Decrease In Light Intensity Research Articles

Effect of surfactants on single bubble sonoluminescence behavior and bubble surface stability.

The effect of surfactants on the radial dynamics of a single sonoluminescing bubble has been investigated. Experimentally, it is observed that an increase in the surfactant concentration leads to a decline in the oscillation amplitude and hence light emission intensity. Numerical simulations support this result, showing that under the driving pressures required to achieve single bubble sonoluminescence (SBSL), the surface properties, namely, the surface elasticity and dilatational viscosity, contribute to the damping of the radial amplitude in the bubble oscillation. In most cases this stabilizes the bubble surface, and contributes to a decreased light intensity. A stronger driving pressure is necessary to achieve equivalent light emission to a surfactant-free bubble. However, as the driving pressure is increased, the surface stability also decreases, making it practically very difficult for a bubble to achieve high SBSL intensities in concentrated surfactant solutions. Although more stable owing to more mild pulsations, the instability mechanism for a surfactant-coated bubble at higher ambient radii is more likely to be of the Rayleigh-Taylor type than that of a clean bubble at the same given acoustic parameters, which can lead to bubble disintegration before correcting mechanisms can bring the bubble back into the stable sonoluminescence regime.

Influence of green, red and blue light emitting diodes on multiprotein complex proteins and photosynthetic activity under different light intensities in lettuce leaves (Lactuca sativa L.).

The objective of this study was to investigate the response of light emitting diodes (LEDs) at different light intensities (70 and 80 for green LEDs, 88 and 238 for red LEDs and 80 and 238 μmol m−2 s−1 for blue LEDs) at three wavelengths in lettuce leaves. Lettuce leaves were exposed to (522 nm), red (639 nm) and blue (470 nm) LEDs of different light intensities. Thylakoid multiprotein complex proteins and photosynthetic metabolism were then investigated. Biomass and photosynthetic parameters increased with an increasing light intensity under blue LED illumination and decreased when illuminated with red and green LEDs with decreased light intensity. The expression of multiprotein complex proteins including PSII-core dimer and PSII-core monomer using blue LEDs illumination was higher at higher light intensity (238 μmol m−2 s−1) and was lowered with decreased light intensity (70–80 μmol m−2 s−1). The responses of chloroplast sub-compartment proteins, including those active in stomatal opening and closing, and leaf physiological responses at different light intensities, indicated induced growth enhancement upon illumination with blue LEDs. High intensity blue LEDs promote plant growth by controlling the integrity of chloroplast proteins that optimize photosynthetic performance in the natural environment.

Effect of multiwalled carbon nanotube (MWNT) on the behavior of swelling of polyacrylamide–MWNT composites

The purpose of this paper is to discuss the role of multiwalled carbon nanotube in the swelling of polyacrylamide–multiwalled carbon nanotube composites. Swelling experiments were performed in water at various temperatures by real-time monitoring of the decrease in pyranine (Py) and emission light intensity ( Iem). The Stern–Volmer equation is modified for low-quenching efficiencies to interpret the behavior of pyranine intensity during the swelling of polyacrylamide–multiwalled carbon nanotube composites. The Li–Tanaka equation was used to determine the swelling time constants, τ, and cooperative diffusion coefficients, D, from fluorescence intensity, weight, and volume variations of the composite at various temperatures. It was observed that when τ decreased, naturally D increased by increasing temperatures.

Growth indices of yield variability in wheat (Triticum aestivumL.) under varying degree of shades

Light is the main environmental factor which regula tes growth and development of crop plants. Decrease in light intensity due to shading adversely affects plant growth and development. The present study was conducted to analyze the effect of varying degree of shades on growth characteristics and yield of wheat crop. Two shading treatments were applied i.e. 33 % shading (L1) and 66 % shading (L2 ) with full sunlight as control (L0). The experiment was conducted during the winter seasons of 2010‐2011 in a split-plot design with three replications with shading treatments in the m ain plot and five varieties of wheat in the sub plots.The findings of the study showed that the mean crop growth rate, mean relative growth rate, net assimilation rate, leaf area ratio , leaf area index and specific leaf weight were significantly influenced by increasing shade. Grain yield of all the wheat varieties decreased with increase in shading during the year (i.e. 2010 -11). Varietal differences in grain under shading are discussed in relation to leaf area inde x and crop growth rate.

The contribution of single and double cones to spectral sensitivity in budgerigars during changing light conditions

Bird colour vision is mediated by single cones, while double cones and rods mediate luminance vision in bright and dim light, respectively. In daylight conditions, birds use colour vision to discriminate large objects such as fruit and plumage patches, and luminance vision to detect fine spatial detail and motion. However, decreasing light intensity favours achromatic mechanisms and eventually, in dim light, luminance vision outperforms colour vision in all visual tasks. We have used behavioural tests in budgerigars (Melopsittacus undulatus) to investigate how single cones, double cones and rods contribute to spectral sensitivity for large (3.4°) static monochromatic stimuli at light intensities ranging from 0.08 to 63.5 cd/m². We found no influences of rods at any intensity level. Single cones dominate the spectral sensitivity function at intensities above 1.1 cd/m², as predicted by a receptor noise-limited colour discrimination model. Below 1.1 cd/m², spectral sensitivity is lower than expected at all wavelengths except 575 nm, which corresponds to double cone function. We suggest that luminance vision mediated by double cones restores visual sensitivity when single cone sensitivity quickly decreases at light intensities close to the absolute threshold of colour vision.

Single and dual fiber nano-tip optical tweezers: trapping and analysis

An original optical tweezers using one or two chemically etched fiber nano-tips is developed. We demonstrate optical trapping of 1 micrometer polystyrene spheres at optical powers down to 2 mW. Harmonic trap potentials were found in the case of dual fiber tweezers by analyzing the trapped particle position fluctuations. The trap stiffness was deduced using three different models. Consistent values of up to 1 fN/nm were found. The stiffness linearly decreases with decreasing light intensity and increasing fiber tip-to-tip distance.

Acclimation to low light by C4 maize: implications for bundle sheath leakiness

C4 plants have a biochemical carbon concentrating mechanism (CCM) that increases CO2 concentration around ribulose bisphosphate carboxylase oxygenase (Rubisco) in the bundle sheath (BS). Under limiting light, the activity of the CCM generally decreases, causing an increase in leakiness, (Φ), the ratio of CO2 retrodiffusing from the BS relative to C4 carboxylation processes. Maize plants were grown under high and low light regimes (respectively HL, 600 versus LL, 100 μE m(-2) s(-1) ). Short-term acclimation of Φ was compared from isotopic discrimination (Δ), gas exchange and photochemistry. Direct measurement of respiration in the light, and ATP production rate (JATP ), allowed us use a novel approach to derive Φ, compared with the conventional fitting of measured and predicted Δ. HL grown plants responded to decreasing light intensities with the well-documented increase in Φ. Conversely, LL plants showed a constant Φ, which has not been observed previously. We explain the pattern by two contrasting acclimation strategies: HL plants maintained a high CCM activity at LL, resulting in high CO2 overcycling and increased Φ; LL plants acclimated by down-regulating the CCM, effectively optimizing scarce ATP supply. This surprising plasticity may limit the impact of Φ-dependent carbon losses in leaves becoming shaded within developing canopies.

Nutrient Removal and Biomass Production in an Outdoor Pilot-Scale Phototrophic Biofilm Reactor for Effluent Polishing

An innovative pilot-scale phototrophic biofilm reactor was evaluated over a 5-month period to determine its capacity to remove nitrogen and phosphorus from Dutch municipal wastewater effluents. The areal biomass production rate ranged between 2.7 and 4.5 g dry weight/m(2)/day. The areal nitrogen and phosphorus removal rates averaged 0.13 g N/m(2)/day and 0.023 g P/m(2)/day, which are low compared to removal rates achieved in laboratory biofilm reactors. Nutrient removal increased during the day, decreased with decreasing light intensity and no removal occurred during the night. Additional carbon dioxide supply was not requisite as the wastewater was comprised of enough inorganic carbon to sustain microalgal growth. The study was not conclusive for the limiting factor that caused the low nutrient removal rate, possibly the process was limited by light and temperature, in combination with pH increases above pH 9 during the daytime. This pilot-scale study demonstrated that the proposed phototrophic biofilm reactor is not a viable post-treatment of municipal wastewater effluents under Dutch climate conditions. However, the reactor performance may be improved when controlling the pH and the temperatures in the morning. With these adaptations, a phototrophic biofilm reactor could be feasible at lower latitudes with higher irradiance levels.

Photosynthetic Characteristics of Picoplankton Compared with Those of Larger Phytoplankton Populations, in Various Water Masses in the Gulf of Maine

AbstractCell numbers of eucaryotes and cyanobacteria in phototrophic picoplankton and ratios of in vivo fluorescence of phycoerythrin: chlorophyll a indicated that chroococcalean cyanobacteria played a more prominent role in phytoplankton communities, at the least productive stations. At stations displaying large vertical density gradients, subsurface maxima of phytoplankton pigments were observed. Ratios of in vivo fluorescence of phycoerythrin: chlorophyll a were always greater at the pigment maximum than at the surface. Cyanobacteria from pigment maxima demonstrated greater phycoerythrin fluorescence intensity and photosynthetic rates than cyanobacteria from the surface. Photosynthetic characteristics of picoplankton ( 3 μm populations. The picoplankton differed from larger phytoplankton, in that (1) their pattern of photosynthetic carbon fixation did not vary significantly with decreasing light intensity, and at optimal intensities ...

Natural spatial variability of algal endosymbiont density in the coralAcropora globiceps: a small-scale approach along environmental gradients around Moorea (French Polynesia)

This study provides a baseline describing natural small scale variability ofSymbiodiniumdensity in the sentinel coralAcropora globicepsduring the summer, under non-bleaching conditions. Spatial scales investigated range from the colony scale (1–10 cm, i.e. among branches of the same colony) to the reef scale (1–10 km, i.e. among stations distributed over several locations and depths), at Moorea Island, French Polynesia. The coral–Symbiodiniumsymbiosis is a key process in scleractinian coral physiology, andSymbiodiniumdensity provides an easy-to-measure and inexpensive biomarker of this symbiosis health. Spatial variability of three major environmental factors: light intensity, sedimentation and water motion was also assessed to evaluate their potential link withSymbiodiniumdensity. Density ofSymbiodiniumdid not significantly differ within colonies or among colonies within a station. However, a marked depth gradient was observed, showing increasing density with increasing depth and decreasing light intensity. These observations provide an interesting reference for forthcoming comparisons with disturbed conditions, such as bleaching events.

Scaling Up ITO‐Free Solar Cells

Indium‐tin‐oxide‐free (ITO‐free) polymer solar cells with composite electrodes containing current‐collecting grids and a semitransparent poly(3,4‐ethylenedioxythiophene):polystyrenesulfonate) (PEDOT:PSS) conductor are demonstrated. The up‐scaling of the length of the solar cell from 1 to 6 cm and the effect of the grid line resistance are explored for a series of devices. Laser‐beam‐induced current (LBIC) mapping is used for quality control of the devices. A theoretical modeling study is presented that enables the identification of the most rational cell dimension for the grids with different resistances. The performance of ITO‐free organic solar cells with different dimensions and different electrode resistances are evaluated for different light intensities. The current generation and electric potential distribution are found to not be uniformly distributed in large‐area devices at simulated 1 Sun illumination. The generated current uniformity increases with decreasing light intensities.

Effects of surface roughness on optical properties and sensitivity of fiber-optic evanescent wave sensors

The effects of surface roughness on the light transmission properties and sensitivity of fiber-optic evanescent wave sensors are investigated. A simple method of increasing the sensitivity based on the surface roughness (pit depth δ and diameter Δ) and incident angle U(i) of light rays on the fiber input end is proposed. We discovered that as 2δ/Δ increases, the transmitted light intensity decreases, but the sensitivity initially increases and then decreases. In sensors containing fibers of various roughnesses, the sensitivity to glucose solutions reached -11.7 mW/riu at 2δ/Δ=0.32 and increased further to -15.3 mW/riu with proper adjustment of U(i).

Physiological basis of yield variability in wheat (Triticum aestivum L.) under varying degree of shades

Light is the main environmental factor which regulates growth and development of crop plants. Decrease in light intensity due to shading adversely affects plant growth and development. The present study was conducted to analyze the effect of varying degree of shades on physiological characteristics and yield of wheat crop. Two shading treatments were applied i.e. 33 % shading (L1) and 66 % shading (L2) with full sunlight as control (L0). The experiment was conducted for 2 years during the winter seasons of 2010–2011 and 2011–2012 in a split-plot design with three replications with shading treatments in the main plot and five varieties of wheat in the sub plots. The findings of the study showed that photosynthetic rate, stomatal conductance and transpiration rate at 10 days after anthesis (DAA) were significantly reduced while the intracellular CO2 concentration (Ci) increased with increase in shading during both the years. The total chlorophyll content increased whereas, chlorophyll a/b ratio decreased under shading. Grain yield of all the wheat varieties decreased with increase in shading during both the years. Varietal differences in grain yield under shading are discussed in relation to Pn rates and stomatal conductance.

Effects of soil moisture and light intensity on ecophysiological characteristics of Amorpha fruticosa seedlings

We investigated the combined effects of soil moisture and light intensity on the growth, development and ecophysiological characteristics of one-year old Amorpha fruticosa seedlings. Soil moisture and light intensity influenced the ecophysiological characteristics of Amorpha fruticosa seedlings. Soil moisture resulted in the decreases of growth rate, individual size, net photosynthetic rate, transpiration rate, leaf water loss rate (WLR), and biomass accumulation of plant parts, and led to increased leaf water saturation deficit (WSD). Under water stress, more photosynthetic products were allocated to root growth. With decreasing light intensity, net photosynthetic rate, transpiration rate, chla/b, water saturation deficit, water use efficiency, water loss rate and biomass accumulation declined, while Chla, Chlb, Chla+b and carotenoids (Car) increased and more photosynthetic products were allocated to stem and leaf growth. Maximum growth vigor, net photosynthetic rate and total biomass accumulation in Amorpha fruticosa seedlings was recorded at 75–80% soil water-holding capacity and 100% light density in greenhouse environments.

Study of the recombination process at crystallite boundaries in CuIn1 − x Ga x Se2 (CIGS) films by microwave photoconductivity

The loss kinetics of photogenerated charge carriers in thin polycrystalline chalcopyrite CuIn1−x Ga x Se2 (CIGS) films has been studied by microwave photoconductivity (at 36 GHz). The films were synthesized using the ampoule method and three variants of physical vapor deposition with subsequent selenization: magnetron sputtering, thermal deposition, and modified thermal deposition with intermetallic precursors. The photoconductivity was excited by 8-ns nitrogen laser pulses with maximum intensity of 4 × 1014 photons/cm per pulse. Measurements were performed in the temperature range 148–293 K. The photoresponse amplitude is found to depend linearly on the sizes of coherent-scattering regions in the film grains, which were calculated from X-ray diffraction data. The photoresponse decay obeys hyperbolic law. The photoresponse half-decay time increases with a decrease in both temperature and light intensity. It is shown that the recombination of free holes with trapped electrons is very efficient near the crystallite boundaries.

Influence of Low Light on the Growth and Development of <i>Vallisneria natans</i> Seedlings

To research influence of low light on macrophyte growth, seedlings of Vallisneria natans were transplanted into the waters with 5%, 1%, 0.5% and 0.1% full sunlights, respectively. The results show that germination rates are significantly inhibited with the experiment. In first 20 days leaf formation of new plants aren’t inhibited, and their leaf elongation are promoted. Since then, them of old plants and new plants are remarkably inhibited with the experiment. Though maximum photochemical quantum yield (Fv/Fm), relative electron transport rate (ETR) and non-photochemical quenching (NPQ) of old plants reduce significantly on low light conditions, but V. natans still hsa a certain degree of photoasynthetic capacity on the 80th day. Fresh weight ratio of roots and stems increase with decreasing light intensity. However, it exhibits an opposite trend for leaves. Thus, V. natans has a strong ability of low-light (≤1% full sunlight) tolerance.

Effects of turbidity and light intensity on foraging success of juvenile mandarin fish Siniperca chuatsi (Basilewsky)

This study aimed to evaluate the effects of turbidity and light intensity on foraging success of juvenile mandarin fish Siniperca chuatsi. Predation on crucian carp Carassius auratus by juvenile mandarin fish was tested at five levels of turbidity combined with two light intensities, imitating daylight and night in two turbidity types. Foraging success was significantly lower in clay-induced turbidity than in algal-induced turbidity. In clay-induced turbidity trials, there was a slight but insignificant increase in foraging success of mandarin fish with increasing turbidity under lighted conditions. In algal-induced turbidity trials, there were no significant differences in foraging success of mandarin fish among turbidity levels at both light and dark levels, but at 80 NTU turbidity level, foraging success was lower than in all the other turbidity levels. There was no significant difference in foraging success at different turbidities under darkness. These results suggest that piscivory of mandarin fish is influenced by different turbidity types but is not significantly influenced by increased turbidity combined with decreased light intensity.

Ameliorated Effect of Shading Treatment in Strong Light Period on Senescence and Photosynthesis in Cucumber ^|^lsquo;Jinchun No. 5^|^rsquo; Seedlings

To gain a physiological understanding of the effects of light intensity on the cucumber (Cucumis sativus L.), we subjected ‘Jinchun No. 5’ seedlings to shading treatment in three plots with light transmission of 100% (unshaded), 80%, and 60% in strong light periods for 45 days, and examined active oxygen species, senescence indicators and photosynthetic properties on the 15th, 30th, and 45th days of shading treatment respectively. The amounts of active oxygen species superoxide anions and hydrogen peroxide in leaves fell with decreasing light intensity on each of the 15th, 30th, and 45th days of shading treatment respectively. The amounts of chlorophyll and protein also decreased and that of malondialdehyde increased — all indicators of senescence — with decreasing light intensity on each of the 15th, 30th, and 45th days of shading treatment respectively. The photosynthetic property stomatal conductance in the 80% and 60% transmission plots exceeded that in the 100% transmission plot on the 15th and 30th days of shading treatment. No significant difference was seen in sub-stomatal CO2 concentration between all three light transmission plots. Both transpiration and net photosynthesis rates rose with decreasing light intensity. These results suggest that the shading treatment during strong light periods may suppress the generation and accumulation of active oxygen species, inhibit senescence and also ameliorate photosynthesis in cucumber ‘Jinchun No. 5’ seedlings.

Effects of Irradiance Level on the Growth and Photosynthesis of Salvia

Seedlings of Salvia coccinea, S. splendens and S. viridis were grown at 100, 50, 25 and 5% of full sunlight level to determine the influence of irradiance level on their grown and photosynthesis. For all species the shoot length and dry weight of wholeplant were decreased at 25% sunlight, but there was little defference in them between at 50 and 100% sunlight. Total leaf area tended to increase at 50% sunlight in S. splendens and S. viridis and to decrease at 25% sunlight in S.coccinea. Leaf area ratio increased with decreasing light intensity in every species, and the degree of increase was the least in S.coccinea. With decreasing light intensity, leaves became thinner and the specific leaf weight decreased for all species. Chlorophyll content and photosynthetic rate more decreased at 25% than those at 100 and 50% sunlight in S. splendens and S. viridis. There were little differences both in the chlorophyll content and photosynthesis among these light intensities in S.coccinea. This indicates that S.coccinea has higher adaptability to low irradiance than other two species. Under weak light condition the stomatal conductance increased for all species. At 5% sunlight, the plant dry weight was less than about 90% of that of 100% sunlight and photosynthetic rate almost decreased to the light compensation point.

Sensitivity to motion and higher-order visual processing in nocturnal and diurnal hawk moths

Event Abstract Back to Event Sensitivity to motion and higher-order visual processing in nocturnal and diurnal hawk moths Anna L. Stöckl1*, David O'Carroll2 and Eric Warrant1 1 Lund University, Biology, Sweden 2 The University of Adelaide, School of Medical Sciences, Australia Even though humans see poorly at night, the majority of the world’s animals – both on land and under water – are active in dim light and many of them have excellent vision. Despite possessing tiny eyes and brains, nocturnal insects can distinguish colour, avoid obstacles during flight and find their way home using learned visual landmarks. But how is this remarkable visual performance possible? How have the properties of the visual circuitry been optimised to maximize visual performance in dim light conditions? In order to approach these questions, we are studying the visual motion processing circuitry in hovering hawkmoths – a group of fast-flying insects renowned for their impressive visual abilities, in which closely related species are active under completely different light conditions, ranging from bright sunlight to starlight. One way of increasing visual performance in dim light is to spatially sum signals from neighbouring visual channels. In the first optic neuropil of insects, the lamina, the monopolar cells of nocturnal species possess an anatomy that makes them well suited to the summation of visual signals: their lateral processes are long and extend to neighbouring cartridges. Using the Golgi staining method, we compared the lengths of these lateral processes between the day-active hawkmoth Macroglossum stellaratum and the night-active Deilephila elpenor. As predicted for a possible function in spatial summation, the lateral processes of D. elpenor are longer than those of M. stellaratum and could potentially pool information from cartridges further away. Wide-field motion-sensitive neurons in the lobula plate are tuned to the optic flow experienced during flight. We recorded from these neurons to quantify the spatial and temporal response characteristics of the visual system of hawkmoths, to extract the amount of spatial and temporal summation implemented in both nocturnal and diurnal species. Preliminary results from intracellular recordings at day-light intensities show that HS-like neurons in M. stellaratum respond to higher spatial and temporal frequencies than those of D. elpenor, even though both species have comparable optics, which strongly suggests spatial and temporal summation of signals. Further recordings at decreasing light intensities will allow us to determine the general neural strategies that nocturnal species use to optimise visual performance at night, principles that are likely to apply to all nocturnal animals. Keywords: motion vision, Lamina, nocturnal vision, Lobula plate, hawkmoths, spatial summation Conference: International Conference on Invertebrate Vision, Fjälkinge, Sweden, 1 Aug - 8 Aug, 2013. Presentation Type: Poster presentation preferred Topic: Motion vision Citation: Stöckl AL, O'Carroll D and Warrant E (2019). Sensitivity to motion and higher-order visual processing in nocturnal and diurnal hawk moths. Front. Physiol. Conference Abstract: International Conference on Invertebrate Vision. doi: 10.3389/conf.fphys.2013.25.00112 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 27 Feb 2013; Published Online: 09 Dec 2019. * Correspondence: Ms. Anna L Stöckl, Lund University, Biology, Lund, 223 62, Sweden, anna.stoeckl@uni-konstanz.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Anna L Stöckl David O'Carroll Eric Warrant Google Anna L Stöckl David O'Carroll Eric Warrant Google Scholar Anna L Stöckl David O'Carroll Eric Warrant PubMed Anna L Stöckl David O'Carroll Eric Warrant Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.