Fabrication, structural characterization and testing of nanostructured tin oxide gas sensor

A nanostructured SnO2 conductometric gas sensor was produced from thermally evaporated Sn clusters using a thermal oxidation process. SnO2 clusters were simultaneously formed in an identical process on a Si3N4 membrane featuring an aperture created by a focused ion beam (FIB). Clusters attached to the vertical edges of the aperture were imaged using a transmission electron microscope. The original morphology of the Sn cluster film was largely preserved after the thermal oxidation process and the thermally oxidized clusters were found to be polycrystalline and rutile in structure. NO2 gas sensing measurements were performed with the sensor operating at various temperatures between 25degC and 290degC. At an operating temperature of 210degC, the sensor demonstrated a normalized change in resistance of 3.1 upon exposure to 510 ppb of NO2 gas. The minimum response and recovery times for this exposure were 45 s and 30 s at an operating temperature of 265degC. The performance of the SnO2 sensor compared favorably with previously published results. Finally, secondary ion mass spectrometry and X-ray photoelectron spectroscopy were used to establish the levels of nitrogen present in the films following exposure to NO2 gas

Nanostructured SnO2 films prepared from evaporated Sn and their application as gas sensors

This paper describes the morphology, stoichiometry, microstructure and gas sensing properties of nanoclustered SnOx thin films prepared by Sn evaporation followed by a rheotaxial growth and thermal oxidation process. Electron microscopy was used to investigate, in detail, the evolution of the films as the oxidation temperature was increased. The results showed that the contact angle, perpendicular height, volume and microstructure of the clusters all changed significantly as a result of the thermal oxidation processes. Electron diffraction and x-ray photoelectron spectroscopy measurements revealed that after oxidation at a temperature of 600 °C, the Sn clusters were fully transformed into porous three-dimensional polycrystalline SnO2 clusters. On the basis of these results, a prototype SnO2 sensor was fabricated and sensing measurements were performed with H2 and NO2 gases. At operating temperatures of 150-200 °C the film produced measurable responses to concentrations of H2 as low as 600 ppm and NO2 as low as 500 ppb

Alkali ratio control for lead-free piezoelectric thin films utilizing elemental diffusivities in RF plasma

High performance piezoelectric thin films are generally lead-based, and find applications in sensing, actuation and transduction in the realms of biology, nanometrology, acoustics and energy harvesting. Potassium sodium niobate (KNN) is considered to be the most promising lead-free alternative, but it is hindered by the inability to control and attain perfect stoichiometry materials in the thin film form while using practical large area deposition techniques. In this work, we identify the contribution of the elemental diffusivities in the radio frequency (RF) plasma in determining the alkali loss in the KNN thin films. We have also examined the effect of the substrate temperature during the RF magnetron sputtering deposition on the crystal structure of the substrate and KNN thin films, as well as the effect of the postannealing treatments. These results indicate the need for well-designed source materials and the potential to use the deposition partial pressure to alter the dopant concentrations

New age constraints on metamorphism, metasomatism and gold mineralisation at Plutonic Gold Mine, Marymia Inlier, Western Australia

The Plutonic Well Greenstone Belt (PWGB) is located in the Marymia Inlier between the Yilgarn and Pilbara cratons in Western Australia, and hosts a series of major Au deposits. The main episode of Au mineralisation in the PWGB was previously interpreted to have either accompanied, or shortly followed, peak metamorphism in the late Archean at ca 2650 Ma with a later, minor, event associated with the Capricorn Orogeny. Here we present new Pb isotope model ages for sulfides and Rb–Sr ages for mica, as well as a new 207Pb–206Pb age for titanite for samples from the Plutonic Gold Mine (Plutonic) at the southern end of the PWGB. The majority of the sulfides record Proterozoic Pb isotope model ages (2300–2100 Ma), constraining a significant Au mineralising event at Plutonic that occurred >300 Myr later than previously thought. A Rb–Sr age of 2296 ± 99 Ma from muscovite in an Au-bearing sample records resetting or closure of the Rb–Sr system in muscovite at about the same time. A younger Rb–Sr age of 1779 ± 46 Ma from biotite from the same sample may record further cooling, or resetting during a late-stage episode of metasomatism in the PWGB. This could have been associated with the 1820–1770 Ma Capricorn Orogeny, or a late-stage hydrothermal event potentially constrained by a new 207Pb–206Pb age of 1725 ± 26 Ma for titanite in a chlorite–carbonate vein. This titanite age correlates with a pre-existing age for a metasomatic event dated at 1719 ± 14 Ma by U–Pb ages of zircon overgrowths in a sample from the Marymia Deposit. Based on the Pb-isotope data presented here, Au mineralising events in the PWGB are inferred to have occurred at ca 2630, 2300–2100 Ma, during the Glenburgh and Capricorn orogenies, and 1730–1660 Ma. The 2300–2100 Ma event, which appears to have been significant based on the amount of sulfide of this age, correlates with the inferred age for rifting of the Marymia Inlier from the northern margin of the Yilgarn Craton. The texturally-later visible Au may have been deposited during the Glenburgh and Capricorn orogenies

Density functional study of the actinide nitrides

The full potential all electron linearized augmented plane wave plus local orbitals (FP-LAPW + lo) method, as implemented in the suite of software WIEN2K, has been used to systematically investigate the structural, electronic, and magnetic properties of the actinide compounds AnN (An = Ac, Th, Pa, U, Np, Pu, Am). The theoretical formalism used is the generalized gradient approximation to density functional theory (GGA-DFT) with the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional. Each compound has been studied at six levels of theory: non-magnetic (NM), non-magnetic with spin-orbit coupling (NM+SOC), ferromagnetic (FM), ferromagnetic with spin-orbit coupling (FM+SOC), anti-ferromagnetic (AFM), and anti-ferromagnetic with spin-orbit coupling (AFM+SOC). The structural parameters, bulk moduli, densities of states, and charge distributions have been computed and compared to available experimental data and other theoretical calculations published in the literature. The total energy calculations indicate that the lowest energy structures of AcN, ThN, and PaN are degenerate at the NM+SOC, FM+SOC, and AFM+SOC levels of theory with vanishing total magnetic moments in the FM+SOC and AFM+SOC cases, making the ground states essentially non-magnetic with spin-orbit interaction. The ground states of UN, NpN, PuN, and AmN are found to be FM+SOC at the level of theory used in the present computations. The nature of the interactions between the actinide metals and nitrogen atom, and the implications on 5f electron delocalization and localization are discussed in detail.Comment: 5 tables, 12 figure

Factors moderating the relationship between childhood trauma and premorbid adjustment in first-episode schizophrenia

CITATION: Kilian, S. et al. 2017. Factors moderating the relationship between childhood trauma and premorbid adjustment in first-episode schizophrenia. PLoS ONE, 12(1):e0170178, doi:10.1371/journal.pone.0170178.The original publication is available at http://journals.plos.org/plosoneChildhood trauma is a recognised risk factor for schizophrenia. It has been proposed that childhood trauma interferes with normal neurodevelopment, thereby establishing a biological vulnerability to schizophrenia. Poor premorbid adjustment is frequently a precursor to schizophrenia, and may be a manifestation of neurodevelopmental compromise. We investigated the relationship between childhood trauma and premorbid adjustment in 77 patients with first-episode schizophrenia spectrum disorders. We also investigated possible mediating roles for other selected risk factors in the relationship. We found several significant correlations between different trauma types and both social and academic premorbid adjustment from childhood to late adolescence. There were no significant moderating effects for family history of schizophrenia or family history of psychiatric disorder. History of obstetric complications, substance abuse and poor motor coordination weakened some of the associations between childhood trauma and premorbid adjustment, while poor sequencing of motor acts strengthened the association. Our results confirm previous studies indicating an association between childhood trauma and premorbid adjustment. Results indicate a general rather than specific association, apparent with different types of trauma, and affecting both social and academic components of premorbid adjustment across childhood, early and late adolescence. Further, our results suggest a complex interplay of various risk factors, supporting the notion of different pathways to psychosis.http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0170178Publisher's versio

'Language has a heart': linguistic markers of evaluation in selected TRC testimonies

This paper explores how two testifiers at the Human Rights Violation hearings of South Africa's Truth and Reconciliation Commission in 1996 used selected markers of evaluation (shifts in tense, the inclusion of direct speech and code-switching) to express evaluative meanings and position themselves, the police and their audiences in relation to their narratives. Both testifiers are mothers of young activists who were pursued, detained and tortured by police in the 1980s. The paper argues that it is through the subtle though significant linguistic choices the women make that their perspective is construed and their 'narrative truth' realized

Conservation laws for vacuum tetrad gravity

Ten conservation laws in useful polynomial form are derived from a Cartan form and Exterior Differential System (EDS) for the tetrad equations of vacuum relativity. The Noether construction of conservation laws for well posed EDS is introduced first, and an illustration given, deriving 15 conservation laws of the free field Maxwell Equations from symmetries of its EDS. The Maxwell EDS and tetrad gravity EDS have parallel structures, with their numbers of dependent variables, numbers of generating 2-forms and generating 3-forms, and Cartan character tables all in the ratio of 1 to 4. They have 10 corresponding symmetries with the same Lorentz algebra, and 10 corresponding conservation laws.Comment: Final version with additional reference

Promoting health equity in European children: design and methodology of the prospective EPHE (Epode for the Promotion of Health Equity) evaluation study

Background: Reducing health inequalities is a top priority of the public health agendas in Europe. The EPHE project aims to analyse the added value of a community-based interventional programme based on EPODE methodology, adapted for the reduction of socio-economic inequalities in childhood obesity. The interventions that will be implemented by this project focus on four energy balance-related behaviours (fruit and vegetable consumption, tap water intake, physical inactivity, sleep duration) and their determinants. This article presents the design of the effect evaluation of the EPHE project. Methods/Design: This is a prospective two-year follow-up evaluation study, which will collect data on the energy balance-related behaviours and potential environmental determinants of 6-8 year olds, depending on the socioeconomic status of the parents. For this purpose a parental self-reported questionnaire is constructed. This assesses the socio-economic status of the parents (5 items) and the dietary (12 items), sedentary (2 items) and sleeping (4 items) behaviour of the child. Alongside potential family-environmental determinants are assessed. The EPHE parental questionnaire will be disseminated in schools of a selected medium-sized city in seven European countries (Belgium, Bulgaria, France, Greece, Portugal, Romania, The Netherlands). Discussion: This study will evaluate the effects of the EPHE community-based interventional programmes. Furthermore, it will provide evidence for children's specific energy balance-related behaviours and family environmental determinants related to socio-economic inequalities, in seven European countries