Antimatter production in supernova remnants

We calculate the energy spectra of cosmic rays (CR) and their secondaries produced in a supernova remnant (SNR), taking into account the time-dependence of the SNR shock. We model the trajectories of charged particles as a random walk with a prescribed diffusion coefficient, accelerating the particles at each shock crossing. Secondary production by CRs colliding with gas is included as a Monte Carlo process. We find that SNRs produce less antimatter than suggested previously: The positron/electron ratio and the antiproton/proton ratio are a few percent and few $\times 10^{-5}$, respectively. Moreover, the obtained positron/electron ratio decreases with energy, while the antiproton/proton ratio rises at most by a factor of two above 10 GeV.Comment: 8 pages, 8 eps figures; extended version of arXiv:1004.1118; v2: minor corrections, matches published versio

Last Straw: The Effect of Guilt on Pro-Environmental Behavior

Honorable Mention Winner Although many environmental campaigns have pushed to eliminate plastic straws from daily consumption, concerns have surfaced that an increase in the simple behavior of refusing plastic straws will generate less action toward more effective pro-environmental behaviors (PEBs). This study implemented a guilt manipulation to urge participants to reduce their straw use and tested spillover effects to various household and travel PEBs. 234 Mturk participants (34% women) indicated their current PEBs at Time 1 and were randomly assigned to the guilt condition or a control condition. One week later (Time 2), participants completed a survey of the same measures, with 184 participants completing an identical survey three months later (Time 3). Results showed that, although the guilt manipulation did not affect straw use, a reduction in straw use positively spilled over to all PEBs at Time 2, with indirect effects through environmental identity for multiple PEBs. Several spillover effects had diminished by Time 3. The results show it is necessary to consider environmental identity when investigating PEB spillover and that negative spillover may not be a concern

Save the Turtles! Examining Motivators for Pro-Environmental Behaviors

In response to multiple vivid images about plastic straw pollution, multiple major corporations have started to reduce their straw waste or completely ban straw use. These images are assumed to lead to increased guilt, environmental identity, and environmental concern that is thought to then motivate additional pro-environmental behaviors (PEBs). In the first part of the study (Time 1), participants were randomly assigned to either watch a saddening video of a turtle struggling with a plastic straw stuck in its nose (the environmental appeal), or to not watch the video (controls). They were then surveyed on their levels of guilt, pro-environmental identity, and concern for the environment. The participants who watched the video were then asked to reduce their use of single-use plastic straws and to track their use for one week, while control participants were only asked to track their straw use for one week. After a week (Time 2), the participants were surveyed on their straw use, environmental policy support, levels of guilt, pro-environmental identity, and concern. This study supports the idea of guilt being a powerful motivator, but that eco-guilt can be reduced over time. On the other hand, other motivators, such as pro-environmental identity and concern, may not be affected by this particular environmental appeal. Overall, an individual’s straw use seems to be unaffected by the chosen environmental appeal, as well as an individual’s support for policies against single-use plastics

Antimatter spectra from a time-dependent modeling of supernova remnants

We calculate the energy spectra of cosmic rays (CR) and their secondaries produced in a supernova remnant (SNR), taking into account the time-dependence of the SNR shock. We model the trajectories of charged particles as a random walk with a prescribed diffusioncoefficient, accelerating the particles at each shock crossing. Secondary production by CRs colliding with gas is included as a Monte Carlo process. We find that SNRs produce less antimatter than suggested previously: The positron/electron ratio and the antiproton/proton ratio are a few percent and few $\times 10^{-5}$, respectively. Both ratios do not rise with energy.Comment: 4 pages, 4 eps figures; v2: results for time-dependent magnetic field adde

The Spillover Effect: Fact or Fiction

In light of recent pro-environmental behavior (PEB) campaigns like banning plastic straws, some have raised concerns that performing small behaviors may undermine support for more difficult, and arguably more effective, political PEBs. Recent psychological research has focused on understanding how performing one PEB may spill over to increase (positive spillover) or decrease (negative spillover) the likelihood of performing additional PEB. We hypothesized that participants asked to perform a PEB due to identity reasons would display positive spillover and that participants asked to perform a PEB due to guilt reasons would display negative spillover. 120 student participants (93 women) were randomly assigned to conditions fostering pro-environmental identity or guilt, or to a control condition. The participants were then asked to commit to use a reusable cup for an entire week (PEB1). One week later participants were asked if they would be willing to write a letter to the governor in support of alternative energy sources (PEB2). We found no evidence of the condition affecting PEB1 or PEB2. Additionally, there was no significant relationship between performing PEB1 and performing PEB2. Therefore, we found no evidence of spillover effects. Worry about negative PEB spillover to political behaviors may be unwarranted

Factors that Influence Canadian Generalist and Physical Education Specialist Elementary School Teachers’ Practices in Physical Education: A Qualitative Study

Interviews were conducted with 16 elementary school teachers across Canada (eight generalists and eight physical education [PE] specialists) to explore their experiences when instructing PE. Questions were phrased to encourage exploration of the perspectives of generalists and specialists, with a particular focus on teaching philosophy, barriers faced while instructing PE, facilitators and resources that enhance PE instruction, and the teachers’ self-efficacy when teaching PE. Generalists noted perceived lack of time, inadequate facilities and equipment, insufficient training, lack of knowledge, and low self-efficacy as barriers. Conversely, specialists noted that their advanced training, professional development opportunities, high self-efficacy, and technology use positively supported their teaching practices. Keywords: physical education, elementary school, generalist, specialist, physical activityDes entrevues menées auprès de 16 enseignants du primaire à travers le Canada (huit généralistes et huit spécialistes de l’éducation physique [ÉP]) ont permis d’explorer leurs expériences lors de l’enseignement de l’ÉP. Les questions ont été formulées de manière à explorer les perspectives des généralistes et des spécialistes, en mettant l’accent sur : la philosophie de l’enseignement ; les obstacles rencontrés lors de l’enseignement de l’ÉP ; les facilitateurs et les ressources qui améliorent l’enseignement de l’ÉP ; et leur efficacité personnelle dans l’enseignement de l’ÉP. Les généralistes ont indiqué le manque de temps, les installations et les équipements inadéquats, le manque de formation et de connaissance, ainsi qu’une faible efficacité personnelle comme des obstacles. À l’inverse, les spécialistes ont révélé que leur formation avancée, leurs opportunités de développement professionnel, leur grande efficacité personnelle et leur utilisation de la technologie soutenaient positivement leurs pratiques d’enseignement. Mots-clés : éducation physique, école primaire, généraliste, spécialiste, activité physiqu

On the Role of Disks in the Formation of Stellar Systems: A Numerical Parameter Study of Rapid Accretion

We study rapidly accreting, gravitationally unstable disks with a series of global, three dimensional, numerical experiments using the code ORION. In this paper we conduct a numerical parameter study focused on protostellar disks, and show that one can predict disk behavior and the multiplicity of the accreting star system as a function of two dimensionless parameters which compare the disk's accretion rate to its sound speed and orbital period. Although gravitational instabilities become strong, we find that fragmentation into binary or multiple systems occurs only when material falls in several times more rapidly than the canonical isothermal limit. The disk-to-star accretion rate is proportional to the infall rate, and governed by gravitational torques generated by low-m spiral modes. We also confirm the existence of a maximum stable disk mass: disks that exceed ~50% of the total system mass are subject to fragmentation and the subsequent formation of binary companions.Comment: 16 pages, 12 figures, submitte

The supernova remnant CTB 37B and its associated magnetar CXOU J171405.7-381031: evidence for a magnetar-driven remnant

We discuss in this Letter the association of the candidate magnetar CXOU J171405.7-381031 with the supernova remnant CTB 37B. The recent detection of the period derivative of the object allowed an estimation of a young characteristic age of only $\sim 1000 yr$. This value is too small to be compatible even with the minimum radius of the remnant $\geq 10 pc$, the value corresponding to the {\it lower} limit of the estimated distance of $10.2 \pm 3.5 kpc$, unless the true distance happens to be even smaller than the lower limit. We argue that a consistent scenario for the remnant origin, in which the latter is powered by the energy injected by a young magnetar, is indeed more accurate to explain the young age, and points out to its non-standard (i.e. magnetar-driven) nature.Comment: 6 pp., 1 figure, to appear in RAA Letter

Infants’ and toddlers’ physical activity and sedentary time as measured by accelerometry: a systematic review and meta-analysis,

Background: Early experiences in physical activity (PA) are important to shape healthy movement behaviours long-term; as such, it is critical that PA is promoted from infancy, and that detrimental behaviours (e.g., prolonged sedentary time [ST]) are minimized. The purpose of this systematic review and meta-analysis was to examine infants’ and toddlers’ movement behaviours across daytime hours. Methods: Seven online databases were searched for terms related to infants (\u3c 12 months), toddlers (12–35.9 months), PA, ST, and accelerometry. Two independent reviewers examined 4873 articles for peer-reviewed original research, published in English, that assessed infants’ (counts/min) and/or toddlers’ PA or ST (min/day) using accelerometry across daytime hours. Infants’ mean PA level (counts/min) was averaged across studies, and ranges were produced. Estimates of toddlers’ movement behaviours were aggregated meta-analytically to produce average daily rates, and accelerometer placement, cut-point validity, device type, and epoch length were tested as a moderating variables. Results: Twenty-four studies from 16 countries (published 2011–2019), representing 3699 participants, were included in the systematic review. Five studies reported on infants’ PA, which ranged from 78.2 to 2580.5 cpm. Across 20 studies, toddlers’ total PA, light PA, moderate-to vigorous-intensity PA, and ST ranged from 72.9 to 636.5, 48.5 to 582.4, 6.5 to 89.9, and 172.7 to 545.0 min/day, respectively. After taking into account accelerometer placement, cut-point validity, device type, and epoch length, we found that toddlers engaged in 246.19 min/day (SE = 28.50; 95% CI: 190.34, 302.04) of total PA, 194.10 min/day (SE = 28.76; 95% CI: 137.73, 250.47) of light PA, and 60.16 min/day (SE = 5.88; 95% CI: 48.64, 71.69) of moderate-to vigorous-intensity PA. Toddlers engaged in 337.04 min/day (SE = 32.67; 95% CI: 273.01, 401.07) of ST. Conclusions: With limited studies conducted in infants (n = 5), PA estimates are inconclusive and largely heterogeneous. Overall, toddlers tend to exceed the total PA recommendation of 180 min/day; however, very little of this time is spent at higher movement intensities. Even with high PA rates, toddlers still engage in substantial ST. More consistent and valid measurement protocols are needed to improve comparability across studies