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Effects of continuous LED lighting on reducing nitrate content and enhancing edible quality of lettuce during pre-harvest stage
Lettuce easily accumulates higher nitrate content during production, especially in hydroponic system, and higher ni
trate content poses a threat to human health. Light condition (light quality, intensity and duration) significantly affects nitrate content in plants. Lighting
-emitting diodes (LEDs) have showed the great potential for plant growth and development with the higher luminous
efficiency and positive impact compared with other artificial light. The effects of combination of red
(R)/ blue (B) or/and green (G), and white (W) LED lights on the plant growth, plant physiological 8th 45 International Symposium on Light in Horticulture changes, including chlorophyll fluorescence, nitrate contents and phytochemical concentration before harvest were investigated. The results showed that Pre-harvest continuous light exposure
can effectively reduce nitrate accumulation and increase phytochemical concentrations in lettuce plants, and the reduction in nitrate content is dependent on the spectral composition and light intensity of the applied light sources and continuous light duration. Lettuce plants grown under the continuous combined red, green and blue LED light (RGB) with a PPFD at 200 μmol·m-2·s -(RGB-200) and RB-200 treatments exhibited a remarkable decrease of nitrate contents at 24 h compared to other LED light treatments. Moreover, continuous LED light at 24 h significantly enhanced the DPPH free-radical scavenging activity and increase phenolic compound concentrations. In this study, we
suggest that a period of continuous LED light (RGB-200 or RB
-200) exposure is needed in order to decrease nitrate concentrations and enhance lettuce quality. The period of 24 h continuous LED light exposure appears to be the best, and this period should not exceed 48 h
Transmutation prospect of long-lived nuclear waste induced by high-charge electron beam from laser plasma accelerator
Photo-transmutation of long-lived nuclear waste induced by high-charge
relativistic electron beam (e-beam) from laser plasma accelerator is
demonstrated. Collimated relativistic e-beam with a high charge of
approximately 100 nC is produced from high-intensity laser interaction with
near-critical-density (NCD) plasma. Such e-beam impinges on a high-Z convertor
and then radiates energetic bremsstrahlung photons with flux approaching
10^{11} per laser shot. Taking long-lived radionuclide ^{126}Sn as an example,
the resulting transmutation reaction yield is the order of 10^{9} per laser
shot, which is two orders of magnitude higher than obtained from previous
studies. It is found that at lower densities, tightly focused laser irradiating
relatively longer NCD plasmas can effectively enhance the transmutation
efficiency. Furthermore, the photo-transmutation is generalized by considering
mixed-nuclide waste samples, which suggests that the laser-accelerated
high-charge e-beam could be an efficient tool to transmute long-lived nuclear
waste.Comment: 13 pages, 8 figures, it has been submitted to Physics of Plasm
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