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In Crowe & Taylor (J. Fluid Mech., vol. 850, 2018, pp. 179–211) we described a theory for the evolution of density fronts in a rotating reference frame subject to strong vertical mixing using an asymptotic expansion in small Rossby number,
. We found that the front reaches a balanced state where vertical diffusion is balanced by horizontal advection in the buoyancy equation. The depth-averaged buoyancy obeys a nonlinear diffusion equation which admits a similarity solution corresponding to horizontal spreading of the front. Here we use numerical simulations of the full momentum and buoyancy equations to investigate this problem for a wide range of Rossby and Ekman numbers. We examine the accuracy of our asymptotic solution and find that many aspects of the solution are valid for
. However, the asymptotic solution departs from the numerical simulations for small Ekman numbers where the dominant balance in the momentum equation changes. We trace the source of this discrepancy to a depth-independent geostrophic flow that develops on both sides of the front and we develop a modification to the theory described in Crowe & Taylor (2018) to account for this geostrophic flow. The refined theory closely matches the numerical simulations, even for
. Finally, we develop a new scaling for the intense vertical velocity that can develop in thin bands at the edges of the front.
Deep reinforcement learning (deep RL) has achieved superior performance in complex sequential tasks by using deep neural networks as function approximators to learn directly from raw input images. However, learning directly from raw images is data inefficient. The agent must learn feature representation of complex states in addition to learning a policy. As a result, deep RL typically suffers from slow learning speeds and often requires a prohibitively large amount of training time and data to reach reasonable performance, making it inapplicable to real-world settings where data are expensive. In this work, we improve data efficiency in deep RL by addressing one of the two learning goals, feature learning. We leverage supervised learning to pre-train on a small set of non-expert human demonstrations and empirically evaluate our approach using the asynchronous advantage actor-critic algorithms in the Atari domain. Our results show significant improvements in learning speed, even when the provided demonstration is noisy and of low quality.
To describe the relationship between adherence to distinct dietary patterns and nutrition literacy.
We identified distinct dietary patterns using principal covariates regression (PCovR) and principal components analysis (PCA) from the Diet History Questionnaire II. Nutrition literacy was assessed using the Nutrition Literacy Assessment Instrument (NLit). Cross-sectional relationships between dietary pattern adherence and global and domain-specific NLit scores were tested by multiple linear regression. Mean differences in diet pattern adherence among three predefined nutrition literacy performance categories were tested by ANOVA.
Metropolitan Kansas City, USA.
Adults (n 386) with at least one of four diet-related diseases.
Three diet patterns of interest were derived: a PCovR prudent pattern and PCA-derived Western and Mediterranean patterns. After controlling for age, sex, BMI, race, household income, education level and diabetes status, PCovR prudent pattern adherence positively related to global NLit score (P < 0·001, β = 0·36), indicating more intake of prudent diet foods with improved nutrition literacy. Validating the PCovR findings, PCA Western pattern adherence inversely related to global NLit (P = 0·003, β = −0·13) while PCA Mediterranean pattern positively related to global NLit (P = 0·02, β = 0·12). Using predefined cut points, those with poor nutrition literacy consumed more foods associated with the Western diet (fried foods, sugar-sweetened beverages, red meat, processed foods) while those with good nutrition literacy consumed more foods associated with prudent and Mediterranean diets (vegetables, olive oil, nuts).
Nutrition literacy predicted adherence to healthy/unhealthy diet patterns. These findings warrant future research to determine if improving nutrition literacy effectively improves eating patterns.
Public authorities' compliance with judicial dictates is central to legality and constitutionality, may influence broader policy and political outcomes, and can have powerful feedback effects on judicial decision making, independence, and power. As such, it has crucial implications for interbranch relations and the rule of law. Effectively measuring compliance with judicial rulings and clearly explaining when and why elected leaders adhere to courts' mandates present a range of inferential challenges. Building on the groundwork laid in the burgeoning literature on the topic, this article advances two analytic frameworks (one for measuring and one for explaining compliance), offers strategies for grappling with the problems of descriptive and causal inference that arise in studying compliance, and advocates the use of multiple analytic methods to generate and test hypotheses regarding compliance.
Lithium is widely prescribed, but the timing of key effects remains uncertain. The timing of onset of its relapse prevention effects is clarified by placebo-controlled randomised trials (3 studies, n = 1120). Lithium reduced relapse into any mood episode over the first 2 weeks of treatment (hazard ratio 0.40, 95% CI 0.16–0.97). Fewer manic relapses were evident within the first 4 weeks, however, early effects on depressive relapse were not demonstrated. There is an early onset of lithium relapse prevention effects in bipolar disorder, particularly against manic relapse. Full effects against depressive relapse may develop over a longer period.
Declaration of interest
M.J.T. reports personal fees from Sunovion, Otsuka, Lundbeck, outside the submitted work.
Reinforcement learning (RL) can be extremely effective in solving complex, real-world problems. However, injecting human knowledge into an RL agent may require extensive effort and expertise on the human designer’s part. To date, human factors are generally not considered in the development and evaluation of possible RL approaches. In this article, we set out to investigate how different methods for injecting human knowledge are applied, in practice, by human designers of varying levels of knowledge and skill. We perform the first empirical evaluation of several methods, including a newly proposed method named State Action Similarity Solutions (SASS) which is based on the notion of similarities in the agent’s state–action space. Through this human study, consisting of 51 human participants, we shed new light on the human factors that play a key role in RL. We find that the classical reward shaping technique seems to be the most natural method for most designers, both expert and non-expert, to speed up RL. However, we further find that our proposed method SASS can be effectively and efficiently combined with reward shaping, and provides a beneficial alternative to using only a single-speedup method with minimal human designer effort overhead.
Here, we examine the influence of small-scale turbulence on the evolution of fronts in the ocean and atmosphere. Specifically, we consider the evolution of an initially balanced density front subject to an imposed viscosity and diffusivity as a simple analogue for small-scale turbulence. At late times, the dominant balance is found to be the quasisteady turbulent thermal wind balance with time evolution due to an advection–diffusion balance in the buoyancy equation. We use the leading-order balance to determine analytical similarity solutions for the spreading of a front and find that the spreading rate is maximum for an intermediate value of the Ekman number, with the spreading resulting from shear dispersion associated with the cross-front flow and vertical diffusion of density. In response to shear dispersion, the front evolves towards a density profile that is nearly linear in the cross-front coordinate. At the edges of the frontal zone, the density field develops large curvature, and these regions are associated with narrow bands of intense vertical velocity.
Recent modelling estimates up to two-thirds of new HIV infections among men who have sex with men occur within partnerships, indicating the importance of dyadic HIV prevention efforts. Although new interventions are available to promote dyadic health-enhancing behaviours, minimal research has examined what factors influence partners’ mutual engagement in these behaviours, a critical component of intervention success. Actor-partner interdependence modelling was used to examine associations between relationship characteristics and several dyadic outcomes theorised as antecedents to health-enhancing behaviours: planning and decision making, communication, and joint effort. Among 270 male-male partnerships, relationship satisfaction was significantly associated with all three outcomes for actors (p = .02, .02, .06 respectively). Latino men reported poorer planning and decision making (actor p = .032) and communication (partner p = .044). Alcohol use was significantly and negatively associated with all outcomes except actors’ planning and decision making (actors: p = .11, .038, .004 respectively; partners: p = .03, .056, .02 respectively). Having a sexual agreement was significantly associated with actors’ planning and decision making (p = .007) and communication (p = .008). Focusing on interactions between partners produces a more comprehensive understanding of male couples’ ability to engage in health-enhancing behaviours. This knowledge further identifies new and important foci for the tailoring of dyadic HIV prevention and care interventions.
Introduction: Smoking is one of the most important risk factors for cardiovascular disease (CVD). Electronic cigarettes (e-cigarettes) are becoming increasingly popular. However, little is known regarding their patterns of use in patients with established CVD.
Aims: We aimed to assess the perceptions and patterns of use of e-cigarettes in patients presenting to a vascular clinic.
Methods: We performed a qualitative study to identify perceptions and beliefs about e-cigarettes. Semi-structured interviews of consecutive patients consenting to participate were performed over five-months. Individuals were recruited from a vascular surgery outpatient clinic. Initial interviews were based on a questionnaire. Further structured interviews were conducted with patients currently using e-cigarettes, which were transcribed and analysed to assess perceptions and patterns of use.
Results/Findings: Four overarching themes emerged: attraction to e-cigarettes as a harm reduction/smoking cessation strategy; uncertainty regarding the risks of e-cigarettes; use of various types of smoking cessation strategies; dual use and often complete relapse to tobacco products.
Conclusions: Patients with established CVD view e-cigarettes as a means of smoking cessation; however, many relapse to tobacco products or use both simultaneously. Further research is necessary regarding the role of e-cigarettes in smoking cessation in this high-risk group.
This commentary has two aims. First, I raise a practical challenge for accounts of responsible agency: Provide empirically informed strategies for enhancing responsible agency so that actors can become more resistant to the influence of defeaters. Second, I offer an initial sketch of a solution to this practical challenge. My solution is supported by empirical evidence suggesting that responsible agency can be enhanced via self-regulatory strategies (expertise and implementation intentions).
The impact of losing a limb in military service extends well beyond initial recovery and rehabilitation, with long-term consequences and challenges requiring health-care commitments across the lifecourse. This paper presents a systematic review of the current state of knowledge regarding the long-term impact of ageing and limb-loss in military veterans. Key databases were systematically searched including: ASSIA, CINAHL, Cochrane Library, Medline, Web of Science, PsycArticles/PsychInfo, ProQuest Psychology and ProQuest Sociology Journals, and SPORTSDiscus. Empirical studies which focused on the long-term impact of limb-loss and/or health-care requirements in veterans were included. The search process revealed 30 papers relevant for inclusion. These papers focused broadly on four themes: (a) long-term health outcomes, prosthetics use and quality of life; (b) long-term psycho-social adaptation and coping with limb-loss; (c) disability and identity; and (d) estimating the long-term costs of care and prosthetic provision. Findings present a compelling case for ensuring the long-term care needs and costs of rehabilitation for older limbless veterans are met. A dearth of information on the lived experience of limb-loss and the needs of veterans’ families calls for further research to address these important issues.
Guidance for developing economic models recommend that model structure is carefully considered, and assumptions varied in sensitivity analysis (1). Models in smoking cessation have typically used cohort-level approaches, although recently discrete event simulations (DESs) have been developed (2). DESs allow additional flexibility such as modelling changing risk over time, and recurrent events. Our aim was to explore the impact of varying model structure and assumptions on the cost-effectiveness of smoking cessation programs.
We built a cohort state-transition model which related mortality to smoking status and considered the prevalence (based on smoking status) of five comorbidities associated with smoking, each of which has an associated cost and quality of life decrement. We additionally built a patient-level DES, using the Discretely Integrated Condition Event framework (3). The DES used the same data as the cohort model, except considering incidence for comorbidities rather than prevalence. We considered a population of smokers aged 16 years old and an intervention costing GBP827 on which 27 percent of people quit, compared with no treatment. We produced results using the two models for comparable scenarios, and ran additional scenarios considering different assumptions.
In the cohort model, the incremental cost-effectiveness ratio (ICER) for intervention versus no treatment was GBP4,000/quality-adjusted life year (QALY). In the DES, modelling mortality linked to smoker status produced an ICER of GBP1,000/QALY and modelling mortality linked to comorbidities produced an ICER of GBP6,000/QALY. In the DES with mortality linked to comorbidities, varying the relative risk of comorbidities with time since quitting gave an ICER of GBP3,000/QALY. Including relapse increased the ICER to GBP21,000/QALY.
The ICER for the smoking cessation program changes when model assumptions are varied, although the choice of DES versus cohort model appears to make a relatively small difference. Inclusion of relapse substantially changes the ICER, demonstrating the importance of long-term effects in economic models.
Brazilians often complain that investigations of corruption by public servants drag on for years or bring few legal sanctions on the perpetrators. This lack of accountability is so pervasive that a slang phrase, acabou em pizza, is often invoked when investigations are inconclusive. This article investigates the role of four Brazilian public institutions charged with keeping public servants accountable. For analysis, it breaks the accountability process into its three component stages: oversight, investigation, and sanction. Through a study of six prominent cases of corruption, it shows that the weakness of the accountability process in Brazil is due not entirely to the toothlessness of individual institutions of accountability, but also to the independence of such institutions at each of the three stages. These findings suggest that institutional arrangements influence the degree of accountability, and thereby also public trust and confidence, in Latin America's largest democracy.
This article analyzes the evolution of the network of Brazilian federal accountability institutions over the course of the past generation, between the transition to democracy and the end of President Luiz Inácio Lula da Silva’s second term. Substantively, the article charts the significant gains that have been made in accountability institutions. Theoretically, it evaluates the evolution of these institutions as a consequence of the distribution of rules, routines, roles, and resources across a larger institutional network, demonstrating that changes in the various bureaucratic agencies have mutually reinforced each other and generated autocatalytic processes of reform.
This project draws on psychological and sociological social psychology to investigate immigration policy opinions among native-born non-Hispanic Whites. Using data from a suburban Chicago-area county that has seen substantial growth in the Latino immigrant population, we examine Anglos’ opinions on three dimensions of immigration policy: preferred immigration rate, resistance to immigration, and assistance for immigrants. Our central hypothesis is that liberalizing effects of Anglo/Latino interpersonal contact are conditioned on Anglos’ recognition of hardships and barriers faced by Latinos. Five of the six interaction effects we estimated were highly significant: Personal contact with Latinos does promote more positive, progressive immigration policy opinions, but only among some Anglos—those who were acquainted with immigrants who had run afoul of immigration law or believed there is substantial local discrimination against Latinos. The results are reminiscent of James Kluegel’s (1985) analysis of White Americans’ views about affirmative action: “If there isn’t a problem, you don’t need a solution.” Affirmation of local anti-Latino discrimination was the stronger moderator of contact effects and also showed main effects on immigration policy opinion stronger than the effects of interpersonal contact. Denial of anti-Latino discrimination may be a means used by Anglos to defend their group position.