Photo-deterioration

Kiguchi, M. (1997). Photo-deterioration of chemically modified wood surfaces acetylated wood and alkylated wood. Japan Agricultural Research Quarterly, 31(2), 147-154. 

As part of their testing program, the authors exposed sulfonamide tablets and tablets containing the dye D C Orange No, 3 and a benzothiazine derivative, in an open dish and packaged in amber glass containers. The samples stored in the amber bottles showed little photo deterioration with time. This confirmed Arny et al. conclusion regarding the use of amber bottles for photo protection (24). 

Some weighting agents will act to accelerate the photo-deterioration of silks too. Metal ions, such as tin, adopt catalytic roles in degradation reactions, whereas tannin compounds can reduce the pH of the silk to the point where it becomes particularly susceptible to photodegradation. 

For CE—MS, volatile buffers are common. To use MEKC systems combined with mass detection, volatile micelles have been tested.When using atmosferic pressure photo-inonization (APPI), non-volatile BGE constituents do not deteriorate the mass signal to... 

Lee and coworkers report on a photo-initiated polymerization for the preparation of poly(butyl methylacrylate-co-ethylene dimethylacrylate) within fused silica capillaries. UV light-initiated polymerization is well suited to monolith formation in restricted spaces since polymer forms only in those areas that are exposed to irradiation. This leads to far greater control over the length and size of the monolithic column formed. The resulting columns are robnst since their separation ability does not deteriorate with time or number of injections and their reprodncibility is excellent. ... 

Postirradiation reactions are well known in photo and radiation chemistry. Some of the reactions which occur in polymers are of interest here. Of note also are postirradiation-induced changes which occur in proteins. These include deamination, dephosphorylation, and gelation. That radiation-treated food may either improve or deteriorate during storage is therefore a distinct possibility. 

Since the pigment extract deteriorates rapidly by photo-oxidation, it is critical that students work rapidly, but safely and efficiently. Part B must be completed immediately after the extraction. Parts C and D may be com-... 

Essential oils should be protected from the light. Sunlight causes photo-catalytic activity - that is, there are reactions that are speeded up by light. These reactions cause the essential oil to deteriorate. Artificial lights such as filament bulbs and fluorescent tubes are far less active than sunlight, but are still harmful. 

The damaging effects of acid rain can be seen by comparing these photos of a decorative statue on the Field Museum in Chicago. The photo on the left was taken c. 1920 the photo on the right was taken in 1990. Recent renovation has since replaced the deteriorating marble. 

Shellac is dark in colour, and is usually dyed black, red or brown. Its best known uses were as gramophone records. Another use was for American Union cases, which were small boxes used as folding picture frames (Fig. 13.1). They could be closed to preserve the silver nitrate coated glass photo des called Daguerreotypes, which deteriorate in the h t. Shellac was also used fin dressing table sets and for brooches. It is a britde material and can crack or chip. Shellac is compression moulded, and is still produced today. 

Tapley and Giesy (23) had studied the photostability of bismuth subnitrate and concluded that only amber bottles protected the chemical from deterioration by light. Flint glass and blue bottles were found to have little photo protective ability. 

In most cases, the iodide-triiodide redox couple has been employed (presumably because of its success in shuttling the photo-oxidized dye in the sensitization experiments) although other redox electrolytes e.g., SCN /(SCN)2 , [342] have also been employed. For the chalcogenide films, sodium selenosulfite was employed [319]. It must be noted that, aside from losses due to the surface recombination and back-reactions, an additional loss component from the increase in film resistance must also be recognized especially as the film thickness is increased. The resistance loss manifests as a deterioration in the photovoltage and fill factor. 

The stability of canola oil is limited mostly by the presence of linolenic acid, chlorophyll, and its decomposition products and other minor components with high chemical reactivity, such as trace amounts of fatty acids with more than three double bonds. These highly unsaturated fatty acids can possibly be formed during refining and bleaching (52). The presence of 7% to 11% of linolenic acid in the acylglyce-rols of canola oil places it in a similar category with soybean oil with respect to flavor and oxidative stability. The deterioration of flavor as the result of auto -and photo-oxidation of unsaturated fatty acids in oils and fats is referred to as oxidative rancidity. 

Highly oriented PP monofilaments (drawn to break at 25 ) are more resistant to photo-oxidation than medium drawn fiber ( x5 orientation at 230 C) as measured both by oxidation product build up and mechanical deterioration (2 ). Both types of PP monofilaments also show crack formation during photooxidation CFlgure 7). The lower orientation material shows quite wide, deep cracks whereas the fully oriented fiber shows many short, narrow cracks for... 

However, photoactivity requires an optimised semiconductor surface, and in an environment where the surface is constantly changed the surface optimisation is lost. This, combined with the poor kinetics of the p-type photoreduction, results in a continual deterioration of the photoactivity, and causes low photo-efficiency and discharge power density. The storage reaction at one photoelectrode is ... 

Photo 2c is a photomicrograph of IPS that contained the combination of light stabilizers (LS I and LS II) which was exposed outdoors in Florida for six months. Note the minimal amount of surface deterioration. Some surface dirt is present in the photo. 

Bricks and mortar (New Haven, CT) are susceptible to deterioration through the action of acid deposition. (Photo by Robert Baboian.)... 

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