1,721,007 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
NATURAL PRODUCTS AS A SOURCE OF NEW THERAPIES FOR NEURODEGENERATIVE DISEASE AND EFFORTS TOWARD THE DEVELOPMENT OF A METABOLOMICS-BASED DRUG DISCOVERY PLATFORM
Get PDFNatural products have traditionally played an important role in drug discovery research. They have been particularly important in the search for therapies for neurodegenerative diseases. Although there are numerous forms of neurodegenerative diseases, the disorders associated with protein misfolding (e.g. Alzheimer's, Parkinson's, Huntington's and prion diseases) represent a unique area for natural products drug discovery as these diseases share many pathological features, suggesting that therapies developed for any one of these diseases may have applications for the others. There have been many reports of secondary metabolites with biological activities related to neurodegeneration associated with protein misfolding, and emerging drug targets for these diseases are fueling interest in finding natural products which can serve as leads for therapeutic development. The literature surrounding the topic of natural products and neurodegenerative disease has been summarized in the first chapter of this dissertation.Although there have already been many natural products identified as potential therapeutic leads for neurodegenerative diseases, there is still a significant need for the enhancement of methodologies used for bioassay screening of secondary metabolites. Metabolomic approaches to drug discovery have the potential to combine the advantages of phenotypic disease models and molecular target assays. The metabolomic examination of a phenotypic disease model can provide detailed information concerning the molecular target and/or the mechanism of action of a compound while simultaneously revealing its phenotypic effects. The third chapter of this dissertation describes the metabolomic examination of a phenotypic model of Huntington's disease. This detailed exploration of the metabolic changes associated with mutant huntingtin toxicity has revealed many intriguing new insights into the specific processes which are involved in the cellular response to protein aggregation. The results in this chapter show that the metabolic response of cells to mutant huntingtin can be detected using a metabolomic approach and that these metabolic changes can be used to identify potential therapeutic targets for Huntington's disease. These results also show the importance of the metabolites alanine, glutamine, glycerol and valine in the metabolic response to mutant huntingtin in multiple species. This work provides the foundation for the future development of a metabolomic-based drug discovery platform for natural products.In the fourth chapter of this dissertation, the use of metabolic profiling to examine the protective role of the metabolite trehalose is described. Trehalose is a disaccharide that has been previously identified as having therapeutic implications for neurodegenerative diseases. In order to explore the role that trehalose plays in the yeast model of Huntington's disease, a series of yeast strains with gene deletions for each step in the metabolic cycle of trehalose were engineered to express normal and mutant huntingtin protein fragments. One of these gene deletion strains, deficient in the production of the acid trehalase protein, exhibited a prounouced reduction in the toxicity associated with mutant huntingtin, the aggregation of mutant huntingtin and the elimination of the metabolic aberrations associated with mutant huntingtin expression. This investigation of the role of trehalose in the yeast model of Huntington's disease provides evidence for the therapeutic potential of the manipulation of chemical chaperone systems in mammalian cells.The final chapter of this dissertation diverges from the topic of neurodegeneration and instead describes the isolation and characterization of a series of briarane diterpenes from a Briareum sp. of octocoral. The ichthyotoxic properties of these compounds are described as well as their metabolic transformation by fish. The scientific merits of this study make it an important and significant part of my doctoral research and demonstrate the multidisciplinary nature of my research
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
Accessing Natural Products from Silent Biosynthetic Pathways Using Chemical Epigenetics
Get PDFNatural products have played a major role in the history of medicine. Despite this history, many view the area of natural products discovery to be tapped dry, thus the focus of drug development companies has shifted towards other avenues to discover new drug leads (i.e. combinatorial chemistry). In recent years, there has been an expansion of antimicrobial-resistant organisms accompanied by a lack of new drug entities coming to market. These trends illustrate a need to find new approaches other than the current status quo.Analyses of microbial genomes show that there are many more secondary metabolite biosynthetic pathways than known secondary metabolites. These silent biosynthetic pathways (SBPs) offer the opportunity to discover new chemistry and the hope of new drug-like entities. Current methodologies to access SBPs fall into one of two categories: culture-dependent methods or molecular-based techniques, which are highlighted in chapter 1. While both approaches have been utilized to access SBPs, there are many deficiencies which inhibit the overall effectiveness of both methods. We offer another approach to bypass these difficulties. Studies of fungal genomes have demonstrated that many secondary metabolite biosynthetic genes are under epigenetic regulation. It is thought that treating fungi with small molecule epigenetic modifiers will upregulate the transcription of SBPs and allow the isolation of new secondary metabolites. This dissertation describes the work done using small molecules epigenetic modifiers to access SBPs and isolate new secondary metabolites. The third chapter involves pilot studies of cultures which were treated with epigenetic modifiers and the resulting isolation of two new polyketide compounds, lunalides A and B. The fourth chapter follows up this work by demonstrating that the use of epigenetic modifiers results in the transcriptional upregulation of secondary biosynthetic pathways for a well-studied strain of Aspergillus niger. This is followed by the isolation of nygerone A from Aspergillus niger in the fifth chapter, which also presents a structural revision and bioactivity analysis of a set of γ-pyrones and γ-pyridones. The final chapter diverges from the topic of small molecule epigenetic modifiers and investigates the ichthyotoxicity of Prymnesium parvum, an invasive algal species which has transitioned from coastal water regions to local rivers, lakes, and streams
ACTIVATION OF FUNGAL SILENT BIOSYTHETIC PATHWAYS BY EPIGENETIC MODIFICATION
Get PDFNatural products have played an important role as drug leads for different diseases. They provide unique structural cores with diverse biological activities. Because of the overuse of antibiotics many pathogens have developed antibiotic-resistance; there is an urgent and continuing need for new antibiotics.Fungi are a great source for new natural products with diverse biological activities; fungal genomic sequence data have shown that there are more secondary metabolite pathways than known metabolites. To obtain new natural products, an efficient way is needed to access these silent biosynthetic pathways (SBPs). Currently, different strategies have been used to access silent biosynthetic pathways including culture dependent methods like One Strain Many Compound (OSMAC) and co-culture, and genomic-based methods including heterologous expression and promoter activation. All of the above methods have their limitations, which prohibit their broad usage. In our group we have proposed a simple and feasible method for this purpose. Epigenetic regulation is a process commonly used by fungi to regulate biosynthesis. Epigenetic processes may silence/downregulate some secondary metabolite biosynthetic pathways. Small molecular epigenetic modifiers can inhibit epigenetic targets and upregulate gene expression. In this dissertation I have applied this strategy on two fungi and demonstrated that some secondary metabolite pathways can be activated/upregulated by epigenetic modifiers. Chapter 3 and chapter 4 will focus on the description of using small molecules epigenetic modifier (5-azacytidine) to access SBPs. Chapter 3 reports a significant change in the secondary metabolites excreted by an Atlantic-forest-soil-derived Penicillium citreonigrum, which is a rich source of secondary metabolites. Two new metabolites, atlantinones A and B accompanied by eight known compounds were isolated from the guttates. Chapter 4 describes the application of different culture methods let to the production of different secondary metabolites. Waikialoids A and B were isolated from static culture whereas asperonol A and B were from shaking culture. Chapter 5 is different from above chapters and it mainly focuses on the hybrid NRPS-PKS gene coded metabolites, mutanobactin B-D, which are the signal regulators with other microorganisms
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