Heterogeneity in cell populations poses a major obstacle to understanding complex biological processes. Here we present a microfluidic platform containing thousands of nanoliter-scale chambers suitable for live-cell imaging studies of clonal cultures of nonadherent cells with precise control of the conditions, capabilities for in situ immunostaining and recovery of viable cells. We show that this platform mimics conventional cultures in reproducing the responses of various types of primitive mouse hematopoietic cells with retention of their functional properties, as demonstrated by subsequent in vitro and in vivo (transplantation) assays of recovered cells. The automated medium exchange of this system made it possible to define when Steel factor stimulation is first required by adult hematopoietic stem cells in vitro as the point of exit from quiescence. This technology will offer many new avenues to interrogate otherwise inaccessible mechanisms governing mammalian cell growth and fate decisions.

in Wiley InterScience (www.interscience.wiley.com).Computational fluid dynamics (CFD) simulation was applied to a photocatalytic reactor with surface reaction for trichloroethylene (TCE) oxidation at various pollutant concentrations, and flow rates. First-order and Langmuir-Hinshelwood kinetics for TCE removal rate were considered. The results were compared with those from experiments of Demeestere et al. (Appl Catal B Environ. 2004;54:261-274) in a flat plate photocatalytic reactor with serpentine geometry. The flow regime was laminar. Through the CFD simulation, the velocity field and the concentration gradient of TCE in the reactor were studied in detail. At Reynolds numbers around 900, the laminar flow becomes unstable. Under such a condition, when flow passes the 1808 sharp turns, due to formation of secondary flow and consequently vortices, there is a lot of crosssectional mixing in the reactor. This kind of studies can help us to model the photocatalytic reactor as accurately as possible.

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