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The presence of clearances in mechanisms can result in the degradation of the performance of these devices. This question is investigated analytically with particular attention paid to the response of a slider-crank with clearances. The use of a simple model to predict the effects of clearances in planar mechanisms without the need for complex and exhaustive analysis is considered. It is shown that such a model, called an impact pair, will provide adequate design information for considering the effects of clearances.

SYNOPSIS Ochromonas malhamensis cells were allowed to feed on autoclaved Aerobacter aerogenes, biochemically inert polystyrene latex particles of comparable size, shape and density, or a combination of these to determine if this protozoan is capable of phagotrophic selectivity under defined experimental conditions. Electron microscopic examination of Gomoristained food vacuoles indicated that the type of particle ingested was determined entirely by the type available. Apparently the biochemical or physical configuration of the particle surface is not decisive in particle selection. Gomori acid-phosphatase reaction product, which indicates digestive enzyme activity, was present in all particle-containing vacuoles, suggesting that digestive activity in O. malhamensis is due to the presence of particulate material in the vacuole, but not necessarily to the nature of the particle.

The dynamic response of a complex one-dimensional system with clearances is considered. It is shown that the presence of the clearances results in a substantial amplification of the internal dynamic forces of the system. This behavior is compared with the characteristics of a simple general model of the clearance coupling called an impact pair. It is shown that the impact pair is capable of predicting the effects of clearances on the dynamics of one-dimensional systems and represents a valuable design tool.

The theory developed in Part I has been applied to the determination of the dynamic response of the Impact Pair under various operating conditions. Simulation techniques, as well as approximate methods used in control theory, have been used for this purpose.

A mathematical model of an elastic mechanical joint with clearances has been formulated and the dynamical equations of motion derived (Part I). The model, which we have called an Impact Pair, is basic to the determination of the dynamical response of mechanical and electromechanical systems with clearances, including determination of dynamic force amplification, frequency response, time-displacement characteristics, and other dynamic characteristics. Whenever possible, the results for the impact pair under various operating conditions are illustrated by graphs, which may also offer some insight into the behavior of clearance-coupled systems.

The design of an interactive control system used in the electromechanical transport of an optical reading system was performed, using both analog and digital simulations. Included are laboratory data and traces taken from an engineering breadboard. The equations of motion are developed and are found to be highly nonlinear which cannot be solved by a closed-form analytical solution, and thus a simulation approach was required. Results of the digital solution are compared with the analog solution with emphasis on the similarities and differences of the two approaches. Simulation plots are compared to traces of the control signals of the actual system. This leads to significant insight into the strength and weaknesses of the simulation approach.

ISOCITRIC dehydrogenase, an enzyme of the tricarboxylic acid cycle, is responsible for the formation of α-ketoglutarate from isocitrate. During the reaction, oxalosuccinate is formed (as an intermediate) owing to the presence of two pyridine nucleotide-linked dehydrogenases in biological systems. One dehydrogenase is linked with NAD and the other is linked with NADP. They first catalyse the oxidation of isocitrate, and then its decarboxylation in the presence of the manganous ion. If NADP is used in the reaction, it is reduced and, because of the reversibility of the process, carbondioxide is fixed in oxalosuccinate and isocitrate. Isocitric dehydrogenase has been isolated from heart tissue of the pig1, yeasts2, and various animal tissues3. This enzyme was discovered in the supernatant fraction of the homogenates of the fat bodies of the cockroach, Periplaneta americana4,5. Its presence has been reported in the haemolymph of the mealworm, Tenebrio molitor, by Prota (see previous communication). Hence, the purpose of this investigation was twofold: to determine whether this enzyme could be detected in normal and aposymbiotic fat bodies of the cockroach, Leucophaea maderae; and to determine whether the presence of the enzyme in this tissue is due to the action of the tissue, the symbionts or both.

MALATE is reversibly converted to pyruvate through the agency of the malic enzyme. This reaction, which is effected in the presence of NADP+ and Mg++ ions, constitutes the only known means whereby the synthesis of dicarboxylic acids is obtained from pyruvate and carbon dioxide. Simultaneous oxidation and decarboxylation are accomplished by the same enzyme, and although free oxalacetate does not appear in the reaction, this acid is decarboxylated. During equilibrium, there is a tendency for malate to become oxidized, and if NADP+ is removed by coupling action, the process is reversed with the resulting fixation of carbon dioxide.