1,721,048 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
How animal movement defines behaviour: new insights into the ecology of seabirds at sea
Full text linkHow animals move through their environment defines their ecology at an individual and population level. All animals must search for food to survive and how they do this can be influenced by the world around them as well as their own internal state. Our understanding of animal ecology has been dramatically expanded thanks to the continued development and miniaturisation of data loggers that can be attached to animals. Data from these biologgers remain challenging to interpret, but shed light on the behavioural ecology of individual animals. In this thesis, I use movement data from seabirds to explore the mechanisms behind foraging and how these are underpinned by the movement of individual animals. In chapter 1, I provide an introductory overview of the literature and introduce my study species. In chapter 2, I examine the methods available to interpreting behaviour from animal relocation data showing that Hidden Markov Models (HMMs) outcompete other behavioural annotation methods – successfully identifying 81% of plunge dives in northern gannets, Morus bassanus. I then provide recommendations for best practice when defining periods of search and prey capture behaviour. In chapter 3, I show how environmental features may ultimately disrupt the expected movement of optimal foraging, and show that Atlantic puffins, Fratercula arctica, in southeast Ireland have departed from classic Area Restricted Search (ARS). These findings are considered in an energetic perspective and suggest that puffins may be saving between 28-46% of the energy required to fly the same distance. In chapter 4, I utilise acceleration data to document the bioenergetic sex differences of prey capture attempts in northern gannets, examining the links between diet, movement, and energy expenditure. Stable isotope analysis showed dietary differences between the sexes, but energetic content of divergent diets was the same. Prey capture attempts are not energetically expensive for gannets (<4% of energy expenditure in all northern gannets) and females have higher energy demands. However, the differing rate of prey capture attempts highlights that males have a higher minimum prey capture success rate than females to meet energetic demands (29% and 21% respectively). In chapter 5, I further explore acceleration data to determine whether northern gannets display handedness during foraging behaviours. All individuals (n=14) were lateralised in the direction of their pre-plunge dive roll behaviour, with a ‘population’ level right-sided bias (64%). While wind has a small effect on the angle of roll, it did not affect the observed lateralisation in individuals. I conclude with a general discussion summarising my main findings and suggesting future research opportunities. This thesis highlights how investigating animal behaviour using movement data can provide new insights into the behavioural ecology of species
Assessing the distribution and vulnerability of a seabird community at sea to inform conservation and management
Full text linkSeabirds are an apex predator in marine ecosystems and can be important bio-indicators for informing wider marine conservation and management. They face many threats from anthropogenic activities at sea but the interactions and subsequent impacts can often be difficult to monitor, particularly in pelagic regions. Ireland and Britain in the north-eastern Atlantic Ocean host internationally important numbers of many seabird species. However, there are challenges in assessing their distribution at sea, not least the time and costs involved in trying to do this at the community level. The large territorial waters of both countries also provide significant prospective marine fossil fuels and renewable energy. Therefore, there is the potential for detrimental impacts to seabird populations where hotspots of seabird density overlap with marine energy activity. In this thesis I demonstrate how existing data can be combined to assess the at-sea distribution, vulnerability, and gaps in conservation protection of seabird species at the national scale. In Chapter 2, I use a distance-weighted, foraging radius approach to predict at-sea distributions (hereafter called foraging radius distributions) for all breeding seabirds in Britain and Ireland, identifying hotspots of highest density and species richness. Relatively simple foraging radius models have the potential to generate predictive distributions for a large number of species rapidly, thus providing a cost-effective alternative to large-scale surveys or complex modelling approaches. I calculate the percentage population coverage from current marine and coastal protected areas (MPAs) for all seabird species using foraging radius distributions. On average, 33% of coastal populations and 13% of pelagic populations overlap with MPAs, indicating that pelagic species, many of which are near threatened or endangered, have significantly less coverage from protected areas than coastal species. In Chapter 3, I test the effectiveness of the foraging-radius approach by comparing foraging radius distributions to empirical distribution data for multiple species taken from biotelemetry studies and aerial surveys. Foraging radius distributions correlate significantly with GPS tracking data for four species at the colony level. At the regional level, foraging radius distributions show mixed results when compared to aerial survey data, but correlate well with auks and terns in particular. In order to assess seabird vulnerability to oil pollution in European waters I develop a new Oil Vulnerability Index (OVI) that updates information on population size and conservation status, as well as accounting for the potential attraction/avoidance of seabirds to offshore infrastructure (Chapter 4). The OVI scores are applied spatially and overlaid with current offshore petroleum activities to generate maps of seabird vulnerability to oil pollution in the Irish EEZ. Finally, I combine all of the information on seabird distributions, vulnerability to anthropogenic activities, and designated MPAs to carry out a spatial prioritisation analysis for conservation of seabirds in Irish waters (Chapter 5). The results reveal that those areas in the Irish EEZ that are most important for seabird populations and that should be prioritised for conservation, are also the areas that are experiencing the most pressure from anthropogenic activities
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
New insights into the summer distribution of basking sharks (Cetorhinus maximus) in the northeast Atlantic
No full textControlled AccessBasking sharks, Cetorhinus maximus, have undergone widespread historic exploitation in the northeast Atlantic and are of conservation concern. A greater knowledge on their spatial and temporal habitat use in response to environmental conditions is required to better inform subsequent monitoring and management strategies. Several efforts to describe the occurrence and distribution of basking sharks have been already made, however nothing at large spatial scales. Sighting information on basking sharks was derived from three aerial survey programmes which covered extensive inshore and offshore waters within the northeast Atlantic. The occurrence of basking sharks in the area was highly seasonal, with individuals predominately observed during the summer months (May-August). Hotspots of occurrence were within the coastal waters off the south and west of Ireland, whereas areas such as southwest of England and west of Scotland, previously considered to be hotpots for basking sharks, were not aggregation sites during summer months, suggesting a seasonal change in distribution. Based on satellite-derived environmental variables and climate indices, this study revealed that distribution of basking sharks was associated with (1) lower chl-a concentrations (< 2.27 mg/m³), (2) shallow coastal waters which are most likely important summer feeding grounds; and (3) positive North Atlantic Oscillation (NAO) winter index, most likely through association with prey species. Sea surface temperature (SST) had no significant effect on the distribution of basking sharks. This study provided new insights into the seasonal occurrence of basking sharks on a large scale within the northeast Atlantic. The results produced here could be incorporated into future management frameworks for assessing the threat and conservation needs for this regionally protected species, as well as providing guidance for future research efforts
How seabirds respond to a changing oceanic environment: a biologging approach
No full textMarine habitats are undergoing rapid change due to human influences. The intensity and diversity of human impacts on oceanic habitats are increasing with rising demand for energy and resources. For example, fisheries operate in over 90% of the ocean, harvesting marine life and directly affecting ecosystem functions and resilience. Climate change is also changing the physical and chemical properties of the ocean and altering storm frequency and intensity at a global scale. Seabirds are a group of marine predators that are sensitive to such changes, with impacts contributing to global population declines. We broadly understand how stressors affect different species through effects on life histories and physiological traits, and where seabirds are most impacted based on spatiotemporal overlap of seabirds with human activities. However, finer scale behavioural data are required to understand the functional response of seabirds to different stressors.
Biologging devices are continuously improving and miniaturising, being applied to collect fine-scale behavioural information for smaller species and for more protracted durations. In this thesis, biotelemetry is used to investigate the at-sea behaviour of three North Atlantic seabird species in order to understand the drivers of distribution. A better understanding of such drivers sheds light on the challenges facing seabird species when far from land, susceptibility to stressors, and provides insights into more effective monitoring and conservation efforts.
Chapter 1 provides a broad introduction to seabird ecology, the application of biologging, and identifies model species for investigating seabird responses to a range of environmental stressors. Chapter 2 investigates the diving behaviour of Manx shearwaters (Puffinus puffinus) and how this correlates with water clarity, which is predicted to deteriorate with increasing urbanisation, eutrophication, and climate impacts. Chapter 3 highlights the relative importance of commercial fisheries compared to other environmental variables in driving the foraging distribution and behaviour of northern fulmars (Fulmarus glacialis) during the breeding season. Chapter 4 expands on this by identifying fulmar-vessel encounters in the non-breeding season, showing how nocturnal vessel attendance is increasing over time, and the apparent relationship with migration effort and time-activity budgets. Chapter 5 identifies unusual levels of variability in the moult period of Atlantic puffins (Fratercula arctica), when they are flightless and more susceptible to climate impacts that may prevent them from foraging. Variability in moult strategy is tied to susceptibility of populations to risks posed by severe winter storms.
Chapter 6 provides a synthesis of findings from previous chapters, highlighting how the methods and principles developed may be built upon to further improve our knowledge of seabird ecology and design appropriate conservation measures. Building on insights from previous chapters, I discuss how seabirds are likely to functionally respond to several stressors in the marine environment, including fisheries practices, climate change, and shifting prey availability. Several recommendations are made for further research, including exploring mitigative measures that can be employed to tackle the negative effects of changes to their environment
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