Ambipolar Drift Heating in Turbulent Molecular Clouds

Although thermal pressure is unimportant dynamically in most molecular gas, the temperature is an important diagnostic of dynamical processes and physical conditions. This is the first of two papers on thermal equilibrium in molecular clouds. We present calculations of frictional heating by ion-neutral (or ambipolar) drift in three-dimensional simulations of turbulent, magnetized molecular clouds. We show that ambipolar drift heating is a strong function of position in a turbulent cloud, and its average value can be significantly larger than the average cosmic ray heating rate. The volume averaged heating rate per unit volume due to ambipolar drift, H_AD ~ |JxB|^2 ~ B^4/L_B^2, is found to depend on the rms Alfvenic Mach number, M_A, and on the average field strength, as H_AD ~ M_A^2^4. This implies that the typical scale of variation of the magnetic field, L_B, is inversely proportional to M_A, which we also demonstrate.Comment: 37 pages, 9 figures include

Deliberate Apprenticeship in the Pediatric Emergency Department Improves Experience for Third-year Students

INTRODUCTION: The Pediatric Emergency Department (PED) provides medical students with learning in a high-volume, fast-paced environment; characteristics that can be stressful for new students. Shadowing can improve transitioning, yet this alone does not facilitate students’ development of independent medical care competencies. This study evaluates if third-year medical students’ deliberate apprenticeship with senior residents increases students’ comfort and patient exposure in the PED. METHODS: This study took place over the 2011-2012 academic year, and study participants were all third-year medical students during their pediatric clerkship rotation. This was a prospective educational intervention assigning students to randomized control blocks of deliberate apprenticeship (DA) intervention or control. DA students were paired with a senior resident who oriented and worked with the student, while control students were unpaired. All students completed a 20-question structured survey at shift end, which included questions about their perception of the learning environment, comfort with, and number of patient care responsibilities performed. We used independent Mann-Whitney and t-tests to compare experiences between the groups. Statistical significance was defined as p<0.05. We used the constant comparative method to qualitatively analyze students’ comments. RESULTS: Response rate was 85% (145/169). Students also rated on 5-point Likert-scale their level of comfort with defined aspects of working in the PED. DA students (n=76) were significantly more comfortable obtaining histories (4.2 versus 3.8) and formulating differential diagnoses (3.9 versus 3.4). DA students also performed more physical exams (2.9 versus 2.4). We categorized themes from the qualitative analysis of the students’ comments about their PED experience. The titles for these themes are as follows: PED provides a good learning experience; uncertainty about the medical student’s role in the PED; third-year medical students compete with other learners for teaching attention; opportunities provided to medical students for inclusion in patient care; personal knowledge deficits limit the ability to participate in the PED; PED pace affects learning opportunities. CONCLUSION: DA constitutes a feasible approach to the clinical learning environment that increases students’ patient care experiences and may ease transitioning for undergraduate medical students to new clinical environments

The periodic variations of a white-light flare observed with ULTRACAM

High time resolution observations of a white-light flare on the active star EQ PegB show evidence of intensity variations with a period of ≈10 s. The period drifts to longer values during the decay phase of the flare. If the oscillation is interpreted as an impulsively-excited, standing-acoustic wave in a flare loop, the period implies a loop length of ≈3.4 Mm and ≈6.8 Mm for the case of the fundamental mode and the second harmonic, respectively. However, the small loop lengths imply a very high modulation depth making the acoustic interpretation unlikely. A more realistic interpretation may be that of a fast-MHD wave, with the modulation of the emission being due to the magnetic field. Alternatively, the variations could be due to a series of reconnection events. The periodic signature may then arise as a result of the lateral separation of individual flare loops or current sheets with oscillatory dynamics (i.e., periodic reconnection)

Kramers rate theory of ionization and dissociation of bound states

Calculating the microscopic dissociation rate of a bound state, such as a classical diatomic molecule, has been difficult so far. The problem was that standard theories require an energy barrier over which the bound particle (or state) escapes into the preferred low-energy state. This is not the case when the long-range repulsion responsible for the barrier is either absent or screened (as in Cooper pairs, ionized plasma, or biomolecular complexes). We solve this classical problem by accounting for entropic memory at the microscopic level. The theory predicts dissociation rates for arbitrary potentials and is successfully tested on the example of plasma, where it yields an estimate of ionization in the core of Sun in excellent agreement with experiments. In biology, the new theory accounts for crowding in receptor-ligand kinetics and protein aggregation

'The world is full of big bad wolves': investigating the experimental therapeutic spaces of R.D. Laing and Aaron Esterson

In conjunction with the recent critical assessments of the life and work of R.D. Laing, this paper seeks to demonstrate what is revealed when Laing’s work on families and created spaces of mental health care are examined through a geographical lens. The paper begins with an exploration of Laing’s time at the Tavistock Clinic in London during the 1960s, and of the co-authored text with Aaron Esterson entitled, Sanity, Madness and the Family (1964). The study then seeks to demonstrate the importance Laing and his colleague placed on the time-space situatedness of patients and their worlds. Finally, an account is provided of Laing’s and Esterson’s spatial thinking in relation to their creation of both real and imagined spaces of therapeutic care

Promoting medical students’ reflection on competencies to advance a global health equities curriculum

Abstract Background The move to frame medical education in terms of competencies – the extent to which trainees “can do” a professional responsibility - is congruent with calls for accountability in medical education. However, the focus on competencies might be a poor fit with curricula intended to prepare students for responsibilities not emphasized in traditional medical education. This study examines an innovative approach to the use of potential competency expectations related to advancing global health equity to promote students’ reflections and to inform curriculum development. Methods In 2012, 32 medical students were admitted into a newly developed Global Health and Disparities (GHD) Path of Excellence. The GHD program takes the form of mentored co-curricular activities built around defined competencies related to professional development and leadership skills intended to ameliorate health disparities in medically underserved settings, both domestically and globally. Students reviewed the GHD competencies from two perspectives: a) their ability to perform the identified competencies that they perceived themselves as holding as they began the GHD program and b) the extent to which they perceived that their future career would require these responsibilities. For both sets of assessments the response scale ranged from “Strongly Disagree” to “Strongly Agree.” Wilcoxon’s paired T-tests compared individual students’ ordinal rating of their current level of ability to their perceived need for competence that they anticipated their careers would require. Statistical significance was set at p < .01. Results Students’ ratings ranged from “strongly disagree” to “strongly agree” that they could perform the defined GHD-related competencies. However, on most competencies, at least 50 % of students indicated that the stated competencies were beyond their present ability level. For each competency, the results of Wilcoxon paired T-tests indicate – at statistically significant levels - that students perceive more need in their careers for GHD-program defined competencies than they currently possess. Conclusion This study suggests congruence between student and program perceptions of the scope of practice required for GHD. Students report the need for enhanced skill levels in the careers they anticipate. This approach to formulating and reflecting on competencies will guide the program’s design of learning experiences aligned with students’ career goals.http://deepblue.lib.umich.edu/bitstream/2027.42/109541/1/12909_2013_Article_919.pd