No description available.

Thesis--University of Florida. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 219-230).

Current micro-scale electronics technology has been approaching rapidly towards its technological limit. This has shifted the focus towards nano-scale technology in recent years. More and more researchers around the globe are working in pursuit of bringing nano-scale technology into mainstream. The research carried out here is a small step towards a similar goal. The remarkable optical properties exhibited by certain nano-scale structures are in stark contrast to their bulk form and this provides the basis for this research. Two kinds of nanostructures are developed and investigated for their optical properties. One of these is nanofibers processed from a polymer known as polyaniline (PANI). The focus of this study is to investigate its optical and conductive properties under different conditions of doping environments, temperature and polymerization conditions. Optical characterization technique such as UV-Visible spectroscopy is developed to carry out the investigation. The developed nanofibers have been demonstrated to possess optical and conductive properties to be dependent on doping variables. Study of these optical properties could prove very useful in the development of electrochromic devices and gas sensors. Later in the research, UV-Visible spectroscopy has been improved into a low cost Raman spectroscopy setup which is validated by experimentation carried out on some samples. The second type of nano-structure developed and investigated, is an array of nanoparticles of noble metals such as gold and silver. Such an array is shown to exhibit a phenomenon called plasmon resonance effect when excited by light. UV-Visible spectroscopy technique is utilized to investigate this effect for metal nano-arrays. A biologically nano-structured surface (wing of an insect called cicada) is used as the substrate for the fabrication of metal array. A serious attempt has also been made to do 'Surface Enhanced Raman Spectroscopy (SERS)', making use of the metal nano-array developed. This technique improves the raman lines intensities of certain less sensitive samples such as thiophenol, which are known to give weak raman lines. This is carried out by adsorbing the sample on the metal nano-array.

No description available.

Root-feeding insects can have top-down influence on vegetative composition and ecosystem processes; however, they may respond to bottom-up factors such as soil resources, site productivity, and disturbance.  My research addressed the following questions: (1) Do disturbance (fire), vegetative composition, soil resources, and fine root standing mass influence the structure of root-feeding insect assemblages? (2) What types of roots do root-feeding insects eat, and do they forage selectively?  (3) Do root-feeding insects influence fine root productivity?  To address these questions, I studied root-feeding insect assemblages in longleaf pine wiregrass (Pinus palustris-Aristida stricta) ecosystems of southwestern Georgia, U.S.A.  On a random basis, study sites were burned at least every other year (B), or left unburned (UB) for about 9 years.  Fine root productivity and root-feeding insect abundances were sampled repeatedly across 54 random plots in UB and B sites.  In Chapter 2, I characterized spatial and temporal patterns of root-feeding insect abundance, understory plant composition, soil resource availability, and fine root standing mass within each plot.  Insect population densities were low overall, but abundance, patchiness, and diversity were greater in UB sites.  Abundance patterns were significantly related to vegetative composition.  In Chapter 3, I quantified the diet of root-feeding insects by measuring the natural abundance of carbon (C) and nitrogen (N) stable isotopes in insects and fine roots.  Using 13C abundance, I examined the contribution of warm season grass roots to insect diet, relative to the proportion of warm season grass roots within adjacent root standing crop samples; 15N abundance was used to detect omnivory.  Overall, insects appeared to be non-selective herbivores and omnivores that may alter foraging behavior to maintain a mixed diet (i.e. reducing or increasing warm season grass consumption when its abundance was high or low, respectively).  The extent of omnivory varied within and among taxa.  In Chapter 4, I estimated the top-down influence of root-feeding insects on fine root productivity by comparison of ingrowth cores with or without an insecticide treatment.  I detected a weak positive effect of herbivores on the productivity of non-grass fine roots (< 10% of fine root productivity). / Ph. D.

Thesis (M.S.)--Miami University, Dept. of Zoology, 2005. / Title from first page of PDF document. Includes bibliographical references (p. 31-35).

With our contemporary biota under increasing threat of extinction, it is of interest to understand where, why and how biological diversity is generated. If focussed on appropriate taxa, phylogeographic and phylogenetic studies can assist in the identification of both places and processes central to the origin and maintenance of biological diversity. It is explained why southern Africa presents a perfect test-bed for exploring such mechanisms of diversification and why cicadas (Hemiptera: Cicadidae) have proved very suitable tools for studies of historical biogeography. This study then exemplifies these points by providing the first large-scale investigation of the historical biogeography of the tribe Platypleurini Schmidt, 1918, with emphasis on the genus Platypleura Amyot & Seville, 1843 in southern Africa. Standard methods of DNA sequencing provided data from portions of the mitochondrial small subunit ribosomal 16S RNA (16S) and cytochrome oxidase subunits I (COI) and II (COII); and the nuclear elongation factor 1 alpha (EF-1α) from 400 ethanol-preserved specimens. These data were analysed using standard phylogenetic methods and a time scale of diversification was estimated using a Bayesian framework and both fossil data and DNA substitution rates. The results showed that the tribe is too recent to be of Gondwanan origin. The lack of monophyly of the genera represented in both Asia and Africa showed that the tribe needs formal taxonomic revision. Diversification of the African platypleurine genera coincides with aridification in the early Oligocene. Dispersal of Asian platypleurine taxa coincides with the meeting of Africa and Eurasia in the mid-Oligocene. Two radiations within African Platypleura are hypothesised; one distributed over most of sub-Saharan Africa and the second restricted to southern Africa, with clades restricted within regional biomes. Within each of the three focal biomes, cryptic taxonomic diversity was confirmed, suggesting that, even in relatively well understood groups such as the southern African platypleurine cicadas, molecular data can identify further diversity. Although each focal taxon was restricted to non-overlapping biomes, comparison of the three biomes highlighted interactions between palaeoclimates and fixed landscape features (coastal topography, river catchments and escarpments) as causative agents of vicariance, dispersal, extinction and diversification of these volant insects. The results of using co-distributed species for comparative study cautions against making inferences based on single-taxon datasets and highlights the need to use many, evolutionarily independent taxa when identifying mechanisms of diversification. The dating analyses imply that within-species lineage diversification occurred overwhelmingly within the Pleistocene, a trend that is being increasingly recognised in print for other biota. Some caveats about using phylogenetic approaches to estimate ancestral areas are illustrated. Several recommendations are made regarding additional taxa and data sources for understanding the origin and maintenance of biological diversity.

No description available.

No description available.