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Hydrogen is a carbon-free energy source that can be obtained from various sources. The blending of hydrogen represents a transitional phase in the shift from natural gas systems to hydrogen-based systems. However, concerns about the safety implications of introducing hydrogen have led to extensive discussions. This paper utilizes Fluent 17.0 numerical simulation software to simulate the leakage of hydrogen-blended natural gas in a closed domestic kitchen and analyze the concentration distribution and its variation pattern after a leakage. An experimental platform is set up, and a mixture of nitrogen and helium gas is used as a substitute for hydrogen-blended natural gas for the simulations and experiments. The simulation results demonstrate that the leaked gas spreads and accumulates towards the top of the space, gradually filling the entire area as the leak persists. As the hydrogen content in the leaked gas increases, the dispersion capacity of the gas in the confined space also increases. Furthermore, as the flow rate of the leaked gas increases, the average concentration of the leaked gas rises, and the gas stratification in the confined kitchen diminishes. The concentration distribution observed in the experiments aligns with the simulation results. After establishing the feasibility conditions of the model, the dispersion of the hydrogen-blended natural gas in the kitchen is further simulated. The results suggest that blending hydrogen into the gas enhances the dispersion of the gas after a leak, leading to a wider distribution within the kitchen and an increased risk in the event of a leak. Additionally, this paper employs the CASD module of FLACS 11.0 software to construct a three-dimensional geometric model of the domestic kitchen for simulation studies on the explosion of hydrogen-blended natural gas in a confined space. By adjusting the hydrogen ratio in the combustible gases present in the space and examining the variations in hydrogen concentration and external conditions, such as opening or closing the door, the influence on parameters including the peak explosion pressure, explosion overpressure, explosion flame temperature, and explosion response time are examined. Furthermore, the extent of the explosion area is determined, and the effect of hydrogen on the blast is clarified.

Three pretreatment methods, including direct extraction method, neutral alumina column method and molecular imprinted column method, were established for the determination of benzo (a) pyrene in vegetable oil by high performance liquid chromatography-fluorescence detector. The results showed that the linear relationship between the concentration of benzo (a) pyrene standard curve and the corresponding hromatographic peak area was good, and the correlation coefficient was 0.9993, when the concentration was in the range of 0.5~50 ng/mL. The blank vegetable oil was used as the matrix to carry out the spike recovery experiment. When the addition levels of benzo (a) pyrene were 2, 15 and 25 μg/kg, the average recoveries of direct extraction method, molecular imprinted column method and neutral alumina column method were 98.8%~102.8% and 91.1%~101.0% and 91.8%~113.7%, respectively, and the relative standard deviations (RSD) were 0.8%~2.0%, 2.3%~7.3% and 1.9%~8.8%, respectively. The direct extraction method has the advantages of simple pretreatment, good precision, high accuracy and sensitivity, and low cost, and is suitable for the detection of benzo (a) pyrene in vegetable oil.

The current article is concerned with the traveling fronts for a class of double degenerate equations with delay. We first show that the traveling fronts decay algebraically at one end, while those may decay exponentially or algebraically at the other end, which depend on the wave speed of traveling fronts. Based on the asymptotical behavior, the uniqueness and stability of traveling fronts are then proved. Of particular interest is the effect of the lower order term and higher order term on the critical speed. We mention that, under the double degenerate case, the nonlinear reaction is less competitive due to the appearance of degeneracy. This yields that the critical speed depends on the lower order term and higher order term, which is different from the nondegenerate case.

This paper is based on the distribution characteristics of the protective layer current under the fault state of high-voltage cables, and discovers the monotonic variation law between the fault point position and the power frequency phase difference of the protective layer current at both ends of the cable fault section. A method for fault location using the phase difference of the protective layer current at both ends of the cable section is proposed. For a long cable line composed of multiple complete cross-connected sections, the cross-connected section can be located through the current power frequency phase difference P (section) at both ends of the metal sheath section, just like the section positioning within the complete cross-connected section. If P (section) ∈ (90°, 270°), then the section is a fault section; otherwise, it is a non-fault section. Finally, the relationship curve between the power frequency phase difference of the protective layer current at both ends of the fault section and the distance from the fault point is used to determine the fault location.

Chronic alcoholic liver disease has brought great harm to human health. Alcoholic fatty liver disease is the first stage in the progression of all chronic alcoholic liver diseases. At present, there is no cell model that fully matches the etiology (high-fat diet + alcohol) of human alcoholic fatty liver disease. We used 100 mM ethanol +6.25 μM PA to establish the ethanol combined with PA-induced mouse hepatocyte AFLD model (EP-AFLD hepatocyte model) and performed the RNA-seq transcriptome sequencing. Through bioinformatics analysis and comparison, we discovered that the EP-AFLD hepatocyte model was more suitable for studying the pathological mechanism of AFLD than the mouse AFLD hepatocyte model induced by ethanol alone. And through bioinformatics analysis, we further discovered that 77 genes from the differential expression gene set of EP-AFLD hepatocyte model were engaged in the pathological process of mouse AFLD and 40 genes were involved in the pathogenesis of both mouse AFLD and human AFLD. In this study, a novel mouse hepatocyte AFLD model was successfully established by combining ethanol and PA, which can be used to study the molecular mechanism of the pathogenesis of AFLD in mice or humans. This study will provide a brand-new in vitro experimental platform for the in-depth study of AFLD pathogenesis and the screening of AFLD therapeutic drugs.

Given the limited availability of serological testing to date, the seroprevalence of SARS-CoV-2-specific antibodies in different populations has remained unclear. Here, we report very low SARS-CoV-2 seroprevalence in two San Francisco Bay Area populations. Seroreactivity was 0.26% in 387 hospitalized patients admitted for non-respiratory indications and 0.1% in 1,000 blood donors in early April 2020. We additionally describe the longitudinal dynamics of immunoglobulin-G (IgG), immunoglobulin-M (IgM), and in vitro neutralizing antibody titers in COVID-19 patients. The median time to seroconversion ranged from 10.3-11.0 days for these 3 assays. Neutralizing antibodies rose in tandem with immunoglobulin titers following symptom onset, and positive percent agreement between detection of IgG and neutralizing titers was >93%. These findings emphasize the importance of using highly accurate tests for surveillance studies in low-prevalence populations, and provide evidence that seroreactivity using SARS-CoV-2 anti-nucleocapsid protein IgG and anti-spike IgM assays are generally predictive of in vitro neutralizing capacity.