Two-species percolation and Scaling theory of the metal-insulator transition in two dimensions

Recently, a simple non-interacting-electron model, combining local quantum tunneling via quantum point contacts and global classical percolation, has been introduced in order to describe the observed ``metal-insulator transition'' in two dimensions [1]. Here, based upon that model, a two-species-percolation scaling theory is introduced and compared to the experimental data. The two species in this model are, on one hand, the ``metallic'' point contacts, whose critical energy lies below the Fermi energy, and on the other hand, the insulating quantum point contacts. It is shown that many features of the experiments, such as the exponential dependence of the resistance on temperature on the metallic side, the linear dependence of the exponent on density, the $e^2/h$ scale of the critical resistance, the quenching of the metallic phase by a parallel magnetic field and the non-monotonic dependence of the critical density on a perpendicular magnetic field, can be naturally explained by the model. Moreover, details such as the nonmonotonic dependence of the resistance on temperature or the inflection point of the resistance vs. parallel magnetic are also a natural consequence of the theory. The calculated parallel field dependence of the critical density agrees excellently with experiments, and is used to deduce an experimental value of the confining energy in the vertical direction. It is also shown that the resistance on the ``metallic'' side can decrease with decreasing temperature by an arbitrary factor in the degenerate regime ($T\lesssim E_F$).Comment: 8 pages, 8 figure

Galaxy bulges and their massive black holes: a review

With references to both key and oft-forgotten pioneering works, this article starts by presenting a review into how we came to believe in the existence of massive black holes at the centres of galaxies. It then presents the historical development of the near-linear (black hole)-(host spheroid) mass relation, before explaining why this has recently been dramatically revised. Past disagreement over the slope of the (black hole)-(velocity dispersion) relation is also explained, and the discovery of sub-structure within the (black hole)-(velocity dispersion) diagram is discussed. As the search for the fundamental connection between massive black holes and their host galaxies continues, the competing array of additional black hole mass scaling relations for samples of predominantly inactive galaxies are presented.Comment: Invited (15 Feb. 2014) review article (submitted 16 Nov. 2014). 590 references, 9 figures, 25 pages in emulateApJ format. To appear in "Galactic Bulges", E. Laurikainen, R.F. Peletier, and D.A. Gadotti (eds.), Springer Publishin

Impact of advance care planning on the care of patients with heart failure: Study protocol for a randomized controlled trial

10.1186/s13063-016-1414-1Trials17128

Sustaining the ivory tower: Oxbridge formal dining as organizational ritual

In this ethnographic study of formal hall ritual in Oxbridge Colleges, the authors show how this special form of dining plays a key role in organizational cohesion, demarcation, and continuity. Formal hall serves as a central organizing principle of the colleges, having social, political, and pedagogic facets. Drawing upon participant observation of 22 formal dinners, this article explores its significance on different levels. It examines how formal hall creates social stability, provides historical continuity, reaffirms hierarchy and bureaucratic order, perpetuates exclusivity and reverence, and provides college level space for organizational politicking, relationship-building, and information exchange. It also cements important stakeholder relations at broader societal levels. Furthermore, these outcomes feed into its overriding purpose of solidifying shared elite identity through selective membership and participation. Transgressions against this elitist formal dining ritual are also addressed, being conceptualized on a continuum from “higher order” to “lower order” according to degree of potential threat to the ritual. The authors conclude with a discussion of their findings’ implications for research on organizational ritual, whereby inclusion, exclusion, and identity issues lie at the heart of the ritual’s power over organizational processes, and the social control of actors not solely within but also beyond immediate organizational boundaries