Jung-eun Lim

Mesoporous silica: Polymer composite membrane for direct methanol fuel cell

Abstract The mesoporous silica— poly (vinyl alcohol) hybrid polymer electrolyte membranes were successfully synthesized with 140m thickness. The membrane has multiple layered structures, in which the both the top and bottom layers were mainly PVA and middle layer was composed of mesoporous silica hydrogel with PVA. The mesoporous silica - PVA hybrid membranes possessed well-resolved hexagonal mesoporous channel. We found that as increasing the acidity of heteropolyacids, the proton conductivity of the membrane was also increased. The proton conductivities of the hybrid membranes with PW, PMo and SiW at high temperature (70°C ~) were higher than that of Nafion® membrane. Applications of the mesoporous silica PVA composite membranes to DMFC seems to be promising at high temperature (>70°C).

IMPULSIVE NOISE FILTERING BASED ON NOISE DETECTION IN CORRUPTED DIGITAL COLOR IMAGES

This paper is an enhancement to our earlier research with grey-scale images. In this paper, we propose two new detection-estimation based image filtering algorithms that effectively remove corrupted pixels with impulsive noise in digital color images. The existing methods for enhancing corrupted color images typically possess inherent problems in computation time and smoothing out edges because all pixels are filtered. Our proposed algorithms first classify corrupted pixels in each channel or in each pixel. Because marginal or vector median filtering is only performed for the classified pixels, the process is computationally efficient, and edges are preserved well. In addition, because there is no appropriate criterion to evaluate the performance of impulsive noise detectors for color images, the objective comparison of noise detectors is difficult. Thus, we introduce a new efficiency factor for comparing the performance of noise detectors in digital color images. Simulation results show that the proposed algorithms perform better than existing methods, in both objective and subjective evaluations.

Association between serum persistent organic pollutants and DNA methylation in Korean adults

Background Exposure to persistent organic pollutants (POPs) has been associated with epigenetic changes such as DNA methylation, which can influence human health. However, the association between POPs and DNA methylation by sex was not shown in previous studies. Objectives We investigated the association between POPs and DNA methylation in men and women using a larger population. Methods A cross‐sectional study was conducted using the data of 444 Koreans (253 men and 191 women). Measurements for sixteen different POPs, including six organochlorine pesticides (OCPs) and ten polychlorinated biphenyls (PCBs) were taken in serum. DNA methylation via Alu and LINE‐1 in peripheral leukocytes was measured by pyrosequencing. To evaluate the association between POPs and DNA methylation, the Pearsons correlation and multiple linear regression analyses were performed. Results Except for PCB52 and PCB101, we found significant inverse associations between p,p’‐DDE, cis‐Heptachlor epoxide, and PCBs and Alu assay in men after adjusting for age, BMI, smoking status, and alcohol consumption (&bgr; = −0.67 for p,p′‐DDE; −0.28 for cis‐Heptachlor epoxide; in the range from −0.43 to −1.60 for PCBs). In women, PCB153 and PCB180 showed statistically significant inverse association with Alu assay (&bgr; = −0.22 for PCB153; −0.22 for PCB180). Except for PCB101, p,p′‐DDE and PCBs were positively associated with LINE‐1 assay in women (&bgr; = 0.48 for p,p′‐DDE; in the range from 0.40–0.89 for PCBs) while p,p′‐DDE, PCB153, and PCB180 showed positive associations with LINE‐1 assay in men (&bgr; = 0.55 for p,p′‐DDE; 0.65 for PCB153; 1.02 for PCB180). Conclusions We found that several POPs were associated with global DNA hypomethylation in the Alu assay for men and global DNA hypermethylation in the LINE‐1 assay for women. HighlightsExposure to POPs has been associated with epigenetic changes such as DNA methylation.We investigated the association between POPs level and DNA methylation.Measurements for 6 OCPs and 10 PCBs were taken in serum.The sum of POPs level was associated to DNA hypomethylation in men.The sum of POPs level was associated to DNA hypermethylation in women.

Serum persistent organic pollutants (POPs) and prostate cancer risk: A case-cohort study

It is still unclear whether persistent organic pollutants (POPs) exposure increases the prostate cancer incidence risk. This prospective cohort study evaluated the associations between serum POPs concentrations and prostate cancer risk. Within a case-cohort study, we identified 110 people diagnosed with prostate cancer and randomly selected 256 sub-cohort participants without prostate cancer. Serum concentrations of 32 polychlorinated biphenyl (PCB) congeners and 19 organochlorine pesticides (OCPs) were measured. The hazard ratios (HRs) and 95% confidence interval (95% CI) for determining the associations between POPs and risk of prostate cancer were estimated using the weighted Cox regression model. Compared to the lowest tertile, increased risks of prostate cancer incidence were observed in the upper tertile of following PCBs: the moderately chlorinated (HR: 4.19; 95% CI: 1.30-13.54), the highly chlorinated (HR: 4.14; 95% CI: 1.75-9.79), biologically persistent as CYP1A and CYP2B inducers (HR: 4.44; 95% CI: 1.33-14.83), the sum of non- dioxin-like (HR: 3.47; 95% CI: 1.21-9.98), and ∑PCBs (HR: 4.29; 95% CI: 1.52-12.08). In dose-response curves, ∑PCBs was associated with the increased risk of prostate cancer. Our findings suggested a possible role of POPs in the etiology of prostate cancer.

Association between serum concentrations of persistent organic pollutants and smoking in Koreans: A cross-sectional study

Background Studies on the associations between persistent organic pollutants (POPs) and smoking according to gender and smoking amount (cigarettes/day) are limited, and the results regarding the relationship between POPs and smoking are not completely consistent across studies. Objectives The smoking rate in Korea is one of the highest among the Organization for Economic Cooperation and Development (OECD) countries. We investigated the association between serum concentrations of POPs and cigarette smoking in Koreans by smoking status (never-smoker/ever-smoker) and smoking amount (cigarettes/day) according to gender. Methods Serum concentrations of 32 polychlorinated biphenyls (PCBs) and 19 organochlorine pesticides (OCPs) were measured in 401 participants (232 men and 169 women) who received health examinations during the Korean Cancer Prevention Study-II. We compared POP levels in ever-smokers and never-smokers and conducted multivariate logistic regression analyses to identify associations between POPs and smoking. Results Among women, the concentrations of PCB 156, PCB 167, and PCB 180 were significantly higher in ever-smokers than in never-smokers. After adjustments for age, body mass index, gamma-glutamyl transpeptidase, and alcohol intake, serum PCB 157 concentration was positively associated with male ever-smokers (OR 2.26; 95% CI, 1.01–5.04). In addition, trans-nonachlordane in OCPs as well as PCBs was significantly positively related with female ever-smokers (OR 3.21; 95% CI, 1.04–9.86). We found that subjects who smoked fewer than 15 cigarettes/day had a higher risk of having high POP concentrations than never-smokers. Conclusions These results indicate that smoking may be associated with human serum POPs levels.

Combined effects of smoking and bilirubin levels on the risk of lung cancer in Korea: the severance cohort study.

Background Smoking is a major risk factor for lung cancer. Bilirubin, an antioxidant, is inversely associated with the risk of diseases related to oxidative stress. This study was conducted to determine the influence of smoking and bilirubin levels on the risk of lung cancer in the Severance cohort study. Methods This study included 68,676 Korean who received a health examination at Severance Health Promotion Center from 1994 to 2004. Serum bilirubin measurements within normal range were divided into tertiles whereas smoking states were divided as never-smokers, former smokers and current smokers. A diagnosis of lung cancer was coded as occurring based on the report from the National Cancer Registry. Hazard ratios (HRs) and 95% confidence intervals (95% CIs) were calculated using Cox proportional hazards model. Results At the end of the study period, 240 patients (men: 181, women: 59) developed lung cancer. Compared to those with bilirubin levels ≥1.0 mg/dL, HRs (95% CI) for lung cancer were 2.8 (1.8–4.2) for subjects having bilirubin levels from 0.2 to 0.7 mg/dL in men. When we stratified our analysis by smoking status, bilirubin consistently showed a protective effect on the risk of lung cancer on both never- and current smokers. Current smokers having bilirubin levels from 0.2 to 0.7 mg/dL had a risk of lung cancer by 6.0-fold higher than never-smokers with bilirubin levels ≥1.0 mg/dL in men. Conclusion In this large prospective study, higher baseline bilirubin level in the normal range was associated with low risk of lung cancer. Smoking and low bilirubin levels were cumulatively associated with a higher risk of lung cancer.

Association of Persistent Organic Pollutants (POPs) with Age and Body Mass Index in Korean Adults

Objectives: Persistent organic pollutants (POPs) are known to be the detrimental chemicals in the body, even at low levels, and are stored in adipose tissue. Recently, POPs have been reported to be associated with chronic diseases, including cancer and cardiovascular disease, and aging and obesity are reported as common factors in chronic disease. However, there have been only a few studies on the associations of POPs with age and body mass index (BMI) in Korea. Therefore, we analyzed the associations of serum POPs levels with age and BMI in Korea. Methods: This cross-sectional study includes 444 subjects (253 men and 191 women) from the Korean Cancer Prevention Study-II (2004-2011). Serum levels of 33 polychlorinated biphenyls (PCBs) and 19 organochlorine pesticides (OCPs) were measured by a gas chromatographer (Agilent 6890) coupled to high resolution mass spectrometer (JEOL JMS-800D). Results: Concentrations of PCB 153 (men: 12.26 ng/g lipid, women: 10.50 ng/g lipid) and p,p`-DDE (men: 94.66 ng/g lipid, women: 96.66 ng/g lipid) were the highest among serum PCBs and OCPs, respectively. PCBs and OCPs were significantly positively correlated with age in both sexes. After adjustment for age, non-dioxin like PCBs were significantly negatively correlated with body mass in women. However, cis-heptachlor epoxide was significantly positively correlated with body mass index in both sexes. When analyzed by sex, stronger associations were shown between POPs and age in men and POPs and BMI in women. Conclusion: These results may provide baseline data for the study of POPs and for the health management field in Korea.

Proton conducting silica mesoporous/heteropolyacid-PVA/SSA nano- composite membrane for polymer electrolyte membrane fuel cell

Abstract Silica mesoporous/heteropolyacid(HPA)-PVA/SSA hybrid membrane was prepared by sol- gel processes to make a proton conducting membrane. The method involves stabilization of HPA in inorganic-organic hybrid membrane. By adding HPA in the silica mesoporous- PVA/SSA matrix, the membrane showed high proton conductivities of 10-3 S/cm at room temperature. Methanol crossover was decreased with increasing the contents of mesoporous material. This simple method can be applied to make a proton conducting membrane involving mesoporous structure.