Shock wave formation in radiative plasmas.

The temporal evolution of weak shocks in radiative media is theoretically investigated in this work. The structure of radiative shocks has traditionally been studied in a stationary framework. Their systematic classification is complex because layers of optically thick and thin regions alternate to form a radiatively driven precursor and a temperature-relaxation layer, between which the hydrodynamic shock is embedded. In this work we analyze the formation of weak shocks when two radiative plasmas with different pressures are put in contact. Applying a reductive perturbative method yields a Burgers-type equation that governs the temporal evolution of the perturbed variables including the radiation field. The conditions upon which optically thick and thin solutions exist have been derived and expressed as a function of the shock strength and Boltzmann number. Below a certain Boltzmann number threshold, weak shocks always become optically thick asymptotically in time, while thin solutions appear as transitory structures. The existence of an optically thin regime is related to the presence of an overdense layer in the compressed material. Scaling laws for the characteristic formation time and shock width are provided for each regime. The theoretical analysis is supported by FLASH simulations, and a comprehensive test case has been designed to benchmark radiative hydrodynamic codes.

A mixed methods study to compare models of spirometry delivery in primary care for patients at risk of COPD.

BACKGROUND: To increase recognition of airflow obstruction in primary care, we compared two models of spirometry delivery in a target group at risk of chronic obstructive pulmonary disease (COPD). METHODS: A 6 month qualitative/quantitative cluster randomised study in eight practices compared opportunistic spirometry by "visiting trained nurses" (TN) with optimised "usual care" (UC) from general practitioners (GPs) for smokers and ex-smokers, aged over 35 years. Outcomes were: spirometry uptake and quality, new diagnoses of COPD and GPs' experiences of spirometry. RESULTS: In the eligible target population, 531/904 (59%) patients underwent spirometry in the TN model and 87/1130 (8%) patients in the UC model (p < 0.0001). ATS spirometry standards for acceptability and reproducibility were met by 76% and 44% of tests in the TN and UC models, respectively (p < 0.0001). 125 (24%) patients tested with the TN model and 38 (44%) with the UC model reported a pre-existing respiratory diagnosis (p < 0.0001). Three months after spirometry, when the ratio of forced expiratory volume in 1 s/forced vital capacity (FEV(1)/FVC) was < 0.7 and no prior COPD diagnosis was reported, nine (8%) participants had a new doctor recorded COPD diagnosis in practices with the TN model and two (8%) participants in practices with the UC model. Mislabelling of participants with a diagnosis of COPD when FEV(1)/FVC was > or = 0.7 was present in both models prior to and after spirometry. GPs valued high quality spirometry and increased testing of patients at risk of COPD in the TN model. They identified limitations, including the need for better systematic follow-up of abnormal spirometry and support with interpretation, which may explain persisting underdiagnosis of COPD in practice records. CONCLUSIONS: Although opportunistic testing by visiting trained nurses substantially increased and improved spirometry performance compared with usual care, translating increased detection of airflow obstruction into diagnosis of COPD requires further development of the model. TRIAL REGISTRATION NUMBER: Australian Clinical Trials Registry: registration No 12605000019606.

A severe case of myasthenia gravis during pregnancy.

Myasthenia gravis is characterised by muscle weakness and fatigability, particularly of the facial and extremity muscles, deteriorating during the day. During pregnancy, myasthenia gravis is rare and the course of illness is unpredictable. The present case illustrates that first diagnosed during pregnancy, recurrent exacerbations can appear and lead to life-threatening situations.

New high-flow "cloud" catheter for safer delivery of contrast material.

The authors describe a new angiographic catheter, which delivers equal flow rates through the side holes and reduced flow through the end hole compared with conventional catheters. Computer analysis of catheter-flow models revealed that placement of larger side holes proximally and smaller side holes distally produces more uniform flow rates out of the holes. This decreases the risk of potentially hazardous delivery of high-pressure jets of contrast material from the end hole. The flow pattern is so uniform that it resembles a cloud of contrast material on injection. This catheter design is particularly applicable for 3-5-F catheters, which require high-pressure injections. Clinical testing in 50 cases revealed no extravasations or unintentional selective injections with use of this catheter.