Assessment of standing balance in patients after ankle fractures

Purpose: The objective of the study is to evaluate the degree of balance disorders in patients with surgical treatment of ankle fractures with the use of stabilometric examinations.Methods: The subjects in the study were 21 patients with ankle fractures treated surgically, within one year of the procedure. The control group were 20 healthy subjects. The balance was evaluated with the use of force platform in standing posture in both single and double limb stance. The analysed parameters were the transition area of the centre of feet pressure (COP), the length of the COP path and the COP velocity. The range of movement in the ankle joint and the intensification of pain were also measured.Results: In the balance evaluation in double limb stance, there were no statistically significant differences. A significant difference was found in the attempts of single limb-stance An average value of COP transition area in the study group was 261.2 mm2 in single stance (on the right operated limb) and in the control group – 93.2 mm2, so the difference was statistically significant (p=0,0096). The presence of pain, the presence or the removal of anastomosis had no significant influence on the balance of the studied subjects. Also a significant correlation between the balance of the subjects and their age was found.Conclusions: The balance in single limb stance after an instable ankle fracture within one year of the surgical procedure is significantly poorer in comparison with healthy subjects. Elderly persons have significantly poorer balance control

Cation Dynamics and Structural Stabilization in Formamidinium Lead Iodide Perovskites

The vibrational dynamics of pure and methylammonium-doped formamidinium lead iodide perovskites (FAPbI3) has been investigated by high-resolution neutron spectroscopy. For the first time, we provide an exhaustive and accurate analysis of the cation vibrations and underlying local structure around the organic moiety in these materials using first-principles electronic-structure calculations validated by the neutron data. Inelastic neutron scattering experiments on FAPbI3 provide direct evidence of the formation of a low-temperature orientational glass, unveiling the physicochemical origin of phase metastability in the tetragonal structure. Further analysis of these data provides a suitable starting point to explore and understand the stabilization of the perovskite framework via doping with small amounts of organic cations. In particular, we find that the hydrogen-bonding interactions around the formamidinium cations are strengthened as a result of cage deformation. This synergistic effect across perovskite cages is accompanied by a concomitant weakening of the methylammonium interactions with the surrounding framework

Fractal dimension as a scaling law for nuclear quantum effects: a neutron Compton scattering study on carbon allotropes

In this work, we tackle the problem of the sensitivity of neutron Compton scattering, measured through the widths of nuclear momentum distributions, to the degree of complexity and ordering of the structural motif characterising the surrounding environment felt by a particular nucleus (carbon). In doing so, we replace the usual concept of the bond strength categorised in terms of its thermodynamical or electronic properties with a novel observable inspired by the language of mathematical topology, the Hausdorff-Besicovitch fractal dimension. We derive a relatively straightforward connection between the fractal dimension of a given system under consideration and the nuclear kinetic energy. To achieve this, we modify the concept of the energy equipartition theorem for solid-state systems composed of carbon atoms where the atom-ordering topology does not follow a simple two or three-dimensional order, but rather atoms are placed along curves in space that have an intermediate dimension related to the varying amounts of information they contain. A series of results from past neutron Compton scattering studies, as well as new results on Buckminsterfullerene (C-60), correlate with the topological measures of surface roughness and bending, as categorised quantitatively by the fractal dimension of the system. Namely, for the same formal chemical binding motif (sp(2) C) and with decreasing system dimensionality from nearly 3 towards 1, the quantum nature of the system becomes more pronounced. The simple scaling law developed in this work allows for relatively simple assessment of the nuclear "quantumness" of a given system with potentially important ramifications in the ab initio modelling of nuclear quantum effects in condensed matter

The use of the Gait Variability Index for the evaluation of individuals after a stroke

The Gait Variability Index (GVI) summarizes overall gait quality, taking into account spatiotemporal parameters from a 3-dimensional gait analysis. However, there are no studies evaluating changes in gait patterns after stroke, based on the GVI. The study was designed to assess usefulness of the GVI for evaluation of gait pathology in subjects with stroke, compared to healthy individuals. Methods: Spatiotemporal gait parameters were examined in a group of 50 subjects at a chronic stage post-stroke and in 50 healthy controls. The GVI was calculated based on the 9 spatiotemporal data. Results: The findings show statistically significant differences between the values of the GVI for paretic and non-paretic limbs ( p < 0.001). Higher values of the index were identified in the case of non-paretic limb: 80.74 vs. 76.32. The GVI scores were decreased for both paretic and non-paretic limbs, compared to the controls – p < 0.001. Conclusions: The GDI score seems to be a viable tool for quantifying changes in gait pattern during evaluation of subjects with chronic post-stroke hemiparesis. Further studies should be conducted to validate the use of GVI in the post-stroke population

Model selection in neutron Compton scattering - a Bayesian approach with physical constraints

This work analyses the performance of the maximum-likelihood estimation approach in fitting Gram-Charlier expansion curves to nuclear momentum distributions with non-negativity constraints. The presented approach guarantees that the most likely model selected to describe the recorded data is also a physically meaningful one, i.e., corresponds to a non-negative probability distribution function. For the case of the most popular momentum distribution model, containing the information about the variance and excess kurtosis of the distribution, we derive a simple and easy to implement non-negativity criterion. We test the performance of the newly developed approach by applying it to interpret proton momentum distribution obtained from neutron Compton scattering from solid phosphoric acid, a system in which nuclear quantum tunnelling was proposed in the limit of low temperature. From a methodological point of view, this work provides a screening tool in the search for systems exhibiting the so-called 'non-trivial nuclear quantum effects'

Hydrogen dynamics in solid formic acid: insights from simulations with quantum colored-noise thermostats

With an increase of computational capabilities, ab initio molecular dynamics becomes the natural choice for exploring the nuclear dynamics of solids. As based on classical mechanics, the validity of this approach is, in-principle, limited to the high-T regime, whilst low-temperature simulations require inclusion of quantum effects. The methods commonly used to account for nuclear quantum effects are based on the path-integral formalism, which become, however, particularly time consuming when high accuracy methods are used for calculating forces. Recently, new efficient alternative approaches to account for quantum nature of nuclei have been proposed, using so-called quantum thermostats. In this work, we examine the simulations performed with the quantum colored-noise thermostat introduced by Ceriotti [Phys. Rev. Lett., 103: 030603, 2009]. We present the tests of portable implementation of the quantum thermostat in the ABIN program, which has been extended to periodic systems through the interface to CASTEP, a leading spectroscopy-oriented plane-wave density functional theory code. The range of applicability of quantum-thermostatted molecular dynamics simulations for the interpretation of neutron scattering data was examined and compared to classical molecular dynamics and lattice-dynamics simulations, using solid formic acid case as a test bed. We find that the approach is particularly useful for the modeling of low-temperature inelastic neutron scattering spectra as well as provides some theoretical estimate for the low-limit of the mean kinetic energy. While finding the quantum-thermostat to seriously affect the dynamic properties of the title system, we illustrate to which extent the unperturbed response can be successfully recovered