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The ignition and combustion behaviors of titanium aluminide (TiAl alloy) were studied by using laser oxygen concentration experimental method combined with ultra-high temperature infrared thermometer, high-speed camera in-situ observation, scanning electron microscopy and X-ray diffraction. The formation and movement laws of the molten body, types and structural characteristics during the combustion process were revealed, and the molten body mechanism was further explored. The results show that the critical conditions of laser power and oxgyen concentration for the ignition and sustained burning of TiAl alloy follow parabolic and parabolic+linear laws, respectively, which are significantly higher than those of near α high temperature titanium alloy, indicating the better flame retardant properties of TiAl alloy. The ignition temperature of TiAl alloy is higher than the melting point. During the ignition period, the partial melting of the matrix causes the transition of Al element from internal oxidation to external oxidation. The oxides formed during the sustained burning stage are characterized as Al2O3, Al2Ti7O15, Al2TiO5, and Al6Ti2O13 phases from the inner side to the burning surface. The continuous network Al2O3 layer formed in the fusion zone can hinder the movement of the melt. The Ti-Al-O ternary phase formed in the combustion zone can improve the stability of the Al2O3 protective layer by reducing the decomposition pressure of Al2O3, thus leading to the better flame retardant performance of TiAl alloy.

With the improvement of thrust-to-weight ratio and other properties of future aero-engine，the high temperature mechanical property and structural stability of titanium alloy components are required. The limitation of traditional experiments in time and space scale has become increasingly prominent，and it is difficult to deeply study the microscopic transient phenomena and mechanisms. Moreover，the molecular dynamics（MD）calculation method takes the atomic/molecular model as the calculation object，on the basis of Newton classical mechanics and empirical parameters，the calculation efficiency is greatly improved compared with the quantum calculation method. Therefore，MD has become an important method to optimize the process parameters and calculate the microstructure properties of aero-engine titanium alloy. Based on an overview of the basic principle of MD computing space and time scale advantages，this paper reviews the relevant domestic and foreign achievements in the study of molding，microstructure characterization and performance testing of aero-engine titanium alloys by MD method in recent years，as well as representative conclusions that contribute to the improvement of high temperature resistance of aero-engine titanium alloys. Finally，the future prospect is discussed based on the demand for MD computing technology for aircraft engine titanium alloys，thus pointing out the challenges faced on the following aspects，including high-throughput composition design based on MD computing method，training molecular force fields for mature titanium alloy systems，and introducing the new ReaxFF（Reactive Force Field）into the study of combustion mechanisms.

A versatile reactor system analysis code RESYS for advanced nuclear reactor was developed by using object-oriented language C++. Based on RESYS code, the model of thermionic nuclear reactor TOPAZ-Ⅱ developed in the former Soviet Union was established, and its start-up process was simulated. The established TOPAZ-Ⅱ reactor system model included reactor core thermal model, thermionic conversion system model and the radiator model. The current density model of cesium thermionic converter used model by Rasor. And the 6 groups of delayed neutron point reactor kinetic model was used to consider the influence of various structural components on reactivity. The point reactor equation with strong rigidity was solved using the Gear algorithm in the RESYS code. The reactivity feedback model of TOPAZ-Ⅱ reactor took into account the Doppler reactivity feedback of the fuel, the reactivity feedback of the electrodes, the reactivity feedback of the moderator and reflector, and the introduction of reactivity control drums. The steady state and start-up transient were simulated based on established thermal-hydraulic model and RESYS code. At steady state, the maximum temperature on the inner surface of the central thermionic fuel element is 2 291 K, the maximum temperature on the outer surface is 2 066.55 K, the maximum temperature on the emitter is 1 961 K, the maximum temperature difference between the electrodes is close to 1 200 K, the temperature at the coolant inlet is 743 K, and the temperature at the core outlet is 837 K. The comparison between the steady-state operating conditions calculated by the RESYS code and the TOPAZ-Ⅱ design values was carried out. The calculated steady-state electric power output is consistent with the calculation results of TITAM code. The calculation results verify the correctness of the developed RESYS code and the established TOPAZ-Ⅱ system model. During the startup process, the reactivity feedback of the moderator and reflection layer is positive feedback, which dominates all feedback effects. The overall reactivity feedback of the TOPAZ-Ⅱ reactor core is positive and does not have a self-stable negative feedback effect, which increases the difficulty of reactor control. During the start-up process of TFE, due to changes in the gas thermal conductivity of the electrode gap, the temperature of the fuel pellets and emitter rapidly increases. At this time, some of the thermal energy generated by fission is stored in the fuel pellets, causing a decrease in coolant temperature and the power of the radiation radiator.

In this work, the distribution and segregation behaviors of helium (He) and the effect of yttrium (Y) on these behaviors in the symmetrical tilt tungsten (W) Σ5(310)/[001] grain boundary (GB) region were studied using first-principles calculations. The results revealed that the GB has a significant impact on the behaviors of He in W. The solution and segregation energies of He in the W Σ5(310)/[001] GB region increase with increasing the distance from He to the GB and are inversely proportional to the effective electrons of He. The density of states analysis showed that the GB can suppress partial hybridization between He and W atoms. In addition, we find that the strengthening element Y facilitates the dissolution of He in the W GB region. [ABSTRACT FROM AUTHOR]

Photocatalytic CH4 coupling into high-valued C2H6 is highly attractive, whereas the photosynthetic rate, especially under oxygen-free system, is still unsatisfying. Here, we designed the negatively charged metal supported on metal oxide nanosheets to activate the inert C–H bond in CH4 and hence accelerate CH4 coupling performance. As an example, the synthetic Au/ZnO porous nanosheets exhibit the C2H6 photosynthetic rate of 1,121.6 µmol gcat−1 h−1 and the CH4 conversion rate of 2,374.6 µmol gcat−1 h−1 under oxygen-free system, 2 orders of magnitude higher than those of previously reported photocatalysts. By virtue of several in situ spectroscopic techniques, it is established that the generated Auδ− and O− species together polarized the C–H bond, while the Auδ− and O− species jointly stabilized the CH3 intermediates, which favored the coupling of CH3 intermediate to photosynthesize C2H6 instead of overoxidation into COx. Thus, the design of dual active species is beneficial for achieving high-efficient CH4-to-C2H6 photoconversion. [ABSTRACT FROM AUTHOR]

To find a high-efficiency and environment-friendly biogenic molluscicide against Oncomelania hupensis, and prevent aquatic ecosystem from being contaminated by chemical molluscicides and being toxic. We extracted and purified raphides from the tubers of Arisaema erubescent, and determined the active constituents and molluscicidal activity of the raphides, detoxification enzyme activity, and liver damage. The results showed that the raphides had a strong molluscicidal activity. O. hupensis snails were exposed to the lethal concentration (LC 50 ) of 70.95 mg/L and 44.25 mg/L for treatment with raphides for 48 h and 72 h, respectively. The raphides of molluscicidal activity of the main constituents was as follows: intact raphides > calcium oxalate crystals > AEL (Arisaema erubescens Lectin). The activities of peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT) in the snail livers increased significantly at the early stage of treatment (24 h), but decreased sharply in the later stage (120 h), compared with that in the control group. The results indicated that after treatment with 1/2 LC 50 raphides for 120 h, the activities of POD, SOD, and CAT in the snail livers decreased by 82.5 %, 62.9 %, and 84.7 %, respectively. In addition, electron micrographs have shown that the raphides were needle-shaped crystals and tended to be sharp at both ends (with a groove down both sides) and some were barbed, which caused damage to the snail livers to different extent. Overall, our results indicate that the mechanism of toxicity of raphides against O. hupensis may be that the calcium oxalate crystals pricked the liver surface of snail and produced mechanical damage; and then the harmful protease AEL in the raphides was injected into the liver, which reduced the activities of detoxification enzymes, produced severe toxic reactions and eventually killed the O. hupensis snails., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Inc.)

Background: Hainan Island and the Leizhou Peninsula, the southernmost part of mainland China, are areas where Aedes aegypti and Ae. albopictus are sympatric and are also high-incidence areas of dengue outbreaks in China. Many studies have suggested that Aedes endogenous viral components (EVEs) are enriched in piRNA clusters which can silence incoming viral genomes. Investigation the EVEs present in the piRNA clusters associated with viral infection of Aedes mosquitoes in these regions may provide a theoretical basis for novel transmission-blocking vector control strategies., Methods: In this study, specific primers for endogenous Flaviviridae elements (EFVEs) and endogenous Rhabdoviridae elements (ERVEs) were used to detect the distribution of Zika virus infection associated EVEs in the genomes of individuals of the two Aedes mosquitoes. Genetic diversity of EVEs with a high detection rate was also analyzed., Results: The results showed that many EVEs associated with Zika virus infection were detected in both Aedes species, with the detection rates were 47.68% to 100% in Ae. aegypti and 36.15% to 92.31% in sympatric Ae. albopictus populations. EVEs detection rates in another 17 Ae. albopictus populations ranged from 29.39% to 89.85%. Genetic diversity analyses of the four EVEs (AaFlavi53, AaRha61, AaRha91 and AaRha100) of Ae. aegypti showed that each had high haplotype diversity and low nucleotide diversity. The number of haplotypes in AaFlavi53 was 8, with the dominant haplotype being Hap_1 and the other 7 haplotypes being further mutated from Hap_1 in a lineage direction. In contrast, the haplotype diversity of the other three ERVEs (AaRha61, AaRha91 and AaRha100) was more diverse and richer, with the haplotype numbers were 9, 15 and 19 respectively. In addition, these EVEs all showed inconsistent patterns of both population differentiation and dispersal compared to neutral evolutionary genes such as the Mitochondrial COI gene., Conclusion: The EFVEs and ERVEs tested were present at high frequencies in the field Aedes mosquito populations. The haplotype diversity of the EFVE AaFlavi53 was relatively lower and the three ERVEs (AaRha61, AaRha91, AaRha100) were higher. None of the four EVEs could be indicative of the genetic diversity of the Ae. aegypti population. This study provided theoretical support for the use of EVEs to block arbovirus transmission, but further research is needed into the mechanisms by which these EVEs are antiviral to Aedes mosquitoes., Competing Interests: Declaration of competing interest The authors declare that they have no competing interests including financial and nonfinancial interests., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Engineering probiotics have emerged as a potential strategy for the treatment of metabolic diseases. However, due to the exceptional complexity of these metabolic disorders and the intricate relationship between gut microbes, it is difficult to achieve an ideal therapeutic effect in a specific metabolic disorder using only a single engineered strain. In this work, we proposed a probiotic cocktail strategy by engineering two cascade metabolic bacteria to treat hyperlysinemia, an inherited lysine metabolic disorder with loss of α-aminoadipate semialdehyde synthase (AASS) activity. A probiotic E. coli Nissle 1917 strain EcNT (pTLS) with a heterologous enzyme pathway in Saccharomyces cerevisiae was engineered to metabolize the excess lysine. Another one EcNT (pK25) was engineered to consume the products of lysine metabolism. The bacterial cocktail enables the maintenance of a metabolic cascade with AASS-like functional activity to maintain the blood lysine concentrations and downstream metabolites. In vitro experimental results showed that the cocktail bacteria had a better metabolic capacity and metabolites balance at a ratio of EcNT (pTLS) and EcNT (pK25) of 1:2. Feeding of the cocktail bacteria to the mouse model effectively reduced the concentration of lysine and balanced saccharopine in the plasma of hyperlysinemia-like mice. These findings not only provide a promising strategy of probiotic stains for the treatment of hyperlysinemia but also highlight the potential of engineered cascade cocktails to intervene and even cure other inherited metabolic diseases., Competing Interests: JL, MW, FG, and YW are co-inventors in a provisional application for patents on the engineering method and probiotics for the treatment of hyperlysinemia. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Geng, Wu, Yang, Li, Pan, Wang and Lü.)

Photocatalytic conversion of methane (CH 4 ) to ethane (C 2 H 6 ) has attracted extensive attention from academia and industry. Typically, the traditional oxidative coupling of CH 4 (OCM) reaches a high C 2 H 6 productivity, yet the inevitable overoxidation limits the target product selectivity. Although the traditional nonoxidative coupling of CH 4 (NOCM) can improve the product selectivity, it still encounters unsatisfied activity, arising from being thermodynamically unfavorable. To break the activity-selectivity trade-off, we propose a conceptually new mechanism of H 2 O 2 -triggered CH 4 coupling, where the H 2 O 2 -derived ·OH radicals are rapidly consumed for activating CH 4 into ·CH 3 radicals exothermically, which bypasses the endothermic steps of the direct CH 4 activation by photoholes and the interaction between ·CH 3 and ·OH radicals, affirmed by in situ characterization techniques, femtosecond transient absorption spectroscopy, and density-functional theory calculation. By this pathway, the designed Au-WO 3 nanosheets achieve unprecedented C 2 H 6 productivity of 76.3 mol mol Au -1 h -1 with 95.2% selectivity, and TON of 1542.7 (TOF = 77.1 h -1 ) in a self-designed flow reactor, outperforming previously reported photocatalysts regardless of OCM and NOCM pathways. Also, under outdoor natural sunlight irradiation, the Au-WO 3 nanosheets exhibit similar activity and selectivity toward C 2 H 6 production, showing the possibility for practical applications. Interestingly, this strategy can be applied to other various photocatalysts (Au-WO 3 , Au-TiO 2 , Au-CeO 2 , Pd-WO 3 , and Ag-WO 3 ), showing a certain universality. It is expected that the proposed mechanism adds another layer to our understanding of CH 4 -to-C 2 H 6 conversion.