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

On the uniqueness of paths for spin-0 and spin-1 quantum mechanics

The uniqueness of the Bohmian particle interpretation of the Kemmer equation, which describes massive spin-0 and spin-1 particles, is discussed. Recently the same problem for spin-1/2 was dealt with by Holland. It appears that the uniqueness of boson paths can be enforced under well determined conditions. This in turn fixes the nonrelativistic particle equations of the nonrelativistic Schrodinger equation, which appear to correspond with the original definitions given by de Broglie and Bohm only in the spin-0 case. Similar to the spin-1/2 case, there appears an additional spin-dependent term in the guidance equation in the spin-1 case. We also discuss the ambiguity associated with the introduction of an electromagnetic coupling in the Kemmer theory. We argue that when the minimal coupling is correctly introduced, then the current constructed from the energy-momentum tensor is no longer conserved. Hence this current can not serve as a particle probability four-vector.Comment: 19 pages, no figures, LaTex, shortened version for Phys. Lett.

PO-0638: Adaptive dose painting by numbers for head and neck cancer: interim analysis of a randomised trial

International audience1. Recherches sur le Fayuan zayuan yuanshi ji de Sengyou (445-518), première anthologie de rites bouddhiques (suite : le contenu des juan 4 et 5) Notre travail de reconstruction du Fayuan zayuan yuanshi ji 法苑雜緣原始集 (Anthologie [pour comprendre] le commencement et l’origine de diverses [pratiques] dans le jardin des devoirs ; ci-après Fayuan) de Sengyou 僧祐 (445-518) nous a amenés cette année à nous pencher sur les 22 premiers titres de la section sur le saṃgha (Sengbao 僧寶, « Le joyau de la Loi ..

"It's the poverty"-Stakeholder perspectives on barriers to secondary education in rural Burkina Faso

Universal primary and secondary education is a key target of the Sustainable Development Goals. While substantial gains have been made at the primary school level, progress towards universal secondary education has slowed, particularly in sub-Saharan Africa. In this study, we aimed to determine perceived barriers of secondary schooling in rural Burkina Faso, where secondary school completion is among the lowest globally (<10%). We conducted a two-stage qualitative study using semi-structured interviews (N = 49). In the first stage, we sampled enrolled students (n = 10), out-of-school adolescents (n = 9), parents of enrolled students (n = 5), parents of out-of-school adolescents (n = 5) and teachers (n = 10) from a random sample of five secondary schools. In a second stage, we interviewed key informants knowledgeable of the school context using snowball sampling (n = 10). Systematic analysis of the pooled sample was based on a reading of interview transcripts and coding of the narratives in NVivo12 using the diathesis-stress model. Recurring themes were classified using a priori developed categories of hypothesized barriers to secondary schooling. Major reported barriers included school-related expenses and the lack of school infrastructure and resources. Insufficient and heterogeneous French language skills (the official language of instruction in Burkina Faso) were seen as a major barrier to secondary schooling. Forced marriages, adolescent pregnancies, and the low perceived economic benefits of investing in secondary schooling were reported as key barriers among young women. Our results guide future interventions and policy aimed at achieving universal secondary education and gender equity in the region

A Continuous Quality Improvement Intervention to Improve Antenatal HIV Care Testing in Rural South Africa: Evaluation of Implementation in a Real-World Setting

BACKGROUND: We evaluated continuous quality improvement (CQI) targeting antenatal HIV care quality in rural South Africa using a stepped-wedge cluster-randomised controlled trial (Management and Optimisation of Nutrition, Antenatal, Reproductive, Child health, MONARCH) and an embedded process evaluation. Here, we present results of the process evaluation examining determinants of CQI practice and 'normalisation.' METHODS: A team of CQI mentors supported public-sector health workers in seven primary care clinics to (1) identify root causes of poor HIV viral load (VL) monitoring among pregnant women living with HIV and repeat HIV testing among pregnant women not living with HIV, and (2) design and iteratively test their own solutions. We used a mixed methods evaluation with field notes from CQI mentors ('dose' and 'reach' of CQI, causes of poor HIV care testing rates, implemented change ideas); patient medical records (HIV care testing by clinic and time step); and semi-structured interviews with available health workers. We analysed field notes andsemi-structured interviews for determinants of CQI implementation and 'normalisation' using Normalisation Process Theory (NPT) and Tailored Implementation of Chronic Diseases (TICD) frameworks. RESULTS: All interviewed health workers found the CQI mentors and methodology helpful for quality improvement. Total administered 'dose' was higher than planned but 'reach' was limited by resource constraints, particularly staffing shortages. Simple workable improvements to identified root causes were implemented, such as a patient tracking notebook and results filing system. VL monitoring improved over time, but not repeat HIV testing. Besides resource constraints, gaps in knowledge of guidelines, lack of leadership, poor clinical documentation, and data quality gaps reduced CQI implementation fidelity and normalisation. CONCLUSION: While CQI holds promise, we identified several health system challenges. Priorities for policy makers include improving staffing and strategies to improve clinical documentation. Additional support with implementing clinical guidelines and improving routine data quality are needed. Normalising CQI may be challenging without concurrent health system improvements

CD4+ T-cell count at antiretroviral therapy initiation in the "treat all" era in rural South Africa: an interrupted time series analysis

BACKGROUND: South Africa implemented universal test and treat (UTT) in September 2016 in an effort to encourage earlier initiation of antiretroviral therapy (ART). METHODS: We therefore conducted an interrupted time series (ITS) analysis to assess the impact of UTT on mean CD4 count at ART initiation among adults ≥16 years old attending 17 public sector primary care services in rural South Africa between July 2014 and March 2019. RESULTS: Among 20,599 individuals (69% women), CD4 counts were available for 74%. Mean CD4 at ART initiation increased from 317.1 cells/μL (95% confidence interval, CI, 308.6 to 325.6)-one to eight months prior to UTT-to 421.0 cells/μL (95% CI 413.0 to 429.0) one to twelve months after UTT, including an immediate increase of 124.2 cells/μL (95% CI 102.2 to 146.1). However, mean CD4 count subsequently fell to 389.5 cells/μL (95% CI 381.8 to 397.1) 13 to 30 months after UTT, but remained above pre-UTT levels. Men initiated ART at lower CD4 counts than women (-118.2 cells/μL, 95% CI -125.5 to -111.0) throughout the study. CONCLUSIONS: Although UTT led to an immediate increase in CD4 count at ART initiation in this rural community, the long-term effects were modest. More efforts are needed to increase initiation of ART early in HIV infection, particularly among men

Pre-segmented 2-Step IMRT with subsequent direct machine parameter optimisation – a planning study

<p>Abstract</p> <p>Background</p> <p>Modern intensity modulated radiotherapy (IMRT) mostly uses iterative optimisation methods. The integration of machine parameters into the optimisation process of step and shoot leaf positions has been shown to be successful. For IMRT segmentation algorithms based on the analysis of the geometrical structure of the planning target volumes (PTV) and the organs at risk (OAR), the potential of such procedures has not yet been fully explored. In this work, 2-Step IMRT was combined with subsequent direct machine parameter optimisation (DMPO-Raysearch Laboratories, Sweden) to investigate this potential.</p> <p>Methods</p> <p>In a planning study DMPO on a commercial planning system was compared with manual primary 2-Step IMRT segment generation followed by DMPO optimisation. 15 clinical cases and the ESTRO Quasimodo phantom were employed. Both the same number of optimisation steps and the same set of objective values were used. The plans were compared with a clinical DMPO reference plan and a traditional IMRT plan based on fluence optimisation and consequent segmentation. The composite objective value (the weighted sum of quadratic deviations of the objective values and the related points in the dose volume histogram) was used as a measure for the plan quality. Additionally, a more extended set of parameters was used for the breast cases to compare the plans.</p> <p>Results</p> <p>The plans with segments pre-defined with 2-Step IMRT were slightly superior to DMPO alone in the majority of cases. The composite objective value tended to be even lower for a smaller number of segments. The total number of monitor units was slightly higher than for the DMPO-plans. Traditional IMRT fluence optimisation with subsequent segmentation could not compete.</p> <p>Conclusion</p> <p>2-Step IMRT segmentation is suitable as starting point for further DMPO optimisation and, in general, results in less complex plans which are equal or superior to plans generated by DMPO alone.</p