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Alternative fuels and green aviation
Published in Emily S. Nelson, Dhanireddy R. Reddy, Green Aviation: Reduction of Environmental Impact Through Aircraft Technology and Alternative Fuels, 2018
Currently, open-pond design is based on deep familiarity and experience with such systems. Is there a way to move toward the theoretical maximum in a more scientific, cost-effective way? In high-density cell cultures, the cells nearest to the surface absorb most or all of the available light (Chisti, 2007) due to self-shading. An engineering solution is to improve the vertical mixing in the system, so that more cells have access to light. One design choice in pond construction is whether to use a rectangular cross section or an angled cross section with a wider top than bottom. Recent work at NASA Glenn Research Center showed that the addition of passive mixing devices is more effective in providing access to light than the cross-sectional geometry in dense suspensions. This knowledge permits the choice of channel geometry to be based on other factors, such as ease of construction or maintenance. Other, more sophisticated approaches are needed to examine in greater depth the stochastic effects of hydrodynamic mixing on cell growth. This requires better understanding of the time scales that are relevant to industrial production. There is a great deal of research on the short time scales associated with photosynthesis, such as the amount of time it takes a cell to absorb a photon, convert it into food, and be ready to absorb another one: on the order of milliseconds. There are similarly small hydrodynamic time scales associated with turbulence, as well as larger ones linked to pond traversal. In current designs, the primary locations for vertical mixing occur at the paddlewheel and at the circular bends at either end of the pond, so that time scales associated with the unmixed state are on the order of tens of minutes. Algae that are near the surface will be continuously in the light during that stage, while the those near the bottom may be in the dark. There are also photoadaptation time scales that appear to be on the order of hours. Exposure to too much light can lead to photoinhibition. There are growth time scales with doubling time on the order of days. The complex, species-specific interplay among all of these factors with the biokinetics is an area that is ripe for exploration and may provide a scientific basis for effective pond design.
Crop Improvement and Applied Nanobiotechnology
Published in Cherry Bhargava, Amit Sachdeva, Nanotechnology, 2020
In 1970, dwarfism of wheat (Triticum aestivum) contributed to the Green Revolution. Dwarfism decreased the lodging and prevented the loss of energy in non-yield biomass (Swaminathan, 1993). The other major crops were maize (Zea mays), rice (Oryza sativa), and soya bean (Glycine max) in this row. One of the usual methods of increasing the production of these plants is to prolong their growing season, as they do not get proper ecology to grow in different locations (Vass, 2012). Their growth is largely dependent on the exploitation of solar energy during the process of photosynthesis, to increase its efficiency to absorb the required amount of light with maximum conversion of light energy to chemical energy. In the process of photosynthesis, light energy is held by the light harvesting complex to synthesize starch, thus releasing oxygen. We essentially classify plants as C3 and C4, depending upon the requirement of the light source. There are many plants which are short-day, which means they need a smaller amount of light during photoperiodism. The increased intensity of light in such plants may cause photoinhibition due to the release of the reactive oxygen species (Vass, 2012). Despite this, the plant has a mechanism to fight against such deleterious effects by dissipating the spare energy in the form of heat. Researchers are looking to overcome this problem using different light-intensity controlling techniques. Quantum dots (QDs) has always been a choice in this respect because of the adjustable wavelength property (Li et al., 2020). The emerging importance of nanotechnology has enabled us to branch out with the use organic-inorganic nanoparticles, metal nanoparticles, and semiconducting polymer nanoparticles, along with QDs. Increasing the efficiency of photosynthesis is a promising factor for sustainable agriculture when fundamentally under abiotic stress conditions. There are various artificially designed light-harvesting systems which can increase the light absorption by the plants during abiotic conditions. In 1972, Fujishima and Honda succeeded in the photolysis of water with semiconductor electrodes which mimic photosynthesis (Fujishima and Honda, 1972). This technique was largely implemented, and enhanced the efficiency of photosynthesis. Semiconductor-based nanoparticles are more efficient than semiconductor alone in the photolysis of water. The common semiconductor-based nanoparticles are TiO2-Pt, TiO2-CdS, TiO2-CdS-Pt, CdS-Pt, CdS-graphene-Pt, CdSe-MoS2, and MoS2-graphene/TiO2 (Tang et al., 2008; Girginer et al., 2009; Zhou et al., 2012; Maitra et al., 2014).
Roles of phytohormones in mitigating abiotic stress in plants induced by metal(loid)s As, Cd, Cr, Hg, and Pb
Published in Critical Reviews in Environmental Science and Technology, 2023
Zhi-Hua Dai, Dong-Xing Guan, Jochen Bundschuh, Lena Q. Ma
Photosynthesis is critical for plant growth and development, which is regulated by phytohormones. For example, brassinosteroids enhance chlorophyll content by increasing chlorophyll biosynthesis enzymes (Siddiqui et al., 2018). However, photosystem-II in the photosynthesis system splits water to oxygen, generating reactive oxygen species (ROS) as a byproduct, which destabilizes photosystem-II repair protein-D1 and leads to photoinhibition in plants. Fortunately, brassinosteroids promote protein-D1 stabilization, thus enhancing photosystem-II efficiency in plants (Siddiqui et al., 2018). Moreover, brassinosteroids also increase the stomatal aperture to allow more CO2 uptake into the photosynthesis system (Serna et al., 2012). Further, brassinosteroids induce formation of ribulose bisphosphate carboxylase/oxygenase in the Calvin cycle, the most common CO2 fixation pathway in plants, thereby increasing sugar synthesis (X. J. Li et al., 2016). Thus, brassinosteroid-mediated increase in photosynthetic efficiency enhances plant growth and development.
Recent advances of algae-bacteria consortia in aquatic remediation
Published in Critical Reviews in Environmental Science and Technology, 2023
Sheng-Nan Li, Chaofan Zhang, Fanghua Li, Nan-Qi Ren, Shih-Hsin Ho
To facilitate the industrialization, efficiency, and security of algae-bacteria consortia, it is crucial to allow the mathematical models to enhance performance and reliability through optimizing process performance and operational conditions (Del Rio-Chanona et al., 2019). So far, kinetic modeling as the main methodology has been primarily advanced for biological process simulations (Del Rio-Chanona et al., 2017). Clearly, kinetic modeling built on the well-established Droop, Monod, Haldane/Andrews, and Logistic models (Adesanya et al., 2014), these models with the correlated equations were displayed in Table S3, supplementary material. In addition, the Eilers and Peeters model often specified the photosynthesis as well as processes associated with photoinhibition and recovery from photoinhibition (Eilers & Peeters, 1988). According to a recent study by Shoener et al. (2019), in the context of microalgae and cyanobacteria modeling for wastewater treatment, the Droop formula for nutrient absorption and the Eilers and Peeters formula for irradiation response can precisely simulate internal and external conditions.
Screening of most potential candidate among different lemongrass varieties for phytoremediation of tannery sludge contaminated sites
Published in International Journal of Phytoremediation, 2019
Janhvi Pandey, Rajesh Kumar Verma, Saudan Singh
Chlorophyll a fluorescence kinetics was also analyzed for each harvest. It has been shown to be valuable in screening for several abiotic stresses, such as heat, chilling, drought, and salinity (KrishnaRaj et al. 1993). In the present study, nondestructive chlorophyll fluorescence kinetics has been used for estimating the physiological effects of metal stress. Mainly two parameters were observed in it: Fv/Fm and Fv/Fo. Fv/Fm is interpreted as a measure of photoinhibition of photochemistry in Photosystem II (Krause and Weis 1991). Number and size of active photosynthetic reaction centers are indicated by Fv/Fo ratio. A Fv/Fm ratio of >0.80 is characteristic of a healthy plant, while a ratio of <0.3 represents a physiologically restricted plant (Smillie and Hetherington 1983). Effect on chlorophyll a fluorescence kinetics (Fv/Fm and Fv/Fo) in different varieties of lemongrass grown in sole TS is shown in Figure 2(a and b). It is clear from the figure that different varieties of lemongrass can sustain high heavy metal stress successfully as Fv/Fm ratio in all varieties came to be near about 0.80. Both the ratios were highest in Suwarna variety which can be related to its good performance as compared to other varieties tested.