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Razaq M, Pareek V, Srivastava A, Ramesh R. P2.01-83 Role of Exosomal MicroRNAs (miRNAs) as Predictors of Response to Treatment and Prognosis in Non-Small Cell Lung Cancer (NSCLC). J Thorac Oncol 2019. [DOI: 10.1016/j.jtho.2019.08.1426] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Hsu SL, McCarter MR, Dai C, Hong Z, Chen LQ, Nelson CT, Martin LW, Ramesh R. Emergence of the Vortex State in Confined Ferroelectric Heterostructures. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1901014. [PMID: 31322297 DOI: 10.1002/adma.201901014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Revised: 06/17/2019] [Indexed: 06/10/2023]
Abstract
The manipulation of charge and lattice degrees of freedom in atomically precise, low-dimensional ferroelectric superlattices can lead to exotic polar structures, such as a vortex state. The role of interfaces in the evolution of the vortex state in these superlattices (and the associated electrostatic and elastic boundary conditions they produce) has remained unclear. Here, the toroidal state, arranged in arrays of alternating clockwise/counterclockwise polar vortices, in a confined SrTiO3 /PbTiO3 /SrTiO3 trilayer is investigated. By utilizing a combination of transmission electron microscopy, synchrotron-based X-ray diffraction, and phase-field modeling, the phase transition as a function of layer thickness (number of unit cells) demonstrates how the vortex state emerges from the ferroelectric state by varying the thickness of the confined PbTiO3 layer. Intriguingly, the vortex state arises at head-to-head domain boundaries in ferroelectric a1 /a2 twin structures. In turn, by varying the total number of PbTiO3 layers (moving from trilayer to superlattices), it is possible to manipulate the long-range interactions among multiple confined PbTiO3 layers to stabilize the vortex state. This work provides a new understanding of how the different energies work together to produce this exciting new state of matter and can contribute to the design of novel states and potential memory applications.
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Yadav AK, Nguyen KX, Hong Z, García-Fernández P, Aguado-Puente P, Nelson CT, Das S, Prasad B, Kwon D, Cheema S, Khan AI, Hu C, Íñiguez J, Junquera J, Chen LQ, Muller DA, Ramesh R, Salahuddin S. Author Correction: Spatially resolved steady-state negative capacitance. Nature 2019; 568:E13. [PMID: 30971827 DOI: 10.1038/s41586-019-1106-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In this Letter, the first name of author Bhagwati Prasad was misspelled Bhagawati. This error has been corrected online.
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Stoica VA, Laanait N, Dai C, Hong Z, Yuan Y, Zhang Z, Lei S, McCarter MR, Yadav A, Damodaran AR, Das S, Stone GA, Karapetrova J, Walko DA, Zhang X, Martin LW, Ramesh R, Chen LQ, Wen H, Gopalan V, Freeland JW. Optical creation of a supercrystal with three-dimensional nanoscale periodicity. NATURE MATERIALS 2019; 18:377-383. [PMID: 30886403 DOI: 10.1038/s41563-019-0311-x] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Accepted: 02/04/2019] [Indexed: 06/09/2023]
Abstract
Stimulation with ultrafast light pulses can realize and manipulate states of matter with emergent structural, electronic and magnetic phenomena. However, these non-equilibrium phases are often transient and the challenge is to stabilize them as persistent states. Here, we show that atomic-scale PbTiO3/SrTiO3 superlattices, counterpoising strain and polarization states in alternate layers, are converted by sub-picosecond optical pulses to a supercrystal phase. This phase persists indefinitely under ambient conditions, has not been created via equilibrium routes, and can be erased by heating. X-ray scattering and microscopy show this unusual phase consists of a coherent three-dimensional structure with polar, strain and charge-ordering periodicities of up to 30 nm. By adjusting only dielectric properties, the phase-field model describes this emergent phase as a photo-induced charge-stabilized supercrystal formed from a two-phase equilibrium state. Our results demonstrate opportunities for light-activated pathways to thermally inaccessible and emergent metastable states.
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Spaldin NA, Ramesh R. Advances in magnetoelectric multiferroics. NATURE MATERIALS 2019; 18:203-212. [PMID: 30783227 DOI: 10.1038/s41563-018-0275-2] [Citation(s) in RCA: 298] [Impact Index Per Article: 59.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Accepted: 12/17/2018] [Indexed: 05/05/2023]
Abstract
The manipulation of magnetic properties by an electric field in magnetoelectric multiferroic materials has driven significant research activity, with the goal of realizing their transformative technological potential. Here, we review progress in the fundamental understanding and design of new multiferroic materials, advances in characterization and modelling tools to describe them, and the exploration of devices and applications. Focusing on the translation of the many scientific breakthroughs into technological innovations, we identify the key open questions in the field where targeted research activities could have maximum impact in transitioning scientific discoveries into real applications.
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Yi D, Yu P, Chen YC, Lee HH, He Q, Chu YH, Ramesh R. Tailoring Magnetoelectric Coupling in BiFeO 3 /La 0.7 Sr 0.3 MnO 3 Heterostructure through the Interface Engineering. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1806335. [PMID: 30663174 DOI: 10.1002/adma.201806335] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2018] [Revised: 12/15/2018] [Indexed: 06/09/2023]
Abstract
Electric field control of magnetism ultimately opens up the possibility of reducing energy consumption of memory and logic devices. Electric control of magnetization and exchange bias are demonstrated in all-oxide heterostructures of BiFeO3 (BFO) and La0.7 Sr0.3 MnO3 (LSMO). However, the role of the polar heterointerface on magnetoelectric (ME) coupling is not fully explored. Here, the ME coupling in BFO/LSMO heterostructures with two types of interfaces, achieved by exploiting the interface engineering at the atomic scale, is investigated. It is shown that both magnetization and exchange bias are reversibly controlled by switching the ferroelectric polarization of BFO. Intriguingly, distinctly different modulation behaviors that depend on the interfacial atomic sequence are observed. These results provide new insights into the underlying physics of ME coupling in the model system. This study highlights that designing interface at the atomic scale is of general importance for functional spintronic devices.
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Ganesh S, Nandhini T, Samuel VD, Sreeraj CR, Abhilash KR, Purvaja R, Ramesh R. Marine snakes of Indian coasts: historical resume, systematic checklist, toxinology, status, and identification key. JOURNAL OF THREATENED TAXA 2019. [DOI: 10.11609/jott.3981.11.1.13132-13150] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
We compile an up-to-date checklist of 26 species of marine snakes known from the Indian coastlines. We furnish information on the original orthography, authorship, date of publication, current binominal representation, synonymy and chresonymy lists for each recognized taxon. In addition, we provide details of name-bearing types, repository and type locality (both original and subsequent restrictions where applicable) of the prevailing nomen for all recognized species. We summarise the history of research on Indian marine snakes from Linnaeus to the present day, including taxonomic and regional treatises, and highlight the taxonomic flux. We also provide a revised key for this group to facilitate easier identification and support effective conservation.
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Parthasarathy P, Aithal RR, Raghavendra Rao RS, Raghuram S, Ramesh R, Nazneen A. Correlation of Symphysiofundal Height and Abdominal Girth with the Incidence of Hypotension in Cesarean Section Under Spinal Anesthesia using Bupivacaine with Fentanyl as Adjuvant: A Clinical Study. Anesth Essays Res 2019; 13:214-218. [PMID: 31198233 PMCID: PMC6545932 DOI: 10.4103/aer.aer_36_19] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
Background and Aims: A decreased lumbosacral subarachnoid space volume is a major factor in cephalad intrathecal spread of local anesthetic in term parturients due to compressive effect of the gravid uterus. The aim of this study was to assess the relationship of symphysiofundal height (SFH) and abdominal girth (AG) with the incidence of hypotension and the highest level of sensory blockade. Settings and Design: This study was a prospective observational study. Materials and Methods: Ninety parturients under the American Society of Anesthesiologists physical status class II within the age range of 20–30 years, weighing between 60 and 65 kg, and height between 150 and 155 cm were studied, and the SFH and AG of all parturients had been measured just before spinal anesthesia. Hyperbaric bupivacaine 9 mg with 12.5 μg intrathecal fentanyl was administered for subarachnoid block. The incidence of hypotension and the highest level of sensory block were assessed. Statistical Analysis: Correlation analysis (Spearman's rank test) was applied to analyze the data, and P < 0.05 was considered to be statistically significant. Results: The incidence of hypotension was higher with increasing SFH (16.9% with SFH of 30–35 cm, 78.37% with SFH of 36–40 cm; correlation coefficient ρ =0.338) and with increasing AG (5.3% with AG between 85 and 89 cm, 35.7% with AG 90–94 cm, 62.8% with AG 95–99 cm; ρ =0.341), and both were statistically significant (P < 0.001). There was a statistically significant correlation between increasing SFH and maximum sensory block achieved (ρ =0.157, P < 0.001). There was increased level of sensory blockade with increased AG but was not statistically significant (ρ =0.011, P = 0.32). Conclusion: In term parturients undergoing cesarean section under spinal anesthesia, the SFH has a significant positive correlation with the incidence of hypotension and ascent of spinal anesthesia. AG also has a positive correlation with the incidence of hypotension but is not significant with the ascent of spinal anesthesia.
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Karthik R, Robin RS, Purvaja R, Ganguly D, Anandavelu I, Raghuraman R, Hariharan G, Ramakrishna A, Ramesh R. Microplastics along the beaches of southeast coast of India. THE SCIENCE OF THE TOTAL ENVIRONMENT 2018; 645:1388-1399. [PMID: 30248861 DOI: 10.1016/j.scitotenv.2018.07.242] [Citation(s) in RCA: 178] [Impact Index Per Article: 29.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Revised: 07/16/2018] [Accepted: 07/16/2018] [Indexed: 05/18/2023]
Abstract
Occurrence of microplastics (plastic debris <5 mm) along the coast is a growing concern worldwide, due to increased input of discarded wastes from various sources. In order to evaluate the extent of microplastic pollution on the sandy beaches (25 locations) along Tamil Nadu coast (1076 km), India, microplastic debris were quantified and categorized into four different size classes. The beaches were classified according to potential sources of pollution i.e. riverine, tourism and fisheries. Beach samples collected from the high tide line contained significantly higher abundance of microplastic than at the low tide line. Beaches adjacent to rivers exhibited relatively higher microplastic abundance compared to those influenced by tourism and fishing activities. Out of the total detected debris, plastic fragments were the maximum (47-50%), followed by line/fibres (24-27%) and foam (10-19%) materials. Fourier Transform Infrared Spectroscopy (FTIR) analysis revealed that polyethylene, polypropylene, and polystyrene were the main types of microplastics present in these beaches. Gut content analysis of commercially important fishes, collected from the coastal waters, revealed microplastics ingestion in 10.1% of fishes. The results indicate that microplastics accumulation in the coastal environment, especially close to the river mouths, may be a serious concern, due to its ability to enter into the marine food web and highlights the necessity of microplastics screening from estuarine, coastal waters and other potential sources.
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Prasad MHK, Ganguly D, Paneerselvam A, Ramesh R, Purvaja R. Seagrass litter decomposition: an additional nutrient source to shallow coastal waters. ENVIRONMENTAL MONITORING AND ASSESSMENT 2018; 191:5. [PMID: 30523426 DOI: 10.1007/s10661-018-7127-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Accepted: 11/23/2018] [Indexed: 06/09/2023]
Abstract
Seagrass ecosystems are vital for its regulatory services yet, highly threatened by degradation due to human pressures. Decomposition of two tropical seagrass species (Cymodocea serrulata and Cymodocea rotundata) was studied and compared, to understand their potential in generating additional nutrients to coastal waters. Release of carbon, nitrogen and phosphorus during the decomposition process of seagrass wracks was estimated in bacteria-active (non-poisoned) and bacteria-inhibited (poisoned) conditions from shore-washed fresh seagrass, sampled from Palk Bay, India. Incubation experiments for 25 days indicated a near three times higher concentration of dissolved organic carbon (DOC) in bacteria-inhibited flasks compared to bacteria-active conditions for both species. The maximum leaching rates of DOC, TDN and TDP were found to be 294, 65.1 and 11.2 μM/g dry wt/day, respectively. Further, higher release of dissolved inorganic nitrogen (DIN) (> 1.3 times) was documented from the bacteria-active flask, highlighting the significance of microbial process in generating bio-available nutrients from decaying seagrass. Faster decomposition (0.014 ± 0.004 day-1) in the initial stages (up to 8 days) compared to the later stages (0.005 ± 0.001 day-1) indicated a rapid loss of biomass carbon during the initial leaching process and its relative importance in the decomposition pathway. The decomposition rate is best described by a single-stage exponential decay model with a half-life of 41 days. It is estimated that the total seagrass litter available along the Palk Bay coast is about ~ 0.3 Gg with high potential of additional nitrogen (0.9 ± 0.5 Mg) and phosphorus (0.3 ± 0.1 Mg) supply to the adjacent coastal waters.
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Yuan S, Das S, Ramesh R, Qiao C. Service Agreement Trifecta: Backup Resources, Price and Penalty in the Availability-Aware Cloud. INFORMATION SYSTEMS RESEARCH 2018. [DOI: 10.1287/isre.2017.0755] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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112
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Rajarajan S, Prabhu J, Korlimarla A, Nair M, Alexander A, Kaluve R, Ps H, Raja U, Ramesh R, Patil S, Bs S, Ts S. MicroRNA based immune response signature identifies poor prognostic subgroup within ER negative breast cancers. Ann Oncol 2018. [DOI: 10.1093/annonc/mdy428.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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113
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Manipatruni S, Nikonov DE, Lin CC, Prasad B, Huang YL, Damodaran AR, Chen Z, Ramesh R, Young IA. Voltage control of unidirectional anisotropy in ferromagnet-multiferroic system. SCIENCE ADVANCES 2018; 4:eaat4229. [PMID: 30480090 PMCID: PMC6251722 DOI: 10.1126/sciadv.aat4229] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2018] [Accepted: 10/25/2018] [Indexed: 05/12/2023]
Abstract
Demonstration of ultralow energy switching mechanisms is imperative for continued improvements in computing devices. Ferroelectric (FE) and multiferroic (MF) order and their manipulation promise an ideal combination of state variables to reach attojoule range for logic and memory (i.e., ~30× lower switching energy than nanoelectronics). In BiFeO3 (BFO), the coupling between the antiferromagnetic (AFM) and FE order is robust at room temperature, scalable in voltage, stabilized by the FE order, and can be integrated into a fabrication process for a beyond-CMOS (complementary metal-oxide semiconductor) era. The presence of the AFM order and a canted magnetic moment in this system causes exchange interaction with a ferromagnet such as Co0.9Fe0.1 or La0.7Sr0.3MnO3. Previous research has shown that exchange coupling (uniaxial anisotropy) can be controlled with an electric field. However, voltage modulation of unidirectional anisotropy, which is preferred for logic and memory technologies, has not yet been demonstrated. Here, we present evidence for electric field control of exchange bias of laterally scaled spin valves that is exchange coupled to BFO at room temperature. We show that the exchange bias in this bilayer is robust, electrically controlled, and reversible. We anticipate that magnetoelectricity at these scaled dimensions provides a powerful pathway for computing beyond modern nanoelectronics by enabling a new class of nonvolatile, ultralow energy computing elements.
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Banerjee K, Paneerselvam A, Ramachandran P, Ganguly D, Singh G, Ramesh R. Seagrass and macrophyte mediated CO2 and CH4 dynamics in shallow coastal waters. PLoS One 2018; 13:e0203922. [PMID: 30296285 PMCID: PMC6175284 DOI: 10.1371/journal.pone.0203922] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Accepted: 08/30/2018] [Indexed: 11/27/2022] Open
Abstract
Seagrass meadows are among the most important coastal/ marine ecosystems for long-term carbon storage and conditioning of coastal waters. A combined air-water flux of CO2 and CH4 from the seagrass meadows was studied for the first time from Asia's largest brackish-water lagoon, Chilika, India. Ecosystem-based comparisons were carried out during two hydrologically different conditions of dry and wet seasons in the seagrass dominated southern sector (SS); macrophyte-dominated northern sector (NS); the largely un-vegetated central sector (CS) and the tidally active outer channel (OC) of the lagoon. The mean fluxes of CO2 from SS, NS, CS and OC were 9.8, 146.6, 48.4 and 33.0mM m-2d-1, and that of CH4 were 0.12, 0.11, 0.05 and 0.07mM m-2d-1, respectively. The net emissions (in terms of CO2 equivalents), considering the global warming potential of CO2 (GWP: 1) and CH4 (GWP: 28) from seagrass meadows were over 14 times lower compared to the macrophyte-dominated sector of the lagoon. Contrasting emissivity characteristics of CO2 and CH4 were observed between macrophytes and seagrass, with the former being a persistent source of CO2. It is inferred that although seagrass meadows act as a weak source of CH4, they could be effective sinks of CO2 if land-based pollution sources are minimized.
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Kumar S, Bhavya PS, Ramesh R, Gupta GVM, Chiriboga F, Singh A, Karunasagar I, Rai A, Rehnstam-Holm AS, Edler L, Godhe A. Nitrogen uptake potential under different temperature-salinity conditions: Implications for nitrogen cycling under climate change scenarios. MARINE ENVIRONMENTAL RESEARCH 2018; 141:196-204. [PMID: 30213661 DOI: 10.1016/j.marenvres.2018.09.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Revised: 08/25/2018] [Accepted: 09/02/2018] [Indexed: 06/08/2023]
Abstract
As projected by climate change models, increase in sea surface temperature and precipitation in the future may alter nutrient cycling in the coastal regions due to potential changes in phytoplankton community structure and their ability to assimilate nitrogen (N) and carbon (C). An experiment simulating different temperature and salinity conditions (28°C-35 ambient conditions, 28ºC-31, 31ºC-35 and 31ºC-31) in mesocosms containing 1000 L of coastal water from the Arabian Sea was performed and N uptake rates were measured using 15N tracer technique on 2nd, 5th, 7th and 10th day of the experiment. The results show that, under all conditions, the total N (NO3- + NH4+) uptake rates were lower in the beginning and on the final day of the tracer experiment, while it peaked during middle, consistent with chlorophyll a concentrations. Total N uptake rate was significantly lower (p = 0.003) under ambient temperature-lower salinity condition (28ºC-31) than the others. This indicates that lowering of salinity in coastal regions due to excessive rainfall in the future may affect the N uptake potential of the phytoplankton, which may change the regional C and N budget.
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Harish S, Naveen AN, Abinaya R, Archana J, Ramesh R, Navaneethan M, Shimomura M, Hayakawa Y. Enhanced performance on capacity retention of hierarchical NiS hexagonal nanoplate for highly stable asymmetric supercapacitor. Electrochim Acta 2018. [DOI: 10.1016/j.electacta.2018.06.161] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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117
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Shanmugasundaram OL, Syed Zameer Ahmed K, Sujatha K, Ponnmurugan P, Srivastava A, Ramesh R, Sukumar R, Elanithi K. Fabrication and characterization of chicken feather keratin/polysaccharides blended polymer coated nonwoven dressing materials for wound healing applications. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2018; 92:26-33. [PMID: 30184750 DOI: 10.1016/j.msec.2018.06.020] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Revised: 05/20/2018] [Accepted: 06/11/2018] [Indexed: 02/05/2023]
Abstract
In this research work, three kinds of nonwoven wound dressings were developed from chicken feather keratin (CFK-NW), keratin‑sodium alginate (CFK-SA-NW) and keratin-chitosan (CFK-CS-NW) and characterized using FTIR and SEM. The physical characteristics such as air permeability, thickness and areal density test results revealed the suitability of fabricated materials for wound dressing applications. CFK-SA-NW and CFK-CS-NW indicated a positive antibacterial effect against Gram's positive Staphylococcus aureus and Gram's negative Klebsiella pneumoniae and Escherichia coli bacteria with the zone of inhibition enhanced over >2.0 cm. Moreover, the biomedical potentials of dressing materials has been investigated by cell viability and cytotoxicity tests. Further, the wound healing ability was demonstrated using in vivo model (Albino Wistar rat). The fabricated materials exhibited good support for cell viability and a strong cytocompatibility. Furthermore, the hundred percent wound healing ability of CFK-CS-NW, CFK-SA-NW, CFK-NW and untreated control rats was observed at 15, 17, 21 and 23 days, respectively, Moreover, the wound healing potential of CFK-CS-NW and CFK-SA-NW was found to be better than that of CFK-NW and control group of rats. The outcome of the present study discloses the prospective applications of the developed materials as wound dressing biomaterial.
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Arumugam K, Srinivasalu S, Purvaja R, Ramesh R. Distribution of Major and trace elements in Koppunuru area, Guntur district, Andhra Pradesh, India. Data Brief 2018; 18:180-189. [PMID: 29896509 PMCID: PMC5995752 DOI: 10.1016/j.dib.2018.02.060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Revised: 02/22/2018] [Accepted: 02/22/2018] [Indexed: 11/18/2022] Open
Abstract
From koppunuru study area totally 58 samples were collected in 7 different boreholes, minimum depth of 28 m and Maximum depth of 157.7 m. The borehole samples geochemical analysis (major and trace elements) was carried out at Atomic Minerals Directorate for Exploration & Research (AMD), Hyderabad, India. Major and trace element studies have been conducted on the Neoproterozoic Palnad sub-basin Andhra Pradesh, South India, to determine their Geochemistry, Uranium mineralization and provenance characteristics. Geochemically, this sedimentary basin has a different litho – unit like as gritty quartzite, conglomerate, and Shale. This study area mainly dominated by Uranium deposited and radioactive elements are predominately deposit. Strong positive correlation between Uranium and Lead (r = 0.887) suggested radiogenic nature of this system.
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Carmel S, Pon A, Meenakshisundaram N, Ramesh R, Bhattacharyya A. Bandgap scaling and negative differential resistance behavior of zigzag phosphorene antidot nanoribbons (ZPANRs). Phys Chem Chem Phys 2018; 20:14855-14863. [PMID: 29781502 DOI: 10.1039/c8cp01435c] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
This work examines the prospect of phosphorene antidot nanoribbons (PANRs) using the density functional based tight binding (DFTB) method. Horizontally perforated PANRs with both armchair (A) and zigzag (Z) configurations were considered for electrical simulations. Our simulation results found that the APANRs cannot be scaled down with nanoribbon width, whereas ZPANRs can be scaled easily. Bandgap scaling in terms of ribbon width, length and antidot number was thoroughly analyzed for ZPANRs. In the end, a two-terminal device was constructed and transmission analysis was performed using the non-equilibrium Green's function (NEGF) methodology. A negative differential resistance (NDR) region appeared in the current-voltage characteristics of the ZPANRs, which paved a pathway for nano-device application.
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Huang BC, Yu P, Chu YH, Chang CS, Ramesh R, Dunin-Borkowski RE, Ebert P, Chiu YP. Atomically Resolved Electronic States and Correlated Magnetic Order at Termination Engineered Complex Oxide Heterointerfaces. ACS NANO 2018; 12:1089-1095. [PMID: 29384356 DOI: 10.1021/acsnano.7b06004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We map electronic states, band gaps, and interface-bound charges at termination-engineered BiFeO3/La0.7Sr0.3MnO3 interfaces using atomically resolved cross-sectional scanning tunneling microscopy. We identify a delicate interplay of different correlated physical effects and relate these to the ferroelectric and magnetic interface properties tuned by engineering the atomic layer stacking sequence at the interfaces. This study highlights the importance of a direct atomically resolved access to electronic interface states for understanding the intriguing interface properties in complex oxides.
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Campanini M, Erni R, Yang CH, Ramesh R, Rossell MD. Periodic Giant Polarization Gradients in Doped BiFeO 3 Thin Films. NANO LETTERS 2018; 18:717-724. [PMID: 29314853 DOI: 10.1021/acs.nanolett.7b03817] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The ultimate challenge for the development of new multiferroics with enhanced properties lies in achieving nanoscale control of the coupling between different ordering parameters. In oxide-based multiferroics, substitutional cation dopants offer the unparalleled possibility to modify both the electric and magnetic properties at a local scale. Herein it is demonstrated the formation of a dopant-controlled polar pattern in BiFeO3 leading to the spontaneous instauration of periodic polarization waves. In particular, nonpolar Ca-doped rich regions act as spacers between consecutive dopant-depleted regions displaying coupled ferroelectric states. This alternation of layers with different ferroelectric state creates a novel vertical polar structure exhibiting giant polarization gradients as large as 70 μC cm-2 across 30 Å thick domains. The drastic change in the polar state of the film is visualized using high-resolution differential phase-contrast imaging able to map changes in ferroelectric polarization at atomic scale. Furthermore, a periodic distortion in the Fe-O-Fe bonding angle suggests a local variation in the magnetic ordering. The findings provide a new insight into the role of doping and reveal hitherto unexplored means to tailor the functional properties of multiferroics by doping engineering.
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Sreeraj CR, Abhilash KR, Deepak Samuel V, Krishnan P, Purvaja R, Ramesh R. Occurrence of Live Rhodolith Bed of <i>Lithophyllum kotschyanum</i> Unger (Corallinaceae:Lithophylloideae) in Palk Bay:First Record from India. CURR SCI INDIA 2018. [DOI: 10.18520/cs%2fv114%2fi03%2f445-446] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Sreeraj CR, Abhilash KR, Deepak Samuel V, Krishnan P, Purvaja R, Ramesh R. Occurrence of Live Rhodolith Bed of <i>Lithophyllum kotschyanum</i> Unger (Corallinaceae:Lithophylloideae) in Palk Bay:First Record from India. CURR SCI INDIA 2018. [DOI: 10.18520/cs/v114/i03/445-446] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Krishnan P, Purvaja R, Sreeraj CR, Raghuraman R, Robin RS, Abhilash KR, Mahendra RS, Anand A, Gopi M, Mohanty PC, Venkataraman K, Ramesh R. Differential Bleaching Patterns in Corals of Palk Bay and the Gulf of Mannar. CURR SCI INDIA 2018. [DOI: 10.18520/cs/v114/i03/679-685] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Kim KE, Jeong S, Chu K, Lee JH, Kim GY, Xue F, Koo TY, Chen LQ, Choi SY, Ramesh R, Yang CH. Configurable topological textures in strain graded ferroelectric nanoplates. Nat Commun 2018; 9:403. [PMID: 29374260 PMCID: PMC5785989 DOI: 10.1038/s41467-017-02813-5] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Accepted: 12/28/2017] [Indexed: 11/20/2022] Open
Abstract
Topological defects in matter behave collectively to form highly non-trivial structures called topological textures that are characterised by conserved quantities such as the winding number. Here we show that an epitaxial ferroelectric square nanoplate of bismuth ferrite subjected to a large strain gradient (as much as 105 m−1) associated with misfit strain relaxation enables five discrete levels for the ferroelectric topological invariant of the entire system because of its peculiar radial quadrant domain texture and its inherent domain wall chirality. The total winding number of the topological texture can be configured from − 1 to 3 by selective non-local electric switching of the quadrant domains. By using angle-resolved piezoresponse force microscopy in conjunction with local winding number analysis, we directly identify the existence of vortices and anti-vortices, observe pair creation and annihilation and manipulate the net number of vortices. Our findings offer a useful concept for multi-level topological defect memory. Exploring topological textures in ferroelectrics facilitates the understanding and application of topological features in matter. Here the authors demonstrate the strain field induced evolution of topological vortices in nanoplatelets of rhombohedral phase BiFeO3 using the angle-resolved piezoresponse force microscopy.
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