Effect of metallic walls on dynamos generated by laminar boundary-driven flow in a spherical domain

We present a numerical study of dynamo action in a conducting fluid encased in a metallic spherical shell. Motions in the fluid are driven by differential rotation of the outer metallic shell, which we refer to as "the wall". The two hemispheres of the wall are held in counter-rotation, producing a steady, axisymmetric interior flow consisting of differential rotation and a two-cell meridional circulation with radial inflow in the equatorial plane. From previous studies, this type of flow is known to maintain a stationary equatorial dipole by dynamo action if the magnetic Reynolds number is larger than about 300 and if the outer boundary is electrically insulating. We vary independently the thickness, electrical conductivity, and magnetic permeability of the wall to determine their effect on the dynamo action. The main results are: (a) Increasing the conductivity of the wall hinders the dynamo by allowing eddy currents within the wall, which are induced by the relative motion of the equatorial dipole field and the wall. This processes can be viewed as a skin effect or, equivalently, as the tearing apart of the dipole by the differential rotation of the wall, to which the field lines are anchored by high conductivity. (b) Increasing the magnetic permeability of the wall favors dynamo action by constraining the magnetic field lines in the fluid to be normal to the wall, thereby decoupling the fluid from any induction in the wall. (c) Decreasing the wall thickness limits the amplitude of the eddy currents, and is therefore favorable for dynamo action, provided that the wall is thinner than the skin depth. We explicitly demonstrate these effects of the wall properties on the dynamo field by deriving an effective boundary condition in the limit of vanishing wall thickness.Comment: accepted for publication in Physical Review

Learning Approach, Thinking Style and Critical Inquiry: The Online Community

The study examined if a thematically designed online introductory psychology course set in a cooperative and collaborative learning environment led to deeper learning. Using the revised two-factor Study Process Questionnaire (R-SPQ-2F; Biggs, Kember & Leung, 2001), the study predicted peer and teacher guided asynchronous dialogue would lead to increasing students’ self-perceptions of deeper learning approaches (DA) and higher levels of thinking. Individual thinking style (ITS; Sternberg & Wagner, 1992) was presumed to be an important mediator on both student pre- and post-DA scores. It was also hypothesized that thinking styles would influence student perceptions towards participating in a learning community, as measured by the Classroom Community Scale (CCS; Rovai, 2002). Contrary to the hypotheses, thinking styles didn’t predict either pre- or post DA nor end of semester CCS scores. The two main hypotheses, premised on Vygotsky’s theory of social constructivism and post Vygotskian thinking on conceptual learning, demonstrated mixed results. The expected increase in self perceptions of deep learning and a predictive relationship between DA and CCS to reflect this contextualized learning were not found. While post DA scores weren’t significantly correlated with CCS, CCS was correlated with students’ perceptions of which types of discussions guided their learning. Qualitative evidence from the online dialogue demonstrated deeper, conceptual and applied understanding than students’ self-reports. What requires further study is whether students develop an explicit metacognitive understanding of how cooperative discussions aren’t an added burden, but rather, a means of constructing a deeper meaning and approach to learning

Exploring consultant interview skills within the employment process in sport psychology

Academic interest in the professional practice of sport psychology has meant a proliferation in models, theories, and guides to successful service provision, from gaining entry into practice to the evaluation and/or termination of service. However, there is an absence of research that examines the stage before practice can begin, and in particular, the formal employment interview. In order to address this gap in the literature, this thesis developed an understanding of the skills necessary to navigate the employment interview as a sport psychology consultant (SPC). The first study identified the features of experience that influenced gatekeepers to sport psychology s previous hiring decisions (study one). Assuming an interpretative phenomenological approach, data were collected through interviews with seven gatekeepers in positions directly responsible for hiring SPCs within United Kingdom elite sport organisations. The participants experiences were interpreted to be influenced by four key features of the sport psychologists; (a) consultant affability, (b) consultant confidence versus arrogance, (c) consultant collaboration, and (d) presentation of consultant competencies. These features of experience were then used to create two short video vignettes simulating the employment interview between gatekeeper and practitioner (study two). Utilising these vignettes to stimulate discussion, Trainee Sport Psychologists were interviewed (n=31) concerning their ability to identify interview skills, their perception of their own skills, the sources of such skills and how they could be developed. Findings revealed that despite possessing desirable levels of both affability and collaboration skills, participants reported low levels of confidence in sport psychology and the ability to present their competencies. Parent and peer attachment, educational background and specific experiential features were proposed as sources of these skills. In an attempt to further examine the potential interactions between these proposed sources of interview skills, currently accredited, practicing Sport Psychologists and those undertaking practical training routes (n=214) were surveyed (study three). The findings of this study indicated that a SPC s peer attachment, educational background, applied experience, and interview experience variably relate to self-perceived levels of consultant affability, confidence in sport psychology, collaboration, and presentation of competencies. However, there was no significant effect observed for parent attachment, as suggested within study two. Together, the studies within this thesis provide the first examination of the features of experience that have influenced historic consumer decisions within the hiring of SPCs, the skills which SPCs should possess in order to gain entry through an employment interview, and the sources from which these skills may be derived

A self-consistent model of the solar tachocline

We present a local but fully nonlinear model of the solar tachocline, using three-dimensional direct numerical simulations. The tachocline forms naturally as a statistically steady balance between Coriolis, pressure, buoyancy and Lorentz forces beneath a turbulent convection zone. Uniform rotation is maintained in the radiation zone by a primordial magnetic field, which is confined by meridional flows in the tachocline and convection zone. Such balanced dynamics has previously been found in idealised laminar models, but never in fully self-consistent numerical simulations.Comment: Accepted for publication in the Astrophysical Journa