Radical Chemistry in a Femtosecond Laser Plasma: Photochemical Reduction of Ag+ in Liquid Ammonia Solution

Plasmas with dense concentrations of reactive species such as hydrated electrons and hydroxyl radicals are generated from focusing intense femtosecond laser pulses into aqueous media. These radical species can reduce metal ions such as Au3+ to form metal nanoparticles (NPs). However, the formation of H2O2 by the recombination of hydroxyl radicals inhibits the reduction of Ag+ through back-oxidation. This work has explored the control of hydroxyl radical chemistry in a femtosecond laser-generated plasma through the addition of liquid ammonia. The irradiation of liquid ammonia solutions resulted in a reaction between NH3 and OH·, forming peroxynitrite and ONOO−, and significantly reducing the amount of H2O2 generated. Varying the liquid ammonia concentration controlled the Ag+ reduction rate, forming 12.7 ± 4.9 nm silver nanoparticles at the optimal ammonia concentration. The photochemical mechanisms underlying peroxynitrite formation and Ag+ reduction are discussed

Complementary action of chemical and electrical synapses to perception

Acknowledgements This study was possible by partial financial support from the following agencies: Fundação Araucária, EPSRC-EP/I032606/1, CNPq No. 441553/2014-1, CAPES No. 17656-12-5 and Science Without Borders Program— Process Nos. 17656125, 99999.010583/2013-00 and 245377/2012-3.Peer reviewedPostprin

Behavior of the diffractive cross section in hadron-nucleus collisions

A phenomenological analysis of diffractive dissociation of nuclei in proton-nucleus and meson-nucleus collisions is presented. The theoretical approach employed here is able to take into account at once data of the HELIOS and EHS/NA22 collaborations that exhibit quite different atomic mass dependences. Possible extensions of this approach to hard diffraction in nuclear processes are also discussed.Comment: 5 pages, 2 figure

Some aspects of the synchronization in coupled maps

Through numerical simulations we analyze the synchronization time and the Lyapunov dimension of a coupled map lattice consisting of a chain of chaotic logistic maps exhibiting power law interactions. From the observed behaviors we find a lower bound for the size $N$ of the lattice, independent of the range and strength of the interaction, which imposes a practical lower bound in numerical simulations for the system to be considered in the thermodynamic limit. We also observe the existence of a strong correlation between the averaged synchronization time and the Lyapunov dimension. This is an interesting result because it allows an analytical estimation of the synchronization time, which otherwise requires numerical simulations.Comment: 4 pages, 6 figure

Regge Analysis of Diffractive and Leading Baryon Structure Functions from DIS

In this paper we present a combined analysis of the H1 data on leading baryon and diffractive structure functions from DIS, which are handled as two components of the same semi-inclusive process. The available structure function data are analyzed in a series of fits in which three main exchanges are taking into account: pomeron, reggeon and pion. For each of these contributions, Regge factorization of the correspondent structure function is assumed. By this procedure, we extract information about the interface between the diffractive, pomeron-dominated, region and the leading proton spectrum, which is mostly ruled by secondary exchanges. One of the main results is that the relative reggeon contribution to the semi-inclusive structure function is much smaller than the one obtained from a analysis of the diffractive structure function alone.Comment: ps file, 22 pages, 5 figures. Totally revised version with major changes, to appear in Physical Review

Electron Spin Resonance of defects in the Haldane System Y(2)BaNiO(5)

We calculate the electron paramagnetic resonance (EPR) spectra of the antiferromagnetic spin-1 chain compound Y(2)BaNi(1-x)Mg(x)O(5) for different values of x and temperature T much lower than the Haldane gap (~100K). The low-energy spectrum of an anisotropic Heisenberg Hamiltonian, with all parameters determined from experiment, has been solved using DMRG. The observed EPR spectra are quantitatively reproduced by this model. The presence of end-chain S=1/2 states is clearly observed as the main peak in the spectrum and the remaining structure is completely understood.Comment: 5 pages, 4 figures include

Quantum Topology Change in (2 + 1)d

The topology of orientable (2 + 1)d spacetimes can be captured by certain lumps of non-trivial topology called topological geons. They are the topological analogues of conventional solitons. We give a description of topological geons where the degrees of freedom related to topology are separated from the complete theory that contains metric (dynamical) degrees of freedom. The formalism also allows us to investigate processes of quantum topology change. They correspond to creation and annihilation of quantum geons. Selection rules for such processes are derived.Comment: LaTeX file, 33 pages, 10 postscript figures, some typos corrected, references updated, and other minor change

Persistence, seasonal dynamics and pathogenic potential of Vibrio communities from pacific oyster hemolymph

Bacteria of the genus Vibrio occur at a continuum from free-living to symbiotic life forms, including opportunists and pathogens, that can contribute to severe diseases, for instance summer mortality events of Pacific oysters Crassostrea gigas. While most studies focused on Vibrio isolated from moribund oysters during mortality outbreaks, investigations of the Vibrio community in healthy oysters are rare. Therefore, we characterized the persistence, diversity, seasonal dynamics, and pathogenicity of the Vibrio community isolated from healthy Pacific oysters. In a reciprocal transplant experiment we repeatedly sampled hemolymph from adult Pacific oysters to differentiate population from site-specific effects during six months of in situ incubation in the field. We characterized virulence phenotypes and genomic diversity based on multilocus sequence typing in a total of 70 Vibrio strains. Based on controlled infection experiments we could show that strains with the ability to colonize healthy adult oysters can also have the potential to induce high mortality rates on larvae. Diversity and abundance of Vibrio varied significantly over time with highest values during and after spawning season. Vibrio communities from transplanted and stationary oysters converged over time, indicating that communities were not population specific, but rather assemble from the surrounding environment forming communities, some of which can persist over longer period