처녀자리 은하단에서 충차압에 의한 가스 손실을 겪는 은하들의 항성 형성 활동

학위논문 (석사) -- 서울대학교 대학원 : 자연과학대학 천문학과, 2020. 8. 이명균.We study galaxies undergoing ram pressure stripping in the Virgo cluster to examine whether we can identify any discernible trend in their star formation activity. We first use 48 galaxies undergoing different stages of stripping based on HI morphology, HI deficiency, and relative extent to the stellar disk, from the VIVA survey (VLA Imaging survey of Virgo galaxies in Atomic gas). We then employ a new scheme for galaxy classification which combines HI mass fractions and locations in projected phase space, resulting in a new sample total of 241 galaxies. We utilize a variety of star formation tracers, which include g - r, WISE [3.4] - [12] colors, and starburstiness that are defined by stellar mass and star formation rates to compare the star formation activity of galaxies at different stripping stages. We find no clear evidence for enhancement in the integrated star formation activity of galaxies undergoing early to active stripping. We are instead able to capture the overall quenching of star formation activity with increasing degree of ram pressure stripping, in agreement with previous studies. Our results suggest that if there is any ram pressure stripping induced enhancement, it is at best locally modest, and galaxies undergoing enhancement make up a small fraction of the total sample. Our results also show that it is possible to trace galaxies at different stages of stripping with the combination of HI gas content and location in projected phase space, which can be extended to other galaxy clusters that lack high-resolution HI imaging.처녀자리 (Virgo) 은하단에서 충차압에 의한 가스 손실 (ram pressure stripping) 을 겪는 은하들의 항성 형성 활동 (star formation activity) 이 시간에 따라 어떻게 변하는지에 대한 연구를 수행하였다. 먼저, VLA Imaging survey of Virgo galaxies in Atomic gas (VIVA)를 통해서 고해상도 중성 수소 (HI) 선 관측이 이루어진 48개의 은하들을 기반으로 연구를 시작하였다. 이 48개의 은하들은 중성 수소 형태 (HI morphology), 중성 수소 결핍 (HI deficiency), 그리고 중성 수소 대 항성 원반 범위의 비율 (relative extent to the stellar disk) 으로 각각 다른 가스 손실 단계로 분류가 가능하였다. 그 후, 중성 수소 대 항성 질량비 (HI mass fraction)와 투영 위상 공간 (projected phase space) 에서의 위치를 결합하여 새로운 은하 분류 방법을 적용하며 최종 샘플 수가 241개로 늘어났다. 다른 가스 손실 단계에서의 항성 형성 활동의 차이를 비교하기 위해 다양한 항성 형성 추적자 (star formation tracers) 을 사용하는데, g - r, WISE [3.4] - [12] 색지수, 그리고 항성 질량과 항성 형성률로 정의 된 starburstiness이라는 매개 변수를 사용했다. 가스 손실을 활발하게 겪고 있는 은하들의 적분 된 항성 형성 활동이 향상이 됐다는 명확한 증거는 찾을 수가 없었다. 반면에 충차압의 강도가 증가하면서 전체적으로 항성 형성이 억제되는 현상을 확인할 수 있었고, 이 점은 선행 연구의 결과와 일치하였다. 충차압에 의해 가스 손실이 일어나면서 항성 형성 향상이 있다한들, 기껏해야 국지적으로 미미하거나 그러한 은하들이 총 샘플에서 작은 부분을 차지하는 것으로 보인다. 본 연구에서 강조하고 싶은 점은, 중성 수소 대 항성 질량비와 투영 위상 공간에서의 위치를 결합을 하여 은하를 분류할 경우, 각각 다른 손실 단계에 있는 은하들을 추적할 수 있을 뿐더러, 이 방법은 고해상도 중성 수소 자료가 없는 은하단에도 적용이 가능할 것으로 보인다.1 Introduction 1 2 Data 7 2.1 EVCC 7 2.2 Physical Parameters of Galaxies 8 2.2.1 Stellar Masses 8 2.2.2 Star Formation Rates & Mid-Infrared Colors 10 2.2.3 Atomic Gas Masses 13 3 Results 15 3.1 Star Formation Properties of Galaxies Undergoing Different Stages of RPS 15 3.1.1 Definition of RPS Classes 15 3.1.2 Star Formation Properties of Galaxies with Different RPS Classes 21 3.2 Star Formation Properties of Galaxies Classified by HI Mass Fractions and Positions in Phase Space 27 3.2.1 Definition of HI Stripping Groups 28 3.2.2 Star Formation Properties of New HI Stripping Groups 34 4 Discussion 41 4.1 Locally Enhanced Star Formation in Galaxies Undergoing Gas Stripping 41 4.1.1 Implications from Observational Studies Based on the Virgo Cluster 41 4.1.2 Impact of RPS on the Global Star Formation Activity of Galaxies as Predicted by Simulations 44 4.2 Depletion of HI Gas Content According to Time Since Infall in Phase Space 48 4.2.1 Overall Quenching of Star Formation with Decreasing HI Gas Content and Increasing Time Since Infall 48 4.2.2 Potential Backsplashing Population 50 5 Summary & Conclusions 53 Bibliography 56 요약 67Maste

Retrograde coronary interventions of chronic total occlusions

ope

Incidence and Predictors of Late Secondary Tricuspid Regurgitation after Mitral Valve Replacement

Background: Severe tricuspid regurgitation (TR) may develop later after mitral valve replacement(MVR) in the absence of prosthetic mitral valve(MV) dysfunction and other causes of left heart failure. The aim of this study was to investigate the incidence and predictors of severe TR late after MVR for rheumatic MV disease. Method: From 309 patients who underwent MVR between 1995 and 1997 at Yonsei Cardiovascular Hospital, we selected 193 patients(M:F=52:141; mean age 48.5±11.3) who underwent MVR for rheumatic valvular disease [concomitant TAP (Tricuspid annuloplasty) group: 56, No TAP group: 137]. The mean follow up duration was 83.2± 26.4 months. Primary end point was time to clinical events, such as death, reoperation for tricuspid valve, admission due to right heart failure and the development of severe TR without left side heart failure. Patients were classified into 3 groups based on the degree of TR at the time of MVR: Group I; patients with coexisting mild TR (Grade 0, trivial), Group II; mild to moderate TR (Grade I-II), Group III; severe TR (Grade III-IV). Result: Twenty-one patients(10.9%) developed clinical events[Group I: 2/78(2.6%), Group II: 8/76(10.5%), Group III: 11/33(28.2%)]. Event free survival rate was different during the follow-up period between groups. By Cox regression analysis, initial severe TR (Hazard Ratio: 5.2, 95%CI 2.2-12.3), old age (Hazard Ratio: 4.3, 95%CI 1.4-12.8), and TAP (Hazard Ratio: 4.3, 95%CI 1.8-10.5) were the risk factors for the development of late severe TR. Conclusion: The incidence of severe TR or right heart failure in the absence of prosthetic MV dysfunction was 10.9% in MVR patients. Despite of successful TAP, the severity of TR at the time of MVR was the most important factor for prediction of late severe TR. It can be suggested that initial TR grade and RV function rather than TAP, is the important factor for the recurrence of severe TR after MV surgery.ope

The Cardioprotective Effect of Intravenous Nicorandil for Ischemia/Reperfusion Injury

BACKGROUND AND OBJECTIVES: Nicorandil is a potassium channel opener, and it has been known to have a cardioprotective effect against ischemia/reperfusion injury. However, the exact mechanisms of the effect are not known. In the previous studies on cardioprotection, administration of nicorandil was started early during the coronary occlusion. Therefore, it is not clear whether nicorandil can also be beneficial when it is administered from the time of coronary recannalization. MATERIALS AND METHODS: We studied 15 cats that had their chests surgically opened (8 nicorandil cats and 7 control cats). The proximal portion of the left anterior descending artery (LAD) was occluded with ligation for 90 minutes, then it was recannalized for 60 minutes. Intravenous injection of nicorandil was started at the time of recannalization of the artery (a bolus of 100 microgram.kg(-1) plus an infusion at a rate of 10 microgram.kg(-1).min(-1) ). At each stage of the experiments, the risk area and myocardial perfusion were assessed using color microspheres and myocardial contrast echocardiography. The size of the infarction was evaluated by postmortem triphenyltetrazolium chloride staining. Myocardial contrast echocardiography was performed with Pulse Inversion Harmonic Imaging (Sonoace9900, Medison). RESULTS: The risk area during coronary occlusion was 18.8±12.6% in the nicorandil group and 19.3±9.6% in the control group (p=NS). The perfusion defect immediately after and 1 hour after reperfusion was 13.0±8.7% and 8.4 ±7.6%, respectively, in nicorandil group, and 16.7 ±11.1 % and 13.4±8.8%, respectively, in the control group, (p=NS between groups). Myocardial blood flow in the LAD territory during occlusion immediately after and 1 hour after reperfusion was 56±31 %, 73±31 % and 69±28%, respectively, of the normal myocardium in the nicorandil group, and 65±20%, 101±75% and 77±42%, respectively, in the control group (p=NS between groups). The postmortem infarction size was 8.1±9.6% in the nicorandil group and 7.7±7.5% in the control group (p=NS). CONCLUSION: With administration of nicorandil from the time of recannalization in the ischemia/reperfusion injury model, we could not find any significant cardioprotective effect. The cardioprotective effect of nicorandil may be associated with preconditioning before reperfusion.ope

The Impact of Apolipoprotein A-I Polymorphisms on the Lipid Profiles in Middle Aged Healthy Men and Women

Background and Objectives：Apolipoprotein A-I is the major lipoprotein constituent of high density lipoprotein in plasma. In this study, the role of two polymorphisms in the apo A-I gene was investigated on the serum lipid profiles and apo A-I levels in healthy men and women. Subjects and Methods：Blood samples were obtained from 417 subjects (M：F=169：248, mean age 47.2 years). The apo A-I genotypes were determined by SNP-IT assays using the SNPstream 25KTM system. Results：The frequencies of the A allele at the XmnI restriction site and position -75 bp were 0.25/0.23 and 0.19/0.17 in men and women, respectively. A strong positive linkage disequilibrium (D’=0.990) between two polymorphisms was detected. In men, the A allele at the XmnI restriction site was associated with significantly lower levels of triglyceride (p=0.028) compared to the G/G subjects, but no significant associations were detected between the G-75A polymorphism and any of the lipid traits examined. In women, each A allele for the XmnI restriction site and -75 bp polymorphisms were significantly associated with higher levels of apo A-I (p=0.032 and p=0.012). In the multiple regression analysis, the HDL, being a current drinker and the A allele of the XmnI restriction site polymorphism were major determinants of the serum apo A-I levels in women (R2=0.272, p<0.05). Conclusion：Our study showed that the A allele at XmnI restriction site in the apo A-I gene was associated with decreased triglyceride levels in men. Each A allele of two polymorphisms was associated with an elevated apo A-I level in women.ope

수정된 3ω 방법을 이용한 적층 구조물에서의 열전도계수 및 접촉 열저항의 정밀 측정

학위논문 (석사)-- 서울대학교 대학원 : 기계항공공학부, 2012. 2. 이준식.3ω method는 박막이나 기판의 열전도도를 매우 정밀하게 측정할 수 있는 잘 알려진 실험 방법이다. 하지만, 까다로운 실험적 제약에 의해 적용할 수 있는 물질이 제한적이므로 다양한 물질에 대하여 적용한 연구가 부족하다. 본 연구에서는 박막의 두께가 매우 두꺼운 multi-layer 구조에서도 적용할 수 있는 수정된 3ω method를 개발하였다. 이를 이용하여 LED의 정확한 방열설계를 위해 필수적인 다이 본딩용 접착물질 (ag paste)의 열전도도와 접촉 열저항을 정량적으로 계측하였다. 또한, 열 침투 깊이 조절을 이용하여 multi-layer에서 각 층의 열전도도 및 thermal effusivity를 계측 할 수 있음을 수학적으로 증명하고 실험적으로 검증하였다. 마지막으로 두 가지 검증실험을 통하여 본 연구에서 제시한 새로운 컨셉으로 구한 결과와 비교하였고 그 정확성을 입증하였다.The 3ω method is a well known experimental technique to measure the film thermal conductivity very precisely. However, to date little effort has been made to extend its applicability because film samples are limited due to rigid experimental restrictions. In this study, we develop the modified 3ω method that can be applied to very thick film case in a multi-layer structure. The thermal conductivity and contact resistance of die bonding material (ag paste) that is a very important in thermal design of LED are measured quantitatively with this new method. In addition, we demonstrate that the thermal conductivity and thermal effusivity of each layer can be measured with the penetration depth control in the multi-layer system analytically and measure the values experimentally. Finally, the results of this new method are compared to two verification experiments and we confirm the accuracy.Maste

Multi-detector row spiral CT(16 channel) scan을 통한 관상동맥 질환의 진단 및 진단적 유용성

Dept. of Medicine/석사[한글] 최근 들어 관상동맥질환의 진단에 있어서 Multi-dector row spiral computed tomography(이하 MDCT)는 관상동맥질환 진단의 비침습적인 방법으로 도입되고 있다. 물론 현재까지도 관상동맥질환의 확진을 위한 진단적인 방법으로는 관상동맥 조영술이 가장 정확한 방법일 것이지만, 침습적인 관상동맥 조영술의 위험성 및 합병증을 고려할 때 MDCT의 역할은 관상동맥 조영술을 대체하거나 혹은 보조할 수 있을 것으로 생각된다. MDCT를 통해 비침습적 심장영상을 얻는 것은 죽상반에 의한 관상동맥의 협착 정도를 파악할 수 있을 뿐만 아니라 관상동맥의 기형등과 같은 다른 관상동맥 질환을 발견할 수도 있으며 또한 관상동맥의 석회화 정도를 평가할 수 있다는 점은 큰 매력이나, 심장이나 호흡에 의한 움직임에 의해 이미지를 얻는데 방해를 받을 수도 있으며 또한 관상동맥 석회화에 따른 artifact 또한 고려해야 한다는 문제점 및 비교적 내경이 작은 혈관의 평가에서는 정확성이 떨어진다는 어려움 또한 있다. 본 연구에서는 이러한 관상동맥질환의 진단에 있어서의 MDCT 의 진단적인 유용성을 평가하기 위해 진행되었다. 관상동맥질환이 의심되는 총 61명의 환자(59.2±10.0 M:F=44:17)들이 관상동맥조영술과 MDCT scan을 동시에 시행하였다. 연구대상자들은 심박동수를 조절하기 위해 모두 atenolol 을 복용하였으며 MDCT의 Image를 scan하는 동안 심박동수가 65 bpm 이하로 유지하였다. MDCT Image의 결과는 두명의 방사선과 의사들에 의해 검토되었으며, 이들은 관상동맥조영술의 결과를 모르는 상태에서 판독을 진행하였다. 관상동맥조영술의 결과는 각각의 관상동맥 및 관상동맥 분지 별로 QCA 를 통해 분석되었으며 50% 이상의 협착을 의미 있는 협착으로 평가하였다. MDCT 조영술을 시행한 총 61명중 58명에게서 평가가 가능한 Image를 얻어냈으며(95%) 좌주간지를 포함한 총 244개의 관상동맥에서 229개의 관상동맥에서 평가가 가능했다. 결과를 살펴보면, 고식적 관상동맥조영술에서 관상동맥질환이 있는 것으로 분류된 35명의 관상동맥질환자 중에서 30명을 적어도 한군데 이상의 관상동맥의 협착이 있는 관상동맥질환으로 분류했으며, 관상동맥 질환이 없는 23명중 21명에서 관상동맥 협착이 없는 것으로 분류해냈다 (sensitivity 85.7%, specificity 80.8%, positive predictive value 93.8%, negative predictive value 80.8%). 각각의 관상동맥별로 분석한 결과 MDCT 조영술은 평가가 가능했던 229개 중 62개의 협착이 있었던 관상동맥 중 50개를 정확히 판독해 냈으며 협착이 없었던 167개의 관상동맥 중 156개에서 협착이 없었던 것으로 평가했다 (sensitivity 80.6%, specificity 93.4% positive predictive value 81.9%, negative predictive value 79.3%). 각 협착 병변에 따른 분석을 살펴보면 MDCT조영술은 판독 가능했던 82개의 협착 병변 중 65개의 병변을 정확히 판독해냈다. (detection rate 79.3%) MDCT조영술의 판독 불가능했던 경우는 대부분은 원위부 협착 또는 작은 가지들의 병변이 많았으며 근위부 협착이나 직경이 큰 관상동맥에서는 훨씬 높은 발견율을 나타냈다. 이는 관상동맥질환에서 관상동맥중재시술을 고려할 때 MDCT가 더 효과적임을 나타내 주는 결과라 할 수 있겠다. 마지막으로 기존에 스텐트를 삽입했던 환자들에게서도 스텐트의 개존성을 평가하는데도 도움이 될 수 있는데 스텐트의 내부를 직접 눈으로 확인함과 동시에 스텐트 내부 및 스텐트 바깥 부위와의 density 의 차이를 통해 스텐트의 개존성을 평가해 낼 수 있었다. 이러한 점은 향후 스텐트 개존성 및 스텐트 재협착을 평가해내는 방법으로서의 MDCT가 쓰일 수 있음을 시사한다고 할 수 있으며 이에 대한 연구는 차후에도 필요하리라 생각된다. 베타 차단제의 전처치를 통한 심박동수의 조절, 기술적인 측면의 발전을 통해 더욱 더 좋은 영상을 얻음과 동시에 짧은 시간에 많은 영상들을 얻어내는 일들이 가능해짐에 따라 MDCT조영술의 단점으로 생각되었던 영상의 해상도 및 관상동맥의 움직임에 따른 잘못된 영상등의 문제들이 해결 되어 가고 있는 상황이다. 본 연구를 통해 관상동맥질환의 진단적인 유용성을 확인하였으며, 향후 기술의 발전 등을 통해 더욱 나은 MDCT가 나오게 된다면 고식적인 관상동맥조영술을 통한 관상동맥질환의 진단은 이제 MDCT조영술에게 자리를 양보해야 하는 상황이 될 수도 있을 것이다. [영문]Background: Contrast-enhanced multi-detector row spiral computed tomography (MDCT) has been introduced as a promising noninvasive method for vascular imaging. We investigated the accuracy of this technique in the detection of significant coronary artery stenoses. Method: Both MDCT(Sensation 16, Siemens, Germany, 12x0.75mm collimation and 0.42sec rotation speed, 120kV, 500 effective mA, and 2.7 mm rotation table-feed) and invasive coronary angiography(CAG) were performed in 61 consecutive patients (mean age 59.2¡3/410, 44 men) who were suspected to have coronary artery disease. All patients were treated with atenolol(25-50mg) prior to imaging and heart rate was maintained below 65 beats per minutes during image acquisition. Images were reconstructed in diastole around TI -400ms with 0.5mm increment and 1.0mm thickness. All coronary arteries with a diameter of 2.0mm or more were assessed for the presence of stenosis(> 50% luminal narrowing). MDCT data were evaluated by two independent radiologists who were unaware of the results of invasive CAG and were compared with the results of invasive CAG (interval 1-27, mean 11days). Result: Evaluation of CT coronary angiogram (CTCA) was possible in 58 of 61 patients (95%). Image acquisition of major coronary arteries including the left main trunk was available in 229 out of 244 arteries. Thirty-five of 58 patients had significant coronary artery stenoses by invasive CAG. By patient analysis in evaluable patients, CT coronary angiography correctly classified 30 of 35 patients as having at least 1 coronary stenoses (sensitivity 85.7%, specificity 91.3%, positive predictive value 93.8%, negative predictive value 80.8%). By each coronary artery analysis, CAG found 62 stenotic coronary arteries in evaluable 229 coronary arteries. MDCT correctly detected 50 of 62 stenotic coronary artery and absence of stenosis was correctly identified in 156 of 167 normal coronary arteries (sensitivity 80.6%, specificity 93.4%, positive predictive value 81.9%, negative predictive value 92.8%). Conclusion: The non-invasive technique of MDCT for coronary artery appears to be a useful method for detection of coronary artery stenoses with high accuracy especially to the proximal portion and large arteries.ope

miR-133a에 의한 노에피네프린으로 유도된 심근비대 억제효과

Dept. of Medicine/박사Cardiac hypertrophy is associated with the development of heart failure and has been known as a predictor for cardiovascular morbidity and mortality. A recent study unveiled potential regulatory roles for microRNA-133a (miR-133a) in cardiac hypertrophy. However, it has not been studied to elucidate the connection between miR-133a and norepinephrine-induced cardiomyocyte hypertrophy. Here, we investigated the expression and functional role of miR-133a in a norepinephrine-induced hypertrophic cardiomyocyte and determined the target of miR-133a in hypertrophic signaling. Neonatal rat cardiomyocytes were isolated, and cardiac hypertrophy was induced by treatment with 10 μM norepinephrine. In this study, we determined that miR-133a plays a pivotal role in the regulation of norepinephrine-induced cardiac hypertrophy. miR-133a expression is inversely related to cardiac hypertrophy, and the treatment with miR-133a mimics before norepinephrine management prevents norepinephrine-induced cardiac hypertrophy. Second, we found that the direct target of miR-133a is Protein Kinase C δ (PKCδ), which was confirmed by both Luciferase assay and Western blot analysis. We found no relationship between miR-133a and G protein. Finally, after transfection with miR-133a, MEK and ERK, which are in the downstream pathway, and proto-oncogenes such as c-fos, c-myc and c-jun were down-regulated in hypertrophic cardiomyocytes, suggesting that PKCδ is a novel target of miR-133a in cardiomyocytes, and that administration of or treatment with miR-133a mimics could be used in the future as a therapeutic application in the clinical settingope

Correlation of serial cardiac magnetic resonance imaging parameters with early resolution of ST-segment elevation after primary percutaneous coronary intervention

BACKGROUND: The aim of the present study was to determine whether the parameters of cardiac magnetic resonance imaging (CMRI) might correlate with early ST-segment resolution (STR) after primary percutaneous coronary intervention (PCI) in ST-elevation myocardial infarction (STEMI). METHODS AND RESULTS: CMRI was performed in 45 STEMI patients (age: 56.6+/-13.0 years) at 8.2+/-8.0 days (early phase) and 3.3+/-1.1 months (late phase) after successful PCI. CMRI parameters were compared between 2 groups: > or = 70% STR (group 1, n = 21) and or = 2 myocardial blush grade and shorter pain-to-balloon time in group 1. Early-phase CMRI showed that persistent microvascular obstruction (PMO) (38.1% vs 91.7%, p < 0.001) occurred less frequently and the percent infarct mass against total left ventricular (LV) mass (17.7+/-8.7% vs 29.1+/-13.4%, p = 0.001) was smaller in group 1. Late-phase CMRI revealed a significant increase in LV end-diastolic volume (-1.5+/-8.7 vs 14.5+/-25.5 ml, p = 0.026) and reduced ejection fraction (55.0+/-9.9% vs 47.8+/-11.1%, p = 0.027) in group 2. CONCLUSIONS: CMRI demonstrated that early STR might be related to PMO and infarct size, and predicts LV dysfunction and adverse LV remodeling. Also, early-phase CMRI findings are comparable to late-phase CMRI in association with early STR.ope

Right ventricular remodeling and dysfunction with subsequent annular dilatation and tethering as a mechanism of isolated tricuspid regurgitation

BACKGROUND: Secondary tricuspid regurgitation (TR) as a result of pulmonary hypertension and/or left-sided heart disease is caused by tricuspid valve (TV) annular dilatation and tethering of the tricuspid leaflet after right ventricular (RV) dilatation. However, the mechanism of isolated TR without significant pulmonary hypertension remains unknown. The present study investigated the RV function and TV deformations in patients with isolated TR to find out the mechanism and etiology of the disease. METHODS AND RESULTS: Twelve patients with isolated, severe TR were included. RV area, volume, ejection fraction (EF), tenting distance and tenting area were measured. These parameters were compared with 12 age-and gender-matched controls and 12 patients with secondary TR. The cause of isolated TR was incomplete coaptation associated with annular dilatation without other problems. Compared with the controls, RV end-diastolic volumes and annular diameters were significantly larger and RVEF was significantly lower in patients with isolated TR. Tenting area and tenting distance were also significantly higher. However, there were no significant differences in these parameters between patients with isolated and secondary TR. CONCLUSIONS: Isolated TR was associated with RV remodeling, systolic dysfunction and resultant annular dilatation and tethering of tricuspid leaflets.ope