A ring system detected around the Centaur (10199) Chariklo.

Hitherto, rings have been found exclusively around the four giant planets in the Solar System. Rings are natural laboratories in which to study dynamical processes analogous to those that take place during the formation of planetary systems and galaxies. Their presence also tells us about the origin and evolution of the body they encircle. Here we report observations of a multichord stellar occultation that revealed the presence of a ring system around (10199) Chariklo, which is a Centaur--that is, one of a class of small objects orbiting primarily between Jupiter and Neptune--with an equivalent radius of 124 ± 9 kilometres (ref. 2). There are two dense rings, with respective widths of about 7 and 3 kilometres, optical depths of 0.4 and 0.06, and orbital radii of 391 and 405 kilometres. The present orientation of the ring is consistent with an edge-on geometry in 2008, which provides a simple explanation for the dimming of the Chariklo system between 1997 and 2008, and for the gradual disappearance of ice and other absorption features in its spectrum over the same period. This implies that the rings are partly composed of water ice. They may be the remnants of a debris disk, possibly confined by embedded, kilometre-sized satellites.

Albedo and atmospheric constraints of dwarf planet Makemake from a stellar occultation.

Pluto and Eris are icy dwarf planets with nearly identical sizes, comparable densities and similar surface compositions as revealed by spectroscopic studies. Pluto possesses an atmosphere whereas Eris does not; the difference probably arises from their differing distances from the Sun, and explains their different albedos. Makemake is another icy dwarf planet with a spectrum similar to Eris and Pluto, and is currently at a distance to the Sun intermediate between the two. Although Makemake's size (1,420 ± 60 km) and albedo are roughly known, there has been no constraint on its density and there were expectations that it could have a Pluto-like atmosphere. Here we report the results from a stellar occultation by Makemake on 2011 April 23. Our preferred solution that fits the occultation chords corresponds to a body with projected axes of 1,430 ± 9 km (1σ) and 1,502 ± 45 km, implying a V-band geometric albedo p(V) = 0.77 ± 0.03. This albedo is larger than that of Pluto, but smaller than that of Eris. The disappearances and reappearances of the star were abrupt, showing that Makemake has no global Pluto-like atmosphere at an upper limit of 4-12 nanobar (1σ) for the surface pressure, although a localized atmosphere is possible. A density of 1.7 ± 0.3 g cm(-3) is inferred from the data.

A Pluto-like radius and a high albedo for the dwarf planet Eris from an occultation.

The dwarf planet Eris is a trans-Neptunian object with an orbital eccentricity of 0.44, an inclination of 44 degrees and a surface composition very similar to that of Pluto. It resides at present at 95.7 astronomical units (1 AU is the Earth-Sun distance) from Earth, near its aphelion and more than three times farther than Pluto. Owing to this great distance, measuring its size or detecting a putative atmosphere is difficult. Here we report the observation of a multi-chord stellar occultation by Eris on 6 November 2010 UT. The event is consistent with a spherical shape for Eris, with radius 1,163 ± 6 kilometres, density 2.52 ± 0.05 grams per cm(3) and a high visible geometric albedo, Pv = 0.96(+0.09)(-0.04). No nitrogen, argon or methane atmospheres are detected with surface pressure larger than ∼1 nanobar, about 10,000 times more tenuous than Pluto's present atmosphere. As Pluto's radius is estimated to be between 1,150 and 1,200 kilometres, Eris appears as a Pluto twin, with a bright surface possibly caused by a collapsed atmosphere, owing to its cold environment. We anticipate that this atmosphere may periodically sublimate as Eris approaches its perihelion, at 37.8 astronomical units from the Sun.

A transiting giant planet with a temperature between 250 K and 430 K.

Of the over 400 known exoplanets, there are about 70 planets that transit their central star, a situation that permits the derivation of their basic parameters and facilitates investigations of their atmospheres. Some short-period planets, including the first terrestrial exoplanet (CoRoT-7b), have been discovered using a space mission designed to find smaller and more distant planets than can be seen from the ground. Here we report transit observations of CoRoT-9b, which orbits with a period of 95.274 days on a low eccentricity of 0.11 +/- 0.04 around a solar-like star. Its periastron distance of 0.36 astronomical units is by far the largest of all transiting planets, yielding a 'temperate' photospheric temperature estimated to be between 250 and 430 K. Unlike previously known transiting planets, the present size of CoRoT-9b should not have been affected by tidal heat dissipation processes. Indeed, the planet is found to be well described by standard evolution models with an inferred interior composition consistent with that of Jupiter and Saturn.

An orbital period of 0.94 days for the hot-Jupiter planet WASP-18b.

The 'hot Jupiters' that abound in lists of known extrasolar planets are thought to have formed far from their host stars, but migrate inwards through interactions with the proto-planetary disk from which they were born, or by an alternative mechanism such as planet-planet scattering. The hot Jupiters closest to their parent stars, at orbital distances of only approximately 0.02 astronomical units, have strong tidal interactions, and systems such as OGLE-TR-56 have been suggested as tests of tidal dissipation theory. Here we report the discovery of planet WASP-18b with an orbital period of 0.94 days and a mass of ten Jupiter masses (10 M(Jup)), resulting in a tidal interaction an order of magnitude stronger than that of planet OGLE-TR-56b. Under the assumption that the tidal-dissipation parameter Q of the host star is of the order of 10(6), as measured for Solar System bodies and binary stars and as often applied to extrasolar planets, WASP-18b will be spiralling inwards on a timescale less than a thousandth that of the lifetime of its host star. Therefore either WASP-18 is in a rare, exceptionally short-lived state, or the tidal dissipation in this system (and possibly other hot-Jupiter systems) must be much weaker than in the Solar System.

The role of groundwater in CO2 production and carbon storage in Mediterranean peatlands: An isotope geochemistry approach.

Peatlands are permanent wetlands recognized for ecosystem services such as biodiversity conservation and carbon storage capacity. Little information is available about their response to global change, the reason why most Earth system climate models consider a linear increase in the release of greenhouse gases (GHG), such as CO2, with increasing temperatures. Nevertheless, numerous studies suggest that an increase in the temperature may not imply a decrease in photosynthesis and carbon storage rates if water availability is sufficient, the latter being under the control of local hydrology mechanisms. Mediterranean peatlands well illustrate this fact. Since they are groundwater-dependent, they are hydrologically resilient to the strong seasonality of hydroclimatic conditions, especially during the summer drought. In the present study, we demonstrate that, even if such peatlands release CO2 into the atmosphere, they can maintain a carbon storage capacity. To this end, a geochemical study disentangles the origin and fate of carbon within a Mediterranean peatland at the watershed scale. Field parameters, major ions, dissolved organic and inorganic carbon content and associated δ13C values allow for characterizing the seasonality of hydrochemical mechanisms and carbon input from an alluvial aquifer (where rain, river, shallow, and deep groundwater flows are mixing) to the peatland. The inorganic and organic content of peat soil and δ13C values of total organic matter and CO2 complete the dataset, making it possible to provide arguments in favour of lower organic matter oxidation compared to primary production. Overall, this study highlights the groundwater role in the fluxes of CO2 at the peatland-atmosphere interface, and more broadly the need to understand the interactions between the water and carbon cycles to build better models of the future evolution of the global climate.

Assessing the hydrogeological resilience of a groundwater-dependent Mediterranean peatland: Impact of global change and role of water management strategies.

Mediterranean peatlands remain largely under-documented, except for detailed biological data such as fauna and flora taxa lists, and yet are increasingly threatened by water withdrawal and agriculture practices. This lack of information, particularly on their hydrogeological functioning, makes it impossible to evaluate their response to changing climate conditions. A pilot study on a representative Mediterranean peatland on the island of Corsica (France) was conducted to evaluate recharge modalities in the peatland using a coupled water-level monitoring, geochemical and isotope multi-tracing approach (electric conductivity, major ions, δ18O, δ2H, 3H, 87Sr/86Sr). The goal was to understand how water budgets in peatland ecosystems were maintained throughout the year, especially during the summer. Despite the remarkable stability of the peatland water level, the recharge contributions of varied water bodies through an alluvial aquifer vary significantly from one season to another. An end-member mixing analysis (EMMA) indicates that the peatland is mainly recharged by an alluvial aquifer. During fall-winter, the alluvial aquifer on which the peatland depends is recharged by the rainfall, a river, and shallow groundwater (colluvium). During spring-summer, water supply is provided mostly by a river, shallow, and deep groundwater (fractured granite). However, this specific hydrogeological functioning is not taken into account by environmental management policies making peatlands vulnerable to anthropogenic and climatic pressures. Thus, their actual status regarding water and aquatic environment management policies is discussed to provide recommendations for better consideration and preservation.

The 67P/Churyumov-Gerasimenko observation campaign in support of the Rosetta mission.

We present a summary of the campaign of remote observations that supported the European Space Agency's Rosetta mission. Telescopes across the globe (and in space) followed comet 67P/Churyumov-Gerasimenko from before Rosetta's arrival until nearly the end of the mission in September 2016. These provided essential data for mission planning, large-scale context information for the coma and tails beyond the spacecraft and a way to directly compare 67P with other comets. The observations revealed 67P to be a relatively 'well-behaved' comet, typical of Jupiter family comets and with activity patterns that repeat from orbit to orbit. Comparison between this large collection of telescopic observations and the in situ results from Rosetta will allow us to better understand comet coma chemistry and structure. This work is just beginning as the mission ends-in this paper, we present a summary of the ground-based observations and early results, and point to many questions that will be addressed in future studies.This article is part of the themed issue 'Cometary science after Rosetta'.

[Cardiac perforation and tamponade during TIPS placement]. / Un cas de tamponnade cardiaque par perforation du ventricule droit au décours immédiat d'une pose de TIPS.

A patient developed an acute severe haemodynamic compromise immediately after a transjugular intrahepatic portosystemic shunt (TIPS) procedure for intractable ascites. Rapid clinical and echographic evaluation disclosed pericardial blood and cardiac tamponade, probably due to right heart perforation from guidewire and catheter manipulation. Needle drainage of pericardial fluid restored the haemodynamic status. A right ventricular perforation was then successfully treated (sternotomy and closure of right ventricle perforation) and the patient survived. Cardiac tamponade should be considered in the differential diagnosis of patients who develop hypotension and haemodynamic impairment during or immediately after TIPS placement.

[What is the method of choice for hemodynamic monitoring in liver transplantation?]. / Quel monitorage hémodynamique lors des transplantations hépatiques?

Orthotopic liver transplantation requires close hemodynamic monitoring. Technological advances provide new possibilities of improving this monitoring. The most recent devices are the mixed venous oxygen saturation catheter, which gives continuous SVO2 values, and the right ejection fraction catheter used discontinuously. Our experience of 100 liver transplantations has enabled us to investigate the advantages of these catheters over the conventional Swan Ganz catheters.

Pancreatic function in the reserpinized rabbit--a model for cystic fibrosis. I. Effect of secretin.

Pancreatic juice was collected from rabbits treated with reserpine and from untreated controls. The volume of pancreatic juice secreted, flow rate and the bicarbonate output were all significantly reduced in the treated animals during both spontaneous flow and during secretin-stimulated flow. On the other hand, the total protein concentration, the amylase activity and the calcium concentration of the pancreatic juice were all significantly elevated in the treated animals. The elevation in the total protein concentration appeared to be due to both increased amounts of protein and decreased amounts of water. Of particular interest was that secretin stimulation caused the same % increase in the flow rate and output of pancreatic juice in both control and reserpine treated rabbits. The method by which fluid is secreted by the treated animal, therefore, appeared to be depressed at all times and under all conditions. Decreased volumes of pancreatic juice, a decreased bicarbonate output and increased concentrations of protein and calcium are found in this model and are consistent with clinical findings present in the pancreatic secretions obtained from individuals with cystic fibrosis. Therefore, the similarities between secretions of the reserpine treated rabbit and those observed in the cystic fibrosis patient support its use as an experimental model for investigating the abnormal pancreatic secretions in this disease.

A membrane defect in cystic fibrosis: decreased red cell permeability to water.

The abnormally high concentrations of electrolytes and organic solutes found in the glandular secretions of individuals with cystic fibrosis may arise from decreased water content rather than perturbed solute transport. Thus, it is possible that the abnormalities insolute concentrations are a result of a reduced water movement into the secretory product. It is our hypothesis that if an abnormality exists in the transport of water across secretory cell membranes, this defect may also be expressed in nonsecretory cell membrane permeability to water. We report here osmotic water permeability measurements on red cells and 11 cystic fibrosis patients ranging in age from 2 to 20 years and eight normal individuals. The mean hydraulic conductivity for the patients of 1.23 +/- 0.13 cm3/dyne sec is significantly less (P < 0.001) than that of normal individuals who have permeabilities of 1.45 +/- 0.11 cm3/dyne sec. Analysis showed that the osmotic water permeability correlates well with the Shwachman score (r = 0.76). Patients who are in the poorest clinical condition show the lowest hydraulic conductivities.

Effects of vagotomy on drinking in the rat.

1. Left or right cervical vagotomy caused elevated intakes of water after hypertonic saline, isoprenaline and polyethylene glycol compared with normal rats. In cervically vagotomized rats sodium nitrite caused a dose-dependent water intake whereas in normal rats it produced a smaller, more variable response. The same procedure also reduced the extent to which drinking following overnight water deprivation was inhibited by plasma volume expansion. Drinking after diazoxide or in response to ligation of the abdominal inferior vena cava was not affected by cervical vagotomy. 2. The antidiuresis that followed isoprenaline treatment was greater in cervically vagotomized than normal rats; that which occurred after caval ligation was unaffected. 3. Subdiaphragmatic vagotomy did not alter water intake in response to hypertonic saline, isoprenaline or polyethylene glycol. 4. It is concluded that nerves within the supradiaphragmatic distribution of the vagi modify water intake in response to changes in the degree of vascular filling.

Comparative effects of small and large aprotinin doses on bleeding during orthotopic liver transplantation.

Large prophylactic doses of aprotinin efficiently reduce blood loss during orthotopic liver transplantation (OLT). Small doses of aprotinin are usually used to treat fibrinolysis. However, no studies have investigated the benefit of prophylactic administration of a smaller dose of aprotinin during liver transplantation. We compared two methods of aprotinin therapy on transfusion outcome in liver transplant patients in a prospective study of 199 patients undergoing OLT who were randomized to large or small prophylactic doses of aprotinin during the transplant procedure. In the large-dose group (n = 94) an initial dose of 2,000,000 kallikrein inactivation units (KIU) was followed by infusion of 500,000 KIU/h until the patient's return to the intensive care unit. In the small-dose group (n = 95), an initial dose of 500,000 KIU was followed by an infusion of 150,000 KIU/h. Outcome measurements included intraoperative transfusion requirements (packed red blood cells, fresh frozen plasma, platelets, intraoperative salvage) and postoperative hematologic values. There were no differences in transfusion requirements in the two groups of patients. Patients treated with low-dose aprotinin had slightly higher postoperative fibrinogen concentrations. Large-dose aprotinin therapy does not appear to offer additional benefit compared to low-dose aprotinin administration.

Pulmonary vein-atrial junction stretch receptors and the inhibition of drinking.

A chronically implanted inflatable balloon was used to produce distension of a left pulmonary vein at its junction with the left atrium in trained conscious dogs. Balloon inflation caused a fall in the amounts of water drunk in response to injection of isoproterenol, infusion of hypertonic NaCl, or overnight water deprivation. There was also a significant increase in heart rate, but arterial, central venous, and left atrial pressures were unaltered. Blockade of the left vagosympathetic nerve prevented the inhibitory action of distension of a pulmonary vein on water intake in response to injection of isoproterenol. In experiments where the balloon was left inflated for 24 h, distension also caused a fall in the spontaneous daily water intake, whereas food intake was unaffected. Despite the fall in water intake, urine flow increased so that the dog went into negative fluid balance. In conclusion, distension of a pulmonary vein at its junction with the left atrium causes reduction in both spontaneous and induced water intake, and this inhibition is not secondary to circulatory changes or fluid retention by the kidney. The action of the receptors concerned may complement the actions of the same or similar receptors on renal function whose effects have been observed previously in acute experiments in anesthetized animals and here for the first time in conscious animals.

Renin-dependence of drinking induced by partial aortic obstruction in the dog.

1. Inflation of a balloon implanted in the abdominal aorta above the level of the renal arteries was used to produce partial obstruction to aortic blood flow in trained, conscious mongrel dogs.2. Following inflation, heart rate and arterial blood pressure downstream from the point of inflation fell, whilst arterial blood pressure upstream from the point of inflation rose. Central venous pressure was unaltered.3. In sixteen out of eighteen experiments, balloon inflation led to drinking. Inflations maintained for 3 days led to a sustained increase in daily water intakes, but intakes of 0.9% NaCl were unaltered when both water and 0.9% NaCl were available to drink.4. There was a significant inverse correlation between the amount drunk in the first 60 min following balloon inflation and the ratio of the change in the arterial pressure upstream of the obstruction to the change in pressure downstream of the obstruction.5. In experiments where the inflation was maintained for 90 min, there was no further drinking between the 60th and 90th min. In experiments where the inflation was released after 60 min, there was another bout of drinking between the 60th and 90th min.6. Plasma renin activity and plasma renin concentration both rose following balloon inflation. Drinking following balloon inflation was abolished by infusion of the competitive angiotensin II antagonist saralasin.7. Inflation of an aortic balloon to a size that produced drinking in other experiments also led to a reduction in urinary water and electrolyte loss in fluid pre-loaded dogs.8. In conclusion, water intake in response to partial aortic obstruction above the level of the kidneys is caused by renin released from the kidneys. However, the dipsogenic effectiveness of the endogenous renin released is reduced as a result of the simultaneous increase in arterial pressure above the obstruction.

Drinking and antidiuresis in response to reductions in venous return in the dog: neural and endocrine mechanisms.

1. In order to investigate the mechanisms of hypovolaemic thirst and sodium appetite an inflatable balloon in the upper abdominal inferior vena cava was used to produce acute, graded and reversible reductions in venous return to the heart in conscious dogs. 2. Reducing venous return caused a fall in central venous, arterial and pulse pressures. Heart rate and venous pressure upstream from the point of inflation rose. 3. Within 6--28 min of inflating the balloon the dogs started drinking. The amount drunk in a 1 h experiment was significantly correlated with the changes in central venous and arterial pressures. 4. More prolonged obstruction to venous return led to a sustained increase in water intake and the development of a sodium appetite. 5. Plasma renin activity and concentration rose following caval obstruction. 6. Drinking in response to reductions in venous return was reduced, but not abolished, by simultaneous infusion of the competitive angiotensin II antagonist saralasin acetate. 7. When the left vagosympathetic nerve was blocked at the same time as balloon inflation the response was enhanced. 8. Urine flow fell after partial obstruction of the vena cava. Therefore drinking led to the development of a positive fluid balance. 9. We have shown that hypovolaemia is a potent and quantitatively defined stimulus to drinking in the dog and that the renal renin-angiotensin system makes an important contribution to it.