Aims: The aim of this study was to enrich and isolate bacteria from a tannery soil that were capable of utilizing tannic acid and gallic acid as sole source of carbon aerobically, and to characterize their diversity in order to identify efficient strains that can be used for tannin bioremediation. Methods and Results: Bacterial strains were isolated after enrichment in minimal medium with tannic acid or gallic acid as sole carbon source. Polymerase chain reaction (PCR) restricted fragment length polymorphism of 16S rDNA [amplified ribosomal DNA restriction analysis (ARDRA)] and BOX-PCR was used to characterize their diversity. Two strains showing relatively high efficiency in degrading tannic acid and gallic acid were identified on the basis of carbon source utilization pattern (BIOLOG) and 16S rDNA sequence. Conclusions: Bacterial strains capable of degrading tannic acid and gallic acid could be grouped into six and seven clusters on the basis of ARDRA and BOX-PCR, respectively. On the basis of 16S rDNA sequence, the most efficient isolate degrading tannic acid belonged to Pseudomonas citronellolis, whereas the most efficient gallic acid degrader showed maximum phylogenetic relatedness to P. plecoglossicida. Significance and Impact of the Study: Aerobic tannic acid degraders such as the two strains isolated in this study can be used for tannin bioremediation, and in the study of genes involved in the production of tannase, an industrially important enzyme.
This qualitative case study examines the initial implementation of a problem-based version of an undergraduate course in materials science for the purpose of identifying areas of improvement to the curriculum prior to a planned second implementation. The course was designed around problems that students work in small teams to solve under the guidance of facilitators, with early sequence problems designed to foster the problem-solving skills required to succeed in the course. This report describes students' impressions of and experiences in the course as they worked to solve the final problem at the end of the semester and compares those impressions, where applicable, to impressions gathered after they had completed the first problem near the beginning of the semester. Using grounded theory techniques to analyze the data, six central themes emerged from the implementation: course structure, facilitation roles, student roles, group processes, coconstruction, and resources. Implications for practice and potential instructional design solutions that may aid in future implementations are discussed.
Glass fiber reinforced polymer composites are widely used as structural materials. These two-component materials can be tailored to suit a large variety of applications. A better understanding of the properties of the fiber-matrix “interphase” can facilitate optimum design of the composite structure. The interphase is a microscopic region around the fiber and hence nano-scale investigation using nano-indentation techniques is appropriate to determine mechanical property variations within this region. In this study the atomic force microscope adapted with a commercial nanoindenter has been used to determine the variation of the elastic modulus across the interphase for different silane coated glass fiber reinforced polyester matrix composites. A comparative study of the elastic modulus variation in the various interphases is reported. The results are discussed in the light of the current limitations of the instrumentation and analysis.
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