Quantifying heteroskedasticity using slope of local variances index

In econometrics, heteroskedasticity refers to the case when the variances of the error terms of the data in hand are not equal. Heteroskedastic time series are challenging to different forecasting models. However, all available solutions adopt the strategy of accommodating heteroskedasticity in the time series and consider it as a type of noise. Some statistical tests were developed over the past three decades to determine whether a time series features heteroskedastic behaviour. This paper presents a novel strategy to handle this problem by deriving a quantifying measure for heteroskedasticity. The proposed measure relies on the definition of heteroskedasticity as a time-variant variance in the time series. In this work, heteroskedasticity is measured by calculating local variances using linear filters, estimating variance trends, calculating changes in variance slopes, and finally obtaining the average slope angle. The results confirm that the proposed index complies with the widely popular heteroskedasticity tests.

Binding affinities of amino acid analogues at the charged aqueous titania interface : implications for titania-binding peptides

Despite the extensive utilization of biomolecule-titania interfaces, biomolecular recognition and interactions at the aqueous titania interface remain far from being fully understood. Here, atomistic molecular dynamics simulations, in partnership with metadynamics, are used to calculate the free energy of adsorption of different amino acid side chain analogues at the negatively-charged aqueous rutile TiO2 (110) interface, under conditions corresponding with neutral pH. Our calculations predict that charged amino acid analogues have a relatively high affinity to the titania surface, with the arginine analogue predicted to be the strongest binder. Interactions between uncharged amino acid analogues and titania are found to be repulsive or weak at best. All of the residues that bound to the negatively-charged interface show a relatively stronger adsorption compared with the charge-neutral interface, including the negatively-charged analogue. Of the analogues that are found to bind to the titania surface, the rank ordering of the binding affinities is predicted to be "arginine" > "lysine" ≈ aspartic acid > "serine". This is the same ordering as was found previously for the charge-neutral aqueous titania interface. Our results show very good agreement with available experimental data and can provide a baseline for the interpretation of peptide-TiO2 adsorption data.

Prediction of pedestrians routes within a built environment in normal conditions

Modelling and prediction of pedestrian routing behaviours within known built environments has recently attracted the attention of researchers across multiple disciplines, owing to the growing demand on urban resources and requirements for efficient use of public facilities. This study presents an investigation into pedestrians' routing behaviours within an indoor environment under normal, non-panic situations. A network-based method using constrained Delaunay triangulation is adopted, and a utility-based model employing dynamic programming is developed. The main contribution of this study is the formulation of an appropriate utility function that allows an effective application of dynamic programming to predict a series of consecutive waypoints within a built environment. The aim is to generate accurate sequence waypoints for the pedestrian walking path using only structural definitions of the environment as defined in a standard CAD format. The simulation results are benchmarked against those from the A* algorithm, and the outcome positively indicates the usefulness of the proposed method in predicting pedestrians' route selection activities. © 2014 Elsevier Ltd. All rights reserved.

CO2 laser manufacturing of miniaturised lenses for lab-on-a-chip systems

This article describes the manufacturing and characterisation of plano-convex miniaturised lenses using a CO2 laser engraving process in PMMA substrates. The technique allows for lenses to be fabricated rapidly and in a reproducible manner at depths of over 200 µm and for lens diameters of more than 3 mm. Experimental characterisation of the lens focal lengths shows good correlation with theory. The plano-convex lenses have been successfully embedded into capillary microfluidic systems alongside planar microlenses, allowing for a significant reduction of ancillary optics without a loss of detection sensitivity when performing fluorescence measurements. Such technology provides a significant step forward towards the portability of fluorescence- or luminescence-based systems for biological/chemical analysis.

Corporate social responsibility, economic globalization and developing countries: a case study of the ready made garments industry in Bangladesh

Purpose – This paper aims to examine the state of corporate social responsibility (CSR) in labour-intensive industries in developing countries in the context of economic globalization. Using the ready-made garments’ (RMG) industry in Bangladesh as a case study, challenges and key issues relating to CSR are highlighted. Design/methodology/approach – The paper draws from the review of existing literature, and the content analysis of two leading newspapers in Bangladesh for a period of one year (July 2012-June 2013) to identify the key and contemporary issues related to CSR in the RMG industry. Findings – Findings identify the contemporary issues of concerns associated with CSR in the RMG industry, relating them to the debate on the applicability of Carroll’s CSR pyramid to developing countries. The findings suggest that non-compliance of CSR in labour-intensive industries is a function of the nature of economic globalization. The need for a stakeholder approach towards CSR for the profitability and sustainability of this industry is also highlighted. Practical implications – This paper makes contributions to two different but important interrelated discourses on CSR and economic globalization. It also provides insights into the complexity involved in CSR in labour-based export industries in developing countries and acts as a springboard for further research. Originality/value – The paper is the first to look at all major issues of concern regarding CSR in theRMG industry in Bangladesh. As Bangladesh is an exemplar of developing countries andRMGis a typical starter industry, the findings are generalizable to similar industries in other developing countries.