Metal-silicate Partitioning Behavior of Molybdenum, Tungsten, and Nickel: Implications for Core Formation

The interior structure of Earth, particularly the metal core, is responsible for the core dynamo and thus our magnetic field and supplying the mantle with heat to encourage solid state convection and thus decompression melting and hot spot volcanism. Therefore determining how Earth\u27s core formed and if that process was unique to our planet in the solar system is of great scientific interest. Core formation can be studied experimentally by examining the metal-silicate partitioning behavior of siderophile elements and using the results to explain their observed upper mantle depletions relative to bulk Earth abundances. This study investigated the partitioning behavior of the moderately siderophile elements molybdenum and tungsten by conducting experiments using multi-anvil presses and obtaining compositional analyses of the run products using electron probe microanalysis. Molybdenum was found to dissolve as Mo4+ in silicate melts, whereas tungsten dissolved as W6+. The partition coefficients [Di = ci(metal)/ci(silicate)] for both molybdenum and tungsten decrease with increasing pressure; however, DW increases slightly with increasing temperature whereas DMo decreases. Both elements become less siderophile as silicate melt polymerization decreases. The addition of carbon to the metal phase causes DMo and DW to increase, while addition of sulfur causes DMo and DW to decrease. Parameterization of the data from this study and literature data allowed for core formation modeling to determine what conditions could explain Earth\u27s mantle abundances of molybdenum, tungsten, and nickel (the most extensively studied element). The modeling suggests that the abundances of these elements were set by a global magma ocean near the end of accretion with conditions of 35-37 GPa (~1100 km depth) and 2950-3000 K with XC = 0.07, XS = 0.05, and XSi = 0.06. Thus implying that large impacts in the late stages of Earth\u27s accretion were energetic enough to re-equilibrate the already differentiated metal and silicate, leaving the distinct chemical signature of a single equilibration event in the mantle. Applying the parameterizations to other differentiated bodies for which we have compositional data indicates that magma oceans were common occurrences in the early solar system, but each body underwent a unique differentiation history

Creative Evolution from Matthew Arnold to the Post-Moderns

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Biochemical Characterization of Drosophila Receptor Tyrosine Phosphatases

Two classes of enzymes are responsible for modulation of intracellular phosphotyrosine levels, namely protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs). Together these enzymes maintain the appropriate balance of phosphoproteins required for a variety of developmental processes including axon pathfinding. In Drosophila, five receptor-like protein tyrosine phosphatases (RPTPs) regulate axon pathfinding, but little is known about their downstream signaling pathways or the means by which their enzymatic activity is regulated. Chapter 2 of this thesis deals with experiments to test whether dimerization regulates the activity of these enzymes. Crystallographic data indicates that some RPTPs form dimers in which each monomer is precluded from binding substrate due to the insertion of a helix-turn-helix segment of the opposing monomer into the active site. I introduced ?tagged? RPTP constructs into Drosophila S2 tissue culture cells and tested for dimer formation using immunoprecipitation and Western blotting. I did not detect stable dimers, however. This may suggest that dimer formation requires other protein components (such as the putative RPTP ligands) that are not expressed in S2 cells. In Chapter 3 I investigated the possibility that Roundabout (Robo), a receptor mediating axonal repulsion from the embryonic midline, is a substrate for RPTPs DPTP69D and/or DPTP10D. Previous genetic studies implicate these RPTPs in participating in the Robo signaling pathway. Experiments detailed here show that Robo can be phosphorylated on tyrosine residues in S2 cells, characteristic of an RPTP substrate. However, Robo did not co-immunoprecipitate with ?substrate trap? mutants of either of these RPTPs, possibly because their interaction is dependent on co-factors not present in the cell culture system. Chapter 4 is a characterization of DPTP69D-associated proteins purified from embryos expressing a substrate trap version of DPTP69D. We identified one of the associated proteins as non-muscle myosin II heavy chain (nmm II hc). Proper regulation of nmm II hc is essential for axon patterning in mushroom bodies (MBs). I found that expression of the DPTP69D trap in MBs results in an axon retraction phenotype similar to that seen when nmm II hc activity is elevated, suggesting that this protein may be a target for DPTP69D activity.</p

Effectuation as Ineffectual? Applying the 3E Theory-Assessment Framework to a Proposed New Theory of Entrepreneurship

Effectuation is a proposed new theory of entrepreneurship, with insufficient empirical testing and critical analysis. Drawing on a new, comprehensive set of theory-building criteria—sourced from and complementing those of Robert Dubin and others—we provide the first formal assessment of effectuation as a theory. We highlight its strengths and weaknesses, leveraging the former to address the latter in five different directions that would build on the existing work to improve this theory. The assessment exercise also displays the value of our assessment framework in guiding the evaluation and development of other existing and future theories in entrepreneurship and management

Effectuation, Not Being Pragmatic or Process Theorizing, Remains Ineffectual: Responding to the Commentaries

We appreciate the opportunity to respond to the provocative Dialogue pieces of Read, Sarasvathy, Dew, and Wiltbank (2016; henceforth, “RSDW”); Reuber, Fischer, and Coviello (2016; henceforth, “RFC”); Gupta, Chiles, and McMullen (2016; henceforth, “GCM”); and Garud and Gehman (2016; henceforth, “GG”), each of which makes several claims in defense of effectuation, as well as describes several ways forward in entrepreneurship- and process-related theorizing. We respond in a manner consistent with the traditional perspective in management theorizing that “good theory is practical” (Lewin, 1945), where “theory is theory” (Simon, 1967; Van de Ven, 1989) based on our discipline’s collective commitment to knowledge production (Suddaby, 2014). In fact, we respond in the tradition of scientific theory—its building, its critique, and its defense. Leveraging the logic behind that tradition, we thus refute every point contained in RSDW’s, RFC’s, GCM’s, and GG’s commentaries and attempt to build on what is common to all theory while celebrating what is valuable in the diversity of theorizing (i.e., in the ways we produce theory)

The Influence of Director Human Social Capital and Firms' Entrepreneurial Orientation on Corporate Entrepreneurship

Title from PDF of title page viewed March 1, 2017Dissertation advisor: Jeffrey S. HornsbyThesis (Ph.D.)--Henry W. Bloch School of Management. University of Missouri-Kansas City, 2016VitaIncludes bibliographical references (pages 75-85)This dissertation explores the link between corporate governance and corporate entrepreneurship. Surprisingly, our understanding of how boards of directors influence corporate entrepreneurship decisions and actions has been limited to date. To address this gap, the current study develops a resource dependence theoretical framework to investigate how corporations leverage directors’ experience and networks to enhance organizational rejuvenation efforts. Entrepreneurial orientation also is examined as a contextual factor in the director capital-corporate entrepreneurship relationship. After collecting an original dataset of 2,289 firm-year observations from 524 U.S. corporations and creating a new measure of organizational rejuvenation, I implemented a hybrid methodological approach to simultaneously test the within- and between-firm influences of the variables of interest. The analytical results demonstrate surprising reverse effects of director human capital, social capital, and the contextual influence of entrepreneurial orientation on firms’ corporate entrepreneurship initiatives. These findings support prior theoretical arguments that directors serve a dual role: not only monitoring and controlling firm decisions but also serving an important advice and counsel function.Introduction -- Theoretical development - Research method -- Analysis and results -- Discussion and conclusio

Independent Orbiter Assessment (IOA): Analysis of the orbital maneuvering system

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA approach features a top-down analysis of the hardware to determine failure modes, criticality, and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. The independent analysis results for the Orbital Maneuvering System (OMS) hardware are documented. The OMS provides the thrust to perform orbit insertion, orbit circularization, orbit transfer, rendezvous, and deorbit. The OMS is housed in two independent pods located one on each side of the tail and consists of the following subsystems: Helium Pressurization; Propellant Storage and Distribution; Orbital Maneuvering Engine; and Electrical Power Distribution and Control. The IOA analysis process utilized available OMS hardware drawings and schematics for defining hardware assemblies, components, and hardware items. Each level of hardware was evaluted and analyzed for possible failure modes and effects. Criticality was asigned based upon the severity of the effect for each failure mode

Independent Orbiter Assessment (IOA): Analysis of the reaction control system, volume 3

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA approach features a top-down analysis of the hardware to determine failure modes, criticality, and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. This report documents the independent analysis results for the Reaction Control System (RCS). The RCS is situated in three independent modules, one forward in the orbiter nose and one in each OMS/RCS pod. Each RCS module consists of the following subsystems: Helium Pressurization Subsystem; Propellant Storage and Distribution Subsystem; Thruster Subsystem; and Electrical Power Distribution and Control Subsystem. Volume 3 continues the presentation of IOA analysis worksheets and the potential critical items list

Instruction in the Responsible Conduct of Research: An Inventory of Programs and Materials within CTSAs

The National Institutes of Health (NIH) require instruction in the responsible conduct of research (RCR) as a component of any Clinical and Translational Science Award (CTSA). The Educational Materials Group of the NIH CTSA Consortium's Clinical Research Ethics Key Function Committee (CRE-KFC) conducted a survey of the 38 institutions that held CTSA funding as of January 2009 to determine how they satisfy RCR training requirements. An 8-item questionnaire was sent by email to directors of the Clinical Research Ethics, the Educational and Career Development, and the Regulatory Knowledge cores. We received 78 completed surveys from 38 CTSAs (100%). We found that there is no unified approach to RCR training across CTSAs, many programs lack a coherent plan for RCR instruction, and most CTSAs have not developed unique instructional materials tailored to the needs of clinical and translational scientists. We recommend collaboration among CTSAs and across CTSA key function committees to address these weaknesses. We also requested that institutions send electronic copies of original RCR training materials to share among CTSAs via the CTSpedia website. Twenty institutions submitted at least one educational product. The CTSpedia now contains more than 90 RCR resources.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/79071/1/j.1752-8062.2010.00193.x.pd