Effect of TiO2 nanotube length and lateral tubular spacing on photovoltaic properties of back illuminated dye sensitized solar cell

The main objective of this study is to show the effect of TiO₂ nanotube length, diameter and intertubular lateral spacings on the performance of back illuminated dye sensitized solar cells (DSSCs). The present study shows that processing short TiO₂ nanotubes with good lateral spacings could significantly improve the performance of back illuminated DSSCs. Vertically aligned, uniform sized diameter TiO₂ nanotube arrays of different tube lengths have been fabricated on Ti plates by a controlled anodization technique at different times of 24, 36, 48 and 72?h using ethylene glycol and ammonium fluoride as an electrolyte medium. Scanning electron microscopy (SEM) showed formation of nanotube arrays spread uniformly over a large area. X-ray diffraction (XRD) of TiO₂ nanotube layer revealed the presence of crystalline anatase phases. By employing the TiO₂ nanotube array anodized at 24?h showing a diameter ??80?nm and length ??1·5???m as the photo-anode for back illuminated DSSCs, a full-sun conversion efficiency (??) of 3·5 % was achieved, the highest value reported for this length of nanotubes.     

RECOVERY AND GROWTH OF SOME FOOD-BORNE PATHOGENS IN IRRADIATED LOW AND HIGH FAT FISH DURING STORAGE AT 2-4C

This report presents results of the investigations carried out to understand the role of fat levels in fish on postirradiation recovery/survival and growth of four pathogens generally encountered in seafoods. Fish of low [golden anchoy, (Coillia dussumierij, 0.39%] as well as high fat [Indian sardine , (Sardinella longiceps), 7.1 %] content (with endogenous biota were inoculated separately with cells of Listeria monocytogenes 036 , Yersinia enterocolitica 5692 , Bacillus cereus and Salmonella typhimurium; and irradiated at doses of 1 and 3 kGy. The number of viable organisms for each was monitored for two weeks at 2-4C on appropriate selective media. The four pathogens studied exhibited variation in their ability to recover from radiation damage as evidenced in terms of lag period; but their recovery and subsequent growth was not influenced by the fat levels offish. No increased growth of any of the pathogens tested was evidenced in irradiated fish, when compared with nonirradiated one .     

MICROBIOLOGICAL QUALITY OF THE DAIRY PRODUCT PEDHA AND ITS IMPROVEMENT USING GAMMA RADIATION

Eighteen pedha samples procured from A and B grade retail shops were examined for their overall microbiological quality and for the presence of foodborne pathogens viz. Staphylococcus aureus, Salmonella sp., Coliforms , Listeria monocytogenes, Yersinia enterocolitica and Bacillus cereus. The microbiological quality of pedha samples from B grade shops was very poor as compared to pedha from A grade shop as evidenced by the very high total bacterial counts (6 × 10⁷ cfu/g), high counts of S. aureus (as high as 7 × 10⁶ cfu/g) and presence of coliforms and Listeria and Yersinia sp. in 33% of the samples. All the samples from A grade shops were also positive for S. aureus though negative for coliforms , Yersinia, Salmonella, Listeria and B. cereus. Gamma irradiation of pedha at a dose of 3kGy at 0C reduced overall bacterial load by five log cycles and S. aureus and coliforms could be totally eliminated. However, 5 kGy dose was necessary to eliminate S. aureus if the initial number exceed 1 × 10⁵ cfu/g. Inoculated pack studies confirmed that 3 kGy dose was sufficient for the complete elimination of up to 1 × 10⁵ cfu/g of S. aureus. A dose of 3 kGy had minimal effect on the sensory quality of pedha and even pedha samples irradiated at 5 kGy dose were acceptable. Treatment with 3 kGy dose of gamma radiation totally eliminated S. aureus and coliforms in pedha, thereby ensuring their microbial safety.     

N-NITROSOPROLINE AND N-NITROSOSARCOSINE IN ESTONIAN FOODSTUFFS

The N-nitrosoamino acids (NNA) N-nitrosoproline (NPRO) and N-nitrososarcosine (NSAR) are precursors of the carcinogenic N-nitrosamines. Methodology using gas chromatography for their determination and data on their contents in 52 food products are presented. Food products consisted of smoked meats (12), smoked (9) and boiled (11) sausage, cheese (10), fish (7) and beer (3). Results showed that NNA formed during processing, particularly in meat, where levels of NPRO were as high as 353μg/kg. The compounds accumulated in the adipose tissue and surface portion of the product. Smoking caused increased formation of NPRO, while the use of liquid smoke minimized it. NPRO in meat products in natural casings was higher than in synthetic ones, and frying of boiled sausage and hams further enchanced NPRO formation. Like meat, smoked cheese and fish showed consistently higher NNA levels than the non-smoked products. These data indicate means of reducing NNA contents in foods by modification of processing techniques .