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In this paper, the hydroxyl radical yield of a cavitation bubble and its influencing factors in the process of chitosan degradation with hydrodynamic cavitation in a single-hole orifice plate was investigated by a numerical simulation method. The hydroxyl radical yield of the cavitation bubble was calculated and analyzed by the Gilmore equation as the dynamic equation combined with the mass transfer equation, heat transfer equation, energy balance equation, and the principle of Gibbs free energy minimization. The influence of geometric parameters of the orifice plate and operating parameters on the formation of hydroxyl radicals was investigated. The results showed that the hydroxyl radicals produced at the moment of cavitation bubble collapse increased with the increase of the initial radius (R0), upstream inlet pressure (P1), downstream recovery pressure (P2), downstream pipe diameter (dp), and the ratio of the orifice diameter to the pipe diameter (β). The simulation results provide a certain basis for the regulation of hydrodynamic cavitation degradation of chitosan.

Additional file 1: Table S1. Primers of ARGs for conventional PCR. Table S2. Primers of ARGs and 16S rRNA for quantitative PCR. Table S3. Standard curves of ARGs and 16S rRNA for quantitative PCR. Table S4. Concentration and purity of standard plasmid of ARGs. Table S5. Primers of housekeeping genes of s. epidermidis [13]. Table S6. Effect of gender on thefrequencies of fecal resistance genes in newborns. Table S7. Difference and association of the frequencies of blaTEM in colostrums and the feces on the third day of newborns. Table S8. Difference and association of the frequencies of ampC in colostrums and the feces on the third day of newborns. Table S9. Difference and association of the frequencies of tetM in colostrums and the feces on the third day of newborns. Table S10. Difference and association of the frequencies of aac(6���)-Ib in colostrums and the feces on the third day of newborns. Table S11. Difference and association of the frequencies of ermB in colostrums and the feces on the third day of newborns. Table S12. Difference and association of the frequencies of sul2 in colostrums and the feces on the third day of newborns. Table S13. Difference and association of the frequencies of mecA in colostrums and the feces on the third day of newborns. Figure S1. The median of ARGs amount in the feces of six newborns on 3th day, 7th day and 30th day, respectively. Table S14. ST number of Staphylococcus epidermidis isolated from colostrum. Table S15. ST number of Staphylococcus epidermidis isolated from faeces on the third day. Table S16. ST number of Staphylococcus epidermidis isolated from ward air. Table S17. Resistance phenotypes and ARGs of Staphylococcus epidermidis isolated from colostrum. Table S18. Resistance phenotypes and ARGs of Staphylococcus epidermidis isolated from faeces on third day. Table S19. Resistance phenotypes and ARGs of Staphylococcus epidermidis isolated from ward air.

Additional file 1. Fig. S1: Diurnal expression of Ehd1, OsphyB, and OsGI in GLA 4 and the osftl4 mutants under CLD and CSD conditions. Fig. S2 Protein sequence alignment of 14-3-3 proteins. Fig. S3 Analysis of OsFTL4 expression in ABA-treated rice seedlings. Fig. S4 Day length in Yangzhou and Lingshui during the period from sowing to flowering.

For the degradation of chitosan, a novel physical method of self-resonating cavitation with strong cavitation effects was investigated in this paper. The effects of initial concentration, pH, temperature, inlet pressure and cavitation time on the degradation efficiency of chitosan were evaluated. It was found that the degradation efficiency was positively correlated with temperature and cavitation time, but was negatively correlated with the solution concentration. The degradation efficiency was maximized at pH of 4.4 and inlet pressure of 0.4 MPa. Under the experimental conditions, the intrinsic viscosity of chitosan solution was reduced by 92.2%, which was twice as high as the degradation efficiency where a Venturi tube cavitator was used. The viscosity-average molecular weights of initial and degraded chitosan were 651 and 104 kD, respectively. The deacetylation degree of chitosan slightly decreased from 89.34% to 88.05%. Structures and polydispersity of initial and degraded chitosan were measured by Fourier-transform infrared spectroscopy (FT-IR), nuclear magnetic resonance hydrogen spectroscopy (1H NMR), X-ray diffraction (XRD) and gel permeation chromatography (GPC). The results showed that the degradation process did not change the natural structure of chitosan. XRD peaks of the original chitosan were observed at 2θ of 9.59° and 20.00°, and the one at 2θ of 20.00° was obviously weakened after the degradation process, which indicated that the crystallinity of chitosan decreased significantly after the degradation. The polydispersity index of chitosan samples decreased from 3.17 to 2.75, indicating that the molecular-weight distribution of products after the degradation was more concentrated. The results proved that self-resonating cavitation prompted the degradation of chitosan and could reduce the polydispersity of the products for the production of oligochitosan with homogeneous molecular weights.

Unlike general long-wall mining, the roof activity is more intense when long-wall face passes through the abandoned roadway. Technically, the coal pillar between the abandoned roadway and the long-wall face will suddenly fail with a certain critical value of its width, leading to the roof breaks in advance and other production-restricted problems because of the support loss, which will be a great threat to underground mining activities. In order to guarantee a safe mining condition, therefore, it is greatly necessary to uncover how the roof breaks in advance and how to cope with it. From the stability maintaining of the key block perspective, this paper took for research that the 12404-1 long-wall face of Wulanmulun coal mine, China. The critical value of the coal pillar’s width was determined to be about 5m by theoretical analysis, likely, the appropriate support force of the abandoned roadway’s roof is about 4020KN per meter. Meanwhile, a numerical simulation method was adopted to study the ground pressure when the long-wall face passing through the abandoned roadway. Correspondingly, a compound supporting technology involving the roof presplit technique, anchor cable supporting and pumping pillar supporting were proposed for the roof of the abandoned roadway, and it practically worked well.