Surface and subsurface dispersal of radioactive materials from Fukushima by subpolar gyre and intermediate waters in the North Pacific.

Radioactive materials were released into the ocean following the Fukushima Daiichi Nuclear Power Plant accident in 2011. Six years after the accident, the radioactive material concentration was markedly increased in the Okhotsk Intermediate Water (OIW) of the Sea of Okhotsk. This material may have been subjected to southward subsurface dispersal by the North Pacific Intermediate Water (NPIW), which originates from the OIW. The spatiotemporal limitations of available methods have made it challenging to track the dispersal paths of radioactive materials in the North Pacific Subpolar region. Here, we performed a tracer experiment using a three-dimensional numerical model to determine the path of 137Cs from Fukushima to the Sea of Okhotsk via surface subpolar gyre currents and subsurface dispersion by OIW and NPIW. The results showed that the 137Cs concentration in the Sea of Okhotsk increased via the surface current and moved progressively southward via OIW six years after the accident and eastward via OIW and NPIW nine years after the accident, indicating that 137Cs transported by NPIW entered the subtropical region. Based on experiments, this temporal change was mainly caused by ocean currents. Thus, subsurface recirculation of radioactive material via the OIW and NPIW should be considered based on the predicted path and travel time of additional materials released from the power plant.

Comprehensive rear surface passivation of superstrate Sb2Se3 solar cells via post-deposition selenium annealing treatments and the application of an electron blocking layer.

Sb2Se3, a quasi-1D structured binary chalcogenide, has great potential as a solar cell light absorber owing to its anisotropic carrier transport and benign grain boundaries when the absorber layer is properly aligned along the [hk1] direction perpendicular to the substrate. A growth technique with a high deposition rate, such as vapor transport deposition, is preferred to form an [hk1]-oriented Sb2Se3 film. However, the possible decomposition of Sb2Se3 during cooling after the high-temperature deposition appears to result in Se deficiency, accompanied by the formation of deep-level donor-like defects, such as Se vacancies and Sb on Se antisite defects. Here, we present comprehensive passivation strategies for the rear interface of Sb2Se3 solar cells in a superstrate configuration, namely a post-deposition annealing treatment (PAT) under Se, and the introduction of an electron-blocking layer between Sb2Se3 and the rear metal contact. The PAT effectively passivated the defects associated with Se deficiency and greatly improved the open-circuit voltage and fill factor of Sb2Se3 solar cells. With the further introduction of a poly(N,N-bis(4-butylphenyl)-N,N-bis(phenyl)benzidine) electron-blocking layer, the Sb2Se3 solar cell achieved an efficiency of 7.0%.

Differentiation of osteosarcoma from osteomyelitis using microarchitectural analysis on panoramic radiographs.

Diagnosing osteosarcoma (OS) is very challenging and OS is often misdiagnosed as osteomyelitis (OM) due to the nonspecificity of its symptoms upon initial presentation. This study investigated the possibility of detecting OS-induced trabecular bone changes on panoramic radiographs and differentiating OS from OM by analyzing fractal dimensions (FDs) and degrees of anisotropy (DAs). Panoramic radiographs of patients with histopathologically proven OS and OM of the jaw were obtained. A total of 23 patients with OS and 40 patients with OM were enrolled. To investigate whether there was a microarchitectural difference between OS lesions and normal trabecular areas in each patient, two regions of interest (ROIs) were located on the CT images. Three microarchitectural parameters (box-counting FD, fast Fourier transform-based FD, and DA) were calculated. For both OS and OM, significant differences were found for all three microarchitectural parameters. Compared to normal trabecular bone, trabecular bone affected by OS and OM became isotropic and more complex. When comparing OS and OM, a statistically significant difference was found only in DA. Trabecular bones affected by OS became more isotropic than those affected by OM. Microarchitectural analysis, especially DA, could be useful for detecting OS-induced trabecular alterations and differentiating OS from OM.

Persistence of coastal upwelling after a plunge in upwelling-favourable wind.

Unprecedented coastal upwelling off the southern coast of the Korean Peninsula was reported during the summer of 2013. The upwelling continued for more than a month after a plunge in upwelling-favourable winds and had serious impacts on fisheries. This is a rare phenomenon, as most coastal upwelling events relax a few days after the wind weakens. In this study, observational data and numerical modelling results were analysed to investigate the cause of the upwelling and the reason behind it being sustained for such an extended period. Coastal upwelling was induced by an upwelling-favourable wind in July, resulting in the dynamic uplift of deep, cold water. The dynamic uplift decreased the steric sea level in the coastal region. The sea level difference between the coastal and offshore regions produced an intensified cross-shore pressure gradient that enhanced the surface geostrophic current along the coast. The strong surface current maintained the dynamic uplift due to geostrophic equilibrium. This positive feedback between the dynamic uplift and geostrophic adjustment sustained the coastal upwelling for a month following a plunge in the upwelling-favourable wind.

Detection of Pathogenic Viruses in the Ambient Air in Seoul, Korea.

The possible transport of pathogenic microorganisms during Asian dust events could be an important concern for health workers; however, this is still uncertain owing to a lack of supporting evidence. The present study aimed to investigate the presence of pathogenic microorganisms in air samples collected during the Asian and non-Asian dust periods. Between March and September 2016, air samples were collected at three weather observation stations in Seoul using a high-volume air sampler. Multiplex PCR was performed using the Allplex™ respiratory and gastrointestinal panel assay kits to detect 46 microorganisms. RT-PCR was performed for klassevirus, Aichivirus, and human parechovirus (HPeV) detection. In total, 71 air samples were collected during the Asian (8 samples) and non-Asian (63 samples) dust events. During an Asian dust event, only one human rhinovirus (HRV)-positive air sample was collected on April 23. During the non-Asian dust period, HRV, HPeV, norovirus (NoV), enteroaggregative Escherichia coli (EAEC), enterotoxigenic E. coli (ETEC), and Blastocystis hominis were detected in four, two, one, one, one, and one air samples, respectively. Pathogenic viruses were mostly detected in ambient air samples during the non-Asian dust period, which suggests a possible air-borne transmission of viral pathogens; however, the role of Asian dust in epidemics caused by pathogenic viruses is unclear.

Isolation of Legionella pneumophila from cooling towers, public baths, hospitals, and fountains in Seoul, Korea, from 2010 to 2012.

Legionnaire's disease is associated with a high mortality rate. The authors collected 3,495 water samples in Seoul, Korea, between 2010 and 2012 from public facilities (cooling towers, public baths, hospitals, and decorative fountains), which are considered the major habitats of Legionella pneumophila. In all, 527 (15.1%) isolates of L. pneumophila were obtained by microbial culture and polymerase chain reaction. Serological diagnosis and pulsed-field gel electrophoresis (PFGE) analysis were performed for the samples. The authors categorized the samples into four groups (A-D) on the basis of PFGE results. The analysis revealed that cooling towers containing the most samples with L. pneumophila serogroup 1 constituted the highest proportion of isolate. Samples from public facilities and serogroups could be distinctively classified by PFGE patterns. Thus, it is expected that source-specific features revealed through PFGE and serological analyses could serve as the basis for effectively coping with future outbreaks of L. pneumophila.

Antimicrobial resistance patterns and corresponding multilocus sequence types of the Campylobacter jejuni isolates from human diarrheal samples.

A total of 121 Campylobacter isolates from 4,788 humans with gastroenteritis were identified and characterized by biochemical detection methods, polymerase chain reaction, and multilocus sequence typing (MLST). These samples were obtained during a 3-year period, from January 2007 to December 2009, using the National Notifiable Diseases Surveillance System at the Research Institute of Public Health and Environment in Seoul Metropolitan, Korea. Antimicrobial susceptibilities of the bacterium were also determined with the agar dilution method. All 121 isolates were identified as Campylobacter jejuni, with all (100%) of them having two virulence genes (ceuE and cadF) and a toxin gene (cdtB). Twenty-three different sequence types (STs), including 9 new STs, were determined by MLST. The most prevalent ST and clonal complex (CC) observed in this study were ST-45 (28.9%) and ST-45 CC (53.7%), respectively. Percentages of antimicrobial-resistant isolates were 1.9% for ampicillin, 0.8% for chloramphenicol, 24% for ciprofloxacin, 46.3% for enrofloxacin, 0.8% for erythromycin, 6.6% for gentamicin, and 46.3% for tetracycline. This study demonstrated that the majority of the Campylobacter isolates obtained from human samples in Korea were C. jejuni with ST-45 CC, which has been detected mainly in broilers worldwide, and all strains with new STs were uniformly resistant to enrofloxacin and tetracycline. This study indicates that broilers may be a breeding ground for bacteria as well as an important potential source of human campylobacteriosis.

Characterization of norovirus infections in Seoul, Korea.

The present study has determined the detection rate of norovirus (NoV) with acute gastroenteritis (AGE) in hospitalized children and describes the molecular epidemiology of NoV circulating in Seoul, Korea. Six hundred and eighty-three (9.8%) of samples were positive for NoV. Of these, the NoV GII genogroup was the most commonly found, with a prevalence of 96.2% (683 of 710). Only 27 samples were positive for the NoV GI genogroup. Ten kinds of GI genotype (GI/1, GI/2, GI/3, GI/4, GI/5, GI/6, GI/7, GI/9, GI/12, and GI/13) and eight kinds of GII genotype (GII/2, GII/3, GII/4, GII/8, GII/14, GII/15, GII/16, and GII/17) were identified in children with AGE during the years 2008-2011.

Therapeutic effect of korean red ginseng extract on infertility caused by polycystic ovaries.

Polycystic ovarian syndrome (PCOS) is a very common endocrine disorder in women of reproductive age. Nerve growth factor (NGF) may be involved in the pathogenesis of PCOS. In this study, we investigated the effect of Korean red ginseng extract (KRGE) on the ovarian morphology and NGF expression in an estradiol valerate (EV)-induced rat model. Polycystic ovaries were induced by a single intramuscular injection of estadiol valerate (4 mg, dissolved in sesame oil) in adult cycling rats. KRGE was administered orally (200 mg/kg body weight/day) for 60 consecutive days, beginning 60 days after the induction. Ovarian morphology was almost normalized and NGF was normalized in the EV+KRGE group. KRGE lowered the high numbers of antral follicles and increased the number of corpora lutea in the polycystic ovaries. The results are consistent with a beneficial effect of KRGE in the treatment of PCOS.

Antimicrobial resistance patterns and characterization of integrons of Shigella sonnei isolates in Seoul, 1999-2008.

A total of 66 Shigella sonnei isolates from 1999 to 2008 in Seoul was analyzed for their antimicrobial resistance, carriage of integron, and the patterns of Pulsed-field gel electrophoresis (PFGE). A high level of antimicrobial resistance to streptomycin (100%), trimethoprim/sulfamethoxazole (95%), tetracycline (94%), nalidixic acid (65%), and ampicillin (41%) was observed among S. sonnei isolates. Fourteen profiles of antimicrobial resistance were identified with the most common resistance profile being nalidixic acid, streptomycin, tetracycline, and trimethoprim/sulfamethoxazole (35%). PCR and DNA sequencing analysis revealed the presence of class 2 integron in all isolates, and class 1 and 2 integrons in 7 isolates. The class 2 integron carried two types of gene cassettes. One cassette array was dfrI, sat2, and aadA1 (91%), and the other was dfr1 and sat1 (8%). dfrA12 and aadA2 gene cassette was found in one isolate containing class 1 integron. PFGE was carried out to examine the genetic relatedness among isolates. All isolates except for one showed similar PFGE patterns (similarity of 80.1%). These results suggest that the S. sonnei isolated during 1999-2008 in Seoul have similar lineages that have not undergone evolutionary changes with time.

Genotypic and phenotypic diversity of Salmonella enteritidis isolated from chickens and humans in Korea.

Salmonella Enteritidis is the most common cause of salmonellosis in humans in South Korea. It has been recognized that the principal source of human infection with S. Enteritidis is chickens and their products such as meat and eggs. A total of 173 S. Enteritidis isolates from humans (65 isolates) and chickens or their products (108 isolates) were analyzed by antibiotic susceptibility assay, phage typing, and pulsed-field gel electrophoresis (PFGE). Drug resistance was found to streptomycin (32.3%), ampicillin (30.6%), nalidixic acid (30.1%), ticarcillin (30.1%), and tetracycline (28.3%). More than 70% of the isolates were found to be resistant to one or more antibiotics tested. The most frequent patterns of resistant isolates were resistance to nalidixic acid only (28.3%) and resistance to two antibiotics (four combinations; 20.2%). The most predominant phage type (PT) was PT1 (27.2%) followed by PT21 (20.8%) and PT4 (8.7%) in chicken and human isolates. Nineteen different PFGE patterns were found among the 173 isolates, and A1 was the most common PFGE pattern, followed by A6 (17.3%). Most S. Enteritis isolates (except two isolates with patterns B and C) showed similar PFGE patterns that differed by only a few bands. These results show that 2 or 3 subtypes of S. Enteritidis are shared to a large extent by humans and chickens. This implies the possibility of the spread of chicken S. Enteritidis to humans.

Contamination of chicken meat with Salmonella enterica Serovar Haardt with nalidixic acid resistance and reduced fluoroquinolone susceptibility.

Salmonella contamination in chicken meat was studied with 100 chicken meat samples purchased from 55 shops located in various regions. A total of 21 isolates of Salmonella enterica were isolated from 21 chicken meat samples from four shops located at open markets, whereas there were none from supermarkets with well-equipped cold systems. Among these, 18 isolates were identified as Salmonella enterica serotype Haardt (S. Haardt) and three isolates were S. enterica serotype Muenchen. When the minimal inhibitory concentrations of the S. Haardt isolates were assayed with the agar dilution method to determine susceptibility to ampicillin, chloramphenicol, sulfisoxazole, tetracycline, and nalidixic acid, all 18 isolates were resistant to tetracycline and nalidixic acid and nine of these were resistant to ampicillin. These isolates showed reduced susceptibility to eight fluoroquinolones including ciprofloxacin, enrofloxacin, levofloxacin, gatifloxacin, gemifloxacin, moxifloxacin, norfloxacin, and ofloxacin. When quinolone resistance determining regions of gyrA and gyrB were sequenced, every isolate had the same missense mutation Ser83-->Tyr (TCC-->TAC) in gyrA, whereas no mutation was found in gyrB. Pulsed-field gel electrophoresis with XbaI revealed a close relationship among these isolates, suggesting a contamination of raw chicken meat with clonal spread of nalidixic acid-resistant and quinolone-reduced susceptibility S. Haardt in chickens. Results in this study show the importance of a wellequipped cold system and the prudent use of fluoroquinolone in chickens to prevent the occurrence of quinolone resistant isolates.

Characteristics of non-typhoidal Salmonella isolates from human and broiler-chickens in southwestern Seoul, Korea.

Non-typhoidal Salmonella (NTS) is an important commensal microorganism. The purpose of this study was to determine the epidemiological relation between NTS isolates from livestock and NTS isolates from human by analyzing antimicrobial susceptibilities and performing molecular typing. We determined the serotypes of 36 human clinical isolates and 64 livestock isolates, performed antimicrobial susceptibility testing against 8 antibiotics, and determined the molecular types of isolated NTS spp. by pulsed field gel electrophoresis (PFGE). In human isolates, S. enteritidis was the most common serotype (17 isolates; 47.2%) and S. typhimurium the second most (8 isolates; 22.2%). In livestock isolates, S. typhimurium was the most common serotype (15 isolates; 23.44%), and S. enteritidis was the second most (14 isolates; 21.88%). Ampicillin and tetracycline resistance were 50% (32/64 isolates) each among broiler-chicken NTS isolates. No human or livestock NTS isolates showed resistance to ciprofloxacin, TMP-SMX, or ceftriaxone. However, 19.4% (7/36) and 46.8% (30/64) of the human and livestock NTS isolates were resistant to nalidixic acid (MIC > or = 16 mg/mL), respectively. The presence of the three identical PFGE molecular types from human and broiler-chicken NTS isolates suggests the possibility of transmission from livestock to humans.