Velocity Distribution of Topological Defects in Phase-Ordering Systems

The distribution of interface (domain-wall) velocities ${\bf v}$ in a phase-ordering system is considered. Heuristic scaling arguments based on the disappearance of small domains lead to a power-law tail, $P_v(v) \sim v^{-p}$ for large v, in the distribution of $v \equiv |{\bf v}|$. The exponent p is given by $p = 2+d/(z-1)$, where d is the space dimension and 1/z is the growth exponent, i.e. z=2 for nonconserved (model A) dynamics and z=3 for the conserved case (model B). The nonconserved result is exemplified by an approximate calculation of the full distribution using a gaussian closure scheme. The heuristic arguments are readily generalized to conserved case (model B). The nonconserved result is exemplified by an approximate calculation of the full distribution using a gaussian closure scheme. The heuristic arguments are readily generalized to systems described by a vector order parameter.Comment: 5 pages, Revtex, no figures, minor revisions and updates, to appear in Physical Review E (May 1, 1997

Molecular random tilings as glasses

We have recently shown [Blunt et al., Science 322, 1077 (2008)] that p-terphenyl-3,5,3',5'-tetracarboxylic acid adsorbed on graphite self-assembles into a two-dimensional rhombus random tiling. This tiling is close to ideal, displaying long range correlations punctuated by sparse localised tiling defects. In this paper we explore the analogy between dynamic arrest in this type of random tilings and that of structural glasses. We show that the structural relaxation of these systems is via the propagation--reaction of tiling defects, giving rise to dynamic heterogeneity. We study the scaling properties of the dynamics, and discuss connections with kinetically constrained models of glasses.Comment: 5 pages, 5 figure

Early stage scaling in phase ordering kinetics

A global analysis of the scaling behaviour of a system with a scalar order parameter quenched to zero temperature is obtained by numerical simulation of the Ginzburg-Landau equation with conserved and non conserved order parameter. A rich structure emerges, characterized by early and asymptotic scaling regimes, separated by a crossover. The interplay among different dynamical behaviours is investigated by varying the parameters of the quench and can be interpreted as due to the competition of different dynamical fixed points.Comment: 21 pages, latex, 7 figures available upon request from [email protected]

Non-equilibrium Condensation Process in a Holographic Superconductor

We study the non-equilibrium condensation process in a holographic superconductor. When the temperature T is smaller than a critical temperature T_c, there are two black hole solutions, the Reissner-Nordstrom-AdS black hole and a black hole with a scalar hair. In the boundary theory, they can be regarded as the supercooled normal phase and the superconducting phase, respectively. We consider perturbations on supercooled Reissner-Nordstrom-AdS black holes and study their non-linear time evolution to know about physical phenomena associated with rapidly-cooled superconductors. We find that, for T<T_c, the initial perturbations grow exponentially and, eventually, spacetimes approach the hairy black holes. We also clarify how the relaxation process from a far-from-equilibrium state proceeds in the boundary theory by observing the time dependence of the superconducting order parameter. Finally, we study the time evolution of event and apparent horizons and discuss their correspondence with the entropy of the boundary theory. Our result gives a first step toward the holographic understanding of the non-equilibrium process in superconductors.Comment: 20 pages, 7 figure

Scaling and Crossover in the Large-N Model for Growth Kinetics

The dependence of the scaling properties of the structure factor on space dimensionality, range of interaction, initial and final conditions, presence or absence of a conservation law is analysed in the framework of the large-N model for growth kinetics. The variety of asymptotic behaviours is quite rich, including standard scaling, multiscaling and a mixture of the two. The different scaling properties obtained as the parameters are varied are controlled by a structure of fixed points with their domains of attraction. Crossovers arising from the competition between distinct fixed points are explicitely obtained. Temperature fluctuations below the critical temperature are not found to be irrelevant when the order parameter is conserved. The model is solved by integration of the equation of motion for the structure factor and by a renormalization group approach.Comment: 48 pages with 6 figures available upon request, plain LaTe

Renormalization group and perfect operators for stochastic differential equations

We develop renormalization group methods for solving partial and stochastic differential equations on coarse meshes. Renormalization group transformations are used to calculate the precise effect of small scale dynamics on the dynamics at the mesh size. The fixed point of these transformations yields a perfect operator: an exact representation of physical observables on the mesh scale with minimal lattice artifacts. We apply the formalism to simple nonlinear models of critical dynamics, and show how the method leads to an improvement in the computational performance of Monte Carlo methods.Comment: 35 pages, 16 figure

In vitro evaluation on HeLa cells of protective mechanisms of probiotic lactobacilli against Candida clinical isolates

Aims: To characterize in vitro the ability of human Lactobacillus strains to inhibit the adhesion, to displace and to compete with clinically isolated Candida strains. Methods and Results: Three types of assays were performed to determine the inhibitory effect of Lactobacillus plantarum 319, Lactobacillus rhamnosus IMC 501, Lactobacillus paracasei IMC 502 and a specific probiotic combination (SYNBIO) on adhesion of Candida pathogens to HeLa cells: blockage by exclusion (lactobacilli and HeLa followed by pathogens), competition (lactobacilli, HeLa and pathogens together) and displacement (pathogens and HeLa followed by the addition of lactobacilli). Bacterial adhesion to HeLa was quantified by microscopy after May-Grunwald/Giemsa stain. The inhibition results highlight a significant (P < 0.05) competition of the considered probiotics against all the Candida strains. The results suggest that the probiotic strains used in this study could prevent colonization of the urogenital tract by relevant pathogens such as Candida strains through barrier and interference mechanisms (mainly displacement and competition), but the degree of inhibition of adhesion was bacterial strain-dependent. Conclusions: The results support the potential of these Lactobacillus probiotic strains as anti-infective agents in the vagina and encourage further studies about their capacity to prevent and manage urogenital tract infections in females. Significance and Impact of the Study: To optimize the defensive properties of the vaginal microbiota, improving the health of many women by probiotic intervention

Structural changes of tissue samples exposed to low frequency electromagnetic field: A FT-IR absorbance study

In the present work, we report on a preliminary Fourier Transform Infrared (FT-IR) Absorbance study performed on different kind of rat tissues, such as kidney and heart, exposed to a "non-ionizing" radiation source at low frequency, in the range typical of micro-waves (300 MHz <v< 300 GHz). The data were collected in a wide wavenumber region, from 400 cm−1to 4000 cm−1. The comparison of the absorbance spectra in the case of the normal tissues with the irradiated ones has shown significant differences in the spectral features in accordance with the morphological analysis performed by the optical microscopy

Naphthalenone polyketides produced by Neofusicoccum parvum , a fungus associated with grapevine Botriosphaeria dieback

A strain of Neofusicoccum parvum isolated from declining vines was pathogenic to grapevine cultivar Inzolia in Sicily. This strain produced some metabolites in liquid medium. Crude extract, through a bio-guided purification process, yielded four naphthalenone polyketides. They were identified by comparison with spectroscopic data and optical proprieties reported in literature as: (3S, 4S)-7-ethyl-3,4,8-trihydroxy-6-methoxy-3,4-dihydro-1-(2H)-naphthalenone, (3S*, 4S*)-3,4-dihydro-3,4,8-trihydroxy-7-(1-hydroxyethyl)-6-methoxy-1-(2H)-naphthalenone, (4S)-3,4-dihydro-4,8-dihydroxy-1-(2H)-naphthalenone, named botryosphaerones D and A, isosclerone, respectively, and (3S*,4S*)-3,4,5-trihydroxy-1-tetralone (1-4). Phytotoxic activity of the isolated compounds (1-4) was tested on grapevine leaves at using the leaf puncture assay. All tested compounds were phytotoxic, with botryosphaerone D showing the greatest activity. The phytotoxic effects decreased when treated leaves were exposed to light. All of the metabolites did not show in vitro antifungal activity against Diplodia seriata, Lasiodiplodia mediterranea, Neofusicoccum vitifusiforme, or Phytophthora citrophthora. This is the first report of in vitro production of botryosphaerones D and A, and 3,4,5-trihydroxy-1-tetralone by N. parvum

Antiulcer Activity of Salvadora persica on Experimental ASA-Induced Ulcer in Rats: Ultrastructural Modifications

The lyophilized decoction of Salvadora persica L. roots possesses a significant protective effect on ulceration induced by ethanol, indomethacin and cold restraint stress in rats. In this work, we study the effect of chronic intragastric administration of S. persica decoction on experimental acetylsalicylic acid (ASA)-induced ulcer in rats. The ulcer index significantly decreased (U.I. 0.9 ± 1.6; P < 0.05) after treatment with a lyophilized decoction of S. persica (500 mg/kg, os), once daily for seven days, with respect to controls (U.I. 11.4 ± 2.3). The modification of gastric mucosa was observed by transmission electronic microscopy (TEM) confirming this result. In fact, in treated rats, the mucosa recovered to normal distribution. After S. persica treatment, some changes were detected in profiles of various cytoplasm organelles of parietal cells. Particularly, the intracellular canaliculi show an enlarged lumen with an increase in the number and length of microvilli. These morphological features of ..