Locally Adaptive Frames in the Roto-Translation Group and their Applications in Medical Imaging

Locally adaptive differential frames (gauge frames) are a well-known effective tool in image analysis, used in differential invariants and PDE-flows. However, at complex structures such as crossings or junctions, these frames are not well-defined. Therefore, we generalize the notion of gauge frames on images to gauge frames on data representations $U:\mathbb{R}^{d} \rtimes S^{d-1} \to \mathbb{R}$ defined on the extended space of positions and orientations, which we relate to data on the roto-translation group $SE(d)$, $d=2,3$. This allows to define multiple frames per position, one per orientation. We compute these frames via exponential curve fits in the extended data representations in $SE(d)$. These curve fits minimize first or second order variational problems which are solved by spectral decomposition of, respectively, a structure tensor or Hessian of data on $SE(d)$. We include these gauge frames in differential invariants and crossing preserving PDE-flows acting on extended data representation $U$ and we show their advantage compared to the standard left-invariant frame on $SE(d)$. Applications include crossing-preserving filtering and improved segmentations of the vascular tree in retinal images, and new 3D extensions of coherence-enhancing diffusion via invertible orientation scores

Winter Wheat In South Dakota

Winter wheat production in South Dakota has been constantly on the decline since 1916. In that year 2,775,000 bushels were produced. The crop reporter reports the 1920 production at a figure of 1,325,000 bushels less. At the same time the acreage decreased by 75,000 acres. Spring wheat also shows a steady decrease in production since 1918. The yield in 1916 was low. The decrease in spring wheat production based upon the highest year\u27s average is 63.2 per cent, while, basing our calculation upon the highest year\u27s production on winter wheat we have a decrease of only 47.7 percent. This in encouraging for the winter wheat growers of South Dakota when compared with that of spring wheat

Morfologische, ecologische en governance principes voor ecodynamisch ontwerpen: toegespitst op de 'Bouwen met Natuur' pilots Friese IJsselmeerkust : building with nature, case Markermeer IJsselmeer, MIJ 4.2, Deliverable 1.6

Het concept ‘Bouwen met Natuur’ richt zich op gebiedsgerichte ontwerpprocessen langs kusten met het doel om de interactie tussen menselijke ingrepen en ecosysteem processen te vergroten. Het concept maakt maximaal gebruik van dynamiek van natuurlijke processen en van de inzet van bio@engineers bij de ontwikkeling van nieuwe kustlandschappen. De uitdaging bij ‘Bouwen met Natuur’ projecten is om een menselijke ambitie m.b.t. waterbouw te realiseren op een wijze die maximaal gebruik maakt van het ecosysteem en tevens dit ecosysteem versterkt. Het zoeken naar een win@win situatie voor zowel de menselijke waterbouwambitie als voor de natuurwaarden is dus iets anders dan natuur behouden die er is of nieuwe natuur ontwikkelen. Ook is het concept fundamenteel anders dan het compenseren van natuur die elders verloren gaat

Mean-field scaling function of the universality class of absorbing phase transitions with a conserved field

We consider two mean-field like models which belong to the universality class of absorbing phase transitions with a conserved field. In both cases we derive analytically the order parameter as function of the control parameter and of an external field conjugated to the order parameter. This allows us to calculate the universal scaling function of the mean-field behavior. The obtained universal function is in perfect agreement with recently obtained numerical data of the corresponding five and six dimensional models, showing that four is the upper critical dimension of this particular universality class.Comment: 8 pages, 2 figures, accepted for publication in J. Phys.

The optimal schedule for pulsar timing array observations

In order to maximize the sensitivity of pulsar timing arrays to a stochastic gravitational wave background, we present computational techniques to optimize observing schedules. The techniques are applicable to both single and multi-telescope experiments. The observing schedule is optimized for each telescope by adjusting the observing time allocated to each pulsar while keeping the total amount of observing time constant. The optimized schedule depends on the timing noise characteristics of each individual pulsar as well as the performance of instrumentation. Several examples are given to illustrate the effects of different types of noise. A method to select the most suitable pulsars to be included in a pulsar timing array project is also presented.Comment: 16 pages, 6 figures, accepted by MNRA

Finite-size scaling of directed percolation above the upper critical dimension

We consider analytically as well as numerically the finite-size scaling behavior in the stationary state near the non-equilibrium phase transition of directed percolation within the mean field regime, i.e., above the upper critical dimension. Analogous to equilibrium, usual finite-size scaling is valid below the upper critical dimension, whereas it fails above. Performing a momentum analysis of associated path integrals we derive modified finite-size scaling forms of the order parameter and its higher moments. The results are confirmed by numerical simulations of corresponding high-dimensional lattice models.Comment: 4 pages, one figur

Electron-phonon coupling in the C60 fullerene within the many-body GW approach

We study the electron-phonon coupling in the C60 fullerene within the first-principles GW approach, focusing on the lowest unoccupied t1u three-fold electronic state which is relevant for the superconducting transition in electron doped fullerides. It is shown that the strength of the coupling is significantly enhanced as compared to standard density functional theory calculations with (semi)local functionals, with a 48% increase of the electron-phonon potential Vep. The calculated GW value for the contribution from the Hg modes of 93 meV comes within 4% of the most recent experimental values. The present results call for a reinvestigation of previous density functional based calculations of electron-phonon coupling in covalent systems in general.Comment: 4 pages, 0 figur