Temperature perception

Temperature Perception and Cold Acclimatization of Plants and Algae... 

Cameron, J. and M.F. Capra (1993). The basis of the paradoxical disturbance of temperature perception in ciguatera poisoning. Clin. Toxicol. 31, 571-579. 

Airborne material affecting the quality of indoor air may be classified as gases or particulate matter. Gases which may be potential problems are radon, CO, NOj, and hydrocarbons. Particulate matter may come from tobacco smoke, mold spores, animal dander, plant spores, and others as shown in Table 23-1. Other factors interact to influence our perception of indoor air quality, including humidity, temperature, lighting, and sound level. 

Local air motion is another thermal nonuniformity that can cause a local cooling of the skin and the feeling of a draft. Draft discomfort from local air motion increases as the air temperature decreases below skin temperature. Fluctuations in the local air motion increase the perception of drafts and should be avoided. The unsteadiness of air motion is often described in terms of its turbulence intensity (Tu) ... 

The disulfide is dissolved by aqueous potassium hydroxide, yielding a greenish-yellow solution. At low temperatures no perceptible evolution of gas takes place. Since the disulfide in many respects behaves as a pseudo-halogen, Brown et al. have supposed that the reaction described by Eq. (8) takes place, i.e. a reaction analogous to the formation of halide and halite ions from a halogen and alkali. 

This is a doubtful conclusion since if temperature-vapour tension curves for volatile substances be examined it will be seen that at low temperatures the rate of diminution of the vapour tension falls off rapidly and hence the-vapour tension at — 190° C. is often not vastly different from what it is at normal temperature, and hence is not by any means negligible when we take into account the very small quantity of substance that needs to be inspired in order for its odour to be perceptible. 

It is hardly surprising that the preparation of surfaces of plain specimens for stress-corrosion tests can sometimes exert a marked influence upon results. Heat treatments carried out on specimens after their preparation is otherwise completed can produce barely perceptible changes in surface composition, e.g. decarburisation of steels or dezincification of brasses, that promote quite dramatic changes in stress-corrosion resistance. Similarly, oxide films, especially if formed at high temperatures during heat treatment or working, may influence results, especially through their effects upon the corrosion potential. 

A solution of iodine in aqueous iodide has an intense yellow to brown colour. One drop of 0.05M iodine solution imparts a perceptible pale yellow colour to 100 mL of water, so that in otherwise colourless solutions iodine can serve as its own indicator. The test is made much more sensitive by the use of a solution of starch as indicator. Starch reacts with iodine in the presence of iodide to form an intensely blue-coloured complex, which is visible at very low concentrations of iodine. The sensitivity of the colour reaction is such that a blue colour is visible when the iodine concentration is 2 x 10 " 5 M and the iodide concentration is greater than 4x 10 4M at 20 °C. The colour sensitivity decreases with increasing temperature of the solution thus at 50 °C it is about ten times less sensitive than at 25 °C. The sensitivity decreases upon the addition of solvents, such as ethanol no colour is obtained in solutions containing 50 per cent ethanol or more. It cannot be used in a strongly acid medium because hydrolysis of the starch occurs. 

The heat absorbed when a mol of the solvent is evaporated at a constant temperature T from a volume of solution so large that no perceptible change of concentration occurs during the process, is called the heat of volatilisation A (x, T). From (7) ... 

Accumulatory pressure measurements have been used to study the kinetics of more complicated reactions. In the low temperature decomposition of ammonium perchlorate, the rate measurements depend on the constancy of composition of the non-condensable components of the product mixture [120], The kinetics of the high temperature decomposition [ 59] of this compound have been studied by accumulatory pressure measurements in the presence of an inert gas to suppress sublimation of the solid reactant. Reversible dissociations are not, however, appropriately studied in a closed system, where product readsorption and diffusion effects within the product layer may control, or exert perceptible influence on, the rate of gas release [121]. 

For example, we know that water (a liquid) will chemge to ice (a solid) if its internal temperature falls below a certain temperature. Likewise, if its internal temperature rises above a certain point, water changes to steam (a gas). Because water is so abundant on the Earth, it was used in the past to define Changes of State and even to define Temperature Scales. However, the concept of "heat" is also involved, and we need to also define the perception of heat as it is used in this context. Note that defining heat implies that we have a reproducible way to measure temperature. A great deal of work was required in the past to reach that stage. First, you have to establish that certcun liquids expand when heated. Then you must establish... 

The behavior of mayonnaise emulsions when thawed after some exposure to temperatures below room temperature, is considered first. The mayonnaise emulsions are of such a stability that on standing at room temperature for one year or even longer, they show no perceptible oil separation. Such mayonnaise emulsions fall into two categories when thawed back to room temperature after exposure at a given temperature below room temperature those that show no oil separation and those that do show oil separation. Another way to... 

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