Temperature regulation in the new-born lamb. VI. Heat exchanges in lambs in a hot environment

1962 ◽  
Vol 13 (1) ◽  
pp. 122 ◽  
Author(s):  
G Alexander ◽  
D Williams
Keyword(s):  
Water Loss ◽  
Good Evidence ◽  
Sweat Glands ◽  
Second Phase ◽  
Ambient Temperatures ◽  
Respiratory Loss ◽  
Air Temperatures ◽  
Cutaneous Evaporation ◽  
Heat Exchanges ◽  
Respiratory Evaporation

At ambient temperatures below about 30°C, respiratory and cutaneous evaporation were constant in normal lambs and lambs without sweat glands. Above 30°C, respiratory water loss increased steeply. Cutaneous water loss also increased, but at a slower rate than respiratory loss and only in the lambs with sweat glands. The efficiency of evaporation in cooling the lamb was close to 100%. The contribution of cutaneous blood flow to facilitation of heat loss in lambs lying down appeared to be low. At low environmental humidity, respiratory evaporation at all rates of normal shallow panting was approximately 4 mg per respiration; but in "second phase" breathing this was increased up to 12 mg per respiration, and total respiratory evaporation was not reduced. Lambs showed no evidence of distress when exposed for 6–12 hr to air temperatures of 40°C and water vapour pressures of' less than I5 mm Hg. Cutaneous loss tended to fall and respiratory loss to increase. Maximum rates of cutaneous and respiratory evaporation were estimated by suppressing evaporation from the skin or respiratory tract at 43°C. These values tended to be higher in crossbred lambs then in Merinos, and Merinos tended to reach maximum "sweating" rates under less severe heat stress than the crossbreds. Homeothermic equilibrium was approached when evaporation from neither site was suppressed, but rectal temperatures increased rapidly when cutaneous evaporation was prevented, and more rapidly still when respiratory evaporation was much reduced. The results also illustrate how a high metabolic rate decreases heat tolerance. These experiments provide good evidence that sheep do sweat, but that respiratory evaporation is quantitatively more important than sweating.

Sweating in cattle. I. Cutaneous evaporative losses in calves and its relationship with respiratory evaporative loss and skin and rectal temperatures

1958 ◽  
Vol 50 (1) ◽  
pp. 73-81 ◽  
Author(s):  
G. C. Taneja
Keyword(s):  
Skin Temperature ◽  
Air Temperature ◽  
Water Loss ◽  
The Other ◽  
Sweat Glands ◽  
Water Losses ◽  
Evaporative Loss ◽  
Cutaneous Evaporation ◽  
The University ◽  
Respiratory Evaporation

Three calves (Australian Illawara Shorthorn, Shorthorn and Zebu × Australian Illawara Shorthorn) were exposed to different combinations of wet- and dry-bulb temperatures in a psychrometric chamber at the Physiology Department of the University of Queensland. These animals were 2–3 months old when first exposed to heat.Measurements were made on these animals for cutaneous and respiratory water losses, and skin and rectal temperatures.Cutaneous water losses in all the animals studied increased with increases in air temperature. Comparing these results with those on men with congenital absence of sweat glands exposed to high air temperature below the sweat point, suggests that the cutaneous evaporative losses in cattle are more than those that can be accounted for by diffusionmoisture alone.Increase in cutaneous evaporation under hot conditions is accompanied by increase in skin and rectal temperatures. In the Zebu cross, however, the skin temperature did not rise with rise in air temperature.Keeping the humidity constant, rise in dry-bulb temperature caused increase in respiratory water loss. On the other hand, rising humidity at a constant dry-bulb temperature resulted in decrease in respiratory evaporation. Respiratory evaporative loss was, therefore, greater in hot-dry than in hot-wet conditions.

Respiration in exercising fowl. II. Respiratory water loss and heat balance

1981 ◽  
Vol 93 (1) ◽  
pp. 327-332
Author(s):  
J. H. Brackenbury ◽  
M. Gleeson ◽  
P. Avery
Keyword(s):  
Rectal Temperature ◽  
Water Loss ◽  
Heat Balance ◽  
Domestic Fowl ◽  
Metabolic Energy ◽  
Air Temperatures ◽  
Respiratory Heat Loss ◽  
All Speeds ◽  
Body Heat ◽  
Respiratory Evaporation

1. Respiratory water loss and rectal temperature were measured in domestic fowl running for 10 min on a treadmill at speeds of 1.24-4.3 km h-1 in air temperatures of 20 +/− 2 degrees C or 32 +/− 2 degrees C. 2. At given speeds the water loss at 32 +/− 2 degrees C was approximately twice that at 20 +/− 2 degrees C and the end-exercise rectal temperature was 0.5-0.8 degrees C higher. 3. At 20 +/− 2 degrees C, respiratory evaporation accounted for 10–12% of the total metabolic energy used at all speeds. At 32 +/− 2 degrees C, the fractional respiratory heat loss fell from 26.5% at 1.24 km h-1 to 17% at 3.6 km h-1. The fraction of the total metabolic energy stored as body heat rose progressively with air temperature.

Sweating in cattle. IV. Control of sweat glands secretion

1959 ◽  
Vol 52 (1) ◽  
pp. 66-71 ◽  
Author(s):  
G. C. Taneja
Keyword(s):  
Nervous System ◽  
Body Temperature ◽  
Sympathetic Nervous System ◽  
Sweat Glands ◽  
Appreciable Effect ◽  
Air Temperatures ◽  
Before And After ◽  
Sympathetic Nervous ◽  
Cutaneous Evaporation ◽  
The University

Two calves (Aberdeen Angus and American Brahman) were used exposed to different combinations of wet- and dry-bulb temperatures in a psychromatric chamber at the Physiology Department of the University of Queensland. These animals were 7–8 months old when first exposed to heat.Effect of various drugs affecting the sympathetic nervous system (adrenaline, noradrenaline, Dibenamine, Priscol, atropine and acetylcholine) on the rate of cutaneous evaporation in calves was tested. Cutaneous evaporation was measured by means of a capsule before and after the administration of these drugs.Cutaneous evaporation increased with the introduction of adrenaline and was suppressed by the administration of Dibenamine. Noradrenaline and Priscol had no appreciable effect. Acetylcholine failed to stimulate sweating and atropine did not block the sweat glands.Sweat glands of cattle were, therefore, found to be functional and their innervation adrenergic. Cattle use sweat to prevent body temperature from rising, yet the amount of sweat secreted is not large enough to allow cattle to maintain thermoneutrality at high air temperatures.

scholarly journals Latent heat loss of Holstein cows in a tropical environment: a prediction model

2008 ◽  
Vol 37 (10) ◽  
pp. 1837-1843 ◽  
Author(s):  
Alex Sandro Campos Maia ◽  
Roberto Gomes da Silva ◽  
Cintia Maria Battiston Loureiro
Keyword(s):  
Heat Loss ◽  
Latent Heat ◽  
Air Temperature ◽  
Holstein Cows ◽  
Tropical Region ◽  
Weight Class ◽  
Air Temperatures ◽  
Latent Heat Loss ◽  
Cutaneous Evaporation ◽  
Respiratory Evaporation

Nine lactating Holstein cows with average 526 ± 5 kg of BW, five predominantly black and four predominantly white, bred in a tropical region and managed in open pasture were observed to measure cutaneous and respiratory evaporation rates under different environmental conditions. Cows were separated in three weight class: 1 (<450 kg), 2 (450-500 kg) and 3 (>500 kg). Latent heat loss from cutaneous surface was measured using a ventilated capsule; evaporation in the respiratory system was measured using a facial mask. The results showed that heaviest cows (2 and 3 classes) presented the least evaporation rates. When air temperature increased from 10 to 36ºC the relative humidity decreased from 90 to 30%. In these conditions the heat loss by respiratory evaporation increased from 5 to 57 Wm-2, while the heat loss by cutaneous evaporation increased from 30 to 350 Wm-2. The results confirm that latent heat loss was the main way of thermal energy elimination under high air temperatures (>30ºC); cutaneous evaporation was the main mechanism of heat loss, responding for about 85% of the heat loss. A model was presented for the prediction of the latent heat loss that was based on physiological and environmental variables and could be used to estimate the contribution of evaporation to thermoregulation; a second, based on air temperature only, should be used to make a simple characterization of the evaporation process.

Cost of locomotion and heat balance during rest and running from 0 to 55 degrees C in a patas monkey

1980 ◽  
Vol 49 (5) ◽  
pp. 789-800 ◽  
Author(s):  
S. A. Mahoney
Keyword(s):  
Thermal Conductance ◽  
Whole Body ◽  
Patas Monkey ◽  
Ambient Temperatures ◽  
High Speeds ◽  
Air Temperatures ◽  
Cost Of Locomotion ◽  
Similar Weight ◽  
Cutaneous Evaporation ◽  
Heat Loads

A young patas monkey was run on a treadmill for 15-20 min at speeds in excess of 15 km times h-1 over a range of laboratory air temperatures from 0 to 55 degrees C. Cost of locomotion for the monkey was 83% that predicted for a running mammal of similar weight, 4 kg. At the highest steady-state running of speeds, the patas monkey's energy expenditure was 11 times the resting rate. Heat storage and respiratory evaporation during running each accounted for less than 16% of the heat production. Cutaneous evaporation, mainly sweating, was the major means of heat loss at high ambient temperatures and during heavy exercise. Maximum sweat rates of 0.5 mg times cm-2 times min-1 found in these experiments approach the sweat rates of humans. Whole-body dry thermal conductance increased 2-3 times the rest value at a given temperature. Environmentally gained heat contributed about two-thirds of the total heat load on the patas monkey at rest at 53 degrees C. At these same temperatures, environmental and metabolic heat loads were about equal when the animal ran at moderately high speeds (11-13.4 km times h-1).

Microstructural Refinement in a Commercial Aluminum Alloy Processed by ECAP Using a Die Channel Angle of 110 Degrees

2015 ◽  
Vol 1114 ◽  
pp. 3-8
Author(s):  
Nicolae Şerban ◽  
Doina Răducanu ◽  
Nicolae Ghiban ◽  
Vasile Dănuţ Cojocaru
Keyword(s):  
Grain Refinement ◽  
Cross Section ◽  
High Strength ◽  
Secondary Phase ◽  
Coarse Grained ◽  
Metallographic Analysis ◽  
Second Phase ◽  
Channel Angle ◽  
Ambient Temperatures ◽  
Fine Grained

The properties of ultra-fine grained materials are superior to those of corresponding conventional coarse grained materials, being significantly improved as a result of grain refinement. Equal channel angular pressing (ECAP) is an efficient method for modifying the microstructure by refining grain size via severe plastic deformation (SPD) in producing ultra-fine grained materials (UFG) and nanomaterials (NM). The grain sizes produced by ECAP processing are typically in the submicrometer range and this leads to high strength at ambient temperatures. ECAP is performed by pressing test samples through a die containing two channels, equal in cross-section and intersecting at a certain angle. The billet experiences simple shear deformation at the intersection, without any precipitous change in the cross-section area because the die prevents lateral expansion and therefore the billet can be pressed more than once and it can be rotated around its pressing axis during subsequent passes. After ECAP significant grain refinement occurs together with dislocation strengthening, resulting in a considerable enhancement in the strength of the alloys. A commercial AlMgSi alloy (AA6063) was investigated in this study. The specimens were processed for a number of passes up to nine, using a die channel angle of 110°, applying the ECAP route BC. After ECAP, samples were cut from each specimen and prepared for metallographic analysis. The microstructure of the ECAP-ed and as-received material was investigated using optical (OLYMPUS – BX60M) and SEM microscopy (TESCAN VEGA II – XMU). It was determined that for the as-received material the microstructure shows a rough appearance, with large grains of dendritic or seaweed aspect and with a secondary phase at grain boundaries (continuous casting structure). For the ECAP processed samples, the microstructure shows a finished aspect, with refined, elongated grains, also with crumbled and uniformly distributed second phase particles after a typical ECAP texture.

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.

Inhibiting ventilatory evaporation produces an adaptive increase in cutaneous evaporation in mourning doves Zenaida macroura

1999 ◽  
Vol 202 (21) ◽  
pp. 3021-3028 ◽  
Author(s):  
T.C. Hoffman ◽  
G.E. Walsberg
Keyword(s):  
Skin Surface ◽  
The Body ◽  
Evaporative Heat Loss ◽  
Evaporative Water ◽  
Zenaida Macroura ◽  
Ambient Temperatures ◽  
Rapid Adjustment ◽  
Mourning Doves ◽  
A Minor ◽  
Cutaneous Evaporation

We tested the hypothesis that birds can rapidly change the conductance of water vapor at the skin surface in response to a changing need for evaporative heat loss. Mourning doves (Zenaida macroura) were placed in a two-compartment chamber separating the head from the rest of the body. The rate of cutaneous evaporation was measured in response to dry ventilatory inflow at three ambient temperatures and in response to vapor-saturated ventilatory inflow at two ambient temperatures. At 35 degrees C, cutaneous evaporation increased by 72 % when evaporative water loss from the mouth was prevented, but no increase was observed at 45 degrees C. For both dry and vapor-saturated treatments, cutaneous evaporation increased significantly with increased ambient temperature. Changes in skin temperature made only a minor contribution to any observed increase in cutaneous evaporation. This indicates that Z. macroura can effect rapid adjustment of evaporative conductance at the skin in response to acute change in thermoregulatory demand.

scholarly journals Performance Evaluation of a CO2 Refrigeration System Enhanced with a Dew Point Cooler

Energies ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 1079 ◽  
Author(s):  
Martin Belusko ◽  
Raymond Liddle ◽  
Alemu Alemu ◽  
Edward Halawa ◽  
Frank Bruno
Keyword(s):  
Weather Conditions ◽  
Dew Point ◽  
Coefficient Of Performance ◽  
Experimental Program ◽  
Refrigeration System ◽  
Conventional System ◽  
Ambient Temperatures ◽  
Air Temperatures ◽  
Condenser Temperature

Dew point cooling (DPC) is a novel indirect evaporative cooling concept capable of delivering air temperatures approaching the dew point. Coupling this technology with CO2 refrigeration is well suited to minimising transcritical operation when the coefficient of performance (COP) is dramatically reduced in hot climates. A substantial experimental program was conducted to characterise this combination by testing a 20 kW CO2 refrigeration system subject to ambient temperatures above 40 °C. It was demonstrated that DPC operation not only avoided transcritical operation during such weather conditions, but also increased the COP by up to 140% compared to the conventional system. The combination of these technologies was successfully mathematically modelled, from which the optimum condenser inlet air temperature was identified for each condenser temperature. Using this optimum condition, it was possible to maximise the COP for a range of conditions applicable to the psychometric chart. An annual case study for Adelaide, Australia was conducted which demonstrated that optimally coupling DPC with CO2 refrigeration can reduce the annual energy consumption and peak demand by 16% and 47%, respectively, compared to a conventional CO2 booster system. Furthermore, the number of hours of transcritical operation was reduced from 3278 to 27.

scholarly journals RECURRENT MALIGNANT APOCRINE SWEAT GLAND CARCINOMA - A CASE REPORT

2021 ◽  
pp. 1-2
Author(s):  
AKHILA JANGA ◽  
MOHAMMED ZIAUDDIN ◽  
RAVI CHANDER PATLOLLA
Keyword(s):  
Local Excision ◽  
Wide Local Excision ◽  
Sweat Gland ◽  
Early Stage ◽  
Case Reports ◽  
Case Series ◽  
Biological Behavior ◽  
Sweat Glands ◽  
Second Phase ◽  
Apocrine Carcinoma

Apocrine carcinomas arise from normal or modified sweat glands. The slow-growing nature and rarity of sweat gland carcinomas complicate their diagnosis at the early stage. The incidence of PASGC is quite low at 0.0049–0.0173 cases/100,000 persons/year. A 21-year-old male patient was presented in February 2016 with small solitary mass in the right axilla with mild tenderness and pain. Underwent wide local excision and axillary dissection at our institution followed by adjuvant radio and chemotherapy. Later on, after 18 months developed local recurrence and was planned for re-surgery and a second phase of palliative radiotherapy. After a year, presented to the hospital with pin sized irregular swelling in the axilla. Sweat gland carcinomas which are rarely diagnosed create a pathological dilemma due to their unpredicted biological behavior. However, wide local excision with or without nodal dissection is the primary treatment till date. In this particular case even though patient had underwent axillary node dissection, patient had recurrence twice with no distant metastasis which is a key point to be noted. Thorough study of the available apocrine carcinoma case reports or case series, the better knowledge regarding the apocrine carcinoma can be obtained.

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