| 11. |
- Wang, Z. B., et al.
(författare)
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Characteristics of regional new particle formation in urban and regional background environments in the North China Plain
- 2013
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Ingår i: Atmos. Chem. Phys.. - : Copernicus Publications. - 1680-7324. ; 13:24, s. 12495-12506
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Tidskriftsartikel (refereegranskat)abstract
- Long-term measurements of particle number size distributions were carried out both at an urban background site (Peking University, PKU) and a regional Global Atmospheric Watch station (Shangdianzi, SDZ) from March to November in 2008. In total, 52 new particle formation (NPF) events were observed simultaneously at both sites, indicating that this is a regional phenomenon in the North China Plain. On average, the mean condensation sink value before the nucleation events started was 0.025 s−1 in the urban environment, which was 1.6 times higher than that at regional site. However, higher particle formation and growth rates were observed at PKU (10.8 cm−3 s−1 and 5.2 nm h−1) compared with those at SDZ (4.9 cm−3 s−1 and 4.0 nm h−1). These results implied that precursors were much more abundant in the polluted urban environment. Different from the observations in cleaner environments, the background conditions of the observed particle homogeneous nucleation events in the North China Plain could be characterized as the co-existing of a stronger source of precursor gases and a higher condensational sink of pre-existing aerosol particles. Secondary aerosol formation following nucleation events results in an increase of particle mass concentration, particle light scattering coefficient, and cloud condensation nuclei (CCN) number concentration, with consequences on visibility, radiative effects, and air quality. Typical regional NPF events with significant particle nucleation rates and subsequent particle growth over a sufficiently long time period at both sites were chosen to investigate the influence of NPF on the number concentration of "potential" CCN. As a result, the NPF and the subsequent condensable growth increased the CCN number concentration in the North China Plain by factors in the range from 5.6 to 8.7. Moreover, the potential contribution of anthropogenic emissions to the CCN number concentration was more than 50%, to which more attention should be drawn in regional and global climate modeling, especially in the polluted urban areas.
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| 12. |
- Yang, Tien-Nan, et al.
(författare)
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Variations in monsoonal rainfall over the last 21 kyr inferred from sedimentary organic matter in Tung-Yuan Pond, southern Taiwan
- 2011
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 30:23-24, s. 3413-3422
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Tidskriftsartikel (refereegranskat)abstract
- Changes in paleorainfall intensity linked to the strength of the East Asian (EA) summer monsoon since 21 cal kyr BP are inferred from the organic matter contents of a 15-m sediment core from Tung-Yuan Pond in southern Taiwan. High total organic carbon/total nitrogen (TOC/TN) values in association with increased TOC content suggest that more soil-derived material containing terrestrial organic matter (OM) was delivered to the lake during periods of increased runoff associated with extensive precipitation that resulted from intensified summer monsoons, whereas low values indicate OM possessing a dominant algal origin during weakened summer monsoons. Rainfall intensity in terms of the proportion of terrestrial OM was high in four periods: the last deglaciation (similar to 17.2 to similar to 12.2 ka), the early Holocene (similar to 10.6 to similar to 8.6 ka), the middle Holocene Thermal Optimum (similar to 7.7 to similar to 5 ka) and the late Holocene (similar to 4.2 to similar to 2 ka), whereas it was low in the intervening time periods. High TOC/TN values coincide with peak values of summer insolation, and thus the strongest EA summer monsoon during the early and middle Holocene: small drops in these ratios correspond to increasing and decreasing solar radiation in the deglacial period and the late Holocene, respectively. The four intervals with low TOC/TN ratios, as well as episodic drops of the ratios during the deglaciation and the early and late Holocene are concordant with the late last glacial (similar to 21 to similar to 17.2 ka), the Oldest (similar to 14.8 ka), the Older (similar to 13.3 ka) and the Younger Dryas (similar to 13 to similar to 11.5 ka), the 8.2 cold event (similar to 8.6-7.7 ka) and a late Holocene cold event (similar to 5-4.2 ka), and suggest a weakened EA summer monsoon during these times. Moreover, high frequency hydrological variability occurred during the early Holocene, heavy rainfall persisted during the middle Holocene, and precipitation intensity generally diminished after similar to 5 ka. The Tung-Yuan Pond sediment record indicates that the TOC/TN ratio can be used as a paleorainfall intensity proxy to trace variations in the EA summer monsoon strength in other small lakes. Crown Copyright
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| 13. |
- Zhao, Li Na, et al.
(författare)
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S100A9 induces aggregation-prone conformation in Abeta peptides : a combined experimental and simulation study
- 2013
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Ingår i: RSC Advances. - : RSC Publishing. - 2046-2069. ; 3:46, s. 24081-24089
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Tidskriftsartikel (refereegranskat)abstract
- Inflammation is one of the prominent pathological features in Alzheimer's disease (AD). Recently, there have been various proposed roles of neuroinflammation, such as the driving forces, bystander, byproduct or the neuroprotective response. Notwithstanding these diverse possible mechanisms, experiments have found that S100A9 is one of the pro-inflammatory proteins abundant and over-expressed in the inflammation sites of AD. In this paper, we examine the role of S100A9 in the oligomerization process of A beta peptides by means of replica exchange molecular dynamics simulation and experimental investigations. Our experiments, based on atomic force microscopy and Thioflavin T spectroscopic assays, have clearly indicated that the close interaction between S100A9 and A beta has significantly enhanced the A beta oligomerization. In line with the experimental observation, our simulation studies have revealed that the pro-inflammatory S100A9 protein interacts with the A beta peptides directly, mainly through hydrophobic interactions with the A beta central hydrophobic core region. In addition, the formation of hydrogen bonds between the residues of the S100A9 homodimer and the two ends of the A beta peptides is found to cause a straightening of the A beta(12-24) peptides. A more straight A beta(12-24) peptide with a higher beta-content then may function as a template to induce the folding of new incoming A beta peptides, which leads to the formation of aggregation-prone oligomers.
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