The Feedforward and Feedback Controls on Gait in Adults with Diabetes

There are nearly 26 million people with diabetes mellitus (DM) in the US, and half of chronic DMs develop somatosensory deficits due to diabetic polyneuropathy or diabetic peripheral neuropathy (DPN). The absence or impaired somatosensory feedback (e.g. touch sensation or joint proprioception) resulted from the damage of large nerve fiber, and motor deficits such as attenuated muscle strength and abnormal plantar pressure of lower extremity have been identified in DPN, and these sensorimotor impairments lead to an increased number of falls. To reduce the risk of falling, a well-coordinated and adapted limb movement driven by the feedforward (anticipatory) and feedback (reactive) control movement strategies are required to deal with forthcoming and instantaneous perturbations during walking respectively. The top-down feedforward control communicates with the central nervous system (CNS) and forms the basis for computing necessary motor output by simultaneously predicting or correcting errors of event information from the bottom-up feedback control. The altered spatiotemporal gait pattern in DM can either be the compensation of somatosensory feedback deficits or the compromised CNS-driven motor command. Exploring the feedforward and feedback controls not only illustrates the potential cause of the DM’s altered gait pattern but also offer the future opportunity to design prospective clinical intervention for DM’s safety and wellness. The overall objective of this study unveiled the impacts of feedforward and feedback control on DM/DPN’s dynamic balance during walking. This dissertation adopted a virtual reality-based obstacle crossing task to examine our central hypothesis of potential altered sensory and CNS-driven motor command of DPN would be manifested through the adjustment of spatiotemporal gait characteristics compared with healthy controls. In addition, we investigated how the visual guidance played a role to the on-line adjustment of these altered gait measures as the compensation. In results, DM demonstrated the compromised feedback control by lowering their maximal toe elevation during crossing and increasing their step width after crossing; while DPN presented the both compromised feedforward and feedback controls by decreasing the toe elevation during crossing and increasing stride/stance time after crossing of obstacle. Besides, the adjustment of the altered spatiotemporal gait characteristics were observed through the visual guidance. With the combination of virtual obstacle crossing task design with the guidance of visual information, the future virtual obstacle crossing training paradigm can be implemented for training diabetes population to reduce the risk of falling

Generalized Hyperbolic Distributions And Value-At-Risk Estimation For The South African Mining Index

South Africa is a cornucopia of mineral riches and the performance of its mining industry has significant impacts on the economy. Hence, an accurate distributional assumption of the underlying mining index returns is imperative for the forecasting and understanding of the financial market. In this paper, we propose three subclasses of the generalized hyperbolic distributions as appropriate models for the Johannesburg Stock Exchange (JSE) Mining Index returns. These models are shown to outperform the traditional assumption of normality and accommodate for a number of stylized features, such as excess kurtosis and volatility clustering, embedded within the financial data. The models are compared using the Akaike Information Criterion (AIC), the Bayesian Information Criterion (BIC) and log-likelihoods. In addition, Value-at-Risk (VaR) estimation and backtesting were also performed to test the extreme tails. The various criteria utilized suggest the generalized hyperbolic (GH) skew Student’s t-distribution as the most robust model for the South African Mining Index returns

Extreme Risk, Value-At-Risk And Expected Shortfall In The Gold Market

Extreme value theory (EVT) has been widely applied in fields such as hydrology and insurance. It is a tool used to reflect on probabilities associated with extreme, and thus rare, events. EVT is useful in modeling the impact of crashes or situations of extreme stress on investor portfolios. It describes the behavior of maxima or minima in a time series, i.e., tails of a distribution. In this paper, we propose the use of generalised Pareto distribution (GPD) to model extreme returns in the gold market. This method provides effective means of estimating tail risk measures such as Value-at-Risk (VaR) and Expected Shortfall (ES). This is confirmed by various backtesting procedures. In particular, we utilize the Kupiec unconditional coverage test and the Christoffersen conditional coverage test for VaR backtesting, while the Bootstrap test is used for ES backtesting. The results indicate that GPD is superior to the traditional Gaussian and Student’s t models for VaR and ES estimations

Special topics in probabilistic exchangeability and its applications.

Doctor of Philosophy in Mathematics, Statistics and Computer Science. University of KwaZulu-Natal, Durban, 2017.This thesis evolves around a probabilistic concept called exchangeability and its generalised forms. It is aimed at exploring connections between exchangeability and other sub-areas in mathematical statistics. These connections include theoretical implications, generalisation of existing methodologies and applications to real-world data. There are three topics of particular interest. The rst topic is related to the linkage between de Finetti's representation theorem (for exchangeable sequences) and existence conditions for Hausdor moment problems over k-dimensional simplexes. The equivalence of these two results are proved over the most general case in nite spaces. This is a generalisation of existing theory and uses an alternative approach to previous work in the literature. This connection, while theoretically interesting in its own right, may also lead to further cross- eld applications, such as distribution re-construction from nite moments or in the approximations to nite exchangeable sequences and nite moment problems. Secondly, we explore a currently popular topic, namely extreme value theory (EVT), which has been widely applied to areas such as hydrology, earth sciences and nance. Classical results from EVT assume that the data sequence is independent and identically distributed (IID). We generalise this assumption to exchangeable random sequences. This caters for more general approaches to EVT that allows for data dependency. Resampling techniques are utilised for estimating the parameters' prior distributions. We utilise these new methods for Value-at-Risk (VaR) estimation in nancial stock returns. This is done for both cases with and without GARCH lters. These new VaR models are also compared to existing models in the literature and shows promising improvements. For the nal topic, exchangeability is applied to two-phase sampling with an auxiliary variable. In particular, our focus is on a two-phase strati ed sampling design, under the assumption that readings for the study variable are exchangeable within stratum. This will again provide a generalisation from the usual IID assumption in applications of multiple-phase sampling. It is amalgamated with stationary bootstrapping at various levels of sampling to estimate within stratum and cross strata covariances. We show that our approach provides a more conservative estimate for the sampling variance of the two-phase estimator for the mean (i.e., the ratio estimator), as compared to the conventional IID method by Rao (1973

Andreev and Single Particle Tunneling Spectroscopies in Underdoped Cuprates

We study tunneling spectroscopy between a normal metal and underdoped cuprate superconductor modeled by a phenomenological theory in which the pseudogap is a precursor to the undoped Mott insulator. In the transparent tunneling limit, the spectra show a small energy gap associated with Andreev reflection. In the Giaever limit, the spectra show a large energy gap associated with single particle tunneling. Our theory semi-quantitatively describes the two gap behavior observed in tunneling experiments.Comment: 5 pages, 4 figures, submitted to Phys. Rev. Lett. minor changes of reference

Combining a non-immersive virtual reality gaming with motor-assisted elliptical exercise increases engagement and physiologic effort in children

A grant from the One-University Open Access Fund at the University of Kansas was used to defray the author's publication fees in this Open Access journal. The Open Access Fund, administered by librarians from the KU, KU Law, and KUMC libraries, is made possible by contributions from the offices of KU Provost, KU Vice Chancellor for Research & Graduate Studies, and KUMC Vice Chancellor for Research. For more information about the Open Access Fund, please see http://library.kumc.edu/authors-fund.xml.Virtual reality (VR) gaming is promising in sustaining children’s participation during intensive physical rehabilitation. This study investigated how integration of a custom active serious gaming with a robot-motorized elliptical impacted children’s perception of engagement (Intrinsic Motivation Inventory), physiologic effort (i.e., exercise speed, heart rate, lower extremity muscle activation), and joint kinematics while overriding the motor’s assistance. Compared to Non-VR condition, during the VR-enhanced condition participants’ perceived engagement was 23% greater (p = 0.01), self-selected speed was 10% faster (p = 0.02), heart rate was 7% higher (p = 0.08) and muscle demands increased. Sagittal plane kinematics demonstrated only a small change at the knee. This study demonstrated that VR plays an essential role in promoting greater engagement and physiologic effort in children performing a cyclic locomotor rehabilitation task, without causing any adverse events or substantial disruption in lower extremity joint kinematics. The outcomes of this study provide a foundation for understanding the role of future VR-enhanced interventions and research studies that weigh/balance the need to physiologically challenge a child during training with the value of promoting task-related training to help promote recovery of walking

Review on the Conflicts between Offshore Wind Power and Fishery Rights: Marine Spatial Planning in Taiwan

In recent years, Taiwan has firmly committed itself to pursue the green energy transition and a nuclear-free homeland by 2025, with an increase in renewable energy from 5% in 2016 to 20% in 2025. Offshore wind power (OWP) has become a sustainable and scalable renewable energy source in Taiwan. Maritime Spatial Planning (MSP) is a fundamental tool to organize the use of the ocean space by different and often conflicting multi-users within ecologically sustainable boundaries in the marine environment. MSP is capable of definitively driving the use of offshore renewable energy. Lessons from Germany and the UK revealed that MSP was crucial to the development of OWP. This paper aims to evaluate how MSP is able to accommodate the exploitation of OWP in Taiwan and contribute to the achievement of marine policy by proposing a set of recommendations. It concludes that MSP is emerging as a solution to be considered by government institutions to optimize the multiple use of the ocean space, reduce conflicts and make use of the environmental and economic synergies generated by the joint deployment of OWP facilities and fishing or aquaculture activities for the conservation and protection of marine environments.Peer Reviewe