6,749 research outputs found

    Warm molecular hydrogen in outflows from Ultraluminous Infrared Galaxies

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    Ultraluminous infrared galaxies (ULIRGs) show on average three times more emission in the rotational transitions of molecular hydrogen than expected based on their star formation rates. Using Spitzer archival data we investigate the origin of excess warm H_2 emission in 115 ULIRGs of the IRAS 1 Jy sample. We find a strong correlation between H_2 and [FeII] line luminosities, suggesting that excess H_2 is produced in shocks propagating within neutral or partially ionized medium. This view is supported by the correlations between H_2 and optical line ratios diagnostic of such shocks. The galaxies powered by star formation and those powered by active nuclei follow the same relationship between H_2 and [FeII], with emission line width being the major difference between these classes (about 500 and 1000 km/sec, respectively). We conclude that excess H_2 emission is produced as the supernovae and active nuclei drive outflows into the neutral interstellar medium of the ULIRGs. A weak positive correlation between H_2 and the length of the tidal tails indicates that these outflows are more likely to be encountered in more advanced mergers, but there is no evidence for excess H_2 produced as a result of the collision shocks during the final coalescence.Comment: 16 pages, MNRAS accepted. Complete data tables and Spitzer spectra are available at http://www.pha.jhu.edu/~zakamska/ULIRGS

    Salary & Benefits Schedule and Teacher Tenure Study

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    House Bill 278, passed by the legislature in spring 2014, instructed the Department of Administration to “present to the legislature a written proposal for a salary and benefits schedule for school districts, including an evaluation of, and recommendations for, teacher tenure” (Sec. 52). In order to meet this mandate, the Alaska Department of Administration contracted with the UAA Center for Alaska Education Policy Research (CAEPR) to produce the following deliverables: Develop geographic cost differentials for different school districts Develop base salary and benefit schedules for teachers and principals Describe superintendent duties, compensation, and responsibilities in Alaska districts Prepare a list of different benefit options school districts offer their employees and their associated costs Provide recommendations regarding teacher tenure policy Describe similarities and differences between the certified and classified labor markets in Alaska Each section of this report responds to a specific task or responsibility from this list.Alaska Department of Administration, State of AlaskaIntroduction / Report overview / Research activities / Context / The landscape of teachers in Alaska / Key findings / Recommendations / Methodology /Key informant interviews / Focus groups / Literature review / Teachers survey / District data compilation / Statistical analysis / Superintendent interviews / Base salary schedule and community salary differentials / Findings: Modeling salaries and differentials / Salary schedule development / Salary differentials estimation / Cost of living and the community salary differentials / Superintendent duties / Benefits / Tenure / Research tasks / Defining tenure / Tenure's historical origins / Current context for tenure / Empirical studies of tenure / Certified and classified labor markets / Summary and recommendations / teacher salary schedule / Teacher tenure / Final thought

    Credit Line Availability and Utilization in REITs

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    Analysis of REIT credit line availability and use under normal conditions and during the recent financial crisis are provided. Descriptive statistics indicate REIT credit lines represent an important component of capital structure, credit line availability and utilization have increased substantially over the sample period, and REITs maintain precautionary liquidity via credit lines rather than holding cash. Multivariate results indicate that credit line availability is directly associated with cash flow uncertainty, dividend distributions, acquisitions, and capital market access and is inversely linked to the market-to-book ratio. Credit line use is unrelated to cash flow volatility and dividends, but is correlated with operating cash flow, acquisitions, and capital market access. Unlike with non-REITs, when setting credit limits lenders focus on dividends and not just operating cash flow. Despite finding that line availability is influenced by dividend payments, REITs do not systematically use lines to pay dividends implying that dividends are paid from operating cash flows.

    Investigation of the in vitro interactions between two common Cystic Fibrosis pathogens, Staphylococcus aureus and Stenotrophomonas maltophilia.

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    Cystic Fibrosis (CF) is one of the most common autosomal disorders in Caucasian populations. This disorder creates a very opportune environment for many pathogens within the patient’s lung. Two common pathogens that infect CF patient’s lungs are Staphylococcus aureusand Stenotrophomonas maltophilia. These two species of bacteria can colonize host environments and establish mats of cells known as biofilms that become very difficult to eradicate with antibiotics. Once inside a CF lung, these pathogens must not only evade the host immune response but they also interact and compete with each other; however, how bacterial pathogens interact inside the host lung has not been well studied. This study will look specifically at the interactions between these two pathogens in vivo. S. maltophilia inhibits S. aureus biofilm formation over time in a dose-dependent manner though the mechanism is still unclear. The findings of this study could provide insight into these interactions between both Staphylococcus aureus and Stenotrophomonas maltophilia

    Half-breeds, squatters, land speculators, and settler colonialism in the Des Moines-Mississippi confluence

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    Americans are accustomed to a standard historical version of American expansion: The United States pushed West, removing Indians in its wake and filled the land with American settlers. This is often seen as a form of settler colonialism. Westward expansion and settler colonialism were much more complicated. They often occurred on the periphery of the American centralized state, proceeding any serious government involvement, and involved a wide mix of culturally indeterminate people. This paper examines westward expansion in the Des Moines-Mississippi Confluence, a 119,000-acre region in what is now southeastern Iowa. At one time or another, Sauk and Meskwaki Indians, mixed-race people then called “half-breeds,” lawless squatters, and manipulative land speculators all claimed the land, fighting over it using an array of tools and without much government interference. This mixing of racially and culturally indeterminate people shows that westward expansion was often more complicated than a meeting of two developed cultures, that we need to rethink the role of extralegal squatters in westward expansion, and the federal government often exercised less power in the American West than we usually believe

    Life in the Times of Coronavirus

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    Stories from DMACC students, faculty, and staff.https://openspace.dmacc.edu/coronaviruslife/1008/thumbnail.jp