Showing papers in "Journal of the Indian Institute of Science in 1999"

Microbial exopolysaccharides: Effect on corrosion and partial chemical characterization

Abstract: Test panels of mild steel were deployed in the surface waters of the Dona Paula Bay over a period of 28 days. Biofilm material on mild steel panels was analyzed for biofilm biomass (as organic carbon), exopolysacchande (EPS) production and corrosion rates. Concentrations of biofilm carbon and BPS increased whereas corrosion rate of mild steel decreased over the period of immersion Corrosion of mild steel showed significant inverse relationships with biofilm carbon and BPS. This implies that biofilm organic matter inhibits the corrosion of mild steel. A few bacterial cultures isolated from the microfouling material were screened for EPS production. One of the cultures identlfied as vibrio sp produced the highest amount of exopolysaccharides. Production, isolation and charactenzation of the exopolysaccharides produced by the bactenum were evaluated. Exopolysaccharide was produced in all the phases of growth and with all the substrates tested. Production of the exopolysnccharide was influenced by source and concentration of carbon and nitrogen as well as concentration of phosphate in the growth medium. Ex:opolysacchacide is a heteropolysaccharide- containing glucose as the most abundant monosaccharide and mannose, xylose. galactose and fucose as minor sugars. The presence of uronic acid and pyruvate indicates the acidic nature of the polysacchande.

Marine biofouling and its control with particular reference to condenser-cooling circuits of power plants - An overview

Abstract: Biofouling has been a major problem to ships, offshore platforms, marine intakes, data buoys and to almost all marine technology ventures. With the emergence of multi-megawatt power plants during the last three decades more and more nuclear and thermal power stations are turning to the sea to meet their cooling water needs. The use of sea water for condenser cooling has brought the problem of marine biofouling into power-plant mtake and discharge conduits as well as heat exchangers. The problem is paticularly severe in tropics and even more so in ocean thermal energy conversion (OTEC) plants wherein the sell, water flows through evaporator as well as condensers. While many approaches are followed for control of biofouling involving chemical, antifouling paints. foul-release coalings, electric charges, velocity and heat, there is no method which can totally prevent It The paper reviews the state of the art in this area largely based on experience from a power station at Kalpakkam, south of Chennai.

Ploughing a lonely furrow: the curious case of the P1 promoter in the osmotically regulated proU operon of Escherichia coli

Abstract: Evidence is reviewed for the existence of a a-controlled promoter for the osmotically regulated proU operon in Escherichia coli and Salmonella typhimurium. Expression from the promoter is rendered cryptic in both the organisms, most likely by a mechanism of factor- dependent termination of transcription (attenuation) in the region upstream of the structural genes. The possible role of PI in proU expression and regulation is discussed.

Projection on convex sets approach to design of near- equiripple NPR banks

Abstract: A projection on convex sets (POeS) approach to design an M-channel near-perfect reconstruction (NPR) banks is described. The method is conceptually simpler than previously reported methods and allows the design of high-stopband filterbanks.