Effect of Spatially Varying Thermal Conductivity on the Magnitude of Thermal Stress in Brittle Ceramics Subjected to Convective Heating

The effect of a spatial variation of the thermal conductivity on the magnitude of the maximum tensile thermal stress in a solid circular cylinder subjected to sudden convective heating was calculated by finite element methods. The general results show that by lowering the thermal conductivity in the surface region of the cylinder, the magnitude of the maximum tensile thermal stress at the center of the cylinder is reduced significantly. The negative temperature dependence of the thermal conductivity in dielectric materials, which indirectly creates a spatial variation in thermal conductivity, also causes a significant decrease in the magnitude of the tensile thermal stresses, as demonstrated by a numerical example for aluminum oxide. It is also shown that a spatial variation in thermal conductivity can significantly affect the time to maximum tensile stress as well.     

INCIDENCE OF LISTERIA SPECIES IN INDIAN SEAFOODS AND MEAT

Thirty eight samples of fresh, frozen and dry seafoods and 27 samples of fresh and cold stored meat and meat products obtained from retail shops were examined for the presence of Listeria spp. Direct plating of the sample homogenate on Listeria Selective Agar (LSA) was compared with the two step enrichment method devised by Hao et al. for detecting Listeria spp. in vegetables. We report that modification of this methodology involving cold enrichment for 48 h in Brain Heart Infusion (BHI) at 10C followed by enrichment at 37C in Listeria enrichment broth (LE) resulted the enumeration of a large population of Listeria from flesh foods. Listeria isolates from fish and meat were identified by employing the cultural methods given in modified version of the Bacteriological Analytical Manual (Lovett and Hitchins 1988). Listeria spp. from seafoods were identified, with the order of predominance as L. grayi, L. innocua, L. murrayi, L. seeligeri. Samples of meat and their products were found to be contaminated mainly with L. innocua and L. murrayi. In contrast, screening of an independent batch of 20 fish and meat samples by adopting the PHLS (UK) method revealed predominance of L. grayi and L. seeligeri in fish and presence of additional species like L. seeligeri, L. ivanovii and L. welshimeri in meat products. None of the methods however could detect incidence of L. monocytogenes in any of the samples tested from local market in Bombay.     

THE NATURE OF TOXINS PRODUCED BY BACILLUS CEREUS BIS-59

Eight strains of Bacillus spp. were examined for production of toxin(s). Three strains of Bacillus cereus produced toxins lethal to mice. The culture filtrate of Bacillus cereus BIS-59 contained two lethal toxins. One was a hemolysin and the other a nonhemolytic glycoprotein. The growth of cells in fresh beef infusion broth resulted in high toxin production, compared to growth in tryptone-glucose-yeast extract or nutrient broth. Separate identities for the two toxins from B. vcereus BIS-59 were established on the basis of hemolytic activity, separation profiles on Sephadex gel filtration, responses to heat and radiation and kinetics of their production during the growth of the organism.     

Correlation of LANDSAT data with surface and subsurface information—a synergistic,quantitative approach to oil exploration in Gujarat,India

An attempt has been made to correlate the optical-density values derived from LANDSAT imagery of a part of the oil field areas of Gujarat, India, with all the available surface and subsurface information by employing a mathematical model specifically developed for this purpose. An excellent two-dimensional linear correlation exists between optical-density values of tonal anomaly areas and gravity and magnetic values. A high correlation coefficient factor was also obtained when a multiple correlation of different parameters with optical density was carried out. This study has proved that such a synergistic, quantitative approach is much more useful in oil exploration than simple visual interpretation of remotely sensed data.     

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.     

OPTIMIZATION OF STIFFENED LAMINATED COMPOSITE PLATES WITH FREQUENCY CONSTRAINTS

The problem considered in this paper concerns the maximization of frequencies of stiffened laminated composite plates subject to frequency separation constraints and an upper bound on weight. The number of plies of given fiber orientations and the stiffener areas form the two sets of design variables and the problem belongs to the class of nonlinear mixed integer programming ( NMIP) Several efficiency measures are adopted to reduce the computational cost of the optimization process. As a result of these efficiency measures, structural optimization of laminated composite plates using nonlinear mixed integer programming becomes a viable alternative to using the conventional practice of obtaining designs by an ad hoc rounding off of the continuous designs.     

Discrimination of winter crops using temporal spectral profiles

The possibility of discriminating three winter crops namely wheat (Triticum aestivum linn, emend Thell), Chickpea (Cicer arietinum L.) and mustard (Brasica compestris), on the basis of their temporal spectral profile, has been studied. The profile for each crop has a characteristic overall form showing different profile duration, amplitude, rise and fall time. The profile can be used to discriminate spectrally the three Indian winter crops which are grown in the same season.     

Monitoring changes in ecology in the Kudremukh mining region

Iron-ore deposits of the Kudremukh region in Karnataka State, India, were discovered at the beginning of the present century. These deposits have only recently begun to be exploited by the Kudremukh Iron Ore Company. As a result the land cover, particularly the grassland areas, are becoming disturbed.

This paper is the outcome of a joint study undertaken by three central and state government agencies in India for monitoring the ecological changes in the above region. Multitemporal LANDSAT MSS data together with aerial CIR photographs and ground data were used for the study. The study was mainly addressed to the mapping of land-cover changes, which is one of the most important indicators of ecological monitoring.     

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 .