12,625 research outputs found
Mirror matter admixtures in K_S to gamma gamma
The latest measurement of the K_S to gamma gamma branching ratio clearly
shows an enhancement over the current theoretical prediction. As in other K and
B meson decays, this invites to consider the possibility of the contribution of
new physics. We study a particular form of the latter, which may be referred to
as manifest mirror symmetry. The experimental data are described using
previously determined values for the mixing angles of the admixtures of mirror
matter in ordinary hadrons and by assuming that for pi^0, eta, eta', the mirror
decay amplitudes have the same magnitudes as their ordinary counterparts
Kink stability, propagation, and length scale competition in the periodically modulated sine-Gordon equation
We have examined the dynamical behavior of the kink solutions of the
one-dimensional sine-Gordon equation in the presence of a spatially periodic
parametric perturbation. Our study clarifies and extends the currently
available knowledge on this and related nonlinear problems in four directions.
First, we present the results of a numerical simulation program which are not
compatible with the existence of a radiative threshold, predicted by earlier
calculations. Second, we carry out a perturbative calculation which helps
interpret those previous predictions, enabling us to understand in depth our
numerical results. Third, we apply the collective coordinate formalism to this
system and demonstrate numerically that it accurately reproduces the observed
kink dynamics. Fourth, we report on a novel occurrence of length scale
competition in this system and show how it can be understood by means of linear
stability analysis. Finally, we conclude by summarizing the general physical
framework that arises from our study.Comment: 19 pages, REVTeX 3.0, 24 figures available from A S o
Characterization of Microbial Communities Associated with Ceramic Raw Materials as Potential Contributors for the Improvement of Ceramic Rheological Properties
Technical ceramics are being widely employed in the electric power, medical and engineering
industries because of their thermal and mechanical properties, as well as their high resistance qualities.
The manufacture of technical ceramic components involves complex processes, including milling
and stirring of raw materials in aqueous solutions, spray drying and dry pressing. In general, the
spray-dried powders exhibit an important degree of variability in their performance when subjected
to dry-pressing, which affects the efficiency of the manufacturing process. Commercial additives, such
as deflocculants, biocides, antifoam agents, binders, lubricants and plasticizers are thus applied to
ceramic slips. Several bacterial and fungal species naturally occurring in ceramic raw materials, such
as Sphingomonas, Aspergillus and Aureobasidium, are known to produce exopolysaccharides. These
extracellular polymeric substances (EPS) may confer unique and potentially interesting properties
on ceramic slips, including viscosity control, gelation, and flocculation. In this study, the microbial
communities present in clay raw materials were identified by both culture methods and DNA-based
analyses to select potential EPS producers based on the scientific literature for further assays based
on the use of EPS for enhancing the performance of technical ceramics. Potential exopolysaccharide
producers were identified in all samples, such as Sphingomonas sp., Pseudomonas xanthomarina,
P. stutzeri, P. koreensis, Acinetobacter lwoffi, Bacillus altitudinis and Micrococcus luteus, among bacteria.
Five fungi (Penicillium citrinum, Aspergillus niger, Fusarium oxysporum, Acremonium persicinum and
Rhodotorula mucilaginosa) were also identified as potential EPS producers.Fundação para a Ciência e a Tecnologia-EXPL/CTM-CER/0637/201
Acoustic Attenuation by Two-dimensional Arrays of Rigid Cylinders
In this Letter, we present a theoretical analysis of the acoustic
transmission through two-dimensional arrays of straight rigid cylinders placed
parallelly in the air. Both periodic and completely random arrangements of the
cylinders are considered. The results for the sound attenuation through the
periodic arrays are shown to be in a remarkable agreement with the reported
experimental data. As the arrangement of the cylinders is randomized, the
transmission is significantly reduced for a wider range of frequencies. For the
periodic arrays, the acoustic band structures are computed by the plane-wave
expansion method and are also shown to agree with previous results.Comment: 4 pages, 3 figure
An Evolutionary Algorithm to Generate Real Urban Traffic Flows
In this article we present a strategy based on an evolutionary algorithm to calculate the real vehicle ows in cities according to data from sensors placed in the streets. We have worked with a map imported from OpenStreetMap into the SUMO traffic simulator so that the resulting scenarios can be used to perform different optimizations with the confidence of being able to work with a traffic distribution close to reality. We have compared the results of our algorithm to other competitors and achieved results that replicate the real traffic distribution with a precision higher than 90%.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. This research has been partially funded by project number 8.06/5.47.4142 in collaboration with the VSB-Technical University of Ostrava and Universidad de Málaga UMA/FEDER FC14-TIC36, programa de fortalecimiento de las capacidades de I+D+i en las universidades 2014-2015, de la Consejería de Economía, Innovación, Ciencia y Empleo, cofinanciado por el fondo europeo de desarrollo regional (FEDER). Also, partially funded by the Spanish MINECO project TIN2014-57341-R (http://moveon.lcc.uma.es). The authors would like to thank the FEDER of European Union for financial support via project Movilidad Inteligente: Wi-Fi, Rutas y Contaminación (maxCT) of the "Programa Operativo FEDER de Andalucía 2014-2020. We also thank all Agency of Public Works of Andalusia Regional Government staff and researchers for their dedication and professionalism. Daniel H. Stolfi is supported by a FPU grant (FPU13/00954) from the Spanish Ministry of Education, Culture and Sports
Experimental observation of fractional topological phases with photonic qudits
Geometrical and topological phases play a fundamental role in quantum theory.
Geometric phases have been proposed as a tool for implementing unitary gates
for quantum computation. A fractional topological phase has been recently
discovered for bipartite systems. The dimension of the Hilbert space determines
the topological phase of entangled qudits under local unitary operations. Here
we investigate fractional topological phases acquired by photonic entangled
qudits. Photon pairs prepared as spatial qudits are operated inside a Sagnac
interferometer and the two-photon interference pattern reveals the topological
phase as fringes shifts when local operations are performed. Dimensions and were tested, showing the expected theoretical values.Comment: 6 pages, 4 figure
Coherent electronic transport through a superconducting film
We study coherent quantum transport through a superconducting film connected
to normal-metal electrodes. Simple expressions for the differential conductance
and the local density of states are obtained in the clean limit and for
transparent interfaces. Quasiparticle interference causes periodic vanishing of
the Andreev reflection at the energies of geometrical resonances, subgap
transport, and gapless superconductivity near the interfaces. Application of
the results to spectroscopic measurements of the superconducting gap and the
Fermi velocity is analyzed.Comment: 5 pages, 4 figure
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