Light stimulation

Any factor that affects the size or shape of a molecule, the hindered movement of a fluorophore within a molecule, or the energy transfer within the molecule will affect the measured depolarization of its fluorescence emission. Therefore, the conformation of humic fractions in solution can be studied as a function of pH, ionic strength, temperature, and other factors by depolarization measurements. The principle of the method is that excitation of fluorescent samples with polarized light stimulates... 

Van Volkenburgh, E. Davies, W.J. (1983). Inhibition of light-stimulated leaf expansion by ABA. Journal of Experimental Botany, 345, 835-45. 

Bachowski GJ, Girotti AW (1988) Light-stimulated formation of hydrogen peroxide and hydroxyl radical in the presence of uroporphyrin and ascorbate. Free Radic Biol Med 5 3-6... 

Khramov, M.I. and Parmon, V.N. (1993) Synthesis of ultrafine particles of transition-metal sulfides in the cavities of lipid vesicles and the light-stimulated transmembrane electron-transfer catalyzed by these particles. Journal of Photochemistry and Photobiology A-Chemistry, 71, 279-284. 

Contraction of the pupil in response to light stimulation of the retina. 

The photons produced by stimulated emission are in phase with the stimulating photons and travel in the same direction that is, the light produced by stimulated emission is coherent light. Stimulated emission forms the basis of laser action. 

The phosphor has the following characteristics which are suitable to obtain a high-quality image with a low X-ray dose 1) the absorption coefficient for X-rays is high, 2) PSL radiation is efficiently released under such visible-light stimulation as a He Ne laser beam, 3) the PSL-radiation spectrum falls within the range of... 

Further on, one realizes that Kandinsky s approach is actually synesthesia, a simultaneous blending of all the sense perceptions. According to the painter-theorist, the expression scented colors is frequently encountered. And finally the sound of colors is so definite that it would be hard to find anyone who would try to express bright yellow in the bass notes, or dark lake in the treble. Red lights stimulate and excite the heart while blue... 

Fig. 12.13 Polarity change of colloidal silica surface by light stimulation. (From Ref. 51.)...

Finally, processes inverse to light-stimulated electrode reactions can also be referred to as processes of photoelectrochemistry of semiconductors. Such processes include, in particular, electrode reactions accompanied with light emission. 

To compare quantitatively the current-voltage characteristic of an illuminated electrode, given by formula (31), with experimental data, Butler (1977) and Wilson (1977) measured the photocurrent, which arises in a cell with an n-type semiconductor photoanode ( 2, W03) when irradiated with monochromatic light at a frequency satisfying the condition ha>> Eg. In this case a light-stimulated electrochemical reaction of water oxidation with oxygen evolution... 

There is a possibility, in principle, of developing the inverse process namely, the emission of coherent light stimulated by an electrochemical reaction. This process could form the basis for a new type of laser with electrochemical pumping. 

Weller, M. Virmaux, N. Mandel, P. Light-stimulated phosphorylation of rhodopsin in the retina the presence of a protein kinase that is specific for photobleached rhodopsin. Proc. Natl. Acad. Sci. USA, 72, 381-385 (1975)... 

The BaFBr Eu2 + phosphors are gaining increasing industrial importance because of their storage effect. On irradiation with X rays (or UV light) some of the Eu2 + ions are ionized to Eu3+ with loss of electrons to the conduction band. These electrons are captured by F+ centers (anion vacancies) and can be liberated from these traps by the action of light (stimulation). The electrons return to the Eu3 + ions via the conduction band, converting them to Eu2+ [5.413]-[5.417],... 

A mechanism by which electronic energy is sometimes made available for chemical purposes is that which occurs in the so-called Stoss zweiter Art , or collision of the second kind . Cario and Franck found that on exposure of a mixture of mercury vapour and hydrogen to the mercury line 2536-7 A, the absorbed light stimulated the mercury atoms electronically, and that the excited mercury atoms were able on collision with hydrogen molecules to resolve them into atoms. The atomic hydrogen so produced was detected by its great chemical activity. A number of other examples of this phenomenon were found Z. Phyaik, 1922, 21, 161. 

Douglas, C., Hoffmann, H., Schulz, W. Hahlbrock, K. (1987). Structure and elicitor or UV-light-stimulated expression of two 4-coumarate CoA ligase genes in parsley. The EMBO Journal 6, 1189-95. 

Indeed elucidation and understanding of the many processes that can occur upon light stimulation, and the chemical dynamics associated therewith, are major goals of current excited state chemistry. 

Photoswitchable sub strate-protein / cofactor- enzyme/antigen-antibody interactions Light-stimulated affinity chromatography Immobilization of photoactive separation component on solid matrices... 

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