Acceptable degradation

The resistance to gamma radiation is good with acceptable degradation after 1000 Mrad exposure. For a given grade, property retentions are ... 

While the use of pure metals and eutectic alloys as brazes is generally good practice, exceptions do occur. Thus it may be necessary to use brazes that deviate from eutectic compositions to minimise the concentration of an embrittling temperature depressant, or to complicate the melting characteristics and accept degraded fluidity by introducing elements that enhance the corrosion resistance of the solidified braze. Thus recommended Al-Si brazes have hypo-eutectic compositions and Cr is introduced into Ni-P and Ni-Si-B braze alloys. 

The suspension was divided over a number of ampoules which were sealed under air or nitrogen. The ampoules were heated at 116 °C, removed at various time intervals and assayed spectrophotometrically by the base-line method (principle see Figure 4-A). From the obtained data, shown in Table 2, it was concluded that during a sterilization period of 30 minutes at 116 °C only a slight, acceptable degradation occurs. 

The degree of purity, as well as the individual and total amounts of degradation products of the biotechnological/biological product entered into the stability studies, should be reported and documented whenever possible. Limits of acceptable degradation should be derived from the analytical profiles of batches of the DS and DP used in the preclinical and clinical studies. 

Durability is a fundamental and necessary feature for PEM fuel cells to see a wide diffusion as a practical power source in any application field. The requirements for fuel cell lifetime vary with the specific application, in particular a duration of at least 5000 h is mandatory for use on cars, while even longer periods are needed for bus and stationary employments (for most applications an acceptable degradation rate is considered to be comprised in the range 2-10 pV/h [51]). However, the wide variability of operative conditions usually encountered in automotive applications, such as dynamic driving cycles, startup/shutdown phases, and freeze/thaw, makes also the target for car very difficult to be met with the current technologies. 

Hill climbers continuously modify a single structure, ideally with each change bringing some kind of improvement, but often accepting degradations, in the hope that they may eventually lead to a long-term gain. 

When the feed gas is air, degradation seems to be less pronounced. Acceptable degradation rates in the range of 5-6 pVh have been reported with PBI based MEAs under steady-state or dynamic conditions. 

In contrast to PVA, it was found [199-201] that when nylon-6,6 was subjected to temperatures above 300°C in an inert atmosphere it completely decomposed. The wide range of degradation products, which included several simple hydrocarbons, cyclopentanone, water, CO, COj and NHj suggested that the degradation mechanism must have been highly complex. Further research has led to a generally accepted degradation mechanism for aliphatic... 

The currently accepted degradation mchanism for PHBV is a random scission, j8-elimination process [49-52]. As Fig. 5.10a demonstrates, a sterically favourable six-membered transition state may be formed which on scission leads to the formation of unsaturated and carboxylic acid terminated chain fragments. 

Note, these definitions do not quantify the extent of degradation by any of the pathways they only indicate of the mechanism that is operating to promote degradation. While this is acceptable in a scientific sense to define a process or mechanism, the definitions do not meet or satisfy the requirement for environmentally acceptable degradable and biodegradable polymers, which, in the minds of legislators and lay people, is the key issue. To satisfy this very practical requirement, specifications for acceptability have to be set and monitored by standard testing protocols, based on the above definitions, which will be discussed later. 

The SOFC has seen tremendous advancement in recent years, especially in terms of cost per kilowatt. High system reliability with acceptable degradation has been observed in... 

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