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In this work we present a framework to explain the prediction of the velocity fluctuation at a certain wall-normal distance from wall measurements with a deep-learning model. For this purpose, we apply the deep-SHAP (deep Shapley additive explanations) method to explain the velocity fluctuation prediction in wall-parallel planes in a turbulent open channel at a friction Reynolds number ${\textit{Re}}_\tau =180$. The explainable-deep-learning methodology comprises two stages. The first stage consists of training the estimator. In this case, the velocity fluctuation at a wall-normal distance of 15 wall units is predicted from the wall-shear stress and wall-pressure. In the second stage, the deep-SHAP algorithm is applied to estimate the impact each single grid point has on the output. This analysis calculates an importance field, and then, correlates the high-importance regions calculated through the deep-SHAP algorithm with the wall-pressure and wall-shear stress distributions. The grid points are then clustered to define structures according to their importance. We find that the high-importance clusters exhibit large pressure and shear-stress fluctuations, although generally not corresponding to the highest intensities in the input datasets. Their typical values averaged among these clusters are equal to one to two times their standard deviation and are associated with streak-like regions. These high-importance clusters present a size between 20 and 120 wall units, corresponding to approximately 100 and 600 $\unicode{x03BC} \textrm {m}$ for the case of a commercial aircraft.
This study investigates the wake dynamics of a wall-mounted square cylinder with an aspect ratio of 2, subjected to varying inflow turbulence intensities, employing high-fidelity large-eddy simulation complemented by spectral proper orthogonal decomposition. The simulations are conducted at a Reynolds number of 43 000. A synthetic momentum source term is integrated within the Navier–Stokes equations to generate turbulence consistent with the von Kármán spectrum. Four inflow cases, comprising an undisturbed inflow and three disturbed inflows with turbulence intensities of 10 %, 20 % and 30 %, are examined to elucidate their impact on vortex shedding, shear-layer behaviours and coherent structures. Results demonstrate that increased turbulence intensity significantly modifies vortex coherence, suppresses recirculation regions, promotes earlier shear-layer reattachment on the top surface and leads to reattachment of the shear layer on the side surface. Spectral proper orthogonal decomposition analysis, conducted on 17 orthogonal planes in the streamwise (x), wall-normal (y) and spanwise (z) directions, reveals two dominant energetic frequencies: a primary vortex-shedding frequency around a Strouhal number of 0.084, and a secondary high frequency associated with Kelvin–Helmholtz instabilities. The imposed turbulence effectively redistributes spectral energy, diminishing the coherence and altering the spatial organisation of vortical structures. These findings enhance fundamental understanding of turbulent wake dynamics and flow–structure interactions in bluff-body flows.
Rare Earth Elements (REEs) are essential for green energy technologies and defense systems, yet global supply chains remain concentrated in China. This has intensified geopolitical competition for alternative sources, positioning the Arctic as a strategic frontier, as retreating ice exposes mineral deposits. A comprehensive discourse analysis of strategic documents, scholarly literature, and media sources from 2010 to 2025 reveals a dramatic shift from geological characterization and economic speculation to urgent securitization and strategic alliance formation. Academic research has evolved from establishing natural baselines to governance and social conflict analysis. Media coverage of REE in the Arctic peaked in 2025, with rising emphasis on governance, sovereignty, geopolitics, and Greenland’s strategic position. Critical gaps persist in addressing Indigenous rights, holistic impact assessments, and Arctic-specific innovation. Sustainable Arctic REE development requires integrated frameworks that balance geopolitical imperatives with environmental protection and Indigenous self-determination, preventing the region from becoming a sacrifice zone for global decarbonization.
Fully resolved three-dimensional simulations of planar gravity currents are conducted to investigate the influence of imposed spanwise perturbations on flow evolution and mixing at two Reynolds numbers ($ \textit{Re}=3450$ and 10 000). The initial perturbations consist of sinusoidal waves with a varying number of repeating waves, $k_y$, with simulations spanning $0 \leqslant k_y \leqslant 8$. At low-$ \textit{Re} $, cases with perturbations ($k_y \gt 0$) exhibit a more rapid breakdown of spanwise coherence compared with the unperturbed case ($k_y = 0$), although the resulting structures retain spatial periodicity and remain relatively ordered. This earlier disruption leads to greater front propagation distances beyond the self-similar inertial phase compared with the unperturbed case. Notably, imposed perturbations exhibit minimal influence on the flow transition; all cases follow the slumping velocity reported in the literature, with the transition into the inertial phase occurring at comparable times across different $k_y$ values at both $ \textit{Re} $. The increased propagation speed is accompanied by reduced mixing efficiency due to the premature disruption of coherent Kelvin–Helmholtz (K–H) billows, which play a key role in maintaining multi-scale mixing. At high-$ \textit{Re} $, the influence of initial spanwise perturbations diminishes, as three-dimensional turbulence induces a more chaotic, fine-scale breakdown of spanwise coherence across all $k_y$ cases, overriding the effects of the initial perturbations. Consequently, the dominant stirring mechanism shifts from K–H billows to vortices within the current head. Nevertheless, the unperturbed case maintains comparatively higher mixing efficiency at both low- and high-$ \textit{Re} $. This is attributed to the persistence of recognisable K–H billow structures, which, despite undergoing chaotic breakdown at high-$ \textit{Re} $, still contribute to effective stirring by stretching and folding the density interface. These results highlight the dual role of K–H billows: they promote efficient mixing, yet the enhanced mixing reduces the density difference between the current and the ambient fluid, weakening buoyancy and slowing front propagation despite stronger stirring. These findings are supported by consistent trends in streamwise density distribution and ‘local’ energy exchange analyses.
The annelid genus Diopatra is a well-known example of marine ecosystem engineering, as it creates tubes in coastal sediments all around the world. In the Amazon coast, this annelid is common in intertidal estuarine areas and protected beaches. However, there are no data for the Amazon coast regarding studies on the meiofauna associated with Diopatra sp. tubes. Therefore, the present study characterized, for the first time, the meiofauna community found on a muddy-sandy tidal flat of the Amazon coast in areas with and without the presence of Diopatra sp. tubes. Samples were collected in February 2014 in two different areas: (1) an area in which Diopatra sp. tubes were present, and (2) an area without tubes. A total of 13 major meiofaunal groups were found, with Nematoda as the dominant group. Overall, a significant increase in meiofauna density and richness of the meiofauna was observed in the area with the presence of Diopatra sp. tubes. While no large aggregations of Diopatra sp. tubes were observed in the study region, the presence of even a single tube had significant effects on the environmental conditions available to the meiofauna community. The present findings add knowledge about the presence of the bioconstructor in coastal areas and reinforce the role of tube-building polychaetes as ecosystem engineers.
This study presents a framework that combines Bayesian inference with reinforcement learning to guide drone-based sampling for methane source estimation. Synthetic gas concentration and wind observations are generated using a calibrated model derived from real-world drone measurements, providing a more representative testbed that captures atmospheric boundary layer variability. We compare three path planning strategies—preplanned, myopic (short-sighted), and non-myopic (long-term)—and find that non-myopic policies trained via deep reinforcement learning consistently yield more precise and accurate estimates of both source location and emission rate. We further investigate centralized multi-agent collaboration and observe comparable performance to independent agents in the tested single-source scenario. Our results suggest that effective source term estimation depends on correctly identifying the plume and obtaining low-noise concentration measurements within it. Precise localization further requires sampling in close proximity to the source, including slightly upwind. In more complex environments with multiple emission sources, multi-agent systems may offer advantages by enabling individual drones to specialize in tracking distinct plumes. These findings support the development of intelligent, data-driven sampling strategies for drone-based environmental monitoring, with potential applications in climate monitoring, emission inventories, and regulatory compliance.
Politicians and business leaders tell us that climate change can be solved with new technologies, but global emissions keep rising. Engineers show us technological options that could be deployed quickly, but there is no plan there to save us. We can no longer wait for solutions to climate change. To reduce our emissions quickly, we need to cut back on some aspects of modern life through inventive tweaks – and via restraint. Restraint is normal. It is also fundamental across all religious faiths. In this volume, Julian Allwood, an engineer, and Andrew Davison, a theologian, offer a fresh perspective and prescription for combatting climate change. Rather than starting from the vantage points of economics and politics, they rethink climate action in the long tradition of the virtues – Courage, Justice, Prudence, and Temperance -- along with Faith, Hope, and Love from the Bible. By acting in good faith now, a safe climate becomes an expression of our faith in and love for humanity.
The idea that the world needs to transition to a more sustainable future is omnipresent in environmental politics and policy today. Focusing on the energy transition as a solution to the ecological crisis represents a shift in environmental political thought and action. This Element employs a political theory approach and draws on empirical developments to explore this shift by probing the temporal, affective, and technological dimensions of transition politics. Mobilising the framework of ecopolitical imaginaries, it maps five transition imaginaries and sketches a counter-hegemonic, decolonial transition that integrates decolonial approaches to knowledge and technology. Transition Imaginaries offers a nuanced exploration of the ways in which transition politics unfolds, and a novel argument on the importance of attending to the coloniality of transition politics. A transition to just sustainable futures requires the mobilisation of post-extractivist visions, knowledges, and technologies. This title is also available as Open Access on Cambridge Core.
This Element argues for the benefits of integrating the perspectives of a new historiography of paleontology in the training of upcoming paleontologists and in the paleontological community's culture more broadly. Wrestling with the complex legacy of its past, the paleontological community is facing the need to reappreciate its history to address issues of accessibility and equity affecting the field, such as gender gap, parachute science, and specimen repatriation. The ability of the paleontological community to address these issues depends partly on the nature of its engagement with the past in which they find their source. This Element provides a conceptual toolkit to help with the interpretation of the unprecedented position in which the paleontological community finds itself regarding its past. It also introduces historiographical resources and provides some suggestions to foster collaboration between paleontology and the history of paleontology.
Paleolake coring initiatives result in large datasets from various proxies taken at different resolutions, ranging from continuous scans to samples collected at coarser intervals. Higher-resolution data (e.g., core-scan X-ray fluorescence [XRF]) can detect short-duration changes in the paleolake and help identify unit boundaries with precision; however, interpreting the causes of such changes may require sampling and more intensive laboratory analysis like X-ray diffraction (XRD). This study applies a published wide and deep learning model, developed for the Olduvai Gorge Coring Project (OGCP) 2014 cores from the Pleistocene Olduvai basin, Tanzania, to reconstruct the mineral assemblages from saline-alkaline paleolake Olduvai using core-scan XRF data and core lithology. A classification model (predicting mineral presence or absence) and a regression model (predicting relative abundances of minerals) yielded predictions for two OGCP cores (2A and 3A), which were compared with published XRD mineral data and detailed core sedimentological descriptions. The models were excellent at identifying dolomite-rich layers, carbonate-rich intervals, intervals of sandstone within claystone, and altered tuffs within claystone and at predicting whether illitic or smectitic clays dominate. The models struggled with less-altered tuffs and with zeolites in non-tuff sediments, especially when XRD identified chabazite and erionite (rather than phillipsite) as the dominant, non-analcime zeolite.
La Viña rock shelter is a relevant archaeological site for understanding the late Middle and Upper Palaeolithic cultural development in northern Iberia as evidenced by the Mousterian, Aurignacian, Gravettian, Solutrean and Magdalenian bone and lithic industries, parietal engravings and human subsistence remains recovered during the 1980s excavations by J. Fortea in the western and central excavation areas. This paper aims to present 16 new radiocarbon dates, which are added to the previous radiocarbon dates obtained, using different analytical methods on bone and charcoal. These are now 57 dates in total. Bayesian models have been applied to assess and discern the chronology of the archaeological sequence in each sector of the rock shelter. The results provide details on the chronostratigraphy of each excavation area, documenting the duration of the different technocultural phases and confirming in-site postdepositional events.
Recent palaeobiological studies have emphasized the need for interpretations of the fossil record to consider spatial changes in environmental conditions (e.g. topography, climate). Establishing the role the environment plays in determining the distributions of extinct and existing organisms is complicated by biological evolution. Using available observations to ‘see through’ the randomness of biological evolution to determine contributions from environmental change is not trivial because of the sparsity of the fossil record, lack of precise information about rates of evolution, and because we obviously cannot physically re-run the evolutionary history that resulted in modern biodiversity or the fossil record. To address these issues, we establish scales and scenarios in which spatial environmental change is manifested in records of the number of species in a given area (richness) generated by eco-evolutionary simulation. Evolutionary processes that are likely to be random on the timescales of environmental change are included. Signals of environmental change that are likely to be hidden by the effects of ‘noisy’ evolutionary processes and those likely to emerge are identified. The ‘experiment of life’ is simulated many times, producing statistical insights. Results show that the spatial rate of environmental change is strongly correlated with species richness when the ability of organisms to disperse is high. Interaction between scale, dispersal and environmental structure is shown to determine both statistical and spatial distributions of richness. As a proof-of-concept, we compare predictions to bird species richness. The results emphasize the need to consider the randomness of evolution when interpreting the observations of extinct or present life on Earth.
We experimentally investigate the structure and evolution of planar, inertia-dominated intrusions from a constant source into linearly stratified ambients that are either quiescent or uniformly flowing. The source is either a negatively buoyant plume or a diffuser at the level of neutral buoyancy. The intrusions generated by plumes in a quiescent ambient form self-similar wedges, with constant thickness at the source $(2.5\pm 0.3)\sqrt {Q/N}$ and the wedge lengthening in time $t$ as $(0.32\pm 0.03)\sqrt {\textit{NQ}}\,t$, where $N$ is the buoyancy frequency, and $Q$ is the areal supply rate. In a flowing ambient, the intrusions remain self-similar with the same functional dependence on parameters. However, they become increasingly asymmetric as the ambient flow speed increases, and for speeds greater than approximately $0.3\sqrt {\textit{NQ}}$, there is no upstream propagation. Intrusions generated by diffusers are structurally different and not clearly self-similar. Immediately adjacent to the source, they thicken significantly through a turbulent, entraining hydraulic jump. Beyond this is a gently thinning region that lengthens over time. Ahead of this is a more rapidly tapering nose. Both the area of these intrusions and the front positions increase as power laws in time, with exponents between $0.6$ and $0.7$. With an ambient flow, this overall structure persists with asymmetry. We compare our experimental observations for plume-generated intrusions with predictions from the intrusive shallow-water model of Ungarish (2005, J. Fluid Mech., vol. 535, pp. 287–323). The model explains some of the observed behaviours, but does not provide an accurate description of the thickness profiles.
The present account describes a new species of alpheid shrimp, Alpheus madhusoodanai sp. nov., belonging to the brevirostris group, collected from the Cochin estuary, the south west coast of India. This represents the first species of alpheid shrimps described from the estuary. The morphological and molecular characteristics of the new species are compared with those of its closely related congeners. The newly described species is separated from its morphological congener A. rapax, by its wider major chela and longer merus of the first cheliped. Molecular data also confirmed the delimitation of A. rapax with A. madhusoodanai sp. nov. Habitat and distribution details are also discussed, highlighting the potential for further taxonomic exploration in the Cochin estuary and the importance in uncovering its hidden biodiversity.
The high-Rayleigh-number asymptotic behaviour of three-dimensional steady exact coherent states (ECS) in Rayleigh–Bénard convection is studied. The steady square and hexagonal convection cell states, whose horizontal scales are optimised to maximise Nusselt number, persist into the Rayleigh-number regime where a clear asymptotic trend emerges. A detailed asymptotic analysis of the governing equations reinforces that this trend persists in the limit of infinite Rayleigh number, with the corresponding Nusselt number following the classical scaling to leading order. The optimised Nusselt number of the three-dimensional ECS far exceeds that of the two-dimensional roll solutions, which are believed to bound currently available experimental and simulation results, reaching nearly twice the typical experimental values. This is an interesting result from an applied perspective, although our solutions are unstable at high Rayleigh numbers.
In the decay region around the centreline of three qualitatively different turbulent plane wakes, the turbulence is non-homogeneous and two-point turbulent diffusion counteracts the turbulence cascade all the way down to scales smaller than the Taylor length. It is found that the sum of the inter-space transfer rate and the horizontal part of the inter-scale transfer rate of horizontal two-point turbulent kinetic energy is approximately proportional to the turbulence dissipation rate in the inertial range with a constant of proportionality between $-0.6$ and $-1$ depending on wake and location within the wake, except at the near-field edge of the decay region.