16 results on '"Krishnan, P. S."'
Search Results
2. Misfit strain driven cation inter-diffusion across an epitaxial multiferroic thin film interface.
- Author
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Rama Krishnan, P. S. Sankara, Morozovska, Anna N., Eliseev, Eugene A., Ramasse, Quentin M., Kepaptsoglou, Demie, Wen-I. Liang, Ying-Hao Chu, Munroe, Paul, and Nagarajan, V.
- Subjects
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CATIONS , *FERRITES , *LANTHANUM compounds , *DIFFUSION , *INTERFACES (Physical sciences) , *TRANSMISSION electron microscopy , *ELECTRON energy loss spectroscopy , *BOUNDARY value problems - Abstract
Cation intermixing at functional oxide interfaces remains a highly controversial area directly relevant to interface-driven nanoelectronic device properties. Here, we systematically explore the cation intermixing in epitaxial (001) oriented multiferroic bismuth ferrite (BFO) grown on a (001) lanthanum aluminate (LAO) substrate. Aberration corrected dedicated scanning transmission electron microscopy and electron energy loss spectroscopy reveal that the interface is not chemically sharp, but with an intermixing of ~2 nm. The driving force for this process is identified as misfit-driven elastic strain. Landau-Ginzburg-Devonshire-based phenomenological theory was combined with the Sheldon and Shenoy formula in order to understand the influence of boundary conditions and depolarizing fields arising from misfit strain between the LAO substrate and BFO film. The theory predicts the presence of a strong potential gradient at the interface, which decays on moving into the bulk of the film. This potential gradient is significant enough to drive the cation migration across the interface, thereby mitigating the misfit strain. Our results offer new insights on how chemical roughening at oxide interfaces can be effective in stabilizing the structural integrity of the interface without the need for misfit dislocations. These findings offer a general formalism for understanding cation intermixing at highly strained oxide interfaces that are used in nanoelectronic devices. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
3. Effect of processing kinetics on the structure of ferromagnetic-ferroelectric-ferromagnetic interfaces.
- Author
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Sankara Rama Krishnan, P. S., Ramasse, Q. M., Liang, Wen-I, Chu, Ying-Hao, Nagarajan, V., and Munroe, P.
- Subjects
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HETEROSTRUCTURES , *FERROELECTRIC devices , *BISMUTH compounds , *FERROMAGNETIC materials , *LANTHANUM strontium manganese oxide , *THIN films - Abstract
Trilayer heterostructures consisting of a ferroelectric bismuth ferrite (BFO) film sandwiched between ferromagnetic lanthanum strontium manganese oxide (LSMO) films were fabricated using pulsed laser deposition. Both BFO thicknesses (20 nm, 5 nm) and cooling rates were varied to investigate the role of processing parameters on the chemistry of the interfaces. The interfaces were investigated using a dedicated aberration corrected scanning transmission electron microscope (STEM) operated at 100 kV via STEM-high angle annular dark field (STEM-HAADF) and STEM-electron energy loss spectroscopy (STEM-EELS) modes. Combined analysis through STEM-HAADF and STEM-EELS revealed the formation of lattice distortion in certain regions of the BFO layer for the ∼5 nm film. Piezoresponse force microscopy (PFM) studies of the ∼5 nm BFO sample revealed weak ferroelectric domain switching. Stacking fault defects with mixed valence manganese (Mn-B site cation) were formed in the top LSMO layer when the heterostructure was cooled at a slower rate irrespective of BFO thickness, thereby demonstrating the effect of processing kinetics on the physical integrity of the heterostructure. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
4. Microstructural analysis of interfaces in a ferromagnetic-multiferroic epitaxial heterostructure.
- Author
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Rama Krishnan, P. S. Sankara, Arredondo, Miryam, Saunders, Martin, Ramasse, Q. M., Valanoor, Nagarajan, and Munroe, Paul
- Subjects
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BISMUTH , *FERRITES , *HETEROSTRUCTURES , *MICROSTRUCTURE , *LANTHANUM , *STRONTIUM , *MANGANESE oxides - Abstract
We report a study on multiferroic bismuth ferrite (BiFeO3, BFO)-ferromagnetic lanthanum strontium manganese oxide (La0.7Sr0.3MnO3, LSMO) epitaxial interfaces by scanning transmission electron microscopy-energy dispersive spectroscopy (STEM-EDS) and energy-filtered transmission electron microscopy (EFTEM). Epitaxial (001) oriented LSMO/BFO heterostructures were fabricated on a (001) strontium titanate (SrTiO3, STO) substrate using pulsed laser deposition (PLD). Different cooling conditions to room temperature (rapid or slow) were used to investigate the effect of fabrication conditions on the structural quality of the interfaces. The combined analysis of bright field transmission electron microscopy imaging, STEM-EDS and EFTEM data reveals that the LSMO-BFO heterostructure interface is free from any defects but the phases are chemically interdiffused over a length scale of ∼4 nm. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
5. Enzymatic Activity in Mitochondria from Orobanche.
- Author
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SINGH, PRIKHSHAYAT and KRISHNAN, P. S.
- Subjects
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MITOCHONDRIA , *ORGANELLES , *ENZYMES , *PROTOPLASM , *ADENOSINE triphosphatase , *PHOSPHATASES , *ACONITATE hydratase - Abstract
Mitochondria from Orobanche were analysed for the activities of aconitate hydratase, isocitrate dehydrogenase, succinate dehydrogenase, fumarate hydratase, malate dehydrogenase, NADH oxidase, substrate-cytochrome c oxidoreductases, glutamate dehydrogenase, aminotransferases, ATPase and "malic" enzyme. The specific activities of isocitrate dehydrogenase, NADH oxidase, substrate-cytochrome c oxidoreductases and glutamate dehydrogenase in the mitochondrial fraction from parasite tissue compared favourably with those reported for most of the mitochondria from growing and storage tissues. Succinate dehydrogenase, fumarate hydratase and aspartate aminotransferase were of intermediate activity, while aconitate hydratase and malate dehydrogenase had rather low activity, and "malic" enzyme had very low activity in comparison with other preparations. The relevance of these findings in relation to mitochondrial metabolism in the parasite is discussed. No evidence was obtained to suggest any basic abnormality in the biochemical properties of the mitochondria from Orobanche cernua which may be correlated with its obligatorily parasitic existence. [ABSTRACT FROM AUTHOR]
- Published
- 1977
- Full Text
- View/download PDF
6. Isolation of Mitochondria from Orobanche, a "Total" Root Angiospermic Parasite.
- Author
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Singh, Prikhshayat and Krishnan, P. S.
- Subjects
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MITOCHONDRIA , *PYRUVATES , *PHOSPHORYLATION , *ORGANS (Anatomy) , *ETHYLENEDIAMINETETRAACETIC acid , *PLANT cells & tissues - Abstract
Mitochondria were isolated from the scapes of Orobanche cernua. On the basis of comparative studies with four media, a mannitol grinding medium was selected at a slightly alkaline pH and supplemented with EDTA, metabisulphite, BSA and soluble PVP. Various intermediates of the Krebs cycle, pyruvate, glutamate and NADH were oxidized by the isolated particles, though with different efficiencies. The rate of oxidation was steady for every intermediate tested over a 60 min period, except for NADH. In the majority of cases, the oxidation was accompanied by efficient coupling with phosphorylation. Antimycin A led to significant reduction in the oxygen uptake in the presence of succinate and complete suppression of phosphate‐esterification. The amount of protein recovered in the mitochondrial fraction was comparable with the reported recoveries from a number of plant tissues. The biochemical integrity of mitochondria in the particulate fraction appeared possible from: (a) the absence of respiratory response to added cytochrome c during the oxidation of succinate, (b) insignificant oxidation of exogenously added pyruvate in the absence of sparker and (c) the ability to satisfactorily couple phosphorylation to the oxidation of a number of substrates. [ABSTRACT FROM AUTHOR]
- Published
- 1977
- Full Text
- View/download PDF
7. Influence of Shading on the Gross Composition of Cuscuta Species on Medicago sativa.
- Author
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Setty, Pravina N. and Krishnan, P. S.
- Subjects
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CUSCUTACEAE , *ALFALFA , *PHOSPHORUS , *BRIGHTNESS perception , *PLANT parasites , *PLANT physiology - Abstract
A study was made of the alterations iii growth characteristics of Cuscuta campestris, Cuscuta indecora and Cuscuta reflexa on Medicago sativa as a consequence of a limitation in light intensity. There was a decrease in the content of dry solids, protein and total phosphorus in the filament mass. A decrease in these parameters occurred also in the tissues of the host, but was less pronounced than in the parasite. The response by the host to parasite growth was not always the same in the shade as in light. Phosphorus showed a distinct tendency toward firm retention in the infection complex in the dark. [ABSTRACT FROM AUTHOR]
- Published
- 1970
- Full Text
- View/download PDF
8. Lowering thermal conductivity in thermoelectric Ti2−xNiCoSnSb half Heusler high entropy alloys.
- Author
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Mishra, Soumya Ranjan, Karati, Anirudha, Ghosh, Sanyukta, Mallik, Ramesh Chandra, Shabadi, Rajashekhara, Krishnan, P. S. Sankara Rama, Yadav, Satyesh Kumar, Ramanujan, R. V., and Murty, B. S.
- Subjects
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THERMAL conductivity , *HEAT of formation , *ENTROPY , *PHONON scattering , *ELECTRIC conductivity , *BOLTZMANN'S constant , *THERMOCHEMISTRY , *ALLOYS - Abstract
Ti2−xNiCoSnSb (x = 0.125, 0.250, 0.375, and 0.500) half Heusler (HH) high-entropy thermoelectric alloys were synthesized by the arc melting—ball milling—spark plasma sintering route. The impact of secondary phase content on the thermoelectric properties in these alloys was examined. Ni-rich intermetallic (Ni3Sn2, Ni3Sn4) compounds were observed; the intermetallic content increased for lower Ti content, e.g., Ti1.5NiCoSnSb. A Ni-rich full Heusler (FH) secondary phase was also observed. These results were consistent with first-principles calculations that show that the formation enthalpy of Ti1.5NiCoSnSb was higher than that of Ti2NiCoSnSb and the full Heusler (FH) TiNi2Sn phase. In lower Ti content samples, the electrical conductivity increased, and lattice thermal conductivity decreased at the expense of thermopower owing to higher FH and the Ni3Sn2 phase content. Ti1.5NiCoSnSb exhibited lower lattice thermal conductivity of 3.5 W/mK, compared to 5.4 W/mK at 823 K for Ti2NiCoSnSb due to increased phonon scattering at HH/Ni3Sn2 interfaces. But considering the decreasing power factor with lower Ti content, the maximum ZT obtained in Ti1.875NiCoSnSb (0.171 at 973 K) was only marginally higher than the value for Ti2NiCoSnSb. Further, compositional tuning is hence necessary to maximize the power factor. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
9. The microstructural evolution in high sodium epitaxial sodium potassium niobate films deposited by low-temperature hydro-thermal method.
- Author
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Krishnan, P. S. Sankara Rama, Shiraishi, Takahisa, and Funakubo, Hiroshi
- Abstract
Sodium potassium niobate [(K x Na1−x )NbO3] films with high sodium composition (x = 0.06 and 0.24) were fabricated using a low-temperature (240 °C) hydro-thermal method on (001) niobium-doped strontium titanate (Nb-STO) substrate. The films were annealed subsequently at 600 °C. Thicknesses of the films were maintained in the range of ~800–1000 nm. Transmission electron microscopy-selected area electron diffraction studies revealed the appearance of super-spots, thereby confirming the tilting of the oxygen sub-lattice at both high Na compositions. The bright-field imaging and scanning transmission electron microscopy-energy dispersive spectroscopy elemental mapping revealed KNN film with K-rich interfacial regions and Na-rich top region of the film at both the high Na composition, whereas the potassium niobate (KNbO3,x = 1) film showed no such oxygen sub-lattice tilting, and a sharp substrate-film interface was observed. The observed tilting of oxygen sub-lattice is a direct consequence of the reduced structural stability in high Na compositions in the KNN solid solutions.Sodium potassium niobate [(K x Na1−x )NbO3] films with high sodium composition (x = 0.06 and 0.24) were fabricated using a low-temperature (240 °C) hydro-thermal method on (001) niobium-doped strontium titanate (Nb-STO) substrate. The films were annealed subsequently at 600 °C. Thicknesses of the films were maintained in the range of ~800–1000 nm. Transmission electron microscopy-selected area electron diffraction studies revealed the appearance of super-spots, thereby confirming the tilting of the oxygen sub-lattice at both high Na compositions. The bright-field imaging and scanning transmission electron microscopy-energy dispersive spectroscopy elemental mapping revealed KNN film with K-rich interfacial regions and Na-rich top region of the film at both the high Na composition, whereas the potassium niobate (KNbO3,x = 1) film showed no such oxygen sub-lattice tilting, and a sharp substrate-film interface was observed. The observed tilting of oxygen sub-lattice is a direct consequence of the reduced structural stability in high Na compositions in the KNN solid solutions.Sodium potassium niobate [(K x Na1−x )NbO3] films with high sodium composition (x = 0.06 and 0.24) were fabricated using a low-temperature (240 °C) hydro-thermal method on (001) niobium-doped strontium titanate (Nb-STO) substrate. The films were annealed subsequently at 600 °C. Thicknesses of the films were maintained in the range of ~800–1000 nm. Transmission electron microscopy-selected area electron diffraction studies revealed the appearance of super-spots, thereby confirming the tilting of the oxygen sub-lattice at both high Na compositions. The bright-field imaging and scanning transmission electron microscopy-energy dispersive spectroscopy elemental mapping revealed KNN film with K-rich interfacial regions and Na-rich top region of the film at both the high Na composition, whereas the potassium niobate (KNbO3,x = 1) film showed no such oxygen sub-lattice tilting, and a sharp substrate-film interface was observed. The observed tilting of oxygen sub-lattice is a direct consequence of the reduced structural stability in high Na compositions in the KNN solid solutions.Sodium potassium niobate [(K x Na1−x )NbO3] films with high sodium composition (x = 0.06 and 0.24) were fabricated using a low-temperature (240 °C) hydro-thermal method on (001) niobium-doped strontium titanate (Nb-STO) substrate. The films were annealed subsequently at 600 °C. Thicknesses of the films were maintained in the range of ~800–1000 nm. Transmission electron microscopy-selected area electron diffraction studies revealed the appearance of super-spots, thereby confirming the tilting of the oxygen sub-lattice at both high Na compositions. The bright-field imaging and scanning transmission electron microscopy-energy dispersive spectroscopy elemental mapping revealed KNN film with K-rich interfacial regions and Na-rich top region of the film at both the high Na composition, whereas the potassium niobate (KNbO3,x = 1) film showed no such oxygen sub-lattice tilting, and a sharp substrate-film interface was observed. The observed tilting of oxygen sub-lattice is a direct consequence of the reduced structural stability in high Na compositions in the KNN solid solutions.Sodium potassium niobate [(K x Na1−x )NbO3] films with high sodium composition (x = 0.06 and 0.24) were fabricated using a low-temperature (240 °C) hydro-thermal method on (001) niobium-doped strontium titanate (Nb-STO) substrate. The films were annealed subsequently at 600 °C. Thicknesses of the films were maintained in the range of ~800–1000 nm. Transmission electron microscopy-selected area electron diffraction studies revealed the appearance of super-spots, thereby confirming the tilting of the oxygen sub-lattice at both high Na compositions. The bright-field imaging and scanning transmission electron microscopy-energy dispersive spectroscopy elemental mapping revealed KNN film with K-rich interfacial regions and Na-rich top region of the film at both the high Na composition, whereas the potassium niobate (KNbO3,x = 1) film showed no such oxygen sub-lattice tilting, and a sharp substrate-film interface was observed. The observed tilting of oxygen sub-lattice is a direct consequence of the reduced structural stability in high Na compositions in the KNN solid solutions.Sodium potassium niobate [(K x Na1−x )NbO3] films with high sodium composition (x = 0.06 and 0.24) were fabricated using a low-temperature (240 °C) hydro-thermal method on (001) niobium-doped strontium titanate (Nb-STO) substrate. The films were annealed subsequently at 600 °C. Thicknesses of the films were maintained in the range of ~800–1000 nm. Transmission electron microscopy-selected area electron diffraction studies revealed the appearance of super-spots, thereby confirming the tilting of the oxygen sub-lattice at both high Na compositions. The bright-field imaging and scanning transmission electron microscopy-energy dispersive spectroscopy elemental mapping revealed KNN film with K-rich interfacial regions and Na-rich top region of the film at both the high Na composition, whereas the potassium niobate (KNbO3,x = 1) film showed no such oxygen sub-lattice tilting, and a sharp substrate-film interface was observed. The observed tilting of oxygen sub-lattice is a direct consequence of the reduced structural stability in high Na compositions in the KNN solid solutions.Sodium potassium niobate [(K x Na1−x )NbO3] films with high sodium composition (x = 0.06 and 0.24) were fabricated using a low-temperature (240 °C) hydro-thermal method on (001) niobium-doped strontium titanate (Nb-STO) substrate. The films were annealed subsequently at 600 °C. Thicknesses of the films were maintained in the range of ~800–1000 nm. Transmission electron microscopy-selected area electron diffraction studies revealed the appearance of super-spots, thereby confirming the tilting of the oxygen sub-lattice at both high Na compositions. The bright-field imaging and scanning transmission electron microscopy-energy dispersive spectroscopy elemental mapping revealed KNN film with K-rich interfacial regions and Na-rich top region of the film at both the high Na composition, whereas the potassium niobate (KNbO3,x = 1) film showed no such oxygen sub-lattice tilting, and a sharp substrate-film interface was observed. The observed tilting of oxygen sub-lattice is a direct consequence of the reduced structural stability in high Na compositions in the KNN solid solutions.Sodium potassium niobate [(K x Na1−x )NbO3] films with high sodium composition (x = 0.06 and 0.24) were fabricated using a low-temperature (240 °C) hydro-thermal method on (001) niobium-doped strontium titanate (Nb-STO) substrate. The films were annealed subsequently at 600 °C. Thicknesses of the films were maintained in the range of ~800–1000 nm. Transmission electron microscopy-selected area electron diffraction studies revealed the appearance of super-spots, thereby confirming the tilting of the oxygen sub-lattice at both high Na compositions. The bright-field imaging and scanning transmission electron microscopy-energy dispersive spectroscopy elemental mapping revealed KNN film with K-rich interfacial regions and Na-rich top region of the film at both the high Na composition, whereas the potassium niobate (KNbO3,x = 1) film showed no such oxygen sub-lattice tilting, and a sharp substrate-film interface was observed. The observed tilting of oxygen sub-lattice is a direct consequence of the reduced structural stability in high Na compositions in the KNN solid solutions.Sodium potassium niobate [(K x Na1−x )NbO3] films with high sodium composition (x = 0.06 and 0.24) were fabricated using a low-temperature (240 °C) hydro-thermal method on (001) niobium-doped strontium titanate (Nb-STO) substrate. The films were annealed subsequently at 600 °C. Thicknesses of the films were maintained in the range of ~800–1000 nm. Transmission electron microscopy-selected area electron diffraction studies revealed the appearance of super-spots, thereby confirming the tilting of the oxygen sub-lattice at both high Na compositions. The bright-field imaging and scanning transmission electron microscopy-energy dispersive spectroscopy elemental mapping revealed KNN film with K-rich interfacial regions and Na-rich top region of the film at both the high Na composition, whereas the potassium niobate (KNbO3,x = 1) film showed no such oxygen sub-lattice tilting, and a sharp substrate-film interface was observed. The observed tilting of oxygen sub-lattice is a direct consequence of the reduced structural stability in high Na compositions in the KNN solid solutions.Sodium potassium niobate [(K x Na1−x )NbO3] films with high sodium composition (x = 0.06 and 0.24) were fabricated using a low-temperature (240 °C) hydro-thermal method on (001) niobium-doped strontium titanate (Nb-STO) substrate. The films were annealed subsequently at 600 °C. Thicknesses of the films were maintained in the range of ~800–1000 nm. Transmission electron microscopy-selected area electron diffraction studies revealed the appearance of super-spots, thereby confirming the tilting of the oxygen sub-lattice at both high Na compositions. The bright-field imaging and scanning transmission electron microscopy-energy dispersive spectroscopy elemental mapping revealed KNN film with K-rich interfacial regions and Na-rich top region of the film at both the high Na composition, whereas the potassium niobate (KNbO3,x = 1) film showed no such oxygen sub-lattice tilting, and a sharp substrate-film interface was observed. The observed tilting of oxygen sub-lattice is a direct consequence of the reduced structural stability in high Na compositions in the KNN solid solutions.Sodium potassium niobate [(K x Na1−x )NbO3] films with high sodium composition (x = 0.06 and 0.24) were fabricated using a low-temperature (240 °C) hydro-thermal method on (001) niobium-doped strontium titanate (Nb-STO) substrate. The films were annealed subsequently at 600 °C. Thicknesses of the films were maintained in the range of ~800–1000 nm. Transmission electron microscopy-selected area electron diffraction studies revealed the appearance of super-spots, thereby confirming the tilting of the oxygen sub-lattice at both high Na compositions. The bright-field imaging and scanning transmission electron microscopy-energy dispersive spectroscopy elemental mapping revealed KNN film with K-rich interfacial regions and Na-rich top region of the film at both the high Na composition, whereas the potassium niobate (KNbO3,x = 1) film showed no such oxygen sub-lattice tilting, and a sharp substrate-film interface was observed. The observed tilting of oxygen sub-lattice is a direct consequence of the reduced structural stability in high Na compositions in the KNN solid solutions.Sodium potassium niobate [(K x Na1−x )NbO3] films with high sodium composition (x = 0.06 and 0.24) were fabricated using a low-temperature (240 °C) hydro-thermal method on (001) niobium-doped strontium titanate (Nb-STO) substrate. The films were annealed subsequently at 600 °C. Thicknesses of the films were maintained in the range of ~800–1000 nm. Transmission electron microscopy-selected area electron diffraction studies revealed the appearance of super-spots, thereby confirming the tilting of the oxygen sub-lattice at both high Na compositions. The bright-field imaging and scanning transmission electron microscopy-energy dispersive spectroscopy elemental mapping revealed KNN film with K-rich interfacial regions and Na-rich top region of the film at both the high Na composition, whereas the potassium niobate (KNbO3,x = 1) film showed no such oxygen sub-lattice tilting, and a sharp substrate-film interface was observed. The observed tilting of oxygen sub-lattice is a direct consequence of the reduced structural stability in high Na compositions in the KNN solid solutions.Sodium potassium niobate [(K x Na1−x )NbO3] films with high sodium composition (x = 0.06 and 0.24) were fabricated using a low-temperature (240 °C) hydro-thermal method on (001) niobium-doped strontium titanate (Nb-STO) substrate. The films were annealed subsequently at 600 °C. Thicknesses of the films were maintained in the range of ~800–1000 nm. Transmission electron microscopy-selected area electron diffraction studies revealed the appearance of super-spots, thereby confirming the tilting of the oxygen sub-lattice at both high Na compositions. The bright-field imaging and scanning transmission electron microscopy-energy dispersive spectroscopy elemental mapping revealed KNN film with K-rich interfacial regions and Na-rich top region of the film at both the high Na composition, whereas the potassium niobate (KNbO3,x = 1) film showed no such oxygen sub-lattice tilting, and a sharp substrate-film interface was observed. The observed tilting of oxygen sub-lattice is a direct consequence of the reduced structural stability in high Na compositions in the KNN solid solutions.Sodium potassium niobate [(K x Na1−x )NbO3] films with high sodium composition (x = 0.06 and 0.24) were fabricated using a low-temperature (240 °C) hydro-thermal method on (001) niobium-doped strontium titanate (Nb-STO) substrate. The films were annealed subsequently at 600 °C. Thicknesses of the films were maintained in the range of ~800–1000 nm. Transmission electron microscopy-selected area electron diffraction studies revealed the appearance of super-spots, thereby confirming the tilting of the oxygen sub-lattice at both high Na compositions. The bright-field imaging and scanning transmission electron microscopy-energy dispersive spectroscopy elemental mapping revealed KNN film with K-rich interfacial regions and Na-rich top region of the film at both the high Na composition, whereas the potassium niobate (KNbO3,x = 1) film showed no such oxygen sub-lattice tilting, and a sharp substrate-film interface was observed. The observed tilting of oxygen sub-lattice is a direct consequence of the reduced structural stability in high Na compositions in the KNN solid solutions.[ABSTRACT FROM AUTHOR] - Published
- 2017
- Full Text
- View/download PDF
10. Exploring the ability of stroke survivors in using the contralesional hemisphere to control a brain–computer interface.
- Author
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Mansour, Salem, Giles, Joshua, Ang, Kai Keng, Nair, Krishnan P. S., Phua, Kok Soon, and Arvaneh, Mahnaz
- Abstract
Brain-computer interfaces (BCIs) have recently been shown to be clinically effective as a novel method of stroke rehabilitation. In many BCI-based studies, the activation of the ipsilesional hemisphere was considered a key factor required for motor recovery after stroke. However, emerging evidence suggests that the contralesional hemisphere also plays a role in motor function rehabilitation. The objective of this study is to investigate the effectiveness of the BCI in detecting motor imagery of the affected hand from contralesional hemisphere. We analyzed a large EEG dataset from 136 stroke patients who performed motor imagery of their stroke-impaired hand. BCI features were extracted from channels covering either the ipsilesional, contralesional or bilateral hemisphere, and the offline BCI accuracy was computed using 10 × 10-fold cross-validations. Our results showed that most stroke patients can operate the BCI using either their contralesional or ipsilesional hemisphere. Those with the ipsilesional BCI accuracy of less than 60% had significantly higher motor impairments than those with the ipsilesional BCI accuracy above 80%. Interestingly, those with the ipsilesional BCI accuracy of less than 60% achieved a significantly higher contralesional BCI accuracy, whereas those with the ipsilesional BCI accuracy more than 80% had significantly poorer contralesional BCI accuracy. This study suggests that contralesional BCI may be a useful approach for those with a high motor impairment who cannot accurately generate signals from ipsilesional hemisphere to effectively operate BCI. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
11. Agitation after traumatic brain injury and predictors of outcome.
- Author
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Singh, Rajiv, Venkateshwara, Guru, Nair, Krishnan P. S., Khan, Muhammed, and Saad, Rafat
- Subjects
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COMPLICATIONS of brain injuries , *ACADEMIC medical centers , *ALCOHOLISM , *BRAIN injuries , *CHI-squared test , *LONGITUDINAL method , *NEUROPSYCHOLOGICAL tests , *EVALUATION of medical care , *MEDICAL rehabilitation , *PATIENTS , *PROBABILITY theory , *REHABILITATION centers , *T-test (Statistics) , *TOMOGRAPHY , *AGITATION (Psychology) , *MULTIPLE regression analysis , *SEVERITY of illness index , *DISEASE duration , *DATA analysis software , *DESCRIPTIVE statistics , *PROGNOSIS - Abstract
Objectives: To measure the incidence of agitation after traumatic brain injury (TBI) in an inpatient population and to identify any features associated with an adverse outcome Design: Prospective study of TBI admissions over 30 months in consecutive admissions with TBI to a regional neurorehabilitation unit. Outcome of agitation was compared to patient, injury and treatment features and any associations were sought. The presence of agitation was measured by the Agitation Behaviour Score. A good outcome for agitation was defined as a return to independent living with minimal care requirement at 6 months using an Extended Glasgow Outcome Scale (GOSE) score >4. Results: Over 30 months, there were 146 TBI admissions, of whom 53 cases had agitation (36.3%). Achieving 100% follow-up, 27 (51%) had a good outcome. On a multivariable logistic regression analysis, a good outcome was associated with the type of lesions seen on CT scan, the severity of agitation and the duration of the behaviour. Alcohol excess and type of treatment used for the behaviour were initially significant on univariate testing but dropped out of the logistic regression model. Conclusions: Over a third of TBI admissions, developed agitation and poor functional outcome was associated with CT scan findings, severity and duration of agitation. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
12. Defect thermodynamics and kinetics in thin strained ferroelectric films: The interplay of possible mechanisms.
- Author
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Morozovska, Anna N., Eliseev, Eugene A., Sankara Rama Krishnan, P. S., Tselev, Alexander, Strelkov, Evgheny, Borisevich, Albina, Varenyk, Olexander V., Morozovsky, Nicola V., Munroe, Paul, Kalinin, Sergei V., and Nagarajan, Valanoor
- Subjects
- *
THIN films , *FERROELECTRIC materials , *THERMODYNAMICS , *MECHANICS (Physics) , *ANALYTICAL mechanics , *ELECTRIC currents , *CONDENSED matter physics - Abstract
We present a theoretical description of the influence of misfit strain on mobile defects dynamics in thin strained ferroelectric films. Self-consistent solutions obtained by coupling the Poisson's equation for electric potential with continuity equations for mobile donor and electron concentrations and time-dependent Landau-Ginzburg-Devonshire equations reveal that the Vegard mechanism (chemical pressure) leads to the redistribution of both charged and electro-neutral defects in order to decrease the effective stress in the film. Internal electric fields, both built-in and depolarization ones, lead to a strong accumulation of screening space charges (charged defects and electrons) near the film interfaces. Importantly, the corresponding screening length is governed by the misfit strain and Vegard coefficient. Mobile defects dynamics, kinetics of polarization, and electric current reversal are defined by the complex interplay between the donor, electron and phonon relaxation times, misfit strain, finite size effect, and Vegard stresses. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
13. Dielectric tunability analysis of pyrochlore Bi1.5Zn1.0Nb1.5O7 using epitaxial films on pyrochlore Bi2Ru2O7 conductive layers.
- Author
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Nakajima, Mitsumasa, Ikariyama, Rikyu, Sankara Rama Krishnan, P. S., Yamada, Tomoaki, and Funakubo, Hiroshi
- Subjects
- *
DIELECTRIC devices , *PYROCHLORE , *CONDUCTIVE ceramics , *PHONONS , *MAGNETIC dipoles , *CHEMICAL vapor deposition - Abstract
To investigate the origin of the dielectric tunability, epitaxial Bi1.5Zn1.0Nb1.5O7 (BZN) films are grown on a pyrochlore Bi2Ru2O7 conductive layer by metal-organic chemical vapor deposition. The dielectric tunability is 41% at 2.5 MV/cm in the temperature range of 100-300 K, but is significantly suppressed below ∼100 K, suggesting that the dielectric tunability of the BZN film is due to random dipole contributions. However, a non-negligible dielectric tunability remains even at 4 K, implying that additional factors, such as phonons, contribute to the tunability. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
14. Low temperature neutron diffraction studies showing evidence for charge-exchange-type magnetic ordering in Mn doped SrRuO3.
- Author
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Singh, Brajendra, Sundar Manoharan, S., Sahu, R. K., Krishnan, P. S. R., Shinde, A. B., and Jain, Karishma
- Subjects
- *
LOW temperature research , *NEUTRON diffraction , *CHARGE exchange , *TRANSITION metal oxides , *MANGANITE , *ANTIFERROMAGNETISM - Abstract
SrRuO3 is a 4d transition metal oxide having a metallic and itinerant ferromagnetic character with TC∼165 K. Mn doping in SrRuO3 induces antiferromagnetic interaction, with the equiatomic composition SrRu0.5Mn0.5O3 showing TC∼125 K. Temperature dependent zero field cooled and field cooled magnetization data, resistivity data, and neutron diffraction studies on SrRu0.5Mn0.5O3 show the signature of the presence of two ferromagnetic zigzag chains coupled antiferromagnetically, called charge exchange (CE)-type antiferromagnetic ordering; this is contrary to the role of Ru+4, which is reported to remove charge ordering in manganites. The presence of significant amount of Mn+3 ions plays an important role in stabilizing the CE-type antiferromagnetic ordering. [ABSTRACT FROM AUTHOR]
- Published
- 2007
- Full Text
- View/download PDF
15. Growth of (111)-oriented epitaxial magnesium silicide (MgSi) films on (001) AlO substrates by RF magnetron sputtering and their properties.
- Author
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Katagiri, Atsuo, Ogawa, Shota, Uehara, Mutsuo, Sankara Rama Krishnan, P. S., Kurokawa, Mao, Matsushima, Masaaki, Shimizu, Takao, Akiyama, Kensuke, and Funakubo, Hiroshi
- Subjects
- *
ALUMINUM oxide , *MAGNETRON sputtering , *METALLIC films , *ORIENTATION (Chemistry) , *TRANSMISSION electron microscopy - Abstract
Epitaxial MgSi films with (111) orientation were successfully grown at 300 °C on (001) AlO insulating substrates by RF magnetron sputtering method. The optimal conditions for the epitaxial growth were identified as a low deposition rate and high deposition pressure above 60 mTorr. X-ray diffraction and transmission electron microscopy analysis confirmed the growth of (111)-oriented epitaxial MgSi films with the following relationship: (111) MgSi//(001)AlO. The conduction type of the epitaxial films was p-type up to 450 °C, which is same conduction type of the (110)-one-axis oriented ones. The electrical conductivity of the epitaxial films was lower than that of (110)-one-axis oriented ones. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
16. Heterogeneity in Composition along the Length of Cuscuta filaments.
- Author
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Misra, P. C., Setty, P. N., Singh, D. V., Lal, R. K., Viswanathan, P. N., Saxena, Y. R., and Krishnan, P. S.
- Subjects
- *
AMINO acids , *CARBOHYDRATES , *STARCH , *DNA , *RNA , *PARASITIC plants - Abstract
Considerable variations in the content of free amino acids, ethanol soluble carbohydrates, starch, protein, chlorophyll, phytic acid, RNA and DNA exist in different regions of the long filaments of Cuscuta reflexa. The distinction is especially pronounced when comparison is made between the haustoria-bearing curls of the parasite and the apical potions of the overhaniging filament. [ABSTRACT FROM AUTHOR]
- Published
- 1970
- Full Text
- View/download PDF
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