An efficient parametric algorithm for octree traversal

An octree is a well known hierarchical spatial structure which is widely used in Computer Graphics algorithms. One of the most frequent operations is the computation of the octree voxels intersected by a straight line. This has a number of applications, such as ray-object intersection tests speed-up and visualisation of hierarchical density models by ray-casting. Several methods have been proposed to achieve this goal, which differ in the order in which intersected voxels are visited. In this paper we introduce a new top-down parametric method. The main difference with previously proposed methods is related to descent movements, that is, the selection of a child sub-voxel from the current one. This selection, as the algorithm, is based on the parameter of the ray and comprises simple comparisons. The resulting algorithm is easy to implement, and efficient when compared to other related top-down and bottom-up algorithms for octrees. Finally, a comparison with Kelvin’s method for binary trees is presented

Excitation Enhancement of a Quantum Dot Coupled to a Plasmonic Antenna

Plasmonic antennas are key elements to control the luminescence of quantum emitters. However, the antenna's influence is often hidden by quenching losses. Here, the luminescence of a quantum dot coupled to a gold dimer antenna is investigated. Detailed analysis of the multiply excited states quantifies the antenna's influence on the excitation intensity and the luminescence quantum yield separately

Quintessence and cosmic acceleration

A cosmological model with perfect fluid and self-interacting quintessence field is considered in the framework of the spatially flat Friedmann-Robertson-Walker (FRW) geometry. By assuming that all physical quantities depend on the volume scale factor of the Universe, the general solution of the gravitational field equations can be expressed in an exact parametric form. The quintessence field is a free parameter. With an appropriate choice of the scalar field a class of exact solutions is obtained, with an exponential type scalar field potential fixed via the gravitational field equations. The general physical behavior of the model is consistent with the recent cosmological scenario favored by supernova Type Ia observations, indicating an accelerated expansion of the Universe.Comment: 6 pages, 3 figures, to appear in Int. J. Mod. Phys.

Non-minimally coupled scalar field cosmology on the phase plane

In this publication we investigate dynamics of a flat FRW cosmological model with a non-minimally coupled scalar field with the coupling term $\xi R \psi^{2}$ in the scalar field action. The quadratic potential function $V(\psi)\propto \psi^{2}$ is assumed. All the evolutional paths are visualized and classified in the phase plane, at which the parameter of non-minimal coupling $\xi$ plays the role of a control parameter. The fragility of global dynamics with respect to changes of the coupling constant is studied in details. We find that the future big rip singularity appearing in the phantom scalar field cosmological models can be avoided due to non-minimal coupling constant effects. We have shown the existence of a finite scale factor singular point (future or past) where the Hubble function as well as its first cosmological time derivative diverges.Comment: revtex4, 20 pages, 12 figs; (v2) title changed, analysis of critical points at infinity added, accepted to JCA

Galacitic Collapse of Scalar Field Dark Matter

We present a scenario for galaxy formation based on the hypothesis of scalar field dark matter. We interpret galaxy formation through the collapse of a scalar field fluctuation. We find that a cosh potential for the self-interaction of the scalar field provides a reasonable scenario for galactic formation, which is in agreement with cosmological observations and phenomenological studies in galaxies

Blueprint for a european calciphylaxis registry initiative. the european calciphylaxis network (eucalnet)

Calcific uraemic arteriolopathy (CUA) is a rare disease and continues to be a clinical challenge. The typical course of CUA is characterized by painful skin discolouration and induration evolving to necrotic ulcerations. Medial calcification of cutaneous arterioles and extensive extracellular matrix remodelling are the hallmarks of CUA. The epidemiology and risk factors associated with this disease are still not fully understood. Moreover, CUA treatment strategies vary significantly among centres and expert recommendations are heterogeneous. Registries may provide important insights and information to increase our knowledge about epidemiology and clinical aspects of CUA and may help to optimize its therapeutic management. In 2006, we established an internet-based registry in Germany (www.calciphylaxie.de) to allow online notification of patients with established or suspected CUA. The registry includes a comprehensive database with questions covering >70 parameters and items regarding patient-related and laboratory data, clinical background and presentation as well as therapeutic strategies. The next phase will be to allow international patient registration via www.calciphylaxis.net as part of the multinational EuCalNet (European Calciphylaxis Network) initiative, which is supported by the ERA-EDTA scientific working group 'CKD-MBD'. Based on the valuable experience with the previous German CUA registry, EuCalNet will be a useful tool to collect data on the rare disease CUA and may become a basis for prospective controlled trials in the near future