Publications by authors named "Ji-Woo Lee"

24 Publications

  • Page 1 of 1

Daily Life Changes and Life Satisfaction among Korean School-Aged Children in the COVID-19 Pandemic.

Int J Environ Res Public Health 2021 03 23;18(6). Epub 2021 Mar 23.

Department of Child Development and Family Studies, College of Human Ecology, Seoul National University, Seoul 08826, Korea.

The recent COVID-19 pandemic has been disrupting the daily lives of people across the world, causing a major concern for psychological well-being in children. This study aimed to examine (1) how life satisfaction and its potential predictors have been affected by the pandemic among school-aged children in Korea, and (2) which factors would predict their life satisfaction during the pandemic. We surveyed 166 fourth-graders in the Seoul metropolitan area to assess their psychological well-being and potentially related variables during the pandemic. The data were compared with those available from two pre-COVID-19 surveys, the 2018 Korean Children and Youth Panel Survey ( = 1236) and the 2019 Korean Children and Youth Well-being Index Survey ( = 334). Higher levels of stress were observed in children during the COVID-19 pandemic; however, the level of their life satisfaction remained unchanged when compared with data from the pre-COVID-19 surveys. The pandemic also affected peer relationship quality and susceptibility to smartphone addiction, but not perceived parenting style nor academic engagement. Interestingly, peer relationship quality no longer predicted life satisfaction during the pandemic; perceived parenting styles and parent-child conversation time predicted life satisfaction. The results suggest a central role of parent-child relationship in supporting the psychological well-being of school-aged children during the pandemic.
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http://dx.doi.org/10.3390/ijerph18063324DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8004811PMC
March 2021

A method of forensic authentication of audio recordings generated using the Voice Memos application in the iPhone.

Forensic Sci Int 2021 Mar 23;320:110702. Epub 2021 Jan 23.

Digital Analysis Division, National Forensic Service, 10, Ipchun-ro, Wonju-si, Gangwon-do 26460, Republic of Korea. Electronic address:

Considering the widespread use of mobile phones, audio recordings of crime scenes are widely used as digital evidence; however, it is important to authenticate the audio recordings before consideration as legal evidence. This study aimed to develop a method to authenticate audio recordings generated using the iPhone through three steps: 1) bitrate/audio latency time analysis of audio recordings, 2) comparison of the file structure/timestamp on audio recordings, and 3) device-based log history examinations for the provenance of audio recordings. Herein, we analyzed audio recording samples from ten different models of mobile handsets of the iPhone with Advanced Audio Coding (AAC) or Apple Lossless Audio Codec (ALAC), through the Voice Memos application depending on the iPhone Operating System (iOS). To analyze the characteristics of these audio recordings, we compared features including audio latency, file format/structure, and timestamps between the audio recordings generated in the iPhone and those edited through the built-in audio editing function. Furthermore, we investigated the log history registered in devices during the generation of the audio recordings. Differences in the audio latency, file size, timestamps, bitrate, and log history were confirmed on the iPhone when manipulating the audio recordings. The present results show that it is possible to verify the authentication of audio recordings generated using the Voice Memos application on iPhone.
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http://dx.doi.org/10.1016/j.forsciint.2021.110702DOI Listing
March 2021

Effects of prolonged continuous computer gaming on physical and ocular symptoms and binocular vision functions in young healthy individuals.

PeerJ 2019 4;7:e7050. Epub 2019 Jun 4.

Department of Optometry, Kangwon National University, Samcheok, South Korea.

Background And Objective: Addiction to computer gaming has become a social problem in Korea and elsewhere, and it has been enlisted as a mental health disorder by the World Health Organization. Most studies related to computer use and vision have individually assessed physical and ocular symptoms and binocular vision. Accordingly, the present study comprehensively assessed subjective physical and ocular symptoms and functions related to binocular vision after prolonged continuous computer gaming. This study aimed to investigate the effects of prolonged continuous computer gaming on physical and ocular health and visual functions in young healthy individuals.

Methods: Fifty healthy college students (35 male/15 female), aged 19-35 years old, were enrolled in this study. The inclusion criteria were no binocular vision problems and no reported history of ocular disease. Participants played continuously for 4 h from 6:00 to 10:00 p.m. Physical and ocular symptoms and visual functions such as convergence, accommodation, phoria, and the blink rate were assessed before and after continuous computer gaming for 4 h.

Results: Continuous computer gaming for 4 h resulted in convergence and accommodation disturbances and increased physical and ocular discomfort. Near phoria showed an exophoric shift, whereas distance phoria showed no change. Moreover, the accommodative and vergence facilities and blink rate were significantly decreased. All visual functions recovered to the baseline levels by the following morning.

Discussion: Our findings suggest that excessive and continuous computer gaming impairs visual functions and causes ocular and physical fatigue. Our findings further the understanding of the adverse effects of excessive computer use on physical and ocular health, and adequate breaks are necessary to reduce physical and visual discomfort during computer gaming.
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http://dx.doi.org/10.7717/peerj.7050DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6555390PMC
June 2019

A Survey on Banknote Recognition Methods by Various Sensors.

Sensors (Basel) 2017 Feb 8;17(2). Epub 2017 Feb 8.

Division of Electronics and Electrical Engineering, Dongguk University, 30 Pildong-ro 1-gil, Jung-gu, Seoul 100-715, Korea.

Despite a decrease in the use of currency due to the recent growth in the use of electronic financial transactions, real money transactions remain very important in the global market. While performing transactions with real money, touching and counting notes by hand, is still a common practice in daily life, various types of automated machines, such as ATMs and banknote counters, are essential for large-scale and safe transactions. This paper presents studies that have been conducted in four major areas of research (banknote recognition, counterfeit banknote detection, serial number recognition, and fitness classification) in the accurate banknote recognition field by various sensors in such automated machines, and describes the advantages and drawbacks of the methods presented in those studies. While to a limited extent some surveys have been presented in previous studies in the areas of banknote recognition or counterfeit banknote recognition, this paper is the first of its kind to review all four areas. Techniques used in each of the four areas recognize banknote information (denomination, serial number, authenticity, and physical condition) based on image or sensor data, and are actually applied to banknote processing machines across the world. This study also describes the technological challenges faced by such banknote recognition techniques and presents future directions of research to overcome them.
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http://dx.doi.org/10.3390/s17020313DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5335928PMC
February 2017

Determination and characterization of pharmaceuticals in sludge from municipal and livestock wastewater treatment plants.

Chemosphere 2017 Feb 3;168:1211-1221. Epub 2016 Nov 3.

Department of Civil and Environmental Engineering, Pusan National University, Busan, 46241, Republic of Korea. Electronic address:

This study investigated 24 pharmaceuticals compounds belonging to the classes of analgesics, stimulants, anti-seizures, non-steroidal anti-inflammatory drugs (NSAIDs), and antibiotics in the sludge of 12 municipal sewage treatment plants (S-sludge) and 4 livestock wastewater treatment plants (L-sludge) located across Korea. Over 70% of the target compounds were detected in at least one sample of S-sludge and L-sludge. The total concentration of the target pharmaceutical compounds detected in S-sludge was 2.622-422.8 mg kgand the most dominant compound was acetylsalicylic acid (ASA: 0.374-367.0 mg kg) whereas in L-sludge, the total concentration was 43.87-156.8 mg kgand the most abundant compound was oxytetracycline (OTC: 34.54-86.39 mg kg). Cluster analysis revealed two distinct groups: group A, which were S-sludge samples including ASA, carbamazepine (CBM), and others, and group B were L-sludge samples, dominated by antibiotics (CTC, OTC, LIN). The total daily load amount of the target pharmaceuticals in S-sludge was 0.010-268.9 kg day while the L-sludge was 0.021-0.529 kg day. The estimated amounts of the target pharmaceutical discharged from S-sludge and L-sludge into the Korean environment were 150.2 ± 47.94 ton yr and 15.05 ± 5.671 ton yr respectively, but the discharged amount of antibiotics from S-sludge (6.945 ton yr) was lower than that from L-sludge (9.234 ton yr).
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http://dx.doi.org/10.1016/j.chemosphere.2016.10.077DOI Listing
February 2017

Significant adverse reactions to long-acting gonadotropin-releasing hormone agonists for the treatment of central precocious puberty and early onset puberty.

Ann Pediatr Endocrinol Metab 2014 Sep 30;19(3):135-40. Epub 2014 Sep 30.

Department of Pediatrics, Inha University Hospital, Grauduate School of Medicine, Inha University, Incheon, Korea.

Purpose: Long-acting gonadotropin-releasing hormone agonists (GnRHa) are commonly used to treat central precocious puberty (CPP) in Korea. Although rare, there have been reports on the characteristic of adverse reactions of GnRHa in CPP among the Korean population. This study was intended to report on our clinical experience regarding significant adverse reactions to long-acting GnRHa in CPP and early onset puberty and to evaluate the prevalence rate of serious side effects.

Methods: This retrospective study included children with CPP and early onset puberty, who were administered monthly with long-acting GnRHa (leuprolide acetate, triptorelin acetate) at the outpatient clinic of Department of Pediatrics, at Inha University Hospital, between January 2011 and December 2013. We analyzed the clinical characteristics of patients who experienced significant adverse reactions and evaluated the prevalence rate.

Results: Six serious side effects (0.9%) were observed among total of 621 CPP and early onset puberty children with GnRHa therapy. The number of sterile abscess formation was four in three patients (4 events of 621). Anaphylaxis occurred in only one patient, and unilateral slipped capital femoral epiphysis (SCFE) in another one patient. Anaphylaxis occurred after the 6th administration of the monthly depot triptorelin acetate. Unilateral SCFE developed in GnRHa therapy.

Conclusion: Sterile abscess formation occurred in 0.6% of CPP and early onset puberty patients from the administration of a monthly depot GnRHa therapy. The occurrences of anaphylaxis and SCFE are extremely rare, but can have serious implications on patients. Clinicians should be aware of these potential adverse effects related to GnRHa therapy in CPP.
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http://dx.doi.org/10.6065/apem.2014.19.3.135DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4208261PMC
September 2014

Enantioselective N-demethylation and hydroxylation of sibutramine in human liver microsomes and recombinant cytochrome p-450 isoforms.

J Toxicol Environ Health A 2014 ;77(22-24):1419-30

a Albany Molecular Research, Inc. (AMRI) , Waluj , Aurangabad , India.

The enantioselective metabolism of sibutramine was examined using human liver microsomes (HLM) and recombinant cytochrome P-450 (CYP) isoforms. This drug is metabolized to N-mono-desmethyl- (M1) and N,N-di-desmethylsibutramine (M2), and subsequent hydroxylation results in hydroxyl M1 (HM1) and hydroxyl M2 (HM2). No significant difference was noted in formation of M1from sibutramine between R- and S-sibutramine in HLM. However, S-enantiomers of M1 and M2 were preferentially metabolized to M2, HM1, and HM2compared to R-enantiomers in HLM, and intrinsic clearance (Clint) ratios of S-enantiomers/R-enantiomers were 1.97, 4.83, and 9.94 for M2, HM1, and HM2, respectively. CYP3A4 and CYP3A5 were only involved in the formation of M1, whereas CYP2B6 and CYP2C19 were responsible for all metabolic reactions of sibutramine. CYP2C19 and CYP3A5 displayed catalytic preference for S-sibutramine to S-M1, whereas CYP2B6 and CYP3A4 showed little or no stereoselectivity in metabolism of sibutramine to M1. In the case of M2 formation, CYP2B6 metabolized S-M1 more rapidly than R-M1 with a Clint ratio of 2.14. However, CYP2C19 catalyzed less S-M1 than R-M1 and the Clint ratio of S-M1 to R-M1 was 0.65. The most significant enantioselectivity was observed in formation of HM1 from M1, and HM2 from M2. CYP2B6 and CYP2C19 exhibited preferential catalysis of formation of hydroxyl metabolites from S-enantiomers rather than R-enantiomers. These results indicate that S-sibutramine was more rapidly metabolized by CYP isoforms than R-sibutramine, and that enantioselective metabolism needs to be considered in drug interactions involving sibutramine and co-administered drugs.
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http://dx.doi.org/10.1080/15287394.2014.951758DOI Listing
December 2014

Nonwearable gaze tracking system for controlling home appliance.

ScientificWorldJournal 2014 14;2014:303670. Epub 2014 Sep 14.

Division of Electronics and Electrical Engineering, Dongguk University, Seoul 100-715, Republic of Korea.

A novel gaze tracking system for controlling home appliances in 3D space is proposed in this study. Our research is novel in the following four ways. First, we propose a nonwearable gaze tracking system containing frontal viewing and eye tracking cameras. Second, our system includes three modes: navigation (for moving the wheelchair depending on the direction of gaze movement), selection (for selecting a specific appliance by gaze estimation), and manipulation (for controlling the selected appliance by gazing at the control panel). The modes can be changed by closing eyes during a specific time period or gazing. Third, in the navigation mode, the signal for moving the wheelchair can be triggered according to the direction of gaze movement. Fourth, after a specific home appliance is selected by gazing at it for more than predetermined time period, a control panel with 3 × 2 menu is displayed on laptop computer below the gaze tracking system for manipulation. The user gazes at one of the menu options for a specific time period, which can be manually adjusted according to the user, and the signal for controlling the home appliance can be triggered. The proposed method is shown to have high detection accuracy through a series of experiments.
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http://dx.doi.org/10.1155/2014/303670DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4178921PMC
June 2015

Foodstuff analyses show that seafood and water are major perfluoroalkyl acids (PFAAs) sources to humans in Korea.

J Hazard Mater 2014 Aug 14;279:402-9. Epub 2014 Jul 14.

Department of Civil and Environmental Engineering, Pusan National University, Busan, 609-735, Republic of Korea. Electronic address:

We measured concentrations of PFAAs in 397 foods, of 66 types, in Korea, and determined the daily human dietary PFAAs intake and the contribution of each foodstuff to that intake. The PFAAs concentration in the 66 different food types ranged from below the detection limit to 48.3ng/g. Perfluorooctane sulfonate (PFOS) and long-chain perfluorocarboxylic acids (PFCAs) were the dominant PFAAs in fish, shellfish, and processed foods, while perfluorooctanoic acid (PFOA) and short-chain PFCAs dominated dairy foodstuffs and beverages. The Korean adult dietary intake ranges, estimated for a range of scenarios, were 0.60-3.03 and 0.17-1.68ngkg(-1)bwd(-1) for PFOS and PFOA, respectively, which were lower than the total daily intake limits suggested by European Food Safety Authority (PFOS: 150ngkg(-1)bwd(-1); PFOA: 1500ngkg(-1)bwd(-1)). The major contributors to PFAAs dietary exposure varied with subject age and PFAAs. For example, fish was a major contributor of PFOS but dairy foods were major contributors of PFOA. However, tap water was a major contributor to PFOA intake when it was the main source of drinking water (rather than bottled water).
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http://dx.doi.org/10.1016/j.jhazmat.2014.07.004DOI Listing
August 2014

The ratio of estimated average glucose to fasting plasma glucose level is superior to glycated albumin, hemoglobin A1c, fructosamine, and GA/A1c ratio for assessing β-cell function in childhood diabetes.

Biomed Res Int 2014 10;2014:370790. Epub 2014 Jun 10.

Department of Laboratory Medicine, Inha University Hospital, College of Medicine, Inha University, 7-206 Shinheung-dong 3-Ga Jung-gu, Incheon 400-711, Republic of Korea.

Objective: This study investigated the use of the estimated average glucose to fasting plasma glucose ratio (eAG/fPG ratio) to screen for β-cell function in pediatric diabetes.

Methods: Glycated hemoglobin (HbA1c), glycated albumin (GA), fructosamine, insulin, and C-peptide levels were measured. The ratio of GA to HbA1c (GA/A1c ratio) was calculated, and the homeostasis model assessment of β-cell function (HOMA-β) was determined.

Results: Median values of C-peptide, insulin, and HOMA-β levels were significantly higher in patients with an increased eAG/fPG ratio than in those with a decreased eAG/fPG ratio. C-peptide and HOMA-β levels were more closely correlated with the eAG/fPG ratio than with GA, HbA1c, the GA/A1c ratio, and fructosamine. In contrast, body mass index was significantly associated with GA, GA/A1c ratio, and fructosamine, but not with the eAG/fPG ratio and HbA1c levels. To test the diagnostic accuracies of the eAG/fPG ratio for identifying HOMA-β>30.0% in patients with type 2 diabetes, the area under the ROC curve of the eAG/fPG ratio was significantly larger than that of the GA/A1c ratio [0.877 (95% CI, 0.780-0.942) versus 0.775 (95% CI, 0.664-0.865), P=0.039].

Conclusions: A measurement of the eAG/fPG ratio may provide helpful information for assessing β-cell function in pediatric patients with diabetes.
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http://dx.doi.org/10.1155/2014/370790DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4071783PMC
March 2015

Serum glycated albumin as a new glycemic marker in pediatric diabetes.

Ann Pediatr Endocrinol Metab 2013 Dec 31;18(4):208-13. Epub 2013 Dec 31.

Department of Pediatrics, Inha University Hospital, Inha University School of Medicine, Incheon, Korea.

Purpose: Serum glycated albumin (GA) has been recently used as another glycemic marker that reflects shorter term glycemic control than glycated hemoglobin (HbA1c). Insulin secretory function and glycemic fluctuation might be correlated with the ratio of GA to HbA1c (GA/HbA1c) in diabetic adult patients. This study investigated the association of GA and GA/HbA1c ratio with the levels of fasting C-peptide, fasting plasma glucose in type 1 and type 2 pediatric diabetes.

Methods: Total 50 cases from 42 patients were included. The subjects were classified into type 1 diabetes mellitus (T1DM) (n=30) and type 2 diabetes mellitus (T2DM) (n=20) group. The associations among HbA1c, GA, and GA/HbA1c ratio were examined. The relationship between the three glycemic indices and fasting glucose, fasting C-peptide were analyzed.

Results: Mean values of GA, the GA/HbA1c ratio were significantly higher in T1DM than T2DM. GA (r=0.532, P=0.001), HbA1c (r=0.519, P=0.002) and the GA/HbA1c ratio (r=0.409, P=0.016) were correlated with the fasting plasma glucose. Fasting C-peptide level arranged 4.22±3.22 ng/mL in T2DM, which was significantly above the values in T1DM (0.26±0.49 ng/mL). There were no significant correlation between HbA1c and fasting C-peptide level. However, GA and the GA/HbA1c ratio exhibited inverse correlations with fasting C-peptide level (r=-0.214, P=0.002; r=-0.516, P<0.001).

Conclusion: GA seems to more accurately reflects fasting plasma glucose level than HbA1c. GA, GA/HbA1c ratio appear to reflect insulin secretory function.
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http://dx.doi.org/10.6065/apem.2013.18.4.208DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4027086PMC
December 2013

A novel gaze tracking method based on the generation of virtual calibration points.

Sensors (Basel) 2013 Aug 16;13(8):10802-22. Epub 2013 Aug 16.

Division of Electronics and Electrical Engineering, Dongguk University, Seoul 100-715, Korea.

Most conventional gaze-tracking systems require that users look at many points during the initial calibration stage, which is inconvenient for them. To avoid this requirement, we propose a new gaze-tracking method with four important characteristics. First, our gaze-tracking system uses a large screen located at a distance from the user, who wears a lightweight device. Second, our system requires that users look at only four calibration points during the initial calibration stage, during which four pupil centers are noted. Third, five additional points (virtual pupil centers) are generated with a multilayer perceptron using the four actual points (detected pupil centers) as inputs. Fourth, when a user gazes at a large screen, the shape defined by the positions of the four pupil centers is a distorted quadrangle because of the nonlinear movement of the human eyeball. The gaze-detection accuracy is reduced if we map the pupil movement area onto the screen area using a single transform function. We overcame this problem by calculating the gaze position based on multi-geometric transforms using the five virtual points and the four actual points. Experiment results show that the accuracy of the proposed method is better than that of other methods.
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http://dx.doi.org/10.3390/s130810802DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3812629PMC
August 2013

Caffeic acid phenethyl ester activation of Nrf2 pathway is enhanced under oxidative state: structural analysis and potential as a pathologically targeted therapeutic agent in treatment of colonic inflammation.

Free Radic Biol Med 2013 Dec 26;65:552-562. Epub 2013 Jul 26.

College of Pharmacy, Pusan National University, Busan 609-735, Republic of Korea. Electronic address:

Caffeic acid phenethyl ester (CAPE) is a polyphenolic natural product that possesses numerous biological activities including anti-inflammatory effects. CAPE-mediated nuclear factor-erythroid 2 p45 (NF-E2)-related factor 2 (Nrf2) activation is likely responsible for some of its biological effects. CAPE was chemically modified to yield CAPE analogues that were subjected to experiments examining cellular Nrf2 activity. CAPE and the CAPE analogue with a catechol moiety, but not the other analogues, activated the Nrf2 pathway. In addition, only biotin-labeled CAPE analogues with the catechol moiety precipitated Kelch-like ECH associated protein 1 (Keap1) when incubated with cell lysates and streptavidin agarose beads. Sodium hypochlorite (NaOCl) oxidation of the catechol moiety in CAPE produced an oxidized, electrophilic form of CAPE (Oxi-CAPE) and greatly enhanced the ability of CAPE to activate Nrf2 and to bind to Keap1. Rectal administration of CAPE ameliorated 2,4,6-trinitrobenzene sulfonic acid-induced rat colitis and activated the Nrf2 pathway in the inflamed colon, and incubation of CAPE in the lumen of the inflamed distal colon generated Oxi-CAPE. However, these biological effects and chemical change of CAPE were not observed in the normal colon. Our data suggest that CAPE requires the catechol moiety for the oxidation-enhanced activation of the Nrf2 pathway and has potential as a pathologically targeted Nrf2-activating agent that is exclusively activated in pathological states with oxidative stress such as colonic inflammation.
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http://dx.doi.org/10.1016/j.freeradbiomed.2013.07.015DOI Listing
December 2013

Monitoring of perchlorate in diverse foods and its estimated dietary exposure for Korea populations.

J Hazard Mater 2012 Dec 24;243:52-8. Epub 2012 Sep 24.

Department of Civil and Environmental Engineering, Pusan National University, Busan, 609-735, Republic of Korea.

The perchlorate concentrations in various Korean food samples were monitored, and 663 samples belonging to 39 kinds of food were analyzed. The analysis results revealed that dairy products contain the highest average concentration of 6.34 μg/kg and high detection frequency of over 85%. Fruit and vegetables showed the next highest perchlorate concentration with an average of 6.17 μg/kg. Especially, with its average concentration of 39.9 μg/kg, spinach showed the highest perchlorate level among all target food samples studied. Tomato was followed by spinach, which showed a high perchlorate average concentration of 19.8 μg/kg, and over 7 μg/kg was detected in ham and sausage (avg. 7.31 μg/kg) and in instant noodles (avg. 7.58 μg/kg). Less than 2 μg/kg was detected in fishes, meats and beverages. The exposure dose of perchlorate in Korean by food intake was calculated on the basis of the analyzed perchlorate levels in this study. The daily perchlorate dose to which Korean adults are exposed is 0.04 μg/kg bw/day, which is lower than the RfD (0.7 μg/kg bw/day) value suggested by US NAS. This result indicates that Korean people's current exposure to perchlorate from domestic food consumption is evaluated as safe.
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http://dx.doi.org/10.1016/j.jhazmat.2012.09.037DOI Listing
December 2012

Analysis and Exposure Assessment of Perchlorate in Korean Dairy Products with LC-MS/MS.

Environ Health Toxicol 2011 18;26:e2011011. Epub 2011 Aug 18.

Department of Civil and Environmental Engineering, Pusan National University, Busan, Korea.

Objectives: Perchlorate is an emerging contaminant that is found everywhere, including various foods. Perchlorate is known to disturb the production of thyroid hormones and leads to mental disorders in fetuses and infants, as well as metabolic problems in adults. In this study, we attempted to establish an LC-MS/MS method for measuring perchlorate in dairy products and used this developed method to investigate perchlorate levels in Korean milk and yogurt samples.

Methods: The developed method of perchlorate analysis requires a shaker and 1% acetic acid/acetonitrile as the extracting solvent. Briefly, the samples were extracted and then centrifuged (4000 rpm, 1hour), and the supernatant was then passed through a Envi™ Carb SPE cartridge that had been prewashed sequentially with 6 mL of acetonitrile and 6 mL of 1% acetic acid in water. The final volume of the sample extract was adjusted to 40 mL with reagent water and the final sample was filtered through a 0.20-µm pore size PTFE (Polytetrafluoroethylene) syringe filter prior to LC-MS/MS.

Results: The average levels of perchlorate in milk and yogurt samples were 5.63 ± 3.49 µg/L and 3.65 ± 2.42 µg/L, respectively. The perchlorate levels observed in milk samples in this study were similar to those reported from China, Japan, and the United States.

Conclusions: The exposure of Koreans to perchlorate through the consumption of dairy products was calculated based on the results of this study. For all age groups, the calculated exposure to perchlorate was below the reference of dose (0.7 µg/kg-day) proposed by the National Academy of Science, USA, but the perchlorate exposure of children was higher than that of adults. Therefore, further investigation of perchlorate in other food samples is needed to enable a more exact assessment of exposure of children to perchlorate.
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http://dx.doi.org/10.5620/eht.2011.26.e2011011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3214986PMC
October 2012

Experimental investigations of pupil accommodation factors.

Invest Ophthalmol Vis Sci 2011 Aug 17;52(9):6478-85. Epub 2011 Aug 17.

Division of Fusion and Convergence of Mathematical Sciences, National Institute for Mathematical Sciences (NIMS), Daejeon, Republic of Korea.

PURPOSE. The contraction and dilation of the iris muscle that controls the amount of light entering the retina causes pupil accommodation. In this study, experiments were performed and two of the three factors that influence pupil accommodation were analyzed: lighting conditions and depth fixations. The psychological benefits were not examined, because they could not be quantified. METHODS. A head-wearable eyeglasses-based, eye-capturing device was designed to measure pupil size. It included a near-infrared (NIR) camera and an NIR light-emitting diode. Twenty-four subjects watched two-dimensional (2D) and three-dimensional (3D) stereoscopic videos of the same content, and the changes in pupil size were measured by using the eye-capturing device and image-processing methods: RESULTS. The pupil size changed with the intensity of the videos and the disparities between the left and right images of a 3D stereoscopic video. There was correlation between the pupil size and average intensity. The pupil diameter could be estimated as being contracted from approximately 5.96 to 4.25 mm as the intensity varied from 0 to 255. Further, from the changes in the depth fixation for the pupil accommodation, it was confirmed that the depth fixation also affected accommodation of pupil size. CONCLUSIONS. It was confirmed that the lighting condition was an even more significant factor in pupil accommodation than was depth fixation (significance ratio: approximately 3.2:1) when watching 3D stereoscopic video. Pupil accommodation was more affected by depth fixation in the real world than was the binocular convergence in the 3D stereoscopic display.
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http://dx.doi.org/10.1167/iovs.10-6423DOI Listing
August 2011

Assessment of fates of estrogens in wastewater and sludge from various types of wastewater treatment plants.

Chemosphere 2011 Mar 13;82(10):1448-53. Epub 2010 Dec 13.

Department of Civil and Environmental Engineering, Pusan National University, Busan 609-735, Republic of Korea.

We measured five estrogens in the wastewater samples from the municipal wastewater treatment plants (M-WWTPs), livestock wastewater treatment plants (L-WWTPs), hospital WWTPs (H-WWTPs) and pharmaceutical manufacture WWTPs (P-WWTPs) in Korea. The L-WWTPs showed the highest total concentration (0.195-10.4 μg L(-1)) of estrogens in the influents, followed by the M-WWTPs (0.028-1.15 μg L(-1)), H-WWTPs (0.068-0.130 μg L(-1)) and P-WWTPs (0.015-0.070 μg L(-1)). Like the influents, the L-WWTPs (0.003-0.729 μg L(-1)) and the M-WWTPs (0.001-0.299μgL(-1)) also showed higher total concentration of estrogens in the effluents than the H-WWTPs (0.002-0.021 μg L(-1)) and P-WWTPs (0.011 μg L(-1) in one sample). The L-WWTPs (37.5-543 μg kg(-1), dry weight) showed higher total concentrations in sludge than the M-WWTPs (3.16-444 μg kg(-1), dry weight) like the wastewater. The distribution of estrogens in the WWTPs may be affected by their metabolism in the human body, their transition through biological treatment processes, and their usage for livestock growth. Unlike the concentration results, the daily loads of estrogens from the M-WWTPs were the highest, which is related to the high capacities of WWTPs.
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http://dx.doi.org/10.1016/j.chemosphere.2010.11.045DOI Listing
March 2011

Occurrence and distribution of pharmaceuticals in wastewater from households, livestock farms, hospitals and pharmaceutical manufactures.

Chemosphere 2011 Jan 30;82(2):179-86. Epub 2010 Oct 30.

Department of Civil and Environmental Engineering, Pusan National University, Busan 609-735, Republic of Korea.

Twenty-four pharmaceuticals were measured in wastewater from 12 municipal wastewater treatment plants (M-WWTPs), four livestock WWTPs (L-WWTPs), four hospital WWTPs (H-WWTPs) and four pharmaceutical manufacture WWTPs (P-WWTPs). The total concentration of pharmaceuticals in the influent samples was highest in the L-WWTPs followed by the P-WWTPs, H-WWTPs and M-WWTPs. The effluents had different patterns of pharmaceuticals than their corresponding influents because of the different fate of each compound in the WWTPs. Non-steroidal anti-inflammatory drugs (NSAIDs) were the most dominant in the influents from the M-WWTPs and P-WWTPs, while antibiotics were dominantly detected in the L-WWTP. In the H-WWTP influents, NSAIDs, caffeine and carbamazepine were dominant. In the P-WWTPs, the distribution of pharmaceuticals in the effluents varied with sampling sites and periods. The M-WWTP influents had the highest daily loads, while the effluents showed somewhat similar levels in all source types.
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http://dx.doi.org/10.1016/j.chemosphere.2010.10.026DOI Listing
January 2011

Occurrence and fate of pharmaceuticals in wastewater treatment plants and rivers in Korea.

Environ Pollut 2010 May 13;158(5):1938-47. Epub 2009 Nov 13.

Department of Civil and Environmental Engineering, Pusan National University, Jangjeon-dong, Geumjeong-gu, Busan 609-735, Republic of Korea.

We measured 25 pharmaceuticals in ten municipal wastewater treatment plants (WWTPs), one hospital WWTP and five rivers in Korea. In the municipal WWTP influents, acetaminophen, acetylsalicylic acid and caffeine showed relatively high concentrations. The occurrence of pharmaceuticals in the wastewater seems to be influenced by production and consumption of pharmaceuticals. The hospital WWTP influent showed higher total concentrations of pharmaceuticals than the municipal WWTPs, and caffeine, ciprofloxacin and acetaminophen were dominant. In the rivers, caffeine was dominant, and the distribution of pharmaceuticals was related to the inflow of the wastewater. In the municipal WWTPs, the concentrations of acetaminophen, caffeine, acetylsalicylic acid, ibuprofen and gemfibrozil decreased by over 99%. The decrease of these pharmaceuticals occurred mainly during the biological processes. In the physico-chemical processes, the decrease of pharmaceuticals was insignificant except for some cases. In the hospital WWTP, ciprofloxacin, acetylsalicylic acid, acetaminophen and carbamazepine showed the decrease rates of over 80%.
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http://dx.doi.org/10.1016/j.envpol.2009.10.036DOI Listing
May 2010

17-Allylamino-17-demethoxygeldanamycin down-regulates hyaluronic acid-induced glioma invasion by blocking matrix metalloproteinase-9 secretion.

Mol Cancer Res 2008 Nov 30;6(11):1657-65. Epub 2008 Oct 30.

Research Institute and Hospital, National Cancer Center, Gyeonggi, Korea.

Hyaluronic acid (HA) has been implicated in cell adhesion, motility, and tumor progression in gliomas. We previously reported that HA stimulates secretion of matrix metalloproteinase-9 (MMP-9) and induces glioma invasion. However, the molecular mechanism of HA action and therapeutic strategies for blocking HA-induced MMP-9 secretion remain unknown. Here, we report that the Hsp90 inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG) blocks MMP-9 secretion and that HA-induced nuclear factor-kappaB (NF-kappaB) activation is mediated by IkappaB kinase, which phosphorylates the NF-kappaB inhibitor IkappaBalpha and promotes its degradation. In addition, using an RNA interference approach, we show that the focal adhesion kinase plays a critical role in mediating HA-induced NF-kappaB activation, which resulted in increased MMP-9 expression and secretion, cell migration, and invasion. Importantly, we show that 17-AAG acts by blocking focal adhesion kinase activation, thereby inhibiting IkappaB kinase-dependent IkappaBalpha phosphorylation/degradation, NF-kappaB activation, and MMP-9 expression. This leads to suppression of HA-induced cell migration and invasion. Based on our data, we propose that 17-AAG is a candidate drug for treatment of highly invasive gliomas resulting from HA-induced, NF-kappaB-mediated MMP-9 secretion.
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http://dx.doi.org/10.1158/1541-7786.MCR-08-0034DOI Listing
November 2008

An evolutionary Monte Carlo algorithm for predicting DNA hybridization.

Biosystems 2008 Jan 6;91(1):69-75. Epub 2007 Aug 6.

Department of Physics and Astronomy, Seoul National University, San 56-1, Shillim-Dong, Kwanak-Gu, Seoul 151-747, Republic of Korea.

Many DNA-based technologies, such as DNA computing, DNA nanoassembly and DNA biochips, rely on DNA hybridization reactions. Previous hybridization models have focused on macroscopic reactions between two DNA strands at the sequence level. Here, we propose a novel population-based Monte Carlo algorithm that simulates a microscopic model of reacting DNA molecules. The algorithm uses two essential thermodynamic quantities of DNA molecules: the binding energy of bound DNA strands and the entropy of unbound strands. Using this evolutionary Monte Carlo method, we obtain a minimum free energy configuration in the equilibrium state. We applied this method to a logical reasoning problem and compared the simulation results with the experimental results of the wet-lab DNA experiments performed subsequently. Our simulation predicted the experimental results quantitatively.
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http://dx.doi.org/10.1016/j.biosystems.2007.07.005DOI Listing
January 2008

Finite-temperature phase transitions in a two-dimensional boson Hubbard model.

Phys Rev Lett 2007 Jun 29;98(26):266406. Epub 2007 Jun 29.

Department of Applied Physics, Hanyang University, Ansan 426-791, Korea.

We study finite-temperature phase transitions in a two-dimensional boson Hubbard model with zero-point quantum fluctuations via Monte Carlo simulations of a quantum rotor model and construct the corresponding phase diagram. Compressibility shows a thermally activated gapped behavior in the insulating regime. Finite-size scaling of the superfluid stiffness clearly shows the nature of the Kosterlitz-Thouless transition. The transition temperature T(c) confirms a scaling relation T(c) proportional, rho(0)(x), with x=1.0. Some evidence of anomalous quantum behavior at low temperatures is presented.
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http://dx.doi.org/10.1103/PhysRevLett.98.266406DOI Listing
June 2007

LY-6K gene: a novel molecular marker for human breast cancer.

Oncol Rep 2006 Dec;16(6):1211-4

Department of Biological Science, Sookmyung Women's University, Seoul 140-742, Korea.

A full-length cDNA was identified using one STS sequence containing an SNP (single nucleotide polymorphism) derived from genomic DNAs of breast cancer patients using a variety of bioinformatics tools. The cDNA encodes LY-6K, a novel member protein of the Ly-6/uPAR superfamily. It has been annotated as a target antigen for the HNSCC (head-and neck squamous cell carcinoma). We isolated the LY-6K gene from genomic DNAs obtained from breast cancer patients through large scale, case-control-screening. We performed northern blot hybridization and semi-quantitative RT-PCR on a human multiple-tissue mRNA blot from several breast cancer patients. We investigated the expression level of the LY-6K gene in human breast cancer, and compared this to expression in human normal breast tissue. We found that LY-6K was more highly expressed in the mRNA of breast tumors compared to its expression in normal breast tissue. These results suggest that LY-6K is not only a target antigen for HNSCC but also a significant new molecular marker for diagnosis and gene therapy in patients with breast cancer.
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December 2006

Quantum phase transitions of hard-core bosons in background potentials.

Phys Rev Lett 2006 Sep 13;97(11):115703. Epub 2006 Sep 13.

Department of Physics, Box 90305, Duke University, Durham, North Carolina 27708-0305, USA.

We study the zero temperature phase diagram of hard-core bosons in two dimensions subjected to three types of background potentials: staggered, uniform, and random. In all three cases there is a quantum phase transition from a superfluid (at small potential) to a normal phase (at large potential), but with different universality classes. As expected, the staggered case belongs to the XY universality, while the uniform potential induces a mean field transition. The disorder driven transition is clearly different from both; in particular, we find z approximately 1.4, nu approximately 1, and beta approximately 0.6.
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http://dx.doi.org/10.1103/PhysRevLett.97.115703DOI Listing
September 2006
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