Scaling microscopic origin

The introductory discussion on thermal analysis begins with a brief outline of the history of the understanding of heat and temperature. Heat is obviously a macroscopic quantity. One can feel its effect directly with one s senses. The microscopic origin of heat, the origin on a molecular scale, rests with the motion of the molecules of matter discussed in Sect. 2.3. The translation, rotation, internal rotation, and vibration of molecules are the cause of heat. Temperature, in turn, is more difficult to comprehend. It is the intensive parameter of heat. Before we can arrive at this conclusion, several aspects of heat and temperature must be considered. A short description based on experiments is given in Sects. 2.1.5 and 2.1.4 and more details are found in Sects. 4.2 and 4.1. 

The macroscopic structure of matter can be assessed, for example, by optical microscopy and can then be linked to its microscopic origin through X-ray, neutron, or electron diffraction experiments and the various forms of electron and atomic-force microscopy. A factor of 10 -10 separates the atomic, nanometer scale from the macroscopic, micrometer scale. Macroscopic dynamic techniques ultimately linked to molecular motion are, for example, dynamic mechanical and dielectric analyses and calorimetry. In order to have direct access to the details of the underlying microscopic motion, one must, however, use computational methods. A realistic microscopic description of motion has recently become possible through accurate molecular dynamics simulations and will be described in this review. It will be shown that the basic large-ampHtude molecular motion exists on a picosecond time scale (1 ps = 10 s), a ffictor at... 

The microscopic origins that set the scale of both o>o and E, are certainly very instructive but remain quite elusive so far. The natural frequency (t>o, as mentioned before, may be written as the produet of two terms v and (f>. One is related to... 

Careflil examination of a piece of coal shows that it is usually made up of layers or bands of different materials which upon microscopic examination are distinct entities distinguishable by optical characteristics (10—12). The study of the origin, composition, and technological appHcation of these materials is called coal petrology, whereas coal petrography involves the systematic quantification of the amounts and characteristics by microscopic study. The petrology of coal may involve either a macroscopic or microscopic scale. 

Intervention of localized microscopic high temperatures is possible [8, 14, 24], as advocated in sonochemistry to justify the sonochemical effect. There is an inevitable lack of experimental evidence, because we can necessarily have access to macroscopic temperature only. It has been suggested [6, 19] that, in some examples, MW activation could originate from hot spots generated by dielectric relaxation on a molecular scale. 

Figure 24, presented originally by Belton (1995), illustrates the enormous range in distance scales that can be probed using various magnetic resonance spectroscopy and imaging techniques. Approximate distance ranges for molecular, microscopic, and macroscopic regions are provided for perspective on the left side of Figure 24. The criterion used for the demarcation between macroscopic and microscopic regions was based on the size of objects that are no longer visible with the naked or unaided eye, i.e., less than 40 xm (Hills, 1998).

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