• Neonatal Medicine
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• v.15 no.1
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• pp.67-74
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• 2008

Purpose : The purpose of this study was to assess the natural history and perinatal outcomes of twin gestations according to chorionicity. Methods : We retrospectively reviewed the medical records of 99 monochorionic (MC) and 206 dichorionic (DC) twin gestations delivered at Il Sin Christian Hospital in Busan between January 2002 and December 2007. The incidences of twin-to-twin transfusion syndrome (TTS) and selective intrauterine growth restriction (sIUGR), as well as perinatal morbidity and mortality, were evaluated. Results : MC twins had a lower gestational age (35.7 vs. 36.6 weeks, P=0.03) at birth and a higher incidence of intrauterine fetal loss (10% vs. 1.5%, P<0.001) than DC twins. The incidence of intrauterine fetal loss was higher in MC sIUGR than in DC sIUGR (19% vs. 2.5%, P=0.025) twins. The number of admissions to the neonatal intensive care unit (NICU; 31% vs. 16%, P=0.042), and the incidence of periventricular leukomalacia (7% vs. 0%, P=0.031), and respiratory distress syndrome with surfactant treatment (27% vs. 11%, P=0.049) were higher in MC than DC twins. The incidences of sIUGR and TTS were 21 and 9% among the MC twins. The incidences of intrauterine fetal loss were higher in MC twins with TTS [6 of 9 (67%)] or sIUGR [4 of 21 (19%)] than uncomplicated MC twins (P<0.001). The frequency of admission to the NICU (P=0.001), the length of hospital stay (P=0.033), the prevalence of periventricular leukomalacia (P=0.011), and intraventricular hemorrhage (P=0.007) were also higher in MC with TTS or sIUGR than in uncomplicated MC twins. Conclusion : The incidence of neonatal complications was higher in MC twins, especially those gestations complicated by TTS or sIUGR.

• Journal of the Korean Chemical Society
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• v.29 no.5
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• pp.522-532
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• 1985

The reactions of p-nitrophenyldiphenylphosphate (p-NPDPP) with anions of benzimidazole (BI) and its 2-alkyl derivatives (R-BI) are strongly catalyzed by the micelles of cetyltrimethyl ammonium bromide (CTABr). On the other hand, the first order rate constants $(k'_{R-BI^-})$ and the second order rate constants $(k_{m(R-BI^-)})$ of the reactions mediated by R-$BI^-$in the micellar pseudophase are much smaller than those mediated by $BI^-$. In order to explain the slower rates of the micellar reactions mediated by R-$BI^-$, we compared the concentration-ratios ([R-$BI^-$]/[$BI^-$]) with the first order rate constant-ratios $(k'_{R-BI^-}/k'_{BI^-})$ and the second order constant-ratios $(k_{m(R-BI^-)}/k_{m(BI^-)})$ for the reactions taking place in the micellar pseudophase. The rate constant-ratios were much smaller than the concentration-ratios. For example in a 5 ${\times}10^{-4}$M butyl-BI solution, the two ratios were 0.089 and 0.430 (for the first order) respectively, and in a $10^{-4}$M butyl-BI solution the former was 0.100 (for the second order). This predicts that the reactivities of R-$BI^-$ in the micellar pseudophase are much smaller than that of $BI^-$. Based on the values of several kinetic parameters measured for dephosphorylation of p-NPDPP mediated by R-$BI^-$, a schemetic model is proposed. Due to the hydrophobicity and the steric effect of the alkyl substituents, these groups would penetrate into the core of the micelle for stabilization by van der Waals interaction with long cetyl groups of CTABr. Consequently, the movements of R-$BI^-$ bound to the micelle should be restricted, leading to decreased collison frequencies between the nucleophiles and p-NPDPP. We refer this as an "anchor effect". This effect became more predominent when a larger alky group in R-BI was employed and when a greater concentration of R-BI was used.

• Applied Chemistry for Engineering
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• v.29 no.3
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• pp.342-349
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• 2018

In this study, the physicochemical properties, emulsifying capacity, moisture content and cytotoxicity of the composite material produced by transesterification reactions of the olive oil (olive oil esters) were investigated for cosmetic applications. Olive oil esters with short (S) and long (L) reaction times were studied. From the TLC-image analysis, composition ratios of the olive oil esters S were found to be 5.2, 24.1, 46.4, and 21.9% for mono-, di-, tri-glyceride, and fatty acid ethyl ester, respectively. Those of the olive oil esters L were 4.1, 24.7, 40.6, and 28.8% for mono-, di-, tri-glyceride, and fatty acid ethyl ester, respectively. The iodine value, acid value, saponification value, unsaponified matter, refractive index, and specific gravity were determined and purity tests were also carried out and normalized to establish standards and testing methods for using olive oil esters in cosmetics. To evaluate their emulsifying capacities, the O/W emulsion was prepared without surfactants and the formation of the emulsified particles were confirmed. After 5 days of applying the olive oil esters to human skin, the skin moisture retention was improved by 13.1% from the initial state. For the evaluation of toxicity on human skin cells, the olive oil esters showed 90% or more of the cell viability at $0.2-200{\mu}g/mL$. These results suggested that olive oil esters can be applied as natural/non-toxic ingredients to cosmetics industries.