Fire Research Articles

Insight into the purification of arsenic-contaminated acid water by metal–organic framework MIL-53(Fe) with sulfite: The generation and effect of Fe(IV)

Iron based metal–organic frameworks (Fe-MOFs) have garnered international interest as a novel and promising category of adsorbent materials for the elimination of arsenic from neutral waters. Nevertheless, their practical implementation is constrained by their inadequate adsorption capacity for aqueous arsenite (As(III)), a prevalent arsenic species found in acidic environments such as acid mine drainage. Herein, a novel oxidation-adsorption process to effectively purify As(III)-contaminated water is constructed by combining the MIL-53(Fe) of high acid resistance with sulfite (S(IV)). Notably, the adsorption capacity of the MIL-53(Fe)/S(IV) process for As(III) at pH 3.5 reached 86.4 mg g−1, surpassing the values achieved by MIL-53(Fe) alone by 21.6 times for As(III) and 1.62 times for As(V) (oxidized As(III)). During the oxidation process, MIL-53(Fe) effectively activated S(IV), leading to the formation of the crucial intermediate SO5•−, which then underwent two distinct pathways to respectively generate Fe(IV) and SO4•−, accounting for rapid oxidation of As(III). In the adsorption process, the S(IV) activation (i.e., complexation and electron transfer) on the MIL-53(Fe) surface created additional adsorption sites by dredging the pores and altering the electron cloud distribution within the adsorbent. Furthermore, As(V) trended to form monodentate complexes with surface Fe (e.g., FeOAs bond) in the MIL-53(Fe)/S(IV) process. Notably, this oxidative removal process demonstrated reliable performance in complex water matrices and practical arsenic-contaminated waters. Overall, this study presents a promising strategy to enhance the efficacy of Fe-MOFs for the removal of As(III).

Analytical methods for detecting butane, propane, and their metabolites in biological samples: Implications for inhalant abuse detection

Worldwide, various inhalants are widely abused for recreational purposes, with butane and propane emerging as among the most commonly misused volatile substances, posing a significant risk of sudden death. The rapid elimination and oxidation of these highly volatile compounds upon inhalation necessitate the identification of butane and propane along with their metabolites in biological samples. Hence, the primary objective of this study is twofold: firstly, to establish a method for analyzing butane, propane, and metabolites, and secondly, to demonstrate the detection window and exposure indicators associated with the inhalation of butane and propane. In pursuit of this objective, we developed analytical methods for the determination of isobutane, n-butane, propane, and their nine metabolites in both blood and urine. Headspace-gas chromatography–mass spectrometry (GC–MS) and solid-phase microextraction-GC–MS were employed for the analyses, demonstrating acceptable precision and accuracy. An animal study revealed that isobutane and n-butane were only detectable below the limit of quantification (LOQ) in rat blood 5 min after exposure. Meanwhile, the three major metabolites—2-methyl-2-propanol, 2-butanol, and 2-butanone—were observed 5 min after exposure but persisted in rat urine even 5 h post-exposure. Additionally, human urine samples identified other metabolites, including acetone, acetoin, and 2,3-butanediol isomers. The presence of specific metabolites corresponding to each inhalant confirmed the abuse of butane and propane. This comprehensive approach provides valuable insights into the detection and assessment of inhalation to these volatile substances.

ZIF-67 Anchored on MoS2/rGO Heterostructure for Non-Enzymatic and Visible-Light-Sensitive Photoelectrochemical Biosensing.

Graphene and graphene-like two-dimensional layered nanomaterials-based photoelectrochemical (PEC) biosensors have recently grown rapidly in popularity thanks to their advantages of high sensitivity and low background signal, which have attracted tremendous attention in ultrahigh sensitive small molecule detection. This work proposes a non-enzymatic and visible-light-sensitive PEC biosensing platform based on ZIF-67@MoS2/rGO composite which is synthesized through a facile and one-step microwave-assisted hydrothermal method. The combination of MoS2 and rGO could construct van der Waals heterostructures, which not only act as visible-light-active nanomaterials, but facilitate charge carriers transfer between the photoelectrode and glassy carbon electrode (GCE). ZIF-67 anchored on MoS2/rGO heterostructures provides large specific surface areas and a high proportion of catalytic sites, which cooperate with MoS2 nanosheets, realizing rapid and efficient enzyme-free electrocatalytic oxidation of glucose. The ZIF-67@MoS2/rGO-modified GCE can realize the rapid and sensitive detection of glucose at low detection voltage, which exhibits a high sensitivity of 12.62 μAmM-1cm-2. Finally, the ZIF-67@MoS2/rGO PEC biosensor is developed by integrating the ZIF-67@MoS2/rGO with a screen-printed electrode (SPE), which exhibits a high sensitivity of 3.479 μAmM-1cm-2 and a low detection limit of 1.39 μM. The biosensor's selectivity, stability, and repeatability are systematically investigated, and its practicability is evaluated by detecting clinical serum samples.

SEM Image-based Porosity Analysis of Fire Damaged High Strength Concrete

The porosity of concrete affects the durability of reinforced concrete structures, wherein high levels of porosity are linked to a shorter service life. Recent works have noted that high porosity levels naturally exist in the aftermath of a fire exposure – especially when concrete is classified as high strength concrete (HSC). To shed more light into this phenomenon, this paper showcases a method for measuring the porosity of HSC under elevated temperatures through scanning electron microscopy (SEM). In this method, SEM-based images were examined to quantify the surface porosity of fire-affected HSC. Detailed image analysis was performed for HSC exposed to various heating durations. The study concludes that the surface porosity obtained via the SEM processing method is in good agreement with that from the SEM-based method (with a minor average difference of 3.8%). As such, the proposed method is expected to be reliable for the porosity analysis of fire-damaged concrete.

High Performance and Efficiency Recovery in Sn‐Based Flexible Perovskite Solar Cells by Antioxidant Vanillin and Microwave Treatment

AbstractPerovskite based on Sn have attracted extensive attention to address the toxicity challenge associated with Pb‐based perovskite solar cells. However, Sn‐based perovskite solar cells（SPSCs）are notable for their poor stability and loss of efficiency due to rapid oxidation of Sn2+ to Sn4+ in air. To slow down the rapid oxidation, a number of antioxidants are suggested. Nevertheless, the antioxidant normally gets oxidized to non‐antioxidizing by‐products in a single‐stage redox reaction and loses the function of oxidation prevention. Herein, vanillin is introduced, a natural antioxidant with a double‐staged redox reaction to inhibit the oxidation of Sn2+ or reduce Sn4+ back to Sn2+, which improves the efficiency and prolongs the open‐air stability of SPSCs. With 7.5% vanillin doping, an outstanding efficiency of 13.18% is achieved. Moreover, exposure of the solar cell to 160 W microwave irradiation for 3 minutes resulted in significant efficiency recovery from 88% to 96.5% at 812 hours and from 35.7% to 65.4% after 2200 hours of aging. This work reveals the potential of natural antioxidation and short microwave irradiation as suitable approaches to elevate the efficiency and lifetime of SPSCs.

Forest fire risk mapping with Landsat 8 OLI images: Evaluation of the potential use of vegetation indices

Fire is one of the most important natural catastrophes threatening the forest ecosystem. The severity and frequency of forest fires are increasing daily due to the increase in population in vulnerable areas and the effects of global climate change. Creating fire risk maps and using them to take the required protective actions to prevent fires will decrease the adverse effects of forest fires. This study focused on producing and comparing fire risk maps based on four vegetation indices, the Normalized Burn Ratio (NBR) index, Normalized Burn Ratio Thermal (NBRT) index, Normalized Difference Vegetation Index (NDVI), and Normalized Difference Water Index (NDWI) and data gathered with the use of remote sensing devices. The Muğla Regional Directorate of Forestry, which is in the Mediterranean climate zone and has experienced mega-fires, was selected as the case study area. Fire risk maps were prepared for the four vegetation indices from Landsat 8 OLI satellite images. Receiver operating characteristic curves and 195 fire ignition points that occurred in 2021 from July 5 to the end of the year were used to assess the accuracy of fire risk maps. Most fire ignition locations (>90%) were in high- and extremely high-risk fire areas on the maps prepared according to the NBR, NDWI, and NDVI. The fact that almost all of the fires occurred in high-risk areas revealed that the study area was sensitive to fire and that the vegetation indices used to draw up the risk maps were highly accurate in predicting where fires might occur. The accuracy results showed that the area under the curve was 0.842 for the NBR, 0.835 for the NDWI, 0.812 for the NBRT, and 0.810 for the NDVI. The NBR approach was more precise than the other models in providing information for fire risk maps. Risk maps created with the NBR could help decision-makers to take precautions and minimize fire damage.

Mesopore engineering of Co3O4 nanoplates for enhanced detection of toluene vapor

It remains a significant challenge for efficient detection of toluene vapor because of the low chemical reactivity. In this paper, the Co3O4 nanoplates with various mesopore widths (5.1, 12.6, and 19.8 nm) onto their surfaces have been successfully achieved using a simple hydrothermal and followed annealing route. Moreover, the sensor based on this Co3O4 nanoplate with mesopore width of 5.1 nm presents an obvious toluene-sensing response (including actual detection limit of 1 ppm, and excellent selectivity) at a low working temperature (140 °C). The improved toluene-sensing can be tracked from suitable mesopore size and specific catalytic activity of the Co3O4 nanoplates, which are advantageous for gas adsorption and diffusion, as well as facilitating the rapid oxidation of toluene gas. This work announces a reliable strategy to detect low reactive gas by constructing rational mesopores-width over the catalytic oxide.

Biological oxidation of As(III) and Sb(III) by a novel bacterium with Sb(III) oxidase rather than As(III) oxidase under anaerobic and aerobic conditions

Sb and As are chemically similar, but the sequences and structures of Sb(III) and As(III) oxidase are totally distinct. It is thus interesting to explore whether Sb(III) oxidase oxidizes As(III), and if so, how microbial oxidations of Sb(III) and As(III) influence one another. Previous investigations have yielded ambiguous or even erroneous conclusions. This study aimed to clarify this issue. Firstly, we prepared a consortium of Sb(III)-oxidizing prokaryotes (SOPs) by enrichment cultivation. Metagenomic analysis reveals that SOPs with the Sb(III) oxidase gene, but lacking the As(III) oxidase gene are predominant in the SOP community. Despite this, SOPs exhibit comparable Sb(III) and As(III)-oxidizing activities in both aerobic and anaerobic conditions, indicating that at the microbial community level, Sb(III) oxidase can oxidize As(III). Secondly, we isolated a representative cultivable SOP, Ralstonia sp. SbOX with Sb(III) oxidase gene but without As(III) oxidase gene. Genomic analysis of SbOX reveals that this SOP strain has a complete Sb(III) oxidase (AnoA) gene, but lacks As(III) oxidase (AioAB or ArxAB) gene. It is interesting to discover that, besides its Sb(III) oxidation activities, SbOX also exhibits significant capabilities in oxidizing As(III) under both aerobic and anaerobic conditions. Moreover, under aerobic conditions and in the presence of both Sb(III) and As(III), SbOX exhibited a preference for oxidizing Sb(III). Only after the near complete oxidation of Sb(III) did SbOX initiate rapid oxidation of As(III). In contrast, under anaerobic conditions and in the presence of both Sb(III) and As(III), Sb(III) oxidation notably inhibited the As(III) oxidation pathway in SbOX, while As(III) exhibited minimal effects on the Sb(III) oxidation. These findings suggest that SOPs can oxidize As(III) under both aerobic and anaerobic conditions, exhibiting a strong preference for Sb(III) over As(III) oxidation in the presence of both. This study unveils a novel mechanism of interaction within the Sb and As biogeochemical cycles.

Indium-free flexible NiO/Ag NW composite transparent conductive thin films for transparent heater

The rapid oxidation and decomposition of the Ag nanowires (Ag NWs) in ambient conditions can lead to irreversible structural damage, largely overshadows their practical application in transparent conducting films. In this paper, we develop the highly transparent and low resistance composite thin films with a bilayer structure composed of NiO and Ag NWs. The transmittance and sheet resistance can be adjusted via controlling the density of nanowires. The NiO/Ag NW composites show a high figure of merit of 224 with the sheet resistance of 7.2 Ω/sq. and the average optical transmittance is about 80.3 % in the visible range. The mechanisms of improved transmittance and conductivity of NiO/Ag NW composites are proposed. Moreover, the resistance has no significant change after taping test, suggesting a strong adhesion of NiO/Ag NWs to the PET substrate. Furthermore, flexible NiO/Ag NW TCFs display an excellent stability to resist high temperature, high humidity and strong oxidation environment. Finally, transparent heater employing the flexible NiO/Ag NW TCFs as the electrode is obtained, showing a satisfactory heating behavior.

Влияние скорости воздушного потока на тепловое излучение от углеводородного пожара в резервуаре для хранения нефти

Purpose. The article assesses the effect of air flow velocity on the intensity of thermal radiation from a fire in a vertical steel tank with a floating roof of 65 000 m3 capacity (VSTWFR-65000) with crude oil. The indicators of hazardous fire factors - open flame, smoke and temperature at different wind speeds – have been studied. Methods. The method of numerical modeling in the Fire Dynamics Simulator software package, as well as the method of processing the obtained research results have been used in the study. Findings. The dependence of the flame inclination angle at different air flow speeds has been obtained. The simulation results have been shown: smoke distribution at different wind speeds, as well as temperature change at a distance from the fire source depending on the air flow velocity. Research application field. The results of the study can be used in the development of design documentation for measures to ensure fire safety of a tank farm with floating roof tanks, as well as in adjusting fire extinguishing plans. Conclusions. Based on the simulation results it has been found that with an increase in the air flow velocity the intensity of thermal radiation initially increases and then decreases. It has been found that at an air flow velocity of 9 m/s the maximum thermal radiation reaches 23.43 kW/m2 at the nearest point of the adjacent tank in the projection from the central axis of the burning tank. At an air flow velocity of 6.5 m/s the temperature at the top of the adjacent tank reaches 176 °C, and at 9 m/s – 426 °C, which is higher than the autoignition temperature of oil, which is within 222–256 °C, there by creating a threat of fire spread. The study has defined the maximum distances from the burning VSTWFR-65000 for the safe presence of people, amounting to 47.3; 48.9; 50.2; 53.4; 55.7; 56.8; 59.4 m for wind speed of classes 0, 1, 2, 3, 4, 5 and 6 respectively.

Analysis of Experience of Using Small UAVs in the Battlefield: Training Enhancement Perspectives

The article analyzes the experience of the State Border Guard Service units in fighting russian occupying forces inflicting the fire damage with the help of small UAVs and describes the ways to use the acquired experience to develop a training course for the border guard UAV operators. The authors state that nowadays, in the conditions of the of full-scale invasion to Ukraine, active using of unmanned aerial vehicles (hereinafter – UAVs) proved their ability to perform combat tasks, making them one of the new and effective types of weapons in modern military conflicts. It is impossible to imagine a contemporary army without UAVs, as today they perform multiple roles: adjusting artillery fire, pointing and tracking targets, transmitting intelligence information to the headquarters, delivering fire strikes, and most importantly – they can help save the lives of soldiers. Analysis of a year and a half term of full-scale invasion of Ukraine showed that the use of UAVs is several times more effective than the use of traditional types of weapons. In the first days of the war, a huge number of the russian battalion tactical groups (hereinafter – BTGs) were concentrated on the borders of Ukraine, and that significantly outweighed the forces and means of military formations of Ukraine. Analysis also proves that the main striking force during the offensive, according to the governing documents, were armored fighting vehicles, infantry fighting vehicles, amphibious assault vehicles, armored personnel carriers. And it was possible to stop enemy columns only with the help of artillery, aviation, and anti-tank missile systems. Therefore, in modern conditions, it is necessary to create fire damage to enemy armored vehicle groups with the help of attack UAVs of the border guard units. The article considers the effectiveness of such a unit, taking into account the tasks, organizational structure, forces and means necessary to respond to modern challenges and threats on the state border. The authors used the acquired experience of the Border Guard units to develop a training course for the UAV operators of the border guard units. The developers of the course took into account the combat experience and the best European practices in UAV operators training. The learning strategy of the course is based on a student-centred learning approach. It is designed to provide learners with theoretical knowledge and practical skills on the operators of the UAV crews deployed in border surveillance and combat operations. The course is divided in three phases: Independent Learning Phase (online), Contact Learning Phase (offline) and Experiential Learning Phase (at the border guard units).

Определение пожарной опасности большегрузных карьерных транспортных средств

Purpose. Heavy wheel-load mining trucks present a fire hazard. A key distinction from other vehicles, aside from their large size, is the presence of significant volumes (over 3 000 liters) of flammable lubricants and other operating fluids, as well as inaccessible areas in the event of a fire. Based on statistical data on fire locations and combustible materials, this article identifies the main sources of fire hazards in heavy wheel-load mining trucks, using a haul truck as an example. Methods. The study employed the following theoretical methods: analysis, modeling, and deduction. Findings. The analysis of statistical data on fire locations and combustible materials in heavy wheel-load mining trucks revealed that such equipment generates a significant amount of thermal energy and contains large amounts of flammable materials. The study identified the main fire-prone mechanisms and components, which are crucial for further evaluating the effectiveness of automatic fire suppression systems used in this type of trucks. Research application field. The results of this study provide basis for approaches to ensuring fire safety of heavy wheel-load mining trucks. Conclusions. The study identified potential sources of ignition in heavy wheel-load mining trucks. Further research on comprehensive protection measures for heavy wheel-load mining trucks will lead to new integrated design solutions to protect mining equipment from fire, prevent direct and indirect material damage, and reduce the risk of injury or death.

Understanding the ignition process and flame structure of conventional and oxygenated fuels under engine relevant conditions – An optical study

Renewably generated synthetic fuels such as poly-oxymethylene ethers (OME) have a significant potential to effectively break the soot-NOX trade-off in compression ignition engines by using exhaust gas recirculation (EGR) to maintain low nitrogen oxide (NOX) emissions while maintaining good efficiency and simultaneously contributing to circular carbon economy. However, owing to the fundamental differences in properties of OME when compared to fossil-based diesel fuels, it is critical to fully understand its ignition and combustion phenomenology to take advantage of this fuel to its utmost potential. In this context, this work outlines the results of a systematic experimental study performed in a heavy-duty, single-cylinder, optical engine probing the spatial and temporal progression of fuel decomposition and ignition behavior of OME when compared to n-dodecane, a diesel-fuel surrogate. Thermodynamic analysis and optical diagnostics techniques including simultaneous HCHO-PLIF and OH-PLIF complemented by high-speed OH* chemiluminescence were employed along with parametric sweeps of intake temperature and EGR dilution rates. OME does not exhibit any observable low temperature heat release irrespective of the ambient oxygen concentration. Differences in the observed diffusive flame structure such as longer flame lift-off length, less pronounced combustion recession, faster premixed burn at ignition (“volumetric” ignition), non-sooting behavior suggest that the inherent presence of fuel-bound oxygen in OME can skew the air-fuel ratio (AFR) distribution within the jet thereby reducing the reliance of combustion on mixing and air entrainment. This leads to rapid late-cycle oxidation leading to shorter combustion duration and favorable combustion phasing. Results also suggest that OME exhibits relatively weak negative temperature coefficient (NTC) behavior, however, the OME fuel-decomposition kinetic-pathways produce significant concentration of HCHO, which might be erroneously interpreted as a product of cool-flames.

Математические модели поддержки управленческих решений по снижению уровня пожарной опасности в административно-территориальных единицах Вьетнама

Purpose. The article classifies and analyzes significant factors affecting fire situation and fire risks in the administrativeterritorial units (ATUs) of Vietnam from 2019 to 2022. Based on this data, mathematical models have been developed to show the relationship between fire risks and influencing factors. Optimal managerial decisions have been formulated to reduce fire risks and the level of fire hazard in Vietnam's ATUs based on the obtained models. Methods. Methods of mathematical statistics, systems analysis, and mathematical modeling were used. Findings. The study analyzed statistical data and developed three multiple regression mathematical models showing the dependence of fire risks on significant factors. Research application field. The results of the study can be used to support managerial decisions to ensure fire safety in Vietnam. Conclusions. The analysis of various significant and less significant factors affecting fire situation draws attention to specialists in fire prevention. The developed mathematical models have a sufficiently high level of adequacy and significance. The application of the managerial decisions derived from these models had a positive impact on reducing fire risks and the level of fire hazard in ATUs. Specifically, the risk of human fatalities in fires (Rf) decreased by 22.1%, the risk of injuries from fires (Ri) decreased by 14%, and the risk of direct fire damage (Rd) decreased by 16.1%. The obtained research results enable the improvement of managerial decisions in fire safety operations and reduce fire hazard levels across the country's territories.

THREE-DIMENSIONAL MATHEMATICAL MODEL OF THE INDUCTION-TYPE HEAT GENERATOR. VOLTAGE MODE

Induction type heat generators are widely used in technologies for drying materials of natural and artificial origin. This allows using non-contact action on the heat carrier, unlike traditional heat generators, where air heated by the products of combustion of mineral fuel acts as a drying agent, to exclude the impact of carcinogens on the final product, to ensure fire safety in the absence of an open flame, does not pollute the environment with combustion products in due to their absence. Despite the fairly wide industrial implementation of these technologies, the issue of creating new and improving known induction heating systems for drying technologies of natural and artificial origin remains relevant, and their design methods require further development and generalization. The purpose of this work is to develop, using the method of secondary sources, a mathematical model for the analysis of the three-dimensional magnetic field in a three-phase heat generator of the induction type, taking into account the symmetry of its geometry, powered by a three-phase voltage source. On the basis of the method of secondary sources, a three-dimensional mathematical model of an induction-type heat generator was developed when it is powered by a three-phase voltage source with a load in the form of unbonded ferromagnetic conductive tubes/rods, taking into account the symmetry of the density distribution of secondary sources of the electromagnetic field, which allows rational use of computing resources, conducting analysis influence of the geometrical, electrophysical, mode parameters of the induction type heat generator on heat losses in the loaded, which are heat sources for heating the coolant.

Analytical developments in the synergism of copper particles and cysteine: a review.

Cysteine, a sulfur-containing amino acid, is a vital candidate for physiology. Coinage metal particles (both clusters and nanoparticles) are highly interesting for their spectacular plasmonic properties. In this case, copper is the most important candidate for its cost-effectiveness and abundance. However, rapid oxidation destroys the stability of copper particles, warranting the necessity of suitable capping agents and experimental conditions. Cysteine can efficiently carry out such a role. On the contrary, cysteine sensing is a vital step for biomedical science. This review article is based on a comparative account of copper particles with cysteine passivation and copper particles for cysteine sensing. For the deep understanding of readers, we discuss nanoparticles and nanoclusters, properties of cysteine, and importance of capping agents, along with various synthetic protocols and applications (sensing and bioimaging) of cysteine-capped copper particles (cysteine-capped copper nanoparticles and cysteine-capped copper nanoclusters). We also include copper nanoparticles and copper nanoclusters for cysteine sensing. As copper is a plasmonic material, fluorometric and colorimetric methods are mostly used for sensing. Real sample analysis for both copper particles with cysteine and copper particles for cysteine sensing are also incorporated in this review to demonstrate their practical applications. Both cysteine-capped copper particles and copper particles for cysteine sensing are the main essence of this review. The aspect of the synergism of copper and cysteine (unlike other amino acids) is quite promising for future researchers.

A critical factor in reactive oxygen species (ROS) studies: the need to understand the chemistry of the solvent used: the case of DMSO.

Reactive oxygen species (ROS) play critical roles in normal physiological processes including cellular signaling and immune responses. Various pathological conditions including infections of various types, inflammation, cancer, and respiratory conditions are associated with elevated levels of ROS. Therefore, there is widespread interest in understanding ROS concentrations under various pathophysiological conditions for diagnostic and therapeutic applications including ROS-triggered drug delivery. However, in determining ROS concentration, there are major concerns of inappropriate use of various methods that lead to erroneous results; this has prompted the publication of a consensus paper in Nature Metabolism by a group of ROS experts stating "Unfortunately, the application and interpretation of these measurements are fraught with challenges and limitations. This can lead to misleading claims." Along this line, we have identified an overlooked factor, which can significantly skew the results and results interpretation: the organic co-solvent. DMSO is one of the most widely used organic co-solvents to dissolve a reagent for bioassays. Herein, we describe the rapid oxidation of DMSO by hypochlorite and how this oxidation impacts results of ROS determination in buffer, cell culture media, cell culture, and cell lysates. We hope to use this one example to draw attention to the convoluted roles that DMSO and possibly other organic co-solvents can play and skew experimental results. We also hope to stimulate additional studies to bring more rigor to studying ROS concentration and biology.

Analysis of the adhesive secreting cells of Arion subfuscus: insights into the role of microgels in a tough, fast-setting hydrogel glue.

The slug Arion subfuscus produces a tough, highly adhesive defensive secretion. This secretion is a flexible hydrogel that is toughened by a double network mechanism. While synthetic double network gels typically require extensive time to prepare, this slug creates a tough gel in seconds. To gain insight into how the glue forms a double-network hydrogel so rapidly, the secretory apparatus of this slug was analyzed. The goal was to determine how the major components of the glue were distributed and mixed. Most of the glue comes from two types of large unicellular glands; one secretes polyanionic polysaccharides in small, membrane-bound packets, the other secretes proteins that appear to form a cross-linked network. The latter gland shows distinct regions where cross-linking appears to be occurring. These regions are darker, more homogeneous and appear more solid than the rest of the secretory material. The enzyme catalase is highly abundant in these regions, as are basic proteins. These results suggest that a rapid oxidation event occurs in this protein-containing gland, triggering cross-linking before the glue is released. The cross-linked microgels would then join together after secretion to form a granular hydrogel. The polysaccharide-filled packets would be mixed and interspersed among these microgels and may contribute to joining them together. This is an unexpected and highly effective way to form a tough gel rapidly.

Microstructure and properties of CoCrFeNiAlxMo2-x high-entropy alloy coating by laser cladding

CoCrFeNiAlxMo2-x (x = 0, 0.5, 1, 1.5, and 2) high-entropy alloy coatings were applied to Q235 steel, and this study investigated the effect of x variations on microstructure evolution and properties. It was fount that as x increased, the crystal structure of the coatings transitioned from a face-centred cubic (FCC) + body-centred cubic (BCC) + σ + B2 phase to a BCC + σ + B2 phase, and eventually it become a BCC phase. Concurrently, the microhardness, wear resistance, corrosion resistance, and high-temperature oxidation resistance of the coatings initially increased and then decreased with the rise in x. The optimal values were achieved at x = 1. The enhancement in microhardness and wear resistance of high-entropy alloy (HEA) coatings was attributed to the change of phase type, dispersion strengthening and solid solution strengthening. Adding of the Al element generated a passivation film on the coatings’ surface, which mitigated galvanic corrosion. Furthermore, an appropriate amount of Mo increased the thickness and density of the passivation film, thereby improving its corrosion resistance. During early-stage high-temperature oxidation, the Al underwent element undergoes rapid oxidation, while Mo promoted the formation of Al2O3, leading to an excellent high-temperature oxidation resistance. Additionally, mathematical model equations were used to fit the results, adding insights into the effects of Al and Mo content changes (x value) on the wear resistance, corrosion resistance, and high-temperature oxidation resistance of the coatings.

Efficient Thermoelectric Conversion of Sulfide Chimneys in Submarine Volcanic Systems

AbstractSubmarine volcanos are the most active areas in the deep sea, but the environmental consequences of frequent volcanic activity on the geophysical fields and biogeochemical processes near hydrothermal chimneys have not been fully understood yet. In particular, how continuous high‐flux thermal energy, the most typical form of energy in active submarine volcanic systems, affects electron transport and geoelectric field remains unknown. This study provides the first evidence that thermal energy can be efficiently converted to electrical energy at an extremely small spatial scale of the submarine black chimneys. The Seebeck coefficient of sulfide chimneys can reach more than 200 μV/K, with high electrical conductivity of 104 S/m and low thermal conductivity of 1.0 W/(m·K) within 300–700 K. A maximal potential gradient of 300 mV/cm under a temperature difference of 300–700 K can be generated by the thermoelectric conversion of sulfide chimneys, with a maximum energy converting efficiency up to 1%. The thermoelectric conversion effect of a global‐scale submarine volcanos could enable electroactive bacteria to fix appromaxiately 105–106 tons of carbon per year. In addition, the thermal‐electrochemical experiments indicated sulfides underwent rapid oxidation under thermoelectric effects, which may help explain the intense oxidative weathering of sulfides in some anoxic deep‐sea hydrothermal zones.