Interventions to Reduce Spasticity and Improve Function in People With Chronic Incomplete Spinal Cord Injury: Distinctions Revealed by Different Analytical Methods.

Background. Spinal cord injury (SCI) results in impaired function, and ankle joint spasticity is a common secondary complication. Different interventions have been trialed with variable results. Objective. We investigated the effects of pharmacological and physical (locomotor training) interventions on function in people living with incomplete motor function loss caused by SCI and used different analytical techniques to understand whether functional levels affect recovery with different interventions. Methods. Participants with an incomplete SCI were assigned to 3 groups: no intervention, Lokomat, or tizanidine. Outcome measures were the 10-m walk test, 6-minute walk test, and the Timed Up and Go. Participants were classified in 2 ways: (1) based on achieving an improvement above the minimally important difference (MID) and (2) using growth mixture modeling (GMM). Functional levels of participants who achieved the MID were compared and random coefficient regression (RCR) was used to assess recovery in GMM classes. Results. Overall, walking speed and endurance improved, with no difference between interventions. Only a small number of participants achieved the MID. Both MID and GMM-RCR analyses revealed that tizanidine improved endurance in high-functioning participants. GMM-RCR classification also showed that speed and mobility improved after locomotor training. Conclusions. Improvements in function were achieved in a limited number of people with SCI. Using the MID and GMM techniques, differences in responses to interventions between high-and low-functioning participants could be identified. These techniques may, therefore, have potential to be used for characterizing therapeutic effects resulting from different interventions

The combined electrochemical and microstructural characterisation of the electrochemical reduction of uranium dioxide to uranium metal in molten lithium chloride-potassium chloride eutectic

The electrochemical reduction of uranium (IV) oxide to metallic uranium has been studied in lithium chloride-potassium chloride eutectic at 450°C using electrochemical and advanced material characterisation techniques. Electrochemical characterisation identified a single reduction peak occurring at -2.57V with respect to the Ag|Ag+ reference electrode. Sweep voltammetry has identified that the electroreduction of uranium dioxide to metallic uranium occurs via a single, 4-electron transfer, process. The electrochemical reduction has also been observed to be dependent on the activity of O2- ions: An increase in the bulk activity of the oxygen anion impeded the electroreduction process. This phenomena was thermodynamically predicted using Littlewood diagrams produced for the system. In addition, in situ energy dispersive X-ray diffraction investigations were carried out on the I12 JEEP beamline at the Diamond Light Source which resulted in the direct observation of the formation of uranium metal when a uranium dioxide electrode was exposed to electroreduction potentials. No intermediate phases were observed which supports the electrochemical characterisation of this process occurring in a single step. Moreover, microstructural characterisation has been performed on micro-bucket electrodes and metallic cavity electrodes. A coral-like structure was identified after reduction of uranium dioxide and has been attributed to the volume change associated with the reduction. Microstructural reconstructions were performed on four separate sub-volumes in the direction of propagation of the electroreduction process. The porosity was seen to decrease significantly from 16% to 4%. The pore connectivity was also observed to decrease from 93% to 18%. This drastic change in porosity and pore connectivity is reflected in the pore tortuosity which is seen to increase to infinity. This microstructural evaluation is concluded to impede the diffusion of O2- ions out of the electrode resulting in an increased probability of impediment of the electrochemical reduction process

Investigating microstructural evolution during the electroreduction of UO2 to U in LiCl-KCl eutectic using focused ion beam tomography

Reprocessing of spent nuclear fuels using molten salt media is an attractive alternative to liquid-liquid extraction techniques. Pyroelectrochemical processing utilizes direct, selective, electrochemical reduction of uranium dioxide, followed by selective electroplating of a uranium metal. Thermodynamic prediction of the electrochemical reduction of UO2 to U in LiCl-KCl eutectic has shown to be a function of the oxide ion activity. The pO2− of the salt may be affected by the microstructure of the UO2 electrode. A uranium dioxide filled “micro-bucket” electrode has been partially electroreduced to uranium metal in molten lithium chloride-potassium chloride eutectic. This partial electroreduction resulted in two distinct microstructures: a dense UO2 and a porous U metal structure were characterised by energy dispersive X-ray spectroscopy. Focused ion beam tomography was performed on five regions of this electrode which revealed an overall porosity ranging from 17.36% at the outer edge to 3.91% towards the centre, commensurate with the expected extent of reaction in each location. The pore connectivity was also seen to reduce from 88.32% to 17.86% in the same regions and the tortuosity through the sample was modelled along the axis of propagation of the electroreduction, which was seen to increase from a value of 4.42 to a value of infinity (disconnected pores). These microstructural characteristics could impede the transport of O2− ions resulting in a change in the local pO2− which could result in the inability to perform the electroreduction

Predominance diagrams of uranium and plutonum species in both lithium chloride-potassium chloride eutectic and calcium chloride

Electro-reduction of spent nuclear fuel has the potential to significantly reduce the amount of high level waste from nuclear reactors. Typically, spent uranium and plutonium are recovered via the PUREX process leading to a weapons-grade recovery; however, electro-reduction would allow spent nuclear fuel to be recovered effectively whilst maintaining proliferation resistance. Here, we pres- ent predominance diagrams (also known as Littlewood diagrams) for both uranium and plutonium species in molten lithium chloride–potassium chloride eutectic (LKE) at 500 C and in calcium chloride at 800 C. All diagrams presented depict regions of stability of various phases at unit activity in equilibrium with their respective dissociated ions. The diagrams thermodynamically define the electro- chemical system leading to predictions of reaction condi- tions necessary to electrochemically separate species. The diagrams have been constructed using a pure thermody- namic route; identifying stable species within the molten salt with an assumption of unit activity for each of the phases. These thermodynamically predicted diagrams have been compared to the limited available experimental data; demonstrating good correlation. The diagrams can also be used to predict regions of stability at activities less than unity and is also demonstrated

The effect of felt compression on the performance and pressure drop of all-vanadium redox flow batteries

The compression of carbon felt electrodes for redox flow batteries leads to changes in the electrochemical performance and has a large effect on the pressure drop of electrolyte flow through the system. In this investigation, the authors have characterised the electrochemical performance of all-vanadium redox flow batteries by studying the effect of compression on the contact resistance, polarisation behaviour and efficiency. Contact resistance was seen to reduce from ca. 2.0 Ω cm2 to 1.2 Ω cm2 and an energy efficiency of 85% was obtained from a felt compressed to 75%. Moreover, X-ray computed tomography (CT) has been employed to study the microstructure of felt electrodes at compressions up to 70%, showing a linear decrease in porosity and a constant fibre surface area-to-volume ratio. The pressure drop was modelled using computational fluid dynamics and employing the 3D structure of the felts obtained from CT, revealing that a 60% increase in compression related to a 44.5% increase in pressure drop

Following the electroreduction of uranium dioxide to uranium in LiCl-KCl eutectic in situ using synchrotron radiation

The electrochemical reduction of uranium dioxide to metallic uranium has been investigated in lithium chloride–potassium chloride eutectic molten salt. Laboratory based electrochemical studies have been coupled with in situ energy dispersive X-ray diffraction, for the first time, to deduce the reduction pathway. No intermediate phases were identified using the X-ray diffraction before, during or after electroreduction to form α-uranium. This suggests that the electrochemical reduction occurs via a single, 4-electron-step, process. The rate of formation of α-uranium is seen to decrease during electrolysis and could be a result of a build-up of oxygen anions in the molten salt. Slow transport of O2− ions away from the UO2 working electrode could impede the electrochemical reduction

A novel molten-salt electrochemical cell for investigating the reduction of uranium dioxide to uranium metal by lithium using in situ synchrotron radiation

A novel electrochemical cell has been designed and built to allow for in situ energy-dispersive X-ray diffraction measurements to be made during reduction of UO2 to U metal in LiCl-KCl at 500C. The electrochemical cell contains arecessed well at the bottom of the cell into which the working electrode sits, reducing the beam path for the X-rays through the molten-salt and maximizing the signal-to-noise ratio from the sample. Lithium metal was electrodeposited onto the UO2 working electrode by exposing the working electrode to more negative potentials than the Li deposition potential of the LiCl-KCl eutectic electrolyte. The Li metal acts as a reducing agent for the chemical reduction of UO2 to U, which appears to proceed to completion. All phases were fitted using Le Bail refinement. The cell is expected to be widely applicable to many studies involving molten-salt systems

Investigating the effect of thermal gradients on stress in solid oxide fuel cell anodes using combined synchrotron radiation and thermal imaging

Thermal gradients can arise within solid oxide fuel cells (SOFCs) due to start-up and shut-down, non-uniform gas distribution, fast cycling and operation under internal reforming conditions. Here, the effects of operationally relevant thermal gradients on Ni/YSZ SOFC anode half cells are investigated using combined synchrotron X-ray diffraction and thermal imaging. The combination of these techniques has identified significant deviation from linear thermal expansion behaviour in a sample exposed to a one dimensional thermal gradient. Stress gradients are identified along isothermal regions due to the presence of a proximate thermal gradient, with tensile stress deviations of up to 75Â MPa being observed across the sample at a constant temperature. Significant strain is also observed due to the presence of thermal gradients when compared to work carried out at isothermal conditions

Facilitatory effects of anti-spastic medication on robotic locomotor training in people with chronic incomplete spinal cord injury

Background: The objective of this study was to investigate whether an anti-spasticity medication can facilitate the effects of robotic locomotor treadmill training (LTT) to improve gait function in people with incomplete spinal cord injury (SCI). / Methods: Individuals with chronic incomplete SCI were recruited and carried out a 4 week intervention of either locomotor treadmill training (LTT) alone (n = 26) or LTT combined with Tizanidine (TizLTT), an anti-spasticity medication (n = 22). Gait function was evaluated using clinical outcome measures of gait, speed and endurance. To better understand the underlying mechanisms of the therapeutic effects, maximal strength, active range of motion (AROM) and peak velocity (Vp) of ankle dorsi- and planter-flexor muscles were also measured. Differences were assessed using two-way mixed design analysis of variance. The number of subjects that achieved the minimal important difference (MID) for clinical scores was also measured for each group, and the results of those that did attain the MID were compared with those that did not. / Results: Both LTT and TizLTT resulted in significant improvements in walking speed and dorsiflexion maximum strength, with no significant differences between them, using group-averaging analysis. However, using the MID analysis, a higher proportion of subjects in the TizLTT group achieved the MID for walking speed (40%) compared with LTT alone (13%). Those that achieved the MID for walking speed were significantly higher functioning at baseline than those that did not in the TizLTT group, and the change in walking speed was associated with the change in dorsiflexion peak velocity (R2 = 0.40; P < 0.05). / Conclusion: Tizanidine appears to facilitate the effects of LTT on gait function in individuals with chronic SCI that are higher functioning at baseline. We speculate that this may be due to restoration of inhibitory mechanisms by Tizanidine, resulting in greater stretch in the planterflexor muscles during the LTT