The motion of a glow discharge under the influence of a transverse magnetic field

ix, 282 leavesThis thesis describes an experimental study of the motion of a glow discharge under the influence of a strong transverse magnetic field, at moderate gas pressures. Conditions were generally such that WeTe was of the order of 1, where We is the electron cyclotron frequency, and Te the mean time between the collisions of an electron with neutral gas molecules. Experiments were mostly performed with discharge currents of the order of tens of milliamperes, so that the directed velocity given to the gas by the ions and electrons of the moving discharge was negligible compared with the velocity of the discharge. (First paragraph of introduction)

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Exploring EUV Spicules Using 304 Ang He II Data from SDO/AIA

We present results from a statistical study of He II 304 Angstrom EUV spicules and macrospicules at the limb of the Sun. We use high-cadence (12 sec) and high-resolution (0.6 arcsec pixels) resolution data from the Atmospheric Imaging Array (AIA) instrument on the Solar Dynamic Observatory (SDO). All of the observed events occurred in quiet or coronal hole regions near the solar pole. Spicules and macrospicules are typically transient jet-like chromospheric-material features, the macrospicules are wider and have taller maximum heights than the spicules. We looked for characteristics of the populations of these two phenomena that might indicate whether they have the same or different initiation mechanisms. We examined the maximum heights, time-averaged rise velocities, and lifetimes of about two dozen EUV spicules and about five EUV macrospicules. For spicules, these quantities are, respectively, approx. 5-30 km, 5-50 km/s, and a few 100- approx. 1000 sec. Macrospicules were approx. 60,000 km, 55 km/s, and had lifetimes of approx. 1800 sec. Therefore the macrospicules were taller and longer-lived than the spicules, and had velocities comparable to that of the fastest spicules. The rise profiles of both the spicules and the macrospicules matched well a second-order ("parabolic'') trajectory, although the acceleration was generally weaker than that of solar gravity in the profiles fitted to the trajectories. The Macrospicules also had obvious brightenings at their bases at their birth, while such brightenings were not apparent for most of the spicules. Most of the spicules and several of the macrospicules remained visible during their decent back to the solar surface, although a small percentage of the spicules faded out before their fall was completed. Are findings are suggestive of the two phenomena possibly having different initiation mechanisms, but this is not yet conclusive. Qualitatively the EUV 304 Angstrom spicules match well the properties quoted for "Type I'' Hinode Ca II spicules, even though we observed these 304 Angstrom spicules at a polar location, where typically only "Type II'' spicules are seen in the Hinode Ca II images. A.C.S. and R.L.M. were supported by funding from the Heliophysics Division of NASA's Science Mission Directorate through the Living With a Star Targeted Research and Technology Program, and the Hinode Project. I.S. was supported by NSF's Research Experience for Undergraduates Progra

Exploring EUV Spicules Using 304 Angstrom He II Data from SDO AIA

We present results from a statistical study of He II 304 Angstrom Extreme Ultraviolet (EUV) spicules at the limb of the Sun. We also measured properties of one macrospicule; macrospicules are longer than most spicules, and much broader in width than spicules. We use high-cadence (12 second) and high-resolution (0.6 arcseconds pixels) resolution data from the Atmospheric Imaging Array (AIA) instrument on the Solar Dynamic Observatory (SDO). All of the observed events occurred near the solar north pole, where quiet Sun or coronal hole environments ensued. We examined the maximum lengths, maximum rise velocities, and lifetimes of 33 Extreme Ultraviolet (EUV) spicules and the macrospicule. For the bulk of the Extreme Ultraviolet (EUV) spicules these quantities are, respectively, approximately 10,000-40,000 kilometers, 20-100 kilometers per second, and approximately 100- approximately 1000 seconds. For the macrospicule the corresponding quantities were respectively approximately 60,000 kilometers, approximately 130 kilometers per second, approximately 1800 seconds, which is typical of macrospicules measured by other workers. Therefore macrospicules are taller, longer-lived, and faster than most Extreme Ultraviolet (EUV) spicules. The rise profiles of both the spicules and the macrospicules match well a second-order ("parabolic" ) trajectory, although the acceleration was often weaker than that of solar gravity in the profiles fitted to the trajectories. Our macrospicule also had an obvious brightening at its base at birth, while such brightening was not apparent for the Extreme Ultraviolet (EUV) spicules. Most of the Extreme Ultraviolet (EUV) spicules remained visible during their descent back to the solar surface, although a small percentage of the spicules and the macrospicule faded out before falling back to the surface. Our sample of macrospicules is not yet large enough to determine whether their initiation mechanism is identical to that of Extreme Ultraviolet (EUV) spicules

Evidence of moderation effects in predicting active transport to school

Distance from home to school is an important influence on the decision to use active transport (AT); however, ecological perspectives would suggest this relationship may be moderated by individual, interpersonal and environmental factors. This study investigates whether (i) gender, (ii) biological maturation, (iii) perceived family support for physical activity (PA) and (iv) multiple deprivation moderate the relationship between distance to school and AT.A total of 611 children (11-12 years old, 334 females) were recruited from schools in Leicestershire, UK. Gender, family support for PA, and AT were self-reported. Home and school postcodes were used to determine multiple deprivation and distance to school (km). Predicted age at peak height velocity was used to indicate biological maturation.Logistic regressions revealed the main effects explained 40.2% of the variance in AT; however; distance to school was the only significant predictor. Further analyses revealed that distance to school had a greater negative impact on the use of AT in late-maturing (OR: 3.60, CI: 1.45-8.96), less deprived (OR: 3.54, CI: 1.17-10.72) and children with low family support of PA (OR: 0.26, CI: 0.11-0.61).This study provides evidence that, although distance to school might be the strongest predictor of AT, this relationship is complex

Health Risk Assessment for Cyanobacterial Toxins in Seafood

Cyanobacteria (blue-green algae) are abundant in fresh, brackish and marine waters worldwide. When toxins produced by cyanobacteria are present in the aquatic environment, seafood harvested from these waters may present a health hazard to consumers. Toxicity hazards from seafood have been internationally recognised when the source is from marine algae (dinoflagellates and diatoms), but to date few risk assessments for cyanobacterial toxins in seafood have been presented. This paper estimates risk from seafood contaminated by cyanobacterial toxins, and provides guidelines for safe human consumption

Exploring He II 304 A Spicules and Macrospicules at the Solar Limb

No abstract availabl

Exploring He II 304 Angstrom Spicules and Macrospicules at the Solar Limb

No abstract availabl

Can Text Messages Reach the Parts Other Process Measures Cannot Reach: An Evaluation of a Behavior Change Intervention Delivered by Mobile Phone?

BackgroundProcess evaluation is essential in developing, piloting and evaluating complex interventions. This often involves observation of intervention delivery and interviews with study participants. Mobile telephone interventions involve no face to face contact, making conventional process evaluation difficult. This study assesses the utility of novel techniques for process evaluation involving no face to face contact.MethodsText messages were delivered to 34 disadvantaged men as part of a feasibility study of a brief alcohol intervention. Process evaluation focused on delivery of the text messages and responses received from study participants. The computerized delivery system captured data on receipt of the messages. The text messages, delivered over 28 days, included nine which asked questions. Responses to these questions served as one technique for process evaluation by ascertaining the nature of engagement with the study and with steps on the causal chain to behavior change.ResultsA total of 646 SMS text messages were sent to participants. Of these, 613 messages (95%) were recorded as delivered to participants’ telephones. 88% of participants responded to messages that asked questions. There was little attenuation in responses to the questions across the intervention period. Content analysis of the responses revealed that participants engaged with text messages, thought deeply about their content and provided carefully considered personal responses to the questions.ConclusionsSocially disadvantaged men, a hard to reach population, engaged in a meaningful way over a sustained period with an interactive intervention delivered by text message. The novel process measures used in the study are unobtrusive, low cost and collect real-time data on all participants. They assessed the fidelity of delivery of the intervention and monitored retention in the study. They measured levels of engagement and identified participants’ reactions to components of the intervention. These methods provide a valuable addition to conventional process evaluation techniques