Prepontine non-giant neurons drive flexible escape behavior in zebrafish

Many species execute ballistic escape reactions to avoid imminent danger. Despite fast reaction times, responses are often highly regulated, reflecting a trade-off between costly motor actions and perceived threat level. However, how sensory cues are integrated within premotor escape circuits remains poorly understood. Here, we show that in zebrafish, less precipitous threats elicit a delayed escape, characterized by flexible trajectories, which are driven by a cluster of 38 prepontine neurons that are completely separate from the fast escape pathway. Whereas neurons that initiate rapid escapes receive direct auditory input and drive motor neurons, input and output pathways for delayed escapes are indirect, facilitating integration of cross-modal sensory information. These results show that rapid decision-making in the escape system is enabled by parallel pathways for ballistic responses and flexible delayed actions and defines a neuronal substrate for hierarchical choice in the vertebrate nervous system

Maximum Entropy Linear Manifold for Learning Discriminative Low-dimensional Representation

Representation learning is currently a very hot topic in modern machine learning, mostly due to the great success of the deep learning methods. In particular low-dimensional representation which discriminates classes can not only enhance the classification procedure, but also make it faster, while contrary to the high-dimensional embeddings can be efficiently used for visual based exploratory data analysis. In this paper we propose Maximum Entropy Linear Manifold (MELM), a multidimensional generalization of Multithreshold Entropy Linear Classifier model which is able to find a low-dimensional linear data projection maximizing discriminativeness of projected classes. As a result we obtain a linear embedding which can be used for classification, class aware dimensionality reduction and data visualization. MELM provides highly discriminative 2D projections of the data which can be used as a method for constructing robust classifiers. We provide both empirical evaluation as well as some interesting theoretical properties of our objective function such us scale and affine transformation invariance, connections with PCA and bounding of the expected balanced accuracy error.Comment: submitted to ECMLPKDD 201

Organised crime and public sector corruption

Foreword: In 2006, the Australian Government introduced the Anti-money Laundering and Counter-Terrorism Financing Act 2006 (Cth) which increased regulatory controls over businesses potentially able to facilitate organised criminal activities such as money laundering. The implementation of tougher legislation and associated law enforcement interventions may result in criminal organisations adjusting their tactics in order to continue their activities without detection. In this paper, the risk and potential impact of tactical displacement by organised criminals is discussed with regard to the potential for increased attempts by organised crime groups to corrupt public servants. There is a paucity of research exploring the nature and extent of public sector corruption committed by organised crime groups. This discussion is informed by literature on ‘crime scripts’ originally developed by Cornish (1994) and the 5I’s crime prevention framework developed by Ekblom (2011). Making use of public-source information about the commission of such crimes, as exemplified in two recent corruption cases, some intervention strategies are proposed that may be effective in reducing the risks of corruption of public sector officials by organised crime groups in Australia

Models of Galaxy Clusters with Thermal Conduction

We present a simple model of hot gas in galaxy clusters, assuming hydrostatic equilibrium and energy balance between radiative cooling and thermal conduction. For five clusters, A1795, A1835, A2199, A2390 and RXJ1347.5-1145, the model gives a good description of the observed radial profiles of electron density and temperature, provided we take the thermal conductivity $\kappa$ to be about 30% of the Spitzer conductivity. Since the required $\kappa$ is consistent with the recent theoretical estimate of Narayan & Medvedev (2001) for a turbulent magnetized plasma, we consider a conduction-based equilibrium model to be viable for these clusters. We further show that the hot gas is thermally stable because of the presence of conduction. For five other clusters, A2052, A2597, Hydra A, Ser 159-03 and 3C295, the model requires unphysically large values of $\kappa$ to fit the data. These clusters must have some additional source of heat, most likely an active galactic nucleus since all the clusters have strong radio galaxies at their centers. We suggest that thermal conduction, though not dominant in these clusters, may nevertheless play a significant role by preventing the gas from becoming thermally unstable.Comment: Published in ApJ; 22 pages, including 2 tables, 4 figures; typos corrected to match the published versio

Evaluating the Australasian Consumer Fraud Awareness Month, 2007

As part of a global effort to fight mass-marketed consumer scams, consumer protection agencies in 33 western countries have participated in a month of fraud prevention activities each year to raise awareness of the problem and to provide advice to consumers on how to avoid being victimised. In Australia and New Zealand, nineteen government agencies now comprise the Australasian Consumer Fraud Taskforce (ACFT) that conducted a campaign in March 2007, the theme of which was ‘Scams Target You – Protect Yourself’. This paper provides an evaluation of the impact of the activities undertaken by the Taskforce, including the effect that the extensive publicity had on the official reporting of scams by consumers. The results of an online survey of 841 self-selected respondents are also presented. It is concluded that the campaign was highly effective in raising consumer awareness, with reporting rates increasing substantially throughout the period of the campaign

Observable Properties of Orbits in Exact Bumpy Spacetimes

We explore the properties of test-particle orbits in "bumpy" spacetimes - stationary, reflection-symmetric, asymptotically flat solutions of Einstein equations that have a non-Kerr (anomalous) higher-order multipole-moment structure but can be tuned arbitrarily close to the Kerr metric. Future detectors should observe gravitational waves generated during inspirals of compact objects into supermassive central bodies. If the central body deviates from the Kerr metric, this will manifest itself in the emitted waves. Here, we explore some of the features of orbits in non-Kerr spacetimes that might lead to observable signatures. As a basis for this analysis, we use a family of exact solutions proposed by Manko & Novikov which deviate from the Kerr metric in the quadrupole and higher moments, but we also compare our results to other work in the literature. We examine isolating integrals of the orbits and find that the majority of geodesic orbits have an approximate fourth constant of the motion (in addition to the energy, angular momentum and rest mass) and the resulting orbits are tri-periodic to high precision. We also find that this fourth integral can be lost for certain orbits in some oblately deformed Manko-Novikov spacetimes. However, compact objects will probably not end up on these chaotic orbits in nature. We compute the location of the innermost stable circular orbit (ISCO) and find that the behavior of orbtis near the ISCO can be qualitatively different depending on whether the ISCO is determined by the onset of an instability in the radial or vertical direction. Finally, we compute periapsis and orbital-plane precessions for nearly circular and nearly equatorial orbits in both the strong and weak field, and discuss weak-field precessions for eccentric equatorial orbits.Comment: 42 pages, 20 figures, accepted by Phys. Rev. D, v2 has minor changes to make it consistent with published versio

Computational fluid dynamics of vortex flow controls at low flow rates

PublishedJournal ArticleA vortex flow control with differing outlet shapes is investigated computationally at low flow rates. The volume of fluid method was utilised to track the moving free surface. In order to achieve a smooth free surface, interface compression coupled with the inter-gamma compressive scheme was used. The turbulent evolution of the two-phase flow was modelled by solving the Reynolds-averaged Navier-Stokes equations with the k-ε model for turbulent quantities. Validation of the results was carried out by analysing the total head and discharge coefficient for the three outlet shapes at various flow rates and comparing these results with experimental data. Very good agreement with the experimental data was obtained

Multiscale computational fluid dynamics

This is the final version. Available on open access from MDPI via the DOI in this recordComputational Fluid Dynamics (CFD) has numerous applications in the field of energy research, in modelling the basic physics of combustion, multiphase flow and heat transfer; and in the simulation of mechanical devices such as turbines, wind wave and tidal devices, and other devices for energy generation. With the constant increase in available computing power, the fidelity and accuracy of CFD simulations have constantly improved, and the technique is now an integral part of research and development. In the past few years, the development of multiscale methods has emerged as a topic of intensive research. The variable scales may be associated with scales of turbulence, or other physical processes which operate across a range of different scales, and often lead to spatial and temporal scales crossing the boundaries of continuum and molecular mechanics. In this paper, we present a short review of multiscale CFD frameworks with potential applications to energy problems

CFD simulation of an industrial spiral refrigeration system

This is the final version. Available on open access from MDPI via the DOI in this recordIn the food industry, heating and cooling are key processes where CFD can play an important role in improving quality, productivity and reducing energy costs. Cooling products after baking is crucial for storage and transportation; the product has to be cooled efficiently to a specified temperature (often to fulfill regulatory requirements) whilst preserving its quality. This study involves the analysis of spiral cooling refrigerators used in cooling food products, in this case, Cornish Pasties. Three separate sets of CFD models were developed and validated against experimental data taken in the laboratory and measurements taken in use in industry. In the first set of models a full CFD model was developed of a refrigeration spiral including the pasties, and used to study the heat transfer from the products to the air. Further simulations were carried out on individual pasties to explore the pasty cooling and heat transfer to the air in more detail, with the pasty geometry being determined from MRI scans. In the final set of simulations, Image Based Meshing (IBM) was used to determine the interior structure of the pasty and develop a full heat conduction model of the interior, which was compared with separate laboratory experiments using jets of cold air to cool the pasty. In all cases, good agreement was obtained between the CFD results and experimental data, whilst the CFD simulations provide valuable information about the air flows and cooling in the industrial system.Innovate U