University of Exeter
  • Exeter, United Kingdom
Recent publications
Globally, fish have been severely affected by the widespread, chronic degradation of fresh waters, with a substantial proportion of species declining in abundance or range in recent decades. This has especially been the case in densely populated countries with an industrial heritage and intensive agriculture, where the majority of river catchments have been affected by deteriorations in water quality and changes in land use. This study used a spatially and temporally extensive dataset, encompassing 16,124 surveys at 1180 sites representing a wide range of river typologies and pressures, to examine changes in the fish populations of England’s rivers over four decades (1980s–2010s). The analyses revealed gradual, nationwide increases in mean fish species richness and diversity across the range of pressure gradients. In the majority of cases, increases were most pronounced in the 1980s, since when any further changes have been comparatively minor, but there were no declining trends across the full time series. There were also temporal, nationwide changes in fish assemblage structure, driven largely by variations in the densities of brown trout Salmo trutta or roach Rutilus rutilus, but no consistent increases in the abundance of sensitive, pollution-intolerant species in response to improvements in wastewater treatment and, consequently, water quality. Although the increases in fish species richness and diversity over the last four decades are encouraging, subtle and contrasting changes in the abundance of a range of species require further investigation, and causal relationships between fish assemblage structure and putative drivers should be modelled at a national scale. This study is the first to examine long-term, nationwide trends in the freshwater fish populations of England, and significantly advances our understanding of the ecological health of rivers in densely populated and heavily modified countries.
Objective The relationship between sleep and epilepsy is important but imperfectly understood. We sought to understand the mechanisms that explain the differences in sleep homeostasis observed in children with epilepsy. Methods We used a neural mass model to replicate sleep electroencephalography (EEG) recorded from 15 children with focal lesional epilepsies and 16 healthy age‐matched controls. Different parameter sets were recovered in the model for each subject. Results The model revealed that sleep EEG differences are driven by enhanced firing rates in the neuronal populations of patients, which arise predominantly due to enhanced excitatory synaptic currents. These differences were more marked in patients who had seizures within 72 h after the sleep recording. Furthermore, model parameters inferred from patients resided closer to model parameters inferred from a typical seizure rhythm. Significance These results demonstrate that brain mechanisms relating to epilepsy manifest in the interictal EEG in slow‐wave sleep, and that EEG recorded from patients can be mapped to synaptic deficits that may explain their predisposition to seizures. Neural mass models inferred from sleep EEG data have the potential to generate new biomarkers to predict seizure occurrence and inform treatment decisions.
The propagation of elastic waves on discrete periodic Euler–Bernoulli mass-beam lattices is characterised by the competition between coupled translational and rotational degrees-of-freedom at the mass-beam junctions. We influence the dynamics of this system by coupling junctions with beyond-nearest-neighbour spatial connections, affording freedom over the locality of dispersion extrema in reciprocal space, facilitating the emergence of interesting dispersion relations. A generalised dispersion relation for an infinite monatomic mass-beam chain, with any integer order combination of non-local spatial connections, is presented. We demonstrate that competing power channels, between mass and rotational inertia, drive the position and existence of zero group velocity modes within the first Brillouin zone.
Home range size and metabolic rate of animals are theorized to scale in relation to body mass with similar exponents. This expectation has only been indirectly tested using lab‐derived estimates of basal metabolic rate as proxies for field energy requirements. Therefore, it is unclear if existing theory aligns with observed patterns of home range scaling since field metabolic rates may scale differently than basal metabolic rates. We conducted the first direct field test of the relationship between home range and metabolic rate allometry. Using acoustic telemetry, we simultaneously measured the home range sizes and field metabolic rates of lemon sharks (Negaprion brevirostris) spanning one order of magnitude in body mass and compared the allometric scaling exponents of these traits. Similarity between allometric scaling exponents confirmed an expected strong association between metabolic rate and home range size. However, a nonsignificant but negative association between standard metabolic rate (SMR) and home range size suggests a complex relationship between metabolism and home range, contrasting previous assumptions of a positive relationship. Nevertheless, an overall positive association between home range size and total metabolic rate persisted, driven by a strong association between active energy expenditure and home range size. These findings underscore the intricate relationship between energetics and home range size, emphasizing the need for additional direct field investigations and the potential for modern tagging technologies to gather relevant data.
Plant cytokinesis requires coordination between the actin cytoskeleton, microtubules, and membranes to guide division plane formation and cell plate expansion; how these regulatory factors are coordinated remains unknown. The actin cytoskeleton assembly is controlled by several actin nucleation factors, such as the SCAR/WAVE complex, which regulates actin nucleation and branching through the activation of the ARP2/3 complex. The activity of these actin regulatory proteins is likely influenced by interactions with specific membranes; however, the molecular basis and the biological relevance of SCAR–membrane interactions are also unclear. In this study, we demonstrate that the ER–PM tethering protein VAP27-1 directly interacts with SCAR2 at the ER membrane and that they colocalize to guide cell plate orientation during cell division. In the root meristem, both VAP27-1 and SCAR2 exhibit polarized localization at the cell plates, where the interaction between ER and PM is abundant. VAP27-1 recruits SCAR2 to the cell division plane, where there is a high concentration of actin filaments. In the vap27-1346 mutant, the densities of cortical ER, SCAR2, and consequently actin filaments are significantly reduced at the cell division plane, affecting cell plate orientation, cell division, and root development. A similar phenomenon is also observed in the scar1234 mutant, suggesting that VAP27 and SCAR proteins regulate cell division through a similar pathway. In conclusion, our data reveal a plant-specific function of VAP27-regulated ER–PM interaction and advance our understanding of plant ER–PM contact site and its role in cell division.
Waste is an important socio‐ecological challenge of contemporary capitalism, contributing to climate change and environmental degradation. Despite its pervasiveness and its impacts on diverse stakeholders, it yet remains largely underexplored in management and organization studies. Addressing this gap, this paper investigates waste's crucial role in shaping specific stakeholder relations by theorizing it as a technique of power. By examining the case of a socio‐ecological crisis in Naples, Italy, characterized by illegal waste practices linked to Mafia organizations, we unpack two entangled techniques of power: commodifying waste – transforming it into something that can be traded on a market and perpetuating its exploitation; and ignoring waste – involving failing or refusing to consider and recognize waste. Our findings elucidate how these two techniques produced and reinforced socio‐ecological hierarchies, in which local stakeholders were wasted. By highlighting the lived experiences of local communities affected by waste, our study contributes to a deeper understanding of power dynamics among diverse stakeholders in socio‐ecological crises and demonstrates how waste functions as a mechanism of dispossession within capitalist accumulation.
The need to maintain strong social bonds is widely thought to be a key driver of cognitive evolution. Cognitive abilities to track and respond to information about social partners may be favoured by selection if they vary within populations and confer fitness benefits. Here we evaluate four key assumptions of this argument in wild jackdaws (Corvus monedula), corvids whose long-term pair bonds exemplify one of the putative social drivers of cognitive evolution in birds. Combining observational and experimental behavioural data with long-term breeding records, we found support for three assumptions: (i) pair-bond strength varies across the population, (ii) is consistent within pairs over time and (iii) is positively associated with partner responsiveness, a measure of socio-cognitive performance. However, (iv) we did not find clear evidence that stronger pair bonds lead to better fitness outcomes. Strongly bonded pairs were better able to adjust hatching synchrony to environmental conditions but they did not fledge more or higher quality offspring. Together, these findings suggest that maintaining strong pair bonds is linked to socio-cognitive performance and may facilitate effective coordination between partners. However, they also imply that these benefits are insufficient to explain how selection acts on social cognition. We argue that evaluating how animals navigate trade-offs between investing in long-term relationships versus optimizing interactions in their wider social networks will be a crucial avenue for future research.
Bee declines have been partly attributed to the impacts of invasive or emerging parasite outbreaks. For western honeybees, Apis mellifera, major losses are associated with the virus-vectoring mite, Varroa destructor. In response, beekeepers have focused breeding efforts aimed at conferring resistance to this key parasite. One method of many is survival-based beekeeping where colonies that survive despite significant Varroa infestations produce subsequent colonies. We argue that this ‘hands-off’ approach will not always lead to Varroa resistance evolving but rather tolerance. Tolerance minimizes host fitness costs of parasitism without reducing parasite abundance, whereas resistance either prevents parasitism outright or keeps parasitism intensity low. With clear epidemiological distinctions, and as honeybee disease dynamics impact other wild bees owing to shared pathogens, we discuss why tolerance outcomes in honeybee breeding have important implications for wider pollinator health. Crucially, we argue that unintentional selection for tolerance will not only lead to more spillover from honeybees but may also select for pathogens that are more virulent in wild bees leading to ‘tragedies of tolerance’. These tragedies can be avoided through successful breeding regimes that specifically select for low Varroa. We emphasize how insights from evolutionary ecology can be applied in ecologically responsible honeybee management.
Atmospheric models used for weather forecasting and climate predictions discretise the atmosphere onto a vertical grid. There are however atmospheric phenomena that occur on scales smaller than the thickness of those model layers. The formation of low‐level clouds due to temperature inversions is an example. This leads to atmospheric models underestimating, or even missing, these clouds and their radiative effects. Using radiosonde observations as training data, a machine learning model is used to improve the vertical detail of modelled profiles of temperature and specific humidity. In addition, a physics‐informed machine learning model is developed and compared to the traditional approach; showing improvements in the cloud fraction profiles calculated from its predictions. The vertically enhanced profiles also improve the representation of layers of convective inhibition and anomalous refractivity gradients. This work facilitates targeted improvements to the representation of certain atmospheric processes without the burden of increased memory and computational cost from increasing vertical resolution throughout the whole model.
Objectives The current study aimed to explore participants’ views on the acceptability, impact and mechanisms of change of Augmented Depression Therapy (ADepT), a novel wellbeing-focused and recovery-oriented psychological therapy for depression. Design A semi-structured qualitative interview design was used, with data analysed using the framework approach. Participants 20 participants with anhedonic depression who had received up to 20 sessions of ADepT, sampled from a pilot randomised controlled trial of ADepT versus Cognitive Behavioural Therapy (CBT). Setting A primary care psychological therapy clinic in Devon, UK, with interviews occurring between May 2018 and February 2020. Results Participants found the wellbeing focus of ADepT acceptable. Helpful aspects of therapy were a positive therapeutic bond, the structure and flow of therapy scaffolding the learning journey, the tools and techniques of therapy helping building wellbeing and booster sessions supporting long-term recovery. Negative aspects for some participants were therapy feeling too intense and triggering feelings of failure. Participants reported significant positive impacts of treatment on wellbeing, functioning and hope. Perceived mechanisms of change were reorienting to the positive, engaging with valued goals, taking a proactive life stance, gaining confidence and motivation for change, breaking down tasks into small steps, cultivating self-care and self-compassion, enhancing help seeking and interpersonal effectiveness, changing the relationship to depression, and rediscovering the self beyond depression. Conclusions Findings suggest that the wellbeing focus of ADepT is acceptable and leads to positive impacts, supports the logic model underpinning the intervention, and warrants continuation to a definitive trial. Trial registration number ISRCTN85278228 .
Wnt signalling is an essential signalling system in neurogenesis, with a crucial role in synaptic plasticity and neuronal survival, processes that are disrupted in Alzheimer's disease (AD). Within this network, the Wnt/β-catenin pathway has been studied for its neuroprotective role, and this is suppressed in AD. However, the involvement of the non-canonical Wnt-planar cell polarity (Wnt/PCP) pathway in AD remains to be determined. This study investigates the role of ROR2, a Wnt/PCP co-receptor, in synaptogenesis. We demonstrate that WNT5A-ROR2 signalling activates the JNK pathway, leading to synapse loss in mature neurons. This effect mirrors the synaptotoxic actions of Aβ1-42 and DKK1, which are elevated in AD. Notably, blocking ROR2 and JNK mitigates Aβ1-42 and DKK1-induced synapse loss, suggesting their dependence on ROR2. In induced pluripotent stem cell (iPSC)-derived cortical neurons carrying a PSEN1 mutation, known to increase the Aβ42/40 ratio, we observed increased WNT5A-ROR2 clustering and reduced numbers of synapses. Inhibiting ROR2 or JNK partially rescued synaptogenesis in these neurons. These findings suggest that, unlike the Wnt/β-catenin pathway, the Wnt/PCP-ROR2 signalling pathway can operate in a feedback loop with Aβ1-42 to enhance JNK signalling and contribute to synapse loss in AD.
A mismatch of species’ thermal preferences to their environment may indicate how they will respond to future climate change. Averaging this mismatch across species may forewarn that some assemblages will undergo greater reorganization, extirpation, and possibly extinction, than others. Here, we examine how regional warming determines species occupancy and assemblage composition of marine bivalves, brachiopods, and gastropods over one-million-year time steps during the Early Jurassic. Thermal bias, the difference between modelled regional temperatures and species’ long-term thermal optima, predicts a gradient of species occupancy response to warming. Species that become extirpated or extinct tend to have cooler temperature preferences than immigrating species, while regionally persisting species fell midway. Larger regional changes in summer seawater temperatures (up to +10 °C) strengthen the relationship between species thermal bias and the response gradient, which is also stronger for brachiopods than for bivalves, while the relationship collapses during severe seawater deoxygenation. At +3 °C regional seawater warming, around 5 % of pre-existing benthic species in a regional assemblage are extirpated, and immigrating species comprise around one-fourth of the new assemblage. Our results validate thermal bias as an indicator of immigration, persistence, extirpation, and extinction of marine benthic species and assemblages under modern-like magnitudes of climate change.
Enhanced weathering (EW) with agriculture uses crushed silicate rocks to drive carbon dioxide removal (CDR)1,2. If widely adopted on farmlands, it could help achieve net-zero emissions by 20502, 3–4. Here we show, with a detailed US state-specific carbon cycle analysis constrained by resource provision, that EW deployed on agricultural land could sequester 0.16–0.30 GtCO2 yr⁻¹ by 2050, rising to 0.25–0.49 GtCO2 yr⁻¹ by 2070. Geochemical assessment of rivers and oceans suggests effective transport of dissolved products from EW from soils, offering CDR on intergenerational timescales. Our analysis further indicates that EW may temporarily help lower ground-level ozone and concentrations of secondary aerosols in agricultural regions. Geospatially mapped CDR costs show heterogeneity across the USA, reflecting a combination of cropland distance from basalt source regions, timing of EW deployment and evolving CDR rates. CDR costs are highest in the first two decades before declining to about US$100–150 tCO2⁻¹ by 2050, including for states that contribute most to total national CDR. Although EW cannot be a substitute for emission reductions, our assessment strengthens the case for EW as an overlooked practical innovation for helping the USA meet net-zero 2050 goals5,6. Public awareness of EW and equity impacts of EW deployment across the USA require further exploration7,8 and we note that mobilizing an EW industry at the necessary scale could take decades.
Debates surrounding the nature of mental disorder have tended to divide into an objectivist camp that takes psychiatric classification to be a value-free scientific matter, and a normativist camp that takes it to be irreducibly values-based. Here we present an overlooked distinction between status and constitution. Questions of the form “What is x?” are ambiguous between status questions (“What gives something the status of an x?”), and constitution questions (“Given that something has the status of an x, what is it made of?”). We elucidate this distinction in detail, and argue that normativism is uniquely well-placed to answer status questions while objectivism provides answers, where they are available, to constitution questions.
Understanding the processes that drive phenotypic diversification and underpin speciation is key to elucidating how biodiversity has evolved. Although these processes have been studied across a wide array of clades, adaptive radiations (ARs), which are systems with multiple closely related species and broad phenotypic diversity, have been particularly fruitful for teasing apart the factors that drive and constrain diversification. As such, ARs have become popular candidate study systems for determining the extent to which ecological features, including aspects of organisms and the environment, and inter- and intraspecific interactions, led to evolutionary diversification. Despite substantial past empirical and theoretical work, understanding mechanistically how ARs evolve remains a major challenge. Here, we highlight a number of understudied components of the environment and of lineages themselves, which may help further our understanding of speciation and AR. We also outline some substantial remaining challenges to achieving a detailed understanding of adaptation, speciation, and the role of ecology in these processes. These major challenges include identifying factors that have a causative impact in promoting or constraining ARs, gaining a more holistic understanding of features of organisms and their environment that interact resulting in adaptation and speciation, and understanding whether the role of these organismal and environmental features varies throughout the radiation process. We conclude by providing perspectives on how future investigations into the AR process can overcome these challenges, allowing us to glean mechanistic insights into adaptation and speciation
In recent years, colonic capsule endoscopy has become available in clinical practice as an alternative modality to colonoscopy. However, it faces challenges such as prolonged examination time and the absence of clinician navigation. Leveraging their pioneering work in the field of vibro-impact self-propulsion technique for gastrointestinal endoscopy, Zhang et al. (IEEE Robot. Autom. Lett. 8:1842–1849, 2023) developed a novel, untethered, self-propelled, endoscopic capsule robot, with the aim of providing a new means of examining bowel cancer in real time. To evaluate and optimize the passage of this capsule robot self-propelling in the large intestine, this work adopts multibody dynamics analysis and experimental investigation to study the robot’s dynamics and its interaction with the intestinal environment. Considering the complex anatomy of the large intestine, containing different sections, e.g., cecum, ascending, transverse, descending, and sigmoid colon, and variations of the haustra, e.g., with various radii, lengths, and heights, the robot was driven by the square-wave excitation of an inner mass interacting with the capsule body and tested on a real porcine colon. The robot’s driving parameters, including the excitation frequency, amplitude, and duty cycle, and the dimensions of the haustra are the two main factors influencing the robot’s progression in the intestine. By comparing with the experimental results, the proposed multibody dynamics model developed using MSC Adams can estimate the movement of the capsule robot and the intestinal resistance quantitatively. Extensive numerical and experimental studies suggest an excitation frequency of 60 Hz and a duty cycle of 0.4 as the optimal parameters for driving the robot, and the longer the haustral length is, the faster the robot passes through. These results ensure the validity of the proposed multibody dynamics platform, which can be used by robotic engineers for developing medical robots for intestinal examinations.
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31,753 members
Junning Chen
  • Biomedical Engineering
Craig Anthony Williams
  • Children's Health and Exercise Research Centre, Sport and Health Sciences
Dana Wilson-Kovacs
  • Department of Social and Political SciencesPhilosophy and Anthropology
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