Robust pole placement control of a fermentor

This paper deals with robust pole placement control of a continuous flow alcoholic fermention process. The strain used for experiments is Saccharomyces cerevisae UG5. The fermentor is subject to changs in pH, temperature, mixing, etc. The regularized pole placement adaptive control algorithm is used for regulation and tracking purposes. The substrate concentration and the dilution rate have been respectively selected as controlled and control variables. The eliminant matrix associated to the pole placement problem is non-singular if the identified input-output model has common poles and zeros. Two solutions have been adopted to deal with this ill-conditioning problem. The first solution consists of monitoring the determinant of the eliminant matrix and the second consists of adding a correction term to the highest degree coefficient of either the numerator or denominator of the process transfer function. A robust recursive identification scheme is used for parameters estimation. The fermentor was interfaced with PC computer using a multitasking operating system. Experiments carried out with the fermentor, illustrate the use of the regularized pole placement adaptive control algorithm.     

Internal air current patterns depend on the ventilation method in a scaled-up culture vessel for micropropagation

Air current patterns were visualized inside a scaled-up culture vessel under natural or forced ventilation. Metaldehyde particles were used as tracers, and their patterns were recorded as video images by a high-resolution-and-contrast camera. Under natural conditions, the air currents were mainly influenced by natural convection that developed due to the lighting scheme, which caused differences in temperature among various articles in the chamber, including a sweet potato plantlet, supporting material, a multi-cell tray, and the culture vessel. Under forced ventilation, the air current pattern and air speed were affected by ventilation rates and by air-supply methods that were either parallel downward or circular upward. Uniformity of air movement could be achieved with air distribution pipes inside a modified vessel. Under forced ventilation, growth, photosynthetic rate, and transpiration of the micropropagated plantlets were enhanced around the air outlet as well as the inlet in the large-scale vessel. Those plant responses were probably induced by uniform spatial distribution of air current and gas concentrations.     

Development of a shaking bioreactor system for animal cell cultures

The feasibility of using shake flasks to culture animal cells was evaluated using various sizes of cylindrical shaped vessels as bioreactors. It was found that conditions can be optimized so that hybridoma, Chinese Hamster Ovary cells, and insect cells can be efficiently cultured in the shaking reactors to cell densities comparable to that obtained with stirred-jar bioreactors, and the system is scalable to larger volumes for the production of recombinant proteins or cell mass production in the laboratory.     

Sealed with a Kiz: How Plk1 ensures spindle pole integrity

The kinase Plk1 plays multiple roles in regulating mitotic progression, including stabilization of spindle poles, but its substrates are largely unknown. A new study by Yamamoto and coworkers has identified a centrosomal protein, Kizuna (Kiz), as a mitotic substrate of Plk1 (Oshimori et al., 2006). Phosphorylation of Kiz ensures the integrity of spindle poles in the face of severe pulling forces exerted by the chromosome-attached spindle microtubules.     

Measurement of the evaporation rate of liquid in a shaking flask

The evaporation rate (N_H2O) of liquid in a shaking flask was measured under various shaking conditions: temperature, humidity, flask shape, liquid volume in the flask (V_L), length of the stopper in the flask neck (L_C), rotational speed of the shaker (N), and wind velocity (V_W). The rate was significantly affected by these factors, and the existence of a distribution of water vapor pressure was suggested inside and outside the flask. To predict the evaporation rate, the following empirical equation was derived by the least squares method: N_H2O=1.26×10⁻²S_F^1.18L_F^−1.3 (p_s–p)^1.24V_L^0.11N^0.05V_W^0.26L_C^−0.37 where, S_F is the cross-sectional area of flask neck, L_F is the length of flask neck, p_s is the saturated partial pressure of water vapor at the temperature of the air surrounding the flask, and p is the partial pressure of water vapor in the flask.     

Scale-up of purine nucleoside fermentation from a shaking flask to a stirred-tank fermentor

Scaling-up purine nucleoside fermentation by a mutant strain of Bacillus subtilis from a shaking flask to a stirred-tank fermentor was attempted. The dimensions and the operating conditions of the stirred tank were determined in order to satisfy the optimum conditions of O₂ transfer and power consumption per unit volume for the shaking flask. When the purine nucleoside fermentation was carried out in the stirred-tank fermentor under these conditions, in which the temperature simulated that in the shaking flask, the total amount of purine nucleosides produced was almost the same as that in the shaking flask, but the accumulation ratio of guanosine to total nucleotides was different from that in the flask. Since urea could not be utilized so efficiently in the stirred-tank fermentor, the NH^p+ _f4 concentration and the pH of the culture broth were lower than those in the shaking-flask culture during fermentation. The activity of inosine monosphosphate dehydrogenase and the accumulation ratio were significantly affected by the NH^p+ _f4 concentration. When the pH of the stirred-tank culture was maintained at 6.9 by ammonia water to keep the NH^p+ _f4 level higher, the ratio was improved to the same level as that observed in the shaking-flask culture. The fermentation heat calculated from the shaking-flask data and its pattern of change were similar to those in the stirred-tank fermentor. Correspondence to: Y. Sumino     

Structure of blood flow through a curved vessel with an aneurysm

A fine structure of blood flow through a curved vessel with an aneurysm was studied in in vitro experiments in relation to rheological factors of arterial diseases such as arteriosclerosis or thrombosis. On the basis of the in vivo data related to cerebral circulation, red blood cell suspension was flowed through curved vessel models with an asymmetrical aneurysm. Flow visualization was made with a microscope 16 mm cinecamera-TV monitor system, and the velocity profile was measured using the laser Doppler velocimeter. Vortices induced in aneurysm influenced flow structure and velocity at the presence of the secondary flow due to the vessel curvature. This suggests strongly that blood flow in curved arteries with an aneurysm must be understood under the influence of the secondary flow.     

A simple model of a vessel with a wall sensitive to mechanical stimuli

Smooth muscles in the walls of small blood vessels under normal conditions are always moderately active, so that there is a certain reserve for blood flow adaptation to changed conditions by either narrowing or expanding of the vessel lumen. The previous studies of small vessel hydrodynamics have shown that the activity can cause specific instability of vessel steady states. In order to trace qualitatively the influence of numerous factors on the active state of the vessel, a simplified model of the vessel was proposed, which is reduced to a nonlinear ordinary equation of the first order with delayed argument.     

Influence of pole plant time on the performance of a special jump and plant exercise in the pole vault

The purpose of this study was to examine the effect of the timing of the pole plant during the stance phase of the jump on the energy level of the vaulter/pole system at take-off for a special pole vault take-off exercise (Jagodin). We hypothesised that an earlier pole plant would increase the pole energy at take-off compared to the energy decrease of the vaulter during the jump and plant complex and so lead to a higher total energy of the vaulter/pole system at take-off. Six male pole vaulters experienced three Jagodins each with different pole plant time building three groups of vaults (early, intermediate, late pole plant). Kinematic data of vaulter and pole were recorded, as were ground reaction forces measured at the end of the pole under the planting box and under the take-off foot. These measurements allowed the energy exchange between the vaulter and pole to be determined. We found neither statistical significant differences in the mechanical energy level of the vaulter/pole system during take-off between the three groups nor a relationship between the timing of the pole plant and the energy level of the vaulter-pole system during take-off. We conclude that although the timing of the pole plant influences the interactions between the vaulter, the pole, and the ground, it does not affect the athlete's performance. Although a late pole plant decreases the loss of energy by the vaulter during the take-off, this is counterbalanced by a decrease in the energy stored in the pole at take-off.     

RHAMM is a centrosomal protein that interacts with dynein and maintains spindle pole stability

The receptor for hyaluronan-mediated motility (RHAMM), an acidic coiled coil protein, has previously been characterized as a cell surface receptor for hyaluronan, and a microtubule-associated intracellular hyaluronan binding protein. In this study, we demonstrate that a subset of cellular RHAMM localizes to the centrosome and functions in the maintenance of spindle integrity. We confirm a previous study showing that the amino terminus of RHAMM interacts with microtubules and further demonstrate that a separate carboxy-terminal domain is required for centrosomal targeting. This motif overlaps the defined hyaluronan binding domain and bears 72% identity to the dynein interaction domain of Xklp2. RHAMM antibodies coimmunprecipitate dynein IC from Xenopus and HeLa extracts. Deregulation of RHAMM expression inhibits mitotic progression and affects spindle architecture. Structure, localization, and function, along with phylogenetic analysis, suggests that RHAMM may be a new member of the TACC family. Thus, we demonstrate a novel centrosomal localization and mitotic spindle-stabilizing function for RHAMM. Moreover, we provide a potential mechanism for this function in that RHAMM may cross-link centrosomal microtubules, through a direct interaction with microtubules and an association with dynein.     

Morphofunctional restoration of a nerve trunk by filling the defect with a blood vessel

Dynamics of morphologic and functional restoration of the nerve trunk and separate receptive skin formations have been investigated in white rats after a sutureless connection of the cut nerve by means of the implanted artery. For testing the reparative processes neurohistological and electrophysiological techniques have been used. In spite of a relatively early restoration of the integrity of the injured nerve and reaching the nervous fibers up to the skin, functional organization of the dermal sensory apparatus is observed only in a year after the operation.     

Out-of-phase operating conditions, a hitherto unknown phenomenon in shaking bioreactors

One of the important parameters in characterising fermentations of aerobic microorganisms is the specific power consumption. A new method has been introduced which enables the accurate determination of the power consumption in shaking bioreactors. It is based on torque measurements in the drive and the appropriate compensation of the friction losses. Measurements of the power consumption revealed the phenomenon of the liquid being 'out-of-phase' for the first time for shaking bioreactors. This occurs at certain operating conditions and is characterised by an increasing amount of liquid not following the rotating movement of the shaker table, thus reducing the specific power consumption, mixing and the gas/liquid mass transfer. With respect to this, different hydrodynamic cases have to be distinguished. All these cases have in common, however, that the probability of 'out-of-phase' conditions increases with lower shaking diameters, lower filling volumes, larger number and sizes of baffles and higher viscosity. For unbaffled flasks with a nominal volume 相似文献   

Measurement of the overall volumetric coefficient of heat transfer of a shaking flask

The overall volumetric coefficient of heat transfer (Ua) of a shaking flask was measured under various shaking conditions using three types of flask. Ua was significantly affected by flask weight (W_F), which could be attributed to the thickness of the flask wall, the rotational speed of the shaker (N), wind velocity (V_W), and the liquid volume in the flask (V_L). The limiting step of heat transfer seemed to be the heat radiation process from the surface of the flask to the surroundings. To predict the value of Ua, the following empirical equations were obtained for each type of flask by the least squares method:

• 1.(1) for deformed creased flask (M-type flask), Ua=17.4 W_F^−0.43V_L^−0.61N^0.12V_W^0.36
• 2.(2) for creased flask (N-type flask), Ua=9.2 W_F^−0.36V_L^−0.57N^0.17V_W^0.27
• 3.(3) for smooth flask (S-type flask), Ua=5.3 W_F^−0.26V_L^−0.62N^0.19V_W^0.25.

     

Catalase activity measured with a micro oxygen electrode in a pressurized reaction vessel

The assembly and the use of a simple airtight pressurized reaction vessel are described for the measurement of catalase activity with a micro oxygen electrode in an optically heterogenous medium. The oxygen concentration is expressed as the ratio of observed current to the current in an air-saturated solution. Thus, an individual standard can be obtained for each measurement and the calibration is less affected by changes in the amplification factor. Different procedures for calibration of the oxygen electrode were compared. Specific activities of crystalline catalase, of red blood cells from humans and from normal or acatalasemic mice, and of liver homogenates from normal or amino-triazole-pretreated rats were determined. The specific catalase activity of human erythrocytes, as found by this method, agrees with that obtained photometrically.