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Transcatheter right ventricle decompression in neonates with pulmonary atresia and intact ventricular septum is technically challenging, with risk of cardiac perforation and death. Further, despite successful right ventricle decompression, re-intervention on the pulmonary valve is common. The association between technical factors during right ventricle decompression and the risks of complications and re-intervention are not well described.
This is a multicentre retrospective study among the participating centres of the Congenital Catheterization Research Collaborative. Between 2005 and 2015, all neonates with pulmonary atresia and intact ventricular septum and attempted transcatheter right ventricle decompression were included. Technical factors evaluated included the use and characteristics of radiofrequency energy, maximal balloon-to-pulmonary valve annulus ratio, infundibular diameter, and right ventricle systolic pressure pre- and post-valvuloplasty (BPV). The primary end point was cardiac perforation or death; the secondary end point was re-intervention.
A total of 99 neonates underwent transcatheter right ventricle decompression at a median of 3 days (IQR 2–5) of age, including 63 patients by radiofrequency and 32 by wire perforation of the pulmonary valve. There were 32 complications including 10 (10.5%) cardiac perforations, of which two resulted in death. Cardiac perforation was associated with the use of radiofrequency (p=0.047), longer radiofrequency duration (3.5 versus 2.0 seconds, p=0.02), and higher maximal radiofrequency energy (7.5 versus 5.0 J, p<0.01) but not with patient weight (p=0.09), pulmonary valve diameter (p=0.23), or infundibular diameter (p=0.57). Re-intervention was performed in 36 patients and was associated with higher post-intervention right ventricle pressure (median 60 versus 50 mmHg, p=0.041) and residual valve gradient (median 15 versus 10 mmHg, p=0.046), but not with balloon-to-pulmonary valve annulus ratio, atmospheric pressure used during BPV, or the presence of a residual balloon waist during BPV. Re-intervention was not associated with any right ventricle anatomic characteristics, including pulmonary valve diameter.
Technical factors surrounding transcatheter right ventricle decompression in pulmonary atresia and intact ventricular septum influence the risk of procedural complications but not the risk of future re-intervention. Cardiac perforation is associated with the use of radiofrequency energy, as well as radiofrequency application characteristics. Re-intervention after right ventricle decompression for pulmonary atresia and intact ventricular septum is common and relates to haemodynamic measures surrounding initial BPV.
The in situ dry matter disappearance technique (Ørskov and McDonald, 1979) evaluates forages for their rate and extent of degradation in the rumen. However, this method does not allow the evaluation of a large number of samples at one and the same time and therefore which limits screening of treatments applied to forages. The in vitro gas production method is faster and allows handling of many samples per batch; therefore, gas production could be an alternative to the use of nylon bags if the response to treatments between the two methods is similar among treated forages. The objective of this experiment was to compare results obtained with both the gas production and the nylon bag techniques for forages treated with four levels of maceration and conserved as hay or silage.
The GRIG-2 geodetic VLBI experiment was conducted in 1985, linking for the first time South America, Europe and Africa. At the single frequency band of 1.66 GHz which was used, the monitoring of the ionosphere is a critical aspect and several predictions of Total Electron Content (TEC) were used. One of them is derived from dual band Doppler observations of TRANSIT satellites, which were simultaneously conducted. The influence of these models on the solution is presented, with comparisons with other VLBI solutions. Decimetric accuracy has been achieved.
A global array of 20 radio observatories was used to measure the three-dimensional position and velocity of the two meteorological balloons that were injected into the equatorial region of the Venus atmosphere by the VEGA spacecraft.
Deuterium content, microparticle concentration, ice crystal size and bubble concentration have been studied along an 82 m ice core drilled down to the bedrock in the ice-sheet margin in East Antarctica. The Last Glacial Maximum (LGM) is distinctly marked by low deuterium content, high concentration of microparticles, small ice crystals and high bubble concentrations. This core covers a significant part of the Last Glacial Period with ice from a warmer period recovered around a depth of 60 m.
The climate of the Holocene is, for continental regions from middle and low latitudes, relatively well documented from pollen studies and other sources. To obtain a global picture, these data must be supplemented by climatic series from polar regions. Such information may be extracted from δD or δ18O ice-core profiles but the interpretation of these isotopic records suffers some limitations, (1) because, expected temperature changes being small, they can be obscured by noise effects in the isotope-temperature relationship, and (2) because they can be influenced, especially in coastal regions, by changes in origin of the ice.
With this in mind, we focus our presentation on Dome C and Vostok cores drilled on the East Antarctica Plateau and essentially undisturbed by ice-flow conditions. The detailed comparison between these continuous isotopic records makes it possible to know which part of the isotopic signal is climatically significant. Spectral properties of these two records are also examined over the Holocene period. In addition, we present isotopic results obtained on a 950 m ice core drilled at Komsomolskaia (also on the East Antarctica Plateau) by the Soviet Antarctic Expedition. This core fully covers the Holocene and, although discontinuous, the new data help us to document the East Antarctica isotopic record.
From these data, an average climatic record is constructed which shows that the East Antarctica climate was fairly stable during the Holocene, marginally warmest around 10 kyear B.P. and coldest in periods around 1.5 and 6 kyear B P. These features are discussed in relation with other Antarctic data (Byrd, Law Dome, Ross Ice Shelf) and with climate records from both southern and northern hemispheres
A 2 200 m-deep ice core from Vostok Station (East Antarctica) has been used for a comprehensive study of a series of ions (Na+ NH4+, K+, H+, Ca2+, Mg2+, C1−, F−, NO3− and SO42−) originating from impurities deposited over the whole last climatic cycle (180 000 years) as depicted from the isotopic composition of the ice.
Concentration profiles confirm that both marine and terrestrial aerosol inputs were higher (up to five and 30 times the Holocene values respectively) during cold climatic conditions. Such large variations of marine and terrestrial aerosol concentrations measured in ice mainly reflect global (source strength and atmospheric transport efficiency) changes, and to a lesser extent local (deposition) changes.
As opposed to these primary aerosols, secondary aerosols or gases (HNO3, HC1) exhibit more moderate variations. Finally, variations of other minor ions such as NH4+ provide information on the capacity of ammonia to neutralize the natural acidity of the past background atmosphere.
Spectral analyses performed on our chemical profiles (200 samples) exhibit several specific periodicities (around 20 and 40 k year) close to the Earth's orbit tilt and precession frequencies which are discussed in terms of atmospheric response to climatic fluctuations.
A review of Byrd, Vostok and Dome C Antarctic ice-core records indicates significant changes in atmospheric characteristics between the late glacial maximum (LGM) and the Holocene. This data is relevant to general circulation model (GCM) boundary conditions and validation of output results. Reciprocally, GCM data could help to interpret ice-core results and to extend observed high-latitude changes to a larger scale.
During the LGM, low troposphere temperatures were colder by about 5 to 7°C and surface temperatures by 8 to 10°C over the Antarctic ice sheet. There are indications that snow accumulation was slightly lower and isotopic data suggests higher relative humidity over the ocean. A large increase in continental dust (up to a factor of 20) and marine aerosols (up to a factor of 5) is observed on the high Antarctic plateau, both explained by the increased (possibly up to 1.4 to 2 times) intensity of the large-scale atmospheric circulation modulated by desert and sea-ice area extension. Ice-core results show large changes in atmospheric CO2 concentrations with LGM values around 200 ppmv and “pre-industrial” values of about 260 ppmv. Finally, determinations of total gas content suggest that central West and East Antarctica were not thicker during the LGM, in contrast with higher surface elevations inferred from coastal-ice studies.
The debris-rich ice from the bottom 6 m of the 82 m deep CAROLINE (Coastal Antarctic Record of Last Interglacial Natural Environment) ice core reaching bedrock, and from five 2 m long surface cores at Moraine Prudhomme in Terre Adélie (Antarctica) is described and compared to debris-laden ice from the core-drilling site DIO. Isotopic, total-gas content, CO2 concentration and SEM investigations of embedded particles, together with ice textures and fabrics, rule out “pressure-melting” regelation around bed obstacles or “freezing-on” as possible mechanisms for the debris entrainment at the ice-bedrock interface. It is suggested that the debris entrapment by purely mechanical means (e.g. shearing) is an efficient process in forming basal ice layers (BIL) at sub-freezing temperatures. This process might be dominant at the margin of the Antarctic ice sheet where no ice shelf exists and where a ramp terminus or a buttressing coastal relief induces compressive flow.
Oceanic studies have convincingly demonstrated that there is a link between the Pleistocene ice ages and the variations in the elements of the Earth’s orbit (Imbrie and others 1984). In contrast, the climatic conditions which prevailed over continental areas have been far less well documented and then rarely on a quantitative basis.
In this context, the 2083 m ice core recovered by the Soviet Antarctic Expeditions at Vostok (East Antarctica) is of fundamental importance because it covers fully the last glacial-interglacial cycle, back to the ice age which preceded the last interglacial (∽160 ka B.P.). Potentially it allows access to many climatic and climate-related parameters as illustrated by the oxygen-18 data we have recently published (Lorius and others 1985), from 10Be measurements (Yiou and others 1985, Raisbeck and others 1987), from aerosol concentration (De Angelis and others 1987) and from CO2 measurement (Barnola and others 1988, this volume).
Our first isotopic data set was largely discontinuous over the last 100 ka (only about 7% of the core was analyzed), but continuous beyond that time. Sampling of the ice was completed later, in the field, and we now have continuous deuterium data for the whole core (total ice recovery is about 85%), combining the data of the 2083 m core below 138 m and a complementary data set above. The core chronology was established using a two-dimensional ice-flow model and, for snow accumulation, taking into account change with time (Lorius and others 1985).
There is a general correspondence between this curve and the previously published δ18O record (Lorius and others 1985). However, there is obviously far more information in this continuous δD record, which we will examine from the deduced temperature record.
The 2083 m Vostok Antarctic ice core provides a unique opportunity for access to many paleoclimatic and paleo-environmental proxy data. This core, which has been dated by using a glaciological model, fully covers the last glacial-interglacial cycle, and goes back to the ice age which preceded the last interglaciai (−160 ka B P ).
A continuous deuterium record is now available and we have interpreted it in terms of local temperature changes. This record is dominated by the large 100 ka glacial-inter-glacial oscillation, with a maximum temperature amplitude of about 11°C; the long Last Glacial period is very well documented and it is confirmed that the warmest part of the Last Interglaciai period was about 2°C warmer than the Holocene. Comparison with the ice-volume marine record shows that the Vostok climate record is of relatively large geographical significance, which makes it possible to establish, over the last 160 ka, the link between worldwide climatic changes and the Vostok dust record that we present here.
This dust content corresponds to the non-soluble microparticles. It was obtained on a discontinuous basis (1 sample = about ∼10 m). Due to the very low concentration of some samples (down to 20 x 10−9gg−1) and cracks in the ice from the first 1000 m depth, we used stringent decontamination procedures. Size distribution and total concentration were measured, using a Coulter counter and an optical microscope; the results were tested against chemical measurements (aluminium concentration). In previous studies, it has been shown that the main proportion of insoluble microparticles is of terrigenous origin and represents the small-sized (radius <2 μm) dust produced on the continents.
The Vostok record displays an increase in dust concentration of up to 20 times during the coldest climatic periods, coupled with the presence of larger particles. It confirms, on a much longer time-scale, a characteristic previously noted in Antarctic and Greenland ice cores over the Last Glacial Maximum. This large increase is attributed to a greater areal extent of global tropical aridity during the cold periods, coupled with higher efficiency of atmospheric circulation in respect of dust production and transport. Beyond this, the relationship between the dust input and the successive stages during the Last Glacial is now very well documented and will be discussed with a view to correlating the Vostok climatic record with other marine and terrestrial paleodata.
399 individual microparticles in nine samples from the Dome C ice core were studied under scanning electron microscope and analysed by an energy dispersive X-ray system. The studied particles were either continental quartz or various silico-aluminates of continental or volcanic origin. Observations lead to the conclusion that the increase in micro particle concentration by a factor of 10 to 20 during the last glacial stage is explained by a large input of continental dust, as already indicated by trace element analysis (Petit and others 1981) and previously suggested by chemical analysis of other polar ice cores (Cragin and others 1977).This increase is considered to be a consequence of the ice-age climate and earth surface conditions which were characterized by the increase of arid regions and more vigorous atmospheric circulation. Both these conclusions are further supported by the existence of a higher quartz content in the Antarctic ice core as was already found in tropical deep-sea core studies.
We have reconstructed temperature changes over the past 15 000 years from ice-core data in Antarctica. We used measurements of the D/H isotope ratio in ice as a proxy of temperature for central sites (Vostok, Dome C and Komsomolskaya; as well as coastal sites (D47, D15 and D10). First, we examined the dating of each core and built up a common temporal framework for the ensemble of the data. Secondly, we addressed the problem of inferring small-amplitude temperature fluctuations from the isotope data, in the light of noise-generating mechanisms involved in snow deposition. Temperature was reconstructed so as to minimize distortion created by the sampling of ice cores in the field. The seven ice cores studied yield an average temperature curve which can be put in perspective with nearby paleoclimatic records. The early Holocene experienced climates warmer than today by 1-2°C. The late Holocene period shows more discernible, shorter-duration, temperature fluctuations, superimposed on a fairly stable "base-line" temperature.
The stable-isotope content of precipitation (δD and δ18O) is governed by the successive fractionation processes which occur during the atmospheric water cycle. As a result there is, in polar areas, a well-obeyed and theoretically well-understood linear relationship between the mean istopic content of snow and its mean temperature of formation. This relationship is well documented on a spatial scale but poorly known for a given site on a temporal basis, the main reason being that relatively long-term and sufficiently detailed meteorological data are only available for a few polar sites. The South Pole appears to be a suitable place for such a study because: (i) snow accumulation is high enough (∼20 cm of snow per year), thus reducing the possibility that annual layers will be lost as a result of wind; (ii) seasonal variation in isotope content is still preserved in snow up to 50 years old; (iii) meteorological data are available from the time the station was opened in 1957.
Our previous studies of surface and recently deposited snow at the South Pole were very encouraging in this respect; they have been extended with a two-fold purpose: (i) to test the geographical representativity of the isotope record by comparing results from various cores taken within a 10 km radius of the station. The cores are dated by various techniques, such as stratigraphy, seasonal variation in isotopic content, beta-radioactivity fall-out layers, and detection by solid conductivity measurements of the high “spike” which is thought to correspond to the 1815 Tambora eruption; (ii) to discuss the South Pole isotope record over the last 1000 years as recovered from a 127 m deep ice core.
Recent spectropolarimetric surveys of bright, hot stars have found that ~10% of OB-type stars contain strong (mostly dipolar) surface magnetic fields (~kG). The prominent paradigm describing the interaction between the stellar winds and the surface magnetic field is the magnetically confined wind shock (MCWS) model. In this model, the stellar wind plasma is forced to move along the closed field loops of the magnetic field, colliding at the magnetic equator, and creating a shock. As the shocked material cools radiatively it will emit X-rays. Therefore, X-ray spectroscopy is a key tool in detecting and characterizing the hot wind material confined by the magnetic fields of these stars. Some B-type stars are found to have very short rotational periods. The effects of the rapid rotation on the X-ray production within the magnetosphere have yet to be explored in detail. The added centrifugal force due to rapid rotation is predicted to cause faster wind outflows along the field lines, leading to higher shock temperatures and harder X-rays. However, this is not observed in all rapidly rotating magnetic B-type stars. In order to address this from a theoretical point of view, we use the X-ray Analytical Dynamical Magnetosphere (XADM) model, originally developed for slow rotators, with an implementation of new rapid rotational physics. Using X-ray spectroscopy from ESA’s XMM-Newton space telescope, we observed 5 rapidly rotating B-types stars to add to the previous list of observations. Comparing the observed X-ray luminosity and hardness ratio to that predicted by the XADM allows us to determine the role the added centrifugal force plays in the magnetospheric X-ray emission of these stars.
Large magnetometric surveys have contributed to the detection of an increasing number of magnetic massive stars, and to the recognition of a population of magnetic massive stellar objects with distinct properties. Among these, NGC 1624-2 possesses the largest magnetic field of any O-type star; such a field confines the stellar wind into a circumstellar magnetosphere, which can be probed using observations at different wavelength regimes. Recent optical and X-ray observations suggest that NGC 1624-2’s magnetosphere is much larger than that of any other magnetic O star. By modeling the variations of UV resonance lines, we can constrain its velocity structure. Furthermore, recent spectropolarimetric observations raise the possibility of a more complex field topology than previously expected. Putting all of these multi-wavelength constraints together will allow us to paint a consistent picture of NGC 1624-2 and its surprising behavior, giving us valuable insight into the very nature of massive star magnetospheres.
Much can be learned from terrestrial planets that appear to have had the potential to be habitable, but failed to realize that potential. Mars shows evidence of a once hospitable surface environment. The reasons for its current state, and in particular its thin atmosphere and dry surface, are of great interest for what they can tell us about habitable zone planet outcomes. A main goal of the MAVEN mission is to observe Mars’ atmosphere responses to solar and space weather influences, and in particular atmosphere escape related to space weather ‘storms’ caused by interplanetary coronal mass ejections (ICMEs). Numerical experiments with a data-validated MHD model suggest how the effects of an observed moderately strong ICME compare to what happens during a more extreme event. The results suggest the kinds of solar and space weather conditions that can have evolutionary importance at a planet like Mars.
We present a 3D magnetohydrodynamic study of the effect that stellar and planetary magnetic fields have on the calculated Lyα absorption during the planetary transit, employing parameters that resemble the exoplanet HD209458b. We assume a dipolar magnetic field for both the star and the planet, and use the Parker solution to initialize the stellar wind. We also consider the radiative processes and the radiation pressure.
We use the numerical MHD code Guacho to run several models varying the values of the planetary and stellar magnetic moments within the range reported in the literature.
We found that the presence of magnetic fields influences the escaping neutral planetary material spreading the absorption Lyα line for large stellar magnetic fields.
The evolution of rotational velocity and magnetic activity with age follows approximately a t−1/2 relation, the famous Skumanich law. Using a large sample of about 80 solar twins with precise ages, we show departures from this law. We found a steep drop in rotational velocity and activity in the first 2-3 Gyr and afterwards there seems to be a shallow decrease. Our inferred rotational periods suggest that the Sun will continue to slow down, validating thus the use of gyrochronology beyond solar age. The Sun displays normal rotational velocity and activity when compared to solar twins of solar age. We also show that stars with exceedingly high stellar activity for their age are spectroscopic binaries that also exhibit enhanced rotational velocities and chemical signatures of mass transfer.