CHEMICAL Terms Links

Two-Stage Resins. The ratio of formaldehyde to phenol is low enough to prevent the thermosetting reaction from occurring during manufacture of the resin. At this point the resin is termed novolac resin. Subsequently, hexamethylenetetramine is incorporated into the material to act as a source of chemical cross-links during the molding operation (and conversion to the thermoset or cured state). 

Networks with tri- and tetra-functional cross-links produced by end-linking of short strands give moduli which are more in accord with the new theory if quantitative reaction can be assumed (3...13) However, the data on polydimethylsiloxane networks, may equally well be analyzed in terms of modulus contributions from chemical cross-links and chain entangling, both, if imperfect reaction is taken into account (J 4). Absence of a modulus contribution from chain entangling has therefore not been demonstrated by end-linked networks. 

Chemical cross-linking is given many names depending on the particular area of application. For instance, for hair, the term setting is often associated with the breakage and subsequent reformation of thiol cross-links. For tires, the terms vulcanization and curing are associated with the formation of sulfur-associated chemical cross-links (Figure 2.19). 

Hierarchies, such as primary, secondary, and working level, or certified RMs and RMs are extensively used in describing traceability chains. Whilst such terms can be useful in explaining processes and links, they can also be confusing. For this reason their use has been limited in this paper. It is considered preferable to describe hierarchies in terms of the associated uncertainties. It can also be noted that, whereas in physical measurement it is common to have a hierarchy of references of the same basic type (e.g., a series of mass standards), this is rare in chemical measurement where the chain usually contains only one chemical RM, linked to a higher reference by a measurement process. 

It can be directly derived from the rule of three functions (see below. Section 2.2.7) that three substrates (it might suffice that these are different enantiomers or diastereomers) correspond to three enzymes which can be distinguished in both functional and chemical terms. For each essential element, there thus must be at least four substances (three solid or dispersed/membrane-attached enzymes and the very speciation form of the essential element in dissolved or atmospheric (N, O, C, H, S) states) in the organism or directly linked to it in the enviromnent (soil, water, food, for photoautotrophs also the atmosphere (CO )). Living beings share one more property with traditional multiphase systems the... 

Plastic materials are sometimes termed resins . These can be synthetic or natural. Copals are natural resins, some of which can turn into amber, given enough time. This happens by an evaporation of some of the chemicals, while other chemicals cross-link and polymerise. 

How were these results to be interpreted in terms of the configuration of apoBlOO on the surface of the LDL The obvious interpretation was that apoB surrounds the LDL like a belt moreover, it was also suggested that chemical cross-linking buckles the belt (Fig. 6) (Phillips and Schumaker, 1989). 

In analytical chemical terms this means all steps of the analytical procedure should be performed and recorded in such a way that all essential information is available and no wrong information is introduced. In other words, the results of the determination and not only the final measurement should be linked through an unbroken chain of comparisons. This link must be demonstrated. Depending on the type of analytical method applied and the property of interest to be determined, various steps may be necessary to demonstrate the link between the end signal recorded from the detector and the reference to which it is linked. 

In multimedia box models, the environmental fate of a chemical is described by a set of coupled mass-balance equations for all boxes of the model. These equations include terms for degradation, inter-media exchange such as settling and resuspension of particles, and transport with air and water flows [19,20]. Equations for different boxes are coupled by inter-media exchange terms (linking different environmental media) and terms for trans-... 

The term carbohydrate includes a wide range of molecules which in many cases are quite complex structures. In chemical terms a carbohydrate is either a polyhydroxy aldehyde, a polyhydroxy ketone or, alternatively, it is a compound that can be hydrolysed to such a structure. The smallest unit that cannot be hydrolysed any further is called a monosaccharide. Glucose (Fig. 11.4.1) is the most abundant monosaccharide known and is by far the most important. Other examples include fructose and mannose. A carbohydrate which has been hydrolysed to two monosaccharide units is cabled a disaccharide and the best known example is sucrose, which is composed of a unit of glucose covalently linked to a unit of fructose. The nomenclature system continues in a logical fashion until one can refer to an ohgosaccharide as being a chain composed of several monosaccharide units. Depending upon whether a monosaccharide is an aldehyde or a... 

This phase transition is initially reversible, as demonstrated by Lewis (10), but as carbonization progresses chemical cross-linking makes it irreversible The liquid crystal droplets grow and coalesce until all the isotropic melt has undergone the phase transition This new phase is then termed the liquid crystal mesophase, i e the phase intermediate between the isotropic fluid pitch and solid semi-coke ... 

Tristearin is simply the chemical term for a type of fat. Fats are composed of fatty acids joined to a molecule of glycerol, so they are also called triglycerides. Tristearin, a fat found in tallow, is made of three molecules of stearic acid linked to a glycerol molecule. When it is chemically reacted with a base — like sodium carbonate, which is found in ashes — it forms sodium stearate, otherwise known as soap. 

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