1,721,033 research outputs found
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
SNP-based genetic linkage mapping and whole-genome diversity assessment in cassava (Manihot esculenta Crantz) accessions from Africa and Latin America
Get PDFDissertation (MSc)--University of Pretoria, 2017.Cassava is a staple crop grown in the tropics and supplies food to over half a billion people. It is
recognised as a valuable crop for food security in the face of climate change, since it grows in
resource poor areas and displays tolerance to drought conditions. Furthermore, the high starch
content of the storage roots makes cassava a suitable feedstock for biofuel production. Considerable
advancements have been made towards the development of cassava genomic resources, such as the
release of the first draft genome sequence in 2012, leading to the identification of new DNA markers
and the use of genotyping-by-sequencing technology.
The aim of this MSc was to i) construct a genetic linkage map using single nucleotide polymorphism
(SNP) and simple sequence repeat (SSR) markers implemented in a drought-tolerant mapping population (MCOL1734 x VEN77), ii) assess genetic diversity and genetic structure within African
and Latin American cassava landraces and breeding varieties using SNP markers, iii) to assess
genome-wide patterns of diversity, and iv) to select 128 SNP markers for routine genotyping of
cassava germplasm.
Genetic diversity and structure was assessed within genetic material from African and Latin
American germplasm collections, research institutes and breeding programmes. Three potentially
heterotic genetic groupings were identified predominantly representing: a) Latin American
germplasm, b) West and East African improved varieties, and c) East African landraces.
Interestingly, one West African landrace displayed higher than average relatedness to landraces
from East Africa, suggesting that it was widely distributed as a favourable variety and hybridised
to local landraces in East Africa. Furthermore, evidence of mislabelling and redundancy was
observed, highlighting the need for improved management of germplasm collections through the
use of molecular markers.
A genetic linkage map, representing 23 linkage groups, was constructed using 443 SNP and 73 SSR
markers. Alignment to the Manihot esculenta v6.1 genome assembly revealed regions of the
genome with poor marker coverage, resulting in some chromosomes being split into several small
linkage groups. Minor allele frequency for all mapped SNP markers was plotted to assess the
genome-wide distribution of diversity for each genetic group. This revealed one region of the
genome with low heterozygosity across all three groups and one region displaying divergence in
the East African landraces, likely as a result of local adaptation and selection by farmers. Using this
data, 128 highly informative SNP markers, distributed throughout the genome, were selected as
candidates for routine genotyping in cassava. This study contributes to our understanding of genetic diversity and structure in African and Latin
American cassava landraces and improved varieties. Furthermore, two new molecular breeding
tools were developed: a) a genetic linkage map, constructed using a drought-tolerant mapping
population, will provide future opportunities to identify markers associated with this important trait
for marker-assisted breeding, and b) a set of informative SNP markers that will provide a costeffective
tool for routine genotyping for improved management of germplasm collections and
breeding applications, such as the identification of genetically distant accessions for controlled
crosses, pedigree reconstruction and maintenance of identity of accessions.GeneticsMScUnrestricte
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
QTL mapping for pest and disease host plant resistance in cassava cultivars Kiroba and AR37-80 and coincidence of QTL with introgression regions from Manihot glaziovii
Get PDFThesis (PhD)--University of Pretoria, 2019.Cassava (Manihot esulenta Crantz.) is a staple food crop for more than 800 million people worldwide. It is drought tolerant and offers a flexible harvesting regime since the roots can remain in the soil and be harvested when needed. It is a food security crop when cereal crops fail. Biotic and abiotic stresses including pest and diseases negate this potential. Its heterozygous nature, long growing cycle and low seed yield per pollination poses challenges in breeding. In addition, it is highly outcrossing making it difficult to develop an adequately sized F2 population hence limiting genetic studies to F1 progenies.
Cassava brown streak disease (CBSD) has emerged to be the great threat to cassava production reducing useable roots or leading to total crop loss, and if not checked it can impact more than 200 million people in Africa who depend on the crop for their food and income generation.
The plausible approach to combat CBSD is to combine breeding for host plant resistance with sanitation measures and the planting of virus-free stakes. The breeding for host plant resistance should be performed as quickly and efficiently as possible, taking advantage of genomic, transformation and molecular marker technology. Conventional breeding, which does not use data generated from molecular tools, takes up to 10 years to deliver a new cultivar since the plants have to be grown for 12 months before selection can be made. If molecular markers were found to be associated with field resistance, then F1 progeny generated in a breeding program could be screened and selected at the seedling stage, thereby drastically reducing the breeding cycle and providing an accurate way of efficiently pyramiding resistance from different sources.
In this project, quantitative trait loci (QTL) mapping for resistance to CBSD, cassava Mosaic disease (CMD), and cassava green mites (CGM) was performed using an F1 mapping population developed between CBSD resistant Tanzanian landrace, Kiroba, and a susceptible breeding clone, AR37-80. This aimed to construct a SNP based linkage map using the segregating population and provide a tool to identify QTL. The study investigated the presence of genomic regions in Kiroba derived from M. glaziovii and their contribution to the field resistance observed in Kiroba. The introgression regions in Kiroba were compared to those from Namikonga, the well-known CBSD resistant cultivar and other genotypes of African origin to understand the source of their resistance.
The results show that only two QTL are linked to CBSD root necrosis and are located on chromosomes V and XII, while seven are associated with CBSD foliar symptoms only and are located on chromosomes IV, VI, XVII, and XVIII. The QTL on chromosomes XI and XV are linked with both CBSD foliar and root necrosis symptoms. Two QTL found on chromosome XII and XIV are linked to CMD, while two QTL located on chromosomes V and X are linked to CGM resistance.
The analysis of introgression regions in Kiroba revealed the existence of large Manihot glaziovii like regions on chromosome I, XVII, and XVIII. The introgression segments on chromosomes XVII and XVIII overlap with QTL associated with CBSD foliar symptoms. These regions contain domains associated with host plant disease resistance. The introgression region on chromosome I in Kiroba is of a different haplotype to the characteristic “Amani haplotype” found in the landrace Namikonga and other genotypes analyzed in this study. Kiroba also does not have a large introgression block on chromosome IV found in other genotypes. Kiroba is closely related to a sampled Tanzanian “tree cassava.” This supports the observation that some of the QTL associated with CBSD resistance in Kiroba are different to those observed in Namikonga.
This study provides an understanding of the genetic basis of the field resistance observed in the local cassava landraces, the genomic regions contributing to the resistance and the source of the resistance. This information is valuable in pyramiding QTL for host plant disease resistance.GeneticsPhDUnrestricte
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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