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Biomedical subjects

J Starck

Publications and source records attributed to J Starck.

84 records · Page 5Linked to original sources
PubMed1979

Hand grip forces during chain saw operation and vibration white finger in lumberjacks.

The hand grip forces at the front and rear handles of a chain saw were measured during work, in 89 professional lumberjacks. The symptoms caused by vibration to the upper limbs were compared with the hand grip force (HGF) during work. To allow better comparison between subjects we used the ratio of hand grip force (HGF) to the maximal voluntary compression force (MVC), HGF/MVC expressed as a percentage. The mean HGF during sawing varied from 5 to 12 N in all subjects. The variation in HGF was greater at the front handle than at the rear handle, during sawing. The lumberjacks who had vibration-induced white fingers (VWF), had a higher HGF/MVC in both hands than the lumberjacks without VWF. Those lumberjacks affected by VWF used over 12% of their MVC at work. Subjects without HGF/MVC ratio. The lumberjacks with and without numbness in their hands had equal HGF/MVC ratios.

Adolescent↗
PubMed1977

[Autoradiographic localization of RNA synthesis in vitro during oogenesis in Parascaris equorum].

Technical elaboration of in vitro incubation of Parascaris equorum gonads with 3H-Uridine has permitted, for the first time, the study of RNA synthesis during oogenesis along the whole gonadic tube. In germ cells, oocytes in diakinesis (oviduct) and in division of maturation (uterus) show no label. On the contrary oogonia and growing oocytes in ovary are labelled. RNA synthesis is always detected in all parietal cells but is more active in oviduct and uterus where the gonadic wall is particularly developed.

Animals↗
PubMedDate not supplied

Smoking habits and postural stability.

PURPOSE: It has been reported that tobacco smoking temporarily affects postural stability We have examined whether smoking habits have a long-term effect on the body balance control using computer-aided posturography. SUBJECTS AND METHODS: The postural stability of 80 male forest workers was measured with a force platform technique with eyes closed. Average body sway velocity (ASV [mm/s]) was determined and used as a stability index. Detailed interviews on tobacco smoking and otologic examinations were carried out. Smoking habits were classified into five categories: nonsmokers (53.8%), ex-smokers (17.5%) and current smokers, comprising light (3.8%), moderate (15%), and heavy (10%) smokers. RESULTS: The smoking habits of the subjects correlated significantly with ASV, but hours of the exposure to noise and hand-arm vibration from chain saws did not. The correlation of the smoking habits remained significant even after eliminating the effect of age and exposure by partialization. Age in itself had no effect on ASV but interacted with smoking to increase ASV. The group means of ASV increased with the increase in smoking. Significant differences in ASV were found in the moderate and heavy smokers compared with the nonsmokers. CONCLUSION: Smokers exhibited more unstable posturographic results than nonsmokers. Smoking habits were suggested to have a long-term effect on the posture control system.

Adult↗
PubMedDate not supplied

Further evidence of a relation between noise-induced permanent threshold shift and vibration-induced digital vasospasms.

The relation between noise-induced permanent threshold shift (NIPTS) and vibration-induced dysfunction in the digital circulation was examined in a longitudinal survey among forest workers. The survey was based on annual examinations done between 1972 and 1983. Thirty-two forest workers with digital vasospasms were compared with referents matched for age, exposure, and use of ear protectors. No significant differences between the groups were observed at 1,000 or 2,000 Hz. The forest workers with digital vasospasms had significantly greater NIPTS at 4,000 and 8,000 Hz than the symptom-free referents. During the follow-up period, the gap in NIPTS between the two groups did not increase. Vibration measurements from chain saws manufactured in different years indicated that chain saws manufactured after 1970 had a tenfold reduction in vibration, whereas the reduction in noise levels was only slight. The results suggest that vibration-induced activation of the autonomic nervous system, which is thought to elicit digital vasospasms, may also contribute to the development of NIPTS.

Adult↗
PubMedDate not supplied

Effects of coldness on the protective performance of earmuffs.

The type test of hearing protectors (HPD) for certification purposes will be conducted in laboratory at room temperature. Optionally, the mechanical durability of HPDs will be tested in cold environment by a drop test. The purpose of this study was to find out the relevance of the drop test, the change of performance in HPD protection, and finally to estimate the possible change of protection efficiency against noise in cold environment. In total, 22 HPDs were selected to the measurements: 18 earmuffs, and 4 earmuffs attached to an industrial helmet. Attenuation of each earmuff cup was measured by applying insertion loss method for the test subjects in cold. The change of attenuation and temperature of cushion ring was followed up to nine minutes using 30-second intervals for sampling. Three HPDs were damaged in the test. The replaceable cushion was broken in two earmuffs and in one helmet-mounted HPD. The replaceable parts were replaced, and the HPD with attachment failure was removed from insertion loss measurement. In nine HPDs the relative change was less than 3 dB, and was at worst 10 dB. This change was typically at low frequencies, 125 Hz at the beginning when cooled HPDs were placed. In various HPDs the time to get the attenuation levelled varied from 1.5 minutes to 8 minutes. The recovery was dependent on the temperature of the cushion ring. In all cases the temperature of the full attenuation was achieved when the cushion ring reached 7 degrees C. This temporary decrease in attenuation will have a minor effect to the protection efficiency, when the HPD is used full time during the whole exposure duration. A typical group of forest workers will have their exposure interrupted. The chain saws have to refuel, and the chain needs to be sharpened about every 40 minutes. During 6 hour daily operational time there will be about 9-10 minute break, long enough to cool the cushion ring back to below zero at -10 degrees C, if the helmet mounted earmuffs are placed in stand-by position. In the worst case this will cause 1.6 dB increase in daily exposure level to noise.

Cold Temperature↗
PubMedDate not supplied

The use of hearing protectors among forest, shipyard and paper mill workers in Finland--a longitudinal study.

From 1953 to 1995 the usage rate of hearing protective devices (HPD) was tracked at a paper mill, a shipyard, and in selected areas of forestry work. For each work period, observations were made of HPD use among workers. In the paper mill, the usage rate increased steadily from 1965. In 1990, 39% of workers used HPDs full-time. At the shipyard, the usage rate remained low up to the mid-1980s, but thereafter the proportion of full-time users rose to 70%. A similar trend was noted in forest workers, with the full-time use at 97% by the 1990s. Due to the increased usage rate in all measured industries, the mean effective noise level at the ear has decreased to below 85 dB.

Cross-Sectional Studies↗
PubMedDate not supplied

Measurements of postural stability: development of a force platform and some excitation systems.

Technical data are given for the construction of a low cost transportable force platform to measure postural stability. The measuring elements in the platform are placed between two rigid metal plates to give information about the movements of the center point of force of a standing subject. The system utilizes a microcomputer for data collection, and data analysis routines are used to calculate the movement of the center point of force. Postural perturbation was excited with a vibrating platform, a low frequency noise source and a vibration stimulator for the calf muscles.

Amplifiers, Electronic↗
PubMedDate not supplied

Impulse noise and risk criteria.

Impulse noise causes evidently more severe hearing loss than steady state noise. The additional effect of occupational impulse noise on hearing has been shown to be from 5 to 12 dB at 4 kHz audiometric frequency. Reported cases for compensated for hearing loss are prevalent in occupations where noise is impulsive. For impulse noise two measurement methods have been proposed: the peak level method and energy evaluation method. The applicability of the peak level method is difficult as even the recurrent impulses have different time and frequency characteristics. Various national risk criteria differ from international risk criteria. In France the maximum A-weighted peak level is 135 dB, and in the United Kingdom the C-weighted peak sound pressure is limited to 200 Pa (140 dB). This criterion of unweighted 200 Pa (140 dB) is used in European Union (EU) directive 86/188 and ISO 1999-1990 regardless of the number of impulses. The American Conference of Governmental Industrial Hygienists (ACGIH) has recommended that no exposure in excess of a C-weighted peak sound pressure level of 140 dB should be permitted. At work places these norms do not cause any practical consequences since the impulses seldom exceed 140 dB peak level. In several occupations the impulses are so rapid that they contribute only a minimal amount to the energy content of noise. These impulses can damage the inner ear even though they cause reduced awareness of the hazard of noise. Based to the present knowledge it is evident that there is the inadequacy of the equal energy principle in modelling the risk for hearing loss. The hearing protectors attenuate industrial impulse noise effectively due to the high frequency contents of impulses. Directive regarding the exposure of workers to the risks arising from noise requires that in risk assessment attention should be paid also to impulsive noise. So far there is no valid method to combine steady state and impulse noise. A statistical method for the measurements of industrial impulse noise is needed to get a preferably single number for risk assessment. There is an urgent task to develop risk assessment method and risk criteria for impulsive noise to meet the requirements of the upcoming European Union noise directive.

Adult↗