Relevant SI Units and Conversions

Temperature Kelvin K degree Celsius degree Fahrenheit 0°C=273.15K F=9/5 °C+32 

Energy, work, heat Joule J TJ,GJ,MJ,kJ, mj electron volt eV=1.60- lO- J 

In this chapter, the fundamentals and the most common methods and techniques for the synthesis, processing, characterization, and modification of mac-romolecular materials are described briefly, as an introduction to the special Chaps. 3,4, and 5. The main emphasis is on the description of methods and techniques used in laboratories, but some examples from industrial practice are also mentioned. 

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Each enzyme has a working name, a specific name in relation to the enzyme action and a code of four numbers the first indicates the type of catalysed reaction the second and third, the sub- and sub-subclass of reaction and the fourth indentifies the enzyme [18]. In all relevant studies, it is necessary to state the source of the enzyme, the physical state of drying (lyophilized or air-dried), the purity and the catalytic activity. The main parameter, from an analytical viewpoint is the catalytic activity which is expressed in the enzyme Unit (U) or in katal. One U corresponds to the amount of enzyme that catalyzes the conversion of one micromole of substrate per minute whereas one katal (SI unit) is the amount of enzyme that converts 1 mole of substrate per second. The activity of the enzyme toward a specific reaction is evaluated by the rate of the catalytic reaction using the Michaelis-Menten equation V0 = Vmax[S]/([S] + kM) where V0 is the initial rate of the reaction, defined as the activity Vmax is the maximum rate, [S] the concentration of substrate and KM the Michaelis constant which give the relative enzyme-substrate affinity. 

From these nine basic quantities, numerous other SI units may be derived. Table B.2 lists a number of these derived units, particularly those relevant to colloid and surface chemistry. The table is arranged alphabetically according to the name of the physical quantity involved. Note that instructions for the use of the conversion factors —depending on the direction of the conversion —are given in the top and bottom headings of the columns. Table B.2 is by no means an exhaustive list of the various derived SI units Hopkins (1973) reports on many additional conversions, as do most handbooks and numerous other references. 

For the foreseeable future, you will need to make conversions from other units to SI units, as much of the literature quotes data using imperial, c.g.s. or other systems. You will need to recognize these units and find the conversion factors required. Examples relevant to chemistry are given in Box 9.1. Table 9.4 provides values of some important physical constants in SI units. 

For free space, it is straight-forward to translate between CGS (Gaussian) and SI units, by substituting So —> 1/(477) and fio —> 4tt/c. For dielectric and magnetic materials, conversion between the two quantities is not so easy. For details, see a treatise on electromagnetism. An abbreviated set of conversion factors between CGS and SI units that are relevant to the quantities of interest in this text is given in Table D.2. The convenience of Gaussian units is illustrated by the fact that all quantities presented in Table D.2 can be related to the three fundamental units of the CGS system—cm, g, and s. 

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