The effect on lower spine muscle activation of walking on a narrow beam in virtual reality

To what extent do people behave in immersive virtual environments as they would in similar situations in a physical environment? There are many ways to address this question, ranging from questionnaires, behavioral studies, and the use of physiological measures. Here, we compare the onsets of muscle activity using surface electromyography (EMG) while participants were walking under three different conditions: on a normal floor surface, on a narrow ribbon along the floor, and on a narrow platform raised off the floor. The same situation was rendered in an immersive virtual environment (IVE) Cave-like system, and 12 participants did the three types of walking in a counter-balanced within-groups design. The mean number of EMG activity onsets per unit time followed the same pattern in the virtual environment as in the physical environment-significantly higher for walking on the platform compared to walking on the floor. Even though participants knew that they were in fact really walking at floor level in the virtual environment condition, the visual illusion of walking on a raised platform was sufficient to influence their behavior in a measurable way. This opens up the door for this technique to be used in gait and posture related scenarios including rehabilitation.     

The Kemeny Constant for Finite Homogeneous Ergodic Markov Chains

A quantity known as the Kemeny constant, which is used to measure the expected number of links that a surfer on the World Wide Web, located on a random web page, needs to follow before reaching his/her desired location, coincides with the more well known notion of the expected time to mixing, i.e., to reaching stationarity of an ergodic Markov chain. In this paper we present a new formula for the Kemeny constant and we develop several perturbation results for the constant, including conditions under which it is a convex function. Finally, for chains whose transition matrix has a certain directed graph structure we show that the Kemeny constant is dependent only on the common length of the cycles and the total number of vertices and not on the specific transition probabilities of the chain.     

A Convergent-Divergent Approach to Context Processing, General Intellectual Functioning, and the Genetic Liability to Schizophrenia.

Convergent and divergent validity are critically important in developing psychological measures that reveal interpretable deficits in disordered populations. This article reports on 2 studies that evaluated the validity of context processing measures. In Experiment 1, a confirmatory factor analysis of data from 481 healthy adults established the convergent validity of 2 context processing measures and showed that context processing accounted for significant amounts of variance in standard IQ and working memory measures. In Experiment 2, 20 schizophrenia patients, 16 of their healthy siblings, and 28 controls were evaluated using a novel, short context processing measure, the dot pattern expectancy (DPX) task. The DPX was sensitive to specific deficits in schizophrenia patients and their healthy siblings. These findings support the construct validity of context processing measures, suggest context processing is a component of intellectual functioning, and demonstrate that brief context processing measures remain sensitive to psychopathological deficits. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of tilt on high-resolution ADF-STEM imaging

A study of the effects of small-angle specimen tilt on high-resolution annular dark field images was carried out for scanning transmission electron microscopes with uncorrected and aberration-corrected probes using multislice simulations. The results indicate that even in the cases of specimen tilts of the order of 1 degree a factor of 2 reduction in the contrast of the high-resolution image should be expected. The effect holds for different orientations of the crystal. Calculations also indicate that as the tilted specimen gets thicker the contrast reduction increases. Images simulated with a low-angle annular dark field detector show that tilt effects are more pronounced in this case and suggest that these low-angle detectors can be used to correct specimen tilt during scanning transmission electron microscopes operation.     

A quantitative risk assessment of a domestic property connected to a hydrogen distribution network

The increased reliance on natural gas for heating worldwide makes the search for carbon-free alternatives imperative, especially if international decarbonisation targets are to be met. Hydrogen does not release carbon dioxide (CO₂) at the point of use which makes it an appealing candidate to decarbonise domestic heating. Hydrogen can be produced from either 1) the electrolysis of water with no associated carbon emissions, or 2) from methane reformation (using steam) which produces CO₂, but which is easily captured and storable during production. Hydrogen could be transported to the end-user via gas distribution networks similar to, and adapted from, those in use today. This would reduce both installation costs and end-user disruption. However, before hydrogen can provide domestic heat, it is necessary to assess the ‘risk’ associated with its distribution in direct comparison to natural gas. Here we develop a comprehensive and multi-faceted quantitative risk assessment tool to assess the difference in ‘risk’ between current natural gas distribution networks, and the potential conversion to a hydrogen based system. The approach uses novel experimental and modelling work, scientific literature, and findings from historic large scale testing programmes. As a case study, the risk assessment tool is applied to the newly proposed H100 demonstration (100% hydrogen network) project. The assessment includes the comparative risk of gas releases both upstream and downstream of the domestic gas meter. This research finds that the risk associated with the proposed H100 network (based on its current design) is lower than that of the existing natural gas network by a factor 0.88.     

Performance-driven design of Biocompatible Mg alloys

Magnesium (Mg) and its alloys provide numerous benefits as a resorptive biomaterial and present the very real possibility of replacing current metallic implant materials in a variety of roles. The development of suitable biodegradable implant alloys is a multidisciplinary challenge, since alloy design must be confined to a range of alloying additions that are biologically nontoxic, whilst still providing the requisite mechanical properties. This leaves a small number of compatible elements that can provide benefits when alloyed with Mg, including calcium (Ca) and zinc (Zn). To date, although a range of different Mg alloys have been investigated both in vitro and in vivo, little work has been performed to characterize the relationship between the composition of Mg alloys, their corrosion and resulting mechanical properties over time. Consequently it is crucial to understand how these properties may be related if alloys are to be successfully screened for implantation in the body.     

Ferritinophagy and α-Synuclein: Pharmacological Targeting of Autophagy to Restore Iron Regulation in Parkinson’s Disease

A major hallmark of Parkinson’s disease (PD) is the fatal destruction of dopaminergic neurons within the substantia nigra pars compacta. This event is preceded by the formation of Lewy bodies, which are cytoplasmic inclusions composed of α-synuclein protein aggregates. A triad contribution of α-synuclein aggregation, iron accumulation, and mitochondrial dysfunction plague nigral neurons, yet the events underlying iron accumulation are poorly understood. Elevated intracellular iron concentrations up-regulate ferritin expression, an iron storage protein that provides cytoprotection against redox stress. The lysosomal degradation pathway, autophagy, can release iron from ferritin stores to facilitate its trafficking in a process termed ferritinophagy. Aggregated α-synuclein inhibits SNARE protein complexes and destabilizes microtubules to halt vesicular trafficking systems, including that of autophagy effectively. The scope of this review is to describe the physiological and pathological relationship between iron regulation and α-synuclein, providing a detailed understanding of iron metabolism within nigral neurons. The underlying mechanisms of autophagy and ferritinophagy are explored in the context of PD, identifying potential therapeutic targets for future investigation.