A hierarchy of models for superconducting thin films

A hierarchy of models for type-II superconducting thin films is presented. Through appropriate asymptotic limits this hierarchy passes from the mesoscopic Ginzburg--Landau model to the London model with isolated vortices as $\delta$-function singularities to vortex-density models and finally to macroscopic critical-state models. At each stage it is found that a key nondimensional parameter is $\Lambda = \lambda^2/d L$, where $\lambda$ is the penetration depth of the magnetic field, a material parameter, and d and L are a typical thickness and lateral dimension of the film,respectively. The models simplify greatly if this parameter is large or small

Electron kinetic effects in the nonlinear evolution of a driven ion-acoustic wave

The electron kinetic effects are shown to play an important role in the nonlinear evolution of a driven ion-acoustic wave. The numerical simulation results obtained (i) with a hybrid code, in which the electrons behave as a fluid and the ions are described along the particle-in-cell (PIC) method, are compared with those obtained (ii) with a full-PIC code, in which the kinetic effects on both species are retained. The electron kinetic effects interplay with the usual fluid-type nonlinearity to give rise to a broadband spectrum of ion-acoustic waves saturated at a low level, even in the case of a strong excitation. This low asymptotic level might solve the long-standing problem of the small stimulated Brillouin scattering reflectivity observed in laser-plasma interaction experiments

Electron and ion kinetic effects in the saturation of a driven ion acoustic wave

The role of ion and electron kinetic effects is investigated in the context of the nonlinear saturation of a driven ion acoustic wave(IAW) and its parametric decay into subharmonics. The simulations are carried out with a full–particle-in-cell (PIC) code, in which both ions and electrons are treated kinetically. The full-PIC results are compared with those obtained from a hybrid-PIC code (kinetic ions and Boltzmann electrons). It is found that the largest differences between the two kinds of simulations take place when the IAW is driven above the ion wave-breaking limit. In such a case of a strong drive, the hybrid-PIC simulations lead to a Berstein-Greene-Kruskal-like nonlinear IAW of a large amplitude, while in the full-PIC the IAW amplitude decays to a small level after a transient stage. The electron velocity distribution function is significantly flattened in the domain of small electron velocities. As a result the nonlinear frequency shift due to the electron kinetic effects compensates partly the nonlinear frequency shift due to the ion kinetic effects, allowing then for the parametric decay of the driven IAW into subharmonics. These observations lead to the conclusion that electron kinetic effects become important whenever the nonlinear effects come into play

The motion of superconducting vortices in thin films of varying thickness

The interaction of superconducting vortices with superconductor/vacuum interfaces is considered. A vortex is first shown to intersect such an interface normally. Various thin-film models are then formulated, corresponding to different parameter regimes. A local analysis of a vortex is performed, and a law of motion for each vortex deduced. This law of motion implies that the vortex will move to the locally thinnest part of the film, and is consistent with the vortex moving under the curvature induced by being forced to intersect the boundaries of the film normall

From feedback-as-information to feedback-as-process: a linguistic analysis of the feedback literature

Feedback is a term used so frequently that it is commonly taken that there is a shared view about what it means. However, in recent years, the notion of feedback as simply the provision of information to students about their work has been substantially challenged and learning-centred views have been articulated. This paper employs a corpus linguistics approach to analyse the use of the term ‘feedback’ in research articles published in key higher education journals on the topic over two five-year periods: 2009–2013 and 2015–2019. Analysis focused on the most common noun modifiers of ‘feedback’ and nouns modified by ‘feedback’, verbs with ‘feedback’ as the object, possessors of ‘feedback’, and prepositions representing an action or concept on or with ‘feedback’. Whilst the analysis demonstrated that transmission-focused conceptions dominate publications on feedback, linguistic signifiers of a shift over time in representation of feedback away from a transmission-focus towards a learning-focus were evident within each grammatical relation category. The data indicate that the term ‘feedback’ is used by different authors to refer to very different representations of the concept, and the paper proposes that greater clarity in the representation of feedback is needed

#MeToo in EM: A Multicenter Survey of Academic Emergency Medicine Faculty on Their Experiences with Gender Discrimination and Sexual Harassment

Introduction: Gender-based discrimination and sexual harassment of female physicians are well documented. The #MeToo movement has brought renewed attention to these problems. This study examined academic emergency physicians’ experiences with workplace gender discrimination and sexual harassment.Methods: We conducted a cross-sectional survey of a convenience sample of emergency medicine (EM) faculty across six programs. Survey items included the following: the Overt Gender Discrimination at Work (OGDW) Scale; the frequency and source of experienced and observed discrimination; and whether subjects had encountered unwanted sexual behaviors by a work superior or colleague in their careers. For the latter question, we asked subjects to characterize the behaviors and whether those experiences had a negative effect on their self-confidence and career advancement. We made group comparisons using t-tests or chi-square analyses, and evaluated relationships between gender and physicians’ experiences using correlation analyses.Results: A total of 141 out of 352 (40.1%) subjects completed at least a portion of the survey. Women reported higher mean OGDW scores than men (15.4 vs 10.2; 95% confidence interval [CI], 3.6–6.8). Female faculty were also more likely to report having experienced gender-based discriminatory treatment than male faculty (62.7% vs 12.5%; 95% CI, 35.1%-65.4%), although male and female faculty were equally likely to report having observed gender-based discriminatory treatment of another physician (64.7% vs 56.3%; 95% CI, 8.6%-25.5%). The three most frequent sources of experienced or observed gender-based discriminatory treatment were patients, consulting or admitting physicians, and nursing staff. The majority of women reported having encountered unwanted sexual behaviors in their careers, with a significantly greater proportion of women reporting them compared to men (52.9% vs 26.2%, 95% CI, 9.9%-43.4%). The majority of unwanted behaviors were sexist remarks and sexual advances. Of those respondents who encountered these unwanted behaviors, 22.9% and 12.5% reported at least somewhat negative effects on their self-confidence and career advancement.Conclusion: Female EM faculty perceived more gender-based discrimination in their workplaces than their male counterparts. The majority of female and approximately a quarter of male EM faculty encountered unwanted sexual behaviors in their careers.

Evidence for competition between the superconducting and the pseudogap state in (BiPb)_2(SrLa)_2CuO_{6+\delta} from muon-spin rotation experiments

The in-plane magnetic penetration depth \lambda_{ab} in optimally doped (BiPb)_2(SrLa)_2CuO_{6+\delta} (OP Bi2201) was studied by means of muon-spin rotation. The measurements of \lambda_{ab}^{-2}(T) are inconsistent with a simple model of a d-wave order parameter and a uniform quasiparticle weight around the Fermi surface. The data are well described assuming the angular gap symmetry obtained in ARPES experiments [Phys. Rev. Lett {\bf 98}, 267004 (2007)], where it was shown that the superconducting gap in OP Bi2201 exists only in segments of the Fermi surface near the nodes. We find that the remaining parts of the Fermi surface, which are strongly affected by the pseudogap state, do not contribute significantly to the superconducting condensate. Our data provide evidence that high temperature superconductivity and pseudogap behavior in cuprates are competing phenomena.Comment: 5 pages, 3 figure

Assessing the effect of a Cognitive Behaviour Therapy (CBT)-based workshop on work-related rumination, fatigue, and sleep

This quasi-experimental longitudinal study assessed the effect of a one-day Cognitive Behaviour Therapy (CBT)-based workshop on work-related rumination, chronic fatigue and sleep quality. We hypothesised that participants who attended the workshop would report lower levels of affective work-related rumination and chronic fatigue and improved sleep quality, at follow-up, six months after workshop completion. Two hundred and twenty seven participants took part in the study, with 102 participants attending a one-day workshop delivered in their place of work. Participants completed an online questionnaire at two time-points, with follow-up occurring 6 months after initial survey completion. Results showed that participants who took part in the CBT workshop reported significantly lower levels of affective rumination (p=.03) and chronic fatigue (p=.003), at follow-up in comparison to individuals who did not attend the workshop; however there were no significant differences between the groups in self-reported sleep quality (p=.06). A combination of more effective recovery both at work and outside of work may explain the reductions in both affective rumination and fatigue over time. This study adds to the recovery from work literature by providing initial support for a one-day CBT-based workshop delivered in the workplace