Primary objectives for the International Space Station (ISS) in support of the Vision for Space Exploration include conducting research to counteract the harmful effects of space on human health, test new space techno...
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ISBN:
(纸本)1563478900
Primary objectives for the International Space Station (ISS) in support of the Vision for Space Exploration include conducting research to counteract the harmful effects of space on human health, test new space technologies, and learn to operate long-duration space missions. In pursuit of these objectives, NASA is interested in closer cooperation between the ISS operational community, scientists, and engineers. To develop the exploration vehicles for missions to the moon and Mars, NASA must test materials, foods, and medicines to ensure their performance in the space environment. These results will enable important decisions on the materials to be used for future space vehicles. Another critical factor for the success on future missions beyond Earth orbit is the capability for repairs of equipment. On the ISS, the practice of crewmembers performing repairs in microgravity will increase our understanding of the repair processes in space;when these capabilities are needed during future space exploration missions, we will have the knowledge and experience to perform them. The ISS is a unique and irreplaceable training ground for building the operational knowledge required to safely conduct future exploration missions, and the growing links within the science, engineering and operations communities are reinforcing the value of that training. Current interactions between the communities that support the ISS have already produced many synergies that are significantly accelerating NASA's advancement towards future exploration missions in support of the Vision.
In vitro corrosion tests have not evaluated the role of cells on the corrosion of implant quality 316L stainless steel. A new cell-culture corrosion cell was used to simulate the clinical condition of cells attached t...
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In vitro corrosion tests have not evaluated the role of cells on the corrosion of implant quality 316L stainless steel. A new cell-culture corrosion cell was used to simulate the clinical condition of cells attached to and growing on the alloy to evaluate the effects of cells on alloy corrosion and the effect of corrosion products on cells. The corrosion potential, charge transfer, and surface composition of the alloy were measured in the presence and absence of macrophage cells (RAW 264.7) or cells stimulated to release NO over 72 hours. Whereas there was no statistical difference in the corrosion of 316L stainless steel in the presence of macrophage cells as compared to culture media alone, there was a trend for higher corrosion to occur in the presence of the cells. Corrosion was further reduced when cells were stimulated to release NO which may have oxidized the implant and contributed to an enhancement of its surface oxide. These data suggest that cells may alter alloy surface oxides and affect alloy corrosion.
Two approaches were used to gain an understanding of the spatial variations in membrane potential resulting from exposure of cultured adrenal medullary chromaffin cells to a 20 V/cm DC electric field of different orie...
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Two approaches were used to gain an understanding of the spatial variations in membrane potential resulting from exposure of cultured adrenal medullary chromaffin cells to a 20 V/cm DC electric field of different orientations. The finite element method was used to solve Poisson's equation for the potential in a Petri dish containing isolated spherical chromaffin cells or chromaffin cell aggregates of various configurations and the results of the computations were compared to the results obtained experimentally. The latter used fluorescence imaging of chromaffin cell membranes stained with the fluorescent voltage-sensitive dye di-8-ANEPPS to monitor variations in membrane potential. For single cells, the numerical results for membrane potential variation were in good agreement with the experimental results. For realistic chains of two or three cells, the results from both methods were in agreement only when the long axis of the chain was perpendicular to the electric field. For three cells forming a realistic, irregularly shaped aggregate, variations in membrane potential determined experimentally were more complex than those predicted by the numerical computations for regions of cell contact. The results provide a foundation for understanding how excitable cells respond to DC electric fields and identify parameters that influence these responses.
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