10,645 research outputs found

    Correction of the definition of mass-flow parameter in dynamic inflow modelling

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    NRTI-Associated hyperlactataemia and lactic acidosis

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    Validity of the Cauchy-Born rule applied to discrete cellular-scale models of biological tissues

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    The development of new models of biological tissues that consider cells in a discrete manner is becoming increasingly popular as an alternative to PDE-based continuum methods, although formal relationships between the discrete and continuum frameworks remain to be established. For crystal mechanics, the discrete-to-continuum bridge is often made by assuming that local atom displacements can be mapped homogeneously from the mesoscale deformation gradient, an assumption known as the Cauchy-Born rule (CBR). Although the CBR does not hold exactly for non-crystalline materials, it may still be used as a first order approximation for analytic calculations of effective stresses or strain energies. In this work, our goal is to investigate numerically the applicability of the CBR to 2-D cellular-scale models by assessing the mechanical behaviour of model biological tissues, including crystalline (honeycomb) and non-crystalline reference states. The numerical procedure consists in precribing an affine deformation on the boundary cells and computing the position of internal cells. The position of internal cells is then compared with the prediction of the CBR and an average deviation is calculated in the strain domain. For centre-based models, we show that the CBR holds exactly when the deformation gradient is relatively small and the reference stress-free configuration is defined by a honeycomb lattice. We show further that the CBR may be used approximately when the reference state is perturbed from the honeycomb configuration. By contrast, for vertex-based models, a similar analysis reveals that the CBR does not provide a good representation of the tissue mechanics, even when the reference configuration is defined by a honeycomb lattice. The paper concludes with a discussion of the implications of these results for concurrent discrete/continuous modelling, adaptation of atom-to-continuum (AtC) techniques to biological tissues and model classification

    Object categorisation, object naming, and viewpoint-independence in visual remembering: Evidence from young children's drawings of a novel object

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    A simple object-drawing task confirms a three-way association between object categorisation, viewpoint independence, and longer-term visual remembering. Young children (5- to 7-year-olds) drew a familiar object or a novel object, immediately after it had been hidden from view or on the following day. Both objects were shown from a full range of viewpoints or from just two viewpoints, from neither of which would either object normally be drawn after unrestricted viewing. When drawing from short-term memory after restricted viewing, both objects were most likely to be depicted from a seen viewpoint. When drawing from longer-term memory after restricted viewing, the novel object continued to be drawn from a seen viewpoint, but the mug was now most likely to be drawn from a preferred viewpoint from which it had not been seen. Naming the novel object with a novel count noun ("Look at this. This is a dax"), to signal that it belonged to an object category, resulted in it being drawn in the same way as the familiar object. The results concur with other evidence indicating that short-term and longer-term visual remembering are differentially associated with viewpoint-dependent representations of individual objects and viewpoint independent representations of object categories, respectively

    A chemistry scale-up exercise

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    Second year students take a bench scale synthesis and work out how to scale it up. They simulate the process with salt and water to determine practical handlingproblems and thereby develop a set of instructions for process operators

    Solute transport within porous biofilms: diffusion or dispersion?

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    Many microorganisms live within surface-associated consortia, termed biofilms, that can form intricate porous structures interspersed with a network of fluid channels. In such systems, transport phenomena, including flow and advection, regulate various aspects of cell behaviour by controllling nutrient supply, evacuation of waste products and permeation of antimicrobial agents. This study presents multiscale analysis of solute transport in these porous biofilms. We start our analysis with a channel-scale description of mass transport and use the method of volume averaging to derive a set of homogenized equations at the biofilmscale. We show that solute transport may be described via two coupled partial differential equations for the averaged concentrations, or telegrapher’s equations. These models are particularly relevant for chemical species, such as some antimicrobial agents, that penetrate cell clusters very slowly. In most cases, especially for nutrients, solute penetration is faster, and transport can be described via an advection-dispersion equation. In this simpler case, the effective diffusion is characterised by a second-order tensor whose components depend on: (1) the topology of the channels’ network; (2) the solute’s diffusion coefficients in the fluid and the cell clusters; (3) hydrodynamic dispersion effects; and (4) an additional dispersion term intrinsic to the two-phase configuration. Although solute transport in biofilms is commonly thought to be diffusion-dominated, this analysis shows that dispersion effects may significantly contribute to transport

    Collective attention and active consumer participation in community energy systems

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    Community energy systems, which rely on demand-side self-organisation of energy distribution, can encounter situations in which demand exceeds supply, and unless the community members schedule energy usage by and between themselves, there will be a blackout. This is effectively a collective action dilemma typically modelled as a repeated game and analysed using Game Theory. In this paper, we investigate the situation from an empirical (rather than analytic) perspective using instead a Serious Game. Motivated firstly by Elinor Ostrom's institutional design principles for sustainable common-pool resource management, and secondly by the idea that collective attention is a prerequisite for successful collective action, we present the design and implementation of a Serious Game which both encapsulates (some of) the design principles and promotes collective attention within the game's interface, affordances and interactions. Our experimental results show that as more interface design features which promote collective attention are enabled, then more often successful collective action is observed. These results have, we argue, important implications for Smart Meter design and roll-out programmes, as well as leveraging the active participation of prosumers in innovative operational and management principles for future Smart Grids

    Review of the ACT Government's harm minimisation measures

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    This report outlines research on the effects of three harm minimisation measures introduced between 1993 and 2002 in the ACT: • a 10maximumbetonEGMs(electronicgamingmachines,orpokermachines);amandatorythreehourshutdownofgamingmachineseachday;restrictiononcashpaymentofwinnings.TheGamblingandRacingControl(CodeofPractice)Regulationsrequirethatwinningsabove10 maximum bet on EGMs (electronic gaming machines, or ‘poker’ machines); • a mandatory three-hour shutdown of gaming machines each day; • restriction on cash payment of winnings. The Gambling and Racing Control (Code of Practice) Regulations require that winnings above 1,000 must be paid by non-cash means such as a cheque or electronic transfer. ¶ The report also provides a summary of the ACT gambling and regulatory environment and a policy chronology, with particular focus on the history and objectives of the ACT harm minimisation measures under review.This report was commisioned by ACT GAmbling and Racing Commissio
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