1,720,962 research outputs found
Neurogenesis in the brains of subadult and adult South African ground squirrels (Xerus inauris)
No full textDissertation submitted to the Faculty of Health Sciences, University of the Witwatersrand in fulfilment of the requirements for the degree of Master of Science in Medicine
School of Anatomical Sciences
Faculty of Health Sciences
University of the WitwatersrandNeurogenesis is the ability of the brain to generate new neurons. Neurogenic sites and rates of neuronal proliferation were investigated in the brains of subadult and adult South African ground squirrels. Seven female ground squirrels were trapped; euthanised and their ages determined using body masses and paired dry lens masses. Their brains were perfusion fixed with 4% paraformaldehyde before sectioning at 50 μm in a sagittal plane from which every fifth section was stained with cresyl violet to determine the architecture of the brain. Immunolocalisation of Ki-67 for neuronal cell proliferation and doublecortin (DCX) for immature neurons was also carried out on adjacent sections to those stained for cresyl violet. Ki-67 immunopositive neurons were counted in the dentate gyrus of the hippocampus to determine the changes in the rate of cell proliferation with age. Proliferating and immature neurons, DCX immunopositive, were observed in the subventricular zone (SVZ) of the lateral ventricles, the subgranular zone (SGZ) of the dentate gyrus, the rostral migratory stream (RMS), olfactory bulb, piriform cortex and neocortex of both age groups. Adult squirrel brains were heavier than the subadult brains, but showed significantly lower numbers of proliferating neurons in the dentate gyrus when compared to subadult brains
Anatomy of the brain of the African wild dog (Lycaon pictus)
No full textA thesis submitted to the School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, in fulfilment of the requirements for the degree of Doctor of
PhilosophyThe African wild dog is an interesting species for the study of potential
specializations of the brain owing to an array of seemingly species-specific features, such as
complex sociality, conspecific reproductive suppression, allo-parenting, variegated individual
specific pelage, and the widest vocal repertoire of all canid species. Thus, this species
inhabits a complex social setting within a complex environment – leading to the obvious
question of how do their brains manage to cope with or permit this complexity? The aim of
this study therefore, was to initiate a detailed description of the brain of the African wild dog,
first by providing an overview of their brain and contextualizing this in their phylogenetic
setting, followed by detailed analyses of the olfactory, auditory and visual sensory systems to
determine whether the complexity experienced by the African wild dog in their natural
habitat is achieved through sensory specialization, or whether we need to look further at the
cognitive and affective regions of the brain to understand this unique African mammal. In
order to achieve this, we took a qualitative and a quantitative approach, employing magnetic
resonance imaging, stereological analyses, and a range of basic and immunohistochemical
staining techniques to reveal the precise anatomy of portions of the brain of the African wild
dog. In brief, we observed that the brain of the African wild dog is large for its body size, but
that this does not appear to be an adaptive enlargement, rather it is the result of an
evolutionary reduction in body mass. The overall structure of the brain, and the specific
sensory systems examined appear to be very similar to that observed in other carnivores,
especially the closely related canids. Notably, the African wild dog appears to be able to
detect up to 1700 different odorants, and has a semiochemical detection system that hints at
complex processing of pheromonal signals. Despite these potential olfactory specializations,
no specific specializations of the other sensory systems were noted, when compared in a
phylogenetically relevant context. This leads to the conclusion that the complex behavioural repertoire of the African wild dog is the result of higher-order cognitive or affective neuronal
processes, and it is in the analysis of these higher-order regions that will allow us to develop
a stronger understanding of the behaviour of this speciesCK202
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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