Marius Turnea

Succinic acid fermentation in a stationary-basket bioreactor with a packed bed of immobilized Actinobacillus succinogenes: 1. Influence of internal diffusion on substrate mass transfer and consumption rate

This paper is dedicated to the study on external and internal mass transfers of glucose for succinic fermentation under substrate and product inhibitions using a bioreactor with a stationary basket bed of immobilized Actinobacillus succinogenes cells. By means of the substrate mass balance for a single particle of biocatalysts, considering the Jerusalimsky kinetic model including both inhibitory effects, specific mathematical expressions have been developed for describing the profiles of the substrate concentrations and mass flows in the outer and inner regions of biocatalyst particles, as well as for estimating the influence of internal diffusion on glucose consumption rate. The results indicated that very low values of internal mass flow could be reached in the particles center. The corresponding region was considered biologically inactive, with its extent varying from 0.24% to 44% from the overall volume of each biocatalyst. By immobilization of bacterial cells and use of a basket bed, the rate of glucose consumption is reduced up to 200 times compared with the succinic fermentation system containing free cells.

Interfacial Mass Transfer in the Reactive Extraction Process of Succinic Acid from Viscous Aqueous Solutions

The reactive extraction of succinic acid with TOA dissolved in butyl acetate from viscous aqueous solutions which simulate the rheological behavior of Actinobacillus succinogenes broths underlined the strong influence of viscosity and pH on interfacial mass flow, mass transfer driving force, and mass transfer coefficient. The magnitudes of these effects are attenuated by 1-octanol addition into the solvent phase, the interfacial mass transfer rate being accelerated for 1.2-3 times, depending on the apparent viscosity and the pH-value of the aqueous solution. The influences of the extraction parameters and mechanism have been included in a mathematical model adequate for the solute mass transfer coefficient from aqueous to organic phase.

Biodegradation of lipids from olive oil mill wastewaters in a stationary basket bioreactor with immobilized Bacillus spp. cells – Influence of internal diffusion

The study is focused on the external and internal mass transfers of lipids during their biodegradation process in a bioreactor with stationary basket bed of immobilized Bacillus spp. cells. By means of the lipid mass balance for a single particle of biocatalyst, considering the kinetic model adapted for the immobilized bacterial cells, specific mathematical models have been developed to estimate their mass flows in the liquid boundary layer surrounding the particle and inside the particle. The values of mass flows are significantly influenced by the internal diffusion velocity of lipids and the rate of their consumption, but also by the position inside the basket bed. These influences accumulated led to the appearance of a biological inactive region near the particle centre, its magnitude varying from 1.3 to 49.4% of the overall volume of particles.

Distribution of Mixing Efficiency in a Split-Cylinder Gas-Lift Bioreactor with Immobilized Yarrowia Lipolytica Cells Used for Olive Oil Mill Wastewater Treatment

The distribution of mixing in a split-cylinder gas-lift bioreactor has been investigated for suspensions of immobilized Yarrowia lipolytica cells with particles diameter varying between 3 and 4.2 mm. The results indicated important variation of mixing time on the height of riser or downcomer, as well as different behavior of suspensions flows in these two regions. Therefore, for the riser, the mixing efficiency increases from its bottom to the top, allowing the biocatalyst particles with intermediate size (3.6-mm diameter) reaching the most intense circulation of suspension. The analysis of the suspension flow in the downcomer region revealed that the intermediate positions are associated with the highest mixing mainly for the largest immobilized yeast particles (4.2-mm diameter). In both cases, the influence of aeration on turbulence extent is positive only for air superficial velocity up to 1.05–1.35 × 10−3 m/s, the magnitude of this effect being correlated with the biocatalyst size and position on the riser or downcomer. By means of the experimental data, mathematical correlations for mixing time have been proposed for each circulation region, taking into consideration both the operational parameters and the distance from the bioreactor bottom. These equations offer a good concordance with the experiment, the average deviation being of 5.82% for the riser and 6.06% for the downcomer zone.

Synergic Extraction and Transport of Folic Acid through Liquid Membranes

The influence of carrier concentration on the synergic effect induced in the facilitated pertraction of folic acid with the mixture of Amberlite LA-2 and D2EHPA has been analyzed for two liquid membranes with different polarities. The results indicated that the most important synergism can be obtained in the pertraction systems containing low concentrations of D2EHPA and high Amberlite LA-2 concentrations dissolved in a low-polar solvent, namely n-heptane. On the other hand, the stronger synergism corresponding to the acid extraction from the feed phase could lead to a weak synergic effect or negative synergism related to the reextraction into the stripping phase.

Graphical interface that interprets the moments collected from the contact between the stump and socket

Mathematical modeling is an interdisciplinary scientific research field with a wide range of applications in bioengineering (biomechanics processes) and rehabilitation. The vast majority of quantitative models of Bioengineering are formulated in terms of differential equations. Modeling and simulating the Biomechanics of rehabilitation process is an area of major interest in the current medical research. In this study, we aimed to develop an interface graphics, allowing the changing rates of transfer between any two compartments of the vital blunt-socket system. One method to obtain the status of recovery and balance is to develop a mathematical model in order to reduce the time of assessment and prediction. Analysis of the strength and the speed of muscle contraction can be described using a model of mathematically hyperbolic, which could open new avenues for the optimal choice of specific transfer rates to the level of prosthesis. An optimal choice for the recovery method gives more chances to maintain and improve the quality of life of the patient after amputation. A wrong choice for recovery methods and of type of dentures can determine major changes in the position and orientation of the foot joints and may cause points pressure maxima stump area. Experimental data collected from pressure sensors can be used to determine if the forces, moments that can change loading rates and determine if it has achieved good contact when the initial prosthesis and residual limb socket.

Probabilistic gate matrix for axon-inspired communication

Communication on an axon could be modeled by an array of logic gates, where each logic gate emulates a voltage-gated ion channel. In this paper the probability of correct communication is estimated using such a model and an associated reliability analysis for logic gates/circuits known as probabilistic gate matrix (PGM). Such an approach can easily be extended to other types of (regular) arrays of logic gates, and to more complex connection patterns, including even feedbacks (that could model the time dependence of neighboring voltage-gated ion channels on any given voltage-input ion channel).

Improvement of enzymatic conversion of methylbenzylamine by direct extraction of acetophenone

ABSTRACT The individual and selective extraction of acetophenone and methylbenzylamine with n-heptane without and with 1-octanol has been analysed at different pH values, using an extraction system that avoids the reciprocal dispersion of the two phases. For individual extraction, the values of acetophenone mass flow were for 1.6–2.1 times higher than that of methylbenzylamine. The interfacial transfer has been accelerated by adding 1-octanol into the organic phase. The difference between the interfacial mass transfer rates of acetophenone and methylbenzylamine has been amplified during the separation of these compounds from their mixture. In the presence of 1-octanol the selectivity factor reached values over 1,000.

Analyze of liner influence in transtibial prosthetic taking into account tribological aspects

An objective method is proposed to evaluate the performance of a prosthetic patient in order to choose an optimized pair of prosthetic material for liner and cup. The surface pressure map over the residual limb is monitored in order to identify the zones where the mechanical work over the skin is increased and a decision system identifies the most suitable liner-cup pair according to stump geometry, patients characteristics and friction coefficient between skin and liner. The pressure and forces are considered to be the best probable ones during a gait cycle (an average value during a predefined number of trials). Experimental results and simulation are presented.

Graphical interface for analyze of temperature of skin at skin-liner interface

Patients comfort is one of the most important issues in prosthetics Pressures and forces, at skin-liner interface play the most important role in evaluation of this requirement. Beside this, temperature is an important factor that must be considered for analyze and prevent the deterioration of skin in wearing prosthesis. A graphical interface that display and analyze the temperature of the skin at skin-liner interface is proposed in this paper. The software has modules for sensor calibration, display records and prediction of temperature in location where sensors are located as function of ambient temperature. The predictor is based on a linear interpolator/extrapolator that is used to evaluate the temperature during a normal cycle of gait (normal walk for a defined period).