4,536 research outputs found
Critical Behaviour of the Drossel-Schwabl Forest Fire Model
We present high statistics Monte Carlo results for the Drossel-Schwabl forest
fire model in 2 dimensions. They extend to much larger lattices (up to
) than previous simulations and reach much closer to the
critical point (up to ). They are incompatible with
all previous conjectures for the (extrapolated) critical behaviour, although
they in general agree well with previous simulations wherever they can be
directly compared. Instead, they suggest that scaling laws observed in previous
simulations are spurious, and that the density of trees in the critical
state was grossly underestimated. While previous simulations gave , we conjecture that actually is equal to the critical threshold
for site percolation in . This is however still far from
the densities reachable with present day computers, and we estimate that we
would need many orders of magnitude higher CPU times and storage capacities to
reach the true critical behaviour -- which might or might not be that of
ordinary percolation.Comment: 8 pages, including 9 figures, RevTe
The role of the tangent bundle for symmetry operations and modulated structures
An equivalence relation on the tangent bundle of a manifold is defined in order to extend a structure (modulated or not) onto it. This extension affords a representation of a structure in any tangent space and that in another tangent space can easily be derived. Euclidean symmetry operations associated with the tangent bundle are generalized and their usefulness for the determination of the intrinsic translation part in helicoidal axes and glide planes is illustrated. Finally, a novel representation of space groups is shown to be independent of any origin point
Broken scaling in the Forest Fire Model
We investigate the scaling behavior of the cluster size distribution in the
Drossel-Schwabl Forest Fire model (DS-FFM) by means of large scale numerical
simulations, partly on (massively) parallel machines. It turns out that simple
scaling is clearly violated, as already pointed out by Grassberger [P.
Grassberger, J. Phys. A: Math. Gen. 26, 2081 (1993)], but largely ignored in
the literature. Most surprisingly the statistics not seems to be described by a
universal scaling function, and the scale of the physically relevant region
seems to be a constant. Our results strongly suggest that the DS-FFM is not
critical in the sense of being free of characteristic scales.Comment: 9 pages in RevTEX4 format (9 figures), submitted to PR
Recommended from our members
A humanized monoclonal antibody that inhibits platelet-surface ERp72 reveals a role for ERp72 in thrombosis
Background: Within the endoplasmic reticulum, thiol isomerase enzymes modulate the formation and rearrangement of disulphide bonds in newly folded proteins entering the secretory pathway to ensure correct protein folding. In addition to their intracellular importance, thiol isomerases have been recently identified to be present on the surface of a number of cell types where they are important for cell function. Several thiol isomerases are known to be present on the resting platelet surface including PDI, ERp5 and ERp57 and levels are increased following platelet activation. Inhibition of the catalytic activity of these enzymes results in diminished platelet function and thrombosis.
Aim: We previously determined that ERp72 is present at the resting platelet surface and levels increase upon platelet activation, however its functional role on the cell surface was unclear. We aimed to investigate the role of ERp72 in platelet function and its role in thrombosis.
Methods: Using HuCAL technology, fully humanised Fc-null anti-ERp72 antibodies were generated. Eleven antibodies were screened for their ability to inhibit ERp72 activity and the most potent inhibitory antibody (anti-ERp72) selected for further testing in platelet functional assays.
Results and conclusions: Anti-ERp72 inhibited platelet aggregation, granule secretion, calcium mobilisation and integrin activation revealing an important role for extracellular ERp72 in the regulation of platelet activation. Consistent with this, infusion of anti-ERp72 into mice protected against thrombosis
Chimeric polyomavirus-derived virus-like particles: the immunogenicity of an inserted peptide applied without adjuvant to mice depends on its insertion site and its flanking linker sequence
We inserted the sequence of the carcinoembryonic antigen-derived T cell epitope CAP-1-6D (CEA) into different positions of the hamster polyomavirus major capsid protein VP1. Independently from additional flanking linkers, yeast-expressed VP1 proteins harboring the CEA insertion between VP1 amino acid residues 80 and 89 (site 1) or 288 and 295 (site 4) or simultaneously at both positions assembled to chimeric virus-like particles (VLPs). BALB/c mice immunized with adjuvant-free VLPs developed VP1- and epitope-specific antibodies. The level of the CEA-specific antibody response was determined by the insertion site, the number of inserts, and the flanking linker. The strongest CEA-specific antibody response was observed in mice immunized with VP1 proteins harboring the CEA insert at site 1. Moreover, the CEA-specific antibodies in these mice were still detectable 6 mo after the final booster immunization. Our results indicate that hamster polyomavirus-derived VLPs represent a highly immunogenic carrier for foreign insertions that might be useful for clinical and therapeutic applications
Inactivation of the Saccharomyces cerevisiae SKY1 gene induces a specific modification of the yeast anticancer drug sensitivity profile accompanied by a mutator phenotype
The therapeutic potential of the highly active anticancer agent cisplatin
is severely limited by the occurrence of cellular resistance. A better
understanding of the molecular pathways involved in cisplatin-induced cell
death could potentially indicate ways to overcome cellular
unresponsiveness to the drug and thus lead to better treatment results. We
used the budding yeast Saccharomyces cerevisiae as a model organism to
identify and characterize novel genes involved in cisplatin-induced cell
kill, and found that SKY1 (SR-protein-specific kinase from budding yeast)
is a cisplatin sensitivity gene whose disruption conferred cisplatin
resistance. In cross-resistance studies, we observed resistance of yeast
sky1 Delta cells (i.e., cells from which the SKY1 gene had been disrupted)
to cisplatin, carboplatin (but not oxaliplatin), doxorubicin and
daunorubicin, and hypersensitivity to cadmium chloride and 5-fluorouracil.
Furthermore, these cells did not display reduced platinum accumulation,
DNA platination or doxorubicin accumulation, indicating that the
resistance is unrelated to decreased drug import or increased drug export.
Based on the modification of the anticancer drug sensitivity profile and
our finding that sky1 Delta cells display a mutator phenotype, we propose
that Sky1p might play a significant role in specific repair and/or
tolerance pathways. Disruption of the S. cerevisiae SKY1 gene would thus
result in deregulation of such mechanisms and, consequently, lead to
altered drug sensitivity
A 15-year perspective of the fabry outcome survey
The Fabry Outcome Survey (FOS) is an international long-term observational registry sponsored by Shire for patients diagnosed with Fabry disease who are receiving or are candidates for therapy with agalsidase alfa (agala). Established in 2001, FOS provides long-term data on agala safety/efficacy and collects data on the natural history of Fabry disease, with the aim of improving clinical management. The FOS publications have helped establish prognostic and severity scores, defined the incidence of specific disease variants and implications for clinical management, described clinical manifestations in special populations, confirmed the high prevalence of cardiac morbidity, and demonstrated correlations between ocular changes and Fabry disease severity. These FOS data represent a rich resource with utility not only for description of natural history/therapeutic effects but also for exploratory hypothesis testing and generation of tools for diagnosis/management, with the potential to improve future patient outcomes
The random case of Conley's theorem: III. Random semiflow case and Morse decomposition
In the first part of this paper, we generalize the results of the author
\cite{Liu,Liu2} from the random flow case to the random semiflow case, i.e. we
obtain Conley decomposition theorem for infinite dimensional random dynamical
systems. In the second part, by introducing the backward orbit for random
semiflow, we are able to decompose invariant random compact set (e.g. global
random attractor) into random Morse sets and connecting orbits between them,
which generalizes the Morse decomposition of invariant sets originated from
Conley \cite{Con} to the random semiflow setting and gives the positive answer
to an open problem put forward by Caraballo and Langa \cite{CL}.Comment: 21 pages, no figur
- …