Salmonella Typhimurium is a common pathogen infecting the gastrointestinal tract of humans and animals, causing host gastroenteritis and typhoid fever. Heat shock protein (HtpG) as a molecular chaperone is involved in the various cellular processes of bacteria, especially under environmental stress. However, the potential association of HtpG with S. Typhimurium infection remains unknown. In this study, we clarified that HtpG could also play a role as an effector in S. Typhimurium infection. RNA-seq indicated that the flagellar assembly pathway, infection pathway, and chemotaxis pathway genes of S. Typhimurium were downregulated after the mutation of HtpG, which resulted in compromises of S. Typhimurium motility, biofilm formation, adhesion, invasion, and inflammation-inducing ability. In addition, HtpG recombinant protein was capable of promoting the proliferation of S. Typhimurium in host cells and the resultant inflammation. Collectively, our results illustrated an important role of HtpG in S. Typhimurium infection.
This paper establishes a Finite Element (FE) model of a rigid barrier impact of a single vehicle constructed from carbon steel, stainless steel, and aluminum alloy, which are three typical materials used in metro vehicle car body structures. The different responses of the three materials during the collision are compared. According to the energy absorption, velocity, deformation and collision force flow characteristics of each vehicle, the relationship between the energy absorption ratio of the vehicle body and the energy absorption ratio of its key components is proposed. Based on the collision force flow distribution proportion of each component, the causes of the key components’ deformation are analysed in detail. The internal relationship between the deformation, energy absorption and impact force of the key components involved in a car body collision is elucidated. By determining the characteristic parameters describing the vehicle’s dynamic stiffness, a metro vehicle frontal impact model using lumped parameters is established that provides a simple and efficient conceptual design method for railway train safety design. These research results can be used to guide the design of railway trains for structural crashworthiness.
The microstructures and corrosion resistance of electromagnetic stirring (EMS) semi-solid slurry and as-cast 7A04 aluminum alloy were compared in this work. The results show that the primary microstructure of the as-cast 7A04 aluminum alloy is mainly dendritic and columnar dendrite with obvious elements segregation. In contrast, semi-solid processing can effectively form homogeneous and round primary α-Al grains, and significantly reducing element segregation. In addition, the main phases of the two forming methods (as-cast and semi-solid) both involved α-Al, η-MgZn2, θ-Al2Cu. With the decrease of solidification temperature, the semi-solid alloy formed by electromagnetic stirring increases the precipitation of brittle phase S-Al2CuMg. The self-corrosion potential of the semi-solid alloy is greater than that of the as-cast alloy, and the polarization curve has obvious passivation characteristics. Semi-solid processing could improve corrosion resistance of 7A04 aluminum alloy obviously.
An efficient procedure for the fabrication of highly force‐sensitive aligned and suspended primitive single‐walled carbon nanotube (SWNT) devices is developed. First, an array of individual ultra‐long SWNTs is grown by chemical vapor deposition and suspended between two adjacent Au electrodes adhered on a breakable Si wafer. Armchair metallic SWNTs and low‐resistivity quasi‐metallic SWNTs are then selectively removed from the suspended SWNT array to upgrade the electromechanical mechanism of this type of sensitive device by strain‐based electrical burn‐off. Second, energy band and thermoelectronic emission theories in semiconductor physics are combined to calculate and analyze the effect of the length of the suspended SWNT on the aforementioned burn‐off method. The increase in length of the suspended SWNT section facilitates the easy electromechanical characteristic optimization of the suspended SWNT array. Moreover, the suspended SWNT array has a strong electromechanical response after strain‐based electrical burn‐off with sensitivity (gauge factor) of more than 600, linearity of less than 8.27%, and no hysteresis. Finally, the thermal effect is discussed in terms of this analytical method and experimental results.
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