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3D characterization of thermo-hydro-geological fields and estimation of power potential from Puga geothermal reservoir, Ladakh, India
No full textPuga geothermal reservoir in India shows promising thermal manifestation zones. However, no systematic study is done to develop the 3D characterization of thermo-hydro-geological fields for this reservoir. A new methodology is developed to characterize porosity, thermal conductivity, density, specific heat, radioactive heat capacity and permeability as 3D block heterogeneity till a depth of 4 km from resistivity maps. The temperature field and stored heat energy in a geothermal reservoir are dependent on these parameters. Based on the developed characterization, 3D coupled flow and heat transport processes are simulated to estimate the extractable temperature and power to be generated from doublet extraction scheme with various operational conditions. The study finds energy recovery factor of 8.16% and 37.83% and minimum electrical power potential of 1.2 MWe and 50.4 MWe with 12% conversion efficiency from the depths of 250 m and 1875 m respectively over 50 years from Puga field. Sensitivity for fluid injection/extraction rate and well spacing is studied. The results show promising power potential from 1.4 to 2 km of depth. The block heterogeneity characterization is more reliable than layered and homogeneous characterization. The outcomes would certainly acquire a significant role in decision-making strategies for Puga geothermal exploitation
Microstructures and mechanical properties of ternary Ti-Si-Sn alloys
No full textTitanium based alloys are one of the important structural materials with applications ranging from aerospace to biomedical industries. Several ternary Ti-Si-Sn alloys were explored in this study to design the microstructure comprising of binary and ternary eutectics corresponding to Ti-Si, Ti-Sn and Ti-Si-Sn system. The microstructural evolution in these alloys was studied using a combination of characterization techniques and thermodynamic calculations. The predicted solidification path from thermodynamic calculations well supported the experimental microstructural data. In addition, mechanical property and microstructure relationship were determined by performing hardness measurements and evaluating stress-strain curves under compression
Eocene-Oligocene cooling and the diversification of Hemidactylus geckos in Peninsular India
No full textThe Eocene-Oligocene cooling marks a global shift towards a cooler and drier climate, concurrent with significant turnover in biota globally. In Peninsular India, palynological investigations suggest a shift from wet rainforest vegetation to dry and seasonal species during this period. However, the grassland and open habitats that dominate this region at present expanded relatively recently due to Late Miocene intensification of monsoon seasonality. We test the possible role of these climatic shifts in generating the dry habitat diversity of an endemic radiation of Hemidactylus geckos distributed in both wet and dry habitats, by investigating whether (a) the beginning of the diversification of dry habitat lineages overlap with the Eocene-Oligocene cooling or late Miocene aridification and (b) accompanied by an increase in diversification. Molecular data (two nuclear and two mitochondrial gene fragments) were generated for samples collected across Peninsular India, and along with previously published data, a time-calibrated phylogeny was reconstructed. Ancestral state reconstruction of dry and wet habitat states was carried out on the time-calibrated phylogeny and gamma-statistics along with a test for diversity-dependent diversification utilized to examine the trend in lineage accumulation. Results show the ancestral node of this radiation to have a dry habitat state, which began diversifying between 39 and 32 million years ago, concurrent with the Eocene-Oligocene cooling. Furthermore, lineage diversification fit a diversity-dependent model of diversification and the gamma-statistics revealed an early increase in diversification followed by a slow-down later. The deep divergences of dry habitat lineages concurrent with the Eocene-Oligocene cooling suggest that this could have served as an ecological opportunity facilitating an early increase in lineage diversification of Hemidactylus in this region. These results suggest an ancient origin and long persistence of arid ecosystems in Peninsular India
Evolution of local flame displacement speeds in turbulence
No full textgIn this study, we assess the veracity of models for density-weighted local flame displacement speed of turbulent premixed flames. It will be shown that a combination of two models, one for the weakly stretched laminar flame state and another derived for a configuration where a curved laminar flame interacts with itself to annihilate, can describe most local realizations of a turbulent premixed flame. To that end, we have performed direct numerical simulations of a reactive mixture of hydrogen-air at atmospheric pressure using a detailed chemical reaction mechanism and analysed the dataset with recently developed flame particle tracking techniques. Forward tracking a large number of flame particles from the generating locations of the corresponding flame surfaces (given by backward tracking) to the corresponding annihilating locations, creates a manifold of local states that can represent nearly all possible states realizable for the turbulent premixed flame under consideration. With all the states of the flame accessible over time, we first assess the applicability of the two-parameter Markstein length based flame speed model. It is found that the model prediction is reasonably accurate for a significant part of the flame particles' lifetime, for turbulent premixed flames with Karlovitz number O.10 /. However, during the final stage of annihilation of the flame particles in the negatively curved trailing regions, the local structure of the flame no longer resembles a standard premixed flame, even qualitatively. A new interaction model for the flame displacement speed, during these final stages of annihilation of the flame elements, has been derived
Shear behavior of cement stabilized rammed earth assemblages
No full textAdoption of rammed earth technology in building construction has witnessed a surge during the recent times and hence it is essential to understand the mechanical behavior of rammed earth under various loading conditions. In this study, in-plane shear behavior of cement stabilized rammed earth (CSRE) is assessed by conducting two types of tests namely (i) Direct shear test of CSRE causing shearing along two adjacent rammed earth layers similar to triplet shear test of masonry bed joints which is henceforth called as triplet test and (ii) Diagonal tension (shear) test of CSRE panels. Three types of bonding techniques between the rammed layers of CSRE are explored in this study, namely, (i) making conical dents which act as shear connectors between rammed earth layers, (ii) applying a coat of fresh cement slurry along the interfaces of rammed layers and (iii) combination of dents and fresh cement slurry and their influence in enhancing the interface shear strength of CSRE is assessed. The bonding techniques are adopted for both, triplet specimens and diagonal panels. Further, the effect of compressive stress normal to the rammed earth layers on the interface shear behavior of triplet specimens is examined. The different levels of normal pre-compression considered are 0.05 MPa, 0.3 MPa and 0.9 MPa. The triplet and diagonal tension (shear) tests on CSRE assemblages are conducted under both, dry and wet conditions. Shear behavior is assessed in terms of shear strength, shear modulus, strain at peak stress, post-peak behavior and failure patterns. Among the different bonding techniques assessed in this study, CSRE specimens with a coat of fresh cement slurry exhibited higher shear strength in comparison to specimens with other types of bonding techniques or no bonding technique. Further, CSRE triplet specimens exhibited steady increase in interface shear strength with increase in normal pre-compression, both in dry and wet conditions. Also, shear strength of CSRE was found to be lower in wet condition, in comparison to shear strength in dry condition, for all the bonding techniques. A Mohr-Coulomb failure envelope was developed for CSRE under wet and dry conditions based on the results of triplet tests conducted in this study. Overall, the study aims to understand the efficacy of the proposed bonding techniques in enhancing the shear strength of CSRE and the influence of normal pre-compression and moisture content on shear behavior of CSRE
Bioethanol from macroalgae: Prospects and challenges
No full textBurgeoning dependence on fossil fuels for transport and industrial sectors has been posing challenges such as depletion of fossil fuel reserves, enhanced greenhouse gas (GHG) footprint, with the imminent changes in the climate, etc. This has necessitated an exploration of sustainable, eco-friendly and carbon neutral energy alternatives. Recent studies on biofuels indicate that algal biomass, particularly from marine macroalgae (seaweeds) have the potential to supplement oil fuel. Marine macroalgae are fast growing and carbohydrate rich biomass having advantage over other biofuel feedstock in terms of land dependence, freshwater requirements, not competing with food crops, which were the inherent drawback of the first- and second-generation feedstock. The present communication reviews the macroalgal feedstock availability, screening and selection of viable feedstock based on the biochemical composition, process involved, scope and opportunities in bioethanol production as well as technology interventions. The prospect of bioethanol production from algal feedstock of Central West Coast of India has been evaluated taking into account challenges (feedstock sustenance, technical feasibility, economic viability) in order to achieve energy sustainability. The green algae exhibited growth during all seasons and highest total carbohydrate was recorded from green seaweed Ulva lactuca (62.15 +/- 12.8%). Elemental (CHN) analyses of seaweed samples indicate 25.31-37.95% of carbon, 4.52-6.48% hydrogen and 1.88-4.36% Nitrogen. Highest carbon, hydrogen and nitrogen content were recorded respectively from G.pusillum (C: 37.95%), G. pusillum (H: 6.48%) and E.intestinalis (N: 4.36%). Green seaweeds are rich in cellulose content (>10%) compared to other seaweeds (2-10%). Higher cellulose content was estimated in U.lactuca (14.03 +/- 0.14%), followed by E. intestinalis (12.10 +/- 0.53%) and C.media (10.53 +/- 0.17%). Cellulose is a glucan present in green seaweeds, which can easily be hydrolysed through enzyme and subsequently fermented to produce bioethanol. Lower sugar removal in acid hydrolysate neutralization process (Na2CO3) was recorded in U.lactuca (39.8%) and E.intestinalis (14.7%). Highest ethanol yield of 1.63 g and 0.49 g achieving 25.8% and 77.4% efficiency in SHF (Separate Hydrolysis and Fermentation) and SSF (Simultaneous Saccharification and Fermentation) process respectively was recorded for green alga E. intestinalis
2,3-di(2-furyl) quinoxaline bearing 3-ethyl rhodanine and 1,3 indandione based heteroaromatic conjugated T-shaped push -pull chromophores: Design, synthesis, photophysical and non-linear optical investigations
No full textThe design, synthesis, computational, spectroscopic, and, the second and third order non-linear optical studies of a two new pi-deficient cross-conjugated T-shaped push-pull molecules (QFR and QFI) consisting of 3-ethyl rhodanine and 1,3 indandione substituted with heterocyclic quinoxaline ring were synthesized by Knoevenagel condensation reaction of the precursor dialdehydes with active dye molecules were described in detail. In the as synthesized molecule, the electron donating thiophene moiety acts as an efficient pi-bridge on either side to the quinoxaline core that permits good viability in fine-tuning the optical absorption spectrum with good solubility. The computational studies of these molecules show efficient intra molecular charge transfer (ICT) processes analyzed through their molecular orbital characteristics, excitation energy, absorption maxima, oscillator strength and Mulliken population analysis. The comparison study between the structures of these push-pull molecules were done by their photophysical characteristics including CIE coordinates; thermal characteristics, XRD studies and electrochemical analysis. The time-resolved fluorescence spectra with nanosecond time profile were measured to detect the delayed fluorescent performance of the push-pull molecules QFR and QFI. HyperRayleigh scattering (HRS) in chloroform solution of varying concentrations, using a standard wavelength at 1064 nm was used to assess their first order hyperpolarizability. Optical non-linear property was again proved by open-aperture Z-scan technique investigated at 532 nm and the observed optical limiting behavior was originated from the reverse saturable absorption (RSA) process. The second and third order NLO studies reveals that 3-ethyl rhodanine substituted QFR molecule (beta value from HRS, 84.64 x 10(-30) esu and beta(eff) from Z scan, 10 x 10(-10) m/W) shows high non-linear optical properties and thermal stability compared with 1,3 indandione substituted QFI (beta value from HRS, 48.00 x 10(-30) esu and beta(eff) value from Z scan, 2 x 10(-10)m/W)
Isolation and structural characterization of a Zn2+-bound single-domain antibody against NorC, a putative multidrug efflux transporter in bacteria
No full textSingle-chain antibodies from camelids have served as powerful tools ranging from diagnostics and therapeutics to crystallization chaperones meant to study protein structure and function. In this study, we isolated a single-chain antibody from an Indian dromedary camel (ICab) immunized against a bacterial 14TM helix transporter, NorC, from Staphylococcus aureus We identified this antibody in a yeast display screen built from mononuclear cells isolated from the immunized camel and purified the antibody from Escherichia coli after refolding it from inclusion bodies. The X-ray structure of the antibody at 2.15 Ã resolution revealed a unique feature within its CDR3 loop, which harbors a Zn2+-binding site that substitutes for a loop-stabilizing disulfide bond. We performed mutagenesis to compromise the Zn2+-binding site and observed that this change severely hampered antibody stability and its ability to interact with the antigen. The lack of bound Zn2+ also made the CDR3 loop highly flexible, as observed in all-atom simulations. Using confocal imaging of NorC-expressing E. coli spheroplasts, we found that the ICab interacts with the extracellular surface of NorC. This suggests that the ICab could be a valuable tool for detecting methicillin-resistant S. aureus strains that express efflux transporters such as NorC in hospital and community settings
Drilling induced exit-ply delamination model considering torque
No full textAmongst all the drilling induced damage in laminated multi-directional fiber reinforced plastics (MD FRPs), exit-ply delamination is the most serious one. Exit-ply delamination is mainly caused due to the axial thrust force exerted by the chisel edge of the drill. Several attempts have been made in the past to provide analytical models relating material properties, layups, machining parameters (feed) with the delamination on the exit-side of the drilled hole. In the current work, a modified exit-ply delamination model has been presented using first order shear deformation theory (FSDT) in conjunction with classical lamination plate theory (CLPT) to account for the out-of-plane shear stresses txz and tyz that are generated due to the rotation of the drill bit. The delamination zone is assumed to be an elliptical plate that is clamped on all edges and subjected to thrust force and torque along the axis of the drill. Suitable displacements fields have been assumed and a mixed-mode fracture criterion has been used to estimate the critical thrust force. These results have been verified experimentally. These forces can further be related to the process variables, viz., feed rate and cutting speed
Asian elephants modulate their vocalizations when disturbed
No full textWhen disturbed, animals use various modes of communication to alert conspecifics about the source of danger. Some species have evolved graded or continuous signals specific to the type of threats. African elephants, Loxodonta africana, are known to differentiate between threats from bees and humans by changing the energy concentrations of their alarm calls. However, the mechanism by which Asian elephants, Elephas maximus, use vocalizations to alert conspecifics about imminent danger remains poorly explored. To understand disturbance-induced communication in free-ranging Asian elephants, we compared two call types, �rumbles� (low-frequency calls) and �trumpets� (high-frequency calls), produced in disturbed (by humans or other animals) and undisturbed (social interaction) states. We then analysed acoustic characters for both call types: absolute frequency parameters including fundamental frequency (F0), mean, minimum, maximum and range; temporal parameters including call duration, time to minimum F0, time to maximum F0, peak time and minimum time; and filter-related parameters including mean, minimum and maximum of first (F1) and second (F2) formant locations. We found that under disturbed conditions, Asian elephants increased the duration of rumbles and decreased the duration of trumpets. Similarly, the mean F0 and mean positions of F1 and F2 of rumbles decreased compared with the undisturbed condition; among trumpets, no significant differences were observed in mean F0 or formant position in either F1 or F2 between the two contexts. We also found that the duration of rumbles was influenced by an interaction between group size and context: smaller groups produced longer rumbles when disturbed. These results suggest that when disturbed Asian elephants can modify vocal signals whose likely function could be to alert conspecifics about potential threats