1,721,001 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
Habitat use of young-of-year Arctic Grayling (Thymallus arcticus) in Barrenland streams of central Nunavut, Canada
Get PDFArctic Grayling, a species within the family Salmonidae that is valued by sport fishers and Indigenous communities, is distributed throughout a diversity of northern landscapes. While Arctic Grayling are known to be sensitive to perturbations in habitat and water quality, our understanding of constraints on their distribution is incomplete, particularly in the vast subarctic Barrenlands region. Understanding the habitat requirements and distribution of Barrenland populations of Arctic Grayling is necessary to develop effective conservation policies, avoid or mitigate potential impacts of mining and other development, and evaluate population distribution trends over time. Barrenland populations of Arctic Grayling rely on seasonally connected networks of lakes and streams to migrate, spawn, and rear. Knowledge of stream conditions and characteristics that are suitable for rearing young-of-year Arctic Grayling is critical for understanding and predicting variability in recruitment, and thus to ensuring the continued persistence of Barrenland populations. In summer 2019, visual surveys assessing the presence/absence of young-of-year Arctic Grayling were conducted at 49 streams in the Barrenlands region near Baker Lake, Nunavut. Occupancy modeling was used to relate a comprehensive suite of stream habitat (e.g., depth, velocity, water temperature) and landscape (e.g., land cover, contributing upstream lake area) variables to the presence/absence of young-of-year Arctic Grayling. Quantification of detection efficiency, and variables that affect detection efficiency, allowed for improved inferences on species-habitat relationships. While detection efficiency was negatively influenced by water depth and water velocity, the best predictors of young-of-year grayling occupancy were the total area of contributing upstream lakes and the landcover (upland/lowland) of the stream basin. These results suggest that the position of streams within Barrenland landscapes is related to reliability of stream connectivity, and thus suitability for young-of-year. Both explanatory variables are important in promoting hydrologic connectivity throughout the summer rearing period and facilitating the migration of young-of-year to overwintering lakes prior to freeze up. Contributing upstream lake area and land classification data may be obtained remotely, which allows for preliminary predictions of stream suitability to be conducted with minimal financial and logistic effort, and more spatially focused field operations. The occupancy model developed here can be used as a valuable predictive tool for Arctic Grayling young-of-year stream use in the Barrenlands, and will facilitate regulators, scientists, resource managers, and industry in developing more effective conservation and mitigation plans for fish and fish habitat in areas of resource development
Investigating trophic ecology and dietary niche overlap among morphs of Lake Trout in Lake Superior
No full textFour morphs of Lake Trout (Salvelinus namaycush, Walbaum 1792) have been identified in Lake Superior: leans, siscowets, humpers, and redfins. In this comprehensive study, the trophic ecology of Lake Trout morphs were characterized using stomach content, fatty acid, and stable isotope data. Stomach content results indicated a predominately piscivorous diet for leans, siscowets, and redfins, whereas humper diets were comprised of 50% fish and 50% Mysis by mass. Humper and siscowets were most similar in their dietary fatty acid profiles, whereas redfins had the most distinct dietary fatty acid profile. Results from stable isotope analysis revealed some among-morph differences along a pelagic-profundal consumption gradient (34S), but there were no significant differences in trophic position (15N) or basal carbon sources among morphs (13C). Using the recently developed nicheROVER software package, 4-dimensional trophic niches for each morph were quantified using stable isotope ratios (δ13C, δ15N, and δ34S) and fatty acid profiles (30 dietary fatty acids, condensed to one axis). Humpers had the largest 4-dimensional niche regions of all four morphs, and redfins had the smallest. Pairwise probability of overlap among morphs in these four-dimensional niche regions was determined to be < 50% in most cases. Overall, stomach content results indicate that humpers diets were more planktivorous than the other morphs, consistent with previous research. Results of the niche overlap analysis suggests some degree of generalist feeding for all morphs. Better characterization of seasonal variation in diet using tracers that reflect more recent feeding (e.g., fatty acids, stomach contents, and/or stable isotope analyses performed on tissues that turnover more quickly than muscle) are needed to further elucidate among-morph differences and similarities in diet and trophic ecology
Comparing habitat use and mercury accumulation in Arctic Grayling (Thymallus arcticus) from two northern ecosystems
Get PDFAn improved understanding of the distribution and habitat requirements for mountain stream populations of Arctic Grayling (Thymallus arcticus) is necessary to assess their vulnerability to environmental stressors, establish thresholds for development activities, and evaluate population distribution trends over time. Life stage-specific habitat use may be a particularly sensitive indicator of environmental change, but baseline data is lacking, especially for young-of year (YOY) Arctic Grayling. Occupancy-based survey methods were used in the Little Nahanni River watershed in 2015 to quantify Arctic Grayling occupancy across the landscape. Data on a suite of associated habitat variables were also collected to explain YOY occupancy, and to relate to detection efficiency during field surveys, as detection efficiency is an often-neglected aspect of field sampling that affects our understanding of species-habitat relationships. Occupancy modelling has revealed that stream temperature (>8°C) and elevation (<1150 masl) best explain YOY occupancy in the Little Nahanni River. Increasing percent boulder substrate and percent riffle decreased the detection efficiency during surveys. By accounting for imperfect detection, my research helps to better quantify habitat that is important for a sensitive life stage of Arctic Grayling and establishes a baseline against which results from future monitoring efforts can be compared. Similar occupancy methods can be used by industry and regulatory organizations to increase standardization and efficiency of sampling in remote areas, and assess changes in Arctic Grayling distribution that may reflect changes in water quality and stream features.
Abiotic and biotic habitat features can also affect bioaccumulation of contaminants, such as mercury, which have increased in remote northern regions since industrialization, bioaccumulating in fish tissues consumed by northerners. Given that mercury bioaccumulation is habitat-specific, differences in life history type and associated habitat features may affect mercury concentrations in populations of Arctic Grayling. I assessed differences in mercury bioaccumulation between fluvial Arctic Grayling in mountain streams and adfluvial Arctic Grayling in barrenland tundra streams. Overall, mercury bioaccumulation was higher in adfluvial Arctic Grayling from tundra barrenland streams compared to fluvial, mountain populations. Differences in mercury concentration between these populations of Arctic Grayling may be due to differences in methylation rates caused by a number of habitat factors, such as increased water temperatures, as well as differences in baseline methyl-mercury (MeHg) concentrations that may reflect a difference in foraging strategies by each respective population. As well, trophic interactions and the role of terrestrial prey items may influence mercury concentrations in fish tissue, however; further investigation is required to quantify these potential effects. All mercury concentrations in Arctic Grayling sampled during my study were below guidelines for human consumption of fish
Migration timing and overwintering habitat of anadromous Arctic Char (Salvelinus alpinus) near Kugluktuk, Nunavut
Get PDFArctic Char (Salvelinus alpinus) is a key component of subsistence diets in Inuit communities across the Arctic. The Hamlet of Kugluktuk, in the Kitikmeot region of Nunavut, relies on the Coppermine River to support an important fishery of anadromous (i.e., sea-run) Arctic Char, which feed in the ocean in summer and return to freshwater in fall to spawn and overwinter. Arctic Char is a highly plastic species, and while the exhibited diversity of life history strategies and migration patterns likely contributes to their persistence across a challenging landscape, it also necessitates population level information to identify stressors and effectively manage subsistence fisheries. The migration patterns of Arctic Char using the Coppermine River and surrounding area are poorly understood, and overwintering movements and habitat use in fluvial environments in general are largely unknown for Arctic Char. To address these knowledge gaps, acoustic transmitting tags were surgically implanted in 164 healthy adult Arctic Char captured in the Coppermine River and Coronation Gulf in 2018 and 2019. An array of forty-seven acoustic receivers was deployed in freshwater and marine environments during the 2018 and 2019 ice-free seasons, with a subset left to detect 2018 winter movements in the Coppermine River. Consistent with local knowledge, telemetry data indicate that some Arctic Char do not overwinter in typical (i.e., lacustrine) habitats, and instead overwinter in the Coppermine River below Kugluk Falls (a substantial migration obstacle). Overwintering in fluvial environments is likely energetically costly and hazardous in a dynamic system such as the Coppermine River, which experiences substantial surface ice accumulation, slush, anchor ice, and hanging dams. Within the lower reaches of the Coppermine River, net downstream movement in winter was observed for ten (37%) individuals and five individuals were observed to enter the marine environment prior to river break-up in the spring. Under-ice movement into the marine environment has not been previously documented for Arctic Char, and this behavior suggests that the fitness benefit gained through early spring migration to rich ocean feeding grounds may outweigh the risks associated with fluvial overwintering. Following summer marine feeding, adult anadromous Arctic Char that migrated above Kugluk Falls entered freshwater earlier than those overwintering below Kugluk Falls, indicating that the length and difficulty of the migratory pathway affect fall migration timing. Particularly for those individuals overwintering below Kugluk Falls, smaller individuals entered freshwater later than larger individuals, likely due to the potential for proportionately greater gains in body condition for smaller individuals in the marine environment. This descriptive study helps further understanding of the variation in migration patterns and life history tactics employed by Arctic Char in the region. The high inter-individual and inter annual variability that was observed in migration destination and timing provide a basis for future research on drivers of these patterns, such as spawning status, environmental cues, and population dynamics. Results will help in the management of local fisheries and in ensuring the future sustainability of this important food source
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