Responding to change in a medical student rural community service: Insights from activity theory.

INTRODUCTION: Medical students have voluntarily initiated service-learning programmes with the aim of providing assistance to medically underserved communities, especially within remote indigenous villages. However, their values and goals have been challenged because rural health care demands have changed considerably since the introduction of integrated delivery system (IDS) programmes, that is, programmes that integrate local health care providers with outreach services provided by contracted hospitals. Our study aimed to explore how a health care service-learning group negotiates its position and how it responds to the tension of IDS implementation and changes in rural health care demand. METHODS: Medical students who have been engaged in building or operating the health care service-learning group of one university in Taiwan were invited to participate in the study. We used cultural-historical activity theory (CHAT) to help us interpret the interactions between students, indigenous communities and the public health sectors and to understand the evolution of the service-learning relationship and its effectiveness. RESULTS: Eighteen participants were recruited for in-depth interviews. The implementation of IDS programmes brought change to the rural community and challenges to students' service learning. Utilising cultural-historical activity theory, we highlighted points of fragmentation within the system. This tension lead to medical students' personal conflict and also served as an impetus for change and learning. Flexible goal setting and coping ability were considered critical to the sustainability and maintenance of students' value systems. CONCLUSIONS: IDS implementation can upset the balance of rural health care supply and demand, resulting in accumulating tensions within and between activity systems. Those contradictions exposed medical students to an expansive learning cycle, resulting in transformational change and learning. Under the context of IDS programmes, health care service-learning can create a 'win-win' situation. Not merely medical students but also community residents gain benefits. This result may be extrapolated to health care service-learning programmes with similar context.

Thrombin Induces COX-2 and PGE2 Expression via PAR1/PKCalpha/MAPK-Dependent NF-kappaB Activation in Human Tracheal Smooth Muscle Cells.

The inflammation of the airway and lung could be triggered by upregulation cyclooxygenase (COX)-2 and prostaglandin E2 (PGE2) induced by various proinflammatory factors. COX-2 induction by thrombin has been shown to play a vital role in various inflammatory diseases. However, in human tracheal smooth muscle cells (HTSMCs), how thrombin enhanced the levels of COX-2/PGE2 is not completely characterized. Thus, in this study, the levels of COX-2 expression and PGE2 synthesis induced by thrombin were determined by Western blot, promoter-reporter assay, real-time PCR, and ELISA kit. The various signaling components involved in the thrombin-mediated responses were differentiated by transfection with siRNAs and selective pharmacological inhibitors. The role of NF-κB was assessed by a chromatin immunoprecipitation (ChIP) assay, immunofluorescent staining, as well as Western blot. Our results verified that thrombin markedly triggered PGE2 secretion via COX-2 upregulation which were diminished by the inhibitor of thrombin (PPACK), PAR1 (SCH79797), Gi/o protein (GPA2), Gq protein (GPA2A), PKCα (Gö6976), p38 MAPK (SB202190), JNK1/2 (SP600125), MEK1/2 (U0126), or NF-κB (helenalin) and transfection with siRNA of PAR1, Gq α, Gi α, PKCα, JNK2, p38, p42, or p65. Moreover, thrombin induced PAR1-dependent PKCα phosphorylation in HTSMCs. We also observed that thrombin induced p38 MAPK, JNK1/2, and p42/p44 MAPK activation through a PAR1/PKCα pathway. Thrombin promoted phosphorylation of NF-κB p65, leading to nuclear translocation and binding to the COX-2 promoter element to enhance promoter activity, which was reduced by Gö6976, SP600125, SB202190, or U0126. These findings supported that COX-2/PGE2 expression triggered by thrombin was engaged in PAR1/Gq or Gi/o/PKCα/MAPK-dependent NF-κB activation in HTSMCs.

Quantification of dental prostheses on cone-beam CT images by the Taguchi method.

The gray values accuracy of dental cone-beam computed tomography (CBCT) is affected by dental metal prostheses. The distortion of dental CBCT gray values could lead to inaccuracies of orthodontic and implant treatment. The aim of this study was to quantify the effect of scanning parameters and dental metal prostheses on the accuracy of dental cone-beam computed tomography (CBCT) gray values using the Taguchi method. Eight dental model casts of an upper jaw including prostheses, and a ninth prosthesis-free dental model cast, were scanned by two dental CBCT devices. The mean gray value of the selected circular regions of interest (ROIs) were measured using dental CBCT images of eight dental model casts and were compared with those measured from CBCT images of the prosthesis-free dental model cast. For each image set, four consecutive slices of gingiva were selected. The seven factors (CBCTs, occlusal plane canting, implant connection, prosthesis position, coping material, coping thickness, and types of dental restoration) were used to evaluate scanning parameter and dental prostheses effects. Statistical methods of signal to noise ratio (S/N) and analysis of variance (ANOVA) with 95% confidence were applied to quantify the effects of scanning parameters and dental prostheses on dental CBCT gray values accuracy. For ROIs surrounding dental prostheses, the accuracy of CBCT gray values were affected primarily by implant connection (42%), followed by type of restoration (29%), prostheses position (19%), coping material (4%), and coping thickness (4%). For a single crown prosthesis (without support of implants) placed in dental model casts, gray value differences for ROIs 1-9 were below 12% and gray value differences for ROIs 13-18 away from pros-theses were below 10%. We found the gray value differences set to be between 7% and 8% for regions next to a single implant-supported titanium prosthesis, and between 46% and 59% for regions between double implant-supported, nickel-chromium alloys (Ni-Cr) prostheses. Quantification of the effect of prostheses and scanning parameters on dental CBCT gray values was assessed.

Reverse ray tracing for transformation optics.

Ray tracing is an important technique for predicting optical system performance. In the field of transformation optics, the Hamiltonian equations of motion for ray tracing are well known. The numerical solutions to the Hamiltonian equations of motion are affected by the complexities of the inhomogeneous and anisotropic indices of the optical device. Based on our knowledge, no previous work has been conducted on ray tracing for transformation optics with extreme inhomogeneity and anisotropicity. In this study, we present the use of 3D reverse ray tracing in transformation optics. The reverse ray tracing is derived from Fermat's principle based on a sweeping method instead of finding the full solution to ordinary differential equations. The sweeping method is employed to obtain the eikonal function. The wave vectors are then obtained from the gradient of that eikonal function map in the transformed space to acquire the illuminance. Because only the rays in the points of interest have to be traced, the reverse ray tracing provides an efficient approach to investigate the illuminance of a system. This approach is useful in any form of transformation optics where the material property tensor is a symmetric positive definite matrix. The performance and analysis of three transformation optics with inhomogeneous and anisotropic indices are explored. The ray trajectories and illuminances in these demonstration cases are successfully solved by the proposed reverse ray tracing method.