R.M. van Aalst

The physical and physiological workload of refuse collectors

In order to secure a safer and healthy work situation, the heavy physical loads imposed on 23 refuse collectors (aged 26-54) working in the city of Haarlem, in The Netherlands, were studied in a series of three experiments between 1984 and 1987. The aims were respectively (1) to study the load for workers collecting dustbins or polythene bags; (2) to introduce changes to reduce the load to avoid exceeding the overload criteria by individual refuse collectors; and (3) to investigate the effects of interventions to improve the efficiency of refuse collecting. The maximal isometric lifting force (Fmax) and the maximal aerobic power (VO2max) of 23 refuse collectors were measured in the laboratory. Fmax was measured with an isometric dynamometer pulling with one arm from the floor; the mean value was 912 (+/- 127)N. VO2max was measured running on a treadmill; the mean value was 43.3 (+/- 0.8)ml O2 per kg body mass per min. The physical load on the oxygen transport system was measured through work analysis and by a continuous registration of the heart rate over three working days. Criteria for overload were set at a mean external load of 20% Fmax and a mean energy expenditure of 30% VO2max and an energy expenditure of 50% VO2max or more for a maximum of 60 min per day. Replacement of dustbins by polythene bags resulted in a 70% increase in the total amount of refuse collected, an increase in throwing frequency, but a lower mean load per throw, and no significant differences in the mean heart rate over the working day. When polythene bags were used the mean values did not exceed the overload criteria, but 39% of the individual collectors did have a workload that was too high with respect to one of the criteria. In the last experiment the collectors were advised to reduce their work load by (a) lifting no more than two bags at a time; (b) reducing their walking pace; and (c) taking more breaks. Although compliance with the recommendations was good, and the weight lifted and the walking speed decreased, the physiological load remained the same. This may have been caused by a 15% increase in the total amount of refuse that had to be collected at that time.

The far-infrared spectra of hydrogen chloride in liquid argon and in liquid krypton

Abstract Absorption spectra of hydrogen chloride dissolved in liquid argon and liquid krypton in the region between 12 and 210 cm −1 are reported. Both spectra show a residual rotational fine structure. It is concluded that, apart from the effect of molecular collisions, some effect arising from the characteristic liquid properties must come into play.

Temperature dependence of the pressure induced width and shift of the rotational lines of HCl

Abstract The pure rotational spectra of HCl mixed with argon, krypton and xenon gas of varying pressures at different temperatures have been measured. From the linewidths and shifts the cross sections can be calculated as a function of the temperature. With the insertion of a Boltzmann distribution of translational energy the temperature dependence can be converted to a dependence of the cross section σ( E ) on the relative kinetic energy of the colliding pairs. A comparison of the experimentally determined σ( E ) values with the values predicted by a semi-classical calculation by Neilsen and Gordon leads to the conclusion that the elastic contribution to the cross sections remains of importance even at energies so high that the inelastic contribution has become constant because of the attainment of the sudden perturbation limit. Furthermore it must be concluded that the coefficient of the first Legendre polynomial in the series development of the attractive anisotropic potential is considerably larger than has hitherto been assumed.

The far-infrared spectrum of hydrogen chloride in liquid xenon

Abstract The absorption spectrum of hydrogen chloride in liquid xenon in the region between 10 and 240 cm −1 is reported. The spectrum shows a residual rotational fine structure that is even more pronounced than the fine structure in the corresponding spectra in lighter noble gas liquids. Therefore there is no positive correlation with the atomic polarizabilities.

Determination of the half-life of C3 in patients and its relation to the presence of C3-breakdown products and/or circulating immune complexes

SummaryMeasurement of complement components in serum may not accurately assess the degree of activation of the complement system. An alternative approach is the measurement of conversion products of the complement components. The relation between the presence of an increased concentration of C3-conversion products and the metabolism of C3 was investigated. In a group of patients, circulating immune complexes were also measured (Clq-binding test) to see whether the combination of those markers yielded information on the C3 metabolism. In this study it is shown that static measurements of serum C3 levels is of no value for the degree of complement activation. Measurement of C3-conversion products may indicate C3 hypercatabolism (in 8 of the 11 patients with C3-conversion products), but it does not imply depressed C3 synthesis. Detection of circulating immune complexes by the Clq-binding assay did not always indicate a C3 hypercatabolism. Of 12 SLE patients studied, in 9 of them, a C3 hypercatabolism was detected, and 5 of these patients were clinically characterized by the presence of minor disease symptoms. Overall, the results indicated that detection of circulating immune complexes and/or C3-conversion products could not be used as an absolute measure for insight into the C3 metabolism.

Pressure Effect of Noble Gases on the Pure Rotational Spectrum of Hydrogen Chloride

The changes of the pure rotational spectrum of HCl in the region 15–170 cm−1 under the influence of compression with helium and argon up to 100 atm have been investigated. The experimental results are compared with the spectra calculated on the basis of correlation theory. Energy and momentum transfer in collisions of short duration give full account of the observed features.

The pressure effect of noble gases on the pure rotational spectrum of hydrogen chloride

Abstract The experimental spectra of hydrogen chloride under various pressures of noble gases are compared with spectra calculated on the basis of a simple perturbation theory. Energy and momentum transfer in a collision of short duration give full account of the observed features.

Basic Biological Sciences Root Canal-simulating Experimental Model for Evaluation of Tissue Responses to Chronic Influx of Foreign Fluid Substances

Searching for an experimental model simulating the root canal, a two-stage procedure was evolved using polyethylene tubes implanted subcutaneously in rabbits. The reaction to the model was histologically evaluated, and the rate of release of macromolecules from the tubes was studied using radio-labeled endotoxin and albumin. The model proved suitable for evaluating an animals tissue response to the slow and prolonged influx of foreign fluids.Searching for an experimental model simulating the root canal, a two-stage procedure was evolved using polyethylene tubes implanted subcutaneously in rabbits. The reaction to the model was histologically evaluated, and the rate of release of macromolecules from the tubes was studied using radio-labeled endotoxin and albumin. The model proved suitable for evaluating an animals tissue response to the slow and prolonged influx of foreign fluids.

Temperature dependence of the pressure induced width and shift of the first HCl rotational line

Abstract The line widths and frequencies of the j = 0 → j = 1 pure rotational line of HCl in a gaseous mixture with argon at different pressures and different temperatures are reported and compared with existing theories.

Interpretation of dipole correlation functions in some liquid systems

The dipole correlation functions determined from far infra-red absorption measurements of a variety of liquids are compared with correlation functions calculated with different models for the motion of the molecules. These models vary from simple rotational diffusion models to models derived from solid state theory. Experimental results are presented of far infra-red measurements of HCl dissolved in liquid argon and of solutions of CH3CN in some organic solvents. For these liquid systems good agreement can be obtained between experiment and model calculations. It is pointed out that the description of these systems in terms of a model has a strong phenomenological character.