Performance of vortex shedding from a circular cylinder with a slit normal to the stream

Flow-field study was conducted concerning vortex shedding from a circular cylinder with a slit normal to the stream. Experiments were carried out in a low-speed wind tunnel and a water channel, respectively, with emphasis on the impact of the slit width on the quality of the vortex shedding signal measured. It is found that among the cases studied, whose slit widths ranging from 0 to 0.3 d, where d denotes the diameter of the circular cylinder, an optimal range of slit width, 0.1-0.15 d, was identified, within which not only the vortex shedding signals show the best quality, but also the relation of the Strouhal numbers against the Reynolds numbers studied appears to be the most linear. By spanwise correlation measurements made in the wind tunnel, it is further found that among the cases of s/d = 0, 0.05, 0.15, 0.2, and 0.3 studied, the vortex shedding flow structures of s/d = 0.15 appear to be the most two-dimensional. Moreover, it is worthwhile to mention that for the slit circular cylinders, the signal quality of vortex shedding remains well acceptable for the Reynolds number as low as 2.4 x 10(3). Thus, the rangeability of flow measurement is increased significantly. (c) 2011 Elsevier Ltd. All rights reserved.National Science Council; Ministry of Educatio

Cell culture-based profiling across mammals reveals DNA repair and metabolism as determinants of species longevity

Mammalian lifespan differs by >100 fold, but the mechanisms associated with such longevity differences are not understood. Here, we conducted a study on primary skin fibroblasts isolated from 16 species of mammals and maintained under identical cell culture conditions. We developed a pipeline for obtaining species-specific ortholog sequences, profiled gene expression by RNA-seq and small molecules by metabolite profiling, and identified genes and metabolites correlating with species longevity. Cells from longer lived species up-regulated genes involved in DNA repair and glucose metabolism, down-regulated proteolysis and protein transport, and showed high levels of amino acids but low levels of lysophosphatidylcholine and lysophosphatidylethanolamine. The amino acid patterns were recapitulated by further analyses of primate and bird fibroblasts. The study suggests that fibroblast profiling captures differences in longevity across mammals at the level of global gene expression and metabolite levels and reveals pathways that define these differences. DOI: http://dx.doi.org/10.7554/eLife.19130.00