The second largest family of oxide ferroelectrics, after perovskites, are the tetragonal tungsten bronzes (TTB) with the general formula A24A12C4B12B28O30. Cation disorder in TTBs is known to occur if the size difference between cations is small, but the impact of cation disorder on structure and properties has not yet been extensively addressed. In this study we investigate the effect of the size of the M cation, including cation disorder, on the crystal structure and dielectric properties in the two series Ba4M2Nb10O30 (BMN, A = Na, K and Rb) and Ba4M2Nb8Ti2O30 (BMNT, M = Ca, Sr). Dense and phase pure ceramics in the two series were prepared by a two-step solid state synthesis route. The crystal structures of the materials were characterized by powder X-ray diffraction combined with Rietveld refinement. A close to linear relation between the in-plane lattice parameter (a) and the size of the M-cation were observed. Ba4M2Nb8Ti2O30 was shown to possess cation disorder on the A-sites in line with previous work on Ba4M2Nb10O30. Thermodynamic calculations from density functional theory also indicated a drive for cation disorder in the three BMN compositions. Non-ambient temperature X-ray diffraction revealed contraction of the in-plane (a) and expansion of the out-of-plane (c) lattice parameters at the ferroelectric phase transition for Ba4M2Nb10O30. The ferroelectric transition temperature acquired by dielectric spectroscopy showed a systematically increasing TC with decreasing size of the M-cation within both compositional series studied. The compositional dependence of TC is discussed with respect to the size of the M-cation, cation disorder and the tetragonality, as well as the Ti-content. The relaxor to ferroelectric properties observed by polarization-electric field hysteresis loops are discussed in relation to the relative size of cations on the on A1 and A2 sites and the Ti-content.
Today, ≈20% of the electric consumption is devoted to refrigeration; while, ≈50% of the final energy is dedicated to heating applications. In this scenario, many cooling devices and heat-pumps are transitioning toward the use of CO2 as an eco-friendly refrigerant, favoring carbon circular economy. Nevertheless, CO2 still has some limitations, such as large operating pressures (70-150 bar) and a critical point at 31 °C, which compromises efficiency and increases technological complexity. Very recently, an innovative breathing-caloric mechanism in the MIL-53(Al) compound is reported, which implies gas adsorption under CO2 pressurization boosted by structural transitions and which overcomes the limitations of stand-alone CO2. Here, the breathing-caloric-like effects of MOF-508b are reported, surpassing by 40% those of MIL-53(Al). Moreover, the first thermometry device operating at room temperature and under the application of only 26 bar of CO2 is presented. Under those conditions, this material presents values of ΔT ≈ 30 K, reaching heating temperatures of 56 °C and cooling temperatures of -10 °C, which are already useful for space heating, air-conditioning, food refrigeration, and freezing applications.
The effect of point defects and interactions with the substrate are shown by density functional theory calculations to be of significant importance for the structure and functional properties of hexagonal boron nitride (h-BN) films on highly ordered pyrolytic graphite (HOPG) and Ni(111) substrates. The structure, surface chemistry, and electronic properties are calculated for h-BN systems with selected intrinsic, oxygen, and carbon defects and with graphene hybrid structures. The electronic structure of a pristine monolayer of h-BN is dependent on the type of substrate, as h-BN is decoupled electronically from the HOPG surface and acts as bulk-like h-BN, whereas on a Ni(111) substrate, metallic-like behavior is predicted. These different film/substrate systems therefore show different reactivities and defect chemistries. The formation energies for substitutional defects are significantly lower than for intrinsic defects regardless of the substrate, and vacancies formed during film deposition are expected to be filled by either ambient oxygen or carbon from impurities. Significantly lower formation energies for intrinsic and oxygen and carbon substitutional defects were predicted for h-BN on Ni(111). In-plane h-BCN hybrid structures were predicted to be terminated by N-C bonding. Substitutional carbon on the boron site imposes n-type semiconductivity in h-BN, and the n-type character increases significantly for h-BN on HOPG. The h-BN film surface becomes electronically decoupled from the substrate when exceeding monolayer thickness, showing that the surface electronic properties and point defect chemistry for multilayer h-BN films should be comparable to those of a freestanding h-BN layer.
PURPOSE: To investigate the practices of repair that exist for users of mobility assistive products in low resource settings, as well as the psychosocial impact that the repair, or non-repair, of these devices has on users' lives. MATERIALS AND METHODS: This article collates data on repair practices and the responses from participants on the topic of repair from studies conducted by the authors across four different low resource settings in Kenya, Uganda, Sierra Leone, and Indonesia. This data was then analyzed to identify the common themes found across geographies. RESULTS: Three major models of repair practice emerged from the data: "Individual or Informal Repair in the Community"; "Local Initiatives"; and "Specialist AT Workshop Repair". Additionally, the wider impact on the participants' lives of "Problems & Concerns with Repair"; "Experiences of Breakages & Frequencies of Repair" and the "Impact of Broken Devices" are explored. CONCLUSIONS: The results of this analysis demonstrate the paramount importance of community-based repair of devices, and how despite this importance, repair is often overlooked in the planning and design of assistive products and services. There is a need to further incorporate and support these informal contributions as part of the formal provision systems of assistive device.IMPLICATIONS FOR REHABILITATIONA lack of available specialist repair services in low resource settings hinders the potential impact of assistive technology provision systems.Community-based repair is the major route by which assistive devices are repaired in low resource settings.Appropriate community-based repair strategies should be incorporated into and supported by the formal assistive technology provision models in order to optimise outcomes.A lack of data on outcomes across the lifecycle of assistive products hinders progress on improving focus on follow-up services - in particular repair & maintenance.By supporting community-based repair, repairs that are inappropriate for that approach could be better directed to specialist repair services.
While BiFeO3-based solid solutions show great promise for applications in energy conversion and storage, realizing this promise necessitates understanding the structure-property relationship in particular pertaining to the relaxor-like characteristics often exhibited by solid solutions with polar-to-non-polar morphotropic phase boundaries. To this end, we investigated the role of the compositionally-driven relaxor state in (100 - x)BiFeO3-xSrTiO3 [BFO-xSTO], via in situ synchrotron X-ray diffraction under bipolar electric-field cycling. The electric-field induced changes to the crystal structure, phase fraction and domain textures were monitored via the {111}pc, {200}pc, and 1/2{311}pc Bragg peaks. The dynamics of the intensities and positions of the (111) and (111Ì) reflections reveal an initial non-ergodic regime followed by long-range ferroelectric ordering after extended poling cycles. The increased degree of random multi-site occupation in BFO-42STO compared to BFO-35STO is correlated with an increase of the critical electric field needed to induce the non-ergodic-to-ferroelectric transition, and a decrease in the degree of domain reorientation. Although both compositions show an irreversible transition to a long-range ferroelectric state, our results suggest that the weaker ferroelectric response in BFO-42STO is related to an increase in ergodicity. This, in turn, serves to guide the development of BFO-based systems into promising platform for further property engineering towards specific capacitor applications.
Promoting the use of assistive technology (AT) is crucial for the health and well-being of users, but there is a huge global problem of unmet need for AT. In this context informal (unregulated) providers of AT play a significant role of meeting AT user need, particularly in less-resourced settings. This study draws on research into formal and informal AT provision in low-income urban communities in Indonesia and Sierra Leone to explore the potential of informal providers in addressing unmet need. Specifically, it looks at the different performance of formal and informal providers regarding the availability and the adequacy of AT that they provide. The study concludes by proposing further research into the scope for coproduction of AT between formal and informal providers.
Assistive technology (AT) (e.g. wheelchairs, hearing aids, or products for people with visual impairments) are crucial for the wellbeing of users, but there is huge and growing unmet need for AT globally. In low-income settings many users access AT from the informal (unregulated) economy, which tends to provide AT in under-served communities, and at lower cost, helping to address this gap. However, AT from informal providers often fails to meet minimum product standards and/or lacks associated services such as assessment, fitting, user training, maintenance and repairs. On the other hand, many users of AT from informal sources value, in addition to low cost, some other features, such as their ability to customize assistive products and innovate in product development. This study therefore proposes exploring ways in which formal and informal providers of AT could work together to improve access at the same time as ensuring the safety and quality of AT for low-income users.
Self-Help Devices , Humans , Sierra Leone , Indonesia , Poverty
The crystal structure of tetragonal tungsten bronzes, with the general formula A12A24C4B12B28O30, is flexible both from a chemical and structural viewpoint, resulting in a multitude of compositions. The A1 and A2 lattice sites, with different coordination environments, are usually regarded to be occupied by two different cations such as in Ba4Na2Nb10O30 with Na+ and Ba2+ occupying the A1 and A2 sites, respectively. Here, we report on a systematic study of the lattice site occupancy on the A1 and A2 sites in the series Ba4M2Nb10O30 (M = Na, K, and Rb). The three compounds were synthesized by a two-step solid-state method. The site occupancy on the A1 and A2 sites were investigated by a combination of Rietveld refinement of X-ray diffraction patterns and scanning transmission electron microscopy with simultaneous energy-dispersive spectroscopy. The two methods demonstrated consistent site occupancy of the cations on the A1 and A2 sites, rationalized by the variation in the size of the alkali cations. The cation order-disorder phenomenology in the tungsten bronzes reported is discussed using a thermodynamic model of O'Neill and Navrotsky, originally developed for cation interchange in spinels.
Objectives. To create causal loop diagrams that characterize intersectional stigma experiences among Black, gay, bisexual, same gender-loving, and other men who have sex with men and to identify intervention targets to reduce stigma and increase testing and prevention access. Methods. Between January and July 2020, we conducted focus groups and in-depth interviews with 80 expert informants in New York City, which were transcribed, coded, and analyzed. These qualitative insights were developed iteratively, visualized, and validated in a causal loop diagram (CLD) using Vensim software. Results. The CLD revealed 3 key feedback loops-medical mistrust and HIV transmission, serosorting and marginalization of Black and gay individuals, and family support and internalized homophobia-that contribute to intersectional HIV and related stigmas, homophobia, and systemic racism. On the basis of these results, we designed 2 novel intervention components to integrate into an existing community-level anti-HIV stigma and homophobia intervention. Conclusions. HIV stigma, systemic racism, and homophobia work via feedback loops to reduce access to and uptake of HIV testing, prevention, and treatment. Public Health Implications. The CLD method yielded unique insights into reciprocal feedback structures that, if broken, could interrupt stigmatization and discrimination cycles that impede testing and prevention uptake. (Am J Public Health. 2022;112(S4):S444-S451. https://doi.org/10.2105/AJPH.2022.306725).
HIV Infections , Sexual and Gender Minorities , HIV Infections/prevention & control , HIV Serosorting , Homosexuality, Male , Humans , Male , New York City , Trust
The importance of assistive technology (AT) is gaining recognition, with the World Health Organisation (WHO) set to publish a Global Report in 2022. Yet little is understood about access for the poorest, or the potential of AT to enable this group to participate in the activities of citizenship; both formal and informal. The aim of this qualitative study was to explore AT as mediator of participation in citizenship for persons with disabilities who live in two informal settlements in Freetown, Sierra Leone (SL). The paper presents evidence from 16 participant and 5 stakeholder interviews; 5 focus groups and 4 events; combining this with the findings of a house-to-house AT survey; and two national studies-a country capacity assessment and an informal markets deep-dive. Despite citizenship activities being valued, a lack of AT was consistently reported and hindered participation. Stigma was also found to be a major barrier. AT access for the poorest must be addressed if citizenship participation for persons with disabilities is a genuine global intention and disability justice is to become a reality.
Disabled Persons , Self-Help Devices , Humans , Poverty Areas , Sierra Leone , World Health Organization
Ferroelectric films are often constrained by their substrates and subject to scaling effects, including suppressed dielectric permittivity. In this work, the thickness dependence of intrinsic and extrinsic contributions to the dielectric properties was elucidated. A novel approach to quantitatively deconstruct the relative permittivity into three contributions (intrinsic, reversible extrinsic, and irreversible extrinsic) was developed using a combination of X-ray diffraction (XRD) and Rayleigh analysis. In situ synchrotron XRD was used to understand the influence of residual stress and substrate clamping on the domain state, ferroelastic domain reorientation, and electric field-induced strain. For tetragonal {001} textured Pb0.99(Zr0.3Ti0.7)0.98Nb0.02O3 thin films clamped to an Si substrate, a thickness-dependent in-plane tensile stress developed during processing, which dictates the domain distribution over a thickness range of 0.27- [Formula: see text]. However, after the films were partially declamped from the substrate and annealed, the residual stress was alleviated. As a result, the thickness dependence of the volume fraction of c -domains largely disappeared, and the out-of-plane lattice spacings ( d ) for both a - and c -domains increased. The volume fraction of c -domains was used to calculate the intrinsic relative permittivity. The reversible Rayleigh coefficient was then used to separate the intrinsic and reversible extrinsic contributions. The reversible extrinsic response accounted for ~50% of the overall relative permittivity (measured at 50 Hz and alternating current (ac) field of 0.5·Ec ) and was thickness dependent even after poling and upon release.
The data presented here is related to the research article titled "Evicting the poor in the 'overriding public interest': Crisis of rights and interests, and contestations in Nigerian cities" [1]. This data brief presents relevant national and sub-national data on patterns, trends, and impacts of reported urban infrastructure-related displacements in Nigeria between 2010 and 2016. The data of reported cases of displacements in Nigeria are presented in tabular matrix. On the horizontal side are nested rows designated as the six geopolitical zones (South East, South South, South West, North Central, North East, and North West), 36 States of the country, and Abuja Federal Capital Territory. It was also necessary to identify particular local government areas where displacements occurred or were imminent (case locations). On the vertical side, 14 columns itemized diverse variables such as type of infrastructure project, as well as the mode/type, status, and mechanisms of displacement. Other columns include reasons given for displacement, project funder/initiator, number of project affected persons (PAPs), reported social characteristics of PAPs, response of PAPs, actions/outcomes, information sources and link, date(s) of reported displacement in addition to a section for notes. Besides chronicling urban infrastructure-related displacement cases in the period under review, this brief might equally serve as a benchmark for a prospective national displacement register. It will also function as a useful information resource not only for facilitating advocacy and research in built environment disciplines and civil rights campaigns, but also serve to conscientize policy makers and development practitioners on the cumulative cost implications of displacement. Further interpretive insights could be achieved through data mining and cross-tabulation.
BACKGROUND: Mental health services aim to provide recovery-focused care and facilitate coproduced care planning. In practice, mental health providers can find supporting individualized coproduced care with service users difficult while balancing administrative and performance demands. To help meet this aim and using principles of coproduction, an innovative mobile digital care pathway tool (CPT) was developed to be used on a tablet computer and piloted in the West of England. OBJECTIVE: The aim of this study was to examine mental health care providers' views of and experiences with the CPT during the pilot implementation phase and identify factors influencing its implementation. METHODS: A total of 20 in-depth telephone interviews were conducted with providers participating in the pilot and managers in the host organization. Interviews were audio recorded, transcribed, anonymized, and thematically analyzed guided by the Consolidated Framework for Implementation Research. RESULTS: The tool was thought to facilitate coproduced recovery-focused care planning, a policy and organizational as well as professional priority. Internet connectivity issues, system interoperability, and access to service users' health records affected use of the tool during mobile working. The organization's resources, such as information technology (IT) infrastructure and staff time and IT culture, influenced implementation. Participants' levels of use of the tool were dependent on knowledge of the tool and self-efficacy; perceived service-user needs and characteristics; and perceptions of impact on the therapeutic relationship. Training and preparation time influenced participants' confidence in using the tool. CONCLUSIONS: Findings highlight the importance of congruence between staff, organization, and external policy priorities and digital technologies in aiding intervention engagement, and the need for ongoing training and support of those intended to use the technology during and after the end of implementation interventions.
Community Mental Health Services/standards , Telemedicine/methods , Female , Humans , Male , Qualitative Research
This article aims to explore and report on violent thinking and alcohol misuse; how these factors may predict self-reported violence. The role of violent thinking in violent behavior is both well established in theoretical models, yet there are few measures that explain this role. One measure that has been identified is the Maudsley Violence Questionnaire (MVQ). This is the first study to explore the use of the MVQ with a general (nonoffender) adult sample, having already been shown to be valid with young people (under 18 years old), adult male offenders, and mentally disordered offenders. This study involved 808 adult participants-569 female and 239 male participants. As figures demonstrate that around half of all violent crime in the United Kingdom is alcohol related, we also explored the role of alcohol misuse. Regression was used to explore how these factors predicted violence. The results demonstrate the important role of violent thinking in violent behavior. The MVQ factor of "Machismo" was the primary factor in regression models for both male and female self-reported violence. The role of alcohol in the regression models differed slightly between the male and female participants, with alcohol misuse involved in male violence. The study supports theoretical models including the role of violent thinking and encourages those hoping to address violence, to consider "Machismo" as a treatment target. The study also provides further validation of the MVQ as a helpful tool for clinicians or researchers who may be interested in "measuring" violent thinking.
Criminals , Violence , Adolescent , Adult , Alcohol Drinking/epidemiology , Female , Humans , Male , Surveys and Questionnaires , United Kingdom
Background: Mental health policies advocate service user participation in care planning. However, service users often feel they're not fully involved and direct access to users' own electronic care plans in the community can be an obstacle. To address this, an electronic care pathway tool (CPT) was co-designed by service users, staff and software developers, to facilitate co-production of care and crisis plans. Aims: To investigate the feasibility and acceptability of the pilot implementation of the CPT in professionals' practice to co-produce care plans and enable efficient working. Method: Qualitative interviews with fifteen mental health practitioners, and five service development/management staff. Normalisation process theory, which outlines the social processes involved in implementing technology, and co-production theory, informed interviews and data analysis. Results: Multiple factors influenced CPT usage, including people's views of technology, practitioners' relationships with service users, service users' mental health needs, and their capacity for reflective thinking. The CPT's visual and interactive features could enable co-production of care plans. The CPT supported practitioners' efficiency, but its features did not easily streamline with electronic patient records. Conclusions: CPT interactive touchpoints supported service users' therapeutic reflection and facilitated care planning involvement. Information technology system interoperability was an obstacle.
Attitude of Health Personnel , Mental Health , Patient Care Planning , Humans , Patient Participation , Pilot Projects , Qualitative Research , Software
Lynx, a next generation X-ray observatory concept currently under study, requires lightweight, high spatial resolution X-ray mirrors. Here we detail the development and fabrication of one of the candidate technologies for Lynx, piezoelectric adjustable X-ray optics. These X-ray mirrors are thin glass shell mirrors with Cr/Ir X-ray reflective coatings on the mirror side and piezoelectric thin film actuators on the actuator side. Magnetron sputtering was used to deposit metal electrodes and metal-oxide piezoelectric layers. The piezoelectric (Pb0.995(Zr0.52Ti0.48)0.99Nb0.01O3) was divided into 112 independent piezoelectric actuators, with 100% yield achieved. We discuss the fabrication procedure, residual thermal stresses and tuning of the Cr/Ir coating stress for the purposes of stress balancing.
Many technologically critical materials are metastable under ambient conditions, yet the understanding of how to rationally design and guide the synthesis of these materials is limited. This work presents an integrated approach that targets a metastable lead-free piezoelectric polymorph of SrHfO3 . First-principles calculations predict that the previous experimentally unrealized, metastable P4mm phase of SrHfO3 should exhibit a direct piezoelectric response (d33 ) of 36.9 pC N-1 (compared to d33 = 0 for the ground state). Combining computationally optimized substrate selection and synthesis conditions lead to the epitaxial stabilization of the polar P4mm phase of SrHfO3 on SrTiO3 . The films are structurally consistent with the theory predictions. A ferroelectric-induced large signal effective converse piezoelectric response of 5.2 pm V-1 for a 35 nm film is observed, indicating the ability to predict and target multifunctionality. This illustrates a coupled theory-experimental approach to the discovery and realization of new multifunctional polymorphs.
It has long been hypothesized that feelings of inferiority or low self-esteem lead individuals to aggress against those they view as being threatening. However, recent studies suggest that it is not just the level of self-esteem but stability that is relevant to understanding this process. As such, researchers have looked to related constructs, such as narcissism, in trying to understand aggressive behaviors. Narcissism is characterized by a dissociation between an unconscious sense of inadequacy and a conscious feeling of superiority. A large number of studies examining the relationship between narcissism and violence have recently been published within both clinical and student populations. This review aimed to systematically collate the findings of such studies and integrate them within current theories of violence. Electronic literature databases such as Web of Science, MEDLINE, PsychINFO, EMBASE, Cochrane databases, and LexisNexis (legal database) were searched to identify studies examining the relationship between narcissism and violence. Twenty articles were included in this review, describing 25 separate samples. Findings suggest that narcissism is relevant in understanding aggression and violence. This was consistent across both clinical and nonclinical populations and therefore does not appear to be an artifact of studying either very violent or student samples. Evidence from student samples strongly supported the association between narcissism and aggression following an ego threat, while studies using clinical samples did not examine the effect of an ego threat. These findings may have an impact on how we understand, predict, and reduce violence.
Aggression/psychology , Narcissism , Violence/psychology , Anger/physiology , Cross-Sectional Studies , Female , Humans , Male , Observational Studies as Topic , Risk Assessment , Self Concept
BACKGROUND: There is little evidence on the accuracy of psychosis relapse prediction models. Our objective was to undertake a systematic review of relapse prediction models in psychosis. METHOD: We conducted a literature search including studies that developed and/or validated psychosis relapse prediction models, with or without external model validation. Models had to target people with psychosis and predict relapse. The key databases searched were; Embase, Medline, Medline In-Process Citations & Daily Update, PsychINFO, BIOSIS Citation Index, CINAHL, and Science Citation Index, from inception to September 2016. Prediction modelling studies were assessed for risk of bias and applicability using the PROBAST tool. RESULTS: There were two eligible studies, which included 33,088 participants. One developed a model using prodromal symptoms and illness-related variables, which explained 14% of relapse variance but was at high risk of bias. The second developed a model using administrative data which was moderately discriminative (C = 0.631) and associated with relapse (OR 1.11 95% CI 1.10, 1.12) and achieved moderately discriminative capacity when validated (C = 0.630). The risk of bias was low. CONCLUSIONS: Due to a lack of high quality evidence it is not possible to make any specific recommendations about the predictors that should be included in a prognostic model for relapse. For instance, it is unclear whether prodromal symptoms are useful for predicting relapse. The use of routine data to develop prediction models may be a more promising approach, although we could not empirically compare the two included studies.
Models, Statistical , Psychotic Disorders/diagnosis , Computational Biology , Humans , Prognosis , Recurrence
Mobile charged defects, accumulated in the domain-wall region to screen polarization charges, have been proposed as the origin of the electrical conductivity at domain walls in ferroelectric materials. Despite theoretical and experimental efforts, this scenario has not been directly confirmed, leaving a gap in the understanding of the intriguing electrical properties of domain walls. Here, we provide atomic-scale chemical and structural analyses showing the accumulation of charged defects at domain walls in BiFeO3. The defects were identified as Fe4+ cations and bismuth vacancies, revealing p-type hopping conduction at domain walls caused by the presence of electron holes associated with Fe4+. In agreement with the p-type behaviour, we further show that the local domain-wall conductivity can be tailored by controlling the atmosphere during high-temperature annealing. This work has possible implications for engineering local conductivity in ferroelectrics and for devices based on domain walls.
Electromechanical properties such as d33 and strain are significantly enhanced at morphotropic phase boundaries (MPBs) between two or more different crystal structures. Many actuators, sensors and MEMS devices are therefore systems with MPBs, usually between polar phases in lead (Pb)-based ferroelectric ceramics. In the search for Pb-free alternatives, systems with MPBs between polar and non-polar phases have recently been theorized as having great promise. While such an MPB was identified in rare-earth (RE) modified bismuth ferrite (BFO) thin films, synthesis challenges have prevented its realization in ceramics. Overcoming these, we demonstrate a comparable electromechanical response to Pb-based materials at the polar-to-non-polar MPB in Sm modified BFO. This arises from 'dual' strain mechanisms: ferroelectric/ferroelastic switching and a previously unreported electric-field induced transition of an anti-polar intermediate phase. We show that intermediate phases play an important role in the macroscopic strain response, and may have potential to enhance electromechanical properties at polar-to-non-polar MPBs.
