The semiclassical energy density of kinks and solitons

We compute semiclassical corrections to the energy density of kinks in $\phi^4$ theory and of solitons in the sine-Gordon model in $1+1$ dimensions, using local and covariant renormalization techniques from quantum field theory in curved spacetimes. For the semiclassical correction to the energy, we recover the known results. Our analysis highlights a subtlety in the definition of a conserved stress tensor for scalar field theories in $1+1$ dimension.Comment: 12 pages; Mathematica notebook containing the relevant calculations as ancillary fil

Measuring Economic Disadvantage During Childhood: A Group-Based Modeling Approach

Recent research suggest that child well-being and subsequent status attainment are influenced not only by the overall magnitude of exposure to family economic disadvantage during childhood, but also by the age of exposure and significant changes in family economic circumstances. Unfortunately, traditional measures of children's economic deprivation, such as permanent and transitory income, persistent or cumulative poverty, and the number and length of poverty spells, fail to differentiate between exposure to disadvantage at different stages in childhood and largely ignore how family economic circumstances are changing over time. In this paper, the authors propose a new method for assessing economic disadvantage during childhood that captures both children's overall levels of exposure to economic disadvantage and their patterns of exposure. This new method, which takes advantage of recent advances in finite mixture modeling, uses a longitudinal latent class model to classify children into a limited number of groups with similar histories of exposure to family economic disadvantage. Using this new methodology, group membership can be related to both family background characteristics and achievement in childhood and early adulthood, making it possible both to assess how family characteristics affect patterns of exposure to disadvantage during childhood and directly test alternative theories about the effect of different patterns of exposure on achievement. In this paper, the relationship between background factors, such as race, parental education, and family structure, and group membership is investigated, as is the association between group membership and achievement in early adulthood. The use of this technique is demonstrated using data from the Panel Study of Income Dynamics (PSID)

Pilot Study of Gaze Scanning and Intersection Detection Failures by Drivers with Hemianopia

In a prior study, intersection detection failures of individuals with hemianopia were strongly associated with inadequate head scanning; however, eye position was not tracked. In this pilot study, we tracked eye and head movements, and examined the relationship between gaze scanning and detection of pedestrians at intersections in a driving simulator. Gaze scan deficits, in particular not scanning sufficiently far into the blind hemifield, were the main reason for detection failures at the extreme edge of the clear-sight triangle in the blind hemifield. In addition, the gaze data revealed detection failures due to looked-but-failed-to-see events. The results suggest that HH drivers may be at increased risk for collisions at intersections

SuperHF: Supervised Iterative Learning from Human Feedback

While large language models demonstrate remarkable capabilities, they often present challenges in terms of safety, alignment with human values, and stability during training. Here, we focus on two prevalent methods used to align these models, Supervised Fine-Tuning (SFT) and Reinforcement Learning from Human Feedback (RLHF). SFT is simple and robust, powering a host of open-source models, while RLHF is a more sophisticated method used in top-tier models like ChatGPT but also suffers from instability and susceptibility to reward hacking. We propose a novel approach, Supervised Iterative Learning from Human Feedback (SuperHF), which seeks to leverage the strengths of both methods. Our hypothesis is two-fold: that the reward model used in RLHF is critical for efficient data use and model generalization and that the use of Proximal Policy Optimization (PPO) in RLHF may not be necessary and could contribute to instability issues. SuperHF replaces PPO with a simple supervised loss and a Kullback-Leibler (KL) divergence prior. It creates its own training data by repeatedly sampling a batch of model outputs and filtering them through the reward model in an online learning regime. We then break down the reward optimization problem into three components: robustly optimizing the training rewards themselves, preventing reward hacking-exploitation of the reward model that degrades model performance-as measured by a novel METEOR similarity metric, and maintaining good performance on downstream evaluations. Our experimental results show SuperHF exceeds PPO-based RLHF on the training objective, easily and favorably trades off high reward with low reward hacking, improves downstream calibration, and performs the same on our GPT-4 based qualitative evaluation scheme all the while being significantly simpler to implement, highlighting SuperHF's potential as a competitive language model alignment technique.Comment: Accepted to the Socially Responsible Language Modelling Research (SoLaR) workshop at NeurIPS 202

Facilitators and barriers to teaching undergraduate medical students in general practice

CONTEXT Globally, primary health care is facing workforce shortages. Longer and higher-quality placements in primary care increase the likelihood of medical students choosing this specialty. However, the recruitment and retention of community primary care teachers are challenging. Relevant research was predominantly carried out in the 1990s. We seek to understand contemporary facilitators and barriers to general practitioner (GP) engagement with undergraduate education. Communities of practice (CoP) theory offers a novel conceptualisation, which may be pertinent in other community-based teaching settings. METHODS Semi-structured interviews were undertaken with 24 GP teachers at four UK medical schools. We purposively sampled GPs new to teaching, established GP teachers and GPs who had recently stopped teaching. We undertook NVivo-assisted deductive and inductive thematic analysis of transcripts. We used CoP theory to interpret data. RESULTS Communities of practice theory illustrated that teachers negotiate membership of three CoPs: (i) clinical practice; (ii) the medical school, and (iii) teaching. The delivery of clinical care and teaching may be integrated or exist in tension. This can depend upon the positioning of the teaching and teacher as central or peripheral to the clinical CoP. Remuneration, workload, space and the expansion of GP trainee numbers impact on this. Teachers did not identify strongly as members of the medical school or a teaching community. Perceptions of membership were affected by medical school communication and support. The findings demonstrate gaps in medical school recruitment. CONCLUSIONS This research demonstrates the marginalisation of primary care-based teaching and proposes a novel explanation rooted in CoP theory. Concepts including identity and membership may be pertinent to other community-based teaching settings. We recommend that medical schools review and broaden recruitment methods. Teacher retention may be improved by optimising the interface between medical schools and teachers, fostering a teaching community, increasing professional rewards for teaching involvement and altering medical school expectations of learning in primary care

Rectifiability of Optimal Transportation Plans

The purpose of this note is to show that the solution to the Kantorovich optimal transportation problem is supported on a Lipschitz manifold, provided the cost is $C^{2}$ with non-singular mixed second derivative. We use this result to provide a simple proof that solutions to Monge's optimal transportation problem satisfy a change of variables equation almost everywhere

SpectroCube: a European 6U nanosatellite spectroscopy platform for astrobiology and astrochemistry

SpectroCube is a CubeSat-based miniaturized in-situ space exposure platform for astrochemistry and astrobiology research. Within a 6 unit (6U, with 1U corresponding to 10 cm x 10 cm x 10 cm) nanosatellite structure, an infrared spectrometer is interfaced with a sample handling system to measure photochemical changes of organic molecules, representing important biomarkers for the detection of life in our solar system and beyond. Monitoring degradation profiles and photochemical reaction kinetics of such biomarkers allows to identify suitable search targets for current and future planetary exploration and life-detection missions. SpectroCube is designed to be launched into a highly elliptical orbit around Earth and therefore allows to expose samples to higher solar UV and energetic particle radiation levels than previous exposure platforms in low Earth orbit, as for example on the International Space Station. In-situ data will be telemetered back to Earth and compared with solar and planetary simulation experiments in ground-based laboratory. We here present the design of SpectroCube, the scientific payload and its subsystems. We demonstrate that with the miniaturisation potential of infrared spectroscopy it is possible to fit the entire optical setup plus a sample handling system for up to 60 individually contained and hermetically sealed samples within less than half of the volume of a 6U CubeSat structure. Therefore, the remaining volume can be entirely used for additional subsystems such as attitude control, propulsion, fuel, onboard computer and telemetry. The design of the scientific payload is based on a commercial off-the-shelf miniaturised Fourier-transform spectrometer consisting of an infrared light source, an interferometer and infrared detector units. The mechanical robustness and suitability of such a system for space applications was assessed. Shock and vibration testing of the mechanically most sensitive unit, the interferometer, was performed and revealed that with adequate damping the spectroscopic performance can be maintained. Additional measurements of test samples conducted with the selected commercial off-the-shelf spectrometer candidate showed that the spectroscopic range, resolution and sensitivity is capable to monitor in situ the photochemical kinetics of important classes of organic molecules and biomarkers for astrobiology and astrochemistry research

Geographic Distribution and Mortality Risk Factors during the Cholera Outbreak in a Rural Region of Haiti, 2010-2011

In 2010 and 2011, Haiti was heavily affected by a large cholera outbreak that spread throughout the country. Although national health structure-based cholera surveillance was rapidly initiated, a substantial number of community cases might have been missed, particularly in remote areas. We conducted a community-based survey in a large rural, mountainous area across four districts of the Nord department including areas with good versus poor accessibility by road, and rapid versus delayed response to the outbreak to document the true cholera burden and assess geographic distribution and risk factors for cholera mortality

Fate and Complex Pathogenic Effects of Dioxins and Polychlorinated Biphenyls in Obese Subjects before and after Drastic Weight Loss

BACKGROUND: In humans, persistent organic pollutants (POPs) are stored primarily in adipose tissue. Their total body burden and their contribution to obesity-associated diseases remain unclear. OBJECTIVES: We characterized POP total body burden and their redistribution in obese individuals before and after drastic weight loss and compared these values with a variety of molecular, biological, and clinical parameters. METHODS: Seventy-one obese subjects were enrolled and underwent bariatric surgery. Blood and adipose tissue samples were obtained at different times from these individuals as well as from 18 lean women. RESULTS: POP content (17 dioxins/furans and 18 polychlorinated biphenyl congeners) in different adipose tissue territories was similar, allowing us to assess total POP body burden from a single biopsy. Total POP body burden was 2 to 3 times higher in obese than in lean individuals. We also found increased expression of some POP target genes in obese adipose tissue. Drastic weight loss led to increased serum POPs and, within 6-12 months, to a significant 15% decrease in total polychlorinated biphenyl body burden. Importantly, serum POP levels were positively correlated with liver toxicity markers and lipid parameters, independently of age and body mass index. CONCLUSIONS: POP content in adipose tissue and serum correlate with biological markers of obesity-related dysfunctions. Drastic weight loss leads to a redistribution of POPs and to a moderate decrease of their total body burden