The Virtual Runner Learning Game

A learning game has been developed which allows learners to study and learn about the significance of three important variables in human physiology (lactate, glycogen, and hydration) and their influence on sports performance during running. The player can control the speed of the runner, and as a consequence the resulting physiological processes are simulated in real-time. The performance degradation of the runner due to these processes requires that different strategies for pacing the running speed are applied by the player, depending on the total length of the run. The game has been positively evaluated in a real learning context of academic physiology teaching

Mathematical Modelling of Turning Delays in Swarm Robotics

We investigate the effect of turning delays on the behaviour of groups of differential wheeled robots and show that the group-level behaviour can be described by a transport equation with a suitably incorporated delay. The results of our mathematical analysis are supported by numerical simulations and experiments with e-puck robots. The experimental quantity we compare to our revised model is the mean time for robots to find the target area in an unknown environment. The transport equation with delay better predicts the mean time to find the target than the standard transport equation without delay.Comment: Submitted to the IMA Journal of Applied Mathematic

The influence of laser hardening on wear in the valve and valve seat contact

In internal combustion engines it is important to manage the wear in the valve and valve seat contact in order to minimise emissions and maximise economy. Traditionally wear in this contact has been controlled by the use of a valve seat insert and the careful selection of materials for both the valve and the insert. More recently, due to the increasing demands for both performance and cost, alternative methods of controlling the wear, and the resulting valve recession, have been sought. Using the heating effect of a laser to induce localised phase transformations, to increase hardness and wear resistance, in materials has been used since the 1970s, however it is only in recent years that it has been able to compete with more established surface treatment techniques, particularly in terms of cost, as new laser hardware has been developed. In this work, a laser has been used to treat the valve seat area of a cast iron cylinder head. In order to optimise the laser parameters for use on the head, preliminary tests were carried out to investigate the fundamental wear characteristics of untreated cast iron and also cast iron with a range of laser treatments. Previous work has identified the predominant wear mechanism in the valve and valve seat contact as impact on valve closure. Two bespoke test machines, one for testing basic specimens and one for testing components, were used to identify the laser parameters most likely to yield acceptable results when applied to a cylinder head to be used in a fired dynamometer test. © 2009 Elsevier B.V. All rights reserved

A combined NMR and DFT study of Narrow Gap Semiconductors: The case of PbTe

In this study we present an alternative approach to separating contributions to the NMR shift originating from the Knight shift and chemical shielding by a combination of experimental solid-state NMR results and ab initio calculations. The chemical and Knight shifts are normally distinguished through detailed studies of the resonance frequency as function of temperature and carrier concentration, followed by extrapolation of the shift to zero carrier concentration. This approach is time-consuming and requires studies of multiple samples. Here, we analyzed $^{207}$Pb and $^{125}$Te NMR spin-lattice relaxation rates and NMR shifts for bulk and nanoscale PbTe. The shifts are compared with calculations of the $^{207}$Pb and $^{125}$Te chemical shift resonances to determine the chemical shift at zero charge carrier concentration. The results are in good agreement with literature values from carrier concentration-dependent studies. The measurements are also compared to literature reports of the $^{207}$Pb and $^{125}$Te Knight shifts of $n$- and $p$-type PbTe semiconductors. The literature data have been converted to the currently accepted shift scale. We also provide possible evidence for the "self-cleaning effect" property of PbTe nanocrystals whereby defects are removed from the core of the particles, while preserving the crystal structure.Comment: 34 pages, 9 figure

Trafficking of cholinesterases and neuroligins mutant proteins. An association with autism

Autism encompasses a wide spectrum of disorders arising during brain development. Recent studies reported that sequence polymorphisms in neuroligin-3 (NLGN3) and neuroligin-4 (NLGN4) genes have been linked to autism spectrum disorders indicating neuroligin genes as candidate targets in brain disorders. We have characterized a single mutation found in two affected brothers that substituted Arg451 to Cys in NL3. Our data show that the exposed Cys causes retention of the protein in the endoplasmic reticulum (ER) when expressed in HEK-293 cells. To examine whether the introduction of a Cys in the C-terminal region of other α/β-hydrolase fold proteins could promote the same cellular phenotype, we made homologous mutations in acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) and found a similar processing deficiency and intracellular retention (De Jaco et al., J Biol Chem. 2006, 281:9667-76). NL3, AChE and BChE mutant proteins are recognized as misfolded in the ER, and degraded via the proteasome pathway. A 2D electrophoresis coupled with mass spectrometry based approach was used to analyze proteins co-immunoprecipitating with NL3 and show differential expression of factors interacting with wild type and mutant NL3. We identified several proteins belonging to distinct ER resident chaperones families, including calnexin, responsible for playing a role in the folding steps of the AChE and NLs. © 2008 Elsevier Ireland Ltd. All rights reserved

Analytical response time estimation in parallel relational database systems

Techniques for performance estimation in parallel database systems are well established for parameters such as throughput, bottlenecks and resource utilisation. However, response time estimation is a complex activity which is difficult to predict and has attracted research for a number of years. Simulation is one option for predicting response time but this is a costly process. Analytical modelling is a less expensive option but requires approximations and assumptions about the queueing networks built up in real parallel database machines which are often questionable and few of the papers on analytical approaches are backed by results from validation against real machines. This paper describes a new analytical approach for response time estimation that is based on a detailed study of different approaches and assumptions. The approach has been validated against two commercial parallel DBMSs running on actual parallel machines and is shown to produce acceptable accuracy