Context. The Juno probe that currently orbits Jupiter measures its gravitational moments with great accuracy. Preliminary results suggest that the core of the planet may be eroded. While great ...attention has been paid to the material properties of elements constituting the envelope, little is known about those that constitute the core. This situation clutters our interpretation the Juno data and modeling of giant planets and exoplanets in general. Aims. We calculate the high-pressure melting temperatures of three potential components of the cores of giant planets, water, iron, and a simple silicate, MgSiO3, to investigate the state of the deep inner core. Methods. We used ab initio molecular dynamics simulations to calculate the high-pressure melting temperatures of the three potential core components. The planetary adiabats were obtained by solving the hydrostatic equations in a three-layer model adjusted to reproduce the measured gravitational moments. Recently developed ab initio equations of state were used for the envelope and the core. Results. We find that the cores of the giant and ice-giant planets of the solar system differ because the pressure–temperature conditions encountered in each object correspond to different regions of the phase diagrams. For Jupiter and Saturn, the results are compatible with a diffuse core and mixing of a significant fraction of metallic elements in the envelope, leading to a convective and/or a double-diffusion regime. We also find that their solid cores vary in nature and size throughout the lifetimes of these planets. The solid cores of the two giant planets are not primordial and nucleate and grow as the planets cool. We estimate that the solid core of Jupiter is 3 Gyr old and that of Saturn is 1.5 Gyr old. The situation is less extreme for Uranus and Neptune, whose cores are only partially melted. Conclusions. To model Jupiter, the time evolution of the interior structure of the giant planets and exoplanets in general, their luminosity, and the evolution of the tidal effects over their lifetimes, the core should be considered as crystallizing and growing rather than gradually mixing into the envelope due to the solubility of its components.
Ab initio equation of state of iron up to 1500 GPa Bouchet, J.; Mazevet, S.; Morard, G. ...
Physical review. B, Condensed matter and materials physics,
03/2013, Letnik:
87, Številka:
9
Journal Article
Recenzirano
Odprti dostop
Using ab initio molecular dynamics simulations, we calculate the equation of state of iron in the solid phase for both the hcp and bcc structures as well as the high-pressure melting curve up to 15 ...Mbars. We first find that the melting temperature increases up to 11 000 K at the highest pressures investigated following a semiempirical melting law over the entire pressure domain. We also investigate the stability of the bcc phase of iron beyond Earth's core conditions (3 Mbars) and find that the temperature at which the bcc phase is mechanically stabilized increases with density. Finally, we provide simple fits of these results for convenient use in the modeling of Earth-like exoplanets up to ten Earth masses, which requires accurate knowledge of the properties of iron up to 15 Mbars.
Taking advantage of the new opportunities provided by x-ray free electron laser (FEL) sources when coupled to a long laser pulse as available at the Linear Coherent Light Source (LCLS), we have ...performed x-ray absorption near-edge spectroscopy (XANES) of laser shock compressed iron up to 420 GPa (+ or -50) and 10 800 K (+ or -1390). Visible diagnostics coupled with hydrodynamic simulations were used to infer the thermodynamical conditions along the Hugoniot and the release adiabat. A modification of the pre-edge feature at 7.12 keV in the XANES spectra is observed above pressures of 260 GPa along the Hugoniot. Comparing with ab initio calculations and with previous laser-heated diamond cell data, we propose that such changes in the XANES pre-edge could be a signature of molten iron. This interpretation then suggests that iron is molten at pressures and temperatures higher than 260 GPa (+ or -29) and 5680 K (+ or -700) along the principal Fe Hugoniot.
We report an experimental study of the phase diagrams of MgO, MgSiO3, and Mg2SiO4 at high pressures. We measured the shock compression response, including pressure‐temperature Hugoniot curves of MgO, ...MgSiO3, and Mg2SiO4 between 0.2–1.2 TPa, 0.12–0.5 TPa, and 0.2–0.85 TPa, respectively, using laser‐driven decaying shocks. A melting signature has been observed in MgO at 0.47 ± 0.04 TPa and 9860 ± 810 K, while no such phase changes were observed either in MgSiO3 or in Mg2SiO4. Increases of reflectivity of MgO, MgSiO3, and Mg2SiO4 liquids have been detected above 0.55 TPa (12760 K), 0.15 TPa (7540 K), 0.2 TPa (5800 K), respectively. In contrast to SiO2, melting and metallization of these compounds do not coincide, implying the presence of poorly electrically conducting liquids close to the melting lines. This has important implications for the generation of dynamos in super‐Earth's mantles.
Key Points
Magnesium oxides phase diagrams investigated along the Hugoniots between 0.2 and 1.2 TPa with decaying shocks and optical diagnostics
New MgO experimental melting point proposed at 0.47 ± 0.04 TPa and 9860 ± 810 K
No evidences of phase transition have been found for MgSiO3 and Mg2SiO4 between 0.12–0.5 TPa and 0.2–0.85 TPa, respectively
Using ab initio molecular dynamics simulations, we calculate the physical properties of MgO at conditions extending from the ones encountered in the Earth mantle up to the ones anticipated in giant ...planet interiors such as Jupiter. We pay particular attention to the high-pressure melting temperature throughout this large density range as this is a key ingredient for building accurate planetary interior models with a realistic description of their inner cores. We compare our simulation results with previous ab initio calculations that have been so far limited to the pressure range corresponding to the Earth mantle and the B1-B2 transition around 6 Mbar. We provide our results for both the equation of state and high-pressure melting curve in parametric forms for direct use in planetary models. Finally, we compare our predictions of the high-pressure melting temperature with various planetary interior profiles to deduce the state of differentiated layer within the core made of MgO in differentiated cores of various types of planets and exoplanets.
We describe 11 cases of anti-tuberculosis DRESS (drug-related rash with eosinophilia and systemic symptoms) syndrome, a potentially serious complication of treatment that led to interruption of ...treatment for prolonged periods, systemic corticosteroid use and the resumption of treatment with less effective regimens. All patients had rash and toxic hepatitis, one died of multi-organ failure and, contrary to expectations, the evolution of tuberculosis (advanced in most cases) did not progress under corticosteroid treatment. The drug most frequently involved was rifampicin, while retreatment schemes included, in most cases, levofloxacin, ethambutol, streptomycin and cycloserine.
Tuberculous pleural effusion is characterized by a T helper type 1 (Th1) profile, but an excessive Th1 response may also cause tissue damage that might be controlled by regulatory mechanisms. In the ...current study we investigated the role of regulatory T cells (Treg ) in the modulation of Th1 responses in patients with tuberculous (TB) pleurisy. Using flow cytometry we evaluated the proportion of Treg (CD4(+) CD25(high) forkhead box protein 3(+) ), interferon (IFN)-γ and interleukin (IL)-10 expression and CD107 degranulation in peripheral blood (PB) and pleural fluid (PF) from patients with TB pleurisy. We demonstrated that the proportion of CD4(+) CD25(+) , CD4(+) CD25(high) FoxP3(+) and CD8(+) CD25(+) cells were increased in PF compared to PB samples. Mycobacterium tuberculosis stimulation increased the proportion of CD4(+) CD25(low/neg) IL-10(+) in PB and CD4(+) CD25(low/neg) IFN-γ(+) in PF; meanwhile, CD25(high) mainly expressed IL-10 in both compartments. A high proportion of CD4(+) CD107(+) and CD8(+) CD107(+) cells was observed in PF. Treg depletion enhanced the in-vitro M. tuberculosis-induced IFN-γ and CD4(+) and CD8(+) degranulation responses and decreased CD4(+) IL-10(+) cells in PF. Our results demonstrated that in TB pleurisy Treg cells effectively inhibit not only IFN-γ expression but also the ability of CD4(+) and CD8(+) cells to degranulate in response to M. tuberculosis.
Summary
Tuberculous pleural effusion is characterized by a T helper type 1 (Th1) profile, but an excessive Th1 response may also cause tissue damage that might be controlled by regulatory mechanisms. ...In the current study we investigated the role of regulatory T cells (Treg) in the modulation of Th1 responses in patients with tuberculous (TB) pleurisy. Using flow cytometry we evaluated the proportion of Treg (CD4+CD25highforkhead box protein 3+), interferon (IFN)‐γ and interleukin (IL)‐10 expression and CD107 degranulation in peripheral blood (PB) and pleural fluid (PF) from patients with TB pleurisy. We demonstrated that the proportion of CD4+CD25+, CD4+CD25highFoxP3+ and CD8+CD25+ cells were increased in PF compared to PB samples. Mycobacterium tuberculosis stimulation increased the proportion of CD4+CD25low/negIL‐10+ in PB and CD4+CD25low/negIFN‐γ+ in PF; meanwhile, CD25high mainly expressed IL‐10 in both compartments. A high proportion of CD4+CD107+ and CD8+CD107+ cells was observed in PF. Treg depletion enhanced the in‐vitro M. tuberculosis‐induced IFN‐γ and CD4+ and CD8+ degranulation responses and decreased CD4+IL‐10+ cells in PF. Our results demonstrated that in TB pleurisy Treg cells effectively inhibit not only IFN‐γ expression but also the ability of CD4+ and CD8+ cells to degranulate in response to M. tuberculosis.
Tuberculous pleurisy is a naturally occurring site of Mycobacterium tuberculosis (Mtb) infection. Herein, we describe the expression of activation, natural killer (NK) and cell migration markers, as ...well as effector functions from γδT cells in peripheral blood (PB) and pleural effusion (PE) from tuberculosis patients (TB). We observed a decreased percentage of circulating γδT from TB patients and differential expression of NK as well as of chemokine receptors on PB and PE. Two subsets of γδT cells were differentiated by the CD3/γδT cell receptor (γδTCR) complex. The γδTCRlow subset had a higher CD3 to TCR ratio and was enriched in Vδ2⁺ cells, whereas most Vδ1⁺ cells belonged to the γδTCRhigh subset. In PB from TB, most γδTCRhigh were CD45RA⁺CCR7⁻ and γδTCRlow were CD45RA⁺/⁻CCR7⁺CXCR3⁺. In the pleural space the proportion of CD45RA⁻CCR7⁺CXCR3⁺ cells was higher. Neither spontaneous nor Mtb-induced interferon (IFN)-γ production was observed in PB-γδT cells from TB; however, PE-γδT cells showed a strong response. Both PB- and PE-γδ T cells expressed surface CD107a upon stimulation with Mtb. Notably, PE-γδTCRlow cells were the most potent effector cells. Thus, γδT cells from PB would acquire a further activated phenotype within the site of Mtb infection and exert full effector functions. As γδT cells produce IFN-γ within the pleural space, they would be expected to play a beneficial role in tuberculous pleurisy by helping to maintain a T helper type 1 profile.
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