Experimental study on the combustion and explosion process induced by the entrainment of deposited coal dust

During the operation of pulverizing systems in power plants, high ambient temperatures create conditions in which coal dust deposited on equipment surfaces is prone to thermal runaway. When these self-ignited coal dust particles are lifted by airflow, there is a significant risk of combustion and explosion. To reveal the processes and mechanisms of dust cloud explosions induced by airflow entrainment, we constructed an experimental setup to monitor coal dust self-ignition, dispersion in a dust cloud, and the subsequent ignition and explosion. Next, we investigated the self-ignition process, characteristic parameters, critical conditions for entrainment-induced explosions, explosion behavior, and underlying mechanisms. The experimental procedure involved first placing the coal powder on a high-temperature flat plate and then using a high-pressure airflow to entrain the coal powder into the air under various spontaneous combustion conditions. Subsequently, the phenomena of spontaneous combustion, explosion, and their transitions were observed. The results indicated that thermal conduction and oxidative heat release were the primary causes of high-temperature spot migration during the self-ignition process of the deposited coal dust, with the high-temperature point moving upward from the hot surface and then downward. As the deposition thickness increased, both the peak temperature and the duration of the combustion propagation and decay stages increased, reaching 538 ℃, 510 ℃, 810 s, and 1520 s for thicknesses of 8 mm and 10 mm, respectively. The degree of self-ignition and the mass of coal dust significantly influenced the occurrence of explosions, with the central temperature representing the self-ignition level. When the central temperature of the coal dust layer ranged from 280 ℃ to 420 ℃, the entrained coal dust could trigger an explosion. As the central temperature increased, the flame propagation speed first increased and then decreased, whereas the particle size and surface smoothness of the solid residue decreases. The flame propagation speed of the explosion was the largest (4.76 m·s−1) at a mass of 6.0 g and central temperature of 340 ℃. Additionally, the explosion intensity initially increased and then decreased with an increasing coal dust mass. Moreover, the maximum flame length and flame area occurred at 6.0 g, measuring 26.81 cm and 301.4 cm2, respectively. A lower dust mass resulted in insufficient combustible particles, leading to a decrease in flame intensity, whereas a higher dust mass limited combustion owing to an inadequate oxygen supply. Furthermore, the combined effects of the heterogeneous combustion of carbon particles and homogeneous combustion of volatiles, such as CO and H2, are the primary trigger mechanisms driving the explosion of deposited coal dust. The homogeneous combustion of combustible gases ignited the coal dust particles, thus further promoting the pyrolysis and combustion of coal dust, and producing more combustible gases and strengthening the explosion process. When coal dust has a low concentration and a low degree of spontaneous combustion, the combustion and explosions are dominated by heterogeneous combustion. Additionally, the coupling of these two ignition mechanisms leads to incomplete combustion, secondary ignition, and multiple ignition sources. This study provides a theoretical basis for the prevention and control of spontaneous combustion-induced explosion hazards in pulverized industrial systems

From pixels to patches: a cloud classification method based on a bag of micro-structures

Abstract. Automatic cloud classification has attracted more and more attention with the increasing development of whole sky imagers, but it is still in progress for ground-based cloud observation. This paper proposes a new cloud classification method, named bag of micro-structures (BoMS). This method treats an all-sky image as a collection of micro-structures mapped from image patches, rather than a collection of pixels. It represents the image with a weighted histogram of micro-structures. Based on this representation, BoMS recognizes the cloud class of the image by a support vector machine (SVM) classifier. Five classes of sky condition are identified: cirriform, cumuliform, stratiform, clear sky, and mixed cloudiness. BoMS is evaluated on a large data set, which contains 5000 all-sky images captured by a total-sky cloud imager located in Tibet (29.25° N, 88.88° E). BoMS achieves an accuracy of 90.9 % for 10-fold cross-validation, and it outperforms state-of-the-art methods with an increase of 19 %. Furthermore, influence of key parameters in BoMS is investigated to verify their robustness. </jats:p

The bidirectional interation between pancreatic cancer and diabetes

Abstract The bidirectional interation between pancreatic cancer (PanCa) and diabetes has been confirmed by epidemiological studies, which provide evidence-based medical support for further research into the mechanisms involved in the interaction. We reviewed the literature regarding the role of diabetes in the generation and progression of PanCa and the mechanism by which PanCa induces diabetes for its malignant progression. The effect of antidiabetic drugs on the occurrence and prognosis of PanCa was also reviewed. Diabetes may directly promote the progression of PanCa by pancreatic duct enlargement and hypertension, as well as by enabling an increased tumor volume. Hyperinsulinemia, insulin resistance, cytokines, hyperglycemia and genotype change are also important factors in the progression of PanCa with diabetes. Hyperglycemia may be the first clinical manifestation and is helpful in the early diagnosis of PanCa. Furthermore, antidiabetic drugs can have different effects on the occurrence and prognosis of PanCa. The bidirectional interation between PanCa and diabetes is involved in the occurrence, proliferation, invasion, metastasis and prognosis of PanCa with diabetes. The discovery of biomarkers for the early diagnosis of PanCa, as well as the novel usage of metformin for its antitumor effects and determining the potential mechanisms of these effects, may be the next direction for PanCa research and treatment.</p

Micro-/nanobubble oxygenation irrigation enhances soil phosphorus availability and yield by altering soil bacterial community abundance and core microbial populations

Micro-/nanobubble oxygenation irrigation, as a novel irrigation technique, has been widely utilized to enhance soil phosphorus availability and maize yield. Nevertheless, currently, most of the studies remain unclear about the precise mechanism through which micro-/nanobubble oxygenation improves soil phosphorus availability and maize yield. Therefore, we established two irrigation methods, conventional irrigation (CF) and micro-/nanobubble oxygenation irrigation (MB), to investigate the combined effects on enzyme activity, microbial communities, and soil phosphorus availability in the rhizosphere soil of maize.The results showed that compared to the CF treatment, the MB treatment significantly increased available phosphorus content and alkaline phosphatase activity in maize rhizosphere soil by 21.3% and 15.4%, respectively. Furthermore, MB significantly influenced bacterial diversity in the maize rhizosphere soil but did not considerably affect fungal diversity. Specifically, MB regulated the microbial community structure in the maize rhizosphere by altering the relative abundances of the bacterial phylum Firmicutes and the fungal phyla Mucoromycota, Chytridiomycota, and Basidiomycota. In addition, MB reduced the complexity of the bacterial network while increasing the interaction density among bacterial species. Meanwhile, MB enhanced the complexity of the fungal network. Structural equation modeling indicated that MB primarily promoted soil alkaline phosphatase activity by regulating bacterial community diversity, thereby enhancing soil phosphorus availability. In conclusion, the application of micro-/nanobubble oxygenation irrigation enhances the activity of alkaline phosphatasein the soil by modulating the microbial community within the rhizosphere, thereby facilitating increased phosphorus availability in the rhizosphere of maize

Activation of Nrf2 by Sulforaphane Inhibits High Glucose-Induced Progression of Pancreatic Cancer via AMPK Dependent Signaling

Background/Aims: Sulforaphane (SFN) is known for its potent bioactive properties, such as anti-inflammatory and anti-tumor effects. However, its anti-tumor effect on pancreatic cancer is still poorly understood. In the present study, we explored the therapeutic potential of SFN for pancreatic cancer and disclosed the underlying mechanism. Methods: Panc-1 and MiaPaca-2 cell lines were used in vitro. The biological function of SFN in pancreatic cancer was measured using EdU staining, colony formation, apoptosis, migration and invasion assays. Reactive oxygen species (ROS) production was measured using 2’-7’-Dichlorofluorescein diacetate (DCF-DA) fluorometric analysis. Western blotting and immunofluorescence were used to measure the protein levels of p-AMPK and epithelial-mesenchymal transition (EMT) pathway-related proteins, and cellular translocation of nuclear factor erythroid 2-related factor 2 (Nrf2). Nude mice and transgenic pancreatic cancer mouse model were used to measure the therapeutic potential of SFN on pancreatic cancer. Results: SFN can inhibit pancreatic cancer cell growth， promote apoptosis, curb colony formation and temper the migratory and invasion ability of pancreatic cancer cells. Mechanistically, excessive ROS production induced by SFN activated AMPK signaling and promoted the translocation of Nrf2, resulting in cell viability inhibition of pancreatic cancer. Pretreatment with compound C, a small molecular inhibitor of AMPK signaling, reversed the subcellular translocation of Nrf2 and rescued cell invasion ability. With nude mice and pancreatic cancer transgenic mouse, we identified SFN could inhibit tumor progression, with smaller tumor size and slower tumor progression in SFN treatment group. Conclusion: Our study not only elucidates the mechanism of SFN-induced inhibition of pancreatic cancer in both normal and high glucose condition, but also testifies the dual-role of ROS in pancreatic cancer progression. Collectively, our research suggests that SFN may serve as a potential therapeutic choice for pancreatic cancer

Reactive Oxygen Species and Targeted Therapy for Pancreatic Cancer

Pancreatic cancer is the fourth leading cause of cancer-related death in the United States. Reactive oxygen species (ROS) are generally increased in pancreatic cancer cells compared with normal cells. ROS plays a vital role in various cellular biological activities including proliferation, growth, apoptosis, and invasion. Besides, ROS participates in tumor microenvironment orchestration. The role of ROS is a doubled-edged sword in pancreatic cancer. The dual roles of ROS depend on the concentration. ROS facilitates carcinogenesis and cancer progression with mild-to-moderate elevated levels, while excessive ROS damages cancer cells dramatically and leads to cell death. Based on the recent knowledge, either promoting ROS generation to increase the concentration of ROS with extremely high levels or enhancing ROS scavenging ability to decrease ROS levels may benefit the treatment of pancreatic cancer. However, when faced with oxidative stress, the antioxidant programs of cancer cells have been activated to help cancer cells to survive in the adverse condition. Furthermore, ROS signaling and antioxidant programs play the vital roles in the progression of pancreatic cancer and in the response to cancer treatment. Eventually, it may be the novel target for various strategies and drugs to modulate ROS levels in pancreatic cancer therapy

Establishing the carrier scattering phase diagram for ZrNiSn-based half-Heusler thermoelectric materials

Chemical doping is one of the most important strategies for tuning electrical properties of semiconductors, particularly thermoelectric materials. Generally, the main role of chemical doping lies in optimizing the carrier concentration, but there can potentially be other important effects. Here, we show that chemical doping plays multiple roles for both electron and phonon transport properties in half-Heusler thermoelectric materials. With ZrNiSn-based half-Heusler materials as an example, we use high-quality single and polycrystalline crystals, various probes, including electrical transport measurements, inelastic neutron scattering measurement, and first-principles calculations, to investigate the underlying electron-phonon interaction. We find that chemical doping brings strong screening effects to ionized impurities, grain boundary, and polar optical phonon scattering, but has negligible influence on lattice thermal conductivity. Furthermore, it is possible to establish a carrier scattering phase diagram, which can be used to select reasonable strategies for optimization of the thermoelectric performance.Comment: 21 pages, 5 figure