• 대한의용생체공학회:의공학회지
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• 제43권5호
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• pp.331-340
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• 2022

Early afterdepolarization (EAD), a significant cause of fatal ventricular arrhythmias including Torsade de Pointes (TdP) in long QT syndromes, is a depolarizing afterpotential at the plateau or repolarization phase in action potential (AP) profile early before completing one pace. AP duration prolongation is related to EAD but is not necessarily accounted for EAD. Several computational studies suggested EAD can form from an abnormality in the late plateau and/or repolarization phase of AP shape. In this sense, we hypothesized the slope during repolarization has the characteristics to predict TdP risk, mainly focusing on the maximum slope during repolarization (dVm/dt_{max_repol}). This study aimed to predict the sensitivity of dVm/dt_{max_repol} to ion channel conductances as a TdP risk metric through a population simulation considering multiple effects of simultaneous reduction in six ion channel conductances of g_NaL, g_Kr, g_Ks, g_to, g_K1, and g_CaL. Additionally, we verified the availability of dVm/dt_{max_repol} for TdP risk prediction through the correlation analysis with qNet, the representative TdP metric. We performed the population simulations based on the methodology of Gemmel et al. using the human ventricular myocyte model of Dutta et al. Among the sixion channel conductances, dVm/dt_{max_repol} and qNet responded most sensitively to the change in g_Kr, followed by g_NaL. Furthermore, dVm/dt_{max_repol} showed a statistically significant high negative correlation with qNet. The dVm/dt_{max_repol} values were significantly different according to three TdP risk levels of high, intermediate, and low by qNet (p<0.001). In conclusion, we suggested dVm/dt_{max_repol} as a new biomarker metric for TdP risk assessment.

• 한국가스학회지
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• 제16권5호
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• pp.7-13
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• 2012

알루미늄 분진폭발특성에 미치는 입경과 농도 변화에 따른 영향을 20 L 구형 분진폭발시험장치를 사용하여 실험적으로 조사하였다. 실험에 사용한 알루미늄 분진의 체적 평균 입경은 15.1 및 $34.8{\mu}m$이다. 실험결과, 평균 입경 $15.1{\mu}m$에서의 폭발하한농도(LEL)는 $40g/m^3$, 최대폭발압력($P_{max}$)은 9.8 bar, 폭발압력상승속도는 ($[dP/dt]_{max}$)는 1852 bar/s이었으며, 평균입경 $34.8{\mu}m$의 경우에는 LEL이 $70g/m^3$, $P_{max}$는 7.9 bar, $[dP/dt]_{max}$는 322 bar/s가 얻어졌다. Al분진의 폭발하한농도는 입경 증가에 따라 증가하는 경향이 관찰되었다. 또한 평균입경 $15.1{\mu}m$에서의 Al분진폭발압력으로부터의 화염전파속도의 계산값은 평균입경 $34.8{\mu}m$의 경우보다 5배의 크기를 나타내었다.

• 약학회지
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• 제41권6호
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• pp.829-836
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• 1997

Studies on the effect of quinones on cardiac function has been conducted with normal hearts. But not with injured hearts, I.e. ischemia/reperfusion-injured heart. Quinone compounds are known to produce oxygen free radicals during metabolism, and for this reason, quinones are implicated in the aggravation of ischemia/reperfusion injury or cardioprotection, as in the case of ischemic preconditioning depending on the experimental conditions. The present study was carried out to examine the effect of 2-chloro-3-(4-cyanophenylamino)-1.4-naphthoquinone (NQ-Y15) on cardiac function of ischemic/reperfused and normal rat hearts. In isolated perfused hearts, various functional parameters such as left ventricular developed pressure (LVDP), left ventricular end-diastolic pressure (EDP) and maximum positive and negative dP/dt ($[\pm}dP/dt_{max}$), time to contracture, heart rate (HR) and coronary flow rate (CFR) were measured before and 30 min after dosing and following 25 min ischemia/30min reperfusion. NQ-Y15 increased LVDP, +dP/$d_{max}$and -dP/$dt_{min}$ by 18%. 30%, and 40%, respectively. There were no significant changes in other haemodynamic parameters. After ischemia/reperfusion injury, pretreatment with NQ-Y15 induced a significant decrease in LVDP and $[\pm}dP/dt_{max}$, but an increase in EDP. LDH-release was not significantly increased. These results suggested that NQ-Y15 may augment the ventricular contractility but it makes hearts more vulnerable to ischemia/reperfusion injury.

• Journal of Ginseng Research
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• 제37권3호
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• pp.273-282
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• 2013

The present study was designed to investigate the cardioprotective effects of Korean Red Ginseng extract (KRG) on isoproterenol (ISO)-induced cardiac injury in rats, particularly in regards to electrocardiographic changes, hemodynamics, cardiac function, serum cardiac enzymes, components of the myocardial antioxidant defense system, as well as inflammatory markers and histopathological changes in heart tissue. ISO (150 mg/kg, subcutaneous, two doses administered at 24-hour intervals) treatment induced significant decreases in P waves and QRS complexes (p<0.01), as well as a significant increase in ST segments. Moreover, ISO-treated rats exhibited decreases in left-ventricular systolic pressure, maximal rate of developed left ventricular pressure ($+dP/dt_{max}$) and minimal rate of developed left ventricular pressure ($-dP/dt_{max}$), in addition to significant increases in lactate dehydrogenase, aspartate transaminase, alanine transaminase and creatine kinase activity. Heart rate, however, was not significantly altered. And the activities of superoxide dismutase, catalase and glutathione peroxidase were decreased, whereas the activity of malondialdehyde was increased in the ISO-treated group. ISO-treated group also showed increased caspase-3 level, release of inflammatory markers and neutrophil infiltration in heart tissue. KRG pretreatment (250 and 500 mg/kg, respectively) significantly ameliorated almost all of the parameters of heart failure and myocardial injury induced by ISO. The protective effect of KRG on ISO-induced cardiac injury was further confirmed by histopathological study. In this regard, ISO treatment induced fewer morphological changes in rats pretreated with 250 or 500 mg/kg of KRG. Compared with the control group, all indexes in rats administered KRG (500 mg/kg) alone were unaltered (p>0.05). Our results suggest that KRG significantly protects against cardiac injury and ISO-induced cardiac infarction by bolstering antioxidant action in myocardial tissue.

• 한국화재소방학회:학술대회논문집
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• 한국화재소방학회 2011년도 춘계학술논문발표회 논문집
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• pp.376-377
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• 2011

최근 Mg, Mg-Al합금, Al은 전자제품의 케이스, 차량의 휠 등의 신소재로서 활용성이 높아 사회적 수요가 급격히 늘고 있다. 이러한 수요 증가와 함께 관련 사업장에서는 취급 과정에서 폭발사고 위험성이 높아지고 있는데, 2010년도에는 국내 사업장에서 금속 분진에 의한 폭발사고가 4건이 발생하여 인명 및 재산피해가 발생하였다. Mg-Al합금의 폭발사고로 사망 1명과 부상 2명이 발생하였으며, Al분진의 폭발사고는 3건이 발생하여 사망 2명과 부상 3명의 인명피해로 이어졌다. 사고조사를 통하여 사업장에서의 금속분진에 대한 위험인식이 매우 낮은 것이 유사 사고가 반복되고 있는 가장 큰 이유로 알려지고 있는데, 이는 금속분진에 대한 부족한 안전기술정보와 밀접한 관련이 있다. 본 연구에서는 Mg, Mg-Al합금, Al등을 취급하는 관련 사업장에서 폭발사고 예방대책을 위하여 활용할 수 있는 폭발특성에 관한 안전기술정보 제공을 목적으로 하고 있다. 보다 구체적으로는 사고 다발 금속분진에 대한 위험성 이해에 도움을 될 수 있도록 동일 입경분포 조건에서의 위험성을 정량적으로 평가하였으며, 이를 위하여 각 금속분진의 동일 입경 조건에서 최대폭발압력, 폭발하한계 등의 폭발위험성 데이터를 실험적으로 조사 하였다. 조사한 시료는 평균입경 200 mesh의 Al, Mg, Mg-Al(60:40 wt%)로서 입도분석기(Beckman Coulter LSI 3320)를 사용하여 측정한 결과 평균입경은 약 $155{\mu}m$로 나타났다. Al분진의 농도변화에 따른 폭발압력을 조사한 결과, 최대폭발압력(Pmax)은 7.9 bar였으며 최대폭발압력상승속도 (dt/dP)max는 농도 $1500[g/m^3]$에서 322 [bar/s]로 최대가 되었으며 폭발 하한계(LEL)는 $70[g/m^3]$가 얻어졌다. 반면에 순수한 Mg의 LEL은 $30[g/m^3]$였으며 Pmax는 6.4 bar, (dP/dt)max는 100 [bar/s]가 얻어졌다. 이러한 결과로부터 LEL이 낮은 Mg는 Al보다 연소성이 큰 것으로 나타났으며, Al은 화염을 유지하는데 필요한 최저 열분해 가스농도를 확보하는데 Mg보다도 고농도의 분진이 필요함을 알 수 있었다. 또한 Mg-Al(60:40 wt%)의 LEL은 $50g/m^3$이었으며 Pmax는 9.4 bar, (dP/dt)max는 472 [bar/s]가 얻어졌다. 이러한 결과로부터 Mg-Al(60:40 wt%)합금의 연소성을 살펴보면 착화하기 쉬운 정도는 Mg와 Al의 성분비에 의해 변화하지만 Mg와 Al의 중간 정도로 나타나는 반면, Pmax는 Mg 또는 Al의 단독 물질 성분보다도 매우 큰 것을 알 수 있었다. 본 연구를 통하여 단일 성분의 Mg와 Al보다도 Mg와 Al이 일정 비율로 구성된 Mg-Al합금의 경우가 화재폭발 위험성이 증가한다는 사실을 알 수 있었으며, 이와 같은 폭발위험특성 자료를 활용하여 분진의 보관, 취급, 폐기 등의 지속적 관리가 필요하며 사업장 특성에 적합한 안전대책을 통한 사고예방대책이 요구된다.

• Korean Chemical Engineering Research
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• 제57권6호
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• pp.790-803
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• 2019

디옥틸테레프탈산(DOTP) 제조공정은 분말형태의 테레프탈산(PTA) 주원료와 옥탄올(Octanol)의 에스테르화 반응을 통해 플라스틱 가소제를 생산하는 공정이다. 본 연구에서는 이 공정의 반응기 내에 가연성 용제나 유증기가 존재하고 있는 상태에서 분말형태로 맨홀에 직접 투입하는 테레프탈산의 분진폭발 특성에 관하여 고찰하였다. 분진의 입경과 입도분포 분진특성 실험을 하였고, 화재 폭발특성과 발화온도를 추정하기 위한 분진의 열분해 특성을 조사하였다. 또한 폭발민감도를 평가하기 위한 최소점화에너지 실험을 실시하였다. 실험결과 테레프탈산의 분체 특성은 평균입경이 $143.433{\mu}m$으로 나타났다. 이러한 입경과 입도분포 조건에서 실시한 열분석으로부터 분진의 발화온도는 약 $253^{\circ}C$로 나타났다. 테레프탈산의 폭발민감도를 알기 위해 조사한 폭발하한 농도(LEL)는 $50g/m^3$으로 측정되었다. 폭발민감도를 나타내는 최소점화에너지(MIE)는 (10 < MIE < 300) mJ로 나타났으며, 점화 확률에 기반하여 추산한 최소점화에너지 추정값(Es)은 210 mJ로서 충분한 점화원이 있는 경우 폭발할 수 있음을 알 수 있었다. 또한 폭발피해 예측에 필요한 폭발강도 특성을 조사한 결과, 테레프탈산 분진의 최대폭발압력($P_{max}$), 최대폭발압력상승속도[$({\frac{dP}{dt}})_{max}$]는 각각 7.1 bar, 511 bar/s로 나타났다. 분진폭발지수(Kst)는 139 mbar/s로 분진폭발등급 St 1에 해당되는 것으로 나타났다.

• Journal of Ginseng Research
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• 제44권3호
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• pp.483-489
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• 2020

Background: Korean Red Ginseng (KRG) has been known to possess many ginsenosides. These ginsenosides are used for curing cardiovascular problems. The present study show the protective potential of KRG against doxorubicin (DOX)-induced myocardial dysfunction, by assessing electrocardiographic, hemodynamic, and biochemical parameters and histopathological findings. Methods: Animals were fed a standard chow and adjusted to their environment for 3 days before the experiments. Next, the rats were equally divided into five groups (n = 9, each group). The animals were administered with KRG (250 and 500 mg/kg) for 10 days and injected with DOX (20 mg/kg, subcutaneously, twice at a 24-h interval) on the 8th and 9th day. Electrocardiography and echocardiography were performed to study hemodynamics. Plasma levels of superoxide dismutase, catalase, glutathione peroxidase, and malondialdehyde were measured. In addition, the dose of troponin I and activity of myeloperoxidase in serum and cardiac tissue were analyzed, and the histopathological findings were evaluated using light microscopy. Results: Administration of KRG at a dose of 250 and 500 mg/kg recovered electrocardiographic changes, ejection fraction, fractional shortening, left ventricular systolic pressure, the maximal rate of change in left ventricle contraction (-dP/dt_max), and left ventricle relaxation (-dP/dt_max). In addition, KRG treatment significantly normalized the oxidative stress markers in plasma, dose dependently. In addition, the values of troponin I and myeloperoxidase were ameliorated by KRG treatment, dose dependently. And, KRG treatment showed better histopathological findings when compared with the DOX control group. Conclusion: These mean that KRG mitigates myocardial damage by modulating the hemodynamics, histopathological abnormality, and oxidative stress related to DOX-induced cardiomyopathy in rats. The results of the present study show protective effects of KRG on cardiac toxicity.

• Journal of Ginseng Research
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• 제39권3호
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• pp.206-212
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• 2015

Background: Ginseng total saponin (GTS) contains various ginsenosides. These ginsenosides are widely used for treating cardiovascular diseases in Asian communities. The aim of this study was to study the effects of GTS on cardiac injury after global ischemia and reperfusion (I/R) in isolated guinea pig hearts. Methods: Animals were subjected to normothermic ischemia for 60 minutes, followed by 120 minutes of reperfusion. GTS significantly increased aortic flow, coronary flow, and cardiac output. Moreover, GTS significantly increased left ventricular systolic pressure and the maximal rate of contraction ($+dP/dt_{max}$) and relaxation ($-dP/dt_{max}$). In addition, GTS has been shown to ameliorate electrocardiographic changes such as the QRS complex, QT interval, and RR interval. Results: GTS significantly suppressed the biochemical parameters (i.e., lactate dehydrogenase, creatine kinase-MB fraction, and cardiac troponin I levels) and normalized the oxidative stress markers (i.e., malondialdehyde, glutathione, and nitrite). In addition, GTS also markedly inhibits the expression of interleukin-$1{\beta}$ (IL-$1{\beta}$), IL-6, and nuclear factor-${\kappa}B$, and improves the expression of IL-10 in cardiac tissue. Conclusion: These data indicate that GTS mitigates myocardial damage by modulating the biochemical and oxidative stress related to cardiac I/R injury.

• The Korean Journal of Physiology and Pharmacology
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• 제17권4호
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• pp.283-289
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• 2013

This study was designed to evaluate the protective effect of Korean red ginseng (KRG) against ischemia/reperfusion (I/R) injury in isolated guinea pig heart. KRG has been shown to possess various ginsenosides, which are the major components of Panax ginseng. These components are known naturally occurring compounds with beneficial effects and free radical scavenging activity. The heart was induced to ischemia for 60 min, followed by 120 min reperfusion. The hearts were randomly allocated into five groups (n=8 for each group): normal control (N/C), KRG control, I/R control, 250 mg/kg KRG group and 500 mg/kg KRG group. KRG significantly increased hemodynamics parameters such as aortic flow, coronary flow and cardiac output. Moreover, KRG significantly increased left ventricular systolic pressure (LVSP), the maximal rate of contraction (+dP/$dt_{max}$) and maximal rate of relaxation (-dP/$dt_{max}$). Also, treatment of KRG ameliorated electrocardiographic index such as the QRS, QT and RR intervals. Moreover, KRG significantly suppressed the lactate dehydrogenase, creatine kinase-MB fraction and cardiac troponin I and ameliorated the oxidative stress markers such as malondialdehyde and glutathione. KRG was standardized through ultra performance liquid chromatograph analysis for its major ginsenosides. Taken together, KRG has been shown to prevent cardiac injury by normalizing the biochemical and oxidative stress.

• Korean Chemical Engineering Research
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• 제61권1호
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• pp.80-88
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• 2023

저밀도 폴리에틸렌(Low-density polyethylene, LDPE)은 분진폭발 관련 특성치에 대한 기준이 제시되고 있지 않아 제조 및 취급설비의 안전한 설계가 어렵다. 이 연구에서는 LDPE 제조공정 중 Bag Filter에서 채취한 분진(LDPE 1)과 Silo 등의 설비 외부에 누설된 퇴적 분진(LDPE 2)에서 채취한 2개 시료에 대하여 분진폭발 시험을 수행하였고 그 중 LDPE 2 분진에 대하여 요약하였다. 입도분석 결과, 체적기준 평균입경은 95.04 ㎛, 수밀도는 0~1 ㎛로 나타났다. 최대폭발압력(P_max)은 6.6 bar, 최대폭발압력상승속도는 1500 g/m³에서 366 [bar/s]로 분진폭발지수(K_st)는 99.4 bar·m/s로 ST-1 등급임을 확인하였다. 또한, 최소점화에너지는 10 mJ이며 최소점화온도는 450 ℃로 나타났다. 현재, 제조 및 취급 설계는 고밀도 폴리에틸렌(HDPE)의 특성값을 기초로 한다. 그러나, 시험 결과 LDPE 2 분진이 HDPE(입자지름 61.6 ㎛)보다 위험성이 높은 것으로 나타나 LDPE 제조공정에서 HDPE 설계기준을 적용할 때는 주의가 필요하다.