Diseases vectored by mosquitoes cause millions of deaths each year. In modern times Florida*s disease risk has been reduced due to efforts to lessen the prevalence of mosquitoes through habitat modification of non-adults. With emerging diseases (i.e. Dengue and Chikunguya) encroaching into Florida from the Caribbean, this traditional approach may not be enough. Alternatively, we can better understand the ecology of how disease works in an ecosystem. One possible way is through the Dilution Effect, which states that the more species that are in a system the lower the chance for zoonosis. This project models mosquito diversity across regions, land use, and vegetation height in South-Central Florida, for the purpose of identifying predictors that indicate a higher disease risk using information theory (AICc). The plains and coastal regions as well as the developed areas have a relatively higher risk of disease. Florida is a fire maintained habitat, but has been fire suppressed for the last century. Archbold Biological Station (ABS) has used prescribed fires since the early 1980s to try and restore a more natural system. This has created a mosaic of different fire histories. Fire affects the structures that mosquitoes rest under during the day (they are vulnerable to desiccation during the day and hide in darker/shady places), therefore there is a high likelihood that fire will have some effect on mosquito assemblages. This project used model selection to determine the most plausible set of predictors that describe the effect of fire on mosquito assemblages at ABS, using information theory (AICc). In general, time of season accounted for the largest proportion of the variation in the data and TSF had negligible effect on adult mosquito assemblages measured as abundance, speices richness, and Jost D.

I corporate equity warrant rappresentano un affascinante metodo di finanziamento “ibrido” disponibile per le imprese. In prima approssimazione, un warrant è assimilabile ad una opzione call e, pertanto, il pricing è spesso effettuato applicando le formule di valutazione sviluppate per tali strumenti dalla teoria finanziaria. Tuttavia, la valutazione dei warrant presenta complicazioni ulteriori rispetto alla determinazione del prezzo di opzioni call, e la ragione risiede principalmente in alcuni elementi distintivi di maggiore complessità, tra cui l’effetto diluitivo del capitale esistente derivante dall’esercizio, ed il c.d. effetto “risk-shifting”, in base al quale si verifica un trasferimento di rischio sistematico dagli azionisti ai possessori di warrant, non appena questi strumenti vengono emessi. L’obiettivo di questa tesi è di analizzare il tema dell’emissione dei corporate warrant dal punto di vista della finanza d’impresa e derivare un metodo di pricing innovativo per tener conto di un fenomeno (risk-shifting effect) tuttora non considerato dalla letteratura finanziaria. Dopo aver derivato formalmente tale approccio e le formule ad esso conseguenti, il lavoro propone una simulazione teorica ed un test empirico condotto su un campione di warrant quotati sul mercato italiano. Entrambi tali verifiche dimostrano come il modello presentato incorpori una maggiore bontà previsiva del prezzo di mercato rispetto agli approcci esistenti. / Corporate equity warrants are one of the more fascinating capital-raising tools available to corporate finance officers. At a first approximation, they are option-like securities and according to this similarity, the pricing is usually performed by application of the standard option pricing theory. However, the theoretical and empirical analysis of warrants still remains an interesting research field within the finance literature. The reason is that warrants are more complex than call options. From an asset pricing point of view, the presence of some specific features (e.g., the equity dilution) prevents from using simple plain-vanilla formulas, while from a corporate finance standpoint, warrants offer several implications, principally because they affect the systematic risk of common stocks and are related to the choice of the firm’s capital structure. The purpose of this thesis is to analyse corporate warrants and address some of the main open questions about their value. In particular, after reviewing the financial literature about warrant pricing and presenting some commonly accepted formulas, the relationship between warrants and the volatility of the underlying stock return is examined. Contrarily to the classical call options, in fact, warrants affect the capital structure of the issuing firm and produce a risk-shifting effect among equity claimants. We derive an alternative approach to pricing equity warrant, embedding this risk-shifting feature, and we propose both a theoretical simulation and an empirical test based on a sample of Italian warrants proving its accuracy.

Selon l'hypothèse de l'effet de dilution, les écosystèmes les plus riches en espèces seraient également les moins propices à la circulation des agents infectieux du fait de la présence d'hôtes non compétents constituant des impasses épidémiologiques. Dans cette thèse, nous explorons l'existence de ce phénomène sur le modèle des leishmanioses cutanées zoonotiques en Guyane. Des outils moléculaires basés sur l'utilisation des technologies de séquençage haut-débit ont été développés pour étudier le système épidémiologique. Ces outils ont ensuite été employés pour caractériser le cycle de transmission des leishmanioses dans des sites forestiers sujets à différents niveaux de perturbation d'origine humaine. Nos résultats semblent globalement congruents avec l'hypothèse de l'effet de dilution, et indiquent un risque infectieux plus élevé sur le site le plus perturbé. Toutefois, les différences observées entre les sites ne sont pas significatives et d'avantage de données seraient nécessaires pour tirer des conclusions générales. / The dilution effect hypothesis states that more diverse ecological communities are less prone to pathogen transmission because of the presence of non-competent hosts acting as epidemiological dead-ends. In this work, we investigate the existence of this phenomenon in the case of zoonotic cutaneous leishmaniases in French Guiana. Molecular tools based on high-throughput sequencing technologies have been developed to study the epidemiological system. These tools were employed to explore leishmaniases transmission cycles in forest sites undergoing different levels of human-induced perturbations. Our results seem generally congruent with the dilution effect hypothesis, indicating higher disease risk in the most perturbed site. However, differences observed between sites were not significant, and more data is needed to draw general conclusions.

Group (pooled) testing, i.e., testing multiple subjects simultaneously with a single test, is essential for classifying a large population of subjects as positive or negative for a binary characteristic (e.g., presence of a disease, genetic disorder, or a product defect). While group testing is used in various contexts (e.g., screening donated blood or for sexually transmitted diseases), a lack of understanding of how an optimal grouping scheme should be designed to maximize classification accuracy under a budget constraint hampers screening efforts. We study Dorfman and Array group testing designs under subject-specific risk characteristics, operational constraints, and imperfect tests, considering classification accuracy-, efficiency-, robustness-, and equity-based objectives, and characterize important structural properties of optimal testing designs. These properties provide us with key insights and allow us to model the testing design problems as network flow problems, develop efficient algorithms, and derive insights on equity and robustness versus accuracy trade-off. One of our models reduces to a constrained shortest path problem, for a special case of which we develop a polynomial-time algorithm. We also show that determining an optimal risk-based Dorfman testing scheme that minimizes the expected number of tests is tractable, resolving an open conjecture. Our case studies, on chlamydia screening and screening of donated blood, demonstrate the value of optimal risk-based testing designs, which are shown to be less expensive, more accurate, more equitable, and more robust than current screening practices. / PHD / Group (pooled) testing, i.e., testing multiple subjects simultaneously with a single test, is essential for classifying a large population of subjects as positive or negative for a binary characteristic (e.g., presence of a disease, genetic disorder, or a product defect). While group testing is used in various contexts (e.g., screening donated blood or for sexually transmitted diseases), a lack of understanding of how an optimal grouping scheme should be designed to maximize classification accuracy under a budget constraint hampers screening efforts. We study Dorfman and Array group testing designs under subject-specific risk characteristics, operational constraints, and imperfect tests, considering classification accuracy-, efficiency-, robustness-, and equity-based objectives, and characterize important structural properties of optimal testing designs. These properties provide us with key insights and allow us to model the testing design problems as network flow problems, develop efficient algorithms, and derive insights on equity and robustness versus accuracy trade-off. We also show that determining an optimal risk-based Dorfman testing scheme that minimizes the expected number of tests is tractable, resolving an open conjecture. Our case studies, on chlamydia screening and screening of donated blood, demonstrate the value of optimal risk-based testing designs, which are shown to be less expensive, more accurate, more equitable, and more robust than current screening practices.

雖然許多研究已針對認股權證評價進行調整，但是其價格低估的問題仍無法解決。因此，本文將探討認股權證發行對股價報酬動態過程的影響。本文將證實是否認股權證發行將影響其標的股價之動態過程，倘若股價報酬的動態過程已反應了認股權證發行的潛在稀釋效果，則進行充分調整的股權稀釋模型將低估認股權證的價格。為了確認在評價認購權證時充分調整稀釋效果的必要性，本文將檢測權證發行對股票報酬過程的影響。本文利用延伸Garch-M模型，導出四個檢驗稀釋效果的模型。實證結果顯示，在發行認股權證之後，股價報酬的變異數顯著降低，該結果在釐清股權稀釋效果與不對稱效果之後，該稀釋效果依然顯著。 / As the underestimation of warrants remains unsolved after many adjustments presented by previous researchers, we further investigate the impact of the warrant introduction on the underlying stock return processes. This research attempts to determine whether the introduction of warrants influences the return processes of underlying stocks. If the introduction creates a potential dilution effect in stock return processes, full dilution adjustment pricing models would lead to underestimation. To exam whether full dilution adjustments are required for warrant pricing, the GARCH-M model has been extended to derive four models for testing the dilution effect on stock return processes. Empirical results show that the volatilities of underlying stock return processes are significantly reduced following warrant introduction even after clarification and distinguishing dilution from asymmetric effect.

Many external parties such as investors, creditors, and regulatory agencies, use a company’s financial statements in their decision-making. In doing so, they rely on audit opinions on whether financial statements are fairly stated. However, evidence suggests that there are factors in the audit environment that influence auditor judgments. For example, nondiagnostic client information dilutes auditor judgments when compared to judgments based on diagnostic information alone, especially for less experienced auditors (Hackenbrack 1992; Hoffman and Patton 1997; Glover 1994; Shelton 1999). High time pressure conditions mitigate this effect by refocusing auditor attention toward relevant client information, therefore reducing the impact of nondiagnostic information (Glover 1994, 1997). This research study examines other common audit environment factors to determine if they too influence audit judgment results. An online questionnaire of 149 auditors, CPAs and other accounting professionals indicate that the inclusion of nondiagnostic client information results in a significant change in auditor judgments. The direction of this change follows a theorized pattern; risk assessments that were initially high are reduced, while those that were initially low are increased. Significance was not consistently found for a workload and PCAOB effect on auditor judgment. However, a comparison of the absolute value of dilution effect means across conditions reveals some trending for the proposed unwanted effect of high workload, and the beneficial effect of PCAOB guidance. These results have important implications for auditing research and practice. It extends previous archival research on workload effects and uses a unique questionnaire design to reexamine workload pressures in a behavioral setting. The results of hypothesis testing on workload pressure and PCAOB guidance, although lacking consistent statistical significance; exhibit trends that agree with proposed theoretical relationships. Tests on the effects of nondiagnostic information show strong statistical support for previous studies in the area of psychology and audit. This study’s greatest contribution suggests that audit pressures do not produce equivalent effects on auditor judgment; time pressure improves audit judgment, while workload pressure does not (Glover 1994, 1997). These results can be explained by examining the relationship between stress and audit judgment performance (Choo 1995, Yerkes and Dodson 1908). Different types and different degrees of audit pressures may correspond to different levels of audit pressure. Low to moderate levels of audit pressure, such as the level of time pressure used in Glover’s (1994, 1997) study improve audit performance. Higher audit pressures, such as high workload during an auditor’s busy season, may lower audit performance.

Předložená magisterská práce se zabývá možným použitím vitrifikovaného lignitového lóžového popele jako náhrada slinku v kompozitních cementech. Byly zkoumány vlivy přidaného vitrifikovaného lóžového popele, jeho jemnosti, alkalických roztoků a jejich koncentrací. Byly připraveny kompozitní cementy v souladu s normou DIN EN 197 – 1. V těchto cementech bylo nahrazeno 30 % slinku vitrifikovaným lóžovým popelem. Konkrétně byly připraveny kompozitní cementy s vitrifikovaným lóžovým popelem o jemnosti 5549 cm2/g a 8397 cm2/g. Dále byly přidány alkalické roztoky hydroxidů a síranů vždy o dvou různých koncentracích, za účelem stimulace pucolánové a/nebo geopolymerní reakce. Mechanické vlastnosti připravených vzorků byly charakterizovány mechanickým testováním na prizmách s rozměry 40×40×160 mm, jak je specifikováno v normě DIN EN 196 – 1. Byla provedena nedestruktivní měření dynamického elastického modulu a destruktivní testovaní na pevnosti v tlaku a v ohybu. Distribuce velikosti částic a chemická analýza vstupních materiálů byla vykonána pomocí laserové granulometrie a rentgenové fluorescence. U zatvrdlých kompozitů bylo dále zkoumáno po 2 a 28 dnech hydratace fázové složení s využitím metody rentgenové difrakce a mikrostruktura s využitím skenovací elektronové mikroskopie. Výsledky ukázaly, že mechanické vlastnosti jsou nezávislé na množství přidaných alkálií stejně jako na jemnosti přidaného vitrifikovaného lóžového popele. Nicméně, znatelně nižší mechanické pevnosti byly pozorovány pro vzorky, které byly aktivovány hydroxidy, pravděpodobně kvůli brzké tvorbě silikátového hydrogelu. Vzorky aktivované sírany nedosáhly pevností jako referenční malta.