Corrosion Behaviors of Disinfectants on Dental Unit Waterlines

To investigate the corrosion behaviors and antibacterial effects of sodium hypochlorite(NaClO)and hydrogen peroxide silver ion(HPSI)disinfectants with different concentrations against dental unit waterlines and provide guidance and reference for the use of chemical disinfectants,polyurethane tubes were immersed in ultrapure water(control group),0.1%NaClO,0.5%NaClO,1.0%NaClO,2.5%HPSI,5.0%HPSI,and 10%HPSI solutions for 6,12,and 18 weeks.Contact angles and Fourier transform infrared spectra were detected.Surface morphologies were observed using scanning electron microscopy and antibacterial activity was evaluated using Gram-positive Staphylococcus aureus(S.aureus).The results showed that sodium hypochlorite and hydrogen peroxide silver ion disinfectants presented good antibacterial activity against S.aureus.However,sodium hypochlorite could cause serious damage to the water pipes where corrosion pits and cracks were observed,and increasing the concentration of sodium hypochlorite could accelerate the corrosion process.Hydrogen peroxide silver ion disinfectants had no obvious damage to the water pipes.Therefore,hydrogen peroxide silver ion disinfectants are recommended to use for controlling bacterial infection in dental unit waterlines which can reduce the damage to the water pipes.

Using video imagery to reconstruct the 3D intertidal terrain along a beach with multiple cusps

A high-frequency,high-resolution shore-based video monitoring system(VMS)was installed on a macrotidal(tidal amplitude>4 m)beach with multiple cusps along the Quanzhou coast,China.Herein,we propose a video imagery-based method that is coupled with waterline and water level observations to reconstruct the terrain of the intertidal zone over one tidal cycle.Furthermore,the beach cusp system(BCS)was precisely processed and embedded into the digital elevation model(DEM)to more effectively express the microrelief and detailed characteristics of the intertidal zone.During a field experiment conducted in January 2022,the reconstructed DEM was deemed satisfactory.The DEM was verified by RTK-GPS and had an average vertical root mean square error along corresponding RTK-GPS-derived intertidal profiles and corresponding BCS points of 0.134 m and 0.065 m,respectively.The results suggest that VMSs are an effective tool for investigating coastal geomorphic processes.

Spatial variations of tidal water level and their impact on the exposure patterns of tidal land on the central Jiangsu coast

The exposed area of intertidal zone varies with tidal water level changes, If intercomparisons of satellite images are adopted as a method to determine geomorphological changes of the intertidal zone in response to accretion or erosion processes, then the effect of water level variations must be evaluated. In this study, two Landsat TM images overpassing the central Jiangsu coastal waters on 2 January and 7 March 2002, respectively, were treated by the changing detection analysis using Image Differencing and Post-classification Comparison. The simultaneous tide level data from four tide gauge stations along the coast were used for displaying the spatial variations of water levels and determining the elevations of waterlines. The results show that the spatial variations of water levels are highly significant in the central Jiangsu coastal waters. The huge differences of tidal land exposure patterns between the two imaging times are related mainly to the spatial variations of tidal water levels, which are controlled by the differences in tidal phases for different imaging times and the spatial variations of water level over the study area at each imaging time. Under complex tidal conditions, e.g., those of the central Jiangsu coastal waters, the tide-surge model should be used to eliminate effectively the effects of water level variations on remote sensing interpretation of geomorphological changes in the intertidal zone.