Effect of variation of dielectric constant on the magnetic field modulation of exciplex luminescence

The effect of variation of dielectric constant on the relative magnetic field effect in singlet luminescence has been studied using a typical exciplex system at a saturating field. The study indicates strong specificity in the perturbation of the magnetic field effect by alcoholic solvents. In contrast to alcohols where relative singlet magnetic field effect is of the order of 2% only, the magnetic field effect in non-alcoholic medium reaches as high as 9%. Moreover, dielectric constant variation in alcohols yields curves which are distinctly different from those in non-alcoholic media. It turns out that this dependence of magnetic field effect on dielectric constant is similar in all non-alcoholic solvent mixtures. An analytical study based on Hong and Noolandi's solution of Smoluchowski equation has been made. Derived expressions can interpret experimental curves reasonably well

Radiationless transitions in trivalent lanthanide ions embedded in solids

Radiationless transitions in lanthanide ions embedded in glassy and crystalline hosts have been briefly reviewed. The correlations of multiphonon relaxation rates with energy gaps, vibrational frequencies, temperatures and electronic symmetries have been discussed. The essence of various theories, such as Nth order methods, non-adiabatic Hamiltonian method, dynamic coupling model has also been presented

Molecular and morphological confirmation of \u3cem\u3eIsometrus maculatus\u3c/em\u3e (DeGeer, 1778) (Scorpiones: Buthidae) from Northeast India and East Asia

We present molecular data on Isometrus maculatus (DeGeer, 1778) for the first time from India, Japan, and Taiwan based on the COI gene and justify the cosmopolitan nature of this species. We also address the first population of I. maculatus found in Teliamura, Tripura, India and give its detailed description and comparison with the rest of the Isometrus species from India. Furthermore, we discuss the justification for considering Sri Lanka as the true home of I. maculatus

Unusual premonsoon eddy and Kelvin wave activities in the Bay of Bengal during Indian Summer monsoon deficit in June 2009 and 2012

An investigation of the eddy and coastal Kelvin wave activities in the Bay of Bengal (BoB) is carried out during premonsoon season in two years of Indian summer monsoon deficit in June (2009 and 2012), occurred in the recent warming hiatus period. Using altimeter observations, our study reveals that over the northern BoB cyclonic eddy kinetic energy is reduced by 35% and 50% from the climatology during premonsoon seasons in 2009 and 2012, respectively, while the cyclonic eddy area is reduced by 18% and 24%, respectively. A concurrent reduction is observed in the first upwelling Kelvin wave (uKW) activities in the eastern equatorial Indian Ocean as well as in the coastal BoB for these years. The reduction in the generation of the first uKW in the eastern equatorial Indian Ocean is attributed to the westerly wind anomalies in January-March of these years. Additionally, meridional wind stress anomalies during March-April in these years are found to be southerly, causing anomalous coastal downwelling in the eastern rim of BoB. This coastal downwelling blocks the propagation of the first uKW. The decrease in the first uKW activities in the coastal waveguide of the BoB reduces the radiation of upwelling Rossby waves, thereby decreasing the cyclonic eddy activities in the northern BoB. The results from this letter could be helpful for further understanding of upper ocean mixing processes in the BoB during monsoon deficit years

Unusual Premonsoon Eddy and Kelvin Wave Activities in the Bay of Bengal During Indian Summer Monsoon Deficit in June 2009 and 2012

An investigation of the eddy and coastal Kelvin wave activities in the Bay of Bengal (BoB) is carried out during premonsoon season in two years of Indian summer monsoon deficit in June (2009 and 2012), occurred in the recent warming hiatus period. Using altimeter observations, our study reveals that over the northern BoB cyclonic eddy kinetic energy is reduced by 35% and 50% from the climatology during premonsoon seasons in 2009 and 2012, respectively, while the cyclonic eddy area is reduced by 18% and 24%, respectively. A concurrent reduction is observed in the first upwelling Kelvin wave (uKW) activities in the eastern equatorial Indian Ocean as well as in the coastal BoB for these years. The reduction in the generation of the first uKW in the eastern equatorial Indian Ocean is attributed to the westerly wind anomalies in January-March of these years. Additionally, meridional wind stress anomalies during March-April in these years are found to be southerly, causing anomalous coastal downwelling in the eastern rim of BoB. This coastal downwelling blocks the propagation of the first uKW. The decrease in the first uKW activities in the coastal waveguide of the BoB reduces the radiation of upwelling Rossby waves, thereby decreasing the cyclonic eddy activities in the northern BoB. The results from this letter could be helpful for further understanding of upper ocean mixing processes in the BoB during monsoon deficit years

Pyrite Textures, Trace Elements and Sulfur Isotope Chemistry of Bijaigarh Shales, Vindhyan Basin, India and Their Implications

The Vindhyan Basin in central India preserves a thick (~5 km) sequence of sedimentary and lesser volcanic rocks that provide a valuable archive of a part of the Proterozoic (~1800-900 Ma) in India. Here, we present an analysis of key sedimentary pyrite textures and their trace element and sulfur isotope compositions in the Bijaigarh Shale (1210 ± 52 Ma) in the Vindhyan Supergroup, using reflected light microscopy, LA-ICP-MS and SHRIMP-SI, respectively. A variety of sedimentary pyrite textures (fine-grained disseminated to aggregates, framboids, lags, and possibly microbial pyrite textures) are observed reflecting quiet and strongly anoxic water column conditions punctuated by occasional high-energy events (storm incursions). Key redox sensitive or sensitive to oxidative weathering trace elements (Co, Ni, Zn, Mo, Se) and ratios of (Se/Co, Mo/Co, Zn/Co) measured in sedimentary pyrites from the Bijaigarh Shale are used to infer atmospheric redox conditions during its deposition. Most trace elements are depleted relative to Proterozoic mean values. Sulfur isotope compositions of pyrite, measured using SHRIMP-SI, show an increase in δ34S as we move up stratigraphy with positive δ34S values ranging from 5.99% (lower) to 26.08� (upper). We propose limited sulphate supply caused the pyrites to incorporate the heavier isotope. Overall, we interpret these low trace element signatures and heavy sulfur isotope compositions to indicate relatively suppressed oxidative weathering on land during the deposition of the Bijaigarh Shale

Barrier layer characteristics of the Indian Ocean sector of the Southern Ocean during austral summer and autumn

Barrier layer in the Enderby Basin (EB) and the Australian Antarctic Basin (AAB) during late summer (December & January) and early autumn (February & March) are studied using temperature-salinity profiles collected between 1975 and 2012. A distinct difference in mixed layer depth is observed over the eastern (i.e. the EB) compared to western (i.e. the AAB) side of the Kerguelen Plateau (KP), with shallower mixed layer depths on the eastern side. Mixed layers show an increase from less than 50 m–∼150 m from south to north in the EB. During autumn, the wind strengthens and the upwelling over the eastern side of the KP (i.e. in the AAB) weakens, resulting in deeper mixed layers (∼80 m–100 m) compared to summer. During summer, deep barrier layer (BL) values (∼50 m or more) with porosity less than 0.3 was seen over the Chun Spur region. The fresher melt water from the EB brought by the Fawn trough current (FTC) across the KP may be responsible for the occurrence of BL over the region. During autumn, BL is spread over a much larger area around the Chun Spur, which could be attributed to the increase in the strength of FTC due to the intensification of wind over the region. A thorough study of BL condition over this region is required to understand the processes behind the discrepancies in sea ice conditions

Theory of ligand-induced non-radiative relaxation in lanthanide complexes

A theory of ligand-induced non-radiative relaxation in rare earth crystals has been developed within the framework of the dynamic coupling model. We have analysed the role played by the following important guiding factors determining the rate of the fN-fN radiationless transition: (a) the states with opposite parity, (b) the electronic symmetries of the initial and the final states of the rare ion, (c) the energy gaps between the involved states, (d) the symmetry of the crystal field, (e) the internal promoting and accepting modes of the ligand and (f) the dipole moment and polarisability of the ligand