Low-cost struvite production using source-separated urine in Nepal.

This research investigated the possibility of transferring phosphorus from human urine into a concentrated form that can be used as fertilizer in agriculture. The community of Siddhipur in Nepal was chosen as a research site, because there is a strong presence and acceptance of the urine-diverting dry toilets needed to collect urine separately at the source. Furthermore, because the mainly agricultural country is landlocked and depends on expensive, imported fertilizers, the need for nutrient security is high. We found that struvite (MgNH(4)PO(4)·6H(2)O) precipitation from urine is an efficient and simple approach to produce a granulated phosphorus fertilizer. Bittern, a waste stream from salt production, is a practical magnesium source for struvite production, but it has to be imported from India. Calculations show that magnesium oxide produced from locally available magnesite would be a cheaper magnesium source. A reactor with an external filtration system was capable of removing over 90% of phosphorus with a low magnesium dosage (1.1 mol Mg mol P), with coarse nylon filters (pore width up to 160±50 µm) and with only one hour total treatment time. A second reactor setup based on sedimentation only achieved 50% phosphate removal, even when flocculants were added. Given the current fertilizer prices, high volumes of urine must be processed, if struvite recovery should be financially sustainable. Therefore, it is important to optimize the process. Our calculations showed that collecting the struvite and calcium phosphate precipitated spontaneously due to urea hydrolysis could increase the overall phosphate recovery by at least 40%. The magnesium dosage can be optimized by estimating the phosphate concentration by measuring electrical conductivity. An important source of additional revenue could be the effluent of the struvite reactor. Further research should be aimed at finding methods and technologies to recover the nutrients from the effluent.

Self-organising discovery, recognition and prediction of haemodynamic patterns in the intensive care unit.

To care properly for critically ill patients in the intensive care unit (ICU), clinicians must be aware of haemodynamic patterns. In a typical ICU, a variety of physiological measurements are made continuously and intermittently in an attempt to provide clinicians with the most accurate and precise data needed for recognising such patterns. However, the data are disjointed, yielding little information beyond that provided by instantaneous high/low limit checking. Although instantaneous limit checking is useful for determining immediate dangers, it does not provide much information about temporal patterns. As a result, the clinician is left to sift manually through an excess of data in the interest of generating information. In the study, an arrangement of self-organising artificial neural networks is used to automate the discovery, recognition and prediction of haemodynamic patterns in real time. It is shown that the network is capable of recognising the same haemodynamic patterns recognised by an expert system, DYNASCENE, without being explicitly programmed to do so. Consequently, the system is also capable of discovering new haemodynamic patterns. Results from real clinical data are presented.

A system for studying the gas exchange of whole plants at subambient total gas pressures.

A whole-plant gas exchange system that has been designed and constructed to study the feasibility of growing plants at subambient total gas pressures is described. This system will allow for the study of whole-plant gas exchange over the entire life cycle of a plant. The system also will allow for the regulation of atmospheric composition by providing control over the amount of nitrogen, oxygen, and carbon dioxide in a chamber atmosphere. The chamber's environmental performance is discussed in relation to selected design requirements. This system is a major technological advance over other systems used to study low-pressure effects on plant growth.

Evaluation of a multiple disk centrifugal pump as an artificial ventricle.

A multiple-disk centrifugal pump based on the Tesla Turbine design has been modified for potential use as an artificial ventricle or ventricular assist device. The pump consists of a series of interconnected parallel disks placed within a spiral volute housing. This pump normally operates as a continuous flow device; however, a controller circuit has been developed to also allow for pulsatile operation. Frequency, systolic duration, systolic rise time, and diastolic decay time can be independently controlled to produce a wide range of pulsatile pressures and flows. This pumping system was tested in vitro on a mock circulatory system using a blood analogue. Inlet and outlet pressures, outlet flow, and motor rotations per minute were continually monitored over a wide range of physiologic operating conditions. The disk pump output was compared with that of other artificial ventricles and produced favorable results. Direct experimental comparisons were made with a Harvard Apparatus pulsatile piston pump. Unlike the Harvard pump, the disk pump does not use valves. Rather, a slight forward rotation of the disks is used to offset the adverse diastolic pressure gradient, which avoids backflow through the device.

A multiple disk centrifugal pump as a blood flow device.

A multiple disk, shear force, valveless centrifugal pump was studied to determine its suitability as a blood flow device. A pulsatile version of the Tesla viscous flow turbine was designed by modifying the original steady flow pump concept to produce physiological pressures and flows with the aid of controlling circuitry. Pressures and flows from this pump were compared to a Harvard Apparatus pulsatile piston pump. Both pumps were connected to an artificial circulatory system. Frequency and systolic duration were varied over a range of physiological conditions for both pumps. The results indicated that the Tesla pump, operating in a pulsatile mode, is capable of producing physiologic pressures and flows similar to the Harvard pump and other pulsatile blood pumps.