Light Irradiance levels

P vs I Relationships. In our investigation we em-ployed a technique widely used by plant physiologists, namely, the study of rate of photosynthesis (P) as a function of irradiance (I). The results of one experiment in which phytoplankton were kept under the four experimental treatment conditions for 24 hours arc shown in Fig. 4. It is clear from this figure that phytoplankton exposed to visible light alone (i.e., when UV was excluded) had the highest photosynthctic rates, and these rates were maintained over a higher range of irradiance levels. On the other hand, the lowest carbon fixation rates occurred when the phytoplankton were exposed to ambient and enhanced levels of UV. 

The relationship of degradation to light intensity is certainly nearer to linear than is the case with temperature. This implied time scale would add considerably to the effort needed to collect data at a series of acceleration levels. Also, only very recent weathering apparatus would be capable of operating over a range of irradiance levels. The result, in practice, is that it is extremely uncommon for more than one irradiance level to be used and degradation is assumed to be proportional to irradiance. By this is meant irradiance of the same spectral distribution. Different distributions, particularly in the UV regions, will inevitably produce different results. 

When exposure to oxygen and light irradiation were commenced simultaneously, the infectious activity of the vims remained on the initial level for 30-50 min. This period of induction was observed both in the allantoic fluid and saline. 

It is important to emphasize that the photocatalytic reactivity of the metal ion-implanted titanium oxides under UV light (X < 380 nm) retained the same photocatalytic efficiency as the unimplanted original pure titanium oxides under the same UV light irradiation conditions. When metal ions were chemically doped into the titanium oxide photocatalyst, the photocatalytic efficiency decreased dramatically under UV irradiation due to the effective recombination of the photo-formed electrons and holes through the impurity energy levels formed by the doped metal ions within the band gap of the photocatalyst (in the case of Fig. 6)... 

Fig. 37. Band edge profile of a (In,Mn)As/GaSb heterostmcture. Eq. E. and Ep denote band edges of conduction band, valence band, and Fermi level, respectively, (b) Temperature dependence of the magnetization observed during cooldown in the dark (open circles) and warmup (solid circles) under a fixed magnetic field of 0.02 T. The effect of light irradiation at 5 K is also shown by an arrow, (c) Magnetization curves at 5 K observed before (open circles) and after (solid circles) light irradiation. Solid line shows a theoretical curve, (d) Hall resistivity />Hall observed at 5 K before (dashed line) and after (solid line) light irradiation (Koshihara...

These units are claimed to provide conversion efficiencies of up to 25%, or even 30% if the irradiation level is high enough. High irradiation is defined as 200-300 suns (1 sun = 0.1 W/cm2), which correspond to 20-30 W/cm2 of solar irradiation. To obtain such levels of solar irradiation, the solar light has to be focused 200-300 times. For a light concentration ratio of 100x, the high-performance PV cells are claimed to have a conversion efficiency of 28%. 

Light source The UV part of the solar spectrum should be correctly simulated, using e.g., a long-arc xenon lamp filtered through a Schott WG 320/2 mm or a spectrally equivalent setup. The irradiance level should not exceed 4 MED/hr at sample level in order to avoid potential problems due to nonreciprocity of UV filters, e.g., DBM filters. 

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