The relationship between alkaloid-based chemical defenses and diet in dendrobatid poison frogs

Chemical defenses are common among organisms and represent some of the most complex adaptations for avoiding predation, yet our understanding of the ecological nature of these systems remains incomplete. Poison frogs are a group of chemically defended organisms that are dependent entirely on diet for chemical defense. In this study, I identified the dietary arthropods responsible for chemical defense in poison frogs, described spatial and temporal patterns in alkaloid composition of poison frogs, and established links between patterns of variation in alkaloid defense and arthropod diet in poison frogs. Identifying dietary sources and studying patterns of variation in alkaloid composition is fundamental to understanding the ecology and evolution of chemical defense in poison frogs. ^ The dendrobatid poison frog Oophaga pumilio shares many alkaloids in common with other poison frogs and is known to vary in alkaloid composition throughout its geographic range. I designed my dissertation to take advantage of these characteristics and use O. pumilio as a model species for the study of chemical defense in poison frogs. Here, I identified siphonotid millipedes as a source for spiropyrrolizidine alkaloids, formicine ants as a source for pumiliotoxin alkaloids, and oribatid mites as dietary sources for the majority of alkaloids found in poison frogs. I found that alkaloid composition varied spatially and temporally, on both small and large scales, within and among populations of O. pumilio. Alkaloid variation between populations was related to geographic distance, and closer populations tended to have alkaloid compositions more similar to each other than to distant populations. ^ The findings of my study suggest that oribatid mites are the most important dietary source of alkaloids in poison frogs. However, overall alkaloid defense in poison frogs is based on a combination of dietary arthropods, including mites, ants, millipedes, and beetles. Variation in chemical defenses of poison frogs is due to (1) spatial and temporal differences in the presence of alkaloids in certain arthropods and (2) differences in the availability of certain alkaloid-containing arthropods, which are likely the result of differences as well as successional changes in forest structure among locations and through time. ^

Landscape of fear: A social history of the missile during the early years of the Cold War, 1950–1965

The missile's significance has been central to national security since the Soviet launching of Sputnik, and became increasingly important throughout the years of the Cold War. Much has been written about missile technology, but little has been written about how the development and deployment of this weapon affected Americans. The missile was developed to both deter war but also to win war. Its presence, however, was not always reassuring. Three areas of the United States are studied to evaluate the social implications of the missile during these pivotal years: San Francisco, home of multiple Nike installations; of Cape Canaveral, Florida, the nation's primary missile test center; the Great Plains, the location of the largest ICBM concentration in the country. Interviews were conducted, tours of facilities were taken, and local newspapers were reviewed. In conjunction with national newspapers and magazines and public opinion polls, this information provided a local social context for missile history. Nationally and locally, Americans both feared and praised the new technology. They were anxious for government funding in their cities and often felt that the danger the missile brought to their communities by making it as a Soviet target was justified in the larger cause for national security.

Landscape of fear : a social history of the missile during the early years of the cold war, 1950-1965

The missile's significance has been central to national security since the Soviet launching of Sputnik, and became increasingly important throughout the years of the Cold War. Much has been written about missile technology, but little has been written about how the development and deployment of this weapon affected Americans. The missile was developed to both deter war but also to win war. Its presence, however, was not always reassuring. Three areas of the United States are studied to evaluate the social implications of the missile during these pivotal years: San Francisco, home of multiple Nike installations; of Cape Canaveral, Florida, the nation's primary missile test center; the Great Plains, the location of the largest ICBM concentration in the country. Interviews were conducted, tours of facilities were taken, and local newspapers were reviewed. In conjunction with national newspapers and magazines and public opinion polls, this information provided a local social context for missile history. Nationally and locally, Americans both feared and praised the new technology. They were anxious for government funding in their cities and often felt that the danger the missile brought to their communities by making it as a Soviet target was justified in the larger cause for national security.

Hybrid multi-objective optimization and hybridized self-organizing response surface method

Numerical optimization is a technique where a computer is used to explore design parameter combinations to find extremes in performance factors. In multi-objective optimization several performance factors can be optimized simultaneously. The solution to multi-objective optimization problems is not a single design, but a family of optimized designs referred to as the Pareto frontier. The Pareto frontier is a trade-off curve in the objective function space composed of solutions where performance in one objective function is traded for performance in others. A Multi-Objective Hybridized Optimizer (MOHO) was created for the purpose of solving multi-objective optimization problems by utilizing a set of constituent optimization algorithms. MOHO tracks the progress of the Pareto frontier approximation development and automatically switches amongst those constituent evolutionary optimization algorithms to speed the formation of an accurate Pareto frontier approximation. Aerodynamic shape optimization is one of the oldest applications of numerical optimization. MOHO was used to perform shape optimization on a 0.5-inch ballistic penetrator traveling at Mach number 2.5. Two objectives were simultaneously optimized: minimize aerodynamic drag and maximize penetrator volume. This problem was solved twice. The first time the problem was solved by using Modified Newton Impact Theory (MNIT) to determine the pressure drag on the penetrator. In the second solution, a Parabolized Navier-Stokes (PNS) solver that includes viscosity was used to evaluate the drag on the penetrator. The studies show the difference in the optimized penetrator shapes when viscosity is absent and present in the optimization. In modern optimization problems, objective function evaluations may require many hours on a computer cluster to perform these types of analysis. One solution is to create a response surface that models the behavior of the objective function. Once enough data about the behavior of the objective function has been collected, a response surface can be used to represent the actual objective function in the optimization process. The Hybrid Self-Organizing Response Surface Method (HYBSORSM) algorithm was developed and used to make response surfaces of objective functions. HYBSORSM was evaluated using a suite of 295 non-linear functions. These functions involve from 2 to 100 variables demonstrating robustness and accuracy of HYBSORSM.

Characterizing Internet worm spatial-temporal infection structures

Since the Morris worm was released in 1988, Internet worms continue to be one of top security threats. For example, the Conficker worm infected 9 to 15 million machines in early 2009 and shut down the service of some critical government and medical networks. Moreover, it constructed a massive peer-to-peer (P2P) botnet. Botnets are zombie networks controlled by attackers setting out coordinated attacks. In recent years, botnets have become the number one threat to the Internet. The objective of this research is to characterize spatial-temporal infection structures of Internet worms, and apply the observations to study P2P-based botnets formed by worm infection. First, we infer temporal characteristics of the Internet worm infection structure, i.e., the host infection time and the worm infection sequence, and thus pinpoint patient zero or initially infected hosts. Specifically, we apply statistical estimation techniques on Darknet observations. We show analytically and empirically that our proposed estimators can significantly improve the inference accuracy. Second, we reveal two key spatial characteristics of the Internet worm infection structure, i.e., the number of children and the generation of the underlying tree topology formed by worm infection. Specifically, we apply probabilistic modeling methods and a sequential growth model. We show analytically and empirically that the number of children has asymptotically a geometric distribution with parameter 0.5, and the generation follows closely a Poisson distribution. Finally, we evaluate bot detection strategies and effects of user defenses in P2P-based botnets formed by worm infection. Specifically, we apply the observations of the number of children and demonstrate analytically and empirically that targeted detection that focuses on the nodes with the largest number of children is an efficient way to expose bots. However, we also point out that future botnets may self-stop scanning to weaken targeted detection, without greatly slowing down the speed of worm infection. We then extend the worm spatial infection structure and show empirically that user defenses, e.g. , patching or cleaning, can significantly mitigate the robustness and the effectiveness of P2P-based botnets. To counterattack, we evaluate a simple measure by future botnets that enhances topology robustness through worm re-infection.

The ineffectiveness of multilateral sanctions regimes under globalization: The case of Iraq

This dissertation examines the effectiveness and limits of multilateral sanctions regimes as instruments of foreign policy, particularly when trying to prevent the acquisition, development and proliferation of weapons of mass destructions. I hypothesize that globalization undermines the overall effectiveness of sanctions regimes. I analyze the agents and means of globalization. Agents are nation-states, corporations, non-state actors and organizations, and individuals. Means are the global import-export industry, global banking and investment, global corporate models, and global manufacturing industries. They all have contributed to vast increases in transnational economic activity and, furthermore, to more political tensions between nation-states, all of which jeopardize the implementation and enforcement of multilateral sanctions regimes. ^ To test this thesis, I examine how those factors impacted the multilateral sanctions regime imposed against Iraq from 1991 to 2002. This multilateral sanctions regime was conceived, approved and enforced by most nations in the United Nations. ^ Indeed, evidence collected for this dissertation suggests that Iraq did manage to consistently circumvent the UN sanctions regime, and that it did it by astutely utilizing the agents and means of globalization. Evidence also indicates that Iraq managed to rebuild parts of its military infrastructure, and that Iraq was on its way to rebuild its missile capability, for which it purchased large quantities of parts, components, technologies and manpower in the global market.^