The ability of dispersing carbon nanotubes (CNTs) in aqueous solutions by a starlike amphiphilic block copolymer with PPO-PEO segments (AP432) was investigated in detail. For comparison, two commercially available linear amphiphilic block copolymers, Pluronics L64 and F127, were also selected. It was found that AP432 and F127 can get good CNT dispersions, while L64 was proved to be unable to disperse CNTs. AP432 with five branches could disperse CNTs efficiently at much lower concentrations compared with the linear F127, although it has a smaller molecular weight and shorter terminal EO groups. This indicated clearly that, once branched, copolymers would get a much better ability to disperse CNTs. Increasing concentration of AP432 or F127 would disperse more CNTs, but at high copolymer concentrations the aggregation of dispersed CNTs was observed, which may be related to the free micelles formed by AP432 or F127 around CNTs. Other influencing factors such as the mass ratio of CNTs to copolymers and sonication time and strength were also discussed. From the molecular dynamics simulation results, it can be found that copolymers with five branches can gain better steric repulsions between adjacent CNTs, which is consistent with the experimental results.
Passive-active immunoprophylaxis with hepatitis B immunoglobulin (HBIG) and hepatitis B vaccine provides a high level of protection against vertical transmission of hepatitis B virus (HBV). Nevertheless, 1 in 10 children of HBV carriers have chronic hepatitis B early in their lives despite immunoprophylaxis because they were infected in utero. This study of 469 pregnant women testing positive for hepatitis B surface antigen (HbsAg) was conducted to learn whether giving HBIG to HBV carriers in the third trimester can prevent vertical transmission of the virus. Of the women entered into the study, all of whom were asymptomatic, 126 (group 1) tested positive for hepatitis B e antigen (HbeAg), while 343 (group 2) did not. HBIG was given intramuscularly in a dose of 200 IU at 28, 32, and 36 weeks of pregnancy. All newborn infants received 100 IU of HBIG within 12 hours of birth as well as the first of 3 doses of hepatitis B vaccine (the subsequent doses were given at ages 1 and 6 months).In group 1, 16% of infants whose mothers received HBIG in the third trimester tested positive for HbsAg at birth and 7% at age 6 months. The respective figures for infants whose mothers were not treated were significantly higher at 39% and 23%. No such treatment-related difference was observed in group 2 infants. At age 6 months, rates of protective levels of anti-Hbs antibody were 32% in group 1 infants whose mothers were HbeAg-positive and 56% in group 2 infants when the mothers had not received HBIG while pregnant. The respective figures for infants whose mothers were treated in the third trimester were 76% and 89%. Neither mothers nor their infants experienced adverse effects related to the administration of HBIG or hepatitis B vaccine.The investigators conclude that, if all HbsAg-positive pregnant women, regardless of HbeAg status, were to receive HBIG in the last weeks of pregnancy, their infants would be better protected against chronic HBV infection. ABSTRACTFetal karyotyping of cells obtained by amniocentesis may take as long as 3 weeks, and many pregnant women experience anxiety during the interval. This randomized, controlled study evaluated 2 tactics for lessening anxiety: issuing karyotyping results on a prespecified date rather than when they become available and presenting early results Preconception and Prenatal Care 495 496 Obstetrical and Gynecological Survey ABSTRACTAbout 1 in 4 primary cesarean deliveries take place during the second stage of labor. Not only is second-stage surgery technically more difficult, but the fetus is at risk of hypoxia-related morbidity. This prospective observational study of primary cesarean deliveries was carried out at 13 university centers that make up the National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network. Of 11,981 primary cesarean deliveries, 9265 were done in the first and 2716 in the second stage of labor. Women in the latter group were likely to be older, nulliparous, and white, and they had a smaller body mass index at the time of del...
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