193 research outputs found
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Extraction of tidal channel networks from airborne scanning laser altimetry and aerial photography
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
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
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
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
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 (E). The near E states are
primarily composed of Bi-6p with a little admixture of Pd-4d
orbitals. There are various spin-orbit split bands involved in the crossing of
E 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
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
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LiDAR mapping of tidal marshes for ecogeomorphological modelling in the TIDE project
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
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
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
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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