Controlling internal barrier in low loss BaTiO3 supercapacitors

Supercapacitor behavior has been reported in a number of oxides including reduced BaTiO3 ferroelectric ceramics. These so-called giant properties are however not easily controlled. We show here that the continuous coating of individual BaTiO3 grains by a silica shell in combination with spark plasma sintering is a way to process bulk composites having supercapacitor features with low dielectric losses and temperature stability. The silica shell acts both as an oxidation barrier during the processing and as a dielectric barrier in the final composite

High-frequency dielectric spectroscopy of batio3 core - silica shell nanocomposites: Problem of interdiffusion

Three types of BaTiO3 core - amorphous nano-shell composite ceramics were processed from the same core-shell powder by standard sintering, spark-plasma sintering and two-step sintering techniques and characterized by XRD, HRSEM and broad-band dielectric spectroscopy in the frequency range 10^3 - 10^13 Hz including the THz and IR range. The samples differed by porosity and by the amount of interdiffusion from the cores to shells, in correlation with their increasing porosity. The dielectric spectra were also calculated using suitable models based on effective medium approximation. The measurements revealed a strong dielectric dispersion below the THz range, which cannot be explained by the modeling, and whose strength was in correlation with the degree of interdiffusion. We assigned it to an effect of the interdiffusion layers, giving rise to a strong interfacial polarization. It appears that the high-frequency dielectric spectroscopy is an extremely sensitive tool for detection of any gradient layers and sample inhomogeneities even in dielectric materials with negligible conductivity

Effect of ochratoxin A on the intestinal mucosa and mucosa-associated lymphoid tissues in broiler chickens

The immunotoxic effect of ochratoxin A (OTA) on the intestinal mucosa-associated lymphoid tissue and its cytotoxic action on the intestinal epithelium were studied in broiler chickens experimentally treated with the toxin. From the 7th day of life, 80 male broiler chickens (Ross 308) were randomly divided into four groups of 20 birds each. The three experimental groups (E1-3) were treated with OTA for 28 days (E1: 50 μg/kg body weight [bw]/day; E2: 20 μg/kg bw/day; E3: 1 μg/kg bw/day) and the fourth group served as control. Histological examination of the intestinal mucosa and immunohistochemical staining for identification of CD4+, CD8+, TCR1 and TCR2 lymphocytes in the duodenum, jejunum and ileocaecal junction were performed, and CD4+/CD8+ and TCR1/TCR2 ratios were calculated. OTA toxicity resulted in decreased body weight gain, poorer feed conversion ratio, lower leukocyte and lymphocyte count, and altered intestinal mucosa architecture. After 14 days of exposure to OTA, immunohistochemistry showed a significant reduction of the lymphocyte population in the intestinal epithelium and the lamina propria. After 28 days of exposure, an increase in the CD4+ and CD8+ values in both the duodenum and jejunum of chickens in Groups E1 and E2 was observed, but the TCR1 and TCR2 lymphocyte counts showed a significant reduction. No significant changes were observed in Group E3. The results indicate that OTA induced a decrease in leukocyte and lymphocyte counts and was cytotoxic to the intestinal epithelium and the mucosa-associated lymphoid tissue, altering the intestinal barrier and increasing susceptibility to various associated diseases

Knowledge mobilization in the context of health technology assessment: an exploratory case study

<p>Abstract</p> <p>Background</p> <p>Finding measures to enhance the dissemination and implementation of their recommendations has become part of most health technology assessment (HTA) bodies' preoccupations. The Quebec government HTA organization in Canada observed that some of its projects relied on innovative practices in knowledge production and dissemination. A research was commissioned in order to identify what characterized these practices and to establish whether they could be systematized.</p> <p>Methods</p> <p>An exploratory case study was conducted during summer and fall 2010 in the HTA agency in order to determine what made the specificity of its context, and to conceptualize an approach to knowledge production and dissemination that was adapted to the mandate and nature of this form of HTA organization. Six projects were selected. For each, the HTA report and complementary documents were analyzed, and semi-structured interviews were carried out. A narrative literature review of the most recent literature reviews of the principal knowledge into practice frameworks (2005-2010) and of articles describing such frameworks (2000-2010) was undertaken.</p> <p>Results and discussion</p> <p>Our observations highlighted an inherent difficulty as regards applying the dominant knowledge translation models to HTA and clinical guidance practices. For the latter, the whole process starts with an evaluation question asked in a problematic situation for which an actionable answer is expected. The objective is to produce the evidence necessary to respond to the decision-maker's request. The practices we have analyzed revealed an approach to knowledge production and dissemination, which was multidimensional, organic, multidirectional, dynamic, and dependent on interactions with stakeholders. Thus, HTA could be considered as a knowledge mobilization process per se.</p> <p>Conclusions</p> <p>HTA's purpose is to solve a problem by mobilizing the types of evidence required and the concerned actors, in order to support political, organizational or clinical decision-making. HTA relies on the mediation between contextual, colloquial and scientific evidence, as well as on interactions with stakeholders for recommendation making. Defining HTA as a knowledge mobilization process might contribute to consider the different orders of knowledge, the social, political and ethical dimensions, and the interactions with stakeholders, among the essential components required to respond to the preoccupations, needs and contexts of all actors concerned with the evaluation question's issues.</p

ESPON Italian evidence in changing Europe

Il volume, che rientra nelle attività dell’ESPON Contact Point Italia, accoglie i risultati del contributo dei Partner Italiani allo sviluppo dei progetti del Programma ESPON 2013, acronimo di European Observation Network for Territorial Development and Cohesion. I testi sintetizzano ed evidenziano, tra l’altro, le relazioni con le politiche di sviluppo regionale dell’Italia, inserendole in un quadro di cooperazione transnazionale che coinvolge 28 + 4 paesi dell’Unione europea. Affrontando aspetti della politica territoriale europea che spaziano dall’innovazione e conoscenza all’accessibilità, dal policentrismo alle aree metropolitane, dalla migrazione alla globalizzazione, gli Autori mettono in luce la posizione dell’Italia e delle regioni anche rispetto agli obiettivi fissati da Europe 2020. Uno spazio è dedicato alle esperienze regionali che hanno trovato in ESPON uno stimolo e un’occasione di confronto; come pure ai concetti che sottendono il lessico, i principi di orientamento e i nuovi modelli della pianificazione in Europa; e alle esperienze formative rivolte alle giovani generazioni e ai decision maker Il libro si inquadra nelle iniziative del Semestre di Presidenza Italiana dell’Unione europea ed è cofinanziato dal Ministero delle Infrastrutture e dei Trasporti (MIT) responsabile nazionale del Programma ESPON. E’ rivolto ai ricercatori, agli utilizzatori istituzionali, ai policy maker, ai “practioner” e ai “non specialisti”, tra cui gli studenti, affinché possano fare propri i risultati dell’impegno costante, rigoroso e rispettoso delle diversità territoriali che hanno contraddistinto, dal 2007 ad oggi, il contributo della ricerca, anche sperimentale e applicata, alla crescita della società italiana come parte integrante del sistema europeo. L’Osservatorio ESPON, per chi ancora non lo conosce, può rappresentare un viaggio nel territorio europeo, nelle sue diversità territoriali, economiche, sociali, culturali da integrare e rendere coese, sostenibili, mantenendo e sviluppando potenziali di competitività crescenti e, nel contempo, innovando e diffondendo nuovi modi, metodologie, strumenti e prassi per fare del territorio un bene comune e condiviso. Dati, riferimenti e raccomandazioni politiche utili alla crescita del Paese completano il quadro. Presentazione del Ministro delle Infrastrutture, On. Maurizio Lupi Postfazione del Direttore della Coordination Unit del Programma ESPON, Peter MehlbyeThe book is part of the activities of ESPON Contact Point Italy. It includes the results of the contribution of the Italian partners in the development of projects under the ESPON 2013 Programme, which stands for European Observation Network for Territorial Development and Cohesion. The texts summarise and highlight, among other things, the relations with the regional development policies of Italy, placing them in a framework of transnational cooperation involving the 28 + 4 EU Countries. Addressing aspects of European territorial policy, ranging from innovation and knowledge accessibility, from the polycentrism to metropolitan areas, from migration to globalization, the authors highlight the position of Italy and of regions also in relation to the objectives set by Europe 2020. A place is devoted to the regional experiences that in the ESPON found a stimulus and an opportunity for discussion, as well as to the concepts behind the vocabulary, to the principles of guidance, and new planning models in Europe, and to the training experiences aimed at the younger generations and the decision makers The book forms part of the initiatives of the Italian Presidency of the European Union and is co-financed by the Ministry of Infrastructure and Transportation (MIT) in charge of the national ESPON Programme. It is aimed at researchers, institutional users, policy makers, at "practitioners" and "non-specialists" including students, so that they can make use of the results of the constant and rigorous work also respectful of the territorial diversities that have characterized the experimental and applied research since 2007, so contributing to the growth of Italian society as an integral part of the European system. The ESPON Monitoring Centre, for those who still do not know, can be a journey into the European territory, its territorial, economic, social, cultural diversities to integrate and make cohesive and sustainable, by maintaining and developing the increasing potentials of competitiveness and, at the same time, by innovating and disseminating new ways, methodologies, tools and practices to make the territory a common and shared good. Data, references and useful policy recommendations to the growth of the country are also included in the book. Presentation by the Minister of Infrastructure, Mr. Maurizio Lupi Afterword by the Director of the Coordination Unit ESPON Programme , Peter Mehlby

High frequency dielectric relaxation in Pb(Sc1/2Ta1/2)O-3 ceramics

Pb(Sc1/2Ta1/2)O-3 ceramics have been characterized by dielectric measurements in a wide range of frequencies (10(2)-10(9) Hz). A strong dispersion occurs with two low and high frequency contributions below the transition temperature. Only high frequency relaxation is still observed at high temperature. A microscopic model of correlated chains was used in order to explain the latter relaxation. Dipole correlations at low temperature are responsible for the low frequency dispersion. A minimum in the high frequency relaxation appears at the transition temperature. Identical results have been observed for a Pb(Sc1/2Nb1/2)O-3 ceramic

New considerations on the role of covalency in ferroelectric niobates and tantalates

Values of Curie temperature, TC, and microwave relaxation frequency, fr, of ferroelectric niobates and tantalates are found to be closely related to the metal-oxygen network covalency. Correlations previously evidenced in perovskite-type relaxors (PSN, PST) are confirmed here for K(Ta$_{1-x}$Nbx)O3 (KTN) compositions. The investigated physical characteristics, TC and fr, are determined via dielectric measurements performed in a wide frequency range (102–109 Hz) and as a function of temperature (250–800 K). On a theoretical point of view, bond covalencies are evaluated through tight-binding band structure calculations. The complex role of covalency on the metal potential is precised. Two antagonist effects acting on both the short-range interatomic repulsions and the rigidity and stability of the oxygen-metal network are discussed. The validity of this approach is comforted through the example of the oxyfluoride K3Li1.5Ta5O14.5F0.5

All dielectric metamaterials at millimeter wavelengths using single-size TiO2 resonators : simulation and experiments

no abstrac

Bulk rigid terahertz metamaterials based on dielectric microspheres

International audienc

Single-step synthesis of well-crystallized and pure barium titanate nanoparticles in supercritical fluids

Single-step synthesis of ultra-fine barium titanate powder with a crystallinity as high as 90% and without barium carbonate contamination has been successfully performed under supercritical conditions using a continuous-flow reactor in the temperature range 150–380 °C at 16 MPa. To synthesize this bimetallic oxide, alkoxides, ethanol and water were used. The influence of the synthesis parameters on the BaTiO3 powder characteristics was investigated. The results show that the water to alkoxide precursor ratio, the reactor temperature and the Ba:Ti molar ratio of alkoxide precursor play a major role in the crystallization of pure and well-crystallized BaTiO3 nanoparticles. The continuous mode of operation without post-treatments for powder washing, drying or crystallization increase the industrial interest