This investigation was designed to evaluate the need for retaining both Sigmodon hispidus texianus and Sigmodon hispidus berlandieri as subspecific designations. An attempt was made to demonstrate bioclimatic variation and reproductive seasonality in cotton rats. The validity of applying the results of isolated studies of cotton rat populations to the species as a whole was examined.

Laser surface modification involves rapid melting and solidification is an elegant technique used for locally tailoring the surface morphology of alumina in order to enhance its abrasive characteristics. COMSOL Multiphysics® based heat transfer modeling and experimental approaches were designed and used in this study for single and multiple laser tracks to achieve densely-packed multi-facet grains via temperature history, cooling rate, solidification, scanning electron micrographs, and wear rate. Multi-facet grains were produced at the center of laser track with primary dendrites extending toward the edge of single laser track. The multiple laser tracks study indicates the grain/dendrite size increases as the laser energy density increases resulting in multiplying the abrasive edges which in turn enhance the abrasive qualities.

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M.Sc. (Nematology) / Please refer to full text to view abstract

Dissertation submitted to the Faculty of Science, University of the Witswatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. May 2015 in Johannesburg / Claudins are a large gene family found in all vertebrates. Claudins encode tetraspan membrane proteins, involved in the structure and function of the tight junctions. This association of cells leads to the formation of the epithelial sheet which is involved in many functions such as embryo morphogenesis. The NCBI database shows 27 claudins identified in humans; 23 in mice and 17 in Xenopus. This suggests that an increase in gene family size may correlate with the evolution of more complex vertebrates. In this study claudins from the most basal extant vertebrate, the sea lamprey, were investigated. RNA used to build up the lamprey genome by Jeramiah Smith (Smith et al., 2012), was used for lamprey claudin sequences. Additionally this study identified 2 more claudins (Cldn B & Cldn F). The phylogenetic tree constructed using claudins from higher vertebrate model organisms and the invertebrates Ciona intestinalis and Drosophila melanogaster; showed that lamprey claudins are evolutionarily more distantly related to their orthologs in higher vertebrates. Furthermore some claudins in lamprey did not show any homologs in higher vertebrates and vice versa, indicating the emergence of novel members in higher vertebrates. However lamprey Cldn A was found to be homologous to CLDN 3 in higher vertebrates. This is interesting since CLDN 3 is involved in the development of two vertebrate specific traits; one of which is the ear placode. Thus Cldn A (renamed Cldn 3B), was made a focus of this study. RNA in situ hybridization using probes designed from individual UTRs showed localised expression of Cldn 3B in the ear placode, pharyngeal pouch, pericardial cavity and the fin fold whereas Cldn B (renamed Cldn 8B) was mostly expressed in the pharyngeal pouch and ear placode much like its orthologs in higher vertebrates. Knockout experiments showed that Cldn 3B is involved in sealing and expansion of the ear placode and pharyngeal arches during development whereas Cldn 8B is involved in determining ear placode development. Thus claudins are seen to be heavily involved in the morphology of vertebrate specific traits therefore an expansion in this gene family would affect the complexity of vertebrates during evolution.

A dissertation submitted to the Faculty of Science, University of Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. / Dinocephalians form an important part of the Upper Permian therapsid faunas of South Africa and Russia, and have also recently been reported from China and Brazil, and even more recently a diverse dinocephalian fauna has been described from Zimbabwe. This thesis reports a new primitive tapinocephalid dinocephalian, NHMB 1556, from the Upper Madumabisa Mudstone Formation in Zimbabwe. NHMB 1556 is considered to be closely related to Avenantia and it possesses primitive tapinocephalid characters, but is more derived than Tapinocaninus, the most primitive tapinocephalid dinocephalian known. NHMB 1556 is distinguished from other tapinocephalines by having a groove on the squamosal below its dorsal contact with the parietal, a low squamosal-parietal suture on the posterior border of the temporal fenestra, a vomer which extends posteroventrally and forms the anterior margin of the interpterygoidal vacuity and basisphenoid, which is semi-circular anteroventrally. / AC2017

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 2015. / External pollen grain morphology has been widely used in the taxonomy and systematics of flowering plants. The eurypalynous family Acanthaceae is a notable example of a group where these pollen diversities have proved useful in determining relationships between taxa. However, internal pollen wall features have received far less attention due to the difficulty of examining the underlying exine from which the external sculpturing is derived. Consequently, internal wall features have thus far not been used in formulating existing classifications. A new technique involving precise cross sectioning or slicing of pollen grains at a selected position, using a focused ion beam-scanning electron microscope (FIB-SEM), was used on 39 species of Acanthaceae to examine the internal pollen wall structure and identify features of potential systematic relevance. Five basic internal wall structures were described in this study. The study also showed that similar external pollen wall features may have distinctly different underlying structures.

A Dissertation submitted to the Faculty of Science University of the Witwatersrand, .Johannesburg for the Degree of Master of Science. / A detailed morphological study of two skulls of Emydops was undertaken by using the serial grinding technique. Graphical, wax modeI and computer-3D reconstructions of various aspects of the skulls were made. The internal structures are described in detail and compared to other small dicyncdonts such as Eodicmodort, Pristerodon, Tropidostpma, Cistecepnalus and Diictodon. The structure of the skull of Emydops conforms within the limits of variation known for this genus, to descriptions given in the literature. It was found that Emydops is different from other dicynoconts in that the parasphen and has a definite suture with the pterygoid anterior to the pterygoidbasisphenoid suture, which is not noticed and mentioned for other dicynodonts, except for Emydops (Olson, 1944). / Andrew Chakane 2018

Estimating the sex of unknown human skeletal remains is important to the fields of forensic anthropology, bioarchaeology, and other specialties. I studied sexual dimorphism on the first and second ribs to estimate sex from skeletal remains. I employed two approaches. I used geometric morphometrics to analyze landmark and semilandmark coordinate points to examine the overall shape of the ribs. I also examined the sternal end of the ribs for size using the superior-inferior height (SIH) and anteriorposterior breadth (APB) in a binary logistic regression (BLR) model. Differences in male and female first and second ribs are undetectable when landmark coordinate points are used to capture shape variability, but significant differences in the shape of the ribs, however, are detected through the use of semilandmark coordinate points. Using semilandmark points to estimate sex presented an accuracy rate of 80.7% from the first rib, and 72.9% from the second rib. The use of the sternal end presents consistent results in its ability to estimate sex with an accuracy rate of 84.2%. The BLR model reveals significant differences between males and females than the geometric morphometric approach; it is more applicable for discerning sexual dimorphism of unknown individuals. This study reveals that while geometric morphometrics provides a powerful approach to assessing morphological differences, it is not always better than simpler methods, in this case, simple measurements analyzed through BLR. / Includes bibliography. / Thesis (M.A.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

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