A CFD-DEM solver to model bubbly flow. Part I: Model development and assessment in upward vertical pipes

[EN] In the computational modeling of two-phase flow, many uncertainties are usually faced in simulations and validations with experiments. This has traditionally made it difficult to provide a general method to predict the two-phase flow characteristics for any geometry and condition, even for bubbly flow regimes. Thus, we focus our research on studying in depth the bubbly flow modeling and validation from a critical point of view. The conditions are intentionally limited to scenarios where coalescence and breakup can be neglected, to concentrate on the study of bubble dynamics and its interaction with the main fluid. This study required the development of a solver for bubbly flow with higher resolution level than TFM and a new methodology to obtain the data from the simulation. Part I shows the development of a solver based on the CFD-DEM formulation. The motion of each bubble is computed individually with this solver and aspects as inhomogeneity, nonlinearity of the interfacial forces, bubble-wall interactions and turbulence effects in interfacial forces are taken into account. To develop the solver, several features that are not usually required for traditional CFD-DEM simulations but are relevant for bubbly flow in pipes, have been included. Models for the assignment of void fraction into the grid, seeding of bubbles at the inlet, pressure change influence on the bubble size and turbulence effects on both phases have been assessed and compared with experiments for an upward vertical pipe scenario. Finally, the bubble path for bubbles of different size have been investigated and the interfacial forces analyzed. (C) 2017 Elsevier Ltd. All rights reserved.The authors sincerely thank the ''Plan Nacional de I + D+ i" for funding the project MODEXFLAT ENE2013-48565-C2-1-P and ENE2013-48565-C2-2-P.Peña-Monferrer, C.; Monrós Andreu, G.; Chiva Vicent, S.; Martinez-Cuenca, R.; Muñoz-Cobo, JL. (2018). A CFD-DEM solver to model bubbly flow. Part I: Model development and assessment in upward vertical pipes. Chemical Engineering Science. 176:524-545. https://doi.org/10.1016/j.ces.2017.11.005S52454517

Ocrelizumab versus Interferon Beta-1a in Relapsing Multiple Sclerosis

Supported by F. Hoffmann–La Roche

Effectiveness of rifaximin and fluoroquinolones in preventing travelers’ diarrhea (TD): a systematic review and meta-analysis

Abstract Background Recent developments related to a safe and effective nonabsorbable antibiotic, rifaximin, and identification of postinfectious irritable bowel syndrome as a frequent sequela call for a need to reconsider the value of primary prevention of traveler’s diarrhea (TD) with antibiotics. Methods Randomized, placebo-controlled, double-blind studies evaluating the effectiveness and safety of rifaximin or a fluoroquinolone chemoprophylaxis against TD were pooled using a random effects model and assessed for heterogeneity. Results The nine studies (four rifaximin and five fluoroquinolone) included resulted in pooled relative risk estimates of 0.33 (95% CI = 0.24–0.45, I2 = 3.1%) and 0.12 (95% CI = 0.07–0.20, I2 =0.0%), respectively. Similar rates of treatment emergent adverse events were found between antibiotic and placebo groups. Conclusions This meta-analysis supports the effectiveness of antibiotics in preventing TD. However, further studies that include prevention of secondary chronic health outcomes among travelers to different geographic regions, and a formal risk-benefit analysis for antibiotic chemoprophylaxis, are needed.</p

Patients with bicuspid and tricuspid aortic valve exhibit distinct regional microrna signatures in mildly dilated ascending aorta

MicroRNAs are able to modulate gene expression in a range of diseases. We focused on microRNAs as potential contributors to the pathogenesis of ascending aorta (AA) dilatation in patients with stenotic tricuspid (TAV) or bicuspid aortic valve (BAV). Aortic specimens were collected from the ‘concavity’ and the ‘convexity’ of mildly dilated AAs and of normal AAs from heart transplant donors. Aortic RNA was analyzed through PCR arrays, profiling the expression of 84 microRNAs involved in cardiovascular disease. An in silico analysis identified the potential microRNA–mRNA interactions and the enriched KEGG pathways potentially affected by microRNA changes in dilated AAs. Distinct signatures of differentially expressed microRNAs are evident in TAV and BAV patients vs. donors, as well as differences between aortic concavity and convexity in patients only. MicroRNA changes suggest a switch of SMC phenotype, with particular reference to TAV concavity. MicroRNA changes potentially affecting mechanotransduction pathways exhibit a higher prevalence in BAV convexity and in TAV concavity, with particular reference to TGF-β1, Hippo, and PI3K/Akt/FoxO pathways. Actin cytoskeleton emerges as potentially affected by microRNA changes in BAV convexity only. MicroRNAs could play distinct roles in BAV and TAV aortopathy, with possible implications in diagnosis and therapy