A new approach for the ortho-positronium lifetime determination in a vacuum cavity

Currently, the experimental uncertainty for the determination of the ortho-positronium (o-Ps) decay rate is at 150 ppm precision; this is two orders of magnitude lower than the theoretical one, at 1 ppm level. Here we propose a new proof of concept experiment aiming for an accuracy of 100 ppm to be able to test the second-order correction in the calculations, which is $\simeq 45\left(\frac{\alpha}{\pi}\right)^2\approx 200$ ppm. The improvement relies on a new technique to confine the o-Ps in a vacuum cavity. Moreover, a new method was developed to subtract the time dependent pick-off annihilation rate of the fast backscattered positronium from the o-Ps decay rate prior to fitting the distribution. Therefore, this measurement will be free from the systematic errors present in the previous experiments. The same experimental setup developed for our recent search for invisible decay of ortho-positronium is being used. The precision will be limited by the statistical uncertainty, thus, if the expectations are fulfilled, this experiment could pave the way to reach the ultimate accuracy of a few ppm level to confirm or confront directly the higher order QED corrections. This will provide a sensitive test for new physics, e.g. a discrepancy between theoretical prediction and measurements could hint the existence of an hidden sector which is a possible dark matter candidate.Comment: 12 pages, 8 Figures, prepared for the proceedings of the PSAS2018 conference, Vienna (Austria

Un musée pour toute la ville : la nouvelle conception du Musée historique de Francfort (2008-2016)

Le musée historique d’une ville est aujourd’hui souvent compris comme un musée spécialisé, tourné vers une discipline scientifique donnée, en l’occurrence, la science historique. Ceci vaut pour tous les musées municipaux se trouvant dans une position comparable, comme les musées d’histoire de l’art, d’archéologie ou des sciences de la nature, qui, de la même façon, se rapportent à une discipline scientifique, ainsi qu’à une région ou un lieu donné. Cependant les musées historiques sont en mêm..

A comprehensive view of adolescent sexual health and family planning from the perspective of black and hispanic adolescent mothers in New York City

SFP17-ES4 and the Sigma Theta Tau Nursing Honors Society Upsilon Chapter PhD Dissertation Grant.Black and Hispanic adolescents in New York City experience high rates of pregnancy and sexually transmitted infections. A comprehensive understanding of the complexity of adolescent sexual health and family planning decisions and experiences can provide insights into the sustained disparities and inform practice, policy, and future research. The goal of this study was to explore and analyze this complexity, centering Black and Hispanic adolescent mothers as the experts on sexual and reproductive experiences from pre-pregnancy through parenting. As part of formative research for a human-centered design study, we interviewed 16 Black and Hispanic adolescent mothers living in New York City. Using situational analysis, we mapped relationships, discourse, and social structures to explore the various factors that inform adolescent sexual health decisions, in particular choices about contraception. Situational analysis found that, besides interpersonal factors, organizations and non-human elements like social media and physical birth control devices affected adolescent family planning in three social arenas: home, healthcare, and school. Within and across these arenas, adolescents lacked consistent sexual health education and contraceptive counseling and faced gendered expectations of their behaviors. Participants described parents and healthcare providers as most responsible for providing sexual health counseling yet described parents as uncomfortable or overreactive and healthcare workers as paternalistic and biased. A consideration of the many factors that inform sexual health decision-making and recognition of adolescents’ desire for parents and healthcare providers to be a source of education can address health disparities and promote adolescent sexual health and wellbeing.inpres

Thermal imaging of increment cores: a new method to estimate sapwood depth in trees

The cells in tree sapwood form a network of interconnected conduits which enables the transport of water and nutrients from the tree roots to the canopy. Sapwood depth must be assessed when tree water use is estimated from sap flow velocities. However, current approaches to assess sapwood depth are either not applicable universally, or require expensive instruments, the application of chemicals or laborious field efforts. Here, we present a new method, which estimates sapwood depth by thermal imaging of increment cores. Using a low-cost thermal camera for mobile devices, we show that the sapwood-heartwood boundary is detectable by a sharp increase in temperature. Estimated sapwood depths agree with dye estimates (R-2 = 0.84). We tested our approach on a broad range of temperate and tropical tree species: Quercus robur, Pinus sylvestris, Swietenia macrophylla, Guazuma ulmifolia, Hymenaea courbaril, Sideroxylon capiri and Astronium graveolens. In nearly all species, the methods agreed within 0.6 cm. Thermal imaging of increment cores provides a straightforward, low-cost, easy-to-use, and species-independent tool to identify sapwood depth. It has further potential to reveal radial differences in sapwood conductivity, to improve water balance estimations on larger scales and to quickly develop allometric relationships