1,721,800 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
The effects of nitrogen availability on the response of terrestrial ecosystems to elevated carbon dioxide
Get PDFHuman activities are increasing the concentration of carbon dioxide (CO2) in the atmosphere, warming the planet. Terrestrial ecosystems currently sequester about a quarter of human CO2 emissions, slowing climate change. The principal mechanism believed to be responsible for this is an increasing rate of plant growth (that is, “CO2 fertilization”). However, the fate of this ecosystem service is uncertain, as it has been proposed that soil nitrogen (N) availability will limit plants’ capacity to continue absorbing increasing quantities of CO2. Whether N will limit the CO2 fertilization effect in the future will determine the rate at which human CO2 emissions will accumulate in the atmosphere, thereby influencing the climate. In this thesis, I have collected and synthesized the large body of information about the N limitation of CO2 fertilization, using data from experiments in which atmospheric CO2 concentration is manipulated. I have found that the hypothesis that the increase in the strength of the CO2 fertilization effect will be eliminated by restricted N availability is simplistic. Based on the experimental data available, I have found evidence supporting a mechanism by which plants under elevated CO2 can acquire additional N in exchange for carbohydrates via symbiotic fungi. Using this framework, I have quantified the magnitude of the terrestrial CO2 fertilization effect on plant biomass worldwide, and identified the areas of the global land mass that could potentially experience a greater enhancement in biomass under elevated CO2. I propose a framework and areas of further research that may help models better simulate the interactions between the carbon and nitrogen cycles under elevated CO2 using a plant- economics approach, in which nitrogen is a resource that can be acquired by plants in exchange for energy.Open Acces
Modelling the influence of environmental conditions on gross primary production and land-atmosphere carbon exchange
No full textVegetation regulates the land-atmosphere exchanges of water, energy and carbon. Land surface models (LSMs), used to represent these exchanges in climate models, face continuing challenges. Most represent only the (experimentally measured) fast responses of photosynthesis, respiration and transpiration, and neglect longer-term (acclimation and adaptation) processes by which plants are physiologically adjusted to their growth environment, including its seasonal variations and geographic patterns. The proposition of this thesis is that model simulations can be improved when plant processes are represented via eco-evolutionary optimality (EEO) principles. An existing EEO-based light-use efficiency model for gross primary production (GPP), the P model, is further developed here to simulate GPP at the sub-daily timescale required for implementation in LSMs. The resulting model has several advantages. By allowing photosynthetic capacities to vary systematically with environmental conditions, it avoids the need to prescribe different (fixed) parameter values for different vegetation types. It is shown to reproduce diurnal cycle of GPP recorded by eddy-covariance flux towers, across five different well-watered biomes, well – and better than a current, operational LSM. However, soil moisture limitations on GPP degrade the model’s performance in dry climates. A semi-empirical soil-moisture stress function is derived to correct this. The function depends on aridity, with plants in arid climates using water more conservatively while maintaining the ability to extract water under drier conditions than plants from wet climates. The resulting model simulates observed seasonal cycles of GPP well across the full range of climatic aridity. Run at global scale, the model is shown to be able to reproduce major features of the spatial and temporal variations of net ecosystem exchange, NEE (inferred from satellite-derived column concentrations of CO2) and of the differences in NEE patterns between El Niño and La Niña years.Open Acces
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
Towards robust quantification of vegetation responses to global environmental change
No full textClimate change due to greenhouse gas emissions (mainly CO2) threatens ecosystems and human well-being. The land carbon sink through terrestrial vegetation is a key component to absorb atmospheric CO2 to offset global warming. A robust quantification of terrestrial vegetation responses to historical and future environmental changes is necessary to predict the strength of land carbon sink under climate change scenarios. Using a parsimonious model, the P model, I modelled changes in gross primary production (GPP) and demonstrated that this model reproduces historical variation of GPP against observations. Model experiments indicate that CO2 and vegetation greenness (fAPAR) are the major drivers. I further investigated the parameters that affect the sensitivity of modelled vegetation light use efficiency (LUE) to elevated CO2. The ratio of Jmax to Vcmax at 25°C and convexity of light response curve were found to be the most important variables. The effect of CO2 fertilization (CFE) on GPP was estimated to be 15.43% for a 100-ppm increase in CO2, consistent with previous studies. The modelled diminishing CFE during the past decades indicated a potential decreasing benefit from CO2 for vegetation growth under future climate change. An extended version of the P model was used to further quantify changes in the land carbon sink. Although a conceptually simpler model, it achieved similar performance compared to dynamic global vegetation models with reasonable bias. Finally, I predicted vegetation greenness based on the trade-off between vegetation carbon gain and water loss, both of which depend on the amount of leaf area quantified by fAPAR. Predicted seasonal maximum fAPAR explains 95% of the variation compared to observed remotely sensed MODIS fAPAR, with similar temporal trends. These studies provide a mechanistic understanding of vegetation responses to environmental changes and a first step towards more reliable land surface models for future climate projection.Open Acces
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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