Analytical determination of coronal parameters using the period ratio P₁/2P₂

<p>Context. In transverse coronal loop oscillations, two periodicities have been measured simultaneously and are interpreted as the fundamental kink mode (with period P1) and the first harmonic (with period P2). Deviations of the period ratio P1/2P2 from unity provide information about the extent of longitudinal structuring within the loop.</p> <p>Aims. Here we develop an analytical approximation that describes the shift in P1/2P2 in terms of the ratio L/Λc of the length 2L of a coronal loop and the density scale height Λc.</p> <p>Methods. We study the MHD wave equations in a low β plasma using the thin tube approximation. Disturbances are described by a differential equation which may be solved for various equilibrium density profiles, obtaining dispersion relations in terms of Bessel functions. These dispersion relations may be used to obtain analytical approximations to the periods P1 and P2. We also present a variational approach to determining the period ratio and show how the WKB method may be used.</p> <p>Results. Analytical approximations to the period ratio P1/2P2 are used to shed light on the magnitude of longitudinal structuring in a loop, leading to a determination of the density scale height. We apply our formula to the observations in Verwichte et al. (2004) and Van Doorsselaere et al. (2007), obtaining the coronal density scale height.</p> <p>Conclusions. Our simple formula and approximate approaches highlight a useful analytical tool for coronal seismology. We demonstrate that P1/2P2 is linked to the density scale height, with no need for estimates of other external parameters. Given the accuracy of current observations, our formula provides a convenient means of determining density scale heights.</p&gt

The use of national datasets to baseline science education reform: exploring value-added approaches

This paper uses data from the National Pupil Database to investigate the differences in ‘performance’ across the range of science courses available following the 2006 Key Stage 4 (KS4) science reforms in England. This is a value-added exploration (from Key Stage 3 [KS3] to KS4) aimed not at the student or the school level, but rather at that of the course. Different methodological approaches to carrying out such an analysis, ranging from simple non-contextualized techniques, to more complex fully contextualized multilevel models, are investigated and their limitations and benefits are evaluated. Important differences between courses are found in terms of the typical ‘value’ they add to the students studying them with particular applied science courses producing higher mean KS4 outcomes for the same KS3 level compared with other courses. The implications of the emergence of such differences, in a context where schools are judged to a great extent on their value-added performance, are discussed. The relative importance of a variety of student characteristics in determining KS4 outcomes are also investigated. Substantive findings are that across all types of course, science prior attainment at KS3, rather than that of mathematics or English, is the most important predictor of KS4 performance in science, and that students of lower socio-economic status consistently make less progress over KS4 than might be expected, despite prior attainment being accounted for in the modelling

Exploring the feasibility of a cluster pilot randomised control trial to improve children’s 24-hour movement behaviours and dietary intake:happy homework

We aimed to explore the feasibility, acceptability, and potential efficacy of Happy Homework (HH); an 8-week home-focussed intervention, with the purpose of encouraging children’s positive dietary behaviours and engagement in positive physical activity (PA) and sleep behaviours. We randomised four Scottish schools (n = 71 participants; 5 classrooms) to either the HH intervention (n = 2) or usual curriculum control group (n = 2). HH consisted of movement and dietary-focused parent and child tasks. Primary outcome measures were intervention feasibility, acceptability, and potential efficacy. Secondary outcomes were objectively measured PA via ActiGraph GT3X+, sedentary behaviours (SBs) and sleep duration via activPAL4™ accelerometers and dietary behaviours, fruit and vegetable consumption and screen-time via questionnaires. After controlling for pre-test levels, post intervention stepping time and sleep duration were significantly greater for the HH group in comparison to the control group. The HH group reported eating more fruit and vegetables at post-test than the control group. Participants also reported the intervention to be enjoyable and motivating. These findings provide promising evidence that given a greater sample size, better retention and the prioritisation of health and wellbeing homework, HH could enhance children’s health and wellbeing

College Student Perceptions on Campus Alcohol Policies and Consumption Patterns

Environmental strategies for colleges and universities to reduce alcohol consumption among their students include the development and enforcement of campus alcohol policies. This study examines students\u27 knowledge and attitudes toward campus alcohol policies and how they relate to alcohol consumption and alcohol social norms. A sample of 422 freshman students was surveyed during their first month at a 4-year public college. Findings indicated that the majority of students (89%) were aware of campus policies, yet of those who were aware, less than half (44%) were accepting of these campus rules and regulations. In addition, the majority (79%) of students drank at social events, despite this behavior is in direct violation of campus alcohol policies. However, those who supported campus rules consumed significantly less alcohol at social events than those who opposed or had no opinion of the rules. Also, those who supported the rules perceived that their peers and students, in general, consumed significantly less alcohol at social events than those who were opposed or had no opinion. This outcome supports the premise established by several theories of behavior change including the theory of planned behavior, which states that behavior is influenced less by knowledge than by attitude and intention

On the period ratio P₁/2P₂ in the oscillations of coronal loops

<p>Aims. With strong evidence of fast and slow magnetoacoustic modes arising in the solar atmosphere there is scope for improved determinations of coronal parameters through coronal seismology. Of particular interest is the ratio P<sub>1</sub>/2P<sub>2</sub>between the period P<sub>1</sub> of the fundamental mode and the period P<sub>2</sub> of its first harmonic; in an homogeneous medium this ratio is one, but in a more complex configuration it is shifted to lower values.</p> <p>Methods. We consider analytically the effects on the different magnetohydrodynamic modes of structuring and stratification, pointing out that transverse or longitudinal structuring or gravitational stratification modifies the ratio P<sub>1</sub>/2P<sub>2</sub>.</p> <p>Results. The deviations caused by gravity and structure are studied for the fast and slow modes. Structure along the loop is found to be the dominant effect.</p> <p>Conclusions. The departure of P<sub>1</sub>/2P<sub>2</sub> from unity can be used as a seismological tool in the corona. We apply our technique to the observations by Verwichte et al. (2004), deducing the density scale height in a coronal loop.</p&gt

Contact transmission of influenza virus between ferrets imposes a looser bottleneck than respiratory droplet transmission allowing propagation of antiviral resistance

Influenza viruses cause annual seasonal epidemics and occasional pandemics. It is important to elucidate the stringency of bottlenecks during transmission to shed light on mechanisms that underlie the evolution and propagation of antigenic drift, host range switching or drug resistance. The virus spreads between people by different routes, including through the air in droplets and aerosols, and by direct contact. By housing ferrets under different conditions, it is possible to mimic various routes of transmission. Here, we inoculated donor animals with a mixture of two viruses whose genomes differed by one or two reverse engineered synonymous mutations, and measured the transmission of the mixture to exposed sentinel animals. Transmission through the air imposed a tight bottleneck since most recipient animals became infected by only one virus. In contrast, a direct contact transmission chain propagated a mixture of viruses suggesting the dose transferred by this route was higher. From animals with a mixed infection of viruses that were resistant and sensitive to the antiviral drug oseltamivir, resistance was propagated through contact transmission but not by air. These data imply that transmission events with a looser bottleneck can propagate minority variants and may be an important route for influenza evolution

Multi‐scale effects of land cover, weather, and fire on Columbian sharp‐tailed grouse

Columbian sharp‐tailed grouse (Tympanuchus phasianellus columbianus) are endemic to grassland and shrub‐steppe ecosystems of western North America, yet their distribution has contracted to \u3c10% of their historical range. Primary threats to Columbian sharp‐tailed grouse include loss of native habitat and conversion to agriculture, reductions in habitat once provided by the Conservation Reserve Program (CRP), wildfire, and drought conditions, yet population‐level consequences of these threats and their spatio‐temporal scales of effect are poorly understood. We evaluated multi‐scale effects of land cover, weather, and fire histories on patterns of abundance and productivity for Columbian sharp‐tailed grouse populations during 1995–2020 in Idaho, USA, using mixedeffects generalized regression and remotely sensed data. We demonstrated negative effects of fire, tree encroachment, and bare ground, positive effects of spring and summer precipitation and cover of shrubs and perennial forbs and grasses, and positive effects of CRP on grouse abundance that changed in magnitude with cover of perennials and shrubs near leks (i.e., strongest effects when average cover of shrubs and perennial forbs and grasses were less abundant). We also demonstrated per capita recruitment of Columbian sharp‐tailed grouse is positively associated with late‐summer greenness. Our results show that several suspected threats have measurable, population‐level impacts to Columbian sharp‐tailed grouse within Idaho. Moreover, our results suggest ongoing changes occurring within the core range of Columbian sharp‐tailed grouse, including loss of CRP cover to tilled agriculture and changes to wildfire and precipitation dynamics are likely to have negative effects on populations

Playing safe: Assessing the risk of sexual abuse to elite child athletes

Young athletes frequently suffer from being seen as athletes first and children second. This has consequences for their legal, civil and human rights as children (Kelly et al., 1995) and for the way in which sport organisations choose to intervene on their behalf to protect them from physical, psychological and sexual abuses (Brackenridge, 1994). Sport careers peak at different ages depending on the sport: in some, children as young as 12 or 13 may reach the highest levels of competitive performance; in others, full maturity as an athlete may come late into adulthood or even middle age. Recognition of this variation has given rise to the concept of ‘sport age’ (Kirby, 1986) referring to sport-specific athlete development. This concept is of significance in helping to identify the developmental process in terms of athletic, rather than chronological, maturity. The risk of sexual abuse in sport, formerly ignored or denied, has now been documented in a number of studies, using both quantitative and qualitative methods (Kirby & Greaves, 1996; Brackenridge, 1997; Volkwein, 1996). Drawing on data from these studies and from the previous work on sport age and athletic maturation, this paper proposes a possible means of identifying and assessing relative risk of sexual abuse to elite young athletes in selected sports. The concept of a ‘stage of imminent achievement’ (SIA) is proposed as the period of peak vulnerability of young athletes to sexual abuse

Anomalous translational velocity of vortex ring with finite-amplitude Kelvin waves

We consider finite-amplitude Kelvin waves on an inviscid vortex assuming that the vortex core has infinitesimal thickness. By numerically solving the governing Biot-Savart equation of motion, we study how the frequency of the Kelvin waves and the velocity of the perturbed ring depend on the Kelvin wave amplitude. In particular, we show that, if the amplitude of the Kelvin waves is sufficiently large, the perturbed vortex ring moves backwards.Comment: 6 pages, 5 figures, v2: minor changes, v3: typos correcte

Nonparametric survival analysis of epidemic data

This paper develops nonparametric methods for the survival analysis of epidemic data based on contact intervals. The contact interval from person i to person j is the time between the onset of infectiousness in i and infectious contact from i to j, where we define infectious contact as a contact sufficient to infect a susceptible individual. We show that the Nelson-Aalen estimator produces an unbiased estimate of the contact interval cumulative hazard function when who-infects-whom is observed. When who-infects-whom is not observed, we average the Nelson-Aalen estimates from all transmission networks consistent with the observed data using an EM algorithm. This converges to a nonparametric MLE of the contact interval cumulative hazard function that we call the marginal Nelson-Aalen estimate. We study the behavior of these methods in simulations and use them to analyze household surveillance data from the 2009 influenza A(H1N1) pandemic. In an appendix, we show that these methods extend chain-binomial models to continuous time.Comment: 30 pages, 6 figure