Application of Markov decision processes to search problems

Many decision problems contain, in some form, a NP-hard combinatorial problem. Therefore decision support systems have to solve such combinatorial problems in a reasonable time. Many combinatorial problems can be solved by a search method. The search methods used in decision support systems have to be robust in the sense that they can handle a large variety of (user defined) constraints and that they allow user interaction, i.e. they allow a decision maker to control the search process manually. In this paper we show how Markov decision processes can be used to guide a random search process. We first formulate search problems as a special class of Markov decision processes such that the search space of a search problem is the state space of the Markov decision process. In general it is not possible to compute an optimal control procedure for these Markov decision processes in a reasonable time. We therefore, define several simplifications of the original problem that have much smaller state spaces. For these simplifications, decompositions and abstractions, we find optimal strategies and use the exact solutions of these simplified problems to guide a randomized search process. The search process selects states for further search at random with probabilities based on the optimal strategies of the simplified problems. This randomization is a substitute for explicit backtracking and avoids problems with local extrema. These randomized search procedures are repeated as long as we have time to solve the problem. The best solution of those generated during that time is accepted. We illustrate the approach with two examples: the N-puzzle and a job shop scheduling problem

Mega: A Search for the Decay μ → e γ

This research was sponsored by the National Science Foundation Grant NSF PHY-931478

Relative Oscillation Theory, Weighted Zeros of the Wronskian, and the Spectral Shift Function

We develop an analog of classical oscillation theory for Sturm-Liouville operators which, rather than measuring the spectrum of one single operator, measures the difference between the spectra of two different operators. This is done by replacing zeros of solutions of one operator by weighted zeros of Wronskians of solutions of two different operators. In particular, we show that a Sturm-type comparison theorem still holds in this situation and demonstrate how this can be used to investigate the finiteness of eigenvalues in essential spectral gaps. Furthermore, the connection with Krein's spectral shift function is established.Comment: 26 page

Capability, opportunity, and motivation to enact hygienic practices in the early stages of the COVID‐19 outbreak in the United Kingdom

Objectives The COVID‐19 pandemic is one of the greatest global health threats facing humanity in recent memory. This study aimed to explore influences on hygienic practices, a set of key transmission behaviours, in relation to the Capability, Opportunity, Motivation‐Behaviour (COM‐B) model of behaviour change (Michie et al., 2011). Design Data from the first wave of a longitudinal survey study were used, launched in the early stages of the UK COVID‐19 pandemic. Methods Participants were 2025 adults aged 18 and older, representative of the UK population, recruited by a survey company from a panel of research participants. Participants self‐reported motivation, capability, and opportunity to enact hygienic practices during the COVID‐19 outbreak. Results Using regression models, we found that all three COM‐B components significantly predicted good hygienic practices, with motivation having the greatest influence on behaviour. Breaking this down further, the subscales psychological capability, social opportunity, and reflective motivation positively influenced behaviour. Reflective motivation was largely driving behaviour, with those highest in reflective motivation scoring 51% more on the measure of hygienic practices compared with those with the lowest scores. Conclusions Our findings have clear implications for the design of behaviour change interventions to promote hygienic practices. Interventions should focus on increasing and maintaining motivation to act and include elements that promote and maintain social support and knowledge of COVID‐19 transmission. Groups in particular need of targeting for interventions to increase hygienic practices are males and those living in cities and suburbs

Anxiety, depression, traumatic stress, and COVID-19 related anxiety in the UK general population during the COVID-19 pandemic

Background The COVID-19 pandemic has created an unprecedented global crisis necessitating drastic changes to living conditions, social life, personal freedom and economic activity. No study has yet examined the presence of psychiatric symptoms in the UK population in similar conditions. Aims We investigated the prevalence of COVID-19 related anxiety, generalised anxiety, depression and trauma symptoms in a representative sample of the UK population during an early phase of the pandemic, and estimated associations with variables likely to influence these symptoms. Method Between March 23rd and March 28th 2020, a quota sample of 2025 UK adults 18 years and older, stratified by age, sex and household income, was recruited by online survey company Qualtrics. Participants completed measures of depression (PHQ9), generalised anxiety (GAD7), and trauma symptoms relating to the pandemic (ITQ). Bivariate and multivariate associations were calculated for age, gender, rural vs urban environment, presence of children in the household, income, loss of income, pre-existing health conditions in self and someone close, infection in self and someone close, and perceived risk of infection over the next month. Results Higher levels of anxiety, depression and trauma symptoms were reported compared to previous population studies, but not dramatically so. Meeting the criteria for either anxiety or depression, and trauma symptoms was predicted by young age, presence of children in the home, and high estimates of personal risk. Anxiety and depression symptoms were also predicted by low income, loss of income, and pre-existing health conditions in self and other. Specific anxiety about COVID-19 was greater in older participants. Conclusions The UK population, especially older citizens, were largely resilient in the early stages of the pandemic. However, several specific COVID-related variables are associated with psychological distress: particularly having children at home, loss of income because of the pandemic, as well as having a pre-existing health condition, exposure to the virus and high estimates of personal risk. Further similar surveys, particularly of those with children at home, are required as the pandemic progresses

A straw drift chamber spectrometer for studies of rare kaon decays

We describe the design, construction, readout, tests, and performance of planar drift chambers, based on 5 mm diameter copperized Mylar and Kapton straws, used in an experimental search for rare kaon decays. The experiment took place in the high-intensity neutral beam at the Alternating Gradient Synchrotron of Brookhaven National Laboratory, using a neutral beam stop, two analyzing dipoles, and redundant particle identification to remove backgrounds

A network approach to understanding social distancing behaviour during the first UK lockdown of the COVID-19 pandemic

Objective Given the highly infectious nature of COVID-19, social distancing practices are key in stemming the spread of the virus. We aimed to assess the complex interplay among psychological factors, socio-demographic characteristics and social distancing behaviours within the framework of the widely used Capability, Opportunity, Motivation-Behaviour (COM-B) model. Design The present research employed network psychometrics on data collected during the first UK lockdown in April 2020 as part of the COVID-19 Psychological Research Consortium (C19PRC) Study. Using a network approach, we examined the predictions of psychological and demographic variables onto social distancing practices at two levels of analysis: macro and micro. Design The present research employed network psychometrics on data collected during the first UK lockdown in April 2020 as part of the COVID-19 Psychological Research Consortium (C19PRC) Study. Using a network approach, we examined the predictions of psychological and demographic variables onto social distancing practices at two levels of analysis: macro and micro. Results Our findings revealed several factors that influenced social distancing behaviour during the first UK lockdown. The COM-B model was successful in predicting particular aspects of social-distancing via the influence of psychological capability and motivation at the macro-and micro-levels, respectively. Notably, demographic variables, such as education, income, and age, were directly and uniquely predictive of certain social distancing behaviours. Conclusion Our findings reveal psychological factors that are key predictors of social distancing behaviour and also illustrate how demographic variables directly influence such behaviour. Our research has implications for the design of empirically-driven interventions to promote adherence to social distancing practices in this and future pandemics

An 18‐month follow‐up of the Covid‐19 psychology research consortium study panel: survey design and fieldwork procedures for Wave 6

Objectives Established in March 2020, the C19PRC Study monitors the psychological and socio-economic impact of the pandemic in the UK and other countries. This paper describes the protocol for Wave 6 (August–September 2021). Methods The survey assessed: COVID-19 related experiences; experiences of common mental health disorders; psychological characteristics; and social and political attitudes. Adult participants from any previous wave (N = 3170) were re-invited, and sample replenishment procedures helped manage attrition. Weights were calculated using a survey raking algorithm to ensure the on-going original panel (from baseline) was nationally representative in terms of gender, age, and household income, amongst other factors. Results 1643 adults were re-interviewed at Wave 6 (51.8% retention rate). Non-participation was higher younger adults, those born outside UK, and adults living in cities. Of the adults recruited at baseline, 54.3% (N = 1100) participated in Wave 6. New respondent (N = 415) entered the panel at this wave, resulting in cross-sectional sample for Wave 6 of 2058 adults. The raking procedure re-balanced the longitudinal panel to within 1.3% of population estimates for selected socio-demographic characteristics. Conclusions This paper outlines the growing strength of the publicly available C19PRC Study data for COVID-19-related interdisciplinary research

Tackling transition:the value of peer mentoring

This paper is aimed at those interested in the promotion of student retention in higher education; particularly those with an interest in peer mentoring as a means of student support. It critically discusses the results of an exploratory study analysing the perceptions of peer mentors and mentees within five universities in the United Kingdom. The aim of the study was to analyse how student peer mentoring can aid transition into university by focusing specifically on how senior students can support their junior counterparts in their first year at university. The paper discusses the results of a survey which was completed by 329 student peer mentors and mentees. Focusing on the benefits and outcomes of participation in Mentoring Programmes, the survey was distinctive in that it asked mentors and mentees similar questions. From a theoretical perspective, the paper contributes to debates about peer support in higher education showing that participation in such programmes can have positive outcomes from both social and pedagogic perspectives. Practically speaking, the results have important implications for Higher Education Institutions as the research highlights the importance of putting into place formally structured Peer Mentoring Programmes which facilitate student support at a time when new students are most at risk of ‘dropping out’

Vaccination Against SARS-CoV-2 Is Associated With a Lower Viral Load and Likelihood of Systemic Symptoms

Background: Data conflict on whether vaccination decreases severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral load. The objective of this analysis was to compare baseline viral load and symptoms between vaccinated and unvaccinated adults enrolled in a randomized trial of outpatient coronavirus disease 2019 (COVID-19) treatment. Methods: Baseline data from the first 433 sequential participants enrolling into the COVID-OUT trial were analyzed. Adults aged 30-85 with a body mass index (BMI) ≥25 kg/m2 were eligible within 3 days of a positive SARS-CoV-2 test and <7 days of symptoms. Log10 polymerase chain reaction viral loads were normalized to human RNase P by vaccination status, by time from vaccination, and by symptoms. Results: Two hundred seventy-four participants with known vaccination status contributed optional nasal swabs for viral load measurement: median age, 46 years; median (interquartile range) BMI 31.2 (27.4-36.4) kg/m2. Overall, 159 (58%) were women, and 217 (80%) were White. The mean relative log10 viral load for those vaccinated <6 months from the date of enrollment was 0.11 (95% CI, -0.48 to 0.71), which was significantly lower than the unvaccinated group (P = .01). Those vaccinated ≥6 months before enrollment did not differ from the unvaccinated with respect to viral load (mean, 0.99; 95% CI, -0.41 to 2.40; P = .85). The vaccinated group had fewer moderate/severe symptoms of subjective fever, chills, myalgias, nausea, and diarrhea (all P < .05). Conclusions: These data suggest that vaccination within 6 months of infection is associated with a lower viral load, and vaccination was associated with a lower likelihood of having systemic symptoms