Microwave NDE of Defects in Glass Fiber Composites

The attractive properties of Glass Fiber Composites have made it a very popular material for use in several industries including energy, oil & gas, healthcare, transportation and others. As with all materials, composites too have the inherent challenge of defects getting incorporated during manufacture and material getting degraded during service. This demands a reliable and robust nondestructive evaluation (NDE) technique to be used for inspection of this material. The search for newer and more advanced Nondestructive Evaluation (NDE) techniques is a constant endeavor in the industrial world. In the realm of electromagnetic NDE, Microwave NDE has been gaining a lot of attention in the last decade as a potential tool for inspection of various materials especially dielectrics like plastics, ceramics, composites, etc. Microwave NDE is non-contact, portable and fast in addition to offering imaging capability. These features make it an attractive option to be explored seriously as an advanced NDE tool. Glass fiber composites encounter a number of different types of defects such as foreign material inclusions, wrinkle / waviness, resin rich and resin starved areas, etc. Microwave NDE has the advantage of being able to penetrate more easily through dielectric materials, thus enabling detection of deeper defects vis-à-vis techniques like ultrasound or Infrared imaging. This paper explores the application of Microwave NDE to the detection and characterization of different type of defects. The effect of probe frequency and stand-off are explored. A comparative assessment of Microwave NDE capability with that of Ultrasound in terms of the depth of penetration, defect size resolution and signal contrast for the various defect types will also be reported.</p

Evaluation of candidate reference genes for quantitative expression studies in Asian seabass (<em>Lates calcarifer</em>) during ontogenesis and in tissues of healthy and infected fishes

597-605Quantitative real-time PCR (qRT-PCR), used to determine the gene expression profile, is an important tool in functional genomic research, including fishes. To obtain more robust and meaningful result, the best possible normalization of the data is of utmost significance. In the present study, we have evaluated the potential of five commonly used housekeeping genes i.e., elongation factor 1-α (EF1A), β-Actin (ACTB), 18S ribosomal RNA (18S), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and β-2-Microglobulin (B2M) in normal physiological conditions, developmental stages and in response to bacterial infection in Asian seabass, Lates calcarifer (Bloch), an important food fish cultured in the Asia-Pacific region. The expression levels of these  five genes were estimated in 11 tissues of normal seabass juveniles, 14 embryonic and larval developmental stages and six tissues of Vibrio alginolyticus-challenged animals. Further, the expression stability of these genes was calculated based on three algorithms i.e. geNorm, NormFinder and BestKeeper. The results showed that although there are tissue-specific variations for each gene, ACTB and EF1A are the most stable genes across the tissues of normal animals. However, in bacteria-challenged animals, EF1A and 18S were found to be the best reference genes for data normalization. The expression of all the genes tested showed an increasing trend in developmental stages and the increase was significant at blastula stage. Among the five genes tested, EF1A and ACTB were found to be the genes with least variation and highest stability across the developmental stages. This forms the first report on validation of housekeeping genes in L. calcarifer, in the context of ontogenic development and in response to infection