Thesis (Ph. D.)--John Hopkins University, 1906. / Biography. Bibliography: p. [5].

Thesis (Ph. D.)--John Hopkins University, 1906. / Biography. Bibliography: p. [5].

No description available.

Thesis (M.S.)--University of Wisconsin--Madison, 1984. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

The assumption that the colours of the green poison frog, Dendrobates auratus, serve as a warning of unpalatability is not supported because the requirements of the theory of aposematism are not met. The theory predicts that the aposematic coloration be conspicuous to potential predators, yet this cannot be demonstrated. The only predator found for D. auratus was the theraphosid spider, Sericopelma rubronitens, which hunts using vibrational cues. Only after sampling all frogs offered did spiders reject the toxic D. auratus over nontoxic Physalaemus pustulosus. The spider's decision to reject D. auratus as prey was made without visual input, and therefore the colours and toxicity of the frogs are decoupled with respect to this predator. Discovering that the crab Armases angustum is a predator of D. auratus tadpoles suggests that D. auratus is most vulnerable to predation during the nontoxic tadpole stage. Indirect methods of estimating predation were unsuccessful. The use of plasticine model frogs to estimate avian predation yielded no useful information and although traumatic injury is usually attributed to attempted predation, this is not true for tropical anurans. The levels of traumatic injury for D. auratus and a cryptic nontoxic frog Physalaemus pustulosus were similar when the life span of the frogs was taken into account. The traumatic injuries in these frogs are a function of interactions with small invertebrates that are neither predator nor prey. The theory of aposematism also predicts that there should be low pattern variation within an aposematic species so that a single search image can be formed and avoided. The patterns of D. auratus are individually distinct and there is significant interpopulational variation in appearance due to differences in colour, pattern and animal size. Selection for conspicuous visual intraspecific communication may have resulted in these differences in appearance. Mitochondrial 16S rRNA and cytochrome b sequence data ind

No description available.

Living organisms are under selection not only for one, but also for several inheritable characters at the same time. Well-sampled and well-supported phylogenies are necessary for the studies of character evolution and their history. The poison frogs (Dendrobatidae) are a well-known example of aposematism in anurans. They include ~270 species of Neotropical frogs with aposematic (toxic and conspicuous) and non-defended (palatable and cryptic) species. The origin of aposematism in poison frogs is puzzling, because of its predicted low probability of establishment due to the prey's increased conspicuousness. Previous studies suggested a single origin of toxicity and warning coloration. By expanding taxon sampling of the group, I reexamined the phylogenetic correlation between the origins of toxicity and warning coloration. I found four or five independent origins of aposematism; by using simulations, I rejected hypotheses of one, two, or three origins of aposematism (P < 0.002). I also found that diet specialization is linked with the evolution of aposematism and has evolved independently at least two times. Poison frogs are endemic to the Neotropic, which is one of the Earth's largest reservoir of biodiversity. I reconstructed the biogeography of the poison frog clade and rejected an Amazonian center-of-origin in favor of a model expanding over the Neotropics. I inferred 14 dispersals into and 18 out of Amazonia to adjacent regions; the Andes were the major source of dispersals into Amazonia. Significant percentage of dendrobatid diversity in Amazonia and Chocó resulted from repeated immigrations, with radiations at <10.0 million years ago. In contrast, the Andes, Venezuelan Highlands, and Guiana Shield have undergone extended in situ diversification at near constant rate since the Oligocene. Poison frogs have significant variation on their physiological characteristics. I measured resting and active metabolic rates of 54 species. I traced metabolic measurements along aposematism, diet specialization, molecular rates, and body mass. I found a synergistic and co-adapted functionality of active metabolic rates with all previous traits that is perhaps the consequence of the increase in complexity in most biological systems. My thesis has expanded the knowledge of the biology, phylogenetic history, and biogeography of the poison frogs. / text

This dissertation provides a comprehensive analysis of shareholder rights plans and mergers and acquisitions (M&A) for a unique class of securities, i.e., the Real Estate Investment Trusts (REITs) between 1988 and 2000. This research seeks to establish what form of management, ownership structure and financial characteristics are exhibited by REITs which adopted antitakeover amendments as well as determine their impact on REIT values and the market for corporate control. While merger and acquisition transactions involving public REITs have much in common with M&A transactions involving other public companies, the role of governance has not been explored in REITs for these transactions. This paper finds that while firm specific variables can differentiate between targets and acquirers, the role of the governance structure appears to be quite limited. In fact, REITs seem to be driven by firm level performance.

This dissertation provides a comprehensive analysis of shareholder rights plans and mergers and acquisitions (M&A) for a unique class of securities, i.e., the Real Estate Investment Trusts (REITs) between 1988 and 2000. This research seeks to establish what form of management, ownership structure and financial characteristics are exhibited by REITs which adopted antitakeover amendments as well as determine their impact on REIT values and the market for corporate control. While merger and acquisition transactions involving public REITs have much in common with M&A transactions involving other public companies, the role of governance has not been explored in REITs for these transactions. This paper finds that while firm specific variables can differentiate between targets and acquirers, the role of the governance structure appears to be quite limited. In fact, REITs seem to be driven by firm level performance.

A. method for the synthesis of S³⁵-BAL has been described S³⁵-sulphate was reduced to the sulphide and converted to NaS³⁵H. The NaS³⁵H was then reacted with 2:3-dibromopropanol to form S³⁵-BAL. The product was characterized by sulphydryl content, preparation of two crystalline dithiolans, sulphur analysis and chromatographic behavior. The metabolism of S³⁵-BAL was studied in the Wistar rat. The isotopic BAL was administered by intraperitoneal injection and the S³⁵ content of the post-inject ion urine was studied. The maximum rate of S³⁵ excretion in the urine was observed in the first 6 hours after injection and was followed by a rapid decrease in S³⁵ excretion. This was true for both neutral S³⁵- sulphur and inorganic S³⁵-sulphate. The amount of neutral sulphur excreted in the urine also reached a maximum in the first 6 hours and returned to normal within 12 hours. The excretion of inorganic sulphate, however, remained abnormally high throughout the experiment. Approximately 4 - 19% of the excreted was S³⁵ in the form of inorganic sulphate while less than 0.5% was present in the ethereal sulphate. Six possible metabolic products were detected by radiochromatographic studies of the post-injection urine. These compounds were found to have the following Rf values when the chromatograms were run in a tertiary butanol-water solvent (70/35): Compound 1 0.07 - 0.10 Compound 2 0.25 - 0.30 Compound 3 0.45 - 0.50 Compound 4 0.60 - 0.65 Compound 5 0.78 - 0.85 Compound 6 0.95 - 0.98 Compound 1 was characterized as inorganic sulphate while compound 5 was found to be a thiol compound which arose following acid hydrolysis of compound 3. Extraction studies showed only compound 2 to be extracted with ether while all but compounds 1 were found to be soluble in n-butanol. Compound 4, the major metabolite, was shown to be only slightly soluble in n-butanol and insoluble in ether. No glucuronide of BAL or its metabolites have been found in the urine and no increase in glucuronic acid excretion was observed following BAL injection. The presence of a large amount of glucose in the post-injection urine was indicated by chromatographic studies. / Medicine, Faculty of / Biochemistry and Molecular Biology, Department of / Graduate