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This paper reports, fabrication and characterization of unidirectional glass fiber reinforced epoxy composite filled with nano-size alumina, silica and micron-size alumina trihydrate fillers using pultrusion technique. Tensile, flexural and impact strengths were determined to evaluate the effectiveness of fillers on the mechanical properties. Results show that the micro and nanofillers act as secondary reinforcement. The tensile, flexural and impact strengths of 10 wt% (combined alumina, silica and alumina trihydrate)-filled glass fiber reinforced epoxy composite improved by 9, 20 and 28%, respectively, as compared to the unfilled and alumina/silica-filled glass fiber reinforced epoxy composites. The enhanced performance of micro and nanofillers-filled glass fiber reinforced epoxy composites is due to better adhesion and good dispersion of particulates in the epoxy matrix providing increased surface area for strong interfacial interaction and better load transfer. The improved mechanical properties indicate that the unidirectional glass fiber reinforced epoxy with combined micro-and nanofillers-filled composite is a good candidate for structural application.

Background & objectives: Public health and diagnostic laboratories are facing huge sample loads for COVID-19 diagnosis by real-time reverse transcription-polymerase chain reaction (RT-PCR). High sensitivity of optimized real-time RT-PCR assays makes pooled testing a potentially efficient strategy for resource utilization when positivity rates for particular regions or groups of individuals are low. We report here a comparative analysis of pooled testing for 5- and 10-sample pools by real-time RT-PCR across 10 COVID-19 testing laboratories in India. Methods: Ten virus research and diagnostic laboratories (VRDLs) testing for COVID-19 by real-time RT-PCR participated in this evaluation. At each laboratory, 100 nasopharyngeal swab samples including 10 positive samples were used to create 5- and 10-sample pools with one positive sample in each pool. RNA extraction and real-time RT-PCR for SARS-CoV-2-specific E gene target were performed for individual positive samples as well as pooled samples. Concordance between individual sample testing and testing in the 5- or 10-sample pools was calculated, and the variation across sites and by sample cycle threshold (C t ) values was analyzed. Results: A total of 110 each of 5- and 10-sample pools were evaluated. Concordance between the 5-sample pool and individual sample testing was 100 per cent in the C t value ≤30 cycles and 95.5 per cent for C t values ≤33 cycles. Overall concordance between the 5-sample pooled and individual sample testing was 88 per cent while that between 10-sample pool and individual sample testing was 66 per cent. Although the concordance rates for both the 5- and 10-sample pooled testing varied across laboratories, yet for samples with C t values ≤33 cycles, the concordance was ≥90 per cent across all laboratories for the 5-sample pools. Interpretation & conclusions: Results from this multi-site assessment suggest that pooling five samples for SARS-CoV-2 detection by real-time RT-PCR may be an acceptable strategy without much loss of sensitivity even for low viral loads, while with 10-sample pools, there may be considerably higher numbers of false negatives. However, testing laboratories should perform validations with the specific RNA extraction and RT-PCR kits in use at their centres before initiating pooled testing.