Micromechanics of sea ice frictional slip from test basin scale experiments

We have conducted a series of high-resolution friction experiments on large floating saline ice floes in an environmental test basin. In these experiments, a central ice floe was pushed between two other floes, sliding along two interfacial faults. The frictional motion was predominantly stick–slip. Shear stresses, normal stresses, local strains and slip displacement were measured along the sliding faults, and acoustic emissions were monitored. High-resolution measurements during a single stick–slip cycle at several positions along the fault allowed us to identify two phases of frictional slip: a nucleation phase, where a nucleation zone begins to slip before the rest of the fault, and a propagation phase when the entire fault is slipping. This is slip-weakening behaviour. We have therefore characterized what we consider to be a key deformation mechanism in Arctic Ocean dynamics. In order to understand the micromechanics of sea ice friction, we have employed a theoretical constitutive relation (i.e. an equation for shear stress in terms of temperature, normal load, acceleration, velocity and slip displacement) derived from the physics of asperity–asperity contact and sliding (Hatton et al. 2009 Phil. Mag. 89, 2771–2799 (doi:10.1080/14786430903113769)). We find that our experimental data conform reasonably with this frictional law once slip weakening is introduced. We find that the constitutive relation follows Archard's law rather than Amontons' law, with Embedded Image (where τ is the shear stress and σn is the normal stress) and n = 26/27, with a fractal asperity distribution, where the frictional shear stress, τ = ffractal Tmlws, where ffractal is the fractal asperity height distribution, Tml is the shear strength for frictional melting and lubrication and ws is the slip weakening. We can therefore deduce that the interfacial faults failed in shear for these experimental conditions through processes of brittle failure of asperities in shear, and, at higher velocities, through frictional heating, localized surface melting and hydrodynamic lubrication

'Failed' mothers,‘failed’ womxn: Demarcating normative mothering

"This is an Accepted Manuscript of a book chapter published by Routledge in Intersections of Mothering: Feminist Accounts, 2019, available online: http://www.routledge.com/9781138366268This book presents new interdisciplinary and intersectional research about women as mothers, highlighting that alternative accounts of mothering can challenge normative societal assumptions and broaden understandings of women as mothers, ...falseLondo

Sea ice–ocean feedbacks in the Antarctic shelf seas

Observed changes in Antarctic sea ice are poorly understood, in part due to the complexity of its interactions with the atmosphere and ocean. A highly simplified, coupled sea ice–ocean mixed layer model has been developed to investigate the importance of sea ice–ocean feedbacks on the evolution of sea ice and the ocean mixed layer in two contrasting regions of the Antarctic continental shelf ocean: the Amundsen Sea, which has warm shelf waters, and the Weddell Sea, which has cold and saline shelf waters. Modeling studies where we deny the feedback response to surface air temperature perturbations show the importance of feedbacks on the mixed layer and ice cover in the Weddell Sea to be smaller than the sensitivity to surface atmospheric conditions. In the Amundsen Sea the effect of surface air temperature perturbations on the sea ice are opposed by changes in the entrainment of warm deep waters into the mixed layer. The net impact depends on the relative balance between changes in sea ice growth driven by surface perturbations and basal-driven melting. The changes in the entrainment of warm water in the Amundsen Sea were found to have a much larger impact on the ice volume than perturbations in the surface energy budget. This creates a net negative ice albedo feedback in the Amundsen Sea, reversing the sign of this typically positive feedback mechanism

Disclosing physician ratings: performance effects and the difficulty of altering rating consensus

I examine effects of a health care system's policy to publicly disclose patient ratings of its physicians. I find evidence that this policy leads to performance improvement by the disclosed, subjective ratings and also by undisclosed, objective measures of quality. These effects are consistent with multitasking theory, in that physicians respond to the disclosure by providing more of a shared input—time with patients—that benefits performance by ratings and underlying quality. I also find, as predicted by information cascade theory, that the ratings become jammed to some degree near initially disclosed values. Specifically, raters observe the pattern of initial ratings and follow suit by providing similar ratings. Finally, I find evidence that physicians anticipate rating jamming and so concentrate their effort on earlier performance in order to set a pattern of high ratings that later ratings follow. These results demonstrate that the disclosure of subjective ratings can benefit performance broadly but can also shift effort toward earlier performance

The Obliteration of Truth by Management: Badiou, St. Paul and the Question of Economic Managerialism in Education

This paper considers the questions that Badiou’s theory of the subject poses to cultures of economic managerialism within education. His argument that radical change is possible, for people and the situations they inhabit, provides a stark challenge to the stifling nature of much current educational climate. In 'Saint Paul: The Foundation of Universalism', Badiou describes the current universalism of capitalism, monetary homogeneity and the rule of the count. Badiou argues that the politics of identity are all too easily subsumed by the prerogatives of the marketplace and unable to present, therefore, a critique of the status quo. These processes are, he argues, without the potential for truth. What are the implications of Badiou’s claim that education is the arranging of ‘the forms of knowledge in such a way that truth may come to pierce a hole in them’ (Badiou, 2005, p. 9)? In this paper, I argue that Badiou’s theory opens up space for a kind of thinking about education that resists its colonisation by cultures of management and marketisation and leads educationalists to consider the emancipatory potential of education in a new light

Warm winter, thin ice?

Winter 2016/2017 saw record warmth over the Arctic Ocean, leading to the least amount of freezing degree days north of 70° N since at least 1979. The impact of this warmth was evaluated using model simulations from the Los Alamos sea-ice model (CICE) and CryoSat-2 thickness estimates from three different data providers. While CICE simulations show a broad region of anomalously thin ice in April 2017 relative to the 2011–2017 mean, analysis of three CryoSat-2 products show more limited regions with thin ice and do not always agree with each other, both in magnitude and direction of thickness anomalies. CICE is further used to diagnose feedback processes driving the observed anomalies, showing 11–13 cm reduced thermodynamic ice growth over the Arctic domain used in this study compared to the 2011–2017 mean, and dynamical contributions of +1 to +4 cm. Finally, CICE model simulations from 1985–2017 indicate the negative feedback relationship between ice growth and winter air temperatures may be starting to weaken, showing decreased winter ice growth since 2012 as winter air temperatures have increased and the freeze-up has been further delayed

The dose makes the poison: have “field realistic” rates of exposure of bees to neonicotinoid insecticides been overestimated in laboratory studies?

Recent laboratory based studies have demonstrated adverse sub-lethal effects of neonicotinoid insecticides on honey bees and bumble bees, and these studies have been influential in leading to a European Union moratorium on the use of three neonicotinoids, clothianidin, imidacloprid, and thiamethoxam on “bee attractive” crops. Yet so far, these same effects have not been observed in field studies. Here we review the three key dosage factors (concentration, duration and choice) relevant to field conditions, and conclude that these have probably been over estimated in many laboratory based studies

Neural computations of threat in the aftermath of combat trauma

© 2019, The Author(s), under exclusive licence to Springer Nature America, Inc. By combining computational, morphological, and functional analyses, this study relates latent markers of associative threat learning to overt post-traumatic stress disorder (PTSD) symptoms in combat veterans. Using reversal learning, we found that symptomatic veterans showed greater physiological adjustment to cues that did not predict what they had expected, indicating greater sensitivity to prediction errors for negative outcomes. This exaggerated weighting of prediction errors shapes the dynamic learning rate (associability) and value of threat predictive cues. The degree to which the striatum tracked the associability partially mediated the positive correlation between prediction-error weights and PTSD symptoms, suggesting that both increased prediction-error weights and decreased striatal tracking of associability independently contribute to PTSD symptoms. Furthermore, decreased neural tracking of value in the amygdala, in addition to smaller amygdala volume, independently corresponded to higher PTSD symptom severity. These results provide evidence for distinct neurocomputational contributions to PTSD symptoms

A mathematical model of melt lake development on an ice shelf

The accumulation of surface meltwater on ice shelves can lead to the formation of melt lakes. Melt lakes have been implicated in ice shelf collapse; Antarctica's Larsen B Ice Shelf was observed to have a large amount of surface melt lakes present preceding its collapse in 2002. Such collapse can affect ocean circulation and temperature, cause habitat loss and contribute to sea level rise through the acceleration of tributary glaciers. We present a mathematical model of a surface melt lake on an idealised ice shelf. The model incorporates a calculation of the ice shelf surface energy balance, heat transfer through the firn, the production and percolation of meltwater into the firn, the formation of ice lenses and the development and refreezing of surface melt lakes. The model is applied to the Larsen C Ice Shelf, where melt lakes have been observed. This region has warmed several times the global average over the last century and the Larsen C firn layer could become saturated with meltwater by the end of the century. When forced with weather station data, our model produces surface melting, meltwater accumulation, and melt lake development consistent with observations. We examine the sensitivity of lake formation to uncertain parameters, and provide evidence of the importance of processes such as lateral meltwater transport. We conclude that melt lakes impact surface melt and firn density and warrant inclusion in dynamic-thermodynamic models of ice shelf evolution within climate models, of which our model could form the basis for the thermodynamic component

Therapists’ and non-therapists’ constructions of heterosex: A qualitative story completion study

© 2018 The British Psychological Society Objectives: Little research has examined the discourses that shape therapists’ sense-making around heterosex. This paper explores the discourses of sexuality and gender underpinning therapists’ and non-therapists’ responses to a sexual experimentation scenario in a heterosexual relationship. It also considers the value of the novel technique of story completion (SC), in which participants are asked to write a story in response to a hypothetical scenario, for qualitative psychology and psychotherapy research. Design: This research used a comparative SC design (Kitzinger & Powell,). Participants were sequentially presented with and invited to complete two story stems: one in which a male character suggested ‘trying something new’ to his female partner and one in which the female character made the suggestion. The stems were otherwise identical. Methods: A total of 100 SCs were written by 49 (28 female; 21 male) therapists and 51 (29 female; 22 male) non-therapists. Participants were recruited mainly via UK-based email lists and Facebook groups, and therapeutic training organizations, and the data were analysed using a feminist post-structuralist thematic analysis (Braun & Clarke,). Results: Both groups of participants drew on heteronormative discourses of sexuality and gender to make sense of the stem. Engaging in sexual experimentation was often depicted as a demonstration of being normal. In some stories written by women, sex was framed as a site for negotiating ‘equality’ and reciprocity in relationships. Therapists were more likely than non-therapists to frame ‘difficulties’ within relationships as opportunities for personal growth and increased emotional depth, and their stories included greater emotional complexity. Conclusion: These findings raise questions about practitioner training and whether it results in therapists drawing on narrow and restrictive discourses of heterosex in clinical practice. Practitioner points: Training on sexual issues is largely absent from non-specialist practitioner training courses, which potentially means therapists are ill-equipped to respond to clients’ anxiety about sexual issues. Evidence from this and other research indicates that therapists’ sense-making around heterosexual sexual relationships is underpinned by narrow and restrictive discourses that entrench traditional gender relations and limit sexual agency. Psychologists are increasingly taking up positions of clinical leadership and are looked to for models of best practice. Drawing on theorizations of sexual difficulties, and of anxieties about sexual practice, that challenge traditional gender and heteronorms, and the commodification and medicalization of sex, is important for effective psychological leadership relating to the treatment of sexual issues and the furthering of social justice agendas