O2 Concentration Research Articles

Collaborative disposal of exhaust gas and waste wind turbine blades: Mechanical properties of recycled glass fibres and economic analysis

The accumulation of waste wind turbine blades poses significant environmental challenges. Pyrolysis offers an industrially viable solution for both disposal and the recycling of valuable glass fibers from these blades. Exhaust gas from industrials with waste heat can be utilized to reduce the process cost. However, for mixed atmosphere of exhaust gas containing both CO2 and O2, its influence on resin matrix decomposition characteristics and fiber mechanical properties are currently unclear. This work provided a solution collaborated with exhaust gas to disposal of waste wind turbine blades, in which operating parameters (atmosphere composition and process procedure) were optimized. Results showed that the early invention at pyrolysis with low concentration of O2 in exhaust gas played a major role in facilitating the formation of surface protection. Atmosphere during oxidation of pyrolytic residual carbon was crucial in maintaining fiber strength. At this stage, the interaction between CO2 (especially at 15% concentration) and O2 could mitigating fiber degradation through promoting the re-oxidization of Si dangling bonds and reducing water corrosion. However, stepwise processing of pyrolysis first and then oxidation under exhaust gas with O2 containing was not recommended due to its little cost-effectiveness. The single step disposal of wind turbine blades collaborated with coal-fired flue gas could increase the strength of recycled glass fiber by over 50% and reduced process costs by 34%.

Corrosion studies of Inconel 617 in high temperature air and He-ppmO2 atmospheres

Air ingress accident is one of the typical accident conditions in Very High Temperature Reactors (VHTRs). This work investigates the oxidation kinetics, corrosion behavior and mechanism of Inconel 617 alloy in different oxygen concentration atmospheres under air ingress accident. The impact of O2 concentration and oxidation time of the alloy corrosion is investigated. A gas chromatograph was used to measure the impurity content in real time during the helium experiments. After the experiments, the alloys were characterized by electronic balance, were analyzed by Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS), X-ray diffraction (XRD) and carbon and sulfur analyzer. The results show that: the Inconel 617 alloy undergoes similar oxidation behavior and the degree of oxidation is very close in three groups of atmospheres with large differences in oxygen content; the alloy should show two oxidation mechanisms, linear oxidation and parabolic oxidation, during the oxidation process; the parabolic rate constant kp and kt of the alloy is a constant value and does not vary with large changes in oxygen concentration, but when the experimental temperature changes, the oxidation rate constants of the alloy change, and the lowering of the temperature leads to the lowering of the oxidation rate constants; When experimental temperature is at 950 °C, the alloy continues to undergo a “microclimatic reaction” in the atmosphere of He-ppmO2, and the microclimatic reaction disappears when the experimental temperature is lowered to 750 °C; In He-ppmO2 environment, gas chromatograph can be used instead of thermogravimetric analyzer for real-time monitoring.

Development of a Pb(Zr,Ti)O3 capacitor employing an IrO x /Ir bottom electrode for highly reliable ferroelectric random access memories

A highly {111}-oriented metal-organic CVD Pb(Zr,Ti)O3 (PZT) is successfully developed using IrOx/Ir instead of Ir as the bottom electrode. The {111} PZT orientation strongly depends on the IrOx thickness and the O2 content of the atmosphere (PO2) during IrO x deposition. During PZT deposition, the Ir surface easily oxidizes and becomes rough, resulting in poor {111} PZT orientation. IrO x prevents Ir surface oxidation and transforms the Ir metal via O2 reduction after the PZT deposition completion. Highly {111}-oriented PZT can be obtained by optimizing the IrO x thickness and PO2 content.

Numerical Simulation Study of Combustion under Different Excess Air Factors in a Flow Pulverized Coal Burner

The basic national condition that is dominated by coal will not alter in the foreseeable future. Coal-fired boiler is the main equipment for coal utilization, and cyclone burner is a practical type of burner. There is a cyclone formation, a primary air duct inside the center air duct, and a secondary air duct. Introducing a small stream of pulverized coal gas or oil mist stream or gas directly into the reflux zone in the center duct ignites first a stable combustion and a small fluctuation of ignition pressure. In this paper, the variation of furnace temperature for cyclone pulverized coal burner corresponding to different excess air factors and the composition of gases such as O2, CO, CO2, and NOX produced by combustion were investigated using fluent software. A single cyclone pulverized coal burner from an actual coal-fired boiler is used, and a combustion zone applicable to the study of a single pulverized coal burner is established to study the actual operation of a single pulverized coal burner at different excess air coefficients. The findings indicate that the ignition position of pulverized coal combustion advances with decreasing α (Excess Air Factors); however, the length of the produced high-temperature flame gets shorter. As the value of α decreases, the burnout in the furnace decreases and the CO emission concentration increases, with a maximum CO mole fraction of 0.38% at α = 1.2 and a maximum CO mole fraction of 3.13% at the axial position when α decreases to 0.8. The furnace’s concentration of NOX, the NOX emission level decreases significantly with decreasing α. The NOX mole mass increases gradually with increasing α, and in the bottom portion of the primary combustion zone, more NOX is produced. The concentration of NOX in the chamber changes significantly after α exceeds 1.0, and the NOX at the outlet surges from 417.25 ppm to 801.07 ppm, which is attributed to the increase in the average temperature of the chamber, which promotes the generation of thermophilic NOX. The distribution pattern of O2 mole fraction along the furnace height cross-section at different excess air factors is basically the same, with a maximum at the burner inlet and a gradual decrease in the O2 content as it enters the combustion chamber to react with the pulverized coal in a combustion reaction. The value of α = 0.8 when the air supply is obviously insufficient, the fuel cannot be fully combusted, and only a small amount of CO2 is produced.

Comparative Physiological and Gene Expression Analyses Reveal Mechanisms Involved in Maintaining Photosynthesis Capacity, Alleviating Ion Toxicity and Oxidative Stress of Kentucky Bluegrass under NaCl Treatment.

Kentucky bluegrass (Poa pratensis L.), a widely used cool-season turfgrass, shows a high sensitivity to soil salinity. Clarifying the adaptative mechanisms of Kentucky bluegrass that serve to improve its salt tolerance in saline environments is urgent for the application of this turfgrass in salt-affected regions. In this study, physiological responses of the Kentucky bluegrass cultivars "Explorer" and "Blue Best" to NaCl treatment, as well as gene expressions related to photosynthesis, ion transport, and ROS degradation, were analyzed. The results showed that the growth of "Explorer" was obviously better compared to "Blue Best" under 400 mM NaCl treatment. "Explorer" exhibited a much stronger photosynthetic capacity than "Blue Best" under NaCl treatment, and the expression of key genes involved in chlorophyll biosynthesis, photosystem II, and the Calvin cycle in "Explorer" was greatly induced by salt treatment. Compared with "Blue Best", "Explorer" could effectively maintain Na+/K+ homeostasis in its leaves under NaCl treatment, which can be attributed to upregulated expression of genes, such as HKT1;5, HAK5, and SKOR. The relative membrane permeability and contents of O2- and H2O2 in "Explorer" were significantly lower than those in "Blue Best" under NaCl treatment, and, correspondingly, the activities of SOD and POD in the former were significantly higher than in the latter. Moreover, the expression of genes involved in the biosynthesis of enzymes in the ROS-scavenging system of "Explorer" was immediately upregulated after NaCl treatment. Additionally, free proline and betaine are important organic osmolytes for maintaining hydration status in Kentucky bluegrass under NaCl treatment, as the contents of these metabolites in "Explorer" were significantly higher than in "Blue Best". This work lays a theoretical basis for the improvement of salt tolerance in Kentucky bluegrass.

A bio‐based reactive P/N synergistic flame retardant for improving the fire safety and mechanical properties of epoxy resin

AbstractA high‐efficiency bio‐based P/N synergistic flame retardant (PVFD) is synthesized by combining furfurylamine and vanillin. The compound incorporates two different valence states of phosphorus as flame retardant structures, namely phenylphosphoryl dichloride (PPDC) and 9,10‐dihydro‐9‐oxa‐10‐ phosphophenyl‐10‐oxide (DOPO). PVFD and epoxy resin (EP) can cure into a cross‐linked network, thus not only improving the mechanical properties of EP but also achieving P/N synergistic flame retardant effects. Experimental results demonstrate that EP/PVFD‐5 obtained by adding 5 wt% of PVFD to EP passes the UL‐94 test and achieves V‐0 grade, whose limiting oxygen index (LOI) is up to 38.0%. EP/PVFD‐5 exhibits a decrease of 10.14% in peak heat release rate (PHRR), 16.90% in total heat release (THR), and 10.0% in total smoke release (TSP), while the residual carbon content increases by 8.5%. Additionally, the bending strength, bending modulus, tensile strength, and elongation at break of EP/PVFD‐5 increase by 3.9%, 4.9%, 45.1%, and 26.3%, respectively.Highlights The bio‐based raw materials we used are eco‐friendly and readily available. PVFD, an efficient P‐N synergistic compound, was synthesized. PVFD promotes the char formation of EP and dilutes the O2 concentration. PVFD does not cause the degradation of mechanical properties of EP.

Iridium(III)-Incorporating Self-Healing Polysiloxanes as Materials for Light-Emitting Oxygen Sensors.

Polymer-metal complexes (PMCs) based on poly(2,2'-bipyridine-4,4'-dicarboxamide-co-polydimethylsiloxanes) with cyclometalated di(2-phenylpyridinato-C2,N')iridium(III) fragments and cross-linked by Zn2+ (Zn[Ir]-BipyPDMSs) or Ir3+ (Ir[Ir]-BipyPDMSs) represent flexible, stretchable, phosphorescent, and self-healing molecular oxygen sensors. PMCs provide strong phosphorescence at λem = 595-605nm. Zn[Ir]-BipyPDMS with PDMS chain length of Mn = 5000 has the highest quantum yield of 9.3% and is a molecular oxygen sensor at different O2 concentrations (0-100vol%) compared to Ir[Ir]-BipyPDMSs. A Stern-Volmer constant is determined for Zn[Ir]-BipyPDMS as KSV = 0.014%-1, which is similar to the reported oxygen-sensitive iridium(III) complexes. All synthesized PMCs exhibit high elongation at break (up to 1100%) and self-healing efficiency (up to 99%).

In-situ inhibition mechanism of SO3 formation over MoS2 modified V2O5/TiO2 catalyst within selective catalytic reduction process

The utilization of commercial vanadium-titanium based catalysts (V2O5/TiO2) within the selective catalytic reduction (SCR) process is a prominent contributor to the emergence of sulfur trioxide (SO3) in coal-fired boiler environments. The direct modification of vanadium-titanium based catalysts has big potential to be an efficacious strategy for in-situ inhibiting SO3 formation. This research evaluates the effectiveness of MoS2 modified V2O5/TiO2 catalyst on SO2 oxidation under diverse conditions, using controlled condensation for SO3 collection. The results showed that V2O5-MoS2/TiO2 catalysts outperformed conventional V2O5/TiO2 catalysts in inhibiting the oxidation from SO2 to SO3 between 200 and 400 °C, with optimal performance at 350 °C. No significant effect was observed on the catalytic oxidation of SO2 when the O2 concentration was lower than that of SO2, whereas the introduction of appropriate quantities of NO promoted the generation of SO3. The excessive inclusion of NH3 nearly doubled the SO3 generation rate, increasing it from 0.284 % to 0.434 %. The NO and NH3 mixture markedly reduced SO3 generation to 0.085 % at a 62 mL/min mixture concentration, just 30 % of the rate without the mixture. Following the reaction of SO2 and O2, the reacted catalyst exhibited reduced pore volume, enhanced thermochemical stability, and lower susceptibility to SO2 catalytic oxidation. The addition of low-valence sulfur improves catalyst reducibility, reduces V5+–OH reactions in various atmospheres, and decreases the formation of sulphate and gaseous SO3. The Mo-S-Mo group also effectively prevents the formation of HSO4− intermediates. Additionally, MoS2 reacts with SO3 via a reduction reaction, significantly lowering the SO3 levels. Finally, in diverse atmospheric conditions, the catalysts maintained their V5+ content and catalytic efficiency, thus improving SCR performance stability.

Pressure fermentation to boost CO2-based poly(3-hydroxybutyrate) production using Cupriavidus necator

CO2-based poly(3-hydroxybutyrate) (PHB) can be produced by the versatile bacterium Cupriavidus necator through chemolithoautotrophic fermentation, using a gas mixture consisting of CO2, H2, and O2. Despite offering a propitious route for carbon–neutral bioplastic manufacturing, its adoption is currently hampered by the wide explosive range of the required gas mixture, as well as the limited gas-to-liquid mass transfer rates. To address these challenges, pressure fermentation was applied as a robust and effective strategy, while ensuring safe operation by adhering to the limiting O2 concentration, utilizing state-of-the-art bioreactors. Consequently, exponential growth could be prolonged, boosting CO2-based PHB production from 10.8 g/L at 1.5 bar up to 29.6 g/L at 3 bar. The production gain closely aligns with the theoretical calculations, except for when the pressure was increased up to 4 bar. Overall, the demonstrated increase in PHB production underscores the potential of pressure fermentation to enhance aerobic gas fermentation.

Understanding the synergistic effect in green propellants 2-azido-N,N-dimethylethanamine and tetramethylethylenediamine: From drop test to gas-phase autoignition

2-Azido-N,N-Dimethylethanamine (DMAZ) and tetramethylethylenediamine (TMEDA) are promising green propellants for hypergolic applications, and blending DMAZ with TMEDA can achieve short ignition delay time (IDT) and comparable specific impulse to hydrazine-based fuels simultaneously. There are reports of a synergistic effect between DMAZ and TMEDA, but its mechanism is not well understood. In this work, drop tests and gas-phase autoignition experiments were combined to provide insights of this synergistic effect from different aspects. The drop tests of DMAZ/TMEDA blends with white-fuming nitric acid were conducted in a confined transparent chamber with controlled O2 concentration. Results show that the hypergolic ignition is much faster for blends with 20–40 wt% DMAZ under all O2 concentration conditions, and higher concentration of O2 in the environment significantly promotes the hypergolic ignition process. To further investigate the chemistry between DMAZ/TMEDA with O2, gas-phase IDTs were measured using a rapid compression machine and a shock tube in a wide temperature range of 500–1100 K and at pressure of 10 bar. TMEDA shows a higher reactivity at lower temperatures (<690 K), while the autoignition of DMAZ is much faster at higher temperatures (>690 K). A synergistic effect between DMAZ and TMEDA was also observed in the gas-phase autoignition, i.e., fuel blend with 30 % DMAZ showed equal or even lower IDTs than pure TMEDA at lower temperatures. The newly measured IDTs of DMAZ/TMEDA were further adopted to validate a previously developed chemical kinetic model for pure TMEDA and DMAZ, which exhibits good predictions for the blending effects nonetheless. Kinetic analyses reveal that the low-temperature reactivity contributed from the TMEDA can be enhanced by the heat release from DMAZ decomposition, causing the synergistic effect in gas-phase autoignition of DMAZ/TMEDA blends.

A Study on the Efficient Degradation of Sulfur Hexafluoride by Pulsed Dielectric Barrier Discharge Synergistic Active Gas

SF6 is a strong greenhouse effect gas, which is widely used in high-voltage electrical equipment such as circuit breakers and high-voltage switchgear because of its excellent insulation performance and arc extinguishing ability. In recent years, the use and emission of SF6 have been rising, and with the proposal of the dual carbon strategic goal, its harmless degradation has become an urgent problem to be solved. In this paper, SF6 was degraded by pulsed DBD plasma technology and O2. Studies have shown that the addition of O2 can effectively promote the degradation of SF6. With the increase in the added O2 content, the DRE and EY of SF6 first increased and then decreased. Under the conditions of the input power of 50 W, SF6 concentration of 2%, and gas flow rate of 50 mL/min, the reaction system obtained the highest DRE and EY of 58.40% and 5.24 g/kWh when the O2 content was 1%, respectively. In the SF6/Ar/O2/H2O system, the addition of H2O could improve the product selectivity of SO2F2, and when the O2 concentration was 1%, the highest selectivity of SO2F2 was 48.96%, and the concentration was 8006.76 ppm. The addition of O2 inhibited the production of SO2, and with the addition of the O2 system, SO2F2 and SOF4 were the main components of degradation products; however, there were also SOF2, SO2, SiF4, SF4, etc. In this paper, the decomposition path of O2 under SF6 was analyzed in detail according to infrared spectroscopy and decomposition products.

Research on CO Migration Patterns in Shallowly Buried Coal Seam Composite Goafs.

To address the issue of CO exceedance in the close-range composite goaf, this paper focuses on the composite goaf of the Shaping Mine as the research subject and investigated the migration dynamics of CO within shallowly buried composite goaf areas. Sulfur hexafluoride gas (SF6) tracer experiments were conducted at the 13103 working face in Shaping Mine to assess surface fissures and air leakage, yielding insights into the distribution patterns of air leakage channels and facilitating the identification of critical areas for channel sealing. Programmed heating and oxidation experiments were conducted on coal seams 8# and 13# to determine the CO generation patterns during coal oxidation. The results show that higher concentrations of O2 corresponded to elevated CO production at equivalent temperatures. Subsequent data analysis unveiled exponential relationships between the O2 consumption rate and CO production rate within the goaf area, offering a theoretical framework for understanding CO migration patterns. Through numerical simulations, the study analyzed the CO migration patterns in the composite goaf area, observing downward diffusion of CO emanating from coal oxidation in the overlying goaf areas followed by dispersion toward the working face and roadways. Driven by airflow dynamics, CO accrued in the return air corner of the working face. Building upon these insights, comprehensive CO management strategies were implemented, resulting in sustained reductions of temperatures and CO concentrations to safe levels within the original high-temperature, high-concentration CO zones. Notably, CO concentrations at the return air corner of the working face continued to decline over the management period, reaching below 24 ppm within 10 to 15 days, highlighting the effectiveness of the management measures in ensuring safe underground production.

Hybrid CFD/techno-economic assessments of carbon capturing combustion system integrated with PEM electrolyzer for efficient hydrogen production

The issue of global warming is a significant challenge in the field of environmental science, resulting primarily from the burning of fossil fuels and the subsequent increase in greenhouse gas (GHG) emissions, thus emphasizing the importance of utilizing renewable energy vectors, carbon capture technology, oxy-fuel combustion, and carbon-free fuels like hydrogen to mitigate these negative effects. In this study, the possibility of utilizing low-calorific value biogas in a gas turbine (GT) combustor under various combustion conditions is numerically simulated, and techno-economic analysis of energy systems coupled with the GT combustor is conducted. Herein, two distinct energy systems utilizing different combustion modes for H2 production via PEM electrolyzer have been designed and examined. This investigation focuses on the impact of various influencing factors in oxy-fuel combustion mode, such as the equivalence ratio and the O2 content in the two types of oxidizers, on the rate of hydrogen production, power generation, energy/exergy efficiencies, and the economic index of the proposed energy system. Additionally, a suitable system for large-scale operation is identified among the presented systems. The findings of the study demonstrate that the energy system based on the O2/CO2 combustion mode exhibits a higher rate of hydrogen production compared to the O2/H2O combustion mode and particularly, within the equivalence ratio range of 0.55≤ϕ ≤ 0.85, the hydrogen production rate in the O2/CO2 combustion mode decreases from 5.16 kg/h to 3.72 kg/h.

Prochlorococcus marinus responses to light and oxygen.

Prochlorococcus marinus, the smallest picocyanobacterium, comprises multiple clades occupying distinct niches, currently across tropical and sub-tropical oligotrophic ocean regions, including Oxygen Minimum Zones. Ocean warming may open growth-permissive temperatures in new, poleward photic regimes, along with expanded Oxygen Minimum Zones. We used ocean metaproteomic data on current Prochlorococcus marinus niches, to guide testing of Prochlorococcus marinus growth across a matrix of peak irradiances, photoperiods, spectral bands and dissolved oxygen. MED4 from Clade HLI requires greater than 4 h photoperiod, grows at 25 μmol O2 L-1 and above, and exploits high cumulative diel photon doses. MED4, however, relies upon an alternative oxidase to balance electron transport, which may exclude it from growth under our lowest, 2.5 μmol O2 L-1, condition. SS120 from clade LLII/III is restricted to low light under full 250 μmol O2 L-1, shows expanded light exploitation under 25 μmol O2 L-1, but is excluded from growth under 2.5 μmol O2 L-1. Intermediate oxygen suppresses the cost of PSII photoinactivation, and possibly the enzymatic production of H2O2 in SS120, which has limitations on genomic capacity for PSII and DNA repair. MIT9313 from Clade LLIV is restricted to low blue irradiance under 250 μmol O2 L-1, but exploits much higher irradiance under red light, or under lower O2 concentrations, conditions which slow photoinactivation of PSII and production of reactive oxygen species. In warming oceans, range expansions and competition among clades will be governed not only by light levels. Short photoperiods governed by latitude, temperate winters, and depth attenuation of light, will exclude clade HLI (including MED4) from some habitats. In contrast, clade LLII/III (including SS120), and particularly clade LLIV (including MIT9313), may exploit higher light niches nearer the surface, under expanding OMZ conditions, where low O2 relieves the stresses of oxidation stress and PSII photoinhibition.

User-friendly carbon-cycle modelling and aspects of Phanerozoic climate change

Carbon-cycle modelling is essential for testing the main carbon sources and sinks as climate forcings, and we introduce and describe GEOCARB_NET, a graphical user interface for the geologic carbon and sulfur cycle model GEOCARBSULFvolc. The software system is menu-driven, user-friendly, and the user is never far removed from the basic input parameters from which atmospheric CO2 and O2 concentrations can be derived. GEOCARB_NET is supplied with several published models and the user can easily test and refine these models with different parametrizations. GEOCARB_NET also contains libraries of models and proxy data, which easily can be compared with each other. Our examples focus on how to use GEOCARB_NET in the context of Phanerozoic climate change and highlights how certain key input parameters can seriously affect reconstructed CO2 levels.

Effects of mulching and flooding on soil nutrients and bacterial community structure under Phyllostachys praecox

Phyllostachys praecox is a shallow-rooted bamboo that often encounters hypoxia conditions which could be induced by long-term organic material mulching or flooding. It is important to uncover the effect of mulching and flooding on soil nutrient, ammonia-oxidizing microbes, and bacterial diversity. We set up field pot experiments with three treatments (control, mulching, and flooding) under P. praecox. Mulching or flooding altered soil conditions significantly, and both increased ammonium-nitrogen (NH4+-N), total phosphorus (TP), available P (AP), and available potassium (AK) concentrations, and decreased oxygen (O2) concentrations over control. Flooding increased pH and decreased nitrate-nitrogen (NO3−-N), while mulching decreased soil pH and NO3−-N. As O2 content decreased, archaeal 16S rRNA, amoA gene copies of ammonia-oxidizing archaea (AOA) and ammonia oxidizing bacteria (AOB) increased. Mulching and flooding decreased Shannon, ACE and Chao 1 diversity when compared with the control, and as the O2 contents decreased, bacterial diversity decreased. Redundancy Analysis revealed O2, NO3−-N, AK, AP, and pH were the major factors driving bacterial community structure. Correlation Analysis showed AK and O2 contents were highly correlated with bacterial community structure. In addition, structural equation modeling indicated that O2 facilitated efficient soil N use mainly through soil pH, AK content, and bacterial diversity. Mulching or flooding exerted great effects on environment factor and bacterial community structure, which could be exploited to facilitate the regulation of soil O2 conditions for sustainable P. praecox production.

Unraveling the Influence of Nafion Content on the Performance of Proton-Exchange Membrane Fuel Cells from the Perspective of Triple-Phase Boundary.

By combining molecular simulations and experimental measurements, the effect of the Nafion content on the performance of proton-exchange membrane fuel cells (PEMFCs) is explained from the perspective of the triple-phase boundary (TPB). The evaporation process of Nafion solvent is simulated on a triple-phase model to mimic the formation of the TPB, and the influence of the Nafion content on the TPB structure is investigated. When the Nafion content is 1.415 mg/m2, the coverages of Nafion on both Pt particles and the carbon carrier are saturated at 42.1% and 32.7%, respectively. With the increase of Nafion content, the amount of water molecules around Pt particles is increased, and the surrounding O2 content is decreased. The experimental PEMFC performance has confirmed such simulation results, which demonstrates a trend of enhancing first and then weakening with the increase of Nafion content and reaches a maximum with the Nafion content of 2.96 mg/m2. Therefore, the correlation between the structure of the TPB and the cell's efficiency has been established at a molecular level, enabling enhancements in the design of the TPB morphology and an increase in PEMFC efficiency.

Variability of the surface boundary layer of reef-building coral species

The coral-seawater interface is an important, highly dynamic microenvironment for reef-building corals. Also known as the concentration boundary layer (CBL), it is a thin layer of seawater bordering the coral surface that dictates the biochemical exchange between the coral colony and bulk seawater. The CBL is thus a key feature that modulates coral metabolism. However, CBL variation among small-polyped coral species remains largely unknown. Therefore, we recorded over 100 profiles of dissolved O2 concentration using microsensors to characterize CBL traits (thickness, surface O2 concentration, and flux) of three small-polyped branching coral species, Acropora cytherea, Pocillopora verrucosa, and Porites cylindrica. Measurements were conducted during light and darkness combined with low or moderate water flow (2 and 6 cm s−1). We found that CBL traits differed among species. CBL thickness was lowest in A. cytherea, while P. verrucosa showed the largest depletion of surface O2 in dark and highest dark flux. In addition, we found that O2 concentration gradients in the CBL occurred with three main profile shapes: diffusive, S-shaped, and complex. While diffusive profiles were the most common profile type, S-shaped and complex profiles were more frequent in P. verrucosa and P. cylindrica, respectively, and prevailed under low flow. Furthermore, profile types differed in CBL thickness and flux. Finally, low flow thickened CBLs, enhanced changes in surface O2 concentration, and reduced flux, compared to moderate flow. Overall, our findings reveal CBL variability among small-polyped branching corals and help understand CBL dynamics in response to changes in light and water flow conditions.

Morphological and Anatomical Differentiation of Potamogeton gramineus in Relation to the Presence of Invasive Species Elodea nuttallii: A Case Study from Vlasina Lake, Serbia.

Elodea nuttallii represents non-native and highly invasive species in Europe that significantly influence freshwater plant communities by decreasing the diversity of native species. This study aimed to determine whether the morphological and anatomical features of Potamogeton gramineus, a native species in Vlasina Lake, differ between sites where it coexists with E. nuttallii and those where E. nuttallii is not present. Environmental variables such as water depth, temperature, pH, conductivity, saturation, and O2 concentration were included in the analysis. Analyses were conducted on 32 morphological and anatomical features of P. gramineus collected from six sites within Vlasina Lake, comprising three sites where E. nuttallii was present and three sites where it was absent. The datasets containing morphometric and environmental variables underwent analysis using standard univariate techniques (Descriptive, ANOVA), Tukey's Honest Significant Difference (HSD) test, Student's t-test, and the Mann-Whitney U test, as well as multivariate statistical methods such as Canonical Discriminant Analysis (CDA). The results show the presence of morphological differentiation among P. gramineus individuals across the analyzed sites. These findings suggest that morphological and anatomical features, such as epidermis, mesophyll, palisade, and aerenchyma tissue thickness in floating leaves, number, length, width, and the surface area of stomata, as well as the width of submersed leaves and stem aerenchyma tissue thickness, effectively differentiate individuals that coexist with E. nuttallii and individuals that growth without its presence. Moreover, they indicate that P. gramineus exhibits a notable ability to modify its morphological traits in response to invasion.

Numerical investigation of soot formation in methane/n-heptane laminar diffusion flame doped with hydrogen at elevated pressure

The addition of hydrogen in a dual-fuel mode based on natural gas and diesel offers great potential for improving engine efficiency and reducing emissions. Therefore, detailed numerical simulations have been used to explore the effects of soot formation characteristics of natural gas-diesel dual-fuel engines doped by hydrogen at elevated pressure. Numerical simulations are compared with available experimental data, the effects of H2 addition on soot formation in laminar CH4 + n-heptane, H2 + CH4 + n-heptane, FH2 + CH4 + n-heptane diffusion flames at 2, 4, 6 and 8 atm are simulated, FH2 is added to separate the H2 chemical effects. The results show that the dilution and thermal effects of H2 inhibit soot formation, while the chemical effects of H2 promote soot formation under different pressures. The addition of H2 increases the concentration of H and OH radicals, which promotes the formation of C2H2 and benzene (A1). By simplifying the reaction path and analyzing the production rate of A1, the mechanism of H2 addition to promote A1 formation is illustrated. The concentrations of polycyclic aromatic hydrocarbon (PAH) pyrene (A4), benzo(ghi)fluoranthene (BGHIF) and benzo(a)pyrene (BAPYR) are inhibited at higher pressures that result in lower inception and condensation rates. Therefore, the increase of hydrogen abstraction acetylene addition (HACA) rate is the main reason for the increase of soot formation under chemical effects. While the O2 oxidation rate decreases and the OH oxidation rate increases, that is due to the decrease of O2 concentration and the increase of OH concentration in the soot formation area under chemical effects.