Phase transition and enhanced magneto-dielectric response in BiFeO3-DyMnO3 multiferroics

This work is partially supported by DST fast track Project No. SR/FTP/PS-16/2009. Dhiren K. Pradhan acknowledges IFN (NSF Grant No. EPS—01002410) for fellowship. The work at UPR was supported by National Science Foundation (NSF DMR 1410869) and Institute for Functional Nanomaterials (IFN).We report systematic studies on crystal structure and magneto-dielectric properties of (1 − x) BiFeO3-x DyMnO3 (0.0 ≤ x ≤ 0.2) nanoceramics synthesized by auto-combustion method. Rietveld refinement of X-ray diffraction data indicates a structural transition from R3c to R3c + Pn21a at x = 0.1. Field emission scanning electron micrographs display a decrease in grain size with increase in x. The presence of dielectric anomalies around antiferromagnetic transition temperature implies the magnetoelectric coupling. Dielectric measurements showed decrease in magnetic ordering temperature with increasing x in agreement with differential scanning calorimetry results. A significant increase in magnetization has been found with increasing DyMnO3 substitution. Magneto-impedance spectroscopy reveals a significant change (∼18%) in dielectricpermittivity at H = 2 T for x = 0.2.Peer reviewe

Primary neuroendocrine carcinoma of brain radiologically mimicking high grade glioma: A case report and review of literature

Primary neuro-endocrine carcinoma (NEC) of central nervous system is extremely rare; only one case is reported till date. It mainly involves the dura, frontal lobe and paranasal sinus close to anterior skull base. We report a case of intrinsic brain tumor in left frontal lobe with extension to corpus callosum whose pre-operative MRI diagnosis was high grade glioma. He was operated, intra operative squash and post operative histopathological diagnosis of the tumor came as high grade glioma. However, on immunohistochemical (IHC) study the diagnosis turned out to be primary neuro endocrine carcinoma of brain

Phase transition and magneto-electric coupling of BiFeO3-YMnO3 multiferroic nanoceramics

We report the crystal structure, dielectric, magnetic, and magneto-electric properties of (1-x) BiFeO3-xYMnO(3) (0.00 <= x <= 0.2) multiferroic nanoceramics prepared by auto-combustion technique. YMnO3 substitution is found to induce a structural phase transition from R3c to R3c+Pbnm after x approximate to 0.1 using Rietveld refinement technique. Field emission scanning electron micrographs show decrease in grain size with increase in YMnO3 content. The dielectric permittivity and loss tangent are found to be increased with composition x. The anomalies noticed from the temperature dependent dielectric analysis reveal the signature of magneto-electric coupling in the system. A decrease in magnetic ordering temperature as a function of composition is found from dielectric study. At room temperature, the dielectric permittivity of all the YMnO3 modified samples decrease with increasing magnetic field. The maximum value of magneto-electric coupling coefficient (epsilon(H)-epsilon(0))/epsilon(0) is found to be similar to -5.5% at H = 2 T for x = 0.2. The behaviour of the magnetic hysteresis loop observed at room temperature suggests the suppression of space modulated spin structure. (C) 2013 AIP Publishing LLC

Structural, microstructural and magneto-electric properties of single-phase BiFeO3 nanoceramics prepared by auto-combustion method

Polycrystalline nano BiFeO3 powders were synthesized by auto-combustion method using urea as fuel and metal nitrates (Fe(NO3)(3).9H(2)O, Bi(NO3)(3)-5H(2)O) as oxidizers. In order to optimize the single-phase synthesis condition of BiFeO3, different fuel to oxidizer ratios have been investigated. The preliminary structural investigation using X-ray diffraction shows the samples were of single phase and crystallize in rhombohedral structure (R3c). The ferroelectric and antiferromagnetic ordering temperatures of BiFeO3 were found to be 832 degrees C and 364 degrees C respectively, from differential thermal analysis. The temperature dependent dielectric study shows an anomaly around 215 degrees C which corresponds to magneto-electric coupling in the material. Field-emission scanning electron micrographs show effect of fuel to oxidizer ratio on grain size evolution. The ferroelectric hysteresis loops for all the samples were measured at a frequency of 100 Hz confirming the ferroelectric nature. An evidence of magneto-electric coupling was also observed at room temperature from magneto-capacitance measurements. (C) 2013 Elsevier B.V. All rights reserved

Experience of establishing and coordinating a nationwide network for bidirectional intussusception surveillance in India: lessons for multisite research studies

Objectives To document and share the process of establishing the nationally representative multisite surveillance network for intussusception in India, coordination, data management and lessons learnt from the implementation.Design This study combined both retrospective and prospective surveillance approaches.Setting 19 tertiary care institutions were selected in India considering the geographic representation and public and private mixParticipants All children under-2 years of age with intussusceptionPrimary and secondary outcome measures The experience of site selection, regulatory approvals, data collection, quality assurance and network coordination were documented.Results The site selection process involved systematic and objective four steps including shortlisting of potential institutions, information seeking and telephonic interaction, site visits and site selection using objective criteria. Out of over 400 hospitals screened across India, 40 potential institutions were shortlisted and information was sought by questionnaire and interaction with investigators. Out of these, 25 institutes were visited and 19 sites were finally selected to participate in the study. The multistep selection process allowed filtering and identification of sites with adequate capacity and motivated investigators. The retrospective surveillance documented 1588 cases (range: 14–652 cases/site) and prospective surveillance recruited 621 cases (range: 5–191 cases/site). The multilayer quality assurance measures monitored and ensured protocol adherence, complete record retrieval and data completeness. The key challenges experienced included time taken for obtaining regulatory and ethical approvals, which delayed completion of the study. Ten sites continued with another multisite vaccine safety surveillance study.Conclusion The experience and results of this systematic and objective site selection method in India are promising. The systematic multistep site selection and data quality assurance methods presented here are feasible and practical. The lessons from the establishment and coordination of this surveillance network can be useful in planning, selecting the sites and conducting multisite and surveillance studies in India and developing countries