SEASONAL ACCLIMATIZATION IN VARYING HARE (LEPUS AMERICANUS)

1965 ◽  
Vol 43 (5) ◽  
pp. 731-744 ◽  
Author(s):  
J. S. Hart ◽  
Hermann Pohl ◽  
J. S. Tener
Keyword(s):  
Critical Temperature ◽  
Ambient Temperature ◽  
Heat Loss ◽  
Seasonal Changes ◽  
Evaporative Heat Loss ◽  
Total Heat Loss ◽  
Seasonal Differences ◽  
Seasonal Acclimatization ◽  
Lower Critical Temperature ◽  
Approximate Equality

Wild hares were trapped in the vicinity of Ottawa, Canada, and tested during summer and winter. After recovery from implantation of subcutaneous and substernal thermocouples, measurements of oxygen uptake and body temperatures were made during successive stepwise lowering of ambient temperature from 20 °C to −45 °C over about 5 hours. Measurements were also made during stepwise elevation of temperature from 12 °C to 38 °C over a 5-hour period and a final single test was made at 40 °C.Hares trapped during the winter had lower O2 uptake than did summer-caught hares at temperatures below thermal neutrality. The change was very similar in magnitude to the seasonal change in insulation of the fur (27% greater in winter). The lower critical temperature was shifted from +10 °C in summer hares to about −5 °C in winter hares.No seasonal differences were noted in substernal temperatures, but subcutaneous temperatures were significantly higher in winter-caught animals. Colonic temperatures were higher than substernal temperatures at all ambient temperatures.Electromyograms recorded from the mid-back showed that shivering was greater in the cold during summer than during winter in accordance with the higher O2 consumption at any given temperature. Shivering was also slightly greater during summer at the same level of O2 consumption.Varying hares showed a considerable tolerance to elevation of temperature and a capacity to maintain approximate equality of body and ambient temperature at 40 °C for some time through effective respiratory evaporative heat loss, which approached 100% of heat production. Stepwise elevation of ambient temperature did not reveal any seasonal differences in upper critical temperature (about 38 °C) or in elevation of body temperature in spite of differences in insulation of the fur. A slightly greater proportion of the total heat loss was by evaporation during the summer.Caloric intake of captive hares outdoors was similar during winter and summer. It is concluded that seasonal acclimatization in the varying hare is largely insulative with respect to cold and that changes in heat tolerance are minor if present at all. Insulative and behavioral modifications appear to compensate for seasonal changes in temperature in the Ottawa area.

The heat production of oiled mallards and scaup

1973 ◽  
Vol 51 (1) ◽  
pp. 27-31 ◽  
Author(s):  
E. H. McEwan ◽  
A. F. C. Koelink
Keyword(s):  
Critical Temperature ◽  
Metabolic Rate ◽  
Ambient Temperature ◽  
Heat Loss ◽  
Heat Production ◽  
Normal Values ◽  
Thermal Conductance ◽  
Water Repellency ◽  
Regression Analyses ◽  
Lower Critical Temperature

A measure of the thermal conductance of the plumage of normal and oiled ducks was determined from regression analyses that related metabolic rate and ambient temperature. The heat loss of heavily oiled mallards and scaup was 1.7 and 2 times greater than their normal values, respectively. Oiling not only tended to increase the basal heat production, but also shifted the lower critical temperature from 12 to 25C. Attempts to rehabilitate the scaup after oiling and cleaning were rarely successful because of plumage deterioration and the loss of water repellency.

Effects of environmental temperature and humidity on evaporative heat loss through firefighter suit materials made with semi-permeable and microporous moisture barriers

2021 ◽  
pp. 004051752110265
Author(s):  
Huipu Gao ◽  
Anthoney Shawn Deaton ◽  
Xiaomeng Fang ◽  
Kyle Watson ◽  
Emiel A DenHartog ◽  
...  
Keyword(s):  
Heat Loss ◽  
Environmental Temperature ◽  
Moisture Absorption ◽  
Evaporative Heat Loss ◽  
Total Heat Loss ◽  
Evaporative Resistance ◽  
Environmental Testing ◽  
Permeable Barrier ◽  
Moisture Condensation ◽  
Moisture Barriers

The goal of this research was to understand how firefighter protective suits perform in different operational environments. This study used a sweating guarded hotplate to examine the effect of environmental temperature (20–45°C) and relative humidity (25–85% RH) on evaporative heat loss through firefighter turnout materials. Four firefighter turnout composites containing three different bi-component (semi-permeable) and one microporous moisture barriers were selected. The results showed that the evaporative resistance of microporous moisture barrier systems was independent of environmental testing conditions. However, absorbed moisture strongly affected evaporative heat loss through semi-permeable moisture barriers coated with a layer of nonporous hydrophilic polymer. Moisture absorption in mild environment (20–25°C) tests, or when testing at high humidity (>85% RH), significantly increased water vapor transmission in semi-permeable turnout systems. It was also found that environmental conditions used in the total heat loss (THL) test (25°C and 65% RH) produced moisture condensation in bi-component barrier systems, making them appear more breathable than could be expected when worn in hotter environments. Regression models successfully qualified the relationships between moisture uptake levels in semi-permeable barrier systems and evaporative resistance and THL. These findings reveal the limitations in relying on THL, the heat strain index currently called for by the NFPA 1971 Standard for Structural Firefighter personal protective equipment, and supports the need to measure turnout evaporative resistance at 35°C (Ret), in addition to THL at 25°C.

Respiratory water and heat loss of the black duck during flight at different ambient temperatures

1971 ◽  
Vol 49 (5) ◽  
pp. 767-774 ◽  
Author(s):  
M. Berger ◽  
J. S. Hart ◽  
O. Z. Roy
Keyword(s):  
Heat Loss ◽  
Water Loss ◽  
Pulmonary Ventilation ◽  
Evaporative Heat Loss ◽  
Total Heat Loss ◽  
Ambient Temperatures ◽  
Black Duck ◽  
Respiratory Heat Loss ◽  
Metabolic Water ◽  
Expired Air

Pulmonary ventilation and temperature of expired air and of the respiratory passages has been measured by telemetry during flight in the black duck (Anas rubripes) and the respiratory water and heat loss has been calculated.During flight, temperature of expired air was higher than at rest and decreased with decreasing ambient temperatures. Accordingly, respiratory water loss as well as evaporative heat loss decreased at low ambient temperatures, whereas heat loss by warming of the inspired air increased. The data indicated respiratory water loss exceeded metabolic water production except at very low ambient temperatures. In the range between −16 °C to +19 °C, the total respiratory heat loss was fairly constant and amounted to 19% of the heat production. Evidence for the independence of total heat loss and production from changes in ambient temperature during flight is discussed.

Regulation of metabolic rate in Svalbard and Norwegian reindeer

1984 ◽  
Vol 247 (5) ◽  
pp. R837-R841 ◽  
Author(s):  
K. J. Nilssen ◽  
J. A. Sundsfjord ◽  
A. S. Blix
Keyword(s):  
Body Weight ◽  
Critical Temperature ◽  
Food Intake ◽  
Metabolic Rate ◽  
Seasonal Changes ◽  
Serum Levels ◽  
Physiological Adaptation ◽  
Conservation Of Energy ◽  
Winter Food ◽  
Lower Critical Temperature

Food intake, body weight, serum levels of triiodothyronine (T3) and free thyroxine (FT4), and metabolic rate were measured at intervals in Svalbard (SR) and Norwegian (NR) reindeer. From summer to winter food intake decreased 57 (SR) and 55% (NR), while body weight decreased 8.6 (SR) and 3.8% (NR). In SR T3 and FT4 changed seasonally, whereas this was only evident for T3 in NR. Resting (standing) metabolic rate (RMR) in winter was 1.55 (SR) and 2.05 W X kg-1 (NR), lower critical temperature (TLC) being -50 (SR) and -30 degrees C (NR). RMR in summer was 2.15 (SR) and 2.95 W X kg-1 (NR), TLC being -15 (SR) and 0 degrees C (NR). Seasonal changes in T3 and FT4 did not coincide with changes in food intake or RMR in either SR or NR. RMR did, however, correlate with food intake. This indicates that seasonal changes in RMR are due to the thermic effects of feeding and represent no physiological adaptation aimed at conservation of energy during winter.

Thermal sweating in different body regions of sheep

1979 ◽  
Vol 92 (2) ◽  
pp. 511-512 ◽  
Author(s):  
A. K. Rai ◽  
B. S. Mehta ◽  
M. Singh
Keyword(s):  
Thermal Stress ◽  
Ambient Temperature ◽  
Heat Loss ◽  
Evaporative Cooling ◽  
Sweat Glands ◽  
Evaporative Heat Loss ◽  
Body Regions ◽  
Time Period ◽  
Sweat Production ◽  
Thermal Sweating

Although sheep combat thermal stress mainly by panting, a sizeable amount (40%) of total evaporative heat loss, is from sources other than panting (Hales & Brown, 1974). The frequency of sporadic discharge of sweat glands increases with increase in ambient temperature and is accompanied by a decline in respiration rate (Bligh, 1961). The wool coat can reduce evaporative cooling but sweating may have cooling value in sheep breeds with open fleeces (Rai, Singh & More, 1978). In sheep, the number and size of the sweat glands (Waites & Voglmayr, 1962) and the quantum of sweat production in a particular time period (Ghoshal et al. 1977) varies in different body regions. In view of the possible significance of surface evaporative cooling, thermal sweating in different body regions of sheep was investigated.

scholarly journals Protection against Cold in Prehospital Care: Evaporative Heat Loss Reduction by Wet Clothing Removal or the Addition of a Vapor Barrier—A Thermal Manikin Study

2012 ◽  
Vol 27 (1) ◽  
pp. 53-58 ◽  
Author(s):  
Otto Henriksson ◽  
Peter Lundgren ◽  
Kalev Kuklane ◽  
Ingvar Holmér ◽  
Peter Naredi ◽  
...  
Keyword(s):  
Heat Loss ◽  
Prehospital Care ◽  
Ambient Air ◽  
Total Heat ◽  
Thermal Manikin ◽  
Evaporative Heat Loss ◽  
Loss Reduction ◽  
Total Heat Loss ◽  
Cold Environments ◽  
Wet Heat

AbstractIntroduction: In the prehospital care of a cold and wet person, early application of adequate insulation is of utmost importance to reduce cold stress, limit body core cooling, and prevent deterioration of the patient’s condition. Most prehospital guidelines on protection against cold recommend the removal of wet clothing prior to insulation, and some also recommend the use of a waterproof vapor barrier to reduce evaporative heat loss. However, there is little scientific evidence of the effectiveness of these measures.Objective: Using a thermal manikin with wet clothing, this study was conducted to determine the effect of wet clothing removal or the addition of a vapor barrier on thermal insulation and evaporative heat loss using different amounts of insulation in both warm and cold ambient conditions.Methods: A thermal manikin dressed in wet clothing was set up in accordance with the European Standard for assessing requirements of sleeping bags, modified for wet heat loss determination, and the climatic chamber was set to -15 degrees Celsius (°C) for cold conditions and +10°C for warm conditions. Three different insulation ensembles, one, two or seven woollen blankets, were chosen to provide different levels of insulation. Five different test conditions were evaluated for all three levels of insulation ensembles: (1) dry underwear; (2) dry underwear with a vapor barrier; (3) wet underwear; (4) wet underwear with a vapor barrier; and (5) no underwear. Dry and wet heat loss and thermal resistance were determined from continuous monitoring of ambient air temperature, manikin surface temperature, heat flux and evaporative mass loss rate.Results: Independent of insulation thickness or ambient temperature, the removal of wet clothing or the addition of a vapor barrier resulted in a reduction in total heat loss of 19-42%. The absolute heat loss reduction was greater, however, and thus clinically more important in cold environments when little insulation is available. A similar reduction in total heat loss was also achieved by increasing the insulation from one to two blankets or from two to seven blankets.Conclusion: Wet clothing removal or the addition of a vapor barrier effectively reduced evaporative heat loss and might thus be of great importance in prehospital rescue scenarios in cold environments with limited insulation available, such as in mass-casualty situations or during protracted evacuations in harsh conditions.

Technical and Economic Performance Analysis of Utilization of Solar Energy in Indoor Swimming Pools, An Application

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Olcay Kincay ◽  
Zafer Utlu ◽  
Ugur Akbulut
Keyword(s):  
Solar Energy ◽  
Power Systems ◽  
Heat Loss ◽  
Economic Performance ◽  
Energy Demand ◽  
Reduction Rate ◽  
Energy Gain ◽  
Evaporative Heat Loss ◽  
Swimming Pools ◽  
Total Heat Loss

In this study, technical and economic performance analyses are conducted in order to determine the optimum collector surface area for indoor swimming pools. Required heat and economical conditions are taken into consideration while performing these evaluations. A brief summary of solar energy source and heat transfer equations for the Olympic pools are given. An Olympic swimming pool is assumed to be in different cities, and energy losses are calculated. For our sample Olympic pool, convective heat loss obtained is −3.86 kW and evaporative heat loss obtained is 265 kW. Total heat loss always maximum in January from 384 kW to 455.1 kW. Solar energy gain (assumption 1000 m2 collector area) and energy gain from boiler for different cities are calculated as maximum solar energy gain in July between 160 and 175 kW and minimum in January between 54.9 and 82 kW. High investment costs for solar power systems are responsible for low value of the reduction rate. Also, according to the energy demand and economical conditions, technical evaluations are performed in order to obtain optimum surface collector area, and economical analyses are conducted using unified cost method.

RESPIRATORY CONTRIBUTION TO THE THERMAL BALANCE OF THE NEWBORN INFANT UNDER VARIOUS AMBIENT CONDITIONS

PEDIATRICS ◽  
1973 ◽  
Vol 51 (4) ◽  
pp. 641-650
Author(s):  
E. Sulyok ◽  
E. Jéquier ◽  
L. S. Prod'hom
Keyword(s):  
Ambient Temperature ◽  
Heat Loss ◽  
Newborn Infant ◽  
Thermal Environment ◽  
Newborn Infants ◽  
Thermal Balance ◽  
Evaporative Heat Loss ◽  
Ambient Conditions ◽  
Direct Calorimetry ◽  
Respiratory Heat Loss

The influence of environmental humidity and temperature on the thermal balance of 45 full-term newborn infants was studied by direct calorimetry within 24 hours after birth. The respiratory heat loss measured at 32C and 20% relative humidity (RH) represented 9.5% of the total heat production, and it decreased to 2.9% when RH was 80%. In neutral thermal environment (32C, 50% RH), the mean respiratory heat loss was lower than that measured during a warm exposure (36C, 50% RH), in spite of a higher absolute humidity in the latter condition. This suggests that respiration might have a thermoregulatory function during heat exposure in the newborn. Evaporative heat loss from the skin was more elevated than that from the respiratory tract, but it was less sensitive to change in ambient humidity. Convective and radiative heat losses from the skin were inversely related to ambient temperature; similarly, the metabolic rate decreased with increasing ambient temperature up to 36C. This work provides further data on the varying energy exchange between the newborn infant and his environment; it should lead to a more rational planning of infant care and caloric requirements and demonstrates the important effects of different environmental conditions on the newborn infant.

Comparison of non-evaporative heat transfer in different cattle breeds

1985 ◽  
Vol 36 (3) ◽  
pp. 497 ◽  
Author(s):  
VA Finch
Keyword(s):  
Heat Loss ◽  
Air Temperature ◽  
Heat Storage ◽  
Absolute Humidity ◽  
Total Heat ◽  
Evaporative Heat Loss ◽  
Excessive Sweating ◽  
Total Heat Loss ◽  
Evaporative Water ◽  
Rate Of Increase

Tissue conductance and non-evaporative heat loss from the skin were determined from measurements of body temperature, evaporative water loss, metabolic rate and heat storage in six steers in each of three breeds, Brahman (B), Brahman x Hereford-Shorthorn (BX) and Shorthorn (S). A group of six steers, two from each breed, remained in a climate room set at 25�C overnight, and during the following day all were exposed for 1 h to sequential increases in air temperature (28, 32, 37, 41, 43, 45�C). Each steer was measured at 25�C and after a 30-min exposure to each temperature. Tissue conductance increased with air temperature (Ta), reaching maximum values at 41�C, the rate of increase (W m-2 'C-I per degree rise in Ta) being for B 3.95, for BX 2.33 and for S 2,09. Between 41 and 45�C, tissue conductance remained constant in B but declined in BX and S with a concurrent increase in heat storage. Mean tissue conductance (W m-2 �C-1) of B was 63.5; BX, 56.1; and S, 47.8, values that were significantly different (P < 0.01). Expressed in terms of metabolic weight, the breed means of tissue conductance (litres O2 h-1 W-0.75 �C-1) were also significantly different: B, 0.56; BX, 0.43; and S, 0.33 (P < 0.005), with the relative differences similar to those calculated per unit area. Breed differences in tissue conductance may be related to variations in ability to redirect blood from the core to the skin. Non-evaporative heat loss comprised 55-65% of the total heat loss from the skin in all breeds at Ta of 25�C. The remaining heat was lost through sweating. As Ta increased and approached skin temperature, non-evaporative heat loss decreased but in B and BX remained 25% of the total heat loss from the skin. S steers, in contrast, sustained little non-evaporative heat loss as Ta increased because sweating rates increased 50% more than that required to dissipate the heat at the skin. The increase in absolute humidity of the chamber was associated with the excessive sweating in this breed.

scholarly journals Metabolic effects of altering the 24 h energy intake in man, using direct and indirect calorimetry

1980 ◽  
Vol 43 (2) ◽  
pp. 257-269 ◽  
Author(s):  
M. J. Dauncey
Keyword(s):  
Energy Expenditure ◽  
Metabolic Rate ◽  
Heat Loss ◽  
Energy Intake ◽  
Heat Production ◽  
Resting Metabolic Rate ◽  
Metabolic Effects ◽  
Evaporative Heat Loss ◽  
High Intake ◽  
Total Heat Loss

1. The metabolic effects of increasing or decreasing the usual energy intake for only 1 d were assessed in eight adult volunteers. Each subject lived for 28 h in a whole-body calorimeter at 26° on three separate occasions of high, medium or low energy intake. Intakes (mean±SEM) of 13830 ± 475 (high), 8400 ± 510 (medium) and 3700 ± 359 (low) kJ/24 h were eaten in three meals of identical nutrient composition.2. Energy expenditure was measured continuously by two methods: direct calorimetry, as total heat loss partitioned into its evaporative and sensible components; and indirect calorimetry, as heat production calculated from oxygen consumption and carbon dioxide production. For the twenty-four sessions there was a mean difference of only 1.2 ± 0.14 (SEM)% between the two estimates of 24 h energy expenditure, with heat loss being less than heat production. Since experimental error was involved in both estimates it would be wrong to ascribe greater accuracy to either one of the measures of energy expenditure.3. Despite the wide variation in the metabolic responses of the subjects to over-eating and under-eating, in comparison with the medium intake the 24 h heat production increased significantly by 10% on the high intake and decreased by 6% on the low intake. Mean (± SEM) values for 24 h heat production were 8770 ± 288, 7896 ± 297 and 7495 ± 253 kJ on the high, medium and low intakes respectively. The effects of over-eating were greatest at night and the resting metabolic rate remained elevated by 12% 14 h after the last meal. By contrast, during under-eating the metabolic rate at night decreased by only 1%.4. Evaporative heat loss accounted for an average of 25% of the total heat loss at each level of intake. Changes in evaporative heat loss were +14% on the high intake and −10% on the low intake. Sensible heat loss altered by +9% and −5% on the high and low intakes respectively.5. It is concluded that (a) the effects on 24 h energy expenditure of over-feeding for only 1 d do not differ markedly from those estimated by some other workers after several weeks of increasing the energy intake; (b) the resting metabolic rate, measured at least 14 h after the last meal, can be affected by the previous day's energy intake; (c) the zone of ambient temperature within which metabolism is minimal is probably altered by the level of energy intake.

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