390 research outputs found

    Relevant Ground Test Facilities for Outer Planet Entry Missions at NASA Ames Research Center

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    High level summary of ground test capabilities available at NASA Ames Research Center that can aid in the development and design of future Outer Planet (Saturn and Uranus) probe mission

    Rotigaptide protects the myocardium and arterial vasculature from ischaemia reperfusion injury

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    Aim: Ischaemia-reperfusion injury (IRI) causes impaired endothelial function and is a major component of the adverse effects of reperfusion following myocardial infarction. Rotigaptide increases gap junction conductance via connexin-43. We tested the hypothesis that rotigaptide reduces experimental myocardial infarction size and ameliorates endothelial IRI in humans. Methods: Myocardial infarction study: porcine myocardial infarction was achieved by catheter-induced occlusion of the left anterior descending artery. In a randomized double-blind study, rotigaptide (n = 9) or placebo (n = 10) was administered intravenously as a 10 min bolus prior to reperfusion and continuously during 2 h of reperfusion. Myocardial infarction size (IS) was assessed as proportion of the area at risk (AAR). Human translational study: forearm IRI was induced in the presence or absence of intra-arterial rotigaptide. In a randomized double-blind study, forearm arterial blood flow was measured at rest and during intra-arterial infusion of acetylcholine (5–20 Όg min–1; n = 11) or sodium nitroprusside (2–8 mg min–1; n = 10) before and after intra-arterial infusion of placebo or rotigaptide, and again following IRI. Results: Myocardial infarction study: Rotigaptide treatment was associated with a reduction of infarct size (IS/AAR[%]: 18.7 ± 4.1 [rotigaptide] vs. 43.6 ± 4.2 [placebo], P = 0.006). Human translational study: Endothelium-dependent vasodilatation to acetylcholine was attenuated after ischaemia-reperfusion in the presence of placebo (P = 0.007), but not in the presence of rotigaptide (P = NS). Endothelium-independent vasodilatation evoked by sodium nitroprusside was unaffected by IRI or rotigaptide (P = NS). Conclusions: Rotigaptide reduces myocardial infarction size in a porcine model and protects from IRI-related endothelial dysfunction in man. Rotigaptide may have therapeutic potential in the treatment of myocardial infarction

    A scoping review of the use of ethnographic approaches in implementation research and recommendations for reporting

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    Background: Researchers have argued for the value of ethnographic approaches to implementation science (IS). The contested meanings of ethnography pose challenges and possibilities to its use in IS. The goal of this study was to identify sources of commonality and variation, and to distill a set of recommendations for reporting ethnographic approaches in IS. Methods: We included in our scoping review English-language academic journal articles meeting two criteria: (1) IS articles in the healthcare field and (2) articles that described their approach as ethnographic. In March 2019, we implemented our search criteria in four academic databases and one academic journal. Abstracts were screened for inclusion by at least two authors. We iteratively develop a codebook for full-text analysis and double-coded included articles. We summarized the findings and developed reporting recommendations through discussion. Results: Of the 210 articles whose abstracts were screened, 73 were included in full-text analysis. The number of articles increased in recent years. Ethnographic approaches were used within a wide variety of theoretical approaches and research designs. Articles primarily described using interviews and observational methods as part of their ethnographic approaches, though numerous other methods were also employed. The most cited rationales for using ethnographic approaches were to capture context-specific phenomena, understand insiders? perspective, and study complex interactions. In reporting on ethnographic approaches, we recommend that researchers provide information on researcher training and position, reflect on researchers? positionality, describe observational methods in detail, and report results from all the methods used. Conclusion: The number of IS studies using ethnography has increased in recent years. Ethnography holds great potential for contributing further to IS, particularly to studying implementation strategy mechanisms and understanding complex adaptive systems. Plain language summary: Researchers have proposed that ethnographic methods may be valuable to implementation research and practice. Ethnographic approaches have their roots in the field of anthropology, but they are now used in many fields. These approaches often involve a researcher spending time in 'real-world' settings, conducting interviews and observation to understand a group of people. That said, researchers disagree on the meaning of ethnography, which presents a challenge to its use in implementation science (IS). We searched for articles in the field of IS that described their methods as ethnographic. We then reviewed the articles, looking for similarities and differences in how and why ethnographic approaches were used. Many of these articles said they used ethnographic methods because they were interested in issues like context, research participants? views, and complex interactions. We found a large amount of variation in how ethnographic methods were used. We developed recommendations for describing ethnographic methods in a way that readers can clearly understand. We also made several observations of the value ethnographic approaches can bring to IS. Ethnographic methods may be especially useful to studying unplanned and unexpected changes that take place during implementation. These recommendations and observations could be helpful to implementation researchers wishing to use ethnographic methods

    The Mating Systems and Pollination Biology of Three Species of Verbena (Verbenaceae)

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    Because their flowers can be cross- and/or self-pollinated Verbena stricta, V hastata and V urticifolia are facultatively xenogamous. We suggest the flowers can be cross-pollinated because I) the fruit set of caged plants was substantially lower than that of open-pollinated plants, i.e. pollinators were necessary for typical fruit set and 2) the flowers of each species attracted a diverse array of hymenopteran, dipteran and lepidopteran pollinators that were capable of moving pollen between plants. Self-pollination was low due to the spatial separation of anthers and stigmas and/or an angled corolla that decreased the likelihood of pollen dropping from the anthers onto the stigma. However, the limited ability of flowers to self-pollinate was supplemented by the intrafloral movement of pollen by thrips. In addition, both the pollen-ovule ratios and pollination efficiencies of these species were consistent with those of other facultatively xenogamous species, and the available data were consistent with each species being self-compatible. Finally, we discuss a protocol for distinguishing between self-pollination and the intrafloral movement of pollen by thrips

    Investigation into Photoconductivity in Single CNF/TiO2-Dye Core–Shell Nanowire Devices

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    A vertically aligned carbon nanofiber array coated with anatase TiO2 (CNF/TiO2) is an attractive possible replacement for the sintered TiO2 nanoparticle network in the original dye-sensitized solar cell (DSSC) design due to the potential for improved charge transport and reduced charge recombination. Although the reported efficiency of 1.1% in these modified DSSC’s is encouraging, the limiting factors must be identified before a higher efficiency can be obtained. This work employs a single nanowire approach to investigate the charge transport in individual CNF/TiO2 core–shell nanowires with adsorbed N719 dye molecules in dark and under illumination. The results shed light on the role of charge traps and dye adsorption on the (photo) conductivity of nanocrystalline TiO2 CNF’s as related to dye-sensitized solar cell performance

    Dynamic liquefaction of shear zones in intact loess during simulated earthquake loading

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    The 2010-2011 Canterbury earthquake sequence in New Zealand exposed loess-mantled slopes in the area to very high levels of seismic excitation (locally measured as >2 g). Few loess slopes showed permanent local downslope deformation, and most of these showed only limited accumulated displacement. A series of innovative dynamic back pressured shear-box tests were undertaken on intact and remoulded loess samples collected from one of the recently active slopes replicating field conditions under different simplified horizontal seismic excitations. During each test, the strength reduction and excess pore water pressures generated were measured as the sample failed. Test results suggest that although dynamic liquefaction could have occurred, a key factor was likely to have been that the loess was largely unsaturated at the times of the large earthquake events. The failure of intact loess samples in the tests was complex and variable due to the highly variable geotechnical characteristics of the material. Some loess samples failed rapidly as a result of dynamic liquefaction as seismic excitation generated an increase in pore-water pressure, triggering rapid loss of strength and thus of shear resistance. Following initial failure, pore pressure dissipated with continued seismic excitation and the sample consolidated, resulting in partial shear-strength recovery. Once excess pore-water pressures had dissipated, deformation continued in a critical effective stress state with no further change in volume. Remoulded and weaker samples, however, did not liquefy, and instead immediately reduced in volume with an accompanying slower and more sustained increase in pore pressure as the sample consolidated. Thereafter excess pressures dissipated and deformation continued at a critical state. The complex behaviour explained why, despite exceptionally strong ground shaking, there was only limited displacement and lack of run-out: dynamic liquefaction was unlikely to occur in the freely draining slopes. Dynamic liquefaction however remained a plausible mechanism to explain loess failure in some of the low-angle toe slopes, where a permanent water table was present in the loess
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