Effect of temperature on transcapillary water movement in isolated cat hindlimb

1985 ◽  
Vol 249 (4) ◽  
pp. H792-H798
Author(s):  
M. B. Wolf ◽  
P. D. Watson
Keyword(s):  
Low Temperature ◽  
Water Movement ◽  
Control Period ◽  
Ambient Air ◽  
Tissue Temperature ◽  
Thigh Muscle ◽  
Effect Of Temperature ◽  
Air Temperatures ◽  
Initial Control ◽  
Water Viscosity

Capillary filtration coefficient (CFC) was measured in the isolated cat hindlimb preparation, perfused at 20 ml X min-1 X 100 g muscle-1 with a perfusate containing 6 g/dl albumin and normal electrolyte concentrations, to which were added 50 ml of the cat's blood and 6 micrograms of the vasodilator isoproterenol. CFC was determined three to six times in an initial control period during which the tissue temperature (measured by a 5-mm disk thermistor implanted in a thigh muscle) was controlled near 37 degrees C. Tissue temperature was decreased to 5-10 degrees C by lowering perfusate and ambient air temperatures. About 50 min were required for tissue temperature equilibration. CFC was measured at low temperature and then again at 37 degrees C. For nine experiments, the ratio of CFC at low temperature to that in the 37 degrees C control periods averaged 87% of the ratio of water viscosity at 37 degrees C to that at low temperature. The activation energy for water calculated from these data was 5.0 kcal/mol. These results may be explained by all transcapillary water flow moving by diffusion through narrow pores or by about 90% moving by convection, with the remainder going through a lipid pathway. However, the results may be entirely due to a direct effect of temperature on the geometry of the transcapillary pathway for water movement.

Winterization Needs for Platforms Operating in Low Temperature Environment

2013 ◽  
Author(s):  
Ove Tobias Gudmestad ◽  
Yaroslav Efimov ◽  
Konstantin Kornishin
Keyword(s):  
Low Temperature ◽  
Oil And Gas ◽  
Ambient Air ◽  
Cold Climate ◽  
Main Concern ◽  
Common Belief ◽  
Cold Temperatures ◽  
Air Temperatures ◽  
Partial Cover ◽  
Exploration And Production

According to a common belief which is shared by a lot of specialists from different areas petroleum business goes far into the offshore. One of the most promising regions of hydrocarbon production in the nearest future is stated to be Arctic region. But this surprisingly rich region is also happens to be one of the toughest and challenging areas to operate. Due to extremely cold air temperatures, strong winds, presence of ice and other harsh physical and climatic conditions safety requirements and technological demands call for new conceptual solutions for constructions that are panned to be used in Arctic. For exploration and production facilities in the cold climate the following aspects are essential: personnel and environment safety, as well as uninterrupted fail-safe technological process. In cold climates the main concern goes to low ambient air temperatures and presence/accretion of ice. Cold temperatures affect both personnel and equipment on the platform. To protect platform from influence of cold temperatures special heated covers can be used. This solution has certain concerns with heating, ventilation and air conditioning (HVAC) and energy supply systems. Yet another way here might be partial cover of equipment with special shelters and climatic modifications. Ice is considered to be the second limiting factor: sea ice that requires ICE CLASS vessels or specially designed platforms (not to mention ice bergs) and icing that endangers all unprotected systems on the platform. To deal with these threats different strategies might be used but there is still no one answer. Every case is some kind of unique when speaking about Arctic constructions. Ice-induced vibrations observed on platforms in the Bohay bay that haven’t been studied or even considered is a good example. Winterization for platforms is not fully developed yet and requires deeper research. The paper anticipates different codes and standards for offshore oil and gas facilities to be designed to operate in low temperature environments (American Bureau of Shipping ABS, Russian Maritime Register of Shipping, Det Norske Veritas DNV, International Organization for Standardization ISO, Canadian Standards Association CSA). These rules are compared against the experience of several major oil and gas operators and service companies gained during studies of conceptual design for Arctic exploration and production constructions at pre-FEED and FEED stages. The most important winterization concerns are highlighted and scrutinized.

THE EFFECTS OF RADIATION ON THE HABITAT TEMPERATURES OF THE LODGEPOLE NEEDLE MINER, RECURVARIA MILLERI BUSCK (GELECHIIDAE: LEPIDOPTERA)

1952 ◽  
Vol 30 (2) ◽  
pp. 144-153 ◽  
Author(s):  
W. R. Henson ◽  
R. F. Shepherd
Keyword(s):  
Solar Radiation ◽  
Ambient Air ◽  
Effect Of Temperature ◽  
The Sun ◽  
Heating Effect ◽  
Weather Factors ◽  
Radiation Level ◽  
Air Temperatures ◽  
Temperature Radiation ◽  
Effects Of Radiation

The lodgepole needle miner (Recurvaria, milleri Busck) passes the greater part of its life in the interior of needles of its host tree. Investigations of the temperature of needle mines and its relation to ambient air temperature, radiation, and a number of other weather factors are reported. Incoming solar radiation shows a heating effect on the needle mines which is directly proportional to the radiation level. The heating effect of the radiation is modified by other weather factors, by differences in the exposure of the needles, and by the type of mines in the needles. At night, needles are cooled below ambient air temperatures by outgoing radiation, which in turn is dependent on the nocturnal weather. The application of these results to studies of the effect of temperature on the needle miner can only be made with respect to individual needles. Thus, radiation of 1.5 gm-cal. per cm.2 per min. will elevate the temperature of a needle 6.3 Centigrade degrees in air moving at less than one mile per hour if the needle is orientated at right angles to the sun and fully exposed. Shade from other needles, wind over one mile per hour, and needle orientation other than 90° to the sun's rays all tend to reduce the amount of heating at the indicated level of radiation.

THE RELATIONSHIP OF AMBIENT AIR TEMPERATURES TO PREMATURE FLOWERING OF FLUE-CURED TOBACCO

1987 ◽  
Vol 67 (4) ◽  
pp. 1231-1234 ◽  
Author(s):  
MARK J. KING
Keyword(s):  
Nicotiana Tabacum ◽  
Low Temperature ◽  
Positive Relationship ◽  
Ambient Air ◽  
Total Degree ◽  
Air Temperatures ◽  
Nicotiana Tabacum L ◽  
Relationship Of ◽  
The Relationship

Exposure of tobacco (Nicotiana tabacum L.) seedlings to low ambient air temperatures during the 3 weeks prior to transplanting resulted in premature flowering. The percent premature flowering observed varied with the location of the experiment, the year, and the total degree units of temperature below 20 °C. A positive relationship between accumulated hourly temperatures below 20 °C and percent premature flowering was observed over four years at two locations.Key words: low temperature, premature flowering

Analysis of Heat and Mass Transfer of an Adiabatic Cross-Flow Liquid Desiccant Absorber Operating at Low Temperatures

2009 ◽  
Author(s):  
Sergio M. Pineda ◽  
Gerardo Diaz
Keyword(s):  
Mass Transfer ◽  
Low Temperature ◽  
Heat And Mass Transfer ◽  
Cross Flow ◽  
Ambient Air ◽  
Liquid Desiccant ◽  
Cooling Fluid ◽  
Air Temperatures ◽  
Increasing Demand ◽  
Air Conditioning Systems

With the rising costs of electricity due to increasing demand of electric power, liquid desiccant systems have received significant attention as a way to reduce latent loads on air conditioning systems. In particular, the performance of liquid desiccant systems in humid climates has shown significant reductions in energy consumption. In general, these liquid desiccant systems are composed by an absorber or dehumidifier and a regenerator that utilizes a heat source to reject the water from the diluted liquid desiccant. As the humidity of the air is absorbed at the dehumidifier, the temperature of the liquid desiccant increases due to the addition of heat from the enthalpy of condensation of the water vapor. Thus, many designs of liquid desiccant absorbers include the flow of a cooling fluid that removes heat from the liquid desiccant. A novel application of liquid desiccant systems corresponds to the localized removal of moisture from the air inside low temperature rooms that contain relatively high levels of humidity such as refrigerated warehouses for the food industry. The purpose is to reduce the formation of ice at the surface of the evaporator. Due to the low temperature of the air inside these rooms, no cooling fluid is necessary for the removal of heat from the liquid desiccant. Thus, the designs of the absorbers differ from the designs used for ambient air temperatures. In this paper, a mathematical model of the heat and mass transfer for an adiabatic parallel-plate absorber for which a thin film of liquid desiccant flows down its walls and dehumidifies the air in cross-flow configuration is developed.

scholarly journals Analysis and Comparison of Some Low-Temperature Heat Sources for Heat Pumps

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1853 ◽  
Author(s):  
Pavel Neuberger ◽  
Radomír Adamovský
Keyword(s):  
Heat Transfer ◽  
Low Temperature ◽  
Heat Source ◽  
Heat Pump ◽  
Heat Exchangers ◽  
Ambient Air ◽  
Heat Transfer Fluid ◽  
Heat Sources ◽  
Ground Heat Exchangers ◽  
Temperature Heat

The efficiency of a heat pump energy system is significantly influenced by its low-temperature heat source. This paper presents the results of operational monitoring, analysis and comparison of heat transfer fluid temperatures, outputs and extracted energies at the most widely used low temperature heat sources within 218 days of a heating period. The monitoring involved horizontal ground heat exchangers (HGHEs) of linear and Slinky type, vertical ground heat exchangers (VGHEs) with single and double U-tube exchanger as well as the ambient air. The results of the verification indicated that it was not possible to specify clearly the most advantageous low-temperature heat source that meets the requirements of the efficiency of the heat pump operation. The highest average heat transfer fluid temperatures were achieved at linear HGHE (8.13 ± 4.50 °C) and double U-tube VGHE (8.13 ± 3.12 °C). The highest average specific heat output 59.97 ± 41.80 W/m2 and specific energy extracted from the ground mass 2723.40 ± 1785.58 kJ/m2·day were recorded at single U-tube VGHE. The lowest thermal resistance value of 0.07 K·m2/W, specifying the efficiency of the heat transfer process between the ground mass and the heat transfer fluid, was monitored at linear HGHE. The use of ambient air as a low-temperature heat pump source was considered to be the least advantageous in terms of its temperature parameters.

Physical fitness and thermoregulatory reactions in a cold environment in men

1988 ◽  
Vol 65 (5) ◽  
pp. 1984-1989 ◽  
Author(s):  
J. H. Bittel ◽  
C. Nonotte-Varly ◽  
G. H. Livecchi-Gonnot ◽  
G. L. Savourey ◽  
A. M. Hanniquet
Keyword(s):  
Physical Fitness ◽  
Cold Stress ◽  
Heat Production ◽  
Ambient Air ◽  
Metabolic Heat Production ◽  
Adult Males ◽  
Fitness Level ◽  
Metabolic Heat ◽  
Air Temperatures ◽  
Thermoregulatory Reactions

The relationship between the physical fitness level (maximal O2 consumption, VO2max) and thermoregulatory reactions was studied in 17 adult males submitted to an acute cold exposure. Standard cold tests were performed in nude subjects, lying for 2 h in a climatic chamber at three ambient air temperatures (10, 5, and 1 degrees C). The level of physical fitness conditioned the intensity of thermoregulatory reactions to cold. For all subjects, there was a direct relationship between physical fitness and 1) metabolic heat production, 2) level of mean skin temperature (Tsk), 3) level of skin conductance, and 4) level of Tsk at the onset of shivering. The predominance of thermogenic or insulative reactions depended on the intensity of the cold stress: insulative reactions were preferential at 10 degrees C, or even at 5 degrees C, whereas colder ambient temperature (1 degree C) triggered metabolic heat production abilities, which were closely related to the subject's physical fitness level. Fit subjects have more efficient thermoregulatory abilities against cold stress than unfit subjects, certainly because of an improved sensitivity of the thermoregulatory system.

scholarly journals Direct Calculation of Thermodynamic Wet-Bulb Temperature as a Function of Pressure and Elevation

2013 ◽  
Vol 30 (8) ◽  
pp. 1757-1765 ◽  
Author(s):  
Sayed-Hossein Sadeghi ◽  
Troy R. Peters ◽  
Douglas R. Cobos ◽  
Henry W. Loescher ◽  
Colin S. Campbell
Keyword(s):  
Air Temperature ◽  
Mean Absolute Error ◽  
Direct Calculation ◽  
Ambient Air ◽  
Absolute Error ◽  
Mean Square ◽  
Air Temperatures ◽  
Order Polynomial ◽  
The Mean ◽  
Very High

Abstract A simple analytical method was developed for directly calculating the thermodynamic wet-bulb temperature from air temperature and the vapor pressure (or relative humidity) at elevations up to 4500 m above MSL was developed. This methodology was based on the fact that the wet-bulb temperature can be closely approximated by a second-order polynomial in both the positive and negative ranges in ambient air temperature. The method in this study builds upon this understanding and provides results for the negative range of air temperatures (−17° to 0°C), so that the maximum observed error in this area is equal to or smaller than −0.17°C. For temperatures ≥0°C, wet-bulb temperature accuracy was ±0.65°C, and larger errors corresponded to very high temperatures (Ta ≥ 39°C) and/or very high or low relative humidities (5% < RH < 10% or RH > 98%). The mean absolute error and the root-mean-square error were 0.15° and 0.2°C, respectively.

Mineralization of flexible mesoporous TiO2 photoanodes using two low-temperature dielectric barrier discharges in ambient air

2018 ◽  
Vol 59 (1) ◽  
pp. 102-110 ◽  
Author(s):  
Masoud Shekargoftar ◽  
Petr Dzik ◽  
Zuzana Ďurašová ◽  
Monika Stupavská ◽  
David Pavliňák ◽  
...  
Keyword(s):  
Low Temperature ◽  
Ambient Air ◽  
Mesoporous Tio2 ◽  
Dielectric Barrier Discharges ◽  
Dielectric Barrier ◽  
Barrier Discharges

scholarly journals Impact of Exposure to Low Temperature Degrees in Field Conditions on Leaf Pigments and Chlorophyll Fluorescence in Leaves of Mango Trees

2020 ◽  
Vol 10 ◽  
pp. 30-45
Author(s):  
Ali A.S. Sayed ◽  
Farouk M. Gadallah ◽  
Mohamed A. Seif El-Yazal ◽  
Gamal A. Abdel-Samad
Keyword(s):  
Chlorophyll Fluorescence ◽  
Low Temperature ◽  
Chlorophyll Concentration ◽  
Ambient Air ◽  
Sampling Time ◽  
Chlorophyll B ◽  
Physiological And Biochemical ◽  
Sampling Times ◽  
Fayoum Governorate

This experiment was conducted to found the connection between low temperature stress in vivo conditions (ambient-air temperature) and the changes in some physiological and biochemical events (leaf pigments and chlorophyll fluorescence) of mango trees in response to exposure to natural low temperature (cold). To verify this objective, 12 popular commonly mango cultivars (25 years old) which grown in private orchard in Fayoum Governorate, Egypt were selected for this study which carried out during the period from November to March of years; 2012 and 2013. The selected cultivars were: Alphonso, Baladi, Bullock's Heart, Helmand, Hindi Besennara, Mabrouka, Mestekawy, Nabeeh, Oweisi, Spates, Taimour and Zebda. Based on the obtained results, it can be stated that, chlorophyll (a) concentration in the leaves was significantly differed among the cultivars throughout the whole sampling times, in this respect, Helmand one gave the highest one while, and the highest one by sampling times was November one. The concentration of chlorophyll (b) was significant as effected by the effect of cultivars and sampling time recorded the highest value by the cultivar of Spates and December sample, respectively. Total chlorophyll concentration in the leaves reached its peak by the cultivar of Nabeeh and sampling time of December as compared to others. The both of Ewais cultivar and the sample of March showed the highest values of carotenoids concentration in the leaves. The levels of anthocyanin in leaves were significantly differed as affected by the cultivars and sampling times, indicating that the cultivar of Helmand and November sample recorded the highest values of anthocyanin in leaves. The greatest reductions in Fv/Fmratio were recorded at month of November and indicated that the reductions were in the order of Alphonso˃ Mabrouka˃Taimour˃ others. The effect of sampling time, cultivars and their interaction on Fv/Fm were significant, but small between some values of Fv/Fm.

scholarly journals Some like it hot: A differential response to changing temperatures by the malaria vectors Anopheles funestus and An. gambiae s.l.

2016 ◽  
Author(s):  
Jacques D Charlwood
Keyword(s):  
Air Temperature ◽  
Light Trap ◽  
Anopheles Funestus ◽  
Malaria Vectors ◽  
Effect Of Temperature ◽  
Night Time ◽  
Environmental Correlations ◽  
Air Temperatures ◽  
Soil Temperatures ◽  
Gravid Females

Background: With the possible implications of global warming, the effect of temperature on the dynamics of malaria vectors in Africa has become a subject of increasing interest. Information from the field is, however, relatively sparse. We describe the effect of ambient temperature over a five-year period on the dynamics of An. funestus and An. gambiae s.l., collected from a single village in southern Mozambique where temperatures varied from a night-time minimum of 6oC in the cool season to a daytime maximum of 35oC in the hot season. Results: Mean daily air temperatures varied from 34o C to 20oC and soil temperatures varied from 26 o C to 12 o C. Diurnal variation was greatest in the cooler months of the year and were greater in air temperatures than soil temperatures. During the study 301, 705 female An. funestus were collected in 6043 light-trap collections, 161, 466 in 7397 exit collections and 16, 995 in 1315 resting collections. The equivalent numbers for An. gambiae s.l. are 72, 475 in light-traps, 33, 868 in exit collections and 5, 333 from indoor resting collections. Numbers of mosquito were greatest in the warmer months. Numbers of An. gambiae s.l. went through a one hundredfold change (from a mean of 0.14 mosquitoes a night to 14) whereas numbers of An. funestus merely doubled (from a mean of 20 to 40 a night). The highest environmental correlations and mosquito numbers were between mean air temperature (r2 = 0.52 for An. funestus and 0.77 for An. gambiae s.l.). Numbers of mosquito collected were not related to rainfall with lags of up to four weeks. Numbers of both gravid and unfed An. gambiae complex females in exit collections continued to increase at all temperatures recorded but gravid females of An. funestus decreased at temperatures above 28oC. Overall the numbers of gravid and unfed An. funestus collected in exit collections were not correlated (p = 0.07). For an unknown reason the number of An. gambiae s.l. fell below monitoring thresholds during the study. Conclusions: Mean air temperature was the most important environmental parameter affecting both vectors in this part of Mozambique. Numbers of An. gambiae s.l. increased at all temperatures recorded whilst An. funestus appeared to be adversely affected by temperatures of 28oC and above. These differences may influence the distribution of the vectors as the planet warms.

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