271 research outputs found
STEREO observations of stars and the search for exoplanets
The feasibility of using data from the NASA STEREO mission for variable star and asteroseismology studies has been examined. A data analysis pipeline has been developed that is able to apply selected algorithms to the entire data base of nearly a million stars to search for signs of variability. An analysis limited to stars of magnitude 10.5 has been carried out, which has resulted in the extraction of 263 eclipsing binaries (EBs), of which 122 are not recorded as such in the SIMBAD online data base. The characteristics of the STEREO observations are shown to be extremely well suited to variable star studies with the ability to provide continuous phase coverage for extended periods as well as repeated visits that allow both short- and long-term variability to be observed. This will greatly inform studies of particular stars, such as the pre-cataclysmic variable V471 Tau, as well as the entire classes of stars, including many forms of rotational variability. The high-precision photometry has also revealed a potentially substellar companion to a bright (R= 7.5 mag) nearby star (HD 213597), detected with 5σ significance. This would provide a significant contribution to the exoplanet research if follow-up observations ascertain the mass to be within the planetary domain. Some particularly unusual EBs from the recovered sample are discussed, including a possible reclassification of a well-known star as an EB rather than a rotational variable (HR 7355) and several particularly eccentric systems, including very long period EBs
Visualizing Rank Deficient Models: A Row Equation Geometry of Rank Deficient Matrices and Constrained-Regression
Situations often arise in which the matrix of independent variables is not of full column rank. That is, there are one or more linear dependencies among the independent variables. This paper covers in detail the situation in which the rank is one less than full column rank and extends this coverage to include cases of even greater rank deficiency. The emphasis is on the row geometry of the solutions based on the normal equations. The author shows geometrically how constrained-regression/generalized-inverses work in this situation to provide a solution in the face of rank deficiency
Linking migration to community resilience in the receiving basin of a large-scale water transfer project
Large-scale water transfer projects (LWTPs) transfer water to urban and agricultural areas. The Majes-Siguas canal, established in 1983, is an LWTP that created a thriving agricultural area through irrigating the Majes district in the Atacama Desert of Peru. Like other LWTP receiving basins, the project has attracted an influx of migrants who work on the farms. At the same time, the Majes LWTP is the district’s only source of water and has an aging infrastructure which presents significant risks. While many studies critically analyze the consequences of LWTPs in water supply basins, few evaluate the resilience of communities living in LWTP receiving basins. In this study, we ask: what factors stifle or enable resilience of the agricultural community in the Majes-Siguas receiving basin? In 2019, we conducted semi-structured interviews with migrant and residents and water authorities, collected and reviewed historical documents, and conducted participant observations. Using this data, we analyze community resilience by identifying perceived risks, stressors, and vulnerabilities among and between groups of agricultural actors, their adaptations, and their perceptions of water management organizations’ responses. Results show that a single source of water, differential vulnerabilities between groups of agricultural actors, and limited organizational responsiveness stifled community resilience, while communal pooling and self-organization enabled community resilience. Attention to increasing inclusion of migrants in water management decision-making, addressing differential water and land rights, and cultivating space for migrant self-organization could enable the agricultural community to be more resilient
Puut tarjoumina paikkasuhteen muotoutumiseen - viitekehys lasten luontosuhteen tukemiseen
This study, informed by phenomenology and ethnography, explores urban children’s relationship with trees in a garden camp context: what are trees for urban children? Studying Finnish 7- to 12-year-old children, the research employed triangulation: participant and non-participant observation methods with mixed data collection over the course of three years. Engaging in grounded theory analysis after an intermission, the study unites the theoretical constructs of affordance and connectedness to place. Based on empirical observations, this study provides a theoretical framework to clarify the phased process of how urban children’s connectedness to place is evolving. Exploitation of tree affordances during place-based play reflected connectedness to place; utilization of trees became more versatile over time. The results showed trees to be intriguing and multifaceted, satisfying many of the children’s private and social needs. Trees provided the materials, space and often purpose and contents for the actual play that could not have thrived without them. In addition, children learned to manage possible tree-related risks mainly from experience and through scaffolding with peers. Recommendations for supporting beneficial nature contact emphasize allowing child-directed, place-based play time and planning biodiverse, low-maintenance spaces with a wide variety of trees that will invite children to use green spaces according to their needs.This study, informed by phenomenology and ethnography, explores urban children’s relationship with trees in a garden camp context: what are trees for urban children? Studying Finnish 7- to 12-year-old children, the research employed triangulation: participant and non-participant observation methods with mixed data collection over the course of three years. Engaging in grounded theory analysis after an intermission, the study unites the theoretical constructs of affordance and connectedness to place. Based on empirical observations, this study provides a theoretical framework to clarify the phased process of how urban children’s connectedness to place is evolving. Exploitation of tree affordances during place-based play reflected connectedness to place; utilization of trees became more versatile over time. The results showed trees to be intriguing and multifaceted, satisfying many of the children’s private and social needs. Trees provided the materials, space and often purpose and contents for the actual play that could not have thrived without them. In addition, children learned to manage possible tree-related risks mainly from experience and through scaffolding with peers. Recommendations for supporting beneficial nature contact emphasize allowing child-directed, place-based play time and planning biodiverse, low-maintenance spaces with a wide variety of trees that will invite children to use green spaces according to their needs.Peer reviewe
Co-designing transformation research : lessons learned from research on deliberate practices for transformation
Co-production of new knowledge can enhance open and integrative research processes across the social and natural sciences and across research/science, practice and policy interrelationships. Thus, co-production is important in the conduct of research about and for transformations to sustainability. While co-design is an integral part of co-production, it often receives limited attention in the conduct of co-produced research. This paper reports on lessons learned from an early stage of the co-design process to develop research on deliberate practices for transformative change. Key lessons learned are the need to: (1) ensure co-design processes are themselves carefully designed; (2) encourage emergence of new ways of thinking about problem formulation through co-design; (3) carefully balance risks for the participants involved while also enhancing opportunities for intellectual risk taking; (4) facilitate personal transformations in co-design as a way to stimulate and encourage further creativity; and (5) for funders to carefully and constructively align criteria or incentives through which a project or future proposal will be judged to the goals of the co-design, including for instrumental outcomes and objectives for creativity and imagination. Given that co-design necessarily involves a reflective practice to iteratively guide emergence of new thinking about the practices of change, co-design can itself be considered an important deliberate practice for transforming the conduct of research and the contribution of that research to social transformations
Hepatitis B virus and hepatitis D virus infection in women with or at risk for HIV infection in the United States
Hepatitis D virus (HDV) requires co-infection with hepatitis B virus (HBV). Human immunodeficiency virus (HIV) shares transmission routes with these viruses. Among 4,932 US women infected with or at-risk for HIV during 1994–2015, HBV surface antigen (HBsAg) positivity was more common in women with HIV (2.8% vs. 1.2%; p = 0.001); HDV was more common among participants enrolled during 2013–2015 (p = 0.0004) and those with resolved rather than active hepatitis C (1.9% vs. 0.5%; p = 0.02). Among HBsAg-positive women (n = 117), HDV antibody prevalence was 22% and did not vary by HIV status; HDV infection was associated with the presence of advanced fibrosis/cirrhosis at enrollment (adjusted odds ratio, 5.70; 95% confidence interval, 1.46–22.29). Our results demonstrate the importance of HDV testing in HBV-infected US women
Net Charge Fluctuations in Au + Au Interactions at sqrt(s_NN) = 130 GeV
Data from Au + Au interactions at sqrt(s_NN) = 130 GeV, obtained with the
PHENIX detector at RHIC, are used to investigate local net charge fluctuations
among particles produced near mid-rapidity. According to recent suggestions,
such fluctuations may carry information from the Quark Gluon Plasma. This
analysis shows that the fluctuations are dominated by a stochastic distribution
of particles, but are also sensitive to other effects, like global charge
conservation and resonance decays.Comment: 6 pages, RevTeX 3, 3 figures, 307 authors, submitted to Phys. Rev.
Lett. on 21 March, 2002. Plain text data tables for the points plotted in
figures for this and previous PHENIX publications are (will be made) publicly
available at http://www.phenix.bnl.gov/phenix/WWW/run/phenix/papers.htm
Flow Measurements via Two-particle Azimuthal Correlations in Au + Au Collisions at sqrt(s_NN) = 130 GeV
Two particle azimuthal correlation functions are presented for charged
hadrons produced in Au + Au collisions at RHIC sqrt(s_NN) = 130 GeV. The
measurements permit determination of elliptic flow without event-by-event
estimation of the reaction plane. The extracted elliptic flow values v_2 show
significant sensitivity to both the collision centrality and the transverse
momenta of emitted hadrons, suggesting rapid thermalization and relatively
strong velocity fields. When scaled by the eccentricity of the collision zone,
epsilon, the scaled elliptic flow shows little or no dependence on centrality
for charged hadrons with relatively low p_T. A breakdown of this epsilon
scaling is observed for charged hadrons with p_T > 1.0 GeV/c for the most
central collisions.Comment: 6 pages, RevTeX 3, 4 figures, 307 authors, submitted to Phys. Rev.
Lett. on 11 April 2002. Plain text data tables for the points plotted in
figures for this and previous PHENIX publications are (will be made) publicly
available at http://www.phenix.bnl.gov/phenix/WWW/run/phenix/papers.htm
- …