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곽승현(Seung Hyun Gwak) 한국시뮬레이션학회 2021 한국시뮬레이션학회 논문지 Vol.30 No.3
코로나바이러스감염증-19의 지역 간 감염확산을 설명하기 위해 단일 집단의 구획모델(compartmental model)인 SEIQRD 모델을 응용하여 다 집단(multi-group) 구획모델을 설계하였다. 이 모델은 구획을 세분화하여 잠복기 및 무증상자와 같은 숨은 감염자에 대한 설명이 가능하며 각 지역 간 감염지수와 검사율을 비교할 수 있다. 이를 통해 2020년 8월 2차 대유행과 11월 3차 대유행 시기에 어느 지역을 중심으로 전파가 이뤄졌는지 추정해보았다. 대한민국 국민 전체를 모집단으로 두었을 때 하위집단(subgroup)을 서울, 경기+인천, 비수도권으로 설정하였다. 데이터는 보건복지부의 ‘코로나 19국내발생 현황’을 참고하여 격리중인 인원, 누적 사망인원, 완치(격리해제)인원을 적합시켜 지역 간 감염지수와 지역별 감염자들의 평균 검사율, 지역별 평균 완치기간, 지역별 예상되는 숨은 감염자 수를 추정하였다. To explain the interregional infections in COVID-19, we designed a multi-group compartmental model by applying the SEIQRD model, a compartmental model of a single group. The model is segmented by compartments to account for hidden infections, such as latent periods and asymptomatic cases, and is capable of comparing infection indices and test rates between regions. Through this, it estimated which region was centered during the second wave in August 2020 and the third wave in November 2020. Subgroups were set up in Seoul, Gyeonggi (including Incheon), and a non-metropolitan area. We fit the model to the Ministry of Health and Welfare s data to estimate the average infection index between regions, average rate of rT-PCR test by region, and the expected number of hidden infections by region.
곽승현(Seung-hyun Gwak) 육군사관학교 화랑대연구소 2020 한국군사학논집 Vol.76 No.2
In this paper, we construct an epidemic model SEIQQR based on SIR model(1927). Recent studies have constructed SEIQR model or advanced one, however, they don’t contain isolation conditions for people contacted confirmed cases, so that it is difficult to apply to military quarantine policy in COVID-19 circumstance. So we have applied isolation conditions for contactor who contacted with confirmed cases and added the contactor(Q₁) as a subgroup to the SEIQR model. We construct a ODE system, and presented charts and tables showing the minimum value of the number of available personnel(military force) ; the maximum value of the number of quarantined personnel who contacted with people confirmed infection ; the total number of confirmed case.
Joo Hyun Oh,Dong Hyun Sinn,Gyu-Seong Choi,Jong Man Kim,Jae-Won Joh,Tae Wook Kang,Dongho Hyun,Wonseok Kang,Geum-Youn Gwak,Yong-Han Paik,Joon Hyeok Lee,Kwang Cheol Koh,Seung Woon Paik,Moon Seok Choi 대한외과학회 2020 Annals of Surgical Treatment and Research(ASRT) Vol.99 No.4
Purpose: Although surgical resection is usually considered for a single tumor, several reports have suggested that resection can be considered for multiple tumors. The objective of this study was to determine whether resection could provide better long-term outcome for patients with multiple hepatocellular carcinomas (HCCs) within Milan criteria. Methods: A total of 276 patients with multiple HCCs within Milan criteria with liver function preserved who underwent resection, radiofrequency ablation (RFA), or transarterial chemoembolization (TACE) between 2009 and 2013 were analyzed. Propensity-score (PS) matching was conducted. Results: Five-year overall survival (OS) and recurrence-free survival (RFS) were better in the resection group than that in the RFA or TACE group. Patients who underwent resection had more preserved liver function and different tumor characteristics compared to those received RFA or TACE. With similar baseline characteristics generated in the PS model, there was no difference in 5-year OS among 3 groups (79.5% vs. 72.3% or 62.0%, P = 0.232), but the 5-year RFS was better for patients who received resection than those who received RFA or TACE (51.9% vs. 22.0% or 0.0%, P < 0.001). Although the major complication rate was slightly higher than RFA or TACE, there was no significant difference between the 3 groups before and after PS matching. Conclusion: Resection was associated with better RFS than RFA or TACE and showed comparable OS in multiple HCC patients within the Milan criteria, but at a cost of slightly increased risk of complication. Resection can be considered as a first-line option if selected appropriately.
( Hyun Chin Cho ),( Geum Youn Gwak ),( Yong Han Paik ),( Moon Seok Choi ),( Joon Hyeok Lee ),( Kwang Cheol Koh ),( Byung Chul Yoo ),( Seung Woon Paik ) The Editorial Office of Gut and Liver 2013 Gut and Liver Vol.7 No.5
Background/Aims: Pegylated interferon (peginterferon) and ribavirin is the current standard therapy for chronic hepatitis C. The aims of this study were to evaluate the efficacy of peginterferon and ribavirin and to identify predictors of a sustained virological response (SVR) to the retreatment of chronic hepatitis C in Korea. Methods: The clinical records of 91 patients with chronic hepatitis C who were retreated with peginterferon and ribavirin were retrospectively analyzed. None of the patients had previously attained a SVR, and the patients were categorized according to their previous re-sponses (nonresponder, relapser, or inadequate treatment) to conventional interferon/ribavirin. Results: The overall SVR rate was 54.9%. Independent predictors of a SVR were genotypes 2 and 3, relapse, an adherence to peginterferon of over 80%, and an early virological response (EVR). For genotype 1 patients, an adherence to peginterferon of over 80% was an independent predictor of a SVR. Conclusions: Peginterferon and ribavirin therapy is effective for the retreat-ment of Korean chronic hepatitis C patients who have failed interferon/ribavirin, especially in patients with genotypes 2 and 3, relapse, an adherence to peginterferon over 80%, and an EVR. For genotype 1 patients, retreatment was effective in patients with an adherence to peginterferon over 80%. (Gut Liver 2013;7:585-593)
Recent Advancements of Treatment for Leptomeningeal Carcinomatosis
Gwak, Ho-Shin,Lee, Sang Hyun,Park, Weon Seo,Shin, Sang Hoon,Yoo, Heon,Lee, Seung Hoon The Korean Neurosurgical Society 2015 Journal of Korean neurosurgical society Vol.46 No.4
Treatment of Leptomeningeal carcinomatosis (LMC) from solid cancers has not advanced noticeably since the introduction of intra-cerebrospinal fluid (CSF) chemotherapy in the 1970's. The marginal survival benefit and difficulty of intrathecal chemotherapy injection has hindered its wide spread use. Even after the introduction of intraventricular chemotherapy with Ommaya reservoir, frequent development of CSF flow disturbance, manifested as increased intracranial pressure (ICP), made injected drug to be distributed unevenly and thus, the therapy became ineffective. Systemic chemotherapy for LMC has been limited as effective CSF concentration can hardly be achieved except high dose methotrexate (MTX) intravenous administration. However, the introduction of small molecular weight target inhibitors for primary cancer treatment has changed the old concept of 'blood-brain barrier' as the ultimate barrier to systemically administered drugs. Conventional oral administration achieves an effective concentration at the nanomolar level. Furthermore, many studies report that a combined treatment of target inhibitor and intra-CSF chemotherapy significantly prolongs patient survival. Ventriculolumbar perfusion (VLP) chemotherapy has sought to increase drug delivery to the subarachnoid CSF space even in patients with disturbed CSF flow. Recently authors performed phase 1 and 2 clinical trial of VLP chemotherapy with MTX, and 3/4th of patients with increased ICP got controlled ICP and the survival was prolonged. Further trials are required with newly available drugs for CSF chemotherapy. Additionally, new LMC biologic/pharmacodynamic markers for early diagnosis and monitoring of the treatment response are to be identified with the help of advanced molecular biology techniques.
Hyun-Jin Kim,Jun-Seok Lee,Dong-hoon Gwak,Chang-Won Park,Chunil Lim,Seung-Youl Lee 한국자기학회 2022 Journal of Magnetics Vol.27 No.4
This study verifies the feasibility and optimal conditions for using a general-purpose x-ray imaging device with a relatively large detector and excellent image quality compared to dental x-ray imaging devices according to international standards. The dental material test specimens were produced in the form of disks from four companies with different radiopacity, and aluminum step wedges was manufactured according to ISO 13116. In order to find the optimal irradiation conditions for general X-ray imaging devices, the distance between the target and the tube was fixed at 700 mm, and the exposure time was fixed at 100 ms. And the tube voltage was 50, 60, 70 kV and the tube current was changed to 40, 80, and 160 mA. As a result, it was sufficient to use generalpurpose X-ray imaging devices, and the best results were obtained under the optimal conditions of 60 kV and 40 mA.
Seung-Hyun Jung,여상엽,Hyung-Seok Kim,Jae-Ho Ryu,Jung-Woo Gwak,배영기,김철희 한국분자세포생물학회 2012 Molecules and cells Vol.33 No.6
Previous studies have shown that Notch signaling not only regulates the number of early differentiating neurons, but also maintains proliferating neural precursors in the neural tube. Although it is well known that Notch signaling is closely related to the differentiation of adult neural stem cells, none of transgenic zebrafish provides a tool to figure out the relationship between Notch signaling and the dif-ferentiation of neural precursors. The goal of this study was to characterize Her4-positive cells by comparing the expression of a fluorescent Her4 reporter in Tg[her4-dRFP] animals with a GFAP reporter in Tg[gfap-GFP] adult zebrafish. BrdU incorporation indicated that dRFP-positive cells were proliferating and a double labeling assay revealed that a significant fraction of the Her4-dRFP positive population was also GFAP-GFP positive. Our observations suggest that a reporter line with Notch-dependent gene expression can provide a tool to examine proliferating neural precursors and/or neuronal/glial precursors in the development of the adult nervous system to examine the model in which Notch signaling maintains proliferating neural precursors in the neural tube.