Ab initio thermal expansion and thermoelastic properties of ringwoodite (\u3b3-Mg2SiO4) at mantle transition zone conditions

Thermal convection in the Earth\u2019s mantle is driven by lateral variations in temperature and density which are substantially controlled by the local volume thermal expansion of the constituent mineral phases. Ringwoodite is a major component of the lower mantle transition zone, but its thermal expansivity and thermoelastic properties are still affected by large uncertainties. Ambient thermal expansion coefficient (\u3b1_V0), for instance, can vary as much as 100% according to different experimental investigations available from the literature. In this work, we perform ab initio density functional theory calculations of vibrational properties of spinel-structured Mg2SiO4 ringwoodite in order to provide reliable thermophysical data up to mantle transition zone conditions. Temperature- and pressure-dependent thermal expansivity has been obtained by phonon dispersion calculations in the framework of quasi-harmonic approximation (QHA) up to 25 GPa and 2000 K. Theoretical analysis of vibrational spectra reveals that accurate prediction of IR and silent modes, along with their relative mode Gr\ufcneisen parameters, is crucial to define thermal expansivity. A six-parameter analytical function is able to reproduce ab initio values fairly well in the whole investigated P-T range, i.e. \u3b1_V (P,T) = (1.6033\ub710-5 + 8.839\ub710-9 T + 11.586\ub710-3 T-1 \u2013 6.055 T-2 + 804.31 T-3)\ub7exp-(\u20132.52\ub710-2 P), with temperature in Kelvin and pressure in Gigapascal. Ab initio static and isothermal bulk moduli have been derived for ringwoodite along with their P, T and cross derivatives, i.e. K_0 = 184.3 GPa, K_(T,300K) = 176.6 GPa; K_0^' = 4.13, K_(T,300K)^' = 4.16; (\u3016 02K\u3017_T/ 02T)_P = -0.0233 GPa/K and (\u3016 02^2 K\u3017_T/ 02P 02T)_0= 1.0\ub710-4 K-1. Computed thermal expansivity and thermoelastic properties supports the evidence that QHA performs remarkably well for Mg2SiO4 ringwoodite up to mantle transition zone temperatures. Since volume thermal expansion of ringwoodite is strongly pressure-dependent and its pressure dependence becomes more marked with the increasing temperature, internally-consistent assessments and empirical extrapolation of thermoelastic data to deep mantle conditions should be taken with care to avoid inaccurate or spurious predictions in phase equilibrium and mantle convection numerical modelling

Commensurate Growth of Magnetite Microinclusions in Olivine under Mantle Conditions

Magnetite-bearing multiphase solid inclusions hosted in metamorphic olivine have been interpreted as final products of the trapping of the aqueous fluid produced by the subduction-zone dehydration of former serpentinites. We provide here a careful analysis performed by microfocus single-crystal X-ray diffraction of inclusions found in harzburgites from the Almirez Complex (Bétic Cordillera, Spain) to determine the occurrence of preferential crystallographic orientation relationships between the olivine host and the magnetite inclusion. The results demonstrate that the magnetite–olivine interface selectively displays parallelism between crystallographic planes (111) and (100) and between crystallographic directions ⟨110⟩ and ⟨011⟩, respectively. This evidence points to a clear epitaxial growth of magnetite on olivine. The calculation of the geometrical misfit between the two lattices in contact as a function of their relative azimuthal orientation shows that, under the aforementioned reciprocal orientation, a perfect commensurism is achieved; i.e., all of the nodes of the magnetite lattice coincide with nodes of the olivine lattice. This particular relationship must be interpreted as a unique occurrence, playing a fundamental role in favoring the heterogeneous nucleation of magnetite on olivine

L'Italia come modello per l'Europa e per il mondo nelle politiche sanitarie per il trattamento dell'epatite cronica da HCV

The World Health Organization foresees the elimination of HCV infection by 2030. In light of this and the curre nt, nearly worldwide, restriction in direct-acting agents (DAA) accessibility due to their high price, we aimed to evaluate the cost-effectiveness of two alternative DAA treatment policies: Policy 1 (universal): treat all patients, regardless of the fibrosis stage; Policy 2 (prioritized): treat only priori tized patients and delay treatment of the remaining patients until reaching stage F3. T he model was based on patient’s data from the PITER cohort. We demonstrated that extending HC V treatment of patients in any fibrosis stage improves health outcomes and is cost-effective

Economic consequences of investing in anti-HCV antiviral treatment from the Italian NHS perspective : a real-world-based analysis of PITER data

OBJECTIVE: We estimated the cost consequence of Italian National Health System (NHS) investment in direct-acting antiviral (DAA) therapy according to hepatitis C virus (HCV) treatment access policies in Italy. METHODS: A multistate, 20-year time horizon Markov model of HCV liver disease progression was developed. Fibrosis stage, age and genotype distributions were derived from the Italian Platform for the Study of Viral Hepatitis Therapies (PITER) cohort. The treatment efficacy, disease progression probabilities and direct costs in each health state were obtained from the literature. The break-even point in time (BPT) was defined as the period of time required for the cumulative costs saved to recover the Italian NHS investment in DAA treatment. Three different PITER enrolment periods, which covered the full DAA access evolution in Italy, were considered. RESULTS: The disease stages of 2657 patients who consecutively underwent DAA therapy from January 2015 to December 2017 at 30 PITER clinical centres were standardized for 1000 patients. The investment in DAAs was considered to equal €25 million, €15 million, and €9 million in 2015, 2016, and 2017, respectively. For patients treated in 2015, the BPT was not achieved, because of the disease severity of the treated patients and high DAA prices. For 2016 and 2017, the estimated BPTs were 6.6 and 6.2 years, respectively. The total cost savings after 20 years were €50.13 and €55.50 million for 1000 patients treated in 2016 and 2017, respectively. CONCLUSIONS: This study may be a useful tool for public decision makers to understand how HCV clinical and epidemiological profiles influence the economic burden of HCV

Commensurate Growth of Magnetite Microinclusions in Olivine under Mantle Conditions

Magnetite-bearing multiphase solid inclusions hosted in metamorphic olivine have been interpreted as final products of the trapping of the aqueous fluid produced by the subduction-zone dehydration of former serpentinites. We provide here a careful analysis performed by microfocus single-crystal X-ray diffraction of inclusions found in harzburgites from the Almirez Complex (B\ue9tic Cordillera, Spain) to determine the occurrence of preferential crystallographic orientation relationships between the olivine host and the magnetite inclusion. The results demonstrate that the magnetite-olivine interface selectively displays parallelism between crystallographic planes (111) and (100) and between crystallographic directions \u27e8110\ubband \u27e8011\u27e9, respectively. This evidence points to a clear epitaxial growth of magnetite on olivine. The calculation of the geometrical misfit between the two lattices in contact as a function of their relative azimuthal orientation shows that, under the aforementioned reciprocal orientation, a perfect commensurism is achieved; i.e., all of the nodes of the magnetite lattice coincide with nodes of the olivine lattice. This particular relationship must be interpreted as a unique occurrence, playing a fundamental role in favoring the heterogeneous nucleation of magnetite on olivine