Enhancement of optical absorption in multiferroic (1-x)PZT-xPFN thin films: Experiments and first-principles analysis

Multiferroic compounds have gained research attention in the field of ferroelectric photovoltaics due to the presence of transition-metal d states from magnetic ions, which tend to reduce the bandgap value. In this work, 0.5Pb(Zr0.52Ti0.48)O3 - 0.5Pb(Fe0.5Nb0.5)O3 PZTFN0.5 thin films were synthesized using a sol-gel route to investigate the effect of iron doping on optical and multiferroic properties. For comparative analysis, the end-member compositions, Pb(Zr0.52Ti0.48)O3 (PZT) and Pb(Fe0.5Nb0.5)O3 (PFN), were also synthesized under identical conditions. Our results revealed that the presence of Fe ions, besides inducing multiferroic behavior, effectively enhances the optical absorption of the material in the visible light region. Optical transitions at 3.0 eV (2.4 eV) and 2.7 eV (2.2 eV) for the direct (indirect) bandgap were determined for PZTFN0.5 and PFN, respectively, indicating that the absorption edges of the iron-containing films result more promising than PZT (Eg 3.6eV) for photovoltaic applications. Both PZTFN0.5 and PFN thin films exhibit multiferroic behavior at room temperature, with different electric and magnetic properties. While PZTFN0.5 presents saturated hysteresis loops with remanent polarization values around 10 uC/cm2 and magnetization of 1.6 emu/cm2, PFN displays significantly larger remanence (31 emu/cm2) but poorer ferroelectric properties due to the presence of leakage. Microscopic insights into the structural and electronic properties of the PZTFN0.5 solid solution were provided from first-principles calculations

Sol-gel synthesis and multiferroic properties of pyrochlore-free Pb(Fe0.5Nb0.5)O3 thin films

Lead iron niobate (PbFe0.5Nb0.5O3 - PFN) thin films were synthesized by a modified sol-gel route, which offers the advantage of a rapid, simple and non-toxic reaction method. Polycrystalline perovskite-structured PFN thin films without pyrochlore phases were obtained on Pt/Ti/SiO2/Si substrates after sintering by rapid thermal annealing at 650 {\deg}C. TEM and AFM images confirmed the excellent quality of the sintered film, while EDS spectroscopy revealed the presence of oxygen vacancies near the film/substrate interface. Electric measurements show good dielectric properties and ferroelectric behavior, characterized by typical C-V curves and well-defined P-E ferroelectric loops at 1 kHz, with remanent polarization values of ~12 uC/cm2. The polarization, however, increases with decreasing frequency, indicating the presence of leakage currents. I-V measurements show a significant increase in DC-conduction at relatively low fields (around 100 kV/cm). The films display ferromagnetic behavior at room temperature, with magnetic remanence around 30 emu/cm3 and a coercive field of 1 kOe. These values are significantly higher than those obtained for PFN powders fabricated by the same sol-gel route, as well as the magnetization values reported in the literature for epitaxial films.Comment: 24 pages, 10 figure

International nosocomial infection control consortium (INICC) report, data summary of 36 countries, for 2004-2009

The results of a surveillance study conducted by the International Nosocomial Infection Control Consortium (INICC) from January 2004 through December 2009 in 422 intensive care units (ICUs) of 36 countries in Latin America, Asia, Africa, and Europe are reported. During the 6-year study period, using Centers for Disease Control and Prevention (CDC) National Healthcare Safety Network (NHSN; formerly the National Nosocomial Infection Surveillance system [NNIS]) definitions for device-associated health care-associated infections, we gathered prospective data from 313,008 patients hospitalized in the consortium's ICUs for an aggregate of 2,194,897 ICU bed-days. Despite the fact that the use of devices in the developing countries' ICUs was remarkably similar to that reported in US ICUs in the CDC's NHSN, rates of device-associated nosocomial infection were significantly higher in the ICUs of the INICC hospitals; the pooled rate of central line-associated bloodstream infection in the INICC ICUs of 6.8 per 1,000 central line-days was more than 3-fold higher than the 2.0 per 1,000 central line-days reported in comparable US ICUs. The overall rate of ventilator-associated pneumonia also was far higher (15.8 vs 3.3 per 1,000 ventilator-days), as was the rate of catheter-associated urinary tract infection (6.3 vs. 3.3 per 1,000 catheter-days). Notably, the frequencies of resistance of Pseudomonas aeruginosa isolates to imipenem (47.2% vs 23.0%), Klebsiella pneumoniae isolates to ceftazidime (76.3% vs 27.1%), Escherichia coli isolates to ceftazidime (66.7% vs 8.1%), Staphylococcus aureus isolates to methicillin (84.4% vs 56.8%), were also higher in the consortium's ICUs, and the crude unadjusted excess mortalities of device-related infections ranged from 7.3% (for catheter-associated urinary tract infection) to 15.2% (for ventilator-associated pneumonia). Copyright © 2012 by the Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved

Rheoencephalographic observations in migraine Reoencefalografia: observações na enxaqueca

The pathophysiological concept of migraine presently held attributes the major changes to vascular factors. Therefore, it seemed appropriate to use rheoencephalography to test cerebral hemodynamics in cases of migraine. This very harmless and well suited method revealed: (1) on routine tracings during the painless intervall only 1/7 of the cases showed significant changes, while more than 2/3 could be classified with the help of an orthostatic stress test under REG-observation; (2) REG is more often correct for diagnosis than EEG and this does not surprise since REG monitors cerebral hemodynamics directly while EEG records activity for parenchyma and thus only secondarily depends on circulation; (3) similar conditions were previously seen in Meniere's disease where EEG also is less efficient than REG. According to the results of this study, it should be interesting to include REG in the work-up of migrainous patients. In these and under similar conditions, REG will be of diagnostic value.No conceito fisiopatológico da enxaqueca atribui-se grande importância às alterações vasculares. Por esta razão empregamos a reoencefalografia, método simples e inócuo que nos pareceu o mais adequado para estudar a hemodinâmica cerebral em casos de hemicrania. Nossas conclusões foram as seguintes: (1) nos traçados reoencefalográficos de rotina encontramos, em apenas 1/7 dos casos, alterações qualitativas e quantitivas significantes no período intercrítico da enxaqueca, ao passo que mais de 2/3 dos traçados podiam ser classificados como patológicos e característicos, desde que utilizássemos o teste ortostático de Schellong; (2) a reoencefalografia parece ser mais precisa do que a eletrencefalografia para o diagnóstico de hemicrania; este fato é compreensível pois o reoencefalograma registra diretamente a hemodinâmica cerebral, enquanto que o eletrencefalograma registra a atividade bioelétrica do parênquima a qual, por sua vez, apenas secundariamente depende de circulação sangüínea; (3) resultados semelhantes foram, também, observados em casos de síndrome de Menière nos quais a eletrencefalografia seria, também, menos útil que a reoencefalografia. De acordo com estes resultados, parece-nos ser lícito sugerir a inclusão la reoencefalografia na rotina e no controle terapêutico de pacientes com íemicrânia. Nesta e em outras condições similares a reoencefalografia é im método paraclínico de alto valor

Rheoencephalographic observations in migraine

The pathophysiological concept of migraine presently held attributes the major changes to vascular factors. Therefore, it seemed appropriate to use rheoencephalography to test cerebral hemodynamics in cases of migraine. This very harmless and well suited method revealed: (1) on routine tracings during the painless intervall only 1/7 of the cases showed significant changes, while more than 2/3 could be classified with the help of an orthostatic stress test under REG-observation; (2) REG is more often correct for diagnosis than EEG and this does not surprise since REG monitors cerebral hemodynamics directly while EEG records activity for parenchyma and thus only secondarily depends on circulation; (3) similar conditions were previously seen in Meniere's disease where EEG also is less efficient than REG. According to the results of this study, it should be interesting to include REG in the work-up of migrainous patients. In these and under similar conditions, REG will be of diagnostic value

Magnetic and electrical properties of single-phase multiferroic (1-x)Pb(Zr0.52Ti0.48)O3–xPb(Fe0.5Nb0.5)O3 thin films prepared by sol-gel route

Single-phase multiferroic (1-x)Pb(Zr0.52Ti0.48)O3-xPb(Fe0.5Nb0.5)O3 (0≤x≤0.5) thin films were synthesized by sol-gel route and characterized to understand their structural, electrical, and magnetic properties. The films were thermally treated by conventional furnace (CFA) and rapid thermal annealing (RTA). A pyrochlore-free perovskite phase is stabilized only by RTA in samples with high Fe3+/Nb5+ content. The films displayed excellent dielectric and ferroelectric properties in the whole concentration range, with saturated hysteresis loops and remanent polarization values of ∼15μC/cm2. Films with x>0.3 showed ferromagnetic behavior at room temperature. Consequently, the multiferroic behavior in the films occurs in a different concentration range than that observed in bulk ceramics. The origin of the weak ferromagnetism is discussed.The authors thank Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) for financial support. M.G.S thanks support from CIUNR and L.B.S from FONCYT PICT2014-1047. We also acknowledge the financial support of H2020-MSCA-RISE-2020 MELON Grant No. 872631 and the access to TEM equipment at LMA- University of Zaragoza to perform TEM studies.Peer reviewe

Sol-gel synthesis and multiferroic properties of pyrochlore-free Pb(Fe0.5Nb0.5)O3 thin films

Lead iron niobate (PbFe0.5Nb0.5O3 – PFN) thin films were synthesized by a modified sol-gel route, which offers the advantage of a rapid, simple and non-toxic reaction method. Polycrystalline perovskite-structured PFN thin films without pyrochlore phases were obtained on Pt/Ti/SiO2/Si substrates after sintering by rapid thermal annealing at 650 °C. TEM and AFM images confirmed the excellent quality of the sintered film, while EDS spectroscopy revealed the presence of oxygen vacancies near the film/substrate interface. Electric measurements show good dielectric properties and ferroelectric behavior, characterized by typical C–V curves and well-defined P-E ferroelectric loops at 1 kHz, with remanent polarization values of ∼12 μC/cm2. The polarization, however, increases with decreasing frequency, indicating the presence of leakage currents. I–V measurements show a significant increase in DC-conduction at relatively low fields (around 100 kV/cm). The films display ferromagnetic behavior at room temperature, with magnetic remanence around 30 emu/cm3 and a coercive field of 1 kOe. These values are significantly higher than those obtained for PFN powders fabricated by the same sol-gel route, as well as the magnetization values reported in the literature for epitaxial films.This work was supported by Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina (CONICET) by PIP Nº 0374. M.G.S. thanks support from Consejo de Investigaciones de la Universidad Nacional de Rosario (CIUNR). We acknowledge the financial support of the European Commission by the H2020-MSCA RISE projects MELON (Grant Nº 872631) and ULTIMATE-I (Grant Nº 101007825).Peer reviewe