21 research outputs found
Development of a Time-Integration Method for Analyzing the Photoresponse of Image Sensors: Theoretical and Experimental Verification with Digital Cameras
No full textThis study introduces a novel method for analyzing image sensors, supported by both theoretical and experimental verification. We first theoretically derived that when sinusoidal light with constant amplitude is directed onto an image sensor with fixed exposure times, the radiant energy reaching each pixel remains unchanged, irrespective of frequency fluctuations. However, when a rapid brightness variation significantly influences the photoresponse of the photodiodes in the image sensor, pixel values are expected to vary with frequency. To experimentally assess the photoresponse of image sensors, we developed a light-emitting diode (LED) light source capable of emitting sinusoidal waves up to 1 MHz, paired with a photosensor designed for this frequency range. We then exposed the image sensors of three cameras to the sinusoidal light and analyzed the frequency dependence of the pixel values. The experimental results demonstrated that the pixel values remained nearly constant (relative error of approximately 5 % or less) up to 1 MHz, showing no frequency dependence in the photoresponse within this range. These findings validate the theoretical analytical method and confirm that the image sensors of the three cameras accurately captured sinusoidal light up to 1 MHz without being influenced by the physical properties of the sensors or design parameters. However, this does not establish the limit or cutoff frequency of the image sensors
Theoretical formulation and experimental validation of brightness evaluation using digital cameras
No full textIn this study, we formulated the brightness relation of two digital photos captured by a single digital camera and verified it experimentally. The experimental results suggested that the used zoom lens has an intrinsic error, thereby making accurate photometry difficult. However, by dividing the brightness by the intrinsic error of the zoom lens, performing accurate photometry is possible. The photometry results with the single camera suggested that the brightness relation derived, and the magnitude system in astronomical photometry are applicable to widespread general photometry.論
Color analysis based on the color indices of lightning channels obtained from a digital photograph
No full textIn this study, we present an analysis using the color indices B-G,B-R, and G-R of lightning channels obtained from a digital photograph. We used color-magnitude diagrams (CMDs) modified from the traditional CMDs employed in astronomical photometry, (B-G) versus (G-R) color-color diagrams (CCDs), two-dimensional (2D) color-index images for the color indices B-G,B-R, and G-R, and a 2D brightness image to analyze the colors and brightness of the lightning channels. The CMDs and CCDs for the lightning leader channels showed that the intensity of B-band and R-band light from those channels exceeds that of the G-band light. The 2D color-index images for B-G,B-R, and G-R and the 2D brightness image indicate spatial variations in the lightning channels. The spatial variabilities of the 2D color indices and 2D brightness indicate that the intensity of the B-band light exceeds that of the G- and R-band light around a bright channel with a high electric current (i.e., the plasma is highly ionized).論
Evaluation of the brightness of lightning channels and branches using the magnitude system: Application of astronomical photometry
No full textIn this paper, we have evaluated the brightness of lightning leaders shown in a digital still image by applying the astronomical magnitude system. In order to analyze the only lightning leaders, these were extracted from the digital still image. For photometry of the lightning leaders, there is no a standard reference source such as Vega in astronomical photometry. Therefore, assuming the maximum pixel value 255 (in 256 levels) as the brightness of a standard reference source, the magnitude of the lightning leaders was obtained. The result showed that the magnitude of the lightning leaders vary spatially (i.e. 2D spatial variability). Furthermore, the result suggested that a low current channel is high magnitude and a high current channel is low magnitude. Keywords: Lightning, Fechner’s law, Magnitude system, Astronomical photometry, Image analysi
Spatial variability of correlated color temperature of lightning channels
No full textAbstractIn this paper, we present the spatial variability of the correlated color temperature of lightning channel shown in a digital still image. In order to analyze the correlated color temperature, we calculated chromaticity coordinates of the lightning channels in the digital still image. From results, the spatial variation of the correlated color temperature of the lightning channel was confirmed. Moreover, the results suggest that the correlated color temperature and peak current of the lightning channels are related to each other
Caste-biased movements by termites in isolation
No full textAbstractThe caste system of termites is an example of phenotypic plasticity. The castes differ not only in morphology and physiology, but also in behavior. As most of their behaviors within colonies involve nestmates, it is difficult to extract innate differences among castes. In this study, we focused on movement patterns of isolated individuals ofHodotermopsis sjostedti. We observed distinct clusters in movement patterns over 30 min, which indicates that termites have multiple innate modes of movement. The use of these modes is biased among castes, among which neotenics had a caste-specific mode and soldiers moved more actively than workers or neotenics. These caste biases may reflect different adaptive responses to social isolation. Our study provides a basis for a deeper understanding of the roles of individual movements in social behaviors.Summary StatementMovement patterns of termites in isolation were described for different castes. We proposed movements as a novel caste-specific characteristics in social insects.</jats:sec
Nitric oxide suppresses the energy transduction of plant mitochondria
No full textPlant mitochondria are known to possess two respiratory electron transport pathways, i.e. the cytochrome and alternative pathways. The cytochrome pathway, which ends at cytochrome c oxidase (COX), is almost identical to the respiratory electron transport pathway in animal mitochondria. The alternative pathway, which ends at alternative oxidase (AOX), is unique in plants, fungi and parasitic protozoa. Although thermogenesis has been considered as a possible role for alternative pathway. the physiological significance of this non-energy producing pathways is not fully understood. Millar and Day (1996) have proposed that the alternative pathway may play an important role in preventing oxidative damage induced by nitric oxide (NO). Nitric Oxide (NO) is a free radical that can act as a signal messenger in animal cells (Packer 1996). It has been known that NO sometimes disturbs the energy transduction system in animal mitochondria by inhibiting the activity of COX (Brookes e al. 1999), In contrast to extensive knowledge on biochemistry and physiology on NO in animal systems, the source and role of NO in plants have been not yet confirmed. We have recently revealed that plant nitrate reductase (NR) is capable of converting nitrite to NO in the presence of NADH (Yamasaki, Sakihama 2000; Yamasaki 2000). NR is a key enzyme in nitrate assimilation pathway. By using the NR-catalyzed NO production system, here we demonstrate in vitro effects of NO on the energy transduction system of mitochondria. The results presented in this study provide substantial evidence to confirm that the plant alternative pathway is resistant to NO
Adsorption of diatomic molecules on iron tape-porphyrin : A comparative study
No full textWe investigated the adsorption of diatomic molecules, CO, NO, and O_2, denoted by XO on iron tapeporphyrin FeTP using first-principles calculations based on density functional theory. In this work, we present the structure and electronic properties of iron tape-porphyrin and its complexes with CO, NO, and O_2. The binding of such diatomic molecules to FeTP gave rise to significant changes on both the geometric structure and electronic properties of FeTP. We found that in all FeTP complexes with diatomic molecules, the Fe atom moves out of the porphyrin plane toward the adsorbed molecule. The energy of the iron-diatomic molecule bond increases in the order of Fe-O_2 0.554 eV Fe-CO 1.225 eV Fe-NO 1.719 eV . At its stable position, the Fe-X-O angle increases in the order of Fe-C-O Fe-N-O Fe-O-O. The changes in geometric structure are in accordance with other density functional theory calculations and experimental results for porphyrin molecule. As regards the electronic properties, there appears an energy gap between the conduction band and valence band in CO-adsorbed and NO-adsorbed cases with a more pronounced energy gap in the former, while none was observed in the O_2-adsorbed case. We attribute these changes in electronic properties to the strong interaction involving the d orbitals of the Fe atom and the We investigated the adsorption of diatomic molecules, CO, NO, and O_2, denoted by XO on iron tapeporphyrin FeTP using first-principles calculations based on density functional theory. In this work, we present the structure and electronic properties of iron tape-porphyrin and its complexes with CO, NO, and O_2. The binding of such diatomic molecules to FeTP gave rise to significant changes on both the geometric structure and electronic properties of FeTP. We found that in all FeTP complexes with diatomic molecules, the Fe atom moves out of the porphyrin plane toward the adsorbed molecule. The energy of the iron-diatomic molecule bond increases in the order of Fe-O_2 0.554 eV Fe-CO 1.225 eV Fe-NO 1.719 eV . At its stable position, the Fe-X-O angle increases in the order of Fe-C-O Fe-N-O Fe-O-O. The changes in geometric structure are in accordance with other density functional theory calculations and experimental results for porphyrin molecule. As regards the electronic properties, there appears an energy gap between the conduction band and valence band in CO-adsorbed and NO-adsorbed cases with a more pronounced energy gap in the former, while none was observed in the O_2-adsorbed case. We attribute these changes in electronic properties to the strong interaction involving the d orbitals of the Fe atom and the π＾* orbitals of diatomic molecules. Specifically, for the CO and NO adsorbed on FeTP cases, the change in electronic properties is attributed to the strong hybridization of d_ and d_ orbitals of the Fe atom and π＾* orbitals. For O_2 adsorbed on FeTP, the hybridization of the d_z2 orbital of the Fe atom and π* orbitals plays the key role in O_2–iron tape-porphyrin interaction.* orbitals of diatomic molecules. Specifically, for the CO and NO adsorbed on FeTP cases, the change in electronic properties is attributed to the strong hybridization of d_ and d_ orbitals of the Fe atom and π＾* orbitals. For O_2 adsorbed on FeTP, the hybridization of the d_z2 orbital of the Fe atom and π* orbitals plays the key role in O_2–iron tape-porphyrin interaction.論
