Oxygen-transfer rates and efficiencies in one- and two-stage airlift towers

The primary consideration in fermentor design is the supply of oxygen to the growing microorganisms. The oxygen-transfer characteristics of a two-stage splitcylinder airlift tower were compared to those of a similar single-stage airlift tower of equal liquid volume using a sodium sulfite–air system. At superficial gas velocities, from 720 to 1200 cm/min, no difference in K_La was apparent. The K_La was significantly larger in the two-stage tower for a gas velocity between 1200 and 2728 cm/min. At 2728 cm/min a K_La of 25.2 min^?1 was achieved in the two-stage system, and at 2262 cm/min the two-stage tower had a 54% larger K_La than the single stage. A comparison of dispersion-volume based K_La showed a 27% larger value at a gas velocity of 2262 cm/min. The performance ratios for the two-stage tower were larger than those for the single-stage tower at oxygen-transfer rates greater than 180 mmol/liter hr. A comparison of the data with literature values is presented.     

Bubble flow in the downflow section of an airlift tower

Characterization of the two-phase flow in the downflow section of the airlift tower is necessary for accurate modeling of the airlift tower. A Split-cylinder airlift tower was investigated for superficial gas velocities ranging from 0.0683 to 0.3315 m/sec for an air–water system. Statistical cross-covariance techniques were used to yield velocities, void fractions, and flow rates corresponding to upward and downward components of bubble flow in the downflow section of the airlift tower. From these results the fraction of incoming air entrained in the downflow section was determined as a function of superficial gas velocity and position.     

Continuous culture of Candida lipolytica on n-hexadecane

Candida lipolytica was grown continuously on n-hexadecane as the main source of carbon. A transient continuous-culture experiment was also conducted to investigate hydrocarbon-limited growth; the hydrocarbon feed flow rate was stopped for several hours and then resumed at a reduced steady-state flow rate. Interfacial tension, Sauter mean diameter, pseudosolubility, fraction of cells in the aqueous phase, oil-phase volume fraction, and cell concentration were measured to characterize the system. The microorganisms appear to utilize both the submicron drops and the microscopic drops. The effects of interfacial tension, pseudosolubility, and unoccupied interfacial area on the kinetics of hydrocarbon fermentation are discussed here. A conceptual model for hydrocarbon uptake is presented and discussed.     

LONG-TERM DEVELOPMENTAL CHANGES IN XANTHIUM INDUCED BY GIBBERELLIC ACID

One application of gibberellic acid (GA₃) to Xanthium shoots resulted in an initial large stimulation, followed by inhibition, of internode elongation. After presumed translocation of the hormone from the locus of its application to the stem apex several morphological changes were observed. There was a significant increase in number of mitotic figures in the apical meristem and a twofold increase in volume of the apical dome. With time, the rate of leaf production was accelerated about 1.8 times. The phyllotaxis of leaf primordia initiated under the influence of GA:, changed from a (2, 3) contact parastichy pattern in control shoot to a (3, 5) pattern. Final petiole length was smaller than the control, and the absolute rate of lamina expansion decreased under prolonged treatment. Gibberellic acid had a pronounced effect on leaf morphology. GA_a induced the development of lanceolate leaves instead of typical deltoid leaves. The reduction in leaf area coincided with a 32% reduction in the average area of epidermal cells. Plastochron changes were correlated with anatomical and morphological changes during the course of leaf development.     

Synthesis of LDH-1 during mamalian oogenesis and early development.

Nuclear multiplication stage embryos were punctured in either the anterior, midlateral, or posterior regions. Both embryos and adults were examined for defects, and the defects were correlated with whether there had been any leakage of cytoplasmic material from the egg at the time of puncturing. Embryonic defects were found, correlated to the site of damage, in all three regions. A number of embryos was followed through development and it was found that 15.1% of the embryos which leaked cytoplasm hatched into larvae, compared to 82.3% of those which did not leak any cytoplasm. Morphological defects arising as a result of lateral puncture only were observed in adults. Many sterile adults were obtained from eggs in which the posterior region had been punctured. The results show that nuclear multiplication embryos are well able to tolerate the disturbance of the cortical cytoplasm created by puncture, but only rarely are they able to compensate for the actual loss of material by regulation. The results were similar to those observed after puncturing Drosophila embryos at the cellular blastoderm stage.     

Body size and composition of Crabeater seals (Lobodon carcinophagus), with observations on tissue and organ size in Ross seals (Ommatophoca rossi)

Linear body measurements and body weights of 17 Crabeater seals and four Ross seals were recorded, and the relationships of weight to linear dimensions were calculated. There were no significant differences between sexes of these relationships in Crabeater seals. All Ross seals were males.
The major body components (blood, fat, skin, muscle, bone, connective tissue and viscera) of seven Crabeater seals were weighed after dissection.
Blood, fat and skin of two Ross seals were weighed. Weights of 22 visceral organs of the same animals, and linear bone dimensions of eight Crabeater seals and skull measurements of five Ross seals were recorded.
There was no significant difference between sexes or ages in body composition of Crabeater seals. Relatively, Crabeater and Ross seals had less blood (9–10% body weight) than Elephant seals, and less fat (21–22% body weight) than most other marine mammals. The low body fat content may have been attributable to season and physiological status of the animals when dissected. The percentages of body weight represented by the other major components of Crabeater seals were: skin 8%, muscle 44%, bone 10%, connective tissue 0.7% and total viscera 8%. These figures, and the relative sizes of individual organs, were discussed in relation to their possible function in Crabeater and Ross seals.     

Monitoring for multiple malformations in the detection of epidemics of birth defects

Although most known human teratogens often produce a combination of birth defects in an affected infant, surveillance programs aimed at detecting epidemics of birth defects usually only monitor rates of individual defects. A drawback to this approach is that an increase in the rate of infants affected with a specific combination of defects may lead to little or no increase in the rates of component defects. Using the Poisson distribution, we show that, compared with monitoring for individual defects, monitoring for combinations of two and three defects may require fewer numbers of births to detect an epidemic. In general, an increase can be detected more rapidly by monitoring the rates of defect combinations than by monitoring the rates of individual defects if most affected infants have combinations of defects rather than isolated defects. For example, in the case of Congenital rubella syndrome (CRS), monitoring for the combination of cataracts with deafness and/or patent ductus arteriosus could have led to earlier detection of an epidemic than could monitoring for cataracts alone. In contrast, in the case of thalidomide embryopathy, monitoring for reduction defects of upper limbs in combination with reduction defects of lower limbs and/or microtia/anotia would not have led to earlier detection of an epidemic than would monitoring for reduction defects of upper limbs alone. This is due mainly to the low frequency of defect combinations among affected cases. When used with regular monitoring for individual defects, surveillance of defect combinations can enhance the ability of monitoring programs to detect epidemics of birth defects.