scholarly journals Role of elemental carbon in the photochemical aging of soot

2018 ◽  
Vol 115 (30) ◽  
pp. 7717-7722 ◽  
Author(s):  
Meng Li ◽  
Fengxia Bao ◽  
Yue Zhang ◽  
Wenjing Song ◽  
Chuncheng Chen ◽  
...  
Keyword(s):  
Light Absorption ◽  
Elemental Carbon ◽  
Red Light ◽  
Field Measurements ◽  
Light Irradiation ◽  
Photochemical Oxidation ◽  
Chemical Mechanism ◽  
Strong Light ◽  
Electron Transfer Pathway ◽  
Photochemical Aging

Soot, which consists of organic carbon (OC) and elemental carbon (EC), is a significant component of the total aerosol mass in the atmosphere. Photochemical oxidation is an important aging pathway for soot. It is commonly believed that OC is photoactive but EC, albeit its strong light absorption, is photochemically inert. Here, by taking advantage of the different light absorption properties of OC and EC, we provide direct experimental evidence that EC also plays an important role in the photochemical aging of soot by initiating the oxidation of OC, even under red light irradiation. We show that nascent soot, in addition to undergoing photochemical oxidation under blue light with a wavelength of 440 nm, undergoes similar oxidation under red light irradiation of λ = 648 nm (L648). However, separated OC (extracted from soot by n-hexane) and EC exhibit little reactivity under L648. These observations indicate that EC plays a pivotal role in photoaging of soot by adsorbing light to initiate the oxidation of OC. Comparison of in situ IR spectra and photoelectrochemical behaviors suggests that EC-initiated photooxidation of OC proceeds through an electron transfer pathway, which is distinct from the photoaging induced by light absorption of OC. Since the absorption spectra of EC have a much larger overlap with the solar spectra than those of OC, our results provide insight into the chemical mechanism leading to rapid soot aging by organic species observed from atmospheric field measurements.

scholarly journals Red fluorescence of the triplefin Tripterygion delaisi is increasingly visible against background light with increasing depth

2017 ◽  
Vol 4 (3) ◽  
pp. 161009 ◽  
Author(s):  
Pierre-Paul Bitton ◽  
Ulrike K. Harant ◽  
Roland Fritsch ◽  
Connor M. Champ ◽  
Shelby E. Temple ◽  
...  
Keyword(s):  
Colour Vision ◽  
Red Light ◽  
Field Measurements ◽  
Light Environment ◽  
Natural Light ◽  
Ambient Light ◽  
Red Fluorescence ◽  
As Species ◽  
Tripterygion Delaisi ◽  
Red Coloration

The light environment in water bodies changes with depth due to the absorption of short and long wavelengths. Below 10 m depth, red wavelengths are almost completely absent rendering any red-reflecting animal dark and achromatic. However, fluorescence may produce red coloration even when red light is not available for reflection. A large number of marine taxa including over 270 fish species are known to produce red fluorescence, yet it is unclear under which natural light environment fluorescence contributes perceptively to their colours. To address this question we: (i) characterized the visual system of Tripterygion delaisi, which possesses fluorescent irides, (ii) separated the colour of the irides into its reflectance and fluorescence components and (iii) combined these data with field measurements of the ambient light environment to calculate depth-dependent perceptual chromatic and achromatic contrasts using visual modelling. We found that triplefins have cones with at least three different spectral sensitivities, including differences between the two members of the double cones, giving them the potential for trichromatic colour vision. We also show that fluorescence contributes increasingly to the radiance of the irides with increasing depth. Our results support the potential functionality of red fluorescence, including communicative roles such as species and sex identity, and non-communicative roles such as camouflage.

Strong light absorption capability directed by structured profile of vertical Si nanowires

2017 ◽  
Vol 73 ◽  
pp. 449-458 ◽  
Author(s):  
Harsh A. Chaliyawala ◽  
Abhijit Ray ◽  
Ranjan K. Pati ◽  
Indrajit Mukhopadhyay
Keyword(s):  
Light Absorption ◽  
Si Nanowires ◽  
Strong Light

scholarly journals Photomorphogenesis in the Picocyanobacterium Cyanobium gracile Includes Increased Phycobilisome Abundance Under Blue Light, Phycobilisome Decoupling Under Near Far-Red Light, and Wavelength-Specific Photoprotective Strategies

2021 ◽  
Vol 12 ◽  
Author(s):  
Gábor Bernát ◽  
Tomáš Zavřel ◽  
Eva Kotabová ◽  
László Kovács ◽  
Gábor Steinbach ◽  
...  
Keyword(s):  
Electron Transport ◽  
Growth Rates ◽  
Incident Light ◽  
Red Light ◽  
Photosynthetic Performance ◽  
State Transitions ◽  
Photochemical Quenching ◽  
Strong Light ◽  
Antenna Size ◽  
Moderate Growth

Photomorphogenesis is a process by which photosynthetic organisms perceive external light parameters, including light quality (color), and adjust cellular metabolism, growth rates and other parameters, in order to survive in a changing light environment. In this study we comprehensively explored the light color acclimation of Cyanobium gracile, a common cyanobacterium in turbid freshwater shallow lakes, using nine different monochromatic growth lights covering the whole visible spectrum from 435 to 687 nm. According to incident light wavelength, C. gracile cells performed great plasticity in terms of pigment composition, antenna size, and photosystem stoichiometry, to optimize their photosynthetic performance and to redox poise their intersystem electron transport chain. In spite of such compensatory strategies, C. gracile, like other cyanobacteria, uses blue and near far-red light less efficiently than orange or red light, which involves moderate growth rates, reduced cell volumes and lower electron transport rates. Unfavorable light conditions, where neither chlorophyll nor phycobilisomes absorb light sufficiently, are compensated by an enhanced antenna size. Increasing the wavelength of the growth light is accompanied by increasing photosystem II to photosystem I ratios, which involve better light utilization in the red spectral region. This is surprisingly accompanied by a partial excitonic antenna decoupling, which was the highest in the cells grown under 687 nm light. So far, a similar phenomenon is known to be induced only by strong light; here we demonstrate that under certain physiological conditions such decoupling is also possible to be induced by weak light. This suggests that suboptimal photosynthetic performance of the near far-red light grown C. gracile cells is due to a solid redox- and/or signal-imbalance, which leads to the activation of this short-term light acclimation process. Using a variety of photo-biophysical methods, we also demonstrate that under blue wavelengths, excessive light is quenched through orange carotenoid protein mediated non-photochemical quenching, whereas under orange/red wavelengths state transitions are involved in photoprotection.

scholarly journals LED and UV Light Utilizing Flavonoids and Limonoids to Investigate the Effect of Post-harvest Light Irradiation

2020 ◽  
Author(s):  
Shengyu Liu
Keyword(s):  
White Light ◽  
Uv Light ◽  
Light Emitting Diode ◽  
Red Light ◽  
Principal Component ◽  
Experimental Period ◽  
Light Irradiation ◽  
Flavonoid Glycosides ◽  
Clear Correlation ◽  
Post Harvest

To investigate the effect of post-harvest light irradiation on the accumulation of flavonoids and limonoids, harvestedNewhall navel oranges were continuously exposed to light-emitting diode (LED) and ultraviolet (UV) light irradiationfor 6 days, and the composition and content of flavonoids and limonoids in the segments were determined usingUPLC-qTOF-MS at 0, 6, and 15 days after harvest. In total, six polymethoxylated flavonoids (PMFs), fiveflavoneO/C-glycosides, seven flavanone-O-glycosides, and three limonoids were identified in the segments. Theaccumulation of these components was altered by light irradiation. Red and blue light resulted in higher levels ofPMFs during exposure periods. The accumulation of PMFs was also significantly induced after white light, UVBand UVC irradiation were removed. Red and UVC irradiation induced the accumulation of flavone and flavanoneglycosides throughout the entire experimental period. Single light induced limonoid accumulation during exposureperiods, but limonoid levels decreased significantly when irradiation was removed. Principal component analysisshowed a clear correlation between PMFs and white light, between flavonoid glycosides and red light and UVC,and between limonoids and UVC. These results suggest that the accumulation of flavonoids and limonoids in citrusis regulated by light irradiation. White light, red light and UVC irradiation might be a good potential method forimproving the nutrition and flavor quality of post-harvest citrus.

Effect of pH on Absorption Spectra of Pea 114 and 121 Kilodalton Phytochromes during and after Red-Light Irradiation

1986 ◽  
Vol 27 (5) ◽  
pp. 765-773 ◽  
Author(s):  
Satoru Tokutomi ◽  
Yasunori Inoue ◽  
Naoki Sato ◽  
Kotaro T. Yamamoto ◽  
Masaki Furuya
Keyword(s):  
Absorption Spectra ◽  
Red Light ◽  
Light Irradiation ◽  
Effect Of Ph
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