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Background: People with HIV (PWH) have increased cardiovascular events, inflammation, and high-risk coronary atherosclerosis. Statin therapy has been shown to lower the risk of cardiovascular disease (CVD) in the general population, but whether this results from reductions in coronary atherosclerosis and is mediated by decreased inflammation remains unknown.Methods: REPRIEVE is a randomized, placebo-controlled trial of pitavastatin calcium (4 mg/day) vs. placebo enrolling at least 7500 PWH between 40-75 years, on antiretroviral therapy (ART), with low to moderate traditional CVD risk. The Mechanistic Substudy of REPRIEVE (A5333s) is co-enrolling 800 participants from 31 US sites. These participants undergo serial contrast enhanced coronary computed tomography angiography (CCTA) and measurements of biomarkers of inflammation and immune activation at baseline and after 2 years of follow-up. The primary objectives are to determine the effects of pitavastatin on noncalcified coronary atherosclerotic plaque (NCP) volume, low attenuation plaque, and positive remodeling and on changes in immune activation and inflammation and to assess relationships between the two. Changes in CAD will be assessed in a standardized fashion by a core lab with expert readers blinded to time points and participant information; immune activation and inflammation assessment is also performed centrally.Results: To date the Mechanistic Substudy has completed planned enrollment, with 805 participants.Conclusion: This study represents the first large, randomized, CCTA-based assessment of the effects of a primary prevention strategy for CVD on high-risk CAD, immune activation and inflammation among PWH. The study will assess pitavastatin's effects on coronary plaque, and the interrelationship of these changes with biomarkers of immune activation and inflammation in PWH to determine mechanisms of CVD prevention and improved outcomes in this population. [ABSTRACT FROM AUTHOR]

Bypass pneumatic conveying is an alternative way to convey material which does not have dense phase transport capability. The computational fluid dynamics based commercial software Fluent 6.3 is used to investigate the pressure drop as well as the gas–solid flow behaviour in a bypass pneumatic conveying system. The conveyed material was sand with a mean particle size of 378 µm and the solid loading ratio was in the range of 10–123. The conventional frictional-kinetic model combining frictional and kinetic stresses simultaneously was applied for pressure drop prediction. The simulation results were then compared with experimental results from bypass pneumatic conveying tests. Selected image results from the computational fluid dynamics simulations were utilised and compared with images captured from high speed camera. In addition, a test case with low air mass flow rate and high solid loading ratio 82.49 was chosen as an example to show detailed gas–solid flow behaviour in the simulation of highly dense flows. It was found that conventional frictional-kinetic model with modified packing limit and friction packing limit has greatly improved the pressure drop prediction result compared with kinetic theory without friction. The detailed analysis for the selected test case showed how the full bore dune formation and deformation of sand and bypass flutes interact. High amplitude fluctuations and variation in pressure and gas velocity were observed. The gas velocity vectors indicate a high degree of air penetration from the flute into the bypass pipe. This behaviour provides an aeration mechanism which is what makes the bypass system work and allows non-dense phase material to be conveyed in a dense mode of flow. [ABSTRACT FROM AUTHOR]

A new frictional-kinetic model is proposed and modified for pressure drop prediction of alumina in a bypass pneumatic conveying system. This new model is based on the conventional Johnson–Jackson frictional-kinetic model. The critical value of solids volume fraction and maximum packing limit are modified based on the fluidized bulk density and tapped bulk density, respectively. In addition, an offset solid volume fraction is introduced into the frictional pressure model as well as into the radial distribution functions which represents the correction factors to modify the probability of collisions between particles when solid phase becomes excessively dense. For the application of the model, computational fluid dynamics (CFD) simulations were conducted by using kinetic theory, conventional frictional-kinetic model and modified frictional-kinetic model. The simulation results were then compared with the experimental results. It was found that the modified frictional-kinetic model showed the largest improvement on pressure drop prediction results compared with results obtained from applying the kinetic theory and the conventional frictional-kinetic model, especially for denser flows with low air mass flow rates and high solid loading ratios (SLR). In addition, the solids volume investigation of CFD simulations shows a strong comparison to the actual flow conditions in the pipe, as transient slug type flow of alumina is observed. [ABSTRACT FROM AUTHOR]