Multi-scale metabolism: from the origin of life to microbial ecology

Metabolism is a key attribute of life on Earth at multiple spatial and temporal scales, involved in processes ranging from cellular reproduction to biogeochemical cycles. While metabolic network modeling approaches have enabled significant progress at the cellular-scale, extending these techniques to address questions at both the ecosystem and planetary-scales remains highly unexplored. In this thesis, I integrate various multi-scale metabolic network modeling approaches to address key questions with regard to both the long-term evolution of metabolism in the biosphere and the metabolic processes that take place in complex microbial communities. The first portion of my thesis work, focused on the evolution of ancient metabolic networks, attempts to model the emergence of ecosystem-level metabolism from simple geochemical precursors. By integrating network-based algorithms, physiochemical constraints, and geochemical estimates of ancient Earth, I explored whether a complex metabolic network could have emerged without phosphate, a key molecular component in modern-day living systems, known to be poorly available at the onset of life. We found that phosphate may have not been essential in early living systems, and that thioesters may have been the primitive energy currency in ancient metabolic networks. By generalizing this approach to explore the scope of geochemical scenarios that could have given rise to living systems, I found that other key biomolecules, including fixed nitrogen, may have not been required at the earliest stages in biochemical evolution. The second portion of my thesis deals with a different aspect of ecosystem-level metabolism, namely the role of metabolism in shaping the structure of microbial communities. I studied the relationship between metabolism and microbial community assembly using microbial communities grown in synthetic laboratory environments. We found that a generalized statistical consumer-resource model recapitulates the emergent phenomena observed in these experiments. Future work could seek to better clarify the connection between the fundamental rules that led to life’s emergence over 4 billion years ago and the laws that shape microbial ecosystems today. An ecosystems-level metabolic perspective may aid in our understanding of both the emergence and maintenance of the biosphere

Characterization Of Evaporative Metal Bonding In Superalloys For Use In Gasified Coal Turbine Generators

The diffusion bonding of Kanthal APMT, CM247LC, and Rene 80 was studied. The objective of the first part of this work was to create diffusion bonded test samples of Kanthal APMT, CM247LC, and Rene 80 using a 25μm thick zinc interlayer at varying times and temperatures. Then, using scanning electron microscopy to determine the profile of the zinc diffusing into the parent materials, the diffusion coefficients of the zinc interlayer into the materials were determined for each of the materials at each bonding time and temperature. The next objective was to create a finite element model of the bonding process to determine the stresses present at the bondface at the bonding temperature. A model of the geometry used to create the diffusion specimens was created in ANSYS Workbench 14.0. The stress distributions of the model at the bondface were compared to other research of similar bonding conditions to validate the model. The diffusion coefficients of the materials found for the APMT and Rene 80 followed the expected trend of decreasing as the bonding time increased. It was also observed that the approximate amount of zinc at the bond region decreased from the center to the edge of the bond supporting the theory of evaporative metal bonding. In addition, the nickel based alloys, CM247LC and Rene 80, had diffusion coefficients that approached theoretical diffusion coefficients of zinc in pure nickel. The finite element model showed stress distributions that qualitatively agreed with those reported in other studies although there were some discrepancies. However, it was determined that these were a result of the geometry of the jig used to hold the samples in place for bonding

McClellan at Sebastopol: The Delafield Commission and its Impact on the Siege of Yorktown

This study explores how George Brinton McClellan’s experiences as part of the Delafield Commission in 1855 influenced his generalship during the Peninsula Campaign of 1862. The primary object of the Delafield Commission was to study the Siege of Sebastopol, the site of the major Anglo-French effort against the Russians during the Crimean War. Delayed by diplomatic and political setbacks, McClellan failed to reach Sebastopol in time to witness the siege. In part one, I discuss how his European experience reinforced his antipathy towards professional politicians, a temperament cultivated by his Whig father. Congruently, McClellan’s dislike of politicians reappeared at the beginning of the Peninsula Campaign when he ignored President Lincoln, and thus precipitated the removal of the 1st Corps from his command. In part two, I detail how McClellan’s impressions of the ruins of Sebastopol influenced his decision to besiege Yorktown. When McClellan arrived at Yorktown, he believed that an overwhelming Union victory was imperative, and he attempted to recreate the Allied siege of Sebastopol in order to achieve such an outcome. Though he sought to avoid the missteps of the British and French in Crimea, McClellan incorrectly judged the situation at Yorktown, and his decision to initiate a siege there cost the Union Army the initiative, and doomed the ensuing campaign

American disillusionment and the search for self-fulfillment in the 1970\u27s: a cultural history of Taxi Driver, Annie Hall, and Saturday Night Fever

Three popular and critically acclaimed films of the post-Watergate era illustrated and criticized the period’s disillusionment. Likewise, a series of political and economic crises spawned a shift in American culture. The Sixties’ mass social movements dissolved into the Seventies and launched a trend in which Americans became preoccupied with themselves more than the state of the nation. Controlling one’s own destiny became a collective obsession when confronted with the period’s various political and economic ailments. The “Me” decade turned inward rather than concern itself with public issues. Therefore, American culture earned dubious labels such as narcissistic and decadent from critics and scholars. The Culture of Narcissism (1979), written by Christopher Lasch, became one famous cultural attack of the 1970s. Lasch’s commentary serves as an instrumental source to place the era’s films in their historical context. Several other notable sources described ways that searching for self-fulfillment saturated American society. Popular culture’s contributions in the cinema mirrored the period’s social trends. Taxi Driver (1976) and Annie Hall (1977) represented the peak to one of two major waves of a Seventies’ film Renaissance, in which personal narratives appealed to a maturing audience of baby boomers. Films with anti-establishment themes, more intellectual in nature, and cost-effective budgets helped to revive the financial burden of major studios. Ironically, the success of such films spawned the second wave of cinema, in which “blockbusters” ultimately proved a more attractive formula for producers by the end of the decade. Saturday Night Fever (1977), a hybrid of both waves of cinema, presents an interesting case study. The film’s commercial impact influenced the future direction of the industry. Although produced on a restrictive budget and containing cultural criticisms similar to the other two films, its emphasis on commercial considerations to the youth market paved the way for other blockbusters similar to it and a resurgence of optimistic narratives by the beginning of the 1980s. Nevertheless, each analysis describes the period’s disillusionment and search for self-fulfillment projected to audiences in the 1970s

The CLAVATA and SHOOT MERISTEMLESS loci competitively regulate meristem activity in Arabidopsis

The CLAVATA (CLV1 and CLV3) and SHOOT MERISTEMLESS (STM) genes specifically regulate shoot meristem development in Arabidopsis. CLV and STH appear to have opposite functions: c1v1 and Clv3 mutants accumulate excess undifferentiated cells in the shoot and floral meristem, while stm mutants fail to form the undifferentiated cells of the shoot meristem during embryonic development. We have identified a weak allele of stm (stm-2) that reveals STM is not only required for the establish- ment of the shoot meristem, but is also required for the continued maintenance of undifferentiated cells in the shoot meristem and for proper proliferation of cells in the floral meristem. We have found evidence of genetic interactions between the CLV and STM loci. clv1 and c1v3 mutations partially suppressed the stm-1 and stm-2 phenotypes, and were capable of suppression in a dominant fashion. clv stm double mutants and plants homozygous for stm but heterozygous for clv, while still lacking an embryonic shoot meristem, exhibited greatly enhanced postembryonic shoot and floral meristem development. Although stm phenotypes are recessive, stm mutations dominantly suppressed clv homozygous and heterozygous phenotypes. These results indicate that the stm phenotype is sensitive to the levels of CLV activity, while the clv phenotype is sensitive to the level of STM activity. We propose that these genes play related but opposing roles in the regulation of cell division and/or cell differentiation in shoot and floral meristems

Inventory Accuracy of Maintenance Assistance Modules (MAMS) On Ships Utilizing The Organizational Maintenance Management System – Next Generation (OMMS-NG)

Symposium Student Poster ShowMany United States Naval ships require a predetermined inventory of MAMs to troubleshoot failed equipment installed onboard. MAMs are high-value assets that require 100% inventory validity to help reduce equipment downtime. Fleet Logistics Center, San Diego, has raised concerns due to declining MAM inventory accuracy results onboard Naval ships in the Pacific Fleet.Approved for public release; distribution is unlimited

Inventory Accuracy of Maintenance Assistance Modules (MAMS) On Ships Utilizing The Organizational Maintenance Management System – Next Generation (OMMS-NG)

Symposium Student Poster ShowMany United States Naval ships require a predetermined inventory of MAMs to troubleshoot failed equipment installed onboard. MAMs are high-value assets that require 100% inventory validity to help reduce equipment downtime. Fleet Logistics Center, San Diego, has raised concerns due to declining MAM inventory accuracy results onboard Naval ships in the Pacific Fleet.Approved for public release; distribution is unlimited

Eccentric debris disc morphologies II: Surface brightness variations from overlapping orbits in narrow eccentric discs

We present Paper II of the Eccentric Debris Disc Morphologies series to explore the effects that significant free and forced eccentricities have on high-resolution millimetre-wavelength observations of debris discs, motivated by recent ALMA images of HD53143's disc. In this work, we explore the effects of free eccentricity, and by varying disc fractional widths and observational resolutions, show for a range of narrow eccentric discs, orbital overlaps result in dust emission distributions that have either one or two radial peaks at apocentre and/or pericentre. The narrowest discs contain two radial peaks, whereas the broadest discs contain just one radial peak. For fixed eccentricities, as fractional disc widths are increased, we show that these peaks merge first at apocentre (producing apocentre glow), and then at pericentre (producing pericentre glow). Our work thus demonstrates that apocentre/pericentre glows in models with constant free and forced eccentricities can be both width and resolution dependent at millimetre wavelengths, challenging the classical assertion that apocentre/pericentre glows are purely wavelength dependent. We discuss future high-resolution observations that can distinguish between competing interpretations of underlying debris disc eccentricity distributions.Comment: 7 pages, 5 figures. Accepted for publication in MNRAS Letter

Tinkering with Comments: Tailoring Practice by Spying on Written Artifacts

Using data from two IRB-approved research studies, this panel presentation explores methods of and uses for coding tutors\u27 and writers\u27 written comments about documents. Half the presentation focuses on asynchronous online tutorial comments, and the other half focuses on graduate writing group members\u27 comments on their peers\u27 documents. The presentation demonstrates how coding methods have implications for writing center programming because they help us identify areas for potential additional tutor training by highlighting what tutors actually do in online sessions and because they clarify the type of positive impact a writing group might have over time