1,721,123 research outputs found
A metabolomics investigation on experimental interventions of acute alcohol consumption
No full textPhD (Biochemistry), North-West University, Potchefstroom CampusThis thesis, titled: "A metabolomics investigation on experimental interventions of acute alcohol consumption", deals with a current topic of global interest, namely, alcohol use and abuse. Alcohol abuse is associated with many serious, and even detrimental, health, social and economic consequences, and is one of the world’s leading risk factors for disability, morbidity and mortality. For these reasons it is a topic of growing concern in developing, as well as developed, countries. Alcohol is metabolized mainly in the liver by two nicotinamide adenine dinucleotide (NAD)-dependent enzymes — alcohol dehydrogenase and, subsequently, aldehyde dehydrogenase. In both of these reactions oxidized NAD (NAD+) is reduced to NADH, which increases the NAHD:NAD+ ratio in hepatocytes. This ratio controls the activity of several key metabolic enzymes and the direction of many reversible metabolic reactions, and its disruption is known to result in perturbations of various metabolic pathways. Various studies examining the effects of, and diseases related to, chronic alcohol abuse have been performed in the last few decades. However, to date, no comprehensive metabolomics study on the effects of acute alcohol consumption has been done. Thus, with the guidance of experts in the fields of metabolism, metabolomics and biostatistics, the first extensive, multidisciplinary metabolomics cross-over intervention study into the effects of acute alcohol consumption on the urinary metabolite profiles of healthy, young males was designed, and is presented in this thesis. The study consisted of analysing urine samples, collected from experimental participants over a defined period of time following four interventions, on two different analytical platforms — proton nuclear magnetic resonance (1H-NMR) spectroscopy as an untargeted approach, and gas chromatography—mass spectrometry (GC—MS) as a semi-targeted approach. The results from these investigations demonstrated the power of applying metabolomics to this area of research and provided the opportunity to obtain a holistic view of the urinary metabolic profile resulting from acute alcohol consumption. From both of these approaches a list of metabolites perturbed by acute alcohol consumption could be compiled with the use of statistical analyses. Various metabolic pathways were seen to be disrupted, most of them due to the known alcohol-induced increased NADH:NAD+ ratio. Additionally, two urinary metabolites — sorbitol, from the 1H-NMR analysis, and 2-hydroxyisobutyric acid, from the GC—MS investigation — not previously known to be associated with the consequences of acute alcohol consumption were identified in the metabolic profiles of the experimental participants following acute alcohol consumption. These novel findings could possibly be used as a basis for determining biomarkers of acute alcohol consumption, which could have various health, economic and legal benefits. This thesis, the eventual product of a skilfully designed and diligently carried out scientific study, is compiled and presented in article format as per the requirements of North-West University. The scientific contributions made during this study to the existing alcohol-related scientific knowledge resulted in three publications. Two (1 and 3) have already been published, and one (2) has been accepted for publication. 1. Irwin, C., Van Reenen, M., Mason, S., Mienie, L.J., Westerhuis, J.A. & Reinecke, C.J. 2016. Contribution towards a metabolite profile of the detoxification of benzoic acid through glycine conjugation: an intervention study. PLOS ONE, 11(12):e0167309. doi:10.1371/journal.pone. 0167309. 2. Irwin, C., Van Reenen, M., Mason, S., Mienie, L.J., Wevers, R.A., Westerhuis, J.A. & Reinecke, C.J. The 1H-NMR-based metabolite profile of acute alcohol consumption: a metabolomics intervention study. 3. Irwin, C., Mienie, L.J., Wevers, R.A., Mason, S., Westerhuis, J.A., Van Reenen, M. & Reinecke, C.J. 2018. GC—MS-based urinary organic acid profiling reveals multiple dysregulated metabolic pathways following experimental acute alcohol consumption. Scientific Reports, 8:5775. doi:10.1038/s41598-018-24128-1.Doctora
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
Quantitative Raman reaction monitoring using the solvent as internal standard.
No full textDespite its potential, the use of Raman spectroscopy for real-time quantitative reaction monitoring is still rather limited. The problems of fluorescence, laser instability, low intensities, and the inner filter effect often outscore the advantages as narrow bands, the use of glass fibers, and low scattering of water and glass. In this paper, we present real-time quantitative monitoring of the catalyzed Heck reaction by using the solvent as internal standard. In this way, all multiplicative distortions, e.g., laser intensity variations or absorbance of the laser light, can be corrected for. We also show that a limited amount of fluorescence does not hamper the analysis. Finally, we present a new method to correct for the inner filter effect, i.e., the absorbance of Raman scattered light by the reaction medium. Simultaneous absorption measurements of the reaction mixture enable accurate correction of Raman signals for the inner filter effect. Thus, for reaction monitoring applications, a Raman spectrometer should be equipped with an absorbance measurement device
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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