India Institute of Science

Bhubaneshwar, India

India Institute of Science

Bhubaneshwar, India
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Reddy S.R.,Indian Institute of Technology Hyderabad | Bapari S.,India Institute of Science | Bhattacharjee P.P.,Indian Institute of Technology Hyderabad | Chokshi A.H.,India Institute of Science
Materials Research Letters | Year: 2017

A CoCrFeMnNi high-entropy alloy (HEA) showed elongation to failure ∼320% at T = 1023 K and a strain rate (Formula presented.). Strain hardening and texture weakening occurred at low (Formula presented.), whereas flow softening and texture strengthening were observed at high (Formula presented.) experiments. The strain rate sensitivity (m) decreased from 0.5 to ∼0.25 with increasing (Formula presented.). Deformation with m∼0.5 and deformation-enhanced grain growth at low (Formula presented.) indicated superplasticity associated with grain boundary sliding. The grain boundary diffusion coefficient diminished by a factor of ∼4 in the HEA. Concurrent nucleation, growth and cavity interlinkage caused premature failure compared with conventional superplastic alloys. © 2017 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.

Shen W.,Georgetown University | Ge Y.,Georgetown University | Liu A.Y.,Georgetown University | Krishnamurthy H.R.,Jawaharlal Nehru Centre for Advanced Scientific Research | And 4 more authors.
Physical Review Letters | Year: 2014

We employ an exact solution of the simplest model for pump-probe time-resolved photoemission spectroscopy in charge-density-wave systems to show how, in nonequilibrium, the gap in the density of states disappears while the charge density remains modulated, and then the gap reforms after the pulse has passed. This nonequilibrium scenario qualitatively describes the common short-time experimental features in TaS2 and TbTe3, indicating a quasiuniversality for nonequilibrium "melting" with qualitative features that can be easily understood within a simple picture. © 2014 American Physical Society.

Daniel R.J.,Design Center | Bhat K.N.,India Institute of Science
Microelectronic Engineering | Year: 2013

In this paper, a simple but accurate semi analytical charge sheet model is presented for threshold voltage of accumulation mode polycrystalline silicon on insulator (PSOI) MOSFETs. In this model, we define the threshold voltage (VT) of the polysilicon accumulation mode MOSFET as the gate voltage required to raise the surface potential (φs) to a value φsT necessary to overcome the charge trapping in the grain boundary and to create channel accumulation charge that is equal to the channel accumulation charge available in the case of single crystal silicon accumulation mode MOSFET at that φsT. The correctness of the model is demonstrated by comparing the theoretically estimated values of threshold voltage with the experimentally measured threshold voltages on the accumulation mode PSOI MOSFETs fabricated in the laboratory using LPCVD polysilicon layers doped with boron to achieve dopant densities in the range 3.3 × 1015-5 × 1017/cm3. Further, it is shown that the threshold voltage values of accumulation mode PSOI MOSFETs predicted by the present model match very closely with the experimental results, better than those obtained with the models previously reported in the literature. © 2012 Elsevier B.V. All rights reserved.

Background of the Work:The phylogenetic position and evolution of Hemidactylus anamallensis (family Gekkonidae) has been much debated in recent times. In the past it has been variously assigned to genus Hoplodactylus (Diplodactylidae) as well as a monotypic genus 'Dravidogecko' (Gekkonidae). Since 1995, this species has been assigned to Hemidactylus, but there is much disagreement between authors regarding its phylogenetic position within this genus. In a recent molecular study H. anamallensis was sister to Hemidactylus but appeared distinct from it in both mitochondrial and nuclear markers. However, this study did not include genera closely allied to Hemidactylus, thus a robust evaluation of this hypothesis was not undertaken.Methods:The objective of this study was to investigate the phylogenetic position of H. anamallensis within the gekkonid radiation. To this end, several nuclear and mitochondrial markers were sequenced from H. anamallensis, selected members of the Hemidactylus radiation and genera closely allied to Hemidactylus. These sequences in conjunction with published sequences were subjected to multiple phylogenetic analyses. Furthermore the nuclear dataset was also subjected to molecular dating analysis to ascertain the divergence between H. anamallensis and related genera.Results and Conclusion:Results showed that H. anamallensis lineage was indeed sister to Hemidactylus group but was separated from the rest of the Hemidactylus by a long branch. The divergence estimates supported a scenario wherein H. anamallensis dispersed across a marine barrier to the drifting peninsular Indian plate in the late Cretaceous whereas Hemidactylus arrived on the peninsular India after the Indian plate collided with the Eurasian plate. Based on these molecular evidence and biogeographical scenario we suggest that the genus Dravidogecko should be resurrected. © 2013 Bansal, Karanth.

Ashok B.,International Institute of Information Technology Bangalore | Ananthakrishna G.,India Institute of Science
Journal of Chemical Physics | Year: 2014

Irregular force fluctuations are seen in most nanotubulation experiments. The dynamics behind their presence has, however, been neither commented upon nor modeled. A simple estimate of the mean energy dissipated in force drops turns out to be several times the thermal energy. This coupled with the rate dependent nature of the deformation reported in several experiments point to a dynamical origin of the serrations. We simplify the whole process of tether formation through a three-stage model of successive deformations of sphere to ellipsoid, neck-formation, and tubule birth and extension. Based on this, we envisage a rate-softening frictional force at the neck that must be overcome before a nanotube can be pulled out. Our minimal model includes elastic and visco-elastic deformation of the vesicle, and has built-in dependence on pull velocity, vesicle radius, and other material parameters, enabling us to capture various kinds of serrated force-extension curves for different parameter choices. Serrations are predicted in the nanotubulation region. Other features of force-extension plots reported in the literature such as a plateauing serrated region beyond a force drop, serrated flow region with a small positive slope, an increase in the elastic threshold with pull velocity, force-extension curves for vesicles with larger radius lying lower than those for smaller radius, are all also predicted by the model. A toy model is introduced to demonstrate that the role of the friction law is limited to inducing stick-slip oscillations in the force, and all other qualitative and quantitative features emerging from the model can only be attributed to other physical mechanisms included in the deformation dynamics of the vesicle. © 2014 AIP Publishing LLC.

Patel S.,Indian Institute of Technology Bombay | Patel S.,India Institute of Science | Sharma K.K.,India Institute of Science | Datta A.,Indian Institute of Technology Bombay
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2015

(Graph Presented) The binding of chlorin p6, a model photosensitizer for photodynamic therapy (PDT), to the Sudlow's site II of Human Serum Albumin (HSA) has been monitored by different spectroscopic methods. Displacement of Dansyl-L-Proline (DP) from its conjugate with HSA is manifested in the spectral shift and decrease in its fluorescence intensity as well as the emergence of component with lifetime of 2-3 ns, which is characteristic of free DP. As DP is known to bind specifically to the Sudlow's site II of human serum albumin, its displacement by chlorin p6 indicates the residence of the photosensitizer in the same site, in addition to Sudlow's site I. The binding constants for Sudlow's site II, determined by the stopped-flow technique, are found to be two orders of magnitude smaller than that for Sudlow's site I. © 2014 Elsevier B.V. All rights reserved.

Agnihotri S.,Indian Institute of Science | Sundeep P.V.D.S.,India Institute of Science | Seelamantula C.S.,India Institute of Science | Balakrishnan R.,Indian Institute of Science
PLoS ONE | Year: 2014

Objective identification and description of mimicked calls is a primary component of any study on avian vocal mimicry but few studies have adopted a quantitative approach. We used spectral feature representations commonly used in human speech analysis in combination with various distance metrics to distinguish between mimicked and non-mimicked calls of the greater racket-tailed drongo, Dicrurus paradiseus and cross-validated the results with human assessment of spectral similarity. We found that the automated method and human subjects performed similarly in terms of the overall number of correct matches of mimicked calls to putative model calls. However, the two methods also misclassified different subsets of calls and we achieved a maximum accuracy of ninety five per cent only when we combined the results of both the methods. This study is the first to use Mel-frequency Cepstral Coefficients and Relative Spectral Amplitude - filtered Linear Predictive Coding coefficients to quantify vocal mimicry. Our findings also suggest that in spite of several advances in automated methods of song analysis, corresponding cross-validation by humans remains essential. © 2014 Agnihotri et al.

Stout D.A.,Brown University | Basu B.,India Institute of Science | Webster T.J.,Brown University
Acta Biomaterialia | Year: 2011

The objective of the present in vitro research was to investigate cardiac tissue cell functions (specifically cardiomyocytes and neurons) on poly(lactic-co-glycolic acid) (PLGA) (50:50 wt.%)-carbon nanofiber (CNF) composites to ascertain their potential for myocardial tissue engineering applications. CNF were added to biodegradable PLGA to increase the conductivity and cytocompatibility of pure PLGA. For this reason, different PLGA:CNF ratios (100:0, 75:25, 50:50, 25:75, and 0:100 wt.%) were used and the conductivity as well as cytocompatibility of cardiomyocytes and neurons were assessed. Scanning electron microscopy, X-ray diffraction and Raman spectroscopy analysis characterized the microstructure, chemistry, and crystallinity of the materials of interest to this study. The results show that PLGA:CNF materials are conductive and that the conductivity increases as greater amounts of CNF are added to PLGA, from 0 S m-1 for pure PLGA (100:0 wt.%) to 5.5 × 10-3 S m-1 for pure CNF (0:100 wt.%). The results also indicate that cardiomyocyte density increases with greater amounts of CNF in PLGA (up to 25:75 wt.% PLGA:CNF) for up to 5 days. For neurons a similar trend to cardiomyocytes was observed, indicating that these conductive materials promoted the adhesion and proliferation of two cell types important for myocardial tissue engineering applications. This study thus provides, for the first time, an alternative conductive scaffold using nanotechnology which should be further explored for cardiovascular applications. © 2011 Acta Materialia Inc.

Singh P.,Indian Institute of Science | Indi S.S.,India Institute of Science | Savithri H.S.,Indian Institute of Science
PLoS ONE | Year: 2014

Groundnut Bud Necrosis Virus (GBNV) is a tripartite ambisense RNA plant virus that belongs to serogroup IV of Tospovirus genus. Non-Structural protein-m (NSm), which functions as movement protein in tospoviruses, is encoded by the M RNA. In this communication, we demonstrate that despite the absence of any putative transmembrane domain, GBNV NSm associates with membranes when expressed in E. coli as well as in N. benthamiana. Incubation of refolded NSm with liposomes ranging in size from 200-250 nm resulted in changes in the secondary and tertiary structure of NSm. A similar behaviour was observed in the presence of anionic and zwitterionic detergents. Furthermore, the morphology of the liposomes was found to be modified in the presence of NSm. Deletion of coiled coil domain resulted in the inability of in planta expressed NSm to interact with membranes. Further, when the C-terminal coiled coil domain alone was expressed, it was found to be associated with membrane. These results demonstrate that NSm associates with membranes via the C-terminal coiled coil domain and such an association may be important for movement of viral RNA from cell to cell. © 2014 Singh et al.

Reddy D.H.,India Institute of Science | Ramaswamy A.,India Institute of Science
CONCREEP 2015: Mechanics and Physics of Creep, Shrinkage, and Durability of Concrete and Concrete Structures - Proceedings of the 10th International Conference on Mechanics and Physics of Creep, Shrinkage, and Durability of Concrete and Concrete Structures | Year: 2015

A Predicting delayed strains (creep and shrinkage) in concrete proves to be critical to a large number of pre-stressed concrete structures, such as containment vessels of nuclear power plants, post-tensioned bridge girders, etc. These delayed strains include two components of shrinkage, namely, Autogeneous shrinkage and Drying shrinkage and two components of creep strains, namely, Basic creep and Drying creep. The present study focuses to predict the creep and shrinkage of Self Compacted Concrete (SCC) and High volume fly ash normal concrete experimentally. And a Hygro thermo chemo mechanical model (D.Gawin et al, 2006) is implemented to estimate gaseous pressure, capillary pressure and temperature and displacements which in turn varies with the hydration process. The Solidification theory proposed by Bazent (Bazant and Prasannan, 1989), is used to estimate the creep and shrinkage. © ASCE.

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