1,720,964 research outputs found
Distribution and Habitat Characteristics of a Freshwater Gastropod, Pleurocera Proxima, in Eastern Pennsylvania
Get PDFPleurocera proxima is a small, freshwater gastropod that has been recently discovered in four headwater tributaries in the Christina River watershed. The species was previously known only as far north as Virginia, so nothing is known about the species in Pennsylvania or Delaware. The purpose of this study was to determine if the species existed in additional locations in this region, and to assess the habitat where it is found. Fieldwork was conducted in Winter 2012 in the Red Clay Creek, White Clay Creek, and Brandywine Creek subwatersheds of the Christina River basin. In addition to the four streams where P. proxima was already known, 102 new streams were surveyed in this field season for presence of the species. Water chemistry and surrounding land use data were collected at all sites, and substrate characteristics and physical stream data were collected at sites with P. proxima. Only four of the 102 new sites had P. proxima. These data suggest the species is very rare in the region, and mostly populates small, headwater streams in areas with low developed land cover and high forest cover. The streams where P. proxima is found show lower levels of conductivity and salinity than other streams, but it is apparent further research is needed to identify the exact habitat conditions that predict P. proxima presence and density
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
Plant traits and carbon storage in freshwater wetlands
Get PDF© 2019 Saras Mei WindeckerFreshwater wetlands are an important part of the global carbon cycle due to their role in sequestering carbon in the soil. Despite covering less than 8% of global land area, freshwater wetlands are significant reservoirs of soil carbon due to long-term storage in the soil. Soil carbon stocks are high because wetlands are highly productive and can have low rates of decomposition. Plant communities capture carbon during photosynthesis and deposit it as litter. My thesis broadly examines the influence of vegetation communities on soil carbon storage across a range of scales, from the landscape down to the leaf.
To examine the relative contribution of vegetation to carbon stock on a landscape-wide scale, I modelled carbon density of soil cores collected in 100 inland wetlands across Victoria, Australia. I determined that the nonlinear relationship of carbon with soil depth varies between wetlands, which has important implications for extrapolating carbon density necessary in wide-scale comparisons. Using a hierarchical model with continuous spatial data, I found that we could predict soil carbon stock using these globally available datasets and that intermediate inundation was a strong predictor for high soil carbon stock.
At the wetland level, plants take up carbon dioxide during photosynthesis and contribute to soil carbon through deposition of litter. Litter quality, such as nitrogen level, affects how much litter material remains in the soil and for how long. Leaf economics spectrum theory suggests that a range of functional traits correlate along a spectrum of nutrient level that can be used to generalise litter quality. Despite relevance to a range of ecosystem processes including decomposition, direct measures of carbon composition of litter are not included among the economics spectrum traits. To test the generality of the trait correlations to carbon composition, I measured seven traits of litter in 29 wetland plant species: litter area per mass, dry matter content, nitrogen content, carbon content, and relative composition of hemicellulose, cellulose, and lignin. I tested thermogravimetric analysis, an analytic technique for estimating these carbon components. To replace proprietary software currently used in the modelling step of this estimation technique, I developed an open-source statistical R package called 'mixchar'. In general, species invested predominantly in either lignin- or cellulose-based tissue, and variation in this division was not correlated with variation in the other morphologic and chemical traits.
Decomposition of litter impact long-term storage of carbon in the soil and is driven by litter quality. I conducted a mesocosm decomposition experiment of 29 wetland plant species, and evaluated the predictive performance of functional traits related to both nitrogen level and carbon complexity. I prepared a series of Bayesian decay models to test which traits affected rate of overall decay. I evaluated the models by comparing the cross-validative predictive performance on a new species. I found that trait models that include both litter nitrogen and carbon characteristics ranked among the best at predicting decomposition. However, differences among trait models were marginal, suggesting perhaps no single 'best' model for litter decomposition rate based on traits alone. My research improves our understanding of how plants contribute to soil carbon, from the scale of a leaf to the wider landscape, and clarifies how plants decay in wetlands and contribute to carbon storage in wetland soils
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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