Skylight Research Articles

Phenotypic differentiation of species fromAspergillus sectionFlavi on neutral red desiccated coconut agar

In order to facilitate easy and rapid identification of aflatoxin-producingAspergillus species, the phenotypic traits ofAspergillus sectionFlavi isolates were examined on neutral red desiccated coconut agar (NRDCA). Phenotype variations in colony morphology and the relationship between colour/intensity of fluorescence and aflatoxin production were assessed. The isolates included 10Aspergillus minisclerotigenes strains, 11 non-aflatoxigenicAspergillus flavus L strains, 29 aflatoxigenicA. flavus L strains and 20 strains each ofAspergillus parasiticus andAspergillus parvisclerotigenus. The NRDCA medium supported morphological differentiation of the four species based on colony features, conidia type and colour. In particular, the two very closely related minisclerotial species,A. minisclerotigenes andA. parvisclerotigenus, were clearly differentiated by their colony colour on NRDCA. All toxigenic isolates produced aflatoxins in the culture medium in varying quantities. Plates of aflatoxigenicA. flavus L strains fluoresced bluish purple/lavender around the colony on the obverse and pastel blue on the reverse side due to aflatoxin B production while those ofA. minisclerotigenes,A. parasiticus andA. parvisclerotigenus fluoresced with a light blue or light turquoise ring around the colony on the obverse and light sky blue or cadet blue on the reverse side depending on the amount of aflatoxin B and G produced. The colour of fluorescence significantly correlated (r=0.95,P=0.001) with the type(s) of aflatoxins produced by the isolates. In addition, the concentration of aflatoxins significantly (r=0.92;P=0.001) influenced the intensity of fluorescence in the aflatoxin-producing species. NRDCA can therefore be used for the rapid identification ofAspergillus sectionFlavi species based on colonial characteristics, and grouping of species into B and B+G aflatoxin producers within 5 days thus obviating the need for chemical analysis of the culture.

Development of an AutoFlat program for the acquisition of effective flat images in the automated observation system

The purpose of this study is to develop an observation program for obtaining effective flat images that are necessary for photometric observation. The development of the program was achieved by improving the existing method for obtaining twilight flat images. The existing method for obtaining twilight flat images acquires flat images by observing the sky light after sunset or light before sunrise. The decision of when to observe flat images at each night is solely dependent on the judgment of an observer, and thus the obtained flat images for particular nights may not be clean. Especially, in the case of the observatories where an automated observation system is in operation, there is a difficulty that an observer should pay attention during sunrise and sunset in order to obtain flat images. In this study, a computer program is developed to improve this inconvenience and to efficiently perform photometric observation in the observatories where an automated observation system is applied. This program can obtain flat images by calculating the time for obtaining flat images automatically and the exposure time using a numerically calculated function. When obtaining twilight flat images at dusk and at dawn, the developed program performs automated observation and provides effective flat images by acquiring appropriate exposure time considering the sunrise and sunset times that vary depending on the day of observation. The code for performing this task was added to Obs Tool II (Yoon et al. 2006), which is the automated observation system of the Chungbuk National University Observatory, and the usefulness of the developed program was examined by performing an actual automated observation. If this program is applied to other observatories where automated observation is in operation, it is expected that stable and high-quality flat images could be obtained, which can be used for the pre-processing of photometric observation data.

Night sky luminance under clear sky conditions: Theory vs. experiment

Sky glow is caused by both natural phenomena and factors of anthropogenic origin, and of the latter ground-based light sources are the most important contributors for they emit the spatially linked spectral radiant intensity distribution of artificial light sources, which are further modulated by local atmospheric optics and perceived as the diffuse light of a night sky. In other words, sky glow is closely related to a city's shape and pattern of luminaire distribution, in practical effect an almost arbitrary deployment of random orientation of heterogeneous electrical light sources. Thus the luminance gradation function measured in a suburban zone or near the edges of a city is linked to the City Pattern or vice versa.It is shown that clear sky luminance/radiance data recorded in an urban area can be used to retrieve the bulk luminous/radiant intensity distribution if some a-priori information on atmospheric aerosols is available. For instance, the single scattering albedo of aerosol particles is required under low turbidity conditions, as demonstrated on a targeted experiment in the city of Frýdek-Mistek. One of the main advantages of the retrieval method presented in this paper is that the single scattering approximation is satisfactorily accurate in characterizing the light field near the ground because the dominant contribution to the sky glow has originated from beams propagated along short optical paths.

Copper(I) oxide nanoparticle and tryptophan as its biological conjugate: a modulation of cytotoxic effects

Recent investigations indicated that cop- per oxide nanoparticles can selectively induce apop- tosis and effectively suppress the proliferation of tumor cells. Thus, it showed a great potential to be used as a drug for cancer treatment. Here we report an easy synthesis of spheroidal cuprous oxide nanopar- ticles (CuNPs) and their organic conjugate with L-tryptophan (Trp) using surfactant, sodium dodecyl sulfate as a capping reagent. The particles looked golden yellow and showed a strong affinity to bind blood carrier proteins such as bovine serum albumin and human serum albumin. However, both optical behavior and texture of the particles altered upon conjugation with Trp. The average size of the CuNPs was estimated to be *70 nm as appeared under transmission electron microscope or atomic force microscope. The biological conjugate with Trp was *85 nm and looked light sky blue in aqueous suspension. The surface of the conjugated nanoparti- cles was smoother than the bare CuNPs. The CuNPs were found to be toxic to different cultured cancerous cells; however, conjugation with Trp attenuated the toxicity, and indicated its possible utility in develop- ing a drug candidate for cancer in a controlled fashion. Reduced toxicity also indicated a possible use of the conjugated particle as a drug delivery system.

On the exposure of hemispherical photographs in forests

Abstract: At least 10 different methods to determine exposure for hemispherical photographs were used by scientists in the last two decades, severely hampering comparability among studies. Here, an overview of the applied methods is reported. For the standardization of photographic exposure, a time-consuming reference measurement in the open land towards the unobstructed sky was required so far. The two Histogram Methods proposed here make use of the technical advances of digital cameras which enable users to assess a photograph’s histogram directly at the location of measurement. This avoids errors occurring due to variations in sky lighting happening in the time span between taking the reference measurement and reaching the sample location within the forest. The Histogram Methods speed up and simplify taking hemispherical photographs, and introduce an objectively applicable, standardized approach. We highlight the importance of correct exposure by quantifying the overestimation of gap fraction resulting from auto-exposed photographs under a wide range of canopy openness situations. In our study, gap fraction derived from auto-exposed photographs reached values up to 900% higher than those derived from non-overexposed photographs. By investigating the size of the largest gap per photograph and the number of small gaps (gaps contributing less than 0.1% to gap fraction), we concluded that the overestimation of gap fraction resulted mainly from the overexposure of vegetation surrounding large gaps.

Review of Advanced Daylighting Systems

Daylight is the most underutilized resource in modern buildings. Artificial light can be dispensed away in institutional buildings such as offices, banks, schools etc. having only daytime occupancy by proper architectural design of fenestrations The design of a day lighting space is both an art and a science. The biggest challenge facing the lighting designer is to admit only as much light as necessary and distribute it evenly throughout the space without introducing glare or heat. In hot / warm climates, it has become common practice in windows spaces to specify blinds and glazing with high shading coefficients to control glare and minimize heat gain. However, this practice reduces the effectiveness of lighting systems that dim automatically. Improved systems are needed to capture natural daylight and distribute it uniformly throughout a space while controlling heat gain and glare. One such system is the light shelf. Light shelves shade the space from direct sunlight and reflect this sunlight onto the ceiling for a deeper and more uniform distribution. Reflective blinds offer good control of glare and solar protection. Innovative day lighting systems are designed to redirect sunlight or sky light to areas where it is needed with excessive luminance and glare. These systems use optical devices that initiate reflections, refractions, and / or use total internal reflection of sunlight and sky light. Advanced day lighting systems can be designed to actively track the sun or passively control the direct sunlight and sky light. In this paper, we review the state of the art of several advanced day lighting systems which are designed to maximize the energy-saving potential of day lighting, while improving comfort and visual performance at an “affordable” cost.

Chlorophyll fluorescence kinetics, photosynthetic activity, and pigment composition of blue-shade and half-shade leaves as compared to sun and shade leaves of different trees

The chlorophyll (Chl) fluorescence induction kinetics, net photosynthetic CO2 fixation rates P N, and composition of photosynthetic pigments of differently light exposed leaves of several trees were comparatively measured to determine the differences in photosynthetic activity and pigment adaptation of leaves. The functional measurements were carried out with sun, half-shade and shade leaves of seven different trees species. These were: Acer platanoides L., Ginkgo biloba L., Fagus sylvatica L., Platanus x acerifolia Willd., Populus nigra L., Quercus robur L., Tilia cordata Mill. In three cases (beech, ginkgo, and oak), we compared the Chl fluorescence kinetics and photosynthetic rates of blue-shade leaves of the north tree crown receiving only blue sky light but no direct sunlight with that of sun leaves. In these cases, we also determined in detail the pigment composition of all four leaf types. In addition, we determined the quantum irradiance and spectral irradiance of direct sunlight, blue skylight as well as the irradiance in half shade and full shade. The results indicate that sun leaves possess significantly higher mean values for the net CO2 fixation rates P N (7.8-10.7μmol CO2m(-2)s(-1) leaf area) and the Chl fluorescence ratio R Fd (3.85-4.46) as compared to shade leaves (mean P N of 2.6-3.8μmol CO2m(-2)s(-1) leaf area.; mean R Fd of 1.94-2.56). Sun leaves also exhibit higher mean values for the pigment ratio Chl a/b (3.14-3.31) and considerably lower values for the weight ratio total chlorophylls to total carotenoids, (a+b)/(x+c), (4.07-4.25) as compared to shade leaves (Chl a/b 2.62-2.72) and (a+b)/(x+c) of 5.18-5.54. Blue-shade and half-shade leaves have an intermediate position between sun and shade leaves in all investigated parameters including the ratio F v/F o (maximum quantum yield of PS2 photochemistry) and are significantly different from sun and shade leaves but could not be differentiated from each other. The mean values of the Chl fluorescence decrease ratio R Fd of blue-shade and half-shade leaves fit well into the strong linear correlation with the net photosynthetic rates P N of sun and shade leaves, thus unequivocally indicating that the determination of the Chl fluorescence decrease ratio R Fd is a fast and indirect measurement of the photosynthetic activity of leaves. The investigations clearly demonstrate that the photosynthetic capacity and pigment composition of leaves and chloroplasts strongly depend on the amounts and quality of light received by the leaves.

Bright light exposure reduces TH-positive dopamine neurons: implications of light pollution in Parkinson's disease epidemiology

This study explores the effect of continuous exposure to bright light on neuromelanin formation and dopamine neuron survival in the substantia nigra. Twenty-one days after birth, Sprague–Dawley albino rats were divided into groups and raised under different conditions of light exposure. At the end of the irradiation period, rats were sacrificed and assayed for neuromelanin formation and number of tyrosine hydroxylase (TH)-positive neurons in the substantia nigra. The rats exposed to bright light for 20 days or 90 days showed a relatively greater number of neuromelanin-positive neurons. Surprisingly, TH-positive neurons decreased progressively in the substantia nigra reaching a significant 29% reduction after 90 days of continuous bright light exposure. This decrease was paralleled by a diminution of dopamine and its metabolite in the striatum. Remarkably, in preliminary analysis that accounted for population density, the age and race adjusted Parkinson's disease prevalence significantly correlated with average satellite-observed sky light pollution.

Azocalix[4]arene Strapped Calix[4]pyrrole: A Confirmable Fluoride Sensor

A new chromogenic fluoride sensor based on 1,3-di-p-nitrophenylazocalix[4]arene-calix[4]pyrrole (1) was designed and synthesized. The color of the solution of probe 1 changed upon the addition of any F(-), CH(3)CO(2)(-), PhCO(2)(-), and H(2)PO(4)(-) ions. However, from these ions the highly specific sensing of F(-) is achieved by the addition of Ca(2+) which leads to a color change from light sky blue (of 1·F(-)) back to the original light orange color of 1.

Biosignatures as revealed by spectropolarimetry of Earthshine

Low-resolution intensity spectra of Earth's atmosphere obtained from space reveal strong signatures of life ('biosignatures'), such as molecular oxygen and methane with abundances far from chemical equilibrium, as well as the presence of a 'red edge' (a sharp increase of albedo for wavelengths longer than 700 nm) caused by surface vegetation. Light passing through the atmosphere is strongly linearly polarized by scattering (from air molecules, aerosols and cloud particles) and by reflection (from oceans and land). Spectropolarimetric observations of local patches of Earth's sky light from the ground contain signatures of oxygen, ozone and water, and are used to characterize the properties of clouds and aerosols. When applied to exoplanets, ground-based spectropolarimetry can better constrain properties of atmospheres and surfaces than can standard intensity spectroscopy. Here we report disk-integrated linear polarization spectra of Earthshine, which is sunlight that has been first reflected by Earth and then reflected back to Earth by the Moon. The observations allow us to determine the fractional contribution of clouds and ocean surface, and are sensitive to visible areas of vegetation as small as 10 per cent. They represent a benchmark for the diagnostics of the atmospheric composition, mean cloud height and surfaces of exoplanets.

The variation of the polarized downwelling radiance distribution with depth in the coastal and clear ocean

The spectral polarized radiance distribution provides the most complete description of the light field that can be measured. However, this is a very difficult parameter to measure, particularly near the surface, because of its large dynamic range, changes in the skylight illumination, and waves at the air‐sea interface. To measure the Stokes vector of the downwelling light field, which contains the polarization information, requires the combination of four images acquired simultaneously. To achieve this, we used the downwelling polarized radiance distribution camera system (DPOL) during the Radiance in a Dynamic Ocean (RaDyO) program Santa Barbara Channel and Hawaiian experiments. DPOL consists of four fisheye lenses and a spectral filter changer that allow us to capture the downwelling hemisphere of the polarized radiance distribution at seven wavelengths. Our measurements show that very near the surface, for clear sky conditions, the dominant source of polarization is the refracted sky light. As one progresses in the water column the polarization due to light scattering by the water increases and polarization due to light scattering in the water becomes dominant.

Preparation and in vivo biological investigations on a novel radioligand for bone scanning: technetium-99m-labeled zoledronic acid derivative

To enable imaging at an earlier time after injection, a radiopharmaceutical with higher affinity for bone, larger ratio of bone-to-soft tissue uptake and more rapid clearance from blood is required. The nature of diphosphonic acid is a key factor to determine the advantages of the radiopharmaceuticals. The purpose of this study is to optimize the linker chain between the imidazolyl and geminal diphosphonate group in the zoledronic acid (ZL) to develop novel single photon emission computed tomography (SPECT) bone imaging agent. A novel ZL derivative, 1-hydroxy-3-(1H-imidazol-1-yl)propane-1,1-diyldiphosphonic acid (IPrDP), was successfully prepared and labeled with (99m)Tc in a high labeling yield. Biodistribution of (99m)Tc-IPrDP and (99m)Tc-ZL in normal mice were studied and compared. SPECT bone scanning was performed on the rabbit and a series of dynamic and static images were recorded by Philips SKY Light emission computed tomography. In the biodistribution studies, (99m)Tc-IPrDP exhibits significant advantages on the bone resorption and the clearance from soft tissues compared with (99m)Tc-ZL. Kinetics of blood clearance in mice showed that T(1/2α) and T(1/2β) of (99m)Tc-IPrDP were 1.47 min and 46.47 min, while those of (99m)Tc-ZL were 2.28 and 52.63 min respectively. Excellent images of the rabbit skeleton can be quickly obtained for (99m)Tc-IPrDP, which was faster than (99m)Tc-ZL and the clinically widely used bone imaging agent (99m)Tc-MDP (technetium-99m labeled with methylenediphosphonate). (99m)Tc-IPrDP possesses excellent characteristics for the potential application as a novel bone scanning agent.

Aerosol layer properties over Kyiv from AERONET/PHOTONS sunphotometer measurements during 2008–2009

The AErosol RObotic NETwork (AERONET) is one of the most developed ground-based networks for aerosol monitoring. Radiative measurements (solar irradiance extinction, aureole brightness and sky light polarization) are used by the AERONET inversion retrieval technique to derive a wide variety of aerosol particle properties and parameters that are important for estimations of aerosol influences on climate change. Within the framework of scientific cooperation between Université de Lille 1 and Taras Shevchenko National University (TSNU) of Kyiv (Kiev), a CIMEL CE 318-2 sunphotometer has been operating at Kyiv since March 2008. This article presents a preliminary analysis of the columnar aerosol properties retrieved from Kyiv sunphotometer measurements and one case study with unusual behaviour of the aerosol parameters. Version 2 of the AERONET inversion products (spectral aerosol optical thickness (AOT), the Ångström parameter (α), single-scattering albedo (SSA), size distribution and refractive index, and aerosol radiative forcing estimations) is considered in the analysis, demonstrating variability of aerosol properties and radiative forcing at the Kyiv observational site during a 1-year period.

Detecting the light of the night sky in Mars

In this paper a new methodology is outlined to detect the dust content in the Martian atmosphere during nighttime. In the previous Lander missions to Mars, scientists were able to determine the dust load in the Martian atmosphere during daylight using spectral lines of the Sun. Since the dynamics of Martian dust storms had been determined to be very rapid changing over times of hours and not days, it is imperative to determine the dust load during nighttime, so future astronauts to Mars can take protective measures for their equipment. They can also factor this effect for their planned activities during daytime. The new methodology greatly improves on the classical method for determining the extinction in the Earth’s atmosphere. The classical method uses observations of bright stars from which the optical depth, ?total, can then be deduced from the classical brightness equation. The classical method succeeds reasonably well at high elevation angles from the horizon but fails dramatically at low elevation angles. It also determines ?total from the slope of a plot of observed brightness of a bright star vs. air mass at all elevations. The plot shows a straight line at high elevations angles, which then curves and becomes uncertain at low elevation angles. The new methodology bypasses this severe difficulty by simply eliminating this plot, and by acquiring the brightness of a bright star above the atmosphere (no extinction) and compares it to the observed bright- ness of the same star below the atmosphere at all elevations.

基于偏振光传感器的移动机器人导航实验

A novel polarization sensor based on the mechanism of Sahara ant Cataglyphis was developed.To acquire the navigation performance of the sensor outside,several tests which used the output navigation angle of the sensor to control the mobile robot to move along a designed map was conducted.First,the structure and function prototype of the polarization sensor was presented.To improve the performance of polarization sensor,the optic integrating sphere was used as the polarized light source to replace the sky light,and the precision rotating table was taken as the standard angle to compensate the output angle of the sensor.After the compensation process,the angle output error of polarization sensor is within ±0.2°.Then,the mobile robot and how to use the polarization sensor to control the robot were briefly introduced.Finally,the process of navigation tests and the navigation performance comparison of the optical encoder and the polarization sensor were given.Results show that the latter method is better than the first one,and their average navigation position errors are 1.17 cm and 31.6 cm,respectively.According to the tests,the error of the polarization sensor doesn′t ac-cumulate with the time and can give the navigation message independently.In conclusion,it would play an important role in the automation navigation systems in further way.

Equipment and photo exposure in hemispherical photography in forest research

Sprzęt i ekspozycja zdjęć w fotografii hemisferycznej w badaniach leśnych

New evidence for lack of CMB power on large scales

A digitalized temperature map is recovered from the first light sky survey image published by the Planck team, from which an angular power spectrum is derived. The amplitudes of the low multipoles measured from the preliminary Planck power spectrum are significantly lower than that reported by the WMAP team. Possible systematical effects are far from enough to explain the observed low-l differences.

Geophysics: Synthetic sky light

Geophysics: Synthetic sky light

Specialized ommatidia of the polarization-sensitive dorsal rim area in the eye of monarch butterflies have non-functional reflecting tapeta

Many insects exploit sky light polarization for navigation or cruising-course control. The detection of polarized sky light is mediated by the ommatidia of a small specialized part of the compound eye: the dorsal rim area (DRA). We describe the morphology and fine structure of the DRA in monarch butterflies (Danaus plexippus). The DRA consists of approximately 100 ommatidia forming a narrow ribbon along the dorsal eye margin. Each ommatidium contains two types of photoreceptor with mutually orthogonal microvilli orientations occurring in a 2:6 ratio. Within each rhabdomere, the microvilli are well aligned. Rhabdom structure and orientation remain constant at all retinal levels, but the rhabdom profiles, as seen in tangential sections through the DRA, change their orientations in a fan-like fashion from the frontal to the caudal end of the DRA. Whereas these properties (two microvillar orientations per rhabdom, microvillar alignment along rhabdomeres, ommatidial fan array) are typical for insect DRAs in general, we also report and discuss here a novel feature. The ommatidia of monarch butterflies are equipped with reflecting tapeta, which are directly connected to the proximal ends of the rhabdoms. Although tapeta are also present in the DRA, they are separated from the rhabdoms by a space of approximately 55 μm effectively inactivating them. This reduces self-screening effects, keeping polarization sensitivity of all photoreceptors of the DRA ommatidia both high and approximately equal.Electronic supplementary materialThe online version of this article (doi:10.1007/s00441-009-0886-7) contains supplementary material, which is available to authorized users.

Selection of photomultipliers for the Cherenkov Telescope Array facility

The future ground-based gamma-ray facility—Cherenkov Telescope Array (CTA)—is aiming for a sensitivity of 1 mCrab at energies above 20 GeV. This goal in sensitivity is aiming for an order of magnitude increase compared to currently operating instruments H.E.S.S., MAGIC, CANGAROO III and VERITAS. In order to provide high sensitivity and low energy threshold the photosensors should have highest possible photon detection efficiency (PDE), low after-pulsing rate and good single photoelectron resolution. Photosensors of Cherenkov telescopes are permanently exposed to the background light of the night sky, therefore a long life time and low fatigue are also necessary conditions. Various photomultipliers (PMT) of 1–2 in. size from PHOTONIS and HAMAMATSU were tested in MPI for Physics in Munich. Comparative measurements of quantum efficiency, timing, after-pulsing and single photoelectron resolution will be presented here. An evaluation of Electron Tubes photomultipliers is ongoing