Experimental and numerical studies on rock breaking with TBM tools under high stress confinement

The understanding of rock breaking and chipping due to the TBM cutter disks mechanism in deep tunnels is considered in this paper. The interest stems from the use of TBMs for the excavation of long Trans-Alpine tunnels. Some tests that simulate the disk cutter action at the tunnel face by means of an indenter, acting on a rock specimen are proposed. The rock specimen is confined through a flat-jack and a confinement-free area on one side of the specimen simulates the formation of a groove near the indenter, like it occurs in TBM excavation conditions. Results show a limited influence of the confinement stress versus the thrust increment required for breaking the rock between the indenter and the free side of the specimen. Numerical modelling of the cutter disk action on confined material has also been carried out in order to investigate further aspects of the fracture initiation. Also in this case the importance of the relative position between disk cutter and groove is pointed out. © 2006 Springer-Verlag.

Dynamical symmetry breaking with optimal control: Reducing the number of pieces

We analyze the production of defects during the dynamical crossing of a mean-field phase transition with a real order parameter. When the parameter that brings the system across the critical point changes in time according to a power-law schedule, we recover the predictions dictated by the well-known Kibble-Zurek theory. For a fixed duration of the evolution, we show that the average number of defects can be drastically reduced for a very large but finite system, by optimizing the time dependence of the driving using optimal control techniques. Furthermore, the optimized protocol is robust against small fluctuations.

Breaking the Intimate Screen: Pre-Recording, Special Effects and the Aesthetics of Early British Television

The technological constraints of early British television encouraged drama productions which emphasised the immediate, the enclosed and the close-up, an approach which Jason Jacobs described in the title of his seminal study as 'the intimate screen'. While Jacobs' book showed that this conception of early British television drama was only part of the reality, he did not focus on the role that special effects played in expanding the scope of the early television screen. This article will focus upon this role, showing that special effects were not only of use in expanding the temporal and spatial scope of television, but were also considered to be of interest to the audience as a way of exploring the new medium, receiving coverage in the popular press. These effects included pre-recorded film inserts, pre-recorded narration, multiple sets, model work and animation, combined with the live studio performances. Drawing upon archival research into television production files and scripts as well as audience responses and periodical coverage of television at the time of broadcast, this article will focus on telefantasy. This genre offered particular opportunities for utilising effects in ways that seemed appropriate for the experimentation with the form of television and for the drama narratives. This period also saw a variety of shifts within television as the BBC sought to determine a specific identity and understand the possibilities for the new medium.
This research also incorporates the BBC's own research and internal dialogue concerning audiences and how their tastes should best be met, at a time when the television audience was not only growing in terms of number but was also expanding geographically and socially beyond the moneyed Londoners who could afford the first television sets and were within range of the Alexandra Palace transmissions. The primary case study for this article will be the 1949 production of H.G.Wells’ The Time Machine, which incorporated pre-recorded audio and film inserts, which expanded the narrative out of the live studio performance both temporally and spatially, with the effects work receiving coverage in the popular magazine Illustrated. Other productions considered will be the 1938 and 1948 productions of RUR, the 1948 production of Blithe Spirit, and the 1950 adaptation of The Strange Case of Dr Jekyll and Mr Hyde. Despite the focus on telefantasy, this article will also include examples from other genres, both dramatic and factual, showing how the BBC's response to the changing television audience was to restrict drama to a more 'realistic' aesthetic and to move experimentation with televisual form to non-drama productions such as variety performances.

Breaking Glass: Towards a Gendered Analysis of Entrepreneurial Leadership

Despite recent expansion in the literature on entrepreneurial leadership, this has not been matched with the development of appropriate theoretical frameworks, theory building, and conceptual analyses, including the analysis of gender. In this paper, we provide the foundation for a more robust and extensive gendered study of entrepreneurial leadership, through a review of the entrepreneurial leadership literature and of the current debates on gender and leadership. On the basis of this, we propose a research agenda for the gendered analysis of the rapidly expanding interface between leadership and entrepreneurship, comprising three themes around which the future development of entrepreneurial leadership can be organized.

Breaking and Entering: Examining the role of stress and aerial exposure in predator-prey relationships between the common shore crab (Carcinus maenas) and cultivated blue mussels (Mytilus edulis).

During benthic cultivation Mytilus edulis (blue mussels) are subject to predation pressure from a number of predators including Carcinus maenas (shore crabs). This predator can be responsible for substantial losses of mussels from the fishery and a full understanding of the predator–prey relationship between M. edulis and C. maenas is required to ensure attempts that reduce predatory pressure and subsequent commercial loss are successful. Whilst much work has examined the prey–predator size relationships between C. maenas and M. edulis, far less research has investigated how stress, such as periods of extended aerial exposure, may affect these relationships. We tested whether profit in terms of calories gained by crabs consuming mussels stressed by aerial exposure for 48 h differed from that of mussels at ambient conditions and whether being stressed affected the mussel's likelihood of predation. We also tested whether the size relationship between predators and their prey differed when mussels were stressed. We found that the profitability of prey (calories gained per second of handling time) did not vary between stressed and unstressed mussels. Handling times for stressed and unstressed mussels were similar, even when crabs were presented with mussels of the maximum size that they are able to consume. Small crabs were more likely to reject a mussel of preferred size if it was unstressed, suggesting that crabs may be able to assess that these mussels would require extra effort to break into and consume. Our findings suggest that the predator–prey relationship between mussels and crabs is not altered when mussels are stressed. C. maenas remains a voracious predator and regardless of the condition of mussels laid on commercial beds there is a need to control this predator in attempt to reduce losses in the benthic fishery.

‘To me, it's like a little box of tricks’: Breaking the depressive interlock as a programme participant in mindfulness-based cognitive therapy

Objectives. Mindfulness meditation practices have become increasingly popular in clinical therapies, changing patterns of depressogenic thinking for individuals who experience consecutive episodes of depression. We were interested in finding out how Mindfulness Based Cognitive Therapy (MBCT) worked for programme participants by focussing on how meditative practices changed their relationships to their thoughts. Design. Data for the study came from six semi-structured research interviews carried out with individuals who had taken part in an 8 week MBCT programme Methods. We used Interpretative Phenomenological Analysis (IPA) to analyse the experiential accounts. Results. We report on two superordinate themes – Engaging the Neutral Mind (with subordinate themes ‘breaking the paralysis of worry’ and ‘choosing to think differently’) and Experiencing the Neutral Mind (with subordinate themes of ‘reflection on previous thinking styles’ and ‘becoming psychologically self-reliant’). Conclusions. Themes from the present study offer support to the assertion that mindfulness meditation helps facilitate a different mode of meta-cognitive processing with which to handle depression-related cognitions. Practitioner Points Participants reported that they experienced an enhanced capacity to differentiate between their thought processes, experiencing an ability to tolerate some more uncomfortable thoughts and experiencing a/more choice in how to respond to thoughts Participants recognised that ruminating over negative thoughts was related to depressive states and experienced a shift in meta-cognitive processes that actively challenged depressogenic cognitions Participants became more psychologically self-reliant and therapeutically independent following MBCT Integrating mindfulness based practices in therapy may be a mediating factor in sustaining psychological wellbeing and may help clients develop self-compassion Future research looks to examining exit cases to understand elements of MBCT which are experienced as less successful by clients

‘Disability and HIV in Africa: Breaking the barriers to sexual health care’

Three decades in to the HIV pandemic, the issues affecting people with disabilities remains less known. Increasing attention has been given to this overlooked population when it comes to HIV prevention, treatment and care. This is related to the significant unmet sexual and reproductive health care needs facing people with disabilities worldwide. This article discusses the barriers to sexual health for people with disabilities in Africa, and presents an argument about how mainstream HIV prevention work and research does not adequately attend to the sorts of systemic barriers that exclude people with disabilities, which a more targeted, and critical approach could.