192 research outputs found

    Extraction of tidal channel networks from airborne scanning laser altimetry and aerial photography

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    The study of the morphodynamics of tidal channel networks is important because of their role in tidal propagation and the evolution of salt-marshes and tidal flats. Channel dimensions range from tens of metres wide and metres deep near the low water mark to only 20-30cm wide and 20cm deep for the smallest channels on the marshes. The conventional method of measuring the networks is cumbersome, involving manual digitising of aerial photographs. This paper describes a semi-automatic knowledge-based network extraction method that is being implemented to work using airborne scanning laser altimetry (and later aerial photography). The channels exhibit a width variation of several orders of magnitude, making an approach based on multi-scale line detection difficult. The processing therefore uses multi-scale edge detection to detect channel edges, then associates adjacent anti-parallel edges together to form channels using a distance-with-destination transform. Breaks in the networks are repaired by extending channel ends in the direction of their ends to join with nearby channels, using domain knowledge that flow paths should proceed downhill and that any network fragment should be joined to a nearby fragment so as to connect eventually to the open sea

    Photoemission studies of the near Fermi level spectral weight shifts in FeSe1-xTex superconductor

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    Our valence band photoelectron spectroscopic studies show a temperature dependent spectral weight transfer near the Fermi level in the Fe-based superconductor FeSe1-xTex. Using theoretical band structure calculations we have shown that the weight transfer is due to the temperature induced changes in the Fe(Se,Te)4 tetrahedra. These structural changes lead to shifts in the electron occupancy from the xz/yz and x2-y2 orbitals to the 3z2-r2 orbitals indicating a temperature induced crossover from a metallic state to an Orbital Selective Mott (OSM) Phase. Our study presents the observation of a temperature induced crossover to a low temperature OSM phase in the family of Fe chalcogenides.Comment: 10 pages, 4 figure

    Investigation of correlation effects in FeSe and FeTe by LDA + U method

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    Correlation effects are observed strong in Iron chalcogenides superconductors by experimental and theoretical investigations. We present a comparative study of the influence of Coulomb interaction and Hund's coupling in the electronic structure of FeSe and FeTe. The calculation is based on density functional theory (DFT) with local density approximation(LDA+U) framework employed in TB-LMTO ASA code. We found the correlation effects were orbital selective due to the strength of interorbital hybridization among different Fe-3d orbitals mediated via chalcogen (Se/Te-p) orbitals is different in both the compounds, however Coulomb interaction is screened significantly by Te-p bands in FeTe. Similarly the orbital section is different in both the compounds because of the difference in the chalcogen height

    FOOD CONSUMPTION AND NUTRITIONAL INDICES OF OAK TASAR WORM ANTHERAEA PROYLEI (JOLLY) FED ON QUERCUS GLAUCA

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    Studies were conducted under laboratory conditions to evaluate the food consumption and nutritional indices for the development of Antheraea proylei larvae fed on Quercus glauca. Larval duration was 5.4±0.489, 6.4±0.48, 7.2±0.4, 9.8±0.74 and 14.2±0.74 days in the 1st, 2nd, 3rd, 4th and 5th instars, respectively. Larvae consumed a total of 28.85 g insect– ¹ day– ¹, egested 4.164 g insect– ¹ day– ¹ and assimilated 24.69 g insect– ¹ day– ¹ of food  provided. 82.3% of tissue growth was observed in the 4th and 5th instar larvae. Approximate digestibility (AD) decreased from 91.94% in the first instar larva to 80.79% in the 5th instar larva. Efficiency of conversion of digested food (ECD) into body tissue and efficiency of conversion of ingested food into growth (ECI) increased from 1st instar larva to 5th instar larva. The result obtained in the present study indicate that Q. glauca could serve as an alternate host plant for rearing A. proylei in areas where the main host plant Q. serrata is not found

    Fermi surface and band structure of BiPd from ARPES studies

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    We present a detailed electronic structure study of the non-centrosymmetric superconductor BiPd based on our angle resolved photoemission spectroscopy (ARPES) measurements and Density Functional Theory (DFT) based calculations. We observe a high intensity distribution on the Fermi surface (FS) of this compound resulting from various electron and hole like bands which are present in the vicinity of the Fermi energy (Ef_f). The near Ef_f states are primarily composed of Bi-6p with a little admixture of Pd-4dx2y2/zy_{x^2-y^2/zy} orbitals. There are various spin-orbit split bands involved in the crossing of Ef_f making a complex FS. The FS mainly consists of multi sheets of three dimensions which disfavor the nesting between different sheets of the FS. Our comprehensive study elucidates that BiPd could be a s-wave multiband superconductor

    Valence band electronic structure of Nb2Pd1.2Se5 and Nb2Pd0.95S5 superconductors

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    We present a comparative study of our valence band photoemission results on Nb2Pd1.2Se5 and Nb2Pd0.95S5 superconductors which is supported by our DFT based electronic structure calculations. We observe that the VB spectra of both the compounds are qualitatively similar, except slight difference in the binding energy position of all features between the two compounds which could be the result of different electronegativity of Se and S atom. The calculated density of states reveal that the VB features are mainly composed of Pd Se S hybridized states. The nature of DOS originating from the distinctly coordinated Pd atoms is different. Further, the involvement of the various Pd 4d and Nb 4d states in crossing of Fermi level signifies the multiband character of these compounds. In addition, we find a temperature dependent pseudogap in Nb2Pd0.95S5 which is absent in Nb2Pd1.2Se5

    LiDAR mapping of tidal marshes for ecogeomorphological modelling in the TIDE project

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    The European research project TIDE (Tidal Inlets Dynamics and Environment) is developing and validating coupled models describing the morphological, biological and ecological evolution of tidal environments. The interactions between the physical and biological processes occurring in these regions requires that the system be studied as a whole rather than as separate parts. Extensive use of remote sensing including LiDAR is being made to provide validation data for the modelling. This paper describes the different uses of LiDAR within the project and their relevance to the TIDE science objectives. LiDAR data have been acquired from three different environments, the Venice Lagoon in Italy, Morecambe Bay in England, and the Eden estuary in Scotland. LiDAR accuracy at each site has been evaluated using ground reference data acquired with differential GPS. A semi-automatic technique has been developed to extract tidal channel networks from LiDAR data either used alone or fused with aerial photography. While the resulting networks may require some correction, the procedure does allow network extraction over large areas using objective criteria and reduces fieldwork requirements. The networks extracted may subsequently be used in geomorphological analyses, for example to describe the drainage patterns induced by networks and to examine the rate of change of networks. Estimation of the heights of the low and sparse vegetation on marshes is being investigated by analysis of the statistical distribution of the measured LiDAR heights. Species having different mean heights may be separated using the first-order moments of the height distribution

    Valence band electronic structure of Pd based ternary chalcogenide superconductors

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    We present a comparative study of the valence band electronic structure of Pd based ternary chalcogenide superconductors Nb2Pd0.95S5, Ta2Pd0.97S6 and Ta2Pd0.97Te6 using experimental photoemission spectroscopy and density functional based theoretical calculations. We observe a qualitatively similarity between valence band (VB) spectra of Nb2Pd0.95S5 and Ta2Pd0.97S6. Further, we find a pseudogap feature in Nb2Pd0.95S5 at low temperature, unlike other two compounds. We have correlated the structural geometry with the differences in VB spectra of these compounds. The different atomic packing in these compounds could vary the strength of inter-orbital hybridization among various atoms which leads to difference in their electronic structure as clearly observed in our DOS calculations

    Observation of Dirac-like surface state bands on the top surface of BiSe

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    Two quintuple layers of strong topological insulator Bi2Se3 are coupled by a Bi bilayer in BiSe crystal. We investigated its electronic structure using angle resolved photoelectron spectroscopy to study its topological nature. Dirac like linearly dispersive surface state bands are observed on the 001 surface of BiSe and Sb doped BiSe, similar to Bi2Se3. Moreover, the lower part of the SSBs buries deep in the bulk valence band. Overlap region between the SSBs and BVB is large in Sb doped system and the SSBs deviate from the Dirac like linear dispersion in this region. These results highlight the role of interlayer coupling between the Bi bilayer and the Bi2Se3 QLs. Furthermore, we observed a large intensity imbalance in the SSBs located at the positive and negative k parallel directions. This asymmetry pattern gradually reverses as the excitation energy scans from low 14eV to high 34eV value. However, we did not observe signal of surface magnetization resulting from the intensity imbalance in SSBs due to hole-generated uncompensated spin accumulation in the photoexcitation process. The main reason for this could be the faster relaxation process for photo hole due to the presence of the Bi bilayer between the adjacent Bi2Se3 QLs. The observed photon energy dependent intensity variation could be a signature of the mixing between the spin and the orbit texture of the SSBs

    Tobacco Smoke Carcinogens Induce DNA Repair Machinery Function Loss: Protection by Carbon Nanotubes

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    Purpose: DNA damage is a continuous process occurring within the cells caused by intrinsic and extrinsic factors, but it gets repaired regularly. If the DNA repair process is faulty, the incidences of damages/mutations can accumulate in cells resulting in cell transformation. It is hypothesized that the negative variations in DNA repair pathways in even at one point viz. genetic, translational or posttranslational stage may fairly be crucial for the beginning and development of carcinogenesis. Therefore, we investigated the potential of tobacco specific nitrosamines (TSNs) related carcinogens to interact with the enzymes involved in DNA repair mechanisms in the current study. Methods: The derivatives of cigarettes’ smoke like NNK and NNAL are very well known and recognized carcinogens. Therefore, almost 120 enzymes playing crucial role in the DNA repair process have been analysed for their reactivity with NNK and NNAL. Results: The molecular docking study helped to screen out, 07 possible DNA repair enzyme targets for NNK, and 12for NNAL. Present study revealed the loss of activity of DNA repair enzymes in the presence of NNK and NNAL, and this accumulation may induce the tendency of DNA damage which can lead the transformation of exposed normal cells in to cancerous cells. This study also demonstrated the protective potential of nanoparticles like SWCNTs/MWCNTs against TSN’s induced toxicity; here SWCNT against NNK (-17.16 Kcal/Mol) and MWCNT against NNK -17.01 Kcal/Mol were showing maximum binding affinities than the known biomolecular target of NNK 1UGH (Uracil-DNA glycosylase,-7.82Kcal/Mol). Conclusion: CNTs can be applied as chemo-preventive agents against environmental and tobacco induced carcinogens owing to their scavenging potential and warrants for in vivo and in vitro experimental validation of the results obtained from the present study
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