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Polychaetes (Phylum Annelida) respond to sensory stimuli through the usage of sensory organs and appendages, such as palps, which vary in shape and structure depending on lifestyle. The typical palps of nereidid polychaetes are tapered appendages constituted by two articles. The palpophore is the wider and longer basal article, followed by the thinner and shorter palpostyle that contains the majority of sensory cells. Previous studies on Hediste diversicolor palps were focused on these sensory cells. To achieve a more comprehensive view of the histology and ultrastructure of the palps, H. diversicolor specimens were collected from the northern Portuguese Atlantic coast and the palps were processes for light (semithin sections) and transmission electron microscopy. The current study revealed details of the cuticle, which is thinner in the palpostyle than in the palpophore. Five types of secretory cells were distinguished mainly based on the characteristics of their secretory vesicles. Two of these types could be classified as protein-secreting cells, and the other three as mucus-secreting cells. Granulocytes and eleocytes were found in the celom cavity of the palps. The latter contained lipid droplets and a very large amount of glycogen. In the central region of the palpophore, a ring of muscle cells responsible for the retraction of the palpostyle encircled the main palp nerve. The latter was formed by numerous axons and glial cells containing bundles of filaments and gliosomes.
A new genus is established for species of late Paleozoic pterioid bivalves that have substantial ontogenetic change in hinge characters during growth. Juvenile shells have small cardinal and posterior lateral teeth on the hinge that are overgrown on the adult shell and the hinge become edentulous. The shell has a wide ligament plate with a clinovincular ligament (new term). Adjacent to the cardinal teeth on juvenile shell, ligament sheets tend to have small, low amplitude folding and wavy alignment of ligament grooves. A new genus and species, Willipteria nestelli, is described and the species Leptodesma falcata Boyd and Newell, is transferred to genus Willipteria n. gen. Comparison of Willipteria n. gen. to Leptodesma reveals a need to revise Leptodesma. A study of the type lot of genotype species Leptodesma potens Hall, provides a redescription for the genus, presented here. Definition of the new term, clinovincular ligament, is presented. Discussion of muti-sheet ligaments is presented for duplivincular, monovincular, and clinovincular configurations.
Peat is formed by the accumulation of organic material in water-saturated soils. Drainage of peatlands and peat extraction contribute to carbon emissions and biodiversity loss. Most peat extracted for commercial purposes is used for energy production or as a growing substrate. Many countries aim to reduce peat usage but this requires tools to detect its presence in substrates. We propose a decision support system based on deep learning to detect peat-specific testate amoeba in microscopy images. We identified six taxa that are peat-specific and frequent in European peatlands. The shells of two taxa (Archerella sp. and Amphitrema sp.) were well preserved in commercial substrate and can serve as indicators of peat presence. Images from surface and commercial samples were combined into a training set. A separate test set exclusively from commercial substrates was also defined. Both datasets were annotated and YOLOv8 models were trained to detect the shells. An ensemble of eight models was included in the decision support system. Test set performance (average precision) reached values above 0.8 for Archerella sp. and above 0.7 for Amphitrema sp. The system processes thousands of images within minutes and returns a concise list of crops of the most relevant shells. This allows a human operator to quickly make a final decision regarding peat presence. Our method enables the monitoring of peat presence in commercial substrates. It could be extended by including more species for applications in restoration ecology and paleoecology.
The reduction of the hydrodynamic forces exerted on a bluff body in an incoming flow has been an issue of interest in fluid mechanics for many years. However, the Magnus effect indicates possible drag reduction but with the lift being increased significantly. This study is aimed at the simultaneous lift and drag reduction for which we consider a constant incoming flow past a circular cylinder or a sphere in the $x$-direction. Force element analysis (FEA) indicates the possibility of reducing the drag exerted on a circular cylinder or a sphere by rotating (say, clockwise about the $z$-axis) only the front half of the circular cylinder or the sphere. More precisely, we rotate the object but with the rear half covered by a closely spaced hood. Numerical simulations show that by increasing the dimensionless rotational speed $\alpha$: (i) the flow can be quickly stabilised to a steady state; (ii) the mean drag steadily decreases to zero and then becomes negative as $\alpha$ is further increased across the critical $\alpha _I = 4.11$ for the circular cylinder at $Re$ = 200, $\alpha _I = 4.81$ for the sphere at $Re$ = 200 and $\alpha _I = 4.92$ for the sphere at $Re$ = 300; (iii) the mean value of the lift decreases from zero to negative and then increases beyond zero, and in addition, the amplitude of the lift gradually decreases for the circular cylinder; the mean value of the lift decreases from zero to negative for the sphere; (iv) the side force is almost zero – the flow over the sphere is plane-symmetric about the $x{-}y$ plane. These features are compared with the flow past a rotating circular cylinder or a rotating sphere (Magnus effect). Notably, there is a range of flows that can be of practical use for: (a) the circular cylinder where the drag is greatly reduced while the lift is small in magnitude and (b) the sphere where the drag is greatly reduced while the lift is negative in magnitude and the side force is close to 0.
Despite the importance of the commercially harvested benthopelagic fish Beryx mollis, little information is available on their adult phase and reproduction. This is likely due to the low abundance of this species compared to Beryx splendens and Beryx decadactylus as well as misidentification of Beryx spp. In this study, early life stages of B. mollis were found in the southwest region off Sri Lanka during a survey with research vessel Dr Fridtjof Nansen in 2018, coinciding with the southwest monsoon period. As morphological characteristics of eggs and larval stages of the three Beryx spp. are very similar, visual identification to differentiate to species level has always been challenging. Therefore, in this study, DNA barcoding was carried out targeting the mitochondrial COI gene. Molecular analysis confirmed that the collected egg and larvae belonged to the B. mollis species due to their high identity (>99%) with reference to previously submitted adult B. mollis sequences in the GenBank. Phylogenetic analysis showed a closer evolutionary relationship among B. mollis and B. splendens than with B. decadactylus. To the best of our knowledge this is the first genetic and morphological confirmation of B. mollis egg and larvae worldwide and suggests the southwest coastal area in Sri Lanka, in the north central Indian Ocean, as a potential spawning ground for this species.
We examined a zooarchaeological assemblage from Badger Island, a 12.4 km2 landbridge island in the Furneaux Group, Bass Strait, south-eastern Australia. The accumulation consisted of Pleistocene and Holocene strata that were rich in mammal remains. Small mammal remains were accumulated by owls, whereas large mammal remains were accumulated by people and/or autochthonous mortality. The Pleistocene fauna was dominated by grassland mammals, particularly Mastacomys fuscus (Broad-toothed Rat), but these gradually declined and were largely replaced by forest–woodland dwelling mammals in the Holocene. The same pattern of faunal change has been observed on the large main island of Tasmania (∼65,000 km2), suggesting changes observed at Beeton Rockshelter are representative of the region. Because all of the Furneaux Group Islands were united as one landmass in the past, the fossil fauna observed in Beeton Rockshelter is relevant to conservation-oriented mammal-restoration initiatives, which are being considered throughout the entire Furneaux Group.
Increasing penetration of variable and intermittent renewable energy resources on the energy grid poses a challenge for reliable and efficient grid operation, necessitating the development of algorithms that are robust to this uncertainty. However, standard algorithms incorporating uncertainty for generation dispatch are computationally intractable when costs are nonconvex, and machine learning-based approaches lack worst-case guarantees on their performance. In this work, we propose a learning-augmented algorithm, RobustML, that exploits the good average-case performance of a machine-learned algorithm for minimizing dispatch and ramping costs of dispatchable generation resources while providing provable worst-case guarantees on cost. We evaluate the algorithm on a realistic model of a combined cycle cogeneration plant, where it exhibits robustness to distribution shift while enabling improved efficiency as renewables penetration increases.
As climate change intensifies, conflict-prone tropical regions face heightened vulnerabilities, yet little is known about how climate adaptation and food security efforts affect conflict dynamics. Using South Sudan – a country highly susceptible to climate stress and conflict – as a test case, this Element analyzes how international nongovernmental organizations' (INGO) climate adaptation interventions influence civil war and local social conflicts. It develops a theoretical framework linking climate adaptation to conflict, positing both positive and negative externalities. Drawing on original high-resolution data on INGO-driven adaptation and food security efforts, alongside climate, conflict, and development data, findings are substantiated with interviews from policy workers in South Sudan. The results indicate that while adaptation generally does not reduce conflict, interventions that promote preparedness and are implemented during periods of high climate stress can mitigate social conflicts between militias, pastoralists, and farmers. These insights provide guidance for designing climate adaptation strategies that reduce conflict risks.
We propose an analytical approach based on the Frenet–Serret (FL) frame field, where an FL frame and the corresponding curvature and torsion are defined at each point along magnetic field lines, to investigate the evolution of magnetic tubes and their interaction with vortex tubes in magnetohydrodynamics. Within this framework, simplified expressions for the Lorentz force, its curl, the dynamics of flux tubes and helicity are derived. We further perform direct numerical simulations on the linkage between the magnetic and vortex tubes and investigate the effect of the initial angle $\theta$, ranging from $0^{\,\circ}$ to $45^{\,\circ}$, on their evolution. Our results show that magnetic tubes with non-zero curvature generate Lorentz forces, which in turn produce dipole vortices. These dipole vortices lead to the splitting of the magnetic tubes into smaller structures, releasing magnetic energy. Both magnetic and vortex tubes exhibit quasi-Lagrangian behaviour, maintaining similar shapes during initial evolution and consistent relative positions over time. A vortex tube with strength comparable to that of the magnetic tube, where the kinetic energy induced by the vortex tube is of the same order as the magnetic energy in the magnetic tube, can inhibit magnetic tube splitting by disrupting the formation of vortex dipoles. Additionally, minor variations in the angular configuration of the vortex tubes significantly influence their interaction with the magnetic field and the evolution of large-scale flow structures.
Globally, glaciers are changing in response to climate warming, with those that terminate in water often undergoing the most rapid change. In Alaska and northwest Canada, proglacial lakes have grown in number and size but their influence on glacier mass loss is unclear. We characterized the rates of retreat and mass loss through frontal ablation of 55 lake-terminating glaciers (>14 000 km2) in the region using annual Landsat imagery from 1984 to 2021. We find a median retreat rate of 60 m a−1 (interquartile range = 35–89 m a−1) over 1984–2018 and a median loss of 0.04 Gt a−1 (0.01–0.15 Gt a−1) mass through frontal ablation over 2009–18. Summed over 2009–18, our study glaciers lost 6.1 Gt a−1 to frontal ablation. Analysis of bed profiles suggest that glaciers terminating in larger lakes and deeper water lose more mass to frontal ablation, and that the glaciers will remain lake-terminating for an average of 74 years (38–177 a). This work suggests that as more proglacial lakes form and as lakes become larger, enhanced frontal ablation could cause higher mass losses, which should be considered when projecting the future of lake-terminating glaciers.
There is a reasonable possibility that the present-day Atlantic Meridional Overturning Circulation is in a bistable regime, hence it is relevant to compute pathways of noise-induced transitions between the stable equilibrium states. Here, the most probable transition pathway of a noise-induced tipping of the northern overturning circulation in a spatially-continuous two-dimensional model with surface temperature and stochastic salinity forcings is computed directly using large deviation theory. This pathway reveals the fluid dynamical mechanisms of such a tipping. Paradoxically it starts off with a strengthening of the northern overturning circulation before a short but strong salinity pulse induces a second overturning cell. The increased atmospheric energy input of this two-cell configuration cannot be mixed away quickly enough, leading to the collapse of the northern overturning cell, and finally resulting in a southern overturning circulation. Additionally, the approach allows us to compare the probability of this transition under different parameters in the deterministic part of the salinity surface forcing, which quantifies the increase in transition probability as the bifurcation point of the system is approached.
The mass balance of lake-terminating glaciers responds to annual atmospheric variations, while calving-induced ice loss at the front is driven by local ice–water interactions. The current glaciological studies underestimate glacier response by neglecting the significant annual ice loss at the terminus through calving processes. This study integrates field measurements with remote sensing data to investigate the glaciological characteristics and proglacial lake evolution of the Gepang Gath glacier in the Chandra basin, Western Himalaya, India. Long-term observations reveal a continuous expansion of the proglacial lake from 0.21 ± 0.06 km2 (1962) to 1.21 ± 0.05 km2 (2023), along with terminus retreat of ∼2.76 km, attributed to calving at the ice–water interface. The glacier’s surface exhibits complex debris cover, with thicknesses up to 35 cm, creating significant spatial variations in surface mass balance. In-situ, glaciological measurements reveal a highly negative glacier-wide mass balance of −0.90 ± 0.30 m w.e. a−1 between the years 2014 and 2023. The geodetic estimates also reveal a negative mass balance of −0.61 ± 0.1 m w.e. a−1 over the past decade (2013–2023). The frontal area change (0.42 km2) and geodetic mass balance show a total volumetric ice loss of −21.77 × 106 m3 w.e. during the same period. Overall, the yearly frontal ice loss exacerbates the mass loss by 17–22%. These findings suggest that the presence of proglacial lakes plays a significant role in intensifying ice mass loss from Himalayan glaciers, strongly regulating their overall evolution.
We investigate the statistical properties of kinetic and thermal dissipation rates in two-dimensional/three-dimensional vertical convection of liquid metal ($Pr = 0.032$) within a square cavity. Two situations are specifically discussed: (i) classical vertical convection with no external forces and (ii) vertical magnetoconvection with a horizontal magnetic field. Through an analysis of dissipation fields and a reasonable approximation of buoyancy potential energy sourced from vertical heat flux, the issue of the ‘non-closure of the dissipation balance relation’, which has hindered the application of the GL theory in vertical convection, is partially resolved. The resulting asymptotic power laws are consistent with existing laminar scaling theories and even show certain advantages in validating simulations with large Prandtl number ($Pr$). Additionally, a full-parameter model and prefactors applicable to low-$Pr$ fluids are provided. The extension to magnetoconvection naturally introduces the approximate expression for total buoyancy potential energy and necessitates adjustments to the contributions of kinetic dissipation in both the bulk and boundary layer. The flow dimensionality and boundary layer thickness are key considerations in this analysis. The comprehension of Joule dissipation has been updated: the Lorentz force generates positive dissipation in the bulk by suppressing convection, while in the Hartmann layer, shaping the exponential boundary layer requires the fluid to perform positive work to accelerate, leading to negative dissipation. Finally, the proposed transport equations for magnetoconvection are supported by current direct numerical simulation (DNS) and literature data, and the applicability of the model is discussed.
New approaches to ensure the resilience of urban water supply are urgently needed. This requires moving beyond managing water scarcity through infrastructural measures to understanding resilience as an outcome of complex interactions between people, water resources, and technological infrastructure. We conducted expert interviews and a household survey in a water scarcity ‘hotspot’ and found that water experts emphasize water system deficits and inefficiencies, while citizens complement public water service deficits through (unaccounted-for) coping mechanisms. This leads to uncertainties regarding the outcomes of management interventions. We suggest that integrating different stakeholder perspectives into water management strategies could enhance urban water resilience.
Technical summary
There is limited understanding of how to address the complex dynamics shaping the resilience of increasingly water-scarce cities, globally. By conceptualizing urban water systems as social–ecological–technological systems (SETS) and analysing their interactions from different stakeholder perspectives, we create a pluralistic, yet systematic, understanding of SETS interactions. We conducted expert interviews (N = 19) and a household survey (N = 300) in Amman, one of the world’s water scarcity hotspots, and analysed the data in three steps: (1) We analysed the SETS through the lens of its different actor groups, and, inspired by frame analysis, interpreted each group's system perspective – local experts focus on deficits of SETS elements and aim to increase available resources, while international experts emphasize the efficiency of SETS interactions. Households cope with deficient water supplies by mobilizing adaptive strategies. (2) Combining these three perspectives, we derived uncertainties resulting from different (and unrecognized) stakeholder views, missing knowledge, and unpredictable system dynamics. (3) We identified and characterized new SETS interactions for an urban, resource-constrained environment, which contributes to a typology aiming for better comparability across SETS. Our results have implications for resilience-oriented urban water management and governance in terms of what to manage (fast/slow variables, connectivity), how (learning/experimenting), and by whom (broad participation).
Social media summary
Addressing uncertainty by reframing resilience-oriented urban water management with complementary system perceptions.
The shallow-water equations are widely used to model interactions between horizontal shear flows and (rotating) gravity waves in thin planetary atmospheres. Their extension to allow for interactions with magnetic fields – the equations of shallow-water magnetohydrodynamics (SWMHD) – is often used to model waves and instabilities in thin stratified layers in stellar and planetary atmospheres, in the perfectly conducting limit. Here we consider how magnetic diffusion should be added to the equations of SWMHD. This is crucial for an accurate balance between advection and diffusion in the induction equation, and hence for modelling instabilities and turbulence. For the straightforward choice of Laplacian diffusion, we explain how fundamental mathematical and physical inconsistencies arise in the equations of SWMHD, and show that unphysical dynamo action can result. We then derive a physically consistent magnetic diffusion term by performing an asymptotic analysis of the three-dimensional equations of magnetohydrodynamics in the thin-layer limit, giving the resulting diffusion term explicitly in both planar and spherical coordinates. We show how this magnetic diffusion term, which allows for a horizontally varying diffusivity, is consistent with the standard shallow-water solenoidal constraint, and leads to negative semidefinite Ohmic dissipation. We also establish a basic type of antidynamo theorem.