Degradative, definition

Standards Organizations have shown an interest in biodegradation tests only for a short time (five years) [35-36]. This explains why standard tests are rather simple, similar to one another and still very few. Table 2 gives a rapid review of these tests and the bio degradability definition they refer to. 

Ede [56] has also examined the limitations of m-cresol as the mobile phase in the SEC of nylon. He noted that Waters Inc. had recommended that the instrument be operated at 130°C to reduce the pressure drop across the columns and to improve the resolution of the chromatogram, and suspected that degradation of nylon was occurring under these conditions. Accordingly, the relative viscosities of the nylon m-cresol solutions were determined after heating for various times at 130°C. Three nylon solutions were prepared and examined by SEC. The solutions were also held in the injection loop of the SEC for 3 h prior to injection. In each case the sample which had been held in the sample loop eluted later. The retention time in the SEC was 2-4 h, and it was concluded that degradation definitely occurred during this time. 

In applying the definition of rehabihty, the concept of adequate performance must be estabhshed clearly. Products usually do not fail suddenly, but degrade over time. Gasket leaks on equipment, for example, may start as a slow weep and increase in volume over time. The point at which this undesirable occurrence is called a failure must be clear before rehabihty can be measured objectively. Changing the failure definition for a product changes its rehabihty level, although the product itself has not changed. 

Litde is known about metaboHc inactivation of ( -endorphin and the dynorphins. NEP, and to a lesser extent APN, are only weaMy active against P-endorphin (183). Enzymes are known which degrade P-endorphin in vitro under nonphysiological conditions (202) or which inactivate P-endorphin by N-acetjlation (203). Alack of specific degradative enzymes for these peptides may account for their relatively long half-life in vivo though this has not been definitively estabUshed. 

International agreement is close as of 1996 on what an acceptable environmentally degradable polymer should do ia the environment succiacdy put, it must not harm the environment. There has been much progress ia the early 1990s on this issue standard protocols are available to determine degradation ia the environment of disposal, and definitions are understood and accepted ia a broad sense, if not ia detail. Fate and effects issues for these new polymers are being addressed, and these will be resolved and appropriate tests developed. 

Asbestos and other fibers in a wide variety of bundle sizes or even individual fibrils are in commercial usage. The handling of asbestos and other fibers causes degradation of the larger fiber bundles to fibers having diameters less than two micrometers that remain airborne for extended periods of time. These airborne fibers are prone to inhalation and lung entrapment. The exact definition of harmfiil fibers and the mechanism by which they affect the body is not accurately known. 

When a flocculated feed is added to a filter tank, there is a definite time lag before this material reaches the surface of the filter medium. Since this lag time is not known at the time of testing, a lag time of 8 to 10 minutes should be allowed before starting the first leaf test on a flocculated shiny. Two, or perhaps three, tests can be run before the elapsed time exceeds the probable retention time in the full-scale filter tank. With knowledge of the elapsed time after flocculation and data relating to the rate of degradation, the rates obtained on the leaf test runs can be adjusted to some constant lag time consistent with the anticipated full-sc e design. 

Practitioners of SELF explicitly include the dependencies either in the event trees or in the fault trees. Examples of the LESF method that have been examined, treat major dependencies by the definition of degraded states and reevaluate the systems and event trees for the assumed degraded state as well as for the probability of being in that state. Mathematically this is very effective but the dependency coupling is not as pictorial as the SELF method. 

Free energy of solution, containing chain molecules of a definite length (before the beginning of degradation), can be written as follows ... 

Corrosion is generally taken to be the waste of a metal by the action of corrosive agents. However, a wider definition is the degradation of a material through contact with its environment. Thus, corrosion can include non-metallic materials such as concrete and plastics and mechanisms such as cracking in addition to wastage (i.e. loss of material). This chapter is primarily concerned with metallic corrosion, through a variety of mechanisms. 

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