• Journal of Biomedical Engineering Research
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• v.43 no.5
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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.

• Communications of the Korean Mathematical Society
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• v.19 no.2
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• pp.307-319
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• 2004

In this paper, we establish some new oscillation criteria for the functional differential equations of the form $\frac{d}{dt}$$\frac{1}{a_{n-1}(t)}$$\frac{d}{dt}(\frac{1}{{a_{n-2}(t)}\frac{d}{dt}(...(\frac{1}{a_1(t)}\frac{d}{dt}x(t))...)))^\alpha$ + $\delta[f_1(t,s[g_1(t)],\frac{d}{dt}x[h_1(t)])$ + $f_2(t,x[g_2(t)],\frac{d}{dt}x[h_2(t)])]=0$ via comparing it with some other functional differential equations whose oscillatory behavior is known.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.9C
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• pp.669-675
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• 2008

For an odd prime p, n=4k and $d=((p^2k+1)/2)^2$, there are $(p^{2k}+1)/2$ distinct decimated sequences, s(dt+1), $0{\leq}l<(p^{2k}+1)/2$, of a p-ary m-sequence, s(t) of period $p^n-1$. In this paper, it is shown that the cross-correlation function between s(t) and s(dt+l) takes the values in $\{-1,-1{\pm}\sqrt{p^n},-1+2\sqrt{p^n}\}$ and their, cross-correlation distribution is also derived.

• Journal of the Korean Statistical Society
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• v.32 no.3
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• pp.311-311
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• 2003

This paper contains the following errors. 1. "$I_{\{x>D\}}{\lambda}dt_{p0}(t)s(x)$" should be added to the right hand side of (2.3). 2. "$I_{\{x>D\}}{\lambda}_{p0}(t)s(x)$" should be added to the right hand side of (2.6). 3. "$I_{\{x>D\}}{\lambda}_{p0}s(x)$" should be added to the right hand side of (2.9). 4. In Theorem 2.3 and its proof, "${\lambda}{\int}_{0}^{D}f(y)s(x-y)dy$" appears three times (including one in (2.20)). To each of these, "${\lambda}_{po}s(x)$" should be added. 5. In Remark 2.5, "${\lambda}dt_{p0}/s(x)dx" should be added to "${\int}_{0}^{D}{\lambda}dt\;s(x-y)dxf(y)dy$". As a result of these corrections, a simpler proof of Theorem 2.3 becomes available. Substituting (2.18), (2.21), (2.22) into the left hand side of (2.20) and comparing the result with (2.10), we have the right hand side of (2.20).

• YAKHAK HOEJI
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• v.41 no.6
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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 the Korean Institute of Gas
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• v.16 no.5
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• pp.7-13
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• 2012

An experimental study has been done to investigate the explosion characteristics of aluminum powders with different sizes and concentrations in a 20 L spherical explosion vessel. Two different sizes of aluminum powder were used : $15.1{\mu}m$ and $34.8{\mu}m$ with a volume mean diameter. The results revealed that $15.1{\mu}m$ Al powder has a Lower explosion limit (LEL) of $40g/m^3$, a maximun explosion pressure ($P_{max}$) of 9.8 bar and a maximum rate of pressure rise ($[dP/dt]_{max}$) of 1852 bar/s, in $34.8{\mu}m$ Al powder, LEL of $70g/m^3$, $P_{max}$ of 7.9 bar and $[dP/dt]_{max}$ of 322 bar/s. The LEL of Al powders tended to increase with the increase of particle size. Also, it was found that the flame velocity calculated from the powder with $15.1{\mu}m$ was about 5 times higher than that of the powder of $34.8{\mu}m$.

• Communications of the Korean Mathematical Society
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• v.20 no.2
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• pp.339-350
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• 2005

We obtain the following two inequalities on a strongly pseudoconvex domain $\Omega\;in\;\mathbb{C}^n\;:\;for\;f\;{\in}\;O(\Omega)$ $$\int_{0}^{{\delta}0}t^{a{\mid}a{\mid}+b}M_p^a(t, D^{a}f)dt\lesssim\int_{0}^{{\delta}0}t^{b}M_p^a(t,\;f)dt\;\int_{O}^{{\delta}O}t_{b}M_p^a(t,\;f)dt\lesssim\sum_{j=0}^{m}\int_{O}^{{\delta}O}t^{am+b}M_{p}^{a}\(t,\;\aleph^{i}f\)dt$$. In [9], Shi proved these results for the unit ball in $\mathbb{C}^n$. These are generalizations of some classical results of Hardy and Littlewood.

• Journal of Microbiology and Biotechnology
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• v.29 no.12
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• pp.1882-1893
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• 2019

β-Glucosidases and β-xylosidases are two categories of enzymes that could cleave out non-reducing, terminal β-D-glucosyl and β-D-xylosyl residues with release of D-glucose and D-xylose, respectively. In this paper, two functional β-glucosidase Dth3 and β-xylosidase Xln-DT from Dictyoglomus thermophilum were heterologously expressed in E.coli BL21 (DE3). Dth3 and Xln-DT were relatively stable at 75℃ and were tolerant or even stimulated by glucose and xylose. Dth3 was highly tolerant to glucose with a K_i value of approximately 3 M. Meanwhile, it was not affected by xylose in high concentration. The activity of Xln-DT was stimulated 2.13-fold by 1 M glucose and 1.29-fold by 0.3 M xylose, respectively. Furthermore, the βglucosidase Dth3 and β-xylosidase Xln-DT showed excellent selectivity to cleave the outer C-6 and C-3 sugar moieties of ASI, which established an effective and green method to produce the more pharmacologically active CAG, an exclusive telomerase activator. We measured temperature, pH and dosage of enzyme using a single-factor experiment in ASI biotransformation. After optimization, the optimal reaction conditions were as follows: 75℃, pH 5.5, 1 U of Dth3 and 0.2 U of Xln-DT, respectively. Under the optimized conditions, 1 g/l ASI was transformed into 0.63 g/l CAG with a corresponding molar conversion of 94.5% within 3 h. This is the first report to use the purified thermostable and sugar-tolerant enzymes from Dictyoglomus thermophilum to hydrolyze ASI synergistically, which provides a specific, environment-friendly and cost-effective way to produce CAG.

• 한국생물공학회:학술대회논문집
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• 2003.04a
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• pp.327-330
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• 2003

The denitrification characteristics of free- and gel- D photosynthetic bacteria were studied. At various salt concentrations (0, 1, 2, 3.5%), the maximum specific growth rates were found to be 0.22, 0.22, 0.20 and 0.11 $h^{-1}$, respectively. At lower pH, pH affected the growth significantly. In experiments of PVA beads, the maximum $N_2$ production rate $(dN_2/dt)$ were calculated to be 0.09-0.10 (D= 0.7cm) and 0.09-0.11(D= 1.0cm) ml/h, respectively, and those per bead were 5 and $5.5\;{\mu}l$/h/bead.

• 순환기질환의공학회:학술대회논문집
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• 2002.11a
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• pp.48-49
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• 2002