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1
Rocher, Javier, Jose M. Jimenez, Jesus Tomas, and Jaime Lloret. "Low-Cost Turbidity Sensor to Determine Eutrophication in Water Bodies." Sensors 23, no. 8 (2023): 3913. http://dx.doi.org/10.3390/s23083913.
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Eutrophication is the excessive growth of algae in water bodies that causes biodiversity loss, reducing water quality and attractiveness to people. This is an important problem in water bodies. In this paper, we propose a low-cost sensor to monitor eutrophication in concentrations between 0 to 200 mg/L and in different mixtures of sediment and algae (0, 20, 40, 60, 80, and 100% algae, the rest are sediment). We use two light sources (infrared and RGB LED) and two photoreceptors at 90° and 180° of the light sources. The system has a microcontroller (M5stacks) that powers the light sources and obtains the signal received by the photoreceptors. In addition, the microcontroller is responsible for sending information and generating alerts. Our results show that the use of infrared light at 90° can determine the turbidity with an error of 7.45% in NTU readings higher than 2.73 NTUs, and the use of infrared light at 180° can measure the solid concentration with an error of 11.40%. According to the determination of the % of algae, the use of a neural network has a precision of 89.3% in the classification, and the determination of the mg/L of algae in water has an error of 17.95%.
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Lerch, Ph, P. Dumas, T. Schilcher, et al. "Assessing noise sources at synchrotron infrared ports." Journal of Synchrotron Radiation 19, no. 1 (2011): 1–9. http://dx.doi.org/10.1107/s0909049511041884.
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Today, the vast majority of electron storage rings delivering synchrotron radiation for general user operation offer a dedicated infrared port. There is growing interest expressed by various scientific communities to exploit the mid-IR emission in microspectroscopy, as well as the far infrared (also called THz) range for spectroscopy. Compared with a thermal (laboratory-based source), IR synchrotron radiation sources offer enhanced brilliance of about two to three orders of magnitude in the mid-IR energy range, and enhanced flux and brilliance in the far-IR energy range. Synchrotron radiation also has a unique combination of a broad wavelength band together with a well defined time structure. Thermal sources (globar, mercury filament) have excellent stability. Because the sampling rate of a typical IR Fourier-transform spectroscopy experiment is in the kHz range (depending on the bandwidth of the detector), instabilities of various origins present in synchrotron radiation sources play a crucial role. Noise recordings at two different IR ports located at the Swiss Light Source and SOLEIL (France), under conditions relevant to real experiments, are discussed. The lowest electron beam fluctuations detectable in IR spectra have been quantified and are shown to be much smaller than what is routinely recorded by beam-position monitors.
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Niu, Jin Xing, and Heng Can Li. "Principal-Component Calculation of Stray Light for Infrared Detection." Applied Mechanics and Materials 138-139 (November 2011): 387–90. http://dx.doi.org/10.4028/www.scientific.net/amm.138-139.387.
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Analysis and calculation of stray light is important to improve the performance of infrared detection system. In this article, we mainly discussed two sources: earth and atmosphere emission and thermal stray radiation. A method based on Monte Carlo ray-tracing in TracePro is proposed to calculate the irradiance of detector arisen from earth and atmosphere emission. The thermal stray light irradiance on detector can also be obtained by simulation in TracePro.
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Tolvaj, László, and Dénes Varga. "Photodegradation of Timber of Three Hardwood Species Caused by Different Light Sources." Acta Silvatica et Lignaria Hungarica 8, no. 1 (2012): 145–56. http://dx.doi.org/10.2478/v10303-012-0012-5.
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Abstract - In this study, resistance of black locust, beech and poplar wood to photodegradation was tested, applying sunlight, a xenon lamp and a mercury vapour lamp. The irradiation time was 200 hours for sunlight and the xenon light and 20 hours for the mercury light. The changes were monitored by colour measurements and infrared spectroscopy. The colour change of black locust was more intensive at the beginning of the irradiation than that of the beech and poplar. The degradation of aromatic structure of lignin (absorbing at 1510 and 1596 cm-1) in black locust was minor compared to the same changes of beech and poplar during the first 10 hours. The mercury lamp induced more intensive changes both in colour and in infrared spectrum than the other two light sources. The results show that the high extractive content of black locust absorbs a considerable amount of light radiation protecting the main chemical components of wood.
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Cao, Tun, Meng Lian, Kuan Liu, Xianchao Lou, Yaoming Guo, and Dongming Guo. "Wideband mid-infrared thermal emitter based on stacked nanocavity metasurfaces." International Journal of Extreme Manufacturing 4, no. 1 (2021): 015402. http://dx.doi.org/10.1088/2631-7990/ac3bb1.
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Abstract Efficient thermal radiation in the mid-infrared (M-IR) region is of supreme importance for many applications including thermal imaging and sensing, thermal infrared light sources, infrared spectroscopy, emissivity coatings, and camouflage. The ability to control light makes metasurfaces an attractive platform for infrared applications. Recently, different metamaterials have been proposed to achieve high thermal radiation. To date, broadening the radiation bandwidth of a metasurface emitter (meta-emitter) has become a key goal to enable extensive applications. We experimentally demonstrate a broadband M-IR thermal emitter using stacked nanocavity metasurface consisting of two pairs of circular-shaped dielectric (Si3N4)–metal (Au) stacks. A high thermal radiation can be obtained by engineering the geometry of nanocavity metasurfaces. Such a meta-emitter provides wideband and broad angular absorptance of both p- and s-polarized light, offering a wideband thermal radiation with an average emissivity of more than 80% in the M-IR atmospheric window of 8–14 μm. The experimental illustration together with the theoretical framework establishes a basis for designing broadband thermal emitters, which, as anticipated, will initiate a promising avenue to M-IR sources.
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Murakawa, Shion, Kishalay De, Michael C. B. Ashley, et al. "The First Palomar Gattini-IR Catalog of J-band Light Curves: Construction and Public Data Release." Publications of the Astronomical Society of the Pacific 136, no. 10 (2024): 104501. http://dx.doi.org/10.1088/1538-3873/ad7db1.
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Abstract Palomar Gattini-IR (PGIR) is a wide-field, synoptic infrared time domain survey covering ≈15,000 sq. deg. of the accessible sky at ≈1–3 night cadence to a depth of J ≈ 13.0 and ≈14.9 Vega mag in and outside the Galactic plane, respectively. Here, we present the first data release of J-band light curves of Two Micron All Sky Survey (2MASS) sources within the survey footprint covering approximately the first four years of operations. We describe the construction of the source catalog based on 2MASS point sources, followed by exposure filtering criteria and forced PSF photometry. The catalog contains light curves of ≈286 million unique sources with 2MASS magnitudes of J < 15.5 mag, with a total of ≈50 billion photometric measurements and ≈20 billion individual source detections at signal-to-noise-ratio > 3. We demonstrate the photometric fidelity of the catalog by (i) quantifying the magnitude-dependent accuracy and uncertainty of the photometry with respect to 2MASS and (ii) comparing against forced PGIR aperture photometry for known variable sources. We present simple filtering criteria for selecting reliable photometric measurements as well as example Python notebooks for users. This catalog is one of the largest compilation of nightly cadence, synoptic infrared light curves to date, comparable to those in the largest optical surveys, providing a stepping stone to upcoming infrared surveys in the coming decade.
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Kourkoumelis, Nikolaos, and Margaret Tzaphlidou. "Eye Safety Related to Near Infrared Radiation Exposure to Biometric Devices." Scientific World JOURNAL 11 (2011): 520–28. http://dx.doi.org/10.1100/tsw.2011.52.
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Biometrics has become an emerging field of technology due to its intrinsic security features concerning the identification of individuals by means of measurable biological characteristics. Two of the most promising biometric modalities are iris and retina recognition, which primarily use nonionizing radiation in the infrared region. Illumination of the eye is achieved by infrared light emitting diodes (LEDs). Even if few LED sources are capable of causing direct eye damage as they emit incoherent light, there is a growing concern about the possible use of LED arrays that might pose a potential threat. Exposure to intense coherent infrared radiation has been proven to have significant effects on living tissues. The purpose of this study is to explore the biological effects arising from exposing the eye to near infrared radiation with reference to international legislation.
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Tyler, David W., and Gary C. Loos. "Simulation Study of a Low-Light-Level Wavefront Sensor Driving a Low-Order, Near-IR Adaptive Optics System." Symposium - International Astronomical Union 158 (1994): 308–10. http://dx.doi.org/10.1017/s007418090010779x.
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Two high-fidelity computer simulations are used to study low-order adaptive optics systems operating in the near-infrared. We study obtainable system performance using very dim reference sources at three IR wavelengths.
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Jiang, Ning, Ziying Zhou, Jiazheng Zhu, Yibo Wang, and Tinggui Wang. "Two Candidate Obscured Tidal Disruption Events Coincident with High-energy Neutrinos." Astrophysical Journal Letters 953, no. 1 (2023): L12. http://dx.doi.org/10.3847/2041-8213/acebe3.
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Abstract Recently, three optical tidal disruption event (TDE) candidates discovered by the Zwicky Transient Facility (ZTF) have been suggested to be coincident with high-energy neutrinos. They all exhibit unusually strong dust infrared echoes, with their peak times matching the neutrino arrival time even better than the optical peaks. We hereby report on two new TDE candidates that are spatially and temporally coincident with neutrinos by matching our sample of mid-infrared outbursts in nearby galaxies (MIRONG) with Gold alerts of IceCube high-energy neutrino events up to 2022 June. The two candidates show negligible optical variability according to their ZTF light curves and can therefore be classified as part of the growing population of obscured TDE candidates. The chance probability of finding two such candidates is about ∼3% by redistributing the MIRONG sources randomly in the Sloan Digital Sky Survey footprint, which will be as low as ∼0.1% (or ∼0.2%) if we limit to sources with increased fluxes (or variability amplitudes) comparable with the two matched sources. Our findings further support the potential connection between high-energy neutrinos and TDEs in dusty environments by increasing the total number of neutrino-associated TDE and TDE candidates to five, although the underlying physics remains poorly understood.
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Randriamampandry, S. M., S. M. Crawford, C. M. Cress, K. M. Hess, E. Giovannoli, and M. Vaccari. "Multi-wavelength Studies of Cluster Star Forming Galaxies at z∼0.54." Proceedings of the International Astronomical Union 8, S292 (2012): 337. http://dx.doi.org/10.1017/s1743921313001634.
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AbstractWe carry out a multi-wavelength analysis of star forming galaxies in the massive cluster MS0451.6-0305 at z∼0.54 to shed light on the evolution of the far-infrared-radio relationship in rich clusters. We have performed Spectral Energy Distribution (SED) fitting of IRAC 3.6μ, IRAC 4.5μ and MIPS 24μ photometry from Spitzer to derive the total infrared bolometric luminosity of spectroscopically confirmed cluster members with radio counterparts. The radio flux densities were measured from deep Very Large Array (VLA) radio continuum observations. The relationship between the infrared and radio luminosities for our sources show the strong correlation found between these two parameters for star forming galaxies. The far-infrared to radio luminosity ratio (qIR) values measured for these sources are comparable to those measured in low redshift clusters and indicative of an excess of radio emission.
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Xing, Xiaoxue, Yanmin Lei, Weiwei Shang, Limin Du, and Pan Guo. "Theoretical Research on Ellipsoidal Structure Methane Gas Detection Based on Near Infrared Light Sources of PbSe Quantum Dots." Journal of Nanomaterials 2017 (2017): 1–6. http://dx.doi.org/10.1155/2017/6548380.
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To improve the precision and sensitivity of the detection in near infrared gas detection system, the selection of light source and design of gas chamber structure are two key links. In this paper, the near infrared (NIR) light sources fabricated with PbSe quantum dots (QDs) and a new gas cell structure using an ellipsoid reflector were designed to test the concentration of methane (CH4). The double wavelengths differential detection method was used in the paper. The signal wavelength is 1.665 μm from the NIR QD-based light source with 5.1 nm PbSe QDs. The reference wavelength is 1.943 μm from the NIR QD-based light source with 6.1 nm PbSe QDs. The experimental results show that the differential gain signal could be enhanced 80 times when the major axis, the focus, and the open length of the ellipsoid reflector are 4.18 cm, 3.98 cm, and 0.36 cm, respectively. The structure will be convenient for the signal amplifying, AD converting, and other process in the latter circuits, and therefore both the detection sensitivity and precision can be improved.
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Włodarczyk, Michał, Paweł Krotewicz, Damian Kacperski, Wojciech Sankowski, and Kamil Grabowski. "Inter-Device Periocular Recognition Under Near-Infrared Light." Image Processing & Communications 21, no. 4 (2016): 33–44. http://dx.doi.org/10.1515/ipc-2016-0021.
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Abstract Periocular biometrics is a relatively new field of research, and only several publications on this topic can be found in the literature. It can become a promising feature that can be used independently or as a complement to other biometrics. In this work, the recognition rates of periocular biometrics on a single acquisition device and inter-device database is verified and the impact of different image sources on the performance of recognition algorithms is investigated. For this purpose a NearInfrared Light database was collected. The database contains images taken by two acquisition devices. In order to test the periocular biometric trait, three feature extraction methods are chosen: Histograms of Oriented Gradients, Local Binary Patterns and Scale Invariant Feature Transform. The fusion of these methods is also proposed and it is tested on inter-device database. The feasibility of applying periocular recognition as an individual decision module for a biometric system is assessed. Experimental results yield Equal Error Rate of 17.65 for right eye using inter-device database of 640 gallery periocular images for each eye side taken from 32 different individuals (20 images per individual for each eye side). These results are obtained by the optimal weighted sum fusion of the three feature extraction methods.
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Chang, Yu-Ling, Bruno Arsioli, Wenlian Li, Donglian Xu, and Liang Chen. "Hunting for Neutrino Emission from Multifrequency Variable Sources." Astrophysical Journal 939, no. 2 (2022): 123. http://dx.doi.org/10.3847/1538-4357/ac8c32.
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Abstract Pinpointing the neutrino sources is crucial to unveil the mystery of high-energy cosmic rays. The search for neutrino source candidates from coincident neutrino-photon signatures and objects with particular electromagnetic flaring behaviors can increase our chances of finding neutrino emitters. In this paper, we first study the temporal correlations of astrophysical flares with neutrinos, considering a few hundred multifrequency sources from the Atacama Large Millimeter/submillimeter Array, the Wide-field Infrared Survey Explorer (WISE), Swift, and Fermi in the containment regions of IceCube high-energy alerts. Furthermore, the spatial correlations between blazars and neutrinos are investigated using the subset of 10 yr IceCube track-like neutrinos with around 250,000 events. In a second test, we account for 2700 blazars with different types of flaring stages in addition to their position. No significant neutrino emissions were found from our analyses. Our results indicate an interesting trend showing that the infrared flaring phases of WISE blazars might be correlated with the arrival times of the neutrino alerts. A possible overflow of neutrinos associated with two of our selected blazar samples is discussed in detail. One is characterized by a significant flaring lag in infrared with respect to γ-rays, as seen for TXS 0506+056, and the other is characterized by highly simultaneous infrared and γ-ray flares. Our investigation suggests the need to improve current multifrequency light-curve catalogs to pair with the advent of more sensitive neutrino observatories.
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Nansen, Christian, Patrice Jacob Savi, Tora Ward, Haleh Khodaverdi, Johann Heinrich Lieth, and Anil V. Mantri. "Manipulation of Phototactic Responses by Two-Spotted Spider Mites to Improve Performance of Miticides." Crops 4, no. 4 (2024): 568–83. http://dx.doi.org/10.3390/crops4040040.
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Insight into phototactic responses by herbivorous crop pests may be used to manipulate their vertical distribution in crop canopies. Here, we tested the hypothesis that the deployment of specific light sources elicits positive or negative phototactic responses and can be used to enhance performance of miticide applications. We characterized movement responses by two-spotted spider mites (Tetranychus urticae) (spider mites) to seven light sources [ambient (control), UV-C, UV-B, blue, red, white, and near-infrared (NIR)] under experimental conditions. Separate experiments were conducted with/without the presence of a shelter. An analytical approach based on linear regression coefficients (intercept and slope) from observations in ascending order was used. Linear regression coefficients from UV-B indicated significantly negative phototactic bio-response. We examined settlement of spider mites when exposed to 11 light source configurations and with adaxial leaf sides facing either upwards or downwards. This experiment revealed strong positive and negative phototactic bio-responses to blue light and UV-B light, respectively. As a validation experiment, soybean plants were experimentally infested with spider mites and subjected to one of the following three treatments: (1) no treatment (control), (2) miticide [pyrethrins and Beauveria bassiana (BotaniGard Maxx)] only, and (3) a combination of blue and UV-B for 10 min immediately prior to miticide application. Integration of miticide application with prior deployment of blue and UV-B lights significantly increased the performance of miticide application. Results from this study supported the hypothesis. As a pest management approach, the integration of blue light (to elicit positive phototactic response) and UV-B (to elicit negative phototactic response) is believed to be of particular relevance to organic crop producers and/or to producers of crops for which limited numbers of miticides are registered.
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Singh, Rakesh Kumar. "Night vision technology and night vision device: a technical review." Anusandhaan - Vigyaan Shodh Patrika 9, no. 1 (2021): 96–102. https://doi.org/10.22445/avsp.v9i1.18.
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Night vision is the ability to see in low light conditions. Night vision is made possible by a combination of two approaches: sufficient spectral range and sufficient intensity range. Image intensification increases the amount of photons received from various natural sources such as starlight or moonlight so that a dimly lit scene can be viewed in real time. Active infrared night-vision systems include illuminators that produce high levels of infrared light, with the resulting images typically having higher resolution than other night-vision techniques. Thermal vision detects the temperature difference between background and foreground objects. Night vision device allows to see in no light or in low light at night time. Recently, night vision technology has become more widely available for civilian use. Night vision devices exist in many forms, from gunners to drivers and pilots.
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Kaaret, Philip, Steve Tammes, Jun Wang, et al. "On the Potential of Flaming Hotspot Detection at Night via Multiband Visible/Near-Infrared Imaging." Remote Sensing 14, no. 19 (2022): 5019. http://dx.doi.org/10.3390/rs14195019.
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The severity of wildfires is increasing and has driven increases in nighttime fire activity. Enhanced capability to detect the active burning regions of wildfires at night could significantly improve the effectiveness of wildfire management operations. Potassium line emission in the NIR near 770 nm is a signature of active burning. We test the use of multi-band imaging from an aircraft at night to distinguish a wood-burning fire from artificial light sources. We find that a simple ratio of the signals in two broad bands, one including 770 nm, effectively discriminates the fire from artificial light sources. This offers the possibility of nighttime fire detection with high spatial resolution using silicon sensors sensitive in the NIR.
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Juvela, M., K. Mattila, and D. Lemke. "Far Infrared Extragalactic Background Radiation: Source Counts with ISOPHOT." Symposium - International Astronomical Union 204 (2001): 261. http://dx.doi.org/10.1017/s0074180900226144.
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We have searched for point-like sources in eight fields mapped at two or three wavelengths between 90 μm and 180 μm with the ISOPHOT instrument aboard the ISO satellite. Most of the 55 sources detected are suspected to be extragalactic and cannot be associated with previously known objects. It is probable, also from the far-infrared (FIR) spectral energy distributions, that dust-enshrouded, distant galaxies form a significant fraction of the sources.We present a tentative list of the detected extragalactic FIR-sources. Based on the analyzed data we estimate the number density of extragalactic sources at wavelengths 90 μm, 150 μm and 180 μm and at flux density levels down to 100 mJy to be 1 x 105 sr−1, 2x105 sr−1, and 3xl05 sr−1, respectively.Models of strong galaxy evolution are in best agreement with our results, although the number of detections exceeds predictions of most models. No-evolution models can be rejected at a high confidence level. Comparison with COBE results indicates that at 90 μm the detected sources correspond to >20% of the extragalactic background light. At longer wavelengths the corresponding fraction is ~ 10%.
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Oshima, Jin, Nobuhiko Ozaki, Hisaya Oda, et al. "Near-infrared dual-wavelength surface-emitting light source using InAs quantum dots resonant with vertical cavity modes." Japanese Journal of Applied Physics 61, SD (2022): SD1003. http://dx.doi.org/10.35848/1347-4065/ac5b24.
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Abstract We developed a compact dual-wavelength surface-emitting light source using InAs quantum dots (QDs) embedded in a vertical cavity (VC). The VC was designed to possess two optical cavity modes that resonate with the discrete emission lines of the QDs. The fabricated light source exhibited significant enhancements in the vertical light emission corresponding to the VC modes. In addition, the light source demonstrated selectivity to the enhanced emission wavelengths with changes in temperature. Compared to conventional dual-wavelength vertical external cavity surface-emitting lasers, these QD-based dual-wavelength emission devices allow for the realization of simple structures because the InAs QDs act as dual-light-emitting materials. These results can be applied to simple dual-wavelength surface-emitting light sources.
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Chiti, Lavinia E., Brian Park, Faustine d’Orchymont, Jason P. Holland, and Mirja C. Nolff. "Impact of Surgical Lights on the Performance of Fluorescence-Guided Surgery Systems: A Pilot Study." Animals 13, no. 14 (2023): 2363. http://dx.doi.org/10.3390/ani13142363.
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Fluorescence-guided surgery can aid in the intraoperative visualization of target tissues, with promising applications in human and veterinary surgical oncology. The aim of this study was to evaluate the performances of two fluoresce camera systems, IC-FlowTM and VisionsenseTM VS3 Iridum, for the detection of two non-targeted (ICG and IRDye-800) and two targeted fluorophores (AngiostampTM and FAP-Cyan) under different room light conditions, including ambient light, new generation LED, and halogen artificial light sources, which are commonly used in operating theaters. Six dilutions of the fluorophores were imaged in phantom kits using the two camera systems. The limit of detection (LOD) and mean signal-to-background ratio (mSBR) were determined. The highest values of mSBR and a lower LOD were obtained in dark conditions for both systems. Under room lights, the capabilities decreased, but the mSBR remained greater than 3 (=clearly detectable signal). LOD and mSBR worsened under surgical lights for both camera systems, with a greater impact from halogen bulbs on VisionsenseTM VS3 Iridium and of the LED lights on IC-Flow due to a contribution of these lights in the near-infrared spectrum. When considering implementing FGS into the clinical routine, surgeons should cautiously evaluate the spectral contribution of the lights in the operating theater.
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Xu, Gang, Xiaoli Li, Duan Li, and Xiaomin Liu. "A DAQ-Device-Based Continuous Wave Near-Infrared Spectroscopy System for Measuring Human Functional Brain Activity." Computational and Mathematical Methods in Medicine 2014 (2014): 1–9. http://dx.doi.org/10.1155/2014/107320.
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In the last two decades, functional near-infrared spectroscopy (fNIRS) is getting more and more popular as a neuroimaging technique. The fNIRS instrument can be used to measure local hemodynamic response, which indirectly reflects the functional neural activities in human brain. In this study, an easily implemented way to establish DAQ-device-based fNIRS system was proposed. Basic instrumentation components (light sources driving, signal conditioning, sensors, and optical fiber) of the fNIRS system were described. The digital in-phase and quadrature demodulation method was applied in LabVIEW software to distinguish light sources from different emitters. The effectiveness of the custom-made system was verified by simultaneous measurement with a commercial instrument ETG-4000 during Valsalva maneuver experiment. The light intensity data acquired from two systems were highly correlated for lower wavelength (Pearson’s correlation coefficientr= 0.92,P< 0.01) and higher wavelength (r= 0.84,P< 0.01). Further, another mental arithmetic experiment was implemented to detect neural activation in the prefrontal cortex. For 9 participants, significant cerebral activation was detected in 6 subjects (P< 0.05) for oxyhemoglobin and in 8 subjects (P< 0.01) for deoxyhemoglobin.
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Coesfeld, Jacqueline, Theres Kuester, Helga U. Kuechly, and Christopher C. M. Kyba. "Reducing Variability and Removing Natural Light from Nighttime Satellite Imagery: A Case Study Using the VIIRS DNB." Sensors 20, no. 11 (2020): 3287. http://dx.doi.org/10.3390/s20113287.
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Temporal variation of natural light sources such as airglow limits the ability of night light sensors to detect changes in small sources of artificial light (such as villages). This study presents a method for correcting for this effect globally, using the satellite radiance detected from regions without artificial light emissions. We developed a routine to define an approximate grid of locations worldwide that do not have regular light emission. We apply this method with a 5 degree equally spaced global grid (total of 2016 individual locations), using data from the Visible Infrared Imaging Radiometer Suite (VIIRS) Day-Night Band (DNB). This code could easily be adapted for other future global sensors. The correction reduces the standard deviation of data in the Earth Observation Group monthly DNB composites by almost a factor of two. The code and datasets presented here are available under an open license by GFZ Data Services, and are implemented in the Radiance Light Trends web application.
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Cheng, Yun-Ting, Benjamin D. Wandelt, Tzu-Ching Chang, and Olivier Doré. "Data-driven Cosmology from Three-dimensional Light Cones." Astrophysical Journal 944, no. 2 (2023): 151. http://dx.doi.org/10.3847/1538-4357/acb350.
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Abstract We present a data-driven technique to analyze multifrequency images from upcoming cosmological surveys mapping large sky area. Using full information from the data at the two-point level, our method can simultaneously constrain the large-scale structure (LSS), the spectra and redshift distribution of emitting sources, and the noise in the observed data without any prior assumptions beyond the homogeneity and isotropy of cosmological perturbations. In particular, the method does not rely on source detection or photometric or spectroscopic redshift estimates. Here, we present the formalism and demonstrate our technique with a mock observation from nine optical and near-infrared photometric bands. Our method can recover the input signal and noise without bias, and quantify the uncertainty on the constraints. Our technique provides a flexible framework to analyze the LSS observation traced by different types of sources, which has potential for wide application to current or future cosmological data sets such as SPHEREx, Rubin Observatory, Euclid, or the Nancy Grace Roman Space Telescope.
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Solbrig, Jeremy E., Steven D. Miller, Jianglong Zhang, Lewis Grasso, and Anton Kliewer. "Assessing the stability of surface lights for use in retrievals of nocturnal atmospheric parameters." Atmospheric Measurement Techniques 13, no. 1 (2020): 165–90. http://dx.doi.org/10.5194/amt-13-165-2020.
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Abstract. The detection and characterization of aerosols are inherently limited at night because the important information provided by visible spectrum observations is not available and infrared bands have limited sensitivity to aerosols. The VIIRS Day–Night Band (DNB) onboard the Suomi-NPP satellite is a first-of-its-kind calibrated sensor capable of collecting visible and near-infrared observations during both day and night. Multiple studies have suggested that anthropogenic light emissions such as those from cities and gas flares may be useable as light sources for the retrieval of atmospheric properties, including cloud and aerosol optical depth. However, their use in this capacity requires proper characterization of their intrinsic variation, which represents a source of retrieval uncertainty. In this study we use 18 months of cloud-cleared VIIRS data collected over five selected geographic domains to assess the stability of anthropogenic light emissions and their response to varied satellite and lunar geometries. Time series are developed for each location in each domain for DNB radiance, four infrared channels, and satellite and lunar geometric variables, and spatially resolved correlation coefficients are computed between DNB radiance and each of the other variables. This analysis finds that while many emissive light sources are too unstable to be used reliably for atmospheric retrievals, some sources exhibit a sufficient stability (relative standard deviation <20 %). Additionally, we find that while the radiance variability of surrounding surfaces (i.e., unpopulated land and ocean) is largely dependent on lunar geometry, the anthropogenic light sources are more strongly correlated with satellite viewing geometry. Understanding the spatially resolved relationships between DNB radiance and other parameters is a necessary first step towards characterizing anthropogenic light emissions and establishes a framework for a model to describe variability in a more general sense.
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Xie 谢, Jia-Yong 嘉泳, Jun-ichi 淳一 Nakashima 中岛, and Yong 泳. Zhang 张. "A Search for Asymmetric Kinematic Components in Circumstellar Envelopes Using OH Main Line Masers." Astrophysical Journal 978, no. 1 (2024): 114. https://doi.org/10.3847/1538-4357/ad927d.
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Abstract Circumstellar OH maser lines are useful for studying the dynamics of the circumstellar envelope (CSE) around evolved stars. This study aims to identify CSEs around cold stars, which exhibit deviations from the spherical expansion, by comparing the velocity ranges of the OH main lines (1665/1667 MHz) with those of the satellite line (1612 MHz), using a database of circumstellar OH maser sources. We performed this comparison for 377 circumstellar OH maser sources. In addition, using infrared two-color diagrams, we examined the evolutionary stages and infrared properties of objects showing velocity excess (velocity excess means the detection of the main lines outside the velocity range of the satellite line). A periodicity analysis of the Wide-field Infrared Survey Explorer (WISE) light curves was also carried out. As a result of the velocity range comparison, eight circumstellar OH maser sources were found to exhibit velocity excess. The infrared colors of these objects match those of postasymptotic giant branch (AGB) stars. Periodic variations were observed in the WISE light curves of five of these eight objects. The results suggest that examining the velocity excess of the main lines relative to the satellite line is scientifically significant because mainline masers probe the CSE dynamics over a broader range of evolutionary stages compared to the 22.235 GHz H2O maser line. Additionally, during the post-AGB phase, the emission regions of the mainline and 22.235 GHz H2O masers may overlap in a CSE, whereas they originate from different regions during the AGB phase.
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Tomimasu, T., S. Koda, Y. Iwasaki, et al. "Two-color infrared FEL facility at the Saga synchrotron light source in 2003." Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 528, no. 1-2 (2004): 566–70. http://dx.doi.org/10.1016/j.nima.2004.04.103.
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Jackrel, Sara L., and Raymond S. Matlack. "Influence of Surface Area, Water Level and Adjacent Vegetation on Bat Use of Artificial Water Sources." American Midland Naturalist 164, no. 1 (2010): 74–79. https://doi.org/10.5281/zenodo.13446729.
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(Uploaded by Plazi for the Bat Literature Project) Reliable natural water sources often are unavailable for bats in semi-arid regions such as the Texas Panhandle. Metal stock tanks commonly are used to supply water to livestock and are used by bats as a water source. It is unknown how surface area, water level and adjacent vegetation influence use of tanks by bats. Infrared video cameras and supplemental infrared lights were used to video tape bat behavior and use of stock tanks in Palo Duro Canyon State Park, Texas. Treatment tanks were set out in pairs approximately 80 m apart in a cross-over design to account for influence of location on use of tanks by bats. Treatments included three sizes of tanks (1.2 m, 1.8 m and 3.0 m in diameter), three levels of cover of adjacent vegetation (no vegetation, light vegetation and heavy vegetation) and two water levels (full and K full). The number of bats that passed over 3.0 m and 1.2 m tanks was similar; however, bats drank from large tanks more than small tanks. Passes were similar between the tanks surrounded by light vegetation and tanks with no vegetation, but bats drank more from tanks surrounded by light vegetation. Tanks surrounded by heavy vegetation experienced fewer passes and fewer drinks than tanks without vegetation. Water level had no effect on the number of passes by bats but K full tanks were used for drinking less frequently than full tanks. Our research indicates that size of tank, water level in tanks and characteristics of adjacent vegetation influence use of metal livestock tanks by bats. Use of larger tanks, keeping tanks full and managing vegetation around tanks increases use of tanks by bats.
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Jackrel, Sara L., and Raymond S. Matlack. "Influence of Surface Area, Water Level and Adjacent Vegetation on Bat Use of Artificial Water Sources." American Midland Naturalist 164, no. 1 (2010): 74–79. https://doi.org/10.5281/zenodo.13446729.
Full textAbstract:
(Uploaded by Plazi for the Bat Literature Project) Reliable natural water sources often are unavailable for bats in semi-arid regions such as the Texas Panhandle. Metal stock tanks commonly are used to supply water to livestock and are used by bats as a water source. It is unknown how surface area, water level and adjacent vegetation influence use of tanks by bats. Infrared video cameras and supplemental infrared lights were used to video tape bat behavior and use of stock tanks in Palo Duro Canyon State Park, Texas. Treatment tanks were set out in pairs approximately 80 m apart in a cross-over design to account for influence of location on use of tanks by bats. Treatments included three sizes of tanks (1.2 m, 1.8 m and 3.0 m in diameter), three levels of cover of adjacent vegetation (no vegetation, light vegetation and heavy vegetation) and two water levels (full and K full). The number of bats that passed over 3.0 m and 1.2 m tanks was similar; however, bats drank from large tanks more than small tanks. Passes were similar between the tanks surrounded by light vegetation and tanks with no vegetation, but bats drank more from tanks surrounded by light vegetation. Tanks surrounded by heavy vegetation experienced fewer passes and fewer drinks than tanks without vegetation. Water level had no effect on the number of passes by bats but K full tanks were used for drinking less frequently than full tanks. Our research indicates that size of tank, water level in tanks and characteristics of adjacent vegetation influence use of metal livestock tanks by bats. Use of larger tanks, keeping tanks full and managing vegetation around tanks increases use of tanks by bats.
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Wei, Yongchao, Yuchen Yue, and Zihan Zhu. "Dual Modal Face Recognition Based on Visible Light and Thermal Infrared." Journal of Physics: Conference Series 2872, no. 1 (2024): 012040. http://dx.doi.org/10.1088/1742-6596/2872/1/012040.
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Abstract In recent years, face recognition has received widespread attention, in the use of visible light for face recognition, there are a series of problems that require auxiliary light sources, may be attacked by photos, and camouflage is difficult to penetrate. Compared with visible light recognition, thermal infrared face recognition shows usability, and it can still be stable in low light or dark extreme environmental conditions, but due to low resolution, it can not capture rich face feature information. In view of this paper proposes that dual mode face recognition can effectively integrate two single mode information and make up for the deficiency of single feature. Using a Bimodal Face network model based on visible light and thermal infrared, the idea of feature decoupling is introduced into image fusion. The cross-modal information is decomposed into common information and unique information, and the common information and unique information of different modes are fused respectively according to the feature fusion method. It is tested on the self-built dual modal dataset that this fusion strategy can achieve the optimal effect, and the accuracy rate can reach 97.08%, which is better than other five face recognition network models.
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Hideki, Toda, and Fujiuti Kouhei. "50 m-range distance and position measurement method by using two searchlights for autonomous flight device." International Journal of Engineering Research & Science 4, no. 7 (2018): 29–35. https://doi.org/10.5281/zenodo.1324112.
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<strong><em>Abstract</em></strong><strong>—</strong> <em>In the present study, 50 m-range distance and position measurement method for autonomous flight device such as four-rotor drone by using two searchlights was proposed, and the precise distance/position measurement performance was evaluated in an outdoor situation. To realize over 10 m long-distance flight of the drone under unstable GPS signal situations such as under the bridge or inside tunnels for periodic inspections, the correct self-position measurement is important for the stable control. This study is to propose a simple method of over 50 m range autonomous four-rotor helicopter movement control using high power 300W two searchlights as InfraRed sources on the ground and the direction of the searchlights sets to the investigation target position such as bridge side. High power light sources of the two searchlights are enabled to measure the correct drone position via an attached drone's camera with an InfraRed filter, and it realizes 1.5 m standard deviation position estimation error when 50 m distance in an outdoor daylight situation. In addition, the limitation of the position detectable condition also measured and analyzed in other experiments. Our proposed method would be effective in the situation that there is no skilled the drone control operator and the flight by visual confirmation of man are hard conditions, and useful to develop the position measurement system with low cost.</em>
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Lu, Ying, Xi Chen, Shi-Min Song, et al. "Sample and Statistical Analysis on NEOWISE Variability of ATLASGAL Sources." Astrophysical Journal Supplement Series 272, no. 2 (2024): 44. http://dx.doi.org/10.3847/1538-4365/ad41e2.
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Abstract This study focuses on the analysis of mid-infrared variability in a sample of high-mass young stellar objects (YSOs) associated with the cataloged sources from the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL). The Near-Earth Object Wide-field Infrared Survey Explorer Reactivation Mission (NEOWISE) database was used to explore the long-term mid-infrared variability of these high-mass YSOs at a half-year scale. After matching with NEOWISE photometric measurements, a total of 2230 ATLASGAL sources were selected for the variability analysis, out of which 717 were identified as variables. The derived proportions of variables at different evolutionary stages show that the variability rate of high-mass YSOs is highest during the YSO stage and decreases with evolution toward the H ii region stage, resembling the behavior of low-mass YSOs. The variables can be classified into six types based on their light curves, divided into two categories: secular (linear, sin, sin+linear) and stochastic variables (burst, drop, and irregular). The magnitude–color variations observed in ∼160 secular variables can be mainly divided into “bluer when brighter/redder when dimming” and “redder when brighter/bluer when dimming,” likely originating from changes in accretion rate or the effect of extinction due to obscuration. Moreover, several episodic accretion candidates were selected for further observational studies.
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Sajadian, Sedighe, and Ali Salehi. "Detecting the inner regions of discs around sources of microlensing with Roman Space Telescope." Monthly Notices of the Royal Astronomical Society 498, no. 1 (2020): 1298–307. http://dx.doi.org/10.1093/mnras/staa2377.
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ABSTRACT The inner region of circumstellar discs makes an extra near-infrared emission (NIR bump). Detecting and studying these NIR bumps from nearby stars have been done mostly through infrared interferometry. In this work, we study the feasibility of detecting NIR bumps for Galactic bulge stars through microlensing from observations by The Nancy Grace Roman Space Telescope (RST) survey. We first simulate microlensing light curves from source stars with discs in NIR. Four main conclusions can be extracted from the simulations. (i) If the lens is crossing the disc inner radius, two extra and wide peaks appear and the main peak of microlensing light curve is flattened. (ii) In microlensing events with the lens impact parameters larger than the disc inner radius, the disc can break the symmetry of light curves with respect to the time of closest approach. (iii) In caustic-crossing binary microlensing, the discs produce wide peaks right before entering and immediately after exiting from the caustic curves. (iv) The disc-induced perturbations are larger in the W149 filter than in the Z087 filter, unless the lens crosses the disc condensation radius. By performing a Monte Carlo simulation, the probabilities of detecting the disc perturbations by RST are estimated ∼3 and 20 per cent in single and binary microlensing, respectively. We anticipate that RST detects around 109 disc-induced perturbations during its microlensing survey if 5 per cent of its source stars have discs.
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Franco, Alfredo, Jorge A. García-Macedo, and Jeffrey I. Zink. "Hybrid Organic-Inorganic Photodriven Nanoimpellers for Drug Release." Advances in Science and Technology 82 (September 2012): 25–31. http://dx.doi.org/10.4028/www.scientific.net/ast.82.25.
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Mesostructured SiO2 films functionalized with the azo-chromophore Disperse Red 1 were synthesized by sol-gel method. The mesostructured long-range order in the films was determined by X-Ray Diffraction. The azo-chromophores in the films work as nano-impellers through their photo-induced trans-cis reversible isomerization. When the films are doped, they are able to control the release of the dopant by all-optical processes. We used the dye laser Rhodamine 6G as dopant, its very distinctive luminescence around 550 nm allows to follow the release. Polarized green and infrared laser light were used as pump sources to direct the movement of the nano-impellers. 299 nm light was used as a probe to induce the Rhodamine 6G luminescence, which was measured as function of the pumping time with a photomultiplier coupled to a monochromator. The results corresponding to the green and to the infrared pumping sources are compared in order to determine the feasibility to photo-control the nano-impellers movement through a two-photon absorption process.
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Foteinopoulou, Stavroula, Ganga Chinna Rao Devarapu, Ganapathi S. Subramania, Sanjay Krishna, and Daniel Wasserman. "Phonon-polaritonics: enabling powerful capabilities for infrared photonics." Nanophotonics 8, no. 12 (2019): 2129–75. http://dx.doi.org/10.1515/nanoph-2019-0232.
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AbstractHere, we review the progress and most recent advances in phonon-polaritonics, an emerging and growing field that has brought about a range of powerful possibilities for mid- to far-infrared (IR) light. These extraordinary capabilities are enabled by the resonant coupling between the impinging light and the vibrations of the material lattice, known as phonon-polaritons (PhPs). These PhPs yield a characteristic optical response in certain materials, occurring within an IR spectral window known as the reststrahlen band. In particular, these materials transition in the reststrahlen band from a high-refractive-index behavior, to a near-perfect metal behavior, to a plasmonic behavior – typical of metals at optical frequencies. When anisotropic they may also possess unconventional photonic constitutive properties thought of as possible only with metamaterials. The recent surge in two-dimensional (2D) material research has also enabled PhP responses with atomically-thin materials. Such vast and extraordinary photonic responses can be utilized for a plethora of unusual effects for IR light. Examples include sub-diffraction surface wave guiding, artificial magnetism, exotic photonic dispersions, thermal emission enhancement, perfect absorption and enhanced near-field heat transfer. Finally, we discuss the tremendous potential impact of these IR functionalities for the advancement of IR sources and sensors, as well as for thermal management and THz-diagnostic imaging.
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Garufi, A., C. Dominik, C. Ginski, et al. "A SPHERE survey of self-shadowed planet-forming disks." Astronomy & Astrophysics 658 (February 2022): A137. http://dx.doi.org/10.1051/0004-6361/202141692.
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To date, nearly two hundred planet-forming disks have been imaged at high resolution. Our propensity to study bright and extended objects does, however, bias our view of the disk demography. In this work, we aim to help alleviate this bias by analyzing fifteen disks targeted with VLT/SPHERE that look faint in scattered light. Sources were selected based on a low far-infrared excess from the spectral energy distribution. The comparison with the ALMA images available for a few sources shows that the scattered light surveyed by these datasets is only detected from a small portion of the disk extent. The mild anticorrelation between the disk brightness and the near-infrared excess demonstrates that these disks are self-shadowed: the inner disk rim intercepts much starlight and leaves the outer disk in penumbra. Based on the uniform distribution of the disk brightness in scattered light across all spectral types, self-shadowing would act similarly for inner rims at a different distance from the star. We discuss how the illumination pattern of the outer disk may evolve with time. Some objects in the sample are proposed to be at an intermediate stage toward bright disks from the literature, with either no shadow or with signs of azimuthally confined shadows.
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Gantri, M., H. Trabelsi, E. Sediki, and R. Ben Salah. "Computational Laser Spectroscopy in a Biological Tissue." Journal of Biophysics 2010 (April 7, 2010): 1–9. http://dx.doi.org/10.1155/2010/253763.
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We present a numerical spectroscopic study of visible and infrared laser radiation in a biological tissue. We derive a solution of a general two-dimensional time dependent radiative transfer equation in a tissue-like medium. The used model is suitable for many situations especially when the external source is time-dependent or continuous. We use a control volume-discrete ordinate method associated with an implicit three-level second-order time differencing scheme. We consider a very thin rectangular biological-tissue-like medium submitted to a visible or a near infrared light sources. The RTE is solved for a set of different wavelength source. All sources are assumed to be monochromatic and collimated. The energetic fluence rate is computed at a set of detector points on the boundaries. According to the source type, we investigate either the steady-state or transient response of the medium. The used model is validated in the case of a heterogeneous tissue-like medium using referencing experimental results from the literature. Also, the developed model is used to study changes on transmitted light in a rat-liver tissue-like medium. Optical properties depend on the source wavelength and they are taken from the literature. In particular, light-transmission in the medium is studied for continuous wave and for short pulse.
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Franceschini, A., L. Foffano, E. Prandini, and F. Tavecchio. "Very high-energy constraints on the infrared extragalactic background light." Astronomy & Astrophysics 629 (August 22, 2019): A2. http://dx.doi.org/10.1051/0004-6361/201935617.
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Context. Measurements of the extragalactic background light (EBL) are a fundamental source of information on the collective emission of cosmic sources. Aims. At infrared wavelengths, however, these measurements are precluded by the overwhelming dominance from interplanetary dust emission and the Galactic infrared foreground. Only at λ > 300 μm, where the foregrounds are minimal, has the infrared EBL (IR EBL) been inferred from analysis of the COBE maps. The present paper aims to assess the possibility of evaluating the IR EBL from a few micrometers up to the peak of the emission at > 100 μm using an indirect method that avoids the foreground problem. Methods. To this purpose we exploit the effect of pair-production from gamma-gamma interaction by considering the highest-energy photons emitted by extragalactic sources and their interaction with the IR EBL photons. We simulate observations of a variety of low-redshift emitters with the forthcoming Imaging Atmospheric Cherenkov Telescope (IACT) arrays (CTA in particular) and water Cherenkov observatories (LHAASO, HAWC, SWGO) to assess their suitability to constrain the EBL at such long wavelengths. Results. We find that even under the most extremely favorable conditions of huge emission flares, extremely high-energy emitting blazars are not very useful for our purpose because they are much too distant (> 100 Mpc the nearest ones, MKN 501 and MKN 421). Observations of more local AGNs displaying very high-energy emission, like low-redshift radio galaxies (M 87, IC 310, Centaurus A), are better suited and will potentially allow us to constrain the EBL up to λ ≃ 100 μm.
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Wang, Yibo, Ning Jiang, Tinggui Wang, et al. "Mid-infrared Outbursts in Nearby Galaxies (MIRONG). II. Optical Spectroscopic Follow-up." Astrophysical Journal Supplement Series 258, no. 1 (2022): 21. http://dx.doi.org/10.3847/1538-4365/ac33a6.
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Abstract Infrared echo has proven to be an effective means to discover transient accretion events of supermassive black holes (SMBHs), such as tidal disruption events (TDEs) and changing-look active galactic nuclei (AGNs), in dusty circumnuclear environments. To explore the dusty populations of SMBH transient events, we have constructed a large sample of mid-infrared outbursts in nearby galaxies (MIRONG) and performed multiwavelength observations. Here we present the results of multiepoch spectroscopic follow-up observations of a subsample of 54 objects spanning a timescale of 4 yr. Emission-line variability was detected in 22 of them with either emergence or enhancement of broad Balmer emission lines in comparison with pre-outburst spectra. Coronal lines, He ii λ4686, and Bowen line N iii λ4640 appeared in the spectra of nine, seven, and two sources, respectively. These results suggest that MIRONG is a mixed bag of different transient sources. We have tentatively classified them into different subclass according to their spectral evolution and light curves. Two sources have been in a steady high broad Hα flux up to the latest observation and might be turn-on AGNs. Broad lines faded out in the remaining sources, indicating a transient ionizing source ignited by TDE or sporadic gas accretion. Thirty-one sources do not show noticeable spectral change with respect to their pre-outburst spectra. They have a statistically redder MIR color and lower MIR luminosity of the outbursts, which are consistent with heavily obscured events.
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Li, Zhi Xiang, and Wen Fei Hu. "Research on the New Double-Wave-Bands Treatment System." Applied Mechanics and Materials 43 (December 2010): 312–16. http://dx.doi.org/10.4028/www.scientific.net/amm.43.312.
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Presently for single function and high cost of the phototherapy equipments, this paper introduces a kind of Double-Wave-Bands therapeutic apparatus, which fully utilizes the principle of near-infrared wavelengths treating various pains and UVC sterilizing. This apparatus uses two different kinds of wave bands by selecting different light sources, but a set of control system. Because of a machine with multi-purpose and less cost, this apparatus can treat all forms of disease safely and effectively through using output light of the optical system by various forms of curing probes to be helpful for a promotion.
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Qiu, Yan, and Ying Guo. "Explaining Colour Change in Pyrope-Spessartine Garnets." Minerals 11, no. 8 (2021): 865. http://dx.doi.org/10.3390/min11080865.
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A colour-changing garnet exhibits the “alexandrite effect”, whereby its colour changes from green in the presence of daylight to purplish red under incandescent light. This study examines this species of garnets as well as the causes of the colour change by using infrared and ultraviolet visible (UV-Vis) spectroscopy. The infrared spectra show that the colour-changing garnets in this paper belong to the solid solution of pyrope-spessartine type. CIE1931 XYZ colour matching functions are used to calculate the colour parameters influencing garnet colour-changing under different light sources. The UV-Vis spectra show two zones of transmittance, in the red region at 650–700 nm and the blue-green region at 460–510 nm. As they exhibit the same capacity to transmit light, the colour of the gem is determined by the external light source. The absorption bands of Cr3+ and V3+ at 574 nm in the UV-Vis spectra are the main cause of the change in colour. With the increase in the area of peak absorption, the differences in the chroma and colour of the garnet gradually increase in daylight and incandescent light, and it exhibits a more prominent colour-changing effect.
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Ma, Xingfa, Xintao Zhang, Mingjun Gao, Ruifen Hu, You Wang, and Guang Li. "In2S3/C3N4 Nanocomposite and Its Photoelectric Properties in the Broadband Light Spectrum Range." Coatings 15, no. 6 (2025): 718. https://doi.org/10.3390/coatings15060718.
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To extend the spectral utilisation of In2S3, an In2S3/C3N4 nanocomposite was prepared. The effects of different sulphur sources, electrodes, and bias voltages on the optoelectronic performance were examined. Photoelectric properties in response to light sources with wavelengths of 405, 532, 650, 780, 808, 980, and 1064 nm were investigated using Au electrodes and the carbon electrodes with 5B pencil drawings. This study shows that the aggregation states of the In2S3/C3N4 nanocomposite possess photocurrent switching responses in the broadband region of the light spectrum. Combining two types of partially visible light-absorbing material extends utilisation to the near-infrared region. Impurities or defects embody an electron-donating effect. Since the energy levels of defects or impurities with an electron-donating effect are close to the conduction band, low-energy lights (especially NIR) can be utilised. The non-equilibrium carrier concentration (photogenerated electrons) of the nanocomposites increases significantly under NIR photoexcitation conditions. Thus, photoconductive behaviour is manifested. A good photoelectric signal was still measured when zero bias was applied. This demonstrates self-powered photoelectric response characteristics. Different sulphur sources significantly affect the photoelectric performance, suggesting that they create different defects that affect charge transport and base current noise. It is believed that interfacial interactions in the In2S3/C3N4 nanocomposite create a built-in electric field that enhances the separation and transfer of electrons and holes produced by light stimulation. The presence of the built-in electric field also leads to energy band bending, which facilitates the utilisation of the light with longer wavelengths. This study provides a reference for multidisciplinary applications.
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Du Le, Vinh Nguyen Du, Sophia Fronckowiak, and Elizabeth Badolato. "A Cost-Effective Method for the Spectral Calibration of Photoplethysmography Pulses: The Optimal Wavelengths for Heart Rate Monitoring." Sensors 25, no. 7 (2025): 2311. https://doi.org/10.3390/s25072311.
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A photoplethysmography (PPG) pulse in reflection mode represents the change in diffuse reflectance at the skin surface during a cardiac cycle and is commonly used in wearable devices to monitor heart rate. Commercial PPG sensors often rely on the reflectance signal from light sources at two different wavelength regions, green, such as 523 nm, and near infrared (NIR), such as 945 nm. Early in vivo studies of wearable sensors showed that green light is more beneficial than NIR light in optimizing PPG sensitivity. This contradicts the common trends in the standard near infrared spectroscopy techniques, which rely on the long optical pathlengths at NIR wavelengths to achieve optimal depth sensitivity. To quantitatively analyze the spectral characteristics of PPG across the wavelength region of 500–900 nm in a controlled environment, this study performs the spectral measurement of PPG signals using a simple and cost-effective optical phantom model with two distinct layers and a customized diffuse reflectance spectroscopy system. In addition, Monte Carlo simulations are used to elaborate the underlying phenomena at the green and NIR wavelengths when considering different epithelial thicknesses and source–detector distances (SDD).
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Surkova, Anastasiia, Andrey Bogomolov, Aleksandra Paderina, et al. "Optical Multisensor System Based on Lanthanide(III) Complexes as Near-Infrared Light Sources for Analysis of Milk." Chemosensors 10, no. 7 (2022): 288. http://dx.doi.org/10.3390/chemosensors10070288.
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Optical multisensor systems are easy-to-use and inexpensive analytical devices. In this work, we propose an optical multisensor system based on the luminescence of Nd(III) and Yb(III) complexes in the near-infrared (NIR) spectral region. The observed emission bands play the role of secondary light sources for further analysis of milk—for the determination of fat content and for the recognition of adulteration. The samples for analysis were prepared by putting a drop of milk upon a thin glass covering the powdered mixture of lanthanide complexes, which were excited by a light-emitting diode (LED) in the ultraviolet region (the maximum intensity at 365 nm). The diffuse-reflectance spectra of samples were acquired in the short-wave NIR range 750–1100 nm using a portable NIR spectrometer. The developed optical system was tested using two sets of milk samples with varying concentration levels of fat and added urea. The obtained spectral data were analyzed using a number of multivariate prediction and classification methods of chemometrics and the results were statistically compared. The regression and classification model performances achieved in this proof-of-concept study illustrate the feasibility of the optical multisensor analysis based on luminescent light sources in the short-wave NIR range, in particular, for their application in the dairy.
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Almeida, Catherine Torres de, Lênio Soares Galvão, Jean Pierre H. B. Ometto, et al. "Advancing Forest Degradation and Regeneration Assessment Through Light Detection and Ranging and Hyperspectral Imaging Integration." Remote Sensing 16, no. 21 (2024): 3935. http://dx.doi.org/10.3390/rs16213935.
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Integrating Light Detection And Ranging (LiDAR) and Hyperspectral Imaging (HSI) enhances the assessment of tropical forest degradation and regeneration, which is crucial for conservation and climate mitigation strategies. This study optimized procedures using combined airborne LiDAR, HSI data, and machine learning algorithms across 12 sites in the Brazilian Amazon, covering various environmental and anthropogenic conditions. Four forest classes (undisturbed, degraded, and two stages of second-growth) were identified using Landsat time series (1984–2017) and auxiliary data. Metrics from 600 samples were analyzed with three classifiers: Random Forest, Stochastic Gradient Boosting, and Support Vector Machine. The combination of LiDAR and HSI data improved classification accuracy by up to 12% compared with single data sources. The most decisive metrics were LiDAR-based upper canopy cover and HSI-based absorption bands in the near-infrared and shortwave infrared. LiDAR produced significantly fewer errors for discriminating second-growth from old-growth forests, while HSI had better performance to discriminate degraded from undisturbed forests. HSI-only models performed similarly to LiDAR-only models (mean F1 of about 75% for both data sources). The results highlight the potential of integrating LiDAR and HSI data to improve our understanding of forest dynamics in the context of nature-based solutions to mitigate climate change impacts.
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Barcelo, Leo Agustin, Nacita Lantican, Ruby Lynn Ventura, and Jey-R. Ventura. "Selected physiological requirements of Purple non-sulfur bacteria isolated from Los Baños, Laguna for potential biohydrogen production." Palawan Scientist 15, no. 2 (2023): 31–40. http://dx.doi.org/10.69721/tps.j.2023.15.2.04.
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Biohydrogen is gaining traction in energy research due to its high energy content and minimal carbon footprint. A typical method of producing biohydrogen is photofermentation using purple non-sulfur bacteria (PNSB). Exploring novel strains of PNSB and studying their versatile metabolism can aid in bioprospecting their potentially valuable by-products and applications, particularly in energy generation. This study investigated the physiological requirements of top biohydrogen-producing PNSB isolated from various Los Baños, Laguna, Philippines sites by measuring their biogas production and growth when subjected to different incubation conditions and macronutrient requirements. Results showed that the three local isolates grown anaerobically in mesophilic conditions without agitation preferred incandescent light. The high biogas yield and growth may be attributed to the light-harvesting pigments in PNSB, which are excited primarily by infrared and near-infrared wavelengths of incandescent light. Furthermore, the isolates can grow from various carbon sources, such as volatile fatty acids (malate, succinate, acetate, butyrate, and propionate) and sugars (glucose and starch). However, two of the isolates (MAY2 and PR2) did not produce biogas when supplied with acetate as a carbon source, which suggests a competing pathway that may have affected the photofermentation of the isolates. Also, the isolates prefer more complex organic sources such as yeast extract and peptone than inorganic sources such as ammonium and less complex organic sources such as urea. Finally, experiments on salt tolerance showed that 0.04% and 0.85% NaCl concentration favors biohydrogen production and growth, as exhibited by high biogas production, yield, and optical density. Results from this study can serve as a basis for future research on optimizing media composition and conditions for biohydrogen production from these isolates.
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Garter, M., R. Birkhahn, A. J. Steckl, and J. Scofield. "Visible and Infrared Rare-Earth Activated Electroluminescence from Erbium Doped GaN." MRS Internet Journal of Nitride Semiconductor Research 4, S1 (1999): 940–45. http://dx.doi.org/10.1557/s109257830000363x.
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Room temperature visible and IR light electroluminescence (EL) has been obtained from Er-doped GaN Schottky barrier diodes. The GaN was grown by molecular beam epitaxy on Si substrates using solid sources (for Ga and Er) and a plasma source for N2. Transparent contacts utilizing indium tin oxide were employed. Strong green light emission was observed under reverse bias due to electron impact excitation of the Er atoms. Weaker emission was present under forward bias. The emission spectrum consists of two narrow green lines at 537 and 558 nm and minor peaks at 413, 461, 665, and 706 nm. There is also emission at 1000 nm and 1540 nm in the IR. The green emission lines have been identified as Er transitions from the 2H11/2 and 4S3/2 levels to the 4I15/2 ground state. The IR emission lines have been identified as transitions from the 4I11/2 and 4I13/2 levels to the 4I15/2 ground state. EL intensity for visible and IR light has a sub-unity power law dependence on bias current. An external quantum efficiency of 0.1% has also been demonstrated under a reverse bias current of 3.85 mA.
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Ren, Zhehao, Yufu Liu, Bin Chen, and Bing Xu. "Where Does Nighttime Light Come From? Insights from Source Detection and Error Attribution." Remote Sensing 12, no. 12 (2020): 1922. http://dx.doi.org/10.3390/rs12121922.
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Nighttime light remote sensing has aroused great popularity because of its advantage in estimating socioeconomic indicators and quantifying human activities in response to the changing world. Despite many advances that have been made in method development and implementation of nighttime light remote sensing over the past decades, limited studies have dived into answering the question: Where does nighttime light come from? This hinders our capability of identifying specific sources of nighttime light in urbanized regions. Addressing this shortcoming, here we proposed a parcel-oriented temporal linear unmixing method (POTLUM) to identify specific nighttime light sources with the integration of land use data. Ratio of root mean square error was used as the measure to assess the unmixing accuracy, and parcel purity index and source sufficiency index were proposed to attribute unmixing errors. Using the Visible Infrared Imaging Radiometer Suite (VIIRS) nighttime light dataset from the Suomi National Polar-Orbiting Partnership (NPP) satellite and the newly released Essential Urban Land Use Categories in China (EULUC-China) product, we applied the proposed method and conducted experiments in two China cities with different sizes, Shanghai and Quzhou. Results of the POTLUM showed its relatively robust applicability of detecting specific nighttime light sources, achieving an rRMSE of 3.38% and 1.04% in Shanghai and Quzhou, respectively. The major unmixing errors resulted from using impure land parcels as endmembers (i.e., parcel purity index for Shanghai and Quzhou: 54.48%, 64.09%, respectively), but it also showed that predefined light sources are sufficient (i.e., source sufficiency index for Shanghai and Quzhou: 96.53%, 99.55%, respectively). The method presented in this study makes it possible to identify specific sources of nighttime light and is expected to enrich the estimation of structural socioeconomic indicators, as well as better support various applications in urban planning and management.
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Lin, Hongtao, Zhengqian Luo, Tian Gu, et al. "Mid-infrared integrated photonics on silicon: a perspective." Nanophotonics 7, no. 2 (2017): 393–420. http://dx.doi.org/10.1515/nanoph-2017-0085.
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AbstractThe emergence of silicon photonics over the past two decades has established silicon as a preferred substrate platform for photonic integration. While most silicon-based photonic components have so far been realized in the near-infrared (near-IR) telecommunication bands, the mid-infrared (mid-IR, 2–20-μm wavelength) band presents a significant growth opportunity for integrated photonics. In this review, we offer our perspective on the burgeoning field of mid-IR integrated photonics on silicon. A comprehensive survey on the state-of-the-art of key photonic devices such as waveguides, light sources, modulators, and detectors is presented. Furthermore, on-chip spectroscopic chemical sensing is quantitatively analyzed as an example of mid-IR photonic system integration based on these basic building blocks, and the constituent component choices are discussed and contrasted in the context of system performance and integration technologies.
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Büker, Linda, Michel Hackbarth, Vincent Quinten, Andreas Hein, and Sandra Hellmers. "Towards comparable quality-assured Azure Kinect body tracking results in a study setting—Influence of light." PLOS ONE 19, no. 8 (2024): e0308416. http://dx.doi.org/10.1371/journal.pone.0308416.
Full textAbstract:
Quality assurance in research helps to ensure reliability and comparable results within a study. This includes reliable measurement equipment and data-processing. The Azure Kinect DK is a popular sensor used in studies with human subjects that tracks numerous joint positions with the Azure Kinect Body Tracking SDK. Prior experiments in literature indicate that light might influence the results of the body tracking. As similar light conditions are not always given in study protocols, the impact needs to be analyzed to ensure comparable results. We ran two experiments, one with four different light conditions and one with repeated measures of similar light conditions, and compared the results by calculating the random error of depth measurement, the mean distance error of the detected joint positions, and the distance between left and right ankle. The results showed that recordings with similar light conditions produce comparable results, with a maximum difference in the median value of mean distance error of 0.06 mm, while different light conditions result in inconsistent outcomes with a difference in the median value of mean distance error of up to 0.35 mm. Therefore, light might have an influence on the Azure Kinect and its body tracking. Especially additional infrared light appears to have a negative impact on the results. Therefore, we recommend recording various videos in a study under similar light conditions whenever possible, and avoiding additional sources of infrared light.
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Pichel, Ana, Laura G. Donoso, Laura D. Baravalle, et al. "High-energy gamma-ray sources in the VVV survey – I. The blazars." Monthly Notices of the Royal Astronomical Society 491, no. 3 (2019): 3448–60. http://dx.doi.org/10.1093/mnras/stz3239.
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ABSTRACT There is a lack of blazar detections in the galactic plane area, even in the most recent blazar catalogues, mainly due to incompleteness resulting from interstellar dust and stellar contamination of our Galaxy. The VISTA Variables in the Vía Láctea survey (VVV) aims to map variable sources towards the galactic plane in the near-infrared (IR). There are three catalogued and one candidate blazars in the VVV area, which are also detected by Fermi-LAT in the gamma-ray band and by the Wide-field Infrared Survey Explorer (WISE) at mid-IR wavelengths. We study the physical properties of these blazars in order to use them as a reference that would allow us to find counterparts of other unidentified gamma-ray sources in the future. All four sources have VVV counterparts, and two of them, 5BZUJ1731−3003 and 5BZQJ1802−3940 are also associated with WISE sources. They present very different properties compared with stellar or extragalactic objects. Their VVV Ks light curves show significant variability, and are characterized using a machine learning analysis. In particular, the blazar 5BZQJ1802−3940, a flat spectrum radio quasar, exhibits the smallest uncertainties in the Fermi-LAT position and it is a bright WISE source. Its near-IR properties in the colour–magnitude and colour–colour diagrams are very different from the stars and extragalactic objects in the field. It has the highest amplitude in the Ks differential light curve and fractional variability amplitude. This pilot study will allow us to search for and identify other blazars hidden behind the Galactic plane using the VVV survey data base.
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Elvidge, Christopher, Mikhail Zhizhin, Kimberly Baugh, Feng Hsu, and Tilottama Ghosh. "Extending Nighttime Combustion Source Detection Limits with Short Wavelength VIIRS Data." Remote Sensing 11, no. 4 (2019): 395. http://dx.doi.org/10.3390/rs11040395.
Full textAbstract:
The Visible Infrared Imaging Radiometer Suite (VIIRS) collects low light imaging data at night in five spectral bands. The best known of these is the day/night band (DNB) which uses light intensification for imaging of moonlit clouds in the visible and near-infrared (VNIR). The other four low light imaging bands are in the NIR and short-wave infrared (SWIR), designed for daytime imaging, which continue to collect data at night. VIIRS nightfire (VNF) tests each nighttime pixel for the presence of sub-pixel IR emitters across six spectral bands with two bands each in three spectral ranges: NIR, SWIR, and MWIR. In pixels with detection in two or more bands, Planck curve fitting leads to the calculation of temperature, source area, and radiant heat using physical laws. An analysis of January 2018 global VNF found that inclusion of the NIR and SWIR channels results in a doubling of the VNF pixels with temperature fits over the detection numbers involving the MWIR. The addition of the short wavelength channels extends detection limits to smaller source areas across a broad range of temperatures. The VIIRS DNB has even lower detection limits for combustion sources, reaching 0.001 m2 at 1800 K, a typical temperature for a natural gas flare. Comparison of VNF tallies and DNB fire detections in a 2015 study area in India found the DNB had 15 times more detections than VNF. The primary VNF error sources are false detections from high energy particle detections (HEPD) in space and radiance saturation on some of the most intense events. The HEPD false detections are largely eliminated in the VNF output by requiring multiband detections for the calculation of temperature and source size. Radiance saturation occurs in about 1% of the VNF detections and occurs primarily in the M12 spectral band. Inclusion of the radiances affected by saturation results in temperature and source area calculation errors. Saturation is addressed by identifying the presence of saturation and excluding those radiances from the Planck curve fitting. The extremely low detection limits for the DNB indicates that a DNB fire detection algorithm could reveal vast numbers of combustion sources that are undetectable in longer wavelength VIIRS data. The caveats with the DNB combustion source detection capability is that it should be restricted to pixels that are outside the zone of known VIIRS detected electric lighting.