No abstract

Abstract:Since the 1970s, cognitive psychological perspectives have dominated pedagogical frameworks and models for designing technology-mediated teaching and learning environments. More recently, social learning perspectives have received attention as viable or even desirable frames for research and practice related to teaching and learning, particularly in Web-based learning environments (WBLEs). In this article, the authors analyze these social learning perspectives and how they can be used in the design and implementation of online learning. This review and analysis of the research related to social learning perspectives on WBLEs provides several implications for future research and practice: (1) examining learners' individual characteristics in WBLEs, (2) identifying strategies for promoting social interaction in WBLEs, and (3) developing effective design principles for WBLEs.This article explores how social learning perspectives can be used in the design, development, and implementation of Web-based learning environments (WBLEs). The purposes of this article are (1) to review and analyze the literature of WBLEs from the perspective of social learning theory and (2) to provide suggestions for the design and development of WBLEs using the frame of social learning theory with implications for future research.To select literature sources for inclusion in our review, we searched major databases for peer-reviewed articles and their reference lists (e.g., ERIC, Correspondence should be sent to Janette R. Hill, University of Georgia, LEAP, River's Crossing, Athens, GA 30602. E-mail: janette@uga.edu SOCIAL LEARNING THEORY 89Education Abstracts), and reviewed the contents of the articles exploring issues related to social learning and online environments. From this pool, we selected those that were most current, exhibited sound research methodologies, and provided a general understanding of social learning in online learning situated primarily in a Web-based context. This process eliminated some studies that addressed online learning generally but not social learning theory factors specifically.For purposes of this article, we explored WBLEs set within a formal learning setting; informal learning environments (e.g., multiuser environments in which learning may occur as a result of interactions) are not included. We view WBLEs as settings that enable learners to interact and observe the results of their interactions while responding to and engaging with others, leading to a possible development of a more cohesive community of learners. Although there are many other useful formats for online learning, the focus of this article is on Web-based learning environments that are interactive in nature. APPLYING CONSTRUCTS FROM SOCIAL LEARNING THEORIES IN WBLEsSeveral factors influence teaching and learning per social learning perspectives: context, culture and community, and learner characteristics. In the following section, we present a description and related attributes, as well as a synthesis of WBLE research, to illustra...

No abstract

Little is known about the bacterial diversity of landfills and how environmental factors impact the diversity. In this study, PCR-based 454 pyrosequencing was used to investigate the bacterial communities of ten landfill leachate samples from five landfill sites in China. A total of 137 K useable sequences from the V3-V6 regions of the 16S rRNA gene were retrieved from 205 K reads. These sequences revealed the presence of a large number of operational taxonomic units (OTUs) in the landfills (709-1599 OTUs per sample). The most predominant bacterial representatives in the landfills investigated, regardless of geographic area, included Gammaproteobacteria, Firmicutes, and Bacteroidetes. The phyla Fusobacteria and Tenericutes were also found for the first time to be predominant in the landfills. The phylum Fusobacteria predominated (51.5 and 48.8%) in two semi-arid landfills, and the phylum Tenericutes dominated (30.6%) at one humid, subtropical landfill. Further, a large number of Pseudomonas was detected in most samples, comprising the dominant group and accounting for 40.9 to 92.4% of the total abundance. Principal component analysis (PCA) and cluster analysis based on OTU abundance showed that the abundant taxa separated the bacterial community. Canonical correlation analysis (CCA) suggested that precipitation and landfilling age significantly impact on the bacterial community structure. The bacterial community function (e.g., cellulolytic bacteria, sulfate-reducing bacteria (SRB), sulfate-oxidizing bacteria, and xenobiotic organic compound (XOC)-degrading bacteria) was also diverse, but the pattern is unclear.

In this study, refuse excavated from a typical refuse landfill in Shanghai after 8-10 years of placement was characterized in terms of particle size, total nitrogen, total phosphorus, and biodegradable matter. The refuse contained a large and diverse population of micro-organisms with a high capacity for decomposing refractory organic matter present in some wastewaters, including leachate. It was found that the aged refuse was quite stable after about a decade of decomposition in the warm, humid climate of southern China. The fine fractions resembled and had the properties of black soil, a medium that is suitable for green construction, organic fertilizer, or as bioreactor media for biological treatment of organic wastewaters. Excavation of the aged refuse would make about 50% of the space available for fresh refuse. The plastics, glass, textiles, and cans can be readily mechanically separated and recycled after cleaning. It is estimated that at least 200 millions tonnes of such aged refuse are available in China alone, and at least 10 times that much is buried worldwide. Hence, the evaluation of mined landfill waste and consideration of its potential uses is of great significance.

Synthetic high polymer flocculants, frequently utilized for flocculating efficiency and low cost, recently have been discovered as producing increased risk to human health and the environment. Development of a more efficient and environmentally sound alternative flocculant agent is investigated in this paper. Bioflocculants are produced by microorganisms and may exhibit a high rate of flocculation activity. The bioflocculant ETH-2, with high flocculating activity (2849 mg Kaolin particle/mg ETH-2), produced by strain Enterobacter sp. isolated from activated sludge, was systematically investigated with regard to its production, characterization, and flocculation mechanism. Analyses of microscopic observation, zeta potential and ETH-2 structure demonstrates the bridging mechanism, as opposed to charge neutralization, was responsible for flocculation of the ETH-2. ETH-2 retains high molecular weight (603 to 1820 kDa) and multi-functional groups (hydroxyl, amide and carboxyl) that contributed to flocculation. Polysaccharides mainly composed of mannose, glucose, and galactose, with a molar ratio of 1∶2.9∶9.8 were identified as the active constituents in bioflocculant. The structure of the long backbone with active sites of polysaccharides was determined as a primary basis for the high flocculation activity. Bioflocculant ETH-2 is cation independent, pH tolerant, and thermally stable, suggesting a potential fit for industrial application.

Silver nanoparticles (AgNPs), the most prevalent commercial nanomaterial products, are widely released into the environment.

Despite the pivotal role of archaea in methane production in landfills, the identity, ecology, and functional diversity of these microorganisms and their link to environmental factors remain largely unknown. We collected 11 landfill leachate samples from six geographically distinct landfills of different ages in China and analyzed the archaeal community by bar-coded 454 pyrosequencing. We retrieved 121,797 sequences from a total of 167,583 sequences (average length of 464 bp). The archaeal community was geographically structured, and nonabundant taxa primarily contributed to the observed dissimilarities. Canonical correlation analysis (CCA) suggested that the total phosphorous (TP), nitrate, and conductivity are important drivers for shaping the archaeal community. The hydrogenotrophic methanogens Methanomicrobiales and Methanobacteriales greatly dominated 9 of 11 samples, ranging from 83.7 to 99.5 %. These methanogens also dominated the remaining two samples, accounting for 70.3 and 58.8 %, respectively. Interestingly, for all of the studied Chinese landfills, 16S rRNA analysis indicated the predominance of hydrogenotrophic methanogens.