Quality, deterioration evaluation

The sensory evaluation differentiates between the stimulation threshold (a just detectable level where a perceptible but not yet definable deviation of the sample from the standard is observed) and the recognition threshold, a level where the odor is identifiable or creates odor problems (a no longer tolerable quality deterioration caused by a definite off odor and/or taste). The difference between a perceptible and identifiable level is usually only one to two steps of a geometric dilution series. Therefore, only undifferentiated odor and taste thresholds are given in Table 13-6, because of the very different sensitivities of individual testers. The perceptible (stimulation) levels of a less sensitive tester can overlap with the identifiable (recognition) level of another more sensitive tester. 

In evaluating natural water quality deterioration we suffer from the lack of a clear baseline. There are few pristine environments that can be used as a reference. For example, hikers must contend with Giardia lamblia in even the most remote places. How long this has been the case is unknown, but there is little reason to believe that the organism has not been historically resident in the wild animal population. Suspended solids in streams are a natural result of erosion caused by floods. Beaches are formed by sand carried downstream in floods. Flood control practices have both decreased erosion and flooding and trapped solids in reservoirs, and sand losses from beaches becomes a problem in places such as southern California. 

This overview deals with some of the chemical marker compounds suited to the requirements of quality control laboratories in the citrus industry. Chemical markers include ascorbic acid, dehydroascorbic acid, hydroxymethylfurfural, furfural, 2,5-dimethyl-4-hydroxy-3(2H)-furanone, 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one, 4-vinyl guaiacol and a-terpineol. Some of these compounds might be applied as useful tools in evaluating quality deterioration due to unsuitable manufacturing and storage as well as for the computation and optimization of the manufacturing processes and parameters. Since they are all chemically reactive compounds, careful evalution of kinetics of these compounds is necessary. 

Quality, unlike beauty is not simply in the eye of the beholder. Quality may be assessed, measured and evaluated, to be expressed in terms such as good-poor, acceptable-unacceptable. Quality may also improve or deteriorate depending on the efforts, enthusiasm and expertise of the analysts and the environment in which the work is carried out. 

This section discusses chemical compatibility (resistance) of geosynthetic and natural liner materials with wastes and leachates. Even in a relatively inert environment, certain materials deteriorate over time when exposed to chemicals contained in both hazardous and nonhazardous leachate. It is important to anticipate the kind and quality of the leachate a site will generate and select liner materials accordingly. The chemical resistance of any FML materials, geonets, geotextiles, and pipe should be evaluated before installation.39... 

In reality, the performance of the LC system will deteriorate over time, especially for noise and drift. If the performance verification tests do not pass the predetermined acceptance criteria, an impact assessment should be made to evaluate the effect of the failure on the quality of the data generated by the system. The impact assessment should cover all the analyses done on the system since the last performance verification, as there is no effective way of determining when the failure occurred. The system suitability data generated together with the analyses will be very useful in demonstrating that system performance is adequate for the application at the time of analysis, so that any data generated are reliable [19]. 

All quality records are legible and identifiable to the product involved. Quality records are stored and maintained in such a way that they are readily retrievable in facilities that provide a suitable environment to minimize deterioration or damage and to prevent loss. Retention times of quality records have been established and recorded. Where agreed contractually, quality records are made available for evaluation by the purchaser (client) or the purchaser s representative for an agreed upon period. 

It is a fact that in recent years, the average quality of crude oil has become worse. This is reflected in a progressive decrease in API gravity (i.e., increase in density) and a rise in sulfur content (Swain, 1991, 1993). However, it is now believed that there has been a continued tendency for the quality of crude oil feedstocks to deteriorate (Swain, 1998). Be that as it may, the nature of crude oil refining has changed considerably. This, of course, has led to the need to manage crude quality more effectively through evaluation (Chapter 2) and prod-... 

An evaluation has been made of the utility of zopiclone substitution in facilitating the withdrawal of flunitrazepam [31]. Twenty-four volunteers with insomnia and a history of long-term benzodiazepine hypnotic use were assessed with both subjective and objective measures during a 5-week substitution with zopiclone and subsequent withdrawal or continuation on flunitrazepam. Withdrawal from flunitrazepam was accompanied a worsening of sleep quality, both subjectively and objectively. No such deterioration was seen in the zopiclone-substituted groups. 

On a process design evaluation level, a number of careful analyses are required. First, with deteriorating water quality on the planet and water scarcity, the question needs to asked how much water needs to be treated to extremely high standards. It may be the rime to treat water for immediate consumption only using more localised facilities thus avoiding troublesome distribution systems. 

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