Structured bleaches

Fig. 1-left gives a general overview of the differential absorption spectra recorded for the free chromophore, oxyblepharismin, dissolved in DMSO for reference the steady-state absorption and (uncorrected) fluorescence spectra are also given below, in dotted lines. At all pump-probe delay times, the overall picture is a superposition of the structured bleaching and gain bands, as expected from the steady-state spectra, and broad transient absorption bands around 530 nm and 750 nm (weaker). These apparently homothetic spectra are very similar to... 

The dyeing process provides for temporary, semipermanent (direct dyes), and oxidation-type reactions (semipermanent or permanent colors). It may involve absorption or adsorption (electrostatic) of the colorant into/to the hair structure, bleaching or otherwise masking the natural melanin col-... 

Most raw materials and many formulated products can be analysed without isolation of the surfactants. For some purposes, however, e.g. determination of molecular weight by titration, the surfactant must be isolated in a pure form. Liquid-solid extraction is useful for this purpose. It is also sometimes desirable to extract fatty acids, neutral fatty matter and/or weak fatty bases, either to determine them or to prevent interference with some other determination. Liquid-liquid extraction is appropriate for this. A special case is the analysis of structured bleaches, which may contain surfactants in strong hypochlorite. The bleach makes most analytical processes for the surfactants difficult or impossible, and the procedure given below is a useful first step. 

Extraction of surfactants from structured bleaches. Structured bleaches usually contain a high concentration of hypochlorite and low concentrations of one or more surfactants. Because of the aggressive nature of... 

Figures 3.35 and 3.36 show spectra of polyene structures bleached in the presence of oxygen and singlet oxygen, respectively.

Voll-bau, m. solid construction or structure, -bleiche, /. full bleach. 

Plastics can be used to make erasable printing media by a number of different techniques. Photo changing dyes could be incorporated into the structure of the plastics. The printer could change the dye to the colored form to read, and the material can be bleached with another unit that would reverse the photo coloring process. An ionic type plastic can be incorporated into the plastics and used to color the printed area by the use of an indicator type reaction with an organic acid or base. Another method would be to use a thermal printer in conjunction with liquid crystal type materials that would alter the state of the liquid crystals in the printed areas. Applying heat and electrical fields to the printed sheet would erase the printing. 

Hontela, A., Daniel, C., and Rasmnssen, J.B. (1997). Structural and functional impairment of the hypothalamo- pituitary-interrenal axis in hsh exposed to bleached kraftmill effluent in the St. Maurice River, Quebec. Ecotoxicology 6, 1-12. 

Solutions of tetrazolium salts, e.g., 53, have been reported to both become colored and bleached under the influence of both UV and visible light. Several workers have attributed this phenomenon to photoreduction to the corresponding formazan (51) and the formation of a fluorescent colorless compound (152) through photooxidation.240- 243 The reduction of 152 under UV or blue light to the intense green radical structure (153) has also been reported (Scheme 21).244 A one-electron reduction product (154) is proposed as a short-lived intermediate in the photoreduction.245... 

Commercial heparin preparations are also frequently bleached with oxidants (for example, KMn04 and H202),32 a treatment that must lead to some modification of their original structure and biological properties. 

In contrast to Ag, these emission profiles are insensitive to variations of the excitation wavelength within the threefold structure of the 2P 2S absorption band. Simultaneous with the photolysis of any of the three 2P - 2S components, one observes gradual bleaching of all lines with concurrent formation of Ci where n =2-5 (34,56). A further intriguing observation concerns the appearance of a weak structured emission near 420 nm for excitations centered on the secondary atomic site band of Cu in all three rare gas films (Figure 4), which has been found from independent studies of the absorption and emission spectra of matrix entrapped CU2 to arise from the A-state of CU2 (34). 

Ordoudi SA and Tsimidou MZ. 2006. Crocin bleaching assay (CBA) in structure-radical scavenging activity studies of selected phenolic compounds. J Agric Food Chem 54(25) 9347-9356. 

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