Cause of Deterioration

Stabilization iavolves the removal of the cause of deterioration which is frequentiy soluble salts present ia the stone. If the stmctural strength of the stone permits it, this can be done through soakiag. The object is placed underwater ia a tank, and the water is changed regularly. Another method is by apphcation of poultices on the surface. 

Ton-exchange resins are used repeatedly in a cyclic manner over many years, and deterioration of both physical and chemical properties can be anticipated. Comparison of the properties of used resin with those of new resin is helpfiil to learning more about the nature and cause of deterioration (12). Corrective action frequendy extends the life of the resin. Comparison of properties must always be made with the resin in the same ionic form. 

In Fig. 16, the single substance approach concerning exposure and effects is depicted. There are comparable approaches and strategies for mixtures and effluents (lowest identified dilution step). There are further diagnostic instruments needed, which allow to identify the possible causes of deteriorated water quality and biota. By these instruments, it will be possible to gather further information about the effectiveness of possible measures. Examples for further diagnostic tools... 

The major cause of deterioration of food products is lipid oxidation, from which low-molecular-weight, off-flavor compounds are formed. This deterioration is often caused by the oxidation of the unsaturated lipids present in foods. Off-flavor compounds are created when the hydroperoxides, formed during the initial oxidation, are degraded into secondary reaction compounds. Free radicals are also formed which can participate in reactions with secondary products and with proteins. Interactions with the latter can result in carbonyl amino... 

Acidity of book papers, cause of deterioration, 13 Acidity of papa, definition, 3 Adhesives, taps doth treatment, 175 Adlerdalmatila... 

The inspection of piping is very well covered in the practical American Petroleum Institutes (API) Recommended Practice 574, Inspection of Piping, Tubing, Valves, and Fittings. [20] The recommended practice addresses the description of piping components, causes of deterioration, frequency of inspection, inspection tools, inspection procedures, and record keeping. 

Paper conservation, as known today, is new to Spain. Until a few years ago, custodians of the nations records on paper and parchment could only despair at the deterioration taking place. The restorers—craftsmen, in reality—scarcely were trained to tackle the broad problem. The pleas and warnings of those who wanted something done went unheeded. Here and there individual authorities sought professional help from abroad, but results proved minimal. In 1969, a dramatic change took place. Conservation was raised from the empirical to the scientific level. The breakthrough a law that provided for a centralized agency to restore the nations archival and library materials, determine the causes of deterioration, and train personnel to carry out these tasks. 

Corrosion of reinforcement is probably the most widespread cause of deterioration in concrete. The expansion produced by rust formation causes the surrounding concrete to crack and spall. In a sound concrete, rusting is prevented by the high pH of the pore solution, which stabilizes an oxide film on the steel that inhibits further attack. This film is unstable at lower pH values, which can result from carbonation or leaching, or in the presence of Cl . Sources of the latter include sea water or salt spray, de-icing salts used on roads, certain aggregates, especially those available in desert climates, and CaClj used as an accelerator. Though now widely prohibited, this can... 

Table 16.3. Neurological causes of deterioration after stroke...

In theory, recurrent embolization may cause deterioration. However, the distinction between propagating thrombosis and embolization is very difficult. There is only anecdotal evidence that full anticoagulation with intravenous heparin slows progression and improves outcome if no other cause of deterioration is evident (SUvka et al. 1989). 

Catalyst life estimation tests were also conducted on four different catalysts used for aromatization of light hydrocarbons in this system, namely H-ZSM-5, Zn/H-ZSM-5, Ga/H-ZSM-5 and H-Ga-silicate. Based on the results of characterization of the spent catalysts, the primary cause of deterioration of catalyst activity is the elimination of active metal from the zeolite framework. 

If air rather than light is the probable cause of deterioration. 

Product quality can be compromised during manufacture, transport, storage or use. The causes of deterioration can be manifold and product-specific. They include microbial spoilage or chemical transformation of the active or physical changes that alter performance in vivo. Deterioration can compromise safety or make the medication less attractive, which means it may not be used. Excipients can contribute to or cause such changes unless carefully screened for possible interactions in preformulation studies. 

Knowledge of the physical stability of a formulation is very important for two reasons. First, a pharmaceutical product must look fresh and elegant as long as it remains on the shelf. Second, the active ingredient must be available to the patient throughout the expected shelf life of the product. The causes of deterioration in quality of active ingredient could be due to incompatibility with excipients, oxidation, reduction, hydrolysis, and racemization to name a few. 

Error in the pH of the standard buffer. Any inaccuracies in the preparation of the buffer used for calibration or any changes in its composition during storage cause an error in subsequent pH measurements. The action of bacteria on organic buffer components is a common cause of deterioration. 

Minimally processed vegetables can be inhabited by invasive microorganisms that may be the cause of deterioration (Martins et al., 2004). 

The photolysis of the polymeric ketones is believed to be the main cause of deterioration in the absence of air. In the presence of air, these reactions can initiate photo-oxidation as a consequence of hydroperoxide formation either by reaction of the free radicals with oxygen... 

Causes of deterioration of plastics may be broadly divided into physical and chemical. 

Lipid oxidation, leading to oxidative rancidity, is a major cause of deterioration in milk and dairy products. The subject has been reviewed by Richardson and Korycka-Dahl (1983) and O Connor and O Brien (1995). 

Figure 3.1 Causes of deterioration of reinforced-concrete structures...

A preliminary assessment of the condition of the structure is required. Techniques described in Chapter 16 may be used to diagnose the causes of deterioration and the extent of damage. Degradation processes that may indirectly contribute to corrosion of the reinforcement (freeze-thaw, sulfate attack, etc.) should also be considered. Distinction should be made between different parts of the structure where ... 

As illustrated in Chapter 18, even before making a decision on the use of conventional repair, the causes of deterioration and the condition of the structure have to be clearly assessed (otherwise, any repair work should only be considered a waste of time and money). If carbonation or chloride contamination is the cause of degradation and the decision of using conventional repair has been made, a more detailed analysis is required. A survey of the structure has to be carried out with the aim of identifying the extent of the areas where concrete has to be removed and the depth that should be removed. A clearly described working plan of the repair should be made. 

Today, thanks to progress made over the past few decades in the chemistry of cement and in the technology of concrete, even these causes of deterioration can be fought effectively. With an appropriate choice of materials and careful, adequately controlled preparation and placement of the mixture, it is possible to obtain concrete structures which will last in time, under a wide variety of operative conditions. 

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