Analysis Of Molecular Composition Research Articles

Coupling Effect of Elemental Carbon and Organic Carbon on the Changes of Optical Properties and Oxidative Potential of Soot Particles under Visible Light.

Soot particles, coming from the incomplete combustion of fossil or biomass fuels, feature a core-shell structure with inner elemental carbon (EC) and outer organic carbon (OC). Both EC and OC are known to be photoactive under solar radiation. However, research on their coupling effect during photochemical aging remains limited. This study examines how the optical properties and oxidative potential (OP) of wood, coal, and diesel soot particles with varying EC and OC levels are affected by exposure to visible light. Wood soot, which has the highest OC content, showed the most significant changes in both optical properties and OP, indicating its highest sensitivity to visible light aging. Molecular composition analysis revealed that the reduction of polycyclic aromatic hydrocarbons (PAHs) and methyl-PAHs primarily affects the optical properties, while oxygenated PAHs play a major role in OP. Combined with the results from reactive oxygen species detection, it is suggested that EC initiates photoreactions by generating superoxide anions, while OC undergoes compositional changes that result in subsequent atmospheric effects. These findings enhance our understanding of the photochemical aging process of soot particles and their implications for climate and health.

Simple Sequence Repeat Marker-Based Genetic Diversity and Chemical Composition Analysis of Ancient Camellia sinensis in Jiulong County, Sichuan Province, China.

The ancient tea plant germplasm resources are rich in genetic diversity and provide an important basis for the genetic diversity in tea germplasm resources. To explore the genetic diversity of ancient tea plant germplasm resources in Jiulong County, Sichuan Province. 59 ancient tea tree germplasm resources were analyzed using simple sequence repeat (SSR) molecular markers and chemical composition analysis. The results showed that a total of 83 alleles were amplified by 23 pairs of SSR primers, with an average observed allele number (Na) of 3.6 and an effective allele number (Ne) of 2.335. The average Shannon information index (I) and the polymorphic information content (PIC) of the primers were 0.896 and 0.446, respectively. The results of the UPGMA cluster analysis showed that 59 ancient tea tree samples could be classified into five different subgroups. Based on the results of chemical composition analysis, two specific tea germplasm resources with high amino acid content, 10 excellent germplasm resources with tea polyphenol content over 20% and some other tea germplasm resources were identified. This study reveals that Jiulong's ancient tea tree germplasm exhibits significant genetic diversity and includes valuable tea tree planting resources. These findings provide a foundational framework for the conservation, detailed exploration and sustainable utilization of these resources.

ELSA-PSYCHE: An Improved Method for Protecting Pure Shift Spectra from Artifacts.

Numerous 1H-1H J couplings contribute to complex multiplets in 1H nuclear magnetic resonance spectroscopy, leading to an ambiguous spectral assignment, particularly for strongly coupled protons. Although the PSYCHE approach has proven to be effective in simplifying complex spectra by collapsing J couplings, the PSYCHE pure shift spectrum of strongly coupled protons always suffers from sideband artifacts and baseline oscillations, which impede spectral identification. Herein, we introduce a novel universal technique designed to separate artifacts from the desired absorption-mode pure shift signals. This new study will significantly benefit the development of molecular structure elucidations and composition analysis in the fields of chemistry, biochemistry, and metabonomics.

O21 Raman spectroscopy for detection of squamous cell carcinoma in recessive dystrophic epidermolysis bullosa skin

Abstract Introduction and aims Recessive dystrophic epidermolysis bullosa (RDEB) is a genetic skin disorder caused by biallelic pathogenic variants in COL7A1, which encodes type VII collagen (C7). Lack of C7 leads to blistering, chronic wounds, scarring and early onset of life-shortening squamous cell carcinomas (SCCs). Currently, the suspicion of SCC is mostly determined by clinical observation of visible changes in chronic wounds, and often requires multiple biopsies for histological diagnosis. This project aims to improve clinical care by developing a new noninvasive means of detecting SCC. To achieve this, we used Raman spectroscopy, a nondestructive analytical technique to study the changes occurring in RDEB skin when SCC is present, with the goal of creating a bedside test that can aid clinicians in the early diagnosis of SCC. Methods Raman spectroscopic imaging was performed on 7-µm frozen skin sections from RDEB (n = 3), RDEB SCC (n = 3) and normal skin (n = 3) to identify signalling changes between nonlesional and lesional states. An in-depth molecular composition analysis of the samples was performed using multivariate analysis with the goal of highlighting changes in abundance of specific molecules when SCC is present. Results For both nonmalignant and RDEB SCC skin sites we found specific Raman peaks associated with protein (1004 cm−1, 1650 cm−1) or lipids (1450 cm−1). RDEB SCC indicated a relative increase in DNA and protein. High-quality Raman spectroscopic images could be acquired that showed clear correlation with histological appearances. Current work is under way to determine which specific biological compounds contribute to the Raman spectra observed. Conclusions Raman spectroscopic imaging can provide comprehensive and noninvasive molecular tissue mapping with resolution comparable to histological sections, enabling molecular-based detection of SCC. Future work will focus on characterization of the SCC molecular profile, in addition to determining whether fibre optic Raman spectroscopy can be used to guide the biopsy/resection of RDEB lesions.

Characterization of chemical composition of high viscosity heavy oils: Macroscopic properties, and semi-quantitative analysis of molecular composition using high-resolution mass spectrometry

Heavy oil is an important resource in current petroleum exploitation, and the chemical composition information of heavy oil is crucial for revealing its viscosity-inducing mechanism and solving practical exploitation issues. In this study, the techniques of high-temperature gas chromatography and high-resolution mass spectrometry equipped with an electrospray ionization source were applied to reveal the chemical composition of typical heavy oils from western, central, and eastern China. The results indicate that these heavy oils display significant variations in their bulk properties, with initial boiling points all above 200 °C. Utilizing pre-treatment and ESI high-resolution mass spectrometry, an analysis of the molecular composition of saturated hydrocarbons, aromatic hydrocarbons, acidic oxygen compounds, sulfur compounds, basic nitrogen compounds, and neutral nitrogen compounds within the heavy oil was conducted. Ultimately, a semi-quantitative analysis of the molecular composition of the heavy oil was achieved by integrating the elemental content. The semi-quantitative analysis results of Shengli-J8 heavy oil and a conventional Shengli crude oil show that Shengli-J8 heavy oil lacks alkanes and low molecular weight aromatic hydrocarbons, which contributes to its high viscosity. Additionally, characteristic molecular sets for different heavy oils were identified based on the semi-quantitative analysis of molecular composition. The semi-quantitative analysis of molecular composition in heavy oils may provide valuable reference data for establishing theoretical models on the viscosity-inducing mechanism in heavy oils and designing viscosity-reducing agents for heavy oil exploitation.

Spatial distribution, environmental behavior, and health risk assessment of PAHs in soils at prototype coking plants in Shanxi, China: Stable carbon isotope and molecular composition analyses

To investigate the environmental behavior of and carcinogenic risk posed by 16 priority-controlled polycyclic aromatic hydrocarbons (PAHs), soil samples and air samples from the coke oven top were collected in two prototype coking plants (named PF and JD). The PF soils contained more PAHs than the JD soils because the PF plant employed the side-charging technique and had a lower coke oven height. The soils from both plants contained enough PAHs to pose a carcinogenic risk, and this risk was higher in the PF plant. Data were collected on the source characteristic spectrum of stable carbon isotopic composition (δ13C) of PAHs emitted from the coke oven top (δ13C values of −36.02‰ to −32.05‰ for gaseous PAHs and −34.09‰ to −25.28‰ for particulate PAHs), and these data fill a research gap and may be referenced for isotopic-technology-based source apportionment. Diagnostic ratios and isotopic technology revealed that the coking plant soils were mainly influenced by the coking process, followed by vehicle exhaust; the soils near the boundary of each plant were slightly affected by C3 plant burning. For most PAHs [excluding fluoranthene, benzo(k)fluoranthene, indeno(1,2,3-c,d)pyrene, and dibenzo(a,h)anthracene], the dominant migration process was the net volatilization of PAHs from soil to air. In the PF plant, 13C was depleted in gaseous PAHs during volatilization.

Exploring the structure and hydrogen storage capacity of CeHn0/+ clusters.

The unique 4f orbitals and abundant electronic energy levels of rare earth elements enable effective doping and modification to enhance hydrogen storage performance, making it an increasingly prominent focus of research. The structures of neutral and cationic CeHn0/+ (n = 2-20) clusters have been determined using the Crystal Structure AnaLYsis by Particle Swarm Optimization (CALYPSO) method in conjunction with density functional theory (DFT). Interestingly, the CeH13 and CeH14+ exhibit remarkable stability in the doublet state with Cs and C2v symmetry, respectively. The adsorption energy of CeHn0/+ (n = 2-20) suggests a preference for H atoms to chemically adsorb on Ce atoms. The analysis of molecular orbital composition reveals that the stability of both CeH13 and CeH14+ is attributed to the significant hybridization between the H 1s and Ce 4f orbitals. Both CeH13 and CeH14+ demonstrate significant hydrogen storage capacities, with values reaching 8.5 wt% and 9.1 wt%, respectively.

Solar radiation stimulates release of semi-labile dissolved organic matter from microplastics

Microplastics can release dissolved organic matter (DOM) into seawater under solar radiation exposure. However, the molecular composition and bioavailability of this DOM remain to be investigated. Here, two popular microplastics, low-density polyethylene (LDPE) and polystyrene (PS), were exposed to solar radiation in an artificial seawater for 10 days. The solar-induced LDPE-DOM and PS-DOM were molecularly characterized using ultra-high-resolution mass spectrometry, and were further incubated in a coastal microbial assemblage to examine their bioavailability. Results showed that solar radiation stimulated release of DOM from the microplastics. Dissolved organic carbon concentration analysis indicated that approximately 19.03 µg C L–1 and 3.85 µg C L–1 were released from each gram of LDPE and PS per day, respectively. Molecular composition analysis showed that both the LDPE-DOM and PS-DOM comprised a proportion of nitrogen- and sulfur-bearing molecules, and that the LDPE-DOM molecules were associated with lower molecular abundance and values of double-equivalent-bond and aromatic-index, but higher average hydrogen-to-carbon ratio than that in the PS-DOM. In addition, a proportion of the assigned formulas in LDPE-DOM (22.3%) and PS-DOM (55.8%) could be found in a coastal-DOM sample, suggesting their potential contribution to coastal DOM pool. The further incubation experiment showed that nearly 18.7% of LDPE-DOM and 9.5% of PS-DOM were utilized or transformed within 30 days. Still, a fraction of the solar-induced LDPE-DOM and PS-DOM resisted rapid microbial utilization, remained as semi-labile DOM. These results underlined unaccounted consequences of microplastic-derived DOM in coastal DOM pool.

Evolution of dissolved organic nitrogen chemistry during transportation to the marginal sea: Insights from nitrogen isotope and molecular composition analyses

Estuaries are hotspots where terrestrially originated dissolved organic matter (DOM) is modified in molecular composition before entering marine environments. However, very few research has considered nitrogen (N) modifications of DOM molecules in estuaries, limiting our understanding of dissolved organic nitrogen (DON) cycling and the associated carbon cycling in estuaries. This study integrated optical, stable isotopes (δ15N and δ13C) and molecular composition (FT-ICR MS) to characterize the transformation of DOM in the Yangtze River Estuary. Both concentration of dissolved organic carbon (DOC) and DON decreased with increasing salinity, while their δ13C and δ15N increased with the increasing salinity. A significant positive correlation was found between δ15N and δ13C during the transportation of DOM to marginal seas, indicating that the behavior of both DOC and DON are primarily controlled by the mixing of freshwater and the seawater in the YRE. During the mixing process, the DON addition was observed using the conservative mixing curves. In the view of molecular composition, DOM molecules became more aromatic as the number of N atoms increased. Spearman correlations reveal that DOM molecules with fewer N atoms exhibited a higher enrichment in protein-like components, while those with more N atoms were more enriched in humic-like components. In addition, the δ15N and δ13C tended to increase as the N content of DOM decreased. Therefore, DON molecules with fewer N atoms were likely to be transformed into those with more N atoms based on the isotopic fractionation theory. This study establishes a linkage between the molecular composition and the δ15N of DOM, and discovers the N transformation pattern within DOM molecules during the transportation to marginal seas.

Single-Cell Analysis with Silver-Coated Pipette by Combined SERS and SICM.

The study of individual cell processes that occur both on their surface and inside is highly interesting for the development of new medical drugs, cytology and cell technologies. This work presents an original technique for fabricating the silver-coated pipette and its use for the cell analysis by combination with surface-enhanced Raman spectroscopy (SERS) and scanning ion-conducting microscopy (SICM). Unlike the majority of other designs, the pipette opening in our case remains uncovered, which is important for SICM. SERS-active Ag nanoparticles on the pipette surface are formed by vacuum-thermal evaporation followed by annealing. An array of nanoparticles had a diameter on the order of 36 nm and spacing of 12 nm. A two-particle model based on Laplace equations is used to calculate a theoretical enhancement factor (EF). The surface morphology of the samples is investigated by scanning electron microscopy while SICM is used to reveal the surface topography, to evaluate Young's modulus of living cells and to control an injection of the SERS-active pipettes into them. A Raman microscope-spectrometer was used to collect characteristic SERS spectra of cells and cell components. Local Raman spectra were obtained from the cytoplasm and nucleus of the same HEK-293 cancer cell. The EF of the SERS-active pipette was 7 × 105. As a result, we demonstrate utilizing the silver-coated pipette for both the SICM study and the molecular composition analysis of cytoplasm and the nucleus of living cells by SERS. The probe localization in cells is successfully achieved.

Use of molecular composition and compound-specific isotope analysis for source appointment of PAHs in sediments of a highly industrialized area

This study utilized both conventional molecular analysis and compound-specific isotopic techniques to identify the sources of polycyclic aromatic hydrocarbons (PAHs) in sediments of Ulsan Bay, South Korea. The concentrations of 15 traditional and 11 emerging PAHs were determined in sediments from 21 source sites and 26 bay sites. The concentrations and compositions of traditional and emerging PAHs varied significantly, even at sites close to the source areas. The results obtained from diagnostic ratios and the positive matrix factorization model for source identification were inconsistent in adjacent source areas. The δ13C profiles of PAHs, such as phenanthrene (Phe), fluoranthene (Fl), pyrene (Py), and benz[a]anthracene (BaA) in the sediments showed distinct features depending on the surrounding sources. In urban sediments, lighter δ13CPhe values were observed (mean: −25.1‰), whereas relatively heavier values of δ13CPy were found in petroleum industry areas (mean: −23.4‰). The Bayesian isotope mixing model indicates that the predominant source of PAHs in Ulsan Bay sediments was the petroleum industry (45%), followed by the non-ferrous metals industry (30%), automobile industry (18%), and urban areas (6.3%). These results demonstrated the utility of stable isotopes in assessing the sources and contributions of PAHs in small-scale regions. However, there are still limitations in compound-specific isotope analysis of PAHs, including insufficient end-members for each source, difficulty in analysis, and the influence of non-point sources; thus, further study is needed to expand its application.

Impact of fossil and non-fossil fuel sources on the molecular compositions of water-soluble humic-like substances in PM2.5 at a suburban site of Yangtze River Delta, China

Abstract. Atmospheric humic-like substances (HULIS) affect the global radiation balance due to their strong light absorption at the ultraviolet wavelength. The potential sources and molecular compositions of water-soluble HULIS at a suburban site in the Yangtze River Delta from 2017 to 2018 were discussed, based on the results of the radiocarbon (14C) analysis and combining the Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) technique in this study. The 14C results showed that the averaged non-fossil-fuel source contributions to HULIS were 39 ± 8 % and 36 ± 6 % in summer and winter, respectively, indicating significant contributions from fossil fuel sources to HULIS. The Van Krevelen diagrams obtained from the FT-ICR-MS results showed that the proportions of tannin-like and carbohydrate-like groups were higher in summer, suggesting significant contribution of HULIS from biogenic secondary organic aerosols (SOAs). The higher proportions of condensed aromatic structures in winter suggested increasing anthropogenic emissions. Molecular composition analysis on the CHO, CHON, CHOS, and CHONS subgroups showed relatively higher intensities of high O-containing macromolecular oligomers in the CHO compounds in summer, further indicating stronger biogenic SOA formation in summer. High-intensity phenolic substances and flavonoids, which were related to biomass burning and polycyclic aromatic hydrocarbon (PAH) derivatives indicating fossil fuel combustion emissions, were found in winter CHO compounds. Besides, two high-intensity CHO compounds containing condensed aromatic ring structures (C9H6O7 and C10H5O8) identified in the summer and winter samples were similar to those from off-road engine samples, indicating that traffic emissions were one of the important fossil fuel sources of HULIS at the study site. The CHON compounds were mainly composed of nitro compounds or organonitrates with significantly higher intensities in winter, which were associated with biomass burning emissions, in addition to the enhanced formation of organonitrates due to high NOx in winter. However, the high-intensity CHON molecular formulas in summer were referring to N-heterocyclic aromatic compounds, which were produced from the atmospheric secondary processes involving reduced N species (e.g., ammonium). The S-containing compounds were mainly composed of organosulfates (OSs) derived from biogenic precursors, namely long-chain alkane and aromatic hydrocarbon, which illustrate the mixed sources of HULIS. Generally, different policies need to be considered for each season due to the different seasonal sources (i.e., biogenic emissions in summer and biomass burning in winter for non-fossil-fuel sources, traffic emissions and anthropogenic SOA formation in both seasons, and additional coal combustion in winter). Measures to control emissions from motor vehicles and industrial processes need to be considered in summer. Additional control measures on coal power plants and biomass burning should be applied in winter. These findings add to our understanding of the interaction between the sources and the molecular compositions of atmospheric HULIS.

Molecular-Composition Analysis of Glass Chemical Composition Based on Time-Series and Clustering Methods.

The weathering of ancient glass relics has long been a concerned. Therefore, a systematic and more comprehensive mathematical model with which to correctly judge the category of ancient glass products whose chemical composition changes due to weathering should be established. This paper systematically analyzes and studies the changes in the composition of ancient glass products as a result of weathering of. We first analyze the surface weathering of glass relics and its correlation with three properties and establish a multivariable time-series model to predict the chemical-composition content before weathering. Next, we use one-way analysis of variance for subclassification and, finally, we use a principal component analysis of the rationality, and change the significance level to determine its sensitivity, for the reasonable prediction of the chemical-composition content and classification to provide a theoretical basis for improving the model. This allows the model to provide reference values, which can be used in the protection of cultural relics, historical research, and other fields.

High-resolution NMR spectroscopy for measuring complex samples based on chemical-shift-difference selection.

NMR spectroscopy serves as an immensely powerful tool for component assignments and molecular structure elucidations. However, proton NMR spectra are generally trapped with spectral congestion caused by limited frequency differences and complex multiplets. 2D NMR can effectively relieve spectral congestion, but its resolution and acquisition efficiency are restricted by the broad spectral bandwidth. Herein, we introduce an NMR method based on chemical-shift-difference selection by chirp excitation to record high-resolution 2D NMR spectra for extracting coupling correlation networks and multiplet structures, suitable for measurements on complex samples. The performance of the proposed method is illustrated in determining diastereotopic methylene protons, small frequency-difference coupled proton pairs of furanose, pyranose and benzene rings. This study is expected to benefit molecular structure elucidation and composition analysis of complex samples in chemistry, biochemistry and metabonomics.

ОПРЕДЕЛЕНИЕ СОДЕРЖАНИЯ АРОМАТИЧЕСКИХ УГЛЕВОДОРОДОВ В МИНЕРАЛЬНЫХ МАСЛАХ МЕТОДОМ ЯМР-РЕЛАКСАЦИИ

Molecular group composition analysis of mineral oils is helpful to predict the performance of a future lubricant and to assess the compatibility of plasticizer oil with rubbers. The method of pulsed low-frequency NMR relaxation was used to determine the molecular group composition of 11 mineral oil samples, and the ratio of aromatic and non-aromatic hydrocarbons in them was calculated. NMR measurements were performed on a Chromatec-Proton 20M NMR analyzer with a 1H resonance frequency of 20 MHz. The method used consists in recording free induction decay signals, reconstructing the total signal amplitude, estimating the relative signal amplitude per unit mass of the sample, and calculating the proportion of aromatic hydrocarbons in the sample. The results were compared with those obtained by the standard chromatographic method. A high degree of correlation (R2 = 0.99) was observed between the results.

Semi-quantitative analysis of molecular composition for petroleum fractions using electrospray ionization high-resolution mass spectrometry

The developments of high-resolution mass spectrometry and soft ionization technologies have enabled the molecular characterization of petroleum fractions. However, quantitative analysis of molecular composition for petroleum is far from being achieved. In this study, semi-quantitative analysis of molecular composition for the whole compounds in heavy petroleum fractions was carried out. Hydrocarbons and various heteroatoms in the heavy petroleum fractions were characterized by only electrospray ionization coupled with high-resolution mass spectrometry. The molecular composition of various types of compounds were calculated and integrated quantitatively based on bulk chemical composition. The semi-quantitative molecular compositions of four heavy petroleum fractions with largely different bulk properties were comprehensively characterized in multiple dimensions such as carbon number distribution, condensation degree, molecular weight, mass fraction, and molecule number. More than 5,000 molecules, which classified into 16 compound classes of seven groups were quantitatively characterized from the four fractions. The accuracy of the analysis seems acceptable according the H/C ratio comparation between that derived from element analysis and the semi-quantitative molecular composition. Representative molecule set containing structural information was also proposed based on the semi-quantitative results.

Vibrational Emission Study of the CN and C2 in Nylon and ZnO/Nylon Polymer Using Laser-Induced Breakdown Spectroscopy (LIBS).

The laser-induced breakdown spectroscopy (LIBS) technique was performed on polymers to study the neutral and ionic emission lines along with the CN violet system (B2Σ+ to X2Σ+) and the C2 Swan system (d3 Пg–a3 Пu). For the laser-based emission analyses, the plasma was produced by focusing the laser beam of a Q-switched Nd: YAG laser (2ω) at an optical wavelength of 532 nm, 5 ns pulse width, and a repetition frequency of 10 Hz. The integration time of the detection system was fixed at 1–10 ms while the target sample was positioned in air ambiance. Two organic polymers were investigated in this work: nylon and nylon doped with ZnO. The molecular optical emission study of nylon and doped nylon polymer sample reveals CN and C2 molecular structures present in the polymer. The vibrational emission analysis of CN and C2 bands gives information about the molecular structure of polymers and dynamics influencing the excitation structures of the molecules. Besides, it was further investigated that the intensity of the molecular optical emission structure strongly depends on the electron number density (cm−3), excitation temperature (eV), and laser irradiance (W/cm2). These results suggest that LIBS is a reliable diagnostic technique for the study of polymers regarding their molecular structure, identification, and compositional analysis.

Contrasting the physical and chemical characteristics of dissolved organic matter between glacier and glacial runoff from a mountain glacier on the Tibetan Plateau

Accelerated melting of mountain glaciers due to global warming has a significant impact on downstream biogeochemical evolution because a large amount of labile dissolved organic matter (DOM) is released. However, the DOM evolution processes from glacier to downstream are not well understood. To investigate these processes, samples from the glacial surface and terminating runoff of a mountain glacier on the Tibetan Plateau were collected simultaneously throughout the melting season. The samples were analyzed to determine the dissolved organic carbon (DOC) contents and chemical compositions by means of a combination of fluorescence excitation-emission matrix coupled with parallel factor analysis (EEM-PARAFAC) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The results indicate that the DOC concentrations were higher in the snow samples than in the glacial runoff samples, although a significantly higher concentration of inorganic ions was found in the glacial runoff samples, suggesting the dominant source of DOM in the glacial runoff was the glacier. The EEM-PARAFAC revealed four fluorescent components in both the snow and glacial runoff samples. However, significantly different ratios between the four components of these two categories of samples suggested chemical, physical and/or biological evolution of DOM during transport. Molecular chemical composition analyses by FT-ICR MS revealed that the DOM composition varied dramatically between the glacier and the glacial runoff. More than 50 % of the molecules were transformed from aliphatic and peptide-like compounds in the snow samples into highly unsaturated and phenolic-like compounds in the glacial runoff samples. The potential chemical transformation of DOM was likely related to biological and/or photolytic evolution during transport. Our results suggest that chemical evolution of glacial DOM could occur during the downstream transport, which is expected to be useful for further research exploring the fate of DOM and carbon cycling from the cryospheric environment and evaluating the biogeochemical effects.

Secondary organic aerosol and organic nitrogen yields from the nitrate radical (NO<sub>3</sub>) oxidation of alpha-pinene from various RO<sub>2</sub> fates

Abstract. The reaction of α-pinene with NO3 is an important sink of both α-pinene and NO3 at night in regions with mixed biogenic and anthropogenic emissions; however, there is debate on its importance for secondary organic aerosol (SOA) and reactive nitrogen budgets in the atmosphere. Previous experimental studies have generally observed low or zero SOA formation, often due to excessive [NO3] conditions. Here, we characterize the SOA and organic nitrogen formation from α-pinene + NO3 as a function of nitrooxy peroxy (nRO2) radical fates with HO2, NO, NO3, and RO2 in an atmospheric chamber. We show that SOA yields are not small when the nRO2 fate distribution in the chamber mimics that in the atmosphere, and the formation of pinene nitrooxy hydroperoxide (PNP) and related organonitrates in the ambient atmosphere can be reproduced. Nearly all SOA from α-pinene + NO3 chemistry derives from the nRO2+ RO2 pathway, which alone has an SOA mass yield of 56 (±7) %. Molecular composition analysis shows that particulate nitrates are a large (60 %–70 %) portion of the SOA and that dimer formation is the primary mechanism of SOA production from α-pinene + NO3 under simulated nighttime conditions. Synergistic dimerization between nRO2 and RO2 derived from ozonolysis and OH oxidation also contribute to SOA formation and should be considered in models. We report a 58 (±20) % molar yield of PNP from the nRO2+ HO2 pathway. Applying these laboratory constraints to model simulations of summertime conditions observed in the southeast United States (where 80 % of α-pinene is lost via NO3 oxidation, leading to 20 % nRO2+ RO2 and 45 % nRO2+ HO2), we estimate yields of 11 % SOA and 7 % particulate nitrate by mass and 26 % PNP by mole from α-pinene + NO3 in the ambient atmosphere. These results suggest that α-pinene + NO3 significantly contributes to the SOA budget and likely constitutes a major removal pathway of reactive nitrogen from the nighttime boundary layer in mixed biogenic–anthropogenic areas.

SERS-based ssDNA composition analysis with inhomogeneous peak broadening and reservoir computing

Surface-enhanced Raman spectroscopy employed in conjunction with post-processing machine learning methods is a promising technique for effective data analysis, allowing one to enhance the molecular and chemical composition analysis of information rich DNA molecules. In this work, we report on a room temperature inhomogeneous broadening as a function of the increased adenine concentration and employ this feature to develop one-dimensional and two dimensional chemical composition classification models of 200 long single stranded DNA sequences. Afterwards, we develop a reservoir computing chemical composition classification scheme of the same molecules and demonstrate enhanced performance that does not rely on manual feature identification.