472 research outputs found
Rediflow Multiprocessing
We discuss the concepts underlying Rediflow, a multiprocessing system being designed to support concurrent programming through a hybrid model of reduction, dataflow, and von Neumann processes. The techniques of automatic load-balancing in Rediflow are described in some detail
Shape complexes: the intersection of label orderings and star convexity constraints in continuous max-flow medical image segmentation.
Optimization-based segmentation approaches deriving from discrete graph-cuts and continuous max-flow have become increasingly nuanced, allowing for topological and geometric constraints on the resulting segmentation while retaining global optimality. However, these two considerations, topological and geometric, have yet to be combined in a unified manner. The concept of shape complexes, which combine geodesic star convexity with extendable continuous max-flow solvers, is presented. These shape complexes allow more complicated shapes to be created through the use of multiple labels and super-labels, with geodesic star convexity governed by a topological ordering. These problems can be optimized using extendable continuous max-flow solvers. Previous approaches required computationally expensive coordinate system warping, which are ill-defined and ambiguous in the general case. These shape complexes are demonstrated in a set of synthetic images as well as vessel segmentation in ultrasound, valve segmentation in ultrasound, and atrial wall segmentation from contrast-enhanced CT. Shape complexes represent an extendable tool alongside other continuous max-flow methods that may be suitable for a wide range of medical image segmentation problems
Black holes and a scalar field in an expanding universe
We consider a model of an inhomogeneous universe including a massless scalar
field, where the inhomogeneity is assumed to consist of many black holes. This
model can be constructed by following Lindquist and Wheeler, which has already
been investigated without including scalar field to show that an averaged scale
factor coincides with that of the Friedmann model. In this work we construct
the inhomogeneous universe with an massless scalar field, where we assume that
the averaged scale factor and scalar field are given by those of the Friedmann
model including a scalar field. All of our calculations are carried out in the
framework of Brans-Dicke gravity. In constructing the model of an inhomogeneous
universe, we define the mass of a black hole in the Brans-Dicke expanding
universe which is equivalent to ADM mass if the mass evolves adiabatically, and
obtain an equation relating our mass to the averaged scalar field and scale
factor. As the results we find that the mass has an adiabatic time dependence
in a sufficiently late stage of the expansion of the universe, and that the
time dependence is qualitatively diffenrent according to the sign of the
curvature of the universe: the mass increases decelerating in the closed
universe case, is constant in the flat case and decreases decelerating in the
open case. It is also noted that the mass in the Einstein frame depends on
time. Our results that the mass has a time dependence should be retained even
in the general scalar-tensor gravitiy with a scalar field potential.
Furthermore, we discuss the relation of our results to the uniqueness theorem
of black hole spacetime and gravitational memory effect.Comment: 16 pages, 3 tables, 5 figure
Evolution of Cosmological Perturbations in the Brane World
The evolution of the cosmological perturbations is studied in the context of
the Randall-Sundrum brane world scenario, in which our universe is realized on
a three-brane in the five dimensional Anti-de Sitter(AdS) spacetime. We develop
a formalism to solve the coupled dynamics of the cosmological perturbations in
the brane world and the gravitational wave in the AdS bulk. Using our
formalism, the late time evolution of the cosmological scalar perturbations at
any scales larger than the AdS curvature scale is shown to be identical
with the one obtained in the conventional 4D cosmology, provided the effect of
heavy graviton modes may be neglected. Here the late time means the epoch when
the Hubble horizon in the 4D brane world is sufficiently larger than
the AdS curvature scale . If the inflation occurs sufficiently lower than
, the scalar temperature anisotropies in the Cosmic Microwave
Background at large scales can be calculated using the constancy of the Bardeen
parameter as is done in the 4D cosmology. The assumption of the result is that
the effect of the massive graviton with mass in the
brane world is negligible, where is the scale factor of the
brane world. We also discuss the effect of these massive gravitons on the
evolution of the perturbations.Comment: 28 pages, 4 figures, typos in published version are correcte
Primordial statistical anisotropy generated at the end of inflation
We present a new mechanism for generating primordial statistical anisotropy
of curvature perturbations. We introduce a vector field which has a non-minimal
kinetic term and couples with a waterfall field in hybrid inflation model. In
such a system, the vector field gives fluctuations of the end of inflation and
hence induces a subcomponent of curvature perturbations. Since the vector has a
preferred direction, the statistical anisotropy could appear in the
fluctuations. We present the explicit formula for the statistical anisotropy in
the primordial power spectrum and the bispectrum of curvature perturbations.
Interestingly, there is the possibility that the statistical anisotropy does
not appear in the power spectrum but does appear in the bispectrum. We also
find that the statistical anisotropy provides the shape dependence to the
bispectrum.Comment: 9 pages, This version supersedes the JCAP version. Minor revision
Delboeuf サクシ ニオケル ハンダン ジュンジョ コウカ
Apparent size of circles in the Delboeuf configuration was judged under variation of their diameters and compared to that of circle singletons of equivalent diameter. The primary purpose of the study was to investigate the effect of judgment order on the perceived size, i.e. starting with either inner or outer circle. In addition,we compared the measured strength of the illusion as obtained by two different methods - category rating and magnitude estimation. We found that the circle judged first had an assimilative effect on the apparent size of the subsequently judged circle,with the amount of the effect being contingent on diameter ratio and diameter difference of the constituent circles. Moreover,assimilation of the inner circle was more pronounced than that of the outer circle. The judgment-order effect may be accounted for by attentional mechanisms: if the outer circle is judged first,spatial span of attention is large,so that the inner circle falls in the span. Conversely,if the inner circle is judged initially,spatial span of attention is too small to take up the outer circle. The amount of illusion was greater when judged using magnitude estimation than category rating, conceivably due to a coarser internal mapping at the latter procedure
Quantifying epistatic interactions among the components constituting the protein translation system
In principle, the accumulation of knowledge regarding the molecular basis of biological systems should allow the development of large-scale kinetic models of their functions. However, the development of such models requires vast numbers of parameters, which are difficult to obtain in practice. Here, we used an in vitro translation system, consisting of 69 defined components, to quantify the epistatic interactions among changes in component concentrations through Bahadur expansion, thereby obtaining a coarse-grained model of protein synthesis activity. Analyses of the data measured using various combinations of component concentrations indicated that the contributions of larger than 2-body inter-component epistatic interactions are negligible, despite the presence of larger than 2-body physical interactions. These findings allowed the prediction of protein synthesis activity at various combinations of component concentrations from a small number of samples, the principle of which is applicable to analysis and optimization of other biological systems. Moreover, the average ratio of 2- to 1-body terms was estimated to be as small as 0.1, implying high adaptability and evolvability of the protein translation system
Inhomogeneity of Spatial Curvature for Inflation
We study how the initial inhomogeneities of the spatial curvature affect the
onset of inflation in the closed universe. We consider a cosmological model
which contains a radiation and a cosmological constant. In order to treat the
inhomogeneities in the closed universe, we improve the long wavelength
approximation such that the non-small spatial curvature is tractable in the
lowest order. Using the improved scheme, we show how large inhomogeneities of
the spatial curvature prevent the occurrence of inflation.Comment: 17 pages, revtex, 6 figures included using eps
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