Reduction in serum requirement for culture of primary human amniotic fluid cells can be achieved by the addition of 10 growth-promoting factors to the nutrient medium. This supplemented medium preserves cell types normally found in amniotic fluid cell cultures supplemented with 20–30 per cent fetal bovine serum. The volume of amniotic fluid required to initiate culture can be as little as 1 ml. Amniotic fluid samples contaminated with red blood cells with no visible clot also grow well in the low serum medium. Cell-free amniotic fluid combined with equal parts of supplemented medium is useful in initiating cell culture. 相似文献
The effects of reduced oxygen concentrations in the gas phase over the culture medium on colony formation and cell proliferation were investigated in high and low cell density primary and secondary cultures of amniotic fluid cells. Using two standard culture methods (25 cm2 plastic flasks and Leighton type tubes) a significantly reduced culture time was observed at high cell density for mass cultures by incubation within a low oxygen tension gas phase (2.5 per cent to 7.5 per cent O2) instead of conventional air (18 per cent O2). At low cell density colony formation was significantly enhanced in cultures grown at reduced oxygen tension. Using gas permeable membranes as support, lowering the oxygen tension from 7.5 per cent to 2.5 per cent yielded an increase in plating efficiency of cells from approximately 5 per cent to 25 per cent, whereas plating efficiency was less than 2 per cent for cells grown at ambient 18 per cent O2. It is suggested that low oxygen tension in the gas phase is an effective means of enhancing clonal growth in amniotic fluid cell cultures, thereby reducing both culture time and risk of culture failure. 相似文献
Urban atmospheric environment contains many trace organic pollutants that are related to the incomplete fuel combustion in domestic heating, industrial plants and automobile traffic. Removal of these pollutants from the atmosphere takes place through wet and dry deposition as well as chemical transformations. In this study, concentrations of polycyclic aromatic hydrocarbons (PAHs) in wet deposition samples were determined at an urban site of Turkey. Wet and dry deposition samples were collected using Andersen Rain Sampler. The sampler was modified accordingly for the collection of organic pollutants. Collected samples were preconcentrated by using solid phase extraction (SPE) disks and consecutively analyzed by Gas Chromatography-Mass Spectrometry (GC-MS). Among the 13 compounds quantified in this study, anthracene, fluoranthene, and pyrene were found more frequently and at elevated concentrations (202, 271 and 260 ng L-1 mean concentrations, respectively).Concentrations of PAHs were found to be high in winter period. 相似文献
During the discharge of flashing liquids through leaks due to abrupt depressurization a transient thermodynamic non-equilibrium in the form of a boiling delay in the superheated liquid flow can occur. As a consequence the actual mass flow quality is smaller than calculated under the assumption of an immediate adjustment of the thermodynamic equilibrium between the phases. For the prediction of the leak mass flow for a given pressure difference the magnitude of this self-adjusting mass flow quality is needed.
Most of the models cited in the literature include only the equilibrium mass quality as limiting quantity and ignore further effects as that of the depressurization velocity or the mean nucleus distance. For the assessment of the maximum possible liquid superheat during flashing only the conduction heat transfer from a stagnant liquid to the bubble surface is used to describe the bubble growth.
The sub-model for the bubble growth due to expansion and mass transfer necessary for the global prediction of the transient thermodynamic non-equilibrium in flashing liquids was validated using bubble radii measured by Hooper et al. [Bubble growth and pressure relationship in the flashing of superheated water. Technical publication 6904, Mechanical Engineering Department, University of Toronto, 1969] for the case of a sudden depressurization of initially saturated water. On this basis the calculated time-dependent temperature field, the actual mass quality, the mean liquid temperature and, in comparison to the corresponding values based on the assumption of immediate thermodynamic equilibrium, the maximum possible liquid superheat are predicted. 相似文献