应对可转移多黏菌素耐药性--饲料添加剂来源的白屈菜红碱具有双重效应

The emergence and spread of the mobile colistin-resistance gene,mcr-1,and its variants pose achallenge to the use of colistin,a last-resort antibiotic used to treat severe infections caused by extensively drug-resistant(XDR)Gram-negative pathogens.Antibiotic adjuvants are a promising strategy to enhance the efficacy of colistin against colistin-resistant pathogens;however,few studies have considered the effects of adjuvants on limiting resistance-gene transmission.We found that chelerythrine(4 mg·L^(-1))derived from Macleaya cordata extract,which is used as an animal feed additive,reduced the minimal inhibitory concentration(MIC)of colistin against an mcr-1 positive Escherichia coli(E.coli)strain by 16-fold(from 2.000 to 0.125 mg·L^(-1)).eliminated approximately 10^(4) colony-forming units(CFUs)of an mcr-1-carrying strain in a murine intestinal infection model,and inhibited the conjugation of an mcr-1-bearing plasmid in vitro(by>100-fold)and in a mouse model(by up to 5-fold).A detailed analysis revealed that chelery-thrine binds to phospholipids on bacterial membranes and increases cytoplasmic membrane fluidity,thereby impairing respiration,disrupting proton motive force(PMF),generating reactive oxygen species(ROS),and decreasing intracellular adenosine triphosphate(ATP)levels,which subsequently downregu-lates mcr-1 and conjugation-associated genes.These dual effects of chelerythrine can expand the use of antibiotic adjuvants and may provide a new strategy for circumventing mobile colistin resistance.

Experimental and numerical study of coal-rock bimaterial composite bodies under triaxial compression

To accurately predict coal burst hazards and estimate the failure of coal pillars in underground coal mining systems,it is of great significance to understand the mechanical behavior of coal-rock bimaterial composite structures.This paper presents experimental and numerical investigations on the response of rock-coal,coal-rock,and rock-coal-rock bimaterial composite structures under triaxial compression.The triaxial compression experiments are conducted under confining pressures in the range of 0-20 MPa.The resulting inside fracture networks are detected using X-ray-based computed tomography(CT).The experimentally observed data indicate that the mechanical parameters of the rock-coalrock composites are superior to those of the rock-coal and coal-rock combinations.After compression failure,the coal-rock combination specimens are analyzed via X-ray CT.The results display that the failure of the coal-rock composite bodies primarily takes place within the coal.Further,the bursting proneness is reduced by increasing confining pressure.Subsequently,the corresponding numerical simulations of the experiments are carried out by using the particle flow code.The numerical results reveal that coal is vulnerable with regard to energy storage and accumulation.

Aerodynamic characteristics of a high-speed train crossing the wake of a bridge tower from moving model experiments

In a strong crosswind,the wake of a bridge tower will lead to an abrupt change of the aerodynamic forces acting on a vehicle passing through it,which may result in problems related to the transportation safety.This study investigates the transient aerodynamic characteristics of a high-speed train moving in a truss girder bridge and passing by a bridge tower in a wind tunnel.The scaled ratio of the train,bridge,and tower are 1:30.Effects of various parameters such as the incoming wind speed,train speed,and yaw angle on the aerodynamic performance of the train were considered.Then the sudden change mechanism of aerodynamic loads on the train when it crosses over the tower was further discussed.The results show that the bridge tower has an apparent shielding effect on the train passing through it,with the influencing width being larger than the width of the tower.The train speed is the main factor affecting the influencing width of aerodynamic coefficients,and the mutation amplitude is mainly related to the yaw angle obtained by changing the incoming wind speed or train speed.The vehicle movement introduces an asymmetry of loading on the train in the process of approaching and leaving the wake of the bridge tower,which should not be neglected.

Presence and Antimicrobial Susceptibility of RE-cmeABC-Positive Campylobacter Isolated from Food-Producing Animals, 2014–2016

Campylobacter spp. are the leading cause of human gastroenteritis worldwide. RE-CmeABC is a newly identified resistance-enhancing multidrug efflux pump of Campylobacter spp. (C. spp.) that confers high-level resistance to fluoroquinolones, phenicols, macrolides, and tetracyclines (TETs), all of which are critical drugs in both human and veterinary medicine. In this study, we analyzed the presence and antimicrobial susceptibility of RE-cmeABC-positive Campylobacter isolates of food-animal origin from three representative regions (Shandong, Shanghai, and Guangdong) in China over three successive years, from 2014 to 2016. A total of 1088 Campylobacter isolates (931 C. coli and 157 C. jejuni) were recovered from the RE-cmeABC screening. We detected 122 (11.2%) RE-cmeABC-positive isolates of chicken origin, including 111 (70.7%) C. jejuni and 11 (1.2%) C. coli. This multidrug efflux pump is more prevalent among C. jejuni than C. coli. The level of resistance was significantly different in 111 RE-cmeABC-positive C. jejuni versus 46 RE-cmeABC-negative C. jejuni for florfenicol, clindamycin, and erythromycin (P < 0.05), but not for ciprofloxacin (CIP), TET, and gentamicin (GEN). However, the isolates harboring RE-cmeABC could shift the minimum inhibitory concentration distribution to the higher range for CIP and TET. Pulsed-field gel electrophoresis (PFGE) analysis suggested that horizontal transmission might be involved in the dissemination of RE-cmeABC in Shanghai and Guangdong, while clonal expansion was predominant in Shandong. Three isolates shared the indiscriminate PFGE types of RE-cmeABC-positive C. jejuni isolates in Shanghai and Guangdong, and four isolates in Shanghai and Shandong. Our study suggests the possibility of a wide dissemination of RE-cmeABC in Campylobacter of food-animal origin, which would pose a significant threat to public health.

Encrypted optical fiber tag based on encoded fiber Bragg grating array

Optical fibers are typically used in telecommunications services for data transmission,where the use of fiber tags is essential to distinguish between the different transmission fibers or channels and thus ensure the working functionality of the communication system.Traditional physical entity marking methods for fiber labeling are bulky,easily confused,and,most importantly,the label information can be accessed easily by all potential users.This work proposes an encrypted optical fiber tag based on an encoded fiber Bragg grating(FBG)array that is fabricated using a point-by-point femtosecond laser pulse chain inscription method.Gratings with different resonant wavelengths and reflectivities are realized by adjusting the grating period and the refractive index modulations.It is demonstrated that a binary data sequence carried by a fiber tag can be inscribed into the fiber core in the form of an FBG array,and the tag data can be encrypted through appropriate design of the spatial distributions of the FBGs with various reflection wavelengths and reflectivities.The proposed fiber tag technology can be used for applications in port identification,encrypted data storage,and transmission in fiber networks.

Transmission of Carbapenem Resistance Between Human and Animal NDM-Positive Escherichia coli Strains

Although carbapenem use is prohibited in animals in China,carbapenem-resistant Escherichia coli(CREC),especially New Delhi metallo-β-lactamase(NDM)-producing strains,are widely prevalent in foodproducing animals.At present,the impact of livestock-associated CREC strains on human populations at the national level is unknown.Here,we conduct a retrospective cross-sectional study to investigate the prevalence of CREC from clinical settings across 22 Chinese provinces or municipalities and analyze anthropogenic factors associated with their presence.We also ascertain the blaNDMand blaKPCabundance among pig and chicken farms and present a detailed genomic framework for CREC of animal and human origin.Overall,631/29799(2.1%)clinical Escherichia coli(E.coli)isolates were identified as CREC.Multivariable analysis revealed that being male,an age below 1,an age between 13 and 18,provinces with greater chicken production,and provinces with higher pig production were associated with higher odds of CREC infection.In general,73.8%(n=45/61)of pig farms and 62.2%(n=28/45)of chicken farms had a blaNDMabundance of 1×10^(-5)to 1×10^(-3)and 1×10^(-3)to 1×10^(-2),respectively.Among all the Chinese NDM-positive E.coli(n=463)available at the National Center for Biotechnology Information(NCBI),the genomic analysis revealed that blaNDM-5and Inc X3 were the predominant carbapenemase gene-plasmid combination,while a highly homogeneous relationship between NDM-positive isolates from humans and animals was demonstrated at the plasmid and core genome levels.All the findings suggest frequent CREC transmission between humans and animals,indicating that further discussions on the use of antibiotics in animals and humans are needed,both in China and across the globe.

Research on mechanical performance of longitudinal joints in segmental tunnel linings strengthened by fiber-reinforced plastic grid with polymer−cement−mortar method

In this study,we propose the use of a fiber-reinforced plastic grid with polymer−cement−mortar(FRP Grid-PCM)to reinforce segment joints in tunnel shield linings.These joints play a crucial role in determining bearing capacity but are vulnerable to deterioration during operation.To investigate how to enhance the flexural performance of longitudinal shield lining joints,we built eccentric short column specimens by bolting two half-corbel columns together and tested them in the laboratory.The test program comprised two control specimens and three strengthened specimens with FRP grid applied on one side,away from the axial load.The tests varied two main parameters:loading eccentricity and the number of FRP grid layers.We conducted a detailed analysis of the failure process,bearing capacity,and bending stiffness of longitudinal joints under different conditions.Furthermore,we developed an analytical model to predict the flexural bearing capacity of longitudinal joints upgraded with the FRP Grid-PCM method and validated it through experimental results.The research demonstrates that the FRP grid effectively reduces joint opening and rotation angles while enhancing the bearing capacity of the short column,particularly with concurrent increases in loading eccentricity and the number of FRP grid layers.Overall,our findings offer a novel alternative for improving the flexural performance of longitudinal joints in shield tunnels.

Epidemiology and genetic characterization of tet(X4)-positive Klebsiella pneumoniae and Klebsiella quasipneumoniae isolated from raw meat in Chengdu City, China

The rapid spread of mobile tigecycline resistance presents a significant public health threat,particularly with the increasing prevalence of tet(X4)-positive Enterobacterales across various species.This study aimed to inves-tigate the epidemic features and transmission dynamics of tet(X4)-positive Klebsiella pneumoniae(K.pneumo-niae)through the analysis of 206 raw meats,including pork(n=182),beef(n=16),duck(n=5),and chicken(n=3).These samples were collected from schools,markets,and restaurants in Chengdu City,China.A total of 25 isolates were obtained from 13 administrative regions.All isolates exhibited resistance to tetracycline,tigecycline,ampicillin,chloramphenicol,and florfenicol.Over half of the isolates also demon-strated resistance to streptomycin(80%),sulfamethoxazole/trimethoprim(72%),ciprofloxacin(64%),and ampicillin/sulbactam(56%).Among these strains,14 distinct sequence types(STs)were identified,revealing evidence of inter-regional clonal spread,notably among 9 K.pneumoniae ST3393.Phylogenetic analysis revealed the presence of two K.pneumoniae ST5 closely resembling hypervirulent K.pneumoniae from Jiangsu.Importantly,12 isolates were capable of transferring tigecycline resistance to Escherichia coli J53.Further plasmid analysis showed that the tet(X4)-harboring plasmids in K.pneumoniae could be classified into four types,primarily belonging to the IncFIA(HI1)/HI1A/HI1B hybrid plasmid(n=16)and IncFII plasmid(n=7),which significantly contributed to the cross-species dissemination of tet(X4).In summary,this study highlights the prevalence of MDR tet(X4)-positive K.pneumoniae in Chengdu,driven predominantly by clonal expansion and plasmid-mediated horizontal gene transfer.These findings emphasize the importance of contin-uous surveillance of tet(X4)-positive K.pneumoniae in raw meat and the implementation of effective measures to control their spread.

Microstructured Cantilever Probe on Optical Fiber Tip for Microforce Sensor

Benefiting from the great advances of the femtosecond laser two-photon polymerization(TPP)technology,customized microcantilever probes can be accurately 3-dimensional(3D)manufactured at the nanoscale size and thus have exhibited considerable potentials in the fields of microforce,micro-vibration,and microforce sensors.In this work,a controllable microstructured cantilever probe on an optical fiber tip for microforce detection is demonstrated both theoretically and experimentally.The static performances of the probe are firstly investigated based on the finite element method(FEM),which provides the basis for the structural design.The proposed cantilever probe is then 3D printed by means of the TPP technology.The experimental results show that the elastic constant k of the proposed cantilever probe can be actively tuned from 2.46N/m to 62.35N/m.The force sensitivity is 2.5nm/μN,the Q-factor is 368.93,and the detection limit is 57.43nN.Moreover,the mechanical properties of the cantilever probe can be flexibly adjusted by the geometric configuration of the cantilever.Thus,it has an enormous potential for matching the mechanical properties of biological samples in the direct contact mode.

Impact of various vaccine boosters on neutralization against omicron following prime vaccinations with inactivated or adenovirus-vectored vaccine

SARS-CoV-2 Omicron变异株已在全球范围内广泛传播.包括中国在内的许多国家广泛接种了SARS-CoV-2灭活疫苗(IAV)、重组蛋白疫苗(PRV)和腺病毒载体疫苗(Ad V),以达到群体免疫效果.该研究系统评价了完成不同疫苗全程接种后以及接种不同疫苗加强针后的341份人血清对原始毒株和Omicron变异株的交叉中和活性.研究发现,所有类型疫苗诱导的针对Omicron变异株BA.1的中和抗体水平都明显低于原始毒株.初免疫IAV和Ad V后,分别接种Ad V和PRV的异源加强针可以最大程度地提高血清对Omicron中和活性.此外,该研究使用m RNA疫苗在小鼠模型中评估了初次免疫编码Spike蛋白的m RNA疫苗后,加强免疫编码原始毒株或者不同突变株RBD蛋白的m RNA疫苗对Omicron中和效果.结果发现,与原始毒株加强针相比,只有Omicron加强针疫苗显著地提升了Omicron的中和抗体水平.该研究对各种疫苗加强针的系统性评价可为接下来对抗Omicron变异株的免疫接种提供参考.

Stress corrosion behavior of 2195-T8 Al-Li alloy with an artificial pit exposed to a 30vol%HNO3 solution

This paper experimentally studied the stress corrosion behavior of 2195-T8 Al-Li alloys with prefabricated pits in 30vol%HNO3.The microstructure was observed and determined by the scanning electron microscopy and the transmission electron microscopy.The typical corrosion features,i.e.,regular or irregular corrosion pits and sub/intergranular corrosion,were investigated,and the role of stress were analyzed.The statistical results of the number and area of corrosion pits in various sizes were studied using an improved image processing method.Experimental results demonstrate that stress affects the intergranular corrosion or sub-intergranular corrosion of the alloy most,and promotes them to evolve into cracks under stress corrosion.Stress also plays a role in accelerating corrosion severity of certain corrosion feature.The number of corrosion pits with an area of 0–50μm~2 can be seen as an index to reflect the degree of corrosion.Besides,a corrosion phenomenon,i.e.,the pit bottom in the site with the maximum stress locally suffering from no severe corrosion,was observed and discussed.

Numerical Simulation of a Multi-Frequency Resistivity Logging-While-Drilling Tool Using a Highly Accurate and Adaptive Higher-Order Finite Element Method

A novel,highly efficient and accurate adaptive higher-order finite element method(hp-FEM)is used to simulate a multi-frequency resistivity loggingwhile-drilling(LWD)tool response in a borehole environment.Presented in this study are the vector expression of Maxwell’s equations,three kinds of boundary conditions,stability weak formulation of Maxwell’s equations,and automatic hpadaptivity strategy.The new hp-FEM can select optimal refinement and calculation strategies based on the practical formation model and error estimation.Numerical experiments show that the new hp-FEM has an exponential convergence rate in terms of relative error in a user-prescribed quantity of interest against the degrees of freedom,which provides more accurate results than those obtained using the adaptive h-FEM.The numerical results illustrate the high efficiency and accuracy of the method at a given LWD tool structure and parameters in different physical models,which further confirm the accuracy of the results using the Hermes library(http://hpfem.org/hermes)with a multi-frequency resistivity LWD tool response in a borehole environment.

Low-velocity impact response and infrared radiation characteristics of thermoplastic/thermoset composites

The low-velocity impact response and infrared radiation characteristics of composites have rarely been focused on simultaneously.This study aims to investigate the low-velocity impact response and infrared radiation characteristics of the glass fiber reinforced thermoplastic polypropylene and carbon fiber reinforced thermosetting epoxy resin laminates wildly used in the aircraft industry.The impact tests were conducted at five energy levels.Characterization parameters such as impact load,displacement,and absorbed energy were measured.The damage evolution and damage modes of the laminates were analyzed through active and passive thermography,ultrasonic C-scan,and optical microscope.The results indicate that Thermosets(TS)laminates exhibit better impact resistance,while Thermoplastics(TP)laminates show higher delamination ductility,and the maximum contact force of TP laminates is much smaller than that of the TS laminates under lowvelocity impacts,but the low bending stiffness and low ductility of the TP matrix cause the difference in energy absorption level between the two not significant.The temperature characteristic changes of passive infrared thermography heat maps could characterize the damage mode of the laminates.The correlation between the heat maps and the impact characteristic curves is explained;the fluctuation of the impact characteristic curves is directly related to the hot spot characteristics changes of the heat maps.More frequent curve fluctuations correspond to a larger and brighter hot spot on the heat map,which peaks at the maximum impact load after the impact force versus time curve fluctuation cutoff point,the maximum center displacement of the impact force versus displacement curve,and the maximum absorbed energy of the absorbed energy versus time curve.

Osthole ameliorates myonecrosis caused by Clostridium perfringens type A infection in mice

This study aimed to investigate the protective effect of the nature product osthole(OST)against Clostridium perfrin-gens type A infection-caused myonecrosis in a mouse model.Male mice were divided into(1)control,(2)infected,(3)OST50 and(4)OST100 treatment groups.In the infected groups,mice were intramuscularly injected with 1×10^(8) CFU of C.perfringens per day for 6 days.Mice in the OST50 and OST100 groups were administrated intraperitoneally with OST at the doses of 50 or 100 mg/kg per day post C.perfringens infection.Our results showed that C.perfringens infection caused marked necrosis and inflammatory cell infiltration in the muscle tissues of mice.Mice in the OST50 and OST100 treatment groups displayed significantly attenuated C.perfringens infection-induced lipid peroxida-tion,oxidative stress,and apoptosis in their muscle tissue.Furthermore,OST treatment significantly downregulated the expressions of NF-κB,IL-1β,and TNF-αmRNA and protein levels,while concomitantly upregulating the expressions of Nrf2 and HO-1 mRNA and protein.OST treatments also inhibited the expression of phosphorylation(p)-p38,p-mTOR,and p-Erk1/2 proteins,and upregulated LC3II and Beclin1 proteins.In summary,our results reveal that OST therapy confers a protective effect against C.perfringens infection-induced oxidative stress and inflammation in muscle tissue,via activation of Nrf2/HO-1 and autophagy pathways and inhibition of p38,Erk1/2 and NF-κB pathways.