Barium titanate: photophysics, photocatalysis & the influence of the ferroelectric effect

Photocatalytic and photoelectrochemical water splitting processes remain hindered by fast recombination of photogenerated electrons and holes. Ferroelectric materials are increasingly being considered to address this issue; their internal electric fields have been shown to spatially separate electrons and holes, and thus should greatly reduce recombination rates. A kinetic understanding of the extent to which electron–hole recombination can be slowed in ferroelectric materials is essential to ascertain if they can play a significant role in achieving higher solar-driven water splitting efficiencies. The focus of this thesis is an experimental investigation of charge carrier dynamics in barium titanate (BaTiO3) to observe the effect of internal electric fields on recombination rates. Time-resolved spectroscopic techniques were used in conjunction with photocatalysis studies to determine whether ferroelectricity can significantly reduce recombination rates and lead to enhanced performance. It is found that, although the transient absorption spectrum of ferroelectric BaTiO3 is similar to previously reported metal oxides, the carrier lifetimes are significantly longer, indicating the potential for ferroelectrics to be used in devices limited by fast electron–hole recombination. In the first results chapter, the transient absorption spectrum of single crystal BaTiO3 is characterised under inert atmosphere over two timescales: femtosecond–nanosecond and microsecond–second. Absorption signals due to photogenerated holes and electrons are identified using electron and hole scavengers, respectively. Comparisons are drawn between BaTiO3 and other single crystal, but non-ferroelectric, metal oxides. It is found that, on timescales relevant for water oxidation, lifetimes in BaTiO3 are at least an order of magnitude longer. In the second results chapter, the origin of long carrier lifetimes in ferroelectric BaTiO3 is explored. When the polarisation is switched off by both temperature and nanostructuring, carrier lifetimes decrease by four orders of magnitude. Recombination rates in BaTiO3 exhibit a much stronger temperature dependence than other metal oxides, which is rationalised by considering the temperature dependence of the spontaneous polarisation. The third results chapter investigates the photocatalytic performance of BaTiO3 nanopowders. It is found that, in the presence of an electron scavenger, BaTiO3 photogenerated holes are reactive and can oxidise water to produce oxygen. Transient and photoinduced absorption spectroscopies indicated that hole accumulation in a BaTiO3 sample with a higher tetragonal (ferroelectric) content, which translates to higher rates of oxygen evolution. The final results chapter probes the influence of a ferroelectric BaTiO3 substrate on α-Fe2O3 thin films. Preliminary data suggests the internal field can penetrate through the film and slow electron–hole recombination rates in α-Fe2O3.Open Acces

More Than a One-Trick Pony: Exploring the Contours of a Multi-Sector Covener

Today\u27s managers must find ways to identify and sustain productive relationships within multi-sector collaborative arrangements. This paper explores empirically the activities of a convener based on tasks identified by Agranoff and McGuire (2001) and applies this framework to the case of Virginia\u27s Coastal Zone Management Program (VCZMP). We find that the convener displays characteristics described by Agranoff and McGuire, as well as characteristics of traditional hierarchical managers. This research suggests that both sets of skills are necessary for effective multi-sector collaborative governance

Mature-age men's experiences of Higher Education: Australia and England compared. A literature review

This literature review was prepared in response to a growing awareness that there is a significant gap in the existing literature on transition to university and university experience of mature-age male undergraduates. Interest in the experiences of students making the transition into Higher Education has been prompted in part by the rapid expansion of the sector. Governments in Organisation for Economic Cooperation and Development (OECD) nations, and most developed nations, have been intent on transforming higher education from an elite to a universal system in which more than 50% of potential applicants are enrolled in a degree in the belief that increasing the number of graduates will increase economic productivity and prosperity (Trow, 2006). Australia and the UK have both set ambitious targets. In Australia the Review of Australian Higher Education [Bradley review] set a target of 40% of young people (especially from low-SES backgrounds) to attain a minimum of a bachelor-level qualification by 2020 (Bradley, Noonan, Nugent & Scales, 2008), while in England it was intended that by 2010 50% of 18-30-year-olds would have some experience of studying courses offered by higher education institutions (Higher Education Funding Council [HEFCE], 2003). The twin and, to some extent competing, aims of increasing opportunities to participate in higher education (as underpinned by values around social justice) and the importance ascribed to higher education as contributing to a nation’s knowledge economy (signifying a more utilitarian and human capital approach) have been key drivers in terms of the access and widening participation policy agenda in both countries

Development of Sézary syndrome following the administration of dupilumab

Dupilumab is a monoclonal antibody that inhibits interleukin-4 and interleukin-13 signaling. It is the first biologic agent to demonstrate efficacy in treating moderate-to-severe refractory atopic dermatitis [1, 2]. Although dupilumab provides promise for the treatment of atopic and allergic conditions, clinicians should take into account its novelty and the potential for unexpected adverse events. We present a patient who developed Sézary syndrome following the initiation of dupilumab

Book Reviews

Reviews of the following books: Lewiston: A Textile City in Transition by James S. Leamon; Massachusetts: A Bibliography of its History edited by John D. Haskell; Bibliography of Maine, 1960-1975 compiled by Eric S. Flower; Maine in the Revolution: A Reader\u27s Guide compiled by Edwin A. Churchill and James Leamon; Maine Communities and War for Independence: A Guide for Study of Local Maine History as Related to the American Revolution compiled by Edwin A Churchill

Noticing trauma responses: the development and validation of the autonomic response screening tool for counselors (ARSTC)

Trauma can impact all people of all identities, and mental health professionals are experiencing an influx of clients presenting for services with symptoms related to trauma (Webber, Kitzinger, Runte, Smith, & Mascari, 2016). According to the U.S. Department of Veterans Affairs (2016), an estimated 6 in 10 men and 5 in 10 women will experience a traumatic experience in their lifetime. Roughly 8 million adults meet diagnostic criteria for Posttraumatic Stress Disorder (PTSD) in a given year (U.S. Department of Veterans Affairs, 2016), and trauma is considered a public health crisis by the U.S. Department of Health and Human Services (2003). In response to this increasingly prevalent concern among the population, it is imperative that counselors are trained to effectively recognize and treat trauma symptomology. Porges’s Polyvagal Theory (PVT; 2018) offered a conceptualization of trauma responses that could prove useful for counselors. Porges outlined the physiological underpinnings of how one’s autonomic nervous system (ANS) responds to stress. PVT explores three types of stress responses: social engagement, sympathetic arousal (fight/flight responses), and dorsal shutdown (freeze responses). These responses are connected with various symptoms that correlate with trauma, and they offer one lens for conceptualizing how clients present to counseling for trauma. Within the literature, authors are conceptually connecting symptoms of psychopathology with ineffective autonomic regulation and vagal dysregulation (DePierro et al., 2013; Fiskum, 2019), as outlined by Porges (2011), but there is limited empirical literature on applying PVT to counseling. Thus, autonomic regulation is an important - but overlooked - factor at play within counseling and trauma treatment. Because autonomic regulation is tied to which trauma response a client experiences (and exhibits in session), it is important for counselors to have a way to screen for it. In the current study, visual markers indicative of autonomic regulation related to the social engagement, fight/flight, and freeze responses were organized into the Autonomic Response Screening Tool for Counselors (ARSTC). These items did not categorize into the specific trauma responses as outlined within PVT, but they did seem to be representative of two broader yet distinct nervous system processes: sympathetic and parasympathetic processes. These analyses suggested initial evidence for the validity the ARSTC, specifically related to changes in heartrate variability (HRV) between the ARSTC categories of social engagement and freeze, and fight/flight and freeze. Limitations of the study and implications of the results are outlined, and offer a launching point for both counselors and researchers to continue exploring the role of autonomic processes and PVT at play in counseling session

Mature-aged men’s experiences of higher education: Australia and England compared. [SRHE Research Scoping Study Award: Final Report February 2016]

This study is intended to improve our understanding of the challenges facing mature-age male undergraduates as they adapt to university study with a view to reducing attrition. On commencement, we identified three specific program goals: to review the literature on mature-age students with a particular focus on men, to develop a more robust understanding mature-age men’s experience of transition through university and their adaptation to university study, to develop a series of research questions, which are informed by a new model of transition and which will be used as the foundation for further study

Technology readiness of a vertical-axis hydro-kinetic turbine

In this paper, the development of a vertical axis hydrokinetic twin turbine for harvesting energy from flowing water in man-made channels is described. The Technology Readiness Level (TRL) assessment procedure, developed by NASA and modified by the US Department of Energy, is followed and it is shown that the hydrokinetic turbine successfully reaches TRL 7, which is a full-scale, similar (prototypical) system demonstrated in a relevant environment. The concept of the twin turbine (TRL 1 - 3) is first validated and tested using a 1:10 scale laboratory model at Cardiff University and efficiencies of up to 75% are achieved (TRL 4 - 5). In order to justify system functionality and performance in a relevant environment as well as up-scalability, a 1:3 scale model of the twin turbine is implemented and tested in a discharge channel of a water treatment plant in Atlanta, thereby achieving TRL6. This paved the way for an application in the form of an array of ten full-scale twin turbine prototypes, including all relevant components such as housing, drive-train, gear-box and generator. Successful deployment and testing in the South Boulder Canal near Denver means that the hydrokinetic twin turbine system reached TRL7