Design of experiments (DOE) analysis of the effects of environmental conditions on bloodstain degradation using spectroscopic methods.

Mechanism of the influence of relative humidity on coal mine dust light scattering and the correction of mass concentration inversion

Chitosan is one of the most difficult polymers to use in electrospinning, and the influence of environmental parameters on the electrospinning process has not been thoroughly investigated, making it particularly difficult to obtain uniform fibres with high reproducibility. This study examines the influence of relative humidity (30%–60% RH) and temperature (20–40 °C) on electrospun chitosan fibres, using trifluoroacetic acid as the solvent. Field emission scanning electron microscopy (SEM), attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy, and differential scanning calorimetry (DSC) were employed to evaluate the morphological, chemical, and thermal characteristics of the resulting fibrous structures, respectively. Although ATR-FTIR analysis indicated that the chemical composition remained consistent, FESEM revealed that variations in the temperature and relative humidity during electrospinning led to changes in the fibre diameter, pore size, and porosity. Furthermore, DSC demonstrated that variations in temperature and humidity during chitosan fibre production influenced the melting enthalpy, glass transition temperature, crystallinity temperature, and melting temperature. Ultimately, the optimal temperature (30 °C) and humidity (50% RH) conditions were determined for the given electrospinning parameters.

BackgroundCommunicable diseases remain a significant public health challenge in Asia, driven by diverse climatic, socioeconomic, and healthcare-related factors. Despite reductions in diseases such as tuberculosis and malaria, persistent hotspots highlight the need for deeper investigation. This study applies machine learning and spatial analysis techniques to examine patterns and determinants of communicable diseases across 41 countries from 2000 to 2022.MethodsData were sourced from global repositories, including WHO, CRU TS, WDI, and UNICEF, covering disease cases (e.g., tuberculosis, dengue, malaria), climaticvariables (e.g., precipitation, humidity), and healthcare metrics (e.g., hospital bed density). Missing values were imputed using random forest methods. Outlier detection was conducted using Mahalanobis distances, identifying and addressing significant deviations to ensure data consistency. Models like XGBoost and Random Forest were assessed using RMSE, MAE, and R². SHAP and XAI frameworks improved interpretability, while Gi* spatial statistics revealed disease hotspots and disparities.ResultsTuberculosis cases declined from 8.01 million (2000) to 7.54 million (2022), with hotspots in India (Gi* = 3.07) and Nepal (Gi* = 4.67). Malaria cases dropped from 27.00 million (2000) to 7.96 million (2022), yet Bangladesh (Gi* = 4.13) and Pakistan (Gi* = 4.17) exhibited sustained risk. Dengue peaked at 2.71 million cases in 2019, with current hotspots in Malaysia (Gi* = 2.4) and Myanmar (Gi* = 0.79). Spatial disparities underscore the influence of precipitation, relative humidity, and healthcare gaps. XGBoost achieved remarkable accuracy (e.g., tuberculosis: RMSE = 0.94, R² = 0.91), and SHAP analysis revealed critical predictors such as climatic factors.ConclusionThis study demonstrates the effectiveness of integrating machine learning, spatial analysis, and XAI to uncover disease determinants and guide targeted interventions. The findings offer actionable insights for improving disease surveillance, resource allocation, and public health strategies across Asia.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12942-025-00433-7.

Patulin is a mycotoxin produced mainly by Penicillium expansum on apples. P. expansum is a fruit pathogen that can cause apple soft rot. However, much is unknown about the characteristics of P. expansum and influence of major environmental parameters on its patulin production and growth on apple puree agar media (APAM). In this study, we evaluated the influence of pH, temperature, and relative humidity (RH) on patulin production by P. expansum OM1 and its growth (colony diameter and mycelial dry weight) on APAM after isolation and identification of the patulin-producing fungal strain from an apple. The fungal isolate produced the largest quantity of patulin on APAM under 15 °C, pH 4.0, and RH 98%, while it had the highest growth rates on the same media under 25 °C, pH 4.0–6.0, and RH 98%. Our data demonstrated that three important physicochemical factors (pH, temperature, and RH) substantially influenced the patulin production by the fungal species and its growth on APAM. Moreover, our results revealed that patulin was not detected on APAM at 5 °C after 7 days of incubation and that a trace amount of patulin was produced by the fungal strain along with its slow growth on the same media at 5 °C after 14 days. It suggests that patulin contamination by P. expansum on apples could be controlled during postharvest storage below 5 °C. These findings could provide fundamental knowledge for development of efficient strategies to prevent the occurrence of apples contaminated with patulin produced by P. expansum on them during postharvest storage.

Abstract Plasma activated water (PAW) and mist (PAM) have gained widespread application as disinfectants in various fields. However, PAW exhibits limited storage stability and bulk activation efficiency, while PAM demands continuous energy supply and shows non-uniform droplet coverage. This study proposes an innovative approach that forms thin water films via in-situ evaporation–condensation during plasma treatment. The contact of high-temperature, high-humidity gas with a cold sample leads to surface condensation, releasing latent heat that increases the sample temperature. This temperature variation subsequently influences water layer formation, creating a dynamic coupling between heat transfer and condensation processes. The process of dynamic liquid film formation incorporates dissolution of plasma-generated gaseous reactive oxygen and nitrogen species (RONS), thereby enhancing both sterilization efficacy and activation efficiency. A numerical model is established to investigate dynamic liquid film formation through evaporation condensation and its interactions with plasma, while incorporating a hierarchical bacterial inactivation framework to evaluate sterilization efficacy. It also examines how variables such as sample temperature, gas temperature, and relative humidity influence liquid film thickness, RONS concentrations and antimicrobial performance in the liquid film. Results indicate that optimizing key parameters of dynamic water films (thickness, temperature, and surface retention time) may serve as critical design criteria for plasma-based surface disinfection systems.

The study used the Optical Properties of Aerosols and Clouds (OPAC 4.0) database to obtain the microphysical characteristics of urban aerosols and performed numerical analyses of the analytical formulas describing how equilibrium relative humidity (RH), effective radius, hygroscopic growth, and the corresponding absolute and fractional changes in these parameters respond to surface-tension influences (Kelvin effect) on atmospheric aerosols. It was determined that the Kelvin effect increase with the increase in water soluble and RH, and for the water activity it increased with the increase in RH but decreased with the increase in water soluble. The three models analyzed, are, two of one parameter models and one of three parameters model. The analysis of the extracted data shows that, to first-order accuracy, variations in equilibrium RH, effective radius, and effective hygroscopic growth are influenced by aerosol composition. Results from all three models further indicate that the fractional changes in ambient RH, effective radius, and hygroscopic growth likewise depend on the aerosol makeup. Overall, the study found that the strength of the Kelvin effect and its resulting impact on atmospheric aerosols is determined by the hygroscopic properties of the aerosols. For lower RHs, (50 and 70) the range of the over estimations of the effective hygroscopic growth and effective radii are less that 1%. As RH increases, the degree of overestimation also rises following a power-law relationship with RH. This indicates a growing deviation from ideal behavior at higher RH, likely due to the electrolytic characteristics of the ionic aerosol mixtures. Consequently, more complex formulations are needed to maintain accuracy at elevated RH levels. Overall, these findings underscore the importance of applying Kelvin corrections when modeling effective hygroscopic growth and effective radii of atmospheric aerosols, particularly under high-RH conditions.

Membrane durability is a major obstacle to the wide adoption of fuel cells for transportation applications and water electrolysers (EL) for green hydrogen production. Membrane chemical degradation is generally attributed to the fact that a small amount of hydrogen peroxide may be formed during cell operation, which can dissociate into HO• or HOO• radicals and subsequently attack the membrane structure1].For perfluorsulfonic acid (PFSA)-type membranes, several degradation mechanisms have been proposed including backbone unzipping through the carboxyl acid end groups, degradation associated with sulfonic acid groups on the side chain. Additionally, both ether links and tertiary fluorine sites are also considered susceptible to radical attacks2]. Conversely, the chemical degradation mechanism in an aromatic hydrocarbon (HC) PEM may be rather different3, 4, 5], and on the whole chemical degradation studies into HC membranes are rather limited.In this work, chemical durability studies were carried out on a range of both PFSA and hydrocarbon (HC) membranes using in cell as well as ex-situ Fenton tests. Effluent water collected from in-cell tests and post-test Fenton solutions were studied by Ion Chromatography (IC) and Liquid Chromatography/Mass Spectroscopy (LC/MS) to determine their respective emissions of fluoride, sulphate, and other membrane degradation products. The obtained data provided valuable insights into membrane degradation pathways.Furthermore, the impact of end group structure on ionomer chemical stability was assessed via Fenton tests on simple model compounds containing end groups of relevance. IC analysis of fluoride ions indicated that the -CF2H end group was most vulnerable to radical attack compared to CF2COOH and -CF3 groups. This conclusion is supported with analysis of other degradation products using LC/MS and solution NMR.Finally, in cell hydrogen peroxide detection method5] was further developed, a number of example studies were described investigating the influence of cell voltage, relative humidity, flow rate and pressure difference on H2O2 generation in cell. The established method may be best suited for evaluating chemical durability properties of different membranes including both PFSA and HC as well as for assessing the influence of different additives.1] M. Yandrasits et. al, J. Electrochem. Soc., 2021 168 0245172] M. Yandrasits et. al, J. Electrochem. Soc., 2022 169 0345263] M. Adamski et. al, Mater. Adv., 2021 2 49664] T. Holmes et. al, Chem. Mater. 2019 31 1441−14495] Z. Han, et. al, ACS Electrochem. 2024

BackgroundScrub typhus is transmitted through vectors and is susceptible to meteorological factors, posing a significant threat to human life and health. Therefore, in this study, the nonlinear relationships between meteorological factors and scrub typhus (ST) and the lag effects of meteorological factors on ST were analyzed, and the explanatory power of these factors on the spatially stratified heterogeneity of ST was evaluated.MethodsMonthly data on ST cases and meteorological factors were collected in Jiangxi from 2014 to 2023. A distributed lag nonlinear model (DLNM) was used to analyze the lag effects and nonlinear relationships between meteorological factors and ST. Geodetector was conducted using 2023 spatial data to evaluate the explanatory power of meteorological factors and their interactions on the spatially stratified heterogeneity of ST.ResultsA total of 9129 cases of newly diagnosed ST were recorded. The DLNM demonstrated nonlinear relationships between meteorological factors and ST and lag effects of meteorological factors on ST. The influence of temperature, relative humidity, and wind speed on the ST initially increased, peaking at 25.50 °C, 84.80%, and 2.00 m/s, respectively, before decreasing. Precipitation was associated with an increasing risk of ST, whereas pressure tended to decrease risk. Compared with median meteorological values, extreme conditions (such as extremely low temperature, extremely low relative humidity, extremely high pressure, and extremely high wind speed) had a protective effect on the incidence of ST. Conversely, extremely high precipitation and extremely low pressure were associated with an elevated risk of ST. Geodetector analysis revealed the following explanatory power for the spatially stratified heterogeneity of ST: temperature (0.357) > relative humidity (0.351) > pressure (0.275) > precipitation (0.225) > wind speed (0.223). Temperature and relative humidity emerged as the most critical indicators affecting ST. Furthermore, the incidence of ST was driven by the combined effects of multiple meteorological factors.ConclusionsThe incidence of ST in Jiangxi Province is significantly influenced by meteorological factors, with both lag effects and nonlinear relationships. Temperature and relative humidity are the key indicators affecting ST. The consideration of meteorological factors is essential for the prevention and control of ST.Supplementary InformationThe online version contains supplementary material available at 10.1186/s41182-025-00835-0.

ABSTRACT Aggregation behavior in arthropods is often a response to environmental stressors, particularly desiccation risk. While this is well documented in small‐bodied and larval arthropods, less is known about whether aggregation behavior provides similar benefits to adult and/or large‐bodied insects. Here, we investigate whether aggregation behavior in adult Madagascar hissing cockroaches ( Gromphadorhina portentosa ), a large insect species, is modulated by ambient relative humidity (RH). We exposed mixed‐sex groups of adult cockroaches to alternating high (75%–90%; “wet‐season”) and low (50%–65%; “dry‐season”) RH in a controlled laboratory setting and measured aggregation behavior over multiple weeks. Aggregation was significantly more likely to be observed under low RH, with a greater proportion of individuals aggregating. RH did not affect the sex ratio of aggregations. These results support the hypothesis that aggregation behavior in adult G. portentosa is, at least in part, a plastic and adaptive response to arid conditions, likely enhancing water retention by creating a humid microenvironment. Our findings highlight the importance of behavioral plasticity in large‐bodied insects facing fluctuating environmental conditions and suggest that increasing aridity due to climate change has the potential to impact the ecologies of G. portentosa and other similarly large, forest‐floor arthropods.

Relative humidity (RH) can have a significant impact on bamboo products, leading to issues such as swelling, shrinking, and even cracking. Unfortunately, these effects are often difficult to detect in bamboo bundles. This research aims to investigate how RH affects the moisture expansion coefficient (β) of bamboo bundles. Samples from the stem of the Dendrocalamus genus were dried in an oven at 105 °C until they reached a stable weight. The samples were then hand-pulled and cut to create cross-sections with areas ranging from 0.06 mm 2 to 0.09 mm 2 and a length of 60 mm. The expansion coefficient of the bamboo bundles was measured using a tensile test, following the ASTM D3379 standard. This was conducted at a constant temperature of 27 °C and a force of 10 N in a controlled chamber with RH levels between 50% and 85% for a full day, with five replicates for accuracy. The results indicate that the strain in bamboo bundles is influenced by both relative humidity (RH) and tensile load. When the RH ranges from 85% to 50%, the bamboo bundles tend to stretch under tensile load. However, when the RH drops to 50% without tensile load, the bundles can return to their original shape. This suggests that while the initial changes in strain may be small, bamboo bundles gradually experience increased strain over time, and prolonged use could result in more significant alterations. Another important factor to consider when using bamboo bundles is the effect of changes in relative humidity (ΔRH) on the average value of β. Indeed, bamboo bundles need time to absorb or release moisture as the surrounding environment changes. The average value of β tends to decrease dramatically in an exponential decay pattern. When ΔRH exceeds 5% in both charge and discharge conditions, the average value of β can be considered equal and constant, as it becomes extremely small and negligible. However, at ΔRH levels higher than 20%, the average value of β converges to 1.5 x 10-4 (%RH)-1, indicating that the bamboo bundles have already adapted to the surrounding humidity. Therefore, it is crucial to carefully assess application areas with rapid humidity fluctuations when using bamboo bundles to prevent potential damage during use.

Bamboo can be used for a variety of purposes, whether using the bamboo culm in structures works or using bamboo bundle or bamboo fibers as a reinforcement in composite materials. However, the critical item that should be considered when using bamboo materials is the humidity condition of the environment. The influence of humidity on the mechanical properties of bamboo materials can potentially lead to damage or degradation. The objective of this research is to investigate the influence of relative humidity (RH) on elastic modulus of bamboo bundle. In this research, 3 years old Dendrocalamus bamboo stem at 3-6 m in height without node was used to prepare the bundle samples. The bamboo stem was dried in the oven at 105 °C then hand pulled and cut to get the bamboo bundle with 30 mm in gage length and 0.06-0.09 mm 2 in cross-section areas. The elastic modulus of bamboo bundles was determined according to ASTM D3379 standard under 8 different relative humidity; 30%, 35%, 50%, 55%, 70%, 75%, 80%, and 85% RH, whereas paper grips technique was applied to prevent damage from the machine clamps. The results indicated that the relative humidity does not affect the value of the loaded or unloaded elastic modulus of bamboo fiber bundle. For the low value of relative humidity, here 35%-55%, the value of elastic modulus of bamboo bundle is quasi-stable with the RH with the average value 25.93 GPa while the elastic modulus was gradually decreased for the high value of RH (>70%) with the minimum value of 24.43 GPa at 85% RH. Implying at high humidity condition, the humidity or the amount of water vapor in the air affects to the bamboo bundle be softened or more flexible, which helps the process of bending or forming bamboo bundles easier.

Penitrem A, an indole–diterpenoid neurotoxin, is produced by several species of Penicillium on cereal grains, meat, dairy products, and fruits. Penicillium crustosum is a well-known penitrem A producer, but much is unknown about physiological characteristics of P. crustosum. In this study, we isolated penitrem A-producing P. crustosum OM1 from pears, and investigated the influence of temperature, pH, and relative humidity [RH] on its growth and penitrem A production. The fungal species exhibited the highest growth at 25 °C and pH 4.5 on mYES4 under RH 98%, whereas it produced the highest level of penitrem A at 22 °C and pH 6.5 on the same media under RH 98%. Furthermore, RT-qPCR analysis of six penitrem A biosynthetic genes (ptmB, ptmJ, ptmK, ptmO, ptmS, and ptmT) expression in P. crustosum OM1 showed that the four penitrem A biosynthetic genes (ptmJ, ptmK, ptmO, and ptmS) were up-regulated in mYES4 (penitrem A conducive medium), whereas they were not in mMEB (penitrem A non-conducive medium). Our results demonstrated that the three key environmental factors significantly affected the growth of P. crustosum OM1 and its penitrem A production. These findings could help find efficient methods to prevent penitrem A contamination from fresh fruits including pears.

BackgroundHand, foot, and mouth disease (HFMD) is a significant public health challenge, particularly in Guangdong Province, China. Although spatio-temporal dynamics of HFMD have been studied, inter-regional transmission patterns remain underexplored. This study investigates these patterns and the influence of meteorological factors to provide insights for more effective prevention strategies in the context of environmental factors.MethodsWe collected HFMD cases surveillance, population, and meteorological data from 21 cities in Guangdong from 2009 to 2017. Endemic-epidemic multivariate time-series model was used to analyze the case data, decomposing the HFMD risk into endemic, autoregressive, and spatio-temporal components, and investigating the influence of temperature and relative humidity on these components.ResultsHFMD in Guangdong shows distinct seasonal peaks in the second and fourth quarters, with regional clusters in Guangzhou, Shenzhen, Foshan, and Dongguan. The endemic-epidemic model indicates that 86.57% (95%CI: 77.17%-97.08%) of infection risk is due to autoregressive transmission, 9.50% (95%CI: 8.46%-10.65%) to spatio-temporal transmission, and 3.94% (95%CI: 3.33%-4.60%) to endemic factors. Shenzhen, Foshan, Meizhou, and Zhanjiang have autoregressive transmission rates of 89%-94.08%, while Yunfu, Jiangmen, Zhaoqing, and Shantou have import rates of 12.27%-21.44%. HFMD risk is positively correlated with temperatures below 25 °C for the endemic component and above 25 °C for the autoregressive and spatio-temporal components.ConclusionHFMD transmission in Guangdong is primarily driven by the autoregressive component, with temperature influencing different transmission components. Health authorities should enhance local preventive measures during high-risk seasons and adjust control strategies based on various transmission components to mitigate HFMD spread.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12879-025-11799-1.

Oak wood (Quercus robur L.) was subjected to thermo-mechanical modification, preceded by two variants of hydrothermal treatment. Samples of non - modified and modified oak wood were conditioned in a climate with a temperature of 20 C, a relative humidity of 9%, 34%, 55%, 75%, and 98%. After the conditioning process was completed, the wood roughness was determined parallel and perpendicular to the grain. The results showed that relative humidity significantly affected the Ra and Rz roughness parameters. Densified (after thermo-mechanical modification) oak wood at 98% relative humidity exhibited higher roughness than wood subjected to hydrothermal treatment and densification. It was also found that the duration (150 min, 300 min) of the hydrothermal treatment influenced changes in Ra and Rz parameters. The oak wood subjected to a longer hydrothermal process and then densified was characterized by lower roughness than oak wood after shorter hydrothermal treatment and densified. Regardless of the thermo-mechanical modification variant, higher Ra and Rz values parallel to the grain were observed in modified wood after conditioning at 98% humidity compared to non-modified oak wood. These findings indicate that a properly selected hydrothermal modification time before densification can mitigate the adverse effects of high ambient humidity on the surface quality of oak wood. The results are of practical relevance for the optimization of finishing processes in thermo-mechanically modified oak wood.

Influence of temperature and relative humidity on the combined efficacy of insecticides and diatomaceous earth for the control of Trogoderma granarium on rough rice

ABSTRACTIn this study we offer an overview of the winter air quality (October 1–December 31, 2024) in Kolkata, one of the largest and most populous megacities of India and the world, using archival records of the Central Control Room for Air Quality Management System for particulate matter (PM2.5 and PM10), carbon monoxide (CO), nitrogen dioxide (NO2), sulfur dioxide (SO2), and BTEX (benzene, toluene, ethylbenzene, xylene) for seven real‐time monitoring stations. Results indicated significant (p < 0.01) spatial variations in species distributions across the city. The highest median PM2.5 levels were recorded at the Bally station (80.80 µg cm−3) while the lowest at RBU (48.38 µg cm−3). Median PM10 levels varied between 146.96 µg cm−3 (Victoria) and 96.83 µg cm−3 (RBU). The highest median NO2 levels were at FW (59.03 µg cm−3) and the lowest at RBU (18.58 µg cm−3). The highest median total BTEX level was at Jadavpur (85.73 µg cm−3) and the lowest at Victoria (7.23 µg cm−3). The Mann–Kendal test, coupled with Sen's slope estimator, indicated increasing (p < 0.00001) PM, CO, and BTEX levels, indicating growing health threats towards the end of winter. The daily PM readings exceeded the World Health Organization (WHO) safety thresholds at all monitoring stations throughout November and December. Daily benzene levels exceeded the safety threshold at Jadavpur and RSV for over 95% of days in November and December. Week‐wise exceedance analyses indicated greater concerns for the weekdays than weekends. Use of T:B ratios indicated a wide variability in BTEX sources across the stations, ranging from fuel combustion to vehicular exhausts to industrial emissions, to more mixed signatures, which call for more targeted approaches (e.g., positive matrix factorization, PMF) for BTEX source apportionment. Moreover, we noticed a significant “temporal shift” over time, with the T:B ratios dropping significantly in December (coal/biomass combustion). Spearman rank correlations revealed a significant (0.05 < p < 0.01) species assemblage, involving the PMs, CO, and total BTEX, implying their similar origin (e.g., vehicular exhaust), with stronger associations in December than October. We identified a significant pollutant‐weather nexus, including negative influences of relative humidity (0.05 < p < 0.01), air temperature (p < 0.05) and solar radiance (p < 0.05) on pollutant concentrations that undermines multiple UN Sustainable Development Goals (UN SDGs). We conclude by identifying future research areas while pondering over policy mechanisms (Clean Air Action Plan, CLAAP). The latter hinges on a participatory action network, melding the social, technological, economic, and institutional machinery of urban environmental protection.

Impact of support on acetone oxidation by Ag@S (S=CeO2, Al2O3, ZSM-5) catalysts under VUV illumination at room temperature: Improving synergy, influence of relative humidity, and in-situ mechanistic studies

This paper presents a comprehensive evaluation of metal foam flow field application within polymer electrolyte fuel cells (PEFCs) and compares it with conventional serpentine channels from both computational fluid dynamics simulation and experimental viewpoints. The experiments are designed to investigate the effects of material, area density, compression ratio, and final thickness of metal foam. Additionally, the influence of housing plate material and relative humidity (RH) is tested here. The results reveal that at RH = 75%–100%, the best flow field design is nickel foam with a compression ratio of 70%, a final thickness of 0.5 mm, and an SS-304 housing plate, which delivers a great limiting current density. In comparison with the serpentine channel case, the PEFC with this foam flow field shows a 10% improvement in maximum power density (901 vs 989 mW cm−2) and a 45% improvement in limiting current density (2140 vs 3110 mA cm−2). While at RH = 30%, the same foam flow field with a final thickness of 1 mm is a superior option. The experiments also indicate that maximum power density increases by 23% (from 684 to 841 mW cm−2) as the compression ratio rises from 0% to 70% while reducing final thickness from 1 to 0.5 mm causes a 5.8% enhancement in (from 935 to 989 mW cm−2) cell performance. Simulation results reveal that metal foam is more effective in evenly distributing reactants, resulting in an average oxygen mass fraction at the cathode catalyst layer that is 38% higher than the serpentine channel case.

Secondary organic aerosol (SOA), a major component ofsubmicrometerparticles, is critical to the climate and human health. SOA can formthrough nucleation of low-volatility organic compounds, followingatmospheric oxidation, or by condensing these vapors onto existingparticles. In either of these cases, the formation of SOA particlescould be affected by atmospheric conditions (e.g., relative humidity(RH)) and particle liquid water content. This study examines the effectsof RH on the formation and composition of SOA from dark α-pinene(C10H16) ozonolysis, as a canonical system,with or without ammonium sulfate (AS, (NH4)2SO4) seed particles across varying RH levels. Using onlineextractive electrospray ionization mass spectrometry, we identifiedmonomers (C7–10) and dimers (C15–20) in the SOA with high chemical and temporal resolution. In bothcases, high RH (>90%) promotes dimer formation in the particlephase,while they appear at the beginning of the experiment when (NH4)2SO4 seeds are present. The promptincrease in dimers in high RH seed containing experiments (60–65%dimers), which are absent at low RH (10%), suggests that intraparticlereactions are responsible for the dimer formation.