Integrons are important genetic elements that allow easy acquisition and dissemination of antimicrobial resistance genes. Studies reporting occurrence of integrons in Staphylococcus aureus (S. aureus) isolated from bovine mastitis in large dairy farms across China are scarce. The aim of this study was to investigate the occurrence of class 1 integrons (intI1), antimicrobial resistance (AMR) and associated genes in S. aureus isolated from bovine mastitis and their associations. Minimum inhibitory concentrations (MICs) were determined to evaluate the AMR phenotypes, whereas PCR was carried out to assess the occurrence of AMR genes and intI1. In addition, index cluster analysis was used to estimate associations between AMR phenotype, genotype and intI1 in 103 isolates. Overall, 83% of S. aureus were intI1-positive and 5 types of gene cassettes were detected. Susceptibility against single antimicrobial agents ranged from 0% (erythromycin), 12% (ampicillin) and 16% (penicillin G) to 96% (gentamicin). Most isolates (64%) were intermediate-resistant against erythromycin, whereas resistance against ceftriaxone (22%), clindamycin (4%), cefotaxime (2%), tetracycline (1%) and ciprofloxacin (1%) were relatively uncommon. The predominant resistant gene was blaZ gene (n = 88, 85%) followed by tetD gene (n = 85, 83%). With an estimated prevalence of 12% of the mecA gene, methicillin-resistant S. aureus isolates had higher MIC50 and MIC90 for majority of antimicrobials than methicillin-susceptible S. aureus isolates. Presence of the ermC gene was associated with erythromycin resistance. Ampicillin, erythromycin and penicillin G resistance were associated with intI1. The data presented in our study indicated that class 1 integron-mediated resistance possibly plays an important role in dissemination of AMR in S. aureus isolated from bovine mastitis.

To contribute to the treatment decision and optimize coagulase-negative staphylococcus (CNS) control programs, we conducted a meta-analysis to investigate the epidemiology and antimicrobial resistance rates of coagulase-negative staphylococcus associated with bovine mastitis in China. Three databases (PubMed, Google scholar and China National Knowledge Infrastructure database) were utilized to obtain relevant publications. A total of 18 publications were included in our research, and 3 of them included antimicrobial resistant (AMR) test. The pooled prevalence of coagulase-negative staphylococcus was 17.28%. Subgroup analysis revealed that the prevalence was higher in South China than in North China, was higher in 2011–2020 than in 2000–2010 and was higher in clinical bovine mastitis cases than in subclinical cases. The pooled AMR were most resistant to β-lactams, followed by tetracyclines, quinolones, nitrofurans, lincosamides, sulfonamides, amphenicol and aminoglycosides. The pooled AMR rate of coagulase-negative staphylococcus was lower in 2011–2020 than in 2000–2010. Although the prevalence of CNS showed an increasing trend over 20 years, the AMR rate showed a decreasing trend, and the clinical type of mastitis was the most frequent and the prevalence was highest in South China. Finally, CNS was most resistant to β-lactams amongst the eight groups of antimicrobial agents.

To generate optical vortex with multiple topological charges, a simple scheme based on the phase mask shaping technique is proposed and applied in a seeded free electron laser. With a tailored phase mask, an extreme-ultraviolet (EUV) vortex with multiple topological charges can be produced. To prove the feasibility of this method, an eight-step phase mask is designed to shape the seed laser. The simulation results demonstrate that 100-MW, fully coherent EUV vortex pulses with topological charge 2 can be generated based on the proposed technique. We have also demonstrated the possibility of generating higher topological charges by using a phase mask with more steps.

Biological hydrogel is important in drug delivery system and tissue engineering. In this paper, we prepared a series of biological hydrogels with N,O-carboxymethyl chitosan (CS) and oxidized safflower and ligusticum wallichii polysaccharide-II (oxidized SLWP-II). Morphological analysis indicated the N,O-carboxymethyl CS/oxidized SLWP-II hydrogels (CSLHs) had porous interior structures, pore diameter ranged from tens to hundreds of micrometers. In vitro release test showed, with proportion of N,O-carboxymethyl CS to oxidized SLWP increasing from 1:1 to 1:3, cumulative release of bovine serum albumin decreased from 99 to 82%. In vitro cytotoxicity study showed that the developed hydrogels were not cytotoxic during one week of culturing with WI-38 cells, and they have a role in promoting cell proliferation. So the N,O-carboxymethyl CS/oxidized safflower and ligusticum wallichii polysaccharide-II hydrogels might have potential application in the drug delivery system and tissue engineering.

The surface microstructure of shot peened (TiB + TiC)/Ti–6Al–4V is investigated using Rietveld whole pattern fitting method. The domain size and microstrain of them are obtained. By comparing the calculated results between them, it can be found that the microstructure variations of Ti–6Al–4V are more severe than those of (TiB + TiC)/Ti–6Al–4V, which is due to the effect of reinforcements' resistance to the deformation of the surface layer. The distribution of average domain size and microstrain of (TiB + TiC)/Ti–6Al–4V at varying depths are calculated, and the results are discussed in detail. Moreover, the probability distribution of the domain size at different depths is obtained using the lognormal distribution model. Based on the discussion, the results obtained from Rietveld whole pattern fitting method agree with the results calculated using the Voigt method, which reveals that the Rietveld method is an effective method of characterizing the surface microstructure of titanium matrix composites after shot peening treatments.

Fatigue crack growth tests of NiAl bronze (NAB) alloy heat treated at different temper temperature after quenching at 920 °C are performed using direct current potential drop method. The influences of heat treatment on the fatigue crack growth behavior of NAB alloy are investigated. The results show that the fatigue crack growth rate (FCGR) of NAB alloy decreases with the increase of temper temperature. A few large secondary cracks are obtained as the sample is tempered at 350 °C and the secondary cracks diminish with the increase of temper temperature. With further increasing temper temperature to 550 °C, a large number of small secondary cracks are obtained, which is responsible for its lower FCGR. The as-cast NAB alloy has a lower FCGR than that tempered at 550 °C at low stress intensity factor range (ΔK) region, and the lower FCGR is attributed to the crack deflection effect of the as-cast microstructure. At high ΔK region, the crack deflection effect diminishes, which leads to the higher FCGR of as-cast sample.

Step height is defined as the vertical spacing between two plane-parallel planes comprising an elevation or an indentation and the substrate. In atomic force microscopy (AFM), there are many algorithms for determining feature dimensions such as step height and width. One common problem of many algorithms is the difficulty for users to accurately determine the corner positions needed to properly implement the said algorithms. A new algorithm based on ISO 5436-1 is proposed that determines the necessary corner positions along with two examples illustrating the implementation of this algorithm. We propose calling this new method the determinant method. Since the corner positions are automatically decided, feature dimensions such as step height of an AFM image are easily determined. Comparative experiments carried out to compare the step height measurement using this algorithm and the SPIP software from Image Metrology show encouraging results.

The reversible switching between the amorphous and crystalline phases of Ge2Sb2Te5 (GST) is investigated with ab initio molecular dynamics. We apply different quench rates (-16 K/ps, -5 K/ps, -2 K/ps, and -0.45 K/ps) and different annealing temperatures (500 K, 600 K, 700 K, and 800 K) to amorphize and crystallize GST respectively. Results show that the generated amorphous is strongly dependent on the quench rate. For -16 K/ps and -5 K/ps, generated amorphous samples have different density of crystal seeds, higher in the later. The amorphous structure formed at -2 K/ps contains a single crystalline cluster, while that formed at the quench rate of -0.45 K/ps had sufficient time to completely crystallize the amorphous phase. Annealing the amorphous systems formed at different rates shows that crystallization depends both on the annealing temperature and on the structure of the initial system (i.e., whether or not it contains crystalline clusters or crystal seeds). At 500 K, formation of crystalline clusters occurs readily within a few ps while the rate at which they grow is slow, taking 0.9 ns to complete the crystallization. In contrast, crystalline cluster formation is inhibited at 800 K. In the intermediate temperature range, both crystalline cluster formation and growth occur within a few hundred ps indicating that these temperatures leads to the fastest crystallization. The crystallization of a 63-atom at ∼900 K resulted in a highly relaxed crystal structure showing a clear tendency for separation of Ge and Sb species in layers. This model also indicates a tendency of segregation of vacancies, suggesting that vacancy layering may play a key role in the crystallization process.

High-temperature titanium matrix composites reinforced with hybrid reinforcements are synthesized by common casting and hot working technologies. Tensile properties are tested at different temperatures and strain rates. Ultimate strengths of the composites are significantly enhanced under all conditions and decrease when the strain rate is lower. Equicohesive temperature of the matrix is around 873 K at the strain rate 10−3s−1 and well below 873 K at 10−5s−1. At higher temperature or lower strain rate, interfacial debonding is more drastic and reduces the strengths of composites. The materials are embrittled under creep-rupture conditions. Strict reinforcement morphology is required for more complex service conditions at high temperatures in metal matrix composites.

We report semi-empirical calculations of modified 3,3'-diethylthiacyanine iodide (DTC1), 3,3'-diethylthiacarbocyanine iodide (DTC3) and 3,3'-diethylthiadicarbocyanine iodide (DTC5), particularly with halogen substitution at the meso position in the polymethine bridge. Primarily we investigate geometrical changes and infer spectral trends from the molecular orbital levels. The semi-empirical calculations for the unsubstituted DTC3 agree well with an ab initio Hartree-Fock result. In all molecules multiple conformations are examined. Significant changes in dipole moments are noted between the cis and trans forms. Calculated electronic spectra at the CI singles level are compared to the measured spectra with reasonable agreement. Halogenation effects show a rotation of the benzthiazole groups out of planarity. We draw conclusions about consequent effects on solubility and excited state spectral changes.