Dispersive line shape in the vicinity of the {\nu} = 1 quantum Hall state: Coexistence of Knight shifted and unshifted resistively detected NMR responses

The frequency splitting between the dip and the peak of the resistively detected nuclear magnetic resonance (RDNMR) dispersive line shape (DLS) has been measured in the quantum Hall effect regime as a function of filling factor, carrier density and nuclear isotope. The splitting increases as the filling factor tends to {\nu} = 1 and is proportional to the hyperfine coupling, similar to the usual Knight shift versus {\nu}-dependence. The peak frequency shifts linearly with magnetic field throughout the studied filling factor range and matches the unshifted substrate signal, detected by classical NMR. Thus, the evolution of the splitting is entirely due to the changing Knight shift of the dip feature. The nuclear spin relaxation time, T1, is extremely long (hours) at precisely the peak frequency. These results are consistent with the local formation of a {\nu} = 2 phase due to the existence of spin singlet D$^-$ complexes.Comment: to be published in Rapid Communication PR

Electrical effects on droplet behaviour

The effect of charge on water droplets modulates various aspects of their behaviour. These include the droplet stability, evaporation, and lifetime. Microphysical models have been developed such that a reasonably good understanding of these processes has been achieved. However, the specific effects of charge deserve further scrutiny as they are an intrinsic component of the factors controlling droplet characteristics. Describing the effects of these requires an understanding of the electrostatic pressure present in the droplet and its surface tension. One way to test these effects and assess droplet response to charge is to take an experimental approach to make observations directly. In this study, individual droplets are levitated in an acoustic wave to allow isolated measurements to be taken. The droplets are monitored using a CCD camera with a microscope objective lens. In some cases, with sufficient charge present, effects on droplet stability can be observed as Rayleigh explosions, where a sudden drop in mass is seen superimposed on the evaporation profile. These events also allow the charge on the droplet to be calculated, which is then compared with the droplet evaporation. Another factor that plays a part in droplet behaviour is droplet composition. Different substances have different surface tension, and this is explored by performing some experiments on sulphuric acid droplets. Theory predicts that the more highly charged a droplet is, the more resistant to evaporation it becomes. Experimental data collected during this study agrees with this, with more highly charged droplets observed to have slower evaporation rates. However, highly charged drops were also observed to periodically become unstable during evaporation and undergo Rayleigh explosions. Each instability of a highly charged drop removes mass, reducing the overall droplet lifetime regardless of the slower evaporation rate. The sulphuric acid droplets were observed to be much more resistant to evaporation and no Rayleigh instabilities were observed

Geometric morphometrics defines shape differences in the cortical area map of C57BL/6J and DBA/2J inbred mice

BACKGROUND: We previously described planar areal differences in adult mouse visual, somatosensory, and neocortex that collectively discriminated C57BL/6J and DBA/2J inbred strain identity. Here we use a novel application of established methods of two-dimensional geometric morphometrics to examine shape differences in the cortical area maps of these inbred strains. RESULTS: We used Procrustes superimposition to align a reliable set of landmarks in the plane of the cortical sheet from tangential sections stained for the cytochrome oxidase enzyme. Procrustes superimposition translates landmark configurations to a common origin, scales them to a common size, and rotates them to minimize an estimate of error. Remaining variation represents shape differences. We compared the variation in shape between C57BL/6J and DBA/2J relative to that within each strain using a permutation test of Goodall's F statistic. Significant differences in shape in the posterior medial barrel subfield (PMBSF), as well as differences in shape across primary sensory areas, characterize the cortical area maps of these common inbred, isogenic strains. CONCLUSION: C57BL/6J and DBA/2J have markedly different cortical area maps, in both size and shape. These differences suggest polymorphism in genetic factors underlying cortical specification, even between common isogenic strains. Comparing cortical phenotypes between normally varying inbred mice or between genetically modified mice can identify genetic contributions to cortical specification. Geometric morphometric analysis of shape represents an additional quantitative tool for the study of cortical development, regardless of whether it is studied from phenotype to gene or gene to phenotype

Ferromagnetic GaMnAs/GaAs superlattices - MBE growth and magnetic properties

We have studied the magnetic properties of (GaMnAs)m/(GaAs)n superlattices with magnetic GaMnAs layers of thickness between 8 and 16 molecular layers (ML) (23-45 \AA), and with nonmagnetic GaAs spacers from 4 ML to 10 ML (11-28 \AA). While previous reports state that GaMnAs layers thinner than 50 \AA are paramagnetic in the whole Mn composition range achievable using MBE growth (up to 8% Mn), we have found that short period superlattices exhibit a paramagnetic-to-ferromagnetic phase transition with a transition temperature which depends on both the thickness of the magnetic GaMnAs layer and the nonmagnetic GaAs spacer. The neutron scattering experiments have shown that the magnetic layers in superlattices are ferromagnetically coupled for both thin (below 50 \AA) and thick (above 50 \AA) GaMnAs layers.Comment: Proceedings of 4th International Workshop on Molecular Beam Epitaxy and Vapour Phase Epitaxy Growth Physics and Technology, September 23 - 28 (2001), Warszawa, Poland, to appear in Thin Solid Films. 24 pages, 8 figure

Films and critical pedagogy in management education: A tourism studies context

This article examines and critically assesses the role of films in the practice of critical pedagogy in undergraduate management education, using tourism studies as a context. Utilising online focus groups, it aims to gain an in-depth knowledge and understanding of the role of films as an effective pedagogical medium in enhancing experiential approaches to learning. It argues that films play an important role in facilitating critical analyses of the studied phenomenon, illustrating and problematising abstract concepts and ideas, as well as in facilitating students’ ability to discern multiple and alternative discourses about management. The findings highlight the role of films in context-specific critical engagement with the studied content and in stimulating emotionality in learning development, thereby enhancing deep approaches to learning. Emotional responses, even negative ones, prove to be critical in engaging with intellectual and critical reflection after watching films. The findings yield new and empirical insights into the pedagogic use of films in management education, thereby contributing to some of the goals of critical management studies

From causes to solutions - insights from lay knowledge about health inequalities

<p>Abstract</p> <p>Background</p> <p>This paper reports on a qualitative study of lay knowledge about health inequalities and solutions to address them. Social determinants of health are responsible for a large proportion of health inequalities (unequal levels of health status) and inequities (unfair access to health services and resources) within and between countries. Despite an expanding evidence base supporting action on social determinants, understanding of the impact of these determinants is not widespread and political will appears to be lacking. A small but growing body of research has explored how ordinary people theorise health inequalities and the implications for taking action. The findings are variable, however, in terms of an emphasis on structure versus individual agency and the relationship between being 'at risk' and acceptance of social/structural explanations.</p> <p>Methods</p> <p>This paper draws on findings from a qualitative study conducted in Adelaide, South Australia, to examine these questions. The study was an integral part of mixed-methods research on the links between urban location, social capital and health. It comprised 80 in-depth interviews with residents in four locations with contrasting socio-economic status. The respondents were asked about the cause of inequalities and actions that could be taken by governments to address them.</p> <p>Results</p> <p>Although generally willing to discuss health inequalities, many study participants tended to explain the latter in terms of individual behaviours and attitudes rather than social/structural conditions. Moreover, those who identified social/structural causes tended to emphasise individualized factors when describing typical pathways to health outcomes. This pattern appeared largely independent of participants' own experience of advantage or disadvantage, and was reinforced in discussion of strategies to address health inequalities.</p> <p>Conclusions</p> <p>Despite the explicit emphasis on social/structural issues expressed in the study focus and framing of the research questions, participants did not display a high level of knowledge about the nature and causes of place-based health inequalities. By extending the scope of lay theorizing to include a focus on solutions, this study offers additional insights for public health. Specifically it suggests that a popular constituency for action on the social determinants of health is unlikely to eventuate from the current popular understandings of possible policy levers.</p

Contrast Enhanced Micro-Computed Tomography Resolves the 3-Dimensional Morphology of the Cardiac Conduction System in Mammalian Hearts

The general anatomy of the cardiac conduction system (CCS) has been known for 100 years, but its complex and irregular three-dimensional (3D) geometry is not so well understood. This is largely because the conducting tissue is not distinct from the surrounding tissue by dissection. The best descriptions of its anatomy come from studies based on serial sectioning of samples taken from the appropriate areas of the heart. Low X-ray attenuation has formerly ruled out micro-computed tomography (micro-CT) as a modality to resolve internal structures of soft tissue, but incorporation of iodine, which has a high molecular weight, into those tissues enhances the differential attenuation of X-rays and allows visualisation of fine detail in embryos and skeletal muscle. Here, with the use of a iodine based contrast agent (I2KI), we present contrast enhanced micro-CT images of cardiac tissue from rat and rabbit in which the three major subdivisions of the CCS can be differentiated from the surrounding contractile myocardium and visualised in 3D. Structures identified include the sinoatrial node (SAN) and the atrioventricular conduction axis: the penetrating bundle, His bundle, the bundle branches and the Purkinje network. Although the current findings are consistent with existing anatomical representations, the representations shown here offer superior resolution and are the first 3D representations of the CCS within a single intact mammalian heart

Principal stress rotation under bidirectional simple shear loadings

Previous researches have indicated the non-coaxiality of sand in unidirectional simple shear tests, in which the direction of the principal axes of stresses does not coincide with the corresponding principal axes of strain rate tensors. Due to the limitation of apparatus that most of testing facilities can only add shear stress in one direction, the influence of stress history on the noncoaxiality of sand is not fully considered in previous tests. In this study, the effect of stress history on the non-coaxiality of sand is systematically studied by using the first commercially available Variable Direction Dynamic Cyclic Simple Shear system (VDDCSS). Samples of Leighton Buzzard sand (Fraction B) are first consolidated under a vertical confining stress and consolidation shear stress, and then sheared by a drained monotonic shear stress. Angle (θ) between the consolidation shear stress and the drained monotonic shear stress is varied from 0° to 180°, with an interval of 30°. The change of principal axes of stresses is predicted by well-established equations, and the principal axe of strain rate is calculated using recorded data. Results show that the level of non-coaxiality is increased by the increasing θ, especially at the initial stage of drained shearing

Developing Student Engagement in China Through Collaborative Action Research

As its market and society open up, China has transformed itself from a closed agrarian socialist economy to an urban state and an economic force. This has released accumulated tourism demand, led to the development of a diversified industry, and the spread of university and vocational courses in this field. However, the industry faces challenges to recruit and retain staff, with tourism education in higher education blamed for the shortfall in numbers and quality of candidates with suitable purpose, knowledge, and passion to serve. This chapter provides a background to the development of and problems facing tourism education in China, and suggests how to support student engagement and hence the future workforce