Complete genome sequence of a novel bacteriophage vB_Pci_PCMW57 infecting phytobacteria pseudomonas cichorii.

BACKGROUND: A novel virulent bacteriophage infecting phytobacteria Pseudomonas cichorii (P. cichorii) was isolated from leafy vegetables in Brazil. P. cichorii is a Gram-negative soil phytobacterium, the causal agent of a number of economically important plant diseases worldwide. METHODS AND RESULTS: In this study, a new phage specific for P. cichorii was isolated from solid samples (lettuce, chicory and cabbage), designated vB_Pci_PCMW57. Electron microscopy revealed a small virion (~ 50-nm-diameter icosahedral capsid) with a short, non-contractile tail. The genome of vB_Pci_PCMW57 is 40,117 bp in size, with a GC content of 57.6% and encodes 49 open reading frames. The phage is genetically similar to P. syringae phages Pst_GM1 and Pst_GIL1, and the P. fluorescens phages WRT and KNP. According to electron microscopy and whole-genome sequence analysis, vB_Pci_PCMW57 should be classified as a Caudoviticetes, family Autographiviridae, subfamily Studiervirinae. CONCLUSIONS: The complete phage genome was annotated, and the sequence identity of the virus with other Pseudomonas viruses was higher than 95%. To our knowledge, this is the first report of a bacteriophage infecting Pseudomonas cichorii.

Force Correlations in Disordered Magnets.

We present a proof of principle for the validity of the functional renormalization group, by measuring the force correlations in Barkhausen-noise experiments. Our samples are soft ferromagnets in two distinct universality classes, differing in the range of spin interactions, and the effects of eddy currents. We show that the force correlations have a universal form predicted by the functional renormalization group, distinct for short-range and long-range elasticity, and mostly independent of eddy currents. In all cases correlations grow linearly at small distances, as in mean-field models, but in contrast to the latter are bounded at large distances. As a consequence, avalanches are anti-correlated. We derive bounds for these anticorrelations, which are saturated in the experiments, showing that the multiple domain walls in our samples effectively behave as a single wall.

Waiting-time statistics in magnetic systems.

Many complex systems, from earthquakes and financial markets to Barkhausen effect in ferromagnetic materials, respond with a noise consisting of discrete avalanche-like events with broad range of sizes and durations, separated by waiting times. Here we focus on the waiting-time statistics in magnetic systems. By investigating the Barkhausen noise in amorphous and polycrystalline ferromagnetic films having different thicknesses, we uncover the form of the waiting-time distribution in time series recorded from the irregular and irreversible motion of magnetic domain walls. Further, we address the question of if the waiting-time distribution evolves with the threshold level, as well as with the film thickness and structural character of the materials. Our results, besides informing on the temporal avalanche correlations, disclose the waiting-time statistics in magnetic systems also bring fingerprints of the universality classes of Barkhausen avalanches and a dimensional crossover in the domain wall dynamics.

Playing with universality classes of Barkhausen avalanches.

Many systems crackle, from earthquakes and financial markets to Barkhausen effect in ferromagnetic materials. Despite the diversity in essence, the noise emitted in these dynamical systems consists of avalanche-like events with broad range of sizes and durations, characterized by power-law avalanche distributions and typical average avalanche shape that are fingerprints describing the universality class of the underlying avalanche dynamics. Here we focus on the crackling noise in ferromagnets and scrutinize the traditional statistics of Barkhausen avalanches in polycrystalline and amorphous ferromagnetic films having different thicknesses. We show how scaling exponents and average shape of the avalanches evolve with the structural character of the materials and film thickness. We find quantitative agreement between experiment and theoretical predictions of models for the magnetic domain wall dynamics, and then elucidate the universality classes of Barkhausen avalanches in ferromagnetic films. Thereby, we observe for the first time the dimensional crossover in the domain wall dynamics and the outcomes of the interplay between system dimensionality and range of interactions governing the domain wall dynamics on Barkhausen avalanches.

Universal properties of magnetization dynamics in polycrystalline ferromagnetic films.

We investigate the scaling behavior in the statistical properties of Barkhausen noise in ferromagnetic films. We apply the statistical treatment usually employed for bulk materials in experimental Barkhausen noise time series measured with the traditional inductive technique in polycrystalline ferromagnetic films having different thickness from 100 to 1000 nm and determine the scaling exponents. Based on this procedure, we group the samples in a single universality class, since the scaling behavior of Barkhausen avalanches is characterized by exponents τ∼1.5, α∼2.0, and 1/σνz∼ϑ∼2.0 for all the films. We interpret these results in terms of theoretical models and provide experimental evidence that a well-known mean-field model for the dynamics of a ferromagnetic domain wall in three-dimensional ferromagnets can be extended for films. We identify that the films present an universal three-dimensional magnetization dynamics, governed by long-range dipolar interactions, even at the smallest thicknesses, indicating that the two-dimensional magnetic behavior commonly verified for films cannot be generalized for all thickness ranges.