Tropical semi‑arid shelves commonly sustain shallow‑water carbonate factories that export bioclasts to adjacent coasts; however, their interactions with relict and modern siliciclastics remain under‑constrained. We investigate a mixed siliciclastic–carbonate system along the Ceará coast (Brazil) by integrating sedimentology, XRF geochemistry, and remote‑sensing mapping across 48 sediment samples spanning inner shelf to coastal environments (barriers, beaches, dunes, lake/lagoonal settings). Inner‑shelf substrates are bioclastic‑rich, sourced primarily from calcareous algae, benthic foraminifera, and molluscs, with mud‑rich seagrass meadows acting as sediment traps. Siliciclastic grains tend to dominate most coastal settings; however, the medium‑sand fractions in some beaches and barriers are bioclastic‑rich, especially where the shelf slope decreases (< 10 m water depth) near the Itapagé Inflexion. A gentle slope, high shallow-water carbonate production, alongshore drift, cross-shore exchange, aeolian sediment transport, and low siliciclastic input from fluvial sources is interpreted to favor accumulation of mixed siliciclastic-carbonates in this semi-arid coastal study area. These results highlight the importance of understanding local controlling factors when developing models of mixed siliciclastic–carbonate sedimentation on semi-arid tropical coasts, rather than relying on a universal model. Future work should quantify bioclastic production and coastal storage, to constrain sediment interaction between highstand coastal zones and the inner shelf.
Closed-form analytical solutions for displacement, strain, and stress serve as essential benchmarks for validating numerical methods. This work constructs complete function sets that generate two classes of strong solutions to the governing partial differential equations of two-dimensional beams. The boundary conditions are of Neumann type, prescribing displacement derivatives (strains) or equivalently stresses along all surfaces. The proposed framework is demonstrated on orthotropic and isotropic beams, effectively reproducing continuous and discontinuous surface stresses. The results provide a versatile set of benchmark solutions for assessing beam mechanics models.
abstract This study aimed to update the review of Brazil’s Report Card on the prevalence of global physical activity (PA) among Brazilian children and adolescents. This systematic review included an electronic search of eight databases (PubMed, Scopus, Web of Science, LILACS, SPORTDiscus, BIREME, Scielo, and Google Scholar) and a manual search of the references of retrieved studies. Studies published in 2018 and 2019 that assessed global PA among Brazilian youth were included. A narrative approach to the results was adopted. The initial search retrieved 1,892 potentially relevant titles (1,244 titles after duplicate analysis), of which 62 (47 different studies) met all the inclusion criteria. Most updated studies were carried out in Southern (40.4%) and Southeastern (25.5%) Brazil. Six studies provided data from national surveys (12.8%), and one study included preschool children (< 5 years old). Ten studies objectively measured PA (accelerometer or pedometer devices). In the updated studies, the overall proportion of young people who were physically active ranged from 9.8% to 79.6%. Three national surveys reported the prevalence of physically active students, ranging from 18.4% to 78.8%. There was an increase of surveys that objectively measured PA and with children under 12 years of age in the 2018 and 2019 studies. However, important research gaps (e.g., variations in the measurement of global PA), even in the same study, should be considered to improve the monitoring and evaluation of global PA in Brazil.
Cosmic voids are underdense regions that can provide an effective large-scale environment with a de Sitter-like gravitational behavior. Motivated by recent black-hole solutions embedded in void density profiles, we construct a symmetric thin-shell wormhole by gluing two copies of the positive-lapse region of a black hole inside a cosmic void. The surface stresses are obtained from the Darmois–Israel junction conditions, and the corresponding null, weak, dominant, and strong energy-condition combinations are written directly in terms of the void mass function and density profile. We further develop the thermodynamics of the static shell, deriving a first law that relates the shell entropy to the black-hole and cosmological-like horizon entropies. We then formulate the radial dynamics of the throat through an effective potential and study the local stability of static configurations when the exotic matter on the shell obeys either a generalized cosmic Chaplygin gas or a modified cosmic Chaplygin gas equation of state. In both models the Chaplygin parameter B is fixed by the static junction condition, so that the remaining stability test is governed by the void geometry and by the equation-of-state parameters. Numerical results reveal that GCCG-supported configurations are generically unstable, whereas MCCG-supported wormholes can be stable for a sufficiently large linear term in the equation of state. The resulting framework connects the de Sitter-like structure of cosmic voids with the standard thin-shell wormhole formalism and provides a starting point for identifying stable or unstable wormhole configurations located between the black-hole and cosmological-like horizons of the void spacetime.
Modified black-hole entropies can induce effective spacetime geometries and thereby provide a thermodynamic route for investigating thin-shell wormholes. In this work, we construct symmetric cut-and-paste wormholes from the generic entropic lapse function F_𝒮(r)=1-4πM/𝒮'(r) and formulate the Darmois–Israel junction conditions directly in terms of the lapse and of the entropy derivatives. We derive the surface stresses, shell energy-condition combinations, conservation equation, and radial effective potential, and then apply the formalism to the Bekenstein–Hawking, Barrow, Tsallis–Cirto, Rényi, Kaniadakis, logarithmic, loop-quantum-gravity-inspired, and exponential entropy prescriptions. The analysis shows that the symmetric construction requires negative surface energy density throughout every admissible positive-lapse domain, although entropy deformations can significantly modify the horizon structure, the allowed throat region, and the localization of the surface stresses. Within the parameter domains considered here, all examined constant-barotropic branches are linearly radially unstable, despite quantitative changes in their near-horizon scales. In contrast, a variable Chaplygin shell can support stable configurations, with the stability domains determined jointly by the entropic geometry, the throat radius, and the radial exponent of the shell equation of state. These results establish a unified framework for comparing entropy-induced black-hole geometries as thin-shell wormhole seeds and show that stability is governed not by the entropy deformation alone, but by its interplay with the dynamical response of the matter localized at the throat.
