Experiments were conducted to study the performance of circular and square tank surface aerators on the oxygen transfer coefficient and to a limited extent on power requirements. All the tanks are geometrically similar except for their shapes. They consist of a rotor of diameter, D, fixed with six flat blades rotating with a speed, N, in pure waters of viscosity, υ, at room temperature. A simul...

Oxygen transfer through a cotton plug follows Fick's law of diffusion. The apparent diffusion constant decreases as the density of cotton packing is increased. Formulas are derived which relate oxygen transfer to cotton-plug dimensions. Calculations indicate that the dimensions of a cotton plug can affect both the maximal oxygen uptake rate and the gas composition inside a shaken flask. In some...

In this study, we identified mass and charge transfer resistances for an oxygen reducing biocathode in a microbial fuel cell (MFC) by electrochemical impedance spectroscopy (EIS). The oxygen reducing biocathode was grown using nitrifying sludge as the inoculum. A standard model for charge transfer at the electrode surface combined with diffusion across a boundary layer was used. EIS measurement...

In order to illuminate the effect of the scale on the oxygen transfer in stirred tank reactors, a combined study of the hydrodynamics and the mass transfer has been carried out. The air water system was used to study the behaviour of different impellers against the gas phase and its result in the volumetric mass transfer coefficient. The correct prediction of the rate of oxygen transfer by mean...

The surface oxygen exchange kinetics of bismuth oxide stabilized with 25 mol% erbia (BE25) has been studied in the temperature and pO2 ranges 773–1,023 K and 0.1– 0.95 atm, respectively, using pulse-response O–O isotope exchange measurements. The results indicate that BE25 exhibits a comparatively high exchange rate, which is rate determined by the dissociative adsorption of oxygen. Defect chem...

The study was to investigate the effects of oxygen concentration at different levels for culturing pre-compaction embryos on human embryo development competence. A total of 1254 oocytes from 92 patients treated with conventional in vitro fertilization (IVF) were harvested in this study. Oocytes were randomly assigned to the atmospheric (~20%) or low (~5%) oxygen concentration groups on the retr...

a down-flow hanging sponge (dhs) reactor has been developed for sewage treatment, mainly in developing countries. this novel reactor employs polyurethane sponge material as a support medium, which promises a proliferation of a large amount of biomass, offering excellent pollutant removal capability. three types of sponge medium were evaluated with respect to water distribution and oxygen mass t...

The performance of airlift bioreactors are closely related with their geometry, especially the gas-liquid separator design. In this study, the influence of the gas-liquid separator geometry on oxygen transfer and gas hold-up was evaluated in 10-L concentric-tube airlift bioreactor operating with distilled water and xanthan gum solution. The specific airflow rate (ɸAIR) exhibited the higher effe...

The intensity of adult diapause in Pyrrhocoris apterus was measured in two series of experiments as the duration of pre-oviposition period at a constant temperature of 25 degrees C after transfer from short (12L:12D) to long day conditions (18L:6D). Higher diapause intensity was induced with a thermoperiod than at constant temperatures. After the induction throughout larval instars 3-5 and duri...

the main factors affecting pregnancy and implantation rates are uterine receptivity, embryo quality, and transfer efficiency. embryo transfer (et) is the last step of critically important procedure of in vitro fertilization (ivf) and probably the least successful step in assisted reproductive technology (art) treatment cascade; though simple in most of the cases, it may pose to be the most diff...