An airlift reactor with the external loop (EXL ALFR) is a widely used modified version of a Bubble Column Reactor (BCR). An EXL ALFR can also be used for a three-phase system with the solid phase in a packed or fluidized form. An EXL ALFR provides design flexibility for conventional chemical reactions as well as biological reactions. Shear is an important factor for the reactors handling immobilized enzymes. In the current investigation, the effect of the design variables, like gas hold-up, the velocity of circulating liquid, and the distribution of bubble dimension, was compared for an EXL ALFR and an external loop airlift reactor with a packed bed (EXL ALFR-PB). Particle Image Velocimetry (PIV) was employed for the liquid axial velocity in the downcomer of the reactors, and the computational fluid dynamic with the Population balance model (CFD-PBM) was employed. The minimum percentage of errors of 2.3% and 1.2% and the maximum of 4.2% and 3.4% were obtained for the experimental and predicted values of gas hold-up in the EXL ALFR and EXL ALFR-PB, respectively. For the velocity of the circulating liquid, the predicted and experimental values of their minimum percentage error were 1.1% and 0.5% and a maximum of 4.3% and 4.5% in EXL ALFR and EXL ALFR-PB, respectively.  Also, the pressure drops calculated from the Ergun equation and CFD simulation had a 0 to 4% difference, indicating good agreement.

Saccharomyces cerevisiae (baker’s yeast) can exhibit sustained oscillations during the operation in a continuous bioreactor that adversely affects its stability and productivity. Because of heterogeneous nature of cell Populations, the cell Population balance equation (PBE) can be used to capture the dynamic behavior of such cultures. In this work, an unstructuredsegregated model is used for dynamic simulation and controller synthesis. The mathematical model consists of a partial integro-differential equation describing the dynamics of the cell mass distribution (PBE) and an ordinary integro-differential equation accounting for substrate consumption. In order to solve the mathematical model, three methods, finite difference, orthogonal collocation on finite elements and Galerkin finite element are used to approximate the PBE model by a coupled set of nonlinear ordinary differential equations (ODEs). Then the resulted ODEs are solved by 4th order Rung-Kutta method. The results indicated that the orthogonal collocation on finite element not only is able to predict the oscillating behavior of the cell culture but also needs much little time for calculations. Therefore this method is preferred in comparison with other methods. In the next step two controllers, a globally linearizing control (GLC) and a conventional proportional-integral (PI) controller are designed for controlling the total cell mass per unit volume, and performances of these controllers are compared through simulation. The results showed that although the PI controller has simpler structure, the GLC has better performance.

Background & Aims: Antidepressants are very common therapeutic agents in medicine. Design and using new antidepressants have built a new scope for depression treatment. Bupropion is an atypical antidepressant but it is used as an anti-smoke agent widely due to its smoke cessation. Its effectiveness in producing smoking cessation seems independent of its antidepressant effects. The study of synaptic effects of bupropion can reveal its mechanism for nicotine dependence cessation. This study has tested the effects of bupropion on evoked responses of rat hippocampal slices.Materials & Methods: 16 hippocampal slices from 18-25 old age rat pops were tested. The hippocampal slices have been prepared according to standard techniques. Bupropion was perfused in ACSF (2 mmol) for 30 minutes. The amplitude of Population spikes (PS) amplitude of Stratum Radiatum was measured before and after bupropion perfusion. Amplitude of PS before bupropion perfusion fitted as 100% for baseline.Results: Bupropion (2 mmol) abolished PS of all slices for different periods. PS disappeared in 37.5% of slices for 1 hour, 25% for 1.5 hour, 12.5 % for 2 hour, and 25% for 4 hour or more. Bupropion disappeared PS 5-15 minutes after perfusion.Conclusion: Bupropion abolished or decreased PS amplitude. The results have showed that bupropion can decreases LTP or synaptic plasticity and alters the synaptic behavior in drug dependence.

A theoretical model is developed to consider the effect of demulsifier agent on demulsification of water-in-crude oil emulsion. A thermodynamic approach is considered to correlate the critical micelle concentration of a demulsifier to the collision frequency function in Population balance equation (PBE). Based on the proposed correlation, the collision frequency function is modified to account the effect of demulsifier agent on water droplets coalescence. The water separation capability of a selected group of demulsifiers is investigated via the conventional bottle test method to obtain the adjustable parameter of the developed equation so that the absolute relative error of predicted demulsification efficiency and experimental data are considered as objective. Comparison between the model simulated results and the experimental data showed that the proposed model could appropriately reproduce the experimental data at different agent concentrations.