Stabilization of the Peregrine soliton and Kuznetsov-Ma breathers by means of nonlinearity and dispersion management

We demonstrate a possibility to make rogue waves (RWs) in the form of the Peregrine soliton (PS) and Kuznetsov-Ma breathers (KMBs) effectively stable objects, with the help of properly defined dispersion or nonlinearity management applied to the continuous-wave (CW) background supporting the RWs. In particular, it is found that either management scheme, if applied along the longitudinal coordinate, making the underlying nonlinear Schr\"odinger equation (NLSE) selfdefocusing in the course of disappearance of the PS, indeed stabilizes the global solution with respect to the modulational instability of the background. In the process, additional excitations are generated, namely, dispersive shock waves and, in some cases, also a pair of slowly separating dark solitons. Further, the nonlinearity-management format, which makes the NLSE defocusing outside of a finite domain in the transverse direction, enables the stabilization of the KMBs, in the form of confined oscillating states. On the other hand, a nonlinearity-management format applied periodically along the propagation direction, creates expanding patterns featuring multiplication of KMBs through their cascading fission.Comment: Physics Letters A, on pres

The cluster of galaxies Abell 376

We present a dynamical analysis of the galaxy cluster Abell 376 based on a set of 73 velocities, most of them measured at Pic du Midi and Haute-Provence observatories and completed with data from the literature. Data on individual galaxies are presented and the accuracy of the determined velocities is discussed as well as some properties of the cluster. We obtained an improved mean redshift value z=0.0478^{+0.005}_{-0.006} and velocity dispersion sigma=852^{+120}_{-76}km/s. Our analysis indicates that inside a radius of 900h_{70}^{-1}kpc (15 arcmin) the cluster is well relaxed without any remarkable feature and the X-ray emission traces fairly well the galaxy distribution. A possible substructure is seen at 20 arcmin from the centre towards the Southwest direction, but is not confirmed by the velocity field. This SW clump is, however, kinematically bound to the main structure of Abell 376. A dense condensation of galaxies is detected at 46 arcmin (projected distance 2.6h_{70}^{-1}Mpc) from the centre towards the Northwest and analysis of the apparent luminosity distribution of its galaxies suggests that this clump is part of the large scale structure of Abell 376. X-ray spectroscopic analysis of ASCA data resulted in a temperature kT = 4.3+/-0.4 keV and metal abundance Z = 0.32+/-0.08 Z_solar. The velocity dispersion corresponding to this temperature using the T_X-sigma scaling relation is in agreement with the measured galaxies velocities.Comment: 11 pages, 10 figures, accepted for publication in A&

Probing the eigenfunction fractality with a stop watch

We study numerically the distribution of scattering phases ${\cal P}(\Phi)$ and of Wigner delay times ${\cal P}(\tau_W)$ for the power-law banded random matrix (PBRM) model at criticality with one channel attached to it. We find that ${\cal P}(\Phi)$ is insensitive to the position of the channel and undergoes a transition towards uniformity as the bandwidth $b$ of the PBRM model increases. The inverse moments of Wigner delay times scale as $\sim L^{- q D_{q+1}}$, where $D_q$ are the multifractal dimensions of the eigenfunctions of the corresponding closed system and $L$ is the system size. The latter scaling law is sensitive to the position of the channel.Comment: 5 pages, 4 figure

Anomalously large critical regions in power-law random matrix ensembles

We investigate numerically the power-law random matrix ensembles. Wavefunctions are fractal up to a characteristic length whose logarithm diverges asymmetrically with different exponents, 1 in the localized phase and 0.5 in the extended phase. The characteristic length is so anomalously large that for macroscopic samples there exists a finite critical region, in which this length is larger than the system size. The Green's functions decrease with distance as a power law with an exponent related to the correlation dimension.Comment: RevTex, 4 pages, 4 eps figures. Final version to be published in Phys. Rev. Let

Influence of net doping, excess carrier density and annealing on the boron oxygen related defect density in compensated n-type silicon

In this study, we present experimental data regarding the concentration of the boron-oxygen complex in compensated n-type silicon when subjected to illumination. We find that the defect density is independent of the net dopant concentration and is strongly dependent on the minority carrier concentration during illumination. We show that annealing at temperatures in the range 500 C to 700 C permanently reduces the defect density possibly via a decrease in the oxygen dimer concentration.This work was supported by the Australian Research Council (ARC)

Serotonergic innervation of the amygdala is increased in autism spectrum disorder and decreased in Williams syndrome.

BackgroundWilliams syndrome (WS) and autism spectrum disorder (ASD) are neurodevelopmental disorders that demonstrate overlapping genetic associations, dichotomous sociobehavioral phenotypes, and dichotomous pathological differences in neuronal distribution in key social brain areas, including the prefrontal cortex and the amygdala. The serotonergic system is critical to many processes underlying neurodevelopment and is additionally an important neuromodulator associated with behavioral variation. The amygdala is heavily innervated by serotonergic projections, suggesting that the serotonergic system is a significant mediator of neuronal activity. Disruptions to the serotonergic system, and atypical structure and function of the amygdala, are implicated in both WS and ASD.MethodsWe quantified the serotonergic axon density in the four major subdivisions of the amygdala in the postmortem brains of individuals diagnosed with ASD and WS and neurotypical (NT) brains.ResultsWe found opposing directions of change in serotonergic innervation in the two disorders, with ASD displaying an increase in serotonergic axons compared to NT and WS displaying a decrease. Significant differences (p < 0.05) were observed between WS and ASD data sets across multiple amygdala nuclei.LimitationsThis study is limited by the availability of human postmortem tissue. Small sample size is an unavoidable limitation of most postmortem human brain research and particularly postmortem research in rare disorders.ConclusionsDifferential alterations to serotonergic innervation of the amygdala may contribute to differences in sociobehavioral phenotype in WS and ASD. These findings will inform future work identifying targets for future therapeutics in these and other disorders characterized by atypical social behavior

The phase-dependent linear conductance of a superconducting quantum point contact

The exact expression for the phase-dependent linear conductance of a weakly damped superconducting quantum point contact is obtained. The calculation is performed by summing up the complete perturbative series in the coupling between the electrodes. The failure of any finite order perturbative expansion in the limit of small voltage and small quasi-particle damping is analyzed in detail. In the low transmission regime this nonperturbative calculation yields a result which is at variance with standard tunnel theory. Our result predicts the correct sign of the quasi-particle pair interference term and exhibits an unusual phase-dependence at low temperatures in qualitative agreement with the available experimental data.Comment: 12 pages (revtex) + 1 postscript figure. Submitted to Phys. Rev. Let

Critical spectral statistics in two-dimensional interacting disordered systems

The effect of Coulomb and short-range interactions on the spectral properties of two-dimensional disordered systems with two spinless fermions is investigated by numerical scaling techniques. The size independent universality of the critical nearest level-spacing distribution $P(s)$ allows one to find a delocalization transition at a critical disorder $W_{\rm c}$ for any non-zero value of the interaction strength. At the critical point the spacings distribution has a small-$s$ behavior $P_c(s)\propto s$, and a Poisson-like decay at large spacings.Comment: 4 two-column pages, 3 eps figures, RevTeX, new results adde