4,828 research outputs found
Modeling reaction-diffusion of molecules on surface and in volume spaces with the E-Cell System
The-Cell System is an advanced open-source simulation platform to model and analyze biochemical reaction networks. The present algorithm modules of the system assume that the reacting molecules are all homogeneously distributed in the reaction compartments, which is not the case in some cellular processes. The MinCDE system in Escherichia coli, for example, relies on intricately controlled reaction, diffusion and localization of Min proteins on the membrane and in the cytoplasm compartments to inhibit cell division at the poles of the rod-shaped cell. To model such processes, we have extended the E-Cell System to support reaction-diffusion and dynamic localization of molecules in volume and surface compartments. We evaluated our method by modeling the in vivo dynamics of MinD and MinE and comparing their simulated localization patterns to the observations in experiments and previous computational work. In both cases, our simulation results are in good agreement
Long wavelength iteration of Einstein's equations near a spacetime singularity
We clarify the links between a recently developped long wavelength iteration
scheme of Einstein's equations, the Belinski Khalatnikov Lifchitz (BKL) general
solution near a singularity and the antinewtonian scheme of Tomita's. We
determine the regimes when the long wavelength or antinewtonian scheme is
directly applicable and show how it can otherwise be implemented to yield the
BKL oscillatory approach to a spacetime singularity. When directly applicable
we obtain the generic solution of the scheme at first iteration (third order in
the gradients) for matter a perfect fluid. Specializing to spherical symmetry
for simplicity and to clarify gauge issues, we then show how the metric behaves
near a singularity when gradient effects are taken into account.Comment: 35 pages, revtex, no figure
Second-order power spectra of CMB anisotropies due to primordial random perturbations in flat cosmological models
Second-order power spectra of Cosmic Microwave Background (CMB) anisotropies
due to random primordial perturbations at the matter dominant stage are
studied, based on the relativistic second-order theory of perturbations in flat
cosmological models and on the second-order formula of CMB anisotropies derived
by Mollerach and Matarrese. So far the second-order integrated Sachs-Wolfe
effect has been analyzed using the three-point correlation or bispectrum. In
this paper we derive the second-order term of power spectra given using the
two-point correlation of temperature fluctuations.
The second-order density perturbations are small, compared with the
first-order ones. The second-order power spectra of CMB anisotropies, however,
are not small at all, compared with the first-order power spectra, because at
the early stage the first-order integrated Sachs-Wolfe effect is very small and
the second-order integrated Sachs-Wolfe effect may be dominant over the
first-order ones. So their characteristic behaviors may be measured through the
future precise observation and bring useful informations on the structure and
evolution of our universe in the future.Comment: 11 page
Deterioration of glomerular endothelial surface layer induced by oxidative stress is implicated in altered permeability of macromolecules in Zucker fatty rats
Changes of variables in modulation and Wiener amalgam spaces
In this paper various properties of global and local changes of variables as well as properties of canonical transforms are investigated on modulation and Wiener amalgam spaces. We establish several relations among localisations of such spaces and, as a consequence, we obtain several versions of local and global Beurling–Helson type theorems. We also establish a number of positive results such as local boundedness of canonical transforms on modulation spaces, properties of homogeneous changes of variables, and local continuity of Fourier integral operators on equation image. Finally, counterparts of these results are discussed for spaces on the torus
Probing violation of the Copernican principle via the integrated Sachs-Wolfe effect
Recent observational data of supernovae indicate that we may live in an
underdense region, which challenges the Copernican principle. We show that the
integrated Sachs-Wolfe (ISW) effect is an excellent discriminator between
anti-Copernican inhomogeneous models and the standard Copernican models. As a
reference model, we consider an anti-Copernican inhomogeneous model that
consists of two inner negatively curved underdense regions and an outer flat
Einstein-de Sitter region. We assume that these regions are connected by two
thin-walls at redshifts z = 0.067 and z=0.45. In the inner two regions, the
first-order ISW effect is dominant and comparable to that in the concordant
flat-Lambda models. In the outer Einstein-de Sitter region, the first-order ISW
effect vanishes but the second-order ISW effect plays a dominant role, while
the first-order ISW effect is dominant in the flat-Lambda models at moderate
redshifts. This difference can discrimate the anti-Copernican models from the
concordant flat-Lambda model. At high redshits, the second-order ISW effect is
dominant both in our inhomogeneous model and the concordant model. In the outer
region, moreover, the ISW effect due to large-scale density perturbations with
a present matter density contrast much less than 0.37 is negligible, while the
effect due to small-scale density perturbations (such as clusters of galaxies,
superclusters and voids) with matter density contrast much larger than 0.37
would generate anisotropies which are larger than those generated by the ISW
effect in the concordant model.Comment: 9 pages, 2 figure
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