Fe-C and Fe-H systems at pressures of the Earth's inner core

The solid inner core of the Earth is predominantly composed of iron alloyed with several percent Ni and some lighter elements, Si, S, O, H, and C being the prime candidates. There have been a growing number of papers investigating C and H as possible light elements in the core, but the results are contradictory. Here, using ab initio simulations, we study the Fe-C and Fe-H systems at inner core pressures (330-364 GPa). Using the evolutionary structure prediction algorithm USPEX, we have determined the lowest-enthalpy structures of possible carbides (FeC, Fe2C, Fe3C, Fe4C, FeC2, FeC3, FeC4 and Fe7C3) and hydrides (Fe4H, Fe3H, Fe2H, FeH, FeH2, FeH3, FeH4) and have found that Fe2C (Pnma) is the most stable iron carbide at pressures of the inner core, while FeH, FeH3 and FeH4 are stable iron hydrides at these conditions. For Fe3C, the cementite structure (Pnma) and the Cmcm structure recently found by random sampling are less stable than the I-4 and C2/m structures found here. We found that FeH3 and FeH4 adopt chemically interesting thermodynamically stable structures, in both compounds containing trivalent iron. The density of the inner core can be matched with a reasonable concentration of carbon, 11-15 mol.percent (2.6-3.7 wt.percent) at relevant pressures and temperatures. This concentration matches that in CI carbonaceous chondrites and corresponds to the average atomic mass in the range 49.3-51.0, in close agreement with inferences from the Birch's law for the inner core. Similarly made estimates for the maximum hydrogen content are unrealistically high, 17-22 mol.percent (0.4-0.5 wt.percent), which corresponds to the average atomic mass in the range 43.8-46.5. We conclude that carbon is a better candidate light alloying element than hydrogen.Comment: Published in Physics-Uspekhi: full text will soon appear at http://ufn.ru/en/articles/2012/5/c/ (currently, only abstract is available

Prediction of genetic merit from data on binary and quantitative variates with an application to calving difficulty, birth weight and pelvic opening

A method of prediction of genetic merit from jointly distributed quanta] and quantitative responses is described. The probability of response in one of two mutually exclusive and exhaustive categories is modeled as a non-linear function of classification and « risk » variables. Inferences are made from the mode of a posterior distribution resulting from the combination of a multivariate normal density, a priori, and a product binomial likelihood function. Parameter estimates are obtained with the Newton-Raphson algorithm, which yields a system similar to the mixed model equations. « Nested » Gauss-Seidel and conjugate gradient procedures are suggested to proceed from one iterate to the next in large problems. A possible method for estimating multivariate variance (covariance) components involving, jointly, the categorical and quantitative variates is presented. The method was applied to prediction of calving difficulty as a binary variable with birth weight and pelvic opening as « risk » variables in a Blonde d’Aquitaine population.Cet article présente une méthode de prédiction de la valeur génétique à partir d’observations quantitatives et qualitatives. La probabilité de réponse selon l’une des deux modalités exclusives et exhaustives envisagées est exprimée comme une fonction non linéaire d’effets de facteurs d’incidence et de variables de risque. L’inférence statistique repose sur le mode de la distribution a posteriori qui combine une densité multinormale a priori et une fonction de vraisemblance produit de binomiales. Les estimations sont calculées à partir de l’algorithme de Newton-Raphson qui conduit à un système d’équations similaires à celles du modèle mixte. Pour les gros fichiers, on suggère des méthodes itératives de résolution telles que celles de Gauss-Seidel et du gradient conjugué. On propose également une méthode d’estimation des composantes de variances et covariances relatives aux variables discrètes et continues. Enfin, la méthodologie présentée est illustrée par une application numérique qui a trait à la prédiction des difficultés de vêlage en race bovine Blonde d’Aquitaine utilisant d’une part, l’appréciation tout-ou-rien du caractère, et d’autre part, le poids à la naissance du veau et l’ouverture pelvienne de la mère comme des variables de risque

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International audienc

Quantifying the commonalities in structure and plastic deformation in disordered materials

The nonequilibrium nature of kinetically frozen solids such as metallic glasses (MGs) is at once responsible for their unusual properties, complex and cooperative deformation mechanisms, and their ability to explore various metastable states in the rugged potential energy landscape. These features coupled with the presence of a glass transition temperature, above which the solid flows like a supercooled liquid, open the door to thermoplastic forming operations at low thermal budget as well as thermomechanical treatments that can either age (structurally relax) or rejuvenate the glass. Thus, glasses can exist in various structural states depending on their synthesis method and thermomechanical history. Nanocrystalline (NC) metals, also considered to be far-from-equilibrium materials owing to the large fraction of atoms residing near grain boundaries (GBs), share many commonalities with MGs both in terms of plastic deformation and its dependence on processing history. Despite these similarities, the disorder intrinsic to both classes of materials has precluded the development of structure-property relationships that can capture the multiplicity of energetic states that glasses and GBs may possess. Here, we report on experimental studies of MG and NC materials and novel synthesis and processing routes for controlling the structural state – and as a consequence, the mechanical properties. A particular focus will be on strategies for rejuvenation of disorder with the goal of suppressing shear localization and endowing damage tolerance. We also describe a microscopic structural quantity designed by machine learning to be maximally predictive of plastic rearrangements and further demonstrate a causal link between this measure and both the size of rearrangements and the macroscopic yield strain. We find remarkable commonality in all of these quantities in disordered materials with vastly different inter-particle interactions and spanning a large range of elastic modulus and particle size

Cognitive-behavioural treatment for subacute and chronic neck pain

BACKGROUND: Although research on non-surgical treatments for neck pain (NP) is progressing, there remains uncertainty about the efficacy of cognitive-behavioural therapy (CBT) for this population. Addressing cognitive and behavioural factors might reduce the clinical burden and the costs of NP in society.OBJECTIVES: To assess the effects of CBT among individuals with subacute and chronic NP. Specifically, the following comparisons were investigated: (1) cognitive-behavioural therapy versus placebo, no treatment, or waiting list controls; (2) cognitive-behavioural therapy versus other types of interventions; (3) cognitive-behavioural therapy in addition to another intervention (e.g. physiotherapy) versus the other intervention alone.SEARCH METHODS: We searched CENTRAL, MEDLINE, EMBASE, CINAHL, PsycINFO, SCOPUS, Web of Science, and PubMed, as well as ClinicalTrials.gov and the World Health Organization International Clinical Trials Registry Platform up to November 2014. Reference lists and citations of identified trials and relevant systematic reviews were screened.SELECTION CRITERIA: We included randomised controlled trials that assessed the use of CBT in adults with subacute and chronic NP.DATA COLLECTION AND ANALYSIS: Two review authors independently assessed the risk of bias in each study and extracted the data. If sufficient homogeneity existed among studies in the pre-defined comparisons, a meta-analysis was performed. We determined the quality of the evidence for each comparison with the GRADE approach.MAIN RESULTS: We included 10 randomised trials (836 participants) in this review. Four trials (40%) had low risk of bias, the remaining 60% of trials had a high risk of bias.The quality of the evidence for the effects of CBT on patients with chronic NP was from very low to moderate. There was low quality evidence that CBT was better than no treatment for improving pain (standard mean difference (SMD) -0.58, 95% confidence interval (CI) -1.01 to -0.16), disability (SMD -0.61, 95% CI -1.21 to -0.01), and quality of life (SMD -0.93, 95% CI -1.54 to -0.31) at short-term follow-up, while there was from very low to low quality evidence of no effect on various psychological indicators at short-term follow-up. Both at short- and intermediate-term follow-up, CBT did not affect pain (SMD -0.06, 95% CI -0.33 to 0.21, low quality, at short-term follow-up; MD -0.89, 95% CI -2.73 to 0.94, low quality, at intermediate-term follow-up) or disability (SMD -0.10, 95% CI -0.40 to 0.20, moderate quality, at short-term follow-up; SMD -0.24, 95% CI-0.54 to 0.07, moderate quality, at intermediate-term follow-up) compared to other types of interventions. There was moderate quality evidence that CBT was better than other interventions for improving kinesiophobia at intermediate-term follow-up (SMD -0.39, 95% CI -0.69 to -0.08, I(2) = 0%). Finally, there was very low quality evidence that CBT in addition to another intervention did not differ from the other intervention alone in terms of effect on pain (SMD -0.36, 95% CI -0.73 to 0.02) and disability (SMD -0.10, 95% CI -0.56 to 0.36) at short-term follow-up.For patients with subacute NP, there was low quality evidence that CBT was better than other interventions at reducing pain at short-term follow-up (SMD -0.24, 95% CI -0.48 to 0.00), while no difference was found in terms of effect on disability (SMD -0.12, 95% CI -0.36 to 0.12) and kinesiophobia.None of the included studies reported on adverse effects.AUTHORS' CONCLUSIONS: With regard to chronic neck pain, CBT was found to be statistically significantly more effective for short-term pain reduction only when compared to no treatment, but these effects could not be considered clinically meaningful. When comparing both CBT to other types of interventions and CBT in addition to another intervention to the other intervention alone, no differences were found. For patients with subacute NP, CBT was significantly better than other types of interventions at reducing pain at short-term follow-up, while no difference was found for disability and kinesiophobia. Further research is recommended to investigate the long-term benefits and risks of CBT including for the different subgroups of subjects with N

Towards a New System for the Assessment of the Quality in Care Pathways: An Overview of Systematic Reviews

Clinical or care pathways are developed by a multidisciplinary team of healthcare practitioners, based on clinical evidence, and standardized processes. The evaluation of their framework/content quality is unclear. The aim of this study was to describe which tools and domains are able to critically evaluate the quality of clinical/care pathways. An overview of systematic reviews was conducted, according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses, using Medline, Embase, Science Citation Index, PsychInfo, CINAHL, and Cochrane Library, from 2015 to 2020, and with snowballing methods. The quality of the reviews was assessed with Assessment the Methodology of Systematic Review (AMSTAR-2) and categorized with The Leuven Clinical Pathway Compass for the definition of the five domains: processes, service, clinical, team, and financial. We found nine reviews. Three achieved a high level of quality with AMSTAR-2. The areas classified according to The Leuven Clinical Pathway Compass were: 9.7% team multidisciplinary involvement, 13.2% clinical (morbidity/mortality), 44.3% process (continuity-clinical integration, transitional), 5.6% financial (length of stay), and 27.0% service (patient-/family-centered care). Overall, none of the 300 instruments retrieved could be considered a gold standard mainly because they did not cover all the critical pathway domains outlined by Leuven and Health Technology Assessment. This overview shows important insights for the definition of a multiprinciple framework of core domains for assessing the quality of pathways. The core domains should consider general critical aspects common to all pathways, but it is necessary to define specific domains for specific diseases, fast pathways, and adapting the tool to the cultural and organizational characteristics of the health system of each country