Recent advances in biologically based ecosystem models of the coupled terrestrial, hydrological, carbon, and nutrient cycles have provided new perspectives on the terrestrial biosphere's behavior globally, over a range of time scales. We used the terrestrial ecosystem model Century to examine relationships between carbon, nitrogen, and water dynamics. The model, run to a quasi-steady-state, sho...

A neural network based optimal control synthesis is presented for solving optimal control problems with control and state constraints. The optimal control problem is transcribed into a nonlinear programming problem which is implemented with adaptive critic neural network. The proposed simulation method is illustrated by the optimal control problem of nitrogen transformation cycle model. Results...

In the present study the influence of hydraulic retention time (HRT) in SBR and sludge age (SRT) on the effectiveness of nitrogen removal from leachate was investigated. Two series were performed. In each series, experiments were carried out in four SBR operated in parallel at HRT 12, 6, 3 and 2d, respectively. Each series differed in sludge age. In series 1, SRT decreased from 51 to 17d with s...

N itrogen is critical for life on Earth: it is an integral component of all amino acids, the basic constituents of protein. Although elemental nitrogen is abundant-the Earth's atmosphere is 79 percent nitrogen-the availability of nitrogen often limits the productivity of plant communities, whether natural vegetation or agricultural crops. This is because only certain forms of nitrogen are avail...

Standard nutritional advice for irrigated sugarcane in South Africa and Swaziland is based on soil sample analysis and threshold values that have been determined experimentally over many years with surface-applied fertilisers. Fertilisers are normally applied in solid form during the early stages of crop development and watered in by the next irrigation cycle. The increasing popularity of subsu...

Isolation of Pleuropneumonialike Orgauisms from the Throats of Hlumans: Paul F. Smith and Harry E. Morton 623 Atmospheric Nitrous Oxide and the Nitrogen Cycle: Arthur Adel _ 624 An Analog of Vitamin B12: R. P. Buhs, E. G. Newetead, and N. R. Trenner _ 625 Pulmonary Edema and Hemorrhage Induced by Hypothalamic Lesions in Rats: J. E. Gamble and Harry D. Patton ________ 626 Physiological Availabil...