1,720,984 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
Characterizing iron complexing ligands in aquatic environments using Immobilized Metal Affinity Chromatography
No full textIron plays an active role in aquatic environments, acting as a key micronutrient for micro-organisms such as phytoplankton. Iron is difficult for these organisms to access in oceanic water due to low ambient concentrations. Iron has two redox states, the II redox form is soluble in water under anoxic conditions; however, it is easily oxidized to its III form in the presence of oxygen and precipitates as Fe₂O₃(s). As a result, dissolved iron concentrations are sub-nanomolar in seawater. Microorganisms have evolved strategies to keep iron in solution, namely via the production of siderophores, specialized iron-chelating mole-cules. 99% of the dissolved iron in the ocean is bound to organic ligand complexes, which help to maintain the bioavailability of the metal. These ligands are considered part of dissolved organic matter (DOM), a complex carbon pool containing eclectic water-soluble compounds of varying chemical compositions. The vast majority of DOM is chemically uncharacterized and often referred to as humic substances (HS), which originate from the breakdown of organic matter of biological origin. A subset of HS can bind selectively to iron and retain it in its dissolved form in marine waters. Recent publications have theorized that uncharacterized humic ligands may play an essential role in the marine iron cycle, and as such, further investigation is needed.1
To further investigate the specific origin and influence of these ligands on aquatic iron cycling, the ligands need to be extracted from the ocean’s complex matrix, isolated from the rest of the DOM. A method for this extraction was developed using immobilized metal affinity chromatography (IMAC). The method works by using a column containing
Sepharose, a cross-linked beaded form of agarose. This Sepharose acts as a chelator al-lowing us to charge the column with iron. By charging the column, the beads bind to the metal forming a coordination complex with available active sites. The iron binding lig-ands in our sample then bind to these available coordination sites, while other compounds pass through the column. A series of different eluants is then used to elute the retained ligands from the column based on different structural and chemical properties. The eluted ligands are then collected in fractions for further analysis. The optimized IMAC method results show three distinct regions of ligand classes of varying binding strength and structural composition.
To validate the method and further explore the chemistry of binding, solutions of known ligands were used as validation samples. These specific ligands were chosen due to their likely presence in aquatic environments. By testing these ligands using the optimized method, we could further infer how the humic-iron ligands interact with our iron-charged column. The results of the model ligand experiments suggest that binding to the column was typically bidentate, with two coordination sites needed for retention to occur. After testing and validation, the method was implemented for riverine, coastal, and open ocean samples. Comparison of the behaviour of natural water samples with the model lig-ands reveals potential binding characteristics and origins of HS ligands
Dissolved organic matter of the spring bloom in the Labrador Sea; chracterized using optical properties and parallel factor analysis
No full textThe dynamics of dissolved organic matter (DOM) during the decline of annual spring phytoplankton bloom in the Labrador Sea in May/June 2022 were investigated using fluorescence spectroscopy coupled with parallel factor analysis (PARAFAC). Samples from two short term bioassays aimed to investigate phytoplankton production of DOM under varying temperature and nutrient conditions. Three series of biodegradation assays were used to investigate the microbial transformations of DOM over a six-month time period. Fluorescence data from both experiments of a five component PARAFAC model was validated and used alongside dissolved organic carbon and total dissolved nitrogen data to gain insight into the DOM dynamics. The PARAFAC model was compared to other models using the OpenFluor database and found that all components had been found in previous studies. Of the five components C1, C4, and C5 have been associated with more refractory DOM while C2 and C3 have been linked to freshly produced, more labile DOM and microbial activity. For the bioassay experiments, there were no distinctive trends in temperature or nutrient conditions that could be used to indicate how changing climate conditions may affect DOM production by phytoplankton. Biodegradation data had slight trends between the series for C1 and C2 but no overall trends across components. The lack of trends in both experiments was largely attributed to the bloom composition being dominated by Phaeocystis spp. which primarily releases polysaccharides which are unable to fluoresce. This data provides a basis into future DOM analysis during the spring bloom in this region and highlights a need of additional analysis techniques for phaeocystis blooms
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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