The effects of clothing thermal resistance and operative temperature on human skin temperature

Skin temperature is an essential physiological parameter of thermal comfort. The purpose of this research was to reveal the effects of clothing thermal resistance and operative temperature on local skin temperature (LST) and mean skin temperature (MST). The LSTs (at 32 sites) in stable condition were measured for different clothing thermal resistances 1.39, 0.5 and 0.1 clo. To study the effect of environmental temperature on LST and MST, the LSTs were also measured for operative temperatures 23, 26 and 33 °C. The experimental data showed that the effect of clothing thermal resistance on the foot was greater compared to the other human parts, and the effect of operative temperature on many parts of the human body was great, such as foot, hand, trunk, and arm. The MSTs measured on the conditions that air speed was under 0.1 m/s, RH was about 30–70%, and metabolic rate was about 1 met, were collected from previous studies. On the basis of these experimental data, a MST prediction equation with the operative temperature and clothing thermal resistance as independent variables, was obtained by multiple linear regression. This equation was a good alternative and provided convenience to predict the MST in different operative temperatures and clothing thermal resistances.     

Metabolic response to air temperature and wind in day-old mallards and a standard operative temperature scale

Most duckling mortality occurs during the week following hatching and is often associated with cold, windy, wet weather and scattering of the brood. We estimated the thermoregulatory demands imposed by cold, windy weather on isolated 1-d-old mallard (Anas platyrhynchos) ducklings resting in cover. We measured O2 consumption and evaporative water loss at air temperatures from 5 degrees to 25 degrees C and wind speeds of 0.1, 0.2, 0.5, and 1.0 m/s. Metabolic heat production increased as wind increased or temperature decreased but was less sensitive to wind than that of either adult passerines or small mammals. Evaporative heat loss ranged from 5% to 17% of heat production. Evaporative heat loss and the ratio of evaporative heat loss to metabolic heat production was significantly lower in rest phase. These data were used to define a standard operative temperature (Tes) scale for night or heavy overcast conditions. An increase of wind speed from 0.1 to 1 m/s decreased Tes by 3 degrees -5 degrees C.     

A simple index of standard operative temperature for mule deer and cattle in winter

1. 1. Scientists often use ambient temperature, relative humidity, or windspeed alone to describe an animal's thermal environment. Standard operative temperature (T_es) incorporates solar and thermal radiation, ambient temperature, and windspeed with a species' resistance to heat loss; thus it more accurately represents an animal's thermal environment. Standard operative temperature is not often recorded in the field because of instruments needed to measure short- and long-wave radiation.

2. 2. Our objective was to determine if regression equations could relate simple micrometeorological measurements to T_es for mule deer and cattle in winter.

3. 3. Blackglobe and ambient temperatures, windspeed, net radiation, total radiation, albedo, and ground surface temperature were recorded during one winter in a field in Bozeman, Montana. We used species specific resistance values for mule deer and cattle in winter to calculate T_es for both species. Then, we regressed T_es with blackglobe and ambient temperatures, and windspeed. The mule deer regression model was applied to an independent data set to determine if it worked well under varying weather conditions.

4. 4. The mule deer and cattle regression models represented T_es for both species well (adjusted R² 0.96 and 0.94, respectively). The mule deer regression model also represented the independent data set well. Standard operative temperatures predicted by our model and those predicted by the independent data set were highly correlated (r > 0.96 for four different comparisons). Our simple micrometeorological measurements are suitable predictors of T_es for mule deer and cattle in winter.

     

Design and performance of a rugged standard operative temperature thermometer for avian studies

The lack of a truly satisfactory sensor which can characterize the thermal environment at the spatial scale experienced by small endotherms has hindered study of their thermoregulatory behavior. We describe a general design for a rugged, easily constructed sensor to measure standard operative temperature, T_es. We present specific designs for adult dark-eyed juncos (Junco hyemalis) and hatchling mallards (Anas platyrhynchos). Sensor response was stable and repeatable (±1.4%) over the course of several months. Over the range of conditions for which validation data were available (variable air temperature and wind with negligible net radiation), sensors predicted the mean net heat production of live animals to within ±0.023 W (equivalent to ±1°C at T_es=15°C). The main limit on accuracy was scatter in the data on metabolism and evaporative water loss in live animals. These sensors are far more rugged and easily constructed than the heated taxidermic mounts previously used to measure T_es. These characteristics facilitate the use of significant numbers of sensors in thermal mapping studies of endotherms.     

Extracting operative temperatures from temperatures of physical models with thermal inertia

Temperatures of operative temperature models, particularly those of thick-walled models of larger ectotherms, lag behind and are more restricted in range than the operative temperatures they estimate.Algorithms are provided to extract estimates of instantaneous operative temperatures from model temperatures.A simple deconvolution method can be used when wind speeds are constant.An iterative estimation method must be used when wind speed varies during the monitoring period.The iterative method is sensitive to measurement error, and so uses a smoothing filter to limit instabilities. The smoothing also limits the short-term fluctuations in the estimated operative temperature.Iterative estimates of operative temperature suggested time lags of up to 90 min between predicted operative temperatures and model temperatures for desert tortoises (mass=3 kg). Differences this large could affect estimates of time available for foraging.     

Does the thermal environment influence vigilance behavior in dark-eyed juncos (Junco hyemalis)? An approach using standard operative temperature

One might expect that increased thermal stress would cause wintering birds to forage faster in order to meet the increased metabolic demand. Faster foraging should, in turn, lead to a reduction in vigilance, since feeding and vigilance are mutually antagonistic activities. We examined these intuitive behavioral expectations using newly developed standard operative temperature sensors designed specifically to characterize the thermal effect of the microclimate environment (rain excluded) on wintering dark-eyed juncos (Junco hyemalis). These sensors allowed us to distinguish the behavioral effects of thermal stress from non-thermal effects associated with micrometeorological conditions (e.g. wind noise). Our analysis indicated that neither thermal nor non-thermal aspects of the physical environment influenced the proportion of time spent vigilant by juncos. However, the rate of food ingestion (measured as pecking rate) exhibited a negative correlation with thermal stress per se. This unexpected result may reflect the effect of thermal stress on feeding posture, peripheral muscle cooling, or both. The effect of thermal stress on pecking rate was nevertheless minor in comparison to the effect of flock size, which exerted by far the largest effect on both vigilance and pecking rate. Our overall results suggest that birds experiencing thermal stress will not necessarily lower their vigilance, but rather increase feeding bout length to compensate for the greater metabolic demand. This interpretation is consistent with theoretical models of vigilance in a non-time-limited environment, and may help explain the contradictory results to date on the effect of thermal stress on vigilance.     

Maximum voluntary temperature of insect larvae reveals differences in their thermal biology

We investigate the thermoregulatory behaviors of larvae of four species of Drosophila (D. melanogaster, D. subobscura, D. pseudoobscura, and D. mojavensis), a thermotolerant strain of Drosophila melanogaster (T strain) known to differ in thermal biology, and two mutant stocks of D. melanogaster that have (as adults) defective thermoregulatory behavior. We describe and evaluate new techniques to measure two indices of maximum voluntary temperature of insect larvae. Both measures were highly repeatable within lines (species, strains, or mutants). One measure (temperature at which larvae stood upright) differed among lines consistent with expectations based on adult thermal ecology, suggesting that this measure will be useful measures of thermoregulatory set-points of larvae. The second measure (temperature of emergence from media) is less discriminatory.     

《生物课程标准》和《生物教学大纲》的比较

2001年教育部颁布的《生物课程标准》是新世纪我国初中生物教学的第一指导性文件。它和新中国成立以来的《生物教学大纲》相比,在许多方面有新的突破。本文着重对《生物课程标准》和《生物教学大纲》在课程目标、内容和体系方面进行比较。     

Use of surname models in human population biology: a review of recent developments

Since 1985, when a bibliography concerning studies on surnames and genetic structure appeared, the number of publications on this subject has increased a thousandfold. New topics and uses have been added, but large gaps in knowledge remain. Only studies on isonymy in cities of nation states for recent times are well covered, and most studies are on populations that were selected because they are isolated and not because they are typical. This review, although not exhaustive, covers the literature published since 1985.     

生物科学的发展与《生物课程标准》

全日制义务教育《生物课程标准》的制订 ,主要是从初中生终身发展的需要、社会需求和生物科学发展 3个方面综合考虑的。此文试从生物科学的发展说明确定课程内容标准的依据。2 0世纪是自然科学发展史上最为辉煌的时代 ,生物科学是自然科学中发展最迅速的学科。因为生物科学与人类生存、人民健康、社会发展密切相关 ,必然成为2 1世纪初的主导学科。在 2 0世纪生物科学的发展中有许多重大突破 ,出现了许多新观念、新思想、新成果和新技术。特别是 2 0世纪 5 0年代以来 ,随着数理科学广泛深入地渗透到生物科学以及一些先进的仪器设备和研究技术…     

Non-local concepts and models in biology

In this paper, we consider local and non-local spatially explicit mathematical models for biological phenomena. We show that, when rate differences between fast and slow local dynamics are great enough, non-local models are adequate simplifications of local models. Non-local models thus avoid describing fast processes in mechanistic detail, instead describing the effects of fast processes on slower ones. As a consequence, non-local models are helpful to biologists because they describe biological systems on scales that are convenient to observation, data collection, and insight. We illustrate these arguments by comparing local and non-local models for the aggregation of hypothetical organisms, and we support theoretical ideas with concrete examples from cell biology and animal behavior.     

Computational models in systems biology

A report of the 6th International Conference on Computational Methods in Systems Biology, Rostock, Germany, 12-15 October 2008.One of the chief goals of systems biology is to build mechanistic mathematical models of biological systems to further the understanding of biological detail. Such models often aim at predicting the outcome of potentially interesting biological experiments, and if such predictions are confirmed by wet-lab observations, an important step forward is made. How exactly such models are constructed and how predictions are computed were at the core of a recent conference on Computational Methods in Systems Biology that brought 80 participants to Rostock, Germany (for conference proceedings see volume 5307 of Lecture Notes in Bioinformatics http://dx.doi.org/10.1007/978-3-540-88562-7).A simplistic approach to model construction might be to capture everything that is known about a system and simulate it in supercomputers. While this is appropriate for some systems, it is impossible or highly impracticable for many others. This is mostly due to the complexity of biological systems, which demand simplification to make them amenable to modeling. Such simplifications have to capture the essence of the processes of interest, while neglecting as many of the less important details as possible. Thus, one can consider model building in systems biology as the art of building caricatures of life: capture the essence, ignore the rest.     

Computational models in systems biology

A report of the 6th International Conference on Computational Methods in Systems Biology, Rostock, Germany, 12-15 October 2008.     

Influence of blood flow and millimeter wave exposure on skin temperature in different thermal models

Recently we showed that the Pennes bioheat transfer equation was not adequate to quantify mm wave heating of the skin at high blood flow rates. To do so, it is necessary to incorporate an "effective" thermal conductivity to obtain a hybrid bioheat equation (HBHE). The main aim of this study was to determine the relationship between non-specific tissue blood flow in a homogeneous unilayer model and dermal blood flow in multilayer models providing that the skin surface temperatures before and following mm wave exposure were the same. This knowledge could be used to develop multilayer models based on the fitting parameters obtained with the homogeneous tissue models. We tested four tissue models consisting of 1-4 layers and applied the one-dimensional steady-state HBHE. To understand the role of the epidermis in skin models we added to the one- and three-layer models an external thin epidermal layer with no blood flow. Only the combination of models containing the epidermal layer was appropriate for determination of the relationship between non-specific tissue and dermal blood flows giving the same skin surface temperatures. In this case we obtained a linear relationship between non-specific tissue and dermal blood flows. The presence of the fat layer resulted in the appearance of a significant temperature gradient between the dermis and muscle layer which increased with the fat layer thickness.     

Experimental evaluation of standard effective temperature a new biometeorological index of man's thermal discomfort

A rationally derived temperature index (SET^*) which can be used as a biometeorological index of man's thermal discomfort has been developed by simple physical theory and has a valid physiological basis. The SET^* index, when referred to a standard environment, has been tested experimentally as a measure of warm and cold discomfort for sedentary subjects under varying conditions of radiant heat and dry and wet bulb temperatures. The reference environment is common to one normally experienced in man's daily living while wearing 0.6 clo with an air movement of 0.25–0.3 m/s.