68 research outputs found
Comparison of different contrast agents when imaging shape memory polymer foams
Get PDFSMP foams have unique properties that make them well suited for certain medical applications. SMP foam has the ability to be programmed to “remember” a temporary shape, and once heated can revert back to its original shape. Scientists have recognized that shape memory foam might have great value in the medical industry. One application for SMP foam that is being developed is an embolic device for the treatment of cerebral aneurysms. One critical component in the development of these foams is the creation of accurate 3D models of the foam to determine strut thickness, pore cell size, anisotropy, and perform flow simulations. To obtain a 3D model of these low density polyurethane foams, they must be imaged using µ-CT. In some cases a contrast agent must be used in order to see the foam when imaging via µ-CT, so an appropriate contrast agent must be determined. Different contrast agents at various concentrations were tested in order to find one that is suitable for this application. Barium sulfate, tungsten, and tungsten carbide were all tested at 1%, 5%, 10%, 25%, and 50% by mass concentrations. The 5% barium sulfate samples produced the best results, although they were still not good enough to produce an accurate 3D model, so further research will need to be conducted
Declines in Puget Sound sediment-dwelling communities and a new focus on climate, nutrient, and other ecosystem stressors
Get PDFThe Washington State Department of Ecology has been collecting data on Puget Sound sediment-dwelling (benthic) invertebrates since 1989, as part of the Marine Sediment Monitoring Program. Benthic organisms serve key functions, including processing and storage of organic material and cycling of nutrients needed by other components of the ecosystem. Benthic invertebrates are an integral part of the marine food web and biogeochemical processes that support salmon, orcas, and humans and are a key component of the Puget Sound ecosystem. We are finding significant declines in the overall condition of benthic communities, with 44% of the study area adversely affected. Many of the adversely affected benthic communities were found in terminal inlets and bays. Throughout Puget Sound, an increase of pollution/hypoxia-tolerant species and a decrease in sensitive species has occurred over time. Deterioration of benthic communities does not correspond well with changes in individual chemical contaminants measured or laboratory tests of sediment toxicity. The spatial distribution of benthic communities is in part defined by the changing physical and oceanographic habitat. Changes in the abundance and composition of the benthic invertebrate community over time may indicate responses of the ecosystem to climatic stressors and large-scale ecological shifts such as changing hydrological, nutrient, oxygen, or acidic conditions
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