Impact Of Light Intensity Research Articles

Investigation on influence factors of optically controlled electrorheological fluid damping system

Abstract Electromagnetic rheological damping control system, as an important control technology, has been widely used in braking, vibration reduction and micro-valve etc. However, the electromagnetic rheological damping control system faces issues of electromagnetic interference due to the high voltage source. To solve this problem, we proposed a novel optically controlled electrorheological fluid damping system. Previous studies have confirmed the feasibility of the optically controlled electrorheological fluid damping control system via numerical simulation and experiment. In this paper, the mechanism and mathematical model of the optically controlled electrorheological fluid damping system are established. The influence factor analyses of the optically controlled damping system, especially the impact of light intensity and microchannel size on system performance, are carried out through experimental and theoretical methods. The research findings of influence factors contribute to a deeper understanding of the working principle of the electrorheological fluid damping system, thereby promoting stability and reliability in microfluidics technology.

Light intensity affects tolerance of pyrene in Chlorella vulgaris and Scenedesmus acutus

The impact of light intensity on the toxicity of pyrene, a 4-ring polycyclic aromatic hydrocarbon (PAH), was studied in Chlorella vulgaris and Scenedesmus acutus. Both species were cultured under low light, LL [50-60 µmol(photon) m-2 s-1], and high light, HL [100-110 µmol(photon) m-2 s-1] conditions to study the effects of pyrene (PYR) toxicity on growth parameters, the content of biomolecules, chlorophyll content, and photosynthetic efficiency. In the presence of PYR, S. acutus could grow well in LL and HL intensity. On the other hand, C. vulgaris showed a drastic decrease in growth and photosynthesis during HL conditions due to PYR toxicity. Regulation of nonphotochemical and photochemical quenching was responsible for the survival of S. acutus under PYR toxicity in LL and HL conditions. Thus, S. acutus seems to be a more promising candidate for pyrene degradation under varying light conditions.

Impact of light intensity and electrolyte volume on performance of photo-electrochemical (PEC) solar cell

The world’s energy demand is continuously increasing. Non-renewable energy sources, such as petroleum and coal, are extremely limited. On the other hand, conversion efficiency of renewable energy sources into useful forms is insufficient. In our study, we pursued methods to make more efficient solar cells – in particular, photo-electrochemical (PEC) solar cells. We selected the Molybdenum diselenide (MoSe2) based PEC solar cell because of its high resistance to corrosion. First, we explored the relationship between light intensity and efficiency of PEC solar cells. We expected that corrosion of the PEC solar cell would increase with increase in intensity of incident light. Thus, we hypothesized that the efficiency of the solar cell would decrease with increased intensity of incident light. Further, we investigated the relationship between solar cell efficiency and electrolyte volume. We hypothesized that efficiency of PEC solar cell would increase as the electrolyte volume increased. We analyzed several parameters— such as light intensity, fill factor, efficiency, etc.—to draw conclusions. First, we found that percentage efficiency of PEC solar cell was proportional to (light intensity)-0.9. Further analysis showed that PEC solar cell performance was positively influenced by increasing the electrolyte volume. Data revealed that this increase in solar cell performance was more consequential at low intensities of light (around 10 mW/cm2). Our study could contribute to improving the quality of PEC solar cells and might help in the development of carbon-free hydrogen economy.

The impact of light intensity and wavelength on the performance of algal-bacterial culture treating domestic wastewater

Light is the main energy source for microalgae, and the intensity and wavelength of light influence cell metabolism and biomass composition, which, in turn, affects wastewater treatment. The objective of this study is to examine how different light intensities and light wavelengths affect the growth of mixed algal-bacterial culture while treating sewage. Three different light intensities (100, 200, and 300 μmol/m2-s) of four different light wavelengths (blue, red, white, and yellow) were selected for this study. The dissolved organic carbon (DOC), dissolved nitrogen (DN), and dissolved phosphorus (DP) in influent and effluent samples were measured, along with chlorophyll content in the biomass. The highest chlorophyll concentration of 3.5 mg/L was observed at 100 μmol/m2-s intensity of red light. The concentration of chlorophyll decreased as light intensity increased, with exception of white light. The highest DOC removal of 84% was observed at 300 μmol/m2-s intensity of blue light whereas the highest DN (51%) and DP (80%) removal was observed with a red light intensity of 100 μmol/m2-s. Overall, blue light with an intensity of 300 μmol/m2-s and red light with an intensity of 100 μmol/m2-s were found to be the most efficient at removing carbon and nutrients. The results suggested that the color and intensity of light influence algal-bacterial growth and wastewater treatment efficiency.

Photocatalytic Degradation of Diazo Dye over Suspended and Immobilized TiO2 Catalyst in Swirl Flow Reactor: Kinetic Modeling

The degradation kinetics of Direct Blue 15 (DB15), a diazo dye, were studied over a suspended and immobilized TiO2 catalyst. For all experiments, the kinetics experiments were performed in a swirl flow photoreactor under the influence of UV light. The effect of different parameters: dye concentration, catalyst loading, and light intensity, on the DB15 kinetics was investigated. The kinetic rates were assessed using apparent (ka) approach, a single value of reaction rate (kr) and adsorption constant (K), and approach of kr as of variable. The DB15 mineralization was discussed as well. Using a dip-coating device, the P25 catalyst was deposited on a Pyrex glass. The thin film surface characterization was examined. The coated catalyst was evaluated by checking the effect of two variables: initial dye concentration and light intensity on the DB15 kinetics. In terms of the ka approach, the results demonstrated that DB15 degradation is described by the pseudo first-order kinetics model. The Langmuir-Hinshelwood (L-H) model was fitted well with the experimental data for the number of process variables. L-H constant kr was determined as a function of three parameters: initial dye concentration, catalyst loading, and light intensity. The ka values were evaluated and compared with experimental results. In terms of three variables, ka can be expressed as ka=0.15 [C]o−0.69 [W]0.73 I0.91 1+0.17 [C]o while the empirical model results in the following expression, ka=0.77 [C]o−1.65 [W]0.73 Io0.89. It was observed that 83.64% mineralization was achieved after a period of 16 hrs. In terms of immobilized catalyst, the DB15 degradation kinetics was described by a pseudo first-order model for different dye concentrations. Meanwhile, a power-law model described the impact of light intensity on dye kinetics. In addition, the coated catalyst was successfully reusable with high efficiency for up to four cycles.

Impact of light intensity or choice of intensity on broiler performance and behavior

The optimal light intensities for broiler production and well-being have been investigated for some time. The use of a minimum 20 lux (lx) is mandated within the European Union (European Commission, 2000; European Union 2007). Light intensities below 20 lx are commonly used in the United States. There have been inconsistent effects of light intensities below 20 lx on broiler performance. The present study evaluated the performance of broiler chickens reared under 5, 10, and 20 lx or a choice between these intensities. The feed: gain ratio was the lowest for birds reared using 5 lx and the choice of 5, 10, and 20 lx (1.71 and 1.70) compared to 20 lx (1.81), with 10 lx being intermediate (1.74). Furthermore, there were no differences observed in carcass yield, breast yield or abdominal fat. Preference for different light intensities (5, 10, and 20 lx) was examined using a remote video system. On d 20, more birds were observed to be feeding under light intensities of 10 and 20 lx compared to 5 lx. All other (not feeding) birds preferred 20 lx on d 20. On d 31 birds feeding no longer displayed a preference while all others preferred 10 and 20 lx over 5 lx. On the final observation d 41 only those birds not feeding or drinking showed a preference for 10 lx. The results agreed with past studies in demonstrating the change of preference for light intensity. The use of choice lighting environments was able to provide the desired light intensity of broilers at a young age while maintaining production parameters of those reared using low intensity (5 lx).

Functional growth, photosynthesis and nutritional property analyses of lettuce grown under different temperature and light intensity

ABSTRACT There is a growing interest in the impact of light intensity and temperature on vegetable growth and dietary quality characteristics. Lettuce (Lactuca sativa L.), as one of the model vegetables in plant factories, was grown under two light levels (G1: 160 µmol m–2 s–1, G2: 200 µmol m–2 s–1) with different day/night temperatures (T1: 20 ± 1°C/15 ± 1°C, T2: 24 ± 1°C/19 ± 1°C) to investigate mutual effects of light intensity and temperature on its growth and quality properties. The results revealed that the T2G2 treatment showed higher plant height, biomass and net photosynthetic rate, while T1G2 resulted in decreased leaf area and lower maximum photochemical efficiency of photosystem II (Fv/Fm) compared to T1G1. Simultaneous increases in light intensity and temperature based on T1G1 significantly increased the contents of anthocyanin, vitamin C (Vc) and soluble protein by 58%, 21% and 172%, respectively. The higher light intensity promoted the nutritional values of lettuce, characterised by lower nitrate level and soluble protein contents. Principal component analysis showed a negative collinearity between the nitrate content and soluble protein and Vc contents. In conclusion, light intensity and temperature co-regulated the lettuce’s growth and development, and their simultaneous increases better for growth and nutritional values of lettuce. These results provide a better understanding of the cultivation of plants in an artificial plant factory while maintaining yield and quality.

Growth Spectrum Complexity Dictates Aromatic Intensity in Coriander (Coriandrum sativum L.).

Advancements in availability and specificity of light-emitting diodes (LEDs) have facilitated trait modification of high-value edible herbs and vegetables through the fine manipulation of spectra. Coriander (Coriandrum sativum L.) is a culinary herb, known for its fresh, citrusy aroma, and high economic value. Studies into the impact of light intensity and spectrum on C. sativum physiology, morphology, and aroma are limited. Using a nasal impact frequency panel, a selection of key compounds associated with the characteristic aroma of coriander was identified. Significant differences (P < 0.05) were observed in the concentration of these aromatics between plants grown in a controlled environment chamber under the same photosynthetic photon flux density (PPFD) but custom spectra: red (100%), blue (100%), red + blue (RB, 50% equal contribution), or red + green + blue (RGB, 35.8% red: 26.4% green: 37.8% blue) wavelengths. In general, the concentration of aromatics increased with increasing numbers of wavelengths emitted alongside selective changes, e.g., the greatest increase in coriander-defining E-(2)-decenal occurred under the RGB spectrum. This change in aroma profile was accompanied by significant differences (P < 0.05) in light saturated photosynthetic CO2 assimilation, water-use efficiency (Wi), and morphology. While plants grown under red wavelengths achieved the greatest leaf area, RB spectrum plants were shortest and had the highest leaf:shoot ratio. Therefore, this work evidences a trade-off between sellable commercial morphologies with a weaker, less desirable aroma or a less desirable morphology with more intense coriander-like aromas. When supplemental trichromatic LEDs were used in a commercial glasshouse, the majority of compounds, with the exception of linalool, also increased showing that even as a supplement additional wavelength can modify the aromatic profile increasing its complexity. Lower levels of linalool suggest these plants may be more susceptible to biotic stress such as herbivory. Finally, the concentration of coriander-defining aromatics E-(2)-decenal and E-(2)-hexenal was significantly higher in supermarket pre-packaged coriander leaves implying that concentrations of aromatics increase after excision. In summary, spectra can be used to co-manipulate aroma profile and plant form with increasing spectral complexity leading to greater aromatic complexity and intensity. We suggest that increasing spectral complexity progressively stimulates signaling pathways giving rise to valuable economic traits.

Low temperature and high light dependent dynamic photoprotective strategies in Arabidopsis thaliana.

Arabidopsis thaliana has been recognized as a chilling tolerant species based on analysis of resistance to low temperature stress, however, the mechanisms involved in this tolerance are not yet clarified. The low temperature-induced effects are exacerbated when plants are exposed to low temperatures in the presence of high light irradiance but the experimental data on the impact of light intensity during cold stress and its influence during recovery from stress are rather limited. The main objective of this study was to re-examine the photosynthetic responses of A. thaliana plants to short term (6 days) low temperature stress (12/10°C) under optimal (150 μmol m-2 s-1 ) and high light (500 μmol m-2 s-1 ) intensity and the subsequent recovery from the stress. Simultaneous measurements of the in vivo and in vitro functional performance of both photosystem II (PSII) and photosystem I (PSI), as well as, net photosynthesis, low temperature (77 K) chlorophyll fluorescence and immunoblot analysis of the relative abundance of PSII and PSI reaction center proteins were used to evaluate the role of light in the development of possible protective mechanisms during low temperature stress and the consequent recovery from exposure to low temperature and different light intensities. The results presented clearly suggest that Arabidopsis plants can employ a number of highly dynamic photoprotective strategies depending on the light intensity. These strategies include one based on LHCII quenching and two other quenching mechanisms localized within the PSII and PSI reaction centers, which are all expressed to different extent depending on the severity of the photoinhibitory treatments under low temperature stress conditions.

Impact of Light Intensity on Antioxidant Activity of Tropical Microalgae.

Twelve microalgae species isolated in tropical lagoons of New Caledonia were screened as a new source of antioxidants. Microalgae were cultivated at two light intensities to investigate their influence on antioxidant capacity. To assess antioxidant property of microalgae extracts, four assays with different modes of action were used: 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2’-azino-bis (3-éthylbenzothiazoline-6-sulphonique) (ABTS), oxygen radical absorbance capacity (ORAC), and thiobabituric acid reactive substances (TBARS). This screening was coupled to pigment analysis to link antioxidant activity and carotenoid content. The results showed that none of the microalgae studied can scavenge DPPH and ABTS radicals, but Chaetoceros sp., Nephroselmis sp., and Nitzschia A sp. have the capacity to scavenge peroxyl radical (ORAC) and Tetraselmis sp., Nitzschia A sp., and Nephroselmis sp. can inhibit lipid peroxidation (TBARS). Carotenoid composition is typical of the studied microalgae and highlight the siphonaxanthin, detected in Nephroselmis sp., as a pigment of interest. It was found that xanthophylls were the major contributors to the peroxyl radical scavenging capacity measured with ORAC assay, but there was no link between carotenoids and inhibition of lipid peroxidation measured with TBARS assay. In addition, the results showed that light intensity has a strong influence on antioxidant capacity of microalgae: Overall, antioxidant activities measured with ORAC assay are better in high light intensity whereas antioxidant activities measured with TBARS assay are better in low light intensity. It suggests that different antioxidant compounds production is related to light intensity.

Impact of Light Intensity on Sleep of Patients in the Intensive Care Unit: A Prospective Observational Study.

ABSTRACTAims and objectivesSleep deprivation in the intensive care unit (ICU) has been linked to numerous complications. Light levels might impact the sleep of patients in the ICU. The aim of the study was to measure light levels during sleep-protected time in the ICU and to assess the impact of light intensity on sleep quantity/quality.Materials and methodsThis prospective, observational study was conducted in a 10-bed, mixed surgical/medical ICU. For measuring light levels, a commercially available smartphone application was used. The measurements were performed between 23:30 and 06:15 hours at 15-minute intervals. To assess sleep quantity, we used Patient's Sleep Observation Behavioral Tool and to assess sleep quality, we used Richards-Campbell Sleep Scale.ResultsThe median number of time points at which patients were asleep was 20 (interquartile range, IQR 14–23) out of 25 (5 hours). The median self-reported quality of sleep (overall score) was 49 (IQR 28–71). The median values for individual questions are: question 1 (sleep depth)—54.0 (IQR 37–78), question 2 (sleep latency)—40.5 (IQR 6–90), question 3 (awakenings)—52.5 (IQR 28–76), question 4 (returning to sleep)—25.5 (IQR 11–78), and question 5 (sleep quality)—67.5 (IQR 5–76). No correlation was found between self-reported sleep quality and time spent asleep (p = 0.36). There was no correlation between average light levels during sleep-protected time and sleep quantity (p = 0.42)/sleep quality (p = 0.13). There was a correlation between average (13 ± 5 lux) light levels before sleep-protected time and sleep quality (p = 0.008).ConclusionMean light levels of 11 ± 9 lux during sleep-protected time have no negative impact on quantity and quality of sleep in intensive care unit patients. Light levels up to 18 lux directly before falling asleep improve patients’ self-reported quality of sleep in the ICU.Clinical significanceFinding safe levels of light intensity during sleep-protected time in ICU.How to cite this articleCzempik PF, Jarosińska A, Machlowska K, Pluta M. Impact of Light Intensity on Sleep of Patients in the Intensive Care Unit: A Prospective Observational Study. Indian J Crit Care Med 2020;24(1):33–37.

Photoenzymatic Hydroxylation of Ethylbenzene Catalyzed by Unspecific Peroxygenase: Origin of Enzyme Inactivation and the Impact of Light Intensity and Temperature

AbstractPhotoenzymatic cascades can be used for selective oxygenation of C−H‐Bonds under mild conditions circumventing the hydrogen peroxide mediated peroxygenase inactivation via in situ H2O2 generation. Here, we report the “on demand” production of hydrogen peroxide via methanol assisted reduction of molecular oxygen using UV‐illuminated titanium dioxide (Aeroxide P25) combined with the enantioselective hydroxylation of ethylbenzene to (R)‐1‐phenylethanole catalyzed by the Unspecific Peroxygenase from Agrocybe Aegerita. For the application of the system it is important to understand the influence of the reaction parameters to be able to optimize the system. Therefore, we systematically investigated product formation and enzyme inactivation as well as ROS formation (H2O2, .OH and .O2−) applying different light intensities and temperatures. As a result, Turnover Numbers up to 220 000, photonic efficiencies up to 13.6 % and production rates up to 0.9 mM h−1 were achieved.

Effect of light intensity on embryonic development of the cuttlefish Sepia lycidas

The effects of light intensity on embryonic development of fertilized eggs of Sepia lycidas were investigated to determine the best light conditions for the embryos’ development. A single-factor experiment was performed to examine the effects of different light intensities (dark or 4.3, 10.2, 29.6, or 50.7 μmol/(m2·s)) on the embryonic development. The hatching rate, incubation period, hatching period and weight, and survival of hatchling cuttlefish were significantly affected by the light intensities (P < 0.05). When light intensity exceeds 10.2 μmol/(m2·s), the weight of hatchling cuttlefish and incubation period gradually decreased with the increase of light intensity, while the hatching rate first increased and later decreased. The sensitivity to light clearly varies among stages of embryonic development; the impact of light intensity on embryonic development appeared from the red-bead stage to hatching. High light intensities can interfere with the development of embryos and lead to abnormal development and premature hatching, reduced hatchability, decreased vitality of cuttlefish hatchlings, and asynchronous hatching, especially at light intensities exceeding 10.2 μmol/(m2·s). Low light intensities are better for embryonic development of S. lycidas than high light, and the light intensity as 10.2 μmol/(m2·s) was thus recommended. During incubation of paralarvae, fertilized eggs should be kept out of direct sunlight, and shading measures should be taken to keep the eggs in low light intensities.

The Impact of Light Intensity and Spectrum-Tuning on Cannabis Yields

The purpose of this study was to analyze the relationship between light intensity, cannabis yields, and profitability. We also look for evidence that spectrum differences across broad-spectrum, horticulture lights and general-purpose LEDs impact the relationship between yield and light intensity. Finally, we discuss the financial return of increasing light intensity in order to increase yields. We find that yields increase linearly with light intensity up to at least 1500 μmols/m2·s, which is at least twice the intensity that is most commonly used by cannabis growers. That relationship did not appear to be influenced by spectrum quality differences across the lamps included in the study. Finally, for all the intensity ranges that we considered, the value of the gain in yields from increasing light intensity far exceeded the cost of using more electricity.

A novel mechanistic model for nitrogen removal in algal-bacterial photo sequencing batch reactors

A comprehensive mathematical model was constructed to evaluate the complex substrate and microbial interaction in algal-bacterial photo sequencing batch reactors (PSBR). The kinetics of metabolite, growth and endogenous respiration of ammonia oxidizing bacteria, nitrite oxidizing bacteria and heterotrophic bacteria were coupled to those of microalgae and then embedded into widely-used activated sludge model series. The impact of light intensity was considered for microalgae growth, while the effect of inorganic carbon was considered for each microorganism. The integrated model framework was assessed using experimental data from algal-bacterial consortia performing sidestream nitritation/denitritation. The validity of the model was further evaluated based on dataset from PSBR performing mainstream nitrification. The developed model could satisfactorily capture the dynamics of microbial populations and substrates under different operational conditions (i.e. feeding, carbon dosing and illuminating mode, light intensity, influent ammonium concentration), which might serve as a powerful tool for optimizing the novel algal-bacterial nitrogen removal processes.

The impact of light intensity on metabolomic profile of Arabidopsis thaliana wild type and reticulata mutant by NMR spectroscopy

Light acclimation involves biochemical, metabolic and developmental adjustments that allow plants to cope with a vast range of growth environments. Arabidopsis thaliana mutants with photoperiod-dependent defects in leaf development and metabolism have been instrumental in deciphering the interlinked regulatory networks in plants. The reticulata (re) mutant displays dark green veins and pale green mesophyll tissues when grown under long day conditions. RE is a chloroplast envelope membrane protein of unknown function and is required for accurate primary metabolism and leaf development under long photoperiod, while its functional significance under short photoperiods has remained poorly understood. In the present study we assessed whether RE impacts primary metabolism or leaf development when Arabidopsis plants acclimate to different light intensities under short photoperiod. We show that growth under short day conditions annuls the metabolic and developmental defects of re mutants, suggesting that RE does not significantly modulate leaf development or primary metabolism under short photoperiod. Based on proton nuclear magnetic resonance spectroscopy (1H NMR) and statistical analysis, however, the metabolite profiles of differentially light-acclimated short-day-grown plants differ with respect to sugars (glucose, fructose and sucrose), TCA cycle intermediates (fumaric, malic, citric and succinic acids) and fatty acids, which become more abundant under high light. Moreover, in contrast to isoleucine, leucine, valine, threonine, serine, tyrosine and phenylalanine, which show increased abundance in high-light-acclimated plants, the contents of alanine, glutamine, glutamic acid and aspartic acid are higher when plants grow under normal growth light. These findings indicate that NMR can detect high-light-induced metabolic adjustments that arise upon plant acclimation to light stress.

Design of Monitoring System for Measuring the Impact of Light Intensity of Artificial Lights on Human Circadian Cycles in Web-Based Inpatient Rooms

Light is a source of energy that is needed in human life. In hospitals, artificial lighting is very necessary, especially in operating rooms that are impermeable to natural light and must be sterile from room bacteria. Artificial light exposure that does not meet the SNI standard for room lighting causes various problems. Therefore, in this study, a tool to control the intensity of artificial light according to the SNI standard in hospitals was designed. This research uses measurement, calculation and comparison methods. The first measurement is to measure the value of the light intensity of the lamp, then measure the temperature value in the room, the last one is to sterilize the room bacteria. From these measurements, values ??are obtained to be compared in reaching conclusions. From this research, it can be concluded that the monitoring system with the LDR light sensor can read the value of the light intensity properly according to the digital lux meter in the morning at 400 lux, 200 lux in the daytime, and 120 lux at night. Then the DHT-11 sensor can read the temperature value in the room according to the HTC comparison with the morning temperature is 25 degrees, daytime 29 degrees, afternoon 27 days, and night is 24 degrees. To help kill room bacteria, a Utraviolet lamp is used with a light for 2 hours in the morning.

Impact of Light Intensity and Nitrogen of Nutrient Solution on Nitrate Content in Three Lettuce Cultivars Prior to Harvest

Nitrate smoothly accumulates in leafy vegetables and poses serious health hazards if connected excessively in the human diet. The objective of this study was to improve the cultivation method of low nitrate lettuce grown in plant factory. A substantial decrease of nitrate content (NO3-) in three lettuce cultivars were subjected by short-term pre-harvest treatment combined with lowing nitrogen supply of nutrient solution to half concentration and high photosynthetic photon flux density (PPFD) by LED lighting. The lettuce (Lactuca sativa L. cv. Frill ice, Lvzhu, Ziwei) were hydroponically grown in full strength of nutrient solution based on Yamasaki formula up to harvest time within a controlled environment under two light sources using fluorescent lamps and LEDs. The results demonstrated that a subsequent 3-days treatment of additional PPFD from 250 µmol m-2 s-1 to 350 µmol m-2 s-1 from 18 days after transplanting and half concentrations of nitrogen (NO3--N) in nutrient solution which is composition to standard resulted in the decrease of nitrate content as compared to plants grown under initial PPFD and full concentration of NO3--Ncomposition. The gradual decrease in nitrate content was accompanied by an increased concentration of nutritionally carbohydrates. Another important indicator of nutritional quality such as vitamin C content exhibited some variation, fresh weight of cultivars in cv. Frill ice and Ziwei observed higher with fluorescent lamps and for cv. Lvzhu with LED treatment section followed by lowest nitrate content of fresh leaves, respectively. Further, presented results disclosed that to avoid high accumulation of nitrate in leafy vegetables, the strategy of lowering nitrogen supply and increasing light intensity prior to harvest benefiting growers and consumers by improving quality of the product also making it consumer friendly.

Optimization of Arthrospira platensis (Spirulina) Growth: From Laboratory Scale to Pilot Scale

Arthrospira platensis (Spirulina) is the most cultivated microalga worldwide. Improving its cultivation in terms of biomass productivity, quality, or production cost could significantly impact the Spirulina industry. The objectives of this paper were defined as to contribute to this goal. Spirulina biomass productivity was investigated through medium choice. A modified Zarrouk’s medium was selected as it gave higher final dry weights and longer sustained growth than Hiri’s and Jourdan’s media. Then, in order to reduce Spirulina production cost, modified Zarrouk’s medium was rationalized by testing different dilutions. It was found that modified Zarrouk’s medium could be diluted up to five times without impacting the growth rates in a 28-days batch cultivation. Higher dry weights were even observed after 21 days of batch cultivation (1.21 g/L for 20%-modified Zarrouk’s medium in comparison to 0.84 g/L for modified Zarrouk’s medium). Iron uptake was then investigated as one of the major contributors to Spirulina nutritional quality. An increase in iron content was obtained by replacing iron sulfate by iron EDTA at a concentration of 10 mgFe/L (2.11 ± 0.13 mgFe/gbiomass for EDTA-FeNa, 3 H2O at 10 mgFe/L compared to 0.18 ± 0.13 for FeSO4,6H2O at 2 mgFe/L). Impact of light intensity on Spirulina biomass productivity was also investigated in a 2 L Photobioreactor (PBR). Specific growth rates were calculated for Photosynthetically Photon Flux Densities (PPFD) from 85 to 430 µmol/m2/s. At 430 µmol/m2/s, photoinhibition was not observed and the specific growth rate was maximum (0.12/day). Finally, a 40-day cultivation experiment was conducted in a 1000 L PBR giving a maximum daily areal productivity of 58.4 g/m2/day. A techno-economic analysis gave production cost two to 20 times higher for PBR (from 18.71 to 74.29 €/kg) than for open ponds (from 3.86 to 9.59 €/kg) depending on Spirulina productivity.

Carrier induced degradation in compensated n-type silicon solar cells: Impact of light-intensity, forward bias voltage, and temperature on the reaction kinetics

We analyze the formation kinetics of the boron–oxygen defect in compensated n-type upgraded metallurgical-grade (UMG) silicon solar cells. Through time-resolved open-circuit voltage measurements, we explore the influence of temperature, forward bias, and light intensity on the formation kinetics of the defect. Our results confirm that the boron–oxygen defect forms more slowly in compensated n-type silicon than in p-type silicon. We present evidence which suggests that the slower kinetics in n-type silicon may be due to a lower frequency factor for defect formation.