Smaller Twin Research Articles

A Cost-Effective Solution for Measuring Vibration and Impact on Small Twin Engine Electric Fixed Wing UAV

A Cost-Effective Solution for Measuring Vibration and Impact on Small Twin Engine Electric Fixed Wing UAV

Intertwin discordance of aldosterone levels in amniotic fluid with placental anastomoses in monochorionic twins: Insight into the pathophysiology of twin-to-twin transfusion syndrome.

Our objective was to investigate the association between the presence of placental anastomoses and intertwin differences in renin-angiotensin-aldosterone activation in monochorionic twins using amniotic fluid aldosterone (AF-ALD) levels. In addition, this study also examined the association between AF-ALD and the ALD levels in the umbilical cord blood (UCB-ALD) in monochorionic twins. This prospective study included monochorionic diamniotic (MD) twin pregnancies that were not complicated by twin-to-twin transfusion syndrome (TTTS) at delivery. Amniotic fluid and umbilical cord vein blood samples were collected from each twin at delivery, and the ALD levels were measured subsequently. The MD twins were divided into two groups: those with placental anastomoses and those without anastomoses owing to fetoscopic laser surgery. The differences in the AF-ALD levels between the larger and smaller twins were analyzed. The AF-ALD levels showed a strong and significant positive correlation with UCB-ALD levels in 131 MD twins (r = 0.804, p < 0.001). Intertwin differences were examined in 41 and 28 pairs of MD twins with and without placental anastomoses, respectively. The AF-ALD levels in the smaller twins were significantly higher than those in the larger twins among the pairs of MD twins with placental anastomoses (p = 0.003); however, no statistically significant intertwin differences were observed among the twins without placental anastomoses (p > 0.05). The AF-ALD levels reflect the UCB-ALD levels in MD twins. The presence of placental anastomoses led to intertwin discordance in the ALD levels in MD twins even uncomplicated with TTTS. It was considered that monochorionic twins have this clinical background, and it leads to the development of TTTS.

Behavior and circadian glucocorticoids in prepubertal monozygotic twins with birthweight differences: A prospective longitudinal cohort study on twin-to-twin transfusion syndrome patients

Background/ObjectiveLow birthweight may have adverse sequelae in later life. Therefore, we analyzed behavioral difficulties and salivary glucocorticoid profiles in monozygotic twins with intra-twin birthweight differences due to twin-to-twin transfusion syndrome (TTTS). Methods46 monozygotic TTTS twin pairs with birthweight differences of <1SDS (concordant; n=29) and ≥1SDS (discordant; n=17) were recruited at a mean age of 6.9 years for a prospective longitudinal cohort study. For glucocorticoid analysis, saliva samples were collected (at 7 h, 13 h, 18 h and 21 h) and analyzed with liquid chromatography-tandem mass spectrometry. Parents completed the Strengths and Difficulties Questionnaire. ResultsFrom the parents’ perspective, the formerly smaller twins had statistically higher scores regarding hyperactivity (mean 4.63 vs 3.48, p=0.003) and emotional problems (mean 2.67 vs 2.02, p=0.042). Less catch-up growth (Δintra-twin height SDS 4 years of age - Δintra-twin birth length SDS) of the smaller twins was associated with higher scores for hyperactivity (Adj. R²=0.261, p<0.001, β=-1.88, F(1.44)=16.86, n=46, f²=0.35), while smaller birthweight (Adj. R²=0.135, p=0.007, β=-0,87, F(1.44)=8.03, n=46, f²=0.16) and birth length (Adj. R²=0.085, p=0.028, β=-0,78, F(1.44)=5.19, n=46, f²=0.09) were associated with higher scores for peer problems. Greater Δintra-twin for cortisol (7 h: rho=0.337, p=0.029; cumulative: rho=0.458; p=0.024) and cortisone (7 h: rho=0.329, p=0.029; 13 h: rho=0.436, p=0.005) correlated with a greater Δintra-twin for conduct problems. In the discordant group, circa 1 SDS in head circumference persisted from birth (mean SDS: smaller twin −1.18, larger twin −0.08, p<0.001) to present (mean SDS: smaller twin −1.16, larger twin −0.14, p<0.001). ConclusionHigher cortisol and cortisone concentrations in smaller twins were associated with higher scores for conduct problems. Lower birthweight and absent catch-up growth affected the parents’ perspective on the smaller twins’ behavior. They saw those children as more hyperactive, with more peer problems and emotional problems. Thus, it seems important to introduce regular check-ups where behavioral difficulties can be assessed, and assistance and advice can be given to the families. Due to the persisting smaller head circumference in the smaller discordant twins, this should be measured regularly.

Reduced lung function during childhood in identical twins with discordant fetal growth: a cohort study

Fetal growth restriction (FGR) can negatively affect lung development, leading to increased respiratory morbidity and reduced lung function later in life. Studies regarding the impact of FGR on lung function in singletons are influenced by genetic, obstetric, and maternal factors. To overcome these confounding factors, we aim to investigate lung function in identical twins with selective FGR (sFGR). Lung function assessments were performed in identical twins with sFGR born in our centre between March 1, 2002, and December 31, 2017, aged between 5 and 17 years. sFGR was defined as birthweight discordance ≥20%. Outcome measures consisted of forced expiratory volume in 1s (FEV1), forced vital capacity (FVC), and transfer factor for carbon monoxide (DLCO) and were compared between the smaller and larger twin. Thirty-nine twin pairs performed spirometry of sufficient quality. Median gestational age at birth was 34.3 (interquartile range (IQR) 32.1-36.0) weeks with median birthweights of 1500 (IQR 1160-1880) grams and 2178 (IQR 1675-2720) grams for the smaller and larger twin, respectively. Smaller twins had significantly lower z-scores for FEV1 (-0.94 versus-0.41, p=0.0015), FVC (-0.56 versus-0.06, p<0.0001) and DLCO (-0.50 versus 0.00, p<0.0001) compared to larger co-twins. Although being genetically identical, sFGR in identical twins is associated with a reduction in static and dynamic lung volume and a reduction in lung diffusion, even when taking the reduced lung volume into account. This indicates that adverse growth conditions in utero negatively affect lung development and function, potentially contributing to an increase in respiratory morbidities later in life. The Dutch Heart Foundation and The Bontius Foundation.

Experimental study of wet deck slamming for a SWATH in regular waves

Small Waterplane Area Twin Hull (SWATH) ships are subjected to severe sea conditions during ocean voyages, which may cause damage to the wet deck structures due to slamming. The flow process of wet deck slamming in catamarans is complex and involves wave breaking and splashing caused by wave impact on the wet deck. The slamming load under the wet deck of vessels is investigated in this paper by experiment. The test measures the slamming pressure of the wet deck in regular waves, and the flow field during slamming is observed using cameras. The experimental data are analyzed to determine the characteristics of the slamming pressure. The influence of wave height and wave length parameters on the magnitude and distribution of the slamming pressure are examined.

Study on the Effect of Hull Attitude on the Resistance Reduction of SWATH with Airflow Injection

With the development of the green ship concept in design and construction, how to reduce the resistance to reduce fuel consumption has become a focus of ship research. As an important drag reduction method, the air lubrication method has been applied to various ship types, but it is still a new method in the study of SWATH (small waterplane area twin hull) drag reduction. In this paper, the air lubrication method is applied to a SWATH model with an overall length of 2.5 m to numerically study the influence of the hull attitude on the air coverage and resistance reduction. The grid is verified by the grid independence and the experiment results. Then, the resistance of the SWATH model under different trim angles and drafts is calculated, and the air coverage on the surface is observed. The drag reduction rates of different areas, including the strut, underwater body, and fins, are analyzed, too. The results show that the slight trim by the head is more conducive to the resistance reduction of the SWATH model, and the resistance reduction rate can reach 39.11%. The draft mainly affects the resistance reduction of the strut, and the difference is more than 10%.

Salivary Diurnal Glucocorticoid Profiles in Monozygotic Twins With Intratwin Birthweight Differences.

Low birthweight (bw) and unfavorable intrauterine conditions have been associated with metabolic sequelae in later life, but little is known about their impact on glucocorticoid metabolism. We studied monozygotic twins with intratwin bw differences to analyze the long-term impact of bw on glucocorticoid metabolism. 46 monozygotic twin pairs with bw differences of <1 SDS (concordant; n = 29) and ≥1 SDS (discordant; n = 17) were recruited. At 6.9 years (mean age), saliva samples were collected (at 7 hours, 13 hours, 18 hours and 21 hour) and analyzed with liquid chromatography-tandem mass spectrometry (LC-MS/MS). We found significant or highly significant intratwin correlations in all twin pairs at 3 of 4 (cortisol), and 4 of 4 (cortisone) time points. Graphic evaluation of the diurnal cortisol patterns for each twin pair showed a distinct alignment in all groups. Analyses of the change of intratwin differences over the day by mixed linear modeling showed no intratwin differences in diurnal patterns. Regression analyses of intratwin differences at 7:00 hours showed a significant influence of catch-up growth, indicating lower cortisol concentrations in smaller twins with more catch-up growth (adj. R2 = 0.159, P = .014, ß = -3.71, F(1,42) = 9.15, f2 = 0.19). In monozygotic twins with intratwin bw differences, intratwin catch-up growth showed a moderate influence on intratwin differences in morning cortisol concentrations. We observed no differences regarding diurnal patterns. In contrast, in all groups, we found significant intratwin correlations for cortisol and cortisone over the day and a pronounced graphic alignment of cortisol diurnal patterns. We therefore suggest a predominant significance of the genetic background compared with bw differences on cortisol metabolism.

Experimental study on the drop test on wet deck slamming for a SWATH segment model

Wet deck slamming is a serious issue for high-speed catamarans if the relative vertical motions are higher. In this study, a drop test on wet deck slamming is conducted for a small waterplane area twin hull segment model, and the vertical water-entry model test is performed under different drop heights and speeds. The slamming pressure under the wet deck and the acceleration are measured. The flow field is obtained through particle image velocimetry measurement. A high-speed camera observation during wet deck slamming shows that air is pressed into water, and a water–gas mixture is formed due to the air compressibility effect. The slamming pressure shows an oscillating property with multiple frequency components, which is due to the air cushion effect caused by the volume variation of the water–gas mixture and the acoustic wave oscillation with the air pocket. The effects of the drop height variation and the constant-drop speed on the slamming load are analyzed. The results show that the pressure peak appears during the demihull's bottom slamming and wet deck slamming. The acceleration time record produces two peaks, one for the demihull's bottom slamming and another for the wet deck slamming. In conclusion, the air cushion effect can reduce the wet deck slamming pressure.

Association between fetal growth-restriction and retinopathy of prematurity using a unique identical twin model.

Research in singletons identified fetal growth restriction (FGR) as a risk factor for retinopathy of prematurity (ROP), but is generally subject to confounding by genetic, obstetric, and maternal factors. We investigated the effect of FGR on ROP in growth-discordant identical twins, thereby controlling for confounding factors. All data of monochorionic (MC) twin pairs with a birth weight discordance ≥20% born in our center between 2010 and 2021 were retrospectively reviewed for the presence of ROP. Potential risk factors for ROP were analyzed. Outcomes were compared between the smaller and larger twin. We included 88 MC twin pairs with growth discordance. In 34% (30/88), both neonates were at risk of ROP. Prevalence of ROP was higher among the smaller twin compared to the larger twin, 30% (9/30) versus 13% (4/30), respectively (OR 2.8, 95% CI: 1.2-6.6). The smaller twin had a longer duration of mechanical ventilation (8 (1-20) versus 2 (1-4) days) and received their first red blood cell transfusion at an earlier postmenstrual age (29.6 (28.1-31.6) versus 30.4 (29.7-32.6) weeks). In this identical twin model, FGR is associated with almost tripled odds of ROP development, suggesting that both unfavorable antenatal growth conditions and adverse neonatal outcomes affect postnatal retinal vascular proliferation. Fetal growth restriction in growth-discordant identical twins is associated with almost tripled odds of developing retinopathy of prematurity in the smaller twin. Since these twins do not only differ in birth weight but also duration of mechanical ventilation and timing of the first red blood cell transfusion, both unfavorable antenatal growth conditions and adverse neonatal outcomes can affect postnatal retinal vascular proliferation. More attention for preventing retinopathy of prematurity is needed in those with fetal growth restriction who received prolonged duration of mechanical ventilation, oxygen supplementation, or a first red blood cell transfusion <32 weeks postmenstrual age.

Congenital heart defects in monochorionic twin pregnancy complicated by selective fetal growth restriction.

To evaluate the prevalence, subtypes and postnatal outcomes of congenital heart defects (CHD) in a cohort of monochorionic diamniotic (MCDA) twin pregnancies complicated by selective fetal growth restriction (sFGR), and to compare this population with a cohort of uncomplicated MCDA pregnancies evaluated during the same period. This was a retrospective analysis of all consecutive MCDA pregnancies referred between 2009 and 2018, including those complicated by sFGR (Group A) and those without complications (Group B). All neonates delivered in our center were screened for CHD before discharge. Discharge letters for all those delivered elsewhere were retrieved. Pregnancies with complications other than sFGR and those without perinatal follow-up were excluded. Pregnancies in Group A were divided into three types according to the Gratacós system of sFGR classification. A total of 870 MCDA twin pregnancies were included: 296 in Group A and 574 in Group B. In Group A, the prevalence of CHD was 3.7% (22/592 twins), with no significant difference in CHD frequency between the three types of sFGR (Type I, 3.7%; Type II, 3.2%; Type III, 4.2%; P = 0.55). Of four Type-III sFGR pregnancies with CHD, one had pulmonary stenosis (PS) in the larger twin and isolated coarctation of the aorta in the smaller cotwin, and three had PS in the larger twin only. No Type-III sFGR pregnancies in which only the smaller twin was affected by CHD were observed. Of 11 CHD cases in the larger twin, 10 (91%) were right ventricular outflow tract abnormalities (RVOTA), and one (9%) was a ventricular septal defect. In the smaller twins, 11 cases of CHD were observed, covering a broad spectrum of cardiac abnormalities. In Group B, the CHD prevalence was 1.1% (13/1148 twins), which was similar to that in the general population, according to the EUROCAT registry for the same period and geographical area of the study (0.96%; P = 0.579). The CHD prevalence was significantly higher in Group A compared with Group B (3.7% vs 1.1%; P = 0.0002; odds ratio, 3.57 (95% CI, 1.78-7.22)). In all pregnancies with CHD in the study population, the anomaly was discordant. In MCDA twin pregnancy, sFGR was associated with a three-fold higher prevalence of CHD. Women with such pregnancies should be referred to a tertiary care hospital for pre- and postnatal cardiac evaluation, treatment and long-term follow-up. In larger twins, the only major CHD observed was RVOTA, while a broad spectrum of CHD was noted in smaller twins. The higher risk of CHD in MCDA pregnancies appears to be due to the typical complications of the monochorionic pregnancy, rather than to the monochorionic nature of the pregnancy itself. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Prevalence and Factors Associated With Intertwin Birth Weight Discordance Among Same-Sex Twins in Lombardy, Northern Italy.

This population-based cohort study investigated the prevalence, potential risk factors, and consequences of birth weight discordance (BWD) among same-sex twins. We retrieved data from the automated system of healthcare utilization databases of Lombardy Region, Northern Italy (2007-2021). BWD was defined as 30% or more disparity in birth weights between the larger and the smaller twin. Multivariate logistic regression was used to analyze the risk factors of BWD in deliveries with same-sex twins. In addition, the distribution of several neonatal outcomes was assessed overall and according to BWD level (i.e., ≤20%, 21-29, and ≥30%). Finally, a stratified analysis by BWD was performed to assess the relationship between assisted reproductive technologies (ART) and neonatal outcomes. We identified 11,096 same-sex twin deliveries; 556 (5.0%) pairs of twins were affected by BWD. Multivariate logistic regression analysis showed that maternal age ≥35 years (OR 1.26, 95% CI [1.05,5.51]), low level of education (OR 1.34, 95% CI [1.05, 1.70]), and ART (OR 1.16, 95% CI [0.94, 1.44], almost significant due to the low power) were independent risk factors for BWD in same-sex twins. Conversely, parity (OR 0.73, 95% CI [0.60, 0.89]) was inversely related. All the adverse outcomes observed were more common among BWD pairs than non-BWD ones. Instead, a protective effect of ART was observed for most neonatal outcomes considered among BWD twins. Our results suggest that conception after ART increases the risk of developing a high disparity between the weights of the two twins. However, the presence of BWD may complicate twin pregnancies, compromising neonatal outcomes, regardless of the modality of conception.

Nanoporous N/O:sp2-C films functionalized at nonbonding electrons of a biogenic husk (green chili) with deep UV-visible light absorption-emission for photocatalysis and other applications

The wastewater, which is released at industries, depleting aquatic ecology, and stringent pollution regulations, is a global issue of safety of the green nature. There is an urgent need for developing sustainable materials for pollutant removal from the polluted ground and/or surface water. In this purview, a sp2_C (a synergistic photocatalyst) offers a special remedy to degrade toxics in the potable water. It is nontoxic and ecological, and readily adsorbs the pollutants in water. Here, we explore synthesis of a biogenic N/O doped C-sp2 (p-GNO) of a nanoporous husk (green chili) of many electron film-shaped particles. Nonbonding n1, n2 → π* electron transitions (≤ 3.0 eV) at N/O mediate to coherently excite p-GNO to its π → π* excited states (5.0 eV) via an up-energy conversion. That lead to separate the electron-hole ‘e−–h+’ pairs so to degrade the pollutants at the redox reactions. The p-GNO exhibits a prominent (002) XRD peak as it consists of (002) sp2-C layers of thin films (2 −5 nm thickness). Two allotropes coexist − one ρc = 2.11 g/cm3 density and other a higher ρc = 2.41 g/cm3, at atomic arrays twisted at the pores at 2 → 5 nm sizes (335.2 m2/g surface area). Small twins are shown at a 2−5 nm scale at the HRTEM images, with atomic thin interfaces at 3 → 25° slips. As tested at two pollutants methylene blue (MB) and 2-chlorophenol (2-CP), as much as 92.5% (87.5 % at 2-CP) ‘degradation removal efficiency’ is obtained at a 3.1 × 10−3 min−1 rate for MB under the identical conditions. So, p-GNO exhibits better features over many high grade photocatalysts. The mechanism of energy-transfer is described with models at n1, n2 ↔ π* energy-conversions at harmonics in deep UV-visible regions. The results are useful to design and develop value aided sp2-C and related hybrids for adsorption, photocatalysis, photonics, and other applications.

Study on the Effect of Air Injection Location on the Drag Reduction in SWATH with Air Lubrication

In this paper, the air lubrication method is applied to high-speed SWATH (small waterplane area twin hull) to reduce the resistance. The influence of air injection locations on drag reduction is investigated. The computed results are compared with experimental results, and the grid independence test is performed. Then, the numerical method is used to simulate the resistance of SWATH in calm water with airflow. The hull is divided into different areas, and the influence of the air injection location on the drag reduction in different areas of the hull is studied through different air injection locations and airflow rates. It could be seen that the air injection location on the underwater body is more conducive to the drag reduction in SWATH than the air injection location on the strut. Besides, the air injection location near the bow of the underwater body could cause a better drag reduction effect of SWATH. There are obvious differences in the drag reduction effect of different areas of the underwater body.

Comparative study of the mating process for a spar-type floating wind turbine using two alternative installation vessels

The offshore wind industry faces many challenges as the water depth of offshore sites increases. For installation of the spar floating offshore wind turbines (OWTs), cost-effective installation methods are needed to facilitate installations at moderate or deep-water depths. In this paper, a novel installation concept initially designed for installing pre-assembled wind turbines is further studied. Two alternative installation vessels (i.e., a catamaran and a small water-plane area twin hull vessel (SWATH)) equipped with a dynamic positioning (DP) system are considered for installing 10-MW OWTs. Hydrodynamic responses of the installation systems are obtained by the fully coupled nonlinear time domain method. Based on the numerical analysis in SIMO-Riflex, a comparative study of the two vessel concepts is conducted to study selected response variables of two mating points. Compared with the catamaran installation vessel, the SWATH substantially reduces dynamic motions during the critical mating phase. The findings of this paper provide references for industrial stakeholders selecting alternative installation vessels and serve as a basis for further optimizing the concept.

ESTRATEGIA DE SELECCIÓN DE HARDWARE Y ALGORITMOS DE INTELIGENCIA ARTIFICIAL EN ENTORNOS 'EDGE COMPUTING'

Currently most of the data collected in companies and industrial manufacturing environments through IoT devices is processed in the cloud [1]. Given the large volume of data that each company manages due to the emergence of IoT, cloud computing is not the best option for certain sectors such as automotive [3]. Within this sector, the quality perceived by the end customer is closely linked to the assembly line. These assembly lines collect a high number of variables (temperatures, pressures, pumps, etc.) and a real-time prediction by means of small digital twins in this process would avoid both material and labor costs. Today, to perform such anticipation through artificial intelligence models in real time is unfeasible due to the latency that exists with cloud processing. Therefore, there is an imminent need to develop applications that are deployed at the edge of the network for the automotive manufacturing and painting process that enable the generation of digital twins. In this regard, the proposal of the 'Edge Computing' concept [2] seeks to mitigate in part this situation. For this reason, this paper has focused not only on demonstrating that splitting the data of a large model by generating small 'Edge' models maintains the predictive capacity of each algorithm, but also stress tests (limits, constraints, etc.) have been performed on the 'Edge Computing' hardware technology currently available on the market that allows generating and processing this type of models. Key Words: Edge Computing, Internet of things, Machine Learning, Industry 4.0

In-line monitoring of solid dispersion preparation in small scale extrusion based on UV–vis spectroscopy

The poor solubility of a large number of active pharmaceutical ingredients (APIs) is a major challenge in pharmaceutical research. Therefore, the extrusion of amorphous solid dispersions (ASDs) is one promising approach to enhance the dissolution rate by molecularly dissolving the API in an amorphous carrier polymer. During ASD extrusion, crucial parameters as the dissolution of the API in the carrier polymer need to be monitored. Within this study, a small scale twin screw extruder was coupled with special ColVisTec UV–vis probes that are characterized by their small dimensions. This setup enables a systematic formulation design and optimization based on in-line monitoring of drug dissolution using small material quantities. In fact, sample quantities of about 5 mg were evaluated for each measurement, representing 50% of the material inside the die. The amount of undissolved drug particles was determined based on the lightness of the extrudates. It was shown that the temperature has a significant effect on the drug dissolution in the polymer. Furthermore, complete drug dissolution was shifted to lower temperatures if higher residence times were applied. Based on the courses of lightness, regime maps were modeled that specify the process conditions where ASDs are successfully manufactured.

Occurrence of live-born twins with birth weight-discordance and its relationship to the adverse birth outcomes

Objective: To investigate the occurrence of live-born twins with birth weight-discordance and its relationship to adverse birth outcomes. Methods: A retrospective analysis was performed on 4 011 pairs of live-born twins in the Third Affiliated Hospital of Guangzhou Medical University from January 2011 to December 2020. Based on the birth-weight discordance (∆BW, ∆BW=(birth-weightbig-birth-weightsmall)/birth-weightbig×100%)), twins were divided into 4 groups, including ∆BW≤15%,>15%-20%,>20%-25%, and>25%. The differences in maternal and neonatal outcomes among 4 groups were explored. Then the correlation between ∆BW and neonatal adverse outcomes were explored. Results: The ΔBW was 9 (4, 16)% and males were accounted for 53.8% (4 315 cases) of 4 011 pairs of twins. The gestational age was (35.3±2.7) weeks at birth. There were 2 908 pairs (72.5%) of twins with ΔBW≤15%, 481 pairs (12.0%) with ΔBW>15%-20%, 281 pairs (7.0%) with ΔBW 20%-≤25%, and 341 twin pairs (8.5%) with ΔBW>25%. With ∆BW of 20% as the diagnostic cutoff, the incidence of birth weight discordance was 15.5% (622/4 011). The proportion of natural births in the ∆BW≤15% group was higher than that in the ∆BW>15%-20% group (10.5% (288/2 740) vs. 6.3% (29/463), P<0.008 3). The ∆BW>25% group had a significantly higher prevalence of maternal hypertensive disorders during pregnancy than that of the other 3 groups (25.5% (87/341) vs. 16.7% (47/281) vs.17.3% (83/480) vs. 13.8% (400/2 899), all P<0.008 3). Univariate analysis found that the ΔBW>25% group had a lower gestational age and a higher rate of preterm birth than the other groups. The rate of extremely low birth weight (ELBW) or very low birth weight (VLBW), small for gestational age (SGA), and transferring to the department of neonatology in the smaller twins were significantly different among the 4 groups (all P<0.05). Multivariate analysis showed that higher degree of birth weight discordance was all positively associated with the rate of ELBW, SGA, and transferring to the department of neonatology in smaller twin, even after adjusting maternal age and gestational hypertension, year of birth, mode of delivery, gender, and gestational age (all P<0.05). Moreover, the Mantel-Haenszel test also indicated that there were significantly low to moderate correlations between ΔBW and the unfavorable outcomes (r=0.22, 0.53, 0.21, all P<0.001, respectively). The receiver operating characteristic (ROC) curve found that adverse birth outcomes would be well predicted by birth weight-discordant when the diagnostic cut-off of ΔBW was 12%-17%, with an acceptable sensitivity (0.53-0.78) and a high specificity (0.72-0.79). Conclusions: Birth weight discordant is not uncommon in live-born twins, and is associated with adverse outcomes including ELBW, SGA, and transferring to the department of neonatology in the small twins. Besides, the risk is linearly related to the increase of ΔBW. In the future, more researches are needed to explore the underline mechanism and long-term impact of birth weight discordance, to guide the prevention and management.

A study on longitudinal motion stability of a variable-structure SWATH USV with and without twin hydrofoils

The form-changeable unmanned surface vehicle (USV) have a high research enthusiasm due to its far-ranging applicability, strong combat capability and low operating cost. This paper constructs a variable-structure Small Waterplane Area Twin Hull (SWATH) USV with twin hydrofoils, and aims at assessing its longitudinal motion stability (LMS) in the catamaran-form state (CFS) by parametric model and CFD method. The parametric representation of the torpedo, double struts and hydrofoils was conducted by uniform B-spline curves, 3-D coordinates conversion and surface generation method. The CFD code was verified, and used to calculate the LMS of the vessel with different strut configurations, form-states and CG position. Based on numerical results, the causes of different instability behaviors were expounded. Further, the LMS of the models with and without hydrofoils was compared at Fr = 0.1–0.8, the adjustment method of fore and aft hydrofoils to sailing attitudes was explained, the rational allocation of attack angles was also offered. The results show that the slender double struts arranged at both ends of torpedo is more conducive to the LMS and resistance, the vessel should sail in the CFS of γs ≤ 10° at Fr > 0.6; the hydrofoils slightly weakens the LMS at low Fr, makes the bow appear slight updip at Fr = 0.4–0.6, but still can sails stably; adjusting attack angles can inhibit the instability, and the most effective allocation of the fore and aft hydrofoil's attack angles is linearly arranged at Fr = 0.7, 0.8, also the adjusting can reduce the upward trim at Fr = 0.9, 1.0, but the hull is lifted higher and arises the bow updip due to the free surface suction force, at this time, the attack angle's graduation should be refined to realize the finer adjustment to the dynamic trim.

Insecure attachment and internalizing behavior problems in growth discordant identical twins

BackgroundPsychosocial development in monochorionic (MC) twins born after selective fetal growth restriction (sFGR) has been unreported to date, despite its importance for daily functioning and future relationships. AimsTo investigate psychosocial development, attachment and school functioning in MC twins with sFGR and compare outcomes with the general population and between smaller and larger twins. Study designObservational cohort study. SubjectsMC twins with sFGR (defined as a birth weight discordance ≥20 %) born between 2002 and 2017 and aged 3–17 years. Outcome measuresMultiple parent report questionnaires: the Child Behavior Checklist (social-emotional development and behavior), the (Early) Childhood Behavior Questionnaire Very Short Form (temperament), the Attachment Insecurity Screening Inventory (attachment) and a school functioning questionnaire. ResultsMedian age for the 48 twin pairs was 11 (interquartile range (IQR) 8–13) years. Attachment insecurity for both twins was higher than in the general population for ambivalence/resistance (34 % (21/62) vs. 16 %, p = 0.024) and total attachment insecurity (35 % (22/62) vs. 16 %, p = 0.016). Smaller twins had more internalizing behavioral problems, i.e. negative emotions and behaviors turned inwards (22 % (10/46) vs. 11 % (5/46), p = 0.021) and a higher negative affect, i.e. more likely to experience negative emotions (3.2 (2.9–3.7) vs. 2.9 (2.2–3.2), p = 0.009) than larger twins, as well as a lower secondary school level (p = 0.031). ConclusionMC twins with sFGR have more ambivalent/resistant attachment insecurity following the complicated pregnancy course. Smaller twins have a tendency towards negative emotions and internalizing behaviors compared to larger twins, indicating an increased sensitivity for depression and anxiety.

Hull form optimization design of SWATH with combination evaluations of resistance and seakeeping performance

With the rapid development of the marine economy, marine operations are gradually diversified. To improve the hydrodynamic performance of SWATH in offshore working conditions, a design optimization method for Small Water-plane Area Twin Hull (SWATH) considering the resistance and seakeeping performance is proposed. The automatic optimization design of SWATH hull form with minimum resistance at different speeds is carried out to obtain a set of Pareto optimal solutions. Then the seakeeping performance of the original and the Pareto optimal solution set are predicted. On this basis, a comprehensive evaluation method based on the composite weight factor of SWATH resistance and seakeeping performance is provided. The results show that the method can obtain a hull form scheme with better hydrodynamic performance than the original hull form. In addition, it can guide the hull form optimization design of SWATH.