A laboratory fire-extinguishing system was applied to investigate the effect of gas-liquid ratio on the fire-extinguishing performance of aqueous film-forming foam (AFFF) in diesel pool fire, and the ...proposed fire-extinguishing mechanism of AFFF is carefully analyzed. The results show that the AFFF foam possesses the shortest extinguishing time of 42s and lowest foam liquid consumption of 210 g at a gas-liquid ratio of 16, exhibiting the best fire-extinguishing performance. Chemical analysis of AFFF indicates that a proper gas-liquid ratio is beneficial to enhance the expansion ratio and drainage rate of AFFF that affect the cooling and covering effects of foam, thus achieving the optimum fire-extinguishing efficiency. Infrared thermal imaging analysis indicates that the main fire-extinguishing mechanism of AFFF is mainly ascribed to the superior cooling, covering and suffocating effects of foam against the transfer of heat and oxygen, thus effectively preventing the underlying fuel from further combustion.
•The best fire-extinguishing effect of AFFF in diesel pool fire is acquired at a gas-liquid ratio of 16.•The expansion ratio and drainage rate of AFFF decrease as the gas-liquid ratio increases.•The fire-extinguishing mechanism of AFFF is manly ascribed to its superior cooling, covering and suffocating effects.
The quality of mitochondria in skeletal muscle is essential for maintaining metabolic homeostasis during adaptive stress responses. However, the precise control mechanism of muscle mitochondrial ...quality and its physiological impacts remain unclear. Here, we demonstrate that FUNDC1, a mediator of mitophagy, plays a critical role in controlling muscle mitochondrial quality as well as metabolic homeostasis. Skeletal-muscle-specific ablation of FUNDC1 in mice resulted in LC3-mediated mitophagy defect, leading to impaired mitochondrial energetics. This caused decreased muscle fat utilization and endurance capacity during exercise. Interestingly, mice lacking muscle FUNDC1 were protected against high-fat-diet-induced obesity with improved systemic insulin sensitivity and glucose tolerance despite reduced muscle mitochondrial energetics. Mechanistically, FUNDC1 deficiency elicited a retrograde response in muscle that upregulated FGF21 expression, thereby promoting the thermogenic remodeling of adipose tissue. Thus, these findings reveal a pivotal role of FUNDC1-dependent mitochondrial quality control in mediating the muscle-adipose dialog to regulate systemic metabolism.
Display omitted
•Muscle FUNDC1 is a crucial regulator of fat utilization and exercise capacity•FUNDC1-dependent mitophagy regulates mitochondrial function in muscle•Loss of muscle FUNDC1 alleviates high-fat-diet-induced obesity and insulin resistance•FUNDC1 deficiency triggers muscle-adipose crosstalk to promote fat burning in adipose
Mitochondrial quality is essential to muscle function. How muscle mitochondrial quality is regulated and its physiological impacts remain unclear. Fu et al. show that loss of FUNDC1-dependent mitochondrial quality control in muscle alleviates high-fat-diet-induced obesity and improves systemic glucose homeostasis through promoting exercise-independent fat burning in adipose tissue.
•Experiments are carried out in a reduced-scale model tunnel.•Linear correlation between critical velocity and tunnel slope is found.•Expression predicting critical velocity for downslope and upslope ...tunnel is proposed.
Experiments based on Froude scaling law were conducted in a 1/10 reduced-scale model tunnel to investigate the effect of slope on critical velocity in tunnel with longitudinal ventilation under fire. Methanol pool fire was used as the fire source. Smoke movement in the model tunnel with different combination of tunnel slope (−3%, −1.8%, −1%, 0%, 1%, 1.8% and 3%) and longitudinal ventilation velocity was studied. The longitudinal distribution of temperature and velocity were measured. Critical longitudinal ventilation velocity for arresting smoke back flowing in the model tunnel was investigated. Critical velocity in horizontal tunnel obtained in this study was used to compare with that of previous studies. The experimental results agreed well with the model proposed by Wu and Bakar. Correlation between the critical velocity and the slope of the tunnel is proposed based on the experiment results. As the tunnel slope increases from downhill to uphill, critical velocity decreases nearly at a rate independent of the heat release rate of the fire source. The correlation proposed in this studied agrees well with the equation adopted in the Subway Environment Simulation Computer Program (SES). However, it has some discrepancy with the expressions proposed by Atkinson and Ko et al. based on their experimental results. The cause of the discrepancy is attributed to different configuration of the experiments.
Mitochondrial proteolysis is an evolutionarily conserved quality-control mechanism to maintain proper mitochondrial integrity and function. However, the physiological relevance of stress-induced ...impaired mitochondrial protein quality remains unclear. Here, we demonstrate that LONP1, a major mitochondrial protease resides in the matrix, plays a role in controlling mitochondrial function as well as skeletal muscle mass and strength in response to muscle disuse. In humans and mice, disuse-related muscle loss is associated with decreased mitochondrial LONP1 protein. Skeletal muscle-specific ablation of LONP1 in mice resulted in impaired mitochondrial protein turnover, leading to mitochondrial dysfunction. This caused reduced muscle fiber size and strength. Mechanistically, aberrant accumulation of mitochondrial-retained protein in muscle upon loss of LONP1 induces the activation of autophagy-lysosome degradation program of muscle loss. Overexpressing a mitochondrial-retained mutant ornithine transcarbamylase (ΔOTC), a known protein degraded by LONP1, in skeletal muscle induces mitochondrial dysfunction, autophagy activation, and cause muscle loss and weakness. Thus, these findings reveal a role of LONP1-dependent mitochondrial protein quality-control in safeguarding mitochondrial function and preserving skeletal muscle mass and strength, and unravel a link between mitochondrial protein quality and muscle mass maintenance during muscle disuse.
The decorative and fireproof performance degradation of the grouting fireproof glass exposed to UV irradiation limits its application in the fire protection of buildings. To solve this issue, a ...transparent polyacrylamide/polyvinyl alcohol (PAM/PVA) interpenetrating network hydrogel was designed to prepare grouting fireproof glass with enhanced theheat insulation and anti-aging properties. The results show that the light transmittance of PAM/PVA interpenetrating network hydrogel decreases with the increased content of PVA, and a proper content of PVA in the PAM/PVA interpenetrating network is beneficial to maintain high optical transparency in the resulting hydrogel. Heat insulation test shows that the PAM/PVA interpenetrating network improves the water-locking ability of the resulting hydrogels, and the fireproof glass containing 3 wt% PVA shows the lowest backside temperature of 92.6 °C at 3600 s, which is 51.9% lower than that of fireproof glass with PAM only. Thermogravimetric (TG) and differential scanning calorimetry (DSC) analysis show that the PAM/PVA interpenetrating network hydrogel improves the thermal stability and charring ability of hydrogel, and the hydrogel containing 3 wt% PVA exhibits the best charring effect among the samples, showing the highest residual yield of 39.2 % at 800 °C. The analyses of decomposition products and char residues show that the PAM/PVA interpenetrating network hydrogel can extend the heat absorption process of water evaporation and improve the gas flame retardant efficiency. Accelerated aging test shows that the presence of PVA greatly slows down the blistering and yellowing phenomenon of fireproof glass, thus endowing the fireproof glass with the super durability of fire resistance. Especially, the backside temperature at 3600 s and light transmittance of the sample containing 2 wt% PVA after 168 h aging test only changed 19.2 °C and 1.9 %, respectively, compared to the those of unaged sample.
Four kinds of polyethylene glycol borate (PEG-BA) with different molecular weights were grafted into cyclic phosphate ester (PEA) to obtain flexible phosphate esters (PPBs), and then applied in amino ...resin to obtain a series of transparent intumescent fire-retardant coatings. The comprehensive properties of the transparent coatings containing different molecular weights of PEG-BA were investigated by various analytical instruments. The transparency and mechanical analyses indicate that the presence of PEG-BA slightly decreases the optical transparency of the coatings but improves the flexibility and adhesion classification of the coatings. The results from fire protection and cone calorimeter tests show that low molecular weight of PEG-BA exerts a positive flame-retarded effect in the coatings, while high molecular weight of PEG800-BA behaves against flame-retarded effect. Thermogravimetric and char residue analyses show that the incorporation of low molecular weight of PEG-BA clearly increases the thermal stability and residual weight of the coatings and generates a more compact and stable intumescent char on the surface of the coatings, thus resulting in superior synergistic flame-retarded effect. In particular, MPPB1 coating containing PEG200-BA exerts the best flame-retarded effect and highest residual weight of 36.3% at 700 °C, which has 57.6% reduction in flame spread rate and 23.9% reduction in total heat release compared to those of MPPB0 without PEG-BA. Accelerated ageing test shows that low molecular weight of PEG-BA promotes to enhance the durability of structural stability and fire resistance of the coatings, while PEG800-BA with high molecular weight weakens the ageing resistance. In summary, the fire-resistant and anti-ageing efficiencies of PEG-BA in the coatings depend on its molecular weight, which present the order of PEG200-BA > PEG400-BA > PEG600-BA > PEG800-BA.
A pneumatic conveying powder device was carried out to investigate the fire-extinguishing performance of cement powder against metal magnesium fire. The fire suppression test shows that pneumatic ...conveying can effectively transport cement powder to the combustion area for suppressing metal magnesium fire, and the fire-extinguishing time increases with the fire load of metal magnesium. The fire suppression effect of cement powder in metal magnesium fire is ascribed to the formation of a thermally insulation layer as physical barrier concomitant with heat absorption during pyrolysis process that effectively weaken the heat transfer and reduces the combustion intensity, as supported by the morphology and DSC analysis. The results of explosion suppression test reveal that cement powder has a significant inhibitory effect on reducing the explosion max-pressure and max-pressure rise rate of methane explosion, exhibiting a high-level security in the fire-extinguishing process. This work provides an effective and safe strategy for extinguishing metal magnesium fires.
Display omitted
•A pneumatic conveying device was designed to transport cement powder in fire extinguishing field.•Pneumatic conveying cement has excellent extinguishing effect in metal magnesium fires.•Inhibition effect of cement powder on methane explosion verifies the safety in extinguishing process.•The fire suppression mechanism of cement powder in metal magnesium fires is proposed.
Previous studies mainly focused on the influences of climate change on wildfires. However, other types of fires are also weather-related (especially temperature-related). The present study is aimed ...to analyze the influences of climate warming on fire risk. By data joining and processing, a dataset was born which includes 20,622 fire incidents and the related weather data from 2011 to 2017 in Changsha, China. Predictive models of fire frequency were established based on different regression methods of machine learning (random forest, support vector machine and polynomial). Among them, random forest regression models had the best fitting performance, and were selected to predict the fire frequency under climate warming scenarios. Under the current warming rate in Changsha, the annual fire frequency in 2067 (50 years after 2017) will increase by 0.69% to 0.89%. By rebuilding predictive models for other cities based on the proposed methods in this study, the influences of climate warming on their fire frequencies can also be analyzed.
This research focuses on the specific uniclinal V-shaped tunnel during a fire, studying the air supplement triggered by the thermal stack effect and further examining the control mechanism of ...upstream smoke. It revealed how the air supplement velocity generated by the thermal stack effect, influenced by longitudinal ventilation, varied in the tunnel. It also established a prediction model for the critical velocity based on different geometric tunnel parameters. Results indicate that internal longitudinal velocity enhances air entrainment, lowers the temperature field, and significantly reduces the stack effect. As longitudinal velocity increases, the air supplement velocity exhibits an exponential decay, with a decay coefficient identified as 3.22. Higher heat release rates and slope heights increase the internal temperature and height differences, promoting air supplementation. Combining air supplement velocity with the critical velocity prediction for horizontal tunnels, the study quantifies the critical velocity in uniclinal V-shaped tunnels under varying conditions. It introduces a P parameter to decide on the necessity of external mechanical ventilation for smoke control. P ≥ 1 indicates that mechanical ventilation is unnecessary; P < 1 suggests the opposite. These findings offer significant insights into the dynamics of smoke and air in tunnels, providing valuable guidance for tunnel fire smoke management.
Display omitted
Fire stations play a key role in controlling typical thermal runaway phenomena (fires). Based on real-time traffic, we develop a data crawling and processing algorithm for travel times, and propose ...an evaluation model for the spatial configuration of fire stations. In the model, the fire service levels are divided into four levels based on the total fire service score (TFSS). The present work gathered 16,448 fire incidents in Changsha, China from 2013 to 2017 as fire service demand points, and the minimum travel times for each fire incident point in the four evaluation scenarios with different real-time traffics were extracted from online maps. The results show that the TFSSs of Changsha varied from 67.92 to 74.05 due to the insufficient firefighting resources and the dynamic traffic conditions, and the fire service level of Changsha can be defined as fair. By employing spatial visualization, we observed that the fire service demand points with moderate and poor fire service levels were mainly located in rural areas, and those with good and fair fire service levels were located in urban areas.
PDF
