Dark effects

Figure 11. Dynamic microwave conductivity-potential curves taken with a ZnO single crystal and shown for two potential sweep velocities (a) and (b) and a corresponding dynamic (photo)current-potential curve (bottom). The dark effects and photoeffects are indicated for the two cases. Curves 1 and 2 correspond to (a) and (b) respectively.

Different results were obtained with respect to the effectiveness of antioxidants for oil stored at 47°C in the dark. Effectiveness was evaluated as the time required for a sample to reach a peroxide value of 10 meq/kg, as estimated from curves of peroxide value as a function of storage time. The estimated effectiveness of TBHQ was approximately 9.6 times higher than that of GP and 51 times higher than for BHT. 

The work of Domlney et al (33) expands upon the work of Bookbinder and Wrighton to include detailed pH dependence and light vs. dark effects to help characterize these surfaces. They noted that the photovoltage developed at different pH s helped clarify the Importance of Fermi level pinning (49) in these systems, which is very significant in understanding the role surface states play in PEC processes. 

Dependence of photoactivation by repetitive flashes on flash interval (Fig. 3) showed that DCIP did not affect the yield of photoactivation with intervals shorter than 0.5 s but suppressed that with longer intervals. With 5 //M DCIP the yield was maximum at an interval of 2 s. On raising DCIP concentration, the interval for the maximum photoactivation became shorter and the maximum level decreased. Taking into account the previously reported model [7], these observations suggest that DCIP does not affect the light-driven formation of the intermediate state but reduces its stability in darkness Effects of... 

Are the two conformational states formed by the flash or do they pre-exist in the dark Effect of background continuous illumination... 

This reaction proceeds very slowly in absence of light, and aqueous solutions of potassium manganate(VII) are effectively stable for long periods if kept in dark bottles. 

Figures 4.1 la and b, respectively, are examples of dark-field and direct transmission electron micrographs of polyethylene crystals. The ability of dark-field imaging to distinguish between features of the object which differ in orientation is apparent in Fig. 4.11a. The effect of shadowing is evident in Fig. 4.11b, where those edges of the crystal which cast the shadows display sharper contrast.

If lighter colors than these are desired it is necessary to decolorize all the melanin in the hair in a preliminary step, and then add color back to the desired depth in a second treatment. This is known as a double-process treatment. The decolorization step consists of treating the hair with an alkaline mixture of persulfate salts and peroxide. The persulfate is added to the peroxide as a dry powder immediately before applying to the hair. Although the persulfate salts alone do not have any bleaching effect, the persulfate—peroxide mixture can remove all the melanin in the hair. Dark brown or darker hair can be lightened to a light blonde shade in about an hour. 

Treatment of Manic—Depressive Illness. Siace the 1960s, lithium carbonate [10377-37-4] and other lithium salts have represented the standard treatment of mild-to-moderate manic-depressive disorders (175). It is effective ia about 60—80% of all acute manic episodes within one to three weeks of adrninistration. Lithium ions can reduce the frequency of manic or depressive episodes ia bipolar patients providing a mood-stabilising effect. Patients ate maintained on low, stabilising doses of lithium salts indefinitely as a prophylaxis. However, the therapeutic iadex is low, thus requiring monitoring of semm concentration. Adverse effects iaclude tremor, diarrhea, problems with eyes (adaptation to darkness), hypothyroidism, and cardiac problems (bradycardia—tachycardia syndrome). 

Equalizers can be either pigmented or dye-type stains used to tone down or lighten dark areas of wood prior to finishing. Although it is not as effective, equalizing is sometimes done in place of bleaching. Because there are no white dyes, white pigment or pead essence is usually incorporated with the dyes to achieve the desired look. 

The use of high concentrations of vanillin in soap perfumery can cause discoloring effects over time, dark or black spots appear on the soap and foaming power is reduced. In some cases, however, the use of Rhodiarome ethylvanillin is possible, because ethylvanillin [121 -32-4] does not cause the same discoloration problems and, being at least three times more powerful than vanillin, can be used alone. Some surprising cases show that with oak or tree mosses and large amounts of methyl ionones, the soap perfume may look fine and have a low discoloration, and yet over time vanillin crystals can appear on the soap itself. 

Cesium forms simple alkyl and aryl compounds that are similar to those of the other alkah metals (6). They are colorless, sohd, amorphous, nonvolatile, and insoluble, except by decomposition, in most solvents except diethylzinc. As a result of exceptional reactivity, cesium aryls should be effective in alkylations wherever other alkaline alkyls or Grignard reagents have failed (see Grignard reactions). Cesium reacts with hydrocarbons in which the activity of a C—H link is increased by attachment to the carbon atom of doubly linked or aromatic radicals. A brown, sohd addition product is formed when cesium reacts with ethylene, and a very reactive dark red powder, triphenylmethylcesium [76-83-5] (C H )2CCs, is formed by the reaction of cesium amalgam and a solution of triphenylmethyl chloride in anhydrous ether. 

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