Natural Light Intensity Research Articles

Ultraviolet-O2 treatment TiO2/Ti anodes for use in Ti grids-based large-area flexible dye-sensitized solar cells

Large-area flexible dye-sensitized solar cells (DSSCs) based on nanocrystalline TiO2/Ti anodes on the Ti foils and platinum/single-wall carbon nanotube (Pt/SWCNT) counter electrodes on the indium-doped tin oxide coated polyethylene naphthalate (ITO/PEN) substrates, were successfully assembled with Ti grids. The resistance of the DSSC could be observably reduced with the Ti grid, which could enhance the fill factor and the efficiency of the DSSC. Ultraviolet-O2 treatment of the TiO2/Ti anode could improve the efficiency of the DSSC, owing to that the passivated Ti foil was enhanced by the ultraviolet-O2 treatment. Based on the optimal preparation conditions, a large-area (40 cm2) flexible DSSC with efficiency of 5.29% was achieved under natural light intensity of 55 mW cm−2 measured outdoors.

Glacier melting and stoichiometric implications for lake community structure: zooplankton species distributions across a natural light gradient

Glaciers around the globe are melting rapidly, threatening the receiving environments of the world's fresh water reservoirs with significant changes. The meltwater, carried by rivers, contains large amounts of suspended sediment particles, producing longitudinal gradients in the receiving lakes. These gradients may result in changes in the light:nutrient ratio that affect grazer performance by altering elemental food quality. Thus, glacial melting may induce a shift in the phytoplankton carbon:nutrient ratio and hence influence the dominance of herbivorous zooplankton through stoichiometric mechanisms. To test this hypothesis, we combined field and experimental data, taking advantage of a natural light intensity gradient caused by glacial clay input in a deep oligotrophic Patagonian lake. Across this gradient, we evaluated the abundances of two consumer taxa with different phosphorus requirements, the copepod Boeckella gracilipes and the cladoceran Daphnia commutata, using a six-station transect along the lake. We found significant differences in light:nutrient ratio and stoichiometric food quality of the seston, together with a switch from dominance of P-rich Daphnia in low carbon:nutrient stations to dominance of low-P copepods in high carbon:nutrient stations. The laboratory experiments confirmed that the difference in the carbon:nutrient ratio across the gradient is sufficient to impair Daphnia growth. The overall patterns are consistent with our prediction that shifts in the environmental light:nutrient ratio as a result of glacial melting would contribute to shifts in the dominance of stoichiometrically contrasting taxa in consumer guilds.

Electrodeposition of high performance PEDOT/Ti counter electrodes on Ti meshes for large-area flexible dye-sensitized solar cells

High performance poly (3,4-ethylenedioxythiophene) (PEDOT) arrays were electrodeposited onto titanium (Ti) meshes to form counter electrodes (CEs) for use in large-area flexible dye-sensitized solar cells (DSSCs). The PEDOT growth was controlled by different cyclic voltammetry parameters. The surface feature, resistance, and photovoltaic properties of the PEDOT/Ti CEs based on different electrodeposition conditions were investigated. The obtained PEDOT/Ti CE showed higher electrocatalytic activity for the I3−/I− redox reaction than that of the Pt/Ti CE. The light-to-electric energy conversion efficiency of the large-area (100cm2) flexible DSSC based on the PEDOT/Ti CE reached 6.33%, and a maximum power output of 0.348W was achieved, under irradiation with a natural light intensity of 55mWcm−2 measured outdoors. Compared with other materials to prepare CEs, the PEDOT/Ti CE could be suitable for the large scale flexible DSSCs.

Warming induces shifts in microzooplankton phenology and reduces time-lags between phytoplankton and protozoan production

Indoor mesocosm experiments were conducted to test for potential climate change effects on the spring succession of Baltic Sea plankton. Two different temperature (Δ0 °C and Δ6 °C) and three light scenarios (62, 57 and 49 % of the natural surface light intensity on sunny days), mimicking increasing cloudiness as predicted for warmer winters in the Baltic Sea region, were simulated. By combining experimental and modeling approaches, we were able to test for a potential dietary mismatch between phytoplankton and zooplankton. Two general predator–prey models, one representing the community as a tri-trophic food chain and one as a 5-guild food web were applied to test for the consequences of different temperature sensitivities of heterotrophic components of the plankton. During the experiments, we observed reduced time-lags between the peaks of phytoplankton and protozoan biomass in response to warming. Microzooplankton peak biomass was reached by 2.5 day °C−1 earlier and occurred almost synchronously with biomass peaks of phytoplankton in the warm mesocosms (Δ6 °C). The peak magnitudes of microzooplankton biomass remained unaffected by temperature, and growth rates of microzooplankton were higher at Δ6 °C (μ∆0 °C = 0.12 day−1 and μ∆6 °C = 0.25 day−1). Furthermore, warming induced a shift in microzooplankton phenology leading to a faster species turnover and a shorter window of microzooplankton occurrence. Moderate differences in the light levels had no significant effect on the time-lags between autotrophic and heterotrophic biomass and on the timing, biomass maxima and growth rate of microzooplankton biomass. Both models predicted reduced time-lags between the biomass peaks of phytoplankton and its predators (both microzooplankton and copepods) with warming. The reduction of time-lags increased with increasing Q10 values of copepods and protozoans in the tritrophic food chain. Indirect trophic effects modified this pattern in the 5-guild food web. Our study shows that instead of a mismatch, warming might lead to a stronger match between protist grazers and their prey altering in turn the transfer of matter and energy toward higher trophic levels.

The surface treatment of Ti meshes for use in large-area flexible dye-sensitized solar cells

We report that NaOH hydrothermal treatment and HF post-treatment of the titanium mesh for the Pt/Ti counter electrode improved the efficiency of dye-sensitized solar cells. High performance platinum nanoparticles have been sprayed onto Ti meshes to form counter electrodes for use in large-area flexible DSSCs using a vacuum thermal decomposition method at low temperature (120°C). The obtained Pt/Ti counter electrode shows low charge-transfer resistance (57.52Ωcm2 with active area of 80cm2) and high electrocatalytic activity for the I3−/I− redox reaction. The photovoltaic properties and resistances of Pt/Ti counter electrodes with different HF post-treatment times of the NaOH treated Ti meshes have been investigated. The efficiency of the large-area (80cm2) flexible DSSC reaches 6.17% under irradiation with a natural light intensity of 55mWcm−2 measured outdoors.

Geolocation by light: accuracy and precision affected by environmental factors

Summary1. Geolocation by light allows for tracking animal movements, based on measurements of light intensity over time by a data‐logging device (‘geolocator’). Recent developments of ultra‐light devices (<2 g) broadened the range of target species and boosted the number of studies using geolocators. However, an inherent problem of geolocators is that any factor or process that changes the natural light intensity pattern also affects the positions calculated from these light patterns. Although the most important factors have been identified, estimation of their effect on the accuracy and precision of positions estimated has been lacking but is very important for the analyses and interpretation of geolocator data.2. The ‘threshold method’ is mainly used to derive positions by defining sunrise and sunset times from the light intensity pattern for each recorded day. This method requires calibration: a predefined sun elevation angle for estimating latitude by fitting the recorded day/night lengths to theoretical values across latitudes. Therewith, almost constant shading can be corrected for by finding the appropriate sun elevation angle.3. Weather, topography and vegetation are the most important factors that influence light intensities. We demonstrated their effect on the measurement of day/night length, time of solar midnight/noon and the resulting position estimates using light measurements from stationary geolocators at known places and from geolocators mounted on birds. Furthermore, we investigated the influence of different calibration methods on the accuracy of the latitudinal positions.4. All three environmental factors can influence the light intensity pattern significantly. Weather and an animal’s behaviour result in increased noise in positioning, whereas topography and vegetation result in systematic shading and biased positions. Calibration can significantly shift the estimated latitudes and potentially increase the accuracy, but detailed knowledge about the particular confounding factors and the behaviour of the studied animal is crucial for the choice of the most appropriate calibration method.

Measures of light in studies on light-driven plant plasticity in artificial environments.

Within-canopy variation in light results in profound canopy profiles in foliage structural, chemical, and physiological traits. Studies on within-canopy variations in key foliage traits are often conducted in artificial environments, including growth chambers with only artificial light, and greenhouses with and without supplemental light. Canopy patterns in these systems are considered to be representative to outdoor conditions, but in experiments with artificial and supplemental lighting, the intensity of artificial light strongly deceases with the distance from the light source, and natural light intensity in greenhouses is less than outdoors due to limited transmittance of enclosure walls. The implications of such changes in radiation conditions on canopy patterns of foliage traits have not yet been analyzed. We developed model-based methods for retrospective estimation of distance vs. light intensity relationships, for separation of the share of artificial and natural light in experiments with combined light and for estimation of average enclosure transmittance, and estimated daily integrated light at the time of sampling (Qint,C), at foliage formation (Qint,G), and during foliage lifetime (Qint,av). The implications of artificial light environments were analyzed for altogether 25 studies providing information on within-canopy gradients of key foliage traits for 70 species × treatment combinations. Across the studies with artificial light, Qint,G for leaves formed at different heights in the canopy varied from 1.8- to 6.4-fold due to changing the distance between light source and growing plants. In experiments with combined lighting, the share of natural light at the top of the plants varied threefold, and the share of natural light strongly increased with increasing depth in the canopy. Foliage nitrogen content was most strongly associated with Qint,G, but photosynthetic capacity with Qint,C, emphasizing the importance of explicit description of light environment during foliage lifetime. The reported and estimated transmittances of enclosures varied between 0.27 and 0.85, and lack of consideration of the reduction of light compared with outdoor conditions resulted in major underestimation of foliage plasticity to light. The study emphasizes that plant trait vs. light relationships in artificial systems are not directly comparable to natural environments unless modifications in lighting conditions in artificial environments are taken into account.

Preparation of a three-dimensional interpenetrating network of TiO2 nanowires for large-area flexible dye-sensitized solar cells

Platinum (Pt) and single-wall carbon nanotubes (SWCNTs) were sprayed onto Titanium (Ti) mesh to form a Pt–SWCNT/Ti counter electrode using a vacuum thermal decomposition method at a low temperature. A three-dimensional interpenetrating network of TiO2 nanowires (3-D IPN TNWs) was successfully prepared on Ti foil through a facile hydrothermal approach. A TiO2 colloid was coated on the 3-D IPN TNWs to form a large-area flexible anode using a doctor-scraping technique. The influences of the concentration of NaOH on the growth of 3-D IPN TNWs and on the photovoltaic performances of dye-sensitized solar cells (DSSCs) were investigated. Under an optimized condition, the power conversion efficiency of a large-area (100 cm2) flexible DSSC reached 6.43%, with a short-circuit current density of 6.83 mA cm−2, an open circuit voltage of 0.724 V, and a fill factor of 0.715. Under irradiation with a natural light intensity of 55 mW cm−2 outdoors, the efficiency of power conversion was increased by 10.29% compared with the flexible DSSC without 3-D IPN TNWs.

Passive Energy-Saving Design in Hot and Humidity Area: A Case Study of Multi-Functional Stadium of Guangdong College of Pharmacy

As stadiums have high energy consumption in architectural lighting and air conditioning, how to make full use of natural lighting and natural ventilation is the key to architectural energy conservation. To this end, many passive energy conservation measures have been taken into account in designing Multifunctional Stadium of Guangdong Pharmaceutical University. For instance, strip light windows with vertical shading have been installed on east and west facade, open external windows on south and north facade etc. Test result of the Stadium shows that the above-mentioned passive design methods are able to increase natural light intensity of the playing field and prevent glare, improve wind velocity of natural ventilation and comfort in spectator areas.

Measurement and Analysis of Multi-Functional Stadium of Guangdong College of Pharmacy

As stadiums have high energy consumption in architectural lighting and air conditioning, how to make full use of natural lighting and natural ventilation is the key to architectural energy conservation. To this end, many passive energy conservation measures have been taken into account in designing Multifunctional Stadium of Guangdong Pharmaceutical University. For instance, strip light windows with vertical shading have been installed on east and west facade, open external windows on south and north facade, and green roof on Auxiliary Stadium etc. Test result of the Stadium shows that the above-mentioned passive design methods are able to increase natural light intensity of the playing field and prevent glare, improve wind velocity of natural ventilation and comfort in spectator areas, reduce inner surface temperature and thermal radiation of the roof on Auxiliary Stadium.

Cost-efficient light control for production of two campanula species

A cost-efficient light control system based on weather forecasts, electricity prices and daily photosynthesis integral (DPI) was evaluated for application in the commercial production of the long-day (LD) plant Campanula portenschlagiana ‘Blue Get Mee’ and C. cochlearifolia ‘Blue Wonder’. Experiments were conducted under both autumn and spring conditions and included four treatments. Three treatments were controlled by the software system DynaLight Desktop which automatically defined the most cost-efficient use of supplemental light, -based on a predefined set point of DPI, forecasted solar irradiance and the market price on electricity. The set points of DPI in the three treatments were 300, 450 and 600 mmol CO 2 m −2 leaf d −1 and the treatments were compared with a traditional LD 19-h treatment. The DPI-based light control strategy resulted in very irregular light patterns including daily periods of solar irradiance combined with supplemental light in low light periods and a night period interrupted by irregular light breaks (NB-lighting). Both campanula species flowered in the DPI-based treatments during spring, but the flowering percentage was low and non-uniform during autumn. This was caused by a combination of the irregular light, low natural light intensities and a decrease in daily light integral (DLI), and could be restored by maintaining a continuous 19 h photoperiod with incandescent lamps (<5 μmol m −2 s −1), illustrating that photoperiod was an important factor for flowering in LD species grown under low light intensities. Growth in terms of carbon gain was marginally affected by the irregular light and a 25% reduction in electricity costs was achieved without major reductions in plant quality in spring. Our results illustrate that plant production of LD species can be maintained in a cost-efficient light control system where the use of supplemental light is based on weather forecasts and electricity prices.

Isolation and application of a wild strain photosynthetic bacterium to environmental waste management

A new photosynthetic bacterium isolate was morphologically identified as a non-motile rod-shape gram-negative bacterium. It produced a dark red culture under phototrophic condition, reproduced by budding and formed a lamellar intracytoplasmic membrane system parallel to cytoplasmic membrane, which contained bacteriochlorophyll a and caratenoids. It's physiological and nutrient requirement tests gave indication that the isolate thrived and multiplied in varied environmental conditions. It was consequently named Z08 and identified as Rhodobacter sphaeroides by 16SrDNA. Adaptation of Z08 to biodegradation of two environmentally concerned wastewaters, i.e. soybean and pharmaceutical wastewaters, attested its potential in wastewater bioremediation. Z08 adaptation in a suspended batch photobioreactor treating pharmaceutical wastewater at 3500lx radiation recorded best result after wastewater dilution of 1:4 with concomitant chemical oxygen demand reduction, biomass yield and specific growth of 50 %, 780 mg/L and 0.015/h, respectively at the lowest hydraulic retention time of three days. Furthermore, gas chromatography mass spectra analyses of treated and raw pharmaceutical wastewater indicated that high molecular weight recalcitrant compounds found in the pharmaceutical wastewater were transformed to less toxic and acceptable lower molecular weight substances through biodegradation. Whilst Z08 treatment of soybean wastewater under natural light intensity radiation recorded 80 % reduction, 1540 mg/L and 0.025/h for chemical oxygen demand, biomass and specific growth rate respectively regardless of the food to microorganism ratio. This preliminary investigation showed that isolate Z08 has some toxic tolerance level which could detoxify refractory substances with great potential for cell protein recovery in high organic strength wastewater. Therefore, strain Z08 could be employed in biodegradation of contaminated wastewater streams.

Leaf development, temperature and light stress control of the expression of early light-inducible proteins (ELIPs) in Vitis vinifera L.

Early light inducible proteins (ELIPs) are thylakoid proteins transiently induced by light. They are found in many species, most of which are annual plants. Studies on perennial plants are scarce and in grapevine almost nil. Because grapevines normally grow in sites with high radiation, we aimed to characterize the ELIP expression to evaluate whether they have a role in photoprotection in this species. ELIP expression was characterized in leaves at different temperatures, times of induction and natural light intensities. Very low expression was found in mature leaves. In young leaves, ELIP expression was high but began at temperatures higher than 13 °C. Maximal expression was obtained at 30 °C after 4 h of induction at 1000 μmol PAR m −2 s −1. At this intensity, the level of photoinhibition was also maximal. We conclude that in grapevine leaves, ELIP expression is developmentally dependent, occurring mainly in developing leaves, Finally, our results showed that the light intensity dependence of the ELIP expression correlated with the extent of photoinhibition indicating that ELIP induction is controlled by the strength of light stress and suggesting a role of these proteins in photoprotection.

Produção fotossintética da macroalga Ulva lactuca Linnaeus (Chlorophyceae) cultivada em efluentes de uma fazenda de camarões marinhos

This study aimed to evaluate the demand for oxygen through the photosynthetic production of macroalgae Ulva lactuca, shrimp cultivated in the effluent, submitted directly to the intensity of natural light in a photoperiod of 14/10 for the latitude of 27 oS in December, and show the potential for cultivation of this kind of integrated systems, the recirculation in marine shrimp farms. Specimens were collected in Lagoa da Conceicao, Florianopolis (Brazil), and transported to the laboratory for selection of the stems. These were washed with fresh water running and then extracted several discs with a diameter of 5cm, which were dry on paper towel and weighed on electronic scales. We used 30 of 500mL Erlenmeyer flasks, previously washed with distilled water with 10% hydrochloric acid. Each received 500mL bottle of water from the canal despesca a marine shrimp farm, containing 32 of salinity and approximately 40 and 5μM ammonia and orthophosphate, respectively. The experiment included four treatments with seaweed and algae without one, as well as their respective controls, all composed of three replications. Controls were involved with laminated paper. The treatments received the following material algal densities of 1 = 1 L-1, 2 = 2 L-1, 3 = 3 L-1 and 4 = 4 L-1. The bottles were covered with paper control rods. On a plastic tank with 1000L of water, the treatments were distributed randomly on a table submerged, allowing 90% of the volume of bottles were submerged. The experiment was kept under constant renewal of water, keeping the temperature uniform, around 26, all in containers. Each time, temperature, light and dissolved oxygen were measured in all bottles, in a period of 27 hours. The photosynthetic production began from 6:30 pm, where they saw an initial increase of the oxygen concentrations in treatments with algae, while all controls remained low until the end of the experiment. There was a first photosynthetic peak around 12:30 pm, where the maximum light intensity was 1,424 lux, and a photoinhibition of algae to UV exposure of between 12:30 and 15:30 h. It was a possible excretion of UV-B at densities of 3 and 4 L-1 arising from the excess of solar irradiation. A second peak production of O2, between 18:30 and 20:30 in the four treatments with algae, resulting in higher rates to 564% of supersaturation, 490% on its photorrespiration and 150% on supersaturation of phitoplancotn showing its potential for cultivation integrated with marine shrimp in a closed system of recycling.

Dynamics of photosynthesis in Eichhornia crassipes solms of Jiangsu of China and their influencing factors.

With LI-6400 portable photosynthesis system, the photosynthetic characteristics of artificially cultured Eichhornia crassipes in Jiangsu, China, were monitored from June 1 to November 14, 2009. Both the net photosynthetic rate (Pn) in different positions and light and temperature-response curves of the top fourth leaf were measured in an open-circuit gas channel system in June, July, and August, respectively. The top third to sixth leaves matured with a high Pn in August, 2009. The values of the maximum net photosynthesis (Pmax), light component point (LCP) and apparent quantum efficiency (AQE) of the top fourth leaf of E. crassipes were 34.5±0.72 and 20.25±3.6 μmol m -2 s -1 as well as 0.0532±0.0014, respectively, significantly higher than those in rice and maize. The light-saturation point (LSP) of leaves of E. crassipes was 2358±69 μmol m -2 s -1 , significantly higher than that in rice and much close to that in maize. The natural light intensity and temperatures in Jiangsu are suitable for E. crassipes to rapidly grow but not good enough for it to show the maximum internal photosynthetic capacity from the perspective of photosynthetic physiology, thus resulting in its low biomass in this region. Key words : Eichhornia crassipes , photosynthetic characteristics, environmental influencing factors.

Seasonal flowering and evolution: the heritage from Charles Darwin.

To survive, plants optimise their seasonal flowering time and set seed to avoid extremes of the environment including frost, heat and drought. Additionally, pollination may need to be tightly regulated in time so that it coincides with flowering of other individuals and/or with the presence of bird or insect pollinators. It is now clear that plants use seasonal changes in natural light intensity, daylight duration and temperature to achieve reproducible timing of flowering year-in-year-out. In more recent studies, genetic and molecular approaches are beginning to provide a basis for understanding heritability, an essential component of Darwin's concept of evolution.

Estimation du flux de sève à partir du bilan thermique de la tige de plants de Quercus robur L. en relation avec l’intensité de la lumière : comparaison de deux méthodes au cours de la phase d’installation

• Knowledge of whole tree seedling water fluxes is important in ecological and forestry research, especially under conditions with low transpiration, but no standard method has yet been established that provides reliable in situ measurements. • The aims were: (1) to assess the performance of two methods for estimating sap-flows in oak seedlings following planting by correlating the data they provided with natural light intensities over a three-week period, and (2) to compare the estimates with transpiration data obtained by weighing pots. • Estimates of sap flows obtained from data provided by constant power (Dayau-type) heat balance gauges under low light conditions (100–450 μmol m−2 s−1) were less variable than estimates from variable power (EMS-type) heat balance gauges. The EMS-type system yielded data with little between-gauge variation, but consistently underestimated transpiration on a daily basis, a systematic error that should be corrected by other methods. The Dayau-type gauges yielded data with substantial variations, and several gauges are probably needed in research to cover these variations. Further, both systems provide rather uncertain estimates of short-time (hour) transpiration rates. • However, provided that these considerations are taken into account, we conclude that it should be possible to use either system in various research contexts.

Spectroscopic Study on Photolysis of Aqueous Solution of Zinc Pyrithione

Photodegradation process of zinc pyrithione (Zn(PT)2) in aqueous solution was investigated using a photo spectroscopic technique. Three characteristic peaks were observed in ultraviolet and visible light absorption spectrum of Zn(PT)2. By xenon lamp irradiation, the spectrum rapidly changes to that of 2-pyridinsulfonic acid (PSA) and finally exhibits nearly flat with several very weak unknown peaks. Rate constants, obtained on a basis of the first order kinetics, do not depend on either the concentration between 0.03 and 3 mg/L or the temperature from 283 to 303 K, but are proportional to the intensity of irradiation light. The half life of Zn(PT)2 in water is estimated to be approximately 25 minutes under an average natural sun light intensity (188 W/m2) on the ocean surface.

THE APPLICATION OF LEDS AS ASSIMILATION LIGHT SOURCE IN GREENHOUSE HORTICULTURE: A SIMULATION STUDY

THE APPLICATION OF LEDS AS ASSIMILATION LIGHT SOURCE IN GREENHOUSE HORTICULTURE: A SIMULATION STUDY

Light perception in ‘blind’ subterranean Zambian mole-rats

Because of their constantly dark habitat and microphthalmia, subterranean African mole-rats have hitherto been considered as blind. Recent morphological findings, however, revealed a qualitatively rather well-developed, although quantitatively reduced, visual system and questioned the prevailing idea of blindness. We investigated the reactions of Zambian mole-rats of the bathyergid genus Fukomys (formerly Cryptomys) to white light during nest building. Using a two-armed test chamber with a choice between strong halogen light and darkness, we found that mole-rat pairs avoided the illuminated chamber and nested significantly more often in the dark box. With the same protocol in an eight-armed maze, we confirmed this heliophobic (or scotophilic) behaviour under natural daylight conditions. Zambian mole-rats can thus perceive natural light intensities and use photic information, for example to decide where to nest.