Relationship model between surface strain of concrete and expansion force of reinforcement rust.

Concrete cracking caused by corrosion of reinforcement could significantly shorten the durability of reinforced concrete structure. It remains critical to investigate the process and mechanism of the corrosion occurring to concrete reinforcement and establish the theoretical prediction model of concrete expansion force for the whole process of corrosion cracking of reinforcement. Under the premise of uniform corrosion of reinforcing steel bars, the elastic mechanics analysis method is adopted to analyze the entire process starting from the corrosion of steel bars to the cracking of concrete due to corrosion. A relationship model between the expansion force of corrosion of steel bars and the surface strain of concrete is established. On the cuboid reinforced concrete specimens with square cross-sections, accelerated corrosion tests are carried out to calibrate and verify the established model. The model can be able to estimate the real-time expansion force of reinforced concrete at any time of the whole process from the initiation of steel corrosion to the end of concrete cracking by measuring the surface strain of concrete. It could be useful for quantitative real-time monitoring of steel corrosion in concrete structures.

Incidence, severity and tolerability of pneumothorax following low-dose CT-guided lung biopsy in different severities of COPD.

BACKGROUND: The feasibility of pneumothorax following low-dose CT-guided puncture lung biopsy in different severities of COPD has not been reported. METHODS: The data of the patients with pulmonary lesion who underwent low-dose CT-guided lung biopsy by one experienced operator in our hospital from January 1st to September 30th in 2019 were retrospectively collected. They were divided into COPD group and non-COPD group. The risk factors, incidence and severity of pneumothorax with the severity of COPD and changes in MMRC score, treatment way and discharge time after pneumothorax were assessed. RESULTS: Two hundred and nineteen patients were retrospectively enrolled in this study with 64 in the COPD group and 155 in the non-COPD group. The average age, MMRC score and the incidence of pneumothorax after biopsy were significantly higher in the COPD group (64.7 ± 1.27 years, 1.02 ± 0.13, 31.3%) than in the non-COPD group (58.8 ± 1.16 years, 0.35 ± 0.06, 17.4%, P < 0.05). The incidence of pneumothorax between I-II and III-IV in COPD did not reach the significant difference (P = 0.863). COPD was the only independent risk factor for pneumothorax after biopsy in a multivariable regression (P < 0.05). MMRC score was significantly increased at post-pneumothorax in the two groups (P < 0.001). There was no significant difference in diagnostic rate, severity of pneumothorax, the proportion of delayed pneumothorax, the changes in treatment way and discharge time between the two groups (P > 0.05). CONCLUSION: Although the incidence of pneumothorax after low dose CT-guided lung biopsy is increased in COPD, there was no difference in the severity of pneumothorax amongst the different severities of COPD and it is well-tolerated without increasing medical burden.

Identification of a multiple drug-resistance gene island in the Haemophilus parasuis chromosome.

OBJECTIVES: The aim of this study was to determine the mechanisms and molecular characterisation of one strain (HPS412) of Haemophilus parasuis, which exhibited high MICs of antimicrobial susceptibility. METHODS: A total of 113 H. parasuis strains isolated from pigs suffering from polyserositis, pneumonia or meningitis in China and screened them for antimicrobial susceptibility. Susceptibility testing of the minimal inhibitory concentrations (MIC) was determined in fastidious medium consisting of tryptone soya broth (TSB) containing 5% bovine serum and 10µg/mL NAD in 96-well microtiter plates. The genomic DNA was completely sequenced by combining PacBio RS II and Illumina HiSeq 4000 platforms. Gene prediction was performed using Glimmer v.3.02 with Hidden Markov models. RESULTS: One strain (HPS412) exhibited high MICs of sulfamethoxazole (256µg/mL), tetracycline (128µg/mL), streptomycin (128µg/mL), gentamicin (128µg/mL), amoxicillin (128µg/mL), chloramphenicol (64µg/mL), penicillin (64µg/mL) and cefaclor (64µg/mL). Sequence analysis showed that numerous drug-resistance genes including tet(B), blaROB-1, sul2, catIII, aph(3″)-Ib, aph(6)-Id and aph(3')-Ia were present in a chromosomal gene island as adjacent duplicate copies and the rep-orf3-blaROB-1 structure most likely had a direct plasmid origin. The tet(B) and blaROB-1 were flanked on one or both by ISApl1 elements. CONCLUSIONS: The acquisition of blaROB-1 and the other antibiotic resistance genes was related to the presence of ISApl1. ISApl1 plays important roles in the horizontal transmission of antibiotic resistance genes.