1,721,187 research outputs found
An evaluation of free amino acids as chemotaxonomic markers in Protea L. species
Get PDFOne of the major functions of a Botanic Garden should be that of research. When a research laboratory was established at Kirstenbosch National Botanic Garden in 1984, it-was decided to start investigating chemical parameters of our indigenous plants, since this is a field that has not received adequate attention in the past. It was hoped to contribute towards the classification of plants by applying chemotaxonomy or chemosystematics, whereby chemical evidence is incorporated with morphological and other information. The genus Protea L. was an obvious choice for the initial material of such research as it is one of the best-known and most prominent genera of our indigenous flora and its taxonomic revision, based mainly on morphological data, was recently completed by Dr. J. P. Rourke (1980) of the National Botanic Gardens, Kirstenbosch. It was hoped that a phytochemical study of Protea species, whereby their free amino acid composition was determined by paper partition chromatography, might be of use in contributing to its taxonomic classification
Introduction to Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie
No full textPresentation presented at the Open Access event, Merensky Library, University of Pretoria, South Africa, 27 October 2011.Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie and its current Open Access status.http://www.library.up.ac.za/openup/oaday.ht
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
An investigation of antibacterial compounds in combretum microphyllum (KLOTZSCH)
No full textDissertation (MSc (Pharmacology))--University of Pretoria, 2008.Please read the abstract (Summary) in the section, 00front of this documentPharmacologyMScunrestricte
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
Extraction of grape seed to produce a proanthocyanidin rich extract
Get PDFDissertation (MSc)--University of Pretoria, 2004.The aim of this study was to develop a cost-effective process to produce a grape seed extract of high quality using only non-toxic extractants. When this study was started no grape seed extract was produced in South Africa. Large quantities were imported to supply the local demand in the human and animal herbal medicine industry. Grape seed extract is mainly used to boost the immune system of humans and animals based on its antioxidant activity.
Initial work with different extractants established the polarity of the compounds with antioxidant activity. Antioxidant related activity was determined with five analysis techniques. Parameters such as the type, preparation and pre-treatment of grape seed, ratio of extractant to grape seed, composition of extractant, extraction time, extraction temperature, the interaction between temperature and time, drying temperature and subsequent treatment of extracts to remove compounds without antioxidant activity were evaluated. In all cases the cost implications of different methods used were kept in mind.
Not only the quality but also the quantity extracted is important in establishing a viable extraction plant. According to the patent literature most techniques used to date produce yields of 0.5 to 2.5 %. The laboratory product went through five stages of development. The percentage extracted for our five laboratory products decreased from 12.0, 10.1, 6.0, 5.9 to 5.5 % whereas antioxidant activity for our product increased from 30, 55, 67 78 to 172 % compared to the best available commercial product.
An important reason for the success of the procedure developed, is that we analyzed the different products developed with sophisticated procedures that gave information about the chemical composition of the extract. From this information procedures could be developed to increase the yield and activity.
The procedure has been licensed to a private company that is in the process of establishing a factory for the large-scale production of grape seed extract. The detail regarding the procedure is confidential to protect the intellectual property and industrial exploitation of the process.gm2014Paraclinical Sciencesunrestricte
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
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