• Journal of applied mathematics & informatics
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• v.38 no.5_6
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• pp.375-406
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• 2020

The anti-predator factor due to fear of predator in eco- epidemiological models has a great importance and cannot be evaded. The present paper consists of a modified Lesli-Gower predator-prey model with contagious disease in the predator population only and also consider the fear effect in the prey population. Boundedness and positivity have been studied to ensure the eco-epidemiological model is well-behaved. The existence and stability conditions of all possible equilibria of the model have been studied thoroughly. Considering the fear constant as bifurcating parameter, the conditions for the existence of limit cycle under which the system admits a Hopf bifurcation are investigated. The detailed study for direction of Hopf bifurcation have been derived with the use of both the normal form and the central manifold theory. We observe that the increasing fear constant, not only reduce the prey density, but also stabilize the system from unstable to stable focus by excluding the existence of periodic solutions.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.3
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• pp.1303-1306
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• 2015

Studies of epidemiological and prognostic factors are very important for oncology practice. There is a rapidly increasing amount of research and resultant knowledge in the scientific literature. This means that health professionals have major challenges in accessing relevant information and they increasingly require best available evidence to make their clinical decisions. Meta-analyses of prognostic and other epidemiological factors are very practical statistical approaches to define clinically important parameters. However, they also feature many obstacles in terms of data collection, standardization of results from multiple centers, bias, and commentary for intepretation. In this paper, the obstacles of meta-analysis are briefly reviewed, and potential problems with this statistical method are discussed.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.13 no.3
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• pp.181-188
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• 2009

Hundreds of thousands of South Korean protesters staged candlelight vigils and demonstrations against US beef imports in 2008. The problems, however, went far beyond that of beef imports. The political party veterans, who lost the presidential election, exploited labor unions that were discontent with the economy and ideological student groups to weaken the majority party. In this study, an epidemiological model is constructed with a system of three nonlinear differential equations. The model seeks to examine the dynamics of the system through stability analysis. Two threshold conditions that spread the protests are identified and a sensitivity analysis on the conditions is performed to isolate the parameters to which the system is most responsive. The results are also explored by deterministic simulations. This model can be easily modified to apply to other protests that may occur in various circumstances.

• Korean Journal of Veterinary Service
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• v.28 no.4
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• pp.387-392
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• 2005

This study was attempted to investigate the properties of brucellosis in Korean indigenous cattle at the Yeongwol and Pyeongchang county. Brucella spp was differentiated and identified from cotyledons, amniotic fluids and supramammary lymph nodes which confirmed with clinical, serological, epidemiological evidences (69 cases) from January to June, 2004. Isolation frequency of this causative agent from supramammary lymph nodes, cotyledons and amniotic fluids from 38 pregnant Korean indigenous cattle were $39.1\%,\;87.5\%,\;and\;63.2\%$, respectively, and finally confirmed with Brucella abortus biotype 1 through biochemical and serological test. A Brucella specific DNA with 711bp band was detected by PCR assay using BCSP primer. The two cases were definite epidemiological evidences that infected Korean indigenous cattle acrossed the border to Yeongwol and Pyeongchang from near two provinces. Effective prevention programs are urgently needed for further spreading this epidemics.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.22 no.1
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• pp.26-31
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• 2012

Objectives: To review the occurrence of cancer cluster in S Electronics semiconductor factories, process of epidemiological researches and lawsuit for industrial accident compensation. Methods: Occupational Safety and Heatlh Research Institute (OSHRI) epidemiological research report, Seoul National University (SNU) field survey report and Seoul Administrative Court ruling were investigated. Result:: OSHRI denied the association between working environment and outbreak of cancers, but SNU survey team reported that carcinogens do exist in workplace and the workers are exposed to them. Seoul Administrative Court ruled that 2 victims got cancer due to hazardous chemicals in working environment and be compensated but 3 victims were not acknowledged. Conclusions: Procedure of current OSHRI epidemiological research should be reassessed by the purpose of Occupational Accident Compensation Insurance Law.

• Journal of Veterinary Science
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• v.24 no.2
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• pp.21.1-21.5
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• 2023

Under the current African swine fever (ASF) epidemic situation, a science-based ASF-control strategy is required. An ASF transmission mechanistic model can be used to understand the disease transmission dynamics among susceptible epidemiological units and evaluate the effectiveness of an ASF-control strategy by simulating disease spread results with different control options. The force of infection, which is the probability that a susceptible epidemiological unit becomes infected, could be estimated by applying an ASF transmission mechanistic model. The government needs to plan an ASF-control strategy based on an ASF transmission mechanistic model.

• Genomics & Informatics
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• v.12 no.4
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• pp.203-207
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• 2014

Hepatitis is a common and serious disease for the Korean population. It is caused by a virus, the A and B types of which are plentiful in Koreans. In this study, we tried to find genetic factors for hepatitis through genome-wide association studies. We took 368 cases and 1,500 controls from Anseong and Ansan cohort data. About 300,000 single-nucleotide polymorphisms and 20 epidemiological variables were analyzed. We did not find any meaningful significant single nucleotide polymorphisms, but we confirmed the influence of major epidemiological variables on hepatitis.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.4
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• pp.2643-2647
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• 2013

Background: Despite anti-smoking campaigns, smoking prevalence among Thai males aged 30 or older is high, at around 50%. The purpose of this study was to determine the relationship between smoking and mortality in a rural Thai community. Materials and Methods: Subjects enrolled into the Khon Kaen cohort study between 1990 and 2001 were followed up for their vital status until $16^{th}$ March 2012. The death resource was from the Bureau of Policy and Strategy, Ministry of Interior, Thailand. A Cox proportional hazards model was used to analyse the association between smoking and death, controlling for age, education level and alcohol drinking, and confidence intervals were calculated using the floating risk method. Results: The study recruited 5,962 male subjects, of whom 1,396 died during a median 13.5 years of follow-up. Current smokers were more likely to die than never smokers after controlling for age, education level and alcohol drinking (HR, 95%CI: 1.41, 1.32-1.51), and the excess mortality was greatest for lung cancer (HR, 95%CI: 3.51, 2.65-4.66). However, there was no increased risk with increasing dose of tobacco, and no difference in risk between smokers of yamuan (hand-rolled cigarettes) and manufactured tobacco. Conclusion: Mortality from cancer, particularly lung cancer, and from all causes combined is dependent on smoking status among men in rural Thailand, but the relative risks are lower than have been reported from studies in high income countries, where the tobacco epidemic is more established.

• Journal of Radiation Protection and Research
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• v.31 no.2
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• pp.69-89
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• 2006

Biological mechanisms for ionizing radiation effects are different at low doses than at high doses. Radiation hormesis involves low-dose-induced protection and high-dose-induced harm. The protective component is associated with a reduction in the incidence of cancer below the spontaneous frequency, brought about by activation of defensive and repair processes. The Linear No-Threshold (LNT) hypothesis advocated by the International Commission on Radiological Protection (ICRP) and the Biological Effects of ionizing Radiation (BEIR) Report VII for cancer risk estimations Ignores hormesis and the presence of a threshold. Cancer incidences significantly less than expected have been found in a large number of epidemiological studies including, airline flight personnel, inhabitants of high radiation backgrounds, shipyard workers, nuclear site workers in scores of locations throughout the world, nuclear power utility workers, plutonium workers, military nuclear test site Participants, Japanese A-bomb survivors, residents contaminated by major nuclear accidents, residents of Taiwan living in $^{60}Co$ contaminated buildings, fluoroscopy and mammography patients, radium dial painters, and those exposed to indoor radon. Significantly increased cancer was not found at doses <200 $mSv^*$. Evidence for radiation hormesis was seen in both sexes for acute or chronic exposures, low or high LET radiations, external whole- or partial body exposures, and for internal radionuclides. The ubiquitous nature of the Healthy Worker Effect (HWE)-like responses in cellular, animal and epidemiological studies negates the HWE as an explanation for radiation hormesis. The LNT hypothesis is wrong and does not represent the true nature of the dose-response relationship, since low doses or dose-rates commonly result in thresholds and reduce cancer incidences below the spontaneous rate. Radiation protection organizations should seriously consider the cost and health implications of radiation hormesis.

• Journal of Environmental Health Sciences
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• v.42 no.2
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• pp.71-84
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• 2016

Objectives: Exposure assessment using questionnaires is effective in large-scale epidemiological studies. However, a limited number of studies have evaluated the questionnaires used in epidemiologic studies in terms of occupational and environmental exposure. The purpose of this study was to summarize and evaluate questionnaire items included in major epidemiological studies conducted in Korea with regard to occupational and environmental exposure. Methods: A total of 12 studies (four cohort studies, six large-scale cross-sectional surveys, and two panel studies) were selected for this study. Various questionnaire items related with occupational and environmental items were collected and summarized into tables. Results: Although job type and address were included in almost all of the studies, the information on occupational or environmental exposure to specific risk factors was collected in a limited number of studies. Moreover, questionnaire items were not standardized, warranting a continuous effort to develop questionnaires and evaluate their validity. Conclusion: Our results suggest that validated questionnaire items focusing on occupational and environmental exposure need to be developed in order to enhance the availability of the information collected from questions in epidemiological studies.