Johan Hedbrant

Data Vagueness and Uncertainties in Urban Heavy-Metal Data Collection

The use of societal data inenvironmental research has indicated a need forconsidering uncertainties of data. Severalfundamental conditions for statistical treatmentare occasionally not met. The choice is either touse or to ignore the uncertain data. If used, itmay impair the quality of the result. If ignored,a possible environmental risk may remainunattended. This article discusses some of theproblems encountered with data in urbanheavy-metal metabolism, and suggests a method based onuncertainty intervals to consider theuncertainties.

A computer simulation model for cost-effectiveness analysis of cardiovascular disease prevention

In this paper a computer simulation model for cost-effectiveness analysis of cardiovascular disease prevention is presented. Cost-effectiveness analysis makes it possible to compare the cost-effectiveness of different interventions in order to maximize the health effects for a given amount of resources. The computer simulation model was written in Turbo-Pascal to be used on an IBM-PC-compatible. The model was based on the 8-year logistic multivariate risk equations for CHD and stroke from the Framingham Heart Study, but the regression coefficients can easily be changed if local data exist. The main advantages with the model are that it is easy to use, transparent, and flexible. The model was mainly developed for scientific purposes, but should be useful also for educational purposes and clinical decision analysis. The modelling approach used should also be useful in many other medical areas.

Särimner: a computer model of diabetes physiology for education of physicians and patients

Often diabetic patients have developed their skills by some trial-and-error-like training over a long period of time. To minimize this inconvenience we have made a mathematical model to facilitate diabetes education. The model consists of a number of blocks involved in diabetes physiology: digestion, blood (transport), pancreas, injected insulin absorption, liver, muscles, kidneys, metabolism and insulin sensitivity. The model serves as a demonstration object and the user can change meals, exercise and injections and see the resulting blood glucose level. A more experienced user can search for further explanations of different phenomena deeper in the physiology of the model. The model does not solve any problem for the user, but creates a learning situation in which the user, led by his own curiosity, successively increases his experience of diabetes physiology. Särimner is implemented as an easy-to-use menu driven computer program for IBM PC-clones with Hercules, EGA or VGA graphics.

Stockhome: A Spreadsheet Model of Urban Heavy Metal Metabolism

Computer models for analysis,visualising and decision support in environmentalresearch have become increasingly popular. TheStockhome project, where the urban metabolism ofheavy metals in Stockholm was studied, resultedin a database with historical data of the use ofgoods containing cadmium (Cd), chromium (Cr),copper (Cu), lead (Pb), mercury (Hg), nickel (Ni)and zinc (Zn). A spreadsheet model was developedto study flows and stocks of the metalconsumption process and emissions. The modelindicates uncertainties of the data, societalaspects such as field of use and rights ofdisposition of the goods. By considering goods asthe drivers of the emissions, the model would bewell suited for policy support.

Copper Emissions from Fuel Combustion Consumption and Industry in Two Urban Areas 1900–1980

The type of energy system andindustrial structure of urban areas is veryimportant for the total amounts of Cu emitted.The total per capita emission for the New Yorkarea is estimated to be approximately 4 timeslarger than Stockholm municipality between 1900–1980. The latter was mainly the result of largedifferences in energy systems and industrialstructure. Hydro-electric power and non fossilfuels were important energy sources for Stockholmwhile coal was a much more significant fuel forthe New York area. Metal processing hascharacterised the industries of Stockholm whilethe New York area was a national centre forcopper and petroleum refining as well as thechemical industry. In both cases the estimated Cuemissions from fuel combustion and industrydecreased from 1900–1980. But in the case ofconsumption related emissions the time trendsdiffer between the two urban areas. In Stockholmend use was the largest category of Cu emissionsduring the whole time period studied. In the NewYork area consumption related emissions becamethe largest source of Cu emission in the 1950s.

A simplified roentgen stereophotogrammetric method. Analysis of small movements between the prosthetic stem and the femur after total hip replacement.

A simplified roentgen stereophotogrammetric method is described. It is based on the use of a 50 mm thick reference plate consisting of a carbon-fibre-reinforced polyester box. The patient is placed directly on this box, which makes the methods less cumbersome and more suitable for routine use. The method has been tested in a model experiment designed for detecting small movements between femur and prosthesis at an early stage after total hip replacement. The head and two hemispheres on the prosthesis and three small tantalum balls inserted in the femur serve as reference points. The model experiment now reported shows that the method has acceptable precision.