1,721,311 research outputs found
MICROBIAL CANNIBALISM IN EXTREME STARVED ENVIRONMENT
No full textDue to their geochemical characteristics, some soils can be considered as extreme. This is the case with some New Caledonia soils, such as ultramafic soils, that are characterized by deficiencies in essential elements and overabundance of heavy metals, particularly nickel. This phenomenon is amplified in mine spoils where carbon and nitrogen concentrations are extremely low, thus, classifying mine spoils as starved environments. Our objective was to determine which adaptive strategies enable bacterial populations to adapt to extreme environments. A comparative metagenomic analysis applied to partial metagenomic sequences of two ultramafic soils (pristine ultramafic soil, mine spoils) and two “classical“ soils (prairie soil and corn field soil) was developed to detect genes and bacterial populations specific to each soil. The new program and the graphical interface that we developed specifically for this study helped highlight the effect of the ultramafic origin, the “human” influence (mining, farming), and the starvation conditions on bacterial community function. Our results highlight the originality of the bacterial community structure and its metabolism in the mine spoils. To adapt to these extreme edaphic conditions, bacterial populations tend to minimize nutrient loss and to enhance biosynthetic pathways reaction by using dead bacterial cells as nutrients
METAGENOMIC: INSIGHTS ON EXTREME METABOLISM
No full textDue to their geochemical characteristics, some soil can be considered as extreme. Such is the case in New Caledonia, where the ultramafic soils are characterized by their deficiency in essential elements, and their excess in heavy metals, particularly nickel. This phenomenon is amplified in mine spoils where carbon and nitrogen concentrations are extremely low. The aim of this work was to evaluate the adaptive strategies of soil microbial communities to extreme environments. A combination of metagenomic tools were used (16S rRNA libraries, microarray, cosmid clone libraries and pyrosequencing) and a comparative metagenomic analysis, including metagenomes of “classical “ soils, was performed to demonstrate the differences between bacterial communities and their functions. Statistical differences were examined in order to explore genes/populations specific to extreme soils. Results highlighted the original bacterial community structure and metabolism in the mine spoils, characteristic of its extreme edaphic conditions. Microbial communities evolved by favoring biosynthetic pathways and minimizing nutrient loss
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
Reductive dechlorination of chlorinated pollutants by metals and organometallics.
No full textReductive dechlorination is an important chemical and biological transformation in anoxic environments, particularly for highly chlorinated compounds. In nature, however, the reaction is slow and certain compounds released into the environment appear recalcitrant. This thesis examines the role of metals and organometallics in enhancing reductive dechlorination of chlorinated pollutants in different biotic and abiotic systems, and the dependence of the reaction rates and product distribution on the redox potential of the system. The ability of denatured heme protein and boiled bacterial suspensions to dechlorinate carbon tetrachloride (CT) under reducing conditions, in addition to the co-metabolic dechlorination of tetrachloroethylene by non-acclimated methanogenic consortia, support the possible non-enzymatic character of reductive dechlorination. The rates and products of reductive dechlorination in a chemical mimetic system are influenced by changes in medium and in reaction components (donor, mediator, acceptor). Donors, such as elemental Zn\sb{\rm (s)} are able to reductively dechlorinate CT to less chlorinated products (even methane). The first dechlorination of a pentachlorobiphenyl is demonstrated in the presence of dithiothreitol (DTT) as donor, vitamin B\sb{12} (B\sb{12}) as mediator and 1,4-dioxane as co-solvent, albeit at much lower rates than for the aliphatic C\sb1 electron acceptor CT in water. B\sb{12} is a better mediator for CT dechlorination than Co(II), Ni(II) and Fe(III)-hematoporphyrin and -DTT complexes. For each ligand, the electron transfer ability of the complex depends on metal type and decreases in the order: Co, Ni, Fe. An empirical rate law relates the disappearance rate of CT to pH and both DTT and B\sb{12} total concentrations, and a free radical pathway with atom transfer is proposed: one-electron reduction of B\sb{12} (cyanocobalamin(III)) to B\sb{\rm 12r} (cobalamin(II)) by DTT and participation of (cobalamin(II)) in the rate-determining electron transfer to CT with formation of an alkyl-cobalamin(III) intermediate. In parallel, an equation is developed linking the redox potential of the system to the concentrations of reduced, oxidized DTT, and pH. The equation coincides well with theoretical predictions based on the number of electrons involved in the oxidation of DTT and its acid-base properties.PhDEnvironmental EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/103543/1/9332013.pdfDescription of 9332013.pdf : Restricted to UM users only
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