116 research outputs found
Refraction in exoplanet atmospheres: Photometric signatures, implications for transmission spectroscopy, and search in Kepler data
Refraction deflects photons that pass through atmospheres, which affects
transit light curves. Refraction thus provides an avenue to probe physical
properties of exoplanet atmospheres and to constrain the presence of clouds and
hazes. In addition, an effective surface can be imposed by refraction, thereby
limiting the pressure levels probed by transmission spectroscopy. The main
objective of the paper is to model the effects of refraction on photometric
light curves for realistic planets and to explore the dependencies on
atmospheric physical parameters. We also explore under which circumstances
transmission spectra are significantly affected by refraction. Finally, we
search for refraction signatures in photometric residuals in Kepler data. We
use the model of Hui & Seager (2002) to compute deflection angles and
refraction transit light curves, allowing us to explore the parameter space of
atmospheric properties. The observational search is performed by stacking large
samples of transit light curves from Kepler. We find that out-of-transit
refraction shoulders are the most easily observable features, which can reach
peak amplitudes of ~10 parts per million (ppm) for planets around Sun-like
stars. More typical amplitudes are a few ppm or less for Jovians and at the
sub-ppm level for super-Earths. Interestingly, the signal-to-noise ratio of any
refraction residuals for planets orbiting Sun-like hosts are expected to be
similar for planets orbiting red dwarfs. We also find that the maximum depth
probed by transmission spectroscopy is not limited by refraction for weakly
lensing planets, but that the incidence of refraction can vary significantly
for strongly lensing planets. We find no signs of refraction features in the
stacked Kepler light curves, which is in agreement with our model predictions.Comment: Accepted for publication in A&
Barriers in Referring Neonatal Patients to Perinatal Palliative Care: A French Multicenter Survey
International audienceBackground When an incurable fetal condition is detected, some women (or couples) would rather choose to continue with the pregnancy than opt for termination of pregnancy for medical reasons, which, in France, can be performed until full term. Such situations are frequently occurring and sometimes leading to the implementation of neonatal palliative care. The objectives of this study were to evaluate the practices of perinatal care french professionals in this context; to identify the potential obstacles that might interfere with the provision of an appropiate neonatal palliative care; and, from an opposite perspective, to determine the criteria that led, in some cases, to offer this type of care for prenatally diagnosed lethal abnormality. Methods We used an email survey sent to 434 maternal-fetal medicine specialists (MFMs) and fetal care pediatric specialists (FCPs) at 48 multidisciplinary centers for prenatal diagnosis (MCPD). Results Forty-two multidisciplinary centers for prenatal diagnosis (87.5%) took part. In total, 102 MFMs and 112 FCPs completed the survey, yielding response rate of 49.3%. One quarter of professionals (26.2%) estimated that over 20% of fetal pathologies presenting in MCPD could correspond to a diagnosis categorized as lethal (FCPs versus MFMs: 24% vs 17.2%, p = 0.04). The mean proportion of fetal abnormalities eligible for palliative care at birth was estimated at 19.30% (+/- 2.4) (FCPs versus MFMs: 23.4% vs 15.2%, p = 0.029). The degree of diagnostic certainty appears to be the most influencing factor (98.1%, n = 207) in the information provided to the pregnant woman with regard to potential neonatal palliative care. The vast majority of professionals, 92.5%, supported considering the practice of palliative care as a regular option to propose antenatally. Conclusions Our study reveals the clear need for training perinatal professionals in perinatal palliative care and for the standardization of practices in this field
Perinatal grief following neonatal comfort care for lethal fetal condition
BACKGROUND: The objective of the study was to assess perinatal grief experienced after continuing pregnancy and comfort care in women diagnosed with lethal fetal condition compared with termination of pregnancy for fetal anomaly (TOPFA).
METHODS: This was a retrospective observational study which included women who chose to continue their pregnancy after the diagnosis of lethal fetal condition with comfort care support at birth at the Prenatal Diagnosis Center of Rennes Hospital from January 2007 to January 2017. Women were matched with controls who underwent TOPFA for the same type of fetal anomaly, gestational age at diagnosis and year. Women were evaluated by a questionnaire including the Perinatal Grief Scale.
RESULTS: There were 28 patients in the continuing pregnancy group matched with 56 patients in the TOPFA group. Interval between fetal loss and completion of questionnaire was 6±3 years. Perinatal grief score was similar at 61±22 vs 58±18 (p = 0.729) in the continuing pregnancy and TOPFA groups, respectively. Women in the TOPFA group expressed more guilt. The cesarean-section rate in the continuing pregnancy group was 25% .
CONCLUSION: Perinatal grief experienced by women opting for continuing pregnancy and comfort care after diagnosis of a potentially lethal fetal anomaly is not more severe than for those choosing TOPFA
Caesarean section at term: the relationship between neonatal respiratory morbidity and microviscosity in amniotic fluid.
None of the authors report any conflicts of interest.International audienceOBJECTIVES: The incidence of neonatal respiratory morbidity following an elective caesarean section is 2-3 times higher than after a vaginal delivery. The microviscosity of surfactant phospholipids, as measured with fluorescence polarisation, is linked with the functional characteristics of fetal surfactant and thus fetal lung maturity, but so far this point has received little attention in new-borns at term. The aim of the study is to evaluate the correlation between neonatal respiratory morbidity and amniotic microviscosity (Fluorescence Polarisation Index) in women undergoing caesarean section after 37 weeks' gestation. STUDY DESIGN: The files of 136 women who had undergone amniotic microviscosity studies during elective caesarean deliveries at term were anonymised. Amniotic fluid immaturity (AFI) was defined as a Fluorescence Polarisation Index higher than 0.335. RESULTS: Respiratory morbidity was observed in 10 babies (7.3%) and was independently associated with AFI (OR: 6.11 [95% CI, 1.20-31.1] with p=0.029) and maternal body mass index (OR: 1.12 [95% CI, 1.02-1.22] with p=0.019). Gestational age at the time of caesarean delivery was inversely associated with AFI (odds ratio, 0.46 [95% confidence interval, 0.29-0.71], p<0.001), especially before 39 weeks, and female gender was associated with an increased risk (odds ratio, 3.29 [95% confidence interval, 1.48-7.31], p=0.004). CONCLUSIONS: AFI assessed by amniotic microviscosity was significantly associated with respiratory morbidity and independently correlated with shorter gestational age especially before 39 weeks. This finding provides a physiological rationale for recommending delaying elective caesarean section delivery until 39 weeks of gestation to decrease the risk for respiratory morbidity
On the abundance of non-cometary HCN on Jupiter
Using one-dimensional thermochemical/photochemical kinetics and transport
models, we examine the chemistry of nitrogen-bearing species in the Jovian
troposphere in an attempt to explain the low observational upper limit for HCN.
We track the dominant mechanisms for interconversion of N2-NH3 and HCN-NH3 in
the deep, hightemperature troposphere and predict the rate-limiting step for
the quenching of HCN at cooler tropospheric altitudes. Consistent with other
investigations that were based solely on time-scale arguments, our models
suggest that transport-induced quenching of thermochemically derived HCN leads
to very small predicted mole fractions of hydrogen cyanide in Jupiter's upper
troposphere. By the same token, photochemical production of HCN is ineffective
in Jupiter's troposphere: CH4-NH3 coupling is inhibited by the physical
separation of the CH4 photolysis region in the upper stratosphere from the NH3
photolysis and condensation region in the troposphere, and C2H2-NH3 coupling is
inhibited by the low tropospheric abundance of C2H2. The upper limits from
infrared and submillimeter observations can be used to place constraints on the
production of HCN and other species from lightning and thundershock sources.Comment: 56 pages, 0 tables, 6 figures. Submitted to Faraday Discussions [in
press
Respiratory support by neurally adjusted ventilatory assist (NAVA) in severe RSV-related bronchiolitis: a case series report
<p>Abstract</p> <p>Background</p> <p>Neurally adjusted ventilatory assist (NAVA) is a new mode of mechanical ventilation controlled by diaphragmatic electrical signals. The electrical signals allow synchronization of ventilation to spontaneous breathing efforts of a child, as well as permitting pressure assistance proportional to the electrical signal. NAVA provides equally fine synchronization of respiratory support and pressure assistance varying with the needs of the child. NAVA has mainly been studied in children who underwent cardiac surgery during the period of weaning from a respirator.</p> <p>Case presentation</p> <p>We report here a series of 3 children (1 month, 3 years, and 28 days old) with severe respiratory distress due to RSV-related bronchiolitis requiring invasive mechanical ventilation with a high level of oxygen (FiO<sub>2 </sub>≥50%) for whom NAVA facilitated respiratory support. One of these children had diagnosis criteria for acute lung injury, another for acute respiratory distress syndrome.</p> <p>Establishment of NAVA provided synchronization of mechanical ventilatory support with the breathing efforts of the children. Respiratory rate and inspiratory pressure became extremely variable, varying at each cycle, while children were breathing easily and smoothly. All three children demonstrated less oxygen requirements after introducing NAVA (57 ± 6% to 42 ± 18%). This improvement was observed while peak airway pressure decreased (28 ± 3 to 15 ± 5 cm H<sub>2</sub>O). In one child, NAVA facilitated the management of acute respiratory distress syndrome with extensive subcutaneous emphysema.</p> <p>Conclusions</p> <p>Our findings highlight the feasibility and benefit of NAVA in children with severe RSV-related bronchiolitis. NAVA provides a less aggressive ventilation requiring lower inspiratory pressures with good results for oxygenation and more comfort for the children.</p
Survival Rate Changes in Neonates with Congenital Diaphragmatic Hernia and its Contributing Factors
The purpose of this study was to demonstrate survival rate changes after the introduction of inhaled nitric oxide (iNO) therapy, and to identify the factors that influence these changes in neonates with a congenital diaphragmatic hernia (CDH) at a single center. A total of 48 neonates were divided into two groups based on the time of admission, i.e., into period I (P1; n=17; before the introduction of iNO therapy) and period II (P2; n=31; after the introduction of iNO therapy). Survival rates of the 48 neonates showed a tendency to increase from 53% during P1 to 77% during P2, but without a statistical significance, but a significant difference was found between survival rates during the two periods after adjusting for initial clinical characteristics, when the postoperative survival rate increased significantly from 69% for P1 to 100% for P2. The mean duration of preoperative respiratory management was significantly longer for P2 than for P1. Seven of 12 patients who received preoperative iNO therapy due to persistent pulmonary hypertension or refractory preductal hypoxemia in P2 survived after operation. We speculate that a management strategy based on iNO therapy and delayed operation, rather than differences between the initial clinical characteristics of the two study groups, might partially contribute to the observed improvements in postoperative and overall survival rates in neonates with CDH
Atmospheric retrieval of exoplanets
Exoplanetary atmospheric retrieval refers to the inference of atmospheric
properties of an exoplanet given an observed spectrum. The atmospheric
properties include the chemical compositions, temperature profiles,
clouds/hazes, and energy circulation. These properties, in turn, can provide
key insights into the atmospheric physicochemical processes of exoplanets as
well as their formation mechanisms. Major advancements in atmospheric retrieval
have been made in the last decade, thanks to a combination of state-of-the-art
spectroscopic observations and advanced atmospheric modeling and statistical
inference methods. These developments have already resulted in key constraints
on the atmospheric H2O abundances, temperature profiles, and other properties
for several exoplanets. Upcoming facilities such as the JWST will further
advance this area. The present chapter is a pedagogical review of this exciting
frontier of exoplanetary science. The principles of atmospheric retrievals of
exoplanets are discussed in detail, including parametric models and statistical
inference methods, along with a review of key results in the field. Some of the
main challenges in retrievals with current observations are discussed along
with new directions and the future landscape
Atmospheric electrification in dusty, reactive gases in the solar system and beyond
Detailed observations of the solar system planets reveal a wide variety of local atmospheric conditions. Astronomical observations have revealed a variety of extrasolar planets none of which resembles any of the solar system planets in full. Instead, the most massive amongst the extrasolar planets, the gas giants, appear very similar to the class of (young) Brown Dwarfs which are amongst the oldest objects in the universe. Despite of this diversity, solar system planets, extrasolar planets and Brown Dwarfs have broadly similar global temperatures between 300K and 2500K. In consequence, clouds of different chemical species form in their atmospheres. While the details of these clouds differ, the fundamental physical processes are the same. Further to this, all these objects were observed to produce radio and X-ray emission. While both kinds of radiation are well studied on Earth and to a lesser extent on the solar system planets, the occurrence of emission that potentially originate from accelerated electrons on Brown Dwarfs, extrasolar planets and protoplanetary disks is not well understood yet. This paper offers an interdisciplinary view on electrification processes and their feedback on their hosting environment in meteorology, volcanology, planetology and research on extrasolar planets and planet formation
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