The Interaction Of Multiple Convection Zones In A-type Stars

A-type stars have a complex internal structure with the possibility of multiple convection zones. If not sufficiently separated, such zones will interact through the convectively stable regions that lie between them. It is therefore of interest to ask whether the typical conditions that exist within such stars are such that these convections zones can ever be considered as disjoint. In this paper we present results from numerical simulations that help in understanding how increasing the distance between the convectively unstable regions are likely to interact through the stable region that separates them. This has profound implications for mixing and transport within these stars.Comment: 9 pages, 15 figures, Preprint accepted for publication in MNRA

The Role of Stereotype Threat in Mental Rotation

Numerous studies have been conducted on mental rotation ability in both males and females. A lot of the literature discusses male superiority in mental rotation task as opposed to females. This paper examined the role of stereotype threat in a mental rotation task. Particularly, the research study focused on gender stereotype threat in female college students. The study was completed in a two part design with students completing two mental rotation task in a group setting. The low numbers in the sample make it impossible to reliably say that the Vandenberg Mental Rotation Task (VMRT) and the Purdue Mental Rotation Task (Purdue) were measuring the exact same thing. There was a confound in part 2 of the study and we were unable to draw conclusions on the role of gender stereotype threat. However, the findings do suggest more support for the research on video game experience and mental rotation performance. The implications are discussed

Things Hold Together John Howard Yoder\u27s Trinitarian theology of Culture

Theologies of culture often focus on either Christ or creation as their primary source, to the exclusion of the other. At best, this approach is incomplete because it does not account for the continuity between creation and redemption. At worst, it posits a divide not simply between Christ and creation, but between persons of the Trinity, presuming contradictory moral and cultural norms issuing from different persons of the Trinity. John Howard Yoder is often depicted as a representative of a Christocentric and creation-deficient approach to culture. Against that faulty representation, this dissertation argues that Yoder advocates a Trinitarian theology of culture that upholds the continuity and coherence between God\u27s work in creation and in redemption. To see why Yoder can be characterized as Trinitarian, his thought must be placed in the context of his engagement with the Niebuhrs, as well as Nicea and Chalcedon. For Yoder, Scripture leads us to the conclusion that Jesus\u27 humanity makes him directly relevant to culture and Jesus\u27 divinity directly connects him to creation. Inasmuch as the creeds are faithful translations of Scripture, they also lead to this conclusion. Yoder\u27s focus on Christ does not come at the expense of his doctrine of creation, for he contends that humans were created to exercise Christ-like power and that the Powers were created to be dynamic servants of peace and flourishing. Moreover, the power unleashed in Jesus restores and re-establishes the politics of creation in that God\u27s original intentions for human life are revealed and validated in Jesus. This does not include sword-bearing, which is not rooted in prelapsarian creation but in postlapsarian preservation. God\u27s providential allowance for the sword must not be confused or conflated with God\u27s creative and redemptive will. Finally, Yoder argues that true cultural transformation depends on the pioneering work of the Spirit and the in-breaking kingdom of God. The practices of the church will inevitably overflow and have transformative effects not only in the church but also in all of human culture. The dissertation concludes with implications of Yoder\u27s contention that creation and redemption must cohere in our theology of culture

Using Instructional Time and Race/Ethnicity to Predict Social Studies Accountability Test Results

This study investigated the relationship among the variables instructional time configuration, gender, race/ethnicity, and poverty to predict the academic performance of seventh-grade students on a state-mandated social studies accountability test. Results of 24,919 seventh-grade student social studies test scores from 117 middle schools, as well as a survey given to principals of the same 117 middle schools, were analyzed. A hierarchical multiple regression analysis showed that when controlling for poverty, the variables instructional time configuration and race/ethnicity were significant, explaining 11% of the variation in student social studies accountability test results; a small effect. Analysis of variance (ANOVA) and analysis of covariance (ANCOVA) were also used to illuminate the relationship of these variables on accountability test performance

Mercury concentration and speciation in coastal rainwater

Mercury exists in mainly two oxidation states in the atmosphere, Hg0 and Hg(II). Inorganic divalent mercury, Hg(II), has a greater solubility; therefore is in higher concentration in rainwater, than Hg0. The toxic species, methylmercury is an organic form of Hg(II) and is present in low concentration. Mercury is released into the atmosphere by natural and anthropogenic sources. Rainwater is thought to be a main removal mechanism for atmospheric mercury. The concentration and speciation of mercury were determined in rainwater from Wilmington, NC, from September 1, 2003 to September 30, 2005. Volume weighted averages for total Hg in unfiltered rainwater, total dissolved Hg, particulate Hg, dissolved gaseous Hg (Hg0) and methyl-Hg were 52.9 ± 4.7 pM, 40.6 ± 4.0 pM, 13.7± 1.5 pM, 4.3 ± 0.9 pM and 1.1 ± 0.1 pM, respectively. All mercury species were present in all seasons with no significant difference in concentrations between summer and winter, except dissolved gaseous mercury concentration was higher in the winter, with a higher ratio of Hg(II)/Hg(0) in summer relative to winter events. Diurnal variation was seen where Hg(II) decreased during the day into the night, suggesting photochemical reduction of Hg(II). All Hg concentrations were higher in continental storms relative to coastal rain events. Both total mercury species (UFHg and TDHg) were positively correlated with particulate mercury. Total mercury species were washed out of the atmosphere by rainwater with lower concentrations for larger rain events. A weak positive correlation was observed between TDHg and NO3 -, TDHg and SO4 2-, DGHg and Cl-, and Hgpart and DOC. The photochemistry of mercury from Wilmington was also investigated. UFHg, TDHg, and DGHg were generally produced upon irradiation of rainwater samples by simulated sunlight. Particulate Hg concentrations generally declined upon irradiation and MMHg concentrations showed no pattern, in some instances, increasing, decreasing or remaining the same. Positive correlation was observed between, production of UFHg and Hgpart and a negative correlation was observed between production of TDHg and Hgpart. Continental events increased in Hgpart while decreasing in TDHg, whereas coastal events increased in TDHg while decreasing in Hgpart after irradiation. Seasonal differences between Hg species were similar with an increase in TDHg and DGHg, while decreasing in Hgpart and greater changes were observed during the winter. Diurnal variations of Hg(II)/Hg(0) ratio increased during the afternoon and decreased there after. Atmospheric global inputs by natural and anthropogenic sources, 4.1 x 106 kg or 2.0 x 107 mol per year, were in good agreement with calculated total flux of mercury removed via wet deposition, 3.8 x 106 kg or 1.9 x 107 mol per year, suggesting that essentially all mercury released into the atmosphere is removed via rain

Integrated motor drives: state of the art and future trends

With increased need for high power density, high efficiency and high temperature capabilities in Aerospace and Automotive applications, Integrated Motor Drives (IMD) offers a potential solution. However, close physical integration of the converter and the machine may also lead to an increase in components temperature. This requires careful mechanical, structural and thermal analysis; and design of the IMD system. This paper reviews existing IMD technologies and their thermal effects on the IMD system. The effects of the power electronics (PE) position on the IMD system and its respective thermal management concepts are also investigated. The challenges faced in designing and manufacturing of an IMD along with the mechanical and structural impacts of close physical integration is also discussed and potential solutions are provided. Potential converter topologies for an IMD like the Matrix converter, 2-level Bridge, 3-level NPC and Multiphase full bridge converters are also reviewed. Wide band gap devices like SiC and GaN and their packaging in power modules for IMDs are also discussed. Power modules components and packaging technologies are also presented