Impact of Dark Matter Microhalos on Signatures for Direct and Indirect Detection

Detecting dark matter as it streams through detectors on Earth relies on knowledge of its phase space density on a scale comparable to the size of our solar system. Numerical simulations predict that our Galactic halo contains an enormous hierarchy of substructures, streams and caustics, the remnants of the merging hierarchy that began with tiny Earth mass microhalos. If these bound or coherent structures persist until the present time, they could dramatically alter signatures for the detection of weakly interacting elementary particle dark matter (WIMP). Using numerical simulations that follow the coarse grained tidal disruption within the Galactic potential and fine grained heating from stellar encounters, we find that microhalos, streams and caustics have a negligible likelihood of impacting direct detection signatures implying that dark matter constraints derived using simple smooth halo models are relatively robust. We also find that many dense central cusps survive, yielding a small enhancement in the signal for indirect detection experiments.Comment: 6 pages, revision in response to referees report. Now accepted by Phys. Rev D., in pres

On the geometry of Hamiltonian chaos

We show that Gutzwiller's characterization of chaotic Hamiltonian systems in terms of the curvature associated with a Riemannian metric tensor in the structure of the Hamiltonian can be extended to a wide class of potential models of standard form through definition of a conformal metric. The geodesic equations reproduce the Hamilton equations of the original potential model when a transition is made to the dual manifold, and the geodesics in the dual space coincide with the orbits of the Hamiltonian potential model. We therefore find a direct geometrical description of the time development of a Hamiltonian potential model. The second covariant derivative of the geodesic deviation in this dual manifold generates a dynamical curvature, resulting in (energy dependent) criteria for unstable behavior different from the usual Lyapunov criteria. We discuss some examples of unstable Hamiltonian systems in two dimensions giving, in particular, detailed results for a potential obtained from a fifth order expansion of a Toda lattice Hamiltonian.Comment: 7 pages TeX, Figure captions, 4 figures (eps). Some clarifications, added reference

Autonomy versus futility? Barriers to good clinical practice in end-of-life care: a Queensland case

Findings from a Queensland coronial inquest highlight the complex clinical, ethical and legal issues that arise in end-of-life care when clinicians and family members disagree about a diagnosis of clinical futility. The tension between the law and best medical practice is highlighted in this case, as doctors are compelled to seek family consent to not commence a futile intervention. Good communication between doctors and families, as well as community and professional education, is essential to resolve tensions that can arise when there is disagreement about treatment at the end of life

Evolving and Ensembling Deep CNN Architectures for Image Classification

Deep Convolutional Neural Networks (CNNs) have traditionally been hand-designed owing to the complexity of their construction and the computational requirements of their training. Recently however, there has been an increase in research interest towards automatically designing deep CNNs for specific tasks. Ensembling has been shown to effectively increase the performance of deep CNNs, although usually with a duplication of work and therefore a large increase in computational resources required. In this paper we present a method for automatically designing and ensembling deep CNN models with a central weight repository to avoid work duplication. The models are trained and optimised together using particle swarm optimisation (PSO), with architecture convergence encouraged. At the conclusion of the joint optimisation and training process a base model nomination method is used to determine the best candidates for the ensemble. Two base model nomination methods are proposed, one using the local best particle positions from the PSO process, and one using the contents of the central weight repository. Once the base model pool has been created, the individual models inherit their parameters from the central weight repository and are then finetuned and ensembled in order to create a final system. We evaluate our system on the CIFAR-10 classification dataset and demonstrate improved results over the single global best model suggested by the optimisation process, with a minor increase in resources required by the finetuning process. Our system achieves an error rate of 4.27% on the CIFAR-10 image classification task with only 36 hours of combined optimisation and training on a single NVIDIA GTX 1080Ti GPU

Diffusion-Limited One-Species Reactions in the Bethe Lattice

We study the kinetics of diffusion-limited coalescence, A+A-->A, and annihilation, A+A-->0, in the Bethe lattice of coordination number z. Correlations build up over time so that the probability to find a particle next to another varies from \rho^2 (\rho is the particle density), initially, when the particles are uncorrelated, to [(z-2)/z]\rho^2, in the long-time asymptotic limit. As a result, the particle density decays inversely proportional to time, \rho ~ 1/kt, but at a rate k that slowly decreases to an asymptotic constant value.Comment: To be published in JPCM, special issue on Kinetics of Chemical Reaction

Global capital markets, housing prices, and partisan fiscal policies

In recent years, global imbalances have channeled the excess savings of surplus countries toward the real estate markets of deficit countries. By consequence, the deficit countries that attracted lots of foreign capital experienced large run-ups in house prices while the surplus countries that exported capital exhibited flat or slow house price growth. We argue that international capital flows affect the fiscal policy preferences of both voters and political parties by way of their impact on housing prices. Where capital inflows are large and housing prices are rising, we expect voters to respond by demanding both lower taxes and less publicly-provided social insurance. This is because rising house prices allow homeowners to “self insure” against income losses due to unemployment, illness, and old age. We present survey evidence that supports this claim. Furthermore, we find that responses to house prices are mirrored in capital exporting countries: households become more supportive of both taxes and social insurance as home prices remain flat or decline. Finally, we show that political parties are the mechanisms through which the fiscal preferences of households find policy expression. Taxes and social insurance spending tend to fall (rise) where the right (left) is in power and capital inflows are driving up housing prices. In capital exporting nations, by contrast, we find an attenuation of these partisan fiscal policy outcomes

Design and Control of an Experimental Tilt-Wing Aircraft

In this project, work has been done in the field of conceptual design of experimental tiltrotors. The main tools that have been used are NDARC (NASA Design and Analysis of Rotorcraft) and SIMPLI-FLYD. NDARC is a conceptual design tool for rotorcraft, and it is used to find trim points under various flight conditions. SIMPLI-FLYD is an integrated collection of software tools that enables a flight dynamics and control assessment of the rotorcraft vehicle design generated from NDARC. Two different tiltrotors have been investigated. Initially, work was done with the Bell XV- 15 tiltrotor. NDARCs ability to correctly model the tiltwing transition between airplane mode and hover mode was looked into. In addition, data from old flight tests were compared to the NDARC output, to see how accurately performance could be predicted. After the XV-15 analysis, an NDRARC model of a novel tiltwing concept from Elytron Aircraft was written and analyzed together with SIMPLI-FLYD. Elytron 2S is an experimental tiltwing aircraft, consisting of a joined-wing design with a small central wing for the proprotor. An alternative approach to hover control is used, where the typical rotor hub and swash plate are substituted for linear actuators controlling pitch, yaw and roll. The objective with the analysis of Elytron is to obtain a more complete understanding of the maneuverability and possible performance of this alternative aircraft configuration

Assessment by finite element analysis of the impact of osteoporosis and osteoarthritis on hip resurfacing

Hip resurfacing is proposed as an alternative to total hip replacement (THR) for treatment of osteoarthritis (OA), especially for younger, heavier and more active sufferers. There is however, concern with regards to the incidence of post operative femoral neck fractures. We have investigated, with finite element models, the changes in stress and strain in the femoral neck following hip resurfacing. We have included several different bone material property values representing normal, elderly, osteoarthritic and osteoporotic bone. We have also modelled two different hip implant orientations. We have shown that hip resurfacing may increase the magnitude of stress and strain in the femoral neck, especially in osteoporotic bone. We have also shown that the superolateral offset associated with the valgus orientation, not the valgus orientation itself, may be what reduces the stress and strain in the neck and leads to lower incidence of fracture