Browsing by Subject "Emergence"
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Item Emergence, survival, and longevity of adult Diamesa mendotae Muttkowski (Diptera: Chironomidae) in groundwater-fed streams(2013-06) Mazack, Jane ElizabethGroundwater-fed streams, which remain cold in summer but ice-free in winter, provide ideal habitat for ultra-cold stenotherm insects. Diamesa mendotae Muttkowski (Diptera: Chironomidae) is a winter-active species common to groundwater-fed streams in Minnesota. In order to improve the understanding of the winter dynamics of this species, we studied the influence of temperature on its emergence, survival, and longevity. The winter emergence dynamics of D. mendotae and other winter-active chironomids were documented by collecting surface-floating pupal exuviae samples from 24 groundwater-fed streams in southeastern Minnesota. Early, mid, and late winter samples were collected from each stream, and mean water temperatures during the week preceding sample collection were estimated using air-water temperature regressions. The results of this assessment indicate that D. mendotae are influenced by both thermal stability and water temperature. Abundance of D. mendotae was positively related to air-water temperature regression slope in early and mid-winter; emergence was negatively related to water temperature in late-winter. Emergence patterns of other genera were related to estimated water temperatures, showing significant thermal partitioning within the chironomid community. Field collections of adult D. mendotae were used to determine survivorship under long-term exposure to controlled sub-freezing conditions. Batches of specimens were placed into a controlled treatment chamber at -5°C for between 7 and 70 days. Survivorship at constant sub-freezing temperatures was negatively related to treatment length, although some individuals survived sub-freezing temperatures for 70 days. Additionally, male D. mendotae had a significantly higher rate of survivorship than females within the same treatment. Post-treatment longevity decreased with increased exposure to sub-freezing temperatures; however, total longevity increased with treatment time. These studies indicate that D. mendotae is well adapted to the cold winter-weather conditions across southeastern Minnesota, suggesting that adults may be able to survive long periods of extreme temperature conditions in the winter to increase their ability to successfully reproduce. Groundwater inputs not only influence the thermal regime of streams in southeastern Minnesota's karst landscape, but also significantly impact chironomid community dynamics, which may play a significant role in the broader invertebrate and fish communities of these streams.Item International institutions and social emergence(2011-08) Leon, Pak YueContemporary empirical research on the importance of international institutions in areas ranging from economic integration to multilateral governance has made many advances. It founders, however, on the key question of establishing defensible theoretical grounds for relative institutional autonomy, without which the empirical accounting of purported institutional effects cannot, on its own, be the arbiter of disputes about the causal influence of institutions. This dissertation develops and defends a theory of international institutions on the basis of their emergence from, and irreducibility to, the conditions of their crafting, contracting, and functionality. It argues that the analytical implications of institutions are derived from the conceptions of their nature, i.e., their ontological underpinnings. If international institutions are to be accorded a proper, non-epiphenomenal place in analysis, their causal efficacy must somehow be reconciled with state power and interests in institutional design, with their contractual entanglements with delegating principals, and with their compositional origins. This dissertation argues that the problem of institutional ontology and its analytical consequences can be mapped onto the general problem of emergence, a converging area of research across a number of disciplines concerning the ways in which certain properties at the constituted level in natural and social systems are different from, and not explicable in terms of, the constituent levels in isolation. As this study demonstrates, the turn to social emergence is well suited to making sense of the tension between institutional autonomy and factors inimical to it, thereby providing firmer grounds for institutional analysis. The complexity inherent in institutional arrangements through the configuration and re-configuration of constituent elements and social tempos at multiple levels over time is such that it becomes difficult to countenance any direct correspondence between the initial conditions of design, delegation, and composition on the one hand, and international institutions and their effects on the other hand. By articulating an alternative account of the nature of international institutions, this work both challenges existing institutional explanations and complements their quest to resolve a problem of longstanding in international relations.Item Solid foundations: structuring American solid state physics, 1939–1993(2013-05) Martin, Joseph DanielWhen solid state physics formed in 1940s America, it was unusual. It violated the longstanding convention that physics should only be subdivided according to natural classes of research problems or consistent sets of techniques. Instead, solid state incorporated a wide range of concepts and methodological approaches that had only the most superficial similarities. The unifying force behind the field was the explicit professional goal of bringing academic and industrial researchers into closer dialogue. The non-traditional manner in which solid state formed was symptomatic of a sea change in the American physics community as some physicists in the 1940s began thinking about professional and institutional structures as tools with which they could actively define and maintain the scope and mission of physics. This shift had consequences both for solid state, and for American physics as a whole. Solid state was initially defined in terms of 1940s professional challenges, and so was forced to continually reimagine itself as the context changed around it. Eventually, it fractured into subgroups with divergent perspectives about the field’s goals and how best to address them. One of these, condensed matter physics, has typically been understood as a simple renaming of solid state physics. A close examination of the process by which condensed matter emerged, however, indicates that it represented an intentional return to defining a sub-disciplinary on the basis of natural phenomena and investigatory techniques. Condensed matter physics grew from pointed reactions against the segment of solid state that was closely aligned with industry. It crafted an identity that emphasized the intellectual puzzles physical studies of complex systems could address. As broadly conceived fields like solid state physics established themselves and grew, both in population and in influence, physics as a whole became a broader enterprise. Research areas that might otherwise have branched off into engineering or become independent specialties were offered a place in sub-disciplines like solid state physics. Additionally, other elements of the physics community adopted solid state’s mode of discipline formation, making the definition of “physics” more fluid and responsive to contemporary professional pressures. The evolution of solid state physics was guided throughout by a philosophical debate over the nature of fundamental knowledge. The disagreement persisted mostly between solid state physicists, who advocated the stance that fundamental knowledge could be found at any level of complexity, and high energy physicists, who restricted fundamental knowledge to the theories and concepts that governed the smallest constituents of matter and energy. The progress of this debate was driven by professional concerns about funding and intellectual prestige, and the philosophical positions physicists developed helped, in turn, to shape the field’s professional infrastructure.