1,720,972 research outputs found
Development and validation of LC-ESI-MS/MS methods for quantification of 27 free and conjugated estrogen-related metabolites
No full textAn imbalance in the estrogen metabolism has been associated with an increased risk of breast cancer development. Evaluation of the estrogen biotransformation capacity requires monitoring of various estrogen metabolites. Up to now, only some estrogen metabolites could be measured in urine. However, in order to offer tailor made nutritional support or therapies, a complete estrogen metabolite profile is required in order to identify specific deficiencies in this pathway for each patient individually. Here, we focused on this need to quantify as many as possible of the estrogen-related metabolites excreted in urine. The method was developed to quantify 27 estrogen-related metabolites in small urine quantities. This entailed sample clean-up with a multi-step solid phase extraction procedure, derivatisation of the metabolites in the less water-soluble fraction through dansylation, and analyses using liquid chromatography–tandem mass spectrometry (LC-MS/MS). The metabolites accurately quantified by the method devised included parent estrogens, hydroxylated and methylated forms, metabolites of the 16α-hydroxyestrogen pathway, sulphate and glucuronide conjugated forms, precursors and a related steroid hormone. This method was validated and enabled quantification in the high picograms and low nanograms per millilitre range. Finally, analyses of urine samples confirmed detection and quantification of each of the metabolite
Data on the optimisation of a solid phase extraction method for fractionating estrogen metabolites from small urine volumes
Get PDFCertain estrogen metabolites have been implicated in the pathophysiology of breast cancer. Moreover, the estrogen metabolite profiles of healthy women and those with (a high risk of) breast cancer differ significantly. The development of an analytical method to determine the relative levels of all the estrogen biotransformation products has been described in van der Berg et al. [1]. An improvement on previously developed methods was the ability to also detect molecules such as sulphate and glucuronide conjugates as well as progesterone, estradiol precursors, and metabolites from the 16-hydroxylation metabolic pathway of estrogens simultaneously with all other estrogen metabolites. The data presented here describe the optimisation of a solid phase extraction method with different fractionation steps for LC-MS/MS analysis of 27 estrogen-related metabolites from small urine volumes. Conditions that were optimised include the elution and washing solvent concentration, the urine, loading, washing, and elution volumes, as well as pH. All raw data used to construct the bar graphs presented in this article are included in the supplementary data file. The data indicated that fractionation was necessary in order to elute estrogen metabolites with different chemical properties at different eluate compositions. Only one of the fractions (containing the less water-soluble metabolites) underwent derivatisation before LC-MS/MS analysi
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
Surface preparation and the effects on rock art deterioration
Get PDFDissertation (MA)--University of Pretoria, 2011.The Drakensberg is the highest part of a 1000-km long escarpment that also forms a natural border between South Africa and eastern Lesotho. The uKhahlamba-Drakensberg Park was declared a World Heritage site in 2000 and is globally significant, in particular due to the rock art painted by San hunter-gatherers who inhabited the area from about 8 000 years ago until the late 19th Century. Approximately 30 000 painted images can be found in nearly 600 rock shelters in the area. Rock art heritage in the Drakensberg is unfortunately being lost through a variety of processes, some natural and others resulting from human impacts. Previous research on the weathering of San paintings has focused largely on either monitoring processes causing weathering in rock shelters or investigating rock surfaces that are adjacent to the rock paintings. Recent findings indicate that some of the San art has been painted onto surfaces that were prepared by smoothing the rock surface with a “grinding stone” and coated with a clay (“ground”) layer prior to the application of pigments. This new information may have important implications for rock art conservation as smoothing of a rock surface could significantly modify the physical and chemical characteristics of the surface, thereby influencing the deterioration of the art. In this study two classification systems are developed from data collected in four rock shelters situated in the Park. The first, a Type of Surface Classification System, is developed for the purpose of identifying different types of rock surfaces within rock shelters. The second, a State of Deterioration Classification System, is developed with the purpose of establishing, through visual inspection, how deteriorated the rock art on different types of rock surfaces is. Linkages between the type of surface and the state of deterioration are also explored. Findings show that it is not only possible to determine which surface type a painting has been painted on, but that different rock surface types can deteriorate through different weathering mechanisms and to a different degree. One type of rock surface, acknowledged but not yet recorded, was found amongst the rock art paintings selected for the purpose of this study. More importantly, the alteration of rock surfaces through human action in the past is found to cause rock surfaces to deteriorate either at an accelerated or a retarded rate as opposed to rock paintings that were made on surfaces that have only been altered by natural weathering mechanisms. For example, if a rock surface has only been smoothed with a grinding stone, results show that weathering mechanisms did not deteriorate the surface as quickly as in the case where a clay ground layer has been applied to the rock surface. Different types of rock surfaces deteriorating through different weathering mechanisms (as a result of surface preparation) might have significant implications in terms of rock art conservation as the strategies implemented to conserve rock art should be adapted to consider surface type. In terms of rock art studies aiming to conserve this precious heritage, the two classification systems presented could, therefore, be useful non-destructive tools in assessing rock art deterioration. CopyrightGeography, Geoinformatics and MeteorologyMAUnrestricte
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
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