A.P. Sugunan’s scientific contributions

The Jarwa, one of the four Negrito tribes of these islands, inhabit the west coast of the South and Middle Andamans district have been living in isolation for several centuries and recently they started coming out of the jungles shedding their hostility. Since than several disease outbreaks have been reported in these classical tribe. An attempt was made to screen the sera collected during one such outbreaks showed the prevalence of leptospirosis in these tribes. MAT, IgM and IgG ELISA were used for the detection of Leptospiral antibodies among Jarwas samples. Among 40 sera samples collected during a febrile out break, 40% of the samples showed antibodies against leptospirosis by MAT. Icterohaemorrhagiae was the major serogroup for the cause of leptospirosis among Jarwas and was followed by Hebdomadis and Pyrogenes. The highest titre observed was 1:320 against serogroup Icterohaemorrhagiae. IgM ELISA showed a seroprevalence rate of 20% where as IgG ELISA showed a prevalence of 63%. The highest titre observed for I gM ELISA was 1:320 and for IgG it was 1:160. The environment of the jungle where they live in is favorable for survival of leptospirosis and their association with domestic and wild animal has to be studied which could be one of the source for acquiring leptospiral infection.

When irradiated with energetic electrons near room temperature, Li2O single crystals exhibit metallic Li colloids, as shown by conduction electron spin resonance (CESR) and 7Li-nuclear magnetic resonance (NMR) experiments. These colloids are established as being of two types represented by two superimposed signals in a CESR spectrum: a Lorentzian line corresponding to small colloids (≪1 μm in diameter); and a Dysonian to much bigger (>1 μm) aggregates. We present isochronal annealing experiments and CESR experiments above room temperature in the range 290–590 K, in which melting of the Li metal is observed. When investigating such colloid-containing crystals by 7Li-NMR we observe a Knight-shifted signal to the metallic colloids, which consists of two components. This duality is due to a result either of the presence of two types of colloids, or of one type having two different orientations inside the crystal. In the latter case the colloids should exhibit anisotropic properties as was already suggested by dielectric constant measurements. Thin Li2O crystals investigated by transmission optical microscopy after irradiation contained disc-like structures of up to 30 μm in diameter, which possibly represent oxygen gas bubbles surrounded by metallic Li corresponding to the large colloids detected by magnetic resonance: this confirms the strong anisotropy of the metallic colloids.