Optimal Control of Epidemic Models Involving Rabies and West Nile Viruses

This research considers the application of Optimal Control theory to minimize the spread of viral infections in disease models. The population models under consideration are systems of ordinary differential equations and represent epidemics arising due to either rabies or West Nile virus. Optimal control strategies are analyzed using Pontryagin’s Maximum Principle and illustrated based upon computer simulations. The first model describes a population of raccoons and its interaction with the rabies virus, thus dividing the animals into four classes: susceptible, exposed, immune, and recovered (SEIR). The model includes a birth pulse during the spring of the year and an equation reflecting the dynamics of a potential vaccine. The vaccine equation contains a linear control variable representing the rate at which the vaccine is distributed. The goal is to minimize the number of infected raccoons and the cost of vaccine distributed. Due to linearity in the control, there is the possibility of a singular control and the generalized Legendre-Clebsch condition will be satisfied to obtain new necessary conditions for the singular case. A scenario with a limited amount of vaccine is also investigated. The system is modified to include a density-dependent death rate for each of the S, E, I, R classes, and the results of this model are compared with those of the non-density dependent model to determine how the different death rates affect control strategies. The second disease model considered describes the dynamics of mosquito, bird and human populations exposed to the West Nile virus. The mosquito and bird categories will be divided into susceptible and infected classes. In addition to these two groups, humans will also have the potential of entering the exposed, hospitalized and recovered classes. In this model, birth and death rates are assumed to be density-dependent. Two controls are applied with one control representing pesticide efforts to decrease the number of mosquitos and a second control representing prevention and repellant methods. The basic reproduction number is considered to justify the need for control. Approximations of the optimal solutions of the models are obtained using an iterative method. The numerical algorithm, Runge-Kutta of order four, is programmed in Matlab. Graphical results show the appropriate amount of control for various situations

Radically decentered in the Middle Kingdom: interpreting the Macartney embassy to China from a contact zone perspective

This dissertation examines artifacts produced by individuals who participated in the Macartney embassy to China from a contact zone perspective. Chapter one claims that works written by Westerners who traveled to and wrote about China and the Chinese are not often included in studies concerned with the rhetoric of othering or Western representations of non-Western others. Chapter 2 of provides a literature review of research related to the Macartney embassy, examining those texts primarily in terms of the methodology that the authors use to interpret embassy artifacts. Chapter 3 considers how Pratt\u27s reading strategies can be applied to both the embassy in general and to the dynamics of the kowtow incident in particular. The historical circumstances that distinguished the Macartney embassy to China makes comparison with other contact zone encounters problematic; therefore, Chapter 3 also identifies seven important features of a contact zone encounter that exist above and beyond specific historical circumstances. In Chapter 4, I use Pratt\u27s ways of reading to identify moments in the travel narratives where genre and ideology intersect. Chapter 5, the (slightly decentered) centerpiece of the dissertation, examines a meeting-of-the-heads-of-state scene as depicted in an English satirical engraving from 1792. The print is an extraordinary depiction of a contact zone encounter, yet its proximity from the actual event demonstrates the potential of the contact zone as an analytical tool for interrogating a range of cross-cultural representations. The last chapter of the dissertation argues that the embassy and the kowtow incident were, in some ways, the realizations of preconceived visual and literary metaphors. The features of a contact zone encounter identified in Chapter 3 should help researchers to access and interpret systematically and comprehensively those visual and literary metaphors associated with a contact zone

Quantification of Volatile Residuals in Polydioxanone by Gas Chromatography: Method Development, Validation and Implementation

Bioresorbable polymers are increasingly utilized for implantable medical devices to avoid complications related to explant and/or long term responses to foreign materials. As with all polymeric materials, residual levels of unreacted monomer, and other volatiles, drastically affect the mechanical and chemical properties as well as the parameters required to process the material into a device. The 1,4-dioxane-2-one (PDO) monomer is a six membered ring that forms an ether-ester polymer via ring-opening polymerization (ROP) with intermediate absorption rate properties that are ideal for numerous implant situations. Developing devices using poly(1,4-dioxane-2-one) (PPDO, PDO, PDX, PPDX, or PDS) is complicated by residual levels of the unreacted, ring-form of the monomer causing the material to be toxic to biologic tissue in addition to the typical negative effects of excessive residual monomer in polymers, especially bioresorbable polymers. It is required to quantify the residual monomer content of PDO polymer throughout the manufacturing and storage of polymer or devices to ensure proper and repeatable processing in addition to the safety aspects related to the end use of the material. This work describes the application and comparison of known gas chromatography techniques, multiple headspace extraction and classical vaporization injection, to separate the residual monomer from the polymer matrix and allow for quantification. Accuracy and repeatability evaluations were used to determine the ideal testing methods to be used in industry as regulated by governing agencies such as the Food and Drug Administration (FDA)

Gender Politics and Secure Services For Women: Reflections on a study of staff understandings of challenging behaviour.

This paper discusses the findings of a Q methodological study that investigated the complexity of professional understandings of (attitudes towards) residents in a secure unit for women with learning disabilities and challenging behaviours. Particular attention is afforded to the critical debate regarding women in psychiatric and secure care, including the significant contribution made to this literature by feminist perspectives. A multiprofessional group of staff (n = 38) participated in the study and nine distinct accounts of women's challenging behaviour are described. Despite a considerable amount of recent policy concern with the position of women in psychiatric services, the findings of this research suggest that many front line staff are reluctant to highlight gender in their explanations of women's behaviour. This supports the assertion by Williams et al. (2001), who were involved in the National Gender Training Initiative (NGTI), that most critical theorizing about women's mental health has had minimal impact at the level of individuals’ understandings of these important issues. This state of affairs suggests a powerful case for the expansion of staff training as provided in the NGTI, which makes gender central to understanding and emphasizes feminist perspectives

CRAFT SPECIALIZATION AND THE EMERGENCE OF THE CHIEFLY CENTRAL PLACE COMMUNITY OF HE-4 (EL HATILLO), CENTRAL PANAMA

The development of chiefdoms has received considerable attention from archaeologists, but there remains little consensus with respect to the underlying causal mechanisms. In particular, the importance of an economic foundation to the emergence of chiefdoms has been the focus of some debate. Some scholars have argued that the mobilization of key resources such as land, labor, agricultural surplus or craft production is critical to the development of chiefdom polities as it implies a material foundation for political power. An alternative view places more importance on status competition and the display and exchange of prestige goods among emergent elites. Because it may be used to support either strategy, craft specialization has figured prominently in discussions of these two kinds of chiefly political economy. The focus of this dissertation is the degree to which specialized craft production was a significant factor in the development of chiefdoms at the central place community of He-4 in the Río Parita valley of Central Panama. The results of this dissertation show that craft specialization was relatively unimportant to the emergence of chiefdoms in the Río Parita valley during the Cubitá phase (A.D. 550-700), suggesting a social hierarchy based more on non-economic forms of social power, perhaps including feasting activities, warfare or involvement in local trade. The data from He-4 also show that the social hierarchy seen in the burial record after A.D. 700-900 develops in tandem with differences in household status that are apparent as early as the Cubitá phase (A.D. 550-700). These differences in household status become increasingly well developed over time; however, they are never as dramatic as the differences seen in the mortuary record for Central Panama. There is also no real connection between the emergence of the social hierarchy at He-4 and craft specialization. It is only during the Parita phase (A.D. 1100-1300) that craft specialization involving the final stages of axe manufacture and use of polished stone chisels becomes important activities in high status households at He-4

Best Management Practices for Aquatic Vegetation Management in Lakes

Aquatic plants are an important component of well functioning lake ecosystems. Plant abundance is influenced by sediments, nutrients and water clarity. Given the dominance of agriculture in Iowa, nutrients and soil lost from “leaky” watersheds combine to create ideal habitat for growth of aquatic plants in lakes and ponds and hasten eutrophication. Under these conditions, plant growth can become a nuisance and reduce recreation, especially shoreline angling and boating. These nuisance growths present special problems to lake managers and those interested in lake-based recreation. Given the complexity of the aquatic vegetation often found in lakes, there is no one long-term solution to their management although grass carp and herbicides have been used with that goal. The best solution to a lake’s specific vegetation problem will be a combination of preventative, physical, biological and chemical options tuned to that specific lake’s environmental conditions and fishery needs. Development of a strategy to address the control of nuisance aquatic vegetation with the ultimate goal of producing a set of BMPs is needed to manage plants in Iowa’s ponds and lakes. This information will provide lake managers with the best methods and techniques to sample, assess, and manage nuisance aquatic vegetation. Plans developed from these strategies will link critical watershed characteristics, lake bathymetry, water quality, and density and diversity of aquatic plants to management options that benefit fish and fishing. Considerations will include the cost and benefit of various alternatives and the likelihood for success. This project was initiated July 2006 and continues through June 2009