The effect of backing material on the transmitting response level and bandwidth of a wideband underwater transmitting transducer using 1-3 piezocomposite material

AbstractIncreasing operating depths of autonomous underwater vehicles have necessitated the development of underwater transducers that can operate at a greater depth. This paper investigates the possibility of incorporating rigid backing material into the transducer design to increase its stiffness and depth capability without adversely affecting its wide bandwidth and high transmitting levels. The transducer design under consideration uses 1-3 piezocomposite material, matching layer, coupling layer, stiff backing material (backing plates) and operates at 300 kHz with 200 kHz 6dB bandwidth

Prediction of stillbirth from maternal demographic and pregnancy characteristics

Objectives: To develop a model for prediction of stillbirth based on maternal characteristics and components of medical history and evaluate the performance of screening of this model for all stillbirths and those due to impaired placentation and unexplained causes. Methods: This was a prospective screening study of 113,415 singleton pregnancies at 11+0-13+6 and 19+0-24+6 weeks’ gestation. The population included 113,019 live births and 396 (0.35%) antepartum stillbirths; 230 (58%) were secondary to impaired placentation and 166 (42%) were due to other or unexplained causes. Multivariate logistic regression analysis was used to determine the factors from maternal characteristics and medical history which provided a significant contribution to the prediction of stillbirth. Results: The risk for stillbirth increased with maternal weight (OR 1.01 per kg after 69 kg), was higher in women of Afro-Caribbean race (OR 2.01), assisted conception (OR 1.79), cigarette smokers (OR 1.71), those with a history of chronic hypertension (OR 2.62), SLE/APS (OR 3.61) or diabetes mellitus (OR 2.55) and was increased in parous women with a history of previous stillbirth (OR 4.81). The model predicted 26% of unexplained stillbirths and 31% of those due to impaired placentation at FPR of 10%; within the impaired placentation group the DR of stillbirth at 37 weeks (38% vs 28%). Conclusions: A model based on maternal characteristics and medical history recorded in early pregnancy can potentially predict one third of subsequent stillbirths. The extent to which such stillbirths could be prevented remains to be determined

Synoptic and dynamic characteristics of selected deep depressions over Cyprus

International audienceIn this study, the spatial and temporal distributions of dynamic and synoptic characteristics of a selection of 32 deep baroclinic depressions have been investigated. The study covers the cold period months of November till March, in the period from 1 November 1986 to 31 March 2003. For the needs of the study, several synoptic characteristics of these depressions have been extracted. Also, several dynamic characteristics during the evolution of the depressions were studied: relative vorticity, divergence, vertical motion and a static stability parameter. The results are presented in the form of isobaric distributions over, three tropospheric isobaric levels, namely the lower 850 hPa, the middle 500 hPa and the upper 300 hPa

The cold frontal depression that affected the area of Cyprus between 28 and 29 January 2008

The baroclinic depression that affected the area of Cyprus during the cold period, between 28 and 29 January 2008 was thoroughly studied and is presented in the present paper. A small perturbation on a northwesterly flow to the north of Cyprus has initiated the generation of the depression and in 24 h this developed into a deep baroclinic system. This depression was associated with intense weather phenomena, such as heavy thunderstorms with hail and near gale force winds. Strong cold advection resulted in a significant temperature decrease; precipitation even in lower altitudes was in the form of snow, while the accumulated rainfall corresponded to the 25% of the monthly normal. January 2008 is considered as a dry month, despite the fact that, on the average, January is considered as the wettest month of the year. In this study, the evolution and development of the depression was investigated from synoptic, dynamic, energetic and thermodynamic perspectives, in order to enhance our knowledge on the life cycle and behaviour of similar depressions over the area with extreme characteristics

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Value of routine ultrasound examination at 35-37 weeks' gestation in diagnosis of fetal abnormalities

Objective: To investigate the potential value of routine ultrasound examination at 35-37 weeks’ gestation in the diagnosis of previously unknown fetal abnormalities. Methods: This was a prospective study in 52,401 singleton pregnancies attending for a routine ultrasound examination at 35+0 - 36+6 weeks’ gestation; all pregnancies had a previous scan at 18-24 weeks and 47,215 also had a scan at 11-13 weeks. We included pregnancies resulting in livebirth or stillbirth but excluded those with known chromosomal abnormalities. The abnormalities were classified according to affected major organ system and the type and incidence of new abnormalities was determined. Results: In the study population the incidence of fetal abnormalities was 2.2% (1,168 / 52,401), including 847 (72.5%) that had been previously diagnosed during the first and / or second trimester, 247 (21.2%) that were detected for the first time at 35-37 weeks and 74 (6.3%) that were detected for the first time postnatally. The most common abnormalities that were diagnosed during the first and / or second trimester, that were also observed at 35-37 weeks, included aberrant right subclavian artery, ventricular septal defect, talipes, unilateral renal agenesis and / or pelvic kidney, hydronephrosis, duplex kidney or unilateral multicystic kidney, cystic pulmonary airway malformation, ventriculomegaly, cleft lip and palate, polydactyly,abdominal cyst or gastroschisis. The most common abnormalities seen at 35-37 weeks were hydronephrosis, mild ventriculomegaly, ventricular septal defect, duplex kidney, ovarian cyst and arachnoid cyst. The incidence of abnormalities first seen at 35-37 weeks was 0.5% and the most common were ovarian cysts, microcephaly, achondroplasia, dacryocystocele and hematocolpos. The incidence of abnormalities first seen postnatally was 0.1% and the most common were isolated cleft palate, polydactyly or syndactyly and ambiguous genitalia or hypospadias; prenatal examination of the genitalia was not a compulsory part of the protocol. Conclusions: A high proportion of fetal abnormalities are detected for the first time during a routine ultrasound examination at 35-37 weeks’ gestation. Such diagnosis and subsequent management, including selection of time and place for delivery and postnatal investigations, could potentially improve postnatal outcome

Comparison of different methods of measuring angle of progression in prediction of labor outcome

Objective: First, to compare the manual sagittal and para-sagittal and automated para-sagittal methods of measuring the angle of progression (AOP) by transperineal ultrasound during labor, and second, to develop models for the prediction of time-to-delivery and need for cesarean section (CS) for failure to progress (FTP) in a population of patients undergoing induction of labor. Methods: This was a prospective observational study of transperineal ultrasound on a cohort of 512 women with singleton pregnancies undergiong induction of labor. A random selection of 50 stored images was assessed for inter- and intra-observer reliability between methods. In the cases of vaginal delivery univariate linear, multivariate linear and quantile regression were performed to predict time-to-delivery. Univariate and multivariate binomial logistic regression were performed to predict CS for FTP in the first stage of labor. Results: The intra correlation coefficients (ICC) for the manual para-sagittal method for a single observer was 0.97 (CI 0.95-0.98) and for two observers was 0.96 (CI 0.93-0.98) indicating good reliability. The ICC for the sagittal method for a single observer was 0.93 (0.88-0.96) and for two observers was 0.74 (0.58-0.84) indicating moderate reliabilty for a single observer and poor reliability between two observers. Bland-Altman analysis demonstrated narrower limits of agreement for the manual para-saggittal approach than for the sagittal approach for both single and two observers. The automated para-sagittal method failed to capture an image in 19% of cases. The mean difference between sagittal and para-sagittal methods was 110. In pregnancies resulting in vaginal delivery, 54% of the variation in time-to-delivery was explained in a model combining parity, epidural and syntocinon use during labour and the sonographic findings of fetal head position and AOP. In the prediction of CS for FTP in the first stage of labour a model which combined maternal factors with the sonographic measurements of AOP and estimated fetal weight was superior to one utilising maternal factors alone (area under the curve 0.80 vs 0.76). Conclusions: First, the method of measuring AOP with greatest reliability is the manual parasagittal technique and future research should focus on this technique, second, over half of the variation in time to vaginal delivery can be explained by a model that combines maternal factors, pregnancy characteristics and ultrasound findings, and third, the ability of AOP to provide clinically useful prediction CS for FTP in the first stage of labour is limited

Prediction of stillbirth from maternal factors, fetal biometry and uterine artery Doppler at 19-24 weeks

Objectives: To evaluate the performance of screening for all stillbirths and those due to impaired placentation and unexplained or other causes by a combination of maternal factors, fetal biometry and uterine artery pulsatility index (UT-PI) at 19-24 weeks’ gestation and compare this performance to that of screening by UT-PI alone. Methods: This was a prospective screening study of 70,003 singleton pregnancies including 69,735 live births and 268 (0.38%) antepartum stillbirths; 159 (59%) were secondary to impaired placentation and 109 (41%) were due to other or unexplained causes. Multivariate logistic regression analysis was used to develop a model for prediction of stillbirth based on a combination of maternal factors, fetal biometry and UT-PI. Results: Combined screening predicted 55% of all stillbirths, including 75% of those due to impaired placentation and 23% of those that were due to other causes or unexplained, at false positive rate of 10%; within the impaired placentation group the detection rate of stillbirth at 37 weeks (88% vs 46%; p<0.001). The performance of screening by the combined test was superior to that of selecting the high-risk group on the basis of UT-PI being above the 90th percentile for gestational age, which predicted 48% of all stillbirths, 70% of those due to impaired placentation and 15% of those that were due to other causes or unexplained. Conclusions: Second-trimester screening by a combination of UT-PI with maternal factors and fetal biometry can predict a high proportion of stillbirths and in particular those due to impaired placentation

Diagnosis of fetal defects in twin pregnancies at routine 11-13-week ultrasound examination

Objective: To examine the performance of the routine 11-13 weeks scan in detecting fetal defects in twin pregnancies and to examine if in pregnancies with fetal defects, compared to those with normal fetuses, there is increased incidence of nuchal translucency (NT) thickness ≥95th and ≥99th percentiles or intertwin discordance in crown-rump length (CRL) ≥10% and ≥15%. Methods: This was a retrospective analysis of prospectively collected data in twin pregnancies undergoing routine ultrasound examination for fetal anatomy, according to standardized protocols, at 11-13 weeks’ gestation between 2002 and 2019. Pregnancies with known chromosomal abnormalities were excluded. The final diagnosis of fetal defects was based on the results of postnatal examination in the case of livebirths and on the findings of the last ultrasound examination in the cases of pregnancy termination, miscarriage or stillbirth. The performance of the 11-13 weeks scan in the detection of fetal defects was determined. Results: The study population of 6,366 twin pregnancies with two live fetuses at 11-13 weeks’ gestation, included 4,979 (78.2%) dichorionic (DC) and 1,387 (21.8%) monochorionic (MC) twin pregnancies. The main findings were: first, the overall incidence of fetal defects was higher in MC than DC twins (2.8% vs. 1.3%); second, the proportion of defects diagnosed in the first-trimester was higher in MC than in DC twins (52.6% vs. 27.1%); third, the pattern of defects in relation to detectability at the 11-13 weeks scan, always detectable, sometimes detectable and never detectable, was similar to that previously reported in singleton pregnancies; fourth, always detectable defects included acrania, alobar holoprosencephaly, encephalocele, pentalogy of Cantrell, exomphalos, body stalk anomaly, TRAP sequence and conjoined twins; fifth, the incidence of fetal NT ≥95th percentile was higher in those with than without defects (16.5% vs. 4.5% in DC twins and 19.2% vs. 5.9% in MC twins) and this was also true for NT >99th percentile (8.3% vs. 1.0% in DC twins and 15.4% vs. 2.0% in MC twins); and sixth, the incidence of CRL discordance ≥10% was higher in those with than without defects (20.2% vs. 7.9% in DC twins and 33.8% vs. 9.3% in MC twins) and this was also true for CRL discordance ≥15% (10.1% vs. 1.9% in DC twins and 28.2% vs. 2.8% in MC twins). Conclusions: First, fetal defects are more common in MC than in DC twin pregnancies, second, first-trimester detection of fetal defects in DC twin pregnancies is similar to that in singleton pregnancies, third, detectability of defects in MC twins is higher than in DC twins, fourth, in twin pregnancies with fetal defects there is a higher intertwin discordance in CRL and incidence of high NT, but the predictive performance of screening by these markers is poor