tree species distributions are not limited by rivers. Even though some areas of relatively sharp species turnover were identified, mostly the tree species composition changed gradually over large extents, which does not support delimiting clear discrete biogeographic regions within Amazonia.

Aim: Amazonia hosts more tree species from numerous evolutionary lineages, both young and ancient, than any other biogeographic region. Previous studies have shown that tree lineages colonized multiple edaphic environments and dispersed widely across Amazonia, leading to a hypothesis, which we test, that lineages should not be strongly associated with either geographic regions or edaphic forest types. Location: Amazonia. Taxon: Angiosperms (Magnoliids; Monocots; Eudicots). Methods: Data for the abundance of 5082 tree species in 1989 plots were combined with a mega-phylogeny. We applied evolutionary ordination to assess how phylogenetic composition varies across Amazonia. We used variation partitioning and Moran's eigenvector maps (MEM) to test and quantify the separate and joint contributions of spatial and environmental variables to explain the phylogenetic composition of plots. We tested the indicator value of lineages for geographic regions and edaphic forest types and mapped associations onto the phylogeny. Results: In the terra firme and v & aacute;rzea forest types, the phylogenetic composition varies by geographic region, but the igap & oacute; and white-sand forest types retain a unique evolutionary signature regardless of region. Overall, we find that soil chemistry, climate and topography explain 24% of the variation in phylogenetic composition, with 79% of that variation being spatially structured (R-2 = 19% overall for combined spatial/environmental effects). The phylogenetic composition also shows substantial spatial patterns not related to the environmental variables we quantified (R-2 = 28%). A greater number of lineages were significant indicators of geographic regions than forest types. Main Conclusion: Numerous tree lineages, including some ancient ones (>66 Ma), show strong associations with geographic regions and edaphic forest types of Amazonia. This shows that specialization in specific edaphic environments has played a long-standing role in the evolutionary assembly of Amazonian forests. Furthermore, many lineages, even those that have dispersed across Amazonia, dominate within a specific region, likely because of phylogenetically conserved niches for environmental conditions that are prevalent within regions.

Porous calcium hexaluminate (CaAl12O19 or CA6) structures show long-term stability at high temperatures, high refractoriness, low thermal conductivity, and excellent chemical resistance, thus being Taylor-made for thermal insulation. Previous works attained porous structures from in situ formation of CA6 combining CaO and Al2O3 sources in solid-state reactive sintering. Although the approach is time-and-energy-saving regarding the production of large parts of complex shapes, it faces considerable difficulties related to the expansive formation of calcium aluminates. To overcome such drawbacks, pre-formed porous CA6 aggregates improve the system's dimensional stability before sintering. Despite the straightforward processing, few studies have investigated such materials systemically. This article addresses the combination of pre-formed porous CA6 aggregates and organic and inorganic binders for the production of porous structures by two shaping processes, namely, uniaxial pressing and direct casting of aqueous suspensions. After drying, the samples' microstructure and physical properties evolution were investigated up to sintering (1100-1500 degrees C) through total porosity, Young's modulus, compression strength, pore diameter, and thermal conductivity measurements, dilatometric analyses, and scanning electron microscopy. Reference samples of coarse calcined alumina were tested under the same conditions to highlight the impacts of CA6 particles' morphology. Compared to them, the CA6-containing samples showed almost no variation in total porosity and average pore size levels during thermal treatments, although their strength and rigidity increased significantly after sintering. Their microstructure remained practically unchanged after drying, showing clusters of large asymmetrical CA6 crystals bonded to each other by their edges, and surrounding a large fraction of 1.8-2.2 mu m pores. According to the results, although water content, processing method, and compacting levels are important parameters, particles' microstructure, ratio of intra-particle pores, and asymmetrical shape are key variables for the development of physical properties. Such characteristics strongly contributed to their densification resistance and lower thermal conductivity after exposure to high temperatures.