The impact of small-scale turbulence on laminar magnetic reconnection

Initial states in incompressible two-dimensional magnetohydrodynamics that are known to lead to strong current sheets and (laminar) magnetic reconnection are modified by the addition of small-scale turbulent perturbations of various energies. The evolution of these states is computed with the aim of ascertaining the influence of the turbulence on the underlying laminar solution. Two main questions are addressed here: (1) What effect does small-scale turbulence have on the energy dissipation rate of the underlying solution? (2) What is the threshold turbulent perturbation level above which the original laminar reconnective dynamics is no longer recognizable. The simulations show that while the laminar dynamics persist the dissipation rates are largely unaffected by the turbulence, other than modest increases attributable to the additional small length scales present in the new initial condition. The solutions themselves are also remarkably insensitive to small-scale turbulent perturbations unless the perturbations are large enough to undermine the integrity of the underlying cellular flow pattern. Indeed, even initial states that lead to the evolution of small-scale microscopic sheets can survive the addition of modest turbulence. The role of a large-scale organizing background magnetic field is also addressed

Aspherical Core-Collapse Supernovae in Red Supergiants Powered by Nonrelativistic Jets

We explore the observational characteristics of jet-driven supernovae by simulating bipolar-jet-driven explosions in a red supergiant progenitor. We present results of four models in which we hold the injected kinetic energy at a constant $10^{51}$ ergs across all jet models but vary the specific characteristics of the jets to explore the influence of the nature of jets on the structure of the supernova ejecta. We evolve the explosions past shock-breakout and into quasi-homologous expansion of the supernova envelope into a red supergiant wind. The oppositely-directed, nickel-rich jets give a large-scale asymmetry that may account for the non-spherical excitation and substructure of spectral lines such as H$\alpha$ and He I 10830\AA. Jets with a large fraction of kinetic to thermal energy punch through the progenitor envelope and give rise to explosions that would be observed to be asymmetric from the earliest epochs, inconsistent with spectropolarimetric measurements of Type II supernovae. Jets with higher thermal energy fractions result in explosions that are roughly spherical at large radii but are significantly elongated at smaller radii, deep inside the ejecta, in agreement with the polarimetric observations. We present shock breakout light curves that indicate that strongly aspherical shock breakouts are incompatible with recent {\it GALEX} observations of shock breakout from red supergiant stars. Comparison with observations indicates that jets must deposit their kinetic energy efficiently throughout the ejecta while in the hydrogen envelope. Thermal energy-dominated jets satisfy this criterion and yield many of the observational characteristics of Type II supernovae.Comment: 21 pages, 19 figures, submitted to ApJ on 4 Nov 200

A psychobiographical study of Sybrand Gerhardus(Brand)Pretorius

The South African businessman, Brand Pretorius, was born in the rural Orange Free State town of Steynsrus in 1953. Pretorius rose to prominence in the motor industry in South Africa and he retired in 2011 as Chairman of McCarthy Motor Holdings Limited the largest motor retailer in South Africa. Pretorius was selected for this psychobiographical study by means of purposive sampling, given his extraordinary business achievements. Pretorius is publicly recognised as one of South Africa’s most successful businessmen and leaders. Psychobiographical research typically takes into consideration the entire life of an individual with the aim of uncovering the story of an individual’s life through the lens of a particular theory. The aim of this study was to explore and describe the leadership development of Brand Pretorius juxtaposed against the model of authentic leadership proposed by Avolio and Luthans (2003). The life history of Brand Pretorius was studied using a qualitative single-case study design. The psychobiographical research method allowed the single-case to be studied spanning his entire career. Data was collected from both primary and secondary sources. Conceptual matrices were used to organise and integrate the findings against the model of authentic leadership. The use of multiple data sources increased the validity and reliability of the research process and findings. To ensure ethical integrity the researcher obtained informed consent from Pretorius. The findings of this research study indicate that Pretorius was able to successfully display the authentic leadership dimensions of self-awareness, internalised moral perspective, balanced processing, relational transparency and positive psychological capacities throughout the course of his career

Young people and the post-crisis precarity: the abnormality of the 'new normal'

Craig Berry and Sean McDaniel draw upon research with focus groups and an online community exercise to examine the attitudes of young people in relation to the apparent 'normalisation' of precarity in the post-2008 economy. They find that although young people recognise the abnormality of labour market conditions, they nevertheless fail to see value in conventional forms of trade union organisation

Intensification and Complexity in Teachers' Narrated Worklives

Reflecting on a previous study of teachers’ narratives, this epistolary conversation follows ideas of intensification and complexity that emerged in the authors’ return to the narrative accounts. Their conversation highlights representations of teaching as a struggle for recognition, personal happiness, and security—all within a system of accountability. Of central concern is the concept of complicity and how it is related to the seduction of consent through which teachers encounter a discourse of professionalism. By way of countering a misrecognized professionalism, the authors suggest that teachers’ narrative writings can be a means of forming a critical stance

The young today may be the first cohort to experience large-scale precarity

The 2008 crisis crystallised the trend towards ‘precarious’ labour market conditions – stagnation in earnings growth, skills under-utilisation, labour market ‘hollowing out’, and the emergence of ‘gig economy’ practices – which disproportionately affect young people. Insecure employment is not new, especially in lower-skilled occupations, although it may have reached a new peak since the crisis. Indeed, two decades ago, Richard Sennett warned of ‘flexible capitalism’, wherein uncertainty and instability were becoming ‘woven into the everyday practices of a vigorous capitalism’

Attention to Place: Learning to Listen

In this paper we set out to explore the speculative function and nature of narrative in autoethnographic research. We consider how place--as locus, milieu, setting in which we narrate the distance between ourselves and events we can remember, places where we can remember being (or, in this case, becoming: becoming authors)--enriches our understanding of autoethnographic research in Education. Determining autoethnography as new frontier and as site for the construction of a way of life, we offer and invite beginnings in literary enjoyment of life through autobiographical writings for the Social Science of Education. We find ourselves digressing, and suggest that this may be a turn our memory takes on its homeward journey. We celebrate life

The subiculum to entorhinal cortex projection is capable of sustaining both short-and long-term plastic changes

The hippocampus communicates with the neocortex via the entorhinal cortex. These areas are thought to be critically involved in the consolidation of memories. The hippocampus is considered to be the site of association of sensory information, which is then laid down for long-term storage in the neocortex. We examined the projection from the subiculum to the entorhinal cortex to determine whether it could function to transfer this hippocampally-processed information to the neocortex. Following stimulation in the subiculum we demonstrate a negative-going deflection followed by a positive-going deflection in the entorhinal cortex. This projection is capable of short-term plastic changes in the form of PPF. FIn addition, we demonstrate that long-term synaptic changes in the form of LTP and LTD could be sustained for at least 30 min on this pathway. Finally we show that PPF changes after LTP and LTD, suggesting that a presynaptic mechanism may be involved in both of these pathways

Diefenbaker, the Cuban Missile Crisis, and the impact of society on foreign policy

Typically, students of foreign policy have viewed the decision-­making process from perspectives that downplay, if not ignore, societal influence. Canadian scholar Patrick Stuart Robinson has gone against this trend, asserting that foreign policy, properly understood, is in fact rooted in society. According to Robinson, the political process is inherently a social activity, and as such, imposes certain constraints on decision-makers. He asserts that decision-makers, like all members of society, have a role to play. Indeed, as the symbolic representatives of their constituency, these individuals have a particularly significant position within society -- they are at the helm of the ongoing process of affirming its values and rules. Like everyone else, they too are aware of, what is expected of them according to their role. However, because of their status, and because of the importance of what they do, decision-makers are especially burdened by societal expectations. Their choices cannot simply be made according to personal preferences; rather, they must be made against the backdrop of their leadership position and its attendant obligations to society. Importantly, as Robinson notes, the "political fortunes [of decision-makers] -- even their survival -- ­depend to a great extent on how they are popularly perceived to have discharged [their] ...responsibility." As a result, considerations of role and appropriateness are often pivotal to the policy-making process. This thesis, a case study of the Canadian response to the Cuban missile crisis, lends credence to Robinson's argument. Specifically, it shows that considerations of role, responsibility, and appropriateness were highly relevant to the Diefenbaker government in the formulation of Canadian policy. Moreover, this thesis dispels the popular notion that Canada's reaction to the crisis can be explained solely by reference to Prime Minister Diefenbaker's propensity for indecision, his personal antipathy for President Kennedy, or his strong Canadian nationalism