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The present article aimed to evaluate the impact of congenital Müllerian anomalies (MA) on twin pregnancy after 24 gestational weeks in Korean women. All records of twin pregnancies in a large maternity hospital in Korea between January 2005 and July 2013 were analyzed. Patients with monochorionic monoamniotic (MCMA) twins, non-Korean patients, patients with twins delivered prior to 24 gestational weeks, and patients with miscarriage of one fetus or intrauterine fetal death (IUFD) before 24 gestational weeks were excluded from data analysis. In total, 1,422 women with twin pregnancy were eligible for data analysis, including 17 (1.2%) who had a known congenital MA (septate uterus, bicornuate uterus, arcuate uterus, and unicornuate uterus). Except for the mode of conception, baseline demographics were similar between women with MA and those without MA. No significant differences were found in pregnancy outcomes of gestational age at delivery (p = .86), birth weight of smaller and larger twins (p = .54 and p = .65), and number of twins with birth weight <5th percentile for gestational age (p = .43).The rates of obstetrical complications such as pre-eclampsia, gestational diabetes mellitus (GDM), placenta previa, cerclage, IUFD, and postpartum hemorrhage were not significantly different between the two groups either. We concluded that the presence of congenital MA may not increase obstetrical risks in outcomes of pregnancy of twins delivered after 24 gestational weeks.
The South Korean Twin Registry (SKTR) is an ongoing nation-wide volunteer registry of South Korean twins and their families, which was established in the year 2001 to understand genetic and environmental etiologies of psychological and physical traits among South Koreans. Recently, the SKTR sampling has been extended in two important ways. First, we began to recruit twins from lower socio-economic families to study interaction effects of gene by environmental context. Second, as a parallel study of the SKTR, the Nigerian Twin and Sibling Registry was developed to understand the origin of the population group differences/similarities in psychological traits between South Koreans and Nigerians. This article summarizes the main findings (based on the SKTR sample to date), recruitment procedures, zygosity assessment, measures, and future plans for the SKTR.
Twin studies of Africans have been scarce although Africans have shown the highest twin birth rate in the world. As a parallel study of the South Korean Twin Registry, the Nigerian Twin and Sibling Registry (NTSR) was developed to understand causal influences on the development of cognitive abilities, personality, and mental health among Nigerians. Currently, 1,134 twins and 404 full- and half-siblings have been registered with NTSR. This article describes research background, goals, major recruitment strategies, measures, and future directions of the NTSR.
Birthweight has implications for physical and mental health in later life. Using data from Caucasian twins collected in Australia, the Netherlands and the United States, and from East Asian twins collected in Japan and South Korea, we compared the total phenotypic, genetic and environmental variances of birthweight between Caucasians and East Asians. Model-fitting analyses yielded four major findings. First, for both males and females, the total phenotypic variances of birthweight were about 45% larger in Caucasians than in East Asians. The larger phenotypic variances were mainly attributable to a greater shared environmental variance of birth- weight in Caucasians (ranging from 62% to 67% of variance) than Asians (48% to 53%). Second, the genetic variance of birthweight was equal in Caucasians and East Asians for both males and females, explaining a maximum of 17% of variance. Third, small variations in total phenotypic variances of birthweight within Caucasians and within East Asians were mainly due to differences in nonshared environmental variances. We speculate that maternal effects (both genetic and environmental) explain the large shared environmental variance in birthweight and may account for the differences in phenotypic variance in birthweight between Caucasians and East Asians. Recent molecular findings and specific environmental factors that are subsumed by maternal effects are discussed.
The South Korean Twin Registry (SKTR), previously called the Seoul Twin Family Study, is a nationwide volunteer registry of South Korean twins and their families. Since 2002, the SKTR has been updated in 4 important ways. First, continued sampling led to an increase in the number of twins. Second, the target area, Seoul, was enlarged to include other cities and rural areas in the country. Third, the target population was extended from school-aged twins to preschool and adult twins. Fourth, the research focus was expanded to include psychiatric and physical disease phenotypes. The present article describes a brief history of the SKTR, goals and current research highlights, recent major accomplishments, and future directions.
Recently, low molecular organic non-volatile memories have been developed as a next generation of non-volatile memory because of nano-meter device-feature size and nano-second access and store-time. We developed a non-volatile memory fabricated with the device structure of Al/ α-NPD/Al nano-crystals surrounded by Al2O3/α-NPD/Al, where α-NPD is N,N'-bis(1-naphthyl)-1,1'biphenyl4-4”diamine. One layer of Al nano-crystals with ∼20 nm-width ∼20 nm length was uniform produced between α-NPD layers, confirmed by 1.2MV high voltage transmission-electron-microscope. This device showed Vth of 3.0 V, Vprogram of 4.3 V, and Verase of 6.3 V. Particularly, this device exhibited an excellent non-volatile memory behavior performing the bi-stability (Iprogrm/Ierase) of >1×102, program/erase cycles of >1×105 and multi-levels. In addition, previous reports about low molecular organic non-volatile memories have showed a bad reproducible memory characteristic. However, this issue was completely solved via isolating Al nano-crystals embedded in α-NPD by O2 plasma oxidation. The uniformity of Vth, Vp, and Ve were 9.91%, 6.94% and 7.92%, respectively. Furthermore, the effect of buffer or barrier layer on non-volatile memory characteristics was investigate to examine the control ability for Vth, Vp, and Ve. The 0.5-nm LiF showed a barrier layer behavior suppressing the bi-stability of non-volatile memory. Otherwise, 15-nm CuPc exhibited a buffer layer behavior enhancing the bi-stability of nonvolatile memory.
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