Heat haze

So we see swirling eddy (or convective ) patterns above a radiator because the density of air is a function of temperature. If all the air had the same temperature, then no such difference in density would exist, and hence we would see no refraction and no eddy currents - which is the case in the summer when the radiator is switched off. Then again, we can sometimes see a heat haze above a hot road, which is caused by exactly the same phenomenon. 

FIGURE 9.57 Electron micrographs of haze aerosol collected in Pasadena in 1973 (A) and of (B) unheated and (C) heated haze particle (adapted from Husar and Shu, 1975). 

Waters, E.J., Wallace, W, Williams, PJ. (1991). Heat haze characteristics of fractionated wine proteins. Am. J. Enol. Vitic., 42, 123-127... 

One other experimental observation demonstrates the difference between old and new technologies. When a composition such as treated fumed silica In polymer B Is heated, haze develops. This haze Is due to the fact that the refractive Index of the polymer changes with temperature quite drastically while that for the solid filler does not. To demonstrate the change In refractive Index with temperature, the refractive Index, of j catalyst free devolatilized polymer A sample gave the following data ... 

A heat haze rises from the decks. This is not a heat haze at all, but rather high concentrations of evaporating light hydrocarbons. 

Lipoproteins may denature on heating and if present during pasteurization can result in the formation of haze or turbidity in the final product. This material was removed traditionally by filtration through asbestos (qv) sheets (6) however, health hazards associated with asbestos have led to its replacement by alternative filter materials (23,37,193). These media have been less effective than asbestos and further measures have been required to ensure the visual clarity of albumin products, eg, further filtration developments for Hpid removal (194), preferential denaturation of contaminants using in-process heat treatment, and anion-exchange chromatography (49). 

Filter P per Processing. In the fabrication of fuel oil and air filters for vehicles such as motorcycles and diesel locomotives, heat processing of the filter paper is required to cure the resin (usually phenoHc) with which the paper (qv) is impregnated (see Phenolic resins). The cure-oven exhaust, which contains water vapor, alcohols, and dimers and trimers of phenol, produces a typical blue haze aerosol having a pungent odor. The concentration of organic substances in the exhaust is usually rather low. 

Aerosol particles - the visible haze in polluted air - reflect and absorb sunlight, directly influencing the heat balance over large (>1000 km)... 

In the context of crystallinity as a crucial factor with respect to haze, it has to be pointed out that PET and PBT as the most industrially used polyesters are both crystallizable depending on the conditions of subsequent processing. The amorphous state can be obtained by a rapid quenching of the melt below the Tg. Heating above the 7 g induces fast crystallization. PBT exhibits a significantly increased crystallization rate when compared with PET. 

ISO 1600 1990 Plastics - Cellulose acetate - Determination of light absorption on moulded specimens produced using different periods of heating ISO 13468-1 1996 Plastics - Determination of the total luminous transmittance of transparent materials - Part 1 Single-beam instrument ISO 13468-2 1999 Plastics - Determination of the total luminous transmittance of transparent materials - Part 2 Double-beam instrument ISO 14782 1999 Plastics - Determination of haze for transparent materials... 

Interest in arabinans has increased significantly in recent years due to their identification as a major cause of haze in apple and pear juice concentrates. These problems can be relieved by using pectic enzyme mixtures containing adequate levels of e do-arabinanase to degrade 1,5-a-L-arabinan produced from branched arabinan either by the action of a-L-arabinofuranosidase or a combination of heat and low pH conditions (23). 

A traditional approach in many cases is prolonged cold storage followed by a sharp filtration, also carried out cold. Cold storage encourages formation and settling out of insoluble complexes. Reduced temperature decreases the solubility of some potential haze material and also reduces the energy from ambient heat that keeps particles suspended. As a result, some of the haze material is precipitated and left on the floor of the storage tank or taken out by the filter. 

Low levels of water, up to approximately 50 to 75 ppm, can be solubilized into most middle distillate fuel at ambient temperature without causing the fuel to appear hazy. However, as fuels cool, dissolved water becomes visible as haze. Conversely, as fuels are heated, water haze disappears. 

PAr is soluble in similar polar organic solvents (e.g., NMP, DMAc, DMSO, etc.) which dissolve PBI. It was observed that miscible solution blends of PBI and PAr could be formed. For example, NMP dopes containing 10 wt % PBI and PAr are visually homogeneous and contain no insolubles as formed. After being kept at room temperature for a period of time (e.g., several days), a PBI-rich phase starts to form precipitate, but this polyphasic material can be easily redissolved into a single phase with a mild heating (i.e., 100 °C for 20 min). Based on the haze level, the stability of the PBI/PAr/NMP solutions appeared to increase with the increase of the relative PAr concentrations. 

This evidently accounts for the presence of isoprene in the breath.34 Isoprene is also formed by many plants and is released into the atmosphere in large amounts, which contribute to photochemical formation of haze. A Mg2+-dependent enzyme catalyzes the elimination of pyrophosphate.35 Isoprene emissions rise with increasing temperature, and it has been suggested that the isoprene may dissolve in chloroplast membranes and in some way confer increased heat resistance.36 37 Hydrolytic dephosphorylation can lead to dimethylallyl alcohol, which is oxidized in the liver to dimethy-lacrylyl-CoA (Eq. 22-1). 

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