Growth and characterisation of certain organic crystals

The thesis presents the results of the investigations on the crystallisation ‘behaviour, detect structure end electrical properties of certain organic crystals---phthslic snhydride end potsssiun scid phthalate Hollow crystals of phthalic snhydride were grown from vapour. the norpholog of these hollow crystals were studied in detail and s. mechanism for their growth has been proposed. A closed crystal—vapour system was used to study the basal plane growth of the whiskers and the sequential growth, observed, confirmed the mechanism suggested for hollow crystals. The dendritic crystals of phthslic enhydride were grown, both iron the melt and solution. The observed morphologies of these dendrites ere described. Bpherulites of phthalic anhydride have been grown by the artificial initiation of nucleation, from melt and solution. The variation of the substructure oi’ these spherulites with the growth tenperature wee investigated. The spherulitic filll having ribbon substructure were etched to reveal dislocations. A mechanism for the formation of the observed etch pattern has been suggested. the slip occurring in these ribbons were studied and the results are presented

Metabolic Efficiency of Penaeus Indicus H.Milne Edwards Under Different Salinity Stress Conditions

The investigation was aimed at establishing the effect of salinity on the culture performance of Peneus Indicus in pokkali fields and also to find out the growth performance of the shrimp at varying salinities. The experiments were laid out at Rice Research Station, Vyttila of Kerala Agriculture University in three fields of area 1000 m2 each. The results of the experiment clearly establish that shrimps when stocked at higher salinity (20-25 ppt) for 45 days has given higher growth, survival and production than those stocked at lower salinity (10-15 ppt) in all the above parameters even when the culture experiment was maintained for longer periods in lower salinity. In the prolonged culture experiments conducted for 120 days in 10-25 ppt salinity, the results were poorer than the short period culture in higher salinity and the production values similar to lower saline culture. This clearly establishes the importance of salinity as an ecological factor which will have profound influence in shrimp farming operations.

“Stress Responses of Stinging Catfish Heteropneustes fassilis (Bloch) to Organophosphorus Insecticide Monocrotophos”

Poisoning by pesticides from agricultural fields is a serious water pollution problem and its environmental long-term effect may result in the incidence of poisoning of fish and other aquatic life forms (jyothi and Narayan, 1999). Fishes like Heteropneustesfbssilis and C/arius batrac/nus are especially prone to serious pesticide pollution as their habitat is mostly the agriculture area. Though only few studies are conducted in this area, it can be assessed from the local information that, population of such fish is on the verge of vulnerability due to extensive use of pesticides. The knowledge of sublethal effects of xenobiotic compounds on hematological parameters, enzyme activities and metabolite concentrations is very important to delineate the fish health status and provide a future understanding of ecological impacts. These pesticides act by causing inhibition of cholinesterase enzymes (ChE) by formation of enzyme inhibitor complex (O'Brien, 1976) and damaging the nervous system. These effects may result in metabolic disorders. Associated to cholinesterase activities, a study of other enzymes such as phosphatases and aminotransferases close to intermediary metabolite determination provides a wider view of metabolism. Interest in toxicological aspects has grown in recent years and research is now increasingly focused on mechanistic aspects of oxidative damage and cellular responses in biological system. The term ‘biomarker’ is generally used in a broad sense to include almost any measurement reflecting an interaction between a biological system and a potential hazard, which may be chemical, physical or biological (WHO, 1993). As biomarker stands for immediate responses, they are used as early warning signals of biological effects caused by environmental pollutants. The present work attempts to assess the toxicity of organophosphorus insecticide monocrotophos on the experimental organism selected for this study namely stinging catfish (Heteropneustesfossi/is) (Bloch), and to probe into the stress responses of the organism

An Investigation into OccasionalWhite Spot Syndrome Virus Outbreak in Traditional Paddy CumPrawn Fields in India

A yearlong (September 2009–August 2010) study was undertaken to find out possible reasons for occasional occurrence of White Spot Syndrome Virus (WSSV) outbreak in the traditional prawn farms adjoining Cochin backwaters. Physicochemical and bacteriological parameters of water and sediment from feeder canal and four shrimp farms were monitored on a fortnightly basis. The physicochemical parameters showed variation during the two production cycles and between the farms studied. Dissolved oxygen (DO) content of water fromfeeder canal showed low oxygen levels (as low as 0.8mg/L) throughout the study period. There was no disease outbreak in the perennial ponds. Poor water exchange coupled with nutrient loading from adjacent houses resulted in phytoplankton bloom in shallow seasonal ponds which led to hypoxic conditions in early morning and supersaturation of DO in the afternoon besides considerably high alkaline pH. Ammonia levels were found to be very high in these ponds.WSSV outbreak was encountered twice during the study leading to mass mortalities in the seasonal ponds. The hypoxia and high ammonia content in water and abrupt fluctuations in temperature, salinity and pH might lead to considerable stress in the shrimps triggeringWSSV infection in these traditional ponds