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The variable stiffness actuator (VSA) is helpful to realize the post-collision safety strategies for safe human–robot interaction.1 The stiffness of the robot will be reduced to protect the user from injury when the collision between the robot and human occurs. However, The VSA has a mechanism limit constraint that can cause harm to users even if the stiffness is minimized. Accordingly, in this article, a concept combining danger index and robust fault detection and isolation is presented and applied to active–passive variable stiffness elastic actuator (APVSEA). APVSEA can actively change joint stiffness with the change of danger index. Experimental results show that this concept can effectively confirm the fault mode and provide additional protection measures to ensure the safety of users when the joint stiffness has been adjusted to the minimum.
Hypoxia is the primary stimulus for the production of erythropoietin (EPO) in both fetal and adult life. Here, we investigated fetal plasma EPO concentrations in monochorionic (MC) twin pregnancies with selective intrauterine growth restriction (sIUGR) and abnormal umbilical artery (UA) Doppler. We diagnosed sIUGR in presence of (1) birth-weight discordance >20% and (2) either twin with a birth weight <10th percentile. An abnormal UA Doppler was defined as a persistent absent-reverse end diastolic flow (AREDF). The intertwin EPO ratio was calculated as the plasma EPO level of the smaller (or small-for-gestational-age) twin divided by the EPO concentration of the larger (or appropriate-for-gestational-age (AGA)) twin. Thirty-two MC twin pairs were included. Of these, 17 pairs were normal twins (Group 1), seven pairs were twins with sIUGR without UA Doppler abnormalities (Group 2), and eight pairs were twins with sIUGR and UA Doppler abnormalities (Group 3). The highest EPO ratio was identified in Group 3 (p < .001) but no significant differences were observed between Groups 1 and 2. Fetal hemoglobin levels did not differ significantly in the three groups, and fetal EPO concentration did not correlate with gestational age at birth. We conclude that fetal plasma EPO concentrations are selectively increased in MC twin pregnancies with sIUGR and abnormal UA Doppler, possibly as a result of uncompensated hypoxia.
This study was conducted to determine the incidence of cerebral injury as detected by postnatal brain scan in monochorionic twins with selective intrauterine growth restriction. Having excluded cases complicated with twin-to-twin transfusion syndrome and one co-twin suffering intrauterine fetal death, a total of 73 monochorionic twin pregnancies divided into absence (group I, n = 46) or presence (group II, n = 27) of selective intrauterine growth restriction. Mild cerebral injury was defined as presenting one of the following abnormal cranial scan findings: intraventricular hemorrhage grade I, grade II, lenticulostiate vasculopathy and/or subependymal pseudocysts, while severe cerebral injury was defined as presenting intraventricular hemorrhage grade III, grade IV, cystic periventricular leukomalacia (PVL) grade II or higher, porencephalic cysts, and/or ventricular dilatation. The incidence of mild cerebral injury was not significantly different between these two groups (eight cases in group I and six cases in group II). Except for one case that later developed a seizure, the majority (13 out of 14) of cases with minor brain scan anomalies were only transient, without significant clinical impact. There was only one case diagnosed with a major brain scan anomaly (periventricular leukomalacia) in group II. One severe brain injury and three neonatal deaths all belonged to group II with abnormal umbilical artery Doppler in the growth restricted twin. In conclusion, the incidence of severe cerebral injury in monochorionic twin pregnancies with selective intrauterine growth restriction was low, at 3.7%.
Multiple pregnancies are thought to be associated with a high incidence of perinatal complications such as preterm labor, preeclampsia and low birth weight. But the true mechanisms of these obstetric complications are still uncertain. The components of amniotic fluid reflect the pathophysiology features of the fetus. Amniotic fluid soluble fms-like tyrosine kinase 1(sFLT1), soluble endoglin (sENG), and adiponectin reflect the oxidative stress and pro-inflammatory status and are associated with preeclampsia and fetal growth restriction. We prospectively collected amniotic fluids during amniocentesis from singleton and twin pregnancies. Samples were analyzed for levels of sFLT1, sENG, and adiponectin by enzyme-linked immunosorbent assay. The levels of sENG and sFLT1 were significantly increased in twin pregnancies. Adiponectin was not significantly different between the two groups. These findings would suggest that twin fetuses suffer from more oxidative stress and pro-inflammatory status from the early trimesters.
This study was conducted to investigate the relationship among umbilical venous volume flow, birthweight and placental share in monochorionic twins with or without selective growth restriction. Having excluded cases complicated with twin-to-twin transfusion syndrome and one co-twin suffering intrauterine fetal death, a total of 51 monochorionic twin pregnancies were divided into two groups as with (group 1) and without (group 2) selective intrauterine growth restriction. Umbilical venous volume flow was calculated by multiplying the umbilical vein cross-sectional area by half of the maximal velocity around mid-trimester. The placentas were cut along the vascular equator into two individual placental masses. The discordance of birthweight was calculated as [(birthweight of larger twin—birthweight of smaller twin)/birthweight of larger twin 100%]. The discordances of umbilical venous volume flow and placental share were calculated in a similar fashion. The median umbilical venous volume flow discordances (68.4% and 15.3% in groups 1 and 2 monochorionic twins, respectively) were similar and correlated well with the placental share discordances (66.6% and 18.5% in groups 1 and 2 monochorionic twins, respectively) but not with the birthweight discordance (28.6% and 6.4% in groups 1 and 2 monochorionic twins, respectively) in both groups. We concluded that the umbilical venous volume flow discordance reflects the placental share discordance rather than the birthweight discordance in monochorionic twin pregnancies.
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