Biomedical subjects

H Håkanson

Publications and source records attributed to H Håkanson.

At least 19 recordsLinked to original sources

PubMed1992

Process monitoring by flow-injection immunoassay. Evaluation of a sequential competitive binding assay.

A new variation on the theme of flow-injection binding assays is presented, namely the sequential competitive binding assay, in which the sample containing the native antigen is first introduced into the flow system followed by a pulse of labelled antigen. The flow-injection binding assay was used in monitoring the effluent from column chromatographic separations of proteins. By applying a computer-based evaluation system, concentrations are automatically read and compensation is made for denaturation in the affinity sorbent.

Binding, Competitive↗

PubMed1992

Immunochemically based assays for process control.

Immunoanalysis for process control is reviewed. The development of non-equilibrium immunoassays from a manually operated flow injection system to a completely computerized system for sample analysis as well as calibration and data evaluation is discussed. Several other approaches in using immunochemistry in biosensors for process control are discussed. The fact that reuse of antibodies raises specific demands on their properties is discussed. Even if the area is young, much progress has been achieved and one can foresee an interesting future development of the area.

Biomedical Engineering↗

PubMed1991

Continuous monitoring of urea in blood during dialysis.

Urease was immobilized to porous glass and used in combination with a conductivity meter for determining urea in standard solutions as well as in blood from a patient undergoing dialysis. The sampling unit involves a possibility for heparinization at the sampling point and a dialysis step prior to exposure to the enzyme column. The unit operates in a linear mode in the concentration range 5-50 mM. Monitoring of dialysis process gave good correlation with off-line analyses.

Biosensing Techniques↗

PubMed1983

Hearing deterioration in shipyard workers. Serial audiometry over a four-year period.

The hearing thresholds of a total of 58 workers aged 20 to 65 years were measured annually over a period of 4 years using Békésy sweep-frequency audiometry. Using these data, accurate values of the yearly rate of change of hearing threshold level were calculated. The rate of change of hearing threshold level due to presbyacusis was obtained from several data sets, and the rate of change of hearing threshold level due to noise was calculated. When the average hearing threshold level over the frequency range 2-8 kHz was considered, it was found to be possible to establish a significant rate of threshold shift caused by exposure to noise for yearly changes as small as approximately 2 dB. In the cases investigated about 30% of the ears showed a significant deterioration in hearing ability due to noise. When comparing the permanent threshold shift caused by noise in groups of younger and older workers, it was found that the younger workers exhibited less threshold shift than expected, whereas the older workers showed a greater threshold shift than expected.

Adult↗

PubMed1980

Calculation of noise dose from time distribution of sound levels.

The noise from ten different sites in a machine factory was measured and cumulative time distributions of the sound pressure were constructed. From these distributions it is possible to calculate the energy mean level, the equivalent sound level as well as the average sound pressure level. Calculations based on knowledge of the times during which only a few sound pressure levels are exceeded give values deviating systematically from the exact value. Because of the systematic nature of the deviations corrections can be made for them. The accuracy of this method is relatively high.

Acoustics↗

PubMed1980

An impulse sound generator and some comparative experiments with different noise dosimeters.

An impulse sound generator has been constructed which gives the same sound pressure wave pattern during over 10(5) impacts with very small variations. This device has been used in evaluating the response of different types of noise dosimeters for impulse sounds.

Acoustics↗

PubMed1980

Noise dose measurements with stationary and ear-borne microphones.

Precision measurement of noise doses with stationary and mobile, ear-borne, microphones were made on ten workers (emery-grinders, welders and platers). The workers selected in each group differed from one another in the amount they moved about during their working day. The differences in the reverberant field at their working places were also taken into account. Very large noise dose differences, up to 20 dB, between stationary and mobile dose measurements were found and it was not possible to find any correction factors for these differences.

Acoustics↗

PubMed1980

The reliability of Békésy sweep audiometry recording and effects of the earphone position.

The hearing thresholds of subjects with hearing impairment of different severity were tested several times. The reliability of the hearing threshold measurements were analysed and compared to the inter-aural variations, the learning effects, the degree of noise-induced hearing impairment and the application of the earphones. The main factor determining the reliability of the hearing threshold is the application of the conventional earphone. A preliminary test-retest with the earphone adapted to an ear speculum for sound transmission to the external ear canal suggests that the precision of the Békésy sweep hearing threshold measurement can obviously be increased in the frequency range of 2 to 8 kHz.

Adult↗

PubMed1980

The difference in protection efficiency between earplugs and earmuffs. An investigation performed at a workplace.

The hearing thresholds of shipyard workers have been measured with a Békésy sweep audiometer. The number of employees at different workplaces is so large that it is possible to select groups of workers of specified ages who have been employed by the shipyard for many years. These workers have used either earplugs of earmuffs for 5--10 years and have also been working all the time in almost the same noise environment. Three ways of investigation have been used to observe differences in the hearing levels between 'plug-men' and 'muff-men'. All three show a greater hearing impairment for 'muff-men' than for 'plug-men'. Under certain conditions earplugs provide the most effective protection although the attenuation is higher for earmuffs than for earplugs.

Adult↗

PubMed1980