Benchmarking Fast-to-Alfven Mode Conversion in a Cold MHD Plasma

Alfv\'en waves may be generated via mode conversion from fast magneto-acoustic waves near their reflection level in the solar atmosphere, with implications both for coronal oscillations and for active region helio-seismology. In active regions this reflection typically occurs high enough that the Alfv\'en speed $a$ greatly exceeds the sound speed $c$, well above the $a=c$ level where the fast and slow modes interact. In order to focus on the fundamental characteristics of fast/Alfv\'en conversion, stripped of unnecessary detail, it is therefore useful to freeze out the slow mode by adopting the gravitationally stratified cold MHD model $c\to0$. This provides a benchmark for fast-to-Alfv\'en mode conversion in more complex atmospheres. Assuming a uniform inclined magnetic field and an exponential Alfv\'en speed profile with density scale height $h$, the Alfv\'en conversion coefficient depends on three variables only; the dimensionless transverse-to-the-stratification wavenumber $\kappa=kh$, the magnetic field inclination from the stratification direction $\theta$, and the polarization angle $\phi$ of the wavevector relative to the plane containing the stratification and magnetic field directions. We present an extensive exploration of mode conversion in this parameter space and conclude that near-total conversion to outward-propagating Alfv\'en waves typically occurs for small $\theta$ and large $\phi$ ($80^\circ$--$90^\circ$), though it is absent entirely when $\theta$ is exactly zero (vertical field). For wavenumbers of helioseismic interest, the conversion region is broad enough to encompass the whole chromosphere.Comment: 14 pages plus supplementary tables. Astrophys J (accepted 25 May 2011). Two ancillary animations (animated gif) attache

I felt that I could be whatever I wanted : Pre-service drama teachers\u27 prior experiences and beliefs about teaching drama

Pre-service drama teachers enter teacher training with established ideas and beliefs about teaching. These beliefs, based on experience, are informed by many hours spent in schools, and the pedagogies – both effective and ineffective – utilised by their teachers. This research explores the influence of some of these prior experiences on pre-service drama teachers’ beliefs about teaching drama, this being important in the way that not only shapes their practicum experiences, but also what will then influence their own teaching of drama. Individual interviews with four pre-service drama teachers revealed the complexity and dynamics of these participants’ lived experience with narrative portraits constructed as part of the process of inquiry. This process not only built on the ways that knowledge is constructed, and the beliefs and values that underscore these, but also how these are shared and made known. Three key beliefs emerged. First, drama both provides and creates a sense of belonging: belonging being key for students and integral to the work of drama teachers. Second, drama education can promote self-discovery and personal development, having therefore the potential to transform lives. Third, effective drama teachers are valued as hardworking, highly skilled professionals dedicated to bringing out their students’ potential. This paper emphasises the importance for pre-service drama teachers to be aware of how their beliefs and subjectivities both influence their own experiences, and consequently have influence over the ways they work with students in the drama space

Biodiversity Offsets: A Cost-Effective Interim Solution to Seabird Bycatch in Fisheries?

The concept of biodiversity offsets is well established as an approach to environmental management. The concept has been suggested for environmental management in fisheries, particularly in relation to the substantial numbers of non-target species—seabirds in particular—caught and killed as incidental bycatch during fishing activities. Substantial areas of fisheries are being closed to protect these species at great cost to the fishing industry. However, other actions may be taken to offset the impact of fishing on these populations at lower cost to the fishing industry. This idea, however, has attracted severe criticism largely as it does not address the underlying externality problems created by the fishing sector, namely seabird fishing mortality. In this paper, we re-examine the potential role of compensatory mitigation as a fisheries management tool, although from the perspective of being an interim management measure while more long-lasting solutions to the problem are found. We re-model an example previously examined by both proponents and opponents of the approach, namely the cost effectiveness of rodent control relative to fishery area closures for the conservation of a seabird population adversely affected by an Australian tuna fishery. We find that, in the example being examined, invasive rodent eradication is at least 10 times more cost effective than area closures. We conclude that, while this does not solve the actual bycatch problem, it may provide breathing space for both the seabird species and the industry to find longer term means of reducing bycatch

Temperature-dependent Hall scattering factor and drift mobility in remotely doped Si:B/SiGe/Si heterostructures

Hall-and-Strip measurements on modulation-doped SiGe heterostructures and combined Hall and capacitance–voltage measurements on metal-oxide-semiconductor (MOS)-gated enhancement mode structures have been used to deduce Hall scattering factors, rH, in the Si1 – xGex two-dimensional hole gas. At 300 K, rH was found to be equal to 0.4 for x = 0.2 and x = 0.3. Knowing rH, it is possible to calculate the 300 K drift mobilities in the modulation-doped structures which are found to be 400 cm2 V – 1 s – 1 at a carrier density of 3.3 × 1011 cm – 2 for x = 0.2 and 300 cm2 V – 1 s – 1 at 6.3 × 1011 cm – 2 for x = 0.3, factors of between 1.5 and 2.0 greater than a Si pMOS control

Raising the Curtain: Investigating the Practicum Experiences of Pre-service Drama Teachers

The practicum is internationally recognised as a valuable component of teacher education. It is an opportunity for pre-service teachers to develop teaching skills in authentic ways and pursue professional inquiry into practice. While extensive research has been conducted into the practicum generally, little research focuses on the practicum experience for pre-service drama teachers. This article, investigates the preparation of drama teachers for the profession with a particular focus on the practicum component of pre-service education. Drawing on the experiences of 19 pre-service drama teachers from a Western Australian university, focus-groups were conducted in order to scope the key components of the enablers and constraints embedded in their practicum. Four key themes were identified: stress, self-efficacy, mentoring practices, and teaching craft. In addition, the dimensions of each theme in relation to the adequate preparation of drama teachers were further revealed. Particular to the research was the role played by the extra curricula demands associated with drama as a learning area, and the mismatch between participant’s experience of drama and the culture shock many experienced in contemporary times. The research further emphasised the highs and lows of practicum, illuminating conditions most conducive to a quality practicum where pre-service drama teachers are able to develop pedagogy and the self-efficacy necessary to be an effective drama teacher, and importantly, one who remains in the profession

The College News, 1929-11-20, Vol. 16, No. 07

Bryn Mawr College student newspaper. Merged with The Haverford News in 1968 to form the Bi-college News (with various titles from 1968 on). Published weekly (except holidays) during the academic year

The varying role of the GP in the pathway between colonoscopy and surgery for colorectal cancer: a retrospective cohort study

Extent: 11p.Objectives: To describe general practitioner (GP) involvement in the treatment referral pathway for colorectal cancer (CRC) patients. Design: A retrospective cohort analysis of linked data. Setting: A population-based sample of CRC patients diagnosed from August 2004 to December 2007 in New South Wales, Australia, using the 45 and Up Study, cancer registry diagnosis records, inpatient hospital records and Medicare claims records. Participants: 407 CRC patients who had a colonoscopy followed by surgery. Primary outcome measures: Patterns of GP consultations between colonoscopy and surgery (ie, between diagnosis and treatment). We investigated whether consulting a GP presurgery was associated with time to surgery, postsurgical GP consultations or rectal cancer cases having surgery in a centre with radiotherapy facilities. Results: Of the 407 patients, 43% (n=175) had at least one GP consultation between colonoscopy and surgery. The median time from colonoscopy to surgery was 27 days for those with an intervening GP consultation and 15 days for those without the consultation. 55% (n=223) had a GP consultation up to 30 days postsurgery; it was more common in cases of patients who consulted a GP presurgery than for those who did not (65% and 47%, respectively, adjusted OR 2.71, 95% CI 1.50 to 4.89, p=0.001). Of the 142 rectal cancer cases, 23% (n=33) had their surgery in a centre with radiotherapy facilities, with no difference between those who did and did not consult a GP presurgery (21% and 25% respectively, adjusted OR 0.84, 95% CI 0.27 to 2.63, p=0.76). Conclusions: Consulting a GP between colonoscopy and surgery was associated with a longer interval between diagnosis and treatment, and with further GP consultations postsurgery, but for rectal cancer cases it was not associated with treatment in a centre with radiotherapy facilities. GPs might require a more defined and systematic approach to CRC management.David Goldsbury, Mark Harris, Shane Pascoe, Michael Barton, Ian Olver, Allan Spigelman, Justin Beilby, Craig Veitch, David Weller, Dianne L O'Connel

Living and Learning With New Media: Summary of Findings From the Digital Youth Project

Summarizes findings from a three-year study of how new media have been integrated into youth behaviors and have changed the dynamics of media literacy, learning, and authoritative knowledge. Outlines implications for educators, parents, and policy makers

Benchmarking Fast-to-Alfv\'en Mode Conversion in a Cold MHD Plasma. II. How to get Alfv\'en waves through the Solar Transition Region

Alfv\'en waves may be difficult to excite at the photosphere due to low ionization fraction and suffer near-total reflection at the transition region (TR). Yet they are ubiquitous in the corona and heliosphere. To overcome these difficulties, we show that they may instead be generated high in the chromosphere by conversion from reflecting fast magnetohydrodynamic waves, and that Alfv\'enic transition region reflection is greatly reduced if the fast reflection point is within a few scale heights of the TR. The influence of mode conversion on the phase of the reflected fast wave is also explored. This phase can potentially be misinterpreted as a travel speed perturbation, with implications for the practical seismic probing of active regions.Comment: 13 pages, 10 figures, accepted by ApJ 17 March 201