Morphological and Physiological Properties of Greenhouse-Grown Cucumber Seedlings as Influenced by Supplementary Light-Emitting Diodes with Same Daily Light Integral

Insufficient light in autumn–winter may prolong the production periods and reduce the quality of plug seedlings grown in greenhouses. Additionally, there is no optimal protocol for supplementary light strategies when providing the same amount of light for plug seedling production. This study was conducted to determine the influences of combinations of supplementary light intensity and light duration with the same daily light integral (DLI) on the morphological and physiological properties of cucumber seedlings (Cucumis sativus L. cv. Tianjiao No. 5) grown in a greenhouse. A supplementary light with the same DLI of 6.0 mol m−2 d−1 was applied with the light duration set to 6, 8, 10, or 12 h d−1 provided by light-emitting diodes (LEDs), and cucumber seedlings grown with sunlight only were set as the control. The results indicated that increasing DLI using supplementary light promoted the growth and development of cucumber seedlings over those grown without supplementary light; however, opposite trends were observed in the superoxide dismutase (SOD) and catalase (CAT) activities. Under equal DLI, increasing the supplementary light duration from 6 to 10 h d−1 increased the root surface area (66.8%), shoot dry weight (24.0%), seedling quality index (237.0%), root activity (60.0%), and stem firmness (27.2%) of the cucumber seedlings. The specific leaf area of the cucumber seedlings decreased quadratically with an increase in supplementary light duration, and an opposite trend was exhibited for the stem diameter of the cucumber seedlings. In summary, increased DLI or longer light duration combined with lower light intensity with equal DLI provided by supplementary light in insufficient sunlight seasons improved the quality of the cucumber seedlings through the modification of the root architecture and stem firmness, increasing the mechanical strength of the cucumber seedlings for transplanting.

Sustainable Cultivation of Desmodesmus armatus SAG276.4d using Leachate as a Growth Supplement for Simultaneous Biomass Production and CO2 Fixation

Microalgae cultivation has been identified to be highly beneficial for the production of valuable biomass. The recent worldwide interest is to cultivate microalgae in wastewater to replace the use of expensive commercial media. Microalgae can utilize nutrients from the wastewater for their biomass growth, which is useful as feedstock in many products. Interestingly, microalgae cultivation is also capable of reducing a greenhouse gas due to absorption of carbon dioxide (CO2) during photosynthesis. This study was conducted to study the growth of microalgae using leachate as a nutrient supplement. The scope of the research involved the cultivation of freshwater microalgae, Desmodesmus armatus, in the synthetics medium with various percentages of leachate under different light exposures. The growth parameters such as the specific growth rate, biomass productivity, and cell division time were used to evaluate the microalgae growth performance. The amount of CO2 absorbed during the cultivation was determined based on the total biomass production. The highest growth rate of 0.423/day was achieved using a 5% leachate medium under 12 h light duration, and the highest carbon fixation of 1.317 g CO2/L/day was calculated using a culture supplemented with 5% leachate with 24 h light period. The high presence of nutrients in the leachate has contributed to the growth of the microalgae; thus, it has great potential as an alternative growth medium to support biomass production and subsequently help to mitigate global warming.

High and low latitude controls on Mid-Brunhes coccolithophore bloom and its implications on ocean carbon cycle

Periodic ~400 kyr orbital scale variations in the ocean carbon cycle, manifest in indicators of deep sea dissolution and benthic 13C, have been observed throughout the Cenozoic but the driving mechanisms remain under debate. Changes in coccolithophore productivity may change the global rain ratio (Corganic: Cinorganic fluxes from ocean into sediment) and the balance of ocean carbonate system and thereby, potentially contributing to the ~400 kyr oscillation of the marine carbon cycle. Some evidence suggests that Pleistocene coccolithophore productivity was characterized by “bloom” events of high productivity coincident with the orbital benthic 13C signal. However, there is no consensus on the mechanism responsible for bloom events nor whether they were regional or global phenomena. In this study, we investigate the timing and spatial pattern of the most recent purported coccolithophore bloom event, which occurred during the Mid-Brunhes period. We find that maximum coccolithophore productivity is diachronous, peaking in the Southern Ocean sub-Antarctic zone with eccentricity minimum (~430 ka), peaking in upwelling zones some ~28 kyr later, and finally peaking in the western tropical Pacific occurred some ~80 kyr later. Simple globally homogeneous mechanisms of driving productivity such as temperature or light duration are not consistent with this pattern. Rather, we propose a dual high and low latitude control on blooms. Coincident with eccentricity minimum, increased high-latitude diatom silica consumption lowers the Si/P, leading to coccolithophorid blooms in the Southern Ocean north of the polar front. Coincident with increasing eccentricity, stronger tropical monsoons deliver higher fluvial nutrients to surface waters, increasing total (diatom and coccolithophore) productivity. Most of the tropical and subtropical locations are influenced by both processes with varying degrees, through the effect of silicic acid leakage on tropical thermocline waters and monsoon-related nutrient supply. Moreover, we propose that the high latitude processes have intensified over the Pleistocene, extending the 405 kyr carbon cycle to about 500 kyr.

Photoperiod Manipulation Reveals a Light-Driven Component to Daily Patterns of Ventilation in Male C57Bl/6J Mice

Obstructive sleep apnea is a common sleep disorder that increases risk for cardiovascular disease and mortality. The severity of sleep-disordered breathing in obstructive sleep apnea patients fluctuates with the seasons, opening the possibility that seasonal changes in light duration, or photoperiod, can influence mechanisms of breathing. Photoperiod can have profound effects on internal timekeeping and can reshape metabolic rhythms in mammals. While the daily rhythm in ventilation is largely shaped by the metabolic rate, less is known about whether ventilatory rhythms are altered in accordance with metabolism under different photoperiods. Here, we investigate the relationship between ventilation and metabolism under different photoperiods using whole-body plethysmography and indirect calorimetry. We find that the daily timing of ventilation is chiefly synchronized to dark onset and that light cues are important for maintaining daily ventilatory rhythms. Moreover, changes in ventilatory patterns are not paralleled by changes in oxygen consumption, energy expenditure, or respiratory exchange rate under different photoperiods. We conclude that ventilatory patterns are not only shaped by the metabolic rate and circadian timing but are also influenced by other light-driven factors. Collectively, these findings have clinical implications for the seasonal variations in sleep-disordered breathing found in individuals with obstructive sleep apnea.

Preparation of Bi2WO6/Fe3O4 Composite and Photocatalytic Degradation of Bisphenol A

Bi2WO6/Fe3O4 nanocomposite materials with uniform morphology and size were successfully synthesized by hydrothermal method, and its catalytic degradation effect on bisphenol A was studied. The composite material was studied to analyze the microstructure and internal composition of the composite material by X-ray diffraction (XRD), energy dispersive X-ray spectrum (EDS), scanning electron microscope (SEM), transmission electron microscope (TEM) and other analytical methods. The degradation rate of BPA can be effectively controlled when the light is applied under the optimal conditions, the degradation rate of bisphenol A by the composite catalyst has reached 93.45% when the light duration lasts for 120 min. The composite material is a magnetic material, which combines the dual characteristics of the catalytic material and the magnetic material. It can not only catalyze the degradation of the target pollutant, but also recycle and reuse the magnetic material, it improves the utilization ratio of the material.

Optogenetic actuation in ChR2-transduced fibroblasts alter excitation-contraction coupling and mechano-electric feedback in coupled cardiomyocytes: a computational modeling study

<abstract> <p>With the help of the conventional electrical method and the growing optogenetic technology, cardiac fibroblasts (Fbs) have been verified to couple electrically with working myocytes and bring electrophysiological remodeling changes in them. The intrinsic properties of cardiac functional autoregulation represented by excitation-contraction coupling (ECC) and mechano-electric feedback (MEF) have also been extensively studied. However, the roles of optogenetic stimulation on the characteristics of ECC and MEF in cardiomyocytes (CMs) coupled with Fbs have been barely investigated. In this study, we proposed a combined model composed of three modules to explore these influences. Simulation results showed that (1) during ECC, an increased light duration (LD) strengthened the inflow of ChR2 current and prolonged action potential duration (APD), and extended durations of twitch and internal sarcomere deformation through the decreased dissociation of calcium with troponin C (CaTnC) complexes and the prolonged duration of Xb attachment-detachment; (2) during MEF, an increased LD was followed by a longer muscle twitch and deformation, and led to APD prolongation through the inward ChR2 current and its inward rectification kinetics, which far outweighed the effects of the delaying dissociation of CaTnC complexes and the prolonged reverse mode of Na⁺-Ca²⁺ exchange on AP shortening; (3) due to the ChR2 current's rectification feature, enhancing the light irradiance (LI) brought slight variations in peak or valley values of electrophysiological and mechanical parameters while did not change durations of AP and twitch and muscle deformation in both ECC and MEF. In conclusion, the inward ChR2 current and its inward rectification feature were found to affect significantly the durations of AP and twitch in both ECC and MEF. The roles of optogenetic actuation on both ECC and MEF should be considered in future cardiac computational optogenetics at the tissue and organ scale.</p> </abstract>

An Intelligent Fuzzy Logic Based Traffic Controller

Increasing road congestion, travel time, number of accidents, carbon dioxide emissions, and fuel consumption are some of the consequences of growth in the vehicle population. Therefore, intelligent traffic controllers are required to solve road traffic congestion problems. The results of prevalent methods, including preset cycle time controller and vehicle-actuated controller, indicated that they do not effectively perform at traffic peak moments. Therefore, due to the deficiency of common methods, fuzzy logic based traffic signal controllers have attracted a lot of attention among researchers. In this article, a fuzzy logic based algorithm for 4-way intersections is proposed and it consists of two main stages for sorting the phase and determining the green light duration. The proposed system is simulated in the MATLAB programming environment and the performance of the designed controller and a conventional controller is compared for some of the presumed conditions. The results of applying the proposed system indicate that this algorithm has a better performance in different traffic conditions in contrast to a preset cycle time controller and it can reduce the number of vehicles behind traffic lights at intersections and the waiting time of passengers.

Distinct Responses to Light in Plants

The development of almost every living organism is, to some extent, regulated by light. When discussing light regulation on biological systems, one is referring to the sun that has long been positioned in the center of the solar system. Through light regulation, all life forms have evolved around the presence of the sun. As soon our planet started to develop an atmospheric shield against most of the detrimental solar UV rays, life invaded land, and in the presence of water, it thrived. Especially for plants, light (solar radiation) is the source of energy that controls a high number of developmental aspects of growth, a process called photomorphogenesis. Once hypocotyls reach soil′s surface, its elongation deaccelerates, and the photosynthetic apparatus is established for an autotrophic growth due to the presence of light. Plants can sense light intensities, light quality, light direction, and light duration through photoreceptors that accurately detect alterations in the spectral composition (UV-B to far-red) and are located throughout the plant. The most well-known mechanism promoted by light occurring on plants is photosynthesis, which converts light energy into carbohydrates. Plants also use light to signal the beginning/end of key developmental processes such as the transition to flowering and dormancy. These two processes are particularly important for plant´s yield, since transition to flowering reduces the duration of the vegetative stage, and for plants growing under temperate or boreal climates, dormancy leads to a complete growth arrest. Understanding how light affects these processes enables plant breeders to produce crops which are able to retard the transition to flowering and avoid dormancy, increasing the yield of the plant.