Aerodynamic performance of a bypass engine with fan nozzle exit area change by warped chevrons

Variation of the bypass nozzle exit area enables optimization of the turbofan engine operating cycle over a wider range of operational conditions resulting in improved thrust and/or fuel consumption. Two mechanisms for varying the nozzle area have been investigated. The first uses an array of chevrons which when closed, form a full body of revolution and when warped/curved, increase the exit area while forming a serrated trailing edge. The second technique incorporates an axially translating section of the nacelle shroud and uses the change in the nozzle boat-tail radial location with the axial location as a means to vary the nozzle exit area. To analyse the effects on a typical rotor/stator stage, computational fluid dynamics simulations of the NASA Rotor 67, Stator 67A stage integrated into a custom-built nacelle were performed. Nozzles with 8, 12, and 16 chevrons were simulated to evaluate the impact of the variation in geometry upon the nacelle wake and local forces. Gross thrust of the nacelle and the turbulent kinetic energy (TKE) variation through the wake is compared. The chevron nozzle attains a nearly 2 per cent maximum thrust improvement over the translating nozzle technique. The chevron nozzle also has significantly lower (nearly 8 per cent) peak TKE levels in the jet plume.

Recurrent lower gastrointestinal bleeding secondary to cytomegalovirus-associated colonic ulcer in a non human immunodeficiency virus infected patient:Timely diagnosis and treatment averted surgery

Mr C, a 68-year-old Chinese male with diabetes mellitus, previous stroke and ischaemic cardiomyopathy on clopidogrel, presented with haematochezia. Colonoscopy showed a sigmoid ulcer, which was treated endoscopically. Histology of the biopsy from the ulcer revealed non-specific changes. However, he presented with recurrent bleeding from this non-healing sigmoid ulcer. A review of the histologic specimen revealed CMV intranuclear inclusion bodies. He was treated with intravenous ganciclovir, with no further hematochezia.

Keywords Hematochezia, cytomegalovirus, ulcer

A virtual surgery in general practice: evaluation of a novel undergraduate virtual patient learning package

Background: A suite of 10 online virtual patients developed using the IVIMEDS ‘Riverside’ authoring tool has been introduced into our undergraduate general practice clerkship. These cases provide a multimedia-rich experience to students. Their interactive nature promotes the development of clinical reasoning skills such as discriminating key clinical features, integrating information from a variety of sources and forming diagnoses and management plans.

Aims: To evaluate the usefulness and usability of a set of online virtual patients in an undergraduate general practice clerkship.
Method: Online questionnaire completed by students after their general practice placement incorporating the System Usability Scale questionnaire.

Results: There was a 57% response rate. Ninety-five per cent of students agreed that the online package was a useful learning tool and ranked virtual patients third out of six learning modalities. Questions and answers and the use of images and videos were all rated highly by students as useful learning methods. The package was perceived to have a high level of usability among respondents.

Conclusion: Feedback from students suggest that this implementation of virtual patients, set in primary care, is user friendly and rated as a valuable adjunct to their learning. The cost of production of such learning resources demands close attention to design.