Time-delay control scheme with adaptive fixed-time convergent super-twisting fractional-order nonsingular terminal sliding mode for piezoelectric displacement amplifier.

Piezoelectric displacement amplifiers (PDAs) have been widely used in precision positioning fields. However, the inherent hysteresis and creep nonlinear effect of piezoelectric actuators (PEAs) and time-varying lumped disturbances bring extreme challenges to the precise motion control of PDAs. Although various control schemes based on PEAs have been developed and have shown significant results. However, due to the high sensitivity of precision positioning to environmental variations, the development and identification of accurate models and the control timeliness often become obstacles in engineering. To realize precise motion control of PDAs under complex lumped disturbances, a new time-delay control scheme (AFSTA-FONTSM) using an adaptive fixed-time convergent super-twisting algorithm (AFSTA) and a fractional-order nonsingular terminal sliding mode (FONTSM) is proposed. Specifically, the time-delay information obtained by time-delay estimation technology is used to estimate the lumped dynamic characteristic of the system, thus establishing a simple control framework without a system dynamic model. FONSTM is constructed as a sliding mode manifold, and satisfactory error dynamic characteristic is obtained. A new AFSTA is designed as the reaching law in the sliding mode phase. AFSTA has fixed-time convergence when the upper bound of lumped disturbances exists, which ensures the control timeliness. Benefiting from the newly designed adaptive algorithm, the upper bound value of lumped disturbances is no longer needed to determine the control gains, which effectively prevents overestimation of the control gains. Correspondingly, the convergence time of AFSTA is estimated, and the stability of the closed-loop system is analyzed by the Lyapunov theory. Three existing time-delay control schemes, namely MSTA-FONTSM, AMSTA-FONTSM, and ASTA-FONTSM are selected, and four scenes are designed for comparative experiments. The experimental results show that MSTA-FONTSM has the worst control performance among the four control schemes. For the step, and continuous cosine trajectories with periods of T = 1 s and T = 2 s, the root-mean-square error of the proposed AFSTA-FONTSM is reduced by 56.86%, 54.03%, and 50.24% compared with MSTA-FONTSM. For disturbance experiments under different loads, the control performance of the proposed AFSTA-FONTSM is still superior to the other three control schemes without load.

The multidrug-resistant Pseudomonas fluorescens strain: a hidden threat in boar semen preservation.

Although the bacterial composition of boar ejaculate has been extensively studied, the bacterial composition of extended boar semen is often overlooked, despite the potential risks these microorganisms may pose to the long-term preservation of extended boar semen at 15-17°C. In this study, we characterized the bacterial community composition of extended semen and discovered that Pseudomonas spp. was the dominant flora. The dominant strains were further isolated and identified as a potential new species in the Pseudomonas fluorescens group and named GXZC strain, which had adverse effects on sperm quality and was better adapted to growth at 17°C. Antimicrobial susceptibility testing showed that the GXZC strain was resistant to all commonly used veterinary antibiotics. Whole-genome sequencing (WGS) and genome annotation revealed the large genetic structure and function [7,253,751 base pairs and 6,790 coding sequences (CDSs)]. Comparative genomic analysis with the closest type strains showed that the GXZC strain predicted more diversity of intrinsic and acquired resistance genes to multi-antimicrobial agents. Taken together, our study highlights a problem associated with the long-term storage of extended boar semen caused by a P. fluorescens group strain with unique biological characteristics. It is essential to develop a new antibacterial solution for the long-term preservation of boar semen.

Fitness Trade-Offs in Phage Cocktail-Resistant Salmonella enterica Serovar Enteritidis Results in Increased Antibiotic Susceptibility and Reduced Virulence.

The rapid emergence of phage-resistant bacterial mutants is a major challenge for phage therapy. Phage cocktails have been considered one approach to mitigate this issue. However, the synergistic effect of randomly selected phages in the cocktails is ambiguous. Here, we rationally designed a phage cocktail consisting of four phages that utilize the lipopolysaccharide (LPS) O antigen, the LPS outer core, the LPS inner core, and the outer membrane proteins BtuB and TolC on the Salmonella enterica serovar Enteritidis cell surface as receptors. We demonstrated that the four-phage cocktail could significantly delay the emergence of phage-resistant bacterial mutants compared to the single phage. To investigate the fitness costs associated with phage resistance, we characterized a total of 80 bacterial mutants resistant to a single phage or the four-phage cocktail. We observed that mutants resistant to the four-phage cocktail were more sensitive to several antibiotics than the single-phage-resistant mutants. In addition, all mutants resistant to the four-phage cocktail had significantly reduced virulence compared to wild-type strains. Our mouse model of Salmonella Enteritidis infection also indicated that the four-phage cocktail exhibited an enhanced therapeutic effect. Together, our work demonstrates an efficient strategy to design phage cocktails by combining phages with different bacterial receptors, which can steer the evolution of phage-resistant strains toward clinically exploitable phenotypes. IMPORTANCE The selection pressure of phage promotes bacterial mutation, which results in a fitness cost. Such fitness trade-offs are related to the host receptor of the phage; therefore, we can utilize knowledge of bacterial receptors used by phages as a criterion for designing phage cocktails. Here, we evaluated the efficacy of a phage cocktail made up of phages that target four different receptors on Salmonella Enteritidis through in vivo and in vitro experiments. Importantly, we found that pressure from phage cocktails with different receptors can drive phage-resistant bacterial mutants to evolve in a direction that entails more severe fitness costs, resulting in reduced virulence and increased susceptibility to antibiotics. These findings suggest that phage cocktail therapy using combinations of phages targeting different important receptors (e.g., LPS or the efflux pump AcrAB-TolC) on the host surface can steer the host bacteria toward more detrimental surface mutations than single-phage therapy, resulting in more favorable therapeutic outcomes.

Effect of Sow Intestinal Flora on the Formation of Endometritis.

Endometritis is the main cause of decreased reproductive performance of sows, while one of the most important factors in the etiology of sow endometritis is an aberration of birth canal microbiota. Therefore, people began to pay attention to the microbiota structure and composition of the birth canal of sows with endometritis. Interestingly, we found that the risk of endometritis was increased in the sows with constipation in clinical practice, which may imply that the intestinal flora is related to the occurrence of endometritis. Therefore, understanding the relationship between birth canal microbiota and intestinal microbiota of the host has become exceptionally crucial. In this study, the microbiota of birth canal secretions and fresh feces of four healthy and four endometritis sows were analyzed via sequencing the V3 + V4 region of bacterial 16S ribosomal (rDNA) gene. The results showed a significant difference between endometritis and healthy sows birth canal flora in composition and abundance. Firmicutes (74.36%) and Proteobacteria were the most dominant phyla in birth canal microbiota of healthy sows. However, the majority of beneficial bacteria that belonging to Firmicutes phylum (e.g., Lactobacillus and Enterococcus) declined in endometritis sow. The abundance of Porphyromonas, Clostridium sensu stricto 1, Streptococcus, Fusobacterium, Actinobacillus, and Bacteroides increased significantly in the birth canal microbiota of endometritis sows. Escherichia-Shigella and Bacteroides were the common genera in the birth canal and intestinal flora of endometritis sows. The abundance of Escherichia-Shigella and Bacteroides in the intestines of sows suffering from endometritis were significantly increased than the intestinal microbiota of the healthy sows. We speculated that some intestinal bacteria (such as Escherichia-Shigella and Bacteroides) might be bound up with the onset of sow endometritis based on intestinal microbiota analysis in sows with endometritis and healthy sows. The above results can supply a theoretical basis to research the pathogenesis of endometritis and help others understand the relationship with the microbiota of sow's birth canal and gut.

Forward and Inverse Dynamics of a Six-Axis Accelerometer Based on a Parallel Mechanism.

The solution of the dynamic equations of the six-axis accelerometer is a prerequisite for sensor calibration, structural optimization, and practical application. However, the forward dynamic equations (FDEs) and inverse dynamic equations (IDEs) of this type of system have not been completely solved due to the strongly nonlinear coupling relationship between the inputs and outputs. This article presents a comprehensive study of the FDEs and IDEs of the six-axis accelerometer based on a parallel mechanism. Firstly, two sets of dynamic equations of the sensor are constructed based on the Newton-Euler method in the configuration space. Secondly, based on the analytical solution of the sensor branch chain length, the coordination equation between the output signals of the branch chain is constructed. The FDEs of the sensor are established by combining the coordination equations and two sets of dynamic equations. Furthermore, by introducing generalized momentum and Hamiltonian function and using Legendre transformation, the vibration differential equations (VDEs) of the sensor are derived. The VDEs and Newton-Euler equations constitute the IDEs of the system. Finally, the explicit recursive algorithm for solving the quaternion in the equation is given in the phase space. Then the IDEs are solved by substituting the quaternion into the dynamic equations in the configuration space. The predicted numerical results of the established FDEs and IDEs are verified by comparing with virtual and actual experimental data. The actual experiment shows that the relative errors of the FDEs and the IDEs constructed in this article are 2.21% and 7.65%, respectively. This research provides a new strategy for further improving the practicability of the six-axis accelerometer.

Complete genomic sequence and analysis of ß2 toxin gene mapping of Clostridium perfringens JXJA17 isolated from piglets in China.

Clostridium perfringens (Cp) is a ubiquitous opportunistic pathogen of humans and animals in the natural environment and animal intestines. The pathogenicity of Cp depends on the production of toxins encoded by genes on the chromosomes or plasmids. In contemporary literature, there is no clear consensus about the pathogenicity of CpA ß2 toxin. To analyze the homology of the genome of piglet source CpA and its ß2 toxin, we sequenced the whole genome of strain JXJA17 isolated from diarrhea piglets using the Illumina Miseq and Pacbio Sequel platforms. The genome was composed of a circular chromosome with 3,324,072 bp (G + C content: 28.51%) and nine plasmids. Genome and 16S rDNA homology analysis revealed a close relation of the JXJA17 strain with the JGS1495, Cp-06, Cp-16, and FORC_003 strains. These strains were isolated from different samples and belonged to different toxin-types. JXJA17 strain was found to carry two toxin genes (plc and cpb2). In contrast to other Cp strains, the cpb2 of JXJA17 was located on a large plasmid (58 kb) with no co-localization of other toxin genes or antibiotic resistance genes. Analysis of JXJA17 genome homology and its cpb2 would facilitate our further study the relationship between ß2 toxin and piglet diarrhea.

Diversity analysis of intestinal microflora between healthy and diarrheal neonatal piglets from the same litter in different regions.

Though the problem of neonatal piglet diarrhea is well known, the differences in the bacterial diversity and community composition between healthy and diarrheal piglets are still unknown. We investigated these differences in neonatal piglets from Jiangxi Province, China. Healthy (H, n = 20) and diarrheal (D, n = 20) piglets were selected from six regions. The fecal microbial communities were analyzed by sequencing the V3V4 region of 16S rRNA gene. We found the ratio of major phyla (Fusobacteria, Bacteroidetes, Firmicutes and Proteobacteria) was >99% of 7 phyla. The overall alpha diversity indices, such as chao, sobs, coverage and Shannon, were not significantly different. Moreover, the relative abundance of the predicted functions was highly similar in the two groups. Our results indicated that Clostridium was divided into two major groups: Clostridium sensu stricto_1 and stricto_2. Sensu stricto_2 was highly abundant in the D group and low abundance in the H group, whereas the results of sensu stricto_1 were opposite. Comparative analyses within the H or D groups showed that Escherichia-Shigella and Streptococcus at the genus level and unclassified Lactobacillus at the species level were significant difference. Comparative analyses of the two groups showed that unclassified Prevotellaceae at the genus level and Fusobacterium mortifierum were significantly different and had high linear discriminant analysis (LDA) scores. The significantly different microbes composition results also existed in the same litter, based on excluding regions influence. These results suggested that piglet diarrhea was closely associated with these microbes. This study provides insights into gut microbial interactions and prevention of piglet diarrhea.

Detection of Gallibacterium anatis by TaqMan fluorescent quantitative PCR.

To better understand the prevalence of Gallibacterium anatis in different poultry species, a rapid and accurate method was developed to detect G. anatis using a TaqMan fluorescent quantitative polymerase chain reaction (qPCR). Specific primers and a TaqMan probe were designed based on the reference gtxA gene sequence. The qPCR standard curve showed a good linear relationship, and the method showed good reproducibility, sensitivity, and specificity, indicating its suitability for G. anatis identification and quantitative analysis. A comparison of the detection results in 160 clinical swab samples showed that the detection rate (54.4%) of the qPCR for G. anatis was better than that of two conventional methods: gyrB gene-based qPCR for G. anatis (51.9%) and culture-based identification (34.4%). G. anatis was detected in layer chicken (77.3%), Silkie chicken (72.7%), and duck (27.1%) with relatively high detection rates, whereas dove (8.8%) and quail (3.0%) showed lower detection rates, indicating the different prevalence of G. anatis in different fowl species.