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The effects of polymer substrates on the interfacial structure and the thermal stability of Ga-doped ZnO (GZO) thin films were investigated. The GZO thin films were deposited on polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) substrates by rf-magnetron sputtering at room temperature, and thermal stability tests of the GZO thin films on the polymer substrates were performed at 150°C up to 8 h in air. Electrical and structural characterizations of the GZO thin films on the PET and the PEN substrates were carried out, and the origins of the stable interfacial structure and the improved thermal stability of the GZO thin film on the PEN substrate were discussed.
Self-Organizing Maps (SOM) have been used for patterning and visualizing ten environmental parameters and phytoplankton biomass in a mactrotidal (>10 m) Gyeonggi Bay and artificial Shihwa Lake during 1986–2004. SOM segregated study areas into four groups and ten subgroups. Two strikingly alternative states are frequently observed: the first is a diverse non-eutrophic state designated by three groups (SOM 1–3), and the second is a eutrophic state (SOM 4: Shihwa Lake and Upper Gyeonggi Bay; summer season) characterized by enhanced nutrients (3 mg l−1 dissolved inorganic nitrogen, 0.1 mg l−1 PO4) that act as a signal and response to that signal as algal blooms (24 µg chlorophyll-a l−1). Bloom potential in response to nitrification is affiliated with high temperature (r = 0.26), low salinity (r = −0.40) and suspended solids (r = –0.27). Moreover, strong stratification in the Shihwa Lake has accelerated harmful algal blooms and hypoxia. The non-eutrophic states (SOM 1–3) are characterized by macro-tidal estuaries exhibiting a tolerance to pollution with nitrogen-containing nutrients and retarding any tendency toward stratification. SOM 1 (winter) is more distinct from SOM 4 due to higher suspended solids (>50 mg l−1) caused by resuspension that induces light limitation and low chlorophyll-a (<5 µg l−1). In addition, eutrophication-induced shifts in phytoplankton communities are noticed during all the seasons in Gyeonggi Bay. Overall, SOM showed high performance for visualization and abstraction of ecological data and could serve as an efficient ecological map that can specify blooming regions and provide a comprehensive view on the eutrophication process in a macrotidal estuary.
This study investigated the relationships of three major aquatic assemblages (diatom, macroinvertebrate, and fish) and environmental variables, including sub-basin, hydrology, land cover, and water quality variables on multiple scales. Samples were collected at 720 sampling sites on the Korean nationwide scale. Geological variables, including altitude and slope, showed a strong positive correlation with proportions of forest in land cover types and cobbles in substrates, while they were negatively correlated with water quality variables, including conductivity and total phosphorus. Considering the concordance of the different assemblages, species richness of fish and macroinvertebrates displayed significant correlation, and diatoms were significantly correlated with fish. However, diatoms did not show significant correlation with macroinvertebrates. Altitude and slope showed significant correlation with all biological variables of the three assemblages. Macroinvertebrates and fish showed positive relations with large substrate sizes. Indices of diatoms and macroinvertebrates well reflected the perturbation of water quality variables. However, fish indices showed a relatively low association with water quality variables, compared with those of diatoms and macroinvertebrates. These patterns were also confirmed by the ordination and prediction of biological indices with environmental variables through the learning process of a self-organizing map as well as random forest. Overall, our study supports the concept of multi-scale habitat filters and functional organization in streams, and is consistent with the recommended use of multiple biological indices with more than one assemblage for the assessment of the biotic integrity of aquatic ecosystems.
Benthic macroinvertebrates are considered as a representative taxon that indicates the ecological status of freshwater ecosystems. Numerous indices derived from community data have been proposed to estimate either biological water quality or ecosystem health. In this study, metrics based on benthic macroinvertebrates at the family level were screened using ecological informatics to provide a multi-metric measurement that would be suitable for presenting ecological integrity across different levels of environmental impact. Benthic macroinvertebrates were collected at a total of 720 sample sites from river basins and streams in Korea in 2009. Based on four categories of community status (i.e., diversity, richness, tolerance, and composition), 37 metrics were selected as initial candidates according to the literature. The candidate metrics were evaluated according to parameters including discriminatory power, redundancy, and responsiveness to stressors. Self-organizing map was utilized to assist the screening procedure by providing ordination, clustering, and visualization of metric and environmental data. Six metrics were finally selected as a multi-metric and were compared with conventional indicators for presenting the ecological integrity of streams.
We characterized the responses of benthic macroinvertebrates to heavy metals released from mines in high mountain streams of the Gangqu River in the Shangrila Gorge, China. Benthic macroinvertebrates were collected with a kick-net at 32 sampling sites. In addition, 25 environmental variables including heavy metal concentrations were measured at each sampling site. Although the concentrations of heavy metals were not seriously high, their effects were reflected in the changes of community composition of benthic macroinvertebrates. Total abundance and species richness decreased with increasing heavy metal concentrations. Species richness of Plecoptera and Trichoptera, Margalef richness index, and percentage of scrapers in functional feeding groups were negatively correlated with heavy metal concentrations. A high variation was observed in the response of different taxa to heavy metals. Heavy metals mainly affected the sensitive taxa of Plecoptera, Ephemeroptera, and Trichoptera. However, some tolerant taxa were observed in Trichoptera (such as Hydropsyche sp.) and Dugesia sp. Cluster analysis and a non-metric multidimensional scaling analysis were applied to characterize specific macroinvertebrate taxa composition. The analyses revealed the effects of different environmental factors such as geographical, hydromorphological, physical, and chemical factors including heavy metals on the distribution of benthic macroinvertebrates in high mountain streams. Although the effects were compounded with different factors such as altitude, temperature, stream width, turbidity, and heavy metals, the influence of heavy metals on benthic macroinvertebrate communities was clearly identified (decreased species richness, changes in species composition). Even though the contamination of heavy metals was low in the sampling area, the consequences were clear, indicating that long-term exposure to heavy metals could seriously impact aquatic communities in high mountain streams.
Chironomid assemblages collected from seven different streams in South Korea were investigated. The subfamily composition of chironomids was clearly differentiated accross different levels of organic pollution. Species abundance distributions (SADs) of chironomid communities were compared with the total macroinvertebrate communities across different levels of pollution. The number of species with minimal range of abundance was lower in SADs for chironomid communities compared with total communities. The log normal distribution was accepted for both total and chironomid communities, while the geometric series was relatively more suitable for chironomids and the log series were more fitted to total communities. The a values in the log normal distribution increased in chironomid communities across different levels of pollution, while γ values increased at the polluted sites for both chironomid and total communities. In the Power law analysis, the parameter decreased in chironomid communities. The dominance decay model was more fitted to chironomid communities in clean conditions while random fraction and assortment models were more suitable for the polluted sites.
General and genetic statistical methods are commonly used to deal with microsatellite data (highly variable neutral genetic markers). In this paper, the self-organizing map (SOM) that belongs to the unsupervised artificial neural networks (ANNs) was applied to analyse the structure of 58 European and two Chinese pig populations (Sus scrofa) including commercial lines, local breeds and cosmopolitan breeds. Results were compared with other unsupervised classification or ordination methods such as factorial correspondence analysis, hierarchical clustering from an allele sharing distance and the Bayesian genetic model and with principal components analysis and neighbour joining from allelic frequencies and genetic distances between populations. Like other methods, SOMs were able to classify individuals according to their breed origin and to visualize similarities between breeds. They provided additional information on the within- and between-population diversity, allowed differences between similar populations to be highlighted and helped differentiate different groups of populations.
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