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Solar emission in meter waves originates from upper layers of the solar corona. We present absolute measurements of solar flux from Irkutsk Incoherent Scatter Radar (161 MHz frequency) and Learmonth Observatory (245 MHz frequency). We perform correlation analysis to investigate the relation between solar flux values at different frequencies. Background emission of the quiet Sun is within the expected limits. We examine the behavior of background and slowly-varying emission components during a solar cycle. By comparing the Pearson correlation coefficient with the Spearman rank correlation coefficient, we have found that the dependence of the meter flux on the F10.7 index is non-linear. The correlation between solar flux measurements at 161 and 245 MHz appeared to be lower than that with the F10.7 index. Analysis of daily correlation and autocorrelation shows a diurnal variation that introduces an error into the measurements.

For data obeying a Poisson statistics, the ML-EM ("Maximum Likelihood - Expectation Maximization"), also known as the Richardson-Lucy algorithm, is frequently used and its convergence properties are well known since several decades. To take into account the ubiquitous presence of background emission in several important applications, e.g. in astronomy and medical imaging, a modified algorithm is used in practice. However, despite of its popularity, the convergence of this modified algorithm with background has been established only recently by Salvo and Defrise (IEEE Trans. Med. Imaging. 38:721–729, 2019) in the usual probabilistic context of EM (Expectation Maximization) methods. We present in this paper an alternative convergence proof, which we deem simpler, in a deterministic framework and using only basic tools from convex analysis and optimization theory. [ABSTRACT FROM AUTHOR]

Purpose: The results of research in continuum decameter-wave radio emission of the Galaxy background, ionized hydrogen regions, supernova remnants, extragalactic discrete sources, extended galaxies, galactic clusters, extragalactic background are given. The aim of this work is reviewing the results achieved for over 50-years of the UTR-2 radiotelescope research of our Galaxy and its population, as well as extragalactic radio sources in the continuum radio emission spectrum at extremely low frequencies for the ground based observations. Design/methodology/approach: The review, analysis, collection of archival data in various publications related to the subjectof this work. Findings: The basic results of studying the ionized hydrogen regions, supernova remnants, Galaxy background emission and its large-scale structure are given, and the maps of these sources are obtained. The catalog of extragalactic discrete radio sources of the most Northern sky part and the cosmological conclusions based on its analysis are described; the estimate of the isotropic extragalactic background brightness temperature is obtained; for the first time, the observational results for the Andromeda galaxy and two galactic clusters Coma and A2255 are given briefly. Conclusions: All the results presented here emphasize the uniqueness and importance of research in the decameter wavelength range, and the large area, flexibility of structure, continuous improvement make the UTR-2 radio telescope an indispensable tool for solving the most important tasks of modern radio astronomy, despite its respectable age. For example, only in the range of 10 to 30 MHz the ionized part of the most common element in the universe, the hydrogen, becomes optically thick and begins to absorb the synchrotron emission on the line of sight, which allows rather easy separation of thermal and non-thermal components of radioemission. This property allows to determine the ionized hydrogen regions’ electron temperature and the electron concentration on the line of sight independently in studying the hydrogen emission regions. When studying the supernova remnants, we can determine the ionized matter location by their spectrum drops ‒ before, inside or behind the remnant. Based on the HB3 supernova remnant radio imagies, an assumption was made on the existence of an ionized hydrogen relic shell aroundit, being caused by the initial ultraviolet flash of a supernova. For the first time, the maps of the Northern sky large-scale structure in the declination range from ‒15° to +85° at extremely low frequencies 10, 12.6, 14.7, 16.7, 20 and 25 MHz for the ground-based observations are published, which, besides their own scientific value, may allow to correct the UTR-2 radio telescope imaging results. Using the full-resolution UTR-2 maps and the developed method of multifrequency T‒T diagrams, it was possible to separate the background radiation into galactic and extragalactic components and construct the spectrum of the latter. From the analysis of the most complete decameter wavelength range catalog of discrete sources, it follows that there is a gap in the redshift spatial distribution for all classes of extragalactic sources. The existence of an ionized hydrogen ring in the Andromeda Nebula disk has been suggested. It is shown that the main partof the galaxy clusters decameter-wave emission comes from haloes and relics.

Significance: Although the depth detection limit of fluorescence objects in tissue has been studied, reports with a model including noise statistics for designing the optimum measurement configuration are missing. We demonstrate a variance analysis of the depth detection limit toward clinical applications such as noninvasively assessing the risk of aspiration., Aim: It is essential to analyze how the depth detection limit of the fluorescence object in a strong scattering medium depends on the measurement configuration to optimize the configuration. We aim to evaluate the depth detection limit from theoretical analysis and phantom experiments and discuss the source-detector distance that maximizes this limit., Approach: Experiments for detecting a fluorescent object in a biological tissue-mimicking phantom of ground beef with background emission were conducted using continuous wave fluorescence measurements with a point source-detector scheme. The results were analyzed using a model based on the photon diffusion equations. Then, variance analysis of the signal fluctuation was introduced., Results: The model explained the measured fluorescence intensities and their fluctuations well. The variance analysis showed that the depth detection limit in the presence of ambient light increased with the decrease in the source-detector distance, and the optimum distance was in the range of 10 to 15 mm. The depth detection limit was found to be ∼ 30    mm with this optimum distance for the phantom., Conclusions: The presented analysis provides a guide for the optimum design of the measurement configuration for detecting fluorescence objects in clinical applications., (© 2024 The Authors.)

The linear dose–response relationship has long been assumed in assessments of health risk from an incremental chemical emission relative to background emissions. In this study, we systematically examine the relevancy of such an assumption with real-world data. We used the reported emission data, as background emissions, from the 2017 U.S. National Emission Inventory for 95 organic chemicals to estimate the central tendencies of exposures of the general U.S. population. Previously published nonlinear dose–response relationships for chemicals were used to estimate health risk from exposure. We also explored and identified four intervals of exposure in which the nonlinear dose–response relationship may be linearly approximated with fixed slopes. Predicted rates of exposure to these 95 chemicals are all within the lowest of the four intervals and associated with low health risk. The health risk may be overestimated if a slope on the dose–response relationship extrapolated from toxicological assays based on high response rates is used for a marginal increase in emission not substantially higher than background emissions. To improve the confidence of human health risk estimates for chemicals, future efforts should focus on deriving a more accurate dose–response relationship at lower response rates and interface it with exposure assessments.

Silver colloidal nanoaggregates have been widely used for surface-enhanced Raman scattering (SERS) measurements. SERS-active nanoaggregates generally show monotone colors, although multicoloured-blinking emissions, which occur at the single-molecule level, have been observed from each Ag colloidal nanoaggregate with poly-L-lysine. For the same single nanoaggregates, SERS peaks of poly-L-lysine were observed at shorter wavelengths than those of the background emission band; thus, their blinking can be measured separately. The background emission is attributed to fluorescence from an Ag atomic cluster. This may be modulated by the surface plasmon enhancement of each Ag nanoaggregate and is the likely cause of multicoloured background emission. Notably, the probability distributions as a function of time for not only the dark events of SERS but also those of the background emission were reproduced via a truncated power law, indicating the same random-walk mechanism for their blinking despite the different illuminants. The power law for the dark background emission events was truncated at a shorter tail than that for the dark SERS events. This result suggests that the fluorescent Ag cluster reaches a junction of the Ag nanoaggregate covered with citrate anions more quickly than the cationic polymer chain. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The remarkable expansion of fertilization and irrigation may stimulate nitrous oxide (N 2 O) emissions from cropping systems in northern China. High-resolution measurements were conducted in irrigated cotton and wheat–maize rotational systems in Shanxi Province, P.R. China, between 2007 and 2010 (three year-round crop cycles, hereinafter referred to as Y1, Y2 and Y3) to investigate the impacts of natural inter-annual variations and agricultural management on annual N 2 O emissions and direct emission factors (EFs). Overall, N 2 O emissions fluctuated diurnally, seasonally and inter-annually in the fertilized treatments. The hourly N 2 O fluxes closely followed the daily air temperature patterns. The daily mean fluxes corresponded to these hourly fluxes, which were observed between 09:00–10:00 and 19:00–20:00. An optimized sampling protocol could improve the reliability of discrete measurements when estimating cumulative emissions. The N 2 O emissions for the fertilized treatments were 2.7 ± 0.2 (Y1) and 1.6 ± 0.1 kg N ha −1 yr −1 (Y2) from the cotton field and 6.2 ± 0.4 (Y1), 4.5 ± 0.3 (Y2) and 4.5 ± 0.2 kg N ha −1 yr −1 (Y3) from the wheat–maize field. Peak N 2 O emissions after fertilization and irrigation/rainfall lasted one to three weeks and accounted for 16–55% of the annual emissions. Leaching losses were estimated at 10.4 ± 3.0 (Y1) and 12.5 ± 3.4 kg N ha −1 yr −1 (Y2), which accounted for 16–17% of the fertilizer-N applied to the cotton field. Annual N 2 O emissions did not increase with increasing fertilization rates or water inputs because significant amounts of fertilizer-N were lost through leaching. Background emissions amounted to one-third to one-half of the total N 2 O emissions from the fertilized treatments. The direct EFs were 2.2 ± 0.3% (Y1) and 0.9 ± 0.2% (Y2) in the cotton field and 1.3 ± 0.2% (Y1), 0.8 ± 0.1% (Y2) and 0.7 ± 0.1% (Y3) in the wheat–maize field. The large inter-annual variations in N 2 O emissions and direct EFs emphasize the importance of multiple-year continuous observations. [ABSTRACT FROM AUTHOR]

In Norway, 65 % of the agricultural land is under grassland for feeding ruminants. The objective of the present study was to quantify NO emissions from grassland on a fertile sandy loam in Western Norway, and to estimate the response of seasonal NO emissions to added inorganic N, cattle slurry (CS) N and clover N. Ammonium nitrate (AN) and CS were applied manually at annual rates of 0, 100, 150, 200 and 250 kg AN-N ha, 80 kg CS-N ha or as a combination of 200 kg AN-N ha and 80 kg CS-N ha. Background NO emissions were five times higher in summer season 2009 than in 2010, but the relative amount of NO derived from AN was constant in both periods, amounting to 0.11 % of applied N. CS had no measurable impact on NO emissions in 2009, but 0.15 % of CS-N was emitted as NO during summer 2010. In the warm year of 2009, which included a drought period, 1-24 % of the NO emissions were attributed to the effect of clover depending on fertilization. Clover had no effect on NO fluxes in the cool and moist year 2010. Our results suggest that NO emissions in fertile Norwegian grasslands are to a great extent controlled by inter-annual variations in background emissions and variable contribution of biologically fixed N and CS-N. [ABSTRACT FROM AUTHOR]

Aims: A field experiment was conducted to quantify annual nitrous oxide (NO) fluxes from control and fertilized plots under open-air and greenhouse vegetable cropping systems in southeast China. We compiled the reported global field annual NO flux measurements to estimate the emission factor of N fertilizer for NO and its background emissions from vegetable fields. Methods: Fluxes of NO were measured using static chamber-GC techniques over the 2010-2011 annual cycle with multiple cropping seasons. Results: The mean annual NO fluxes from the controls were 46.1 ± 2.3 μg NO-N m hr and 68.3 ± 4.1 μg NO-N m hr in the open-air and greenhouse vegetable systems, respectively. For the plots receiving 900 kg N ha, annual NO emissions averaged 90.6 ± 8.9 μg NO-N m hr and 106.4 ± 6.6 μg NO-N m hr in the open-air and greenhouse vegetable systems, respectively. By pooling published field NO flux measurements taken over or close to a full year, the NO emission factor for N fertilizer averaged 0.63 ± 0.09 %, with a background emission of 2.67 ± 0.80 kg NO-N ha in Chinese vegetable fields. Annual NO emissions from Chinese vegetable systems were estimated to be 84.7 Gg NO-N yr, consisting of 72.5 Gg NO-N yr and 12.2 Gg NO-N yr in the open-air and greenhouse vegetable systems, respectively. Conclusions: While NO emissions from the greenhouse vegetable cropping system tended to be slightly higher compared to the open-air system in our experiment, the synthesis of literature data suggests that NO emissions would be greater at low N-rates but smaller at high N-rates in greenhouse systems than in open-air vegetable cropping systems. The estimates of this study suggest that vegetable cropping systems covering 11.4 % in national total cropping area, contributed 21-25 % to the total NO emission from Chinese croplands. [ABSTRACT FROM AUTHOR]

Abstract: Annual paddy rice–winter wheat rotation constitutes one of the typical cropping systems in southeast China, in which various water regimes are currently practiced during the rice-growing season, including continuous flooding (F), flooding-midseason drainage-reflooding (F-D-F), and flooding-midseason drainage-reflooding and moisture but without waterlogging (F-D-F-M). We conducted a field experiment in a rice–winter wheat rotation system to gain an insight into the water regime-specific emission factors and background emissions of nitrous oxide (N2O) over the whole annual cycle. While flooding led to an unpronounced N2O emission during the rice-growing season, it incurred substantial N2O emission during the following non-rice season. During the non-rice season, N2O fluxes were, on average, 2.61 and 2.48mg N2O–Nm− 2 day−1 for the 250kg N ha−1 applied plots preceded by the F and F-D-F water regimes, which are 56% and 49% higher than those by the F-D-F-M water regime, respectively. For the annual rotation system experienced by continuous flooding during the rice-growing season, the relationship between N2O emission and nitrogen input predicted the emission factor and background emission of N2O to be 0.87% and 1.77kg N2O–Nha−1, respectively. For the plots experienced by the water regimes of F-D-F and F-D-F-M, the emission factors of N2O averaged 0.97% and 0.85%, with background N2O emissions of 2.00kg N2O–Nha−1 and 1.61kg N2O–Nha−1 for the annual rotation system, respectively. Annual direct N2O–N emission was estimated to be 98.1Gg yr−1 in Chinese rice-based cropping systems in the 1990s, consisting of 32.3Gg during the rice-growing season and 65.8Gg during the non-rice season, which accounts for 25–35% of the annual total emission from croplands in China. [Copyright &y& Elsevier]

We conducted multi-year observations of nitric oxide (NO) fluxes from typical vegetable fields in the Yangtze River delta, which is located in southeastern China. Flux measurements were performed manually twice per week at intervals of 2¿3 days, in both fertilized and unfertilized fields, over an investigation period of 1448 days (September 2004¿August 2008). In total, twelve vegetable-growing periods and a short fallow period were investigated. On average, the NO fluxes from the fertilized plots were 21 times higher than fluxes from the unfertilized plots (p < 0.001). Peak NO emissions usually occurred soon after the addition of nitrogenous fertilizer. Peak emissions took place during about 15% of the whole investigation time, but contributed to approximately 89% of the total NO release. The annual background NO emissions (from fields without nitrogen amendment) were observed at 0.290 ± 0.019 (standard deviation of 3 observations) kg N ha¿1. The total amounts of NO emitted during the individual vegetable-growing periods correlated positively and exponentially with the products of seasonal mean soil temperatures and nitrogen addition rates (R 2 = 0.87, p < 0.001). The mean direct NO emission factor (EFd, the loss rate of fertilizer nitrogen via NO emissions) for the four-year period was determined to be 0.51% ± 0.11% (standard error of 3 observations). The EFds of individual vegetable-growing seasons ranged from 0.05% to 1.24%, varying linearly and positively with the products of seasonal mean soil temperatures and nitrogen addition rates (R 2 = 0.58, p < 0.01). The observed interaction of soil temperature and nitrogen addition on NO emission in seasonal totals and EFds occurred in soils with moisture contents ranging from 55% to 100% water-filled pore space (mean: 79%; standard deviation: 9%). The results of this study indicate that when other conditions remain relatively stable, the direct emission factor, a key parameter for compiling an inventory of NO emissions from vegetable fields, may vary with not only soil temperature but also nitrogen addition. [Copyright &y& Elsevier]

Various water management regimes, such as continuous flooding (F), flooding-midseason drainage-reflooding (F-D-F), and flooding-midseason drainage-reflooding-moist intermittent irrigation, but without water logging (F-D-F-M), are currently practiced in paddy rice production in mainland China. These water regimes have incurred a sensitive change in direct N2O emission from rice paddy fields. We compiled and statistically analyzed field data on N2O emission from paddy fields during the rice growing season (71 measurements from 17 field studies) that were published in peer-reviewed Chinese and English journals. Seasonal total N2O was, on average, equivalent to 0.02% of the nitrogen applied in the continuous flooding rice paddies. Under the water regime of F-D-F or the F-D-F-M, seasonal N2O emissions increased with N fertilizer applied in rice paddies. An ordinary least square (OLS) linear regression model produced the emission factor (EF) of nitrogen for N2O averaged 0.42%, but background N2O emission was not pronounced under the water regime of F-D-F. Under the F-D-F-M water regime, N2O EF and background emission were estimated to be 0.73% and 0.79kg N2O-Nha−1, respectively, during the paddy rice growing season. Based on results of the present study and national rice production data, subsequently, direct N2O emissions during the rice growing season amounted to 29.0Gg N2O-N with the uncertainty of 30.1%, which accounted for 7–11% of the reported estimates of annual total emission from croplands in mainland China. The results of this study suggest that paddy rice relative to upland crop production could have contributed to mitigating N2O emissions from agriculture in mainland China. [Copyright &y& Elsevier]

Abstract: Fertilized agricultural soils are a major anthropogenic source of atmospheric N2O. A credible national inventory of agricultural N2O emission would benefit its global strength estimate. We compiled a worldwide database of N2O emissions from fertilized fields that were consecutively measured for more than or close to one year. Both nitrogen input (N) and precipitation (P) were found to be largely responsible for temporal and spatial variabilities in annual N2O fluxes (N2O–N). Thus, we established an empirical model (N2O–N=1.49 P+0.0186 P·N), in which both emission factor and background emission for N2O were rectified by precipitation. In this model, annual N2O emission consists of a background emission of 1.49 P and a fertilizer-induced emission of 0.0186 P·N. We used this model to develop a spatial inventory at the 10×10km scale of direct N2O emissions from agriculture in China. N2O emissions from rice paddies were separately quantified using a cropping-specific emission factor. Annual fertilizer-induced N2O emissions amounted to 198.89GgN2O–N in 1997, consisting of 18.50GgN2O–N from rice paddies and 180.39GgN2O–N from fertilized uplands. Annual background emissions and total emissions of N2O from agriculture were estimated to be 92.78GgN2O–N and 291.67GgN2O–N, respectively. The annual direct N2O emission accounted for 0.92% of the applied N with an uncertainty of 29%. The highest N2O fluxes occurred in East China as compared with the least fluxes in West China. [Copyright &y& Elsevier]

Agricultural fields are significant sources of anthropogenic atmospheric nitrous oxide (N2O). We compiled and analyzed data on N2O emissions from Japanese agricultural fields (246 measurements from 36 sites) reported in peer-reviewed journals and research reports. Agricultural fields were classified into three categories: upland fields, tea fields and rice paddy fields. In this analysis, data measured over a period of more than 90 days for upland fields and 209 days for tea fields were used to estimate annual fertilizer-induced emission factors (EF) because of limitations in the available data. The EF is defined as the emission from fertilized plots minus the background emission (emission from a zero-N control plot), and is expressed as a percentage of the N applied. The mean of N2O emissions from upland fields with well-drained soils was significantly lower than that from poorly drained soils. Mean (± standard deviation) N2O emissions measured over a period of more than 90 days from fertilized upland fields were 1.03 ± 1.14 kg N ha−1 and 4.78 ± 5.36 kg N ha−1 for well-drained and poorly drained soils, respectively. Because the ratio of the total areas of well-drained soils and poorly drained soils was different from the ratio of the number of available EF data for each soil category, we used a weighted mean to estimate EF for all upland fields. The EF was estimated to be 0.62 ± 0.48% for all fertilized upland fields. Mean N2O emissions and the estimated EF for fertilized tea fields measured over a period of more than 209 days were 24.3 ± 16.3 kg N ha−1 and 2.82 ± 1.80%, respectively. The mean N2O emission and estimated EF from Japanese rice paddy fields were 0.36 kg N ha−1 and 0.31 ± 0.31% for the cropping season, respectively. Significant uncertainties remain in these results because of limitations in the available data. [ABSTRACT FROM AUTHOR]

Abstract: A field experiment was conducted in a rice–winter wheat rotation agroecosystem to quantify the direct emission of N2O for synthetic N fertilizer and crop residue application in the 2002–2003 annual cycle. There was an increase in N2O emission accompanying synthetic N fertilizer application. Fertilizer-induced emission factor for N2O (FIE) averaged 1.08% for the rice season, 1.49% for the winter wheat season and 1.26% for the whole annual rotation cycle. The annual background emission of N2O totaled 4.81kg N2O–Nha−1, consisting of 1.24kg N2O–Nha−1 for rice, 3.11kg N2O–Nha−1 for wheat seasons. When crop residue and synthetic N fertilizer were both applied in the fields, crop residue-induced emission factor for N2O (RIE) was estimated as well. When crop residue was retained at the rate of 2.25 and 4.50tha−1 for each season, the RIE averaged 0.64% and 0.27% for the whole annual rotation cycle, respectively. Based on available multi-year data of N2O emissions over the whole rice–wheat rotation cycle at 3 sites in southeast China, the FIE averaged 1.02% for the rice season, 1.65% for the wheat season. On the whole annual cycle, the FIE for N2O ranged from 1.05% to 1.45%, with an average of 1.25%. Annual background emission of N2O averaged 4.25kgha−1, ranging from 3.62 to 4.87kgha−1. It is estimated that annual N2O emission in paddy rice-based agroecosystem amounts to 169Gg N2O–N in China, accounting for 26–60% of the reported estimates of total emission from croplands in China. [Copyright &y& Elsevier]

Abstract Agricultural activities have greatly altered the global nitrogen (N) cycle and produced nitrogenous gases of environmental significance. More than half of all chemical N fertilizer produced globally is used in crop production in East, Southeast and South Asia, where rice is central to nutrition. Emissions of nitrous oxide (N2 O), nitric oxide (NO) and ammonia (NH3 ) from croplands in this region were estimated by considering background emission and emissions resulting from N added to croplands, including chemical N, animal manure, biologically fixed N and N in crop residues returned to fields. Background emission fluxes of N2 O and NO from croplands were estimated to be 1.22 and 0.57 kg N ha-1 yr-1 , respectively. Separate fertilizer-induced emission factors were estimated for upland fields and rice fields. Total N2 O emission from croplands in the study region was estimated to be 1.19 Tg N yr-1 , with 43% contributed by background emissions. The average fertilizer-induced N2 O emission, however, accounts for only 0.93% of the applied N, which is less than the default IPCC value of 1.25%, because of the low emission factor from paddy fields. Total NO emission was 591 Gg N yr-1 in the study region, with 40% from background emissions. The average fertilizer-induced NO emission factor was 0.48%. Total NH3 emission was estimated to be 11.8 Tg N yr-1 . The use of urea and ammonium bicarbonate and the cultivation of rice led to a high average NH3 loss rate from chemical N fertilizer in the study region. Emissions were displayed at a 0.5° × 0.5° resolution with the use of a global landuse database. [ABSTRACT FROM AUTHOR]

The linear dose–response relationship has long been assumed in assessments of health risk from an incremental chemical emission relative to background emissions. In this study, we systematically examine the relevancy of such an assumption with real-world data. We used the reported emission data, as background emissions, from the 2017 U.S. National Emission Inventory for 95 organic chemicals to estimate the central tendencies of exposures of the general U.S. population. Previously published nonlinear dose–response relationships for chemicals were used to estimate health risk from exposure. We also explored and identified four intervals of exposure in which the nonlinear dose–response relationship may be linearly approximated with fixed slopes. Predicted rates of exposure to these 95 chemicals are all within the lowest of the four intervals and associated with low health risk. The health risk may be overestimated if a slope on the dose–response relationship extrapolated from toxicological assays based on high response rates is used for a marginal increase in emission not substantially higher than background emissions. To improve the confidence of human health risk estimates for chemicals, future efforts should focus on deriving a more accurate dose–response relationship at lower response rates and interface it with exposure assessments. [ABSTRACT FROM AUTHOR]