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Biomedical subjects

D Karlsson

Publications and source records attributed to D Karlsson.

At least 19 recordsLinked to original sources
PubMed2005

Modelling of different measures for improving removal in a stormwater pond.

The effect of retrofitting an existing pond on removal efficiency and hydraulic performance was modelled using the commercial software Mike21 and compartmental modelling. The Mike21 model had previously been calibrated on the studied pond. Installation of baffles, the addition of culverts under a causeway and removal of an existing island were all studied as possible improvement measures in the pond. The subsequent effect on hydraulic performance and removal of suspended solids was then evaluated. Copper, cadmium, BOD, nitrogen and phosphorus removal were also investigated for that specific improvement measure showing the best results. Outcomes of this study reveal that all measures increase the removal efficiency of suspended solids. The hydraulic efficiency is improved for all cases, except for the case where the island is removed. Compartmental modelling was also used to evaluate hydraulic performance and facilitated a better understanding of the way each of the different measures affected the flow pattern and performance. It was concluded that the installation of baffles is the best of the studied measures resulting in a reduction in the annual load on the receiving lake by approximately 8,000 kg of suspended solids (25% reduction of the annual load), 2 kg of copper (10% reduction of the annual load) and 600 kg of BOD (10% reduction of the annual load).

Models, Theoretical↗
PubMed2004

Medical decision-support systems and the concept of context.

Medical decision-support systems are of necessity multi-contextual in nature. There are always at least two contexts involved in the use of such systems: the expert knowledge-provider context and the end-user context. To show this, we present examples of context-dependent aspects significant to the use of decision-support systems. The existence of discrepancies between the contexts threatens to disrupt the rationale for using decision-support systems: for the system to transfer knowledge from the expert to the end-user. Both theoretical and empirical studies show that such discrepancies exist and that they may be detrimental to the use of decision-support systems. Systems must thus give support in interpreting the output produced by the system in the context of the end-user.

Artificial Intelligence↗
PubMed2002

Significance of house painters' work techniques on shoulder muscle strain during overhead work.

House painters represent a group of construction workers with a high frequency of neck and shoulder complaints and concomitant high risks for early retirements. Shoulder tendinitis, especially supraspinatus tendinitis, occurs frequently among house painters. The tasks of sanding and painting of ceilings with extension handles are particularly strenuous for these body regions. The purpose of this study was to identify work techniques that would be less strenuous to the arms and shoulders during sanding work. A biomechanical model was applied to quantify the shoulder loads during sanding and to determine the likely muscle force distribution. The necessary input data were measured experimentally for the model by means of a load cell and strain gauges on an extension handle, a Kistler force plate, and a MacReflex motion analysis system. Forty experienced male painters participated in the study. Three different work techniques were identified: the normal technique, the reversed grip and the pushing technique. The pushing technique was characterized by shorter stroke length and lower speed of the grinding block than the other techniques. The painters among the group of subjects who used the pushing technique were found to report fewer shoulder disorders during sanding than the others. The most common shoulder tendinitis is the supraspinatus tendinitis, also among house painters, and using the Pushing technique could possibly prevent from this disorder. However, further research in larger groups of house painters is needed to be able to recommend this technique for a wider use.

Adult↗
PubMed2001

Determination of isocyanic acid in air.

A method is presented for the determination of isocyanic acid (ICA), HNCO, in air samples as a di-n-butylamine (DBA) derivative. The method is based on sampling in midget impinger flasks containing 10 ml of 0.01 mol l-1 DBA in toluene. Quantification was made using liquid chromatography (LC) and electrospray mass spectrometry (MS) monitoring positive ions. The instrumental detection limit for the LC-MS was 10 fmol of ICA-DBA. ICA was generated by thermal decomposition of urea. A standard solution containing the DBA derivatives of ICA was prepared by collecting the emitted ICA in an impinger flask containing DBA. ICA in the reference solution was characterised by LC and time-of-flight (TOF) MS and quantified by LC chemiluminescent nitrogen detection (LC-CLND). The instrumental detection limit for the LC-CLND was 1 ng of nitrogen. ICA was emitted during thermal degradation of PFU resins and polyurethane (PUR) lacquers, from car metal sheets. ICA was the most dominant isocyanate and in PUR coating up to 8% of the total weight was emitted as ICA and for PFU resins up to 14% was emitted as ICA. When air samples were collected in an iron foundry during casting in sand moulds with furan resins, concentrations of ICA in the range 50-700 micrograms m-3 were found in the working atmosphere.

Air Pollutants, Occupational↗
PubMed2001

A design and prototype for a decision-support system in the field of urinary tract infections--application of OpenGALEN techniques for indexing medical information.

Differences in expert and end-user contexts may be detrimental to the use of decision-support systems. A way to attend to this problem is to triangulate decision-support methods and information sources such as in the case of the expertext system model. To organize the information contained in the system, a common domain model is suggested as a instrument for annotating information. In this paper, a design and a prototype for a decision-support system in the field of urinary tract infections using techniques and methods developed in the GALEN projects is presented.

Abstracting and Indexing↗
PubMed2000

Airborne thermal degradation products of polyurethene coatings in car repair shops.

A methodology for workplace air monitoring of aromatic and aliphatic, mono- and polyisocyanates by derivatisation with di-n-butylamine (DBA) is presented. Air sampling was performed using midget impinger flasks containing 10 ml of 0.01 mol l(-1) DBA in toluene and a glass-fibre filter in series after the impinger flask, thereby providing the possibility of collecting and derivatising isocyanates in both the gas and particle phases. Quantification was made by LC-MS, monitoring the molecular ions [MH]+. Air samples taken with this method in car repair shops showed that many different isocyanates are formed during thermal decomposition of polyurethane (PUR) coatings. In addition to isocyanates such as hexamethylene (HDI), isophorone (IPDI), toluene (TDI) and methylenediphenyl diisocyanate (MDI), monoisocyanates such as methyl (MIC), ethyl (EIC), propyl (PIC), butyl (BIC) and phenyl isocyanate (PhI) were found. In many air samples the aliphatic monoisocyanates dominated. During cutting and welding operations, the highest levels of isocyanates were observed. In a single air sample from a welding operation in a car repair shop, the highest concentrations found were: MIC, 290; EIC, 60; PIC, 20; BIC, 9; PhI, 27; HDI, 105; IPDI, 39; MDI, 4; and 2,4-TDI and 2,6-TDI 140 microg m(-3). Monitoring the particle size distribution and concentration during grinding, welding and cutting operations showed that ultrafine particles (< 0.1 microm) were formed at high concentrations. Isocyanates with low volatility were mainly found in the particle phase, but isocyanates with a relatively high volatility such as TDI, were found in both the particle and gas phases.

Air Pollution, Indoor↗
PubMed1999

Segmental movements of the spine during treadmill walking with normal speed.

OBJECTIVE: The aim of the present work is to investigate the segmental movement patterns of the spine during normal treadmill gait. DESIGN: The spine movement during treadmill gait of ten healthy subjects (five men and five women) has been investigated using an optoelectronic measuring system. METHODS: The spine was divided into seven segments, from C(7) to S(2). The subjects walked with their normal speed. All data were normalized to per cent of the gait cycle. The normal patterns of the spine segment movements were found in the sagittal and the frontal planes. RESULTS: The behaviour of the spine can be described as the motion of a stiff element with superimposed small, inter-segmental movements. These small inter-segmental movements were found both in the sagittal and the frontal planes. CONCLUSIONS: The small inter-segmental movements could play an important role in the reduction of the energy consumption during gait and in maintenance of the equilibrium. RELEVANCE: Any disability affecting the spine should result in changing spine movement pattern during gait, thus changing the overall gait pattern. Therefore, treatment and rehabilitation should not discard the influence of the spine malfunctioning, regardless of its nature.

Adult↗
PubMed1999

Validation of a diffusive sampler for NO2.

A diffusive sampler for NO2, Willems badge, was validated in laboratory experiments and field tests. The collecting reagent for NO2 in the sampler is triethanolamine, and the analysis is based on a modified colorimetric method, the Saltzman method. The analysis was performed by a flow injection analysis (FIA) technique. The sampling rate for the sampler was determined to be 40.0 ml min-1. There was no effect of NO2 concentration or relative humidity on sampling rate, and the influence of sampling time was found to be small. The detection limit was 4 micrograms m-3 for a 24 h sample. The capacity is high enough to allow sampling of 150 micrograms m-3 for 7 days, which is twice the recommended Swedish short-term (24 h) guideline value as a 98-percentile over 6 months. In field tests, the sampler performed well, even at wind speeds higher than 2 m s-1, and at low temperatures. The overall uncertainty of the method was 24%. The sensitivity and capacity of the method also make it suitable for personal sampling for 2-8 h in working environments.

Air Pollution↗
PubMed1999

Concepts, contexts and expert systems.

This paper describes problems identified in our attempts to develop an expert system for management of urinary tract infections. We found three aspects which we believe are important to consider when developing such systems. The objective of our future work will be to evaluate the impact of these problems on expert system development and usage.

Artificial Intelligence↗
PubMed1998

Determination of complex mixtures of airborne isocyanates and amines. Part 5. Determination of low molecular weight aliphatic isocyanates as dibutylamine derivatives.

A method is presented for the determination of low molecular weight aliphatic isocyanates, methyl isocyanate (MIC), ethyl isocyanate (EIC), propyl isocyanate (PIC) and butyl isocyanate (BIC), as their dibutylamine (DBA) derivatives. The method is based on sampling in midget impinger flasks containing 10 ml of 0.01 mol l-1 DBA in toluene (as in Parts 1-4 in this series). The samples are analysed using liquid chromatography-electrospray mass spectrometry (LC-ESP-MS) or gas chromatography-mass spectrometry using chemical ionisation with ammonia, monitoring positive ions (GC-PCI). Quantification was effected by monitoring the molecular ions MH+. Aliquots of 10 ml of toluene solutions containing 0.01 mol l-1 DBA were spiked with 0.03-0.85 microgram of MIC-, EIC-, PIC- and BIC-DBA. The correlation coefficients for LC-ESP-MS were in the range 0.9952-0.9999 (n = 14). The repeatability (RSD) was in the range 0.37-1.2% (0.12-0.34 microgram ml-1, n = 10). The instrumental detection limit for MIC was about 15 micrograms l-1, which corresponds to about 0.5 microgram m-3 in a 15 l air sample. The correlation coefficients for GC-PCI were in the range 0.9913-0.9990. The repeatability (RSD) was in the range 1.1-4.9% (0.12-0.34 microgram ml-1, n = 10). The instrumental detection limit for MIC was about 0.2 microgram l-1, which corresponds to about 0.05 microgram m-3 in a 15 l air sample. Using electron ionisation, the instrumental detection limit for MIC was about 10 micrograms l-1. No derivatisation reaction losses were seen when the derivatization reaction between PIC and DBA took place in the presence of morpholine, propylamine, ethanol, phenol and water. When mineral wool with a phenol-formaldehyde-urea resin was thermally degraded, 0.1% m/m of MIC was released. In air samples taken on top of a new electric oven insulated with mineral wool, MIC was found in the range 0.1-3 mg m-3. No MIC in air was found from a pre-heated oven.

Air Pollutants, Occupational↗
PubMed1998

Design and application of a terminology management system.

A Swedish data model for handling terminology, Spriterm, is presented in this paper. A prototype terminology management system, using the Spriterm data model in also described. This prototype is implemented is Microsoft ACCESS. Furthermore, two other applications using this prototype as a base are introduced. One World Wide Web based application, and a data dictionary.

Databases as Topic↗
PubMed1997

Extended telemedical consultation using Arden Syntax based decision support, hypertext and WWW technique.

There is an obvious need for geographic distribution of expert knowledge among several health care units without increasing the cost of on-site expertise in locations where health care is provided. This paper describes the design of a knowledge-based decision-support system for extended consultation in clinical medicine. The system is based on Arden Syntax for Medical Logic Modules and hypertext using World Wide Web technology. It provides advice and explanations regarding the given advice. The explanations are presented in a hypertext format allowing the user to browse related information and to verify the relevance of the given advice. The system is intended to be used in a closed local network. With special precautions regarding issues of safety and patient security, the system can be used over wider areas such as in rural medicine. A prototype has been developed in the field of clinical microbiology and infectious diseases regarding infective endocarditis.

Artificial Intelligence↗
PubMed1997

A qualitative study of clinicians ways of using a decision-support system.

We have studied how clinicians approached a decision-support system to manage patient cases. The design of the system under study was based on an integration of hypertext and rule-based systems. World-Wide Web technology was used for the implementation of the system. By using grounded theory and stimulated recall, we found that getting patient-specific support and continuing medical education were the two major usages of the system and that the three parameters relevance, validity, and work were important in describing how the system was experienced by the users.

Attitude to Computers↗
PubMed1996

Measurements of indoor and outdoor nitrogen dioxide concentrations using a diffusive sampler.

The Willems badge, a short-term diffusion sampler, was used to measure nitrogen dioxide concentrations inside and outside the homes of participants in the European study "PEACE' (Pollution Effects on Asthmatic Children in Europe). The main aim of the study was to determine levels of nitrogen dioxide concentrations both outside and inside children's homes, and to estimate the indoor/outdoor ratios for nitrogen dioxide in an urban area, in comparison with a less urbanized control area. We conducted measurements in 23 homes in Umeå, a city of about 100,000 inhabitants in the northern part of Sweden, in addition to 20 homes in a less urbanized control area situated about 20 km from Umeå. Measurements were made on two different occasions in each home during the period January-March, 1994. The houses were not equipped with any gas appliances. The mean outdoor 24-h concentration in Umeå was 28 micrograms m-3 and the mean indoor concentration was 11 micrograms m-3. The mean indoor: outdoor ratio was 0.44 (s = 0.23). The highest outdoor value, measured in the city centre of Umeå, was 54 micrograms m-3. In the control area the mean ambient 24-h concentration was 12 micrograms m-3, approximately half as high as in the urban area, and the mean indoor concentration was 6 micrograms m-3. The mean indoor: outdoor ratio was 0.67 (s = 0.55). The correlation coefficient between indoor and outdoor concentrations was higher in the control area, r = 0.79 (p < 0.001), in comparison with the urban area, r = 0.43 (p < 0.01). It is concluded that the outdoor as well as the indoor concentrations of nitrogen dioxide were approximately twice as high in Umeå as in the control area. This could be explained by heavier traffic density in Umeå. The mean 24-h concentration outside homes in Umeå was, however, below the 24-h national standard level of 75 micrograms m-3. The higher correlation between indoor and outdoor concentrations, combined with higher indoor: outdoor ratio, in the control area is interpreted as a sign of a lower level of penetration of outdoor air into the houses in the urban area. This was not explained by differences in types of buildings between the two areas, but possibly by differences in air-exchange rates and in habits of ventilating rooms with open windows.

Air Pollutants↗
PubMed1996

A design for a World Wide Web decision-support system using a controlled medical terminology.

We have developed a medical decision-support system based on Arden Syntax for Medical Logic Modules and hypertext using the World Wide Web. The two representations are integrated to provide a better platform for decision support. To manage the integration a controlled medical terminology has been used as a well-defined interface between the representations. The terminology is also used to facilitate communication between specialists and non-specialists.

Artificial Intelligence↗
PubMed1995

Structure and internal consistency of a shoulder model.

A three-dimensional biomechanical model of the shoulder is developed for force predictions in 46 shoulder structures. The model is directed towards the analysis of static working situations where the load is low or moderate. Arbitrary static arm postures in the natural shoulder range may be considered, as well as different kinds of external loads including different force and moment directions. The model can predict internal forces for the shoulder muscles, for the glenohumeral, the acromioclavicular and the sternoclavicular joint as well as for the coracohumeral ligament. A solution to the statistically indeterminate force system is obtained by minimising an objective function. The default function chosen for this is the sum of the squared muscle stresses, but other objective functions may be used as well. The structure of the model is described and its ingredients discussed. The internal consistency of the model, its structural stability and the compatibility of the elements that go into it, is investigated.

Acromioclavicular Joint↗
PubMed1992

Towards a model for force predictions in the human shoulder.

In this paper the concept of a three-dimensional biomechanical model of the human shoulder is introduced. This model is used to analyze static load sharing between the muscles, the bones and the ligaments. The model consists of all shoulder structures, which means that different positions and different load situations may be analyzed using the same model. Solutions can be found for the complete range of shoulder motion. However, this article focuses only on elevation in the scapular plane and on forces in structures attached to the humerus. The intention is to expand the model in future studies to also involve the forces acting on the other shoulder bones: the scapula and the clavicle. The musculoskeletal forces in the shoulder complex are predicted utilizing the optimization technique with the sum of squared muscle stresses as an objective function. Numerical results predict that among the muscles crossing the glenohumeral joint parts of the deltoideus, the infraspinatus, the supraspinatus, the subscapularis, the pectoralis major, the coracobrachialis and the biceps are the muscles most activated during this sort of abduction. Muscle-force levels reached values of 150 N when the hand load was 1 kg. The results from the model seem to be qualitatively accurate, but it is concluded that in the future development of the model the direction of the contact force in the glenohumeral joint must be constrained.

Arm↗