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  • 1
    Publication Date: 2017-12-08
    Description: Aviation is a unique anthropogenic source with 4-dimensional varying emissions, peaking at cruise altitudes (9 – 12 km). Aircraft emission budgets in the upper troposphere lower stratosphere region and their potential impacts on upper troposphere and surface air quality are not well understood. Our key objective is to use chemical-transport models (with prescribed meteorology) to predict aircraft emissions impacts on the troposphere and surface air quality. We quantified the importance of including full-flight intercontinental emissions and increased horizontal grid resolution. The full-flight aviation emissions in the Northern Hemisphere contributed ~1.3 % (mean, min – max: 0.46, 0.3 – 0.5 ppbV) and 0.2 % (0.013, 0.004 – 0.02 μg/m 3 ) of total O 3 and PM 2.5 concentrations at the surface, with Europe showing slightly higher impacts (1.9% (O 3 0.69, 0.5 – 0.85 ppbV) and 0.5% (PM 2.5 0.03, 0.01 – 0.05 μg/m 3 )) than North America (NA) and East Asia. We computed seasonal aviation-attributable mass flux vertical profiles and aviation perturbations along isentropic surfaces to quantify the transport of cruise altitude emissions at the hemispheric scale. The comparison of coarse (108 × 108 km 2 ) and fine (36 × 36 km 2 ) grid resolutions in NA showed ~70x and ~13x higher aviation impacts for O 3 and PM 2.5 in coarser domain. These differences are mainly due to the inability of the coarse resolution simulation to capture non-linearities in chemical processes near airport locations and other urban areas. Future global studies quantifying aircraft contributions should consider model resolution and perhaps use finer scales near major aviation source regions.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
    Publication Date: 2013-10-16
    Description: Kallistatin has been recognized as an endogenous angiogenic inhibitor. However, the underlying molecular mechanism remains poorly understood. Taking it into account that vascular endothelial growth factor (VEGF) has been implicated in all aspects of normal and pathological vasculogenesis and angiogenesis, in this study, we investigated whether VEGF signaling pathway was impacted by the anti-angiogenic effect of recombinant human kallistatin (rhKal). It has been found the rhKal inhibited proliferation as well as induced apoptosis of cultured human umbilical vein endothelial cells (HUVECs) in both concentration- and time-dependent manners. The rhKal also suppressed the VEGF-induced migration and tube formation of HUVECs. Furthermore, our data revealed that the rhKal suppressed the VEGF165-stimulated tyrosine phosphorylation of VEGFR-2 as well as its downstream signal molecular activation. The inhibition of receptor phosphorylation was correlated with a decrease in VEGF-triggered phosphorylation of angiogenesis signal molecules AKT and ERK, but not stress-related JNK. Taken together, these findings added the knowledge for us to understand the anti-angiogenic mechanism of kallistatin, which suggested that the rhKal could be worth as a candidate compound for further development for the purpose of anti-angiogenic therapies. J. Cell. Biochem. © 2013 Wiley Periodicals, Inc.
    Electronic ISSN: 0091-7419
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Published by Wiley
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  • 3
    Publication Date: 2012-10-25
    Description: We present case studies of THEMIS multipoint observations of ion distributions in the magnetotail plasma sheet at various locations upstream of earthward-propagating dipolarization fronts. Observations made near the neutral sheet show a characteristic signature, enhancements of earthward-moving ion fluxes about 30 s before dipolarization front arrival. In previous studies, this signature has been well explained as front-reflected ions confined to a region characterized by their gyroradii over the background Bz field that coexist with the ambient population. However, at higher latitudes near the plasma sheet boundary layer, observations suggest that earthward-moving ions appear a few minutes earlier than at the central plasma sheet, indicating that the ions reflected at the same dipolarization front could access farther toward the Earth at higher latitudes. These observed phenomena, as also stated in our companion paper, are associated with transient intensifications of proton auroral brightness, which suggests a direct connection between magnetospheric and ionospheric signatures during geomagnetic disturbed conditions. We carry out numerical simulations and theoretical analysis of ion dynamics to interpret and reproduce these observations, to improve our understanding of interactions between earthward-propagating fronts and the ambient plasma in the near-Earth magnetotail, and to establish the proton auroral effects of dipolarization fronts.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
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