On Peres' statement "opposite momenta lead to opposite directions", decaying systems and optical imaging

We re-examine Peres' statement ``opposite momenta lead to opposite directions''. It will be shown that Peres' statement is only valid in the large distance or large time limit. In the short distance or short time limit an additional deviation from perfect alignment occurs due to the uncertainty of the location of the source. This error contribution plays a major role in Popper's orginal experimental proposal. Peres' statement applies rather to the phenomenon of optical imaging, which was regarded by him as a verification of his statement. This is because this experiment can in a certain sense be seen as occurring in the large distance limit. We will also reconsider both experiments from the viewpoint of Bohmian mechanics. In Bohmian mechanics particles with exactly opposite momenta will move in opposite directions. In addition it will prove particularly usefull to use Bohmian mechanics because the Bohmian trajectories coincide with the conceptual trajectories drawn by Pittman et al. In this way Bohmian mechanics provides a theoretical basis for these conceptual trajectories.Comment: 20 pages, 3 figures, LaTex, to be published in Found. Phy

Offspring schooling associated with increased parental survival in rural KwaZulu-Natal, South Africa

BACKGROUND: Investing in offspring's human capital has been suggested as an effective strategy for parents to improve their living conditions at older ages. A few studies have assessed the role of children's schooling in parental survival in high-income countries, but none have considered lower-resource settings with limited public wealth transfers and high adult mortality. METHODS: We followed 17,789 parents between January 2003 and August 2015 in a large population-based open cohort in rural KwaZulu-Natal, South Africa. We used Cox proportional hazards models to investigate the association between offspring's schooling and time to parental death. We assessed the association separately by parental sex and for four cause of death groups. RESULTS: A one year increase in offspring's schooling attainment was associated with a 5% decline in the hazard of maternal death (adjusted Hazard Ratio [aHR]: 0.95, 95%CI: 0.94-0.97) and a 6% decline in the hazard of paternal death (aHR: 0.94, 95%CI: 0.92-0.96), adjusting for a wide range of demographic and socio-economic variables of the parent and their children. Among mothers, the association was strongest for communicable, maternal, perinatal and nutritional conditions (aHR: 0.87, 95%CI: 0.82-0.92) and AIDS and tuberculosis (aHR: 0.92, 95%CI: 0.89-0.96), and weakest for injuries. Among fathers, the association was strongest for injuries (aHR: 0.87, 95%CI: 0.79-0.95) and AIDS and tuberculosis (aHR: 0.92, 95%CI: 0.89-0.96), and weakest for non-communicable diseases. CONCLUSION: Higher levels of schooling in offspring are associated with increased parental survival in rural South Africa, particularly for mothers at risk of communicable disease mortality and fathers at risk of injury mortality. Offspring's human capital may be an important factor for health disparities, particularly in lower-resource settings

Happiness as a Driver of Risk-Avoiding Behavior

Most governments try to discourage their citizens from taking extreme risks with their health and lives. Yet, for reasons not understood, many people continue to do so. We suggest a new approach to this longstanding question. First, we show that expected-utility theory predicts that 'happier' people will be less attracted to risky behaviors. Second, using BRFSS data on seatbelt use in a sample of 300,000 Americans, we document evidence strongly consistent with that prediction. Our result is demonstrated with various methodological approaches, including Bayesian model-selection and instrumental-variable estimation (based on unhappiness caused by widowhood). Third, using data on road accidents from the Add Health data set, we find strongly corroborative longitudinal evidence. These results suggest that government policy may need to address the underlying happiness of individuals rather than focus on behavioural symptoms.subjective well-being, risky behaviors, effects of well-being, rational carelessness

Happiness as a Driver of Risk-Avoiding Behavior

Understanding the reasons why individuals take risks, particularly unnecessary risks, remains an important question in economics. We provide the first evidence of a powerful connection between happiness and risk-avoidance. Using data on 300,000 Americans, we demonstrate that happier individuals wear seatbelts more frequently. This result is obtained with five different methodological approaches, including Bayesian model-selection and an instrumented analysis based on unhappiness through widowhood. Independent longitudinal data corroborate the finding, showing that happiness is predictive of future motor vehicle accidents. Our results are consistent with a rational-choice explanation: happy people value life and thus act to preserve it.risk preferences, seatbelt usage, vehicle accidents, subjective well-being, happiness

Supplementary feeding increases nestling feather corticosterone early in the breeding season in house sparrows

Several studies on birds have proposed that a lack of invertebrate prey in urbanized areas could be the main cause for generally lower levels of breeding success compared to rural habitats. Previous work on house sparrows Passer domesticus found that supplemental feeding in urbanized areas increased breeding success but did not contribute to population growth. Here, we hypothesize that supplementary feeding allows house sparrows to achieve higher breeding success but at the cost of lower nestling quality. As abundant food supplies may permit both high-and low-quality nestlings to survive, we also predict that within-brood variation in proxies of nestling quality would be larger for supplemental food broods than for unfed broods. As proxies of nestling quality, we considered feather corticosterone (CORTf), body condition (scaled mass index, SMI), and tarsus-based fluctuating asymmetry (FA). Our hypothesis was only partially supported as we did not find an overall effect of food supplementation on FA or SMI. Rather, food supplementation affected nestling phenotype only early in the breeding season in terms of elevated CORTf levels and a tendency for more variable within-brood CORTf and FA. Early food supplemented nests therefore seemed to include at least some nestlings that faced increased stressors during development, possibly due to harsher environmental (e.g., related to food and temperature) conditions early in the breeding season that would increase sibling competition, especially in larger broods. The fact that CORTf was positively, rather than inversely, related to nestling SMI further suggests that factors influencing CORTf and SMI are likely operating over different periods or, alternatively, that nestlings in good nutritional condition also invest in high-quality feathers

Essays in political economy and voting behaviour

This thesis explores how political preferences are shaped by institutions, economic conditions, and personality. Each chapter is a distinct contribution and provides a different perspective on the formation of political preferences and, ultimately, voting behaviour. These different approaches relate to the fields of comparative political economy, behavioural economics, and political psychology. Methodologically, this thesis is empirically applied and the results of these separate enquiries into political preferences are grounded in statistical analysis. A first substantive chapter introduces a median voter data set that provides insight into the ideological position of the electoral centre in over 50 democracies. A second chapter uses this new data and studies cross-national voting behaviour in 18 Western democracies over 1960-2003. It is found that electoral behaviour is closely related to the salience of the following economic institutions: labour organization, skill specificity, and public sector employment. This research shows that political preferences are endogenous to economic institutions and implies the existence of institutional advantages to partisan politics. A third substantive chapter focuses on ideological change in the United States and tests the proposition that voters advance a more liberal agenda in prosperous times and shift towards being more conservative in dire economic times. A reference-dependent utility model relates income growth to political preferences by way of the demand for public goods and the optimal tax rate. This work thus links voting behaviour to economic business cycles and shows that ideological change is endogenous to income growth rates. Finally, a fourth chapter presents the largest study to date of the influence of the big five personality traits on political ideology. In line with prior research in political psychology, it is found that openness to experience strongly predicts liberal ideology and that conscientiousness strongly predicts conservative ideology. A variety of childhood experiences are also studied that may have a differential effect on political ideology based on an individual's personality profile. The findings of this final chapter provide new evidence for the idea that differences in political preferences are deeply intertwined with variation in the nature and nurture of individual personalities. Generally, this thesis provides some new insights into the complex world of political preference formation and does so by exploring the influential role of institutions, economic conditions, and personality

Exploring threshold concepts in population health

Background: Doctors are increasingly expected to improve the health and well-being of populations, as well as to care for individuals. However, despite extensive efforts to integrate population health into undergraduate programmes, engaging students in such learning is notoriously challenging. Threshold concepts are transformative, integrative, irreversible and fundamental to understanding a discipline. Grasping such concepts requires learners to cross a liminal space, which often involves struggle. Methods: We employed a form of transactional curriculum enquiry, involving qualitative and quantitative methods, with experienced population health medical educators to identify and explore threshold and troublesome concepts in population health. Results: Attributing causality, inequalities in health and doctors’ responsibility for populations not just individuals were the concepts most participants thought were threshold. The value of qualitative research, health as politically and socially determined and not taking evidence at face value were the concepts ranked as most troublesome for learners. Participants found the notions of threshold and troublesome concepts helpful and empowering. They described ways these new ideas would influence how they taught population health. Discussion: Transactional curriculum enquiry can offer insights into which population health concepts may be threshold and troublesome. The number of such concepts identified in this study may help explain why students often struggle to engage in population health learning. Understanding which concepts are threshold and particularly which are troublesome can help teachers to better support learners and can also inform curriculum design. If our students are to … take responsibility for populations as well as individuals … it is vital that they cross these fundamental thresholds in learning

Isolation of a Novel Phage with Activity against Streptococcus mutans Biofilms

peer-reviewedStreptococcus mutans is one of the principal agents of caries formation mainly, because of its ability to form biofilms at the tooth surface. Bacteriophages (phages) are promising antimicrobial agents that could be used to prevent or treat caries formation by S. mutans. The aim of this study was to isolate new S. mutans phages and to characterize their antimicrobial properties. A new phage, ɸAPCM01, was isolated from a human saliva sample. Its genome was closely related to the only two other available S. mutans phage genomes, M102 and M102AD. ɸAPCM01 inhibited the growth of S. mutans strain DPC6143 within hours in broth and in artificial saliva at multiplicity of infections as low as 2.5x10-5. In the presence of phage ɸAPCM01 the metabolic activity of a S. mutans biofilm was reduced after 24 h of contact and did not increased again after 48 h, and the live cells in the biofilm decreased by at least 5 log cfu/ml. Despite its narrow host range, this newly isolated S. mutans phage exhibits promising antimicrobial properties

Models of affective decision-making: how do feelings predict choice?

Intuitively, how we feel about potential outcomes will determine our decisions. Indeed, one of the most influential theories in psychology, Prospect Theory, implicitly assumes that feelings govern choice. Surprisingly, however, we know very little about the rules by which feelings are transformed into decisions. Here, we characterize a computational model that uses feelings to predict choice. We reveal that this model predicts choice better than existing value-based models, showing a unique contribution of feelings to decisions, over and above value. Similar to Prospect Theory value function, feelings showed diminished sensitivity to outcomes as value increased. However, loss aversion in choice was explained by an asymmetry in how feelings about losses and gains were weighed when making a decision, not by an asymmetry in the feelings themselves. The results provide new insights into how feelings are utilized to reach a decision