1,721,152 research outputs found
Determining correction factors due to threshold reaction interference in Neutron Activation Analysis
No full textNeutronenactiveringsanalyse (NAA) is een gevoelige, niet-destructieve analysetechniek die gebruikmaakt van neutronenbestraling om elementen in een staal te identificeren. Bij deze techniek treden er soms interferenties op, zoals drempelreacties ten gevolge van de aanwezige snelle neutronen. Dit leidt tot een overschatting van de concentratiebepaling van specifieke elementen waarvoor gecorrigeerd moet worden. Deze masterproef draagt bij tot het bepalen van deze correctiefactoren voor verschillende elementen voor twee bestralingskanalen in de BR1 reactor op het SCK CEN. De werkzame doorsnedes voor deze drempelreacties worden eveneens bepaald.
De aanpak omvat de bestraling van verschillende activatiefolies in twee kanalen van de BR1. De gammaspectra worden gemeten met germanium detectoren en geanalyseerd. De data worden dan verwerkt via een Excel-sjabloon waarin de benodigde berekeningen automatisch worden uitgevoerd met een Python-code. Deze experimentele resultaten worden vergeleken met MCNP-simulaties en met literatuurwaarden van andere onderzoeksreactoren.
Zoals verwacht zijn de correctiefactoren afhankelijk van de reactor en van de bestralingspositie in de reactor. De resultaten van dit onderzoek leveren correctiefactoren op voor een aantal drempelreacties, wat bijdraagt tot nauwkeurigere analyse voor enkele specifieke elementen
Determining correction factors due to threshold reaction interference in Neutron Activation Analysis
No full textNeutronenactiveringsanalyse (NAA) is een gevoelige, niet-destructieve analysetechniek die gebruikmaakt van neutronenbestraling om elementen in een staal te identificeren. Bij deze techniek treden er soms interferenties op, zoals drempelreacties ten gevolge van de aanwezige snelle neutronen. Dit leidt tot een overschatting van de concentratiebepaling van specifieke elementen waarvoor gecorrigeerd moet worden. Deze masterproef draagt bij tot het bepalen van deze correctiefactoren voor verschillende elementen voor twee bestralingskanalen in de BR1 reactor op het SCK CEN. De werkzame doorsnedes voor deze drempelreacties worden eveneens bepaald.
De aanpak omvat de bestraling van verschillende activatiefolies in twee kanalen van de BR1. De gammaspectra worden gemeten met germanium detectoren en geanalyseerd. De data worden dan verwerkt via een Excel-sjabloon waarin de benodigde berekeningen automatisch worden uitgevoerd met een Python-code. Deze experimentele resultaten worden vergeleken met MCNP-simulaties en met literatuurwaarden van andere onderzoeksreactoren.
Zoals verwacht zijn de correctiefactoren afhankelijk van de reactor en van de bestralingspositie in de reactor. De resultaten van dit onderzoek leveren correctiefactoren op voor een aantal drempelreacties, wat bijdraagt tot nauwkeurigere analyse voor enkele specifieke elementen
Interactions of the electron transport proteins of methylotrophic bacteria
No full textThis thesis describes an investigation into the nature of the interactions of the periplasmic electron transport proteins of methylotrophic bacteria. The organisms used in this study were two highly characterised methylotrophs, Methylophilus methylotrophus and Methylobacterium extorquens. Methanol dehydrogenase (MDH) from Methylophilus methylotrophus was shown to contain a small (β) subunit and to exist in an α2β2 subunit conformation. The amino acid sequence of the β-subunit was determined and comparison with the sequence of the same subunit from Methylobacterium extorquens indicated that many of the lysine residues previously proposed to be involved in the reaction with cytochrome cL were absent. This led to doubts about the role of the β-subunit. The interaction of MDH and the novel c-type cytochrome, cytochrome c_L, was investigated using two cytochrome-linked assay systems, the first using horse-heart cytochrome c as the terminal electron acceptor, the second, a novel assay system developed so as to limit protein/protein interactions to a single site, used the dye PIP as the terminal electron acceptor. Introduction of various salts into the cytochrome-linked assay caused inhibition of electron transport, indicating an interaction that is electrostatic in nature. EDTA was shown to be a potent inhibitor of electron transfer. Modification of the side-chains of various amino acid residues indicated that positively-charged lysine residues on MDH interact with negatively-charged carboxyl groups on cytochrome c_L. Two-stage sulpho-NHS enhanced EDC cross-linking of MDH and cytochrome c_L demonstrated that the cytochrome interacts with the α-subunit of MDH, not with the β-subunit as was originally proposed, and that carboxyl groups on cytochrome c_L cross-link with lysine residues on MDH. Cross-linking was inhibited by the introduction of salts, but not by low concentrations of EDTA, suggesting that EDTA is a potent inhibitor of methanol oxidation by inhibiting electron transfer but not by preventing docking of the two proteins. Two-stage cross-linking also demonstrated that cytochrome c_L interacts with its electron acceptor, cytochrome c_H, in an analogous way to MDH. The reaction is, again, electrostatic in nature, involving carboxyl groups on cytochrome c_L and lysine residues on cytochrome c_H. Competition experiments involving all three proteins indicated that cytochrome c_L possesses a single site that binds either MDH or cytochrome c_H. This is evidence against the `wire-like' theory of electron transfer. Using tuna cytochrome c as a model for cytochrome c_H the residues involved in the EDC/sulpho-NHS cross-link with cytochrome c_L were determined, and were shown to be two of the essential lysine residues involved in the binding of this cytochrome to the reductase and oxidase complexes. A glutamate residue situated close to the haem binding site of cytochrome c_L provides one of the carboxyl groups involved in the cross-link with tuna cytochrome c.</p
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
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