Spatial variation of coda wave attenuation in the Southern Indian Shield and its implications

During the recent past the Indian peninsular shield has experienced six damaging earthquakes of M 5.4-7.7 and compelled to readdress our understanding of the seismic attenuation characteristics for better evaluation of the seismic hazards in the so-called stable shield. We have performed the seismic attenuation study using coda waves of the broadband network from 1995 to 2009 for the shield region. About 400 local earthquakes M 2.5-4.0 within an epicentral distance of 250km are used in this study. The broadband seismic stations established are in different geological provinces, such as the Archaean Dharwar craton, the southern granulite terrain, the Proterozoic Cuddapah basin, the Godavari graben, the Cretaceous-Eocene Deccan volcanic province and in the Cambay basin. This allows us to understand the fluctuation of Q0 in terms of spatial variations in the geologic and tectonic provinces. The results reflect a ubiquitous observation of frequency dependence of Qc in the different geologic provinces. The rift basins exhibit lower Q0, which suggests higher attenuation due to a more heterogeneous structure. Higher Q0 in the western Dharwar craton infers lower attenuation. Similarly the Deccan volcanic province is characterized by significantly higher Q0. The results show a good correlation with the observed heat flow. The study fills an important gap in knowledge about the Q factor as well as of crustal attenuation conditions in the whole southern peninsular shield of India

Special variation of coda wave attenuation in the Southern Indian Shield and its implications

Seamounts represent crust-mantle activities and are areas of petrological deviations, biodiversity, seismicity and hydrothermal events. An estimated ~50 million tons/year of basalts are required to produce seamounts suggesting intense oceanic volcanism. Seamounts either occur as chains perpendicular to the ridge or as isolated entities or in clusters. Seamounts may host basalts, hyaloclastites, gabbros and serpentinites and these variants perhaps evolve from multiple melting domains as a consequence of large-scale thermal structure and mantle lithology. Nonhotspot seamounts on a young, thin and hot lithosphere host tholeiites whereas the plume related ones on thick, older lithosphere may be either tholeiitic or alkaline. Seamounts may bear hydrothermal deposits (Fe, Mn, Co) rare metals and phosphorites. The resistance of seamounts to subduction could trigger slides; while shearing of seamounts buried in subduction zones leads to seismicity, both of which could cause tsunamis. Seamounts greatly affect the circulation patterns and currents, which in turn influence the surrounding biota. We review here the seamounts in terms of discovery, characteristics, distribution and their influence on the marine environment

Isolation and characterization of plumbagin (5- hydroxyl- 2- methylnaptalene-1,4-dione) producing endophytic fungi Cladosporium delicatulum from endemic medicinal plants

The rationale of the present study was to isolate and identify endophytic fungi from endemic medicinal plants in Eastern Ghats and screened for antimicrobial potential of isolated fungal crude extracts. A total of 329 endophytic strains were isolated from 600 infected leaves and stem cuttings of endemic plants. The diversity and species richness was analyzed statistically and found to be higher in leaf segments than in stem segments. From isolated fungal strains, Cladosporium delicatulum was identified using molecular identification methods and selected as the most potent plumbagin-producing endophytic strain. Further the isolation and structural characterization of endophytic fungal plumbagin (5-hydroxyl-2-methylnaptalene-1,4-dione) was purified and confirmed through spectroscopy analysis. The molecular weight was determined as m/z 188 in positive mode by ESI-MS, which confirmed to be plumbagin which potentially inhibited all tested pathogens, therefore the endophytic fungal plumbagin from the current study possesses important biological activities against pathogens. Keywords: Endophytic fungi, Cladosporium delicatulum, Structural characterization, Plumbagin, Biological activitie

Conservation of wild orchids in Sri Krishnadevaraya University Botanic Garden, Anantapur, Andhra Pradesh, India

Sri Krishnadevaraya University Botanic Garden currently harbouring 32 species of wild orchids collected from the Eastern Ghats of Andhra Pradesh are listed in this paper

Tb3+ added sulfamic acid single crystals with optimal photoluminescence properties for opto-electric devices

Terbium doped Sulfamic Acid (Tb3+:SA) single crystals were grown successfully by the slow evaporation solution (SEST) technique and the unidirectional method. The lattice parameters and the functional group were identified for the grown crystal by using single crystal X-ray diffraction and Fourier transform infra-red spectroscopy (FTIR), respectively. High resolution X-ray diffraction analysis (HRXRD) shows the crystalline perfection of the grown crystal. The optical transparency and band gap of the grown crystals were determined from UV-VIS spectroscopy. TG/DTA studies reveal that the grown crystals are thermally stable up to 190 °C. The frequency dependent dielectric properties were studied at different temperatures. Vickers micro hardness studies show that Tb3+:SA belongs to the class of soft materials. Second harmonic generation efficiency of Tb3+:SA is 3.7 times that of pure KDP. The photoluminescence emission and excitation studies of Tb3+:SA single crystals indicated the green emission at 543 nm, which is due to a transition from the 5D4 excited state to the 7F5 ground state