Perceptions changing

Regional Haze Visibility Impairment any humanly perceptible change in visibility (light extinction, visual range, contrast, coloration) from that which would have existed under natural conditions, caused predominantly by a combination of many sources from, and occurring over, a wide geographic area. 

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. 

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) ... 

Food colorants play an important role in quality perception. Color is often the first notable characteristic of a food and it influences the expectations of consumers buying the product and also influences food handlers who make quality-related decisions, for example, during visual inspections." More specifically, color predetermines our expectations and perceptions of flavor and taste. " Color is interrelated with flavor intensity (detection threshold), with sweetness and salinity sensations, and also with our susceptibilities to and preferences for products. For example, consumers perceived a strongly red-colored strawberry-flavored drink to be sweeter than a less colored version, and yellow was associated with lemon and pink with grapefruit, but by reversing the colors, flavor perception changed." If food color is not appealing, consumers will not enjoy the flavor and texture of the food. ... 

Experiment (b).—The same should be done with benzoyl chloride. Even on prolonged shaking no perceptible change takes place the mixture must be boiled for some time in order to cause complete decomposition. Treat benzoyl chloride in the same way with 2N-alkali. 

In the above mentioned reaction, platinum oxide and palladium on barium sulfate showed no perceptible change in the rate of hydrogen uptake. On the other hand, platinum oxide was selective in the hydrogenation of cyclohexa-2,4-diene-l,2-dicarboxylic acid to 1,4,5,6-tetrahydrophthalic acid140. A similar result may be the favored reduction of a symmetrical disubstituted double bond over a more hindered trisubstituted bond. The retarding effect of additional substitution is demonstrated in the hydrogenation of a trisubstituted double bond in the presence of a tetrasubstituted double bond (equation 53)141. 

The distance between the two terminal carbon atoms at the TS (central point on the IRC segment) is already 2.291 A, which results in very perceptible changes in the orbital shapes, spin-coupling pattern and overlaps between neighbouring orbitals. Orbital /i (see the central column of orbitals in Fig. 5) becomes less distorted towards the orbital at the other terminal carbon, /g, and this is reflected in a decrease in their overlap (see Fig. 7). Orbitals /2 and /3 (and their symmetry-related counterparts, /5 and /4) attain shapes which are very similar to those of /2 from the TS of the Diels-Alder reaction (see the central column of orbitals in Fig. 1) and of a SC orbital for benzene [8-10]. These changes are accompanied by a tendency towards equalization of the nearest-... 

The induction period, followed by a sharp increase in rate is, however, the most characteristic feature of autocatalysis in closed vessels. One manifestation of this behaviour is the clock reaction . An experimental system which is a typical chemical clock and which also exhibits cubic autocataiysis is the iodate-arsenite reaction. In the presence of excess iodate, the system which is initially colourless eventually undergoes a sudden colour change to brown (or blue in the presence of starch). The potential of an iodide-sensitive electrode shows a barely perceptible change during most of the induction period, but then rises rapidly, reaching a peak at the point of colour change. 

The SMA effect can be traced to properties of two crystalline phases, called martensite and austenite, that undergo facile solid-solid phase transition at temperature Tm (dependent on P and x). The low-temperature martensite form is of body-centered cubic crystalline symmetry, soft and easily deformable, whereas the high-temperature austenite form is of face-centered cubic symmetry, hard and immalleable. Despite their dissimilar mechanical properties, the two crystalline forms are of nearly equal density, so that passage from austenite to a twinned form of martensite occurs without perceptible change of shape or size in the macroscopic object. 

Generally the inclusion reaction is described to take place in a thermal gradient ranging from 90°C to room temperature. The complexes formed are often insoluble and can be separated as precipitates (21, 22). Inclusion complexes such as these often form under normal food processing conditions. The complexing of free starch due to the addition of fatty acid derivatives during production to potato flakes for instant mashed potatoes is a case in point. In this case the desired effect is related to taste due to a perceptible change in texture. 

The combination of sensory evaluation with analytical approaches is required to identify perceptible changes and to identify the potential chemical changes that may be causing the sensory effect. Low concentrations of compounds responsible for changes in food characteristics may not be detectable by even the most sensitive analytical methods but, in combination with appropriately applied sensory methods, the clues provided by both techniques may help identify the problem, provide indications to the cause, and suggest clues for the source of the problem. 

For decades researchers have looked at whether intoxication with certain drugs could mimic the signs and symptoms of schizophrenia. Amphetamines increase dopamine release and can induce some positive symptoms like paranoia. Lysergic acid diethylamide (LSD) affects 5-HT receptors but tends to induce visual perception changes and not frank hallucinations. Phencyclidine (PCP), however, induces a state in healthy controls that seems very similar to schizophrenia. This includes thought disorder and negative symptoms... 

Digitalis purpurea (foxglove) (Scrophulariaceae) [digitalis] high dose yields cloudy yellow vision red-green perception changes (xanthopsia) - anti-epileptic use may have affected late yellow period of Vincent Van Gogh]... 

---