Continuous first-passage percolation and continuous greedy paths model: linear growth

We study a random growth model on $\R^d$ introduced by Deijfen. This is a continuous first-passage percolation model. The growth occurs by means of spherical outbursts with random radii in the infected region. We aim at finding conditions on the distribution of the random radii to determine whether the growth of the process is linear or not. To do so, we compare this model with a continuous analogue of the greedy lattice paths model and transpose results in the lattice setting to the continuous setting.Comment: 13 pages, two appendice

Continuum percolation in high dimensions

26 pages, 3 figuresConsider a Boolean model $\Sigma$ in $\R^d$. The centers are given by a homogeneous Poisson point process with intensity $\lambda$ and the radii of distinct balls are i.i.d.\ with common distribution $\nu$. The critical covered volume is the proportion of space covered by $\Sigma$ when the intensity $\lambda$ is critical for percolation. Previous numerical simulations and heuristic arguments suggest that the critical covered volume may be minimal when $\nu$ is a Dirac measure. In this paper, we prove that it is not the case at least in high dimension. To establish this result we study the asymptotic behaviour, as $d$ tends to infinity, of the critical covered volume. It appears that, in contrast to what happens in the constant radii case studied by Penrose, geometrical dependencies do not always vanish in high dimension

Conflict Resolution by Matrix Reordering for DVB-T2 LDPC Decoders

International audienceLayered decoding is known to provide efficient and high-throughput implementation of LDPC decoders. However, the implementation of the layered architecture is not always straightforward because of the memory access conflicts in the a-posteriori information memory. In this paper, we focus our attention on a particular type of conflict introduced by the existence of multiple diagonal matrices in the DVB-T2 parity check matrix structure. We illustrate how the reordering of the matrix reduces the number of conflicts, at the cost of limiting the level of parallelism. We then propose a parity extending process to solve the remaining conflicts. Fixed point simulation results show coherent performance without modifying the layered architecture

Conflict resolution for pipelined layered LDPC decoders

International audienceMany of the current LDPC implementations of DVB-S2, T2 or WiMAX standard use the so-called layered architecture combined with pipeline. However, the pipeline process may introduce memory access conflicts. The resolution of these conflicts requires careful scheduling combined with dedicated hardware and/or idle cycle insertion. In this paper, based on the DVB-T2 example, we explain explicitly how the scheduling can solve most of the pipeline conflicts. The two contributions of the paper are 1) how to split the matrix to relax the pipeline conflicts at a cost of a reduced maximum available parallelism 2) how to project the problem of the research of an efficient scheduling to the well-known "Travelling Salesman Problem" and use a genetic algorithm to solve it

Interactions of WASp, myosin-I, and verprolin with Arp2/3 complex during actin patch assembly in fission yeast

Yeast actin patches are dynamic structures that form at the sites of cell growth and are thought to play a role in endocytosis. We used biochemical analysis and live cell imaging to investigate actin patch assembly in fission yeast Schizosaccharomyces pombe. Patch assembly proceeds via two parallel pathways: one dependent on WASp Wsp1p and verprolin Vrp1p converges with another dependent on class 1 myosin Myo1p to activate the actin-related protein 2/3 (Arp2/3) complex. Wsp1p activates Arp2/3 complex via a conventional mechanism, resulting in branched filaments. Myo1p is a weaker Arp2/3 complex activator that makes unstable branches and is enhanced by verprolin. During patch assembly in vivo, Wsp1p and Vrp1p arrive first independent of Myo1p. Arp2/3 complex associates with nascent activator patches over 6–9 s while remaining stationary. After reaching a maximum concentration, Arp2/3 complex patches move centripetally as activator proteins dissociate. Genetic dependencies of patch formation suggest that patch formation involves cross talk between Myo1p and Wsp1p/Vrp1p pathways

Solid-state NMR sequential assignments of the C-terminal oligomerization domain of human C4b-binding protein

The complement 4 binding protein (C4bp) plays a crucial role in the inhibition of the complement cascade. It has an extraordinary seven-arm octopus-like structure with 7 tentacle-like identical chains, held together at their C-terminal end. The C-terminal domain does oligomerize in isolation, and is necessary and sufficient to oligomerize full-length C4bp. It is predicted to form a seven-helix coiled coil, and its multimerization properties make it a promising vaccine adjuvant, probably by enhancing the structural stability and binding affinity of the presented antigen. Here, we present the solid-state NMR resonance assignment of the human C4bp C-terminal oligomerization Domain, hC4pbOD, and the corresponding secondary chemical shifts