Length–weight relationship for three estuarine fish species from the Chilika Lagoon, India

501-502We investigated the length–weight relationships (LWRs) for Sillago vincenti McKay, 1980, Triacanthus nieuhofii Bleeker, 1852 and Terapon puta Cuvier, 1829 from the Chilika lagoon in India. Sampling was conducted in central sector of the Chilika from April to November of 2017. Specimens were caught in mono-filament gill nets of mesh size 28-36 mm and fixed set nets of mesh size 16-24 mm. From LWR estimation, the determined intercept (a value) and slope (b value) were found to be 0.007 and 3.039 for Sillago vincenti, 0.010 and 2.997 for Triacanthus nieuhofii and 0.008 and 3.156 for Terapon puta. The relationships between length and weight in all three species were highly correlated (p <0.05)

Switching of the topologically trivial and non-trivial quantum phase transitions in compressed 1T-TiTe2: Experiments and Theory

We report the structural, vibrational and electrical transport properties up to 16 GPa of the 1T-TiTe2, a prominent layered 2D system, which is predicted to show a series of topologically trivial - nontrivial transitions under hydrostatic compression. We clearly show signatures of two iso-structural transition at 2 GPa and 4 GPa obtained from the minima in c/a ratio concomitant with the phonon linewidth anomalies of Eg and A1g modes at around the same pressures, providing strong indication of unusual electron-phonon coupling associated to these transitions. Resistivity presents nonlinear behavior over similar pressure ranges providing a strong indication of the electronic origin of these pressure driven isostructural transitions. Our data thus provide clear evidences of topological changes at A and L point of the Brillouin zone predicted to be present in the compressed 1T-TiTe2. Between 4 GPa and 8 GPa, the c/a ratio shows a plateau suggesting a transformation from an anisotropic 2D layer to a quasi 3D crystal network. First principles calculations suggest that the 2D to quasi 3D evolution without any structural phase transitions is mainly due to the increased interlayer Te-Te interactions (bridging) via the charge density overlap. In addition to the pressure dependent isostructural phase transitions, our data also evidences the occurrence of a first order structural phase transition from the trigonal (P-3m1) phase at higher pressures. We estimate the start of this structural phase transition to be 8 GPa and the symmetric of the new high-pressure phase to be monoclinic (C2/m).Comment: 22 pages, 11 Figures, 2 Table

Structural, vibrational, and electrical properties of 1T-TiTe2 under hydrostatic pressure: Experiments and theory

We report the structural, vibrational, and electrical transport properties up to ∼16 GPa of 1T -TiTe2, a prominent layered 2D system. We clearly show signatures of two isostructural transitions at ∼2 GPa and ∼4 GPa obtained from the minima in c/a ratio concomitant with the phonon linewidth anomalies of Eg and A1g modes around the same pressures, providing a strong indication of unusual electron-phonon coupling associated with these transitions. Resistance measurements present nonlinear behavior over similar pressure ranges shedding light on the electronic origin of these pressure-driven isostructural transitions. These multiple indirect signatures of an electronic transition at ∼2 GPa and ∼4 GPa are discussed in connection with the recent theoretical proposal for 1T -TiTe2 and also the possibility of an electronic topological transition from our electronic Fermi surface calculations. Between 4 GPa and ∼8 GPa, the c/a ratio shows a plateau suggesting a transformation from an anisotropic 2D layer to a quasi-3D crystal network. First-principles calculations suggest that the 2D to quasi-3D evolution without any structural phase transitions is mainly due to the increased interlayer Te-Te interactions (bridging) via the charge density overlap. In addition, we observed a first-order structural phase transition from the trigonal (P3¯m1) to monoclinic (C2/m) phase at higher pressure regions. We estimate the start of this structural phase transition to be ∼8 GPa and also the coexistence of two phases [trigonal (P3¯m1) and monoclinic (C2/m)] was observed from ∼8 GPa to ∼16 GPa