EEG and fNIRS datasets based on Stroop task during two weeks of high-altitude exposure in new immigrants.

Maintaining sufficient cerebral oxygen metabolism is crucial for human survival, especially in challenging conditions such as high-altitudes. Human cognitive neural activity is sensitive to fluctuations in oxygen levels. However, there is a lack of publicly available datasets on human behavioural responses and cerebral dynamics assessments during the execution of conflicting tasks in natural hypoxic environments. We recruited 80 healthy new immigrant volunteers (males, aged 20 ± 2 years) and employed the Stroop cognitive conflict paradigm. After a two-week exposure to both high and low-altitudes, the behavioural performance, prefrontal oxygen levels, and electroencephalography (EEG) signals were recorded. Comparative analyses were conducted on the behavioural reaction times and accuracy during Stroop tasks, and statistical analyses of participants' prefrontal oxygen levels and EEG signals were performed. We anticipate that our open-access dataset will contribute to the development of monitoring devices and algorithms, designed specifically for measuring cerebral oxygen and EEG dynamics in populations exposed to extreme environments, particularly among individuals suffering from oxygen deficiency.

Functional diversity of macrozoobenthos under adverse oxygen conditions in the southern Baltic Sea.

Oxygen deficiency is a major problem in the Baltic Sea. To study the impact of hypoxia on the functional diversity of benthic fauna and the possibility of macrozoobenthos recovery, data were analyzed in a gradient of oxygen conditions in the Gdansk Basin. The research conducted on the basis of biological traits analysis enabled us to analyze the number, type and spatial distribution of biological traits-a proxy for functions performed by macrozoobenthos. A significant depletion of macrofauna was already observed under conditions of reduced oxygen above the bottom, both in terms of functional diversity and biomass. Although taxa observed in hypoxia (DO < 2 mL L-1) perform a number of functions, the remaining species do not form complex structures in the sediments or cause deep bioturbation and bioirrigation. Moreover, their extremely low biomass plays an irrelevant role in benthic-pelagic coupling. Thus, benthic fauna under hypoxia is not an element that ensures the functioning of the ecosystem. We assess that traits important for species dispersal and the presence of taxa resistant to short-term hypoxia in the oxic zone above the halocline provide a "backup" for ecosystem functioning under altered diverse oxygen conditions below the halocline after cessation of hypoxia in the southern Baltic Sea.

Direct elemental analysis of plant oils by inductively coupled plasma mass spectrometry: Simple sample dilution combined with oxygen introduction into the plasma.

Assessment of trace metal concentrations in plant oils has been considered a crucial quality control marker for potential health risks, oil flavour, and oxidative stability. A straightforward inductively coupled plasma mass spectrometry (ICP-MS) methodology was developed and validated through introduction of argon:oxygen gas mixture into plasma, allowing for a direct elemental analysis of organic matrices. This approach offers the advantage of a simple one-step preparation of plant oil samples with negligible contamination risks. The complete solubilization of the oil matrix enables the determination of total metal content from a single test tube with low dilution factor of 5. The modified plasma conditions resulted in the development of a robust and accurate ICP-MS method providing limits of detection at sub ng·g-1 levels. The ICP-MS method allowed the determination of trace levels of Ba, Cd, Cu, Fe, Mn, Pb, Sn, V, and Zn in olive, sunflower and rapeseed oils.

Using Effect Scores to Characterize Heterogeneity of Treatment Effects.

This JAMA Guide to Statistics and Methods article explains effect score analyses, an approach for evaluating the heterogeneity of treatment effects, and examines its use in a study of oxygen-saturation targets in critically ill patients.

Continuous planting of Chinese fir monocultures significantly influences dissolved organic matter content and microbial assembly processes.

Monoculture plantations in China, characterized by the continuous cultivation of a single species, pose challenges to timber accumulation and understory biodiversity, raising concerns about sustainability. This study investigated the impact of continuous monoculture plantings of Chinese fir (Cunninghamia lanceolata [Lamb.] Hook.) on soil properties, dissolved organic matter (DOM), and microorganisms over multiple generations. Soil samples from first to fourth-generation plantations were analyzed for basic chemical properties, DOM composition using Fourier transform ion cyclotron resonance mass spectrometry, and microorganisms via high-throughput sequencing. Results revealed a significant decline in nitrate nitrogen content with successive rotations, accompanied by an increase in easily degradable compounds like carbohydrates, aliphatic/proteins, tannins, Carbon, Hydrogen, Oxygen and Nitrogen- (CHON) and Carbon, Hydrogen, Oxygen and Sulfur- (CHOS) containing compounds. However, the recalcitrant compounds, such as lignin and carboxyl-rich alicyclic molecules (CRAMs), condensed aromatics and Carbon, Hydrogen and Oxygen- (CHO) containing compounds decreased. Microorganism diversity, abundance, and structure decreased with successive plantations, affecting the ecological niche breadth of fungal communities. Bacterial communities were strongly influenced by DOM composition, particularly lignin/CRAMs and tannins. Continuous monoculture led to reduced soil nitrate, lignin/CRAMs, and compromised soil quality, altering chemical properties and DOM composition, influencing microbial community assembly. This shift increased easily degraded DOM, accelerating soil carbon and nitrogen cycling, ultimately reducing soil carbon sequestration. From environmental point of view, the study emphasizes the importance of sustainable soil management practices in continuous monoculture systems. Particularly the findings offer valuable insights for addressing challenges associated with monoculture plantations and promoting long-term ecological sustainability.

Degradation of dissolved sulfide in water using multi-hole dielectric barrier discharge.

Biogas obtained from livestock manure is used as fuel for solid oxide fuel cells. Although H2S is a typical biogas, it is a fatal disadvantage for fuel-cell power generation and, thus, must be removed. In this study, we proposed an effective method for sulfide removal from water using a multi-hole dielectric barrier discharge (DBD) system. In this system, active species, such as ozone, ultraviolet rays, hydroxyl radicals, and hydrogen peroxide, were simultaneously generated. Under optimal conditions, dissolved sulfide (initial concentration: 120 mg/L) was completely degraded within 10 min in air plasma and 6 min in oxygen plasma. Changes in the physical properties of the sulfide-treated water were confirmed by measuring the pH, oxidation-reduction potential, and dissolved oxygen. Results of the by-product analysis showed that sulfide was converted into sulfate by reacting with a large amount of ozone, and the active species were emitted from the multi-hole DBD system. In summary, multi-hole DBD technology has demonstrated merit as a water-contaminant purification technology and for the removal of dissolved sulfide.

Quantifying isotope parameters associated with carbonyl-water oxygen exchange during sucrose translocation in tree phloem.

Stable oxygen isotope ratio of tree-ring α-cellulose (δ18Ocel) yields valuable information on many aspects of tree-climate interactions. However, our current understanding of the mechanistic controls on δ18Ocel is incomplete, with a knowledge gap existent regarding the fractionation effect characterizing carbonyl-water oxygen exchange during sucrose translocation from leaf to phloem. To address this insufficiency, we set up an experimental system integrating a vapor 18O-labeling feature to manipulate leaf-level isotopic signatures in tree saplings enclosed within whole-canopy gas-exchange cuvettes. We applied this experimental system to three different tree species to determine their respective relationships between 18O enrichment of sucrose in leaf lamina (Δ18Ol_suc) and petiole phloem (Δ18Ophl_suc) under environmentally/physiologically stable conditions. Based on the determined Δ18Ophl_suc-Δ18Ol_suc relationships, we estimated that on average, at least 25% of the oxygen atoms in sucrose undergo isotopic exchange with water along the leaf-to-phloem translocation path and that the biochemical fractionation factor accounting for such exchange is c. 34‰, markedly higher than the conventionally assumed value of 27‰. Our study represents a significant step toward quantitative elucidation of the oxygen isotope dynamics during sucrose translocation in trees. This has important implications with respect to improving the δ18Ocel model and its related applications in paleoclimatic and ecophysiological contexts.

Preserved particulate organic carbon is likely derived from the subsurface sulfidic photic zone of the Proterozoic Ocean: evidence from a modern, oxygen-deficient lake.

Biological processes in the Proterozoic Ocean are often inferred from modern oxygen-deficient environments (MODEs) or from stable isotopes in preserved sediment. To date, few MODE studies have simultaneously quantified carbon fixation genes and attendant stable isotopic signatures. Consequently, how carbon isotope patterns reflect these pathways has not been thoroughly vetted. Addressing this, we profiled planktonic productivity and quantified carbon fixation pathway genes and associated organic carbon isotope values (δ13 CPOC ) of size-fractionated (0.2-2.7 and >2.7 µm) particulate matter from meromictic Fayetteville Green Lake, NY, USA. The high-O2 Calvin-Benson-Bassham (CBB) gene (cbbL) was most abundant in the <2.7 µm size fraction in shallow oxic and deep hypoxic waters, corresponding with cyanobacterial and eukaryote algal populations. The low-O2 CBB gene (cbbM) was most abundant near the lower oxycline boundary in the larger size fraction, coincident with purple sulfur bacteria populations. The reverse citric acid cycle gene (aclB) was equally abundant in both size fractions in the deepest photic zone, coinciding with green sulfur bacteria populations. Methane coenzyme reductase A (mcrA), of anaerobic methane cyclers, was most abundant at the lower oxycline boundary in both size fractions, coinciding with Methanoregula populations. δ13 CPOC values overlapped with the high-O2 CBB fixation range except for two negative excursions near the lower oxycline boundary, likely reflecting assimilation of isotopically-depleted groundwater-derived carbon by autotrophs and sulfate-reducers. Throughout aphotic waters, δ13 CPOC values of the large size fraction became 13 C-enriched, likely reflecting abundant purple sulfur bacterial aggregates. Eukaryote algae- or cyanobacteria-like isotopic signatures corresponded with increases in cbbL, cbbM, and aclB, and enrichment of exopolymer-rich prokaryotic photoautotrophs aggregates. Results suggest that δ13 CPOC values of preserved sediments from areas of the Proterozoic Ocean with sulfidic photic zones may reflect a mixture of alternate carbon-fixing populations exported from the deep photic zone, challenging the paradigm that sedimentary stable carbon isotope values predominantly reflect oxygenic photosynthesis from surface waters.

Characterization of Single-Spheroid Oxygen Consumption Using a Microfluidic Platform and Fluorescence Lifetime Imaging Microscopy.

Oxygen consumption has been used to evaluate various cellular activities. In addition, three-dimensional (3D) spheroids have been broadly exploited as advanced in vitro cell models for various biomedical studies due to their capability of mimicking 3D in vivo microenvironments and cell arrangements. However, monitoring the oxygen consumption of live 3D spheroids poses challenges because existing invasive methods cause structural and cell damage. In contrast, optical methods using fluorescence labeling and microscopy are non-invasive, but they suffer from technical limitations like high cost, tedious procedures, and poor signal-to-noise ratios. To address these challenges, we developed a microfluidic platform for uniform-sized spheroid formation, handling, and culture. The platform is further integrated with widefield frequency domain fluorescence lifetime imaging microscopy (FD-FLIM) to efficiently characterize the lifetime of an oxygen-sensitive dye filling the platform for oxygen consumption characterization. In the experiments, osteosarcoma (MG-63) cells are exploited as the spheroid model and for the oxygen consumption analysis. The results demonstrate the functionality of the developed approach and show the accurate characterization of the oxygen consumption of the spheroids in response to drug treatments. The developed approach possesses great potential to advance spheroid metabolism studies with single-spheroid resolution and high sensitivity.

Seasonal sensitivity of groundwater dissolved organic matter in recognition of chronic kidney disease of unknown etiology: Optical and molecular perspectives.

Chronic kidney disease of unknown etiology (CKDu) has aroused a great concern due to its widespread prevalence in many developing countries. Dissolved organic matter (DOM) has been proved to be associated with CKDu in groundwater. However, the responses of their association to abiotic influencing factors like seasonal variation are not carefully disclosed. Herein, we revealed the seasonal variation of DOM in CKDu related groundwater (CKDu groundwater) and control group (non-CKDu groundwater) collected from Sri Lanka during the dry and wet seasons by excitation-emission matrix spectroscopy and Fourier transform ion cyclotron resonance mass spectrometry. In both CKDu and non-CKDu groundwaters, the input of exogenous DOM during wet season improved the degree of humification and molecular weight of DOM, while oxidative processes during the dry season increased the ratios of oxygen to carbon (O/C). Furthermore, compared with non-CKDu groundwater, more DOM with high O/C enriched in CKDu groundwater during the dry season, indicating stronger oxidative processes in CKDu groundwater. It may result in the enrichment of carboxyl group and induce the enhanced leaching of CKDu-related Si and F-. The receiver operating characteristic (ROC) analysis showed that the CKDu-recognition ability of most optical and molecular indicators was susceptible to seasonal factors and their recognition abilities were stronger in the wet season. The linkage between DOM and CKDu was affected by seasonal factors through the occurrence, mobility, degradation, and toxicity of typical organic molecules (e.g., C17H18O10S). The study provides a new insight into screening pathogenic factors of other endemic diseases related to organic molecules.

Response of TCE biodegradation to elevated H2 and O2: Implication for electrokinetic-enhanced bioremediation.

The study investigated the influences of pure H2 and O2 introduction, simulating gases produced from the electrokinetic-enhanced bioremediation (EK-Bio), on TCE degradation, and the dynamic changes of the indigenous microbial communities. The dissolved hydrogen (DH) and oxygen (DO) concentrations ranged from 0.2 to 0.7 mg/L and 2.6 to 6.6 mg/L, respectively. The biological analysis was conducted by 16S rRNA sequencing and functional gene analyses. The results showed that the H2 introduction enhanced TCE degradation, causing a 90.4% TCE removal in the first 4 weeks, and 131.1 µM was reduced eventually. Accordingly, cis-dichloroethylene (cis-DCE) was produced as the only product. The following three ways should be responsible for this promoted TCE degradation. Firstly, the high DH rapidly reduced the oxidation-reduction potential (ORP) value to around -500 mV, beneficial to TCE microbial dechlorination. Secondly, the high DH significantly changed the community and promoted the enrichment of TCE anaerobic dechlorinators, such as Sulfuricurvum, Sulfurospirillum, Shewanella, Geobacter, and Desulfitobacterium, and increased the abundance of dechlorination gene pceA. Thirdly, the high DH promoted preferential TCE dechlorination and subsequent sulfate reduction. However, TCE bio-remediation did not occur in a high DO environment due to the reduced aerobic function or lack of functional bacteria or co-metabolic substrate. The competitive dissolved organic carbon (DOC) consumption and unfriendly microbe-microbe interactions also interpreted the non-degradation of TCE in the high DO environment. These results provided evidence for the mechanism of EK-Bio. Providing anaerobic obligate dechlorinators, and aerobic metabolic bacteria around the electrochemical cathodes and anodes, respectively, or co-metabolic substrates to the anode can be feasible methods to promote remediation of TCE-contaminated shallow aquifer under EK-Bio technology.

Measurements of Electrodermal Activity, Tissue Oxygen Saturation, and Visual Analog Scale for Different Cuff Pressures.

The quantification of comfort in binding parts, essential human-machine interfaces (HMI) for the functioning of rehabilitation robots, is necessary to reduce physical strain on the user despite great achievements in their structure and control. This study aims to investigate the physiological impacts of binding parts by measuring electrodermal activity (EDA) and tissue oxygen saturation (StO2). In Experiment 1, EDA was measured from 13 healthy subjects under three different pressure conditions (10, 20, and 30 kPa) for 1 min using a pneumatic cuff on the right thigh. In Experiment 2, EDA and StO2 were measured from 10 healthy subjects for 5 min. To analyze the correlation between EDA parameters and the decrease in StO2, a survey using the visual analog scale (VAS) was conducted to assess the level of discomfort at each pressure. The EDA signal was decomposed into phasic and tonic components, and the EDA parameters were extracted from these two components. RM ANOVA and a post hoc paired t-test were used to determine significant differences in parameters as the pressure increased. The results showed that EDA parameters and the decrease in StO2 significantly increased with the pressure increase. Among the extracted parameters, the decrease in StO2 and the mean SCL proved to be effective indicators. Such analysis outcomes would be highly beneficial for studies focusing on the comfort assessment of the binding parts of rehabilitation robots.

Understanding the Tail Current Behavior of Electroactive Biofilms Realizes the Rapid Measurement of Biochemical Oxygen Demand.

The use of microbial electrochemical sensors, with electroactive biofilms (EABs) as sensing elements, is a promising strategy to timely measure the biochemical oxygen demand (BOD) of wastewater. However, accumulation of Coulombic yield over a complete degradation cycle is time-consuming. Therefore, understanding the correlation between current output and EAB metabolism is urgently needed. Here, we recognized a tail stage (TS) on a current-time curve according to current increase rate─a period with the least electron harvesting efficiency. EAB adopted a series of metabolic compensation strategies, including slow metabolism of residual BOD, suspended growth, reduced cell activity, and consumption of carbon storage polymers, to cope with substrate deficiency in TS. The supplementary electrons provided by the decomposition of glycogen and fatty acid polymers increased the Coulombic efficiencies of TS to >100%. The tail current produced by spontaneous metabolic compensation showed a trend of convergent exponential decay, independent of BOD concentration. Therefore, we proposed the TS prediction model (TSPM) to predict Coulombic yield, which shortened BOD measurement time by 96% (to ∼0.5 h) with deviation <4 mg/L when using real domestic wastewater. Our findings on current output in TS give insights into bacterial substrate storage and consumption, as well as regulation in substrate-deficient environment, and provide a basis for developing BOD sensors.

Estuarine hydrodynamic processes driving the molecular changes of terrestrial dissolved organic nitrogen: From mixing to biological modification.

Estuaries receive substantial amounts of terrestrial dissolved organic nitrogen (tDON), which will be transported from the freshwater to the oceanic terminus through vigorous exchange processes. However, the intricate migration and transformation dynamics of tDON during this transportation, particularly at a molecular level, remain constrained. To address this knowledge gap, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was used for the analysis of DON molecular composition in the Pearl River Estuary (PRE), a river-dominated estuarine system influenced by intensified anthropogenic activities in southern China. The results showed a pronounced spatial-temporal variation in DON concentration in the study area. At the molecular level, tDON exhibited reduced unsaturation and aromaticity, coupled with an elevated abundance of DON compounds containing one­nitrogen atom (1 N-DON, 53.17 %) and compounds containing carbon, hydrogen, oxygen, nitrogen, and sulfur (CHONS) (27.46 %). It was evident that lignin was depleted while more oxygenated tannin compounds were generated in the freshwater-seawater mixing zone. This transformation is attributed to heightened biological activities, likely influenced by the priming effect of terrestrial nutrient inputs. In summer, the prevailing plume combined with biological activities in the strong mixing area and outer estuary increased the abundance of 3 N-DON molecules and a concurrent rise in the abundance of DON compounds containing only carbon, hydrogen, oxygen, and nitrogen (CHON), DON compounds containing carbon, hydrogen, oxygen, nitrogen, sulfur, and phosphorus (CHONSP), and CHONS. This trend also underscores the expanding role of marine plankton and microbes in the utilization of DON compounds containing carbon, hydrogen, oxygen, nitrogen, and phosphorus (CHONP). These findings provide details of tDON transformation processes at the molecular level in a river-dominated estuary and underline the estuarine hydrodynamics involved in transporting and altering DON within the estuary.

Study on the oxidized gas production characteristics and spontaneous combustion tendency of pre-oxidized water-soaked coal in lean-oxygen environments.

The oxidation characteristics and spontaneous combustion (SC) tendency of raw long-flame coal (RC), water-soaked 200-day coal (S200), pre-oxidized water-soaked coal at 200 °C (O200S200), and pre-oxidized soaked coal at 300 °C (O300S200) in an oxygen-poor environment were investigated using a programmed warming system. The results show that pre-oxidation water-soaked treatment (PWT) promotes the coal-oxygen complex reaction and increases the rate of coal oxygen consumption (OCR) and the rate of carbon and oxygen compound production. The rate of CO and CO2 production of the water-soaked (WS) coal increased by 0.329 mol·(cm3·s)-1 and 0.922 mol·(cm3·s)-1, respectively, compared with that of the original coal sample. PWT reduces the activation energy of coal in the low-temperature oxidation stage (the maximum difference can be up to 110.99 kJ/mol) and enhances the oxidizing and heat-releasing capacity. There was a synergistic effect between the pre-oxidation (PO) and WS treatment, and the lowest comprehensive determination index of the SC propensity of coal in O200S200 samples was 831.92 which was 4.72 lower than that of RC samples, presenting a more SC tendency. Low oxygen concentration has an inhibitory effect on the oxidation characteristic parameters of coal, and the apparent activation energy of the low-temperature oxidation stage of pre-oxidized water-soaked coal (PWC) increased to 206.418 kJ/mol at 3% oxygen concentration. The lower the oxygen concentration of the anoxic environment, the lower the risk of SC of the coal samples. The results of the study can provide theoretical guidance for the identification and prevention of SC disasters in coal seams with shallow burial and close spacing.

Characteristics of microbial community structure and influencing factors of Yangcheng Lake and rivers entering Yangcheng Lake during the wet season.

Yangcheng Lake, a typical fishery lake in the middle and lower reaches of the Yangtze River, is threatened by eutrophication. As the main performers of biogeochemical cycles, microorganisms affect the ecological stability of the lake. To study the structural characteristics of the microbial community in Yangcheng Lake and rivers entering Yangcheng Lake and the response relationship with environmental factors, the microbial community was categorized based on the contour of Yangcheng Lake, the major rivers entering Yangcheng Lake, and the pollution sources. The distribution characteristics of seven physicochemical indices were analyzed, including total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP), water temperature (WT), pH, dissolved oxygen (DO), and ratio of total nitrogen to total phosphorus (TN/TP). Characterization of microbial community structure based on 16S rRNA high-flux sequencing technology and ANOSIM analysis were used to explore the differences in the relative abundance of microorganisms at each sampling point in the lake and rivers, and redundancy analysis (RDA) was used to analyze the relationship between the microbial community and physicochemical factors. The results showed that the dominant phyla, genera of microorganisms, and the total number of OTUs in the lake and rivers were similar. The dominant phyla included Proteobacteria, Actinobacteria, Bacteroidetes, Cyanobacteria, and Verrucomicrobia; the dominant genera included the hgcI clade, CL500-29 marine group, Microcystis PCC-7914, Chloroplast_norank, Clade III_norank, and Flavobacterium. ANOSIM analyses revealed that the microbial community of Yangcheng Lake exhibited an association with geographical space, while the microbial community in the rivers that was linked to the type of pollution source. Redundancy analysis (RDA) indicated that dissolved oxygen (DO), total nitrogen (TN), and pH were significantly correlated with the dominant phyla in Yangcheng Lake (p < 0.05), while total nitrogen (TN), water temperature(WT), and the ratio of total nitrogen to total phosphorus (TN/TP) were significantly related with the dominant genera in Yangcheng Lake (p < 0.05). Total nitrogen (TN) was also significantly linked to the dominant phyla and genera of the tributaries (p < 0.05). Despite the structural similarities in microbial communities between Yangcheng Lake and its inflowing rivers, environmental factors demonstrated significant associations with these communities, providing crucial data support for pollution prevention and the ecological restoration of Yangcheng Lake.

Microbial diversity and abundance vary along salinity, oxygen, and particle size gradients in the Chesapeake Bay.

Marine snow and other particles are abundant in estuaries, where they drive biogeochemical transformations and elemental transport. Particles range in size, thereby providing a corresponding gradient of habitats for marine microorganisms. We used standard normalized amplicon sequencing, verified with microscopy, to characterize taxon-specific microbial abundances, (cells per litre of water and per milligrams of particles), across six particle size classes, ranging from 0.2 to 500 µm, along the main stem of the Chesapeake Bay estuary. Microbial communities varied in salinity, oxygen concentrations, and particle size. Many taxonomic groups were most densely packed on large particles (in cells/mg particles), yet were primarily associated with the smallest particle size class, because small particles made up a substantially larger portion of total particle mass. However, organisms potentially involved in methanotrophy, nitrite oxidation, and sulphate reduction were found primarily on intermediately sized (5-180 µm) particles, where species richness was also highest. All abundant ostensibly free-living organisms, including SAR11 and Synecococcus, appeared on particles, albeit at lower abundance than in the free-living fraction, suggesting that aggregation processes may incorporate them into particles. Our approach opens the door to a more quantitative understanding of the microscale and macroscale biogeography of marine microorganisms.

Combustion conditions influence toxicity of flame-generated soot to ocular (ARPE-19) cells.

Soot is a prevalent aerosol found both indoors and outdoors that has several sources, such as natural (e.g., wildfires), civilian (e.g., cooking), or military (e.g., burn pit operation). Additionally, within the sources, factors that influence the physicochemical properties of the soot include combustion temperature, oxygen availability, and fuel type. Being able to reproduce soot in the laboratory and systematically assess its toxicity is important in the pursuit of elucidating pathologies associated with its exposure. Of the organs of interest, we targeted the eye given the scant attention received. Yet, air pollution constituents such as soot have been linked to diseases such as age-related macular degeneration and proliferative vitreoretinopathy. We developed a bench-scale system to synthesize different types of soot, that is, soot with a systematically varied physical attributes or chemical composition. We used common analytical techniques to probe such properties, and used statistical analyses to correlate them with toxicity in vitro using ARPE-19 cells. Within the range of flame conditions studied, we find that soot toxicity increases with increasing oxygen concentration in fuel-rich premixed flames, and weakly increases with decreasing flame temperature. Additionally, soot particles produced in premixed flames are generally smaller in size, exhibit a lesser fractal structure, and are considerably more toxic to ARPE-19 cells than soot particles produced in non-premixed flames.

Spatiotemporal variation of dissolved oxygen concentration in the northern Gulf of Mexico during the period of 1992-2017.

Dissolved oxygen (DO) concentration is an important index of ocean systems. In this study, spatiotemporal variations in DO were analyzed in the northern Gulf of Mexico (NGM) for the period of 1992-2017. Temporal variation involves annual, monthly, and seasonal variations. The spatial scope ranged from the sea surface to 1000 m depth. The results show that: (1) DO decreased from 1992 to 2017 with a brief increase; (2) clear seasonal variation characteristics of DO were presented, and the seasonal average DO was relatively low in summer; (3) the monthly average trends of sea surface DO in different years were relatively consistent; and (4) with increasing water depth from seawater surface to 1000 m, the average DO of 1992 to 2017 tended to decrease and then increase. The results aim at shedding some light on the assessment of DO change in the NGM over the past quarter century.