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.

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.

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.

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.

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.

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.

Melting of iron at Earth's inner core boundary based on fast X-ray diffraction.

Earth's core is structured in a solid inner core, mainly composed of iron, and a liquid outer core. The temperature at the inner core boundary is expected to be close to the melting point of iron at 330 gigapascal (GPa). Despite intensive experimental and theoretical efforts, there is little consensus on the melting behavior of iron at these extreme pressures and temperatures. We present static laser-heated diamond anvil cell experiments up to 200 GPa using synchrotron-based fast x-ray diffraction as a primary melting diagnostic. When extrapolating to higher pressures, we conclude that the melting temperature of iron at the inner core boundary is 6230 ± 500 kelvin. This estimation favors a high heat flux at the core-mantle boundary with a possible partial melting of the mantle.

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.

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.

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.

[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.

Single-crystal structural characterization of the metallic phase of oxygen.

Angle dispersive x-ray diffraction measurements of oxygen single crystals in a helium pressure transmitting medium have been performed up to 133 GPa at room temperature. The crystalline structure of metallic zeta oxygen, above 96 GPa, is shown to be associated with a continuous displacive structural transformation taking place in the ab plane of the monoclinic C2/m cell of the insulator epsilon phase. Although of first order, the change of crystalline structure to the metallic zeta phase from the epsilon phase is found to be isosymmetric, in agreement with recent calculations. Our Raman spectroscopy measurements on a single crystal of the zeta phase corroborate the present structure assignment. The interplay between metallization and structural changes is disclosed.

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.

[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.

Hugoniot data for helium in the ionization regime.

Hugoniot data were obtained for fluid He in the 100 GPa pressure range by shock compression of samples statically precompressed in diamond-anvil cells. The initial (precompressed) He density (rho_(1)) for each experiment was tuned to a value between rho_(0L) or =3rho_{0L} (i.e., rho/rho_(0L)> or =12). Data show an increase in compressibility at the onset of ionization, similar to theoretical predictions.

Pressure evolution of the high-frequency sound velocity in liquid water.

The high-frequency sound velocity v( infinity ) of liquid water has been determined to densities of 1.37 g/cm(3) by inelastic x-ray scattering. In comparison to the hydrodynamic sound velocity v(0), the increase of v( infinity ) with density is substantially less pronounced, indicating that, at high density, the hydrogen-bond network is decreasingly relevant to the physical properties of liquid water. Furthermore, we observe an anomaly in v( infinity ) at densities around 1.12 g/cm(3), contrasting the smooth density evolution of v(0).

Observation of structural transformations in metal oxygen.

X-ray diffraction and Raman measurements have been performed on solid oxygen up to, respectively, 115 and 120 GPa. Metallization at 96 GPa is shown to be associated with a continuous displacive structural transformation. At 110 GPa, a new structure is stabilized. The evolution of the vibron mode reflects also the sequence of phase transitions through the continuity of the vibron frequency at 96 GPa, then the broadening of the vibron peak into the background and finally the reappearance of a sharp vibron at 110 GPa with a -2.5% discontinuity in the frequency. The observation of the vibron peak demonstrates that metallic oxygen is molecular up to at least 120 GPa.

[Gross tumor volume and clinical target volume in radiotherapy: lung cancer]. / Volume tumoral macroscopique et volume-cible anatomoclinique en radiothérapie: cancer bronchique.

Radiotherapy plays a major role as a curative treatment of various stages non-small cell lung cancers (NSCLC): as an exclusive treatment in curative attempt for patients with unresectable stages I and II; as a preoperative treatment, which is often associated with chemotherapy, for patients with surgically stage IIIA NSCLC in clinical trials; in association with chemotherapy for unresectable stages IIIA and IIIB patients. Currently, three-dimensional conformal radiotherapy allows for some dose escalation, increasing radiation quality. However, the high inherent conformality of this radiotherapy technique requires a rigorous approach and an optimal quality of the preparation throughout the treatment procedure and specifically of the accurate definition of the safety margins (GTV, CTV...). Different questions remain specific to lung cancers: 1) Despite the absence of randomized trials, the irradiated lymph nodes volume should be only, for the majority of the authors, the visible macroscopically involved lymph nodal regions. However, local control remains low and solid arguments suggest the poor local control is due to an insufficient delivered dose. Therefore the goal of radiotherapy, in this particular location, is to improve local control by increasing the dose until the maximum normal tissue tolerance is achieved, which essentially depends on the dose to the organs at risk (OAR) and specifically for the lung, the esophagus and the spinal cord. For this reason, the irradiated volume should be as tiny as possible, leading to not including the macroscopically uninvolved lymph nodes regions in prophylactic view in the target volume; 2) The lung is one of the rare organs with extensive motion within the body, making lung tumors difficult to treat. This particular point is not specifically considered in the GTV and CTV definitions but it is important enough to be noted; 3) When radiation therapy starts after a good response to chemotherapy, the residual tumoral volume should be defined as the target volume in place of the initial tumor volume. These different elements are discussed in this paper.