1,721,000 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
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
Challenges to Defining the Niche of an Invasive Human Commensal Gecko
Full text linkInvasive species threaten global biodiversity by altering ecosystem structure and function. Once most invasive species become established, they are exceedingly difficult to eradicate, so focusing on predicting establishment and preventing invasion is often a more efficient and cost-effective management tool. Recent developments in niche modeling have improved the ability to identify habitats at risk of invasion, facilitating preventative measures. Ecological niche models (ENMs) provide one such tool for estimating the fundamental niche based on environmental and/or physiological variables. Correlational and mechanistic modeling programs have both proven useful in predicting the range potential of invasive species, yet each approach has its own set of advantages and disadvantages. Fundamental to producing an ENM that accurately predicts suitable niche space and potential distribution is identifying the variables that are the most biologically relevant for that species. For example, human-commensal species living in urban environments pose new challenges for characterizing niches with traditional approaches because such species do not experience their environments in the same way as species living in nature. Mediterranean House Geckos (MHGs, Hemidactylus turcicus) are a globally widespread, invasive, human-commensal species. Across their invasive range in the continental United States, MHGs occupy urban/suburban niches in climates as diverse as subtropical, continental, desert, and Mediterranean. Human-created niches provide MHGs with climatically buffered environments and ecological opportunities rarely studied in reptiles, including access to geographic regions that would otherwise prove lethal. Yet the nature of climatic niche buffering has not been characterized or used in predictive models of invasive potential for any human-commensal species. I (1) characterized the microclimate of urban niches commonly occupied by MHGs; (2) validated a microclimate model to predict temperature and water profiles of the characterized microclimate; (3) modeled temperature, water, and energy balances, and life-history characteristics of MHGs; and (4) compared the efficacy of various data sources in predicting the probability of suitable habitat for MHG occupancy. I found that models based on either environmental or physiological data performed similarly well and environmental data-based models have improved accuracy with the addition of landcover type. While models based on both data sources performed well, data from the physiology-based model revealed how abiotic factors in the environment limit the distribution of MHGs and how refugia in urban niches mitigate those effects. Future work in this area of research should focus on characterizing the diverse microhabitats that exist in urban areas and how the strength of the human commensal behavior changes with spatial and/or temporal changes in climate
Assessing the Intensity of Late Holocene Montane Settlement and Subsistence Strategies in the Northern Sierra Nevada, California
Full text linkThis thesis investigates the precontact settlement patterns of the Nisenan in the northern Sierra Nevada and compares these patterns to studies of Mono and Miwok settlement patterns in the central and southern Sierra Nevada. I assess the degree to which Nisenan settlement and subsistence strategies in the montane environment of the Sierra Nevada differs from other groups occupying similar environments in the Sierra. I predicted the Nisenan would share a similar settlement and subsistence strategy to the Miwok based on both groups sharing similar population densities and culture histories in broadly similar environments. The Nisenan, however, use a settlement pattern that more closely resembles the Mono in intensity but differs in important ways. The Nisenan primarily occupied lower elevation ecozones and relied on lower intensity logistical mobility in the montane ecozones above snowline. Comparatively the Mono were more residentially mobile above snowline and the Miwok use a much more intensive residentially mobile strategy above and below snowline. This study indicates that population density and occupational time depth alone are not sufficient predictors of montane settlement and subsistence strategies. Factors like climate, environment, sociopolitical structures, territoriality, culture history, and seasonal resource availability likely also influence hunter-gatherer decision making when it comes to settlement and subsistence. The Nisenan appear to be a group that was more oriented toward the valley margin and foothills of the Sierra Nevada than montane environments. Additionally, montane environments within the study area may have been used by the Nisenan and the Washoe of the Tahoe region as backup resource patches during times of scarcity in lower elevation environments. This project contributes to our understanding of human adaptations in montane environments and the factors that contribute to group decision-making when it comes to determining settlement and subsistence strategies
Prevalence of Decadal Variability Within the Arctic Climate System
No full textThis study presents a modern assessment of the spatial and temporal characteristics of decadal climate variability in the Arctic. Using a combination of observational data, reanalysis, and proxy reconstructions, decadal variability of mean annual and seasonal (winter, DJF; summer, JJA) surface air temperature (SAT) and precipitation are investigated from 1901-2013 across the Arctic region. Singular spectrum analysis was used to separate variability into interannual (1-9 years), decadal (10-30 years), and multidecadal (30-60 years) components. In addition to identifying the presence, prominence, and patterns of decadal variability throughout the region, connections to internal modes of atmospheric and oceanic variability are examined and discussed.Decadal variability is found to be a regionally important and seasonally dependent characteristic of Arctic climate. Overall, decadal variability of temperature displays more coherent and consistent patterns across datasets than precipitation. While increased decadal variability was observed in both temperature and precipitation, a strong seasonal contrast was apparent in temperature patterns. It is reasonable to suggest a link between decadal variability of Arctic temperature and natural modes of variability, although a link to precipitation remains unclear
Climate Driven Variation in Ice-out Impacts Zoobenthos Biodiversity and Production in a Subalpine Lake
No full textChanging winter-ice dynamics due to climate change are impacting lake benthic processes and ultimately lake ecosystem functioning. As lake ice conditions change, the impacts on lake benthic processes during subsequent ice-free seasons remain poorly documented. We examined the connections between ice-off dates and zoobenthic invertebrate diversity and productivity using a long-term ecological dataset from a subalpine lake. Zoobenthos were collected three times following ice-out from seven sites across the benthic habitat of a subalpine lake (four littoral, one sublittoral, and two profundal) over 15 years and identified to family. Ice-off dates were variable, ranging from Julian days 51 to 178. We identified 30 taxa, with Chironomidae, Oligochaeta, and Pisidium being the most dominant. Zoobenthic diversity differed between habitats, with the highest diversity in the littoral habitat, decreasing with depth. Zoobenthic richness was higher in early ice-out years in the littoral and sublittoral habitat, attributed to 13 families with low relative abundances, and some littoral sites were more sensitive than others. Zoobenthic productivity varied between habitats and was higher in the sublittoral habitats in late summer during years with early ice-out. Our results indicate that benthic communities remain resilient, showing no change in evenness with variation in ice-out date due to the robustness of the three dominant species. However, less abundant taxa may respond to continued early ice-out dates, and littoral habitats are more sensitive to these changes. The production of taxa is sensitive to ice-out conditions indicating potential implications for higher level consumers which feed on invertebrates within a lake (e.g.. fishes, amphibians) or rely on the adult insect emergence (e.g., bats, birds). This study suggests that benthic diversity and productivity while heterogeneous within a lake, may be sensitive to ice-out conditions which have been shown to occur earlier due to climate warming
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