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© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Leveraging competition between energetically degenerate states to achieve large field-driven responses is a hallmark of functional materials, but routes to such competition are limited. Here, a new route to such effects involving domain-structure competition is demonstrated, which arises from strain-induced spontaneous partitioning of PbTiO3thin films into nearly energetically degenerate, hierarchical domain architectures of coexisting c/a and a1/a2domain structures. Using band-excitation piezoresponse force microscopy, this study manipulates and acoustically detects a facile interconversion of different ferroelastic variants via a two-step, three-state ferroelastic switching process (out-of-plane polarized c+→ in-plane polarized a → out-of-plane polarized c−state), which is concomitant with large nonvolatile electromechanical strains (≈1.25%) and tunability of the local piezoresponse and elastic modulus (>23%). It is further demonstrated that deterministic, nonvolatile writing/erasure of large-area patterns of this electromechanical response is possible, thus showing a new pathway to improved function and properties.

© 2016 The Author(s). Fluorite-structured oxides find widespread use for applications spanning nuclear energy and waste containment, energy conversion, and sensing. In such applications the host tetravalent cation is often partially substituted by trivalent cations, with an associated formation of charge-compensating oxygen vacancies. The stability and properties of such materials are known to be influenced strongly by chemical ordering of the cations and vacancies, and the nature of such ordering and associated energetics are thus of considerable interest. Here we employ density-functional theory (DFT) calculations to study the structure and energetics of cation and oxygen-vacancy ordering in Ho2Zr2O7. In a recent neutron total scattering study, solid solutions in this system were reported to feature local chemical ordering based on the fluorite-derivative weberite structure. The calculations show a preferred chemical ordering qualitatively consistent with these findings, and yield values for the ordering energy of 9.5 kJ/mol-cation. Similar DFT calculations are applied to additional RE2Th2O7fluorite compounds, spanning a range of values for the ratio of the tetravalent and trivalent (RE) cation radii. The results demonstrate that weberite-type order becomes destabilized with increasing values of this size ratio, consistent with an increasing energetic preference for the tetravalent cations to have higher oxygen coordination.

The Tiermas geothermal system is one of the areas with the greatest geothermal potential in Arago´n, however, its hydrogeological and geochemical features are still poorly known. In this study, the main hydrochemical features of these waters are presented and the reservoir temperature is approached by applying chemical geothermometers. These waters have a sulphate chloride sodium affinity, with nearly 40 oC of spring temperature and an approximate flow rate of 200 l/s. The most likely aquifer seems to be located in the Paleocene and Eocene carbonates. However, due to the structural complexity of the area, the waters would also interact with the evaporitic facies present in the Eocene–Oligocene boundary. Two different hydrochemical groups have been distinguished based on their salinity, Na/Cl ratios, SO4 concentrations and TDS values. Despite the compositional variations detected in the springs, the geothermometric calculations allow to infer a reservoir temperature of 85 ± 17 °C. Good consistency has been obtained with the cationic geothermometers, which is an unusual situation for a geothermal system in carbonate–evaporitic materials.El sistema geotermal de Tiermas representa una de las zonas con mayor potencial geotérmico de Aragón y, sin embargo, se sabe todavía poco acerca de sus características hidrológicas y geoquímicas. En este trabajo se presentan los principales rasgos hidroquímicos de estas aguas y se determina su temperatura en profundidad mediante la aplicación de geotermómetros químicos. Estas aguas tienen una afinidad clorurada sulfatada sódica, una temperatura de surgencia de casi 40 °C y un caudal de unos 200 l/s. El acuífero más probable se localizaría en los carbonatos del Paleoceno y Eoceno, pero debido a la complejidad estruc- tural de la zona, las aguas entrarían en contacto con la facies evaporítica del tránsito Eoceno–Oligoceno, adquiriendo así dicha afinidad. Se han distinguido dos grupos hidroquímicos con una diferente salinidad, relación Na/Cl y concen- traciones de SO4 y TSD. A pesar de las variaciones composicionales detectadas en las surgencias, los cálculos geotermométricos realizados permiten establecer un rango de temperaturas en el reservorio de 85 ± 17 °C, habiéndose obtenido bue- nos resultados con los geotermómetros catiónicos, situación poco habitual en sistemas termales instalados en materiales carbonatados – evaporíticos.

Iron hydroxide is found in a wide range of contexts ranging from biominerals to steel corrosion, and it can transform to anhydrous oxide via releasing O2 gas and H2O. However, it is not well understood how gases transport through a crystal lattice. Here, we present in situ observation of the nucleation and migration of gas bubbles in iron (hydr)oxide using transmission electron microscopy. We create Pb-FeOOH model core-shell nanoparticles in a liquid cell. Under electron irradiation, iron hydroxide transforms to iron oxide, during which bubbles are generated, and they migrate through the shell to the nanoparticle surface. Geometric phase analysis of the shell lattice shows an inhomogeneous stain field at the bubbles. Our modeling suggests that the elastic interaction between the core and the bubble provides a driving force for bubble migration.

Density-functional-theory calculations of twin-boundary energies in hexagonal close packed metals reveal anomalously low values for elemental Tc and Re, which can be lowered further by alloying with solutes that reduce the electron per atom ratio. The anomalous behavior is linked to atomic geometries in the interface similar to those observed in bulk tetrahedrally close packed phases. The results establish a link between twin-boundary energetics and the theory of bulk structural stability in transition metals that may prove useful in controlling mechanical behavior in alloy design.

Vaccinating health care workers is considered to be one of the most important steps in preventing the transmission of the influenza virus to vulnerable patients. Public Health physicians are the main promoters and executors of influenza vaccination campaigns for both healthcare workers and the general population. The objective of the present survey was to analyze the knowledge, attitudes and practices regarding influenza vaccination among Hygiene and Preventive Medicine Residents. 64% of the participants had not been vaccinated against the influenza virus in the past 5 years, and 29% had been vaccinated only occasionally , with only 7.2% of the study popu-lation having been vaccinated every year. 20.3% of those surveyed were vaccinated in the 2010/2011 season. The best strategy to increase vaccination rates among health care workers according to the study participants was the participation of future public health operators to multidisciplinary training (34.8%). the main factors associated with influenza vaccination compliance were having been vaccinated in the previous season for 2011/2012 (OR [95%]: 41.14 [7.56 - 223.87]) and having received the vaccination always or occasionally during the previous 5 years for both 2010/2011 (p-value

Background: Public Health Residents (PHRs) have to be considered of relevant interest among health care workers (HCWs) since they are strongly asked to recommend and perform influenza vaccination to other HCWs and general population. Despite this consideration, Italian HCWs have influenza vaccination rates significantly below the 75% coverage proposed by International Public Health guidelines. In order to increase future coverage towards influenza vaccination, the aim of this study is to assess determinants associated with influenza vaccine uptake among Italian PHR. Methods: A survey was carried out on PHRs attending 25 out 32 Post-Graduate University training programmes on Public Health in Italy (78.1%). Each participant was interviewed through an anonymous self-administered questionnaire including questions on knowledge, attitudes and practices dealing with influenza and influenza vaccination. Each questionnaire included five sections and twenty items. The questionnaire answers were entered in a database created within EpiInfo 3.5.1 software. All the data were analyzed using the R statistical software package. Results: The response rate was 80.1% (365/456). Vaccination coverage was 22.2% for seasonal 2010-2011 influenza, 33,7% for seasonal 2011-2012 influenza. Medical residents who stated they were vaccinated against seasonal 2010-2011 influenza were significantly more likely to be vaccinated against 2011–2012 seasonal influenza (OR 42.07; 95% CI: 19,4 – 94,2). Vaccination against seasonal 2010-2011 influenza (p < 0.0001), and seasonal 2011-2012 influenza (p

Riassunto Uno studio conoscitivo condotto tra i medici in formazione specialistica in Igiene, Medicina Preventiva e Sanità Pubblica italiani è stato condotto in 25 scuole di specializzazione italiane di tale disciplina (78,1% del totale). Ciascun partecipante è stato intervistato tramite un questionario anonimo ed autosomministrato con domande riguardo attitudini, pratiche e conoscenze sull’influenza e la relativa vaccinazione. La vaccinazione contro l’influenza stagionale 2010-2011 e 2011-2012 è significativamente associata con l’essersi vaccinato almeno 3 volte nelle ultime cinque stagioni influenzali. Gli specializzandi che hanno preso parte durante il loro percorso formativo a campagne di vaccinazione nella popolazione generale sono più propensi a vaccinarsi nelle due stagioni vaccinali prese in esame. Secondo i medici in formazione in Igiene e Medicina Preventiva italiani, per implementare le coperture vaccinali e le attitudini a raccomandare la vaccinazione antinfluenzale alla popolazione generale sono necessari corsi di formazione multidisciplinari (48.2%) e una migliore formazione universitaria sull’argomento (23.3%).

© The Royal Society of Chemistry 2015. A new group of thermoelectric materials, trigonal and tetragonal XYZ2(X, Y: rare earth or transition metals, Z: group VI elements), the prototype of which is TmAgTe2, is identified by means of high-throughput computational screening and experiment. Based on density functional theory calculations, this group of materials is predicted to attain high zT (i.e. ∼1.8 for p-type trigonal TmAgTe2at 600 K). Among approximately 500 chemical variants of XYZ2explored, many candidates with good stability and favorable electronic band structures (with high band degeneracy leading to high power factor) are presented. Trigonal TmAgTe2has been synthesized and exhibits an extremely low measured thermal conductivity of 0.2-0.3 W m-1K-1for T > 600 K. The zT value achieved thus far for p-type trigonal TmAgTe2is approximately 0.35, and is limited by a low hole concentration (∼1017cm-3at room temperature). Defect calculations indicate that TmAgantisite defects are very likely to form and act as hole killers. Further defect engineering to reduce such XYantisites is deemed important to optimize the zT value of the p-type TmAgTe2.

In order to study the nature of the precipitates formed on arsenopyrite and marcasite after reacting with neutral to alkaline solutions, a combination of techniques including Scanning Electron Microscope-Energy Dispersive Spectroscopy (SEM-EDS), X-ray Photoelectron Spectroscopy (XPS) and synchrotron-based techniques such as micro-X-Ray diffraction (μXRD) and Micro-X-ray Absorption Near Edge Structure (μXANES) have been used. The results showed that the oxidation of marcasite and arsenopyrite under neutral to alkaline conditions leads to the formation of an Fe rich coating which seems to prevent the oxidation of these sulphides. SEM observations confirmed the presence newly-formed phases after the sulphides reaction under the studied conditions. XPS analysis showed that iron, sulphur and arsenic in the case of the arsenopyrite are in oxidized states in the sulphide surfaces. The microscale analysis of the S and Fe speciation performed by μXANES suggested that due to the sulphide oxidation an increase in the oxidation state of those elements took place together with an increase of the sulphate content in the surface layer (grain boundary). Micro-X-ray diffraction results indicated that goethite (α-FeOOH) is the only crystalline newly-formed phase when the reaction occurs at pH 12 whereas at lower pH the products formed on the sulphide surfaces seem to be poorly crystalline and they do not contribute to the diffraction effects in the XRD diagrams., This research was supported by the project REN 2003-09590-C04-02 from the Spanish Government. MPA has received economical support from the Spanish Ministry of Science and Innovation through a Research Contract from the "Juan de la Cierva" Subprogram. RPL thanks the Spanish Ministry of Science and Innovation and the "Ramon y Cajal" Subprogram (MICINN-RYC 2011). Albert Soler and Angels Canals from the Departament de Cristal center dot lografia, Mineralogia i Diposits Minerals of Universitat de Barcelona supplied the arsenopyrite and marcasite samples. We wish to express our gratitude to Javier Perez, Vanessa Ouro, Rafel Bartroli, Eva Pelegri, Eva Prats, Ana Dominguez and Josep Elvira for their technical assistance. We are indebted to Lorenzo Calvo for his assistance in XPS analyses and to Xavier Llovet who assisted in the obtainment of EMP analyses at the Serveis Tecnics of Universitat de Barcelona. The constructive comments of the Editor, Dr. Josep M. Soler, Dr. Majzlan and an anonymous reviewer have considerably improved the original manuscript. We gratefully acknowledge the support of this study by a grant of the European Synchrotron Radiation Facility (ESRF; proposal EC-632).

The formalism of electronic density-functional-theory, with Hubbard-U corrections (DFT+U), is employed in a computational study of the energetics of U_{1-x} Ce_x O_2 mixtures. The computational approach makes use of a procedure which facilitates convergence of the calculations to multiple self-consistent DFT+U solutions for a given cation arrangement, corresponding to different charge states for the U and Ce ions in several prototypical cation arrangements. Results indicate a significant dependence of the structural and energetic properties on the nature of both charge and cation ordering. With the effective Hubbard-U parameters that reproduce well the measured oxidation-reduction energies for urania and ceria, we find that charge transfer between U(IV) and Ce(IV) ions, leading to the formation of U(V) and Ce(III), gives rise to an increase in the mixing energy in the range of 4-14 kJ/mol of formula unit, depending on the nature of the cation ordering. The results suggest that although charge transfer between uranium and cerium ions is disfavored energetically, it is likely to be entropically stabilized at the high temperatures relevant to the processing and service of urania-based solid solutions., Comment: 8 pages, 6 figures

The capillary-induced structural instability of an elastic circular tube partially filled by a liquid is studied by combining theoretical analysis and molecular dynamics simulations. The analysis shows that, associated with the instability, there is a well-defined length scale (elasto-capillary length), which exhibits a scaling relationship with the characteristic length of the tube, regardless of the interaction details. We validate this scaling relationship for a carbon nanotube partially filled by liquid iron. The capillary-induced structural transformation could have potential applications for nano-devices.

The c(6x2) is a reconstruction of the SrTiO3(001) surface that is formed between 1050-1100oC in oxidizing annealing conditions. This work proposes a model for the atomic structure for the c(6x2) obtained through a combination of results from transmission electron diffraction, surface x-ray diffraction, direct methods analysis, computational combinational screening, and density functional theory. As it is formed at high temperatures, the surface is complex and can be described as a short-range ordered phase featuring microscopic domains composed of four main structural motifs. Additionally, non-periodic TiO2 units are present on the surface. Simulated scanning tunneling microscopy images based on the electronic structure calculations are consistent with experimental images.