Spectroscopy and carrier dynamics in CdSe self-assembled quantum dots embedded in ZnxCdyMg1−x−ySe

Time-resolved and steady-state photoluminescence,reflectivity, and absorption experiments were performed on CdSequantum dots in ZnxCdyMg1−x−ySe barriers. Studies of the capture times of the photoexcited carriers into the quantum dots and of electron-hole recombination times inside the dots were performed. Photoluminescence rise time yielded capture times from 20 ps to 30 ps. All samples exhibit fast and slow photoluminescence decays, consistent with observing two independent but energetically overlapping decays. The faster relaxation times for the sample emitting in the blue range is 90 ps, whereas for the two samples emitting in the green it is 345 ps and 480 ps. The slower relaxation times for the sample emitting in blue is 310 ps, whereas for the samples emitting in green is 7.5 ns. These results are explained on the basis of the structural differences among the quantum-dot samples

Funeral at Dawn

2-Alkenyltriflylanilides react with allenes upon treatment with catalytic amounts of Pd­(OAc)₂ and Cu­(II) to give highly valuable 2,3-dihydro-1<i>H</i>-benzo­[<i>b</i>]­azepines, in good yields, and with very high regio- and diastereoselectivities. Density functional theory (DFT) calculations suggest that the C–H activation of the alkenylanilide involves a classical concerted metalation–deprotonation (CMD) mechanism

Improved detection rate of structural abnormalities in the first trimester using an extended examination protocol

Screening for fetal structural and chromosomal abnormalities has become a routine part of antenatal care. First-trimester fetal structural assessment is reported to have anomaly detection rates (DRs) ranging from 12.5% to 83.7%. First-trimester assessment of the fetal heart using an approach similar to that of the second-trimester anomaly scan is feasible, with similar sensitivity for detecting congenital heart disease (CHD). This 2-year prospective study was designed to screen a low-risk unselected population, using an extended first-trimester morphologic protocol, to determine whether DRs comparable to those of the second-trimester structural assessment for major fetal abnormalities were feasible.The first-trimester ultrasound examination was performed at 12 to 13 weeks&apos; gestation and assessed the genetic and morphologic parameters suitable for evaluation at this gestation. Color Doppler cardiac sweep and contingent markers for early detection of major structural abnormalities were included in the protocol. All fetuses underwent a routine detailed second-trimester anomaly scan at 16 to 26 weeks&apos; gestation. Data included abnormalities diagnosed prenatally by ultrasound and those identified on postnatal neonatal and pathological examination. Increased nuchal translucency (NT) in itself was not considered an abnormality. Abnormalities were considered major if incompatible with life or associated with severe immediate or long-term morbidity. Moderate or minor abnormalities were those associated with short- or long-term morbidity of minor/moderate severity.A total of 5472 consecutive pregnancies were evaluated. The median maternal age was 28 years, and the prevalence of lethal and severe malformations was 1.4% (76/5472). Fifty-eight (76.3%) of the 76 major congenital anomalies were diagnosed during the first trimester. Previously undetected major fetal abnormalities were discovered at later ultrasound examinations in 0.31% (16/5109) of the population scanned and in 0.04% (2/4744) of the population examined postpartum. Follow-up evaluations rather than the first-trimester scan detected 80 of 89 of the minor/medium anomalies (89.9%). The first-trimester scan identified 40.6% (n = 67) of the 165 cases detected. For severity of malformations, 86.57% and 18.37% of cases detected in the first trimester and at follow-up, respectively, had severe or lethal abnormalities. The first-trimester DRs were 90% (27/30) for major CHD and 69.5% (16/23) for major CNS anomalies. Major chromosomal abnormalities were diagnosed in 21 cases (0.38%), 20 during the first-trimester evaluation. A total of 288 fetuses (5.26% of the first-trimester study group) had NT (≥95th percentile); the prevalence of major anomalies was 8.68% (25/288), and their first-trimester DR was 96% (24/25). In 5184 fetuses with normal NT, the prevalence of major anomalies was 0.98%, and the first-trimester DR was 66.7%. The differences in DRs for major CHD between the increased versus normal NT groups were not significant. The first-trimester examination took a median of 34 minutes, about 10 minutes longer than usually allocated for this examination.Although the first-trimester scan detected only ~40% of anomalies overall, its efficiency in identifying 76% of major malformations is one benefit. Before termination of abnormal fetuses, a detailed first-trimester protocol may provide information that would prove useful in counseling, particularly for future pregnancies. © 2014 by Lippincott Williams &amp; Wilkins

Improved detection rate of structural abnormalities in the first trimester using an extended examination protocol

Objective: To assess the potential of first-trimester sonography in the detection of fetal abnormalities using an extended protocol that is achievable with reasonable resources of time, personnel and ultrasound equipment. Methods: This was a prospective two-center 2-year study of 5472 consecutive unselected pregnant women examined at 12 to 13 + 6 gestational weeks. Women were examined using an extended morphogenetic ultrasound protocol that, in addition to the basic evaluation, involved a color Doppler cardiac sweep and identification of early contingent markers for major abnormalities. Results: The prevalence of lethal and severe malformations was 1.39%. The first-trimester scan identified 40.6% of the cases detected overall and 76.3% of major structural defects. The first-trimester detection rate (DR) for major congenital heart disease (either isolated or associated with extracardiac abnormalities) was 90% and that for major central nervous system anomalies was 69.5%. In fetuses with increased nuchal translucency (NT), the first-trimester DR for major anomalies was 96%, and in fetuses with normal NT it was 66.7%. Most (67.1%) cases with major abnormalities presented with normal NT. Conclusions: A detailed first-trimester anomaly scan using an extended protocol is an efficient screening method to detect major fetal structural abnormalities in low-risk pregnancies. It is feasible at 12 to 13 + 6 weeks with ultrasound equipment and personnel already used for routine first-trimester screening. Rate of detection of severe malformations is greater in early- than in mid-pregnancy and on postnatal evaluation. Early heart investigation could be improved by an extended protocol involving use of color Doppler. Copyright © 2013 ISUOG. Published by John Wiley &amp; Sons Ltd

Applications of ultrasound in prelabor and labor

Ultrasound is a crucial part of everyday obstetrical practice and becomes more and more important in the management of traditionally clinical aspects of obstetrics, such as management of labor and delivery, offering a possibly more objective method of examination. The rate of labor induction has doubled in the last two decades and more objective methods are needed to assess the possible outcome of an induction and help clinicians in order to counsel women appropriately. Regarding the management of labor there is extensive evidence that clinical assessment during labor is not accurate, with potential consecutive major implications in the decision-making and the prognosis of the delivery mode. Several studies have shown that ultrasound is an objective method of assessing labor and its progress and is very helpful in decision-making for instrumental deliveries. The purpose of this article is to review the evidence available in literature regarding the benefits and the role in general of ultrasonography in prelabor and labor