397 research outputs found
A deterministic sandpile automaton revisited
The Bak-Tang-Wiesenfeld (BTW) sandpile model is a cellular automaton which
has been intensively studied during the last years as a paradigm for
self-organized criticality. In this paper, we reconsider a deterministic
version of the BTW model introduced by Wiesenfeld, Theiler and McNamara, where
sand grains are added always to one fixed site on the square lattice. Using the
Abelian sandpile formalism we discuss the static properties of the system. We
present numerical evidence that the deterministic model is only in the BTW
universality class if the initial conditions and the geometric form of the
boundaries do not respect the full symmetry of the square lattice.Comment: 7 pages, 8 figures, EPJ style, accepted for publication in European
Physical Journal
Distinct Scaling Regimes of Energy Release Dynamics in the Nighttime Magnetosphere
Based on a spatiotemporal analysis of POLAR UVI images, we show that the
auroral emission events that initiate equatorward of the isotropic boundary
(IB) obtained from a time-dependent empirical model, have systematically
steeper power-law slopes of energy, power, area and lifetime probability
distributions compared to the events that initiate poleward of the IB. The
low-latitude group of events contains a distinct subpopulation of
substorm-scale disturbances violating the power-law behavior, while the high
latitude group is described by nearly perfect power-law statistics over the
entire range of scales studied. The results obtained indicate that the inner
and outer portions of the plasma sheet are characterized by substantially
different scaling regimes of bursty energy dissipation suggestive of different
physics in these regions.Comment: 11 pages, 2 figures, 2 table
A supercritical series analysis for the generalized contact process with diffusion
We study a model that generalizes the CP with diffusion. An additional
transition is included in the model so that at a particular point of its phase
diagram a crossover from the directed percolation to the compact directed
percolation class will happen. We are particularly interested in the effect of
diffusion on the properties of the crossover between the universality classes.
To address this point, we develop a supercritical series expansion for the
ultimate survival probability and analyse this series using d-log Pad\'e and
partial differential approximants. We also obtain approximate solutions in the
one- and two-site dynamical mean-field approximations. We find evidences that,
at variance to what happens in mean-field approximations, the crossover
exponent remains close to even for quite high diffusion rates, and
therefore the critical line in the neighborhood of the multicritical point
apparently does not reproduce the mean-field result (which leads to )
as the diffusion rate grows without bound
Dense transcript profiling in single cells by image correlation decoding
Sequential barcoded fluorescent in situ hybridization (seqFISH) allows large numbers of molecular species to be accurately detected in single cells, but multiplexing is limited by the density of barcoded objects. We present correlation FISH (corrFISH), a method to resolve dense temporal barcodes in sequential hybridization experiments. Using corrFISH, we quantified highly expressed ribosomal protein genes in single cultured cells and mouse thymus sections, revealing cell-type-specific gene expression
Single-Cell Phenotyping within Transparent Intact Tissue through Whole-Body Clearing
Understanding the structure-function relationships at cellular, circuit, and organ-wide scale requires 3D anatomical and phenotypical maps, currently unavailable for many organs across species. At the root of this knowledge gap is the absence of a method that enables whole-organ imaging. Herein, we present techniques for tissue clearing in which whole organs and bodies are rendered macromolecule-permeable and optically transparent, thereby exposing their cellular structure with intact connectivity. We describe PACT (passive clarity technique), a protocol for passive tissue clearing and immunostaining of intact organs; RIMS (refractive index matching solution), a mounting media for imaging thick tissue; and PARS (perfusion-assisted agent release in situ), a method for whole-body clearing and immunolabeling. We show that in rodents PACT, RIMS, and PARS are compatible with endogenous-fluorescence, immunohistochemistry, RNA single-molecule FISH, long-term storage, and microscopy with cellular and subcellular resolution. These methods are applicable for high-resolution, high-content mapping and phenotyping of normal and pathological elements within intact organs and bodies
Meson-Baryon Form Factors in Chiral Colour Dielectric Model
The renormalised form factors for pseudoscalar meson-baryon coupling are
computed in chiral colour dielectric model. This has been done by rearranging
the Lippmann-Schwinger series for the meson baryon scattering matrix so that it
can be expressed as a baryon pole term with renormalized form factors and
baryon masses and the rest of the terms which arise from the crossed diagrams.
Thus we are able to obtain an integral equation for the renormalized
meson-baryon form factors in terms of the bare form factors as well as an
expression for the meson self energy. This integral equation is solved and
renormalized meson baryon form factors and renormalized baryon masses are
computed. The parameters of the model are adjusted to obtain a best fit to the
physical baryon masses. The calculations show that the renormalized form
factors are energy-dependent and differ from the bare form factors primarily at
momentum transfers smaller than 1 GeV. At nucleon mass, the change in the form
factors is about 10% at zero momentum transfer. The computed form factors are
soft with the equivalent monopole cut-off mass of about 500 MeV. The
renormalized coupling constants are obtained by comparing the chiral colour
dielectric model interaction Hamiltonian with the standard form of
meson-nucleon interaction Hamiltonian. The ratio of and
coupling constants is found to be about 2.15. This value is very close to the
experimental value.Comment: 16 pages, 7 postscript figure
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Synthesis of Mesostructured Copper Sulfide by Cation Exchange and Liquid Crystal Templating
The development of synthetic pathways to yield advanced functional materials is an important aspect of materials science. In particular, the ability to control and manipulate the chemical composition and structure of inorganic nanomaterials is highly desirable. Two synthetic approaches which show great promise for producing the next generation of functional inorganic nanomaterials are (1) templating of supramolecular assemblies and (2) ion exchange within nanostructured inorganic solids to manipulate chemical composition. Templating of supramolecular assemblies of surfactants and amphiphilic polymers has already proven to be a powerful technique in synthesizing various inorganic structures. Namely, numerous examples of mesostructured metal oxides (SiO{sub 2}, TiO{sub 2}, WO{sub 3}, etc.) have been synthesized by templating the liquid crystalline phases of amphiphilic polymers and surfactants (i.e. vesicles, 2D and 3D hexagonal and cubic phases, etc.) with inorganic precursors, resulting in the formation of highly ordered inorganic-organic hybrid materials. Although the templating of supramolecular assemblies has been successful in generating highly ordered mesostructured metal oxides, there are only a few examples of non-oxidic mesostructured inorganic materials. The recent developments of ion exchange within nanoparticles offer a promising approach to generating novel nanostructured inorganic materials with unique chemical compositions. Konenkamp et al. and Alivisatos et al. have successfully utilized the ion exchange methods to fully transform the chemical composition of simple nanostructured inorganic materials while retaining their shapes. Although the exact mechanism by which the ions exchange while retaining the overall structure is still unclear, this approach combined with templating of supramolecular assemblies can provide a potent technique for obtaining highly ordered inorganic materials with unique structures and chemical compositions. Herein, we describe for the first time, the successful synthesis of highly ordered, mesostructured Cu{sub x}S, by combining the templating of the supramolecular assemblies of non-ionic amphiphilic polymer method with the cation exchange method to transform mesostructured cadmium sulfide (CdS) into mesostructured copper sulfides (CuS, Cu{sub 2}S)
Dihyperon in Chiral Colour Dielectric Model
The mass of dihyperon with spin, parity and isospin
is calculated in the framework of Chiral colour dielectric model. The wave
function of the dihyperon is expressed as a product of two colour-singlet
baryon clusters. Thus the quark wave functions within the cluster are
antisymmetric. Appropriate operators are then used to antisymmetrize
inter-cluster quark wave functions. The radial part of the quark wavefunctions
are obtained by solving the the quark and dielectric field equations of motion
obtained in the Colour dielectric model. The mass of the dihyperon is computed
by including the colour magnetic energy as well as the energy due to meson
interaction. The recoil correction to the dihyperon mass is incorporated by
Peierls-Yoccoz technique. We find that the mass of the dihyperon is smaller
than the threshold by over 100 MeV. The implications of our
results on the present day relativistic heavy ion experiments is discussed.Comment: LaTeX, 13 page
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