Exploration of the atmospheric chemistry of nitrous acid in a coastal city of southeastern China: results from measurements across four seasons

Because nitrous acid (HONO) photolysis is a key source of hydroxyl (OH) radicals, identifying the atmospheric sources of HONO is essential to enhance the understanding of atmospheric chemistry processes and improve the accuracy of simulation models. We performed seasonal field observations of HONO in a coastal city of southeastern China, along with measurements of trace gases, aerosol compositions, photolysis rate constants (J), and meteorological parameters. The results showed that the average observed concentration of HONO was 0.54 ± 0.47 ppb. Vehicle exhaust emissions contributed an average of 1.45 % to HONO, higher than the values found in most other studies, suggesting an influence from diesel vehicle emissions. The mean conversion frequency of NO2 to HONO in the nighttime was the highest in summer due to water droplets evaporating under high-temperature conditions. Based on a budget analysis, the rate of emission from unknown sources (Runknown) was highest around midday, with values of 4.51 ppb h−1 in summer, 3.51 ppb h−1 in spring, 3.28 ppb h−1 in autumn, and 2.08 ppb h−1 in winter. Unknown sources made up the largest proportion of all sources in summer (81.25 %), autumn (73.99 %), spring (70.87 %), and winter (59.28 %). The photolysis of particulate nitrate was probably a source in spring and summer while the conversion from NO2 to HONO on BC enhanced by light was perhaps a source in autumn and winter. The variation of HONO at night can be exactly simulated based on the HONO / NOx ratio, while the J(NO3-_R) × pNO3- should be considered for daytime simulations in summer and autumn, or 1/4× (J(NO3-_R) × pNO3-) in spring and winter. Compared with O3 photolysis, HONO photolysis has long been an important source of OH except for summer afternoons. Observation of HONO across four seasons with various auxiliary parameters improves the comprehension of HONO chemistry in southeastern coastal China.

A review of exploratory studies at RSC Energia into high-temperature voltage conversion systems for an electrically-propelled transportation spacecraft

The paper presents studies conducted at RSC Energia that looked into the feasibility of developing a high-temperature high-power voltage converter of a low-voltage space power supply system for an electrically-propelled space transportation spacecraft based on classical voltage conversion systems using electroplasma gates (key elements) and high-temperature transformers. It provides electrical schematics fro voltage conversion systems. It presents results of experimental studies on lab prototypes of electroplasma gates with electrical power of tens and hundreds kilowatts, which have demonstrated that in principle it is possible to use them as a basis for development of high-temperature radiation-proof voltage converters with mass fraction of ~0.01 kg/A for such power sources as nuclear power-supply systems with sub-megawatt and megawatt thermionic converter reactor. It provides a rationale for selecting the voltage conversion frequency in systems without forced cooling. It provides an experimental proof that in principle it is possible to implement high-temperature transformers with 600°С operating temperature level, and gives recommendations on selection of materials. Key words: space power system, electrically-propelled transportation spacecraft, voltage converter, electroplasma gate, high-temperature transformer, conversion frequency.

Exploration of the atmospheric chemistry of nitrous acid in a coastal city of southeastern China: Results from measurements across four seasons

Because nitrous acid (HONO) photolysis is a key source of hydroxyl (OH) radicals, identifying the atmospheric sources of HONO is essential to enhance the understanding of atmospheric chemistry processes and improve the accuracy of simulation models. We performed seasonal field observations of HONO in a coastal city of southeastern China, along with measurements of trace gases, aerosol compositions, photolysis rate constants (J), and meteorological parameters. The results showed that the average observed concentration of HONO was 0.54 ± 0.47 ppb. Vehicle exhaust emissions contributed an average of 1.64 % to HONO, higher than the values found in most other studies, suggesting an influence from diesel vehicle emissions. The mean conversion frequency of NO2 to HONO in the nighttime was the highest in summer due to water droplets was evaporated under the condition of high temperatures. Based on a budget analysis, the rate of emission from unknown sources (Runknown) was highest around midday, with values of 4.35 ppb · h−1 in summer, 3.53 ppb · h−1 in spring, 3.13 ppb · h−1 in autumn, and 2.05 in winter. Unknown sources made up the largest proportion of all sources in summer (78.55 %), autumn (71.51 %), spring (69.67 %), and winter (55.63 %). The photolysis of particulate nitrate was probably a source in spring and summer while the conversion from NO2 to HONO on BC enhanced by light was perhaps a source in autumn and winter. The variation of HONO at night can be exactly simulated based on the HONO/NOx ratio, while the J(NO3−_R) × pNO3− should be considered for daytime simulations in summer and autumn, or 1/4 × (J(NO3−_R) × pNO3−) in spring and winter. Compared with O3 photolysis, HONO photolysis has long been an important source of OH except for summer afternoon. Observation on HONO across four seasons with various auxiliary parameters improves the comprehension of HONO chemistry in southeastern coastal China.

Analysis of electrogastroenterographic signals using the computer method

Electrogastroenterography is a field that studies the condition of the gastrointestinal tract. Electrophysiological signals contain artifacts that are not directly related to the activity of the organism, and the filtration of such artifacts is an important issue. Electrogastroenterography is a field that studies the condition of the gastrointestinal tract. This method is associated with radiography, ultrasound, endoscopy. In these methods, electrical signals are taken from the surface of the abdominal cavity. For this purpose, the issues of elimination of artifactors, processing and analysis of signals on the example of electrogastroenterograms for processing and measurement of electrophysiological signals were considered. Keywords:Electrogastroenterography, non-stationary signals, electrophysiological signals, computer processing, wavelet conversion, frequency modulation, wavelet Morle function

Equiprobable Symbolization Pattern Entropy for Time Series Complexity Measurement

In order to more effectively mine the structural features in time series, while simplifying the complexity of time series analysis, equiprobable symbolization pattern entropy (EPSPE) based on time series symbolization combined with sliding window technology is proposed in this paper. Firstly, time series are implemented symbolic procession according to the equal probability distribution of the original data, which greatly simplifies the difficulty of analyzing the signal on the premise of small loss of precision to the original signal. Then, sliding window technique is used to obtain a finite number of different symbolic patterns, and the pattern pairs are determined by calculating the conversion between the symbolic patterns. Next, the conversion frequency between symbolized patterns is counted to calculate the probability of the pattern pairs, thus estimating the complexity measurement of complex signals. The results of test using the Logistic system with different parameters show that compared with multiscale sample entropy(MSE), EPSPE can more concisely and intuitively reflect the structural characteristics of time series. Finally, EPSPE is used to investigate the natural wind field signals collected at an outdoor space in which nine high precision two-dimensional (2D) ultrasonic anemometers are deployed in line with 1m interval. The values of EPSPE show consistent increase or decrease trend with the spatial regular arrangement of the nine anemometers. While the results of MSE are irregular, and cannot accurately predict the spatial deployment relationship of nine 2D ultrasonic anemometers.

A review of exploratory studies at RSC Energia into high-temperature voltage conversion systems for an electrically-propelled transportation spacecraft

The paper presents studies conducted at RSC Energia that looked into the feasibility of developing a high-temperature high-power voltage converter of a low-voltage space power supply system for an electrically-propelled space transportation spacecraft based on classical voltage conversion systems using electroplasma gates (key elements) and high-temperature transformers. It provides electrical schematics fro voltage conversion systems. It presents results of experimental studies on lab prototypes of electroplasma gates with electrical power of tens and hundreds kilowatts, which have demonstrated that in principle it is possible to use them as a basis for development of high-temperature radiation-proof voltage converters with mass fraction of ~0.01 kg/A for such power sources as nuclear power-supply systems with sub-megawatt and megawatt thermionic converter reactor. It provides a rationale for selecting the voltage conversion frequency in systems without forced cooling. It provides an experimental proof that in principle it is possible to implement high-temperature transformers with 600°С operating temperature level, and gives recommendations on selection of materials. Key words: Space power system, electrically-propelled transportation spacecraft, voltage converter, electroplasma gate, high-temperature transformer, conversion frequency.

Characterization of Non-selected Intermolecular Gene Conversion in the Polyploid Haloarchaeon Haloferax volcanii

Gene conversion is defined as the non-reciprocal transfer of genetic information from one site to a homologous, but not identical site of the genome. In prokaryotes, gene conversion can increase the variance of sequences, like in antigenic variation, but can also lead to a homogenization of sequences, like in the concerted evolution of multigene families. In contrast to these intramolecular mechanisms, the intermolecular gene conversion in polyploid prokaryotes, which leads to the equalization of the multiple genome copies, has hardly been studied. We have previously shown the intermolecular gene conversion in halophilic and methanogenic archaea is so efficient that it can be studied without selecting for conversion events. Here, we have established an approach to characterize unselected intermolecular gene conversion in Haloferax volcanii making use of two genes that encode enzymes involved in carotenoid biosynthesis. Heterozygous strains were generated by protoplast fusion, and gene conversion was quantified by phenotype analysis or/and PCR. It was verified that unselected gene conversion is extremely efficient and it was shown that gene conversion tracts are much longer than in antigenic variation or concerted evolution in bacteria. Two sites were nearly always co-converted when they were 600 bp apart, and more than 30% co-conversion even occurred when two sites were 5 kbp apart. The gene conversion frequency was independent from the extent of genome differences, and even a one nucleotide difference triggered conversion.

Microwave Photonic Frequency Conversion Based on a Wavelength Swept Laser

Microwave photonic frequency conversion, with flexible tunability and a simple structure based on a wavelength swept laser (WSL), is proposed and experimentally demonstrated. In the proposed frequency conversion system, a broadband WSL was used to generate a frequency-chirped optical carrier, which was sent to a Mach Zehnder modulator (MZM). A microwave signal, with its frequency to be converted, was applied to the MZM. The modulated signal was then sent to a dispersive device, where the waveform was compressed or expanded depending on the dispersion of the dispersive device. After photodetection, a frequency up-converted or down-converted microwave signal was generated. The tuning of the conversion frequency was achieved by adjusting the chirp rate of the optical carrier from the WSL or the dispersion of the dispersive device. The proposed approach was experimentally demonstrated. A microwave signal, with its frequency at 5 GHz, was up-converted to 5.577 GHz and down-converted to 4.936 GHz. The quality of the frequency converted microwave signal was also evaluated. The conversion performance could be further improved by introducing a WSL with a high duty cycle.

Semi-quantitative understanding of source contribution to nitrous acid (HONO) based on 1 year of continuous observation at the SORPES station in eastern China

<p>Nitrous acid (HONO), an important precursor of the hydroxyl radical (OH), has long been recognized as of significance to atmospheric chemistry, but its sources are still debated. In this study, we conducted continuous measurement of HONO from November 2017 to November 2018 at the SORPES station in Nanjing of eastern China. The yearly average mixing ratio of observed HONO was <span>0.69±0.58</span> ppb, showing a larger contribution to OH relative to ozone with a mean OH production rate of 1.16 ppb h<span><sup>−1</sup></span>. To estimate the effect of combustion emissions of HONO, the emitted ratios of HONO to <span>NO<sub><em>x</em></sub></span> were derived from 55 fresh plumes (<span>NO∕NO<sub><em>x</em></sub></span> > 0.85), with a mean value of 0.79 %. During the nighttime, the chemistry of HONO was found to depend on RH, and the heterogeneous reaction of <span>NO<sub>2</sub></span> on an aerosol surface was presumably responsible for HONO production. The average nighttime <span>NO<sub>2</sub></span>-to-HONO conversion frequency (<span><em>C</em><sub>HONO</sub></span>) was determined to be <span>0.0055±0.0032</span> h<span><sup>−1</sup></span> from 137 HONO formation cases. The missing source of HONO around noontime seemed to be photo-induced, with an average <span><em>P</em><sub>unknown</sub></span> of 1.04 ppb h<span><sup>−1</sup></span>, based on a semi-quantitative HONO budget analysis. An over-determined system of equations was applied to obtain the monthly variations in nocturnal HONO sources. Besides the burning-emitted HONO (accounting for about 23 % of the total concentration), the contribution of HONO formed heterogeneously on ground surfaces to measured HONO was an approximately constant proportion of 36 % throughout the year. The soil emission revealed clear seasonal variation and contributed up to 40 % of observed HONO in July and August. A higher propensity for generating HONO on aerosol surfaces occurred in severe hazes (accounting for 40 % of the total concentration in January). Our results highlight ever-changing contributions of HONO sources and encourage more long-term observations to evaluate the contributions from varied sources.</p>