Peter Bröde

UTCI-Fiala multi-node model of human heat transfer and temperature regulation.

The UTCI-Fiala mathematical model of human temperature regulation forms the basis of the new Universal Thermal Climate Index (UTC). Following extensive validation tests, adaptations and extensions, such as the inclusion of an adaptive clothing model, the model was used to predict human temperature and regulatory responses for combinations of the prevailing outdoor climate conditions. This paper provides an overview of the underlying algorithms and methods that constitute the multi-node dynamic UTCI-Fiala model of human thermal physiology and comfort. Treated topics include modelling heat and mass transfer within the body, numerical techniques, modelling environmental heat exchanges, thermoregulatory reactions of the central nervous system, and perceptual responses. Other contributions of this special issue describe the validation of the UTCI-Fiala model against measured data and the development of the adaptive clothing model for outdoor climates.

The UTCI-clothing model

The Universal Thermal Climate Index (UTCI) was conceived as a thermal index covering the whole climate range from heat to cold. This would be impossible without considering clothing as the interface between the person (here, the physiological model of thermoregulation) and the environment. It was decided to develop a clothing model for this application in which the following three factors were considered: (1) typical dressing behaviour in different temperatures, as observed in the field, resulting in a model of the distribution of clothing over the different body segments in relation to the ambient temperature, (2) the changes in clothing insulation and vapour resistance caused by wind and body movement, and (3) the change in wind speed in relation to the height above ground. The outcome was a clothing model that defines in detail the effective clothing insulation and vapour resistance for each of the thermo-physiological model’s body segments over a wide range of climatic conditions. This paper details this model’s conception and documents its definitions.

Melatonin production during childhood and adolescence: a longitudinal study on the excretion of urinary 6-hydroxymelatonin sulfate.

Abstract: Cross‐sectional data on urinary 6‐hydroxymelatonin sulfate (6‐OHMS) excretion in children suggest a constant melatonin secretion during growth. The present longitudinal study concerned, accordingly, the intra‐individual stability of melatonin production during childhood and adolescence. Urine samples collected during a longitudinal investigation of healthy white children and adolescents were analyzed. Forty‐six boys and 38 girls were chosen for the present study. They had passed 3–15 annual examinations between their 3rd and 18th yr of age. Each examination included the collection of urine over 24 hr. The daily urinary output of 6‐OHMS of the overall 621 samples was quantified by enzyme‐linked immunosorbent assay. The analyses clearly revealed for the first time that, despite huge inter‐individual differences, melatonin production remains constant in one and the same individual during childhood and adolescence. Additionally, neither a significant sex difference was observed nor was the 6‐OHMS output affected by season. The dramatic decrease of plasma melatonin levels as described in the literature is mainly related to an increase in body size rather than to decreasing pineal secretion.

Evaporative cooling: effective latent heat of evaporation in relation to evaporation distance from the skin

Calculation of evaporative heat loss is essential to heat balance calculations. Despite recognition that the value for latent heat of evaporation, used in these calculations, may not always reflect the real cooling benefit to the body, only limited quantitative data on this is available, which has found little use in recent literature. In this experiment a thermal manikin, (MTNW, Seattle, WA) was used to determine the effective cooling power of moisture evaporation. The manikin measures both heat loss and mass loss independently, allowing a direct calculation of an effective latent heat of evaporation (λeff). The location of the evaporation was varied: from the skin or from the underwear or from the outerwear. Outerwear of different permeabilities was used, and different numbers of layers were used. Tests took place in 20°C, 0.5 m/s at different humidities and were performed both dry and with a wet layer, allowing the breakdown of heat loss in dry and evaporative components. For evaporation from the skin, λeff is close to the theoretical value (2,430 J/g) but starts to drop when more clothing is worn, e.g., by 11% for underwear and permeable coverall. When evaporation is from the underwear, λeff reduction is 28% wearing a permeable outer. When evaporation is from the outermost layer only, the reduction exceeds 62% (no base layer), increasing toward 80% with more layers between skin and wet outerwear. In semi- and impermeable outerwear, the added effect of condensation in the clothing opposes this effect. A general formula for the calculation of λeff was developed.

Calculation of clothing insulation by serial and parallel methods: effects on clothing choice by IREQ and thermal responses in the cold.

Cold protective clothing was studied in 2 European Union projects. The objectives were (a) to examine different insulation calculation methods as measured on a manikin (serial or parallel), for the prediction of cold stress (IREQ); (b) to consider the effects of cold protective clothing on metabolic rate; (c) to evaluate the movement and wind correction of clothing insulation values. Tests were carried out on 8 subjects. The results showed the possibility of incorporating the effect of increases in metabolic rate values due to thick cold protective clothing into the IREQ model. Using the higher thermal insulation value from the serial method in the IREQ prediction, would lead to unacceptable cooling of the users. Thus, only the parallel insulation calculation method in EN 342:2004 should be used. The wind and motion correction equation (No. 2) gave realistic values for total resultant insulation; dynamic testing according to EN 342:2004 may be omitted.

Evaluation of performance and load in simulated rescue tasks for a novel design SCBA: effect of weight, volume and weight distribution.

A self-contained breathing apparatus (SCBA) with an innovative rucksack shape that provides a better distribution of its weight over the middle and lower parts of the back (device C: 6l, 13.7 kg) was compared with two conventional SCBA which differed from each other in volume and weight (A: 6l, 15 kg, B: 6.8l, 11.7 kg). Twelve fire-fighters (27-49 yr) performed three exercises while using the three SCBA in a systematically permuted sequence. The exercises consisted of simulated rescue work under natural climatic conditions in a dwelling on the second floor and several typical elements of severe fire-fighting actions. Duration, heart rate, breathing frequency, rectal temperature, and sweat loss were recorded. Perceived exertion was rated and the carrying features of the SCBA were subjectively evaluated. The exercise was executed faster with the rucksack device, heart rates were then lower and the carrying features were evaluated as better. Thus, the weight of the SCBA was shown to be less important than its distribution.

Fixation disparity and nonius bias

Fixation disparity, i.e. the vergence error within Panums area, can be measured psychophysically with two nonius (vernier) lines that are presented dichoptically, i.e. one to each eye. The observer adjusts these nonius lines to subjective alignment; the resulting physical nonius offset indicates the amount of fixation disparity. The present experiments investigate the relation between fixation disparity and the nonius bias, which is the physical offset of the nonius lines that is adjusted by the observer in order to perceive them as aligned when both nonius lines are presented to both eyes (binocular nonius bias) or both to the left or both to the right eye (monocular nonius bias). It was found that (1) the fixation disparity is correlated with the binocular nonius bias in the horizontal and vertical meridian and (2) the binocular nonius bias can be predicted from the average of the right eye and left eye monocular nonius bias. To remove the influence of the nonius bias on measured fixation disparity it is possible to calculate the fixation disparity relative to the individual binocular nonius bias, rather than to the physical coincidence of the nonius lines. This procedure tends to increase the correlation between fixation disparity and the tonic resting position of vergence. We discuss the clinical relevance of the dichoptic nonius method for measuring fixation disparity and its limitations as compared to physical recordings of eye position.

Excretion of 6-Hydroxymelatonin Sulfate (6-OHMS) in Siblings during Childhood and Adolescence

The analysis was performed to support the assumption that in inter-individual variations melatonin production is determined genetically. Sixty-six siblings from 31 families (27 girls, 39 boys, 3–18 years) contributed to this study with 3 to 15 urine samples collected once a year over 24 h. The samples were stored at –20°C and analyzed for the daily output of the melatonin metabolite 6-hydroxymelatonin sulfate (6-OHMS) by an enzyme-linked immunosorbent assay (ELISA). The results indicate that 6-OHMS excretion was significantly correlated in siblings (r = 0.37, p = 0.01), suggesting a possible genetic background of melatonin production. However, prospective studies controlling also lifestyle factors such as diet are required to further confirm the hypothesis.

Pathological excretion patterns of urinary proteins in miners highly exposed to dinitrotoluene.

A cohort of 161 underground miners who had been highly exposed to dinitrotoluene (DNT) in the copper-mining industry of the former German Democratic Republic was reinvestigated for signs of subclinical renal damage. The study included a screening of urinary proteins excreted by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and quantitations of the specific urinary proteins &agr;1-microglobulin and glutathione-S-transferase &agr; (GST &agr;) as biomarkers for damage of the proximal tubule and glutathione-S-transferase &pgr; (GST &pgr;) for damage of the distal tubule. The exposures were categorized semiquantitatively (low, medium, high, and very high), according to the type and duration of professional contact with DNT. A straight dose-dependence of pathological protein excretion patterns with the semiquantitative ranking of DNT exposure was seen. Most of the previously reported cancer cases of the urinary tract, especially those in the higher exposed groups, were confined to pathological urinary protein excretion patterns. The damage from DNT was directed toward the tubular system. In many cases, the appearance of Tamm-Horsfall protein, a 105-kD protein marker, was noted. Data on the biomarkers &agr;1-microglobulin, GST &agr;, and GST &pgr; consistently demonstrated a dose-dependent increase in tubular damage, which confirmed the results of screening by SDS-PAGE and clearly indicated a nephrotoxic effect of DNT under the given conditions of exposure. Within the cluster of cancer patients observed among the DNT-exposed workers, only in exceptional cases were normal biomarker excretions found.

The significance of lateral whole-body vibrations related to separately and simultaneously applied vertical motions. A validation study of ISO 2631

Sensitivity of lateral motions relative to vertical motions were determined and compared to predictions provided by ISO 2631. Two experiments were executed where lateral and vertical motions were applied consecutively or simultaneously and where the magnitude of a single- or dual-axis test signal was adjusted until it was judged as equivalent to a preceding single-axis reference motion of the same frequency. Experiment 1: References consisted of vertical sinusoidal motions presented with 1.6-12.5 Hz and weighted accelerations of a(zw) = 0.3, 0.6 and 1.2 m s(-2) r.m.s., single-axis test signals were lateral motions of the same frequency. 26 subjects (15 men, 11 women, 20-56 yr) participated in the experiments. Accelerations adjusted for lateral vibrations above 1.6 Hz were considerably lower than predicted suggesting that the weighting factors provided in ISO 2631 are incorrect. Experiment 2: References consisted of single-axis vertical or lateral sinusoidal motions presented with 1.6-12.5 Hz and a weighted acceleration of a(zw) = 1.25 m s(-2) r.m.s. The dual-axis test signals consisted of a constant fraction of the reference acceleration (10, 25, 50, 75, 90%) and a perpendicularly oriented adjustable component. 31 subjects (15 men, 16 women, 19-51 yr) participated in the experiments. Both experiments revealed that ISO 2631 is qualitatively valid, the weighting of lateral motions above 1.6 Hz, however, should be increased in order to meet the actual sensitivity particularly in case of multi-axis vibrations.