Surface and bulk transitions in three-dimensional O(n) models

Using Monte Carlo methods and finite-size scaling, we investigate surface criticality in the O$(n)$ models on the simple-cubic lattice with $n=1$, 2, and 3, i.e. the Ising, XY, and Heisenberg models. For the critical couplings we find $K_{\rm c}(n=2)=0.454 1655 (10)$ and $K_{\rm c}(n=3)= 0.693 002 (2)$. We simulate the three models with open surfaces and determine the surface magnetic exponents at the ordinary transition to be $y_{h1}^{\rm (o)}=0.7374 (15)$, $0.781 (2)$, and $0.813 (2)$ for $n=1$, 2, and 3, respectively. Then we vary the surface coupling $K_1$ and locate the so-called special transition at $\kappa_{\rm c} (n=1)=0.50214 (8)$ and $\kappa_{\rm c} (n=2)=0.6222 (3)$, where $\kappa=K_1/K-1$. The corresponding surface thermal and magnetic exponents are $y_{t1}^{\rm (s)} =0.715 (1)$ and $y_{h1}^{\rm (s)} =1.636 (1)$ for the Ising model, and $y_{t1}^{\rm (s)} =0.608 (4)$ and$y_{h1}^{\rm (s)} =1.675 (1)$ for the XY model. Finite-size corrections with an exponent close to -1/2 occur for both models. Also for the Heisenberg model we find substantial evidence for the existence of a special surface transition.Comment: TeX paper and 10 eps figure

Using a Smartphone App and Coaching Group Sessions to Promote Residents' Reflection in the Workplace

Item does not contain fulltextPROBLEM: Reflecting on workplace-based experiences is necessary for professional development. However, residents need support to raise their awareness of valuable moments for learning and to thoughtfully analyze those learning moments afterwards. APPROACH: From October to December 2012, the authors held a multidisciplinary six-week postgraduate training module focused on general competencies. Residents were randomly assigned to one of four conditions with varying degrees of reflection support; they were offered (1) a smartphone app, (2) coaching group sessions, (3) a combination of both, or (4) neither type of support. The app allowed participants to capture in real time learning moments as a text note, audio recording, picture, or video. Coaching sessions held every two weeks aimed to deepen participants' reflection on captured learning moments. Questionnaire responses and reflection data were compared between conditions to assess the effects of the app and coaching sessions on intensity and frequency of reflection. OUTCOMES: Sixty-four residents participated. App users reflected more often, captured more learning moments, and reported greater learning progress than nonapp users. Participants who attended coaching sessions were more alert to learning moments and pursued more follow-up learning activities to improve on the general competencies. Those who received both types of support were most alert to these learning moments. NEXT STEPS: A simple mobile app for capturing learning moments shows promise as a tool to support workplace-based learning, especially when combined with coaching sessions. Future research should evaluate these tools on a broader scale and in conjunction with residents' and students' personal digital portfolios

Morphology of the human internal vertebral venous plexus: a cadaver study after intravenous Araldite CY 221 injection

Reviewing the literature on the vascular anatomy of the spinal epidural space, it appeared that the knowledge of the internal vertebral venous plexus is limited. Injection studies of the entire internal vertebral venous plexus after application of modern techniques, to the best of our knowledge, have never been performed. Based on the clinical importance of these structures, it was decided to study the human vertebral venous system after Araldite CY 221 injection, in order to update the morphological characteristics of the internal vertebral venous system. The vertebral venous systems of ten fresh human cadavers, between 64 and 93 years of age, were injected with Araldite CY 221 mixture. All cadavers were dissected and the posterior and anterior internal vertebral venous plexuses were studied in detail. The anterior part of the internal vertebral venous plexus is fairly constant. On the contrary, the posterior internal vertebral venous plexus showed a striking segmental and interindividual variability. In the thoracic area, two types of traversing veins are observed. Both types show a somewhat symmetrical "inversed V" configuration. No anatomical valves were observed. Nevertheless, anterograde flushing (via the femoral veins) of the vertebral venous system appeared to proceed much faster than retrograde flushing (via the superior vena cava). The classical picture of the internal vertebral venous plexus appears a simplification of the actual situation. Especially in the posterior part, segmental and interindividual differences are prominent. The preferential direction of the flow during flushing suggests the presence of functional valves, which are probably located in the thoracic part of the posterior internal vertebral venous plexus, resulting from the typical shape of the veins in this area. This might explain the difficulties with imaging of the posterior part of the internal vertebral venous plexus in vitro as well as in vivo. Further study is needed to determine whether the configuration of the posterior internal vertebral venous plexus in younger individuals is different, compared with the presently studied aged subjects