Staphylococcus aureus isolates (n = 30) from the environment or from surgical patients in a hospital in Guangzhou, China were investigated for the presence of class 1 integrons. The class 1 integrase (intI1) gene and its 3' conserved segment were detected by PCR. IntI1-positive isolates were further analysed for the presence of resistance gene cassettes using specific primers, intI1-K and In-B. All isolates were also subjected to multilocus sequence typing (MLST) and random amplified polymorphic DNA (RAPD)-PCR analysis. Sixteen (53%) clinical and environmental isolates were positive for the class 1 integrase gene and were also found to possess the aadA2 gene. The 30 isolates were classified into six distinct genotypes by RAPD-PCR analysis: type A (n = 2); type B (n = 2); type C (n = 3); type D (n = 7); type E (n = 8); and type F (n = 8). All isolates belonged to the same sequence type (ST239) by MLST. These results indicated transmission of S. aureus between the environment and patients, as well as the probability of nosocomial infection.

As a novel antibiotic resistance determinant, investigation of the occurrence and characteristics of class 1 integron was performed on nosocomial methicillin-resistant Staphylococcus aureus (MRSA) strains sampled during 2001-2006. Seventy-six out of 179 (42.5%) of the tested strains were found to carry class 1 integrons, with four unique arrays of gene cassettes detected. This is the first report of the comprehensive identification and typing of class 1 integrons in clinical MRSA isolates over a 6-year period, representing the first evidence for class 1 integrons as possible antibiotic resistance determinants in clinical MRSA strains.

The reaction process and corresponding mechanism of coagulation and gelation of native soy protein isolates (SPIs) induced by microbial transglutaminase (MTGase) were investigated. The protein constituents of SPIs, including a majority of subunits of β‐conglycinin and acidic subunits of glycinin, could be polymerized by MTGase to form high weight molecular (WM) biopolymers. Both the coagulation and gelation reactions of native SPI solutions induced by MTGase were dependent upon the initial protein substrate concentration ([C] 0 ). In the coagulating reactions, the turbidity of SPI solutions continually increased with increasing [C] 0 in the range from 0.25 to 3.0%. As for the gelation reactions, with the concentration increasing from 3 to 8% (w/v), the onset time of gelation of native SPIs induced by 0.8 units/mL of MTGase at 37C shortened by ∼5‐fold, and the storage modulus (G′) of finally formed gels (after 4 h) increased from ∼1 to 1300 Pa. Both the coagulation and gelation reactions of SPI solutions were promoted remarkably by increasing the enzyme concentration. Sodium Dodecyl Sulfate‐Polyacrylamide Gel Electrophoresis analysis showed that the protein constituents of MTGase‐induced aggregates of SPI (2% w/v) were mainly composed of basic subunits of glycinin and some of newly cross‐linked high MW biopolymers. The solubility analysis of protein constituents indicated that the covalent cross‐linkage, hydrophobic and H bindings and disulfide bonds were mainly involved in the coagulation of SPI induced by MTGase.

A swirling flow nozzle (SFN) has been proposed and designed for bloom continuous casting based on the idea that the melt flow pattern in the mould region can be controlled by changing the jet direction from outlets of the submerged entry nozzle. The simulated and plant trial results show that, as compared to the conventional straight nozzle, the oversized shrinkage porosity along with centre cracking at the strand cross-section is removed, and the maximum segregation degree fluctuation range of solute element C is reduced from 0.17 to 0.05. The positive effect is attributed to the remarkable superheat dissipation effect of horizontal swirling flow generated by SFN, which is reduced by 10.6 K as compared to the normal nozzle. Moreover, the adoption of SFN can further enhance the metallurgical effect of in-mould electromagnetic stirring (M-EMS), where both better chemical homogeneity and soundness of bloom castings can be obtained by the combined adoption of SFN and M-EMS.

Based on the developed coupled model of electromagnetism, heat and solute transportation, the macrosegregation formation and effect of secondary cooling water ratio on macrosegregation degree in strand during round bloom continuous casting process have been investigated. The solute segregation degree fluctuates from a positive to a negative value with distance from strand surface in the initial solidified shell region within thickness of 20 mm. A negative segregation region in concave shape and an irregular positive segregation zone are presented in the fixed and loosened side of strand respectively due to the gravity and thermosolutal convection. As the secondary cooling water ratio decreases from 0.25 to 0.15 L kg 21 , the solidification ratio at final electromagnetic stirring (F-EMS) centre increases from 73.14 to 77.83%. For the steel grade of 50Mn casted by round bloom casting within diameter of 0.35 m, the optimal solidification ratio at F-EMS centre is 75.05%, where the radial centre crack and shrinkage cavity at strand crosssection are removed.