Experimental Evaluation of the Importance of the Pulmonary Surfactant for Oxygen Transfer Rate in Human Lungs p. 391 Tomasz R. Sosnowski, Leon Gradoń , Magdalena Skoczek, Hanna Droździel The Correlation Between Symptoms, Frequent Use of Dental Polymers, and Evaluation of Health Risk p. 411 Emma-Christin Lönnroth, Houshang Shahnavaz Theoretical Analysis of the Percussive Tests of Products p. 423 Ryszard Korycki Effects of Manual Handling, Posture, and Whole Body Vibrations on Low-back Pain p. 449 Jean-Pierre Meyer, Dominique Flenghi, Jean-Pierre Deschamps Job Redesign Needs for Aged Workers p. 471 Mitsuyuki Kawakami, Fumihiko Inoue, Takao Ohkubo, Toshio Ueno

Notes:

Two-Dimensional Automatic Control Modeling of a Posture Control System p. 485 Kyung S. Park, Un H. Kim Pressure Sensitive Mats as Safety Devices in Danger Zones p. 499 Stanisław Dąbrowski, Zygfryd Brański

Experimental Evaluation of the Importance of the Pulmonary Surfactant for Oxygen Transfer Rate in Human Lungs p. 391
Tomasz R. Sosnowski, Leon Gradoń , Magdalena Skoczek, Hanna Droździel

The rate of oxygen transport from the atmospheric air into water and perfluorocarbon compound (PFC) was investigated. Static and dynamic systems with and without the presence of the lung surfactant monolayer were considered. For the case of water used as an oxygen absorbent, the monolayer activity allowed a simulation of the gas uptake into the lung hypophase. In the second case, a two-phase liquid system with water as a hypophase and PFC as the blood substitute simulated oxygen transport in the alveolus-blood system. Original experimental measurement devices gave the opportunity of determining the gas transport rate with the possibilities of indicating the role of the lung surfactant in the process and evaluating the influence of environmental conditions on the transport phenomena. Results of that work suggest a possible enhancing role of the lung surfactant in the oxygen transfer rate.

The Correlation Between Symptoms, Frequent Use of Dental Polymers, and Evaluation of Health Risk p. 411
Emma-Christin Lönnroth, Houshang Shahnavaz

Dental personnel are at risk as they manually handle polymer products containing monomers and additives that cause irritation and induce allergy. Gloves and face masks can be easily penetrated by monomers. A total of 587 dental personnel and a referent group (585) in the 2 most northern regions of Sweden were included in a questionnaire study (response rate 76%). Questions were asked regarding symptoms of atopy, asthma, conjunctivitis, atopic dermatitis, hand dermatitis, and hay fever/rhinitis. The dental personnel were asked to give the name of polymer products used in their practice and the frequency of use. They were also asked to risk evaluate 5 different types of polymer materials on a scale from 1 to 5. Analysis was done to find if the occurrence of a symptom was associated with a high risk evaluation of a polymer material, or with frequent use of a certain polymer product. Significantly more dentists reported symptoms of atopic dermatitis and conjunctivitis compared to referents and chair assistants. Results show that dental personnel with symptoms risk evaluated most materials significantly higher than dental personnel without symptoms. Further, the occurrence of some symptoms was associated with frequent use of 8 polymer products.

Theoretical Analysis of the Percussive Tests of Products p. 423
Ryszard Korycki

The goal of theoretical research is to establish parameters, which have to be given in standards for percussive tests of products. Those parameters are essential for each user to be able to construct identical (equivalent) testing equipment. This would ensure identical results for identical products. The paper presents a detailed analysis of the distribution and the value of the forces generated during percussive collisions of two bodies. Elastic, plastic, and elastoplastic collisions are considered. Parameters determining the coefficient of restitution, the courses of energy, momenta, and the values of the forces in colliding elements are determined. The dynamic force acting on a product during a percussive test was studied.

Effects of Manual Handling, Posture, and Whole Body Vibrations on Low-back Pain p. 449
Jean-Pierre Meyer, Dominique Flenghi, Jean-Pierre Deschamps

To determine the effect of occupational stress on low-back pain (LBP), a cross-sectional study has been carried out, by interviews, on workers exposed to 3 stresses: manual handling (MH, 82 women and 264 men), whole body vibrations (WBV, 274 men), and static postures (278 women). Anthropometric data, occupational stress, LBP severity and frequency, and a psychological evaluation of these groups were compared to those of a control population of 208 workers (104 men and 104 women). The results show that 30% of the population had never suffered from LBP. Age and the body mass index of the workers were the parameters most closely associated with LBP. Women involved in MH had higher frequency and severity of LBP than their reference population. Men involved in MH or exposed to WBV had higher frequency of painful episodes than their reference population. Workers exposed to one of the stresses were on sick leave for LBP more often, and for longer periods, than workers in the reference group. The results show that individual factors are often decisive in the onset of LBP. Nevertheless, in the more serious LBP cases, occupational stress is an aggravating factor for LBP and its consequences.

Job Redesign Needs for Aged Workers p. 471
Mitsuyuki Kawakami, Fumihiko Inoue, Takao Ohkubo, Toshio Ueno

The aim of this paper is to explore and present a proposal for redesigning elements of the workplace for aged workers. The method of research was to observe, record, and measure the actions of sitting workers performing assembly operations on electrical products in the Kani Plant Nagoya Works of Mitsubishi Electric Co. (Japan). The evaluation index used in the experiment was obtained by measuring time motion elements, cycle time per product, and motion velocity waves of elderly workers. Those motion characteristics were then compared to the motion characteristics of young workers. The results lead to job redesign elements being identified to reduce handling factors of high difficulty for aged workers and to the necessity to consider a coefficient of correction in Method Time Measurement (MTM) according to differences in the manufactured object's weight.

Two-Dimensional Automatic Control Modeling of a Posture Control System p. 485
Kyung S. Park, Un H. Kim

A posture control model has been developed on the basis of the 2-dimensional feedback control theory. Human postural characteristics were investigated in 5 healthy participants. Tests were performed with eyes open and eyes closed. After 5 s of quiet standing, each participant was unexpectedly pulled forward by 30 mm at his pelvis height and then released. Postural sway was measured over 20 s at a rate of 100 per second. Transfer functions to represent the posture control characteristic were identified by the least squares' method. These showed good results of the model's fitness, predictability, and stability. The response of the eyes-closed condition to perturbation is more oscillatory than that of the eyes-open condition. It seems that the model identified could be applicable to ergonomics, sports, or clinical situations.

Pressure Sensitive Mats as Safety Devices in Danger Zones p. 499
Stanisław Dąbrowski, Zygfryd Brański

Developing prototypes of pressure sensitive mats, and testing their practical application were the aims of this study. Two contact plate mats were designed and constructed: rubber-rubber (R) and metal-metal (M). A recipe for rubber mixes and the production technology were prepared. Two laboratory test stands for measuring the actuating force, response time, static pressure resistance, and the durability of the mats were constructed. Computer software was written to control the operation of those test stands. Methods of testing pressure sensitive mats were based on PrDIN 31 006 (Deutsches Institut für Normung [DIN], 1990) and EN 1760-1 (Comité Européen de Normalisation [CEN], 1996). Both prototypes of contact plate mats were tested under laboratory and industrial conditions. The test results proved that the design was correct, the setup requirements were fulfilled, and the mats were efficient and reliable in the industrial environment.