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'.

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.

[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.

Analgesic efficacy and safety of nefopam vs. propacetamol following hepatic resection.

In order to compare the morphine-sparing effect, analgesic efficacy and tolerance of nefopam and propacetamol given at their highest recommended doses, 120 patients undergoing elective hepatic resection were randomly assigned to receive postoperative intravenous patient-controlled analgesia with morphine alone, or in combination with nefopam (20 mg.4 h-1) or propacetamol (2 g.6 h-1). Compared with the control group (43 [7-92] mg), median [range] cumulative morphine consumption for 24 h after the study started was halved in the nefopam group (21 [3-78] mg, p <0.001) and 20% lower in the propacetamol group (35 [6-84] mg, p = 0.15). Analgesia was superior in the nefopam group despite the lower morphine consumption. Adverse effects were comparable in the three groups, except for significantly more nausea in the control group (39% vs. 17 and 26% in the nefopam and propacetamol groups, respectively) and more sweating in the nefopam group (17% vs. 0 and 3% in the control and propacetamol groups, respectively). Overall patient satisfaction was better (p < 0.001) in patients given nefopam (97%) than those receiving morphine alone (82%) or propacetamol (74%).

How to stabilize the level of ionized calcium and citrate during plateletpheresis.

BACKGROUND AND OBJECTIVES: Citrate reactions are uncomfortable and potentially dangerous to apheresis donors. Reduction of citrate increases comfort, but may lead to platelet clumping. MATERIALS AND METHODS: We describe a protocol for stepwise reduction of the volume of ACD-A injected during plateletpheresis. This protocol has been carried out in 45 healthy donors with the Cobe 2997 (Cobe) cell separator, and in 35 with the Fenwal-CS 3000 (CS). RESULTS: Using this protocol, during the first hour of platelet collection, ionised calcium decreased on average by 18% for CS and by 18.4% for Cobe. During the second hour, Ca2+ and citrate ion concentration did not change with either Cobe or CS (about 65% of citrate ion load is eliminated). We observed mild signs of neuromuscular hyperexcitability in only 22% and 28% of donors with Cobe and CS, respectively. We also found a significant reduction of phosphate ions (p < 0.0001) at the end of the procedures. CONCLUSIONS: With this stepdown citrate reduction protocol, we obtained a significant reduction of injected citrate without the complication of platelet clumps.

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.

[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.

[Safety of donors, quality of products, how much to reduce the quantity of citrate]. / Sécurité des donneurs, qualité des produits jusqu'où diminuer la quantité de citrate.

We examined 1,053 blood samples from 48 donors, for the effect of gradual reduction of citrate. We observed that: 1--Platelet count does not show any significant variation between 1/8 to 1/18 ratio. 2--In 13.3% of the cases, platelet clumping starts at 1/18 ratio. 3--There was no significant variation of the thrombin plasma level between 1/8 to 1/16 ratio (by measuring thrombin/ATIII complex). Our results show clearly that we can reduce the citrate ratio to 1/14 without expecting any adverse effect. Therefore we designated 1/14 as the security ratio. Parallel to this we also found that the average level +/- SD of ionized calcium is 100 +/- 10 muMol at 1/14 ratio.

Emergency orthotopic liver transplantation in two patients using one donor liver.

Because of its anatomy, the liver can be divided into two hemilivers suitable for use as two grafts for liver transplantation. The line of division is the main scissure, giving the right hemiliver (segments 5-8) and the left hemiliver (segments 2-4). Segment 1 (caudate lobe) has to be resected. The vessels are divided between the two grafts: the vena cava remains on the right; on the left, the left hepatic vein is sutured into the vena cava of the recipient, which is retained intact. The left graft retains only the left branch of the portal vein, the bile duct and the hepatic artery. The right graft retains the portal trunk, the common bile duct and the right branch of the hepatic artery. This procedure was used for emergency grafting of two patients with fulminant hepatitis when only one donor was available. Both recipients recovered from coma and regained normal liver function. However, both died from causes not specifically related to the operative technique, one from multiple organ failure on the 20th day and the other from diffuse cytomegalovirus infection on the 45th day.

Inappropriate drinking and secretion of vasopressin after caval constriction in dogs.

The object of this study was to determine if chronic thoracic vena caval constriction affected mechanisms regulating water balance, independent of known changes in sodium metabolism in the dog. Fluid and electrolyte balances were determined for 5 days before and 14 days after constriction of the vena cava (n = 5) and in a separate population of time controls (n = 4). Cardiac output was reduced and heart rate was increased in response to chronic caval constriction although blood pressure was maintained at control levels. Water intake and plasma arginine vasopressin (AVP) increased from 31 +/- 4 ml/kg and 1.3 +/- 0.2 pg/ml during the control period to 81 +/- 6 ml/kg and 3.4 +/- 0.6 pg/ml during the period of caval constriction. The caval dogs developed a positive water balance, which preceded the development of a positive sodium balance. This led to a significant fall in plasma osmolality from a control mean of 296 +/- 1 to 284 +/- 4 mosmol/kg during caval constriction and dilutional hyponatremia. Plasma and blood volume increased significantly in response to constriction and were accompanied by formation of 123 +/- 10 ml/kg of ascitic fluid. These results show that water intake and plasma levels of AVP were increased in spite of a fall in plasma osmolality and an increase in vascular volume. These responses cannot be secondary to sodium retention because water was retained in excess of sodium hence hyponatremia. Therefore, chronic caval constriction causes a profound primary disturbance in mechanisms regulating water balance, which may contribute to the formation of edema fluid.