133 research outputs found

    Radiation-induced interface phenomena: Decoration of high-energy density ion tracks

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    The effect of 20 MeV Cl4 + ions incident on Au-SiO2 and Ag-SiO2 interfaces was investigated using high-resolution transmission electron microscopy. Cross-sectional micrographs expose beam-induced gold interfacial transport and migration into the SiO2. No such migration was observed for silver films. The relevance of this phenomenon to the adhesion improvement found at corresponding irradiation doses is discussed

    Short-term effects of thinning, clear-cutting and stump harvesting on methane exchange in a boreal forest

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    Forest management practices can alter soil conditions, affecting the consumption and production processes that control soil methane (CH4) exchange. We studied the short-term effects of thinning, clear-cutting and stump harvesting on the CH4 exchange between soil and atmosphere at a boreal forest site in central Sweden, using an undisturbed plot as the control. Chambers in combination with a highprecision laser gas analyser were used for continuous measurements. Both the undisturbed plot and the thinned plot were net sinks of CH4, whereas the clear-cut plot and the stump harvested plot were net CH4 sources. The CH4 uptake at the thinned plot was reduced in comparison to the undisturbed plot. The shift from sink to source at the clear-cut and stump harvested plots was probably due to a rise in the water table and an increase in soil moisture, leading to lower gas diffusivity and more reduced conditions, which favour CH4 production by archea. Reduced evapotranspiration after harvesting leads to wetter soils, decreased CH4 consumption and increased CH4 production, and should be accounted for in the CH4 budget of managed forests

    Different induction mechanisms of mRNA for inducible nitric oxide synthase in rat smooth muscle cells in culture and in aortic strips

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    AbstractThe expression of mRNA for the inducible form of nitric oxide synthase, (iNOS), was studied in rat aortic smooth muscle cells, (SMCs) in cell culture and in strips of rat aorta by reverse transcriptase coupled to the polymerase chain reaction. iNOS mRNA expression was weak in cultured SMCs when exposed to either interferon-γ (IFNγ) or lipopolysaccharide (LPS), but the combination LPS + IFNγ enhanced the expression. In aortic strips LPS alone induced a pronounced expression, with no further increase by IFNγ. Cycloheximide potentiated the expression of iNOS mRNA in SMCs in culture stimulated with LPS + IFNγ but attenuated the response in aortic strips.The results indicate different cellular signaling pathways for the induction of iNOS mRNA by LPS and/or IFNγ, in cultured SMCs and in rat aortic strips

    Systemic galectin-3 in smokers with chronic obstructive pulmonary disease and chronic bronchitis: The impact of exacerbations

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    Purpose: The carbohydrate-binding protein Galectin-3 is increased in several inflammatory diseases and has recently been forwarded as a systemic biomarker in chronic obstructive pulmonary disease (COPD). In this longitudinal study, we characterized the level of systemic Galectin-3 using blood from smokers with a history of COPD and chronic bronchitis (COPD-CB), during stable clinical conditions and exacerbations. Patients and Methods: The study population comprised 56 long-term smokers with COPD-CB, 10 long-term smokers without lung disease (LTS) and 10 clinically healthy never-smokers (HNS). Blood samples were analyzed for levels of Galectin-3, leukocyte populations and C-reactive protein (CRP). In addition, sputum samples from the COPD-CB group were analyzed for bacterial growth. Results: When comparing stable clinical conditions and exacerbations in the COPD-CB group, we found that the level of Galectin-3, just like that of CRP, leukocytes and neutrophils, respectively, was increased during exacerbations. However, this exacerbation-associated increase of Galectin-3 was modest. During stable clinical conditions of COPD-CB, the level of Galectin-3 was not elevated in comparison with HNS or LTS. Nor did this level of Galectin-3 distinguish patients that remained in a clinically stable condition throughout the study to those that developed an exacerbation. In addition, neither during stable clinical conditions nor during exacerbations, did the presence of bacterial growth in sputum alter Galectin-3 levels. In contrast to Galectin-3, the level of CRP, leukocytes and neutrophils, respectively, were increased during clinical stable conditions in the COPD-CB group compared with the other groups and were further enhanced during exacerbations. Conclusion: Systemic Galectin-3 is increased in a reproducible but modest manner during exacerbations in smokers with COPD-CB. During stable clinical conditions, the level of systemic Galectin-3 does not distinguish patients that remain clinically stable from those that develop exacerbations. This makes it less likely that systemic Galectin-3 may become a clinically useful biomarker in the current setting

    Exploring and contextualizing public opposition to renewable electricity in the United States

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    This article explores public opposition to renewable power technologies in the United States. It begins by discussing the genesis of environmental ethics, or how some Americans have come to place importance on the protection of the environment and preservation of species, ecosystems, and the biosphere. As result, renewable power systems have become challenged on ethical and environmental grounds and are occasionally opposed by local communities and environmentalists. The article finds that, however, such concern may be misplaced. Renewable electricity resources have many environmental benefits compared to power stations fueled by coal, oil, natural gas, and uranium. Opposition towards renewable resources can at times obscure the true costs and risks associated with electricity use and entrench potential racial and class-based inequalities within the current energy system

    Influence of XUV radiation on Pv ionization fraction in hot star winds

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    Different diagnostics of hot star wind mass-loss rates provide results that are difficult to reconcile with each other. The widely accepted presence of clumping in hot star winds implies a significant reduction of observational mass-loss rate estimates from diagnostics that depend on the square of the density. Moreover, the ultraviolet Pv resonance lines indicate a possible need for even stronger reduction of hot star mass-loss rates, provided that Pv is a dominant ionization stage of phosphorus at least in some hot stars. The latter assumption is challenged by a possible presence of the XUV radiation. Here we study the influence of the XUV radiation on the Pv ionization fraction in the hot star winds. By a detailed solution of the hydrodynamical, radiative transfer, and statistical equilibrium equations we confirm that sufficiently strong XUV radiation source may decrease the Pv ionization fraction, possibly depreciating the Pv lines as a reliable mass-loss rate indicator. On the other hand, the XUV radiation influences also the ionization fraction of heavier ions that drive the wind, leading to a decrease of the wind terminal velocity. Consequently, we conclude that the XUV radiation alone can not bring theory and observations in accord. We fit our predicted wind mass-loss rates by a suitable formula and compare the results with the observational mass-loss rate diagnostics. We show that for supergiants and giants the theoretical predictions do not contradict the mass-loss rate estimates based on X-ray line profiles or density squared diagnostics. On the other hand, for main-sequence stars the predicted mass-loss rates are still significantly higher than that inferred from Pv or X-ray lines. This indicates that the "weak wind problem" recently detected in low-luminosity main-sequence stars may occur to some extent also for the stars with higher luminosity.Comment: Accepted for publication in MNRAS. The definitive version is available at www.blackwell-synergy.com. 8 pages, 5 figure
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