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This article presents a low-cost photometer for experimental teaching designed to determine hexavalent chromium in aqueous solutions based on the detection of yellow chromate ions with ultraviolet light at 373 nm. This procedure replaces the colorimetric method that uses a spectrophotometer for the detection of the red-violet 1.5-diphenylcarbazide complex at 540 nm. To demonstrate the operation of the photometer, the Beer-Lambert law was evaluated using the linear regression technique, and the absorbance values obtained by the photometer were compared with those of a Shimadzu UV-2600 series UV-Vis spectrophotometer in five samples of hexavalent chromium in the range of 1 - 25 mg L-1. The experimental results demonstrated the linearity required by the Beer-Lambert law with a determination coefficient of 0.9988, and similarity between both analytical instruments with a relationship of 1.0041 between the absorbance values with a determination coefficient of 0.9993. In conclusion, the low-cost photometer is an excellent proposal for teaching the Beer-Lambert law in the classroom because it reduces the formation of waste, and dispenses with the reagents of the colorimetric method. [ABSTRACT FROM AUTHOR]

The efficiency of photopolymerisation significantly impacts achieving a high degree of conversion and, consequently, determines the success and strength of resin-based composite (RBC) restorations. The study aimed to measure the light irradiance of selected LED curing lamps, taking into account various exposure modes and the increased distance of the light source from the radiometer surface. The study material consisted of 21 LED polymerisation lamps of a single type (Woodpecker Medical Instrument Co., Guilin, China) with three exposure modes: standard, soft start, and pulse. During the measurement, the distance was increased from 0 mm to 8 mm, every 2 mm. Light irradiance measurements were made with a Bluephase Meter II photometer (Ivoclar Vivadent, Opfikon, Switzerland). Increasing the distance affected the soft mode the most, causing a significant drop in light irradiance on the photometer. Standard mode coped best with distance. Even at a distance of 0 mm, the soft start mode does not reach the power of the standard and pulse modes. The standard mode seems to be the most clinically effective, especially if it is planned to polymerise a material in a deep cavity. The soft start mode, as the least resistant to increasing distance, is recommended for use in front teeth or the cervical area. [ABSTRACT FROM AUTHOR]

In this study, we assess the homogeneity of aerosol optical depth (AOD) between two sun photometer networks, the Global Atmosphere Watch-Precision Filter Radiometer (GAW-PFR) and the European SKYNET radiometers network (ESR), at the common wavelengths of their main instruments (500 and 870 nm). The main focus of this work is to evaluate the effect of the improved Langley plot calibration method (ILP) used by SKYNET and to investigate the factors affecting its performance. We used data from three intercomparison campaigns that took place during 2017–2021. Each campaign was organized at two locations (mountainous rural – Davos, Switzerland; urban – Rome, Italy). Our analysis shows that differences in AOD due to post-processing and instrument differences are minor. The main factor leading to AOD differences is the calibration method. We found a systematic underestimation of AOD in ESR compared to in GAW-PFR due to underestimation of the calibration constant calculated with the ILP method compared to the calibration transfers using the PFR as a reference. The calibration and AOD differences are smaller in Davos, where the traceability criteria are satisfied at 870 nm and where the median differences are below 0.01 at 500 nm. In Rome, the AOD median differences at 500 nm were in the 0.015–0.034 range. We conducted a sensitivity study, which shows that part of the difference can potentially be explained by errors in the assumed surface albedo and instrument solid-view angle provided as inputs to the ILP code (based on Skyrad pack 4.2). Our findings suggest that the ILP method is mainly sensitive to the measured sky radiance. The underestimation in calibration is probably caused by an error in the retrieved scattering AOD (sc-AOD) through the sky radiance inversion. Using an alternative retrieval method (Skyrad MRI pack version 2) to derive sc-AOD and to recalibrate the instruments with the ILP method, we found no significant differences between the retrieved sc-AOD and no systematic increase in the ILP-derived calibration constant when using the MRI pack for sc-AOD inversion instead of the Skyrad 4.2. The potential error may be a result of the model assumptions used for the sky radiance simulations. In conclusion, the on-site calibration of sun photometers has several advantages, including the fact that instrument shipments and data gaps can be avoided. However, it has also the disadvantages of a larger uncertainty and significant systematic differences compared to the traditional Langley calibration performed under low- and constant-AOD conditions at high-altitude sites. The larger uncertainty of the ILP method can be attributed to the required modelling and input parameters. [ABSTRACT FROM AUTHOR]

The Triple Ionosophere PhotoMeter (TRIPM) is designed to make the disk observations of the Earth airglow emissions at OI 135.6 nm and N 2 Lyman-Birge-Hopfield (LBH) band that flew aboard the newly launched early morning satellite Fengyun-3E (FY-3E) which was launched on July 5th, 2021. This is the first attempt to obtain the global twilight airglow data in the far ultraviolet band using Ionosophere PhotoMeter. The seasonal behavior of the twilight airglow at the OI 135.6 nm and N 2 LBH band is exhibited and interpreted in the paper. Validity of the TRIPM data is analyzed by comparison with the simulation results of the Global Airglow (GLOW) and the simulation results reveal good consistency with the observational results. Furthermore, based on the ionospheric contributions calculated by GLOW model, we extract the ionospheric information from the TRIPM 135.6 nm emissions. This means the ionospheric signature in the 135.6 nm radiance at the dawn and dusk times can be provided. Comparison between the ionospheric 135.6 nm radiance due to O+ and electron radiative recombination with GPS TEC data shows a similar morphology of equatorial arcs and seasonal variation of the ionosphere. [ABSTRACT FROM AUTHOR]

A simple, cheap, and portable Arduino-based photometer was constructed and used to determine cobalt(II) after extraction by a thin film microextraction strip. The paired emitter-detector diodes configuration was employed for making the photometer. A polymer inclusion membrane was applied to fabricate the thin film microextraction strip. The optimization of the polymer membrane composition was done by response surface methodology (RSM). The optimized membrane was obtained containing 40.8% (w/w) of polyvinyl chloride, 45.0% of (2-ethylhexyl) phosphoric acid extractor, 1.3% of 1-(2-pyridylazo)-2-naphthol as the complexing agent and 12.9% of tri-butyl phosphate plasticizer. The variables affecting microextraction efficiency were optimized to be 0.05 M of sodium sulfate, pH 6.0, and extraction time of 120 min at room temperature (22 ± 1 °C). The analytical performance included a linear range between 3 and 200 µg L−1 with detection and quantitation limits of 1 and 3 µg L−1, respectively. The intra-day and inter-day precision were less than 2.9 and 6.2%, respectively. Finally, the method was used to determine cobalt in the water and tablets. Relative recovery for the tap water sample was from 94 to 111%. [ABSTRACT FROM AUTHOR]

Gaia DR3 photometry and Blue Photometer (BP) and Red Photometer (RP) spectra have been widely used as reference in photometric calibrations. In this work, we check the spatial uniformity of Gaia DR3 photometry and BP/RP spectra by comparing the BP, RP, and G -band photometry with the synthetic ones from the BP/RP spectra. The discrepancies have a small dispersion of 1.07, 0.55, and 1.02 mmag for the BP, RP, and G bands, respectively. However, the discrepancies exhibit obvious spatial patterns, which are clearly associated with Gaia's scanning law. The patterns observed in the BP and G bands are similar, with discrepancies between photometry and spectra being more pronounced in these bands compared to the RP band. A further independent test with the Dark Energy Survey DR2 photometry reveals that the spatial patterns are more likely attributed to the Gaia DR3 BP/RP spectra, particularly in the BP band. On one hand, our results confirm the high spatial uniformity of Gaia data at the mmag level. On the other hand, our results suggest that the spatial uniformity of Gaia DR3 BP/RP spectra is not as good as that of Gaia DR3 photometry, and could be further improved in the future. [ABSTRACT FROM AUTHOR]

This work aims at investigating the effect of NO2 absorption on aerosol-optical-depth (AOD) measurements and Ångström exponent (AE) retrievals of sun photometers by the synergistic use of accurate NO2 characterization for optical-depth estimation from co-located ground-based measurements. The analysis was performed for ∼ 7 years (2017–2023) at several sites worldwide for the AOD measurements and AE retrievals by Aerosol Robotic Network (AERONET) sun photometers which use OMI (Ozone Monitoring Instrument) climatology for NO2 representation. The differences in AOD and AE retrievals by NO2 absorption are accounted for using high-frequency columnar NO2 measurements by a co-located Pandora spectroradiometer belonging to the Pandonia Global Network (PGN). NO2 absorption affects the AOD measurements in UV-Vis (visible) range, and we found that the AOD bias is the most affected at 380 nm by NO2 differences, followed by 440, 340, and 500 nm , respectively. AERONET AOD was found to be overestimated in half of the cases, while also underestimated in other cases as an impact of the NO2 difference from "real" (PGN NO2) values. Overestimations or underestimations are relatively low. About one-third of these stations showed a mean difference in NO2 and AOD (at 380 and 440 nm) above 0.5 × 10-4 molm-2 and 0.002, respectively, which can be considered a systematic contribution to the uncertainties in the AOD measurements that are reported to be of the order of 0.01. However, under extreme NO2 loading scenarios (i.e. 10 % highest differences) at highly urbanized/industrialized locations, even higher AOD differences were observed that were at the limit of or higher than the reported 0.01 uncertainty in the AOD measurement. PGN NO2 -based sensitivity analysis of AOD difference suggested that for PGN NO2 varying between 2 × 10-4 and 8 × 10-4 molm-2 , the median AOD differences were found to rise above 0.01 (even above 0.02) with the increase in NO2 threshold (i.e. the lower limit from 2 × 10-4 to 8 × 10-4 molm-2). The AOD-derivative product, AE, was also affected by the NO2 correction (discrepancies between the AERONET OMI climatological representation of NO2 values and the real PGN NO2 measurements) on the spectral AOD. Normalized frequency distribution of AE (at 440–870 and 340–440 nm wavelength pair) was found to be narrower for a broader AOD distribution for some stations, and vice versa for other stations, and a higher relative error at the shorter wavelength (among the wavelength pairs used for AE estimation) led to a shift in the peak of the AE difference distribution towards a higher positive value, while a higher relative error at a lower wavelength shifted the AE difference distribution to a negative value for the AOD overestimation case, and vice versa for the AOD underestimation case. For rural locations, the mean NO2 differences were found to be mostly below 0.50 × 10-4 molm-2 , with the corresponding AOD differences being below 0.002, and in extreme NO2 loading scenarios, it went above this value and reached above 1.00 × 10-4 molm-2 for some stations, leading to higher AOD differences but below 0.005. Finally, AOD and AE trends were calculated based on the original AERONET AOD (based on AERONET OMI climatological NO2), and its comparison with the mean differences in the AERONET and PGN NO2 -corrected AOD was indicative of how NO2 correction could potentially affect realistic AOD trends. [ABSTRACT FROM AUTHOR]

Purpose: The study aimed to determine the activity of administering Hydrocotyle sibthorpioides Lam. extract in capsule dosage on SGPT and SGOT levels in humans. Methods: The participants involved 20 healthy volunteers aged 20-25 years who were divided into 2 groups with placebo as a comparison. The treatment groups were given capsules containing Hydrocotyle sibthorpioides Lam. extract at a dose of 67 mg. The other group administered a placebo containing lactose for 3 days. SGPT and SGOT levels were measured before and after consuming the test capsules. The examination of SGPT and SGOT levels was carried out using a 5010 v5+ photometer. Results: SGPT levels before the capsules were 28.79 U/L for the placebo and 28.59 U/L for the test preparation group. After administration of Hydrocotyle sibthorpioides Lam. extract capsules were 24.26 U/L and for placebo 32.86 U/L. At the same time, the measurement results of SGOT levels before being given the capsule were 17.37 U/L for the placebo and 17.71 U/L for the test preparation group. After administration of Hydrocotyle sibthorpioides Lam. extract capsules, it was 14.56 U/L and 18.52 U/L for placebo. The study results show that Hydrocotyle sibthorpioides Lam. extract significantly decreases SGPT and SGOT levels in humans (p<0.5). Conclusion: This result indicates that Hydrocotyle sibthorpioides Lam extract is relatively non-toxic and safe for public use as an immunostimulant herbal medicine. [ABSTRACT FROM AUTHOR]

The measured spatial resolution of augmented reality head‐mounted displays (AR HMDs) is determined by three components: optics, display, and the rendering pipeline, which includes the anti‐aliasing method. Therefore, separating and quantifying the contributions from these components is necessary for evaluating the spatial resolution of AR HMDs. We demonstrate a method for quantifying the contributions from the optical performance and the rendering pipeline on the spatial resolution of AR HMD using point‐spread function (PSF) analysis. In this method, an imaging photometer captures a series of rendered scenes on the AR HMD that consist of arrays of spheres of increasing sizes with different anti‐aliasing (AA) methods. The contributions from the optics, display, and anti‐aliasing methods can be separated, and we find that temporal anti‐aliasing (TAA) and multisample anti‐aliasing (MSAA) are in good agreement with the performance of no AA. However, fast approximate anti‐aliasing (FXAA) results in decreased luminance for smaller rendered targets and a different spatial resolution for larger targets. Finally, we repeated our methods on multiple HMDs and characterized the dependence of the spatial resolution across the field of view. These measurements show significant non‐uniformity in the optical contribution to the spatial resolution. [ABSTRACT FROM AUTHOR]

In the autumn of 2021, a multichannel imaging photometer of the Pulsating Aurora Imaging Photometer System was installed at the Verkhnetulomsky Observatory. During the first season of operation (2021/2022), measurements were made over the course of 163 nights in three modes of temporal resolution: 2.5 μs, 320 μs, and 41 ms. The high temporal resolution makes it possible to investigate the fine temporal structure of the emission, which are short (less than 1 s) bursts of UV radiation, so-called "microbursts" that can be single or follow in series. The long-term series of microbursts registered on November 27–29, 2021, were analyzed. It is shown that the series of bursts have a complex temporal structure, individual bursts have several peaks with intervals of 100–400 ms, the intervals between bursts are of the order of 1 s, and they appear in packs lasting from several seconds to minutes. The series appear both in quiet geomagnetic conditions and during substorms; the frequency and amplitude of bursts in the second case are significantly larger. [ABSTRACT FROM AUTHOR]

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Light absorbing carbonaceous aerosols produced from combustion span over a range of physicochemical properties. Soot is the most recognized species in this category and its formation process involves gradual maturation from amorphous young soot with a high hydrogen-to-carbon-ratio toward mature soot aggregates. In this work, the optical response of a single particle soot photometer (SP2) to electrical mobility size selected soot of different maturity produced by a mini-CAST soot generator is investigated. The results show that for soot of a specific mobility diameter, the laser-induced incandescence (LII) signal appears earlier and with a higher LII peak height for increasing soot maturity. The experimental observations are supported by simulations using a numerical model for the LII process. Furthermore, the effect of systematically varying the SP2 laser power on the detection of soot of different maturity using LII is explored. This work can be seen as a step toward the aim of using the SP2 instrument to identify soot particles of different maturity in the atmosphere. [ABSTRACT FROM AUTHOR]

Lightning flashes were observed in Barrancabermeja (Colombia) by two photometers centered at 337 and 777 nm wavelengths, a high‐speed camera, and the Colombia Lightning Mapping Array. Both optical and VHF radio emissions of different lightning processes are investigated. Flash initiations by upward in‐cloud breakdown present a first short optical pulse followed by a period of ∼1 kHz breakdown propagation. The ratio remains at unity or below, associated with the transition to negative horizontal leader propagation. In flash initiations by a fast‐stepped negative downward leader to ground, a dominance of the 337 nm radiance is found. Observations of downward leaders before ground strokes reveal that the luminosity measured by the photometers is dominated most of the time by the light coming from the cloud and not from the visible leader channels. One case of a visible cloud‐to‐ground channel with positive continuing current shows a high similarity in the evolution of the luminosity along the channel, 777 nm radiance, and the energy detected by the Geostationary Lightning Mapper from space. Finally, two types of recoil leaders have been observed: connecting and non‐connecting. Whereas the measured 777 nm peak radiance is similar in both types of recoil leaders, connecting recoil leaders present about seven times higher 337 nm peak radiance. Our observations generally show agreement between the VHF power and optical emissions. Plain Language Summary: Optical lightning observations using high‐speed video and fast photometers at 337 and 777 nm were conducted in Barrancabermeja (Colombia). The Barrancabermeja region is covered by a high‐resolution lightning detection network that provides locations of lightning sources and radio power. This work aims to observe lightning from the ground in the same optical bands as the Atmosphere‐Space Interactions Monitor (ASIM) to provide the optical characteristics of different lightning processes. The investigated lightning processes are flash initiations, downward leaders, positive continuous currents, and recoil leader events. Flash initiations as upward in‐cloud breakdown and fast‐stepped downward negative leaders are found to produce optical emissions consistent with those previously reported from space. An observed cloud‐to‐ground channel with positive continuing current revealed a high similarity between ground and space observations. Two types of recoil leader events have been observed. The connecting type of recoils presents higher 337 nm optical emissions than the non‐connecting ones. In both types, 777 nm emissions remain similar. Our observations generally showed agreement between the VHF power and optical emissions. Key Points: Ground based photometer, video and VHF are combined to study lightning initiations, downward leaders, continuing currents, and recoil leadersFlash initiations by upward in‐cloud breakdown exhibits a drop of the 337‐to‐777 nm ratio as observed from space, with an initial exceptionDownward leaders and recoil leader events produce optical emissions with similar features as the averaged very high frequency power [ABSTRACT FROM AUTHOR]

In this study, we assess the homogeneity of aerosol optical depth (AOD) between the sun photometer networks Global Atmospheric Watch-Precision Filter Radiometer (GAW-PFR) and European Skynet Radiometers network (ESR) at the 2 common wavelengths of their main instruments 500 nm and 870 nm. The main focus of the work is on evaluating the effect of the Improved Langley calibration method, (ILP) used by SKYNET and investigating the factors affecting its performance. We used data from three intercomparison campaigns that took place in the period 2017–2021. Each campaign has two phases in two locations. One is mountainous rural (Davos, Switzerland) and the other urban (Rome, Italy). Our analysis shows that the AOD differences due to post processing and instrument differences are minor. The major factor leading to AOD differences is the calibration method where we found a systematic underestimation of AOD compared to GAW-PFR due to an underestimation in the ILP calibration. The calibration and AOD differences are smaller in Davos where at 870 nm the traceability criteria are satisfied and at 500 nm the median differences are below 0.01. In Rome at 500 nm the AOD median differences per campaign are between 0.015–0.035. Attempting to explain the differences we found no association between the calibration performance and the level or the variability of the aerosol properties. We also conducted a sensitivity study, which shows that part of the difference can be potentially explained by errors in the assumed surface albedo and instrument solid view angle provided as inputs to the ILP code (based on Skyrad pack 4.2). Our findings suggest that the ILP method is mainly sensitive to the measured sky radiance. The calibration underestimation is probably caused by an error on the retrieved scattering aerosol optical depth (sc-AOD) through the sky radiance inversion. Using an alternative retrieval method (Skyrad MRI pack version 2) to derive sc-AOD and repeat ILP calibration, we found no significant differences between the retrieved sc-AOD nor systematic increase of the calibrations. The potential error may be a result of the forward model assumptions, To conclude, calibration of sun photometers on site offers the advantage of avoiding instrument shipments and data gaps. However, ILP shows larger uncertainty and significant systematic difference compared to the traditional Langley calibration performed under low and constant AOD conditions at high altitude sites, due to the uncertainties of the calibration method and the input parameters needed for it. In the following sections we report on results on the AOD retrievals of several instruments in different environments using different principles in their calibration methods. We also perform an investigation to explain the causes of differences. [ABSTRACT FROM AUTHOR]

Photometric technology, characterized by its compact structure and relatively high stability, finds wide application in measuring airglow spectra. This instrumentation is anticipated to assume a pivotal role as the primary equipment for extensive network observations of middle and upper atmospheric temperatures in China, thereby providing crucial support for space environmental monitoring and atmospheric dynamic research. Nevertheless, susceptibility to various factors such as instrument inconsistency, variability in observation conditions, and alterations in the background atmospheric environment across different stations poses a challenge, potentially resulting in data inconsistencies in network observations. In response to these challenges, we propose a multiple-parameter iterative inversion (MPII) algorithm for temperature retrieval based on a mesospheric airglow spectrum photometer (MASP) developed by our research group. This algorithm accurately identifies the center of the image circle, corrects image distortion, and thereby obtains an accurate synthetic spectrum reflective of actual observations. It encompasses five adjustable parameters: sky background light, atmospheric temperature, filter temperature, optical system focal length, and degree of synthetic spectrum modulation. Compared to traditional methods, significant enhancements in the accuracy of the inverted temperature are achieved. To validate the effectiveness of the MPII algorithm, we conducted combined active and passive remote sensing synchronous measurements using MASP in conjunction with a sodium fluorescence Doppler lidar developed by the National Space Science Center. By utilizing the lidar temperature as a reference, atmospheric background radiation is mitigated from the MASP data, and the temperature is inverted using the MPII algorithm. Comparative analysis with the traditional method reveals that temperatures calculated by the MPII algorithm exhibit better consistency than those observed by the lidar. [ABSTRACT FROM AUTHOR]

This work aims at investigating the effect of NO2 absorption on aerosol optical depth (AOD) and Ångström exponent (AE) retrievals of sun photometers by synergistic use of the accurate NO2 characterization for optical depth estimation from co-located ground-based measurements. The analysis was performed for ~7 years (2017–2023) at a global scale for the AOD and AE retrievals by Aerosol Robotic Network (AERONET) sun photometers which uses OMI (Ozone Monitoring Instrument) climatology for NO2 representation. The deviations in AOD and AE retrievals by NO2 absorption is accounted for using high-frequency columnar NO2 measurements by co-located Pandora spectroradiometer belonging to Pandonia Global Network (PGN). The AERONET retrieved AOD was found to be overestimated in half of the cases while also underestimated in other cases as an impact of the NO2 deviation from "real" (PGN NO2) values. Over or underestimations are relatively low. About one-third of these stations showed a mean deviation in NO2 and AOD (at 380 nm and 440 nm) above 0.5x10-4 mol-m-2 and 0.002, respectively, which can be considered as a systematic contribution to the uncertainties of AOD retrievals that are reported to be in the order of 0.01. However, under extreme NO2 loading scenarios (i.e., 10 % highest deviations), even higher AOD deviations were observed that were at the limit or higher than the reported 0.01 uncertainty of the AOD retrieval. The PGN NO2 based sensitivity analysis of AOD deviation suggested that for PGN NO2 varying between 2x10-4 and 8x10-4 mol-m-2, the median AOD differences were found to rise above 0.01 (even above 0.02) with the increase in NO2 threshold (i.e., the lower limit from 2 x10-4 mol-m-2 to 8 x10-4 mol-m-2). The AOD-derivative product, AE, was also affected by the NO2 correction (discrepancies between the AERONET OMI climatological representation of NO2 values and the real PGN NO2 measurements) on the spectral AOD. The normalized frequency distribution of AE (at 440–870 nm and 380–675 nm wavelength pair) was found to be narrower for broader AOD distribution for some stations and vice versa for other stations and a higher relative error at the shorter wavelength (among the wavelength pairs used for AE estimation) lead to a shift in the peak of the AE distribution towards a higher value. Finally, the AOD and AE trends were calculated based on the original AERONET AOD (based on AERONET OMI climatological NO2) according to the data availability and it was further signified the importance of having a correct (real) NO2 representation in AOD retrievals as it would possibly impact the respective trends. [ABSTRACT FROM AUTHOR]

This work introduces CAECENET, a new system capable of automatically retrieving columnar and vertically-resolved aerosol properties running the GRASP (Generalized Retrieval of Atmosphere and Surface Properties) algorithm using sun-sky photometer (aerosol optical depth, AOD; and sky radiance measurements) and ceilometer (range corrected signal; RCS) data as input. This method, so called GRASPpac, is implemented in CAECENET, which assimilates sun-sky photometers data from CÆLIS database and ceilometer data from ICENET database (Iberian Ceilometer Network). CAECENET allows for continuous and near-real-time monitoring of both vertical and columnar aerosol properties. The main characteristics and workflow of CAECENET are explained in detail. This work also explores the potential of CAECENET to monitor and analyze the evolution of transported aerosol events on a regional scale by means of the distribution of CAECENET stations across the Iberian Peninsula. As an example, this paper analyzes, using the CAECENET products, the case of a Saharan dust outbreak that occurred between the 3rd and 5th of October 2022. This was an intense event, with AOD at 440 nm values around 0.5 in Madrid and Valladolid, and reaching 1.55 in Granada. Transport from the Canadian wildfires at the end of June 2023 is also studied. Despite the long-range transport of the smoke particles in this event, measured volume concentrations reached and surpassed 80 μ m3/ μ m2 in some stations. The results obtained point to the utility of this CAECENET tool for analyzing changes in the height and speed of the event propagation, in the aerosol concentration, and how this affects the optical properties. [ABSTRACT FROM AUTHOR]

This article presents a new method for transferring calibration from a reference sun photometer, referred to as the "master", to a secondary sun photometer, referred to as the "field", using a synergetic approach when master and field instruments have different spectral bands. The method was first applied between a precision filter radiometer (denoted PFR) instrument from the World Optical Depth Research and Calibration Center (WORCC), considered the reference by the WMO (World Meteorological Organization), and a CE318-TS photometer (denoted Cimel), the standard photometer used by AERONET (AErosol RObotic NETwork). These two photometers have different optics, sun-tracking systems, and spectral bands. The Langley ratio (LR) method proposed in this study was used to transfer calibration to the closest spectral bands for 1 min synchronous data for air masses between 2 and 5, and it was compared to the state-of-the-art Langley calibration technique. The study was conducted at two different locations, Izaña Observatory (IZO) and Valladolid, where measurements were collected almost simultaneously over a 6-month period under different aerosol regimes. In terms of calibration aspects, our results showed very low relative differences and standard deviations in the calibration constant transferred in IZO from the PFR to the Cimel: up to 0.29 % and 0.46 %, respectively, once external factors such as different fields of view between photometers or the presence of calibration issues were considered. However, these differences were higher in the comparison performed at Valladolid (1.04 %) and in the shorter-wavelength spectral bands (up to 0.78 % in IZO and 1.61 % in Valladolid). Additionally, the LR method was successfully used to transfer calibrations between different versions of the CE318-T photometer, providing an accurate calibration transfer (0.17 % to 0.69 %) in the morning LRs, even when the instruments had differences in their central wavelengths (Δλ up to 91 nm). Overall, our results indicate that the LR method is a useful tool not only for transferring calibrations but also for detecting and correcting possible instrumental issues. This is exemplified by the temperature dependence of the signal on the two Cimel UV spectral bands, which was estimated by means of the LR method, resulting in a signal rate of change of approximately -0.09×10-2 per degree in the case of 380 nm and approximately -0.03×10-2 per degree in the case of 340 nm. This estimation allowed us to implement the first operative temperature correction on ultraviolet (UV) spectral bands. [ABSTRACT FROM AUTHOR]

To retrieve columnar aerosol properties from sun-photometers both irradiance and radiance calibration factors are needed. For the irradiance the solar calibration constant, V0, that is the instrument counts for a direct normal solar flux extrapolated to the top of the atmosphere, must be determined. The solid view angle, SVA, is the measure of the field of view of the instrument, and it is important for obtaining the Radiance from sky diffuse irradiance measurements. Each of the three sun-photometers networks considered in the present study (SKYNET, AERONET, WMO-GAW) adopts different protocols of calibration and we evaluated the performance of the on-site calibration procedures, applied to SKYNET PREDE-POM instruments, during intercomparison campaigns and laboratory calibrations held in the framework of the Metrology for Aerosol Optical Properties (MAPP) EMPIR project. The on-site calibration, performed as frequently as possible (rather monthly) to monitor change of the machine condition, allow operators to track and evaluate the calibration status on a continuous basis considerably reducing the data gaps incurred by the periodical shipments for performing centralized calibrations. The performance of the on-site calibration procedures for V0 was very good in sites with low turbidity, showing an agreement with a reference calibration between 0.5% and 1.5% depending on wavelengths. In the urban area the agreement decreases between 1.7% and 2.5%. For the SVA the difference varied from a minimum of 0.03 % to a maximum of 3.46%. [ABSTRACT FROM AUTHOR]

The shortcomings of satellite monitoring of associated gas burning in the oil industry have been analyzed. The possibility of performing such monitoring using ground-based photometric devices is indicated. The possibility of compensating for errors of multi-wave solar photometers due to the influence of atmospheric aerosols has been studied. The conducted research allowed to identify redundancy in correction procedures in known three-wave solar photometers. Two new methods for constructing compensated photometers are proposed. In the proposed constructions, the correction procedure is limited to the calculation and installation of one correction factor. [ABSTRACT FROM AUTHOR]

A sun photometer is a type of photometer that points at the sun, and it has been playing an increasingly important role in characterizing aerosols across the world. As long as the solar photometer is accurately calibrated, the optical thickness of the aerosol can be obtained from the measured value of this device. When the calibration of a single instrument is not accurate, the inversion quantity varies greatly. The calibration constant of the sun photometer changes during its use process; thus, calibrations are frequently needed in order to ensure the accuracy of the measured value. The calibration constant of the solar photometer is usually determined using the Langley method. Internationally, AERONET has two Langley calibration stations: the Mauna Loa observatory in the United States and the Izaña observatory in Spain. So far, the International Comparison and Calibration System has been established in Beijing, similar to AERONET at GSFC, but the Langley calibration system has not yet been established. Therefore, it is necessary to select a suitable calibration station in China. This paper studies the requirements of the calibration station using the Langley method. We used long-term records of satellite-derived measurements and survey data belonging to the aerosol optical thickness data of SNPP/VIIRS, CERES, MERRA-2, etc., in order to gain a better understanding of whether these stations are suitable for calibration. From the existing astronomical observation stations, meteorological stations, and the Sun–Sky Radiometer Observation Network (SONET) observation stations in China, the qualified stations were selected. According to the statistical data from the Ali observatory, the monthly average of clear sky is 20.21 days, and it is always greater than 15 days. The monthly average of aerosol is not more than 0.15 and is less than 0.3. We believe that the atmosphere above the Ali observatory is stable, and the results show that the Ali observatory has excellent weather conditions. This study can provide a selection of calibration sites for solar photometer calibrations in China that may need to be further characterized and evaluated, and at the same time provide a method to exclude unsuitable calibration sites. [ABSTRACT FROM AUTHOR]

The versatile Generalized Retrieval of Aerosol and Surface Properties (GRASP) algorithm exploits the advantages of synergic ground-based aerosol observations such as radiometric (sensitive to columnar aerosol optical and microphysical properties) and lidar (sensitive to vertical distribution of the optical properties) observations. The synergy is possible when the complementary data is mutually constrained by GRASP parametrization that includes, for the first time ever, the degree of linear polarization (DoLP) parameter measured by a polarized sun-sky-lunar AERONET photometer (380, 440, 500, 675, 870, 1020, and 1640 nm) in synergy with the vertical profiles from an elastic lidar (355, 532, and 1064 nm). First, a series of numerical tests is performed using simulated data generated using a climatology of data and ground-based measurements. The inversions are performed with and without random noise for five different combinations of input data, starting from the AERONET-like dataset and increasing to the complex one by adding more information for three aerosol scenarios: I—high aerosol optical depth (AOD) with dominant coarse mode; II—low AOD with dominant coarse mode; III—high AOD with dominant fine mode. The inclusion of DoLP improves (i) the retrieval accuracy of the fine-mode properties when it is not dominant; (ii) the retrieval accuracy of the coarse-mode properties at longer wavelengths and that of the fine-mode properties at shorter wavelengths; (iii) the retrieval accuracy of the coarse-mode real part of the refractive index (up to 36% reduction), but has no effect on the retrieval of the imaginary part; (iv) reduces up to 83% the bias of the sphere fraction (SF) retrieval in coarse-mode dominated regimes; and (v) the root mean square error (RMSE) of the retrieval for most of the parameters in all scenarios. In addition, the addition of more photometer channels in synergy with a three-wavelength elastic lidar reduces the RMSE for the real part (67% in the coarse mode) and the imaginary part (35% in the fine mode) of the refractive index, the single scattering albedo (38% in the fine mode), the lidar ratio (20% in the coarse mode), and the SF (43%). [ABSTRACT FROM AUTHOR]

The mixing state of black carbon (BC) aerosols, which is the diameter ratio of coated particle to BC core (Dp/Dc), can be retrieved by the single-particle soot photometer (SP2). However, the retrieved Dp/Dc contains errors, because the core–shell model and Mie scattering calculation are normally employed in the retrieval principle of SP2 and the spherical core–shell structure seriously deviated from the real morphology of coated BC. In this study, fractal models are constructed to represent thinly and thickly coated BC particles for optical simulations, the differential scattering cross-sections are selected as references to conduct optical retrieval of particle diameter (Dp) based on Mie theory, just like the retrieval principle of SP2, and the volume equivalent diameter of BC core (Dc) is the same for fractal and spherical models. Then, the retrieval errors of the mixing state (Dp/Dc) of BC are investigated from numerical aspects, and the estimation accuracy of BC radiative forcing is analyzed through the simple forcing efficiency (SFE) equation with SP2 retrieval results taken into consideration. Results show that SP2 retrieved Dp/Dc based on Mie theory underestimates the realistic Dp/Dc of coated BC at most particle sizes. The retrieval errors of Dp/Dc of thinly coated BC for both single particles and particle groups are larger than those of thickly coated BC. In addition, evaluation errors of radiative forcing of coated BC caused by retrieval errors of SP2 are up to about 55 % and 95 % at 1064 and 532 nm , respectively. This study provides meaningful referential understandings of the retrieved Dp/Dc of SP2 based on Mie scattering. [ABSTRACT FROM AUTHOR]

In 1924, the CIE published and standardized the photopic luminous efficiency function. Based on the standardized curve, luminous flux in lumens, luminance in cd/m 2 , and illuminance in lux are determined by an integral of the curve and the incident light spectra in photometers and are considered physical brightness. However, human brightness perception is not only weighted by this simple determination, but is a more complicated combination of all L-cones, M-cones, S-cones, rods and later ipRGCs, which was partly described by the equivalent brightness of Fotios et al. with the correction factor (S / V) 0.24 . Recently, new research has demonstrated the role of ipRGCs in human light perception. However, it is still unclear how these signal components of the human visual system are involved in the overall human brightness perception. In this work, human brightness perception under photopic conditions was investigated by visual experiments with 28 subjects under 25 different light spectra. In this way, the contributions of the signal components can be investigated. An optimization process was then performed on the resulting database. The results show that not only the L + M component, but also the S-cones and ipRGC play a role, although it is smaller. Thus, the visually scaled brightness model based on the database optimization was constructed using not only illuminance but also S-cones and ipRGC with R 2 of 0.9554 and RMSE of 4.7802. These results are much better than the brightness model after Fotios et al. using only S-cones ( R 2 = 0.8161, RMSE = 9.7123) and the traditional model without S-cones and ipRGC ( R 2 = 0.8121, RMSE = 9.8171). [ABSTRACT FROM AUTHOR]

The data retrieved from satellite imagery and ground-based photometers are the two main sources of information on light pollution and are thus the two main tools for tackling the problem of artificial light pollution at night (ALAN). While satellite data offer high spatial coverage, on the other hand, photometric data provide information with a higher degree of temporal resolution. Thus, studying the proper correlation between both sources will allow us to calibrate and integrate them to obtain data with both high temporal resolution and spatial coverage. For this purpose, more than 15,000 satellite measurements and 400,000 measurements from 72 photometers for the year 2022 were used. The photometers used were the Sky-Glow Wireless Autonomous Sensor (SG-WAS) and Telescope Encoder and Sky Sensor WIFI (TESS-W) types, located at different ground-based locations, mainly in Spain. These photometers have a spectral sensitivity closer to that of VIIRS than to the Sky Quality Meter (SQM). In this study, a good correlation of data from the Day–Night Band (DNB) from the Visible Infrared Imaging Radiometer Suite (VIIRS) with a red photometric network between 19.41 mag/arcsec 2 and 21.12 mag/arcsec 2 was obtained. [ABSTRACT FROM AUTHOR]

The results of the analysis of photometric and spectral monitorings of the recurrent symbiotic nova T CrB, carried out using the low-resolution spectrograph TDS of the 2.5-m telescope and the CCD photometer of the 0.6-m telescope of the CMO SAI, are presented. It is shown that the fluxes in the emission lines H , H , He I 5876 change by 6–16 , and in the emission line He II 4686 by about 60 on timescales of 20–60 minutes. The line flux curves on August 25, 2020 are similar to the light curve of T CrB, but with a time delay of up to 600 s for different lines. The observed spectrum is approximated by the radiation of the system components with the following parameters: a red giant of spectral type M4 III, a nebula with K and emission measure of cm , and the accretion disk with , (at inclination ). [ABSTRACT FROM AUTHOR]

Carbon-enhanced metal-poor (CEMP) stars comprise almost a third of stars with [Fe/H] < −2, although their origins are still poorly understood. It is highly likely that one sub-class (CEMP- s stars) is tied to mass-transfer events in binary stars, while another sub-class (CEMP-no stars) are enriched by the nucleosynthetic yields of the first generations of stars. Previous studies of CEMP stars have primarily concentrated on the Galactic halo, but more recently they have also been detected in the thick disc and bulge components of the Milky Way. Gaia DR3 has provided an unprecedented sample of over 200 million low-resolution (R ≈ 50) spectra from the BP and RP photometers. Training on the CEMP catalogue from the SDSS/SEGUE database, we use XGBoost to identify the largest all-sky sample of CEMP candidate stars to date. In total, we find 58 872 CEMP star candidates, with an estimated contamination rate of 12 per cent. When comparing to literature high-resolution catalogues, we positively identify 60–68 per cent of the CEMP stars in the data, validating our results and indicating a high completeness rate. Our final catalogue of CEMP candidates spans from the inner to outer Milky Way, with distances as close as r ∼ 0.8 kpc from the Galactic centre, and as far as r > 30 kpc. Future higher resolution spectroscopic follow-up of these candidates will provide validations of their classification and enable investigations of the frequency of CEMP- s and CEMP-no stars throughout the Galaxy, to further constrain the nature of their progenitors. [ABSTRACT FROM AUTHOR]

Water is a key player in any biological system and it is vital to quality existence of living things. The abundance, assemblage, density, diversity and kinds of macro-vegetation present in a system are pointers to ecological health and the knowledge of biodiversity upsurge or decline is necessary for management decisions at various levels. In the evaluation of Macro-vegetation and some physicochemical factors of Tirwum pond, samples were collected once a month for six consecutive months. According to the manufacturer's operating procedure as approved by EPA, Colorimeter hach DR 890 was used to determine turbidity, HANNA HI 9813-5 was used to determine total dissolved solids (TDS), (pH) and electrical conductivity (EC), dissolved oxygen (DO) was measured by JPB-70A pen type intelligent dissolved oxygen analyzer, nitrate and phosphate were determined by means of PALINTEST photometer Wagtech 7100. The determination of TSS and TS were by filtration and evaporation methods respectively and temperature was measured in situ using mercury in glass thermometer. 60 quadrats of 1x1m2 were thrown and a long, double-headed rake dipped down, turned 360degrees within each quadrant and all plants within the quadrant frame were counted and identified. The species richness was six belonging to four families. Diversity and evenness index were 1.69 and 0.94 correspondingly. Most values of pH were within the optimum range. The above 3mg/L of all nitrogen values branded the pond as polluted. The abundance of three macro-vegetation families negatively correlated with dissolved oxygen (p=0.01, p=0.05), but positively correlated with Temperature (p=0.05). The abundance of macro-vegetation showed negative correlation with EC and TDS (P = 0.05). The absence of submerged macrophytes, high concentration of nitrate and low concentration of dissolved oxygen reflected the impaired state of the pond community and the species richness of six is bad for biodiversity at local and global level. [ABSTRACT FROM AUTHOR]

The drinking water supply in the Prizren Region still poses a challenge to local and central governments. Over 30% of the inhabitants of this region are not supplied with safe drinking water. They are bound by alternative supply solutions. Many households provide drinking water from artisanal wells to provide water for consumption. The water provided by these springs is often unsuitable and unsafe because it is not treated. In this research, we have studied the quality of drinking water in ten artisanal wells that constitute the main source of supply for more than 10 households, in different villages of the Prizren region. Samples were subjected to laboratory analyses evaluating physic-chemical and bacteriological parameters. In assessing the quality of the samples, we used the prospective analytical epidemiological method. Physico-chemical and bacteriological samples were analyzed in the water laboratory of the Regional Institute of Public Health in Prizren. In the research physic-chemical parameters such as; temperature, turbidity, pH, ammonia, nitrates, nitrites, iron, and manganese were investigated with a turbid meter, tempo meter, pH meter, and photometer (Hanna Instruments), while in the microbiological analysis we used the membrane filter method. The results are compared with the standards for drinking water according to National Instruction 16/2012, harmonized with the European Directive on Drinking Water. The results showed that 4 samples of 10, are characterized by increased values compared to the allowed standards for drinking water according to National Instruction 16/20212. Of these, 2 samples had increased turbidity values where the nephelometric turbidity unit was 2.2, and iron 14 mg/L. In 4 samples we found the presence of bacterial contamination like coliform bacteria E. coli. Other samples are within permitted standards. We concluded that the quality of drinking water from artisanal wells is not safe for human consumption, and/or it should be treated before use. Especially bacteriological findings speak of contamination and must necessarily be disinfected before use. Local institutions should increase care for the water supply of these residents, at best monitoring its quality. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Exact Sciences is the property of Master Editora and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This article presents a new method for transferring calibration from a reference photometer, referred to as the "master", to a secondary photometer, referred to as the "field", using a synergetic approach when master and field instruments have different spectral bands. The method was first applied between a PFR, (Precision Filter Radiometer) instrument from the World Optical Depth Research and Calibration Center (WORCC) considered the reference by the WMO (World Meteorological Organiza- tion), and a CE318-TS photometer, the standard photometer used by AERONET (AErosol RObotic NETwork). These two photometers have different optics, sun-tracking systems and spectral bands. The Langley Ratio method (LR) proposed in this study was used to transfer calibration to the closest spectral bands for 1-minute synchronous data, for airmasses between 2 and 5, and was compared to the state of the art Langley calibration technique. The study was conducted at two different locations, Izaña Observatory (IZO) and Valladolid, where measurements were collected almost simultaneously over a six-month period under different aerosol regimes. In terms of calibration aspects, our results showed very low relative differences and standard deviations in the calibration constant transferred in Izaña from PFR to Cimel, up to 0.29 % and 0.46 %, respectively, once external factors such as different field-of-view between photometers or the presence of calibration issues were considered. However, these differences were higher in the comparison performed at Valladolid (1.04 %) and in the shorter wavelengths spectral bands (up to 0.78 % in Izaña and 1.61 % in Valladolid). Additionally, the LR method was successfully used to transfer calibrations between different versions of the CE318-T photometer, providing an accurate calibration transfer (0.17 % to 0.69 %) in the morning LRs, even when the instruments had differences in their central wavelengths (Δλ up to 91 nm). Overall, our results indicate that the LR method is a useful tool not only for transferring calibrations but also for detecting and correcting possible instrumental issues. This is exemplified by the temperature dependence on the two Cimel UV spectral bands, which was estimated by means of the LR method to be ~ -0.09x10-2/° in the case of 380 nm and ~ -0.03x10-2/° in the case of 340 nm. This estimation served us to implement the first operative temperature correction on ultraviolet (UV) spectral bands. [ABSTRACT FROM AUTHOR]

A facility for calibration of temporal light modulation (TLM) photometers has been developed. The facility is based on a laser-fed reference integrating sphere source, the optical input power of which can be modulated with an acousto-optic modulator. A system of photodiodes, amplifiers and an analogue-to-digital converter is used to sample the temporally modulated irradiance at one of the exit ports of the source. With the facility, a TLM photometer was calibrated for display contrast ratio root mean square with an absolute combined standard uncertainty of 0.037%. In addition, the facility has been characterised with the aim of measuring flicker and stroboscopic effect, considering the Ecodesign 'Single Lighting Regulation'. The frequency response of the facility is shown to be sufficient to accommodate measurements of flicker and the stroboscopic effect. [ABSTRACT FROM AUTHOR]

This paper reports on developing a low cost but efficient paired emitter–detector diode (PEDD)-based photometer. The photometer consists of a white light-emitting diode (LED) as the emitter diode, an RGB LED as the detector diode, and a multimeter for recoding the signal. The developed PEDD-based photometer was utilized for the determination of liquid bleach adulteration in cow milk samples. N,N-Diethyl-p-phenylenediamine sulfate aqueous solution of pH 6 was used as a probe to monitor the presence of residual active chlorine in milk. The results showed that the developed method could be used to determine sodium hypochlorite in the concentration range of 0.5 to 20.0 ppm Cl2 with 0.14 and 0.46 ppm Cl2 limit of detection and limit of quantification, respectively. The intraday and interday precisions of the method at two concentration levels of 5.5 and 13.7 ppm Cl2 were 1.04% and 0.52%, and 1.81% and 1.02%, respectively. The recoveries of 114.2% and 106.9% were obtained for 5.5 and 13.7 ppm Cl2 concentrations levels, respectively. Real sample analyzes results showed that "maybe" liquid bleach adulteration in milk is the case for local distributors of raw milk. [ABSTRACT FROM AUTHOR]

Copyright of Technisches Messen is the property of De Gruyter and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the last few decades, various techniques, including spectroscopic, wet chemical and mass spectrometric methods, had been developed and applied for the detection of gaseous ammonia (NH3). We developed an online NH3 monitoring system (SAC-LOPAP) based on Berthelot reactions and a long path absorption photometer (LOPAP), which could run statically for a long time and be applied to the continuous online measurement of low concentrations of ambient air by optimizing the reaction conditions, adding a constant temperature module and liquid flow controller. The detection limit reached with this instrument was 40.5 ppt under stable conditions. In addition, the range of NH3 measurement varied from background contamination (<40.5 ppt) to approximately 100 ppb in the current condition (a stripping liquid flow rate of 0.49 ml min-1 and a gas sample flow rate of 0.70 L min-1 19). An intercomparison of our system with another established system in a field campaign in Beijing was presented, and the results showed that the two instruments had good correlation, indicating that the SAC-LOPAP involved in this study could be used for the accurate measurement of NH3. [ABSTRACT FROM AUTHOR]

The measurement of nitrogen dioxide (NO2) in industrial and residential areas needs comprehensive and reliable instrumentation providing longinterference-free operation and minimum maintenance and recalibration. Differential optical absorption spectroscopy can be used as a direct measurement technique based on the specific absorption characteristics of NO2 following the Berr-Lambert law. This paper proposes a low-cost folded-path photometer to measure NO2 in the air. Cheap tubular acrylic was used as a detection cell with a 3D printed framework, making it compact, modular, and flexible. Evaluation of this differential optical absorption spectroscope (DOAS) was conducted by instrument test responses using NO2 gas. The estimated LOD was ~1263 ppb using a 2-nm resolution of the spectrometer and a 6-meter detection cell length. Deviation of the DOAS was estimated to be 0.8% at high concentration and 2.85% at low concentration based on the calibrated DOAS. Intercomparison of the results was conducted using two different instruments to evaluate the DOAS's performance by measuring NO2 from motorcycle emissions, which indicated that there was a good correlation between the results. The coefficient correlation (R) was 0.649 for the DOAS-ASTM D1607 Griesz Saltzmann method pairing and 0.846 for the DOAS-electrochemical gas analyzer pairing. [ABSTRACT FROM AUTHOR]

The present study proposes a simple and inexpensive photometric method for the selective determination of Ag(I). This method employed a home-made double beam photometer for the determination of silver ions based on an optode sensor prepared by immobilization of 5-(P-Dimethylaminobenzylidene)-rhodanine (PDR) on triacetyl cellulose (TAC) membrane. Two green LEDs as sources of light and lightdependent resistors (LDRs) as detectors were used in the proposed device. The LEDs are turned on by a programmable microcontroller that receives signals from light passed through the sensor, and the absorbance is calculated and displayed on a Liquid-crystal display (LCD) screen. With the optimum conditions, the calibration plot was linear in the concentration range of 0.5-6 μg mL-1. For five replicate determinations of 2 μg mL-1 Ag(I) and the related detection limits, the relative standard deviations were 2.29% and 0.25 μg mL-1, respectively. The method was applied successfully for determining silver in a silver sulphadiazine cream, a radiology effluent, and radiology film samples and the results obtained were in good agreement with those of the standard flame atomic absorption spectroscopy (FAAS) method. [ABSTRACT FROM AUTHOR]

Here, we used a modified single-particle soot photometer (SP2) coupled with a concentric pneumatic nebulizer to measure the size-resolved number and mass concentrations of light-absorbing iron oxide aerosols (FeOx) in liquid water (CNFeOx and CMFeOx, respectively). The SP2 could selectively detect individual FeOx particles in mixed wüstite–fullerene soot laboratory samples and melted Arctic snow samples. The nebulizer efficiency for FeOx particles was about 50% within the 70–650 nm diameter range, as derived from the ratio of the volume of ammonium sulfate before and after extraction by the nebulizer and the size-resolved transmission efficiency in the nebulizer–SP2 sampling line. Uncertainty from the boundary lines empirically drawn to discriminate the scatterplots of FeOx and black carbon in the mixed wüstite–fullerene soot suspensions and snow samples was approximately 3.0% and 10%, respectively. Overall uncertainty in total CNFeOx and CMFeOx (220–1400 nm) was approximately 19% and 18%, respectively. After storage at 4 °C for 16 months, the FeOx particle size distributions in melted Arctic snow had remained stable, and CNFeOx and CMFeOx had changed by less than 19% and 1.0%, on average, respectively. Most of the FeOx on dust particles measured by this system was estimated to be in the diameter range smaller than 1000 nm, considering the nebulizer efficiency for dust particles. The high accuracy of the CNFeOx and CMFeOx measurements will help to improve our quantitative understanding of the wet deposition of FeOx and provide more accurate estimates of the effects of FeOx on snow surface albedo. [ABSTRACT FROM AUTHOR]

Background: Clinicians face barriers when assessing lung maturity at birth due to global inequalities. Still, strategies for testing based solely on gestational age to predict the likelihood of respiratory distress syndrome (RDS) do not offer a comprehensive approach to addressing the challenge of uncertain outcomes. We hypothesize that a noninvasive assessment of skin maturity may indicate lung maturity. Objective: This study aimed to assess the association between a newborn's skin maturity and RDS occurrence. Methods: We conducted a case-control nested in a prospective cohort study, a secondary endpoint of a multicenter clinical trial. The study was carried out in 5 Brazilian urban reference centers for highly complex perinatal care. Of 781 newborns from the cohort study, 640 were selected for the case-control analysis. Newborns with RDS formed the case group and newborns without RDS were the controls. All newborns with other diseases exhibiting respiratory manifestations were excluded. Skin maturity was assessed from the newborn's skin over the sole by an optical device that acquired a reflection signal through an LED sensor. The device, previously validated, measured and recorded skin reflectance. Clinical data related to respiratory outcomes were gathered from medical records during the 72-hour follow-up of the newborn, or until discharge or death, whichever occurred first. The main outcome measure was the association between skin reflectance and RDS using univariate and multivariate binary logistic regression. Additionally, we assessed the connection between skin reflectance and factors such as neonatal intensive care unit (NICU) admission and the need for ventilatory support. Results: Out of 604 newborns, 470 (73.4%) were from the RDS group and 170 (26.6%) were from the control group. According to comparisons between the groups, newborns with RDS had a younger gestational age (31.6 vs 39.1 weeks, P<.001) and birth weight (1491 vs 3121 grams, P<.001) than controls. Skin reflectance was associated with RDS (odds ratio [OR] 0.982, 95% CI 0.979-0.985, R²=0.632, P<.001). This relationship remained significant when adjusted by the cofactors antenatal corticosteroid and birth weight (OR 0.994, 95% CI 0.990-0.998, R²=0.843, P<.001). Secondary outcomes also showed differences in skin reflectance. The mean difference was 0.219 (95% CI 0.200-0.238) between newborns that required ventilatory support versus those that did not and 0.223 (95% CI 0.205-0.241) between newborns that required NICU admission versus those that did not. Skin reflectance was associated with ventilatory support (OR 0.996, 95% CI 0.992-0.999, R²=0.814, P=.01) and with NICU admission (OR 0.994, 95% CI 0.990-0.998, R²=0.867, P=.004). Conclusions: Our findings present a potential marker of lung immaturity at birth using the indirect method of skin assessment. Using the RDS clinical condition and a medical device, this study demonstrated the synchrony between lung and skin maturity. [ABSTRACT FROM AUTHOR]

This work aims to assess differences in the aerosol optical depth (AOD) trend estimations when using high-quality AOD measurements from two different instruments with different technical characteristics and operational (e.g. measurement frequency), calibration and processing protocols. The different types of sun photometers are the CIMEL that is part of AERONET (AErosol RObotic NETwork) and a precision filter radiometer (PFR) that is part of the Global Atmosphere Watch Precision Filter Radiometer network. The analysis operated for two wavelengths (500 and 501 and 870 and 862 nm for CIMEL–PFR) in Davos, Switzerland, for the period 2007–2019. For the synchronous AOD measurements, more than 95 % of the CIMEL–PFR AOD differences are within the WMO-accepted limits, showing very good measurement agreement and homogeneity in calibration and post-correction procedures. AOD trends per decade in AOD for Davos for the 13-year period of analysis were approximately - 0.017 and - 0.007 per decade for 501 and 862 nm (PFR), while the CIMEL–PFR trend differences have been found 0.0005 and 0.0003, respectively. The linear trend difference for 870 and 862 nm is larger than the linear fit standard error. When calculating monthly AODs using all PFR data (higher instrument frequency) and comparing them with the PFR measurements that are synchronous with CIMEL, the trend differences are smaller than the standard error. Linear trend differences of the CIMEL and PFR time series presented here are not within the calculated trend uncertainties (based on measurement uncertainty) for 870 and 862 nm. On the contrary, PFR trends, when comparing high- and low-measurement-frequency datasets are within such an uncertainty estimation for both wavelengths. Finally, for time-varying trends all trend differences are well within the calculated trend uncertainties. [ABSTRACT FROM AUTHOR]

The OI135.6 nm radiation intensity and the associated change with solar activity are very complex, and this is particularly the case during November 2020. In this paper, we investigated the OI135.6 nm radiation intensity in the low-latitude ionosphere during a quiet geomagnetic period. The Ionospheric Photometer (IPM) instrument onboard the FY-3(D) meteorological satellite was employed to measure the OI135.6 nm night airglow at 02:00 LT (local time) and its response to the solar activity. The results showed there is a statistically significant correlation between the intensity of the equatorial ionospheric anomaly (EIA) and solar activity after midnight. The EIA at 02:00 LT and before midnight shared the same climatological characteristics—strong in equinoxes and weak in solstices. In November 2020, when the F10.7 flux significantly increased, the OI135.6 nm radiation intensity in the EIA region recorded a 100–200% increase compared to the previous month, which was much higher than in the same period in the preceding two years. A similar phenomenon was observed at the same time by the Global-scale Observations of Limb and Disk (GOLD), which makes continuous observations of ionospheric structure variation in global patterns. Data analysis suggests that the EIA at 02:00 LT was due to the attenuation of the EIA before midnight after the disappearance of the eastward electric field. The magnetic latitude of the EIA crest (hereafter denoted by θ m l F 2 ) indicates a range-and-seasonal rule of hemispherical asymmetry: closer to the geomagnetic equator in equinoxes and farther away from the geomagnetic equator in solstices. Further studies are needed. [ABSTRACT FROM AUTHOR]

Three dimensional (3D) perovskite solar cells (PSCs) are a promising candidate for third-generation photovoltaics (PV) technology, which aims to produce efficient photon conversion devices to electricity using low-cost fabrication processes. Hybrid organic-inorganic perovskites for-lmed using low-cost solution processing are explored here, which have experienced a stupendous rise in power conversion efficiency (PCE) over the past decade and serve as a prime candidate for third-generation PV systems. While significant progress has been made, the inherent hygroscopic nature and stability issue of the 3D perovskites (3DPs) are an impediment to its commercialization. In this work, we have studied two-dimensional (2D) organometallic halide (CH3(CH2)3NH3)2(CH3NH3)n−1PbnI3n+1) layered perovskites in the Ruddlesden Popper structure, represented as BA2MA3Pb4I13 for the n = 4 formulation, for both photoabsorbers in a two-terminal architecture and solar cells, given that these material are considered to be inherently more stable. In the two-terminal photo absorber devices, the photocurrent and responsivity were measured as a function of incoming laser wavelength, where the location of the peak current was correlated to the emission spectrum arising from the 2DP film using photoluminescence (PL) spectroscopy. The 2D (BA)2(MA)3Pb4I13 films were then integrated into an n-i-p solar cell architecture, and PV device figures of merit tabulated, while our 3D MAPbI3 served as the reference absorber material. A comparative study of the 3DP and 2DP film stability was also conducted, where freshly synthesized films were inspected on FTO substrates and compared to those exposed to elevated humidity levels, and material stability was gauged using various material characterization probes, such as PL and UV-Vis optical absorption spectroscopy, scanning electron microscopy and X-ray diffraction. While the PCE of the 3D-PSCs was higher than the 2D-PSCs, our results confirm the enhanced environmental stability of the 2DP absorber films compared to the 3DP absorbers, suggesting their promise to address the stability issue broadly encountered in 3D PSCs toward third-generation PV technology. [ABSTRACT FROM AUTHOR]

A Pulsating Aurora Imaging Photometers Stereoscopic System (PAIPS) is suggested and described in the paper. The system is based on two lens telescopes with a matrix of multianode photomultiplier tubes as photodetectors placed in two high latitude observatories of the Polar Geophysical Institute. Telescopes provide simultaneous observations of a large volume of the atmosphere at altitudes in the range 50–100 km with high temporal resolution (up to 2.5 μ s) and a spatial resolution of about 2 km. This is a novel system for pulsating aurora study aimed to determine the energies of precipitating electrons responsible for the pulsating aurora occurrence. The system can be used for other atmospheric phenomena studies: meteors, transient luminous events, etc. One telescope has been operating since September 2021 and has measured a variety of optical phenomena. [ABSTRACT FROM AUTHOR]

We present 221 Terrestrial Gamma‐ray Flashes (TGFs) and associated optical pulses observed by the Atmosphere‐Space Interactions Monitor (ASIM) on board the International Space Station. The events were detected between the end of March 2019 and November 2020 and consist of X‐ and gamma‐ray energy detections, as well as photometer data (180–230, 337, and 777 nm) and optical camera data (337 and 777 nm). Using the available ASIM data and applying a consistency check based on TGF characteristics and lightning detections from lightning radio atmospherics close in time, we determine the most likely position of the TGFs in relation to the photometer field of view (FoV), and the association to the observed optical pulses. Out of the 221 events we find 72 events where the TGF and optical data are determined to be associated and inside the photometer FoV. Using the measured TGF durations and the time between the onsets of the TGFs and optical pulses we find: (a) That the TGF onsets are always before or at the same time as the optical pulse onsets (taking into account cloud scattering). (b) A tendency for longer duration TGFs to have longer delays between onsets. (c) Two groups of events: (a) where there is a possible overlap between the TGFs and the optical emissions, as the TGFs last longer than the delay between onsets and (b) where the TGFs and optical emissions do not overlap, as there are long delays between the onsets, which cannot be explained by cloud scattering. Key Points: Terrestrial Gamma‐ray Flashes (TGFs) are produced before or simultaneously with the onset of an optical pulseFor some events the delay of the optical pulse is too long to be explained by the light scattering in the cloudLonger duration TGFs tend to have longer delays between onsets of the TGFs and the optical pulses [ABSTRACT FROM AUTHOR]