Hole polaron formation and migration in olivine phosphate materials

By combining first principles calculations and experimental XPS measurements, we investigate the electronic structure of potential Li-ion battery cathode materials LiMPO4 (M=Mn,Fe,Co,Ni) to uncover the underlying mechanisms that determine small hole polaron formation and migration. We show that small hole polaron formation depends on features in the electronic structure near the valence-band maximum and that, calculationally, these features depend on the methodology chosen for dealing with the correlated nature of the transition-metal d-derived states in these systems. Comparison with experiment reveals that a hybrid functional approach is superior to GGA+U in correctly reproducing the XPS spectra. Using this approach we find that LiNiPO4 cannot support small hole polarons, but that the other three compounds can. The migration barrier is determined mainly by the strong or weak bonding nature of the states at the top of the valence band, resulting in a substantially higher barrier for LiMnPO4 than for LiCoPO4 or LiFePO4

Reverberation Mapping Results from MDM Observatory

We present results from a multi-month reverberation mapping campaign undertaken primarily at MDM Observatory with supporting observations from around the world. We measure broad line region (BLR) radii and black hole masses for six objects. A velocity-resolved analysis of the H_beta response shows the presence of diverse kinematic signatures in the BLR.Comment: To appear in the Proceedings of the IAU Symposium No. 267: Co-Evolution of Central Black Holes and Galaxies, Rio de Janeiro, 200

Unexpected benefits of pre-university skills training for A-level students

First-year undergraduates can find the transition from the prescriptive learning environment at school to one of self-directed learning at university, a considerable challenge. A Pre-university Skills Course (PSC) was developed to address this issue by preparing sixth formers for the university learning style. It was piloted with students in the year prior to A-level examinations at a selective state-funded school in East Anglia. The present paper examines the effect of the course on the students’ A-level tariff. Chi-squared analysis of A-level grades of students with comparable GCSE results, indicate that students who undertook the PSC performed significantly better in their A-level results than those who did not. These data demonstrate how skills training might improve A-level performance and assist in the transition to university

Path integral Monte Carlo simulation of charged particles in traps

This chapter is devoted to the computation of equilibrium (thermodynamic) properties of quantum systems. In particular, we will be interested in the situation where the interaction between particles is so strong that it cannot be treated as a small perturbation. For weakly coupled systems many efficient theoretical and computational techniques do exist. However, for strongly interacting systems such as nonideal gases or plasmas, strongly correlated electrons and so on, perturbation methods fail and alternative approaches are needed. Among them, an extremely successful one is the Monte Carlo (MC) method which we are going to consider in this chapter.Comment: 18 pages, based on talks on Hareaus school on computational methods, Greifswald, September 200

Attitude Control and Stabilization of Spacecraft with a Captured Asteroid

National Aeronautics and Space Administration's Asteroid Redirect Mission (ARM) aims to capture a Near Earth Orbit (NEO) asteroid or a piece of a large asteroid and transport it to the Earth{Moon system. In this paper, we provide a detailed analysis of one of the main control challenges for the first ARM mission concept, namely despinning and three-axis stabilizing the asteroid and spacecraft combination after the ARM spacecraft captures the tumbling NEO asteroid. We first show that control laws, which explicitly use the dynamics of the system in their control law equation, encounter a fundamental limitation due to modeling uncertainties. We show that in the presence of large modeling uncertainties, the resultant disturbance torque for such control laws may well exceed the maximum control torque of the conceptual ARM spacecraft. We then numerically compare the performance of three viable control laws: the robust nonlinear tracking control law, the adaptive nonlinear tracking control law, and the simple derivative plus proportional-derivative linear control strategy. We conclude that under very small mod- eling uncertainties, which can be achieved using online system identification, the robust nonlinear tracking control law guarantees exponential convergence to the fuel-optimal reference trajectory and hence consumes the least fuel. On the other hand, in the presence of large modeling uncertainties, measurement errors, and actuator saturations, the best strategy for stabilizing the asteroid and spacecraft combination is to first despin the system using a derivative (rate damping) linear control law and then stabilize the system in the desired orientation using the simple proportional-derivative linear control law. More-over, the fuel consumed by the conceptual ARM spacecraft using these control strategies is upper bounded by 300 kg for the nominal range of NEO asteroid parameters. We conclude this paper with specific design guidelines for the ARM spacecraft for efficiently stabilizing the tumbling NEO asteroid and spacecraft combination

Collective dynamics of liquid aluminum probed by Inelastic X-ray Scattering

An inelastic X-ray scattering experiment has been performed in liquid aluminum with the purpose of studying the collective excitations at wavevectors below the first sharp diffraction peak. The high instrumental resolution (up to 1.5 meV) allows an accurate investigation of the dynamical processes in this liquid metal on the basis of a generalized hydrodynamics framework. The outcoming results confirm the presence of a viscosity relaxation scenario ruled by a two timescale mechanism, as recently found in liquid lithium.Comment: 8 pages, 7 figure

"How do pilates trained physiotherapists utilize and value pilates exercise for MSK conditions? A qualitative study"

Background Pilates is a popular exercise therapy approach offering numerous benefits, including muscular strength, flexibility, control, and core stability. Pilates has been widely utilized in the prevention and rehabilitation of a variety of musculoskeletal disorders. Objectives The aim of this study was to explore the experiences and opinions of Pilates trained NHS and private practice physiotherapists in the UK, regarding the perceived benefits, risks, delivery and rationale for this exercise method. Methods This qualitative study used a self‐designed electronic survey to retrieve the views of 30 physiotherapists, who had undertaken formal Pilates Instruction training, recruited by a purposive and snowball sampling method. Questions were either multiple choice or open‐ended, examined via thematic analysis. Results Physiotherapists identified the most important benefits of Pilates as reduction in fear‐avoidance, improving bodily awareness and increasing muscular strength. Exercises that promote general movement were highlighted as being particularly useful, with a majority recommending daily practice for optimum benefit. Participants recognized lack of core strength as a key indicator, whereas others criticized excessive focus on this principle. Conclusions Physiotherapists identified a range of inter‐linked benefits and recognized that Pilates is hugely modifiable. Individualizing exercises can further encourage participation and negate the restriction of some health conditions. NHS and Private Practice Therapists utilize Pilates in a similar way, although rationales for its use may differ, as the justification for Pilates exercise may be evolving. Pilates appears a valuable methodology in the NHS, which can help patients engage with activity

Olivine or Impact Melt: Nature of the "Orange" Material on Vesta from Dawn

NASA's Dawn mission observed a great variety of colored terrains on asteroid (4) Vesta during its survey with the Framing Camera (FC). Here we present a detailed study of the orange material on Vesta, which was first observed in color ratio images obtained by the FC and presents a red spectral slope. The orange material deposits can be classified into three types, a) diffuse ejecta deposited by recent medium-size impact craters (such as Oppia), b) lobate patches with well-defined edges, and c) ejecta rays from fresh-looking impact craters. The location of the orange diffuse ejecta from Oppia corresponds to the olivine spot nicknamed "Leslie feature" first identified by Gaffey (1997) from ground-based spectral observations. The distribution of the orange material in the FC mosaic is concentrated on the equatorial region and almost exclusively outside the Rheasilvia basin. Our in-depth analysis of the composition of this material uses complementary observations from FC, the visible and infrared spectrometer (VIR), and the Gamma Ray and Neutron Detector (GRaND). Combining the interpretations from the topography, geomorphology, color and spectral parameters, and elemental abundances, the most probable analog for the orange material on Vesta is impact melt

Multi-Wavelength Monitoring of the Changing-Look AGN NGC 2617 during State Changes

Optical and near-infrared photometry, optical spectroscopy, and soft X-ray and UV monitoring of the changing-look active galactic nucleus NGC 2617 show that it continues to have the appearance of a type-1 Seyfert galaxy. An optical light curve for 2010-2017 indicates that the change of type probably occurred between 2010 October and 2012 February and was not related to the brightening in 2013. In 2016 and 2017 NGC 2617 brightened again to a level of activity close to that in 2013 April. However, in 2017 from the end of the March to end of July 2017 it was in very low level and starting to change back to a Seyfert 1.8. We find variations in all passbands and in both the intensities and profiles of the broad Balmer lines. A new displaced emission peak has appeared in Hβ. X-ray variations are well correlated with UV-optical variability and possibly lead by ̃2-3 d. The K band lags the J band by about 21.5 ± 2.5 d and lags the combined B + J bands by ̃25 d. J lags B by about 3 d. This could be because J-band variability arises predominantly from the outer part of the accretion disc, while K-band variability is dominated by thermal re-emission by dust. We propose that spectral-type changes are a result of increasing central luminosity causing sublimation of the innermost dust in the hollow bi-conical outflow. We briefly discuss various other possible reasons that might explain the dramatic changes in NGC 2617.Fil: Oknyansky, V. L.. Sternberg Astronomical Institute; RusiaFil: Gaskell, C. M.. Department of Astronomy and Astrophysics. University of California. Santa Cruz; Estados UnidosFil: Mikailov, K. M.. Shamakhy Astrophysical Observatory, National Academy of Sciences. Pirkuli; AzerbaiyánFil: Lipunov, V. M.. Sternberg Astronomical Institute. M.V.Lomonosov Moscow State University ; RusiaFil: Shatsky, N. I.. Sternberg Astronomical Institute. M.V.Lomonosov Moscow State University; RusiaFil: Tsygankov, S. S.. Tuorla Observatory, Department of Physics and Astronomy. University of Turku.; FinlandiaFil: Gorbovskoy, E. S.. Sternberg Astronomical Institute. M.V.Lomonosov Moscow State University; RusiaFil: Tatarnikov, A. M.. Sternberg Astronomical Institute. M.V.Lomonosov Moscow State University; RusiaFil: Metlov, V. G.. Sternberg Astronomical Institute. M.V.Lomonosov Moscow State University; RusiaFil: Malanchev, K. L.. Sternberg Astronomical Institute. M.V.Lomonosov Moscow State University; RusiaFil: Brotherton, M.B.. University of Wyoming; Estados UnidosFil: Kasper, D.. University of Wyoming; Estados UnidosFil: Du, P.. Institute of High Energy Physics. Chinese Academy of Sciences; ChinaFil: Chen, X.. School of Space Science and Physics. Shandong University; ChinaFil: Burlak, M. A.. Sternberg Astronomical Institute. M.V.Lomonosov Moscow State University; RusiaFil: Buckley, D. A. H.. The South African Astronomical Observatory; SudáfricaFil: Rebolo, R.. Instituto de Astrofisica de Canarias; EspañaFil: Serra-Ricart, M.. Instituto de Astrofisica de Canarias; EspañaFil: Podestá, R.. Universidad Nacional de San Juan; ArgentinaFil: Levato, O. H.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; Argentin

Effects of Backflow Correlation in the Three-Dimensional Electron Gas: Quantum Monte Carlo Study

The correlation energy of the homogeneous three-dimensional interacting electron gas is calculated using the variational and fixed-node diffusion Monte Carlo methods, with trial functions that include backflow and three-body correlations. In the high density regime the effects of backflow dominate over those due to three-body correlations, but the relative importance of the latter increases as the density decreases. Since the backflow correlations vary the nodes of the trial function, this leads to improved energies in the fixed-node diffusion Monte Carlo calculations. The effects are comparable to those found for the two-dimensional electron gas, leading to much improved variational energies and fixed-node diffusion energies equal to the release-node energies of Ceperley and Alder within statistical and systematic errors.Comment: 14 pages, 5 figures, submitted to Physical Review