3,274 research outputs found

    Riparian corridor vegetation structure and soil function along urban, suburban, and rural streams in Louisville, KY, USA.

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    Stream riparian zones are ecotones between terrestrial and aquatic environments. Studying these areas in urban environments is important since they lie adjacent to stream water supplies. I conducted a study of riparian woody and groundcover vegetation along urban, suburban, and rural streams (land-use designations based on % impervious surface) to assess how cities are affecting plant community structure. I also studied riparian soil gas flux (carbon dioxide, methane, and nitrous oxide) in relation to water table depth and groundwater nutrient concentrations spanning a 10-month period (January to October, 2008). I found distinct woody and groundcover communities associated with proportion of impervious surface surrounding the research sites. These communities differed regarding diversity and proportion of native, exotic, and wetland species distributions. The most urban communities generally had lower species richness, more exotic species, and fewer wetland species when compared to rural areas. Urban areas also exhibited the highest streambanks and lowest water tables. Carbon dioxide gas flux rates were higher in urban areas, but methane and nitrous oxide fluxes did not respond uniformly to site differences as classified by proportion of impervious surface. Methane and nitrous oxide differences, in addition to seasonal variability, were more greatly affected by local site level differences in substrate and nutrient ratios as well as soil moisture

    Prodigal

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    Following a similar pattern of the classic Biblical story of “The Prodigal Son”, the play allows for a modernization of the characters and setting. Set in 1968, the playwright takes a look at what happened after the “Prodigal Son” returned home as well as the effect the return had upon the Son that stayed as well as the Father. How can family relationships survive in the midst of lies and turmoil of a time of great change in America’s history

    Kinetics of Surfactant Adsorption at Fluid-Fluid Interfaces: Surfactant Mixtures

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    The adsorption at the interface between an aqueous solution of several surface-active agents and another fluid (air or oil) phase is addressed theoretically. We derive the kinetic equations from a variation of the interfacial free energy, solve them numerically and provide an analytic solution for the simple case of a linear adsorption isotherm. Calculating asymptotic solutions analytically, we find the characteristic time scales of the adsorption process and observe the behavior of the system at various temporal stages. In particular, we relate the kinetic behavior of the mixture to the properties of its individual constituents and find good agreement with experiments. In the case of kinetically limited adsorption, the mixture kinetics is found to be considerably different from that of the single-surfactant solutions because of strong coupling between the species.Comment: 19 pages, 7 figures, to be published in Langmui

    Evolution of treatment targets in Crohn’s disease

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    Crohn’s disease is a chronic relapsing and remitting inflammatory disorder of the gastrointestinal tract, associated with significantly morbidity due to both symptoms and complications that have a considerable detrimental impact on a patient’s quality of life. An early treat to target approach with disease modifying agents has been shown to significantly improve long term outcomes, demonstrated by a number of therapeutic targets in a number of modalities. This review will outline the current treatment targets and measures of disease burden in Crohn’s disease

    Use of Factors in Development Estimates: Improving the Cost Analysis Toolkit

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    Factor Estimating is a technique commonly used by defense acquisition analysts to develop cost estimations. However, previous studies developing factors for the Engineering and Manufacturing Development (EMD) phase of the life cycle are limited. This research expands the current toolkit for cost analysts by developing cost factors in previously unexplored areas. More specifically, over 400 cost reports are utilized to create new standard cost factors that are delineated by five categories: commodity type, contract type, contractor type, development type, and Service. The factors are developed for those elements that are common in a wide array of projects such as program management, systems engineering, data, or training. This new factor dataset provides cost analysts with the information necessary to appropriately identify and select the most relevant factors to use when developing future cost estimates. Through statistical analysis, the research also helps identify those elements in which more analysts’ time and energy should be allocated when developing their estimates

    Control theory for principled heap sizing

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    We propose a new, principled approach to adaptive heap sizing based on control theory. We review current state-of-the-art heap sizing mechanisms, as deployed in Jikes RVM and HotSpot. We then formulate heap sizing as a control problem, apply and tune a standard controller algorithm, and evaluate its performance on a set of well-known benchmarks. We find our controller adapts the heap size more responsively than existing mechanisms. This responsiveness allows tighter virtual machine memory footprints while preserving target application throughput, which is ideal for both embedded and utility computing domains. In short, we argue that formal, systematic approaches to memory management should be replacing ad-hoc heuristics as the discipline matures. Control-theoretic heap sizing is one such systematic approach
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