Anorexia nervosa with hyperthyroidism: case report

Clinical signs of hypometabolism in anorexia nervosa may result from the "low triiodothyronine syndrome," in which thyroxine (T4) and thyroid stimulating hormone are usually normal, but triiodothyronine (T3) is in a range compatible with hypothyroidism. A case in which anorexia nervosa presented with unsuspected hyperthyroidism is reported.     

The thermophilic anaerobic digestion process

The paper presents a review of the thermophilic anaerobic digestion process, which has been successfully employed in Los Angeles, U.S.A., and Moscow, U.S.S.R. The chief advantages of operating at higher, thermophilic temperatures are lower detention times, improved dewaterability of the sludge, and increased destruction of pathogenic organism. It is anticipated that operation of the thermophilic process will require closer control than is conventionally practised. A dynamic process model is proposed, and the expected response of a thermophilic digester to changes in feed rate, concentration and temperature is illustrated.     

Ammoniacal bromamines: a review of their influence on bromate formation during ozonation

Ammonia can inhibit the formation of bromate in ozonated drinking water by reacting with free bromine (HOBr/OBr-), an intermediate in bromate formation, to form bromamines. Bromamines do not participate in bromate formation, however, they will decay due to autonomous decomposition and through reaction with ozone and hydroxyl radicals. The reaction with ozone controls the overall decay rate. This reaction also results in a net loss of ammonia from the system, leading to the possibility that all ammonia may be oxidized before the ozone residual in the water is eliminated, allowing bromate formation to resume. This paper presents a review of our understanding of bromamine chemistry and identifies areas that are not adequately understood, which may prevent an accurate estimation of ammonia's impact on bromate formation.     

Dynamic models and control strategies for wastewater treatment processes

Consideration of dynamic behavior and the incorporation of modern control systems can lead to substantial improvements in the performance of wastewater treatment plants. Other potential benefits include increased productivity, greater reliability, lower operational costs, more stable operation and faster start-ups. Several powerful tools are available for the study of dynamic behavior. Included among these are dynamic mathematical models, computer simulation, transient response analysis and process stability evaluation. Simple examples illustrating the theory and use of these tools are presented.The development of a control strategy is intimately related to the dynamic behavior of a process. Some of the basic questions which must be answered in developing a control strategy are: (1) What information should be collected? (2) How should the information be transmitted? (3) How should the information be processed? (4) What control actions should be taken? A wide variety of control algorithms are available for the processing of information for control. A discussion of several of these, on-off, PID. ratio, cascade, and feedforward, is presented and an example is given for the application of on-off control to a biological CFSTR. Digital computers are also being increasingly used for control of wastewater treatment plants and a discussion of computer control systems is presented.Examples of dynamic models and control strategies for two wastewater treatment processes, the step feed activated sludge process and the anaerobic digester, are presented and discussed, In addition, dynamic modeling and computer simulations are used to indicate those design and operational factors for the anaerobic digester which are effective in improving process stability. An effective control strategy for the activated sludge process is that provided by the step feed process which permits changing the points at which wastewater is added along the length of the reactor. Example control strategies for the anaerobic digester include the addition of base and the recirculation of the digested sludge. The effectiveness of the control strategy is dependent upon the type of forcing to which the digester is subjected.     

The effect of surface modification on fretting fatigue in Ti Alloy turbine components

Severe fretting damage has been observed on the pressure surfaces of fan and compressor blade dovetails/disks in an aerospace gas turbine engine. A study has been carried out to evaluate the effect of an ion implantation technique in combination with the presently used surface treatments, such as shot peening and coating, on the fretting fatigue life of titanium alloy gas turbine engine components. The results from fretting fatigue tests, residual stress measurements, and nanoindentation tests were used to quantitatively evaluate the effect of various surface treatments on the fretting fatigue life of the fan blade and disk materials. Results from microstructural characterization and analyses of elemental and phase distributions within the implanted region are used to understand the effect of ion implantation on the surface properties of the alloys. Finally, an attempt has been made to evaluate the potential for improving the fretting fatigue life of the engine components using various surface modification techniques.     

Computerized fault tree construction for a train braking system

A new approach for fault tree automation is proposed which is a hybrid of the digraph and decision table methods, using the best features of both. The new method is based on the flexibility of the decision table method but incorporates a way of detecting, classifying and analysing control loops, similar to the use of operators in the digraph approach. As well as using operators to deal with control loops, a new operator is introduced that deals with electrical circuits. This means that when constructing the fault trees, difficulties of handling repeated events are eliminated and the size of the fault trees is significantly reduced. The method has been tested by its application to a braking system on a train. © 1997 John Wiley & Sons, Ltd.