1,721,126 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
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
Chemical and biological study of microorganisms associated with the stingless bee Scaptotrigona depilis
No full textInsetos como formigas cortadeiras, cupins e alguns besouros têm sido descritos como agricultores de fungos mutualistas. No entanto, apenas recentemente esse fenômeno foi descrito em abelhas. O objetivo desse trabalho foi estudar os micro-organismos associados à abelha sem ferrão Scaptotrigona depilis, a primeira abelha agricultora descrita. Foram isolados 149 micro-organismos a partir de diferentes materiais coletados da colônia, e destes, 28% apresentaram atividade antimicrobiana frente a patógenos humanos. Os micro-organismos Bacillus sp. SDLI1, Candida sp. SDCP2, Zygosaccharomyces sp. SDBC30G1 e Monascus ruber SDCP1, isolados do favo de cria de S. depilis, foram selecionados para estudo químico e biológico. Foi demonstrado que o fungo-alimento de S. depilis é Zygosaccharomyces sp., que produz grande quantidade de adipossomos. Os lipídeos e esteroides estocados nessas organelas citoplasmáticas podem ajudar na nutrição larval, uma vez que Zygosaccharomyces sp. é requerido para o desenvolvimento das larvas de S. depilis. Em culturas in vitro de ovos dessa abelha, verificou-se que ergosterol depempenha papel semelhante ao de Zygosaccharomyces sp. para a metamorfose de S. depilis, indicando que esse mutualista serve como fonte de esteroides para as larvas. Verificou-se que compostos voláteis produzidos por Candida sp. SDCP2 estimulam o crescimento de Zygosaccharomyces sp. SDBC30G1. Análises revelaram que os compostos voláteis majoritários produzidos por Candida sp. SDCP2 foram etanol (C1) e álcool isoamílico (C2), e essas substâncias também foram encontradas nas células de cria dessa abelha. Já o fungo M. ruber SDCP1 produz lovastatina (M6), um produto natural reconhecido pela inibição da enzima HMG-CoA redutase, essencial para biossíntese de esteroides, e M6 pode modular o desenvolvimento de Zygosaccharomyces sp. SDBC30G1. Candida sp. SDCP2 estimula a produção de monascinol (M2) e monascina (M3) pelo fungo M. ruber SDCP1 em co-cultura. Monascina (M3) é ativa frente Candida sp. SDCP2, podendo controlar o crescimento dessa levedura, sendo a produção de M3 aumentada em 57 vezes após sete dias de cocultivo. A investigação química de Bacillus sp. SDLI1 revelou que essa bactéria produz sete surfactinas (B1-B7) e bacillomicina D (B8), que apresentam atividade antifúngica. O cromossomo circular de Bacillus sp. SDLI1 possui oito clursters biossintéticos para a produção de diferentes classes de antimicrobianos. Bacillus sp. SDLI1 também produz o fago SDLI1-1, ativo contra Paenibacillus larvae, patógeno causador da cria pútrida americana em Apis mellifera. Cultivos de larvas in vitro revelaram que S. depilis apresenta resistência contra os entomopatógenos Beauveria bassiana e Metarhizium anisopliae, sendo que Bacillus sp. SDLI1 pode desempenhar um papel protetivo para as larvas de S. depilis contra o patógeno P. larvae. Os resultados sugerem que o ambiente encontrado nas colônias de S. depilis favorece o desenvolvimento de uma microbiota especializada. Esses micro- organismos interagem e beneficiam a abelha hospedeira, estabelecendo relações de simbiose que devem ser preservadas para a sobrevivência desse polinizadorSome ants, termites and beetles have established mutualistic relationship with fungi that they culture for food. However, just recently a fungus agricultural behavior has been described for bees. The main goal of this study was to investigate the microbiota associated with the stingless bee Scaptotrigona depilis, the first fungus- farming bee described. Different materials from S. depilis colony were used to isolate 149 microbial strains, and among these microorganisms, 28% showed antimicrobial activity against human pathogens. The microorganisms Bacillus sp. SDLI1, Candida sp. SDCP2, Zygosaccharomyces sp. SDBC30G1 and Monascus ruber SDCP1, isolated from brood cells of S. depilis, were selected for further studies. Using different approaches, it was confirmed that Zygosaccharomyces sp. SDBC30G1 is the fungus required for S. depilis larval development. This fungus accumulates cytoplasmic lipid droplets that can be a source of sterols and lipids to the larvae. Using in vitro eggs culturing, it was verified that ergosterol, the major sterol produced by Zygosaccharomyces sp. SDBC30G1, can stimulates larval metamorphosis, confirming this yeast as an important sterol source. Co-cultures provided information about Candida sp. SDCP2 volatile organic compounds (VOCs) production, which stimulates Zygosaccharomyces sp. SDBC30G1 growth. The majoritarian VOCs produced by Candida sp. SDCP2 were ethanol (C1) and isoamyl alcohol (C2), which were also detected in S. depilis brood cells. The fungus M. ruber SDCP1 produces lovastatin (M6), an inhibitor of HMG-CoA reductase, which can modulate Zygosaccharomyces sp. SDBC30G1 pellicle formation and lipids accumulation. Candida sp. SDCP2 stimulates the production of monascinol (M2) and monascin (M3) by M. ruber SDCP1 in co-culture. Monascin (M3) is active against Candida sp. SDCP2 and can control the growth of this yeast, once M3 biosynthesis increased ~ 57 folds after seven days of co-culturing. Bacillus sp. SDLI1 produces seven surfactins (B1-B7) and bacillomycin D (B8) that presented antifungal activity against pathogenic fungi. This bacterium had its whole-genome sequenced and the circular chromosome harbors biosynthetic gene clusters to produce eight classes of antimicrobial compounds. The phage SDLI1-1, which presented activity against Paenibacillus larvae, a pathogen causative of American Foulbrood Disease, was also produced by Bacillus sp. SDLI1. S. depilis larvae were resistant against Beauveria bassiana and Metarhizium anisopliae infections, and Bacillus sp. SDLI1 was capable to increase larval survival during in vitro culturing with P. larvae. The results suggest that the environmental conditions found in S. depilis colonies favor the development of a specialized microbiota. These microorganisms interact and produce beneficial factors to its host. These stablished symbiotic relationships contribute with the homeostasis inside the colony and they must be preserved to safeguard S. depilis surviva
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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Discovery and Characterization of Diazo-Forming Enzymes in the Cremeomycin Biosynthetic Pathway
No full textNature constructs a wide variety of structurally complex and bioactive small molecules that have critical physiological and ecological roles. These natural products have served as an important source in developing therapeutics that treat a range of human conditions including cancer, infectious disease, and pain management. Investigating the biosynthesis of these natural products offers the opportunity to discover new bioactive small molecules as well as engineer these pathways for the production of novel compounds. Elucidating the enzymes that catalyze the chemical transformations within these biosynthetic pathways will enable applications in genome mining, biocatalysis, and synthetic biology that can afford therapeutic candidates. Here we describe the discovery and characterization of novel enzymes that install the reactive diazo functional group during cremeomycin biosynthesis. These efforts have provided insight into a long- standing challenge within the field of natural products chemistry and provide the knowledge for identifying and engineering novel diazo-containing small molecules.
In Chapter 2 we describe our efforts to identify the biosynthetic gene clusters that are responsible for producing the diazo-containing natural products cremeomycin (cre) and lomaiviticin (lom). We undertook a genome mining strategy, based on the hypothesized intermediacy of the molecule 3-amino-4- hydroxybenzoic acid (3,4-AHBA) in cremeomycin biosynthesis and the polyketide nature of lomaiviticin, to identify the putative cre and lom gene clusters. These clusters were confirmed experimentally using heterologous expression and bacterial genetics, respectively. Based on the enzymatic chemistry encoded within the gene clusters we provided an updated biosynthetic hypothesis for cremeomycin and lomaiviticin assembly.
In Chapter 3 we use a combination of in vivo and in vitro enzyme characterization, synthesis, and stable isotope feeding studies to elucidate the biosynthesis of cremeomycin up to the point of diazotization. We find that following 3,4-AHBA synthesis by the enzymes CreH and CreI, subsequent C2 hydroxylation and C4 O-methylation are carried out sequentially by the flavin-dependent monooxygenase CreL and the SAM-dependent O-methyltransferase CreN to afford 3-amino-2-hydroxy-4-methoxybenzoic acid (3,2,4- AHMBA). Thus, diazotization in cremeomycin biosynthesis occurs as the last step via late-stage N–N bond formation with the aniline 3,2,4-AHMBA.
In Chapter 4 we identify and characterize a novel pair of enzymes that generate nitrite from L- aspartate. Feeding studies with 15N inorganic nitrogen salts suggest that nitrite is the source of the distal nitrogen atom in the diazo group of cremeomycin. In vitro biochemical reconstitution supports a model in which the flavin-dependent monooxygenase CreE catalyzes the six-electron N-oxidation of L-aspartate to nitrosuccinate with subsequent C–N bond cleavage by the aspartase homolog CreD to afford nitrite and fumarate. Interestingly, CreD and CreE appear to form a tightly regulated complex and this complex is essential for nitrite generation.
Finally, in Chapter 5, we identify and conduct preliminary characterization of the diazo-forming enzyme from cremeomycin biosynthesis. Using a combination of an Escherichia coli-based heterologous expression system, lysate experiments, site-directed mutagenesis, and biochemical reconstitution with partially-purified enzyme, we demonstrate that the fatty acid-coenzyme A (CoA) ligase homolog CreM catalyzes diazotization of 3,2,4-AHMBA with nitrite to afford cremeomycin in vivo and in vitro. Our in vivo and in vitro investigations suggest that ATP is required for the diazotization reaction, which we propose is used to activate nitrite and potentially an N–N linked intermediate. Future efforts are focused on structural and further biochemical characterization of CreM in order to develop a detailed mechanistic understanding of the diazotization reaction including the role of ATP.Chemistry and Chemical Biolog
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