No abstract

Microplastics coexist with the chemical reactive oxygen species in natural waters, however, there is still a lack to elucidate the effect of these radicals on the microplastic surficial oxidation. In this study, the ozonation of polyethylene microplastics was carried out under varying ozone dosages ranging from 4 to 7 mg/min for 60, 120 and 180 min, where its ozone uptake was iodometrically compared and surficial modification was spectroscopically analyzed using FTIR and XPS. For that, the lowest ozone uptake was 16% at 4 mg/min ozone supplied for 60 min whereas the highest was observed of 44% at 7 mg/min ozone added for 180 min. Moreover, in the FTIR analysis, carbonyl (1,600-1,800 cm-1) and hydroxyl (3,200-3,600 cm-1) indices were improved more than 20% and 13% when they were ozonized at 7 mg/min for 180 min compared to 4 mg/min for 60 min, respectively. XPS also revealed that 7 mg/min of ozone supplied for 180 min provided the highest of oxygen functionalities, but while there was no significant change in CC bond. It can be concluded that the surficial modification of PE including formation of oxygen functionalities could be more preferably influenced by the reaction time than ozone dosages.

No abstract

Three different methods of bacterial viability monitoring were compared to detect chemically or thermally inactivated Escherichia coli. Direct colony enumeration, live/dead bacterial cell staining with a fluorescent dye, and the dehydrogenase activity assay were compared with respect to their ease of use and time required to perform the three different tests. The green (live cell)/red (dead cell) ratio obtained from the fluorescent bacterial cell staining approach showed a linear relationship with the colony forming units; the result obtained with dehydrogenase was similar to those. The sensitivity of the monitoring methods to detect bacterial deactivation varied with different disinfection conditions. After thermal treatment, the sensitivity of the staining approach was lower, while that of the dehydrogenase activity assay was the highest. After chemical treatment, the sensitivity of detection for both methods was similar.

This paper proposes a new base material, a mixture of alcohol and water, for liquid scintillators. A possibility of using alcohol as a new detection solution in a particle detector is described. A liquid scintillator is widely used in various fields because of its high light yield. In addition, it is very important to develop a stable liquid scintillator for particle detectors or other medical applications. To date, there have been no previous R&D studies elsewhere for the use of alcohol in particle detectors, and no market products are available of this type. Thus, there is a room for improvement. This paper describes the brief synthesizing process of the alcohol-based liquid scintillator by varying the mixing ratio of each component that makes up the liquid scintillator. The several feasible physical and optical properties of an alcohol-based liquid scintillator were investigated and presented. Finally, as one of its applications, a range (beam-path length) measurement using an electron beam in medical physics is introduced after irradiating an alcohol-based liquid scintillator with electron beam energies of 6~12 MeV. The measurement results were compared with a Monte Carlo simulation, Novalis Tx, a phantom, and a CT image. In the near future, the new alcohol-based liquid scintillator could be used for particle detector or medical imaging applications.