Structural and Electronic Transitions in Liquid FeO Under High Pressure.

FeO represents an important end-member for planetary interiors mineralogy. However, its properties in the liquid state under high pressure are poorly constrained. Here, in situ high-pressure and high-temperature X-ray diffraction experiments, ab initio simulations, and thermodynamic calculations are combined to study the local structure and density evolution of liquid FeO under extreme conditions. Our results highlight a strong shortening of the Fe-Fe distance, particularly pronounced between ambient pressure and ∼40 GPa, possibly related with the insulator to metal transition occurring in solid FeO over a similar pressure range. Liquid density is smoothly evolving between 60 and 150 GPa from values calculated for magnetic liquid to those calculated for non-magnetic liquid, compatibly with a continuous spin crossover in liquid FeO. The present findings support the potential decorrelation between insulator/metal transition and the high-spin to low-spin continuous transition, and relate the changes in the microscopic structure with macroscopic properties, such as the closure of the Fe-FeO miscibility gap. Finally, these results are used to construct a parameterized thermal equation of state for liquid FeO providing densities up to pressure and temperature conditions expected at the Earth's core-mantle boundary.

Melting properties by X-ray absorption spectroscopy: common signatures in binary Fe-C, Fe-O, Fe-S and Fe-Si systems.

X-ray absorption spectroscopy (XAS) is a widely used technique to probe the local environment around specific atomic species. Applied to samples under extreme pressure and temperature conditions, XAS is sensitive to phase transitions, including melting, and allows gathering insights on compositional variations and electronic changes occurring during such transitions. These characteristics can be exploited for studies of prime interest in geophysics and fundamental high-pressure physics. Here, we investigated the melting curve and the eutectic composition of four geophysically relevant iron binary systems: Fe-C, Fe-O, Fe-S and Fe-Si. Our results show that all these systems present the same spectroscopic signatures upon melting, common to those observed for other pure late 3d transition metals. The presented melting criterion seems to be general for late 3d metals bearing systems. Additionally, we demonstrate the suitability of XAS to extract melt compositional information in situ, such as the evolution of the concentration of light elements with increasing temperature. Diagnostics presented in this work can be applied to studies over an even larger pressure range exploiting the upgraded synchrotron machines, and directly transferred to time-resolved extreme condition studies using dynamic compression (ns) or fast laser heating (ms).

Author Correction: Thermal equation of state of ruthenium characterized by resistively heated diamond anvil cell.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Thermal equation of state of ruthenium characterized by resistively heated diamond anvil cell.

The high-pressure and high-temperature structural and chemical stability of ruthenium has been investigated via synchrotron X-ray diffraction using a resistively heated diamond anvil cell. In the present experiment, ruthenium remains stable in the hcp phase up to 150 GPa and 960 K. The thermal equation of state has been determined based upon the data collected following four different isotherms. A quasi-hydrostatic equation of state at ambient temperature has also been characterized up to 150 GPa. The measured equation of state and structural parameters have been compared to the results of ab initio simulations performed with several exchange-correlation functionals. The agreement between theory and experiments is generally quite good. Phonon calculations were also carried out to show that hcp ruthenium is not only structurally but also dynamically stable up to extreme pressures. These calculations also allow the pressure dependence of the Raman-active E2g mode and the silent B1g mode of Ru to be determined.

Laser-heating system for high-pressure X-ray diffraction at the Extreme Conditions beamline I15 at Diamond Light Source.

In this article, the specification and application of the new double-sided YAG laser-heating system built on beamline I15 at Diamond Light Source are presented. This system, combined with diamond anvil cell and X-ray diffraction techniques, allows in situ and ex situ characterization of material properties at extremes of pressure and temperature. In order to demonstrate the reliability and stability of this experimental setup over a wide range of pressure and temperature, a case study was performed and the phase diagram of lead was investigated up to 80 GPa and 3300 K. The obtained results agree with previously published experimental and theoretical data, underlining the quality and reliability of the installed setup.

Thermal and magnetic anomalies of α-iron: an exploration by extended x-ray absorption fine structure spectroscopy and synchrotron x-ray diffraction.

The local structure and dynamics of α-iron have been investigated by extended x-ray absorption fine structure (EXAFS) spectroscopy and x-ray diffraction (XRD) in order to shed light on some thermal and magnetic anomalies observed in the last decades. The quantitative EXAFS analysis of the first two coordination shells reveals a peculiar local vibrational dynamics of α-iron: the second neighbor distance exhibits anharmonicity and vibrational anisotropy larger than the first neighbor distance. We search for possible distortions of the bcc structure to justify the unexplained magnetostriction anomalies of α-iron and provide a value for the maximum dislocation of the central Fe atom. No thermal anomalies have been detected from the current XRD data. On the contrary, an intriguing thermal anomaly at about 150 K, ascribed to a stiffening of the Fe-Fe bonds, was found by EXAFS.

Interferon beta-1a alone or in combination with ribavirin: a randomized trial to compare efficacy and safety in chronic hepatitis C.

AIM: To compare the efficacy and safety of recombinant human IFN beta-1a alone or in combination with ribavirin in treatment-naive subjects with chronic hepatitis C. METHODS: Open, randomized trial was performed in 6 Italian tertiary centers: 102 of the 108 patients screened were randomized to receive 6 MIU of recombinant human IFN beta-1a subcutaneously daily for 24 wk, alone (Group 1, n = 51) or in combination with ribavirin 1,000 to 1,200 mg/d (Group 2, n = 51). RESULTS: The end-of-treatment virologic response rate was 29.4% in Group 1 and 41.2% in Group 2 (non-significant). Twenty-four weeks after stopping therapy, sustained virologic response rate was 21.6% in Group 1 and 27.4% in Group 2 (non-significant). All subjects in Group 1 completed treatment, while two subjects in Group 2 stopped therapy due to treatment-related adverse events. CONCLUSION: Recombinant human IFN beta-1a, alone or in combination with ribavirin, has an excellent safety profile and, may represent an alternative for chronic hepatitis C patients who are unable to tolerate pegylated alpha-interferon.

PKR gene expression and response to pegylated interferon plus ribavirin therapy in chronic hepatitis C.

Pegylated interferon (PEG-IFN) alpha combined with ribavirin is the current standard treatment for hepatitis C, but around 50% of patients do not respond for reasons that are not fully understood. To explore the regulation of IFN-inducible protein kinase (PKR), we have measured PKR mRNA levels in peripheral blood mononuclear cells (PBMCs) and in liver biopsies from patients with chronic hepatitis C. PBMCs were also analysed after in vitro incubation with IFN and during antiviral therapy. Non-responders to PEG-IFN plus ribavirin had pre-treatment PKR mRNA levels in PBMCs (0.1+/-0.0074) and in liver (0.102+/-0.051) that were significantly higher than those of responders (PBMCs: 0.023+/-0.014, P=0.0005; liver: 0.034+/-0.020; P=0.0002). On the other hand, PKR mRNA levels in PBMCs were similar in non-responders and in responders after in vitro exposure to IFN (0.434+/-0.301 vs 0.403+/-0.222; P=NS) and during therapy (0.31+/-0.10 vs 0.30+/-0.12; P=NS). These results indicate that in hepatitis C, non-responsiveness to IFN-alpha is associated with pre-treatment up-regulation of the PKR gene, evidence that the infecting hepatitis C virus is able to stimulate endogenous IFN production, being resistant to its antiviral effect. On the other hand, the PKR gene response to exogenous IFN was similar in responders and non-responders, at least in PBMCs, suggesting that variations in its activation are not major determinants of the outcome of antiviral treatment.

Prevalence of liver disease in a population of asymptomatic persons with hepatitis C virus infection.

BACKGROUND: The prevalence of significant liver disease in persons with asymptomatic hepatitis C virus (HCV) infection is unclear. OBJECTIVE: To determine the prevalence and severity of HCV infection in asymptomatic persons. DESIGN: Population-based cross-sectional study. SETTING: Northeastern Italy. PATIENTS: 4820 apparently healthy Telecom Italy employees or their relatives who underwent screening for cardiovascular risk factors. MEASUREMENTS: Initial screening for anti-HCV by enzyme-linked immunosorbent assay followed by HCV RNA testing by polymerase chain reaction and monitoring of alanine aminotransferase levels in viremic persons (92% of viremic persons also had liver biopsies to assess their METAVIR scores). RESULTS: 116 persons (2.4% [95% CI, 1.97% to 2.84%]) were positive for anti-HCV and 85 (1.76% [CI, 1.39% to 2.14%]) were also viremic. The ALT level was persistently normal in 39 (46%) of viremic patients and elevated in 46 (54%). Significant hepatic histologic abnormalities were detected in 19% (CI, 7.21% to 36.4%) of persons with persistently normal ALT levels and in 61% (CI, 45.4% to 74.9%) of viremic persons who had elevated ALT levels (P < 0.001). The prevalence of HCV infection and number of persons with chronic liver fibrosis increased with age (P = 0.003). CONCLUSIONS: Hepatitis C is histologically active and progressive in up to 40% of asymptomatic persons with HCV infection. The severity of liver disease correlates with abnormal ALT levels and increases with age.

Therapy of acute hepatitis C.

Acute hepatitis C has a high propensity to become chronic, which provides the rationale for treating patients with acute disease attempting to prevent chronicity. Almost all published studies on therapy of acute hepatitis C have been small in size, uncontrolled, and highly heterogeneous as to patient features, dose and duration of treatment, follow-up evaluation, and criteria used to define efficacy and safety. The published studies on treatment of acute hepatitis C have used standard alfa or beta interferon monotherapy: none have evaluated combination therapy of interferon and ribavirin or peginterferon. Several meta-analyses of published studies have concluded that initiation of interferon monotherapy during the acute phase of hepatitis C virus (HCV) infection significantly reduces (by 30% to 40%) evolution to chronic hepatitis. The tolerability of interferon in acute hepatitis C has been excellent, even in symptomatic and icteric patients; the side effects and adverse events being similar in type and frequency to those seen when treating chronic cases. Thus, currently available data support treatment of patients with acute hepatitis C, but data are insufficient to draw firm conclusions about which patients to treat, when therapy should be started, or what regimen is optimal. Future studies of adequate size and design should focus on efficacy and tolerability of peginterferons and whether therapy should be started immediately after diagnosis or delayed for 2 to 4 months to avoid treatment of patients who spontaneously recover.