Substantial electric output was delivered from the bioelectrochemical fuel‐cells operated under anaerobic conditions by Anabaena variabilis strain M‐2 and 2‐hydroxy‐1,4‐naphthoquinone. There was a linear relationship between the coulombic output of the fuel‐cells operated in the dark and the glycogen content of the organisms. The coulombic output was increased substantially in the light; the increase was observed even in the absence of CO2. Oxygen was evolved by Anabaena cells under the operating conditions of the fuel‐cells. The results demonstrated that the source of electricity obtained from the fuel‐cells is endogenous glycogen in the dark and both glycogen and electrons produced by photosynthetic oxidation of water in the light.

Potentiometric and amperometric measurements were made with microbial fuel cells containing E. coli or yeast as the anodic reducing agent and glucose as the oxidizable substrate. The catalytic effects of thionine and resorufin on the anode reaction were investigated. Results on the potentiometry, polarization, and coulombic output of the cells support a mediator-coupled mechanism for the transfer of electrons from the organism to the electrode in preference to a mechanism of "direct" electrochemical oxidation of glucose or its degradation products. Experiments with (14)C-labeled glucose show that when a microbial fuel cell produces a current under load, exogenous glucose is metabolized to produce (14)CO(2). The Coulombic yields of the cells indicate a high degree of energy conversion in these systems.

No abstract

The precipitation kinetics of hydroxyapatite from calcium phosphate aggregates was investigated by the continuous-angle laser light-scattering technique in the systems CaCl 2 -H 3 PO 4 -H 2 O and KCl-CaCl 2 -H 3 PO 4 -H 2 O at 25 °C. The apparent molecular weights of aggregates increased with time, and precipitation of hydroxyapatite occurred in both systems. However, the radius of gyration of the aggregate was almost constant in the former system, while it increased with the increase of the molecular weight in the latter system. Fractal dimension analysis revealed that loosely distributed particles in the aggregate transformed to a three-dimensional closely packed structure during the precipitation of hydroxyapatite in the former system, while the aggregate and the crystalline particles within it increased in size with the increased density and act as growth centers of hydroxyapatite in the latter system.