973 resultados para House construction


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(Document pdf contains 42 pages)

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(4pp.)

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(4pp.)

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Hydrilla (Hydrilla verticillata (L.f.)Royle), a serious aquatic weed, reproduces through formation of underground tubers. To date, attacking this life-cycle stage has been problematic. The purpose of this study was to measure the impact of exposure to dilute acetic acid on monoecious hydrilla tubers under field conditions. In this field experiment, treatments were acetic acid concentration (0, 2.5, or 5%) and sediment condition (perforated or not perforated). Each of 60, 1x1 m plots (in the Oregon House Canal) were randomly assigned to one treatment. Two weeks after treatment, we collected three samples from each plot. One was washed over 2 mm wire mesh screens to separate tubers from sediment. Relative electrolyte leakage was measured for one tuber from each plot. Five additional tubers from each plot were placed in a growth chamber and sprouting monitored for four weeks. A second sample from each plot was placed in a plastic tub and placed in an outdoor tank, filled with water. These samples were monitored for tuber sprouting. Relative electrolyte leakage increased significantly for tubers exposed to 2.5% or 5% acetic acid. Effects on tubers in perforated sediment were reduced. Exposure to acetic acid inhibited tuber sprouting by 80 to 100%, in both chamber and outdoor tests. These results confirm findings from earlier laboratory/greenhouse experiments, and suggest that this approach may be useful in the management of hydrilla tuber banks in habitats where the water level can be lowered to expose the sediments.

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This report documents abundance and cover for selected elements of the benthic coral reef assemblage at the site of the 1984 grounding of the M/V Wellwood on Molasses Reef, Florida Keys. The purpose of the effort was to establish a pre-construction baseline before the installation of reef modules at the site. The installation process is intended to stabilize fractured substrates that were recently exposed by storm impacts, and to provide three-dimensional relief in order to enhance reef community recovery. It is hoped that the restoration effort will result in a biological assemblage with the character of the transition community that would exist there had the incident not occurred. To date, the assemblage has developed the character of a comparatively featureless hard ground similar in composition to hard ground areas and transition zones surrounding the grounding site. These data will allow scientists and resource managers to better track the trajectory of recovery following the installation of modules. Direct counts of scleractinian and gorgonian corals, hydrocorals of the genus Millepora, and zoanthids of the genus Palythoa were made in three areas within and around the grounding site. The site is poorly developed with respect to scleractinian colony size and cover compared to surrounding areas. Key scleractinian species necessary for the development of topographic relief in the area denuded by the grounding are not well represented in the current community. Though gorgonian cover and richness is similar in all study areas, gorgonian community recovery in the damaged area is not complete. Unlike surrounding areas, one species, Pseudopterogorgia americana, accounts for over half of all corals at the grounding site, over 80% of all gorgonians, and nearly all the coral cover. Based on these findings and other observations made in the 18 years since the grounding, recommendations are made that should be considered in the course of human intervention targeted at stabilizing and enhancing the site. (PDF contains 24 pages.)

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Single-chain polymeric nanoparticles are artificial folded soft nano-objects of ultra-small size which have recently gained prominence in nanoscience and nanotechnology due to their exceptional and sometimes unique properties. This review focuses on the current state of the investigations of click chemistry techniques for highly-efficient single-chain nanoparticle construction. Additionally, recent progress achieved for the use of well-defined single-chain nanoparticles in some promising fields, such as nanomedicine and catalysis, is highlighted.