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An accelerated electro-migration experiment is carried out to examine the chloride penetration of cement mortar admixed with two types of nanosilica and compared with the natural diffusion measurement. The chloride ion concentration in the destination solution is measured by ultra violet-visible spectrophotometer at different time intervals. In the natural condition, the penetration of chloride ions through a 7-mm thick mortar disc takes approximately 24 h, whereas nanosilica incorporated mortar resists the ingress of chloride ions up to around 72 h. Furthermore, in the accelerated condition, the diffusion coefficient is reduced from 6·8 × 10 m/s to 4·7 × 10 m/s with 3% addition of nanosilica (type I) by weight of cement. The microstructure studies through scanning electron microscopy reveal that the nanosilica refines the pore structure of the mortar and leads to a denser microstructure owing to the formation of additional calcium-silicate-hydrate gel. The pozzolanic reactivity is also determined using a thermogravimetric technique wherein nanosilica and silica fume incorporated cement mortar reduces the calcium hydroxide content by 67 and 30%, respectively. These studies demonstrate that nanosilica efficiently reduces the chloride permeability of cement mortar owing to higher pozzolanic activity. [ABSTRACT FROM AUTHOR]

Background & objectives: The epidemiology of dengue fever (DF) is complex in the Indian subcontinent as all the four serotypes are circulating. This study reports observations on dengue cases from a virus diagnostic laboratory of a north Indian tertiary care hospital catering to areas in and around Lucknow, Uttar Pradesh. Methods: Serum samples were obtained from suspected cases of dengue referred to the virus diagnostic laboratory during 2011 to 2013, and detailed history was taken on a pre-structured datasheet. All samples were tested for anti-dengue virus (DV) IgM antibodies and DV-non structural protein 1 antigen (NS1Ag) by ELISA. NS1Ag positive samples were tested further by conventional RT-PCR for DV-RNA detection and serotyping. Results: Of the 4019 suspected patients of dengue, 886 (22%) showed laboratory evidence of dengue virus infection. Of these, 19, 17 and 27 per cent were positive in 2011, 2012 and 2013, respectively. Children and adults were similarly affected by dengue in all the three years. Males were more commonly affected than females. The predominant DV serotype detected was DV-2, DV-1 and DV-3 in 2011, 2012 and 2013, respectively. DV-4 serotype was not detected. About half the cases positive for DV infection, showed symptoms of dengue with warning signs/ severe dengue. A distinct seasonality with increase in number of dengue cases in the post monsoon period was seen. Interpretation & conclusions: Change in circulating serotype of dengue virus; a distinct adult dengue involvement; and a remarkable number of cases presenting with severe dengue manifestations are the main findings of this study. [ABSTRACT FROM AUTHOR]