A new pneumatic bearing dynamometer for power input measurement in stirred tanks

A turntable dynamometer has been constructed for the accurate measurement of power input and mixing applications in bench stirred tank reactors. The main feature of this device is a pneumatic bearing with complementary conical parts. The conical pneumatic bearing permitted to apply eccentric loads without affecting its stability. The static friction torque in the pneumatic bearing was very small, 4 × 10^?4 Nm, and can be neglected in the experimental ranges of measured torques, i.e. from 5 × 10^?3 to 2.21 Nm. In accordance with the instrumentation used, the deviations obtained with the apparatus are less than 10% at low torque readings. At moderate torques, deviations lower than 1% are routinely obtained. Several power input measurements show that the obtained data scatter is lower than 2.5%. The power input response in the turbulent regime is in agreement with dimensional analysis: the power input depends on the cube of the impeller speed. In addition, data obtained with a turbine impeller under ungassed conditions agree with the predictions of a published correlation, which takes into account several geometrical parameters.     

Identification of Factors Affecting Preservative Efficacy and Chemical Stability of Lamivudine Oral Solution Through Statistical Experimental Design

To identify factors affecting the chemical stability and preservative efficacy of lamivudine oral liquid formulations, an optimization study using a central composite design was performed. In this design, five factors, each at three levels, were investigated: pH (4.5, 5.5, and 73, sucrose (5%, 20%. and 50% w/v), propylene glycol (0% 2%, and 5% w/v), glycerin (4% 8%, and 12% w/v). and EDTA (0.100. 0.175, and 0.250 mg/mL). All formulations contained a constant concentration of lamivudine, parabens, and artificial strawberry and banana flavors. All formulations were evaluated for preservative effectiveness against USP and BP standards and for chemical stability at 30°C and 40°C for three months. All formulations were effective against bacteria and yeasts, but indicated reduced preservative effectiveness against the mold Aspergillus niger. Preservative effectiveness improved with increasing pH (4.5 to 7.5) and to a lesser extent with increasing EDTA concentration (0.100 to 0.250 mg/mL). Increasing glycerin concentration (4% to 12% w/v) slightly decreased preservative effectiveness. Over the concentration ranges tested, no change in preservative effectiveness was noted with concentration changes in sucrose or propylene glycol. The pH was the main factor influencing the chemical stability of the drug and preservatives in this study. Lamivudine chemical stability increased with increasing pH from 4.5 to 7.5. Methyl and propylparaben showed extensive degradation at pH 7.5.     

Using rainbow net simulation to measure fault tolerance in a multiprocessor

The Rainbow net simulation technique is applied to modelling the impact of system load and fault handling on the availability of a fault-tolerant multiprocessor architecture. Rainbow nets are described along with the motivation for creating this modelling technique. A Rainbow net fault-handling model is created for the fault-tolerant multiprocessor architecture and the topology is shown to remain constant in size, independent of the number of processor, memory and I/O elements configured in the system. Simulation is performed with a varying load in terms of the number of active jobs the system must support. Results are given showing how the fault-tolerant capability varies with load. Two new metrics for evaluating fault tolerance are introduced; namely full fault-tolerability and partial fault-tolerability. They are based on simple observations in the model.     

The segmented bidirectional single-loop topology for material flow systems

This paper introduces the segmented bidirectional single-loop (SBSL) flow topology for carrier-based material handling systems. This configuration is based on a single-loop flow-path structure that is divided into non-overlapping segments, each containing a single carrier operating in a bidirectional mode. The design procedure comprises a 0 - 1 mixed-integer formulation to determine the single-loop including the pickup and delivery station location. The second stage is a segmentation procedure to determine the non-overlapping segments in the loop. Finally the performance of the SBSL is evaluated by means of simulation.     

Effects of growth with ethanol on fermentation and membrane fluidity of Saccharomyces cerevisiae

Saccharomyces cerevisiae HSc was grown with ethanol at concentrations up to 10% (v/v). The immediate effects of additions of externally added ethanol on CO₂ production and O₂ consumption of washed organisms were studied by stopped-flow membrane inlet quadrupole mass spectrometry. Fermentative activities of organisms grown with ethanol (0–5% v/v) showed similar sensitivities to inhibition by ethanol, whereas those grown with 10% (v/v) ethanol had become protected and were markedly less sensitive. The fluidity of subcellular membrane fractions was measured by determination of the temperature dependence of the rotational order parameter of the spin label 5-doxyl stearic acid (free radical) by electron spin resonance. Mitochondria prepared from yeasts grown with 0, 7 and 9% (v/v) ethanol showed similar overall fluidity, although differences in temperature-dependent behaviour indicate altered lipid composition or lateral phase separations. On the other hand the microsomal fraction from organisms grown with 9% ethanol showed a remarkable increase in fluidity. These data suggest that the protective effects of growth with ethanol near the limit of tolerance on fermentative activities may arise from altered plasma membrane fluidity properties.