Search Results
You are looking at 1 - 7 of 7 items for
- Author or Editor: Min Kwon x
- Refine by Access: All Content x
Abstract
For the disposal of a high efficiency particulate air (HEPA) glass filter into the environment, the glass fiber should be leached to lower its radioactive concentration to the clearance level. To derive an optimum method for the removal of uranium series from a HEPA glass fiber, five methods were applied in this study. That is, chemical leaching by a 4.0 M HNO3–0.1 M Ce(IV) solution, chemical leaching by a 5 wt% NaOH solution, chemical leaching by a 0.5 M H2O2–1.0 M Na2CO3 solution, chemical consecutive chemical leaching by a 4.0 M HNO3 solution, and repeated chemical leaching by a 4.0 M HNO3 solution were used to remove the uranium series. The residual radioactivity concentrations of 238U, 235U, 226Ra, and 234Th in glass after leaching for 5 h by the 4.0 M HNO3–0.1 M Ce(IV) solution were 2.1, 0.3, 1.1, and 1.2 Bq/g. The residual radioactivity concentrations of 238U, 235U, 226Ra, and 234Th in glass after leaching for 36 h by 4.0 M HNO3–0.1 M Ce(IV) solution were 76.9, 3.4, 63.7, and 71.9 Bq/g. The residual radioactivity concentrations of 238U, 235U, 226Ra, and 234Th in glass after leaching for 8 h by a 0.5 M H2O2–1.0 M Na2CO3 solution were 8.9, 0.0, 1.91, and 6.4 Bq/g. The residual radioactivity concentrations of 238U, 235U, 226Ra, and 234Th in glass after consecutive leaching for 8 h by the 4.0 M HNO3 solution were 2.08, 0.12, 1.55, and 2.0 Bq/g. The residual radioactivity concentrations of 238U, 235U, 226Ra, and 234Th in glass after three repetitions of leaching for 3 h by the 4.0 M HNO3 solution were 0.02, 0.02, 0.29, and 0.26 Bq/g. Meanwhile, the removal efficiencies of 238U, 235U, 226Ra, and 234Th from the waste solution after its precipitation–filtration treatment with NaOH and alum for reuse of the 4.0 M HNO3 waste solution were 100, 100, 93.3, and 100%.
Abstract
Recovered salt can be reused in the electrorefining process and the final removed salt from uranium (U) deposits can be fed into a following U casting process to prepare ingot. Therefore, salt distillation process is very important to increase the throughput of the salt separation system due to the high U content of spent nuclear fuel and high salt fraction of U dendrites. Yields on salt recovered by a batch type vacuum distiller transfer device were processed for obtaining pure eutectic salt and U. In this study, the influence of the various temperature slopes of each zones on salt evaporation and recovery rate are discussed. From the experimental results, the optimal temperature of each zones appear at the Top Zone and Zone 1 is 850 °C, Zone 2 is 650 °C and Zone 3 is 600 °C, respectively. In these conditions, the complete evaporation of pure salt in 1.4 h occurred and the amount of recovered salt was about 99 wt%. The adhered salt in U deposits was separated by a temperature slope zone of salt distillation equipment. From the experimental results using U deposits, the amount of salt evaporation was achieved more than 99 wt% and the salt evaporation rate was about 1.16 g/min. Also, the mount of recovered salt was about 99.5 wt%.
The applicability of gas chromatography–triple quadrupole mass spectrometry (GC–MS/MS) for determination of dioxins in soil was investigated. The analytical method was validated based on US Environmental Protection Agency (EPA) Method 1613 and European Union (EU) Regulation No. 709/2014 for selectivity, linearity of sensitivity, and instrumental limits of quantification (iLOQs). Method development commenced with determination of retention times for 17 native polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) and selection of characteristic ions from GC–MS/MS spectra. The linearity was measured using 1613 standard solutions (CS1–CS5) containing 0.5 to 200 ng/mL tetrachlorodibenzo-p-dioxin/furan (TCDD/F) congeners, 2.5 to 1000 ng/mL pentachlorodibenzo-p-dioxin/furan (PeCDD/F) to heptachlorodibenzo-p-dioxin/furan (HpCDD/F) congeners, and 20 to 2000 ng/mL octachlorodibenzo-p-dioxin/furan (OCDD/F) congeners. The correlation coefficient (R 2) values ranged between 0.9990 and 0.9999, and the iLOQ values ranged from 0.052 to 0.350 pg/μL for TCDD/F congeners, with a relative standard deviation of 2.7–9.6%. The entire analytical method was verified by analysis of certified reference materials (BCR-529 and BCR-530), and the recoveries were 71.79–103.87% and 81.50–103.12%, respectively. Thus, the GC–MS/MS system provides an alternative to GC–high-resolution MS for the simultaneous determination of TCDD/F congeners in soil.
Abstract
For the disposal of the high efficiency particulate air (HEPA) glass filter to environment, the glass fiber should be leached to lower its radioactive concentration. To derive the optimum method for removal of Co and Cs from HEPA glass fiber, four methods were applied in this study. Results of electrochemical leaching of glass fiber by 4.0 M HNO3–0.1 M Ce(IV) solution showed that the removal efficiency of 134Cs, 137Cs, and 60Cs from glass fiber after 5 h was 96.4, 93.6, and 93.8%, respectively. Results by 5 wt% NaOH solution showed that the removal efficiency of 134Cs, 137Cs, and 60Cs after 30 h was 81.7, 82.1, and 10.0%, respectively. Results by repeat 2.0 M HNO3 solution showed that the removal efficiencies of 134Cs, 137Cs, and 60Cs after 2 h of three repetitions were 96.2, 99.4, and 99.1%, respectively. Finally, results by repeat 4.0 M HNO3 solution showed that the removal efficiencies of 134Cs, 137Cs, and 60Cs after 4 h of three repetitions were 100, 99.9, and 99.9%, respectively, and their radioactivities were below 0.1 Bq/g. Therefore, the chemical leaching method by 4.0 M HNO3 solution was considered as an optimum one for removal of cesium and cobalt from HEPA glass fiber for self disposal. Also the removal efficiencies of 60Co, 134Cs, and 137Cs from the waste-solution after its precipitation-filtration treatment for reuse of 4.0 M HNO3 waste-solution were 88.0, 95.0, and 99.8%.
Pseudomonas aeruginosa is one of the causative pathogens of bovine mastitis. Most P. aeruginosa strains possess the type III secretion system (TTSS), which may increase somatic cell counts (SCCs) in milk from mastitis-affected cows. Moreover, most of P. aeruginosa cells can form biofilms, thereby reducing antibiotic efficacy. In this study, the presence and effect of TTSS-related genotypes on increase of SCCs among 122 P. aeruginosa isolates obtained from raw milk samples from mastitis-affected cows and their antibiotic susceptibility at planktonic and biofilm status were investigated. Based on the presence of TTSS-related genes a total of 82.7% of the isolates were found to harbour exoU and/or exoS genes, including the invasive (exoU-/exoS+, 69.4%), cytotoxic (exoU+/exoS-, 8.3%) and cytotoxic/invasive strains (exoU+/ exoS+, 5.0%). Milk containing exoS-positive isolates had higher SCCs than those containing exoS-negative isolates. The majority of isolates showed gentamicin, amikacin, meropenem and ciprofloxacin susceptibility at planktonic status. However, the susceptibility was decreased at the biofilm status. Based on minimum biofilm eradication concentration (MBEC)/minimum inhibitory concentration (MIC) ratios, the range of change in antibiotic susceptibility varied widely depending on the antibiotics (from ≥ 3.1-fold to ≥ 475.0-fold). In conclusion, most P. aeruginosa isolates studied here had a genotype related to increase in SCCs. The efficiency of antibiotic therapy against P. aeruginosa-related bovine mastitis could be improved by analysing both the MBEC and the MIC of isolates.
Abstract
Background and aims
Impulsiveness is an important factor in the pathophysiology of Internet gaming disorder (IGD), and regional brain functions can be different depending on the level of impulsiveness. This study aimed to demonstrate that different brain mechanisms are involved depending on the level of impulsiveness among patients with IGD.
Methods
Resting-state functional MRI data were obtained from 23 IGD patients with high impulsivity, 27 IGD patients with low impulsivity, and 22 healthy controls, and seed-based functional connectivity was compared among the three groups. The seed regions were the ventromedial prefrontal cortex (vmPFC), dorsolateral prefrontal cortex, nucleus accumbens (NAcc), and amygdala.
Results
Connectivity of the vmPFC with the left temporo-parietal junction (TPJ) and NAcc-left insula connectivity were significantly decreased in the patients with high impulsivity, compared with the patients with low impulsivity and healthy controls. On the other hand, amygdala-based connectivity with the left inferior frontal gyrus showed decreases in both patient groups, compared with the healthy controls.
Conclusion
These findings may suggest a potential relationship between impulsivity and deficits in reward-related social cognition processes in patients with IGD. In particular, certain interventions targeted at vmPFC-TPJ connectivity, found to be impulsivity-specific brain connectivity, are likely to help with addiction recovery among impulsive patients with IGD.
Background and Aims
Smartphone addiction, its association with smartphone use, and its predictors have not yet been studied in a European sample. This study investigated indicators of smartphone use, smartphone addiction, and their associations with demographic and health behaviour-related variables in young people.
Methods
A convenience sample of 1,519 students from 127 Swiss vocational school classes participated in a survey assessing demographic and health-related characteristics as well as indicators of smartphone use and addiction. Smartphone addiction was assessed using a short version of the Smartphone Addiction Scale for Adolescents (SAS-SV). Logistic regression analyses were conducted to investigate demographic and health-related predictors of smartphone addiction.
Results
Smartphone addiction occurred in 256 (16.9%) of the 1,519 students. Longer duration of smartphone use on a typical day, a shorter time period until first smartphone use in the morning, and reporting that social networking was the most personally relevant smartphone function were associated with smartphone addiction. Smartphone addiction was more prevalent in younger adolescents (15–16 years) compared with young adults (19 years and older), students with both parents born outside Switzerland, persons reporting lower physical activity, and those reporting higher stress. Alcohol and tobacco consumption were unrelated to smartphone addiction.
Discussion
Different indicators of smartphone use are associated with smartphone addiction and subgroups of young people have a higher prevalence of smartphone addiction.
Conclusions
The study provides the first insights into smartphone use, smartphone addiction, and predictors of smartphone addiction in young people from a European country, which should be extended in further studies.
