Empiric Models of the Earth's Free Core Nutation

Free core nutation (FCN) is the main factor that limits the accuracy of the modeling of the motion of Earth's rotational axis in the celestial coordinate system. Several FCN models have been proposed. A comparative analysis is made of the known models including the model proposed by the author. The use of the FCN model is shown to substantially increase the accuracy of the modeling of Earth's rotation. Furthermore, the FCN component extracted from the observed motion of Earth's rotational axis is an important source for the study of the shape and rotation of the Earth's core. A comparison of different FCN models has shown that the proposed model is better than other models if used to extract the geophysical signal (the amplitude and phase of FCN) from observational data.Comment: 8 pages, 3 figures; minor update of the journal published versio

Report of the IAU/IAG Joint Working Group on Theory of Earth Rotation and Validation

This report focuses on some selected scientific outcomes of the activities developed by the IAU/IAG Joint Working Group on Theory of Earth rotation and validation along the term 2015–2019. It is based on its end-of-term report to the IAG Commission 3 published in the Travaux de l’IAG 2015–2019, which in its turn updates previous reports to the IAG and IAU, particularly the triennial report 2015–2018 to the IAU Commission A2, and the medium term report to the IAG Commission 3 (2015–2017). The content of the report has served as a basis for the IAG General Assembly to adopt Resolution 5 on Improvement of Earth rotation theories and models.JMF, AE, and JG were partially supported by Spanish Project AYA2016-79775-P (AEI/FEDER, UE). The work of RSG described in this paper was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. Support for that work was provided by the Earth Surface and Interior Focus Area of NASA’s Science Mission Directorate

Accession Site Does Not Influence the Risk of Stroke after Diagnostic Coronary Angiography or Intervention: Results from a Large Prospective Registry

INTRODUCTION: Periprocedural stroke represents a rare but serious complication of cardiac catheterization. Pooled data from randomized trials evaluating the risk of stroke following cardiac catheterization via transradial versus transfemoral access showed no difference. On the other hand, a significant difference in stroke rates favoring transradial access was found in a recent meta-analysis of observational studies. Our aim was to determine if there is a difference in stroke risk after transradial versus transfemoral catheterization within a contemporary real-world registry. METHODS: Data from 14,139 patients included in a single-center prospective registry between 2009 and 2016 were used to determine the odds of periprocedural transient ischemic attack (TIA) and stroke for radial versus femoral catheterization via multivariate logistic regression with Firth's correction. RESULTS: A total of 10,931 patients underwent transradial and 3,208 underwent transfemoral catheterization. Periprocedural TIA/stroke occurred in 41 (0.29%) patients. Age was the only significant predictor of TIA/stroke in multivariate analysis, with each additional year representing an odds ratio (OR) = 1.09 (CI 1.05-1.13, p < 0.000). The choice of accession site had no impact on the risk of periprocedural TIA/stroke (OR = 0.81; CI 0.38-1.72, p = 0.577). CONCLUSION: Observational data from a large prospective registry indicate that accession site has no influence on the risk of periprocedural TIA/stroke after cardiac catheterization

Astrometric Control of the Inertiality of the Hipparcos Catalog

Based on the most complete list of the results of an individual comparison of the proper motions for stars of various programs common to the Hipparcos catalog, each of which is an independent realization of the inertial reference frame with regard to stellar proper motions, we redetermined the vector $\omega$ of residual rotation of the ICRS system relative to the extragalactic reference frame. The equatorial components of this vector were found to be the following: $\omega_x = +0.04\pm 0.15$ mas yr$^{-1}$, $\omega_y = +0.18\pm 0.12$ mas yr$^{-1}$, and $\omega_z = -0.35\pm 0.09$ mas yr$^{-1}$.Comment: 8 pages, 1 figur

A Calanais myth and an alignment of the east stone-row with both the rising of the Pleiades and crossovers of Venus at sunrise on the summer solstices

Acknowledgements My thanks to Stefan Sagrott of Historic Environment Scotland for his help in obtaining Patrick Ashmore’s data and to David Forrest, School of Geographical and Earth Sciences, University of Glasgow, for providing a copy of David Tait’s map of Calanais.Peer reviewedPublisher PD

A foundation model for atomistic materials chemistry

Machine-learned force fields have transformed the atomistic modelling of materials by enabling simulations of ab initio quality on unprecedented time and length scales. However, they are currently limited by: (i) the significant computational and human effort that must go into development and validation of potentials for each particular system of interest; and (ii) a general lack of transferability from one chemical system to the next. Here, using the state-of-the-art MACE architecture we introduce a single general-purpose ML model, trained on a public database of 150k inorganic crystals, that is capable of running stable molecular dynamics on molecules and materials. We demonstrate the power of the MACE-MP-0 model - and its qualitative and at times quantitative accuracy - on a diverse set problems in the physical sciences, including the properties of solids, liquids, gases, chemical reactions, interfaces and even the dynamics of a small protein. The model can be applied out of the box and as a starting or "foundation model" for any atomistic system of interest and is thus a step towards democratising the revolution of ML force fields by lowering the barriers to entry.Comment: 119 pages, 63 figures, 37MB PD

q-pac: A Python Package for Machine Learned Charge Equilibration Models

Many state-of-the art machine learning (ML) interatomic potentials are based on a local or semi-local (message-passing) representation of chemical environments. They therefore lack a description of long-range electrostatic interactions and non-local charge transfer. In this context, there has been much interest in developing ML-based charge equilibration models, which allow the rigorous calculation of long-range electrostatic interactions and the energetic response of molecules and materials to external fields. The recently reported kQEq method achieves this by predicting local atomic electronegativities using Kernel ML. This paper describes the q-pac Python package, which implements several algorithmic and methodological advances to kQEq and provides an extendable framework for the development of ML charge equilibration models

The Comparison of Selected Methods of Cast Iron Spheroidization in Industrial Conditions

Production of spheroidal graphite cast iron is today quite mastered technology. There are many methods achieving the nodular graphite morphology. Each of these methods have specific characteristics and requirements to technical support, properties and the type of applied modifier. Selection of the spheroidization method is dependent on foundry disposition, production character, economic balance, quality requirements, etc. In case of centrifugally casting the core, which fills body and neck of the roll, is created by ductile iron. Considering the sophisticated production of centrifugally cast rolls for hot rolling mills it is necessary to ensure a high reproducibility and reliability of ductile cast iron production quality in the bulk range of 9-18 t per tapping. These conditions are in the Roll Foundry in Vítkovicke Slevarny, spol. s r.o. provided and verified mastered overpour method and the newly injection of cored wire in the melt

Durability of carbon-supported manganese oxide nanoparticles for the oxygen reduction reaction (ORR) in alkaline medium

International audienceMnOx/C-based electrocatalysts, prepared by the chemical deposition of manganese oxide nanoparticles on carbon, were tested towards the Oxygen Reduction Reaction (ORR) in their as-synthesized state and after ageing, either in ambient air for a year (mild ageing) or in an O2-saturated molar KOH solution at 80 °C for three weeks (premature ageing). For each electrocatalyst, the morphology and composition were characterised using TEM, XRD and chemical analysis. ORR kinetic parameters were evaluated using the Rotating Disk Electrode (RDE) and Rotating Ring Disk Electrode (RRDE) setups. Whilst the oxygen reduction activity of the electrocatalysts barely changes after mild ageing, it decreases after premature ageing following dramatic modifications to both the chemical and crystalline structures of the carbon-supported MnOx nanoparticles. The peroxide yield also sharply increases after premature ageing. Doping MnOx/C with nickel or magnesium divalent cations is beneficial since it improves both the catalytic activity and selectivity towards the 4-electron ORR pathway, even after ageing

Electrochemical performance of Mo doped high voltage spinel cathode material for lithium-ion battery

This article deals with the properties of high-voltage cathode material LiNi0.5Mn1.5O4 synthesized by a solid-state reaction method and the influence of doping this material by molybdenum. The samples – LiMox+ yNi0.5 - xMn1.5 - yO4 with different Mo contents (x = 0.00, 0.05, y = 0.00, 0.05) were successfully synthesized by two step annealing process and they were then investigated by SEM, EDS spectroscopy, thermo gravimetric analysis, cyclic voltammetry and charge–discharge tests at different loads and high temperature in lithium-ion cells with metal lithium as a counter electrode. Results showed that the initial discharge capacity and capacity during high temperature cycling of the LiMox + yNi0.5 - xMn1.5 - yO4 cathode were improved with addition of Mo when x = 0.05. Thermal analysis results suggested that the Mo doping slightly improved the stability of the crystal structure of the LiNi0.5Mn1.5O4 cathode which leads to an improved stability during high temperature galvanostatic cycling.Fil: Kazda, T.. Brno University of Technology; República ChecaFil: Vondrák, J.. Brno University of Technology; República ChecaFil: Visintin, Arnaldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Sedlaříková, M. Brno University of Technology; República ChecaFil: Tichý, J.. Brno University of Technology; República ChecaFil: Čudek, P.. Brno University of Technology; República Chec