Evidence of hydrogen-helium immiscibility at Jupiter-interior conditions.

The phase behaviour of warm dense hydrogen-helium (H-He) mixtures affects our understanding of the evolution of Jupiter and Saturn and their interior structures1,2. For example, precipitation of He from a H-He atmosphere at about 1-10 megabar and a few thousand kelvin has been invoked to explain both the excess luminosity of Saturn1,3, and the depletion of He and neon (Ne) in Jupiter's atmosphere as observed by the Galileo probe4,5. But despite its importance, H-He phase behaviour under relevant planetary conditions remains poorly constrained because it is challenging to determine computationally and because the extremes of temperature and pressure are difficult to reach experimentally. Here we report that appropriate temperatures and pressures can be reached through laser-driven shock compression of H2-He samples that have been pre-compressed in diamond-anvil cells. This allows us to probe the properties of H-He mixtures under Jovian interior conditions, revealing a region of immiscibility along the Hugoniot. A clear discontinuous change in sample reflectivity indicates that this region ends above 150 gigapascals at 10,200 kelvin and that a more subtle reflectivity change occurs above 93 gigapascals at 4,700 kelvin. Considering pressure-temperature profiles for Jupiter, these experimental immiscibility constraints for a near-protosolar mixture suggest that H-He phase separation affects a large fraction-we estimate about 15 per cent of the radius-of Jupiter's interior. This finding provides microphysical support for Jupiter models that invoke a layered interior to explain Juno and Galileo spacecraft observations1,4,6-8.

Phonon Dispersion and Proton Disorder of Ice VII and VIII.

The phonon dispersion of ice VII and that of its proton-ordered analog ice VIII are investigated through a combination of inelastic x-ray scattering (IXS) measurements and first-principles calculations of the oxygen sublattice dynamic structure factor. Particular attention is devoted to hydrogen-disorder in ice VII, addressed theoretically through a statistical ensemble of fictitious ordered supercell configurations. Similar phonon densities of states are found in both phases but are significantly less structured in the case of ice VII. Our data further show that, despite a full proton disorder, the acoustic phonon branches in this phase clearly inherit the periodicity of its body-centered cubic oxygen lattice. The calculations predict, however, the presence of gap openings in the one-atom phonon dispersion. These predictions are supported by revisiting the analysis of previous single-crystal IXS measurements along the longitudinal [111] branch of ice VII.

Sound velocity and refractive index of pure N2 fluid and of equimolar N2-CO2 fluid mixture up to 15 GPa.

The sound velocity and refractive index of pure N2 and of the equimolar N2-CO2 mixture are measured up to 15 GPa and 700 K in a resistive heating diamond anvil cell. The refractive index vs pressure is obtained by an interferometric method. The adiabatic sound velocity is then determined from the measurement of the Brillouin frequency shift in the backscattering geometry and the refractive index data. No phase separation of the N2-CO2 fluid mixture is observed. The fluid mixture properties are discussed in terms of ideal mixing.

Hexagonal Layered Polymeric Nitrogen Phase Synthesized near 250 GPa.

The nitrogen triple bond dissociates in the 100 GPa pressure range and a rich variety of single-bonded polymeric nitrogen structures unique to this element have been predicted up to the terapascal pressure range. The nonmolecular cubic-gauche (cg-N) structure was first observed above 110 GPa, coupled to high temperature (>2000 K) to overcome the kinetic barrier. A mixture of cg-N with a layered phase was afterwards reported between 120 and 180 GPa. Here, by laser heating pure nitrogen from 180 GPa, a sole crystalline phase is characterized above 240 GPa while an amorphous transparent phase is obtained at pressures below. X-ray diffraction and Raman vibrational data reveal a tetragonal lattice (P4_{2}bc) that matches the predicted hexagonal layered polymeric nitrogen (HLP-N) structure. Density-functional theory calculations which include the thermal and dispersive interaction contributions are performed to discuss the stability of the HLP-N structure.

Pressure-induced chemical reactions in the N2(H2)2 compound: from the N2 and H2 species to ammonia and back down into hydrazine.

Theory predicts a very rich high pressure chemistry of hydronitrogens with the existence of many NxHy compounds. The stability of these phases under pressure is being investigated by the compression of N2-H2 mixtures of various compositions. A previous study had disclosed a eutectic-type N2-H2 phase diagram with two stoichiometric van der Waals compounds: (N2)6(H2)7 and N2(H2)2. The structure and pressure induced chemistry of the (N2)6(H2)7 compound have already been investigated. Here, we determine the structure of the N2(H2)2 compound and characterize using Raman spectroscopy measurements the chemical changes under a pressure cycle up to 60 GPa and back to ambient conditions. A N2(H2)2 single crystal was grown from a 1 : 2 N2-H2 mixture and its crystalline structure was solved using synchrotron X-ray diffraction. Similar to the (N2)6(H2)7 solid, N2(H2)2 has a remarkable host-guest structure containing N2 molecules orientationally disordered with spherical, ellipsoidal and planar shapes. Above 50 GPa, N2(H2)2 was found to undergo a chemical reaction. The reaction products were determined to be of the azane family, with NH3 as the main constituent, along with molecular nitrogen. Upon pressure decrease, the reaction products are found to react in such a way that below 10 GPa, hydrazine is the sole azane detected. Observed down to the opening of the diamond anvil cell, the formation of metastable hydrazine instead of the energetically favorable ammonia is puzzling and remains to be elucidated. That could change the current view of Jovian planets' atmospheres in which ammonia is assumed the only stable hydronitrogen molecule.

Change in inertial confinement fusion implosions upon using an ab initio multiphase DT equation of state.

Improving the description of the equation of state (EOS) of deuterium-tritium (DT) has recently been shown to change significantly the gain of an inertial confinement fusion target [S. X. Hu et al., Phys. Rev. Lett. 104, 235003 (2010)]. Here we use an advanced multiphase EOS, based on ab initio calculations, to perform a full optimization of the laser pulse shape with hydrodynamic simulations starting from 19 K in DT ice. The thermonuclear gain is shown to be a robust estimate over possible uncertainties of the EOS. Two different target designs are discussed, for shock ignition and self-ignition. In the first case, the areal density and thermonuclear energy can be recovered by slightly increasing the laser energy. In the second case, a lower in-flight adiabat is needed, leading to a significant delay (3 ns) in the shock timing of the implosion.

X-ray magnetic circular dichroism measurements in Ni up to 200 GPa: resistant ferromagnetism.

The structural stability of fcc Ni over a very large pressure range offers a unique opportunity to experimentally investigate how magnetism is modified by simple compression. K-edge x-ray magnetic circular dichroism (XMCD) shows that fcc Ni is ferromagnetic up to 200 GPa, contradicting recent predictions of an abrupt transition to a paramagnetic state at 160 GPa. Density functional theory calculations point out that the pressure evolution of the K-edge XMCD closely follows that of the p projected orbital moment rather than that of the total spin moment. The disappearance of magnetism in Ni is predicted to occur above 400 GPa.

Insulator-to-conducting transition in dense fluid helium.

By combining diamond-anvil-cell and laser-driven shock wave techniques, we produced dense He samples up to 1.5 g/cm(3) at temperatures reaching 60 kK. Optical measurements of reflectivity and temperature show that electronic conduction in He at these conditions is temperature-activated (semiconducting). A fit to the data suggests that the mobility gap closes with increasing density, and that hot dense He becomes metallic above approximately 1.9 g/cm(3). These data provide a benchmark to test models that describe He ionization at conditions found in astrophysical objects, such as cold white dwarf atmospheres.

Diagnostic precision of image-guided multisampling core needle biopsy of suspected lymphomas in a primary care hospital.

We evaluated the diagnostic quality of image-guided multisampling core needle biopsy (CNB) in patients investigated for suspected lymphoma in a primary care hospital. A total of 112 patients were consecutively assessed during a 3-year period. There were 80 lymphoid site biopsies and 32 non-lymphoid site biopsies. Eight to nine cores were obtained from different parts of the biopsy site. Two cores were systematically frozen, allowing for further morphological, immunochemistry and molecular studies. The diagnostic yield of CNB for malignancy was 100%. Only 47% (41/87) of patients with initial suspicion of lymphoma were finally diagnosed with Lymphoma. The diagnostic yield of CNB for lymphoma typing was 98% (62/63), according to the WHO classification. The diagnostic yield of CNB for complete lymphoma subtyping/grading was 86% (54/63). The diagnostic yield of CNB for a definite diagnosis of benignity was only 47% (8/17). In a primary care setting, multisampling CNB is a minimally invasive, and very accurate procedure for confirming malignancy in patients with suspected lymphoma, presenting with superficial/deep-seated, lymphoid/non-lymphoid site targets. With a very high diagnostic yield for lymphoma typing and a high diagnostic yield for complete lymphoma subtyping/grading a therapeutic decision can be taken in most patients.

[Endometriosis: review of the literature and clinical management]. / Prise en charge de l'endométriose.

Despite numerous studies, endometriosis remains unclear concerning the etiopathogenesis, the natural history and optimal treatment. It occurs preferentially in young women and may be associated with a series of painful symptoms very disabling, together with infertility and significant psychological problems. Because of the multiple consultations, operations and disability it can cause, endometriosis takes an increasing part in health costs. Delays between onset and diagnosis are still long, and it is important to diagnose as early as possible to stop this disease so as to maintain or restore fertility and quality of life for patients. That is why a careful listening and clinical examination with appropriate investigations will improve our global care.

[Laparoscopy in the management of endometrial cancer]. / Place de la laparoscopie dans le traitement du cancer de l'endomètre.

Recent advance in laparoscopy have changed the surgical approach of endometrial cancer patients. The Swissendos Center, Fribourg, in collaboration with AGO (Groupe de travail pour la gynécologie oncologique) and AGE (groupe de travail pour la gynécologie endoscopique) have established a consensus based on the available evidence for the use of laparoscopy in the management of patients with endometrial cancer The main objective was to define Swiss clinical practice guidelines appropriate to the country and consistent with the needs of the physicians.

High-Pressure Synthesized Lithium Pentazolate Compound Metastable under Ambient Conditions.

Polynitrogen compounds have been actively pursued driven by their potential as ultra-high-performing propellants or explosives. Despite remarkable breakthroughs over the past two decades, the two figures of merit for a compelling material, namely a large fraction of nitrogen by weight and a bulk stability under ambient conditions, have not yet been achieved. We report the synthesis of a lithium pentazolate solid by compressing and laser-heating lithium embedded in molecular N2 around 45 GPa along with its recovery under ambient conditions. The observation by Raman spectroscopy of vibrational modes unique to the cyclo-N5- anion is the signature of the formation of LiN5. Mass spectroscopy experiments confirm the presence of the pentazolate anion in the recovered compound. A monoclinic lattice is obtained from X-ray diffraction measurements and the volume of the LiN5 compound under pressure is in good agreement with the theoretical calculations.

Synthesis of FeH5: A layered structure with atomic hydrogen slabs.

High pressure promotes the formation of polyhydrides with unusually high hydrogen-to-metal ratios. These polyhydrides have complex hydrogenic sublattices. We synthesized iron pentahydride (FeH5) by a direct reaction between iron and H2 above 130 gigapascals in a laser-heated diamond anvil cell. FeH5 exhibits a structure built of atomic hydrogen only. It consists of intercalated layers of quasicubic FeH3 units and four-plane slabs of thin atomic hydrogen. The distribution of the valence electron density indicates a bonding between hydrogen and iron atoms but none between hydrogen atoms, presenting a two-dimensional metallic character. The discovery of FeH5 suggests a low-pressure path to make materials that approach bulk dense atomic hydrogen.

Transplant renal artery stenosis. Evaluation of diagnosis with magnetic resonance angiography compared with color duplex sonography and arteriography.

The goal of this study was to assess the value of a three-dimensional phase contrast magnetic resonance angiography (3D PC MRA) for diagnosing transplant renal artery stenosis (TRAS). Twelve consecutive patients clinically suspected of having TRAS were prospectively enrolled during a period of 18 months. Delays from transplantation varied from 3 months to 4 years (mean: 18.3 months). Patients first had color Doppler sonography, then MRA-and, on the following day, intraarterial digital subtraction angiography (IADSA). The site of the maximum peak systolic velocity was noted when doing the report of each color Doppler sonogram. On MRA images, any signal cutoff or any vascular narrowing of more than 50% of the diameter of the vessel was considered to be a significant stenosis. Eight patients were considered to have TRAS on MRA, but only two stenoses were noted on IADSA. The six false-positive results of MRA (due to major intravoxel phase dispersion) were observed when elevated peak systolic velocities were noted on doppler sonograms (mean: 214 cm/sec). These elevated peak systolic velocities were noted in the proximal part of the renal artery when there was a tortuous vessel or a sharp angle between the renal artery and the parent vessel. It is our opinion that 3D PC MRA is of limited value for the diagnosis of renal transplant artery stenosis because of a high number of false-positive results.

High-resolution computed tomographic findings associated with histologically diagnosed acute lung rejection in heart-lung transplant recipients.

A group of 32 lung (single lung, [n = 14] and double lung [n = 1]) or heart-lung (n = 17) transplant recipients were studied with serial high-resolution computed tomography (HRCT) scans and transbronchial biopsies from the time of surgery. These investigations were carried out routinely every 2 weeks for the first 2 months, every 2 months for a year, every 4 months in the second year, and on any clinical suspicion of acute lung rejection or infection. A total of 190 transbronchial biopsy specimens and concurrent HRCT scans were obtained. Forty (21%) of the biopsy specimens, showed histologic evidence of lung rejection, 111 (58%) were normal, and 39 (21%) were not conclusive. The more frequent HRCT pattern encountered during an acute rejection episode was the presence of patchy "ground-glass" density areas (65%). This finding was sparsely observed during minimal and mild acute rejection episodes. Using histologic diagnosis as a standard for acute rejection, ground-glass opacities on HRCT had a sensitivity of 65% in detecting lung rejection. Although ground-glass opacities were also intermittently observed during cytomegalovirus pneumonia (14%), this finding had a specificity of 85% for detecting occurrence of an acute lung complication. The detection of ground-glass opacities on lung HRCT after lung transplantation, more particularly after the first month after surgery, can aid the decision of when and where to undertake transbronchial lung biopsy.

Thin-section CT detection of emphysema associated with bronchiectasis and correlation with pulmonary function tests.

PURPOSE: To evaluate, on thin-section CT scans, the prevalence of emphysema in patients with bronchiectasis and to correlate the results of thin-section CT scans with the results of pulmonary function tests, in order to question whether there was a particular functional test profile in this group of patients. PATIENTS AND METHODS: This is a retrospective study including 90 patients having both thin-section CT scans and pulmonary function tests for bronchiectasis. A CT scoring system was established for assessing the airway disease by the severity and extent of bronchiectasis and by the extent of emphysema. CT scans were reviewed independently by two reviewers and final interpretation was obtained by consensus. Results of thin-section CT scans were correlated with results of pulmonary function tests, including FEV1 and FEV1/FVC to assess air-way obstruction, total lung capacity and residual volume to assess air trapping, and diffusing capacity for carbon monoxide/alveolar volume (DCO/VA). RESULTS: CT evidence of emphysema, which was noted in 45% of the patients (n = 41), was mainly localized in the same bronchopulmonary segments as bronchiectasis. The presence of emphysema was in relation to the extent and to the severity of bronchiectasis. Only eight patients with CT evidence of emphysema had functional evidence of emphysema (20%). When comparing the group of patients with CT evidence of emphysema with the group of patients with no CT evidence of emphysema, the group of patients with CT evidence of emphysema had significantly higher airflow obstruction and air trapping, had significantly lesser value of diffusing capacity, but with no decreased gas transfer (DCO/VA > 80%). CONCLUSION: Our series suggests that there is a high prevalence of emphysema in patients with bronchiectasis. Emphysema that was not suggested using pulmonary function tests in most of the cases could explain in part the higher airway obstruction observed in the group of patients with CT evidence of emphysema. This study could support the suggestive notion that emphysema, which was mainly localized in bronchiectatic lobes, could be due to the inflammatory airway process.

Carboxymethyl-dextran-gadolinium-DTPA as a blood-pool contrast agent for magnetic resonance angiography. Experimental study in rabbits.

RATIONALE AND OBJECTIVES: The authors evaluate the efficiency of various doses of a paramagnetic macromolecular contrast agent, a gadolinium (Gd)-DTPA-dextran conjugate, as a blood-pool contrast media, in a transverse three-dimensional time-of-flight (TOF) magnetic resonance (MR) angiography sequence of the abdominal aorta in rabbits. METHODS: Imaging experiments were performed on a 1.5-T magnet, using a transverse three-dimensional TOF tilted optimized nonsaturating excitation (TONE) sequence. The macromolecular contrast media used was a carboxymethyl-dextran-Gd-DTPA (CMD-Gd-DTPA). Different concentrations of CMD-Gd-DTPA (0.005, 0.01, 0.03, 0.05 mmol Gd/kg) were evaluated. A comparative study using Gd-DOTA (0.01 and 0.1 mmol/kg) was performed. A visual analysis based on the gain in the visualized length of small arteries (renal arteries), and a quantitative analysis based on the percent contrast enhancement of the aorta plotted against distance in the slab from the top edge of the acquisition volume were obtained. RESULTS: A signal-to-noise ratio enhancement of the distal part of the aorta and an improvement in the visualized length of the renal arteries were noted for concentrations of CMD-Gd-DTPA ranging form 0.01 to 0.05 mmol Gd/kg. Venous enhancement was noted for concentrations greater than 0.01 mmol Gd/kg when using CMD-Gd-DTPA or Gd-DOTA. CONCLUSION: Carboxymethyl-dextran-Gd-DTPA reduced, in part, the saturation effect in a three-dimensional transverse TOF TONE MR angiography in rabbits. To prevent venous enhancement, observed with the higher concentrations used in this study, a decrease in the polydispersity of the polymer should be a goal in the future. Rapid extravasation of the low-molecular weight fraction of the polymer could explain the venous enhancement.

Contrast-enhanced magnetic resonance tomoangiography: a new imaging technique for studying thoracic great vessels.

The authors propose a new imaging approach for studying thoracic great vessels, using high-speed MR imaging combined with intravenous rapid bolus injection of a paramagnetic contrast media. The decrease of the T1 relaxation time of flowing blood induced by the contrast agent (Gd-DOTA) caused an increased signal intensity within the vessel lumen for a time period allowing multiplanar imaging of various vascular structures. The intraluminal signal enhancement is mainly related to the blood concentration of the contrast agent as in conventional X-ray angiography. Information on the aorta and pulmonary arteries obtained by the so-called contrast-enhanced magnetic resonance tomoangiography appears complementary to that obtained with other vascular MR imaging procedures such as cine-MRI and magnetic resonance angiography (MRA).

Three-dimensional phase contrast MR cerebral venography with zero filling interpolation in the slice encoding direction.

The purpose of this study was to evaluate the magnetic resonance (MR) cerebral venography findings of a three-dimensional phase contrast MR sequence with zero filling interpolation of the data in the slice encoding direction. Fifty volunteers were enrolled in the study. Images were obtained on a 1.5 MR imaging system with acquisition time of 12 min. MIP images were reconstructed throughout the entire imaging volume. A grading scale system was used to assess dural venous sinuses, major deep veins, cortical, and cortical eponymic veins. Inferior group of dural venous sinuses, inferior sagittal sinus, and cortical eponymic veins were poorly demonstrated. Score of the superior sagittal sinus, the straight sinus, the confluence of the superior sinus group, the right transverse and sigmoid sinuses, the internal veins, and the vein of Galen was excellent. The score of the left transverse and sigmoid sinuses was good. In conclusion, when using zero filling interpolation of the data in a three-dimensional phase contrast MR cerebral venography sequence, the superior group of dural venous sinuses and main major deep veins are demonstrated with good conspicuity.