Environmental Light Intensity Research Articles

Multidimensional gain control in image representation and processing in vision.

A generic model of automatic gain control (AGC) is proposed as a general framework for multidimensional automatic contrast sensitivity adjustment in vision, as well as in other sensory modalities. We show that a generic feedback AGC mechanism, incorporating a nonlinear synaptic interaction into the feedback loop of a neural network, can enhance and emphasize important image attributes, such as curvature, size, depth, convexity/concavity and more, similar to its role in the adjustment of photoreceptors and retinal network sensitivity over the extremely high dynamic range of environmental light intensities, while enhancing the contrast. We further propose that visual illusions, well established by psychophysical experiments, are a by-product of the multidimensional AGC. This hypothesis is supported by simulations implementing AGC, which reproduce psychophysical data regarding size contrast effects known as the Ebbinghaus illusion, and depth contrast effects. Processing of curvature by an AGC network illustrates that it is an important mechanism of image structure pre-emphasis, which thereby enhances saliency. It is argued that the generic neural network of AGC constitutes a universal, parsimonious, unified mechanism of neurobiological automatic contrast sensitivity control. This mechanism/model can account for a wide range of physiological and psychophysical phenomena, such as visual illusions and contour completion, in cases of occlusion, by a basic neural network. Likewise, and as important, biologically motivated AGC provides attractive new means for the development of intelligent computer vision systems.

Cool temperature effects on photosynthetic parameters of two biomass fuel feedstocks in a low light intensity environment

The ability to attain the feedstock production goal in the USA for biofuel production is limited by available arable land, cool temperatures, and periods of low light intensity. This study investigates the effects of warm and cool temperatures growth conditions in a low light regime on the photosynthesis and growth of switchgrass (Panicum virgatum cv. Alamo) and giant miscanthus (Miscanthus giganteus). Alamo switchgrass did not acclimate to low light conditions and had a 47% lower growth and significantly lower mean light saturated photosynthetic rate (Asat = 10.3 μmol m−2s−1) at 14/12°C day/night, compared with 28/25°C (Asat = 18.8 μmol m−2s−1). In contrast, photosynthesis of giant miscanthus acclimated to low light conditions, but there was no significant decrease in quantum requirement or light saturated photosynthetic rates in cool growing conditions (Asat = 8.2 μmol m−2s−1 and 7.0 μmol m−2s−1 for warm and cool conditions, respectively). In summary, giant miscanthus growth and photosynthesis is relatively more tolerant of cool temperature than switchgrass, but is severely limited by low radiation. In contrast, Alamo switchgrass growth and photosynthesis is very sensitive to cool conditions, but is able to maintain higher growth than miscanthus at low radiation conditions.

A potential physiological role for cyanotoxins in cyanobacteria of arid environments

The ecological or physiological function of most cyanotoxins has remained largely unknown despite much speculation and the development of several hypotheses. The possible role of two of these toxins, microcystin and β-N-methylamino-l-alanine (BMAA) within producing organisms is discussed within the context of survival in arid environments and the consequent potential for the presence of such toxins in these environments. Cellular microcystin and BMAA concentrations are modulated by cellular carbon:nitrogen balance which in turn reflects environmental nitrogen availability and light intensity or duration. Both toxins result in decreased photosynthesis. However, available nitrogen relative to light and/or carbon fixation has opposite effects on the concentration of these toxins. We present data to explain this apparent contradiction and to support the role of these toxins in inhibition of photosynthesis. Additionally, we discuss how their different modes of achieving inhibition of photosynthesis may offer a survival advantage to cyanobacteria exposed to rapid changes in photosynthetic activity in arid environments.

Influence of weather and growing environment on vegetable growth and yield

An experiment was conducted at the Department of Horticulture, Agricultural College and Research Institute, Tamil Nadu Agricultural University, Madurai, Tamil Nadu, India to screen ten vegetables for cultivation under shadenet house (33% shade) and open field for year round production of vegetables. Tomato, eggplant, chilli, cucumber, cluster bean, radish, amaranthus, coriander, bhendi and capsicum were grown in the summer and winter. The influence of environmental variables temperature, relative humidity and light intensity were studied. Tomato, eggplant, chilli, cucumber, radish, amaranthus and coriander registered better performance for growth and yield during both seasons. Cluster bean performed well in the open field during both seasons. Relative humidity was always higher under shadenet house than in open field during both seasons. Light intensity in the shadenet house was lower than in the open field. Mean weekly temperature during summer and winter were higher under open field conditions than in the shadenet house. Lower temperature caused plant height, number of branches, internodal length, average fruit weight and yield per plant to be higher in the shadenet house than in the open field. Hence, the growing of tomato, eggplant, chilli, cucumber, radish, amaranthus and coriander under shade house conditions will be more profitable irrespective of the seasons. Key words: Shadenet cultivation, season, quality.

Plastic responses in tree architecture and specific leaf area of Xylopia aromatica (Annonaceae): adaptations to environments with different light intensities

The capacity of plants to occupy different environments is made possible by the plastic responses they present in heterogeneous environments. Light directly influences the plastic responses of plant functional traits, mainly involving leaf traits (specific leaf area and leaf dry matter content). Our objective was therefore to evaluate the phenotypic plasticity of Xylopia aromatica, a heliophilous species occurring in two physiognomies: cerrado sensu stricto (savanna—high light intensity environment) and Cerradao (woodland savanna—shaded environment). It is expected that trees growing in Cerradao will present adaptations that reduce self-shading and optimize their photosynthetic capacity. We sampled 40 trees (20 in each physiognomy) and collected seven parameters of tree architecture and specific leaf area (SLA) of these individuals. We found that in Cerradao, a closed and shaded physiognomy, X. aromatica showed significantly more cylindrical trunks, greater overall height, first branch height and SLA, and a lower crown length ratio. This differentiation can be defined as a plastic phenomenon, likely related to the higher efficiency of light interception and absorbance by trees and beyond to reduce self-shading in Cerradao. The plastic response of X. aromatica showed in this study is potentially a strong explanation for the adaptive success of cerrado plant species in different environments.

Zeitlupe Senses Blue-Light Fluence To Mediate Circadian Timing in Arabidopsis thaliana

Plants employ a variety of light, oxygen, voltage (LOV) domain photoreceptors to regulate diverse aspects of growth and development. The Zeitlupe (ZTL), Flavin-Kelch-Fbox-1 (FKF1), and LOV-Kelch-Protein-2 (LKP2) proteins dictate measurement of the day length, flowering time, and regulation of the circadian clock by blue-light regulation of protein complex formation. Previous reports indicated that ZTL photochemistry was irreversible, which is inconsistent with its role in marking the day-night transition. A kinetic model of LOV domain function predicts that ZTL has evolved unique photochemical parameters to allow it to function as a sensor of environmental light intensity. Moreover, our model indicates that a photocatalyzed reverse reaction is required for the sensitivity of LOV domains to light fluence. Inclusion of a photocatalyzed rate constant allows the establishment of a photostationary steady state of light-activated proteins, whose relative population is sensitive to daily (circadian) or positional (phototropism) oscillations in light intensity. Photochemical characterization confirms that ZTL undergoes adduct decay on a time scale of hours in contrast to previous reports. The fast photocycle allows detection of the day-night transition facilitating circadian timing. ZTL kinetics reflect an evolutionary adaptation of the ZTL/FKF1/LKP2 family to function in distinct aspects of blue-light signaling.

Differences in timing of mating swarms in sympatric populations of Anopheles coluzzii and Anopheles gambiae s.s. (formerly An. gambiae M and S molecular forms) in Burkina Faso, West Africa

BackgroundThe M and S molecular forms of Anopheles gambiae s.s. Giles appear to have speciated in West Africa and the M form is now formally named An. coluzzii Coetzee & Wilkerson sp.n. and the S form retains the nominotypical name (abbreviated here to An. gambiae). Reproductive isolation is thought to be the main barrier to hybridisation; even though both species are found in the same mating swarms, hybrid fertilisations in copulae have not been found in the study area. The aim of the study, therefore, was to determine whether differences in circadian and/or environmental control over the timing of swarming in the two species contribute to reproductive isolation.MethodsThe timing of male swarming in these species was recorded four nights per month over four years at five swarming sites in each of two villages. The timing of the start and end of swarming, and the concurrent environmental parameters, temperature, humidity and light intensity, were recorded for n = 20 swarms/month/species. The timing of 'spontaneous’ activity at dusk of individual An. coluzzii and An. gambiae males was video-recorded in an actograph outdoors for 21 nights.ResultsOf the environmental parameters considered, swarming was most strongly correlated with sunset (r2 > 0.946). Anopheles gambiae started and stopped swarming earlier than An. coluzzii (3:35 ± 0:68 min:sec and 4:51 ± 1:21, respectively), and the mean duration of swarming was 23:37 ± 0:33 for An. gambiae and 21:39 ± 0:33 for An. coluzzii. Accordingly, in principle, whenever both species swarm over the same marker, a mean of 15.3 ± 3.1% of An. gambiae swarming would occur before An. coluzzii males arrived, and 19.5 ± 4.55% of An. coluzzii swarming would occurred after An. gambiae males had stopped swarming. These results are consistent with the finding that An. gambiae males became active in the actograph 09:35 ± 00:22 min:sec earlier than An. coluzzii males.ConclusionsThe timing of swarming and spontaneous activity at dusk are primarily under circadian control, with the phase linked closely to sunset throughout the year. The mating activity of these two species is temporally segregated for 15-20% of the swarming period, which may contribute to the observed reproductive isolation of these species in local sympatric populations.

A MPPT Control Algorithm Based on Extreme Learning Machine in PV System

At present, there are many commonly used maximum power point tracking (MPPT) control methods for solar photovoltaic system which have different degrees of output fluctuations. In order to solve the problem and improve the response speed further, a novel MPPT algorithm based on the extreme learning machine was put forward in this paper. Using the extreme learning machine which has small error, fast speed and simple structure train a mathematical model with the environmental temperature and light intensity as input and the maximum power point as output, the model can be used as the controller of the photovoltaic cells. The simulation results show that the error of the model meets the requirements, when the ambient temperature and light intensity change, it can respond quickly so as to photovoltaic cells work at the maximum power point and operate stably.

Summer (Subarctic) versus Winter (Subtropic) Production Affects Spinach (Spinacia oleracea L.) Leaf Bionutrients: Vitamins (C, E, Folate, K1, provitamin A), Lutein, Phenolics, and Antioxidants

Comparison of spinach (Spinacia oleracea L.) cultivars Lazio and Samish grown during the summer solstice in the subarctic versus the winter solstice in the subtropics provided insight into interactions between production environment (light intensity), cultivar, and leaf age/maturity/position affecting bionutrient concentrations of vitamins (C, E, folate, K1, provitamin A), lutein, phenolics, and antioxidants. Growing spinach during the winter solstice in the subtropics resulted in increased leaf dry matter %, oxidized (dehydro) ascorbic acid (AsA), α- and γ-tocopherol, and total phenols but lower reduced (free) AsA, α-carotene, folate, and antioxidant capacity compared to summer solstice-grown spinach in the subarctic. Both cultivars had similar bionutrients, except for higher dehydroAsA, and lower α- and γ-tocopherol in 'Samish' compared to 'Lazio'. For most bionutrients measured, there was a linear, and sometimes quadratic, increase in concentrations from bottom to top canopy leaves. However, total phenolics and antioxidant capacity increased basipetally. The current study has thus demonstrated that dehydroAsA, α-tocopherol, and γ-tocopherol were substantially lower in subarctic compared to subtropical-grown spinach, whereas the opposite relationship was found for antioxidant capacity, α-carotene, and folates (vitamin B9). The observations are consistent with previously reported isolated effects of growth environment on bionutrient status of crops. The current results clearly highlight the effect of production environment (predominantly radiation capture), interacting with genetics and plant phenology to alter the bionutrient status of crops. While reflecting the effects of changing growing conditions, these results also indicate potential alterations in the nutritive value of foods with anticipated shifts in global climatic conditions.

Integrated Multifunctional Environmental Sensors

We present the design, microfabrication, and characterization of ten sensors on one silicon die. We demonstrate simultaneous monitoring of multiple environmental parameters, including temperature, humidity, light intensity, pressure, wind speed, wind direction, magnetic field, and acceleration in three axes. Through an integrated design and fabrication process, these ten functions require only six photolithography mask steps. Temperature is measured redundantly using aluminum and doped silicon resistance thermal detectors and a bandgap temperature sensor. Humidity is transduced by the dielectric change of a polymer due to water absorption. Light intensity is measured with a p-n junction photodiode and doped silicon photoresistor. Pressure is transduced using piezoresistor strain gauges on a sealed membrane. Wind speed and direction are measured with two perpendicular hot wire anemometers. Magnetic field strength is measured with a doped Hall effect sensor. Acceleration in three axes is measured using electrostatic comb finger accelerometers, and an additional <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">z</i> -axis accelerometer uses piezoresistor strain gauges. We measured the cross-sensitivity of each function to all other environmental parameters and can use the chip's multifunctional capabilities to compensate for these effects. Sensor integration can enable significant cost, size, and power savings over ten individual devices and facilitate deployment in novel applications.

Optimizing microalgal production in raceway systems

The industrial exploitation of microalgae is characterized by the production of high-value compounds. Optimization of the performance of microalgae culture systems is essential to render the process economically viable. For raceway systems, the optimization based on optimal control theory is rather challenging, because the process is by essence periodically forced and, as a consequence, optimization must be carried out in a periodic framework. In this article, we propose a simple operational criterion for raceway systems that when integrated in a strategy of closed-loop control allows attaining biomass productivities very near to the theoretical maximal productivities. The strategy developed was tested numerically using a mathematical model of microalgae growth in raceways. The model takes into account the temporal variation of the environmental variables temperature and light intensity and their influence on microalgae growth.

A Retinal Ganglion Cell That Can Signal Irradiance Continuously for 10 Hours

A recently discovered type of mammalian retinal ganglion cell encodes environmental light intensity and mediates non-image-forming visual behaviors, such as the pupillary reflex and circadian photoentrainment. These intrinsically photosensitive retinal ganglion cells (ipRGCs) generate endogenous, melanopsin-based photoresponses as well as extrinsic, rod/cone-driven responses. Because the ipRGCs' light responses and the behaviors they control are both remarkably tonic, these cells have been hypothesized to be capable of irradiance detection lasting throughout the day. I tested this hypothesis by obtaining multielectrode-array recordings from ipRGCs in a novel rat eyecup preparation that enhances the regeneration of rod/cone photopigments. I found that 10 h constant light could continuously evoke action potentials in these ganglion cells under conditions that stimulated (1) only melanopsin, (2) mainly the rod input, and (3) both intrinsic and extrinsic responses. In response to a 10 h stimulus with gradual intensity changes to simulate sunrise and sunset, ipRGC firing rates slowly increased during the "sunrise" phase and slowly decreased during the "sunset" phase. Furthermore, I recorded from putative ipRGCs of melanopsin-knock-out mice and found that these cells retained the ability to respond in a sustained fashion to 20 min light steps, indicating that melanopsin is not required for such tonic responses. In conclusion, ipRGCs can signal light continuously for at least 10 h and can probably track gradual irradiance changes over the course of the day. These results further suggest that the photoreceptors and ON bipolar cells presynaptic to ipRGCs may be able to respond to light continuously for 10 h.

ISPECT Robot - Intelligent Shortest Path and Evading Collision Traveler Robot

In this paper a minimalist approach to establish obstacle avoidance and course stabilization behavior of an autonomous robot in a region evaluating 2D virtual world is proposed. The robot uses ultrasonic sensor to evade the hindrances and with distance measurements of barriers predict itself the shortest path to travel on through the destination and updating the virtual environment in database. The robot will be communicated with full duplex communication using ZigBee technology with computer interface. The environment around the rover will be visualized in GUI itself. Even robot can be made navigated searching for maximum light intensity in environment. The proposal is intense to aid the defense system and space exploration. It brings sophisticated method of practice by learning through virtual world of environment which can be enhanced even to 3D with technologies available.

Vehicle License Plate Recognition with Intelligent Materials Based on Color Division

With the development and progress of the economic and technology, transportation has become more and more important in human’s usual life. Intelligent transportation system can be used in many areas. Images in RGB color space are very sensitive to the environment light intensity, and what’s more, there may be some pollution appeared on the plate and so on, these made it difficult to locate the plate area. In this paper, we proposed some new algorithms. In the first stage, car image preprocess, a new algorithm named color division was proposed. Experiments show that, influences from the environment as well as some inevitably differences of colors in the plate into standard color, so the performance of whole system was improved. In the period of license location, a new algorithm based on license color pairs was proposed, and it has good performance after experiments.

Monitoring stress responses in cyanobacterial scytonemin – screening and characterization

Scytonemin is believed to protect a variety of organisms against the negative effects of ultraviolet radiation. Cyanobacteria have evolved different strategies to minimize the potential damage caused by solar ultraviolet radiation. This includes the synthesis of the UV-absorbing compound scytonemin, which acts as a sunscreen During the present study scytonemin was found in 9 out of 19 studied cyanobacterial strains. Aulosira fertilissima showed the maximum amount of scytonemin. The effect of environmental factors, including temperature, light intensity, UV-light and salt was studied on scytonemin synthesis of A. fertilissima. A remarkable change in scytonemin synthesis was observed under salt stress and UV-light stress. Scytonemin increased under all stress conditions but it increased maximally under yellow-light stress.

Self-adaptive image reconstruction inspired by insect compound eye mechanism.

Inspired by the mechanism of imaging and adaptation to luminosity in insect compound eyes (ICE), we propose an ICE-based adaptive reconstruction method (ARM-ICE), which can adjust the sampling vision field of image according to the environment light intensity. The target scene can be compressive, sampled independently with multichannel through ARM-ICE. Meanwhile, ARM-ICE can regulate the visual field of sampling to control imaging according to the environment light intensity. Based on the compressed sensing joint sparse model (JSM-1), we establish an information processing system of ARM-ICE. The simulation of a four-channel ARM-ICE system shows that the new method improves the peak signal-to-noise ratio (PSNR) and resolution of the reconstructed target scene under two different cases of light intensity. Furthermore, there is no distinct block effect in the result, and the edge of the reconstructed image is smoother than that obtained by the other two reconstruction methods in this work.

Age‐related sexual plumage dimorphism and badge framing in the European Robin Erithacus rubecula

Male and female European Robins Erithacus rubecula display their red breasts in year‐round territorial contests. Despite the clear signalling role of the red breast, little is known about its sexual dimorphism or trends in size when Robins age. We studied these patterns in resident and migrant Robins in a Mediterranean population. Both male and female first‐year Robins had smaller red breasts than second‐year individuals. Females, but not males, showed a reduction in badge area after the second year of life, leading to sexual dimorphism in red breast area in the oldest Robins. The grey fringe around the red breast showed a steady increase in width in males when ageing, but not in females, also leading to sexual dimorphism in this trait among oldest Robins. The contrast between the red breast and its surrounding grey fringe was higher than that between the breast and the back at both high and low environmental light intensities. This suggests that the grey fringe could function as a frame to highlight the perimeter of the red breast, and that the Robin’s plumage is equally suited to display in open areas and forest understoreys. Our study suggests that the extent of the red breast and its grey frame could confer information about the age and sex of the birds, and thus be used as a signal in territorial contests and mating decisions.

Spectral composition and visual foraging in the three-spined stickleback (Gasterosteidae: Gasterosteus aculeatus L.): elucidating the role of ultraviolet wavelengths

Visual signalling can be affected by both the intensity and spectral distribution of environmental light. In shallow aquatic habitats, the spectral range available for visually mediated behaviour, such as foraging, can reach from ultraviolet (UV) to long wavelengths in the human visible range. However, the relative importance of different wavebands in foraging behaviour is generally unknown. Here, we test how the spectral composition of ambient light influences the behaviour of three-spined sticklebacks (Gasterosteus aculeatus) when foraging for live cladoceran Daphnia magna. Although paying particular attention to the UV waveband, we measured the foraging preferences of sticklebacks for prey presented under four different spectral conditions. These conditions selectively removed UV (UV‐), short-wave (SW‐), mid-wave (MW‐) or long-wave (LW‐) light from the entire spectrum. The absence of UV and long wavelengths strongly reduced prey attractiveness for G. aculeatus compared with conditions without short-wave and mid-wave light. To control for potential light habitat preferences in the main experiment, we conducted a further choice experiment without prey stimuli. Fish in these trials did not discriminate significantly between the different spectral conditions. When comparing both experiments, it was observed that, although filter preferences for MW‐ and LW‐ conditions were virtually consistent, they differed at shorter wavelengths, with a reduced preference for UV‐ conditions and, at the same time, an increased preference for SW‐ conditions in the presence of prey. Thus, prey choice seems to be strongly affected by visual information at the short-wave end of the spectrum. The foraging preferences were also mirrored by the chromatic contrast values between prey and the experimental background, as calculated for each lighting condition using a series of physiological models on stickleback perception. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105, 359‐368.

선박용 감성조명 LED 제어기의 설계 및 구현

Today the light of mankind since the dawn of mankind and that they were living lives on the huge influence across space is a dynamic energy. Because of this, when all human beings with the light and you can feel more comfortable with a stable mind to the beauty and the pursuit of happiness is to have instincts. In this paper, a fuzzy control system using a combination of external environmental factors, respectively, the conversion of quantitative uncertainty information into the LED lighting is designed to express algorithms, available in indoor circadian control circuit was designed and fabricated LED. Factor in the external environment temperature, humidity, and light intensity values to the controller through the sensor to accept these values and the optimal values for lighting the fuzzy control algorithm is converted into human emotion to feel comfortable to express through the dimming control LED lighting.

Heliotropic responses of soybean cultivars at three phenological stages and under two water regimes

The objectives of this work were to determine the heliotropic movements of the upper trifoliates for two soybean cultivars, BR 16 and Embrapa 48, during a daily cycle, in three phenological stages and two water regimes, and to estimate the impact of irrigation and daily leaflet movements on agronomic characteristics and grain yield. Heliotropic movements were studied in three phenological stages: V4-V6, V7-V10, and R5 in irrigated and non-irrigated plots. For each stage, the leaflet elevation and azimuth were measured hourly. Under a low (V4-V6 stage) and mid (V7-V10 stage) leaf area index (LAI) the diaheliotropism was slightly more frequent and intensive in non-irrigated than in irrigated plants, only at early morning and late afternoon hours. At R5 stage (high LAI) the paraheliotropism of superior trifoliates was predominant and more intensive in non-irrigated plants. The heliotropic movements are correlated to carbon gain, but not to environment (light intensity or temperature), for measurements at 11h. 'Embrapa 48' expresses greater paraheliotropism than 'BR 16' at high LAI, while 'BR 16' displays lower heliotropic plasticity under irrigation. In spite of significant heliotropic differences, genotype and water availability treatments did not influence the final grain yield.