Different Conditions Of Illumination Research Articles

Relative Magnitude of Gaussian Curvature via Self-Calibration

Gaussian curvature encodes important information about object shape. This paper presents a technique to recover the relative magnitude of Gaussian curvature from multiple images acquired under different conditions of illumination. Previous approaches make use of a separate calibration sphere. Here, we require no distinct calibration object. The novel idea is to use controlled motion of the target object itself for self-calibration. The target object is rotated in fixed steps in both the vertical and the horizontal directions. A distinguished point on the object serves as a marker. Neural network training data are obtained from the predicted geometric positions of the marker under known rotations. Four light sources with different directions are used. An RBF neural network learns the mapping of image intensities to marker position coordinates along a virtual sphere. Neural network maps four image irradiances on the target object onto a point on a virtual sphere. The area value surrounded by four mapped points onto a sphere gives an approximate value of Gaussian curvature. The modification neural network is learned for the basis function to obtain more accurate Gaussian curvature. Spatially varying albedo is allowed since the effect of albedo can be removed. It is shown that self-calibration makes it possible to recover the relative magnitude of Gaussian curvature at each point without a separate calibration object. No particular functional model of surface reflectance is assumed. Experiments with real data are demonstrated. Quantitative error analysis is provided for a synthetic example.

分光的な光反射計測に基づいた物体の表面反射特性推定

This paper describes a method for estimating surface properties of an object, including an index of refraction, surface spectral reflectance, and reflection model parameters. These reflection properties of the object surface are modeled using optical parameters of the surface material. These parameters are estimated from camera RGB sensor measurements for reflection intensity of an object surface at different conditions of illumination and viewing. In order to estimate these parameters of the reflection model, we develop an apparatus for measuring reflection intensity on the object surface. The spectral reflectance is estimated by applying the linear finite model and the camera RGB sensor data. Finally, all estimates are combined for rendering of the object under different illumination and viewing conditions.

Effects of visual conditions and prey density on feeding kinetics of paralarvae of Octopus vulgaris from a laboratory spawning

Consumption rate and feeding success of newly hatched paralarvae of the cephalopod Octopus vulgaris preying on Artemia larvae were investigated in relation to visual conditions and prey density. Each paralarva was tested individually using a small-scale experimental setup; consumption over one day was measured at 208C. A factorial experiment was designed to investigate the effects on the consumption rate of two predictor variables: illumination/background (three levels: 7.5 W m 22 white light þ white background, 7.5 W m 22 white light þ blue background, darkness) and prey density (four levels: 2.35, 4.70, 9.40 and 14.10 Artemia metanauplii ml 21 ). Consumption rate varied significantly between different conditions of illumination and prey density. Light enhanced consumption rate, but different backgrounds yielded similar rates. The maximal consumption rate under illumination was close to 16 Artemia paralarva 21 day 21 , and it was around 5 Artemia paralarva 21 day 21 for assays in darkness. The predatory efficiency, measured as the proportion of prey consumed, was significantly affected by prey density, pointing to a type III functional response. The number of nonfeeding paralarvae was significantly higher in darkness and at low prey density.

Rapid Chlorophyll a Fluorescence Transients of Lemna minor Leaves as Indication of Light and Exogenous Electron Carriers Effect on Photosystem II Activity

By using saturating flash, we investigated the change in the rapid fluorescence rise when Lemna minor leaf was exposed to different light conditions and treated with exogenous electron acceptors (methyl viologen and duroquinone) and electron donor (hydroxylamine). Investigation was carried out by using combined pulse amplitude modulated fluorometer and plant efficiency analyzer system, which were employed simultaneously to provide different light conditions and to induce rapid fluorescence rise respectively. We have shown that when leaf of L. minor was exposed to different conditions of illumination, rapid fluorescence rise was greatly influenced by the electron transport functions beyond quinone A-plastoquinone reduction. This was indicated by the change in both fluorescence yield and appearance time of the different transients. When exogenous electron donor (hydroxylamine) and acceptors (methyl viologen and duroquinone) were applied in in vivo condition, we showed that rapid fluorescence rise represented a reliable indicator of PSII-PSI electron transport state and energy dissipation process.

Spectral contrasts for landmark navigation

Visual robot navigation in outdoor environments would benefit from an illumination-independent representation of images. We explore how such a representation, comprising a black skyline of objects in front of a white sky, can be obtained from dual-channel spectral contrast measures. Light from sky and natural objects under different conditions of illumination was analyzed by five spectral channels: ultraviolet, blue, green, red, and near infrared. Linear discriminant analysis was applied to determine the optimal linear separation between sky and object points. A statistical comparison shows that contrasts with large differences in the wavelength of the two channels, specifically ultraviolet-infrared, blue-infrared, and ultraviolet-red, yield the best separation. Within a single channel, the best separation was obtained for ultraviolet light. The gain in separation quality when all five channels were included is relatively small.

Light/dark cycle manipulation influences mice behaviour in the elevated plus maze

The sensitization of animal models of anxiety is of great importance to detect potential anxiolytic drugs. Our goal was to evaluate the influence of manipulations of the light/dark cycle on the basal anxious behaviour of mice and the efficacy of two anxiolytic treatments in the mouse elevated plus maze (EPM). Male Swiss mice were exposed to different conditions of illumination for one week prior to testing. In the first experiment of the study, we evaluated the anxiolytic effects of diazepam, at the dose of 1 mg/kg, intraperitoneally (i.p.) administered 30 min before the test. In the second experiment, we examined the effects of WAY 100635, a 5-HT 1A receptor antagonist, at the doses of 0.03 and 2 mg/kg, i.p. administered 30 min before the test. The locomotor activity of control mice and the anxiolytic efficacy of diazepam in the EPM were not affected by manipulation of the light/dark cycle. Conversely, the effects of WAY 100635, which were qualitatively different from those of diazepam, seemed to be influenced by the illumination conditions imposed before the test. We can conclude that diazepam's effect, which is characterized by a strong “disinhibition”, was more robust than the 5-HT 1A antagonist's effect, which was more anxioselective. Moreover, the light conditions imposed on mice before the test may be an important factor in the variability of the response to serotonergic but not to benzodiazepine treatments.

Evaluating concrete surfaces using an image analysis process

This study concerns the assessment of non-coated concrete surfaces in civil engineering structures and buildings. Imaging is used as an objective tool for evaluation of the surfaces. Because images of surfaces taken under different conditions of illumination are difficult to compare, this paper presents a method suggested by the building firm GTM Construction and the laboratory LMDC for obtaining images of luminance L ∗ simulated for one standard illuminant (D65). Concrete surfaces can be qualified with respect to uniformity of tint and distribution of surface bubbles. The process described is based on image analysis. Not only can the results be compared with current standards, but the method also gives access to additional, accurate information such as the distribution of defects and the size of surface bubbles. This method is already applied on building sites for experts’ assessments and in the laboratory for the study of the parameters influencing surface quality.

Protein-based integrated optical switching and modulation

The static and dynamic response of optical waveguides coated with a thin protein film of bacteriorhodopsin was investigated. The size and kinetics of the light-induced refractive index changes of the adlayer were determined under different conditions of illumination. The results demonstrate the applicability of this protein as an active, programmable nonlinear optical material in all-optical integrated circuits.

Mapping neural network computation of high‐resolution radiant fluxes of inhomogeneous clouds

In this study, we evaluated the ability of Mapping Neural Networks (MNNs) to calculate the high‐resolution radiant fluxes of one‐dimensional and two‐dimensional inhomogeneous clouds. The tests were done for different types of clouds, radiant fluxes, and wavelengths under different conditions of illumination. The MNNs were trained with training data sets composed of the Monte Carlo (MC) radiant fluxes of bounded cascade clouds and used to compute first the high‐resolution MC radiant fluxes (reflectance, transmittance, and absorptance) of bounded cascade inhomogeneous clouds. The tests showed their rather good performance, which was compared with that of the Nonlocal Independent Pixel Approximation when possible. Their generalization ability was, second, tested with inhomogeneous clouds of other types: white noise clouds and bounded cascade inhomogeneous clouds with fractional cloud cover. In these cases, the MNNs, trained with different fields, have still good performance. However, the results were found to be much better for the reflectance than for the transmittance and absorptance. In the case of fractional cloud cover, debased responses appear as well in transition zones. We show that the generalization ability could be improved significantly by completing the training sets with new additional patterns when they are applied to types of inhomogeneous clouds different than the clouds of the training set. These results reveal that the MNNs represent a flexible method of function approximation to compute the high‐resolution radiant flux of bounded cascade and other inhomogeneous clouds.

Neural network analysis of the radiative interaction between neighboring pixels in inhomogeneous clouds

In this study, we analyzed the effect of the radiative interaction between neighboring pixels on the high‐resolution radiant flux of bounded cascade inhomogeneous clouds by using a one‐layer mapping neural network as generalized regression analysis. The analysis was done for reflectance, transmittance, and absorptance at different wavelengths under different conditions of illumination. The sign and magnitude of output coefficients indicate how neighboring pixels contribute to the radiant flux of a target pixel. We found that the variation of output coefficients with the distance from the target pixel changes significantly in its shape and horizontal extent not only with the type of radiant flux we consider but also with the wavelength and solar zenith angle. The mapping neural network clearly reveals the asymmetric feature of radiative interaction between neighboring pixels under oblique illumination, which illustrates the shadowing and enhancing effects of local cloud inhomogeneity. The present analysis shows that the mapping neural network is a flexible method of analysis when used as a generalized regression analysis.

Photosynthetic electron flow regulates transcription of the psaB gene in pea (Pisum sativum L.) chloroplasts through the redox state of the plastoquinone pool.

Plants respond to changing light conditions by altering the stoichiometry between components of the photosynthetic electron transport chain of chloroplast thylakoids. We measured specific run-on transcription of the chloroplast genes psaB, psbA and rbcL in pea (Pisum sativum L.) seedlings grown under three different conditions of illumination: light selective for photosystem I (PSI-light); light selective for photosystem II (PSII-light); and a combination of PSI- and PSII-light (mixed light, ML). The transcriptional rate of the psaB gene increased under PSII-light and decreased under PSI-light, while the transcriptional rates of the psbA and rbcL genes were affected only in a non-specific way. Similar effects also occurred in plants grown under ML and switched to either PSI- or PSII-light for 4 h. Addition of the inhibitors of photosynthetic electron transport 3-(3,4 dichlorophenyl)-1,1-dimethylurea (DCMU) and 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB) influenced psaB transcription in isolated, illuminated chloroplasts: DCMU addition resulted in oxidation of the plastoquinone pool and decreased transcription of psaB; DBMIB addition resulted in reduction of the plastoquinone pool and increased transcription of psaB. The experimental results obtained in vivo and in vitro provide evidence for coupling between the redox state of plastoquinone and the rate of transcription of the psaB gene in pea.

Thermally stimulated processes related to photochromism of scandium doped sillenites

The low temperature photochromism of the scandium doped sillenites was investigated. The time dependence of the light induced absorption was measured for different conditions of the stimulation process. The optical coloring spectrum and the optical bleaching spectrum have been established on the basis of the obtained kinetics. The distinction between short time illumination (<20 s) and long time illumination (>1000 s) in the coloring process has been noticed. The thermal bleaching curves obtained for the different conditions of illumination provided information about energy of the shallow trap levels responsible for the thermal stability of the photochromic effect. It has been shown that there are five energy levels involved in the thermal bleaching processes but their activity is strongly related to the conditions of illumination. Some arguments are presented that the investigation of thermal bleaching could be used as a good tool for the shallow trap spectroscopy as it is in the conventional thermoluminescence and measurements of thermally stimulated currents.

Measurement and analysis of optical inhomogeneities with steep refractive-index gradients in stationary transparent media by speckle-interferometry methods

A version of a scheme of speckle interferometry is considered, which is intended for the analysis of the stationary distribution pattern of steep refractive-index gradients in optically transparent media. The application of this approach to problems of hydrodynamics and gas dynamics allows one to determine the structure of distribution of optical inhomogeneities in liquid and gaseous flows or media. The method is based on the recording of patterns of two speckle structures obtained in the plane of image formation of the object by an optical system when the object is illuminated by radiation having an auxiliary speckle structure. The patterns correspond to the two positions of an object shifted somewhat in the direction of the optical axis of the system. Contrary to the common methods of speckle interferometry, only the state of the object being investigated for two different conditions of illumination by the probe radiation is used for the detection in this case. The difficulties arising in the measurements of the objects with steep refractive-index gradients by the known methods of speckle interferometry are accordingly practically eliminated in the scheme under consideration. In comparison with the schlieren phase methods, this method offers higher possibilities in the variation of sensitivity.

Continuous flow photochemical reactor for solar decontamination of water using immobilized TiO 2

A photochemical reactor is designed for solar decontamination of organic pollutants in water, where the nanocrystalline photocatalyst TiO 2 is immobilized on glass. The reactor modules could be connected in series and/or parallel to achieve desired flow rates under different conditions of illumination and degree of contamination. Methyl violet and phenol was found to completely degrade under solor irradiation and flow rates of 102–138 ml/h.

Patch Utilization by Three Species of Chilean Rodents Differing in Body Size and Mode of Locomotion

Predation risk influences differentially the foraging decisions of rodent species with different morphologies (body size and locomotion type). Explanations for different foraging patterns have been derived largely from the behavior of heteromyid rodents, and there is a lack of information regarding the behavior of other rodent groups with different morphologies. Nevertheless, the explanations are thought to be applicable to other groups. In order to study the generality of hypotheses about the effect of morphology on foraging ecology, I investigated the foraging decisions of Chilean sigmodontine rodents (Muridae) in the laboratory, experimentally manipulating nocturnal illumination (a surrogate of predation risk) and food distribution. Three coexisting rodent species from the Chilean matorral were compared: two quadrupeds, one with large body size (Phyllotis darwini) and another with small body size (Abrothrix olivaceus), and one small species with bipedal escape behavior (Oligoryzomys longicaudatus). The species did not differ in patch utilization and food consumption in response to different food distributions. However, there was an overall significant effect of illumination on food consumption. When illumination was higher, A. olivaceus and P. darwini increased food transportation to the refuge and decreased patch consumption and total food consumption. They also increased significantly the number of trips between food patch and refuge. P. darwini showed the most cautious foraging behavior. O. longicaudatus was insensitive to different conditions of illumination. It is argued that a large body size and quadrupedal locomotion seem to confer higher sensitivity to nocturnal illumination. Bipedality may confer less vulnerability to predation, and quadrupedal species show facultative central—place foraging, diminishing a possible greater vulnerability to potential risk. Former explanations for different foraging behaviors under the risk of predation may not be as general as previously assumed. This study emphasizes the need to consider the particular features of the system under investigation.

Nonsteady state ionosphere‐plasmasphere coupling of superthermal electrons

Numerical solutions to the nonsteady state kinetic equation which describes the transport of superthermal electrons in the ionosphere and plasmasphere between the magnetically conjugate regions of the ionosphere are presented. The distribution function in time, distance along arbitrary geomagnetic field lines, energy, and pitch angle are among the parameters calculated by the model. This model represents a unified approach by self‐consistently coupling the interaction of the two hemispheres and the trapping of superthermal electrons in the plasmasphere. Our calculations take into account the various ionization and excitation processes and the effect of an inhomogeneous magnetic field (i.e., magnetic mirroring of precipitating electrons and focusing of escaping electrons along magnetic field lines). Omnidirectional flux spectra and pitch angle distributions are shown for various L shells and situations, and the features are described in detail. Nonsteady state calculations predict that a depleted flux tube can take several hours to reach steady state levels again. Plasmaspheric transparencies are calculated for different conditions of illumination, scattering processes in the conjugate ionospheres, and field‐aligned gradients of the thermal plasma density. Plasmaspheric transparency is found to be a complicated function of not only the plasmaspheric thermal plasma but also the ionospheric sources and scattering processes. A phenomenological model is used to describe the energy transmission, reflection, and deposition in the plasmasphere. By studying the ionosphere and plasmasphere as one system rather than two separate ones, substantial corrections are introduced in the values of key parameters describing photoelectron fluxes.

Gradient and curvature from the photometric-stereo method, including local confidence estimation

The photometric-stereo method is one technique for three-dimensional shape determination that has been implemented in a variety of experimental settings and that has produced consistently good results. The idea is to use intensity values recorded from multiple images obtained from the same viewpoint but under different conditions of illumination. The resulting radiometric constraint makes it possible to obtain local estimates of both surface orientation and surface curvature without requiring either global smoothness assumptions or prior image segmentation. Photometric stereo is moved one step closer to practical possibility by a description of an experimental setting in which surface gradient estimation is achieved on full-frame video data at near-video-frame rates (i.e., 15 Hz). The implementation uses commercially available hardware. Reflectance is modeled empirically with measurements obtained from a calibration sphere. Estimation of the gradient (p, q) requires only simple table lookup. Curvature estimation additionally uses the reflectance map R(p, q). The required lookup table and reflectance maps are derived during calibration. Because reflectance is modeled empirically, no prior physical model of the reflectance characteristics of the objects to be analyzed is assumed. At the same time, if a good physical model is available, it can be retrofitted to the method for implementation purposes. Photometric stereo is subject to error in the presence of cast shadows and interreflection. No purely local technique can succeed because these phenomena are inherently nonlocal. Nevertheless, it is demonstrated that one can exploit the redundancy in three-light-source photometric stereo to detect locally, in most cases, the presence of cast shadows and interreflection. Detection is facilitated by the explicit inclusion of a local confidence estimate in the lookup table used for gradient estimation.

The gamma subunit of R-phycoerythrin and its possible mode of transport into the plastid of red algae

R-phycoerythrin is the major light-harvesting pigment protein of most red algal phycobilisomes. It is composed of three pigmented polypeptide subunits, the alpha, beta, and gamma. While alpha and beta phycoerythrin subunits are each unique in the red alga Aglaothamnion neglectum, there are two different gamma subunits with distinct molecular masses. Both gamma subunits are pigmented by virtue of covalently attached linear tetrapyrroles. The amino acid sequence of one of the gamma subunits, as deduced from the nucleotide sequence of a cDNA clone, has no significant similarity to any known sequence in the data bases. This result is surprising, since the gamma subunit of phycoerythrin is thought to have a function that is similar to cyanobacterial linker polypeptides. The A. neglectum gamma subunit is synthesized as a 36-kDa precursor protein that is processed at the amino terminus to yield a 33-kDa mature protein. The amino-terminal extension was able to direct the pea small subunit of Rubisco into isolated pea chloroplasts. This result suggests that red algae transport proteins into the plastid by a mechanism similar to that of higher plants. There are significant changes in levels of mRNA encoding the gamma 33 subunit when A. neglectum is grown under different conditions of illumination and in nitrogen-deficient medium. These changes parallel those previously observed for transcripts encoding the alpha and beta phycoerythrin subunits. Hence, there may be coordinated expression of nuclear and plastid-encoded phycoerythrin subunit genes.

Localized thinning of GaAs/GaAlAs nanostructures by a combined scanning electron micrograph/focus ion beam system for high-quality cross-sectional transmission electron microscopy samples

A new versatile procedure combining conventional lithography and focused ion beam coupled to scanning electron microscopy to micromachine high-quality cross-sectional transmission electron microscopy (TEM) samples is proposed. Electron transparent areas are generated with a high degree of localization, within 0.1 μm, over distances of several millimeters in GaAs/GaAlAs heterostructures. TEM observations demonstrate that no defects are introduced during the thinning process and different conditions of illumination are achievable.

Light distribution, transfer and utilization in the marine red alga Porphyra perforata from photoacoustic energy-storage measurements

Light energy utilization in Porphyra perforata was monitored by the photoacoustic method in different conditions of illumination. Auxiliary chlorophyll a fluorescence measurements were made to estimate the fraction of open photosystem II (PS II) reaction centers. These measurements allowed a consistent quantitation of excitation distribution and transfer from PS II to PS I under the physiological conditions used. Maximum energy storage was obtained with modulated light absorbed almost exclusively by the phycobilins (light 2). Modulated light absorbed by chlorophyll a (light I) gave much smaller energy storage (about 1 3 of the maximum), which could be enhanced to the maximum by addition of background light 2. Addition of increasing intensities of background light 1 to modulated light 2 did not initially induce any effect and then decreased the energy storage to about half of the maximum. From the above results and with simple mathematical modelling, numbers were obtained for light distribution and energy transfer parameters. From the enhancement saturation curves of the effect of background light 2 on the energy storage in modulated light 1 we conclude that in state 1 light 2 is exclusively absorbed in PS II and that there is no energy transfer to PS I from open PS II reaction centers. From the value of the energy storage for light 2 in state 1 and the degree of openness of PS II reaction centers it is possible to conclude that energy transfer to PS I occurs from closed PS II reaction centers with a probability approaching 1. In state 2 light 2 is distributed more evenly (approximately in a ratio PS II PS I of 0.55:0.45) either by energy transfer via PS II from open PS II reaction centers, or by direct interactions of the phycobilins and PS I. Comparison of the maximum fluorescence values in the two states favors the second possibility. Energy transfer from PS II units with closed reaction centers occurs again in state 2 with a probability approaching 1. Comparison of energy utilization and oxygen evolution in light 1 relative to light 2 and the inhibitory effect of DCMU, which is complete in light 2 but only partial in light 1, suggests the existence of two types of PS I units: one type is engaged in electron transfer from PS II and the other type specializes in cyclic electron flow. The above quantitative analysis allows to estimate the ratio of the two types of PS I unit to be roughly about 0.3:0.7, respectively.