32151 research outputs found
Sort by
The onset of filamentation on vorticity interfaces in two-dimensional Euler flows
Get PDFTwo-dimensional Euler flows, in the plane or on simple surfaces, possess a material invariant, namely the scalar vorticity normal to the surface. Consequently, flows with piecewise-uniform vorticity remain that way, and moreover evolve in a way which is entirely determined by the instantaneous shapes of the contours (interfaces) separating different regions of vorticity – this is known as ‘contour dynamics’. Unsteady vorticity contours or interfaces often grow in complexity (lengthen and fold), either as a result of vortex interactions (like mergers) or ‘filamentation’. In the latter, wave disturbances riding on a background, equilibrium contour shape appear to inevitably steepen and break, forming filaments, repeatedly– and perhaps endlessly. Here, we revisit the onset of filamentation. Building upon previous work and using a weakly nonlinear expansion to third order in wave amplitude, we derive a universal, parameter-free amplitude equation which applies (with a minor change) both to a straight interface and a circular patch in the plane, as well as circular vortex patches on the surface of a sphere. We show that this equation possesses a local, self-similar form describing the finite-time blow up of the wave slope (in a re-scaled long time proportional to the inverse square of the initial wave amplitude). We present numerical evidence for this self-similar blow-up solution, and for the conjecture that almost all initial conditions lead to finite-time blow up. In the full contour dynamics equations, this corresponds to the onset of filamentation.Peer reviewe
Audience effects in sooty mangabey agonistic behavior
Get PDFFunding: The author(s) declare that financial support was received for the research and/or publication of this article. The research has been funded by the Swiss National Science Foundation (310030_143359), the Swiss National Centre of Competence in Research ‘Evolving Language’ (#51NF40 180888).The term ‘Audience Effects’, refers to behavioral changes triggered by the mere presence of others and has been extensively studied in animals to explore their capacity for social awareness and intentionality. Research shows that a wide range of species—from insects to primates—alter behaviors depending on their audience, with primates, especially great apes, demonstrating the most complex audience-aware behaviors, such as adjusting communication based on the recipient’s attention or understanding. These findings suggest that some animals can infer intentions, remember social dynamics, and strategically act depending on who is watching. However, there is still limited data from non-ape primates and other mammals, raising questions about whether such cognitive traits evolved through shared ancestry or convergent evolution. Aggressive behaviors also reveal audience effects, with individuals, especially lower-ranking ones, using strategic aggression in front of influential bystanders to influence future interactions. In this study, we used focal animal sampling to investigate how free-ranging sooty mangabeys, a terrestrial forest-dwelling primate living in large groups, used aggression depending on the composition of the audience. We found that individuals were significantly more aggressive to opponents if they were observed by large audiences that contained higher ranking individuals. These displays of aggression were often accompanied by vocalizations, further suggesting that aggressors were interested in attracting the audience’s attention. We discuss these patterns of audience-dependent aggressive behavior and propose that sooty mangabeys adjust their social behavior depending on the composition of the bystanding audience, reacting in the most appropriate way depending on the situation, which provides additional support to the growing body of research showing that the underlying mechanisms necessary for the evolution of complex social cognition are more widespread in the animal kingdom than was previously thought.Peer reviewe
Losing control of Tocqueville : J. P. Mayer and the genesis of Gallimard’s Œuvres complètes d’Alexis de Tocqueville
Get PDFIn June 2021, the last of the eighteen volumes of Alexis de Tocqueville’s Œuvres complètes was published by Éditions Gallimard. This mammoth publishing venture had been set in motion more than seventy years earlier by Jacob Peter Mayer, a German-Jewish writer, sometime socialist and anti-Nazi activist, who had fled to England in 1936. Mayer moved from seeing Marx as the source of solutions to world problems to describing Tocqueville as the ‘prophet of mass democracy’. Mayer held that Tocqueville’s insights into democracy, fanaticism, international relations, equality and revolution were more relevant to the nation states of the post-war era than any other author. Mayer commenced a mission, supported by Gallimard and the Tocqueville family, to publish all of Tocqueville’s writings, intended both to make his work more accessible but also to underscore its contemporary relevance. Making use of unpublished letters and documents from Mayer’s own papers as well as from the archives of Gallimard, this article tells the story of how Mayer came to direct the publication of Tocqueville’s complete works. It highlights the importance of his friendship with Tocqueville’s great grandnephew, Comte Jean de Tocqueville, who gave him access to the French writer’s unpublished papers, and it details the early disputes he had with the national commission that was set up by the French government to oversee the project. The article also describes how he eventually lost control of the project – he was certain because of French nationalism - after thirty years as editor-in-chief, an outcome reflecting his growing pessimism about the prospects of the free states of the West. His experience of editing Tocqueville confirmed in his eyes that free states lacked democratic cultures sufficient to sustain them.Peer reviewe
Prehistoric communities of the river Dee : mesolithic and other lithic scatter sites of central Deeside, Aberdeenshire
No full textFunding: National Lottery Heritage Fund; Aberdeenshire Council Archaeology Service; Historic Environment Scotland; University of Aberdeen; Kincardine and Mearns Area Committee; Aberdeenshire Council; Marr Area Committee, Aberdeenshire Council; Small Grant Project Scheme; Mid Hill Wind Farm; Lithic Studies SocietyThis volume presents the results of archaeological fieldwork undertaken along the River Dee, Aberdeenshire, north-east Scotland, by the Mesolithic Deeside voluntary community archaeology group between 2017 and 2019. A total of 42 fields were investigated, from which over 11,000 lithics were recovered, representing at least 15 archaeological sites and a span of human activity covering some 10,000 years from around 12,000 BC to c 2000 BC. Finds from the Late Upper Palaeolithic, Mesolithic, Neolithic and Bronze Age were present. Work comprised fieldwalking, test pitting, specialist analysis, and small-scale excavation. The investigation described here is significant not just for the light it throws on the early prehistoric populations along the River Dee but also for the methodology by which investigation was undertaken, as this provides a potential model for work in other areas. Both aspects are covered in the report. The River Dee flows between postglacial gravel and sand terraces, the structure of which has played an important role for the early settlers of the area, and this is covered in some detail in order to provide the physical background framework for the sites. There are also sections on more specialised geophysical and geoscience techniques where these were undertaken, together with a summary of research on the palaeoenvironmental conditions throughout the millennia of prehistory. The artefactual evidence comprises lithic assemblages which were all catalogued as fieldwork progressed; the contents of each site are presented, together with more detailed analysis of the finds from test pitted sites. Finally, given the rich archaeological record from the area, the results of the present project are set into the wider context of the evidence for prehistoric settlement along the river, and there is consideration of future directions for further fieldwork.Peer reviewe
Characterising PMP22 proximal partners in a Schwann cell model of Charcot-Marie-Tooth disease type1A
Get PDFFunding: This research was funded by the Orthopaedic Institute Ltd., RJAH Orthopaedic Hospital, Oswestry, UK (RPG193). We acknowledge the Neurofibromatosis Therapeutic Acceleration Program at Johns Hopkins (NTAP, Baltimore, MD 21287, USA) for funding support to purchase the CRL-3392 cell line. Mass Spectrometry analysis was performed on a Fusion Lumos Mass spectrometer purchased by BBSRC grant BB/T017686/1.Charcot-Marie-Tooth disease type 1A (CMT1A) is a hereditary condition caused by duplication of the PMP22 gene. Overexpression of peripheral myelin protein 22 in Schwann cells leads to myelin sheath defects and axonal loss. We have produced a cell model to facilitate studies of the molecular mechanisms involved in PMP22 accumulation and clearance. Our model is a stably transfected, clonal, immortalized human Schwann cell line with over-expressed levels of PMP22 fusion protein. A control-transfected cell line (vector lacking PMP22) was also produced. PMP22-transfected cells had reduced levels of mitosis, with the PMP22 fusion protein concentrated in punctate aggregates in the cytoplasm and expressed at the plasma membranes, which were often irregular and spindly. In contrast, control cells (control-transfected and parent cell lines) generally had smooth and regular plasma membrane morphology. Culturing in the presence of NRG1 and forskolin lead to upregulation of markers of myelination potential in the control cells. These markers were more variable in the cells stably transfected with PMP22, including decreased levels of transcripts of SOX10, S100B and NGFR, but increased levels of MPZ andEGR2 compared to controls. Using proximity-dependent biotin identification (BioID2), several hundred proteins were identified in the proximity of the overexpressed PMP22, of which, 291 significant proteins were only detected in the PMP22 and not in control pull-downs. Among the most significantly enriched PMP22-interacting proteins were integrins alpha-2 (ITGA2) and alpha-7 (ITGA7), which play a role in myelination via their interactions with the extracellular matrix. The presence of ITGA2 in just the PMP22-transfected fraction was confirmed by western blot. Some of the proteins were associated with several enriched molecular pathways including molecular transport and protein trafficking and may represent potential therapeutic targets for CMT1A by promoting degradation and enhanced trafficking of PMP22.Peer reviewe
Hotspots and coldspots of seabed organic carbon on the Norwegian continental margin
Get PDFContinental margin sediments are important sinks for organic carbon, thus providing valuable climate regulating functions. Human activities such as mobile bottom fishing might, however, compromise the effectiveness of the seabed in accumulating and storing organic carbon through a net increase of organic carbon remineralisation. While there currently is no consensus on the magnitude of this effect, it can be postulated that seabed areas characterised by high rates of organic carbon accumulation, high organic carbon stocks and a large fraction of labile organic matter might be most vulnerable to mobile bottom fishing. Conversely, areas characterised by low or no organic carbon accumulation, low stocks and a small fraction of labile organic matter might be of least concern. Based on reactivity measurements we spatially predict the thermal reactivity of sedimentary organic matter on the Norwegian continental margin. Surface sediments contain between 13% and 34% labile organic matter, with the highest values attained in the central Barents Sea. Using these results and previously developed maps of organic carbon stocks and accumulation rates, we then carry out a regionalisation using unsupervised classification with the aim to identify distinct seabed areas. We identify hotspots with regard to accumulation, storage and lability in the Skagerrak and the central Barents Sea and coldspots on the North Sea plateau, shelf banks in the Norwegian and southern Barents Seas and along the continental shelf break. Our results have the potential to be used in the ecosystem-based management of marine areas in Norway, and our methodology provides a template for similar analyses in other sea areas.Peer reviewe
Reduced adult survival estimated in areas of decline of harbour seal populations in Scotland
Get PDFFunding: NatureScot; Scottish Government. Grant Numbers: MMSS/002/15, MMSS/003/20; Highlands and Islands Enterprise; Moray Offshore Windfarm (West) Ltd; Moray Offshore Windfarm (East) Ltd; Crown Estate; Beatrice Offshore Windfarm Ltd.Understanding the demographic drivers behind observed changes in wild populations is key to inferring intrinsic and extrinsic causes behind such changes. In Scotland, harbour seal populations have undergone regional declines since the early 2000s. Here we apply mark-recapture models to photo-identification data collected during the breeding season at haulout sites representative of three areas with contrasting population trajectories to estimate sex-specific apparent adult survival and fecundity rates. Apparent adult survival rates were lower at the declining site of Burray, located within the North Coast and Orkney Seal Monitoring Unit (SMU), which has declined by 85% since the mid-1990s: female survival = 0.844 (95%CI 0.803-0.878), male survival = 0.826 (95%CI 0.751-0.883) (photo-ID data collected in 2016-2022). At stable or increasing sites, estimated apparent adult survival rates were higher: at Dunvegan, located in the West Coast SMU, a region that has been generally increasing since monitoring started in the mid-1990s: female survival = 0.878 (95%CI 0.810-0.924), male survival = 0.842 (95%CI 0.756-0.902) (photo-ID data collected in 2016-2022); at Loch Fleet, located in the Moray Firth SMU which has shown no trend since 2003: female survival = 0.941 (95%CI 0.922-0.956), male survival = 0.919 (95%CI 0.888-0.942) (photo-ID data collected 2006-2021). Mark-recapture fecundity rates were generally high at all sites (0.809 to 0.883), with the lowest estimated fecundity at the declining site of Burray. The results indicate that the causes of the decline are likely acting on adult survival, while evidence that a decrease in fecundity is driving the observed declines had less support. The estimated vital rates inform current research into potential causes of the declines and can be incorporated into stage-structured population dynamics models to investigate whether the hypothesized mechanisms for decline are supported by the data.Peer reviewe
Acoustic behaviour and spatiotemporal occurrence of northern bottlenose whales in the Nordic Seas
No full textNorthern bottlenose whales (Hyperoodon ampullatus) are echolocating beaked whales found in arctic and subarctic waters of the North Atlantic. Their offshore distribution and deep-diving behaviour make them challenging to study visually, thus knowledge gaps remain on the species’ behaviour and distribution. This thesis advanced our understanding of northern bottlenose whales’ acoustic behaviour and their occurrence in the Nordic Seas. It combined animal-attached sound and movement tag data and passive acoustic monitoring (PAM), together with visual observations and oceanographic data. Specifically, chapter two describes the acoustic characteristics and contextual production of two types of rapid click trains, buzzes and rasps. The results revealed that these click trains are acoustically and contextually distinct, with buzzes associated with foraging and rasps with communication. Classification of buzzes and rasps can also be applied to PAM data to infer animal behaviour, which was shown in a case study on northern bottlenose whale inshore acoustic behaviour in chapter three. The identification of rasps but not buzzes in inshore recordings, in conjunction with behavioural observations and further inshore sightings, pointed towards a shelter driven movement of bottlenose whales into coastal waters. Occurrence and distribution drivers within offshore waters are then addressed in chapter four using long-term bottom-moored hydrophone data. The results showed a year-round occurrence of northern bottlenose whales in the Nordic Seas, and seasonal variations in distribution were linked to oceanographic variables indicative of prey availability. Acoustic detections were only temporarily low from July into September, discounting the long-standing seasonal north-south migration hypothesis for overwintering but instead supporting potential short-term skin maintenance migrations. Chapter five investigates the species’ acoustic detection probability and discusses the impacts of click characteristics, animal behaviour and duty-cycle choice. The estimated detection functions have important implications for PAM studies and constitute a first step towards acoustic density estimation of northern bottlenose whales."This work was supported by a 1.5-year postgraduate scholarship from the University of St Andrews’ School of Biology, and a 2-year doctoral grant from the University of Iceland’s Doctoral Research Fund. Data collection off Jan Mayen was conducted as part of the 3S and body
condition projects, supported by US Office of Naval Research (ONR grants N00014-15-1-2533 and N00014-16-1-3059), US Strategic Environmental Research and Development Program (SERDP award RC-2337), the French Ministry of Defence (DGA) and the Netherlands Ministry of Defence. Data collection off Iceland was supported by a Project Grant (no. 207081) from the Rannís Icelandic Research Fund."--Fundin
Two decades of IETF affiliations : evolution and impact
Get PDFFunding: This work is supported in part by UK EPSRC (EP/S033564/1, EP/S036075/1), DNSRF, UKRI (EP/W032473/1), Guangzhou Science and Technology Bureau (2024A03J0684).Standards developed by the Internet Engineering Task Force (IETF) are critical to the operation of the Internet. Understanding which organisations employ or support participants in the IETF is therefore critical to understanding the development of the Internet. In this paper, we present a longitudinal analysis of affiliation changes in the period 2001-2023, covering 73,764 individuals affiliated with 6,940 organisations. We show that organisational diversity first grew, before remaining broadly constant or even declining (e.g., meeting attendance and RFC authorship). Affiliations have gradually shifted away from North America-based organisations, with an increase in European and Asian organisations. We also observe that a change in affiliation has a short-lived positive impact on participant output and engagement, and increases the chance that an RFC is published, but slows its publication
Stress-coping styles are associated with energy budgets and variability in energy management strategies in a capital breeder
Get PDFFunding: Funding for this research was originally provided by the Durham Doctoral Studentship (awarded to C.R.S.) and supported by core funding to the Sea Mammal Research Unit at the University of St Andrews from the Natural Environment Research Council (NE/R015007/1 and NE/M01357X/1).Individuals vary in their stress-coping styles, characterized by specific behavioural and physiological traits that influence their response to stressors. Theory suggests that these traits are linked to underlying metabolic mechanisms that affect energy management strategies. Despite the potential of this powerful comparative approach, few studies have explored how stress-coping styles relate to energy management strategies. Using heart rate telemetry data from a large, capital-breeding pinniped, the grey seal (Halichoerus grypus), we sought to investigate the relationship that stress-coping styles (via individual resting heart rate variability, rHRV) may have on energy management strategies. Background energy expenditures, a proxy for metabolic rate and other background processes, and daily energy expenditures were found to be individually repeatable in grey seal mothers across successive breeding seasons. Proactive individuals (low rHRV) exhibited consistently higher background and daily energy expenditures than reactive females (high rHRV). However, reactive phenotypes were more variable overall in energy management strategy, highlighting greater flexibility in their energy management strategy. Our results highlight key energetic trade-offs associated with stress-coping styles in grey seal mothers during this short but critical life-history stage; proactive individuals tended to exhibit a single pattern of energy management, expending greater energy while incurring greater risk of over-spending, than those with a more reactive phenotype.Peer reviewe
Access Repository Dashboard
Do you manage St Andrews Research Repository? Access insider analytics, issue reports and manage access to outputs from your repository in the CORE Repository Dashboard!