Modelling the effect of step and roughness features on swept wing boundary layer instabilities

Destabilisation effects of forward facing steps, backward facing steps and bumps on stationary and travelling crossflow disturbances are investigated computationally for a 40 degree infinitely swept wing. Step and bump heights range from 18% to 82% of the boundary layer thickness and are located at 3%, 10% and 20% chord. The spectral/hp element solver, Nektar++, is used to compute base flow profiles with an embedded swept wing geometry. Parabolised Stability Equations (PSE) and Linearised Harmonic Navier-Stokes (LHNS) models are used to evaluate growth of convecting instabilities. The presence of surface step features impose an extremely rapidly varying flow field locally, which requires accurate resolution of the perturbed flow field. Derivations of these PSE and LHNS models incorporating the excrescence (PSEh, LHNSh) are elucidated. Unlike the PSE, which suffer from a stream-wise numerical step size restriction, the LHNS are a fully elliptic set of equations which may use an arbitrarily fine grid resolution. Unsurprisingly, the PSE codes fail to capture the effect of abrupt changes in surface geometry introduced by the step features. Results for the LHNS and roughness incorporating LHNSh are given for the varying vertical step and ramped type steps. Comparisons are made between the LHNSh model and direct numerical simulations involving the time-stepping linearised Navier-Stokes solver (NekLNS) in the Nektar++ software framework. Most previous work in the topic area has focused on Tollmien-Schlichting perturbations over two-dimensional flat plate flows or aerofoils, the novelty of this work lies with analysing crossflow instability over a swept wing boundary-layer flow with step features. PSEh and LHNSh models are tested with convecting Tollmien Schlichting instability over a dimple and randomly distributed roughness on an overall flat plate flow. The dimple case performs very well whereas it is more difficult to obtain converged results with the random roughness case, likely due to large stream-wise velocity gradient changes. A 45degree ramped shape roughness is investigated and remarkably good agreement between the LHNSh solution and NekLNS solution is found. Forward facing ramps and steps are found to act as greater amplifiers with increased height, whilst backward facing ramps and steps predict very weak changes in the disturbance development. This is contrary to the wider literature and an argument is made that backward facing steps and ramps initiate an immediate non-linear interaction which cannot be captured with linear theory. Vertical forward facing step cases also predict greater amplification with increased step height, which is not observed in the backward facing step cases. Again, this is believed to be due to non-linear mode interaction that is immediately triggered by the step. Bump roughness cases agree well qualitatively with experimental work on a 40 degree swept wing, the AERAST geometry. Good agreement locally to the roughness could not be drawn with the NekLNS solutions, likely due to the presence of strong stream-wise gradients and mesh limitations.Open Acces

Equilibrium binding energies from fluctuation theorems and force spectroscopy simulations

Brownian dynamics simulations are used to study the detachment of a particle from a substrate. Although the model is simple and generic, we attempt to map its energy, length and time scales onto a specific experimental system, namely a bead that is weakly bound to a cell and then removed by an optical tweezer. The external driving force arises from the combined optical tweezer and substrate potentials, and thermal fluctuations are taken into account by a Brownian force. The Jarzynski equality and Crooks' fluctuation theorem are applied to obtain the equilibrium free energy difference between the final and initial states. To this end, we sample non--equilibrium work trajectories for various tweezer pulling rates. We argue that this methodology should also be feasible experimentally for the envisioned system. Furthermore, we outline how the measurement of a whole free energy profile would allow the experimentalist to retrieve the unknown substrate potential by means of a suitable deconvolution. The influence of the pulling rate on the accuracy of the results is investigated, and umbrella sampling is used to obtain the equilibrium probability of particle escape for a variety of trap potentials.Comment: 21 pages, 11 figures, To appear in Soft Matte

My own personal hell: Approaching and exceeding thresholds of too much alcohol

Objectives: Government guidelines aim to promote sensible alcohol consumption but such advice is disconnected from people’s lived experiences. This research investigated how people construct personal thresholds of ‘too much’ alcohol. Design and measures: 150 drinkers completed an online survey (Mage=23.29(5.51); 64.7þmale). Participants were asked whether they had an intuitive sense of what constitutes too much alcohol. They wrote open-ended descriptions of how that threshold had been established and how it felt to approach/exceed it. These qualitative accounts were coded using thematic analysis and interpreted with an experiential theoretical framework. Results: Personal thresholds were based on previously experienced embodied states rather than guidelines, or health concerns. Describing the approach to their threshold, 75% of participants fell into two distinct groups. Group 1’s approach was an entirely negative (nausea/anxiety) and Group 2’s approach was an entirely positive, embodied experience (relaxed/pleasurable). These groups differed significantly in awareness of alcohol’s effects, agency and self-perceptions, but not on alcohol consumption. Exceeding their threshold was an entirely negative embodied experience for all. Conclusion: These findings illustrate that people are guided by experientially grounded conceptions of consumption. Interventions could target different groups of drinker according to their embodied experience during the approach to ‘too much’ alcohol

The Working Culture of Legal Aid Lawyers: Developing a ‘Shared Orientation Model'

This paper critically explores the working culture of legal aid lawyers and develops a novel ‘Shared Orientation’ model to better understand contemporary legal aid work and its workers. Set within a context of changing professional identities, a shrinking industry and financial constraints, the paper draws on ethnographic and interview data conducted with a high-street firm, multiple courtrooms and a law centre. It examines the emerging relevance and applicability of this new conceptual lens, refocusing the gaze on working life in fissured legal workplaces. It is argued that the ‘Shared Orientation’ model upholds multiple functions. Firstly, it captures the cultural heterogeneity of the legal aid profession, across civil-criminal and solicitor-barrister remits alike. Secondly, the model functions as a form of cohesive coping mechanism in response to the changing professional identity of the legal aid lawyers. Moreover, the ‘Shared Orientation’ offers unity as a way of functioning in an otherwise fragmented profession through its preservation of working culture ideal

Defects in Mitochondrial ATP Synthesis in Dystrophin-Deficient Mdx Skeletal Muscles May Be Caused by Complex I Insufficiency

Duchenne Muscular Dystrophy is a chronic, progressive and ultimately fatal skeletal muscle wasting disease characterised by sarcolemmal fragility and intracellular Ca2+ dysregulation secondary to the absence of dystrophin. Mounting literature also suggests that the dysfunction of key energy systems within the muscle may contribute to pathological muscle wasting by reducing ATP availability to Ca2+ regulation and fibre regeneration. No study to date has biochemically quantified and contrasted mitochondrial ATP production capacity by dystrophic mitochondria isolated from their pathophysiological environment such to determine whether mitochondria are indeed capable of meeting this heightened cellular ATP demand, or examined the effects of an increasing extramitochondrial Ca2+ environment. Using isolated mitochondria from the diaphragm and tibialis anterior of 12 week-old dystrophin-deficient mdx and healthy control mice (C57BL10/ScSn) we have demonstrated severely depressed Complex I-mediated mitochondrial ATP production rate in mdx mitochondria that occurs irrespective of the macronutrient-derivative substrate combination fed into the Kreb's cycle, and, which is partially, but significantly, ameliorated by inhibition of Complex I with rotenone and stimulation of Complex II-mediated ATP-production with succinate. There was no difference in the MAPR response of mdx mitochondria to increasing extramitochondrial Ca2+ load in comparison to controls, and 400 nM extramitochondrial Ca2+ was generally shown to be inhibitory to MAPR in both groups. Our data suggests that DMD pathology is exacerbated by a Complex I deficiency, which may contribute in part to the severe reductions in ATP production previously observed in dystrophic skeletal muscle

The good teacher: understanding virtues in practice: research report

This report describes research focusing on virtues and character in teaching, by which we mean the kind of personal qualities professional teachers need to facilitate learning and overall flourishing in young people that goes beyond preparing them for a life of tests. The ‘good’ teacher is someone who, alongside excellent subject knowledge and technical expertise, cares about students, upholds principles of honesty and integrity both towards knowledge and student–teacher relationships, and who does good work (Campbell, 2011, 2013; Sockett, 2012; Gardner, Csikszentmihalyi and Damon, 2001; Damon and Colby, 2014). In the Framework for Character Education (Jubilee Centre for Character and Virtues, 2013), we considered the character of teachers to be a crucial ingredient in the development of flourishing children. This new report describes research that examined how teachers thought about, and drew upon, character strengths and virtues in their daily professional lives

Metabogenic and Nutriceutical Approaches to Address Energy Dysregulation and Skeletal Muscle Wasting in Duchenne Muscular Dystrophy

Duchenne Muscular Dystrophy (DMD) is a fatal genetic muscle wasting disease with no current cure. A prominent, yet poorly treated feature of dystrophic muscle is the dysregulation of energy homeostasis which may be associated with intrinsic defects in key energy systems and promote muscle wasting. As such, supplementative nutriceuticals that target and augment the bioenergetical expansion of the metabolic pathways involved in cellular energy production have been widely investigated for their therapeutic efficacy in the treatment of DMD. We describe the metabolic nuances of dystrophin-deficient skeletal muscle and review the potential of various metabogenic and nutriceutical compounds to ameliorate the pathological and clinical progression of the disease

The influence of spatial and temporal scale in detecting offshore recruitment signals of Atlantic cod (Gadus morhua) based on coastal juvenile surveys

The moratorium on the Newfoundland Atlantic cod (Gadus morhua) fishery in 1992 motivated studies on the factors influencing population stability and tools to forecast future cod abundance. Unfortunately, short-duration time series compromised most efforts to link life stages. I used coastal seine surveys of juveniles (age-0 and -1) to predict offshore pre-adult (age-3) cod abundance at multiple spatial scales (individual bays to offshore regions), temporal scales (short and long-term time series from 7 to 18 years in length) and environmental and biological factors influencing recruitment signal strength. These analyses detected strong recruitment signals among all early age classes from the Newman Sound Survey (1995 – 2013) and demonstrated interactions between juvenile abundance and environmental variables. In contrast, a strong recruitment signal was only detectable from a single bay using the shorter Fleming Survey (1992 – 1997, 2001). For both surveys, recruitment signal strength varied with distance from the index sites, among management zones, and between areas of known ecological and biological significance. Studies evaluating year-class strength often overlook the value of coastal juvenile surveys. These results demonstrate the utility of using information from long-duration coastal seine surveys when forecasting adult population strength. The implications of my results could help stakeholders prepare for socio-economic implications of poor recruitment years, and can be used in management decision-making