Browsing by Subject "Glaciology"
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Item MEMS Actuators for Tuning Nanometer-scale Airgaps in Heterostructures and Optical Instrumentation for Glacier Ice Studies(2016-01) Chan, Wing ShanMEMS Actuators for Tuning Nanometer-scale Airgaps in Heterostructures We developed a new actuator microstructure to control the spacing between closely spaced surfaces. Creating and controlling nanometer gaps is of interest in areas such as plasmonics and quantum electronics. For example, energy states in quantum well heterostructures can be tuned by adjusting the physical coupling distance between wells. Unfortunately, such an application calls for active control of a nano-scale air gap between surfaces which are orders of magnitude larger, which is difficult due to stiction forces. A vertical electrostatic wedge actuator was designed to control the air gap between two closely spaced quantum wells in a collapsed cantilever structure. A six-mask fab- rication process was developed and carried out on an InGaAs/InP quantum well het- erostructure on an InP substrate. Upon actuation, the gap spacing between the surfaces was tuned over a maximum range of 55 nm from contact with an applied voltage of 60 V. Challenges in designing and fabricating the device are discussed. Optical Instrumentation for Glacier Ice Studies We explored new optical instrumentation for glacier ice studies. Glacier ice, such as that of the Greenland and Antarctic ice sheets, is formed by the accumulation of snowfall over hundreds of thousands of years. Not all snowfalls are the same. Their isotopic compositions vary according to the planet’s climate at the time, and may contain part of the past atmosphere. The physical properties and chemical content of the ice are therefore proxies of Earth’s climate history. In this work, new optical methods and instrumentation based on light scattering and polarization were developed to more efficiently study glacier ice. Field deployments in Antarctica of said instrumentation and results acquired are presented.Item A natural laboratory, a National Monument: carving out a place for science in Glacier Bay, Alaska, 1879-1959.(2009-08) Rumore, Gina MariaBeginning with John Muir's "discovery" in 1879, Glacier Bay has become a place constructed in the American imagination. In this construction of place, no single group played a more important role than scientists. While other national parks--e.g. Yellowstone and Yosemite--were greatly the products of commercial lobbies and political maneuverings, Glacier Bay National Monument (later National Park) grew out of a grass roots lobbying effort by the Ecological Society of America (ESA). Since 1879, Glacier Bay has an unbroken history of scientific study: from 1879 forward its glaciers have been regularly mapped, and from 1916 its ecological patterns have been persistently studied. Because of this long, continuous history of scientific study, Glacier Bay serves as an ideal case for the study of the interaction between place and the field sciences. This study analyzes the role played by Glacier Bay in shaping scientific practice and theory in ecology and glaciology between 1879 and 1959. At the same time, it also analyzes the impact scientists and scientific theory had on the place - defined both by physical location and by constructed social spaces. Within the overarching argument about the agency of place in shaping scientific theory, practice, and community, this dissertation makes several arguments that challenge and enhance the standing historiography on American ecology and glaciology: (1) It problematizes and challenges the standard story of the history of ecology in America told over the past quarter century, offering a more continuous view of ecological theory and practice. (2) It works toward a better understanding of field practices and how scientists defined their goals and successes in the early years of ecology and glaciology in the American context. (3) It explores the role of scientists as activists and argues that, over the period under consideration, ecologists' understanding of their role as activists was closely tied to how they thought ecology should be studied. (4) It analyzes how ecologists and glaciologists working in Glacier Bay understood the placedness of their work and how changes in their understanding of place interacted with their understanding of local versus universal knowledge.