Closed-loop stimulation for upper limb rehabilitation following spinal cord injury and stroke

PhD ThesisInnovation is required to improve upper limb rehabilitation for neurological conditions such as stroke and spinal cord injury (SCI). There is growing appreciation of the importance of neural plasticity in recovery, and how this can be facilitated by synchronous activity in peripheral neural circuits and central brain areas. However, despite increasing scientific evidence, technological solutions that exploit associative plasticity have not yet been widely evaluated in clinical practice. In this thesis, I report the development and initial evaluation of a novel device which enabled a reaching and grasping motion in the affected limb by combining assistive functional electrical stimulation (FES) with inferred voluntary brain activity. The device was designed to enable translation from laboratory-to-clinic by overcoming common practical barriers to translational research, such as adaptability and ease of use. The device was demonstrated to be usable by individuals with either chronic stroke or SCI, and received positive qualitative feedback. Some participants showed modest improvements on assessments of upper limb function following a short intervention period. A study with healthy able-bodied volunteers indicated that after using the device, corticospinal pathways to the antagonist (flexor) muscle may be facilitated, and this facilitation might be increased by adjusting the relative timing of stimulation and inferred brain activity. The device could also deliver alternative stimulation techniques, and an exploratory study into transcutaneous spinal cord stimulation (tSCS) was conducted with healthy able-bodied volunteers. It was found that tSCS may activate peripheral and spinal pathways within acceptable comfort levels, but the parameters used in this study did not to generate functional contractions. An unexpected oscillatory motor response provided insights into how tSCS acts upon the motor system. Prior to a large scale evaluation of clinical effectiveness, further research is required to: further develop a theoretical basis for the intervention; demonstrate the mechanisms of action; and to evaluate the efficacy of the device.Wellcome Trust, postgraduate research studentship (2015 to 2018) • EPSRC Preparing for GCRF Award (PI: Dr Andrew Jackson) - Low cost rehabilitation of hand function following stroke (2016 to 2017

Modal Characterization of a Piezoelectric Shaker Table

Piezoelectric actuated shaker tables are often used for high frequency fatigue testing. Since natural frequencies can appear in the operating range of these shaker tables, it is necessary to conduct modal characterization of the system before testing. This thesis describes the design and experimental validation of a mechanical model used for modal analysis of a piezoelectric shaker table. A commercially available three-dimensional scanning device was used to produce a point cloud model of the surface geometry, which was converted to a solid model and imported into a Finite Element Analysis (FEA) package for modal analysis. Using a laser vibrometer to measure displacement and velocity, the physical vibration response of the shaker table was obtained for comparison with FEA frequency response results. The laser vibrometer data was used to validate and tune the FEA modal response

The Criticality Of Cultural Awareness In Global Marketing: Some Case Examples

International trade has taken place for thousands of years. One might assume that with such a long history, those involved with international business would have learned how it is done. For the most part, the major players are sensitive to cultural differences and how important it is to conduct business within the boundaries of the prevailing culture. However, there are hundreds of examples of cultural faux pas. This paper focuses on some of the top trading partners with the United States and the business opportunities that they represent. It also addresses general business etiquette guidelines that should be understood and applied when working with the key trading partners. Several cultural business missteps are presented to illustrate that the simplest decision can lead to embarrassment or worse, major economic loss. The need to research foreign cultural and language differences is just as important as researching the market for sales opportunities. In the global marketplace, the players who are aware and sensitive to the culture of their trading partners have a greater probability of success, than those who do not

The pursuit of locality in quantum mechanics

The rampant success of quantum theory is the result of applications of the 'new' quantum mechanics of Schrödinger and Heisenberg (1926-7), the Feynman-Schwinger-Tomonaga Quantum Electrodynamics (1946-51), the electro-weak theory of Salaam, Weinberg, and Glashow (1967-9), and Quantum Chromodynamics (1973-); in fact, this success of `the' quantum theory has depended on a continuous stream of brilliant and quite disparate mathematical formulations. In this carefully concealed ferment there lie plenty of unresolved difficulties, simply because in churning out fabulously accurate calculational tools there has been no sensible explanation of all that is going on. It is even argued that such an understanding is nothing to do with physics. A long-standing and famous illustration of this is the paradoxical thought-experiment of Einstein, Podolsky and Rosen (1935). Fundamental to all quantum theories, and also their paradoxes, is the location of sub-microscopic objects; or, rather, that the specification of such a location is fraught with mathematical inconsistency. This project encompasses a detailed, critical survey of the tangled history of Position within quantum theories. The first step is to show that, contrary to appearances, canonical quantum mechanics has only a vague notion of locality. After analysing a number of previous attempts at a `relativistic quantum mechanics', two lines of thought are considered in detail. The first is the work of Wan and students, which is shown to be no real improvement on the usual `nonrelativistic' theory. The second is based on an idea of Dirac's - using backwards-in-time light-cones as the hypersurface in space-time. There remain considerable difficulties in the way of producing a consistent scheme here. To keep things nicely stirred up, the author then proposes his own approach - an adaptation of Feynman's QED propagators. This new approach is distinguished from Feynman's since the propagator or Green's function is not obtained by Feynman's rule. The type of equation solved is also different: instead of an initial-value problem, a solution that obeys a time-symmetric causality criterion is found for an inhomogeneous partial differential equation with homogeneous boundary conditions. To make the consideration of locality more precise, some results of Fourier transform theory are presented in a form that is directly applicable. Somewhat away from the main thrust of the thesis, there is also an attempt to explain the manner in which quantum effects disappear as the number of particles increases in such things as experimental realisations of the EPR and de Broglie thought experiments

Coprecipitation of Mixed Radionuclides From Large Volumes of Nuclear Waste Water Via Carbonate Coprecipitation Reactions

Strontium-90 and Carbon-14 are two important radionuclides associated with nuclear waste. Accidental release of these to the environment can cause a hazard which, due to their respective half lives of 28.8 and 5730 years, may persist for hundreds or thousands of years. The coprecipitation of 90Sr and 14C into calcium carbonate may be applied as a treatment process by the addition of Ca(OH)2 and Na2CO3 to groundwater. This has been demonstrated to be a possible process for the removal of these isotopes from groundwater, achieving over 99.9 % removal for both isotopes under optimal conditions. For 14C these conditions comprised high initial Ca2+:CO32- ratios (10:1). For Sr the optimal conditions comprised low initial Ca2+:CO32- ratios (10:100), both treatments were more favourable alongside high seed crystal surface areas. Sr was incorporated into the calcite lattice with a gradually increasing lattice strain which resulted in a change in the coordination from 6-fold (calcite like) to 8-fold (aragonite like). The upper limit of this solid solution was determined by the point at which strontianite began to precipitate. Before this treatment is applied to any site there exist a number of potential complications that should be considered. Since 90Sr and 14C are removed by fundamentally different processes, prolonged Ca2+ and CO32- depletion respectively, achieving simultaneous removal of these radionuclides from the same solution will be less efficient than the values quoted above. Furthermore if 14C bearing carbonate is allowed to equilibrate with a solution containing some 12CO32- (from atmospheric in-gassing), there will be an exchange of isotopes resulting in an accumulation of 14C in solution. Finally, it is believed Sr removal was improved as the proportion of Sr, relative to other divalent cations, increased. This Sr2+ was attracted to the negatively charged calcite surface and generated a localised supersaturation of strontianite. This mechanism however may be inapplicable to Sellafield site conditions as under the higher Sr2+ concentrations used in this study strontianite supersaturation will be reached at lower CO32- concentrations. Groundwater ionic content may also have an impact on this technique; by complexing with Ca2+ and CO32- ions and lowering their activities and thus supersaturations of calcite and strontianite. Disposal of calcite produced from this process may be achieved through encapsulation and immobilisation in cement grout. Preliminary experiments show that the composition of this grout will control the incorporation environment of the 90Sr and 14C therein. In grouts with high Ground Granulated Blast Furnace Slag:Ordinary Portland Cement (GGBFS:OPC) the calcite dissolved and the contaminants contained within were released into the cement blend. In grouts with low GGBFS:OPC the calcite crystals remained intact and were encapsulated by the cement

Energy-adaptive Network Switching via Intra-device Scaling

We propose horizontal intra-device scaling for network switches. Our approach allows for a network device to dynamically scale energy use in response to changing network utilization at a finergrain in comparison to existing monolithic approaches, and enables a reduction in cost and environmental impact via reduced network energy use outside peak operating periods. We demonstrate the feasibility of intra-device switch scaling by designing a network switch architecture comprising multiple, less powerful, network devices leveraging a Multiple Spanning Tree Protocol (MSTP) to operate in parallel in place of a singular powerful device. Our preliminary results demonstrate that our approach can reduce total network energy use by 66.3% in comparison to established approaches with minimal performance penalty, and outlines future work for further improvement for this new form of network switch architecture for reducing energy use within core network infrastructure

Hydration of dicalcium silicate and diffusion through neo-formed calcium-silicate-hydrates at weathered surfaces control the long-term leaching behaviour of basic oxygen furnace (BOF) steelmaking slag

Alkalinity generation and toxic trace metal (such as vanadium) leaching from basic oxygen furnace (BOF) steel slag particles must be properly understood and managed by pre-conditioning if beneficial reuse of slag is to be maximised. Water leaching under aerated conditions was investigated using fresh BOF slag at three different particle sizes (0.5–1.0, 2–5 and 10 × 10 × 20 mm blocks) and a 6-month pre-weathered block. There were several distinct leaching stages observed over time associated with different phases controlling the solution chemistry: (1) free-lime (CaO) dissolution (days 0–2); (2) dicalcium silicate (Ca₂SiO₄) dissolution (days 2–14) and (3) Ca–Si–H and CaCO₃ formation and subsequent dissolution (days 14–73). Experiments with the smallest size fraction resulted in the highest Ca, Si and V concentrations, highlighting the role of surface area in controlling initial leaching. After ~2 weeks, the solution Ca/Si ratio (0.7–0.9) evolved to equal those found within a Ca–Si–H phase that replaced dicalcium silicate and free-lime phases in a 30- to 150-μm altered surface region. V release was a two-stage process; initially, V was released by dicalcium silicate dissolution, but V also isomorphically substituted for Si into the neo-formed Ca–Si–H in the alteration zone. Therefore, on longer timescales, the release of V to solution was primarily controlled by considerably slower Ca–Si–H dissolution rates, which decreased the rate of V release by an order of magnitude. Overall, the results indicate that the BOF slag leaching mechanism evolves from a situation initially dominated by rapid hydration and dissolution of primary dicalcium silicate/free-lime phases, to a slow diffusion limited process controlled by the solubility of secondary Ca–Si–H and CaCO₃ phases that replace and cover more reactive primary slag phases at particle surfaces

Mechanisms of inorganic carbon-14 attenuation in contaminated groundwater: Effect of solution pH on isotopic exchange and carbonate precipitation reactions

Radioactive 14C is a significant contaminant associated with nuclear fuels and wastes that is potentially highly mobile in the environment as dissolved inorganic carbonate species. This study investigated the mechanisms by which dissolved inorganic 14C is retained in surface and groundwater environments via precipitation and isotopic exchange reactions. Precipitation of calcite in the presence and absence of nucleation sites is considered along with isotopic exchange with both atmospheric CO2 and solid carbonates. Precipitation occurs at calcite supersaturation values of SICAL > 1.5 in the absence of nucleation sites and SICAL > 0–0.5 in the presence of nucleation sites, suggesting that precipitation of 14C-bearing carbonates is much more likely in subsurface environments where nucleation sites are abundant. The maximum 14C removal in solid isotopic exchange experiments occurred after approximately 2 weeks equilibration. In these experiments the amount of 14C removed from solution was proportional to the amount of calcite surface area present, and removal from solution was equivalent to rapid equalisation of the isotope ratio in an 8–10 Å active surface layer. Although the reactivity of natural carbonates may be lower than the calcite samples used in this study, these results suggest isotopic exchange with solids will be an important 14C retardation mechanism in subsurface environments containing only modest TIC concentrations. These results suggest that if inorganic 14C is released into sub-surface environments, both precipitation and solid phase isotopic exchange can result in non-conservative 14C-DIC transport and 14C contamination may persist in groundwater for decades following accidental releases. In contrast, in experiments open to atmosphere with pH values below 9.3, complete loss of dissolved inorganic 14C was very rapid and occurred with timescales of 10's of hours. 14C loss was due to a rapid exchange of dissolved 14C species with 12CO2 (g) and the kinetics of 14C removal increased as pH values were lowered (i.e. atmospheric isotopic exchange was first order with respect to the concentration of carbonic acid present). Thus these results suggest that release of inorganic 14C to surface waters with pH values <9.3 would result in rapid exchange with 12CO2 (g) and 14C would not persist in the aqueous environment, whereas 14C-DIC released to saturated subsurface environments may persist close to the release site for decades due to precipitation and solid phase exchange reactions preventing/retarding transport with the groundwater