Relativistic electromagnetic solitons in the electron-ion plasma

We present the results of the investigation about the ion motion influence on relativistic soliton structure, and show that in the case of moving multinode solitons the effect of the ion dynamics results in the limiting of its amplitude. The constraint on the maximum amplitude corresponds to either the ion motion breaking in the low-node-number case, or to the electron trajectory self-intersection in the case of high-node-number solitons. The soliton breaking leads to the generation of fast ions, and provides a novel mechanism for the ion acceleration in the plasma irradiated by the high-intensity laser pulses.     

Particle Creation in a Robertson–Walker Universe Revisited

We reanalyze the problem of particle creation in a 3+1 spatially closed Robertson–Walker space-time. We compute the total number of particles produced by this non-stationary gravitational background as well as the corresponding total energy and find a slight discrepancy between our results and those recently obtained in the literature (Setare, M.R. in Int. J. Theor. Phys. 43:2237, 2004).     

Identification of Regulatory Network Motifs from Gene Expression Data

The modern systems biology approach to the study of molecular cellular biology, consists in the development of computational tools to support the formulation of new hypotheses on the molecular mechanisms underlying the observed cell behavior. Recent biotechnologies are able to provide precise measures of gene expression time courses in response to a large variety of internal and environmental perturbations. In this paper, we propose a simple algorithm for the selection of the “best” regulatory network motif among a number of alternatives, using the expression time course of the genes which are the final targets of the activated signalling pathway. To this aim, we considered the Hill nonlinear ODEs model to simulate the behavior of two ubiquitous motifs: the single input motif and the multi output feed-forward loop motif. Our algorithm has been tested on simulated noisy data assuming the presence of a step-wise regulatory signal. The results clearly show that our method is potentially able to robustly discriminate between alternative motifs, thus providing a useful in silico identification tool for the experimenter.     

On a Poincaré type formula for solutions of singular and degenerate elliptic equations

We provide a geometric Poincaré type formula for stable solutions of ?Δ _p (u) = f(u). From this, we derive a symmetry result in the plane. This work is a refinement of previous results obtained by the authors under further integrability and regularity assumptions.     

Synthesis and Characterization of Star-Branched Nylon 12

Linear and star-branched polyamide 12 were prepared in the presence of mono- and multifunctional acid agents. Molecular masses and molecular mass distributions are discussed according to our model recently presented and are compared with the data obtained by Flory's model. End group titration and SEC data are discussed. Oligomerisation data confirm the general validity of our model.     

Effect of polyfunctional chain transfer agents on molecular weight distribution in free-radical polymerization, 2. The case C ≤ 1

In this part of the series, the influence of polyfunctional chain transfer agents with transfer constant C ≤ 1 on the molecular weight distribution was studied. The analytical expressions for the number- and weight-average degree of polymerization, and dispersion index were derived by kinetic and statistical methods. The expression for the molecular weight distribution can only be obtained by statistical methods. Some numerical examples on the dependence of distribution parameters as a function of the functionality of transfer agents f and transfer constants are illustrated. A critical value of the chain transfer constant was found to exist, which permits the synthesis of linear (for f = 2) or branched polymers (f > 2) with DP _w/DP _n approximately equal to 2 during the entire course of the polymerization.